Abstract 113: Protection Of Cardiomyocytes Against Hypoxia/reoxygenation Injury: Interaction Of Poloxamer 188 And Endothelial Cells

Abstract

Administration of Poloxamer (P) 188, a copolymer-based cell membrane stabilizer, significantly improves myocardial ischemia/reperfusion (IR) injury through its ability to protect cell membranes. Cell-to-cell interactions between endothelial cells (ECs) and cardiomyocytes (CMs) further protect CM from IR injury. Thus, we established a co-culture model of ECs and CMs and could previously demonstrate that the mere presence of ECs potentiates cardioprotection as evidenced by dose-dependent attenuation of LDH release from CMs caused by hypoxia/reoxygenation (HR). Here, we sought to determine if P188 can further potentiate the attenuation of LDH release in the presence of different ECs densities. Mouse CMs cultured in wells underwent 24 h hypoxia followed by 2 h reoxygenation. Mouse coronary artery ECs were plated in well-inserts at densities of 25,000, 50,000, or 100,000 per well which were placed into the CM wells. P188 at 0, 30, 100, 300, or 1,000 μM was administered upon reoxygenation. Statistics: ANOVA and SNK, alpha 0.05. ECs did not have a protective effect by themselves when a low number of ECs (25,000 per well) were present, but P188 could reduce LDH release in CMs after HR injury in a dose-dependent manner (lower panel). When a high number of ECs (100,000 per well) were co-cultured with CMs, ECs themselves exerted a protective effect while P188 did not further decrease LDH release significantly (upper panel). An intermediate number of ECs (50,000 per well) did not produce significant results in either direction (center panel). Our data suggests that the EC-mediated protection of CMs depends on EC density; furthermore, while at low density the role of ECs was limited and allowed P188 to promote additional protection against HR injury, at high density ECs appeared to saturate cardioprotection and blunt additional P188’s CM protection. These findings suggest an important, yet not additive interaction between the protection conferred by ECs and that by P188.