Angiotensin II activates nuclear transcription factor kappaB through AT(1) and AT(2) in vascular smooth muscle cells: molecular mechanisms.

Nuclear factor-kappaB (NF-kappaB) regulates many genes involved in vascular physiopathology. We have previously observed in vivo NF-kappaB 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-kappaB activity in rat vascular smooth muscle cells, evaluating the molecular mechanisms and the specific receptor subtype involved. Ang II increased NF-kappaB DNA binding (5-fold, 10(-)(9) mol/L at 1 hour; electrophoretic mobility shift assay), nuclear translocation of p50/p65 subunits, and cytosolic inhibitor kappaBalpha (IkappaBalpha) degradation. Ang II elicited NF-kappaB-mediated transcription (transfection of a reporter gene) and expression of NF-kappaB-related genes (monocyte chemoattractant protein-1 and angiotensinogen). AT(1) (DUP753) and AT(2) (PD123319 and CGP42112) receptor antagonists inhibited Ang II-induced NF-kappaB DNA binding in a dose-dependent manner ( approximately 85% for each one; 10(-)(5) mol/L at 1 hour). The AT(2) agonist p-aminophenylalanine(6)-Ang II augmented NF-kappaB binding (4.6-fold, 10(-)(9) mol/L at 1 hour), p65 nuclear levels, and transcription of an NF-kappaB reporter gene. AT(1) antagonist markedly inhibited NF-kappaB-mediated transcription and gene expression. Some differences between AT(1)/AT(2) intracellular signals were found. Antioxidants and ceramide inhibitors, but not protein kinase C inhibitors, diminished NF-kappaB activation elicited by both Ang II and the AT(2) agonist, while tyrosine kinase inhibitors only decreased Ang II-induced NF-kappaB activity. Our results demonstrate that Ang II activates NF-kappaB via AT(1) and AT(2), although NF-kappaB-mediated transcription occurred mainly through AT(1). Both receptors share some signaling pathways (oxygen radicals and ceramide); however, tyrosine kinases only participate in AT(1)/NF-kappaB responses. These data provide novel insights into Ang II actions, suggesting a potential implication of the AT(2) in the pathobiology of vascular cells.