Pannexin1 as a new target for prevention of cardiac ischemia/reperfusion injury
Authors: Rusiecka OM , Molica F , Morel S , Chanson M , Kwak BR 
Published: June 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Ischemic heart disease is the main cause of mortality worldwide. Ischemia occurs when blood flow to the myocardium is severely restricted. Reperfusion is crucial to avoid irreversible cell damage, which may lead to heart failure. No effective therapy is available in clinics to protect the heart from ischemia/reperfusion (I/R) injury. An inappropriate inflammatory response may worsen I/R injury. Thus, endothelial cells (ECs) are activated in response to I/R, which may drive an inflammatory response by releasing ATP through Pannexin1 (Panx1) channels. ATP acts further as a ‘find me’ signal for leukocytes. It is known that Panx1 channels open in response to oxygen and glucose deprivation –hallmarks of ischemia.

Purpose
We investigated the potential role of Panx1 in cardiac I/R injury.

Methods
Panx1 expression and function was detected by immunofluorescence, Western blot and ATP release assays. Cardiac function was measured in Langendorff-perfused hearts from WT or Panx1-/- mice and ex vivo subjected to 30min no-flow ischemia followed by 60min reperfusion with/without ischemic pre-conditioning (IPC; 3x5min). We induced in vivo I/R (30min/24h) by ligating the left coronary artery in WT, Panx1-/- mice, mice with Ly6G-Cre-mediated deletion of Panx1 and Panx1fl/fl controls. Infarct size, neutrophil recruitment and Troponin-I release were measured.

Results
Panx1 expression was detected in coronary and microvascular ECs, neutrophils and cardiomyocytes. After in vivo I/R, serum Troponin-I and infarct size were less pronounced in Panx1-/- mice, but neutrophil infiltration into the infarcted area was similar between Panx1-/- and WT mice. Serum Troponin-I and infarct size were not different between mice with neutrophil-specific deletion of Panx1 and Panx1fl/fl mice, suggesting that cardioprotection by Panx1 deletion rather involved cardiomyocytes than the inflammatory response. Physiological cardiac function in WT and Panx1-/- hearts was similar. However, Panx1-/- hearts showed enhanced left ventricle developed pressure and better recovery of cardiac contractility (dP/dtmax) and cardiac relaxation (dP/dtmin) after I/R. Both the time to onset of contracture (TTOC) and time to maximal contracture (TTMC) were delayed in Panx1-/- hearts. This improved cardiac recovery was abolished in Panx1-/- hearts subjected to IPC prior to I/R. Similarly, TTOC and TTMC did not vary between WT and Panx1-/- mice following IPC, suggesting altered mitochondrial function in Panx1-/- cardiomyocytes. Finally, Panx1 was found in mitochondria and mitochondrial ATP content was increased in Panx1-/- cardiomyocytes.

Conclusion
Panx1-/- mice display decreased sensitivity to cardiac I/R injury, resulting in smaller infarcts and increased recovery of left ventricular function. This cardioprotective effect of Panx1 deletion seems to involve cardiac mitochondria rather than a reduced inflammatory response. Thus, Panx1 may represent a new target for controlling cardiac reperfusion damage.