Levels of beta-endorphin in the plasma and skin tissue fluids of patients with vitiligo

New Treatment Modalities for Vitiligo

The development of effective treatment modalities for vitiligo is dependent on an understanding of the events leading to depigmentation. However, the exact pathogenesis of vitiligo is still mostly unknown. Abnormalities in both humoral and cell-mediated immunity have been documented in vitiligo patients and they present a basis for using immunomodulating agents, such as corticosteroids and macrolide immunomodulators, in the treatment of vitiligo. Macrolide immunomodulators, such as tacrolimus and pimecrolimus, which can be used topically, are known as topical immunomodulators (TIMs). TIMs inhibit the action of calcineurin, and consequently inhibit T-cell activation and the production of various cytokines; this is considered the working mechanism of action of TIMs in vitiligo. Several small studies and case reports on the use of TIMs in vitiligo have been published so far. Tacrolimus achieves better results on the face and neck than on other body areas. Particular advantages of TIMs are safety in treating these areas because of lack of skin atrophy and good tolerability. The incidence of application site adverse events in vitiligo seems to be lower than in the treatment of atopic dermatitis. On the face and neck, TIMs may become a useful tool in the treatment of adults and children with vitiligo despite possibly lower efficacy than topical corticosteroids. Further, larger, controlled clinical studies are warranted to determine the definite role of TIMs as monotherapy or in combination with other modalities in the treatment of vitiligo.

Regulation of human epidermal melanocyte biology by beta-endorphin

beta-Endorphin is an opioid peptide cleaved from the precursor pro-hormone pro-opiomelanocortin, from which other peptides such as adrenocorticotropic hormone, beta-lipotropic hormone, and alpha-melanocyte-stimulating hormone are also derived. alpha-Melanocyte-stimulating hormone and adrenocorticotropic hormone are well documented to regulate human skin pigmentation via action at the melanocortin-1 receptor. Whereas plasma beta-endorphin is reported to increase after exposure to ultraviolet radiation, to date a functional role for beta-endorphin in the regulation of human epidermal melanocyte biology has not been demonstrated. This study was designed to examine the involvement of the beta-endorphin/mu-opiate receptor system in human epidermal melanocytes. To address this question we employed reverse transcription-polymerase chain reaction, and immunohistochemistry/cytochemistry and immunoelectron microscopy using beta-endorphin and mu-opiate receptor specific antibodies. A functional role for beta-endorphin was assessed in epidermal melanocyte cultures by direct stimulation with the peptide. This study demonstrated the expression of mu-opiate receptor mRNA in cultured epidermal melanocytes, as well as mRNA for pro-opiomelanocortin. In addition, we have shown that beta-endorphin and mu-opiate receptor are expressed at the protein level in situ in glycoprotein100-positive melanocytes. The expression of both beta-endorphin and mu-opiate receptor correlated positively with their differentiation status in vitro. Furthermore, immunoelectron microscopy studies revealed an association of beta-endorphin with melanosomes. Functional studies showed that beta-endorphin has potent melanogenic, mitogenic, and dendritogenic effects in cultured epidermal melanocytes deprived of any exogenous supply of pro-opiomelanocortin peptides. Thus, we report that human epidermal melanocytes express a fully functioning beta-endorphin/mu-opiate receptor system. In the absence of any data showing cross-talk between the mu-opiate receptor and the melanocortin-1 receptor, we conclude that the beta-endorphin/mu-opiate receptor system participates in the regulation of skin pigmentation.