Denervation Aggravates Renal Ischemia Reperfusion Injury via BMAL1-mediated Nrf2/ARE pathway

Abstract

Background Denervation is an inevitable pathological situation of renal graft. This study was to explore the change of clock gene rhythm under renal denervation (RDN) and its effect on renal function and oxidative stress during renal ischemia-reperfusion (IR) injury. Method C57/BL6 mice were randomly divided into 4 groups at daytime 7AM (zeitgeber time [ZT] 0) or at nighttime 7PM (ZT12) in respectively: Sham (S) group, RDN group, IR group and RDN+ IR (DIR) group. Renal pathological and functional changes were assessed by H&E staining, and serum creatinine, urea nitrogen and neutrophil gelatinase-associated lipocalin levels. Renal oxidative stress was detected by SOD and MDA levels, and renal inflammation was measured by IL-6, IL-17AF and TNF-ɑ levels. BMAL1, CLOCK, Nrf2 and HO-1 mRNA and protein expressions were tested by qPCR and Western Blot. Result Compared with S groups, the rhythm of BMAL1 and CLOCK genes in the kidney was disordered in RDN groups, while renal pathological and functional indexes did not change significantly. Compared with IR groups, renal pathological and functional indexes were significantly higher in the DIR groups, as well as oxidative stress and inflammation in renal tissues. The protein expressions of BMAL1 and Nrf2 were upregulated by RDN at ZT12 timepoint. In DIR groups, renal injury was aggravated after the Brusatol treatment, but there was no significant improvement after the t-BHQ treatment, which might be consistent with the changes of Nrf2 and HO-1 protein expressions. Knockdown BMAL1 gene alone didn’t reverse the aggravation of renal IR injury at nighttime caused by RDN, but it could recover the protective effect of activating Nrf2/ARE pathway by t-BHQ. Conclusion RDN lead to the disruption of BMAL1-mediatedNrf2 rhythm accumulation in the kidney, which reduced the renal ability to resist oxidative stress and inflammation, due to the impaired effect of activating Nrf2/ARE pathway in renal IR injury at nighttime.