Dihydrodiol dehydrogenases and polycyclic aromatic hydrocarbon activation: generation of reactive and redox active o-quinones

Toxicity evaluation of water-accommodated fraction of heavy and light oils on the rainbow trout fish cell line RTL-W1

Fish are currently used models for the toxicity assessment of chemicals, including polycyclic aromatic hydrocarbons (PAHs). Alternative methods including fish cell lines are currently used to provide fast and reliable results on the toxic properties of chemicals while respecting ethical concerns about animal testing. The Rainbow trout liver cell line RTLW1 was used to analyze the effects of two water-accommodated fractions from two crude oils: Arabian Light crude oil (LO) and refined oil from Erika (HO). Several toxicity endpoints were assessed in this study, including cytotoxicity, EROD activity, DNA damage (comet and micronucleus assays), and ROS production. RTL-W1 cells were exposed for 24 h at two or three dilutions of WAF at 1000 µg/L (0.1% (1 μg/L), 1% (10 μg/L), and 10% (100 μg/L)) for cytotoxicity and EROD activity and 1% and 10% for ROS production and genotoxicity). Exposure of RTL-W1 cells to LO WAF induced a significant increase of EROD activity and ROS production and altered DNA integrity as revealed by both the comet assay and the micronucleus test for 10 µg/L of LO. On the other hand, HO WAF exhibited limited toxic effects except for an EROD induction for 1% WAF dilution. These results confirmed the usefulness of RTL-W1 cells for in vitro toxicological assessment of chemical mixtures.

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.

Associations between Urinary Concentrations of Polycyclic Aromatic Hydrocarbons and Overactive Bladder in US Adults: Data from the National Health and Nutrition Examination Survey 2005-2016

INTRODUCTION

Polycyclic aromatic hydrocarbons (PAHs) are a group of chemicals that can induce oxidative stress and related cytotoxicity. Whether urinary concentrations of PAHs have effects on overactive bladder (OAB) in the general population is still unclear. This study investigated the associations between urinary PAHs and OAB.

METHODS

7,146 adults aged over 20 who participated in the US National Health and Nutrition Examination Survey 2005-2016 were studied. The impact of the six PAHs on OAB was evaluated by multivariate logistic regression, and percent changes related to different quartiles of those six PAH levels were calculated. Confounders including age, logarithmic urinary creatinine, gender, race, body mass index, educational level, marriage, poverty income ratio, diabetes, hypertension, and metabolic syndrome were controlled.

RESULTS

There is a significant positive correlation between urinary concentrations of the six PAHs we include in the study and the occurrence of OAB. Furthermore, individuals with higher PAH levels also reported a more severe OAB symptom score (OABSS).

CONCLUSIONS

Our findings revealed that adult men in the USA with higher urinary PAHs had a higher risk of OAB incidence. These findings suggest the importance of strong environmental regulation of PAHs to protect population health. However, the underlying mechanisms still need further exploration.

A pilot study exploring time- and dose-dependent DNA damage and chromosomal instability caused by benzo[a]pyrene in two urothelial cell types

Environmental and occupational exposure to polycyclic aromatic hydrocarbons (PAHs) is associated with adverse health effects in humans. Uncertainty exists regarding the causation of urinary bladder cancer by benzo[a]pyrene (B[a]P) due to a lack of sufficient data. In this work, we focused on in-vitro DNA damage and the formation of micronuclei and chromosomal aberrations as predictors of cancer risk, applying a wide range of dosages and time periods to quantify the onset, intensity, and duration of the response. We chose two urothelial cell types to compare susceptibility and the ability to increase the malignity of a pre-existing bladder cancer: a cancer cell line (T24) and a pooled sample of primary urinary bladder epithelia cells (PUBEC) from pigs. The highest level of DNA damage assessed by comet assay was observed following 24-h treatment in both cell types, whereas PUBEC cells were clearly more susceptible. Even 4-h treatment induced DNA damage in PUBEC cells with benchmark doses of 0.0027 µM B[a]P and 0.00023 µM after 4-h and 24-h exposure, respectively. Nearly no effect was observed for periods of 48 h. The frequency of micronucleus formation increased more markedly in T24 cells, particularly with 24-h treatment. In PUBEC cells, 48-h exposure notably induced the formation of nucleoplasmic bridges and nuclear buds. Even though only one biological replicate was studied due to the sophisticated study design, our results give a strong indication of the potential of B[a]P to induce and increase malignity in human-relevant cell types.

Biological Impact of Organic Extracts from Urban-Air Particulate Matter: An In Vitro Study of Cytotoxic and Metabolic Effects in Lung Cells

Atmospheric particulate matter (PM) with diameters below 10 µm (PM10) may enter the lungs through inhalation and are linked to various negative health consequences. Emergent evidence emphasizes the significance of cell metabolism as a sensitive target of PM exposure. However, the current understanding of the relationship between PM composition, conventional toxicity measures, and the rewiring of intracellular metabolic processes remains limited. In this work, PM10 sampled at a residential area (urban background, UB) and a traffic-impacted location (roadside, RS) of a Portuguese city was comprehensively characterized in terms of polycyclic aromatic hydrocarbons and plasticizers. Epithelial lung cells (A549) were then exposed for 72 h to PM10 organic extracts and different biological outcomes were assessed. UB and RS PM10 extracts dose-dependently decreased cell viability, induced reactive oxygen species (ROS), decreased mitochondrial membrane potential, caused cell cycle arrest at the G0/G1 phase, and modulated the intracellular metabolic profile. Interestingly, the RS sample, richer in particularly toxic PAHs and plasticizers, had a greater metabolic impact than the UB extract. Changes comprised significant increases in glutathione, reflecting activation of antioxidant defences to counterbalance ROS production, together with increases in lactate, NAD+, and ATP, which suggest stimulation of glycolytic energy production, possibly to compensate for reduced mitochondrial activity. Furthermore, a number of other metabolic variations hinted at changes in membrane turnover and TCA cycle dynamics, which represent novel clues on potential PM10 biological effects.

Characterization of airborne particulate matter and its toxic and proarrhythmic effects: A case study in Aburrá Valley, Colombia

Particle matter (PM) is a complex mixture of particles suspended in the air, mainly caused by fuel combustion from vehicles and industry, and has been related to pulmonary and cardiovascular diseases. The Metropolitan Area of Aburrá Valley in Colombia is the second most populous urban agglomeration in the country and the third densest in the world, composed of ten municipalities. Examining the physicochemical properties of PM is crucial in comprehending its composition and its effects on human health, as it varies based on the socioeconomic dynamics specific to each city. This study characterized the PM collected from the north, south, and central zones to evaluate its chemical composition and morphology. Different elements such as silicon, carbon, aluminum, potassium, calcium, sodium, iron, magnesium, and copper and the presence of unburned fuel, motor oil, and silicon fibers were identified. In vitro and in silico studies were conducted to evaluate the toxicity of the PM, and it was found that the PM collected from the central zone had the greatest impact on cell viability and caused DNA damage. The in silico study demonstrated that PM has concentration-dependent proarrhythmic effects, reflected in an action potential duration shortening and an increased number of reentries, which may contribute to the development of cardiac arrhythmias. Overall, the results suggest that the size and chemical composition of ambient PM can induce toxicity and play an important role in the generation of arrhythmias.

Identifying chemicals based on receptor binding/bioactivation/mechanistic explanation associated with potential to elicit hepatotoxicity and to support structure activity relationship-based read-across

The liver is the most common target organ in toxicology studies. The development of chemical structural alerts for identifying hepatotoxicity will play an important role in in silico model prediction and help strengthen the identification of analogs used in structure activity relationship (SAR)- based read-across. The aim of the current study is development of an SAR-based expert-system decision tree for screening of hepatotoxicants across a wide range of chemistry space and proposed modes of action for clustering of chemicals using defined core chemical categories based on receptor-binding or bioactivation. The decision tree is based on ∼ 1180 different chemicals that were reviewed for hepatotoxicity information. Knowledge of chemical receptor binding, metabolism and mechanistic information were used to group these chemicals into 16 different categories and 102 subcategories: four categories describe binders to 9 different receptors, 11 categories are associated with possible reactive metabolites (RMs) and there is one miscellaneous category. Each chemical subcategory has been associated with possible modes of action (MOAs) or similar key structural features. This decision tree can help to screen potential liver toxicants associated with core structural alerts of receptor binding and/or RMs and be used as a component of weight of evidence decisions based on SAR read-across, and to fill data gaps.

Formulation of synthetic bacteria consortia for enzymatic biodegradation of polyaromatic hydrocarbons contaminated soil: soil column study

As an efficient method to remove contaminants from highly polluted sites, enzyme biodegradation addresses unresolved issues such as bioremediation inefficiency. In this study, the key enzymes involved in PAH degradation were brought together from different arctic strains for the biodegradation of highly contaminated soil. These enzymes were produced via a multi-culture of psychrophilic Pseudomonas and Rhodococcus strains. As a result of biosurfactant production, the removal of pyrene was sufficiently prompted by Alcanivorax borkumensis. The key enzymes (e.g., naphthalene dioxygenase, pyrene dioxygenase, catechol-2,3 dioxygenase, 1-hydroxy-2-naphthoate hydroxylase, protocatechuic acid 3,4-dioxygenase) obtained via multi-culture were characterized by tandem LC-MS/MS and kinetic studies. To simulate in situ application of produced enzyme solutions, pyrene- and dilbit-contaminated soil was bioremediated in soil columns and flask tests by injecting enzyme cocktails from the most promising consortia. The enzyme cocktail contained about 35.2 U/mg protein pyrene dioxygenase, 61.4 U/mg protein naphthalene dioxygenase, 56.5 U/mg protein catechol-2,3-dioxygenase, 6.1 U/mg protein 1-hydroxy-2-naphthoate hydroxylase, and 33.5 U/mg protein protocatechuic acid (P3,4D) 3,4-dioxygenase enzymes. It was found that after 6 weeks, the average pyrene removal values showed that the enzyme solution could be effective in the soil column system (80-85% degradation of pyrene).

A Review of the GSTM1 Null Genotype Modifies the Association between Air Pollutant Exposure and Health Problems

Air pollution is one of the significant environmental risks known as the cause of premature deaths. It has deleterious effects on human health, including deteriorating respiratory, cardiovascular, nervous, and endocrine functions. Exposure to air pollution stimulates reactive oxygen species (ROS) production in the body, which can further cause oxidative stress. Antioxidant enzymes, such as glutathione S-transferase mu 1 (GSTM1), are essential to prevent oxidative stress development by neutralizing excess oxidants. When the antioxidant enzyme function is lacking, ROS can accumulate and, thus, cause oxidative stress. Genetic variation studies from different countries show that GSTM1 null genotype dominates the GSTM1 genotype in the population. However, the impact of the GSTM1 null genotype in modifying the association between air pollution and health problem is not yet clear. This study will elaborate on GSTM1's null genotype role in modifying the relationship between air pollution and health problems.

A mutagenic analysis of NahE, a hydratase-aldolase in the naphthalene degradative pathway

NahE is a hydratase-aldolase that converts o-substituted trans-benzylidenepyruvates (H, OH, or CO2-) to benzaldehyde, salicylaldehyde, or 2-carboxybenzaldehyde, respectively, and pyruvate. The enzyme is in a bacterial degradative pathway for naphthalene, which is a toxic and persistent environmental contaminant. Sequence, crystallographic, and mutagenic analysis identified the enzyme as a member of the N-acetylneuraminate lyase (NAL) subgroup in the aldolase superfamily. As such, it has a conserved lysine (Lys183) and tyrosine (Tyr155), for Schiff base formation, as well as a GXXGE motif for binding of the pyruvoyl carboxylate group. A crystal structure of the selenomethionine derivative of NahE shows these active site elements along with nearby residues that might be involved in the mechanism and/or specificity. Mutations of five active site amino acids (Thr65, Trp128, Tyr155, Asn157, and Asn281) were constructed and kinetic parameters measured in order to assess the effect(s) on catalysis. The results show that the two Trp128 mutants (Phe and Tyr) have the least effect on catalysis, whereas amino acids with bulky side chains at Thr65 (Val) and Asn281 (Leu) have the greatest effect. Changing Tyr155 to Phe and Asn157 to Ala also hinders catalysis, and the effects fall in between these extremes. These observations are put into a structural context using a crystal structure of the Schiff base of the reaction intermediate. Trapping experiments with substrate, Na(CN)BH3, and wild type enzyme and selected mutants mostly paralleled the kinetic analysis, and identified two salicylaldehyde-modified lysines: the active site lysine (Lys183) and one outside the active site (Lys279). The latter could be responsible for the observed inhibition of NahE by salicylaldehyde. Together, the results provide new insights into the NahE-catalyzed reaction.

Nitroreduction: A Critical Metabolic Pathway for Drugs, Environmental Pollutants, and Explosives

Nitro group containing xenobiotics include drugs, cancer chemotherapeutic agents, carcinogens (e.g., nitroarenes and aristolochic acid) and explosives. The nitro group undergoes a six-electron reduction to form sequentially the nitroso-, N-hydroxylamino- and amino-functional groups. These reactions are catalyzed by nitroreductases which, rather than being enzymes with this sole function, are enzymes hijacked for their propensity to donate electrons to the nitro group either one at a time via a radical mechanism or two at time via the equivalent of a hydride transfer. These enzymes include: NADPH-dependent flavoenzymes (NADPH: P450 oxidoreductase, NAD(P)H-quinone oxidoreductase), P450 enzymes, oxidases (aldehyde oxidase, xanthine oxidase) and aldo-keto reductases. The hydroxylamino group once formed can undergo conjugation reactions with acetate or sulfate catalyzed by N-acetyltransferases or sulfotransferases, respectively, leading to the formation of intermediates containing a good leaving group which in turn can generate a nitrenium or carbenium ion for covalent DNA adduct formation. The intermediates in the reduction sequence are also prone to oxidation and produce reactive oxygen species. As a consequence, many nitro-containing xenobiotics can be genotoxic either by forming stable covalent adducts or by oxidatively damaging DNA. This review will focus on the general chemistry of nitroreduction, the enzymes responsible, the reduction of xenobiotic substrates, the regulation of nitroreductases, the ability of nitrocompounds to form DNA adducts and act as mutagens as well as some future directions.

Source risk, ecological risk, and bioeffect assessment for polycyclic aromatic hydrocarbons (PAHs) in Laizhou Bay and Jiaozhou Bay of Shandong Peninsula, China

In order to incorporate the contribution of pollution sources to ecological risks into environmental monitoring, positive matrix factorization-risk quotient (PMF-RQ) was used to quantify the contribution of different PAH sources to ecological risks, which indicated that the unburned petroleum, vehicular emissions, and diesel combustion were the main sources of PAHs in Laizhou Bay and Jiaozhou Bay, and they were caused by petrochemical industry, maritime shipping, and urban traffic exhaust as the major sources of PAHs for ecological risk. Meanwhile, integrated biomarker response (IBR) and multi-biomarker pollution index (MPI) suggested that September was the most polluted month for PAHs in Laizhou Bay and Jiaozhou Bay and the pollution in Laizhou Bay was significantly higher than that in Jiaozhou Bay. This research was dedicated to explore the monitoring pattern for PAH pollution from the source to bioeffects, and it may have contributed a scientific support to monitoring and governance of marine PAH pollution.

Protective role of AKBA against benzo(a)pyrene-induced lung carcinogenesis by modulating biotransformation enzymes and oxidative stress

The present study was designed to explore the chemopreventive potential of 3-acetyl-11-keto-β-boswellic acid (AKBA) during the initiation and promotion stage of lung carcinogenesis induced by benzo(a)pyrene (BaP) in female Sprague Dawley rats. BaP was administered at a dose level of 50 mg/kg b.wt. twice a week orally in olive oil for 4 weeks. AKBA administration was started 4 weeks before BaP treatment and continued for another 8 weeks at a dose level of 50 mg/kg b.wt. orally in olive oil three times a week. BaP treatment showed significantly increased in the activities of Phase I biotransformation enzymes (Cytochrome P₄₅₀ , b₅ , and aryl hydrocarbon hydrolase) and inhibited the activity of Phase II enzyme (glutathione-S-transferase). Also, a significant elevation in oxidative stress biomarkers lipid peroxidation, reactive oxygen species, and protein carbonyl content concentration. Further, an appreciable decrease was observed in the activities of endogenous antioxidant enzymes superoxide dismutase, CAT, GPx, GR, and a decline in nonenzymatic GSH levels. As a result of BaP induced oxidative stress, alteration in erythrocytes morphology was observed. Fourier transform infrared spectroscopy spectrum of lung tissue showed structural changes due to BaP exposure. Moreover, levels of tumor biomarkers such as total sialic acid, carcinoembryonic antigen, and alkaline phosphatase were significantly elevated following BaP treatment which was substantiated by alterations noticed in the histoarchitecture of lung tissue. Interestingly, AKBA administration to BaP treated rats appreciably alleviated the changes inflicted by BaP on various biochemical indices and histoarchitecture of lungs. Therefore, the study clearly revealed that AKBA by containing oxidative stress shall prove to be quite effective in providing chemoprevention against BaP induced lung carcinogenesis.

Overcoming Skin Damage from Pollution via Novel Skincare Strategies

Urban pollution is one of the main problems encountered worldwide with major impact on public health as well as the environment. Health impact of urban pollution is not limited to respiratory conditions but also encompasses major skin problems including irritation, skin ageing, and skin cancer. Toxic gases and particulate matter are the main pollutants and exhibit extensive local variability. The aforementioned pollutants are small particles that attach to the skin or penetrate into it, enhancing free radicals' production inside the inner skin layers. This urges the need to propose cosmetic products that help prevent and/or minimise pollutants' effects on the skin whether irritation, ageing and cancer. Furthermore, intrinsic and extrinsic factors contributed to skin irritation and ageing. Intrinsic factors are within skin factors and include genetic and physiological characteristics of individuals. Moreover, extrinsic factors comprise environmental factors such as humidity, temperature, and smoke. Subsequently active ingredients with antipollutant properties addressed the intrinsic and extrinsic factors by four mechanisms being: free radical neutralisation, film-forming ability, skin barrier enhancement and fortification. Such ingredients include vitamin A derivatives, vitamin C derivatives, carbohydrates, and plant-based products. Yet, very limited studies have evaluated the effectiveness of the aforementioned active ingredients against irritation or ageing and this should be considered in future work.

Mechanistic insight into the synergism of IL-27 and IL-28B in regulation of benzo(a)pyrene-induced lung carcinogenesis associated ROS/NF-κB/NLRP3 crosstalk

AIM

Our previous work depicted that benzo(a)pyrene (BaP)-induced lung cancer associated pulmonary redox imbalance and inflammation were effectively regulated by the combinatorial treatment of IL-27 and IL-28B. So in continuation of that finding the present study was designed to reveal the inflammation regulating signaling network modulated by IL-27 and IL-28B treatment related to BaP-induced lung cancer.

METHODS

Male Swiss albino mice were treated with BaP to induce lung tumor. Then they received individual as well as combinatorial treatment of IL-27 and IL-28B. At the end of the experimental schedule, the expression of NF-κB signaling proteins, the formation of NLRP3 inflammasome complex and IL-18; IL-17A expression in the lung were observed using Western blot and RT-PCR. The tissue and serum levels of some proinflammatory cytokines were also studied using ELISA. Mast cell density was also studied using toluidine blue staining procedure.

RESULTS

Treatment with IL-27 or IL-28B alone was successful to regulate the expression of NF-κB signaling proteins and NLRP3 complex in some cases but best attenuation was observed in animals who received both IL-27 and IL-28B in combination. In combination, it was successful in down-regulating the expression of p-ERK1/2 and in reducing the accumulation of mast cells in the lung tissue associated with BaP-induced lung carcinogenesis. The impaired PPARγ expression was also reinstated upon combination treatment.

CONCLUSION

Altogether, the treatment in combination with IL-27 and IL-28B is an effective regimen to attenuate the ROS/NF-κB/NLRP3 axis associated with BaP-induced lung carcinogenesis.

Effects of polycyclic aromatic hydrocarbon structure on PAH mineralization and toxicity to soil microorganisms after oxidative bioremediation by laccase

While bioremediation using soil microorganisms is considered an energy-efficient and eco-friendly approach to treat polycyclic aromatic hydrocarbon (PAH)-contaminated soils, a variety of polar PAH metabolites, particularly oxygenated ones, could increase the toxicity of the soil after biodegradation. In this study, a typical bio-oxidative transformation of PAH into quinones was investigated in soil amended with laccase using three PAHs with different structures (anthracene, benzo[a]anthracene, and benzo[a]pyrene) to assess the toxicity after oxidative bioremediation. The results show that during a 2-month incubation period the oxidation process promoted the formation of non-extractable residues (NERs) of PAHs, and different effects on mineralization were observed among the three PAHs. Oxidation enhanced the mineralization of the high-molecular-weight (HMW) PAHs (benzo[a]anthracene and benzo[a]pyrene) but inhibited the mineralization of the low-molecular-weight (LMW) PAH (anthracene). The inhibition of anthracene suggests increased toxicity after oxidative bioremediation, which coincided with a decrease in soil nitrification activity, bacterial diversity and PAH-ring hydroxylating dioxygenase gene copies. The analysis of PAH metabolites in soil extract indicated that oxidation by laccase was competitive with the natural transformation processes of PAHs and revealed that intermediates other than quinone metabolites increased the toxicity of soil during subsequent degradation. The different metabolic profiles of the three PAHs indicated that the toxicity of soil after PAH oxidation by laccase was strongly affected by the PAH structure. Despite the potential increase in toxicity, the results suggest that oxidative bioremediation is still an eco-friendly method for the treatment of HMW PAHs since the intermediates from HMW PAHs are more easily detoxified via NER formation than LMW PAHs.

Molecular mechanisms of oxidative stress in asthma

The lungs are exposed to reactive oxygen species oxygen (ROS) produced as a result of inhalation of oxygen, as well as smoke and other air pollutants. Cell metabolism and the NADPH oxidases (Nox) generate low levels of intracellular ROS that act as signal transduction mediators by inducing oxidative modifications of histones, enzymes and transcription factors. Redox signalling is also regulated by localised production and sensing of ROS in mitochondria, the endoplasmic reticulum (ER) and inside the nucleus. Intracellular ROS are maintained at low levels through the action of a battery of enzymatic and non-enzymatic antioxidants. Asthma is a heterogeneous airway inflammatory disease with different immune endotypes; these include atopic or non-atopic Th2 type immune response associated with eosinophilia, or a non-Th2 response associated with neutrophilia. Airway remodelling and hyperresponsiveness accompany the inflammatory response in asthma. Over-production of ROS resulting from infiltrating immune cells, particularly eosinophils and neutrophils, and a concomitant impairment of antioxidant responses lead to development of oxidative stress in asthma. Oxidative stress is augmented in severe asthma and during exacerbations, as well as by air pollution and obesity, and causes oxidative damage of tissues promoting airway inflammation and hyperresponsiveness. Furthermore, deregulated Nox activity, mitochondrial dysfunction, ER stress and/or oxidative DNA damage, resulting from exposure to irritants, inflammatory mediators or obesity, may lead to redox-dependent changes in cell signalling. ROS play a central role in airway epithelium-mediated sensing, development of innate and adaptive immune responses, and airway remodelling and hyperresponsiveness. Nonetheless, antioxidant compounds have proven clinically ineffective as therapeutic agents for asthma, partly due to issues with stability and in vivo metabolism of these compounds. The compartmentalised nature of ROS production and sensing, and the role of ROS in homeostatic responses and in the action of corticosteroids and β2-adrenergic receptor agonists, adds another layer of complexity to antioxidant therapy development. Nox inhibitors and mitochondrial-targeted antioxidants are in clinical development for a number of diseases but they have not yet been investigated in asthma. A better understanding of the complex role of ROS in the pathogenesis of asthma will highlight new opportunities for more targeted and effective redox therapies.

First-principles study of benzo[a]pyrene-7,8-dione and DNA adducts

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in environments, and some of them are causative agents of human cancer. Previous studies concluded that benzo[a]pyrene-7,8-dione (BPQ), which is one kind of carcinogenic PAH metabolites, forms covalently bonded adducts with DNA, and the major adduct formed is a deoxyguanosine adduct. In this work, we investigate the interactions between BPQ and DNA molecules via first-principles calculations. We identify six possible DNA adducts with BPQ. In addition to the four adducts forming covalent bonds, there are two adducts bound purely by van der Waals (vdW) interactions. Remarkably, the two vdW-bound adducts have comparable, if not larger, binding energies as the covalent adducts. The results may help us gain more understanding of the interactions between PAH metabolites and DNA.

Interactions between exposure to polycyclic aromatic hydrocarbons and xenobiotic metabolism genes, and risk of breast cancer

PURPOSE

Polycyclic aromatic hydrocarbons (PAHs) are a group of environmental pollutants associated with multiple cancers, including female breast cancer. Several xenobiotic metabolism genes (XMGs), including the CYP450 family, play an important role in activating and detoxifying PAHs, and variations in the activity of the enzymes they encode can impact this process. This study aims to examine the association between XMGs and breast cancer, and to assess whether these variants modify the effects of PAH exposure on breast cancer risk.

METHODS

In a case-control study in Vancouver, British Columbia, and Kingston, Ontario, 1037 breast cancer cases and 1046 controls had DNA extracted from blood or saliva and genotyped for 138 single nucleotide polymorphisms (SNPs) and tagSNPs in 27 candidate XMGs. Occupational PAH exposure was assessed using a measurement-based job-exposure matrix.

RESULTS

An association between genetic variants and breast cancer was observed among six XMGs, including increased risk among the minor allele carriers of AKR1C3 variant rs12387 (OR 2.71, 95% CI 1.42-5.19) and AKR1C4 variant rs381267 (OR 2.50, 95% CI 1.23-5.07). Heterogeneous effects of occupational PAH exposure were observed among carriers of AKR1C3/4 variants, as well as the PTGS2 variant rs5275.

CONCLUSION

Our findings support an association between SNPs of XMGs and female breast cancer, including novel genetic variants that modify the toxicity of PAH exposure. These results highlight the interplay between genetic and environmental factors, which can be helpful in understanding the modifiable risks of breast cancer and its complex etiology.

Pleiotropic Actions of Aldehyde Reductase (AKR1A)

We provide an overview of the physiological roles of aldehyde reductase (AKR1A) and also discuss the functions of aldose reductase (AKR1B) and other family members when necessary. Many types of aldehyde compounds are cytotoxic and some are even carcinogenic. Such toxic aldehydes are detoxified via the action of AKR in an NADPH-dependent manner and the resulting products may exert anti-diabetic and anti-tumorigenic activity. AKR1A is capable of reducing 3-deoxyglucosone and methylglyoxal, which are reactive intermediates that are involved in glycation, a non-enzymatic glycosylation reaction. Accordingly, AKR1A is thought to suppress the formation of advanced glycation end products (AGEs) and prevent diabetic complications. AKR1A and, in part, AKR1B are responsible for the conversion of d-glucuronate to l-gulonate which constitutes a process for ascorbate (vitamin C) synthesis in competent animals. AKR1A is also involved in the reduction of S-nitrosylated glutathione and coenzyme A and thereby suppresses the protein S-nitrosylation that occurs under conditions in which the production of nitric oxide is stimulated. As the physiological functions of AKR1A are currently not completely understood, the genetic modification of Akr1a could reveal the latent functions of AKR1A and differentiate it from other family members.

Cigarette smoking enhances the metabolic activation of the polycyclic aromatic hydrocarbon phenanthrene in humans

Although it is well established that human cytochrome P450 1 family enzymes are induced by cigarette smoking through activation of the Ah receptor, it is not known whether this leads to increased metabolic activation or detoxification of carcinogenic polycyclic aromatic hydrocarbons (PAH), which are present in cigarette smoke and the general environment. We gave oral doses of deuterated phenanthrene ([D10]Phe), a non-carcinogenic surrogate of carcinogenic PAH such as benzo[a]pyrene, to smokers (N = 170, 1 or 10 μg doses) and non-smokers (N = 57, 1 μg dose). Bioactivation products (dihydrodiol and tetraol) and detoxification products (phenols) of [D10]Phe were determined in 6-h urine to obtain a comprehensive metabolic profile. Cigarette smoking increased the bioactivation of [D10]Phe and decreased its detoxification resulting in significantly different metabolic patterns between smokers and non-smokers (P < 0.01), consistent with increased cancer risk in smokers. The Phe bioactivation ratios ([D10]PheT/total [D9]OHPhe) were significantly higher (2.3 (P < 0.01) to 4.8 (P < 0.001) fold) in smokers than non-smokers. With solid human in vivo evidence, our results for the first time demonstrate that cigarette smoking enhances the metabolic activation of Phe, structurally representative of carcinogenic PAH, in humans, strongly supporting their causal role in cancers caused by smoking. The results suggest potential new methods for identifying smokers who could be at particularly high risk for cancer.

Taxifolin ameliorates Benzo[a]pyrene-induced lung injury possibly via stimulating the Nrf2 signalling pathway

Benzo[a]pyrene, an environmental contaminant as well as a mutagen is widely found in cigarette smoke, automobile exhaust particles among other sources. The present study underlines the protective effect of Taxifolin on B[a]P induced lung injury in male Swiss Albino Mice by analyzing the activity/level of various pro and anti-oxidant parameters, Inflammatory markers, Phase II enzyme, as well as lung histology. Taxifolin was administered orally to mice at either dose of 20 or 40 mg/kg body weight for 14 days and then challenged with a single dose of B[a]P (125 mg/kg body weight by oral gavage) on the 14th day. Our results show treatment with B[a]P leads to increased activity/level of CYP450R, EH, pro-inflammatory proteins, as well as lipid peroxidation and reduce level/activity of anti-oxidant molecules while Taxifolin treatment shows ameliorative effect. Administration of B[a]P also leads to decrease in expression of ROS sensitive factor Nrf2 and its downstream target NQO1,HO-1,SOD while Taxifolin treated animals showed a very high level of expression of Nrf2,NQO1,HO-1,SOD. Since Nrf2 plays central role in providing resistance to oxidative stress and also suppresses inflammation by inhibiting NF-κB,we concluded Taxifolin suppresses oxidative stress and inflammation in B[a]P induced lung injury possibly via stimulating the Nrf2 signaling pathway.

Benzo[a]pyrene and Benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide induced locomotor and reproductive senescence and altered biochemical parameters of oxidative damage in Canton-S Drosophila melanogaster

Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon (PAH) commonly found in cigarette smoke, automobile exhaust fumes, grilled meat, and smoked food among others. Exposure to B[a]P is associated with a range of toxic effects including developmental, neurological, oxidative, inflammatory, mutagenic, carcinogenic and mortal. Efficient and more affordable experimental models like Drosophila melanogaster could provide more insight into the mechanism of PAH toxicity and help develop new strategies for prevention, diagnosis and treatment of PAH-related conditions. In this study, we examined the induction of some biochemical changes along with mortality and functional senescence by B[a]P and its metabolite, benzo[a]pyrene- 7,8-dihydrodiol-910-epoxide (BPDE) in the Canton-S strain of Drosophila melanogaster, with the aim to establish an alternative assay medium for B[a]P toxicity in flies. Flies were exposed to 2-200 μM of B[a]P and 1-10 μM of BPDE through diet for a seven-day survival assay followed by a four-day treatment to determine the effects of the compounds on negative geotaxis, fecundity and some biochemical parameters of oxidative damage. BPDE significantly reduced the survival rate of flies along the 7 days of exposure whereas B[a]P did not cause any significant change in the survival rate of flies. B[a]P and BPDE significantly reduced the climbing ability of flies after 4 days of exposure. Rate of emergence of flies significantly reduced at 10-200 μM of B[a]P and 5-10 μM of BPDE. Both compounds caused various levels of alterations in the values of reduced glutathione (GSH), total thiol (T-SH), glutathione-S-transferase (GST), catalase (CAT), hydrogen peroxide (H2O2), nitric oxide (NO) and acetylcholinesterase (AChE) of the flies. The compounds also exhibited high binding affinities and molecular interactions with the active site amino acid residues of Drosophila GST and the inhibitor binding site of Drosophila AChE in an in silico molecular docking analysis, with BPDE forming stable hydrogen bonds with AChE. Hence, the Canton-S strain of Drosophila melanogaster could offer a simple and affordable assay medium to study B[a]P toxicity.

Microbial Degradation of Naphthalene and Substituted Naphthalenes: Metabolic Diversity and Genomic Insight for Bioremediation

Low molecular weight polycyclic aromatic hydrocarbons (PAHs) like naphthalene and substituted naphthalenes (methylnaphthalene, naphthoic acids, 1-naphthyl N-methylcarbamate, etc.) are used in various industries and exhibit genotoxic, mutagenic, and/or carcinogenic effects on living organisms. These synthetic organic compounds (SOCs) or xenobiotics are considered as priority pollutants that pose a critical environmental and public health concern worldwide. The extent of anthropogenic activities like emissions from coal gasification, petroleum refining, motor vehicle exhaust, and agricultural applications determine the concentration, fate, and transport of these ubiquitous and recalcitrant compounds. Besides physicochemical methods for cleanup/removal, a green and eco-friendly technology like bioremediation, using microbes with the ability to degrade SOCs completely or convert to non-toxic by-products, has been a safe, cost-effective, and promising alternative. Various bacterial species from soil flora belonging to Proteobacteria (Pseudomonas, Pseudoxanthomonas, Comamonas, Burkholderia, and Novosphingobium), Firmicutes (Bacillus and Paenibacillus), and Actinobacteria (Rhodococcus and Arthrobacter) displayed the ability to degrade various SOCs. Metabolic studies, genomic and metagenomics analyses have aided our understanding of the catabolic complexity and diversity present in these simple life forms which can be further applied for efficient biodegradation. The prolonged persistence of PAHs has led to the evolution of new degradative phenotypes through horizontal gene transfer using genetic elements like plasmids, transposons, phages, genomic islands, and integrative conjugative elements. Systems biology and genetic engineering of either specific isolates or mock community (consortia) might achieve complete, rapid, and efficient bioremediation of these PAHs through synergistic actions. In this review, we highlight various metabolic routes and diversity, genetic makeup and diversity, and cellular responses/adaptations by naphthalene and substituted naphthalene-degrading bacteria. This will provide insights into the ecological aspects of field application and strain optimization for efficient bioremediation.

Combined Toxicity of Metal Nanoparticles: Comparison of Individual and Mixture Particles Effect

Toxicity of metal nanoparticles (NPs) are closely associated with increasing intracellular reactive oxygen species (ROS) and the levels of pro-inflammatory mediators. However, NP interactions and surface complexation reactions alter the original toxicity of individual NPs. To date, toxicity studies on NPs have mostly been focused on individual NPs instead of the combination of several species. It is expected that the amount of industrial and highway-acquired NPs released into the environment will further increase in the near future. This raises the possibility that various types of NPs could be found in the same medium, thereby, the adverse effects of each NP either could be potentiated, inhibited or remain unaffected by the presence of the other NPs. After uptake of NPs into the human body from various routes, protein kinases pathways mediate their toxicities. In this context, family of mitogen-activated protein kinases (MAPKs) is mostly efficient. Despite each NP activates almost the same metabolic pathways, the toxicity induced by a single type of NP is different than the case of co-exposure to the combined NPs. The scantiness of toxicological data on NPs combinations displays difficulties to determine, if there is any risk associated with exposure to combined nanomaterials. Currently, in addition to mathematical analysis (Response surface methodology; RSM), the quantitative-structure-activity relationship (QSAR) is used to estimate the toxicity of various metal oxide NPs based on their physicochemical properties and levels applied. In this chapter, it is discussed whether the coexistence of multiple metal NPs alter the original toxicity of individual NP. Additionally, in the part of "Toxicity of diesel emission/exhaust particles (DEP)", the known individual toxicity of metal NPs within the DEP is compared with the data regarding toxicity of total DEP mixture.

SARS-CoV-2 infection, COVID-19 pathogenesis, and exposure to air pollution: What is the connection?

Exposure to air pollutants has been previously associated with respiratory viral infections, including influenza, measles, mumps, rhinovirus, and respiratory syncytial virus. Epidemiological studies have also suggested that air pollution exposure is associated with increased cases of SARS-CoV-2 infection and COVID-19-associated mortality, although the molecular mechanisms by which pollutant exposure affects viral infection and pathogenesis of COVID-19 remain unknown. In this review, we suggest potential molecular mechanisms that could account for this association. We have focused on the potential effect of exposure to nitrogen dioxide (NO2 ), ozone (O3 ), and particulate matter (PM) since there are studies investigating how exposure to these pollutants affects the life cycle of other viruses. We have concluded that pollutant exposure may affect different stages of the viral life cycle, including inhibition of mucociliary clearance, alteration of viral receptors and proteases required for entry, changes to antiviral interferon production and viral replication, changes in viral assembly mediated by autophagy, prevention of uptake by macrophages, and promotion of viral spread by increasing epithelial permeability. We believe that exposure to pollutants skews adaptive immune responses toward bacterial/allergic immune responses, as opposed to antiviral responses. Exposure to air pollutants could also predispose exposed populations toward developing COIVD-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage.

Classifying polycyclic aromatic hydrocarbons by carcinogenic potency using in vitro biosignatures

One of the most difficult challenges for risk assessment is evaluation of chemicals that predominately co-occur in mixtures like polycyclic aromatic hydrocarbons (PAHs). We previously developed a classification model in which systems biology data collected from mice short-term after chemical exposure accurately predict tumor outcome. The present study demonstrates translation of this approach into a human in vitro model in which chemical-specific bioactivity profiles from 3D human bronchial epithelial cells (HBEC) classify PAHs by carcinogenic potency. Gene expression profiles were analyzed from HBEC exposed to carcinogenic and non-carcinogenic PAHs and classification accuracies were identified for individual pathway-based gene sets. Posterior probabilities of best performing gene sets were combined via Bayesian integration resulting in a classifier with four gene sets, including aryl hydrocarbon receptor signaling, regulation of epithelial mesenchymal transition, regulation of angiogenesis, and cell cycle G2-M. In addition, transcriptional benchmark dose modeling of benzo[a]pyrene (BAP) showed that the most sensitive gene sets to BAP regulation were largely dissimilar from those that best classified PAH carcinogenicity challenging current assumptions that BAP carcinogenicity (and subsequent mode of action) is reflective of overall PAH carcinogenicity. These results illustrate utility of using systems toxicology approaches to analyze global gene expression towards carcinogenic hazard assessment.

Identification and quantification of phenanthrene ortho-quinones in human urine and their association with lipid peroxidation

Although human exposure to polycyclic aromatic hydrocarbons (PAH) has been associated with in vivo oxidative damage, and hydroxyPAH metabolites have been used as biomarkers to assess PAH-induced oxidative stress, few studies have looked at the likely causative compounds for oxidative stress in humans - PAH quinones. We developed a method using pre-column derivatization - liquid chromatography-heated electrospray ionization-tandem mass spectrometry (LC-HESI-MS/MS) to analyze ortho-phenanthrene quinones (PheQs) in human urine. 1,2-PheQ and 3,4-PheQ were identified and quantified in 3 mL of human urine; their total concentrations were higher in cigarette smokers (0.79 ± 0.98 nmol/6h urine) than in nonsmokers (0.20 ± 0.98 nmol/6h urine) (p < 0.01). The total of 1,2-PheQ and 3,4-PheQ were more strongly correlated with urinary (Z)-7-[1R,2R,3R,5S)-3,5-dihydroxy-2-[(E,3S)-3-hydroxyoct-1-enyl]cyclopentyl]hept-5-enoic acid (8-iso-PGF_2α), a biomarker of lipid peroxidation (R² = 0.53, p < 0.001), than the other phenanthrene metabolites including phenanthrene tetraol (PheT), phenanthrene-1,2-dihydrodiol (1,2-PheD), and total phenanthrene phenols (OHPhe), consistent with the concept that PheQs and likely other PAH quinones play a causal role in the generation of reactive oxygen species (ROS) in humans. Thus, PheQs may be suitable as biomarkers to assess human exposure to oxygenated PAH and the subsequent oxidative damage. This study provides unique support, by analysis of human urinary metabolites, for the PAH quinone mediated oxidative damage hypothesis of PAH carcinogenesis.

IL-27 along with IL-28B ameliorates the pulmonary redox impairment, inflammation and immunosuppression in benzo(a)pyrene induced lung cancer bearing mice

AIMS

The major cause behind lung cancer development is exposure to various polycyclic aromatic hydrocarbons like benzo(a)pyrene (BaP) present in tobacco smoke, motor vehicle, and industrial exhaust. BaP is reported to induce the expression of various pro-inflammatory cytokines and matrix remodeling proteins. It is also responsible for dysfunction and exhaustion of the killing capacity of CD8+ T lymphocytes, one of the important components of the immune system which can kill tumor cells. We tried to evaluate the synergistic role of IL-27 and IL-28B in modulation of BaP-induced lung carcinogenesis associated with various hallmarks like pulmonary redox imbalance, angiogenesis, inflammation and cell proliferation in lung tissue.

MAIN METHOD

BaP was treated to Swiss albino mice to develop lung tumor. After the confirmation of lung tumor development Swiss albino mice were treated with IL-27 and IL-28B alone or in combination intraperitoneally. Histological analysis, immunohistochemistry, biochemical assay, western blot analysis, cell cytotoxicity assay, real-time PCR assay etc. were performed to evaluate the modulatory role of IL-27 and IL-28B.

KEY FINDINGS

We observed that IL-27 and IL-28B were able to suppress the expression of lung cancer-associated NFkB, COX-2, and iNOS. The expression of TNF-α, PCNA and some matrix remodeling enzymes were also modulated upon IL-27 and IL-28B treatment. Although the population of lung residing CD8+ T cells in tumor bearing lung tissue were unresponsive but the activity of systemic CD8+ cells was increased.

SIGNIFICANCE

Results hinted that IL-27 along with IL-28B were able to ameliorate various hallmarks ranging from angiogenesis to inflammation associated with the BaP-induced lung carcinogenesis. From this study, we propose that IL-27 and IL28B can be used as immunotherapeutic agent to regulate lung cancer.

Airborne Aerosols and Human Health: Leapfrogging from Mass Concentration to Oxidative Potential

The mass concentration of atmospheric particulate matter (PM) has been systematically used in epidemiological studies as an indicator of exposure to air pollutants, connecting PM concentrations with a wide variety of human health effects. However, these effects can be hardly explained by using one single parameter, especially because PM is formed by a complex mixture of chemicals. Current research has shown that many of these adverse health effects can be derived from the oxidative stress caused by the deposition of PM in the lungs. The oxidative potential (OP) of the PM, related to the presence of transition metals and organic compounds that can induce the production of reactive oxygen and nitrogen species (ROS/RNS), could be a parameter to evaluate these effects. Therefore, estimating the OP of atmospheric PM would allow us to evaluate and integrate the toxic potential of PM into a unique parameter, which is related to emission sources, size distribution and/or chemical composition. However, the association between PM and particle-induced toxicity is still largely unknown. In this commentary article, we analyze how this new paradigm could help to deal with some unanswered questions related to the impact of atmospheric PM over human health.

Biocompatibility, Cytotoxicity, Antimicrobial and Epigenetic Effects of Novel Chitosan-Based Quercetin Nanohydrogel in Human Cancer Cells

Background

Previous studies have reported that quercetin (Q) has a potential antibacterial and anticancer activity. However, its application is limited by many important factors including high hydrophobicity and low absorption.

Methodology

In the current study, we synthesized and characterized (Patent) a novel chitosan-based quercetin nanohydrogel (ChiNH/Q). Encapsulation efficiency was confirmed by UV/VIS spectrophotometer. Physicochemical characterization of ChiNH/Q was assessed by PDI, DLS, SEM, FTIR, and XRD. The toxicity of the ChiNH/Q against five strains of the pathogen and HepG2 cells was examined. Moreover, the quantification of ChiNH/Q on genomic global DNA methylation and expression of DNMTs (DNMT1/3A/3B) in HepG2 cancer cells were evaluated by ELISA and real-time PCR, respectively.

Results

Under the SEM-based images, the hydrodynamic size of the ChiNH/Q was 743.6 nm. The changes in the PDI were 0.507, and zeta potential was obtained as 12.1 mV for ChiNH/Q. The FTIR peak of ChiNH/Q showed the peak at 627 cm⁻¹ corresponded to tensile vibrational of NH₂-groups related to Q, and it is the indication of Q loading in the formulation. Moreover, XRD data have detected the encapsulation of ChiNH/Q. The ChiNH/Q showed a potent antimicrobial inhibitory effect and exerted cytotoxic effects against HepG2 cancer cells with IC₅₀ values of 100 µg/mL. Moreover, our data have shown that ChiNH/Q effectively reduced (65%) the average expression level of all the three DNMTs (p<0.05) and significantly increased (1.01%) the 5-methylated cytosine (5-mC) levels in HepG2 cells.

Conclusion

Our results showed for the first time the bioavailability and potentiality of ChiNH/Q as a potent antimicrobial and anticancer agent against cancer cells. Our result provided evidence that ChiNH/Q could effectively reduce cellular DNMT expression levels and increase genomic global DNA methylation in HepG2 cancer cells. Our results suggest a potential clinical application of nanoparticles as antimicrobial and anticancer agents in combination cancer therapy.

Threshold collision induced dissociation of pyrene cluster cations

We report threshold collision induced dissociation experiments on cationic pyrene clusters, for sizes n = 2-6. Fragmentation cross sections are recorded as a function of the collision energy and analyzed with a statistical model. This model can account for the dissociation cascades and provides values for the dissociation energies. These values, of the order of 0.7 eV-1 eV, are in excellent agreement with those previously derived from thermal evaporation. They confirm the charge resonance stability enhancement predicted by theoretical calculations. In addition, remarkable agreement is obtained with theoretical predictions for the two smaller sizes n = 2 and 3. For the larger sizes, the agreement remains good, although the theoretical values obtained for the most stable structures are systematically higher by 0.2 eV. This offset could be attributed to approximations in the calculations. Still, there is an indication in the results of an incomplete description of the role of isomerization and/or direct dissociation upon collisions. Finally, by-product clusters containing dehydrogenated species are found to dissociate at energies comparable to the non-dehydrogenated ones, which shows no evidence for covalent bonds within the clusters.

Particulate Matter Induces Tissue OxInflammation: From Mechanism to Damage

Significance: Oxidative stress and oxidative damage are central hypothetical mechanisms for the adverse effects of airborne particulate matter (PM). Activation of inflammatory cells capable of generating reactive oxygen and nitrogen species is another proposed damage pathway. Understanding the interplay between these responses can help us understand the adverse health effects attributed to breathing polluted air. Recent Advances: The consequences of PM exposure on different organs are oxidative damage, decreased function, and inflammation, which can lead to the development/exacerbation of proinflammatory disorders. Mitochondrial damage is also an important event in PM-induced cytotoxicity. Critical Issues: Reactive oxygen species (ROS) are generated during phagocytosis of the particles, leading to enhancement of oxidative stress and triggering the inflammatory response. The activation of inflammatory signaling pathways results in the release of cytokines and other mediators, which can further induce ROS production by activating endogenous enzymes, leading to a positive feedback loop, which can aggravate the effects triggered by PM exposure. Future Directions: Further research is required to elucidate the exact mechanisms by which PM exposure results in adverse health effects, in terms of the relationship between the redox responses triggered by the presence of the particles and the inflammation observed in the different organs, so the development/exacerbation of PM-associated health problems can be prevented.

Effects of DNA Damage and Oxidative Stress in Human Bronchial Epithelial Cells Exposed to PM2.5 from Beijing, China, in Winter

Epidemiological studies have corroborated that respiratory diseases, including lung cancer, are related to fine particulate matter (<2.5 μm) (PM_2.5) exposure. The toxic responses of PM_2.5 are greatly influenced by the source of PM_2.5. However, the effects of PM_2.5 from Beijing on bronchial genotoxicity are scarce. In the present study, PM_2.5 from Beijing was sampled and applied in vitro to investigate its genotoxicity and the mechanisms behind it. Human bronchial epithelial cells 16HBE were used as a model for exposure. Low (67.5 μg/mL), medium (116.9 μg/mL), and high (202.5 μg/mL) doses of PM_2.5 were used for cell exposure. After PM_2.5 exposure, cell viability, oxidative stress markers, DNA (deoxyribonucleic acid) strand breaks, 8-OH-dG levels, micronuclei formation, and DNA repair gene expression were measured. The results showed that PM_2.5 significantly induced cytotoxicity in 16HBE. Moreover, the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and cellular heme oxygenase (HO-1) were increased, and the level of glutathione (GSH) was decreased, which represented the occurrence of severe oxidative stress in 16HBE. The micronucleus rate was elevated, and DNA damage occurred as indicators of the comet assay, γ-H2AX and 8-OH-dG, were markedly enhanced by PM_2.5, accompanied by the influence of 8-oxoguanine DNA glycosylase (OGG1), X-ray repair cross-complementing gene 1 (XRCC1), and poly (ADP-ribose) polymerase-1 (PARP1) expression. These results support the significant role of PM_2.5 genotoxicity in 16HBE cells, which may occur through the combined effect on oxidative stress and the influence of DNA repair genes.

Combined exposure of fine particulate matter and high-fat diet aggravate the cardiac fibrosis in C57BL/6J mice

Cardiac fibrosis is associated with fine particulate matter (PM_2.5) exposure. In addition, whether high-fat diet (HFD) could exacerbate the PM_2.5-induced cardiac injury was unevaluated. Thus, this study was aimed to investigate the combined effects of PM_2.5 and HFD on cardiac fibrosis. The echocardiography and histopathological analysis showed that co-exposure of PM_2.5 and HFD had a significant deleterious effect on both cardiac systolic and diastolic function accompanied the myofibril disorder and myocardial fibrosis in C57BL/6 J mice than exposed to PM_2.5 or HFD alone. The augmented oxidative damage and increased α-SMA area percentage were detected in heart tissue of mice exposed to PM_2.5 and HFD together. PM_2.5 upregulated the expressions of cardiac fibrosis-related special markers, including collagen-I, collagen-III, TGF-β1, p-Smad3 and total Smad3, which had more pronounced activations in co-exposure group. Meanwhile, the factorial analysis exhibited the synergistic interaction regarded to the combined exposure of PM_2.5 and HFD. Simultaneously, PM_2.5 and palmitic acid increased intracellular ROS generation and activated the TGF-β1/Smad3 signaling pathway in cardiomyocytes. While the ROS scavenger NAC had effectively attenuated the ROS level and suppressed the TGF-β1/Smad3 signaling pathway. Taken together, our results demonstrated combined exposure to PM_2.5 and HFD could aggravate cardiac fibrosis via activating the ROS/TGF-β1/Smad3 signaling pathway.

Protective Effects of Myricetin on Benzo[a]pyrene-Induced 8-Hydroxy-2'-Deoxyguanosine and BPDE-DNA Adduct

Benzo[a]pyrene (B[a]P), a group 1 carcinogen, induces mutagenic DNA adducts. Myricetin is present in many natural foods with diverse biological activities, such as anti-oxidative and anti-cancer activities. The aim of this study was to investigate the protective effects of myricetin against B[a]P-induced toxicity. Treatment of B[a]P induced cytotoxicity on HepG2 cells, whereas co-treatment of myricetin with B[a]P reduced the formation of the B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE)-DNA adduct, which recovered cell viability. Furthermore, we found a protective effect of myricetin against B[a]P-induced genotoxicity in rats, via myricetin-induced inhibition of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and BPDE-DNA adduct formation in the liver, kidney, colon, and stomach tissue. This inhibition was more prominent in the liver than in other tissues. Correspondingly, myricetin regulated the phase I and II enzymes that inhibit B[a]P metabolism and B[a]P metabolites conjugated with DNA by reducing and inducing CYP1A1 and glutathione S-transferase (GST) expression, respectively. Taken together, this showed that myricetin attenuated B[a]P-induced genotoxicity via regulation of phase I and II enzymes. Our results suggest that myricetin is anti-genotoxic, and prevents oxidative DNA damage and BPDE-DNA adduct formation via regulation of phase I and II enzymes.

Impact of air pollution on intestinal redox lipidome and microbiome

Air pollution is a rising public health issue worldwide. Cumulative epidemiological and experimental studies have shown that exposure to air pollution such as particulate matter (PM) is linked with increased hospital admissions and all-cause mortality. While previous studies on air pollution mostly focused on the respiratory and cardiovascular effects, emerging evidence supports a significant impact of air pollution on the gastrointestinal (GI) system. The gut is exposed to PM as most of the inhaled particles are removed from the lungs to the GI tract via mucociliary clearance. Ingestion of contaminated food and water is another common source of GI tract exposure to pollutants. Recent studies have associated air pollution with intestinal diseases, including appendicitis, colorectal cancer, and inflammatory bowel disease. In addition to the liver and adipose tissue, intestine is an important organ system for lipid metabolism, and the intestinal redox lipids might be tightly associated with the intestinal and systematic inflammation. The gut microbiota modulates lipid metabolism and contributes to the initiation and development of intestinal disease including inflammatory bowel disease. Recent data support microbiome implication in air pollution-mediated intestinal and systematic effects. In this review, the associations between air pollution and intestinal diseases, and the alterations of intestinal lipidome and gut microbiome by air pollution are highlighted. The potential mechanistic aspects underlying air pollution-mediated intestinal pathology will also be discussed.

Particulate Matter Toxicity Is Nrf2 and Mitochondria Dependent: The Roles of Metals and Polycyclic Aromatic Hydrocarbons

Particulate matter (PM), an important component of air pollution, induces significant adverse health effects. Many of the observed health effects caused by inhaled PM are associated with oxidative stress and inflammation. This association has been linked in particular to the particles’ chemical components, especially the inorganic/metal and the organic/polycyclic aromatic hydrocarbon (PAH) fractions, and their ability to generate reactive oxygen species in biological systems. The transcription factor NF-E2 nuclear factor erythroid-related factor 2 (Nrf2) is activated by redox imbalance and regulates the expression of phase II detoxifying enzymes. Nrf2 plays a key role in preventing PM-induced toxicity by protecting against oxidative damage and inflammation. This review focuses on specific PM fractions, particularly the dissolved metals and PAH fractions, and their roles in inducing oxidative stress and inflammation in cell and animal models with respect to Nrf2 and mitochondria.

Degradation strategies and associated regulatory mechanisms/features for aromatic compound metabolism in bacteria

As a result of anthropogenic activity, large number of recalcitrant aromatic compounds have been released into the environment. Consequently, microbial communities have adapted and evolved to utilize these compounds as sole carbon source, under both aerobic and anaerobic conditions. The constitutive expression of enzymes necessary for metabolism imposes a heavy energy load on the microbe which is overcome by arrangement of degradative genes as operons which are induced by specific inducers. The segmentation of pathways into upper, middle and/or lower operons has allowed microbes to funnel multiple compounds into common key aromatic intermediates which are further metabolized through central carbon pathway. Various proteins belonging to diverse families have evolved to regulate the transcription of individual operons participating in aromatic catabolism. These proteins, complemented with global regulatory mechanisms, carry out the regulation of aromatic compound metabolic pathways in a concerted manner. Additionally, characteristics like chemotaxis, preferential utilization, pathway compartmentalization and biosurfactant production confer an advantage to the microbe, thus making bioremediation of the aromatic pollutants more efficient and effective.

Down-Regulation of p23 in Normal Lung Epithelial Cells Reduces Toxicities From Exposure to Benzo[a]pyrene and Cigarette Smoke Condensate via an Aryl Hydrocarbon Receptor-Dependent Mechanism

The aryl hydrocarbon receptor (AHR) is a ligand-activated signaling molecule which controls tumor growth and metastasis, T cell differentiation, and liver development. Expression levels of this receptor protein is sensitive to the cellular p23 protein levels in immortalized cancer cell lines. As little as 30% reduction of the p23 cellular content can suppress the AHR function. Here we reported that down-regulation of the p23 protein content in normal, untransformed human bronchial/tracheal epithelial cells to 48% of its content also suppresses the AHR protein levels to 54% of its content. This p23-mediated suppression of AHR is responsible for the suppression of (1) the ligand-dependent induction of the cyp1a1 gene transcription; (2) the benzo[a]pyrene- or cigarette smoke condensate-induced CYP1A1 enzyme activity, and (3) the benzo[a]pyrene and cigarette smoke condensate-mediated production of reactive oxygen species. Reduction of the p23 content does not alter expression of oxidative stress genes and production of PGE2. Down regulation of p23 suppresses the AHR protein levels in two other untransformed cell types, namely human breast MCF-10A and mouse immune regulatory Tr1 cells. Collectively, down-regulation of p23 suppresses the AHR protein levels in normal and untransformed cells and can in principle protect our lung epithelial cells from AHR-dependent oxidative damage caused by exposure to agents from environment and cigarette smoking.

Preparation of dihydroxy polycyclic aromatic hydrocarbons and activities of two dioxygenases in the phenanthrene degradative pathway

Dihydroxy phenanthrene, fluoranthene, and pyrene derivatives are intermediates in the bacterial catabolism of the corresponding parent polycyclic aromatic hydrocarbon (PAH). Ring-opening of the dihydroxy species followed by a series of enzyme-catalyzed reactions generates metabolites that funnel into the Krebs Cycle with the eventual production of carbon dioxide and water. One complication in delineating these pathways and harnessing them for useful purposes is that the initial enzymatic processing produces multiple dihydroxy PAHs with multiple ring opening possibilities and products. As part of a systematic effort to address this issue, eight dihydroxy species were synthesized and characterized as the dimethoxy or diacetate derivatives. Several dihydroxy compounds were examined with two dioxygenases in the phenanthrene degradative pathway in Mycobacterium vanbaalenii PYR-1. One, 3,4-dihydroxyphenanthrene, was processed by PhdF with a k_cat/K_m of 6.0 × 10⁶ M^-1s^-1, a value that is consistent with the annotated function of PhdF in the pathway. PhdI processed 1-hydroxy-2-naphthoate with a k_cat/K_m of 3.1 × 10⁵ M^-1s^-1, which is also consistent with the proposed role in the pathway. The observations provide the first biochemical evidence for these two reactions in M. vanbaalenii PYR-1 and, to the best of our knowledge, the first biochemical evidence for the reaction of PhdF with 3,4-dihydroxyphenanthrene. Although PhdF is upregulated in the presence of pyrene, it did not process two dihydroxypyrenes. Methodology was developed for product analysis of the extradiol dioxygenases.

Alveolar macrophage reaction to PM2.5 of hazy day in vitro: Evaluation methods and mitochondrial screening to determine mechanisms of biological effect

Hazy weather in China has recently become a major public health concern due to high levels of atmospheric fine particulate matter (PM_2.5) with a large amount of polycyclic aromatic hydrocarbon (PAHs). In this study, the mass concentration of PAHs in hazy PM_2.5 in urban Taiyuan city, China was determined and toxicities of different dosage of the hazy PM_2.5 on rat alveolar macrophages (AMs) were examined. It was found that the hazy PM_2.5, bounded with many species of PAHs (CHR, BbF, BaP, BaA, and etc.), significantly increased cellular malondialdehyde (MDA) content followed by the decreasing in superoxide (SOD) and glutathione peroxidase (GPx) in AMs. They induced mitochondrial changes in ultrastructure as evidenced by mitochondrial swelling and cristae disorganization, and a dose-dependent decrease in mitochondrial profile density. Also, the mRNA expression levels of mitochondrial fusion-related genes were modified. The Mfn1 and Mfn2 which are essential for mitochondrial fusion increased significantly in hazy PM_2.5-treated group compared to the control in a dose-dependent manner, OPA1 was significantly increased at the highest PM_2.5 dose delivered. These findings suggested that exposure to hazy PM_2.5 could activate oxidative stress pathways in AMs, resulting in abnormal mitochondrial morphology and fusion/fission frequency. Possibly, the toxic effects were mostly attributed to the high burden of varied PAHs in hazy PM_2.5.

In vitro toxicological evaluation of emissions from catalytic oxidation removal of industrial VOCs by air/liquid interface (ALI) exposure system in repeated mode

Toxicity of toluene and by-products formed during its catalytic oxidative degradation was studied in human bronchial BEAS-2B cells repeatedly exposed. BEAS-2B cells were exposed using an Air-Liquid Interface (ALI) System (Vitrocell®) for 1 h per day during 1, 3 or 5 days to gaseous flows: toluene vapors (100 and 1000 ppm) and outflow after catalytic oxidation of toluene (10 and 100%). After exposure to gaseous flow, cytotoxicity, inflammatory response and Xenobiotic Metabolism Enzymes (XME) gene expression were investigated. No significant cytotoxicity was found after 5 days for every condition of exposure. After cells exposure to catalytic oxidation flow, IL-6 level increased no significantly in a time- and dose-dependent way, while an inverted U-shaped profile of IL-8 secretion was observed. XME genes induction, notably CYP2E1 and CYP2F1 results were in line with the presence of unconverted toluene and benzene formed as a by-product, detected by analytical methods. Exposure to pure toluene also demonstrated the activation of these XMEs involved in its metabolism. Repeated exposure permits to show CYP1A1, CYP1B1 and CY2S1 expression, probably related to the formation of other by-products, as PAHs, not detected by standard analytical methods used for the development of catalysts.

n-3 Polyunsaturated fatty acids alter benzo[a]pyrene metabolism and genotoxicity in human colon epithelial cell models

Dietary carcinogens, such as benzo[a]pyrene (BaP), are suspected to contribute to colorectal cancer development. n-3 Polyunsaturated fatty acids (PUFAs) decrease colorectal cancer risk in individuals consuming diets rich in PUFAs. Here, we investigated the impact of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid on metabolism and genotoxicity of BaP in human cell models derived from the colon: HT-29 and HCT-116 cell lines. Both PUFAs reduced levels of excreted BaP metabolites, in particular BaP-tetrols and hydroxylated BaP metabolites, as well as formation of DNA adducts in HT-29 and HCT-116 cells. However, EPA appeared to be a more potent inhibitor of formation of some intracellular BaP metabolites, including BaP-7,8-dihydrodiol. EPA also reduced phosphorylation of histone H2AX (Ser139) in HT-29 cells, which indicated that it may reduce further forms of DNA damage, including DNA double strand breaks. Both PUFAs inhibited induction of CYP1 activity in colon cells determined as 7-ethoxyresorufin-O-deethylase (EROD); this was at least partly linked with inhibition of induction of CYP1A1, 1A2 and 1B1 mRNAs. The downregulation and/or inhibition of CYP1 enzymes by PUFAs could thus alter metabolism and reduce genotoxicity of BaP in human colon cells, which might contribute to known chemopreventive effects of PUFAs in colon epithelium.