Single patch of hair at a denervated site in a patient with alopecia universalis

The role of neuropeptides in the control of regional immunity

Neuropeptides (NPs) and neurotransmitters are a heterogeneous group of soluble factors that make connections within the neuroendocrine and immune systems. NPs, including substance P (SP), vasoactive intestinal peptide (VIP), α melanocyte-stimulating hormone (α-MSH), and calcitonin gene-related peptide (CGRP), released by nerves that innervate the skin, can modulate the action of innate and adaptive skin immunity as well as the skin cells functions. Their role in several inflammatory skin diseases, such as atopic dermatitis, psoriasis, and vitiligo, and in the isotopic response has been reported. Further progress in understanding the various processes that modulate the interactions of the nervous and the skin immune system is essential to develop effective treatment for inflammatory skin conditions with neurogenic components and for understanding signs and symptoms in the isotopic response and, in general, in the control of global and regional immunity.

Immunohistochemical comparison of whisker pad cutaneous innervation in Swiss Webster and hairless mice

To establish the mouse mutant, hairless (Hr), as a useful model for future analyses of target-ending interactions, we assessed the cutaneous innervation in the whisker pad after loss of primary hair targets. Postnatal (P) development of fur in Hr begins similarly to that of "normal" Swiss Webster (SW) mice. Around P10, hairs are shed and the follicles rendered permanently incompetent. Hair loss progresses rostrocaudally until the entire skin is denuded. Substantial alterations in the distribution and density of sensory and autonomic endings in the mystacial pad vibrissal and intervibrissal fur innervation were discovered. Pilo-neural complexes innervating fur hairs were dismantled in Hr. Epidermal innervation in SW was rich; only a few endings expressed growth-associated protein-43 kdal (GAP), suggesting limited changes in axonal elongation. Innervation in Hr formed a dense layer passing upward through the thickened epidermis, with substantial increases among all types of endings. Vibrissal follicle-sinus complexes were also hyperinnervated. Endings in Hr vibrissae and fur were strongly GAP-positive, suggesting reorganization of innervation. Dermal and vascular autonomic innervation in both strains co-localized tyrosine hydroxylase and neuropeptide Y, but only in Hr did neuropeptide Y co-localize calcitonin gene-related peptide (CGRP) and express GAP immunolabeling. Stereological quantitation of trigeminal ganglia revealed no differences in neuron number between Hr and SW, although there were small increases in cell volume in Hr trigeminal ganglion cells. These results suggested that a form of collateral sprouting was active in Hr mystacial pads, not in response to local injury, but as a result of loss of primary target tissues.

Neuropeptídeos na pele

Há evidências crescentes de que a inervação cutânea é capaz de modular uma variedade de fenômenos cutâneos agudos e crônicos, interagindo com as células da pele e seus componentes imunes. Essa forma de sinalização local entre tecido nervoso e tecido cutâneo ocorre especialmente por meio dos neuropeptídeos, uma numerosa família de neurotransmissores de natureza química comum e nomenclatura heterogênea presentes em todo o sistema nervoso e secretados pelas fibras nervosas cutâneas. São alvo desta revisão os neuropeptídeos substância P (SP), o peptídeo relacionado ao gene da calcitonina (CGRP), o peptídeo vasoativo intestinal (VIP), o peptídeo ativador da adenilato-ciclase pituitária (PACAP), o neuropeptídeo Y (NPY) e a somatostatina (SOM). Serão discutidas suas ações sobre as células da pele e sistema imune, bem como estudos recentes que sugerem a participação dos neuropeptídeos nas respostas inflamatórias cutâneas, nas reações de hipersensibilidade e em dermatoses humanas, notadamente na psoríase, dermatite atópica, hanseníase e alopecia.

Isotopic response after herpesvirus infection: an update

The term postherpetic isotopic response describes the occurrence of a new, unrelated disease that appears at the same location as a previously healed herpetic infection. When dealing with the pathogenetic mechanism involved in the isotopic response, several possibilities should be considered: a viral origin, an immunologic origin, a vascular origin, and a neural origin. The aim of this article is to review and discuss the different pathogenetic mechanisms with particular attention to new information related to the possible neural origin of this abnormal response of the skin.

[Is alopecia areata a psychosomatic disease?]

INTRODUCTION

Destruction of hair follicles by lymphocytes induces alopecia aerata. Hence, immunological mechanisms are involved in this disease, as for numerous dermatoses. Nonetheless, alopecia aerata appears to be a psychosomatic disease. Is there any contradiction?

CURRENT KNOWLEDGE AND KEY POINTS

Alopecia aerata often occurs after stress, particularly during mourning. Psychiatric disorders are more frequent in patients with alopecia than in healthy subjects. But these disorders might be secondary to the visible hair disease. Psychopathological mechanisms need to be clarified but alexithymia seems to be the key for understanding how stress could induce hair loss. In the skin (and the scalp) all functions are narrowly controlled by nerve fibers. Among these functions are hair growth and immunity. Immune cells and hair follicle cells possess receptors for neurotransmitters, which are synthesized by neuronal endings. When activated, these receptors are able to modulate cell properties. The same phenomena are described with stress-induced hormones. In alopecia aerata, like in numerous other diseases, psychosomatics and immunology are not opposed because immune cells are controlled by the nervous system through neurotransmitters.

FUTURE PROSPECTS AND PROJECTS

Research needs to be thorough in both the fields of psychology and neurobiology. Psychotherapies or psychotropes appear to be useful in the treatment of alopecia aerata.