Corneal surface injury evokes an inflammatory reaction releasing arachidonic acid (AA) leading to the production of various eicosanoids some of which are thought to be proinflammatory via the cyclooxygenase, lipoxygenase and cytochrome P450 monooxygenase (CYP) pathways. We were the first to identify CYP-dependent AA metabolism in the eye and establish it as a primary corneal epithelial inflammatory pathway in rabbit models of ocular surface inflammation. This corneal epithelial CYP metabolizes AA to two major 12-hydroxyeicosanoids: 12(R)-HETE and 12(R)-HETrE which exhibit potent inflammatory and angiogenic properties. That these two metabolites are critical tissue-derived mediators of ocular surface inflammation is strongly supported by studies from our laboratory demonstrating that: 1) their synthesis/levels are increased following injury in vitro and in vivo; 2) their levels positively correlate with the in situ inflammatory response; 3) inhibition of their synthesis attenuates ocular surface inflammation in vivo suggesting a potential cause-effect relationship; 4) their biological activities, in particular those of 12(R)-HETrE, in vitro and in vivo, are characteristic of potent inflammatory mediators (including vasodilation, neutrophil chemotaxis, and angiogenesis); and 5) these two metabolites are present in human tears and, more significantly, the levels are much higher in tears from subjects with ocular inflammation. The mechanisms that regulate CYP expression and function and its importance to ocular surface inflammation are yet to be explored. The overall goal of this proposal is to identify the CYP-AA isoform in order to elucidate both its role and mechanisms of expression and function in injury-induced inflammation of the ocular surface. We hypothesize that injury to the cornea increases the activity of an epithelial CYP isoform(s) which metabolizes AA to 12(R)-HETE and 12(R)-HETrE and that 12(R)-HE TrE, a cornea! epithelial-derived angiogenic factor, acts directly on the adjacent limbal vessel's endothelial cells to promote neovascularization of the cornea. We propose: (A) the identification and extensive characterization of the CYP-AA in the corneal epithelium emphasizing cellular/molecular mechanisms regulating its increased expression and activity following injury. (B) investigation into the role of the potent angiogenic metabolite 12(R)-HETrE in inflammation with emphasis on cellular/molecular mechanisms of action. Understanding the pathophysiologic ramifications of this pathway and its metabolites will offer insight into the interplay between the corneal epithelium and the surrounding limbal microvasculature following corneal epithelial injury. It will also aid in the development of therapeutics targeted at inhibiting the synthesis of a pro-inflammatory mediator (metabolic inhibitors or molecular probes) or preventing its activity (receptor/functional antagonists) for the treatment of inflammation associated with corneal injury, infection and surgery.
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