Urinary polycyclic aromatic hydrocarbon metabolites, plasma p-tau231 and mild cognitive impairment in coke oven workers

Co-exposure to polycyclic aromatic hydrocarbons and nicotine and their associations with cognitive impairment risk in older adults from southern China

Exposure to polycyclic aromatic hydrocarbons (PAHs) and tobacco smoke is widespread and linked to various adverse health outcomes. Their potential to disturb the neurological system has raised much concern, particularly among older adults. Thus, we conducted a case-control study to assess the associations between co-exposure to PAHs and nicotine, and the risk of cognitive impairment and oxidative stress in older adults. A total of 384 adults aged 60 years and older were recruited from 2017 to 2018 in Shenzhen, China. Morning spot urine samples were collected for the analysis of 6 mono-hydroxylated PAHs, 8 nicotine metabolites, and a typical biomarker for oxidative stress, 8-hydroxy-2'-deoxyguanosine (8-OHdG). The Mini-Mental State Examination was used to assess the cognitive function of participants. Quantile-based g-computation (QGC), weighted quantile sum regression, and Bayesian kernel machine regression were used to analyze the associations between the exposure mixture and outcomes. QGC showed co-exposure to PAHs and nicotine were positively associated with cognitive impairment risk (OR: 1.66, 95% CI: 1.36-2.03, P < 0.001) and 8-OHdG (β:11.19, 95% CI: 3.90-18.48, P < 0.001). The primary contributors to cognitive impairment risk were (S)-nicotine-N-β-glucuronide (NicGluc), cotinine N-β-D-glucuronide (CotGluc) and (S)-cotinine N-oxide (CNO) and Cotinine (Cot), with no-linear dose-response relationships. However, 8-OHdG did not mediate the association between PAHs, nicotine and cognitive impairment risk.

Exposure to urinary polycyclic aromatic hydrocarbon metabolites for the effect of lung function among children and adolescents: Epidemiological study and mechanism exploration

Human are widely exposed to polycyclic aromatic hydrocarbon (PAHs), but existing evidence about exposure to urinary PAHs metabolites for pulmonary health in children and adolescents is limited. Our aim was to examine the effect of single and mixed exposure of urinary PAHs metabolites on lung function among children and adolescents. We included 1417 individuals aged 6-19 years from 3 survey cycles (2007-2008, 2009-2010, 2011-2012) of NHANES program. Multivariable linear regression model was conducted to examine the relationship between urinary PAHs metabolites and lung function index including FEV1, FVC and FEV1/FVC. BKMR and WQS model were used to evaluate the joint effects of PAHs metabolites for lung function index. Mediation analyses were performed to investigate the mediating role of inflammation related index. Hub proteins were screened by network toxicology and validated using molecular docking. Our results indicated that 3-FLU was negatively linked with FEV1 and FEV1/FVC; 1-OHP was negatively linked with FEV1; 1-PYR was negatively linked with FEV1 and FVC. In addition, 3-OHP was positively corrected with three lung function parameters. In BKMR and WQS models, PAHs metabolites co-exposure was all negatively corrected with FEV1 and FVC. Systemic inflammation response index mediated the relationship between I-PYR and FEV1 as well as FVC, with the 8 % and 6 % proportion. IL-6, STAT3, TNF, and TP53 were screened and validated as the common targets related with PAHs, inflammation and lung function by molecular docking analysis. Taken together, our findings raise the concerns about the potential hazards of environmentally relevant PAHs metabolites exposure for respiratory system in the vulnerable population and guide future research into the toxic mechanisms of PAHs metabolites-mediated lung function injury, which has important public health implications.

Maternal Exposure of SD Rats to Benzo[a]Pyrene Impairs Neurobehavior and Hippocampal Synaptic Ultrastructure in Offspring via Downregulating Synaptic-Associated Factors

Benzo[a]pyrene (B[a]P) is a carcinogenic contaminant widely present in the environment. Recently, increasing studies have paid attention to the developmental neurotoxicity of B[a]P in offspring in their early life stages; however, the underlying molecular mechanisms have not been clearly elucidated. In this study, we aimed to evaluate the effects of prenatal B[a]P exposure on neurobehavior of pups during their brain growth spurt (BGS) period and also explore the potential underlying mechanisms. Pregnant Sprague-Dawley (SD) rats were intraperitoneally exposed to 0, 10, 20, or 40 mg/kg-bw B[a]P for three consecutive days during embryonic days 17-19. The physiological development index of pups was observed, and a series of neurobehavioral tests assessing sensory and motor maturation were performed. The complexity of dendritic branches and the basal dendritic spine density of CA1 pyramidal neurons were examined using Golgi-Cox staining during PND 1-14. In addition, the mRNA and protein expression levels of hippocampal BDNF, SYP, Arc, PSD-95, DNMT1, and DNMT3a, and the level of 5-mC were detected using RT-qPCR, Western blotting, or immunohistochemical staining, respectively. We noted that prenatal B[a]P exposure induced body weight loss and neurobehavioral impairments in the early life stages. Furthermore, this study firstly revealed that maternal exposure to B[a]P impaired the dendritic arborization and complexity of pyramidal neurons in the hippocampus CA1 subfield in offspring during the early postnatal period, and the damage of B[a]P to basal dendritic spine density was also observed in a dose-dependent manner. Correspondingly, maternal exposure to B[a]P markedly reduced BDNF, Arc, SYP, and PSD-95 mRNA and protein levels in the offspring hippocampus. Meanwhile, the levels of hippocampal DNMT1, DNMT3a, and 5-mC significantly increased in the offspring prenatally exposed to B[a]P. In summary, this study firstly demonstrated that maternal B[a]P exposure induced neurobehavioral deficits by destroying the hippocampal synaptic ultrastructure, which was possibly associated with the downregulation of BDNF, Arc, SYP, and PSD95 in the hippocampus through increased DNMTs-mediated DNA methylation in offspring during the BGS period.

Air pollution: a latent key driving force of dementia

Many researchers have studied the role of air pollutants on cognitive function, changes in brain structure, and occurrence of dementia. Due to the wide range of studies and often contradictory results, the present systematic review was conducted to try and clarify the relationship between air pollutants and dementia. To identify studies for this review, a systematic search was conducted in Scopus, PubMed, and Web of Science databases (without historical restrictions) until May 22, 2023. The PECO statement was created to clarify the research question, and articles that did not meet the criteria of this statement were excluded. In this review, animal studies, laboratory studies, books, review articles, conference papers and letters to the editors were avoided. Also, studies focused on the effect of air pollutants on cellular and biochemical changes (without investigating dementia) were also excluded. A quality assessment was done according to the type of design of each article, using the checklist developed by the Joanna Briggs Institute (JBI). Finally, selected studies were reviewed and discussed in terms of Alzheimer's dementia and non-Alzheimer's dementia. We identified 14,924 articles through a systematic search in databases, and after comprehensive reviews, 53 articles were found to be eligible for inclusion in the current systematic review. The results showed that chronic exposure to higher levels of air pollutants was associated with adverse effects on cognitive abilities and the presence of dementia. Studies strongly supported the negative effects of PM2.5 and then NO2 on the brain and the development of neurodegenerative disorders in old age. Because the onset of brain structural changes due to dementia begins decades before the onset of disease symptoms, and that exposure to air pollution is considered a modifiable risk factor, taking preventive measures to reduce air pollution and introducing behavioral interventions to reduce people's exposure to pollutants is advisable.

Effect of polycyclic aromatic hydrocarbon exposure on amnestic mild cognitive impairment and Alzheimer's disease: A matched case-control study

There is an emerging body of evidence concerning the neurological effect of air pollutants on cognitive function and increased risk of neurodegeneration. Although previous studies have suggested that polycyclic aromatic hydrocarbons (PAHs) are neurotoxic, the effect of PAHs exposure on neurodegeneration remains unclear. This study aimed to investigate the association between PAH exposure and the risk of developing amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD). For this matched case-control cross-sectional study, we recruited patients aged ≥50 years diagnosed with aMCI and AD from the Samsung Medical Center, Seoul, Korea, between 2014 and 2019. For each patient, we randomly selected four cognitively healthy controls through frequency matching based on sex, age group, and education level. Urinary levels of four PAH metabolites, 1-hydroxypyrene (1-OHP), 1-hydroxyphenanthrene (1-OHPhe), 2-hydroxyfluorene (2-OHFlu), and 2-naphthol (2-NAP), were measured. A conditional logistic regression model was used to evaluate the association, adjusting for potential confounders. A total of 212 patients with aMCI with 848 matched controls, and 267 patients with AD with 1068 matched controls were included in the analyses to estimate the risk of PAH exposure. We found that elevated urinary levels of PAH metabolites (specifically, 1-OHP and 2-NAP) were significantly associated with an increased risk of aMCI and AD. An increase of one unit in log-transformed level of urinary 1-OHP was associated with a 1.15- and 1.16-times higher risk of aMCI and AD, respectively. An increase of one unit in log-transformed level of urinary 2-NAP was associated with a 1.11- and 1.13-times higher risk of aMCI and AD, respectively. These findings indicate that PAH exposure may increase the risk of aMCI and AD, especially for the elderly population. Considering the widespread distribution of PAHs in the environment, reducing PAH exposure may be an effective strategy for the prevention of neurodegenerative diseases.

Association between polycyclic aromatic hydrocarbon exposure and cognitive performance in older adults: a cross-sectional study from NHANES 2011-2014

Background: polycyclic aromatic hydrocarbons (PAHs) are classified as neurotoxins, but the relationship between exposure to PAHs and cognition in adults is unclear, and their non-linear and mixed exposure association hasn't been explored. Objective: to evaluate the non-linear and joint association between co-exposure to PAHs and multiple cognitive tests in U.S. older people. Methods: restricted cubic spline (RCS) and Bayesian kernel machine regression (BKMR) were conducted to evaluate the non-linear and mixed exposure association, based on the cross-sectional data from NHANES 2011-2014: 772 participants over 60 years old, 4 cognitive test scores, including the Immediate Recall Test (IRT), Delayed Recall Test (DRT), Animal Fluency Test (AFT), and Digit Symbol Substitution test (DSST), and 5 urinary PAH metabolites. Results: a V-shaped nonlinear relationship was found between 3-hydroxyfluorene (3-FLUO), 2-hydroxyfluorene (2-FLUO), and DRT. Negative trends between mixed PAH exposure and IRT, DRT, and DSST scores were observed. 2-FLUO contributed the most to the negative association of multiple PAHs with IRT and DRT scores and 2-hydroxynaphthalene (2-NAP) played the most important role in the decreasing relationship between mixed PAH exposure and DSST scores. Conclusion: our study suggested that PAH exposure in the U.S. elderly might be related to their poor performances in IRT, DRT and DSST. Further prospective studies are needed to validate the association.

Independent and joint associations between urinary polycyclic aromatic hydrocarbon metabolites and cognitive function in older adults in the United States

Background

Polycyclic aromatic hydrocarbons (PAHs), as organic pollutants widely present in daily environments, have been shown by existing epidemiological studies to be significantly associated with deficits in learning and memory functions in children and adults. However, the association between exposure to PAHs and cognitive function in older adults remains unclear. Additionally, existing related studies have only assessed the association between individual PAH exposures and cognitive assessments, overlooking the risks posed by mixed exposures. This study aims to use three statistical models to investigate the individual and overall effects of mixed PAH exposures on the cognition of older adults in the United States.

Methods

The study cohort was obtained from the NHANES database, which included individuals aged 60 and older from 2011 to 2014. Weighted generalized linear models (GLM), weighted quantile sum (WQS) models, and Bayesian kernel machine regression (BKMR) models were utilized to evaluate the connections between urinary PAH metabolites and the standardized Z-scores of four cognitive tests: Immediate Recall Test (IRT), Delayed Recall Test (DRT), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST).

Results

Our analysis involved 899 individuals aged 60 and above. In the fully adjusted GLM, 2-hydroxynaphthalene (2-OHNa), 3-hydroxyfluorene (3-OHFlu), and 2-hydroxyfluorene (2-OHFlu) demonstrated negative associations with DSST Z-scores. In the WQS model, six urinary PAH metabolites were negatively linked to AFT Z-scores (β (95% confidence intervals [CI]): -0.120 (-0.208, -0.033), p = 0.007) and DSST Z-scores (β (95% CI): -0.182 (-0.262, -0.103), p < 0.001). In both assessments, 2-OHNa exerted the greatest influence among the urinary PAH metabolites. In the BKMR model, there was an overall negative correlation between urinary PAH metabolites and AFT and DSST Z-scores when the concentration was within the 25th to 75th percentile, where 2-OHNa dominated the main effect of the mixture. The WQS and BKMR models were adjusted for all covariates.

Conclusion

Increased concentrations of urinary PAH metabolites are associated with cognitive decline in older adults, mainly on language ability, executive function, sustained attention, working memory, and information processing speed, with 2-OHNa playing a major effect.

miR-145a-5p/SIK1/cAMP-dependent alteration of synaptic structural plasticity drives cognitive impairment induced by coke oven emissions

Exposure to fine particulate matter (PM) is associated with the neurodegenerative diseases. Coke oven emissions (COEs) in occupational environment are important sources of PM. However, its neurotoxicity is still unclear. Therefore, evaluating the toxicological effects of COE on the nervous system is necessary. In the present study, we constructed mouse models of COE exposure by tracheal instillation. Mice exposed to COE showed signs of cognitive impairment. This was accompanied by a decrease in miR-145a-5p and an increase in SIK1 expression in the hippocampus, along with synaptic structural damage. Our results demonstrated that COE-induced miR-145a-5p downregulation could increase the expression of SIK1 and phosphorylated SIK1, inhibiting the cAMP/PKA/CREB pathway by activating PDE4D, which was associated with reduced synaptic structural plasticity. Furthermore, restoring of miR-145a-5p expression based on COE exposure in HT22 cells could partially reversed the negative effects of COE exposure through the SIK1/PDE4D/cAMP axis. Collectively, our findings link epigenetic regulation with COE-induced neurotoxicity and imply that miR-145a-5p could be an early diagnostic marker for neurological diseases in patients with COE occupational exposure.

Polycyclic aromatic hydrocarbons and changes in brain cortical thickness and an Alzheimer's disease-specific marker for cortical atrophy in adults: A longitudinal neuroimaging study of the EPINEF cohort

Although several epidemiological studies have suggested that exposure to polycyclic aromatic hydrocarbons (PAHs) may induce brain atrophy, no longitudinal study has investigated the effect of PAH exposure on brain structural changes. This study examined the longitudinal associations between urinary PAH metabolites and brain cortical thickness. We obtained urinary concentrations of PAH metabolites and brain magnetic resonance images from 327 adults (≥50 years of age) without dementia at baseline and 3-year follow-up. We obtained whole-brain and regional cortical thicknesses, as well as an Alzheimer's disease (AD)-specific marker for cortical atrophy (a higher score indicated a greater similarity to patients with AD) at baseline and follow-up. We built a linear mixed-effect model including each of urinary PAH metabolites as the time-varying exposure variable of interest. We found that increases in urinary concentrations of 1-hydroxypyrene (β = -0.004; 95% CI, -0.008 to -0.001) and 2-hydroxyfluorene (β = -0.011; 95% CI, -0.015 to -0.006) were significantly associated with a reduced whole-brain cortical thickness. A urinary concentration of 2-hydroxyfluorene was significantly associated with an increased AD-specific cortical atrophy score (β = 2.031; 95% CI, 0.512 to 3.550). The specific brain regions showing the association of urinary concentrations of 1-hydroxypyrene, 2-naphthol, 1-hydroxyphenanthrene, or 2-hydroxyfluorene with cortical thinning were the frontal, parietal, temporal, and cingulate lobes. These findings suggested that exposure to PAHs may reduce brain cortical thickness and increase the similarity to AD-specific cortical atrophy patterns in adults.