Nitric oxide donors as potential additions to anti-alopecia areata armamentarium.

Th1-type cytokines play a critical role in the pathogenesis of alopecia areata (AA) and a Th2 lymphocyte-like response may inhibit the tissue-damaging effects of Th1 lymphocytes. It is suggested that nitric oxide (NO) could induce a switch from Th1 to Th2 lymphocytes in the immune response. Additionally, decreased levels of calcitonin gene-related peptide (CGRP) in lesions have been proposed to play an important role in the pathomechanism of AA and NO augments both the release of CGRP and the vasorelaxation induced by it. Taken together, these data suggest that 1) NO donors could be useful in the treatment of AA through the induction of T cell switching towards Th2 cells and 2) induction of inducible nitric oxide synthase (iNOS) by both allergic and irritant contact dermatitis could provide a mechanism for the efficacy of contact dermatitis in the treatment of AA.