What is the function of melanin?

Morison, W. L.

doi:10.1001/archderm.121.9.1160

Cited by 29 publications

(25 citation statements)

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“…Even in the absence of melanocytes, vitiligous skin showed high values of sun protection factor after repeated exposure to UV radiation (Morison 1985). Whilst our model does not provide an explanation for the hyperproliferation of keratinocytes noted in vivo (Pearse et al 1987, Hashimoto et al 1991 and in vitro (Dissanayake et al 1993) after direct exposure to UV irradiation, the results show that UV exposure causes keratinocytes to release a soluble factor or factors which promote cornification.…”

Section: Discussioncontrasting

confidence: 53%

Modulation of skin cell functions by transforming growth factor-beta1 and ACTH after ultraviolet irradiation

Dissanayake

Mason²

1998

Journal of Endocrinology

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The adaptive responses in skin to ultraviolet (UV) radiation include increased cornification of keratinocytes and increased synthesis and distribution of melanin by melanocytes.The possible involvement of paracrine factors in the generation of these responses was studied in a novel twostage culture model. Human melanocytes or keratinocytes were first irradiated or sham-irradiated and then the conditioned media collected from these cells after 24 h were used to treat unirradiated skin cells.Immunofluorescent staining for transforming growth factor (TGF)-1 was increased in UV-irradiated keratinocytes compared with sham-irradiated cells. Increased TGF-1 was also detected in the culture media of irradiated keratinocytes. Treatment of unirradiated keratinocytes with conditioned media collected from UVirradiated keratinocytes resulted in increased absolute numbers and percentages of cornified envelopes per well compared with treatment with conditioned media from sham-irradiated keratinocytes. The magnitude of this effect increased with increased dose of initial irradiation. The effects of conditioned media from UVR-treated cells were mimicked by authentic TGF-1. Treatment of conditioned media from irradiated cells with an antibody shown to neutralise the effects of TGF-1 but not with a non-immune antibody of similar isotype, abolished this bioactivity of the conditioned media from UV-irradiated cells. Immunofluorescent staining for ACTH was also increased in UV-irradiated keratinocytes. Conditioned media from UV-irradiated keratinocytes increased tyrosinase activity of unirradiated melanocytes, an effect which was mimicked by authentic ACTH. This bioactivity of conditioned media from irradiated keratinocytes was abolished in the presence of an antibody which neutralised the activity of ACTH but not MSH. These results provide evidence to support the involvement of TGF-1 and ACTH in the cornification and pigmentary responses respectively of skin cells after UV exposure.

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Section: Discussioncontrasting

confidence: 53%

Modulation of skin cell functions by transforming growth factor-beta1 and ACTH after ultraviolet irradiation

Dissanayake

Mason²

1998

Journal of Endocrinology

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“…In a time course study however, after solar-simulated irradiation, cornified envelope formation was maximally increased at the 72 hour time point, the latest time point studied. Repeated exposure of vitiligous skin to UVR has been said to induce high values of sun protection factor even in the absence of melanocytes (Morson, 1985). It is likely that this protection is brought about by the increased thickness of epidermis due to the increased proliferation of keratinocytes and increased formation of the cornified layer (Blank, 1987).…”

Section: Discussionmentioning

confidence: 99%

Effects of ultraviolet irradiation on human skin‐derived epidermal cells in vitro

Dissanayake

Greenoak

Mason

1993

Journal Cellular Physiology

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The effects of UVA, mixed UVA + B, and solar-simulated irradiation were examined in human keratinocytes and melanocytes cultured in vitro. Irradiation with UVA, UVA + B, or the solar simulator caused a dose-dependent decrease in keratinocyte cell numbers and thymidine incorporation at 24 hours, with recovery after 48 and 72 hours. Divided dose regimens reduced the inhibitory effect of ultraviolet (UV) irradiation on cell numbers measured 24 hours after the last irradiation. Exposure to both UVA and UVA + B increased formation of cornified envelopes. Similar irradiance doses of UVA 80 minutes (1.12 J/cm2) and UVA + B 40 minutes (1.04 J/cm2) caused 2.4- and 3.3-fold increases in cornified envelope formation, respectively. With solar-simulated irradiation, the cornified envelope formation was increased by 3.5-fold after exposure of 8 minutes (2.6 J/cm2). Irradiation of melanocytes with UVA, UVA + B, or solar-simulated irradiation resulted in a dose-dependent decrease in melanocyte numbers after 24 hours compared with sham-irradiated controls. As a result of UV irradiation, tyrosinase activity of melanocytes measured at 24 hours was stimulated. UVA + B irradiation (1.04 J/cm2) increased tyrosinase activity approximately twofold, while UVA alone (1.1 J/cm2) increased tyrosinase four to sixfold and solar-simulated irradiation (1.3 J/cm2) increased tyrosinase approximately twofold compared to the control cells. Melanin content increased in cells after both UVA and mixed UVA + B irradiation. These results indicate that both UVA and mixed UVA + B irradiation had qualitatively similar effects on the proliferative and functional activity of skin-derived cells but that the type of irradiation and the dosage regimen affect the dose-response relationship.

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“…The sunscreen function of melanin was also questioned in a recent review article in the dermatological literature [10]. Biochem ical work of the last decade has presented evidence that natural human melanin is a mixture of eu-and pheomelanins [13].…”

Section: Discussionmentioning

confidence: 99%

Long-Term Actinic Damage in Sun-Exposed Vitiligo and Normally Pigmented Skin

Calanchini-Postizzi

Frenk

1987

Dermatology

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Vitiligo provides a model system for studying chronic actinic damage in skin devoid of melanin pigments and thereby permits assessment of their photoprotective function. Our study comprised 23 patients with a mean age of 67 years having stable, long-lasting vitiligo on light-exposed body regions. The vitiliginous and normally pigmented, light-exposed skin was examined clinically for manifestations of chronic actinic damage. In 11 patients skin biopsies were obtained from vitiliginous and adjacent pigmented skin for qualitative and quantitative histological comparison. Our study did not reveal evidence for a significant increase of chronic actinic damage in skin devoid of melanin pigments. These results are in agreement with the rareness of reported skin cancer in vitiligo.

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What is the function of melanin?

Cited by 29 publications

References 0 publications

Modulation of skin cell functions by transforming growth factor-beta1 and ACTH after ultraviolet irradiation

Modulation of skin cell functions by transforming growth factor-beta1 and ACTH after ultraviolet irradiation

Effects of ultraviolet irradiation on human skin‐derived epidermal cells in vitro

Long-Term Actinic Damage in Sun-Exposed Vitiligo and Normally Pigmented Skin

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