Elevated production of salivary nitric oxide in oral mucosal diseases

Nitric oxide (NO) is known to play an important role in biological systems. In this study, we measured levels of NO in the saliva of 39 patients with oral mucosal diseases: 21 had oral lichen planus (OLP) and 18 had recurrent aphthous ulceration (RAU). NO was assayed using the Griess reagent, which measures nitrite (NO2), the byproduct of NO. NO2 was detected in all tested samples, and levels in the saliva of patients were significantly increased relative to those of healthy subjects. We also examined the effect of NO on fibroblasts, keratinocytes and NA cells (an epithelial cancer cell line) in vitro. S-nitroso-N-acetyl-DL-penicillamine (SNAP) and 3-morpholinosydnonimine (SIN-1) were used as NO donating reagents. The results revealed that cell viability was significantly reduced by NO derived from SNAP and SIN-1 in a dose-dependent manner. Although the role of salivary NO in normal physiology is as yet unknown, these findings suggest that excessive salivary NO plays a potential role in modifying oral mucosal diseases as a physiopathological regulator.