Transverse Aortic Constriction Research Articles

Myoferlin alleviates pressure overload-induced cardiac hypertrophy and dysfunction by inhibiting NLRP3-mediated pyroptosis

Myoferlin (MYOF) is a muscle-derived secretory protein. Recent studies have found that MYOF protects against cell damage. However, the role of MYOF in cardiac hypertrophy remains unclear. Increasing evidence suggests that NLRP3 (NOD-like receptor protein 3) and the pyroptosis cascade play critical roles in the development of cardiac hypertrophy and inflammation. To investigate the role of MYOF in cardiac hypertrophy, we conducted a transverse aortic constriction (TAC) experiment in a mouse model. We found that MYOF can improve cardiac hypertrophy and cardiac function. Furthermore, our study confirmed a connection between cardiac hypertrophy and myocardial pyroptosis. Cardiac hypertrophy significantly increased the proportion of apoptotic cells and upregulated apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, and gasdermin D (GSDMD). This suggests that pharmacological or genetic inhibition of NLRP3 can effectively reduce cardiac hypertrophy. An abnormal increase in NLRP3 can reverse the cardioprotective effects of MYOF. Our findings indicate that MYOF is a potential therapeutic agent for cardiac hypertrophy.

Abstract 4134449: Increasing Histidyl dipeptides in Skeletal Muscle Preserves Muscle Mass and Function During Heart Failure.

Background: In heart failure patients muscle wasting is a serious comorbidity. Oxidative stress and inflammatory cytokines, which cause muscle wasting, are increased in the skeletal muscle of heart failure patients. Oxidative stress leads to oxidation of lipids, generating toxic lipid peroxidation products, such as acrolein, which activates TNFa. Whether lipid peroxidation products accumulate in muscle and their removal from muscle influences muscle atrophy during heart failure has not been studied. In the muscle there are histidyl dipeptides, such as carnosine, ranging between 5-10 mM, synthesized via enzyme carnosine synthase (CARNS) that bind lipid peroxidation products. We examined whether intramuscular histidyl dipeptides influences heart failure-induced muscle wasting. Hypothesis: Histidyl dipeptides, alleviates intramuscular inflammation, preserves muscle mass and function during heart failure. Methods: Wild type (WT) and muscle-specific CARNS transgenic (Tg) mice were subjected to sham and transverse aortic constriction (TAC) surgeries. Cardiac function, muscle strength, atrophic and inflammatory markers, aldehyde modified protein, CARNS, and histidyl dipeptides were measured after 12 weeks. Results: In heart failure mice, weight of gastrocnemius (sham: 18.64 ± 1.73 vs TAC: 14.10 ± 0.90 mg, p=0.005), soleus (sham: 6.06 ± 0.82 vs TAC: 4.14 ± 0.70 mg, p=0.001), and tibialis anterior (sham:10.76 ± 1.62 vs TAC: 6.22 ± 1.83 mg, p=0.003), were decreased. Muscle strength was diminished (sham: 2.81 ± 0.36 vs TAC: 1.52 ± 0.27 N, p=0.004). Atrophic marker, atrogin1, aldehyde protein adducts and TNF-a were increased in the gastrocnemius muscle of TAC mice (~2-3-fold vs sham, p<0.05). CARNS expression and carnosine was decreased in different muscles of TAC mice (gastrocnemius; sham: 43.38 ± 20.46 vs TAC: 24.48 ± 6.49 nmoles/mg protein, p=0.03; soleus; sham: 22.04 ± 11.36 vs TAC: 11.02 ± 4.69 nmoles/mg protein, p=0.03; and tibialis; sham: 27.9 ± 11.70 vs TAC: 15.50 ± 3.48 nmoles/mg protein, p=0.01). Gastrocnemius muscle weight (WT TAC: 14.38 ± 1.08 vs Tg TAC: 17.30 ± 1.32 mg, p=0.004) and muscle strength (WT TAC: 3.06 ± 0.32 vs Tg TAC: 3.98 ± 0.41 N) were preserved, atrogin and TNFa expressions were decreased in gastrocnemius muscle of Tg TAC mice (~2-3-fold, p=0.04). Conclusion: Increasing intramuscular histidyl dipeptides alleviates muscle inflammation, preserves muscle mass, and function during heart failure.

Abstract 4135531: The Ubiquitin-Specific Protease 30 Inhibitor, MTX652, Attenuates Cardiac Dysfunction And Remodelling In a Murine Model Of Transverse Aortic Constriction

Introduction: Mitochondrial abnormalities are a characteristic of heart failure leading to energy deprivation and disease worsening. The mitochondrial deubiquitinating enzyme USP30, removes ubiquitin and represses PINK1/PARKIN-mediated mitophagy leading to accumulation of dysfunctional mitochondria. In this study we investigated the role of MTX652, a clinical stage USP30 inhibitor, in a mouse model of cardiac hypertrophy using transverse aortic constriction (TAC). Hypothesis: Inhibition of USP30 will promote mitophagy resulting in clearance of dysfunctional mitochondria and improved cellular health leading to cardioprotective effects. Aims: To determine if MTX652 can protect from TAC induced cardiac hypertrophy and remodelling. Methods: Male C57BL/6 mice, 8 weeks old, were subjected to sham surgeries or TAC using a 26G needle to induce cardiac pressure overload. MTX652 (1.5 or 5 mg/kg, n =12-13) or vehicle ( n =11) was administered orally, twice daily, starting 2 days post-surgery. Captopril (30 mg/kg/d, n =13) was also included as a positive control. After 4 weeks, echocardiography assessed left ventricle (LV) function and morphology. Cell based assays assessed MTX652 target engagement and TOM20 ubiquitination in vitro. Results: LV hypertrophy and wall thickening was observed in TAC animals. Treatment with MTX652 decreased systolic LV volume (1.5 mg/kg p<0.05 and 5 mg/kg p<0.01) and diameter (1.5 mg/kg p<0.01 and 5 mg/kg p<0.05,) demonstrating comparable effects to Captopril. A reduction in anterior wall thickness in diastole was also observed with MTX652 (5 mg/kg, p<0.01). Cardiac dysfunction was also evident in TAC animals with MTX652 showing improvements in both ejection fraction (1.5 mg/kg and 5 mg/kg, p<0.0001) and fractional shortening (1.5 mg/kg and 5 mg/kg, p<0.0001). Cellular target engagement for MTX652 was confirmed in HeLa-YFP-Parkin cells with an EC 50 of 2.7 nM ( n =2). Furthermore, the USP30 substrate TOM20 was ubiquitinated following MTX652 treatment in vitro (EC 50 =6.1 nM, n =4) providing evidence of mitophagy activation, a finding also confirmed in mouse heart tissue (MTX652, 5mg/kg). Conclusions: The USP30 inhibitor, MTX652 significantly protected mice from TAC induced cardiac hypertrophy and LV dysfunction. Furthermore, MTX652 potentiates ubiquitylation of TOM20 as a mechanism to promote mitophagy. These data suggest our clinical stage molecule could provide a novel therapeutic approach for the treatment of cardiac hypertrophy and heart failure.

Abstract 4122257: Inhibition of Neutrophil Extracellular Traps Prevents Heart Failure by Preserving Mitochondrial Function of Cardiomyocytes in Mice

Background: We have previously demonstrated that neutrophil extracellular traps (NETs) in myocardial tissue are associated with cardiac dysfunction and adverse outcomes in patients with heart failure with reduced ejection fraction. Here, we aimed to elucidate the underlying mechanisms and to clarify whether inhibiting NETs could rescue the cardiac phenotype using ex vivo and in vivo models. Methods and Results: Given that peptidyl arginine deiminase 4 (PAD4) is essential for the formation of NETs, PAD4 knockout mice were used for this study. First, we assessed the mitochondrial function of cardiomyocytes by conducting real-time measurements of the oxygen consumption rate in ex vivo . Extracellular flux analysis revealed that NETs-containing conditioned medium from wild-type neutrophils or purified NET components led to impaired mitochondrial oxygen consumption of adult mouse cardiomyocytes, while these effects were abolished when PAD4 in neutrophils was genetically ablated (Figure 1). In a murine model of pressure overload-induced heart failure, transverse aortic constriction (TAC) operation was performed on wild-type and PAD4 knockout mice. Immunohistological analysis demonstrated that TAC induced the formation of NETs in the myocardium, with the greatest number of NETs occurring at 1 day, persisting into the failing stage at 4 weeks in wild-type mice, while PAD4-deficient hearts displayed no presence of NETs in the heart tissue (Figure 2). Four weeks after TAC, left ventricular ejection fraction was reduced in wild-type mice, whereas PAD4 knockout mice displayed preserved left ventricular ejection fraction (Figure 2). Finally, we investigated the bioenergetics of cardiomyocytes isolated from PAD4 knockout mice after TAC. Maximal mitochondrial oxygen consumption rate in cardiomyocytes isolated from TAC-operated PAD4 knockout mice was significantly higher than in those from TAC-operated wild-type mice (Figure 3). Conclusion: Our data suggest that NETs directly derived impairment of mitochondrial function in cardiomyocytes. Inhibiting NETs represents a potential therapeutic approach for heart failure, preventing mitochondrial dysfunction of cardiomyocytes.

Abstract 4137996: Effects of Empagliflozin on diuresis in heart failure: Results from the CINNAMON-study and in-vivo experiments

Background and Purpose: Heart failure is associated with renal dysfunction suggesting a pathophysiological link between heart and kidney. Empagliflozin, a SGLT2 inhibitor, showed beneficial effects on both cardiovascular and renal endpoints. However, mechanistically, it is unclear if empagliflozin-dependent kidney protection is mediated via inhibition of tubular SGLT2 or more indirectly via improved cardiac function. We hypothesized that Empagliflozin treatment improves left ventricular ejection fraction (LVEF) independent of diuretic effect of renal SGLT2 inhibition. Methods: We evaluated NTproBNP, hematocrit, hemoglobin and bodyweight in patients with HF with reduced (n=32) and preserved ejection fraction (n=59) after 30 and 180 days (prospective, single-arm CINNAMON-study, DRKS00031101). Furthermore, we conducted transverse aortic constriction (TAC) or sham surgery in C57BL/6J (wildtype, WT) and SGLT2 deficient mice (SGLT2 -/- ). Animals received either Empagliflozin (10 mg/kg bodyweight) or vehicle by daily oral gavage. Water intake and output was evaluated by metabolic cages at 10 weeks and cardiac function by echocardiography. Results: Empagliflozin treatment reduced NT-proBNP levels and increased hematocrit and hemoglobin levels especially in patients with reduced ejection fraction (Fig. A-C). Surprisingly, there was no change in body weight (Fig. D), which would be expected if the diuretic effects were dominant. In mice after 10 weeks, echocardiography confirmed TAC induced pressure-overload, leading to reduced LVEF. Empagliflozin attenuated changes in LVEF (Fig. G) and improved diastolic dysfunction (isovolumetric relaxation time, data not shown). To test if direct inhibition of SGLT2 in the heart and kidney is mechanistically involved, TAC surgery was repeated in SGLT2-deficient mice (SGLT2-KO). In fact, exposure to TAC resulted in comparable reduction of LVEF in SGLT2-KO and Empagliflozin prevented this deterioration similar to WT mice (Fig. G vs. I). Surprisingly, Empagliflozin did not increase drinking and urine volume neither in wildtype nor in SGLT2 deficient mice, suggesting a mechanism of cardioprotection independent of diuretic effects. Conclusion and Outlook: This is the first study investigating the role of SGLT2 in Empagliflozin treated patients and mice with heart failure. Importantly, empagliflozin treatment prevented deterioration of LVEF independent of the presence of SGLT2 and diuresis.

Abstract 4134967: Pericardial Adipose Tissue Hypertrophy Contributes to Heart Failure via β3 Adrenergic Signaling-Mediated Activation of the TGFβ1 Pathway

Background: The heart is surrounded by pericardial adipose tissue (PeAT). An increase in PeAT volume has been associated with the development of heart failure; however, the precise molecular mechanisms by which hypertrophic PeAT contributes to heart failure remain to be elucidated. Aims: To clarify the involvement of PeAT hypertrophy in the development of heart failure. Methods: Male C57BL/6 mice (8-10 weeks old) were fed a high-fat diet (HFD) for 8 weeks to induce PeAT hypertrophy. Cardiac pressure overload was induced by transverse aortic constriction (TAC) with a 26-gauge needle. Results: PeAT volume significantly increased in HFD-fed mice compared to those on a normal diet (ND) (25.28 ± 4.1 mg vs. 9.35 ± 0.73 mg, p<0.01). Eight weeks after TAC, HFD-fed mice (TAC+HFD) exhibited more pronounced cardiac dysfunction (fractional shortening: 45.21 ± 2.21% vs. 55.99 ± 1.91%, p=0.002, left ventricular mass: 130.3 ± 7.80% vs. 106.8 ± 3.77%, p=0.0154), upregulation of cardiac fibrosis-related genes ( Col1a1 , Col3a1 ), and greater fibrotic area in the left ventricle compared to ND-fed TAC mice (TAC+ND). Simultaneously, the TGFβ/Smad pathway was activated in the left ventricles of TAC+HFD mice. Notably, surgical removal of hypertrophic PeAT improved cardiac function in TAC+HFD mice, while transplantation of PeAT from HFD-fed mice into TAC+ND mice worsened cardiac function. In TAC+HFD mice, local noradrenaline concentration in PeAT decreased, along with reduced activation of hormone-sensitive lipase, a downstream target of β3 adrenergic receptor signaling. Local free fatty acid concentrations also decreased in the PeAT of HFD-fed mice. In the RAW 264.7 macrophage cell line, a decrease in palmitic acid, a major fatty acid, led to increased expression of TGFβ1. Conclusions: These results suggest that HFD-induced PeAT hypertrophy suppresses β3 adrenergic receptor signaling and free fatty acid release, increasing TGFβ1 expression in the macrophages and resulting in cardiac fibrosis and dysfunction. Our findings provide new insights into the pathogenesis of PeAT hypertrophy in heart failure development.

Abstract 4134298: Dipeptidyl Peptidase 4 Promotes Pressure Overload-Induced Heart Failure through enhancing Antigen Presentation

Background: Antigen presentation to CD4+ T cells plays a critical role in heart failure (HF). Dipeptidyl peptidase 4 (DPP4) has been shown to promote the activation of T lymphocytes. This study aims to investigate the role of DPP4 in antigen presentation in pressure overload-induced HF. Methods: To examine the role of DPP4 in antigen presentation during HF, we tested the recruitment and function of dendritic cells (DCs) in transverse aortic constriction (TAC)-induced HF mice. To further investigate, we generated DPP4 knockout mice and induced bone marrow-derived dendritic cells (BMDCs) in vitro. BMDCs were then adoptively transferred into OT-II mice, whose DCs require specific exogenous ovalbumin loading to activate CD4+ T cells. RNA-Seq analysis was performed to elucidate the mechanisms by which DPP4 affects the function of DCs. Results: We observed an increased quantity of DCs in the hearts and mediastinal lymph nodes of TAC mice, accompanied by elevated expression of DPP4. These DCs exhibited enhanced antigen-presenting abilities, resulting in increased activation of CD4+ T cells. DPP4 knockout suppressed DC maturation and attenuated their antigen-presenting capabilities. We found that OT-II mice subjected to TAC showed preserved cardiac function compared to wild-type (WT) mice. However, OT-II mice that received adoptive transfer of DPP4+/+ BMDCs exhibited worse cardiac function compared to those receiving DPP4-/- BMDCs, indicating that DPP4 in DCs contributes to HF progression. RNA-Seq analysis indicated that DPP4 in DCs influenced the T cell receptor signaling pathway and T cell differentiation. Mechanistically, DPP4 was found to inhibit the E3 ubiquitin ligase MARCH1 from binding to MHCII, thereby stabilizing MHCII through preventing its ubiquitin-dependent degradation in DCs. Conclusion: This study elucidates the significance of DPP4 in enhancing antigen presentation during heart failure. We propose that DPP4 represents a potential therapeutic target for heart failure.

Abstract 4136598: Osteochondrogenic transdifferentiation of vascular smooth muscle cells and microenvironmental dynamics in medial arterial calcification at single-cell resolution

Background: Medial arterial calcification (MAC) significantly contributes to cardiovascular mortality, yet effective treatments remain limited due to unclear molecular mechanisms. This study aimed to develop a mouse model of MAC using O-ring-induced transverse aortic constriction (OTAC) and to elucidate key genes, pathways, and cellular interactions involved in MAC formation through lineage tracing and single-cell RNA sequencing (scRNA-seq). Methods: An OTAC mouse model was established to replicate MAC. Adult C57BL/6J male mice underwent OTAC, and subsequent analyses were conducted at various time points. Histological and immunohistochemical assessments were performed to monitor changes in vascular smooth muscle cells (VSMCs). Lineage tracing was utilized to verify the origin of osteochondrogenic VSMCs. Furthermore, scRNA-seq was employed to capture dynamic changes in VSMCs and other cell types contributing to MAC development. Results: The OTAC model successfully induced osteochondrogenic transdifferentiation of VSMCs, leading to MAC. Immunohistochemical analysis demonstrated time-dependent decreases in α-SMA expression and increases in SOX9 and RUNX2 expression. Lineage tracing using Myh11CreERT2;ROSA26-EGFP mice confirmed that osteochondrogenic VSMCs originated from contractile VSMCs. scRNA-seq identified osteochondrogenic VSMCs and revealed dynamic changes in surrounding cells, including macrophages and fibroblasts, which were implicated in calcification-related and inflammatory processes. Conclusion: The OTAC method effectively mimicked human MAC pathology, offering comprehensive insights into the microenvironmental dynamics of MAC progression at the single-cell level. This model serves as a robust platform for future research on therapeutic interventions.

Abstract 4134975: ROS-Traf6-Yap Promotes the Development of Cardiac Hypertrophy

Introduction: Heart failure (HF) is caused by structural and functional abnormalities of the heart and is associated with high morbidity and mortality. Pathological myocardial hypertrophy accounts for a significant portion heart failure. The Yap protein was found to be responsive to mechanotransduction signals and can limit organ size by inducing cell cycle arrest during development. In the heart, pathological activation of Yap has been shown to drive cardiac hypertrophy, but regenerative activation of Yap can promote myocardial cell-cycle re-entry. However, how Yap is pathologically activated in the beating cardiomyocyte remains elusive. Hypothesis: ROS-Traf6 promotes the development of cardiac hypertrophy by activating Yap in a non-canonical fashion. Methods: Traf6 protein levels in heart failure patients biopsies as well as in various murine failing hearts were examined by immunofluorescence. Molecular interrogation of ROS-Traf6-Yap signaling axis was performed in primary neonatal rat cardiomyocytes (NRCM) and human induced pluripotent stem cell derived cardiomyocytes. Yap protein stability and activation by Traf6 was examined by immunoprecipitation, CHX induction, and point mutation. Myocardial specific Traf6 knockout and Yap mutant animals were used to evaluate Traf6-Yap signaling in vivo . Results: We found that Traf6 expression was significantly elevated in multiple heart failure models. Using the transverse aortic constriction (TAC)-induced cardiac hypertrophy model, pressure overload increased ROS levels which activated Traf6. Traf6 overexpression induced myocardial hypertrophy while knockdown blocked myocardial hypertrophy in Ang II treated NRCMs. Mechanistically, Traf6 binds to and ubiquitinates Yap-K234 – this promotes Yap protein stability and nuclear translocation evidenced by increase in phosphorylated Yap. Myocardial Traf6 deficiency prevents TAC-induced cardiac hypertrophy. Moreover, overexpression of Yap-K237 mutant did not restore TAC-induced cardiac hypertrophy in myocardial Yap deficient mice. Conclusions: Our results demonstrate that non-canonical Yap activation is responsible for pressure overload induced cardiac hypertrophy. Targeting of the newly identified ROS-Traf6-Yap signaling axis may provide a new approach to prevent pathogenic cardiac hypertrophy.

Abstract 4134695: The Effect and Mechanism of Histone Lactylation In Pathological Cardiac Hypertrophy Induced by Pressure Overload

Introduction: Cardiac hypertrophy is characterized by significant metabolic changes, notably an increase in glycolysis. Histone lactylation, a post-translational modification influenced by the glycolytic state of cells, plays a crucial role in regulating gene transcription. However, the relationship between histone lactylation and cardiac hypertrophy remains unclear. Research Questions: This study aims to elucidate the effects and underlying mechanisms of histone lactylation in the progression of cardiac hypertrophy induced by pressure overload. Methods and Results: We observed an increase in histone lactylation levels in hypertrophic hearts from both humans and mice. To investigate further, male mice underwent transverse aortic constriction (TAC) to induce cardiac hypertrophy, followed by either an intraperitoneal injection of Oxamate (an LDHA inhibitor) to reduce histone lactylation or sodium lactate to increase it. Reducing histone lactylation protected the hearts from TAC-induced hypertrophy and fibrosis, preserving cardiac function, while increased histone lactylation exacerbated cardiac hypertrophy and fibrosis, impairing cardiac function. Cardiomyocyte-specific deletion of LDHA also led to a reduction in cardiac hypertrophy. In vitro experiments showed that inhibiting histone lactylation reduced the expression of hypertrophic markers and the hypertrophic growth of cardiomyocytes stimulated by phenylephrine. Using co-immunoprecipitation, we confirmed that P300 and GCN5 are the transferases mediating histone lactylation in cardiomyocytes. Mechanistic studies using the CUT&Tag technique revealed lactate-dependent histone modification was enriched at the promoter of TGFB2, activating its transcription. Inhibiting cardiac-specific TGFB2 expression through adeno-associated viral delivery of shRNA reduced TAC-induced cardiac hypertrophy. Furthermore, TGFB2 overexpression induced a hypertrophic phenotype in cardiomyocytes and activated the PI3K/AKT/mTOR pathways. This hypertrophic phenotype, induced by TGFB2 overexpression, was suppressed by inhibitors of PI3K or AKT. Conclusion: Our findings reveal a critical role for histone lactylation in the development of pathological cardiac hypertrophy by regulating TGFB2 expression and the PI3K/AKT/mTOR pathway.

Abstract 4115947: Empagliflozin Inhibits the Mobilization of CCR2+ Monocyte-Derived Macrophages by Reducing CCL2 Expression in Fibroblasts and Slows the Progression of Heart Failure After Pressure Overload.

Background: The positive effects of sodium glucose co-transporter-2 (SGLT2) inhibitors on reducing cardiovascular mortality and hospitalizations due to heart failure have been well established. Although numerous theories propose explanations for the cardioprotective actions of SGLT2 inhibitors, these hypotheses primarily rely on initial findings and require further validation. Studies have shown that immune cells, particularly macrophages marked by C-C chemokine receptor type 2 (CCR2), contribute to the progression of heart failure by infiltrating the myocardium and inducing detrimental structural changes following myocardial infarction or pressure overload. Purpose: This study aims to investigate whether SGLT2 inhibitors can mitigate heart damage by inhibiting the migration of CCR2+ monocyte-derived macrophages. Methods: In this experiment, male B6 mice were subjected to transverse aortic constriction (TAC) to induce heart failure. Two weeks post-TAC, with heart function confirmed as equal across all groups by echocardiography, one group began receiving daily oral doses of empagliflozin, while another served as the control. At four weeks post-TAC, cardiac function was reassessed. The animals were then euthanized, and their hearts were analyzed using flow cytometry, staining, and qPCR to evaluate heart failure and the involvement of immune cells. Additionally, isolated cardiac fibroblasts were subjected to cyclic stretching to mimic post-TAC mechanical stress. Results: Treatment with empagliflozin resulted in improved cardiac function and reduced congestion in the heart and lungs, indicating alleviation of heart failure. The treatment notably decreased myocardial fibrosis, evident from Picrosirius-red staining and reduced expression of fibrosis-related mRNA. Importantly, empagliflozin specifically reduced the number of CCR2-positive macrophages in the heart, without affecting other types of immune cells. In cardiac fibroblasts that underwent cyclic stretching, empagliflozin pre-treatment diminished the expression of C-C motif chemokine ligand 2 (CCL2), the ligand for CCR2. Conclusion: Empagliflozin’s ability to suppress CCL2 expression in fibroblasts and curtail the recruitment of CCR2+ macrophages may represent a potential strategy to decelerate heart failure progression. These findings advance our understanding of the cardioprotective mechanisms of SGLT2 inhibitors and propose novel therapeutic avenues for heart failure management.

Abstract 4135476: The Cardiomyocyte Hypertrophy Inhibitor RFN-409, Identified by High Throughput Screening Assay, Suppresses Pressure Overload-induced Systolic Dysfunction in Mice by Suppressing p38 Activity

Purpose: When the heart is exposed to stresses such as myocardial infarction or hypertension, it undergoes compensatory hypertrophy in response. However, continuation of the stress causes this compensatory mechanism to fail, and eventually systolic dysfunction or decompensated heart failure occur. As the hypertrophy of individual cardiomyocytes has been observed in this process, controlling cardiomyocyte hypertrophy is a potential target the prevention and treatment of heart failure. In this study, we constructed a high throughput screening (HTS) assay using cardiomyocyte hypertrophy as an index parameter. Compounds that inhibit cardiomyocyte hypertrophy were selected from our low molecular compound library. Methods and Results: In the primary screening, cultured rat primary cardiomyocytes were treated with each compound at a final concentration of 1 µM and then stimulated with 30 µM phenylephrine (PE) for 48 hours. These cells were subjected to fluorescent immunostaining with α-actinin, and cardiomyocyte area was measured using an ArrayScan™ system. The hypertrophy inhibition rate (%) of each compound was calculated as [(PE(+) - compound) / (PE(+) - PE(-))] × 100. The compounds with a hypertrophy inhibition rate greater than 50% and less than 150% were selected as hit compounds. In the secondary screening, these hit compounds were evaluated based on the dose-dependency of cardiomyocyte hypertrophy inhibition and the inhibition of the mRNA levels of the cardiac hypertrophy response genes ANF and BNP using real-time PCR. From the 269 low molecular-weight compounds in the original compound library, eight were selected through the primary and secondary screenings. Among them, we focused on Reference Number 409 (RFN-409). Western blotting indicated that RFN-409 inhibited PE-induced p38 activation. Next, we investigated the effect of RFN-409 on heart failure. Eight-week-old male C57 BL/6J mice were subjected to transverse aortic constriction (TAC) surgery and then randomly assigned to intraperitoneal treatment with RFN-409 (3, 10 mg/kg) or vehicle for eight weeks. RFN-409 at 10 mg/kg significantly prevented TAC-induced increase in left ventricular posterior wall thickness and decrease in left ventricular fractional shortening. Discussion: RFN-409 suppressed TAC-induced development of heart failure, at least partially by inhibiting p38 activity. These findings suggest that RFN-409 may be an effective agent for heart failure therapy.

Isoprenaline Inhibits Histone Demethylase LSD1 to Induce Cardiac Hypertrophy.

Histone demethylation in cardiac hypertrophy is poorly understood. This study aims to determine the role of the histone demethylase LSD1 in pathological cardiac hypertrophy. Both isoprenaline (ISO)-treated and transverse aortic constriction (TAC)-treated rats developed hypertrophic hearts. LSD1 was significantly decreased; the histone marks mono- and dimethyl H3K4 and H3K9 (H3K4me1/2 and H3K9me1/2) were significantly up-regulated in the hypertrophic heart tissue, as well as the expression of the ANP, α-HMC and MLV-2v genes. An LSD1 inhibitor, OG-L002 could also induce cardiac hypertrophy and enhance the induction of cardiac hypertrophy by ISO. Overexpressed LSD1 abolished ISO-induced cardiac hypertrophy and downregulated H3K4me1/2 and H3K9me1/2 expression. Overexpression of LSD1 also reduced the expression of ANP, α-HMC and MLV-2v. In addition, we have reported isoprenaline (ISO) as one of the histone demethylase LSD1 inhibitors. This was confirmed by molecular docking, molecular dynamic studies and a histone demethylation assay. The H3K4me1/2 expression increases with the incubation of ISO in HEK 293T and HELA cells. CaMKII could be significantly activated by the LSD1 inhibitor OG-L002 as well as by ISO in rats. In summary, we have identified a novel role for LSD1 in initiating and maintaining cardiac hypertrophy.

PINK1-mediated mitophagy attenuates pathological cardiac hypertrophy by suppressing the mtDNA release-activated cGAS-STING pathway.

Sterile inflammation is implicated in the development of heart failure (HF). Mitochondria plays important roles in triggering and maintaining inflammation. Mitophagy is important for regulation of mitochondrial quality and maintenance of cardiac function under pressure overload. The association of mitophagy with inflammation in HF is largely unclear. As PINK1 is a central mediator of mitophagy, our objective was to investigate its involvement in cardiac hypertrophy, and the effect of PINK1-mediated mitophagy on cGAS-STING activation during cardiac hypertrophy. PINK1 knockout and cardiac-specific PINK1-overexpressing transgenic mice were created and subsequently subjected to transverse aortic constriction (TAC) surgery. In order to explore whether PINK1 regulates STING-mediated inflammation during HF, PINK1/STING (stimulator of interferon genes) double-knockout mice were created. Pressure overload was induced by TAC. Our findings indicate a significantly decline in PINK1 expression in TAC-induced hypertrophy. Cardiac hypertrophic stimuli caused the release of mitochondrial DNA (mtDNA) into the cytosol, activating the cGAS-STING signaling, which in turn initiated cardiac inflammation and promoted the progression of cardiac hypertrophy. PINK1 deficiency inhibited mitophagy activity, promoted mtDNA release, and then drove the overactivation of cGAS-STING signaling, exacerbating cardiac hypertrophy. Conversely, cardiac-specific PINK1 overexpression protected against hypertrophy thorough inhibition of the cGAS-STING signaling. Double-knockout mice revealed that the effects of PINK1 on hypertrophy were dependent on STING. Our findings suggest that PINK1-mediated mitophagy plays a protective role in pressure overload-induced cardiac hypertrophy via inhibiting the mtDNA-cGAS-STING pathway.

USP20 deletion promotes eccentric cardiac remodeling in response to pressure overload and increases mortality.

Left ventricular hypertrophy (LVH) caused by chronic pressure overload with subsequent pathological remodeling is a major cardiovascular risk factor for heart failure and mortality. The role of deubiquitinases in LVH has not been well characterized. To define whether the deubiquitinase ubiquitin-specific peptidase 20 (USP20) regulates LVH, we subjected USP20 knockout (KO) and cognate wild-type (WT) mice to chronic pressure overload by transverse aortic constriction (TAC) and measured changes in cardiac function by serial echocardiography followed by histological and biochemical evaluations. USP20-KO mice showed severe deterioration of systolic function within 4 wk of TAC compared with WT cohorts. Both USP20-KO TAC and WT-TAC cohorts presented cardiac hypertrophy following pressure overload. However, USP20-KO-TAC mice showed an increase in cardiomyocyte length and developed maladaptive eccentric hypertrophy, a phenotype generally observed with volume overload states and decompensated heart failure. In contrast, WT-TAC mice displayed an increase in cardiomyocyte width, producing concentric remodeling that is characteristic of pressure overload. In addition, cardiomyocyte apoptosis, interstitial fibrosis, and mouse mortality were augmented in USP20-KO-TAC compared with WT-TAC mice. Quantitative mass spectrometry of LV tissue revealed that the expression of sarcomeric myosin heavy chain 7 (MYH7), a fetal gene normally upregulated during cardiac remodeling, was significantly reduced in USP20-KO after TAC. Mechanistically, we identified increased degradative lysine-48 polyubiquitination of MYH7 in USP20-KO hearts, indicating that USP20-mediated deubiquitination likely prevents protein degradation of MYH7 during pressure overload. Our findings suggest that USP20-dependent signaling pathways regulate the layering pattern of sarcomeres to suppress maladaptive remodeling during chronic pressure overload and prevent cardiac failure.NEW & NOTEWORTHY We identify ubiquitin-specific peptidase 20 (USP20) as an important enzyme that is required for cardiac homeostasis and function, particularly during myocardial pressure overload. USP20 regulates protein stability of cardiac MYH7, an essential molecular motor protein expressed in sarcomeres; loss-of-function mutations of MYH7 are associated with human hypertrophic cardiomyopathy, cardiac failure, and sudden death. Enhancing USP20 activity could be a potential therapeutic approach to prevent the development of maladaptive state of eccentric hypertrophy and heart failure.

Fibroblast-derived miR-425-5p alleviates cardiac remodelling in heart failure via inhibiting the TGF-β1/Smad signalling.

The pathological activation of cardiac fibroblasts (CFs) plays a crucial role in the development of pressure overload-induced cardiac remodelling and subsequent heart failure (HF). Growing evidence demonstrates that multiple microRNAs (miRNAs) are abnormally expressed in the pathophysiologic process of cardiovascular diseases, with miR-425 recently reported to be potentially involved in HF. In this study, we aimed to investigate the effects of fibroblast-derived miR-425-5p in pressure overload-induced HF and explore the underlying mechanisms. C57BL/6 mice were injected with a recombinant adeno-associated virus specifically designed to overexpress miR-425-5p in CFs, followed by transverse aortic constriction (TAC) surgery. Neonatal mouse CFs (NMCFs) were transfected with miR-425-5p mimics and subsequently stimulated with angiotensin II (Ang II). We found that miR-425-5p levels were significantly downregulated in HF mice and Ang II-treated NMCFs. Notably, fibroblast-specific overexpression of miR-425-5p markedly inhibited the proliferation and differentiation of CFs, thereby alleviating myocardial fibrosis, cardiac hypertrophy and systolic dysfunction. Mechanistically, the cardioprotective actions of miR-425-5p may be achieved by targeting the TGF-β1/Smad signalling. Interestingly, miR-425-5p mimics-treated CFs could also indirectly affect cardiomyocyte hypertrophy in this course. Together, our findings suggest that fibroblast-derived miR-425-5p mitigates TAC-induced HF, highlighting miR-425-5p as a potential diagnostic and therapeutic target for treating HF patients.

Temporal dynamics of cardiac remodelling in pressure overload: the key role of visceral adipose tissue

Abstract Background Myocardial fibrosis is a prominent pathological feature of cardiac remodelling in pressure overload. The underlying mechanisms of cardiac remodelling are complex including mechanical, inflammatory and neurohormonal factors. We have recently uncovered a pathological crosstalk between visceral adipose tissue (VAT) and heart in biological aging characterized by profibrotic proteins in both the VAT secretome and the plasma contributing to myocardial interstitial fibrosis. We hypothesize that a model of pressure overload induced by transverse aortic constriction (TAC) is responsible for VAT remodelling and a VAT profibrotic secretome, which in turn worsens cardiac fibrosis and alters cardiac function. Purpose To explore the effect of pressure overload on VAT and identify a crosstalk between heart and VAT. Methods We divided wild-type male mice (5-month-old, n=10/group) into two groups: a visceral Lipectomy group and a Sham group two weeks before a moderate TAC (26G; i.e. gradient between left ventricle and aorta of 30mmHg) or a sham surgery. We sacrificed the mice at 1- and 8-week after TAC. We performed in vivo metabolic tests, echocardiography, and invasive hemodynamics, followed by ex vivo tissue analysis. We then analysed the time-course of the cardiac transcriptomic signature in TAC vs control and the impact of visceral lipectomy in both groups. Results Our results show that TAC induced not only cardiac remodelling affecting the structure and function of the heart, but also VAT fibrosis and inflammation together with activation of adrenergic receptors (Adrb3). VAT became a major source of profibrotic (TGFb and osteopontin) and proinflammatory (TNFa, IL6 and PAI1) factors as early as 1 week after TAC. Interestingly, lipectomy prevented cardiac remodelling and dysfunction. After 1 week of TAC, cardiac transcriptomic profile showed a similar upregulation of profibrotic and prohypertrophic genes in TAC groups in presence or absence of lipectomy. After 8 weeks of TAC, lipectomy prevented the upregulation of those genes and transcriptomic profile of TAC+lipectomy was similar to sham group (Figure). PCR analysis confirmed the lower expression of profibrotic (TGFb, Osteopontin), prohypertrophic (Nppa) and contractility genes (Adr1b) in TAC+Lipectomy vs TAC group after 8 weeks of TAC. Conclusion Our results suggest that VAT is detrimental to cardiac structure and function by releasing a profibrotic and a proinflammatory secretome that aggravates the cardiac remodelling induced by TAC. Conversely, lipectomy prevents the early development of TAC-induced cardiac fibrosis.

Effects of empagliflozin on cardio-renal interaction in heart failure with reduced ejection fraction: results from in-vivo experiments and the CINNAMON-study

Abstract Background Heart failure is often accompanied by renal dysfunction, which indicates a pathophysiological connection between the heart and kidneys. Empagliflozin, a SGLT2 inhibitor, showed beneficial effects on both cardiovascular and renal endpoints. Mechanistically, however, it is unclear whether the empagliflozin-dependent renal protection is mediated via the inhibition of renal SGLT2 or rather indirectly via improved cardiac function. Interestingly, in the EMPEROR trials, there was a significant interaction of empagliflozin-dependent kidney protection with systolic contractile dysfunction. We hypothesized that Empagliflozin treatment ameliorates heart failure in response to chronic pressure overload in mice leading to improved renal function. We correlated these findings with data from our prospective, single-armed trial. Methods Transverse aortic constriction (TAC) or sham surgery was performed in C57BL/6J (wildtype, WT) and SGLT2 deficient mice (SGLT2-/-). Animals received either Empagliflozin (10 mg/kg bodyweight) or vehicle by daily oral gavage. Cardiac function was evaluated by echocardiography and kidney function by transdermal FITC-Sinistrin measurement (GFR), urinary albumin/creatinine ratio (UACR) and Siriusred fibrosis staining. Results After 10 weeks, echocardiography confirmed TAC induced pressure-overload, leading to reduced left ventricular ejection fraction (LVEF) and diastolic dysfunction. Empagliflozin attenuated changes in LVEF (Fig. A) and improved diastolic dysfunction (data not shown). Interestingly, at 10 weeks, TAC reduced GFR, increased UACR and tended to increase renal fibrosis, which was attenuated by empagliflozin (Fig. B, C and D). To test if direct inhibition of SGLT2 in the heart and kidney is mechanistically involved, TAC surgery was repeated in SGLT2-deficient mice (SGLT2-/-). In fact, exposure to TAC resulted in comparable reduction of LVEF in SGLT2-/- mice and Empagliflozin prevented this deterioration similar to WT mice (Fig. E vs. A). Surprisingly, Empagliflozin also prevented GFR deterioration 10 weeks after TAC in mice lacking SGLT2 (SGLT2-/-) with comparable magnitude as in WT mice (Fig. F), suggesting that the reno-protective effect of Empagliflozin was independent from renal SGLT2 inhibition. The effect of empagliflozin on the heart and kidney was also investigated in patients with HF (prospective, single-arm CINNAMON-study, DRKS00031101). After 180 days of Empagliflozin treatment (10 mg), there was a significant improvement in LVEF, NT-proBNP levels and KCCQ-12 Scores (Fig. G-I) and the effects on UACR and GFR are subject of investigation. Conclusion This is the first study investigating the role of SGLT2 in Empagliflozin-dependent kidney protection of mice that develop heart failure after TAC. Importantly, empagliflozin treatment prevented deterioration of LVEF and GFR independent of the presence of SGLT2 in mice and improved cardiac markers and quality of life in patients.

The effect of afterload on right ventricular pacing-induced left ventricular dysfunction: a translational study

Abstract Introduction Right ventricular (RV) pacing (RVP) impairs left ventricular (LV) function. Nevertheless, the interaction between arterial afterload and RVP-associated LV dysfunction has not been investigated yet. Purpose We sought to examine the effect of afterload on RVP-evoked LV hemodynamic changes in patients with aortic stenosis (AS) undergoing transcatheter aortic valve implantation (TAVI) as well as in a small animal model of sustained LV pressure overload (PO). Methods Thirty-five patients with AS and a previously implanted pacemaker underwent detailed echocardiographic examination immediately before TAVI and also on the second postoperative day. The ultrasound measurements were carried out during intrinsic, narrow QRS rhythm and during frequency-matched RVP as well. Global myocardial work index (GMWI) was calculated to assess LV contractility. In parallel, LV pressure-volume analysis was performed in Wistar rats with transverse aortic constriction (TAC) or sham operation (Sham) during intrinsic narrow QRS rhythm (termed as TAC-Vsense and Sham-Vsense) as well as during RVP (termed as TAC-Vpace and Sham-Vpace). RVP was achieved in rats by an octopolar electrophysiology catheter placed in the RV. Results RVP decreased LV contractility in AS patients before and after TAVI as well. Nevertheless, the extent of RVP-evoked LV dysfunction was alleviated following pressure unloading (ΔGMWI: -37±7 vs. -25±8%, before TAVI vs. after TAVI, P<0.05). Similarly, although RVP was associated with reduced LV contractility in both the TAC (the slope of the maximum rate of LV pressure rise-end-diastolic volume relation [dPdtmax-EDV]: 92±8 vs. 53±6mmHg/s/µl, TAC-Vsense vs. TAC-Vpace; P<0.05) and Sham groups (dPdtmax-EDV: 74±5 vs. 60±9 mmHg/s/µl, Sham-Vsense vs. Sham-Vpace; P<0.05), the negative inotropic effect of RVP was found to be stronger in the TAC compared to the Sham group (ΔdPdtmax-EDV: -42±4 vs. -19±6%; TAC vs. Sham, P<0.01). Furthermore, reduction of the maximal rate of LV pressure decrease (ΔdPdtmin: -20±3 vs. -5±5%, TAC vs. Sham, P<0.01) and prolongation of the active relaxation time constant (Δτ: 22±3 vs. 6±3%, TAC vs. Sham, P<0.01) also occurred to a greater extent in case of sustained LV PO, indicating augmented diastolic dysfunction. Conclusion Our translational results indicate that RVP-induced LV dysfunction might be afterload dependent.

Intact DNA repair in differentiated cardiomyocytes is essential for maintaining cardiac function in response to pressure overload in mice

Abstract Introduction DNA in every cell is continuously damaged and DNA repair mechanisms are essential for protection against DNA damage-induced aging-related diseases. For example, deficient repair of endogenously generated DNA damage in mice with cardiomyocyte-restricted inactivation of Xpg, is associated with progressive heart failure. Purpose Here we tested the hypothesis that unrepaired DNA damage in differentiated cardiomyocytes increases cardiac vulnerability in response to hemodynamic overload. Methods To increase the burden of spontaneous DNA damage, we generated mice with cardiomyocyte-restricted inactivation of DNA repair endonuclease XPG. At 8 weeks of age, αMHC-Xpgc/- and control (Ctrl) mice were subjected to pressure overload by transverse aortic constriction (TAC). Eight weeks after TAC, left ventricular (LV) function was assessed using echocardiography and hemodynamic measurements, followed by molecular and histological analyses. Results Cardiomyocyte-restricted inactivation of Xpg resulted in systolic as well as diastolic LV dysfunction (Table). TAC-induced LV hypertrophy is similar in both groups (Ctrl 38%; αMHC-Xpgc/- 34%). In Ctrl mice, LV hypertrophy was accompanied by minimal LV dilation and modest changes in systolic and diastolic LV function. Conversely, TAC in αMHC-Xpgc/- produced severe LV dysfunction and resulted in overt congestive heart failure, demonstrated by aggravation of LV dilation, and marked increases in LV end-diastolic pressure, left atrial weight and lung fluid weight, which was accompanied by further increases in the expression levels of the hypertrophic marker genes atrial natriuretic peptide and beta-myosin heavy chain (Table). Moreover, lectin staining revealed a decrease in capillary density and TUNEL staining revealed further elevated levels of myocardial apoptosis. In addition, a significant increase of myocardial collagen content was observed. Conclusion Cardiomyocyte-restricted loss of DNA repair protein XPG increases cardiac vulnerability to develop heart failure in response to pressure overload. These findings underscore the importance of genomic stability for maintenance of cardiac function, not only during basal conditions, but also in response to a pathological stimulus.