α-Ketoglutarate improves cardiac insufficiency through NAD+-SIRT1 signaling-mediated mitophagy and ferroptosis in pressure overload-induced mice

BACKGROUND

In heart failure (HF), mitochondrial dysfunction and metabolic remodeling lead to a reduction in energy productivity and aggravate cardiomyocyte injury. Supplementation with α-ketoglutarate (AKG) alleviated myocardial hypertrophy and fibrosis in mice with HF and improved cardiac insufficiency. However, the myocardial protective mechanism of AKG remains unclear. We verified the hypothesis that AKG improves mitochondrial function by upregulating NAD+ levels and activating silent information regulator 2 homolog 1 (SIRT1) in cardiomyocytes.

METHODS

In vivo, 2% AKG was added to the drinking water of mice undergoing transverse aortic constriction (TAC) surgery. Echocardiography and biopsy were performed to evaluate cardiac function and pathological changes. Myocardial metabolomics was analyzed by liquid chromatography‒mass spectrometry (LC‒MS/MS) at 8 weeks after surgery. In vitro, the expression of SIRT1 or PINK1 proteins was inhibited by selective inhibitors and siRNA in cardiomyocytes stimulated with angiotensin II (AngII) and AKG. NAD+ levels were detected using an NAD test kit. Mitophagy and ferroptosis levels were evaluated by Western blotting, qPCR, JC-1 staining and lipid peroxidation analysis.

RESULTS

AKG supplementation after TAC surgery could alleviate myocardial hypertrophy and fibrosis and improve cardiac function in mice. Metabolites of the malate-aspartate shuttle (MAS) were increased, but the TCA cycle and fatty acid metabolism pathway could be inhibited in the myocardium of TAC mice after AKG supplementation. Decreased NAD+ levels and SIRT1 protein expression were observed in heart of mice and AngII-treated cardiomyocytes. After AKG treatment, these changes were reversed, and increased mitophagy, inhibited ferroptosis, and alleviated damage in cardiomyocytes were observed. When the expression of SIRT1 was inhibited by a selective inhibitor and siRNA, the protective effect of AKG was suppressed.

CONCLUSION

Supplementation with AKG can improve myocardial hypertrophy, fibrosis and chronic cardiac insufficiency caused by pressure overload. By increasing the level of NAD+, the SIRT-PINK1 and SIRT1-GPX4 signaling pathways are activated to promote mitophagy and inhibit ferroptosis in cardiomyocytes, which ultimately alleviates cardiomyocyte damage.

Alamandine attenuates oxidative stress in the right carotid following transverse aortic constriction in mice

OBJECTIVE

Pressure overload can result in significant changes to the structure of blood vessels, a process known as vascular remodeling. High levels of tension can cause vascular inflammation, fibrosis, and structural alterations to the vascular wall. Prior research from our team has demonstrated that the oral administration of alamandine can promote vasculoprotective effects in mice aorta that have undergone transverse aortic constriction (TAC). Furthermore, changes in local hemodynamics can affect the right and left carotid arteries differently after TAC. Thus, in this study, we aimed to assess the effects of alamandine treatment on right carotid remodeling and the expression of oxidative stress-related substances induced by TAC.

METHODS AND RESULTS

Male C57BL/6 mice were categorized into three groups: Sham, TAC, and TAC treated with alamandine (TAC+ALA). Alamandine treatment was administered orally by gavage (30 µg/kg/day), starting three days before the surgery, and continuing for a period of fourteen days. Morphometric analysis of hematoxylin and eosin-stained sections revealed that TAC induced hypertrophic and positive remodeling in the right carotid artery. Picrosirius Red staining also demonstrated an increase in total collagen deposition in the right carotid artery due to TAC-induced vascular changes. Alamandine treatment effectively prevented the increase in reactive oxygen species production and depletion of nitric oxide levels, which were induced by TAC. Finally, alamandine treatment was also shown to prevent the increased expression of nuclear factor erythroid 2-related factor 2 and 3-nitrotyrosine that were induced by TAC.

CONCLUSION

Our results suggest that alamandine can effectively attenuate pathophysiological stress in the right carotid artery of animals subjected to TAC.

Andrographolide contributes to the attenuation of cardiac hypertrophy by suppressing endoplasmic reticulum stress

CONTEXT

Andrographolide (Andr) is a bioactive Andr diterpenoid extracted from herbaceous Andrographis paniculata (Burm. F.) Wall. ex Nees (Acanthaceae). Andr can relieve cardiac dysfunction in mice by inhibiting the mitogen-activated protein kinases (MAPK) pathway.

OBJECTIVE

This study investigates the efficacy and underlying mechanism of Andr on cardiac hypertrophy in mice.

MATERIALS AND METHODS

Male C57 mice (20-25 g, 6-8 weeks) were divided into four groups (n = 10 mice/group) as sham group (sham operation), transverse aortic constriction (TAC) model group, TAC + Andr 100 mg/kg group and TAC + Andr 200 mg/kg group. Andr groups were given intragastric administration of Andr (100 and 200 mg/kg) once a day for 14 consecutive days. An in vitro hypertrophy model was established by adding 1 μM of Ang II to H9c2 cells for 48 h induction.

RESULTS

In TAC-mice, Andr improved echocardiographic indices [reduced LVESD (30.4% or 37.1%) and LVEDD (24.8% or 26.4%), increased EF (22.9% or 42.6%) and FS (25.4% or 52.2%)], reduced BNP (11.5% or 23.6%) and Ang II levels (10.3% or 32.8%), attenuates cardiac fibrosis and reduces cardiac cell apoptosis in TAC mice. In vitro, Andr attenuated cardiomyocyte hypertrophy and decreased the protein expression of GRP78 (67.8%), GRP94 (47.6%), p-PERK (44.9%) and CHOP (66.8%) in Ang-II-induced H9c2 cells and reversed after endoplasmic reticulum (ER) stress agonist Tunicamycin (TN) treatment.

DISCUSSION AND CONCLUSIONS

Andr was found to be an anti-hypertrophic regulator, which could attenuate cardiac hypertrophy by suppressing ER stress. It may be a new therapeutic drug for cardiac hypertrophy.

Stem cell antigen-1+cell-derived fibroblasts are crucial for cardiac fibrosis during heart failure

AIMS

Mesenchymal stem cells (MSCs) present in the heart cannot differentiate into cardiomyocytes, but may play a role in pathological conditions. Therefore, the aim of this study was to scrutinise the role and mechanism of MSC differentiation in vivo during heart failure.

METHODS AND RESULTS

We performed single-cell RNA sequencing of total non-cardiomyocytes from murine and adult human hearts. By analysing the transcriptomes of single cells, we illustrated the dynamics of the cell landscape during the progression of heart hypertrophy, including those of stem cell antigen-1 (Sca1)+ stem/progenitor cells and fibroblasts. By combining genetic lineage tracing and bone marrow transplantation models, we demonstrated that non-bone marrow-derived Sca1+ cells give rise to fibroblasts. Interestingly, partial depletion of Sca1+ cells alleviated the severity of myocardial fibrosis and led to a significant improvement in cardiac function in Sca1-CreERT2;Rosa26-eGFP-DTA mice. Similar non-cardiomyocyte cell composition and heterogeneity were observed in human patients with heart failure. Mechanistically, our study revealed that Sca1+ cells can transform into fibroblasts and affect the severity of fibrosis through the Wnt4-Pdgfra pathway.

CONCLUSIONS

Our study describes the cellular landscape of hypertrophic hearts and reveals that fibroblasts derived from Sca1+ cells with a non-bone marrow source largely account for cardiac fibrosis. These findings provide novel insights into the pathogenesis of cardiac fibrosis and have potential therapeutic implications for heart failure. Non-bone marrow-derived Sca1+ cells differentiate into fibroblasts involved in cardiac fibrosis via Wnt4-PDGFRα pathway.

Evaluating the effects of mRK35 by targeting myostatin in the pressure-overloaded heart

The transforming growth factor (TGF)-β superfamily member, myostatin, is a negative regulator of muscle growth and may contribute to adverse cardiac remodeling. Whether suppressing myostatin could benefit the pressure-overloaded heart remains unclear. We aimed to investigate the effects of pharmaceutical inhibition of myostatin on cardiac fibrosis and hypertrophy in a mouse model of pressure overload induced by transverse aortic constriction (TAC). C57BL/6J mice underwent either TAC or sham operation. Two weeks after the surgery, TAC and sham animals were randomly divided into groups receiving mRK35, a monoclonal anti-myostatin antibody, or vehicle (PBS) for 8 weeks. Significant progressive cardiac hypertrophy was observed in TAC mice, as reflected by the increased wall thickness, ventricle weight and cross-sectional area of cardiomyocytes. Among groups with mRK35 treatment, compared to the sham mice, cardiac fibrosis was increased in the TAC mice, accompanied with elevated mRNA expression of fibrotic genes. However, 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. Compared to 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 suggested mRK35 does not attenuate cardiac hypertrophy and fibrosis in a TAC mouse model, but have positive effects on muscle mass and muscle strength. Cardiac remodeling, fibrosis and dysfunction may respond differently to anti-myostatin therapy due to different etiologies. Anti-myostatin treatment may have therapeutic value against muscle wasting in cardiac cachexia.

Belumosudil, ROCK2-Specific Inhibitor, alleviates cardiac fibrosis by inhibiting cardiac fibroblasts activation

Cardiac fibrosis is thought to be the hallmark of pathological hypertrophic remodeling, of which the myofibroblasts transdifferentiation is the key cell biological event. However, there is still no specific and effective therapeutic agent approved for cardiac fibrosis. To investigate the effects of Belumosudil, the first ROCK2-specific inhibitor, on cardiac hypertrophy, fibrosis and dysfunction induced by pressure overload, the transverse aortic constriction (TAC) or sham operation was carried out on wild-type C57BL/6 mice (male, 6-8 week old) under pentobarbital anesthesia. After that, mice were randomly divided into three groups: sham operation + vehicle, TAC + vehicle, TAC + 50 mg·kg^-1·d^-1 Belumosudil. We found that Belumosudil effectively ameliorated cardiac hypertrophy, fibrosis and dysfunction in TAC mice. To elucidate the underlying mechanism, we inhibited the expression of ROCK2 in vitro by either Belumosudil or siRNA. We showed that the inhibition of ROCK2 by either Belumosudil or knockdown suppressed cardiac fibroblasts activation and proliferation significantly induced by Transforming Growth Factor-β1 (TGF-β1). Furthermore, our study confirmed ROCK2 mediates cardiac fibrosis by interacting with Transforming Growth Factor-β1 (TGF-β1)/mothers against decapentaplegic homolog (Smad2) pathway. Taken together, we demonstrated that Belumosudil ameliorates cardiac hypertrophy and fibrosis induced by TAC via inhibiting cardiac fibroblasts activation. In conclusion, Belumosudil may be a promising therapeutic drug for cardiac hypertrophy and fibrosis induced by myocardial pressure overload.

Gene expression profiling and functional analysis of ventricular tissues from murine transverse aortic constriction

BACKGROUND

Transverse aortic constriction (TAC) model is widely used to study pressure overload-induced cardiac remodeling. However, the conserved transcriptional features of TAC model and the underlying regulatory mechanisms remain unclear.

METHODS

In this study, we screened out the high-quality microarray data for ventricular tissue from murine TAC model. The transcriptional changes in ventricular tissue were analyzed by identifying the common differently expressed genes (DEGs) and enriched gene sets. We also analyzed the protein-protein interaction and mRNA-mRNA association of DEGs. Furthermore, the potential regulatory elements of the DEGs were explored through comparative analysis between mouse and human.

RESULTS

265 common DEGs and 45 enriched canonical pathways were identified in murine TAC model. 201 DEGs had the protein-protein interaction, whereas 96 DEGs had mRNA-mRNA association. 99 transcription factor (TF)-mRNA and 2997 microRNA (miRNA)-mRNA regulatory relationships were retrieved.

CONCLUSIONS

In pressure overload-induced cardiac remodeling, inflammation, fibrosis, metabolic remodeling and hypoxia were significant features. Approaches to intervene these phenomena may have therapeutic values. TFs and miRNAs are important regulator elements of DEGs in both mouse and human. Examination of miRNAs is a promising tool to detect the occurrence of pressure overload-induced cardiac remodeling in patients.

The Role Played by Transcription Factor E3 in Modulating Cardiac Hypertrophy

Transcription factor E3 (TFE3), which is a key regulator of cellular adaptation, is expressed in most tissues, including the heart, and is reportedly overexpressed during cardiac hypertrophy. In this study, TFE3's role in cardiac hypertrophy was investigated. To understand TFE3's physiological importance in cardiac hypertrophy, pressure-overload cardiac hypertrophy was induced through transverse aortic constriction (TAC) in both wild-type (WT) and TFE3 knockout mice (TFE3-/-). Eleven weeks after TAC induction, cardiac hypertrophy was observed in both WT and TFE3-/- mice. However, significant reductions in ejection fraction and fractional shortening were observed in WT mice compared to TFE3-/- mice. To understand the mechanism, we found that myosin heavy chain (Myh7), which increases during hemodynamic overload, was lower in TFE3-/- TAC mice than in WT TAC mice, whereas extracellular signal-regulated protein kinases (ERK) phosphorylation, which confers cardioprotection, was lower in the left ventricles of WT mice than in TFE3-/- mice. We also found high expressions of TFE3, histone, and MYH7 and low expression of pERK in the normal human heart compared to the hypertensive heart. In the H9c2 cell line, we found that ERK inhibition caused TFE3 nuclear localization. In addition, we found that MYH7 was associated with TFE3, and during TFE3 knockdown, MYH7 and histone were downregulated. Therefore, we showed that TFE3 expression was increased in the mouse model of cardiac hypertrophy and tissues from human hypertensive hearts, whereas pERK was decreased reversibly, which suggested that TFE3 is involved in cardiac hypertrophy through TFE3-histone-MYH7-pERK signaling.

Hirsutella sinensis fungus improves cardiac function in mouse model of heart failure

Cordyceps sinensis, including Hirsutella sinensis, is a highly valuable traditional Chinese medicine and is used to treat patients with pulmonary heart disease in clinical practice. However, the underlying mechanisms of its effects remain unclear. In this study, a mouse model of heart failure established by non-thoracic, transverse aortic constriction (TAC) was developed to determine the underlying mechanisms of therapeutic effects of Hirsutella sinensis fungus (HSF) powder. The results showed that HSF treatment remarkably ameliorated myocardial hypertrophy, collagen fiber hyperplasia, and cardiac function in mice with heart failure. Using transcriptional and epigenetic analyses, we found that the mechanism of HSF mainly involved a variety of signaling pathways related to myocardial fibrosis and determined that HSF could reduce the levels of TGF-β1 proteins in heart tissue, as well as type I and III collagen levels. These data suggest that HSF alleviates heart failure, inhibits irreversible ventricular remodeling, and improves cardiac function through the regulation of myocardial fibrosis-related signaling pathways, which can provide novel opportunities to improve heart failure therapy.

Structural and functional alterations in heart and skeletal muscle following severe TAC in mice: impact of moderate exercise training

Background

Heart failure (HF) is the leading cause of death in western countries. Cardiac dysfunction is accompanied by skeletal alterations resulting in muscle weakness and fatigue. Exercise is an accepted interventional approach correcting cardiac and skeletal dysfunction, thereby improving mortality, re-hospitalization and quality of life. Animal models are used to characterize underpinning mechanisms. Transverse aortic constriction (TAC) results in cardiac pressure overload and finally HF. Whether exercise training improves cardiac remodeling and peripheral cachexia in the TAC mouse model was not analyzed yet. In this study, 2 weeks post TAC animals were randomized into two groups either performing a moderate exercise program (five times per week at 60% VO₂ max for 40 min for a total of 8 weeks) or staying sedentary.

Results

In both TAC groups HF characteristics reduced ejection fraction (− 15% compared to sham, p < 0.001), cardiac remodeling (+ 22.5% cardiomyocyte cross sectional area compared to sham; p < 0.001) and coronary artery congestion (+ 34% diameter compared to sham; p = 0.008) were observed. Unexpectedly, peripheral cachexia was not detected. Furthermore, compared to sedentary group animals from the exercise group showed aggravated HF symptoms [heart area + 9% (p = 0.026), heart circumference + 7% (p = 0.002), right ventricular wall thickness − 30% (p = 0.003)] while muscle parameters were unchanged [Musculus soleus fiber diameter (p = 0.55), Musculus extensor digitorum longus contraction force (p = 0.90)].

Conclusion

The severe TAC model is inappropriate to study moderate exercise effects in HF with respect to cardiac and skeletal muscle improvements. Further, the phenotype induced by different TAC procedures should be well documented and taken into account when planning experiments.

A New Minimally Invasive Method of Transverse Aortic Constriction in Mice

Transverse aortic constriction (TAC) in mice is the most popular model to mimic pressure overload heart disease. In this study, we developed a convenient, quick, and less invasive new TAC mice model. Briefly, after anesthetization, endotracheal intubation was then performed, and the endotracheal tube was connected to a ventilator. The second intercostal space was opened and then the home-made retractors were used to push aside the thymus gently. A tunnel under the aortic arch was made and a segment of 6-0 monofilament polypropylene suture which had been threaded through a specifically modified blunted 26-gauge syringe needle was passed through the tunnel. A blunted 27-gauge needle was placed parallel to the transverse aorta and then three knots were tied quickly. After ligation, the spacer was removed promptly and gently to achieve a constriction of 0.4 mm in diameter. Five weeks after TAC, cardiac hypertrophy, fibrosis, and left ventricular dysfunction were observed. The mouse was anesthetized with pentobarbital (50 mg/kg) via intraperitoneal injection. Endotracheal intubation under direct vision was then performed and the endotracheal tube was connected to a ventilator. The second intercostal space was opened and then the home-made retractors were used to push aside the thymus gently. A tunnel under the aortic arch was made and a segment of 6-0 monofilament polypropylene suture which had been threaded through a specifically modified blunted 26-gauge syringe needle was passed through the tunnel.

An Optimized Model of Hypertrophic Preconditioning Confers Cardioprotection in the Mouse

BACKGROUND

Conventional models of hypertrophic preconditioning (C-HP) can be established surgically through transverse aortic constriction (TAC) → deconstriction (De-TAC) → reconstriction (Re-TAC) characterized by dynamic afterload while it exerts technical difficulty on operators and poses high mortality during perioperative period in mice. We aimed to introduce an optimized method for obtaining a hypertrophic preconditioning (O-HP) model for further study on cardiac hypertrophy.

METHODS

Ninety mice were divided into four groups: sham, TAC, C-HP, and O-HP. The sham group was exerted on three-time thoracotomies. The TAC group experienced twice thoracotomies and one TAC operation. C-HP and O-HP groups were given TAC, De-TAC, and Re-TAC operation at day 0, day 3, and day 7 in conventional and optimized method, respectively. We optimized the operating procedure in O-HP mice compared with the C-HP group by (1) leaving a ∼3-cm suture fixed in the subcutaneous layer after aortic constriction in TAC surgery (2) using two small forceps to untie the constriction knot instead of cutting it in the De-TAC operation. Ultrasound biomicroscopy was used for hemodynamics and cardiac function detection. Four weeks after the third surgery, all mice were sacrificed and pathology was analyzed among four groups.

RESULTS

Four weeks after Re-TAC, the survival of O-HP mice was 63.3% while that of C-HP was 26.7%. Ultrasound biomicroscopy showed a successful establishment of HP models. C-HP and O-HP mice had improved cardiac structure and function indicated by left ventricular end-systolic diameter, left ventricular end-systolic posterior wall thickness, left ventricular ejection fraction, and left ventricular fractional shortening than the TAC group. Pathological analysis showed O-HP as well as C-HP had less hypertrophy than the TAC mice.

CONCLUSIONS

Our results provide a rapid, safe, efficient, and reproducible method for optimized establishment of the HP model, which will facilitate studies for early intervention and prevention of left ventricular hypertrophy and heart failure.

Alpha-ketoglutarate ameliorates pressure overload-induced chronic cardiac dysfunction in mice

Increasing evidence indicates the involvement of myocardial oxidative injury and mitochondrial dysfunction in the pathophysiology of heart failure (HF). Alpha-ketoglutarate (AKG) is an intermediate metabolite of the tricarboxylic acid (TCA) cycle that participates in different cellular metabolic and regulatory pathways. The circulating concentration of AKG was found to decrease with ageing and is elevated after acute exercise and resistance exercise and in HF. Recent studies in experimental models have shown that dietary AKG reduces reactive oxygen species (ROS) production and systemic inflammatory cytokine levels, regulates metabolism, extends lifespan and delays the occurrence of age-related decline. However, the effects of AKG on HF remain unclear. In the present study, we explored the effects of AKG on left ventricular (LV) systolic function, the myocardial ROS content and mitophagy in mice with transverse aortic constriction (TAC). AKG supplementation inhibited pressure overload-induced myocardial hypertrophy and fibrosis and improved cardiac systolic dysfunction; in vitro, AKG decreased the Ang II-induced upregulation of β-MHC and ANP, reduced ROS production and cardiomyocyte apoptosis, and repaired Ang II-mediated injury to the mitochondrial membrane potential (MMP). These benefits of AKG in the TAC mice may have been obtained by enhanced mitophagy, which cleared damaged mitochondria. In summary, our study suggests that AKG improves myocardial hypertrophy remodelling, fibrosis and LV systolic dysfunction in the pressure-overloaded heart by promoting mitophagy to clear damaged mitochondria and reduce ROS production; thus, AKG may have therapeutic potential for HF.

The effect of Guanxin Shutong capsule on alleviating the myocardial fibrosis in heart failure rats

ETHNOPHARMACOLOGICAL RELEVANCE

Guanxin Shutong (GXST) capsule is a renowned traditional Chinese medicine widely used for the treatment of cardiovascular diseases in the clinic. However, no pharmacological experimental studies of GXST has been reported on the treatment of pressure overload-induced heart failure. This study aimed to investigate the effects of GXST capsule on ameliorating myocardial fibrosis conditions in pressure overload-induced heart failure rats.

MATERIAL AND METHODS

Rats were randomly divided into 6 groups: Normal group, Model group, GXST-treated group at a dose of 0.5 g/kg, 1 g/kg, 2 g/kg, respectively, and digoxin positive control group at a dose of 1 mg/kg. After 4 weeks of administration, cardiac function was evaluated by echocardiography. Cardiac injury and fibrotic conditions were evaluated by H&E staining, Masson staining, and Sirius Red staining. Myocardial fibrosis was evaluated by immunohistochemistry staining and Western blot.

RESULTS

GXST significantly inhibited cardiac fibrosis, reduced the excessive deposition of collagen, and finally improved cardiac function. GXST reversed ventricular remodeling might be through the TGF-β/Smad3 pathway.

CONCLUSION

GXST capsule demonstrated a strong anti-fibrosis effect in heart failure rats by inhibiting the TGF-β/Smad3 signaling pathway.

Schisandra chinensis polysaccharides prevent cardiac hypertrophy by dissociating thioredoxin-interacting protein/thioredoxin-1 complex and inhibiting oxidative stress

Cardiac hypertrophy is a current, major, global health challenge. Oxidative stress is an important mechanism that contributes to the pathogenesis of cardiac hypertrophy. Schisandra chinensis polysaccharides (SCP), the primary active constituent in Schisandra chinensis, have antioxidative properties. Here, we investigated the role played by SCP in a cardiac hypertrophy model mouse induced by transverse aortic constriction (TAC). We found that SCP treatment improved cardiac function by inhibiting myocardial hypertrophy and oxidative stress. Angiotensin II was used to induce cardiomyocyte hypertrophy and oxidative stress in vitro. We discovered that the antioxidant effects of SCP were mediated through the regulation of the thioredoxin-interacting protein (TXNIP)/Thioredoxin-1 (Trx-1) pathway. Using molecular docking, we found that SCP binds to Arg207, Ser169, Lys166, Lys286 and Ser285 in TXNIP through hydrogen bonds. TXNIP is an endogenous inhibitor of Trx-1, and the binding SCP with TXNIP may restrict or interfere with the binding between TXNIP and Trx-1, resulting in Trx-1 activation. In conclusion, our findings demonstrated that the potential use of SCP as a TXNIP inhibitor to attenuate oxidative stress, suggesting that TXNIP might represent a potential therapeutic target for the treatment of cardiac hypertrophy.

A multiscale model of cardiac concentric hypertrophy incorporating both mechanical and hormonal drivers of growth

Growth and remodeling in the heart is driven by a combination of mechanical and hormonal signals that produce different patterns of growth in response to exercise, pregnancy, and various pathologies. In particular, increases in afterload lead to concentric hypertrophy, a thickening of the walls that increases the contractile ability of the heart while reducing wall stress. In the current study, we constructed a multiscale model of cardiac hypertrophy that connects a finite-element model representing the mechanics of the growing left ventricle to a cell-level network model of hypertrophic signaling pathways that accounts for changes in both mechanics and hormones. We first tuned our model to capture published in vivo growth trends for isoproterenol infusion, which stimulates β-adrenergic signaling pathways without altering mechanics, and for transverse aortic constriction (TAC), which involves both elevated mechanics and altered hormone levels. We then predicted the attenuation of TAC-induced hypertrophy by two distinct genetic interventions (transgenic Gq-coupled receptor inhibitor overexpression and norepinephrine knock-out) and by two pharmacologic interventions (angiotensin receptor blocker losartan and β-blocker propranolol) and compared our predictions to published in vivo data for each intervention. Our multiscale model captured the experimental data trends reasonably well for all conditions simulated. We also found that when prescribing realistic changes in mechanics and hormones associated with TAC, the hormonal inputs were responsible for the majority of the growth predicted by the multiscale model and were necessary in order to capture the effect of the interventions for TAC.

Angiotensin II Increases HMGB1 Expression in the Myocardium Through AT1 and AT2 Receptors When Under Pressure Overload

High-mobility group box 1 (HMGB1) is increased in the myocardium under pressure overload (PO) and is involved in PO-induced cardiac remodeling. The mechanisms of the upregulation of cardiac HMGB1 expression have not been fully elucidated. In the present study, a mouse transverse aortic constriction (TAC) model was used, and an angiotensin II (Ang II) type 1 (AT1) receptor inhibitor (losartan) or Ang II type 2 (AT2) receptor inhibitor (PD123319) was administrated to mice for 14 days. Cardiac myocytes were cultured and treated with Ang II for 5 minutes to 48 hours conditionally with the blockage of the AT1 or AT2 receptor. TAC-induced cardiac hypertrophy was observed at 14 days after the operation, which was partially reversed by losartan, but not by PD123319. Similarly, the upregulated HMGB1 expression levels observed in both the serum and myocardium induced by TAC were reduced by losartan. Elevated cardiac HMGB1 protein levels, but not mRNA or serum levels, were significantly decreased by PD123319. Furthermore, HMGB1 expression levels in culture media and cardiac myocytes were increased following Ang II treatment in vitro, positively associated with the duration of treatment. Similarly, Ang II-induced upregulation of HMGB1 in vitro was inhibited by both losartan and PD123319. These results suggest that upregulation of HMGB1 in serum and myocardium under PO, which are partially derived from cardiac myocytes, may be induced by Ang II via the AT1 and AT2 receptors. Additionally, amelioration of PO-induced cardiac hypertrophy following losartan treatment may be associated with the reduction of HMGB1 expression through the AT1 receptor.

Protective role of ErbB3 signaling in myeloid cells during adaptation to cardiac pressure overload

BACKGROUND

Myeloid cells play an important role in a wide variety of cardiovascular disorders, including both ischemic and non-ischemic cardiomyopathies. Neuregulin-1 (NRG-1)/ErbB signaling has recently emerged as an important factor contributing to the control of inflammatory activation of myeloid cells after an ischemic injury. However, the role of ErbB signaling in myeloid cells in non-ischemic cardiomyopathy is not fully understood. This study investigated the role of ErbB3 receptors in the regulation of early adaptive response using a mouse model of transverse aortic constriction (TAC) for non-ischemic cardiomyopathy.

METHODS AND RESULTS

TAC surgery was performed in groups of age- and sex-matched myeloid cell-specific ErbB3-deficient mice (ErbB3^MyeKO) and control animals (ErbB3^MyeWT). The number of cardiac CD45 immune cells, CD11b myeloid cells, Ly6G neutrophils, and Ly6C monocytes was determined using flow cytometric analysis. Five days after TAC, survival was dramatically reduced in male but not female ErbB3^MyeKO mice or control animals. The examination of lung weight to body weight ratio suggested that acute pulmonary edema was present in ErbB3^MyeKO male mice after TAC. To determine the cellular and molecular mechanisms involved in the increased mortality in ErbB3^MyeKO male mice, cardiac cell populations were examined at day 3 post-TAC using flow cytometry. Myeloid cells accumulated in control but not in ErbB3^MyeKO male mouse hearts. This was accompanied by increased proliferation of Sca-1 positive non-immune cells (endothelial cells and fibroblasts) in control but not ErbB3^MyeKO male mice. No significant differences in intramyocardial accumulation of myeloid cells or proliferation of Sca-1 cells were found between the groups of ErbB3^MyeKO and ErbB3^MyeWT female mice. An antibody-based protein array analysis revealed that IGF-1 expression was significantly downregulated only in ErbB3^MyeKO mice hearts compared to control animals after TAC.

CONCLUSION

Our data demonstrate the crucial role of myeloid cell-specific ErbB3 signaling in the cardiac accumulation of myeloid cells, which contributes to the activation of cardiac endothelial cells and fibroblasts and development of an early adaptive response to cardiac pressure overload in male mice.

Experimental model of congestive heart failure induced by transverse aortic constriction in BALB/c mice

INTRODUCTION

Murine transverse aortic constriction (TAC) is a frequently used model of pressure overload-induced left ventricular (LV) remodeling. However, there is considerable variability in disease progression to overt heart failure (HF) development in the most commonly used strain of mice (i.e., C57BL/6J). Studies have shown that C57BL/6J mice are more resistant than BALB/c mice to congestive HF development following myocardial infarction or angiotensin II-induced hypertension. Therefore, we tested the hypothesis that BALB/c mice may be a better research model to study TAC-induced progressive HF.

METHODS

Following sham or TAC surgery in both C57BL/6J (n = 29) and BALB/c (n = 32) mice, we evaluated cardiac dimensions and function by echocardiography at 2, 4, 8, and 12 weeks and monitored survival throughout the study. In a separate cohort of BALB/c mice, we repeated the study in the presence of the angiotensin converting enzyme inhibitor enalapril or a vehicle initiated 2 weeks post-TAC and administered for 6 weeks. At the end of the studies, we assessed the heart weight, lung weight, and plasma brain natriuretic peptide (BNP) concentration.

RESULTS

Following comparable TAC, both C57BL/6J and BALB/c mice showed significant LV remodeling compared with the sham control mice. BALB/c mice progressively developed systolic dysfunction, LV dilation, lung congestion, and significant mortality, whereas C57BL/6J mice did not. In the separate cohort of BALB/c TAC mice, enalapril significantly reduced the heart weight, lung weight, and plasma BNP concentration and improved survival compared with the vehicle control.

DISCUSSION

BALB/c mice uniformly developed congestive HF post-TAC. Enalapril was effective in improving survival and reducing lung congestion in this model. The data suggest that BALB/c mice may be a better research tool than C57BL/6J mice to study TAC-induced disease progression to HF and to evaluate novel therapies for the treatment of chronic HF with reduced ejection fraction.

Role of Exercise on Alleviating Pressure Overload-Induced Left Ventricular Dysfunction and Remodeling via AMPK-Dependent Autophagy Activation

Cardiac hypertrophy is one of the significant risk factors that result in maladaptive cardiac remodeling and heart failure, and exercise is known to exert cardioprotection. In this research, the cardioprotective function and exercise mechanisms were explored.The rats underwent transverse aortic constriction (TAC) or a sham operation. The rats that received TAC were randomly assigned to five groups: (1) rats subjected to a sham operation as control group (SC), (2) rats that underwent TAC group (TC), (3) TAC and moderate-intensity exercise group (TE), (4) TE plus 3-MA group (TEM), and (5) TE plus Compound C group (TEC). The heart function was measured via echocardiography. Histological analysis and relative protein testing were conducted to analyze collagen deposition and apoptosis. Furthermore, western blot was employed to measure the protein expression of relevant signaling pathways. Impaired cardiac function, interstitial fibrosis, enhanced apoptosis, and ER stress were observed in the TAC-induced left ventricular hypertrophy. Exercise attenuated TAC-induced cardiac dysfunction, interstitial fibrosis, and ER stress-related apoptosis. In addition, exercise significantly improved autophagy and upregulated AMPK phosphorylation. Furthermore, AMPK inhibitor Compound C repressed the activation of AMPK, and autophagy inhibitor 3-methyladenine reversed exercise-induced autophagy. All of these abolished the protection of exercise against cardiac dysfunction and fibrosis induced by TAC.Our results indicated that 4 weeks of treadmill exercise could alleviate pressure overload-induced LV dysfunction and remodeling via an autophagy-dependent mechanism, which was induced by enhancing autophagy through the activation of AMPK.

Dec1 deficiency protects the heart from fibrosis, inflammation, and myocardial cell apoptosis in a mouse model of cardiac hypertrophy

Cardiac inflammation and fibrosis triggered by left ventricular pressure overload are the major causes of heart dysfunction. Differentiated embryonic chondrocyte gene 1 (Dec1) is a basic helix-loop-helix transcription factor that is comprehensively involved in inflammation and tissue fibrosis, but its role in cardiac hypertrophy remains unclear. This study explored the effects of Dec1 on cardiac fibrosis, inflammation, and apoptosis in hypertrophic conditions. Transverse aortic constriction (TAC) was performed to induce cardiac hypertrophy in wild-type (WT) mice and in Dec1 knock out (KO) mice for 4 weeks. Using the TAC mouse model, prominent differences in cardiac hypertrophy at the morphological, functional, and molecular levels were delineated by Masson's Trichrome and TUNEL staining, immunohistochemistry, RT-PCR and Western Blot. DNA microarray and microRNA (miRNA) array analyses were carried out to identify gene and miRNA expression patterns. Dec1KO mice exhibited a more severe hypertrophic heart, whereas WT mice showed a more pronounced perivascular fibrosis after TAC at 4 weeks. The Dec1 deficiency promoted M2 phenotype macrophages. Dec1KO TAC mice showed fewer apoptotic cells than WT TAC mice. APEX1, WNT16, FGF10 and MMP-10 were differentially expressed according to DNA microarray analysis and expression levels of those genes and the corresponding miRNAs (miR-295, miR-200 b, miR-130a, miR-92a) showed the same trends. Furthermore, luciferase reporter assay confirmed that FGF10 is the direct target gene of miR-130. In conclusion, a Dec1 deficiency protects the heart from perivascular fibrosis, regulates M1/M2 macrophage polarization and reduces cell apoptosis, which may provide a novel insight for the treatment of cardiac hypertrophy.

Tripartite motif 10 regulates cardiac hypertrophy by targeting the PTEN/AKT pathway

The pathogenesis of cardiac hypertrophy is tightly associated with activation of intracellular hypertrophic signalling pathways, which leads to the synthesis of various proteins. Tripartite motif 10 (TRIM10) is an E3 ligase with important functions in protein quality control. However, its role in cardiac hypertrophy was unclear. In this study, neonatal rat cardiomyocytes (NRCMs) and TRIM10-knockout mice were subjected to phenylephrine (PE) stimulation or transverse aortic constriction (TAC) to induce cardiac hypertrophy in vitro and in vivo, respectively. Trim10 expression was significantly increased in hypertrophied murine hearts and PE-stimulated NRCMs. Knockdown of TRIM10 in NRCMs alleviated PE-induced changes in the size of cardiomyocytes and hypertrophy gene expression, whereas TRIM10 overexpression aggravated these changes. These results were further verified in TRIM10-knockout mice. Mechanistically, we found that TRIM10 knockout or knockdown decreased AKT phosphorylation. Furthermore, we found that TRIM10 knockout or knockdown increased ubiquitination of phosphatase and tensin homolog (PTEN), which negatively regulated AKT activation. The results of this study reveal the involvement of TRIM10 in pathological cardiac hypertrophy, which may occur by prompting of PTEN ubiquitination and subsequent activation of AKT signalling. Therefore, TRIM10 may be a promising target for treatment of cardiac hypertrophy.

The urotensin II receptor antagonist DS37001789 ameliorates mortality in pressure-overload mice with heart failure

This study was designed to evaluate the effects of DS37001789, a novel and highly potent urotensin II (U-II) receptor (GPR14) antagonist, against mortality, hypertrophy, and cardiac dysfunction in pressure-overload hypertrophy by transverse aortic constriction (TAC) in mice. In addition, we analyzed the phenotype of GPR14 knockout (KO) mice after TAC induction to confirm the contribution of the U-II/GPR14 system. The oral administration of 0.2% DS37001789 to TAC mice for 12 weeks significantly ameliorated the mortality rate and 0.2% DS37001789 for 4 weeks significantly improved cardiac function by pressure-volume analysis. GPR14 expression was significantly upregulated in the left ventricle in the TAC mice treated with 0.2% DS37001789. Moreover, we confirmed that the significant amelioration of mortality was accomplished by the inhibition of cardiac enlargement and the improvement of cardiac function in GPR14 KO mice after TAC surgery. These results suggest that the U-II/GPR14 system contributes to the progression of heart failure and its blockade ameliorates the mortality via improved cardiac function. The U-II/GPR14 system may thus be an attractive target for treating heart failure with pathological cardiac hypertrophy and DS37001789 may be a novel therapeutic agent for heart failure in patients with pressure-overload conditions such as hypertension and aortic valve stenosis.

Taurine protects against cardiac dysfunction induced by pressure overload through SIRT1-p53 activation

BACKGROUND

Heart failure (HF) is an epidemic disease with increased incidence annually. It has been reported that taurine can improve cardiac function. This study investigated the cardioprotective effects of taurine in pressure-loaded HF mice and elucidated the possible mechanism.

METHODS

HF models were established by transverse aortic constriction (TAC). Animals were treated with either taurine for 9 weeks and/or the SIRT1 inhibitor EX527 (5 mg/kg/day, every 2days) after TAC operation. Cardiac function and geometry were revealed by echocardiography. Myocardial hypertrophy and fibrosis were assessed using Fluorescent wheat germ agglutinin (WGA) staining and Masson's trichrome staining. Western blot and RT-PCR were performed to elucidate the expression of target proteins and genes respectively. Apoptosis in cardiomyocytes was detected by TUNEL staining. Myocardial oxidative stress was assessed by detecting the concentration of myocardial super oxidative dismutase (SOD) and malonyldialdehyde (MDA) and reactive oxygen species (ROS). Taurine concentrations and NAD⁺/NADH ratio were determined by taurine and NAD⁺/NADH assay kit.

RESULTS

Taurine notably relieved cardiac dysfunction after TAC. The mechanisms were attributed to reduced myocyte hypertrophy and fibrosis, and alleviated apoptosis and oxidative stress. Meanwhile, taurine increased NAD+/NADH ratio，promoted the expression of SIRT1 and suppressed p53 acetylation. However, EX-527(inhibitor of SIRT1) decreased NAD⁺/NADH ratio and increased acetyl-p53 levels, and abolished the cardioprotective effects of taurine on mice subjected to TAC and increased apoptosis and oxidative stress.

CONCLUSION

The mechanism responsible for cardiac-protective effects of taurine in HF induced by pressure overload is associated with the activation of the SIRT1-p53 pathway.

Fendrr involves in the pathogenesis of cardiac fibrosis via regulating miR-106b/SMAD3 axis

Cardiovascular diseases (CVDs) is the first cause of death worldwide, generally exhibiting a high morbidity, high disability rate and high mortality especially in the elderly persons (>50 years old). Previously, extensive studies have demonstrated that cardiac fibrosis plays cardinal roles in the pathogenesis of CVDs. However, due to the unclear underlying mechanisms of cardiac fibrosis, its clinical intervention remains very lacking. Long non-coding RNAs (lncRNAs), a class of non-coding RNA but differing from microRNAs, are generally considered as transcripts with a length ranging 200 to 100 nucleotides. Recently, accumulating evidence showed that lncRNAs involve in the pathogenesis of cardiac fibrosis. Fendrr (FOXF1 adjacent non-coding developmental regulatory RNA), is a spliced long non-coding RNA transcribed bi-directionally with FOXF1 on the opposite strand. Fendrr has been demonstrated to be essential for normal development of the heart and body wall in mouse, and shows a good anti-fibrotic activity in pulmonary fibrosis. In this study, we aimed to explore the effects of Fendrr on cardiac fibrosis. Intriguingly, we first observed that lncRNA Fendrr was up-regulated in the heart tissues of transverse aortic constriction (TAC) induced cardiac fibrosis mouse models, determined by RT-QPCR. Loss-function of Fendrr significantly alleviated the cardiac fibrosis phenotypes induced by TAC, indicating that Fendrr is required for the pathogenesis of cardiac fibrosis. In mechanism, we demonstrated experimentally that Fendrr directly targeting miR-106b, by which the lncRNA promotes cardiac fibrosis (indicated by the elevation of Col1a1, Col3a1, CTGF and ACTA2 expression) in a miR-106b mediated manner. Collectively, our findings highlight the axis of Fendrr/miR-106b/Samd3 in the pathogenesis of cardiac fibrosis, which may be a promising target for clinical intervention target of cardiac fibrosis.

Ferulic acid increases intestinal Lactobacillus and improves cardiac function in TAC mice

Ferulic acid, a main ingredient of Ligusticum, exhibits anti-oxidant and anti-inflammation effects in heart diseases. Some studies indicate that gut microbiome is associated with the generation of ferulic acid. Whether the beneficial effect of ferulic is raised by the alteration of gut microbiota is still unknown. This study examined the effect of sodium ferulate on gut microbiome and cardiac function in TAC mice. Cell Counting Kit-8 (CCK8) assay verified that ferulic acid has low toxicity in vitro and that ferulic acid inhibited the up-regulation of β-MHC and ANP induced by Angiotensin II. In addition, daily supplement of 50 mg/kg sodium ferulate improved the ejection fraction and changed the gut microbiota composition of TAC mice. Relative abundance of Lactobacillus and Parabacteroides are increased in TAC mice gavaged with sodium ferulate. In addition, Lactobacillus is negatively correlated with HW/BW and LW/BW ratio. These results suggest that the beneficial effect of ferulic in TAC mice is probably through the regulation of gut microbiota.

Impaired branched chain amino acid oxidation contributes to cardiac insulin resistance in heart failure

BACKGROUND

Branched chain amino acids (BCAA) can impair insulin signaling, and cardiac insulin resistance can occur in the failing heart. We, therefore, determined if cardiac BCAA accumulation occurs in patients with dilated cardiomyopathy (DCM), due to an impaired catabolism of BCAA, and if stimulating cardiac BCAA oxidation can improve cardiac function in mice with heart failure.

METHOD

For human cohorts of DCM and control, both male and female patients of ages between 22 and 66 years were recruited with informed consent from University of Alberta hospital. Left ventricular biopsies were obtained at the time of transplantation. Control biopsies were obtained from non-transplanted donor hearts without heart disease history. To determine if stimulating BCAA catabolism could lessen the severity of heart failure, C57BL/6J mice subjected to a transverse aortic constriction (TAC) were treated between 1 to 4-week post-surgery with either vehicle or a stimulator of BCAA oxidation (BT2, 40 mg/kg/day).

RESULT

Echocardiographic data showed a reduction in ejection fraction (54.3 ± 2.3 to 22.3 ± 2.2%) and an enhanced formation of cardiac fibrosis in DCM patients when compared to the control patients. Cardiac BCAA levels were dramatically elevated in left ventricular samples of patients with DCM. Hearts from DCM patients showed a blunted insulin signalling pathway, as indicated by an increase in P-IRS1ser636/639 and its upstream modulator P-p70S6K, but a decrease in its downstream modulators P-AKT ser473 and in P-GSK3β ser9. Cardiac BCAA oxidation in isolated working hearts was significantly enhanced by BT2, compared to vehicle, following either acute or chronic treatment. Treatment of TAC mice with BT2 significantly improved cardiac function in both sham and TAC mice (63.0 ± 1.8 and 56.9 ± 3.8% ejection fraction respectively). Furthermore, P-BCKDH and BCKDK expression was significantly decreased in the BT2 treated groups.

CONCLUSION

We conclude that impaired cardiac BCAA catabolism and insulin signaling occur in human heart failure, while enhancing BCAA oxidation can improve cardiac function in the failing mouse heart.

Systolic hypertension-induced neurovascular unit disruption magnifies vascular cognitive impairment in middle-age atherosclerotic LDLr-/-:hApoB+/+ mice

Cognitive functions are dependent upon intercommunications between the cellular components of the neurovascular unit (NVU). Vascular risk factors are associated with a more rapid rate of cognitive decline with aging and cerebrovascular diseases magnify both the incidence and the rate of cognitive decline. The causal relationship between vascular risk factors and injury to the NVU is, however, lacking. We hypothesized that vascular risk factors, such as hypertension and dyslipidemia, promote disruption of the NVU leading to early cognitive impairment. We compared brain structure and cerebrovascular functions of 1-year old (middle-aged) male wild-type (WT) and atherosclerotic hypertensive (LDLr^-/-:hApoB^+/+, ATX) mice. In addition, mice were subjected, or not, to a transverse aortic constriction (TAC) for 6 weeks to assess the acute impact of an increase in systolic blood pressure on the NVU and cognitive functions. Compared with WT mice, ATX mice prematurely developed cognitive decline associated with cerebral micro-hemorrhages, loss of microvessel density and brain atrophy, cerebral endothelial cell senescence and dysfunction, brain inflammation, and oxidative stress associated with blood-brain barrier leakage and brain hypoperfusion. These data suggest functional disturbances in both vascular and parenchymal components of the NVU. Exposure to TAC-induced systolic hypertension promoted cerebrovascular damage and cognitive decline in WT mice, similar to those observed in sham-operated ATX mice; TAC exacerbated the existing cerebrovascular dysfunctions and cognitive failure in ATX mice. Thus, a hemodynamic stress such as systolic hypertension could initiate the cascade involving cerebrovascular injury and NVU deregulation and lead to cognitive decline, a process accelerated in atherosclerotic mice.

Captopril attenuates TAC-induced heart failure via inhibiting Wnt3a/β-catenin and Jak2/Stat3 pathways

Captopril (Cap) as angiotensin-converting enzyme inhibitor (ACEi) is commonly used to treat hypertension and some types of congestive heart failure. However, few studies reported on whether Cap exerts a protective effect on myocardial apoptosis induced by transverse aortic constriction (TAC). This study aimed at investigating the possible mechanism of Cap on myocardial apoptosis induced by pressure overload. Results showed that Cap significantly decreased heart-to-body weight ratios (HBWR). Cap markedly improved cardiac function, and reduced inner diameter of ascending aorta (Asc Ao) in TAC mice as shown by echocardiography. Enzyme-linked immunosorbent assay (ELISA) results demonstrated that Cap treatment also markedly decreased the level of N-terminal pro-B-type natriuretic peptide (NT-proBNP), atrial natriuretic peptide (ANP), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Cardiac pathological changes and fibrosis have been improved after Cap treatment as shown by hematoxylin-eosin (H&E) staining and Masson's trichrome staining. Moreover, Terminal deoxynucleotidyl transferase-mediated dexoxyuridine triphosphate nick-end labeling (TUNEL) staining result indicated Cap treatment also significantly inhibited cardiac apoptosis. Western Blot results showed that Cap obviously decreased the expression of cleaved capase-3, Bax, phosphorylated Jak2 (p-Jak2), phosphorylated Stat3 (p-Stat3), Wnt3a and β-catenin proteins, as well as increased Bcl-2 expression. In conclusion, Cap showed a protective effect on TAC-induced cardiac apoptosis, which could be attributed to the inhibition of Wnt3a/β-catenin signaling pathway. Cap also attenuated myocardial hypertrophy induced by TAC via suppression of Jak2/Stat3 pathway.

Pressure Overload Impairs Cardiac Function in Long-Chain Fatty Acid Transporter CD36-Knockout Mice

CD36 is one of the important transporters of long-chain fatty acids (LCFAs) in the myocardium. We previously reported that CD36-deficient patients demonstrate a marked reduction of myocardial uptake of LCFA, while myocardial glucose uptake shows a compensatory increase, and are often accompanied by cardiomyopathy. However, the molecular mechanisms and functional role of CD36 in the myocardium remain unknown.The current study aimed to explore the pathophysiological role of CD36 in the heart. Methods: Using wild type (WT) and knockout (KO) mice, we generated pressure overload by transverse aortic constriction (TAC) and analyzed cardiac functions by echocardiography. To assess cardiac hypertrophy and fibrosis, histological and molecular analyses and measurement of ATP concentration in mouse hearts were performed.By applying TAC, the survival rate was significantly lower in KO than that in WT mice. After TAC, KO mice showed significantly higher heart weight-to-tibial length ratio and larger cross-sectional area of cardiomyocytes than those of WT. Although left ventricular (LV) wall thickness in the KO mice was similar to that in the WT mice, the KO mice showed a significant enlargement of LV cavity and reduced LV fractional shortening compared to the WT mice with TAC. A tendency for decreased myocardial ATP concentration was observed in the KO mice compared to the WT mice after TAC operation.These data suggest that the LCFA transporter CD36 is required for the maintenance of energy provision, systolic function, and myocardial structure.

Focal selective chemo-ablation of spinal cardiac afferent nerve by resiniferatoxin protects the heart from pressure overload-induced hypertrophy

Resiniferatoxin (RTX), a selective transient receptor potential vanilloid 1 (TRPV1) receptor agonist, can eliminate TRPV1+ primary sensory afferents and blunt cardiac sympathetic afferent reflex for a relatively long period. The present study determined the effects of intrathecal RTX administration on transverse aortic constriction (TAC)-induced cardiac dysfunction and cardiac remodeling in rats. Five days before TAC, RTX (2 μg/10 μl) was injected intrathecally into the T2/T3 interspace of rats. Cardiac sympathetic nerve activities (CSNAs) and cardiac structure and function were determined eight weeks after TAC. Intrathecal RTX administration abolished TRPV1 expression in the dorsal horn and reduced over-activated CSNA in the TAC rat model. Hemodynamic analysis revealed that RTX reduced left ventricular end-diastolic pressure, indicating the improvement of cardiac compliance. Histologic analysis, real-time reverse transcription-polymerase chain reaction, and Western blots showed that RTX prevented TAC-induced cardiac hypertrophy, cardiac fibrosis, and cardiac apoptosis and reduced the expression of apoptotic proteins and myocardial mRNAs. In conclusion, these results demonstrate that focal chemo-ablation of TRPV1+ afferents in the spinal cord protects the heart from pressure overload-induced cardiac remodeling and cardiac dysfunction, which suggest a novel promising therapeutic method for cardiac hypertrophy and diastolic dysfunction.

Irisin alleviates pressure overload-induced cardiac hypertrophy by inducing protective autophagy via mTOR-independent activation of the AMPK-ULK1 pathway

In hypertrophic hearts, autophagic flux insufficiency is recognized as a key pathology leading to maladaptive cardiac remodeling and heart failure. This study aimed to illuminate the cardioprotective role and mechanisms of a new myokine and adipokine, irisin, in cardiac hypertrophy and remodeling. Adult male wild-type, mouse-FNDC5 (irisin-precursor)-knockout and FNDC5 transgenic mice received 4 weeks of transverse aortic constriction (TAC) alone or combined with intraperitoneal injection of chloroquine diphosphate (CQ). Endogenous FNDC5 ablation aggravated and exogenous FNDC5 overexpression attenuated the TAC-induced hypertrophic damage in the heart, which was comparable to the protection of irisin against cardiomyocyte hypertrophy induced by angiotensin II (Ang II) or phenylephrine (PE). Accumulated autophagosome and impaired autophagy flux occurred in the TAC-treated myocardium and Ang II- or PE-insulted cardiomyocytes. Irisin deficiency caused reduced autophagy and aggravated autophagy flux failure, whereas irisin overexpression or supplementation induced protective autophagy and improved autophagy flux, which were reversed by autophagy inhibitors Atg5 siRNA, 3-MA and CQ. Irisin boosted the activity of only AMPK but not Akt and MAPK family members in hypertrophic hearts and cultured cardiomyocytes and further activated ULK1 at Ser555 but not Ser757 and did not affect the mTOR-S6K axis. Blockage of AMPK and ULK1 with compund C and SBI-0206965, respectively, both abrogated irisin's protection against cardiomyocyte hypertrophic injury and reversed its induction of both autophagy and autophagy flux. Our results suggest that irisin protects against pressure overload-induced cardiac hypertrophy by inducing protective autophagy and autophagy flux via activating AMPK-ULK1 signaling.

Mitochondrial calcium uniporter inhibition provides cardioprotection in pressure overload-induced heart failure through autophagy enhancement

BACKGROUND

HF incurs high disease burden, and the effectiveness of known HF treatments is unsatisfactory. Therefore, seeking novel therapeutic target of HF is important. The present study aimed to investigate the role of the mitochondrial calcium uniporter (MCU) and its relationship with autophagy in overload-induced heart failure (HF).

METHODS AND RESULTS

In both early-stage and end-stage of pressure overload-induced HF, MCU appeared up-regulated along with heart enlargement, increased microtubule-associated proteins 1A/1B light chain 3B (LC3B) II/I ratio and autophagosome content, damaged cardiac function, and ventricular asynchrony. However, sequestosome-1 (SQSTM1/p62) level decreased indicating blockaded autophagic flux. Seven-week administration of MCU inhibitor ruthenium red improved cardiac function and mitigated its pathological change. MCU inhibition maintained mitochondrial integrity, increased LC3B II/I ratio, up-regulated Parkin and Pink1, and down-regulated SQSTM1/p62. MCU inhibition also alleviated ventricular asynchrony of HF, and this might be related to connexin-43 up-regulation. In vitro study validated intervention on MCU leading to elevation of autophagy and mitophagy. MCU inhibition could partly prevent from excessive cellular enlargement induced by isoprenaline.

CONCLUSIONS

In summary, MCU inhibition played an important role in pressure overload-induced heart failure through autophagy and mitophagy enhancement, and intervention on MCU offered cardioprotective effects. To our knowledge, the role of MCU in HF and its relationship with autophagy and mitophagy are firstly disclosed. Moreover, our study suggests that MCU inhibition could be explored as a novel therapeutic concept in HF.

Role of heat shock transcription factor 1(HSF1)-upregulated macrophage in ameliorating pressure overload-induced heart failure in mice

In order to explore the role of macrophages in HSF1-mediated alleviation of heart failure, mice model of pressure overload-induced heart failure was established using transverse aortic constriction (TAC). Changes in cardiac function and morphology were studied in TAC and SHAM groups using ultrasonic device, tissue staining, electron microscopy, real-time quantitative polymerase chain reaction (RT-QPCR), and Western blotting. We found that mice in the TAC group showed evidence of impaired cardiac function and aggravation of fibrosis on ultrasonic and histopathological examination when compared to those in the SHAM group. The expressions of HSF1, LC3II/LC3I, Becline-1 and HIF-1, as well as autophagosome formation in TAC group were greater than that in SHAM group. On sub-group analyses in the TAC group, improved cardiac function and alleviation of fibrosis was observed in the HSF1 TG subgroup as compared to that in the wild type subgroup. Expressions of LC3II/LC3I, Becline-1 and HIF-1, too showed an obvious increase; and increased autophagosome formation was observed on electron microscopy. Opposite results were observed in the HSF1 KO subgroup. These results collectively suggest that in the pressure overload heart failure model, HSF1 promoted formation of macrophages by inducing upregulation of HIF-1 expression, through which heart failure was ameliorated.

Conventional Method of Transverse Aortic Constriction in Mice

Transverse aortic constriction is a widely used surgical model to reflect the progression from cardiac hypertrophy to heart failure states due to left ventricular pressure overload in mice. It produces afterload increase on the left ventricle in which compensated hypertrophy initially occurs in the first 2 weeks. This develops into maladaptive remodeling of the left ventricle and atrium, leading to heart failure. This model is useful for cardiac studies since transverse aortic constriction can be consistently replicated and has low surgical mortality. Additionally, the gradual progression to cardiac failure makes it a valuable method to evaluate the efficacy of potential therapeutic intervention. We introduce this chapter to offer practical approaches to facilitate a simple methodology for transverse aortic constriction.

Gene expression analysis to identify mechanisms underlying heart failure susceptibility in mice and humans

Genetic factors are known to modulate cardiac susceptibility to ventricular hypertrophy and failure. To determine how strain influences the transcriptional response to pressure overload-induced heart failure (HF) and which of these changes accurately reflect the human disease, we analyzed the myocardial transcriptional profile of mouse strains with high (C57BL/6J) and low (129S1/SvImJ) susceptibility for HF development, which we compared to that of human failing hearts. Following transverse aortic constriction (TAC), C57BL/6J mice developed overt HF while 129S1/SvImJ did not. Despite a milder aortic constriction, impairment of ejection fraction and ventricular remodeling (dilation, fibrosis) was more pronounced in C57BL/6J mice. Similarly, changes in myocardial gene expression were more robust in C57BL/6J (461 genes) compared to 129S1/SvImJ mice (71 genes). When comparing these patterns to human dilated cardiomyopathy (1344 genes), C57BL/6J mice tightly grouped to human hearts. Overlay and bioinformatic analysis of the transcriptional profiles of C57BL/6J mice and human failing hearts identified six co-regulated genes (POSTN, CTGF, FN1, LOX, NOX4, TGFB2) with established link to HF development. Pathway enrichment analysis identified angiotensin and IGF-1 signaling as most enriched putative upstream regulator and pathway, respectively, shared between TAC-induced HF in C57BL/6J mice and in human failing hearts. TAC-induced heart failure in C57BL/6J mice more closely reflects the gene expression pattern of human dilated cardiomyopathy compared to 129S1/SvImJ mice. Unbiased as well as targeted gene expression and pathway analyses identified periostin, angiotensin signaling, and IGF-1 signaling as potential causes of increased HF susceptibility in C57BL/6J mice and as potentially useful drug targets for HF treatment.

SS31 therapy effectively protects the heart against transverse aortic constriction-induced hypertrophic cardiomyopathy damage

This study tested the hypothesis that SS31 therapy could effectively protect the heart against transverse aortic constriction (TAC)-induced hypertrophic cardiomyopathy (HCM) damage. Adult-male B6 mice (n=36) were equally divided into sham-operated control (group 1), TAC only (group 2) and TAC+SS31 (group) (2.0 mg/kg/day by intra-peritoneal administration from day 28 after TAC induction) and euthanized by day 60. In vitro results showed that SS31 markedly suppressed angiotensin-II induced protein expressions of BNP/β-MHC, ATM, p-P38 and P53 and ATP damage in H9C2 cells, and protein expression of pro-collagen-I/CTGF in fibroblasts (all P<0.001). By day 60, left ventricular ejection fraction (LVEF) and sarcomere length were significantly lower in group 2 than groups 1 and 3, and significantly lower in group 3 than in group 1, whereas the LEVDd/LVESd and ratio of heart weight to tibial length showed an opposite pattern to LVEF (all P<0.0001). Microscopic findings of numbers of apoptotic nuclei, inflammatory (CD14+, F4/80+) and oxidative-stress (H2DCFDA+) biomarkers, disorganized score of endocardium, and fibrotic and collagen-deposition areas showed an opposite pattern to LVEF among the three groups (all P<0.0001). The protein expressions of inflammatory (PDGF/TNF-α/NF-κB/COX-2), oxidative-stress (NOX-1/NOX-2/oxidized protein), fibrotic (TGF-β/Smad3) apoptotic (cleaved-caspase-3/cleaved-PARP), pressure/volume overload (BNP/β-MHC), CTGF, mitochondrial-damaged (cytosolic cytochrome-C), p-ERK1/2, p-Akt and PI3K signaling showed an opposite pattern to LVEF among the three groups (all P<0.001). The protein expression of anti-oxidants (HO-1/Nrf2) were significantly progressively increased in groups 1 to 3 (all P<0.001). In conclusion, SS31 therapy effectively protected the heart against TAC-induced damage.

Gallic acid attenuates pulmonary fibrosis in a mouse model of transverse aortic contraction-induced heart failure

Gallic acid, a trihydroxybenzoic acid found in tea and other plants, attenuates cardiac hypertrophy, fibrosis, and hypertension in animal models. However, the role of gallic acid in heart failure remains unknown. In this study, we show that gallic acid administration prevents heart failure-induced pulmonary fibrosis. Heart failure induced in mice, 8weeks after transverse aortic constriction (TAC) surgery, was confirmed by echocardiography. Treatment for 2weeks with gallic acid but not furosemide prevented cardiac dysfunction in mice. Gallic acid significantly inhibited TAC-induced pathological changes in the lungs, such as increased lung mass, pulmonary fibrosis, and damaged alveolar morphology. It also decreased the expression of fibrosis-related genes, including collagen types I and III, fibronectin, connective tissue growth factor (CTGF), and phosphorylated Smad3. Further, it inhibited the expression of epithelial-mesenchymal transition (EMT)-related genes, such as N-cadherin, vimentin, E-cadherin, SNAI1, and TWIST1. We suggest that gallic acid has therapeutic potential for the treatment of heart failure-induced pulmonary fibrosis.

Curcumin inhibits cardiac hypertrophy and improves cardiovascular function via enhanced Na+/Ca2+ exchanger expression after transverse abdominal aortic constriction in rats

BACKGROUND

This study tested the hypothesis that inhibition of cardiac hypertrophy and preservation of cardiac/endothelial function by the natural yellow pigment curcumin are associated with upregulated expression of Na⁺/Ca²⁺ exchanger (NCX) after transverse aortic constriction (TAC).

METHODS

Male Wistar rats were subjected to TAC for 10 weeks and curcumin (50 mg/kg/day) was fed by gastric gavage during TAC. Expression of NCX and endothelial nitric oxide synthase (eNOS) was analyzed by Western blot and immunohistochemistry.

RESULTS

Compared with the animals in the TAC group, curcumin significantly increased the survival rate and reduced the ratio of heart or left ventricle (LV) to body weight and the cross sectional area of cardiomyocytes. In coincidence with improved LV systolic pressure and reduced LV end-diastolic pressure, curcumin significantly reduced LV end-systolic and diastolic diameter/dimension, and enhanced LV ejection fraction and LV fractional shortening as measured by echocardiography. Furthermore, endothelium-dependent relaxation of aortic rings in response to acetylcholine was significantly improved by curcumin. Along with these modifications, the expression and localization of NCX and eNOS in the myocardium and vascular endothelium were significantly upregulated by curcumin. The protective effect of curcumin on endothelium-dependent relaxation was partly blocked by pretreatment with the NCX inhibitor, KB-R7943.

CONCLUSIONS

These results demonstrate that inhibition of cardiac hypertrophy, improvement of cardiac systolic/diastolic function and preservation of vascular endothelium by curcumin might be associated with upregulated NCX expression level in response to increased afterload.

A novel aldosterone synthase inhibitor ameliorates mortality in pressure-overload mice with heart failure

It has been elucidated that mineralocorticoid receptor antagonists reduce mortality in patients with congestive heart failure and post-acute myocardial infarction. A direct inhibition of aldosterone synthase (CYP11B2) is also expected to have therapeutic benefits equal in quality to mineralocorticoid receptor antagonists in terms of reducing mineralocorticoid receptor signaling. Therefore, we have screened our chemical libraries and identified a novel and potent aldosterone synthase inhibitor, 2,2,2-trifluoro-1-{4-[(4-fluorophenyl)amino]pyrimidin-5-y}-1-[1-(methylsulfonyl)piperidin-4-yl]ethanol (compound 1), by lead optimization. Pharmacological properties of compound 1 were examined in in vitro cell-based assays and an in vivo mouse model of pressure-overload hypertrophy by transverse aortic constriction (TAC). Compound 1 showed potent CYP11B2 inhibition against human and mouse enzymes (IC₅₀; 0.003μM and 0.096μM, respectively) in a cell-based assay. The oral administration of 0.06% compound 1 in the food mixture of a mouse TAC model significantly reduced the plasma aldosterone level and ameliorated mortality rate. This study is the first to demonstrate that a CYP11B2 inhibitor improved survival rates of heart failure induced by pressure-overload in mice. The treatment of 0.06% compound 1 did not elevate plasma potassium level in this model, although further evaluation of hyperkalemia is needed. These results suggest that compound 1 can be developed as a promising oral CYP11B2 inhibitor for pharmaceutical applications. Compound 1 could also be a useful compound for clarifying the role of aldosterone in cardiac hypertrophy.

Blockade of receptor for advanced glycation end products protects against systolic overload-induced heart failure after transverse aortic constriction in mice

Heart failure is the consequence of sustained, abnormal neurohormonal and mechanical stress and remains a leading cause of death worldwide. The aim of this work was to identify whether blockade of receptor for advanced glycation end products (RAGE) protected against systolic overload-induced heart failure and investigate the possible underlying mechanism. It was found that RAGE mRNA and protein expression was up-regulated in cardiac tissues from mice subjected to pressure overload by transverse aortic constriction (TAC). Importantly, inhibition of RAGE by treatment with soluble RAGE (sRAGE) or FPS-ZM1 (a high-affinity RAGE-specific inhibitor) for 8 weeks attenuated cardiac remodeling (including cardiac hypertrophy and fibrosis), and dysfunction in mice exposed to TAC. Furthermore, treatment of TAC mice with sRAGE or FPS-ZM1 enhanced phosphorylation of AMPK and reduced phosphorylation of mTOR and protein expression of NFκB p65 in cardiac tissues. In addition, treatment of TAC mice with sRAGE or FPS-ZM1 abated oxidative stress, attenuated endoplasmic reticulum stress, and suppressed inflammation in cardiac tissues. These data demonstrated the benefits of blocking RAGE on the progression of systolic overload-induced heart failure in mice, which was possibly through modulating AMPK/mTOR and NFκB pathways.

Soluble guanylate cyclase stimulator riociguat and phosphodiesterase 5 inhibitor sildenafil ameliorate pulmonary hypertension due to left heart disease in mice

BACKGROUND

Presence of pulmonary hypertension (PH) and right ventricular dysfunction worsens prognosis in patients with chronic heart failure (CHF). Preclinical and clinical studies suggest a role for the impaired nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) signaling pathway in both PH and CHF. Hence, we examined the effects of the NO-sGC-cGMP pathway modulation by the PDE5 inhibitor sildenafil or sGC stimulator riociguat on pulmonary hemodynamics and heart function in a murine model of secondary PH induced by transverse aortic constriction.

METHODS

C57Bl/6N mice were subjected to transverse aortic constriction (TAC) for 6weeks to induce left heart failure and secondary PH and were subsequently treated with either sildenafil (100mg/kg/day) or riociguat (10mg/kg/day) or placebo for 2weeks.

RESULTS

Six weeks after surgery, TAC induced significant left ventricular hypertrophy and dysfunction associated with development of PH. Treatment with riociguat and sildenafil neither reduced left ventricular hypertrophy nor improved its function. However, both sildenafil and riociguat ameliorated PH, reduced pulmonary vascular remodeling and improved right ventricular function.

CONCLUSIONS

Thus, modulation of the NO-sGC-cGMP pathway by the PDE5 inhibitor sildenafil or sGC stimulator riociguat exerts direct beneficial effects on pulmonary hemodynamics and right ventricular function in the experimental model of secondary PH due to left heart disease and these drugs may offer a new therapeutic option for therapy of this condition.

The experimental model of transition from compensated cardiac hypertrophy to failure created by transverse aortic constriction in mice

Background

Transverse aortic constriction (TAC) operation is used as an experimental model of left ventricular (LV) hypertrophy and LV failure in mice. The severity of LV remodeling or failure may depend on the degree of TAC, but is variable among operated animals. Therefore, we tried to identify the optimal diameter of TAC to create this model with ease and high reproducibility.

Methods and results

To produce TAC in C57BL/6J mice (7–9 weeks, body weight 19–26 g, n = 109), a 7–0 nylon suture ligature was tightly tied around the transverse aorta against needles with 3 different diameters (mm); 0.40, 0.385 and 0.375. LV wall thickness, end-diastolic dimension, fractional shortening were measured by echocardiography. At 4 weeks after TAC, no mouse with the 0.400 mm gauge progressed in LV failure. The 0.385 mm pin gauge mouse kept a more survival rate compared with the 0.375 mm (59% vs 48%), representing same efficient in LV failure. With the 0.385 mm pin gauge, hearts of mice remained LV hypertrophy at 1 week after TAC, followed by LV failure at 4 weeks.

Conclusion

TAC with the diameter of 0.385 mm can effectively induce the transition from LV hypertrophy to failure in mice with relatively preserved survival.

Whole transcriptome microarrays identify long non-coding RNAs associated with cardiac hypertrophy

Long non-coding RNAs (lncRNAs) have recently emerged as a novel group of non-coding RNAs able to regulate gene expression. While their role in cardiac disease is only starting to be understood, their involvement in cardiac hypertrophy is poorly known. We studied the association between lncRNAs and left ventricular hypertrophy using whole transcriptome microarrays. Wild-type mice and mice overexpressing the adenosine A2A receptor were subjected to transverse aortic constriction (TAC) to induce left ventricular hypertrophy. Expression profiles of lncRNAs in the heart were characterized using genome-wide microarrays. An analytical pipeline was specifically developed to extract lncRNA data from microarrays. We identified 2 lncRNAs up-regulated and 3 lncRNAs down-regulated in the hearts of A2A-receptor overexpressing-mice subjected to TAC compared to wild-type mice. Differential expression of these 2 lncRNAs was validated by quantitative PCR. Complete microarray dataset is available at Gene Expression Omnibus (GEO) database (http://www.ncbi.nlm.nih.gov/geo/) under the accession number GSE45423. Here, we describe in details the experimental design, microarray performance and analysis.

Berberine improves pressure overload-induced cardiac hypertrophy and dysfunction through enhanced autophagy

Cardiac hypertrophy is a maladaptive change in response to pressure overload, and is also an important risk for developing heart failure. Berberine is known to have cardioprotective effects in patients with hypertension and in animal models of cardiac hypertrophy. In the current study, we observed that transverse aortic contraction (TAC) surgery induced a marked increase in heart size, the ratio of heart weight to body weight, cardiomyocyte apoptosis, myocardial fibrosis, and hypertrophic marker brain natriuretic peptide, all of which were effectively suppressed by berberine administration. In addition, berberine enhanced autophagy in hypertrophic hearts, which was accompanied by a decrease in heart size, cardiac apoptosis, and the attenuation of cardiac dysfunction. Furthermore, use of autophagy inhibitor 3-methyladenine (3-MA) blocked berberine-induced autophagy level, and abrogated the protection of berberine against heart hypertrophy, cardiac dysfunction, and apoptosis. Berberine ameliorated TAC-induced endoplasmic reticulum stress, which was also abolished by 3-MA. Moreover, berberine significantly inhibited the upstream signaling of autophagy, such as the mammalian target of rapamycin (mTOR), extracellular signal-regulated kinase (ERK1/2), and p38 mitogen-activated protein kinase (MAPK) phosphorylation. We conclude that berberine could attenuate left ventricular remodeling and cardiomyocyte apoptosis through an autophagy-dependent mechanism in a rat model of cardiac hypertrophy, which is, at least in part, associated with enhanced autophagy through inhibition of mTOR, p38 and ERK1/2 MAPK signaling pathways.

Evaluation of bi-ventricular coronary flow patterns using high-frequency ultrasound in mice with transverse aortic constriction

Using high-frequency color and pulsed Doppler ultrasound, we evaluated the flow patterns of the left (LCA), septal (SCA) and right (RCA) coronary arteries in mice with and without transverse aortic constriction (TAC). Fifty-two male C57BL/6J mice were subjected to TAC or a corresponding sham operation. At 2 and 8 wk post-surgery, Doppler flow spectra from the three coronary arteries, together with morphologic and functional parameters of the left and right ventricles, were measured. Histology was performed to evaluate myocyte size and neo-angiogenesis in both ventricles. In sham-operated mice, the LCA and SCA both exhibited low-flow waveforms during systole and dominantly higher-flow waveforms during diastole. The RCA exhibited generally lower flow velocity, with similar systolic and diastolic waveforms. TAC significantly increased the systolic flow velocities of all coronary arteries, but enhanced the flow mainly in the LCA and SCA. In the left ventricle, coronary flow reserve was partially preserved 2 wk post-TAC, but decreased at 8 wk, consistent with changes in neo-angiogenesis and systolic function. In contrast, no significant change was found in the coronary flow reserve, structure or function of the right ventricle. This study has established a protocol for evaluating the flow pattern in three principal coronary arteries in mice using Doppler ultrasound and illustrated the difference among three vessels at baseline. In mice with TAC, the difference in the associating pattern of coronary flow dynamics with the myocardial structure and function between the left and right ventricles provides further insights into ventricular remodeling under pressure overload.