Efflux of glutathione and glutathione complexes from human erythrocytes in response to inorganic arsenic exposure

Zinc treatment modulates hematological and morphological changes in rat erythrocytes following arsenic exposure

The aim of this study was to understand the effects of zinc supplementation on antioxidant defense systems, hematological indices, and erythrocyte morphology in conditions of chronic arsenic toxicity. Male Wistar rats were segregated into four groups: control, arsenic treated, zinc supplemented, and arsenic + zinc treated. The animals in the arsenic-treated group were given arsenic orally in drinking water in the form of sodium arsenite at a dose level of 100 mg L^-1, and zinc was administered to zinc-treated animals in the form of zinc sulfate orally in drinking water at a dose level of 227 mg L^-1. The animals were subjected to different treatments for a period of 12 weeks, and various investigations were undertaken that included serum zinc content, activity of antioxidant enzymes, and hematological indices. Further, scanning electron microscopic (SEM) studies were performed to assess morphological changes in erythrocytes. Arsenic treatment significantly reduced serum zinc concentrations, which, however, were restored to near-normal levels upon zinc supplementation. The activities of enzymes involved in antioxidant defense systems were altered in the erythrocyte lysates of arsenic-treated rats, which interestingly revealed a significant improvement upon simultaneous zinc supplementation. A significant reduction in the counts of total leukocytes, neutrophils, and lymphocytes was observed following arsenic intoxication, which came back to near control levels following zinc supplementation. Also, protective effects of zinc were evident from SEM that revealed maintenance of topographical appearances of erythrocytes in conditions of arsenic toxicity. Thus, this study clearly shows the protection afforded by zinc on erythrocytes during arsenic-induced toxicity.

Toxicity of Glutathione-Binding Metals: A Review of Targets and Mechanisms

Mercury, cadmium, arsenic and lead are among priority metals for toxicological studies due to the frequent human exposure and to the significant burden of disease following acute and chronic intoxication. Among their common characteristics is chemical affinity to proteins and non-protein thiols and their ability to generate cellular oxidative stress by the best-known Fenton mechanism. Their health effects are however diverse: kidney and liver damage, cancer at specific sites, irreversible neurological damages with metal-specific features. Mechanisms for the induction of oxidative stress by interaction with the cell thiolome will be presented, based on literature evidence and of experimental findings.

Protection against oxidative stress in beta thalassemia/hemoglobin E erythrocytes by inhibitors of glutathione efflux transporters

In beta thalassemia/hemoglobin E (Hb E), abnormally high levels of oxidative stress account for accelerated senescence and increased destruction of erythrocytes. The present study aimed to investigate the role of glutathione efflux transporters, namely cystic fibrosis transmembrane conductance regulator (CFTR) and multidrug resistance-associated protein 1 (MRP1), in the control of glutathione levels and protection against oxidative challenges in beta thalassemia/Hb E erythrocytes. We found that CFTR protein was expressed in the erythrocytes of beta thalassemia/Hb E patients. Treatments with GlyH-101 (50 µM), a small molecule CFTR inhibitor, and MK571 (50 µM), an MRP1 inhibitor, reduced H₂O₂-induced free radical generation in the erythrocytes by ∼80% and 50%, respectively. Furthermore, combined treatment with GlyH-101 and MK571 completely abolished the induction of reactive oxygen radicals. Increased oxidative stress in the erythrocytes following H₂O₂ challenges was accompanied by a decrease in intracellular level of reduced glutathione (GSH), which was prevented by treatments with GlyH-101 and MK571. CMFDA-based assays revealed that GlyH-101 and MK571 reduced H₂O₂-induced glutathione efflux from the erythrocytes by 87% and 66%, respectively. Interestingly, H₂O₂-induced osmotic tolerance of erythrocytes, a sign of erythrocyte aging, was ameliorated by treatment with GlyH-101. Our study indicates that oxidative stress induces glutathione efflux via CFTR and MRP1 in beta thalassemia/Hb E erythrocytes. Pharmacological inhibition of glutathione efflux represents a potential therapy to delay aging and premature destruction of erythrocytes in beta thalassemia/Hb E.