Extract Inhibits LPS-Triggered Inflammation Markers and Suppresses RANKL-Induced Osteoclastogenesis in RAW264.7.

() leaf decoction, a traditional remedy prepared in North by the Hmong ethnic group, is a tea extract rich in bioactive compounds that may have therapeutic effects in arthritis and backache. Indeed, it has been demonstrated that is able to inhibit Th17 lymphocytes development and to protect mice in an experimental model of collagen-induced arthritis. By resorting to macrophage models of inflammation and osteoclastogenesis, we showed that extract significantly reduced nitric oxide synthase 2 (NOS2) activity and IL-6 production by RAW 264.7 murine cells. Moreover, demonstrated an anti-osteoclastogenic effect, as revealed by complete inhibition of TRAP-positive osteoclast formation and decreased expression of key osteoclast-related genes. This activity likely relies on the inhibition of RANK downstream signaling pathway, as the activation of non-receptor tyrosine kinase Src is reduced upon RANKL- exposure. Protective effect of against bone loss was also enlightened by collagen-induced arthritis (CIA) experiment demonstrating that, although paw edema was only weakly opposed by drinking decoction, bone and cartilage were well preserved in CIA+ mice and joint tissue expressed decreased levels of osteoclast marker genes respect to CIA control group. Maesopsin 4-O-β-D-glucoside (i.e., TAT-2, one of the main decoction bioactive components) was capable to contrast NOS2 activity, IL-6 expression and osteoclast formation, too, albeit to a lesser extent when compared to decoction. Overall, this study enlightens another cell target, macrophages, beside Th17 lymphocytes, and suggests that the anti-arthritic beneficial effects of decoction largely derives from its ability to counteract not only inflammation, but also osteoclastogenesis.