title: Thymoquinone inhibits TNF-α-induced inflammation and cell adhesion in rheumatoid arthritis synovial fibroblasts by ASK1 regulation.
abstract: Tumor necrosis factor-α (TNF-α) is a pro-inflammatory cytokine produced by monocytes/macrophage that plays a pathological role in rheumatoid arthritis (RA). In this study, we investigate the effect of thymoquinone (TQ), a phytochemical found in Nigella sativa, in regulating TNF-α-induced RA synovial fibroblast (RA-FLS) activation. Treatment with TQ (1-5μM) had no marked effect on the viability of human RA-FLS. Pre-treatment of TQ inhibited TNF-α-induced interleukin-6 (IL-6) and IL-8 production and ICAM-1, VCAM-1, and cadherin-11 (Cad-11) expression in RA-FLS (p<0.01). Evaluation of the signaling events showed that TQ inhibited TNF-α-induced phospho-p38 and phospho-JNK expression, but had no inhibitory effect on NF-κB pathway, in RA-FLS (p<0.05; n=4). Interestingly, we observed that selective down-regulation of TNF-α-induced phospho-p38 and phospho-JNK activation by TQ is elicited through inhibition of apoptosis-regulated signaling kinase 1 (ASK1). Furthermore, TNF-α selectively induced phosphorylation of ASK1 at Thr845 residue in RA-FLS, which was inhibited by TQ pretreatment in a dose dependent manner (p<0.01). Pre-treatment of RA-FLS with ASK1 inhibitor (TC ASK10), blocked TNF-α induced expression of ICAM-1, VCAM-1, and Cad-11. Our results suggest that TNF-α-induced ASK1-p38/JNK pathway is an important mediator of cytokine synthesis and enhanced expression of adhesion molecule in RA-FLS and TQ, by selectively inhibiting this pathway, may have a potential therapeutic value in regulating tissue destruction observed in RA.
authors.affiliation: Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, WA, USA.
authors.forename: Sadiq
authors.initials: S
authors.lastname: Umar
authors.affiliation: Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, WA, USA.
authors.forename: Omar
authors.initials: O
authors.lastname: Hedaya
authors.affiliation: Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, WA, USA.
authors.forename: Anil K
authors.initials: AK
authors.lastname: Singh
authors.affiliation: Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, WA, USA. Electronic address: salah.ahmed@wsu.edu.
authors.forename: Salahuddin
authors.initials: S
authors.lastname: Ahmed
mesh_terms: D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000276:immunology / Q000601:surgery; D016227:Benzoquinones / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D006801:Humans; D018836:Inflammation Mediators / Q000276:immunology / Q000378:metabolism; D015850:Interleukin-6 / Q000276:immunology / Q000378:metabolism; D016209:Interleukin-8 / Q000276:immunology / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction / Q000187:drug effects; D013583:Synovial Membrane / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000893:Anti-Inflammatory Agents; D016227:Benzoquinones; C508606:CXCL8 protein, human; D015815:Cell Adhesion Molecules; C508600:IL6 protein, human; D018836:Inflammation Mediators; D015850:Interleukin-6; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; C482858:MAP3K5 protein, human; C003466:thymoquinone
keywords: ASK1; MAP kinase; Rheumatoid arthritis; Synovial fibroblasts; TNF-α; Thymoquinone