Psoriasis and the nervous system.

Both clinical and experimental evidence is accumulating on the role of the nervous system in the pathogenesis of psoriasis. Sporadic reports as well as extensive studies indicate that emotional stress can act as an exacerbating event in psoriasis. Moreover, that neurogenic mechanisms are operating in psoriasis is suggested by clinical, pharmacologic and experimental data. We have focused our investigations on the role of vasoactive intestinal peptide (VIP) and substance P (SP) in psoriatic lesions using a variety of experimental approaches: 1) receptor autoradiography; 2) immunohistochemistry; 3) radio-immunoassay; 4) human keratinocytes cultures. Our results indicate that an imbalance of VIP and SP exists in psoriatic lesions, and that these neuropeptides exert different and specific effects on human keratinocytes. At present, however, the finding of psoriasis being exacerbated by psychological factors cannot be satisfactorily explained merely by alterations of neuropeptides in the skin.