Graphene oxide pretreatment increases myocardial resistance to ischemia-reperfusion in Langendorff isolated rat heart model

Abstract

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NATIONAL RESEARCH FOUNDATION OF UKRAINE Reperfusion injury is accompanied with excessive reactive oxygen species (ROS) and impaired nitric oxide (NO) production. Carbon nanomaterial, such as graphene oxide (GrO), possesses strong antioxidant properties in vitro and can be easily modified with functional groups that make GrO attractive for biomedical purposes. There are evidences that GrO is biocompatible and is decomposed by the cell enzymes and excreted naturally. We hypothesized that GrO might be used for prevention of reperfusion injury both as an effective antioxidant and as a NO-delivery compound. Purpose We tested the cardioprotective potential of GrO and its nitrogen-doped derivative (N-GrO) in ischemia-reperfusion (I/R) model at Langengorff isolated rat heart model. Methods Pristine sample of GrO was used as a dark brown 20-25% water-soluble paste. The N-GrO was obtained via immersing of the initial GrO in a 10 w/w % urea solution and heating for 1 hour in an inert atmosphere (700-800°C). Wistar male rats were injected with GrO or N-GrO (0.03 mg / kg) into the tail vein 30 min before decapitation. Isolated hearts were perfused retrogradely under constant perfusion pressure and underwent I/R protocol (20 min/40 min). Left ventricular developed pressure (LVDP) and the first derivate (dP/dt) were registered via water-filled latex balloon by Global Lab software. Coronary flow, heart rate, oxygen consumption by Neely and oxygen cost of myocardial work (OCMW) were calculated in pre-ischemia and reperfusion period. Heart homogenates were tested for superoxide anion, hydroxyl radical, hydrogen peroxide, diene conjugates and malondialdehyde content. Statistical analysis was made with Kruskal-Wallis rank sum test. Results: basic cardiodynamics did not differ between untreated, GrO or N-GrO pretreated groups. However, coronary flow and OCMW were increased by 32% and 44% respectively in GrO group (P<0.01 for both). Nevertheless, GrO and N-GrO significantly prevented post-ischemic disturbances of heart function, as there was complete recovery of LVDP, dP/dt and no increase of myocardial stiffness and OCMW at reperfusion. Importantly, at 5th min of reperfusion, coronary flow was increased by 18% and 32.5% in GrO (Р<0.05) and N-GrO (Р<0.01) groups respectively, comparing to untreated group. This effect was significant till the end of observation. In addition, GrO and N-GrO significantly diminished I/R-induced ROS production and markers of lipid peroxidation (diene conjugates, malondialdehyde) in cardiac tissues. Conclusions: this study suggested that GrO and N-GrO improved heart contractile function and prevented non-effective oxygen utilization by ischemized myocardium. N-GrO showed pronounced effect at coronary flow restoration at reperfusion. The mechanisms of the anti-ischemic effect of graphenes may involve their antiradical and/or antioxidant enzyme-like properties. Thus, graphenes may have potential applications for treatment of ischemia-reperfusion related conditions.