INCREASED INVITRO EXPRESSION OF BETA(2)-ADRENOCEPTORS IN DIFFERENTIATING LESIONAL KERATINOCYTES OF VITILIGO PATIENTS

Keratinocytes were established in serum-free culture medium from lesio nal and nonlesional skin of a patient with vitiligo (skin type III) an d from an age-matched healthy control subject. Both differentiating an d undifferentiated cells were examined for the presence of beta2-adren oceptors in culture medium containing either low (0.1 x 10(-3) M) or h igh (1.5 x 10(-3) M) calcium concentrations. Binding experiments were performed with saturating levels of radiolabeled (-)-[H-3] CGP 12177, a nonselective beta-adrenergic antagonist. Controls for nonspecific bi nding were determined by the addition of the beta-adrenergic antagonis t, propranolol (5 mumol), before the introduction of (-)-[H-3] CGP 121 77 to cell cultures. Undifferentiated keratinocytes yielded the highes t expression of beta2-adrenoceptors, whereas differentiating keratinoc ytes grown in medium with a low calcium concentration (0.1 X 10(-3) M) had a significantly lower expression of receptors with the exception of vitiliginous cells, which retained high densities of receptors, sim ilar to undifferentiated cells. In addition, these vitiliginous kerati nocytes showed a defect in ''calcium uptake. In contrast, differentiat ed keratinocytes from all three cell strains, grown in medium containi ng a high calcium concentration (1.5 x 10(-3) M) revealed a significan tly lower receptor density compared to undifferentiated cells. This fi nding identified the importance of the extracellular calcium concentra tion in the expression of beta2-adrenoceptors. Our results: (1) confir med the importance of beta2-adrenoceptors in the regulation of intrace llular calcium concentrations in keratinocytes; (2) showed an increase in catecholamine receptors in differentiating vitiliginous keratinocy tes compared to cells established from nonlesional and control skin cu ltured in medium with a low calcium concentration (0.1 x 10(-3) M); an d (3) demonstrated the importance of the extracellular calcium concent ration in the down-regulation of the beta2-adrenoceptors in vitiligino us keratinocytes. These new observations further suggest an associatio n between the sympathetic nervous system and the pathogenesis of vitil igo.