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Proc Natl Acad Sci U S A., 2006; 103(12): 4729-34, PMID: 16537392

Reveromycin A, an agent for osteoporosis, inhibits bone resorption by inducing apoptosis specifically in osteoclasts

Jahr: 2006

Woo JT, Kawatani M, Kato M, Shinki T, Yonezawa T, Kanoh N, Nakagawa H, Takami M, Lee KH, Stern PH, Nagai K, Osada H
Department of Biological Chemistry, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan. jwoo@isc.chubu.ac.jp

Abstract

Mature bone-resorbing osteoclasts (OCs) mediate excessive bone loss seen in several bone disorders, including osteoporosis. Here, we showed that reveromycin A (RM-A), a small natural product with three carboxylic groups in its structure, induced apoptosis specifically in OCs, but not in OC progenitors, nonfunctional osteoclasts, or osteoblasts. RM-A inhibited protein synthesis in OCs by selectively blocking enzymatic activity of isoleucyl-tRNA synthetase. The proapoptotic effect of RM-A was inhibited by neutralization or disruption of the acidic microenvironment, a prominent characteristic of OCs. RM-A was incorporated in OCs but not in nonfunctional osteoclasts and OC progenitors in neutral culture medium. Effects of RM-A on OC apoptosis increased under acidic culture conditions. RM-A not only was incorporated, but also induced apoptosis in OC progenitors in acidic culture medium. RM-A inhibited osteoclastic pit formation, decreased prelabeled (45)Ca release in organ cultures, and antagonized increased bone resorption in ovariectomized mice. These results suggested that preventive effects of RM-A on bone resorption in vitro and in vivo were caused by apoptosis through inhibition of isoleucyl-tRNA synthetase in OCs and that specific sensitivity of OCs to RM-A was due to the acidic microenvironment, which increased cell permeability of RM-A by suppressing dissociation of protons from carboxylic acid moieties, making them less polar. This unique mechanism suggested that RM-A might represent a type of therapeutic agent for treating bone disorders associated with increased bone loss.

GID: 903; Letzte Änderung: 23.01.2008