Endothelial nitric oxide synthase polymorphisms and susceptibility to high-tension primary open-angle glaucoma in an Egyptian cohort

PURPOSE: To analyze the association of polymorphisms of the endothelial nitric oxide synthase (NOS3) gene and nitric oxide (NO) levels with high-tension primary open-angle glaucoma (POAG) in an Egyptian population. METHODS: This case-control study included 160 patients who had high-tension POAG (76 men and 84 women; age range 41–75 years) and 110 controls (56 men and 54 women; age range 55–78 years). Genotyping of T-786C (rs2070744), Glu298Asp (rs1799983), and the 27-bp insertional variable number tandem repeat (VNTR) in intron 4 of the NOS3 gene was performed with an amplification refractory mutation system PCR assay. The NO level was determined by measuring the total nitrate/nitrite (NO(X)) plasma level. RESULTS: The CC genotype of the T-786C polymorphism was significantly associated with POAG (odds ratio [OR] = 2.54, 95% confidence interval [CI] = 1.26–5.13, p = 0.007). The C allele was significantly associated with POAG (OR = 1.86, 95% CI = 1.29–2.69, p<0.001). After stratification by sex, the CC genotype and the C allele were significantly associated with POAG in women only (OR = 3.06, 95% CI = 1.07–8.74, p = 0.03 for the CC genotype, and OR = 2.09, 95% CI = 1.24–3.53, p = 0.005 for the C allele). The genotype and allele frequencies of Glu298Asp and intron 4 were not significant between the patients with POAG and the controls, and after stratification by sex. The mean NO(X) plasma level was significantly lower in patients with POAG than in the controls (p = 0.01) and low in the (TC+CC) genotype compared to the TT genotype of T-786C in the patients and controls (p<0.001). CONCLUSIONS: The results suggest that the CC genotype of T-786C NOS3 may be associated with an increased risk of developing high-tension POAG in Egyptians, particularly women. In addition, decreased NO levels may play a role in the development of POAG.