Synergistic effect of 1,25-dihydroxyvitamin D3 and retinoic acid in inducing U937 cell differentiation.
We examined the effects of retinoic acid (RA), 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), and its synthetic analogue, 22-oxa-1,25-(OH)2D3, on differentiation of U937 cells by studying the cellular growth, surface marker expression and cytosolic free Ca2+ concentration ([Ca2+]i). RA inhibited cellular growth but did not induce expression of Mo2 (CD14), a monocyte/macrophage specific surface marker. To the contrary, 1,25-(OH)2D3 did not inhibit cellular growth, but increased CD 14-positive cells. Simultaneous addition of 1,25-(OH)2D3 and RA had no additive effect on cellular growth inhibition or CD14 expression. With regard to [Ca2+]i, however, 5 days' incubation with either of them increased the basal [Ca2+]i level and induced U937 cells to respond to formyl-methionyl-leucyl-phenylalanine (FMLP). When the cells were incubated with both 10(-6) M RA and 10(-8) M 1,25-(OH)2D3, basal [Ca2+]i was higher and FMLP caused a greater increase in [Ca2+]i than when only RA or 1,25-(OH)2D3 was added. These data suggest that RA and 1,25-(OH)2D3 induce monocytoid differentiation in U937 cells through different pathways and act synergistically in the differentiation process. The 22-oxa-1,25-(OH)2D3 induced CD14 expression, basal [Ca2+]i increase and [Ca2+]i response to FMLP, but did not cause cellular growth inhibition in U937 cells, and in these points, 22-oxa-1,25-(OH)2D3 exhibited no significantly different effects from 1,25-(OH)2D3. Thus, 22-oxa-1,25-(OH)2D3 has the same potent activity as 1,25-(OH)2D3 in inducing differentiation of U937 cells.
Tanaka
Y
Y
Department of Pediatrics, Osaka University School of Medicine, Japan.
Shima
M
M
Yamaoka
K
K
Okada
S
S
Seino
Y
Y
D015703:Antigens, CD / Q000032:analysis; D015214:Antigens, Differentiation, Myelomonocytic / Q000032:analysis; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects*; D003600:Cytosol / Q000737:chemistry; D004357:Drug Synergism; D005434:Flow Cytometry; D006801:Humans; D018950:Lipopolysaccharide Receptors; D016403:Lymphoma, Large B-Cell, Diffuse / Q000473:pathology*; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D018950:Lipopolysaccharide Receptors; D014212:Tretinoin; D002117:Calcitriol; D002118:Calcium