The Dynamic Role of Endoplasmic Reticulum Stress in Chronic Liver Disease

Unveiling the crosstalk between unfolded protein response and apoptosis in triclosan induced hepatotoxicity in Labeo rohita

Triclosan (TCS), a widely used antimicrobial, has emerged as a concerning aquatic pollutant, especially post-COVID-19 due to increased disinfectant use. The study aimed to investigate the toxic impacts of TCS on Labeo rohita, revealing a 96-h LC50 of 0.742 mg/L. Well-acclimatized fish were categorised into three groups: one control and two treatment (T1 and T2) that were exposed to 1/10th and 1/5th of 96-h LC50 i.e., 0.0742 mg/L and 0.148 mg/L, respectively for 6 weeks under semi-static condition. Significantly (p < 0.05) elevated extents of reactive oxygen species (ROS) in the liver indicated enhanced oxidative stress. The activities of enzymatic antioxidants viz. superoxide dismutase (SOD) and catalase (CAT) were significantly (p < 0.05) increased while the reduced glutathione (GSH) levels were significantly (p < 0.05) decreased in a dose- and duration-dependent manner. A significant (p < 0.05) increase was observed in the lipid peroxidation (LPO) rate, which coincided with disruptions in the histological structure of the liver. Significant (p < 0.05) induction in Micronuclei frequency validated genomic instability. Furthermore, Endoplasmic Reticulum (ER) stress was marked by the increased intracellular calcium levels and elevated expression of grp78, chop, atf4, perk, eIF2α and gadd34 in TCS-exposed groups. Moreover, the consequent activation of bax, caspase-3, caspase-9, apaf-1 and the regulation of bcl-2 due to ER-stress, ultimately resulted in apoptosis of hepatocytes. Pearson correlation matrix and Principal Component Analysis (PCA) further underscored key interactions among parameters. Our findings demonstrate that the TCS, at its sub-lethal concentrations, is causing severe anomalies and even cell-death via triggering ER-stress-mediated apoptotic pathway in the fish liver.

FAM134B-mediated ER-phagy alleviates alcohol-related liver fibrosis by reducing endoplasmic reticulum stress

BACKGROUND

Alcohol-related liver fibrosis (ALF), a severe stage of alcohol-related liver disease (ALD), currently lacks effective treatments. Endoplasmic reticulum (ER) stress is a key pathological feature of ALF. FAM134B (JK-1, RETREG1), an ER-phagy receptor, mediates ER-phagy to alleviate ER stress and restore ER homeostasis. However, the molecular mechanisms linking ER stress to ALF remain unclear.

AIMS

This study aimed to investigate the role and molecular mechanisms of FAM134B in ALF, specifically whether FAM134B-mediated ER-phagy reduces ER stress to mitigate ALF.

METHODS

We developed a FAM134B overexpression mouse model using tail vein injection of AAV-8-TBG-m-FAM134B and monitored disease progression in ALF mice. Fibrosis markers (α-SMA, COL1A1), ER stress indicators (GRP78, CHOP, IRE1-α, ATF6), and ER-phagy markers (LC3, p62, VAPB, CANX, Climp63, REEP5) were analyzed. Additionally, further in vitro experiments were carried out to explore whether FAM134B-mediated ER-phagy attenuates ALF by alleviating hepatocyte ER stress.

RESULTS

FAM134B overexpression increased ER-phagy, reduced ER stress, and ameliorated liver fibrosis. In vitro, FAM134B overexpression promoted autophagy, decreased cytokine secretion, and inhibited hepatic stellate cell (JS-1) and macrophage activation (RAW264.7).

CONCLUSION

These findings suggest that FAM134B-mediated ER-phagy mitigates ALF by alleviating ER stress, providing new targets and intervention strategies for ALF.

Homeostasis control in health and disease by the unfolded protein response

Cells rely on the endoplasmic reticulum (ER) to fold and assemble newly synthesized transmembrane and secretory proteins - essential for cellular structure-function and for both intracellular and intercellular communication. To ensure the operative fidelity of the ER, eukaryotic cells leverage the unfolded protein response (UPR) - a stress-sensing and signalling network that maintains homeostasis by rebalancing the biosynthetic capacity of the ER according to need. The metazoan UPR can also redirect signalling from cytoprotective adaptation to programmed cell death if homeostasis restoration fails. As such, the UPR benefits multicellular organisms by preserving optimally functioning cells while removing damaged ones. Nevertheless, dysregulation of the UPR can be harmful. In this Review, we discuss the UPR and its regulatory processes as a paradigm in health and disease. We highlight important recent advances in molecular and mechanistic understanding of the UPR that enable greater precision in designing and developing innovative strategies to harness its potential for therapeutic gain. We underscore the rheostatic character of the UPR, its contextual nature and critical open questions for its further elucidation.

Alpinetin Exhibits Antioxidant and Anti-Inflammatory Effects in C57BL/6 Mice with Alcoholic Liver Disease Induced by the Lieber-DeCarli Ethanol Liquid Diet

Alcohol-associated liver disease (ALD) is a common non-communicable chronic liver disease characterized by a spectrum of conditions ranging from steatosis and alcohol-associated steatohepatitis (AH) to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). The pathogenesis of ALD involves a complex interplay of various molecular, biochemical, genetic, epigenetic, and environmental factors. While the mechanisms are well studied, therapeutic options remain limited. Alpinetin, a natural flavonoid with antioxidant and anti-inflammatory properties, has shown potential hepatoprotective effects, though its efficacy in ALD remains unexplored. This study investigated the hepatoprotective effects of alpinetin using a Lieber-DeCarli ethanol liquid diet model of ALD in C57BL/6 mice. Mice were divided into three groups: the control group, the ethanol group, and the ethanol group treated with alpinetin. Serum activity of ALT, AST, γ-GT, and ALP was measured to assess liver function, along with antioxidative and oxidative/nitrosative stress markers in liver tissue. Pro-inflammatory cytokines and endoplasmic reticulum (ER) stress parameters in liver tissue were also evaluated. Histological assessment of disease activity was performed using the SALVE grading and staging system. Treatment with alpinetin significantly reduced serum levels of ALT, AST, γ-GT, and oxidative/nitrosative stress markers while increasing antioxidative markers. The levels of pro-inflammatory cytokines and ER stress parameters were significantly decreased. Histological analysis demonstrated reduced steatosis, hepatocyte ballooning, and inflammation. These findings suggest that alpinetin holds promise as a potential therapeutic agent for managing ALD.

Sphingosine kinase 2 (SphK2) depletion alters redox metabolism and enhances inflammation in a diet-induced MASH mouse model

BACKGROUND

Sphingosine-1 phosphate (S1P) is a bioactive lipid molecule that modulates inflammation and hepatic lipid metabolism in MASLD, which affects 1 in 3 people and increases the risk of liver fibrosis and hepatic cancer. S1P can be generated by 2 isoforms of sphingosine kinase (SphK). SphK1 is well-studied in metabolic diseases. In contrast, SphK2 function is not well characterized. Both sphingolipid and redox metabolism dysregulation contribute to MASLD pathologic progression. While SphK2 localizes to both the nucleus and mitochondria, its specific role in early MASH is not well defined.

METHODS

This study examined SphK2 depletion effects on hepatic redox metabolism, mitochondrial function, and inflammation in a 16-week western diet plus sugar water (WDSW)-induced mouse model of early MASH.

RESULTS

WDSW-SphK2-/- mice exhibit increased hepatic lipid accumulation and hepatic redox dysregulation. In addition, mitochondria-localized cholesterol and S1P precursors were increased. We traced SphK2-/--mediated mitochondrial electron transport chain impairment to respiratory complex-IV and found that decreased mitochondrial redox metabolism coincided with increased oxidase gene expression and oxylipin production. Consistent with this relationship, we observed pronounced increases in hepatic inflammatory gene expression, prostaglandin accumulation, and innate immune homing in WDSW-SphK2-/- mice compared to WDSW-wild-type mice.

CONCLUSIONS

These studies suggest SphK2-derived S1P maintains hepatic redox metabolism and describe the potential consequences of SphK2 depletion on proinflammatory gene expression, lipid mediator production, and immune infiltration in MASH progression.

Berberine potentiates liver inflammation and fibrosis in the PI*Z hAAT transgenic murine model

BACKGROUND

Alpha-1 antitrypsin deficiency (AATD) is an inherited disease, the common variant caused by a Pi*Z mutation in the SERPINA1 gene. Pi*Z AAT increases the risk of pulmonary emphysema and liver disease. Berberine (BBR) is a nature dietary supplement and herbal remedy. Emerging evidence revealed that BBR has remarkable liver-protective properties against various liver diseases. In the present study, we investigated the therapeutic effects and toxicities of BBR in Pi*Z hepatocytes and Pi*Z transgenic mice.

METHODS

Huh7.5 and Huh7.5Z (which carries the Pi*Z mutation) cells were treated with different concentrations of BBR for 48 hours. MTT was performed for cell viability assay. Intracellular AAT levels were evaluated by western blot. In vivo studies were carried out in wild type, native phenotype AAT (Pi*M), and Pi*Z AAT transgenic mice. Mice were treated with 50 mg/kg/day of BBR or solvent only by oral administration for 30 days. Western blot and liver histopathological examinations were performed to evaluate therapeutic benefits and liver toxicity of BBR.

RESULTS

BBR reduced intracellular AAT levels in Huh7.5Z cells, meanwhile, no Pi*Z-specific toxicity was observed. However, BBR did not reduce liver AAT load but significantly potentiated liver inflammation and fibrosis accompanying the activation of unfolded protein response and mTOR in Pi*Z mice, but not in wild type and Pi*M mice.

CONCLUSIONS

BBR exacerbated liver inflammation and fibrosis specifically in Pi*Z mice. This adverse effect may be associated with the activation of unfolded protein response and mTOR. This study implicates that BBR should be avoided by AATD patients.

Low-Dose Hexavalent Chromium Exposure Induces Endoplasmic Reticulum Stress-Mediated Apoptosis in Rat Liver

This study investigated the toxic effects of low-dose hexavalent chromium (Cr(VI)) on rat liver. Male specific pathogen-free (SPF) Sprague-Dawley (SD) rats (4-5 weeks of age) were randomly divided into groups: saline, 0.05 mg/kg Cr(VI), and 0.25 mg/kg Cr(VI). The rats were subjected to intratracheal instillation of K2Cr2O7 suspensions or saline once weekly, for a total of five times. The results showed that the accumulation of Cr(VI) in the blood of the 0.25 mg/kg K2Cr2O7 group was significantly higher than that in the saline group. Transmission electron microscopy (TEM) showed that exposure to hexavalent chromium caused endoplasmic reticulum (ER) oedema and a disordered arrangement. The levels of endoplasmic reticulum stress (ERS)-related proteins (ATF6, P-PERK, P-IRE1, Grp78, and CHOP) in the 0.25 mg/kg K2Cr2O7 group were significantly higher than those in the saline group. The expression of apoptosis-inhibitory protein Bcl-2 was significantly lower in the 0.25 mg/kg K2Cr2O7 group than that in the saline group, and the expression of apoptosis protein Bax was significantly higher in the 0.25 mg/kg K2Cr2O7 group than that in the saline group, indicating that Cr(VI) increased apoptosis. These findings revealed that Cr(VI) may be involved in rat liver injury by initiating ERS-mediated apoptosis. The expression of ATF6, P-PERK, P-IRE1, and Bax in the 0.05 mg/kg K2Cr2O7 group was not significantly different from that in the saline group, and the different effects produced by the two different dose groups provide a possible experimental basis for further study of occupational exposure limits.

Autophagy and the unfolded protein response shape the non-alcoholic fatty liver landscape: decoding the labyrinth

The incidence of nonalcoholic fatty liver disease (NAFLD) is on the rise, mirroring a global surge in diabetes and metabolic syndrome, as its major leading causes. NAFLD represents a spectrum of liver disorders, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH), which can potentially progress to cirrhosis and hepatocellular carcinoma (HCC). Mechanistically, we know the unfolded protein response (UPR) as a protective cellular mechanism, being triggered under circumstances of endoplasmic reticulum (ER) stress. The hepatic UPR is turned on in a broad spectrum of liver diseases, including NAFLD. Recent data also defines molecular mechanisms that may underlie the existing correlation between UPR activation and NAFLD. More interestingly, subsequent studies have demonstrated an additional mechanism, i.e. autophagy, to be involved in hepatic steatosis, and thus NAFLD pathogenesis, principally by regulating the insulin sensitivity, hepatocellular injury, innate immunity, fibrosis, and carcinogenesis. All these findings suggest possible mechanistic roles for autophagy in the progression of NAFLD and its complications. Both UPR and autophagy are dynamic and interconnected fluxes that act as protective responses to minimize the harmful effects of hepatic lipid accumulation, as well as the ER stress during NAFLD. The functions of UPR and autophagy in the liver, together with findings of decreased hepatic autophagy in correlation with conditions that predispose to NAFLD, such as obesity and aging, suggest that autophagy and UPR, alone or combined, may be novel therapeutic targets against the disease. In this review, we discuss the current evidence on the interplay between autophagy and the UPR in connection to the NAFLD pathogenesis.

Schisandrin B Suppresses Colon Cancer Growth by Inducing Cell Cycle Arrest and Apoptosis: Molecular Mechanism and Therapeutic Potential

Colon cancer is among the most lethal and prevalent malignant tumors in the world, and the lack of effective therapies highlights the need for novel therapeutic approaches. Schisandrin B (Sch B), a lignan extracted from the fruit ofSchisandra chinensis, has been reported for its anticancer properties. However, to date, no studies have been done to characterize the exact molecular mechanisms underlying the antitumorigenic effects of Sch B in colon cancer. This study aimed to explore the antitumorigenic effects of Sch B in colon cancer and to understand the underlying therapeutic mechanism. A comprehensive analysis of the molecular mechanism underlying the antitumorigenic effects of Sch B on human colon cancer cells was performed using a combination of Raman spectroscopy, RNA-seq, computational docking, and molecular biological experiments. The in vivo efficacy was evaluated by a mouse xenograft model. Sch B reduced cell proliferation and triggered apoptosis in human colon cancer cell lines. Raman spectroscopy, computational, RNA-seq, and molecular and cellular studies revealed that Sch B activated unfolded protein responses by interacting with CHOP and upregulating CHOP, which thereby induced apoptosis. CHOP knockdown alleviated the Sch B-induced reduction in cell viability and apoptosis. Sch B reduced colon tumor growth in vivo. Our findings demonstrated that Sch B induced apoptosis and inhibited cell proliferation and tumor growth in vitro and in vivo. These results provided an essential background for clinical trials examining the effects of Sch B in patients with colon cancer.