Abstract P429: Aldehyde Dehydrogenase 2 Regulates Angiogenesis Of Coronary Microvascular Endothelial Cells Via A Novel Signaling Pathway

Coronary microvascular endothelial cell (CMECs) damage is implicated in diabetes-mediated heart failure with preserved ejection fraction (HFpEF). 4-hydroxy-2-nonenal (4HNE), a reactive aldehyde that is increased in diabetic heart, decreases angiogenesis in cultured mouse CMECs by decreasing the mRNA and protein levels of vascular endothelial growth factor receptor (VEGFR)2. Nuclear factor-kappa B (NF-kB), a transcription factor, was shown to transcribe VEGFR2. Thus, we presume 4HNE modulates NF-kB-mediated VEGFR2 transcription and regulates angiogenesis in CMECs. Aldehyde dehydrogenase (ALDH) 2, a mitochondrial enzyme that detoxifies 4HNE and confers cryoprotection. However, ALDH2 activity was reduced in the diabetic hearts which results in the augmentation of 4HNE-induced cardiotoxicity. Thus, we hypothesize that ALDH2 in CMECs reduces 4HNE-mediated cell signaling aberrations, and thereby, preserves coronary angiogenesis. We treated the cultured mouse CMECs with disulfiram (DSF) (2.5 μM), an ALDH2 inhibitor, alda1 (10 μM), an ALDH2 activator and prostratin (1 μM), an NF-κB activator prior to challenging the CMECs with 4HNE (75 μM). Our tube-formation angiogenesis assay revealed that pretreatment with DSF exacerbated a 4HNE-induced decrease in CMECs angiogenesis (P<0.0005 vs con and P<0.05 vs both 4HNE & DSF alone) while pretreatments with alda1 and prostratin attenuated a 4HNE-induced decrease in CMEC angiogenesis (P<0.05 vs 4HNE alone). DSF pretreatment exacerbated 4HNE mediated decrease in ALDH2 (P<0.005 vs con), phospho-IKBα (P<0.0005 vs con and P<0.05 vs both 4HNE and DSF alone), NF-κB levels, and nuclear translocation (P<0.0005 vs con and P<0.05 vs both 4HNE & DSF alone) and VEGFR2 (P<0.0005 vs con and P<0.05 vs both 4HNE and DSF alone) levels in cultured CMECs. Pretreatment with both prostratin and alda1 increased ALDH2 (P<0.0005 vs con), VEGFR2 (P<0.05 vs con) and NF-κB (P<0.005 vs con) levels in CMECs. The cardiac tissue samples of db/db mice when they manifest HFpEF showed increased 4HNE adducts, decreased NF-kB and VEGFR2 levels in CD31+ CMECs besides exhibiting low CMEC density. In conclusion, ALDH2 attenuates 4HNE-mediated decrease in coronary angiogenesis by decreasing VEGFR2 levels via low NF-κB mediated transcription.

Clinical Application of Novel Therapies for Coronary Angiogenesis: Overview, Challenges, and Prospects

Cardiovascular diseases continue to be the leading cause of death worldwide, with ischemic heart disease as the most significant contributor. Pharmacological and surgical interventions have improved clinical outcomes, but are unable to ameliorate advanced stages of end-heart failure. Successful preclinical studies of new therapeutic modalities aimed at revascularization have shown short lasting to no effects in the clinical practice. This lack of success may be attributed to current challenges in patient selection, endpoint measurements, comorbidities, and delivery systems. Although challenges remain, the field of therapeutic angiogenesis is evolving, as novel strategies and bioengineering approaches emerge to optimize delivery and efficacy. Here, we describe the structure, vascularization, and regulation of the vascular system with particular attention to the endothelium. We proceed to discuss preclinical and clinical findings and present challenges and future prospects in the field.

Resident Cardiac Macrophages Mediate Adaptive Myocardial Remodeling

SummaryCardiac macrophages represent a heterogeneous cell population with distinct origins, dynamics, and functions. Recent studies have revealed that C-C Chemokine Receptor 2 positive (CCR2+) macrophages derived from infiltrating monocytes regulate myocardial inflammation and heart failure pathogenesis. Comparatively little is known about the functions of tissue resident (CCR2−) macrophages. Herein, we identify an essential role for CCR2− macrophages in the chronically failing heart. Depletion of CCR2− macrophages in mice with dilated cardiomyopathy accelerated mortality and impaired ventricular remodeling and coronary angiogenesis, adaptive changes necessary to maintain cardiac output in the setting of reduced cardiac contractility. Mechanistically, CCR2− macrophages interacted with neighboring cardiomyocytes via focal adhesion complexes and were activated in response to mechanical stretch through a transient receptor potential vanilloid 4 (TRPV4) dependent pathway that controlled growth factor expression. These findings establish a role for tissue resident macrophages in adaptive cardiac remodeling and introduce a new mechanism of cardiac macrophage activation.

Abstract 17169: Endothelium-Specific Reduction in Mitochondrial ROS Induces Coronary Angiogenesis in Ischemic Myocardium via Activation of PI3k/Akt/ERG, ERK1/2, and Jag-1 Signaling

Introduction: Global reduction in reactive oxygen species (ROS) failed to improve outcomes in cardiovascular disease patients. Recent reports suggest that subcellular, rather than global ROS, play a crucial role in endothelial cell (EC) health. To that end, we generated a novel transgenic mouse model that overexpresses mitochondrial antioxidant MnSOD in EC-specific manner (MnSODVE-OE). Hypothesis: We hypothesized that decreased EC mitochondrial-ROS will improve post-myocardial infarction (MI) cardiac function by inducing coronary angiogenesis in ischemic myocardium. Methods: MnSODVE mice were assigned to Tet-ON (control) or Tet-OFF (MnSODVE-OE) group. To turn off the transgene, Tetracycline (Tet) (2mg/kg) was added to the drinking water (Tet-ON), while Tet-OFF mice did not receive Tet. Both groups underwent left anterior descending coronary artery (LAD) ligation surgery to mimic acute MI. Echocardiography was done 28 days after LAD ligation. Capillaries, arteriole density, and proliferating ECs were measured in heart sections using anti-CD31, anti-αSMA, and anti-PCNA immunofluorescence. Western blot, proteomic and phosphoproteomic analyses of mouse heart ECs isolated from MnSODVE (Tet-ON and Tet-OFF) animals were performed to study modulation of signaling cascades. Results: MnSODVE-OE mice demonstrated improved cardiac function (EF and FS increased by 16±7.87% and 21.73±10.31%, respectively, p <0.01), increase in capillary and arteriole densities by 4.13±4.10-fold, p<0.05 and 5.48±3.51-fold, p<0.001, respectively, and in EC proliferation by 1.46±0.80-fold, p <0.01, suggesting de novo coronary angiogenesis. Western blots showed activation of Akt (80.46±3.95% increase in p-Akt/ t-Akt ratio, p<0.05) and ERK1/2 (21.05±4.45% increase in p-ERK/ t-ERK 1/2 ratio, p<0.05). Proteome and phosphoproteome analyses showed upregulation of mitochondrial complex I biogenesis, RNA metabolism, and upregulation of Notch-related proteins ERG and Jag-1 (p<0.05). Student’s t-test was used for data analyses. Conclusions: Taken together, these results suggest that decreased mito-ROS in ECs improves post-MI cardiac function by inducing coronary angiogenesis through activation of PI3k/Akt/ERG, ERK1/2, and Jag-1 signaling.

Coronary Artery Development: Origin, Malformations, and Translational Vascular Reparative Therapy

After thickening of the cardiac chamber walls during embryogenesis, oxygen and nutrients can no longer be adequately supplied to cardiac cells via passive diffusion; therefore, a primitive vascular network develops to supply these vital structures. This plexus further matures into coronary arteries and veins, which ensures continued development of the heart. Various models have been proposed to account for the growth of the coronary arteries. However, lineage-tracing studies in the last decade have identified 3 major sources, namely, the proepicardium, the sinus venosus, and endocardium. Although the exact contribution of each source remains unknown, the emerging model depicts alternative pathways and progenitor cells, which ensure successful coronary angiogenesis. We aim to explore the current trends in coronary artery development, the cellular and molecular signals regulating heart vascularization, and its implications for heart disease and vascular regeneration.

Repetitive Transient Ischemia-Induced Cardiac Angiogenesis is Mediated by Camkii Activation

Background/Aims: Coronary angiogenesis is an important protective mechanism in response to myocardial ischemia in coronary artery disease. However, the underlying mechanisms remain largely unclear. Here, we investigated the role of CaMKII activation in ischemia-induced cardiac angiogenesis. Methods: Repetitive transient ischemia model was established in C57/BL6 mice by daily multiple episodes (3 times/day) of short time (5 min) occlusion of the left anterior descending coronary artery for 7 days. Coronary angiogenesis was detected by immunofluorescent staining. RT-qPCR and Western blot analyses were used to detect the mRNA and protein levels of CaMKII, p-CaMKII and VEGF. Primary cardiac microvascular endothelial cells (CMECs) were isolated to investigate the effects of KN93 on cell proliferation and migration in hypoxic condition. Results: We found that angiogenesis was induced in the ischemic myocardium and suppressed by chronic intraperitoneal injection of CaMKII inhibitor KN93. RT-qPCR and Western blot analyses showed that myocardial ischemia induced an increased expression and autophosphorylation of CaMKII. VEGF expression was increased in the ischemia model but blunted by KN93. Moreover, KN93 suppressed the proliferation and migration of cardiac endothelial cells in hypoxic condition in which the protein expression of CaMKII, p-CaMKII and VEGF was increased. Conclusion: CaMKII is an important mediator for the ischemia-induced coronary angiogenesis, in which CaMKII-triggered VEGF expression plays a key role.