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The Cytolethal Distending Toxin ( CDT) is a genotoxin produced by several pathogenic bacteria. It is generally admitted that CDT induces double-strand breaks ( DSB) and cell cycle arrest in G2/ M-phase, in an ATM-dependent manner. Most of these results were obtained at high dose (over 1 μg ml−1) of CDT and late after treatment (8-24 h). We provide here evidence that the Escherichia coli CDT ( EcCDT) - at low dose (50 pg ml−1 or LD50) and early after treatment (3-6 h) - progressively induces DNA DSB, mostly in S-phase. DSB formation is related to the single-strand breaks induction by CDT, converted into DSB during the S-phase. We also show that homologous recombination is mobilized to these S-phase-associated DSB. This model unveils a new mechanism for CDT genotoxicity that may play a role in cells partly deficient in homologous recombination. [ABSTRACT FROM AUTHOR]

Since low T cell counts evaluated 1 month after allogeneic bone marrow transplantation (BMT) are associated with an increased risk of leukemia relapse (Powles et al., Blood 1998; 91: 3481–3486), we compared, in a randomized multicentric clinical study, the peripheral blood cells obtained 30 days after allogeneic BMT vs allogeneic G-CSF-mobilized peripheral blood stem cell transplantation (BCT) in an HLA-identical setting. T cell counts were higher 30 days after BCT (718 ± 142 cells/μl, n = 20) than after BMT (271 ± 53 cells/μl, n = 26, P = 0.006). However, T cells were less activated after BCT than after BMT, as demonstrated by a lower expression level of CD25 and a lower percentage of HLA-DR+ and CD95+ T cells. Furthermore, CD4+, CD8+and CD45RA+ post-BCT T cell counts correlated with the number of cells infused with the PBSC graft, while such a correlation was not observed between post-BMT counts and BM graft cell numbers, suggesting that the intensity of post-transplant peripheral lymphoid expansion and/or deletion differed between BCT and BMT. A comparison of the input of T cells expressing different CD45 isoforms with the post-transplant cell recovery further confirmed that, within the CD4+ T cell subset, post-transplant expansions occurred at a higher level after BMT than after BCT, affecting mainly the CD4+ CD45RO+subset. Altogether, our data demonstrate for the first time in a randomized setting that homeostasis of the T cell pool is less altered early after BCT than after BMT. This may have a strong impact on the graft-versus-leukemia (GVL) effect and subsequent relapse rate. Bone Marrow Transplantation (2001) 27, 167–175. [ABSTRACT FROM AUTHOR]

Chimeric antigen receptor (CAR) T cells express an extracellular domain consisting of a single-chain fragment variable (scFv) targeting a surface tumor-associated antigen. scFv selection should involve safety profiling with evaluation of the efficacy/toxicity balance, especially when the target antigen also is expressed on healthy cells. Here, to assess differences in terms of efficacy and on-target/off-tumor effects, we generated five different CARs targeting CD123 by substituting only the scFv. In in vitro models, T cells engineered to express three of these five CD123 CARs were effectively cytotoxic on leukemic cells without increasing lysis of monocytes or endothelial cells. Using the IncuCyte system, we confirmed the low cytotoxicity of CD123 CAR T cells on endothelial cells. Hematotoxicity evaluation using progenitor culture and CD34 cell lysis showed that two of the five CD123 CAR T cells were less cytotoxic on hematopoietic stem cells. Using a humanized mouse model, we confirmed that CD123- cells were not eliminated by the CD123 CAR T cells. Two CD123 CAR T cells reduced tumor infiltration and increased the overall survival of mice in three in vivo models of blastic plasmacytoid dendritic cell neoplasm. In an aggressive version of this model, bulk RNA sequencing analysis showed that these CD123 CAR T cells upregulated genes associated with cytotoxicity and activation/exhaustion a few days after the injection. Together, these results emphasize the importance of screening different scFvs for the development of CAR constructs to support selection of cells with the optimal risk-benefit ratio for clinical development., (©2024 American Association for Cancer Research.)

Scope: Akkermansia muciniphila (A. muciniphila) are Gram negative commensal bacteria, degrading mucin in the intestinal mucosa, modulating intestinal permeability and inflammation in the digestive tract, liver, and blood. Some components can promote the relative abundance of A. muciniphila in the gut microbiota, but lower levels of A. muciniphila are more commonly found in people with obesity, diabetes, metabolic syndromes, or inflammatory digestive diseases. Over-intake of ethanol can also induce a decrease of A. muciniphila, associated with dysregulation of microbial metabolite production, impaired intestinal permeability, induction of chronic inflammation, and production of cytokines., Methods and Results: Using a PRISMA search strategy, a review is performed on the bacteriological characteristics of A. muciniphila, the factors capable of modulating its relative abundance in the digestive tract and its probiotic use in alcohol-related liver diseases (alcoholic hepatitis, cirrhosis, hepatocellular carcinoma, hepatic transplantation, partial hepatectomy)., Conclusion: Several studies have shown that supplementation with A. muciniphila can improve ethanol-related hepatic pathologies, and highlight the interest in using this bacterial species as a probiotic., (© 2023 The Authors. Molecular Nutrition & Food Research published by Wiley-VCH GmbH.)

Background & Aims: The constitutive androstane receptor (CAR) is a nuclear receptor that binds diverse xenobiotics and whose activation leads to the modulation of the expression of target genes involved in xenobiotic detoxification and energy metabolism. Although CAR hepatic activity is considered to be higher in women than in men, its sex-dependent response to an acute pharmacological activation has seldom been investigated., Methods: The hepatic transcriptome, plasma markers, and hepatic metabolome, were analysed in Car +/+ and Car -/- male and female mice treated either with the CAR-specific agonist 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) or with vehicle., Results: Although 90% of TCPOBOP-sensitive genes were modulated in a sex-independent manner, the remaining 10% showed almost exclusive female liver specificity. These female-specific CAR -sensitive genes were mainly involved in xenobiotic metabolism, inflammation, and extracellular matrix organisation. CAR activation also induced higher hepatic oxidative stress and hepatocyte cytolysis in females than in males. Hepatic expression of flavin monooxygenase 3 ( Fmo3 ) was almost abolished and was associated with a decrease in hepatic trimethylamine-N-oxide (TMAO) concentration in TCPOBOP-treated females. In line with a potential role in the control of TMAO homeostasis, CAR activation decreased platelet hyper-responsiveness in female mice supplemented with dietary choline., Conclusions: More than 10% of CAR-sensitive genes are sex-specific and influence hepatic and systemic responses such as platelet aggregation. CAR activation may be an important mechanism of sexually-dimorphic drug-induced liver injury., Impact and Implications: CAR is activated by many drugs and pollutants. Its pharmacological activation had a stronger impact on hepatic gene expression and metabolism in females than in males, and had a specific impact on liver toxicity and trimethylamine metabolism. Sexual dimorphism should be considered when testing and/or prescribing xenobiotics known to activate CAR., Competing Interests: The authors declare no conflicts of interest. Please refer to the accompanying ICMJE disclosure forms for further details., (© 2023 The Authors.)

The whitening and opacifying agent titanium dioxide (TiO 2 ) is used worldwide in various foodstuffs, toothpastes and pharmaceutical tablets. Its use as a food additive (E171 in EU) has raised concerns for human health. Although the buccal mucosa is the first area exposed, oral transmucosal passage of TiO 2 particles has not been documented. Here we analyzed E171 particle translocation in vivo through the pig buccal mucosa and in vitro on human buccal TR146 cells, and the effects on proliferating and differentiated TR146 cells. In the buccal floor of pigs, isolated TiO 2 particles and small aggregates were observed 30 min after sublingual deposition, and were recovered in the submandibular lymph nodes at 4 h. In TR146 cells, kinetic analyses showed high absorption capacities of TiO 2 particles. The cytotoxicity, genotoxicity and oxidative stress were investigated in TR146 cells exposed to E171 in comparison with two TiO 2 size standards of 115 and 21 nm in diameter. All TiO 2 samples were reported cytotoxic in proliferating cells but not following differentiation. Genotoxicity and slight oxidative stress were reported for the E171 and 115 nm TiO 2 particles. These data highlight the buccal mucosa as an absorption route for the systemic passage of food-grade TiO 2 particles. The greater toxicity on proliferating cells suggest potential impairement of oral epithelium renewal. In conclusion, this study emphasizes that buccal exposure should be considered during toxicokinetic studies and for risk assessment of TiO 2 in human when used as food additive, including in toothpastes and pharmaceutical formulations.

Introduction: Cerebral venous sinus thrombosis (CVST) is a rare disease with highly variable clinical presentation and outcomes. Clinical studies suggest a role of inflammation and coagulation in CVST outcomes. The aim of this study was to investigate the association of inflammation and hypercoagulability biomarkers with CVST clinical manifestations and prognosis., Methods: This prospective multicenter study was conducted from July 2011 to September 2016. Consecutive patients referred to 21 French stroke units and who had a diagnosis of symptomatic CVST were included. High-sensitivity C-reactive protein (hs-CRP), neutrophil-to-lymphocyte ratio (NLR), D-dimer, and thrombin generation using calibrated automated thrombogram system were measured at different time points until 1 month after anticoagulant therapy discontinuation., Results: Two hundred thirty-one patients were included. Eight patients died, of whom 5 during hospitalization. The day 0 hs-CRP levels, NLR, and D-dimer were higher in patients with initial consciousness disturbance than in those without (hs-CRP: 10.2 mg/L [3.6-25.5] vs 23.7 mg/L [4.8-60.0], respectively; NLR: 3.51 [2.15-5.88] vs 4.78 [3.10-9.59], respectively; D-dimer: 950 μg/L [520-2075] vs 1220 μg/L [950-2445], respectively). Patients with ischemic parenchymal lesions (n = 31) had a higher endogenous thrombin potential 5pM than those with hemorrhagic parenchymal lesions (n = 31): 2025 nM min (1646-2441) vs 1629 nM min (1371-2090), respectively ( P  = .0082). Using unadjusted logistic regression with values >75th percentile, day 0 hs-CRP levels of >29.7 mg/L (odds ratio, 10.76 [1.55-140.4]; P  = .037) and day 5 D-dimer levels of >1060 mg/L (odds ratio, 14.63 [2.28-179.9]; P  = .010) were associated with death occurrence., Conclusion: Two widely available biomarkers measured upon admission, especially hs-CRP, could help predict bad prognosis in CVST in addition to patient characteristics. These results need to be validated in other cohorts., (© 2023 The Authors.)

The comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility., (© 2023. Springer Nature Limited.)

Background: Acute myeloid leukemia (AML) remains a very difficult disease to cure due to the persistence of leukemic stem cells (LSCs), which are resistant to different lines of chemotherapy and are the basis of refractory/relapsed (R/R) disease in 80% of patients with AML not receiving allogeneic transplantation., Methods: In this study, we showed that the interleukin-1 receptor accessory protein (IL-1RAP) protein is overexpressed on the cell surface of LSCs in all subtypes of AML and confirmed it as an interesting and promising target in AML compared with the most common potential AML targets, since it is not expressed by the normal hematopoietic stem cell. After establishing the proof of concept for the efficacy of chimeric antigen receptor (CAR) T-cells targeting IL-1RAP in chronic myeloid leukemia, we hypothesized that third-generation IL-1RAP CAR T-cells could eliminate AML LSCs, where the medical need is not covered., Results: We first demonstrated that IL-1RAP CAR T-cells can be produced from AML T-cells at the time of diagnosis and at relapse. In vitro and in vivo, we showed the effectiveness of IL-1RAP CAR T-cells against AML cell lines expressing different levels of IL-1RAP and the cytotoxicity of autologous IL-1RAP CAR T-cells against primary cells from patients with AML at diagnosis or at relapse. In patient-derived relapsed AML xenograft models, we confirmed that IL-1RAP CAR T-cells are able to circulate in peripheral blood and to migrate in the bone marrow and spleen, are cytotoxic against primary AML cells and increased overall survival., Conclusion: In conclusion, our preclinical results suggest that IL-1RAP CAR T-based adoptive therapy could be a promising strategy in AML treatment and it warrants the clinical investigation of this CAR T-cell therapy., Competing Interests: Competing interests: CF: consulting: Novartis, BMS, Incyte, and Daichii. Research grants: Novartis, Daiichi, Bellicum Pharmaceuticalo MD and CF: co-founders and shareholders of CanCell Therapeutics SAS, Besançon, Franceo MNdR and WW are employees of CanCell Therapeutics SAS, Besançon, Franceo SD: founder of ErVaccineo VA: ErVaccine consultanto ER: funder and Head of Lymphobank SAS., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

We recently characterized the association between DNA damage and immunoresponse in vivo in colonic mucosa of mice infected with a Salmonella Typhimurium strain expressing a genotoxin, known as typhoid toxin. In this protocol, we describe the specific steps for assessing DNA damage by the alkaline comet assay of colonic mucosal samples. The description of the comet assay protocol follows the international guidelines (Minimum Information for Reporting on the Comet Assay [Moller et al., 2020]). For complete details on the use and execution of this protocol, please refer to Martin et al. (2021)., Competing Interests: The authors declare no competing interests., (© 2021 The Author(s).)

To investigate environmental impacts upon colorectal carcinogenesis (CRC) by diet, we assessed two western diet food contaminants: 4-hydroxynonenal (HNE), a major lipid peroxidation product neoformed during digestion, and a mixture of pesticides. We used human colonic cell lines ectopically eliciting varied genetic susceptibilities to CRC: the non-transformed human epithelial colonic cells (HCECs) and their five isogenic cell lines with the loss of APC (Adenomatous polyposis coli) and TP53 (Tumor protein 53) and/or ectopic expression of mutated KRAS (Kristen-ras). These cell lines have been exposed for either for a short time (2-24 h) or for a long period (3 weeks) to 1 µM HNE and/or 10 µM pesticides. After acute exposure, we did not observe any cytotoxicity or major DNA damage. However, long-term exposure to pesticides alone and in mixture with HNE induced clonogenic transformation in normal HCECs, as well as in cells representing later stages of carcinogenesis. It was associated with genotoxic and non-genomic mechanisms (cell growth, metabolic reprogramming, cell mobility and epithelial-mesenchymal transition) depending on genetic susceptibility. This study demonstrated a potential initiating and promoting effect of food contaminants on CRC after long-term exposure. It supports that these contaminants can accelerate carcinogenesis when mutations in oncogenes or tumor suppressor genes occur.

The comet assay or single cell gel electrophoresis, is the most common method used to measure strand breaks and a variety of other DNA lesions in human populations. To estimate the risk of overall mortality, mortality by cause, and cancer incidence associated to DNA damage, a cohort of 2,403 healthy individuals (25,978 person-years) screened in 16 laboratories using the comet assay between 1996 and 2016 was followed-up. Kaplan-Meier analysis indicated a worse overall survival in the medium and high tertile of DNA damage (p < 0.001). The effect of DNA damage on survival was modelled according to Cox proportional hazard regression model. The adjusted hazard ratio (HR) was 1.42 (1.06-1.90) for overall mortality, and 1.94 (1.04-3.59) for diseases of the circulatory system in subjects with the highest tertile of DNA damage. The findings of this study provide epidemiological evidence encouraging the implementation of the comet assay in preventive strategies for non-communicable diseases., (© 2021. The Author(s).)

DNA damage and repair activity are often assessed in blood samples from humans in different types of molecular epidemiology studies. However, it is not always feasible to analyse the samples on the day of collection without any type of storage. For instance, certain studies use repeated sampling of cells from the same subject or samples from different subjects collected at different time-points, and it is desirable to analyse all these samples in the same comet assay experiment. In addition, flawless comet assay analyses on frozen samples open up the possibility of using this technique on biobank material. In this article we discuss the use of cryopreserved peripheral blood mononuclear cells (PBMCs), buffy coat (BC) and whole blood (WB) for analysis of DNA damage and repair using the comet assay. The published literature and the authors' experiences indicate that various types of blood samples can be cryopreserved with only a minor effect on the basal level of DNA damage. There is evidence to suggest that WB and PBMCs can be cryopreserved for several years without much effect on the level of DNA damage. However, care should be taken when cryopreserving WB and BCs. It is possible to use either fresh or frozen samples of blood cells, but results from fresh and frozen cells should not be used in the same dataset. The article outlines detailed protocols for the cryopreservation of PBMCs, BCs and WB samples., (© The Author(s) 2021. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society.All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Bacterial genotoxins cause DNA damage in eukaryotic cells, resulting in activation of the DNA damage response (DDR) in vitro. These toxins are produced by Gram-negative bacteria, enriched in the microbiota of inflammatory bowel disease (IBD) and colorectal cancer (CRC) patients. However, their role in infection remains poorly characterized. We address the role of typhoid toxin in modulation of the host-microbial interaction in health and disease. Infection with a genotoxigenic Salmonella protects mice from intestinal inflammation. We show that the presence of an active genotoxin promotes DNA fragmentation and senescence in vivo, which is uncoupled from an inflammatory response and unexpectedly associated with induction of an anti-inflammatory environment. The anti-inflammatory response is lost when infection occurs in mice with acute colitis. These data highlight a complex context-dependent crosstalk between bacterial-genotoxin-induced DDR and the host immune response, underlining an unexpected role for bacterial genotoxins., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

The alkaline comet assay, or single cell gel electrophoresis, is one of the most popular methods for assessing DNA damage in human population. One of the open issues concerning this assay is the identification of those factors that can explain the large inter-individual and inter-laboratory variation. International collaborative initiatives such as the hCOMET project - a COST Action launched in 2016 - represent a valuable tool to meet this challenge. The aims of hCOMET were to establish reference values for the level of DNA damage in humans, to investigate the effect of host factors, lifestyle and exposure to genotoxic agents, and to compare different sources of assay variability. A database of 19,320 subjects was generated, pooling data from 105 studies run by 44 laboratories in 26 countries between 1999 and 2019. A mixed random effect log-linear model, in parallel with a classic meta-analysis, was applied to take into account the extensive heterogeneity of data, due to descriptor, specimen and protocol variability. As a result of this analysis interquartile intervals of DNA strand breaks (which includes alkali-labile sites) were reported for tail intensity, tail length, and tail moment (comet assay descriptors). A small variation by age was reported in some datasets, suggesting higher DNA damage in oldest age-classes, while no effect could be shown for sex or smoking habit, although the lack of data on heavy smokers has still to be considered. Finally, highly significant differences in DNA damage were found for most exposures investigated in specific studies. In conclusion, these data, which confirm that DNA damage measured by the comet assay is an excellent biomarker of exposure in several conditions, may contribute to improving the quality of study design and to the standardization of results of the comet assay in human populations., Competing Interests: Declaration of Competing Interest The authors report no declarations of interest., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Background : Community pharmacists are among the frontline health professionals who manage patients with an opioid-related disorder (ORD). Pharmacists frequently have a negative attitude toward these patients, which could have a negative impact on their management. However, education on ORD may improve the attitude of future healthcare professionals. This cross-sectional study aimed to assess French pharmacy students' perceptions of ORD. Methods : This online survey was performed by emails sent to French pharmacy schools (between January 14, 2019 and May 31, 2019). The primary outcome was the perception (visual analogic scale) of ORD as a disease, the roles of community pharmacies (delivery of opioid agonist therapy-OAT and harm reduction kits), and the efficacy of OAT. The secondary outcomes assessed professional experience, university experience of and education on ORD, and the individual characteristics of students. Results : Among the 1,994 students included, 76.3% perceived ORD as a disease and felt that it was normal for pharmacists to deliver OAT (78.9%) and harm reduction kits (74.6%). However, only 46.9% perceived OAT as being effective. Multivariable analyses showed that females had a more positive perception in recognizing ORD as a disease. The progression through university years increased the positive perception of ORD as a disease and the delivery of OAT and harm reduction kits by pharmacists. Education on substance-related disorders had no impact on any scores. Students who had already delivered OAT had a negative perception of their efficacy. The students who had already performed pharmacy jobs or traineeships had a negative perception of harm reduction kit delivery. Conclusion : Education on substance-related disorders had no impact on students' perceptions. It seemed that the maturity acquired through university years had a stronger impact on the students' perceptions of ORD. Efforts must be made to improve our teaching methods and reinforce the confidence of students in the roles of community pharmacists.

The comet assay is a widely used test for the detection of DNA damage and repair activity. However, there are interlaboratory differences in reported levels of baseline and induced damage in the same experimental systems. These differences may be attributed to protocol differences, although it is difficult to identify the relevant conditions because detailed comet assay procedures are not always published. Here, we present a Consensus Statement for the Minimum Information for Reporting Comet Assay (MIRCA) providing recommendations for describing comet assay conditions and results. These recommendations differentiate between 'desirable' and 'essential' information: 'essential' information refers to the precise details that are necessary to assess the quality of the experimental work, whereas 'desirable' information relates to technical issues that might be encountered when repeating the experiments. Adherence to MIRCA recommendations should ensure that comet assay results can be easily interpreted and independently verified by other researchers.

Aflatoxin B 1 (AFB 1 ) is the most potent carcinogen among mycotoxins. Its biosynthesis involves the formation of versicolorin A (VerA), whose chemical structure shares many features with AFB 1 . Our data revealed significant levels of VerA in foodstuff from Central Asia and Africa. Given this emerging food risk, it was of prime interest to compare the toxic effects of the two mycotoxins against cells originating from the intestinal tract. We used human colon cell lines (Caco-2, HCT116) to investigate the cytotoxic process induced by the two mycotoxins. Contrary to AFB 1 , a low dose of VerA (1 µM) disturbed the expression level of thousands of genes (18 002 genes). We show that the cytotoxic effects of low doses of VerA (1-20 µM) were stronger than the same low doses of AFB 1 in both Caco-2 and HCT116 cell lines. In Caco-2 cells, VerA induced DNA strand breaks that led to apoptosis and reduced DNA replication of dividing cells, consequently inhibiting cell proliferation. Although VerA was able to induce the p53 signaling pathway in p53 wild-type HCT116 cells, its toxicity process did not mainly rely on p53 expression since similar cytotoxic effects were also observed in HCT116 cells that do not express p53. In conclusion, this study provides evidence of the risk of food contamination by VerA and shed light on its toxicological effect on human colon cells., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

An antikinetoplastid pharmacomodulation study was conducted at position 6 of the 8-nitroquinolin-2(1 H )-one pharmacophore. Fifteen new derivatives were synthesized and evaluated in vitro against L. infantum , T. brucei brucei , and T. cruzi , in parallel with a cytotoxicity assay on the human HepG2 cell line. A potent and selective 6-bromo-substituted antitrypanosomal derivative 12 was revealed, presenting EC 50 values of 12 and 500 nM on T. b. brucei trypomastigotes and T. cruzi amastigotes respectively, in comparison with four reference drugs (30 nM ≤ EC 50 ≤ 13 μM). Moreover, compound 12 was not genotoxic in the comet assay and showed high in vitro microsomal stability (half life >40 min) as well as favorable pharmacokinetic behavior in the mouse after oral administration. Finally, molecule 12 ( E ° = -0.37 V/NHE) was shown to be bioactivated by type 1 nitroreductases, in both Leishmania and Trypanosoma , and appears to be a good candidate to search for novel antitrypanosomal lead compounds., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

The comet assay is a well-accepted biomonitoring tool to examine the effect of dietary, lifestyle, environmental and occupational exposure on levels of DNA damage in human cells. With such a wide range of determinants for DNA damage levels, it becomes challenging to deal with confounding and certain factors are inter-related (e.g. poor nutritional intake may correlate with smoking status). This review describes the effect of intrinsic (i.e. sex, age, tobacco smoking, occupational exposure and obesity) and extrinsic (season, environmental exposures, diet, physical activity and alcohol consumption) factors on the level of DNA damage measured by the standard or enzyme-modified comet assay. Although each factor influences at least one comet assay endpoint, the collective evidence does not indicate single factors have a large impact. Thus, controlling for confounding may be necessary in a biomonitoring study, but none of the factors is strong enough to be regarded a priori as a confounder. Controlling for confounding in the comet assay requires a case-by-case approach. Inter-laboratory variation in levels of DNA damage and to some extent also reproducibility in biomonitoring studies are issues that have haunted the users of the comet assay for years. Procedures to collect specimens, and their storage, are not standardized. Likewise, statistical issues related to both sample-size calculation (before sampling of specimens) and statistical analysis of the results vary between studies. This review gives guidance to statistical analysis of the typically complex exposure, co-variate, and effect relationships in human biomonitoring studies., (Copyright © 2019 Elsevier B.V. All rights reserved.)