Neonatal exposure to PFOS and PFOA in mice results in changes in proteins which are important for neuronal growth and synaptogenesis in the developing brain

Prenatal Exposure to Per- and Polyfluoroalkyl Substances and ASD-Related Symptoms in Early Childhood: Mediation Role of Steroids

Previous studies regarding the associations between perfluoroalkyl and polyfluoroalkyl substances (PFAS) and autism spectrum disorder (ASD) have yielded inconsistent results, with the underlying mechanisms remaining unknown. In this study, we quantified 13 PFAS in cord serum samples from 396 neonates and followed the children at age 4 to assess ASD-related symptoms. Our findings revealed associations between certain PFAS and ASD-related symptoms, with a doubling of perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA) concentrations associated with respective increases of 1.79, 1.62, and 1.45 units in language-related symptoms and PFDA exhibiting an association with higher score of sensory stimuli. Nonlinear associations were observed in the associations of 6:2 chlorinated polyfluorinated ether sulfonate (Cl-PFAES) and 8:2 Cl-PFAES with ASD-related symptoms. Employing weighted quantile sum (WQS) regression, we observed significant mixture effects of multiple PFAS on all domains of ASD-related symptoms, with PFNA emerging as the most substantial contributor. Assuming causality, we found that 39-40% of the estimated effect of long-chain PFAS (PFUnDA and PFDoDA) exposure on sensory stimuli was mediated by androstenedione. This study provides novel epidemiological data about prenatal PFAS mixture exposure and ASD-related symptoms.

Developmental neurotoxicity of PFOA exposure on hiPSC-derived cortical neurons

PFOA is a legacy Per- and Polyfluorinated Substances (PFAS), a group of chemicals widely used in various industrial applications and consumer products. Although there has been a voluntary phase out of PFOA since 2005, it is still widely detected in various water supplies. A growing body of evidence suggests an association between PFOA exposure, particularly during developmental stages, with increased risks of neurodegenerative diseases (NDs). The neurotoxic mechanism of developmental PFOA exposure, however, remains poorly understood. Utilizing human induced-pluripotent stem cell (hiPSC)-derived cortical neurons, we investigated the effect of PFOA exposure prior to differentiation and assessed changes in neuronal characteristics, transcriptome, and neurodegeneration markers mimicking a Developmental Origin of Health and Disease (DoHAD) paradigm. Exposure to PFOA before neuron differentiation resulted in persistent alterations in nuclear morphology, neuronal network, and calcium activity. RNA sequencing analysis further revealed transcriptomic changes aligning with Alzheimer's Disease (AD) after PFOA exposure. These observations were further corroborated by alterations in tau phosphorylation markers, the presence of fibrillar tau, an increase in liquid droplets, and a decrease in RNA translational efficiency characterized using a battery of biochemical assays. Taken together, our results revealed persistent deficits of key neuronal characteristics induced by pre-differentiation PFOA exposure, suggesting impairments in several AD-related pathways that can together contribute to the elevation of AD risk after pre-differentiation PFOA exposure.

Stereoselective Bioconcentration and Neurotoxicity of Perfluoroethylcyclohexane Sulfonate in Marine Medaka

Perfluoroethylcyclohexane sulfonate (PFECHS) is an emerging per- and polyfluoroalkyl substance used to replace perfluorooctane sulfonate (PFOS), mainly in aircraft hydraulic fluids. However, previous research indicates the potential neurotoxicity of this replacement chemical. In this study, marine medaka (Oryzias melastigma) was exposed to environmentally relevant concentrations of PFECHS (concentrations: 0, 0.08, 0.26, and 0.91 μg/L) from the embryonic stage for 90 days. After exposure, the brain and eyes of the medaka were collected to investigate the bioconcentration potential of PFECHS stereoisomers and their effects on the nervous systems. The determined bioconcentration factors (BCFs) of PFECHS ranged from 324 ± 97 to 435 ± 89 L/kg and from 454 ± 60 to 576 ± 86 L/kg in the brain and eyes of medaka, respectively. The BCFs of trans-PFECHS were higher than those of cis-PFECHS. PFECHS exposure significantly altered γ-aminobutyric acid (GABA) levels in the medaka brain and disrupted the GABAergic system, as revealed by proteomics, implying that PFECHS can disturb neural signal transduction like PFOS. PFECHS exposure resulted in significant alterations in multiple proteins associated with eye function in medaka. Abnormal locomotion was observed in PFECHS-exposed medaka larvae, which was rescued by adding exogenous GABA, suggesting the involvement of disrupted GABA signaling pathways in PFECHS neurotoxicity.

Prenatal exposure to per- and polyfluoroalkyl substances and child behavioral problems

BACKGROUND

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) may adversely affect child behaviors; however, findings of epidemiologic studies are inconsistent. We examined prenatal PFAS exposure in association with child behavioral problems.

METHODS

Participants were 177 mother-child pairs from MARBLES (Markers of Autism Risk in Babies - Learning Early Signs), a cohort with elevated familial likelihood of autism spectrum disorder (ASD). We quantified nine PFAS in maternal serum (1-3 samples per mother) collected from the 1st to 3rd trimesters of pregnancy. Child behavioral problems were assessed at 3 years of age using the Child Behavior Checklist (CBCL), developed to test for various behavioral problems of children. We examined associations of the CBCL scores with individual PFAS concentrations and with their mixture using negative binomial regression and weighted quantile sum regression models.

RESULTS

Higher prenatal perfluorononanoate (PFNA) concentrations were associated with higher scores of externalizing problems [β = 0.16, 95% CI (0.01, 0.32)] and aggressive behavior [β = 0.17 (0.01, 0.32)]. Higher PFNA, perfluorooctane sulfonate (PFOS), and perfluorodecanoate (PFDA) were associated with higher scores of sleep problems [β = 0.34 (0.15, 0.54) for PFNA, β = 0.20 (0.02, 0.37) for PFOS, and β = 0.19 (0.00, 0.37) for PFDA]. No significant associations observed for typically developing children, whereas PFOS, PFNA, and PFDA were associated with several behavioral problems among children diagnosed with ASD or other neurodevelopmental concerns. Exposure to a mixture of PFAS was associated with higher scores of sleep problems and aggressive behavior, mostly contributed by PFNA and PFDA.

CONCLUSIONS

Our study showed that prenatal exposure to some PFAS could increase child behavioral problems at 3 years of age. However, our results should be interpreted with caution because we relied on data from a cohort with increased familial likelihood of ASD and thereby had more behavioral problems.

Environmental Toxins and Alzheimer's Disease: a Comprehensive Analysis of Pathogenic Mechanisms and Therapeutic Modulation

Alzheimer's disease is a leading cause of mortality worldwide. Inorganic and organic hazards, susceptibility to harmful metals, pesticides, agrochemicals, and air pollution are major environmental concerns. As merely 5% of AD cases are directly inherited indicating that these environmental factors play a major role in disease development. Long-term exposure to environmental toxins is believed to progress neuropathology, which leads to the development of AD. Numerous in-vitro and in-vivo studies have suggested the harmful impact of environmental toxins at cellular and molecular level. Common mechanisms involved in the toxicity of these environmental pollutants include oxidative stress, neuroinflammation, mitochondrial dysfunction, abnormal tau, and APP processing. Increased expression of GSK-3β, BACE-1, TNF-α, and pro-apoptotic molecules like caspases is observed upon exposure to these environmental toxins. In addition, the expression of neurotrophins like BDNF and GAP-43 have been found to be reduced as a result of toxicity. Further, modulation of signaling pathways involving PARP-1, PGC-1α, and MAPK/ERK induced by toxins have been reported to contribute in AD pathogenesis. These pathways are a promising target for developing novel AD therapeutics. Drugs like epigallocatechin-gallate, neflamapimod, salsalate, dexmedetomidine, and atabecestat are in different phases of clinical trials targeting the pathways for possible treatment of AD. This review aims to culminate the correlation between environmental toxicants and AD development. We emphasized upon the signaling pathways involved in the progression of the disease and the therapeutics under clinical trial targeting the altered pathways for possible treatment of AD.

Perfluorooctanoate and nano titanium dioxide impair the byssus performance of the mussel Mytilus coruscus

Perfluorooctanoate (PFOA) is widely used as a surfactant and has metabolic, immunologic, developmental, and genetic toxicity on marine organisms. However, the effects of PFOA on individual defense functions in mussels in the presence of titanium dioxide nanoparticles (nano-TiO2) are poorly understood. To investigate the defense strategies and regulatory mechanisms of mussels under combined stressors, the thick-shell mussels Mytilus coruscus were exposed to different PFOA concentrations (0, 2 and 200 μg/L) and nano-TiO2 (0 and 0.1 mg /L, size: 25 nm) for 14 days. The results showed that, compared to the control group, PFOA and nano-TiO2 significantly reduced the number of byssal threads (NBT), byssal threads length (BTL), diameter of proximal threads (DPB), diameter of middle threads (DMB), diameter of distal byssal threads (DDB), adhesive plaque area (BPA), and breaking force of byssal threads (N). Under the influence of PFOA and nano-TiO2, the morphological surface smoothness of the fractured byssal threads surface increased, concurrently inducing an increased surface roughness in the adhesive plaques. Additionally, under the presence of PFOA and nano-TiO2, the foot displayed dispersed tissue organization and damaged villi, accompanied by an increased incidence of cellular apoptosis and an upregulation of the apoptosis gene caspase-8. Expression of the adhesion gene mfp-3 and byssal threads strength genes (preCOL-D, preCOL-NG) was upregulated. An interactive effect on the performance of byssal threads is observed under the combined influence of PFOA and nano-TiO2. Under co-exposure to PFOA and nano-TiO2, the performance of the byssal threads deteriorates, the foot structure is impaired, and the genes mRNA expression of byssal thread secretory proteins have compensated for the adhesion and byssal threads strength by up-regulation. Within marine ecosystems, organic and particulate contaminants exert a pronounced effect on the essential life processes of individual organisms, thereby jeopardizing their ecological niche within community assemblages and perturbing the dynamic equilibrium of the overarching ecosystem. ENVIRONMENTAL IMPLICATION: Perfluorooctanoic acid (PFOA) is prone to accumulate in marine organisms. TiO2 nanoparticles (nano-TiO2) are emerging environmental pollutants frequently found in marine environment. The effects of PFOA and nano-TiO2 on marine mussels are not well understood, and their toxic mechanisms remain largely unknown. We investigated the impacts of PFOA and nano-TiO2 on mussel byssus defense mechanisms. By assessing byssus performance indicators, morphological structures of the byssus, subcellular localization, and changes in byssal secretion-related genes, we revealed the combined effects and mechanisms through which these two types of pollutants may affect the functional capabilities and survival of mussels in the complex marine ecosystem.

PFOS Elicits Cytotoxicity in Neuron Through Astrocyte-Derived CaMKII-DLG1 Signaling In Vitro Rat Hippocampal Model

Both epidemiological investigation and animal experiments demonstrated that pre-/postnatal exposure to perfluorooctane sulfonic acid (PFOS) could induce neurodevelopmental disorders. Previous studies showed that astrocyte was involved in PFOS-induced neurotoxicity, while little information is available. In the present study, the role of astrocyte-derived calmodulin-dependent protein kinase II (CaMKII)-phosphorylated discs large homolog 1 (DLG1) signaling in PFOS eliciting cytotoxicity in neuron was explored with primary cultured hippocampal astrocyte and neuron. The application of PFOS showed a decreased cell viability, synapse length and glutamate transporter 1 (GLT-1) expression, but an increased CaMKII, DLG1 and cyclic AMP response element binding protein (CREB) expression in primary cultured astrocyte. With 2-(2-hydroxyethylamino)-6-aminohexylcarbamic acid tert-butyl ester-9-isopropylpurine (CK59), the CaMKII inhibitor, the disturbed cell viability and molecules induced by PFOS could be alleviated (CREB expression was excluded) in astrocytes. The cytotoxic effect of neuron exposed to astrocyte conditional medium collected from PFOS (PFOS-ACM) pretreated with CK59 was also decreased. These results indicated that PFOS mediated GLT-1 expression through astrocyte-derived CaMKII-DLG signaling, which might be associated with injuries on neurons. The present study gave an insight in further exploration of mechanism in PFOS-induced neurotoxicity.

Carbon-chain length determines the binding affinity and inhibitory strength of per- and polyfluoroalkyl substances on human and rat steroid 5α-reductase 1 activity

Per- and polyfluoroalkyl substances (PFAS) are widely used synthetic chemicals that persist in the environment and bioaccumulate in animals and humans. There is growing evidence that PFAS exposure adversely impacts neurodevelopment and neurological health. Steroid 5α-reductase 1 (SRD5A1) plays a key role in neurosteroidogenesis by catalyzing the conversion of testosterone or pregnenolone to neuroactive steroids, which influence neural development, cognition, mood, and behavior. This study investigated the inhibitory strength and binding interactions of 18 PFAS on human and rat SRD5A1 activity using enzyme assays, molecular docking, and structure-activity relationship analysis. Results revealed that C9-C14 PFAS carboxylic acid at 100 μM significantly inhibited human SRD5A1, with IC50 values ranged from 10.99 μM (C11) to 105.01 μM (C14), and only one PFAS sulfonic acid (C8S) significantly inhibited human SRD5A1 activity, with IC50 value of 8.15 μM. For rat SRD5A1, C9-C14 PFAS inhibited rat SRD5A1, showing the similar trend, depending on carbon number of the carbon chain. PFAS inhibit human and rat SRD5A1 in a carbon chain length-dependent manner, with optimal inhibition around C11. Kinetic studies indicated PFAS acted through mixed inhibition. Molecular docking revealed PFAS bind to the domain between NADPH and testosterone binding site of both SRD5A1 enzymes. Inhibitory potency correlated with physicochemical properties like carbon number of the carbon chain. These findings suggest PFAS may disrupt neurosteroid synthesis and provide insight into structure-based inhibition of SRD5A1.

Time-course transcriptome analysis discloses PFDMO2OA (C8 HFPO-TA)-induced developmental malformations and cardiovascular toxicities in zebrafish

PFDMO2OA (C8 HFPO-TA), a novel substitute for perfluorooctanoic acid (PFOA), has been frequently detected in surface waters. However, information on its toxicity remains scarce. In the present study, zebrafish embryos were exposed to varying concentrations of PFDMO2OA, ranging from 80 to 800 mg/L, until 120 h post-fertilization (hpf) to explore its potential developmental toxicities. The LC50 value for mortality was 505.9 mg/L, comparable to that of PFOA (over 500 mg/L), suggesting a lack of safety of PFDMO2OA compared to PFOA. At 120 hpf, PFDMO2OA exposure led to various malformations in embryos, including uninflated swim bladder, yolk sac oedema, spinal deformation, and pigmentation changes, with pericardial oedema being prominent. Analysis using O-dianisidine stain indicated a decline in erythrocytes over time. Transcriptome analysis further revealed the cardiovascular toxicity caused by PFDMO2OA at the molecular level. Time-course differential analysis pointed to the apoptosis dependent on disrupted mitochondrial function as a significant contributor to erythrocyte disappearance, as confirmed by the TUNEL stain. Therefore, the present findings suggest that PFDMO2OA induces developmental malformations and cardiovascular toxicities in zebrafish embryos, demonstrating a toxic potency comparable to that of PFOA. The results further highlight the significance of evaluating the health risks associated with PFDMO2OA.

Per- and Polyfluoroalkyl Substances in Food Packaging: Migration, Toxicity, and Management Strategies

PFASs are linked to serious health and environmental concerns. Among their widespread applications, PFASs are known to be used in food packaging and directly contribute to human exposure. However, information about PFASs in food packaging is scattered. Therefore, we systematically map the evidence on PFASs detected in migrates and extracts of food contact materials and provide an overview of available hazard and biomonitoring data. Based on the FCCmigex database, 68 PFASs have been identified in various food contact materials, including paper, plastic, and coated metal, by targeted and untargeted analyses. 87% of these PFASs belong to the perfluorocarboxylic acids and fluorotelomer-based compounds. Trends in chain length demonstrate that long-chain perfluoroalkyl acids continue to be found, despite years of global efforts to reduce the use of these substances. We utilized ToxPi to illustrate that hazard data are available for only 57% of the PFASs that have been detected in food packaging. For those PFASs for which toxicity testing has been performed, many adverse outcomes have been reported. The data and knowledge gaps presented here support international proposals to restrict PFASs as a group, including their use in food contact materials, to protect human and environmental health.

Early life poly- and perfluoroalkyl substance levels and adiposity in the first 2 years of life

IMPORTANCE

Poly- and perfluoroalkyl substances (PFASs) are nondegradable, man-made chemicals. They accumulate in humans with potential harmful effects, especially in susceptible periods of human development, such as the first months of life. We found that, in our cohort, exclusively breastfed (EBF) infants had 3 times higher PFAS plasma levels compared with exclusively formula-fed (EFF) infants at the age of 3 months. Thus, PFASs could potentially reduce the health benefits of breastfeeding.

OBJECTIVE

We investigated the associations between PFAS levels at the age of 3 months and accelerated gain in fat mass during the first 6 months of life, body composition at 2 years, and whether these associations differ between EBF and EFF infants.

SETTING

In 372 healthy term-born infants, we longitudinally assessed anthropometrics, body composition (by air-displacement plethysmography and dual-energy X-ray absorptiometry), and visceral and subcutaneous fat (by abdominal ultrasound) until the age of 2 years.

MEASURES

The plasma levels of 5 individual PFASs were determined by liquid chromatography-electrospray ionization-tandem mass spectrometry at the age of 3 months.

MAIN OUTCOMES

We studied associations between PFAS levels and outcomes using multiple regression analyses.

RESULTS

Higher early life plasma perfluorooctanoic acid and total PFAS levels were associated with an accelerated gain in fat mass percentage [FM%; >0.67 SD score (SDS)] during the first 6 months of life. Higher early life PFAS levels were associated with lower fat-free mass (FFM) SDS at the age of 2 years, but not with total FM% SDS at 2 years. Furthermore, we found opposite effects of PFAS levels (negative) and exclusive breastfeeding (positive) at the age of 3 months on FFM SDS at 2 years.

CONCLUSION

Higher PFAS levels in early life are associated with accelerated gains in FM% during the first 6 months of life and with lower FFM SDS at the age of 2 years, which have been associated with an unfavorable body composition and metabolic profile later in life. Our findings warrant further research with longer follow-up times.

Effect modification by maternal vitamin D status in the association between prenatal exposure to per- and polyfluoroalkyl substances and neurodevelopment in 2-year-old children

BACKGROUND

Pregnant women in the Shanghai Birth Cohort (SBC) of China faced dual threats of per- and polyfluoroalkyl substances (PFAS) exposure and vitamin D (VD) insufficiency, potentially impacting offspring neurodevelopment. However, little is known about whether maternal VD status modifies PFAS-related neurodevelopment effect.

OBJECTIVES

To explore the modifying role of maternal VD status in the effect of prenatal PFAS exposure on childhood neurodevelopment.

METHODS

We included 746 mother-child pairs from the SBC. Ten PFAS congeners and VD levels were measured in maternal blood samples collected during the first and second trimester respectively. At 2 years of age, toddlers underwent neurodevelopment assessments using Bayley-III Scales. Multivariate linear, logistic regression, and weighted quantile sum approach were used to estimate associations of Bayley-III scores with individual and mixture PFAS. We stratified participants into VD sufficient and insufficient groups and further balanced PFAS differences between these groups by matching all PFAS levels. We fitted the same statistical models in each VD group before and after matching.

RESULTS

Nearly half (46.5 %) of pregnant women were VD insufficient (<30 ng/mL). In the overall population, PFAS exposure was associated with lower language scores and an increased risk for neurodevelopmental delay, but higher cognitive scores. However, adverse associations with PFAS were mainly observed in the VD sufficient group, while the VD insufficient group showed positive cognitive score associations. Higher PFAS concentrations were found in the VD sufficient group compared to the VD insufficient group. Post-matching, adverse associations in the VD sufficient group were nullified, whereas in the VD insufficient group, positive associations disappeared and adverse associations becoming more pronounced.

CONCLUSION

In this Chinese birth cohort, high prenatal PFAS exposure and low maternal VD levels collectively heighten the risk of adverse childhood neurodevelopment. However, disentangling PFAS and VD interrelationships is crucial to avoid paradoxical findings.

Perinatal exposure to PFOS and sustained high-fat diet promote neurodevelopmental disorders via genomic reprogramming of pathways associated with neuromotor development

Perfluorooctanesulfonic acid (PFOS) is a neurotoxic widespread organic contaminant which affects several brain functions including memory, motor coordination and social activity. PFOS has the ability to traverse the placenta and the blood brain barrier (BBB) and cause weight gain in female mice. It's also known that obesity and consumption of a high fat diet have negative effects on the brain, impairs cognition and increases the risk for the development of dementia. The combination effect of developmental exposure to PFOS and the intake of a high-fat diet (HFD) has not been explored. This study investigates the effect of PFOS and /or HFD on weight gain, behavior and transcriptomic and proteomic analysis of adult brain mice. We found that female mice exposed to PFOS alone showed an increase in weight, while HFD expectedly increased body weight. The combination of HFD and PFOS exacerbated generalized behavior such as time spent in the center and rearing, while PFOS alone impacted the distance travelled. These results suggest that PFOS exposure may promote hyperactivity. The combination of PFOS and HFD alter social behavior such as rearing and withdrawal. Although HFD interfered with memory retrieval, biomarkers of dementia did not change except for total Tau and phosphorylated Tau. Tau was impacted by either or both PFOS exposure and HFD. Consistent with behavioral observations, global cerebral transcriptomic analysis showed that PFOS exposure affects calcium signaling, MAPK pathways, ion transmembrane transport, and developmental processes. The combination of HFD with PFOS enhances the effect of PFOS in the brain and affects pathways related to ER stress, axon guidance and extension, and neural migration. Proteomic analysis showed that HFD enhances the impact of PFOS on inflammatory pathways, regulation of cell migration and proliferation, and MAPK signaling pathways. Overall, these data show that PFOS combined with HFD may reprogram the genome and modulate neuromotor development and may promote symptoms linked to attention deficit-hyperactivity disorders (ADHD) and autism spectrum disorders (ASD). Future work will be needed to confirm these connections.

Differential regulations of neural activity and survival in primary cortical neurons by PFOA or PFHpA

Perfluorinated compounds (PFCs), organofluoride compounds comprising carbon-fluorine and carbon-carbon bonds, are used as water and oil repellents in textiles and pharmaceutical tablets; however, they are associated with potential neurotoxic effects. Moreover, the impact of PFCs on neuronal survival, activity, and regulation within the brain remains unclear. Additionally, the mechanisms through which PFCs induce neuronal toxicity are not well-understood because of the paucity of data. This study elucidates that perfluorooctanoic acid (PFOA) and perfluoroheptanoic acid (PFHpA) exert differential effects on the survival and activity of primary cortical neurons. Although PFOA triggers apoptosis in cortical neurons, PFHpA does not exhibit this effect. Instead, PFHpA modifies dendritic spine morphogenesis and synapse formation in primary cortical neuronal cultures, additionally enhancing neural activity and synaptic transmission. This research uncovers a novel mechanism through which PFCs (PFHpA and PFOA) cause distinct alterations in dendritic spine morphogenesis and synaptic activity, shedding light on the molecular basis for the atypical behaviors noted following PFC exposure. Understanding the distinct effects of PFHpA and PFOA could guide regulatory policies on PFC usage and inform clinical approaches to mitigate their neurotoxic effects, especially in vulnerable population.

Association of prenatal exposure to perfluorinated and polyfluoroalkyl substances with childhood neurodevelopment: A systematic review and meta-analysis

BACKGROUND

Although previous studies have shown an association between prenatal exposure to perfluorinated and polyfluoroalkyl substances (PFAS) and neurodevelopmental disorders in children, the results have been inconsistent. We summarize studies on the association between prenatal PFAS exposure and neurodevelopment in children in order to better understand the relationship.

OBJECTIVE

We conducted a meta-analysis of prenatal PFAS exposure and developmental outcomes associated with intellectual, executive function and behavioral difficulty in children to explore the relationship between prenatal exposure to perfluorinated and polyfluoroalkyl substances (PFAS) and neurodevelopmental disorders in children.

METHODS

We searched for articles published up to August 3, 2023, included and quantified original studies on PFAS and child Intelligence Quotient (IQ), executive function and behavioral difficulty during pregnancy, and systematically summarized articles that could not be quantified.

CONCLUSION

There is evidence of sex-specific relationship between PFAS exposure and children's PIQ. We found that PFOS [β = -1.56, 95% CI = -2.96, - 0.07; exposure = per 1 ln (ng/ml) increase], PFOA [β = -1.87, 95% CI = -3.29, - 0.46; exposure = per 1 ln (ng/ml) increase], PFHxS [β = -2.02, 95% CI = -3.23, - 0.81; exposure = per 1 ln (ng/ml) increase] decreased performance IQ in boys, but PFOS [β = 1.56, 95% CI = 0.06, 3.06; exposure = per 1 ln (ng/ml) increase] increased performance IQ in girls. PFAS are associated with executive function impairments in children, but not related to behavioral difficulty in children.

Gestational GenX and PFOA exposures induce hepatotoxicity, metabolic pathway, and microbiome shifts in weanling mice

Ammonium perfluoro (2-methyl-3-oxahexanoate) (GenX), a replacement for perfluorooctanoic acid (PFOA), has been detected in multiple environmental media and biological samples worldwide. Accumulated evidence implies that GenX exposure might exert adverse health effects, although the underlying mechanisms have not been fully revealed. In this study, pregnant BALB/c mice were exposed to GenX (2 mg/kg/day), PFOA (1 mg/kg/day), or Milli-Q water by gavage from the first day of gestation (GD0) until GD21. Necropsy and tissue collection were conducted in pups at 4 weeks of age. PFOA and GenX induced similar histopathological changes in both the liver and the intestinal mucosa, accompanied by higher serum levels of alanine and aspartate aminotransferase. Moreover, the capacity of hepatic glycogen storage and intestinal mucus secretion were significantly decreased, suggesting dysfunction of liver metabolism and the intestinal mucosal barrier. A total of 637 and 352 differentially expressed genes (DEGs) were identified in the liver tissues of GenX and PFOA group, respectively. Most of the enriched pathways from the DEGs by KEGG enrichment analysis were metabolism-associated. Moreover, overexpression of CYP4A14, Sult2a1, Cpt1b, Acaa1b, Igfbp1, Irs-2 and decreased expression of Gys2 were observed in livers of GenX exposed pups, supporting the hypothesis that there was metabolic disruption. Furthermore, DNA damage and cell cycle arrest proteins (Gadd45β, p21, Ppard) were significantly increased, while cell proliferation-related proteins (Cyclin E, Myc, EGFR) were decreased by gestational GenX exposure in the pups' liver. In addition, imbalance of gut microbiota and dysfunction of the intestinal mucosa barrier might contribute to hepatotoxicity at least in part. Taken together, our results suggested that gestational GenX exposure triggered metabolic disorder, which might be responsible for the hepatotoxicity in the pups in addition to dysfunction of the intestinal mucosa barrier. This study enriches the mechanisms of GenX-induced developmental hepatotoxicity by associating metabolic disorder with intestinal homeostasis.

Prenatal exposure to per-and polyfluoroalkyl substances and child executive function: Evidence from the Shanghai birth cohort study

BACKGROUND

Per-and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment and accumulate in humans. Toxicological studies have indicated the potential neurotoxicity of PFAS during the fetal development. However, in epidemiological studies, the association between prenatal exposure to PFAS and executive function in offspring remains unclear.

OBJECTIVES

To investigate the association between prenatal exposure to PFAS and executive function in offspring.

METHOD

This study included 1765 mother-child pairs in the Shanghai Birth Cohort, a prospective birth cohort enrolled during 2013-2016. The levels of 10 PFAS were measured in maternal plasma samples collected during early gestation. Child executive function was assessed at 4 years of age using the parent-reported Behavior Rating Inventory of Executive Function-Preschool version (BRIEF-P), which provided 4 composite measures: Inhibitory Self-Control Index, Flexibility Index, Emergent Metacognition Index, and Global Executive Composite. We used multivariable linear regression to examine the associations between individual PFAS and BRIEF-P scores. Bayesian kernel machine regression (BKMR) was employed to evaluate the joint effects. We also investigated whether these associations were modified by sex.

RESULT

We found no significant associations between prenatal PFAS exposure and BRIEF-P scores when the child was 4 years old. BKMR analysis showed no joint effect of the PFAS mixture on child executive function. RCS analysis indicated that the majority of relationships between PFAS and BRIEF-P did not deviate from the linear relationship, even though there was a nonlinear association between PFUA and EMI. Additionally, the associations were not modified by sex.

CONCLUSION

Overall, our findings showed that there were no associations between prenatal exposure to PFAS and child executive function at 4 years of age.

Identification of the mechanisms underlying per- and polyfluoroalkyl substance-induced hippocampal neurotoxicity as determined by network pharmacology and molecular docking analyses

Background

Per- and polyfluoroalkyl substances (PFASs) are a class of environmental contaminants that pose significant health risks to both animals and humans. Although the hippocampal neurotoxic effects of numerous PFASs have been reported, the underlying mechanisms of combined exposure to PFASs-induced hippocampal neurotoxicity remain unclear.

Methods

In this study, network pharmacology analysis was performed to identify the intersectional targets of PFASs for possible associations with hippocampal neurotoxicity. The evaluation of the influence of PFASs on intersectional targets was assessed using a weighted method. Additionally, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the screened targets were performed, the intersected hub targets calculated by various algorithms were screened in the network and molecular docking was also used to analyze binding activities.

Results

Our results indicated that eight PFASs, which acted on key targets (MYC, ESR1, STAT3, RELA, MAPK3) impacted the NF-κB signaling pathway, STAT3 signaling pathway, and MAPK signaling pathways to exert neurotoxicity in the hippocampus. The molecular docking results revealed that PFASs have strong binding potential to the hub targets.

Conclusions

Our findings provided a basis for future studies to investigate the detailed mechanisms of PFASs-induced hippocampal neurotoxicity and to develop preventative and control strategies.

Association between prenatal exposure to per- and polyfluoroalkyl substances and neurodevelopment in children: Evidence based on birth cohort

BACKGROUND

Although numerous studies have examined the effect of prenatal per- and polyfluoroalkyl substances (PFAS) exposure on neurodevelopment in children, findings have been inconsistent.

OBJECTIVE

To better understand the effects of PFAS exposure during pregnancy on offspring neurodevelopment, we conducted a systematic review of prenatal exposure to different types of PFAS and neurodevelopment in children.

METHODS

A comprehensive search was conducted in the PubMed, Web of Science, and EMBASE electronic databases up to March 2023. Only birth cohort studies that report a specific association between PFAS exposure during pregnancy and neurodevelopment were included in this review.

RESULTS

31 birth cohort studies that met the inclusion criteria were qualitatively integrated. Among these, 14 studies investigated the impact of PFAS exposure during pregnancy on cognition, 13 on neurobehavior, and 4 on both cognition and neurobehavior. Additionally, 4 studies explored the influence of PFAS on children's comprehensive development.

CONCLUSION

Prenatal PFAS exposure was associated with poor neurodevelopment in children, including psychomotor development, externalizing behavior, and comprehensive development. However, conclusive evidence regarding its effects on other neurological outcomes remains limited. In addition, sex-specific effects on social behavior and sleep problems were identified.

Evaluation of Neural Regulation and Microglial Responses to Brain Injury in Larval Zebrafish Exposed to Perfluorooctane Sulfonate

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are biopersistent, global pollutants. Although some in vitro and epidemiological studies have explored the neurotoxic potential of perfluorooctane sulfonate (PFOS), a prevalent PFAS congener, it is unknown how developmental PFOS exposure affects neuronal signaling, microglia development, and microglial-neuron communication.

OBJECTIVES

We sought to determine the extent to which PFOS exposure disrupts brain health, neuronal activity, and microglia-neuron communication during development. In addition, although PFOS impairs humoral immunity, its impact on innate immune cells, including resident microglia, is unclear. As such, we investigated whether microglia are cellular targets of PFOS, and, if so, whether disrupted microglial development or function could contribute to or is influenced by PFOS-induced neural dysfunction.

METHODS

Zebrafish were chronically exposed to either a control solution [0.1% dimethyl sulfoxide (DMSO)], 7 μ M PFOS, 14 μ M PFOS, 28 μ M PFOS, or 64 μ M perfluorooctanoic acid (PFOA). We used in vivo imaging and gene expression analysis to assess microglial populations in the developing brain and to determine shifts in the microglia state. We functionally challenged microglia state using a brain injury model and, to assess the neuronal signaling environment, performed functional neuroimaging experiments using the photoconvertible calcium indicator calcium-modulated photoactivatable ratiometric integrator (CaMPARI). These studies were paired with optogenetic manipulations of neurons and microglia, an untargeted metabolome-wide association study (MWAS), and behavioral assays.

RESULTS

Developmental PFOS exposure resulted in a shift away from the homeostatic microglia state, as determined by functional and morphological differences in exposed larvae, as well as up-regulation of the microglia activation gene p2ry12. PFOS-induced effects on microglia state exacerbated microglia responses to brain injury in the absence of increased cell death or inflammation. PFOS exposure also heightened neural activity, and optogenetic silencing of neurons or microglia independently was sufficient to normalize microglial responses to injury. An untargeted MWAS of larval brains revealed PFOS-exposed larvae had neurochemical signatures of excitatory-inhibitory imbalance. Behaviorally, PFOS-exposed larvae also exhibited anxiety-like thigmotaxis. To test whether the neuronal and microglial phenotypes were specific to PFOS, we exposed embryos to PFOA, a known immunotoxic PFAS. PFOA did not alter thigmotaxis, neuronal activity, or microglial responses, further supporting a role for neuronal activity as a critical modifier of microglial function following PFOS exposure.

DISCUSSION

Together, this study provides, to our knowledge, the first detailed account of the effects of PFOS exposure on neural cell types in the developing brain in vivo and adds neuronal hyperactivity as an important end point to assess when studying the impact of toxicant exposures on microglia function. https://doi.org/10.1289/EHP12861.

Association Between Prenatal and Early Postnatal Exposure to Perfluoroalkyl Substances and IQ Score in 7-Year-Old Children From the Odense Child Cohort

Perfluoroalkyl substances (PFAS) are persistent chemicals capable of crossing the placenta and passing into breast milk. Evidence suggests that PFAS exposure may affect brain development. We investigated whether prenatal or early postnatal PFAS exposure was associated with intelligence quotient (IQ) scores in schoolchildren from the Odense Child Cohort (Denmark, 2010-2020). We assessed concentrations of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) in maternal serum collected during the first trimester of pregnancy and in child serum at age 18 months. At 7 years of age, children completed an abbreviated version of the Wechsler Intelligence Scale for Children, Fifth Edition, from which Full Scale Intelligence Quotient (FSIQ) and Verbal Comprehension Index scores were estimated. In multiple linear regression analyses conducted among 967 mother-child pairs, a doubling in maternal PFOS and PFNA concentrations was associated with a lower FSIQ score, while no significant associations were observed for PFOA, PFHxS, or PFDA. PFAS concentrations at age 18 months and duration of breastfeeding were strongly correlated, and even in structural equation models it was not possible to differentiate between the opposite effects of PFAS exposure and duration of breastfeeding on FSIQ. PFAS exposure is ubiquitous; therefore, an association with even a small reduction in IQ is of public health concern.

Behavioral outcomes and exposure to perfluoroalkyl substances among children aged 6-13 years: The TEDDY child study

BACKGROUND

Although some studies report that exposure to per- and polyfluoroalkyl substances (PFAS) during pregnancy and early life stages of a child could adversely impact neurodevelopment, literature shows mixed evidence.

OBJECTIVES

Using an ecological framework for human development, we assessed the association of risk factors for environmental PFAS exposure and childhood PFAS concentrations with behavioral difficulties among school-age children exposed to PFAS from birth, while also controlling for the important influence of the parenting and familial environment.

METHODS

The study participants included 331 school-age children (6-13 years) born in a PFAS-contaminated area in the Veneto Region (Italy). We study the associations between environmental risk factors of maternal PFAS exposure (residential time, consumption of tap water, residence in Red zone A or B), and breastfeeding duration with parent assessments of children's behavioral problems (using the Strengths and Difficulties Questionnaire [SDQ]), adjusting for socio-demographic, parenting and familial variables. The direct relationships between serum blood PFAS concentrations and SDQ scores was evaluated in a subset of children (n = 79), both with single PFAS and weighted quantile sum (WQS) regressions.

RESULTS

Poisson regression models reported positive associations between high consumption of tap water and externalizing SDQ scores (Incidence Rate Ratio [IRR]: 1.18; 95% confidence interval [CI]: 1.04-1.32) and total difficulty scores (IRR: 1.14; 95% CI: 1.02-1.26). Childhood perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) were associated with higher internalizing SDQ scores (4th vs. 1st quartile, PFOS IRR: 1.54, 95% CI: 1.06-2.25), externalizing scores (4th vs. 1st quartile, PFHxS IRR: 1.59, 95% CI: 1.09-2.32), and total difficulty scores (4th vs. 1st quartile, PFOS IRR: 1.37, 95% CI: 1.05-1.71; PFHxS IRR: 1.54, 95% CI: 1.09-1.90). The WQS regressions confirmed the associations reported by single-PFAS analyses.

CONCLUSIONS

We observed cross-sectional associations of tap water consumption and childhood PFOS, and PFHxS concentrations with greater behavioral difficulties.

Effects of Perfluorooctane Sulfonate on Cerebellar Cells via Inhibition of Type 2 Iodothyronine Deiodinase Activity

Perfluorooctane sulfonate (PFOS) has been used in a wide variety of industrial and commercial products. The adverse effects of PFOS on the developing brain are becoming of a great concern. However, the molecular mechanisms of PFOS on brain development have not yet been clarified. We investigated the effect of early-life exposure to PFOS on brain development and the mechanism involved. We investigated the change in thyroid hormone (TH)-induced dendrite arborization of Purkinje cells in the primary culture of newborn rat cerebellum. We further examined the mechanism of PFOS on TH signaling by reporter gene assay, quantitative RT-PCR, and type 2 iodothyronine deiodinase (D2) assay. As low as 10-7 M PFOS suppressed thyroxine (T4)-, but not triiodothyronine (T3)-induced dendrite arborization of Purkinje cells. Reporter gene assay showed that PFOS did not affect TRα1- and TRβ1-mediated transcription in CV-1 cells. RT-PCR showed that PFOS suppressed D2 mRNA expression in the absence of T4 in primary cerebellar cells. D2 activity was also suppressed by PFOS in C6 glioma-derived cells. These results indicate that early-life exposure of PFOS disrupts TH-mediated cerebellar development possibly through the disruption of D2 activity and/or mRNA expression, which may cause cerebellar dysfunction.

Neurodegenerative Proteinopathies Induced by Environmental Pollutants: Heat Shock Proteins and Proteasome as Promising Therapeutic Tools

Environmental pollutants' (EPs) amount and diversity have increased in recent years due to anthropogenic activity. Several neurodegenerative diseases (NDs) are theorized to be related to EPs, as their incidence has increased in a similar way to human EPs exposure and they reproduce the main ND hallmarks. EPs induce several neurotoxic effects, including accumulation and gradual deposition of misfolded toxic proteins, producing neuronal malfunction and cell death. Cells possess different mechanisms to eliminate these toxic proteins, including heat shock proteins (HSPs) and the proteasome system. The accumulation and deleterious effects of toxic proteins are induced through HSPs and disruption of proteasome proteins' homeostatic function by exposure to EPs. A therapeutic approach has been proposed to reduce accumulation of toxic proteins through treatment with recombinant HSPs/proteasome or the use of compounds that increase their expression or activity. Our aim is to review the current literature on NDs related to EP exposure and their relationship with the disruption of the proteasome system and HSPs, as well as to discuss the toxic effects of dysfunction of HSPs and proteasome and the contradictory effects described in the literature. Lastly, we cover the therapeutic use of developed drugs and recombinant proteasome/HSPs to eliminate toxic proteins and prevent/treat EP-induced neurodegeneration.

Prenatal exposure to legacy PFAS and neurodevelopment in preschool-aged Canadian children: The MIREC cohort

BACKGROUND

Exposure to perfluoroalkyl substances (PFAS) has been shown to be neurotoxic in experimental studies, but epidemiological evidence linking prenatal PFAS exposure to child neurodevelopment is equivocal and scarce.

OBJECTIVE

To quantify associations between prenatal exposure to legacy PFAS and children's intelligence (IQ) and executive functioning (EF) in a Canadian pregnancy and birth cohort and to determine if these associations differ by child sex.

METHODS

We measured first-trimester plasma concentrations of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorohexanesulfonic acid (PFHxS) in the Maternal-Infant Research on Environmental Chemicals (MIREC) study and assessed children's full-scale (n = 522), performance (n = 517), and verbal (n = 519) IQ using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III). Children's working memory (n = 513) and ability to plan and organize (n = 514) were assessed using a parent-reported questionnaire, the Behavior Rating Inventory of Executive Function - Preschool Version (BRIEF-P). We quantified associations between individual log2-transformed PFAS exposure and children's IQ and EF using multiple linear regression analyses and evaluated effect modification by child sex. We also used Repeated Holdout Weighted Quantile Sum (WQS) regression models with effect modification by child sex to quantify the effect of combined exposure to all three PFAS chemicals on IQ and EF. All models were adjusted for key sociodemographic characteristics.

RESULTS

Geometric mean plasma concentrations (IQR) for PFOA, PFOS and PFHxS were 1.68 (1.10-2.50), 4.97 (3.20-6.20) and 1.09 (0.67-1.60) μg/L respectively. We found evidence of effect modification by child sex in all models examining performance IQ (p < .01). Specifically, every doubling of PFOA, PFOS, and or PFHxS was inversely associated with performance IQ, but only in males (PFOA: B = -2.80, 95% CI: -4.92, -0.68; PFOS: B = -2.64, 95% CI: -4.77, -0.52; PFHxS: B = -2.92, 95% CI: -4.72, -1.12). Similarly, every quartile increase in the WQS index was associated with poorer performance IQ in males (B = -3.16, 95% CI: -4.90, -1.43), with PFHxS contributing the largest weight to the index. In contrast, no significant association was found for females (B = 0.63, 95% CI: -0.99, 2.26). No significant associations were found for EF in either males or females.

CONCLUSIONS

Higher prenatal PFAS exposure was associated with lower performance IQ in males, suggesting that this association may be sex- and domain-specific.

Associations of prenatal exposure to per- and polyfluoroalkyl substances (PFAS) with measures of cognition in 7.5-month-old infants: An exploratory study

BACKGROUND

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) has been linked to a wide array of adverse maternal and child health outcomes. However, studies examining PFAS in relation to offspring cognition have been inconclusive.

OBJECTIVE

We examined whether prenatal exposure to a mixture of PFAS was related to cognition in 7.5-month-old infants.

METHODS

Our analytic sample included participants enrolled in the Chemicals in Our Bodies (CIOB) and Illinois Kids Development Study (IKIDS) cohorts (N = 163). Seven PFAS were measured in 2nd trimester maternal serum samples and were detected in >65% of participants. Infant cognition was measured with a visual recognition memory task using an infrared eye tracker when infants were 7.5 months old. This task included familiarization trials where each infant was shown two identical faces and test trials where each infant was shown the familiar face paired with a novel face. In familiarization, we assessed average run duration (time looking at familiarization stimuli before looking away) as a measure of information processing speed, in addition to time to familiarization (time to reach 20 s of looking at stimuli) and shift rate (the number of times infants looked between stimuli), both as measures of attention. In test trials, we assessed novelty preference (proportion of time looking to the novel face) to measure recognition memory. Linear regression was used to estimate associations of individual PFAS with cognitive outcomes, while Bayesian kernel machine regression (BKMR) was used to estimate mixture effects.

RESULTS

In adjusted single-PFAS linear regression models, an interquartile range increase in PFNA, PFOA, PFOS, PFHxS, PFDeA, and PFUdA was associated with an increase in shift rate, reflecting better visual attention. Using BKMR, increasing quartiles of the PFAS mixture was similarly associated with a modest increase in shift rate. There were no significant associations between PFAS exposure and time to reach familiarization (another measure of attention), average run duration (information processing speed), or novelty preference (visual recognition memory).

CONCLUSION

In our study population, prenatal PFAS exposure was modestly associated with an increase in shift rate and was not strongly associated with any adverse cognitive outcomes in 7.5-month-old infants.

Association between prenatal or early postnatal exposure to perfluoroalkyl substances and language development in 18 to 36-month-old children from the Odense Child Cohort

BACKGROUND

Perfluoroalkyl substances (PFAS) are persistent chemicals used in everyday consumer products leading to ubiquitous human exposure. Findings of impaired neurodevelopment after prenatal exposure to PFAS are contradictory and few studies have assessed the impact of postnatal PFAS exposure. Language development is a good early marker of neurodevelopment but only few studies have investigated this outcome separately. We therefore investigated the association between prenatal and early postnatal PFAS exposure and delayed language development in 18 to 36-month-old Danish children.

METHODS

The Odense Child Cohort is a large prospective cohort. From 2010 to 2012 all newly pregnant women residing in the Municipality of Odense, Denmark was invited to participate. Concentration of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) were assessed in maternal serum collected in the 1st trimester of pregnancy and in child serum at 18 months. Parents responded to the Danish adaption of the MacArthur-Bates Communicative Development Inventories (MB-CDI) when their child was between 18 and 36 months. Language scores were converted into sex and age specific percentile scores and dichotomized to represent language scores above or below the 15th percentile. We applied Multiple Imputation by Chained Equation and conducted logistic regressions investigating the association between prenatal and early postnatal PFAS exposure and language development adjusting for maternal age, pre-pregnancy BMI, education and respectively fish intake in pregnancy or childhood and duration of breastfeeding in early postnatal PFAS exposure models.

RESULTS

We found no significant associations between neither prenatal nor early postnatal PFAS exposure and language development among 999 mother-child pairs.

CONCLUSION

In this low-exposed cohort the finding of no association between early postnatal PFAS exposure and language development should be interpreted with caution as we were unable to separate the potential adverse effect of PFAS exposure from the well documented positive effect of breastfeeding on neurodevelopment. We, therefore, recommend assessment of child serum PFAS at an older age as development of the brain proceeds through childhood and even a small impact of PFAS on neurodevelopment would be of public health concern at population level due to the ubiquitous human exposure.

Prenatal Exposure to Perfluoroalkyl Substances and Cognitive and Neurobehavioral Development in Children at 6 Years of Age

Epidemiological evidence regarding the effects of prenatal exposure to perfluoroalkyl substances (PFASs) on neurodevelopment in children is inconclusive. In 449 mother-child pairs from the Shanghai-Minhang Birth Cohort Study, we measured the concentrations of 11 PFASs in maternal plasma samples obtained at 12-16 weeks of gestation. We assessed children's neurodevelopment at 6 years of age by the fourth edition of the Chinese Wechsler Intelligence Scale for Children and Child Behavior Checklist for ages 6-18. We evaluated the association between prenatal exposure to PFASs and children's neurodevelopment and the effect modification of maternal dietary factors during pregnancy and the child's sex. We found that prenatal exposure to multiple PFASs was associated with increased scores for attention problems, and the individual effect of perfluorooctanoic acid (PFOA) was statistically significant. However, no statistically significant association between PFASs and cognitive development was observed. Additionally, we found the effect modification of maternal nut intake and child's sex. In conclusion, this study suggests that prenatal exposure to PFASs was associated with more attention problems, and maternal nut intake during pregnancy may alter the potential effect of PFASs. However, these findings were exploratory because of multiple testing and the relatively small sample size.

Embryonic exposure to PFAS causes long-term, compound-specific behavioral alterations in zebrafish

Per- and polyfluoroalkyl substances (PFAS) are commonly used as surfactants and coatings for industrial processes and consumer products. These compounds have been increasingly detected in drinking water and human tissue, and concern over their potential effects on health and development is growing. However, relatively little data are available for their potential impacts on neurodevelopment and the degree to which different compounds within this class may differ from one another in their neurotoxicity. The present study examined the neurobehavioral toxicology of two representative compounds in a zebrafish model. Zebrafish embryos were exposed to 0.1-100uM perfluorooctanoic acid (PFOA) or 0.01-1.0uM perfluorooctanesulfonic acid (PFOS) from 5 to 122 h post-fertilization. These concentrations were below threshold for producing increased lethality or overt dysmorphologies, and PFOA was tolerated at a concentration 100× higher than PFOS. Fish were maintained to adulthood, with behavioral assessments at 6 days, 3 months (adolescence) and 8 months of age (adulthood). Both PFOA and PFOS caused behavioral changes in zebrafish, but PFOS and PFOS produced strikingly different phenotypes. PFOA was associated with increased larval motility in the dark (100uM), and enhanced diving responses in adolescence (100uM) but not adulthood. PFOS was associated with a reversed light-dark response in the larval motility test (0.1-1uM), whereby the fish were more active in the light than the dark. PFOS also caused time-dependent changes in locomotor activity in the novel tank test during adolescence (0.1-1.0uM) and an overall pattern of hypoactivity in adulthood at the lowest concentration (0.01uM). Additionally, the lowest concentration of PFOS (0.01uM) reduced acoustic startle magnitude in adolescence, but not adulthood. These data suggest that PFOS and PFOA both produce neurobehavioral toxicity, but these effects are quite distinct from one another.

Prenatal Exposure to Per- and Polyfluoroalkyl Substances and Childhood Autism-related Outcomes

BACKGROUND

Epidemiologic evidence linking prenatal exposure to per- and polyfluoroalkyl substances (PFAS) with altered neurodevelopment is inconclusive, and few large studies have focused on autism-related outcomes. We investigated whether blood concentrations of PFAS in pregnancy are associated with child autism-related outcomes.

METHODS

We included 10 cohorts from the National Institutes of Health (NIH)-funded Environmental influences on Child Health Outcomes (ECHO) program (n = 1,429). We measured 14 PFAS analytes in maternal blood collected during pregnancy; eight analytes met detection criteria for analysis. We assessed quantitative autism-related traits in children via parent report on the Social Responsiveness Scale (SRS). In multivariable linear models, we examined relationships of each PFAS (natural log-transformed) with SRS scores. We further modeled PFAS as a complex mixture using Bayesian methods and examined modification of these relationships by child sex.

RESULTS

Most PFAS in maternal blood were not associated with child SRS T-scores. Perfluorononanoic acid (PFNA) showed the strongest and most consistent association: each 1-unit increase in ln-transformed PFNA was associated with greater autism-related traits (adjusted β [95% confidence interval (CI)] = 1.5 [-0.1, 3.0]). The summed mixture, which included six PFAS detected in >70% of participants, was not associated with SRS T-scores (adjusted β [95% highest posterior density interval] = 0.7 [-1.4, 3.0]). We did not observe consistent evidence of sex differences.

CONCLUSIONS

Prenatal blood concentrations of PFNA may be associated with modest increases in child autism-related traits. Future work should continue to examine the relationship between exposures to both legacy and emerging PFAS and additional dimensional, quantitative measures of childhood autism-related outcomes.

Prenatal exposure to perfluoroalkyl substances and child intelligence quotient: Evidence from the Shanghai birth cohort

BACKGROUND AND AIM

Epidemiological evidence on the association between prenatal exposure to Perfluoroalkyl substances (PFAS) and child cognition remains unclear. Thus, we aimed to investigate whether prenatal exposure to PFAS is associated with intelligence quotient (IQ) in offspring.

METHOD

This study population included 2031 mother-child pairs in the Shanghai Birth Cohort (SBC) enrolled during 2013-2016. Ten PFAS were measured by high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS-MS) in maternal plasma samples collected in early gestation between 9 and 16 weeks of gestation. Child IQ was assessed using the Wechsler Preschool and Primary Scales of Intelligence-Fourth Edition (WPPSI-IV) at 4 years of age. Multivariable linear regression models were used to estimate the associations between individual PFAS concentrations (as a continuous variable or categorized into tertiles) and child IQ. A quantile g-computation approach was used to evaluate the joint and independent effects of PFAS on IQ. We also examined whether the associations varied by child sex.

RESULTS

We found no significant associations between ln-transformed nine individual PFAS and child full scale IQ (FSIQ) or subscale IQ after adjusting for potential confounders. The observed associations were not modified by child sex. PFAS in tertiles showed the same pattern. Results from quantile g-computation showed that PFAS mixture was not associated with child IQ; perfluorobutane sulfonate was negatively associated with FSIQ (β, -0.81; 95 % CI: -1.55, -0.07), and perfluorooctane sulfonate was also associated with lower fluid reasoning index scores (β, -1.61; 95 % CI: -3.07, -0.16) while adjusting for the other PFAS.

CONCLUSION

PFAS mixture during early pregnancy was not associated with child IQ. For certain individual PFAS, there were inverse associations with FSIQ or subscale IQ. Considering the evidence is still inconsistent, further research is needed to confirm or refute these results in other populations and to elucidate the potential neurotoxicology of PFAS.

Prenatal Exposure to Legacy and Alternative Per- and Polyfluoroalkyl Substances and Neuropsychological Development Trajectories over the First 3 Years of Life

The neurotoxic effects of prenatal exposure to per- and polyfluoroalkyl substances (PFAS) on offspring animals are well-documented. However, epidemiological evidence for legacy PFAS is inconclusive, and for alternative PFAS, it is little known. In this investigation, we selected 718 mother-child pairs from the Chinese Maoming Birth Cohort Study and measured 17 legacy and alternative PFAS in the third-trimester serum. Neuropsychological developments (communication, gross motor function, fine motor function, problem solving ability, and personal-social skills) were assessed at 3, 6, 12, 18, 24, and 36 months using the Ages and Stages Questionnaires 3rd edition. Trajectories of each subscale were classified into persistently low and persistently high groups via group-based trajectory modeling. Logistic regression and grouped weighted quantile sum were fitted to assess the potential effects of individual PFAS and their mixtures, respectively. Higher linear PFHxS levels were associated with elevated odds for the persistently low trajectories of communication (OR = 1.73; 95% CI: 1.12, 2.66) and problem solving ability (OR = 2.11; 95% CI: 1.14, 3.90). Similar findings were observed for linear PFOS, 1m-PFOS, PFDA, PFDoDA, PFUnDA, and legacy PFAS mixture. However, no association was observed for alternative PFAS and their mixture. We provided insights into the longitudinal links between prenatal legacy/alternative PFAS exposure and neuropsychological development trajectories over the first 3 years of life.

Perfluorinated chemicals (PFOA) can, by interacting with highly brominated diphenyl ethers (PBDE 209) during a defined period of neonatal brain development, exacerbate neurobehavioural defects

Perfluorinated compounds (PFCs) and polybrominated diphenyl ethers (PBDEs) are ubiquitous persistent environmental compounds, present in humans and at higher levels in infants/children than in adults. This study shows that co-exposure to pentadecafluorooctanoic acid (PFOA) and 2,2',3,3',4,4',5,5',6,6'-decaBDE (PBDE 209) can significantly exacerbate developmental neurobehavioural defects. Neonatal male NMRI mice, 3 and 10 days old, were exposed perorally to PBDE 209 (1.4 or 8.0 μmol/kg bw), PFOA (1.4 or 14 μmol/kg bw), co-exposed to PBDE 209 and PFOA (at the given doses), or a vehicle (20% fat emulsion) and observed for spontaneous behaviour in a novel home environment when 2 and 4 months old. The behavioural defects observed included hyperactivity and reduced habituation indicating cognitive defects. This interaction appears most likely dependent on the presence of PBDE 209 and/or its metabolites together with PFOA, during a defined critical period of neonatal brain development, corresponding to the perinatal and newborn period in humans.

The Threat Posed by Environmental Contaminants on Neurodevelopment: What Can We Learn from Neural Stem Cells?

Exposure to chemicals may pose a greater risk to vulnerable groups, including pregnant women, fetuses, and children, that may lead to diseases linked to the toxicants' target organs. Among chemical contaminants, methylmercury (MeHg), present in aquatic food, is one of the most harmful to the developing nervous system depending on time and level of exposure. Moreover, certain man-made PFAS, such as PFOS and PFOA, used in commercial and industrial products including liquid repellants for paper, packaging, textile, leather, and carpets, are developmental neurotoxicants. There is vast knowledge about the detrimental neurotoxic effects induced by high levels of exposure to these chemicals. Less is known about the consequences that low-level exposures may have on neurodevelopment, although an increasing number of studies link neurotoxic chemical exposures to neurodevelopmental disorders. Still, the mechanisms of toxicity are not identified. Here we review in vitro mechanistic studies using neural stem cells (NSCs) from rodents and humans to dissect the cellular and molecular processes changed by exposure to environmentally relevant levels of MeHg or PFOS/PFOA. All studies show that even low concentrations dysregulate critical neurodevelopmental steps supporting the idea that neurotoxic chemicals may play a role in the onset of neurodevelopmental disorders.

Prenatal perfluoroalkyl substances exposure and neurodevelopment in toddlers: Findings from SMBCS

BACKGROUND

Prenatal perfluoroalkyl substances (PFAS) exposure has been reported to affect offspring neurodevelopment, while epidemiological evidences were limited and inconsistent.

OBJECTIVES

We aimed to evaluate the associations between cord serum PFAS concentrations and neurodevelopment in toddlers from 1 to 3 years of age.

METHODS

A total of 716 children from Sheyang Mini Birth Cohort Study (SMBCS) were included in this study. 12 PFAS concentrations were quantified in cord serum. Neurodevelopment was assessed using the Developmental Screen Test for Children Aged 0-6 Years at 1 year and the Gesell Developmental Schedules (GDS) at 2 and 3 years, respectively. Development quotient (DQ) z-score was standardized from DQ to eliminate the difference caused by two methods. We used generalized linear model (GLM) and Bayesian kernel machine regression (BKMR) to explore the associations of single or mixture PFAS exposure with neurodevelopment measurements at each time point. Associations between PFAS exposure and longitudinal changes in DQ z-score were investigated through generalized estimating equation (GEE) and trajectory analysis.

RESULTS

In general, prenatal PFAS concentrations showed negative associations with neurodevelopment measurements at specific age. When accounting for longitudinal changes from 1 to 3 years of age, PFOA was negatively associated with DQ z-score (β = -0.212, 95% CI: -0.422, -0.003), the association was only found significant in boys after stratified by gender (β = -0.327, 95% CI: -0.616, -0.038). Meanwhile, increased PFBS (OR = 2.159, 95% CI: 1.177, 3.959) and PFHpA (OR = 1.700, 95% CI: 1.016, 2.846) exposure was associated with elevated odds for the low-score trajectory group. The results of mixture of PFAS further confirmed above findings.

CONCLUSIONS

Our findings suggested that prenatal PFAS exposure may be associated with adverse neurodevelopment effects in the first 3 years of life. Further studies are warranted to confirm our findings.

Efficacy and mechanism of lipoic acid in the treatment of reproductive injury caused by perfluorooctanoic acid

Environmental pollutants, including perfluorooctanoic acid (PFOA), cause severe reproductive damage to humans and animals. Lipoic acid (LA) is a strong antioxidant that alleviates the oxidative damage caused by heavy metals, environmental toxicants, chemical poisons, etc. Therefore, the present study investigated the curative effect and mechanism of LA in treating spermatogenesis dysfunction caused by PFOA. A rat reproductive injury model was established by gavage of PFOA for consecutive 30 days and then rats were treated with different doses of LA for 42 days. The effects were assessed by ELISA, western blotting, H&E staining and immunofluorescence staining. The results demonstrated that LA had ameliorating effects on PFOA-induced reproductive injury in rats, it increased the sperm counts, and the levels of serum succinate dehydrogenase, lactate dehydrogenase, glutathione peroxidase and superoxide dismutase returned to normal levels following LA treatment. In addition, LA promoted the expression of estradiol, reduced the expression of serum sex hormones, such as follicle-stimulating hormone, androgen receptor (AR) and malondialdehyde in the testes, and restored the structure of seminiferous tubules. Its therapeutic mechanisms include regulating the testicular oxidative stress pathway and hypothalamic-pituitary-testis axis.

The Association between Prenatal Per- and Polyfluoroalkyl Substances Exposure and Neurobehavioral Problems in Offspring: A Meta-Analysis

Exposure to per- and polyfluoroalkyl substances (PFAS) during pregnancy has been suggested to be associated with neurobehavioral problems in offspring. However, current epidemiological studies on the association between prenatal PFAS exposure and neurobehavioral problems among offspring, especially attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD), are inconsistent. Therefore, we aimed to study the relationship between PFAS exposure during pregnancy and ADHD and ASD in offspring based on meta-analyses. Online databases, including PubMed, EMBASE, and Web of Science, were searched comprehensively for eligible studies conducted before July 2021. Eleven studies (up to 8493 participants) were included in this analysis. The pooled results demonstrated that exposure to perfluorooctanoate (PFOA) was positively associated with ADHD in the highest quartile group. Negative associations were observed between perfluorooctane sulfonate (PFOS) and ADHD/ASD, including between perfluorononanoate (PFNA) and ASD. There were no associations found between total PFAS concentration groups and neurobehavioral problems. The trial sequential analyses showed unstable results. Our findings indicated that PFOA and PFOS exposure during pregnancy might be associated with ADHD in offspring and that prenatal PFOS and PFNA exposure might be associated with ASD in offspring. According to the limited evidence obtained for most associations, additional studies are required to validate these findings.

Childhood exposure to per- and polyfluoroalkyl substances and neurodevelopment in the CHARGE case-control study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are shown to have neurotoxic effects on animals, but epidemiological evidence for associations between childhood PFAS exposure and neurodevelopment is inconclusive. We examined if childhood PFAS concentrations are associated with a diagnosis of autism spectrum disorder (ASD), developmental delay (DD), and other early concerns (OEC) in development.

METHODS

We included 551 children 2-5 years old from the CHildhood Autism Risks from Genetics and Environment (CHARGE) case-control study. Children were clinically diagnosed and classified as having ASD, DD, OEC, and typical development (TD). Fourteen PFAS were quantified in child serum samples collected when diagnostic assessments were performed. We used multinomial logistic regression models to investigate the cross-sectional associations of individual PFAS concentrations with neurodevelopmental outcomes and weighted quantile sum (WQS) regression models with repeated holdout validation to investigate the associations with PFAS mixtures.

RESULTS

Childhood perfluorooctanoic acid (PFOA) was associated with increased odds of ASD (odds ratio [OR] per ln ng/mL increase: 1.99, 95% confidence interval [CI]: 1.20, 3.29) and DD (OR: 2.16, 95% CI: 1.21, 3.84) versus TD. Perfluoroheptanoic acid (PFHpA) was associated with increased odds of ASD (OR: 1.61, 95% CI: 1.21, 2.13). However, perfluroundecanoic acid (PFUnDA) was associated with decreased odds of ASD (OR: 0.43, 95% CI: 0.26, 0.69). From mixture analyses, the WQS index was associated with increased odds of ASD (average OR: 1.57, 5th and 95th percentile: 1.16, 2.13). Child's sex and homeownership modified associations of perfluorodecanoic acid (PFDA) with DD and ASD, respectively.

CONCLUSIONS

In this case-control study, childhood PFOA, PFHpA, and a PFAS mixture was associated with increased odds of ASD, while PFUnDA was associated with decreased odds of ASD. Because we used concurrent measurements of PFAS, our results do not imply causal relationships and thus need to be interpreted with caution.

Neurotransmission Targets of Per- and Polyfluoroalkyl Substance Neurotoxicity: Mechanisms and Potential Implications for Adverse Neurological Outcomes

Per- and polyfluoroalkyl substances (PFAS) are a group of persistent environmental pollutants that are ubiquitously found in the environment and virtually in all living organisms, including humans. PFAS cross the blood-brain barrier and accumulate in the brain. Thus, PFAS are a likely risk for neurotoxicity. Studies that measured PFAS levels in the brains of humans, polar bears, and rats have demonstrated that some areas of the brain accumulate greater amounts of PFAS. Moreover, in humans, there is evidence that PFAS exposure is associated with attention-deficit/hyperactivity disorder (ADHD) in children and an increased cause of death from Parkinson's disease and Alzheimer's disease in elderly populations. Given possible links to neurological disease, critical analyses of possible mechanisms of neurotoxic action are necessary to advance the field. This paper critically reviews studies that investigated potential mechanistic causes for neurotoxicity including (1) a change in neurotransmitter levels, (2) dysfunction of synaptic calcium homeostasis, and (3) alteration of synaptic and neuronal protein expression and function. We found growing evidence that PFAS exposure causes neurotoxicity through the disruption of neurotransmission, particularly the dopamine and glutamate systems, which are implicated in age-related psychiatric illnesses and neurodegenerative diseases. Evaluated research has shown there are highly reproduced increased glutamate levels in the hippocampus and catecholamine levels in the hypothalamus and decreased dopamine in the whole brain after PFAS exposure. There are significant gaps in the literature relative to the assessment of the nigrostriatal system (striatum and ventral midbrain) among other regions associated with PFAS-associated neurologic dysfunction observed in humans. In conclusion, evidence suggests that PFAS may be neurotoxic and associated with chronic and age-related psychiatric illnesses and neurodegenerative diseases. Thus, it is imperative that future mechanistic studies assess the impact of PFAS and PFAS mixtures on the mechanism of neurotransmission and the consequential functional effects.

Associations between prenatal exposure to perfluoroalkyl substances and neurobehavioral development in early childhood: A prospective cohort study

Findings from epidemiological studies on the associations between prenatal perfluoroalkyl substances (PFASs) exposure and children's neurodevelopment were inconclusive, and most studies did not account for the co-exposure to multiple PFASs with strong inter-correlations. The present study aimed to assess the effects of prenatal multiple PFAS exposure on children's neurobehavioral development based on 614 mother-infant pairs in the Shanghai-Minhang Birth Cohort Study. Eight PFAS concentrations were measured in maternal plasma at 12-16 weeks of gestation. Children's neurobehavioral development at 2 and 4 years of age was assessed by the Child Behavior Checklist for Ages 1.5-5. In Bayesian kernel machine regression (BKMR) analyses that could address the inter-correlations between multiple PFASs, PFAS mixture appeared to be associated with fewer Somatic Complaints and more Externalizing Problems in boys, but more Somatic Complaints and Sleep Problems in girls. There were suggestive associations of PFNA and PFOS with decreased risk of Somatic Complaints and of PFUdA and PFTrDA with increased risk of Externalizing Problems in boys; trends of increased risk in girls were observed between PFUdA and Somatic Complaints and between PFTrDA and Sleep Problems. Overall, we found no clear evidence that prenatal exposure to PFASs had negative effects on neurobehavioral development in children. However, the modest associations still suggested the potential developmental neurotoxicity of prenatal PFAS exposure.

Challenges of fluoride pollution in environment: Mechanisms and pathological significance of toxicity - A review

Fluoride is an important trace element in the living body. A suitable amount of fluoride has a beneficial effect on the body, but disproportionate fluoride entering the body will affect various organs and systems, especially the liver, kidneys, nervous system, endocrine system, reproductive system, bone, and intestinal system. In recent years, with the rapid development of agriculture and industry, fluoride pollution has become one of the important factors of environmental pollution, and fluoride pollution in any form is becoming a serious problem. Although countries around the world have made great breakthroughs in controlling fluoride pollution, however fluorosis still exists. A large amount of fluoride accumulated in animals will not only produce the toxic effects, but it also causes cell damage and affect the normal physiological activities of the body. There is no systematic description of the damage mechanism of fluoride. Therefore, the study on the toxicity mechanism of fluoride is still in progress. This review summarizes the existing information of several molecular mechanisms of the fluoride toxicity comprehensively, aiming to clarify the toxic mechanism of fluoride on various body systems. We have also summerized the pathological changes of those organ systems after fluoride poisoning in order to provide some ideas and solutions to the reader for the prevention and control of modern fluoride pollution.

Poly- and perfluoroalkyl substances (PFAS) exposure through infant feeding in early life

BACKGROUND AND AIMS

Per- and polyfluoroalkyl substances (PFAS) are non-degradable, man-made-chemicals with an elimination half-life of multiple years, causing accumulation in the environment and humans with potential harmful effects. However, longitudinal PFAS levels in human milk, daily PFAS intake and the association with infant plasma PFAS levels have never been reported. We investigated longitudinal PFOA and PFOS levels in human milk and the daily PFAS intake through infant feeding in the first 3 months of life, the most important determinants and the correlation with PFAS plasma levels at age 3 months and 2 years.

METHODS

In 372 healthy term-born Dutch infants, we determined PFOA and PFOS levels in human milk given at age 1 and 3 months, in 6 infant formula brands and in infant plasma at 3 months and 2 years, using liquid-chromatography-electrospray-ionization-tandem-mass-spectrometry(LC-ESI-MS/MS). We studied the associations between daily PFAS intake and predictive characteristics by multiple regression models.

RESULTS

PFOA and PFOS levels in human milk decreased between 1 and 3 months after delivery, regardless whether breastfeeding was given exclusively(EBF) or in combination with formula feeding. PFOA and PFOS could not be detected in any formula feeding. Daily PFAS intake(ng/kg) was highest in EBF-infants. Higher amount of human milk, older maternal age, lower parity and first-time breastfeeding were associated with higher daily intake. Daily PFAS intake in early life was strongly correlated with PFAS plasma levels at age 3 months and 2 years(R = 0.642-0.875, p < 0.001).

CONCLUSIONS

Human milk contains PFOA and PFOS, in contrast to formula feeding. Daily PFOA and PFOS intake in early life is highest in exclusively breastfed infants and it is highly correlated with infant's plasma levels throughout infancy. Our findings show that breastfeeding is an important PFAS exposure pathway in the first months of life, with unknown but potential adverse effects. Knowing the important health benefits of breastfeeding, our findings warrant more research about the health outcomes in later life.

Mixed effects of perfluoroalkyl and polyfluoroalkyl substances exposure on cognitive function among people over 60 years old from NHANES

The relationship between perfluoroalkyl and polyfluoroalkyl substances (PFAS) and cognitive function are inconsistent, and the mixed effects of PFAS on cognitive function are still unclear. We aimed to evaluate the joint effects of PFAS on cognitive function assessed using four tests as follows: the Consortium to Establish a Registry for Alzheimer's Disease Immediate Recall Test (IRT), Delayed Recall Test (DRT), the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST) in the US elderly. A total of 777 individuals aged ≥ 60 from the National Health and Nutrition Examination Survey (NHANES) 2011-2014 were included in this study. Multivariable logistic regression and Bayesian kernel machine regression (BKMR) were constructed to estimate the overall and the individual effects of PFAS exposure on cognitive function. There were 21.36%, 22.65%, 21.62%, and 21.24% participants with cognitive decline in IRT, DRT, AFT, and DSST, respectively. After multivariable adjustment, perfluorooctanoic acid (PFOA) was inversely associated with cognitive decline in IRT, DRT, and AFT, while no significant association was observed between any other PFAS and cognitive decline. Compared with the lowest quartile, the adjusted odds ratio of cognitive decline with a 95% confidence interval (CI) for the highest quartile of PFOA was 0.33 (95% CI: 0.15-0.69) in IRT, 0.50 (0.26-0.96) in DRT, and 0.45 (0.21-0.95) in AFT. In BKMR analysis, the overall effect of mixtures was significantly protective on cognitive decline in IRT, of which PFOA made the greatest contribution. The consistent protective effect in DRT and DSST was observed when all the chemicals were at their 50th percentile or below it. No significant interaction was observed among PFAS for cognitive function. These findings suggested that PFAS mixture at a low level of current exposure of the US population may have a protective effect on cognitive function.

Prediction of the endocrine-disrupting ability of 49 per- and polyfluoroalkyl substances: In silico and epidemiological evidence

The toxic effects of per- and polyfluoroalkyl substances (PFASs) on humans are mediated by nuclear hormone receptors (NHRs). However, data on the interaction of PFASs and NHRs is limited. Endocrine Disruptome, an inverse docking tool, was used in this study to simulate the docking of 49 common PFASs with 14 different types of human NHRs. According to the findings, 25 PFASs have a high or moderately high probability of binding to more than five NHRs, with androgen receptor (AR) and mineralocorticoid receptor (MR) being the most likely target NHRs. Molecular docking analyses revealed that the binding modes of PFASs with the two NHRs were similar to those of their corresponding co-crystallized ligands. PFASs, in particular, may disrupt the endocrine system by binding to MR. This finding is consistent with epidemiological research that has linked PFASs to MR-related diseases. Our findings may contribute to a better understanding of the health risks posed by PFASs.

Perfluorohexane sulfonate induces memory impairment and downregulation of neuroproteins via NMDA receptor-mediated PKC-ERK/AMPK signaling pathway

Perfluorohexane sulfonate (PFHxS) is a widely used industrial chemical detected in human umbilical cord blood and breast milk, and has been suggested to exhibit developmental neurotoxicity. Previous studies on mice reported that neonatal exposure to PFHxS altered neuroprotein levels in the developing brain, and caused behavioral toxicity and cognitive dysfunction in the mature brain. However, the underlying mechanisms responsible for PFHxS-induced neuroprotein dysregulation are poorly understood. In this study, we examined the effect of neonatal exposure to PFHxS on memory function using an in vivo mice model. Furthermore, we examined the levels of growth associated protein-43 (GAP-43) and calcium/calmodulin dependent protein kinase II (CaMKII) (biomarkers of neuronal development) and the involved signaling pathways using differentiated neuronal PC12 cells. PFHxS decreased cell viability, GAP-43 and CaMKII levels, and neurite formation. These effects were mediated by the NMDA receptor, PKC-α, PKC-δ, AMPK and ERK pathways. MK801, an NMDA receptor antagonist, reduced the activation of PKC-α, PKC-δ, ERK and AMPK. The activation of ERK was suppressed by pharmacological and knockdown inhibition of PKC-α and -δ. Interestingly, the AMPK pathway was selectively inhibited by inhibiting PKC-δ but not PKC-ɑ. Consistent with PFHxS-induced neuronal death, and GAP-43 and CaMKII downregulation, neonatal exposure to PFHxS caused significant memory impairment in adult mice. Collectively, these results demonstrate that PFHxS induces persistent developmental neurotoxicity, as well as GAP-43 and CaMKII downregulation via the NMDA receptor-mediated PKCs (α and δ)-ERK/AMPK pathways.

Longitudinal poly- and perfluoroalkyl substances (PFAS) levels in Dutch infants

BACKGROUND AND AIMS

Per- and polyfluoroalkyl substances (PFAS) are a potential hazard for public health. These man-made-chemicals are non-degradable with an elimination half-life of multiple years, causing accumulation in the environment and humans. Rodent studies demonstrated that PFAS are harmful, especially when present during the critical window in the first months of life. Because longitudinal data during infancy are limited, we investigated longitudinal plasma levels in infants aged 3 months and 2 years and its most important determinants.

METHODS

In 369 healthy term-born Dutch infants, we determined plasma PFOS, PFOA, PFHxS, PFNA and PFDA levels at age 3 months and 2 years, using liquid chromatography-electrospray-ionization-tandem-mass-spectrometry (LC-ESI-MS/MS). We studied the associations with maternal and child characteristics by multiple regression models.

RESULTS

At age 3 months, median plasma levels of PFOS, PFOA, PFHxS, PFNA and PFDA were 1.48, 2.40, 0.43, 0.23 and 0.07 ng/mL, resp. Levels decreased slightly until age 2 years to 1.30, 1.81, 0.40, 0.21 and 0.08 ng/mL, resp. Maternal age, first born, Caucasian ethnicity and exclusive breastfeeding were associated with higher infant's plasma levels at age 3 months. Levels at 3 months were the most important predictor for PFAS levels at age 2 years. Infants with exclusive breastfeeding during the first 3 months of life (EBF) had 2-3 fold higher levels throughout infancy compared to infants with exclusive formula feeding (EFF), with PFOA levels at 3 months 3.72 ng/mL versus 1.26 ng/mL and at 2 years 3.15 ng/mL versus 1.22 ng/mL, respectively.

CONCLUSION

Plasma PFAS levels decreased only slightly during infancy. Higher levels at age 3 months were found in Caucasian, first-born infants from older mothers and throughout infancy in EBF-infants. Our findings indicate that trans-placental transmission and breastfeeding are the most important determinants of PFAS exposure in early life.

The association between prenatal perfluoroalkyl substance exposure and symptoms of attention-deficit/hyperactivity disorder in 8-year-old children and the mediating role of thyroid hormones in the Hokkaido study

BACKGROUND

Disruption of thyroid hormone (TH) levels during pregnancy contributes to attention deficit hyperactivity disorder (ADHD). Exposure to perfluoroalkyl substances (PFAS) during gestation may affect levels of maternal and neonatal TH; however, little is known about the effect of PFAS on ADHD mediated by TH.

OBJECTIVES

We investigated the impact of maternal PFAS exposure on children's ADHD symptoms with the mediating effect of TH.

METHODS

In a prospective birth cohort (the Hokkaido study), we included 770 mother-child pairs recruited between 2002 and 2005 for whom both prenatal maternal and cord blood samples were available. Eleven PFAS were measured in maternal serum obtained at 28-32 weeks of gestation using ultra-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry. TH and thyroid antibody, including thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured in maternal blood during early pregnancy (median 11 gestational weeks) and in cord blood at birth. ADHD symptoms in the children at 8 years of age were rated by their parents using the ADHD-Rating Scale (ADHD-RS). The cut-off value was set at the 80th percentile for each sex.

RESULTS

Significant inverse associations were found between some PFAS in maternal serum and ADHD symptoms among first-born children. Assuming causality, we found only one significant association: maternal FT4 mediated 17.6% of the estimated effect of perfluoroundecanoic acid exposure on hyperactivity-impulsivity among first-born children.

DISCUSSION

Higher PFAS levels in maternal serum during pregnancy were associated with lower risks of ADHD symptoms at 8 years of age. The association was stronger among first-born children in relation to hyperactivity-impulsivity than with regard to inattention. There was little mediating role of TH during pregnancy in the association between maternal exposure to PFAS and reduced ADHD symptoms at 8 years of age.

The impact of perfluoroalkyl substances on pregnancy, birth outcomes and offspring development: A review of data from mouse models1

Per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are persistent in the environment and bioaccumulate in wildlife and humans, potentially causing adverse health effects at all stages of life. Studies from human pregnancy have shown that exposure to these contaminants are associated with placental dysfunction and fetal growth restriction; however, studies in humans are confounded by genetic and environmental factors. Here, we synthesize the available results from mouse models of pregnancy to show the causal effects of prenatal exposure to PFOA and PFOS on placental and fetal development and on neurocognitive function and metabolic disorders in offspring. We also propose gaps in the present knowledge and provide suggestions for future research studies.

Absorption, distribution, and toxicity of per- and polyfluoroalkyl substances (PFAS) in the brain: a review

Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic chemicals colloquially known as "forever chemicals" because of their high persistence. PFAS have been detected in the blood, liver, kidney, heart, muscle and brain of various species. Although brain is not a dominant tissue for PFAS accumulation compared to blood and liver, adverse effects of PFAS on brain functions have been identified. Here, we review studies related to the absorption, accumulation, distribution and toxicity of PFAS in the brain. We summarize evidence on two potential mechanisms of PFAS entering the brain: initiating blood-brain barrier (BBB) disassembly through disrupting tight junctions and relying on transporters located at the BBB. PFAS with diverse structures and properties enter and accumulate in the brain with varying efficiencies. Compared to long-chain PFAS, short-chain PFAS may not cross cerebral barriers effectively. According to biomonitoring studies and PFAS exposure experiments, PFAS can accumulate in the brain of humans and wildlife species. With respect to the distribution of PFAS in specific brain regions, the brain stem, hippocampus, hypothalamus, pons/medulla and thalamus are dominant for PFAS accumulation. The accumulation and distribution of PFAS in the brain may lead to toxic effects in the central nervous system (CNS), including PFAS-induced behavioral and cognitive disorders. The specific mechanisms underlying such PFAS-induced neurotoxicity remain to be explored, but two major potential mechanisms based on current understanding are PFAS effects on calcium homeostasis and neurotransmitter alterations in neurons. Based on the information available about PFAS uptake, accumulation, distribution and impacts on the brain, PFAS have the potential to enter and accumulate in the brain at varying levels. The balance of existing studies shows there is some indication of risk in animals, while the human evidence is mixed and warrants further scrutiny.

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) and associations with attention-deficit/hyperactivity disorder and autism spectrum disorder in children

BACKGROUND

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) may be a risk factor for neurodevelopmental deficits and disorders, but evidence is inconsistent.

OBJECTIVES

We investigated whether prenatal exposure to PFAS were associated with childhood diagnosis of attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD).

METHODS

This study was based on the Norwegian Mother, Father and Child Cohort Study and included n = 821 ADHD cases, n = 400 ASD cases and n = 980 controls. Diagnostic cases were identified by linkage with the Norwegian Patient Registry. In addition, we used data from the Medical Birth Registry of Norway. The study included the following PFAS measured in maternal plasma sampled mid-pregnancy: Perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorohexane sulfonate (PFHxS), perfluoroheptanesulfonic acid (PFHpS), and perfluorooctane sulfonate (PFOS). Relationships between individual PFAS and ADHD or ASD diagnoses were examined using multivariable adjusted logistic regression models. We also tested for possible non-linear exposure-outcome associations. Further, we investigated the PFAS mixture associations with ASD and ADHD diagnoses using a quantile-based g-computation approach.

RESULTS

Odds of ASD was significantly elevated in PFOA quartile 2 [OR = 1.71 (95% CI: 1.20, 2.45)] compared to quartile 1, and PFOA appeared to have a non-linear, inverted U-shaped dose-response relationship with ASD. PFOA was also associated with increased odds of ADHD, mainly in quartile 2 [OR = 1.54 (95% CI: 1.16, 2.04)] compared to quartile 1, and displayed a non-linear relationship in the restricted cubic spline model. Several PFAS (PFUnDA, PFDA, and PFOS) were inversely associated with odds of ADHD and/or ASD. Some of the associations were modified by child sex and maternal education. The overall PFAS mixture was inversely associated with ASD [OR = 0.76 (95% CI: 0.64, 0.90)] as well as the carboxylate mixture [OR = 0.79 (95% CI: 0.68, 0.93)] and the sulfonate mixture [OR = 0.84 (95% CI: 0.73, 0.96)].

CONCLUSION

Prenatal exposure to PFOA was associated with increased risk of ASD and ADHD in children. For some PFAS, as well as their mixtures, there were inverse associations with ASD and/or ADHD. However, the inverse associations reported herein should not be interpreted as protective effects, but rather that there could be some unresolved confounding for these relationships. The epidemiologic literature linking PFAS exposures with neurodevelopmental outcomes is still inconclusive, suggesting the need for more research to elucidate the neurotoxicological potential of PFAS during early development.