title: Mitogen-activated protein kinase and nuclear factor kappaB together regulate interleukin-17-induced nitric oxide production in human osteoarthritic chondrocytes: possible role of transactivating factor mitogen-activated protein kinase-activated proten kinase (MAPKAPK).
abstract: OBJECTIVE
  To explore the signaling pathways by which the proinflammatory cytokine interleukin-17 (IL-17) may contribute to cartilage catabolism in osteoarthritis (OA) by inducing inducible nitric oxide synthase (iNOS) expression in chondrocytes.
  
  
  METHODS
  We examined the IL-17-induced NO production in human OA chondrocytes, in combination with the proinflammatory cytokines IL-1beta, tumor necrosis factor alpha (TNF alpha), and leukemia inhibitory factor (LIF); the antiinflammatory cytokines IL-4, IL-10, and IL-13; and IL-1 receptor antagonist (IL-1Ra). Further, we explored the major intracellular signaling pathways through which IL-17 induced iNOS expression and NO production.
  
  
  RESULTS
  Treatment with IL-17 induced a dose-dependent increase in the level of NO. When IL-17 was combined with the above factors, it resulted in a synergistic effect with TNF alpha, an additive effect with LIF, and no further effect than when used alone with IL-1beta. IL-4, IL-10, IL-13, and IL-1Ra had no true effect on IL-17-induced NO production. The cAMP mimetics, 3-isobutyl-1-methyl xanthine plus forskolin, completely blocked IL-17-induced NO production. KT-5720, genistein, and Calphostin C, inhibitors of protein kinase A (PKA), tyrosine kinase, and protein kinase C, respectively, reduced the IL-17-induced NO production by 72%, 56%, and 42%, respectively. Within minutes, IL-17 induced the phosphorylation of mitogen-activated protein kinase kinase-1/2 (MEK-1/2), -3/6 (MKK-3/6), p44/42, p38, and inhibitor of nuclear factor kappaB (I kappaB)-alpha, as well as the activation of mitogen-activated protein kinase-activated protein kinase-1 and -2 (MAPKAPK-1 and -2). Interestingly, IL-17 induced phosphorylation of the stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK) (p54/46) only when PKA was inhibited. Specific protein kinase inhibitors for MEK-1/2 (PD98059), p38 (SB202190), and nuclear factor kappaB (NF-kappaB) (pyrrolidine dithiocarbamate) each markedly decreased the IL-17-increased iNOS level and NO production. Inhibiting MAPK, including MEK-1/2 and p38, had no effect on the IL-17-induced activation of IkappaB-alpha, but reversed the IL-17 activation of MAPKAPK-1 and -2, respectively.
  
  
  CONCLUSIONS
  These findings show that the stimulation of NO production by IL-17 is mediated mainly by a complex activation of kinases, especially PKA, NF-kappaB, and MAPK. NF-kappaB appears to require MAPK activation, with downstream activation of MAPKAPK probably acting as a transactivating factor, to induce iNOS expression.
authors.affiliation: Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame, Quebec, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Martel-Pelletier
authors.forename: F
authors.initials: F
authors.lastname: Mineau
authors.forename: D
authors.initials: D
authors.lastname: Jovanovic
authors.forename: J A
authors.initials: JA
authors.lastname: Di Battista
authors.forename: J P
authors.initials: JP
authors.lastname: Pelletier
mesh_terms: D000368:Aged; D002478:Cells, Cultured; D019902:Chondrocytes / Q000201:enzymology / Q000378:metabolism*; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D020381:Interleukin-17 / Q000494:pharmacology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010003:Osteoarthritis / Q000378:metabolism* / Q000473:pathology; D019893:Ribosomal Protein S6 Kinases / Q000502:physiology; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D015398:Signal Transduction; D015533:Transcriptional Activation
chemical_list: D020381:Interleukin-17; D016328:NF-kappa B; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D019893:Ribosomal Protein S6 Kinases; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D020928:Mitogen-Activated Protein Kinases