Poloxamer 188 Protects Isolated Cardiomyocytes from Hypoxia/Reoxygenation Injury
Authors: Salzman Michele M. , Hackel Benjamin J. , Bates Frank S. , Bartos Jason A. , Yannopoulos Demetris , Riess Matthias L. 
Published: November 2023

IntroductionIschemia/reperfusion (I/R) injury, such that occurs during heart attack and cardiac arrest, is a complex physio‐pathological event involving many processes that can lead to disruptions in the cell membrane and cellular dysfunctions. Many patients who experience a heart attack or cardiac arrest still die or suffer severe cardiac damage, even when the best cardiopulmonary resuscitation (CPR) is delivered. This is due to the fact that the reintroduction of blood flow at the start of CPR after the ischemic episode may cause additional injury to the heart beyond that caused by the ischemia itself. Loss of cell membrane integrity may allow an influx of calcium (Ca2+) into the cardiomyocytes, leading to hyper‐contracture and cell death. Methods to improve the endogenous membrane resealing capacity of cells that get overwhelmed due to pathological disruptions, such as I/R injury, are needed to prevent cardiomyocyte loss, because the ability of the myocardium to regenerate is limited. Therefore, determining the mechanism of action of a protective compound administered during reperfusion on cardiomyocyte dysfunction caused by I/R injury could improve clinical practices in the future.HypothesisPoloxamer 188 (P188), with its unique hydrophilic/lipophilic chemical properties, protects isolated cardiomyocytes against hypoxia/reoxygenation (H/R; simulated I/R) injury.MethodsConfluent cultures of cardiomyocytes (mouse, MCMs) underwent 5 hours of hypoxia (0.1% O2; serum‐& glucose‐free medium; 37°C) then 2 hours reoxygenation (21% O2; complete medium; 37°C) ± P188 or polyethylene glycol (PEG) [30μM, 100μM, 300μM, 1mM]. PEG was used as a completely hydrophilic control molecule. Endpoints were markers of cell number/viability, cellular injury (lactate dehydrogenase [LDH] release), and intracellular Ca2+ ([Ca2+]i). Statistics: ANOVA and SNK post hoc comparisons, p<0.05 *vs normoxia, † vs vehicle.ResultsThere was a significant decrease in cell number/viability, as well as significantly increased LDH release and [Ca2+]i, following H/R compared to cells in control/normoxic conditions. All P188 concentrations present during reoxygenation significantly increased cell number/viability and significantly decreased Ca2+ influx in the H/R conditions. Only 1mM P188 significantly decreased LDH release in the H/R conditions; the other P188 concentrations (30μM, 100μM, 300μM) exhibited a non‐significant trend towards decreased LDH release. No PEG concentration had an effect on any of the endpoint parameters in the H/R conditions.ConclusionsP188, at the concentrations used in these experiments, administered during reoxygenation, protected isolated cardiomyocytes from H/R‐induced injury by improving cell number/viability, reducing Ca2+ influx, and decreasing LDH release. These results support a possible protective role of P188 against I/R injury when it is administered during reperfusion.Support or Funding InformationThis work was supported by NIH grant (RO1 HL095122) and institutional funds.