Angiotensin Type 2 Receptor–Mediated Phosphorylation of eNOS in the Aortas of Mice With 2-Kidney, 1-Clip Hypertension

Abstract

Abstract-To evaluate the role of vascular angiotensin II (Ang II) type 2 (AT 2 ) receptor in renovascular hypertension, we investigated expressions of AT 2 receptor and endothelial nitric oxide synthase (eNOS) in thoracic aortas of mice with 2-kidney, 1-clip (2K1C) hypertension. The mRNA levels of AT 2 receptor in aortas, but not those of AT 1 and bradykinin B 2 receptors, increased 14 days but not 42 days after clipping. The contractile response to Ang II (Ͼ0.1 mol/L) was attenuated in aortic rings excised 14 days after clipping and was restored to that of rings from sham mice by antagonists of AT 2 receptor (PD123319) and B 2 receptor (icatibant). The aortic levels of total eNOS, phosphorylated eNOS at Ser 1177 (p-eNOS), total Akt, and phosphorylated Akt at Ser 473 (p-Akt) were increased in 2K1C mice on day 14, whereas only eNOS levels were increased on day 42. The aortic cGMP levels were Ϸ20-fold greater in 2K1C mice on day 14 compared with sham mice. Administration of nicardipine for 4 days before the excision of aortas 14 days after clipping not only reduced blood pressure but also decreased the aortic levels of eNOS, p-eNOS, Akt, p-Akt, and cGMP to sham levels, whereas the administration of PD123319 or icatibant to 2K1C mice decreased p-eNOS and cGMP to sham levels without affecting blood pressure and the levels of eNOS, Akt and p-Akt. These results suggest that vascular NO production is enhanced by increased eNOS phosphorylation via the activation of AT 2 receptors in the course of 2K1C hypertension. Key Words: angiotensin II Ⅲ bradykinin Ⅲ cyclic GMP Ⅲ nitric oxide synthase Ⅲ hypertension, renovascular T he 2-kidney, 1-clip (2K1C) Goldblatt model of hypertension is an experimental model that in many respects resembles human renovascular hypertension. It is welldocumented that the increased activity of the renin-angiotensin system by the renal secretion of renin plays an important role in the development and maintenance of 2K1C hypertension. 1 The critical role of the angiotensin II (Ang II) type 1 (AT 1 ) receptor in mediating 2K1C hypertension has been confirmed, 2,3 whereas the role of the Ang II type 2 (AT 2 ) receptor in the development of 2K1C hypertension remains poorly understood. Recent studies have demonstrated that the acute and chronic AT 2 receptor blockade by PD123319 does not worsen the course of hypertension in 2K1C hypertensive mice, suggesting that the AT 2 receptor does not play a major counterbalancing role against the vasoconstricting actions of Ang II in 2K1C hypertension. 2,4 In a previous study using mice with abdominal aortic banding, we demonstrated the upregulation of AT 2 receptors in thoracic aortas, and that the stimulation of AT 2 receptors by Ang II attenuated the AT 1 receptor-mediated contractile response to Ang II in the aorta via the activation of the kinin-nitric oxide (NO)-cGMP cascade. 5 In addition, we provided evidence that the elevation of plasma renin levels after the banding-induced reduction of renal blood pressure is associated with the upregulation of AT 2 re...

Angiotensin II Type 2 Receptors and Nitric Oxide Sustain Oxygenation in the Clipped Kidney of Early Goldblatt Hypertensive Rats

“…[31][32][33] The mRNA for AT 2 receptors is upregulated in the aorta of mice with early 2K,1C hypertension. 34 Moreover, AT 2 receptor activation limits aortic contractions to Ang II in this model by phosphorylation of endothelial NOS and increasing vascular cGMP. 34 NO generation in the clipped kidney may account for our finding that blockade of AT 1 or AT 2 receptors or NOS apparently prevented any further fall in the CBF of clipped kidneys with enalaprilat ( Figure 2A).…”

“…34 Moreover, AT 2 receptor activation limits aortic contractions to Ang II in this model by phosphorylation of endothelial NOS and increasing vascular cGMP. 34 NO generation in the clipped kidney may account for our finding that blockade of AT 1 or AT 2 receptors or NOS apparently prevented any further fall in the CBF of clipped kidneys with enalaprilat ( Figure 2A). This confirms the conclusions of Beierwaltes and colleagues 20,35 that the RBF of the clipped kidney of early 2K,1C renovascular hypertensive rats is highly dependent on NOS, although this effect wanes with time.…”

Differences in Cardiovascular Responses to Alamandine in Two-Kidney, One Clip Hypertensive and Normotensive Rats

“…29 Additionally, expression of the AT2 receptors within the heart under normal conditions is extremely low; however, during hypertension, its expression increases to the degree that its action predominates over that of the AT1 receptors. 32 AT2R messenger ribonucleic acid (mRNA) is upregulated in the aorta of mice with early 2K1C hypertension, 33 and AT2R activation limits Ang II-induced aortic contractions in 2K1C hypertensive rats (via the phosphorylation of endothelial NO synthase and the increased production of vascular cGMP). 33 Thus, the increased expression of AT1 receptors and the decreased expression of PD123319-sensitive receptors in the normotensive rats in comparison to that in the 2K1C hypertensive rats may be responsible for the alamandine's pressor effect that was observed in the normotensive rats.…”

“…32 AT2R messenger ribonucleic acid (mRNA) is upregulated in the aorta of mice with early 2K1C hypertension, 33 and AT2R activation limits Ang II-induced aortic contractions in 2K1C hypertensive rats (via the phosphorylation of endothelial NO synthase and the increased production of vascular cGMP). 33 Thus, the increased expression of AT1 receptors and the decreased expression of PD123319-sensitive receptors in the normotensive rats in comparison to that in the 2K1C hypertensive rats may be responsible for the alamandine's pressor effect that was observed in the normotensive rats. 29, 33 It is possible that alamandine's pressor effect masks the depressor response in normotensive rats.…”

Increased expression of insulin-like growth factor-binding protein-3 is implicated in erectile dysfunction in two-kidney one-clip hypertensive rats after propranolol treatment

“…3 A large body of evidence has shown that nitric oxide (NO) production is increased as a buffer against hypertension in two-kidney one-clip (2K-1C) hypertensive animal models. [4][5][6] The increase in NO production that is observed in several vascular beds from 2K-1C hypertensive animals may not completely prevent high blood pressure but could serve as a protective vascular mechanism that contributes to the preservation of the erectile function in this model. 7 Insulin-like growth factor-binding protein-3 (IGFBP-3) is a member of the insulin-like growth factor (IGF) family.…”