Heart failure (HF) is still a major cause of morbidity and mortality, contributing significantly to global health expenditure, although there have been significant advances in HF therapy in recent decades. Adrenergic nervous system hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart. Adenosine is an important endogenous physiological modulator of the heart function and it has been demonstrated to serve as a negative feedback regulator of sympathetic overstimulation by the β1-adrenoceptors (β1ARs). It is well known that the antiadrenergic action of adenosine, through activation of A1 adenosine receptors (A1ARs), serves as a mechanism of cardioprotection against cardiotoxicity which may accompany excessive adrenergic stimulation. The study presented here aims to assess, in both atrial and ventricular myocytes, spatial distribution of adrenergic and adenosine receptors in different subcellular microdomains and explore their functional interplay in normal heart and HF. The study aimed to: (1) investigate the functional role of the anti-adrenergic effect of adenosine in normal heart and HF, measuring the cell contractility via IonOptix system; (2) dissect cellular mechanisms, elucidating the cyclic nucleotide response to catecholamine stimulation following both global (in the bath) or local (in the nano-pipette) stimulation of either β1ARs or A1ARs. The cAMP levels were measured via Förster Resonance Energy Transfer (FRET) for the whole-cell recording and via a combination of FRET and scanning ion conductance microscopy (SICM) for local stimulation and measurement of cAMP within the specific microdomains; (3) study molecular mechanisms of the anti-adrenergic effect of adenosine by quantitative PCR (qPCR) and western blot technique. It was found that A1ARs agonist significantly decreases cAMP concentration following β1AR stimulation, in both atrial and ventricular myocytes. In contrast, corresponding reduction in the sarcomere shortening was found exclusively in atrial myocytes. Using animal model, heart failure condition was found to be associated with the significant reduction of the anti- 2 adrenergic effect of A1ARs stimulation for both contractility and cAMP production in atrial cardiomyocytes. Such effect could be associated with structural changes occurring during HF conditions, such as t-tubule and/or caveolae degradation. Indeed, with the caveolae disruption a similar situation was observed. In addition, molecular investigation shows that A1ARs are upregulated in left atrium. This study presents evidence of a population of A1ARs that are localized specifically within the cholesterol lipid microdomains on the surface of myocytes and suggests that A1ARs may interact with the β1ARs in these microdomains. During the HF the antiadrenergic effect of adenosine is significantly lower. The loss of the antiadrenergic effect of A1ARs could be associated with the loss of cardiac cytoarchitecture occurring during HF conditions that may cause a disruption of adrenergic/adenosine signalling compartmentation and interplay. On the other hand, the increase of A1ARs density during failing conditions appears to follow the loss of the adenosine effects, suggesting the establishment of a potential compensatory mechanism that could be a driving factor of the failing phenotype.

β-adrenergic and adenosine receptors interaction during heart failure in atrial cardiomyocytes

Mazzola, Marta
Writing – Original Draft Preparation
2018-01-01

Abstract

Heart failure (HF) is still a major cause of morbidity and mortality, contributing significantly to global health expenditure, although there have been significant advances in HF therapy in recent decades. Adrenergic nervous system hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart. Adenosine is an important endogenous physiological modulator of the heart function and it has been demonstrated to serve as a negative feedback regulator of sympathetic overstimulation by the β1-adrenoceptors (β1ARs). It is well known that the antiadrenergic action of adenosine, through activation of A1 adenosine receptors (A1ARs), serves as a mechanism of cardioprotection against cardiotoxicity which may accompany excessive adrenergic stimulation. The study presented here aims to assess, in both atrial and ventricular myocytes, spatial distribution of adrenergic and adenosine receptors in different subcellular microdomains and explore their functional interplay in normal heart and HF. The study aimed to: (1) investigate the functional role of the anti-adrenergic effect of adenosine in normal heart and HF, measuring the cell contractility via IonOptix system; (2) dissect cellular mechanisms, elucidating the cyclic nucleotide response to catecholamine stimulation following both global (in the bath) or local (in the nano-pipette) stimulation of either β1ARs or A1ARs. The cAMP levels were measured via Förster Resonance Energy Transfer (FRET) for the whole-cell recording and via a combination of FRET and scanning ion conductance microscopy (SICM) for local stimulation and measurement of cAMP within the specific microdomains; (3) study molecular mechanisms of the anti-adrenergic effect of adenosine by quantitative PCR (qPCR) and western blot technique. It was found that A1ARs agonist significantly decreases cAMP concentration following β1AR stimulation, in both atrial and ventricular myocytes. In contrast, corresponding reduction in the sarcomere shortening was found exclusively in atrial myocytes. Using animal model, heart failure condition was found to be associated with the significant reduction of the anti- 2 adrenergic effect of A1ARs stimulation for both contractility and cAMP production in atrial cardiomyocytes. Such effect could be associated with structural changes occurring during HF conditions, such as t-tubule and/or caveolae degradation. Indeed, with the caveolae disruption a similar situation was observed. In addition, molecular investigation shows that A1ARs are upregulated in left atrium. This study presents evidence of a population of A1ARs that are localized specifically within the cholesterol lipid microdomains on the surface of myocytes and suggests that A1ARs may interact with the β1ARs in these microdomains. During the HF the antiadrenergic effect of adenosine is significantly lower. The loss of the antiadrenergic effect of A1ARs could be associated with the loss of cardiac cytoarchitecture occurring during HF conditions that may cause a disruption of adrenergic/adenosine signalling compartmentation and interplay. On the other hand, the increase of A1ARs density during failing conditions appears to follow the loss of the adenosine effects, suggesting the establishment of a potential compensatory mechanism that could be a driving factor of the failing phenotype.
2018
β-adrenergic receptors, adenosine receptors, atria, cardiovascular system, cardiomyocytes
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11562/977136
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