The gp130/STAT3-endoplasmic reticulum stress axis regulates hepatocyte necroptosis in acute liver injury

Necroptosis in obesity: a complex cell death event

Obesity is an exceedingly prevalent and frequent health issue in today's society. Fat deposition is accompanied by low-grade inflammation in fat tissue and throughout the body, leading to metabolic disorders that ultimately promote the onset of obesity-related diseases. The development of obesity is accompanied by cell death events such as apoptosis as well as pyroptosis, however, the role of necroptosis in obesity has been widely reported in recent years. Necroptosis, a mode of cell death distinct from apoptosis and necrosis, is associated with developing many inflammatory conditions and their associated diseases. It also exhibits modulation of apoptosis and pyroptosis. It is morphologically similar to necroptosis, characterized by the inhibition of caspase-8, the formation of membrane pores, and the subsequent rupture of the plasma membrane. This paper focuses on the key pathways and molecules of necroptosis, exploring its connections with apoptosis and pyroptosis, and its implications in obesity. This paper posits that the modulation of necroptosis-related targets may represent a novel potential therapeutic avenue for the prevention and treatment of obesity-induced systemic inflammatory responses, and provides a synopsis of potential molecular targets that may prove beneficial in obesity-associated inflammatory diseases.

CTGF regulated by ATF6 inhibits vascular endothelial inflammation and reduces hepatic ischemia-reperfusion injury

Vascular endothelial inflammation is crucial in hepatic ischemia-reperfusion injury (IRI). Our previous research has shown that connective tissue growth factor (CTGF), secreted by endothelial cells, protects against acute liver injury, but its upstream mechanism is unclear. We aimed to clarify the protective role of CTGF in endothelial cell inflammation during IRI and reveal the regulation between endoplasmic reticulum stress-induced activating transcription factor 6 (ATF6) and CTGF. Hypoxia/reoxygenation in endothelial cells, hepatic IRI in mice and clinical specimens were used to examine the relationships between CTGF and inflammatory factors and determine how ATF6 regulates CTGF and reduces damage. We found that activating ATF6 promoted CTGF expression and reduced liver damage in hepatic IRI. In vitro, activated ATF6 upregulated CTGF and downregulated inflammation, while ATF6 inhibition had the opposite effect. Dual-luciferase assays and chromatin immunoprecipitation confirmed that activated ATF6 binds to the CTGF promoter, enhancing its expression. Activated ATF6 increases CTGF and reduces extracellular regulated protein kinase 1/2 (ERK1/2) phosphorylation, decreasing inflammatory factors. Conversely, inhibiting ATF6 decreases CTGF and increases the phosphorylation of ERK1/2, increasing inflammatory factor levels. ERK1/2 inhibition reverses this effect. Clinical samples have shown that CTGF increases after IRI, inversely correlating with inflammatory cytokines. Therefore, ATF6 activation during liver IRI enhances CTGF expression and reduces endothelial inflammation via ERK1/2 inhibition, providing a novel target for diagnosing and treating liver IRI.

Mangiferin Ameliorates CCl4-Triggered Acute Liver Injury by Inhibiting Inflammatory Response and Oxidative Stress: Involving the Nrf2-ARE Pathway

Purpose

Acute liver injury (ALI) is characterized by inflammation and oxidative stress (OS). Although mangiferin (MGF) has antioxidant and anti-inflammatory effects, its role in ALI remains unclear. Accordingly, we investigated the MGF molecular mechanism in carbon tetrachloride (CCl4)-induced ALI in vivo and in vitro.

Materials and Methods

The CCl4 was utilized to induce ALI in mice. In vivo, the therapeutic effects of MGF on CCl4-induced liver injury were evaluated through biochemical assays and histomorphological analysis. Additionally, immunohistochemistry, immunofluorescence, ELISA and Western blotting were further applied to explore the mechanism. In vitro, The CCK-8 assay and flow cytometry were employed to investigate the protective effects of MGF against CCl4-induced toxicity in HepG2 cells, while mitochondrial reactive oxygen species levels and Western blotting were used to explore the biological effects and molecular mechanisms.

Results

MGF treatment resulted in a reduction in serum levels of AST and ALT, diminished concentrations of TNF-α, IL-6, and IL-1β in liver tissue, and concurrently decreased cellular apoptosis. Furthermore, MGF pretreatment enhanced the activity of SOD and GSH while concurrently diminishing the MDA production. This study further demonstrated the upregulation of Nrf2, NQO1, and HO-1 protein expression levels, as well as the downregulation of p-p65 protein expression levels. In vitro investigations revealed that the mitigation of CCl4-induced inflammation and OS by MGF was mediated via the Nrf2- antioxidant response element (ARE) pathway, which was disrupted by ML385 in HepG2 cells.

Conclusion

CCl4 can induce liver injury, while treatment with MGF mitigates ALI by inhibiting oxidative stress, inflammation, and apoptosis. The protective mechanism of MGF is mediated by the Nrf2-ARE pathway activation.

Derlin-1 promotes diet-induced non-alcoholic fatty liver disease via increasing RIPK3-mediated necroptosis

BACKGROUND & AIMS

Unrestricted endoplasmic reticulum (ER) stress and the continuous activation of ER associated protein degradation (ERAD) pathway might lead to the aggravation of non-alcoholic steatohepatitis (NASH). Derlin-1 has been considered to be an integral part of the ERAD pathway, which is involved in the regulation of the transport and excretion of protein degradation products within ER. However, the regulatory role and mechanism of Derlin-1 in NASH remains unclear.

METHODS

The expression of Derlin-1 was firstly detected in the liver of normal and NASH animal model and patient. Then, western diet (WD)-induced NASH mice were administrated with the lentivirus-mediated Derlin-1 knockdown or overexpression. Finally, RIPK3 knockout mice were used to explore the mechanism. The liver injury, hepatic steatosis, inflammation, and fibrosis as well as ER stress signal pathway were evaluated.

RESULTS

The levels of Derlin-1 were significantly elevated in the liver of WD-fed mice and NASH patients when compared to the control group. Furthermore, Derlin-1 knockdown attenuated WD-induced liver injury, lipid accumulation, inflammatory response, and fibrosis. Conversely, overexpression of Derlin-1 presented the completely opposite results. Mechanistically, Derlin-1 enhanced ER stress pathways and led to necroptosis, and RIPK3 knockout dramatically reduced Derlin-1 expression and reversed the progression of NASH aggravated by Derlin-1.

CONCLUSIONS

Notably, Derlin-1 is a critical modulator in NASH. It may accelerate the progression of NASH by regulating the activation of the ERAD pathway and further aggravating the ER stress, which might be involved in RIPK3-mediated necroptosis. Therefore, targeting Derlin-1 as a novel intervention point holds the potential to delay or even reverse NASH.