Angiotensin II induces interleukin-6 transcription in vascular smooth muscle cells through pleiotropic activation of nuclear factor-kappa B transcription factors.
Interleukin-6 (IL-6) is a multifunctional cytokine expressed by angiotensin II (Ang II)-stimulated vascular smooth muscle cells (VSMCs) that functions as an autocrine growth factor. In this study, we analyze the mechanism for Ang II-inducible IL-6 expression in quiescent rat VSMCs. Stimulation with the Ang II agonist Sar1 Ang II (100 nmol/L) induced transcriptional expression of IL-6 mRNA transcripts of 1.8 and 2.4 kb. In transient transfection assays of IL-6 promoter/luciferase reporter plasmids, Sar1 Ang II treatment induced IL-6 transcription in a manner completely dependent on the nuclear factor-kappaB (NF-kappaB) motif. Sar1 Ang II induced cytoplasmic-to-nuclear translocation of the NF-kappaB subunits Rel A and NF-kappaB1 with parallel changes in DNA-binding activity in a biphasic manner, which produced an early peak at 15 minutes followed by a nadir 1 to 6 hours later and a later peak at 24 hours. The early phase of NF-kappaB translocation was dependent on weak simultaneous proteolysis of the IkappaBalpha and beta inhibitors, whereas later translocation was associated with enhanced processing of the p105 precursor into the mature 50-kDa NF-kappaB1 form. Pretreatment with a potent inhibitor of IkappaBalpha proteolysis, TPCK, completely blocked Sar1 Ang IIAng II-induced NF-kappaB activation and induction of endogenous IL-6 gene expression, which indicated the essential role of NF-kappaB in mediating IL-6 expression. We conclude that Ang II is a pleiotropic regulator of the NF-kappaB transcription factor family and may be responsible for activating the expression of cytokine gene networks in VSMCs.
Han
Y
Y
Department of Internal Medicine, University of Texas Medical Branch, Galveston, Tex.77555-1060, USA.
Runge
M S
MS
Brasier
A R
AR
D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002467:Cell Nucleus / Q000737:chemistry; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D020672:I-kappa B Proteins; D015850:Interleukin-6 / Q000096:biosynthesis / Q000235:genetics*; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D011480:Protease Inhibitors / Q000494:pharmacology; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D051996:Transcription Factor RelA; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D000093242:Interleukin-6 Inhibitors
D000804:Angiotensin II; D004247:DNA; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D015850:Interleukin-6; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D011480:Protease Inhibitors; D020033:Protein Isoforms; D051996:Transcription Factor RelA; D014662:Vasoconstrictor Agents; D000093242:Interleukin-6 Inhibitors; C083487:I kappa B beta protein; C000606206:Nfkbia protein, rat