Therapeutic resistance poses a significant challenge in treating most cancers and often leads to poor clinical outcomes and even treatment failure. One of the primary mechanisms that confer multidrug resistance phenotype to cancer cells is the hyperactivity of certain drug efflux transporters. P-GP, MRP1, and BCRP are the key ABC efflux pumps that collectively extrude a broad spectrum of chemotherapeutic drugs. Besides, HIF1A, a master transcription regulatory protein, is also associated with cancer development and therapeutic resistance. Thereby, this study aimed to delve into the mechanisms of drug resistance, specifically focusing on HIF1A-driven overexpression of ABC transporters. A total of 57 chemoresistant and 57 paired control tissue samples (breast, colorectal, and ovarian) from Bangladeshi cancer patients were analyzed to determine the co-expression level of ABC transporters and HIF1A. Molecular docking was also conducted to evaluate the interactions of HIF1A protein and hypoxia response element (HRE) sequences in the promoter regions transporter genes. This study revealed that HIF1A is significantly overexpressed in chemoresistant tissues, suggesting its pivotal role in chemoresistance mechanisms across malignancies and its potential as a target to overcome therapeutic resistance. The findings from this study also suggest a direct upregulation of ABCB1, ABCC1, and ABCG2 transcription by HIF1A in chemoresistant cancer cells by binding to the HRE sequence in the promoter regions. Thus, inhibition of these interactions of HIF1A appears to be a promising approach to reverse chemoresistance. The findings of this study can serve as a foundation for future research, resolving molecular intricacies to improve treatment outcomes in chemoresistant patients.

Carotid body glomus cells are essential for stimulating breathing in response to hypoxia. They contain specialized mitochondria in which hypoxia induces the accumulation of NADH and H2O2 that modulate membrane ion channel activity. We investigated whether hypoxia induces reverse electron transport (RET) at mitochondrial complex I (MCI). We studied glomus cells from mice with a mutation in ND6, a core protein of MCI, which maintain normal MCI NADH dehydrogenase activity but cannot catalyze RET. The ND6 mutation increases the propensity of MCI to deactivate, and glomus cells with deactivated MCI are insensitive to acute hypoxia. These findings further indicate that MCI function is necessary for glomus cell responsiveness to hypoxia, although MCI RET does not seem to be required for this process.

This study investigated the effects of body weight (BW) reduction and hypoxia on physiological and perceptual responses during high-intensity interval exercise (HIIE) on the anti-gravity AlterG® treadmill.

Twenty-six participants (12 women, age: 26.2 years, height: 170.4 cm, weight: 67.8 kg, VO2max: 61.1 mL/min/kg) completed a HIIE in 5 randomized conditions: normoxia at 100%BW; normoxia at 80%BW; normoxia at 60%BW; hypoxia (FIO2 = 0.14) at 80%BW; and hypoxia at 60%BW. The HIIE included 3 sets of 8 × 30-s efforts interspersed with 30-s rest at 110% peak treadmill speed. Heart rate (HR), pulse arterial O2 saturation (SpO2), muscle deoxyhemoglobin concentration ([HHb]), and rate of perceived exertion (RPE) were continuously recorded. Blood lactate concentration ([Lac-]) was measured post-session.

BW reduction decreased HR, [Lac-] and RPE compared to control (p < 0.05) and [HHb] in men at the lowest %BW. When hypoxia was added, SpO2 was reduced from 98% to 85%. HR remained lower in all conditions compared to control (p < 0.05). RPE and [HHb] were higher in hypoxia than normoxic equivalent conditions (p < 0.05). [Lac-] was higher in Hyp80% compared to other conditions for men (p < 0.05). Despite subtle differences, men and women responded similarly to this exercise-environment combination.

Hypoxia effectively restored physiological stress during HIIE despite BW reduction, primarily impacting systemic rather than local muscular physiological parameters. This combination of methods may be beneficial in the rehabilitation and performance context.

The main O2 arterial chemoreceptors are the carotid bodies (CBs), which mediate hyperventilation in response to short-term sustained hypoxia (SH). CBs contain glomus cells expressing K+ channels, which are inhibited by hypoxia, leading to neurotransmitter release. ATP released by CBs and type II cells has been considered essential for chemosensory processing under physiological and pathophysiological conditions. Although the systemic effects of chronic activation of CBs by SH are well known, the early (first 24 h) cellular and molecular mechanisms in CBs as well as the effects of short-term SH on populations of glomus cells are still poorly understood. Here, we show that SH (10% O2 for 24 h) depolarizes the membrane potential of one population of glomus cells, mediated by increases in inward current, but does not affect the ATP release by CBs. In addition, SH promotes a reduction in their maximum outward current, mediated by voltage-gated K+ channels. SH also affected sensitivity to acute hypoxia in one glomus cell subpopulation. As for the content of mitochondrial proteins, we observed increases in the citrate synthase, Tom-20, and succinate dehydrogenase (mitochondrial complex II) per cell of CBs after SH. Our results demonstrate important cellular and molecular mechanisms of plasticity in CBs from rats after only 24 h of SH, which may contribute to the generation of cardiovascular and ventilatory adjustments observed in this experimental model.NEW & NOTEWORTHY Our study revealed two subpopulations of glomus cells of carotid bodies (CBs) with specific electrophysiological properties, which were differentially affected by short-term sustained hypoxia (SH; 10% O2 for 24 h). Our experiments showed that SH also affected the sensitivity to acute hypoxia of these glomus cell subpopulations differently. Our molecular analyses allowed us to identify important adaptations in the content of CB mitochondrial proteins that participate in the Krebs cycle and form the electron transport chain.

In this study, whole genome sequence data of Ladakhi cattle from high altitude region of Leh-Ladakh and Sahiwal cattle from arid, semi-arid tropical region were compared. To gain a deeper understanding of the selective footprints in the genomes of Ladakhi and Sahiwal cattle, two strategies namely run of homozygosity (ROH), and fixation index (FST) were employed. A total of 975 and 1189 ROH regions were identified in Ladakhi and Sahiwal cattle, respectively. Several genes associated with high-altitude adaptation were enriched in many of the ROH hot spots in genome of Ladakhi cattle such as; HIF1A, VEGFA, VEGFC, EPHB1, ZEB1, CAV3, TEK, SENP2, GATA6, RAD51 and ADAMTSL4 etc.. The FST value of 0.32 also indicated strong genetic differentiation between Ladakhi and Sahiwal cattle. A total of 3616 genomic regions were identified to be under selection in the two cattle breeds. The FST selection signature analysis led to identification of several genes such as HIF1A, VEGFC, ZEB1, SOD1, EGLN3, EPAS1, ZNF, DYSF, ADAM, SENP2, MMP16, and CDK2 etc., that could be associated with high altitude adaptation in Ladakhi cattle. Additionally, several signalling pathways found in Ladakhi cattle like HIF1A, VEGF, DNA repair, and angiogenesis, which are associated with adaptation to high-altitude hypoxic environments. The phylogenetic, PCA and admixture analysis separated the individuals of Ladakhi and Sahiwal cattle according to their geographic origin. In the present study, the WGS data has helped to identify key genes and genic regions that contribute to high altitude adaptation in Ladakhi cattle.

Hypoxia-inducible factors (HIFs) are key regulators of intracellular oxygen homeostasis. The marked increase in HIFs activity in hypoxia as compared to normoxia, together with their transcriptional control of primary metabolic pathways, motivated the widespread view of HIFs as responsible for the cell's metabolic adaptation to hypoxic stress. In this work, we suggest that this prevailing model of HIFs regulation is misleading. We propose an alternative model focused on understanding the dynamics of HIFs' activity within its physiological context. Our model suggests that HIFs would not respond to but rather prevent the onset of hypoxic stress by regulating the traffic of electrons between catabolic substrates and oxygen. The explanatory power of our approach is patent in its interpretation of the Warburg effect, the tendency of tumor cells to favor anaerobic metabolism over respiration, even in fully aerobic conditions. This puzzling behavior is currently considered as an anomalous metabolic deviation. Our model predicts the Warburg effect as the expected homeostatic response of tumor cells to the abnormal increase in metabolic demand that characterizes malignant phenotypes. This alternative perspective prompts a redefinition of HIFs' function and underscores the need to explicitly consider the cell's metabolic activity in understanding its responses to changes in oxygen availability.

Aging is marked by a progressive decrease in physiological function and reserve capacity, which results in increased susceptibility to diseases. Understanding the mechanisms of driving aging is crucial for extending health span and promoting human longevity. Hypoxia, marked by reduced oxygen availability, has emerged as a promising area of study within aging research. This review explores recent findings on the potential of oxygen restriction to promote healthy aging and extend lifespan. While the role of hypoxia-inducible factor 1 (HIF-1) in cellular responses to hypoxia is well-established, its impact on lifespan remains complex and context-dependent. Investigations in invertebrate models suggest a role for HIF-1 in longevity, while evidence in mammalian models is limited. Hypoxia extends the lifespan independent of dietary restriction (DR), a known intervention underlying longevity. However, both hypoxia and DR converge on common downstream effectors, such as forkhead box O (FOXO) and flavin-containing monooxygenase (FMOs) to modulate the lifespan. Further work is required to elucidate the molecular mechanisms underlying hypoxia-induced longevity and optimize clinical applications. Understanding the crosstalk between HIF-1 and other longevity-associated pathways is crucial for developing interventions to enhance lifespan and healthspan. Future studies may uncover novel therapeutic strategies to promote healthy aging and longevity in human populations.

Age-related macular degeneration (AMD), the leading cause of irreversible vision loss in the US, is on the rise among the elderly. Uncontrolled mitochondria-derived peptide production from mtDNA disruption and 16S or 12S rRNA damage could worsen AMD. Our previous work has shown that Humanin G possesses cytoprotective effects in retinal pigment epithelial (RPE) cells. However, MOTS-c, a highly efficient mitochondrial peptide, has yet to be evaluated on retinal cell survival. In this study, we show that there are differences in effects between wild-type (wt-) and differentiated ARPE19 cells (diff-ARPE19), implying that the cellular differentiation status may influence how cells respond to MOTS-c. MOTS-c has dose-dependent effects on apoptosis, inflammation, and mitochondrial biogenesis in diff-ARPE19 cells. Lower doses (500 nM) have more significant impacts than 5 µM concentrations. In diff-ARPE19 cells, a lower dose of MOTS-c can reduce the negative impact of hypoxia on cellular survival and gene expression, including apoptosis (CASP3, CASP9), mitochondrial biogenesis (TFAM, PGC-1α), and metabolic sensor (AMPK). However, it had no significant effect on ROS levels or NRF1 expression, regardless of MOTS-c dose. Exposing diff-ARPE19 cells to varied MOTS-c dosages before and after therapy in a chemically induced hypoxic environment yields no extra benefits as compared to MOTS-c treatment alone. MOTS-c had different effects on the expression of genes linked with apoptosis, mitochondrial biogenesis, and antioxidant activity in AMD patients versus age-matched control cybrids. The MOTS-c peptide appears to enhance cellular metabolism and regulate gene expression, which could potentially provide therapeutic benefits in AMD.

CYP2C9 metabolizes approximately 20% of clinically administered drugs. Several single-nucleotide polymorphisms (SNPs) of CYP2C9 (e.g., *2, *3, *8, and rs12777823) are used as biomarkers to predict CYP2C9 activity. However, a large proportion of variability in CYP2C9 expression remains unexplained.

We previously identified a variable number tandem repeat (pVNTR) polymorphism in the CYP2C9 promoter. The short repeat (pVNTR-S) showed reduced transcriptional activity in reporter gene assays and was associated with decreased CYP2C9 mRNA expression. However, because pVNTR-S is in high linkage disequilibrium (LD) with CYP2C9*3 in the European population, whether pVNTR-S directly impacts CYP2C9 expression remains unclear. The objective of this study was to clarify the association between the pVNTR-S and CYP2C9 mRNA expression in human liver samples and to assess its impact on CYP2C9 expression independently of known CYP2C9 biomarkers.

Gene expression was measured by real-time qPCR. SNPs and pVNTRs were genotyped using SNapShot assays and fragment analysis, respectively. Associations between CYP2C9 and the pVNTR-S or SNPs were analyzed using multiple linear regression.

Our results showed that pVNTR-S was associated with lower CYP2C9 expression (34% reduction, p-value = 0.032) in human liver samples (n = 247), while the known CYP2C9 biomarkers (CYP2C9*2, *3, *8, or rs12777823) were not. These results suggest that pVNTR-S reduces CYP2C9 expression independently of known biomarkers. Therefore, pVNTR-S may explain additional variability in CYP2C9 expression when present alone or in conjunction with other CYP2C9 alleles.

The aim of the current study was to test normobaric 100% oxygen (NBO) (PiO2 = 713 mmHg) for stem cell mobilization and cytokine modulation. Although current oxygen therapy (PiO2 = 1,473-2,233 mmHg) is well known to mobilize stem cells and modulate cytokine, little is known about NBO and its place on the low dose stimulation phase of the hormetic dose curve of oxygen. We asked the question, will NBO mobilize stem cells and modulate cytokines. A positive outcome presents the potential to create and refine oxygen treatment protocols, expand access, and optimize patient outcomes.

Healthy 30-35-year-old volunteers were exposed to 100% normobaric oxygen for 60 min, M-F, for 10 exposures over 2 weeks. Venous blood samples were collected at four time points: 1) prior to the first exposure (serving as the control for each subject), 2) immediately after the first exposure (to measure the acute effect), 3) immediately before the ninth exposure (to measure the chronic effect), and 4) three days after the final exposure (to assess durability). Blinded scientists used flow cytometry to gate and quantify the Stem Progenitor Cells (SPCs).

CD45dim/CD34+/CD133+ and CD45+/CD34+/CD133+ were significantly mobilized following nine daily one-hour exposures to normobaric 100% oxygen. Conversely CD45-/CD34+/CD133+, CD45-/CD34+/CD133- and CD45-/CD34-/CD133+ phenotypes were downregulated suggesting differentiation into more mature phenotypes. The CD133+ phenotype exhibited a maturing from CD45- to CD45dim stem cells. CD45-/CD34, CD45-/CD31 and CD45-/CD105 were downregulated with no changes in related CD45dim and CD45+ phenotypes. The cytokines "macrophage migration inhibitory factor" (MIF) and "a proliferation inducing ligand" (APRIL) were significantly upregulated.

This study demonstrates that 100% normobaric oxygen mobilizes stem cells and upregulates the expression of the inflammatory cytokines marking a new point on the low dose stimulation phase of the hormetic dose curve of oxygen.

Nicotinamide adenine dinucleotide (NAD) is an essential regulator of cellular metabolism and redox processes. NAD levels and the dynamics of NAD metabolism change with increasing age but can be modulated via the diet or medication. Because NAD metabolism is complex and its regulation still insufficiently understood, achieving specific outcomes without perturbing delicate balances through targeted pharmacological interventions remains challenging. NAD metabolism is also highly sensitive to environmental conditions and can be influenced behaviorally, e.g., by exercise. Changes in oxygen availability directly and indirectly affect NAD levels and may result from exposure to ambient hypoxia, increased oxygen demand during exercise, ageing or disease. Cellular responses to hypoxic stress involve rapid alterations in NAD metabolism and depend on many factors, including age, glucose status, the dose of the hypoxic stress and occurrence of reoxygenation phases, and exhibit complex time-courses. Here we summarize the known determinants of NAD-regulation by hypoxia and evaluate the role of NAD in hypoxic stress. We define the specific NAD responses to hypoxia and identify a great potential of the modulation of NAD metabolism regarding hypoxic injuries. In conclusion, NAD metabolism and cellular hypoxia responses are strongly intertwined and together mediate protective processes against hypoxic insults. Their interactions likely contribute to age-related changes and vulnerabilities. Targeting NAD homeostasis presents a promising avenue to prevent/treat hypoxic insults and - conversely - controlled hypoxia is a potential tool to regulate NAD homeostasis.

Oxidative stress caused by hypoxia can lead to serious bodily damage and functional degradation. Our previous study in pigs showed that the insulin-like growth factor II receptor (IGF2R) gene might participate in the process of hypoxia adaptability. To investigate the function and mechanism of IGF2R in cellular hypoxia tolerance, we analyze the effect of IGF2R on cell survival capacity under hypoxia conditions in intestinal porcine enterocyte cell line (IPEC-J2) cells. The results show that under hypoxia condition (3% O2), cell viability is significantly reduced, the expression of IGF2R and cell apoptosis are significantly increased. Functional analysis suggests that suppressing IGF2R expression under hypoxia does not affect cell cycle and cell proliferation but increases cellular viability. Meanwhile, the expression of the pro-apoptotic gene BAX is reduced, the hypoxia-induced apoptosis is rescued, and cell survival is significantly improved. Transcriptome analysis suggests that global gene expression changes in knockdown IGF2R under hypoxia, IGF2R may regulate apoptosis through oxidative phosphorylation. Our findings demonstrate that suppressing IGF2R expression under hypoxia can rescue hypoxia-induced cell injury by reducing the expression of BAX, highlighting the potential ability of IGF2R regulation for the treatment of hypoxia stress.

Hypoxia-inducible factors (HIFs) are central regulators of gene expression in response to oxygen deprivation, a common feature in critical illnesses. The significant burden that critical illnesses place on global healthcare systems highlights the need for a deeper understanding of underlying mechanisms and the development of innovative treatment strategies. Among critical illnesses, impaired lung function is frequently linked to hypoxic conditions. This review focuses on the expression and regulation of HIF signalling in experimental models of acute lung injury (ALI) and clinical studies in critically ill patients with acute respiratory distress syndrome (ARDS). We explore the potential dual role of HIF signalling in acute lung inflammation. Furthermore, its role in key biological processes and its potential prognostic significance in clinical scenarios are discussed. Finally, we explore recent pharmacological advancements targeting HIF signalling, which have emerged as promising alternatives to existing therapeutic approaches, potentially enabling more effective management strategies.

In this work, we present a novel modeling framework for understanding the dynamics of homeostatic regulation. Inspired by engineering control theory, this framework incorporates unique features of biological systems. First, biological variables often play physiological roles, and taking this functional context into consideration is essential to fully understand the goals and constraints of homeostatic regulation. Second, biological signals are not abstract variables, but rather material molecules that may undergo complex turnover processes of synthesis and degradation. We suggest that the particular nature of biological signals may condition the type of information they can convey, and their potential role in shaping the dynamics and the ultimate purpose of homeostatic systems. We show that the dynamic interplay between regulated variables and control signals is a key determinant of biological homeostasis, challenging the necessity and the convenience of strictly extrapolating concepts from engineering control theory in modeling the dynamics of homeostatic systems. This work provides a simple, unified framework for studying biological regulation and identifies general principles that transcend molecular details of particular homeostatic mechanisms. We show how this approach can be naturally applied to apparently different regulatory systems, contributing to a deeper understanding of homeostasis as a fundamental process in living systems.

Berkemeier, Quint N., Michael R. Deyhle, James J. McCormick, Kurt A. Escobar, and Christine M. Mermier. The potential interplay between HIF-1α, angiogenic, and autophagic signaling during intermittent hypoxic exposure and exercise High Alt Med Biol. 25:326-336, 2024.-Environmental hypoxia as a result of decreased barometric pressure upon ascent to high altitudes (>2,500 m) presents increased physiological demands compared with low altitudes, or normoxic environments. Competitive athletes, mountaineers, wildland firefighters, military personnel, miners, and outdoor enthusiasts commonly participate in, or are exposed to, forms of exercise or physical labor at moderate to high altitudes. However, the majority of research on intermittent hypoxic exposure is centered around hematological markers, and the skeletal muscle cellular responses to exercise in hypoxic environments remain largely unknown. Two processes that may be integral for the maintenance of cellular health in skeletal muscle include angiogenesis, or the formation of new blood vessels from preexisting vasculature and autophagy, a process that removes and recycles damaged and dysfunctional cellular material in the lysosome. The purpose of this review is to is to examine the current body of literature and highlight the potential interplay between low-oxygen-sensing pathways, angiogenesis, and autophagy during acute and prolonged intermittent hypoxic exposure in conjunction with exercise. The views expressed in this paper are those of the authors and do not reflect the official policy of the Department of Army, DOD, DOE, ORAU/ORISE or U.S. Government.

Anemia and mineral and bone disorder (MBD) are significant complications of chronic kidney disease (CKD). The erythropoietin (Epo) pathway plays a key role in both of these processes in CKD. Another molecule that plays an important role in CKD-MBD is fibroblast growth factor (FGF)-23, whose main role is to maintain serum phosphate levels in the normal range, acting via its co-receptor Klotho; however, its activity may also be related to anemia and inflammation. In this review, the regulation of Epo and FGF-23 and the molecular mechanisms of their action are outlined. Furthermore, the complex interaction between EPO and FGF-23 is discussed, as well as their association with other anemia-related factors and processes such as Klotho, vitamin D, and iron deficiency. Together, these may be part of a "kidney-bone marrow-bone axis" that promotes CKD-MBD.

The major pathological characteristics of Alzheimer's disease (AD) include senile plaques and neurofibrillary tangles (NFTs), which are mainly composed of aggregated amyloid-beta (Aβ) peptide and hyperphosphorylated tau protein, respectively. The excessive production of reactive oxygen species (ROS) and neuroinflammation are crucial contributing factors to the pathological mechanisms of AD. Hypoxia-inducible factor-1 (HIF-1) is a transcription factor critical for tissue adaption to low-oxygen tension. Growing evidence has suggested HIF-1 as a potential therapeutic target for AD; conversely, other experimental findings indicate that HIF-1 induction contributes to AD pathogenesis. These previous findings thus point to the complex, even contradictory, roles of HIF-1 in AD. In this review, we first introduce the general pathogenic mechanisms of AD as well as the potential pathophysiological roles of HIF-1 in cancer, immunity, and oxidative stress. Based on current experimental evidence in the literature, we then discuss the possible beneficial as well as detrimental mechanisms of HIF-1 in AD; these sections also include the summaries of multiple chemical reagents and proteins that have been shown to exert beneficial effects in AD via either the induction or inhibition of HIF-1.

Aging is a complex biological process characterized by the gradual decline of cellular functions, increased susceptibility to diseases, and impaired stress responses. Hypoxia, defined as reduced oxygen availability, is a critical factor that influences aging through molecular pathways involving hypoxia-inducible factors (HIFs), oxidative stress, inflammation, and epigenetic modifications. This review explores the interconnected roles of hypoxia in aging, highlighting how hypoxic conditions exacerbate cellular damage, promote senescence, and contribute to age-related pathologies, including cardiovascular diseases, neurodegenerative disorders, cancer, metabolic dysfunctions, and pulmonary conditions. By examining the molecular mechanisms linking hypoxia to aging, we identify key pathways that serve as potential therapeutic targets. Emerging interventions such as HIF modulators, antioxidants, senolytics, and lifestyle modifications hold promise in mitigating the adverse effects of hypoxia on aging tissues. However, challenges such as the heterogeneity of aging, lack of reliable biomarkers, and safety concerns regarding hypoxia-targeted therapies remain. This review emphasizes the need for personalized approaches and advanced technologies to develop effective antiaging interventions. By integrating current knowledge, this review provides a comprehensive framework that underscores the importance of targeting hypoxia-induced pathways to enhance healthy aging and reduce the burden of age-related diseases.

This study was performed to evaluate the changes in oxygen supply-demand balance during induction of general anesthesia using an indirect calorimeter capable of measuring oxygen consumption (VO2) and carbon dioxide production (VCO2).

This study included patients scheduled for surgery in whom remimazolam was administered as a general anesthetic. VO2 and VCO2 were measured at different intervals: upon awakening (T1), 15 min after tracheal intubation (T2), and 1 h after T2 (T3). Oxygen delivery (DO2) was calculated simultaneously with these measurements. VO2 was ascertained using an indirect calorimeter and further calculated using vital signs, among other factors. DO2 was derived from cardiac output and arterial blood gas analysis performed with an arterial pressure-based cardiac output measurement system.

VO2, VCO2, and DO2 decreased significantly from T1 to T2 and T3 [VO2/body surface area (BSA) (ml/min/m2): T1, 130 (122-146); T2, 107 (83-139); T3, 97 (93-121); p = 0.011], [VCO2/BSA (ml/min/m2): T1, 115 (105-129); T2, 90 (71-107); T3, 81 (69-101); p = 0.011], [DO2/BSA (ml/min/m2): T1, 467 (395-582); T2, 347 (286-392); T3, 382 (238-414); p = 0.0020]. Among the study subjects, a subset exhibited minimal reduction in VCO2. Although the respiratory frequency was titrated on the basis of end-tidal CO2 levels, there was no significant difference between the groups.

General anesthetic induction with remimazolam decreased VO2, VCO2, and DO2.

Type 2 diabetes mellitus (T2DM) and cancer share common risk factors including obesity, inflammation, hyperglycemia, and hyperinsulinemia. High insulin levels activate the PI3K/Akt/mTOR signaling pathway promoting cancer cell growth, survival, proliferation, metastasis, and anti-apoptosis. The inhibition of the PI3K/Akt/mTOR signaling pathway for cancer remains a promising therapy; however, drug resistance poses a major problem in clinical settings resulting in limited efficacy of agents; thus, combination treatments with therapeutic inhibitors may solve the resistance to such agents. Understanding the metabolic link between diabetes and cancer can assist in improving the therapeutic strategies used for the management of cancer patients with diabetes and vice versa. This review provides an overview of shared molecular mechanisms between diabetes and cancer as well as discusses established and emerging therapeutic anti-cancer agents targeting the PI3K/Akt/mTOR pathway in cancer management.

Rapid proliferation and outgrowth of tumor cells frequently result in localized hypoxia, which has been implicated in the progression of lung cancer. The present study aimed to identify key long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) involved in hypoxia-induced A549 lung cancer cells, and to investigate their potential underlying mechanisms of action.

High-throughput sequencing was utilized to obtain the expression profiles of lncRNA and mRNA in both hypoxia-induced and normoxia A549 lung cancer cells. Subsequently, a bioinformatics analysis was conducted on the differentially expressed molecules, encompassing functional enrichment analysis, protein-protein interaction (PPI) network analysis, and competitive endogenous RNA (ceRNA) analysis. Finally, the alterations in the expression of key lncRNAs and mRNAs were validated using real-time quantitative PCR (qPCR).

In the study, 1155 mRNAs and 215 lncRNAs were identified as differentially expressed between the hypoxia group and the normoxia group. Functional enrichment analysis revealed that the differentially expressed mRNAs were significantly enriched in various pathways, including the p53 signaling pathway, DNA replication, and the cell cycle. Additionally, key lncRNA-miRNA-mRNA relationships, such as RP11-58O9.2-hsa-miR-6749-3p-XRCC2 and SNAP25-AS1-hsa-miR-6749-3p-TENM4, were identified. Notably, the qPCR assay demonstrated that the expression of SNAP25-AS1, RP11-58O9.2, TENM4, and XRCC2 was downregulated in the hypoxia group compared to the normoxia group. Conversely, the expression of LINC01164, VLDLR-AS1, RP11-14I17.2, and CDKN1A was upregulated.

Our findings suggest a potential involvement of SNAP25-AS1, RP11-58O9.2, TENM4, XRCC2, LINC01164, VLDLR-AS1, RP11-14I17.2, and CDKN1A in the development of hypoxia-induced lung cancer. These key lncRNAs and mRNAs exert their functions through diverse mechanisms, including the competitive endogenous RNA (ceRNA) pathway.

Clinical biomarkers such as fasting glucose, HbA1c, and fasting insulin, which gauge glycemic status in the body, are highly influenced by diet. Indians are genetically predisposed to type 2 diabetes and their carbohydrate-centric diet further elevates the disease risk. Despite the combined influence of genetic and environmental risk factors, Indians have been inadequately explored in the studies of glycemic traits. Addressing this gap, we investigate the genetic architecture of glycemic traits at genome-wide level in 4927 Indians (without diabetes). Our analysis revealed numerous variants of sub-genome-wide significance, and their credibility was thoroughly assessed by integrating data from various levels. This identified key effector genes, ZNF470, DPP6, GXYLT2, PITPNM3, BEND7, and LORICRIN-PGLYRP3. While these genes were weakly linked with carbohydrate intake or glycemia earlier in other populations, our findings demonstrated a much stronger association in the Indian population. Associated genetic variants within these genes served as expression quantitative trait loci (eQTLs) in various gut tissues essential for digestion. Additionally, majority of these gut eQTLs functioned as methylation quantitative trait loci (meth-QTLs) observed in peripheral blood samples from 223 Indians, elucidating the underlying mechanism of their regulation of target gene expression. Specific co-localized eQTLs-meth-QTLs altered the binding affinity of transcription factors targeting crucial genes involved in glucose metabolism. Our study identifies previously unreported genetic variants that strongly influence the diet-glycemia relationship. These findings set the stage for future research into personalized lifestyle interventions integrating genetic insights with tailored dietary strategies to mitigate disease risk based on individual genetic profiles.

Transcription factors are challenging to target with small-molecule inhibitors due to their structural plasticity and lack of catalytic sites. Notable exceptions include naturally ligand-regulated transcription factors, including our prior work with the hypoxia-inducible factor (HIF)-2 transcription factor, showing that small-molecule binding within an internal pocket of the HIF-2α Per-Aryl hydrocarbon Receptor Nuclear Translocator (ARNT)-Sim (PAS)-B domain can disrupt its interactions with its dimerization partner, ARNT. Here, we explore the feasibility of targeting small molecules to the analogous ARNT PAS-B domain itself, potentially opening a promising route to modulate several ARNT-mediated signaling pathways. Using solution NMR fragment screening, we previously identified several compounds that bind ARNT PAS-B and, in certain cases, antagonize ARNT association with the transforming acidic coiled-coil containing protein 3 transcriptional coactivator. However, these ligands have only modest binding affinities, complicating characterization of their binding sites. We address this challenge by combining NMR, molecular dynamics simulations, and ensemble docking to identify ligand-binding "hotspots" on and within the ARNT PAS-B domain. Our data indicate that the two ARNT/transforming acidic coiled-coil containing protein 3 inhibitors, KG-548 and KG-655, bind to a β-sheet surface implicated in both HIF-2 dimerization and coactivator recruitment. Furthermore, while KG-548 binds exclusively to the β-sheet surface, KG-655 can additionally bind within a water-accessible internal cavity in ARNT PAS-B. Finally, KG-279, while not a coactivator inhibitor, exemplifies ligands that preferentially bind only to the internal cavity. All three ligands promoted ARNT PAS-B homodimerization, albeit to varying degrees. Taken together, our findings provide a comprehensive overview of ARNT PAS-B ligand-binding sites and may guide the development of more potent coactivator inhibitors for cellular and functional studies.

Renal cell carcinoma (RCC) is a heterogenous disease which the incidence is increasing worldwide. The identification and understanding of the role of the Von Hipple Lindau (VHP) in regulating the hypoxia-inducible factor signaling pathway has revolutionized the treatment of this disease. Belzutifan is an oral hypoxia-inducible factor (HIF)-2α inhibitor, which has demonstrated efficacy in treating von Hippel-Lindau (VHL) disease and for the treatment of adults with RCC who experienced disease progression after PD-1/PD-L1- and VEGFR-targeted therapies. One of the most common adverse effect of this drug is anemia; however, it is treatment is not well known. This review summarizes role of the VHL-HIF pathway in ccRCC aroused the interest of targeting HIF activity, the history of belzutifan development and their relationship to anemia as well as propose a management algorithm.

Occupational pulmonary diseases (OPDs) pose a significant global health challenge, contributing to high mortality rates. This review delves into the pathophysiology of hypoxia and the safety of intermittent hypoxic conditioning (IHC) in OPD patients. By examining sources such as PubMed, Relemed, NLM, Scopus, and Google Scholar, the review evaluates the efficacy of IHC in clinical outcomes for OPD patients. It highlights the complexities of cardiovascular and respiratory regulation dysfunctions in OPDs, focusing on respiratory control abnormalities and the impact of intermittent hypoxic exposures. Key areas include the physiological effects of hypoxia, the role of hypoxia-inducible factor-1 alpha (HIF-1α) in occupational lung diseases, and the links between brain ischemia, stroke, and OPDs. The review also explores the interaction between intermittent hypoxic exposures, mitochondrial energetics, and lung physiology. The potential of IHE to improve clinical manifestations and underlying pathophysiology in OPD patients is thoroughly examined. This comprehensive analysis aims to benefit molecular pathologists, pulmonologists, clinicians, and physicians by enhancing understanding of IHE's clinical benefits, from research to patient care, and improving clinical outcomes for OPD patients.

The present study was conducted to understand transcriptional response of skin fibroblast of yak (Bos grunniens) and cows of Bos indicus origin to hypoxia stress. Six primary fibroblast cell lines derived from three individuals each of Ladakhi yak (Bos grunniens) and Sahiwal cows (Bos indicus) were exposed to low oxygen concentration for a period of 24 h, 48 h and 72 h. The expression of 10 important genes known to regulate hypoxia response such as HIF1A, VEGFA, EPAS1, ATP1A1, GLUT1, HMOX1, ECE1, TNF-A, GPx and SOD were evaluated in fibroblast cells of Ladakhi yak (LAY-Fb) and Sahiwal cows (SAC-Fb) during pre- and post-hypoxia stress. A panel of 10 reference genes (GAPDH, RPL4, EEF1A1, RPS9, HPRT1, UXT, RPS23, B2M, RPS15, ACTB) were also evaluated for their expression stability to perform accurate normalization. The expression of HIF1A was significantly (p < 0.05) induced in both LAY-Fb (2.29-fold) and SAC-Fb (2.07-fold) after 24 h of hypoxia stress. The angiogenic (VEGFA), metabolic (GLUT1) and antioxidant genes (SOD and GPx) were also induced after 24 h of hypoxia stress. However, EPAS1 and ATP1A1 induced significantly (p < 0.05) after 48 h whereas, ECE1 expression induced significantly (p < 0.05) at 72 h after exposure to hypoxia. The TNF-alpha which is a pro-inflammatory gene induced significantly (p < 0.05) at 24 h in SAC-Fb and at 72 h in LAY-Fb. The induction of hypoxia associated genes indicated the utility of skin derived fibroblast as cellular model to evaluate transcriptome signatures post hypoxia stress in populations adapted to diverse altitudes.

Hypoxia is a common environmental stressor in aquatic ecosystems, and during the cultivation process, Megalobrama amblycephala is prone to death because it is hypoxia-intolerant, which brings huge economic losses to farmers. The pituitary gland is a crucial endocrine gland in fish, and it is mainly involved in the secretion, storage, and regulation of hormones. In the present study, we compared the transcriptional responses to serious hypoxia in the pituitary gland among hypoxia-sensitive (HS) and hypoxia-tolerant (HT) M. amblycephala and a control group that received a normal oxygen supply (C0). The fish were categorized according to the time required to lose balance during a hypoxia treatment. A total of 129,251,170 raw reads were obtained. After raw sequence filtering, 43,461,745, 42,609,567, and 42,730,282 clean reads were obtained for the HS, HT, and C0 groups, respectively. A transcriptomic comparison revealed 1234 genes that were differentially expressed in C0 vs. HS, while 1646 differentially expressed genes were obtained for C0 vs. HT. In addition, the results for HS vs. HT showed that 367 upregulated and 41 downregulated differentially expressed genes were obtained for a total of 408 differentially expressed genes. A KEGG analysis of C0 vs. HS, C0 vs. HT, and HS vs. HT identified 315, 322, and 219 enriched pathways, respectively. Similar hypoxia-induced transcription patterns suggested that the downregulated DEGs and enriched pathways were related to pathways of neurodegeneration in multiple diseases, pathways in cancer, thermogenesis, microRNAs in cancer, diabetic cardiomyopathy, and renin secretion. However, in the upregulated DEGs, the PI3K-Akt signaling pathway (C0 vs. HS), microRNAs in cancer (C0 vs. HT), and HIF-1 signaling pathway (HS vs. HT) were significantly enriched. There is a lack of clarity regarding the role of the pituitary gland in hypoxic stress. These results not only provide new insights into the mechanism by which pituitary tissue copes with hypoxia stress in M. amblycephala but also offer a basis for breeding M. amblycephala with hypoxia-resistant traits.

Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid derived from Cannabis sativa. It has therapeutic effects in different paradigms of brain injury, acting as a neuroprotectant. As oxidative stress is a primary risk factor for brain damage after neonatal hypoxia, we tested the effect of CBD on oxidative status and non-protein-bound iron accumulation in the immature brain after hypoxia. Moreover, we tested whether cannabidiol affects the accumulation of hypoxia-inducible factor-1 alpha (HIF-1α) which plays a key role in the regulation of cellular adaptation to hypoxia and oxidative stress. We used 7-day-old mice randomly assigned to hypoxic or control groups. Immediately after hypoxia or control exposure, pups were randomly assigned to a vehicle or CBD treatment. 24 h later, they were decapitated and the brains were immediately removed and stored for further biochemical analyses. We found that CBD reduced lipid peroxidation and prevented antioxidant depletion. For the first time, we also demonstrated that CBD upregulated HIF-1α protein level. This study indicates that CBD may effective agent in attenuating the detrimental consequences of perinatal asphyxia.

Transcription factors are generally challenging to target with small molecule inhibitors due to their structural plasticity and lack of catalytic sites. Notable exceptions include several naturally ligand-regulated transcription factors, including our prior work with the heterodimeric HIF-2 transcription factor which showed that small molecule binding within an internal pocket of the HIF-2α PAS-B domain can disrupt its interactions with its dimerization partner, ARNT. Here, we explore the feasibility of similarly targeting small molecules to the analogous ARNT PAS-B domain itself, potentially opening a promising route to simultaneously modulate several ARNT-mediated signaling pathways. Using solution NMR screening of an in-house fragment library, we previously identified several compounds that bind ARNT PAS-B and, in certain cases, antagonize ARNT association with the TACC3 transcriptional coactivator. However, these ligands have only modest binding affinities, complicating characterization of their binding sites. We address this challenge by combining NMR, MD simulations, and ensemble docking to identify ligand-binding 'hotspots' on and within the ARNT PAS-B domain. Our data indicate that the two ARNT/TACC3 inhibitors, KG-548 and KG-655, bind to a β-sheet surface implicated in both HIF-2 dimerization and coactivator recruitment. Furthermore, while KG-548 binds exclusively to the β-sheet surface, KG-655 can additionally bind within a water-accessible internal cavity in ARNT PAS-B. Finally, KG-279, while not a coactivator inhibitor, exemplifies ligands that preferentially bind only to the internal cavity. All three ligands promoted ARNT PAS-B homodimerization, albeit to varying degrees. Taken together, our findings provide a comprehensive overview of ARNT PAS-B ligand-binding sites and may guide the development of more potent coactivator inhibitors for cellular and functional studies.

Hypoxia-inducible factors (HIFs) are transcription factors that reprogram the transcriptome for cells to survive hypoxic insults and oxidative stress. They are important during embryonic development and reprogram the cells to utilize glycolysis when the oxygen levels are extremely low. This metabolic change facilitates normal cell survival as well as cancer cell survival. The key feature in survival is the transition between acute hypoxia and chronic hypoxia, and this is regulated by the transition between HIF-1 expression and HIF-2/HIF-3 expression. This transition is observed in many human cancers and endothelial cells and referred to as the HIF Switch. Here we discuss the mechanisms involved in the HIF Switch in human endothelial and cancer cells which include mRNA and protein levels of the alpha chains of the HIFs. A major continuing effort in this field is directed towards determining the differences between normal and tumor cell utilization of this important pathway, and how this could lead to potential therapeutic approaches.

Placental nutrient transport capacity influences fetal growth and development; however, it is affected by environmental factors, which are poorly understood. The objective of this study was to understand the impact of the ovine placentome morphological subtype, tissue type, and maternal parenteral supplementation of arginine mono-hydrochloride (Arg) on nutrient transport capacity using a gene expression approach. Placentomal tissues of types A, B, and C morphologic placentome subtypes were derived from 20 twin-bearing ewes, which were infused thrice daily with Arg (n = 9) or saline (Ctrl, n = 11) from 100 to 140 days of gestation. Samples were collected at day 140 of gestation. Expression of 31 genes involved in placental nutrient transport and function was investigated. Differential expression of specific amino acid transporter genes was found in the subtypes, suggesting a potential adaptive response to increase the transport capacity. Placentomal tissues differed in gene expression, highlighting differential transport capacity. Supplementation with Arg was associated with differential expressions of genes involved in amino acid transport and angiogenesis, suggesting a greater nutrient transport capacity. Collectively, these results indicate that the morphological subtype, tissue type, and maternal Arg supplementation can influence placental gene expression, which may be an adaptive response to alter the transport capacity to support fetal growth in sheep.

This study aimed to separately compare and rank the effect of various living-low and training-high (LLTH) modes on aerobic and anaerobic performances in athletes, focusing on training intensity, modality, and volume, through network meta-analysis. We systematically searched PubMed, Web of Science, Embase, EBSCO, and Cochrane from their inception date to June 30, 2023. Based on the hypoxic training modality and the intensity and duration of work intervals, LLTH was divided into intermittent hypoxic exposure, continuous hypoxic training, repeated sprint training in hypoxia (RSH; work interval: 5-10 s and rest interval: approximately 30 s), interval sprint training in hypoxia (ISH; work interval: 15-30 s), short-duration high-intensity interval training (s-IHT; short work interval: 1-2 min), long-duration high-intensity interval training (l-IHT; long work interval: > 5 min), and continuous and interval training under hypoxia. A meta-analysis was conducted to determine the standardized mean differences (SMDs) among the effects of various hypoxic interventions on aerobic and anaerobic performances. From 2,072 originally identified titles, 56 studies were included in the analysis. The pooled data from 53 studies showed that only l-IHT (SMDs: 0.78 [95% credible interval; CrI, 0.52-1.05]) and RSH (SMDs: 0.30 [95% CrI, 0.10-0.50]) compared with normoxic training effectively improved athletes' aerobic performance. Furthermore, the pooled data from 29 studies revealed that active intermittent hypoxic training compared with normoxic training can effectively improve anaerobic performance, with SMDs ranging from 0.97 (95% CrI, 0.12-1.81) for l-IHT to 0.32 (95% CrI, 0.05-0.59) for RSH. When adopting a program for LLTH, sufficient duration and work intensity intervals are key to achieving optimal improvements in athletes' overall performance, regardless of the potential improvement in aerobic or anaerobic performance. Nevertheless, it is essential to acknowledge that this study incorporated merely one study on the improvement of anaerobic performance by l-IHT, undermining the credibility of the results. Accordingly, more related studies are needed in the future to provide evidence-based support. It seems difficult to achieve beneficial adaptive changes in performance with intermittent passive hypoxic exposure and continuous low-intensity hypoxic training.

Thiram, a commonly used agricultural insecticide and fungicide, has been found to cause tibial dyschondroplasia (TD) in broilers, leading to substantial economic losses in the poultry industry. In this study, we aimed to investigate the mechanism of action of leucine in mitigating thiram-induced TD and leucine effects on gut microbial diversity. Broiler chickens were randomly divided into five equal groups: control group (standard diet), thiram-induced group (thiram 80 mg/kg from day 3 to day 7), and different concentrations of leucine groups (0.3%, 0.6%, 0.9% leucine from day 8 to day 18). Performance indicator analysis and tibial parameter analysis showed that leucine positively affected thiram-induced TD broilers. Additionally, mRNA expressions and protein levels of HIF-1α/VEGFA and Ihh/PTHrP genes were determined via quantitative real-time polymerase chain reaction and western blot. The results showed that leucine recovered lameness disorder by downregulating the expression of HIF-1α, VEGFA, and PTHrP while upregulating the expression of Ihh. Moreover, the 16 S rRNA sequencing revealed that the leucine group demonstrated a decrease in the abundance of harmful bacteria compared to the TD group, with an enrichment of beneficial bacteria responsible for producing short-chain fatty acids, including Alistipes, Paludicola, CHKCI002, Lactobacillus, and Erysipelatoclostridium. In summary, the current study suggests that leucine could improve the symptoms of thiram-induced TD and maintain gut microbiota homeostasis.

Metazoan animals rely on oxygen for survival, but during normal development and homeostasis, animals are often challenged by hypoxia (low oxygen). In metazoans, many of the critical hypoxia responses are mediated by the evolutionarily conserved hypoxia-inducible transcription factors (HIFs). The stability and activity of HIF complexes are strictly regulated. In the model organism C. elegans, HIF-1 stability and activity are negatively regulated by VHL-1, EGL-9, RHY-1 and SWAN-1. Importantly, C. elegans mutants carrying strong loss-of-function mutations in these genes are viable, and this provides opportunities to interrogate the molecular consequences of persistent HIF-1 over-activation. We find that the genome-wide gene expression patterns are compellingly similar in these mutants, supporting models in which RHY-1, VHL-1 and EGL-9 function in common pathway(s) to regulate HIF-1 activity. These studies illuminate the diversified biological roles played by HIF-1, including metabolism and stress response. Genes regulated by persistent HIF-1 over-activation overlap with genes responsive to pathogens, and they overlap with genes regulated by DAF-16. As crucial stress regulators, HIF-1 and DAF-16 converge on key stress-responsive genes and function synergistically to enable hypoxia survival.

Liu, Bo, Minlan Yuan, Mei Yang, Hongru Zhu, and Wei Zhang. The effect of high-altitude hypoxia on neuropsychiatric functions. High Alt Med Biol. 25:26-41, 2024. Background: In recent years, there has been a growing popularity in engaging in activities at high altitudes, such as hiking and work. However, these high-altitude environments pose risks of hypoxia, which can lead to various acute or chronic cerebral diseases. These conditions include common neurological diseases such as acute mountain sickness (AMS), high-altitude cerebral edema, and altitude-related cerebrovascular diseases, as well as psychiatric disorders such as anxiety, depression, and psychosis. However, reviews of altitude-related neuropsychiatric conditions and their potential mechanisms are rare. Methods: We conducted searches on PubMed and Google Scholar, exploring existing literature encompassing preclinical and clinical studies. Our aim was to summarize the prevalent neuropsychiatric diseases induced by altitude hypoxia, the potential pathophysiological mechanisms, as well as the available pharmacological and nonpharmacological strategies for prevention and intervention. Results: The development of altitude-related cerebral diseases may arise from various pathogenic processes, including neurovascular alterations associated with hypoxia, cytotoxic responses, activation of reactive oxygen species, and dysregulation of the expression of hypoxia inducible factor-1 and nuclear factor erythroid 2-related factor 2. Furthermore, the interplay between hypoxia-induced neurological and psychiatric changes is believed to play a role in the progression of brain damage. Conclusions: While there is some evidence pointing to pathophysiological changes in hypoxia-induced brain damage, the precise mechanisms responsible for neuropsychiatric alterations remain elusive. Currently, the range of prevention and intervention strategies available is primarily focused on addressing AMS, with a preference for prevention rather than treatment.

Hypoxia is a significant source of metabolic stress that activates many cellular pathways involved in cellular differentiation, proliferation, and cell death. Hypoxia is also a major component in many human diseases and a known driver of many cancers. Despite the challenges posed by hypoxia, there are animals that display impressive capacity to withstand lethal levels of hypoxia for prolonged periods of time and thus offer a gateway to a more comprehensive understanding of the hypoxic response in vertebrates. The weakly electric fish genus Brachyhypopomus inhabits some of the most challenging aquatic ecosystems in the world, with some species experiencing seasonal anoxia, thus providing a unique system to study the cellular and molecular mechanisms of hypoxia tolerance. In this study, we use closely related species of Brachyhypopomus that display a range of hypoxia tolerances to probe for the underlying molecular mechanisms via hypoxia inducible factors (HIFs)-transcription factors known to coordinate the cellular response to hypoxia in vertebrates. We find that HIF1⍺ from hypoxia tolerant Brachyhypopomus species displays higher transactivation in response to hypoxia than that of intolerant species, when overexpressed in live cells. Moreover, we identified two SUMO-interacting motifs near the oxygen-dependent degradation and transactivation domains of the HIF1⍺ protein that appear to boost transactivation of HIF1, regardless of the genetic background. Together with computational analyses of selection, this shows that evolution of HIF1⍺ are likely to underlie adaptations to hypoxia tolerance in Brachyhypopomus electric fishes, with changes in two SUMO-interacting motifs facilitating the mechanism of this tolerance.

Succinate, one of the intermediates of the tricarboxylic acid (TCA) cycle, plays an essential role in the metabolism of mitochondria and the production of energy, and is considered as a signaling molecule in metabolism as well as in initiation and progression of hepatic diseases. Of note, succinate activates a downstream signaling pathway through GPR91, and elicits a variety of intracellular responses, such as succinylation, production of reactive oxygen species (ROS), stabilization of hypoxia-inducible factor-1α (HIF-1α), and significant impact in cellular metabolism because of the pivotal role in the TCA cycle. Therefore, it is intriguing to deeply elucidate signaling mechanisms of succinate in hepatic fibrosis, metabolic reprogramming in inflammatory or immune responses, as well as carcinogenesis. This manuscript intends to review current understanding of succinate in mediating metabolism, inflammatory and immunologic reactions in liver diseases in order to establish molecular basis for the development of therapeutic strategies.

Head and neck cancer (HNC) is one of the most frequent malignancies in Asian males with a poor prognosis. Apart from well-known prognostic indicators, markers of tumor hypoxia can help us predict response to treatment and survival.

A review of the literature on the present evidence and potential clinical importance of tumor hypoxia in head and neck cancer was carried out. The data obtained from the literature search is presented as a narrative review.

The literature shows possible associations between prognosis and low tumor oxygenation. Intermediate hypoxia biomarkers like HIF-1, GLUT-1, miRNA, and lactate, can help in predicting the response to therapy and survival as their altered expression is related to prognosis.

Hypoxia is common in HNC and can be detected by use of biomarkers. The tumors that show expression of hypoxia biomarkers have poor prognosis except for patients with human papilloma virus-associated or VHL-associated cancers. Therapeutic targeting of hypoxia is emerging; however, it is still in its nascent stage, with increasing clinical trials hypoxia is set to emerge as an attractive therapeutic target in HNC.

In this study we explored the role of hypoxia and the hypoxia-inducible transcription factor EPAS1 in regulating spermatogonial stem cell (SSC) function in the mouse testis. We have demonstrated that SSCs reside in hypoxic microenvironments in the testis through utilization of the oxygen-sensing probe pimonidazole, and by confirming the stable presence of EPAS1, which is degraded at >5% O2. Through the generation of a germline-specific Epas1 knockout mouse line, and through modulation of EPAS1 levels in primary cultures of spermatogonia with the small drug molecule Daprodustat, we have demonstrated that EPAS1 is required for robust SSC function in regenerative conditions (post-transplantation and post-chemotherapy), via the regulation of key cellular processes such as metabolism. These findings shed light on the relationship between hypoxia and male fertility and will potentially facilitate optimization of in vitro culture conditions for infertility treatment pipelines using SSCs, such as those directed at pediatric cancer survivors.

Although depletion of neuronal nitric oxide synthase (NOS1)-expressing neurons contributes to gastroparesis, stimulating nitrergic signaling is not an effective therapy. We investigated whether hypoxia-inducible factor 1α (HIF1A), which is activated by high O2 consumption in central neurons, is a Nos1 transcription factor in enteric neurons and whether stabilizing HIF1A reverses gastroparesis.

Mice with streptozotocin-induced diabetes, human and mouse tissues, NOS1+ mouse neuroblastoma cells, and isolated nitrergic neurons were studied. Gastric emptying of solids and volumes were determined by breath test and single-photon emission computed tomography, respectively. Gene expression was analyzed by RNA-sequencing, microarrays, immunoblotting, and immunofluorescence. Epigenetic assays included chromatin immunoprecipitation sequencing (13 targets), chromosome conformation capture sequencing, and reporter assays. Mechanistic studies used Cre-mediated recombination, RNA interference, and clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9)-mediated epigenome editing.

HIF1A signaling from physiological intracellular hypoxia was active in mouse and human NOS1+ myenteric neurons but reduced in diabetes. Deleting Hif1a in Nos1-expressing neurons reduced NOS1 protein by 50% to 92% and delayed gastric emptying of solids in female but not male mice. Stabilizing HIF1A with roxadustat (FG-4592), which is approved for human use, restored NOS1 and reversed gastroparesis in female diabetic mice. In nitrergic neurons, HIF1A up-regulated Nos1 transcription by binding and activating proximal and distal cis-regulatory elements, including newly discovered super-enhancers, facilitating RNA polymerase loading and pause-release, and by recruiting cohesin to loop anchors to alter chromosome topology.

Pharmacologic HIF1A stabilization is a novel, translatable approach to restoring nitrergic signaling and treating diabetic gastroparesis. The newly recognized effects of HIF1A on chromosome topology may provide insights into physioxia- and ischemia-related organ function.