Protection of mouse bone marrow from etoposide-induced genomic damage by dexrazoxane

Guidance for the use and interpretation of assays for monitoring anti-genotoxicity

Since DNA damage can occur spontaneously or be produced by the environmental genotoxins in living cells, it is important to investigate compounds that can reverse or protect DNA damage. An appropriate methodology is essential for the responsive identification of protection offered against DNA damage. This review includes information on the current state of knowledge on prokaryotic cell-based assays (SOS chromotest, umu test, vitotox assay) and cytogenetic techniques (micronucleus assay, chromosome aberration test and sister chromatid exchange assay) with an emphasis on the possibility to explore genoprotective compounds. Throughout the last decade, studies have extrapolated the scientific methodologies utilized for genotoxicity to assess genoprotective compounds. Therefore, shortcomings of genotoxicity studies are also mirrored in antigenotoxicity studies. While regulatory authorities around the world (OECD, US-EPA and ICH) continue to update diverse genotoxic assay strategies, there are still no clear guidelines/approaches for efficient experimental design to screen genoprotective compounds. As a consequence, non-synergetic and inconsistent implementation of the test method by the researchers to execute such simulations has been adopted, which inevitably results in unreliable findings. The review has made the first attempt to collect various facets of experimentally verified approaches for evaluating genoprotective compounds, as well as to acknowledge potential significance and constraints, and further focus on the assessment of end points which are required to validate such action. Henceforth, the review makes an incredible commitment by permitting readers to equate several components of their test arrangement with the provided simplified information, allowing the selection of convenient technique for the predefined compound from a central repository.

Saxagliptin, a selective dipeptidyl peptidase-4 inhibitor, alleviates somatic cell aneugenicity and clastogenicity in diabetic mice

Diabetes-related complications are becoming increasingly common as the global prevalence of diabetes increases. Diabetes is also linked to a high risk of developing cancer. This raises the question of whether cancer vulnerability is caused by diabetes itself or the use of antidiabetic drugs. Chromosomal instability, a source of genetic modification involving either an altered chromosomal number or structure, is a hallmark of cancer. Saxagliptin has been approved by the FDA for diabetes treatment. However, the detailed in vivo effects of prolonged saxagliptin treatment on chromosomal instability have not yet been reported. In this study, streptozotocin was used to induce diabetes in mice, and both diabetic and non-diabetic mice received saxagliptin for five weeks. Fluorescence in situ hybridization was conducted in combination with a bone marrow micronucleus test for measuring chromosomal instability. Our results indicated that saxagliptin is neither mutagenic nor cytotoxic, under the given treatment regimen. Diabetic mice had a much higher incidence of micronuclei formation, and a centromeric DNA probe was present inside the majority of the induced micronuclei, indicating that most of these were caused by chromosome nondisjunction. Conversely, diabetic mice treated with saxagliptin exhibited a significant decrease in micronuclei induction, which were centromeric-positive and centromeric-negative. Diabetes also causes significant biochemical changes indicative of oxidative stress, such as increased lipid peroxidation and decreased reduced/oxidized glutathione ratio, which was reversed by saxagliptin administration. Overall, saxagliptin, the non-mutagenic antidiabetic drug, maintains chromosomal integrity in diabetes and reduces micronuclei formation by restoring redox imbalance, further indicating its usefulness in diabetic patients.

Aflatoxin B1 Exacerbates Genomic Instability and Apoptosis in the BTBR Autism Mouse Model via Dysregulating DNA Repair Pathway

The pathophysiology of autism is influenced by a combination of environmental and genetic factors. Furthermore, individuals with autism appear to be at a higher risk of developing cancer. However, this is not fully understood. Aflatoxin B1 (AFB1) is a potent food pollutant carcinogen. The effects of AFB1 on genomic instability in autism have not yet been investigated. Hence, we have aimed to investigate whether repeated exposure to AFB1 causes alterations in genomic stability, a hallmark of cancer and apoptosis in the BTBR autism mouse model. The data revealed increased micronuclei generation, oxidative DNA strand breaks, and apoptosis in BTBR animals exposed to AFB1 when compared to unexposed animals. Lipid peroxidation in BTBR mice increased with a reduction in glutathione following AFB1 exposure, demonstrating an exacerbated redox imbalance. Furthermore, the expressions of some of DNA damage/repair- and apoptosis-related genes were also significantly dysregulated. Increases in the redox disturbance and dysregulation in the DNA damage/repair pathway are thus important determinants of susceptibility to AFB1-exacerbated genomic instability and apoptosis in BTBR mice. This investigation shows that AFB1-related genomic instability can accelerate the risk of cancer development. Moreover, approaches that ameliorate the redox balance and DNA damage/repair dysregulation may mitigate AFB1-caused genomic instability.

Crosstalk of TNF-α, IFN-γ, NF-kB, STAT1 and redox signaling in lipopolysaccharide/D-galactosamine/dimethylsulfoxide-induced fulminant hepatic failure in mice

Purpose

The clinical study of fulminant hepatic failure is challenging due to its high mortality and relative rarity, necessitating reliance on pre-clinical models to gain insight into its pathophysiology and develop potential therapies.

Methods and Results

In our study, the combination of the commonly used solvent dimethyl sulfoxide to the current-day model of lipopolysaccharide/d-galactosamine-caused fulminant hepatic failure was found to cause significantly greater hepatic damage, as indicated by alanine aminotransferase level. The effect was dose-dependent, with the maximum increase in alanine aminotransferase observed following 200 μl/kg dimethyl sulfoxide co-administration. Co-administration of 200 μl/kg dimethyl sulfoxide also remarkably increased histopathological changes induced by lipopolysaccharide/d-galactosamine. Importantly, alanine aminotransferase levels and survival rate in the 200 μl/kg dimethyl sulfoxide co-administration groups were both greater than those in the classical lipopolysaccharide/d-galactosamine model. We found that dimethyl sulfoxide co-administration aggravated lipopolysaccharide/d-galactosamine-caused liver damage by stimulating inflammatory signaling, as indicated by tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) levels. Further, nuclear factor kappa B (NF-kB) and transcription factor activator 1 (STAT1) were upregulated, as was neutrophil recruitment, indicated by myeloperoxidase activity. Hepatocyte apoptosis was also increased, and greater nitro-oxidative stress was noted, as determined based on nitric oxide, malondialdehyde, and glutathione levels.

Conclusion

Co-treatment with low doses of dimethyl sulfoxide enhanced the lipopolysaccharide/d-galactosamine-caused hepatic failure in animals, with higher toxicity and greater survival rates. The current findings also highlight the potential danger of using dimethyl sulfoxide as a solvent in experiments involving the hepatic immune system, suggesting that the new lipopolysaccharide/d-galactosamine/dimethyl sulfoxide model described herein could be used for pharmacological screening with the goal to better understand hepatic failure and evaluate treatment approaches.

Multiple exposure to methylmercury aggravates DNA damage in the BTBR T + Itpr3 tf/J autistic mouse model: the role of DNA repair efficiency

Environmental and genetic factors have been recognized to play major roles in the pathogenesis of autism. Here we examined the BTBR T⁺Itpr3^tf/J (BTBR) mice's susceptibility, an autistic model, to the genotoxic effects and DNA repair dysregulation of methylmercury. Micronuclei formation and oxidative DNA damage were analyzed using the micronucleus/fluorescence in situ hybridization test and modified comet assay, respectively. The results showed higher centromeric-positive micronuclei and oxidative DNA damage in BTBR mice exposed to methylmercury than the unexposed mice, which indicates that mutagenesis aggravated in BTBR mice after methylmercury exposure. Lipid peroxides in BTBR mice were significantly elevated, with a decrease in reduced/oxidized glutathione ratio after methylmercury exposure, indicating an augmenting oxidant-antioxidant imbalance. The expression of several genes involved in DNA repair was markedly altered in BTBR mice after methylmercury exposure as evaluated via PCR array and RT-PCR analyses. Declining of the antioxidant defense and dysregulation in DNA repair process after methylmercury exposure may explain the aggravated genotoxic susceptibility of BTBR mice. Thus, autistic individuals exposed to methylmercury must be under regular medical follow-up through standard timetabled medical laboratory inquiry to allow for early recognition of any mutagenic changes. Additionally, strategies that elevate cellular antioxidants/DNA repair efficiency may counteract methylmercury-induced genotoxicity.

Identification of new halogen-containing 2,4-diphenyl indenopyridin-5-one derivative as a boosting agent for the anticancer responses of clinically available topoisomerase inhibitors

Based on previous reports on the significance of halogen moieties and the indenopyridin-5-one skeleton, we designed and synthesized a novel series of halogen (F-, Cl-, Br-, CF₃- and OCF₃-)-containing 2,4-diphenyl indenopyridin-5-ones and their corresponding -5-ols. Unlike indenopyridin-5-ols, most of the prepared indenopyridin-5-ones with Cl-, Br-, and CF₃- groups at the 2-phenyl ring conferred a strong dual topoisomerase I/IIα inhibitory effect. Among the series, para-bromophenyl substituted compound 9 exhibited the most potent topoisomerase inhibition and antiproliferative effects, which showed dependency upon the topoisomerase gene expression level of diverse cancer cells. In particular, as a DNA minor groove-binding non-intercalative topoisomerase I/IIα catalytic inhibitor, compound 9 synergistically promoted the anticancer efficacy of clinically applied topoisomerase I/IIα poisons both in vitro and in vivo, having the great advantage of alleviating poison-related toxicities.

Evaluation of the in vivo genotoxicity of liposomal formulation for delivering anticancer estrogenic derivative (ESC8) in a mouse model

The genotoxic potential of glucocorticoid receptor (GR)-targeted liposomal formulations of the anticancer drug molecule ESC8 was studied in vivo. A methodical literature review discovered no previous studies on the genotoxicity of ESC8. Genotoxicity was assessed in both male and female mice by various assay systems, such as comet assay, chromosomal aberrations and micronuclei assay, which detect different abnormalities. Eleven groups of male mice and eleven groups of female mice, containing six animals per group, were used in the present study: group I served as vehicle control; group II received the positive control (cyclophosphamide 40 mg/kg; CYP); and animals in group III to XI received free drug (ESC8), DX liposome and drug-associated DX liposomal formulation (DXE), respectively, dissolved in 5% solution of glucose at a drug-dose of 1.83, 3.67 and 7.34 mg/kg, respectively. Same drug treatments were followed for the female mice groups. The obtained data revealed the safety of DXE, which did not show substantial genotoxic effects at different dose levels. In contrast, the positive control, CYP, exhibited highly substantial irregular cytogenetic variations in comparison with the control group in different assays.

GMZ-1 is a podophyllotoxin derivative that suppresses growth and induces apoptosis in adriamycin-resistant K562/A02 cells through modulation of MDR1 expression

The incidence of multidrug resistance (MDR) during cancer chemotherapy is a major challenge for treatment. With the aim of identifying drugs that are capable of targeting treatment‑resistant cancer cells, the present study evaluated the efficacy of GMZ‑1 in cancer chemotherapy using K562/A02, an MDR leukemia cell line. Cell viability and apoptosis were measured by MTT assay and flow cytometry/Giemsa staining, respectively. The expression levels of the MDR protein 1 (MDR1) gene transcript and protein in K562/A02 cells were determined by reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. GMZ‑1 suppressed the viability of various human cancer cell lines and induced apoptosis in the K562/A02 cell line in a time‑ and concentration‑dependent manner. GMZ‑1 toxicity may be associated with a decrease in MDR gene expression. These findings demonstrated that GMZ‑1 may have efficacy as a potential antitumor drug to overcome leukemia cell resistance to apoptosis induced by chemotherapy.

Deleterious effects of reactive metabolites

A number of drugs have been withdrawn from the market or severely restricted in their use because of unexpected toxicities that become apparent only after the launch of new drug entities. Circumstantial evidence suggests that, in most cases, reactive metabolites are responsible for these unexpected toxicities. In this review, a general overview of the types of reactive metabolites and the consequences of their formation are presented. The current approaches to evaluate bioactivation potential of new compounds with particular emphasis on the advantages and limitation of these procedures will be discussed. Reasonable reasons for the excellent safety record of certain drugs susceptible to bioactivation will also be explored and should provide valuable guidance in the use of reactive-metabolite assessments when nominating drug candidates for development. This will, in turn, help us to design and bring safer drugs to the market.

Utility of Dexrazoxane for the Attenuation of Epirubicin-Induced Genetic Alterations in Mouse Germ Cells

Dexrazoxane has been approved to treat anthracycline-induced cardiomyopathy and extravasation. However, the effect of dexrazoxane on epirubicin-induced genetic alterations in germ cells has not yet been reported. Thus, the aim of this study was to determine whether dexrazoxane modulates epirubicin-induced genetic damage in the germ cells of male mice. Our results show that dexrazoxane was not genotoxic at the tested doses. Furthermore, it protected mouse germ cells against epirubicin-induced genetic alterations as detected by the reduction in disomic and diploid sperm, spermatogonial chromosomal aberrations, and abnormal sperm heads. The attenuating effect of dexrazoxane was greater at higher dose, indicating a dose-dependent effect. Moreover, sperm motility and count were ameliorated by dexrazoxane pretreatment. Epirubicin induced marked biochemical changes characteristic of oxidative DNA damage including elevated 8-hydroxy-2'-deoxyguanosine levels and reduction in reduced glutathione. Pretreatment of mice with dexrazoxane before epirubicin challenge restored these altered endpoints. We conclude that dexrazoxane may efficiently mitigate the epirubicin insult in male germ cells, and prevent the enhanced risk of abnormal reproductive outcomes and associated health risks. Thus, pretreating patients with dexrazoxane prior to epirubicin may efficiently preserve not only sperm quality but also prevent the transmission of genetic damage to future generations.

Impact of dexrazoxane on doxorubicin-induced aneuploidy in somatic and germinal cells of male mice

PURPOSE

Despite dexrazoxane's increasing use in mitigating doxorubicin-induced cardiotoxicity, no data are available in the literature on the potential aneugenicity of drug combination. Therefore, detailed evaluation of aneugenic potential of this combination is essential to provide more insights into aneuploidy induction that may play a role in the development of secondary malignancies and reproductive toxicity after treatment with doxorubicin. Thus, our aim was to determine whether dexrazoxane has influence on the aneuploidy induced by doxorubicin in germinal and somatic cells of male mice.

METHODS

Sperm BrdU-incorporation assay, sperm FISH assay and the bone marrow micronucleus test complemented by FISH assay were used to determine aneuoploidy. Moreover, the formation of 8-OHdG, one of the oxidative DNA damage by-products, has been evaluated.

RESULTS

Dexrazoxane was not aneugenic at the doses tested. Pre-treatment of mice with dexrazoxane significantly reduced doxorubicin-induced aneuploidy in a dose-dependent manner. Doxorubicin induced marked biochemical alterations characteristic of oxidative DNA damage, and prior administration of dexrazoxane before doxorubicin challenge ameliorated this biochemical marker.

CONCLUSION

This study provides evidence that dexrazoxane has a protective role in the abatement of doxorubicin-induced aneuploidy. This activity resides, at least in part, in its radical scavenger activity. Thus, dexrazoxane can avert secondary malignancies and abnormal reproductive outcomes in cured cancer patients exposed to doxorubicin.

Wogonin attenuates etoposide-induced oxidative DNA damage and apoptosis via suppression of oxidative DNA stress and modulation of OGG1 expression

Damage to DNA can lead to many different acute and chronic pathophysiological conditions, ranging from cancer to endothelial damage. The current study has been initiated to determine whether the flavonoid wogonin can attenuate etoposide-induced oxidative DNA damage and apoptosis in mouse bone marrow cells. We found that oral administration of wogonin before etoposide injection significantly attenuates etoposide-induced oxidative DNA damage and apoptosis in a dose dependent manner. Etoposide induced a significant down-regulation of mRNA expression of the OGG1 repair gene and marked biochemical alterations characteristic of oxidative DNA stress, including increased 8-OHdG, enhanced lipid peroxidation and reduction in reduced glutathione. Prior administration of wogonin ahead of etoposide challenge restored these altered parameters. Importantly, wogonin had no antagonizing effect on etoposide-induce topoisomerase-II inhibition. Conclusively, our study indicates that wogonin has a protective role in the abatement of etoposide-induced oxidative DNA damage and apoptosis in the bone marrow cells of mice via suppression of oxidative DNA stress and enhancing DNA repair through modulation of OGG1 repair gene expression. Therefore, wogonin can be a promising chemoprotective agent and might be useful to avert secondary leukemia and other drug-related cancers in cured cancer patients and medical personnel exposing to the potent carcinogen etoposide.

A novel topoisomerase inhibitor, daurinol, suppresses growth of HCT116 cells with low hematological toxicity compared to etoposide

We report that daurinol, a novel arylnaphthalene lignan, is a promising potential anticancer agent with adverse effects that are less severe than those of etoposide, a clinical anticancer agent. Despite its potent antitumor activity, clinical use of etoposide is limited because of its adverse effects, including myelosuppression and the development of secondary leukemia. Here, we comprehensively compared the mechanistic differences between daurinol and etoposide because they have similar chemical structures. Etoposide, a topoisomerase II poison, is known to attenuate cancer cell proliferation through the inhibition of DNA synthesis. Etoposide treatment induces G(2)/M arrest, severe DNA damage, and the formation of giant nuclei in HCT116 cells. We hypothesized that the induction of DNA damage and nuclear enlargement due to abnormal chromosomal conditions could give rise to genomic instability in both tumor cells and in actively dividing normal cells, resulting in the toxic adverse effects of etoposide. We found that daurinol is a catalytic inhibitor of human topoisomerase IIa, and it induces S-phase arrest through the enhanced expression of cyclins E and A and by activation of the ATM/Chk/Cdc25A pathway in HCT116 cells. However, daurinol treatment did not cause DNA damage or nuclear enlargement in vitro. Finally, we confirmed the in vivo antitumor effects and adverse effects of daurinol and etoposide in nude mice xenograft models. Daurinol displayed potent antitumor effects without any significant loss of body weight or changes in hematological parameters, whereas etoposide treatment led to decreased body weight and white blood cell, red blood cell, and hemoglobin concentration.