The skin as a mirror of the soul: exploring the possible roles of serotonin

Abstract

Serotonin (5-hydroxytryptamine; 5-HT) is an important mediator of bidirectional interactions between the neuroendocrine system and the skin. The rate of synthesis of 5-HT from l-tryptophan can be enhanced by brain-derived neuronal growth factor, cytokines, exposure to ultraviolet light and steroids. The major source of 5-HT in the skin are platelets, which, upon aggregation, release this biogenic amine. Moreover, the epidermal and dermal skin express the enzymes required for the transformation of tryptophan to 5-HT, and certain skin cells, such as melanocytes, have been demonstrated to produce 5-HT. In addition, rodent mast cells produce 5-HT, but human mast cells have not yet been fully examined in this respect. Skin cells express functionally active, membrane-bound receptors for 5-HT, as well as proteins that transport 5-HT. The interactions of 5-HT with these various proteins determines the nature, magnitude and duration of serotonergic responses.The immune and vasculature systems in the skin are traditional targets for bioregulation by 5-HT. Moreover, recent findings indicate that keratinocytes, melanocytes and dermal fibroblasts also respond to this amine in various ways. Thus, mammalian skin is both a site for the production of and a target for bioregulation by 5-HT. This indicates that agonists and antagonists directed towards specific 5-HT receptors could be useful in connection with treatment of skin diseases. Based on our increasing knowledge concerning these receptors and their plasticity, future research will focus on the development of serotonergic drugs that exert metabotrophic effects on the cells of the skin without affecting the central nervous system.

Functional magnetic resonance imaging in dermatology: The skin, the brain and the invisible

“…The skin has its own "peripheral" HPA axis to respond to stress and interact with the central HPA axis. [6,[25][26][27][28][29] Furthermore, the skin and brain age together as their intrinsic ageing strongly depends on a similar endocrine environment leading to the suggestion that skin ageing models represent an effective tool for understanding molecular ageing mechanisms of the brain. [30] The notion that skin may reflect a "diagnostic window into the brain" is tempting and the use of alpha-synuclein in skin nerve fibres biopsies to support diagnoses of Parkinson's disease [31,32] and fibroblast-based tests for Alzheimer's disease [33] is currently under investigation.…”

Neuroendocrinology of the skin

“…1 The skin is not only a classical source of vitamin D 8 but also a place of synthesis and metabolism of several neuropeptides including elements of hypothalamic-pituitary-adrenal (HPA), 1,[9][10][11][12] and hypothalamic-pituitary-thyroid (HPT), [13][14][15][16] axes. Skin cells also possess fully functional serotonin-and melatoninergic systems [17][18][19][20][21][22] and express steroidogenic activity. 1,12 The presence of several neuropeptides and other biologically active compounds in the skin is due to both their local synthesis and active transport from blood or release form nerves endings or migrating immune cells.…”

Radiation-induced mast cell mediators differentially modulate chemokine release from dermal fibroblasts

“…Human mast cells derived from CD34 + peripheral blood progenitors were also found to be capable of serotonin synthesis and release [7]. Serotonin has been implicated in immunomodulation, cell growth and development, mast cell adhesion and chemotaxis, tumorigenesis, and tissue regeneration [44]. Based on the fact that serotonin, likewise histamine and tryptase, is stored in secretory granules of mast cells we presumed that it is also secreted after irradiation.…”