雷帕霉素抑制JAK/STAT通路对急性肝损伤大鼠肝组织HMGB1表达的影响

Lp-PLA2 silencing ameliorates inflammation and autophagy in nonalcoholic steatohepatitis through inhibiting the JAK2/STAT3 pathway

Background

Nonalcoholic steatohepatitis (NASH), a common cause of liver-related morbidity and mortality worldwide, is characterized by inflammation and hepatocellular injury. Our research focuses on lipoprotein-associated phospholipase A2 (Lp-PLA2), an inflammation-related biomarker that has recently garnered interest in the context of NASH due to its potential roles in disease pathogenesis and progression.

Methods

We established a NASH mouse model using a high-fat diet (HFD) and treated it with sh-Lp-PLA2 and/or rapamycin (an mTOR inhibitor). Lp-PLA2 expression in NASH mice was detected by qRT-PCR. Serum levels of liver function parameters and inflammatory cytokines were detected using corresponding assay kits. We examined pathological changes in liver using hematoxylin-eosin, oil red O, and Masson staining, and observed autophagy through transmission electron microscopy. The protein levels of Lp-PLA2, mTOR, light chain 3 (LC3) II/I, phosphorylated Janus kinase 2 (p-JAK2)/JAK2, and phosphorylated signal transducer and activator of transcription 3 (p-STAT3)/STAT3 were determined by western blotting. Kupffer cells extracted from C57BL/6J mice were treated to replicate NASH conditions and treated with sh-Lp-PLA2, rapamycin, and/or a JAK2-inhibitor to further verify the roles and mechanisms of Lp-PLA2 in NASH.

Results

Our data indicate an upregulation of Lp-PLA2 expression in HFD-induced NASH mice. Silencing Lp-PLA2 in NASH mice reduced liver damage and inflammation markers (aspartate aminotransferase (AST), alanine aminotransferase (ALT), total cholesterol (TC), triglycerides (TG), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6)), while increasing IL-10 levels, an anti-inflammatory cytokine. Additionally, Lp-PLA2 silencing decreased lipid and collagen accumulation and promoted autophagy. The beneficial effects of sh-Lp-PLA2 on NASH were enhanced by rapamycin. Furthermore, Lp-PLA2 silencing resulted in the downregulation of the expression of p-JAK2/JAK2 and p-STAT3/STAT3 in NASH mice. Similar results were observed in Kupffer cells treated under NASH conditions; Lp-PLA2 silencing promoted autophagy and repressed inflammation, effects which were potentiated by the addition of rapamycin or a JAK2-inhibitor.

Conclusion

Our findings suggest that silencing Lp-PLA2 promotes autophagy via deactivating the JAK2/STAT3 signaling pathway, thereby restraining NASH progression. This highlights the potential therapeutic value of targeting Lp-PLA2, adding a new dimension to our understanding of NASH pathogenesis and treatment strategies.

Study on the mechanism of JAK2/STAT3 signaling pathway-mediated inflammatory reaction after cerebral ischemia

The present study aimed to investigate the mechanism by which the Janus kinase (JAK)2/signal transducer and activator of transcription (STAT)3 signaling pathway mediates cerebral ischemia and the efficacy of pharmaceutical intervention. The rat model of middle cerebral artery occlusion (MCAO) was established and confirmed via assessment of changes in the expression of phosphorylated (p)‑JAK2, p‑STAT3, high‑mobility group box 1 (HMGB1), and inflammatory factors using ELISA and western blot analysis. The effects of JAK2/STAT3 inhibitor and curcumin on the expression of p‑JAK2, p‑STAT3, HMGB1, and inflammatory factors after cerebral ischemia were observed with ELISA, western blotting and immunohistochemical staining. The concentrations of tumor necrosis factor (TNF)‑α and HMGB1 in brain tissue homogenate of MCAO group were significantly higher than in the sham group (P<0.01). The concentration of p‑JAK2/JAK2 and p‑STAT3/STAT3 in the brain tissue homogenate of MCAO group was significantly higher than in the sham group (P<0.05). The concentrations of TNF‑α, interleukin (IL)‑1β, IL‑6, and HMGB1 in the group treated with STAT3 inhibitor (MCAO + rapamycin), JAK2 inhibitor (MCAO + AG490), and MCAO + curcumin were significantly lower than in the MCAO group (P<0.01), as well as the relative content of p‑JAK2/JAK2 and p‑STAT3/STAT3 (P<0.05). Inhibition of the JAK2/STAT3 signaling pathway, such as curcumin can reduce the expression of HMGB1 in brain tissue after cerebral ischemia, which can significantly reduce the inflammatory response after cerebral ischemia.