Abstract 176: The Pathological Role of Aldose Reductase in Isolated Cardiomyocytes Undergoing Hypoxia / Reoxygenation After Prior Exposure to High Glucose Concentrations

Abstract

Hyperglycemia increases the vulnerability of the cardiovascular system to ischemia/reperfusion (IR) injury. There are currently no effective therapeutic strategies. We hypothesized that hyperglycemia would increase glucose flux through the polyol pathway. Aldose reductase (AR) catalyzes the first step of this pathway by converting glucose to sorbitol. This reaction generates more oxidative stress due to the depletion of NADPH and osmotic stress caused by sorbitol accumulation, making the heart more susceptible to IR injury. This study aimed to better understand the injury mechanism in cardiomyocytes after high glucose exposure and IR injury. Confluent cardiomyocytes were exposed for 24 hours to 25, 50, or 100 mM glucose or 25 mM glucose with 25 or 75 mM sucrose concentrations added. The non-metabolizable sugar sucrose was used as an osmolarity control. Epalrestat, an AR inhibitor, was added at 0, 1, or 10 μM per well (n = 18 per group) during glucose or sucrose exposure. Cells were then subjected to 24 hours of hypoxic conditions (glucose-, sucrose- and serum-free media; 0.01% O 2 , 37 °C; hypoxic chamber) or normoxic conditions (complete media; 21% O 2 , 37 °C), followed by a 2-hour reoxygenation period in normoxic conditions. Cell injury was quantified by measurement of lactate dehydrogenase (LDH) release. Data were normalized to 25 mM glucose after control/normoxic conditions without AR inhibitor. A three-way ANOVA was conducted to compare groups, followed by the Holm-Šidák test. Increasing glucose concentrations lead to increased cell damage after hypoxia/reoxygenation. Adding the AR inhibitor during the glucose exposure period reduced LDH release after hypoxia/reoxygenation in a dose-dependent manner. The addition of sucrose did not increase cell injury. The AR inhibitor did not affect cells exposed to sucrose. The polyol pathway may play a dominant role in increased cell injury by hyperglycemia after hypoxia/reoxygenation.