Tear Nitrite and Nitrate Levels as Nitric Oxide End Products in Patients with Behçet’s Disease and Non-Behçet’s Uveitis

Abstract

To evaluate the role of nitric oxide (NO) in ocular inflammation, tear nitrite and nitrates (NN) as NO end products were determined in 11 patients with Behçet’s disease (BD) and in 11 with non-Behçet’s uveitis (NBU) during the active and remission stages and in 12 healthy controls. Median (with the range) NN levels were 82.29 (59.60–98.25) µmol/l in the active and 98.25 (52.88–246.92) µmol/l in the remission stage of BD; 88.17 (25.99–116.73) µmol/l in the active and 83.00 (31.04–250.28) µmol/l in the remission stage of NBU and 109.17 (88.17–158.74) µmol/l in the controls. The NN levels in the active stage of BD and NBU were significantly decreased when compared to the controls (p < 0.05; Kruskal-Wallis test). Decreased NN levels at the activation stage may be caused by the rapid transformation of the NO to peroxynitrites, which are highly oxidizing and cytotoxic substances.

Endothelial nitric oxide synthase gene polymorphism is associated with Behçet's disease in Tunisian population

“…Other researchers have described the opposite and argued that decreased NO levels in the active stage might be attributable to the rapid transformation of NO to peroxynitrites [31,32]. When analyses were done according to the clinical features, a significant difference was observed in patients with skin lesions.…”

Potential roles of nitrate and nitrite in nitric oxide metabolism in the eye

“…In the eye, there is a similar exocrine gland, the lacrimal gland, which produces important tear components to help protect ocular surfaces. It has been reported that human tears contain relatively high concentrations of nitrate 20-109 μM 31,32 and we hypothesized that lacrimal glands would have similar functions to salivary glands in nitrate metabolism. Our results from porcine tissues show that the lacrimal gland itself contains the most nitrate (234 ± 101 nmol/g) compared to other organs examined, including salivary glands.…”

Tear Nitric Oxide Levels in Behçet’s Disease

“…A study by Yilmaz et al demonstrated that the patients who received the treatment of Behçet uveitis had the elevated levels of NO in the aqueous humor (21). A study by Mirza et al with a small number of patients with BD (6 patients) showed that the tear nitrate/nitrite levels were decreased in the active group (6 patients) (17). However, our study demonstrated opposite results, and we think that the sample size of that study was quite small when compared with that of our study.…”

“…In this regard, some experimental studies suggest that NO may play a role in the pathogenesis of endotoxin-induced uveitis (EIU) as a proinflammatory mediator and that increased NO production may lead to hemodynamic and vascular permeability changes (8)(9)(10)(11)(12)(13). Although several studies (14-16) have investigated the blood NO levels in patients with BD, to our knowledge, there is only one study (17) that assessed the tear NO levels of those patients. Therefore, the aim of our study was to evaluate the tear nitrate/nitrite levels as NO end products in patients with BD in comparison with those of healthy subjects.…”