Induction of cell death by ascorbic acid derivatives in human renal carcinoma and glioblastoma cell lines.

Sodium-L-ascorbate, L-ascorbic acid, D-isoascorbic acid, sodium 5,6-benzylidene-L-ascorbate and sodium-6-beta-O-galactosyl-L-ascorbate, which produce ascorbyl radicals during the oxidative degradation, also induced cytotoxicity against cultured human renal carcinoma (TC-1) and glioblastoma multiform tumor (T98G) cell lines. On the other hand, L-ascorbic acid 2-phosphate magnesium and L-ascorbic acid 2-sulfate dipotassium salt, which do not produce the ascorbyl radical, were inactive. This suggests the possible role of the ascorbyl radical for cell death induction. T98G cells were more resistant to ascorbate analogs than TC-1 and HL-60 cells, possibly due to higher intracellular glutathione concentrations. Ascorbate treatment induced rapid elevation of both intracellular concentration of cAMP and Ca2+ in HL-60 cells, but not in TC-1 and T98G cells. However, the elevation of cAMP by theophyline and N,2-dibutyryl adenosine 3,5 cyclic monophosphate (dibutyryl cAMP) resulted in a decrease in the viable cell number. This suggests the possible role of cAMP for ascorbate-induced cell death.