title: Tyrphostin B42 inhibits IL-12-induced tyrosine phosphorylation and activation of Janus kinase-2 and prevents experimental allergic encephalomyelitis.
abstract: IL-12 is a macrophage-derived cytokine that induces proliferation, cytokine production, and cytotoxic activity of T and NK cells. Signaling through its receptor, IL-12 induces these cellular responses by tyrosine phosphorylation and activation of Janus kinase-2 (Jak-2), Tyk-2, Stat3, and Stat4. We have used tyrphostin B42 (AG490), a Jak-2 inhibitor, to determine the role of Jak-2 kinase in IL-12 signaling and IL-12-induced T cell functions. Treatment of activated T cells with tyrphostin B42 inhibited the IL-12-induced tyrosine phosphorylation and activation of Jak-2 without affecting Tyk-2 kinase. In contrast, treatment with tyrphostin A1 inhibited the tyrosine phosphorylation of Tyk-2 but not that of Jak-2 kinase. Inhibition of either Jak-2 or Tyk-2 leads to a decrease in the IL-12-induced tyrosine phosphorylation of Stat3, but not of Stat4, protein. While inhibition of Jak-2 lead to programmed cell death, the inhibition of Jak-2 or Tyk-2 resulted a decrease in IFN-gamma production. We have further tested the in vivo effects of tyrphostin B42 in experimental allergic encephalomyelitis, a Th1 cell-mediated autoimmune disease. In vivo treatment with tyrphostin B42 decreased the proliferation and IFN-gamma production of neural Ag-specific T cells. Treatment of mice with tyrphostin B42 also reduced the incidence and severity of active and passive EAE. These results suggest that tyrphostin B42 prevents EAE by inhibiting IL-12 signaling and IL-12-mediated Th1 differentiation in vivo.
authors.affiliation: Multiple Sclerosis Research Center, Department of Neurology, Vanderbilt University School of Medicine, Nashville, TN 37212, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Bright
authors.forename: C
authors.initials: C
authors.lastname: Du
authors.forename: S
authors.initials: S
authors.lastname: Sriram
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000209:etiology / Q000517:prevention & control*; D004789:Enzyme Activation / Q000187:drug effects; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000494:pharmacology*; D053614:Janus Kinase 2; D051379:Mice; D008815:Mice, Inbred Strains; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D050796:STAT3 Transcription Factor; D050797:STAT4 Transcription Factor; D053634:TYK2 Kinase; D018417:Th1 Cells / Q000276:immunology; D015534:Trans-Activators / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050796:STAT3 Transcription Factor; D050797:STAT4 Transcription Factor; C494087:Stat3 protein, mouse; C494091:Stat4 protein, mouse; D015534:Trans-Activators; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D018664:Interleukin-12; D007371:Interferon-gamma; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D053634:TYK2 Kinase; C499356:Tyk2 protein, mouse