In vitro cytotoxicity of glyco- S-nitrosothiols : a novel class of nitric oxide donors

Abstract

The cytotoxicities of the nitric oxide (NO) donors, S-nitroso- N-acetylpencillamine (SNAP) and three glyco-SNAPs, glucose-1-SNAP, glucose-2-SNAP, and fructose-1-SNAP, towards the human gingival epithelioid S-G cell line and three human carcinoma cell lines derived from tissues of the oral cavity were compared using the neutral red (NR) assay. In general, the glucose-SNAPs were more cytotoxic than SNAP, which, in turn, was more cytotoxic than fructose-1-SNAP. Further studies focused on the response of S-G cells to glucose-2-SNAP. The cytotoxicity of glucose-2-SNAP was attributed to NO, as glucose-2-SNAP ( t1/2=20 h at 28°C) aged for 4 days was nontoxic, toxicity was eliminated in the presence of hydroxocobalamin, a specific NO scavenger, and toxicity was not noted with glucose-2-AP (the parent compound used to construct glucose-2-SNAP). Exposure of cells to glucose-2-SNAP resulted in a lessening of the intracellular level of glutathione and cells pretreated with the glutathione-depleter, 1,3-bis-(chloroethyl)-1-nitrosourea, were more sensitive to a subsequent challenge with glucose-2-SNAP. Cytotoxicity of glucose-2-SNAP was lessened upon coexposure with the antioxidants, myricetin, N-acetyl- l-cysteine, and l-ascorbic acid. S-G cells exposed to glucose-2-SNAP exhibited bi- and multinucleation. Death of S-G cells exposed to glucose-2-SNAP apparently occurred by apoptosis, as demonstrated with fluorescence microscopy by the appearance of brightly stained, hypercondensed chromatin in spherical cells and of membrane blebbing and by the DNA-ladder of oligonucleosome-length fragments noted with gel electrophoresis. In comparison with other classes of NO donors the sequence of toxicity towards S-G cells was S-nitrosoglutathione>glucose-SNAPs>SNAP, sodium nitroprusside>spermine NONOate>DPTA NONOate>DETA NONOate>fructose-1-SNAP>>SIN-1.