Biology subjects

Benitah, J.-P.

Publications and source records attributed to Benitah, J.-P..

3 recordsLinked to original sources

bioRxiv2026

RyR2-Mediated Ca2+ Leak Drives Progressive Arrhythmogenic Cardiomyopathy

Background Abnormal sarcoplasmic reticulum (SR) Ca2+ release through ryanodine receptor 2 (RyR2) is a well-established mechanism of ventricular arrhythmias. Whether persistent RyR2 dysfunction can also initiate the structural remodeling characteristic of arrhythmogenic cardiomyopathy (ACM) remains unknown. We tested the hypothesis that chronic RyR2-mediated Ca2+ leak is sufficient to couple electrical instability to progressive cardiomyopathy. Methods We generated a rabbit carrying the severe gain-of-function RyR2-V2475F mutation and characterized disease progression using longitudinal cardiac phenotyping, continuous electrocardiographic monitoring, cellular electrophysiology and Ca2+ imaging, histopathology, biochemical analyses, and single-nucleus RNA sequencing (snRNA-seq). Therapeutic potential was evaluated by continuous treatment with the selective RyR2 inhibitor ent-verticilide for two months. Results RyR2-V2475F rabbits developed spontaneous ventricular tachyarrhythmias, sudden cardiac death, and progressive right ventricular (RV)-dominant fibrofatty cardiomyopathy recapitulating major features of human ACM. Malignant ventricular arrhythmias preceded overt structural remodeling and were associated at the cellular level with early spontaneous Ca2+ release and early afterdepolarizations. Early disease was characterized by remodeling of excitation-contraction coupling with preserved SR Ca2+ load and contractile function despite RyR2 dysfunction; upon disease progression, these compensatory changes were accompanied by SR Ca2+ depletion, impaired RV contractility and reduced left ventricular filling. Single-nucleus transcriptomics identified early fibroblast expansion and predicted cardiomyocyte-centered paracrine signaling before advanced fibrofatty infiltration. Cardiomyocytes also exhibited an altered lipid-metabolic transcriptome and intracellular lipid accumulation, accompanied by enhanced mitochondrial Ca2+ uptake. Selective RyR2 inhibition markedly reduced ventricular tachycardia burden and preserved RV contraction and LV filling during disease progression. Conclusions Severe RyR2 gain-of-function can lead to both malignant ventricular arrhythmias and progressive arrhythmogenic cardiomyopathy in a large-animal model, establishing persistent intracellular Ca2+ dysregulation as a mechanistic link between electrical and structural heart disease. The ability of selective RyR2 inhibition to suppress arrhythmias and preserve cardiac function identifies RyR2 as a potentially actionable therapeutic target in arrhythmogenic cardiomyopathy.

physiology↗

bioRxiv2024

Circadian regulation of CaV1.2 expression by RORalpha in the mouse heart

BackgroundIn addition to show autonomous beating rhythmicity, the physiological functions of the heart present daily periodic oscillations. Notably the ventricular repolarization itself varies throughout the circadian cycle which was mainly related to the periodic expression of K+ channels. However, the involvement of the L-type Ca2+ channel (CaV1.2 encoded by Cacna1c gene) in these circadian variations remains elusive. MethodsWe used a transgenic mouse model (PCa-luc) that expresses the luciferase reporter under the control of the cardiac Cacna1c promoter and analyzed promoter activity by bioluminescent imaging, qPCR, immunoblot, Chromatin immunoprecipitation assay (ChIP) and CaV1.2 activity. ResultsUnder normal 12:12h light-dark cycle, we observed in vivo a biphasic diurnal variation of promoter activities peaking at 9 and 19.5 Zeitgeber time (ZT). This was associated with a periodicity of Cacna1c mRNA levels preceding 24-h oscillations of CaV1.2 protein levels in ventricle (with a 1.5 h phase shift) but not in atrial heart tissues. The periodicity of promoter activities and CaV1.2 proteins, which correlated with biphasic oscillations of L-type Ca2+ current conductance, persisted in isolated ventricular cardiomyocytes from PCa-Luc mice over the course of the 24-h cycle, suggesting an endogenous cardiac circadian regulation. Comparison of 24-h temporal patterns of clock gene expressions in ventricles and atrial tissues of the same mice revealed conserved circadian oscillations of the core clock genes except for the retinoid-related orphan receptor gene (ROR), which remained constant throughout the course of a day in atrial tissues. In vitro we found that ROR is recruited to two specific regions on the Cacna1c promoter and that incubation with specific ROR inhibitor disrupted 24-h oscillations of ventricular promoter activities and CaV1.2 protein levels. Similar results were observed for pore forming subunits of the K+ transient outward currents, KV4.2 and KV4.3. ConclusionsThese findings raise the possibility that the ROR-dependent rhythmic regulation of cardiac CaV1.2 and KV4.2/4.3 throughout the daily cycle may play an important role in physiopathology of heart function.

physiology↗

bioRxiv2021

EPAC1 Inhibition Protects the Heart from Doxorubicin-Induced Toxicity

Anthracyclines, such as doxorubicin (Dox), are widely used chemotherapeutic agents for the treatment of solid tumors and hematologic malignancies. However, they frequently induce cardiotoxicity leading to dilated cardiomyopathy and heart failure. This study sought to investigate the role of the Exchange Protein directly Activated by cAMP (EPAC) in Dox-induced cardiotoxicity and the potential cardioprotective effects of EPAC inhibition. We show that Dox induces DNA damage and cardiomyocyte cell death with apoptotic features. Dox also led to an increase in both cAMP concentration and EPAC1 activity. The pharmacological inhibition of EPAC1 (with CE3F4) but not EPAC2 alleviated the whole Dox-induced pattern of alterations. When administered in vivo, Dox-treated WT mice developed a dilated cardiomyopathy which was totally prevented in EPAC1 KO mice. Moreover, EPAC1 inhibition potentiated Dox-induced cell death in several human cancer cell lines. Thus, EPAC1 inhibition appears as a potential therapeutic strategy to limit Dox-induced cardiomyopathy without interfering with its antitumoral activity.

pathology↗