Central administration of angiotensin-(1–7) stimulates nitric oxide release and upregulates the endothelial nitric oxide synthase expression following focal cerebral ischemia/reperfusion in rats

doi:10.1016/j.npep.2008.09.005

Neuropeptides

Volume 42, Issues 5–6, October–December 2008, Pages 593-600

https://doi.org/10.1016/j.npep.2008.09.005 Get rights and content

Abstract

Angiotensin-(1–7) [Ang-(1–7)] is an endogenous peptide of the renin–angiotensin system with several beneficial effects that are often opposite to those attributed to angiotensin II (Ang II). Since there are no data available so far on the role of Ang-(1–7) after cerebral ischemia/reperfusion, in this paper, we investigated the central administration of Ang-(1–7) modulates in vivo the nitric oxide(NO) release and the endothelial NO synthase (eNOS) expression following focal cerebral ischemia/reperfusion in rats. Cerebral ischemia–reperfusion injury was induced by intraluminal thread occlusion of middle cerebral artery in the adult male rats. The levels of NO in ischemic tissues were measured by NO detection kits. Reverse transcription (RT)-PCR and western blot were used to determine messenger RNA (mRNA) and protein levels of the eNOS in ischemic tissues. The cerebral ischemic lesion resulted in a significant increase of NO release at 3 and 6 h compared with sham operation group in our model after reperfusion, whereas both medium and high doses Ang-(1–7) markedly enhanced NO levels at 3–24 h, and 3–72 h after reperfusion, respectively. In addition, NO release increased was significantly induced by high-dose Ang-(1–7) compared with medium-dose Ang-(1–7) at 24–72 h after reperfusion. Medium and high-dose Ang-(1–7) significantly stimulated eNOS activation when compared with artificial cerebrospinal fluid (aCSF) treatment group at 3, 6, 12, 24, and 48 h after reperfusion, however, no significant changes in eNOS expression were found between medium and high-dose Ang-(1–7) at different times after the ischemic insult. These findings indicate that medium and high-dose Ang-(1–7) stimulate NO release and upregulate eNOS expression in ischemic tissues following focal cerebral ischemia/reperfusion in rats.

Introduction

The renin–angiotensin system (RAS) is responsible for the homeostasis of arterial blood pressure and water and hydroelectrolyte balance (McKinley et al., 2003), being an important and intensively studied its role in the regulation of the cardiovascular, cerebrovascular and renal functions. Accumulation of a large number of evidence during the past two decades testifies to the complexity of the RAS (Varagic et al., 2008). Ang-(1–7) was first discovered more than 30 years ago and since then it has been explored in the context of cardiovascular function. It is known that it often counteracts the effects caused by Ang II (Santos et al., 2000, Schmaier, 2003) and that makes it an excellent target for experimental and pharmacological research (Iusuf et al., 2008).

Acting both peripherally and centrally, Ang II is a multifunctional hormone that regulates blood pressure, vascular tone, and fluid volume. The biological effects of Ang II are mediated by two major types of receptors, type 1 (AT₁) and type 2 (AT₂). It is widely accepted that Ang II stimulates the production of NO (Yan et al., 2003, Olson et al., 2004, Yin et al., 2008), a key regulator of blood pressure, vascular remodeling, and angiogenesis. However, there are inconsistencies in the literature concerning the mechanism of activation. The Ang II-dependent increase in NO has been linked to both the AT₁ (Saito et al., 1996, Gragasin et al., 2003) and the AT₂ receptors (Olson et al., 2004, Ritter et al., 2003). It has been generally accepted that Ang II and NO are important agents which regulate cardiovascular and cerebrovascular activities.

In recent years, it became apparent that the balance between the two opposing effector peptides, Ang II and Ang-(1–7), may have a pivotal role in determining different renal and cardiovascular pathophysiologies. Furthermore, the vasodilator response associated with Ang-(l–7) therapy may be due to local accumulation of bradykinin (BK) and NO (Feterik et al., 2000), whereas Ang-(l–7) responses were mediated by NO release. Many studies have in addition provided evidence that the actions of Ang-(1–7) involve a NO-mediated mechanism, suggested in accordance with previous reports that demonstrated NO dependence in various Ang-(1–7) effects (Brosnihan et al., 1996, Nakamoto et al., 1995, Heitsch et al., 2001). In addition to Ang II, Ang-(1–7) may also have important biological activities in the brain. More recent in our laboratory, (Lu et al., 2008) provided evidence for the complex interactions between Ang-(1–7) and kallikrein–kinin system in the CNS after focal cerebral ischemia/reperfusion in rats.

Nitric oxide exerts both beneficial and harmful effects in the pathogenesis of cerebral ischemic injury(Vallance and Leiper, 2002) and eNOS-derived NO is beneficial in promoting collateral circulation and microvascular flow during the early stages of cerebral ischemia(Veltkamp et al., 2002, Osuka et al., 2004). Up to now, the role of Ang-(1–7) in regulating NO release remains unclear. This studies were conducted to explore whether the central administration of Ang-(1–7) modulates in vivo the NO release and the eNOS expression following focal cerebral ischemia/reperfusion in rats.

Section snippets

Drugs and animals

Ang-(1–7) was purchased from Bachem, Inc (Bachem, Switzerland) and was dissolved in an artificial cerebrospinal fluid (aCSF, pH 7.4, composition in mM: NaCl 130, KCl 2.99, CaCl₂ 0.98, MgCl₂ 6H₂O 0.80, NaHCO₃ 25, Na₂HPO₄ 12H₂O 0.039, NaH₂PO₄ 2H₂O 0.46, equilibrated with 95%O₂/5%CO₂). Male Sprague–Dawley rats (280–320 g) were offered by National Rodent Laboratory Animal Resources Shanghai branch of China. Food and water were provided ad-libitum. All experimental protocols were performed in

The levels of NO in cerebral ischemic tissues

It has a significant two-factor interaction between Ang-(1–7) treatment and time point after reperfusion (P < 0.001, two-way ANOVA).The cerebral ischemic lesion resulted in a significant increase of NO release at 3 h and 6 h compared with sham operation group in our model after reperfusion (Fig. 1), whereas medium and high-dose Ang-(1–7) markedly enhanced NO levels at 3–24 h, and 3–72 h after reperfusion, respectively. In addition, NO release increased was significantly induced by high-dose Ang-(1–7)

Discussion

Ang-(1–7) is currently considered as one of the bioactive end products of the RAS and is originated either from Ang I or Ang II by the action of peptidases (Santos et al., 2000). Conversely, some of the effects of Ang-(1–7) are opposite to those elicited by Ang II and Ang-(1–7) is considered as an Ang II counter-regulatory peptide within the RAS. Moreover, the recent identification of the Ang-(1–7)-forming enzyme ACE2 and of the G-protein-coupled receptor Mas as one of Ang-(1–7) receptors (

Acknowledgments

This work was supported by a grant from the National Science Foundation of JiangSu Province (No. BK 2007007), People’s Republic of China.

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Central administration of angiotensin-(1–7) stimulates nitric oxide release and upregulates the endothelial nitric oxide synthase expression following focal cerebral ischemia/reperfusion in rats

Abstract

Introduction

Section snippets

Drugs and animals

The levels of NO in cerebral ischemic tissues

Discussion

Acknowledgments

Brain Res.

Eur. J. Pharmacol.

Brain Res.

Brain Res.

Int. J. Biochem. Cell Biol.

Cell Calcium

Regul. Pept.

Peptides

Brain Res.

Brain Res.

Nitric oxide synthases: structure, function and inhibition

Biochem. J.

Core and penumbral nitric oxide synthase activity during cerebral ischemia and reperfusion

Stroke

Immunofluorescence localization of the receptor Mas in cardiovascular-related areas of the rat brain

Am. J. Physiol. Heart Circ. Physiol.

The interactions of nitric oxide with oxygen radicals and scavengers in cerebral ischemic injury

Adv. Neurol.

Angiotensin-(1–7) dilates canine coronary arteries through kinins and nitric oxide

Hypertension

Short-term angiotensin(1–7) receptor MAS stimulation improves endothelial function in normotensive rats

Hypertension

The antithrombotic effect of angiotensin-(1–7) involves mas-mediated NO release from platelets

Mol. Med.

Estrogen reduces angiotensin II-induced nitric oxide synthase and NAD(P)H oxidase expression in endothelial cells

Arterioscler. Thromb. Vasc. Biol.