Loss of caveolar A₁ adenosine receptor signalling blunts anti-adrenergic control in heart failure

Adenosine, acting through A₁ adenosine receptors (A₁ARs), exerts anti-adrenergic effects by inhibiting β₁-adrenergic receptor (β₁AR)–mediated cyclic adenosine monophosphate (cAMP) production and contractility in the heart. While the functional interaction between A₁ARs and β₁ARs is well established in both atrial and ventricular myocytes, the subcellular compartmentalization of this crosstalk and how it is disrupted in heart failure (HF) remains incompletely understood. This study investigates the spatial confinement of A₁AR–β₁AR signalling within atrial microdomains and assesses how structural remodelling in HF alters this regulatory axis.

Quantitative polymerase chain reaction (qPCR) analysis revealed that A₁AR is the predominant adenosine receptor subtype in both rat and human atrial tissues. In healthy rat and mouse atrial myocytes, A₁AR activation reduced β₁AR-induced cAMP production and sarcomere shortening, with suppression of cAMP signals at sarcolemmal microdomains enriched in protein kinase A Type II. This was further supported by scanning ion conductance microscopy–guided scanning patch-clamp, which showed that A₁AR suppressed β₁AR-driven L-type Ca²⁺ channel activity at both T-tubule and crest membrane domains. In atrial myocytes isolated from failing rat and human hearts, A₁AR-mediated inhibition of β₁AR-induced cAMP production and contractility was impaired. Caveolar disruption by methyl-β-cyclodextrin in rat atrial myocytes or via cardiac-specific caveolin-3 (Cav3) knockout in mice abolished this A₁AR-mediated inhibition. Notably, cholesterol repletion alone did not restore membrane cAMP regulation, whereas Cav3 overexpression rescued A₁AR-dependent suppression, supporting a requirement for Cav3-dependent organization. In mouse atrial preparations isolated from failing hearts, high-resolution optical mapping showed that A₁AR-mediated anti-adrenergic regulation of Ca²⁺ cycling was selectively lost in the intercaval region, correlating with the regional absence of T-tubule and downregulation of caveolae structures.

A₁ARs provide anti-adrenergic restraint of β₁AR signalling through Cav3-dependent membrane organization. In HF, regional caveolar disorganization uncouples this protective pathway, contributing to spatially heterogeneous Ca²⁺ dysregulation in the atrium.