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

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.

Multi-marker study of the responses of the Unio tumidus from the areas of small and micro hydropower plants at the Dniester River Basin, Ukraine

The impact of the hydropower plants (HPPs) on the aquatic life is expected, but the biochemical markers of ecotoxicity have not been investigated in relation to HPP proximity. The aim of this study was to compare the responses of mollusk Unio tumidus from the small HPP (reservoir (Ku) and downstream of the dam (Kd)) and micro HPP (upstream (Zu) and downstream of the dam (Zd)). In total, 11 indexes (n) from digestive gland, hemocytes (lysosomal integrity), and gonads (alkali-labile phosphates, ALP) were analyzed. The mollusks from the reservoir demonstrate the typical signs of toxic impact: cholinesterase and glutathione depletion, the highest glutathione S-transferase activity, and ratio of extralysosomal cathepsin D compare to all other groups. The specimens from the micro HPP have the highest levels of glutathione (Zd) and lipid peroxidation (Zu) and lesser Cu/Zn-SOD activity (Zu) than other groups. These indications of stressful conditions may derive from the regular oscillations in the water flow regimes at the micro HPP. For both HPPs, the responses of upstream and downstream groups are distinct. The calculated IBR/n (4.17, 3.85, 3.12, and 0.26 for Ku, Kd, Zu, and Zd correspondingly) gives a quantitative basis for the evaluation of environmental impact of HPPs. Graphical abstract .

Biochemical responses of freshwater mussel Unio tumidus to titanium oxide nanoparticles, Bisphenol A, and their combination

Multiple interactions between different pollutants in the surface waters can cause unpredictable consequences. The aim of the study was to evaluate the combined effect of two widespread xenobiotics, titanium oxide nanoparticles (TiO₂) and bisphenol A (BPA), on freshwater bivalve Unio tumidus. The specimens were exposed for 14 days to TiCl₄ (Ti, 1.25 µM), TiO₂ (1.25 μM), BPA (0.88 nM), or their combination (TiO₂ + BPA). Every type of exposure resulted in a particular oxidative stress response: TiO₂ had antioxidant effect, decreasing the generation of reactive oxygen species (ROS) and phenoloxidase (PhO) activity, and doubling reduced glutathione (GSH) concentration in the digestive gland; Ti caused oxidative changes by increasing levels of ROS, PhO and superoxide dismutase; BPA decreased the GSH level by a factor of two. In the co-exposure treatment, these indices as well as lysosomal membrane stability were not affected. All Ti-containing exposures caused elevated levels of metalated metallothionein (Zn,Cu-MT), its ratio to total metallothionein protein, and lactate/pyruvate ratio. Both BPA-containing exposures decreased caspase-3 activity. All exposures, and particularly co-exposure, up-regulated CYP450-dependent oxidation, lipid peroxidation and lipofuscin accumulation, lysosomal cathepsin D and its efflux, as well as alkali-labile phosphates in gonads and caused DNA instability (except for TiO₂). To summarize, co-exposure to TiO₂ + BPA produced an overlap of certain individual responses but strengthened the damage. Development of water purification technologies using TiO₂ requires further studies of the biological effects of its mixtures. U. tumidus can serve as a sentinel organism in such studies.