Aqueous extract of Codium fragile alleviates osteoarthritis through the MAPK/NF-κB pathways in IL-1β-induced rat primary chondrocytes and a rat osteoarthritis model

Codium fragile (Suringar) Hariot has been used as a potential remedy in traditional medicine because of its anti-inflammatory and anti-oxidant effects. Osteoarthritis is a chronic progressive joint disease, characterized by complex mechanisms related to inflammation and degeneration of articular cartilage. In this study, we aimed to evaluate the cartilage protective effect of an aqueous extract of Codium fragile (AECF) using rat primary chondrocytes and the osteoarthritis animal model induced by destabilization of the medial meniscus (DMM). In vitro, rat primary cultured chondrocytes were pre-treated with AECF (0.5, 1, and 2 mg/mL) for 1 h and then incubated with interleukin-1β (10 ng/mL) for 24 h. Nitrite production was detected by the Griess reagent. Alteration of the protein levels of iNOS, MMP-13, ADAMTS-4, ADAMTS-5, mitogen-activated protein kinases (MAPKs), and nuclear factor-κB (NF-κB) was detected by western blotting. In vivo, osteoarthritis was induced by DMM of Sprague Dawley (SD) rats. The rats subjected to destabilization of the medial meniscus (DMM) surgery were orally administered with AECF (50, 100, and 200 mg/kg bodyweight) or distilled water for 8 w. The severity of cartilage lesions was evaluated by safranin O staining and the Osteoarthritis Research Society International (OARSI) score. These results demonstrated that AECF significantly inhibited nitrite production and inhibited the levels of iNOS, MMP-13, ADAMTS-4, and ADAMTS-5 in interleukin-1β-induced rat primary cultured chondrocytes. Moreover, AECF suppressed interleukin-1β-induced NF-κB activation in the nucleus and phosphorylation of ERK1/2 and JNK in the cytosol. In vivo, the cartilage lesions in AECF‐treated osteoarthritis rats exhibited less proteoglycan loss and lower OARSI scores. These results suggested that AECF is a potential therapeutic agent for the alleviation of osteoarthritis progression.