Association between polymorphic <i>eNOS</i> gene markers and risk of primary open-angle glaucoma in the Perm Region population

Abstract

Glaucoma is widely known to have a progressive course and occupy a leading place among the causes of vision loss and blindness. Increased intraocular pressure is the key harmful factor among the causes of glaucoma occurrence. In some cases, however, the progressive disease is also observed at normal values of ophthalmic tonus. Early diagnosis of glaucoma will allow for timely therapy, which in turn will reduce the risk of complications and prevent neuroopticopathy progression. According to the literature data, the pathogenesis of primary open-angle glaucoma is associated with nitric oxide (NO), due to imbalance between endothelium-produced vasoconstrictors and vasodilators, especially, endotelin-1 and nitric oxide. Decreased NO level combined with endotelin-1 hyperproduction is associated with development and progression of a number of ocular disorders including glaucomatous atrophy of the optic nerve. Since nitric oxide is produced by endothelial NO-synthase (eNOS), one may assume that eNOS is involved in pathogenesis of neurodegenerative changes in primary open-angle glaucoma. However, despite numerous studies on the pathogenesis of glaucoma, the distinct factors of innate immune response remain poorly studied. The purpose of the present study was a search for association between polymorphic markers (C774T, T786C, Glu298Asp) of the eNOS gene and the risk of primary open-angle glaucoma among the Perm Region residents. Peripheral blood of patients with primary open-angle glaucoma (the main group) and cataract without glaucoma (a comparison group) was used as initial biomaterial. In comparison group, arterial hypertension was most often encountered as concomitant pathology. Genomic DNA was first isolated from the blood samples, followed by rt-PCR using reagent kits for determining C774T, T786C, Glu298Asp polymorphic markers in the eNOS gene. The prevalence of polymorphic variants of the innate immunity genes T786C, C774T and Glu298Asp of the eNOS gene was analyzed in patients with primary open-angle glaucoma. There were no significant differences in the distribution of genotypes and alleles of eNOS gene for the C774T and Glu298Asp polymorphic markers. An increased frequency of homozygous TT genotype was found, along with decreased occurrence of C allele at the polymorphic T786C locus of the eNOS gene, as well as a trend for decreased frequency of the TC and CC genotypes. Arterial hypertension potentiated the negative effect of increased intraocular pressure upon the glaucoma-associated optic neuropathy. Conclusions. The studied changes in genotypes and allelic frequencies of eNOS gene may be regarded as risk factors that increase probability of the primary open-angle glaucoma and predict severity of the disease.