Cardiovascular Disease (CVD) remains the leading cause of death worldwide and is linked to a variety of co- morbidities including Type 2 Diabetes Mellitus (T2DM), and Obesity. Work over the last 20 years by our group and others have identified the Angiotensin II Type 2 Receptor (AT2R) as a key player in the development and pathogenesis of cardiac and vascular structural damage. Clinically, in men, loss of Agtr2 expression is associated with increased arterial stiffness, impaired kidney function, and increased pulse pressure. Literature shows that female-specific increase in AT2R expression protects murine female models from vascular injury. Healthy female (ZL-F) rats have higher cardiac expression of the X-linked Agtr2 compared to male (ZL-M) rats; but T2DM suppressed cardiac Agtr2 expression only in ZDF-F (female), not in ZDF-M (male). We posit that increasing Agtr2 expression in ZDF-F rat heart will render protection from cardiomyocyte loss and scarring and this treatment will be of particular benefit to women suffering from CVD. However, there are no AT2R agonists that can increase Agtr2 expression. We observed that NP-6A4, a novel peptide agonist of AT2R, could increase Agtr2 expression in rat and human CV cells and mitigate cardiac hypertrophy, fibrosis and capillary rarefaction in male Zucker obese rats. Our conceptually novel central hypothesis is based on these observations and states that NP-6A4-AT2R-signaling offers a new therapeutic approach to mitigate sex differences in CVD by increasing Agtr2 gene expression. We discovered two new cross-talks induced by NP- 6A4-AT2R; first is activation of ALK2-ALK1 pathway that mitigates capillary rarefaction, and the second is suppression of the mineralocorticoid receptor (MR) involved in pathological CV remodeling.
In Aim 1, we will validate our hypothesis that NP-6A4 improves structural and functional cardiac and vascular parameters in rat models with chronic CVD induced by T2DM via increasing Agtr2 expression and signaling. We will use our new methods of detecting subclinical damage and subsequent protective remodeling via speckle tracking echocardiography (STE) in combination with histopathology, and extensive molecular signaling approaches.
In Aim 2, we will investigate if NP-6A4 mitigates cardiac and vascular structural damage caused by acute mechanical- and drug-induced injury. We will also investigate a) the role of cross-talk between NP-6A4-AT2R and the Activin-like kinases (ALK2-ALK1 pathway) in improving capillary density, and b) the significance of the cross-talk between NP-6A4-AT2R and MR in mitigating pathological cardiovascular remodeling. Collectively, positive results of this study will have high clinical relevance since they validate a) the efficacy of NP-6A4 as a novel therapeutic for acute and chronic CVD, and for mitigating sex differences in CVD, and b) the efficacy of STE-based diagnosis of the progression and mitigation of T2DM-induced subclinical cardiovascular damage.

Public Health Relevance

. Cardiovascular Disease (CVD) remains the leading cause of death worldwide and is linked to a variety of co- morbidities including Type 2 Diabetes Mellitus (T2DM) and Obesity. Both pre-menopausal and post- menopausal diabetic women are more susceptible to hypertension, impaired microcirculation and ischemic vascular diseases compared to age-matched men and non-diabetic women. Why diabetic females succumb faster to CVD is unclear and remains an understudied topic. We have developed a female diabetic rodent model that recapitulates the phenotype of human diabetic female. We have also identified a novel therapeutic, NP-6A4 that activates the cardio-protective AT2R that can mitigate sex differences in the severity of CVD. The goal of this pre-clinical study using diabetic rat models, and mouse models for vascular injury, is to develop a new therapeutic approach to detect and treat early subclinical damage to the heart caused by both chronic illness (diabetes) and acute injury and mitigate the severity of microvascular and cardiac damage in females.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Wong, Renee P
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Tufts University
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Toedebusch, Ryan; Belenchia, Anthony; Pulakat, Lakshmi (2018) Cell-Specific Protective Signaling Induced by the Novel AT2R-Agonist NP-6A4 on Human Endothelial and Smooth Muscle Cells. Front Pharmacol 9:928
Sharma, Neekun; Dev, Rishabh; Belenchia, Anthony M et al. (2018) Deficiency of IL12p40 (Interleukin 12 p40) Promotes Ang II (Angiotensin II)-Induced Abdominal Aortic Aneurysm. Arterioscler Thromb Vasc Biol :ATVBAHA118311969
Toedebusch, Ryan; Belenchia, Anthony; Pulakat, Lakshmi (2018) Diabetic Cardiomyopathy: Impact of Biological Sex on Disease Development and Molecular Signatures. Front Physiol 9:453