Redox-sensitive glycogen synthase kinase 3β-directed control of mitochondrial permeability transition: rheostatic regulation of acute kidney injury

Mitochondrial dysfunction plays a pivotal role in necroapoptotic cell death and in the development of acute kidney injury (AKI). Evidence suggests that glycogen synthase kinase (GSK) 3 beta resides at the nexus of multiple signaling pathways implicated in the regulation of rnitochondrial permeability transition (MPT). In cultured renal tubular epithelial cells, a discrete pool of GSK3 beta was detected in mitochondria. Coimmunoprecipitation assay confirmed that GSK3 beta physically interacts with cyclophilin F and voltage-dependent anion channel (VDAC), key MPT regulators that possess multiple GSK3 beta phosphorylation consensus motifs, suggesting that GSK3 beta has a direct control of MPT. Upon a strong burst of reactive oxygen species elicited by the pro-oxidant herbicide paraquat, the activity of the redox-sensitive GSK3 beta was drastically enhanced. This was accompanied by augmented phosphorylation of cyclophilin F and VDAC, associated with MPT and cell death. Inhibition of GSK3 beta by either the selective inhibitor 4-Benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8) or forced expression of a kinase-dead mutant obliterated paraquat-induced phosphorylation of cyclophilin F and VDAC, prevented MPT, and improved cellular viability. Conversely, ectopic expression of a constitutively active GSK3 beta amplified the effect of paraquat on cyclophilin F and VDAC phosphorylation and sensitized cells to paraquat-induced MPT and death. In vivo, paraquat injection elicited marked oxidant stress in the kidney and resulted in acute kidney dysfunction and massive tubular apoptosis and necrosis. Consistent with in vitro findings, the activity of GSK3 beta was augmented in the kidney after paraquat injury, associated with increased phosphoiylation of cyclophilin F and VDAC and sensitized MPT. TDZD-8 blocked GSK3 beta activity in the kidney, intercepted cyclophilin F and VDAC phosphorylation, prevented MPT, attenuated tubular cell death, and ameliorated paraquat-induced AKI. Our data suggest that the redox-sensitive GSK3 beta regulates renal tubular injury in AKI by controlling the activity of MPT regulators. (C) 2013 Elsevier Inc. All rights reserved.