Disruption of Epac1 protects the heart from adenylyl cyclase type 5-mediated cardiac dysfunction

Reduced coronary reserve (CR) is a cardinal feature of human cardiomyopathy, but it has not been studied extensively in mouse models of cardiomyopathy, potentially because of difficulties inherent to measuring CR in such a small heart. The first goal of this study was to determine if reduced CR is a potential mechanism involved in a transgenic (Tg) mouse model of cardiomyopathy, induced by cardiac overexpression of beta 2 -adrenergic receptors (beta 2 -AR Tg). Older beta 2 -AR Tg mice (16–17 months, n=7) developed cardiomyopathy, as reflected by decreased LV ejection fraction (LVEF, 50±7%), and increased fibrosis (5.2±0.4%) and apoptosis (3.8±0.6%). CR was obtained by measuring LV coronary blood flow at baseline and with adenosine (160 microg/kg/min) induced hyperemia using high resolution ultrasound (Vevo 770). CR was significantly decreased in beta 2 -AR Tg (1.8±0.2) compared with wild type (WT) (3.0±0.3, n=6). The next goal was to determine if the rescue of the beta 2 -AR Tg cardiomyopathy resulted in a rescue of reduced CR. Since adenylyl cyclase type 5 knockout (AC5 KO) mice are protected against catecholamine stress and the development of heart failure (HF), and exhibit enhanced CR (3.7±0.4, n=5), we hypothesized that mating these mice with beta 2 -AR Tg might rescue the cardiomyopathy. Older (16–17 months, n=4) bigenic mice (beta 2 -AR Tg x AC5 KO) demonstrated a rescue of cardiomyopathy, as reflected by normalized LVEF (71±1%) and levels of apoptosis (0.11±0.01%) and fibrosis (1.09±0.33%), similar to WT. In these mice, CR was also normalized (3.4±0.6). Reduced CR in beta 2 -AR Tg cardiomyopathy is similar to that observed in large mammalian models, and in patients with cardiomyopathy. Thus, this mechanism is important to consider in mouse models of cardiomyopathy, in general, and also in particular for the mechanism of the rescue of the beta 2 -AR Tg cardiomyopathy by AC5 KO.

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Abstract 212: Inhibition of Protein Phosphatase 2A (PP2A) Leads to Beta-adrenergic Receptor Dysfunction With Cardiac Stress Following Pressure-overload Hypertrophy

Circulation Research ◽

10.1161/res.117.suppl_1.212 ◽

2015 ◽

Vol 117 (suppl_1) ◽

Author(s):

Arunachal Chatterjee ◽

Neelakantan Vasudevan ◽

Maradumane Mohan ◽

Elizabeth Martelli ◽

John George ◽

...

Keyword(s):

Cardiac Hypertrophy ◽

Adenylyl Cyclase ◽

Cardiac Dysfunction ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Cyclase Activity ◽

Adenylyl Cyclase Activity ◽

Cardiac Stress ◽

Phosphatase 2A

Beta-Adrenergic receptors (bARs) play a key role in regulating cardiac function. Loss of surface receptors and desensitization (impaired G-protein coupling) of bARs are hallmarks of a failing heart. Desensitization occurs by phosphorylation of bARs. The bARs are resensitized by protein phosphatase 2A (PP2A) mediated dephosphorylation in the endosomes before recycling to the plasma membrane. While mechanisms of desensitization are well understood, little is known about mechanisms regulating resensitization. Our previous work has shown that PI3Kg phosphorylates an endogenous inhibitor of PP2A (I2PP2A) on serine 9 & 93, which then robustly binds to PP2A inhibiting bAR resensitization. Since it is not known whether resensitization is altered in response to cardiac stress or whether altered bAR resensitization contributes to cardiac hypertrophy and failure, we generated transgenic mice with cardiomyocyte specific overexpression of wild type I2PP2A (WT I2PP2A Tg), I2PP2A phospho-mimetic mutants S9, 93D and mutants with constitutively dephosphorylated S9, 93A state. To test whether resensitization is critical in the development of bAR dysfunction during cardiac hypertrophy, WT I2PP2A Tg mice were subjected to transverse aortic constriction (TAC) for 8 weeks. Echocardiographic analysis post-TAC showed that WT I2PP2A Tg mice had accelerated cardiac dysfunction compared to their littermate controls [HW (mg)/BW(g): Sham: WT - 4.83, WT I2PP2A Tg - 4.82, TAC: WT- 6.47, WT I2PP2A Tg - 7.61; %EF: Sham: WT - 83.53, WT I2PP2A Tg - 74.72, TAC: WT - 70.47, WT I2PP2A Tg - 49.62]. To directly test whether resensitization mechanisms are altered, plasma membranes and endosomes were isolated and in vitro Adenylyl Cyclase activity assessed. Our studies show that compared to littermate controls, WT I2PP2A Tg had altered in vitro adenylyl cyclase activity showing that resensitization mechanisms in the endosomes may in part, contribute to cardiac dysfunction. Mechanistic underpinnings of the resensitization pathways using the I2PP2A S9, 93A and S9, 93D will be presented showing that bAR resensitization a process considered passive is altered in conditions of cardiac stress that in part may contribute to bAR dysfunction leading to cardiac hypertrophy and heart failure.

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Modification of cardiac β-adrenoceptor mechanisms by H2O2

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1998.274.2.h416 ◽

1998 ◽

Vol 274 (2) ◽

pp. H416-H423 ◽

Cited By ~ 4

Author(s):

Sujata Persad ◽

Heinz Rupp ◽

Rashi Jindal ◽

Jugpal Arneja ◽

Naranjan S. Dhalla

Keyword(s):

Oxidative Stress ◽

Signal Transduction ◽

Adenylyl Cyclase ◽

G Proteins ◽

Cardiac Dysfunction ◽

Biochemical Parameters ◽

Adenylyl Cyclase Activity ◽

High Concentrations ◽

Stimulation Of

From the role of oxidative stress in cardiac dysfunction, we investigated the effect of H2O2, an activated species of oxygen, on β-adrenoceptors, G proteins, and adenylyl cyclase activities. Rat heart membranes were incubated with different concentrations of H2O2before the biochemical parameters were measured. Both the affinity and density of β1-adrenoceptors were decreased, whereas the density of the β2-adrenoceptors was decreased and the affinity was increased by 1 mM H2O2. Time- and concentration-dependent biphasic changes in adenylyl cyclase activities in the absence or presence of isoproterenol were observed when membranes were incubated with H2O2; however, activation of the enzyme by isoproterenol was increased or unaltered. The adenylyl cyclase activities in the absence or presence of forskolin, NaF, and Gpp(NH)p were depressed by H2O2. Catalase alone or in combination with mannitol was able to significantly decrease the magnitude of alterations due to H2O2. The cholera toxin-stimulated adenylyl cyclase activity and ADP ribose labeling of Gs proteins were decreased by treatment with 1 mM H2O2, whereas Gi protein activities, as reflected by pertussis toxin-stimulation of adenylyl cyclase and ADP ribosylation, were unaltered. The Gs and Gi protein immunoreactivities, estimated by labeling with respective antibodies, indicate a decrease in binding to the 45-kDa band of Gs protein, whereas no change in the binding of antibodies to the 52-kDa band of Gs protein or the 40-kDa subunit of Gi protein was evident when the membranes were treated with 1 mM H2O2. These results suggest that H2O2in high concentrations may attenuate the β-adrenoceptor-linked signal transduction in the heart by changing the functions of Gs proteins and the catalytic subunit of the adenylyl cyclase enzyme.

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Disruption of adenylyl cyclase type 5 mimics exercise training

Basic Research in Cardiology ◽

10.1007/s00395-017-0648-8 ◽

2017 ◽

Vol 112 (6) ◽

Cited By ~ 10

Author(s):

John J. Guers ◽

Jie Zhang ◽

Sara C. Campbell ◽

Marko Oydanich ◽

Dorothy E. Vatner ◽

...

Keyword(s):

Exercise Training ◽

Adenylyl Cyclase ◽

Adenylyl Cyclase Type 5

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PHARMACOLOGICAL INHIBITION OF ADENYLYL CYCLASE TYPE 5: A NOVEL THERAPEUTIC MODALITY TO REDUCE INFARCT SIZE EVEN WHEN DELIVERED AFTER CORONARY ARTERY REPERFUSION

Journal of the American College of Cardiology ◽

10.1016/s0735-1097(18)30550-3 ◽

2018 ◽

Vol 71 (11) ◽

pp. A9

Author(s):

Jie Zhang ◽

Daniel Levy ◽

Thomas Richardson ◽

Christopher Meenan ◽

Seonghun Yoon ◽

...

Keyword(s):

Coronary Artery ◽

Infarct Size ◽

Adenylyl Cyclase ◽

Therapeutic Modality ◽

Reduce Infarct Size ◽

Pharmacological Inhibition ◽

Novel Therapeutic ◽

Adenylyl Cyclase Type 5

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Cardiac-Directed Expression of Adenylyl Cyclase Catalytic Domain Reverses Cardiac Dysfunction Caused by Sustained Beta-Adrenergic Receptor Stimulation

JACC Basic to Translational Science ◽

10.1016/j.jacbts.2016.08.004 ◽

2016 ◽

Vol 1 (7) ◽

pp. 617-629 ◽

Cited By ~ 4

Author(s):

Mei Hua Gao ◽

N. Chin Lai ◽

Dimosthenis Giamouridis ◽

Young Chul Kim ◽

Zhen Tan ◽

...

Keyword(s):

Adenylyl Cyclase ◽

Cardiac Dysfunction ◽

Adrenergic Receptor ◽

Catalytic Domain ◽

Beta Adrenergic Receptor ◽

Receptor Stimulation ◽

Beta Adrenergic

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Cardiac adenylyl cyclase overexpression precipitates and aggravates age-related myocardial dysfunction

Cardiovascular Research ◽

10.1093/cvr/cvy306 ◽

2019 ◽

Vol 115 (12) ◽

pp. 1778-1790 ◽

Cited By ~ 2

Author(s):

Nathalie Mougenot ◽

Delphine Mika ◽

Gabor Czibik ◽

Elizabeth Marcos ◽

Shariq Abid ◽

...

Keyword(s):

Strain Rate ◽

Adenylyl Cyclase ◽

Cardiac Dysfunction ◽

Contractile Function ◽

Myocardial Dysfunction ◽

Cardiac Contraction ◽

Doppler Imaging ◽

Hypertrophic Growth ◽

Camp Signalling ◽

Age Related

Abstract Aims Increase of cardiac cAMP bioavailability and PKA activity through adenylyl-cyclase 8 (AC8) overexpression enhances contractile function in young transgenic mice (AC8TG). Ageing is associated with decline of cardiac contraction partly by the desensitization of β-adrenergic/cAMP signalling. Our objective was to evaluate cardiac cAMP signalling as age increases between 2 months and 12 months and to explore whether increasing the bioavailability of cAMP by overexpression of AC8 could prevent cardiac dysfunction related to age. Methods and results Cardiac cAMP pathway and contractile function were evaluated in AC8TG and their non-transgenic littermates (NTG) at 2- and 12 months old. AC8TG demonstrated increased AC8, PDE1, 3B and 4D expression at both ages, resulting in increased phosphodiesterase and PKA activity, and increased phosphorylation of several PKA targets including sarco(endo)plasmic-reticulum-calcium-ATPase (SERCA2a) cofactor phospholamban (PLN) and GSK3α/β a main regulator of hypertrophic growth and ageing. Confocal immunofluorescence revealed that the major phospho-PKA substrates were co-localized with Z-line in 2-month-old NTG but with Z-line interspace in AC8TG, confirming the increase of PKA activity in the compartment of PLN/SERCA2a. In both 12-month-old NTG and AC8TG, PLN and GSK3α/β phosphorylation was increased together with main localization of phospho-PKA substrates in Z-line interspaces. Haemodynamics demonstrated an increased contractile function in 2- and 12-month-old AC8TG, but not in NTG. In contrast, echocardiography and tissue Doppler imaging (TDI) performed in conscious mice unmasked myocardial dysfunction with a decrease of systolic strain rate in both old AC8TG and NTG. In AC8TG TDI showed a reduced strain rate even in 2-month-old animals. Development of age-related cardiac dysfunction was accelerated in AC8TG, leading to heart failure (HF) and premature death. Histological analysis confirmed early cardiomyocyte hypertrophy and interstitial fibrosis in AC8TG when compared with NTG. Conclusion Our data demonstrated an early and accelerated cardiac remodelling in AC8TG mice, leading to the development of HF and reduced lifespan. Age-related reorganization of cAMP/PKA signalling can accelerate cardiac ageing, partly through GSK3α/β phosphorylation.

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