Molecular Influence of the ATM Protein in the Treatment of Human Cells with Different Radioprotective Drugs: Comparisons between Antioxidative and Pro-Episkevic Strategies

Abstract

The radiation protection strategy with chemical agents has long been based on an antioxidative approach consisting in reducing the number of radical oxygen and nitrogen species responsible for the formation of the radiation-induced (RI) DNA damage, notably the DNA double-strand breaks (DSB), whose subset participates in the RI lethal effect as unrepairable damage. Conversely, a DSB repair-stimulating strategy that may be called the “pro-episkevic” approach (from the ancient Greek episkeve, meaning repair) can be proposed. The pro-episkevic approach directly derives from a mechanistic model based on the RI nucleoshuttling of the ATM protein (RIANS) and contributes to increase the number of DSB managed by NHEJ, the most predominant DSB repair and signaling pathway in mammalians. Here, three radioresistant and three radiosensitive human fibroblast cell lines were pretreated with antioxidative agents (N-acetylcysteine or amifostine) or to two pro-episkevic agents (zoledronate or pravastatin or both (ZOPRA)) before X-ray irradiation. The fate of the RI DSB was analyzed by using γH2AX and pATM immunofluorescence. While amifostine pretreatment appeared to be the most efficient antioxidative process, ZOPRA shows the most powerful radiation protection, suggesting that the pro-episkevic strategy may be an alternative to the antioxidative one. Additional investigations are needed to develop some new drugs that may elicit both antioxidative and pro-episkevic properties and to quantify the radiation protection action of both types of drugs applied concomitantly.

Toward an Early Diagnosis for Alzheimer’s Disease Based on the Perinuclear Localization of the ATM Protein

“…In the frame of the RIANS model, it was shown that bringing more ATM monomers into the nucleus significantly contributed to enhancing the radioresistance [ 17 , 35 ]. A radioprotective effect with the combination of bisphosphonates and statins, particularly with zoledronate and pravastatin (ZOPRA), was reported: the ZOPRA treatment accelerated the diffusion of the ATM monomers across the nuclear membrane in a number of genetic diseases [ 22 , 23 , 24 , 26 , 35 ]. Surprisingly, when applied to the 10 AD fibroblast cell lines, the ZOPRA treatment did not significantly change the yield of RI micronuclei ( Figure 5 A).…”

“…Regarding the MRE11 foci, the late MRE11 foci disappeared in only 4 of the 10 AD fibroblast cell lines ( Figure 5 D). Altogether, these findings suggest that the ZOPRA treatment may protect, at least partially, some AD fibroblasts from IR, while it has been applied more successfully in cancer syndromes with similar radiobiological features as AD cells [ 35 ]. It must be stressed that the ZOPRA treatment is not efficient in protecting the ATM -mutated cells since it cannot overcome the loss of the ATM protein function [ 35 ].…”

“…Altogether, these findings suggest that the ZOPRA treatment may protect, at least partially, some AD fibroblasts from IR, while it has been applied more successfully in cancer syndromes with similar radiobiological features as AD cells [ 35 ]. It must be stressed that the ZOPRA treatment is not efficient in protecting the ATM -mutated cells since it cannot overcome the loss of the ATM protein function [ 35 ]. Besides, applying ATM inhibitors in our conditions would not help to understand the specificities of AD cells since the activity of ATM kinase is required for the formation of ATM dimers, whether cytoplasmic or nuclear.…”

“…The combination of zoledronate and pravastatin was called ZOPRA treatment, as described elsewhere [ 34 ], and it was applied to more than ten different genetic diseases associated with a delayed RIANS [ 35 ]. Briefly, cells were incubated with 1 µM of pravastatin (Sigma-Aldrich, Saint-Quentin-Fallavier, France) in phosphatase-buffered saline solution (PBS) for 24 h at 37 °C.…”

“…The combination of zoledronate and pravastatin was called ZOPRA treatment, as described elsewhere [34], and it was applied to more than ten different genetic diseases associated with a delayed RIANS [35]. Briefly, cells were incubated with 1 µM of pravastatin (Sigma-Aldrich, Saint-Quentin-Fallavier, France) in phosphatase-buffered saline solution (PBS) for 24 h at 37 • C. Thereafter, 1 µM of zoledronate (Sigma-Aldrich) in PBS was added into the culture medium and cells were incubated for 12 h at 37 • C. The culture medium was renewed immediately before irradiation.…”