Neuropeptides in skin.

Neuropeptides are a heterogeneous group of more than 50 molecules that play a role in various cutaneous functions and diseases; they act as neuromodulators, neurotransmitters, neurohormones, and hormones. In the skin, neuropeptides are synthesized locally (i.e., in keratinocytes and in endothelial cells) and are transported by nerve fibers or immune cells (i.e., lymphocytes, monocytes, and polymorphonuclear cells). Specific receptors and binding sites for neuropeptides have been described in different cell lines in the skin (keratinocytes, endothelial cells, immune cells, fibroblasts). Many different biologic actions of neuropeptides have been demonstrated. Depletion of cutaneous neuropeptides (i.e., with capsaicin cream) or therapeutic use of neuropeptide agonists and/or antagonists may aid in the treatment of skin diseases.