NR4A1 knockdown confers hepatoprotection against ischaemia‐reperfusion injury by suppressing TGFβ1 via inhibition of CYR61/NF‐κB in mouse hepatocytes

Nuclear receptor subfamily 4, group A, member 1 (NR4A1) can aggravate ischaemia‐reperfusion (I/R) injury in the heart, kidney and brain. Thus, the present study aimed to unravel the role of NR4A1 on hepatic I/R injury. For this purpose, the mouse hepatic I/R model and H/R‐exposed mouse hepatocytes model were established to stimulate the hepatic and hepatocellular damage. Then, the levels of ALT and AST as well as TNF‐α and IL‐1β expression were measured in the mouse serum and supernatant of hepatocyte s, respectively. Thereafter, we quantified the levels of NR4A1, CYR61, NF‐kB p65 and TGFβ1 under pathological conditions, and their interactions were analysed using ChIP and dual‐luciferase reporter gene assays. The in vivo and in vitro effects of NR4A1, CYR61, NF‐kB p65 and TGFβ1 on I/R‐induced hepatic and H/R‐induced hepatocellular damage were evaluated using gain‐ and loss‐of‐function approaches. NR4A1 was up‐regulated in the hepatic tissues of I/R‐operated mice and in H/R‐treated hepatocytes. Silencing NR4A1 relieved the I/R‐induced hepatic injury, as supported by suppression of ALT and AST as well as TNF‐α and IL‐1β. Meanwhile, NR4A1 knockdown attenuated the H/R‐induced hepatocellular damage by inhibiting the apoptosis of hepatocyte s. Moreover, we also found that NR4A1 up‐regulated the expression of CYR61 which resulted in the activation of the NF‐κB signalling pathway, thereby enhancing the transcription of TGFβ1, which was validated to be the mechanism underlying the contributory role of NR4A1 in hepatic I/R injury. Taken together, NR4A1 silencing reduced the expression of CYR61/NF‐κB/TGFβ1, thereby relieving the hepatic I/R injury.