The role of excessive sun exposure in the etiology of skin cancers is well recognized. Human melanocytes respond directly to UV irradiation with increased melanin formation and inhibition of proliferation. It has been documented that the mutagenic effects of UV light, particularly in the form of UVB, result from DNA damage, mostly in the form of cyclobutane pyrimidine dimers, and pyrimidine (6,4) pyrimidone photoproducts. Previous studies on murine melanoma cells have implicated alpha-melanocyte stimulating hormone (alpha-MSH) as the mediator of the UV-induced effects on proliferation and melanogenesis. The role of alpha-MSH as a physiologic regulator of human melanocytes is controversial. So far, there has been no convincing evidence that alpha-MSH directly affects human melanocytes in a significant manner. We have just been able to demonstrate that human melanocytes respond to alpha-MSH with a marked increase in proliferation and melanogenesis. This response required establishing melanocyte cultures in the absence of cholera toxin, and maintaining them in the absence of cAMP inducers for the duration of treatment with alpha-MSH. We have also found that UV-irradiated melanocytes respond to alpha-MSH with augmentation of the UV-induced melanogenesis and enhancement of proliferation. The ability of alpha-MSH to override the inhibitory effect of UV light on the proliferation of human melanocytes might result in the persistence of the UV-induced DNA damage, which potentially can lead to carcinogenesis. We propose that alpha-MSH might act as a transducer for the effects of UV light on human melanocytes. Therefore, we will investigate the mechanisms by which UV light and alpha-MSH interact to affect human melanocyte proliferation, melanogenesis, genotoxicity and gene expression. We will compare the amount of cyclobutane pyrimidine dimers and pyrimidine (6,4) pyrimidone photoproducts in melanocytes irradiated with UV light, or irradiated with UV light then treated with alpha-MSH. We will also investigate the regulation of expression of the melanocortin receptors by alpha-MSH and UV light, and the signal transduction pathways induced by UV irradiation and alpha-MSH. Since stimulation of melanogenesis by sun exposure is directly related to the constitutive pigmentation of human skin, melanocyte strains with different constitutive melanin contents, derived from individuals with different skin types, will be used in all the studies proposed. Our results, and the reports that alpha-MSH is synthesized in the skin and by human melanoma cells suggest a role for alpha-MSH in photocarcinogenesis, as an autocrine/paracrine regulator of melanoma tumor formation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES006882-04
Application #
2684431
Study Section
Radiation Study Section (RAD)
Project Start
1995-04-01
Project End
2000-03-31
Budget Start
1998-04-01
Budget End
2000-03-31
Support Year
4
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of Cincinnati
Department
Dermatology
Type
Schools of Medicine
DUNS #
City
Cincinnati
State
OH
Country
United States
Zip Code
45221
Abdel-Malek, Z A; Scott, M C; Furumura, M et al. (2001) The melanocortin 1 receptor is the principal mediator of the effects of agouti signaling protein on mammalian melanocytes. J Cell Sci 114:1019-24
Abdel-Malek, Z; Scott, M C; Suzuki, I et al. (2000) The melanocortin-1 receptor is a key regulator of human cutaneous pigmentation. Pigment Cell Res 13 Suppl 8:156-62
Suzuki, I; Im, S; Tada, A et al. (1999) Participation of the melanocortin-1 receptor in the UV control of pigmentation. J Investig Dermatol Symp Proc 4:29-34
Can, G; Abdel-Malek, Z; Porter-Gill, P A et al. (1998) Identification and sequencing of a putative variant of proopiomelanocortin in human epidermis and epidermal cells in culture. J Invest Dermatol 111:485-91
Tada, A; Suzuki, I; Im, S et al. (1998) Endothelin-1 is a paracrine growth factor that modulates melanogenesis of human melanocytes and participates in their responses to ultraviolet radiation. Cell Growth Differ 9:575-84
Im, S; Moro, O; Peng, F et al. (1998) Activation of the cyclic AMP pathway by alpha-melanotropin mediates the response of human melanocytes to ultraviolet B radiation. Cancer Res 58:47-54
Scott, G; Cassidy, L; Abdel-Malek, Z (1997) Alpha-melanocyte-stimulating hormone and endothelin-1 have opposing effects on melanocyte adhesion, migration, and pp125FAK phosphorylation. Exp Cell Res 237:19-28
Suzuki, I; Tada, A; Ollmann, M M et al. (1997) Agouti signaling protein inhibits melanogenesis and the response of human melanocytes to alpha-melanotropin. J Invest Dermatol 108:838-42
Suzuki, I; Cone, R D; Im, S et al. (1996) Binding of melanotropic hormones to the melanocortin receptor MC1R on human melanocytes stimulates proliferation and melanogenesis. Endocrinology 137:1627-33
Medrano, E E; Im, S; Yang, F et al. (1995) Ultraviolet B light induces G1 arrest in human melanocytes by prolonged inhibition of retinoblastoma protein phosphorylation associated with long-term expression of the p21Waf-1/SDI-1/Cip-1 protein. Cancer Res 55:4047-52

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