Juan-Juan Qin1, Wenzhe Mao2, Xiaozhan Wang2, Peng Sun3, Daqing Cheng3, Song Tian4, Xue-Yong Zhu4, Ling Yang4, Zan Huang5, Hongliang Li6. 1. Medical Science Research Center, Zhongnan Hospital of Wuhan University, Wuhan 430071, China; Medical Research Institute, School of Medicine, Wuhan University, Wuhan 430071, China; Basic Medical School, Wuhan University, Wuhan 430060, China; Institute of Model Animals of Wuhan University, Wuhan 430060, China. 2. Basic Medical School, Wuhan University, Wuhan 430060, China; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, China; Institute of Model Animals of Wuhan University, Wuhan 430060, China. 3. Department of General Surgery, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200336, China. 4. Medical Science Research Center, Zhongnan Hospital of Wuhan University, Wuhan 430071, China; Basic Medical School, Wuhan University, Wuhan 430060, China; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, China; Institute of Model Animals of Wuhan University, Wuhan 430060, China. 5. College of Life Sciences, Hubei Key Laboratory of Cell Homeostasis, Wuhan University, Wuhan 430072, China. Electronic address: z-huang@whu.edu.cn. 6. Medical Science Research Center, Zhongnan Hospital of Wuhan University, Wuhan 430071, China; Basic Medical School, Wuhan University, Wuhan 430060, China; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, China; Institute of Model Animals of Wuhan University, Wuhan 430060, China. Electronic address: lihl@whu.edu.cn.
Abstract
BACKGROUND & AIMS: The hepatic injury caused by ischemia/reperfusion (I/R) insult is predominantly determined by the complex interplay of sterile inflammation and liver cell death. Caspase recruitment domain family member 6 (CARD6) was initially shown to play important roles in NF-κB activation. In our preliminary studies, CARD6 downregulation was closely related to hepatic I/R injury in liver transplantation patients and mouse models. Thus, we hypothesized that CARD6 protects against hepatic I/R injury and investigated the underlying molecular mechanisms. METHODS: A partial hepatic I/R operation was performed in hepatocyte-specific Card6 knockout mice (HKO), Card6 transgenic mice with CARD6 overexpression specifically in hepatocytes (HTG), and the corresponding control mice. Hepatic histology, serum aminotransferases, inflammatory cytokines/chemokines, cell death, and inflammatory signaling were examined to assess liver damage. The molecular mechanisms of CARD6 function were explored in vivo and in vitro. RESULTS: Liver injury was alleviated in Card6-HTG mice compared with control mice as shown by decreased cell death, lower serum aminotransferase levels, and reduced inflammation and infiltration, whereas Card6-HKO mice had the opposite phenotype. Mechanistically, phosphorylation of ASK1 and its downstream effectors JNK and p38 were increased in the livers of Card6-HKO mice but repressed in those of Card6-HTG mice. Furthermore, ASK1 knockdown normalized the effect of CARD6 deficiency on the activation of NF-κB, JNK and p38, while ASK1 overexpression abrogated the suppressive effect of CARD6. CARD6 was also shown to interact with ASK1. Mutant CARD6 that lacked the ability to interact with ASK1 could not inhibit ASK1 and failed to protect against hepatic I/R injury. CONCLUSIONS: CARD6 is a novel protective factor against hepatic I/R injury that suppresses inflammation and liver cell death by inhibiting the ASK1 signaling pathway. LAY SUMMARY: The protein CARD6 plays an important role during the process of liver blood flow restriction (ischemia) and restoration (reperfusion). By suppressing the activity of ASK1, CARD6 can protect against hepatocyte injury. Targeting CARD6 is a potential strategy for prevention and treatment of ischemia/reperfusion injury.
BACKGROUND & AIMS: The hepatic injury caused by ischemia/reperfusion (I/R) insult is predominantly determined by the complex interplay of sterile inflammation and liver cell death. Caspase recruitment domain family member 6 (CARD6) was initially shown to play important roles in NF-κB activation. In our preliminary studies, CARD6 downregulation was closely related to hepatic I/R injury in liver transplantation patients and mouse models. Thus, we hypothesized that CARD6 protects against hepatic I/R injury and investigated the underlying molecular mechanisms. METHODS: A partial hepatic I/R operation was performed in hepatocyte-specific Card6 knockout mice (HKO), Card6transgenic mice with CARD6 overexpression specifically in hepatocytes (HTG), and the corresponding control mice. Hepatic histology, serum aminotransferases, inflammatory cytokines/chemokines, cell death, and inflammatory signaling were examined to assess liver damage. The molecular mechanisms of CARD6 function were explored in vivo and in vitro. RESULTS:Liver injury was alleviated in Card6-HTG mice compared with control mice as shown by decreased cell death, lower serum aminotransferase levels, and reduced inflammation and infiltration, whereas Card6-HKO mice had the opposite phenotype. Mechanistically, phosphorylation of ASK1 and its downstream effectors JNK and p38 were increased in the livers of Card6-HKO mice but repressed in those of Card6-HTG mice. Furthermore, ASK1 knockdown normalized the effect of CARD6 deficiency on the activation of NF-κB, JNK and p38, while ASK1 overexpression abrogated the suppressive effect of CARD6. CARD6 was also shown to interact with ASK1. Mutant CARD6 that lacked the ability to interact with ASK1 could not inhibit ASK1 and failed to protect against hepatic I/R injury. CONCLUSIONS:CARD6 is a novel protective factor against hepatic I/R injury that suppresses inflammation and liver cell death by inhibiting the ASK1 signaling pathway. LAY SUMMARY: The protein CARD6 plays an important role during the process of liver blood flow restriction (ischemia) and restoration (reperfusion). By suppressing the activity of ASK1, CARD6 can protect against hepatocyte injury. Targeting CARD6 is a potential strategy for prevention and treatment of ischemia/reperfusion injury.
Authors: Zhou Jiangqiao; Wang Tianyu; Chen Zhongbao; Zhang Long; Zou Jilin; Ma Xiaoxiong; Qiu Tao Journal: Front Immunol Date: 2020-09-29 Impact factor: 7.561