Combined effects of co-exposure to formaldehyde and acrolein mixtures on cytotoxicity and genotoxicity in vitro

The mutagenic properties of formaldehyde and acetaldehyde: Reflections on half a century of progress

Formaldehyde and acetaldehyde are reactive, small compounds that humans are exposed to routinely, variously from endogenous and exogenous sources. Both small aldehydes are classified as human carcinogens. Investigation of the DNA damaging properties of these two compounds began some 50 years ago. In this review, we summarize progress in this field since its inception over half a century ago, distilling insights gained by the collective efforts of many research groups while highlighting areas for future directions. Over the decades, general consensus about aspects of the mutagenicity of formaldehyde and acetaldehyde has been reached. But other characteristics of formaldehyde and acetaldehyde remain incompletely understood and require additional investigation. These include crucial details about the mutational signature(s) induced and possible mechanistic role(s) during carcinogenesis.

Optimization Strategy for Formaldehyde Removal by Carbon Cathode Electro-Fenton: Enhancement of Formaldehyde and Oxygen Co-adsorption by Rational Nitrogen Doping Types

This study investigates the effect of N-doped coal-based activated carbon cathode on formaldehyde-oxygen coadsorption. Further investigation investigates the effect of formaldehyde-oxygen coadsorption on H2O2 generation and formaldehyde removal in an electro-Fenton system. Nitrogen doping enhances formaldehyde and oxygen coadsorption by modulating competitive adsorption. Density Functional Theory (DFT) calculations confirm pyrrole nitrogen favors formaldehyde, and graphite nitrogen favors oxygen adsorption. N-doped activated carbon adsorbs 0.36 mg of formaldehyde and 0.1 mg of oxygen in 120 min and removes 82.43% of formaldehyde after electro-Fenton treatment. N-doped activated carbon enhances the synergistic adsorption of formaldehyde and oxygen. In the synergistic adsorption process, the amount of formaldehyde adsorbed is greater than the amount of oxygen adsorbed. This improves the removal efficiency of formaldehyde by electro-Fenton technology. It provides a new method for electro-Fenton removal of organic pollutants.

Scientific opinion on the renewal of the authorisation of Zesti Smoke Code 10 (SF-002) as a smoke flavouring Primary Product

The EFSA Panel on Food Additives and Flavourings (FAF) was requested to evaluate the safety of the smoke flavouring Primary Product Zesti Smoke Code 10 (SF-002), for which a renewal application was submitted in accordance with Article 12(1) of Regulation (EC) No 2065/2003. This opinion refers to the assessment of data submitted on chemical characterisation, dietary exposure and genotoxicity of the Primary Product. Zesti Smoke Code 10 is obtained by pyrolysis of hickory and oak woods. Given the limitations of the quantification approach employed by the applicant, the Panel could not judge whether the applied methods meet the legal quality criterion that at least 80% of the volatile fraction shall be identified and quantified. At the maximum proposed use levels, dietary exposure estimates calculated with DietEx ranged from 0.02 to 4.6 mg/kg body weight (bw) per day at the mean and from no dietary exposure to 13.0 mg/kg bw per day at the 95th percentile. The Panel concluded that four components in the Primary Product raise a potential concern for genotoxicity. In addition, a potential concern for genotoxicity was identified for the unidentified part of the mixture. The Primary Product contains furan-2(5H)-one and benzene-1,2-diol, for which a concern for genotoxicity was identified in vivo upon oral administration. Considering that the exposure estimates for these two components are above the threshold of toxicological concern (TTC) of 0.0025 μg/kg bw per day for DNA-reactive mutagens and/or carcinogens, the Panel concluded that the Primary Product raises concern with respect to genotoxicity.

Scientific opinion on the renewal of the authorisation of SmokEz C-10 (SF-005) as a smoke flavouring Primary Product

The EFSA Panel on Food Additives and Flavourings (FAF) was requested to evaluate the safety of the smoke flavouring Primary Product SmoKEz C-10 (SF-005), for which a renewal application was submitted in accordance with Article 12(1) of Regulation (EC) No 2065/2003. This opinion refers to the assessment of data submitted on chemical characterisation, dietary exposure and genotoxicity of the Primary Product. SmoKEz C-10 is obtained by pyrolysis of maple, oak, hickory, ash, birch, beech and cherry woods. Given the limitations of the quantification approach employed by the applicant, the Panel could not judge whether the applied methods meet the legal quality criterion that at least 80% of the volatile fraction shall be identified and quantified. At the maximum proposed use levels, dietary exposure estimates calculated with DietEx ranged from 0.01 to 5.1 mg/kg body weight (bw) per day at the mean and from no dietary exposure to 18.1 mg/kg bw per day at the 95th percentile. The Panel concluded that five components in the Primary Product raise a potential concern for genotoxicity. In addition, a potential concern for genotoxicity was identified for the unidentified part of the mixture. The Primary Product contains furan-2(5H)-one and benzene-1,2-diol, for which a concern for genotoxicity was identified in vivo upon oral administration. Considering that the exposure estimates for these two components are above the threshold of toxicological concern (TTC) of 0.0025 μg/kg bw per day for DNA-reactive mutagens and/or carcinogens, the Panel concluded that the Primary Product raises concern with respect to genotoxicity.

Personal exposure to aldehydes and potential health risks among schoolchildren in the city

Schoolchildren are sensitive to airborne aldehyde exposures. The knowledge regarding inhalation exposure to aldehydes and the factors influencing exposure in schoolchildren is limited. This study aimed to assess the variability and potential health risks of exposure to aldehydes (including formaldehyde) in schoolchildren. The important factors affecting personal exposure to aldehydes were also explored. Forty schoolchildren were recruited from the urban and suburban areas of Taiwan for aldehyde samplings and questionnaire surveys. Personal and indoor home samples of aldehydes were collected simultaneously during warm and cold seasons. We also identified the potential variables associated with aldehyde exposure based on the participant's responses to the questionnaires using mixed-effects models. The dominant three abundant aldehydes identified in personal exposure samples were formaldehyde (geometric mean, GM = 12.2 µg/m3), acetaldehyde (GM = 5.53 µg/m3), and hexaldehyde (GM = 8.79 µg/m3), accounting for approximately 80% of the total selected aldehydes. Higher personal exposure to aldehydes was observed during the warm season. Moreover, the within-subject variance was predominant, accounting for 66.6 to > 99.9% of the total variance in exposure. Schoolchildren had a high probability of overexposure to formaldehyde and acrolein, which resulted in an incremental lifetime cancer risk of 1.59 × 10-4 (95th percentile = 4.64 × 10-4). Season, location, household refurbishment, and indoor ventilation variables were significantly associated with personal exposure to aldehydes. The results can improve our understanding of aldehyde exposure among schoolchildren to propose mitigation strategies. These findings may be applied to further epidemiological studies.

14-3-3 proteins regulate the HCHO stress response by interacting with AtMDH1 and AtGS1 in tobacco and Arabidopsis

Formaldehyde (HCHO) is one of the most essential common carcinogenic environmental pollutants. While 14-3-3 proteins are known to regulate the response of plants to HCHO stress, the regulatory mechanisms responsible for a tolerant phenotype remain unclear. We first performed qPCR analysis of HCHO-treated Arabidopsis and tobacco and determined that the expression of At14-3-3PSI and Nt14-3-3C genes was rapidly upregulated after HCHO stress. Furthermore, overexpression of 14-3-3, AtMDH1 or AtGS1 genes enhanced plant HCHO absorption capacity and resistance, and knockdown or knockout of 14-3-3, AtMDH1 or AtGS1 genes reduced plant HCHO absorption capacity and resistance. However, overexpression of the AtGS1 and AtMDH1 genes in the At14-3-3 psi mutant restored HCHO uptake and resistance in Arabidopsis. Moreover, 14-3-3 bound to the N-terminus of AtMDH1 and the C-terminus of AtGS1, respectively, and repressed and enhanced their expression. The ¹³C NMR results of HCHO stress mutants Atgs1 and Atmdh1 showed that the metabolites Glu and Asp rapidly increased, indicating that AtGS1 and AtMDH1 were indeed indispensable for Arabidopsis to metabolize HCHO. In conclusion, we uncovered a HCHO stress response mechanism mediated by 14-3-3, which enhances the plant's ability to absorb HCHO, deepening our understanding of how plants respond to HCHO stress.

Evaluation of the effects of e-cigarette aerosol extracts and tobacco cigarette smoke extracts on human gingival epithelial cells

Smoking increases the risk of a number of diseases, including cardiovascular, oral and lung diseases. E-cigarettes are gaining popularity among young people as an alternative to cigarettes, but there is debate over whether they are less harmful to the mouth than e-cigarettes. In this study, human gingival epithelial cells (HGECs) were treated with four commercially available e-cigarette aerosol condensates (ECAC) or commercially available generic cigarette smoke condensates (CSC) with different nicotine concentrations. Cell viability was determined by MTT assay. Cell apoptosis was observed by acridine orange (AO) and Hoechst33258 staining. The levels of type I collagen, matrix metalloproteinase (MMP-1, MMP-3), cyclooxygenase 2 and inflammatory factors were detected by ELISA and RT-PCR. Finally, ROS levels were analyzed by ROS staining. The different effects of CSC and ECAC on HGECs were compared. The results showed that higher nicotine concentration of CS significantly reduced the activity of HGECs. By contrast, all ECAC had no significant effect. The levels of matrix metalloproteinase, COX-2, and inflammatory factors were higher in HGECs treated with CSC than those treated with ECAC. In contrast, the level of type I collagen was higher in HGECs treated with ECAC than those treated with CSC. In conclusion, all four flavors of e-cigarettes were less toxic to HGE cells than tobacco, but further clinical studies are needed to determine whether e-cigarettes are less harmful to oral health than conventional cigarettes.

Flavored E-cigarette product aerosols induce transformation of human bronchial epithelial cells

OBJECTIVES

E-cigarettes are the most commonly used nicotine containing products among youth. In vitro studies support the potential for e-cigarettes to cause cellular stress in vivo; however, there have been no studies to address whether exposure to e-liquid aerosols can induce cell transformation, a process strongly associated with pre-malignancy. We examined whether weekly exposure of human bronchial epithelial cell (HBEC) lines to e-cigarette aerosols would induce transformation and concomitant changes in gene expression and promoter hypermethylation.

MATERIALS AND METHODS

An aerosol delivery system exposed three HBEC lines to unflavored e-liquid with 1.2% nicotine, 3 flavored products with nicotine, or the Kentucky reference cigarette once a week for 12 weeks. Colony formation in soft agar, RNA-sequencing, and the EPIC Beadchip were used to evaluate transformation, genome-wide expression and methylation changes.

RESULTS

Jamestown e-liquid aerosol induced transformation of HBEC2 and HBEC26, while unflavored and Blue Pucker transformed HBEC26. Cigarette smoke aerosol transformed HBEC4 and HBEC26 at efficiencies up to 3-fold greater than e-liquids. Transformed clones exhibited extensive reprogramming of the transcriptome with common and distinct gene expression changes observed between the cigarette and e-liquids. Transformation by e-liquids induced alterations in canonical pathways implicated in lung cancer that included axonal guidance and NRF2. Gene methylation, while prominent in cigarette-induced transformed clones, also affected hundreds of genes in HBEC2 transformed by Jamestown. Many genes with altered expression or epigenetic-mediated silencing were also affected in lung tumors from smokers.

CONCLUSIONS

These studies show that exposure to e-liquid aerosols can induce a pre-malignant phenotype in lung epithelial cells. While the Food and Drug Administration banned the sale of flavored cartridge-based electric cigarettes, consumers switched to using flavored products through other devices. Our findings clearly support expanding studies to evaluate transformation potency for the major categories of e-liquid flavors to better inform risk from these complex mixtures.

Evaluation of the Effects of E-Cigarette Aerosol Extracts and Tobacco Cigarette Smoke Extracts on Human Gingival Epithelial Cells

Smoking increases the risk of a number of diseases, including cardiovascular, oral, and lung diseases. E-cigarettes are gaining popularity among young people as an alternative to cigarettes, but there is debate over whether they are less harmful to the mouth than e-cigarettes. In this study, human gingival epithelial cells (HGECs) were treated with four commercially available e-cigarette aerosol condensates (ECAC) or commercially available generic cigarette smoke condensates (CSC) with different nicotine concentrations. Cell viability was determined by MTT assay. Cell apoptosis was observed by acridine orange (AO) and Hoechst33258 staining. The levels of type I collagen, matrix metalloproteinase (MMP-1, MMP-3), cyclooxygenase 2, and inflammatory factors were detected by ELISA and RT-PCR. Finally, ROS levels were analyzed by ROS staining. The different effects of CSC and ECAC on HGECs were compared. The results showed that higher nicotine concentration of CS significantly reduced the activity of HGECs. By contrast, all ECAC had no significant effect. The levels of matrix metalloproteinase, COX-2, and inflammatory factors were higher in HGECs treated with CSC than those treated with ECAC. In contrast, the level of type I collagen was higher in HGECs treated with ECAC than those treated with CSC. In conclusion, all four flavors of e-cigarettes were less toxic to HGE cells than tobacco, but further clinical studies are needed to determine whether e-cigarettes are less harmful to oral health than conventional cigarettes.

Impact of sub-acute acrolein inhalation on the molecular regulation of mitochondrial metabolism in rat lung

Nowadays, mitochondria are recognized as key players in the pathogenesis of a variety of smoking-associated lung diseases. Acrolein, a component of cigarette smoke, is a known driver of biological mechanisms underlying smoking-induced respiratory toxicity. The impact of sub-acute acrolein inhalation in vivo on key processes controlling mitochondrial homeostasis in cells of the airways however is unknown. In this study, we investigated the activity/abundance of a myriad of molecules critically involved in mitochondrial metabolic pathways and mitochondrial quality control processes (mitochondrial biogenesis and mitophagy) in the lungs of Sprague-Dawley rats that were sub-acutely exposed to filtered air or 3 ppm acrolein by whole-body inhalation (5 h/day, 5 days/week for 4 weeks). Acrolein exposure induced a general inflammatory response in the lung as gene expression analysis revealed an increased expression of Icam1 and Cinc1 (p < 0.1; p < 0.05). Acrolein significantly decreased enzyme activity of hydroxyacyl-Coenzyme A dehydrogenase (p < 0.01), and decreased Pdk4 transcript levels (p < 0.05), suggestive of acrolein-induced changes in metabolic processes. Investigation of constituents of the mitochondrial biogenesis pathways and mitophagy machinery revealed no pronounced alterations. In conclusion, sub-acute inhalation of acrolein did not affect the regulation of mitochondrial metabolism and quality control, which is in contrast to more profound changes after acute exposure in other studies.

Occupational health risk assessment of airborne formaldehyde in medical laboratories

The professional use of formaldehyde is a major occupational health concern in medical laboratory operations. Quantification of various risks associated with chronic exposure to formaldehyde may help in understanding the related hazards. This study designed to assess the health risks associated with inhalation exposure to formaldehyde involving biological, cancer, and non-cancer risks in medical laboratories. This study was performed in the hospital laboratories at Semnan Medical Sciences University. Risk assessment was performed in pathology, bacteriology, hematology, biochemistry, and serology laboratories with 30 employees, using formaldehyde in their daily routine operations. We determined area and personal exposures to airborne contaminant, applied standard air sampling, and analytical method recommended by National Institute of Occupational Safety and Health (NIOSH). We addressed formaldehyde-specific hazard by estimating peak blood level, life cancer risk, and the hazard quotient of non-cancer risks, adapted from Environmental Protection Agency (EPA) assessment method. The airborne formaldehyde concentrations in the laboratory personal samples ranged 0.0156-0.5940 ppm (mean = 0.195 ppm, SD = 0.048) and area exposure ranged 0.0285-1.0810 ppm (mean = 0.462 ppm, SD = 0.087). Based on workplace exposure, peak blood levels of formaldehyde were estimated at minimum 0.0026 mg/l to maximum 0.152 mg/l (mean = 0.015 mg/l, SD = 0.016). The mean cancer risk levels in terms of area and personal exposures were estimated respectively at 3.93 E - 8 μg/m³ and 1.84 E - 4 μg/m³, and for the non-cancer risk levels of the same exposures measured respectively at 0.03 μg/m³ and 0.07 μg/m³. Formaldehyde levels were significantly higher among laboratory employees, especially bacteriology workers. Exposure and risk could be minimized by strengthening control measures including the use of management controls, engineering controls, and respiratory protection equipment to reduce exposure levels of all workers to less than the allowed exposure limits and improve indoor air quality in the workplace.

Disruption of the Molecular Regulation of Mitochondrial Metabolism in Airway and Lung Epithelial Cells by Cigarette Smoke: Are Aldehydes the Culprit?

Chronic obstructive pulmonary disease (COPD) is a devastating lung disease for which cigarette smoking is the main risk factor. Acetaldehyde, acrolein, and formaldehyde are short-chain aldehydes known to be formed during pyrolysis and combustion of tobacco and have been linked to respiratory toxicity. Mitochondrial dysfunction is suggested to be mechanistically and causally involved in the pathogenesis of smoking-associated lung diseases such as COPD. Cigarette smoke (CS) has been shown to impair the molecular regulation of mitochondrial metabolism and content in epithelial cells of the airways and lungs. Although it is unknown which specific chemicals present in CS are responsible for this, it has been suggested that aldehydes may be involved. Therefore, it has been proposed by the World Health Organization to regulate aldehydes in commercially-available cigarettes. In this review, we comprehensively describe and discuss the impact of acetaldehyde, acrolein, and formaldehyde on mitochondrial function and content and the molecular pathways controlling this (biogenesis versus mitophagy) in epithelial cells of the airways and lungs. In addition, potential therapeutic applications targeting (aldehyde-induced) mitochondrial dysfunction, as well as regulatory implications, and the necessary required future studies to provide scientific support for this regulation, have been covered in this review.

Smoking-Associated Exposure of Human Primary Bronchial Epithelial Cells to Aldehydes: Impact on Molecular Mechanisms Controlling Mitochondrial Content and Function

Chronic obstructive pulmonary disease (COPD) is a devastating lung disease primarily caused by exposure to cigarette smoke (CS). During the pyrolysis and combustion of tobacco, reactive aldehydes such as acetaldehyde, acrolein, and formaldehyde are formed, which are known to be involved in respiratory toxicity. Although CS-induced mitochondrial dysfunction has been implicated in the pathophysiology of COPD, the role of aldehydes therein is incompletely understood. To investigate this, we used a physiologically relevant in vitro exposure model of differentiated human primary bronchial epithelial cells (PBEC) exposed to CS (one cigarette) or a mixture of acetaldehyde, acrolein, and formaldehyde (at relevant concentrations of one cigarette) or air, in a continuous flow system using a puff-like exposure protocol. Exposure of PBEC to CS resulted in elevated IL-8 cytokine and mRNA levels, increased abundance of constituents associated with autophagy, decreased protein levels of molecules associated with the mitophagy machinery, and alterations in the abundance of regulators of mitochondrial biogenesis. Furthermore, decreased transcript levels of basal epithelial cell marker KRT5 were reported after CS exposure. Only parts of these changes were replicated in PBEC upon exposure to a combination of acetaldehyde, acrolein, and formaldehyde. More specifically, aldehydes decreased MAP1LC3A mRNA (autophagy) and BNIP3 protein (mitophagy) and increased ESRRA protein (mitochondrial biogenesis). These data suggest that other compounds in addition to aldehydes in CS contribute to CS-induced dysregulation of constituents controlling mitochondrial content and function in airway epithelial cells.

New approach methods for assessing indoor air toxicity

Indoor air is typically a mixture of many chemicals at low concentrations without any adverse health effects alone, but in mixtures they may cause toxicity and risks to human health. The aim of this study was by using new approach methods to assess the potential toxicity of indoor air condensates. In specific, different in vitro test methods including cyto-and immunotoxicity, skin sensitization and endocrine disruption were applied. In addition to biological effects, the indoor air samples were subjected to targeted analysis of 25 volatile organic compounds (VOCs) and Genapol X-80 (a nonionic emulsifier) suspected to be present in the samples, and to a non-targeted "total chemical scan" to find out whether the chemical composition of the samples is associated with the biological effects. The results confirm that assessing health risks of indoor air by analysing individual chemicals is not an adequate approach: We were not able to detect the VOCs and Genapol X-80 in the indoor air samples, yet, several types of toxicity, namely, cytotoxicity, immunotoxicity, skin sensitization and endocrine disruption were detected. In the non-targeted total chemical scan of the indoor air samples, a larger number of compounds were found in the cytotoxic samples than in the non-cytotoxic samples supporting the biological findings. If only one biological method would be selected for the screening of indoor air quality, THP-1 macrophage/WST-1 assay would best fit for the purpose as it is sensitive and serves as a good representative for different sub-toxic end points, including immunotoxicity, (skin) sensitization and endocrine disruption.

A Hydrothermal Method to Generate Carbon Quantum Dots from Waste Bones and Their Detection of Laundry Powder

Surfactants are one of the major pollutants in laundry powder, which have an impact on the environment and human health. Carbon quantum dots (CQDs) are spherical zero-dimensional fluorescent nanoparticles with great potential for fluorescent probing, electrochemical biosensing and ion sensing. Herein, a bottom-up approach was developed for the synthesis of CQDs from biomass to detect laundry detergent and laundry powder. Waste chicken bones were used as carbon precursors after being dried, crushed and reacted with pure water at 180 °C for 4 h to generate CQDs, which exhibited a monodisperse quasi-spherical structure with an average particle size of 3.2 ± 0.2 nm. Functional groups, including -OH, C=O, C=C and C-O, were identified on the surface of the prepared CQDs. The optimal fluorescence excitation wavelength of the yellow-brown CQDs was 380 nm, with a corresponding emission peak at 465 nm. CQDs did not significantly increase cell death in multiple cell lines at concentrations of 200 µg·mL⁻¹. Fluorescence enhancement of CQDs was observed after addition of sodium dodecyl benzene sulphonate, a major anionic surfactant in laundry powder. A linear relationship between fluorescence enhancement CQDs and the concentration of laundry powder was established. Thus, a hydrothermal method was developed to generate CQDs from waste biomass that may be used as a fluorescent probe to detect laundry powder.

Determination of Carbonyl Compounds in Different Work Environments: Comparison between LC-UV/DAD and LC-MS/MS Detection Methods

There were two analytical methods for the determination of 12 carbonyl compounds (CCs) by using liquid chromatography (LC) coupled with mass spectrometry (MS/MS) and diode array detector (UV/DAD) that were developed and applied to 52 samples that were collected in 10 workplaces. Linearity (0.996 < R² < 0.999), intra-day repeatability (0.7 < RSD% < 10), and inter-day repeatability (5 < RSD% < 16) were acceptable for both techniques, but the highest sensibility of the MS/MS method allowed us to correctly quantify 98% of the samples (versus 32% by UV/DAD). The comparison of the concentrations that were obtained by quantifying the same sample with both techniques showed good agreement for acetaldehyde and formaldehyde (0.1 < % deviation < 30) but much higher for the less abundant congeners. In real samples, formaldehyde was the most abundant congener (concentrations between 2.7 and 77 µg m^-3), followed by acetaldehyde (concentrations between 1.5 and 79 µg m^-3) and butyraldehyde (concentrations between 0.4 and 13 µg m^-3). In all the beauty salon samples, instead, the most abundant congener was acetaldehyde (concentrations between 19 and 79 µg m^-3), probably associated with the use of beauty products. Principal components analysis (PCA) confirms the ubiquitous character of formaldehyde and highlights the influence of minority CCs on different workplaces.

Acrolein inhalation acutely affects the regulation of mitochondrial metabolism in rat lung

Exposure of the airways to cigarette smoke (CS) is the primary risk factor for developing several lung diseases such as Chronic Obstructive Pulmonary Disease (COPD). CS consists of a complex mixture of over 6000 chemicals including the highly reactive α,β-unsaturated aldehyde acrolein. Acrolein is thought to be responsible for a large proportion of the non-cancer disease risk associated with smoking. Emerging evidence suggest a key role for CS-induced abnormalities in mitochondrial morphology and function in airway epithelial cells in COPD pathogenesis. Although in vitro studies suggest acrolein-induced mitochondrial dysfunction in airway epithelial cells, it is unknown if in vivo inhalation of acrolein affects mitochondrial content or the pathways controlling this. In this study, rats were acutely exposed to acrolein by inhalation (nose-only; 0-4 ppm), 4 h/day for 1 or 2 consecutive days (n = 6/group). Subsequently, the activity and abundance of key constituents of mitochondrial metabolic pathways as well as expression of critical proteins and genes controlling mitochondrial biogenesis and mitophagy were investigated in lung homogenates. A transient decreasing response in protein and transcript abundance of subunits of the electron transport chain complexes was observed following acrolein inhalation. Moreover, acrolein inhalation caused a decreased abundance of key regulators associated with mitochondrial biogenesis, respectively a differential response on day 1 versus day 2. Abundance of components of the mitophagy machinery was in general unaltered in response to acrolein exposure in rat lung. Collectively, this study demonstrates that acrolein inhalation acutely and dose-dependently disrupts the molecular regulation of mitochondrial metabolism in rat lung. Hence, understanding the effect of acrolein on mitochondrial function will provide a scientifically supported reasoning to shortlist aldehydes regulation in tobacco smoke.

Comparative Genotoxicity and Mutagenicity of Cigarette, Cigarillo, and Shisha Tobacco Products in Epithelial and Cardiac Cells

Epidemiology studies link cigarillos and shisha tobacco (delivered through a hookah waterpipe) to increased risk for cardiopulmonary diseases. Here we performed a comparative chemical constituent analysis between 3 cigarettes, 3 cigarillos, and 8 shisha tobacco products. The potency for genotoxicity and oxidative stress of each product's generated total particulate matter (TPM) was also assessed using immortalized oral, lung, and cardiac cell lines to represent target tissues. Levels of the carcinogenic carbonyl formaldehyde were 32- to 95-fold greater, while acrolein was similar across the shisha aerosols generated by charcoal heating compared to cigarettes and cigarillos. Electric-mediated aerosol generation dramatically increased acrolein to levels exceeding those in cigarettes and cigarillos by up to 43-fold. Equivalent cytotoxic-mediated cell death and dose response for genotoxicity through induction of mutagenicity and DNA strand breaks was seen between cigarettes and cigarillos, while minimal to no effect was observed with shisha tobacco products. In contrast, increased potency of TPM from cigarillos compared to cigarettes for inducing oxidative stress via reactive oxygen radicals and lipid peroxidation across cell lines was evident, while positivity was seen for shisha tobacco products albeit at much lower levels. Together, these studies provide new insight into the potential harmful effects of cigarillos for causing tobacco-associated diseases. The high level of carbonyls in shisha products, that in turn is impacted by the heating mechanism, reside largely in the gas phase which will distribute throughout the respiratory tract and systemic circulation to likely increase genotoxic stress.

Glutathione is a potential therapeutic target for acrolein toxicity in the cornea

Toxic and volatile chemicals are widely used in household products and previously used as warfare agents, causing a public health threat worldwide. This study aimed to evaluate the extent of injury and mechanisms of acrolein toxicity in the cornea. Primary human corneal stromal fibroblasts cultures (hCSFs) from human donor cornea were cultured and exposed to acrolein toxicity with -/+ N-acetylcysteine (NAC) to study the mode of action in the presence of Buthionine sulphoximine (BSO). PrestoBlue and MTT assays were used to optimize acrolein, NAC, and BSO doses for hCSFs. Cell-based assays and qRT-PCR analyses were performed to understand the acrolein toxicity and mechanisms. Acrolein exposure leads to an increased reactive oxygen species (ROS), compromised glutathione (GSH) levels, and mitochondrial dysfunction. The TUNEL and caspase assays showed that acrolein caused cell death in hCSFs. These deleterious effects can be mitigated using NAC in hCSFs, suggesting that GSH can be a potential target for acrolein toxicity in the cornea.

Mitigation of indoor air pollution: A review of recent advances in adsorption materials and catalytic oxidation

Indoor air pollution with toxic volatile organic compounds (VOCs) and fine particulate matter (PM2.5) is a threat to human health, causing cancer, leukemia, fetal malformation, and abortion. Therefore, the development of technologies to mitigate indoor air pollution is important to avoid adverse effects. Adsorption and photocatalytic oxidation are the current approaches for the removal of VOCs and PM2.5 with high efficiency. In this review we focus on the recent development of indoor air pollution mitigation materials based on adsorption and photocatalytic decomposition. First, we review on the primary indoor air pollutants including formaldehyde, benzene compounds, PM2.5, flame retardants, and plasticizer: Next, the recent advances in the use of adsorption materials including traditional biochar and MOF (metal-organic frameworks) as the new emerging porous materials for VOCs absorption is reviewed. We review the mechanism for mitigation of VOCs using biochar (noncarbonized organic matter partition and adsorption) and MOF together with parameters that affect indoor air pollution removal efficiency based on current mitigation approaches including the mitigation of VOCs using photocatalytic oxidation. Finally, we bring forward perspectives and directions for the development of indoor air mitigation technologies.

The multiplex interactions and molecular mechanism on genotoxicity induced by formaldehyde and acrolein mixtures on human bronchial epithelial BEAS-2B cells

Aldehydes are common air pollutants with carcinogenicity. Genotoxicity of single aldehyde has been studied well, but the combined genotoxicity is rarely known. Here, we evaluated the combined genotoxicity of formaldehyde and acrolein on BEAS-2B cells in terms of DNA strands breakage, chromosome damage and gene mutation below subcytotoxic concentrations covering smoking-related concentrations. Meanwhile, the molecular mechanism was investigated further based on oxidative stress, DNA-protein crosslinks (DPCs), cell cycle and DNA damage-repair pathway. Co-exposure to formaldehyde and acrolein mixtures showed significantly synergistic interaction on DNA strands breakage and chromosome damage in a concentration/time-dependent manner, while antagonism was shown on the late genotoxic endpoints (e.g. cytoplasmic block micronucleus (CBMN) and HPRT gene mutation). Moreover, formaldehyde synergistically potentiated acrolein-induced S-phase arrest, inhibition of DNA repair and up-regulation of genes related to cell stress, which conversely strengtherned mixture-induced DNA/chromosome damage and finally resulted in antagonism on late genotoxic events. Additionally, formaldehyde-induced DNA damage mainly resulted from the direct covalent bonding (e.g. DPCs), while acrolein-induced DNA damage mainly generated from oxidative damage (e.g. oxidative stress), which dominated the synergistic DNA strand breakage induced by mixtures. Summarily, aldehyde mixtures (formaldehyde and acrolein) induced multiplex combined genotoxicity on BEAS-2B cells even at smoking-related concentrations, which was dependent on genotoxic endpoints and closely related to that formaldehyde potentiated acrolein-induced cell stress, S-phase arrest and inhibition of DNA repair. So prolonged exposure to aldehyde mixtures may have a more serious risk to respiratory system in animal and human than the expectation based on the toxicity of single aldehyde even at environmentally relevant concentrations.

Harmful chemicals emitted from electronic cigarettes and potential deleterious effects in the oral cavity

Use of electronic nicotine delivery systems (ENDS), such as electronic cigarettes (e-cigs), is increasing across the US population and is particularly troubling due to their adoption by adolescents, teens, and young adults. The industry’s marketing approach for these instruments of addiction has been to promote them as a safer alternative to tobacco, a behavioral choice supporting smoking cessation, and as the ‘cool’ appearance of vaping with flavored products (e.g. tutti frutti, bubble gum, and buttered popcorn etc.). Thus, there is a clear need to better document the health outcomes of e-cig use in the oral cavity of the addicted chronic user. There appears to be an array of environmental toxins in the vapors, including reactive aldehydes and carbonyls resulting from the heating elements action on fluid components, as well as from the composition of chemical flavoring agents. The chemistry of these systems shows that the released vapors from the e-cigs frequently contain levels of environmental toxins that considerably exceed federal occupational exposure limits. Additionally, the toxicants in the vapors appear to be retained in the host fluids/tissues at levels often approximating 90% of the levels in the e-cig vapors. These water-soluble reactive toxins can challenge the oral cavity constituents, potentially contributing to alterations in the autochthonous microbiome and host cells critical for maintaining oral homeostasis. This review updates the existing chemistry/environmental aspects of e-cigs, as well as providing an overview of the somewhat limited data on potential oral health effects that could occur across the lifetime of daily e-cig users.

Interaction of Acrylamide, Acrolein, and 5-Hydroxymethylfurfural with Amino Acids and DNA

Acrylamide, acrolein, and 5-hydroxymethylfurfural (HMF) are food-borne toxicants produced during the thermal processing of food. The α,β-unsaturated carbonyl group or aldehyde group in their structure can react easily with the amino, imino, and thiol groups in amino acids, proteins, and DNA via Michael addition and nucleophilic reactions in food and in vivo. This work reviews the interaction pathways of three toxins with amino acids and the cytotoxicity and changes after the digestion and absorption of the resulting adducts. Their interaction with DNA is also discussed. Amino acids ubiquitously exist in foods and are added as nutrients or used to control these food-borne toxicants. Hence, the interaction widely occurring in foods would greatly increase the internal exposure of these toxins and their derived compounds after food intake. This review aims to encourage further investigation on toxin-derived compounds, including their types, exposure levels, toxicities, and pharmacokinetics.

Acrolein exerts a genotoxic effect in the Leydig cells by stimulating DNA damage-induced apoptosis

Acrolein is a highly reactive unsaturated organic molecule and has harmful effects on human health. Acrolein is generally formed in heat-treated foods above 150 °C, as well as in the combustion of gasoline, wood industry, plastic waste, and tobacco smoke. In this study, the effects of acrolein on genotoxicity in Leydig cells and the underlying mechanisms are aimed to be clarified. In addition, the toxicogenomic profile of acrolein was studied in terms of both apoptosis and steroidogenesis. Real-time PCR and ELISA tests were used to analyses of steroidogenic endpoints. Apoptosis was evaluated with double fluorescence staining and gene expression analyses of related genes. Comet assay was used to determine the genotoxicity. The results showed that acrolein caused concentration-dependent inhibition on cell viability at 8 μM and above concentrations, decreased testosterone production at 13.6 and 19.7 μM concentrations, and suppressed expression levels of genes that play an important role in steroidogenic pathway. Furthermore, acrolein downregulated expression of anti-apoptotic Bcl2 gene and upregulated expression of pro-apoptotic Bax, Casp3, and Trp53 gene after 24-h treatment in 7.4, 13.6, and 19.7 μM acrolein-exposed Leydig cells. The results of comet assay showed that acrolein significantly induced tail length, tail % DNA, and Olive tail moment. Overall, it was concluded that acrolein-induced cell damage in Leydig cells may be due to formation of genetic damage in steroidogenesis and apoptosis.

Combined cell death of co-exposure to aldehyde mixtures on human bronchial epithelial BEAS-2B cells: Molecular insights into the joint action

Aldehydes are common air pollutants and metabolites of the organism, which widely exist in many in vivo (e.g. Alzheimer's disease) and in vitro (e.g. cigarette smoke) situations. Individual aldehydes have been studied well alone, while their combined toxicity is still obscure. Here, we examined the combined apoptosis of aldehyde mixtures in BEAS-2B cells at smoking-related environmental/physiologically relevant concentrations, and the potential mechanism was investigated further based on the related signaling pathway. Co-exposure to aldehyde mixtures demonstrated significant synergistic interaction on apoptosis in a concentration-dependent manner, which differed from the expectation based on single aldehydes. Moreover, formaldehyde significantly potentiated the induction of death receptor-5, caspase 8/10, cleaved caspase 3/7/9, pro-apoptotic proteins (Bim, Bad and Bax), depolarization of MMP (mitochondrial membrane potential) and AIF (apoptosis-inducing factor) induced by acrolein, and synergistically decreased expressions of pro-survival proteins (Bcl-2 and Bcl-XL) and poly ADP-ribose polymerase. Therefore, aldehyde mixture-induced synergistic apoptosis was mediated both by TRAIL death receptor and mitochondrial pathway. Additionally, reactive oxygen species, Ca²⁺ levels, DNA damage, and phosphorylated MDM2 were all synergistically induced by aldehyde mixtures, while total p53, phosphorylated p53 and phosphorylated AKT (serine/threonine kinase) were inhibited. Antioxidants N-acetylcysteine suppressed the aldehyde mixture-induced ROS, DNA damage and apoptosis, and blocked the TRAIL death receptor and mitochondrial pathway, while it did not rescue the p53 and AKT pathway. Briefly, aldehyde mixtures induced synergistic apoptosis even at smoking-related environmental/physiologically relevant concentrations, which could be enhanced through ROS-mediated death receptor/mitochondrial pathway, and the down-regulation of phosphorylated AKT.

Ameliorative effect of boric acid against formaldehyde-induced oxidative stress in A549 cell lines

Formaldehyde (HCHO) is a reactive agent and the most essential common carcinogenic environmental pollutant. The present study investigated the protective and ameliorative effects of boric acid (BA) against formaldehyde-induced oxidative stress in A549 cell lines. The first group served as a control, the second group was treated with only 100 μM formaldehyde, and the third, fourth, and fifth groups were treated with 2.5, 5, and 10 mM BA, respectively. The sixth, seventh, and eighth groups were treated with 2.5, 5, and 10 mM BA plus 100 μM formaldehyde, respectively. In A549 cell lines, formaldehyde treatment significantly decreased cell viability, glutathione level, and enzyme activities of superoxide dismutase and catalase; however, malondialdehyde levels of the cell lysate were found to increase compared with the control group. In addition, formaldehyde treatment did not significantly alter nitric oxide levels. Meanwhile, mRNA expression levels of Tnf-α, NFĸB, and caspase-3 significantly increased but the Bcl-XL level did not show significant alteration by formaldehyde treatment. In contrast, the BA treatment reversed the formaldehyde-induced alteration in A549 cell lines. Consequently, BA exhibited a protective effect in A549 cell line against formaldehyde-induced lipid peroxidation. Furthermore, it ameliorated the antioxidant status and mRNA expression levels of proinflammatory cytokines.

Efficient removal of gaseous formaldehyde by amine-modified diatomite: a combined experimental and density functional theory study

Amine-modified diatomite with remarkable formaldehyde (HCHO) removal efficiency was prepared by grafting 3-aminopropyltrimethoxysilane (APTMS) in this research. The interfacial properties and microstructures of the prepared adsorbents were characterized and analyzed. The HCHO adsorption properties of the amine modified diatomite were also systematically studied, and it has been proven to be effective adsorbent with better adsorption performance than activated carbon for the removal of gaseous HCHO. Furthermore, to better explain the experimental results, we performed density functional theory (DFT) study on the adsorption system and calculated the geometry, energy, and charge parameters based on first principles. Also, the underlying adsorption mechanism was proposed detailedly by combining experimentation with DFT calculation, suggesting that amine modified diatomite can be efficient adsorbent for the elimination of gaseous formaldehyde.

Combined cytotoxicity of co-exposure to aldehyde mixtures on human bronchial epithelial BEAS-2B cells

Aldehydes are well-known air pollutants and often studied alone, while co-exposure to aldehyde mixtures is more common than single aldehydes. Unfortunately, it has been very little known about the (mechanism of) combined toxicity of aldehyde mixtures. Here, formaldehyde and acrolein were selected as the typical representatives of common aldehydes, and were used to explore to get in-depth insight into the mechanism of combined toxicity of aldehyde mixtures. The NOECs (non-observed effect concentrations) are 60 μmoL/L for formaldehyde, and 0.5 μmoL/L for acrolein, so acrolein is more toxic than formaldehyde. Formaldehyde and acrolein mixtures showed significant cytotoxicity and synergistic effects in a concentration/time-dependent way on BEAS-2B cells based on acute and chronic cytotoxicity assay. Acrolein was dominant in aldehyde mixtures in inducing cytotoxicity at environmentally relevant doses because of higher toxicity. Moreover, aldehyde mixtures significantly synergistically increased the intracellular reactive oxygen species (ROS), malondialdehyde (MDA) and lactate dehydrogenase (LDH) leakage, while caused an antagonistic effects on glutathione (GSH). Besides, formaldehyde could significantly potentiated the activation of environmental stress sensitive Nrf2 pathway induced by acrolein, even at doses at which formaldehyde treatment alone had no any response. Furthermore, as the downstream components of Nrf2 pathway, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) and heme oxygenase-1 (HO-1) were significantly synergistically induced by formaldehyde and acrolein mixtures. Antioxidants N-acetylcysteine and reduced glutathione could significantly suppress the acute and chronic combined cytotoxicity of acrolein and formaldehyde mixtures, and changed their interactions (synergism) on cytotoxicity. Taken together, aldehyde mixtures have higher toxicity than that expected for additivity based on single aldehydes even at environmentally relevant concentrations, and the combined cytotoxicity may be enhanced through oxidative stress and the related Nrf2 pathway. Prolonged exposure to pollutants containing aldehyde mixtures through inhalation may have more serious threat to respiratory system in animal and human.