1α,25-Dihydroxyvitamin D 3-26,23-lactam analogues function as vitamin D receptor antagonists in human and rodent cells

Abstract

(23 S,25 S)- N-Benzyl-1α,25-dihydroxyvitamin D 3-26,23-lactam ((23 S,25 S)- N-benzyl-1α,25-(OH) 2D 3-26,23-lactam, (23 S,25 S)-DLAM-1P) antagonizes nuclear vitamin D receptor (VDR)-mediated differentiation of human promyelocytic leukemia (HL-60) cells [Y. Kato, Y. Nakano, H. Sano, A. Tanatani, H. Kobayashi, R. Shimazawa, H. Koshino, Y. Hashimoto, K. Nagasawa, Synthesis of 1α,25-dihydroxy vitamin D 3-26,23-lactams (DLAMs), a novel series of 1α,25-dihydroxy vitamin D 3 antagonist, Bioorg. Med. Chem. Lett. 14 (2004) 2579–2583]. To enhance its VDR antagonistic actions, we synthesized multiple analogues of 1α,25-(OH) 2D 3-26,23-lactam. Among these analogues, (23 S,25 S)- N-phenetyl-1α,25-(OH) 2D 3-26,23-lactam, ((23 S,25 S)-DLAM-2P) had the strongest VDR binding affinity, which was 3 times higher than that of (23 S,25 S)-DLAM-1P. The 1α,25-(OH) 2D 3-26,23-lactam analogues never induced HL-60 cell differentiation even at 10 −6 M, but (23 S,25S)-DLAM-1P and (23 S,25 S)-DLAM-2P significantly and dose-dependently inhibited HL-60 differentiation induced by 10 −8 M 1α,25-dihydroxyvitamin D 3 (1α,25-(OH) 2D 3). These compounds also inhibited human and mouse cultures of osteoclast formation by marrow cells treated with 1α,25-(OH) 2D 3. Moreover, the 1α,25-(OH) 2D 3-26,23-lactam analogues minimally induced 25-hydroxyvitamin D 3-24-hydroxylase gene expression in HL-60 cells and human and mouse osteoblastic cells, but 10 −6 M (23 S,25 S)-DLAM-1P or (23 S,25 S)-DLAM-2P significantly blocked 24-hydroxylase gene expression induced by 10 −8 M 1α,25-(OH) 2D 3. (23 S,25 S)-DLAM-2P was 5–12 times more potent as a vitamin D antagonist than (23 S,25 S)-DLAM-1P in HL-60 cells, human and mouse bone marrow cultures. These results demonstrate that (23 S,25 S)-DLAM-1P and (23 S,25 S)-DLAM-2P antagonize HL-60 cell differentiation and osteoclast formation by human and mouse osteoclast precursors induced by 1α,25-(OH) 2D 3 through blocking VDR-mediated gene transcription. In contrast, (23 S)-25-deoxy-1α-hydroxyvitamin D 3-26,23-lactone, which only blocks human VDR, these vitamin D antagonists can block VDR in human cells and rodent cells.