Osteoporosis is a metabolic bone disease. Osteoclasts are significantly involved in the pathogenesis of osteoporosis. AS-605240 (AS) is a small molecule PI3K-γ inhibitor and is less toxic compared to pan-PI3K inhibitors. AS also exerts multiple biological effects including anti-inflammatory, anti-tumor, and myocardial remodeling promotion. However, the involvement of AS in the differentiation and functions of osteoclasts and the effect of AS in treating patients with osteoporosis is still unclear.
This study aimed to investigate if AS inhibits the differentiation of osteoclasts and resorption of the bones induced by M-CSF and RANKL. Next, we evaluated the therapeutic effects of AS on bone loss in ovariectomy (OVX)-induced osteoporosis mice models.
We stimulated bone marrow-derived macrophages with an osteoclast differentiation medium containing different AS concentrations for 6 days or 5μM AS at different times. Next, we performed tartrate-resistant acid phosphatase (TRAP) staining, bone resorption assay, F-actin ring fluorescence, real-time quantitative polymerase chain reaction (RT-qPCR), and Western blotting (WB). Next, MC3T3-E1s (pre-osteoblast cells) were differentiated to osteoblast by stimulating the cells with varying AS concentrations. Next, we performed alkaline phosphatase (ALP) staining, RT-qPCR, and WB on these cells. We established an OVX-induced osteoporosis mice model and treated the mice with 20mg/kg of AS. Finally, we extracted the femurs and performed micro-CT scanning, H&E, and TRAP staining.
AS inhibits the formation of osteoclasts and resorption of bone triggered by RANKL by inhibiting the PI3K/Akt signaling pathway. Furthermore, AS enhances the differentiation of osteoblasts and inhibits bone loss due to OVX in vivo.