Published online Nov 7, 2019. doi: 10.3748/wjg.v25.i41.6205
Peer-review started: August 8, 2019
First decision: September 18, 2019
Revised: September 26, 2019
Accepted: October 17, 2019
Article in press: October 17, 2019
Published online: November 7, 2019
Chronic biliary obstruction results in ischemia and hypoxia of hepatocytes, and leads to apoptosis. Apoptosis is very important in regulating the homeostasis of the hepatobiliary system. Endoplasmic reticulum (ER) stress is one of the signaling pathways that induce apoptosis. Moreover, the protein kinase RNA-like endoplasmic reticulum kinase (PERK)-induced apoptotic pathway is the main way; but its role in liver injury remains unclear. Yinchenhao decoction (YCHD) is a traditional Chinese medicine formula that alleviates liver injury and apoptosis, yet its mechanism is unknown. We undertook this study to investigate the effects of YCHD on the expression of ER stress proteins and hepatocyte apoptosis in rats with obstructive jaundice (OJ).
To investigate whether YCHD can attenuate OJ-induced liver injury and hepatocyte apoptosis by inhibiting the PERK-CCAAT/enhancer-binding protein homologous protein (CHOP)-growth arrest and DNA damage-inducible protein 34 (GADD34) pathway and B cell lymphoma/leukemia-2 related X protein (Bax)/B cell lymphoma/leukemia-2 (Bcl-2) ratio.
For in vivo experiments, 30 rats were divided into three groups: control group, OJ model group, and YCHD-treated group. Blood was collected to detect the indicators of liver function, and liver tissues were used for histological analysis. For in vitro experiments, 30 rats were divided into three groups: G1, G2, and G3. The rats in group G1 had their bile duct exposed without ligation, the rats in group G2 underwent total bile duct ligation, and the rats in group G3 were given a gavage of YCHD. According to the serum pharmacology, serum was extracted and centrifuged from the rat blood to cultivate the BRL-3A cells. Terminal deoxynucleotidyl transferase mediated dUTP nick end-labelling (TUNEL) assay was used to detect BRL-3A hepatocyte apoptosis. Alanine aminotransferase (ALT) and aspartate transaminase (AST) levels in the medium were detected. Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) analyses were used to detect protein and gene expression levels of PERK, CHOP, GADD34, Bax, and Bcl-2 in the liver tissues and BRL-3A cells.
Biochemical assays and haematoxylin and eosin staining suggested severe liver function injury and liver tissue structure damage in the OJ model group. The TUNEL assay showed that massive BRL-3A rat hepatocyte apoptosis was induced by OJ. Elevated ALT and AST levels in the medium also demonstrated that hepatocytes could be destroyed by OJ. Western blot or qRT-PCR analyses showed that the protein and mRNA expression levels of PERK, CHOP, and GADD34 were significantly increased both in the rat liver tissue and BRL-3A rat hepatocytes by OJ. The Bax and Bcl-2 levels were increased, and the Bax/Bcl-2 ratio was also increased. When YCHD was used, the PERK, CHOP, GADD34, and Bax levels quickly decreased, while the Bcl-2 levels increased, and the Bax/Bcl-2 ratio decreased.
OJ-induced liver injury and hepatocyte apoptosis are associated with the activation of the PERK-CHOP-GADD34 pathway and increased Bax/Bcl-2 ratio. YCHD can attenuate these changes.
Core tip: Chronic biliary obstruction results in ischaemia and hypoxia of hepatocytes and leads to apoptosis. The protein kinase RNA-like endoplasmic reticulum kinase (PERK)-induced apoptotic pathway is the main and important way, however, its role in liver injury and hepatocyte apoptosis remains unclear. Yinchenhao decoction (YCHD) can alleviate liver injury and apoptosis, but whether YCHD can attenuates obstructive jaundice (OJ)-induced liver injury and hepatocyte apoptosis by inhibiting the PERK-induced pathway is still unknown. In this research study, we found that OJ induced liver injury and hepatocyte apoptosis by activating the PERK- CCAAT/enhancer-binding protein homologous protein (CHOP)-growth arrest and DNA damage-inducible protein 34 (GADD34) pathway and upregulating the B cell lymphoma/leukemia-2 related X protein (Bax)/ B cell lymphoma/leukemia-2 (Bcl-2) ratio. YCHD attenuated these changes by inhibiting the PERK-CHOP-GADD34 pathway and Bax/Bcl-2 ratio.