Increased plasma asymmetric dimethylarginine (ADMA) levels in retinal venous occlusive disease

Background: We investigated the levels of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA), as well as homocysteine and cysteine thiols, in a cohort of subjects affected by retinal vein occlusion (RVO) disease. Methods: Capillary electrophoresis analysis was performed in both RVO subjects (n = 54) and in a control group (n = 32). Results: No differences were found between controls and patients; however, after categorisation for RVO type, central RVO (CRVO) patients showed higher levels of ADMA (0.710 +/- 0.139 mu mol/L) than controls (0.635 +/- 0.117 mu mol/L) and branch RVO patients (0.642 +/- 0.096 mu mol/L. Moreover, cysteine plasma levels were also significantly higher in CRVO patients than in controls (265.8 +/- 46.9 vs. 226.7 +/- 51.9 mu mol/L, p < 0.01), while homocysteine plasma concentration was more or less identical in all groups. Conclusions: We hypothesise that the elevated levels of cysteine in CRVO patients may post-translationally inhibit dimethylarginine dimethylaminohydrolase enzyme activity, as already described for homocysteine, thus contributing to the accumulation of ADMA in this patient group.