Modern aspects of cutaneous neurogenic inflammation.

Recent findings have shed new light on the role of peripheral nerves in the skin and established a modern concept of cutaneous neurobiology. Closely related monodirectional and/or bidirectional pathways exist in which the central and peripheral nervous system, the endocrine and immune system, and almost all skin cells are involved. Information is emerging about the factors involved in these immunomodulatory mechanisms, which are defined as neuropeptides, neurotransmitters, neurotrophins, and neurohormones. The interaction between peripheral nerves and the immune system is mediated by different types of cutaneous nerve fibers that release neuromediators and activate specific receptors on target cells in the skin such as keratinocytes, mast cells, Langerhans cells, microvascular endothelial cells, fibroblasts, and infiltrating immune cells. These interactions influence a variety of physiologic and pathophysiologic functions including cellular development, growth, differentiation, immunity, vasoregulation, leukocyte recruitment, pruritus, and wound healing. A variety of mechanisms lead to the termination of cellular responses to released neuropeptides under physiologic circumstances. Herein, we highlight some of the recent advances of neurocutaneous biology and discuss the role of nerves in mediating cutaneous inflammation. Understanding the mechanisms and the factors controlling neuromediators and their receptors and degrading enzymes will lead to the identification of novel therapeutic targets for the treatment of cutaneous diseases.