The genus Rhodiola has been used to treat cough, hemoptysis, fever, pain, bruise and other symptoms which are related to injury and inflammation over a thousand years in traditional Tibetan medicine. Salidroside (p-hydroxyphenethyl-β-D-glucoside) is one of the most potent bioactive ingredients of the genus Rhodiola.The present study aimed to explore whether salidroside could alleviate the clinical symptom and sign in the early acute stage of osteoarthritis (OA) in monosodium iodoacetate (MIA) rat model, and its underlying mechanisms.Osteoarthritis (OA) was induced in rat knees by intra-articular injection of MIA; simultaneously salidroside was administered by intravenous injection. Pain behaviors were evaluated by knee-bend test, hind limb weight-bearing asymmetry and hind paw mechanical withdrawal threshold. The joint swelling was determined by the difference of knee joint diameter. Inflammatory exudates in synovial fluid were evaluated by leukocyte counting and protein content. Cytokines, chemokines, reactive oxygen species (ROS) and reactive nitrogen species (RNS) markers were determined by Enzyme-linked immunosorbent assay (ELISA) and colorimetric assay in synovial fluid. Pro-inflammatory gene expressions in synovial tissue were detected by quantitative real time RT-PCR (qRT-PCR). Nuclear factor kappa-B (NF-κB) DNA binding assay and western blot were used to determine NF-κB activation and ROS marker protein expression in synovial tissue. Glycosaminoglycan (GAG) content in the cartilage was measured by dimethylmethylene blue method. Hematoxylin and eosin (H&E), Safranin O-fast green and a modified Mankin grading system were used to evaluate the histology of articular cartilage.Salidroside could alleviate pain and joint swelling in the early acute stage of OA in rat model, reduced the number of leukocytes, total protein content, proinflammatory mediators and ROS/RNS markers in synovial fluid, down regulated the expression of proinflammatory genes in synovium, inhibited the activation of NF- κ B and oxidative stress response in synovium, promoted the synthesis of cartilage GAG, prevented the loss of proteoglycan and chondrocyte degeneration.Salidroside effectively alleviates acute symptom and sign of OA in rat model by its anti-inflammatory and antioxidant affects to inhibit synovial inflammation, which provides a new strategy to prevent the onset and progression of OA.
