Nephrol Dial Transplant (1995) 10: 2027-2034
© 1995 European Renal Association-European Dialysis and Transplant Association
research-article
Extracellular ATP augments mesangial cell growth induced by multiple growth factors
Medizinische Klinik IV and Institut für Biochemie, Universität Erlangen-Nürnberg Erlangen, Germany
Correspondence and offprint requests to: Correspondence and offprint requests to: Dr Eckhard Schulze-Lohoff, Medizinische Klinik IV, Universität Erlangen-Nürnberg, Loschgestr. 8 1/2, D-91054 Erlangen, Germany
BACKGROUND.: ATP is released into the extracellular milieu during tissue injury and platelet aggregation and has a modest mitogenic effect on cultured rat glomerular mesangial cells (MCs). In this study we investigated the interaction of ATP with multiple growth factors during MC mitogenesis.
METHODS.: Replication of MCs was determined by direct cell counting and DNA synthesis was measured by 3H-thymidine uptake. Activity of phosphatidylinositol-specific phospholipase C (PI-PLC) was assessed by measuring formation of inositol phosphates from 3H-labelled precursors.
RESULTS.: Extracellular ATP (1–100 µM) exerted a powerful synergistic effect on DNA synthesis of MCs when used simultaneously with various mitogens, including epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF-BB), endothelin-1 (ET-1), arginine vasopressin (AVP), thrombin (Thr), serotonin (5-HT), and interleukin-1ß (IL-1ß). ATP synergized with these factors by increasing the maximum of DNA synthesis, without changing the half-maximal concentration of the growth factor. In addition cell counts revealed that ATP significantly augments MC growth induced by EGF, bFGF, PDGF-BB, ET-1, AVP, Thr, 5-HT, and IL-1ß. ATP caused activation of PI-PLC, but did not synergize with any of the tested growth factors in this respect. ATP-induced PI-PLC activation was inhibited by preincubation with pertussis toxin by 40–93%. This treatment did not suppress DNA synthesis induced by ATP alone, by PDGF, or by PDGF plus ATP. The calcium antagonists, TMB-8 and verapamil, as well as the inhibitors of protein kinase C, calphostin C and H7, had no effect on DNA synthesis induced by ATP or PDGF plus ATP. Also, ATP synergistically stimulated DNA synthesis in combination with the direct activator of protein kinase C, phorbol myristate acetate (PMA), and with the reaction product of phospholipase D, phosphatidic acid. Finally, ATP was mitogenic in an MC line of higher passage which did not respond with PI-PLC activation.
CONCLUSIONS.: Extracellular ATP synergistically augments MC growth induced by multiple growth factors. While the ATP-induced mitogenic signal is presently unclear, our observations support the concept that ATP may play a role during the course of glomerulonephritis when multiple growth factors are released from glomerular and inflammatory cells.
Keywords: cell growth; nucleotides; phospholipase C; purinergic receptors
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