Calpains mediate acute renal cell death: role of autolysis and translocation

The goals of this study were to determine 1) the expression of calpain isof orms in rabbit renal proximal tubules (RPT); 2) calpain autolysis and trans location, and calpastatin levels during RPT injury; and 3) the effect of a calpain inhibitor (PD-150606) on calpain levels, mitochondrial function, an d ion transport during RPT injury. RT-PCR, immunoblot analysis, and FITC-ca sein zymography demonstrated the presence of only mu- and m-calpains in rab bit RPT. The mitochondrial inhibitor antimycin A decreased RPT mu- and m-ca lpain and calpastatin levels in conjunction with cell death and increased p lasma membrane permeability. No increases in either mu- or m-calpain were o bserved in the membrane nor were increases observed in autolytic forms of e ither mu- or m-calpain in antimycin A-exposed RPT. PD-150606 blocked antimy cin A-induced cell death, preserved calpain levels in antimycin A-exposed R PT, and promoted the recovery of mitochondrial function and active Na+ tran sport in RPT after hypoxia and reoxygenation. The present study suggests th at calpains mediate RPT injury without undergoing autolysis or translocatio n, and ultimately they leak from cells subsequent to RPT injury/death. Furt hermore, PD-150606 allows functional recovery after injury.