Angiotensin II Activates Nuclear Transcription Factor κB Through AT 1 and AT 2 in Vascular Smooth Muscle Cells

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Abstract
—Nuclear factor-κB (NF-κB) regulates many genes involved in vascular physiopathology. We have previously observed in vivo NF-κB activation in injured vessels that diminished by angiotensin-converting enzyme inhibition. In the present work, we investigated the effect of angiotensin II (Ang II) on NF-κB activity in rat vascular smooth muscle cells, evaluating the molecular mechanisms and the specific receptor subtype involved. Ang II increased NF-κB DNA binding (5-fold, 10−9 mol/L at 1 hour; electrophoretic mobility shift assay), nuclear translocation of p50/p65 subunits, and cytosolic inhibitor κBα (IκBα) degradation. Ang II elicited NF-κB–mediated transcription (transfection of a reporter gene) and expression of NF-κB–related genes (monocyte chemoattractant protein-1 and angiotensinogen). AT1 (DUP753) and AT2 (PD123319 and CGP42112) receptor antagonists inhibited Ang II–induced NF-κB DNA binding in a dose-dependent manner (≈85% for each one; 10−5 mol/L at 1 hour). The AT2 agonist p-aminophenylalanine6–Ang II augmented NF-κB binding (4.6-fold, 10−9 mol/L at 1 hour), p65 nuclear levels, and transcription of an NF-κB reporter gene. AT1 antagonist markedly inhibited NF-κB–mediated transcription and gene expression. Some differences between AT1/AT2 intracellular signals were found. Antioxidants and ceramide inhibitors, but not protein kinase C inhibitors, diminished NF-κB activation elicited by both Ang II and the AT2 agonist, while tyrosine kinase inhibitors only decreased Ang II–induced NF-κB activity. Our results demonstrate that Ang II activates NF-κB via AT1 and AT2, although NF-κB–mediated transcription occurred mainly through AT1. Both receptors share some signaling pathways (oxygen radicals and ceramide); however, tyrosine kinases only participate in AT1/NF-κB responses. These data provide novel insights into Ang II actions, suggesting a potential implication of the AT2 in the pathobiology of vascular cells.