RESUMO
Transient glucose deprivation (TGD) has been shown to induce a resistance to a subsequent ischemia and reperfusion injury in the heart. Induction of cyclooxygenase-2 (COX-2) and heme oxygenase-1 (HO-1) is known to mediate the powerful defensive adaptation of the heart against oxidative stress. In this study, we found that a 30-min incubation in the absence of glucose resulted in a rapid increased expression of COX-2 and HO-1 in cardiac fibroblasts as examined by real-time quantitative polymerase chain reaction (PCR) and western blot analysis. Interestingly, TGD increased the generation of reactive oxygen species (ROS) and caused the transient phosphorylation of p38 mitogen-activated protein kinase (MAPK) as well as the translocation of protein kinase C (PKC)- from the cytosolic to the membrane fraction. However, no significant change in the distribution of PKC-delta isoform was observed compared with the control. Pretreatment of the cells with an antioxidant, N-acetylcysteine (NAC), resulted in the inhibition of p38 MAPK phosphorylation and PKC- translocation during TGD. In addition, the induction of COX-2 and HO-1 expression by TGD was prevented by pretreatment with NAC or SB203580, a p38 MAPK inhibitor. Surprisingly, pretreatment with chelerythrine, an inhibitor of PKC, strongly augmented the HO-1 mRNA expression but blocked the COX-2 mRNA induction by TGD. These results demonstrate that briefly removing glucose from cultured cardiac fibroblasts induces COX-2 and HO-1 expression via generation of ROS and p38 MAPK phosphorylation, while the translocation of PKC- to the membrane fraction may participate in the induction of COX-2 but not in the HO-1 expression.
