Janus kinase-signal transducer and activator of transcription mediates phosphatidic acid-induced interleukin (IL)-1beta and IL-6 production.
We have found previously that phosphatidic acid (PA) can induce inflammatory mediators such as cytokines, which implies that PA plays a role in inflammatory response. In the present study, we provide evidence of the PA-mediated activation of the Janus tyrosine kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, which results in the production of interleukin (IL)-1beta and IL-6. PA elicited the rapid phosphorylations of JAK2 and STAT1/3, and the subsequent nuclear translocation. Macrophages that had been transiently transfected with a luciferase reporter construct containing eight consecutive gamma-interferon activating sequence (GAS) elements, a known STAT binding site, exhibited enhanced reporter gene activity in response to PA stimulation, which further supports the involvement of JAK-STAT activation in the PA-induced signaling pathway. Of the inflammatory cytokines, IL-1beta, IL-6, and tumor necrosis factor (TNF)-alpha were detected in media from macrophages stimulated with PA. Moreover, the JAK2 inhibitor alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide (AG-490) abolished PA-induced IL-1beta and IL-6 release but not TNF-alpha production, which is consistent with the notion that IL-1beta and IL-6 but not TNF-alpha contain a STAT binding element in their promoter region. The knockdown of JAK2 in macrophages by small interfering RNA significantly attenuated PA-induced IL-1beta and IL-6 production. In addition, JAK2 inhibitor suppressed PA-induced Akt phosphorylation, and the Akt inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) blocked GAS activation (GAS contains a promoter that responds to PA), suggesting that PA-mediated JAK2 activation leads to phosphatidylinositol 3-kinase/Akt phosphorylation and STAT activation, and the subsequent translocation of STAT to the nucleus. Together, our data demonstrate that PA-activated macrophages produce IL-1beta and IL-6 and that these processes require the activation of the JAK2-STAT1/3 or JAK2-Akt-STAT signaling pathways.
Lee
ChuHee
C
Department of Biochemistry and Molecular Biology, College of Medicine, Yeungnam University, Nam-Gu, Daegu 705-035, South Korea.
Lim
Hyung-Kyu
HK
Sakong
Joon
J
Lee
Yun-Sik
YS
Kim
Jae-Ryong
JR
Baek
Suk-Hwan
SH
D021581:Active Transport, Cell Nucleus; D000818:Animals; D004789:Enzyme Activation; D007375:Interleukin-1 / Q000096:biosynthesis*; D015850:Interleukin-6 / Q000096:biosynthesis*; D053614:Janus Kinase 2; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology; D051379:Mice; D010712:Phosphatidic Acids / Q000494:pharmacology*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction
D007375:Interleukin-1; D015850:Interleukin-6; D010712:Phosphatidic Acids; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D051057:Proto-Oncogene Proteins c-akt