Pressure-overload Heart Failure Research Articles

Rat Model of Right-Sided Cardiac Remodeling and Arrhythmia using Pulmonary Artery Banding.

Clinical conditions, including chronic obstructive pulmonary disease or pulmonary arterial hypertension (PAH), can lead to chronic right ventricle pressure overload and progressive right heart failure (RHF). RHF can be identified by right-sided cardiac hypertrophy and dilation associated with abnormal myocardial function affecting the RV and the right atrium (RA). We recently demonstrated that severe RHF is accompanied by an increased risk of atrial inflammation, atrial fibrosis, and atrial fibrillation (AF), the most common type of cardiac arrhythmia (CA). Recent studies have shown that RV and RA inflammation plays an important role in the arrhythmogenesis of CA, including AF. However, the impact of inflammation in the development of CA and AF in RHF is poorly described. Experimental models of RHF are required to better understand the association between right-sided myocardial inflammation and CA. The rat model of monocrotaline (MCT)-induced pulmonary hypertension (PH) is well-established to provoke RHF. However, MCT triggers severe pneumo-toxicity and pulmonary inflammation. Hence, MCT-induced RHF does not help to distinguish whether the subsequent myocardial inflammation originates from the RHF per se or circulating inflammatory signals secreted by the injured lung. In this article, a mechanical method involving pulmonary artery trunk banding (PAB) was used to provoke right-sided cardiac arrhythmogenesis. The PAB consists of performing a permanent suture of the pulmonary artery trunk for 3 weeks. Such an approach generates increased right-sided pressure overload. At D21 post-PAB, the suture results in hypertrophied, dilated, and inflamed RV and RA. The PAB-induced RHF is also accompanied by vulnerability to ventricular and atrial arrhythmias, including AF.

Abstract Tu083: Oxytocin improves cardiovascular outcomes in a rat model of pressure-overload heart failure

Oxytocin (OT) is a peptide made in the hypothalamus and released into circulation by the pituitary gland. Known for its role in childbirth and lactation, recent research suggests that OT has significant cardiovascular benefits, reducing the risk of cardiovascular diseases such as hypertension and atherosclerosis. We tested if OT has beneficial effects on cardiovascular function in a rat model of pressure overload heart failure (HF). Neonatal Sprague Dawley rats underwent transaortic constriction (TAC). Pressure overload and cardiac dysfunction progressed as animals matured. Echocardiography at 5 weeks of age confirmed reduced ejection fraction. Animals were then randomly assigned to receive daily IP injections of either OT (treatment) or saline (control) for two weeks. Echocardiography was performed again before hearts were excised for optical mapping studies to test for electrophysiological differences between groups. Hearts were electromechanically uncoupled using blebbistatin and transmembrane potential (RH237) and intracellular Ca2+ (Rhod2am) were simultaneously mapped during a dynamic restitution protocol. Preliminary results indicate that rats in the treatment (OT, n=3) group had improved cardiac function compared to controls (saline, n=3), with higher ejection fraction (66.71 ± 9.44 vs. 25.83 ± 17.93, p=0.0125), higher cardiac output (62.4 ± 11.45 vs. 20.35 ± 6.12, p=0.0025), and greater stroke volume (180.2 ± 18.19 vs. 73.96 ± 37.29, p=0.0057). Preliminary optical mapping results indicate that the hearts of OT-treated rats (n=3) have lower steady state action potential duration (APD) compared to controls (n=2). APD60 decreased from 109.5 ± 10.09 to 75.79 ± 21.94 (p=.0725) and APD80 decreased from 133.1 ± 10.22 to 101.1 ± 24.5 (p=.09595), indicating preservation of repolarizing currents corresponding to healthier electrophysiological function. In summary, our preliminary results suggest exogenous IP OT administration could have a potent cardioprotective effect on chronic and severe pressure overload hearts. Future work will investigate potential mechanisms of OT mediated cardio-protection, including sites of action.

Inhalable cardiac targeting peptide modified nanomedicine prevents pressure overload heart failure in male mice

Heart failure causes considerable morbidity and mortality worldwide. Clinically applied drugs for the treatment of heart failure are still severely limited by poor delivery efficiency to the heart and off-target consumption. Inspired by the high heart delivery efficiency of inhaled drugs, we present an inhalable cardiac-targeting peptide (CTP)-modified calcium phosphate (CaP) nanoparticle for the delivery of TP-10, a selective inhibitor of PDE10A. The CTP modification significantly promotes cardiomyocyte and fibroblast targeting during the pathological state of heart failure in male mice. TP-10 is subsequently released from TP-10@CaP-CTP and effectively attenuates cardiac remodelling and improved cardiac function. In view of these results, a low dosage (2.5 mg/kg/2 days) of inhaled medication exerted good therapeutic effects without causing severe lung injury after long-term treatment. In addition, the mechanism underlying the amelioration of heart failure is investigated, and the results reveal that the therapeutic effects of this system on cardiomyocytes and cardiac fibroblasts are mainly mediated through the cAMP/AMPK and cGMP/PKG signalling pathways. By demonstrating the targeting capacity of CTP and verifying the biosafety of inhalable CaP nanoparticles in the lung, this work provides a perspective for exploring myocardium-targeted therapy and presents a promising clinical strategy for the long-term management of heart failure.

Nuclear ATP-citrate lyase regulates chromatin-dependent activation and maintenance of the myofibroblast gene program

Differentiation of cardiac fibroblasts to myofibroblasts is necessary for matrix remodeling and fibrosis in heart failure. We previously reported that mitochondrial calcium signaling drives α-ketoglutarate-dependent histone demethylation, promoting myofibroblast formation. Here we investigate the role of ATP-citrate lyase (ACLY), a key enzyme for acetyl-CoA biosynthesis, in histone acetylation regulating myofibroblast fate and persistence in cardiac fibrosis. We show that inactivation of ACLY prevents myofibroblast differentiation and reverses myofibroblasts towards quiescence. Genetic deletion of Acly in post-activated myofibroblasts prevents fibrosis and preserves cardiac function in pressure-overload heart failure. TGFβ stimulation enhances ACLY nuclear localization and ACLY–SMAD2/3 interaction, and increases H3K27ac at fibrotic gene loci. Pharmacological inhibition of ACLY or forced nuclear expression of a dominant-negative ACLY mutant prevents myofibroblast formation and H3K27ac. Our data indicate that nuclear ACLY activity is necessary for myofibroblast differentiation and persistence by maintaining histone acetylation at TGFβ-induced myofibroblast genes. These findings provide targets to prevent and reverse pathological fibrosis.

Targeting a cardiac abundant and fibroblasts-specific piRNA (CFRPi) to attenuate and reverse cardiac fibrosis in pressure-overloaded heart failure

Cardiac fibrosis under chronic pressure overload is an end-stage adverse remodeling of heart. However, current heart failure treatments barely focus on anti-fibrosis and the effects are limited. We aimed to seek for a cardiac abundant and cardiac fibrosis specific piRNA, exploring its underlying mechanism and therapeutic potential. Whole transcriptome sequencing and the following verification experiments identified a highly upregulated piRNA (piRNA-000691) in transverse aortic constriction (TAC) mice, TAC pig, and heart failure human samples, which was abundant in heart and specifically expressed in cardiac fibroblasts. CFRPi was gradually increased along with the progression of heart failure, which was illustrated to promote cardiac fibrosis by gain- and loss-of-function experiments in vitro and in vivo. Knockdown of CFRPi in mice alleviated cardiac fibrosis, reversed decline of systolic and diastolic functions from TAC 6 weeks to 8 weeks. Mechanistically, CFRPi inhibited APLN, a protective peptide that increased in early response and became exhausted at late stage. Knockdown of APLN in vitro notably aggravated cardiac fibroblasts activation and proliferation. In vitro and in vivo evidence both indicated Pi3k-AKT-mTOR as the downstream effector pathway of CFRPi-APLN interaction. Collectively, we here identified CFPPi as a heart abundant and cardiac fibrosis specific piRNA. Targeting CFRPi resulted in a sustainable increase of APLN and showed promising therapeutical prospect to alleviate fibrosis, rescue late-stage cardiac dysfunction, and prevent heart failure.

Mac-1 deficiency ameliorates pressure overloaded heart failure through inhibiting macrophage polarization and activation

Persistent pressure overload commonly leads to pathological cardiac hypertrophy and remodeling, ultimately leading to heart failure (HF). Cardiac remodeling is associated with the involvement of immune cells and the inflammatory response in pathogenesis. The macrophage-1 antigen (Mac-1) is specifically expressed on leukocytes and regulates their migration and polarization. Nonetheless, the involvement of Mac-1 in cardiac remodeling and HF caused by pressure overload has not been determined. The Mac-1-knockout (KO) and wild-type (WT) mice were subjected to transverse aortic constriction (TAC) for 6 weeks. Echocardiography and pressure–volume loop assessments were used to evaluate cardiac function, and cardiac remodeling and macrophage infiltration and polarization were estimated by histopathology and molecular techniques. The findings of our study demonstrated that Mac-1 expression was markedly increased in hearts subjected to TAC treatment. Moreover, compared with WT mice, Mac-1-KO mice exhibited dramatically ameliorated TAC-induced cardiac dysfunction, hypertrophy, fibrosis, oxidative stress and apoptosis. The potential positive impacts may be linked to the inhibition of macrophage infiltration and M1 polarization via reductions in NF-kB and STAT1 expression and upregulation of STAT6. In conclusion, this research reveals a new function of Mac-1 deficiency in reducing pathological cardiac remodeling and HF caused by pressure overload. Additionally, inhibiting Mac-1 could be a potential treatment option for patients with HF in a clinical setting.

Generation of inducible mitophagy mice.

Mitophagy is programmed selective autophagy of mitochondria and is important for mitochondrial quality control and cellular homeostasis. Mitochondrial dysfunction and impaired mitophagy are closely associated with various diseases, including heart failure and diabetes. To better understand the pathophysiological role of mitophagy, we generated doxycycline-inducible mitophagy mice using a synthetic mitophagy adaptor protein consisting of an outer mitochondrial membrane targeting sequence and an engineered LIR. To evaluate the activation of mitophagy upon doxycycline treatment, we also generated mitophagy reporter mito-QC mice in which mitochondria tandemly express mCherry and GFP, and only GFP signals are lost in acidic lysosomes subjected to mitophagy. With the ROSA26 promoter-driven rtTA, mitophagy was observed at least in heart, liver, and skeletal muscle. We investigated the relationship between mitophagy activation and pressure overload heart failure or high fat diet-induced obesity. Unexpectedly, we were unable to confirm the protective effect of mitophagy in these two pathological models. Further titration of the level of mitophagy induction is required to demonstrate the potency of the protective effects of mitophagy in disease models.

GFPT1 deficiency is a novel cause of a dilated cardiomyopathy and is required for myocardial adaptation to chronic pressure-overload stress-induced heart failure

Abstract Background GFPT1 is the rate-limiting enzyme of a pathway called the hexosamine biosynthesis pathway (HBP) that turns fructose 6-phosphate derived from glucose into another monosaccharide called N-acetylglucosamine (GlcNAc). GlcNAc is an important substrate for modifying diverse cellular proteins on their serine and threonine residues termed O-GlcNAcylation often competing with phosphorylation and altering their activity or stability (Bond & Hanover; 2015). Increased GFPT1 activity is known to stimulate the cellular integrated stress response improving protein quality control and cell survival (Denzel et al 2014). In the heart, GFPT1 expression and O-GlcNAcylation increases in the early stages of chronic cardiac stress but the physiological role of GFPT1 in regulating heart function including its role during chronic stress remains unclear. Identifying molecular pathways that promote adaptive cardiac remodelling is a promising approach to discover novel therapies for heart failure. Methods Cardiomyocyte-specific GFPT1 knockout mice were generated to study the effects of GFPT1 deletion in hearts. Heart function was examined by echocardiography. HBP activity was quantified using Western blotting of O-GlcNAc-modified proteins. Abdominal aortic banding (AAB) was used to induce chronic pressure-overload heart failure. Results Homozygous GFPT1 KO mice spontaneously develop a dilated cardiomyopathy (DCM) with a 30% mortality rate (ejection fraction 32% compared with 62% for floxed controls and end diastolic volume 125 microL versus 60 microL; n=5-6 per group; p <0.05). Hearts showed reduced levels of total protein O-GlcNAcylation suggesting impaired hexosamine biosynthesis pathway activity. Heart function could be rescued by supplementing their diets with oral glucosamine bypassing GFPT1 to provide metabolites required for hexosamine biosynthesis and normalising O-GlcNAcylation (ejection fraction improved to 40% in KO with supplementation versus KO without; n=4-6 per group; p <0.05). Heterozygous KO mice do not develop a DCM but when subject to pressure-overload cardiac stress, develop worse heart failure with a 50% mortality rate over 9 weeks of pressure-overload (ejection fraction 43% in het KO versus 53% in floxed control; n= 3-6 per group; p = 0.0025). Conclusion Deficiency of GFPT1 is a novel cause of a spontaneous dilated cardiomyopathy. GFPT1 is required for physiological growth of the heart that may in part involve the O-GlcNAcylation of proteins. Partial GFPT1 deficiency is associated with adverse cardiac remodelling following pressure-overload stress. Increasing GFPT1 activity may be a key therapeutic target in developing novel heart failure treatments.

Abstract 14585: Early Right Ventricular Snail Expression is a Druggable Target to Improve Right Ventricular Function in Pressure-Overloaded Right Heart Failure

Introduction: Cardiac fibrosis disrupts the myocardial architecture, impairs the exchange of oxygen and nutrients, and puts the heart at risk of failure. Snail (SNAI1) is a transcriptional factor involved in cell plasticity that has been linked to fibroblast-to-myofibroblast transition (FMT) in the hypoxic heart, however, it is unknown whether inhibition of FMT reduces fibrosis and improves right ventricular (RV) function in the pressure overloaded RV. We hypothesized that Snail is necessary for FMT and, as BMP signaling inhibits Snail, that two BMPR2 activators, FK506 and Enzastaurin, reduce cardiac fibrosis and improve cardiac function in a pulmonary artery banding (PAB) mouse model. Methods and Results: We performed PAB surgery on snail-YFP reporter mice and observed transient Snail expression exclusively in the RV 3-7 days after inducing pressure overload (Fig. 1). In PeriostinCre-TdTomato reporter mice we showed that Snail was expressed in proliferating Periostin and vimentin positive fibroblasts representing activated myofibroblasts. In vitro , stimulation of cardiac fibroblasts with TGFbeta resulted in the early expression of Snail at 2 hours, followed by a Snail-dependent Acta2 expression after 24 hours and Col1 after 48 hours, suggesting the critical role of Snail in fibroblast activation. Furthermore, application of stretch and pressure (50kPa) to cardiac fibroblasts, mimicking pressure-overload in vivo , increased Snail expression. FK506 and Enzastaurin inhibited Tgf-b induced Snail expression in vitro as well as in vivo when administered immediately after PAB surgery (Fig. 2). Finally, long-term treatment with Enzastaurin resulted in preserved RV function at week 7 as assessed by cardiac MRI (Fig. 3, N=6). Conclusions: Snail expression is strongly associated with fibroblast activation in the pressure-overloaded RV. Inhibiting Snail with BMPR2 pathway modulators is a promising approach to improve RV function in the pressure-overloaded RV.

Stabilizing cardiac ryanodine receptor with dantrolene treatment prevents left ventricular remodeling in pressure-overloaded heart failure mice

Dantrolene (DAN) directly binds to cardiac ryanodine receptor 2 (RyR2) through Leu601–Cys620 in the N-terminal domain and subsequently inhibits diastolic Ca2+ leakage through RyR2. We previously reported that therapy using RyR2 V3599K mutation, which inhibits diastolic Ca2+ leakage by enhancing calmodulin (CaM) binding ability to RyR2, prevents left ventricular (LV) remodeling in transverse aortic constriction (TAC) heart failure. Here, we examined whether chronic administration of DAN prevents LV remodeling in TAC heart failure via the same mechanism as genetic therapy. A pressure-overloaded hypertrophy mouse model was developed using TAC. Wild-type (WT) mice were divided into three groups: sham-operated mice (Sham group), TAC mice (TAC group), and TAC mice treated with DAN (TAC-DAN group, 20 mg/kg/day, i.p.). They were then followed up for 8 weeks. The survival rate was higher in the TAC-DAN group (83%) than in the TAC group (49%), and serial echocardiography studies and pathological tissue analysis showed that LV remodeling was significantly prevented in the TAC-DAN group compared to the TAC group. An increase in the diastolic Ca2+ spark frequency and a decrease in the binding affinity of CaM to RyR2 were observed at 8 weeks in the TAC group but not in the TAC-DAN group. Stabilization of RyR2 with DAN prevented LV remodeling and improved survival after TAC by enhancing CaM binding to RyR2 and inhibiting RyR2-mediated diastolic Ca2+ leakage.

Abstract 14533: Molecular Imaging of Fibroblast Activity in Pressure Overload Heart Failure

Introduction: Cardiac fibrosis, mediated by the activation of cardiac fibroblasts, is critical in pressure overload-induced heart failure. Fibroblast activation protein (FAP), specifically expressed by activated fibroblasts, can be visualized by radiolabeled FAP inhibitors (FAPI) PET/CT. Hypothesis: To evaluate whether 68Ga-FAPI-04 could characterize the early stages of cardiac fibrosis in pressure overload heart failure. Methods: Sprague-Dawley rats underwent abdominal aortic constriction (AAC) (n = 12) and sham surgery (n = 10). All rats were scanned with 68 Ga-FAPI-04 PET/CT at 2, 4, and 8 weeks after surgery. Cardiac function was measured by echocardiography. The expression of FAP in the myocardium was detected by immunohistochemistry. Results: Compared with the sham group, the AAC group presented with decreased ejection fraction (EF) and fractional shortening (FS) and increased left ventricular internal dimensions in diastole (LVIDd) and systole (LVIDs) at 4 and 8 weeks (all p < 0.01). The AAC group showed higher 68 Ga-FAPI-04 accumulation in the heart than the sham group at 2, 4, and 8 weeks, respectively (all p < 0.001), and FAPI increased significantly from 2 to 8 weeks. Immunohistochemistry confirmed the higher density of the FAP + area in the AAC group. The intensity of the 68 Ga-FAPI-04 PET signal correlated with the density of the FAP + area on histology (p < 0.001). The expression of the 68 Ga-FAPI-04 at 4 weeks correlated with the deterioration of cardiac function at 8 weeks (EF: R = -0.87; FS: R = -0.72; LVIDd: R = 0.77; LVIDs: R= 0.79; all p < 0.001). The AAC group also showed an increased 68 Ga-FAPI-04 signal in the liver, peaking at 4 weeks and then declining. Cardiac and liver PET signals directly correlated at 4 weeks in the AAC group (R = 0.69, p = 0.0010). A combination of the FAPI intensity in the heart and liver at 4 weeks better predicted the deterioration of cardiac function at 8 weeks. Conclusion: The activated fibroblasts in the heart and liver after pressure overload can be monitored by 68 Ga-FAPI-04 PET/CT. This imaging technique reveals an early fibrotic link in cardio-liver interactions and could better predict nonischemic heart failure prognosis.

Pressure overload and volume overload-induced chronic heart failure are associated with characteristic left ventricular myocardial proteomic alterations

Abstract Introduction Hemodynamic overload induces pathological remodeling of the left ventricle (LV) and eventually heart failure (HF). The two types of chronic hemodynamic stress, namely pressure overload (PO) and volume overload (VO) evoke characteristically different functional and structural alterations in the myocardium. Nevertheless, whether PO- and VO-induced HF are also associated with distinct LV proteomic alterations has not been investigated yet. Aim Hence, we thought to perform a proteomic analysis on LV myocardial samples from rat models of PO- and VO-induced HF. Methods PO–induced HF was evoked by transverse aortic constriction (TAC). VO–induced HF was established by creating an aortocaval fistula (ACF). Age-matched sham-operated animals served as controls for TAC (ShamT) and ACF (ShamA), respectively. Pressure-volume (P-V) analysis, echocardiography, histology and quantitative real-time PCR were carried out to provide a detailed characterization of the two HF models. Peptides obtained via the digestion of myocardial proteins with trypsin and LysC were labeled with isobaric tags (TMT16) and measured with LC-MS/MS in a bottom-up explorative proteomic approach. Differential expression and gene ontology enrichment analysis (GO:BP) was carried out on summarized protein reporter ion intensities. Results In both the TAC and ACF groups, presence of typical signs and symptoms of HF (dyspnea at rest, fatigue, ascites) increased lung-to-tibial length ratio and elevated LV natriuretic peptide mRNA expression levels confirmed the development of advanced HF. Furthermore, the TAC model was associated with massive wall thickening, concentric LV hypertrophy (LVH), marked interstitial fibrosis and substantially impaired active relaxation and passive filling (slope of end-diastolic P-V relationship: 0.103±0.015 vs. 0.023±0.003mmHg/μl, TAC vs. ShamT, P<0.001). In contrast, the ACF model was predominantly characterized by LV dilatation, eccentric LVH, moderate fibrosis and severely reduced LV contractility (slope of end-systolic P-V relationship: 0.5±0.1 vs. 2.3±0.3mmHg/μl, ACF vs. ShamA, P<0.001). Proteomic analysis revealed that out of the 4691 identified and quantified proteins, 1404 and 913 have shown upregulation, while 1359 and 886 downregulation in the TAC and ACF groups respectively compared to their corresponding sham groups. GO:BP analysis has indicated that the downregulation of mitochondrion organization, ATP metabolic processes and oxidative phosphorylation and the upregulation of actin cytoskeleton organization were the most profound alterations in the TAC model. In contrast, the ACF model was associated with robust downregulation of fatty acid oxidation and upregulation of endocytosis, defense and immune response on the proteomic level. Conclusions PO and VO-induced advanced HF are not only associated with characteristically different functional and structural remodeling but also with distinct LV proteomic alterations. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Research, Development and Innovation Office (NKFIH) of Hungary

Molecular imaging of fibroblast activity in pressure overload heart failure using [68Ga]Ga-FAPI-04 PET/CT.

We aimed to evaluate whether [68Ga]Ga-FAPI-04 PET/CT could characterize the early stages of cardiac fibrosis in pressure overload heart failure. Sprague-Dawley rats underwent abdominal aortic constriction (AAC) (n = 12) and sham surgery (n = 10). All rats were scanned with [68Ga]Ga-FAPI-04 PET/CT at 2, 4, and 8weeks after surgery. The expression of fibroblast activation protein (FAP) in the myocardium was detected by immunohistochemistry. [68Ga]Ga-FAPI-04 PET signal and FAP expression were compared between two groups. Compared with the sham group, the AAC group presented with decreased ejection fraction (EF) and fractional shortening (FS) and increased left ventricular internal dimensions in diastole (LVIDd) and systole (LVIDs) at 4 and 8weeks (all p < 0.01). The AAC group showed higher [68Ga]Ga-FAPI-04 accumulation in the heart than the sham group at 2, 4, and 8weeks, and FAPI increased significantly from 2 to 8weeks (all p < 0.001). Immunohistochemistry confirmed the higher density of the FAP+ area in the AAC group. The intensity of the [68Ga]Ga-FAPI-04 correlated with the density of the FAP+ area (p < 0.001). The expression of the [68Ga]Ga-FAPI-04 at 4weeks correlated with the deterioration of cardiac function at 8weeks (EF: R = - 0.87; FS: R = - 0.72; LVIDd: R = 0.77; LVIDs: R = 0.79; all p < 0.001). The AAC group also showed an increased [68Ga]Ga-FAPI-04 signal in the liver, peaking at 4weeks and then declining. Cardiac and liver PET signals correlated at 4weeks in the AAC group (R = 0.69, p = 0.0010), suggesting an early fibrotic link between organs. A combination of the [68Ga]Ga-FAPI-04 intensity in the heart and liver at 4weeks better predicted the deterioration of cardiac function at 8weeks. The activated fibroblasts in the heart and liver after pressure overload can be monitored by [68Ga]Ga-FAPI-04 PET/CT, which reveals an early fibrotic link in cardio-liver interactions and could better predict nonischemic heart failure prognosis.

Abstract P2050: Acetyl-coa Synthesis Is Required For Chromatin Remodeling In Myofibroblast Differentiation And Persistence

Heart failure (HF) features fibrotic remodeling by myofibroblasts, a differentiated fibroblast population responsible for wound repair. Discovering mechanisms of myofibroblast formation and function may yield novel targets to delay or reverse HF. Myofibroblasts metabolically reprogram to mediate transcriptional activation of fibrotic genes through chromatin remodeling. We previously reported that α-ketoglutarate production for histone demethylation is essential for cardiac fibrosis, but metabolic regulation of histone acetylation in fibrosis is unclear. ATP-citrate lyase (ACLY) and Acetyl-coenzyme A synthetase 2 (ACSS2) synthesize acetyl-CoA in the cytoplasm and have also been reported to supply substrate for histone acetyltransferases in the nucleus to modify regulatory histone residues. To investigate acetyl-CoA metabolism in myofibroblast formation, we stimulated adult mouse and human cardiac fibroblasts (CFs) with the pro-fibrotic agonist transforming growth factor β (TGFβ) and treated cells with pharmacological inhibitors of ACLY and ACSS2. Either ACLY or ACSS2 inhibition sufficiently reverted differentiated myofibroblasts to a non-fibrotic phenotype, even during continuous TGFβ stimulation. Genetic deletion of ACLY in fibroblasts recapitulated these results. Further, ACLY inactivation was sufficient to decrease global histone acetylation. ACLY deletion, specifically in activated myofibroblasts in the adult mouse heart, slowed LV functional decline and remodeling in a model of pressure overload HF. Our data indicate that ACLY and ACSS2 are necessary for myofibroblast differentiation and persistence. We hypothesize that acetyl-CoA synthesis is necessary for histone acetylation required for activation of myofibroblast genes. Ongoing work will determine the molecular mechanisms of both enzymes in chromatin remodeling and in cardiac injury. In summary, acetyl-CoA producing enzymes are attractive clinical targets to reverse cardiac fibrosis.

Mitochondrial H2S Regulates BCAA Catabolism in Heart Failure.

Hydrogen sulfide (H2S) exerts mitochondria-specific actions that include the preservation of oxidative phosphorylation, biogenesis, and ATP synthesis, while inhibiting cell death. 3-MST (3-mercaptopyruvate sulfurtransferase) is a mitochondrial H2S-producing enzyme whose functions in the cardiovascular disease are not fully understood. In the current study, we investigated the effects of global 3-MST deficiency in the setting of pressure overload-induced heart failure. Human myocardial samples obtained from patients with heart failure undergoing cardiac surgeries were probed for 3-MST protein expression. 3-MST knockout mice and C57BL/6J wild-type mice were subjected to transverse aortic constriction to induce pressure overload heart failure with reduced ejection fraction. Cardiac structure and function, vascular reactivity, exercise performance, mitochondrial respiration, and ATP synthesis efficiency were assessed. In addition, untargeted metabolomics were utilized to identify key pathways altered by 3-MST deficiency. Myocardial 3-MST was significantly reduced in patients with heart failure compared with nonfailing controls. 3-MST KO mice exhibited increased accumulation of branched-chain amino acids in the myocardium, which was associated with reduced mitochondrial respiration and ATP synthesis, exacerbated cardiac and vascular dysfunction, and worsened exercise performance following transverse aortic constriction. Restoring myocardial branched-chain amino acid catabolism with 3,6-dichlorobenzo1[b]thiophene-2-carboxylic acid (BT2) and administration of a potent H2S donor JK-1 ameliorates the detrimental effects of 3-MST deficiency in heart failure with reduced ejection fraction. Our data suggest that 3-MST derived mitochondrial H2S may play a regulatory role in branched-chain amino acid catabolism and mediate critical cardiovascular protection in heart failure.

SS31 Alleviates Pressure Overload-Induced Heart Failure Caused by Sirt3-Mediated Mitochondrial Fusion

Heart failure caused by pressure overload is one of the leading causes of heart failure worldwide, but its pathological origin remains poorly understood. It remains critical to discover and find new improvements and treatments for pressure overload-induced heart failure. According to previous studies, mitochondrial dysfunction and myocardial interstitial fibrosis are important mechanisms for the development of heart failure. The oligopeptide Szeto-Schiller Compound 31 (SS31) can specifically interact with the inner mitochondrial membrane and affect the integrity of the inner mitochondrial membrane. Whether SS31 alleviates pressure overload-induced heart failure through the regulation of mitochondrial fusion has not yet been confirmed. We established a pressure-overloaded heart failure mouse model through TAC surgery and found that SS31 can significantly improve cardiac function, reduce myocardial interstitial fibrosis, and increase the expression of optic atrophy-associated protein 1 (OPA1), a key protein in mitochondrial fusion. Interestingly, the role of SS31 in improving heart failure and reducing fibrosis is inseparable from the presence of sirtuin3 (Sirt3). We found that in Sirt3KO mice and fibroblasts, the effects of SS31 on improving heart failure and improving fibroblast transdifferentiation were disappeared. Likewise, Sirt3 has direct interactions with proteins critical for mitochondrial fission and fusion. We found that SS31 failed to increase OPA1 expression in both Sirt3KO mice and fibroblasts. Thus, SS31 can alleviate pressure overload-induced heart failure through Sirt3-mediated mitochondrial fusion. This study provides new directions and drug options for the clinical treatment of heart failure caused by pressure overload.

Exercise training improves cardiac function and regulates myocardial mitophagy differently in ischaemic and pressure‐overload heart failure mice

What is the central question of this study? What are the cardioprotective effects of different aerobic exercises on chronic heart failure with different aetiologies, and is mitophagy involved? What is the main finding and its importance? Moderate-intensity continuous training may be the 'optimum' modality for improving cardiac structure and function in ischaemic heart failure, while both moderate-intensity continuous training and high-intensity interval training were suitable for pressure-overload heart failure. Various mitophagy pathways, especially parkin-dependent pathways, participated in the protective effects of exercise on heart failure. The cardioprotective effects of different aerobic exercises on chronic heart failure with different aetiologies and whether mitophagy is involved remain elusive. In the current research, left anterior descending ligation and transverse aortic constriction surgeries were used to establish mouse models of heart failure, followed by 8weeks of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT). The results showed that for ischaemic heart failure MICT significantly improved ejection fraction (P<0.05) and fractional shortening (P<0.05), mitigated left ventricular end-systolic dimension (P<0.01), decreased brain natriuretic peptide (P<0.0001) and mitigated fibrosis (P<0.0001), while HIIT only decreased brain natriuretic peptide (P<0.0001) and fibrosis (P<0.0001). For pressure-overload heart failure, both MICT and HIIT significantly increased ejection fraction (P<0.0001) and fractional shortening (MICT: P<0.001, HIIT: P<0.0001), and reduced left ventricular end-diastolic and end-systolic dimensions, brain natriuretic peptide (P<0.0001), and fibrosis (MICT: P<0.01, HIIT: P<0.0001); HIIT was even better in reducing brain natriuretic peptide. Myocardial autophagy and mitophagy were compromised in heart failure, and the exercises improved myocardial autophagic flux and mitophagy inconsistently in heart failure with different aetiologies. Significant correlations were found between multiple mitophagy pathways and the cardioprotection of the exercises. Collectively, MICT may be the 'optimum' modality for ischaemic heart failure, while both MICT and HIIT (especially HIIT) were suitable for pressure-overload heart failure. Exercises differently improved myocardial autophagy/mitophagy, and multiple mitophagy-related pathways were closely implicated in cardioprotection of exercises for chronic heart failure.

Alpha-Calcitonin Gene Related Peptide: New Therapeutic Strategies for the Treatment and Prevention of Cardiovascular Disease and Migraine.

Alpha-calcitonin gene-related peptide (α-CGRP) is a vasodilator neuropeptide of the calcitonin gene family. Pharmacological and gene knock-out studies have established a significant role of α-CGRP in normal and pathophysiological states, particularly in cardiovascular disease and migraines. α-CGRP knock-out mice with transverse aortic constriction (TAC)-induced pressure-overload heart failure have higher mortality rates and exhibit higher levels of cardiac fibrosis, inflammation, oxidative stress, and cell death compared to the wild-type TAC-mice. However, administration of α-CGRP, either in its native- or modified-form, improves cardiac function at the pathophysiological level, and significantly protects the heart from the adverse effects of heart failure and hypertension. Similar cardioprotective effects of the peptide were demonstrated in pressure-overload heart failure mice when α-CGRP was delivered using an alginate microcapsules-based drug delivery system. In contrast to cardiovascular disease, an elevated level of α-CGRP causes migraine-related headaches, thus the use of α-CGRP antagonists that block the interaction of the peptide to its receptor are beneficial in reducing chronic and episodic migraine headaches. Currently, several α-CGRP antagonists are being used as migraine treatments or in clinical trials for migraine pain management. Overall, agonists and antagonists of α-CGRP are clinically relevant to treat and prevent cardiovascular disease and migraine pain, respectively. This review focuses on the pharmacological and therapeutic significance of α-CGRP-agonists and -antagonists in various diseases, particularly in cardiac diseases and migraine pain.

An assessment of thermoneutral housing conditions on murine cardiometabolic function.

Mouse models are used to model human diseases and perform pharmacological efficacy testing to advance therapies to humans; most of these studies are conducted in room temperature conditions. At room temperature (22°C), mice are cold-stressed and must use brown adipose tissue (BAT) to maintain body temperature. This cold stress increases catecholamine tone to maintain adipocyte lipid release via lipolysis, which will fuel adaptive thermogenesis. Maintaining rodents at thermoneutral temperatures (28°C) ameliorates the need for adaptive thermogenesis, thus reducing catecholamine tone and BAT activity. Cardiovascular tone is also determined by catecholamine levels in rodents, as β-adrenergic stimuli are primary drivers of not only lipolytic but also ionotropic and chronotropic responses. As mice have increased catecholamine tone at room temperature, we investigated how thermoneutral housing conditions would impact cardiometabolic function. Here, we show a rapid and reversible effect of thermoneutrality on both heart rate and blood pressure in chow-fed animals, which was blunted in animals fed a high-fat diet. Animals subjected to transverse aortic constriction displayed compensated hypertrophy at room temperature, whereas animals displayed less hypertrophy and a trend toward worse systolic function at thermoneutrality. Despite these dramatic changes in blood pressure and heart rate at thermoneutral housing conditions, enalapril effectively improved cardiac hypertrophy and gene expression alterations. There were surprisingly few differences in cardiac parameters in high-fat-fed animals at thermoneutrality. Overall, these data suggest that thermoneutral housing may alter some aspects of cardiac remodeling in preclinical mouse models of heart failure.NEW & NOTEWORTHY Thermoneutral housing conditions cause rapid and reversible changes in mouse heart rate and blood pressure. Despite dramatic reductions in heart rate and blood pressure, thermoneutrality reduced the compensatory hypertrophic response in a pressure overload heart failure model compared with room temperature housing, and ACE inhibitors were still efficacious to prevent pressure overload-induced cardiac remodeling. The effects of thermoneutrality on heart rate and blood pressure are abrogated in the context of diet-induced obesity.

Decrease of Pdzrn3 is required for heart maturation and protects against heart failure

Heart failure is the final common stage of most cardiopathies. Cardiomyocytes (CM) connect with others via their extremities by intercalated disk protein complexes. This planar and directional organization of myocytes is crucial for mechanical coupling and anisotropic conduction of the electric signal in the heart. One of the hallmarks of heart failure is alterations in the contact sites between CM. Yet no factor on its own is known to coordinate CM polarized organization. We have previously shown that PDZRN3, an ubiquitine ligase E3 expressed in various tissues including the heart, mediates a branch of the Planar cell polarity (PCP) signaling involved in tissue patterning, instructing cell polarity and cell polar organization within a tissue. PDZRN3 is expressed in the embryonic mouse heart then its expression dropped significantly postnatally corresponding with heart maturation and CM polarized elongation. A moderate CM overexpression of Pdzrn3 (Pdzrn3 OE) during the first week of life, induced a severe eccentric hypertrophic phenotype with heart failure. In models of pressure-overload stress heart failure, CM-specific Pdzrn3 knockout showed complete protection against degradation of heart function. We reported that Pdzrn3 signaling induced PKC ζ expression, c-Jun nuclear translocation and a reduced nuclear ß catenin level, consistent markers of the planar non-canonical Wnt signaling in CM. We then show that subcellular localization (intercalated disk) of junction proteins as Cx43, ZO1 and Desmoglein 2 was altered in Pdzrn3 OE mice, which provides a molecular explanation for impaired CM polarization in these mice. Our results reveal a novel signaling pathway that controls a genetic program essential for heart maturation and maintenance of overall geometry, as well as the contractile function of CM, and implicates PDZRN3 as a potential therapeutic target for the prevention of human heart failure.