Poor glycemic control impairs the cardioprotective effects of red blood cells on myocardial ischemia/reperfusion injury.

Red blood cells (RBCs) play an important role in the cardiac ischemia/reperfusion (I/R) injury. Cardiovascular risk factors impair the RBC function in an endothelial nitric oxide synthase (eNOS) dependent manner. However, it is unclear whether the protective role of RBCs can be rescued by modifying cardiovascular risk factors or by pharmacologic intervention. RBCs obtained from elderly patients with or without diabetes as well as from young volunteers were treated with vehicle, eNOS inhibitor l-NAME and/or arginase inhibitor nor-NOHA before loading to the coronary system of isolated murine hearts in a Langendorff system before 40 min of global ischemia. RBCs from young and healthy volunteers as well as from aged persons and elderly diabetes patients with satisfying blood glucose control improved left ventricular function upon 60 min of reperfusion with Krebs-Henseleit buffer and reduced the infarct size compared to buffer treated controls. This cardioprotective effect was abolished in RBCs from aged diabetes patients with poor blood glucose control. Treatment of RBCs from elderly diabetes patients with nor-NOHA partly rescued the cardioprotective function. Thus, effective glucose control in aged diabetes patients rescues RBC-dependent cardioprotection in an ex-vivo model of myocardial I/R injury.

A Model of Blood Component-Heart Interaction in Cardiac Ischemia-Reperfusion Injury using a Langendorff-Based Ex Vivo Assay.

INTRODUCTION: Myocardial infarction is one of the leading causes of morbidity and mortality worldwide. Cellular interactions of red blood cells (RBCs) and platelets with endothelial cells and cardiomyocytes play a crucial role in cardiac ischemia/reperfusion (I/R) injury. However, addressing the specific impact of such cell-to-cell interactions in commonly employed in vivo models of cardiac I/R injury is challenging due to overlap of neuronal, hormonal, and immunological pathways. This study aimed to refine a Langendorff-based ex vivo transfer model to evaluate the impact of specific blood components on cardiac I/R injury. MATERIAL AND METHODS: Murine whole blood, defined murine blood components (RBCs, platelet-rich plasma [PRP], and platelet-poor plasma [PPP], respectively) as well as human RBCs were loaded to the coronary system of isolated murine hearts in a Langendorff system before initiating global ischemia for 40 minutes. Following 60 minutes of reperfusion with Krebs Henseleit Buffer, left ventricular function and coronary flow were assessed. Infarct size was determined by specific histological staining following 120 minutes of reperfusion. RESULTS: Loading of murine whole blood to the coronary system of isolated murine hearts at the beginning of 40 minutes of global ischemia improved left ventricular function after 60 minutes of reperfusion and reduced the infarct size in comparison to buffer-treated controls. Similarly, isolated murine RBCs, PRP, and PPP mediated a protective effect in the cardiac I/R model. Furthermore, human RBCs showed a comparable protective capacity as murine RBCs. CONCLUSION: This Langendorff-based transfer model of cardiac I/R injury is a feasible, time-, and cost-effective model to evaluate the impact of blood components on myocardial infarction. The presented method facilitates loading of blood components of genetically modified mice to murine hearts of a different mouse strain, thus complementing time- and cost-intensive chimeric models and contributing to the development of novel targeted therapies.