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

PeerJ. 2023 Jun 26:11:e15639. doi: 10.7717/peerj.15639. eCollection 2023.

Abstract

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.

Keywords: Autophagy; JAK2/STAT3 pathway; Kupffer cells; Lp-PLA2; Nonalcoholic steatohepatitis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Alkyl-2-acetylglycerophosphocholine Esterase / metabolism
  • Animals
  • Autophagy / genetics
  • Cytokines / metabolism
  • Inflammation / genetics
  • Janus Kinase 2 / genetics
  • Mice
  • Mice, Inbred C57BL
  • Non-alcoholic Fatty Liver Disease* / genetics
  • STAT3 Transcription Factor / genetics
  • TOR Serine-Threonine Kinases / genetics

Substances

  • 1-Alkyl-2-acetylglycerophosphocholine Esterase
  • Cytokines
  • Janus Kinase 2
  • STAT3 Transcription Factor
  • TOR Serine-Threonine Kinases
  • Pla2g7 protein, mouse

Grants and funding

This work was supported by the National Natural Science Foundation of Zhejiang Province (No. LY19H200003) and the National Natural Science Foundation of Zhejiang Province (No. LY20H200005). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.