Mangiferin Relieves Lipopolysaccharide-Induced Injury by Up-Regulating miR-181a via Targeting PTEN in ATDC5 Cells

Ceibinin, a new positional isomer of mangiferin from the inflorescence of Ceiba pentandra (Bombacaceae), elicits similar antioxidant effect but no anti-inflammatory potential compared to mangiferin

Ceiba pentandra (L.) Gaertn. (Bombacaceae) is popular for the quality of its wood. However, its leaf, stem bark and root bark have been popular in ethnomedicine and, apart from the inflorescence, have been subject of extensive phytochemical investigations. In this study, two compounds were isolated from the crude methanol extract of the inflorescence. Through data from UV, NMR, MS, electrochemical studies, differential scanning calorimetry, and thermogravimetric analysis, the structures were elucidated as 3-C-β-d-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (1) and 2-C-β-d-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (mangiferin, 2). They were assessed for antioxidant efficacy (DCFDA assay) and for anti-inflammatory efficacy using the lipopolysaccharide (LPS)-induced inflammation model in the RAW 264.7 macrophages (nitrite levels quantified, using Griess Assay, as surrogate for nitric oxide (NO)). Compound 1 (named ceibinin) was established as a novel positional isomer of mangiferin (2). While both 1 and 2 were antioxidant against basal and hydrogen peroxide (100 μM)-induced oxidative stress (6.25 μg/ml abrogated peroxide-induced oxidative stress), ceibinin (1) demonstrated no anti-inflammatory potential, unlike mangiferin (2) which, as previously reported, showed anti-inflammatory effect. Our work reports a positional isomer of mangiferin for the first time in C. pentandra and demonstrates how such isomerism could underlie differences in biological activities and thus the potential for development into therapeutics.

A review of non-coding RNA related to NF-κB signaling pathway in the pathogenesis of osteoarthritis

Osteoarthritis (OA), often called as "wear and tear" arthritis, is the most common form of degenerative joint arthritis and is a leading cause of disability. The nuclear factor-kappaB (NF-κB) transcription factor has long been recognized as a disease-contributing factor for OA. More and more evidences show that targeting NF-κB signaling could offer novel potential therapeutic options for OA damage and reduce the risk of potential side-effects. In recent years, it has been shown that non-coding RNAs(ncRNAs) can trigger the expression of an array of genes and widely activate NF-κB signaling pathway, which induces destruction of the articular joint, leading to OA onset and progression. In this review, we discuss the involvement of NF-κB in OA pathogenesis and how ncRNAs attend and affect OA incidence and evolution, offering novel potential therapeutic options for OA treatment.

Plantamajoside Ameliorates Inflammatory Response of Chondrocytes via Regulating NF-κB/NLRP3 Inflammasome Pathway

The damage of articular cartilage in osteoarthritis involves the oxidative stress and inflammation. The aim of the present study was to explore the role of plantamajoside (PM) in chondrocytes and elucidate the underlying mechanism. The cell viability following treatment with PM or lipopolysac-charide (LPS) was assessed by cell counting kit-8 (CCK-8). Enzyme-Linked Immunosorbent Assay (ELISA) was supplied to determine the levels of pro-inflammatory cytokines. Moreover, the oxidative stress-related markers were evaluated via assay kits. TUNEL assay was employed to stain the apoptotic cells. The components of nuclear factor-κB (NF-κB) pathway and NLRP3 inflammasome were estimated by western blot analysis. LPS-insulted cell viability of ATDC5 was restored by PM. PM alleviated the inflammatory response and oxidative stress of ATDC5 cells induced by LPS. Furthermore, it was found that the apoptotic cells were reduced following PM treatment. The protein levels of NF-κB, IκB kinase β (IKKβ) and NLRP3 inflammasome were decreased by PM. These results suggested that PM protected the ATDC5 cells from LPS stimulation, alleviated the inflammatory response may through regulating the NF-κB and NLRP3 inflammasome.

Positive feedback regulation between USP15 and ERK2 inhibits osteoarthritis progression through TGF-β/SMAD2 signaling

Background

The transforming growth factor-β (TGF-β) signaling pathway plays an essential role in maintaining homeostasis in joints affected by osteoarthritis (OA). However, the specific mechanism of non-SMAD and classical SMAD signaling interactions is still unclear, which needs to be further explored.

Methods

In ATDC5 cells, USP15 overexpression and knockout were performed using the transfected lentivirus USP15 and Crispr/Cas9. Western blotting and immunofluorescence staining were used to test p-SMAD2 and cartilage phenotype-related molecular markers. In rat OA models, immunohistochemistry, hematoxylin and eosin (HE)/Safranin-O fast green staining, and histology were used to examine the regulatory activity of USP15 in TGF-β/SMAD2 signaling and the cartilage phenotype. Then, ERK2 overexpression and knockout were performed. The expressions of USP15, p-SMAD2, and the cartilage phenotype were evaluated in vitro and in vivo. To address whether USP15 is required for ERK2 and TGF-β/SMAD2 signaling, we performed rescue experiments in vitro and in vivo. Immunoprecipitation and deubiquitination assays were used to examine whether USP15 could bind to ERK2 and affect the deubiquitination of ERK2. Finally, whether USP15 regulates the level of p-ERK1/2 was evaluated by western blotting, immunofluorescence staining, and immunohistochemistry in vitro and in vivo.

Results

Our results indicated that USP15 stimulated TGF-β/SMAD2 signaling and the cartilage phenotype. Moreover, ERK2 required USP15 to influence TGF-β/SMAD2 signaling for regulating the cartilage phenotype in vivo and in vitro. And USP15 can form a complex with ERK2 to regulate ubiquitination of ERK2. Interestingly, USP15 did not regulate the stability of ERK2 but increased the level of p-ERK1/2 to further enhance the TGF-β/SMAD2 signaling pathway.

Conclusions

Taken together, our study revealed positive feedback regulation between USP15 and ERK2, which played a critical role in TGF-β/SMAD2 signaling to inhibit OA progression. Therefore, this specific mechanism can guide the clinical treatment of OA.

Regulatory role of microRNAs on PTEN signaling

Phosphatase and tensin homolog (PTEN) gene encodes a tumor suppressor protein which is altered in several malignancies. This protein is a negative regulator of the PI3K/AKT signaling. Several transcription factors regulate the expression of PTEN in positive or negative directions. Moreover, numerous microRNAs (miRNAs) have functional interactions with PTEN and inhibit its expression. Suppression of PTEN can attenuate the response of cancer cells to chemotherapeutic agents. Based on the critical role of this tumor suppressor gene, the identification of negative regulators of its expression has practical significance particularly in the prevention and management of cancer. Meanwhile, the interaction between miRNAs and PTEN has functional consequences in non-malignant disorders including myocardial infarction, osteoporosis, cerebral ischemic stroke, and recurrent abortion. In the present review, we describe the role of miRNAs in the regulation of expression and activity of PTEN.