Differential Expression of Nitric Oxide Synthase Isoforms nNOS and iNOS in Patients with Non-Segmental Generalized Vitiligo

Nitric oxide (NO) is involved in several biological processes, but its role in human melanogenesis is still not well understood. Exposure to UVA and UVB induces nitric oxide production in keratinocytes and melanocytes through the activation of constitutive nitric oxide synthase, increasing tyrosinase activity and melanin synthesis, whereas inducible nitric oxide synthase over expression might be involved in hypopigmentary disorders. The aim of this study was to evaluate whether inducible nitric oxide synthase and neuronal nitric oxide synthase expression were modified in vitiligo skin compared to healthy controls. Skin biopsies were obtained from inflammatory/lesional and white/lesional skin in 12 patients with active, non-segmental vitiligo; site-matched biopsies of
normal skin from eight patients were used as controls. Nitric oxide synthase isoforms expression was evaluated by confocal laser scanning microscopy andWestern Blot analysis. Inducible nitric oxide synthase expression was significantly increased in inflammatory/lesional skin compared to healthy
skin; melanocytes showed a moderate neuronal nitric oxide synthase expression in white/lesional skin, demonstrating that metabolic function still goes on. The obtained data demonstrated that vitiligo lesions were characterized by modifications of nitric oxide synthase isoforms, thus confirming the hypothesis that nitric oxide imbalance is involved in vitiligo and supporting the idea that nitric oxide synthase inhibitors might be used as a possible therapeutic approach for the management of vitiligo.