Genes and Environment最新文献

Aflatoxin B₁ (AFB₁) is a mycotoxin produced by several species of Aspergillus fungi which can cause liver cancer in animals and humans. This study aims to perform the risk assessment of AFB₁ in herbal medicines and plant food supplements (PFS) in Malaysian market. A total of 31 herbal medicines and PFS were purchased through online platforms and over the counter using a targeted sampling strategy. Of 31 samples analysed using the ELISA method, 25 (80.6%) were contaminated with AFB₁ at levels ranged from 0.275 to 13.941 μg/kg. The Benchmark Dose Lower Confidence level of 10 (BMDL₁₀) of 63.46 ng/kg bw/day and the estimated dietary intake of the adult population ranged from 0.006 to 10.456 ng/kg bw/day were used to calculate the Margin of Exposure (MOE). The MOEs for 24 (96%) out of the 25 positive samples were lower than 10,000. The RISK21 matrix revealed that AFB₁ exposure levels from herbal medicines and PFS differed greatly over the world. The calculated population risk of acquiring liver cancer from AFB₁ exposure ranged from 0 to 0.261 cancers/100,000 populations/year and accounted for an estimated percentage of liver cancer incidence ranged from 0.002 to 4.149%. This study revealed a moderate risk of liver cancer attributable to AFB₁ from herbal medicine and PFS among Malaysian populations and emphasised an urgency for risk management actions.

Background: Mutagenicity, the ability of chemical agents to cause mutations and potentially lead to cancer, is a critical aspect of substance safety assessment for protecting human health and the environment. Metabolic enzymes activate multiple mutagens in living organisms, thus in vivo animal models provide highly important information for evaluating mutagenicity in human. Rats are considered suitable models as they share a similar metabolic pathway with humans for processing toxic chemical and exhibit higher responsiveness to chemical carcinogens than mice. To assess mutagenicity in rats, transgenic rodents (TGRs) are widely used for in vivo gene mutation assays. However, such assays are labor-intensive and could only detect transgene mutations inserted into the genome. Therefore, introducing a technology to directly detect in vivo mutagenicity in rats would be necessary. The next-generation sequencing (NGS) based error-corrected sequencing technique is a promising approach for such purposes.

Results: We investigated the applicability of paired-end and complementary consensus sequencing (PECC-Seq), an error-corrected sequencing technique, for detecting in vivo mutagenicity in the rat liver samples. PECC-Seq allows for the direct detection of ultra-rare somatic mutations in the genomic DNA without being constrained by the genomic locus, tissue, or organism. We tested PECC-Seq feasibility in rats treated with diethylnitrosamine (DEN), a mutagenic compound. Interestingly, the mutation and mutant frequencies between PECC-Seq and the TGR assay displayed a promising correlation. Our results also demonstrated that PECC-Seq could successfully detect the A:T > T:A mutation in rat liver samples, consistent with the TGR assay. Furthermore, we calculated the trinucleotide mutation frequency and proved that PECC-Seq accurately identified the DEN treatment-induced mutational signatures.

Conclusions: Our study provides the first evidence of using PECC-Seq for in vivo mutagenicity detection in rat liver samples. This approach could provide a valuable alternative to conventional TGR assays as it is labor- and time-efficient and eliminates the need for transgenic rodents. Error-corrected sequencing techniques, such as PECC-Seq, represent promising approaches for enhancing mutagenicity assessment and advancing regulatory science.

Background: tert-Butyl hydroperoxide (TBHP; CAS 75-91-2), a hydroperoxide, is mainly used as a polymerization initiator to produce polyethylene, polyvinyl chloride, and unsaturated polyester. It is a high-production chemical, widely used in industrial countries, including Japan. TBHP is also used as an additive for the manufacturing of food utensils, containers, and packaging (UCP). Therefore, there could be consumer exposure through oral intake of TBHP eluted from UCPs. TBHP was investigated in various in vitro and in vivo genotoxicity assays. In Ames tests, some positive results were reported with and/or without metabolic activation. As for the mouse lymphoma assay, the positive result was reported, regardless of the presence or absence of metabolic activation enzymes. The results of some chromosomal aberrations test and comet assay in vitro also demonstrated the genotoxic positive results. On the other hand, in in vivo tests, there are negative results in the bone marrow micronucleus test of TBHP-administered mice by single intravenous injection and the bone marrow chromosomal aberration test using rats exposed to TBHP for 5 days by inhalation. Also, about dominant lethal tests, the genotoxic positive results appeared. In contrast, there is little information about in vivo mutagenicity and no information about carcinogenicity by oral exposure.

Results: We conducted in vivo gene mutation assay using MutaMice according to the OECD Guidelines for the Testing of Chemicals No. 488 to investigate in vivo mutagenicity of TBHP through oral exposure. After repeated dosing for 28 days, there were no significant differences in the mutant frequencies (MFs) of the liver and glandular stomach up to 300 mg/kg/day (close to the maximum tolerable dose (MTD)). The positive and negative controls produced the expected responses.

Conclusions: These findings show that orally administrated TBHP is not mutagenic in the mouse liver and glandular stomach under these experimental conditions.

Background: The species of genus Macaranga are widely found in Malaysian secondary forests and has been used as an alternative for treating varieties of illness. Studies have shown that the medicinal properties of this genus contain anti-inflammatory, antioxidant, and anti-cancer effects. This study aimed to determine the cytotoxicity of six isolated phytochemicals from Macaranga heynei (M. heynei), Macaranga lowii and Shorea leprosula on HT-29 human colorectal adenocarcinoma cell lines.

Results: One out of six isolated phytochemical compounds, identified as "Laevifolin A", showed a cytotoxicity with an IC₅₀ value of 21.2 µM following 48 h treatment as detected using Sulforhodamine B (SRB) assay. Additionally, no induction of apoptosis and oxidative stress were observed on Laevifolin A treated HT-29 cells as determined using Annexin V-FITC/PI assay and dihydroethidine (HE) staining, respectively. Additionally, no damage to the DNA were observed as measured using the Alkaline Comet assay. Further investigation on menadione-induced oxidative DNA damage showed the genoprotective potential of Laevifolin A on HT-29 cells.

Conclusions: In conclusion, this study indicated that only one compound (Laevifolin A) that extracted from M. heynei has the cytotoxicity potential to be developed as an anticancer agent in human colorectal adenocarcinoma. However, besides exhibiting cytotoxic effect, the compound also exhibits genoprotective capability that warrant further investigation.

Background: Chronic obstructive pulmonary disease (COPD) is a serious health burden worldwide with high mortality. LncRNA plasmacytoma variant translocation 1 (PVT1) has been illustrated to serve as a biomarker for COPD progression. Nonetheless, its specific functions and mechanisms in COPD are unclarified.

Methods: Cigarette smoke extract (CSE) was utilized to stimulate 16HBE cells, and cigarette smoke combining with lipopolysaccharide (LPS) was employed to induce COPD in rats. Western blotting and RT-qPCR were utilized for measuring protein and RNA levels. Flow cytometry was implemented for detecting cell apoptosis. Concentrations of inflammatory factors TNF-α and IFN-γ were examined using ELISA. Luciferase reporter assay was utilized for verifying the interaction between molecules. Hematoxylin-eosin staining was performed for histological analysis of rat lung tissues.

Results: PVT1 was highly expressed in CSE-stimulated 16HBE cells and the lungs of COPD rats. PVT1 depletion restored the viability, restrained apoptosis and hindered inflammatory cytokine production in 16HBE cells under CSE treatment and alleviated pathological damages in COPD rats. PVT1 bound to miR-30b-5p and miR-30b-5p targeted BCL2 like 11 (BCL2L11). Overexpressing BCL2L11 offset the above effects mediated by PVT1 in CSE-triggered 16HBE cells.

Conclusion: PVT1 enhances apoptosis and inflammation of 16HBE cells under CSE stimulation by modulating miR-30b-5p/BCL2L11 axis.

Background: Single-stranded (ss) DNAs are utilized in various molecular biological and biotechnological applications including the construction of double-stranded DNAs with a DNA lesion, and are commonly prepared by using chimeric phage-plasmids (phagemids) plus M13-derived helper phages. However, the yields of ss DNA with these methods are poorly reproducible, and multiple factors must be optimized.

Results: In this report, we describe a new arabinose-inducible ss phagemid production method without helper phage infection. The newly exploited DNA derived from VCSM13 expresses the pII protein, which initiates ss DNA synthesis, under the control of the araBAD promoter. In addition, the packaging signal is deleted in the DNA to reduce the contamination of the phage-derived ss DNA. The phagemid DNA of interest, carrying the M13 origin of replication and the packaging signal, was introduced into bacterial cells maintaining the modified VCSM13 DNA as a plasmid, and the ss phagemid DNA production was induced by arabinose. The DNA recovered from the phage particles had less contamination from VCSM13 DNA, as compared to the conventional method. Moreover, we extended the method to purify the ss DNAs by using an anion-exchange column, to avoid the use of hazardous chemicals.

Conclusion: Using this combination of methods, large quantities of phagemid ss DNAs of interest can be consistently obtained.

Background: Multiwalled carbon nanotubes (MWCNTs) are suspected lung carcinogens because their shape and size are similar to asbestos. Various MWCNT types are manufactured; however, only MWNT-7 is classified into Group 2B by The International Agency for Research on Cancer. MWNT-7's carcinogenicity is strongly related to inflammatory reactions. On the other hand, inconsistent results on MWNT-7 genotoxicity have been reported. We previously observed no significant differences in both Pig-a (blood) and gpt (lung) mutant frequencies between MWNT-7-intratracheally treated and negative control rats. In this study, to investigate in vivo MWNT-7 genotoxicity on various endpoints, we attempted to develop a lung micronucleus assay through ex vivo culture targeting the cellular fraction of Clara cells and alveolar Type II (AT-II) cells, known as the initiating cells of lung cancer. Using this system, we analyzed the in vivo MWNT-7 genotoxicity induced by both whole-body inhalation exposure and intratracheal instillation. We also conducted an erythrocyte micronucleus assay using the samples obtained from animals under intratracheal instillation to investigate the tissue specificity of MWNT-7 induced genotoxicities.

Results:  We detected a significant increase in the incidence of micronucleated cells derived from the cellular fraction of Clara cells and AT-II cells in both MWNT-7-treated and positive control groups compared to the negative control group under both whole-body inhalation exposures and intratracheal instillation. Additionally, the erythrocyte micronucleus assay detected a significant increase in the incidence of micronucleated reticulocytes only in the positive control group.

Conclusions: Our findings indicated that MWNT-7 was genotoxic in the lungs directly exposed by both the body inhalation and intratracheal instillation but not in the hematopoietic tissue.

Background: Chronic obstructive pulmonary disease (COPD) is characterized by pulmonary vascular remodeling, which can be caused by abnormal proliferation and migration of pulmonary artery smooth muscle cells (PASMCs). Several microRNAs were demonstrated to regulate the PASMC dysfunction. Our study intends to evaluate whether miR-627-5p affects cigarette smoke extract (CSE)-induced aberrant biological behaviors of PASMCs.

Methods: PASMCs was treated with CSE to create the in vitro cellular model of COPD. The viability and LDH release of PASMCs was detected by CCK-8 assay and LDH release assay. MiR-627-5p and MAP 2 K4 expression in CSE (2%)-treated PASMCs was detected by qRT-PCR. PASMC proliferation was observed under a microscope, and PASMC migration was assessed by Transwell migration assays. The binding of miR-627-5p on MAP 2 K4 was verified by dual-luciferase reporter assay. Protein levels of MAP2K4 and the PI3K/AKT signaling markers were examined by western blotting.

Results: The viability of PASMCs treated with 2% CSE reached a peak. CSE dose-dependently downregulated miR-627-5p expression in PASMCs. MiR-627-5p overexpression attenuated the CSE-induced abnormal proliferation and migration of PASMCs. However, MAP2K4 overexpression antagonized the effects of miR-627-5p on PASMC dysfunction. Importantly, miR-627-5p inhibited CSE-stimulated activation of the PI3K/AKT pathway via downregulating MAP2K4.

Conclusion: MiR-627-5p improves CSE-induced abnormal proliferation and migration of PASMCs by inhibiting MAP2K4 expression and the PI3K/AKT pathway.

Background: The repeated-dose liver micronucleus (RDLMN) assay has been well-developed and applied because of its simplicity and the ease of integration into general toxicity studies which is the preferred method from the 3R's point of view. In this assay, we observed micronucleated hepatocytes which accumulated during a rather long-term dosing period. When considering integration into general toxicity studies, the effects of age of the animals used in the micronucleus assay becomes a major issue. The effect of age on the micronucleus induction rate has been reported in bone marrow micronucleus assays, and it is considered that the decrease in cell proliferation rate due to aging is the cause of the decrease in sensitivity. A decrease in sensitivity due to aging was also reported in a liver micronucleus assay using clofibrate and the cause is considered to be a decrease in hepatocyte proliferation activity due to aging. However, no actual decrease in hepatocyte proliferation rate due to aging has been reported. In addition, there are no reports, so far, on whether similar effects of aging appear when other substances were administered. To investigate the effects of aging in the RDLMN assay, this study focused on the effects of 14-day repeated administration of DEN, a well-known genotoxic hepatocarcinogen with the hepatocyte toxicity which should cause an elevation of cell proliferation rate as a reflective regeneration.

Results: The liver micronuclei induced by DEN were equivalent between the two age groups (i.e., six and eight weeks of age at the start of dosing). In the histopathological examination for the liver, single cell necrosis, karyomegaly, and increased mitosis were observed in the hepatocytes, and the frequency and severity were increased dose-dependently. Ki-67 immunohistochemical analysis which can detect all cells in the cell cycle other than those in the G0 phase revealed dose-dependent increase of cell proliferation activity, and the difference between ages was not observed.

Conclusion: The effect of aging on the RDLMN assay could not be recognized when DEN was administered for 14 days in rats. Meanwhile, it was supported by the histopathological examination and Ki-67 immunohistochemical analysis that such an effect of aging was masked by the compensatory hepatocyte proliferation which was induced by the hepatocyte toxicity of DEN.

Bisphenol-A (BPA) is an important environmental contaminant with adverse health effects suspected to be mediated through epigenetic mechanisms. We had reported that the FLO1-dependent flocculation of transgenic yeast expressing human DNA methyltransferase (DNMT yeast) is a useful tool in epigenotoxicology studies. In this report, we have investigated the effects of BPA in the presence of metabolic activation (S-9 mix) on the transcription level of the FLO1 gene in the DNMT yeast. In the presence of metabolic activation, BPA inhibited the intensity of green fluorescence reporter protein (GFP) driven by the FLO1 promoter. A metabolite of BPA, 4-methyl-2,4-bis(p-hydroxyphenyl) pent-1-ene (MBP), also exhibited similar inhibitory effect. Furthermore, BPA in the presence of S-9 mix had only a weak while MBP had no inhibitory effects on the expression of modified GFP reporter gene under the control of FLO1 promoter with reduced CpG motifs. Aforementioned behavior was confirmed by the inhibition of flocculation as well as FLO1 gene mRNA expression. In addition, the global DNA methylation level in the human HEK293 cells was also reduced by MBP. These results indicate that BPA metabolites have inhibitory effect on DNA methylation. Our approach offers a novel in vitro method for screening for chemicals that can alter the epigenome by a mechanism dependent on their metabolic activation.