GSK3β Promotes Apoptosis after Renal Ischemic Injury

The mechanism by which the serine-threonine kinase glycogen synthase kinase-3 beta (GSK3 beta) affects survival of renal epithelial cells after acute stress is unknown. Using in vitro and in vivo models, we tested the hypothesis that GSK3 beta promotes Bax-mediated apoptosis, contributing to tubular injury and organ dysfunction after acute renal ischemia. Exposure of renal epithelial cells to metabolic stress activated GSK3 beta, Bax, and caspase 3 and induced apoptosis. Expression of a constitutively active GSK3 beta mutant activated Bax and decreased cell survival after metabolic stress. In contrast, pharmacologic inhibition (4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione [TDZD-8]) or RNA interference-mediated knockdown of GSK3 beta promoted cell survival. Furthermore, RNA interference-mediated knockdown of Bax abrogated the cell death induced by constitutively active GSK3 beta. In a cell-free assay, TDZD-8 inhibited the phosphorylation of a peptide containing the Bax serine(163) site targeted by stress-activated GSK3 beta. In rats, TDZD-8 inhibited ischemia-induced activation of GSK3 beta, Bax, and caspase 3; ameliorated tubular and epithelial cell damage; and significantly protected renal function. Taken together, GSK3 beta-mediated Bax activation induces apoptosis and tubular damage that contribute to acute ischemic kidney injury.