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Background: Polymorphisms in the adenylate cyclase 9 (ADCY9) gene influence the benefits of the cholesteryl ester transfer protein (CETP) modulator dalcetrapib on cardiovascular events after acute coronary syndrome. We hypothesized that Adcy9 inactivation could improve cardiac function and remodelling following myocardial infarction (MI) in absence of CETP activity., Methods: Wild-type (WT) and Adcy9-inactivated (Adcy9 Gt/Gt ) male mice, transgenic or not for human CETP (tgCETP +/- ), were subjected to MI by permanent left anterior descending coronary artery ligation and studied for 4 weeks. Left ventricular (LV) function was assessed by echocardiography at baseline, 1, and 4 weeks after MI. At sacrifice, blood, spleen and bone marrow cells were collected for flow cytometry analysis, and hearts were harvested for histologic analyses., Results: All mice developed LV hypertrophy, dilation, and systolic dysfunction, but Adcy9 Gt/Gt mice exhibited reduced pathologic LV remodelling and better LV function compared with WT mice. There were no differences between tgCETP +/- and Adcy9 Gt/Gt tgCETP +/- mice, which both exhibited intermediate responses. Histologic analyses showed smaller cardiomyocyte size, reduced infarct size, and preserved myocardial capillary density in the infarct border zone in Adcy9 Gt/Gt vs WT mice. Count of bone marrow T cells and B cells were significantly increased in Adcy9 Gt/Gt mice compared with the other genotypes., Conclusions: Adcy9 inactivation reduced infarct size, pathologic remodelling, and cardiac dysfunction. These changes were accompanied by preserved myocardial capillary density and increased adaptive immune response. Most of the benefits of Adcy9 inactivation were only observed in the absence of CETP., (Copyright © 2023 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: We previously demonstrated that high-density lipoprotein (HDL) infusions may improve left ventricular diastolic dysfunction (LVDD) in an aortic valve stenosis (AVS) model. Whether the benefit was direct or mediated by the observed reduction in AVS severity is not clear. Here, we aimed to test the direct effect of an ApoA-I mimetic on LVDD in the absence of AVS., Methods: Rabbits were exposed to three different protocols to develop LVDD. First, rabbits were exposed to 0.5% cholesterol-rich diet for an average of 17 weeks. Second, rabbits were subjected to surgical ascending aortic constriction (AAC), to mimic the effect of fixed reduced aortic valve area, and studied after 10 weeks. The third model combined both cholesterol-enriched diet (for 12 weeks) and surgical AAC. The control group consisted of age-matched rabbits under normal diet. After development of LVDD, rabbits were randomized to receive infusions of saline or apoA-I mimetic (25 mg/kg) 3 times per week for 4 weeks. Detailed cardiac structure and function measurements were assessed at baseline and weekly during treatment period. Histological and molecular analyses were performed on LV samples., Results: In the three models, echocardiographic results showed development of LVDD over time, with preserved LV systolic and aortic valve functions versus controls. ApoA-I mimetic infusions did not significantly improve echocardiographic parameters nor molecular markers of cardiac inflammation, oxidative stress and fibrosis., Conclusion: ApoA-I mimetic therapy did not directly improve LVDD. These results indicate that previously observed changes of LVDD were caused by AVS improvement induced by this treatment., Competing Interests: Declaration of Competing Interest Patents on the theme of HDL and both aortic valve stenosis and diastolic dysfunction were submitted by the Montreal Heart Institute and Drs Tardif and Rhéaume are mentioned as authors., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Objectives: High-density lipoprotein (HDL) infusions induce rapid improvement of experimental atherosclerosis in rabbits but their effect on ventricular function remains unknown. We aimed to evaluate the effects of the HDL mimetic peptide CER-522 on left ventricular diastolic dysfunction (LVDD)., Methods: Rabbits were fed with a cholesterol- and vitamin D2-enriched diet until mild aortic valve stenosis and hypercholesterolemia-induced LV hypertrophy and LVDD developed. Animals then received saline or 10 or 30mg/kg CER-522 infusions 6 times over 2weeks. We performed serial echocardiograms and LV histology to evaluate the effects of CER-522 therapy on LVDD., Results: LVDD was reduced by CER-522 as shown by multiple parameters including early filling mitral deceleration time, deceleration rate, Em/Am ratio, E/Em ratio, pulmonary venous velocities, and LVDD score. These findings were associated with reduced macrophages (RAM-11 positive cells) in the pericoronary area and LV, and decreased levels of apoptotic cardiomyocytes in CER-522-treated rabbits. CER-522 treatment also resulted in decreased atheromatous plaques and internal elastic lamina area in coronary arteries., Conclusions: CER-522 improves LVDD in rabbits, with reductions of LV macrophage accumulation, cardiomyocyte apoptosis, coronary atherosclerosis and remodelling., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Background: Autoantibodies directed against various cardiac receptors have been implicated in cardiomyopathy and heart rhythm disturbances. In a previous study among patients with dilated cardiomyopathy, autoantibodies targeting the cardiac voltage-gated KCNQ1 K(+) channel were associated with shortened corrected QT intervals (QTc). However, the electrophysiologic actions of KCNQ1 autoimmunity have not been assessed experimentally in a direct fashion., Objective: The purpose of this study was to investigate the cardiac electrophysiologic effects of KCNQ1 autoantibody production induced by vaccination in a rabbit model., Methods: Rabbits were immunized with KCNQ1 channel peptide. ECG recordings were obtained during a 1-month follow-up period. Rabbits then underwent in vivo electrophysiologic study, after which cardiomyocytes were isolated for analysis of slow delayed rectifier current (IKs) and action potential properties via patch-clamp., Results: KCNQ1-immunized rabbits exhibited shortening of QTc compared to sham-immunized controls. Reduced ventricular effective refractory periods and increased susceptibility to ventricular tachyarrhythmia induction were noted in KCNQ1-immunized rabbits upon programmed ventricular stimulation. Action potential durations were shortened in cardiomyocytes isolated from KCNQ1-immunized rabbits compared to the sham group. IKs step and tail current densities were enhanced after KCNQ1 immunization. Functional and structural changes of the heart were not observed. The potential therapeutic significance of KCNQ1 immunization was then explored in a dofetilide-induced long QT rabbit model. KCNQ1 immunization prevented dofetilide-induced QTc prolongation and attenuated long QT-related arrhythmias., Conclusion: Induction of KCNQ1 autoimmunity accelerates cardiac repolarization and increases susceptibility to ventricular tachyarrhythmia induction through IKs enhancement. On the other hand, vaccination against KCNQ1 ameliorates drug-induced QTc prolongation and might be useful therapeutically to enhance repolarization reserve in long QT syndrome., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Objective: Excessive neointima formation often occurs after arterial injury. Interleukin-1β (IL-1β) is a potent pleiotropic cytokine that has been shown to regulate neointimal proliferation. We investigated the effects of the IL-1β modulator gevokizumab in a rat carotid denudation model., Methods: Sprague-Dawley rats were subjected to balloon denudation of the right carotid artery and were then randomized to receive a single subcutaneous infusion immediately after balloon injury of saline (control group, n = 13) or gevokizumab (gevokizumab groups, n = 15 in each group: 1, 10 and 50 mg/kg). We evaluated the treatment effects on carotid intima-media thickness (IMT) using ultrasonography, on endothelial regrowth using Evans Blue staining and on inflammatory response using histology. We also assessed the effects of IL-1β and gevokizumab on human umbilical vein endothelial cells (HUVEC) and rat smooth muscle cells., Results: We found that carotid IMT, in the proximal part of the denuded artery at day 28, was decreased by gevokizumab 1 mg/kg compared with controls. Neointima area and the intima/media area ratio were both reduced in the gevokizumab 1 mg/kg-treated group. Gevokizumab at the 1 mg/kg dose also improved endothelial regrowth. No effect was observed with gevokizumab 10 or 50 mg/kg. Gevokizumab also decreased the inflammatory effect of IL-1β in in vitro cell experiments and protected HUVECs from IL-1β's deleterious effects on cell migration, apoptosis and proliferation., Conclusion: A single administration of gevokizumab 1 mg/kg improves endothelial regrowth and reduces neointima formation in rats following carotid denudation, at least in part through its beneficial effects on endothelial cells., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Background: Diastolic dysfunction often precedes the onset of diastolic heart failure. We previously demonstrated that diastolic dysfunction and left ventricular hypertrophy (LVH) in Dahl salt-sensitive rats can be ameliorated by quantitative trait loci (QTLs)., Methods: We analyzed cardiac phenotypes of 2 "single" congenic strains, C10S.L33 and C10S.L28, by echocardiography, in which a specific Dahl salt-sensitive rat chromosome segment was replaced by its Lewis homologue. C10S.L33 improves diastolic function (DF) and LVH only in rats aged 10 weeks, not aged 15 weeks. C10S.L28 alleviated LVH, but not diastolic dysfunction. Thus, the QTLs captured by C10S.L33 and C10S.L28 are designated as DF/LVH C10QTL7 and LVH C10QTL4, respectively. We then combined multiple single strains to form 2 congenic combinations. One of the 2 congenic combinations included the chromosome segments covered by C10S.L33 and C10S.L28., Results: Diastolic dysfunction was either completely or partially reversed by 15 weeks in the 2 congenic combinations. LVH was permanently improved from 10 to 15 weeks., Conclusions: Distinct QTLs exist that regulate diastolic function and/or LVH in the short term when acting alone, but durably when combined. The Ccl2 chemokine (C-C motif) ligand 1 (Ccl2) gene is the prime candidate for DF/LVH C10QTL7, owing to a nonconserved coding mutation. Schlafen genes are candidates for LVH C10QTL4. Since CCL2 and Schlafens are not known for influencing diastolic function and left ventricular mass, novel long-term strategies of prognosis, diagnosis, and therapy for diastolic heart failure and LVH appear from this work., (Copyright © 2013 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: Obesity and obstructive sleep apnea (OSA) are risk factors for atrial fibrillation (AF), but the underlying mechanisms are poorly understood., Objective: The purpose of this study was to assess the mechanisms underlying AF promotion by obesity and OSA in rat models., Methods: Zucker obese rats (ORs) and lean rats (LRs) were intubated and ventilated with air and 2% isoflurane. OSA was mimicked by stopping the ventilator and closing the airway for 40 seconds. For nonobstructive control periods, the protocol was repeated with an open airway. Fifteen seconds after apnea onset, AF susceptibility was tested with 6 atrial burst pacing cycles (25 Hz, 3 seconds, 1-second intercycle pauses)., Results: AF was not inducible in ORs or LRs at baseline or in nonobstructive control periods. AF was induced in 24 of 28 ORs (85.7%) vs 5 of 18 LRs (27.8%) during obstructive apnea (P <.001). Negative intrathoracic pressure generation (esophageal pressure monitoring) was substantial during obstructive apnea. Echocardiography showed left ventricular hypertrophy with diastolic dysfunction in ORs. Obstructive apnea caused acute left atrial (LA) dilation, increasing LA diameter significantly more in ORs than in LRs. To clarify AF mechanisms, 24 AF-inducible ORs were divided into 4 groups: saline (n = 5), pharmacologic autonomic blockade (n = 7), respiratory muscle paralysis with rocuronium (n = 6), and inferior vena cava (IVC) balloon occlusion to unload the LA (n = 6). Balloon catheter-induced IVC occlusion prevented LA distension during obstructive apnea, leading to 83.3% AF prevention (P <.05). Rocuronium also was protective (66.7%), but autonomic blockade had smaller effects (42.9% prevention)., Conclusion: Obesity and acute obstructive apnea interacted to promote AF in this model. Forced inspiration-induced acute LA distension related to diastolic dysfunction may be an important component of the arrhythmogenic substrate for AF during OSA episodes in obese patients., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)