Mismatched effects of receptor interacting protein kinase-3 on hepatic steatosis and inflammation in nonalcoholic fatty liver disease

摘要

AIM To validate the effects of receptor interacting protein kinase-3(RIP3) deletion in non-alcoholic fatty liver disease(NAFLD) and to clarify the mechanism of action.METHODS Wild-type(WT) and RIP3 knockout(KO) mice werefed normal chow and high fat(HF) diets for 12 wk. The body weight was assessed once weekly. After 12 wk, the liver and serum samples were extracted. The liver tissue expression levels of RIP3, microsomal triglyceride transfer protein, protein disulfide isomerase, apolipoprotein-B, X-box binding protein-1, sterol regulatory element-binding protein-1c, fatty acid synthase, cluster of differentiation-36, diglyceride acyltransferase, peroxisome proliferator-activated receptor alpha, tumor necrosis factor-alpha(TNF-α), and interleukin-6 were assessed. Oleic acid treated primary hepatocytes from WT and RIP3 KO mice were stained with Nile red. The expression of inflammatory cytokines, including chemokine(C-X-C motif) ligand(CXCL) 1, CXCL2, and TNF-α, in monocytes was evaluated.RESULTS RIP3 KO HF diet fed mice showed a significant gain in body weight, and liver weight, liver to body weight ratio, and liver triglycerides were increased in HF diet fed RIP3 KO mice compared to HF diet fed WT mice. RIP3 KO primary hepatocytes also had increased intracellular fat droplets compared to WT primary hepatocytes after oleic acid treatment. RIP3 overexpression decreased hepatic fat content. Quantitative real-time polymerase chain reaction analysis showed that the expression of very-low-density lipoproteins secretion markers(microsomal triglyceride transfer protein, protein disulfide isomerase, and apolipoprotein-B) was significantly suppressed in RIP3 KO mice. The overall NAFLD Activity Score was the same between WT and RIP3 KO mice; however, RIP3 KO mice had increased fatty change and decreased lobular inflammation compared to WT mice. Inflammatory signals(CXCL1/2, TNF-α, and interleukin-6) increased after lipopolysaccharide and pancaspase inhibitor(necroptotic condition) treatment in monocytes. Neutrophil chemokines(CXCL1, and CXCL2) were decreased, and TNF-α was increased after RIP3 inhibitor treatment in monocytes.CONCLUSION RIP3 deletion exacerbates steatosis, and partially inhibits inflammation in the HF diet induced NAFLD model.