IL-37 improves palmitic acid-induced lipid deposition in liver cells by inhibiting ferroptosis to regulate macrophage polarization

Abstract

Non-alcoholic fatty liver disease (NAFLD), which acts as a predominant contributor to chronic liver disease, remains a pervasive global epidemic. Interleukin-37（IL-37） is documented to have protective effects against various liver diseases. This work focuses on investigating the role and relevant action mechanism of IL-37 in NAFLD. Immunofluorescence assay and Western blot（WB）were used to estimate M1 macrophage markers. For immunofluorescence analysis, images from five randomly selected fields per sample were captured using a confocal microscope (Leica). Fluorescence intensity was quantified by ImageJ software (version 1.53) with background subtraction, and data were normalized to DAPI-positive cells.The lipid Reactive Oxygen Species（ROS）and cell lipid droplet deposition were assessed via BODIPY 581/591 C11 staining and Oil Red O staining. Fe^2 +, triglycerides and cholesterol levels were assessed utilizing appropriate assay kits. WB was adopted for the estimation of proteins associated with ferroptosis and apoptosis. Protein band intensities were quantified using Image Lab software (Bio-Rad) and normalized to β-actin expression. Three technical replicates were analyzed for each biological replicate (n = 3). Our data revealed that IL-37 alleviated PA-stimulated（Palmitic acid-stimulaed）M1 macrophage polarization. It was also identified that IL-37 suppressed lipid accumulation and apoptosis in RAW264.7 cells through inhibiting the polarization of M1 macrophages. Collectively, IL-37 could improve PA-stimulated lipid accumulation and apoptosis in liver cells through suppressing M1 macrophage polarization, which might be mediated by ferroptosis.