Ghrelin prevents articular cartilage matrix destruction in human chondrocytes.

Osteoarthritis (OA) is the most common form of arthritis worldwide. Excessive production of pro-inflammatory cytokines such as interleukin-1β (IL-1β) plays a key role in the pathogenesis of OA. OA is generally characterized by degradation of extracellular matrixes such as type II collagen and aggrecans mediated by matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS). Ghrelin is a secreted peptide hormone regulating appetite and the distribution and rate of use of energy. However, the physiological and pharmacological roles of Ghrelin on the pathological progression of OA haven't been reported before. In the current study, our results indicate that Ghrelin reduced IL-1β-induced expression of MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5 in a concentration-dependent manner. Notably, Ghrelin ameliorated IL-1β-induced degradation of type II collagen and aggrecan. Mechanistically, Ghrelin is able to inhibit the expression of IRF-1 mediated by inactivating the JAK2/STAT3 pathway. However, Ghrelin didn't have any impact on IL-1β induced activation of p38. Taken together, our findings identify a novel function of Ghrelin on inhibiting the degradation of type II collagen and aggrecan.

Liu J ，Cao L ，Gao X ，Chen Z ，Guo S ，He Z ，Qian Y ，Yu Y ，Wang G ... -  《-》

Emodin ameliorates cartilage degradation in osteoarthritis by inhibiting NF-κB and Wnt/β-catenin signaling in-vitro and in-vivo.

The overproduction of MMPs (matrix metalloproteinases) and members of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) protein family plays an important role in the pathogenesis of osteoarthritis (OA). The potential of selective MMPs or ADAMTS inhibitors as chemopreventive agents for OA has been demonstrated in several studies. In this study, we investigated the protective effects of emodin (1,3,8-trihydroxy-6-methylanthaquinone), isolated from the root of Rheum palmatum L., in the inhibition of MMP and ADAMTS expression in both rat chondrocytes and an animal model of OA. The expression of MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, aggrecan, and collagen II mRNA and protein in interleukin-1beta (IL-1β)-induced rat chondrocytes was followed by quantitative real-time PCR and western blot. The activation of the NF-κB and Wnt/β-catenin pathways by IL-1β was assessed by western blot. The in vivo effects of emodin were evaluated by intra-articular injection in rats in an experimental model of OA induced by anterior cruciate ligament transection. Emodin dose-dependently down-regulated the expression of MMP-3, MMP-13, ADAMTS-4 and ADAMTS-5 at both the mRNA and protein level in IL-1β-stimulated rat chondrocytes. In addition, the IL-1β-induced activation of NF-κB and Wnt signals was attenuated by emodin, as determined by western blotting. The intra-articular injection of emodin in a rat OA model ameliorated OA progression, as determined in morphological and histological analyses in vivo. Taken together, our findings demonstrate that emodin is a promising therapeutic agent for the prevention and treatment of OA.

Ding QH ，Ye CY ，Chen EM ，Zhang W ，Wang XH ... -  《-》

Ivabradine abrogates TNF-α-induced degradation of articular cartilage matrix.

Ivabradine is most commonly used for the treatment of worsening cardiac failure in patients who cannot tolerate the maximum dose of β-blockers or in whom treatment with β-blockers is contraindicated. While ivabradine is regarded as a highly selective "funny current" (If) inhibitor, the molecular mechanism behind the effect of this drug remains poorly understood. In the present study, we applied ivabradine in the context of osteoarthritis by treating primary human chondrocytes with tumor necrosis factor-α (TNF-α) and measuring degradation of the articular cartilage matrix as well as the expression of various enzymes and pro-inflammatory cytokines. Our results indicate that ivabradine significantly abrogated TNF-α-induced up-regulation of matrix metalloproteinase-3 (MMP-3), MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, and ADAMTS-5 at both the gene and protein levels. Notably, ivabradine attenuated TNF-α-induced reduction of type II collagen and aggrecan at both the mRNA and protein levels. Also, we found that ivabradine inhibited the expression and secretion of interleukin-6 (IL-6) and interleukin-1β (IL-1β) as well as the production of reactive oxygen species (ROS). Mechanistically, our results indicate that ivabradine abolished the activation of nuclear factor (NF-κB) by inhibiting nuclear translocation of NF-κB p65. Knockdown of HCN2 enhanced the protective effects of ivabradine against TNF-α- induced degradation of both type II collagen and aggrecan, suggesting that the inhibitory effects of ivabradine in ECM degradation might be mediated by HCN2. Our findings demonstrate that ivabradine may indeed have a potential application in preventing excessive degradation of the articular cartilage matrix, thereby preventing the pathological development and progression of osteoarthritis.

Xiang X ，Zhou Y ，Sun H ，Tan S ，Lu Z ，Huang L ，Wang W ... -  《-》

Vildagliptin reduced extracellular matrix degradation in human primary chondrocytes.

In the present study, we investigated the effects of the specific DPP-4 inhibitor vildagliptin on degradation of type II collagen and aggrecan, the main components of the articular extracellular matrix, in primary human chondrocytes. The results of our study reveal that vildagliptin reduced degradation of the articular extracellular matrix (ECM) by downregulating IL-1β-induced expression of matrix metalloproteinases-3 (MMP-3), matrix metalloproteinases-13 (MMP-13), a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4) and a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5). We also found that vildagliptin ameliorated IL-1β-induced activation of the JNK/AP-1 and nuclear factor-κB (NF-κB) pro-inflammatory signaling pathways by downregulating phosphorylation of JNK and nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor α (IκBα), activation of c-Fos/c-Jun, and nuclear translocation of p65. Our findings suggest that vildagliptin may serve as a novel treatment for excessive degradation of the articular ECM in osteoarthritis (OA).

Wang Z ，Xu M ，Bai J ，Ge G ，Guo X ，Yu B ，Xiao L ，Geng D ，Hao Y ... -  《-》

Systemic inhibition of IL-6/Stat3 signalling protects against experimental osteoarthritis.

To investigate the impact of systemic inhibition of interleukin 6 (IL-6) or signal transducer and activator of transcription (Stat3) in an experimental model of osteoarthritis (OA). Expression of major catabolic and anabolic factors of cartilage was determined in IL-6-treated mouse chondrocytes and cartilage explants. The anti-IL-6-receptor neutralising antibody MR16-1 was used in the destabilisation of the medial meniscus (DMM) mouse model of OA. Stat3 blockade was investigated by the small molecule Stattic ex vivo and in the DMM model. In chondrocytes and cartilage explants, IL-6 treatment reduced proteoglycan content with increased production of matrix metalloproteinase (MMP-3 and MMP-13) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-4 and ADAMTS-5). IL-6 induced Stat3 and extracellular signal-regulated kinase (ERK) 1/2 signalling but not p38, c-Jun N-terminal kinase or Akt. In the DMM model, Stat3 was activated in cartilage, but neither in the synovium nor in the subchondral bone. Systemic blockade of IL-6 by MR16-1 alleviated DMM-induced OA cartilage lesions, impaired the osteophyte formation and the extent of synovitis. In the same model, Stattic had similar beneficial effects on cartilage and osteophyte formation. Stattic, but not an ERK1/2 inhibitor, significantly counteracted the catabolic effects of IL-6 on cartilage explants and suppressed the IL-6-induced chondrocytes apoptosis. IL-6 induces chondrocyte catabolism mainly via Stat3 signalling, a pathway activated in cartilage from joint subjected to DMM. Systemic blockade of IL-6 or STAT-3 can alleviate DMM-induced OA in mice.

Latourte A ，Cherifi C ，Maillet J ，Ea HK ，Bouaziz W ，Funck-Brentano T ，Cohen-Solal M ，Hay E ，Richette P ... -  《-》