Identification of a transcriptomic signature of food-relevant genotoxins in human HepaRG hepatocarcinoma cells

Deciphering Aflatoxin B1 affected critical molecular pathways governing cancer: A bioinformatics study using CTD and PANTHER databases

Aflatoxin B1 (AFB1) is a fungal toxin consistently found as a contaminant in food products such as cereals, nuts, spices, and oilseeds. AFB1 exposure can lead to hepatotoxicity, cancer, immune suppression, reproductive deficiency, nutritional dysfunction, and growth impairment. AFB1 has also been listed as one of the most potent human carcinogens by the International Agency for Research on Cancer. Although the correlation between AFB1 exposure and cancer initiation and progression is already reported in the literature, very little information is available about what molecular pathways are affected during cancer development. Considering this, we first selected AFB1-responsive genes involved in five deadliest cancer types including lung, colorectal, liver, stomach, and breast cancers from the Comparative Toxicogenomics Database (CTD). Then, using the PANTHER database, a statistical overrepresentation test was performed to identify the significantly affected pathways in each cancer type. The gonadotropin-releasing hormone receptor (GnRHR) pathway, the CCKR signaling pathway, and angiogenesis were found to be the most affected pathways in lung, breast, liver, and stomach cancers. In addition, AFB1 toxicity majorly impacted apoptosis and Wnt signaling pathways in liver and stomach cancers, respectively. Moreover, the most affected pathways in colorectal cancer were the Wnt, CCKR, and GnRHR pathways. Furthermore, gene analysis was also performed for the most affected pathways associated with each cancer and identified thirteen key genes (e.g., FOS, AKT1) that may serve as biological markers for a particular type of AFB1-induced cancer as well as for in vitro AFB1 toxicological studies using specific cancer cell lines.

GWAS-significant loci and severe COVID-19: analysis of associations, link with thromboinflammation syndrome, gene-gene, and gene-environmental interactions

Objective

The aim of this study was to replicate associations of GWAS-significant loci with severe COVID-19 in the population of Central Russia, to investigate associations of the SNPs with thromboinflammation parameters, to analyze gene-gene and gene-environmental interactions.

Materials and Methods

DNA samples from 798 unrelated Caucasian subjects from Central Russia (199 hospitalized COVID-19 patients and 599 controls with a mild or asymptomatic course of COVID-19) were genotyped using probe-based polymerase chain reaction for 10 GWAS-significant SNPs: rs143334143 CCHCR1, rs111837807 CCHCR1, rs17078346 SLC6A20-LLZTFL1, rs17713054 SLC6A20-LLZTFL1, rs7949972 ELF5, rs61882275 ELF5, rs12585036 ATP11A, rs67579710 THBS3, THBS3-AS1, rs12610495 DPP9, rs9636867 IFNAR2.

Results

SNP rs17713054 SLC6A20-LZTFL1 was associated with increased risk of severe COVID-19 in the entire group (risk allele A, OR = 1.78, 95% CI = 1.22-2.6, p = 0.003), obese individuals (OR = 2.31, 95% CI = 1.52-3.5, p = 0.0002, (p bonf = 0.0004)), patients with low fruit and vegetable intake (OR = 1.72, 95% CI = 1.15-2.58, p = 0.01, (p bonf = 0.02)), low physical activity (OR = 1.93, 95% CI = 1.26-2.94, p = 0.0035, (p bonf = 0.007)), and nonsmokers (OR = 1.65, 95% CI = 1.11-2.46, p = 0.02). This SNP correlated with increased BMI (p = 0.006) and worsened thrombodynamic parameters (maximum optical density of the formed clot, D (p = 0.02), delayed appearance of spontaneous clots, Tsp (p = 0.02), clot size 30 min after coagulation activation, CS (p = 0.036)). SNP rs17078346 SLC6A20-LZTFL1 was linked with increased BMI (p = 0.01) and severe COVID-19 in obese individuals (risk allele C, OR = 1.72, 95% CI = 1.15-2.58, p = 0.01, (p bonf = 0.02)). SNP rs12610495 DPP9 was associated with increased BMI (p = 0.01), severe COVID-19 in obese patients (risk allele G, OR = 1.48, 95% CI = 1.09-2.01, p = 0.01, (p bonf = 0.02)), and worsened thrombodynamic parameters (time to the start of clot growth, Tlag (p = 0.01)). For rs7949972 ELF5, a protective effect against severe COVID-19 was observed in non-obese patients (effect allele T, OR = 0.67, 95% CI = 0.47-0.95, p = 0.02, (p bonf = 0.04)), improving thrombodynamic parameters (CS (p = 0.02), stationary spatial clot growth rates, Vst (p = 0.02)). Finally, rs12585036 ATP11A exhibited a protective effect against severe COVID-19 in males (protective allele A, OR = 0.51, 95% CI = 0.32-0.83, p = 0.004). SNPs rs67579710 THBS3, THBS3-AS1, rs17713054 SLC6A20-LZTFL1, rs7949972 ELF5, rs9636867 IFNAR2-were involved in two or more of the most significant G×G interactions (p perm ≤ 0.01). The pairwise combination rs67579710 THBS3, THBS3-AS1 × rs17713054 SLC6A20-LZTFL1 was a priority in determining susceptibility to severe COVID-19 (it was included in four of the top five most significant SNP-SNP interaction models).

Conclusion

Overall, this study represents a comprehensive molecular-genetic and bioinformatics analysis of the involvement of GWAS-significant loci in the molecular mechanisms of severe COVID-19, gene-gene and gene-environmental interactions, and provides evidence of their relationship with thromboinflammation parameters in patients hospitalized in intensive care units.

Lufenuron treatment temporarily represses gene expression and affects the SUMO pathway in liver of Atlantic salmon

Lufenuron is a benzoylurea insecticide currently in use to combat sea lice infestation in salmon aquaculture in Chile. With pending approval in Norway, the aim of this work was to study the uptake and toxicity of lufenuron in liver tissue of Atlantic salmon. Juvenile salmon weighing 40 g were given a standard 7-day oral dose, and bioaccumulation and transcriptional responses in the liver were examined 1 day after the end-of-treatment (day 8) and after 1 week of elimination (day 14). Bioaccumulation levels of lufenuron were 29 ± 3 mg/kg at day 8 and 14 ± 1 mg/kg at day 14, indicating relatively rapid clearance. However, residues of lufenuron were still present in the liver after 513 days of depuration. The exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs, p-adj < .05), followed by a weaker compensatory response at day 14 (169 significant DEGs). Pathways associated with RNA metabolism such as the sumoylation pathway were most strongly affected at day 8, while the apelin pathway was most profoundly affected at day 14. In conclusion, this study shows that lufenuron easily bioaccumulates and that a standard 7-day oral dose induces a transient inhibition of transcription in liver of salmon.

The Methylation Analysis of the Glucose-Dependent Insulinotropic Polypeptide Receptor (GIPR) Locus in GH-Secreting Pituitary Adenomas

The glucose-dependent insulinotropic polypeptide receptor (GIPR) is aberrantly expressed in about one-third of GH-secreting pituitary adenomas (GH-PAs) and has been associated with a paradoxical increase of GH after a glucose load. The reason for such an overexpression has not yet been clarified. In this work, we aimed to evaluate whether locus-specific changes in DNA methylation patterns could contribute to this phenomenon. By cloning bisulfite-sequencing PCR, we compared the methylation pattern of the GIPR locus in GIPR-positive (GIPR⁺) and GIPR-negative (GIPR^-) GH-PAs. Then, to assess the correlation between Gipr expression and locus methylation, we induced global DNA methylation changes by treating the lactosomatotroph GH3 cells with 5-aza-2'-deoxycytidine. Differences in methylation levels were observed between GIPR⁺ and GIPR^- GH-PAs, both within the promoter (31.9% vs. 68.2%, p < 0.05) and at two gene body regions (GB_1 20.7% vs. 9.1%; GB_2 51.2% vs. 65.8%, p < 0.05). GH3 cells treated with 5-aza-2'-deoxycytidine showed a ~75% reduction in Gipr steady-state level, possibly associated with the observed decrease in CpGs methylation. These results indicate that epigenetic regulation affects GIPR expression in GH-PAs, even though this possibly represents only a part of a much more complex regulatory mechanism.

The Joint Link of the rs1051730 and rs1902341 Polymorphisms and Cigarette Smoking to Peripheral Artery Disease and Atherosclerotic Lesions of Different Arterial Beds

Genome-wide association studies (GWAS) have discovered numerous single nucleotide polymorphisms (SNP) contributing to peripheral artery disease (PAD), but their joint effects with risk factors like cigarette smoking (CS) on disease susceptibility have not been systematically investigated. The present study looked into whether CS mediates the effects of GWAS loci on the development of PAD and atherosclerotic lesions in different arterial beds. DNA samples from 1263 unrelated individuals of Slavic origin including 620 PAD patients and 643 healthy subjects were genotyped by the MassArray-4 system for rs1051730, rs10134584, rs1902341, rs10129758 which are known as PAD-associated GWAS loci. The rs1051730 polymorphism was strongly associated with an increased risk of PAD (p = 5.1 × 10^-6), whereas rs1902341 did not show an association with disease risk. The rs1051730 polymorphism was associated with increased plasma levels of LDL cholesterol (p = 0.001), and conferred a greater risk of PAD in cigarette smokers than in nonsmokers (p < 0.01). Interestingly, the rs1902341T allele was associated with an increased risk of PAD in smokers and a decreased disease risk in nonsmokers. SNPs and CS were both linked to unilateral and/or bilateral atherosclerotic lesions of peripheral vessels, as well as the abdominal aorta, coronary, and cerebral arteries. The studied polymorphisms exert pleiotropic and cigarette smoking-mediated effects on atherosclerotic lesions of different arterial beds.

Use of transcriptomics in hazard identification and next generation risk assessment: A case study with clothianidin

Toxicological risk assessment is essential in the evaluation and authorization of different classes of chemical substances. Genotoxicity and mutagenicity testing are of highest priority and rely on established in vitro systems with bacterial and mammalian cells, sometimes followed by in vivo testing using rodent animal models. Transcriptomic approaches have recently also shown their value to determine transcript signatures specific for genotoxicity. Here, we studied how transcriptomic data, in combination with in vitro tests with human cells, can be used for the identification of genotoxic properties of test compounds. To this end, we used liver samples from a 28-day oral toxicity study in rats with the pesticidal active substances imazalil, thiacloprid, and clothianidin, a neonicotinoid-type insecticide with, amongst others, known hepatotoxic properties. Transcriptomic results were bioinformatically evaluated and pointed towards a genotoxic potential of clothianidin. In vitro Comet and γH2AX assays in human HepaRG hepatoma cells, complemented by in silico analyses of mutagenicity, were conducted as follow-up experiments to check if the genotoxicity alert from the transcriptomic study is in line with results from a battery of guideline genotoxicity studies. Our results illustrate the combined use of toxicogenomics, classic toxicological data and new approach methods in risk assessment. By means of a weight-of-evidence decision, we conclude that clothianidin does most likely not pose genotoxic risks to humans.

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Analysis of clothianidin genotoxicity in silico, in vitro and in vivo.

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Application of a toxicogenomics approach to analyze genotoxicity.

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Weight-of-evidence decision supports classification as “non-genotoxic”.

Comparative Analysis of Transcriptional Responses to Genotoxic and Non-Genotoxic Agents in the Blood Cell Model TK6 and the Liver Model HepaRG

Transcript signatures are a promising approach to identify and classify genotoxic and non-genotoxic compounds and are of interest as biomarkers or for future regulatory application. Not much data, however, is yet available about the concordance of transcriptional responses in different cell types or tissues. Here, we analyzed transcriptomic responses to selected genotoxic food contaminants in the human p53-competent lymphoblastoid cell line TK6 using RNA sequencing. Responses to treatment with five genotoxins, as well as with four non-genotoxic liver toxicants, were compared with previously published gene expression data from the human liver cell model HepaRG. A significant overlap of the transcriptomic changes upon genotoxic stress was detectable in TK6 cells, whereas the comparison with the HepaRG model revealed considerable differences, which was confirmed by bioinformatic data mining for cellular upstream regulators or pathways. Taken together, the study presents a transcriptomic signature for genotoxin exposure in the human TK6 blood cell model. The data demonstrate that responses in different cell models have considerable variations. Detection of a transcriptomic genotoxin signature in blood cells indicates that gene expression analyses of blood samples might be a valuable approach to also estimate responses to toxic exposure in target organs such as the liver.

In silico assessment of DNA damage response gene variants associated with head and neck cancer

Head and neck cancer (HNC), the sixth most common cancer globally, stands first in India, especially Northeast India, where tobacco usage is predominant, which introduces various carcinogens leading to malignancies by accumulating DNA damages. Consequently, the present work aimed to predict the impact of significant germline variants in DNA repair and Tumour Suppressor genes on HNC development. WES in Ion Proton^TM platform on 'discovery set' (n = 15), followed by recurrence assessment of the observed variants on 'confirmation set' (n = 40) using Sanger Sequencing was performed on the HNC-prevalent NE Indian populations. Initially, 53 variants were identified, of which seven HNC-linked DNA damage response gene variants were frequent in the studied populations. Different tools ascertained the biological consequences of these variants, of which the non-coding variants viz. EXO1_rs4150018, RAD52_rs6413436, CHD5_rs2746066, HACE1_rs6918700 showed risk, while FLT3_rs2491227 and BMPR1A_rs7074064 conferred protection against HNC by affecting transcriptional regulation and splicing mechanism. Molecular Dynamics Simulation of the full-length p53 model predicted that the observed coding TP53_rs1042522 variant conferred HNC-risk by altering the structural dynamics of the protein, which displayed difficulty in the transition between active and inactive conformations due to high-energy barrier. Subsequent pathway and gene ontology analysis revealed that EXO1, RAD52 and TP53 variants affected the Double-Strand Break Repair pathway, whereas CHD5 and HACE1 variants inactivated DNA repair cascade, facilitating uncontrolled cell proliferation, impaired apoptosis and malignant transformation. Conversely, FLT3 and BMPR1A variants protected against HNC by controlling tumorigenesis, which requires experimental validation. These findings may serve as prognostic markers for developing preventive measures against HNC.

Evaluating adaptive stress response gene signatures using transcriptomics

Stress response pathways (SRPs) mitigate the cellular effects of chemicals, but excessive perturbation can lead to adverse outcomes. Here, we investigated a computational approach to evaluate SRP activity from transcriptomic data using gene set enrichment analysis (GSEA). We extracted published gene signatures for DNA damage response (DDR), unfolded protein response (UPR), heat shock response (HSR), response to hypoxia (HPX), metal-associated response (MTL), and oxidative stress response (OSR) from the Molecular Signatures Database (MSigDB). Next, we used a gene-frequency approach to build consensus SRP signatures of varying lengths from 50 to 477 genes. We then prepared a reference dataset from perturbagens associated with SRPs from the literature with their transcriptomic profiles retrieved from public repositories. Lastly, we used receiver-operator characteristic analysis to evaluate the GSEA scores from matching transcriptomic reference profiles to SRP signatures. Our consensus signatures performed better than or as well as published signatures for 4 out of the 6 SRPs, with the best consensus signature area under the curve (% performance relative to median of published signatures) of 1.00 for DDR (109%), 0.86 for UPR (169%), 0.99 for HTS (103%), 1.00 for HPX (104%), 0.74 for MTL (150%) and 0.83 for OSR (148%). The best matches between transcriptomic profiles and SRP signatures correctly classified perturbagens in 78% and 88% of the cases by first and second rank, respectively. We believe this approach can characterize SRP activity for new chemicals using transcriptomics with further evaluation.

RNA A-to-I editing, environmental exposure, and human diseases

Epigenetic modifications have gained attention since they can be potentially changed with environmental stimuli and can be associated with adverse health outcomes. Epitranscriptome field has begun to attract attention with several aspects since RNA modifications have been linked with critical biological processes and implicated in diseases. Several RNA modifications have been identified as reversible indicating the dynamic features of modification which can be altered by environmental cues. Currently, we know more than 150 RNA modifications in different organisms and on different bases which are modified by various chemical groups. RNA editing, which is one of the RNA modifications, occurs after transcription, which results in RNA sequence different from its corresponding DNA sequence. Emerging evidence reveals the functions of RNA editing as well as the association between RNA editing and diseases. However, the RNA editing field is beginning to grow up and needs more empirical evidence in regard to disease and toxicology. Thus, this review aims to provide the current evidence-based studies on RNA editing modifying genes for genotoxicity and cancer. The review presented the association between environmental xenobiotics exposure and RNA editing modifying genes and focused on the association between the expression of RNA editing modifying genes and cancer. Furthermore, we discussed the future directions of scientific studies in the area of RNA modifications, especially in the RNA editing field, and provided a knowledge-based framework for further studies.

Insights into Aflatoxin B1 Toxicity in Cattle: An In Vitro Whole-Transcriptomic Approach

Aflatoxins, and particularly aflatoxin B1 (AFB1), are toxic mycotoxins to humans and farm animal species, resulting in acute and chronic toxicities. At present, AFB1 is still considered a global concern with negative impacts on health, the economy, and social life. In farm animals, exposure to AFB1-contaminated feed may cause several untoward effects, liver damage being one of the most devastating ones. In the present study, we assessed in vitro the transcriptional changes caused by AFB1 in a bovine fetal hepatocyte-derived cell line (BFH12). To boost the cellular response to AFB1, cells were pre-treated with the co-planar PCB 3,3′,4,4′,5-pentachlorobiphenyl (PCB126), a known aryl hydrocarbon receptor agonist. Three experimental groups were considered: cells exposed to the vehicle only, to PCB126, and to PCB126 and AFB1. A total of nine RNA-seq libraries (three replicates/group) were constructed and sequenced. The differential expression analysis showed that PCB126 induced only small transcriptional changes. On the contrary, AFB1 deeply affected the cell transcriptome, the majority of significant genes being associated with cancer, cellular damage and apoptosis, inflammation, bioactivation, and detoxification pathways. Investigating mRNA perturbations induced by AFB1 in cattle BFH12 cells will help us to better understand AFB1 toxicodynamics in this susceptible and economically important food-producing species.