Zhichao Yu1, Zhe Feng2, Ling Fu3, Jing Wang4, Changqing Li5, Huaxu Zhu6, Tong Xie7, Jie Zhou8, Lingling Zhou9, Xueping Zhou10. 1. The First Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: zcyu3017@163.com. 2. The First Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: 260583@njucm.edu.cn. 3. The First Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: fuling0524@126.com. 4. The First Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: wjtcm@qq.com. 5. The First Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: lcq2021@126.com. 6. Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources, Industrialization, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China; Jiangsu Botanical Medicine Refinement Engineering Research Center, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: Huaxu72@126.com. 7. Jiangsu Key Laboratory of Pediatric Respiratory Disease, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: xietong@njucm.edu.cn. 8. The First Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: zhoujie@njucm.edu.cn. 9. School of Pharmacy, Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: zhoulingling@njucm.edu.cn. 10. The First Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, 210023, PR China. Electronic address: zxp@njucm.edu.cn.
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE: Tripterygium wilfordii Hook. f. (TW) is widely used to treat autoimmune and inflammatory diseases; however, its development and application is limited by its significant association with liver injury. The compound formula Qingluotongbi (QLT) employs TW as its main component and is used to treat rheumatoid arthritis with no adverse reactions, suggesting that QLT may reduce the liver toxicity of TW. AIM OF THE STUDY: We examined whether TW interferes with lipid metabolism to induce liver injury, and evaluated the protective effect of QLT in in vivo and in vitro experiments. MATERIALS AND METHODS: After administration of QLT and its ingredients, HepaRG cells and SD rats were tested for biochemical indicators, hepatocytes lipid changes, and rat liver pathological changes, and then we analyzed for the gene expression of liver X receptor α (LXRα), endoplasmic reticulum stress (ERS) key proteins, sterol regulatory element binding protein-1c (SREBP-1c), and lipid-synthesizing enzymes. In HepaRG cells, the protein expression of glucose-regulated protein 78 kDa (GRP78) and LXRα was detected after addition of an LXRα inhibitor, LXRα agonist, and ERS inhibitor. RESULTS: TW caused significant elevation of biochemical indicators and lipid droplet deposition in hepatocytes, as well as upregulated the gene expression of LXRα, ERS key proteins, SREBP-1c, and lipid-synthesizing enzymes in both in vitro and in vivo settings, and caused liver injury in rats. QLT can alleviate the lipotoxic liver injury caused by TW. LXRα agonist further activated ERS induced by TW, whereas LXRα inhibitor significantly reduced ERS and lipotoxic injury induced by TW in HepaRG cells. CONCLUSIONS: TW upregulated LXRα to activate ERS and increased the gene expression of SREBP-1c and lipid-synthesizing enzymes, leading to increased lipid synthesis in hepatocytes to result in liver injury. QLT inhibited the LXRα-ERS-SREBP-1c pathway and reduced abnormal lipid synthesis in hepatocytes and the hepatotoxicity of TW.
ETHNOPHARMACOLOGICAL RELEVANCE: Tripterygium wilfordii Hook. f. (TW) is widely used to treat autoimmune and inflammatory diseases; however, its development and application is limited by its significant association with liver injury. The compound formula Qingluotongbi (QLT) employs TW as its main component and is used to treat rheumatoid arthritis with no adverse reactions, suggesting that QLT may reduce the liver toxicity of TW. AIM OF THE STUDY: We examined whether TW interferes with lipid metabolism to induce liver injury, and evaluated the protective effect of QLT in in vivo and in vitro experiments. MATERIALS AND METHODS: After administration of QLT and its ingredients, HepaRG cells and SD rats were tested for biochemical indicators, hepatocytes lipid changes, and rat liver pathological changes, and then we analyzed for the gene expression of liver X receptor α (LXRα), endoplasmic reticulum stress (ERS) key proteins, sterol regulatory element binding protein-1c (SREBP-1c), and lipid-synthesizing enzymes. In HepaRG cells, the protein expression of glucose-regulated protein 78 kDa (GRP78) and LXRα was detected after addition of an LXRα inhibitor, LXRα agonist, and ERS inhibitor. RESULTS: TW caused significant elevation of biochemical indicators and lipid droplet deposition in hepatocytes, as well as upregulated the gene expression of LXRα, ERS key proteins, SREBP-1c, and lipid-synthesizing enzymes in both in vitro and in vivo settings, and caused liver injury in rats. QLT can alleviate the lipotoxic liver injury caused by TW. LXRα agonist further activated ERS induced by TW, whereas LXRα inhibitor significantly reduced ERS and lipotoxic injury induced by TW in HepaRG cells. CONCLUSIONS: TW upregulated LXRα to activate ERS and increased the gene expression of SREBP-1c and lipid-synthesizing enzymes, leading to increased lipid synthesis in hepatocytes to result in liver injury. QLT inhibited the LXRα-ERS-SREBP-1c pathway and reduced abnormal lipid synthesis in hepatocytes and the hepatotoxicity of TW.