Protein kinase C-ϵ modulates mitochondrial function and active Na+transport after oxidant injury in renal cells

Abstract

The aim of this study was to determine whether protein kinase C-ϵ (PKC-ϵ) is involved in the repair of mitochondrial function and/or active Na+transport after oxidant injury in renal proximal tubular cells (RPTC). Sublethal injury was produced in primary cultures of RPTC using tert-butylhydroperoxide (TBHP), and the recovery of functions was examined. PKC-ϵ was activated three- to fivefold after injury. Active PKC-ϵ translocated to the mitochondria. Basal oxygen consumption (Qo2), uncoupled Qo2, and ATP production decreased 58, 60, and 41%, respectively, at 4 h and recovered by day 4 after injury. At 4 h, complex I-coupled respiration decreased 50% but complex II- and IV-coupled respirations were unchanged. Inhibition of PKC-ϵ translocation using a peptide selective inhibitor, PKC-ϵV1-2, reduced decreases in basal and uncoupled Qo2values and increased complex I-linked respiration in TBHP-injured RPTC at 4 h of recovery. Furthermore, PKC-ϵV1-2 prevented decreases in ATP production in injured RPTC. Na+-K+-ATPase activity and ouabain-sensitive86Rb+uptake were decreased by 60 and 53%, respectively, at 4 h of recovery. Inhibition of PKC-ϵ activation prevented a decline in Na+-K+-ATPase activity and reduced decreases in ouabain-sensitive86Rb+uptake. We conclude that during early repair after oxidant injury in RPTC 1) PKC-ϵ is activated and translocated to mitochondria; 2) PKC-ϵ activation decreases mitochondrial respiration, electron transport rate, and ATP production by reducing complex I-linked respiration; and 3) PKC-ϵ mediates decreases in active Na+transport and Na+-K+-ATPase activity. These data show that PKC-ϵ activation after oxidant injury in RPTC is involved in the decreases in mitochondrial function and active Na+transport and that inhibition of PKC-ϵ activation promotes the repair of these functions.