NOS2 Expression During HSV-1-Induced Corneal Stromal Disease

Abstract

Abstract: : Purpose:The role of specific enzymes involved in the pathogenesis of herpes simplex virus type 1(HSV-1)- induced stromal disease is unclear. These studies determine the role of nitric oxide synthase 2(NOS2) in the inflammatory response to HSV-1 in the anterior segment. Methods: Primary infections of rabbits were established by injecting 10 ₅ pfu of HSV-1 strain (RE) beneath the alveolar mucosa of the mandible. After establishment of latency (about 30 days) initial corneal infections were established by intrastromal injection of 10 ₃ pfu of HSV-1. Rabbits were given the NOS inhibitor, L-NAME, a non-isoform selective inhibitor or the NOS 2 specific inhibitor 1400W in combination with acyclovir(ACV). Corneal disease was measured by fluorescein staining and measurement of corneal thickness using an ultrasonic pachymeter. Rabbits were killed at various times post-infection and anterior segment tissues analyzed using immunohistochemistry and in situ hybridization to detect cells expressing NOS isoforms and the production of nitrotyrosine. Results:L-NAME /ACV but not 1400W /ACV produced significant reductions(p<.05) in corneal thickness relative to controls thus implying a NOS isoform was a contributor to HSV-1 induced corneal inflammation. Immunohistochemistry using antibodies specific to the NOS isoforms indicated that NOS2 expression was increased in vascular endothelium of the iris, vessels of the limbus and vessels which neovascularize the cornea. Cells which infiltrate the cornea near the peak of the inflammatory response as measured by corneal thickness also expressed NOS2. At early periods in disease NOS2 was detected in the vascular endothelium of the iris and limbus. In situ hybridization confirmed the results when using a NOS 2 specific probe to detect the expression of NOS2 mRNA. Conclusion: NOS2 is a likely contributor to the pathogenesis of HSV-1 induced stromal disease at two levels (1) in oxidative damage caused by inflammatory cells and (2) the function of the vascular endothelium.

Keywords: 425 herpes simplex virus • 437 inflammation • 491 nitric oxide