Effects of oxidised α-lipoic acid and α-tocopherol on xenobiotic-mediated methaemoglobin formation in diabetic and non-diabetic human erythrocytes in-vitro

The effects of oxidised α-lipoic acid and α-tocopherol were investigated on a human erythrocytic in vitro model of diabetic metabolic stress. Preincubation of non-diabetic and diabetic erythrocytes with oxidised α-lipoic acid or α-tocopherol resulted in marked increases in nitrite-mediated methaemoglobin formation. In contrast, oxidised α-lipoic acid resulted in considerable reductions in 4-aminophenol-mediated methaemoglobin formation in both diabetic and non-diabetic cells. α-Tocopherol showed an increase only in diabetic cells, at one time point. Monoacetyl dapsone hydroxylamine (MADDS-NHOH)-mediated methaemoglobin formation was reduced by oxidised α-lipoic acid in non-diabetic and diabetic cells at all three time points, although α-tocopherol had no effect with MADDS-NHOH. In diabetic cells only, α-tocopherol incubation caused a reduction in GSH levels compared with non-diabetic cells. As the agents showed pro- as well as anti-oxidant effects in this study, further studies are required to demonstrate potential diabetic benefit from α-lipoic acid adminstration.