Abstract MP172: Y-chromosome Gene, Uty, Confers Male Protection Against Pulmonary Hypertension by Mediating Pro-inflammatory Chemokine Effects

Background: Idiopathic pulmonary arterial hypertension (PAH) is a terminal vascular lung disease characterized by increased PA pressure resulting in right ventricular (RV) failure and death. For reasons largely unknown, PAH is up to 4x more prevalent in females. We published that the Y-Chromosome (Chrm) is protective against hypoxia (Hx)-induced pulmonary hypertension (PH) in mice and identified four Y-Chrm genes expressed in the lung. Here, we identify the protective Y-Chrm gene, investigate its mechanism and demonstrate a novel therapeutic approach.

Methods and Results: To test the effect of Y-Chrm candidate genes on PH development, we knocked down (KD) each Y-Chrm gene via sequential intratracheal instillation of siRNA in the lungs of male mice exposed to Hx. KD of Y-Chrm gene Uty, but none of the other genes, resulted in more severe PH measured by increased RV systolic pressure (RVSP) and decreased pulmonary arterial acceleration time (PAAT) compared to control (n=4/group; RVSP: Uty-KD= 48.93mmHg, Control= 37.33mmHg, p=0.04; PAAT: Uty-KD= 11.88ms, Control= 14.43ms, p=0.01). RNAseq analysis (Uty-KD vs Control) revealed an increase in pro-inflammatory cytokines Cxcl9 (Log2FC: 1.3, p-adjusted=0.05) and Cxcl10 (Log2FC: 0.9, p-adjusted=0.002). We found Cxcl9/10 significantly upregulated in human PAH lungs vs healthy and female PAH lungs vs male (RT-qPCR). Fluorescent in-situ hybridization revealed Uty and Cxcl9/10 expression co-localized in CD68 + macrophages within the lung. Treatment of human pulmonary artery endothelial cells (PAEC) with Cxcl9/10 resulted in significantly increased apoptosis. We inhibited Cxcl9/10 activity in female rats 14 days post monocrotaline (MCT) injection by treating them with a small molecular inhibitor. Treated rats (n=6) had less severe PH than vehicle-treated controls (n=5) when measured 28-days post MCT (RVSP: Treated= 36.75mmHg, Vehicle=43.62 mmHg, p=0.03; PAAT: Treated= 26.7ms, Vehicle=20 ms, p=0.01; RV hypertrophy index (RV/(LV+IVS)): Treated= 0.48, Vehicle= 0.35, p=0.01).

Conclusion: Y-Chrm gene, Uty, is protective against PH. Uty inhibition increases pro-inflammatory cytokines Cxcl9/10 which contribute to PAEC death. Inhibition of Cxcl9/10 activity may provide a novel therapy for the treatment of PH.

Abstract MP155: Oxidized Lipids Diet Causes Pulmonary Hypertension Through T-cell Dependent Endothelial Cell Apoptosis

Background: Pulmonary hypertension (PH) is a fatal disease characterized by an increased mean pulmonary arterial pressure above 25mmHg. This increased pressure is, at least in part, due to thickening of the distal pulmonary arteries. Recently, numerous studies demonstrated an increased plasma concentration of oxidized lipids in PH and in diseases where secondary PH developed. Furthermore, 15-hydroxyeicosatetraenoic acid (15-HETE) an oxidized lipid and a major metabolite of arachidonic acid in the lung, has been implicated in dysregulation of major biological pathways in PH. However, the mechanisms involved in the causal role of 15-HETE in pulmonary hypertension development are not known.

Methods and Results: To study the role of 15-HETE in PH development, we fed C57BL6/J mice a diet supplemented with 15-HETE for 3 weeks with no other insults. After 3 weeks on the diet with added 15-HETE, C57BL6/J mice had increased concentrations of not only 15-HETE but also of other oxidized lipids (5-, 11- and 12-HETE) in plasma and lung, and they developed PH. RNA-seq analysis revealed the activation of pathways involved in antigen processing and presentation, and with evidence of T cell mediated cytotoxicity in lungs of mice fed 15-HETE. Transcriptomic profiling of lung tissues obtained from patients with pulmonary arterial hypertension (PAH) demonstrated activation of pathways similar to those seen mice. In mice fed a 15-HETE diet, there was an increase in the number of CD8/CD69 double positive cells, as well as an increase in pulmonary arterial endothelial cell (PAEC) apoptosis. Furthermore, PAEC exposed to 15-HETE were more prone to apoptosis when exposed to CD8 cells. Adding Tg6F, an apoA-I mimetic peptide to the 15-HETE diet prevented and rescued PH in C57BL6/J mice, in part, by inhibiting PAEC apoptosis.

Conclusions: 15-HETE diet induced PH in C57Bl6/J mice by triggering PAEC death in a T-cell dependent mechanism. The apoA-I mimetic peptide Tg6F was able to prevent and rescue PH induced by 15-HETE.

Oral 15-Hydroxyeicosatetraenoic Acid Induces Pulmonary Hypertension in Mice by Triggering T Cell-Dependent Endothelial Cell Apoptosis

Pulmonary arterial hypertension (PAH) is a fatal disease characterized by increased mean pulmonary arterial pressure. Elevated plasma and lung concentrations of oxidized lipids, including 15-hydroxyeicosatetraenoic acid (15-HETE), have been demonstrated in patients with PAH and animal models. We previously demonstrated that feeding mice with 15-HETE is sufficient to induce pulmonary hypertension, but the mechanisms remain unknown. RNA sequencing data from the mouse lungs on 15-HETE diet revealed significant activation of pathways involved in both antigen processing and presentation and T cell-mediated cytotoxicity. Analysis of human microarray from patients with PAH also identified activation of identical pathways compared with controls. We show that in both 15-HETE-fed mice and patients with PAH, expression of the immunoproteasome subunit 5 is significantly increased, which was concomitant with an increase in the number of CD8/CD69 (cluster of differentiation 8 / cluster of differentiation 69) double-positive cells, as well as pulmonary arterial endothelial cell apoptosis in mice. Human pulmonary arterial endothelial cells cultured with 15-HETE were more prone to apoptosis when exposed to CD8 cells. Cultured intestinal epithelial cells secreted more oxidized lipids in response to 15-HETE, which is consistent with accumulation of circulating oxidized lipids in 15-HETE-fed mice. Administration of an apoA-I (apolipoprotein A-I) mimetic peptide, Tg6F (transgenic 6F), which is known to prevent accumulation of circulating oxidized lipids, not only inhibited pulmonary arterial endothelial cell apoptosis but also prevented and rescued 15-HETE-induced pulmonary hypertension in mice. In conclusion, our results suggest that (1) 15-HETE diet induces pulmonary hypertension by a mechanism that involves oxidized lipid-mediated T cell-dependent pulmonary arterial endothelial cell apoptosis and (2) Tg6F administration may be a novel therapy for treating PAH.

The Role of Estrogen Receptors in Cardiovascular Disease

Cardiovascular Diseases (CVDs) are the leading cause of death globally. More than 17 million people die worldwide from CVD per year. There is considerable evidence suggesting that estrogen modulates cardiovascular physiology and function in both health and disease, and that it could potentially serve as a cardioprotective agent. The effects of estrogen on cardiovascular function are mediated by nuclear and membrane estrogen receptors (ERs), including estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and G-protein-coupled ER (GPR30 or GPER). Receptor binding in turn confers pleiotropic effects through both genomic and non-genomic signaling to maintain cardiovascular homeostasis. Each ER has been implicated in multiple pre-clinical cardiovascular disease models. This review will discuss current reports on the underlying molecular mechanisms of the ERs in regulating vascular pathology, with a special emphasis on hypertension, pulmonary hypertension, and atherosclerosis, as well as in regulating cardiac pathology, with a particular emphasis on ischemia/reperfusion injury, heart failure with reduced ejection fraction, and heart failure with preserved ejection fraction.

Pregnancy-associated cardiac dysfunction and the regulatory role of microRNAs

Many crucial cardiovascular adaptations occur in the body during pregnancy to ensure successful gestation. Maladaptation of the cardiovascular system during pregnancy can lead to complications that promote cardiac dysfunction and may lead to heart failure (HF). About 12% of pregnancy-related deaths in the USA have been attributed to HF and the detrimental effects of cardiovascular complications on the heart can be long-lasting, pre-disposing the mother to HF later in life. Indeed, cardiovascular complications such as gestational diabetes mellitus, preeclampsia, gestational hypertension, and peripartum cardiomyopathy have been shown to induce cardiac metabolic dysfunction, oxidative stress, fibrosis, apoptosis, and diastolic and systolic dysfunction in the hearts of pregnant women, all of which are hallmarks of HF. The exact etiology and cardiac pathophysiology of pregnancy-related complications is not yet fully deciphered. Furthermore, diagnosis of cardiac dysfunction in pregnancy is often made only after clinical symptoms are already present, thus necessitating the need for novel diagnostic and prognostic biomarkers. Mounting data demonstrates an altered expression of maternal circulating miRNAs during pregnancy affected by cardiovascular complications. Throughout the past decade, miRNAs have become of growing interest as modulators and biomarkers of pathophysiology, diagnosis, and prognosis in cardiac dysfunction. While the association between pregnancy-related cardiovascular complications and cardiac dysfunction or HF is becoming increasingly evident, the roles of miRNA-mediated regulation herein remain poorly understood. Therefore, this review will summarize current reports on pregnancy-related cardiovascular complications that may lead to cardiac dysfunction and HF during and after pregnancy in previously healthy women, with a focus on the pathophysiological role of miRNAs.

Involvement of Low-Density Lipoprotein Receptor in the Pathogenesis of Pulmonary Hypertension

Background

Recently, we and others have reported a causal role for oxidized lipids in the pathogenesis of pulmonary hypertension (PH). However, the role of low‐density lipoprotein receptor (LDL‐R) in PH is not known.

Methods and Results

We examined the role of LDL‐R in the development of PH and determined the efficacy of high‐density lipoprotein mimetic peptide 4F in mitigating PH. Explanted human lungs and plasma from patients with PH and control subjects were analyzed for gene expression, histological characteristics, and lipoprotein oxidation. Male LDL‐R null (LDL‐R knockout) mice (12–15 months old) were fed chow, Western diet (WD), WD with 4F, and WD with scramble peptide for 12 weeks. Serial echocardiography, cardiac catheterization, oxidized LDL assay, real‐time quantitative reverse transcription–polymerase chain reaction, and histological analysis were performed. The effect of LDL‐R knockdown and oxidized LDL on human pulmonary artery smooth muscle cell proliferation was assessed in vitro. LDL‐R and CD36 expression levels were significantly downregulated in the lungs of patients with PH. Patients with PH also had increased lung lipid deposits, oxidized LDL, E06 immunoreactivity, and plasma oxidized LDL/LDL ratio. LDL‐R knockout mice on WD developed PH, right ventricular hypertrophy, right ventricular dysfunction, pulmonary vascular remodeling, fibrosis, and lipid deposition in lungs, aortic atherosclerosis, and left ventricular dysfunction, which were prevented by 4F. Interestingly, PH in WD group preceded left ventricular dysfunction. Oxidized LDL or LDL‐R knockdown significantly increased proliferation of human pulmonary artery smooth muscle cells in vitro.

Conclusions

Human PH is associated with decreased LDL‐R in lungs and increased oxidized LDL in lungs and plasma. WD‐fed LDL‐R knockout mice develop PH and right ventricular dysfunction, implicating a role for LDL‐R and oxidized lipids in PH.

Oxidative Stress and Its Implications in the Right Ventricular Remodeling Secondary to Pulmonary Hypertension

Pulmonary hypertension (PH) is a pulmonary vascular disease characterized by increased pulmonary artery pressures. Long standing pulmonary arterial pressure overload leads to right ventricular (RV) hypertrophy, RV failure, and death. RV failure is a major determinant of survival in PH. Oxidative stress has been associated with the development of RV failure secondary to PH. Here we summarize the structural and functional changes in the RV in response to sustained pulmonary arterial pressure overload. Furthermore, we review the pre-clinical and clinical studies highlighting the association of oxidative stress with pulmonary vasculature and RV remodeling in chronic PH. Targeting oxidative stress promises to be an effective therapeutic strategy for the treatment of RV failure.

Histological hallmarks and role of Slug/PIP axis in pulmonary hypertension secondary to pulmonary fibrosis

Pulmonary hypertension secondary to pulmonary fibrosis (PF-PH) is one of the most common causes of PH, and there is no approved therapy. The molecular signature of PF-PH and underlying mechanism of why pulmonary hypertension (PH) develops in PF patients remains understudied and poorly understood. We observed significantly increased vascular wall thickness in both fibrotic and non-fibrotic areas of PF-PH patient lungs compared to PF patients. The increased vascular wall thickness in PF-PH patients is concomitant with a significantly increased expression of the transcription factor Slug within the macrophages and its target prolactin-induced protein (PIP), an extracellular matrix protein that induces pulmonary arterial smooth muscle cell proliferation. We developed a novel translational rat model of combined PF-PH that is reproducible and shares similar histological features (fibrosis, pulmonary vascular remodeling) and molecular features (Slug and PIP upregulation) with human PF-PH. We found Slug inhibition decreases PH severity in our animal model of PF-PH. Our study highlights the role of Slug/PIP axis in PF-PH.

Radiation mitigation of the intestinal acute radiation injury in mice by 1-[(4-nitrophenyl)sulfonyl]-4-phenylpiperazine

The objective of the study was to identify the mechanism of action for a radiation mitigator of the gastrointestinal (GI) acute radiation syndrome (ARS), identified in an unbiased high‐throughput screen. We used mice irradiated with a lethal dose of radiation and treated with daily injections of the radiation mitigator 1‐[(4‐nitrophenyl)sulfonyl]‐4‐phenylpiperazine to study its effects on key pathways involved in intestinal stem cell (ISC) maintenance. RNASeq, quantitative reverse transcriptase‐polymerase chain reaction, and immunohistochemistry were performed to identify pathways engaged after drug treatment. Target validation was performed with competition assays, reporter cells, and in silico docking. 1‐[(4‐Nitrophenyl)sulfonyl]‐4‐phenylpiperazine activates Hedgehog signaling by binding to the transmembrane domain of Smoothened, thereby expanding the ISC pool, increasing the number of regenerating crypts and preventing the GI‐ARS. We conclude that Smoothened is a target for radiation mitigation in the small intestine that could be explored for use in radiation accidents as well as to mitigate normal tissue toxicity during and after radiotherapy of the abdomen.

Connecting sex differences, estrogen signaling, and microRNAs in cardiac fibrosis

Sex differences are evident in the pathophysiology of heart failure (HF). Progression of HF is promoted by cardiac fibrosis and no fibrosis-specific therapies are currently available. The fibrotic response is mediated by cardiac fibroblasts (CFs), and a central event is their phenotypic transition to pro-fibrotic myofibroblasts. These myofibroblasts may arise from various cellular origins including resident CFs and epicardial and endothelial cells. Both female subjects in clinical studies and female animals in experimental studies generally present less cardiac fibrosis compared with males. This difference is at least partially considered attributable to the ovarian hormone 17β-estradiol (E2). E2 signals via estrogen receptors to regulate genes are involved in the fibrotic response and myofibroblast transition. Besides protein-coding genes, E2 also regulates transcription of microRNA that modulate cardiac fibrosis. Sex dimorphism, E2, and miRNAs form multi-level regulatory networks in the pathophysiology of cardiac fibrosis, and the mechanism of these networks is not yet fully deciphered. Therefore, this review is aimed at summarizing current knowledge on sex differences, E2, and estrogen receptors in cardiac fibrosis, emphasizing on microRNAs and myofibroblast origins. KEY MESSAGES: • E2 and ERs regulate cardiac fibroblast function. • E2 and ERs may distinctly affect male and female cardiac fibrosis pathophysiology. • Sex, E2, and miRNAs form multi-level regulatory networks in cardiac fibrosis. • Sex-dimorphic and E2-regulated miRNAs affect mesenchymal transition.

Abstract 226: Apoai Mimetic Peptide 6f Prevent Pulmonary Hypertension Induced by Oxidized Lipids

Introduction: Pulmonary arterial hypertension (PAH) is characterized by pulmonary arterial occlusion leading to increased pulmonary arterial pressure. Recently, a growing body of evidence demonstrated a robust increase in oxidized lipids, including 15-hydroxyeicosatetraenoic acids (15HETE), in the lungs and plasma of PAH patients and animal models of pulmonary hypertension (PH). Nonetheless, the the causal role of 15HETE in promoting PH development remains elusive. In order to investigate this mechanism, we fed wild type mice with a diet rich in 15HETE and examine whether ApoA-I mimetic peptide can rescue PH induced by 15HETE.

Methods: Wild type male mice (C57BL/6) were fed for 3 weeks with regular chow (n=16-21 mice/group), 15HETE (5μg/day), 15HETE diet supplemented with either empty vector or 6F for the last week of 15HETE diet. PH development was assessed every week via serial echocardiography. Right ventricular systolic pressure (RVSP) was measured via heart catheterization. RV hypertrophy index (RV/[IVS+LV]) was measured. Lung morphology and lipid accumulation were assessed using H&E and Oil red O staining.

Results: Echocardiography revealed the first sign of PH as early as one week after starting 15HETE diet and a significant decrease in the pulmonary arterial acceleration time (PAAT) after 2 weeks of treatment (16.6±1.9 vs. 20.6±1.4 msec, p<0.05). At the end of three weeks, mice on 15HETE diet had significantly higher RVSP (31.3±1.1 vs. 38.4±2.3 mmHg, p<0.05) and RV hypertrophy index (0.26 ± 0.02 vs. 0.33 ±0.02, p<0.05). This increased pressure was concomitant with a significant increase in pulmonary arteriolar thickness in mice on 15-HETE diet compared to regular diet (35.1±0.8 vs 53.4±1, p<0.05). At the end of three weeks mice treated with 6F showed a PAAT similar to control value(19±0.5 msec) concomitant with a significantly lower RVSP than mice fed with 15HETE+empty vector (33.6 ±5.7 vs 40.3±4.6, p<0.05).

Conclusion: Our data demonstrates that APOA-I mimetic peptide 6F is able to rescue pre-exisiting PH induced by 15-HETE diet in wild type mice.

Abstract 494: Role of Slug / PIP Axis in Pulmonary Hypertension Secondary to Pulmonary Fibrosis

Pulmonary hypertension (PH) secondary to pulmonary fibrosis (PF-PH) is the second most common cause of PH. While never studied in detail, pathology reports suggest that vascular remodeling (VR) differs between PF and PF-PH. In PF, VR is mainly limited to fibrotic areas, whereas in PF-PH, it also exist in non-fibrotic areas. These histological differences suggest potential molecular differences. To better understand this mechanism, we investigated the expression of the transcription factor Slug which is known to play a role in PH and PF.

Using explanted rat (n=7/group) and human (n=7-14/group) lungs, we compared lung fibrosis, VR and Slug expression between non-fibrotic and fibrotic areas in PF and PF-PH. Online microarray data (GSE24988) were used to find the targets of Slug that are implicated in VR. A new animal model recapitulating our findings in patients was used to test the therapeutic potential of Slug inhibition (n=10/group). This model is based on intra-tracheal instillation of bleomycin (2.5mg/Kg) at day 0 and 2weeks later, an injection of monocrotaline (60mg/kg). PH was assessed by right ventricular systolic pressure (RVSP). P<0.05 are considered significant.

In both PF and PF-PH patients, fibrotic areas (PF29±4; PF-PH37±3) exhibit significantly increased VR when compared to non-fibrotic areas of the lung (PF 22±1; PF-PH 31±6). PF-PH patients have increased pulmonary vascular thickening in both areas vs PF patients. This is concomitant with an increased number of Ki67+ vascular cells in PF-PH (12±2%) vs PF (8±1%) as well as an upregulation of Slug in PF-PH patients (2.3±0.5) vs PF (1±0.1). Co-immunolabeling with CD68 demonstrate that macrophages are the main cell type responsible for Slug up-regulation in PF-PH. Human microarray data reveal an up-regulation of the Prolactin-induced protein (PIP) in PF-PH vs PF (9±3 vs 1±0.4). PIP is an extracellular transcriptional target of Slug, known to promote cell proliferation. In-vitro, PIP significantly increases pulmonary arterial smooth muscle cell proliferation in a dose dependent manner. Finally, Slug inhibition decreases RVSP (47±3 vs 62±3mmHg) in an animal model of PF-PH.

There are histological differences between PF-PH and PF lungs that are at least in part mediated by a Slug/PIP axis leading to VR.

Abstract 225: Evaluating Pro-Inflammatory and Pro-Resolving Lipid Modulations in an Oral 15-HETE Model of Pulmonary Hypertension

Pulmonary arterial hypertension (PH) is a chronic lung disease with a mortality rate of 50% at 5 years after diagnosis. PH is characterized by progressive increase in pulmonary arterial pressure leading to right ventricular (RV) increase in afterload, hypertrophy, and failure. Despite the availability of multiple animal models of PH, finding relief or cure for PH patients has been elusive to date. Recent studies in our laboratory have shown that levels of hydroxyeicosatetraenoic acids (HETEs) and hydroxyoctadecadienoic acids (HODEs) are elevated in the lungs and plasma of patients with PH as well as in animal models of PH. In testing for causality, we showed that administration of 5 μg of 15-HETE/day to wild type male mice for 3 weeks was sufficient to cause increase in pulmonary pressure, vascular resistance, plasma levels of HETEs and HODEs, right ventricle hypertrophy, and right ventricle systolic pressure (RVSP), consistent with PH. We set out to utilize this new mouse model of PH to understand the mechanisms in PH pathology by first examining the role of lipid mediators of inflammation in the development of PH. Our lab has developed a mass spectrometry method for measuring the levels of 39 inflammatory pathway lipid mediators from the cyclooxygenase (COX) and lipoxygenase (LOX) pathways that has been validated for use in tissue, plasma, and cell supernatant. Utilizing this panel with samples from mice fed 15-HETE and supernatant from an intestinal epithelial cell line; IEC-6 cells treated with 15-HETE, we have observed significant changes in multiple lipid mediators of inflammation. In addition to seeing increases in HETEs and HODEs with 15-HETE treatment, we observed significant increases in leukotriene C4 (LTC4) and 14(S)-hydroxy docosahexaenoic acid (14S-HDHA) and trending increases in thromboxane B2 (TXB2), and leukotriene E4 (LTE4) in the plasma, significant increases in 20 different lipids in lung tissue, including LTC4, TXB2, and LTE4, and significant increases in LTC4 and 5-oxo-eicosatetraenoic acid (5-oxoETE) in the supernatant of IEC-6 cells incubated with 15-HETE for 12 hours. These results indicate that novel inflammatory lipids and pathways may play an important in the development of hypertension and help identify new targets for therapies.

Progression of myocardial ischemia leads to unique changes in immediate-early gene expression in the spinal cord dorsal horn

The pathological consequences of ischemic heart disease involve signaling through the autonomic nervous system. Although early activation may serve to maintain hemodynamic stability, persistent aberrant sympathoexcitation contributes to the development of lethal arrhythmias and heart failure. We hypothesized that as the myocardium reacts and remodels to ischemic injury over time, there is an analogous sequence of gene expression changes in the thoracic spinal cord dorsal horn, the processing center for incoming afferent fibers from the heart to the central nervous system. Acute and chronic myocardial ischemia (MI) was induced in a large animal model of Yorkshire pigs, and the thoracic dorsal horn of treated pigs, along with control nonischemic pigs, was harvested for transcriptome analysis. We identified 32 differentially expressed genes between healthy and acute ischemia cohorts and 46 differentially expressed genes between healthy and chronic ischemia cohorts. The canonical immediate-early gene c-fos was upregulated after acute MI, along with fosB, dual specificity phosphatase 1 and 2 ( dusp1 and dusp2), and early growth response 2 (egr2). After chronic MI, there was a persistent yet unique activation of immediate-early genes, including fosB, nuclear receptor subfamily 4 group A members 1-3 ( nr4a1, nr4a2, and nr4a3), egr3, and TNF-α-induced protein 3 ( tnfaip3). In addition, differentially expressed genes from the chronic MI signature were enriched in pathways linked to apoptosis, immune regulation, and the stress response. These findings support a dynamic progression of gene expression changes in the dorsal horn with maturation of myocardial injury, and they may explain how early adaptive autonomic nervous system responses can maintain hemodynamic stability, whereas prolonged maladaptive signals can predispose patients to arrhythmias and heart failure. NEW & NOTEWORTHY Activation of the autonomic nervous system after myocardial injury can provide early cardiovascular support or prolonged aberrant sympathoexcitation. The later response can lead to lethal arrhythmias and heart failure. This study provides evidence of ongoing changes in the gene expression signature of the spinal cord dorsal horn as myocardial injury progresses over time. These changes could help explain how an adaptive nervous system response can become maladaptive over time.

Estrogen rescues heart failure through estrogen receptor Beta activation

Background

Recently, we showed that exogenous treatment with estrogen (E2) rescues pre-existing advanced heart failure (HF) in mice. Since most of the biological actions of E2 are mediated through the classical estrogen receptors alpha (ERα) and/or beta (ERβ), and both these receptors are present in the heart, we examined the role of ERα and ERβ in the rescue action of E2 against HF.

Methods

Severe HF was induced in male mice by transverse aortic constriction-induced pressure overload. Once the ejection fraction (EF) reached ~ 35%, mice were treated with selective agonists for ERα (PPT, 850 μg/kg/day), ERβ (DPN, 850 μg/kg/day), or E2 (30 μg/kg/day) together with an ERβ-antagonist (PHTPP, 850 μg/kg/day) for 10 days.

Results

EF of HF mice was significantly improved to 45.3 ± 2.1% with diarylpropionitrile (DPN) treatment, but not with PPT (31.1 ± 2.3%). E2 failed to rescue HF in the presence of PHTPP, as there was no significant improvement in the EF at the end of the 10-day treatment (32.5 ± 5.2%). The improvement of heart function in HF mice treated with ERβ agonist DPN was also associated with reduced cardiac fibrosis and increased cardiac angiogenesis, while the ERα agonist PPT had no significant effect on either cardiac fibrosis or angiogenesis. Furthermore, DPN improved hemodynamic parameters in HF mice, whereas PPT had no significant effect.

Conclusions

E2 treatment rescues pre-existing severe HF mainly through ERβ. Rescue of HF by ERβ activation is also associated with stimulation of cardiac angiogenesis, suppression of fibrosis, and restoration of hemodynamic parameters.

The heart of an acrobatic bird

The courtship behavior of some species of birds can be energetically demanding, but it is unknown if cardiovascular specializations enable such behaviors. While performing a highly acrobatic courtship dance, heart rate in male golden-collared manakins increases briefly to 1300 beats per minute, among the highest heart rates recorded in any bird or mammal. We hypothesize that male manakins have enhanced cardiovascular capabilities to meet these demands on the heart. Using histological and molecular techniques, we examined manakin heart structure as well as expression of genes involved in Ca²⁺ handling, action potential duration, steroidal signaling and cardiac growth. These measures were also made on the hearts of zebra finches, a similar-sized bird with limited cardiovascular demands. Compared to the zebra finch, the manakin had a significantly thicker left ventricular (LV) muscle (cross-sectional thickness of the free LV wall and septum) with a smaller LV chamber. In addition, compared to zebra finches, manakin hearts had significantly greater gene expression of ryanodine receptors as well as androgen receptors. Testosterone (T) treatment of non-breeding manakins (with low T) increased gene expression of the Ca²⁺ pump SERCA. These observations suggest that hearts of breeding male manakins require specialized Ca²⁺ handling and androgens may facilitate manakin cardiovascular function.

Abstract 250: Pulmonary Hypertension Induced by 15-HETE is Reverse by Apoai Mimetic Peptide 6f Administration

Pulmonary arterial hypertension (PAH) is characterized by pulmonary arterial occlusion leading to increased pulmonary arterial pressure. Recently, a growing body of evidence demonstrated a robust increase in oxidized lipids, including 15-hydroxyeicosatetraenoic acids (15HETE), in the lungs and plasma of PAH patients and animal models of pulmonary hypertension (PH). Recently, our group demonstrated that 15HETE induce PH. Nonetheless, the precise mechanism by which 15HETE participates in PH development remains elusive. In order to investigate this mechanism, we fed wild type mice with a diet rich in 15HETE and examine whether ApoA-I mimetic peptide can rescue PH induced by 15HETE.

Methods: Wild type male mice (C57BL/6) were fed for 3 weeks for 3 weeks with regular chow (n=16-21 mice/group), 15HETE (5μg/day), 15HETE diet supplemented with either empty vector or 6F for the last week of 15HETE diet. PH development was assessed every week via serial echocardiography. Right ventricular systolic pressure (RVSP) was measured via heart catheterization. RV hypertrophy index (RV/[IVS+LV]) was measured. Lung morphology and lipid accumulation were assessed using H&E and Oil red O staining.

Results: Echocardiography revealed the first sign of PH as early as one week after starting 15HETE diet and a significant decrease in the pulmonary arterial acceleration time (PAAT) after 2 weeks of treatment (16.6±1.9 vs. 20.6±1.4 msec, p<0.05). At the end of three weeks, mice on 15HETE diet had significantly higher RVSP (31.3±1.1 vs. 38.4±2.3 mmHg, p<0.05) and RV hypertrophy index (0.26 ± 0.02 vs. 0.33 ±0.02, p<0.05). This increased pressure was concomitant with a significant increase in pulmonary arteriolar thickness in mice on 15-HETE diet compared to regular diet (35.1±0.8 vs 53.4±1, p<0.05). Furthermore, these WT mice did not develop atherosclerosis as there was no detectable plaque in aorta of the mice on 15HETE diet. At the end of three weeks mice treated with 6F showed a PAAT similar to control value(19±0.5 msec) concomitant with a significantly lower RVSP than mice fed with 15HETE +empty vector (33.6 ±5.7 vs 40.3±4.6, p<0.05).

Conclusion: Our data demonstrates that APOA-I mimetic peptide 6F is able to rescue pre-exisiting PH induced by 15-HETE diet in wild type mice.

An Introduction to Epigenetics in Cardiovascular Development, Disease, and Sexualization

Epigenetic regulation of gene expression is integral to cell differentiation, development, and disease. Modes of epigenetic regulation-including DNA methylation, histone modifications, and ncRNA-based regulation-alter chromatin structure, promotor accessibility, and contribute to posttranscriptional modifications. In the cardiovascular system, epigenetic regulation is necessary for proper cardiovascular development and homeostasis, while epigenetic dysfunction is associated with improper cardiac development and disease.Early sexualization of tissues, including X-inactivation in females and maternal and paternal imprinting, is also orchestrated through epigenetic mechanisms. Furthermore, sex chromosomes encode various sex-specific genes involved in epigenetic regulation, while sex hormones can act as regulatory cofactors that may predispose or protect males and females against developing diseases with a marked sex bias.The following book chapter summarizes the field of epigenetics in the context of cardiovascular development and disease while also highlighting the role of epigenetic regulation as a powerful source of sex differences within the cardiovascular system.

Autonomic nervous system involvement in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a chronic pulmonary vascular disease characterized by increased pulmonary vascular resistance (PVR) leading to right ventricular (RV) failure. Autonomic nervous system involvement in the pathogenesis of PAH has been demonstrated several years ago, however the extent of this involvement is not fully understood. PAH is associated with increased sympathetic nervous system (SNS) activation, decreased heart rate variability, and presence of cardiac arrhythmias. There is also evidence for increased renin-angiotensin-aldosterone system (RAAS) activation in PAH patients associated with clinical worsening. Reduction of neurohormonal activation could be an effective therapeutic strategy for PAH. Although therapies targeting adrenergic receptors or RAAS signaling pathways have been shown to reverse cardiac remodeling and improve outcomes in experimental pulmonary hypertension (PH)-models, the effectiveness and safety of such treatments in clinical settings have been uncertain. Recently, novel direct methods such as cervical ganglion block, pulmonary artery denervation (PADN), and renal denervation have been employed to attenuate SNS activation in PAH. In this review, we intend to summarize the multiple aspects of autonomic nervous system involvement in PAH and overview the different pharmacological and invasive strategies used to target autonomic nervous system for the treatment of PAH.

The protective role of estrogen and estrogen receptors in cardiovascular disease and the controversial use of estrogen therapy

Epidemiologic studies have previously suggested that premenopausal females have reduced incidence of cardiovascular disease (CVD) when compared to age-matched males, and the incidence and severity of CVD increases postmenopause. The lower incidence of cardiovascular disease in women during reproductive age is attributed at least in part to estrogen (E2). E2 binds to the traditional E2 receptors (ERs), estrogen receptor alpha (ERα), and estrogen receptor beta (ERβ), as well as the more recently identified G-protein-coupled ER (GPR30), and can exert both genomic and non-genomic actions. This review summarizes the protective role of E2 and its receptors in the cardiovascular system and discusses its underlying mechanisms with an emphasis on oxidative stress, fibrosis, angiogenesis, and vascular function. This review also presents the sexual dimorphic role of ERs in modulating E2 action in cardiovascular disease. The controversies surrounding the clinical use of exogenous E2 as a therapeutic agent for cardiovascular disease in women due to the possible risks of thrombotic events, cancers, and arrhythmia are also discussed. Endogenous local E2 biosynthesis from the conversion of testosterone to E2 via aromatase enzyme offers a novel therapeutic paradigm. Targeting specific ERs in the cardiovascular system may result in novel and possibly safer therapeutic options for cardiovascular protection.

Abstract 321: Protein Tyrosine Phosphatase 1B: a Novel Regulator of Proliferation and Apoptosis in the Development of Pulmonary Arterial Hypertension

Background: Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling that leads to an increase in pulmonary arterial pressure resulting in right ventricle failure and death. PAH is driven by pulmonary artery smooth muscle cell (PASMC) proliferation and resistance to apoptosis. Protein Tyrosine Phosphatase 1B (PTP1B), a negative regulator for platelet-derived growth factor (PDGF) and BCL-2, has recently been implicated in PAH in humans. While PDGF and BCL-2 are increased in PAH patients, the pathway for regulating BCL-2 and PDGF is poorly understood. We aim to investigate if PTP1B has a role in proliferation and resistance to apoptosis in PAH in human PACMCs and in the Sugen/Hypoxia/Normoxia (Su/Hx/Nx) PH rat model.

Method: Adult male Sprague-Dawley rats were treated with single intraperitoneal dose of SU5416 (20 mg/kg) and kept in Hx for 3 weeks followed by Nx for 2 weeks. Saline treated rats kept in Nx for 5 weeks served as control (n=4/group). RV catheterization was performed terminally for recording RV systolic pressure (RVSP). RV, LV, and interventricular septum (IVS) were isolated for Fulton index (FI, RV/IVS+LV). We analyzed gene expression in lungs via qPCR. Healthy hPASMCs were incubated with a PTP1B inhibitor (Ethyl-3,4-dephostatin) at IC50=0.58ug/ml for 24hrs under Nx conditions and cells were stained with Ki67 to assess proliferation.

Results: Su/Hx/Nx rats had severe PH evidenced by a significantly elevated RVSP compared to control (88.97+/- 13.67 vs 28.47+/- 2.22 mmHg, p<0.05). PH rats also showed severely reduced RV function and increased RV hypertrophy (FI= 0.7+/- 0.063 vs 0.274 +/-0.01, p<0.05). PH lungs exhibited severe pulmonary vascular remodeling with excessive growth of the PASMCs. PTP1B was significantly decreased in PH lungs compared to controls (0.158+/-0.0647 vs 1+/-0.06, P<0.05). BCL-2 expression was significantly increased in PAH compared to control (2.01+/-0.162 vs 1 +/-0.1, P<0.01). Inhibition of PTP1B in cultured hPASMCs increased proliferation by ~2 fold as assessed by Ki67 positive cells (n=3).

Conclusion: Severe angioproliferative PH in rats is associated with a downregulation of PTP1B and increased expression of BCL-2 and PASMC proliferation.