Perfluoroalkyl acids potentiate glutamate excitotoxicity in rat cerebellar granule neurons

Prenatal exposure to per- and polyfluoroalkyl substances, fetal thyroid function, and intelligence quotient at 7 years of age: Findings from the Sheyang Mini Birth Cohort Study

BACKGROUND

Prenatal exposure to per- and polyfluoroalkyl substances (PFASs) influences neurodevelopment. Thyroid homeostasis disruption is thought to be a possible underlying mechanism. However, current epidemiological evidence remains inconclusive.

OBJECTIVES

This study aimed to explore the effects of prenatal PFAS exposure on the intelligence quotient (IQ) of school-aged children and assess the potential mediating role of fetal thyroid function.

METHODS

The study included 327 7-year-old children from the Sheyang Mini Birth Cohort Study (SMBCS). Cord serum samples were analyzed for 12 PFAS concentrations and 5 thyroid hormone (TH) levels. IQ was assessed using the Wechsler Intelligence Scale for Children-Chinese Revised (WISC-CR). Generalized linear models (GLM) and Bayesian Kernel Machine Regression (BKMR) were used to evaluate the individual and combined effects of prenatal PFAS exposure on IQ. Additionally, the impact on fetal thyroid function was examined using a GLM, and a mediation analysis was conducted to explore the potential mediating roles of this function.

RESULTS

The molar sum concentration of perfluorinated carboxylic acids (ΣPFCA) in cord serum was significantly negatively associated with the performance IQ (PIQ) of 7-year-old children (β = -6.21, 95 % confidence interval [CI]: -12.21, -0.21), with more pronounced associations observed among girls (β = -9.57, 95 % CI: -18.33, -0.81) than in boys. Negative, albeit non-significant, cumulative effects were noted when considering PFAS mixture exposure. Prenatal exposure to perfluorooctanoic acid, perfluorononanoic acid, and perfluorooctanesulfonic acid was positively associated with the total thyroxine/triiodothyronine ratio. However, no evidence supported the mediating role of thyroid function in the link between PFAS exposure and IQ.

CONCLUSIONS

Increased prenatal exposure to PFASs negatively affected the IQ of school-aged children, whereas fetal thyroid function did not serve as a mediator in this relationship.

Prenatal exposure to per- and polyfluoroalkyl substances and infant sleep disturbance: A prospective cohort study

BACKGROUND

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) may adversely affect fetal brain development, yet no study has investigated the potential association between prenatal PFAS exposure and infant sleep.

OBJECTIVES

To explore the associations of prenatal PFAS exposure with infant sleep disturbances during the first year of life in a prospective cohort study.

METHODS

We recruited 4127 pregnant women from the Shanghai Birth Cohort (SBC) and followed their children from birth to 12 months old. A total of 2366 infants were included in the 6-month analyses, and 2466 infants in the 12-month analyses. Ten PFAS were quantified in blood serum collected in the first trimester. Sleep quality was measured using the Brief Infant Sleep Questionnaire. We used multiple linear regression and multinomial logistic regression to estimate the individual effects of PFAS on sleep outcomes. We utilized a quantile-based g-computation model to determine the joint effects of the PFAS mixture on infant sleep outcomes. Additionally, generalized estimating equation (GEE) models were performed to examine the longitudinal effects of PFAS exposure during pregnancy.

RESULTS

In infants aged 6 months, perfluorooctane sulfonate and perfluoroheptanoic acid were associated with a more than 2-fold risk of parent-reported sleep problems as severe. Perfluorodecanoic acid was associated with an increased risk of often or almost always snoring in one-year-old infants (relative risk ratios, 1.79; 95% CI, 1.12-2.86). PFAS mixtures were positively associated with nighttime awakenings both among infants aged 6 months (β, 0.11; 95% CI, 0.04-0.19) and 12 months (β, 0.11; 95% CI, 0.05-0.18). Prenatal exposure to PFAS were associated with longer sleep latency, increased nighttime awakenings, longer nocturnal wakefulness hours, snoring, and earlier sleep-onset time in infants aged 6-12 months, according to GEE models.

CONCLUSIONS

Our study suggests that prenatal exposure to PFAS may increase the risk of sleep disturbance in infants.

The pollutome-connectome axis: a putative mechanism to explain pollution effects on neurodegeneration

The study of pollutant effects is extremely important to address the epochal challenges we are facing, where world populations are increasingly moving from rural to urban centers, revolutionizing our world into an urban world. These transformations will exacerbate pollution, thus highlighting the necessity to unravel its effect on human health. Epidemiological studies have reported that pollution increases the risk of neurological diseases, with growing evidence on the risk of neurodegenerative disorders. Air pollution and water pollutants are the main chemicals driving this risk. These chemicals can promote inflammation, acting in synergy with genotype vulnerability. However, the biological underpinnings of this association are unknown. In this review, we focus on the link between pollution and brain network connectivity at the macro-scale level. We provide an updated overview of epidemiological findings and studies investigating brain network changes associated with pollution exposure, and discuss the mechanistic insights of pollution-induced brain changes through neural networks. We explain, in detail, the pollutome-connectome axis that might provide the functional substrate for pollution-induced processes leading to cognitive impairment and neurodegeneration. We describe this model within the framework of two pollutants, air pollution, a widely recognized threat, and polyfluoroalkyl substances, a large class of synthetic chemicals which are currently emerging as new neurotoxic source.

Perfluorooctanesulfonic acid exposure altered hypothalamic metabolism and disturbed male fecundity

Previous studies have examined the effects of perfluorooctanesulfonic acid (PFOS) on disruption of the blood-testis barrier and spermatogenesis. Sertoli and Leydig cells were perturbed, resulting in a decrease in testosterone levels and sperm counts. However, the effects of PFOS on male fecundity are not limited to the testes. In this study, we demonstrated that oral PFOS exposure (1 μg/g BW and 5 μg/g BW) decreased the function of the Luteinizing hormone (LH)/Luteinizing hormone receptor (LHr) and decreased epididymal sperm motility. Consistently, testicular transcriptome analysis revealed that PFOS altered the expression of a cluster of genes associated with sperm motility and steroidogenesis. In mice exposed to PFOS, c-Fos immunostaining showed activation of the lateral septal nucleus (LS), paraventricular thalamus (PVT), locus coeruleus (LC), which are known to be related to anxiety-like behaviors. Metabolomic analyses of the hypothalamus revealed that exposure to PFOS perturbed the translation of proteins, as well as the biosynthesis of neurotransmitters and neuromodulators. Altogether, the activation of brain nuclei, shift of hypothalamic metabolome, and reduction of LH/LHr circuit resulted from PFOS exposure suggested the toxicant's systematic effects on male reproduction.

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.

Perfluorooctane sulfonate induces suppression of testosterone biosynthesis via Sertoli cell-derived exosomal/miR-9-3p downregulating StAR expression in Leydig cells

Perfluorooctane sulfonate (PFOS) is associated with male reproductive disorder, but the related mechanisms are still unclear. In this study, we used in vivo and in vitro models to explore the role of Sertoli cell-derived exosomes (SC-Exo)/miR-9-3p/StAR signaling pathway on PFOS-induced suppression of testosterone biosynthesis. Forty male ICR mice were orally administrated PFOS (0.5-10 mg/kg/bw) for 4 weeks. Bodyweight, organ index, sperm count, reproductive hormones were evaluated. Primary Sertoli cells and Leydig cells were used to delineate the molecular mechanisms that mediate the effects of PFOS on testosterone biosynthesis. Our results demonstrated that PFOS dose-dependently induced a decrease in sperm count, low levels of testosterone, and damage in testicular interstitium morphology. In vitro models, PFOS significantly increased miR-9-3p levels in Sertoli cells and SC-Exo, accompanied by a decrease in testosterone secretion and StAR expression in Leydig cells when Leydig cells were exposed to SC-Exo. Meanwhile, inhibition of SC-Exo or miR-9-3p by their inhibitors significantly rescued PFOS-induced decreases in testosterone secretion and the mRNA and protein expression of the StAR gene in Leydig cells. In summary, the present study highlights the role of the SC-Exo/miR-9-3p/StAR signaling pathway in PFOS-induced suppression of testosterone biosynthesis, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.

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.

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.

Perfluorooctane sulfonate (PFOS) disrupts testosterone biosynthesis via CREB/CRTC2/StAR signaling pathway in Leydig cells

Perfluorooctane sulfonate (PFOS), a stable end-product of perfluorinated compounds (PFCs), is associated with male reproductive disorders, but its underlying mechanisms are still unclear. We used in vivo and in vitro models to investigate the effects of PFOS on testosterone biosynthesis and related mechanisms. First, male ICR mice were orally administered PFOS (0-10 mg/kg/bw) for 4 weeks. Bodyweight, sperm count, reproductive hormones, mRNA expression of the genes related to testosterone biosynthesis, and the protein expression of protein kinase A (PKA), p38 mitogen-activated protein kinase (MAPK), cAMP-response element binding protein (CREB), CREB regulated transcription coactivator 2 (CRTC2) and steroidogenic acute regulatory protein (StAR) were evaluated. Furthermore, mouse primary Leydig cells were used to delineate the molecular mechanisms that mediate the effects of PFOS on testosterone biosynthesis. Our results demonstrated that PFOS dose-dependently decreased sperm count, testosterone level, CRTC2/StAR expression, and damaged testicular interstitium morphology, paralleled by increase in phosphorylated PKA, CREB and p38 in testes. Additionally, similar to the in vivo results, PFOS significantly decreased testosterone secretion, CRTC2/StAR expression, interaction between CREB and CRTC2 and binding of CREB/CRTC2 to StAR promoter region, paralleled by increase in phosphorylated-p38, PKA, and CREB expression. Meanwhile, inhibition of p38 by SB203580, or inhibition of PKA by H89 can significantly alleviate the above PFOS-induced effects. As such, the present study highlights a role of the CREB/CRTC2/StAR signaling pathway in PFOS-induced suppression of testosterone biosynthesis, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.