Mouse Model Of Pressure Overload Research Articles

Sacubitril/valsartan reduces proteasome activation and cardiomyocyte area in an experimental mouse model of hypertrophy

Sacubitril/valsartan (Sac/Val) belongs to the group of angiotensin receptor–neprilysin inhibitors and has been used for the treatment of heart failure (HF) for several years. The mechanisms that mediate the beneficial effects of Sac/Val are not yet fully understood. In this study we investigated whether Sac/Val influences the two proteolytic systems, the ubiquitin-proteasome system (UPS) and the autophagy-lysosomal pathway (ALP), in a mouse model of pressure overload induced by transverse aortic constriction (TAC) and in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) treated with endothelin-1 (ET1) serving as a human cellular model of hypertrophy. TAC mice showed a continuous decline in cardiac function starting from day 14 after surgery. Administration of Sac/Val for 6 weeks counteracted the deterioration of cardiac function and attenuated hypertrophy and fibrosis in TAC mice. The expression of ALP key markers did not differ between the groups. Proteasome activity was higher in TAC mice and normalized by Sac/Val. In hiPSC-CMs, all treatments (Sac, Val or Sac/Val) normalized mean cell area. However, Sac alone or in combination with Val, but not Val alone prevented ET1-induced hypertrophic gene program and proteomic changes. In conclusion, Sac/Val normalized proteasome activity, improved cardiac function and reduced fibrosis and hypertrophy in TAC mice. Molecular analysis in hiPSC-CMs suggests that a major part of the beneficial effects of Sac/Val is derived from the Sac action rather than from Val.

Abstract 15096: miR-132 Inhibition Shows Anti-Hypertrophic Effects in Preclinical Heart Failure Models and in Exploratory Pharmacodynamic Parameters of a First-in-Human Phase 1b Clinical Trial

Introduction: Cardiac expression levels of miR-132 are elevated in patients with heart failure (HF) and have been associated and provoke pathological cardiac hypertrophy. To inhibit these cardiac remodeling processes and restore normal cardiac function, we developed the synthetic antisense oligonucleotide inhibitor CDR132L targeting miR-132. Anti-hypertrophic effects of miR-132 inhibition have been shown previously in cell culture models and a mouse model of pressure overload-induced HF. Methods and Results: MiR-132 inhibition with CDR132L was now tested in a mouse model of pressure overload induced HF induced by transverse aortic constriction (TAC) and in three different porcine HF models to further confirm the translatability of therapeutic effects. The first pig model was an early post-myocardial infarction (MI). Pigs were treated with CDR132L by intravenous (IV) or intracoronary (IC) infusion on day 3 and day 28 and analyzed on day 56 post-MI. As a second model, chronic post-MI HF pigs received monthly IV treatments over 3 or 5 months starting from month 1 post-MI. Third, percutaneous aortic constriction was induced in pigs by reduction stent implantation and CDR132L was administered IC on day 0 and day 28 followed by analysis on day 56. Hypertrophy was determined by cell size measurements in wheat germ agglutinin (WGA) stained cardiac sections and was significantly decreased between 15% and 29% in CDR132L-treated groups with sufficient dose levels compared to placebo-treatment independent from the large animal model and dosing regimen. Furthermore, TAC mice treated with CDR132L showed a significant decrease in left ventricular mass by 14 % compared to placebo. In line with these data, the cardiac remodeling marker lipocalin-2 (NGAL) was reduced in plasma of chronic HF patients assessed in a first-in-human phase 1b clinical to test safety, efficacy, and also exploratory pharmacodynamics of CDR132L (NCT04045405). Conclusions: Our results confirm beneficial effects of CDR132L treatment on pathological cardiac remodeling in HF.

Tumor Progression Reverses Cardiac Hypertrophy and Fibrosis in a Tetracycline-Regulated ATF3 Transgenic Mouse Model.

Cardiovascular diseases (CVD) and cancer are the top deadly diseases in the world. Both CVD and cancer have common risk factors; therefore, with the advances in treatment and life span, both diseases may occur simultaneously in patients. It is becoming evident that CVD and cancer are highly connected, establishing a novel discipline known as cardio-oncology. This includes the cardiomyocyte death following any anti-tumor therapy known as cardiotoxicity as well the intricate interplay between heart failure and cancer. Recent studies, using various mouse models, showed that heart failure promotes tumor growth and metastasis spread. Indeed, patients with heart failure were found to be at higher risk of developing malignant diseases. While the effect of heart failure on cancer is well established, little is known regarding the effect of tumors on heart failure. A recent study from our lab has demonstrated that tumor growth and metastasis ameliorate cardiac remodeling in a pressure-overload mouse model. Nevertheless, this study was inconclusive regarding whether tumor growth solely suppresses cardiac remodeling or is able to reverse existing heart failure outcomes as well. Here, we used a regulable transgenic mouse model for cardiac hypertrophy and fibrosis. Cancer cell implantation suppressed cardiac dysfunction and fibrosis as shown using echocardiography, qRT-PCR and fibrosis staining. In addition, tumor growth resulted in an M1 to M2 macrophage switch, which is correlated with cardiac repair. Macrophage depletion using clodronate liposomes completely abrogated the tumors' beneficial effect. This study highly suggests that harnessing tumor paradigms may lead to the development of novel therapeutic strategies for CVDs and fibrosis.

Abstract P2031: Myofibroblast-specific Smad7 Attenuates Fibrosis Of The Pressure-overloaded Heart By Inhibiting Mmp2-mediated Collagen Denaturation And By Restraining Macrophage Activation.

Expansion and activation of cardiac fibroblasts contributes to adverse remodeling, fibrosis and dysfunction in the pressure-overloaded heart. Although early fibroblast TGF-β/Smad3 activation protects the pressure overloaded heart by preserving the matrix, sustained TGF-β activation may be deleterious, accentuating fibrosis and dysfunction. We hypothesized that induction of the endogenous TGF-β inhibitory Smad, Smad7, may attenuate fibroblast activation and deposition of collagen, limiting myocardial fibrosis and dysfunction in the pressure-overloaded heart. In a mouse model of pressure overload induced through transverse aortic constriction (TAC), Smad7 was upregulated in cardiac fibroblasts and myofibroblasts. Mice with myofibroblast-specific loss of Smad7 had increased mortality, systolic dysfunction, dilative remodeling and accelerated diastolic dysfunction in response to TAC. Moreover, myofibroblast-specific Smad7 loss hearts had higher collagen deposition and denaturation, as well as increased deposition of the fibrogenic protein periostin. Secretomic analysis showed that fibroblast Smad7 loss accentuates secretion of matrix metalloproteinase-2 (MMP2), extracellular matrix proteins and structural collagens. In vitro, the antifibrotic effects of Smad7 on fibroblast-induced collagen denaturation and pad contraction were partly mediated via MMP2 downregulation. Ingenuity pathway analysis predicted the fibrogenic matricellular protein CCN2/CTGF to be activated in Smad7 null fibroblasts. Surprisingly, myofibroblast-specific Smad7 loss increased myocardial macrophage infiltration in the pressure-overloaded heart. In vitro experiments suggested paracrine effects of Smad7 KO fibroblasts on macrophage proliferation and fibrogenic activation that involved the fibroblast-secreted mediators CD5L, SPARC, CTGF and TGFBI. In summary, the anti-fibrotic effects of Smad7 in the pressure-overloaded heart involve not only reduction in collagen deposition, but also suppression of MMP2-mediated matrix denaturation and paracrine effects inducing fibrogenic activation of macrophages.

Divergent effects of myostatin inhibition on cardiac and skeletal muscles in a mouse model of pressure overload.

The transforming growth factor-β (TGF-β) superfamily member, myostatin, is a negative regulator of muscle growth and may contribute to adverse cardiac remodeling. Whether suppressing myostatin could benefit pressure-overloaded heart remains unclear. We investigated the effects of pharmacological inhibition of myostatin on cardiac fibrosis and hypertrophy in a mouse model of pressure overload induced by transverse aortic constriction (TAC). Two weeks after the surgery, TAC and sham mice were randomly divided into groups receiving mRK35, a monoclonal anti-myostatin antibody, or vehicle (PBS) for 8 wk. Significant progressive cardiac hypertrophy was observed in TAC mice, as reflected by the increased wall thickness, ventricular weight, and cross-sectional area of cardiomyocytes. In the groups treated with mRK35, compared with sham mice, cardiac fibrosis was increased in TAC mice, accompanied with elevated mRNA expression of fibrotic genes. However, among the TAC mice, mRK35 did not reduce cardiac hypertrophy or fibrosis. Body weight, lean mass, and wet weights of tibialis anterior and gastrocnemius muscle bundle were increased by mRK35. When compared with the TAC-PBS group, the TAC mice treated with mRK35 demonstrated greater forelimb grip strength and a larger mean size of gastrocnemius fibers. Our data suggest that mRK35 does not attenuate cardiac hypertrophy and fibrosis in a TAC mouse model but has positive effects on muscle mass and muscle strength. Anti-myostatin treatment may have therapeutic value against muscle wasting in cardiac vascular disease.NEW & NOTEWORTHY Recent research has highlighted the importance of inhibiting TGF-β signaling in mitigating cardiac dysfunction and remodeling. As myostatin belongs to the TGF-β family, we evaluated the impact of myostatin inhibition using mRK35 in TAC-operated mice. Our data demonstrate that mRK35 significantly increased body weight, muscle mass, and muscle strength but did not attenuate cardiac hypertrophy or fibrosis. Pharmacological inhibition of myostatin may provide therapeutic benefits for the management of muscle wasting in cardiovascular diseases.

Targeting interleukin-21 inhibits stress overload-induced cardiac remodelling via the TIMP4/MMP9 signalling pathway

BackgroundIncreased inflammatory mediators produced by inflamed cells are often connected with pressure-induced cardiac remodelling and heart failure. Interleukin-21 (IL-21) serves as an immunomodulator involved in multiple pathological processes, while the role of IL-21 in pressure-induced cardiac remodelling remains unclear. Experiment approachCardiac function, CD4+T-cell infiltration, and IL-21 and IL-21 receptor expression levels were investigated in a pressure overload mouse model induced by aortic banding (AB) surgery. Western blotting and qPCR were used to detect the effects of IL-21 on inflammation, apoptosis, and fibrosis in the myocardium after AB surgery. In addition, the signal transduction mechanisms underlying these effects were investigated in vivo and in vitro by qPCR and western blotting. Key resultsIL-21 levels in mice rapidly increased in the acute phase after AB surgery. Compared with those in the control group, the transverse aortas of mice in the AB surgery group contracted. However, it must be noted that neutralizing IL-21 could reduce myocardial injury and remodelling, while the administration of exogenous IL-21 recombinant protein had the opposite effect. Mechanistically, we learned that IL-21 is effective in inducing the activation of tissue inhibitor of metalloproteinase 4 (TIMP4) and matrix metalloproteinase 9 (MMP-9) signalling in vitro and in vivo. We believe that increased activation and secretion of IL-21 and CD4+ T cells may contribute to stress overload-induced cardiac remodelling. ConclusionThese findings reveal a novel mechanism by which IL-21 stimulates myocardial inflammation, apoptosis, and fibrosis to induce stress-overload-induced myocardial remodelling by activating the TIMP4/MMP9 signalling pathway.

Abstract 15417: Dual Ampk Activator/mtor Inhibitor Improves Metabolic Parameters in T2d Mice and Protects Cardiomyocytes Against Ischemic Injury

Background: Type 2 diabetes (T2D) is a major metabolic disorder associated with increased morbidity and mortality, predominantly due to heart failure resulting from superimposed ischemic heart disease. Dual AMPK activation/mTOR inhibition (NovoMedix compound, NMX2) has been shown to attenuate adverse cardiac remodeling and fibrosis in a pressure-overload mouse model of heart failure. Given the importance of AMPK signaling in T2D, we investigated the beneficial effects of chronic treatment with NMX2 in T2D mice. Methods & Results: Adult male db/db T2D mice were treated daily with NMX2 (50 mg/kg, p.o.) or equal volume of vehicle (7% DMSO, as control) for 15 weeks. Increase in body weight was significantly attenuated along with reduction in insulin levels with NMX2 treatment as compared to control ( A-B ). NMX2 treatment improved glucose homeostasis (glucose and insulin tolerance tests) and reduced adiposity (fat mass percentage, measured by body composition analysis) ( C-G ). Respiratory exchange ratio (RER) measured by indirect calorimetry analysis (Phenomaster, TSE) was significantly improved in NMX2-treated mice, which indicates increased glucose utilization as compared to control mice ( H & I ). Cardiomyocytes isolated from control and NMX2-treated db/db mice were subjected to simulated ischemia/reoxygenation (SI/RO, 40 minutes SI and 1 hour RO). NMX2 significantly reduced necrosis (trypan blue staining, J ), apoptosis (TUNEL assay, K ) and activation of the NLRP3 inflammasome (apoptosis speck-like protein, ASC aggregation by immunofluorescence staining, L & M ) in cardiomyocytes compared to control. Conclusion: Chronic treatment with NMX2 improves glucose homeostasis and RER and reduces adiposity and body weight in diabetic mice. NMX2 also protects cardiomyocytes from diabetic mice against ischemic injury by reducing sterile inflammation, which supports the development of this treatment modality for T2D and its related cardiac complications.

Abstract P2030: Defining Transcription Factor Dependent Regulatory Networks In Cardiac Rhythm And Disease

The transcriptional basis of homeostasis and disease is implied by the non-coding nature of genetic variation identified by GWAS. Functional genomic approaches to unveil the gene regulatory networks (GRNs) relevant to disease is therefore a high priority. Most models for transcriptional dysregulation presume that perturbation of a wild-type GRN causes disease risk. For example, the T-box transcription factor, TBX5, is essential for atrial rhythm homeostasis and directly drives a physiologically relevant GRN composed of cardiac channel genes. Alternatively, examination of the upregulated genes after the deletion of Tbx5 implicates the activation of a disease-specific GRN. Using TF-dependent noncoding RNA (ncRNA) profiling, through the differential deep ncRNA sequencing from atria of wild-type and Tbx5 mutant mice, we focused on the ncRNAs that were only active following the deletion of TBX5. Therefore, we identified putative TBX5-dependent enhancers, based on knowledge that ncRNAs can identify transcription at regulatory elements. We hypothesized that these regulatory elements may reveal disease-response enhancers, essential for coping with atrial dysfunction. We sought to identify the cell-specificity of these enhancers and therefore generated cell-type specific ATAC-seq datasets for left atrial tissue, cardiac fibroblasts, and cardiomyocytes, then overlapped each dataset with the ncRNAs. These candidate regulatory elements included a putative enhancer upstream of Sox9, a known modulator of cardiac fibrosis, along with other cardiac stress-response pathways, including mediators of TGF-β signaling. The ncRNA candidate is expressed in isolated cardiac fibroblasts treated with TGF-β, and the enhancer demonstrated luciferase activation in fibroblasts. To examine the hypothesis that the disease-acquired GRN in TBX5 mutant atria may be generalizable to other cardiac insults, we examined the transcriptional changes occurring in the left atria of a Transverse Aortic Constriction (TAC) mouse model. We revealed remarkable correlation between the differentially expressed genes between these disparate disease models. We also performed differential ncRNA profiling from this pressure overload mouse model, and identified the conservation of acquired ncRNAs when compared to the cardiac arrhythmia mouse model. The conservation of the transcriptional analysis and ncRNA candidates supports the paradigm of a common disease-specific GRN that mediates and may participate in the physiologic consequences of disease.

Abstract EC104: Mitochondrial Microdomain Disruption Results In Sinus Node Dysfunction In Heart Failure

Introduction: Sinoatrial node (SAN), the leading pacemaker region, generates electrical impulses that propagate throughout the heart. SAN dysfunction with bradyarrhythmia is well documented in heart failure (HF). However, the underlying mechanisms are not entirely understood. Mitochondria are critical to cellular processes that determine life or death of the cell. Therefore, proper communication with the mitochondria is essential for normal cellular function. We tested the hypothesis that alterations in the mitochondria-sarcoplasmic reticulum (SR) connectomics underlie SAN dysfunction in HF. Methods: We took advantage of a mouse model of pressure-overload induced HF by transverse aortic constriction (TAC) and a SAN-specific CRISPR/Cas9 mediated gene silencing of mitofusin-2 ( Mfn2 ). Results: TAC mice exhibited impaired cardiac function with HF, cardiac fibrosis, and profound SAN dysfunction. Ultrastructural imaging using electron microscope (EM) tomography revealed abnormal mitochondrial structure with increased SR-mitochondria distance. The expression of the SR-mitochondria tether GTPase protein Mfn-2 was significantly down-regulated and showed reduced colocalization with ryanodine receptor (RyR2) in HF SAN cells. Indeed, SAN-specific gene silencing of Mfn-2 led to alterations in the mitochondrial-SR microdomains[MFN1] and SAN dysfunction. Finally, disruption in the mitochondrial-SR microdomains resulted in abnormal mitochondrial Ca 2+ handling, alterations in localized PKA activity, and impaired mitochondrial function in HF SAN cells. Conclusion: The study provides insight on the role of mitochondrial-SR microdomains in SAN automaticity and into possible therapeutic targets for SAN dysfunction in HF patients.

Cardiac Wnt5a and Wnt11 promote fibrosis by the crosstalk of FZD5 and EGFR signaling under pressure overload

Progressive cardiac fibrosis accelerates the development of heart failure. Here, we aimed to explore serum Wnt5a and Wnt11 levels in hypertension patients, the roles of Wnt5a and Wnt11 in cardiac fibrosis and potential mechanisms under pressure overload. The pressure overload mouse model was built by transverse aortic constriction (TAC). Cardiac fibrosis was analyzed by Masson’s staining. Serum Wnt5a or Wnt11 was elevated and associated with diastolic dysfunction in hypertension patients. TAC enhanced the expression and secretion of Wnt5a or Wnt11 from cardiomyocytes (CMs), cardiac fibroblasts (CFs), and cardiac microvascular endothelial cells (CMECs). Knockdown of Wnt5a and Wnt11 greatly improved cardiac fibrosis and function at 4 weeks after TAC. In vitro, shWnt5a or shWnt11 lentivirus transfection inhibited pro-fibrotic effects in CFs under mechanical stretch (MS). Similarly, conditional medium from stretched-CMs transfected with shWnt5a or shWnt11 lentivirus significantly suppressed the pro-fibrotic effects induced by conditional medium from stretched-CMs. These data suggested that CMs- or CFs-derived Wnt5a or Wnt11 showed a pro-fibrotic effect under pressure overload. In vitro, exogenous Wnt5a or Wnt11 activated ERK and p38 (fibrotic-related signaling) pathway, promoted the phosphorylation of EGFR, and increased the expression of Frizzled 5 (FZD5) in CFs. Inhibition or knockdown of EGFR greatly attenuated the increased FZD5, p-p38, and p-ERK levels, and the pro-fibrotic effect induced by Wnt5a or Wnt11 in CFs. Si-FZD5 transfection suppressed the increased p-EGFR level, and the fibrotic-related effects in CFs treated with Wnt5a or Wnt11. In conclusion, pressure overload enhances the secretion of Wnt5a or Wnt11 from CMs and CFs which promotes cardiac fibrosis by activation the crosstalk of FZD5 and EGFR. Thus, Wnt5a or Wnt11 may be a novel therapeutic target for the prevention of cardiac fibrosis under pressure overload.

Abstract P389: Free Fatty Acid Receptor 4 Is Necessary For An Adaptive Response Following Heart Failure Induced By Metabolic Syndrome In Mice

Non-resolving inflammation is central to the pathogenesis of heart failure (HF). Heart failure preserved ejection fraction (HFpEF) is a type of HF that is particularly associated with inflammation provoked by metabolic syndrome (MetS). The G-protein coupled receptor, free fatty acid receptor 4 (Ffar4), is a receptor for medium and long chain fatty acids (FA) that regulates metabolism and attenuates inflammation. Ffar4 is expressed in the human heart, and downregulated in heart failure. Furthermore, polymorphisms in Ffar4 have been associated with eccentric remodeling in a patient cohort. Previously, Ffar4 was shown to protect the heart from pathologic stress by attenuating oxidative stress in a mouse model of pressure overload. Here, we tested the hypothesis that Ffar4 would attenuate the development of heart failure using a mouse model of MetS-induced HFpEF. Metabolic syndrome was induced in mice by feeding a high-fat, high-sucrose diet (42% fat, 30% sucrose) to produce obesity and delivering the nitric oxide synthase inhibitor, L-NAME, in the drinking water to induce hypertension. The combined intervention (referred to as HFpEF diet) resulted in mice developing excessive adiposity, glucose intolerance (in males only), and mild hypertension. After 20 weeks on the HFpEF diet, both male and female WT mice, developed diastolic dysfunction (increased E/A and E/e’) and preserved ejection fraction (EF), consistent with clinical HFpEF. In Ffar4KO male mice HFpEF diet induced a greater degree of diastolic dysfunction compared to WT mice, despite equivalent metabolic parameters. Female Ffar4KO mice fed the HFpEF diet had a greater increase in weight gain and adiposity compared to WT female mice. Surprisingly, diastolic function was equivalent between WT and FFAR4KO female mice, suggesting a sex-based difference in FFAR4 cardioprotection. Our data show that Ffar4 attenuates HFpEF secondary to MetS.

Abstract P467: Cardiac-specific Deletion Of Voltage Dependent Anion Channel 2 Leads To Dilated Cardiomyopathy By Altering Calcium Homeostasis

Voltage dependent anion channel 2 (VDAC2) is a mitochondrial outer membrane porin known to play a significant role in apoptosis and calcium signaling. Abnormalities in cellular calcium homeostasis often leads to electrical and contractile dysfunction and can cause dilated cardiomyopathy and heart failure. Previous literature suggests that improving mitochondrial calcium uptake via VDAC2 rescues arrhythmia phenotypes in genetic models of impaired cellular calcium signaling. However, the direct role of VDAC2 in intracellular calcium signaling and cardiac function is not well understood. To elucidate the role of VDAC2 in calcium homeostasis, we generated a cardiac-specific deletion of Vdac2 in mice. Our results indicate that loss of VDAC2 in the myocardium during development causes severe impairment in excitation-contraction coupling by reducing mitochondrial calcium uptake (n=3, p<0.05) and thereby impairing intracellular calcium signaling. VDAC2 knock-out mice showed a significant reduction in RYR-mediated calcium release (F/F 0 ) and rate of calcium uptake by SERCA2a [tau(msec)] compared to control mice (N=3, WT=54, KO=38, p<0.0001 (F/F 0 ) and p<0.05 (tau)). We also observed adverse cardiac remodeling which progressed to severe dilated cardiomyopathy and death (N=6, p<0.0001). Reintroducing VDAC2 in 6-week-old knock-out mice partially rescued the cardiomyopathy phenotype evident from improvement in ejection fraction and fractional shortening (n=3, p<0.05). Improving mitochondrial calcium uptake via VDAC2 using a VDAC2 agonist efsevin, increased cardiac contractile force in a mouse model of pressure-overload induced heart failure (N=8, n=22, p<0.05). In conclusion, our findings demonstrate that VDAC2 plays a crucial role in cardiac function by influencing mitochondrial and cellular calcium signaling. Through this role in cellular calcium dynamics and excitation-contraction coupling VDAC2 emerges as a plausible therapeutic target for heart failure.

Cardiac-specific deletion of voltage dependent anion channel 2 leads to dilated cardiomyopathy by altering calcium homeostasis

Voltage dependent anion channel 2 (VDAC2) is an outer mitochondrial membrane porin known to play a significant role in apoptosis and calcium signaling. Abnormalities in calcium homeostasis often leads to electrical and contractile dysfunction and can cause dilated cardiomyopathy and heart failure. However, the specific role of VDAC2 in intracellular calcium dynamics and cardiac function is not well understood. To elucidate the role of VDAC2 in calcium homeostasis, we generated a cardiac ventricular myocyte-specific developmental deletion of Vdac2 in mice. Our results indicate that loss of VDAC2 in the myocardium causes severe impairment in excitation-contraction coupling by altering both intracellular and mitochondrial calcium signaling. We also observed adverse cardiac remodeling which progressed to severe cardiomyopathy and death. Reintroduction of VDAC2 in 6-week-old knock-out mice partially rescued the cardiomyopathy phenotype. Activation of VDAC2 by efsevin increased cardiac contractile force in a mouse model of pressure-overload induced heart failure. In conclusion, our findings demonstrate that VDAC2 plays a crucial role in cardiac function by influencing cellular calcium signaling. Through this unique role in cellular calcium dynamics and excitation-contraction coupling VDAC2 emerges as a plausible therapeutic target for heart failure.

Zonisamide alleviates cardiac hypertrophy in rats by increasing Hrd1 expression and inhibiting endoplasmic reticulum stress.

Antiepileptic drug zonisamide has been shown to be curative for Parkinson's disease (PD) through increasing HMG-CoA reductase degradation protein 1 (Hrd1) level and mitigating endoplasmic reticulum (ER) stress. Hrd1 is an ER-transmembrane E3 ubiquitin ligase, which is involved in cardiac dysfunction and cardiac hypertrophy in a mouse model of pressure overload. In this study, we investigated whether zonisamide alleviated cardiac hypertrophy in rats by increasing Hrd1 expression and inhibiting ER stress. The beneficial effects of zonisamide were assessed in two experimental models of cardiac hypertrophy: in rats subjected to abdominal aorta constriction (AAC) and treated with zonisamide (14, 28, 56 mg · kg-1 · d-1, i.g.) for 6 weeks as well as in neonatal rat cardiomyocytes (NRCMs) co-treated with Ang II (10 μM) and zonisamide (0.3 μM). Echocardiography analysis revealed that zonsiamide treatment significantly improved cardiac function in AAC rats. We found that zonsiamide treatment significantly attenuated cardiac hypertrophy and fibrosis, and suppressed apoptosis and ER stress in the hearts of AAC rats and in Ang II-treated NRCMs. Importantly, zonisamide markedly increased the expression of Hrd1 in the hearts of AAC rats and in Ang II-treated NRCMs. Furthermore, we demonstrated that zonisamide accelerated ER-associated protein degradation (ERAD) in Ang II-treated NRCMs; knockdown of Hrd1 abrogated the inhibitory effects of zonisamide on ER stress and cardiac hypertrophy. Taken together, ourresults demonstrate that zonisamide is effective in preserving heart structure and function in the experimental models of pathological cardiac hypertrophy. Zonisamide increases Hrd1 expression, thus preventing cardiac hypertrophy and improving the cardiac function of AAC rats.

A surgical mouse model of neonatal pressure overload by transverse aortic constriction.

Cardiac disease is the main cause of death worldwide. Insufficient regeneration of the adult mammalian heart is a major driver of cardiac morbidity and mortality. Cardiac regeneration occurs in early postnatal mice, thus understanding mechanisms of mammalian cardiac regeneration could facilitate the development of novel therapeutic strategies. Here, we provide a detailed description of a neonatal mouse model of pressure overload by transverse aortic constriction (nTAC) that can be applied at postnatal days 1 and 7. We have previously used this model to demonstrate that mice are able to fully adapt to pressure overload following nTAC on postnatal day 1. In contrast, when nTAC is applied in the non-regenerative phase (at postnatal day 7), it is associated with a maladaptive response similar to that seen when transverse aortic constriction (TAC) is applied to adult mice. Once a user is experienced in nTAC surgery, the procedure can be completed in less than 10 min per mouse. We anticipate that this model will facilitate the discovery of therapeutic targets to treat patients or prevent pressure overload-induced cardiac failure in the future.

YAP Circular RNA, circYap, Attenuates Cardiac Fibrosis via Binding with Tropomyosin-4 and Gamma-Actin Decreasing Actin Polymerization

Cardiac fibrosis is a common pathological feature of cardiac hypertrophy. This study was designed to investigate a novel function of Yes-associated protein (YAP) circular RNA, circYap, in modulating cardiac fibrosis and the underlying mechanisms. By circular RNA sequencing, we found that three out of fifteen reported circYap isoforms were expressed in nine human heart tissues, with the isoform hsa_circ_0002320 being the highest. The levels of this isoform in the hearts of patients with cardiac hypertrophy were found to be significantly decreased. In the pressure overload mouse model, the levels of circYap were reduced in mouse hearts with transverse aortic constriction (TAC). Upon circYap plasmid injection, the cardiac fibrosis was attenuated, and the heart function was improved along with the elevation of cardiac circYap levels in TAC mice. Tropomyosin-4 (TMP4) and gamma-actin (ACTG) were identified to bind with circYap in cardiac cells and mouse heart tissues. Such bindings led to an increased TPM4 interaction with ACTG, resulting in the inhibition of actin polymerization and the following fibrosis. Collectively, our study uncovered a novel molecule that could regulate cardiac remodeling during cardiac fibrosis and implicated a new function of circular RNA. This process may be targeted for future cardio-therapy.

Abstract 17055: Novel Dual mTOR Inhibitor/AMPK Activator Mitigates Doxorubicin Cardiotoxicity and Potentiates Its Chemotherapeutic Efficacy Against Triple Negative Breast Cancer

Background: Doxorubicin (DOX) is a first-line anticancer drug for the treatment of triple negative breast cancer (TNBC). However, its dose-dependent delayed and progressive cardiotoxicity limits its therapeutic application. NovoMedix (NM922) is a novel dual mTOR inhibitor/AMPK activator that was shown to attenuate adverse cardiac remodeling and fibrosis in a pressure-overload mouse model of heart failure. We investigated whether combination therapy with DOX and NM922 exhibits synergistic chemotherapeutic effect while mitigating DOX cardiotoxicity. Methods & Results: Tumors were generated in athymic female BALB/cAnNCr-nu/nu mice by implanting MDA-MB-231 cells into the rear right flank. Mice with tumors (volume≈200mm 3 ) were randomized into 6 groups and treated as follows: 1) Control (n=10); 2) DOX (3 mg/kg; i.p. twice weekly, total 15 mg/kg; n=10); 3) NM922 (25 mg/kg/d; p.o. n=5); 4) DOX+NM922 (25 mg/kg/d; p.o. n=15); 5) NM922 (100 mg/kg/d; p.o. n=5); 6) DOX+NM922 (100 mg/kg/d; p.o. n=15). Tumor size, body weight and cardiac function were assessed throughout the study. DOX alone, and to a significant extent when in combination with NM922 (25 mg/kg) reduced tumor growth compared to control. NM922 (100 mg/kg) with/without DOX significantly reduced tumor growth as compared to DOX alone (Fig A). DOX caused reduction in body weight and survival of tumor-bearing mice. NM922 did not prevent DOX-induced cachexia, but significantly improved survival in DOX-treated mice (Fig B). DOX treatment caused a significant decline in left ventricular ejection fraction compared to control over 3 weeks, which was ameliorated with NM922 (100 mg/kg) co-treatment (Fig C&D). Conclusion: Our results suggest that NM922 may potentiate the chemotherapeutic efficacy of DOX in TNBC, while mitigating its cardiotoxicity. Moreover, these findings advocate the potential efficacy of utilizing lower DOX dosages when combined with NM922, which would have significant clinical implications.

X-ray diffraction and second harmonic imaging reveal new insights into structural alterations caused by pressure-overload in murine hearts

We demonstrate a label-free imaging approach to study cardiac remodeling of fibrotic and hypertrophic hearts, bridging scales from the whole organ down to the molecular level. To this end, we have used mice subjected to transverse aortic constriction and imaged adjacent cardiac tissue sections by microfocus X-ray diffraction and second harmonic generation (SHG) imaging. In this way, the acto-myosin structure was probed in a spatially resolved manner for entire heart sections. From the recorded diffraction data, spatial maps of diffraction intensity, anisotropy and orientation were obtained, and fully automated analysis depicted the acto-myosin filament spacing and direction. X-ray diffraction presented an overview of entire heart sections and revealed that in regions of severe cardiac remodeling the muscle mass is partly replaced by connective tissue and the acto-myosin lattice spacing is increased at these regions. SHG imaging revealed sub-cellular structure of cardiac tissue and complemented the findings from X-ray diffraction by revealing micro-level distortion of myofibrils, immune cell infiltration at regions of cardiac remodeling and the development of fibrosis down to the scale of a single collagen fibril. Overall, our results show that both X-ray diffraction and SHG imaging can be used for label-free and high-resolution visualization of cardiac remodeling and fibrosis progression at different stages in a cardiac pressure-overload mouse model that cannot be achieved by conventional histology.

Overexpression of Ubiquitin-Specific Protease 2 (USP2) in the Heart Suppressed Pressure Overload-Induced Cardiac Remodeling.

Ubiquitin-specific protease 2 (USP2) is an important member of the deubiquitination system. GEO dataset revealed that USP2 was downregulated in the hearts under pressure overload. However, the cardiomyocyte-specific function of USP2 in the setting of pressure overload is unknown. In the current study, a mouse model of pressure overload was induced by transverse aortic constriction (TAC, 2 weeks). Overexpression of USP2 in the heart was conducted by AAV9 infection. Changes in heart histology were detected by Masson's trichrome staining and hematoxylin-eosin staining (H&E). Echocardiography was used to assess cardiac function. The size of cardiomyocytes was examined by wheat germ agglutinin (WGA) staining. Cardiac oxidative stress was detected by dihydroethidine staining. Our results showed that USP2 was downregulated in the cardiomyocytes following 2 weeks of TAC. Overexpression of cardiac USP2 preserved ventricular function following 2 weeks of TAC. Overexpression of cardiac USP2 inhibited TAC-induced cardiac remodeling, by suppressing cardiac hypertrophy, inhibiting inflammatory responses and fibrosis, and attenuating oxidative stress. Our findings reveal a previously unrecognized role of USP2 in regulating pressure overload-induced cardiac remodeling.

Abstract 365: Ponatinib Triggers Cardiac Inflammation by STAT-3 Dependent Immune Checkpoint Blockade

Background: Ponatinib is a potent anticancer tyrosine kinase inhibitor (TKI) with considerable cardiotoxicity. The manifestation of cardiovascular adverse events, including fatal myocardial infarction and congestive heart failure, has hampered its clinical use. Therefore, a better understanding of the mechanism by which ponatinib exerts cardiotoxicity is urgently warranted to efficiently counteract treatment-related adversities. Methods: Wild type C57BL/6, comorbidity mouse model ApoE -/- , and pressure overload (PO) mouse model were used to investigate the cardiotoxic mechanism of ponatinib. Echocardiography was performed to assess cardiac function. Flow cytometry analysis was performed to assess the dynamics of inflammation. Results: We observed that high-fat diet (HFD) fed ApoE -/- mice develop cardiac dysfunction within 2 weeks of ponatinib treatment. An unbiased RNA-Seq analysis revealed significant upregulation of inflammatory genes (CCR1, CCR5, CCL6, CCL8, CCL9, CXCL4) in ponatinib treated hearts. Since ApoE -/- background, and HFD are known confounder of inflammation signal, we validated this observation in naïve C57BL/6 mice. Despite the lack of cardiac dysfunction in ponatinib treated naïve C57BL/6 mice, comprehensive immune profiling depicted upregulation of myocardial inflammation as evident by infiltrated immune cells (CD45 + TNFα + , CD45 + CD11b + F4/80 + Ly6C + CCR2 + , CD45 + Gal1 + ). Interestingly, we also demonstrated the downregulation of immune checkpoints over T cells (TCRαβ + CTLA4 + , TCRαβ + PD1 + ) in ponatinib treated hearts. Next, in the PO mouse model, ponatinib treated mice showed significant cardiac dysfunction with myocardial inflammation as reflected by increased frequencies of inflammatory parameters (TNFα + , IL1β + , IL6 + , MCP1 + , CXCL9 + ). Mechanistically, we demonstrated that ponatinib potentially suppresses PD-L1 expression over cardiomyocytes via inhibition of STAT3, subsequently leading to immune cells mediated myocardial inflammation. Conclusions: These findings uncover a novel mechanism of ponatinib induced cardiac inflammation leading to adverse cardiac function. It also suggests that strategies to attenuate inflammation may be an effective therapy to prevent ponatinib induced cardiac adverse events.