title: Cross-talk between alpha(1B)-adrenergic receptor (alpha(1B)AR) and interleukin-6 (IL-6) signaling pathways. Activation of alpha(1b)AR inhibits il-6-activated STAT3 in hepatic cells by a p42/44 mitogen-activated protein kinase-dependent mechanism.
abstract: Treatment of primary rat hepatocytes or tranfected HepG2 cells with the alpha(1B)-adrenergic receptor (alpha(1B)AR) agonist phenylephrine (PE) significantly inhibited interleukin 6 (IL-6)-induced STAT3 binding, tyrosine phosphorylation, and IL-6-induced serum amyloid A mRNA expression. Western analyses and in vitro kinase assays indicate that this inhibition is not due to either down-regulation of STAT3 protein expression nor inactivation of upstream-located JAK1 and JAK2. Blocking the new RNA and protein syntheses antagonized the inhibitory effect of PE on IL-6-activated STAT3, suggesting synthesis of an inhibitory factor(s) is involved. The inhibitory effect of PE on IL-6 activation of STAT3 was also abolished by the tyrosine phosphatase inhibitor sodium vanadate, indicating involvement of protein tyrosine phosphatases. Furthermore, preincubation of the cells with the specific MEK1 inhibitor PD98059 or a dominant negative MEK1 reversed the inhibitory effect of PE, and expression of constitutively activated MEK1 alone abolished IL-6-activated STAT3. Taken together, these data indicate that PE inhibits IL-6 activation of STAT3 in hepatic cells by a p42/44 mitogen-activated protein kinase-dependent mechanism, and tyrosine phosphatases are involved. This inhibitory cross-talk between the alpha(1B)AR and IL-6 signaling pathways implicates the alpha(1B)AR involvement in regulating the IL-6-mediated inflammatory responses.
authors.affiliation: Department of Pharmacology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, USA.
authors.forename: V A
authors.initials: VA
authors.lastname: Nguyen
authors.forename: B
authors.initials: B
authors.lastname: Gao
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D015850:Interleukin-6 / Q000494:pharmacology / Q000502:physiology*; D008099:Liver / Q000187:drug effects / Q000502:physiology*; D048369:MAP Kinase Kinase 1; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000502:physiology*; D050796:STAT3 Transcription Factor; D000685:Serum Amyloid A Protein / Q000235:genetics*; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C547718:Adra1b protein, rat; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D015850:Interleukin-6; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D050796:STAT3 Transcription Factor; D000685:Serum Amyloid A Protein; C494088:Stat3 protein, rat; D015534:Trans-Activators; D010656:Phenylephrine; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D017027:Protein Tyrosine Phosphatases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one