Ectoine Inhibits IL-1β-Induced Inflammation by Suppressing the NF-κB Pathway in Chondrocytes and Alleviates Osteoarthritis in a Rat Model

Background: Osteoarthritis (OA) is a degenerative joint disease characterized by inflammation and cartilage destruction, partly mediated by interleukin (IL)-1β-induced nucle factor (NF)-κB activation. Ectoine (Ec) is a natural osmoprotectant with anti-inflammatory properties; however, its effects on NF-κB signaling in OA remain unclear. This study investigated whether ectoine attenuates IL-1β-induced inflammation in chondrocytes by suppressing NF-κB activation and mitigates OA progression in a rat model. Methods: Primary rat chondrocytes were pretreated with ectoine (0–3.0% w/v) and then stimulated with IL-1β (10 ng/mL). Cell viability was evaluated. RT-qPCR and Western blotting were used to determine the expression of inflammatory markers (inducible nitric oxide synthase [iNOS], cyclooxygenase [COX]-2, tumor necrosis factor [TNF]-α, and matrix metalloproteinase [MMP]-3/13), and NF-κB pathway activity was assessed through p65 phosphorylation and inhibitor of NF-κB alpha (IκBα) degradation. In vivo, OA was induced using the modified Hulth method, followed by intra-articular injection of ectoine alone or combined with hyaluronic acid (HA). Cartilage integrity was assessed using Osteoarthritis Research Society International (OARSI) scoring at 8 weeks. Results: Ectoine at 1.5% significantly inhibited IL-1β-induced NF-κB activation, reducing p65 phosphorylation by 59% and IκBα degradation by 41%. This inhibition decreased proinflammatory mediators (iNOS 43%, COX-2 35%, TNF-α 41%) and matrix-degrading enzymes (MMP-3 23%, MMP-13 31%), while increasing type II collagen by 84%. In vivo, ectoine reduced cartilage erosion (OARSI score: 7.0 vs. 10.2 in OA group). The Ec–HA combination improved cartilage retention by 43% compared with ectoine alone. Conclusions: These preclinical findings suggest that ectoine was associated with reduced NF-κB activation markers and attenuated OA-like changes in rat models. The enhanced effect observed with HA supports further investigation of combined therapeutic strategies for OA management.