Angiotensin II-derived reactive oxygen species underpinning the processing of the cardiovascular reflexes in the medulla oblongata

Abstract

The brainstem is a major site in the central nervous system involved in the processing of the cardiovascular reflexes such as the baroreflex and the peripheral chemoreflex. The nucleus tractus solitarius and the rostral ventrolateral medulla are 2 important brainstem nuclei, and they play pivotal roles in autonomic cardiovascular regulation. Angiotensin II is one of the neurotransmitters involved in the processing of the cardiovascular reflexes within the brainstem. It is well-known that one of the mechanisms by which angiotensin II exerts its effect is via the activation of pathways that generate reactive oxygen species (ROS). In the central nervous system, ROS are reported to be involved in several pathological diseases such as hypertension, heart failure and sleep apnea. However, little is known about the role of ROS in the processing of the cardiovascular reflexes within the brainstem. The present review mainly discussed some recent findings documenting a role for ROS in the processing of the baroreflex and the peripheral chemoreflex in the brainstem.

Brain stem adenosine receptors modulate centrally mediated hypotensive responses in conscious rats: A review

“…A large body of evidence supports the view that the RVLM is the major brain stem area that controls sympathetic drive by projecting directly to the spinal cord [1,8–10] . Neuronal activation in the RVLM causes an increase in arterial pressure mediated by an increase in peripheral resistance, cardiac output, and secretion of catecholamines [1] .…”

NADPH Oxidases in Vascular Pathology

“…However, Ang II induces expression of individual NADPH oxidase homologues, particularly Nox2 in the brain, which may be related to increased sympathetic nervous system activation (92). Taken together, it is possible that an increase in NADPH oxidase-derived ROS in CVOs, hypothalamic nuclei, and brainstem sites plays a central role in the neurocardiovascular dysfunction observed in hypertension (21). Vascular NADPH oxidases could also be important, as Nox2 appears to be a prominent mediator of the harmful effects of Ang II in the cerebral circulation during hypertension (34).…”

Angiotensin-II-derived reactive oxygen species on baroreflex sensitivity during hypertension: new perspectives

“…One limitation is that, in a variety of cell types, Nox transcript levels at baseline do not necessarily predict stimulus-induced activation of the enzymes, and opposing functions of various enzymes have been detected under different physiological conditions. Taken together, it is possible to suggest that an increase in NADPH oxidase-derived ROS in circumventricular organs CVOs, hypothalamic nuclei, and brainstem sites play a central role in the neurocardiovascular dysfunction observed in hypertension (Braga et al, 2011a,b). …”