Nitric oxide synthase-II is expressed in severe corneal alkali burns and inhibits neovascularization.

PURPOSE Inducible nitric oxide synthase (NOS-II) is expressed in many inflammatory conditions. The implication of nitric oxide (NO) in angiogenesis remains controversial. The role of NOS-II and its influence on angiogenesis in corneal neovascularization is unknown and was investigated in this study. METHODS A mouse model of corneal neovascularization induced by chemical cauterization was used. NOS-II mRNA expression was analyzed by reverse transcriptase-polymerase chain reaction, and NOS-II protein was studied in situ by immunohistochemical analysis of the cornea. The influence of NOS-II on neovascularization was determined by comparison of vessel development in "normal" wild-type mice and mice with a targeted disruption of the NOS-II gene. RESULTS NOS-II mRNA was induced to very high levels after corneal cauterization and remained upregulated throughout the disease. Migratory cells in the center of the cauterization area expressed NOS-II protein. The neovascular response in mice lacking the NOS-II gene was significantly stronger than in wild-type mice, and the difference increased over time. CONCLUSIONS These data are the first evidence that NOS-II is expressed in this model of sterile corneal inflammation. NOS-II expression inhibited angiogenesis in severe corneal alkali burns.