Roddy Hiram - Montreal Heart Institute - Post-Doctorate Fellow

Roddy Hiram

Montreal Heart Institute

Post-Doctorate Fellow

Montreal, Quebec | Canada

Main Specialties: Cardiovascular Disease, Pulmonary Disease

Additional Specialties: Physiology, Pharmacology, Cell and Molecular Biology, Biophysics, Cardiovascular Diseases, Cardiac Electrophysiology, Lung diseases, Pulmonary Hypertension Inflammation


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Roddy Hiram - Montreal Heart Institute - Post-Doctorate Fellow

Roddy Hiram

Education

Jun 2016 - Jun 2020
Montreal Heart Institute
Post-Doctorate/Dr
Cardiology
Sep 2012 - Apr 2016
Université de Sherbrooke
Doctorate
Pharmacology et Physiology

Experience

Jun 2016
Montreal Heart Institute/Dr Stanley Nattel
Post-Doctoral Fellow
Cardiology

Publications

7Publications

213Reads

437Profile Views

Role of atrial arrhythmia and ventricular response in atrial fibrillation induced atrial remodeling.

Cardiovasc Res 2020 Jan 24. Epub 2020 Jan 24.

Department of Medicine and Research Center Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada.

Aims: No studies have assessed the specific contributions of atrial fibrillation (AF)-related atrial versus associated ventricular arrhythmia to remodeling. This study assessed the roles of atrial arrhythmia versus high ventricular rate in AF-associated remodeling.

Methods And Results: Four primary dog-groups (12/group) were subjected to 3-week pacing: 600-bpm atrial-tachypacing maintaining AF (AF w/o-AVB); atrial-tachypacing with atrioventricular-node ablation (AF+AVB) and ventricular-demand pacing (80-bpm); 160-bpm ventricular-tachypacing (V160) reproducing the response-rate during AF; and sinus rhythm with AVB/ventricular-pacing at 80-bpm (CTL). At terminal study, left-atrial (LA) effective refractory period (ERP) was reduced equally in both AF-groups (w/o-AVB and AF+AVB). AF-inducibility was increased strongly in AF-groups (w/o-AVB and AF+AVB) and modestly in V160. AF-duration was significantly increased in AF w/o-AVB but not in AF+AVB or V160. Conduction velocity was decreased in AF w/o-AVB, to a greater extent than in AF+AVB and V160. Atrial fibrous-tissue content was increased in AF w/o-AVB, AF+AVB and V160, with collagen-gene upregulation only in AF w/o-AVB. Connexin43 gene-expression was reduced only in AF w/o-AVB. An additional group of 240-bpm ventricular tachypacing dogs (VTP240; to induce heart failure) was studied: versus other tachypaced groups, VTP240 caused greater fibrosis, but no change in LA-ERP or AF-inducibility. VTP240 also increased AF-duration, strongly decreased left-ventricular ejection fraction, and was the only group with LA natriuretic-peptide activation.

Conclusions: The atrial tachyarrhythmia and rapid ventricular response during AF produce distinct atrial remodeling; both contribute to the arrhythmogenic substrate, providing new insights into AF-related remodeling and novel considerations for ventricular rate-control.

Translational Perspective: AF often produces a rapid and irregular arrhythmia in both the atria and ventricles. This study evaluates the contributions of AF-induced atrial versus ventricular arrhythmia to atrial remodeling. Each component produced discrete features: AF-induced atrial arrhythmia caused accelerated repolarization and abbreviated refractoriness, strongly increased vulnerability to AF-induction by premature ectopic beats, conduction slowing and moderate atrial fibrosis; whereas ventricular arrhythmia slightly increased vulnerability, slowed conduction and induced moderate fibrosis without affecting repolarization/refractoriness,. Combined atrial and ventricular arrhythmia abbreviated refractoriness, strongly increased vulnerability and fibrosis and greatly increased AF stability/duration. This work suggests that in the absence of ventricular rate control, the rapid ventricular response can cause AF-promoting atrial remodeling without overt heart failure; further research is needed to clarify the clinical relevance of these findings.

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http://dx.doi.org/10.1093/cvr/cvaa007DOI Listing
January 2020
7.014 Impact Factor

Right Atrial Mechanisms of Atrial Fibrillation in a Rat Model of Right Heart Disease.

J Am Coll Cardiol 2019 09;74(10):1332-1347

Montreal Heart Institute (MHI), Department of Medicine, Université de Montréal, Montreal, Quebec, Canada; Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada; IHU Liryc and Fondation Bordeaux Université, Bordeaux, France; Institute of Pharmacology, West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany. Electronic address:

Background: Conditions affecting the right heart, including diseases of the lungs and pulmonary circulation, promote atrial fibrillation (AF), but the mechanisms are poorly understood.

Objectives: This study sought to determine whether right heart disease promotes atrial arrhythmogenesis in a rat model of pulmonary hypertension (PH) and, if so, to define the underlying mechanisms.

Methods: PH was induced in male Wistar rats with a single intraperitoneal injection of 60 mg/kg of monocrotaline, and rats were studied 21 days later when right heart disease was well developed. AF vulnerability was assessed in vivo and in situ, and mechanisms were defined by optical mapping, histochemistry, and biochemistry.

Results: Monocrotaline-treated rats developed increased right ventricular pressure and mass, along with right atrial (RA) enlargement. AF/flutter was inducible in 32 of 32 PH rats (100%) in vivo and 11 of 12 (92%) in situ, versus 2 of 32 (6%) and 2 of 12 (17%), respectively, in control rats (p < 0.001 vs. PH for each). PH rats had significant RA (16.1 ± 0.5% of cross-sectional area, vs. 3.0 ± 0.6% in control) and left atrial (LA: 11.8 ± 0.5% vs. 5.4 ± 0.8% control) fibrosis. Multiple extracellular matrix proteins, including collagen 1 and 3, fibronectin, and matrix metalloproteinases 2 and 9, were up-regulated in PH rat RA. Optical mapping revealed significant rate-dependent RA conduction slowing and rotor activity, including stable rotors in 4 of 11 PH rats, whereas no significant conduction slowing or rotor activity occurred in the LA of monocrotaline-treated rats. Transcriptomic analysis revealed differentially enriched genes related to hypertrophy, inflammation, and fibrosis in RA of monocrotaline-treated rats versus control. Biochemical results in PH rats were compared with those of AF-prone rats with atrial remodeling in the context of left ventricular dysfunction due to myocardial infarction: myocardial infarction rat LA shared molecular motifs with PH rat RA.

Conclusions: Right heart disease produces a substrate for AF maintenance due to RA re-entrant activity, with an underlying substrate prominently involving RA fibrosis and conduction abnormalities.

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http://dx.doi.org/10.1016/j.jacc.2019.06.066DOI Listing
September 2019
213 Reads
20.589 Impact Factor

MAG-DPA curbs inflammatory biomarkers and pharmacological reactivity in cytokine-triggered hyperresponsive airway models.

Pharmacol Res Perspect. 2016 Oct 18;4(6):e00263

Pharmacology Research and Perspectives

Bronchial inflammation contributes to a sustained elevation of airway hyperresponsiveness (AHR) in asthma. Conversely, omega‐3 fatty acid derivatives have been shown to resolve inflammation in various tissues. Thus, the effects of docosapentaenoic acid monoacylglyceride (MAG‐DPA) were assessed on inflammatory markers and reactivity of human distal bronchi as well as in a cultured model of guinea pig tracheal rings. Human bronchi were dissected and cultured for 48 h with 10 ng/mL TNF‐α or IL‐13. Guinea pig tracheas were maintained in organ culture for 72 h which was previously shown to trigger spontaneous AHR. All tissues were treated with increasing concentrations of MAG‐DPA (0.1, 0.3, and 1 μmol/L). Pharmacomechanical reactivity, Ca2+ sensitivity, and western blot analysis for specific phosphoproteins and transcription factors were performed to assess the effects of both cytokines, alone or in combination with MAG‐DPA, on human and guinea pig airway preparations. Although 0.1 μmol/L MAG‐DPA did not significantly reduce inflammatory biomarkers, the higher concentrations of MAG‐DPA (0.3 and 1 μmol/L) blunted the activation of the TNF‐α/NF κB pathway and abolished COX‐2 expression in human and guinea pig tissues. Moreover, 0.3 and 1 μmol/L MAG‐DPA consistently decreased the Ca2+ sensitivity and pharmacological reactivity of cultured bronchial explants. Furthermore, in human bronchi, IL‐13‐stimulated phosphorylation of CPI‐17 was reversed by 1 μmol/L MAG‐DPA. This effect was further amplified in the presence of 100 μmol/L aspirin. MAG‐DPA mediates antiphlogistic effects by increasing the resolution of inflammation, while resetting Ca2+ sensitivity and contractile reactivity.

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October 2016
21 Reads

Resolvin E1 normalizes contractility, Ca2+ sensitivity and smooth muscle cell migration rate in TNF-α- and IL-6-pretreated human pulmonary arteries.

Am J Physiol Lung Cell Mol Physiol. 2015 Oct 15;309(8):L776-88

American Journal of Physiology Lung Cellular and Molecular Physiology.

Pulmonary hypertension (PH) is a rare disease in which pathophysiology is characterized by an increase in proinflammatory mediators, chronic endothelial dysfunctions, and a high migration rate of smooth muscle cells (SMC). Over the course of the last decade, various treatments have been proposed to relax the pulmonary arteries, none of which have been effective in resolving PH. Our hypothesis is that artery-relaxing drugs are not the long-term solution, but rather the inhibition of tissue inflammation, which underlies human pulmonary artery (HPA) dysfunctions that lead to abnormal vasoconstriction. The goal of the present study was to assess the anti-inflammatory effects of resolvin E1 (RvE1) with concomitant effects on SMC migration and on HPA reactivity. The role and mode of action of RvE1 and its precursor, monoacylglyceride eicosapentaenoic acid were assessed on HPA under proinflammatory conditions, involving a combined pretreatment with 10 ng/ml TNF-α and 10 ng/ml IL-6. Our results show that TNF-α and IL-6 treatment induced hyperreactivity and Ca(2+) hypersensitivity in response to pharmaco-mechanical stimuli, including 80 mM KCl, 1 μM phorbol 12-13-dibutyrate, and 30 nM U-46619. Furthermore, the proinflammatory treatment increased the migration rate of SMC isolated from HPA. The phosphorylation level of regulatory contractile proteins (CPI-17, MYPT-1), and proinflammatory signaling pathways (c-Fos, c-Jun, NF-κB) were also significantly increased compared with control conditions. Conversely, 300 nM RvE1 was able to normalize all of the above abnormal events triggered by proinflammation. In conclusion, RvE1 can resolve human arterial hyperreactivity via the resolution of inflammatory markers.

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October 2015

Impact Factor 4.060

199 Reads

Resolvin D1 reverses reactivity and Ca2+ sensitivity induced by ET-1, TNF-α, and IL-6 in the human pulmonary artery.

Am J Physiol Heart Circ Physiol. 2014 Dec 1;307(11):H1547-58

American Journal of Physiology and Heart Circulation Physiology.

Pulmonary hypertension (PH) is a rare and progressive disease characterized by an inflammatory status and vessel wall remodeling, resulting in increased pulmonary artery resistance. During the last decade, treatments have been proposed; most of them target the endothelial pathways that stimulate smooth muscle cell relaxation. However, PH remains associated with significant morbidity. We hypothesized that inflammation plays a crucial role in the severity of the abnormal vasoconstriction in PH. The goal of this study was to assess the effects of resolvin D1 (RvD1), a potent anti-inflammatory agent, on the pharmacological reactivity of human pulmonary arteries (HPAs) via an in vitro model of induced hyperreactivity. The effects of RvD1 and monoacylglyceride compounds were measured on contractile activity and Ca2+ sensitivity developed by HPAs that had been pretreated (or not) under proinflammatory conditions with either 10 ng/ml TNF-α or 10 ng/ml IL-6 or under hyperreactive conditions with 5 nM endothelin-1. The results demonstrated that, compared with controls, 24-h pretreatment with TNF-α, IL-6, or endothelin-1 increased reactivity and Ca2+ sensitivity of HPAs as revealed by agonist challenges with 80 mM KCl, 1 μM serotonin (5-hydroxytryptamine), 30 nM U-46619, and 1 μM phorbol 12,13-dibutyrate. However, 300 nM RvD1 as well as 1 μM monoacylglyceride-docosapentaenoic acid monoglyceride strongly reversed the overresponsiveness induced by both proinflammatory and hyperreactive treatments. In pretreated pulmonary artery smooth muscle cells, Western blot analyses revealed that RvD1 treatment decreased the phosphorylation level of CPI-17 and expression of transmembrane protein member 16A while increasing the detection of G protein-coupled receptor 32. The present data demonstrate that RvD1, a trihydroxylated docosahexaenoic acid derivative, decreases induced overreactivity in HPAs via a reduction in CPI-17 phosphorylation and transmembrane protein member 16A expression.

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December 2014

Impact Factor 4.048

285 Reads

Docosapentaenoic acid monoacylglyceride reduces inflammation and vascular remodeling in experimental pulmonary hypertension.

Am J Physiol Heart Circ Physiol. 2014 Aug 15;307(4):H574-86

American Journal of Physiology Heart and Circulatory Physiology.

n-3 Polyunsaturated fatty acids (n-3 PUFA) have been shown to reduce inflammation and proliferation of pulmonary artery smooth muscle cells under pathophysiological conditions. However, the anti-inflammatory effect of the newly synthesized docosapentaenoic acid monoacylglyceride (MAG-DPA) on key signaling pathways in pulmonary hypertension (PH) pathogenesis has yet to be assessed. The aim of the present study was to determine the effects of MAG-DPA on pulmonary inflammation and remodeling occurring in a rat model of PH, induced by a single injection of monocrotaline (MCT: 60 mg/kg). Our results demonstrate that MAG-DPA treatment for 3 wk following MCT injection resulted in a significant improvement of right ventricular hypertrophy (RVH) and a reduction in Fulton's Index (FI). Morphometric analyses revealed that the wall thickness of pulmonary arterioles was significantly lower in MCT + MAG-DPA-treated rats compared with controls. This result was further correlated with a decrease in Ki-67 immunostaining. Following MAG-DPA treatments, lipid analysis showed a consistent increase in DPA together with lower levels of arachidonic acid (AA), as measured in blood and tissue samples. Furthermore, in MCT-treated rats, oral administration of MAG-DPA decreased NF-κB and p38 MAPK activation, leading to a reduction in MMP-2, MMP-9, and VEGF expression levels in lung tissue homogenates. Altogether, these data provide new evidence regarding the mode of action of MAG-DPA in the prevention of pulmonary hypertension induced by MCT.

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August 2014
246 Reads

Top co-authors

Stanley Nattel
Stanley Nattel

Montreal Heart Institute and Université de Montréal

2
Patrice Naud
Patrice Naud

Montreal Heart Institute

2
Jean-Claude Tardif
Jean-Claude Tardif

Montreal Heart Institute

2
Feng Xiong
Feng Xiong

Institute of Hydrobiology

2
Vincent Algalarrondo
Vincent Algalarrondo

Antoine Béclère Hospital

1
Martin G Sirois
Martin G Sirois

Research Center

1
Jiening Xiao
Jiening Xiao

Montreal Heart Institute

1
Xiao-Yan Qi
Xiao-Yan Qi

Montreal Heart Institute

1