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.
Martino
Luisa
L
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.
Novelli
Michela
M
Masini
Matilde
M
Chimenti
Daniele
D
Piaggi
Simona
S
Masiello
Pellegrino
P
De Tata
Vincenzo
V
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