Disruption of the integrity and function of brain microvascular endothelial cells in culture by exposure to diesel engine exhaust particles

Prenatal diesel exhaust exposure alters hippocampal synaptic plasticity in offspring

Diesel exhaust particles (DEPs) are major air pollutants emitted from automobile engines. Prenatal exposure to DEPs has been linked to neurodevelopmental and neurodegenerative diseases associated with aging. However, the specific mechanism by DEPs impair the hippocampal synaptic plasticity in the offspring remains unclear. Pregnant C57BL/6 mice were administered DEPs solution via the tail vein every other day for a total of 10 injections, then the male offsprings were studied to assess learning and memory by the Morris water maze. Additionally, protein expression in the hippocampus, including CPEB3, NMDAR (NR1, NR2A, NR2B), PKA, SYP, PSD95, and p-CREB was analyzed using Western blotting and immunohistochemistry. The alterations in the histomorphology of the hippocampus were observed in male offspring on postnatal day 7 following prenatal exposure to DEPs. Furthermore, 8-week-old male offspring exposed to DEPs during prenatal development exhibited impairments in the Morris water maze test, indicating deficits in learning and memory. Mechanistically, the findings from our study indicate that exposure to DEPs during pregnancy may alter the expression of CPEB3, SYP, PSD95, NMDAR (NR1, NR2A, and NR2B), PKA, and p-CREB in the hippocampus of both immature and mature male offspring. The results offer evidence for the role of the NMDAR/PKA/CREB and CPEB3 signaling pathway in mediating the learning and memory toxicity of DEPs in male offspring mice. The alterations in signaling pathways may contribute to the observed damage to synaptic structure and transmission function plasticity caused by DEPs. The findings hold potential for informing future safety assessments of DEPs.

Evaluating the effect of acute diesel exhaust particle exposure on P-glycoprotein efflux transporter in the blood-brain barrier co-cultured with microglia

A growing public health concern, chronic Diesel Exhaust Particle (DEP) exposure is a heavy risk factor for the development of neurodegenerative diseases like Alzheimer's (AD). Considered the brain's first line of defense, the Blood-Brain Barrier (BBB) and perivascular microglia work in tandem to protect the brain from circulating neurotoxic molecules like DEP. Importantly, there is a strong association between AD and BBB dysfunction, particularly in the Aβ transporter and multidrug resistant pump, P-glycoprotein (P-gp). However, the response of this efflux transporter is not well understood in the context of environmental exposures, such as to DEP. Moreover, microglia are seldom included in in vitro BBB models, despite their significance in neurovascular health and disease. Therefore, the goal of this study was to evaluate the effect of acute (24 hr.) DEP exposure (2000 μg/ml) on P-gp expression and function, paracellular permeability, and inflammation profiles of the human in vitro BBB model (hCMEC/D3) with and without microglia (hMC3). Our results suggested that DEP exposure can decrease both the expression and function of P-gp in the BBB, and corroborated that DEP exposure impairs BBB integrity (i.e. increased permeability), a response that was significantly worsened by the influence of microglia in co-culture. Interestingly, DEP exposure seemed to produce atypical inflammation profiles and an unexpected general downregulation in inflammatory markers in both the monoculture and co-culture, which differentially expressed IL-1β and GM-CSF. Interestingly, the microglia in co-culture did not appear to influence the response of the BBB, save in the permeability assay, where it worsened the BBB's response. Overall, our study is important because it is the first (to our knowledge) to investigate the effect of acute DEP exposure on P-gp in the in vitro human BBB, while also investigating the influence of microglia on the BBB's responses to this environmental chemical.

Hesperetin protects against diesel exhaust particles-induced cardiovascular oxidative stress and inflammation in Wistar rats

Air particulate matter exposure has been linked to cardiovascular and atherosclerosis as a result of increase oxidative stress and inflammatory response. This study aims to determine the effect of the use of hesperetin (HESP) as a therapeutic agent to mitigate the cardiovascular oxidative and pro-inflammatory effects of diesel exhaust particles in Wistar rats. DEP was collected from an Iveco cargo engine truck, and n-hexane fraction (hDEP) was obtained. Forty Wistar strains of male albino rats (6 weeks) were divided into 8 groups: control group received DMSO and CMC-Na; other groups received either n-hexane extract of DEP (0.064 or 0.640 mg/kg hDEP) or Standard Reference Material 2975 (0.064 mg/kg hSRM) in the presence or absence of 200 mg/kg HESP. Extracts were administered orally. Serum lipids, lipid peroxidation (LPO), conjugated dienes (CDs), and GSH levels were determined. Also, inflammatory cytokines, PCSK-9, LDL-receptor, and antioxidant genes expression were assessed by RT-PCR in both the heart and aorta. The molecular interaction of targeted proteins with HESP was assessed by the in silico approach. Extracts of DEP caused a significant (p < 0.001) increase in serum lipids but significantly decreased HDL-CHOL. It also increased CDs and MDA levels but decreased GSH levels. In addition, the particulate extracts caused a significant (p < 0.001) increase in pro-inflammatory genes expression in the heart and aorta but significantly decreased IL-10 and LDL-R gene expressions. Pre-treatment with hesperetin significantly reversed all these effects. This study shows that hesperetin has the ability to protect against DEP-induced oxidative stress and inflammation in the cardiovascular system.

Reconstituting neurovascular unit based on the close relations between neural stem cells and endothelial cells: an effective method to explore neurogenesis and angiogenesis

The discovery of neural stem cells (NSCs) and their microenvironment, the NSC niche, brought new therapeutic strategies through neurogenesis and angiogenesis for stroke and most neurodegenerative diseases, including Alzheimer's disease. Based on the close links between NSCs and endothelial cells, the integration of neurogenesis and angiogenesis of the NSC niche is also a promising area to the neurovascular unit (NVU) modeling and is now offering a powerful tool to advance our understanding of the brain. In this review, critical aspects of the NVU and model systems are discussed. First, we briefly describe the interaction of each part in the NSC niche. Second, we introduce the co-culture system, microfluidic platforms, and stem cell-derived 3D reconstitution used in NVU modeling based on the close relations between NSCs and endothelial cells, and various characteristics of cell interactions in these systems are also described. Finally, we address the challenges in modeling the NVU that can potentially be overcome by employing strategies for advanced biomaterials and stem cell co-culture use. Based on these approaches, researchers will continue to develop predictable technologies to control the fate of stem cells, achieve accurate screening of drugs for the nervous system, and advance the clinical application of NVU models.

Evaluating the endothelial-microglial interaction and comprehensive inflammatory marker profiles under acute exposure to ultrafine diesel exhaust particles in vitro

Exposure to combustion-derived particulate matter (PM) such as diesel exhaust particles (DEP) is a public health concern because people in urban areas are continuously exposed, and once inhaled, fine and ultrafine DEP may reach the brain. The blood-brain barrier (BBB) endothelial cells (EC) and the perivascular microglia protect the brain from circulating pathogens and neurotoxic molecules like DEP. While the BBB-microglial interaction is critical for maintaining homeostasis, no study has previously evaluated the endothelial-microglial interaction nor comprehensively characterized these cells' inflammatory marker profiles under ultrafine DEP exposures in vitro. Therefore, the goal of this study was to investigate the in vitro rat EC-microglial co-culture under acute (24 h.) exposure to ultrafine DEP (0.002-20 μg/mL), by evaluating key mechanisms associated with PM toxicity: lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) generation, cell metabolic activity (CMA) changes, and production of 27 inflammatory markers. These parameters were also evaluated in rat microglial and endothelial monocultures to determine whether the EC-microglial co-culture responded differently than the cerebrovasculature and microglia alone. While results indicated that ultrafine DEP exposure caused concentration-dependent increases in LDH leakage and ROS production in all groups, as expected, exposure also caused mixed responses in CMA and atypical cytokine/chemokine profiles in all groups, which was not expected. The inflammation assay results further suggested that the microglia were not classically activated under this exposure scenario, despite previous in vitro studies showing microglial activation (priming) at similar concentrations of ultrafine DEP. Additionally, compared to the cerebrovasculature alone, the EC-microglia interaction in the co-culture did not appear to cause changes in any parameter save in pro-inflammatory marker production, where the interaction appeared to cause an overall downregulation in cytokine/chemokine levels after ultrafine DEP exposure. Finally, to our knowledge, this is the first study to evaluate the influence of microglia on the BBB's ultrafine DEP-induced cytotoxic and inflammatory responses, which are heavily implicated in the pathogenesis of PM-related cerebrovascular dysfunction and neurodegeneration.

DNA Adducts as Biomarkers To Predict, Prevent, and Diagnose Disease-Application of Analytical Chemistry to Clinical Investigations

Characterization of the chemistry, structure, formation, and metabolism of DNA adducts has been one of the most significant contributions to the field of chemical toxicology. This work provides the foundation to develop analytical methods to measure DNA adducts, define their relationship to disease, and establish clinical tests. Monitoring exposure to environmental and endogenous toxicants can predict, diagnose, and track disease as well as guide therapeutic treatment. DNA adducts are one of the most promising biomarkers of toxicant exposure owing to their stability, appearance in numerous biological matrices, and characteristic analytical properties. In addition, DNA adducts can induce mutations to drive disease onset and progression and can serve as surrogate markers of chemical exposure. In this perspective, we highlight significant advances made within the past decade regarding DNA adduct quantitation using mass spectrometry. We hope to expose a broader audience to this field and encourage analytical chemistry laboratories to explore how specific adducts may be related to various pathologies. One of the limiting factors in developing clinical tests to measure DNA adducts is cohort size; ideally, the cohort would allow for model development and then testing of the model to the remaining cohort. The goals of this perspective article are to (1) provide a summary of analyte levels measured using state-of-the-art analytical methods, (2) foster collaboration, and (3) highlight areas in need of further investigation.

Neurobehavioral Consequences of Traffic-Related Air Pollution

Traffic-related air pollution (TRAP) is a major contributor to global air pollution. The World Health Organization (WHO) has reported that air pollution due to gasoline and diesel emissions from internal combustion engines of automobiles, trucks, locomotives, and ships leads to 800,000 premature deaths annually due to pulmonary, cardiovascular, and neurological complications. It has been observed that individuals living and working in areas of heavy vehicle traffic have high susceptibility to anxiety, depression, and cognitive deficits. Information regarding the mechanisms that potentially lead to detrimental mental health effects of TRAP is gradually increasing. Several studies have suggested that TRAP is associated with adverse effects in the central nervous system (CNS), primarily due to increase in oxidative stress and neuroinflammation. Animal studies have provided further useful insights on the deleterious effects of vehicle exhaust emissions (VEEs). The mechanistic basis for these effects is unclear, although gasoline and diesel exhaust-induced neurotoxicity seems the most plausible cause. Several important points emerge from these studies. First, TRAP leads to neurotoxicity. Second, TRAP alters neurobehavioral function. Exactly how that happens remains unclear. This review article will discuss current state of the literature on this subject and potential leads that have surfaced from the preclinical work.

Blood-brain barrier function, cell viability, and gene expression of tight junction-associated proteins in the mouse are disrupted by crude oil, benzo[a]pyrene, and the dispersant COREXIT

Exposure to crude oil, its components, and oil dispersants during a major crude oil spill, such as the Deepwater Horizon Oil Spill, can elicit behavioral changes in animals and humans. However, the underlying mechanisms by which oil spill-related compounds alters behavior remains largely unknown. A major cause of behavioral changes generally is dysfunction of the blood-brain barrier (BBB). We investigated the impact of a crude oil high energy water accommodated fraction (HEWAF), benzo[a] pyrene (BaP; a major component of crude oil), and the oil dispersant COREXIT, on BBB function. BBB function was assessed by measuring transendothelial electrical resistance (TEER) of mouse brain microvascular endothelial cells (BMECs). Within 3 h after treatment, TEER was significantly reduced by exposure to high concentrations of all test compounds. TEER remained reduced in response to COREXIT after 48 h, but this effect waned in BMECs treated with HEWAF and BaP, with low-mid range concentrations inducing increased TEER compared to vehicle controls. At 48 h of treatment, BMEC viability was significantly reduced in response to 2% HEWAF, but was increased in response to BaP (25 and 50 μM). BMEC viability was increased with 80 ppm COREXIT, but was reduced with 160 ppm. Gene expression of tight junction-associated proteins (claudin-5 and tight junction protein-1), and cell adhesion receptor (vascular cell adhesion molecule-1) was reduced in response to HEWAF and COREXIT, but not BaP. Taken together, these data suggest that oil spill-related compounds markedly affect BBB function, and that these changes may underlie the observed behavioral changes due to crude oil exposure.

Prenatal exposure to diesel exhaust particles causes anxiety, spatial memory disorders with alters expression of hippocampal pro-inflammatory cytokines and NMDA receptor subunits in adult male mice offspring

Air pollution by Diesel exhaust (DE) consists of gaseous compounds and diesel exhaust particles (DEPs). Previous studies show associations between prenatal exposure to diesel exhaust affects the central nervous system (CNS). However, there was not reported that these effects were caused by gaseous compounds, diesel exhaust particles, or both. A limited number of studies in rodent models have shown that exposure to DEPs can result in CNS. Here, we explored the effects of prenatal exposure to DEPs on anxiety and learning and memory in NMRI mice male offspring. Three groups of pregnant mice were exposed to 350-400 μg DEPs/m³ for 2, 4 and 6 h daily in a closed system room. We examined anxiety and learning and memory in 8-to-9-week-old male offspring using the Elevated plus maze and Morris water maze (MWM) test. Hippocampi were isolated after the behavioral tests and measured pro-inflammatory cytokines and N-methyl-D-aspartate (NMDA) receptor expression by quantitative RT-PCR analysis. Mice exposed to DEPs in utero showed deficits in the Elevated plus maze and Morris water maze test. In addition, DEPs exposed mice exhibited decreased hippocampal NR2A and NR3B expression. Taken together, our data suggest that maternal DEP exposure is associated with anxiety, disrupts learning and memory and reduction hippocampal NR2A and NR3B expression in male offspring.

Rooibos (Aspalathus linearis) and honeybush (Cyclopia species) modulate the oxidative stress associated injury of diesel exhaust particles in human umbilical vein endothelial cells

BACKGROUND

Previous evidence show foods and beverages rich in polyphenolic compounds to have favourable effects on the cardiovascular system.

HYPOTHESIS

The current study assessed the modulation of oxidative stress and associated inflammation induced by diesel exhaust particles (DEP - SRM 2975) by pre-treatment of human umbilical vein endothelial cells (HUVECs) with aqueous extracts of rooibos [fermented (FR) as well as green form (GR)] and honeybush [fermented form (FH)].

STUDY DESIGN

HUVEC are either exposed to DEP (10 µg/ml) for 4 h or pre-treated with 40 and 60 µg/ml of FR or GH or FR, or 50 µg/ml orientin (OR) for 6 h prior to DEP exposure.

METHODS

In vitro antioxidant capacity of the extracts was assessed and the polyphenol contents were also assessed by HPLC. ROS, cell viability, lactate dehydrogenase leakage, lipid peroxidation, GSH:GSSG ratios, conjugated diene and protein carbonyl levels were determined as indices of oxidative stress and cytotoxicity. RT-qPCR and western blot were used to assess inflammatory cytokines and antioxidant genes expression.

RESULTS

DEP caused a dose and time-dependent increase in ROS production, significant (p < 0.001) increase in protein carbonyl (PC) formation, thiobarbituric acid reactive substances and conjugated dienes levels (p < 0.01) and a significant reduction in glutathione (GSH) redox status. Pre-incubation with either the herbal extracts or orientin attenuated these effects. The significant increase in IL-1α, IL-6, IL-8, VCAM-1 and ATF4 gene expression caused by DEP (10 µg/ml) were also attenuated by the presence of the FR, GR and FH extracts, and OR . Pre-treatment with the rooibos extracts or flavone orientin enhanced cell viability, reduced LDH leakage, enhanced mRNA expression of NQO1 and Nrf2, but repressed CYP1B1 mRNA induced by DEP. Western blot showed both the herbal tea extracts and orientin to enhance NQO1 and γGSC protein induction by DEP.

CONCLUSION

Taken together, the herbal extracts offer protection against DEP-induced oxidative stress and inflammatory response.

The cardiovascular protective effects of rooibos (Aspalathus linearis) extract on diesel exhaust particles induced inflammation and oxidative stress involve NF-κB- and Nrf2-dependent pathways modulation

Studies have shown that diesel exhaust particles (DEP) induced oxidative stress and inflammation. This present study examined the molecular effects of aqueous rooibos extract (RE) on the cardiovascular toxic effect of methanol extract of DEP in exposed Wistar rats. The results showed that DEP caused significant (p < 0.001) increase in MDA and CDs levels in the aorta and heart but this increase was significantly (p < 0.001) attenuated by rooibos extract. DEP induced IL-8, TNFα, IL-1β and decreased IL-10 gene expressions, all of which were reversed in the presence of rooibos extract. The expression of NF-κB, and IκKB genes were also significantly (p < 0.001) induced by DEP in both tissues, but pre-treatment with RE attenuated these effects. In contrast, DEP repressed IκB mRNA level, which was significantly (p < 0.001) reversed by rooibos extract pre-treatment. In addition, pre-treatment with rooibos extract attenuated the increased Nrf2 and HO-1 mRNA levels caused by DEP. This indicates the potential of rooibos extract to protect against DEP-induced cardiovascular toxicity.

Limited developmental neurotoxicity from neonatal inhalation exposure to diesel exhaust particles in C57BL/6 mice

Background

Recent epidemiological studies indicate early-life exposure to pollution particulate is associated with adverse neurodevelopmental outcomes. The need is arising to evaluate the risks conferred by individual components and sources of air pollution to provide a framework for the regulation of the most relevant components for public health protection. Previous studies in rodent models have shown diesel particulate matter has neurotoxic potential and could be a health concern for neurodevelopment. The present study shows an evaluation of pathological and protracted behavioral alterations following neonatal exposure to aerosolized diesel exhaust particles (NIST SRM 1650b). The particular behavioral focus was on temporal control learning, a broad and fundamental cognitive domain in which reward delivery is contingent on a fixed interval schedule. For this purpose, C57BL/6 J mice were exposed to aerosolized NIST SRM 1650b, a well-characterized diesel particulate material, from postnatal days 4–7 and 10–13, for four hours per day. Pathological features, including glial fibrillary-acidic protein, myelin basic protein expression in the corpus callosum, and ventriculomegaly, as well as learning alterations were measured to determine the extent to which NIST SRM 1650b would induce developmental neurotoxicity.

Results

Twenty-four hours following exposure significant increases in glial-fibrillary acidic protein (GFAP) in the corpus callosum and cortex of exposed male mice were present. Additionally, the body weights of juvenile and early adult diesel particle exposed males were lower than controls, although the difference was not statistically significant. No treatment-related differences in males or females on overall locomotor activity or temporal learning during adulthood were observed in response to diesel particulate exposure.

Conclusion

While some sex and regional-specific pathological alterations in GFAP immunoreactivity suggestive of an inflammatory reaction to SRM 1650b were observed, the lack of protracted behavioral and pathological deficits suggests further clarity is needed on the developmental effects of diesel emissions prior to enacting regulatory guidelines.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0287-8) contains supplementary material, which is available to authorized users.

Effects of inhaled particulate matter on the central nervous system in mice

Little is known regarding the adverse effects of chronic particulate matter (PM) inhalation on the central nervous system (CNS). The present study aimed to examine how PM exposure impacts on oxidative stress and inflammatory processes, as well as the expression of interneurons and perineuronal nets (PNNs) in the CNS. BALB/c mice (6-week-old females, n = 32) were exposed to 1 to 5 μm size diesel-extracted particles (DEPs) (100 μg/m³, 5 d/week, 5 h/day) and categorized into the following four groups: 1) 4-week DEP (n = 8); 2) 4-week control (n = 8), 3) 8-week DEP (n = 8); and 4) 8-week control (n = 8). The olfactory bulb, prefrontal cortex, temporal cortex, striatum, and cerebellum were harvested from the animals in each group. The expression of antioxidants (heme oxygenase 1 [HO-1] and superoxide dismutase 2 [SOD-2]), and markers of the unfolded protein response (X-box binding protein [XBP]-1S), inflammation (tumor necrosis factor-alpha [TNF-α]), and proliferation (neurotrophin-3 and brain-derived neurotrophic factor [BDNF]) were measured using reverse transcription polymerase chain reaction (PCR) and Western blotting. The expression levels of HO-1, SOD-2, XBP-1S, TNF-α, neurotrophin-3, and BDNF were compared among groups using the Mann-Whitney U test. The temporal cortex was immunostained for parvalbumin (PV) and Wisteria floribunda agglutinin (WFA). The numbers of PV- and WFA-positive cells were counted using a confocal microscope and analyzed with the Mann-Whitney U test. HO-1 expression was elevated in the prefrontal cortex, temporal cortex, striatum, and cerebellum of mice in the 8-week DEP group compared with the control group. Expression of SOD-2 and XBP-1S was elevated in the prefrontal cortex and striatum of the 8-week DEP group compared with the control group. TNF-α expression was elevated in the prefrontal cortex, temporal cortex, striatum, and cerebellum in the 4- and 8-week DEP groups compared with the control group. Neurotrophin-3 expression was decreased in the olfactory bulb and striatum of the 8-week DEP group compared with the control group. WFA density was increased in the 8-week DEP group compared with the control group. The PV and PV + WFA densities were decreased in the 4-week DEP group compared with the control group. Chronic DEP inhalation activated oxidative stress and inflammation in multiple brain regions. Chronic DEP inhalation increased PNNs and decreased the number of interneurons, which may contribute to PM exposure-related CNS dysfunction.

Air particulate matter induced oxidative stress and inflammation in cardiovascular disease and atherosclerosis: The role of Nrf2 and AhR-mediated pathways

Air particulate matter (PM) is an important component of air pollution, which has been reported to play important role in the adverse health effects of the latter. Extensive experimental data and epidemiological studies have shown that the increased cardiovascular morbidity and mortality and atherosclerosis caused by air pollution are mainly due to the PM component. Implicated in these adverse health effects of PM, is their ability to induce oxidative stress and pro-inflammatory events in the vascular system. The association between the cardiovascular ischemic events and atherosclerosis induced by PM has been linked to the ultrafine and fine components. These particles have a high content of redox cyclic chemicals. This, together with their ability to combine with proatherogenic molecules enhanced tissue oxidative stress. Studies have shown that the oxidative stress induced by PM could up-regulates the expression of phase I and phase II metabolize enzymes. This up-regulation occurs by the activation of transcription factors (such as nuclear factor (erythroid-derived 2) -like 2-related factor (Nrf2) and aryl hydrocarbon receptor (AhR)). This review will focus on data supporting the role of oxidative stress and inflammation in PM-induced cardiovascular diseases and atherosclerosis and the importance of Nrf2-and AhR- dependent regulatory pathways in the PM-induced cardiovascular events and atherosclerosis.

Increased levels of urinary biomarkers of lipid peroxidation products among workers occupationally exposed to diesel engine exhaust

Diesel engine exhaust (DEE) was found to induce lipid peroxidation (LPO) in animal exposure studies. LPO is a class of oxidative stress and can be reflected by detecting the levels of its production, such as malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), and etheno-DNA adducts including 1,N(6)-etheno-2'-deoxyadenosine (ɛdA) and 3,N(4)-etheno-2'-deoxycytidine (ɛdC). However, the impact of DEE exposure on LPO has not been explored in humans. In this study, we evaluated urinary MDA, 4-HNE, ɛdA, and ɛdC levels as biomarkers of LPO among 108 workers with exclusive exposure to DEE and 109 non-DEE-exposed workers. Results showed that increased levels of urinary MDA and ɛdA were observed in subjects occupationally exposed to DEE before and after age, body mass index (BMI), smoking status, and alcohol use were adjusted (all p < 0.001). There was a statistically significant relationship between the internal exposure dose (urinary ΣOH-PAHs) and MDA, 4-HNE, and ɛdA (all p < 0.001). Furthermore, significant increased relations between urinary etheno-DNA adduct and MDA, 4-HNE were observed (all p < 0.05). The findings of this study suggested that the level of LPO products (MDA and ɛdA) was increased in DEE-exposed workers, and urinary MDA and ɛdA might be feasible biomarkers for DEE exposure. LPO induced DNA damage might be involved and further motivated the genomic instability could be one of the pathogeneses of cancer induced by DEE-exposure. However, additional investigations should be performed to understand these observations.

In utero exposure of mice to diesel exhaust particles affects spatial learning and memory with reduced N-methyl-D-aspartate receptor expression in the hippocampus of male offspring

Diesel exhaust consists of diesel exhaust particles (DEPs) and gaseous compounds. Previous studies reported that in utero exposure to diesel exhaust affects the central nervous system. However, there was no clear evidence that these effects were caused by diesel exhaust particles themselves, gaseous compounds, or both. Here, we explored the effects of in utero exposure to DEPs on learning and memory in male ICR mice. DEP solutions were administered subcutaneously to pregnant ICR mice at a dose of 0 or 200 μg/kg body weight on gestation days 6, 9, 12, 15, and 18. We examined learning and memory in 9-to-10-week-old male offspring using the Morris water maze test and passive avoidance test. Immediately after the behavioral tests, hippocampi were isolated. Hippocampal N-methyl-D-aspartate receptor (NR) expression was also measured by quantitative RT-PCR analysis. Mice exposed to DEPs in utero showed deficits in the Morris water maze test, but their performance was not significantly different from that of control mice in the passive avoidance test. In addition, DEP-exposed mice exhibited decreased hippocampal NR2A expression. The present results indicate that maternal DEP exposure disrupts learning and memory in male offspring, which is associated with reduced hippocampal NR2A expression.

Comparative evaluation of N-acetylcysteine and N-acetylcysteineamide in acetaminophen-induced hepatotoxicity in human hepatoma HepaRG cells

Acetaminophen (N-acetyl-p-aminophenol, APAP) is one of the most widely used over-the-counter antipyretic analgesic medications. Despite being safe at therapeutic doses, an accidental or intentional overdose can result in severe hepatotoxicity; a leading cause of drug-induced liver failure in the U.S. Depletion of glutathione (GSH) is implicated as an initiating event in APAP-induced toxicity. N-acetylcysteine (NAC), a GSH precursor, is the only currently approved antidote for an APAP overdose. Unfortunately, fairly high doses and longer treatment times are required due to its poor bioavailability. In addition, oral and intravenous administration of NAC in a hospital setting are laborious and costly. Therefore, we studied the protective effects of N-acetylcysteineamide (NACA), a novel antioxidant, with higher bioavailability and compared it with NAC in APAP-induced hepatotoxicity in a human-relevant in vitro system, HepaRG. Our results indicated that exposure of HepaRG cells to APAP resulted in GSH depletion, reactive oxygen species (ROS) formation, increased lipid peroxidation, mitochondrial dysfunction (assessed by JC-1 fluorescence), and lactate dehydrogenase release. Both NAC and NACA protected against APAP-induced hepatotoxicity by restoring GSH levels, scavenging ROS, inhibiting lipid peroxidation, and preserving mitochondrial membrane potential. However, NACA was better than NAC at combating oxidative stress and protecting against APAP-induced damage. The higher efficiency of NACA in protecting cells against APAP-induced toxicity suggests that NACA can be developed into a promising therapeutic option for treatment of an APAP overdose.

Exposure to vehicle emissions results in altered blood brain barrier permeability and expression of matrix metalloproteinases and tight junction proteins in mice

Background

Traffic-generated air pollution-exposure is associated with adverse effects in the central nervous system (CNS) in both human exposures and animal models, including neuroinflammation and neurodegeneration. While alterations in the blood brain barrier (BBB) have been implicated as a potential mechanism of air pollution-induced CNS pathologies, pathways involved have not been elucidated.

Objectives

To determine whether inhalation exposure to mixed vehicle exhaust (MVE) mediates alterations in BBB permeability, activation of matrix metalloproteinases (MMP) -2 and −9, and altered tight junction (TJ) protein expression.

Methods

Apolipoprotein (Apo) E^−/− and C57Bl6 mice were exposed to either MVE (100 μg/m³ PM) or filtered air (FA) for 6 hr/day for 30 days and resulting BBB permeability, expression of ROS, TJ proteins, markers of neuroinflammation, and MMP activity were assessed. Serum from study mice was applied to an in vitro BBB co-culture model and resulting alterations in transport and permeability were quantified.

Results

MVE-exposed Apo E^−/− mice showed increased BBB permeability, elevated ROS and increased MMP-2 and −9 activity, compared to FA controls. Additionally, cerebral vessels from MVE-exposed mice expressed decreased levels of TJ proteins, occludin and claudin-5, and increased levels of inducible nitric oxide synthase (iNOS) and interleukin (IL)-1β in the parenchyma. Serum from MVE-exposed animals also resulted in increased in vitro BBB permeability and altered P-glycoprotein transport activity.

Conclusions

These data indicate that inhalation exposure to traffic-generated air pollutants promotes increased MMP activity and degradation of TJ proteins in the cerebral vasculature, resulting in altered BBB permeability and expression of neuroinflammatory markers.