p300/CBP inhibitor A-485 inhibits the differentiation of osteoclasts and protects against osteoporotic bone loss

Osteoporosis is one of the most common metabolic bone diseases among pre- and post-menopausal women. Despite numerous advances in the treatment of osteoporosis in recent years, the outcomes remain poor due to severe side effects. In this study, we investigated whether A-485, a highly selective catalytic p300/CBP inhibitor, could attenuate RANKL-induced osteoclast differentiation and explored the underlying molecular mechanisms. The protective role of A-485 in osteoporosis was verified using a mouse model of ovariectomy (OVX)-induced bone loss and micro-CT scanning. A-485 inhibited RANKL-induced osteoclast differentiation in vitro by reducing the number of tartrate-resistant acid phosphatase-positive osteoclasts without inducing significant cytotoxicity. In particular, A-485 dose-dependently disrupted F-actin ring formation and downregulated the expression of genes associated with osteoclast differentiation, such as CTSK, c-Fos, TRAF6, VATPs-d2, DC-STAMP, and NFATc1, in a time- and dose-dependent manner. Moreover, A-485 inhibited the RANKL-induced phosphorylation of MAPK pathways and attenuated OVX-induced bone loss in the mouse model while rescuing the loss of bone mineral density. Our in vitro and in vivo findings suggest for the first time that A-485 has the potential to prevent postmenopausal osteoporosis and could therefore be considered as a therapeutic molecule against osteoporosis.

骨质疏松症是绝经前和绝经后女性中最常见的代谢性骨病之一。尽管近年来在骨质疏松症的治疗方面取得了众多进展，但由于严重的副作用，治疗效果仍然不佳。在本研究中，我们探讨了一种高选择性的p300/CBP催化抑制剂A - 485是否能够减弱核因子κB受体活化因子配体（RANKL）诱导的破骨细胞分化，并探究了其潜在的分子机制。通过卵巢切除（OVX）诱导的骨丢失小鼠模型和微型计算机断层扫描（micro - CT）验证了A - 485在骨质疏松症中的保护作用。A - 485在体外通过减少抗酒石酸酸性磷酸酶阳性破骨细胞的数量来抑制RANKL诱导的破骨细胞分化，且未引起明显的细胞毒性。特别是，A - 485以时间和剂量依赖的方式，剂量依赖性地破坏F - 肌动蛋白环的形成，并下调与破骨细胞分化相关的基因的表达，如组织蛋白酶K（CTSK）、c - Fos、肿瘤坏死因子受体相关因子6（TRAF6）、空泡型ATP酶 - d2（VATPs - d2）、树突状细胞特异性跨膜蛋白（DC - STAMP）和活化T细胞核因子c1（NFATc1）。此外，A - 485抑制RANKL诱导的丝裂原活化蛋白激酶（MAPK）通路的磷酸化，并减轻小鼠模型中卵巢切除诱导的骨丢失，同时挽救骨矿物质密度的降低。我们的体外和体内研究结果首次表明，A - 485具有预防绝经后骨质疏松症的潜力，因此可被视为一种治疗骨质疏松症的分子。