Protein kinase C-epsilon modulates mitochondrial function and active Na+ transport after oxidant injury in renal cells.
The aim of this study was to determine whether protein kinase C-epsilon (PKC-epsilon) 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-epsilon was activated three- to fivefold after injury. Active PKC-epsilon 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-epsilon translocation using a peptide selective inhibitor, PKC-epsilonV1-2, reduced decreases in basal and uncoupled Qo2 values and increased complex I-linked respiration in TBHP-injured RPTC at 4 h of recovery. Furthermore, PKC-epsilonV1-2 prevented decreases in ATP production in injured RPTC. Na+-K+-ATPase activity and ouabain-sensitive 86Rb+ uptake were decreased by 60 and 53%, respectively, at 4 h of recovery. Inhibition of PKC-epsilon activation prevented a decline in Na+-K+-ATPase activity and reduced decreases in ouabain-sensitive 86Rb+ uptake. We conclude that during early repair after oxidant injury in RPTC 1) PKC-epsilon is activated and translocated to mitochondria; 2) PKC-epsilon activation decreases mitochondrial respiration, electron transport rate, and ATP production by reducing complex I-linked respiration; and 3) PKC-epsilon mediates decreases in active Na+ transport and Na+-K+-ATPase activity. These data show that PKC-epsilon activation after oxidant injury in RPTC is involved in the decreases in mitochondrial function and active Na+ transport and that inhibition of PKC-epsilon activation promotes the repair of these functions.
Nowak
Grazyna
G
Dept. of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. gnowak@uams.edu
Bakajsova
Diana
D
Clifton
Ginger L
GL
D058186:Acute Kidney Injury / Q000139:chemically induced / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D019069:Cell Respiration; D005260:Female; D008564:Membrane Potentials; D008928:Mitochondria / Q000201:enzymology*; D018384:Oxidative Stress / Q000502:physiology*; D010101:Oxygen Consumption; D011493:Protein Kinase C / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D011817:Rabbits; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D020122:tert-Butylhydroperoxide
D012414:Rubidium Radioisotopes; D000255:Adenosine Triphosphate; D020122:tert-Butylhydroperoxide; D012964:Sodium; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D000254:Sodium-Potassium-Exchanging ATPase