Lead exposure in late adolescence through adulthood impairs short-term spatial memory and the neuronal differentiation of adult-born cells in C57BL/6 male mice

Shrinking the footprint of the criminal legal system through policies informed by psychology and neuroscience

The footprint of the legal system in the United States is expansive. Applying psychological and neuroscience research to understand or predict individual criminal behavior is problematic. Nonetheless, psychology and neuroscience can contribute substantially to the betterment of the criminal legal system and the outcomes it produces. We argue that scientific findings should be applied to the legal system through systemwide policy changes. Specifically, we discuss how science can shape policies around pollution in prisons, the use of solitary confinement, and the law's conceptualization of insanity. Policies informed by psychology and neuroscience have the potential to affect meaningful-and much-needed-legal change.

Evaluation of the oxidative toxicity induced by lead, manganese, and cadmium using genetically modified nrf2a-mutant zebrafish

Heavy metal pollution has become a serious environmental concern and a threat to public health. Three of the most common heavy metals are cadmium (Cd), lead (Pb), and manganese (Mn). Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important transcription factor activated in the response to oxidative stress. In this study, mutant zebrafish with an nrf2a deletion of 7 bp were constructed by the CRISPR/Cas9 system to investigate the oxidative toxicity of these three heavy metals. The results of general toxicity tests showed that Pb exposure did not cause significant damage to mutant zebrafish compared with wild-type (WT) zebrafish. However, high Mn exposure increased mortality and malformation rates in mutant zebrafish. Of concern, Cd exposure caused significant toxic damage, including increased mortality and malformation rates, apoptosis of brain neurons, and severe locomotor behavior aberration in mutant zebrafish. The results of qRT-PCR indicated that Cd exposure could induce the activation of genes related to oxidative stress resistance in WT zebrafish, while the expression of these genes was inhibited in mutant zebrafish. This study showed that of the three heavy metals, Cd had the strongest oxidative toxicity, Mn had medium toxicity, and Pb had the weakest toxicity.

Lead Disrupts Mitochondrial Morphology and Function through Induction of ER Stress in Model of Neurotoxicity

Lead exposure may weaken the ability of learning and memory in the nervous system through mitochondrial paramorphia and dysfunction. However, the underlying mechanism has not been fully elucidated. In our works, with SD rats, primary culture of hippocampal neuron and PC12 cell line model were built up and behavioral tests were performed to determine the learning and memory insults; Western blot, immunological staining, and electron microscope were then conducted to determine endoplasmic reticulum stress and mitochondrial paramorphia and dysfunction. Co-immunoprecipitation were performed to investigate potential protein–protein interaction. The results show that lead exposure may cripple rats’ learning and memory capability by inducing endoplasmic reticulum stress and mitochondrial paramorphia and dysfunction. Furthermore, we clarify that enhanced MFN2 ubiquitination degradation mediated by PINK1 may account for mitochondrial paramorphia and endoplasmic reticulum stress. Our work may provide important clues for research on the mechanism of how Pb exposure leads to nervous system damage.

Forced swimming stress increases natatory activity of lead-exposed mice

Recent evidence points to the relationship between lead toxicity and the function of the hypothalamic-pituitary-adrenal axis, which suggests that lead exposure could influence how an individual cope with stress. Here we test this hypothesis by investigating the behavioral effects of lead exposure in mice during the forced swimming test (FST), a parading in which animals are exposed to a stressful situation and environment. Swiss mice received either 180 ppm or 540 ppm of lead acetate (Pb) in their ad-lib water supply for 60-90 days, starting at postnatal day 30. Control (Ctrl) mice drank tap water. At the end of the exposure period, mice were submitted to a 5-min session of FST or to an open-field session of the same duration. Data from naïve animals showed that corticosterone levels were higher for animals tested in the FST compared to animals tested in the open-field. Blood-lead levels (BLL) in Pb-exposed mice ranged from 14.3 to 106.9 µg/dL. No differences were observed in spontaneous locomotion between Ctrl and Pb-exposed groups in the open-field. However, in the FST, Pb-treated mice displayed higher swimming activity than Ctrl ones and this effect was observed even for animals with BLL higher than 20 µg/dL. Furthermore, significant differences in brain glutathione levels, used as an indicator of led toxicity, were only observed for BLL higher than 40 µg/dL. Overall, these findings suggest that swimming activity in the FST is a good indicator of lead toxicity and confirm our prediction that lead toxicity influences behavioral responses associated to stress.

Disruption of synaptic expression pattern and age-related DNA oxidation in a neuronal model of lead-induced toxicity

Lead (Pb) is recognized as a potent inducer of synaptic toxicity generally associated with reduced synaptic transmission and increased neuronal fiber excitability, becoming an environmental risk for neurodegenerative processes. Despite numerous toxicological studies on Pb have been directed to the developing brain, attention concerning long-term consequences of pubertal chronic Pb exposure on neuronal activity is still lacking. Thus, we exposed 4-week-old male mice to 0.2 % lead acetate solution for one month, then, conducted behavioral tests or extracted brain homogenate from mice prefrontal cortex (PFC) and hippocampus at the age of 4, 13 and 16-month-old respectively. Our results showed that treated mice exhibited an evident increase in latency to reach platform following pubertal Pb exposure and aging. The increase of 8-OHdG revealed evident neural DNA oxidative damage across time upon pubertal Pb exposure. In the hippocampus of lead exposed mice at three age nodes, the expression of brain-derived neurotrophic factor precursor (proBDNF) increased, while that of mature BDNF (mBDNF), cAMP-response element binding protein (CREB) and phosphorylated CREB (pCREB) decreased compared with the control group. Furthermore, the expression of BACE1 protein and tau phosphorylation level in PFC and hippocampus increased, APP mRNAs in PFC and prolonged induction of BACE1 in hippocampus. Our results show that chronic Pb exposure from pubertal stage onward can either initiate divergent synaptic-related gene expression patterns in adulthood or trigger time-course of neurodegenerative profile within the PFC or hippocampus, which can contribute consistent deficits of cognition across subsequent age-nodes.

Chronic Exposure to Low Concentration Lead Chloride-Induced Anxiety and Loss of Aggression and Memory in Zebrafish

Lead and lead-derived compounds have been extensively utilized in industry, and their chronic toxicity towards aquatic animals has not been thoroughly addressed at a behavioral level. In this study, we assessed the risk of exposure to lead at a waterborne environmental concentration in adult zebrafish by behavioral and biochemical analyses. Nine tests, including three-dimension (3D) locomotion, novel tank exploration, mirror biting, predator avoidance, social interaction, shoaling, circadian rhythm locomotor activity, color preference, and a short-term memory test, were performed to assess the behavior of adult zebrafish after the exposure to 50 ppb PbCl₂ for one month. The brain tissues were dissected and subjected to biochemical assays to measure the relative expression of stress biomarkers and neurotransmitters to elucidate the underlying mechanisms for behavioral alterations. The results of the behavioral tests showed that chronic exposure to lead could elevate the stress and anxiety levels characterized by elevated freezing and reduced exploratory behaviors. The chronic exposure to PbCl₂ at a low concentration also induced a sharp reduction of aggressiveness and short-term memory. However, no significant change was found in predator avoidance, social interaction, shoaling, or color preference. The biochemical assays showed elevated cortisol and reduced serotonin and melatonin levels in the brain, thus, altering the behavior of the PbCl₂-exposed zebrafish. In general, this study determined the potential ecotoxicity of long-term lead exposure in adult zebrafish through multiple behavioral assessments. The significant findings were that even at a low concentration, long-term exposure to lead could impair the memory and cause a decrease in the aggressiveness and exploratory activities of zebrafish, which may reduce their survival fitness.