Cell type-dependent response to benzo(a)pyrene exposure of human placental cell lines under normoxic, hypoxic, and pro-inflammatory conditions

Benzo(a)pyrene (BaP) can be detected in the human placenta. However, little is known about the effects of BaP exposure on different placental cells under various conditions. In this study, we aimed to investigate the effects of BaP on mitochondrial function, pyrin domain-containing protein 3 (NLRP3) inflammasome, and apoptosis in three human trophoblast cell lines under normoxia, hypoxia, and inflammatory conditions. JEG-3, BeWo, and HTR-8/SVneo cell lines were exposed to BaP under normoxia, hypoxia, or inflammatory conditions for 24 h. After treatment, we evaluated cell viability, apoptosis, aryl hydrocarbon receptor (AhR) protein and cytochrome P450 (CYP) gene expression, mitochondrial function, including mitochondrial DNA copy number (mtDNAcn), mitochondrial membrane potential (ΔΨm), intracellular adenosine triphosphate (iATP), and extracellular ATP (eATP), nitric oxide (NO), NLPR3 inflammasome proteins, and interleukin (IL)-1β. We found that BaP upregulated the expression of AhR or CYP genes to varying degrees in all three cell lines. Exposure to BaP alone increased ΔΨm in all cell lines but decreased NO in BeWo and HTR-8/SVneo, iATP in HTR-8/SVneo, and cell viability in JEG-3, without affecting apoptosis. Under hypoxic conditions, BaP did not increase the expression of AhR and CYP genes in JEG-3 cells but increased CYP gene expression in two others. Pro-inflammatory conditions did not affect the response of the 3 cell lines to BaP with respect to the expression of CYP genes and changes in the mitochondrial function and NLRP3 inflammasome proteins. In addition, in HTR-8/SVneo cells, BaP increased IL-1β secretion in the presence of hypoxia and poly(I:C). In conclusion, our results showed that BaP affected mitochondrial function in trophoblast cell lines by increasing ΔΨm. This increased ΔΨm may have rescued the trophoblast cells from activation of the NLRP3 inflammasome and apoptosis after BaP treatment. We also observed that different human trophoblast cell lines had cell type-dependent responses to BaP exposure under normoxia, hypoxia, or pro-inflammatory conditions.

Human CYP1A1-activated aneugenicity of aflatoxin B1 in mammalian cells and its combined effect with benzo(a)pyrene

Aflatoxin B1 (AFB1) is the most toxic mycotoxin and a proven human carcinogen that requires metabolic activation, known by cytochrome P450 (CYP) 1A2 and 3A4. Previous evidence showed that AFB1 is activated by human recombinant CYP1A1 expressed in budding yeast. Yet, the toxicity, in particular the genotoxicity of the reactive metabolites formed from AFB1 remains unclear. Humans could be exposed to both AFB1 and benzo(a)pyrene (BaP) simultaneously, thus we were interested in their combined genotoxic effects subsequent to metabolic activation by CYP1A1. In this study, molecular docking of AFB1 to human CYP1A1 indicated that AFB1 is valid as a substrate. In the incubations with AFB1 in human CYP1A1-expressed microsomes, AFM1 as a marking metabolite of AFB1 was detected. Moreover, AFB1 induced micronucleus formation in a Chinese hamster V79-derived cell line and in a human lung epithelial BEAS-2B cell line, both expressing recombinant human CYP1A1, V79-hCYP1A1 and 2B-hCYP1A1 cells, respectively. Immunofluorescence of centromere protein B stained micronuclei was dominant in AFB1-treated BEAS-2B cells exposed to AFB1, suggesting an aneugenic effect. Moreover, AFB1 elevated the levels of ROS, 8-OHdG, AFB1-DNA adduct, and DNA breaks in 2B-hCYP1A1 cells, compared with those in the parental BEAS-2B cells. Meanwhile, AFB1 increased CYP1A1, RAD51, and γ-H2AX protein levels in 2B-hCYP1A1 cells, which were attenuated by the CYP1A1 inhibitor bergamottin. Co-exposure of AFB1 with BaP increased 8-OHdG, RAD51, and γ-H2AX levels (indicating DNA damage). In conclusion, AFB1 could be activated by human CYP1A1 for potent aneugenicity, which may be further enhanced by co-exposure to BaP.

Transcriptional and phenotypical alterations associated with a gradual benzo[a]pyrene-induced transition of human bronchial epithelial cells into mesenchymal-like cells

The role of benzo[a]pyrene (BaP), a prominent genotoxic carcinogen and aryl hydrocarbon receptor (AhR) ligand, in tumor progression remains poorly characterized. We investigated the impact of BaP on the process of epithelial-mesenchymal transition (EMT) in normal human bronchial epithelial HBEC-12KT cells. Early morphological changes after 2-week exposure were accompanied with induction of SERPINB2, IL1, CDKN1A/p21 (linked with cell cycle delay) and chemokine CXCL5. After 8-week exposure, induction of cell migration and EMT-related pattern of markers/regulators led to induction of further pro-inflammatory cytokines or non-canonical Wnt pathway ligand WNT5A. This trend of up-regulation of pro-inflammatory genes and non-canonical Wnt pathway constituents was observed also in the BaP-transformed HBEC-12KT-B1 cells. In general, transcriptional effects of BaP differed from those of TGFβ1, a prototypical EMT inducer, or a model non-genotoxic AhR ligand, TCDD. Carcinogenic polycyclic aromatic hydrocarbons could thus induce a unique set of molecular changes linked with EMT and cancer progression.

Low levels of nicotine and cotinine but not benzo[a]pyrene induce human trophoblast cell proliferation

E-cigarettes use constitutes a source of thirdhand nicotine exposure. The increasing use of electronic cigarettes in homes and public places increases the risk of exposure of pregnant women to thirdhand nicotine. The effects of exposure of pregnant women to very low levels of nicotine have not been studied in humans but detrimental in experimental animals. The objective of this study is to investigate the effect of nanomolar concentrations of nicotine and its metabolite cotinine on the proliferation of JEG-3, a human trophoblast cell line. We also studied the proliferative effect of nanomolar concentrations of benzo[a]pyrene (B[a]P), a polycyclic hydrocarbon in tobacco smoke, for comparison. We treated JEG-3 cells in culture with nanomolar concentrations of nicotine, cotinine, and B[a]P. Their effect on cell proliferation was determined, relative to untreated cells, by MTT assay. Western blotting was used to assess the mitogenic signaling pathways affected by nicotine and cotinine. In contrast to the inhibitory effects reported with higher concentrations, we showed that nanomolar concentrations of nicotine and cotinine resulted in significant JEG-3 cell proliferation and a rapid but transient increase in levels of phosphorylated ERK and AKT, but not STAT3. Biphasic, non-monotonic effect on cell growth is characteristic of endocrine disruptive chemicals like nicotine. The mitogenic effects of nicotine and cotinine potentially contribute to increased villous epithelial thickness, seen in placentas of some smoking mothers. This increases the diffusion distance for oxygen and nutrients between mother and fetus, contributing to intrauterine growth restriction in infants of smoking mothers.

Histone H3K36me3 mediates the genomic instability of Benzo[a]pyrene in human bronchial epithelial cells

Histone modifications maintain genomic stability and orchestrate gene expression at the chromatin level. Benzo [a]pyrene (BaP) is the ubiquitous carcinogen widely spread in the environment, but the role and regulatory mechanism of histone modification in its toxic effects remain largely undefined. In this study, we found a dose-dependent reduction of histone H3 methylations at lysine4, lysine9, lysine27, lysine36 in HBE cells treated with BaP. We observed that inhibiting H3K27 and H3K36 methylation impaired cell proliferation, whereas the loss of H3K4, H3K9, H3K27, and H3K36 methylation led to increased genomic instability and delayed DNA repair. H3K36 mutation at both H3.1 and H3.3 exhibited the most significant impacts. In addition, we found that the expression of SET domain containing 2 (SETD2), the unique methyltransferase catalyzed H3K36me3, was downregulated by BaP dose-dependently in vitro and in vivo. Knockdown of SETD2 aggravated DNA damage of BaP exposure, which was consistent with the effects of H3K36 mutation. With the aid of chromatin immunoprecipitation (ChIP) -seq and RNA-seq, we found that H3K36me3 was responsible for transcriptional regulation of genes involved in pathways related to cell survival, lung cancer, metabolism and inflammation. The enhanced enrichment of H3K36me3 in genes (CYP1A1, ALDH1A3, ACOXL, WNT5A, WNT7A, RUNX2, IL1R2) was positively correlated with their expression levels, while the reduction of H3K36me3 distribution in genes (PPARGC1A, PDE4D, GAS1, RNF19A, KSR1) were in accordance with the downregulation of gene expression. Taken together, our findings emphasize the critical roles and mechanisms of histone lysine methylation in mediating cellular homeostasis during BaP exposure.

Transcriptomic and biochemical analysis of metabolic remodeling in Bacillus subtilis MSC4 under Benzo[a]pyrene stress

Polyaromatic benzo[a]pyrene (B[a]P) is a toxic carcinogenic environmental pollutant, and the use of microorganisms to remediate B[a]P contamination is considered to be one of the most effective strategies. However, there is still a gap in studying the metabolic remodeling of microorganisms under B[a]P stress. In this study, our systematically investigated the effects of B[a]P on the metabolism of Bacillus subtilis MSC4 based on transcriptomic, molecular and biochemical analyses. The results showed that in response to B[a]P stress, MSC4 formed more biofilm matrix and endospores, the structure of the endospores also was changed, which led to a reduction in their resistance and made them more difficult to germinate. In addition to an increase in glycolysis activity, the activities of tricarboxylic acid cycle, pentose phosphate pathway and the electron transport chain were decreased. B[a]P stress forced MSC4 to strengthen arginine synthesis, urea cycle, and urea decomposition, meanwhile, synthesize more ribonucleotides. The activity of DNA replication, transcription activities and the expression of multiple ribosomal protein genes were reduced. Moreover, all of the reported enzymes involved in B[a]P degradation showed decreased transcript abundance, and the degradation of B[a]P caused significant up-regulation of the gene expression of the acid inducible enzyme OxdC and the synthesis of acetoin. In addition, the cytotoxicity of B[a]P to bacteria was directly displayed in four aspects: increased intracellular level of reactive oxygen species (ROS), elevated cell membrane permeability, up-regulation of the cell envelope stress-sensing two-component system LiaRS, and downregulation of siderophores biosynthesis. Finally, B[a]P also caused morphological changes in the cells, with some cells exhibiting significant deformation and concavity. These findings provide effective research directions for targeted improvement the cellular activity of B[a]P-degrading strains, and is beneficial for further application of microorganisms to remediate B[a]P -contaminated soils.

Circ0087385 promotes DNA damage in benzo(a)pyrene-induced lung cancer development by upregulating CYP1A1

Increasing environmental genotoxic chemicals have been shown to induce epigenetic alterations. However, the interaction between genetics and epigenetics in chemical carcinogenesis is still not fully understood. Here, we constructed an in vitro human lung carcinogenesis model (16HBE-T) by treating human bronchial epithelial cells with a typical significant carcinogen benzo(a)pyrene (BaP). We identified a novel circular RNA, circ0087385, which was overexpressed in 16HBE-T and human lung cancer cell lines, as well as in lung cancer tissues and serum exosomes from lung cancer patients. The upregulated circ0087385 after exposure to BaP promoted DNA damage in the early stage of chemical carcinogenesis and affected the cell cycle, proliferation, and apoptosis of the malignantly transformed cells. Overexpression of circ0087385 enhanced the expression of cytochrome P450 1A1 (CYP1A1), which is crucial for metabolically activating BaP. Interfering with circ0087385 or CYP1A1 reduced the levels of ultimate carcinogen benzo(a)pyrene diol epoxide (BPDE) and BPDE-DNA adducts. Interfering with CYP1A1 partially reversed the DNA damage induced by high expression of circ0087385, as well as decreased the level of BPDE and BPDE-DNA adducts. These findings provide novel insights into the interaction between epigenetics and genetics in chemical carcinogenesis which are crucial for understanding the epigenetic and genetic toxicity of chemicals.

The toxicity response of the electrochemical signal of the cell to the drug metabolized by the S9 system

The electrochemical detection method of cytotoxicity using intracellular purines as biomarkers has shown great potential for in vitro drug toxicity evaluation. However, no electrochemical detection system based on an in vitro drug metabolism mechanism has been devised. In this paper, electrochemical voltammetry was used to investigate the effect of the S9 system on the electrochemical behavior of HepG2 cells, and benzo[a]pyrene, fluoranthene, and pyrene were employed to investigate the sensitivity of electrochemical signals of cells to the cytotoxicity of drugs metabolized by the S9 system. The results showed that, within 8 h of exposure to the S9 system, the electrochemical signal of HepG2 cells at 0.7 V did not alter noticeably. The levels of xanthine, guanine, hypoxanthine, and adenine in the cells were not significantly altered. Compared with the absence of S9 system metabolism, benzo[a]pyrene and fluoranthene processed by the S9 system decreased the electrochemical signal of the cells in a dose-dependent manner, while pyrene did not change it appreciably. HPLC also revealed that benzo[a]pyrene and fluoranthene metabolized by the S9 system decreased the intracellular purine levels, whereas pyrene had no effect on them before and after S9 system metabolism. The cytotoxicity results of the three drugs examined by electrochemical voltammetry and MTT assay showed a strong correlation and good agreement. The S9 system had no effect on the intracellular purine levels or the electrochemical signal of cells. When the drug was metabolized by the S9 system, variations in cytotoxicity could be precisely detected by electrochemical voltammetry.

A low dose of benzo(a)pyrene during prepuberty in male rats generated immediate oxidative stress in the testes and compromised steroidogenic enzymes/proteins

The prepubertal period is crucial for sexual development and any alterations can interfere with the reproductive system in adulthood. The aim of this study was to evaluate how Benzo(a)pyrene (BaP) can affect the testes during the prepubertal period. Juvenile male Wistar rats were divided into a control (corn oil + DMSO) and a BaP-group (0.1 μg/kg/day), exposed to BaP for 31 days (gavage), and all parameters were evaluated on postnatal day (PND) 54. Leukocyte counts were decreased. Histological analyses of the testes revealed that height and seminiferous tubules diameters (STDs) were reduced, tubular dynamics were altered, and Leydig cell atrophy was evident in the BaP-group. The testosterone concentration was decreased while FSH levels increased within the BaP-exposed group. Steroidogenic enzymes in the testes were decreased, but steroidogenic acute regulatory protein was not altered. The expression of gstp1 and ckit enzymes was decreased. Reduced glutathione (GSH) and superoxide dismutase (SOD) were increased, whereas malondialdehyde (MDA) was decreased in the testes. In conclusion, BaP or its metabolites causes low systemic toxicity; however, it adversely influences testicular function by disrupting the hormonal axis, unbalancing testicular antioxidative, and blocking the action of the steroidogenic mechanisms.

Delayed clearance of the pro-carcinogen benzo[a]pyrene in PLHC-1 cells when co-exposed to the antifungal drug clotrimazole and effects on the CYP1A biomarker

Cytochrome P450 1 A (CYP1A) is a key enzyme in the metabolism of the polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BaP) in animals, and a biomarker for environmental PAH exposure. The common antimycotic imidazole drug clotrimazole (CLO) has been detected in the aquatic environment and likely co-exists with BaP. Like BaP, CLO can bind to CYP1A enzymes and can act as a CYP1A inhibitor. Co-exposure of BaP with CLO significantly delayed BaP elimination in a fish liver cell line (PLHC-1). Intracellular BaP concentration was 2.4 times higher after 6 h in co-exposed cells, compared to cells exposed to BaP alone. Higher BaP concentrations in cells co-exposed to CLO positively correlated with CLO dose, indicating CLO-mediated delays in BaP clearance. After 24 h, BaP was undetectable irrespective of CLO co-exposure. In contrast, intracellular CLO concentrations remained constant over the 72 h experimental period. Co-exposure of BaP with CLO caused synergistic and time-dependent increases on the CYP1A biomarker both on CYP1A mRNA levels and on CYP1A enzyme activity, in accordance with an apparent delayed BaP elimination in the presence of CLO. These results indicate a toxicokinetic interaction between BaP and CLO on the CYP1A enzyme that delays metabolic clearance of BaP.

Metformin alleviates benzo[a]pyrene-induced alveolar injury by inhibiting necroptosis and protecting AT2 cells

Exposure to benzo[a]pyrene (B[a]P) has been linked to lung injury and carcinogenesis. Airway epithelial cells express the B[a]P receptor AHR, so B[a]P is considered to mainly target airway epithelial cells, whereas its potential impact on alveolar cells remains inadequately explored. Metformin, a first-line drug for diabetes, has been shown to exert anti-inflammatory and tissue repair-promoting effects under various injurious conditions. Here, we explored the effect of chronic B[a]P exposure on alveolar cells and the impact of metformin on B[a]P-induced lung injury by examining the various parameters including lung histopathology, inflammation, fibrosis, and related signal pathway activation. MLKL knockout (Mlkl-/-) and AT2-lineage tracing mice (SftpcCre-ERT2;LSL-tdTomatoflox+/-) were used to delineate the role of necroptosis in B[a]P-induced alveolar epithelial injury and repair. Mice receiving weekly administration of B[a]P for 6 weeks developed a significant alveolar damaging phenotype associated with pulmonary inflammation, fibrosis, and activation of the necroptotic cell death pathway. These effects were significantly relieved in MLKL null mice. Furthermore, metformin treatment, which were found to promote AMPK phosphorylation and inhibit RIPK3, as well as MLKL phosphorylation, also significantly alleviated B[a]P-induced necroptosis and lung injury phenotype. However, the protective efficacy of metformin was rendered much less effective in Mlkl null mice or by blocking the necroptotic pathway with RIPK3 inhibitor. Our findings unravel a potential protective efficacy of metformin in mitigating the detrimental effects of B[a]P exposure on lung health by inhibiting necroptosis and protecting AT2 cells.

Differential effects of benzo[a]pyrene exposure on glutathione and purine metabolism in keratinocytes: Dose-dependent and UV co-exposure effects

Polycyclic aromatic hydrocarbons with the key substance benzo[a]pyrene (B[a]P) are widespread pollutants in the environment and at working places. Nonetheless, the exact underlying mechanisms of toxicological effects caused by B[a]P especially in absence and presence of UV irradiation remain uncertain. This study examines variations in exposure conditions: low B[a]P (4 nM), low B[a]P + UV and high B[a]P (4 μM), selected based on pertinent cytotoxicity assessments. Following cell viability evaluations post-treatment with varied B[a]P concentrations and UV irradiation, the identified concentrations underwent detailed metabolomic analysis via gas chromatography-mass spectrometry. Subsequently, resulting changes in metabolic profiles across these distinct exposure groups are comprehensively compared. Chemometric analyses showed modest regulation of metabolites after low B[a]P exposure compared to control conditions. High B[a]P and low B[a]P + UV exposure significantly increased regulation of metabolic pathways, indicating that additional UV irradiation plus low B[a]P is as demanding for the cells as higher B[a]P treatment alone. Further analysis revealed exposure-dependent regulation of glutathione-important for oxidative defence-and purine metabolism-important for DNA base synthesis. Only after low B[a]P, oxidative defence appeared to be able to compensate for B[a]P-induced perturbations of the oxidative homeostasis. In contrast, purine metabolism already responded towards adversity at low B[a]P. The metabolomic results give an insight into the mechanisms leading to the toxic response and confirm the strong effects of co-exposure on oxidative defence and DNA repair in the model studied.

Study on epigenotoxicity, sex hormone synthesis, and DNA damage of benzo[a]pyrene in the testis of male Ruditapes philippinarum

Research on the mechanisms of reproductive toxicity caused by persistent organic pollutants (POPs) in marine animals has received significant attention. One group of typical POPs, called polycyclic aromatic hydrocarbons (PAHs), has been found to cause various reproductive toxicities in aquatic organisms, including epigenotoxicity, reproductive endocrine disruption, DNA damage effects and other reproductive toxicity, thereby affecting gonadal development. Interestingly, male aquatic animals are more susceptible to the disturbance and toxicity of environmental pollutants. However, current studies primarily focus on vertebrates, leaving a large gap in our understanding of the reproductive toxicity and mechanisms of PAHs interference in marine invertebrates. In this study, male Ruditapes philippinarum was used as an experimental subject to investigate reproduction-related indexes in clams under the stress of benzo[a]pyrene (B[a]P) at different concentrations (0, 0.8, 4 and 20 μg/L) during the proliferative, growth, maturity, and spawning period. We analyzed the molecular mechanisms of reproductive toxicity caused by PAHs in marine bivalves, specifically epigenotoxicity, reproductive endocrine disruption, and gonadal damage-apoptotic effect. The results suggest that DNA methylation plays a crucial role in mediating B[a]P-induced reproductive toxicity in male R. philippinarum. B[a]P may affect sex hormone levels, impede spermatogenesis and testis development in clams, by inhibiting the steroid hormone synthesis pathway and downregulating genes critical for cell proliferation, testis development, and spermatid expulsion. Moreover, the spermatids of male R. philippinarum were severely impaired under the B[a]P stress, leading to reduced reproductive performance in the clams. These findings contribute to a better understanding of the reproductive toxicity response of male marine invertebrates to POPs stress.

Mechanisms and targeted reversion/prevention of hepatic fibrosis caused by the non-hereditary toxicity of benzo(a)pyrene

The effect of long term exposure to low concentrations of environmental pollutants on hepatic disorders is a major public health concern worldwide. Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants. In recent years, an increasing number of studies have focused on the deleterious effects of low concentrations of PAHs in the initiation or exacerbation of the progression of chronic liver disease. However, the underlying molecular mechanisms and effective intervention methods remain unclear. Here, we found that in hepatocytes, a low concentration of benzo(a)pyrene (B[a]P, an indicator of PAHs) chronic exposure continuously activated 14-3-3η via an epigenetic accumulation of DNA demethylation. As a "switch like" factor, 14-3-3η activated its downstream PI3K/Akt signal, which in turn promoted vascular endothelial growth factor (VEGF) production and secretion. As the characteristic fibrogenic paracrine factor regulated by B[a]P/14-3-3η, VEGF significantly induced the neovascularization and activation of hepatic stellate cells, leading to the development of hepatic fibrosis. Importantly, targeted 14-3-3η by using its specific inhibitor invented by our lab could prevent B[a]P-induced hepatic fibrosis, and could even reverse existent hepatic fibrosis caused by B[a]P. The present study not only revealed novel mechanisms, but also proposed an innovative approach for the targeted reversion/prevention of the harmful effects of exposure to PAHs on chronic liver disease.

Resveratrol and quercetin protect from Benzo(a)pyrene-induced autophagy in retinal pigment epithelial cells

PURPOSE

This study aims to investigate the role of Resveratrol (RES) and quercetin (QR) treatments against Benzo(a)pyrene (B(a)p)-induced autophagy in retinal pigment epithelial cells.

METHODS

The IC50 doses of B(a)p, RES and QR in retinal pigment epithelial cells were determined by MTT assay and the relevant agents were administered singly or in combinations to ARPE-19 cells for 24 h. Occurrence of autophagy in the cells was verified by detection of autophagosomes using fluorescence microscope. Also, the mRNA expression levels of LC3 and Beclin 1 genes were analyzed by RT-PCR to collect further data on autophagy. Caspase-3 and IL-1β levels in lysed cells were analyzed by ELISA.

RESULTS

Autophagosomes were detected in B(a)p-treated ARPE-19 cell lines, as well as a 1.787-fold increase in LC3 mRNA expression levels. No autophagosome occurred in RES and QR treatments, and a significant decrease in their percentage amounts were observed in B(a)p + RES and B(a)p + QR. The mRNA expression levels of LC3 and Beclin 1 also supported these findings. B(a)p had no effect on Caspase-3 levels in ARPE-19 cells, but combined with RES and QR, it increased Caspase-3 levels significantly.IL-1β levels were higher in B(a)p, B(a)p + QR, B(a)p + RES, RES and QR than control group. This rise in IL-1β levels was correlated with suppression of mRNA expression levels of Beclin 1.

CONCLUSION

B(a)p exposure caused autophagy in ARPE-19 cells, but did not induce apoptosis. RES and QR treatments prevented B(a)p-induced autophagy. Therefore, RES and QR treatments showed protective effect against potential degenerative diseases caused by chronic exposure to B(a)p.

Interference mechanism of benzo[a]pyrene exposure on the taste substance metabolisms in Ruditapes philippinarum

Aquatic animals are popular for their unique umami and high-quality protein. However, under the realistic background of increasing marine pollution, whether it affects the aquatic animal tastes, and what the interference mechanism is still remains unknown. Benzo[a]pyrene (B[a]P) is a typical Polycyclic aromatic hydrocarbons (PAHs) with high toxicity. In this study, we investigated the effects of B[a]P (0, 0.8, 4 and 20 μg/L) on the content and taste evaluation of Ruditapes philippinarum taste substances, and clarified the interference mechanism of B[a]P on taste substance metabolisms with transcriptome analysis. The results demonstrated that B[a]P significantly altered the contents and taste activity values (TAVs) of free amino acids (FAAs), 5'-nucleotides, organic acids, flavor peptides, organic bases, sugars and inorganic ions, as well as the gene expressions within their synthesis and decomposition, indicating that B[a]P affected these taste substance contents by interfering with their metabolisms, thereby changing the clam tastes (decreases of umami and sweetness, and increase of bitter taste). This study provided scientific basis for quality assurance of bivalve cultivation and control of marine pollution.

Mediation of association between benzo[a]pyrene exposure and lung cancer risk by plasma microRNAs: A Chinese case-control study

Epidemiologic studies have reported the positive relationship of benzo[a]pyrene (BaP) exposure with the risk of lung cancer. However, the mechanisms underlying the relationship is still unclear. Plasma microRNA (miRNA) is a typical epigenetic biomarker that was linked to environment exposure and lung cancer development. We aimed to reveal the mediation effect of plasma miRNAs on BaP-related lung cancer. We designed a lung cancer case-control study including 136 lung cancer patients and 136 controls, and measured the adducts of benzo[a]pyrene diol epoxide-albumin (BPDE-Alb) and sequenced miRNA profiles in plasma. The relationships between BPDE-Alb adducts, normalized miRNA levels and the risk of lung cancer were assessed by linear regression models. The mediation effects of miRNAs on BaP-related lung cancer were investigated. A total of 190 plasma miRNAs were significantly related to lung cancer status at Bonferroni adjusted P < 0.05, among which 57 miRNAs showed different levels with |fold change| > 2 between plasma samples before and after tumor resection surgery at Bonferroni adjusted P < 0.05. Especially, among the 57 lung cancer-associated miRNAs, BPDE-Alb adducts were significantly related to miR-17-3p, miR-20a-3p, miR-135a-5p, miR-374a-5p, miR-374b-5p, miR-423-5p and miR-664a-5p, which could in turn mediate a separate 42.2%, 33.0%, 57.5%, 36.4%, 48.8%, 32.5% and 38.2% of the relationship of BPDE-Alb adducts with the risk of lung cancer. Our results provide non-invasion biomarker candidates for lung cancer, and highlight miRNAs dysregulation as a potential intermediate mechanism by which BaP exposure lead to lung tumorigenesis.

Differential eigengene network analysis reveals benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin consensus regulatory network in human liver cell line HepG2

Aryl hydrocarbon receptor (AHR) is one of the main mediators of the toxic effects of benzo[a]pyrene (BaP) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, a vast number of BaP- and TCDD-affected genes may suggest a more complex transcriptional regulatory network driving common adverse effects of these two chemicals. Unlike TCDD, BaP is rapidly metabolized in the liver, yielding products with a questionable ability to bind and activate AHR. In this study, we used transcriptomics data from the BaP- and TCCD-exposed human liver cell line HepG2, and performed differential eigengene network analysis to understand the correlation among genes and to untangle the common regulatory mechanism in the action of BaP and TCDD. The genes were grouped into 11 meta-modules with an overall preservation of 0.72 and were also segregated into three consensus time clusters: 12, 24, and 48 h. The analysis showed that the consensus genes in each time cluster were either directly regulated by the AHR or the AHR-TF interactions. Some TFs form a direct physical interaction with AHR such as ESR1, FOXA1, and E2F1, whereas others, including CTCF, RXRA, FOXO1, CEBPA, CEBPB, and TP53 show an indirect interaction with AHR. The analysis of biological processes (BPs) identified unique and common BPs in BaP and TCDD samples, with DNA damage response detected in all three time points. In summary, we identified a consensus transcriptional regulatory network common for BaP and TCDD consisting of direct AHR targets and AHR-TF targets. This analysis sheds new light on the common mechanism of action of a genotoxic (BaP) and non-genotoxic (TCDD) chemical in liver cells.

Benzo[a]pyrene exposure affects colorectal cancer susceptibility by regulating ERβ-mediated LINC02977 transcription

Environmental pollutants known as polycyclic aromatic hydrocarbons (PAHs) are produced through the incomplete combustion of organic material. While PAHs have been investigated as genotoxicants, they can also operate through nongenotoxic pathways in estrogen-dependent malignancies, such as breast, cervical and ovarian cancer. However, whether PAHs induce colorectal cancer (CRC) risk through estrogenic effects is still illusive. Here, we systematically investigated the abnormal expression and activation of estrogen receptor beta (ERβ) regulated by PAHs in CRC as well as the underlying mechanisms of ERβ-mediated CRC risk. Based on the 300 plasma samples from CRC patients and healthy controls detected by GC-MS/MS, we found that the plasma concentrations of benzo[a]pyrene (BaP) were significantly higher in CRC cases than in healthy controls, with significant estrogenic effects. Moreover, histone deacetylase 2 (HDAC2)-induced deacetylation of the promoter decreases ERβ expression, which is associated with poor overall survival and advanced tumor stage. The study also revealed that BaP and estradiol (E2) had different carcinogenic effects, with BaP promoting cell proliferation and inhibiting apoptosis, while E2 had the opposite effects. Additionally, this study mapped ERβ genomic binding regions by performing ChIP-seq and ATAC-seq and identified genetic variants of rs1411680 and its high linkage disequilibrium SNP rs6477937, which were significantly associated with CRC risk through meta-analysis of two independent Chinese population genome-wide association studies comprising 2,248 cases and 3,173 controls and then validation in a large-scale European population. By integrating data from functional genomics, we validated the regulatory effect of rs6477937 as an ERβ binding-disrupting SNP that mediated allele-specific expression of LINC02977 in a long-range chromosomal interaction manner, which was found to be highly expressed in CRC tissues. Overall, this study suggests that the different active effects on ERβ by PAHs and endogenous E2 may play a crucial role in the development and progression of CRC and highlights the potential of targeting ERβ and its downstream targets for CRC prevention and treatment.

Ameliorative potential of synbiotic combination of Lactobacillus sp. and polyphenols against Benzo[a]pyrene-induced toxicity in Caco-2 cell line

Exposure to benzo[a]pyrene (B[a]P), a major global food safety concern, is often associated with increasing incidence of colorectal cancers. This in-vitro study was focused on the identification of potential B[a]P-adsorbing Lactobacillus strains and evaluation of the ameliorative effect of synbiotic combination of selected Lactobacillus sp. and polyphenols (quercetin or resveratrol) against B[a]P-induced intestinal toxicity in Caco-2 cells. Preliminary studies lead to the selection of Lactiplantibacillus plantarum MTCC 25433 strain that showed 86% of B[a]P adsorption in 2 h as compared to L. rhamnosus GG that showed 74% of B[a]P adsorption. B[a]P adsorption by MTCC 25433 was reduced to 9%, 16% and 20% upon pre-treatment with SDS, NaIO4 and mutanolysin, attributing the involvement of cell wall proteins and polysaccharides in the adsorption. Additionally, peptidoglycan of both strains adsorbed >50% of B[a]P. In-vitro assays revealed that the selected LAB mitigated the B[a]P-induced epithelial cell damage. Among the polyphenols, quercetin, resveratrol and curcumin, varied in their potency to mitigate B[a]P-induced oxidative stress, with curcumin being least effective. Combinations of selected Lactobacillus sp. and polyphenols were more potent in averting B[a]P-induced toxicity via increase in GSH (17-30 %), SOD (50-88 %), catalase (19-45 %), and reduction in IL-8 secretion (14-28 %) and barrier dysfunction. Principal component analysis affirmed the superior potency of combination of L. plantarum MTCC 25433 and quercetin in averting B[a]P-induced toxicity. Overall, this study highlighted a novel promising strategy of synbiotic combination of Lactobacillus sp. and polyphenols (quercetin or resveratrol) in alleviating the B[a]P-induced toxicity in intestinal epithelial cells.

Qufeng Xuanbi Formula inhibited benzo[a]pyrene-induced aggravated asthma airway mucus secretion by AhR/ROS/ERK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Excessive secretion of airway mucus may be an important pathological factor of air pollution-induced acute asthma attacks. Treatment of airway mucus hypersecretion improves asthma aggravated by air pollutants. Qufeng Xuanbi Formula (QFXBF) has been used to treat asthma for more than 30 years. However, whether QFXBF inhibits asthmatic mucus secretion exacerbated by air pollutants has not yet been established.

AIM OF THE STUDY

This study aimed to evaluate the effect of QFXBF on airway mucus secretion and the mechanism of action in an air pollutant benzo[a]pyrene (BaP)-induced mouse model of aggravated asthma.

MATERIALS AND METHODS

Ovalbumin (OVA) and BaP co-exposure were used to establish the aggravated asthma model. The average enhanced pause (Penh), serum OVA-specific IgE, and changes in lung histopathology were determined. 16HBE cells exposed to BaP, treatment with QFXBF, arylhydrocarbon receptor (AhR) signal antagonist SR1, reactive oxygen species (ROS) antagonist NAC, or extracellular signal-regulated kinase (ERK1/2) signal antagonist U0126 were established to investigate the effect of QFXBF on BaP-induced mucus secretion and its target. The mRNA and protein expression levels of MUC5AC in the lung tissue and 16HBE cells were examined. We also studied the effect of QFXBF on ROS production. Finally, the protein expression of AhR, phospho-extracellular signal-regulated kinases (p-ERK1/2), and ERK1/2 in 16HBE cells and lung tissues was determined by western blotting.

RESULTS

Administration of QFXBF significantly alleviated the pathological symptoms, including Penh, serum OVA-specific IgE, and changes in lung histopathology in a BaP-induced mouse model of aggravated asthma. QFXBF inhibited MUC5AC expression in asthmatic mice and 16HBE cells exposed to BaP. ROS production, AhR expression, and ERK1/2 phosphorylation were significantly increased in BaP-induced asthmatic mice and 16HBE cells. Signaling pathway inhibitors StemRegenin 1 (SR1), NAC, and U0126 significantly inhibitedBaP-induced MUC5AC expression in 16HBE cells. SR1 reversed Bap-induced ROS production and ERK activation, and NAC inhibited Bap-induced ERK activation. In addition, QFXBF regulated AhR signaling, inhibited ROS production, reversed ERK activation, and downregulated mucus secretion to improve asthma aggravated by air pollutant BaP.

CONCLUSIONS

QFXBF can ameliorate mucus secretion in BaP-induced aggravated asthmatic mice and 16HBE cells, and the specific mechanism may be related to the inhibition of the AhR/ROS/ERK signaling pathway.

Regulation of Benzo[a]pyrene-Induced Hepatic Lipid Accumulation through CYP1B1-Induced mTOR-Mediated Lipophagy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is caused by lipid accumulation within the liver. The pathogenesis underlying its development is poorly understood. Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon and a group 1 carcinogen. The aryl hydrocarbon receptor activation by B[a]P induces cytochrome P450 (CYP) enzymes, contributing to hepatic lipid accumulation. However, the molecular mechanism through which the B[a]P-mediated induction of CYP enzymes causes hepatic lipid accumulation is unknown. This research was conducted to elucidate the role of CYP1B1 in regulating B[a]P-induced lipid accumulation within hepatocytes. B[a]P increased hepatic lipid accumulation, which was mitigated by CYP1B1 knockdown. An increase in the mammalian target of rapamycin (mTOR) by B[a]P was specifically reduced by CYP1B1 knockdown. The reduction of mTOR increased the expression of autophagic flux-related genes and promoted phagolysosome formation. Both the expression and translocation of TFE3, a central regulator of lipophagy, were induced, along with the expression of lipophagy-related genes. Conversely, enhanced mTOR activity reduced TFE3 expression and translocation, which reduced the expression of lipophagy-related genes, diminished phagolysosome production, and increased lipid accumulation. Our results indicate that B[a]P-induced hepatic lipid accumulation is caused by CYP1B1-induced mTOR and the reduction of lipophagy, thereby introducing novel targets and mechanisms to provide insights for understanding B[a]P-induced MASLD.

The Garlic Compound, Diallyl Trisulfide, Attenuates Benzo[a]Pyrene-Induced Precancerous Effect through Its Antioxidant Effect, AhR Inhibition, and Increased DNA Repair in Human Breast Epithelial Cells

Exposure to B[a]P, the most characterized polycyclic aromatic hydrocarbon, significantly increases breast cancer risk. Our lab has previously reported that diallyl trisulfide (DATS), a garlic organosulfur compound (OSC) with chemopreventive and cell cycle arrest properties, reduces lipid peroxides and DNA damage in normal breast epithelial (MCF-10A) cells. In this study, we evaluated the ability of DATS to block the B[a]P-induced initiation of carcinogenesis in MCF-10A cells by examining changes in proliferation, clonogenic formation, reactive oxygen species (ROS) formation, 8-hydroxy-2-deoxyguanosine (8-OHdG) levels, and protein expression of ARNT/HIF-1β, CYP1A1, and DNA POLβ. The study results indicate that B[a]P increased proliferation, clonogenic formation, ROS formation, and 8-OHdG levels, as well as increasing the protein expression of ARNT/HIF-1β and CYP1A1 compared to the control. Conversely, DATS/B[a]P co-treatment (CoTx) inhibited cell proliferation, clonogenic formation, ROS formation, and 8-OHdG levels compared to B[a]P alone. Treatment with DATS significantly inhibited (p < 0.0001) AhR expression, implicated in the development and progression of breast cancer. The CoTx also attenuated all the above-mentioned B[a]P-induced changes in protein expression. At the same time, it increased DNA POLβ protein expression, which indicates increased DNA repair, thus causing a chemopreventive effect. These results provide evidence for the chemopreventive effects of DATS in breast cancer prevention.

Toxic effects of polystyrene microbeads and benzo[α]pyrene on bioaccumulation, antioxidant response, and cell damage in goldfish Carassius auratus

Microplastics (MP) are harmful, causing stress in aquatic species and acting as carriers of hydrophobicity. In aquatic environments, benzo[α]pyrene (BaP) is an endocrine-disrupting chemical that accumulates in the body and causes toxic reactions in living organisms. We investigated the effects of single and combined microbead (MB) and BaP environments on goldfish antioxidant response and apoptosis. For 120 h, goldfish were exposed to single (MB10, MB100, and BaP5) and combined (MB10+BaP5 and MB100+BaP5) environments of 10 and 100 beads/L of 0.2 µm polystyrene MB and 5 µg/L BaP. We measured MB and BaP bioaccumulation as well as plasma parameters including ALT, AST, and glucose. The level of oxidative stress was determined by evaluating lipid peroxidation (LPO) and total antioxidant capacity (TAC) in plasma, as well as antioxidant-related genes for superoxide dismutase and catalase (SOD and CAT) and caspase-3 (Casp3) mRNA expression in liver tissue. The TUNEL assay was used to examine SOD in situ hybridization and apoptosis in goldfish livers. Except for the control group, plasma LPO levels increased at the end of the exposure period in all experimental groups. TAC increased up to 24 h of exposure and then maintained a similar level until the trial ended. SOD, CAT, and Casp3 mRNA expression increased substantially up to 120 h as the exposure concentration and time increased. The TUNEL assay revealed more signals and apoptotic signals in the combined exposure environments as a consequence of SOD in situ hybridization than in single exposure environments. These results suggest that combined exposure to toxic substances causes oxidative stress in organisms, which leads to apoptosis.

Benzo[a]pyrene disrupts LH/hCG-dependent mouse Leydig cell steroidogenesis through receptor/Gαs protein targeting

Steroidogenesis of gonadal cells is tightly regulated by gonadotropins. However, certain polycyclic aromatic hydrocarbons, including Benzo[a]pyrene (BaP), induce reproductive toxicity. Several existing studies have considered higher than environmentally relevant concentrations of BaP on male and female steroidogenesis following long-term exposure. Also, the impact of short-term exposure to BaP on gonadotropin-stimulated cells is understudied. Therefore, we evaluated the effect of 1 nM and 1 µM BaP on luteinizing hormone/choriogonadotropin (LH/hCG)-mediated signalling in two steroidogenic cell models, i.e. the mouse tumor Leydig cell line mLTC1, and the human primary granulosa lutein cells (hGLC) post 8- and 24-h exposure. Cell signalling studies were performed by homogeneous time-resolved fluorescence (HTRF) assay, bioluminescence energy transfer (BRET) and Western blotting, while immunostainings and immunoassays were used for intracellular protein expression and steroidogenesis analyses, respectively. BaP decreased cAMP production in gonadotropin-stimulated mLTC1 interfering with Gαs activation. Therefore, decrease in gonadotropin-mediated CREB phosphorylation in mLTC1 treated with 1 μM BaP was observed, while StAR protein levels in gonadotropin-stimulated mLTC1 cells were unaffected by BaP. Further, BaP decreased LH- and hCG-mediated progesterone production in mLTC1. Contrastingly, BaP failed to mediate any change in cAMP, genes and proteins of steroidogenic machinery and steroidogenesis of gonadotropin-treated hGLC. Our results indicate that short-term exposure to BaP significantly impairs steroidogenic signalling in mLTC1 interfering with Gαs. These findings could have a significant impact on our understanding of the mechanism of reproductive toxicity by endocrine disruptors.

In silico simulation of benzo[a]pyrene toxicity in the worm Caenorhabditiselegans

This study aimed to develop a toxicological screening tool using a virtual (in silico) population of Caenorhabditis elegans exposed to different concentrations of benzo[a]pyrene (BAP). The model used computational tools based on a previous study to simulate the life cycle and characteristics of C. elegans. The model was implemented in Python and adapted with fewer repetitions of simulations to reduce execution time. The toxicity function was based on in vivo data from previous studies, and the results of the model were compared with experimental results. The model showed good accuracy in reproducing the survival data of worms exposed to BAP since the lethal concentration for 50% (LC50) and the 95% confidence interval of exposed worms during 72 h was 77.92 μg/L (71.32-85.12 μg/L). The LC50 of the simulated data was 87.10 μg/L (76.13-99.85 μg/L). It was concluded that the in silico model can be a useful alternative to conventional in vivo testing methods, saving cost and time and addressing ethical concerns.

Prolonged exposure of environmental concentration benzo[a]pyrene promoted cancer stemness through AhR/PKA/SOX2 dependent pathway in small cell lung cancer

Benzo[a]pyrene (BaP) is commonly found in the environment as a result of incomplete combustion of organic materials and cigarette smoke. Epidemiological studies have consistently suggested that elderly smokers are at higher risk for small cell lung cancer (SCLC), with risks and clinical stages increasing with the intensity and duration of smoking. However, the underlying mechanism remains insufficiently investigated. Here, we established a positive correlation between smoking and BaP metabolite 3-hydroxybenzo[a]pyrene (3OH-BaP) in urine. The pooled standardized mean difference of urinary 3OH-BaP concentration for smokers versus nonsmokers was 5.18 (95 % CI 2.86-7.50). Clinical data suggested that smoking led to more lymph node metastasis, higher pathological N-stage, and worse overall survival in SCLC patients. We identified 75 genes that participate in BaP-associated cancer stemness of SCLC from Comparative Toxicogenomics Database and validated the expression of these candidate genes in SCLC patient samples. Protein kinase cAMP-activated catalytic subunit alpha (PRKACA) was found to be most upregulated in SCLC patients and in vitro experiments indicated that long-term exposure of SCLC cells to BaP, at the concentration equivalent to those detected in blood, increased PKA protein level. Further investigation revealed that PKA could directly interact with SOX2 and protect SOX2 from COP1-mediated ubiquitination and degradation. Upregulated SOX2 then contributed to the stemness and metastasis of SCLC cells while inhibition of aryl hydrocarbon receptor (AhR) signaling pathway abolished BaP induced PKA expression and downstream PKA/SOX2 axis. Our findings firstly pinpoint BaP exposure as a high-risk factor for SCLC and worse outcomes in patients, with the underlying mechanism being the activation of cancer stemness of SCLC via the AhR/PKA/SOX2 axis.

Immunomodulatory effect of Myrtenol on benzo (a) pyrene-induced lung cancer in Swiss albino mice via modulation of tumor markers, cytokines and inhibition of PCNA expression

Lung cancer is one of the most common cancers in men. Although many diagnostic and treatment regimens have been followed in the treatment for lung cancer, increasing mortality rate due to lung cancer is depressing and hence requires alternative plant based therapeutics with with less side-effects. Myrtenol exhibits anti-inflammatory and antioxidant properties. Hence we intended to study the effect of Myrtenol on B(a)P-induced lung cancer. Our study showed that B(a)P lowered hematological count, decreased phagocyte and avidity indices, nitroblue tetrazolium (NBT) reduction, levels of immunoglubulins, antioxidant levels, whereas Myrtenol treatment restored them back to normal levels. On the other hand, xenobiotic and liver dysfunction marker enzymes and pro-inflammatory cytokines were elevated on B(a)P exposure, which retuned back to normal by Myrtenol. This study thus describes the immunomodulatory and antioxidant effects of Myrtenol on B[a]P-induced immune destruction.

6-Shogaol prevents benzo (A) pyrene-exposed lung carcinogenesis via modulating PRDX1-associated oxidative stress, inflammation, and proliferation in mouse models

In this study, we have investigated the chemopreventive role of 6-shogaol (6-SGL) on benzopyrene (BaP) exposed lung carcinogenesis by modulating PRDX1-associated oxidative stress, inflammation, and proliferation in Swiss albino mouse models. Mice were exposed to BaP (50 mg/kg b.wt) orally twice a week for four consecutive weeks and maintained for 16 weeks, respectively. 6-SGL (30 mg/kg b.wt) were orally administered to mouse 1 h before BaP exposure for 16 weeks. After the experiment's termination, 6-SGL (30 mg/kg b.wt) prevented the loss in body weight, increased lung weight, and the total number of tumors in the mice. Moreover, we observed that 6-SGL treatment reverted the activity of BaP-induced lipid peroxidation and antioxidants in mice. Also, 6-SGL impeded the phosphorylation of MAPK family proteins such as Erk1, p38, and Jnk1 in BaP-exposed mice. PRDX1 is an essential antioxidant protein that scavenges toxic radicals and enhances several antioxidant proteins. Overexpression of PRDX1 substantially inhibits MAPKs, proliferation, and inflammation signaling axis. Hence, PRDX1 is thought to be a novel targeting protein for preventing BaP-induced lung cancer. In this study, we have obtained the 6-SGL treatment in a mouse model that reverted BaP-induced depletion of PRDX1 expression. Moreover, pretreatment of 6-SGL (30 mg/kg b.wt) significantly inhibited enhanced proinflammatory cytokines (TNF-α, IL-6, IL-β1, IL-10) and proliferative markers (Cyclin-D1, Cyclin-D2, and PCNA) in BaP-exposed mice. The histopathological studies also confirmed that 6-SGL effectively protected the cells with less damage. Thus, the study demonstrated that 6-SGL could be a potential phytochemical and act as a chemopreventive agent in BaP-induced lung cancer by enhancing PRDX1 expression.

Air pollution in major Polish cities in the period 2005-2021: Intensity, effects and attempts to reduce it

Air quality in Poland is among the lowest in Europe due to high emissions of harmful substances. This causes the development of diseases and leads to a high number of premature deaths. Particularly high pollution occurs in parts of urban areas. The most serious problem is unregulated emissions from buildings and vehicles. That is why it is so important to take action to improve air quality at the local level. The study assessed changes in the concentrations of NO2, O3, PM10, PM2.5 and benzo(a)pyrene in 11 major Polish cities between 2005 and 2021. In 2021 average levels were: NO2 - 25 μg/m3, O3 - 45 μg/m3, PM10 - 26 μg/m3, PM2.5 -17 μg/m3, benzo(a)pyrene - 2.1 ng/m3. The highest exceedances of WHO standards over the studied period were for PM2.5, followed by NO2 and PM10. The annual average levels fell by 17% for NO2 and by 18% for PM10 between 2005 and 2021, and by 34% for PM2.5 and 27% for benzo(a)pyrene between 2010 and 2021. The most polluted cities are Kraków, Katowice and Łódź. The highest concentrations of pollutants typically occurred in 2006 and 2011, the lowest in 2020. Strategic documents and programmes that formulate objectives for reducing emissions and improving air quality were evaluated. Policy documents enable numerous measures to improve air quality. Plans are not always effectively implemented due to a lack of formal tools and financial resources.

Saffron stigma extract and crocin play an important neuroprotective role in therapeutic measures against benzo[a]pyrene-induced behavioral alterations in zebrafish

Saffron is a well-known expensive spice, which has many pharmacological properties against a variety of ailments. Saffron stigma and leaf contain apocarotenoids and bioactive phytochemicals having therapeutic potential against human disorders. Polycyclic aromatic hydrocarbons (PAHs) are one of the most common toxins in today's aquatic environment. Benzo[a]pyrene (B[a]P), a high molecular weight PAHs prototype, and reported as a potent neurotoxicant, which is profoundly contaminating the environment. The present study investigated the therapeutic efficacy of Saffron stigma extracts and crocin, on B[a]P-induced behavioral changes, altered antioxidant activities, and neurodegeneration in zebrafish. The behavioral responses monitored through the light-dark preference test and novel tank diving test suggested that B[a]P treated zebrafish group showed alteration in anxiolytic-like behavior. Animals exhibited their native behavior when treated alone with Saffron Stigma Extract (SSE) and crocin, an apocarotenoid which also reduced the altered behavior induced by B[a]P. The SSE and crocin stimulated the antioxidant activities with an accumulation of reduced glutathione and catalase enzymes, indicating a protective role against B[a]P-induced oxidative stress and behavioral deficits. The histopathological studies showed the percentage change of pyknotic cell counts in the Periventricular Gray Zone region of the Optic Tectum was 1.74 folds high in B[a]P treated animals as compared to control. Furthermore, the treatment of SSE and crocin reduced the pyknosis process induced by B[a]P-mediated neurodegeneration, possibly due to a better protective mechanism. Future studies may reveal the detailed mechanisms of action of potent SSE and crocin like bioactive compounds having neuroprotective potentials against neurodegenerative diseases.

Study on reproductive endocrine disturbance and DNA damage mechanism of female Ruditapes philippinarum under Benzo[a]pyrene stress

The reproductive toxicity of polycyclic aromatic hydrocarbons (PAHs) in aquatic organisms has attracted increasing attention from scholars. Currently, research in this field primarily focuses on vertebrates such as zebrafish and other model species. However, there is still a significant knowledge gap in the toxicity of PAHs to invertebrates and its potential mechanisms. Benzo[a]pyrene (B[a]P) is one of the most representative PAHs. In this study, female Ruditapes philippinarum (R. philippinarum) was treated with B[a]P concentrations of 0, 0.8, 4, and 20 μg/L to investigate reproductive indicators in the proliferative, growth, mature, and spawn stages. Transcriptomics was used to investigate the expression of genes associated with the reproductive endocrine system, DNA repair, autophagy, apoptosis, and ovarian development at different reproductive stages. Our results suggested that B[a]P disrupted the endocrine system by interfering with the production of steroid hormones and the transmission of estrogen signals in female R. philippinarum. The structure of the ovarian DNA duplex is severely damaged under the stress of B[a]P, and a series of cellular responses caused by DNA damage are also interfered. Additionally, we observed a reduction in the gonadosomatic index (GSI) and mature oocytes numbers after B[a]P exposed. Tissue section indicated that severe damage to the ovarian structure at mature and spawn stages. In conclusion, this study combined transcriptomic and toxicological to explore the negative effects on ovarian development induced by B[a]P, focusing on reproductive endocrine disturbance and DNA damage.

Concentration and probabilistic health risk assessment of benzo(a)pyrene in extra virgin olive oils supplied in Tehran, Iran

One hundred and sixteen samples of extra virgin olive oils (VOOs) from markets of Tehran were analyzed by high-performance liquid chromatography (HPLC) to detect the amount of benzo (a)pyrene. The values of LOD and LOQ were calculated as 0.03 and 0.05 µg/kg, respectively. The concentration of benzo (a) pyrene was from 0.03 to 0.95 µg/kg. The results indicate that the levels of benzo (a) pyrene are lower than the limits approved. Target Hazard quotient (THQ) and Margin of Exposure (MOE) were estimated. The mean of THQ for adults and children was 0.0006 and 0.0028 and also mean of MOE for adults and children was 43,503 and 9438, respectively. The probabilistic health risk shows that THQ is less than 1 value; hence consumers are not at non-cancer risk. The mean of MOE value for adults was more than 10,000 but for children was less than 10,000. Hence, children are at health risk borderline.

AHR-mediated DNA damage contributes to BaP-induced cardiac malformations in zebrafish

Benzo[a]pyrene (BaP) is a representative polycyclic aromatic hydrocarbon widely present in the environment. We previously reported that the aryl hydrocarbon receptor (AHR) mediates BaP-induced apoptosis and cardiac malformations in zebrafish embryos, but the underlying molecular mechanisms were unclear. Since BaP is a mutagenetic compound, we hypothesize that BaP induces apoptosis and heart defects via AHR-mediated DNA damage. In this study, zebrafish embryos were exposed to BaP at a concentration of 0.1 μM from 2 to 72 h post fertilization, either with or without inhibitors/agonists. AHR activity and levels of reactive oxygen species (ROS) were examined under a fluorescence microscope. mRNA expression levels were quantified by qPCR. DNA damage and apoptosis were detected by immunofluorescence. Our findings revealed that BaP exposure significantly increased BPDE-DNA adducts, mitochondrial damage, apoptosis and heart defects in zebrafish embryos. These effects were counteracted by inhibiting AHR/cyp1a1 using pharmaceutical inhibitors or genetic knockdown. Furthermore, we observed that spironolactone, an antagonist of nucleotide excision repair (NER), significantly enhanced BaP-induced BPDE-DNA adducts, mitochondrial damage, apoptosis and heart malformation rates. Conversely, SRT1720, a SIRT1 agonist, reduced the adverse effects of BaP. Supplementation with spironolactone also enhanced γ-H2AX signals in the heart of zebrafish embryos exposed to BaP. Additional experiments demonstrated that BaP suppressed the expression of SIRT1. We further established that AHR, when activated by BaP, directly inhibited SIRT1 transcription, leading to downregulation of XPC and XPA, which are essential NER genes involved in the recognition and verification steps of the NER process. Taken together, our results indicate that AHR mediates BaP-induced DNA damage in the heart of zebrafish embryos by inducing BPDE-DNA adduct formation via the AHR/Cyp1a1 signalling pathway, as well as suppressing NER via AHR-mediated inhibition of SIRT1.

Combination therapy of metformin and atorvastatin against benzopyrene-induced lung cancer via inflammatory signaling pathway

The most prevalent cause of lung cancer is smoking tobacco, but exposure to second hand smoke, air pollution, and certain chemicals and substances at work can also raise the risk of disease. In this study, we scrutinized the chemoprotective effect of the metformin and atorvastatin combination against benzo[a]pyrene (BaP)-induced lung cancer in mice of Swiss albino. BaP (50 mg/kg) was used for induction of lung cancer and mice were treated with metformin, atorvastatin or their combination. Metformin + atorvastatin combination significantly (p< 0.001) improved the body weight, liver weight, suppressed the lung weight and tumor incidence and altered the levels of immunocompetent cells, polyamines, lung tumor markers, lung parameters and antioxidant parameters, respectively. Metformin + atorvastatin combination also suppressed cytokines levels, inflammatory parameters and caspase parameters. On the basis of the results, we can conclude that metformin + atorvastatin combination remarkably suppressed lung cancer via the inflammatory pathway.

Environmental carcinogen benzo[a]pyrene alters neutral lipid storage via a cyp-35A2 mediated pathway in Caenorhabditis elegans

Polycyclic aromatic hydrocarbons (PAHs), in particular benzo [a]pyrene (BaP), have been identified as carcinogenic components of tobacco smoke. In mammals, the toxicological response to BaP-diol-epoxide is driven by cytochrome P450 (CYP1A1), a pathway which is absent in Caenorhabditis elegans. In contrast, in worms prominently the CYP-35 enzyme family seems to be induced after BaP exposure. In C. elegans, BaP exposure reduces the accumulation of lysosomal neutral lipids in a dose dependent manner and the deletion of cyp-35A2 results in a significant elevation of neutral lipid metabolism. A cyp-35A2:mCherry;unc-47:GFP dual-labelled reporter strain facilitated the identification of three potential upstream regulators that drive BaP metabolism in worms, namely elt-2, nhr-49 and fos-1. This newly described reporter line is a powerful resource for future large-scale RNAi regarding toxicology and lipid metabolism screens.

Up-regulation of RNA m6A methyltransferase like-3 expression contributes to arsenic and benzo[a]pyrene co-exposure-induced cancer stem cell-like property and tumorigenesis

While arsenic or BaP alone exposure can cause lung cancer, studies showed that arsenic plus BaP co-exposure displays a significantly stronger lung tumorigenic effect. However, the underlying mechanism has not been well understood. Studies showed that RNA molecules are chemically modified. The most frequently occurring RNA modification in eukaryotic messenger RNAs is the N6-methyladenosine (m6A) methylation. This study aimed to determine whether arsenic plus BaP exposure alters RNA m6A methylation and its role in lung tumorigenic effect of arsenic plus BaP exposure. Human bronchial epithelial cells transformed by exposure to arsenic or BaP alone, and arsenic plus BaP and mouse xenograft tumorigenesis models were used in this study. It was found that arsenic plus BaP exposure-transformed cells have significantly higher levels of RNA m6A methylation than arsenic or BaP alone exposure-transformed human bronchial epithelial cells. Western blot analysis showed that arsenic plus BaP exposure greatly up-regulates the m6A writer methyltransferase like-3 (METTL3) expression levels in cultured cells and mouse lung tissues. METTL3 knockdown in cells transformed by arsenic plus BaP exposure drastically reduced their RNA m6A methylation levels. Functional studies revealed that METTL3 knockdown in cells transformed by arsenic plus BaP exposure greatly reduces their anchorage-dependent and -independent growth, cancer stem cell characters and tumorigenesis. The findings from this study suggest that arsenic plus BaP co-exposure causes epitranscriptomic dysregulation, which may contribute significantly to arsenic plus BaP co-exposure-caused synergistic lung tumorigenic effect.

Evaluation of amino acid profile by targeted metabolomics in the eukaryotic model under exposure of benzo[a]pyrene as the exclusive stressor

Amino acids (AAs) are a class of important metabolites in metabolomics methodology that investigates metabolite changes in a cell, tissue, or organism for early diagnosis of diseases. Benzo[a]pyrene (BaP) is considered a priority contaminant by different environmental control agencies because it is a proven carcinogenic compound for humans. Therefore, it is important to evaluate the BaP interference in the metabolism of amino acids. In this work, a new amino acid extraction procedure (derivatized with propyl chloroformate/propanol) using functionalized magnetic carbon nanotubes was developed and optimized. A hybrid nanotube was used followed by desorption without heating, and excellent extraction of analytes was obtained. After exposure of Saccharomyces cerevisiae, the BaP concentration of 25.0 μmol L-1 caused changes in cell viability, indicating metabolic changes. A fast and efficient GC/MS method using a Phenomenex ZB-AAA column was optimized, enabling the determination of 16 AAs in yeasts exposed or not to BaP. A comparison of AA concentrations obtained in the two experimental groups showed that glycine (Gly), serine (Ser), phenylalanine (Phe), proline (Pro), asparagine (Asn), aspartic acid (Asp), glutamic acid (Glu), tyrosine (Tyr), and leucine (Leu) statistically differentiated, after subsequent application of ANOVA with Bonferroni post-hoc test, with a confidence level of 95%. This amino acid pathway analysis confirmed previous studies that revealed the potential of these AAs as toxicity biomarker candidates.

Uncovering SOD3 and GPX4 as new targets of Benzo[α]pyrene-induced hepatotoxicity through Metabolomics and Chemical Proteomics

Benzo[α]pyrene (Bap) is recognized as a ubiquitous environmental pollutant among the polycyclic aromatic hydrocarbons (PAHs) class. Previous studies have shown that the hepatotoxicity of Bap is mainly caused by its metabolites, although it remains unclear whether Bap itself induces such damage. This study integrated metabolomics and chemical proteomics approaches to comprehensively identify the potential target proteins affected by Bap in liver cells. The results from the metabolomics showed that the significant changed metabolites were related with cellular redox homeostasis. CEllular Thermal Shift Assay (CETSA) showed that Bap induced protein thermal displacement of superoxide dismutase 3 (SOD3) and glutathione peroxidase 4 (GPX4), which are closely related to oxidative homeostasis. Further validation through in vitro CETSA and drug affinity response target stability (DARTS) revealed that Bap directly affected the stability of SOD3 and GPX4 proteins. The binding affinities of Bap to the potential target proteins were further evaluated using molecular docking, while the isothermal titration calorimetry (ITC) interaction measurements indicated nanomolar-level Kd values. Importantly, we found that Bap weakened the antioxidant capacity by destroying the activities of SOD3 and GPX4, which provided a new understanding of the mechanism of hepatotoxicity induced by Bap. Moreover, our provided workflow integrating metabolomics and label-free chemical proteomics, can be regarded as a practical way to identify the targets and inter-mechanisms for the various environmental compounds.

Ameliorative effects of Bifidobacterium longum peptide-1 on benzo(α)pyrene induced oxidative damages via daf-16 in Caenorhabditis elegans

Oxidative stress is implicated in numerous diseases, with benzo(α)pyrene (BaP) known for causing substantial oxidative damage. Bifidobacterium longum (B. longum) is recognized as an antioxidant bacterium for certain hosts, yet its influence on oxidative damages instigated by BaP remains undetermined. In our study, we introduced various strains of Caenorhabditis elegans (C. elegans) to BaP to trigger oxidative stress, subsequently treating them with different forms of B. longum to evaluate its protective effects. Additionally, we explored the role of daf-16 in this context. Our findings indicated that in wild-type N2 C. elegans, B. longum-even in the form of inactivated bacteria or bacterial ultrasonic lysates (BULs)-significantly extended lifespan. BaP exposure notably decreased lifespan, superoxide dismutase (SOD) activity, and motility, while simultaneously down-regulating the expression of reactive oxygen species (ROS)-associated genes (sod-3, sek-1, cat-1) and daf-16 downstream genes (sod-3, ctl-2). However, it significantly increased the ROS level, malondialdehyde (MDA) content, and lipofuscin accumulation and up-regulated another daf-16 downstream gene (clk-1) (P <0.05). Interestingly, when further treated with B. longum peptide-1 (BLP-1), opposite effects were observed, and all the aforementioned indices changed significantly. In the case of RNAi (daf-16) C. elegans, BaP exposure significantly shortened the lifespan (P <0.05), which was only slightly prolonged upon further treatment with BLP-1. Furthermore, the expression of daf-16 downstream genes showed minor alterations in RNAi C. elegans upon treatment with either BaP or BLP-1. In conclusion, our findings suggest that B. longum acts as a probiotic for C. elegans. BLP-1 was shown to safeguard C. elegans from numerous oxidative damages induced by BaP, but these protective effects were contingent upon the daf-16 gene.

Estradiol and Benzo[a]pyrene Co-Exposure Contributes to Lung Cancer Cell A549 Proliferation through AHR/AKT/ERK1/2 Pathway

OBJECTIVE

Estrogen may have a certain role in promoting lung cancer caused by tobacco. Our understanding of the carcinogenic effects and mechanisms of carcinogen mixture estrogen is limited and mostly relies on the findings from studying individual factors.

METHODS

To test this hypothesis, an in-vitro study was used to investigate the effects of 17 β-estradiol (E2) on benzo[a]pyrene (Bap)-induced lung cancer cell A549 proliferation.

RESULTS

We first found that E2 was increased in serum samples from lung adenocarcinoma cancer (LUAD) patients, even to a small extent. We found that Bap could enhance colony formation ability, up-regulate proliferating cell nuclear antigen (PCNA) and B-cell lymphoma-2 (Bcl-2) expression, induce cell proliferation and inhibit apoptosis in A549 cells. E2 promoted these effects of Bap. Moreover, E2 and Bap co-exposure promoted lung cancer cell proliferation by activating the aryl hydrocarbon receptor (AHR)/protein kinase B (AKT)/extracellular regulated protein kinases (ERK1/2) signaling pathway. Inhibition of the AKT and ERK1/2 signaling pathways suppressed E2 and Bap co-exposure's effect on A549 cells proliferation and apoptosis.

CONCLUSIONS

Collectively, we conclude that E2 could promote the proliferative and antiapoptotic effects of Bap on A549 cells, and activation of the AHR/AKT/ERK1/2 pathway may be involved in this process.

Long-term reproductive effects of benzo(a)pyrene at environmentally relevant dose on juvenile female rats

Since studies on the reproductive consequences after the exposure to environmentally relevant doses of Benzo(a)pyrene (BaP) during critical stages of development are scarce, this study evaluated female reproductive parameters of adult rats exposed to a low dose of BaP during the juvenile phase. Female rats (Post-natal 21) were treated with BaP (0 or 0.1 µg/kg/day; gavage) for 21 consecutive days. During the treatment, no clinical signs of toxicity were observed. Nevertheless, the ages of vaginal opening and first estrus were anticipated by the BaP-exposure. At the sexual maturity, the juvenile exposure compromised the sexual behavior, as well as the placental efficiency, follicle stimulating hormone levels, placenta histological analysis, and ovarian follicle count. A decrease in erythrocyte, platelet, and lymphocyte counts also was observed in the exposed-females. Moreover, the dose of BaP used in this study was not able to produce estrogenic activity in vivo. These data showed that juvenile BaP-exposure, at environmentally relevant dose, compromised the female reproductive system, possibly by an endocrine deregulation; however, this requires further investigation.

Insights into mechanism of DNA damage and repair-apoptosis in digestive gland of female scallop Chlamys farreri under benzo[a]pyrene exposure during reproductive stage

As one of the most carcinogenic persistent organic pollutants (POPs), benzo[a]pyrene (B [a]P) brings high toxicity to marine bivalves. Digestive gland is the most important metabolism-related organ of aquatic animals. This study conducted the digestive gland transcriptome of Chlamys farreri under B[a]P treatment at reproductive stages. And the reproductive-stage dependence metabolism-DNA repair-apoptosis process of scallops under 0, 0.04, 0.4 and 4 μg/L B[a]P was studied by qRT-PCR. The results demonstrated that the detoxification metabolism was disturbed after ovulation except for CYP3A4. In antioxidant system, antioxidant enzyme CAT and GPX, and GGT1 (one of the non-enzymatic antioxidants synthesis gene) continuously served the function of antioxidant defense. Three types of DNA repair were activated under B[a]P stress, however, DNA strand breaks were still serious. B[a]P exposure weakened death receptor pathway as well as enhanced mitochondrial pathway, surprisingly suppressing apoptosis in scallops. In addition, ten indicators were screened by Spearman correlation analysis. This study will provide sound theoretical basis for bivalve toxicology and contribute to the biomonitoring of marine POPs pollution.

Role and mechanism of WNT5A in benzo(a)pyrene-induced acute lung injury and lung function decline

Benzo(a)pyrene was sparsely studied for its early respiratory impairment. The non-canonical ligand WNT5A play a role in pneumonopathy, while its function during benzo(a)pyrene-induced adverse effects were largely unexplored. Individual benzo(a)pyrene, plasma WNT5A, and spirometry 24-hour change for 87 residents from Wuhan-Zhuhai cohort were determined to analyze potential role of WNT5A in benzo(a)pyrene-induced lung function alternation. Normal bronchial epithelial cell lines were employed to verify the role of WNT5A after benzo(a)pyrene treatment. RNA sequencing was adopted to screen for benzo(a)pyrene-related circulating microRNAs and differentially expressed microRNAs between benzo(a)pyrene-induced cells and controls. The most potent microRNA was selected for functional experiments and target gene validation, and their mechanistic link with WNT5A-mediated non-canonical Wnt signaling was characterized through rescue assays. We found significant associations between increased benzo(a)pyrene and reduced 24-hour changes of FEF50% and FEF75%, as well as increased WNT5A. The benzo(a)pyrene-induced inflammation and epithelial-mesenchymal transition in BEAS-2B and 16HBE cells were attenuated by WNT5A silencing. hsa-miR-122-5p was significantly and positively associated with benzo(a)pyrene and elevated after benzo(a)pyrene induction, and exerted its effect by downregulating target gene TP53. Functionally, WNT5A participates in benzo(a)pyrene-induced lung epithelial injury via non-canonical Wnt signaling modulated by hsa-miR-122-5p/TP53 axis, showing great potential as a preventive and therapeutic target.

Compound effect and mechanism of oxidative damage induced by nanoplastics and benzo [a] pyrene

Nanoplastics and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soil environments. In order to objectively evaluate the toxic interaction between polystyrene nanoplastics (PS NPs) and benzo [a] pyrene (BaP), oxidative damage at the level of earthworm cells and biomacromolecules was investigated by experiments combined with molecular dynamics simulation. Studies on cells reveal that PS NPs and BaP had synergistic toxicity when it came to causing oxidative stress. Cellular reactive oxygen species (ROS) levels under combined pollutant exposure were 24% and 19% higher, respectively than when PS NPs and BaP were exposed alone (compared to the blank group). In addition, BaP and PS NPs inhibited the ability of CAT to decompose H2O2 by affecting the structure of the proximal amino acid Tyr 357 in the active center of CAT, which exacerbated oxidative stress to a certain extent. Therefore, the synergistic toxic effect of BaP and PS NPs is due to the mutual complement of the two to the induction of protein structural looseness, and the strengthening of the stability of the conjugate (CAT-BaP-PS) under the weak interaction. This work provides a new perspective and approach on how to talk about the toxicity of combined pollutants.

Regulation of Xenobiotic-Metabolizing Enzymes by 5-Demethylnobiletin and Nobiletin to Mitigate Benzo[a]pyrene-Induced DNA Damage In Vitro and In Vivo

Benzo[a]pyrene (B[a]P) is a genotoxic polycyclic aromatic hydrocarbon that is metabolized by cytochrome P450 family 1 enzymes (CYP 1s) and can bind to DNA to form DNA adducts, leading to DNA damage and increased colorectal cancer risk. Previous studies have shown polymethoxyflavones to have a high potential for anticancer effects by regulating CYP 1s, especially nobiletin (NBT) and 5-demethylnobiletin (5-DMNB). However, the effects of NBT and 5-DMNB on B[a]P metabolism remain unclear. Therefore, this study aimed to clarify the effects of NBT and 5-DMNB on B[a]P-induced DNA damage in vitro and in vivo. In NCM460 cells, 5-DMNB and NBT appeared to reduce the metabolic conversion of B[a]P by regulating the aryl hydrocarbon receptor (AhR)/CYP 1s signaling pathway. This process protected NCM460 cells from B[a]P's cytotoxic effects by decreasing DNA damage and suppressing B[a]P diol-epoxide-DNA adduct formation. In BALB/c mice, 5-DMNB and NBT also protected against B[a]P-induced DNA damage. Altogether, these findings indicate that 5-DMNB and NBT attenuate B[a]P-induced DNA damage by modulating biotransformation, highlighting their chemopreventive potential against B[a]P-induced carcinogenesis. Therefore, 5-DMNB and NBT are promising agents for colorectal cancer chemoprevention in the future.

Heterogeneous aggregation of carbon and silicon nanoparticles with benzo[a]pyrene modulates their impacts on the pulmonary surfactant film

Inhaled nanoparticles (NPs) can deposit in alveoli where they interact with the pulmonary surfactant (PS) and potentially induce toxicity. Although nano-bio interactions are influenced by the physicochemical properties of NPs, isolated NPs used in previous studies cannot accurately represent those found in atmosphere. Here we used molecular dynamics simulations to investigate the interplay between two types of NPs associated with benzo[a]pyrene (BaP) at the PS film. Silicon NPs (SiNPs), regardless of aggregation and adsorption, directly penetrated through the PS film with minimal disturbance. Meanwhile, BaPs adsorbed on SiNPs were rapidly solubilized by PS, increasing the BaP's bioaccessibility in alveoli. Carbon NPs (CNPs) showed aggregation and adsorption-dependent effects on the PS film. Compared to isolated CNPs, which extracted PS to form biomolecular coronas, aggregated CNPs caused more pronounced PS disruption, especially around irregularly shaped edges. SiNPs in mixture exacerbated the PS perturbation by piercing PS film around the site of CNP interactions. BaPs adsorbed on CNPs were less solubilized and suppressed PS extraction, but aggravated biophysical inhibition by prompting film collapse under compression. These results suggest that for proper assessment of inhalation toxicity of airborne NPs, it is imperative to consider their heterogeneous aggregation and adsorption of pollutants under atmospheric conditions.

The activation of SIRT1 ameliorates BPDE-induced inflammatory damage in BEAS-2B cells via HMGB1/TLR4/NF-κB pathway

Benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), the metabolite of environmental pollutant benzo(a)pyrene (B(a)P) could induce pulmonary toxicity and inflammation. SIRT1, an NAD+ -dependent histone deacetylase, is known to regulate inflammation in the occurrence and development of various diseases, but its effects on BPDE-induced acute lung injury are still unknown. The present study aimed to explore the role of SIRT1 in BPDE-induced acute lung injury. Here, human bronchial epithelial (HBE) cells (BEAS-2B) cells were stimulated with BPDE at different concentrations (0.50, 0.75, and 1.00 μmol/L) for 24 h, we found that the levels of cytokines in the supernatant were increased and the expression of SIRT1 in cells was down-regulated, at the same time, BPDE stimulation up-regulated the protein expression of HMGB1, TLR4, and p-NF-κBp65 in BEAS-2B cells. Then the activator and inhibitor of SIRT1 were used before BPDE exposure, it was shown that the activation of SIRT1 significantly attenuated the levels of inflammatory cytokines and HMGB1, and reduced the expression of HMGB1, AC-HMGB1, TLR4, and p-NF-κBp65 protein; while these results were reversed by the inhibition of SIRT1. This study revealed that the SIRT1 activation may protect against BPDE-induced inflammatory damage in BEAS-2B cells by regulating the HMGB1/TLR4/NF-κB pathway.

BPDE-DNA adduct formation and alterations of mRNA, protein, and DNA methylation of CYP1A1, GSTP1, and GSTM1 induced by benzo[a]pyrene and the intervention of aspirin in mice

Benzo[a]pyrene (B[a]P), one typical environmental pollutant, the toxicity mechanisms, and potential prevention remain perplexing. Available evidence suggests cytochrome P450 1A1 (CYP1A1) and glutathione S-transferases (GSTs) metabolize B[a]P, resulting in metabolic activation and detoxification of B[a]P. This study aimed to reveal the impact of B[a]P exposure on trans-7,8-diol-anti-9,10-epoxide DNA (BPDE-DNA) adduct formation, level of CYP1A1, glutathione S-transferase pi (GSTP1) and glutathione S-transferase mu1 (GSTM1) mRNA, protein and DNA methylation in mice, and the potential prevention of aspirin (ASP). This study firstly determined the BPDE-DNA adduct formation in an acute toxicity test of a large dose in mice induced by B[a]P, which subsequently detected CYP1A1, GSTP1, and GSTM1 at levels of mRNA, protein, and DNA methylation in the organs of mice in a subacute toxicity test at appropriate doses and the potential prevention of ASP, using the methods of real-time quantitative PCR (QPCR), western blotting, and real-time methylation-specific PCR (MSP), respectively. The results verified that B[a]P induced the formation of BPDE-DNA adduct in all the organs of mice in an acute toxicity test, and the order of concentration of which was lung > kidney > liver > brain. In a subacute toxicity test, following B[a]P treatment, mice showed a dose-dependent slowdown in body weight gain and abnormalities in behavioral and cognitive function and which were alleviated by ASP co-treatment. Compared to the controls, following B[a]P treatment, CYP1A1 was significantly induced in all organs in mice at mRNA level (P < 0.05), was suppressed in the lung and cerebrum of mice at protein level, and inhibited at DNA methylation level in the liver, lung, and cerebrum, whereas GSTP1 and GSTM1 at mRNA, protein, and DNA methylation levels showed organ-specific changes in mice following B[a]P treatment, which was generally alleviated by ASP intervention. In conclusion, B[a]P induced BPDE-DNA adduct formation in all organs in mice and altered the mRNA, protein, and DNA methylation levels in CYP1A1, GSTP1, and GSTM1 in an organ-dependent pattern, which could be related to the organ toxicity and mechanism of B[a]P. ASP intervention may be an effective measure to prevent B[a]P toxicity. The findings provide scientific evidence for further study on the organ toxicity and mechanisms of B[a]P.

Potential molecular mechanism underlying the harmed haemopoiesis upon Benzo[a]pyrene exposure in Chlamys farreri

Benzo[a]pyrene (B[a]P), a ubiquitous contamination in the marine environments, has the potential to impact the immune response of bivalves by affecting the hemocyte parameters, especially total hemocyte count (THC). THC is mainly determined by haematopoietic mechanisms and apoptosis of hemocytes. Many studies have found that B[a]P can influence the proliferation and differentiation of hemocytes. However, the link between the toxic mechanisms of haematopoietic and environmental pollutants is not explicitly stated. This study is to investigate the toxic effects of B[a]P on haematopoietic mechanisms in C. farreri. Through the tissue expression distribution experiment and EDU assay, gill is identified as a potential haematopoietic tissue in C. farreri. Subsequently, the scallops were exposed to B[a]P (0.05, 0.5, 5 μg/L) for 1d, 3d, 6d, 10d and 15d. Then BPDE content, DNA damage, gene expression of haematopoietic factors and haematopoietic related pathways were determined in gill and hemocytes. The results showed that the expression of CDK2 was significantly decreased under B[a]P exposure through three pathways: RYR/IP3-calcium, BPDE-CHK1 and Notch pathway, resulting in cell cycle arrest. In addition, B[a]P also significantly reduced the number of proliferating hemocytes by affecting the Wnt pathway. Meanwhile, B[a]P can significantly increase the content of ROS, causing a downregulation of FOXO gene expression. The gene expression of Notch pathway and ERK pathway was also detected. The present study suggested that B[a]P disturbed differentiation by multiple pathways. Furthermore, the expression of SOX11 and CD9 were significantly decreased, which directly indicated that differentiation of hemocytes was disturbed. In addition, phagocytosis, phenoloxidase activity and THC were also significant decreased. In summary, the impairment of haematopoietic activity in C. farreri further causes immunotoxicity under B[a]P exposure. This study will improve our understanding of the immunotoxicity mechanism of bivalve under B[a]P exposure.