Abstract
Activation of the sympathetic nervous system (SNS) has an important role in the pathogenesis of hypertension, and is determined by the brain. Previous many studies have demonstrated that oxidative stress, mainly produced by angiotensin II type 1 (AT1) receptor and nicotinamide adenine dinucleotide phosphate (NAD (P) H) oxidase, in the autonomic brain regions was involved in the activation of the SNS of hypertension. In this concept, we have investigated the role of oxidative stress in the rostral ventrolateral medulla (RVLM), which is known as the cardiovascular center in the brainstem, in the activation of the SNS, and demonstrated that AT1 receptor and NAD (P) H oxidase-induced oxidative stress in the RVLM causes sympathoexcitation in hypertensive rats. The mechanisms in which brain oxidative stress causes sympathoexcitation have been investigated, such as the interactions with nitric oxide (NO), effects on the signal transduction, or inflammations. Interestingly, the environmental factors of high salt intake and high calorie diet may also increase the oxidative stress in the brain, particularly in the RVLM, thereby activating the central sympathetic outflow and increasing the risk of hypertension. Furthermore, several orally administered AT1 receptor blockers have been found to cause sympathoinhibition via reduction of oxidative stress through the inhibition of central AT1 receptor. In conclusion, we must consider that AT1 receptor and the related oxidative stress production in the brain cause the activation of SNS in hypertension, and that AT1 receptor in the brain could be novel therapeutic target of the treatments for hypertension.
Highlights
Recent many studies have suggested that sympathetic nervous system (SNS) is important in the pathogenesis, initial pathological events, development, and end organ damages of hypertension (Grassi, 2009, 2010; Esler, 2010; Grassi et al, 2010; Mauo et al, 2010)
The rostral ventrolateral medulla (RVLM) neurons determine the basal central sympathetic outflow and integrate the inputs from baroreceptors, chemoreceptors, and visceral receptors via the nucleus of the solitary tract (NTS) (Pilowsky and Goodchild, 2002; Dampney et al, 2003; Sved et al, 2003; Campos and Bergamschi, 2006; Guyenet, 2006; Carlson and Wyss, 2008), and it receives the inputs from the paraventricular nucleus (PVN) of the hypothalamus, which is known as a key nucleus of the central cardiovascular regulation (Pilowsky and Goodchild, 2002; Dampney et al, 2005; Coote, 2007)
Our these findings indicate that oxidative stress in the RVLM increased blood pressure, which may have occurred via an activation of the SNS, and this mechanism was involved in the neural pathophysiology of hypertension in SHRSPs
Summary
Reviewed by: Saurabh Aggarwal, Georgia Health Sciences University, USA Marcos Lopez, Fundación Cardiovascular de Colombia, Colombia. Previous many studies have demonstrated that oxidative stress, mainly produced by angiotensin II type 1 (AT1) receptor and nicotinamide adenine dinucleotide phosphate (NAD (P) H) oxidase, in the autonomic brain regions was involved in the activation of the SNS of hypertension. In this concept, we have investigated the role of oxidative stress in the rostral ventrolateral medulla (RVLM), which is known as the cardiovascular center in the brainstem, in the activation of the SNS, and demonstrated that AT1 receptor and NAD (P) H oxidase-induced oxidative stress in the RVLM causes sympathoexcitation in hypertensive rats.
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