GSDMD-mediated pyroptosis promotes cardiac remodeling in pressure overload.

BACKGROUND: Gasdermin D (GSDMD) forms membrane pores to execute pyroptosis. But the mechanism of how cardiomyocyte pyroptosis induces cardiac remodeling in pressure overload remains unclear. We investigated the role of GSDMD-mediated pyroptosis in the pathogenesis of cardiac remodeling in pressure overload. METHODS: Wild-type (WT) and cardiomyocyte-specific GSDMD-deficient (GSDMD-CKO) mice were subjected to transverse aortic constriction (TAC) to induce pressure overload. Four weeks after surgery, left ventricular structure and function were evaluated by echocardiographic, invasive hemodynamic and histological analysis. Pertinent signaling pathways related to pyroptosis, hypertrophy and fibrosis were investigated by histochemistry, RT-PCR and western blotting. The serum levels of GSDMD and IL-18 collected from healthy volunteers or hypertensive patients were measured by ELISA. RESULTS: We found TAC induced cardiomyocyte pyroptosis and release of pro-inflammatory cytokines IL-18. The serum GSDMD level was significantly higher in hypertensive patients than in healthy volunteers, and induced more dramatic release of mature IL-18. GSDMD deletion remarkably mitigated TAC-induced cardiomyocyte pyroptosis. Furthermore, GSDMD deficiency in cardiomyocytes significantly reduced myocardial hypertrophy and fibrosis. The deterioration of cardiac remodeling by GSDMD-mediated pyroptosis was associated with activating JNK and p38 signaling pathways, but not ERK or Akt signaling pathway. CONCLUSION: In conclusion, our results demonstrate that GSDMD serves as a key executioner of pyroptosis in cardiac remodeling induced by pressure overload. GSDMD-mediated pyroptosis activates JNK and p38 signaling pathways, and this may provide a new therapeutic target for cardiac remodeling induced by pressure overload.

In vivo mouse myocardial (31)P MRS using three-dimensional image-selected in vivo spectroscopy (3D ISIS): technical considerations and biochemical validations.

(31)P MRS provides a unique non-invasive window into myocardial energy homeostasis. Mouse models of cardiac disease are widely used in preclinical studies, but the application of (31)P MRS in the in vivo mouse heart has been limited. The small-sized, fast-beating mouse heart imposes challenges regarding localized signal acquisition devoid of contamination with signal originating from surrounding tissues. Here, we report the implementation and validation of three-dimensional image-selected in vivo spectroscopy (3D ISIS) for localized (31)P MRS of the in vivo mouse heart at 9.4 T. Cardiac (31)P MR spectra were acquired in vivo in healthy mice (n = 9) and in transverse aortic constricted (TAC) mice (n = 8) using respiratory-gated, cardiac-triggered 3D ISIS. Localization and potential signal contamination were assessed with (31)P MRS experiments in the anterior myocardial wall, liver, skeletal muscle and blood. For healthy hearts, results were validated against ex vivo biochemical assays. Effects of isoflurane anesthesia were assessed by measuring in vivo hemodynamics and blood gases. The myocardial energy status, assessed via the phosphocreatine (PCr) to adenosine 5'-triphosphate (ATP) ratio, was approximately 25% lower in TAC mice compared with controls (0.76 ± 0.13 versus 1.00 ± 0.15; P < 0.01). Localization with one-dimensional (1D) ISIS resulted in two-fold higher PCr/ATP ratios than measured with 3D ISIS, because of the high PCr levels of chest skeletal muscle that contaminate the 1D ISIS measurements. Ex vivo determinations of the myocardial PCr/ATP ratio (0.94 ± 0.24; n = 8) confirmed the in vivo observations in control mice. Heart rate (497 ± 76 beats/min), mean arterial pressure (90 ± 3.3 mmHg) and blood oxygen saturation (96.2 ± 0.6%) during the experimental conditions of in vivo (31)P MRS were within the normal physiological range. Our results show that respiratory-gated, cardiac-triggered 3D ISIS allows for non-invasive assessments of in vivo mouse myocardial energy homeostasis with (31)P MRS under physiological conditions.

miR-222 inhibits pathological cardiac hypertrophy and heart failure.

AIMS: Physiological cardiac hypertrophy occurs in response to exercise and can protect against pathological stress. In contrast, pathological hypertrophy occurs in disease and often precedes heart failure. The cardiac pathways activated in physiological and pathological hypertrophy are largely distinct. Our prior work demonstrated that miR-222 increases in exercised hearts and is required for exercise-induced cardiac hypertrophy and cardiomyogenesis. Here, we sought to define the role of miR-222 in pathological hypertrophy. METHODS AND RESULTS: We found that miR-222 also increased in pathological hypertrophy induced by pressure overload. To assess its functional significance in this setting, we generated a miR-222 gain-of-function model through cardiac-specific constitutive transgenic miR-222 expression (TgC-miR-222) and used locked nucleic acid anti-miR specific for miR-222 to inhibit its effects. Both gain- and loss-of-function models manifested normal cardiac structure and function at baseline. However, after transverse aortic constriction (TAC), miR-222 inhibition accelerated the development of pathological hypertrophy, cardiac dysfunction, and heart failure. Conversely, miR-222-overexpressing mice had less pathological hypertrophy after TAC, as well as better cardiac function and survival. We identified p53-up-regulated modulator of apoptosis, a pro-apoptotic Bcl-2 family member, and the transcription factors, Hmbox1 and nuclear factor of activated T-cells 3, as direct miR-222 targets contributing to its roles in this context. CONCLUSION: While miR-222 is necessary for physiological cardiac growth, it inhibits cardiac growth in response to pressure overload and reduces adverse remodelling and cardiac dysfunction. These findings support the model that physiological and pathological hypertrophy are fundamentally different. Further, they suggest that miR-222 may hold promise as a therapeutic target in pathological cardiac hypertrophy and heart failure.

Empagliflozin rescues pro-arrhythmic and Ca2+ homeostatic effects of transverse aortic constriction in intact murine hearts.

We explored physiological effects of the sodium-glucose co-transporter-2 inhibitor empagliflozin on intact experimentally hypertrophic murine hearts following transverse aortic constriction (TAC). Postoperative drug (2-6 weeks) challenge resulted in reduced late Na+ currents, and increased phosphorylated (p-)CaMK-II and Nav1.5 but not total (t)-CaMK-II, and Na+/Ca2+ exchanger expression, confirming previous cardiomyocyte-level reports. It rescued TAC-induced reductions in echocardiographic ejection fraction and fractional shortening, and diastolic anterior and posterior wall thickening. Dual voltage- and Ca2+-optical mapping of Langendorff-perfused hearts demonstrated that empagliflozin rescued TAC-induced increases in action potential durations at 80% recovery (APD80), Ca2+ transient peak signals and durations at 80% recovery (CaTD80), times to peak Ca2+ (TTP100) and Ca2+ decay constants (Decay30-90) during regular 10-Hz stimulation, and Ca2+ transient alternans with shortening cycle length. Isoproterenol shortened APD80 in sham-operated and TAC-only hearts, shortening CaTD80 and Decay30-90 but sparing TTP100 and Ca2+ transient alternans in all groups. All groups showed similar APD80, and TAC-only hearts showed greater CaTD80, heterogeneities following isoproterenol challenge. Empagliflozin abolished or reduced ventricular tachycardia and premature ventricular contractions and associated re-entrant conduction patterns, in isoproterenol-challenged TAC-operated hearts following successive burst pacing episodes. Empagliflozin thus rescues TAC-induced ventricular hypertrophy and systolic functional, Ca2+ homeostatic, and pro-arrhythmogenic changes in intact hearts.

O-GlcNAcylation-induced GSK-3ß activation deteriorates pressure overload-induced heart failure via lack of compensatory cardiac hypertrophy in mice.

O-GlcNAc transferase (OGT) modulates many functions of proteins via O-GlcNAcylation that adds O-linked ß-N-acetylglucosamine (O-GlcNAc) to the serine/threonine residues of proteins. However, the role of O-GlcNAcylation in cardiac remodeling and function is not fully understood. To examine the effect of O-GlcNAcylation on pressure overload-induced cardiac hypertrophy and subsequent heart failure, transverse aortic constriction (TAC) surgery was performed in wild type (WT) and Ogt transgenic (Ogt-Tg) mice. Four weeks after TAC (TAC4W), the heart function of Ogt-Tg mice was significantly lower than that of WT mice (reduced fractional shortening and increased ANP levels). The myocardium of left ventricle (LV) in Ogt-Tg mice became much thinner than that in WT mice. Moreover, compared to the heart tissues of WT mice, O-GlcNAcylation of GSK-3ß at Ser9 was increased and phosphorylation of GSK-3ß at Ser9 was reduced in the heart tissues of Ogt-Tg mice, resulting in its activation and subsequent inactivation of nuclear factor of activated T cell (NFAT) activity. Finally, the thinned LV wall and reduced cardiac function induced by TAC4W in Ogt-Tg mice was reversed by the treatment of a GSK-3ß inhibitor, TDZD-8. These results imply that augmented O-GlcNAcylation exacerbates pressure overload-induced heart failure due to a lack of compensatory cardiac hypertrophy via O-GlcNAcylation of GSK-3ß, which deprives the phosphorylation site of GSK-3ß to constantly inactivate NFAT activity to prevent cardiac hypertrophy. Our findings may provide a new therapeutic strategy for cardiac hypertrophy and subsequent heart failure.

Identification of Transcriptional Variation in Aortic Remodeling Using a Murine Transverse Aortic Constriction (TAC) Model.

Arterial remodeling is a major pathological consequence of hypertension, which is recognized as the most common chronic non-communicable disease. However, the detailed mechanism of how arterial remodeling is induced by hypertension has not yet been fully elucidated. Evaluating the transcriptional changes in arterial tissue in response to elevated blood pressure at an early stage may provide new insights and identify novel therapeutic candidates in preventing arterial remodeling. Here, we used the ascending aorta of the transverse aortic constriction (TAC) model to induce arterial remodeling in C57BL/6 male mice. Age-matched mice were subjected to sham surgery as controls. The TAC model was only considered successful if the mice conformed to the criteria (RC/LC blood flow velocity with 5-10-fold change) 1 week after the surgery. Two weeks after surgery, the ascending aorta developed severe remodeling in TAC mice as compared to the sham group. High throughput sequencing was then applied to identify differentially expressed (DE) transcripts. In silicon analysis were then performed to systematically network transcriptional changes. A total of 1,019 mRNAs were significantly changed between TAC and the sham group at the transcriptional level. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis revealed that stress/stimulus/immune-related biological processes played a crucial role during arterial remodeling. Our data provide a comprehensive understanding of global gene expression changes in the TAC model, which suggests that targeting inflammation and vascular smooth cell transformation are potential therapeutic strategies to interfere with the aortic remodeling at an early stage in the development of hypertension.

Cardiac hypertrophy or failure? - A systematic evaluation of the transverse aortic constriction model in C57BL/6NTac and C57BL/6J substrains.

BACKGROUND: The mouse model of transverse aortic constriction (TAC) has been widely used as a cardiac stress in the investigation of the molecular mechanisms of cardiac hypertrophy. Recently, the International Knockout Mouse Consortium has selected the C57BL/6NTac (BL/6N) mouse strain to generate null alleles for all mouse genes; however, a range of genetic and cardiac phenotypic differences have been reported between this substrain and the commonly used C57BL/6J (BL/6J) substrain. It has been reported by Garcia-Menendez and colleagues that 12-week C57BL/6NTac mice are susceptible to heart failure but little is known about the cardiac remodeling in this substrain as cardiac function progresses from compensation to decompensation. METHODS: BL/6J and BL/6N mice were subjected to pressure overload via TAC. The impact of both age and duration of cardiac pressure overload induced by TAC on cardiac remodelling were systematically assessed. RESULTS: Our data showed that BL/6N mice developed eccentric hypertrophy with age- and time-dependent deterioration in cardiac function, accompanied by considerable interstitial fibrosis. In contrast, BL/6J mice were more resilient to TAC-induced cardiac stress and developed variable cardiac phenotypes independent of age and the duration of pressure overload. This was likely due to the greater variability in pre-TAC aortic arch dimension as measured by echocardiography. In addition to increased expression of brain natriuretic peptide and collagen gene type 1 and 3, BL/6N mice also had greater angiotensin II type 2 receptor (AT2R) gene expression than BL/6J counterparts at baseline and after 2-weeks TAC, which may contribute to the exacerbated interstitial fibrosis. CONCLUSIONS: BL/6N and BL/6J mice have very different responses to TAC stimulation and these differences should be taken into consideration when using the substrains to investigate the mechanisms of hypertrophy and heart failure.

Early echocardiographic predictors of outcomes in the mouse transverse aortic constriction heart failure model.

INTRODUCTION: Mouse transverse aortic constriction (TAC) is a widely-used model of pressure overload-induced heart failure. An intrinsic limitation of the model is variability in the response to pressure overload even when employing a standard severity of stenosis. Few literature studies have explicitly reported the use of entry criteria or early predictors to mitigate variability and enrich outcomes in this model. METHODS: Eleven-week-old male C57BL/6J mice underwent TAC or sham surgery. Left ventricular (LV) function and dimensions were assessed by M-mode echocardiography at baseline (pre) and 3, 9 and 12weeks post-procedure (end-study). At 24h post-procedure, transverse aortic flow velocities were obtained for estimating trans-TAC pressure gradients. Invasive LV hemodynamic assessments were performed and terminal heart and lung weights obtained at end-study. RESULTS: TAC mice displayed early development of LV hypertrophy and wall thickening followed by the later development of LV chamber dilation, and progressive development of LV systolic and diastolic dysfunction. The use of a pre-defined trans-TAC pressure gradient criterion of 45-60mmHg did not affect end-study organ weight, echocardiographic and invasive hemodynamic outcomes. A post-hoc receiver operator characteristic (ROC) analysis identified early 3week echocardiographic measures of LVmass(echo) and ejection fraction, with threshold changes of ~+30% and -10% normalized to baseline respectively, as good predictors for multiple end-study organ weight, echocardiographic and invasive hemodynamic outcomes. DISCUSSION: This ROC analysis has identified early predictive threshold changes which may serve, alone or in combination, as entry criteria to enrich outcome in this model.

Pathological Process Observation and Non-targeted Metabolomics Analysis of Heart Failure Rat Model Established by Transverse Aortic Constriction / 中国实验方剂学杂志

ObjectiveTo study the pathological process and changes of metabolites in myocardial tissue of heart failure induced by transverse aortic constriction （TAC） in rats. MethodRats were treated with TAC operation and divided into TAC-30 d group and TAC-60 d group， and sham operation group at the same period was set up as control. Echocardiography and pathological staining of myocardial tissue were performed on rats in each group. Enzyme-linked immunosorbent assay was used to determine the expression of amino-terminal pro-brain natriuretic peptide （NT-proBNP） and adenosine triphosphate （ATP） in serum. Liquid chromatography-mass spectrometry was used to observe the changes of metabolites and related pathways in myocardial tissue， the mobile phase consisted of 25 mmol·L-1 ammonium acetate and 25 mmol·L-1 ammonia hydroxide in water （A） and acetonitrile （B） for gradient elution （0-0.5 min， 95%B； 0.5-7 min， 95%-65%B； 7-8 min， 65%-40%B； 8-9 min， 40%B； 9-9.1 min， 40%-95%B； 9.1-12 min， 95%B）， electrospray ionization was used under positive and negative ion detection modes， acquisition range was m/z 70-1 050. ResultCompared with the sham-30 d group， the left ventricular internal diameter at end-systole （LVIDs） in TAC-30 d group was significantly decreased （P<0.01）， and left ventricular ejection fraction （LVEF）， fraction shortening （FS）， left ventricular end-diastolic posterior wall thickness （LVPWd）， left vebtricular end-systolic posterior wall thickness （LVPWs） were significantly increased （P<0.01）， there were cardiomyocyte arrangement disorder， edema， collagen fibre hyperplasia， the content of NT-probNP was significantly increased， while the content of ATP was significantly decreased （P<0.01）， and 15 metabolites with abnormal expression were involved in pyrimidine metabolic pathway， pantothenic acid and coenzyme A biosynthesis pathway. Compared with the sham-60 d group， LVEF and FS in the TAC-60 d group were significantly decreased （P<0.01）， and left ventricular internal diameter at end-diastole （LVIDd）， LVIDs and LVPWd were increased （P<0.05， P<0.01）， the edema of myocardial cells increased obviously， myocardium fibers degenerated， coagulation necrosis appeared， and a large amount of collagen fibers were deposited， the expression of NT-proBNP increased and the expression of ATP decreased （P<0.01）， there were 21 metabolites with abnormal expression， involving pyrimidine metabolic pathway， and starch and sucrose metabolic pathway. ConclusionAt 30 d after TAC， there are myocardial hypertrophy， lipid metabolism disorder， pyrimidine metabolism disorder and energy imbalance. At 60 d after TAC， there are heart failure， aggravation of lipid metabolism disorder， excessive activation of glucose metabolism， and continuous disorder of pyrimidine metabolism.

Exploration on Syndrome Types and Metabolic Markers of Rat Model with Heart Failure Caused by Transverse Aortic Constriction Based on Theory of Correspondence of Prescription and Syndrome / 中国实验方剂学杂志

ObjectiveTo observe the difference in the efficacy of three kinds of traditional Chinese medicine （TCM） injections on rat model of heart failure induced by transverse aortic constriction （TAC）， explore the TCM syndrome of the model based on the theory of correspondence of prescription and syndrome， and reveal the biological basis of prescription-syndrome from the perspective of metabolism. MethodRats were treated with TAC for modeling and were divided into Shenmai injection group （6.0 mL·kg-1）， model group， Danhong injection group （6.0 mL·kg-1）， Shenfu injection group （6.0 mL·kg-1） and trimetazidine group （10 mg·kg-1）， and sham operation group was set up as control. After drug intervention for 15 days， echocardiography， serum N-terminal pro-brain natriuretic peptide （NT-proBNP） and myocardial histopathological staining were performed for each group， so as to compare the efficacy to select the effective injection. Colorimetry was used to detect the serum glucolipid metabolism after the intervention of the effective injection， and ultra high performance liquid chromatography-mass spectrometry was used to observe the metabolites and related metabolic pathways in myocardial tissue. ResultCompared with the sham operation group， the left ventricular ejection fraction （LVEF） and left ventricular fractional shortening （FS） in the model group decreased （P<0.01）， while the left ventricular end-diastolic diameter （LVIDd）， left ventricular internal diameter at end-systole （LVIDs） and NT-proBNP level increased （P<0.01）. Compared with model group， LVEF and FS increased （P<0.01）， LVIDd， LVIDs and NT-proBNP level decreased （P<0.05， P<0.01） in Danhong injection group， NT-proBNP level in Shenfu injection group decreased （P<0.05）， LVIDd and NT-proBNP level increased （P<0.05， P<0.01） in Shenmai injection group， in trimetazidine group， LVEF and FS increased （P<0.01）， while LVIDs and NT-proBNP level decreased （P<0.05， P<0.01）. Serum glucose， low-density lipoprotein cholesterol and high-density lipoprotein cholesterol levels in Danhong injection group and trimetazidine group were adjusted by callbacks （P<0.01， P<0.05）. There were the callback of 9 myocardial metabolites in Danhong injection group， including glycine， serine and threonine metabolism， glyoxylate and dicarboxylate metabolism， glycerol phospholipid metabolism. There were the callback of 10 myocardial metabolites in trimetazidine group， including glycerol phospholipid metabolism. ConclusionThe efficacy of Danhong injection on heart failure model induced by TAC is significant and superior to Shenfu injection and Shenmai injection， suggesting that the model is closely related to heart-blood stasis. The biological mechanism of Danhong injection interfering with the model involves regulating the metabolic disorder of lipid， glucose， amino acid and butyric acid.

THE AUTOCRINE ROLE OF TRYPTASE IN PRESSURE OVERLOAD-INDUCED MAST CELL ACTIVATION, CHYMASE RELEASE AND CARDIAC FIBROSIS.

BACKGROUND: Cardiac mast cell (MC) proteases, chymase and tryptase, increase proliferation and collagen synthesis in cultured cardiac fibroblasts. However, the question as to why preventing individually the actions of either protease prevents fibrosis when both are released upon MC activation remains unanswered. Since tryptase has the ability to activate MCs in noncardiac tissues via the protease-activated receptor-2 (PAR-2), there is the possibility that its, in vivo, fibrotic role is due to its ability to induce MC degranulation thereby amplifying the release of chymase. METHODS: This study sought to delineate the interactions between tryptase and chymase in myocardial remodeling secondary to transverse aortic constriction (TAC) for 5 wks in male Sprague Dawley rats untreated or treated with either the tryptase inhibitor, nafamostat mesilate or MC membrane stabilizing drug, nedocromil (n=6/group). In addition, ventricular slices from 6 rat hearts were incubated with tryptase, tryptase plus nafamostat mesilate or chymostatin for 24 h. RESULTS AND CONCLUSION: The results indicate the presence of PAR-2 on MCs and that tryptase inhibition and nedocromil prevented TAC-induced fibrosis and increases in MC density, activation, and chymase release. Tryptase also significantly increased chymase concentration in ventricular tissue culture media, which was prevented by the tryptase inhibitor. Hydroxyproline concentration in culture media was significantly increased with tryptase incubation as compared to the control group and the tryptase group incubated with nafamostat mesilate or chymostatin. We conclude that tryptase contributes to TAC-induced cardiac fibrosis primarily via activation of MCs and the amplified release of chymase.