Exposure to lead during critical windows of embryonic development: differential immunotoxic outcome based on stage of exposure and gender

Prenatal heavy metal exposure and pediatric asthma, allergic rhinitis, atopic dermatitis: a systematic review and meta-analysis

OBJECTIVE

We review the prevalence of allergic diseases in children across prenatal exposures to heavy metals.

METHODS

This systematic review and meta-analysis is registered in the PROSPERO database (CRD42023478471). A comprehensive search of PubMed, Web of Science, Medline and Cochrane library was conducted from the database inception until 31 October 2023. The Newcastle-Ottawa Quality Assessment Scale (NOS) was used to assess the quality of included studies. We used a random-effects model to summarize the effects from the studies.

RESULTS

A total of 16 studies were included, 120,065 mother-child pairs enrolled. The NOS scores indicated that the quality of the literature included in the study was of a high standard.

CONCLUSION

The final results indicate that prenatal exposure to Pb increased the incidence of wheeze and Eczema in infants, and exposure to Ni and CD increased the incidence of AD in infants.

The Exposure to Lead (Pb) Exacerbates Immunological Abnormalities in BTBR T+ Itpr3tf/J Mice through the Regulation of Signaling Pathways Relevant to T Cells

Autism spectrum disorder (ASD) is a common neurodevelopmental illness characterized by abnormal social interactions, communication difficulties, and repetitive and limited behaviors or interests. The BTBR T+ Itpr3tf/J (BTBR) mice have been used extensively to research the ASD-like phenotype. Lead (Pb) is a hazardous chemical linked to organ damage in the human body. It is regarded as one of the most common metal exposure sources and has been connected to the development of neurological abnormalities. We used flow cytometry to investigate the molecular mechanism behind the effect of Pb exposure on subsets of CD4+ T cells in the spleen expressing IFN-γ, T-bet, STAT1, STAT4, IL-9, IRF4, IL-22, AhR, IL-10, and Foxp3. Furthermore, using RT-PCR, we studied the effect of Pb on the expression of numerous genes in brain tissue, including IFN-γ, T-bet, STAT1, STAT4, IL-9, IRF4, IL-22, AhR, IL-10, and Foxp3. Pb exposure increased the population of CD4+IFN-γ+, CD4+T-bet+, CD4+STAT1+, CD4+STAT4+, CD4+IL-9+, CD4+IRF4+, CD4+IL-22+, and CD4+AhR+ cells in BTBR mice. In contrast, CD4+IL-10+ and CD4+Foxp3+ cells were downregulated in the spleen cells of Pb-exposed BTBR mice compared to those treated with vehicle. Furthermore, Pb exposure led to a significant increase in IFN-γ, T-bet, STAT1, STAT4, IL-9, IRF4, IL-22, and AhR mRNA expression in BTBR mice. In contrast, IL-10 and Foxp3 mRNA expression was significantly lower in those treated with the vehicle. Our data suggest that Pb exposure exacerbates immunological dysfunctions associated with ASD. These data imply that Pb exposure may increase the risk of ASD.

Prenatal Metal Exposure Alters the Placental Proteome in a Sex-Dependent Manner in Extremely Low Gestational Age Newborns: Links to Gestational Age

Prenatal exposure to toxic metals is associated with altered placental function and adverse infant and child health outcomes. Adverse outcomes include those that are observed at the time of birth, such as low birthweight, as well as those that arise later in life, such as neurological impairment. It is often the case that these adverse outcomes show sex-specific responses in relation to toxicant exposures. While the precise molecular mechanisms linking in utero toxic metal exposures with later-in-life health are unknown, placental inflammation is posited to play a critical role. Here, we sought to understand whether in utero metal exposure is associated with alterations in the expression of the placental proteome by identifying metal associated proteins (MAPs). Within the Extremely Low Gestational Age Newborns (ELGAN) cohort (n = 230), placental and umbilical cord tissue samples were collected at birth. Arsenic (As), cadmium (Cd), lead (Pb), selenium (Se), and manganese (Mn) concentrations were measured in umbilical cord tissue samples via ICP-MS/MS. Protein expression was examined in placental samples using an LC-MS/MS-based, global, untargeted proteomics analysis measuring more than 3400 proteins. MAPs were then evaluated for associations with pregnancy and neonatal outcomes, including placental weight and gestational age. We hypothesized that metal levels would be positively associated with the altered expression of inflammation/immune-associated pathways and that sex-specific patterns of metal-associated placental protein expression would be observed. Sex-specific analyses identified 89 unique MAPs expressed in female placentas and 41 unique MAPs expressed in male placentas. Notably, many of the female-associated MAPs are known to be involved in immune-related processes, while the male-associated MAPs are associated with intracellular transport and cell localization. Further, several MAPs were significantly associated with gestational age in males and females and placental weight in males. These data highlight the linkage between prenatal metal exposure and an altered placental proteome, with implications for altering the trajectory of fetal development.

Lead (Pb) exposure exacerbates behavioral and immune abnormalities by upregulating Th17 and NF-κB-related signaling in BTBR T+ Itpr3tf/J autistic mouse model

Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder that are characterized by abnormal social interaction impairments in communication and repetitive and restricted activities or interests. Even though the exact etiology of ASD remains unknown. Lead (Pb) is a toxin known to harm many organs in the body, it is one of the most ubiquitous metal exposures which is associated with neurological deficits. Previous studies have shown that the exposure to Pb may play a role in ASD. BTBR T⁺ Itpr3^tf/J (BTBR) mouse model is commonly used as a preclinical model for ASD. In this study, we investigated the effects of Pb exposure on sociability, self-grooming and marble burying behaviors tests in BTBR mice. We further examined the effects of Pb on IL-17A- RORγT-, STAT3-, NF-κB p65-, iNOS-, TLR-2- and TLR-4-producing CD45⁺ cells in spleen using flow cytometry. We also explored the effects of Pb on IL-17A, RORγT, STAT3, NF-κB p65, and TLR-2 mRNA expression in the brain tissue using RT-PCR analysis. Our results demonstrated that Pb exposure substantially increased repetitive behavior, marble burying and decrease social interactions in BTBR mice. In addition, in spleen cells, Pb exposure exaggerated CD45⁺IL-17A⁺, CD45⁺RORγT⁺, CD45⁺STAT3⁺, CD45⁺NF-κB p65⁺, CD45⁺iNOS⁺, CD45⁺TLR-2⁺ and CD45⁺TLR-4⁺ in BTBR mice. We also found that Pb significantly increased IL-17A, RORγT, STAT3, NF-κB p65, and TLR-2 mRNA in the brain tissue. Therefore, Pb exposure exacerbates behavioral and neuroimmune function in BTBR mice, suggesting a potentially strong role for Pb in ASD.

Joint association of prenatal bisphenol-A and phthalates exposure with risk of atopic dermatitis in 6-month-old infants

BACKGROUND

Prenatal exposure to bisphenol A (BPA) and phthalates could trigger immune response. Few studies have investigated the association between prenatal BPA and phthalate exposure and atopic dermatitis (AD) in infants.

OBJECTIVE

We aimed to clarify the joint association of prenatal exposure to BPA and phthalate metabolites with AD incidence in 6-month-old infants.

METHODS

We included 413 mother-child pairs from the Mothers and Children's Environmental Health (MOCEH) in a prospective birth cohort study. Maternal urinary BPA, mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP), mono-2-ethyl-5-oxohexyl phthalate (MEOHP), and mono-n-butyl phthalate (MnBP) concentrations were measured during early and late pregnancy. We applied the Bayesian kernel machine regression (BKMR) with probit regression to estimate the association of BPA and phthalate metabolites with AD incidence after adjusting for potential confounders. Individual association was estimated by differences in predicted probabilities comparing each individual chemical concentration at 75th versus 25th percentiles, while other chemicals were set at their median. Overall joint effect was estimated by differences in predicted probabilities comparing all chemical concentrations at 75th versus 25th percentiles.

RESULTS

Individual effect of MEHHP in late pregnancy was strongly associated with incident AD [Difference: 0.244 (95% credible interval: -0.066, 0.554)] in the model including both early and late exposures. Furthermore, we confirmed overall joint association of urinary BPA and phthalate metabolites during pregnancy with a higher risk of AD [0.347 (0.168, 0.526) for late pregnancy exposure, and 0.307 (0.094, 0.521) for both early and late pregnancy]. Additionally, the joint association was more prominent among girls than that in boys.

CONCLUSIONS

The joint association of prenatal exposure to BPA and phthalates could be associated with the incident AD in 6-month-old infants. Further studies are needed to confirm the synergistic effect of BPA and phthalate exposures on AD in children.

Microbiome First Medicine in Health and Safety

Microbiome First Medicine is a suggested 21st century healthcare paradigm that prioritizes the entire human, the human superorganism, beginning with the microbiome. To date, much of medicine has protected and treated patients as if they were a single species. This has resulted in unintended damage to the microbiome and an epidemic of chronic disorders [e.g., noncommunicable diseases and conditions (NCDs)]. Along with NCDs came loss of colonization resistance, increased susceptibility to infectious diseases, and increasing multimorbidity and polypharmacy over the life course. To move toward sustainable healthcare, the human microbiome needs to be front and center. This paper presents microbiome-human physiology from the view of systems biology regulation. It also details the ongoing NCD epidemic including the role of existing drugs and other factors that damage the human microbiome. Examples are provided for two entryway NCDs, asthma and obesity, regarding their extensive network of comorbid NCDs. Finally, the challenges of ensuring safety for the microbiome are detailed. Under Microbiome-First Medicine and considering the importance of keystone bacteria and critical windows of development, changes in even a few microbiota-prioritized medical decisions could make a significant difference in health across the life course.

Developmental lead exposure and adult criminal behavior: A 30-year prospective birth cohort study

Using a variety of research designs and measures of lead absorption, numerous studies link childhood lead exposure to a range of cognitive and behavioral deficits, including low IQ, impulsivity, juvenile delinquency, and criminal behavior in adolescence and early adulthood. In this study, we tested the association between multiple measures of blood lead concentration assessed in childhood with criminal behavior in adulthood and across the life-course. Prospective data from the Cincinnati Lead Study (CLS) included blood lead measures quarterly across the first 78 months of life and the number of times a person was arrested across the life-course (from age 18 to 33 years) and in later adulthood (age 27 to 33 years). Childhood blood lead concentration prospectively predicted variation in adult arrests and arrests over the life-course, indicating lead absorption is implicated in the etiology of crime-especially in geographic areas where environmental sources of lead are more prevalent and concentrated. Efforts to decrease lead exposure in both developed and developing countries should be part of a comprehensive strategy to reduce social dislocation and crime.

Prenatal heavy metal exposures and atopic dermatitis with gender difference in 6-month-old infants using multipollutant analysis

BACKGROUND

Prenatal exposure to heavy metals during critical developmental phases has been implicated in allergic phenotypes. However, few studies have been conducted on the gender-specific association of prenatal heavy metal exposure with atopic dermatitis (AD) in infants.

OBJECTIVE

To examine the gender-specific association of prenatal exposure to multiple heavy metals with AD incidence in 6-month-old infants using data from the Mothers and Children's Environmental Health (MOCEH).

METHODS

We evaluated 738 mother-child pairs from the MOCEH study, an ongoing prospective birth cohort. The concentrations of three heavy metals (lead, mercury and cadmium) in maternal blood samples were measured during early and late pregnancy. Each quartile of heavy metal concentration was used to consider the possible nonlinear association with AD. For assessing the multi-pollutant model, we constructed the multivariate regression model including all three heavy metals at both early and late pregnancy. Further, the group Lasso model was used to perform the variable selection with categorized exposures and assess the effect of multiple pollutants including their pairwise interactions.

RESULTS

A total of 200 incident cases of AD were diagnosed in 6-month-old infants. In the multivariate regression model of the boy group, adjusted odds ratios comparing the second, third and fourth quartile of lead exposure in boys with the first quartile were 1.83 (95% CI: 1.00, 3.38), 1.04 (0.91, 3.32) and 2.40 (1.18, 4.90), respectively. However, the only second quartile of lead exposure compared to first quartile was significantly associated with AD in girls. In addition, the results of the group Lasso model were similar with the results of multivariate regression model.

CONCLUSION

The results suggest that lead exposure in late pregnancy increases risk of AD in 6-month-old boys although the strength of association is weak. Further studies are needed to confirm the susceptibility window and gender differences in lead-induced AD.

Associations between prenatal and postnatal lead exposure and preschool children humoral and cellular immune responses

Studies have shown that lead exposure affected the immune function, but few studies have examined the relationships between in utero lead exposure, a sensitive period that is important for immune development, and later immune responses. To investigate the effects of prenatal and childhood lead exposure on the preschool-aged children's immune responses, a prospective birth cohort study was established in Wuhan, China, in which lead concentrations were analyzed in maternal urine during the third trimester and in plasma samples from children aged about 3 years. We assessed immune responses by measuring immune cytokines in the children's plasma (n = 326) and peripheral blood T lymphocyte subsets (n = 394) at 3 years of age. Each unit increase in maternal urinary lead concentration (μg/g creatinine) was associated with reduced IL-10 (β = -5.93%, 95%CI: -11.82%, -0.03%) and reduced IL-4 levels (β = -5.62%, 95%CI: -10.44%, -0.80%). Lead in children's plasma (μg/L) was associated with significant increase in TNF-α (β = 10.78%, 95%CI: 3.97%, 17.59%). No statistically significant relationship of childhood lead exposure with T lymphocyte subsets was observed. The study suggested prenatal and childhood lead exposure was associated with changes in preschool children's plasma cytokine levels.

Effects of glyphosate, cypermethrin, and chlorpyrifos on hematological parameters of the tegu lizard (Salvator merianae) in different embryo stages

Different studies have demonstrated effects of pesticides during embryo development in vertebrates and stage-dependent effects, but there is no information concerning this for Salvator merianae. We evaluated the effects of the herbicides Glyphosate Roundup (GLY-RU) and Glyphosate Panzer Gold (GLY-PZ); and the insecticides Chlorpyrifos (CPF) and Cypermethrin (CYP), and their complex mixtures, at different concentrations in hematological parameters of S. merianae embryos at two different development stages. The analyzed parameters were Total and Differential White Blood Cells Count, Heterophils/Lymphocytes index (H/L), Lobularity index, and Natural Antibodies (Nabs titres), as well as growth, embryo mortality and birth delay. Heterophils decreased in the intermediate concentrations tested of CYP and GLY-RU, in animals exposed at 33-days development. Lymphocytes increased in the intermediate concentration tested of GLY-RU, and the H/L index decreased in the maximum concentration tested of GLY-RU. NAbs titres increased in those animals exposed to the maximum CYP concentration tested. However, animals exposed at 3/5-days development showed no differences among treatments in most of the analyzed parameters, suggesting a stage-dependent response. Nevertheless, those animals exposed to GLY-PZ showed lower Nabs titres in relation to negative control. These results suggest effects on different hematological parameters related to the immune system of S. merianae, according to the used pesticide (herbicide or insecticide), its concentration and commercial formulation (GLY-RU or GLY-PZ), and the stages of development of the exposed animals. Our results reveal the importance of carrying out studies that evaluate the effects of permanent exposure of living beings and their environments to these toxics.

Evaluating the effects between metal mixtures and serum vaccine antibody concentrations in children: a prospective birth cohort study

BACKGROUND

Many populations are exposed to arsenic, lead, and manganese. These metals influence immune function. We evaluated the association between exposure to single and multiple metals, including arsenic, lead, and manganese, to humoral immunity as measured by antibody concentrations to diphtheria and tetanus toxoid among vaccinated Bangladeshi children. Additionally, we examined if this association was potentially mediated by nutritional status.

METHODS

Antibody concentrations to diphtheria and tetanus were measured in children's serum at age 5 (n = 502). Household drinking water was sampled to quantify arsenic (W-As) and manganese (W-Mn), whereas lead was measured in blood (B-Pb). Exposure samples were taken during pregnancy, toddlerhood, and early childhood. Multiple linear regression models (MLRs) with single or combined metal predictors were used to determine the association with antibody outcomes. MLR results were transformed to units of percent change in outcome per doubling of exposure to improve interpretability. Structural equation models (SEMs) were used to further assess exposure to metal mixtures. SEMs regressed a latent exposure variable (Metals), informed by all measured metal variables (W-As, W-Mn, and B-Pb), on a latent outcome variable (Antibody), informed by measured antibody variables (diphtheria and tetanus). Weight-for-age z-score (WFA) at age 5 was evaluated as a mediator.

RESULTS

Diphtheria antibody was negatively associated with W-As during pregnancy in MLR, but associations were attenuated after adjusting for W-Mn and B-Pb (- 2.9% change in diphtheria antibody per doubling in W-As, 95% confidence interval [CI]: - 7%, 1.5%). Conversely, pregnancy levels of B-Pb were positively associated with tetanus antibody, even after adjusting for W-As and W-Mn (13.3%, 95% CI: 1.7%, 26.3%). Overall, null associations were observed between W-Mn and antibody outcomes. Analysis by SEMs showed that the latent Metals mixture was significantly associated with the latent Antibody outcome (β = - 0.16, 95% CI: - 0.26, - 0.05), but the Metals variable was characterized by positive and negative loadings of W-As and B-Pb, respectively. Sex-stratified MLR and SEM analyses showed W-As and B-Pb associations were exclusive to females. Mediation by WFA was null, indicating Metals only had direct effects on Antibody.

CONCLUSIONS

We observed significant modulation of vaccine antibody concentrations among children with pregnancy and early life exposures to drinking water arsenic and blood lead. We found distinct differences by child sex, as only females were susceptible to metal-related modulations in antibody levels. Weight-for-age, a nutritional status proxy, did not mediate the association between the metal mixture and vaccine antibody.

Exposure to lead and vaccine-specific IgG titers in South African children participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE): A longitudinal study

BACKGROUND

While successes have been achieved in reducing global exposure to lead, few studies have investigated the potential health effects of low-level exposure (e.g. blood lead levels [BLLs] below the CDC reference level of 5 μg/dL), particularly among children from low- and middle-income countries. In addition, lead is immunotoxic in animals but human data on immune response to vaccines is limited. Our aim was to determine whether low-level exposure to lead is associated with humoral response to vaccines among rural South African children.

METHODS

We used data from the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE), a birth cohort study conducted in Limpopo, South Africa. BLLs were measured in whole blood collected at age 1 year and IgG titers for measles, tetanus and Haemophilus influenzae type B (Hib) were determined at age 3.5 years among 425 fully-vaccinated children.

RESULTS

BLLs were low (median = 1.90 μg/dL) and 94% of children had a BLL below 5 μg/dL. Overall, BLLs were associated with higher risks of having IgG titers below the protective limit for tetanus (RR = 1.88 per 10-fold increase; 95%CI = 1.08, 3.24) but not measles (RR = 1.02; 95%CI = 0.26, 3.95) or Hib (RR = 0.96; 95%CI = 0.54, 1.71). BLLs were also associated with low Hib IgG titers among children exposed to HIV in utero and with low measles IgG titers among females. In contrast, the association with measles IgG titers was positive among males.

CONCLUSION

Low-level exposure to lead may compromise the humoral response to vaccines. Children exposed to HIV in utero and females may be particularly susceptible.

Prenatal lead exposure and childhood executive function and behavioral difficulties in project viva

BACKGROUND

Lead is an established neurotoxicant and early life exposure to lead is associated with detrimental impacts on IQ and several neurobehavioral domains. Less is known, however, about effects of prenatal lead exposure below 5 μg/dL on executive function and on social, emotional and self-regulatory behaviors in childhood.

OBJECTIVES

To examine the association between prenatal lead exposure and childhood executive function and social, emotional and self-regulatory behaviors.

METHODS

We included 1006 mother-child pairs from the Project Viva prospective pre-birth cohort. We measured prenatal maternal lead in second-trimester erythrocytes. In mid-childhood (median 7.7 years), parents and teachers rated executive function related behaviors using the Behavior Rating Inventory of Executive Function (BRIEF) and behavioral difficulties using the Strengths and Difficulties Questionnaire (SDQ). We used multivariable linear regression models adjusted for maternal, paternal, and child characteristics and metal co-exposures.

RESULTS

Mean maternal erythrocyte lead concentration was 1.2 μg/dL (interquartile range [IQR] 0.8-1.5 μg /dL), equivalent to approximately 0.4 μg/dL in whole blood. In adjusted models, associations with parent and teacher-rated scales were largely null, although effect estimates were consistently positive, suggesting worse scores with increasing lead levels. For an IQR increase in lead, BRIEF Global Executive Composite (GEC) was 0.73 (95% CI: -0.06, 1.52) points higher for parent-rated scores and 0.42 (95% CI: -0.39, 1.23) points higher for teacher-rated scores. Associations were strongest for parent-rated BRIEF plan/organize (β = 0.85; 95% CI: 0.12, 1.59) and shift (β = 0.88; 95% CI: 0.01, 1.75) subscales, as well as the SDQ emotional problems subscale (β = 0.18; 95% CI: 0.03, 0.33).

DISCUSSION

In this cohort with lead levels commonly experienced by U.S. women, there were few statistically significant associations with childhood executive function and behavior. However, there was a trend of worse neurobehavioral scores with increasing prenatal lead concentrations, in particular for childhood emotional problems and capacity to plan/organize and shift. Our results highlight the importance of continuing efforts to eliminate lead exposure in the general population.

Dietary selenium supplementation alleviates immune toxicity in the hearts of chickens with lead-added drinking water

Lead (Pb) is an environmental pollutant and can damage organisms. Selenium (Se) can alleviate Pb poisoning. The present study aimed to investigate the alleviative effect of Se on Pb-induced immune toxicity in chicken hearts. One-hundred-and-eighty Hy-line male chickens were randomly divided into four groups at 7 days of age. The control group was offered a standard commercial diet (SD) and drinking water (DW); the Se group was offered SD supplemented with sodium selenite (SeSD) and DW; the Pb + Se group was offered SeSD and DW supplemented with lead acetate (PbDW); and the Pb group was offered SD and PbDW. Relative mRNA expression of inducible nitric oxide synthase (iNOS), interleukins (IL-2, IL-4, IL-6, IL-12β, IL-17 and IFN-γ), and heat shock proteins (HSP27, HSP40, HSP60, HSP70, and HSP90) were determined by means of quantitative real-time PCR. Relative protein expression of iNOS, HSP60, HSP70, and HSP90 was assessed, as well as nitric oxide (NO) content and iNOS activity in heart tissue. The results indicated a down-regulation of interleukin (IL)-2 and IFN-γ and an up-regulation of NO, iNOS, interleukins (IL-4, IL-6, IL-12β, IL-17), and heat shock proteins (HSP27, HSP40, HSP60, HSP70, and HSP90) in Pb-damaged hearts. Se alleviated all of the above Pb-induced changes. There were time-dependent effects on NO content, iNOS activity, and mRNA levels of iNOS, IL-2, IL-4, IL-6, IL-17, HSP27, HSP40, HSP60, HSP70, and HSP90 after Pb treatment in the chicken hearts. Se alleviated Pb-induced immune toxicity in the chicken hearts.

Hematological and immunological impairment following in-utero and postnatal exposure to aluminum sulfate in female offspring of albino rats

Aim: Aluminum (Al) is a ubiquitous element extensively utilized in many products like food additives, pharmaceuticals, and vaccines, but its hematotoxic and immunotoxic effects are not entirely clarified. The present study explored the developmental hematotoxic and immunotoxic properties of aluminum sulfate (AS) in rats' offspring. Methods: Forty female offspring (10 rats each) were given three incremental AS doses plus a control group, from conception through lactation and after weaning until reached eight weeks old (near adults). Spleen relative weights along with total and differential blood counts were evaluated. Spectroscopic Al levels in spleen and brain were analyzed. Three immunoglobulins (IgG, IgM, and IgE) and two cytokines, interferon-γ and tumor necrosis factor-α, were measured through the ELISA technique. Results: The results revealed a significant relative increase in splenic weights mostly observed in the highest AS dose treated group. Reduction in the total leukocytic count was noticed in the three AS treated groups with relative lymphocytosis. Additionally, a significant decline in RBCs counts and hemoglobin concentrations were recorded. Tumor necrosis factor-α was significantly elevated in the three Al treated groups, while, interferon- γ showed a non-significant reduction compared to the control group. A significant increment in IgG and decline in IgE concentrations with no change in IgM level among groups were observed. Conclusion: Perinatal AS exposure caused mostly non-linear dose-dependent hematotoxicity and immunological impairment especially for the acquired immunity either cellular or humoral. Further studies can examine the immunotoxic effect of Al on male offspring during different stages of immune development.

The effect of environmental lead exposure on human health and the contribution of inflammatory mechanisms, a review

Lead (Pb) pollution has been considered as a major threat for human health due to induction of inflammatory cascades in various tissues. The aim of present review is to summarize the literature on the effects of lead exposure on respiratory, neurologic, digestive, cardiovascular and urinary disorders and the role of inflammation as an underlying mechanism for these effects. Various databases such as ISI Web of Knowledge, Medline, PubMed, Scopus, Google Scholar and Iran Medex, were searched from 1970 to November 2017 to gather the required articles using appropriate keywords such as lead, respiratory disorders, neurologic disorders, digestive disorders, cardiovascular disorders, urinary disorders and inflammation. Disorders of various body systems and the role of inflammation due to lead exposure has been proven by various studies. These studies indicate that lead exposure may cause respiratory, neurologic, digestive, cardiovascular and urinary diseases. The results were also indicated the increased inflammatory cells and mediators due to lead exposure including cytokines and chemokines due to lead exposure which suggested to be the cause various organ disorders.

Sex-Dependent Impact of Low-Level Lead Exposure during Prenatal Period on Child Psychomotor Functions

The impact of exposure to lead on child neurodevelopment has been well established. However, sex differences in vulnerability are still not fully explained. We aimed at evaluating the effect of a low-level lead exposure, as measured between 20 to 24 weeks of pregnancy and in cord blood, on developmental scores up to 24 months of age in 402 children from the Polish Mother and Child Cohort (REPRO_PL). Additionally, sex-dependent susceptibility to lead at this very early stage of psychomotor development was assessed. The blood lead levels were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). In order to estimate the children’s neurodevelopment, the Bayley Scales of Infant and Toddler Development was applied. The geometric mean (GM) for blood lead level during 20–24 weeks of pregnancy was 0.99 ± 0.15 µg/dL and, in the cord blood, it was 0.96 ± 0.16 µg/dL. There was no statistically significant impact of lead exposure during prenatal period on the girls’ psychomotor abilities. Among the boys, we observed lower scores for cognitive functions, along with increasing cord blood lead levels (β = −2.07; p = 0.04), whereas the results for the language and motor abilities were not statistically significant (p > 0.05). Our findings show that fetal exposure to very low lead levels might affect early cognitive domain, with boys being more susceptible than girls. Education on health, higher public awareness, as well as intervention programs, along with relevant regulations, are still needed to reduce risks for the vulnerable population subgroups.

Recent advances on Toll-like receptor 4 modulation: new therapeutic perspectives

Activation or inhibition of TLR4 by small molecules will provide in the next few years a new generation of therapeutics. TLR4 stimulation (agonism) by high-affinity ligands mimicking lipid A gave vaccine adjuvants with improved specificity and efficacy that have been licensed and entered into the market. TLR4 inhibition (antagonism) prevents cytokine production at a very early stage; this is in principle a more efficient method to block inflammatory diseases compared to cytokines neutralization by antibodies. Advances in TLR4 modulation by drug-like small molecules achieved in the last years are reviewed. Recently discovered TLR4 agonists and antagonists of natural and synthetic origin are presented, and their mechanism of action and structure-activity relationship are discussed.

Enhanced thymocyte apoptosis induced by maternal undernutrition in late gestation results in declined mature T cells in rat fetal thymus

This study was designed to observe the effects of maternal food restriction (MFR) on the development of fetal thymus in different gestation periods. Timed pregnant rats were randomized into 3 groups: CN (free access to standard chow throughout gestation), MFR_0-21 (50% MFR throughout gestation), MFR_0-14 (50% MFR from gestational day (GD) 0 to GD14, early-mid gestation). Results showed that MFR during early-mid period had few impact on the fetal thymus and T cell subpopulations. However, MFR throughout gestation resulted in thymic atrophy, deceased frequency of both CD4⁺ and CD8⁺ single positive (SP) T cells and enhanced thymocyte apoptosis in fetus. Our results suggest the fetal thymus is more vulnerable to the adverse intrauterine environments in the late gestation period, and the decreased number of SP T cells could result from the enhanced thymocyte apoptosis.

Exposure to Low Levels of Lead in Utero and Umbilical Cord Blood DNA Methylation in Project Viva: An Epigenome-Wide Association Study

BACKGROUND

Early-life exposure to lead is associated with deficits in neurodevelopment and with hematopoietic system toxicity. DNA methylation may be one of the underlying mechanisms for the adverse effects of prenatal lead on the offspring, but epigenome-wide methylation data for low levels of prenatal lead exposure are lacking.

OBJECTIVES

We investigated the association between prenatal maternal lead exposure and epigenome-wide DNA methylation in umbilical cord blood nucleated cells in Project Viva, a prospective U.S.-based prebirth cohort with relatively low levels of lead exposure.

METHODS

Among 268 mother-infant pairs, we measured lead concentrations in red blood cells (RBC) from prenatal maternal blood samples, and using HumanMethylation450 Bead Chips, we measured genome-wide methylation levels at 482,397 CpG loci in umbilical cord blood and retained 394,460 loci after quality control. After adjustment for batch effects, cell types, and covariates, we used robust linear regression models to examine associations of prenatal lead exposure with DNA methylation in cord blood at epigenome-wide significance level [false discovery rate (FDR)<0.05].

RESULTS

The mean [standard deviation (SD)] maternal RBC lead level was 1.22 (0.63) μg/dL. CpG cg10773601 showed an epigenome-wide significant negative association with prenatal lead exposure (-1.4% per doubling increase in lead exposure; p=2.3×10-7) and was annotated to C-Type Lectin Domain Family 11, Member A (CLEC11A), which functions as a growth factor for primitive hematopoietic progenitor cells. In sex-specific analyses, we identified more CpGs with FDR<0.05 among female infants (n=38) than among male infants (n=2). One CpG (cg24637308), which showed a strong negative association with prenatal lead exposure among female infants (-4.3% per doubling increase in lead exposure; p=1.1×10-06), was annotated to Dynein Heavy Chain Domain 1 gene (DNHD1) which is highly expressed in human brain. Interestingly, there were strong correlations between blood and brain methylation for CpG (cg24637308) based on another independent set of samples with a high proportion of female participants.

CONCLUSION

Prenatal low-level lead exposure was associated with newborn DNA methylation, particularly in female infants. https://doi.org/10.1289/EHP1246.

Developmental toxicant exposure in a mouse model of Alzheimer’s disease induces differential sex-associated microglial activation and increased susceptibility to amyloid accumulation

As the resident macrophage of the central nervous system, microglia are thought to contribute to Alzheimer’s disease (AD) pathology through lack of neuroprotection. The role of immune dysfunction in AD may be due to disruption of regulatory signals for the activation of microglia that may occur early in development. We hypothesized that early toxicant exposure would systematically activate microglia, possibly reversing the pathological severity of AD. Offspring of a triple transgenic murine model for AD (3×TgAD) were exposed to a model neurotoxicant, lead acetate, from postnatal days (PND) 5–10. Our results indicated that female mice exposed to Pb had a greater and earlier incidence of amyloid burden within the hippocampus, coinciding with decreased markers of microglial activation at PND 50. Pb-exposed males had increased microglial activation at PND 50, as evidence by CD11b expression and microglial abundance, with no significant increase in amyloid burden at that time. There was greater amyloid burden at PND 90 and 180 in both male and female mice exposed to Pb compared with control. Together, these data suggest that activated microglia are neuroprotective against amyloid accumulation early in AD pathology, and that early exposure to Pb could increase susceptibility to later-life neurodegeneration. Likewise, females may be more susceptible to early-life microglial damage, and, subsequently, AD. Further investigation into the sex biased mechanisms by which microglial activation is altered by an early-life immune insult will provide critical insight into the temporal susceptibility of the developing neuroimmune system and its potential role in AD etiopathology.

The effects of neonicotinoid exposure on embryonic development and organ mass in northern bobwhite quail (Colinus virginianus)

Since their emergence in the early 1990s, neonicotinoid use has increased exponentially to make them the world's most prevalent insecticides. Although there has been considerable research concerning the lethality of neonicotinoids, their sub-lethal and developmental effects are still being explored, especially with regard to non-mammalian species. The goal of this research was to investigate the effects of the neonicotinoid imidacloprid on the morphological and physiological development of northern bobwhite quail (Colinus virginianus). Bobwhite eggs (n=390) were injected with imidacloprid concentrations of 0 (sham), 10, 50, 100, and 150mg/kg of egg mass, which was administered at day 0 (pre-incubation), 3, 6, 9, or 12 of growth. Embryos were dissected, weighed, staged, and examined for any overt structural deformities after 19days of incubation. The mass of the embryonic heart, liver, lungs and kidneys was also recorded. The majority of treatments produced no discernible differences in embryo morphology; however, in some instances, embryos were subject to increased frequency of anatomical deformity and altered organ masses. Some impacts were more pronounced in specific dosing periods, implying that there may be critical windows of development when embryos are more susceptible to neonicotinoid exposure. This investigation suggests that imidacloprid has the potential to impact bobwhite quail embryonic development and chick survival.

Alleviation of lead-induced oxidative stress and immune damage by selenium in chicken bursa of Fabricius

We investigated lead (Pb)-induced oxidative stress and immune damage in the chicken bursa of Fabricius (BF) and the ameliorative effect of selenium (Se). Seven-day-old male chickens were randomly divided into four groups and were provided standard diet and drinking water, Na₂SeO₃ added to the standard diet and drinking water, standard diet and (CH₃COO)₂Pb added to drinking water, and Na₂SeO₃ added to the standard diet and (CH₃COO)₂Pb added to drinking water for 30, 60, and 90 days. The presence of Pb inhibited total antioxidant capacity (T-AOC), glutathione peroxidase (GPx), glutathione S-transferase (GST), superoxide dismutase (SOD), and catalase (CAT) activities; decreased glutathione (GSH) content; increased malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents; inhibited interleukin (IL)-2 and interferon-γ (IFN-γ) messenger RNA (mRNA) expression; and increased IL-4, IL-6, IL-10, IL-12β, and IL-17 mRNA expression. The presence of Se relieved all of the above Pb-induced changes. There were close correlations among GSH, CAT, T-AOC, SOD, GPx, MDA, and H₂O₂ and among IL-2, IL-4, IL-6, IL-12β, IL-17, and IFN-γ. Our data showed that Pb caused oxidative stress and immune damage in the chicken BF. Se alleviated Pb-induced oxidative stress and immune damage in the chicken BF.

Effect of Lead (Pb) on Inflammatory Processes in the Brain

That the nervous system is the main target of lead (Pb) has long been considered an established fact until recent evidence has linked the Pb effect on the immune system to the toxic effects of Pb on the nervous system. In this paper, we present recent literature reports on the effect of Pb on the inflammatory processes in the brain, particularly the expression of selected cytokines in the brain (interleukin 6, TGF-β1, interleukin 16, interleukin 18, and interleukin 10); expression and activity of enzymes participating in the inflammatory processes, such as cyclooxygenase 2, caspase 1, nitrogen oxide synthase (NOS 2) and proteases (carboxypeptidases, metalloproteinases and chymotrypsin); and the expression of purine receptors P2X4 and P2X7. A significant role in the development of inflammatory processes in the brain is also played by microglia (residual macrophages in the brain and the spinal cord), which act as the first line of defense in the central nervous system, and astrocytes—Whose most important function is to maintain homeostasis for the proper functioning of neurons. In this paper, we also present evidence that exposure to Pb may result in micro and astrogliosis by triggering TLR4-MyD88-NF-κB signaling cascade and the production of pro-inflammatory cytokines.

Air Pollution During Pregnancy and Cord Blood Immune System Biomarkers

OBJECTIVES

We aimed to determine whether average and trimester-specific exposures to ambient measures of nitrogen dioxide (NO2) and particular matter (PM2.5) were associated with elevated cord blood concentrations of immunoglobulin E (IgE) and two epithelial cell produced cytokines: interleukin-33 (IL-33) and thymic stromal lymphopoietin (TSLP).

METHODS

This study utilized data and biospecimens from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study. There were 2001 pregnant women recruited between 2008 and 2011 from 10 Canadian cities. Maternal exposure to NO2 and PM2.5 was estimated using land use regression and satellite-derived models.

RESULTS

We observed statistically significant associations between maternal NO2 exposure and elevated cord blood concentrations of both IL-33 and TSLP among girls but not boys.

CONCLUSIONS

Maternal NO2 exposure may impact the development of the newborn immune system as measured by cord blood concentrations of two cytokines.

Protective and ameliorative effect of sea buckthorn leaf extract supplementation on lead induced hemato-biochemical alterations in Wistar rats

Aim:

To evaluate the protective and ameliorative effect of aqueous sea buckthorn leaf extract (SLE) on hemato-biochemical profile in lead intoxicated Wistar rats.

Materials and Methods:

An experiment was conducted for 60 days. 36 adult male Wistar rats with a mean body weight of 177.8±12.6 g were divided into five groups and were subjected to various daily oral treatment regimens. Group I served as a negative control receiving only feed and water, Group II (positive control for lead) received lead acetate at 250 ppm in drinking water, and Group III (positive control for SLE) received SLE at 100 mg/kg b.wt. Animals in Group IV received a combination of lead acetate at 250 ppm in drinking water for the first 45 days and SLE at 100 mg/kg b.wt. throughout the experimental period of 60-day, and in Group V for the last 15 days of the trial after the administration of lead acetate until the first 45 days of the trial to study the protective and ameliorating effects of SLE, respectively. Blood samples were collected from retro-orbital fossa of each rat on 0^th, 45^th, and 60^th day of the experiment for hemato-biochemical analysis including hemoglobin (Hb), packed cell volume (PCV), serum total protein, albumin, globulin, albumin:globulin ratio, cholesterol, urea, and creatinine.

Results:

Significantly (p<0.01) lower levels of serum total proteins and albumin, and a significantly (p<0.01) higher serum cholesterol, urea and creatinine levels were observed in Group II (lead intoxicated group) in comparison to Group I (negative control). Administration of SLE at 100 mg/kg body wt. to lead intoxicated Wistar rats resulted in normalization of almost all the biochemical parameters studied in both the treatment Groups, i.e., IV and V (protective and ameliorative). However, the effects were more pronounced in the protective group. No effects of SLE supplementation were observed on Hb levels. PCV levels improved in protective groups, but no effect was observed in ameliorative group in comparison to lead intoxicated groups.

Conclusion:

SLE administration at 100 mg/kg b.wt. to lead intoxicated Wistar rats may be used to protect/ameliorate lead induced biochemical alterations in Wistar rats.

Original Research: The expression of MMP2 and MMP9 in the hippocampus and cerebral cortex of newborn mice under maternal lead exposure

The current study focused on the MMP2 and MMP9 expression in cerebral cortex and hippocampus of newborn mice under maternal lead exposure. Lead exposure was initiated from gestation to weaning. Lead acetate was dissolved in deionized water with concentration of 0.1, 0.2, and 0.5% and was absorbed through daily drinking. On day 21 after birth, lead in blood and tissue levels was examined by Graphite Furnace Atomic Absorption Spectrum (GFAAS). The protein expressions of MMP2 and MMP9 in hippocampus and cerebral cortex tissues were tested by western blotting and immunohistochemistry. Compared to the control group, blood, cerebral cortex, and hippocampus lead levels of newborn mice in 0.1, 0.2, and 0.5% lead exposure groups were markedly high (P < 0.05), and mice within the 0.2 and 0.5% lead exposure groups performed much worse than that of the control group in Water Maze test (P < 0.05). Compared with the control group, MMP2 and MMP9 expressions in hippocampus were up-regulated in the lead exposure groups (P < 0.05), and the MMP2 and MMP9 expressions in cerebral cortex were also higher (P < 0.05). The increased expression of MMP2 and MMP9 in the hippocampus and cerebral cortex may lead to the neurotoxicity in the context of maternal lead exposure.

Environmental factors in the development of autism spectrum disorders

Autism spectrum disorders (ASD) are highly heterogeneous developmental conditions characterized by deficits in social interaction, verbal and nonverbal communication, and obsessive/stereotyped patterns of behavior and repetitive movements. Social interaction impairments are the most characteristic deficits in ASD. There is also evidence of impoverished language and empathy, a profound inability to use standard nonverbal behaviors (eye contact, affective expression) to regulate social interactions with others, difficulties in showing empathy, failure to share enjoyment, interests and achievements with others, and a lack of social and emotional reciprocity. In developed countries, it is now reported that 1%-1.5% of children have ASD, and in the US 2015 CDC reports that approximately one in 45 children suffer from ASD. Despite the intense research focus on ASD in the last decade, the underlying etiology remains unknown. Genetic research involving twins and family studies strongly supports a significant contribution of environmental factors in addition to genetic factors in ASD etiology. A comprehensive literature search has implicated several environmental factors associated with the development of ASD. These include pesticides, phthalates, polychlorinated biphenyls, solvents, air pollutants, fragrances, glyphosate and heavy metals, especially aluminum used in vaccines as adjuvant. Importantly, the majority of these toxicants are some of the most common ingredients in cosmetics and herbicides to which almost all of us are regularly exposed to in the form of fragrances, face makeup, cologne, air fresheners, food flavors, detergents, insecticides and herbicides. In this review we describe various scientific data to show the role of environmental factors in ASD.

Decreased IDE and IGF2 expression but increased Aβ40 in the cerebral cortex of mouse pups by early life lead exposure

As the abbreviation of plumbum and a chemical symbol for lead, Pb produces neurotoxic effects, which result into an impairment of learning and memory and other neurological dysfunctions. However, the mechanism of neurotoxicity of Pb exposure is unclear. The present study was undertaken to investigate the effects of maternal lead exposure on expression of insulin-degrading enzyme (IDE),insulin-like growth factor 2 (IGF2) and beta amyloid protein 40 (Aβ40) in the cerebral cortex of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.2% and 0.5% groups respectively. On the 21st postnatal day, On the PND21, the learning and memory ability were tested by water maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IDE, IGF2 and Aβ40 in cerebral cortex was examined by immunohistochemistry, immunofluorescence and western blotting. The lead levels in blood and cerebral cortex of all lead exposure groups were significantly higher than that of the control group (P<0.05). In water maze test, the performances of 0.5% and 1% lead exposure groups were worse than that of the control group (P<0.05).The expression of IDE and IGF2 was decreased, but Aβ40 was increased in lead exposed groups than that of the control group (P<0.05). The decreased expression of IDE and IGF2 and increased expression of Aβ40 in the cerebral cortex of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

The Effects of Early Life Lead Exposure on the Expression of Glycogen Synthase Kinase-3β and Insulin-like Growth Factor 1 Receptor in the Hippocampus of Mouse Pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of GSK-3β and IGF1R in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1, 0.5, and 1%, respectively. On the 21st postnatal day, the Pb levels were determined by graphite furnace atomic absorption spectrometry. The expression of GSK-3β and IGF1R in hippocampus was examined by immunohistochemistry and Western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than those of the control group (P < 0.05). Compared with the control group, the expression of GSK-3β was increased in lead-exposed groups (P < 0.05), but the expression of IGF1R was decreased (P < 0.05). The high expression of GSK-3β and low expression of IGF1R in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Early-life Exposure to Widespread Environmental Toxicants and Health Risk: A Focus on the Immune and Respiratory Systems

Evidence has accumulated that exposure to widespread environmental toxicants, such as heavy metals, persistent organic pollutants, and tobacco smoke adversely affect fetal development and organ maturation, even after birth. The developing immune and respiratory systems are more sensitive to environmental toxicants due to their long-term physical development, starting from the early embryonic stage and persisting into early postnatal life, which requires complex signaling pathways that control proliferation and differentiation of highly heterogeneous cell types. In this review, we summarize the effect of early-life exposure to several widespread environmental toxicants on immune and lung development before and after birth, including the effects on immune cell counts, baseline characteristics of cell-mediated and humoral immunity, and alteration of lung structure and function in offspring. We also review evidence supporting the association between early-life exposure to environmental toxicants and risk for immune-related diseases and lung dysfunction in offspring in later life.

Long-term changes in brain cholinergic system and behavior in rats following gestational exposure to lead: protective effect of calcium supplement

Our earlier studies showed that lactational exposure to lead (Pb) caused irreversible neurochemical alterations in rats. The present study was carried out to examine whether gestational exposure to Pb can cause long-term changes in the brain cholinergic system and behavior of rats. The protective effect of calcium (Ca) supplementation against Pb toxicity was also examined. Pregnant rats were exposed to 0.2% Pb (Pb acetate in drinking water) from gestational day (GD) 6 to GD 21. The results showed decrease in body weight gain (GD 6-21) of dams, whereas no changes were observed in offspring body weight at different postnatal days following Pb exposure. Male offspring treated with Pb showed marginal alterations in developmental landmarks such as unfolding of pinnae, lower and upper incisor eruption, fur development, eye slit formation and eye opening on postnatal day (PND) 1, whereas significant alterations were found in the righting reflex (PNDs 4-7), slant board behavior (PNDs 8-10) and forelimb hang performance (PNDs 12-16). Biochemical analysis showed decrease in synaptosomal acetylcholinesterase (AChE) activity and an increase in acetylcholine (ACh) levels in the cortex, cerebellum and hippocampus on PND 14, PND 21, PND 28 and in the four-month age group of rats following Pb exposure. Significant deficits were also observed in total locomotor activity, exploratory behavior and open field behavior in selected age groups of Pb-exposed rats. These alterations were found to be maximal on PND 28, corresponding with the greater blood lead levels observed on PND 28. Addition of 0.02% Ca to Pb reversed the Pb-induced impairments in the cholinergic system as well as in behavioral parameters of rats. In conclusion, these data suggest that gestational exposure to Pb is able to induce long-term changes in neurological functions of offspring. Maternal Ca administration reversed these neurological effects of Pb later in life, suggesting a protective effect of calcium in Pb-exposed animals.

Histologic Features of Postnatal Development of Immune System Organs in the Sprague-Dawley Rat

The immune system of the rat undergoes substantial functional and morphological development during the postnatal period. Some aspects of this development are genetically predetermined, while other aspects depend on environmental influences. Detailed information on postnatal development is important in the interpretation of histopathologic findings in juvenile toxicology and pubertal assay studies, as well as other studies conducted in juvenile rats. Studies were conducted to provide detailed characterization of histologic features of the major functional compartments of immune system organs in male and female Sprague-Dawley rats at weekly intervals from the day of birth through postnatal day (PND) 42. Maturation of the individual immune system organs occurred across a range of ages, with histologic maturation of T-cell-related compartments typically occurring prior to maturation of B-cell-related compartments. The sequence of histologic maturation was bone marrow and thymus on PND 14, mesenteric lymph node on PND 21, Peyer's patches and bronchus-associated lymphoid tissue on PND 28, mandibular lymph node, nasopharynx-associated lymphoid tissue, and diffuse mucosal mononuclear cell population of small intestine on PND 35, and spleen on PND 42. An estimation of functional maturation can be made based on the morphological indications of maturity of each compartment of immune system organs, but histologic indications of maturity do not confirm functional immunocompetence.

Cross-fostering increases TH1/TH2 expression in a prenatal dexamethasone exposure rat model

BACKGROUND

Prenatal dexamethasone exposure has been reported to increase allergy potential in childhood possibly by interference with normal immunological development in utero. This study investigated the effects of prenatal dexamethasone on T helper cell immune responses in a rat model.

METHODS

Pregnant rats received either dexamethasone 0.1 mg/kg/day or normal saline from gestational day 14-21. Off-springs were cared for by their biological mother, or cross-fostered by the opposing group. Spleen and blood samples were collected at post-natal day 7 and 120 and tested for mRNA expression and plasma cytokine levels of Th1/Th2/Th17 immune response.

RESULTS

Both Th1 (T-bet) and Th2 (GATA-3) mRNA expression were shown to have a significant increase in the prenatal dexamethasone exposure group at day 120 (p<0.05). The plasma levels for Th1 (IFNγ and IL-2) and Th2 (IL-4, IL-5, IL-13) were found to have no significant differences between the two group (p>0.05). The mRNA expression of Th17 (RORγt) showed a significant decrease at post-natal day 120 as well as the plasma level of IL-17A at day 7 (11.21±1.67 vs. 6.23±1.06 pg/ml, p = 0.02). Cross-fostering by a dexamethasone exposed mother resulted in a significant increase in Th1/Th2 mRNA expression (p<0.05) and decrease of Th17.

CONCLUSIONS

Prenatal dexamethasone exposure increased Th1, Th2 and decreased Th17 expression. Cross-fostering by a dexamethasone exposed mother results in more prominent increase of Th1 and Th2 expression.

Lead exposure and increased food allergic sensitization in U.S. children and adults

BACKGROUND

Whether blood lead levels are associated with sensitization to food allergens in adults and children is unclear. Prior studies have shown that exposure to lead is associated with atopic sensitization and modulation of several cytokines (eg, interleukin [IL]-12, IL-10, interferon [IFN]-γ, and IL-4 production) and with T-cell dysregulation and bias toward T helper 2 (Th2) activity. The objective of this work was to assess whether exposure to lead is independently associated with allergic symptoms and sensitizations in a large nationally representative sample of children and adults.

METHODS

We studied 2712 children and 4333 adults enrolled in the 2005-2006 cycle of the National Health and Nutritional Examination Surveys (NHANES). Participants were tested for serum-specific immunoglobulin E (IgE) levels to food allergens as well as blood lead levels. Food allergens tested included shrimp, egg, peanut, and milk. Logistic regression models adjusted for demographic factors, body mass index, history of asthma, smoking, housing characteristics, and current exposure to animals in the home, to assess the association of blood lead levels with sensitization to food allergens.

RESULTS

Median (interquartile range [IQR]) for serum blood was 0.87 μg/L (0.61 to 1.31) in children and 1.48 μg/L (0.92 to 2.34) in adults. At baseline, 672 (24.7%) of children participants and 719 (16.6%) of adult participants tested positive for increased sensitization to food allergens. A 2-fold increase in blood lead levels in adult participants was associated with increased sensitization to food allergens (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.02 to 1.22). Blood lead was not associated with sensitization to food allergens among pediatric participants (OR, 0.95; 95% CI, 0.82 to 1.10).

CONCLUSION

Exposure to lead was associated with increased odds of sensitization to food allergens in adult but not children participants.

Olive leaf extract inhibits lead poisoning-induced brain injury

Olive leaves have an antioxidant capacity, and olive leaf extract can protect the blood, spleen and hippocampus in lead-poisoned mice. However, little is known about the effects of olive leaf extract on lead-induced brain injury. This study was designed to determine whether olive leaf extract can inhibit lead-induced brain injury, and whether this effect is associated with antioxidant capacity. First, we established a mouse model of lead poisoning by continuous intragastric administration of lead acetate for 30 days. Two hours after successful model establishment, lead-poisoned mice were given olive leaf extract at doses of 250, 500 or 1 000 mg/kg daily by intragastric administration for 50 days. Under the transmission electron microscope, olive leaf extract attenuated neuronal and capillary injury and reduced damage to organelles and the matrix around the capillaries in the frontal lobe of the cerebral cortex in the lead-poisoned mice. Olive leaf extract at a dose of 1 000 mg/kg had the greatest protective effect. Spectrophotometry showed that olive leaf extract significantly increased the activities of superoxide dismutase, catalase, alkaline phosphatase and acid phosphatase, while it reduced malondialdehyde content, in a dose-dependent manner. Furthermore, immunohistochemical staining revealed that olive leaf extract dose-dependently decreased Bax protein expression in the cerebral cortex of lead-poisoned mice. Our findings indicate that olive leaf extract can inhibit lead-induced brain injury by increasing antioxidant capacity and reducing apoptosis.

The effects of early life lead exposure on the expression of interleukin (IL) 1β, IL-6, and glial fibrillary acidic protein in the hippocampus of mouse pups

The present study was undertaken to investigate the effects of maternal lead (Pb) exposure on the expression of interleukin (IL) 1β, IL 6, and glial fibrillary acidic protein (GFAP) in hippocampus of mice offspring. Pb exposure initiated from the beginning of gestation to weaning. Lead acetate (PbAc) administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1, 0.5 and 1% groups ,respectively. On the postnatal day 21, the Pb levels in their blood and hippocampus were determined by graphite furnace atomic absorption spectrometry. The expression of IL 1β, IL 6, and GFAP in hippocampus was measured by immunohistochemistry and Western blotting. The Pb levels in blood and hippocampus of all Pb-exposed groups were significantly higher than that of the control group ( p < 0.05). The expression of IL-1β, IL-6, and GFAP was increased in Pb-exposed groups in comparison with the control group ( p < 0.05). The high expression of IL-1β, IL-6, and GFAP in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Differential immunotoxicity induced by two different windows of developmental trichloroethylene exposure

Developmental exposure to environmental toxicants may induce immune system alterations that contribute to adult stage autoimmune disease. We have shown that continuous exposure of MRL+/+ mice to trichloroethylene (TCE) from gestational day (GD) 0 to postnatal day (PND) 49 alters several aspects of CD4(+) T cell function. This window of exposure corresponds to conception-adolescence/young adulthood in humans. More narrowly defining the window of TCE developmental exposure causes immunotoxicity that would establish the stage at which avoidance and/or intervention would be most effective. The current study divided continuous TCE exposure into two separate windows, namely, gestation only (GD0 to birth (PND0)) and early-life only (PND0-PND49). The mice were examined for specific alterations in CD4(+) T cell function at PND49. One potentially long-lasting effect of developmental exposure, alterations in retrotransposon expression indicative of epigenetic alterations, was found in peripheral CD4(+) T cells from both sets of developmentally exposed mice. Interestingly, certain other effects, such as alterations in thymus cellularity, were only found in mice exposed to TCE during gestation. In contrast, expansion of memory/activation cell subset of peripheral CD4(+) T cells were only found in mice exposed to TCE during early life. Different windows of developmental TCE exposure can have different functional consequences.

Developmental Immunotoxicity, Perinatal Programming, and Noncommunicable Diseases: Focus on Human Studies

Developmental immunotoxicity (DIT) is a term given to encompass the environmentally induced disruption of normal immune development resulting in adverse outcomes. A myriad of chemical, physical, and psychological factors can all contribute to DIT. As a core component of the developmental origins of adult disease, DIT is interlinked with three important concepts surrounding health risks across a lifetime: (1) the Barker Hypothesis, which connects prenatal development to later-life diseases, (2) the hygiene hypothesis, which connects newborns and infants to risk of later-life diseases and, (3) fetal programming and epigenetic alterations, which may exert effects both in later life and across future generations. This review of DIT considers: (1) the history and context of DIT research, (2) the fundamental features of DIT, (3) the emerging role of DIT in risk of noncommunicable diseases (NCDs) and (4) the range of risk factors that have been investigated through human research. The emphasis on the human DIT-related literature is significant since most prior reviews of DIT have largely focused on animal research and considerations of specific categories of risk factors (e.g., heavy metals). Risk factors considered in this review include air pollution, aluminum, antibiotics, arsenic, bisphenol A, ethanol, lead (Pb), maternal smoking and environmental tobacco smoke, paracetamol (acetaminophen), pesticides, polychlorinated biphenyls, and polyfluorinated compounds.

The interactive effects of chytrid fungus, pesticides, and exposure timing on gray treefrog (Hyla versicolor) larvae

Aquatic organisms are often exposed to a wide variety of perturbations in nature, including pathogens and chemical contaminants. Despite the co-occurrence of these 2 stressors, few studies have examined the effects of chemical contaminants on host-pathogen dynamics. The authors tested the individual and combined effects on gray treefrog (Hyla versicolor) tadpoles of 2 commonly used pesticides (Roundup® and Sevin®) and the pathogenic fungus Batrachochytrium dendrobatidis (Bd). A fully factorial design was used, and tadpoles were exposed to Bd, Roundup, or Sevin alone, or a combination of Bd and either pesticide at 3 points during larval development (early, mid, late). It was predicted that pesticides would mediate the effect of Bd on tadpoles and reduce the likelihood of negative consequences of infection and that timing of exposure would influence these effects. Tadpoles exposed to Bd at the mid point experienced higher survival through metamorphosis than those exposed to Bd at the early or late points, while tadpoles exposed to Sevin at the early point experienced reduced survival compared with those exposed to Roundup or no-pesticide control at the same exposure point. Roundup ameliorated the effects of Bd on survival compared with tadpoles exposed to Bd alone, while there was no interactive effect of Sevin on survival. In addition, Sevin reduced mass of new metamorphs compared with Roundup and reduced snout-vent length compared with all other treatments. The present study supports the hypothesis that pesticides can mitigate the effects of Bd on amphibian hosts and that such effects may depend on the timing of exposure.

The effects of early life lead exposure on the expression of insulin-like growth factor 1 and 2 (IGF1, IGF2) in the hippocampus of mouse pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of IGF1 and IGF2 in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups respectively. On the 21st postnatal day, the learning and memory ability was tested by Water Maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IGF1 and IGF2 in hippocampus was examined by immunohistochemistry and western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than that of the control group (P<0.05). In Water Maze test, the performances of 0.5% and 1% lead exposure groupswere worse than that of the control group (P<0.05). The expression of IGF1 and IGF2 was decreased in lead exposed groups than that of the control group (P<0.05). The low expression of IGF1 and IGF2 in the hippocampus of pups may contribute to the impairment of learning and memory associated with maternal Pb exposure.

Validation of a Candida albicans delayed-type hypersensitivity (DTH) model in female juvenile rats for use in immunotoxicity assessments

Establishing an in vivo cell-mediated immunity (CMI) assay, such as the delayed-type hypersensitivity (DTH) assay, has been identified as an important gap and recommended to receive highest priority for new model development in several workshops on developmental immunotoxicity. A Candida albicans DTH model has recently been developed that has the advantage over other DTH models, which use alternative sensitizing antigens, in that antigen-specific antibodies, which may interfere with the assay, are not produced. In addition, the in vivo C. albicans DTH model was demonstrated to be more sensitive in detecting immunosuppression than DTH models using keyhole limpet hemocyanin (KLH) or sheep red blood cells as antigens, as well as some ex vivo CMI assays. While KLH and sheep red blood cells are non-physiological immunogens, C. albicans is an important human pathogen. The present studies were conducted in order to optimize and validate the C. albicans DTH model for use in developmental immunotoxicity studies using juvenile rats. Three known immunosuppressive compounds with different mechanisms of action were tested in this model, cyclosprorin A (CsA), cyclophosphamide (CPS), and dexamethasone (DEX). Animals were sensitized with formalin-fixed C. albicans on postnatal day (PND) 28 and challenged with chitosan on PND 38. Drug was administered beginning on PND 23 and continued until PND 37. Exposure to each of the three immunotoxicants resulted in statistically significant decreases in the DTH response to C. albicans-derived chitosan. Decreases in footpad swelling were observed at ≥10 mg CsA/kg/day, ≥5 mg CPS/kg/day, and ≥0.03 mg DEX/kg/day. These results demonstrate that the C. albicans DTH model, optimized for use in juvenile rats, can be used to identify immunotoxic compounds, and fills the need for a sensitive in vivo CMI model for assessments of developmental immunotoxicity. Abbreviations Ab, antibody APC, antigen presenting cell BSA, bovine serum albumin C. albicans, Candida albicans CI, challenge interval CMI, cell-mediated immunity CO, challenge only CPS, cyclophosphamide CsA, cyclosporin A CTL, cytotoxic T lymphocyte DEX, dexamethasone DIT, developmental immunotoxicity DTH, delayed-type hypersensitivity ip, intraperitoneal KLH, keyhole limpet hemocyanin MLR, mixed lymphocyte reaction OVA, ovalbumin PBS, phosphate-buffered saline PND, postnatal day sc, subcutaneous SEM, standard error of the mean SRBC, sheep red blood cells.