Myofibrillogenesis Regulator 1 Rescues Renal Ischemia/Reperfusion Injury by Recruitment of PI3K-Dependent P-AKT to Mitochondria

Abstract

To investigate whether myofibrillogenesis regulator 1 (MR-1) attenuates renal ischemia/reperfusion (I/R) injury via inhibiting phosphorylated Akt (p-Akt) mitochondrial translocation-mediated opening of the mitochondrial permeability transition pore (mPTP), we injected adenovirus containing MR-1 gene or its siRNAs to the left kidney subcapsular areas of Sprague-Dawley rats, which subsequently underwent experimental renal I/R injury. Renal functions and the severity of the tubular injury were evaluated by the serum creatinine and blood urea nitrogen levels and the pathological scores. We also examined the mitochondrial morphology and functions. Total/p-Akt were assessed by western blot using the mitochondrial and the cytosolic fractions of cortex of renal tissue, respectively. We found that mitochondrial and cytosolic MR-1 levels and mitochondrial p-Akt decreased, and cytosolic p-Akt increased after reperfusion. Subcapsular injection of adenovirus led to higher MR-1 expression in the mitochondria/cytosol, inhibited mPTP opening, and alleviated renal I/R injury; adenovirus injection also upregulated mitochondrial total and p-Akt levels more prominently compared with the normal saline (NS) group. Subcapsular injection of MR-1 siRNAs significantly lowered MR-1 expression and induced renal injury, with increased mPTP opening and mitochondrial damage, similar to I/R injury. MR-1 interacted with Akt in renal cortex homogenate. Wortmannin, a phosphatidylinositol 3 kinase (PI3K) inhibitor, abolished both mitochondrial p-Akt recruitment and the protective effect of MR-1 overexpression on I/R injury. To conclude, MR-1 protects kidney against I/R injury through inhibiting mPTP opening and maintaining mitochondrial integrity, through the recruitment of PI3K-dependent p-Akt to the mitochondria. MR-1 could be a new therapeutic strategy for renal I/R injury.