Toxicological evaluation of exhaust emissions from light-duty vehicles using different fuel alternatives in sub-freezing conditions

Comparison of the neurotoxic potency of different ultrafine particle fractions from diesel engine exhaust following direct and simulated inhalation exposure

Exposure to traffic-related air pollution and ultrafine particles (<100 nm; UFP) is linked with neurodegeneration. However, the impact of the aromatic content in fuels and the contribution of different fractions of UFP, i.e., solid UFP vs SVOC UFP, on neuronal function is unknown. We therefore studied effects on neuronal activity and viability in rat primary cortical cells exposed for up to 120 h to copper oxide particles (CuO) or UFP (solid and SVOC) emitted from a heavy-duty diesel engine fueled with petroleum diesel (A20; 20 % aromatics) or Hydrotreated Vegetable Oil-type fuel (A0; 0.1 % aromatics), or solid UFP emitted from a non-road Kubota engine fueled with A20. Moreover, effects of UFP and CuO upon simulated inhalation exposure were studied by exposing an lung model (Calu-3 and THP-1 cells) for 48 h and subsequently exposing the cortical cells to the medium collected from the basal compartment of the lung model. Additionally, cell viability, cytotoxicity, barrier function, inflammation, and oxidative and cell stress were studied in the lung model after 48 h exposure to UFP and CuO. Compared to control, direct exposure to CuO and SVOC UFP decreased neuronal activity, which was partly associated with cytotoxicity. Effects on neuronal activity upon direct exposure to solid UFP were limited. A20-derived UFP (solid and SVOC) were more potent in altering neuronal function and viability than A0 counterparts. Effects on neuronal activity from simulated inhalation exposure were minor compared to direct exposures. In the lung model, CuO and A20-derived UFP increased cytokine release compared to control, whereas CuO and SVOC A20 altered gene expression indicative for oxidative stress. Our data indicate that SVOC UFP exhibit higher (neuro)toxic potency for altering neuronal activity in rat primary cortical cells than the solid fraction. Moreover, our data suggest that reducing the aromatic content in fuel decreases the (neuro)toxic potency of emitted UFP.

In vitro neurotoxicity of particles from diesel and biodiesel fueled engines following direct and simulated inhalation exposure

Combustion-derived particulate matter (PM) is a major source of air pollution. Efforts to reduce diesel engine emission include the application of biodiesel. However, while urban PM exposure has been linked to adverse brain effects, little is known about the direct effects of PM from regular fossil diesel (PMDEP) and biodiesel (PMBIO) on neuronal function. Furthermore, it is unknown to what extent the PM-induced effects in the lung (e.g., inflammation) affect the brain. This in vitro study investigates direct and indirect toxicity of PMDEP and PMBIO on the lung and brain and compared it with effects of clean carbon particles (CP). PM were generated using a common rail diesel engine. CP was sampled from a spark generator. First, effects of 48 h exposure to PM and CP (1.2-3.9 µg/cm2) were assessed in an in vitro lung model (air-liquid interface co-culture of Calu-3 and THP1 cells) by measuring cell viability, cytotoxicity, barrier function, inflammation, and oxidative and cell stress. None of the exposures caused clear adverse effects and only minor changes in gene expression were observed. Next, the basal medium was collected for subsequent simulated inhalation exposure of rat primary cortical cells. Neuronal activity, recorded using microelectrode arrays (MEA), was increased after acute (0.5 h) simulated inhalation exposure. In contrast, direct exposure to PMDEP and PMBIO (1-100 µg/mL; 1.2-119 µg/cm2) reduced neuronal activity after 24 h with lowest observed effect levels of respectively 10 µg/mL and 30 µg/mL, indicating higher neurotoxic potency of PMDEP, whereas neuronal activity remained unaffected following CP exposure. These findings indicate that combustion-derived PM potently inhibit neuronal function following direct exposure, while the lung serves as a protective barrier. Furthermore, PMDEP exhibit a higher direct neurotoxic potency than PMBIO, and the data suggest that the neurotoxic effects is caused by adsorbed chemicals rather than the pure carbon core.

Dynamic crosslinked polymeric nano-prodrugs for highly selective synergistic chemotherapy

To achieve highly selective synergistic chemotherapy attractive for clinical translation, the precise polymeric nano-prodrugs (PPD-NPs) were successfully constructed via the facile crosslinking reaction between pH-sensitive poly(ortho ester)s and reduction-sensitive small molecule synergistic prodrug (Pt(IV)-1). PPD-NPs endowed the defined structure and high drug loading of cisplatin and demethylcantharidin (DMC). Moreover, PPD-NPs exhibited steady long-term storage and circulation via the crosslinked structure, suitable negative potentials and low critical micelle concentration (CMC), improved selective tumour accumulation and cellular internalization via dynamic size transition and surficial amino protonation at tumoural extracellular pH, promoted efficient disintegration and drug release at tumoural intracellular pH/glutathione, and enhanced cytotoxicity via the synergistic effect between cisplatin and DMC with the feed ratio of 1:2, achieving significant tumour suppression while decreasing the side effects. Thus, the dynamic crosslinked polymeric nano-prodrugs exhibit tremendous potential for clinically targeted synergistic cancer therapy.

Air Pollution, Ultrafine Particles, and Your Brain: Are Combustion Nanoparticle Emissions and Engineered Nanoparticles Causing Preventable Fatal Neurodegenerative Diseases and Common Neuropsychiatric Outcomes?

Exposure to particulate matter (PM) pollution damages the human brain. Fossil fuel burning for transportation energy accounts for a significant fraction of urban air and climate pollution. While current United States (US) standards limit PM ambient concentrations and emissions, they do not regulate explicitly ultrafine particles (UFP ≤ 100 nm in diameter). There is a growing body of evidence suggesting UFP may play a bigger role inflicting adverse health impacts than has been recognized, and in this perspective, we highlight effects on the brain, particularly of young individuals. UFP penetrate the body through nasal/olfactory, respiratory, gastrointestinal, placenta, and brain-blood barriers, translocating in the bloodstream and reaching the glymphatic and central nervous systems. We discuss one case study. The 21.8 million residents in the Metropolitan Mexico City (MMC) are regularly exposed to fine PM (PM_2.5) above the US 12 μg/m³ annual average standards. Alzheimer's disease (AD), Parkinson's disease (PD), and TAR DNA-binding protein (TDP-43) pathologies and nanoparticles (NP ≤ 50 nm in diameter) in critical brain organelles have been documented in MMC children and young adult autopsies. MMC young residents have cognitive and olfaction deficits, altered gait and equilibrium, brainstem auditory evoked potentials, and sleep disorders. Higher risk of AD and vascular dementia associated with residency close to high traffic roadways have been documented. The US is not ready or prepared to adopt ambient air quality or emission standards for UFP and will continue to focus regulations only on the total mass of PM_2.5 and PM₁₀. Thus, this approach raises the question: are we dropping the ball? As research continues to answer the remaining questions about UFP sources, exposures, impacts, and controls, the precautionary principle should call us to accelerate and expand policy interventions to abate or eliminate UFP emissions and to mitigate UFP exposures. For residents of highly polluted cities, particularly in the developing world where there is likely older and dirtier vehicles, equipment, and fuels in use and less regulatory oversight, we should embark in a strong campaign to raise public awareness of the associations between high PM pollution, heavy traffic, UFP, NP, and neuropsychiatric outcomes, including dementia. Neurodegenerative diseases evolving from childhood in polluted, anthropogenic, and industrial environments ought to be preventable.

Genotoxic and inflammatory effects of spruce and brown coal briquettes combustion aerosols on lung cells at the air-liquid interface

Solid fuel usage in residential heating and cooking is one of the largest sources of ambient and indoor air particulate matter, which causes adverse effects on the health of millions of peoples worldwide. Emissions from solid fuel combustion, such as biomass or coal, are detrimental to health, but toxicological responses are largely unknown. In the present study, we compared the toxicological responses regarding cytotoxicity, inflammation and genotoxicity of spruce (SPR) and brown coal briquette (BCB) combustion aerosols on human alveolar epithelial cells (A549) as well as a coculture of A549 and differentiated human monocytic cells (THP-1) into macrophages exposed at the air-liquid interface (ALI). We included both the high emissions from the first hour and moderate emissions from the third hour of the batch combustion experiment in one ALI system, whereas, in the second ALI system, we exposed the cells during the whole 4-hour combustion experiment, including all combustion phases. Physico-chemical properties of the combustion aerosol were analysed both online and offline. Both SPR and BCB combustion aerosols caused mild cytotoxic but notable genotoxic effects in co-cultured A549 cells after one-hour exposure. Inflammatory response analysis revealed BCB combustion aerosols to cause a mild increase in CXCL1 and CXCL8 levels, but in the case of SPR combustion aerosol, a decrease compared to control was observed.

Markers of lipid oxidation and inflammation in bronchial cells exposed to complete gasoline emissions and their organic extracts

Road traffic emissions consist of gaseous components, particles of various sizes, and chemical compounds that are bound to them. Exposure to vehicle emissions is implicated in the etiology of inflammatory respiratory disorders. We investigated the inflammation-related markers in human bronchial epithelial cells (BEAS-2B) and a 3D model of the human airways (MucilAir™), after exposure to complete emissions and extractable organic matter (EOM) from particles generated by ordinary gasoline (E5), and a gasoline-ethanol blend (E20; ethanol content 20% v/v). The production of 22 lipid oxidation products (derivatives of linoleic and arachidonic acid, AA) and 45 inflammatory molecules (cytokines, chemokines, growth factors) was assessed after days 1 and 5 of exposure, using LC-MS/MS and a multiplex immunoassay, respectively. The response observed in MucilAir™ exposed to E5 gasoline emissions, characterized by elevated levels of pro-inflammatory AA metabolites (prostaglandins) and inflammatory markers, was the most pronounced. E20 EOM exposure was associated with increased levels of AA metabolites with anti-inflammatory effects in this cell model. The exposure of BEAS-2B cells to complete emissions reduced lipid oxidation, while E20 EOM tended to increase concentrations of AA metabolite and chemokine production; the impacts on other inflammatory markers were limited. In summary, complete E5 emission exposure of MucilAir™ induces the processes associated with the pro-inflammatory response. This observation highlights the potential negative health impacts of ordinary gasoline, while the effects of alternative fuel are relatively weak.