Early chronic low-level lead exposure reduced C-C chemokine receptor 7 in hippocampal microglia

Hippocampal and amygdala volumes vary with residential proximity to toxicants at Birmingham, Alabama's 35th Avenue Superfund site

Exposure to environmental toxicants have serious implications for the general health and well-being of children, particularly during pivotal neurodevelopmental stages. The Environmental Protection Agency's (EPA) Superfund program has identified several areas (Superfund sites) across the United States with high levels of environmental toxicants, which affect the health of many residents in nearby communities. Exposure to these environmental toxicants has been linked to changes in the structure and function of the brain. However, limited research has investigated the relationship between the proximity of childhood homes to a Superfund site and the development of subcortical structures like the hippocampus and amygdala. The present study investigated the hippocampal and amygdala volumes of young adults in relation to the proximity of their childhood homes to Birmingham, Alabama's 35th Avenue Superfund site. Forty participants who either lived within or adjacent to the Superfund site (Proximal group; n = 20) or who lived elsewhere in the greater Birmingham metropolitan area (Distal group; n = 20) were included in this study. Both groups were matched on age, sex, race, and years of education. Magnetic resonance imaging (MRI) was used to compare the gray matter volume of the hippocampus and amygdala between groups. Differences in bilateral hippocampal and left amygdala volumes were observed. Specifically, hippocampal and amygdala volumes were greater in the Proximal than Distal group. These findings suggest that the proximity of children's homes to environmental toxicants may impact the development of the hippocampus and amygdala. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Improving Equitability and Inclusion for Testing and Detection of Lead Poisoning in US Children

Policy Points Child lead poisoning is associated with socioeconomic inequity and perpetuates health inequality. Methods for testing and detection of child lead poisoning are ill suited to the current demographics and characteristics of the problem. A three-pronged revision of current testing approaches is suggested. Employing the suggested revisions can immediately increase our national capacity for equitable, inclusive testing and detection. ABSTRACT: Child lead poisoning, the longest-standing child public health epidemic in US history, is associated with socioeconomic inequity and perpetuates health inequality. Removing lead from children's environments ("primary prevention") is and must remain the definitive solution for ending child lead poisoning. Until that goal can be realized, protecting children's health necessarily depends on the adequacy of our methods for testing and detection. Current methods for testing and detection, however, are no longer suited to the demographics and magnitude of the problem. We discuss the potential deployment and feasibility of a three-pronged revision of current practices including: 1) acceptance of capillary samples for final determination of lead poisoning, with electronic documentation of "clean" collection methods submitted by workers who complete simple Centers for Disease Control and Prevention-endorsed online training and certification for capillary sample collection; 2) new guidance specifying the analysis of capillary samples by inductively coupled plasma mass spectrometry or graphite furnace atomic absorption spectrometry with documented limit of detection ≤0.2 μg/dL; and 3) adaptive "census tract-specific" universal testing and monitoring guidance for children from birth to 10 years of age. These testing modifications can bring child blood lead level (BLL) testing into homes and communities, immediately increasing our national capacity for inclusive and equitable detection and monitoring of dangerous lower-range BLLs in US children.

Microglial Activation in Metal Neurotoxicity: Impact in Neurodegenerative Diseases

Neurodegenerative processes encompass a large variety of diseases with different pathological patterns and clinical features, such as Alzheimer's and Parkinson's diseases. Exposure to metals has been hypothesized to increase oxidative stress in brain cells leading to cell death and neurodegeneration. Neurotoxicity of metals has been demonstrated by several in vitro and in vivo experimental studies, and most probably, each metal has its specific pathway to trigger cell death. As a result, exposure to essential metals, such as manganese, iron, copper, zinc, and cobalt, and nonessential metals, including lead, aluminum, and cadmium, perturbs metal homeostasis at the cellular and organism levels leading to neurodegeneration. In this contribution, a comprehensive review of the molecular mechanisms by which metals affect microglia physiology and signaling properties is presented. Furthermore, studies that validate the disruption of microglia activation pathways as an essential mechanism of metal toxicity that can contribute to neurodegenerative disease are also presented and discussed.

Role of p53 methylation in manganese-induced cyclooxygenase-2 expression in BV2 microglial cells

Manganese (Mn) is an essential cofactor for many enzymes and plays an important role in normal growth and development. However, excess exposure to manganese (Mn) may be an important environmental factor leading to neurodegeneration. The overexpression of microglial cyclooxygenase-2 (COX-2) plays a key role in neuroinflammation in neurodegenerative diseases. The existing data suggest that Mn can induce neuroinflammation by up-regulating COX-2 expression. However, the mechanisms involved in Mn-induced microglial COX-2 up-regulation remain to be determined. The aim of this study was to investigate the role of p53 in Mn-induced COX-2 expression in microglial cells. The results showed that Mn exposure induced the up-regulation of COX-2 and inhibited the expression of p53 in BV2 microglial cells. The addition of p53 activator and the over-expression of p53 blocked the expression of COX-2 and prostaglandin E2 (PGE2), a COX-2 downstream effector, induced by Mn. Further, Mn increased the methylation of p53 DNA in microglia, while the addition of demethylation reagent 5-Aza-dC enhanced the expression of p53 but decreased the expression of COX-2. These results suggested that Mn may inhibit p53 expression through induction of DNA methylation, which can further induce the expression of COX-2 in microglial cells.

Statistical modeling with litter as a random effect in mixed models to manage "intralitter likeness"

"Intralitter likeness," the possibility that the shared genetics and/or maternal environment in multiparous species causes strong similarity for outcome variables in littermates, violates a core statistical assumption, that of observation independence, when littermate outcomes are analyzed. Intralitter likeness has been of major concern to investigators for several decades. Despite consensus and guidance, many research reports in the rodent literature continue to ignore intralitter likeness. A historical review of the literature revealed that the long-preferred solution was to include litter as an effect in statistical models. Limitations in software development and computing capacity prior to 1990, however, appear to have led researchers and guidance authorities to endorse instead the method of using one value per litter. Here, the history of discussions regarding intralitter likeness in developmental neurotoxicological research is reviewed; growing knowledge regarding the biological bases and significance of intralitter likeness is discussed; principles underlying the use of litter as a random effect in mixed models are presented; statistical examples are provided illustrating the advantages and critical importance of including litter as a random effect in mixed models; and results using all data points (all pups from all litters) with litter as a random effect, are compared to results based on random selections of representative littermates. Mixed models with litter included as a random effect have distinct advantages for the analysis of clustered data. Modern computing capacity provides ready accessibility to mixed models for all researchers. Accessibility however does not preclude the need for appropriate expertise and consultation in the use of mixed (hierarchical) models.