Hepatic encephalopathy, defined as neuropsychiatric dysfunction secondary to liver disease, is a frequent decompensating event in cirrhosis. Its clinical impact is highlighted by a notable increase in patient mortality rates and a concomitant reduction in overall quality of life. Systemically, liver disease, liver function failure, portosystemic shunting, and associated multi-organ dysfunction result in the increase of disease-causing neurotoxins in the circulation, which impairs cerebral homeostasis. Key circulating neurotoxins are ammonia and inflammatory mediators. In the brain, pathophysiology is less well understood, but is thought to be driven by glial cell dysfunction. Astrocytes are the only brain resident cells that have ammonia-metabolizing machinery and are therefore putatively most susceptible to ammonia elevation. Based on a large body of mostly in vitro evidence, ammonia-induced cellular and molecular disturbances include astrocyte swelling and oxidative stress. Microglia, the brain resident macrophages, have been linked to the translation of systemic inflammation to the brain microenvironment. Recent evidence from animal studies has provided novel insights into old and new downstream effects of astrocyte and microglial dysfunction such as toxin clearance disruption and myeloid cell attraction to the central nervous system parenchyma. Furthermore, state of the art research increasingly implicates neuronal dysfunction and possibly even irreversible neuronal cell death. Cell-type specific investigation in animal models highlights the need for critical revision of the contribution of astrocytes and microglia to well-established and novel cellular and molecular alterations in hepatic encephalopathy. In this review, we therefore give a current and comprehensive overview of causes, features, and consequences of astrocyte and microglial dysfunction in hepatic encephalopathy, including areas of interest for future investigation.

Humans are exposed to complex per- and polyfluoroalkyl substances (PFAS) mixtures, yet their neurotoxicity and mechanisms remains unclear. This study exposed male mice to 17 PFAS mixtures at low levels (0.2-20 µg/L) for 49 days via drinking water. Perfluoropentanoic acid (PFPeA), perfluoroheptanoic acid (PFHpA), 6:2 fluorotelomer sulfonic acid (6:2 FTS), and perfluorooctane Sulfonate (PFOS) accumulated in brain tissues, with brain/plasma ratios of 2.03-5.87, 2.94-12.88, 1.90-3.19, and 0.62-0.93, respectively. Electroencephalogram (EEG) results showed significant alterations, including a reduction in beta spectral edge (21.47-13.85 Hz) and an increase in gamma spectral edge (57.64-79.07 Hz). Histopathological analysis revealed necrosis in the hippocampus, contributing to the observed anxiety-like behaviors and memory impairments in exposed mice. Plasma metabolomics highlighted disrupted osmoprotectants, impaired glutamatergic synapse function, and tryptophan metabolism. Brain metabolomics demonstrated suppression of purine metabolism and activation of arachidonic acid metabolism, suggesting involvement in neurotoxic effects. Transcriptomic profiling further identified dysregulation in neuroactive ligand-receptor interactions, cholinergic and GABAergic synapses, and calcium signaling pathways, with oxytocin signaling highlighted as a critical mechanism. This study, for the first time, links PFAS mixture to neurotoxicity via neurotransmitter-related pathways, underscoring the need for public health policies and preventive strategies to mitigate PFAS exposure risks.

Basal forebrain cholinergic neurons (BFCNs) are the sole source of cholinergic innervation to the cerebral cortex and hippocampus in humans and the primary source in rodents. This system undergoes early degeneration in Alzheimer's disease. BFCNs terminal synapses are involved in the regulation of the cerebral blood flow by making classical synaptic contacts with other neurons. Additionally, they are located in proximity to cortical cerebral blood vessels, forming connections with various cell types of the neurovascular unit (NVU), including vascular smooth muscle cells, endothelial cells, and astrocytic end-feet. However, the effects of the BFCNs input on NVU components remain unresolved. To address this issue, we immunolesioned the nucleus basalis by administering bilateral stereotaxic injections of the cholinergic immunotoxin 192-IgG-Saporin in 2.5-month-old Wistar rats. Seven months post-lesion, we observed a significant reduction in cortical vesicular acetylcholine transporter-immunoreactive synapses. This was accompanied by changes in the diameter of cortical capillaries and precapillary arterioles, as well as lower levels of vascular endothelial growth factor A (VEGF-A). Additionally, the cholinergic immunolesion increased the density of cortical astrocytes and microglia in the cortex. At these post-BFCN-lesion stages, astrocytic end-feet exhibited an increased co-localization with arterioles. The number of microglia in the parietal cortex correlated with cholinergic loss and exhibited morphological changes indicative of an intermediate activation state. This was supported by decreased levels of proinflammatory mediators IFN-γ, IL-1β, and KC/GRO (CXCL1), and by increased expression of M2 markers SOCS3, IL4Rα, YM1, ARG1, and Fizz1. Our findings offer a novel insight: that the loss of nucleus basalis cholinergic input negatively impacts cortical blood vessels, NVU components, and microglia phenotype.

Mitochondria are central to cellular energy metabolism, contributing to synaptic transmission and plasticity. The mitochondrial membranes present the cannabinoid type-1 receptor (mito-CB1R), which has been functionally linked to neuronal energy supply and cognitive processing. Prenatal exposure to Δ9-tetrahydrocannabinol (pTHC) has been associated with cognitive impairments associated with molecular cellular and functional abnormalities in several brain regions, including the hippocampus. This study aims at assessing whether, besides the memory impairment, pTHC exposure may result in mitochondrial molecular and functional alterations in the hippocampus of the offspring. Moreover, the assessment of CB1R expression is also carried out as a proxy of CB1 signalling in pTHC-exposed offspring. THC (2 mg/Kg), or vehicle, was administered to the dams from gestational day (GD) 5 to GD20, and the offspring were tested for declarative memory using the Novel Object Recognition test in the L-maze. We also assessed: mitochondrial respiration by high-resolution respirometry; mitochondrial respiratory complex-I subunit NDUFS1 protein levels, and mito-CB1R expression by ELISA. Our results revealed: significant memory impairment in pTHC-exposed offspring; attenuated mitochondrial respiration in the hippocampus alongside a marked reduction in complex-I-subunit NDUFS1; a significant increase in mito-CB1R expression. This is the first evidence of pTHC exposure-induced impairment in memory processing in the offspring that suggests a functional link between an attenuation in mitochondrial bioenergetics and abnormal CB1R signalling in the hippocampus.

The last few years have seen an explosion in the number of tools available to measure neuronal activity using fluorescence imaging (Chen et al., 2013; Feng et al., 2019; Jing et al., 2019; Sun et al., 2018; Wan et al., 2021). When performed in vivo, these measurements are invariably contaminated by hemodynamic occlusion artifacts. In widefield calcium imaging, this problem is well recognized. For two-photon imaging, however, the effects of hemodynamic occlusion have only been sparsely characterized. Here, we perform a quantification of hemodynamic occlusion effects using measurements of fluorescence changes observed with GFP expression using both widefield and two-photon imaging in mouse cortex. We find that in many instances the magnitude of signal changes attributable to hemodynamic occlusion is comparable to that observed with activity sensors. Moreover, we find that hemodynamic occlusion effects were spatially heterogeneous, both over cortical regions and across cortical depth, and exhibited a complex relationship with behavior. Thus, hemodynamic occlusion is an important caveat to consider when analyzing and interpreting not just widefield but also two-photon imaging data.

Stroke-induced brain remodeling involves a complex interplay of neurovascular components, including endothelial cells, microglia, astrocytes, and pericytes, which collectively contribute to the restoration of brain function. These processes are crucial for repairing the blood-brain barrier, regulating inflammation, and promoting neurogenesis. This review examines the mechanisms underlying brain remodeling and the role of advanced neuroimaging techniques-such as functional MRI (fMRI), positron emission tomography (PET), functional near-infrared spectroscopy (fNIRS), and functional ultrasound (fUS)-in assessing these changes. We also discuss various therapeutic approaches aimed at enhancing brain remodeling, including pharmacological agents, stem cell therapy, and rehabilitation strategies that target neurovascular repair and functional recovery. Despite significant progress, challenges remain in translating imaging insights into effective treatments. Future research should focus on integrating multiple imaging modalities to provide a comprehensive view of neurovascular changes and refining therapeutic interventions to optimize recovery and functional outcomes in stroke patients.

Background: The aim of this study was to assess the agreement between different analysis protocols for the determination of retinal vessel dilation response to flicker light (FL) and its relation to static and metabolic parameters of retinal vessels in healthy subjects. Methods: In total, 24 right eyes of 24 healthy controls (mean age: 36.04 ± SD 14.4 years) who underwent dynamic and static retinal diameter and oxygen saturation measurements on a Retinal Vessel Analyzer (RVA, Imedos, Jena, Germany) were included. Using repeated video analyses, responses to FL were measured with RVA. These measurements were conducted at three specific retinal locations: within the superotemporal area-within a distance of less than one optic disk (OD) diameter to optic nerve head (ONH) (group 1); greater than one OD diameter to ONH (group 2); and areas near the ONH within the VesselMap region (group 3). For comparability, the static and oxygen saturation parameters were also calculated in the superotemporal peripapillary area using the VesselMap tool of the RVA and were evaluated in relation to the corresponding dynamic area (group 3). Results: In all groups, the vascular FL response of arteries was less pronounced compared to venules (p = 0.0014). Even though FL responses (mean ± SD: FL-A; FL-V) in group 1 were more pronounced (3.36 ± 2.31; 4.42 ± 1.69) compared to those in group 2 (2.97 ± 2.40; 4.08 ± 1.55) and group 3 (2.84 ± 2.29; 4.21 ± 2.03), they did not reach statistically significant values. The mean flicker response of venules (VDil) in all groups showed negative correlations to the corresponding static parameter: central retinal venous equivalent (CRV) (r = -0.0437; p = 0.015). The mean flicker response of arteries (ADil) in all groups showed negative correlations to the corresponding metabolic parameter: arterio-venous oxygen extraction fraction (r = -0.101; p = 0.041). Conclusions: Our study confirms that the flicker light response, despite slight variations in its duration and location, allows for reliable measurements, proving the Retinal Vessel Analyzer to be a valuable diagnostic tool. Furthermore, we were able to highlight the relationship between the dynamic and metabolic components of retinal supply, which enables early diagnosis concerning the development of diseases within this spectrum.

Exosomes are extracellular vesicles secreted by almost all types of cells. Their release allows for the transport of specific regulatory cargo into the recipient cells and the modulation of their activity. Vesicular communication has also been identified as an important mechanism for the regulation of numerous cellular activities in the brain tissue, contributing to proper neuronal functions and brain homeostasis. In this work, we focus on the role of exosomes and extracellular vesicles in the communication between astrocytes and brain endothelial cells, two major components of the blood-brain barrier. We perform a comprehensive review of the latest studies highlighting the role of exosomes in astrocyte-endothelial cell crosstalk within the blood-brain barrier. We have also described the role of particular exosomal miRNAs in the regulation of astrocytes and brain endothelial cell functions, and discuss some future implications.

Glucose uptake and metabolism are linked to microvascular blood flow and cellular swelling events, which are altered during obesity and can be quantified using magnetic resonance imaging (MRI). Aquaporin-4 (AQP4), the most abundant water-transporting transmembrane protein in the central nervous system, facilitates glucose transport and metabolism-derived water influx. However, its significance and regulatory capacity remain largely unknown. To better understand these processes, we acquired sequential diffusion tensor and T2*-weighted images of the brains of obese and non-obese mice, both before administering an AQP4 inhibitor and after a subsequent glucose challenge. We then subjected the resulting variables to principal component and linear mixed model analyses to assess the influence of diet, sex, administration of the inhibitor, and brain region on the data. Our findings indicate that AQP4-inhibited mice exhibit MRI values consistent with reduced microvascular blood flow and region-specific inhibition of glucose-induced cell swelling during obesity, highlighting a key role for AQP4 in glucose uptake and metabolism. Additionally, we observed that, prior to any experimental manipulation, obese mice displayed MRI signs of lower hippocampal blood flow and cerebral cellular anisotropy compared to controls, in agreement with vascular alterations and reactive gliosis processes.

Blood vessels are critical to deliver oxygen and nutrients to tissues and organs throughout the body. The blood vessels that vascularize the central nervous system (CNS) possess unique properties, termed the blood-brain barrier (BBB), which allow these vessels to tightly regulate the movement of ions, molecules, and cells between the blood and the brain. This precise control of CNS homeostasis allows for proper neuronal function and protects the neural tissue from toxins and pathogens, and alterations of this barrier are important components of the pathogenesis and progression of various neurological diseases. The physiological barrier is coordinated by a series of physical, transport, and metabolic properties possessed by the brain endothelial cells (ECs) that form the walls of the blood vessels. These properties are regulated by interactions between different vascular, perivascular, immune, and neural cells. Understanding how these cell populations interact to regulate barrier properties is essential for understanding how the brain functions in both health and disease contexts.

Ultrahigh dose rate radiotherapy (RT) with electrons and protons has shown potential for cancer treatment by effectively targeting tumors while sparing healthy tissues (FLASH effect). This study aimed to investigate the potential FLASH sparing effect of ultrahigh dose rate helium ion irradiation, focusing on acute brain injury and subcutaneous tumor response in a preclinical in vivo setting. Raster-scanned helium ion beams were used to compare the effects of standard dose rate (SDR; at 0.2 Gy/second) and FLASH (at 141 Gy/second) RT on healthy brain tissue. Irradiation-induced brain injury was studied in C57BL/6 mice via DNA damage response, using nuclear γH2AX as a marker for double-strand breaks. The integrity of neurovascular and immune compartments was assessed through CD31+ microvascular density and activation of microglia/macrophages. IBA1+ ramified and CD68+ phagocytic microglia/macrophages were quantified, along with the expression of inducible nitric oxide synthetase. Tumor response to SDR (0.2 Gy/second) and FLASH (250 Gy/second) RT was evaluated in an A549 carcinoma model, using tumor volume and Kaplan-Meier survival as endpoints. The results showed that helium FLASH RT significantly reduced acute brain tissue injury compared with SDR, evidenced by lower levels of double-strand breaks and preserved the neurovascular endothelium. Additionally, FLASH RT reduced neuroinflammatory signals compared with SDR, as indicated by fewer CD68+ inducible nitric oxide synthetase-positive microglia/macrophages. FLASH RT achieved tumor control comparable with that of SDR RT. To the best of our knowledge, this is the first study to report the FLASH sparing effect of raster scanning helium ion RT in vivo, highlighting its potential for neuroprotection and effective tumor control.

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive method that has been used to treat various brain disorders. The modulatory effects of rTMS can be adjusted by changing the repetition patterns. Theta-burst magnetic stimulation (TBS) is a magnetic stimulation pattern that can induce long-lasting modulatory effects with a short stimulation period. However, its effects on auditory brain regions remain unclear because of a lack of animal studies in which invasive techniques allow for a detailed exploration of the underlying neural mechanisms. In the current study, we investigated the effects of TBS on the C57BL/6J mouse auditory cortex using a custom-built 7 mm magnetic stimulation coil. Extracellular recordings were made before, during, and after the application of intermittent TBS (iTBS), continuous TBS (cTBS), or sham stimulation. Local field potential amplitudes were increased for 5-20 min post-iTBS compared with the sham condition and were decreased at 10 min post-cTBS compared with the sham condition. The bidirectional modulatory effects observed in our study are consistent with previous findings from other brain regions. Additionally, multiunit activities were significantly altered in cortical layers 2/3 and 4 but not layer 5, indicating that the modulatory effects were localized to the surface region of the auditory cortex. Interestingly, in the iTBS group, the amplitude of average spike waveforms increased with a 15 min delay. Our findings provide physiological evidence of TBS modulation of the rodent auditory cortex and may guide future research seeking to optimize rTMS for modulating hearing abilities.

High fidelity neuronal signaling is enabled by a stable local microenvironment. A high degree of homeostatic regulation of the brain microenvironment, and its separation from the variable and potentially neurotoxic contents of the blood, is brought about by the central nervous system barriers. Evidence from clinical and preclinical studies implicates brain microcirculation, cerebral hypoperfusion, blood-brain barrier dysfunction, and reduced amyloid clearance in Alzheimer pathophysiology. Studying this dysregulation is key to understanding Alzheimer disease (AD), identifying drug targets, developing treatment strategies, and improving prescribing to this vulnerable population. This review has 2 parts: part 1 describes the cerebral microcirculation, cerebral blood flow, extracellular fluid drainage, and the neurovascular unit components with an emphasis on the blood-brain barrier, and part 2 summarizes how each aspect is altered in AD. Discussing the neurovascular unit structures separately allows us to conclude that aberrant pericytes are an early contributor and central to understanding AD pathophysiology. Pericytes have multiple functions including maintenance of blood-brain barrier integrity and the control of capillary blood flow, capillary stalling, neurovascular coupling, intramural periarterial drainage, glia-lymphatic (glymphatic) drainage, and consequently amyloid and tau clearance. Pericytes are vasoactive, express cholinergic and adrenergic receptors, and exhibit apolipoprotein E isoform-specific transport pathways. Hypoperfusion in AD is linked to a pericyte-mediated response. Deficient endothelial cell-pericyte (PDGBB-PDGFRβ) signaling loops cause pericyte dysfunction, which contributes and even initiates AD degeneration. We conclude that pericytes are central to understanding AD pathophysiology, are an interesting therapeutic target in AD, and have an emerging role in regenerative therapy. SIGNIFICANCE STATEMENT: Dysregulation and dysfunction of the neurovascular unit and fluid circulation (including blood, cerebrospinal fluid, and interstitial fluid) occurs in Alzheimer disease. A central player is the aberrant pericyte. This has fundamental implications to understanding disease pathophysiology and the development of therapies.

Zero echo time (zero-TE) pulse sequences provide a quiet and artifact-free alternative to conventional functional magnetic resonance imaging (fMRI) pulse sequences. The fast readouts (<1 ms) utilized in zero-TE fMRI produce an image contrast with negligible contributions from blood oxygenation level-dependent (BOLD) mechanisms, yet the zero-TE contrast is highly sensitive to brain function. However, the precise relationship between the zero-TE contrast and neuronal activity has not been determined. Therefore, we aimed to derive a function to model the temporal dynamics of the zero-TE fMRI signal in response to neuronal activity. Furthermore, we examined the correlation of zero-TE fMRI with neuronal activity across stimulation frequencies. To these ends, we performed simultaneous electrophysiological recordings and zero-TE fMRI in rats subjected to whisker stimulation. The presented impulse response function provides a basis for the statistical modeling of neuronal activity-induced changes in the zero-TE fMRI signal. The temporal characteristics of the zero-TE fMRI response were found to be consistent with the previously postulated non-BOLD hemodynamic origin of the functional contrast. The zero-TE fMRI signal was well predicted by electrophysiological recordings, although systematic stimulation-dependent residuals were also observed, suggesting nonlinearities in neurovascular coupling. We conclude that zero-TE fMRI provides a robust proxy for neuronal activity.

Astrocytes are the most abundant type of macroglia in the brain and play crucial roles in regulating neural development and functions. The diverse functions of astrocytes are largely determined by their morphology, which is regulated by genetic and environmental factors. However, whether and how the astrocyte morphology is affected by temperature remains largely unknown. Here we discovered that elevated cultivation temperature (26°C) stimulates Caenorhabditis elegans ventral CEPsh glia endfoot extension during early developmental stages. This extension depends on the activation of glutamate AWC neurons, which inhibit the postsynaptic cholinergic AIY interneurons through glutamate-gated chloride channels, GLC-3 and GLC-4. In responding to the thermosensory signal, the guanyl-nucleotide exchange factor EPHX-1 and Rho GTPase CDC-42/Cdc42 in the glia facilitate the endfoot extension via F-actin assembly. This study elucidates the significant role of thermosensory circuitry in glia morphogenesis and the underlying molecular mechanism.

The high metabolic demand of retinal neurons requires a precisely regulated vascular system that can deliver rapid changes in blood flow in response to neural need. In the retina, this is achieved via the action of a coordinated group of cells that form the neurovascular unit. While cells such as pericytes, Müller cells, and astrocytes have long been linked to neurovascular coupling, more recently the resident microglial population have also been implicated. In the healthy retina, microglia make extensive contact with blood vessels, as well as neuronal synapses, and are important in vascular patterning during development. Work in the brain and retina has recently indicated that microglia can directly regulate the local vasculature. In the retina, the fractalkine-Cx3cr1 signalling axis has been shown to induce local capillary constriction within the superficial vascular plexus via a mechanism involving components of the renin-angiotensin system. Furthermore, aberrant microglial induced vasoconstriction may be at the centre of early vascular reactivity changes observed in those with diabetes. This review summarizes the recent emerging evidence that microglia play multiple roles in retinal homeostasis especially in regulating the vasculature. We highlight what is known about the role of microglia under normal circumstances, and then build on this to discuss how microglia contribute to early vascular compromise during diabetes. Further understanding of the mechanisms of microglial-vascular regulation may allow alternate treatment strategies to be devised to reduce vascular pathology in diseases such as diabetic retinopathy.

Dynamic control of membrane potential lies at the nexus of a wide spectrum of biological processes, ranging from the control of individual cell secretions to the orchestration of complex thought and behaviour. Electrical signals in all vascular cell types (smooth muscle cells, endothelial cells and pericytes) contribute to the control of haemodynamics and energy delivery across spatiotemporal scales and throughout all tissues. Here, our goal is to review and synthesize key studies of electrical signalling within the brain vasculature and integrate these with recent data illustrating an important electrical signalling role for pericytes, in doing so attempting to work towards a holistic description of blood flow control in the brain by vascular electrical signalling. We use this as a framework for generating further questions that we believe are important to pursue. Drawing parallels with electrical signal integration in the nervous system may facilitate deeper insights into how signalling is organized within the vasculature and how it controls blood flow at the network level.

Characterizing the transition or switching behavior between multistable brain states in functional connectivity dynamics (FCD) holds promise for uncovering the underlying neuropathology of Autism Spectrum Disorder (ASD). However, whether and how switching behaviors in FCD change in patients with developmental ASD, as well as their cellular and molecular basis, remains unexplored. This study develops a region-wise FCD switching index (RFSI) to investigate the drivers of FCD. This work finds that brain regions within the salience, default mode, and frontoparietal networks serve as abnormal drivers of FCD in ASD across different developmental stages. Additionally, changes in RFSI at different developmental stages of ASD correlated with transcriptomic profiles and neurotransmitter density maps. Importantly, the abnormal RFSI identifies in humans has also been observed in genetically edited ASD monkeys. Finally, single-nucleus RNA sequencing data from patients with developmental ASD are analyzed and aberrant switching behaviors in FCD may be mediated by somatostatin-expressing interneurons and altered differentiation patterns in astrocyte State2. In conclusion, this study provides the first evidence of abnormal drivers of FCD across different stages of ASD and their associated cellular and molecular mechanisms. These findings deepen the understanding of ASD neuropathology and offer valuable insights into treatment strategies.

Neurovascular coupling, linking neuronal activity to cerebral blood flow, is essential for brain function and underpins functional brain imaging. Whereas mechanisms involved in vasodilation are well-documented, those controlling vasoconstriction remain overlooked. This study unravels the mechanisms by which pyramidal cells elicit arteriole vasoconstriction. Using patch-clamp recording, vascular and Ca2+ imaging in mouse cortical slices, we show that strong optogenetic activation of layer II/III pyramidal cells induces vasoconstriction, correlating with firing frequency and somatic Ca2+ increase. Ex vivo and in vivo pharmacological investigations indicate that this vasoconstriction predominantly recruits prostaglandin E2 through the cyclooxygenase-2 pathway, and activation of EP1 and EP3 receptors. We also present evidence that specific interneurons releasing neuropeptide Y, and astrocytes, through 20-hydroxyeicosatetraenoic acid, contribute to this process. By revealing the mechanisms by which pyramidal cells lead to vasoconstriction, our findings shed light on the complex regulation of neurovascular coupling.

Nicotine addiction, a multifaceted neuropsychiatric disorder, profoundly impacts brain functions through interactions with neural pathways. Despite its significance, the impact of tobacco smoking on the whole-brain functional connectome remains largely unexplored.

We conducted a whole-brain analysis on 24 539 adults aged 40 and above from the United Kingdom Biobank cohort. Subjects were categorized into individuals who use nicotine and those who do not use nicotine based on current and chronic tobacco smoking information. Functional connectivity was assessed using resting-state functional magnetic resonance imaging. We employed a network analysis method to assess the systematic effects of tobacco smoking on brain connectome by identifying subnetworks that show nicotine-use-related differences.

Our analyses revealed two nicotine-use-related subnetworks with distinct network structure (permutation p < .001). In the first network, there is a significant decrease in resting-state functional connectivity (rsFC) between the basal ganglia regions (eg, nucleus accumbens) and 73% of the remaining brain regions, emphasizing the central hub role of basal ganglia in addictive smoking behaviors. Additionally, a data-driven subnetwork, mainly involving regions from frontal and occipital lobes, showed reduced rsFC among individuals who use nicotine.

The results suggest significant alterations in the communication and coordination among the basal ganglia and the broader network of brain regions. The observed changes in rsFC indicate a widespread disruption in the connectivity patterns associated with nicotine use.

This study identifies rsFC subnetworks related to chronic nicotine use through whole-brain connectome analysis. The findings confirm that widespread alterations in rsFC are centered around hub nodes within the basal ganglia, including bilateral nucleus accumbens, putamen, caudate, and globus pallidus. In addition, our analysis found a clique-forming subnetwork vulnerable to tobacco smoking consisting of regions from the visual, dorsal/ventral attention, and frontoparietal networks.

Crosstalk mechanisms between retinas were never documented in humans despite being documented for several other species, including non-human primates. Results of the first-in-human study that documents the crosstalk between retinas by measuring the vascular response in one retina to the photic stimulation of the contralateral eye in health and disease are reported herein. A stimulation apparatus was developed and integrated into an adaptive-optics fundus camera to image 32 healthy control (HC) subjects and 20 type 1 diabetes mellitus (DM) patients. Ipsilateral and contralateral neurovascular coupling effects were documented, and criteria were established to consider an actual response and find positive and negative responses. Ten (31.2%) and two (6.2%) subjects of the HC group presented contralateral positive and negative responses, respectively, and three (15.0%) positive and four (20.0%) negative responses were found for the DM group. Also, statistically significant differences in the ipsilateral (p < 0.001) and contralateral (p = 0.027) responses were found for the HC group, rejecting the null (non-response) hypothesis. This finding raises the need to revisit the current knowledge of neurovascular coupling mechanisms and the association between its dysregulation and neurological disorders. Further studies involving distinct populations and imaging centers are necessary to validate the findings herein.

Functional OCT angiography (fOCTA) enables non-invasive detection of retinal neurovascular coupling (rNVC) function. However, involuntary eye movements during dynamic imaging can displace the field of view, thereby challenging the accurate quantification of rNVC function at the single-capillary level. In this Letter, we develop a vessel skeleton-based vasodynamic optical flow (VDO flow) algorithm designed for fOCTA video stabilization and vasodynamic preservation. This method not only registers dynamic OCTA images with high speed (∼0.39 s per frame) and high accuracy (63.4% vascular skeleton recombination rate) but also effectively preserves critical vasodynamic responses. By applying VDO flow, we could precisely detect rNVC dysfunction at the single-capillary level in early diabetic retinopathy, even in the absence of significant changes in retinal vascular morphology. This advancement facilitates the clinical application of fOCTA.

Microsomal epoxide hydrolase (mEH), first identified as detoxifying enzyme, can hydrolyze epoxyeicosatrienoic acids (EETs) to less active diols (DHETs). EETs are potent vasodilatory and pro-angiogenic lipids, also implicated in neurovascular coupling. In mouse brain, mEH is strongly expressed in vascular and perivascular cells in contrast to the related soluble epoxide hydrolase (sEH), predominantly found in astrocytes. While sEH inhibition in stroke has demonstrated neuroprotective effects and increases cerebral blood flow (CBF), data regarding the role of mEH in brain are scarce. Here, we explored the function of mEH in cerebral vasculature by comparing mEH-KO, sEH-KO and WT mice. Basal cerebral volume (CBV0) was significantly higher in various mEH-KO brain areas compared to WT and sEH-KO. In line, quantification of cerebral vasculature in cortex and thalamus revealed a higher capillary density in mEH-KO, but not in sEH-KO brain. Whisker-stimulated CBF changes were by factor two higher in both mEH-KO and sEH-KO. In acutely isolated cerebral endothelial cells the loss of mEH, but not of sEH, augmented total EET levels and decreased the DHET:EET ratio. Collectively, these data suggest an important function of mEH in the regulation of cerebral vasculature and activity-modulated CBF, presumably by controlling local levels of endothelial-derived EETs.

In the last 20 years, there has been a revolution in our understanding of how blood flow is regulated in many tissues. Whereas it used to be thought that essentially all blood flow control occurred at the arteriole level, it is now recognized that control of capillary blood flow by contractile pericytes plays a key role both in regulating blood flow physiologically and in reducing it in clinically relevant pathological conditions. In this article, we compare and contrast how brain and cardiac pericytes regulate cerebral and coronary blood flow, focusing mainly on the pathological events of cerebral and cardiac ischaemia. The cerebral and coronary capillary beds differ dramatically in morphology, yet in both cases, pericyte-mediated capillary constriction plays a key role in restricting blood flow after ischaemia and possibly in other pathological conditions. We conclude with suggestions for therapeutic approaches to relaxing pericytes, which may prove useful in the long-term for reducing pericyte-induced ischaemia.

We report a parametric simulation study of traveling calcium waves in two classes of cellular structures: dendrite-like processes and an idealized cell body. It is motivated by the hypothesis that calcium waves may participate in spatiotemporal sensory processing; accordingly, its objective is to elucidate the dependence of traveling wave characteristics (e.g., propagation speed and amplitude) on various anatomical and physiological parameters. The models include representations of inositol trisphosphate and ryanodine receptors (which mediate transient calcium entry into the cytoplasm from the endoplasmic reticulum), as well as other entities involved in calcium transport or reactions. These support traveling cytoplasmic calcium waves, which are fully regenerative for significant ranges of model parameters. We also observe Hopf bifurcations between stable and unstable regimes, the latter being characterized by periodic calcium spikes. Traveling waves are possible in unstable processes during phases with sufficiently high calcium levels in the endoplasmic reticulum. Damped and abortive waves are observed for some parameter values. When both receptor types are present and functional, we find wave speeds on the order of 100 to several hundred micrometers per second and cytosolic calcium transients with amplitudes of tens of micromolar; when ryanodine receptors are absent, these values are on the order of tens of micrometers per second and 1-6 micromolar. Even with significantly downgraded channel conductance, ryanodine receptors can significantly impact wave speeds and amplitudes. Receptor areal densities and the diffusion coefficient for cytoplasmic calcium are the parameters to which wave characteristics are most sensitive.

Interfacing artificial devices with the human brain is the central goal of neurotechnology. Yet, our imaginations are often limited by currently available paradigms and technologies. Suggestions for brain-machine interfaces have changed over time, along with the available technology. Mechanical levers and cable winches were used to move parts of the brain during the mechanical age. Sophisticated electronic wiring and remote control have arisen during the electronic age, ultimately leading to plug-and-play computer interfaces. Nonetheless, our brains are so complex that these visions, until recently, largely remained unreachable dreams. The general problem, thus far, is that most of our technology is mechanically and/or electrically engineered, whereas the brain is a living, dynamic entity. As a result, these worlds are difficult to interface with one another. Nanotechnology, which encompasses engineered solid-state objects and integrated circuits, excels at small length scales of single to a few hundred nanometers and, thus, matches the sizes of biomolecules, biomolecular assemblies, and parts of cells. Consequently, we envision nanomaterials and nanotools as opportunities to interface with the brain in alternative ways. Here, we review the existing literature on the use of nanotechnology in brain-machine interfaces and look forward in discussing perspectives and limitations based on the authors' expertise across a range of complementary disciplines─from neuroscience, engineering, physics, and chemistry to biology and medicine, computer science and mathematics, and social science and jurisprudence. We focus on nanotechnology but also include information from related fields when useful and complementary.

Alzheimer's disease (AD) is an increasing global healthcare crisis with few effective treatments. The accumulation of amyloid plaques and hyper-phosphorylated tau are thought to underlie the pathogenesis of AD. However, current studies have recognized a prominent role of cerebrovascular dysfunction in AD. We recently reported that SNPs in soluble epoxide hydrolase (sEH) are linked to AD in human genetic studies and that long-term administration of an sEH inhibitor attenuated cerebral vascular and cognitive dysfunction in a rat model of AD. However, the mechanisms linking changes in cerebral vascular function and neuroprotective actions of sEH inhibitors in AD remain to be determined. This study investigated the effects of administration of an sEH inhibitor, 1-(1-Propanoylpiperidin-4-yl)-3-[4-(trifluoromethoxy)phenyl]urea (TPPU), on neurovascular coupling, blood-brain barrier (BBB) function, neuroinflammation, and cognitive dysfunction in an hAPP/PS1 TgF344-AD rat model of AD. We observed predominant β-amyloid accumulation in the brains of 9-10-month-old AD rats and that TPPU treatment for three months reduced amyloid burden. The functional hyperemic response to whisker stimulation was attenuated in AD rats, and TPPU normalized the response. The sEH inhibitor, TPPU, mitigated capillary rarefaction, BBB leakage, and activation of astrocytes and microglia in AD rats. TPPU increased the expression of pre- and post-synaptic proteins and reduced loss of hippocampal neurons and cognitive impairments in the AD rats, which was confirmed in a transcriptome and GO analysis. These results suggest that sEH inhibitors could be a novel therapeutic strategy for AD.

High-resolution three-dimensional (3D) tissue analysis has emerged as a transformative innovation in the life sciences, providing detailed insights into the spatial organization and molecular composition of biological tissues. This review begins by tracing the historical milestones that have shaped the development of high-resolution 3D histology, highlighting key breakthroughs that have facilitated the advancement of current technologies. We then systematically categorize the various families of high-resolution 3D histology techniques, discussing their core principles, capabilities, and inherent limitations. These 3D histology techniques include microscopy imaging, tomographic approaches, single-cell and spatial omics, computational methods and 3D tissue reconstruction (e.g. 3D cultures and spheroids). Additionally, we explore a wide range of applications for single-cell 3D histology, demonstrating how single-cell and spatial technologies are being utilized in the fields such as oncology, cardiology, neuroscience, immunology, developmental biology and regenerative medicine. Despite the remarkable progress made in recent years, the field still faces significant challenges, including high barriers to entry, issues with data robustness, ambiguous best practices for experimental design, and a lack of standardization across methodologies. This review offers a thorough analysis of these challenges and presents recommendations to surmount them, with the overarching goal of nurturing ongoing innovation and broader integration of cellular 3D tissue analysis in both biology research and clinical practice.

The neural and cardiovascular systems are pivotal in regulating human physiological, cognitive and emotional states, constantly interacting through anatomical and functional connections referred to as the brain-heart axis. When this axis is dysfunctional, neurological conditions can lead to cardiovascular disorders and, conversely, cardiovascular dysfunction can substantially affect brain health. However, the mechanisms and fundamental physiological components of the brain-heart axis remain largely unknown. In this Review, we elucidate these components and identify three primary pathways: neural, mechanical and biochemical. The neural pathway involves the interaction between the autonomic nervous system and the central autonomic network in the brain. The mechanical pathway involves mechanoreceptors, particularly those expressing mechanosensitive Piezo protein channels, which relay crucial information about blood pressure through peripheral and cerebrovascular connections. The biochemical pathway comprises many endogenous compounds that are important mediators of neural and cardiovascular function. This multisystem perspective calls for the development of integrative approaches, leading to new clinical specialties in neurocardiology.

Cerebral small vessel disease (SVD) is a vascular disorder that increases the risk of stroke and dementia and is diagnosed through brain MRI. Current primary prevention and secondary treatment of SVD are focused on lifestyle interventions and vascular risk factor control, including blood pressure reduction. However, these interventions have limited effects, a proportion of individuals with sporadic SVD do not have hypertension, and SVD shows strong familial and genetic underpinnings. Here, we describe the increasing evidence that cerebral endothelial cell dysfunction is a key mechanism of SVD. Dysfunctional endothelial cells can cause cerebral blood vessel dysfunction, alter blood-brain barrier integrity and interfere with cell-cell interactions in the neuro-glial-vascular unit, thereby causing damage to adjacent brain tissue. Endothelial cells in SVD may become dysfunctional through intrinsic mechanisms via genetic vulnerability to SVD and/or via extrinsic factors such as hypertension, smoking and diabetes. Drugs that act on endothelial pathways are already looking promising in clinical trials, and understanding their action on endothelial cells and the surrounding brain may lead to the development of other therapies to limit disease progression and improve outcomes for individuals with SVD.

The retina allows noninvasive in vivo assessment of the microcirculation. Autoregulation of the retinal microvasculature meets the changing requirements of local metabolic demand and maintains adequate blood flow. Analysis of the retinal vascular reactivity contributes to the understanding of regulatory physiology and its relationship to the systemic microcirculation. We conducted a literature review on the effect of different acute stimuli onto the retinal vasculature was conducted in accordance with the PRISMA guidelines. A literature search between 1-1-2005 and 17-10-2022 was performed in Medline, Embase, Web of Science and the Cochrane Library. We report the retinal vascular behavior of healthy individuals in response to both physiological and pathological stressors in 106 included articles. We provide ables of methodological characteristics for each stressor. Hypoxia, hypercapnia, high altitude, flicker light stimulation, rise of core temperature, blood pressure lowering, and the condition immediately after endurance exercise associate with larger retinal vessels. Hyperoxia, hypocapnia, blood pressure rise (Bayliss effect), and the condition during isometric exercise associate with smaller retinal vessels. The retinal vasculature is highly reactive to physiological and pathological stressors. This autoregulatory capacity is hypothesized to be a source of biomarkers for vascular health. Dynamic and static retinal vessel analysis are noninvasive methods to assess this (micro)vascular function. Exploring its diagnostic potential and application into clinical practice requires the development of standardized assessment methods, for which some recommendations are made.

Both transcranial direct current stimulation (tDCS) and acupuncture are promising methods for managing chronic low back pain (cLBP), however, their underlying mechanisms remain unclear.

To explore the neural mechanisms of tDCS and acupuncture on cLBP, we examined how real and sham tDCS applied to the bilateral motor cortex (M1), combined with real or sham acupuncture, influenced cerebral blood flow (CBF) using pulsed continuous arterial spin labeling (pCASL) imaging. tDCS was administered over six sessions, combined with real or sham acupuncture, over one month.

Following real tDCS, we observed increased CBF in the bilateral occipital cortex, precuneus, left hippocampus, and parahippocampal gyrus/posterior cingulate cortex. After sham tDCS, CBF decreased in regions including the bilateral superior parietal lobule, precuneus, bilateral precentral and postcentral gyri, and left angular gyrus. Real acupuncture led to reduced CBF in the bilateral occipital cortex and hippocampus, and left posterior cingulate gyrus, and increased CBF in the right postcentral gyrus, superior parietal lobule, and frontal areas. Sham acupuncture was associated with decreased CBF in the bilateral hippocampus and anterior cingulate gyrus.

These results suggest both shared and distinct patterns of CBF changes between real and sham tDCS, as well as between real and sham acupuncture, reflecting mode-dependent effects on brain networks involved in pain processing and modulation. Our findings highlight the different neural circuits implicated in the therapeutic mechanisms of tDCS and acupuncture in the management of cLBP.

Exercise not only regulates neurotransmitters and synapse formation but also enhances the function of multiple brain regions, beyond cortical activation. Prolonged aerobic or resistance exercise modality has been widely applied to reveal the beneficial effects on the brain, but few studies have investigated the direct effects of different exercise modalities and variations in exercise intensity on the neuroinflammatory response in the brain and overall health. Therefore, in this study, we investigated changes in brain cells and the immune environment of the brain according to exercise modalities. This study was conducted to confirm whether different exercise modalities affect the location and function of dopaminergic neurons, which are responsible for regulating voluntary movement, before utilizing animal models of disease. The results showed that high-intensity interval exercise (HIE) increased the activity of A2-reactive astrocytes in the striatum (STR), which is directly involved in movement control, resulting in neuroprotective effects. Both HIE and combined exercises (CE) increased the expression of dopamine transporter (DAT) in the STR without damaging dopamine neurons in the ventral midbrain (VM). This means that exercise training can help improve and maintain exercise capacity. In conclusion, specific exercise modalities or intensity of exercise may contribute to preventing neurodegenerative diseases such as Parkinson's disease or enhancing therapeutic effects when combined with medication for patients with neurodegenerative diseases.