Increased expression of arginase I and II in allergic nasal mucosa

Abstract Objectives/Hypothesis: It is known that arginase may be a regulator of diverse pathways, including production of nitric oxide (NO). Increased expression of arginase has been reported in several inflammatory lung diseases, including allergic asthma, suggesting that this may be a common feature underlying the pathophysiology of airway hyperreactivity. Thus, arginase I and II may play a role in the pathogenesis of allergic rhinitis. The distribution pattern and level of expression of arginase I and II were therefore determined in normal and allergic nasal mucosa. Study Design: Controlled, prospective study. Methods: The distribution pattern and level of expression of arginase I and II in normal and allergic nasal mucosa were evaluated using RT‐PCR, immunohistochemistry, and Western blotting. Results: The level of expression of arginase I and II mRNA was increased in allergic nasal mucosa in comparison with normal nasal mucosa. In normal nasal mucosa, arginase I and II were expressed in the surface epithelium, submucosal glands, vascular endothelium, and fibroblasts. In allergic nasal mucosa, both enzymes were also localized to similar sites, in addition to inflammatory cells, and the level of expression were greatly increased compared with normal nasal mucosa. These findings were verified by Western blotting. Conclusions: These results indicate that arginase I and II may play a role in the pathophysiology of allergic rhinitis, and suggest the possible role of the L‐arginine metabolic pathway through modulation of L‐arginine availability as a substrate for nitric oxide synthase (NOS) and arginase in the pathogenesis of allergic rhinitis.