Perinatal Lead Exposure Alters Calsyntenin-2 and Calsyntenin-3 Expression in the Hippocampus and Causes Learning Deficits in Mice Post-weaning

Childhood blood-lead level predicts lower general, non-selective hippocampal subfield volumes in midlife

Millions of adults and children are exposed to high levels of lead, a neurotoxicant, each year. Recent evidence suggests that lead exposure may precipitate neurodegeneration, particularly if the exposure occurs early or late in life, with unique alterations to the structure or function of specific subfields of the hippocampus, a region involved in memory and Alzheimer's disease. It has been proposed that specific hippocampal subfields may thus be useful biomarkers for lead-associated neurological disease. We turned to a population-representative New Zealand birth cohort where the extent of lead exposure was not confounded by social class (the Dunedin Study; born 1972-1973 and followed to age 45) to test the hypothesis that early life lead exposure (blood-lead level at age 11 years) is associated with smaller MRI-assessed gray matter volumes of specific subfields of the hippocampus at age 45 years. Among the 508 Dunedin Study members with childhood lead data and adult MRI data passing quality control (93.9 % of those with lead data who attended the age-45 assessment wave, 240[47.2 %] female), childhood blood-lead levels ranged from 4 to 31 µg/dL (M[SD]=10.9[4.6]). Total hippocampal volumes were lower among adults with higher childhood blood-lead levels (b=-102.6 mm3 per 5 ug/dL-unit greater blood-lead level, 95 %CI: -175.4 to -29.7, p=.006, β=-.11), as were all volumes of the 24 hemisphere-specific subfields of the hippocampus. Of these 24 subfields, 20 demonstrated negative lead-associations greater than β=-.05 in size, 14 were statistically significant after adjustment for multiple comparisons (pFDR<.05), and 9 remained significant after adjustment for potential confounders and multiple comparisons. Children exposed to lead demonstrate smaller volumes across all subfields of the hippocampus in midlife. The hypothesis that lead selectively impairs specific subfields of the hippocampus, or that specific subfields may be markers for lead-associated neurological disease, requires further evaluation.

Sesamin mitigates lead-induced behavioral deficits in male rats: The role of oxidative stress

Lead (Pb) is a well-known toxic pollutant that has negative effects on behavioral functions. Sesamin, a phytonutrient of the lignan class, has shown neuroprotective effects in various neurological disorder models. The present study was undertaken to evaluate the putative protective effects of sesamin against Pb-induced behavioral deficits and to identify the role of oxidative stress in male rats. The rats were exposed to 500 ppm of Pb acetate in their drinking water and simultaneously treated orally with sesamin at a dose of 30 mg/kg/day for eight consecutive weeks. Standard behavioral paradigms were used to assess the behavioral functions of the animals during the eighth week of the study. Subsequently, oxidative stress factors were evaluated in both the cerebral cortex and hippocampal regions of the rats. The results of this study showed that Pb exposure triggered anxiety-/depression-like behaviors and impaired object recognition memory, but locomotor activity was indistinguishable from the normal control rats. These behavioral deficiencies were associated with suppressed enzymatic and non-enzymatic antioxidant levels, and enhanced lipid peroxidation in the investigated brain regions. Notably, correlations were detected between behavioral deficits and oxidative stress generation in the Pb-exposed rats. Interestingly, sesamin treatment mitigated anxio-depressive-like behaviors, ameliorated object recognition memory impairment, and modulated oxidative-antioxidative status in the rats exposed to Pb. The results suggest that the anti-oxidative properties of sesamin may be one of the underlying mechanisms behind its beneficial effect in ameliorating behavioral deficits associated with Pb exposure.

Goat CLSTN2 gene: tissue expression profile, genetic variation, and its associations with litter size

Calsyntenin-2 (CLSTN2) is involved in cell proliferation, differentiation, cell death, tumorigenesis, and follicular expression. Although CLSTN2 has been identified as a potential candidate gene for sheep prolificacy, no studies have been done on its effect on goat prolificacy. The purpose of this study was to identify mRNA expression and genetic variation within goat CLSTN2, and its association with prolificacy. Herein, we uncovered significant differences in mRNA levels of the CLSTN2 gene in different tissues in female goats (p < 0.01), including ovary tissue. Nine putative indels were designed to investigate their correlation to litter size, but only one 16-bp deletion was discovered in female Shaanbei white cashmere goats (n = 902). We discovered that a 16-bp deletion within the CLSTN2 gene was significantly correlated with first-born litter size (p = 0.0001). As shown by the chi-squared test, the genotypic II of single-lambs and multi-lambs was dramatically higher than with genotype ID (p = 0.005). Our findings suggest that indel within the CLSTN2 gene is a candidate gene affecting prolificacy in goats and may be used for Marker Assisted Selection (MAS) in goats.

Early environmental exposure to oxytetracycline in Danio rerio may contribute to neurobehavioral abnormalities in adult zebrafish

The common antibiotic oxytetracycline (OTC) is nowadays commonly found in natural aquatic environments. However, the underlying mechanisms of low-dose OTC exposure and its neurotoxic effects on aquatic animals remain unknown. In this study, we exposed zebrafish larvae to environmental concentrations of OTC in early life and performed neurobehavioral, 16S rRNA gene sequencing, and transcriptomic analyses. OTC exposure resulted in hyperactivity of larvae and a significant reduction in the number of neurons in the midbrain. The expression levels of 15 genes related to neural function changed. Additionally, the composition of 65 genera of the gut microbiota of larvae was altered, which may be one of the reasons for the abnormal neural development. We further studied the long-term outcomes among adult fish long after cessation of OTC exposure. OTC treatment caused adult fish to be depressive and impulsive, symbolizing bipolar disorder. Adult fish exposed to OTC had significantly fewer neurons and their gut bacteria composition did not recover 104 days after terminating OTC exposure. Finally, we analyzed the correlation between the gut microbiota of larvae, genes related to neural function, and metabolites of adult fish brain tissue. The results showed that the abundance of several members of the biome in larvae was related to the transcription levels of genes related to neural function, which were related to the metabolic levels in the adult brain. In conclusion, our study showed that early-life exposure to environmental concentrations of OTC can lead to persistent neurobehavioral abnormalities until adulthood through dysbiosis in the gut microbiota.

High blood lead level correlates with selective hippocampal subfield atrophy and neuropsychological impairments

BACKGROUND

Lead contamination is a major public health concern. Previous studies have demonstrated that lead exposure could affect the hippocampus, which is a complex and heterogeneous structure composed of 12 subregions. Here, we explored volumetric and functional changes in hippocampal subfields and neuropsychological alterations after lead exposure.

METHODS

We performed a cross-sectional study at a smelting company between September 2020 and December 2021. Blood lead level was recorded, and neuropsychological functions were assessed by Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE), Self-rating Anxiety Scale (SAS), and Self-rating Depression Scale (SDS). The hippocampus was segmented into 12 subfields in each hemisphere in magnetic resonance images (MRIs). Then, the effect of altered hippocampal subfield volumes on brain functions were studied by seed-based functional connectivity (FC) analysis. Finally, the relationships between the lead level with hippocampal subfield volumes and neuropsychological functions were investigated. Baseline characteristics, hippocampal subfield volumes, and FC analysis were compared between lead-exposed (≥ 300 μg/L) and the control group (≤ 100 μg/L).

RESULTS

In 76 participants, lead level positively correlated with SDS(r = 0.422) and negatively correlated with MoCA(r = -0.414), MMSE(r = -0.251), Concentration(r = -0.331), Recall(r = -0.319), Orientation(r = -0.298) and Executive Function/Visuospatial abilities(r = -0.231). Lead group (26 participants) had lower MoCA and MMSE and higher SDS than control group (23 participants). A significantly decreased volume in the left CA4 and GC-ML-DG subfields was found in the lead group compared with the control group. The left GC-ML-DG of the lead group showed a decreased FC with the bilateral postcentral gyrus. The left CA4(r = -0.409) and left GC-ML-DG (r = -0.383) volumes negatively correlated with lead level. The FC between left GC-ML-DG and left postcentral gyrus positively correlated with MoCA(r = 0.318), MMSE(r = 0.379) and Recall(r = 0.311). The FC between left GC-ML-DG and right postcentral gyrus positively correlated with MoCA(r = 0.326), Executive Function/Visuospatial abilities(r = 0.307) and Concentration(r = 0.297).

CONCLUSION

High blood lead level was associated with neuropsychological alterations, hippocampal structural and functional changes. The left GC-ML-DG and CA4 atrophy might serve as predictive imaging markers for neurological damage associated with high lead exposure.

Role of NF-κB in lead exposure-induced activation of astrocytes based on bioinformatics analysis of hippocampal proteomics

Lead (Pb), as a heavy metal, is used in batteries, ceramics, paint, pipes, certain ceramics, e-waste recycling, etc. Chronic Pb exposure can result in the inflammation of the central nervous system, as well as neurobehavioral changes. Both glial cells and neurons are involved in central nervous injury following Pb exposure. However, significant cellular events and their key regulators following Pb exposure remain to be elucidated. In this study, rats were randomly exposed to 250 or 500 mg/L PbAc for 9 weeks. Hippocampal proteomics was performed using isobaric tags for relative absolute quantification. Bioinformatics analysis was used to identify 301 and 267 differentially expressed proteins-which were involved in biological processes, including glial cell activation, neural nucleus development, and mRNA processing-in the low and high Pb exposure groups, respectively. Gene Set Enrichment Analysis showed that astrocyte activation was identified as a significant cellular event occurring in the low- or high-dose Pb exposure group. Subsequently, in vivo and in vitro models of Pb exposure were established to confirm astrocyte activation. As a result, glial fibrillary acidic protein expression in astrocytes was much higher in the Pb exposure group. Moreover, the mRNA expression of neurotoxic reactive astrocyte genes was much higher than that of the control group. The analysis of transcription factors indicated that NF-κB was screened as the top transcription factor, which might regulate astrocyte activation following Pb exposure in the rat hippocampus. The data also showed that the inhibition of NF-κB transcription suppressed astrocyte activation following Pb exposure. Overall, astrocyte activation was one of the significant cellular events following Pb exposure in the rat hippocampus, which was regulated by the NF-κB transcription factor, suggesting that inhibiting astrocyte activation may be a potential target for the prevention of Pb neurotoxicity.

Effects of folic acid on oxidative damage of kidney in lead-exposed rats

INTRODUCTION

Lead (Pb) has many applications in daily life, but in recent years, various problems caused by lead exposure have aroused people's concern. Folic acid is widely found in fruits and has received more attention for its antioxidant function. However, the role of folic acid in lead-induced kidney injury in rats is unclear. This study was designed to investigate the effects of folic acid on oxidative stress and endoplasmic reticulum stress in the kidney of rats caused by lead exposure.

METHODS

Forty specific pathogen-free male Rattus norvegicus rats were randomly divided into control, lead, intervention, and folic acid groups. The levels of SOD, GSH-Px, GSH, and MDA were measured by biochemical kits. The protein levels of Nrf2, HO-1, CHOP, and GRP78 were measured by immunofluorescence.

RESULTS

This study showed that lead exposure increased the blood levels of lead in mice. However, the intervention of folic acid decreased the levels of lead, but the difference was not statistically significant. Lead exposure causes oxidative stress by decreasing kidney SOD, GSH-Px, and GSH levels and increasing MDA levels. However, folic acid alleviated the oxidative damage caused by lead exposure by increasing the levels of GSH-Px and GSH and decreasing the levels of MDA. Immunofluorescence results showed that folic acid intervention downregulated the upregulation of kidney Nrf2, HO-1, GRP78, and CHOP expression caused by lead exposure.

DISCUSSION

Overall, folic acid alleviates kidney oxidative stress induced by lead exposure by regulating Nrf2 and HO-1, while regulating CHOP and GRP78 to mitigate apoptosis caused by excessive endoplasmic reticulum stress.

Environmental pollution, a hidden culprit for health issues

The environmental and health impacts from the massive discharge of chemicals and subsequent pollution have been gaining increasing public concern. The unintended exposure to different pollutants, such as heavy metals, air pollutants and organic chemicals, may cause diverse deleterious effects on human bodies, resulting in the incidence and progression of different diseases. The article reviewed the outbreak of environmental pollution-related public health emergencies, the epidemiological evidence on certain pollution-correlated health effects, and the pathological studies on specific pollutant exposure. By recalling the notable historical life-threatening disasters incurred by local chemical pollution, the damning evidence was presented to criminate certain pollutants as the main culprit for the given health issues. The epidemiological data on the prevalence of some common diseases revealed a variety of environmental pollutants to blame, such as endocrine-disrupting chemicals (EDCs), fine particulate matters (PMs) and heavy metals. The retrospection of toxicological studies provided illustrative clues for evaluating ambient pollutant-induced health risks. Overall, environmental pollution, as the hidden culprit, should answer for the increasing public health burden, and more efforts are highly encouraged to strive to explore the cause-and-effect relationships through extensive epidemiological and pathological studies.