The Anti-osteoarthritic Properties And Corresponding Molecular Mechanisms Of Baicalein

Osteoarthritis (OA) is the most prevalent joint disease in the old people. This disease is characterized by the degradation of articular cartilage, synovial inflammation and subchondral sclerosis. Articular cartilage degradation is the central feature of OA. All these changes lead to the clinical symptoms including pain, malformation and dysfunction of joint. A number of drugs including nonsteroidal anti-inflammatory drugs (NSAIDs), cyclooxygenase-2 (COX-2) inhibitors, glucosamine, steroids and hyaluronan (HA) were used for the treatment of OA. These drugs can alleviate the symptom of OA. However, they are not satisfied due to the side effects. For example, the selective COX-2 inhibitors might increase the risk of cardiovascular diseases while NSAIDs may injury gastrointestinal system. Moreover, current drugs are failed to reverse cartilage damage. An ideal therapeutic agent for OA would not only reduce clinical symptom, but also reverse the damage of articular cartilage. Therefore, there is a great interest in finding a novel potential biotherapeutic approaches for the treatment of OA.Baicalein is a flavonoid isolated from Scutellaria baicalensis Georgi (Huangqin). It has been shown to possess anti-inflammatory, anti-oxidative and anti-carcinogenic activities. However, whether baicalein possesses anti-osteoarthritic properties is still unknown. In the present study, we investigated the anti-osteoarthritic properties of baicalein as well as the corresponding molecular mechanisms. We first investigated the effects of baicalein on the expression of matrix metalloproteinase-1 (MMP-1), MMP-3, MMP-13 in interleukin-1p (IL-1β)-induced human chondrocytes. We found that baicalein inhibited the gene expression of MMP-1, MMP-3 and MMP-13 in chondrocytes at both mRNA and protein levels. Next, we investigated the molecular mechanisms about the inhibitory effects on MMPs of baicalein. We found that baicalein inhibited IL-β-induced phosphorylation of extracellular signal regulated kinase (ERK) and p38 as well as the degradation of IκBα. The in vivo study in rabbit model of OA induced by anterior cruciate ligament transection (ACLT) showed that baicalein suppressed cartilage degradation. These results demonstrate that baicalein possesses anti-osteoarthritic properties.Part 1 The effects of baicalein on MMPs expression in human chondrocytesObjective:To investigate the effects of baicalein on MMPs expression in IL-1β-induced human chondrocytes.Methods:Specimens were obtained from patients underwent total knee arthroplasty after consent for chondrocyte culture. Human chondrocytes were pre-treated with various concentration of baicalein, followed by stimulation with IL-1βExpression levels of MMP-1, MMP-3 and MMP-13 were examined by real-time PCR and ELISA. Results:Baicalein inhibited the gene expression of MMP-1, MMP-3 and MMP-13 in IL-1β-induced chondrocytes and the protein levels in culture medium.Conclusions:These results demonstrate that baicalein exerts inhibitory effects on MMPs expression in chondrocytes.Part 2 The molecular mechanisms of the anti-osteoarthritic properties of baicalein in human chondrocytesObjective:To investigate the molecular mechanisms of the anti-osteoarthritic properties of baicalein in IL-1β-induced human chondrocytes.Methods:Human chondrocytes were pre-treated with various concentration of baicalein. followed by stimulation with IL-1β. Western blot analyses were performed to analyze the protein levels of mitogen-activated protein kinase (MAPK) and inhibitor of nuclear factor-KB (IκB-α). The effects of inhibitors of p38:ERK and NF-κB on MMP-1, MMP-3 and MMP-13 were investigated by EL1SA. Results:Baicalein inhibited IL-1β-induced phosphorylation of ERK and P38 as well as the degradation of IkB-αThe inhibitors of p38. ERK and NF-κB inhibited the production of MMP-1. MMP-3 and MMP-13.Conclusions:These results demonstrate that the MAPK and NF-κB signalling pathway were involved in the inhibition effects of baicalein on MMPs in chondrocytes.Part 3 The in vivo effects of baicalein on cartilage degradation in experimental osteoarthrtis in rabbitsObjective:To investigated the effects of baicalein on cartilage degradation in an experimental model of osteoarthritis (OA).Methods:Thirty-two New Zealand rabbits underwent unilateral anterior cruciate ligament transection (ACLT) on right knee joints to induce OA and were randomly divided into four groups (n=8). based on the following treatments:the low concentration group, the moderate concentration group, the high concentration group, and the control group. Rabbits received intra-articular injection with 0.3 ml of different concentration of baicalein in right knee, the control group received vehicle intra-articular injection. Baicalein was dissolved in dimethylsulphoxide (DMSO). Weekly injections started on the day of operation, and continued for six weeks. Additional eight rabbits were used as normal control. Rabbits were killed seven days after the last injection. Right knee cartilage was collected for morphological, histological and genetic analysis.Results:The moderate and high concentration group showed less cartilage degradation as compared to the control group assessed by morphological and histological evaluation. Gene expression of MMP-1, MMP-3 and MMP-13 was increased significantly in the control group compared to the normal group, and the elevated expression was reduced by baicalein.Conclusions:Baicalein can reduce the cartilage degradation in experimental OA.