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

Abstract

Purpose: This in vitro study aims at evaluating the effect of the combination of pentoxifylline (PTX) and trolox (Tx), the water-soluble analogue of a-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.

Studies of the in vivo radiosensitivity of human skin fibroblasts

“…Such results are consistent with work on the bystander effect in vitro that suggests that following irradiation there can be chronic production of ROS that could cause cellular DNA damage [35,36]. Recent studies in human skin have demonstrated evidence for prolonged oxidative stress following irradiation [29].…”

“…4) or according to median radiosensitivity (Table 2). Since the number of patients (29) contributing to this part of the study was relatively small this negative finding has low power but the overlap of the data indicates that even if a significant correlation did exist the difference in radiosensitivity is too small (or the assay error is too large) for it to be used as a predictive factor. We also observed no relation between WHC and the maximum dose measured on the irradiated skin for the individual patients since these infield skin samples were taken from skin near the wound margin.…”

Effects of Gamma Radiation on FcεRI and TLR-Mediated Mast Cell Activation

“…Although IgE-mediated activation, but not TLRmediated activation, induces small physiological amounts of ROS in mast cells (Swindle, E. J., unpublished data), these results clearly demonstrate that superphysiological amounts of ROS produced after irradiation can lead to transient inhibition of mast cell degranulation. The generation of intracellular ROS by gamma radiation is an area of intense research (26,52,53). It has been clearly established that gamma radiation induces free radical formation in living cells, and free radicals are believed to be responsible for much of the damage that results after irradiation (27,32,54,55).…”

Catalase ameliorates polychlorinated biphenyl-induced cytotoxicity in nonmalignant human breast epithelial cells

“…Micronuclei arise from acentric chromosome fragments or a whole chromosome that lags behind during cell division. Several studies have reported that ionizing radiation-induced DNA damage correlates with an increase in the frequency of micronuclei [23 – 25]. H2AX, a minor variant of histone 2A, is phosphorylated via ataxia telangiectasia mutant (ATM) in response to radiation [26].…”