Oroxin B alleviates osteoarthritis through anti-inflammation and inhibition of PI3K/AKT/mTOR signaling pathway and enhancement of autophagy

Abstract

BackgroundOsteoarthritis (OA) is a common aging-related degenerative joint disease with chronic inflammation as its possible pathogenesis. Oroxin B (OB), a flavonoid isolated from traditional Chinese herbal medicine, possesses anti-inflammation properties which may be involved in regulating the pathogenesis of OA, but its mechanism has not been elucidated. Our study was the first to explore the potential chondroprotective effect and elucidate the underlying mechanism of OB in OA.MethodsIn vitro, primary mice chondrocytes were stimulated with IL-1β along with or without the administration of OB or autophagy inhibitor 3-methyladenine (3-MA). Cell viability assay was measured with a cell counting kit-8 (CCK-8). The phenotypes of anabolic-related (Aggrecan and Collagen II), catabolic-related (MMP3, MMP13, and ADAMTS5), inflammation-related (iNOS, COX-2, TNF-α, IL-6, and IL-1β), and markers of related signaling pathways in chondrocytes with different treatment were detected through western blot, RT-qPCR, and immunofluorescent staining. In vivo, the destabilized medial meniscus (DMM) operation was performed to establish the OA mice model. After knee intra-articular injection with OB for 8 weeks, the mice’s knee joints were obtained for subsequent histological staining and analysis.ResultsOB reversed the expression level of anabolic-related proteins (Aggrecan and Collagen II) and catabolic-related (MMP3, MMP13, and ADAMTS5) in IL-1β-induced chondrocytes. Mechanistically, OB suppressed the inflammatory response stimulated by IL-1β, as the inflammation-related (iNOS, COX-2, TNF-α, IL-6, and IL-1β) markers were downregulated after the administration of OB in IL-1β-induced chondrocytes. Besides, the activation of PI3K/AKT/mTOR signaling pathway induced by IL-1β could be inhibited by OB. Additionally, the autophagy process impaired by IL-1β could be rescued by OB. What’s more, the introduction of 3-MA to specifically inhibit the autophagic process impairs the protective effect of OB on cartilage. In vivo, histological staining revealed that intra-articular injection of OB attenuated the cartilage degradation, as well as reversed the expression level of anabolic and catabolic-related proteins such as Aggrecan, Collagen II, and MMP13 induced in DMM-induced OA models.ConclusionsThe study verified that OB exhibited the chondroprotective effect by anti-inflammatory, inhibiting the PI3K/AKT/mTOR signaling pathway, and enhancing the autophagy process, indicating that OB might be a promising agent for the treatment of OA.

Physalin A alleviates intervertebral disc degeneration via anti-inflammatory and anti-fibrotic effects

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Mulberroside A alleviates osteoarthritis via restoring impaired autophagy and suppressing MAPK/NF-κB/PI3K-AKT-mTOR signaling pathways

“… 36 In addition, the PI3K-AKT-mTOR pathway is also an important inflammatory signaling pathway which associates with NF-κB signaling pathway, as AKT could trigger the activation of NF-κB signal and contribute to the production of inflammatory mediators. 37 , 38 Thus, in this study, we explored the role of MA in inflammatory signaling pathways in chondrocytes and revealed that MA was a protective agent against the progression of OA via suppressing the MAPK, NF-κB, and PI3K-AKT-mTOR signaling pathways and promoting the autophagy process in IL-1β-induced chondrocytes.…”

Cucurbitacin E reduces IL-1β-induced inflammation and cartilage degeneration by inhibiting the PI3K/Akt pathway in osteoarthritic chondrocytes

“…Previous studies have shown that the PI3K/Akt pathway is closely related to osteoarthritis and that IL-1β can trigger a strong inflammatory response by activating a complex network of signalling pathways, in which PI3K/Akt signalling is closely intertwined with IL-1β-induced inflammation [ 37 ]. A large number of studies have shown that PI3K and Akt are rapidly phosphorylated under stimulation with IL-1β [ 38 , 39 ], suggesting that the PI3K/Akt pathway may mediate the initiation of the inflammatory response. PI3K inhibition is considered to be an anti-inflammatory therapeutic strategy [ 40 ].…”