GSK3β Promotes Apoptosis after Renal Ischemic Injury

The mechanism by which the serine-threonine kinase glycogen synthase kinase-3β (GSK3β) affects survival of renal epithelial cells after acute stress is unknown. Using in vitro and in vivo models, we tested the hypothesis that GSK3β promotes Bax-mediated apoptosis, contributing to tubular injury and organ dysfunction after acute renal ischemia. Exposure of renal epithelial cells to metabolic stress activated GSK3β, Bax, and caspase 3 and induced apoptosis. Expression of a constitutively active GSK3β 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 GSK3β promoted cell survival. Furthermore, RNA interference–mediated knockdown of Bax abrogated the cell death induced by constitutively active GSK3β. In a cell-free assay, TDZD-8 inhibited the phosphorylation of a peptide containing the Bax serine 163 site targeted by stress-activated GSK3β. In rats, TDZD-8 inhibited ischemia-induced activation of GSK3β, Bax, and caspase 3; ameliorated tubular and epithelial cell damage; and significantly protected renal function. Taken together, GSK3β-mediated Bax activation induces apoptosis and tubular damage that contribute to acute ischemic kidney injury.