Amifostine protection against induced DNA damage in gamma-irradiated Escherichia coli cells depend on recN DNA repair gene product activity

Advances of Amifostine in Radiation Protection: Administration and Delivery

Amifostine (AMF, also known as WR-2721) is the only approved broad-spectrum small-molecule radiation protection agent that can combat hematopoietic damage caused by ionizing radiation and is used as an antitumor adjuvant and cell protector in cancer chemotherapy and radiotherapy. Amifostine is usually injected intravenously before chemotherapy or radiotherapy and has been used in the treatment of head and neck cancer. However, the inconvenient intravenous administration and its toxic side effects such as hypotension have severely limited its further application in clinic. In order to reduce the toxic and side effects, scientists are trying to develop a variety of drug administration methods and are devoted to developing a wide application of amifostine in radiation protection. This paper reviews the research progress of amifostine for radiation protection in recent years, discusses its mechanism of action, clinical application, and other aspects, with focus on summarizing the most widely studied amifostine injection administration and drug delivery systems, and explored the correlation between various administrations and drug efficacies.

Two New Faces of Amifostine: Protector from DNA Damage in Normal Cells and Inhibitor of DNA Repair in Cancer Cells

Amifostine protects normal cells from DNA damage induction by ionizing radiation or chemotherapeutics, whereas cancer cells typically remain uninfluenced. While confirming this phenomenon, we have revealed by comet assay and currently the most sensitive method of DNA double strand break (DSB) quantification (based on γH2AX/53BP1 high-resolution immunofluorescence microscopy) that amifostine treatment supports DSB repair in γ-irradiated normal NHDF fibroblasts but alters it in MCF7 carcinoma cells. These effects follow from the significantly lower activity of alkaline phosphatase measured in MCF7 cells and their supernatants as compared with NHDF fibroblasts. Liquid chromatography-mass spectrometry confirmed that the amifostine conversion to WR-1065 was significantly more intensive in normal NHDF cells than in tumor MCF cells. In conclusion, due to common differences between normal and cancer cells in their abilities to convert amifostine to its active metabolite WR-1065, amifostine may not only protect in multiple ways normal cells from radiation-induced DNA damage but also make cancer cells suffer from DSB repair alteration.

Heavy ions, radioprotectors and genomic instability: implications for human space exploration

The risk associated with space radiation exposure is unique from terrestrial radiation exposures due to differences in radiation quality, including linear energy transfer (LET). Both high- and low-LET radiations are capable of inducing genomic instability in mammalian cells, and this instability is thought to be a driving force underlying radiation carcinogenesis. Unfortunately, during space exploration, flight crews cannot entirely avoid radiation exposure. As a result, chemical and biological countermeasures will be an important component of successful extended missions such as the exploration of Mars. There are currently several radioprotective agents (radioprotectors) in use; however, scientists continue to search for ideal radioprotective compounds-safe to use and effective in preventing and/or reducing acute and delayed effects of irradiation. This review discusses the agents that are currently available or being evaluated for their potential as radioprotectors. Further, this review discusses some implications of radioprotection for the induction and/or propagation of genomic instability in the progeny of irradiated cells.

Amifostine metabolite WR-1065 disrupts homologous recombination in mammalian cells

Repair of DNA damage through homologous recombination (HR) pathways plays a crucial role in maintaining genome stability. However, overstimulation of HR pathways in response to genotoxic stress may abnormally elevate recombination frequencies, leading to increased mutation rates and delayed genomic instability. Radiation-induced genomic instability has been detected after exposure to both low- and high-linear energy transfer (LET) radiations, but the mechanisms responsible for initiating or propagating genomic instability are not known. We have demonstrated that WR-1065, the active metabolite of amifostine, protects against radiation-induced cell killing and delayed genomic instability. We hypothesize that hyperstimulation of HR pathways plays a mechanistic role in radiation-induced genomic instability and that, in part, WR-1065 exerts it radioprotective effect through suppression of the HR pathway. Results of this study demonstrate that WR-1065 treatment selectively protected against radiation-induced cell killing in HR-proficient cell lines compared to an HR-deficient cell line. Further, WR-1065 treatment decreases HR in response to DNA damage using two different mammalian cell systems. This suppression of hyper-recombination is a previously unrecognized mechanism by which WR-1065 effects radioprotection in mammalian cells.