Loss of RIP3 initiates annihilation of high-fat diet initialized nonalcoholic hepatosteatosis: A mechanism involving Toll-like receptor 4 and oxidative stress

Ge Chenxu  ¹ , Xu Minxuan  ² , Qin Yuting  ³ , Gu Tingting  ⁴ , Feng Jing  ⁵ , Lv Jinxiao  ³ , Wang Sujun  ⁶ , Ma Yongjie  ⁶ , Lou Deshuai  ¹ , Li Qiang  ¹ , Hu Linfeng  ¹ , Nie Xuyuan  ¹ , Wang Mingxing  ⁶ , Huang Ping  ⁷ , Tan Jun  ⁸

Affiliations

• ¹ Chongqing Key Laboratory of Medicinal Resources in the Three Gorges Reservoir Region, School of Biological and Chemical Engineering, Chongqing University of Education, Chongqing 400067, PR China; Research Center of Brain Intellectual Promotion and Development for Children Aged 0-6 Years, Chongqing University of Education, Chongqing 400067, PR China.
• ² Chongqing Key Laboratory of Medicinal Resources in the Three Gorges Reservoir Region, School of Biological and Chemical Engineering, Chongqing University of Education, Chongqing 400067, PR China; Research Center of Brain Intellectual Promotion and Development for Children Aged 0-6 Years, Chongqing University of Education, Chongqing 400067, PR China. Electronic address: minxuanxu@foxmail.com.
• ³ School of Medicine and Pharmacy, Ocean University of China, Qingdao 266100, PR China.
• ⁴ College of Engineering and Applied Sciences, Nanjing University, Nanjing 210023, PR China.
• ⁵ Chongqing Key Laboratory of Medicinal Resources in the Three Gorges Reservoir Region, School of Biological and Chemical Engineering, Chongqing University of Education, Chongqing 400067, PR China.
• ⁶ College of Food and Drug, Luoyang Normal University, Luoyang 471934, PR China.
• ⁷ Department Hepatobiliary Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400000, PR China.
• ⁸ Chongqing Key Laboratory of Medicinal Resources in the Three Gorges Reservoir Region, School of Biological and Chemical Engineering, Chongqing University of Education, Chongqing 400067, PR China; Research Center of Brain Intellectual Promotion and Development for Children Aged 0-6 Years, Chongqing University of Education, Chongqing 400067, PR China. Electronic address: tanjun@cque.edu.cn.

Abstract

Non-alcoholic fatty liver disease (NAFLD) is a prevalent and complex disease that confers a high risk of severe liver disorders. Although such public and clinical health importance, very few effective therapies are presently available for NAFLD. Here, we showed that receptor-interacting kinase-3 (RIP3) was up-regulated in liver of mouse with hepatic steatosis induced by high fat diet (HFD). After 16 weeks on a HFD, obesity, insulin resistance, metabolic syndrome, hepatic steatosis, inflammatory response and oxidative stress were significantly alleviated in liver of mice with the loss of RIP3. We provided mechanistic evidence that RIP3 knockdown attenuated hepatic dyslipidemia through preventing the expression of lipogenesis-associated genes. Furthermore, in the absence of RIP3, the transcription factor of nuclear factor-κB (NF-κB) signaling pathway activated by HFD was blocked, accompanied with the inhibition of NLRP3 inflammasome. We also found that RIP3 knockdown-induced activation of nuclear factor-erythroid 2 related factor 2/heme oxygenase-1 (Nrf-2/HO-1) led to the inhibition of oxidative stress. The detrimental effects of RIP3 on hepatic steatosis and related pathologies were confirmed in palmitate (PAL)-treated mouse liver cells. Of note, lipopolysaccharide (LPS)- or PAL-activated TLR-4 resulted in the up-regulation of RIP3 that was accompanied by the elevated inflammation and lipid deposition, and these effects were reversed in TLR-4 knockdown cells. Furthermore, promoting Nrf-2 pathway activation effectively reduced reactive oxygen species (ROS) generation and RIP3 expression in PAL-stimulated cells, consequently leading to the suppression of cellular inflammation and lipid accumulation. In contrast, blocking Nrf-2/HO-1 signaling abrogated RIP3 knockdown-reduced reactive oxygen species (ROS), inflammatory response and lipid deposition in PAL-stimulated cells. Taken together, the present study helped to elucidate how HFD-induced hepatic steatosis was regulated by RIP3, via the TLR-4/NF-κB and Nrf-2/HO-1 signaling pathways.

Keywords: Inflammation and oxidative stress; NAFLD; Nrf-2/HO-1; RIP3; TLR-4/NF-κB.