Chronic intracerebroventricular infusion of angiotensin II causes dose- and sex-dependent effects on intake behaviors and energy homeostasis in C57BL/6J mice.

The renin-angiotensin system (RAS) within the brain is implicated in the control of fluid and electrolyte balance, autonomic functions, blood pressure, and energy expenditure. Mouse models are increasingly used to explore these mechanisms; however, sex and dose dependencies of effects elicited by chronic intracerebroventricular (ICV) angiotensin II (ANG II) infusion have not been carefully established in this species. To examine the interactions among sex, body mass, and ICV ANG II on ingestive behaviors and energy balance, young adult C57BL/6J mice of both sexes were studied in a multiplexed metabolic phenotyping system (Promethion) during chronic infusion of ANG II (0, 5, 20, or 50 ng/h). At these infusion rates, ANG II caused accelerating dose-dependent increases in drinking and total energy expenditure in male mice, but female mice exhibited a complex biphasic response with maximum responses at 5 ng/h. Body mass differences did not account for sex-dependent differences in drinking behavior or total energy expenditure. In contrast, resting metabolic rate was similarly increased by ICV ANG II in a dose-dependent manner in both sexes after correction for body mass. We conclude that chronic ICV ANG II stimulates water intake, resting, and total energy expenditure in male C57BL/6J mice following straightforward accelerating dose-dependent kinetics, but female C57BL/6J mice exhibit complex biphasic responses to ICV ANG II. Furthermore, control of resting metabolic rate by ANG II is dissociable from mechanisms controlling fluid intake and total energy expenditure. Future studies of the sex dependency of ANG II within the brain of mice must be designed to carefully consider the biphasic responses that occur in females.

Exercise training increases GAD65 expression, restores the depressed GABAA receptor function within the PVN and reduces sympathetic modulation in hypertension.

GABAergic inhibitory input within the paraventricular hypothalamic nucleus (PVN) plays a key role in restraining sympathetic outflow. Although experimental evidence has shown depressed GABAA receptor function plus sympathoexcitation in hypertension and augmented GABA levels with reduced sympathetic activity after exercise training (T), the mechanisms underlying T-induced effects remain unclear. Here we investigated in T and sedentary (S) SHR and WKY: (1) time-course changes of hemodynamic parameters and PVN glutamic acid decarboxylase (GAD) isoforms' expression; (2) arterial pressure (AP) and heart rate (HR) responses, sympathetic/parasympathetic modulation of heart and vessels and baroreflex sensitivity to GABAA receptor blockade within the PVN. SHR-S versus WKY-S exhibited higher AP and HR, increased sympathetic reduced parasympathetic modulation, smaller baroreflex sensitivity, and reduced PVN GAD65 immunoreactivity. SHR-T and WKY-T showed prompt maintained increase (2-8 weeks) in GAD65 expression (responsible for GABA vesicular pool synthesis), which occurred simultaneously with HR reduction in SHR-T and preceded MAP fall in SHR-T and resting bradycardia in WKY-T. There was no change in GAD67 expression (mainly involved with GABA metabolic pool). Resting HR in both groups and basal MAP in SHR were negatively correlated with PVN GAD65 expression. Normalized baroreflex sensitivity and autonomic control observed only in SHR-T were due to recovery of GABAA receptor function into the PVN since bicuculline administration abolished these effects. Data indicated that training augments in both groups the expression/activity of GABAergic neurotransmission within presympathetic PVN neurons and restores GABAA receptors' function specifically in the SHR, therefore strengthening GABAergic modulation of sympathetic outflow in hypertension.

Endothelial PPARγ (Peroxisome Proliferator-Activated Receptor-γ) Protects From Angiotensin II-Induced Endothelial Dysfunction in Adult Offspring Born From Pregnancies Complicated by Hypertension.

Preeclampsia is a hypertensive disorder of pregnancy associated with vascular dysfunction and cardiovascular risk to offspring. We hypothesize that endothelial PPARγ (peroxisome proliferator-activated receptor-γ) provides cardiovascular protection in offspring from pregnancies complicated by hypertension. C57BL/6J dams were bred with E-V290M sires, which express a dominant-negative allele of PPARγ selectively in the endothelium. Arginine vasopressin was infused throughout gestation. Vasopressin elevated maternal blood pressure at gestational day 14 to 15 and urinary protein at day 17 consistent. Systolic blood pressure and vasodilation responses to acetylcholine were similar in vasopressin-exposed offspring compared to offspring from control pregnancies. We treated offspring with a subpressor dose of angiotensin II to test if hypertension during pregnancy predisposes offspring to hypertension. Male and female angiotensin II-treated E-V290M offspring from vasopressin-exposed but not control pregnancy exhibited significant impairment in acetylcholine-induced relaxation in carotid artery. Endothelial dysfunction in angiotensin II-treated E-V290M vasopressin-exposed offspring was attenuated by tempol, an effect which was more prominent in male offspring. Nrf2 (nuclear factor-E2-related factor) protein levels were significantly elevated in aorta from male E-V290M offspring, but not female offspring compared to controls. Blockade of ROCK (Rho-kinase) signaling and incubation with a ROCK2-specific inhibitor improved endothelial function in both male and female E-V290M offspring from vasopressin-exposed pregnancy. Our data suggest that interference with endothelial PPARγ in offspring from vasopressin-exposed pregnancies increases the risk for endothelial dysfunction on exposure to a cardiovascular stressor in adulthood. This implies that endothelial PPARγ provides protection to cardiovascular stressors in offspring of a pregnancy complicated by hypertension and perhaps in preeclampsia.

Temporal changes in cardiac oxidative stress, inflammation and remodeling induced by exercise in hypertension: Role for local angiotensin II reduction.

Exercise training reduces renin-angiotensin system (RAS) activation, decreases plasma and tissue oxidative stress and inflammation in hypertension. However, the temporal nature of these phenomena in response to exercise is unknown. We sought to determine in spontaneously hypertensive rats (SHR) and age-matched WKY controls the weekly effects of training on blood pressure (BP), plasma and left ventricle (LV) Ang II and Ang-(1-7) content (HPLC), LV oxidative stress (DHE staining), gene and protein expression (qPCR and WB) of pro-inflammatory cytokines, antioxidant enzymes and their consequence on hypertension-induced cardiac remodeling. SHR and WKY were submitted to aerobic training (T) or maintained sedentary (S) for 8 weeks; measurements were made at weeks 0, 1, 2, 4 and 8. Hypertension-induced cardiac hypertrophy was accompanied by acute plasma Ang II increase with amplified responses during the late phase of LV hypertrophy. Similar pattern was observed for oxidative stress markers, TNF alpha and interleukin-1ß, associated with cardiomyocytes' diameter enlargement and collagen deposition. SHR-T exhibited prompt and marked decrease in LV Ang II content (T1 vs T4 in WKY-T), normalized oxidative stress (T2), augmented antioxidant defense (T4) and reduced both collagen deposition and inflammatory profile (T8), without changing cardiomyocytes' diameter and LV hypertrophy. These changes were accompanied by decreased plasma Ang II content (T2-T4) and reduced BP (T8). SHR-T and WKY-T showed parallel increases in LV and plasma Ang-(1-7) content. Our data indicate that early training-induced downregulation of LV ACE-AngII-AT1 receptor axis is a crucial mechanism to reduce oxidative/pro-inflammatory profile and improve antioxidant defense in SHR-T, showing in addition this effect precedes plasma RAS deactivation.

Downregulation of the vascular renin-angiotensin system by aerobic training - focus on the balance between vasoconstrictor and vasodilator axes - .

BACKGROUND: Hyperactivity of the renin-angiotensin system (RAS) and functional deficits in hypertension are reduced after exercise training. We evaluate in arteries, kidney and plasma of hypertensive rats the sequential effects of training on vascular angiotensinogen, Ang II and Ang (1-7) content. METHODS AND RESULTS: Spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were trained or kept sedentary (S) for 3 months. After hemodynamic measurements (weeks 0, 1, 2, 4, 8 and 12), blood, arteries and kidneys were obtained to quantify the angiotensin content (HPLC) and angiotensinogen expression (Western Blotting). SHR-S vs. WKY-S exhibited elevated pressure, increased angiotensinogen and angiotensins' content in the renal artery with a high Ang II/Ang (1-7) ratio (~5-fold higher than in the femoral artery, kidney and plasma, and 14-fold higher than in the aorta). Training promptly reduced angiotensinogen expression and downregulated the RAS in the renal SHR artery (1st-12th week), with a specific reduction of the vasoconstrictor axis; significant reduction of the AngII/Ang (1-7) ratio (36%, T4-T8) occurred simultaneously with significant pressure fall (5%). In other SHR arteries, plasma and kidneys and in all WKY tissues, T-induced AngII and Ang (1-7) reductions were proportional, maintaining the AngII/Ang (1-7) ratio. CONCLUSIONS: Vascular RAS is not equally expressed in vessels, having crucial importance in the renal artery. In the renal SHR artery, training downregulates the vasoconstrictor and preserves the vasodilator axis while in other tissues and plasma training reduces both RAS axes, thus maintaining the vasoconstriction/vasodilatation balance in a lower level.