Bardoxolone methyl improves nonalcoholic steatohepatitis through inhibition of macrophage recruitment

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease caused by excess fat accumulation, closely associated with obesity and metabolic syndrome.Bardoxolone methyl (2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid methyl ester, CDDO-Me) is a potent activator of nuclear factor erythroid 2-related factor 2 (Nrf2). Some clinical trials of CDDO-Me were conducted for chronic kidney diseases and pulmonary arterial hypertension, whereas the hepatoprotective effect of CDDO-Me on nonalcoholic steatohepatitis (NASH) has not yet been elucidated. The purpose of this study was to determine the hepatoprotective potential and mechanisms of CDDO-Me in a diet-induced NASH mouse model. Whole transcriptome analysis revealed that CDDO-Me markedly inhibited the expressions of chemokine ligands, Ccl3 and Ccl4, and the chemokine receptors, Ccr1 and Ccr5 that increased in NASH mice while activating Nrf2-dependent pathway. Serum protein levels of CCL3 and CCL4 upregulated in NASH mice were inhibited in a dose-dependent manner by treatment with CDDO-Me. CDDO-Me inhibited the expression levels of Ccr1 and Ccr5, and simultaneously blocked Ccl3 and Ccl4 the ligands of the receptors, respectively in RAW264.7 cell line. Taken together with the observations, CDDO-Me directly inhibits the expression of CCL3-CCR1 and CCL4-CCR5 axes in macrophages of NASH mice, which might contribute to the improvement of nonalcoholic steatohepatitis and fibrosis through the interference of monocyte-derived macrophage migration. To investigate the mechanisms of hepatoprotective effect of CDDO-Me in a diet-induced NASH mouse model, CDDO-Me was orally administered to NASH mouse models for 8 weeks and the livers were collected at the end of the experiment . We then performed gene expression profiling analysis using the data obtained from RNA-seq of the livers from vehicle or CDDO-Me treated NASH mouse models.