An adenosinergic positive feedback loop extends pharmacological cardioprotection duration.

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Pharmacology

Background:

• Adenosine receptor activation provides delayed cardioprotection against ischemia-reperfusion (IR) injury.
• Mechanisms for the extended duration (24-72 hours) of adenosine-induced cardioprotection remain unclear.
• Hypothesized positive feedback loop involving adenosine kinase (ADK) degradation and reduced adenosine metabolism.

Purpose of the Study:

• To investigate the role of adenosine kinase (ADK) degradation in extending adenosine-mediated cardioprotection.
• To elucidate the positive feedback mechanisms sustaining cardioprotection.
• To explore the therapeutic potential of sustained adenosinergic signaling.

Main Methods:

• Mice treated with ADK inhibitor (ABT-702) to induce endogenous adenosine signaling.
• Analysis of cardiac ADK protein and mRNA levels at various time points.
• Pharmacological inhibition of adenosine receptors or proteasomes to assess late effects.
• Evaluation of cardioprotection using Langendorff technique and IR tolerance assays.
• Assessment in cardiac-specific ADK knockout (cADK+/-) mice.

Main Results:

• ABT-702 treatment reduced cardiac ADK protein and conferred cardioprotection from 24-72 hours.
• Adenosine receptor or proteasome inhibition reversed the ADK deficit and abolished cardioprotection.
• Cardiac-specific ADK heterozygous knockout hearts demonstrated continuous cardioprotection.
• Various preconditioning agents also decreased cardiac ADK protein expression.

Conclusions:

• A positive feedback loop, initiated by adenosine receptor-mediated ADK degradation, sustains cardioprotection.
• This mechanism prolongs the protective effects of ABT-702 and potentially other preconditioning agents.
• Sustained adenosinergic cardioprotection shows therapeutic promise, as evidenced by cADK+/- mice.