Human leukemic (HMC-1) mast cells are responsive to 1 alpha,25-dihydroxyvitamin D-3: Selective promotion of ICAM-3 expression and constitutive presence of vitamin D-3 receptor

Expression levels of adhesion molecules on HMC-1 mast cells were examined p rior to and following administration of 1 alpha,25-dihydroxyvitamin D-3 [1, 25(OH)(2)D-3]. While most receptors (including ICAM-1) remained unchanged b y the treatment, solely ICAM-3 expression was promoted in a dose- and time- dependent fashion, peaking at 50 nM of 1,25(OH)(2)D-3 and 72 h, illustratin g that like other myeloid cells, human mast cells are 1,25(OH)(2)D-3 respon sive, yet in a highly selective manner. Flow cytometric results were confir med by ELISA, by semiquantitative RT-PCR, and functionally by showing enhan ced anti-ICAM-3 mediated homotypic aggregation of 1,25(OH)(2)D-3 pretreated cells. Since cellular responsiveness is conferred by the vitamin D-3 recep tor (VDR), we examined human mast cells for its expression. VDR was constit utively present in both HMC-1 and skin mast cells by RT-PCR technique and i n nuclear extracts of HMC-1 cells by Western blot analysis. Our data thus s uggest that human mast cells are direct targets of 1,25(OH)(2)D-3 action. ( C) 2000 Academic Press.