Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock

Alpha-thiol deoxynucleotide triphosphates (S-dNTPs) as radioprotective agents: A novel approach.

Abstract

In this study, the ability of a mixture of four different alpha-thiol deoxynucleotide triphosphates (S-dNTPs) each at a concentration of 10muM when incorporated into the genomic DNA of proliferating human HL-60 and Mono-Mac-6 (MM-6) cells in vitro to provide protection from 2, 5, and 10 Gy of gamma radiation was investigated. Incorporation of the four different S-dNTPs into nuclear DNA at 10 muM concentration for five days was validated by agarose gel electrophoretic band shift analysis. S-dNTP-treated genomic DNA reacted with BODIPY-iodoacetamide demonstrated a band shift to higher molecular weight to confirm the presence of sulfur moieties in the resultant phosphorothioate DNA backbones. No overt signs of toxicity or obvious morphologic cellular differentiation were noted in the presence of 10 muM S-dNTPs even after 8 days in culture. Significantly reduced radiation-induced persistent DNA damage measured at 24 and 48 h post-exposure by gamma-H2AX histone phosphorylation using FACS analysis in S-dNTP incorporated HL-60 and MM6 cells indicated protection against radiation-induced direct and indirect DNA damage. Statistically significant protection by S-dNTPs was noted at the cellular level by CellEvent Caspase-3/7 assay, which assess the extent of apoptotic events, and by trypan blue dye exclusion to assed cell viability. The results appear to support an innocuous antioxidant thiol radioprotective effect built into genomic DNA backbones as the last line of defense against ionizing radiation and free radical-induced DNA damage.