1,25-Dihydroxyvitamin D3 receptor RNA: expression in hematopoietic cells

Abstract

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] induces differentiation and inhibits proliferation of myeloid leukemic cells from various lines and patients; these effects are probably mediated through the 1,25(OH)2D3 receptor. Little is known of expression of 1,25(OH)2D3 receptor RNA in hematopoietic cells. We examined the expression and modulation of expression of 1,25(OH)2D3 receptor RNA in various proliferating and nonproliferating hematopoietic cells. Constitutive expression of 1,25(OH)2D3 receptor RNA was detected in various kinds of hematopoietic cells, including macrophages and activated T lymphocytes, as well as in cell lines KG-1 (myeloblasts), HL-60 (promyelocytes), ML-3 (myelomonoblasts), U937, THP-1 (monoblasts), K562 (erythroblasts), and S-LB1 (HTLV-1-transfected T lymphocytes). Receptor transcripts were 4.6 kilobases (kb), and no variant sizes were observed. All cell lines examined in this group also expressed 1,25(OH)2D3 receptors. Most B lymphocyte lines expressed negligible levels of 1,25(OH)2D3 receptor RNA and protein; however; analysis of a lymphoid/myeloid somatic hybrid suggested that suppression of expression of 1,25(OH)2D3 receptor RNA in B lymphocytes may be a dominant characteristic. HL-60 cells were cultured with 10(-7) mol/L 1,25(OH)2D3 for 24 to 72 hours, and levels of expression of 1,25(OH)2D3 receptor and its RNA were examined. Levels of RNA coding for the receptor were not modulated by exposure to high levels of ligand. Levels of occupied 1,25(OH)2D3 receptor protein increased in these HL-60 cells; but the total number of 1,25(OH)2D3 receptors decreased about 50% at 24 hours and returned toward normal at 72 hours. Steady-state levels of 1,25(OH)2D3 receptor RNA were not affected by terminal differentiation of HL-60 toward either granulocytes or macrophages. Nondividing macrophages from normal individuals also expressed 1,25(OH)2D3 receptor RNA. In contrast, nondividing peripheral blood lymphocytes from normal individuals did not express 1,25(OH)2D3 receptor RNA; with stimulation of proliferation of these cells, accumulation of 1,25(OH)2D3 receptor RNA increased markedly. Half-life (t1/2) of 1,25(OH)2D3 receptor RNA in T lymphocytes was short (1 hour) as determined by measuring decay of the message after addition of actinomycin D. Consistent with this short t1/2, accumulation of 1,25(OH)2D3 receptor RNA increased in cells as their protein synthesis was inhibited. Further studies are required to understand the physiologic role of 1,25(OH)2D3 receptors in myeloid cells and proliferating T lymphocytes.

1α,25-dihydroxyvitamin D3 inhibits anti-CD40 plus IL-4-mediated IgE production in vitro

“…The VD ligand-receptor complex recognizes specific DNA sequences (VDRE) localized in the promoter regions of target genes and modulates their transcription [19] (summarized in Table 4). Resting B and T cells [20] and most B cell lines [21] have been shown to lack expression of the VDR at mRNA and protein level. IL-4 caused a weak upregulation of the VDR, but failed to generate or initiate genomic transcription of the 25-hydroxyvitamin D 3 -24hydroxylase in human B lymphocytes [22].…”

Prostaglandin E2 Induces Expression of Receptor Activator of Nuclear Factor–κB Ligand/Osteoprotegrin Ligand on Pre-B Cells: Implications for Accelerated Osteoclastogenesis in Estrogen Deficiency

“…The lack of response of B220 ϩ cells to 1,25(OH) 2 D 3 may be attributable, at least in part, to the low level of expression of the receptor for 1,25(OH) 2 D 3 in B lineage lymphocytes. (28,29) Cell-to-cell contact between osteoclast progenitors and either stromal cells or pre-B cells seems essential for signaling by RANKL expressed on the surface of the latter cell types. (11) Adhesion of osteoclast progenitors to stromal cells is mediated by the binding of leukocyte function-associated antigen 1 to intracellular adhesion molecule 1, (30) whereas the binding of very late antigen 4␣ to vascular cell adhesion molecule 1 may be important for the attachment of pre-B cells to stromal cells.…”

Normal myelopoiesis but abnormal T lymphocyte responses in vitamin D receptor knockout mice

“…Expression of VDR has been detected in various normal and leukemic hematopoietic cells, including macrophages and activated T lymphocytes (8,9). Evidence from other studies strongly suggests a role for VDR in hematopoiesis: Normal and leukemic myeloid progenitor cells can be induced to differentiate into monocytes and macrophages by 1,25(OH) 2 D 3 (10)(11)(12)(13)(14); activated normal macrophages are able to synthesize 1,25(OH) 2 D 3 (15,16); and 1,25(OH) 2 D 3 inhibits proliferation of activated T lymphocytes (17) and suppresses their synthesis of GM-CSF (18), IFN-γ (19), and IL-2 (17,20).…”