Melatonin and Melanocyte Functions

Iyengar, B

doi:10.1159/000014648

Cited by 19 publications

(19 citation statements)

References 15 publications

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“…Since tubulin forms the cytoskeleton in dendrites as well as the mitotic spindle, melatonin binding to monomers appears to take place during dark incubation to divert monomers from the cytoskeleton to spindle formation. This has also been observed in organ cultures incubated in melatonin [12] where high melatonin positivity is associated with prominent mitosis.…”

Section: Discussionsupporting

confidence: 53%

Photomodulation of the Melanocyte Cell Cycle by Indoleamines

Iyengar¹

1998

Neurosignals

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Melanocytes are photoresponsive cells which respond to varying doses of UV exposure in the G₂ phase of the cell cycle by prominent dendricity. This photoresponse is related to indoleamine light sensitivity. The present study highlights the role of indoleamines in the photomodulation of the melanocyte cell cycle. The study was conducted on 40 whole-skin organ cultures taken from the marginal zone of vitiligo. Twenty organ cultures were subjected to G₂-phase arrest, while 20 were incubated in tryptamine. The organ cultures were incubated in the dark, exposed to a pulse of 120 s UV at 2 h of incubation and harvested 3 and 6 h after UV exposure. It has been reported that the photosensitive enzymes N-acetyl transferase (NAT) and hydroxyindole-o-methyl transferase (HIOMT) are activated during the G₂ phase. The conversion of serotonin to melatonin is inhibited by UV exposure as seen at 3 h. This activity recovers on continued dark incubation 6 h after UV exposure. On incubation with tryptamine, UV exposure results in utilisation of tryptamine as seen by prominent indoleamine positivity. Three hours after UV exposure, there is 75% dendricity indicating G₂ phase traverse. There is a corresponding high serotonin positivity with a low melatonin positivity. This is reversed following 6 h of dark incubation with high melatonin positivity indicating reactivation of NAT and HIOMT. This is accompanied by a doubling of the melanocyte number due to mitotic traverse and an arrest in G₁ phase with low utilisation of tryptamine. Thus tryptamine is utilised by melanocytes on UV exposure to be synchronised and traversed into G₂ phase activating the photosensitive enzymes NAT and HIOMT. When followed by a dark phase, melatonin accumulates to traverse the melanocytes through M-phase of the cell cycle with doubling of the cell number. Thus the uptake and metabolisation of indoleamine precursors photomodulate the melanocyte cell cycle on UV exposure.

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Section: Discussionsupporting

confidence: 53%

Photomodulation of the Melanocyte Cell Cycle by Indoleamines

Iyengar¹

1998

Neurosignals

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“…The melanopsin system of mammals, expressed in a small subset of retinal ganglion cells, regulating and adjusting circadian rhythms, to the environmental light/dark cycle, known as photoentrainment, was in fact isolated from the photosensitive dermal melanophores of frogs Xenopus laevis responding to light (Daniolos et al 1990; Provencio et al 1998, 2000). Extensive studies on the melanocytes by the present author reveal that these fascinating and versatile cells form a photoresponsive network which reads the environmental seasonal variations in the light cycles (Iyengar 1992ab, 1994, 1996a, 1998abc, 2000) in the same manner. The present work was undertaken to study the organization of this system in the human skin.…”

Section: Introductionmentioning

confidence: 76%

The melanocyte photosensory system in the human skin

Iyengar¹

2013

SpringerPlus

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The pigment cells form the largest population of neural crest cells to migrate into the epidermis and hair follicle along each dermatomic area from the neural folds. The melanopsin system responsible for photoentrainment, was isolated from the photosensitive dermal melanophores of frogs Xenopus laevis responding to light. Melanocytes form a photoresponsive network which reads the environmental seasonal variations in the light cycles in the same manner. The present work was undertaken to study the organization of this system by: I. Experimental assessment of photoresponse and II. Evidence of an organized system of photoreception in the skin. Melanocytes, in whole skin organ cultures and epidermal strips, from margin of vitiligo in G2 phase show prominent dendricity, and express pigment, biogenic amines and hormones on UV exposure. The photoresponse depends on the photosensitive enzymes NAT/HIOMT and dopaoxidase. Melanocytes interact with adjacent keratinocytes, dermal capillaries, and nerve endings. The melanocyte network reads the diurnal and seasonal photophase by the melatonin/serotonin switch like the pineal. Sleep disorders and winter depression are corrected by phototherapy utilising this mechanism. Melanocytes showing photoactivity, aplasia, hypoplasia and hyperplasia, and interactive keratinocytes occupy the trigeminal, brachial and lumbosacral dermatomes, zones of high embryonic induction, forming an ectodermal placodal system. Melanin units and hair follicles serve as photoreceptors. Migration of active melanocytes to defined areas is evident in pigment patterns in guinea pigs. This study identifies defined photoreceptor melanocyte/epidermal domains which read the seasonal photophase and control the sleep waking cycle in response to the environmental light. I. Whole skin organ cultures, and epidermal strips from margin of vitiligo in G2 phase are exposed to UV and IR to study sequential and dose response of marginal melanocytes, using histochemistry, immunohistochemistry to assess pigment, biogenic amines and hormones on UV exposure. II. Dermatomic Distributions: Detailed maps of melanocyte photoresponse in 356 biopsies, lesions in 297 vitiligo, 100 melanosis, 165 melanomas 142 leprosy and 442 basal cell/keratinocytes lesions were assessed for patterns of dermatomic distribution. Embryonal melanocyte migration along dermatomes was assessed in 285 guinea pigs from an inbred colony having black, brown and white patches.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-158) contains supplementary material, which is available to authorized users.

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“…Earlier studies have identified the presence of biogenic amines in melanocytes. These include catechol amines as well as indole amines [2][3][4][5][6][7].…”

Section: Discussionmentioning

confidence: 99%

“…Since this activity is cyclical with light and dark phases, both SER & MLT are expressed in these layers. In turn, the indoleamines modulate the melanocyte cell cycle in response to UV exposure [4][5][6][7].…”

Section: Discussionmentioning

confidence: 99%