Differential antigenotoxic and cytoprotective effect of amifostine in idarubicin-treated mice

Comparative aneugenicity of doxorubicin and its derivative idarubicin using fluorescence in situ hybridization techniques

The present study was designed to evaluate and compare the aneugenicity of idarubicin and doxorubicin, topoisomerase-targeting anticancer anthracyclines, using fluorescence in situ hybridization techniques. It was found that idarubicin and doxorubicin treatment (12 mg/kg) induced sperm meiotic delay of 24h. To determine the frequencies of disomic and diploid sperm, groups of 5 male Swiss albino mice were treated with 3, 6 and 12 mg/kg idarubicin or doxorubicin. Significant increases in the frequencies of disomic and diploid sperm were caused by treatment with all doses of idarubicin and the two highest doses of doxorubicin compared with the controls. Moreover, both compounds significantly increased the frequency of diploid sperm, indicating that complete meiotic arrest occurred. The observation that XX- and YY-sperm significantly prevailed XY-sperm indicates missegregation during the second meiotic division. The results suggest also that earlier prophase stages contribute relatively less to idarubicin and doxorubicin-induced aneuploidy. Effects of the same doses were investigated by the bone-marrow micronucleus test. Significant increases in the frequencies of micronuclei were found after treatment with all doses of both compounds. The responses were also directly correlated with bone marrow suppression. Idarubicin was more toxic than doxorubicin. Exposure to 12 mg/kg of idarubicin and doxorubicin yielded 3.82 and 2.64% micronuclei, respectively, and of these an average of 58.3 and 62.8%, respectively, showed centromeric signals, indicating their formation by whole chromosomes and reflecting the aneugenic activity of both compounds. Correspondingly, about 41.7 and 37.2% of the induced micronuclei, respectively, were centromere-negative, demonstrating that both compounds not only induce chromosome loss but also DNA strand breaks. Based on our data, aneuploidy assays such as sperm-fluorescence in situ hybridization assay and micronucleus test complemented by fluorescence in situ hybridization with centromeric DNA probes have been to some extent validated to be recommended for the assessment of aneuploidogenic effects of chemicals.

Amifostine (WR2721) confers DNA protection to in vivo cisplatin-treated murine peripheral blood leukocytes

Amifostine [S-2-3-aminopropyl amino ethyl phosphorotioic acid], a modulator agent for antineoplastic drugs involved in free radicals generation has given controversial results in cisplatin treated leukocytes in vitro. We have evaluated the amifostine protection over leukocytes in vivo, using comet assay. Groups of five OF1 male mice were given one of three doses of amifostine (56, 105 and 200 mg/Kg) after a cisplatin single injection (10 mg/Kg). Serum malonyldialdehyde levels, catalase and superoxide dismutase activity were also evaluated. Amifostine showed significant DNA protection (p< 0.01) at the two lower doses evaluated. Malonyldialdehyde decreased in all amifostine treatments with respect to cisplatin while antioxidant enzyme activities remained unchanged. However, DNA migration increased with the highest amifostine dose; in fact highest dose of amifostine did no protect damage caused by cisplatin this result have implications on amifostine treatment schedules in clinical practice.

Interaction of amifostine and ionizing radiation on transcriptional patterns of apoptotic genes expressed in human microvascular endothelial cells (HMEC)

PURPOSE

Amifostine is a prodrug that requires dephosphorylation by alkaline phosphatase to become activated. This process occurs rapidly within the bloodstream after its i.v. administration to patients undergoing cancer treatment with selected radiation and chemotherapies. Vascular endothelial cells will, therefore, represent a normal cell system that is among the first to experience the radioprotective effects of this agent. Amifostine's active free thiol WR-1065 was investigated to determine its effect on radiation-induced changes in transcriptional patterns and subsequent apoptosis in human microvascular endothelial cells (HMEC) growing in vitro.

METHODS AND MATERIALS

Human microvascular endothelial cells were grown to confluency and then exposed to WR-1065 at a concentration of 4 mM for 30 min, radiation doses that ranged from 0 to 6 Gy, and WR-1065 at a concentration of 4 mM for 30 min before exposure to ionizing radiation. Cell survival was assessed by clonogenic assay, cell cycle phase was analyzed by flow cytometry, apoptosis was also assessed by flow cytometry in which Anexin V staining and sub-G1 fraction analysis were applied, and gene expression was analyzed by the Clontech Atlas Human cDNA array to identify synergistic and antagonistic effects as a function of amifostine and radiation exposure conditions with a focus on apoptotic-related factors.

RESULTS

Exposure of HMEC to 4 mM WR-1065 30 min before irradiation resulted in a protection enhancement factor of 2.0; that is, D(O-IRR) of 1.25 Gy and D(O-IRR+WR) of 2.56 Gy. Expression profiling revealed 29 genes that were synergistically activated by the combined action of WR-1065 and ionizing radiation, and an additional 12 genes were synergistically or additively suppressed. In particular, a subset of apoptosis-related genes that included caspases 2, 4, and 9 and different members of the bcl family, along with apoptosis-related receptors, were identified as being significantly affected by the combined treatment of WR-1065 and radiation exposure. In addition, a number of cell cycle-related genes that express cyclins A, G1, G2, and D3 and DNA damage/check point proteins ATM, DNA-PK and RAD23B were also found to be significantly affected. Functional assays of apoptosis were also performed that demonstrated the ability of WR-1065 to protect against radiation-induced apoptosis.

CONCLUSIONS

WR-1065, the active thiol form of amifostine, is an effective radioprotector of HMEC as determined by use of clonogenic and apoptotic assays for cell survival. Expression profiling successfully defined the transcriptional response of HMEC to both WR-1065 and ionizing radiation exposure, either alone or in combination, and demonstrated both synergistic and antagonistic effects on the expression of different cellular genes, along with corresponding functional responses. The radioprotective effects of amifostine are not limited to its well-characterized physiochemical properties, which include free-radical scavenging, auto-oxidation leading to intracellular hypoxia, and chemical repair by hydrogen atom donation, but include its ability to modulate the complex transcriptional regulation of genes that are involved in apoptosis, cell cycle, and DNA repair.

Activity of topoisomerase inhibitors daunorubicin, idarubicin, and aclarubicin in the Drosophila Somatic Mutation and Recombination Test

Anthracyclines have been widely used as anticancer drugs against different types of human cancers. The present study evaluated the mutagenic and recombinagenic properties of two anthracycline topoisomerase II (topo II) poisons, daunorubicin (DNR) and idarubicin (IDA), as well as the related topo II catalytic inhibitor aclarubicin (ACLA), using the wing Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. The three anthracyclines were positive in this bioassay, producing mainly mitotic homologous recombination. The results for spot-size distribution and recombinagenic activity indicate that recombinational DNA damage accounts for approximately 91, 86, and 62% of DNR, IDA, and ACLA genotoxicity, respectively. Besides being a catalytic inhibitor of topo II, ACLA is also a topoisomerase I (topo I) poison. This dual topo I and II inhibitory effect, associated with its DNA-intercalating activity, could contribute to the activity of ACLA in the SMART assay.