Abstract-Hypertension caused by angiotensin II (Ang II) infusion is associated with oxidative stress in the peripheral vasculature and kidney. The role of redox mechanisms in the central nervous system (CNS), a tissue known to be pivotal in Ang II-dependent hypertension, has not been investigated. ) over a 2-week period in mice caused a gradually developing hypertension that was correlated with marked elevations in O 2 ⅐Ϫ production specifically in the subfornical organ (SFO), a brain region lying outside the blood-brain barrier and known to be a primary sensor for blood-borne Ang II. Adenoviral-mediated delivery of cytoplasmically targeted superoxide dismutase (SOD) selectively to this site prevented the hypertension and the increased O 2 ⅐Ϫ production, whereas gene transfer of SOD targeted to the extracellular matrix had no effect. These data suggest that increased intracellular O 2 ⅐Ϫ production in the SFO is critical in the development of Ang II-induced hypertension. Key Words: reactive oxygen species Ⅲ brain Ⅲ subfornical organ Ⅲ neurons Ⅲ blood pressure V arious forms of hypertension are characterized by an elevation in angiotensin II (Ang II) levels. 1,2 Abundant evidence now suggests that a key mechanism by which Ang II influences blood pressure is via its ability to produce reactive oxygen species (ROS). A decade ago, Griendling et al first discovered that Ang II activates the vascular smooth muscle NAD(P)H oxidase, an important cellular source of ROS. 3 Subsequently, it was shown that hypertension caused by Ang II infusion, but not norepinephrine infusion, increased vascular superoxide (O 2 ⅐Ϫ ) production in vivo 4 and that treatment with liposome-encapsulated superoxide dismutase (SOD) was effective in preventing this form of hypertension. 5 More recent studies demonstrating that genetic disabling of the NADPH oxidase complex attenuates Ang II-induced increases in vascular O 2 ⅐Ϫ production and hypertension further implicates ROS, particularly O 2 ⅐Ϫ

Abstract-Angiotensin II (Ang II) has profound effects in the central nervous system (CNS), including promotion of thirst, regulation of vasopressin secretion, and modulation of sympathetic outflow. Despite its importance in cardiovascular and volume homeostasis, angiotensinergic mechanisms are incompletely understood in the CNS. Recently, a novel signaling mechanism for Ang II involving reactive oxygen species (ROS) has been identified in a variety of peripheral tissues, but the involvement of ROS as second messengers in Ang II-mediated signaling in the CNS has not been reported. The hypothesis that superoxide is a key mediator of the actions of Ang II in the CNS was tested in mice using adenoviral vector-mediated expression of superoxide dismutase (AdSOD). Changes in blood pressure, heart rate, and drinking elicited by injection of Ang II in the CNS were abolished by prior treatment with AdSOD in the brain, whereas the cardiovascular responses to carbachol, another central vasopressor agent, were unaffected. In addition, Ang II stimulated superoxide generation in primary CNS cell cultures, and this was prevented by the Ang II receptor (

Angiotensin-converting enzyme 2 (ACE2) is a newly discovered carboxy-peptidase responsible for the formation of vasodilatory peptides such as angiotensin-(1-7). We hypothesized that ACE2 is part of the brain renin-angiotensin system, and its expression is regulated by the other elements of this system. ACE2 immunostaining was performed in transgenic mouse brain sections from neuron-specific enolase-AT(1A) (overexpressing AT(1A) receptors), R(+)A(+) (overexpressing angiotensinogen and renin), and control (nontransgenic littermates) mice. Results show that ACE2 staining is widely distributed throughout the brain. Using cell-type-specific antibodies, we observed that ACE2 staining is present in the cytoplasm of neuronal cell bodies but not in glial cells. In the subfornical organ, an area lacking the blood-brain barrier and sensitive to blood-borne angiotensin II, ACE2 was significantly increased in transgenic mice. Interestingly, ACE2 mRNA and protein expression were inversely correlated in the nucleus of tractus solitarius/dorsal motor nucleus of the vagus and the ventrolateral medulla, when comparing transgenic to nontransgenic mice. These results suggest that ACE2 is localized to the cytoplasm of neuronal cells in the brain and that ACE2 levels appear highly regulated by other components of the renin-angiotensin system, confirming its involvement in this system. Moreover, ACE2 expression in brain structures involved in the control of cardiovascular function suggests that the carboxypeptidase may have a role in the central regulation of blood pressure and diseases involving the autonomic nervous system, such as hypertension.

Cigarette smoking is the single most important risk factor for the development of cardiovascular and pulmonary diseases (CVPD). Although cigarette smoking has been in constant decline since the 1950's, the introduction of e-cigarettes or electronic nicotine delivery systems 10 years ago has attracted former smokers as well as a new generation of consumers. Nicotine is a highly addictive substance, and it is currently unclear whether e-cigarettes are "safer" than regular cigarettes or whether they have the potential to reverse the health benefits, notably on the cardiopulmonary system, acquired with the decline of tobacco smoking. Of great concern, nicotine inhalation devices are becoming popular among young adults and youths, emphasizing the need for awareness and further study of the potential cardiopulmonary risks of nicotine and associated products. This review focuses on the interaction between nicotine and the renin-angiotensin system (RAS), one of the most important regulatory systems on autonomic, cardiovascular and pulmonary functions in both health and disease. The literature presented in this review strongly suggests that nicotine alters the homeostasis of the RAS by up-regulating the detrimental angiotensin converting enzyme (ACE)/Angiotensin (Ang)-II/Ang-II type 1 receptor (ATR) axis and down-regulating the compensatory ACE2/Ang-(1-7)/Mas receptor axis, contributing to the development of CVPD.