Oral communication, iL24

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

Introduction to the neuroendocrinology of the pigmentary system

The field of the neuroendocrinology of the pigmentary system was funded with proposals that L-tyrosine and L-DOPA can act as hormone-like bioregulators with melanocytes acting as targets and producers of these molecules (J Theor Biol 1990: 143: 123-138, Mol Cell Endocrinol 1994: 99: C7-11), and that melanocytes are sensory and regulatory cells of the epidermis with computing capability, that transform external and/or internal signals/energy into organized regulatory networks for the maintenance of the cutaneous homeostasis (J Theor Biol 1993: 164: 103-120). Due to their exposed location in the skin, the body’s largest as well as most directly and constantly environmentally threatened organ, melanocytes primarily transduce environmental cues (Physiol Rev 2004: 84: 1155-1228, Exp Derm 2009: 19; 760-76) that include but are not limited to the UVR as well as numerous intraepithelial and systemic signals into complex auto-regulatory local networks of the skin neuroendocrine system (Endocrine Rev 2000: 21; 457-487; Drug Discovery Today: Dis Mech 2008: 5; e137-e144) that has established in the periphery for the maintenance of cutaneous homeostasis (J Clin Invest 2007: 117: 3166-3169). Melanogenesis and melanin transfer via melanosomes into keratinocytes is a particularly prominent response pattern of melanocytes with a capability of inducing several local and perhaps systemic bioregulatory responses due to the intrinsic nature of melanosomes, melanin and intermediates of melanogenesis (J Theor Biol 1993: 164: 103-120, Anticancer Res 1998: 18; 3709-3716, Physiol Rev 2004: 84: 1155-1228; Exp Derm 2009: 19; 760-763). Consistent with their neural crest-origin, melanocytes have preserved sensory (expression of wide range of receptors), regulatory (production of classical stress neurotransmitters, neuropeptides and neurohormones (Endocrine Rev 2000: 21; 457-487, Physiol Rev 2000: 80: 979-1020, FASEB J 2001: 15: 1678-1693, Front Biosci 2006: 11; 2230-2248, FASEB J 2005: 19: 176-194, Trend End Metab 2008: 19: 17-24) and computing properties that allow them to serve as primitive “neurons of the skin” (Exp Derm 2009: 19; 760-76). These neuroendocrine activities of melanocytes are profoundly regulated by environmental stimuli including UVR and biological and chemical insults and the production of the signaling molecules is hierarchical and displays typical negative or positive feedback loops, following the algorithms of classical neuroendocrine axes (e.g. hypothalamic pituitary adrenal axis (Mol Cell Endocrinol 2007: 265-266: 143-149), hypothalamo-pituitary-thyroid axis (J Invest Dermatol 2002: 119: 1449-1455, J Clin Endocrinol Metab 2008: 93; 4381-4388) serotoninergic/melatoninergic (FASEB J 2005: 19: 176-194, Trend End Metab 2008: 19: 17-24), catecholaminergic (Exp Dermatol 2008: 17: 395-404) and cholinergic systems (J Invest Dermatol 2006: 126: 1948-1965)). Melanocyte-derived signals may also activate cutaneous sensory nerve endings to alert the central nervous system (Endocrine Rev 2000: 21; 457-487, Exp Derm 2009: 19; 760-76). Also melanocytes might contain receptors for visible and UV spectra of solar radiation, as originally proposed by M. Lerner and J. Pawelek, respectively, a subject deserving future careful studies. These remarkable capabilities of melanocytes indicate that they are far more than simple pigment producing cells but represent an important element of the local neuroendocrine system defining them as sensory and regulatory neuroendocrine computing systems that have co-evolved during the evolution of stress response systems in vertebrates and perhaps non-vertebrates.

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