Saturated Fat-Mediated Upregulation of IL-32 and CCL20 in Hepatocytes Contributes to Higher Expression of These Fibrosis-Driving Molecules in MASLD

Int J Mol Sci. 2023 Aug 25;24(17):13222. doi: 10.3390/ijms241713222.

Abstract

Metabolic dysfunction-associated steatotic liver disease (MASLD) comprises a spectrum of liver diseases, ranging from liver steatosis to metabolic dysfunction-associated steatohepatitis (MASH), increasing the risk of developing cirrhosis and hepatocellular carcinoma (HCC). Fibrosis within MASLD is critical for disease development; therefore, the identification of fibrosis-driving factors is indispensable. We analyzed the expression of interleukin 32 (IL-32) and chemokine CC ligand 20 (CCL20), which are known to be linked with inflammation and fibrosis, and for their expression in MASLD and hepatoma cells. RT-PCR, ELISA and Western blotting analyses were performed in both human liver samples and an in vitro steatosis model. IL-32 and CCL20 mRNA expression was increased in tissues of patients with NASH compared to normal liver tissue. Stratification for patatin-like phospholipase domain-containing protein 3 (PNPLA3) status revealed significance for IL-32 only in patients with I148M (rs738409, CG/GG) carrier status. Furthermore, a positive correlation was observed between IL-32 expression and steatosis grade, and between IL-32 as well as CCL20 expression and fibrosis grade. Treatment with the saturated fatty acid palmitic acid (PA) induced mRNA and protein expression of IL-32 and CCL20 in hepatoma cells. This induction was mitigated by the substitution of PA with monounsaturated oleic acid (OA), suggesting the involvement of oxidative stress. Consequently, analysis of stress-induced signaling pathways showed the activation of Erk1/2 and p38 MAPK, which led to an enhanced expression of IL-32 and CCL20. In conclusion, cellular stress in liver epithelial cells induced by PA enhances the expression of IL-32 and CCL20, both known to trigger inflammation and fibrosis.

Keywords: MAPK pathway; MASH; MASLD; NAFLD; NASH; chemokine CC ligand 20; interleukin 32; oxidative stress; saturated fatty acid; steatosis.

MeSH terms

  • Carcinoma, Hepatocellular / genetics
  • Chemokine CCL20 / genetics
  • Chemokines
  • Fats, Unsaturated / metabolism
  • Fatty Liver*
  • Hepatocytes* / metabolism
  • Humans
  • Ligands
  • Liver Cirrhosis / genetics
  • Liver Neoplasms / genetics
  • Metabolic Diseases*
  • Palmitic Acid
  • Up-Regulation

Substances

  • CCL20 protein, human
  • Chemokine CCL20
  • Chemokines
  • Ligands
  • Palmitic Acid
  • Fats, Unsaturated

Grants and funding

This work was supported by an intramural grant of the medical school, University of Regensburg Hospital, Regensburg, Germany to KS and the Robert Bosch Foundation, Stuttgart, Germany to KK.