Update on genotoxicity and carcinogenicity testing of 472 marketed pharmaceuticals

[Cancer risk evaluation in individuals occupationally exposed to organic solvents]

OBJECTIVE

To evaluate the frequency of micronuclei (MNs) and influence of GSTM1 and GSTT1 gene polymorphisms as biomarkers of cancer risk in car painters (n=152) compared to unexposed individuals (n=152).

METHODS

Molecular epidemiology study, cross-sectional analysis of gen and environment interaction. The evaluation of MN and genetic polymorphisms was determined by molecular tests in lymphocytes from subjects involved in the study.

RESULTS

It was determined that the frequency of MNs is 1.6 higher in the exposed group compared to the reference group (1.39 ± 0.92 versus 0.87 ± 0.78, p<0.0001). There was no increase in the frequency of MNs associated with the polymorphisms in GSTM1 and GSTT1.

CONCLUSIONS

The increase of MNs in car painters serves to alert the increased risk of cancer in this population exposed to organic solvents. These results can be used in Occupational Epidemiological Surveillance Programs, as a prevention strategy and policies to regulate and control the use of solvents at a national level and in other countries with a large informal sector of individuals exposed to these chemicals to reduce the risk of cancer.

Regulatory Experiences with Root Causes and Risk Factors for Nitrosamine Impurities in Pharmaceuticals

N-Nitrosamines (also referred to as nitrosamines) are a class of substances, many of which are highly potent mutagenic agents which have been classified as probable human carcinogens. Nitrosamine impurities have been a concern within the pharmaceutical industry and by regulatory authorities worldwide since June 2018, when regulators were informed of the presence of N-nitrosodimethylamine (NDMA) in the angiotensin-II receptor blocker (ARB) medicine, valsartan.  Since that time, regulatory authorities have collaborated to share information and knowledge on issues related to nitrosamines with a goal of promoting convergence on technical issues and reducing and mitigating patient exposure to harmful nitrosamine impurities in human drug products. This paper shares current scientific information from a quality perspective on risk factors and potential root causes for nitrosamine impurities, as well as recommendations for risk mitigation and control strategies.

A substructure-based screening approach to uncover N-nitrosamines in drug substances

Drug substances are at risk of contamination with N-nitrosamines (NAs), well-known carcinogenic agents, during synthesis processes and/or long-term storage. Therefore, in this study, we developed an efficient data-based screening approach to systemically assess marketed products and investigated its scalability for benefiting both regulatory agencies and pharmaceutical industries. A substructure-based screening method employing DataWarrior, an open-source software, was established to evaluate the risks of NA impurities in drug substances. Eight NA substructures containing susceptible amino sources for N-nitrosation have been identified as screening targets: dimethylamine (DMA), diethylamine, isopropylethylamine, diisopropylamine, N-methyl-2-pyrrolidone, dibutylamine, methylphenylamine, and tetrazoles. Our method detected 192 drug substances with a theoretical possibility of NA impurity, 141 of which had not been reported previously. In addition, the DMA moiety was significantly dominant among the eight NA substructures. The results were validated using data from the literature, and a high detection sensitivity of 0.944 was demonstrated. Furthermore, our approach has the advantage of scalability, owing to which 31 additional drugs with suspected NA-contaminated substructures were identified using the substructures of 1-methyl-4-piperazine in rifampin and 1-cyclopentyl-4-piperazine in rifapentine. In conclusion, the reported substructure-based approach provides an effective and scalable method for the screening and investigation of NA impurities in various pharmaceuticals and might be used as an ancillary technique in the field of pharmaceutical quality control for risk assessments of potential NA impurities.

[Genotoxicity of psychotropic drugs in experimental and clinical studies]

The analysis of experimental data on the study of the genotoxic activity of psychotropic drugs published over the past 25 years has been carried out. It has been shown that the information describing the genotoxicity of psychotropic drugs is characterized by fragmentation, contradictions, and the conditions for their experimental production often do not meet modern requirements. Conclusions about the presence or absence of genotoxic properties can be made only for 9.6% 94 examined drugs. The need for a large-scale systematic reassessment of the genotoxicity of psychotropic drugs, especially drugs of the first generation, on the basis of modern methodology, including studies of mutagen-modifying activity, has been proven. The expediency of monitoring the genotoxic status of patients receiving psychotropic drugs is emphasized, which should contribute to an adequate assessment of the genotoxic risk of their use and objectification of approaches when choosing a drug for the safe therapy. The urgency of conducting research to determine the role of primary DNA damage in the pathogenesis of mental illnesses has been substantiated.

In Silico Prediction of Chemically Induced Mutagenicity: A Weight of Evidence Approach Integrating Information from QSAR Models and Read-Across Predictions

Information on genotoxicity is an essential piece of information in the framework of several regulations aimed at evaluating chemical toxicity. In this context, QSAR models that can predict Ames genotoxicity can conveniently provide relevant information. Indeed, they can be straightforwardly and rapidly used for predicting the presence or absence of genotoxic hazards associated with the interactions of chemicals with DNA. Nevertheless, and despite their ease of use, the main interpretative challenge is related to a critical assessment of the information that can be gathered, thanks to these tools. This chapter provides guidance on how to use freely available QSAR and read-across tools provided by VEGA HUB and on how to interpret their predictions according to a weight-of-evidence approach.

Nano-adsorbents an effective candidate for removal of toxic pharmaceutical compounds from aqueous environment: A critical review on emerging trends

Advancements in medical research has resulted in the modernization of healthcare facilities, subsequently leading to a higher level of production and usage of pharmaceuticals to sustain better quality of life. Pharmaceutical active compounds (PhACs) possess high genotoxicity and eco-toxicity thus presenting numerous side effects to living beings on long-term exposure. The fate and toxicity of PhACs were explored in detail, aiming to elucidate their occurrence and transmission in wastewater treatment systems (WWTPs). Adsorption of pharmaceutical compounds using Nano-adsorbents has gained momentum in recent years owing to their low-cost, high surface area and effectiveness. This review has been conducted in order to widen the utilization of Nano adsorbents in the adsorption of pharmaceutical compounds with a focus on the aqueous environment. The synthesis routes and properties of Nano-adsorbents for removal of PhACs were assessed in a comprehensive way. The recovery and reuse ability of nano-adsorbents also forms an integral part of its application in the removal of PhACs and has hence been delineated.

Active pharmaceutical contaminants in dietary supplements: A tier-based risk assessment approach

The presence of active pharmaceutical ingredients (APIs) in adulterated or contaminated dietary supplements is a current product safety concern. Since there are limited guidelines, and no published consensus methods, we developed a tier-based framework incorporating typical lines of evidence for determining the human health risk associated with APIs in dietary supplements. Specifically, the tiered approach outlines hazard identification and decision to test for APIs in products based on criteria for likelihood of contamination or adulteration, and evaluation of manufacturer production standards. For products with detectable levels of APIs, a variety of default approaches, including the use of fraction of the therapeutic dose and the threshold of toxicological concern (TTC), as well as health-based exposure limits (HBELs) are applied. In order to demonstrate its practical use, as well as any limitations and/or special considerations, this framework was applied to five dietary supplements (currently available to the public). We found that the detected levels of APIs in some dietary supplements were above the recommended dose of the drugs, and thus, pose a significant health risk to consumers and potentially workers involved in manufacturing of these supplements. The results support the value of increased product quality surveillance and perhaps regulatory activity.

Comprehensive review of genotoxicity data for diclofenac

Diclofenac is a non-steroidal anti-inflammatory drug discovered several decades ago, which has since been used by an estimated one billion patients and has demonstrated an acceptable safety profile. In support of its marketing approval, a comprehensive set of genotoxicity studies were conducted in vitro and in vivo. Despite the fact that these studies preceded both Good Laboratory Practice (GLP) requirements and International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines on genotoxicity testing, they were conducted using the best scientific principles and are considered appropriate by contemporary standards. In addition to bacterial mutagenicity and mammalian in vitro assays, repeat-dose somatic, germ cell and dominant lethal assays were conducted. These data are made available for the first time to offer researchers an opportunity to review the existing data set that unequivocally demonstrates that diclofenac sodium is not genotoxic. This is further substantiated by long-term bioassay data demonstrating that diclofenac sodium has no carcinogenic potential in rodents. However, more recently, new studies have been published showing a genotoxic potential for diclofenac in novel or modified in vitro test systems. These new publications are discussed in the context of the existing comprehensive data package.

Two-stage Enzymatic Hydrolysis of Soybean Concentrated Phospholipid to Prepare Glycerylphosphorylcholine: Optimized by Response Surface Methodology

A two-stage enzymatic hydrolysis method, in which phospholipase A1 (PLA1) was added after phospholipase A2 (PLA2) was added for a certain time, was successfully carried out to prepare glycerylphosphorylcholine (GPC) from soybean concentrated phospholipid. Effects of reaction variables on hydrolysis reaction were optimized using response surface methodology, and the optimal conditions were as follows: PLA2 load of 1.25%, PLA1 load of 0.70%, substrate concentration of 13%, reaction temperature of 41°C, and stirring rate of 680 rpm. Under the optimal conditions, the GPC yield reached 83.07%, which is close to the predicted value by the fitted model. This paper not only provides an efficient and low-cost method to prepare GPC, but also improves the high-value utilization of soybean concentrated phospholipid.

A Systematic Review on the Genotoxic Effects of Selective Serotonin Reuptake Inhibitors

Depression is a mental disorder and a major public health concern affecting millions of people worldwide. It is a common disorder that has been associated with several medical comorbidities often linked with aging, such as dementia, type II diabetes, cardiovascular and cerebrovascular diseases, as well as metabolic syndrome. There are a variety of medications available for depression treatment. Selective serotonin reuptake inhibitors (SSRIs) are one of the antidepressant drug classes that are most widely used to treat depressive disorders and depressive symptoms in other diseases. Due to many contradictory findings on the adverse effects and toxicities of SSRIs (especially genotoxicities), we reviewed the genotoxic effects of these drugs. Based on the guidelines proposed in the PRISMA statement, we performed a systematic review by searching international electronic databases including PubMed, Scopus, Embase, and Web of Science to find the published documents on SSRIs and their genotoxic effects from January 1990 to November 2019. After the removal of 203 duplicate articles, 385 articles were screened and 167 articles met the inclusion criteria and qualified for evaluation of their full texts. After this, 26 articles were appropriate for final review. This revealed that the proportion of genotoxicities was highest for citalopram and fluoxetine, with a smaller proportion for sertraline. Limited documentations showed genotoxic and partial genotoxic effects for paroxetine and escitalopram, respectively. Although a number of studies have found genotoxic effects of SSRIs, there are also some factors including doses, duration of exposure, model of experiments, and the type of technique assay that may affect the results.

Species differences in micronucleus induction of the clastogenic compounds associated with drug metabolic profile

Genotoxicity and carcinogenicity profiles of drugs occasionally vary across species due to species difference in drug metabolic profile. To clarify the effect of species differences in the metabolic profile on micronucleus induction, we conducted an in vitro micronucleus test for seven clastogens (benzo[a]pyrene: BaP, cyclophosphamide monohydrate: CPA coumarin, diclofenac, piroxicam, lansoprazole, and chlorpheniramine) with rat, mouse, monkey, dog, or human liver S9. BaP, CPA, coumarin, diclofenac, piroxicam, and lansoprazole induced micronucleus formation with all species of S9s, whereas chlorpheniramine did not induce micronucleus formation in any of the S9s. BaP and CPA revealed remarkable species differences in micronucleus induction, whereas coumarin, diclofenac, piroxicam, and lansoprazole did not present any differences. Interestingly, the amounts of hydroxy-BaP-epoxides and phosphamide mustard, which might be associated with micronucleus induction by BaP and CPA, respectively, were correlated with the degree of micronucleus induction among the five species. In conclusion, the species difference in micronucleus induction by BaP and CPA was attributable to the differences in the metabolic profiles of these drugs among species. Our results indicate that it is crucial to understand the effect of species differences in the metabolic profile of drug candidates on genotoxicity and carcinogenicity potential and to predict their risk in human.

Multifaceted Role of PARP-1 in DNA Repair and Inflammation: Pathological and Therapeutic Implications in Cancer and Non-Cancer Diseases

PARP-1 (poly(ADP-ribose)-polymerase 1), mainly known for its protective role in DNA repair, also regulates inflammatory processes. Notably, defects in DNA repair and chronic inflammation may both predispose to cancer development. On the other hand, inhibition of DNA repair and inflammatory responses can be beneficial in cancer therapy and PARP inhibitors are currently used for their lethal effects on tumor cells. Furthermore, excess of PARP-1 activity has been associated with many tumors and inflammation-related clinical conditions, including asthma, sepsis, arthritis, atherosclerosis, and neurodegenerative diseases, to name a few. Activation and inhibition of PARP represent, therefore, a double-edged sword that can be exploited for therapeutic purposes. In our review, we will discuss recent findings highlighting the composite multifaceted role of PARP-1 in cancer and inflammation-related diseases.

Effect of the metabolic capacity in rat liver S9 on the positive results of in vitro micronucleus tests

A high incidence of positive results is obtained with in vitro genotoxicity tests, which do not correlate with the in vivo negative results in many cases. To address this issue, the metabolic profile of rat liver 9000 × g supernatant fraction (S9) pretreated with phenobarbital (PB) and 5,6-benzoflavone (BNF) was characterized. Furthermore, the in vitro micronucleus tests of 10 compounds were performed with PB-BNF-induced rat S9. PB-BNF increased cytochrome P450 (CYP) activity and CYP1A1, CYP1A2, CYP2B1/2, CYP2C6, CYP3A1, and CYP3A2 expression in rat S9, whereas it decreased CYP2C11 and CYP2E1 expression. PB-BNF-induced S9 enhanced the micronucleus induction (MI) of benzo[a]pyrene (BaP), cyclophosphamide (CPA), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine hydrochloride (PhIP), which are metabolized by CYP1A1, CYP2C6, and CYP1A2, respectively. In contrast, coumarin and chlorpheniramine showed MI with PB-BNF-induced S9 despite the fact that they show negative results in the in vivo studies. Furthermore, diclofenac, piroxicam, lansoprazole, and caffeine showed MI regardless of the enzyme induction by PB-BNF, whereas phenacetin did not show MI. These results indicate that PB-BNF-induced rat S9 is effective in detecting the genotoxic potential of promutagens, such as BaP, CPA, and PhIP, but not of coumarin and chlorpheniramine, probably due to the differences in the in vitro and in vivo metabolic profile and its exposure levels of the drugs.

Mequindox induces apoptosis, DNA damage, and carcinogenicity in Wistar rats

Mequindox (MEQ) is a synthetic antibacterial agent. Recent studies showed that MEQ and its primary metabolites exhibit strong genotoxicity to mammalian cells, and MEQ induced carcinogenicity in mice. These findings suggest that chronic exposure to MEQ could lead to an increased risk of cancer later in life. In the present study, four groups of Wistar rats (55 rats/sex/group) were fed with diets containing MEQ (0, 25, 55, and 110 mg/kg) for 2 years. The results showed that the hematological system, liver, kidneys, and adrenal glands, as well as the developmental and reproductive systems, were the main targets for MEQ. Liver toxicity mediated by MEQ was associated with apoptosis and the nuclear factor κB (NF-κB) signaling pathway. In addition, MEQ increased the incidence of tumors in rats. Phosphorylated histone H2AX (γ-H2AX) is identified as a biomarker of cellular response to DNA double-strand breaks (DSB). Our data demonstrated that γ-H2AX expression was significantly increased in tumors. Thus, high levels of DSB might be responsible for carcinogenesis in rats, and further investigation is absolutely required to clarify the exact molecular mechanisms for carcinogenicity caused by MEQ in vivo.

Assessment of toxic effects of the antibiotic erythromycin on the marine fish gilthead seabream (Sparus aurata L.) by a multi-biomarker approach

Erythromycin (ERY) is one of the most common antibiotics used in human and veterinary practices, leading to ubiquitous environmental distribution and possible toxicity to non-target organisms. The purpose of this study was to determine sub-lethal effects of ERY towards the marine fish Sparus aurata (gilthead seabream). S. aurata were acutely (0.3-323 μg/L, 96 h) and chronically (0.7-8.8 μg/L, 28 d) exposed to ERY. Detoxification [7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferases (GSTs), uridine-diphosphate-glucuronosyltransferase (UGT)], oxidative stress [catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GRed)], lipid peroxidation [thiobarbituric acid reactive substances - (TBARS)], genotoxicity [genetic damage index (GDI) and erythrocytic nuclear abnormalities (ENAs)], neurotransmission [acetylcholinesterase (AChE)] and energy metabolism [lactate dehydrogenase (LDH)] biomarkers were evaluated. Results showed that ERY did not promote significant effects in detoxification biomarkers, but induced slight pro-oxidative effects (decrease of GPx activity in the liver after acute exposure and an increase in gills after chronic exposure; and an increase of hepatic GRed activity following chronic exposure). There was a significant decrease in TBARS after chronic exposure, which contradicts a full scenario of oxidative stress. In terms of genotoxicity, both ERY exposures caused only a significant increase of GDI. Neurotransmission and energy metabolism were not also affected by ERY. Although few toxic effects of ERY have been previously documented (involving different metabolic pathways, as tested in this work), these were mainly observed for freshwater species. These findings suggest low vulnerability of S. aurata to ERY at levels close to the ones found in the wild.

The mutagenic effect of psychostimulant modafinil in Wistar rats in vivo

The demands imposed by today's world require a fast and efficient society, then, significant section of the population looks for support from psychotropic medicine. Modafinil is a psychostimulant that promotes wakefulness, it being recommended for treatment of narcolepsy, obstructive sleep apnea, and shift-work sleep disorder, besides being a cognitive function potentiator. However, chemical components of drugs can alter genetic material. Thus, the present study evaluated the cytotoxic and clastogenic/mutagenic potential of 0.25, 0.50, and 0.75 mg of Modafinil/mL of corn oil/100g body weight in acute treatments and subacute treatments, 15 days, to Rattus norvegicus, treated via gavage in a single daily dose. The drug was not cytotoxic at any of the evaluated doses in either of the treatments. However, the medicine showed clastogenic/mutagenic activity in the acute treatment group at the standard dose and at double dose. Data from the present study indicates that there should be greater caution as to the use of this psychostimulant by human beings.

Cytogenotoxic effects of venlafaxine hydrochloride on cultured human peripheral blood lymphocytes

The potential genotoxic effect of venlafaxine hydrochloride (venlafaxine), an antidepressant drug-active ingredient, was investigated by using in vitro chromosome aberrations (CAs) and cytokinesis-block micronucleus (CBMN) assays in human peripheral blood lymphocytes (PBLs). Mitotic index (MI) and cytokinesis-block proliferation index (CBPI) were also calculated to determine the cytotoxicity of this active drug. For this aim, the human PBLs were treated with 25, 50, and 100 µg/ml venlafaxine for 24 h and 48 h. The results of this study showed that venlafaxine significantly induced the formation of structural CA and MN for all concentrations (25, 50, and 100 µg/ml) and treatment periods (24 h and 48 h) when compared with the negative and the solvent control (except 25 µg/ml at 48 h for MN). In addition, the increases in the percentage of structural CA and MN were concentration-dependent for both treatment times. With regard to cell cycle kinetics, venlafaxine significantly decreased the MI at all concentrations, and also CBPI at the higher concentrations for both treatment times as compared to the control groups. The present results indicate for the first time that venlafaxine had significant clastogenic and cytotoxic effects at the tested concentrations (25, 50, and 100 µg/ml) in the human PBLs, in vitro; therefore, its excessive and careless use may pose a potential risk to human health.

Mequindox Induced Genotoxicity and Carcinogenicity in Mice

Mequindox (MEQ), acting as an inhibitor of deoxyribonucleic acid (DNA) synthesis, is a synthetic heterocyclic N-oxides. To investigate the potential carcinogenicity of MEQ, four groups of Kun-Ming (KM) mice (50 mice/sex/group) were fed with diets containing MEQ (0, 25, 55, and 110 mg/kg) for one and a half years. The result showed adverse effects on body weights, feed consumption, hematology, serum chemistry, organ weights, relative organ weights, and incidence of tumors during most of the study period. Treatment-related changes in hematology, serum chemistry, relative weights and histopathological examinations revealed that the hematological system, liver, kidneys, and adrenal glands, as well as the developmental and reproductive system, were the main targets after MEQ administration. Additionally, MEQ significantly increased the frequency of micronucleated normochromatic erythrocytes in bone marrow cells of mice. Furthermore, MEQ increased the incidence of tumors, including mammary fibroadenoma, breast cancer, corticosuprarenaloma, haemangiomas, hepatocarcinoma, and pulmonary adenoma. Interestingly, the higher incidence of tumors was noted in M25 mg/kg group, the lowest dietary concentration tested, which was equivalent to approximately 2.25 and 1.72 mg/kg b.w./day in females and males, respectively. It was assumed that the lower toxicity might be a reason for its higher tumor incidence in M25 mg/kg group. This finding suggests a potential relationships among the dose, general toxicity and carcinogenicity in vivo, and further study is required to reveal this relationship. In conclusion, the present study demonstrates that MEQ is a genotoxic carcinogen in KM mice.

The potential ecotoxicological impact of pharmaceutical and personal care products on humans and freshwater, based on USEtox™ characterization factors. A Spanish case study of toxicity impact scores

Pharmaceutical and personal care products (PPCPs) are being increasingly included in Life Cycle Assessment studies (LCAs) since they have brought into evidence both human and ecological adverse effects due to their presence in different environmental compartments, wastewater facilities and industry. Therefore, the main goal of this research was to estimate the characterization factors (CFs) of 27 PPCPs widely used worldwide in order to incorporate their values into Life Cycle Impact Assessment studies (LCIA) or to generate a toxicity impact score ranking. Physicochemical properties, degradation rates, bioaccumulation, ecotoxicity and human health effects were collected from experimental data, recognized databases or estimated using EPI Suite™ and the USEtox™ software, and were subsequently used for estimating CFs. In addition, a Spanish toxicity impact score ranking was carried out for 49 PPCPs using the 27 newly calculated CFs, and 22 CFs already available in the literature, besides the data related to the occurrence of PPCPs in the environment in Spain. It has been highlighted that emissions into the continental freshwater compartment showed the highest CFs values for human effects (ranging from 10^-9 to 10^-3Cases·kg^-1), followed by emissions into the air (10^-9 to 10^-5Cases·kg^-1), soil (10^-11 to 10⁵Cases·kg^-1) and seawater (10^-12 to 10^-4Cases·kg^-1). CFs regarding the affectation of freshwater aquatic environments were the highest of those proceeding from emissions into continental freshwater (between 1 to 10⁴PAF·m³·day·kg_emission^-1) due to the direct contact between the source of emission and the compartment affected, followed by soil (among 10^-1 to 10⁴PAF·m³·day·kg_emission^-1), and air (among 10^-2 to 10⁴PAF·m³·day·kg_emission^-1) while the lowest were the CFs of continental seawater (among 10^-28 to 10^-3PAF·m³·day·kg_emission^-1). Freshwater aquatic ecotoxicological CFs are much higher than human toxicity CFs, demonstrating that the ecological impact of PPCPs in aquatic environments must be a matter of urgent attention. According to the Spanish toxicity impact score calculated, the PPCPs with the highest impact are hormones, antidepressants, fragrances, antibiotics, angiotensin receptor blockers and blood lipid regulators, which have already been found in other kinds of score rankings. These results, which were not available until now, will be useful in order to perform better LCIA studies, incorporating the micro-pollutants whose CFs have been estimated, or in order to carry out single hazard/risk environmental impact assessments.

Evaluation of genotoxic effects of 3-methyl-5-(4-carboxycyclohexylmethyl)-tetrahydro-2H-1,3,5-thiadiazine-2-thione on human peripheral lymphocytes

CONTEXT

Tranexamic acid is commonly used for curing abnormal bleeding in a variety of diseases. In a previous study, 12 different tetrahydro-2H-1,3,5-thiadiazine derivatives were synthesized from the amine group of tranexamic acid. Their antifibrinolytic and antimicrobial activities were compared with tranexamic acid. 3-Methyl-5-(4-carboxycyclohexylmethyl)-tetrahydro-2H-1,3,5-thiadiazine-2-thione (3-MTTT) was the most remarkable one, which may be used as a drug.

OBJECTIVES

In vitro genotoxicity of 3-MTTT was investigated using chromosome aberrations (CAs), sister chromatid exchanges (SCEs), micronucleus (MN) and comet assays.

MATERIALS AND METHODS

Various concentrations 0.78, 1.56, 3.13, 6.25, 12.50 and 25.00 μg/mL of 3-MTTT were applied to lymphocytes obtained from two donors for periods of 24 and 48 h. A negative (distilled water), a solvent (2:1 PBS:10% NaOH for cultured lymphocyte, and PBS for isolated lymphocytes) and a positive control (MMC for cultured lymphocytes and H₂O₂ for isolated lymphocytes) were also maintained.

RESULTS

While this compound did not increase the frequency of abnormal cells and CA/cell ratio compared to negative control (except 48 h, 25 μg/mL), it significantly increased the frequency of SCEs at the four highest concentrations at both treatment periods (except 6.25 μg/mL, 48 h). It significantly decreased the MI in all the concentrations at 24 h (except 0.78 μg/mL) and in the highest three concentrations at 48 h. This compound did not significantly increase the frequency of MN and DNA damage compared to negative control. This compound did not affect the replication and nuclear division index.

DISCUSSION AND CONCLUSION

Our results demonstrated that this compound does not represent a significant risk at the genetic level in in vitro human lymphocytes.

Identification and risk assessment of human and veterinary antibiotics in the wastewater treatment plants and the adjacent sea in Tunisia

In the following study, we came up with and validated a prompt, sensitive and precise method for the simultaneous determination of 56 antimicrobial drugs (tetracyclines, sulfonamides, β-lactams, macrolides and quinolones) using the ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). This method was implemented with success to determine antibiotics in samples collected from four wastewater treatment plants and five coasts in Tunisia. Results showed the presence of high concentrations of antibiotics that ranged from 0.1 to 646 ng mL^-1, which can induce many negative impacts on health and the environment. For this reason, we have opted to evaluate toxicity of wastewater samples using a battery of biotests. In fact, genotoxicity was assessed using three tests: Vitotox, comet and micronucleus assays. The input and output of wastewater treatment plants induced a strongly genotoxic effect on the Salmonella typhimurium TA104 prokaryotic Vitotox assay. This result was confirmed using the comet and the micronucleus assays performed on the human liver hepatocellular carcinoma cells. The genotoxic power of the tested wastewater treatment plants' samples could be attributed to the presence of the higher quantities of antibiotics that are detected in these samples and to the antibiotic and organic compound cocktails.

Hypersensitivity of mouse embryonic fibroblast cells defective for DNA polymerases η, ι and κ to various genotoxic compounds: Its potential for application in chemical genotoxic screening

Genotoxic agents cause modifications of genomic DNA, such as alkylation, oxidation, bulky adduct formation, and strand breaks, which potentially induce mutations and changes to the structure or number of genes. Majority of point mutations are generated during error-prone bypass of modified nucleotides (translesion DNA synthesis, TLS); however, when TLS fails, replication forks stalled at lesions eventually result in more lethal effects, formation of double-stranded breaks (DSBs). Here we compared sensitivities to various compounds among mouse embryonic fibroblasts derived from wild-type and knock-out mice lacking one of the three Y-family TLS DNA polymerases (Polη, Polι, and Polκ) or all of them (TKO). The compounds tested in this study include genotoxins such as methyl methanesulfonate (MMS) and nongenotoxins such as ammonium chloride. We found that TKO cells exhibited the highest sensitivities to most of the tested genotoxins, but not to the non-genotoxins. In order to quantitatively evaluate the hypersensitivity of TKO cells to different chemicals, we calculated ratios of half-maximal inhibitory concentration for WT and TKO cells. The ratios for 9 out of 10 genotoxins ranged from 2.29 to 5.73, while those for 5 nongenotoxins ranged from 0.81 to 1.63. Additionally, the two markers for DNA damage, ubiquitylated proliferating cell nuclear antigen and γ-H2AX after MMS treatment, were accumulated in TKO cells more greatly than in WT cells. Furthermore, following MMS treatment, TKO cells exhibited increased frequency of sister chromatid exchange compared with WT cells. These results indicated that the hypersensitivity of TKO cells to genotoxins resulted from replication fork stalling and subsequent DNA double-strand breaks, thus demonstrating that TKO cells should be useful for evaluating chemical genotoxicity.

A Novel Strategy to Predict Carcinogenicity of Antiparasitics Based on a Combination of DNA Lesions and Bacterial Mutagenicity Tests

Genotoxicity and carcinogenicity testing of pharmaceuticals prior to commercialization is requested by regulatory agencies. The bacterial mutagenicity test was considered having the highest accuracy of carcinogenic prediction. However, some evidences suggest that it always results in false-positive responses when the bacterial mutagenicity test is used to predict carcinogenicity. Along with major changes made to the International Committee on Harmonization guidance on genotoxicity testing [S2 (R1)], the old data (especially the cytotgenetic data) may not meet current guidelines. This review provides a compendium of retrievable results of genotoxicity and animal carcinogenicity of 136 antiparasitics. Neither genotoxicity nor carcinogenicity data is available for 84 (61.8%), while 52 (38.2%) have been evaluated in at least one genotoxicity or carcinogenicity study, and only 20 (14.7%) in both genotoxicity and carcinogenicity studies. Among 33 antiparasitics with at least one old result in in vitro genotoxicity, 15 (45.5%) are in agreement with the current ICH S2 (R1) guidance for data acceptance. Compared with other genotoxicity assays, the DNA lesions can significantly increase the accuracy of prediction of carcinogenicity. Together, a combination of DNA lesion and bacterial tests is a more accurate way to predict carcinogenicity.

Genotoxicity testing: Comparison of the γH2AX focus assay with the alkaline and neutral comet assays

Genotoxicity testing relies on the quantitative measurement of adverse effects, such as chromosome aberrations, micronuclei, and mutations, resulting from primary DNA damage. Ideally, assays will detect DNA damage and cellular responses with high sensitivity, reliability, and throughput. Several novel genotoxicity assays may fulfill these requirements, including the comet assay and the more recently developed γH2AX assay. Although they are thought to be specific for genotoxicants, a systematic comparison of the assays has not yet been undertaken. In the present study, we compare the γH2AX focus assay with the alkaline and neutral versions of the comet assay, as to their sensitivities and limitations for detection of genetic damage. We investigated the dose-response relationships of γH2AX foci and comet tail intensities at various times following treatment with four prototypical genotoxicants, methyl methanesulfonate (MMS), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), mitomycin C, and hydrogen peroxide (H₂O₂) and we tested whether there is a correlation between the endpoints, i.e., alkali-labile sites and DNA strand breaks on the one hand and the cell's response to DNA double-strand breaks and blocked replication forks on the other. Induction of γH2AX foci gave a linear dose response and all agents tested were positive in the assay. The increase in comet tail intensity was also a function of dose; however, mitomycin C was almost completely ineffective in the comet assay, and the doses needed to achieve a significant effect were somewhat higher for some treatments in the comet assay than in the γH2AX foci assay, which was confirmed by threshold analysis. There was high correlation between tail intensity and γH2AX foci for MMS and H₂O₂, less for MNNG, and none for mitomycin C. From this we infer that the γH2AX foci assay is more reliable, sensitive, and robust than the comet assay for detecting genotoxicant-induced DNA damage.

Opportunities for the repurposing of PARP inhibitors for the therapy of non-oncological diseases

The recent clinical availability of the PARP inhibitor olaparib (Lynparza) opens the door for potential therapeutic repurposing for non-oncological indications. Considering (a) the preclinical efficacy data with PARP inhibitors in non-oncological diseases and (b) the risk-benefit ratio of treating patients with a compound that inhibits an enzyme that has physiological roles in the regulation of DNA repair, we have selected indications, where (a) the severity of the disease is high, (b) the available therapeutic options are limited, and (c) the duration of PARP inhibitor administration could be short, to provide first-line options for therapeutic repurposing. These indications are as follows: acute ischaemic stroke; traumatic brain injury; septic shock; acute pancreatitis; and severe asthma and severe acute lung injury. In addition, chronic, devastating diseases, where alternative therapeutic options cannot halt disease development (e.g. Parkinson's disease, progressive multiple sclerosis or severe fibrotic diseases), should also be considered. We present a preclinical and clinical action plan for the repurposing of PARP inhibitors.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Digoxin reduces the mutagenic effects of Mitomycin C in human and rodent cell lines

Digoxin is a drug widely used to treat heart failure and studies have demonstrated its potential as anticancer agent. In addition, digoxin presents the potential to interact with a series of other compounds used in medicine. The aim of the present study was to evaluate in vitro the cytotoxicity, genotoxicity and mutagenicity of digoxin and its potential to interact with the mutagen Mitomycin C (MMC). The cytotoxicity of digoxin was assessed by employing the MTT method and the comet assay was performed to assess the genotoxicity of this medicine in CHO-K1 and HeLa cell lines. Besides, the cytokinesis-block micronucleus assay was performed to assess the mutagenicity and the antimutagenicity of this drug. The Ames assay was also performed with TA98 and TA100 strains of S. typhimurium. Results showed that digoxin was cytotoxic, genotoxic and mutagenic for HeLa and CHO-K1 cell lines at concentrations many times higher than those observed in human therapeutic conditions. Nevertheless, an antimutagenic effect against the mutagen MMC was observed on both cell lines in concentrations near those used therapeutically in humans. This chemoprotective effect observed is an interesting finding that should be better explored regarding its impact in anticancer chemotherapy.

Exploiting microRNA and mRNA profiles generated in vitro from carcinogen-exposed primary mouse hepatocytes for predicting in vivo genotoxicity and carcinogenicity

The well-defined battery of in vitro systems applied within chemical cancer risk assessment is often characterised by a high false-positive rate, thus repeatedly failing to correctly predict the in vivo genotoxic and carcinogenic properties of test compounds. Toxicogenomics, i.e. mRNA-profiling, has been proven successful in improving the prediction of genotoxicity in vivo and the understanding of underlying mechanisms. Recently, microRNAs have been discovered as post-transcriptional regulators of mRNAs. It is thus hypothesised that using microRNA response-patterns may further improve current prediction methods. This study aimed at predicting genotoxicity and non-genotoxic carcinogenicity in vivo, by comparing microRNA- and mRNA-based profiles, using a frequently applied in vitro liver model and exposing this to a range of well-chosen prototypical carcinogens. Primary mouse hepatocytes (PMH) were treated for 24 and 48h with 21 chemical compounds [genotoxins (GTX) vs. non-genotoxins (NGTX) and non-genotoxic carcinogens (NGTX-C) versus non-carcinogens (NC)]. MicroRNA and mRNA expression changes were analysed by means of Exiqon and Affymetrix microarray-platforms, respectively. Classification was performed by using Prediction Analysis for Microarrays (PAM). Compounds were randomly assigned to training and validation sets (repeated 10 times). Before prediction analysis, pre-selection of microRNAs and mRNAs was performed by using a leave-one-out t-test. No microRNAs could be identified that accurately predicted genotoxicity or non-genotoxic carcinogenicity in vivo. However, mRNAs could be detected which appeared reliable in predicting genotoxicity in vivo after 24h (7 genes) and 48h (2 genes) of exposure (accuracy: 90% and 93%, sensitivity: 65% and 75%, specificity: 100% and 100%). Tributylinoxide and para-Cresidine were misclassified. Also, mRNAs were identified capable of classifying NGTX-C after 24h (5 genes) as well as after 48h (3 genes) of treatment (accuracy: 78% and 88%, sensitivity: 83% and 83%, specificity: 75% and 93%). Wy-14,643, phenobarbital and ampicillin trihydrate were misclassified. We conclude that genotoxicity and non-genotoxic carcinogenicity probably cannot be accurately predicted based on microRNA profiles. Overall, transcript-based prediction analyses appeared to clearly outperform microRNA-based analyses.

Further investigations into the genotoxicity of quinoxaline-di-N-oxides and their primary metabolites

Quinoxaline-di-N-oxides (QdNOs) are potential antibacterial agents with a wide range of biological properties. Quinocetone (QCT), carbadox (CBX), olaquindox (OLA), mequindox (MEQ) and cyadox (CYA) are classical QdNOs. Though the genotoxicity of parent drugs has been evaluated, the genotoxicity of their primary N → O reduced metabolites remains unclear. In the present study, a battery of four different short-term tests, mouse lymphoma assay (MLA), Ames test, chromosomal aberration assay in vitro and bone marrow erythrocyte micronucleus assay in vivo was carried out to investigate the genotoxicity of the six primary N → O reduced metabolites. Additionally, the genotoxicity of five parent drugs was evaluated by the MLA. Strong genotoxicity of N1-MEQ, B-MEQ and B-CBX was found in three of the assays but not in the Ames assay, and the rank order was N1-MEQ>B-MEQ>B-CBX that is consistent with prototype QdNOs. Negative results for the five QdNOs were noted in the MLA. We present for the first time a comparison of the genotoxicity of primary N → O reduced metabolites, and evaluate the ability of five QdNOs to cause mutations in the MLA. The present study demonstrates that metabolites are involved in genetic toxicity mediated by QdNOs, and improve the prudent use of QdNOs for public health.

Identification of Associations Between Prescribed Medications and Cancer: A Nationwide Screening Study

Purpose

We present a systematic screening for identifying associations between prescribed drugs and cancer risk using the high quality Danish nationwide health registries.

Methods

We identified all patients (cases) with incident cancer in Denmark during 2000–2012 (n = 278,485) and matched each case to 10 controls. Complete prescription histories since 1995 were extracted. Applying a two-phased case–control approach, we first identified drug classes or single drugs associated with an increased or decreased risk of 99 different cancer types, and further evaluated potential associations by examining specificity and dose–response patterns.

Findings

22,125 drug–cancer pairs underwent evaluation in the first phase. Of 4561 initial signals (i.e., drug–cancer associations), 3541 (78%) failed to meet requirements for dose–response patterns and specificity, leaving 1020 eligible signals. Of these, 510 signals involved the use of single drugs, and 33% (166 signals) and 67% (344 signals) suggested a reduced or an increased cancer risk, respectively. While a large proportion of the signals were attributable to the underlying conditions being treated, our algorithm successfully identified well-established associations, as well as several new signals that deserve further investigation.

Conclusion

Our results provide the basis for future targeted studies of single associations to capture novel carcinogenic or chemopreventive effects of prescription drugs.

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We conducted a nationwide register-based screening study aimed at identifying potential drug–cancer associations.

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Screening initiatives using registry data may serve as an important tool for identification of drug–cancer associations.

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Future research should address the signals provided by our study, i.e. in studies of the single putative associations.

The use of prescription drugs may influence the risk of developing cancer. In this study, we sought to identify such effects by combining data from Danish nationwide health care registries on drug use and cancer occurrence. We compared drug use among 278,485 cancer patients to use among cancer-free control individuals. Thereby, we identified 1020 putative drug–cancer associations. Future research should address the signals provided by our study, either as studies focusing on single associations or as a replication of our study using other data sources.

Evaluation of Possible Genotoxic Activity of Dirithromycin in Cultured Human Lymphocytes

Dirithromycin antibiotic is a 14-membered lactone ring macrolide and is widely used in medicine to treat many different types of bacterial infections. In the present study, the possible genotoxicity of dirithromycin was evaluated in cultured human lymphocytes by using sister chromatid exchanges (SCEs), chromosome aberration (CA), and micronucleus (MN) tests and also cell proliferation kinetics such as mitotic index (MI), replication index (RI), and nuclear division index (NDI) were analyzed for cytotoxicity. Cell cultures were treated with four different concentrations of dirithromycin (37.75, 67.50, 125, and 250 µg/mL) for 24 and 48 h periods. Dirithromycin significantly induced SCE and MN frequency at all concentrations in both 24 and 48 h treated cells. In addition, CA level has been markedly increased in the cells treated with almost all concentrations of dirithromycin for 24 (except 37.75 µg/mL) and 48 h treatment periods as compared to control. However, MI, RI, and NDI values were not affected by the dirithromycin treatment (p > 0.05). The results of this study indicated that dirithromycin treatment caused genetic damage by increasing the level of cytogenetic endpoints, suggesting its genotoxic and mutagenic action on human lymphocytes in vitro.

Complementarity of phosphorylated histones H2AX and H3 quantification in different cell lines for genotoxicity screening

The in vitro micronucleus assay is broadly used, but is not per se able to discriminate aneugenic from clastogenic compounds, and cytotoxicity can be a confounding factor. In vitro genotoxicity assays generally rely on cell lines with limited metabolic capabilities. Recently, the use of histone H2AX and H3 phosphorylation markers (γH2AX and p-H3) was proposed to discriminate aneugenic from clastogenic chemicals. The aim of the present study was to develop a new genotoxic screening strategy based on the use of the γH2AX and p-H3 biomarkers in combination with cell lines with distinct biotransformation properties. First, we tested a training set of 20 model chemicals comprised of 10 aneugens, five clastogens and five cytotoxics on three human cell lines (HepG2, LS-174T and ACHN). Our data confirm the robustness of these two biomarkers to discriminate efficiently clastogens, aneugens and misleading cytotoxic chemicals in HepG2 cells. Aneugenic compounds induced either an increase or a decrease in p-H3 depending on their mode of action. Clastogens induced γH2AX, and cytotoxic compounds generated a marked decrease in these two biomarkers. Moreover, the use of different cell lines permits to discriminate direct from bioactivated genotoxins without the need of an exogenous metabolic activation system. Finally, we further evaluated this strategy using a test set of 13 chemicals with controversial genotoxic potential. The resulting data demonstrate that the combined analysis of γH2AX and p-H3 is an efficient strategy. Notably, we demonstrated that three compounds (fisetin, hydroquinone and okadaic acid) display both aneugenic and clastogenic properties.

Carcinogenicity of psychotropic drugs: A systematic review of US Food and Drug Administration-required preclinical in vivo studies

OBJECTIVE

The US Food and Drug Administration approval process for psychotropic drugs requires safety studies of carcinogenicity in animals. These studies are consistently conducted and provide a database for assessment of potential biological risk of carcinogenicity in humans. This report is a systematic review of that database for psychotropic drugs.

METHOD

US Food and Drug Administration-approved registration data ('package inserts') were examined, where available, for all psychotropic drugs in the following classes: antidepressants, antipsychotics, benzodiazepines/sedative-hypnotics, amphetamines and anticonvulsants.

RESULTS

Overall, new generation (atypical) antipsychotics (90%, 9/10 agents) and anticonvulsants (85.7%, 6/7 agents) showed the highest evidence of carcinogenicity among psychotropic drugs classes assessed. Antidepressants (63.6%, 7/11) and benzodiazepines/sedative-hypnotics (70%, 7/10) were next, and stimulants (with the exception of methylphenidate) were last (25%, 1/4 agents). Overall, 71.4% of all drugs examined (30/42) showed evidence of carcinogenicity in 43.2% (38/88) of specific experimental studies.

CONCLUSIONS

US Food and Drug Administration-based analyses demonstrate that almost all atypical antipsychotics and anticonvulsants are carcinogenic in animals, as are the majority of antidepressants and benzodiazepines and methylphenidate. These animal-based results are not sufficient to draw definitive conclusions in humans, but they provide data that could be acknowledged in the informed consent process of clinical treatment.

Genotoxic and immunotoxic potential effects of selected psychotropic drugs and antibiotics on blue mussel (Mytilus edulis) hemocytes

The potential toxicity of pharmaceuticals towards aquatic invertebrates is still poorly understood and sometimes controversial. This study aims to document the in vitro genotoxicity and immunotoxicity of psychotropic drugs and antibiotics on Mytilus edulis. Mussel hemocytes were exposed to fluoxetine, paroxetine, venlafaxine, carbamazepine, sulfamethoxazole, trimethoprim and erythromycin, at concentrations ranging from μg/L to mg/L. Paroxetine at 1.5 μg/L led to DNA damage while the same concentration of venlafaxine caused immunomodulation. Fluoxetine exposure resulted in genotoxicity, immunotoxicity and cytotoxicity. In the case of antibiotics, trimethoprim was genotoxic at 200 μg/L and immunotoxic at 20 mg/L whereas erythromycin elicited same detrimental effects at higher concentrations. DNA metabolism seems to be a highly sensitive target for psychotropic drugs and antibiotics. Furthermore, these compounds affect the immune system of bivalves, with varying intensity. This attests the relevance of these endpoints to assess the toxic mode of action of pharmaceuticals in the aquatic environment.

Antiarrhythmic agents and the risk of malignant neoplasm of liver and intrahepatic bile ducts

Background

The objective of this study was to determine the association between the use of antiarrhythmic agents and the risk of malignant neoplasm of liver and intrahepatic bile ducts (MNLIHD).

Methods

We used the research database of the Taiwan National Health Insurance Program to conduct a population-based, case-control study. We identified 9944 patients with antiarrhythmic history who were first diagnosed as having MNLIHD between 2005 and 2010. We identified an additional 19,497 patients with antiarrhythmic history in the same period who did not develop MNLIHD and were frequency-matched using age, sex, and index year to form a control group. Five commercially available antiarrhythmic agents, amiodarone, mexiletine, propafenone, quinidine, and procainamide, were analyzed.

Results

The adjusted odds ratio (OR) of MNLIHD was 1.60 (95% confidence interval [CI], 1.45–1.77) for amiodarone users versus nonamiodarone users. In subgroup analysis, amiodarone use was significantly associated with an increased risk of MNLIHD with an adjusted OR of 18.0 (95% CI, 15.7–20.5) for patients with comorbidities compared to an OR of 2.43 (95% CI, 1.92–3.06) for those without comorbidities. After adjustment for age, sex, statins, anti-diabetes medications, non-steroidal antiinflammatory drugs, propafenone use, quinidine use, and comorbidities, the ORs were 1.49, 1.66, and 1.79 for MNLIHD associated with annual mean defined daily doses of ≤30, 31–145, and >145, respectively.

Conclusions

The results of the present study indicated that amiodarone might be associated with the development of MNLIHD in a dose-dependent manner, particularly among patients with comorbidities.

21-Benzylidene digoxin: a proapoptotic cardenolide of cancer cells that up-regulates Na,K-ATPase and epithelial tight junctions

Cardiotonic steroids are used to treat heart failure and arrhythmia and have promising anticancer effects. The prototypic cardiotonic steroid ouabain may also be a hormone that modulates epithelial cell adhesion. Cardiotonic steroids consist of a steroid nucleus and a lactone ring, and their biological effects depend on the binding to their receptor, Na,K-ATPase, through which, they inhibit Na+ and K+ ion transport and activate of several intracellular signaling pathways. In this study, we added a styrene group to the lactone ring of the cardiotonic steroid digoxin, to obtain 21-benzylidene digoxin (21-BD), and investigated the effects of this synthetic cardiotonic steroid in different cell models. Molecular modeling indicates that 21-BD binds to its target Na,K-ATPase with low affinity, adopting a different pharmacophoric conformation when bound to its receptor than digoxin. Accordingly, 21-DB, at relatively high µM amounts inhibits the activity of Na,K-ATPase α1, but not α2 and α3 isoforms. In addition, 21-BD targets other proteins outside the Na,K-ATPase, inhibiting the multidrug exporter Pdr5p. When used on whole cells at low µM concentrations, 21-BD produces several effects, including: 1) up-regulation of Na,K-ATPase expression and activity in HeLa and RKO cancer cells, which is not found for digoxin, 2) cell specific changes in cell viability, reducing it in HeLa and RKO cancer cells, but increasing it in normal epithelial MDCK cells, which is different from the response to digoxin, and 3) changes in cell-cell interaction, altering the molecular composition of tight junctions and elevating transepithelial electrical resistance of MDCK monolayers, an effect previously found for ouabain. These results indicate that modification of the lactone ring of digoxin provides new properties to the compound, and shows that the structural change introduced could be used for the design of cardiotonic steroid with novel functions.

Usefulness of monitoring γ-H2AX and cell cycle arrest in HepG2 cells for estimating genotoxicity using a high-content analysis system

Formation of the phosphorylated protein γ-H2AX is a well-established marker of DNA strand breakage induced by DNA-damaging compounds. Many of these genotoxic compounds also inhibit cell division, leading to arrest at specific points in the cell cycle. Detection of γ-H2AX in combination with cell cycle arrest may therefore be useful for estimating the genotoxicity of experimental compounds. In this study, we examined γ-H2AX formation and cell cycle arrest using high-content screening (HCS) as a method for determining genotoxicity. HepG2 cells were treated with a panel of compounds and then stained with Hoechst 33342 and anti-γ-H2AX, anti-phospho-histone H3, and anti-tubulin antibodies. In total, 19 genotoxic and 7 nongenotoxic compounds were tested in this study. γ-H2AX production was observed within 1 h posttreatment for the majority of Ames-positive compounds, topoisomerase inhibitors, and DNA polymerase inhibitors. Cell cycle arrest in either the S or G2 phase was detected for all DNA-damaging compounds 24 h posttreatment, whereas tubulin-targeting compounds were shown to induce cell cycle arrest in the mitotic phase. Together, these results show that HCS is a simple, rapid, and effective tool for estimating the genotoxicity of compounds through detection of γ-H2AX production and cell cycle arrest.

Evaluation of cytotoxicity and mutagenicity of the benzodiazepine flunitrazepam in vitro and in vivo

Flunitrazepam (FNZ) is a sedative benzodiazepine prescribed for the short-term treatment of insomnia. However, there are concerns regarding possible carcinogenic or genotoxic effects of this medicine. Thus, the aim of this study was to evaluate the cytotoxic, clastogenic and aneugenic effects of FNZ in hepatoma cells from Rattus norvegicus (HTC) in vitro and in bone marrow cells of Wistar rats in vivo. These effects were examined in vitro following treatment with 0.2, 1.0, 5.0 or 10 μg/mL FNZ using a micronucleus test with a cytokinesis block or in vivo using a chromosomal aberration test following treatment with 7, 15 or 30 μg/mL/kg body weight. The results showed that the benzodiazepine concentrations tested were not cytotoxic, aneugenic or clastogenic. However, considering the adverse effects of using this benzodiazepine, more studies are required.

Investigation of cytotoxic and genotoxic effects of the antihistaminic drug, loratadine, on human lymphocytes

CONTEXT

Loratadine (LOR) is a new generation antihistamine used in the treatment of allergic disorders.

OBJECTIVE

The aim of this study was to evaluate the cytogenotoxic effect of LOR on human peripheral blood lymphocytes.

MATERIALS AND METHODS

We investigated the genotoxic effect of this drug in cultured human peripheral blood lymphocytes using sister chromatid exchange (SCE), chromosomal aberrations (CA) and micronucleus (MN) assay in culture conditions. Proliferation index (PI), mitotic index (MI) and nuclear division index (NDI) were also calculated to determine the cytotoxic/cytostatic effect. Cultures were treated with LOR at three concentrations (5, 15 and 25 µg/ml) for 48 h.

RESULTS

Although the MI significantly decreased at the higher concentrations (15 and 25 µg/ml) compared with negative (solvent) control, LOR indicated weaker cytotoxic potential in PI and NDI values at all the tested concentrations. LOR increased the frequencies of SCE, CA and MN in all lymphocyte cultures. However, significant increase was observed in MN at the medium and highest doses (15 and 25 µg/ml) and in CA at the medium dose (15 µg/ml) compared with negative (solvent) control culture. Our results indicate that LOR has cytotoxic and genotoxic effects on human peripheral blood lymphocyte cultures.

DISCUSSION

Although most of previously findings have shown that LOR does not reflect genotoxicity, our results indicated that it may be a genotoxic drug.

CONCLUSION

More studies are necessary to elucidate the relationship between cytotoxic, genotoxic and apoptotic effects, and to make a possible risk assessment in patients receiving therapy with this drug.

Is murine gammaherpesvirus-68 (MHV-68) a suitable immunotoxicological model for examining immunomodulatory drug-associated viral recrudescence?

Immunosuppressive agents are used for treatment of a variety of autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosis (SLE), and psoriasis, as well as for prevention of tissue rejection after organ transplantation. Recrudescence of herpesvirus infections, and increased risk of carcinogenesis from herpesvirus-associated tumors are related with immunosuppressive therapy in humans. Post-transplant lymphoproliferative disorder (PTLD), a condition characterized by development of Epstein Barr Virus (EBV)-associated B-lymphocyte lymphoma, and Kaposi's Sarcoma (KS), a dermal tumor associated with Kaposi Sarcoma-associated virus (KSHV), may develop in solid organ transplant patients. KS also occurs in immunosuppressed Acquired Immunodeficiency (AIDS) patients. Kaposi Sarcoma-associated virus (KSHV) is a herpes virus genetically related to EBV. Murine gammaherpes-virus-68 (MHV-68) is proposed as a mouse model of gammaherpesvirus infection and recrudescence and may potentially have relevance for herpesvirus-associated neoplasia. The pathogenesis of MHV-68 infection in mice mimics EBV/KSHV infection in humans with acute lytic viral replication followed by dissemination and establishment of persistent latency. MHV-68-infected mice may develop lymphoproliferative disease that is accelerated by disruption of the immune system. This manuscript first presents an overview of gammaherpesvirus pathogenesis and immunology as well as factors involved in viral recrudescence. A description of different types of immunodeficiency then follows, with particular focus on viral association with lymphomagenesis after immunosuppression. Finally, this review discusses different gammaherpesvirus animal models and describes a proposed MHV-68 model to further examine the interplay of immunomodulatory agents and gammaherpesvirus-associated neoplasia.