Effect of PGE2 on Radiation Response of Chinese Hamster V79 Cells in Vitro
Several recent investigations have reported that 16, 16-dimethyl prostaglandin E2 (DiPGE2) can protect murine intestinal epithelial cells and hematopoietic stem cells (CFU-S) in vivo from ionizing radiation. It has been postulated that PGE2 may also increase radiation resistance in vitro by stimulating free radical scavenging or repair systems for oxidative damage. This study reports on the effect of PGE2 in modifying radiation sensitivity in an in vitro mammalian cell line.
Chinese hamster V79A03 cells were cultured as monolayers in 6 ml of α-MEM medium supplemented with Earle’s salts, 25 mM HEPES buffer, and 10% fetal bovine serum. Exponentially growing cells were incubated in medium containing 14 μM (5 μg/ ml) PGE2 for either 2 hr (acute) or >3 weeks (chronic) before exposure to graded doses of 250 kVp X rays. Cells were assayed for variations in intracellular levels of cyclic 3•,5′-adenosine monophosphate (cAMP), total protein, and glutathione (GSH), and radiation sensitivity was measured by cell survival before and after PGE2 treatment.
An acute (2-hr) exposure induced a 25% increase in cAMP content with no significant change in intracellular GSH or protein and no effect on cell survival after exposure to radiation. Chronic exposure to PGE2 increased intracellular GSH, protein, and cAMP levels by 82%, 3%, and 74%, respectively. However, no increase in radiation resistance was apparent following chronic exposure to PGE2. Chronic PGE2 exposures marginally increased the doubling time of the cells (10 versus 11 hr), although this perturbation was insufficient to alter radioresponse as a result of cell cycle perturbations. Consequently, the increase in the in vivo radiation response associated with PGE2 treatment may not be the result of an intracellular response. Instead, the increased radiation resistance observed in vivo may be due to modifications such as localized tissue or organ system hypoxia.
KeywordsRadiation Resistance Radiation Response Chinese Hamster Cell cAMP Content Cell Cycle Perturbation
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