Assessment of homocysteine, neopterin and nitric oxide levels in Behcet's disease

Background: Behcet's disease is a multysystemic immunoinflammatory disease with a wide variety of clinical manifestations, whereas recurrent aphthous stomatitis is a local oral disease. The aim of this study was to examine the distribution of homocysteine levels in patients with active Behcet's disease, possible association of homocysteine with nitric oxide and neopterin levels, and to characterize the differences between patients with Behcet's disease and those with recurrent aphthous stomatitis in terms of these parameters compared with healthy controls. Methods: A total of 23 patients with active Behcet's disease, 25 patients with recurrent aphthous stomatitis as positive controls, and 21 healthy subjects were included in this study. Serum homocysteine and neopterin levels were measured flourimetrically by HPLC. Serum nitric oxide production was assayed by measuring total nitrite levels with Griess reagent. Results: Significantly higher homocysteine (12.9 +/- 3.3 mu mol/L) and lower nitric oxide (41.5 +/- 10.9 mu mol/L) and neopterin (6.4 +/- 1.0 nmol/L) levels were observed in patients with Behcet's disease compared with healthy controls (10.7 +/- 2.0 mu mol/L, 49.7 +/- 16.2 mu mol/L, 8.7 +/- 2.2 nmol/L, respectively) (p < 0.03 for neopterin, p < 0.04 for homocysteine and nitric oxide). However, homocysteine, nitric oxide, biopterin and neopterin levels and the neopterin/biopterin ratio for recurrent aphthous stomatitis patients were not significantly different compared to healthy controls. A significant positive correlation was observed between serum homocysteine and serum neopterin/biopterin ratio in patients with Behcet's disease (r=0.975, p < 0.005). Conclusions: In contrast to recurrent aphthous stomatitis, there is a higher prevalence of hyperhomocysteinemia in Behcet's disease. Homocysteine may have deleterious effects on the pathology of Behcet's disease by decreasing nitric oxide levels and interfering with the immune system.