Capsaicin, TRPV1 ligand, suppresses inflammatory bone resorption

Abstract

Capsaicin, a pungent component in capsicum, is a ligand for TRPV1 (transient receptor potential vanilloid 1)which regulates nerve-related pein-sensitive signal and inflammation. However, the effects of capsaicin on bone metabolism are not elucidated. We have showed that capsaicin inhibited LPS-induced osteoclast differentiation and bone resorbing activity. The receptor of capsaicin, TRPV1 was only expressed in osteoblasts but not in macrophages and osteoclast precursor cells. In osteoblasts, capsaicin suppressed PG (prostaglandin) E₂ production through the downregulation of COX (cyclooxygenase)-2 and mPGES (membrane-bound PGE synthase)-1 expression, resulting in suppression of RANKL (receptor activator of NF-κB ligand) expression. In vivo study, intraperitoneally injection of LPS resulted in severe bone loss in the femur and treatment of capsaicin attenuated its bone loss. Current reports showed that capsaicin has a protective effect on periodontal bone resorption through a nerve system-mediated mechanism, and other report suggested capsaicin has abilities to direct inhibition of periodontal pathogens. Controversially, TRPV1 knockout mice have shown resistance to periodontal disease. In this review, we described the effects of capsaicin on inflammatory bone diseases. We suggest functional food capsaicin is one of a candidate for maintaining bone health.