Objective: Given the important role of Ang II/Ang 1-7 in atherogenesis, we investigated the impact of ACE2 deficiency on the development of atherosclerosis. Methods and Results:C57Bl6, Ace2 knockout (KO), apolipoprotein E (ApoE) KO and ApoE/Ace2 double KO mice were followed until 30 weeks of age. Plaque accumulation was increased in ApoE/Ace2 double KO mice when compared to ApoE KO mice. This was associated with increased expression of adhesion molecules and inflammatory cytokines, including interleukin-6, monocyte chemoattractant protein-1, and vascular cell adhesion molecule-1, and an early increase in white cell adhesion across the whole aortae on dynamic flow assay. In the absence of a proatherosclerotic (ApoE KO) genotype, ACE2 deficiency was also associated with increased expression of these markers, suggesting that these differences were not an epiphenomenon. ACE inhibition prevented increases of these markers and atherogenesis in ApoE/ACE2 double KO mice. Bone marrow macrophages isolated from Ace2 KO mice showed increased proinflammatory responsiveness to lipopolysaccharide and Ang II when compared to macrophages isolated from C57Bl6 mice. Endothelial cells isolated from Ace2 KO mice also showed increased basal activation and elevated inflammatory responsiveness to TNF-␣. Similarly, selective inhibition of ACE2 with MLN-4760 also resulted in a proinflammatory phenotype with a physiological response similar to that observed with exogenous Ang II (10 ؊7 mol/L). Conclusions: Genetic

Early studies indicate that the hypertension observed in the Schlager inbred mouse strain may be attributed to a neurogenic mechanism. In this study, we examined the contribution of the sympathetic nervous system in maintaining hypertension in the BPH/2J mouse and used c-Fos immunohistochemistry to elucidate whether neuronal activation in specific brain regions was associated with waking blood pressure. Male hypertensive (BPH/2J; n=14), normotensive (BPN/3J; n=18), and C57/Bl6 (n=5) mice were implanted with telemetry devices, and after 10 days of recovery, recordings of blood pressure, heart rate, and locomotor activity were measured to determine circadian variation. Mean arterial pressure was higher in BPH/2J than in BPN/3J or C57/Bl6 mice (P<0.001), and BPH/2J animals showed exaggerated day-night differences (17+/-2 versus 6+/-1 mm Hg in BPN/3J or +8+/-2 mm Hg in C57/Bl6 mice; P<0.001). Acute sympathetic blockade with pentolinium (7.5 mg/kg IP) during the active and inactive phases reduced blood pressure to comparable levels in BPH/2J and BPN/3J mice. The number of c-Fos-labeled cells was greater in the amygdala (+180%; P<0.01), paraventricular nucleus (+110%; P<0.001), and dorsomedial hypothalamus (+48%; P<0.001) in the active (hypertensive) phase in BPH/2J compared with BPN/3J mice. The level of neuronal activation was mostly similar in these regions in the inactive phase. Of all of the regions studied, neuronal activation in the medial amygdala, as detected by c-Fos, was highly correlated to mean arterial pressure (r=0.98). These findings indicate that the hypertension is largely attributable to sympathetic nervous system activity, possibly generated through greater levels of arousal regulated by neurons located in the medial amygdala.

BPH/2J mice are a genetic model of hypertension developed by Schlager 1 by crossing 8 normotensive strains and selecting for elevated blood pressure (BP). Normotensive BPN/3J control mice were bred concurrently by crossing randomly selected mice from the same base population. Recently, the mechanism of the hypertension has been recognized as neurogenic because ganglion blockade abolished the hypertension in BPH/2J mice.2 Furthermore, spectral analysis of BP revealed greater power in the autonomic frequency band, suggesting overactivity of the sympathetic nervous system (SNS), most prominently during the nocturnal active period.2 BPH/2J mice also display exaggerated daynight differences in BP, which are associated with greater neuronal activity in regions of the hypothalamus and amygdala known to be important for cardiovascular regulation. Given the recent success of renal sympathetic nerve ablation for the treatment of resistant hypertension, 3 the importance of renal influences on the expression of neurogenic hypertension has been highlighted. Importantly, the peripheral renin-angiotensin system (RAS) is closely linked to renal sympathetic nerve activity (RSNA) via its ability to stimulate renin secretion, 4 and also through angiotensin II-mediated facilitation of SNA. 5 However, the interaction of the kidney and renal RAS with SNS-mediated hypertension in BPH/2J mice has not been investigated thoroughly. The role of the RAS has been examined in a variety of ways in BPH/2J mice including by measurement of messenger RNA (mRNA) in tissues and various pharmacological assessments. [6][7][8][9][10] Iwao et al 8 reported normal renin activity in plasma, kidney, and submandibular gland of BPH/2J mice, although others found greater renin activity Abstract-Genetically hypertensive mice (BPH/2J) are hypertensive because of an exaggerated contribution of the sympathetic nervous system to blood pressure. We hypothesize that an additional contribution to elevated blood pressure is via sympathetically mediated activation of the intrarenal renin-angiotensin system. Our aim was to determine the contribution of the reninangiotensin system and sympathetic nervous system to hypertension in BPH/2J mice. BPH/2J and normotensive BPN/3J mice were preimplanted with radiotelemetry devices to measure blood pressure. Depressor responses to ganglion blocker pentolinium (5 mg/kg IP) in mice pretreated with the angiotensin-converting enzyme inhibitor enalaprilat (1.5 mg/kg IP) revealed a 2-fold greater sympathetic contribution to blood pressure in BPH/2J mice during the active and inactive period. However, the depressor response to enalaprilat was 4-fold greater in BPH/2J compared with BPN/3J mice, but only during the active period (P=0.01). This was associated with 1.6-fold higher renal renin messenger RNA (mRNA; P=0.02) and 0.8-fold lower abundance of micro-RNA-181a (P=0.03), identified previously as regulating human renin mRNA. Renin mRNA levels correlated positively with depressor responses to pentolinium (r=0.99; P=0.001), and BPH/2...