Role of cAMP signalosomes in cardiomyocyte senescence and age-associated heart failure – SIGNALAGE

First, we will evaluate if cAMP, via EPAC1, could regulate mitochondrial ROS accumulation, DNA Damage Response (DDR), excitation-contraction coupling and senescence in the ageing heart. Second, we will explore if specific regulation of PDEs isoforms during ageing could impact on subcellular cAMP levels wih a particular emphasis on mitochondria and nucleus, two major actors of senescence. Third, we will assess if overexpression of PDEs to limit cAMP levels, or inhibition of EPAC1 activity, could alleviate senescence and age-associated HF in mice models of normal or accelerated ageing. Thus, a unique feature of this program will be the capacity to carry out highly integrated approaches in animal and cellular studies.

We evaluated the regulation of the different actors of the EPAC / PDE signalosome during cardiac aging. We observed overexpression of the Epac1 protein, but not Epac2. At the level of PDEs, the expression of genes encoding PDE1, PDE2, PDE4, PDE5 is not modified, while an increase in PDE3B and PDE9A is observed. We then evaluated in vitro the consequences of an activation of Epac1 on various events associated with senescence. Activation of Epac1 leads to DNA damage in cardiomyocytes, which is accompanied by induction of senescence. This indicates a major role of Epac1 in cardiomyocyte senescence. In parallel, we compared ß-adrenergic responses on cAMP levels measured by FRET imaging and excitation-contraction coupling in young and old cardiomyocytes. Our results show desensitization of ß-adrenergic responses in aged cardiomyocytes.
The role of Epac1 in physiological aging was studied in young (6 months) and old (24 months) WT or KO Epac1 mice. Functional echocardiographic analyzes showed that baseline diastolic function was impaired in elderly animals. We observe an altered acute response to isoproterenol in aged WT mice that is not seen in KO mice. This would indicate that the functional reserve is preserved in KO Epac1 mice. Analyzes of senescence markers showed a significant decrease in the hearts of KO Epac1 mice compared to aged WT mice. In parallel, we examined the impact of cardiac overexpression of a particular phosphodiesterase isoform (PDE4B) on cardiac function during aging. Our results show that a moderate increase in PDE4B decreases cardiac function but protects against prolonged adrenergic stress and does not affect the life expectancy of mice

By better understanding the role of cAMP during cardiac aging, we hope to identify new therapeutic targets in order to find new treatments for HFpEF, a pathology whose prevalence is constantly increasing in the elderly and for which there is no treatments.

1. Santin Y, Resta J, Parini A and Mialet-Perez J. Ageing Res Rev (2021). Doi: 10.1016/j.arr.2021.101256
2. Formoso K, Lezoualc’h F, Mialet-Perez J. Cells (2020). Doi : 10.3390/cells9091954
3. Mialet-Perez J and Parini A. Cell Death and Disease (2020). doi: 10.1038/s41419-020-2251-4.
4. Martini H, Lefevre L, Sayir S, Itier R, Maggiorani D, Dutaur M, Marsal D, Roncalli J, Pizzinat N, Cussac D, Parini A, Mialet-Perez J and Douin-Echinard V. International Journal of Molecular Sciences (2021) doi: 10.3390/ijms22052245
5. Karam S, Margaria JP, Bourcier A, Mika D, Varin A, Bedioune I, Lindner M, Bouadjel K, Dessillons M, Gaudin F, Lefebvre F, Mateo P, Lechene P, Gomez S, Domergue V, Robert P, Coquard C, Algalarrondo V, Samuel JL, Michel JB, Charpentier F, Ghigo A, Hirsch E, Fischmeister R, Leroy J, Vandecasteele G. Cardiac Overexpression of PDE4B Blunts beta-Adrenergic Response and Maladaptive Remodeling in Heart Failure. Circulation. 2020;142:161-174.

The increase in longevity is associated with a wider prevalence of heart failure with preserved ejection fraction (HFpEF). While the incidence of HFpEF in terms of mortality is constantly growing, treatments remain unsuccessful because of insufficient knowledge on the mechanisms of cardiac ageing. In an original approach, our consortium proposes to develop and share appropriate models to better understand HF in the context of ageing. Recently, senescent cells accumulation has emerged as a main driver of age-associated diseases. In the lab, we have recently shown that aged cardiomyocytes acquire a senescent-like phenotype characterized by persistent telomere DNA damage and activation of classical markers of senescence. In addition, pharmacological or genetic removal of senescent cells in the ageing heart protects from hypertrophy and fibrosis. This has led to the concept that targeting specific senescence pathways in the heart could alleviate some features of age-associated HF. Our RNA sequencing performed in senescent cardiomyocytes demonstrated activation of key signaling pathways related to cAMP. cAMP is a second messenger regulating major pathophysiological processes in the heart but its role in cardiac ageing is poorly understood. Among the downstream effectors of cAMP are the recently identified cAMP binding proteins, Exchange Proteins directly Activated by cAMP (EPACs). EPAC1 and EPAC2 act as guanine-nucleotide exchange factors for the small G protein, Rap and regulate key events in cardiac remodelling such as hypertrophy and apoptosis. Our preliminary data indicate that EPAC1 is overexpressed in the mice ageing heart and that chronic activation of EPAC1 in vitro promotes senescence of cardiomyocytes. Compelling evidence indicates that cAMP/EPAC1 signalosome is highly compartmentalized and occurs in several subcellular compartments, such as the mitochondria and the nuclear/perinuclear region of cardiomyocytes where it can regulate different signalling pathways eventually leading to senescence. The availability and subcellular pools of cAMP are controlled by a superfamily of enzymes called phosphodiesterases (PDEs). As PDE isoforms are spatially segregated into the cell, this could allow tailoring of cAMP signalling in mitochondria or nucleus versus cytoplasmic compartments by the use of selective PDEs inhibitors. However at present, the role and the regulation of the different isoforms of PDEs in cardiac ageing are unknown.
In this project, we will combine in vitro and in vivo approaches to study the regulation and function of cAMP signalosomes during ageing. First, we will evaluate if cAMP, via EPAC1, could regulate mitochondrial ROS accumulation, DNA Damage Response (DDR), excitation-contraction coupling and senescence in the ageing heart. Second, we will explore if specific regulation of PDEs isoforms during ageing could impact on subcellular cAMP levels wih a particular emphasis on mitochondria and nucleus, two major actors of senescence. Third, we will assess if overexpression of PDEs to limit cAMP levels, or inhibition of EPAC1 activity, could alleviate senescence and age-associated HF in mice models of normal or accelerated ageing. Thus, a unique feature of this program will be the capacity to carry out highly integrated approaches in animal and cellular studies.
SIGNALAGE will bring together scientists covering the fields of senescence and cardiac ageing at INSERM “institute of metabolic and cardiovascular diseases” (I2MC) in Toulouse (Partner 1), excitation-contraction coupling at INSERM U1180 (Labex LERMIT) in Châtenay-Malabry (Partner 2) and cAMP signalosomes and compartimentalization (Partners 1 and 2) in the hope of finding new perspectives for the treatment of HFpEF.