Protein kinase C activation generates superoxide and contributes to impairment of cerebrovasodilation induced by G protein activation after brain injury

Previous studies have observed that activation of protein kinase C (PKC) contributes to generation of superoxide anion (O(-)(2)) after fluid percussion brain injury (FPI). This study was designed to characterize the effects of FPI on the vascular activity of two activators of a pertussis toxin sensitive G protein, mastoparan and mastoparan-7, and the role of PKC dependent O(-)(2) generation in such effects in newborn pigs equipped with a closed cranial window. Mastoparan (10(-8), 10(-6) M) elicited pial artery dilation that was blunted by FPI and partially restored by the PKC inhibitor chelerythrine (10(-7) M) or the O(-)(2) free radical scavengers polyethylene glycol superoxide dismutase and catalase (SODCAT) (9+/-1 and 16+/-1, sham control; 3+/-1 and 5+/-1, FPI; and 7+/-1 and 11+/-1%, FPI SODCAT pretreated). Similar results were observed for mastoparan-7 but the inactive analogue mastoparan-17 had no effect on pial artery diameter. Exposure of the cerebral cortex to a xanthine oxidase O(-)(2) generating system blunted mastoparan induced pial artery dilation similar to FPI (10+/-1 and 17+/-1 vs. 2+/-1 and 3+/-1%). Pertussis toxin (1 microg/ml) exposure blocked mastoparan and mastoparan-7 vasodilation. These data show that pertussis toxin sensitive G protein activation elicits cerebrovasodilation that is blunted following FPI in a PKC dependent manner. These data also show that O(-)(2) generation similarly blunts G protein mediated cerebrovasodilation. These data suggest that PKC dependent O(-)(2) generation contributes to impaired G protein mediated cerebrovasodilation after FPI.