Strategies in genotoxicology: Acceptance of innovative scientific methods in a regulatory context and from an industrial perspective

Evaluation of infliximab-induced genotoxicity and possible action on BCL-2 and P53 genes

Although the last pandemic created an urgency for development of vaccines, there was a continuous and concerted effort to search for therapeutic medications among existing drugs with different indications. One of the medications of interest that underwent this change was infliximab (IFM). This drug is used as an anti-inflammatory, predominantly in patients with Crohn 's disease, colitis ulcerative, and rheumatoid arthritis. In addition to these patients, individuals infected with Coronavirus Disease (COVID-19) were administered this chimeric monoclonal antibody (IMF) to act as an immunomodulator for patients in the absence of comprehensive research. Consequently, the present study aimed to examine the genotoxic effects attributed to IFM treatment employing different assays in vivo using mouse Mus musculus. Therefore, IFM was found to induce genotoxic effects as evidenced by the comet assay but did not demonstrate genotoxic potential utilizing mouse bone marrow MN test. The results of evaluating the expression of the P53 and BCL-2 genes using RT-qPCR showed stimulation of expression of these genes at 24 hr followed by a decline at 48 hr. Although the comet assay provided positive results, it is noteworthy that based upon negative findings in the micronucleus test, the data did not demonstrate significant changes in the genetic material that might affect the therapeutic use of IFM. The stimulation of expression of P53 and BCL-2 genes at 24 hr followed by a decline at 48 hr suggest a transient, if any, effect on genetic material. However, there is still a need for more research to more comprehensively understand the genotoxic profile of this medication.

Gene expression response of the non-target gastropod Physella acuta to Fenoxycarb, a juvenile hormone analog pesticide

Pesticides are an environmental problem. The search for new pest control methods has focused on compounds with low or no toxic effects in non-target organisms. Analogs of the juvenile hormone (JH) interfere endocrine system of arthropods. However, the lack of effect on non-target species requires confirmation. This article analyzes the impact of Fenoxycarb, an analog of JH, on Physella acuta, an aquatic gastropod. For 1 week, animals were exposed to 0.01, 1, and 100 μg/L and the RNA was isolated to analyze the gene expression by retrotranscription and Real-Time PCR. Forty genes related to the endocrine system, the DNA repair mechanisms, the detoxification mechanisms, oxidative stress, the stress response, the nervous system, hypoxia, energy metabolism, the immune system, and apoptosis were analyzed. Three of the genes, AchE, HSP17.9, and ApA, showed responses to the presence of Fenoxycarb at 1 μg/L, with no statistically significant responses in the rest of the genes and at the remaining concentrations. From the results, it can be concluded that Fenoxycarb shows a weak response at the molecular level in P. acuta in the tested time and concentrations. However, Aplysianin-A, a gene related to immunity, was altered so the long-term effect could be relevant. Therefore, additional research is required to confirm the safety of Fenoxycarb in non-arthropod species in the long term.

Assessing testicular germ cell DNA damage in the comet assay; introduction of a proof-of-concept

The in vivo comet assay is widely used to measure genotoxicity; however, the current OECD test guideline (TG 489) does not recommend using the assay to assess testicular germ cells, due to the presence of testicular somatic cells. An adapted approach to specifically assess testicular germ cells within the comet assay is certainly warranted, considering regulatory needs for germ cell-specific genotoxicity data in relation to the increasing global production of and exposure to potentially hazardous chemicals. Here, we provide a proof-of-concept to selectively analyze round spermatids and primary spermatocytes, distinguishing them from other cells of the testicle. Utilizing the comet assay recordings of DNA content (total fluorescence intensity) and DNA damage (% tail intensity) of individual comets, we developed a framework to distinguish testicular cell populations based on differences in DNA content/ploidy and appearance. Haploid round spermatid comets are identified through (1) visual inspection of DNA content distributions, (2) setting DNA content thresholds, and (3) modeling DNA content distributions using a normal mixture distribution function. We also describe an approach to distinguish primary spermatocytes during comet scoring, based on their high DNA content and large physical size. Our concept allows both somatic and germ cells to be analyzed in the same animal, adding a versatile, sensitive, rapid, and resource-efficient assay to the limited genotoxicity assessment toolbox for germ cells. An adaptation of TG 489 facilitates accumulation of valuable information regarding distribution of substances to germ cells and their potential for inducing germ cell gene mutations and structural chromosomal aberrations.

The State of the Art and Challenges of In Vitro Methods for Human Hazard Assessment of Nanomaterials in the Context of Safe-by-Design

The Safe-by-Design (SbD) concept aims to facilitate the development of safer materials/products, safer production, and safer use and end-of-life by performing timely SbD interventions to reduce hazard, exposure, or both. Early hazard screening is a crucial first step in this process. In this review, for the first time, commonly used in vitro assays are evaluated for their suitability for SbD hazard testing of nanomaterials (NMs). The goal of SbD hazard testing is identifying hazard warnings in the early stages of innovation. For this purpose, assays should be simple, cost-effective, predictive, robust, and compatible. For several toxicological endpoints, there are indications that commonly used in vitro assays are able to predict hazard warnings. In addition to the evaluation of assays, this review provides insights into the effects of the choice of cell type, exposure and dispersion protocol, and the (in)accurate determination of dose delivered to cells on predictivity. Furthermore, compatibility of assays with challenging advanced materials and NMs released from nano-enabled products (NEPs) during the lifecycle is assessed, as these aspects are crucial for SbD hazard testing. To conclude, hazard screening of NMs is complex and joint efforts between innovators, scientists, and regulators are needed to further improve SbD hazard testing.

Genotoxicity of Graphene-Based Materials

Graphene-based materials (GBMs) are a broad family of novel carbon-based nanomaterials with many nanotechnology applications. The increasing market of GBMs raises concerns on their possible impact on human health. Here, we review the existing literature on the genotoxic potential of GBMs over the last ten years. A total of 50 articles including in vitro, in vivo, in silico, and human biomonitoring studies were selected. Graphene oxides were the most analyzed materials, followed by reduced graphene oxides. Most of the evaluations were performed in vitro using the comet assay (detecting DNA damage). The micronucleus assay (detecting chromosome damage) was the most used validated assay, whereas only two publications reported results on mammalian gene mutations. The same material was rarely assessed with more than one assay. Despite inhalation being the main exposure route in occupational settings, only one in vivo study used intratracheal instillation, and another one reported human biomonitoring data. Based on the studies, some GBMs have the potential to induce genetic damage, although the type of damage depends on the material. The broad variability of GBMs, cellular systems and methods used in the studies precludes the identification of physico-chemical properties that could drive the genotoxicity response to GBMs.

[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.

Recent advancements and application of in vitro models for predicting inhalation toxicity in humans

Animals have been indispensable in testing chemicals that can pose a risk to human health, including those delivered by inhalation. In recent years, the combination of societal debate on the use of animals in research and testing, the drive to continually enhance testing methodologies, and technology advancements have prompted a range of initiatives to develop non-animal alternative approaches for toxicity testing. In this review, we discuss emerging in vitro techniques being developed for the testing of inhaled compounds. Advanced tissue models that are able to recreate the human response to toxic exposures alongside examples of their ability to complement in vivo techniques are described. Furthermore, technology being developed that can provide multi-organ toxicity assessments are discussed.

Expanding the toxicologist's statistical toolbox: Using effect size estimation and dose-response modelling for holistic assessments instead of generic testing

It is tempting to base (eco-)toxicological assay evaluation solely on statistical significance tests. The approach is stringent, objective and facilitates binary decisions. However, tests according to null hypothesis statistical testing (NHST) are thought experiments that rely heavily on assumptions. The generic and unreflected application of statistical tests has been called "mindless" by Gigerenzer. While statistical tests have an appropriate application domain, the present work investigates how unreflected testing may affect toxicological assessments. Dunnett multiple-comparison and Williams trend testing and their compatibility intervals are compared with dose-response-modelling in case studies, where data do not follow textbook behavior, nor behave as expected from a toxicological point of view. In such cases, toxicological assessments based only on p-values may be biased and biological evaluations based on plausibility may be prioritized. If confidence in a negative assay outcome cannot be established, further data may be needed for a robust toxicological assessment.

Multiple-endpoint in vitro carcinogenicity test in human cell line TK6 distinguishes carcinogens from non-carcinogens and highlights mechanisms of action

Current in vitro genotoxicity tests can produce misleading positive results, indicating an inability to effectively predict a compound's subsequent carcinogenic potential in vivo. Such oversensitivity can incur unnecessary in vivo tests to further investigate positive in vitro results, supporting the need to improve in vitro tests to better inform risk assessment. It is increasingly acknowledged that more informative in vitro tests using multiple endpoints may support the correct identification of carcinogenic potential. The present study, therefore, employed a holistic, multiple-endpoint approach using low doses of selected carcinogens and non-carcinogens (0.001-770 µM) to assess whether these chemicals caused perturbations in molecular and cellular endpoints relating to the Hallmarks of Cancer. Endpoints included micronucleus induction, alterations in gene expression, cell cycle dynamics, cell morphology and bioenergetics in the human lymphoblastoid cell line TK6. Carcinogens ochratoxin A and oestradiol produced greater Integrated Signature of Carcinogenicity scores for the combined endpoints than the "misleading" in vitro positive compounds, quercetin, 2,4-dichlorophenol and quinacrine dihydrochloride and toxic non-carcinogens, caffeine, cycloheximide and phenformin HCl. This study provides compelling evidence that carcinogens can successfully be distinguished from non-carcinogens using a holistic in vitro test system. Avoidance of misleading in vitro outcomes could lead to the reduction and replacement of animals in carcinogenicity testing.