Dehydroascorbate protection against dioxin-induced toxicity in the beta-cell line INS-1E.
Oxidative stress has been proposed as a mechanism of the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The aim of this research was to evaluate the protective effects of increased intracellular ascorbate levels against TCDD acute toxicity in the insulin-secreting beta-cell line INS-1E. Ascorbate is considered a potent antioxidant, but its therapeutic efficacy is greatly limited by its slow achievement of high intracellular levels. This might be circumvented by administration of dehydroascorbate (DHA), which is transported at a much higher rate and undergoes rapid intracellular reduction to ascorbate. Indeed, 30 min incubation of INS-1E cells with various concentrations of DHA caused a remarkable, dose-related increase of the intracellular ascorbate levels. INS-1E cells preincubated with 0.5 and 1.0mM DHA showed a greater viability than control cells after 1h exposition to cytotoxic TCDD concentrations. In our experimental conditions, TCDD surprisingly failed to increase ROS production in INS-1E cells, but induced a dose-related mitochondrial depolarisation which was significantly improved by DHA preincubation. Furthermore, DHA preincubation completely prevented the low dose TCDD-induced inhibition of glucose-stimulated insulin secretion. Thus, our results suggest that DHA preincubation protects INS-1E cells against TCDD acute toxicity by partially preserving mitochondrial function.
Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Sezione di Patologia Generale, Università degli Studi di Pisa, Via Roma, 55 - Scuola Medica, Pisa 56126, Italy.
Luisa
L
Martino
Michela
M
Novelli
Matilde
M
Masini
Daniele
D
Chimenti
Simona
S
Piaggi
Pellegrino
P
Masiello
Vincenzo
V
De Tata
D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003683:Dehydroascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
D000975:Antioxidants; D007328:Insulin; D000072317:Polychlorinated Dibenzodioxins; D017382:Reactive Oxygen Species; D003683:Dehydroascorbic Acid