Glycochenodeoxycholic acid impairs transcription factor E3 -dependent autophagy-lysosome machinery by disrupting reactive oxygen species homeostasis in L02 cells

Role of Microbiota-Modified Bile Acids in the Regulation of Intracellular Organelles and Neurodegenerative Diseases

Bile acids (BAs) are amphiphilic steroidal molecules generated from cholesterol in the liver and facilitate the digestion and absorption of fat-soluble substances in the gut. Some BAs in the intestine are modified by the gut microbiota. Because BAs are modified in a variety of ways by different types of bacteria present in the gut microbiota, changes in the gut microbiota can affect the metabolism of BAs in the host. Although most BAs absorbed from the gut are transferred to the liver, some are transferred to the systemic circulation. Furthermore, BAs have also been detected in the brain and are thought to migrate into the brain through the systemic circulation. Although BAs are known to affect a variety of physiological functions by acting as ligands for various nuclear and cell-surface receptors, BAs have also been found to act on mitochondria and autophagy in the cell. This review focuses on the BAs modified by the gut microbiota and their roles in intracellular organelles and neurodegenerative diseases.

TFE3-mediated impairment of lysosomal biogenesis and defective autophagy contribute to fluoride-induced hepatotoxicity

Excessive fluoride exposure can cause liver injury, but the specific mechanisms need further investigation. We aimed to explore the role of impaired lysosomal biogenesis and defective autophagy in fluoride-induced hepatotoxicity and its potential mechanisms, focusing on the role of transcription factor E3 (TFE3) in regulating hepatocyte lysosomal biogenesis. To this end, we established a Sprague-Dawley (SD) rat model exposed to sodium fluoride (NaF) and a rat liver cell line (BRL3A) model exposed to NaF. The results showed that NaF exposure diminished liver function and led to apoptosis as well as autophagosome accumulation and impaired autophagic degradation. In addition, NaF exposure caused compromised lysosome biogenesis and decreased lysosomal degradation, and inhibited TFE3 nuclear translocation. Notably, the mTOR inhibitors rapamycin (RAPA) and Ad-TFE3 promoted lysosomal biogenesis and enhanced lysosomal degradation function. Furthermore, RAPA and Ad-TFE3 reduced NaF-induced apoptosis by alleviating impaired autophagic degradation. In conclusion, NaF impairs lysosomal biogenesis by inhibiting TFE3 nuclear translocation, decreasing lysosomal degradation function, resulting in impaired autophagic degradation, and ultimately inducing apoptosis. Therefore, TFE3 may be a promising therapeutic target for fluoride-induced hepatotoxicity.

SEMA7AR148W mutation promotes lipid accumulation and NAFLD progression via increased localization on the hepatocyte surface

Genetic polymorphisms are associated with the development of nonalcoholic fatty liver disease (NAFLD). Semaphorin7a (Sema7a) deficiency in mouse peritoneal macrophages reduces fatty acid (FA) oxidation. Here, we identified 17 individuals with SEMA7A heterozygous mutations in 470 patients with biopsy-proven NAFLD. SEMA7A heterozygous mutations increased susceptibility to NAFLD, steatosis severity, and NAFLD activity scores in humans and mice. The Sema7aR145W mutation (equivalent to human SEMA7AR148W) significantly induced small lipid droplet accumulation in mouse livers compared with WT mouse livers. Mechanistically, the Sema7aR145W mutation increased N-glycosylated Sema7a and its receptor integrin β1 proteins in the cell membranes of hepatocytes. Furthermore, Sema7aR145W mutation enhanced its protein interaction with integrin β1 and PKC-α and increased PKC-α phosphorylation, which were both abrogated by integrin β1 silencing. Induction of PKCα_WT, but not PKCα_dominant negative, overexpression induced transcriptional factors Srebp1, Chrebp, and Lxr expression and their downstream Acc1, Fasn, and Cd36 expression in primary mouse hepatocytes. Collectively, our findings demonstrate that the SEMA7AR148W mutation is a potentially new strong genetic determinant of NAFLD and promotes intrahepatic lipid accumulation and NAFLD in mice by enhancing PKC-α-stimulated FA and triglyceride synthesis and FA uptake. The inhibition of hepatic PKC-α signaling may lead to novel NAFLD therapies.

Mechanism of Bile Acid-Induced Programmed Cell Death and Drug Discovery against Cancer: A Review

Bile acids are major signaling molecules that play a significant role as emulsifiers in the digestion and absorption of dietary lipids. Bile acids are amphiphilic molecules produced by the reaction of enzymes with cholesterol as a substrate, and they are the primary metabolites of cholesterol in the body. Bile acids were initially considered as tumor promoters, but many studies have deemed them to be tumor suppressors. The tumor-suppressive effect of bile acids is associated with programmed cell death. Moreover, based on this fact, several synthetic bile acid derivatives have also been used to induce programmed cell death in several types of human cancers. This review comprehensively summarizes the literature related to bile acid-induced programmed cell death, such as apoptosis, autophagy, and necroptosis, and the status of drug development using synthetic bile acid derivatives against human cancers. We hope that this review will provide a reference for the future research and development of drugs against cancer.

Bile acids as regulatory molecules and potential targets in metabolic diseases

Bile acids are important hydroxylated steroids that are synthesized in the liver from cholesterol for intestinal absorption of lipids and other fatty-nutrient. They also display remarkable and immense functions such as regulating immune responses, managing the apoptosis of cells, participating in glucose metabolism, and so on. Some bile acids were used for the treatment or prevention of diseases such as gallstones, primary biliary cirrhosis, and colorectal cancer. Meanwhile, the accumulation of toxic bile acids leads to apoptosis, necrosis, and inflammation. Alteration of bile acids metabolism, as well as the gut microbiota that interacted with bile acids, contributes to the pathogenesis of metabolic diseases. Therefore, the purpose of this review is to summarize the current functions and pre-clinical or clinical applications of bile acids, and to further discuss the alteration of bile acids in metabolic disorders as well as the manipulation of bile acids metabolism as potential therapeutic targets.

A homozygous R148W mutation in Semaphorin 7A causes progressive familial intrahepatic cholestasis

Semaphorin 7A (SEMA7A) is a membrane-bound protein that involves axon growth and other biological processes. SEMA7A mutations are associated with vertebral fracture and Kallmann syndrome. Here, we report a case with a mutation in SEMA7A that displays familial cholestasis. WGS reveals a SEMA7AR148W homozygous mutation in a female child with elevated levels of serum ALT, AST, and total bile acid (TBA) of unknown etiology. This patient also carried a SLC10A1S267F allele, but Slc10a1S267F homozygous mice exhibited normal liver function. Similar to the child, Sema7aR145W homozygous mice displayed elevated levels of serum ALT, AST, and TBA. Remarkably, liver histology and LC-MS/MS analyses exhibited hepatocyte hydropic degeneration and increased liver bile acid (BA) levels in Sema7aR145W homozygous mice. Further mechanistic studies demonstrated that Sema7aR145W mutation reduced the expression of canalicular membrane BA transporters, bile salt export pump (Bsep), and multidrug resistance-associated protein-2 (Mrp2), causing intrahepatic cholestasis in mice. Administration with ursodeoxycholic acid and a dietary supplement glutathione improved liver function in the child. Therefore, Sema7aR145W homozygous mutation causes intrahepatic cholestasis by reducing hepatic Bsep and Mrp2 expression.

Serum Metabolomic Analysis of Chronic Drug-Induced Liver Injury With or Without Cirrhosis

Background: Chronic drug-induced liver injury (DILI) occurs in up to 20% of all DILI patients. It presents a chronic pattern with persistent or relapsed episodes and may even progress to cirrhosis. However, its underlying development mechanism is poorly understood. Aims: To find serum metabolite signatures of chronic DILI with or without cirrhosis, and to elucidate the underlying mechanism. Methods: Untargeted metabolomics coupled with pattern recognition approaches were used to profile and extract metabolite signatures from 83 chronic DILI patients, including 58 non-cirrhosis (NC) cases, 14 compensated cirrhosis (CC) cases, and 11 decompensated cirrhosis (DC) cases. Results: Of the 269 annotated metabolites associated with chronic DILI, metabolic fingerprints associated with cirrhosis (including 30 metabolites) and decompensation (including 25 metabolites), were identified. There was a significantly positive correlation between cirrhosis-associated fingerprint (eigenmetabolite) and the aspartate aminotransferase-to-platelet ratio index (APRI) (r = 0.315, P = 0.003). The efficacy of cirrhosis-associated eigenmetabolite coupled with APRI to identify cirrhosis from non-cirrhosis patients was significantly better than APRI alone [area under the curve (AUC) value 0.914 vs. 0.573]. The decompensation-associated fingerprint (eigenmetabolite) can effectively identify the compensation and decompensation periods (AUC value 0.954). The results of the metabolic fingerprint pathway analysis suggest that the blocked tricarboxylic acid cycle (TCA cycle) and intermediary metabolism, excessive accumulation of bile acids, and perturbed amino acid metabolism are potential mechanisms in the occurrence and development of chronic DILI-associated cirrhosis. Conclusions: The metabolomic fingerprints characterize different stages of chronic DILI progression and deepen the understanding of the metabolic reprogramming mechanism of chronic DILI progression to cirrhosis.

Regulation of autophagy by bile acids and in cholestasis - CholestoPHAGY or CholeSTOPagy

Autophagy is a lysosomal degradation pathway in which the cell self-digests its own components to provide nutrients in harsh environmental conditions. It also represents an opportunity to rid the cell of superfluous and damaged organelles, misfolded proteins or invaded microorganisms. Liver autophagy contributes to basic hepatic functions such as lipid, glycogen and protein turnover. Deregulated hepatic autophagy has been linked to many liver diseases including alpha-1-antitrypsin deficiency, alcoholic and non-alcoholic fatty liver diseases, hepatitis B and C infections, liver fibrosis as well as liver cancer. Recently, bile acids and the bile acid receptor FXR have been implicated in the regulation of hepatic autophagy, which implies a role of autophagy also for cholestatic liver diseases. This review summarizes the current evidence of bile acid mediated effects on autophagy and how this affects cholestatic liver diseases. Although detailed studies are lacking, we suggest a concept that the activity of autophagy in cholestasis depends on the disease stage, where autophagy may be induced at early stages ("cholestophagy") but may be impaired in prolonged cholestatic states ("cholestopagy").