Heparin down-regulates the phorbol ester-induced protein kinase C gene expression in human endothelial cells: enzyme-mediated autoregulation of protein kinase C-α and -δ genes11This work was supported by Consiglio Nazionale delle Ricerche (C.N.R.), Ministero Università-Ricerca Scientifica e Tecnologica (M.U.R.S.T.) and Ministero della Sanità ‘ricerca finalizzata 1998’

AbstractOverexpression of protein kinase C-α and protein kinase C-δ has been shown to modulate a number of biological effects, including the cell growth and differentiation. We hypothesized that heparin, a potent antimitogenic drug, could affect the cell proliferation by inhibiting the expression of specific protein kinase C genes. Heparin, markedly but not completely, inhibited the serum-stimulated protein kinase C-α and -δ mRNA expression. Protein kinase C inhibition or down-regulation significantly decreased the serum-induced protein kinase C isoenzyme gene expression. Heparin failed to inhibit the residual effect of serum that was resistant to the above-mentioned treatments. Phorbol 12-myristate 13-acetate elicited an increase of protein kinase C isoenzyme gene expression that was completely prevented by protein kinase C inhibition or down-regulation. Heparin dose-dependently counteracted and ultimately abolished the increase in the protein kinase C isoenzyme gene expression elicited by phorbol 12-myristate 13-acetate. These results suggest that the inhibition of an autoregulatory role wielded by protein kinase C on the protein kinase C-α and -δ gene expression might represent a possible mechanism by which glycosaminoglycans modulate the cell growth