Disruption of endothelial actin microfilaments by protein kinase C inhibitors

In this study, we report that the isoquinolinesulfonamide inhibitors of protein kinase C (PKC), H-7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine] and its related derivatives H-8 and HA-1004, in addition to staurosporine cause depletion and reorganization of microfilament bundles of porcine aortic endothelial cells in both low-density and confluent monolayer cultures. Concomitantly, significant loss of cell adhesion was noted following treatment with H-7. The effects of these compounds were found to be reversible upon wash-out, with restoration of the microfilament network. In addition, longer term incubation with phorbol myristate acetate (PMA) carried out to deplete PKC results in depletion of microfilaments as well. After 24 hr of PMA incubation, however, addition of H-7 or staurosporine is associated with further loss of the remaining microfilaments, suggesting that these agents act, at least in part, through a PKC-independent mechanism.