Consequences of lead exposure, and it’s emerging role as an epigenetic modifier in the aging brain

Hearing Loss and Associated 7-Year Cognitive Outcomes Among Hispanic and Latino Adults

Importance

Hearing loss appears to have adverse effects on cognition and increases risk for cognitive impairment. These associations have not been thoroughly investigated in the Hispanic and Latino population, which faces hearing health disparities.

Objective

To examine associations between hearing loss with 7-year cognitive change and mild cognitive impairment (MCI) prevalence among a diverse cohort of Hispanic/Latino adults.

Design, Setting, and Participants

This cohort study used data from a large community health survey of Hispanic Latino adults in 4 major US cities. Eligible participants were aged 50 years or older at their second visit to study field centers. Cognitive data were collected at visit 1 and visit 2, an average of 7 years later. Data were last analyzed between September 2023 and January 2024.

Exposure

Hearing loss at visit 1 was defined as a pure-tone average (500, 1000, 2000, and 4000 Hz) greater than 25 dB hearing loss in the better ear.

Main outcomes and measures

Cognitive data were collected at visit 1 and visit 2, an average of 7 years later and included measures of episodic learning and memory (the Brief-Spanish English Verbal Learning Test Sum of Trials and Delayed Recall), verbal fluency (word fluency-phonemic fluency), executive functioning (Trails Making Test-Trail B), and processing speed (Digit-Symbol Substitution, Trails Making Test-Trail A). MCI at visit 2 was defined using the National Institute on Aging-Alzheimer Association criteria.

Results

A total of 6113 Hispanic Latino adults were included (mean [SD] age, 56.4 [8.1] years; 3919 women [64.1%]). Hearing loss at visit 1 was associated with worse cognitive performance at 7-year follow-up (global cognition: β = -0.11 [95% CI, -0.18 to -0.05]), equivalent to 4.6 years of aging and greater adverse change (slowing) in processing speed (β = -0.12 [95% CI, -0.23 to -0.003]) equivalent to 5.4 years of cognitive change due to aging. There were no associations with MCI.

Conclusions and relevance

The findings of this cohort study suggest that hearing loss decreases cognitive performance and increases rate of adverse change in processing speed. These findings underscore the need to prevent, assess, and treat hearing loss in the Hispanic and Latino community.

Structural, physical, and radiation absorption properties of a significant nuclear power plant component: A comparison between REX-734 and 316L SS austenitic stainless steels

Austenitic stainless steels (SSs) are commonly used as in-core and surrounding structural materials in today’s industrial BWR and PWR systems. Such adaptable steels have also been the primary materials studied and used in several advanced nuclear reactor technologies, such as fast breeding and magnetic fusion reactors. In this study, some critical material properties, such as structural, physical, and radiation-shielding properties of REX-734 and 316L SS, were experimentally evaluated and compared to those of a number of other alloys. In addition to homogeneous element distribution, both alloys exhibit strong crystal orientation. The REX-734 alloy has a tensile strength of 1,259 MPa, whereas the 316L SS alloy has a tensile strength of 495 MPa. Moreover, nitrogen in the REX-734 alloy formed ultra-hard nitrides with Cr, Nb, and Si and precipitated into the structure and increased the strength. According to our findings, the mass attenuation coefficient values of the 316L SS sample were slightly higher than those of the REX-734 sample at all energies. It can be concluded that the REX-734 sample, with its exceptional strength qualities and excellent radiation attenuation capabilities, may be a viable nuclear power plant material for future investigations.

Effect of WO3 on the radiation shielding ability of TeO2–TiO2–WO3 glass system

In this study, glass composition based on tungsten oxide (WO3) doped tellurium, titanium glasses: (100 − x − y) TeO2–xTiO2–yWO3: where (x = 5) and (y = 5, 10, 15, 20, 25) coded as TT5W5, TT5W10, TT5W15, TT5W20, and TT5W25 were investigated for shielding properties against ionizing radiation. Gamma radiation shielding parameters such as mass attenuation coefficients (MAC) are calculated through MCNPx code and Phy-X/PSD software in the energy range of 0.015–15 MeV. Obtained MAC values are then used to calculate other gamma radiation shielding parameters such as mean free path (MFP) and effective atomic number (Z eff). Besides this, the exposure buildup factor (EBF) was also calculated by using EXABCal software at different penetration depths (PDs) in the energy range of 0.015–15 MeV. Sample TT5W25, which has a larger WO3 content of 25 mol% shows higher values of MAC and lower values of MFP among all the examined glass samples. Our investigated TeO2–TiO2–WO3 glass samples possess the lowest MFP values in comparison with the different types of concretes and commercially available shielding glasses. In addition, fast neutron shielding characteristics in light of fast neutron removal cross-section have also been computed. Glass sample TT5W25 possesses the higher values of fast neutron removal cross-section as compared to the other glass samples. The results indicate that the adding up of WO3 improves shielding against the fast neutron and gamma radiation.

Multifunctional Fiber-Enabled Intelligent Health Agents

The application of wearable devices is promoting the development toward digitization and intelligence in the field of health. However, the current smart devices centered on human health have disadvantages such as weak perception, high interference degree, and unfriendly interaction. Here, an intelligent health agent based on multifunctional fibers, with the characteristics of autonomy, activeness, intelligence, and perceptibility enabling health services, is proposed. According to the requirements for healthcare in the medical field and daily life, four major aspects driven by intelligent agents, including health monitoring, therapy, protection, and minimally invasive surgery, are summarized from the perspectives of materials science, medicine, and computer science. The function of intelligent health agents is realized through multifunctional fibers as sensing units and artificial intelligence technology as a cognitive engine. The structure, characteristics, and performance of fibers and analysis systems and algorithms are reviewed, while discussing future challenges and opportunities in healthcare and medicine. Finally, based on the above four aspects, future scenarios related to health protection of a person's life are presented. Intelligent health agents will have the potential to accelerate the realization of precision medicine and active health.

Increased lead and glucocorticoid concentrations reduce reproductive success in house sparrows along an urban gradient

Urbanization is increasing at a rapid pace globally. Understanding the links among environmental characteristics, phenotypes, and fitness enables researchers to predict the impact of changing landscapes on individuals and populations. Although avian reproductive output is typically lower in urban compared with natural areas, the underlying reasons for this discrepancy may lie at the intersection of abiotic and biotic environmental and individual differences. Recent advances in urban ecology highlight the effect of heavy metal contamination on stress physiology. As high levels of glucocorticoid hormones decrease parental investment, these hormones might be the link to decreased reproductive success in areas of high environmental pollution. In this study, we aimed to identify which abiotic stressors are linked to avian reproductive output in urban areas and whether this link is mediated by individual hormone levels. We used fine-scaled estimates (2 m2 spatial resolution) of nighttime light, noise, and urban density to assess their impacts on the physiological condition of adult house sparrows (Passer domesticus). We measured circulating levels of lead and glucocorticoid concentrations in 40 breeding pairs of free-living house sparrows and related these physiological traits to reproductive success. Using structural equation modeling, we found that increased urban density levels linked directly to increased plasma corticosterone and lead concentrations that subsequently led to decreased fledgling mass. Sparrows with increased lead concentrations in plasma also had higher corticosterone levels. Although urban areas may be attractive due to decreased natural predators and available nesting sites, they may act as ecological traps that increase physiological damage and decrease fitness. To illustrate, avian development is strongly explained by parental corticosterone levels, which vary significantly in response to urban density and lead pollution. With fine-scale ecological mapping for a species with small home ranges, we demonstrated the presence and impacts of urban stressors in a small city with high human densities.

Lead-induced neurodevelopmental lesion and epigenetic landscape: Implication in neurological disorders

Lead (Pb) was implicated in multiple genotoxic, neuroepigenotoxic, and chromosomal-toxic mechanisms and interacted with varying synaptic plasticity pathways, likely underpinning previous reports of links between Pb and cognitive impairment. Epigenetic changes have emerged as a promising biomarker for neurological disorders, including cognitive disorders, Alzheimer's disease (AD), and Parkinson's disease (PD). In the present review, special attention is paid to neural epigenetic features and mechanisms that can alter gene expression patterns upon environmental Pb exposure in rodents, primates, and zebrafish. Epigenetic modifications have also been discussed in population studies and cell experiment. Further, we explore growing evidence of potential linkage between Pb-induced disruption of regulatory pathway and neurodevelopmental and neurological disorders both in vivo and in vitro. These findings uncover how epigenome in neurons facilitates the development and function of the brain in response to Pb insult.

Sesamin: Insights into its protective effects against lead-induced learning and memory deficits in rats

BACKGROUND

Lead (Pb) is one of the most hazardous pollutants that induce a wide spectrum of neurological changes such as learning and memory deficits. Sesamin, a phytonutrient of the lignan class, exhibits anti-inflammatory, anti-apoptotic, and neuroprotective properties. The present study was designed to investigate the effects of sesamin against Pb-induced learning and memory deficits, disruption of hippocampal theta and gamma rhythms, inflammatory response, inhibition of blood δ-aminolevulinic acid dehydratase (δ-ALA-D) activity, Pb accumulation, and neuronal loss in rats.

METHODS

Sesamin treatment (30 mg/kg/day; P.O.) was started simultaneously with Pb acetate exposure (500 ppm in standard drinking water) in rats, and they continued for eight consecutive weeks.

RESULTS

The results showed that chronic exposure to Pb disrupted the learning and memory functions in both passive-avoidance and water-maze tests, which was accompanied by increase in spectral theta power and theta/gamma ratio, and a decrease in spectral gamma power in the hippocampus. Additionally, Pb exposure resulted in an enhanced tumor necrosis factor-alpha (TNF-α) content, decreased interleukin-10 (IL-10) production, inhibited blood δ-ALA-D activity, increased Pb accumulation, and neuronal loss of rats. In contrast, sesamin treatment improved all the above-mentioned Pb-induced pathological changes.

CONCLUSION

This data suggests that sesamin could improve Pb-induced learning and memory deficits, possibly through amelioration of hippocampal theta and gamma rhythms, modulation of inflammatory status, restoration of the blood δ-ALA-D activity, reduction of Pb accumulation in the blood and the brain tissues, and prevention of neuronal loss.

Systematic and state-of the science review of the role of environmental factors in Amyotrophic Lateral Sclerosis (ALS) or Lou Gehrig's Disease

The etiology of sporadic amyotrophic lateral sclerosis (ALS) is still unclear. We evaluate environmental factors suspected to be associated with ALS for their potential linkage to disease causality and to model geographic distributions of susceptible populations and expected cases worldwide. A PRISMA systematic literature review was performed 2021. Bradford Hill criteria were used to identify and rank environmental factors and a secondary review of ALS diagnoses in population studies and ALS case or cohort studies was conducted. Prevalence rate projection informed estimates of impacted regions and populations. Among 1710 papers identified, 258 met the inclusion criteria, of which 173 responded to at least one of nine Bradford Hill criteria among 83 literature-identified ALS environmental factors. Environmental determinants of ALS in order of decreasing significance were β-N-methylamino-L-alanine (BMAA), formaldehyde, selenium, and heavy metals including manganese, mercury, zinc, and copper. Murine animal models were the most common methodology for exploring environmental factors. Another line of investigation of 62 population exposure studies implicated the same group of environmental agents (mean odds ratios): BMAA (2.32), formaldehyde (1.54), heavy metals (2.99), manganese (3.85), mercury (2.74), and zinc (2.78). An age-adjusted incidence model estimated current total ALS cases globally at ~85,000 people compared to only ~1600 cases projected from the reported ALS incidence in the literature. Modeling with the prevalence microscope equation forecasted an increase in U.S. ALS cases from 16,707 confirmed in 2015 to ~22,650 projected for 2040. Two orthogonal methods employed implicate BMAA, formaldehyde, manganese, mercury, and zinc as environmental factors with strong ALS associations. ALS cases likely are significantly underreported globally, and high vulnerability exists in regions with large aging populations. Recent studies on other diseases with environmental determinants suggest the need to consider additional potential triggers and mechanisms, including exposures to microbial agents and epigenetic modifications.

Integrating Environment and Aging Research: Opportunities for Synergy and Acceleration

Despite significant overlaps in mission, the fields of environmental health sciences and aging biology are just beginning to intersect. It is increasingly clear that genetics alone does not predict an individual’s neurological aging and sensitivity to disease. Accordingly, aging neuroscience is a growing area of mutual interest within environmental health sciences. The impetus for this review came from a workshop hosted by the National Academies of Sciences, Engineering, and Medicine in June of 2020, which focused on integrating the science of aging and environmental health research. It is critical to bridge disciplines with multidisciplinary collaborations across toxicology, comparative biology, epidemiology to understand the impacts of environmental toxicant exposures and age-related outcomes. This scoping review aims to highlight overlaps and gaps in existing knowledge and identify essential research initiatives. It begins with an overview of aging biology and biomarkers, followed by examples of synergy with environmental health sciences. New areas for synergistic research and policy development are also discussed. Technological advances including next-generation sequencing and other-omics tools now offer new opportunities, including exposomic research, to integrate aging biomarkers into environmental health assessments and bridge disciplinary gaps. This is necessary to advance a more complete mechanistic understanding of how life-time exposures to toxicants and other physical and social stressors alter biological aging. New cumulative risk frameworks in environmental health sciences acknowledge that exposures and other external stressors can accumulate across the life course and the advancement of new biomarkers of exposure and response grounded in aging biology can support increased understanding of population vulnerability. Identifying the role of environmental stressors, broadly defined, on aging biology and neuroscience can similarly advance opportunities for intervention and translational research. Several areas of growing research interest include expanding exposomics and use of multi-omics, the microbiome as a mediator of environmental stressors, toxicant mixtures and neurobiology, and the role of structural and historical marginalization and racism in shaping persistent disparities in population aging and outcomes. Integrated foundational and translational aging biology research in environmental health sciences is needed to improve policy, reduce disparities, and enhance the quality of life for older individuals.

Taurine-Derived Compounds Produce Anxiolytic Effects in Rats Following Developmental Lead Exposure

Lead (Pb2+) is a developmental neurotoxicant that disrupts the GABA-shift and subsequently causes alterations in the brain's excitation-to-inhibition (E/I) balance. Taurine is a well-established neuroprotective and inhibitory compound for regulating brain excitability. Since mechanistically taurine can facilitate neuronal inhibition through the GABA-AR, the present study examined the anxiolytic potential of taurine derivatives. Treatment groups consisted of the following developmental Pb2+-exposures: Control (0 ppm) and Perinatal (150 ppm or 1,000 ppm lead acetate in the drinking water). Rats were scheduled for behavioral tests between postnatal days (PND) 36-45 with random drug assignments to either saline, taurine, or taurine-derived compound (TD-101, TD-102, or TD-103) to assess the rats' responsivity to each drug in mitigating the developmental Pb2+-exposure and anxiety-like behaviors through the GABAergic system. Long-Evans hooded rats were assessed using an open field (OF) test for preliminary locomotor assessment. Twenty-four hours later, the same rats were exposed to the elevated plus maze (EPM) and were given an i.p. injection of 43 mg/Kg of the saline, taurine, or TD drugs 15 min prior to testing. Each rat was tested using the triple-blind random assignment method for each drug condition. The OF data revealed that Control female rats had increased locomotor activity over Control male rats, and the Pb2+-exposed males and females had increased locomotor activity when compared to the Control male and female rats. However, in the EPM, the Control female rats exhibited more anxiety-like behaviors over Control male rats, and the Pb2+-exposed male and female rats showed selective responsivity to TD drugs when compared to taurine. For Pb2+-exposed males, TD-101 showed consistent recovery of anxiety-like behaviors similar to that of taurine regardless of Pb2+ dose, whereas in Pb2+-exposed females TD-101 and TD-103 showed greater anxiolytic responses in the EPM. The results from the present psychopharmacological study suggests that taurine and its derivatives are interesting drug candidates to explore sex-specific mechanisms and actions of taurine and the associated GABAergic receptor properties by which these compounds alleviate anxiety as a potential behavioral pharmacotherapy for neurodevelopmental Pb2+ exposure.

Early environmental exposures and life-long risk of chronic non-respiratory disease

Exposure to environmental hazards occurs from the earliest stages of development. There are a broad range of environmental hazards, and virtually all children are exposed to these hazards during the critical period of growth and development. The burden of many chronic diseases continues to rise, and life course studies have shown that early exposure to environmental hazards is associated with non-communicable disease in later years. This review will discuss the environmental exposures associated with four non-respiratory chronic diseases: obesity, diabetes, cardiovascular disease and neurodevelopmental /neurodegenerative conditions.

Plant Polyphenols: Potential Antidotes for Lead Exposure

Lead is one of the most common heavy metal elements and has high biological toxicity. Long-term lead exposure will induce the contamination of animal feed, water, and food, which can cause chronic lead poisoning including nephrotoxicity, hepatotoxicity, neurotoxicity, and reproductive toxicity in humans and animals. In the past few decades, lead has caused widespread concern because of its significant threat to health. A large number of in vitro and animal experiments have shown that oxidative stress plays a key role in lead toxicity, and endoplasmic reticulum (ER) stress and the mitochondrial apoptosis pathway can also be induced by lead toxicity. Therefore, plant polyphenols have attracted attention, with their advantages of being natural antioxidants and having low toxicity. Plant polyphenols can resist lead toxicity by chelating lead with their special chemical molecular structure. In addition, scavenging active oxygen and improving the level of antioxidant enzymes, anti-inflammatory, and anti-apoptosis are also the key to relieving lead poisoning by plant polyphenols. Various plant polyphenols have been suggested to be useful in alleviating lead toxicity in animals and humans and are believed to have good application prospects.

Genome-wide DNA methylation of the liver reveals delayed effects of early-life exposure to 17-α-ethinylestradiol in the self-fertilizing mangrove rivulus

Organisms exposed to endocrine disruptors in early life can show altered phenotype later in adulthood. Although the mechanisms underlying these long-term effects remain poorly understood, an increasing body of evidence points towards the potential role of epigenetic processes. In the present study, we exposed hatchlings of an isogenic lineage of the self-fertilizing fish mangrove rivulus for 28 days to 4 and 120 ng/L of 17-α-ethinylestradiol. After a recovery period of 140 days, reduced representation bisulphite sequencing (RRBS) was performed on the liver in order to assess the hepatic genome-wide methylation landscape. Across all treatment comparisons, a total of 146 differentially methylated fragments (DMFs) were reported, mostly for the group exposed to 4 ng/L, suggesting a non-monotonic effect of EE2 exposure. Gene ontology analysis revealed networks involved in lipid metabolism, cellular processes, connective tissue function, molecular transport and inflammation. The highest effect was reported for nipped-B-like protein B (NIPBL) promoter region after exposure to 4 ng/L EE2 (+ 21.9%), suggesting that NIPBL could be an important regulator for long-term effects of EE2. Our results also suggest a significant role of DNA methylation in intergenic regions and potentially in transposable elements. These results support the ability of early exposure to endocrine disruptors of inducing epigenetic alterations during adulthood, providing plausible mechanistic explanations for long-term phenotypic alteration. Additionally, this work demonstrates the usefulness of isogenic lineages of the self-fertilizing mangrove rivulus to better understand the biological significance of long-term alterations of DNA methylation by diminishing the confounding factor of genetic variability.

Alterations in gene expression due to chronic lead exposure induce behavioral changes

Lead (Pb) is a pollutant commonly found in the environment, despite the implementation of public health policies intended to remove it. Due to its chemical characteristics as a divalent ion, Pb interacts with cells, enzymes, and tissues, causing pathological, physical, and behavioral alterations. Recent biotechnological advances have helped us to understand the mechanisms underlying the damage caused by Pb in human populations and in experimental models, and new evidence on the epigenetic alterations caused by exposition to environmental Pb is available. It is known that Pb exposure impacts on behavior (causing aggressiveness, anxiety, and depression), leading to learning deficit and locomotor activity alterations, and its presence has been linked with the abnormal release of neurotransmitters and other biochemical changes involved in these disorders. Still, further reductionist studies are required to determine the effects of Pb exposure on DNA and protein expression and understand the processes underlying the diseases caused by Pb. This will also indicate possible therapeutic targets to offset the negative effects of the heavy metal. By elucidating the epigenetic changes involved, it would be possible to manipulate them and propose novel therapeutic approaches in this area. This review is aimed to provide an overview of studies that link Pb exposure to behavioral changes, as well as biochemical and epigenetic alterations at a neurotransmitter level, considering the importance of this metal in behavior abnormalities.

Response of Saccharomyces cerevisiae W303 to Iron and Lead Toxicity in Overloaded Conditions

Yeast Saccharomyces cerevisiae is an ideal model organism for studying molecular mechanisms of the stress response provoked by metals. In this work, yeast cells response to iron (Fe³⁺) or lead (Pb²⁺) exposure was tested and compared. Survival test was used to determine testing doses of metal ions-for Fe³⁺ it was 4 mM and for Pb²⁺ 8 mM. These (high, over-loaded) doses provoked comparable values of growth inhibition, but different values in vitality measurement. The percentage of metabolically active cells, determined by fluorescent FUN-1 dye, was lower in Pb²⁺ than in Fe³⁺ treated cells. Besides, endogenous antioxidant defence systems in the cells treated with Pb²⁺ were less efficient compared to Fe³⁺. At the mitochondrial level, the effects of metal ions were in correlation with the results of cell metabolic activity. The mitochondrial proteome of Pb²⁺ treated cells showed the domination of protein downregulation. Yeast cells treated either with Fe³⁺ or Pb²⁺ shared 19 common significantly changed proteins. The affected proteins were involved in different cellular process and amongst them only five proteins belong to energy and carbohydrate metabolism, and protein biosynthesis. Based on all obtained results, it is possible to conclude that the effects of Fe³⁺ and Pb²⁺ on yeast cells show rather specific patterns of toxicity and stress response.

Heavy metals levels in raw cow milk and health risk assessment across the globe: A systematic review

This systematic review presents the potential toxicity of heavy metals such as lead (Pb), mercury (Hg), cadmium (Cd), iron (Fe), nickel (Ni), aluminum (Al), and copper (Cu) in raw cow milk, focusing on their contamination sources and on the assessment of the related human health risk. Multiple keywords such as "raw cow milk, heavy metals, and human health" were used to search in related databases. A total of 60 original articles published since 2010 reporting the levels of these metals in raw cow's milk across the world were reviewed. Data showed that the highest levels of Ni (833 mg/L), Pb (60 mg/L), Cu (36 mg/L) were noticed in raw cow milk collected in area consists of granites and granite gneisses in India, while the highest level of Cd (12 mg/L) was reported in barite mining area in India. Fe values in raw cow milk samples were above the WHO maximum limit (0.37 mg/L) with highest values (37.02 mg/L) recorded in India. The highest Al level was (22.50 mg/L) reported for raw cow's milk collected close to food producing plants region in Turkey. The Target Hazard Quotients (THQ) values of Hg were below 1 suggesting that milk consumers are not at a non-carcinogenic risk except in Faisalabad province (Pakistan) where THQ values = 7.7. For the other heavy metals, the THQ values were >1 for Pb (10 regions out of 70), for Cd (6 regions out of 59), for Ni (3 out of 29), and for Cu (3 out of 54). Exposure to heavy metals is positively associated with diseases developments. Moreover, data actualization and continuous monitoring are necessary and recommended to evaluate heavy metals effects in future studies.

(Ascorb)ing Pb Neurotoxicity in the Developing Brain

Lead (Pb) neurotoxicity is a major concern, particularly in children. Developmental exposure to Pb can alter neurodevelopmental trajectory and has permanent neuropathological consequences, including an increased vulnerability to further stressors. Ascorbic acid is among most researched antioxidant nutrients and has a special role in maintaining redox homeostasis in physiological and physio-pathological brain states. Furthermore, because of its capacity to chelate metal ions, ascorbic acid may particularly serve as a potent therapeutic agent in Pb poisoning. The present review first discusses the major consequences of Pb exposure in children and then proceeds to present evidence from human and animal studies for ascorbic acid as an efficient ameliorative supplemental nutrient in Pb poisoning, with a particular focus on developmental Pb neurotoxicity. In doing so, it is hoped that there is a revitalization for further research on understanding the brain functions of this essential, safe, and readily available vitamin in physiological states, as well to justify and establish it as an effective neuroprotective and modulatory factor in the pathologies of the nervous system, including developmental neuropathologies.

The Chemical Exposome of Human Aging

Aging is an inevitable biological phenomenon displayed by single cells and organs to entire organismal systems. Aging as a biological process is characterized as a progressive decline in intrinsic biological function. Understanding the causative mechanisms of aging has always captured the imagination of researchers since time immemorial. Although both biological and chronological aging are well defined and studied in terms of genetic, epigenetic, and lifestyle predispositions, the hallmarks of aging in terms of small molecules (i.e., endogenous metabolites to chemical exposures) are limited to obscure. On top of the endogenous metabolites leading to the onset and progression of healthy aging, human beings are constantly exposed to a natural and anthropogenic "chemical" environment round the clock, from conception till death, affecting one's physiology, health and well-being, and disease predisposition. The research community has started gaining sizeable insights into deciphering the aging factors such as immunosenescence, nutrition, frailty, inflamm-aging, and diseases till date, without much input from their interaction with exogenous chemical exposures. The "exposome" around us, mostly, accelerates the process of aging by affecting the internal biological pathways and signaling mechanisms that result in the deterioration of human health. However, the entirety of exposome on human aging is far from established. This review intends to catalog the known and established associations of the exposome from past studies focusing on aging in humans and other model organisms. Further discussed are the current technologies and informatics tools that enable the study of aging exposotypes, and thus, provide a window of opportunities and challenges to study the "aging exposome" in granular details.

Association of Childhood Lead Exposure With MRI Measurements of Structural Brain Integrity in Midlife

IMPORTANCE

Childhood lead exposure has been linked to disrupted brain development, but long-term consequences for structural brain integrity are unknown.

OBJECTIVE

To test the hypothesis that childhood lead exposure is associated with magnetic resonance imaging (MRI) measurements of lower structural integrity of the brain in midlife.

DESIGN, SETTING, AND PARTICIPANTS

The Dunedin Study followed a population-representative 1972-1973 birth cohort in New Zealand (N = 564 analytic sample) to age 45 years (until April 2019).

EXPOSURES

Childhood blood lead levels measured at age 11 years.

MAIN OUTCOMES AND MEASURES

Structural brain integrity at age 45 years assessed via MRI (primary outcomes): gray matter (cortical thickness, surface area, hippocampal volume), white matter (white matter hyperintensities, fractional anisotropy [theoretical range, 0 {diffusion is perfectly isotropic} to 100 {diffusion is perfectly anisotropic}]), and the Brain Age Gap Estimation (BrainAGE), a composite index of the gap between chronological age and a machine learning algorithm-estimated brain age (0 indicates a brain age equivalent to chronological age; positive and negative values represent an older and younger brain age, respectively). Cognitive function at age 45 years was assessed objectively via the Wechsler Adult Intelligence Scale IV (IQ range, 40-160, standardized to a mean of 100 [SD, 15]) and subjectively via informant and self-reports (z-score units; scale mean, 0 [SD, 1]).

RESULTS

Of 1037 original participants, 997 were alive at age 45 years, of whom 564 (57%) had received lead testing at age 11 years (302 [54%] male) (median follow-up, 34 [interquartile range, 33.7-34.7] years). Mean blood lead level at age 11 years was 10.99 (SD, 4.63) μg/dL. After adjusting for covariates, each 5-μg/dL higher childhood blood lead level was significantly associated with 1.19-cm2 smaller cortical surface area (95% CI, -2.35 to -0.02 cm2; P = .05), 0.10-cm3 smaller hippocampal volume (95% CI, -0.17 to -0.03 cm3; P = .006), lower global fractional anisotropy (b = -0.12; 95% CI, -0.24 to -0.01; P = .04), and a BrainAGE index 0.77 years older (95% CI, 0.02-1.51 years; P = .05) at age 45 years. There were no statistically significant associations between blood lead level and log-transformed white matter hyperintensity volume (b = 0.05 log mm3; 95% CI, -0.02 to 0.13 log mm3; P = .17) or mean cortical thickness (b = -0.004 mm; 95% CI, -0.012 to 0.004 mm; P = .39). Each 5-μg/dL higher childhood blood lead level was significantly associated with a 2.07-point lower IQ score at age 45 years (95% CI, -3.39 to -0.74; P = .002) and a 0.12-point higher score on informant-rated cognitive problems (95% CI, 0.01-0.23; P = .03). There was no statistically significant association between childhood blood lead levels and self-reported cognitive problems (b = -0.02 points; 95% CI, -0.10 to 0.07; P = .68).

CONCLUSIONS AND RELEVANCE

In this longitudinal cohort study with a median 34-year follow-up, higher childhood blood lead level was associated with differences in some MRI measures of brain structure that suggested lower structural brain integrity in midlife. Because of the large number of statistical comparisons, some findings may represent type I error.

Epigenetic Basis of Lead-Induced Neurological Disorders

Environmental lead (Pb) exposure is closely associated with pathogenesis of a range of neurological disorders, including Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), attention deficit/hyperactivity disorder (ADHD), etc. Epigenetic machinery modulates neural development and activities, while faulty epigenetic regulation contributes to the diverse forms of CNS (central nervous system) abnormalities and diseases. As a potent epigenetic modifier, lead is thought to cause neurological disorders through modulating epigenetic mechanisms. Specifically, increasing evidence linked aberrant DNA methylations, histone modifications as well as ncRNAs (non-coding RNAs) with AD cases, among which circRNA (circular RNA) stands out as a new and promising field for association studies. In 23-year-old primates with developmental lead treatment, Zawia group discovered a variety of epigenetic changes relating to AD pathogenesis. This is a direct evidence implicating epigenetic basis in lead-induced AD animals with an entire lifespan. Additionally, some epigenetic molecules associated with AD etiology were also known to respond to chronic lead exposure in comparable disease models, indicating potentially interlaced mechanisms with respect to the studied neurotoxic and pathological events. Of note, epigenetic molecules acted via globally or selectively influencing the expression of disease-related genes. Compared to AD, the association of lead exposure with other neurological disorders were primarily supported by epidemiological survey, with fewer reports connecting epigenetic regulators with lead-induced pathogenesis. Some pharmaceuticals, such as HDAC (histone deacetylase) inhibitors and DNA methylation inhibitors, were developed to deal with CNS disease by targeting epigenetic components. Still, understandings are insufficient regarding the cause–consequence relations of epigenetic factors and neurological illness. Therefore, clear evidence should be provided in future investigations to address detailed roles of novel epigenetic factors in lead-induced neurological disorders, and efforts of developing specific epigenetic therapeutics should be appraised.

Occupational Lead Exposure and Brain Tumors: Systematic Review and Meta-Analysis

(1) Background: Due to inconsistencies in epidemiological findings, there has been uncertainty regarding the association of lead compounds with brain tumors. We performed a meta-analysis of published case-control and cohort studies exploring lead compound exposure and brain tumor risk. (2) Methods: We searched PubMed, Embase^®, and Cochrane to find eligible studies. Eighteen studies were selected for assessment of occupational exposure to lead compound and brain tumor. Pooled estimates of odds ratios (ORs) were obtained using random effects models. We assessed the differences through subgroup analysis according to tumor type, study design, measurements of exposure, and tumor outcome. Statistical tests for publication bias, heterogeneity, and sensitivity analysis were applied. (3) Results: Our systematic review and meta-analysis showed a not significant association with lead exposure and risk of benign and malignant brain tumors (pooled OR = 1.11, 95% Confidence Interval (CI): 0.95–1.29). Including only malignant brain tumors, the risk of brain tumor was significantly increased (pooled OR = 1.13, 95% CI: 1.04–1.24). (4) Conclusions: This meta-analysis provides suggestive evidence for an association between lead compound exposure and brain tumor. In future studies, it will be necessary to identify the effect of lead compounds according to the types of brain tumor.

Long-term probiotic intervention mitigates memory dysfunction through a novel H3K27me3-based mechanism in lead-exposed rats

Chronic lead exposure is associated with the development of neurodegenerative diseases, characterized by the long-term memory decline. However, whether this pathogenesis could be prevented through adjusting gut microbiota is not yet understood. To address the issue, pregnant rats and their female offspring were treated with lead (125 ppm) or separately the extra probiotics (10¹⁰ organisms/rat/day) till adulthood. For results, memory dysfunction was alleviated by the treatment of multispecies probiotics. Meanwhile, the gut microbiota composition was partially normalized against lead-exposed rats, which in turn mediated the memory repairment via fecal transplantation trials. In the molecular aspect, the decreased H3K27me3 (trimethylation of histone H3 Lys 27) in the adult hippocampus was restored with probiotic intervention, an epigenetic event mediated by EZH2 (enhancer of zeste homolog 2) at early developmental stage. In a neural cellular model, EZH2 overexpression showed the similar rescue effect with probiotics, whereas its blockade led to the neural re-damages. Regarding the gut-brain inflammatory mediators, the disrupted IL-6 (interleukin 6) expression was resumed by probiotic treatment. Intraperitoneal injection of tocilizumab, an IL-6 receptor antagonist, upregulated the hippocampal EZH2 level and consequently alleviated the memory injuries. In conclusion, reshaping gut microbiota could mitigate memory dysfunction caused by chronic lead exposure, wherein the inflammation-hippocampal epigenetic pathway of IL-6-EZH2-H3K27me3, was first proposed to mediate the studied gut-brain communication. These findings provided insight with epigenetic mechanisms underlying a unique gut-brain interaction, shedding light on the safe and non-invasive treatment of neurodegenerative disorders with environmental etiology.

DNA methylation profile is a quantitative measure of biological aging in children

DNA methylation changes within the genome can be used to predict human age. However, the existing biological age prediction models based on DNA methylation are predominantly adult-oriented. We established a methylation-based age prediction model for children (9-212 months old) using data from 716 blood samples in 11 DNA methylation datasets. Our elastic net model includes 111 CpG sites, mostly in genes associated with development and aging. The model performed well and exhibited high precision, yielding a 98% correlation between the DNA methylation age and the chronological age, with an error of only 6.7 months. When we used the model to assess age acceleration in children based on their methylation data, we observed the following: first, the aging rate appears to be fastest in mid-childhood, and this acceleration is more pronounced in autistic children; second, lead exposure early in life increases the aging rate in boys, but not in girls; third, short-term recombinant human growth hormone treatment has little effect on the aging rate of children. Our child-specific methylation-based age prediction model can effectively detect epigenetic changes and health imbalances early in life. This may thus be a useful model for future studies of epigenetic interventions for age-related diseases.

Autophagy delays progression of the two most frequent human monogenetic lethal diseases: cystic fibrosis and Wilson disease

Cystic fibrosis (CF) and Wilson disease (WD) are two monogenetic, recessively inherited lethal pathologies that are caused by ionic disequilibria. CF results from loss-of-function mutations in CF transmembrane conductance regulator (CFTR), a channel that conducts chloride across epithelial cell membranes, while WD is due to a deficiency of ATPase copper transporting beta (ATP7B), a plasma membrane protein that pumps out copper from cells. Recent evidence suggests that both diseases are linked to perturbations in autophagy. CFTR deficiency causes an inhibition of autophagic flux, thus locking respiratory epithelial cells in a pro-inflammatory state and subverting the bactericidal function of macrophages. WD is linked to an increase in autophagy, which, however, is insufficient to mitigate the cytotoxicity of copper. Pharmacological induction of autophagy may delay disease progression, as indicated by preclinical evidence (for CF and WD) and results from clinical trials, in particular in CF patients with the most frequent CTRT mutation (CFTRdel506). Thus, CF and WD exemplify pathologies in which insufficient autophagy plays a major role in determining the chronology of disease progression, much like the pace of 'normal' aging that is dictated by disabled autophagy as well.

Interplay of miR-137 and EZH2 contributes to the genome-wide redistribution of H3K27me3 underlying the Pb-induced memory impairment

Compromised learning and memory is a common feature of multiple neurodegenerative disorders. A paradigm spatial memory impairment could be caused by developmental lead (Pb) exposure. Growing evidence implicates epigenetic modifications in the Pb-mediated memory deficits; however, how histone modifications exemplified by H3K27me3 (H3 Lys27 trimethylation) contribute to this pathogenesis remains poorly understood. Here we found that Pb exposure diminished H3K27me3 levels in vivo by suppressing EZH2 (enhancer of zeste homolog 2) expression at an early stage. EZH2 overexpression in Pb-treated rats rescued the H3K27me3 abundance and partially restored the normal spatial memory, as manifested by the rat performance in a Morris water maze test, and structural analysis of hippocampal spine densities. Furthermore, miR-137 and EZH2 constitute mutually inhibitory loop to regulate the H3K27me3 level, and this feedback regulation could be specifically activated by Pb treatment. Considering genes targeted by H3K27me3, ChIP-chip (chromatin immunoprecipitation on chip) studies revealed that Pb could remodel the genome-wide distribution of H3K27me3, represented by pathways like transcriptional regulation, developmental regulation, cell motion, and apoptosis, as well as a novel Wnt9b locus. As a Wnt isoform associated with canonical and noncanonical signaling, Wnt9b was regulated by the opposite modifications of H3K4me3 (H3 Lys4 trimethylation) and H3K27me3 in Pb-exposed neurons. Rescue trials further validated the contribution of Wnt9b to Pb-induced neuronal impairments, wherein canonical or noncanonical Wnt signaling potentially exhibited destructive or protective roles, respectively. In summary, the study reveals an epigenetic-based molecular change underlying Pb-triggered spatial memory deficits, and provides new potential avenues for our understanding of neurodegenerative diseases with environmental etiology.

Long-term consequences of early postnatal lead exposure on hippocampal synaptic activity in adult mice

INTRODUCTION

Lead (Pb) exposure yielding blood lead levels (BLL) as low as 2 µg/dl in children is an international problem. More common in US low-income neighborhoods, childhood Pb exposure can cause behavioral and cognitive deficits, including working memory impairments, which can persist into adulthood. So far, studies characterized short-term effects of high Pb exposure on neuronal structure and function. However, long-term consequences of early chronic Pb exposure on neuronal activity are poorly documented.

METHODS

Here, we exposed male and female mice (PND [postnatal day] 0 to PND 28) to one of three Pb treatments: 0 ppm (sodium-treated water, control), 30 ppm (low dose), and 330 ppm (high dose) lead acetate. Once the male and female mice were 9-12 months old, extracellular field recordings on hippocampal slices were performed.

RESULTS

We show that at CA3 to CA1 synapses, synaptic transmission was decreased and neuronal fiber activity was increased in males exposed to lowest level Pb. In contrast, both synaptic transmission and neuronal fiber activity were increased in females exposed to high Pb. The ventral hippocampus-medial prefrontal cortex (vHPC-mPFC) synapses are crucial for working memory in rodents. The lowest level Pb decreased vHPC-mPFC synaptic transmission, whereas high Pb decreased short-term synaptic depression.

CONCLUSIONS

Overall, we show for the first time that early exposure to either high or lowest level Pb has long-term consequences on different synaptic properties of at least two hippocampal synapses. Such consequences of early Pb exposure might worsen the cognitive decline observed in aging men and women. Our results suggest that additional efforts should focus on the consequences of early Pb exposure especially in at-risk communities.

Childhood Lead Exposure and Adult Neurodegenerative Disease

Millions of Americans now entering midlife and old age were exposed to high levels of lead, a neurotoxin, as children. Evidence from animal-model and human observational studies suggest that childhood lead exposure may raise the risk of adult neurodegenerative disease, particularly dementia, through a variety of possible mechanisms including epigenetic modification, delayed cardiovascular and kidney disease, direct degenerative CNS injury from lead remobilized from bone, and lowered neural and cognitive reserve. Within the next ten years, the generation of children with the highest historical lead exposures, those born in the 1960s, 1970s, and 1980s, will begin to enter the age at which dementia symptoms tend to emerge. Many will also enter the age in which lead stored in the skeleton may be remobilized at greater rates, particularly for women entering menopause and men and women experiencing osteoporosis. Should childhood lead exposure prove pro-degenerative, the next twenty years will provide the last opportunities for possible early intervention to forestall greater degenerative disease burden across the aging lead-exposed population. More evidence is needed now to characterize the nature and magnitude of the degenerative risks facing adults exposed to lead as children and to identify interventions to limit long-term harm.

Animal Models and Their Contribution to Our Understanding of the Relationship Between Environments, Epigenetic Modifications, and Behavior

The use of non-human animals in research is a longstanding practice to help us understand and improve human biology and health. Animal models allow researchers, for example, to carefully manipulate environmental factors in order to understand how they contribute to development, behavior, and health. In the field of behavioral epigenetics such approaches have contributed novel findings of how the environment physically interacts with our genes, leading to changes in behavior and health. This review highlights some of this research, focused on prenatal immune challenges, environmental toxicants, diet, and early-life stress. In conjunction, we also discuss why animal models were integral to these discoveries and the translational relevance of these discoveries.

Epigenetics as a mechanism linking developmental exposures to long-term toxicity

A variety of experimental and epidemiological studies lend support to the Developmental Origin of Health and Disease (DOHaD) concept. Yet, the actual mechanisms accounting for mid- and long-term effects of early-life exposures remain unclear. Epigenetic alterations such as changes in DNA methylation, histone modifications and the expression of certain RNAs have been suggested as possible mediators of long-term health effects of environmental stressors. This report captures discussions and conclusions debated during the last Prenatal Programming and Toxicity meeting held in Japan. Its first aim is to propose a number of criteria that are critical to support the primary contribution of epigenetics in DOHaD and intergenerational transmission of environmental stressors effects. The main criteria are the full characterization of the stressors, the actual window of exposure, the target tissue and function, the specificity of the epigenetic changes and the biological plausibility of the linkage between those changes and health outcomes. The second aim is to discuss long-term effects of a number of stressors such as smoking, air pollution and endocrine disruptors in order to identify the arguments supporting the involvement of an epigenetic mechanism. Based on the developed criteria, missing evidence and suggestions for future research will be identified. The third aim is to critically analyze the evidence supporting the involvement of epigenetic mechanisms in intergenerational and transgenerational effects of environmental exposure and to particularly discuss the role of placenta and sperm. While the article is not a systematic review and is not meant to be exhaustive, it critically assesses the contribution of epigenetics in the long-term effects of environmental exposures as well as provides insight for future research.

Transgenerational epigenetics and environmental justice

Human transmission to offspring and future generations of acquired epigenetic modifications has not been definitively established, although there are several environmental exposures with suggestive evidence. This article uses three examples of hazardous substances with greater exposures in vulnerable populations: pesticides, lead, and diesel exhaust. It then considers whether, if there were scientific evidence of transgenerational epigenetic inheritance, there would be greater attention given to concerns about environmental justice in environmental laws, regulations, and policies at all levels of government. To provide a broader perspective on environmental justice the article discusses two of the most commonly cited approaches to environmental justice. John Rawls's theory of justice as fairness, a form of egalitarianism, is frequently invoked for the principle that differential treatment of individuals is justified only if actions are designed to benefit those with the greatest need. Another theory, the capabilities approach of Amartya Sen and Martha Nussbaum, focuses on whether essential capabilities of society, such as life and health, are made available to all individuals. In applying principles of environmental justice the article considers whether there is a heightened societal obligation to protect the most vulnerable individuals from hazardous exposures that could adversely affect their offspring through epigenetic mechanisms. It concludes that unless there were compelling evidence of transgenerational epigenetic harms, it is unlikely that there would be a significant impetus to adopt new policies to prevent epigenetic harms by invoking principles of environmental justice.

Immunological effects of occupational exposure to lead (Review)

It is well-known that occupational and environmental exposure to several factors, including benzene, heavy metals, chemicals and mineral fibers, is associated with the risk of developing a great number of diseases. Numerous studies have been carried out in order to investigate the mechanisms of toxicity of these substances, with particular regard to the possible toxic effects on the immune system. However, little is known about the influence of heavy metals, such as lead, on the immune system in human populations. Lead is a heavy metal still used in many industrial activities. Human exposure to lead can induce various biological effects depending upon the level and duration of exposure, such as toxic effects on haematological, cardiovascular, nervous and reproductive systems. Several studies demonstrated that exposure to lead is associated to toxic effects also on the immune system, thus increasing the incidence of allergy, infectious disease, autoimmunity or cancer. However, the effects of lead exposure on the human immune system are not conclusive, mostly in occupationally exposed subjects; nevertheless some immunotoxic abnormalities induced by lead have been suggested. In particular, in vivo, in vitro and ex vivo lead is able to improve T helper 2 (Th2) cell development affecting Th1 cell proliferation. Further studies are required to better understand the mechanisms of lead immunotoxicity and the ability of lead to affect preferentially one type of immune response.

The Evolution of Epigenetics: From Prokaryotes to Humans and Its Biological Consequences

The evolution process includes genetic alterations that started with prokaryotes and now continues in humans. A distinct difference between prokaryotic chromosomes and eukaryotic chromosomes involves histones. As evolution progressed, genetic alterations accumulated and a mechanism for gene selection developed. It was as if nature was experimenting to optimally utilize the gene pool without changing individual gene sequences. This mechanism is called epigenetics, as it is above the genome. Curiously, the mechanism of epigenetic regulation in prokaryotes is strikingly different from that in eukaryotes, mainly higher eukaryotes, like mammals. In fact, epigenetics plays a significant role in the conserved process of embryogenesis and human development. Malfunction of epigenetic regulation results in many types of undesirable effects, including cardiovascular disease, metabolic disorders, autoimmune diseases, and cancer. This review provides a comparative analysis and new insights into these aspects.