Isorhapontigenin Suppresses Interleukin-1β-Induced Inflammation and Cartilage Matrix Damage in Rat Chondrocytes

Osteoarthritis (OA) is a common cause of joint pain and physical disability in the elderly. It is highly associated with local inflammatory reactions and cartilage degradation. Isorhapontigenin (ISO), a natural compound existing in various plants, has shown prominent anti-inflammatory and anti-oxidative properties in several inflammatory diseases. However, the effects of ISO on OA remain to be elucidated. Here, we investigated the effects of ISO on interleukin-1β (IL-1β)-treated rat chondrocytes and cartilage explants. Our results revealed that ISO could suppress the IL-1β-induced elevated levels of nitric oxide (NO), inducible nitric oxide synthase (iNOS), prostaglandin E2 (PGE2), and cyclooxygenase-2 (COX2). Besides, ISO could also inhibit the IL-1β-induced up-regulation of cartilage matrix catabolic enzymes such as matrix metalloproteinases (MMPs) and aggrecanase-2 (ADAMTS5). Moreover, the IL-1β-induced downregulation of collagen II and aggrecan could be reversed by ISO. Furthermore, ISO prevented rat cartilage explant damage induced by IL-1β. Mechanistically, ISO worked partly by suppressing mitogen-activated protein kinase (MAPK)-associated ERK and p38 pathways. Taken together, our study indicated the anti-inflammatory potential of ISO on IL-1β-treated rat chondrocytes, providing a new idea for OA treatment.