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.

TAK1 Activation by NLRP3 Deficiency Confers Cardioprotection Against Pressure Overload-Induced Cardiomyocyte Pyroptosis and Hypertrophy.

A comprehensive view of the role of NLRP3/caspase-1/GSDMD-mediated pyroptosis in pressure overload cardiac hypertrophy is presented in this study. Furthermore, mitigation of NLRP3 deficiency-induced pyroptosis confers cardioprotection against pressure overload through activation of TAK1, whereas this salutary effect is abolished by inhibition of TAK1 activity, highlighting a previously unrecognized reciprocally regulatory role of NLRP3-TAK1 governing inflammation-induced cell death and hypertrophic growth. Translationally, this study advocates strategies based on inflammation-induced cell death might be exploited therapeutically in other inflammatory and mechanical overload disorders, such as myocardial infarction and mitral regurgitation.

Surgically Induced Cardiac Volume Overload by Aortic Regurgitation in Mouse.

Aortic regurgitation (AR) is a common valvular heart disease that exerts volume overload on the heart and represents a global public health problem. Although mice are widely applied to shed light on the mechanisms of cardiovascular disease, mouse models of AR, especially those induced by surgery, are still paucity. Here, a mouse model of AR was described in detail which is surgically induced by disruption of the aortic valves under high-resolution echocardiography. In accordance with regurgitated blood flow, AR mouse hearts present a distinctive and clinically relevant volume overload phenotype, which is characterized by eccentric hypertrophy and cardiac dysfunction, as evidenced by echocardiographic and invasive hemodynamic evaluation. Our proposal, in a reliable and reproducible manner, provides a practical guide on the establishment and assessment of a mouse model of AR for future studies on molecular mechanisms and therapeutic targets of volume overload cardiomyopathy.

Long-term prognostic value of dynamic function assessment of intermediate coronary lesion with computational physiology.

This study sought to investigate the dynamic functional changes of coronary intermediate lesions using quantitative flow ratio (QFR) and its implication on long-term clinical outcomes. Physiology-guided percutaneous coronary intervention in patients with angiographic intermediate lesions has been associated with favorable outcomes. This study consecutively enrolled 1130 patients with deferred intermediate lesions at baseline angiography and subsequently received second-time angiography between 9 months and 2 years later from two centers in China. The functional changes of intermediate lesions at angiographic follow-up (ΔQFR) were defined as (baseline QFR-follow-up QFR)/years. The primary outcome was vessel-oriented composite endpoint (VOCE), defined as the composite of vessel-related cardiac death, vessel-related myocardial infarction (MI), and ischemia-driven target vessel revascularization (ID-TVR) at angiographic follow-up for up to 5 years. Retrospective QFR assessment was available in 820 patients (996 intermediate lesions). QFR ≤ 0.80 at second-time angiography was associated with significantly higher 5-year VOCE (41.9% vs. 13.4%, p < 0.0001). In 777 intermediate lesions with baseline QFR > 0.80, mean ΔQFR was 0.03 ± 0.07 (median: 0.006; Q1: 0; and Q3: 0.04). The optimal cutoff of ΔQFR for predicting the primary outcome was 0.03 (area under the curve [AUC]: 0.68). The cumulative event rate of VOCE in patients with ΔQFR ≥ 0.03 was significantly higher than in those with ΔQFR < 0.03 (33.8% vs. 12.2%, p < 0.0001), driven by higher vessel-related MI and ID-TVR. The ΔQFR was a useful tool for evaluating the dynamic functional change of deferred intermediate lesions, as it demonstrates good prognostic value for long-term target vessel-related adverse events.

Involvement of Endoplasmic Reticulum Stress-Mediated Activation of C/EBP Homologous Protein in Aortic Regurgitation-Induced Cardiac Remodeling in Mice.

Aortic regurgitation (AR) is a volume overload disease causing eccentric left ventricular (LV) hypertrophy and eventually heart failure. There is currently no approved drug to treat patients with AR. Endoplasmic reticulum (ER) stress and ER stress-mediated apoptosis is involved in many cardiovascular diseases, but whether they also participate in AR-induced heart failure is still elusive. In this study, we found ER stress activation in myocardial samples from patients with AR. With a unique murine model of AR which induced eccentric cardiac hypertrophy and heart failure, we also found aggravation of cardiac ER stress and apoptosis, as evidenced by a reduction of Bcl-2/Bax ratio and an increase of caspase-3 cleavage. We then examined the signaling effectors involved in ER-initiated apoptosis and found volume overload specifically activated C/EBP homologous protein (CHOP), but not caspase-12 or Jun N-terminal kinase (JNK). Interestingly, tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, improved cardiac function, and suppressed ER stress, apoptosis, and CHOP. Furthermore, genetic knockdown of CHOP inhibited cardiac Bcl-2/Bax ratio reduction and caspase-3 activation and rescued cardiac dysfunction. In summary, our findings suggest that ER stress-CHOP signaling is involved in the development of volume overload cardiac hypertrophy induced by AR through promoting cardiomyocytes apoptosis and provide a previously unrecognized target in heart failure induced by volume overload.

Troponin T Elevation After Percutaneous Left Atrial Appendage Occlusion.

Background: Cardiac troponin T (cTNT) has been widely used in detecting cardiac damage. Elevated cTNT level has been reported to be associated with increased mortality in multiple cardiac conditions. It is not uncommon to observe an increased level of cTNT in patients after left atrial appendage occlusion (LAAO). The objective of the study is to study the incidence, significance, and factors associated with cTNT elevation after LAAO. Methods: We prospectively included patients who underwent LAAO from January 2019 to July 2020 in Fudan Zhongshan Hospital. Patients were divided into those with elevated cTNT after procedure and those with normal postprocedure cTNT. All individuals were followed up for 1 year. The primary outcome is major adverse cardiovascular events, which include myocardial infarction, heart failure, cardiac death, and stroke. The second outcome is periprocedure complication, including chest pain, tachycardia, cardiac tamponade, change of electrocardiograph, and atrial thrombus. Results: A total of 190 patients were enrolled. Of the patients, 85.3% had elevated cTNT after LAAO, while 14.7% of them did not. Exposure time, dosage of contrast, types of devices, shapes, and sizes of LAA could contribute to elevated postprocedure cTNT. We found that patients with a Watchman device were more likely to have elevated postprocedure cTNT than those with a Lambre device (89.2 vs. 76.7%, p = 0.029). LAAO shapes were associated with cTNT levels in patients with a Watchman device, while the diameter of the outer disc and LAA depth mattered for the Lambre device. There was no significant difference in the primary and second outcome between the two groups (p-value: 0.619, 0.674). Conclusion: LAAO was found to be commonly accompanied with cTNT elevation, which might not to be related to the complications and adverse cardiac outcomes within 1 year of follow-up. Moreover, eGFR at baseline, exposure time, dosage of contrast, types of LAAO device, and LAA morphology could contribute to cTNT elevation.

Predictors and long-term prognosis of left ventricular aneurysm in patients with acute anterior myocardial infarction treated with primary percutaneous coronary intervention in the contemporary era.

BACKGROUND: Primary percutaneous coronary intervention (PCI) has been the standard reperfusion strategy for patients with acute myocardial infarction (AMI) in the contemporary era. Meanwhile, the incidence and prognosis of left ventricular aneurysm (LVA) in AMI patients remain ambiguous. The aim of the current study is to identify the predictor and long-term prognosis of LVA in patients with acute anterior myocardial infarction. METHODS: We prospectively enrolled 942 consecutive patients with acute anterior myocardial infarction who were treated by primary PCI. The baseline characteristics, procedural features, and one-year clinical outcomes were compared between the patients with and without LVA. The primary endpoint of major adverse cardiovascular and cerebrovascular events (MACCEs) was defined as a composite of cardiac death, target vessel revascularization, and ischemic stroke. Multiple logistic regression was applied to predict LVA formation and the receiver operating characteristic (ROC) curves were plotted to evaluate the accuracy of the multivariate analysis model. RESULTS: The general incidence of LVA was 15.92%. At one-year clinical follow-up, patients in the LVA group had significantly higher incidence of MACCEs (15.33% vs. 6.44%, P<0.01), mainly driven by an increased incidence of cardiac death (8.00% vs. 2.78%, P<0.01), target vessel revascularization (5.33% vs. 2.27%, P=0.03), and ischemic stroke (4.00% vs. 1.39%, P=0.03). Multivariate analysis found that longer symptom-to-balloon time (S2B) [odds ratio (OR): 1.16, 95% confidence interval (CI): 1.11-1.21, P<0.01], higher initial and residual SYNTAX score (iSS, OR: 1.19, 95% CI: 1.14-1.24, P<0.01; rSS, OR: 1.33, 95% CI: 1.22-1.45, P<0.01), lower left ventricular ejection fraction (LVEF) (OR: 1.15, 95% CI: 1.11-1.18, P<0.01), and persistent ST segment elevation (OR: 1.89, 95% CI: 1.06-3.38, P=0.03) were independent predictors of LVA formation. CONCLUSIONS: LVA is still common in patients with acute anterior myocardial infarction in the contemporary PCI era, and the prognosis of these patients was significantly worse during the one-year clinical follow-up. Strategies of prompt reperfusion and complete revascularization may be helpful in preventing LVA formation and improving clinical outcomes.

Left ventricular response in the transition from hypertrophy to failure recapitulates distinct roles of Akt, ß-arrestin-2, and CaMKII in mice with aortic regurgitation.

BACKGROUND: Although aortic regurgitation (AR) is a clinically important condition that is becoming increasingly common, few relevant murine models and mechanistic studies exist for this condition. In this study, we attempted to delineate the pathological and molecular changes and address the roles of some potentially relevant molecules in an animal model of surgically induced AR. METHODS: AR was induced by puncturing the aortic valve leaflets in C57BL/6J mice under echocardiographic guidance. RESULTS: As early as 1 week following AR, the left ventricles (LV) displayed marked impairments in diastolic function and coronary flow reserve (CFR), as well as cardiac hypertrophy and chamber dilatation at both end-systole and end-diastole. LV free wall thickening and cardiomyocyte hypertrophy in LV were observed 2 weeks following of AR while a decline in ejection fraction was not seen until after 4 weeks. Nppa (natriuretic peptide A) and Nppb (natriuretic peptide B) increased over time, in conjunction with prominent Akt activation as well as slight CaMKII (Ca2+/calmodulin-dependent protein kinase II) activation and biphasic changes in ß-arrestin-2 expression. Treatment of AR mice with Akt inhibition exacerbated the eccentric hypertrophy, while neither inhibition of CaMKII nor ß-arrestin-2 overexpression influenced the response to AR. CONCLUSIONS: Our structural, functional, molecular and therapeutic analyses reveal that Akt, but not CaMKII or ß-arrestin-2, plays a regulatory role in the development of LV remodeling after AR in Mice. These results may shed important light on therapeutic targets for volume overloaded cardiomyopathy.

Platelet function testing guided antiplatelet therapy reduces cardiovascular events in Chinese patients with ST-segment elevation myocardial infarction undergoing percutaneous coronary intervention: The PATROL study.

BACKGROUND: Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor has become the standard of care to reduce thrombotic events in patients with acute coronary syndrome or after percutaneous coronary intervention (PCI). The role of routine platelet function testing (PFT) in patients treated with DAPT after PCI remains controversial and evidence of PFT-guided antiplatelet therapy for patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary PCI is limited. METHODS: We analyzed 1,353 consecutive STEMI patients undergoing primary PCI. PFT was performed 72 hr postprocedure using a vasodilator-stimulated phosphoprotein assay. The primary endpoint of major adverse cardio-cerebral events (MACCEs) was defined as a composite of all-cause death, cardiac death, nonfatal myocardial infarction, target vessel revascularization, and ischemic stroke. Patients with high platelet reactivity (HPR) were randomized to receive an intensified antiplatelet strategy by switching from clopidogrel to ticagrelor (HPR switch group) or to continue on clopidogrel (HPR nonswitch group). One-year clinical outcomes were compared among the groups. RESULTS: The baseline clinical characteristics were comparable across all groups (all p > .05). At the 1-year clinical follow-up, the primary endpoint of MACCE was significantly higher in the HPR nonswitch group than in the non-HPR and HPR switch groups (19.49% vs. 10.20% or 8.57%, p < .05), which was mainly caused by higher mortality (14.87% vs. 4.51% or 5.71%, p < .05). Major bleeding events were comparable across the groups. CONCLUSIONS: In STEMI patients with HPR, identified by vasodilator stimulated phosphoprotein (VASP)-determined PFT, switching clopidogrel to ticagrelor could significantly improve 1-year clinical outcomes without increasing the risk of bleeding.

Variations in Energy Metabolism Precede Alterations in Cardiac Structure and Function in Hypertrophic Preconditioning.

Recent studies have unveiled that myocardial hypertrophic preconditioning (HP), which is produced by de-banding (De-TAC) of short-term transverse aortic constriction (TAC), protects the heart against hypertrophic responses caused by subsequent re-constriction (Re-TAC) in mice. Although cardiac substrate metabolism is impaired in heart failure, it remains unclear about the role of HP-driven energetics in the development of cardiac hypertrophy. Here, we investigated energy metabolism, cardiac hypertrophy, and function following variational loading conditions, as well as their relationships in HP. Male C57BL/6J mice (10-12 weeks old) were randomly subjected to Sham, HP [TAC for 3days (TAC 3d), de-banding the aorta for 4 days (De-TAC 4d), and then re-banding the aorta for 4 weeks (Re-TAC 4W)], and TAC (TAC for 4 weeks without de-banding). Cardiac echocardiography, hemodynamics, and histology were utilized to evaluate cardiac remodeling and function. The mRNA expression levels of fetal genes (ANP and BNP), glucose metabolism-related genes (glut4, pdk4), and fatty acid oxidation-related genes (mcad, pgc1α, mcd, pparα) were quantitated by real-time quantitative PCR. Activation of hypertrophy regulators ERK1/2, a metabolic stress kinase AMP-activated protein kinase (AMPK), and its downstream target acetyl-coA carboxylase (ACC) were explored by western blot. Compared with TAC 4W mice, Re-TAC 4W mice showed less impairment in glucose and fatty acid metabolism, as well as less cardiac hypertrophy and dysfunction. Moreover, no significant difference was found in myocardial hypertrophy, fibrosis, and cardiac function in TAC 3d and De-TAC 4d groups compared with Sham group. However, glut4, pdk4, mcad, pgc1α, mcd, and pparα were all decreased, while AMPK and ACC were activated in TAC 3d and returned to Sham level in De-TAC 4d, suggesting that the change in myocardial energy metabolism in HP mice was earlier than that in cardiac structure and function. Collectively, HP improves energy metabolism and delays cardiac remodeling, highlighting that early metabolic improvements drive a potential beneficial effect on structural and functional restoration in cardiac hypertrophy.

Co-loading antioxidant N-acetylcysteine attenuates cytotoxicity of iron oxide nanoparticles in hypoxia/reoxygenation cardiomyocytes.

PURPOSE: Myocardial delivery of magnetic iron oxide nanoparticles (MNPs) might produce iron overload-induced myocardial injury, and the oxidative stress was regarded as the main mechanism. Therefore, we speculated antioxidant modification might be a reasonable strategy to mitigate the toxicity of MNPs. METHODS AND RESULTS: Antioxidant N-acetylcysteine (NAC) was loaded into magnetic mesoporous silica coated Fe3O4 nanoparticles. Neonatal rat hypoxia/reoxygenation (H/R) cardiomyocytes were incubated with nanoparticles for 24 hrs. NAC can effectively mitigate iron-induced oxidative injury of cardiomyocytes, evidenced by reduced production of MDA, 8-iso-PGF2α, and 8-OHDG and maintained concentrations of SOD, CAT, GSH-Px, and GSH in ELISA and biochemical tests; downregulated expression of CHOP, GRP78, p62, and LC3-II proteins in Western Blot, and less cardiomyocytes apoptosis in flow cytometric analysis. CONCLUSIONS: NAC modifying could suppress the toxic effects of Fe3O4 nanoparticles in H/R cardiomyocytes model in vitro, indicating a promising strategy to improve the safety of iron oxide nanoparticles.

Predictive Value of CHA2DS2-VASc Score for Ischemic Events in Patients Undergoing Percutaneous Coronary Intervention.

We evaluated the association of preprocedure CHA2DS2-VASc (congestive heart failure, hypertension, age, diabetes mellitus, stroke, vascular disease, and sex) score with ischemic events in patients undergoing percutaneous coronary intervention (PCI). The Dryad Digital Repository enrolled 2533 patients between July 2009 and August 2011. We recorded 1-year ischemic events. Univariate and multivariable logistic regression analyses were used to analyze the association between CHA2DS2-VASc score and ischemic events. Receiver operating characteristic curves were used to evaluate the accuracy of CHA2DS2-VASc score in predicting long-term ischemic events. Long-term death (9.5 vs 2.8%), cardiac death (2.9 vs 1.4%), and nonfatal stroke (1.9 vs 0.7%) were significantly higher in the CHA2DS2-VASc score ≥2 group than the CHA2DS2-VASc score ≤1 group. The CHA2DS2-VASc score was a predictor for all-cause death (odds ratio [95% confidence interval]: 3.71 [1.89-7.30]). The risk factors for all-cause death in CHA2DS2-VASc score ≥2 patients included age, diagnosis, heart failure, older myocardial infarction, diabetes, and chronic obstructive pulmonary disease, while the risk factor for CHA2DS2-VASc score ≤1 patients was age. In conclusion, the CHA2DS2-VASc score is associated with long-term all-cause death, cardiac death, and stroke in patients undergoing PCI, and it may have a potential use for risk stratification for patients who undergo PCI.

Predictors and prognosis of left ventricular thrombus in post-myocardial infarction patients with left ventricular dysfunction after percutaneous coronary intervention.

BACKGROUND: We aimed to investigate the predictors and prognosis of left ventricular thrombus (LVT) in patients admitted for post-myocardial infarction (MI) and left ventricular dysfunction after contemporary percutaneous coronary intervention (PCI). METHODS: We prospectively enrolled 267 consecutive post-MI patients with left ventricular ejection fraction (LVEF) <0.45 based on the Shanghai East Hospital PCI database since 2012. Altogether 25 (9.36%) patients were selected as the LVT group. Baseline, angiographic, procedural characteristics and 1-year clinical outcomes were compared by Chi-square test, t-test or Kaplan-Meier survival analysis as appropriate. Receiver operating characteristic (ROC) curves were plotted for the accuracy of the multivariate analysis model. A multiple logistic regression was applied to predict LVT formation. RESULTS: The independent risk factors of LVT were left ventricular aneurysm [odds ratio (OR): 1.29, 95% confidence interval (CI): 1.09-1.52, P<0.01], incomplete revascularization (OR: 0.05, 95% CI: 0.01-0.35, P<0.01), SYNTAX score (OR: 1.28, 95% CI: 1.14-1.43, P<0.01) and D-dimer (OR: 1.90, 95% CI: 1.19-3.04, P<0.01). The SYNTAX score and D-dimer effectively indicated the development of LVT with optimal cutoff values of 29.50 and 1.53 mg/L, respectively. Patients with LVT had significantly worse outcomes at 1-year clinical follow-up, especially higher incidence of ischemic or hemorrhagic stroke. CONCLUSIONS: This study indicated that the presence of left ventricular aneurysm, incomplete revascularization, higher SYNTAX score and D-dimer level were the independent predictors of LVT formation in post-MI and LV dysfunction patients, which related to worse clinical outcomes. Future studies for early intervention and complete revascularization in high-risk subgroup patients are expected.

HSF1 deficiency accelerates the transition from pressure overload-induced cardiac hypertrophy to heart failure through endothelial miR-195a-3p-mediated impairment of cardiac angiogenesis.

Heat shock transcription factor 1 (HSF1) deficiency aggravates cardiac remodeling under pressure overload. However, the mechanism is still unknown. Here we employed microRNA array analysis of the heart tissue of HSF1-knockout (KO) mice to investigate the potential roles of microRNAs in pressure overload-induced cardiac remodeling under HSF-1 deficiency, and the profiles of 478 microRNAs expressed in the heart tissues of adult HSF1-KO mice were determined. We found that the expression of 5 microRNAs was over 2-fold higher expressed in heart tissues of HSF1-KO mice than in those of wild-type (WT) control mice. Of the overexpressed microRNAs, miR-195a-3p had the highest expression level in HSF1-null endothelial cells (ECs). Induction with miR-195a-3p in ECs significantly suppressed CD31 and VEGF, promoted AngII-induced EC apoptosis, and impaired capillary-like tube formation. In vivo, the upregulation of miR-195a-3p accentuated cardiac hypertrophy, increased the expression of ß-MHC and ANP, and compromised systolic function in mice under pressure overload induced by transverse aortic constriction (TAC). By contrast, antagonism of miR-195a-3p had the opposite effect on HSF1-KO mice. Further experiments confirmed that AMPKα2 was the direct target of miR-195a-3p. AMPKα2 overexpression rescued the reduction of eNOS and VEGF, and the impairment of angiogenesis that was induced by miR-195a-3p. In addition, upregulation of AMPKα2 in the myocardium of HSF1-null mice by adenovirus-mediated gene delivery enhanced CD31, eNOS and VEGF, reduced ß-MHC and ANP, alleviated pressure overload-mediated cardiac hypertrophy and restored cardiac function. Our findings revealed that the upregulation of miR-195a-3p due to HSF1 deficiency impaired cardiac angiogenesis by regulating AMPKα2/VEGF signaling, which disrupted the coordination between the myocardial blood supply and the adaptive hypertrophic response and accelerated the transition from cardiac hypertrophy to heart failure in response to pressure overload.

Differential cardiac hypertrophy and signaling pathways in pressure versus volume overload.

Mechanical overload can be classified into pressure overload and volume overload, causing concentric and eccentric cardiac hypertrophy, respectively. Here, we aimed to differentiate the load-mediated signaling pathways involved in pressure versus volume overload cardiac hypertrophy. Pressure or volume overload was imposed on C57BL/6J mice by transverse aortic constriction (TAC) or aortic regurgitation (AR), respectively. After surgery (2 wk), left ventricular structure and function were evaluated by echocardiographic, hemodynamic, and histological analyses. Signaling pathways related to hypertrophy, fibrosis, angiogenesis, and apoptosis were studied by histological analysis, RT-PCR, and Western blot analysis. Although mean wall stress was similar in both TAC and AR mice, systolic wall stress was significantly increased in TAC and diastolic wall stress was mainly elevated in AR. TAC or AR induced concentric or eccentric compensated hypertrophy, respectively. TAC was associated with more significant fibrosis and apoptosis, whereas AR was associated with more significant angiogenesis. MAPK kinase family, ß-arrestin-2, Akt, and Ca2+-related signaling pathways were markedly activated in TAC but mildly upregulated or unchanged in AR. Pressure overload and volume overload induce different phenotypic and molecular adaptations in cardiac hypertrophy. Most load-related signaling pathways assessed in this study predominate in pressure but not volume overload. The stimulus-specific heterogeneity in the signaling pathways requires distinct manipulations for further mechanistic and pharmacological studies. NEW & NOTEWORTHY Using the transverse aortic constriction mouse model and the newly developed aortic regurgitation mouse model, we delineated the prominent differences between concentric and eccentric cardiac hypertrophy on morphological, functional, and molecular levels. Our findings are important for the precise diagnosis and treatment of these two types of cardiac hypertrophy. Listen to this article's corresponding podcast at http://ajpheart.podbean.com/e/chinese-english-language-podcast-on-differential-cardiac-remodeling-in-tac-vs-ar/ .

Ultrasound biomicroscopy validation of a murine model of cardiac hypertrophic preconditioning: comparison with a hemodynamic assessment.

In mice, myocardial hypertrophic preconditioning (HP), which is produced by the removal of short-term transverse aortic constriction (TAC), was recently reported to render the heart resistant to hypertrophic responses induced by subsequent reconstriction (Re-TAC). However, there is no efficient noninvasive method for ensuring that the repeated aortic manipulations were successfully performed. We previously demonstrated that ultrasound biomicroscopy (UBM) is a noninvasive and effective approach for predicting TAC success. Here, we investigated the value of UBM for serial predictions of load conditions in establishing a murine HP model. C57BL/6J mice were subjected to a sham operation, TAC, or Re-TAC, and the peak flow velocity at the aortic banding site (PVb) was measured by UBM. Left ventricular end-systolic pressure (LVESP) was examined by micromanometric catheterization. The PVb was positively associated with LVESP (R2 = 0.8204, P < 0.001, for TAC at 3 days and R2 = 0.7746, P < 0.001, for Re-TAC at 4 wk). PVb and LVESP values were markedly elevated after aortic banding, became attenuated to the sham-operated level after debanding, and increased after aortic rebanding. The cardiac hypertrophic responses were examined by UBM, histology, RT-PCR, and Western blot analysis. Four weeks after the last operation, with PVb ≥ 3.5 m/s as an indicator of successful aortic constriction, Re-TAC mice showed less cardiac hypertrophy, fetal gene expression, and ERK1/2 activation than TAC mice. Therefore, we successfully established a UBM protocol for the serial assessment of aortic flow and the prediction of LVESP during repeated aortic manipulations in mice, which might be useful for noninvasive evaluations of the murine HP model.NEW & NOTEWORTHY We successfully developed an ultrasound biomicroscopy protocol for the serial assessment of aortic bandings and the relevant left ventricular pressure in a murine model of cardiac hypertrophic preconditioning. The protocol may be of great importance in the successful establishment of the hypertrophic preconditioning model for further mechanistic and pharmacological studies.

Characterization of coronary flow reserve and left ventricular remodeling in a mouse model of chronic aortic regurgitation with carvedilol intervention.

OBJECTIVES: We hypothesized that left ventricular (LV) remodeling might be exaggerated by an impaired coronary flow reserve in mice with chronic severe aortic regurgitation, and carvedilol, a ß-adrenoceptor blocker, could regress the course. METHODS: Severe aortic regurgitation was induced by retrograde puncture of the aortic valve leaflets under sonographic guidance in 12-week-old male C57BL/6J mice. Four weeks after regurgitation, the mice were treated with carvedilol (30 mg/kg/d) or not treated (control). Before and 4 weeks after carvedilol treatment, the coronary flow reserve and LV structure and function were evaluated by echocardiography. Cardiomyocytes and fibrosis were validated by histologic analysis. RESULTS: Four-week aortic regurgitation caused a decreased LV ejection fraction and an increased LV end-systolic volume index. Regurgitation also impaired the coronary flow reserve due to an increase in the basal coronary peak diastolic velocity and velocity-time integral combined with the absence of substantial changes in the hyperemic coronary peak diastolic velocity and velocity-time integral. Four more weeks of regurgitation further deteriorated LV remodeling and coronary perfusion in the control group. In contrast, the carvedilol-treated group showed attenuated LV remodeling and a higher coronary flow reserve by decreasing the basal peak diastolic velocity and velocity-time integral without substantial changes in the hyperemic peak diastolic velocity and velocity-time integral. The coronary flow reserve and its pretreatment versus posttreatment difference were positively correlated with the pretreatment versus posttreatment LV ejection fraction and end-systolic volume index differences. In the carvedilol-treated group, subendocardial fibrosis was significantly reduced (P < .05), and the cardiomyocyte cross-sectional area tended to be smaller. CONCLUSIONS: In mice with chronic severe aortic regurgitation, carvedilol therapy significantly improves the impaired coronary flow reserve and sufficiently attenuates adverse LV remodeling. Sustained coronary flow reserve impairment indicates progressive LV remodeling.

Aliskiren ameliorates pressure overload-induced heart hypertrophy and fibrosis in mice.

AIM: Aliskiren (ALK) is a renin inhibitor that has been used in the treatment of hypertension. The aim of this study was to determine whether ALK could ameliorate pressure overload-induced heart hypertrophy and fibrosis, and to elucidate the mechanisms of action. METHODS: Transverse aortic constriction (TAC) was performed in mice to induce heart pressure overload. ALK (150 mg·kg(-1)·d(-1), po), the autophagy inhibitor 3-methyladenine (10 mg·kg(-1) per week, ip) or the PKCßI inhibitor LY333531 (1 mg·kg(-1)·d-(1), po) was administered to the mice for 4 weeks. Heart hypertrophy, fibrosis and function were evaluated based on echocardiography, histological and biochemical measurements. Mechanically stretched cardiomyocytes of rats were used for in vitro experiments. The levels of signaling proteins were measured using Western blotting, while the expression of the relevant genes was analyzed using real-time QRT-PCR. RESULTS: TAC induced marked heart hypertrophy and fibrosis, accompanied by high levels of Ang II in plasma and heart, and by PKCßI/α and ERK1/2 phosphorylation in heart. Meanwhile, TAC induced autophagic responses in heart, i.e. increases in autophagic structures, expression of Atg5 and Atg16 L1 mRNAs and LC3-II and Beclin-1 proteins. These pathological alterations in TAC-mice were significantly ameliorated or blocked by ALK administration. In TAC-mice, 3-methyladenine administration also ameliorated heart hypertrophy, fibrosis and dysfunction, while LY333531 administration inhibited ERK phosphorylation and autophagy in heart. In mechanically stretched cardiomyocytes, CGP53353 (a PKCßI inhibitor) prevented ERK phosphorylation and autophagic responses, while U0126 (an ERK inhibitor) blocked autophagic responses. CONCLUSION: ALK ameliorates heart hypertrophy, fibrosis and dysfunction in the mouse model in setting of chronic pressure overload, via suppressing Ang II-PKCßI-ERK1/2-regulated autophagy.