Cardiac Response Research Articles

Endurance Exercise Does Not Exacerbate Cardiac Inflammation in BALB/c Mice Following mRNA COVID-19 Vaccination.

The mechanism underlying myopericarditis associated with mRNA COVID-19 vaccination, including increased susceptibility in young males, remains poorly understood. This study aims to explore the hypothesis that engaging in physical exercise at the time of mRNA COVID-19 vaccination may promote a cardiac inflammatory response, leading to the development of myopericarditis. Male BALB/c mice underwent treadmill running or remained sedentary for five weeks. Subsequently, two doses of the Pfizer/BioNTech vaccine or vehicle were administered with a 14-day interval, while the exercise regimen continued. The animals were euthanized days after the second vaccination. Vaccination was followed by body weight loss, increased hepatic inflammation, and an antigen-specific T cell response. Small foci of fibrovascular inflammation and focal cell loss were observed in the right ventricle, irrespective of vaccination and/or exercise. Vaccination did not elevate cardiac troponin levels. Cardiac tissue from the vaccinated mice showed upregulated mRNA expression of the genes IFNγ and IL-1β, but not IL-6 or TNFα. This pro-inflammatory signature in the heart was not exacerbated by endurance exercise. Ex vivo vascular reactivity remained unaffected by vaccination. Our data provide evidence for the cardiac safety of mRNA COVID-19 vaccination. The role of exercise in the development of pro-inflammatory cardiac changes post mRNA vaccination could not be established.

Cardiac autonomic responses in relation to cognitive workload during simulated military flight

Understanding the operator's cognitive workload is crucial for efficiency and safety in human–machine systems. This study investigated how cognitive workload modulates cardiac autonomic regulation during a standardized military simulator flight. Military student pilots completed simulated flight tasks in a Hawk flight simulator. Continuous electrocardiography was recorded to analyze time and frequency domain heart rate variability (HRV). After the simulation, a flight instructor used a standardized method to evaluate student pilot's individual cognitive workload from video-recorded flight simulator data. Results indicated that HRV was able to differentiate flight phases that induced varying levels of cognitive workload; an increasing level of cognitive workload caused significant decreases in many HRV variables, mainly reflecting parasympathetic deactivation of cardiac autonomic regulation. In conclusion, autonomic physiological responses can be used to examine reactions to increased cognitive workload during simulated military flights. HRV could be beneficial in assessing individual responses to cognitive workload and pilot performance during simulator training.

Blunted cardiac autonomic dynamics to active standing test in postmenopausal women.

Although both aging and menopause influence cardiovascular autonomic control, the effect of menopause per se remains unclear. The current study was undertaken to test the hypothesis that post-menopausal women (PMW) have a blunted cardiovascular autonomic adjustment to active standing compared to pre-menopausal women. Thus, we compared the heart rate variability (HRV) indexes from supine (SUP) to orthostatic (ORT) positions among young women (YW), young men (YM), older men (OM), and PMW. The participants rested for 10 min in SUP and then stood up and remained for 5 min in ORT. ECG was continuously recorded, and R-R time series of about 300 beats were analyzed using linear (spectral analysis) and non-linear (symbolic analysis) methods. The variation from SUP to ORT was calculated (Δ = ORT-SUP) for each HRV index. In SUP, no difference was found for any HRV index among groups. However, Δ0V% and ΔLFn (cardiac sympathetic modulation) were reduced in PWM compared to all groups (OM, YW, and YM), while Δ2UV% and ΔHFn (cardiac vagal modulation) were reduced in PMW than the younger group (YW and YM). No differences were found among the male groups (OM and YM). In light of our results, the cardiac autonomic dynamic response to orthostatic stress is blunted in post-menopausal women compared to younger women and older men, a finding that might be influenced not only by aging.

Left Atrium Reverse Remodeling in Fusion CRT Pacing: Implications in Cardiac Resynchronization Response and Atrial Fibrillation Incidence.

Background: When compared to biventricular pacing, fusion CRT pacing was linked to a decreased incidence of atrial fibrillation (AF). There is a gap in the knowledge regarding exclusive fusion CRT without interference with RV pacing, and all the current data are based on populations of patients with intermittent fusion pacing. Purpose: To assess left atrium remodeling and AF incidence in a real-life population of permanent fusion CRT-P. Methods: Retrospective data were analyzed from a cohort of patients with exclusive fusion CRT-P. Device interrogation, exercise testing, transthoracic echocardiography (TE), and customized medication optimization were all part of the six-monthly individual follow-up. Results: Study population: 73 patients (38 males) with non-ischemic dilated cardiomyopathy aged 63.7 ± 9.3 y.o. Baseline characteristic: QRS 159.8 ± 18.2 ms; EF 27.9 ± 5.1%; mitral regurgitation was severe in 38% of patients, moderate in 47% of patients, and mild in 15% of patients; 43% had type III diastolic dysfunction (DD), 49% had type II DD, 8% had type I DD. Average follow-up was 6.4 years ± 27 months: 93% of patients were responders (including 31% super-responders); EF increased to 40.4 ± 8.5%; mitral regurgitation decreased in 69% of patients; diastolic profile improved in 64% of patients. Paroxysmal and persistent AF incidence was 11%, with only 2% of patients developing permanent AF. Regarding LA volume, statistically significant LA reverse remodeling was observed. Conclusions: Exclusive fusion CRT-P was associated with important LA reverse remodeling and a low incidence of AF.

The effect of foot immersion and neck cooling on cardiac autonomic function in older adults exposed to indoor overheating: a randomized crossover trial.

Foot immersion and neck cooling are recommended cooling strategies for protecting heat-vulnerable persons during heat waves. While we recently showed that these strategies do not limit core temperature increases in older adults during prolonged heat exposure, we did observe small reductions in heart rate. Expanding on these findings, we examined the effects of foot immersion with and without neck cooling on cardiac autonomic function. Seventeen adults (9 females; 65-81 years) underwent 3 randomized, 6 h exposures to 38 °C and 35% relative humidity with: no cooling (control), foot immersion (20°C water), or foot immersion with a wet towel (20°C) around the neck. Cardiac autonomic responses were measured at baseline and end-exposure. These included heart rate variability, cardiac and systolic blood pressure responses to standing, indexed via the 30:15 ratio and supine-to-standing systolic pressure change, respectively, and baroreflex sensitivity during repeated sit-to-stand maneuvers. The 30:15 ratio was 0.04 [95% CI: 0.01, 0.07] greater with foot immersion and neck cooling (1.08 (SD: 0.04)) relative to control (1.04 (0.06); P=0.018). Similarly, standing systolic blood pressure was elevated 9 [0, 17] mmHg with foot immersion and neck cooling (P=0.043). That said, neither difference remained statistically significant after adjusting for multiplicity (Padjusted≥0.054). No differences in 30:15 ratio or standing systolic blood pressure were observed with foot immersion alone, while heart rate variability and baroreflex sensitivity were unaffected by either cooling intervention. While foot immersion with neck cooling potentially improved cardiac autonomic responses in older adults exposed to simulated indoor overheating, these effects were small and of questionable clinical importance.

Characterization of cardiac resynchronization therapy response through machine learning and personalized models

Introduction: The characterization and selection of heart failure (HF) patients for cardiac resynchronization therapy (CRT) remain challenging, with around 30% non-responder rate despite following current guidelines. This study aims to propose a novel hybrid approach, integrating machine-learning and personalized models, to identify explainable phenogroups of HF patients and predict their CRT response. Methods:The paper proposes the creation of a complete personalized model population based on preoperative CRT patient strain curves. Based on the parameters and features extracted from these personalized models, phenotypes of patients are identified thanks to a clustering algorithm and a random forest classification is provided. Results:A close match was observed between the 162 experimental and simulated myocardial strain curves, with a mean RMSE of 4.48% (±1.08) for the 162 patients. Five phenogroups of personalized models were identified from the clustering, with response rates ranging from 52% to 94%. The classification results show a mean area under the curves (AUC) of 0.86 ± 0.06 and provided a feature importance analysis with 22 features selected. Results show both regional myocardial contractility (from 22.5% to 33.0%), tissue viability and electrical activation delays importance on CRT response for each HF patient (from 55.8 ms to 88.4 ms). Discussion:The patient-specific model parameters’ analysis provides an explainable interpretation of HF patient phenogroups in relation to physiological mechanisms that seem predictive of the CRT response. These novel combined approaches appear as promising tools to improve understanding of LV mechanical dyssynchrony for HF patient characterization and CRT selection.

Human heart-on-a-chip microphysiological system comprising endothelial cells, fibroblasts, and iPSC-derived cardiomyocytes.

In recent years, research on organ-on-a-chip technology has been flourishing, particularly for drug screening and disease model development. Fibroblasts and vascular endothelial cells engage in crosstalk through paracrine signaling and direct cell-cell contact, which is essential for the normal development and function of the heart. Therefore, to faithfully recapitulate cardiac function, it is imperative to incorporate fibroblasts and vascular endothelial cells into a heart-on-a-chip model. Here, we report the development of a human heart-on-a-chip composed of induced pluripotent stem cell (iPSC)-derived cardiomyocytes, fibroblasts, and vascular endothelial cells. Vascular endothelial cells cultured on microfluidic channels responded to the flow of culture medium mimicking blood flow by orienting themselves parallel to the flow direction, akin to in vivo vascular alignment in response to blood flow. Furthermore, the flow of culture medium promoted integrity among vascular endothelial cells, as evidenced by CD31 staining and lower apparent permeability. The tri-culture condition of iPSC-derived cardiomyocytes, fibroblasts, and vascular endothelial cells resulted in higher expression of the ventricular cardiomyocyte marker IRX4 and increased contractility compared to the bi-culture condition with iPSC-derived cardiomyocytes and fibroblasts alone. Such tri-culture-derived cardiac tissues exhibited cardiac responses similar to in vivo hearts, including an increase in heart rate upon noradrenaline administration. In summary, we have achieved the development of a heart-on-a-chip composed of cardiomyocytes, fibroblasts, and vascular endothelial cells that mimics in vivo cardiac behavior.

The cardiovascular exercise response in children with overweight or obesity measured by cardiovascular magnetic resonance imaging.

Overweight and obesity are among the main causes of cardiovascular diseases. Exercise testing can aid in the early detection of subtle cardiac dysfunction not present in rest. We hypothesized that the cardiovascular response to exercise is impaired among children with overweight or obesity, characterized by the inability of the cardiovascular system to adapt to exercise by increasing cardiac volumes and blood pressure. We performed a cardiovascular stress test to investigate whether the cardiovascular exercise response is altered in children with overweight and obesity, as compared to children with a normal weight. A subgroup of the Generation R population-based prospective cohort study, consisting of 41 children with overweight or obesity and 166 children with a normal weight with a mean age of 16 years, performed an isometric exercise. Continuous heart rate and blood pressure were measured during rest, exercise and recovery. Cardiovascular magnetic resonance (CMR) measurements were performed during rest and exercise. Higher BMI was associated with a higher resting systolic and diastolic blood pressure (difference: 0.24 SDS (95% CI 0.10, 0.37) and 0.20 SDS (95% CI 0.06, 0.33)) and lower systolic and diastolic blood pressure increases from rest to peak exercise (-0.11 SDS (95% CI -0.20, -0.03) and -0.07 SDS (95% CI -0.07, -0.01)). BMI was also associated with a slower decrease in systolic and diastolic blood pressure during recovery (p values < 0.05). Higher childhood BMI was associated with lower BSA corrected left ventricular mass, end-diastolic volume and stroke volume (p values < 0.05). There were no associations of childhood BMI with the cardiac response to exercise measured by heart rate and CMR measurements. Childhood BMI is, across the full range, associated with a blunted blood pressure response to static exercise but there were no differences in cardiac response to exercise. Our findings suggest that adiposity may especially affect the vascular exercise reaction without affecting cardiac response.

Myeloid Cells in Myocardial Ischemic Injury: The Role of the Macrophage Migration Inhibitory Factor.

Ischemic heart disease, manifesting as myocardial infarction (MI), remains the leading cause of death in the western world. Both ischemia and reperfusion (I/R) cause myocardial injury and result in cardiac inflammatory responses. This sterile inflammation in the myocardium consists of multiple phases, involving cell death, tissue remodeling, healing, and scar formation, modulated by various cytokines, including the macrophage migration inhibitory factor (MIF). Meanwhile, different immune cells participate in these phases, with myeloid cells acting as first responders. They migrate to the injured myocardium and regulate the initial phase of inflammation. The MIF modulates the acute inflammatory response by affecting the metabolic profile and activity of myeloid cells. This review summarizes the role of the MIF in regulating myeloid cell subsets in MI and I/R injury and discusses emerging evidence of metabolism-directed cellular inflammatory responses. Based on the multifaceted role of the MIF affecting myeloid cells in MI or I/R, the MIF can be a therapeutic target to achieve metabolic balance under pathology and alleviate inflammation in the heart.

Apelin-13 administration allows for norepinephrine sparing in a rat model of cecal ligation and puncture-induced septic shock

BackgroundInfusion of exogenous catecholamines (i.e., norepinephrine [NE] and dobutamine) is a recommended treatment for septic shock with myocardial dysfunction. However, sustained catecholamine infusion is linked to cardiac toxicity and impaired responsiveness. Several pre-clinical and clinical studies have investigated the use of alternative vasopressors in the treatment of septic shock, with limited benefits and generally no effect on mortality. Apelin-13 (APL-13) is an endogenous positive inotrope and vasoactive peptide and has been demonstrated cardioprotective with vasomodulator and sparing life effects in animal models of septic shock. A primary objective of this study was to evaluate the NE-sparing effect of APL-13 infusion in an experimental sepsis-induced hypotension.MethodsFor this goal, sepsis was induced by cecal ligation and puncture (CLP) in male rats and the arterial blood pressure (BP) monitored continuously via a carotid catheter. Monitoring, fluid resuscitation and experimental treatments were performed on conscious animals. Based on pilot assays, normal saline fluid resuscitation (2.5 mL/Kg/h) was initiated 3 h post-CLP and maintained up to the endpoint. Thus, titrated doses of NE, with or without fixed-doses of APL-13 or the apelin receptor antagonist F13A co-infusion were started when 20% decrease of systolic BP (SBP) from baseline was achieved, to restore SBP values ≥ 115 ± 1.5 mmHg (baseline average ± SEM).ResultsA reduction in mean NE dose was observed with APL-13 but not F13A co-infusion at pre-determined treatment time of 4.5 ± 0.5 h (17.37 ± 1.74 µg/Kg/h [APL-13] vs. 25.64 ± 2.61 µg/Kg/h [Control NE] vs. 28.60 ± 4.79 µg/Kg/min [F13A], P = 0.0491). A 60% decrease in NE infusion rate over time was observed with APL-13 co-infusion, (p = 0.008 vs NE alone), while F13A co-infusion increased the NE infusion rate over time by 218% (p = 0.003 vs NE + APL-13). Associated improvements in cardiac function are likely mediated by (i) enhanced left ventricular end-diastolic volume (0.18 ± 0.02 mL [Control NE] vs. 0.30 ± 0.03 mL [APL-13], P = 0.0051), stroke volume (0.11 ± 0.01 mL [Control NE] vs. 0.21 ± 0.01 mL [APL-13], P < 0.001) and cardiac output (67.57 ± 8.63 mL/min [Control NE] vs. 112.20 ± 8.53 mL/min [APL-13], P = 0.0036), and (ii) a reduced effective arterial elastance (920.6 ± 81.4 mmHg/mL/min [Control NE] vs. 497.633.44 mmHg/mL/min. [APL-13], P = 0.0002). APL-13 administration was also associated with a decrease in lactate levels compared to animals only receiving NE (7.08 ± 0.40 [Control NE] vs. 4.78 ± 0.60 [APL-13], P < 0.01).ConclusionAPL-13 exhibits NE-sparing benefits in the treatment of sepsis-induced shock, potentially reducing deleterious effects of prolonged exogenous catecholamine administration.

Effects of electrical and percussive stunning on neural, ventilatory and cardiac responses of rainbow trout

From an ethical standpoint, it is imperative that rainbow trout (Oncorhynchus mykiss) are humanely slaughtered, which entails that they are rendered unconscious immediately by a stunning method and remain so until death. The efficacy of electrical stunning following dewatering (i.e., in-air electrical stunning at intensities of 50 to 920 mA and durations of 5 to 30 s) and percussive stunning, both advocated as humane stunning and/or killing methods, are evaluated here for this species via the presence or absence of visually evoked responses (VERs). In addition, ventilatory and cardiac responses were evaluated to elucidate the physiological basis for the lethality of both methods. While the present study was unable to determine the capability of in-air electrical stunning to induce immediate unconsciousness, our findings revealed that irreversible stuns were induced by both in-air electrical stunning (i.e., ∼25 to 70% of individuals did not recover VERs across the various combinations of stunning intensities and/or durations) and percussive stunning (i.e., ∼100% of individuals did not recover VERs). The efficacy of in-air electrical stunning for permanently abolishing VERs was marginally, but significantly, impacted by stun intensity (i.e., explained 8% of the variation). Furthermore, due to substantial inter-specific variability and a limited sample size, significant impacts of stun intensity and/or duration on the recovery of VERs in reversibly stunned individuals were not detected in the present study (i.e., VERs recovered between <0.5 to 28.8 min). Further investigation is therefore necessary before in-air electrical stunning can be endorsed as a standalone humane slaughter method for rainbow trout. This includes determining its capacity to induce immediate unconsciousness, as well as to identify additional factors that could be modified or enhanced to improve its efficacy. Furthermore, since death following in-air electrical stunning likely entails a prolonged process involving ventilatory failure, hypoxemia, and subsequent vital organ malfunction, rather than immediate cardiac arrest or central nervous system failure, the sequential use of methods such as percussive stunning is recommended to safeguard the welfare of rainbow trout during slaughter.

Abstract We119: Treatment of Viral Myocarditis by Targeting the TRIM29-PERK Axis-Mediated ER Stress Immune Response

Viral myocarditis, an inflammatory disease of the myocardium, is a significant cause of sudden death in children and young adults. The current coronavirus disease 19 pandemic emphasizes the need to understand the pathogenesis mechanisms and potential treatment strategies for viral myocarditis. Here, we found that TRIM29 was highly induced by cardiotropic viruses and promoted protein kinase RNA-like endoplasmic reticulum kinase (PERK)-mediated endoplasmic reticulum (ER) stress, apoptosis, and reactive oxygen species (ROS) responses that promote viral replication in cardiomyocytes in vitro . TRIM29 deficiency protected mice from viral myocarditis by promoting cardiac antiviral functions and reducing PERK-mediated inflammation and immunosuppressive monocytic myeloid-derived suppressor cells (mMDSC) in vivo . Mechanistically, TRIM29 interacted with PERK to promote SUMOylation of PERK to maintain its stability, thereby promoting PERK-mediated signaling pathways. Finally, we demonstrated that the PERK inhibitor GSK2656157 mitigated viral myocarditis by disrupting the TRIM29-PERK connection, thereby bolstering cardiac function, enhancing cardiac antiviral responses, and curbing inflammation and immunosuppressive mMDSC in vivo . Our findings offer insight into how cardiotropic viruses exploit TRIM29-regulated PERK signaling pathways to instigate viral myocarditis, suggesting that targeting the TRIM29-PERK axis could mitigate disease severity.

Abstract Mo125: Translating ECG responses to drugs across sexes: model development and validation in the clinic

Background: Sex-based differences in cardiac electrophysiology and their potential to impact susceptibility to cardiac arrhythmia and response to treatment are widely recognized. For example, female sex is an independent risk factor for drug-induced Long QT syndrome, Torsade de Pointes, and sudden cardiac death. However, arrhythmia studies have been predominantly performed in males, thus limiting our understanding of sex-specific arrhythmia mechanisms and the development of sex-specific metrics for arrhythmia risk. Computational tools are a powerful approach for integrating sex differences across scales and studying such multi-level phenomena, accelerating challenging and costly human and animal experiments. Aim: To develop a quantitative tool that predicts drug-induced responses in female electrocardiogram (ECG) features based on ECG data collected in males (and vice versa). Methods: Male and female 1D cable models of ventricular cardiomyocytes were constructed by incorporating transmural heterogeneity and sex-specific parameterizations. We constructed populations of male and female models by randomly perturbing baseline parameters, and derived pseudo-ECGs from computed extracellular potentials. We then utilized lasso regression to map ECG features (QRS duration, QT interval, T-peak-end duration, and T-wave amplitude) extracted from the male pseudo-ECG onto the female ECG features (and vice versa) ( Fig 1 ). Results: Our simulated data-driven translator accurately predicted female pseudo-ECG features from male data in an independent simulated test set (R 2 &gt;0.95). This predictive capability was further assessed in an independent dataset simulating the effects of 95 drugs at different concentrations ( Fig 2A ), exhibiting an average translation error &lt;1% for the QT interval ( Fig 2B ). Proof-of-concept application to ECG data sourced from publicly available FDA-approved datasets, in patients of both sexes under various anti-arrhythmic drugs and drug combinations, demonstrates high accuracy ( Fig 3 ) and validates the translator's applicability to the clinic. Conclusions: Our findings underscore the translator's potential in conducting sex-specific cardiac safety and efficacy assessments, enhancing the precision of evaluations in females. We plan to expand our translator capability to predict sex-specific effects of perturbations, including physiological and pathophysiological stressors.

Cardiac regeneration in goldfish (Carassius auratus) associated with increased expression of key extracellular matrix molecules.

Cardiac regeneration is a natural phenomenon that occurs in many species outside of humans. The goldfish (Carassius auratus) is an understudied model of cardiac wound response, despite its ubiquity as pets as well as its relationship to the better-studied zebrafish. In this study, we examined the response of the goldfish heart to a resection injury. We found that by 70 days post-injury, goldfish scarlessly heal cardiac wounds under a certain size, with local cardiomyocyte proliferation driving the restoration of the myocardial layer. We also found the upregulation of extracellular matrix components related to cardiac regeneration in the injury site. This upregulation correlated with the level of cardiomyocyte proliferation occurring in the injury site, indicating an association between the two that warrants further exploration.

Abstract We079: Program Macrophage Phenotypes and Cardiac Remodeling After Myocardial Infarction with Interleukin-10

Introduction: Macrophages (Mφ) and their phenotypic polarization play essential roles in modulating cardiac inflammation and recovery after myocardial infarction (MI). Interleukin-10 (IL-10) is a potent immunomodulatory cytokine that directs Mφ polarization to beneficial reparative phenotypes and is widely investigated in diseases involving extensive inflammation. However, high-dose IL-10 treatment may not lead to the expected therapeutic outcome, raising the question of whether IL-10 has dose-dependent effects on Mφ polarization and cardiac remodeling post-MI. Hypothesis: IL-10 can program Mφ phenotypes under inflammation and has functional impact in cardiac remodeling post-MI in dose-dependent manner. Goals: We use RAW264.7 Mφ and mouse permanent MI models to test our hypothesis. Approach: We applied 25-1000 ng/mL IL-10 in vitro before or after inducing M1 (with interferon-g) and M2 (with interleukin-4) polarization for pro-inflammatory and anti-inflammatory phenotypes, respectively. We intramyocardially administered 25-2000 ng IL-10 in vivo immediately after inducing MI and examined cardiac function, inflammatory responses, fibrosis and revascularization for 6 weeks (n=5/group). Results: IL-10 at 100-250 ng/mL directed Mφ phenotype shift from M1 to M2 most effectively after inducing polarization in vitro (both p &lt;0.01); groups with ≥500 ng/mL IL-10 exhibited high M1/low M2 phenotypes, similar to no IL-10 controls. Cells treated with ≥100 ng/mL IL-10 before polarization exhibited a notable reduction in M1 phenotype after induction (all p &lt;0.05). Echocardiography showed that with single IL-10 administration, only 250 ng IL-10 notaly improved left ventricular (LV) function and reduced LV chamber size compared with the saline control ( p &lt;0.05) whilst ≥1000 ng caused a transient negative impact in LV function at 5 days post-MI ( p &lt;0.05), Phagocyte infiltration at MI was notably diminished in ≥100 ng groups at 6 weeks post-MI (all p &lt;0.05). Only 250 ng IL-10 led to a notable 53% reduction in LV fibrosis ( p =0.05) and nearly 200% increase in CD31+ cell counts at MI ( p =0.013). Conclusion: Our results suggest an optimal range of IL-10 doses for macrophage polarization and cardiac benefits post-MI, with risks of side effects from IL-10 overdose.

Abstract Mo137: Modulation of the Inflammatory and Fibrotic Effects of Angiotensin on Cardiomyocytes through YAP-mediated Transcription.

Introduction: Signaling through the transcriptional co-activator Yes-associated protein (YAP) has been shown to protect the myocardium against ischemic or mechanical stress. Research Question: In light of the critical role of inflammation on adverse cardiac responses we examined the possibility that YAP regulates inflammatory responses to Angiotensin II (AngII)-mediated stress. Approach: Cardiomyocyte specific YAP-KO mice were generated, implanted with AngII minipumps, infused with AngII (1.5 mg/kg/min) or vehicle for periods of 3 hrs to 3 days and hearts collected for analysis. Results: YAP deletion markedly enhanced AngII-induced mRNA expression of pro-inflammatory cytokines and chemokines (e.g. CCL2, CXCL2, IL-6) at 3 or 24 hrs in the cardiomyocyte, but not non-myocyte cell fraction. Expression of mRNA for the hypertrophic genes ANP and MHC-β, in contrast, was decreased in YAP KO mice. After 3 days of AngII infusion there was enhanced mRNA for pro-fibrotic genes (Col1a1, Col3a1 and Periostin) and increased staining for COL1A1 and F4/80, indicative of increased fibrosis and inflammatory cell recruitment in the absence of YAP signaling. Single cell RNA sequencing revealed specific subsets of genes that were upregulated in the cardiomyocyte subcluster from YAP KO mice. These included pro-inflammatory cytokines, cJun family genes, TLR4 and, surprisingly, CaMKIId. Elevated activation of CaMKIIδ in response to AngII in YAP KO hearts was confirmed by increased phosphorylation of phospholamban. Cardiomyocytes expressing siYAP also showed enhanced expression of TLR4 and CaMKIIδ. Conclusion: Upregulated expression of cJun, TLR4 and CaMKII occurs in the absence of YAP and this conspires to create a greatly enhanced inflammatory milieu which fuels adverse responses to external insults. YAP activation serves to suppress these responses and thus temper development of maladaptive inflammation.

Abstract Tu110: CD36-Mediated Transendothelial Fatty Acid Transport Determines Cardiomyocyte Uptake and is Critical to Limiting a Lipotoxic Ceramide Profile and Supporting Cardiac Function during Pathological Stress.

The heart primarily relies on long chain fatty acid oxidation (LCFA) to meet ATP demand. CD36, is a transmembrane glycoprotein transferase for LCFA uptake widely expressed in several cell types including endothelial cells (ECs), cardiomyocytes (CMs), skeletal myocytes, adipocytes, and monocyte/macrophages. Notably, genetic deficiency of CD36 in humans is associated with hypertrophic cardiomyopathy. The role of CD36 in transendothelial LCFA delivery to CMs under physiologic vs pathologic conditions is unknown. We explored consequences of EC-specific CD36 deletion (EC-CD36 KO mice) on the cardiac response to pressure overload. Lack of EC-CD36 increased severity of left ventricular hypertrophy (LVH), and systolic and diastolic dysfunction at 8 weeks of pressure overload via transverse aortic constriction (TAC), with increases in HW:TL ratio, LV mass by echo, reduced EF (p&lt;0.05), and elevated E/E’ in EC-CD36-KO vs. flox/flox littermate controls (f/f) (p&lt;0.5) (Fig 1). Dynamic mode 13 C NMR revealed delayed 13 C LCFA uptake kinetics (time constant, τ) in CMs of isolated, sham and TAC EC-CD36 KO hearts provided 13 C palmitate + 13 C oleate (0.02 mM each) + 10 mM glucose + 1 mM lactate (Fig 2). 13 C LCFA esterification into triglyceride (TG) was also reduced in EC-CD36-KO vs f/f controls, but without evidence for an additional effect of TAC. The contribution of 13 C LCFA to acetyl CoA entry into oxidation via the TCA cycle, was reduced by lack of EC-CD36 in sham and TAC hearts (p&lt;0.0001) (Fig 2). Consistent with diminished LCFA oxidation, phosphocreatine (PCr) to ATP ratio was also compromised in EC-CD36-KO-TAC hearts (p&lt;0.05). Lack of EC-CD36 during TAC increased 13 C LCFA trafficking to lipotoxic C16 ceramide in EC-CD36 KO hearts (Fig 3). CD36 in ECs is critical to LCFA delivery to CMs during pathological stress on the heart. The imbalance in intramyocellular LCFA dynamics due to restricted transendothelial delivery of LCFA to CMs increased lipotoxic ceramide formation. Thus, EC CD36 is critical to the adaptive cardiac response to pathological stress, and the absence of EC CD36-dependent delivery of LCFA to CMs exacerbates reduced energy potential, adverse cardiac remodeling, and dysfunction during afterload stress.

Abstract Tu116: Neurofibromin 2 regulates metabolic gene expression and cardiac responses to pressure overload stress

Background: Neurofibromin 2 (NF2) is a tumor suppressor that can engage multiple signaling pathways to modulate cell proliferation and survival. We previously demonstrated that NF2 mediates cardiomyocyte apoptosis and cardiac injury caused by acute myocardial infarction. Research Aim: The role of NF2 in heart failure remains uncharacterized. This study sought to determine whether NF2 modulates heart failure due to chronic stress. Approach: We generated cardiomyocyte-specific NF2 knockout (cKO) mice, and used transverse aortic constriction (TAC) to generate chronic pressure overload (PO) stress, which elicits cardiac remodeling and failure. Complementary cell-based experiments were performed in neonatal rat ventricular myocytes (NRVMs). We analyzed cardiac function by echocardiographic and hemodynamic analysis. We used RNAseq, ChIP, Seahorse metabolic profiling, and biochemical analyses to investigate underlying mechanisms. Results: We found that NF2 is transiently upregulated in wild-type mouse myocardium in response to early phase of PO, but is downregulated during heart failure. Following TAC, NF2 cKO hearts unexpectedly showed significantly worsened cardiac function, compared to controls. RNAseq analysis indicated downregulation of several metabolic pathways and impaired ERR activity in NF2 cKO hearts. qPCR confirmed significantly reduced ERRβ and ERRγ transcripts and decreased metabolic gene expression. Experiments employing NRMVs confirmed that NF2 promoted expression of ERRβ and ERRγ, and DNA pulldown assays demonstrated NF2 association with ERRβ and ERRγ proximal promoters. Analysis of NRVM bioenergetics demonstrated that NF2 depletion impaired mitochondrial respiration, which was reversed by concomitant expression of ERRγ. Moreover, AAV9-mediated restoration of ERRγ in NF2 cKO mice normalized cardiac function in response to PO. Because NF2 does not directly bind DNA, ongoing studies are leveraging a proteomics-based approach to identify the mediator linking NF2 to ERR isoform expression. Conclusion: Based on these findings, we conclude that transient upregulation of myocardial NF2 expression during PO stress is compensatory and regulates metabolic gene expression according to energy demand.

Abstract Mo008: Sub-strain Dependent Vulnerability to Psychosocial Stress Exacerbates Doxorubicin-induced Cardiotoxicity in Adult Male Mice

Introduction: Psychosocial stress is a significant cardiovascular risk factor and an enormous burden on cancer patients. However, limited knowledge is available on the underlying mechanisms at least in part because of lack of translationally relevant animal models. Previous work from our lab established that adult exposure to social stress can exacerbate the cardiovascular effect of juvenile doxorubicin (DOX) exposure. However, the effect of concomitant DOX and stress exposure in adult mice is unknown. Methods: In this study, a ‘two-hit’ mouse model was established, in which chronic subordination stress (CSS) and DOX treatment were given simultaneously. Twelve-week-old male C57BL/6N (6N) and C57BL/6J (6J) mice were subjected to daily episodes of social defeat by dominant CD1 mice with whom they remained in continuous sensory contact with for 28 days, thus establishing social subordination. One week after the start of CSS, mice were administered DOX (8 mg/kg/week) for 3 weeks. Thereafter, cardiac function was assessed by echocardiography and gene expression of inflammatory and pro-fibrotic markers were determined by real-time PCR. Cardiac fibrosis and inflammation were assessed by histopathologic analysis. Results: Cardiac dysfunction and significant cardiac fibrosis were observed in 6N but not in 6J mice that were exposed to both DOX and CSS, as evidenced by reduced ejection fraction, cardiac output, and increased trichrome staining, respectively. Additionally, gene expression analysis demonstrated significant upregulation of atrial natriuretic peptide and interleukin-6 in 6N mice exposed to both DOX and CSS compared to 6J mice. Finally, DOX caused cardiac atrophy and abrogated CSS-induced cardiac hypertrophy in 6N but not in 6J mice, as evidenced by measuring left ventricular mass and heart weight/tibia length. Conclusion: Exposure to CSS exacerbated the cardiotoxic effects of DOX in a sub-strain dependent manner. These findings highlight psychosocial stress as a risk factor for worse cardiovascular outcome in cancer patients receiving cardiotoxic regimens. The study underscores sub-strain differences in the cardiac responses of 6N and 6J mouse to CSS alone and CSS/DOX treatment that may serve as a discovery platform for the identification of genetic biomarkers of resilience.

Pericardial Fluid Accumulates microRNAs That Regulate Heart Fibrosis after Myocardial Infarction.

Pericardial fluid (PF) has been suggested as a reservoir of molecular targets that can be modulated for efficient repair after myocardial infarction (MI). Here, we set out to address the content of this biofluid after MI, namely in terms of microRNAs (miRs) that are important modulators of the cardiac pathological response. PF was collected during coronary artery bypass grafting (CABG) from two MI cohorts, patients with non-ST-segment elevation MI (NSTEMI) and patients with ST-segment elevation MI (STEMI), and a control group composed of patients with stable angina and without previous history of MI. The PF miR content was analyzed by small RNA sequencing, and its biological effect was assessed on human cardiac fibroblasts. PF accumulates fibrotic and inflammatory molecules in STEMI patients, namely causing the soluble suppression of tumorigenicity 2 (ST-2), which inversely correlates with the left ventricle ejection fraction. Although the PF of the three patient groups induce similar levels of fibroblast-to-myofibroblast activation in vitro, RNA sequencing revealed that PF from STEMI patients is particularly enriched not only in pro-fibrotic miRs but also anti-fibrotic miRs. Among those, miR-22-3p was herein found to inhibit TGF-β-induced human cardiac fibroblast activation in vitro. PF constitutes an attractive source for screening diagnostic/prognostic miRs and for unveiling novel therapeutic targets in cardiac fibrosis.