Activation of Endothelial Nitric Oxide Synthase by the Angiotensin II Type 1 Receptor

Abstract

Enhanced angiotensin II (AngII) action has been implicated in endothelial dysfunction that is characterized as decreased nitric oxide availability. Although endothelial cells have been reported to express AngII type 1 (AT1) receptors, the exact role of AT1 in regulating endothelial NO synthase (eNOS) activity remains unclear. We investigated the possible regulation of eNOS through AT1 in bovine aortic endothelial cells (BAECs) and its functional significance in rat aortic vascular smooth muscle cells (VSMCs). In BAECs infected with adenovirus encoding AT1 and in VSMCs infected with adenovirus encoding eNOS, AngII rapidly stimulated phosphorylation of eNOS at Ser1179. This was accompanied with increased cGMP production. These effects were blocked by an AT1 antagonist. The cGMP production was abolished by a NOS inhibitor as well. To explore the importance of eNOS phosphorylation, VSMCs were also infected with adenovirus encoding S1179A-eNOS. AngII did not stimulate cGMP production in VSMCs expressing S1179A. However, S1179A was able to enhance basal NO production as confirmed with cGMP production and enhanced vasodilator-stimulated phosphoprotein phosphorylation. Interestingly, S1179A prevented the hypertrophic response similar to wild type in VSMCs. From these data, we conclude that the AngII/AT1 system positively couples to eNOS via Ser1179 phosphorylation in ECs and VSMCs if eNOS and AT1 coexist. However, basal level NO production may be sufficient for prevention of AngII-induced hypertrophy by eNOS expression. These data demonstrate a novel molecular mechanism of eNOS regulation and function and thus provide useful information for eNOS gene therapy under endothelial dysfunction.

Thromboxane A2-induced Bi-directional Regulation of Cerebral Arterial Tone

“…Nonetheless, U-46619 stimulation results in increased contractile force and RLC 20 phosphorylation, suggesting that Ca 2ϩ -sensitized force generation overcomes the up-regulation of cGMP. Signaling through G ␣12/13 (64), angiotensin II (type-1) receptor (AT 1 ) activation has been shown to stimulate NO production and release in cultured bovine aortic endothelial cells (65) and rat carotid arteries in vivo (66). We observe significant increases in cGMP in intact cerebral vessels following TXA 2 R activation, likely through NOS activation.…”

Mechanism of Endothelial Nitric Oxide Synthase Phosphorylation and Activation by Thrombin

“…We also confirmed recently the requirement of Ser 1179 phosphorylation for eNOS activation via a G q -coupled angiotensin II receptor. 25 Moreover, the relationship between Ca 2ϩ and the regulation of eNOS phosphorylation by G protein-coupled receptors (GPCRs) has not been established previously. Therefore, our findings are novel in that Ca 2ϩ is also required for eNOS activation by a GPCR agonist through its input on the phosphorylation of Ser 1179 .…”

Novel Role of Protein Kinase C-δ Tyr 311 Phosphorylation in Vascular Smooth Muscle Cell Hypertrophy by Angiotensin II

“…After aspiration of the medium, cells were washed twice with ice-cold Hanks' balanced salt solution, and the total amount of cellular protein was measured as described previously. 27 …”