Prostaglandins, thromboxanes and hydroxyeicosatetraenoic acids (HETEs), collectively known as prostanoids (PG) are produced by biologic oxidation of arachidonic acid by the cyclooxygenase (Cox) pathway. Increased synthesis of PG are associated with inflammatory and angiogenic conditions and enzymatic inhibitors of the Cox pathway are potent anti-inflammatory agents. PG are short-lived mediators that induce hyperalgesia, vasodilatation, stromal cell proliferation and angiogenesis. Whereas PGE1 and PGE2 are potent inducers of angiogenesis, molecular mechanisms involved are not understood. Because the PGs act transiently, the levels of PG-synthetic enzymes, particularly Cox, determine in part, the bioactivity of PG within tissues. While the Cox enzyme is encoded by two genes, Cox-2 is the isoform that is induced by pro-inflammatory factors and is suppressed by anti-inflammatory steroids. In addition, Cox-2 expression is exaggerated in the chronic inflammatory disease of rheumatoid arthritis, suggesting that production of Cox-2-derived PG results in the promotion and/or the maintenance of the inflammatory phenotype. To better understand the specific pathological consequences of Cox enzyme expression, the Cox enzyme was globally over-expressed in transgenic mice. Preliminary analysis suggests that global over-expression resulted in neonatal lethality. The central hypothesis of this proposal is that exaggerated synthesis of Cox-2-derived PG results in the chronic changes in the local vasculature such as dysregulated angiogenesis. The Cox-2 enzyme will be over-expressed in the basal epidermal layer of the skin using the tissue-specific keratin K14 promoter. To assess the biological consequences of the non-prostaglandin effects of Cox-2 expression, similar transgenic strategy will be used to express the active-site mutant of Cox-2 that produces only 15-HETE. The pathological and cell biological phenotype of the Cox-2 wild-type and mutant transgenic dermal microvasculature will be analyzed under basal, wounded and UV- induced inflamed conditions. Non-steroidal antiinflammatory drugs that specifically inhibit Cox-2 will be used to attempt to reverse the phenotypes. Molecular mechanisms involved in the PG-induced vascular pathology will be studied in the Cox-2 transgenic skin. Emphasis will be on the PGE induction of vascular endothelial growth factor gene expression. These studies are anticipated to yield a better understanding of the chronic biological consequences of Cox-2 over-expression on the local vasculature.
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