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Pomegranate extract inhibits the interleukin-1β-induced activation of MKK-3, p38α-MAPK and transcription factor RUNX-2 in human osteoarthritis chondrocytesDOI: 10.1186/ar3166 Abstract: Human chondrocytes were derived from OA cartilage by enzymatic digestion, treated with PE and then stimulated with IL-1β. Gene expression of p38-MAPK isoforms was measured by RT-PCR. Western immunoblotting was used to analyze the activation of MAPKs. Immunoprecipitation was used to determine the activation of p38-MAPK isoforms. DNA binding activity of RUNX-2 was determined using a highly sensitive and specific ELISA. Pharmacological studies to elucidate the involved pathways were executed using transfection with siRNAs.Human OA chondrocytes expressed p38-MAPK isoforms p38α, -γ and -δ, but not p38β. IL-1β enhances the phosphorylation of the p38α-MAPK and p38γ-MAPK isoforms but not of p38δ-MAPK isoform in human OA chondrocytes. Activation of p38-MAPK in human OA chondrocytes was preferentially mediated via activation of MKK3. In addition, we also demonstrate that polyphenol rich PE inhibited the IL-1β-induced activation of MKK3, p38α-MAPK isoform and DNA binding activity of the transcription factor RUNX-2.Our results provide an important insight into the molecular basis of the reported cartilage protective and arthritis inhibitory effects of pomegranate extract. These novel pharmacological actions of PE on IL-1β stimulated human OA chondrocytes impart a new suggestion that PE or PE-derived compounds may be developed as MKK and p38-MAPK inhibitors for the treatment of OA and other degenerative/inflammatory diseases.Osteoarthritis (OA), the most common forms of arthritis, is a progressive degenerative joint disease that has a major impact on joint function and the patient's quality of life. This disorder is regulated by proinflammatory cytokines such as IL-1 and TNF-α that can activate a broad array of intracellular signal transduction mechanisms [1]. Of the cytokine- activated pathways, MAP kinases are especially important because they regulate the production of several mediators of inflammation and cartilage damage [2]. Members of the MAP kinase family phosphorylate a
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