DNA damage in cultured skin microvascular endothelial cells exposed to gamma rays and treated by the combination pentoxifylline and alpha-tocopherol.

PURPOSE: This in vitro study aims at evaluating the effect of the combination of pentoxifylline (PTX) and trolox (Tx), the water-soluble analogue of alpha-tocopherol, on the oxidative state and DNA damage in dermal microvascular endothelial cells exposed to doses up to 10 Gy of ionizing radiation.
MATERIALS AND METHODS: Confluent primary cultures of dermal endothelial cells were gamma irradiated at 3 and 10 Gy, and 0.5 mM of both drugs, PTX and Tx, was added either before (15 min) or after (30 min or 24 h) irradiation. Reactive oxygen species (ROS), measured by the dichlorodihydrofluorescein diacetate assay, and DNA damage, assessed by the comet and micronucleus assays, were measured at different times after exposure (0 - 21 days).
RESULTS: The PTX/Tx treatment decreased the early and delayed peak of ROS production by a factor of 2.8 in 10 Gy-irradiated cells immediately after irradiation and the basal level by a factor of 2 in non-irradiated control cells. Moreover, the level of DNA strand breaks, as measured by the comet assay, was shown to be reduced by half immediately after irradiation when the PTX/Tx treatment was added 15 min before irradiation. However, unexpectedly, it was decreased to a similar extent when the drugs were added 30 min after radiation exposure. This reduction was accompanied by a 2.2- and 3.6-fold higher yield in the micronuclei (MN) frequency observed on days 10 and 14 post-irradiation, respectively.
CONCLUSION: These results suggest that oxidative stress and DNA damage induced in dermal microvascular endothelial cells by radiation can be modulated by early PTX/Tx treatment. These drugs acted not only as radical scavengers, but they were also responsible for the increased MN frequency in 10 Gy-irradiated cells. Thus, these drugs may cause a possible interference with DNA repair processes.