The Intersection of Cardiovascular Health and Maternal Health: Portfolio Analysis of Federal Grant Funding 2016-2021

Background: The United States has high and increasing rates of maternal morbidity and mortality, large proportions of which are related to cardiovascular health (CVH). Methods: We searched for National Institutes of Health (NIH) supported research as well as that of two other Agencies in the U.S. Department of Health and Human Services (DHHS) for fiscal years (FY) 2016-2021. Grants included maternal health conditions or exposures across all pregnancy stages, but excluded grants that focused entirely on birth, neonatal, infant/childhood outcomes. Results were manually curated by reviewing the abstract and specific aims. Grants deemed to be relevant were grouped by category. Results: Between FY 2016-2021, overall Maternal Health grants remained unchanged at an average of 1.4% of total DHHS grant funding. Maternal CVH-specific (MCVH) funding amounted to $278,926,105 for 755 grants, $191,344,649 was for 534 Type-1 grants, representing a twofold increase. Non-NIH DHHS agencies most commonly funded general Maternal Health related to CVH; NIH focused funding classified as hypertensive disorders of pregnancy, maternal morbidity and mortality, obesity, and diabetes. Non-NIH DHSS Agencies most commonly funded clinical applied research. In addition to clinical applied grants, NIH funded substantial proportions of grants classified as basic research, clinical trials, and/or translational. National Heart, Lung, and Blood Institute (NHLBI) MCVH grants studied participants in the pre-partum period (78.5%), followed by the post-partum period (50.5%), with relatively few in pre-pregnancy and peri-partum periods (10.8% and 9.7%, respectively); at the NIH level, the peri-partum period had better representation at 20.3%, whereas the pre-pregnancy period remained low at 9.9%. Conclusions: Federal grant funding for maternal health including MCVH increased at the same rate as its funding for overall research, and represented only 1.4% of overall total funding. The pre-pregnancy period was understudied in overall NIH funding and represents a gap area whereby funding agencies could further foster research advances.

Body Mass Index, Adverse Pregnancy Outcomes, and Cardiovascular Disease Risk

BACKGROUND

Obesity is a well-established risk factor for both adverse pregnancy outcomes (APOs) and cardiovascular disease (CVD). However, it is not known whether APOs are mediators or markers of the obesity-CVD relationship. This study examined the association between body mass index, APOs, and postpartum CVD risk factors.

METHODS

The sample included adults from the nuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be) Heart Health Study who were enrolled in their first trimester (6 weeks-13 weeks 6 days gestation) from 8 United States sites. Participants had a follow-up visit at 3.7 years postpartum. APOs, which included hypertensive disorders of pregnancy, preterm birth, small-for-gestational-age birth, and gestational diabetes, were centrally adjudicated. Mediation analyses estimated the association between early pregnancy body mass index and postpartum CVD risk factors (hypertension, hyperlipidemia, and diabetes) and the proportion mediated by each APO adjusted for demographics and baseline health behaviors, psychosocial stressors, and CVD risk factor levels.

RESULTS

Among 4216 participants enrolled, mean±SD maternal age was 27±6 years. Early pregnancy prevalence of overweight was 25%, and obesity was 22%. Hypertensive disorders of pregnancy occurred in 15%, preterm birth in 8%, small-for-gestational-age birth in 11%, and gestational diabetes in 4%. Early pregnancy obesity, compared with normal body mass index, was associated with significantly higher incidence of postpartum hypertension (adjusted odds ratio, 1.14 [95% CI, 1.10-1.18]), hyperlipidemia (1.11 [95% CI, 1.08-1.14]), and diabetes (1.03 [95% CI, 1.01-1.04]) even after adjustment for baseline CVD risk factor levels. APOs were associated with higher incidence of postpartum hypertension (1.97 [95% CI, 1.61-2.40]) and hyperlipidemia (1.31 [95% CI, 1.03-1.67]). Hypertensive disorders of pregnancy mediated a small proportion of the association between obesity and incident hypertension (13% [11%-15%]) and did not mediate associations with incident hyperlipidemia or diabetes. There was no significant mediation by preterm birth or small-for-gestational-age birth.

CONCLUSIONS

There was heterogeneity across APO subtypes in their association with postpartum CVD risk factors and mediation of the association between early pregnancy obesity and postpartum CVD risk factors. However, only a small or nonsignificant proportion of the association between obesity and CVD risk factors was mediated by any of the APOs, suggesting APOs are a marker of prepregnancy CVD risk and not a predominant cause of postpartum CVD risk.

Association between aspirin use during pregnancy and cardiovascular risk factors 2-7 years after delivery: The nuMoM2b Heart Health Study

OBJECTIVES

To evaluate the association between aspirin use during first pregnancy and later maternal cardiovascular risk.

STUDY DESIGN

In this secondary analysis of a prospective cohort, we included participants who carried their first pregnancy to 20 + weeks, had data regarding aspirin use, and attended a study visit 2-7 years following delivery. The exposure was aspirin use during the first pregnancy. We calculated aspirin use propensity scores from logistic regression models including baseline variables associated with aspirin use in pregnancy and cardiovascular risk. Outcomes of interest were incident cardiovascular-related diagnoses 2-7 years following delivery. Robust Poisson regression calculated the risk of outcomes by aspirin exposure, adjusting for the aspirin use propensity score.

MAIN OUTCOME MEASURES

The primary outcome was a composite of incident cardiovascular diagnoses at the time of the study visit: cardiovascular events, chronic hypertension, metabolic syndrome, prediabetes or type 2 diabetes, dyslipidemia, and chronic kidney disease.

RESULTS

Of 4,480 women included, 84 (1.9%) reported taking aspirin during their first pregnancy. 52.6% of participants in the aspirin-exposed group and 43.0% in the unexposed group had the primary outcome. After adjusting for the aspirin use propensity scores, aspirin use during the first pregnancy was not associated with any of the outcomes.

CONCLUSION

We did not detect an association between aspirin use during the first pregnancy and cardiovascular-related diagnoses 2-7 years later. Our study was only powered to detect a large difference in relative risk, so we cannot rule out a smaller difference that may be clinically meaningful.

Cardiometabolic health after first pregnancy: Associations with social determinants of health. A nuMoM2b-HHS study

Study objective

This study sought to evaluate the associations between social determinants of health (SDOH) at the time of first pregnancy and subsequent cardiometabolic health, defined as the development of metabolic syndrome.

Design

nuMoM2b-HHS (Nulliparous Pregnancy Outcomes Study- Monitoring Mothers-to-Be-Heart Health Study) is an ongoing prospective cohort study.

Setting

Eight academic medical centers enrolled and continue to follow participants.

Participants

4484 participants followed a mean of 3.2 years from the time of their first pregnancy.

Interventions

N/a.

Main outcome measure

Unadjusted and adjusted Poisson regression models with robust standard errors were used to obtain relative risks and 95% confidence intervals estimating the risk of metabolic syndrome for each baseline SDOH. In secondary analyses we examined the associations between SDOH and incident hypertension, obesity, and diabetes mellitus.

Results

Metabolic syndrome developed in 13.6% of participants. Higher socioeconomic position at the time of pregnancy was associated with lower rates of metabolic syndrome [income > 200% poverty level aRR 0.55 (95% CI, 0.42-0.71), attainment of a bachelor's degree aRR 0.62 (0.46-0.84) or higher aRR 0.50 (0.35-0.71)], while being single [aRR 1.45 (95% CI, 1.18-1.77)] and having low health literacy were associated with a greater risk of metabolic syndrome [aRR 1.98 (95% CI, 1.28-3.07)].

Conclusions

Over a short interval following first pregnancy, participants accumulated high proportions of cardiovascular risk factors and metabolic syndrome, with some risk associated with SDOH. The impact of interventions addressing SDOH in pregnant people on cardiometabolic health should be tested as a means of reducing health inequities at the population level.

Maternal Morbidity and Mortality: Are We Getting to the "Heart" of the Matter?

Cardiovascular disease (CVD), including hypertensive disorders of pregnancy (HDP) and peripartum cardiomyopathy, is a leading cause of pregnancy-related death in the United States. Women who are African American or American Indian/Alaskan Native, have HDP, are medically underserved, are older, or are obese have a major risk for the onset and/or progression of CVD during and after pregnancy. Paradoxically, women with no preexisting chronic conditions or risk factors also experience significant pregnancy-related cardiovascular (CV) complications. The question remains whether substantial physiologic stress on the CV system during pregnancy reflected in hemodynamic, hematological, and metabolic changes uncovers subclinical prepregnancy CVD in these otherwise healthy women. Equally important and similarly understudied is the concept that women's long-term CV health could be detrimentally affected by adverse pregnancy outcomes, such as preeclampsia, gestational hypertension, and diabetes, and preterm birth. Thus, a critical life span perspective in the assessment of women's CV risk factors is needed to help women and health care providers recognize and appreciate not only optimal CV health but also risk factors present before, during, and after pregnancy. In this review article, we highlight new advancements in understanding adverse, pregnancy-related CV conditions and will discuss promising strategies or interventions for their prevention, diagnosis, and treatment.

Atrial angiotensin-(1-12)/chymase expression data in patient of heart diseases

The data presented here are related to the research article entitled “Differential expression of the angiotensin-(1-12) [Ang-(1-12)]/chymase axis in human atrial tissue [1]. We have showed that chymase gene transcripts, chymase activity, and immunoreactive- Ang-(1-12) expression levels were higher in left compared to right atrial tissue, irrespective of cardiac disease. This article presents the echocardiographic characteristics of 111 patients undergoing heart surgery for the correction of valvular heart disease, resistant atrial fibrillation or ischemic heart disease. Left atrial chymase mRNA expression and activity, and left atrial Ang-(1-12) levels were compared between patients with stroke vs. non-stroke, congestive heart failure vs. non-heart failure, and in cardiac surgery patients who had a history of postoperative atrial fibrillation vs. non-atrial fibrillation.

Angiotensin-(1–7) reduces doxorubicin-induced cardiac dysfunction in male and female Sprague-Dawley rats through antioxidant mechanisms

Doxorubicin (Dox) is an effective chemotherapeutic for a variety of pediatric malignancies. Unfortunately, Dox administration often results in a cumulative dose-dependent cardiotoxicity that manifests with marked oxidative stress, leading to heart failure. Adjunct therapies are needed to mitigate Dox cardiotoxicity and enhance quality of life in pediatric patients with cancer. Angiotensin-(1–7) [Ang-(1–7)] is an endogenous hormone with cardioprotective properties. This study investigated whether adjunct Ang-(1–7) attenuates cardiotoxicity resulting from exposure to Dox in male and female juvenile rats. Dox significantly reduced body mass, and the addition of Ang-(1–7) had no effect. However, adjunct Ang-(1–7) prevented Dox-mediated diastolic dysfunction, including markers of decreased passive filling as measured by reduced early diastole mitral valve flow velocity peak ( E) ( P < 0.05) and early diastole mitral valve annulus peak velocity ( e′; P < 0.001) and increased E/e′ ( P < 0.001), an echocardiographic measure of diastolic dysfunction. Since Dox treatment increases reactive oxygen species (ROS), the effect of Ang-(1–7) on oxidative by-products and enzymes that generate or reduce ROS was investigated. In hearts of male and female juvenile rats, Dox increased NADPH oxidase 4 ( P < 0.05), a major cardiovascular NADPH oxidase isozyme that generates ROS, as well as 4-hydroxynonenal ( P < 0.001) and malondialdehyde ( P < 0.001), markers of lipid peroxidation; Ang-(1–7) prevented these effects of Dox. Cotreatment with Dox and Ang-(1–7) increased the antioxidant enzymes SOD1 (male: P < 0.05; female: P < 0.01) and catalase ( P < 0.05), which likely contributed to reduced ROS. These results demonstrate that Ang-(1–7) prevents diastolic dysfunction in association with a reduction in ROS, suggesting that the heptapeptide hormone may serve as an effective adjuvant to improve Dox-induced cardiotoxicity.

NEW & NOTEWORTHY Ang-(1–7) is a clinically safe peptide hormone with cardioprotective and antineoplastic properties that could be used as an adjuvant therapy to improve cancer treatment and mitigate the long-term cardiotoxicity associated with doxorubicin in pediatric patients with cancer.

Activation of the Human Angiotensin-(1-12)-Chymase Pathway in Rats With Human Angiotensinogen Gene Transcripts

Angiotensin-(1-12) [Ang-(1-12)], an alternate substrate for tissue angiotensin II (Ang II) formation, underscores the importance of alternative renin-independent pathway(s) for the generation of angiotensins. Since renin enzymatic activity is species-specific, a transgenic model of hypertension due to insertion of the human angiotensinogen (AGT) gene in Sprague Dawley rats allowed for characterizing the contribution of a non-renin dependent mechanism for Ang II actions in their blood and heart tissue. With this in mind, we investigated whether TGR(hAGT)L1623 transgenic rats express the human sequence of Ang-(1-12) before and following a 2-week oral therapy with the type I Ang II receptor (AT1-R) antagonist valsartan. Plasma and cardiac expression of angiotensins, plasma renin activity, cardiac angiotensinogen, and chymase protein and the enzymatic activities of chymase, angiotensin converting enzyme (ACE) and ACE2 were determined in TGR(hAGT)L1623 rats given vehicle or valsartan. The antihypertensive effect of valsartan after 14-day treatment was associated with reduced left ventricular wall thickness and augmented plasma concentrations of angiotensin I (Ang I) and Ang II; rat and human concentrations of angiotensinogen or Ang-(1-12) did not change. On the other hand, AT₁-R blockade produced a 55% rise in left ventricular content of human Ang-(1-12) concentration and no changes in rat cardiac Ang-(1-12) levels. Mass-Spectroscopy analysis of left ventricular Ang II content confirmed a >4-fold increase in cardiac Ang II content in transgenic rats given vehicle; a tendency for decreased cardiac Ang II content following valsartan treatment did not achieve statistical significance. Cardiac chymase and ACE2 activities, significantly higher than ACE activity in TGR(hAGT)L1623 rats, were not altered by blockade of AT₁-R. We conclude that this humanized model of angiotensinogen-dependent hypertension expresses the human sequence of Ang-(1-12) in plasma and cardiac tissue and responds to blockade of AT₁-R with further increases in the human form of cardiac Ang-(1-12). Since rat renin has no hydrolytic activity on human angiotensinogen, the study confirms and expands knowledge of the importance of renin-independent mechanisms as a source for Ang II pathological actions.

Angiotensin-(1-12)/chymase axis modulates cardiomyocyte L-type calcium currents in rats expressing human angiotensinogen

BACKGROUND

Activation of the intracrine renin angiotensin systems (RAS) is increasingly recognized as contributing to human pathologies, yet non-canonical renin-independent mechanisms for angiotensin II (Ang II) biosynthesis remain controversial. Direct Ang II generation from angiotensin-(1-12) [Ang-(1-12)] by chymase is an essential intracrine source for regulation of cardiac function. Using a transgenic rat model that overexpresses the human angiotensinogen gene [TGR(hAGT)L1623] and displays increased cardiac Ang II levels, this study aimed to provide evidence for intracrine activation of L-type calcium currents (I_Ca-L) mediated by the Ang-(1-12)/chymase axis.

METHODS AND RESULTS

On patch clamp, I_Ca-L density was significantly higher in TGR(hAGT)L1623 (-6.4 ± 0.3 pA/pF) compared to Sprague Dawley (SD) cardiomyocytes (-4.8, ± 0.5 pA/pF). Intracellular administration of Ang II and Ang-(1-12) elicited a I_Ca-L increase in both SD and TGR(hAGT)L1623 cardiomyocytes, albeit blunted in transgenic cells. I_Ca-L activation by intracellular Ang II and Ang-(1-12) was abolished by the specific Ang II type 1 receptor blocker E-3174. Co-administration of a chymase inhibitor prevented activation of I_Ca-L by Ang-(1-12). Confocal micrographs revealed abundant chymase (mast cell protease 5) immunoreactive protein in SD and TGR(hAGT)L1623 cardiomyocytes.

CONCLUSIONS

Our data demonstrate the existence in cardiomyocytes of a calcium channel modulatory activity responsive to Ang II generated by the Ang-(1-12)/chymase axis that signals via intracellular receptors. Chronically elevated Ang II in TGR(hAGT)L1623 hearts leading to increased intracellular calcium through I_Ca-L suggests that activation of this Ang-(1-12)/chymase-governed cardiac intracrine RAS may contribute to the pathological phenotypes observed in the humanized model of chronic hypertension and cardiac hypertrophy.

Abstract P3006: Angiotensin-(1-7) Prevents Doxorubicin-Induced Aortic Dysfunction Through Anti-Fibrotic Mechanisms in Juvenile Male and Female Sprague Dawley Rats

Doxorubicin (Dox) is an effective, anthracycline chemotherapeutic administered for a variety of malignancies, but clinical use of the drug is limited by a cumulative, dose-dependent cardiotoxicity. Thus, adjuvant therapies are needed to mitigate Dox-induced cardiovascular damage in cancer patients, especially in pediatric patients with decades of life ahead. Our group showed that angiotensin-(1-7) [Ang-(1-7)], an endogenous peptide hormone with anti-cancer properties, improved vascular dysfunction in coronary vessels and cremaster muscle microvessels in Ang II-infused rats. In this study, juvenile male and female Sprague Dawley rats (n = 8-10) were administered a clinically equivalent dose of Dox (21-24 mg/kg) over 6 weeks, in the presence or absence of Ang-(1-7) [24 μg/kg/h]. Aortic function was measured using echocardiography. In both sexes, Ang-(1-7) blocked the Dox-mediated increase in pulse wave velocity (PWV), a measure of arterial stiffness (75% in males and 179% in females, p<0.05 and p<0.001). Dox decreased aortic lumen diameter (by 18%, p<0.01) and increased wall thickness at systole (p<0.01) in males, which was attenuated by Ang-(1-7). In male but not female aortas, Dox increased media hypertrophy by 16% (p<0.01) and reduced elastin content by 17% compared to control rats (p<0.001), changes prevented by Ang-(1-7). Conversely, collagen deposition was increased 2.5-fold in the aortic arches of female rats treated with Dox (p<0.001), which was blocked by Ang-(1-7). Dox increased nuclear ERK1/2 by 2-fold in the aortic media of male rats (p<0.01) and Ang-(1-7) significantly attenuated nuclear ERK1/2 localization. In contrast, neither Dox nor Ang-(1-7) changed total or nuclear ERK1/2 in the aortic arches of female rats. Dox increased nuclear pSMAD2 4-fold in males (p<0.05) and 3-fold in females (p<0.05); prophylactic treatment with Ang-(1-7) reduced the Dox-induced increases in nuclear pSMAD2 while the heptapeptide hormone had no effect alone. These results demonstrate that Ang-(1-7) prevented Dox-induced aortic dysfunction in both sexes, albeit through different mechanisms, suggesting that treatment with Ang-(1-7) may serve as an effective adjuvant to improve Dox-induced vascular dysfunction in pediatric patients.

Abstract P3052: A Muscadine Grape Extract Improves Hypertension-Induced Aortic Damage in Conjunction With a Reduction in Fibrosis, Oxidative Stress, and Inflammation

Hypertension-induced arterial stiffness contributes to both reduced vascular and cardiac function. While the pathophysiology of aortic stiffness is not completely understood, significant vascular remodeling occurs in response to stimuli such as vascular stress and Ang II. The goal of this study was to determine whether a polyphenol-enriched muscadine grape skin and seed extract (MGE) improves Ang II-induced aortic remodeling. Sprague-Dawley rats (male, 8 weeks old) received normal drinking water (Control), 0.2 mg total phenolics/mL in their drinking water (MGE), 24 μg/kg/h of Ang II via osmotic minipump (Ang II), or both Ang II and MGE (Ang II/MGE, pre-treated with MGE for 1 week prior to Ang II treatment). MGE had no effect on systolic blood pressure, measured by tail cuff plethysmography, in normotensive or Ang II-treated rats. Aortic stiffness, determined by echocardiographic pulse wave velocity, was increased 2.5-fold in Ang II-treated animals but was significantly improved by co-administration of MGE. MGE prevented the Ang II-induced increase in aortic media thickness (Control: 95.8 ± 2.1 μm, Ang II: 135.1 ± 3.7 μm, and Ang II/MGE: 118.2 ± 2.9 μm) and lumen diameter (Control: 2.7 ± 0.2, Ang II: 2.1 ± 0.1 mm, and Ang II/MGE: 2.6 ± 0.1 mm). Nuclear phosphorylated ERK (pERK) in aortic medial cells was increased by 131% in Ang II-treated rats compared to Controls (p < 0.05); MGE co-administration prevented this by 83% (p < 0.001). Ang II-induced aortic fibrosis, measured by total collagen and collagen III, was significantly attenuated in hypertensive animals treated with MGE, in association with reduced pSMAD2 and CTGF. 4-HNE, a marker of lipid peroxidation, and subunits of NADPH oxidases--Nox1, Nox2, p-p47phox--were significantly upregulated by Ang II and normalized with MGE. The inflammatory markers IL-6 and NF-κB were also increased in Ang II-treated aortas (8.9- and 12.7-fold, respectively) and attenuated by MGE. This study is the first to demonstrate that Ang II-induced vascular remodeling is prevented by co-administration of MGE. MGE reduced aortic stiffness, in association with a decrease in fibrotic, oxidative stress, and inflammatory signaling, suggesting that MGE supplementation may improve vascular function in hypertensive patients.

Abstract P131: A Selective Chymase Inhibitor, TEI-f00806, Eliminates the Ang II Production From Rat Ang-(1-12) in Bone Marrow Tissue

Background: Rat bone marrow (BM)-chimeric experiments reveal a critical role of locally formed angiotensin II (Ang II) in mediating the oxidant-rich inflammatory milieu associated with cardiovascular disease pathogenesis. Extending our first demonstration of renin angiotensin system (RAS) components in the BM, we recently reported a primary role of chymase rather than angiotensin converting enzyme (ACE) in BM generation of Ang II from the novel substrate angiotensin-(1-12) [Ang-(1-12)]. To verify chymase contribution over other proteases such as cathepsins, Ang-(1-12) metabolism studies in rat BM were carried out in the absence and in the presence of a selective orally active chymase inhibitor (TEI-F00806).

Methods: Plasma membrane (PM) of BM and left ventricle (LV) tissues were obtained from 12 week-old Sprague Dawley rats following systemic perfusion with phosphate buffered saline with or without the secondary addition of Zamboni’s fixative. PMs were incubated with 125 I-Ang-(1-12) and the metabolic products during incubation were determined by high-performance liquid chromatography. All data were analyzed using GraphPad PRISM 7.0 with P<0.05 to determine statistical significance.

Results: Assessment of 125 I-Ang-(1-12) hydrolysis in the absence of the chymase inhibitor revealed that chymase activity in BM membranes was 280 fold higher than that in LV (4,531 ± 137 fmol/mg/min and 16.3 ± 0.3 fmol/mg/min, respectively, n = 6, P < 0.001). In the presence of TEI-F00806, 96% of the chymase-mediated Ang II production was inhibited in BM. Confocal microscopy showed chymase-positive but tryptase-negative cells as the most dominant in BM, indicating that stem/progenitor cells rather than mature mast cells might be the source of chymase in BM.

Conclusion: The current findings demonstrate that BM has tremendously higher chymase-mediated Ang II producing activity from Ang-(1-12) compared to heart tissue. The fact that TEI-00806 inhibited the Ang II producing activity of chymase underscores a tissue-selective enzymatic mechanism for Ang II formation from Ang-(1-12) contributing to the chronic inflammatory processes accompanying the pathogenesis of cardiovascular disease.

Abstract P2033: Rationale For A Novel Approach To Hypertension Treatment Based On Immuno-neutralization Of Angiotensin-(1-12) Catalytic Sites With A Polyclonal Antibody

The biochemical pathways for the formation of biological active angiotensins continues to undergo significant revision with the demonstration of angiotensin-(1-12) as an endogenous substrate forming angiotensin II (Ang II) by a non-renin dependent mechanism. Research done in our laboratory established that Ang II generation from Ang-(1-12) is primarily mediated by ACE in the circulation and by chymase in cardiac tissues. In this study, we have utilized an antigen-antibody binding approach to block the cleavage sites of human Ang-(1-12) peptide with an anti-Ang-(1-12) polyclonal antibody (pAb) as a potential therapeutic strategy to prevent the catalytic action of chymase and ACE enzymes to generate Ang II. The pAb was generated against the C-terminus of the human Ang-(1-12) peptide sequence and its specificity for human Ang-(1-12) and cross-reactivity with other angiotensin peptides were determined in competitive binding assays. To block the cleavage sites, the radiolabeled human Ang-(1-12) [ 125 I-Ang-(1-12)] substrate was first neutralized by pre-incubating with or without anti-Ang-(1-12) pAb and then re-incubated with human recombinant chymase (hrChymase, 0.325 μg/mL) or 10 μL of rat serum (for ACE) in 50 mM Tris-HCl buffer solution containing 150 mM NaCl (pH 8.0) for 30 min at 37 o C. The reaction was stopped by adding an equal volume of 1% phosphoric acid and 125 I-Ang metabolic products were quantified by HPLC connected to an in-line flow-through gamma detector. Anti-Ang-(1-12) pAb showed high specificity for the human Ang-(1-12) sequence (EC 50 = 29.6 ng/mL) and negligible cross-reactivity with closely related angiotensin peptides. The non-neutralized human 125 I-Ang-(1-12) substrate was rapidly metabolized by both hrChymase and rat serum ACE to 125 I-Ang II (81% and 35%, respectively). In contrast, generation of 125 I-Ang II from neutralized 125 I-Ang-(1-12) substrate by either hrChymase or ACE was only 17% and 7%, respectively. The effective and potent blockade of Ang II generation from either chymase or ACE by combining Ang-(1-12) with an anti-Ang-(1-12) pAb now paves the way to develop new therapeutic approaches to hypertension treatment using Ang-(1-12) antibodies directed against the human sequence of this Ang II-forming substrate.

Abstract 2885: Angiotensin-(1-7) prevents doxorubicin-induced cardiotoxicity by reducing oxidative stress and fibrosis

Doxorubicin (Dox) is an effective chemotherapeutic agent for various malignancies including childhood leukemias and lymphomas. Unfortunately, Dox administration often results in a cumulative dose-dependent cardiotoxicity that manifests as cardiomyopathy with marked oxidative stress and fibrosis leading to a long-term reduction in cardiovascular function and heart failure. Adjunct therapies to mitigate Dox-induced cardiotoxicity and enhance long-term quality-of-life in cancer patients are needed, particularly for pediatric patients. Angiotensin-(1-7) [Ang-(1-7)] is an endogenous heptapeptide hormone of the renin-angiotensin system with cardioprotective properties. We investigated whether adjunct Ang-(1-7) attenuates cardiotoxicity resulting from acute (6 week) exposure to Dox (21-24 mg/kg) in male and female juvenile rats (n = 7-10). Dox treatment reduced body/heart mass in male and female rats and co-administration of Ang-(1-7) had no effect on these morphological changes. However, co-administration of the heptapeptide hormone prevented Dox-mediated diastolic dysfunction, including decreased passive filling (E; 16%, p&lt;0.05) and mitral annulus tissue movement (e'; 45% in males and 31% in females, p&lt;0.001) and the subsequent increased filling pressure (E/e'; 47% in males and 43% in females, p&lt;0.001). In both male and female rat hearts, Dox administration increased NADPH oxidase 4 (Nox4; 2-fold in males and females, p&lt;0.05), the major Nox isozyme that generates ROS in the heart, as well as 4-hydroxynonenal (4-HNE; 7.5-fold in males and 3.5-fold in females, p&lt;0.001) and malondialdehyde (MDA; 20-fold in males and 15-fold in females, p&lt;0.001), markers of lipid peroxidation. Co-administration of Ang-(1-7) prevented these effects of Dox while Ang-(1-7) alone had no effect. Treatment of rats with Dox and Ang-(1-7) also increased cardiac superoxide dismutase 1 (SOD1; 4-fold in males and 5-fold in females, p&lt;0.05 and p&lt;0.01 respectively) and catalase (10-fold in males and 4-fold in females, p&lt;0.05), further contributing to reduced oxidative stress. Oxidative stress is associated with an increase in cardiac fibrosis, a maladaptive change that exacerbates cardiac dysfunction. Treatment of male and female rats with Dox increased collagen deposition in the heart which was associated with an increase in the fibrogenic cytokine TGF-β1 and TGF-β1-activated phospho-SMAD2; co-administration of Ang-(1-7) mitigated the Dox-induced increase in fibrosis while the heptapeptide hormone alone had no effect. The anti-oxidant and anti-fibrotic effects of Ang-(1-7) may account for the improvement in diastolic function by the heptapeptide hormone, suggesting that treatment with Ang-(1-7) may serve as an effective adjuvant to improve Dox-induced cardiac dysfunction.

Citation Format: Patricia E. Gallagher, Omeed Rahimi, Brian Westwood, Jay Kirby, Jasmina Varagic, Elisabeth Ann Tallant. Angiotensin-(1-7) prevents doxorubicin-induced cardiotoxicity by reducing oxidative stress and fibrosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2885.

MRI evaluation of the effects of whole brain radiotherapy on breast cancer brain metastasis

PURPOSE

To assess early changes in brain metastasis in response to whole brain radiotherapy (WBRT) by longitudinal Magnetic Resonance Imaging (MRI).

MATERIALS AND METHODS

Using a 7T system, MRI examinations of brain metastases in a breast cancer MDA-MD231-Br mouse model were conducted before and 24 hours after 3 daily fractionations of 4 Gy WBRT. Besides anatomic MRI, diffusion-weighted (DW) MRI and dynamic contrast-enhanced (DCE) MRI were applied to study cytotoxic effect and blood-tumor-barrier (BTB) permeability change, respectively.

RESULTS

Before treatment, high-resolution T2-weighted images revealed hyperintense multifocal lesions, many of which (∼50%) were not enhanced on T1-weighted contrast images, indicating intact BTB in the brain metastases. While no difference in the number of new lesions was observed, WBRT-treated tumors were significantly smaller than sham controls (p < .05). DW MRI detected significant increase in apparent diffusion coefficient (ADC) in WBRT tumors (p < .05), which correlated with elevated caspase 3 staining of apoptotic cells. Many lesions remained non-enhanced post WBRT. However, quantitative DCE MRI analysis showed significantly higher permeability parameter, K_trans, in WBRT than the sham group (p < .05), despite marked spatial heterogeneity.

CONCLUSIONS

MRI allowed non-invasive assessments of WBRT induced changes in BTB permeability, which may provide useful information for potential combination treatment.

Abstract P134: Sex Differences in the Effects of Chronic Muscadine Grape Extract Treatment on Cardiac Function Parameters and Aortic Pulse Wave Velocity (PWV) in Hypertensive Transgenic (mRen2)27 Rats

Muscadine grape extract (MGE) polyphenolics have potential beneficial cardiovascular effects. Whether the effects are sex-specific during progression of hypertension is unknown. We measured aortic arch PWV and cardiac function parameters using transthoracic echocardiography (Vevo LAZR 2100) after 15 weeks of MGE-treatment (0.2 mg polyphenolics /mL in drinking water) in transgenic hypertensive (mRen2)27 rats (n = 4 each, control male and female, MGE-treated female; n = 3 MGE-treated male) starting at 15 weeks of age. As expected, systolic blood pressure (SBP) measured via tail cuff after acclimation was higher in males than females at 15 weeks of age (179 ± 3 vs. 169 ± 3 mm Hg, p = 0.04). By 30 weeks of age, SBP did not differ between male and female rats (171 ± 4 vs. 171 ± 3 mm Hg). Body weight was higher in male than female rats (589 ± 8 vs. 326 ± 5 g, p < 0.0001); thus, cardiac output (CO), stroke volume (SV) and left ventricular mass (cLVM) were normalized to body weight. Systolic cardiac function was lower in male compared with female rats: SV (0.34 ± 0.04 vs. 0.59 ± 0.03 μL/g, p < 0.001); CO (0.13 ± 0.001 vs. 0.26 ± 0.02 mL/min/g, p < 0.001); ejection fraction (46 ± 4 vs. 74 ± 5 %, p < 0.05); fractional shortening (24 ± 3 vs. 45 ± 4 %, p < 0.05). In contrast, there was no difference between male and female rats in cLVM (2.35 ± 0.20 vs. 2.85 ± 0.14); heart rate (367 ± 19 vs. 432 ± 22 bpm); E/e’ (12 ± 2 vs. 14 ± 0.4), or PWV (2.74 ± 0.21 vs. 2.85 ± 0.09 m/s). Sex differences in systolic cardiac function remained after 15 weeks of MGE treatment and MGE did not alter SBP or diastolic function (E/e’). However, aortic PWV was 36% lower in MGE treated males compared to control males (1.75 ± 0.13 vs. 2.74 ± 0.21 m/s, p < 0.005), which was also significantly lower than MGE treated females (2.40 ± 0.05 m/s, p < 0.05). Aortic PWV was 16% lower in MGE-treated females than control females, which did not reach significance (2.40 ± 0.05 vs. 2.85 ± 0.09 m/s). In conclusion, MGE intake improves arterial stiffness in male (mRen2)27 rats independent of differences in blood pressure or cardiac function. That aortic PWV in female rats did not derive benefit implies a potentially unique therapeutic profile for MGE in targeting mechanisms important for arterial stiffness in a sex-specific manner.

Combination of anthracyclines and anti-CD47 therapy inhibit invasive breast cancer growth while preventing cardiac toxicity by regulation of autophagy

BACKGROUND

A perennial challenge in systemic cytotoxic cancer therapy is to eradicate primary tumors and metastatic disease while sparing normal tissue from off-target effects of chemotherapy. Anthracyclines such as doxorubicin are effective chemotherapeutic agents for which dosing is limited by development of cardiotoxicity. Our published evidence shows that targeting CD47 enhances radiation-induced growth delay of tumors while remarkably protecting soft tissues. The protection of cell viability observed with CD47 is mediated autonomously by activation of protective autophagy. However, whether CD47 protects cancer cells from cytotoxic chemotherapy is unknown.

METHODS

We tested the effect of CD47 blockade on cancer cell survival using a 2-dimensional high-throughput cell proliferation assay in 4T1 breast cancer cell lines. To evaluate blockade of CD47 in combination with chemotherapy in vivo, we employed the 4T1 breast cancer model and examined tumor and cardiac tissue viability as well as autophagic flux.

RESULTS

Our high-throughput screen revealed that blockade of CD47 does not interfere with the cytotoxic activity of anthracyclines against 4T1 breast cancer cells. Targeting CD47 enhanced the effect of doxorubicin chemotherapy in vivo by reducing tumor growth and metastatic spread by activation of an anti-tumor innate immune response. Moreover, systemic suppression of CD47 protected cardiac tissue viability and function in mice treated with doxorubicin.

CONCLUSIONS

Our experiments indicate that the protective effects observed with CD47 blockade are mediated through upregulation of autophagic flux. However, the absence of CD47 in did not elicit a protective effect in cancer cells, but it enhanced macrophage-mediated cancer cell cytolysis. Therefore, the differential responses observed with CD47 blockade are due to autonomous activation of protective autophagy in normal tissue and enhancement immune cytotoxicity against cancer cells.

Blunting of cardioprotective actions of estrogen in female rodent heart linked to altered expression of cardiac tissue chymase and ACE2

Background:

Diastolic dysfunction develops in response to hypertension and estrogen (E2) loss and is a forerunner to heart failure (HF) in women. The cardiac renin–angiotensin system (RAS) contributes to diastolic dysfunction, but its role with respect to E2 and blood pressure remain unclear.

Methods:

We compared the effects of ovariectomy (OVX) or sham surgery on the cardiac RAS, left ventricular (LV) structure/function, and systemic/intracardiac pressures of spontaneously hypertensive rats (SHRs: n = 6 intact and 6 OVX) and age-matched Wistar-Kyoto (WKY: n = 5 intact and 4 OVX) controls.

Results:

WKY rats were more sensitive to OVX than SHRs with respect to worsening of diastolic function, as reflected by increases in Doppler-derived filling pressures (E/e′) and reductions in myocardial relaxation (e′). This pathobiologic response in WKY rats was directly linked to increases in cardiac gene expression and enzymatic activity of chymase and modest reductions in ACE2 activity. No overt changes in cardiac RAS genes or activities were observed in SHRs, but diastolic function was inversely related to ACE2 activity.

Conclusion:

Endogenous estrogens exert a more significant regulatory role upon biochemical components of the cardiac RAS of WKY versus SHRs, modulating the lusitropic and structural components of its normotensive phenotype.

Critical role of the chymase/angiotensin-(1-12) axis in modulating cardiomyocyte contractility

BACKGROUND

Angiotensin-(1-12) [Ang-(1-12)] is a chymase-dependent source for angiotensin II (Ang II) cardiac activity. The direct contractile effects of Ang-(1-12) in normal and heart failure (HF) remain to be demonstrated. We assessed the hypothesis that Ang-(1-12) may modulate [Ca²⁺]_i regulation and alter cardiomyocyte contractility in normal and HF rats.

METHODS AND RESULTS

We compared left ventricle (LV) myocyte contractile and calcium transient ([Ca²⁺]_iT) responses to angiotensin peptides in 16 SD rats with isoproterenol-induced HF and 16 age-matched controls. In normal myocytes, versus baseline, Ang II (10^-6 M) superfusion significantly increased myocyte contractility (dL/dt_max: 40%) and [Ca²⁺]_iT (29%). Ang-(1-12) (4 × 10^-6 M) caused similar increases in dL/dt_max (34%) and [Ca²⁺]_iT (25%). Compared with normal myocytes, superfusion of Ang II and Ang-(1-12) in myocytes obtained from rats with isoproterenol-induced HF caused similar but significantly attenuated positive inotropic actions with about 42% to 50% less increases in dL/dt_max and [Ca²⁺]_iT. Chymostatin abolished Ang-(1-12)-mediated effects in normal and HF myocytes. The presence of an inhibitory cAMP analog, Rp-cAMPS prevented Ang-(1-12)-induced inotropic effects in both normal and HF myocytes. Incubation of HF myocytes with pertussis toxin (PTX) further augmented Ang II-mediated contractility.

CONCLUSIONS

Ang-(1-12) stimulates cardiomyocyte contractile function and [Ca²⁺]_iT in both normal and HF rats through a chymase mediated action. Altered inotropic responses to Ang-(1-12) and Ang II in HF myocytes are mediated through a cAMP-dependent mechanism that is coupled to both stimulatory G and inhibitory PTX-sensitive G proteins.

Blunting of estrogen modulation of cardiac cellular chymase/RAS activity and function in SHR

The relatively low efficacy of ACE-inhibitors in the treatment of heart failure in women after estrogen loss may be due to their inability to reach the intracellular sites at which angiotensin (Ang) II is generated and/or the existence of cell-specific mechanisms in which ACE is not the essential processing pathway for Ang II formation. We compared the metabolic pathway for Ang II formation in freshly isolated myocytes (CMs) and non-myocytes (NCMs) in cardiac membranes extracted from hearts of gonadal-intact and ovariectomized (OVX) adult WKY and SHR rats. Plasma Ang II levels were higher in WKY vs. SHR (strain effect: WKY: 62 ± 6 pg/ml vs. SHR: 42 ± 9 pg/ml; p < 0.01), independent of OVX. The enzymatic activities of chymase, ACE, and ACE2 were higher in NCMs versus CMs, irrespective of whether assays were performed in cardiac membranes from WKY or SHR or in the presence or absence of OVX. E2 depletion increased chymase activity, but not ACE activity, in both CMs and NCMs. Moreover, cardiac myocyte chymase activity associated with diastolic function in WKYs and cardiac structure in SHRs while no relevant functional and structural relationships between the classic enzymatic pathway of Ang II formation by ACE or the counter-regulatory Ang-(1-7) forming path from Ang II via ACE2 were apparent. The significance of these novel findings is that targeted cell-specific chymase rather than ACE inhibition may have a greater benefit in the management of HF in women after menopause.

Obesity: A Perspective from Hypertension

The prevalence of obesity-related hypertension is high worldwide and has become a major health issue. The mechanisms by which obesity relates to hypertensive disease are still under intense research scrutiny, and include altered hemodynamics, impaired sodium homeostasis, renal dysfunction, autonomic nervous system imbalance, endocrine alterations, oxidative stress and inflammation, and vascular injury. Most of these contributing factors interact with each other at multiple levels. Thus, as a multifactorial and complex disease, obesity-related hypertension should be recognized as a distinctive form of hypertension, and specific considerations should apply in planning therapeutic approaches to treat obese individuals with high blood pressure.

Abstract P285: Diastolic Dysfunction After Estrogen Loss is Linked to Cardiac Chymase in WKY but Not SHR Rats

Left ventricular diastolic dysfunction (LVDD) develops in response to hypertension and estrogen (E2) loss and is consequent to heart failure in women. To understand the mechanisms underlying the development of LVDD as a result of the interaction between E2 loss and the cardiac RAS, we compared the relationships of LV tissue RAS components and E/e′ between adult SHR (n=13) and WKY (n=9) female rats after ovariectomy (OVX) or sham surgery (intact). In intact rats, E/e′ was higher in SHR vs. WKY rats (P<0.05 strain effect) and after OVX, the diastolic phenotype of WKY’s mimicked that of intact SHR counterparts (Figure).

While relationships between RAS enzymatic activities and E/e′ were not significant in SHRs with respect to estrogen status (data not shown), OVX-induced increases in E/e′ were significantly linked to increases in chymase gene expression and enzymatic activity in the WKY strain (Figure). These data indicate that 1) the altered diastolic function in SHR is relatively insensitive to loss of estrogen while the opposite is true in WKY rats, and 2) OVX-induced LVDD in WKY is directly related to increases in cardiac chymase activity. Further elucidation of the interplay between an activated cardiac chymase-mediated RAS metabolism and LVDD following estrogen loss in normotensive subjects is warranted.

Abstract P276: Tissue Primacy of Chymase as an Angiotensin II-forming Enzyme from Angiotensin-(1-12)

Breaking the prevailing acceptance of ACE primacy as the Ang II-forming enzyme, we have demonstrated that cardiac Ang II production in human and rat heart tissues are primarily mediated by chymase. In this study, we compared the affinity of cardiac chymase to generate Ang II from Ang-(1-12) or Ang I in plasma membranes (PMs) isolated from the diseased left atria of humans and SHR left ventricle. PMs (50-100 μg) were exposed to increasing concentrations of either Ang-(1-12) or Ang I substrate (0-300 μM) for 30 min at 37 o C in the presence of lisinopril (200 μM). The K m and V max of human cardiac chymase (Mean ± SE) were 29 ± 0.9 vs 87 ± 8.8 μM and 57 ± 1.4 vs 145 ± 3.7 μM/min/mg for Ang-(1-12) and Ang I substrates, respectively. Similarly, the K m and V max of rat cardiac chymase were 64 ± 6.3 vs 142 ± 17 μM and 13.2 ± 1.3 vs 1.9 ± 0.2 μM/min/mg for Ang-(1-12) and Ang I substrate, respectively. These data suggest that cardiac chymase has a higher affinity for Ang-(1-12) substrate compared to Ang I in both human and rat heart tissues. Further, our kinetic data show that the catalytic efficiency (ratio of V max /K m ) of human and rat chymase were 1.2 and 15.4-fold higher for Ang-(1-12) substrate compared to Ang I. Overall, our findings suggest that Ang-(1-12), rather than Ang I, is the preferred substrate for chymase in the generation of Ang II by human and rat heart tissue.

Abstract P283: Effects of Ovarian Estrogens on Local RAS Activity in Cardiomyocytes and Non-cardiomyocytes

The relatively low efficacy of ACE-Is in the treatment of heart failure (HF) in women after estrogen (E2) loss may be due to their inability to reach the intracellular sites at which Ang II is generated and/or the existence of cell-specific mechanisms in which ACE is not the essential processing pathway for Ang II formation. We compared the metabolic pathway for Ang II formation in freshly isolated cardiomyocytes (CMs) and non-cardiomyocytes (NCMs) extracted from hearts of gonadal-intact and ovariectomized (OVX) adult WKY and SHR rats. Circulating levels of angiotensinogen (AOGEN) were higher in WKY (958 ± 47 pg/mL) vs. SHR (SHR: 626 ± 40 pg/mL; P<0.05 strain effect) and E2 loss augmented this effect in WKY (WKY OVX: 1,169 ± 66 pg/mL vs. SHR OVX: 625 ± 41 pg/mL). Correspondingly, plasma Ang II levels were higher in WKY vs. SHR (strain effect: WKY: 62 ± 6 pg/mL vs. SHR: 42 ± 9 pg/mL), independent of OVX. Chymase activity was nearly 40-fold higher in NCMs compared to CMs, and for the NCMs, activities were highest in cells from WKY vs. SHR and OVX vs. intact rats (P<0.05 strain and E2 effects, respectively) (Figure).

Neither strain nor gonad status influenced the lower ACE activity found in both NCMs and CMs. In contrast, ACE2 activity in CMs and NCMs was higher in cells from WKY vs. SHR (P<0.05 strain effect), independent of E2 status. We conclude that NCMs from WKY and SHR express significantly higher levels of chymase, ACE, and ACE2 activities. E2 loss leads to selective changes in the activity of chymase, but not ACE, in NCMs. The significance of these novel findings is that targeted cell-specific chymase rather than ACE inhibition may have a greater benefit in the management of HF in women after menopause.

Intracrine angiotensin II functions originate from noncanonical pathways in the human heart

Although it is well-known that excess renin angiotensin system (RAS) activity contributes to the pathophysiology of cardiac and vascular disease, tissue-based expression of RAS genes has given rise to the possibility that intracellularly produced angiotensin II (Ang II) may be a critical contributor to disease processes. An extended form of angiotensin I (Ang I), the dodecapeptide angiotensin-(1-12) [Ang-(1-12)], that generates Ang II directly from chymase, particularly in the human heart, reinforces the possibility that an alternative noncanonical renin independent pathway for Ang II formation may be important in explaining the mechanisms by which the hormone contributes to adverse cardiac and vascular remodeling. This review summarizes the work that has been done in evaluating the functional significance of Ang-(1-12) and how this substrate generated from angiotensinogen by a yet to be identified enzyme enhances knowledge about Ang II pathological actions.

Primacy of cardiac chymase over angiotensin converting enzyme as an angiotensin-(1-12) metabolizing enzyme

We showed previously that rat angiotensin-(1-12) [Ang-(1-12)] is metabolized by chymase and angiotensin converting enzyme (ACE) to generate Angiotensin II (Ang II). Here, we investigated the affinity of cardiac chymase and ACE enzymes for Ang-(1-12) and Angiotensin I (Ang I) substrates. Native plasma membranes (PMs) isolated from heart and lung tissues of adult spontaneously hypertensive rats (SHR) were incubated with radiolabeled (125)I-Ang-(1-12) or (125)I-Ang I, in the absence or presence of a chymase or ACE inhibitor (chymostatin and lisinopril, respectively). Products were quantitated by HPLC connected to an in-line flow-through gamma detector. The rate of (125)I-Ang II formation from (125)I-Ang-(1-12) by chymase was significantly higher (heart: 7.0 ± 0.6 fmol/min/mg; lung: 33 ± 1.2 fmol/min/mg, P < 0.001) when compared to (125)I-Ang I substrate (heart: 0.8 ± 0.1 fmol/min/mg; lung: 2.1 ± 0.1 fmol/min/mg). Substrate affinity of (125)I-Ang-(1-12) for rat cardiac chymase was also confirmed using excess unlabeled Ang-(1-12) or Ang I (0-250 μM). The rate of (125)I-Ang II formation was significantly lower using unlabeled Ang-(1-12) compared to unlabeled Ang I substrate. Kinetic data showed that rat chymase has a lower Km (64 ± 6.3 μM vs 142 ± 17 μM), higher Vmax (13.2 ± 1.3 μM/min/mg vs 1.9 ± 0.2 μM/min/mg) and more than 15-fold higher catalytic efficiency (ratio of Vmax/Km) for Ang-(1-12) compared to Ang I substrate, respectively. We also investigated ACE mediated hydrolysis of (125)I-Ang-(1-12) and (125)I-Ang I in solubilized membrane fractions of the SHR heart and lung. Interestingly, no significant difference in (125)I-Ang II formation by ACE was detected using either substrate, (125)I-Ang-(1-12) or (125)I-Ang I, both in the heart (1.8 ± 0.2 fmol/min/mg and 1.8 ± 0.3 fmol/min/mg, respectively) and in the lungs (239 ± 25 fmol/min/mg and 248 ± 34 fmol/min/mg, respectively). Compared to chymase, ACE-mediated Ang-(1-12) metabolism in the heart was several fold lower. Overall our findings suggest that Ang-(1-12), not Ang I, is the better substrate for Ang II formation by chymase in adult rats. In addition, this confirms our previous observation that chymase (rather than ACE) is the main hydrolyzing enzyme responsible for Ang II generation from Ang-(1-12) in the adult rat heart.

Beneficial Cardiovascular Actions of Eplerenone in the Spontaneously Hypertensive Rat

Background: Aldosterone has been implicated as a potential mediator of cardiac and vascular damage in a variety of disorders. This study examined the role of aldosterone and its interplay with the renin-angiotensin system in the pathogenesis of hypertension. To this end, the effects of the aldosterone antagonist eplerenone and the angiotensin converting enzyme inhibitor lisinopril on cardiovascular mass, myocardial collagen, and coronary circulation were examined in spontaneously hypertensive rats.

Methods: Male, 22-week-old rats were randomly divided into 4 groups (12 in each). The control group received no treatment, the second group was given eplerenone (100 mg/kg/day), the third received lisinopril (3 mg/kg/day), and the fourth was given eplerenone and lisinopril. After 12 weeks of respective treatments, systemic and regional hemodynamics and cardiovascular mass indexes were measured in conscious instrumented rats.

Results: Eplerenone decreased arterial pressure but did not affect left ventricular mass or hydroxyproline concentration (an estimate of collagen). It did, however, reduce minimal coronary vascular resistance and increased coronary flow reserve. Lisinopril decreased arterial pressure and ventricular mass but did not affect regional hemodynamics. The combination therapy produced synergistic effects.

Conclusion: Aldosterone antagonism improved coronary and systemic hemodynamics in adult spontaneously hypertensive rats but did not affect cardiovascular mass indexes. The finding that lisinopril and eplerenone decreased arterial pressure to the same extent but had different cardiovascular effects suggested that these effects might be pressure independent.

Cardiac angiotensin-(1-12) expression and systemic hypertension in rats expressing the human angiotensinogen gene

Angiotensin-(1-12) [ANG-(1-12)] is processed into ANG II by chymase in rodent and human heart tissue. Differences in the amino acid sequence of rat and human ANG-(1-12) render the human angiotensinogen (hAGT) protein refractory to cleavage by renin. We used transgenic rats harboring the hAGT gene [TGR(hAGT)L1623] to assess the non-renin-dependent effects of increased hAGT expression on heart function and arterial pressure. Compared with Sprague-Dawley (SD) control rats (n= 11), male homozygous TGR(hAGT)L1623 (n= 9) demonstrated sustained daytime and nighttime hypertension associated with no changes in heart rate but increased heart rate lability. Increased heart weight/tibial length ratio and echocardiographic indexes of cardiac hypertrophy were associated with modest reduction of systolic function in hAGT rats. Robust human ANG-(1-12) immunofluorescence within myocytes of TGR(hAGT)L1623 rats was associated with a fourfold increase in cardiac ANG II content. Chymase enzymatic activity, using the rat or human ANG-(1-12) as a substrate, was not different in the cardiac tissue of SD and hAGT rats. Since both cardiac angiotensin-converting enzyme (ACE) and ACE2 activities were not different among the two strains, the changes in cardiac structure and function, blood pressure, and left ventricular ANG II content might be a product of an increased cardiac expression of ANG II generated through a non-renin-dependent mechanism. The data also underscore the existence in the rat of alternate enzymes capable of acting on hAGT protein. Homozygous transgenic rats expressing the hAGT gene represent a novel tool to investigate the contribution of human relevant renin-independent cardiac ANG II formation and function.

Functional changes in the uterine artery precede the hypertensive phenotype in a transgenic model of hypertensive pregnancy

The pregnant female human angiotensinogen (hAGN) transgenic rat mated with the male human renin (hREN) transgenic rat is a model of preeclampsia (TgA) with increased blood pressure, proteinuria, and placenta alterations of edema and necrosis at late gestation. We studied vascular responses and the role of COX-derived prostanoids in the uterine artery (UA) at early gestation in this model. TgA UA showed lower stretch response, similar smooth muscle α-actin content, and lower collagen content compared with Sprague-Dawley (SD) UA. Vasodilation to acetylcholine was similar in SD and TgA UA (64 ± 8 vs. 75 ± 6% of relaxation, P > 0.05), with an acetylcholine-induced contraction in TgA UA that was abolished by preincubation with indomethacin (78 ± 6 vs. 83 ± 11%, P > 0.05). No differences in the contraction to phenylephrine were observed (159 ± 11 vs. 134 ± 12 %KMAX, P > 0.05), although in TgA UA this response was greatly affected by preincubation with indomethacin (179 ± 16 vs. 134 ± 9 %KMAX, P < 0.05, pD2 5.92 ± 0.08 vs. 5.85 ± 0.03, P < 0.05). Endothelium-independent vasodilation was lower in TgA UA (92 ± 2 vs. 74 ± 5% preconstricted tone, P < 0.05), and preincubation with indomethacin restored the response to normal values (90 ± 3 vs. 84 ± 3%). Immunostaining showed similar signals for α-actin, COX-2, and eNOS between groups (P > 0.05). Plasma thromboxane levels were similar between groups. In summary, TgA UA displays functional alterations at early gestation before the preeclamptic phenotype is established. Inhibition of COX enzymes normalizes some of the functional defects in the TgA UA. An increased role for COX-derived prostanoids in this model of preeclampsia may contribute to the development of a hypertensive pregnancy.

Abstract P603: Age and Angiotensin-(1-12) Expression in Human Atrial Tissue of Patients with Left Heart Disease

In the human heart formation of angiotensin (Ang) II results from the hydrolysis of an alternate angiotensin substrate, -Ang-(1-12)-, by chymase rather than angiotensin converting enzyme. In our recent study a higher Ang-(1-12) expression and upregulation of chymase mRNA and enzymatic activity was found in left (LAA) versus right atrial appendages (RAA) of subjects with left heart disease. Since aging is associated with prominent changes in cardiac structure and function, we assessed the relationships among age, Ang-(1-12), and chymase gene expression and activity in both LAA and RAA in 44 patients undergoing cardiac surgery for the correction of valvular heart disease, resistant atrial fibrillation or ischemic heart disease. Immunohistochemistry for Ang-(1-12) detection was performed using an affinity purified polyclonal antibody directed to the COOH terminus of the full length of the sequence of human Ang-(1-12). Quantitative real-time polymerase chain reaction was used to detect chymase mRNA levels whereas chymase activity was assessed by HPLC. We report that Ang-(1-12) immunostaining in atrial appendages (r=0.30; p<0.05), but not chymase mRNA expression or activity, correlated directly with patients age. While a tendency for higher Ang-(1-12) expression in LAA (Intensity: 5.88 ± 0.91 units; n=11) when compared to RAA (Intensity: 3.948 ± 0.55 units; n=15) was noted in patients younger than 65 yrs, this difference was more prominent and statistically significant in patients older than 65 yrs of age (LAA Intensity: (n=12): 7.39 ± 1.06 units versus RAA Intensity (n=13): 4.74 ±0.54 units; p < 0.05). The results of the present study suggest an age-related increase in Ang-(1-12) expression in human atrial tissue that may be more prominent in the LAA of patients with left heart disease. We suggest that higher availability of Ang-(1-12) for direct Ang II formation may be an underlying mechanism responsible, at least in part, for age- and disease-related atrial and ventricular remodeling and dysfunction.

Abstract MP04: Cardiac ACE2/Angiotensin-(1-7) in Rats Expressing Human Angiotensinogen Gene

When compared to Sprague Dawley (SD) control rats, transgenic rats expressing the human angiotensinogen (AGT) gene [TGR(hAGT)L1623] exhibit hypertension associated with cardiac hypertrophy and higher cardiac tissue angiotensin (Ang) II. Whether the hypertension and cardiac hypertrophy in these rats expressing the human AGT are related to a non-canonical pathway for Ang II formation or suppression of the counter regulatory mechanism mediated by ACE2 and Ang-(1-7) has not been established. Consequently, cardiac peptides were determined by RIA in 9 [TGR(hAGT)L1623] and 11 SD male rats (17 weeks of age). ACE2 activities in homogenized heart tissues were determined by HPLC. Cardiac Ang II content was four times higher (37.05 ± 5.04 vs. 9.62 ± 0.93 fmol/mg protein; p <0.0001) while the Ang-(1-7) level increased only 1.3 times (18.02 ± 1.62 vs 13.37 ± 1.74 fmol/mg protein; p=0.06) in TGR(hAGT)L1623 rats when compared with SD rats. Although, the Ang II/Ang-(1-7) ratio was higher in transgenic rats harboring the human AGT gene (2.10 ± 0.27 vs 0.90 ± 0.19; p <0.005), ACE2 activities between these two strains of animals were not different (12.21 ± 0.76 vs. 10.80 ± 0.91 fmol/min/mg; p >0.05). Since human AGT protein is not cleaved by rat renin, our data continues to support the view that hypertension and cardiac hypertrophy in this transgenic strain are induced by activation of a non-renin mechanism rather than a primary suppression of the compensatory Ang II degrading pathway mediated by ACE2. Further studies are necessary to determine the role of enzymes affecting Ang-(1-7) metabolism in the observed inadequate balance between Ang II and Ang-(1-7).

Abstract 078: Functional Significance of the Chymase/Ang-(1-12) Pathway on Cardiomyocytes

Angiotensin-(1-12) [Ang-(1-12)] functions in rodents and humans as a tissue substrate for the direct generation of Ang II via chymase. Since its direct cardiac effect have not been studied, the importance of this renin-independent mechanism for Ang II paracrine/intracrine actions in modulating cardiac contractility were determined in freshly isolated myocytes from 11 normal SD rats. Systolic amplitude (SA), peak velocity of shortening (dL/dtmax), the peak velocity of relengthening (dR/dtmax), and changes in the peak calcium transient ([Ca2+]i) were evaluated before and following exposure to Ang II (10-6 M), Ang-(1-12) delivered alone (range: 2x10-6 to 4x10-6 M) or after 1 h incubation with human recombinant chymase (10 μg protein/mL at 37°C). Both Ang II and the mixture of Ang-(1-12) with chymase elicited positive inotropic responses in freshly isolated cardiac myocytes associated with significant increases in peak systolic [Ca2+]i (Figure) while superfusion of Ang-(1-12) alone elicited an increase in dL/dtmax without significant changes in [Ca2+]i. The increases in contractility elicited by Ang II or the Ang-(1-12)/chymase mixture were abolished by prior exposure of the myocytes to losartan (10-5 M) or the chymase inhibitor chymostatin (8x10-5 M). We conclude that in single adult rat myocytes Ang-(1-12) stimulates contractile function through a chymase mediated action and by mechanisms that implicate a paracrine/intracrine activation of intracellular calcium.

Abstract 126: Systemic Administration of (Pyr1)-Apelin-13 at Late Pregnancy Reduces Blood Pressure, Proteinuria, and Improves Autonomic Function in Preeclamptic Rats

Preeclampsia is associated with maternal perinatal morbidity and mortality and a high risk of premature birth and intrauterine growth restriction. The apelin system is a novel pleiotropic pathway with a potential for therapeutic targeting in preeclampsia. We have previously reported that total apelin content is lower in human preeclamptic chorionic villi. In this study, we determined whether (Pyr1)-apelin-13 improves hypertension, proteinuria, fetal characteristics, uteroplacental hemodynamics, and the autonomic function in preeclamptic rats (TgA, female transgenic for human angiotensinogen mated to male transgenic for human renin). (Pyr1)-apelin-13 (2 mg/kg/day) (n=7) or saline (n=5) was infused in TgA via osmotic minipumps starting at day 13 of gestation, when blood pressure begins to increase in these animals. Pregnant SD (n=6) rats were used as controls. At the 20th day of pregnancy, TgA rats had higher MAP (138±6 vs. 79±3 mmHg in SD, p<0.001) which was reduced by (Pyr1)-apelin treatment to 119±2 mmHg vs. TgA, p<0.006. TgA rats also had impaired heart rate variability measured as root of mean successive differences (rMSSD) compared with SD (2.7±0.4 vs. 3.8±0.3 ms in SD, p<0.05). Apelin treatment normalized rMSSD to 3.6±0.3, p<0.05. Similarly, baroreflex sensitivity measured in the sequence domain was lower in TgA (0.7±0.1 vs. 2.6±0.5 ms/mmHg in SD, p<0.01) and normalized with (Pyr1)-apelin-13 to 2.0 ± 0.4 ms/mmHg, p<0.05. Proteinuria was greater in TgA (53±9 vs. 10±2 mg/kg/day, p<0.001), and normalized by (Pyr1)-apelin-13 (18±6, p<0.05). Pup (3.0±0.1 vs. 3.7±0.1 g, p<0.01) and placental weight (0.41±0.01 vs. 0.45±0.01 g, p<0.01), and pup number (10.7±1.1 vs. 14.0±0.8, p<0.01) were lower in TgA vs. SD; however they were not changed by (Pyr1)-apelin-13. Uterine artery peak systolic velocity was not different between SD and TgA, but increased with (Pyr1)-apelin-13 treatment (179.5±16.7 vs. 122.6±16.7 ml/min, p<0.05) with no change in resistance index. In conclusion, our findings suggest that (Pyr1)-apelin-13 may be beneficial for the treatment of preeclampsia due to its hemodynamic and renoprotective effects. We also report for the first time that these changes may involve central control of the cardiovascular system.

Abstract P205: Angiotensin II Metabolic Pathways In Isoproterenol-Induced Heart Failure: Myocytes vs Non-myocytes

Although myocytes represent three-fours of the ventricular volume in mammalian hearts 90% of the remaining myocardial cells are interstitial cardiac fibroblasts. To shed light into the paracrine mechanisms that contribute to the expression and function of the cardiac angiotensins, we investigated the comparative activity of chymase, ACE, and ACE2 in freshly isolated myocytes and non-cardiac myocytes (NCM) from the left ventricle of rats in which heart failure (HF) was induced by two injections of isoproterenol (Iso) (170 mg/kg body weight, s.c.) spaced 24 h apart. Consistently, chymase enzymatic activity was approximately 10-fold higher in NCM (8.37 ± 0.66 in normal and 6.76 ± 2.7 fmol/min/mg in Iso-induced HF, P < 0.05) compared to myocytes obtained from normal (0.43 ± 0.11 fmol/min/mg) or Iso-induced HF rats (0.65 ± 0.17 fmol/min/mg). Compared to chymase, ACE activity was several folds lower in both NCM (1.37 ± 0.21 in normal and 1.45 ± 0.49 fmol/min/mg in Iso-induced HF) and myocytes (0.28 ± 0.01 fmol/min/mg in normal and 0.37 ± 0.07 fmol/min/mg in Iso-induced HF). As illustrated in the Figure, both chymase and ACE2 activity tended to be higher in myocytes from HF rats. These data suggest that Iso-induced HF causes selective changes in the activity of chymase and ACE2 in myocytes but not in NCM. The clinical significance of these novel findings suggest that chymase rather than ACE inhibitors will have a greater benefit in the management of adverse cardiac remodeling.

Uterine artery dysfunction in pregnant ACE2 knockout mice is associated with placental hypoxia and reduced umbilical blood flow velocity

Angiotensin-converting enzyme 2 (ACE2) knockout is associated with reduced fetal weight at late gestation; however, whether uteroplacental vascular and/or hemodynamic disturbances underlie this growth-restricted phenotype is unknown. Uterine artery reactivity and flow velocities, umbilical flow velocities, trophoblast invasion, and placental hypoxia were determined in ACE2 knockout (KO) and C57Bl/6 wild-type (WT) mice at day 14 of gestation. Although systolic blood pressure was higher in pregnant ACE2 KO vs. WT mice (102.3 ± 5.1 vs. 85.1 ± 1.9 mmHg, n = 5-6), the magnitude of difference was similar to that observed in nonpregnant ACE2 KO vs. WT mice. Maternal urinary protein excretion, serum creatinine, and kidney or heart weights were not different in ACE2 KO vs. WT. Fetal weight and pup-to-placental weight ratio were lower in ACE2 KO vs. WT mice. A higher sensitivity to Ang II [pD2 8.64 ± 0.04 vs. 8.5 ± 0.03 (-log EC50)] and greater maximal contraction to phenylephrine (169.0 ± 9.0 vs. 139.0 ± 7.0% KMAX), were associated with lower immunostaining for Ang II receptor 2 and fibrinoid content of the uterine artery in ACE2 KO mice. Uterine artery flow velocities and trophoblast invasion were similar between study groups. In contrast, umbilical artery peak systolic velocities (60.2 ± 4.5 vs. 75.1 ± 4.5 mm/s) and the resistance index measured using VEVO 2100 ultrasound were lower in the ACE2 KO vs. WT mice. Immunostaining for pimonidazole, a marker of hypoxia, and hypoxia-inducible factor-2α were higher in the trophospongium and placental labyrinth of the ACE2 KO vs. WT. In summary, placental hypoxia and uterine artery dysfunction develop before major growth of the fetus occurs and may explain the fetal growth restricted phenotype.

Differential expression of the angiotensin-(1-12)/chymase axis in human atrial tissue

OBJECTIVE

Heart chymase rather than angiotensin converting enzyme has higher specificity for angiotensin (Ang) I conversion into Ang II in humans. A new pathway for direct cardiac Ang II generation has been revealed through the demonstration that Ang-(1-12) is cleaved by chymase to generate Ang II directly. We address here whether Ang-(1-12) and chymase gene expression and activity are detected in the atrial appendages of 44 patients (10 females) undergoing heart surgery for the correction of valvular heart disease, resistant atrial fibrillation or ischemic heart disease.

METHODS AND RESULTS

Immunoreactive Ang-(1-12) expression was 54% higher in left atrial compared with right atrial appendages. This was associated with higher abundance of left atrial appendage chymase gene transcripts and chymase activity, but no differences in angiotensinogen mRNA. Atrial chymase enzymatic activity was highly correlated with left atrial but not right atrial enlargement as determined by echocardiography, while both tyrosine hydroxylase and neuropeptide Y atrial appendage mRNAs correlated with atrial angiotensinogen mRNAs.

CONCLUSIONS

Higher Ang-(1-12) expression and upregulation of chymase gene transcripts and enzymatic activity from the atrial appendages connected to the enlarged left versus right atrial chambers of subjects with left heart disease defines a role of this alternate Ang II forming pathway in the processes accompanying adverse atrial and ventricular remodeling.

Clinical utility of fixed-dose combinations in hypertension: evidence for the potential of nebivolol/valsartan

Despite significant advances in pharmacologic approaches to treat hypertension during the last decades, hypertension- and hypertension-related organ damage are still a high health and economic burden because a large proportion of patients with hypertension do not achieve optimal blood pressure control. There is now general agreement that combination therapy with two or more antihypertensive drugs is required for targeted blood pressure accomplishment and reduction of global cardiovascular risk. The goals of combination therapies are to reduce long-term cardiovascular events by targeting different mechanism underlying hypertension and target organ disease, to block the counterregulatory pathways activated by monotherapies, to improve tolerability and decrease the adverse effects of up-titrated single agents, and to increase persistence and adherence with antihypertensive therapy. Multiple clinical trials provide evidence that fixed-dose combinations in a single pill offer several advantages when compared with loose-dose combinations. This review discusses the advances in hypertension control and associated cardiovascular disease as they relate to the prospect of combination therapy targeting a third-generation beta (β) 1-adrenergic receptor (nebivolol) and an angiotensin II receptor blocker (valsartan) in fixed-dose single-pill formulations.

Angiotensin-(1-12): a chymase-mediated cellular angiotensin II substrate

The classical view of biochemical pathways for the formation of biologically active angiotensins continues to undergo significant revision as new data uncovers the existence of important species differences between humans and rodents. The discovery of two novel substrates that, cleaved from angiotensinogen, can lead to direct tissue angiotensin II formation has the potential of radically altering our understanding of how tissues source angiotensin II production and explain the relative lack of efficacy that characterizes the use of angiotensin converting enzyme inhibitors in cardiovascular disease. This review addresses the discovery of angiotensin-(1-12) as an endogenous substrate for the production of biologically active angiotensin peptides by a non-renin dependent mechanism and the revealing role of cardiac chymase as the angiotensin II convertase in the human heart. This new information provides a renewed argument for exploring the role of chymase inhibitors in the correction of cardiac arrhythmias and left ventricular systolic and diastolic dysfunction.

Abstract 577: Increased Uterine Interimplantation Levels of Ang II, AT 1 R, and CB 1 R are Associated with Reduced Uterine Permeability at Early Pregnancy in a Transgenic Model of Preeclampsia

Both the renin-angiotensin (RAS) and endocannabinoid (ECS) systems are down-regulated at the early stages of normal pregnancy. The striking similarity of the pattern of distribution of the two systems and their required down-regulation in early events of pregnancy make a compelling argument to compare their regulation in the early events of pregnancy in an animal that has placental activation of the RAS at l ate gestation. Female transgenic rats with overexpression of human (h) angiotensinogen were mated with male rats with h renin [Preeclamptic model (PRE)]. At day 7 of gestation, normal pregnant Sprague Dawley (SD) and PRE animals were anesthetized and bovine serum albumin (BSA) conjugated to Alexa Fluor 488 was injected systemically to assess uterine permeability in the implantation (IS) and interimplantation (IIS) uterine sites. Mean blood pressures were not different between SD and PRE animals (98.8±2 vs 97±3 mmHg, p>0.05). Uterine permeability measured as the IS/IIS ratio of fluorescent BSA signal was decreased in PRE vs. SD (1.36±0.2 vs 0.68±0.1, p<0.05). The levels of Ang II and AT 1 R mRNA were increased in the IIS of PRE vs IS of PRE and IIS of SD ( FIGURE ). CB 1 R mRNA was increased in the IIS vs. IS of PRE rats, and this was associated with a significant increase in the levels of total 1+2-arachidonoylglycerol (24.9±4.1 vs 12.2±3.5 ng/mg protein, p<0.05) in IIS of PRE vs IIS of SD. These data demonstrate a synergistic up-regulation of the RAS and ECS associated with reduced uterine permeability at early pregnancy in a PRE model. These changes precede the hypertensive phenotype and are consistent with a critical role for the disrupted RAS and alterations in the ECS in early pregnancy.

Abstract 622: Angiotensin-(1-12) Is A Better Substrate Compared To Angiotensin I To Generate Angiotensin Ii By Rat Chymase

Angiotensin-(1-12) [Ang-(1-12)] is metabolized by chymase to generate angiotensin II (Ang II). We investigated the affinity of rat chymase to generate Ang II from Ang-(1-12) or angiotensin I (Ang I). Plasma membranes isolated from the heart of spontaneously hypertensive rats (SHR) were incubated with radiolabeled 125I-Ang-(1-12) or 125I-Ang I substrate in the absence or in the presence of a chymase inhibitor (chymostatin, 50 μM). 125I-Ang II formation was quantified by HPLC. The rate of 125I-Ang II formation from 125I-Ang-(1-12) by chymase in cardiac plasma membranes was significantly higher (5.7±0.2 fmol/min/mg protein, P<0.001) when compared to 125I-Ang I (0.82±0.13 fmol/min/mg protein). Substrate affinity of 125I-Ang-(1-12) for rat chymase was also confirmed by using an excess amount of unlabeled Ang-(1-12) or Ang I (0-250 μM). 125I-Ang II formation was significantly decreased by unlabeled Ang-(1-12) as compared to Ang I. We also investigated angiotensin-converting enzyme (ACE) mediated hydrolysis of 125I-Ang-(1-12) and 125I-Ang I in generating Ang II in SHR cardiac plasma membranes. No significant difference in 125I-Ang II formation was detected with either substrate. Moreover, the rate of 125I-Ang II production by ACE was lower (1.8±0.4 fmol/min/mg protein for Ang-(1-12) and 2.1±1.2 fmol/min/mg protein for Ang I) as compared to chymase. These data suggest that in the rat heart, Ang II formation from Ang-(1-12) is primarily mediated by chymase rather than ACE. Overall our findings suggest in the heart of SHR that compared to Ang I, Ang-(1-12) is the better substrate for Ang II formation. In addition, we confirm our previous observation that chymase is the main hydrolyzing enzyme responsible for Ang II generation from Ang-(1-12) in the rat heart.

Abstract 579: Increased Role of COX-derived Prostanoids in Regulating Ang II Induced Uterine Artery Contraction at Early Pregnancy in a Transgenic Model of Preeclampsia

The balance between vasodilatory and vasoconstrictor prostanoids contributes to vascular control during pregnancy. Alterations in this balance are involved in the development of hypertensive pregnancy. The transgenic female rat containing the human angiotensinogen (hAGN) gene mated with the male transgenic containing human renin (hREN) is a model of preeclampsia (TgA), and shows hypertension and proteinuria at late gestation. We investigated the role COX-derived mediators have on contractility of the uterine artery (UA) in TgA rats before the hypertensive phenotype develops. UA were isolated from transgenic TgA (n=9) and Sprague-Dawley (n=7) control rats at 7 days of gestation. UA were mounted in a wire myograph for determinations of isometric tension (DMT USA, 620M). Responses to acetylcholine (ACh), phenylephrine (Phe) and sodium nitroprusside (SNP) were measured in control conditions and after preincubation with indomethacin (Indo, 10-5M). Data were fitted to a dose response curve, vasodilatation was expressed as percent of pre-constriction and sensitivity as pD2 (pD2= -Log [EC50]). Responses to ACh reached similar maximal relaxations (64±8 vs 75±6%, p>0.05), and an increased contraction in TgA UA at ACh >10μM (p<0.05) was eliminated by Indo. Contraction to Phe was similar in both groups with an inhibitory effect of Indo on TgA UA (p<0.05). Relaxation to SNP was lower in TgA vs SD UA (92±2 vs 74±5%, p<0.05), this difference was abolished by Indo. Thus, inhibition of COX enzymes had a greater effect on TgA UA suggesting an imbalance towards an increased prostanoids-derived constrictor tone in TgA UA. This imbalance appears before the hypertensive phenotype is established.