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Pigmented melanocytes are protected against ultraviolet-A-induced membrane damage
1Department of Biophysics, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway. egil.kvam@labmed.uio.no
Abstract:
The dominant skin pigment melanin is believed to protect human skin against several harmful effects of ultraviolet radiation. It is not clear, however, how melanin located inside melanin-producing melanocytes modulates the effect of ultraviolet radiation on melanocytes themselves. We have determined membrane damage in pigmented and unpigmented albino mouse melanocytes after ultraviolet A radiation, which is suspected to induce melanoma. Unpigmented cells were much more susceptible to ultraviolet-A-induced membrane permeability than pigmented cells. Unpigmented cells were also more susceptible to ultraviolet-A-induced lipid peroxidation than strongly pigmented cells. Furthermore, unpigmented cells were much more susceptible to ultraviolet-A-induced depletion of glutathione than pigmented cells. Reduced glutathione is known to be a major antioxidant of unpigmented skin cells such as fibroblasts and keratinocytes. To examine whether or not glutathione is also a major antioxidant in melanocytes, melanocytes were depleted of glutathione by means of buthionine sulfoximine. We found that depletion of glutathione in pigmented melanocytes did not change lipid damage induced by ultraviolet A radiation. In unpigmented melanocytes, however, depletion of glutathione significantly increased lipid damage induced by ultraviolet A radiation. Thus, pigmented melanocytes apparently contain antioxidants more potent than glutathione, protecting them from ultraviolet-A-induced membrane damage.
Insights
Melanin protects skin cells from UV radiation damage. Pigmented melanocytes have potent antioxidants, unlike unpigmented cells, which are more susceptible to UV-induced damage.
Area of Science:
- Dermatology
- Cell Biology
- Photobiology
Background:
- Melanin, the primary skin pigment, is thought to shield against harmful ultraviolet (UV) radiation effects.
- The precise mechanism by which melanin within melanocytes influences UV radiation's impact on these cells remains unclear.
Purpose of the Study:
- To investigate the role of melanin in protecting melanocytes from ultraviolet A (UV-A) radiation-induced damage.
- To compare the susceptibility of pigmented and unpigmented melanocytes to UV-A radiation.
Main Methods:
- Assessing membrane damage, lipid peroxidation, and glutathione levels in pigmented and unpigmented mouse melanocytes following UV-A exposure.
- Depleting glutathione in melanocytes using buthionine sulfoximine to evaluate its antioxidant role.
Main Results:
- Unpigmented melanocytes exhibited significantly higher susceptibility to UV-A-induced membrane permeability, lipid peroxidation, and glutathione depletion compared to pigmented cells.
- Glutathione depletion did not affect UV-A-induced lipid damage in pigmented melanocytes but exacerbated it in unpigmented cells.
Conclusions:
- Pigmented melanocytes possess potent endogenous antioxidants, surpassing glutathione's protective capacity against UV-A-induced membrane damage.
- Melanin's presence confers significant protection to melanocytes against UV-A-induced cellular damage, highlighting its critical role in skin photoprotection.