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Betulin Alleviates the Inflammatory Response in Mouse Chondrocytes and Ameliorates Osteoarthritis via AKT/Nrf2/HO-1/NF-κB Axis

ABSTRACT: Osteoarthritis (OA) is a common degenerative joint disease featuring the degeneration, destruction, and ossification of cartilage. Inflammation which may facilitate OA occurrence and development is considered as the main pathological factor. Betulin, a natural product extracted from birch bark, has been commonly used for inflammation treatment; however, its role in OA remains unclear. This study is aimed to explore whether betulin can suppress IL-1β–induced inflammation in chondrocytes and alleviate OA in vitro and in vivo. In in vitro studies, the generation of pro-inflammatory factors, such as interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), prostaglandin E2 (PGE2), and nitric oxide (NO), was assessed using the enzyme-linked immunosorbent assay (ELISA) and Griess reaction. As revealed by results, betulin inhibited the expression of pro-inflammatory mediators. In addition, the protein expressions of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), matrix metalloproteinase (MMP-13), thrombospondin motifs 5 (ADAMTS5), Collagen II, and Aggrecan were quantified using Western blot analysis. We found that betulin could inhibit the generation of COX-2 and iNOS induced by IL-1β, indicating that betulin has anti-inflammatory effects in chondrocytes. Furthermore, betulin downregulates the expression of MMP-13 and ADAMTS-5 and upregulates the expression of Collagen II and Aggrecan, indicating that it can inhibit the degradation of the extracellular matrix. In mechanism, betulin activated the AKT/Nrf2 pathway and inhibited the phosphorylation of p65. In in vivo studies, administration of betulin in vivo could inhibit cartilage destruction and inflammatory progression. Therefore, these findings suggest that betulin may alleviate IL-1β–induced OA via the AKT/Nrf2/HO-1/NF-κB signal axis, and betulin may be a potential drug for the treatment of OA.

SUBMITTER: Ren C

PROVIDER: S-EPMC8548689 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:As part of our continuous effort to find potential anti-inflammatory agents from endophytic fungi, a Fusariumsolani strain, isolated from the plant Aponogetonundulatus Roxb., was investigated. Cerevisterol (CRVS) was identified from endophytic fungi, a Fusariumsolani strain, and moreover exhibited anti-inflammatory activity. However, the underlying mode of action remains poorly understood. The aim of this study is to reveal the potential mechanisms of CRVS against inflammation on a molecular level in LPS-activated RAW 264.7 peritoneal macrophage cells. CRVS was isolated from F.solani and characterized based on spectral data analysis. The MTT assay was performed to measure cell viability in CRVS-treated macrophages. Anti-inflammatory activity was assessed by measurement of nitric oxide (NO) and prostaglandin E2 (PGE2) levels, as well as the production of various cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and -6 (IL-6) in LPS-stimulated macrophages. RT-PCR and immunoblotting analyses were done to examine the expression of various inflammatory response genes. A reporter gene assay was conducted to measure the level of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and activator protein-1 (AP-1) transactivation. CRVS suppresses the LPS-induced production of NO and PGE2, which is a plausible mechanism for this effect is by reducing the expression of iNOS and COX-2. CRVS also decreases the expression of pro-inflammatory cytokines, such as TNF-α, IL-6, and IL-1β. CRVS halted the nuclear translocation of NF-κB by blocking the phosphorylation of inhibitory protein κBα (IκBα) and suppressing NF-κB transactivation. The mitogen-activated protein kinases (MAPK) signaling pathways are also suppressed. CRVS treatment also inhibited the transactivation of AP-1 and the phosphorylation of c-Fos. Furthermore, CRVS could induce the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) by down-regulating Kelch-like ECH-associated protein 1 (Keap-1) and up-regulating hemeoxygenases-1 (HO-1) expression. The results suggest that CRVS acts as a natural agent for treating inflammatory diseases by targeting an MAPK, NF-κB, AP-1, and Nrf2-mediated HO-1 signaling cascade.

Project description:Nrf2 (Nuclear Factor Erythroid 2 Related Factor 2) transcription factor not only regulates oxidative stress response, but also represses inflammation by regulating cytokines production and cross-talking with NF-κB signaling pathways. Nrf2 plays an essential role in liver injury induced by oxidative stress and inflammation. Triptriolide (T11) is a minor component of Tripterygium wilfordii Hook F. (TwHF), which can be obtained by hydrolysis reaction of triptolide (T9). The major purpose of this study is to clarify the regulating effects of T11 on oxidative stress and inflammation in vivo and in vitro. LPS-stimulated RAW 264.7 cells were used to verify the regulating effects of T11 on oxidative stress (ROS and Nrf2 signaling pathway) and inflammatory cytokines production (TNF-α, IL-6 and IL-1β). The antioxidant responsive element (ARE) luciferase assay was employed to evaluate Nrf2 activation effect of T11 in HEK-293T cells. Lipopolysaccharides (LPS) induced acute liver injury (ALI) in BALB/c mice were used to study the protective effects (ALT, AST, MDA, SOD, histopathology and neutrophils/macrophages filtration) and the underlying protection mechanisms of ALI amelioration (Nrf2 and NF-κB signaling pathway) of T11. Firstly, the results showed that T11 can not only effectively decrease the productions of inflammatory cytokines (TNF-α, IL-6 and IL-1β), ROS and NO in LPS-stimulated RAW 264.7 cells, but also further significantly increase the activity of Nrf2 in HEK-293T cells. Secondly, the results suggested that T11 could dramatically decrease the oxidative stress responses (SOD and MDA) and inflammation (histopathology, neutrophils/macrophages filtration, TNF-α, IL-6 and IL-1β production) in LPS-induced ALI in BALB/c mice. Finally, the results implied that T11 could dramatically increase Nrf2 protein expression and decrease p-TAK1, p-IκBα and NF-κB protein expression both in vivo and in vitro. In conclusion, our findings indicated that T11 could alleviate LPS induced oxidative stress and inflammation by regulating Nrf2 and NF-κB signaling pathways in vitro and in vivo, which offers a novel insights for the application of TwHF in clinical.

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Betulin Alleviates the Inflammatory Response in Mouse Chondrocytes and Ameliorates Osteoarthritis via AKT/Nrf2/HO-1/NF-κB Axis

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