Abstract 161: EP3 Receptor Overexpression Attenuates Oxidative Cardiomyocyte Injury
Prostaglandin EP3-receptors have been identified in the heart and suggested to mediate E-type prostaglandin-mediated protection against ischemia-induced myocardial injury. In order to investigate the anti-ischemic activity of the EP3-receptor, transgenic (tg) mice with cardiospe-cific overexpression of the porcine EP3-receptor under the control of the alpha-MHC promoter were previously generated. Langendorff perfusion of isolated hearts of these mice has shown a protective effect in ischemia / reperfusion compared to wild type (wt). To confirm an increased anti-oxidative protection in EP3-tg hearts, we assessed cardiomyocyte viability in presence of H2O2 by SYTOX Green. After treatment with 50–200 μM H2O2 for 10 minutes, wt-myocytes revealed increased cell death (16,7 ± 8.3 to 45 ± 22 -fold vs. control) whereas tg-cardiomyocytes only showed an 3,5 ± 0,6 to 9 ± 2 fold increase in cell death vs control (n=7– 8 per group; p<0.05). Microarray analysis of tg-heart RNA identified two genes probably involved in the increased anti-oxidative protection of the EP3-receptor. Thioredoxin interacting protein (TXNIP) a regulator of the ubiquitously expressed thioredoxin system (a control element of the redox balance), was significantly downregulated in tg-mice in comparison to wt. Cardiac ankyrin repeat protein (CARP), which is also considered to attenuate oxidative injury by decreasing apoptotic cell death under oxidative stress was significantly upregualted in tg hearts. The regulation of TXNIP and CARP were verified by semi-quantitative RT-PCR. In summary, we demonstrate for the first time that EP3 receptor overexpression regulates TXNIP and CARP, which may result in the observed increased protection against oxidative damage.