Induction of macrophage plasminogen activator by asbestos is independent of PKC activation.

This study was undertaken to assess whether plasminogen activator (PA) induction in macrophages exposed to chrysotile fibers is mediated by protein kinase C (PKC) activation. In PKC depleted J774 cells, PA induction could be elicited by chrysotile whereas, as expected, the response to phorbol myristate acetate (PMA) was abolished. The effect of PMA and chrysotile on the distribution of PKC activity in the J774 cell line was also compared by measuring the enzyme catalytic activity and phorbol dibutyrate (PDBu) binding sites. No redistribution of PKC was observed after stimulation with PA inducing doses of chrysotile, whereas a clear translocation was observed with PMA. It is concluded that the mechanism of PA induction by chrysotile in this macrophage-like cell line is independent of PKC activation.