Induction of Cyclooxygenase‐2 by Overexpression of the Human Catalase Gene in Cerebral Microvascular Endothelial Cells

Prostaglandin (PG) formation by the inducible (type 2) cyclooxygenase (COX‐2) and reactive oxygen species (ROS) have been proposed to play important roles in cerebrovascular pathological processes. To explore the relationship between ROS and COX‐2 expression, adenovirus (Ad) vectors containing cDNA for human antioxidant enzymes including catalase (AdCat), copper/zinc superoxide dismutase (AdCu/ZnSOD), and manganese superoxide dismutase (AdMnSOD) were transferred into murine cerebral microvascular endothelial cells. AdCat (100 multiplicity of infection) infection increased the content and enzymatic activity of cellular Cat threefold and decreased the intracellular peroxide level. The expression of COX‐2 mRNA and protein in cell lysates was up‐regulated, and the amount of PGE2 formed from exogenous arachidonic acid increased following AdCat infection in a dose‐dependent manner, paralleling the expression of COX‐2 protein. The AdCat‐induced increase in PGE2 formation was inhibited by NS‐398, a selective inhibitor of COX‐2 enzymatic activity. AdCat infection did not change the expression of the constitutive (type 1) COX protein. Although AdCu/ZnSOD and AdMnSOD infection increased the expression of superoxide dismutase proteins, COX‐2 expression was not induced. An in vitro nuclear transcription assay indicated that overexpression of the Cat gene increases the transcription of the COX‐2 gene. Furthermore, the stability of COX‐2 mRNA induced by lipopolysaccharide was increased after AdCat gene transfer. These results indicate that AdCat gene transfer induces the transcriptional activation of the COX‐2 gene and increases COX‐2 mRNA stability. Therefore, peroxide may have regulatory effect on COX‐2 function in the cerebral microcirculation.