NO is described as capable of initiating psoriasis mainly by releasing calcitonin gene-related peptide and substance P. These substances are considered to play important roles in the pathogenesis of psoriasis by inducing the production of adhesion molecules, keratinocyte hyperproliferation, mast cell degranulation, vasodilatation, and chemotaxis of neutrophils [112]. This evidence concerns the gene TAC1 and psoriasis.