Beneficial effect of pristimerin against the development of osteoporosis in ovariectomy-induced osteoporosis rats by the RANKL/TRAF6/NF-κB pathway

INTRODUCTION: Osteoporosis is a major cause of bone fracture in post-menopausal women. We evaluated the effects of pristimerin treatment on ovariectomy-induced osteoporosis, and its possible molecular mechanism. MATERIAL AND METHODS: Rats were ovariectomised and biochemical markers of bone formation were determined from serum samples. The microarchitectures of bone tissues were analyzed via micro-CT scans and Western blotting assays. The cytotoxic effects of pristimerin, the differentiation of osteoclasts, and bone reabsorption were evaluated in vitro using RAW 264.7 cells. RESULTS: Treatment with pristimerin attenuated changes in markers of bone formation and reabsorption such as creatine kinase (CK), alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), collagen type I fragments (CTX), bone Gla-protein (BGP), and osteocalcin (OC) in the serum of ovariectomised rats. It also appeared to restore the microarchitecture of bone tissue. The expression levels of TNF receptor-associated factor 6 (TRAF-6), nuclear factor κ light chain enhancer of activated B cells (NF-κB p65), and receptor activator of nuclear factor-κB ligand (RANKL) protein were significantly lower, while those of Akt and PI3K were significantly higher, in the bone tissues of the pristimerin-treated group than in negative controls. Pristimerin had no cytotoxic effect on RAW 264.7 cells and reduced the differentiation of osteoclasts, bone reabsorption, and translocation of p65 in RANKL-stimulated RAW 264.7 cells in vitro. CONCLUSIONS: Pristimerin reduces the effects of osteoporosis by restoring the altered RANKL/TRAF-6/NF-κB pathway in ovariectomised rats.