Cytosolic calcium and protein kinase C reduce complement-mediated glomerular epithelial injury.
In rat membranous nephropathy, protein-uria is due to formation of the C5b-9 membrane attack complex of complement (C), and is associated with morphological evidence of glomerular epithelial cell (GEC) injury. Analogous morphological changes are induced by C5b-9 in cultured GEC. In addition, in cultured GEC C5b-9 induces Ca2+ influx, as well as Ca2+ mobilization and increased 1,2-diacylglycerol due to the activation of phospholipase C. In this study we investigated how this GEC activation pattern might influence C-mediated GEC injury. We demonstrate that the C5b-9-induced increase in cytosolic Ca2+ concentration ([Ca2+]i) did not impair ATP generation by mitochondria, suggesting that it does not contribute to cytotoxicity. Moreover, this increase in [Ca2+]i protected GEC from C-mediated cytolysis. However, a large increase in [Ca2+]i (produced by the Ca2+ ionophore A23187) impaired ATP generation and aggravated C-mediated cytotoxicity, suggesting that intact mitochondrial activity is necessary for GEC to withstand C attack. Activation of protein kinase C (PKC) by phorbol myristate acetate (PMA) also decreased C-mediated cytolysis. Conversely, C lysis was enhanced in GEC that had been pretreated for 18 hours with a high dose of PMA to deplete PKC, and following PKC inhibition with H-7. Therefore, PKC activation, possibly resulting from C5b-9-induced increase in 1,2-diacylglycerol, triggered mechanisms that protected GEC from C-mediated injury. Thus, as a consequence of C5b-9-induced phospholipase activation, the amount of C-induced GEC injury is diminished.
Cybulsky
A V
AV
Department of Medicine, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
Bonventre
J V
JV
Quigg
R J
RJ
Lieberthal
W
W
Salant
D J
DJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002470:Cell Survival; D015938:Complement Membrane Attack Complex / Q000276:immunology*; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000276:immunology* / Q000473:pathology; D010740:Phospholipases / Q000378:metabolism; D011493:Protein Kinase C / Q000494:pharmacology*; D051381:Rats
D015938:Complement Membrane Attack Complex; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D010740:Phospholipases; D002118:Calcium