Elevated blood pressure in normotensive rats produced by ‘knockdown’ of the angiotensin type 2 receptor

Abstract

Most of our knowledge of the function of the angiotensin type 2 receptor (AT 2 R) has been obtained from transgenic mouse models. The aim of the present study was to investigate the role of the AT 2 R in normotensive Sprague-Dawley (SD) rats by using antisense gene transfer technology to 'knockdown' this specific receptor subtype. A retroviral vector containing full-length AT 2 R antisense cDNA (AT 2 R-AS) was constructed and the effectiveness of the transduction of AT 2 R-AS was studied in vitro. In subsequent in vivo studies, 5-day-old normotensive SD rats received a single intracardiac bolus (25 µl) of AT 2 R-AS viral particles. When animals reached adulthood, direct blood pressure (BP), and both pressor and dipsogenic responses to angiotensin II were investigated. Long-lasting expression of the AT 2 R-AS transcript and a reduction in mRNA and binding of the AT 2 R was observed in vitro. Expression of AT 2 R-AS transcript was maintained for 90 days in heart, kidney, lung and brain, indicating a high degree of transgene transduction in vivo. As adults, systolic BP and the pressor responses to angiotensin were significantly elevated in AT 2 R-AS-treated rats. However, AT 2 R-AS-treated rats displayed significantly reduced dipsogenic responses to both angiotensin and water deprivation. Collectively, these data demonstrate that a single neonatal injection of the retroviral vector containing antisense to the AT 2 receptors in rats results in similar cardiovascular and dipsogenic responses as reported in AT 2 R knockout mice.

Nicotine Modulates the Renin–Angiotensin System of Cultured Neurons and Glial Cells from Cardiovascular Brain Areas of Wistar Kyoto and Spontaneously Hypertensive Rats

“…For this reason, we analyzed AT 2 R in cultured neurons only. In spite of some participation of AT 2 R in cardiovascular control of adult rats (Ichiki et al 1995, Li et al 2003, Wang et al 2004), this receptor is recognized for its major roles during brain development and neural differentiation (Cote et al 1999, Rodriguez-Pallares et al 2004, Li et al 2007) as well as neuroprotection (Lu et al 2004).…”

C-Reactive Protein Causes Downregulation of Vascular Angiotensin Subtype 2 Receptors and Systolic Hypertension in Mice

“…22 Although not observed in all prior studies of genetic knockdown of AT 2 , the loss of AT 2 has been found to cause an elevation in basal BP in both mice and rats. [23][24][25] In Sprague-Dawley rats in which AT 2 knockdown was accomplished by administering AT 2 antisense cDNA in the neonatal period, primarily basal systolic BP was increased during adulthood. 25 Mice and rats with AT 2 deficiency have uniformly exhibited exaggerated increases in BP in response to angiotensin II infusion, [23][24][25] whereas the BP response to AT 1 blockade in mice with AT 2 deficiency is identical to that of wild-type mice.…”

“…[23][24][25] In Sprague-Dawley rats in which AT 2 knockdown was accomplished by administering AT 2 antisense cDNA in the neonatal period, primarily basal systolic BP was increased during adulthood. 25 Mice and rats with AT 2 deficiency have uniformly exhibited exaggerated increases in BP in response to angiotensin II infusion, [23][24][25] whereas the BP response to AT 1 blockade in mice with AT 2 deficiency is identical to that of wild-type mice. 23 Thus, multiple characteristics of the hypertension phenotype of the CRP transgenic mice mimic those of genetic AT 2 deficiency.…”

Pharmacological, Immunological, and Gene Targeting of the Renin-Angiotensin System for Treatment of Cardiovascular Disease

“…For that reason, many investigators have used an antisense inhibition technique in vivo to decrease genes for vasoconstriction (ACE, AT 1 receptor, angiotensinogen, or renin) [169][170][171][172][173][174][175]. In another strategy, the goal was to increase genes for vasodilation, for example, insertion of gene copies for ACE2 [119], AT 2 receptor [176], kallikrein [177], atrial natriuretic peptide [178], and endothelial nitric oxide synthase [179].…”