The effect of protein kinase C activation on colonic epithelial cellular integrity

We have investigated whether activation of protein kinase C has a direct cytotoxic effect on colonic mucosal epithelial cells and whether oxidant- induced damage to colonocytes is mediated by activation of cellular protein kinase C. Incubation of freshly harvested cells from rat colon with the protein kinase C activator, phorbol 12-myristate, resulted in a concentration-dependent increase in the extent of cell injury. Phorbol 12- myristate acetate (0.1-10 μM) also increased cellular protein kinase C activity and this was reduced significantly by treating cells with the antagonists staurosporine or 2-[1-(3-dimethylaminopropyl)-indol-3-yl]3-(- indol-3-yl)maleimide (GF 109203X; 10 μM). Phorbol 12-myristate acetate treatment also resulted in increased translocation of proteins for protein kinase C isoforms α, δ and ε from cytosol to membrane particulate fractions. The antagonists reduced the extent of cell damage in response to phorbol 12-myristate acetate. Furthermore, cell injury in response to the phorbol acetate was also inhibited by the addition of the oxidant scavengers, superoxide dismutase or catalase to the cell suspension. Addition of H₂O₂ to the incubation medium (0.1-100 μM) resulted in an increase in cellular protein kinase C activity, an increase in the expression of the α, β and ζ isoforms and a reduction in cell integrity. The cellular damaging actions of H₂O₂ were significantly reduced by the protein kinase C antagonists, staurosporine or 2-[1-(3-dimethylaminopropyl)-indol-3-yl]-3-(-indol-3- yl)maleimide (GF 109203X). These findings suggest that protein kinase C activation results in colonic cellular injury and this damage is mediated, at least in part, by release of reactive oxidants. Furthermore, oxidant-mediated damage to these cells also involves protein kinase C activation. (C) 2000 Elsevier Science B.V.