USP14-mediated IκBα degradation exacerbates NF-κB activation and IL-1β-stimulated chondrocyte dedifferentiation.

Osteoarthritis (OA) is an inflammatory joint disease. USP14, a deubiquitinating enzyme critical for ubiquitin-mediated proteasomal protein degradation, is implicated in inflammation regulation. However, its role and mechanism in OA are poorly understood. Here, we report that USP14 is upregulated in OA articular cartilage as well as in chondrocytes treated with IL-1β in vitro. USP14 upregulation depends on NF-κB pathway activation, since inhibition of this pathway by ACHP, a selective inhibitor of IKK-β, abolishes USP14 upregulation. We further show that USP14 in turn exacerbates NF-κB activation through promoting IκBα deubiquitination and degradation. Functionally, USP14 aggravates the dedifferentiation effect of IL-1β on chondrocytes, and NF-κB inhibition remarkably reverses this effect, highlighting an important role of NF-κB in mediating USP14 function. Collectively, our data reveal a previously unidentified feed-forward loop driven by USP14 and NF-κB pathway in promoting the dedifferentiation effect of IL-1β on chondrocytes. This mechanism might offer a useful hint for OA intervention.

Li M ，Zhao J ，Jia L 《-》

Anemonin attenuates osteoarthritis progression through inhibiting the activation of IL-1β/NF-κB pathway.

The osteoarthritis (OA) progression is now considered to be related to inflammation. Anemonin (ANE) is a small natural molecule extracted from various kinds of Chinese traditional herbs and has been shown to inhibiting inflammation response. In this study, we examined whether ANE could attenuate the progression of OA via suppression of IL-1β/NF-κB pathway activation. Destabilization of the medial meniscus (DMM) was performed in 10-week-old male C57BL/6J mice. ANE was then intra-articularly injected into joint capsule for 8 and 12 weeks. Human articular chondrocytes and cartilage explants challenged with interleukin-1β (IL-1β) were treated with ANE. We found that ANE delayed articular cartilage degeneration in vitro and in vivo. In particular, proteoglycan loss and chondrocyte hypertrophy were significantly decreased in ANE -treated mice compared with vehicle-treated mice. ANE decreased the expressions of matrix metalloproteinase-13 (MMP13), A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), collagen X (Col X) while increasing Aggrecan level in murine with DMM surgery. ANE treatment also attenuated proteoglycan loss in human cartilage explants treated with IL-1β ex vivo. ANE is a potent protective molecule for OA; it delays OA progression by suppressing ECM loss and chondrocyte hypertrophy partially by suppressing IL-1β/NF-κB pathway activation.

Wang Z ，Huang J ，Zhou S ，Luo F ，Xu W ，Wang Q ，Tan Q ，Chen L ，Wang J ，Chen H ，Chen L ，Xie Y ，Du X ... -  《-》

Lithium protects against cartilage degradation in osteoarthritis.

To determine the actions of lithium chloride (LiCl) on catabolic events in human articular chondrocytes, and the effects of LiCl on the progression and severity of cartilage degradation in interleukin-1β (IL-1β)-treated mouse knee joints and after surgical induction of osteoarthritis (OA) in a mouse model. Human articular chondrocytes were treated with LiCl followed by IL-1β, and the expression levels of catabolic genes were determined by real-time polymerase chain reaction. To understand the mechanism by which LiCl affects catabolic events in articular chondrocytes after IL-1β treatment, the activation of NF-κB was determined using luciferase reporter assays, and the activities of MAPKs and the STAT-3 signaling pathway were determined by immunoblot analysis of total cell lysates. Cultures of mouse femoral head explants treated with IL-1β and a mouse model of surgically induced OA were used to determine the effects of LiCl on proteoglycan loss and cartilage degradation. LiCl treatment resulted in decreased catabolic marker messenger RNA levels and activation of NF-κB, p38 MAPK, and STAT-3 signaling in IL-1β-treated articular chondrocytes. Furthermore, LiCl directly inhibited IL-6-stimulated activation of STAT-3 signaling. Consequently, the loss of proteoglycan and severity of cartilage destruction in LiCl-treated mouse knee joints 8 weeks after OA induction surgery or in LiCl-treated mouse femoral head explants after IL-1β treatment were markedly reduced compared to that in vehicle-treated joints or explants. LiCl reduced catabolic events in IL-1β-treated human articular chondrocytes and attenuated the severity of cartilage destruction in IL-1β-treated mouse femoral head explants and in the knee joints of mice with surgically induced OA, acting via inhibition of the activities of the NF-κB, p38, and STAT-3 signaling pathways.

Minashima T ，Zhang Y ，Lee Y ，Kirsch T ... -  《-》

Semaphorin 4A acts in a feed-forward loop with NF-κB pathway to exacerbate catabolic effect of IL-1β on chondrocytes.

Inflammation is fundamental in osteoarthritis (OA) pathogenesis. Semaphorin 4A (Sema4A) has been implicated in immune-associated diseases, however, its role in OA remains unclear. In this study, we show that Sema4A is upregulated in knee OA articular cartilage as well as in chondrocytes exposed to IL-1β treatment in vitro. Moreover, IL-1β-induced Sema4A upregulation is abrogated in the presence of BAY 11-7082, a specific inhibitor of NF-κB pathway, suggesting that the activation of NF-κB is required for Sema4A upregulation under this pathological condition. Intriguingly, Sema4A in turn activates NF-κB through facilitating Rac1/AKT-dependent IκBα phosphorylation and subsequent degradation. Functionally, Sema4A aggravates the catabolic effect of IL-1β on chondrocytes, which can be largely attributed to exacerbated NF-κB activation, since NF-κB inhibition remarkably abolishes this effect. In conclusion, our study suggests that Sema4A is a novel regulator of NF-κB-dependent catabolic events in chondrocytes, which may underlie OA pathogenesis.

Zhang H ，Wei Q ，Xiang X ，Zhou B ，Chen J ，Li J ，Li Q ，Xiong H ，Liu F ... -  《-》

TNF/TNFR signal transduction pathway-mediated anti-apoptosis and anti-inflammatory effects of sodium ferulate on IL-1β-induced rat osteoarthritis chondrocytes in vitro.

Qin J ，Shang L ，Ping AS ，Li J ，Li XJ ，Yu H ，Magdalou J ，Chen LB ，Wang H ... -  《-》