A comparative analysis of in vitro toxicity of diesel exhaust particles from combustion of 1st- and 2nd-generation biodiesel fuels in relation to their physicochemical properties-the FuelHealth project

In vitro toxicity evaluation in A549 cells of diesel particulate matter from two different particle sampling systems and several resuspension media

In urban areas, inhalation of fine particles from combustion sources such as diesel engines causes adverse health effects. For toxicity testing, a substantial amount of particulate matter (PM) is needed. Conventional sampling involves collection of PM onto substrates by filtration or inertial impaction. A major drawback to those methodologies is that the extraction process can modify the collected particles and alter their chemical composition. Moreover, prior to toxicity testing, PM samples need to be resuspended, which can alter the PM sample even further. Lastly, the choice of the resuspension medium may also impact the detected toxicological responses. In this study, we compared the toxicity profile of PM obtained from two alternative sampling systems, using in vitro toxicity assays. One system makes use of condensational growth before collection in water in an impinger - BioSampler (CG-BioSampler), and the other, a Dekati® Gravimetric Impactor (DGI), is based on inertial impaction. In addition, various methods for resuspension of DGI collected PM were compared. Tested endpoints included cytotoxicity, formation of cellular reactive oxygen species, and genotoxicity. The alternative collection and suspension methods affected different toxicological endpoints. The water/dimethyl sulfoxide mixture and cell culture medium resuspended particles, along with the CG-BioSampler sample, produced the strongest responses. The water resuspended sample from the DGI appeared least toxic. CG-BioSampler collected PM caused a clear increased response in apoptotic cell death. We conclude that the CG-BioSampler PM sampler is a promising alternative to inertial impaction sampling.

Role of different mechanisms in pro-inflammatory responses triggered by traffic-derived particulate matter in human bronchiolar epithelial cells

BACKGROUND

Traffic-derived particles are important contributors to the adverse health effects of ambient particulate matter (PM). In Nordic countries, mineral particles from road pavement and diesel exhaust particles (DEP) are important constituents of traffic-derived PM. In the present study we compared the pro-inflammatory responses of mineral particles and DEP to PM from two road tunnels, and examined the mechanisms involved.

METHODS

The pro-inflammatory potential of 100 µg/mL coarse (PM10-2.5), fine (PM2.5-0.18) and ultrafine PM (PM0.18) sampled in two road tunnels paved with different stone materials was assessed in human bronchial epithelial cells (HBEC3-KT), and compared to DEP and particles derived from the respective stone materials. Release of pro-inflammatory cytokines (CXCL8, IL-1α, IL-1β) was measured by ELISA, while the expression of genes related to inflammation (COX2, CXCL8, IL-1α, IL-1β, TNF-α), redox responses (HO-1) and metabolism (CYP1A1, CYP1B1, PAI-2) was determined by qPCR. The roles of the aryl hydrocarbon receptor (AhR) and reactive oxygen species (ROS) were examined by treatment with the AhR-inhibitor CH223191 and the anti-oxidant N-acetyl cysteine (NAC).

RESULTS

Road tunnel PM caused time-dependent increases in expression of CXCL8, COX2, IL-1α, IL-1β, TNF-α, COX2, PAI-2, CYP1A1, CYP1B1 and HO-1, with fine PM as more potent than coarse PM at early time-points. The stone particle samples and DEP induced lower cytokine release than all size-fractionated PM samples for one tunnel, and versus fine PM for the other tunnel. CH223191 partially reduced release and expression of IL-1α and CXCL8, and expression of COX2, for fine and coarse PM, depending on tunnel, response and time-point. Whereas expression of CYP1A1 was markedly reduced by CH223191, HO-1 expression was not affected. NAC reduced the release and expression of IL-1α and CXCL8, and COX2 expression, but augmented expression of CYP1A1 and HO-1.

CONCLUSIONS

The results indicate that the pro-inflammatory responses of road tunnel PM in HBEC3-KT cells are not attributed to the mineral particles or DEP alone. The pro-inflammatory responses seem to involve AhR-dependent mechanisms, suggesting a role for organic constituents. ROS-mediated mechanisms were also involved, probably through AhR-independent pathways. DEP may be a contributor to the AhR-dependent responses, although other sources may be of importance.

Psychiatric disorders associated with immune checkpoint inhibitors: a pharmacovigilance analysis of the FDA Adverse Event Reporting System (FAERS) database

Background

With the increasing use of immune checkpoint inhibitors (ICIs) for tumour immunotherapy, the immune-related adverse events (irAEs) caused by their collateral effect on the immune system pose a key challenge for the clinical application of ICIs. Psychiatric adverse events are a class of adverse events associated with ICIs that are realistically observed in the real world. We aim to provide a comprehensive study and summary of psychiatric adverse events associated with ICIs.

Methods

We obtained ICI adverse reaction reports during January 2012-December 2021 from the FDA Adverse Event Reporting System (FAERS) database. ICI reports underwent screening to minimize the influence of other adverse reactions, concomitant medications, and indications for medication use that may also contribute to psychiatric disorders. Disproportionality analysis was performed to find psychiatric adverse events associated with ICIs by comparing ICIs with the full FAERS database using the reporting odds ratio (ROR). Influencing factors were explored based on univariate logistic regression analysis. Finally, the Cancer Genome Atlas (TCGA) pan-cancer transcriptome data were combined to explore the potential biological mechanisms associated with ICI-related pAEs.

Findings

Reports of psychiatric adverse events accounted for 2.71% of the overall ICI adverse event reports in the FAERS database. Five categories of psychiatric adverse events were defined as ICI-related psychiatric adverse events (pAEs). The median age of reports with ICI-related pAEs was 70 (interquartile range [IQR] 24-95), with 21.54% of reports having a fatal outcome. Cases with indications for lung cancer, skin cancer and kidney site cancer accounted for the majority. The odds of ICI-related pAEs increased in older patients (65-74: OR = 1.44 [1.22-1.70], P < 0.0001: ≥75: OR = 1.84 [1.54-2.20], P < 0.0001). The occurrence of ICI-related pAEs may be related to NOTCH signalling and dysregulation of synapse-associated pathways.

Interpretation

This study investigated psychiatric adverse events highly associated with ICI treatment, their influencing factors and potential biological mechanisms, which provides a reliable basis for further in-depth study of ICI-related pAEs. However, as an exploratory study, our findings need to be further confirmed in a large-scale prospective study.

Funding

This work was supported by the Natural Science Foundation of Guangdong Province (2018A030313846 and 2021A1515012593), the Science and Technology Planning Project of Guangdong Province (2019A030317020) and the National Natural Science Foundation of China (81802257, 81871859, 81772457, 82172750 and 82172811). Guangdong Basic and Applied Basic Research Foundation (Guangdong - Guangzhou Joint Fouds) (2022A1515111212). This work was supported by Key Research and Development Projects of Sichuan Science and Technology (2022YFS0221, 2022YFS0074, 2022YFS0156 and 2022YFS0378). Sichuan Provincial People's Hospital Hospital Young Talent Fund (2021QN08).

Utilization of Nanotechnology and Nanomaterials in Biodiesel Production and Property Enhancement

In today’s world, the applications of nanotechnology and nanomaterials are attracting interest in a wide variety of study domains because of their appealing qualities. The use of nanotechnology and nanomaterials in biodiesel processing and manufacturing is a focus of research globally. For accelerating the progress and development of biodiesel production, more focus is being given to the application of advanced nanotechnology for maximum yield in low cost. Hence, this paper will discuss the utilization of numerous nanomaterials/nanocatalysts for biodiesel synthesis from multiple feedstocks. This study will also focus on nanomaterials’ applications in algae cultivation and lipid extraction. Furthermore, the current study will comprehensively overview the nanoadditives blended biodiesel in diesel engines and the significant challenges and future opportunities. Moreover, this paper will also focus on human and environmental safety concerns of nanotechnology-based large-scale biodiesel production. Hence, this review will provide perception for future manufacturers, researchers, and academicians into the extent of research in nanotechnology and nanomaterials assisted biodiesel production and its efficiency enhancement.

Biodiesel feedstock determines exhaust toxicity in 20% biodiesel: 80% mineral diesel blends

To address climate change concerns, and reduce the carbon footprint caused by fossil fuel use, it is likely that blend ratios of renewable biodiesel with commercial mineral diesel fuel will steadily increase, resulting in biodiesel use becoming more widespread. Exhaust toxicity of unblended biodiesels changes depending on feedstock type, however the effect of feedstock on blended fuels is less well known. The aim of this study was to assess the impact of biodiesel feedstock on exhaust toxicity of 20% blended biodiesel fuels (B20). Primary human airway epithelial cells were exposed to exhaust diluted 1/15 with air from an engine running on conventional ultra-low sulfur diesel (ULSD) or 20% blends of soy, canola, waste cooking oil (WCO), tallow, palm or cottonseed biodiesel in diesel. Physico-chemical exhaust properties were compared between fuels and the post-exposure effect of exhaust on cellular viability and media release was assessed 24 h later. Exhaust properties changed significantly between all fuels with cottonseed B20 being the most different to both ULSD and its respective unblended biodiesel. Exposure to palm B20 resulted in significantly decreased cellular viability (96.3 ± 1.7%; p < 0.01) whereas exposure to soy B20 generated the greatest number of changes in mediator release (including IL-6, IL-8 and TNF-α, p < 0.05) when compared to air exposed controls, with palm B20 and tallow B20 closely following. In contrast, canola B20 and WCO B20 were the least toxic with only mediators G-CSF and TNF-α being significantly increased. Therefore, exposure to palm B20, soy B20 and tallow B20 were found to be the most toxic and exposure to canola B20 and WCO B20 the least. The top three most toxic and the bottom three least toxic B20 fuels are consistent with their unblended counterparts, suggesting that feedstock type greatly impacts exhaust toxicity, even when biodiesel only comprises 20% of the fuel.

Dietary Intervention with Blackcurrant Pomace Protects Rats from Testicular Oxidative Stress Induced by Exposition to Biodiesel Exhaust

The exposure to diesel exhaust emissions (DEE) contributes to negative health outcomes and premature mortality. At the same time, the health effects of the exposure to biodiesel exhaust emission are still in scientific debate. The aim of presented study was to investigate in an animal study the effects of exposure to DEE from two types of biodiesel fuels, 1st generation B7 biodiesel containing 7% of fatty acid methyl esters (FAME) or 2nd generation biodiesel (SHB20) containing 7% of FAME and 13% of hydrotreated vegetable oil (HVO), on the oxidative stress in testes and possible protective effects of dietary intervention with blackcurrant pomace (BC). Adult Fisher344/DuCrl rats were exposed by inhalation (6 h/day, 5 days/week for 4 weeks) to 2% of DEE from B7 or SHB20 fuel mixed with air. The animals from B7 (n = 14) and SHB20 (n = 14) groups subjected to filtered by a diesel particulate filter (DPF) or unfiltered DEE were maintained on standard feed. The rats from B7+BC (n = 12) or SHB20+BC (n = 12), exposed to DEE in the same way, were fed with feed supplemented containing 2% (m/m) of BC. The exposure to exhaust emissions from 1st and 2nd generation biodiesel resulted in induction of oxidative stress in the testes. Higher concentration of the oxidative stress markers thiobarbituric acid-reactive substances (TBARS), lipid hydroperoxides (LOOHs), 25-dihydroxycholesterols (25(OH)2Ch), and 7-ketocholesterol (7-KCh) level), as well as decreased level of antioxidant defense systems such as reduced glutathione (GSH), GSH/GSSG ratio, and increased level of oxidized glutathione (GSSG)) were found. Dietary intervention reduced the concentration of TBARS, 7-KCh, LOOHs, and the GSSG level, and elevated the GSH level in testes. In conclusion, DEE-induced oxidative stress in the testes was related to the biodiesel feedstock and the application of DPF. The SHB20 DEE without DPF technology exerted the most pronounced toxic effects. Dietary intervention with BC in rats exposed to DEE reduced oxidative stress in testes and improved antioxidative defense parameters, however the redox balance in the testes was not completely restored.

Toxicity of different biodiesel exhausts in primary human airway epithelial cells grown at air-liquid interface

Biodiesel is created through the transesterification of fats/oils and its usage is increasing worldwide as global warming concerns increase. Biodiesel fuel properties change depending on the feedstock used to create it. The aim of this study was to assess the different toxicological properties of biodiesel exhausts created from different feedstocks using a complex 3D air-liquid interface (ALI) model that mimics the human airway. Primary human airway epithelial cells were grown at ALI until full differentiation was achieved. Cells were then exposed to 1/20 diluted exhaust from an engine running on Diesel (ULSD), pure or 20% blended Canola biodiesel and pure or 20% blended Tallow biodiesel, or Air for control. Exhaust was analysed for various physio-chemical properties and 24-h after exposure, ALI cultures were assessed for permeability, protein release and mediator response. All measured exhaust components were within industry safety standards. ULSD contained the highest concentrations of various combustion gases. We found no differences in terms of particle characteristics for any of the tested exhausts, likely due to the high dilution used. Exposure to Tallow B100 and B20 induced increased permeability in the ALI culture and the greatest increase in mediator response in both the apical and basal compartments. In contrast, Canola B100 and B20 did not impact permeability and induced the smallest mediator response. All exhausts but Canola B20 induced increased protein release, indicating epithelial damage. Despite the concentrations of all exhausts used in this study meeting industry safety regulations, we found significant toxic effects. Tallow biodiesel was found to be the most toxic of the tested fuels and Canola the least, both for blended and pure biodiesel fuels. This suggests that the feedstock biodiesel is made from is crucial for the resulting health effects of exhaust exposure, even when not comprising the majority of fuel composition.

The pro-inflammatory effects of combined exposure to diesel exhaust particles and mineral particles in human bronchial epithelial cells

BACKGROUND

People are exposed to ambient particulate matter (PM) from multiple sources simultaneously in both environmental and occupational settings. However, combinatory effects of particles from different sources have received little attention in experimental studies. In the present study, the pro-inflammatory effects of combined exposure to diesel exhaust particles (DEP) and mineral particles, two common PM constituents, were explored in human lung epithelial cells.

METHODS

Particle-induced secretion of pro-inflammatory cytokines (CXCL8 and IL-1β) and changes in expression of genes related to inflammation (CXCL8, IL-1α, IL-1β and COX-2), redox responses (HO-1) and xenobiotic metabolism (CYP1A1 and CYP1B1) were assessed in human bronchial epithelial cells (HBEC3-KT) after combined exposure to different samples of DEP and mineral particles. Combined exposure was also conducted using lipophilic organic extracts of DEP to assess the contribution of soluble organic chemicals. Moreover, the role of the aryl hydrocarbon receptor (AhR) pathway was assessed using an AhR-specific inhibitor (CH223191).

RESULTS

Combined exposure to DEP and mineral particles induced increases in pro-inflammatory cytokines and expression of genes related to inflammation and redox responses in HBEC3-KT cells that were greater than either particle sample alone. Moreover, robust increases in the expression of CYP1A1 and CYP1B1 were observed. The effects were most pronounced after combined exposure to α-quartz and DEP from an older fossil diesel, but enhanced responses were also observed using DEP generated from a modern biodiesel blend and several stone particle samples of mixed mineral composition. Moreover, the effect of combined exposure on cytokine secretion could also be induced by lipophilic organic extracts of DEP. Pre-incubation with an AhR-specific inhibitor reduced the particle-induced cytokine responses, suggesting that the effects were at least partially dependent on AhR.

CONCLUSIONS

Exposure to DEP and mineral particles in combination induces enhanced pro-inflammatory responses in human bronchial epithelial cells compared with exposure to the individual particle samples. The effects are partly mediated through an AhR-dependent pathway and lipophilic organic chemicals in DEP appear to play a central role. These possible combinatory effects between different sources and components of PM warrant further attention and should also be considered when assessing measures to reduce PM-induced health effects.

Diesel particulate matter exposure deteriorates cardiovascular health and increases the sensitivity of rat heart towards ischemia reperfusion injury via suppressing mitochondrial bioenergetics function

Documents from previous studies do not sufficiently explain the pathophysiological alterations involved in rat hearts exposed to PM2.5 from diesel exhaust, termed as Diesel Particulate matter (DPM). In the present study, we explored the cardiovascular effect of DPM exposure on the recovery of heart from Ischemia reperfusion injury (IR) and explored the probable cause-effect relationship. Two groups of female Wistar rats were exposed to 0.5 mg/ml DPM for 1 h and 3 h durations daily for 21 days via a whole-body exposure system. At the end of 21st day, the animals were sacrificed and the heart was subjected to IR via Langendorff isolated rat heart perfusion system. 21 days of exposure altered cardiac electrophysiology and the ultra-structure of myocardium. Also, the same group of animals exhibited calcification in the vasculature. These changes were prominent in animals exposed to DPM for 3 h daily. Administration of DPM to H9C2 cells resulted in 15% and 36% cell death after 1hr and 3hrs of incubation, respectively. When the hearts were challenged to IR, both 1 h and 3 h exposed hearts exhibited a significant decline in IR recovery. At the sub-cellular level, DPM exposure reduced ATP levels, mitochondrial copy number, and increased oxidative stress after IR in both exposure groups. These changes were markedly seen in the interfibrillar mitochondrial fraction of the mitochondria. Hence, we conclude that exposure to PM2.5 from diesel exhaust alters electrophysiology and ultrastructure of heart and reduces the level of cellular mediators, thereby compromising the ability of heart to withstand IR injury.

Application of three-dimensional Raman imaging to determination of the relationship between cellular localization of diesel exhaust particles and the toxicity

A diesel exhaust particle (DEP) is a type of particulate matter that is easily produced from combustion in a diesel power engine. It has been reported that DEPs can cause short- and long-term health problems. This is because DEPs are complex mixtures that are highly inhalable through the airways due to their small particle size. However, the relationship between intracellular localization of DEPs after their deposition in the lungs and the subsequent biological responses remains to be clarified. This is due to difficulties in distinguishing particles that are inside the cells from those that are outside. In this study, A549 human lung epithelial cells were exposed to DEPs at concentrations of 0, 25, 75, or 200 µg/mL for different periods, after that particles in the A549 cells were analyzed by three-dimensional (3D) images obtained from a Raman microscope. The cytotoxic effects of DEPs on the A549 cells were investigated by measuring cell viability, the levels of intracellular reactive oxygen species (ROS) and cell death. The Raman microscopy revealed that the particles invaded the A549 cells, and at a concentration of 200 µg/mL, they markedly decreased cell viability, increased intracellular ROS production, triggered late apoptosis/necrosis and induced nuclear damage. These results suggest that intracellular DEPs exposed at a high concentration may be highly toxic and can impair the viability of A549 cells. Furthermore, the 3D images from the Raman microscopy can be used to evaluate intracellular particle dynamics.

Inhalation of hydrogenated vegetable oil combustion exhaust and genotoxicity responses in humans

Biofuels from vegetable oils or animal fats are considered to be more sustainable than petroleum-derived diesel fuel. In this study, we have assessed the effect of hydrogenated vegetable oil (HVO) exhaust on levels of DNA damage in peripheral blood mononuclear cells (PBMCs) as primary outcome, and oxidative stress and inflammation as mediators of genotoxicity. In a randomized cross-over study, healthy humans were exposed to filtered air, inorganic salt particles, exhausts from combustion of HVO in engines with aftertreatment [i.e. emission with nitrogen oxides and low amounts of particulate matter less than 2.5 µm (approximately 1 µg/m³)], or without aftertreatment (i.e. emission with nitrogen oxides and 93 ± 13 µg/m³ of PM_2.5). The subjects were exposed for 3 h and blood samples were collected before, within 1 h after the exposure and 24 h after. None of the exposures caused generation of DNA strand breaks and oxidatively damaged DNA, or affected gene expression of factors related to DNA repair (Ogg1), antioxidant defense (Hmox1) or pro-inflammatory cytokines (Ccl2, Il8 and Tnfa) in PBMCs. The results from this study indicate that short-term HVO exhaust exposure is not associated with genotoxic hazard in humans.

Proliferation of Lung Epithelial Cells Is Regulated by the Mechanisms of Autophagy Upon Exposure of Soots

Background

Soots are known to cause many diseases in humans, but their underlying mechanisms of toxicity are still not known. Here, we report that soots induce cell proliferation of lung epithelial cells via modulating autophagy pathways.

Results

Fullerene soot and diesel exhaust particles (DEP) induced cell proliferation of lung epithelial, A549 cells via distinct autophagic mechanisms and did not cause cell death. Exposure of fullerene soot protected the cell death of A549 cells, caused by hydrogen peroxide, and inhibited LPS-induced autophagy. Fullerene soot co-localized with the autophagic proteins and inhibited starvation-induced autophagy (downregulated ATG-5, beclin-1, p62, and LC3 expressions) independent of its antioxidant properties. Similarly, it decreased the expression profile of autophagic genes and upregulated the proliferation-responsive gene, Ki-67, in mice. We observed that expressions of fullerene soot-responsive genes (Beclin-1, ATG-5, and p62) were reverted by Akt Inhibitor X, indicating an important role of the Akt pathway. At an elemental level, we found that elemental carbon of fullerene soot may be converted into organic carbon, as measured by OCEC, which may point fullerene soot as a source of carbon. On the other hand, DEP upregulated the expressions of autophagy genes. Akt Inhibitor X did not attenuate DEP-induced cell proliferation and autophagic response. However, an autophagic inhibitor, chloroquine, and significantly inhibited DEP-induced cell proliferation.

Conclusion

It can be said that distinct autophagic mechanisms are operational in cell proliferation of lung epithelial cells due to soots, which may be responsible for different diseases. Understanding the mechanism of these pathways provides some important targets, which can be utilized for the development of future therapeutics.

Toxicity of Water- and Organic-Soluble Wood Tar Fractions from Biomass Burning in Lung Epithelial Cells

Widespread smoke from wildfires and biomass burning contributes to air pollution and the deterioration of air quality and human health. A common and major emission of biomass burning, often found in collected smoke particles, is spherical wood tar particles, also known as "tar balls". However, the toxicity of wood tar particles and the mechanisms that govern their health impacts and the impact of their complicated chemical matrix are not fully elucidated. To address these questions, we generated wood tar material from wood pyrolysis and isolated two main subfractions: water-soluble and organic-soluble fractions. The chemical characteristics as well as the cytotoxicity, oxidative damage, and DNA damage mechanisms were investigated after exposure of A549 and BEAS-2B lung epithelial cells to wood tar. Our results suggest that both wood tar subfractions reduce cell viability in exposed lung cells; however, these fractions have different modes of action that are related to their physicochemical properties. Exposure to the water-soluble wood tar fraction increased total reactive oxygen species production in the cells, decreased mitochondrial membrane potential (MMP), and induced oxidative damage and cell death, probably through apoptosis. Exposure to the organic-soluble fraction increased superoxide anion production, with a sharp decrease in MMP. DNA damage is a significant process that may explain the course of toxicity of the organic-soluble fraction. For both subfractions, exposure caused cell cycle alterations in the G2/M phase that were induced by upregulation of p21 and p16. Collectively, both subfractions of wood tar are toxic. The water-soluble fraction contains chemicals (such as phenolic compounds) that induce a strong oxidative stress response and penetrate living cells more easily. The organic-soluble fraction contained more polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs and induced genotoxic processes, such as DNA damage.

Learning and memory disorders related to hippocampal inflammation following exposure to air pollution

It has been demonstrated that sub-chronic exposure to air pollution containing nanoscale (˂100 nm) diesel exhaust particles (DEPs) may lead to excessive oxidative stress and neuro-inflammation in adult male mice. Hereby, we investigated the effects of DEPs on hippocampus-dependent spatial learning and neuro-inflammation and memory-related gene expression in male mice. In this study, we divided 48 adult NMRI male mice into control group VS. three exposure groups. Mice were exposed to 300-350 μg/m³ DEPs for 2, 5, and 7 h daily for 12 weeks. The Morris Water Maze (MWM) and Elevated Plus Maze device were used to examine anxiety, spatial memory and learning, respectively. The mRNAs expression of pro-inflammatory cytokines, N-methyl-D-aspartate (NMDA) receptor subunits, and glutaminase were studied in hippocampus (HI) by real-time RT-PCR. Besides, malondialdehyde (MDA) tests were used to determine the state of oxidative stress. After 5 and 7 h. of DEPs exposure, mRNA expression of NR2A and NR3B IL1α, IL1β, TNFα, NMDA receptor subunits and MDA levels increased significantly (P < 0.05). Also, DEPs exposed mice for 2, 5, and 7 h. showed diminished entrance into open arms with short time spent there. Indeed, 5 and 7 h/day exposed mice required a longer time to reach the hidden platform. Sub-chronic exposure to DEPs increased oxidative stress markers, neuroinflammation, anxiety, impaired spatial learning and memory.

Inflammation, oxidative stress and genotoxicity responses to biodiesel emissions in cultured mammalian cells and animals

Biodiesel fuels are alternatives to petrodiesel, especially in the transport sector where they have lower carbon footprint. Notwithstanding the environmental benefit, biodiesel fuels may have other toxicological properties than petrodiesel. Particulate matter (PM) from petrodiesel causes cancer in the lung as a consequence of delivery of genotoxic polycyclic aromatic hydrocarbons, oxidative stress and inflammation. We have reviewed articles from 2002 to 2019 (50% of the articles since 2015) that have described toxicological effects in terms of genotoxicity, oxidative stress and inflammation of biodiesel exhaust exposure in humans, animals and cell cultures. The studies have assessed first generation biodiesel from different feedstock (e.g. rapeseed and soy), certain second generation fuels (e.g. waste oil), and hydrogenated vegetable oil. It is not possible to rank the potency of toxicological effects of specific biodiesel fuels. However, exposure to biodiesel exhaust causes oxidative stress, inflammation and genotoxicity in cell cultures. Three studies in animals have not indicated genotoxicity in lung tissue. The database on oxidative stress and inflammation in animal studies is larger (13 studies); ten studies have reported increased levels of oxidative stress biomarkers or inflammation, although the effects have been modest in most studies. The cell culture and animal studies have not consistently shown a different potency in effect between biodiesel and petrodiesel exhausts. Both increased and decreased potency have been reported, which might be due to differences in feedstock or combustion conditions. In conclusion, combustion products from biodiesel and petrodiesel fuel may evoke similar toxicological effects on genotoxicity, oxidative stress and inflammation.

A multi-scale approach to study biochemical and biophysical aspects of resveratrol on diesel exhaust particle-human primary lung cell interaction

Diesel exhaust particles (DEPs) are major air pollutants that lead to numerous human disorders, especially pulmonary diseases, partly through the induction of oxidative stress. Resveratrol is a polyphenol that ameliorates the production of reactive oxygen species (ROS) and delays aging-related processes. Herein we studied the cytoprotective effect of resveratrol on DEP-exposed human lung cells in a factorial experimental design. This work investigates biophysical features including cellular compositions and biomechanical properties, which were measured at the single-cell level using confocal Raman microspectroscopy (RM) and atomic force microscopy (AFM), respectively. Principal component analysis (PCA), hierarchical cluster analysis (HCA) and partial least square regression (PLS) analysis were applied to analyze Raman spectra with and without resveratrol protection. The health status of individual cells could be effectively predicted using an index derived from characteristic Raman spectral peak (e.g., 1006 cm⁻¹) based on PLS model. AFM measurements indicated that cellular adhesion force was greatly reduced, while Young’s modulus was highly elevated in resveratrol treated DEP-exposed cells. Anti-oxidant resveratrol reduced DEP-induced ROS production and suppressed releases of several cytokines and chemokines. These findings suggest resveratrol may enhance resistance of human lung cells (e.g., SAEC) to air pollutants (e.g. DEPs).

Biodiesel fuels: A greener diesel? A review from a health perspective

Biodiesels have been promoted as a greener alternative to diesel with decreased emissions and health effects. To investigate the scientific basis of the suggested environmental and health benefits offered by biodiesel, this review examines the current state of knowledge and key uncertainties of pollutant profiles of biodiesel engine exhaust and the associated the respiratory and cardiovascular outcomes. The ease and low cost of biodiesel production has facilitated greater distribution and commercial use. The pollutant profile of biodiesel engine exhaust is distinct from diesel, characterised by increased NOx and aldehyde emissions but decreased CO and CO₂. Lower engine-out particulate matter mass concentrations have also been observed over a range of feedstocks. However, these reduced emissions have been attributable to a shift towards smaller sized particulate emissions. The toxicity of biodiesel engine exhaust has been investigated in vitro using various lung cell, in vivo evaluating responses induced in animals and through several human exposure studies. Discrepancies exist across results reported by in vitro and in vivo studies, which may be attributable to differences in biodiesel feedstocks, engine characteristics, operating conditions or use of aftertreatment systems across test scenarios. The limited human testing further suggests short-term exposure to biodiesel engine exhaust is associated with cardiopulmonary outcomes that are comparable to diesel. Additional information about the health effects of biodiesel engine exhaust exposure is required for effective public health policy.

Inflammatory and functional responses after (bio)diesel exhaust exposure in allergic sensitized mice. A comparison between diesel and biodiesel

Many cities fail to meet air quality standards, which results in increased risk for pulmonary disorders, including asthma. Human and experimental studies have shown that diesel exhaust (DE) particles are associated with worsening of allergic asthma. Biodiesel (BD), a cleaner fuel from renewable sources, was introduced in the eighties. Because of the reduction in particulate matter (PM) emissions, BD was expected to cause fewer adverse pulmonary effects. However, only limited data on the effect of BD emissions in asthma are available.

OBJECTIVE

Determine whether BD exhaust exposure in allergic sensitized mice leads to different effects on inflammatory and functional responses compared to DE exposure.

METHODS

Balb/C mice were orotracheally sensitized with House Dust Mite (HDM) or a saline solution with 3 weekly instillations. From day 9 until day 17 after sensitization, they were exposed daily to filtered air (FA), DE and BD exhaust (concentration: 600 μg/m³ PM_2.5). Lung function, bronchoalveolar lavage fluid (BALF) cell counts, cytokine levels (IL-2, IL-4, IL-5, IL-17, TNF-α, TSLP) in the BALF, peribronchiolar eosinophils and parenchymal macrophages were measured.

RESULTS

HDM-sensitized animals presented increased lung elastance (p = 0.046), IgG1 serum levels (p = 0.029), peribronchiolar eosinophils (p = 0.028), BALF levels of total cells (p = 0.020), eosinophils (p = 0.028), IL-5 levels (p = 0.002) and TSLP levels (p = 0.046) in BALF. DE exposure alone increased lung elastance (p = 0.000) and BALF IL-4 levels (p = 0.045), whereas BD exposure alone increased BALF TSLP levels (p = 0.004). BD exposure did not influence any parameters after HDM challenge, while DE exposed animals presented increased BALF levels of total cells (p = 0.019), lymphocytes (p = 0.000), neutrophils (p = 0.040), macrophages (p = 0.034), BALF IL-4 levels (p = 0.028), and macrophagic inflammation in the lung tissue (p = 0.037), as well as decreased IgG1 (p = 0.046) and IgG2 (p = 0.043) levels when compared to the HDM group.

CONCLUSION

The results indicate more adverse pulmonary effects of DE compared to BD exposure in allergic sensitized animals.

Effect of collection methods on combustion particle physicochemical properties and their biological response in a human macrophage-like cell line

In vitro studies are a first step toward understanding the biological effects of combustion-derived particulate matter (cdPM). A vast majority of studies expose cells to cdPM suspensions, which requires a method to collect cdPM and suspend it in an aqueous media. The consequences of different particle collection methods on particle physiochemical properties and resulting biological responses are not fully understood. This study investigated the effect of two common approaches (collection on a filter and a cold plate) and one relatively new (direct bubbling in DI water) approach to particle collection. The three approaches yielded cdPM with differences in particle size distribution, surface area, composition, and oxidative potential. The directly bubbled sample retained the smallest sized particles and the bimodal distribution observed in the gas-phase. The bubbled sample contained ∼50% of its mass as dissolved species and lower molecular weight compounds, not found in the other two samples. These differences in the cdPM properties affected the biological responses in THP-1 cells. The bubbled sample showed greater oxidative potential and cellular reactive oxygen species. The scraped sample induced the greatest TNFα secretion. These findings have implications for in vitro studies of air pollution and for efforts to better understand the underlying mechanisms.

Toxicity of Exhaust Fumes (CO, NOx) of the Compression-Ignition (Diesel) Engine with the Use of Simulation

Nowadays more and more emphasis is placed on the protection of the natural environment. Scientists notice that global warming is associated with an increase of carbon dioxide emissions, which results inter alia from the combustion of gasoline, oil, and coal. To reduce the problem of pollution from transport, the EU is introducing increasingly stringent emission standards which should correspond to sustainable conditions of the environment during the operation of motor vehicles. The emissivity value of substances, such as nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), as well as solid particles, was determined. The aim of this paper was to examine, by means of simulation in the Scilab program, the exhaust emissions generated by the 1.3 MultiJet Fiat Panda diesel engine, and in particular, carbon monoxide and nitrogen oxides (verified on the basis of laboratory tests). The Fiat Panda passenger car was selected for the test. The fuels supplied to the tested engine were diesel and FAME (fatty acid methyl esters). The Scilab program, which simulated the diesel engine operation, was the tool for analyzing the exhaust toxicity test. The combustion of biodiesel does not necessarily mean a smaller amount of exhaust emissions, as could be concluded on the basis of information contained in the subject literature. The obtained results were compared with the currently valid EURO-6 standard, for which the limit value for CO is 0.5 g/km, and for NOx − 0.08 g/km, and it can be seen that the emission of carbon monoxide did not exceed the standards in any case examined. Unfortunately, when analyzing the total emissions of nitrogen oxides, the situation was completely the opposite and the emissions were exceeded by 20–30%.

Lung effects of 7- and 28-day inhalation exposure of rats to emissions from 1st and 2nd generation biodiesel fuels with and without particle filter - The FuelHealth project

Increased use of 1st and 2nd generation biofuels raises concerns about health effects of new emissions. We analyzed cellular and molecular lung effects in Fisher 344 rats exposed to diesel engine exhaust emissions (DEE) from a Euro 5-classified diesel engine running on B7: petrodiesel fuel containing 7% fatty acid methyl esters (FAME), or SHB20 (synthetic hydrocarbon biofuel): petrodiesel fuel containing 7% FAME and 13% hydrogenated vegetable oil. The Fisher 344 rats were exposed for 7 consecutive days (6 h/day) or 28 days (6 h/day, 5 days/week), both with and without diesel particle filter (DPF) treatment of the exhaust in whole body exposure chambers (n = 7/treatment). Histological analysis and analysis of cytokines and immune cell numbers in bronchoalveolar lavage fluid (BALF) did not reveal adverse pulmonary effects after exposure to DEE from B7 or SHB20 fuel. Significantly different gene expression levels for B7 compared to SHB20 indicate disturbed redox signaling (Cat, Hmox1), beta-adrenergic signaling (Adrb2) and xenobiotic metabolism (Cyp1a1). Exhaust filtration induced higher expression of redox genes (Cat, Gpx2) and the chemokine gene Cxcl7 compared to non-filtered exhaust. Exposure time (7 versus 28 days) also resulted in different patterns of lung gene expression. No genotoxic effects in the lungs were observed. Overall, exposure to B7 or SHB20 emissions suggests only minor effects in the lungs.

The effects of 1st and 2nd generation biodiesel exhaust exposure on hematological and biochemical blood indices of Fisher344 male rats - The FuelHealth project

Diesel exhaust emissions (DEE), being one of the main causes of ambient air pollution, exert a detrimental effect on human health and increase morbidity and mortality related to cardiovascular and pulmonary diseases. Therefore, the objective of the present study was to investigate potential adverse effects of exhausts emissions from B7 fuel, the first-generation biofuel containing 7% of fatty acid methyl esters (FAME), and SHB20 fuel, the second-generation biofuel containing 20% FAME/hydrotreated vegetable oil (HVO), after a whole-body exposure with and without diesel particle filter (DPF). The experiment was performed on 95 male Fischer 344 rats, divided into 10 groups (8 experimental, 2 control). Animals were exposed to DEE (diluted with charcoal-filtered room air to 2.1-2.2% (v/v)) for 7 or 28 days (6 h/day, 5 days/week) in an inhalation chamber. DEE originated from Euro 5 engine with or without DPF treatment, run on B7 or SHB20 fuel. Animals in the control groups were exposed to clean air. Our results showed that the majority of haematological and biochemical parameters examined in blood were at a similar level in the exposed and control animals. However, exposure to DEE from the SHB20 fuel caused an increase in the number of red blood cells (RBC) and haemoglobin concentration. Moreover, 7 days exposure to DEE from SHB20 fuel induced genotoxic effects manifested by increased levels of DNA single-strand breaks in peripheral blood lymphocytes. Furthermore, inhalation of both types of DEE induced oxidative stress and caused imbalance of anti-oxidant defence enzymes. In conclusion, exposure to DEE from B7, which was associated with higher exposure to polycyclic aromatic hydrocarbons, resulted in decreased number of T and NK lymphocytes, while DEE from SHB20 induced a higher level of DNA single-strand breaks, oxidative stress and increased red blood cells parameters. Additionally, DPF technology generated increased number of smaller PM and made the DEE more reactive and more harmful, manifested as deregulation of redox balance.

Genotoxic potential of diesel exhaust particles from the combustion of first- and second-generation biodiesel fuels-the FuelHealth project

Epidemiological data indicate that exposure to diesel exhaust particles (DEPs) from traffic emissions is associated with higher risk of morbidity and mortality related to cardiovascular and pulmonary diseases, accelerated progression of atherosclerotic plaques, and possible lung cancer. While the impact of DEPs from combustion of fossil diesel fuel on human health has been extensively studied, current knowledge of DEPs from combustion of biofuels provides limited and inconsistent information about its mutagenicity and genotoxicity, as well as possible adverse health risks. The objective of the present work was to compare the genotoxicity of DEPs from combustion of two first-generation fuels, 7% fatty acid methyl esters (FAME) (B7) and 20% FAME (B20), and a second-generation 20% FAME/hydrotreated vegetable oil (SHB: synthetic hydrocarbon biofuel) fuel. Our results revealed that particulate engine emissions from each type of biodiesel fuel induced genotoxic effects in BEAS-2B and A549 cells, manifested as the increased levels of single-strand breaks, the increased frequencies of micronuclei, or the deregulated expression of genes involved in DNA damage signaling pathways. We also found that none of the tested DEPs showed the induction of oxidative DNA damage and the gamma-H2AX-detectable double-strand breaks. The most pronounced differences concerning the tested particles were observed for the induction of single-strand breaks, with the greatest genotoxicity being associated with the B7-derived DEPs. The differences in other effects between DEPs from the different biodiesel blend percentage and biodiesel feedstock were also observed, but the magnitude of these variations was limited.