Guangqin Fan

Lead-induced ER calcium release and inhibitory effects of methionine choline in cultured rat hippocampal neurons

Lead, a ubiquitous neurotoxicant, can result in learning and memory dysfunction. Long term potentiation in the hippocampus, a potential neural substrate for learning and memory, is thought to be linked to calcium-triggered intracellular events. In this study, laser scanning confocal microscopy was used to examine the effects of Pb(2+) on intracellular and endoplasmic reticulum free calcium concentration ([Ca(2+)](i) and [Ca(2+)](ER)) in cultured neonatal rat hippocampal neurons and their possible antagonism by methionine choline; understanding these effects would help explain the lead-induced cognitive and learning dysfunction and explore efficient safety and relief strategies. The results showed that Pb(2+) increased [Ca(2+)](i) and decreased [Ca(2+)](ER) linearly in a time- and concentration-dependant manner, and Pb(2+) addition after the applying of a ryanodine receptor (RyR) antagonist and an inositol-1,4,5-triphosphate receptor (IP(3)R) antagonist did not increase [Ca(2+)](i). The addition of 10, 20, or 40 mmol/L methionine choline simultaneously with addition of 10 μmol/L Pb(2+) decreased [Ca(2+)](i) in Ca(2+)-free culture medium by 39.0%, 66.0%, and 61.6%, respectively, in a concentration-dependant manner in a certain dose range. Our results suggest that Pb(2+) induces ER calcium release to increase the resting [Ca(2+)](i); and methionine choline inhibit this increase in [Ca(2+)](i).

The effect of lead exposure on expression of SIRT1 in the rat hippocampus.

Based on how the silent information regulator 2 homolog 1 (SIRT1) regulates the cyclic AMP response element binding protein (CREB), which is the molecular switch of long-term memory that maintains cognitive function, it is postulated that the impact of lead (Pb) on SIRT1 is one of the mechanisms leading to Pb-induced cognitive and learning deficits. Hence, the purpose of this study was to investigate the effect of Pb exposure on the expression of SIRT1, and the reversion effect of resveratrol, which is an activator of SIRT1. We examined the effects of maternal rat ingestion of Pb in drinking water during gestation and lactation on the expression of SIRT1 and CREB in the hippocampus of their offspring at postnatal week 3 (PNW3) and 52 (PNW52), and then reexamined these effects in offspring after intragastric administration of resveratrol for 4 weeks. Pb exposure decreased SIRT1 and CREB phosphorylation in a dose-dependent manner in the rat hippocampus at both PNW3 and 52, and resveratrol reversed those losses. These results indicated that SIRT1 might be a novel target to prevent Pb neurotoxicity.

Dietary, Nutrient Patterns and Blood Essential Elements in Chinese Children with ADHD

Dietary or nutrient patterns represent the combined effects of foods or nutrients, and elucidate efficaciously the impact of diet on diseases. Because the pharmacotherapy on attention deficit hyperactivity disorder (ADHD) was reported be associated with certain side effects, and the etiology of ADHD is multifactorial, this study investigated the association of dietary and nutrient patterns with the risk of ADHD. We conducted a case-control study with 592 Chinese children including ADHD (n = 296) and non-ADHD (n = 296) aged 6–14 years old, matched by age and sex. Dietary and nutrient patterns were identified using factor analysis and a food frequency questionnaire. Blood essential elements levels were measured using atomic absorption spectrometry. A fish-white meat dietary pattern rich in shellfish, deep water fish, white meat, freshwater fish, organ meat and fungi and algae was inversely associated with ADHD (p = 0.006). Further analysis found that a mineral-protein nutrient pattern rich in zinc, protein, phosphorus, selenium, calcium and riboflavin was inversely associated with ADHD (p = 0.014). Additionally, the blood zinc was also negatively related to ADHD (p = 0.003). In conclusion, the fish-white meat dietary pattern and mineral-protein nutrient pattern may have beneficial effects on ADHD in Chinese children, and blood zinc may be helpful in distinguishing ADHD in Chinese children.

Lead-induced iron overload and attenuated effects of ferroportin 1 overexpression in PC12 cells.

Lead (Pb) neurotoxicity has received renewed interest with the growing evidence that Pb contributes to Alzheimers disease (AD). However, the mechanism is not clear. In our previous study of long-term Pb exposure in vivo, a brain iron (Fe) overload induced by Pb was observed in elderly rats. It is well known that brain Fe overload is the mechanism of AD. Therefore, we have reason to believe that Pb induced Fe overload and caused neurodegenerative disease. However, the mechanism or route of Pb-induced Fe overload is unknown. In the current study, the effect of Pb exposure on Fe homeostasis in PC12 cells was determined at different Pb-exposure concentrations and periods with differing Fe exposure, and the role of ferroportin 1 (FP1), the sole iron efflux protein, in Pb-induced Fe metabolic disorders was further investigated. The results showed a Pb-induced cellular increase in Fe accompanying a decrease in the expression of FP1 in a concentration- and time-dependent manner in Pb-exposed PC12 cells. Furthermore, FP1 overexpression could attenuate Fe accumulation in Pb-exposed PC12 cells. These results indicated that FP1 might be a novel target to prevent cellular Fe accumulation induced by Pb exposure and subsequent neurotoxic consequences.

The effect of the hemochromatosis (HFE) genotype on lead load and iron metabolism among lead smelter workers.

Background Both an excess of toxic lead (Pb) and an essential iron disorder have been implicated in many diseases and public health problems. Iron metabolism genes, such as the hemochromatosis (HFE) gene, have been reported to be modifiers for lead absorption and storage. However, the HFE gene studies among the Asian population with occupationally high lead exposure are lacking. Objectives To explore the modifying effects of the HFE genotype (wild-type, H63D variant and C282Y variant) on the Pb load and iron metabolism among Asian Pb-workers with high occupational exposure. Methods Seven hundred and seventy-one employees from a lead smelter manufacturing company were tested to determine their Pb intoxication parameters, iron metabolic indexes and identify the HFE genotype. Descriptive and multivariate analyses were conducted. Results Forty-five H63D variant carriers and no C282Y variant carrier were found among the 771 subjects. Compared with subjects with the wild-type genotype, H63D variant carriers had higher blood lead levels, even after controlling for factors such as age, sex, marriage, education, smoking and lead exposure levels. Multivariate analyses also showed that the H63D genotype modifies the associations between the blood lead levels and the body iron burden/transferrin. Conclusions No C282Y variant was found in this Asian population. The H63D genotype modified the association between the lead and iron metabolism such that increased blood lead is associated with a higher body iron content or a lower transferrin in the H63D variant. It is indicated that H63D variant carriers may be a potentially highly vulnerable sub-population if they are exposed to high lead levels occupationally.

Pb 2+ modulates ryanodine receptors from the endoplasmic reticulum in rat brain

ABSTRACT Although the neurotoxic mechanism of lead (Pb2 +) has been extensively studied, it is not well understood. The effects of Pb2 + on free cytosolic calcium (Ca2 +) concentration and calcium‐regulated events have been suggested to be major mechanisms in Pb2 + toxicity. Based on our previous findings that Pb2 + changes calcium release through ryanodine receptors (RyRs), the modulation of endoplasmic reticulum (ER) vesicular RyRs by Pb2 + was investigated further in the present study. The results of [3H]ryanodine binding assays showed that in the presence of a free Ca2 + concentration ([Ca2 +]f) of 100 &mgr;M, Pb2 + modulated the equilibrium of [3H]ryanodine binding to brain RyRs, with a U‐type dose‐response curve, where minimal binding was observed at a free Pb2 + concentration ([Pb2 +]f) of 0.39 &mgr;M. This modulation was also observed over a time course. Scatchard analysis indicated that both an increase in Kd and a possible decrease in Bmax were responsible for the decrease in binding induced by low [Pb2 +]f. Moreover, the effects of Pb2 + on the function of ER RyRs in neurons might also be controlled by other RyR modulators. Whole‐cell patch‐clamp experiments revealed that dynamic calcium oscillations evoked by specific RyR agonists were depressed rapidly and reversibly by exposure to 10 &mgr;M Pb2 +. Our study indicates that RyRs are molecular targets of Pb2 +, and this interaction disturbs Ca2 + signals and leads to neurotoxicity. HighlightsPb2 + inhibited [3H]ryanodine binding to RyRs with a U‐shaped dose‐response curve.Modulators of RyRs can change the binding of Pb2 + to RyRs.Calcium oscillation induced by RyR agonists was depressed by Pb2 + exposure.RyRs may be the targets of Pb2 + neurotoxicity through disturbing Ca2 + signaling.

1374 Combined exposure to lead, cadmium, arsenic, and mercury alters synaptic homeostasis through snk-spar pathway in neuronal cells

Introduction Lead, cadmium, arsenic, and mercury are widely used in industry and among the leading toxic agents detected in the environment. The deleterious effects encountered after exposure to these individual metals in low doses are well documented. However, human exposure to environmental chemicals is most correctly characterised as an exposure to mixtures, and little is known about the combined impact of these metals. Methods In our study, the combined impacts of these four metal mixtures (MM) in low doses on synaptic homeostasis as well as the related mechanisms were investigated in cultured hippocampal neurons and NGF-differentiated PC12 cells. F-actin staining was used to emerge the structure of dendrites and spines for synaptic morphology analysis. Immunofluorescence and RT-PCR were applied to examine the expressions of serum-inducible kinase (Snk) and spine-associated Rap guanosinetriphosphatase activating protein (SPAR). The plasmids of shRNA-Snk, SPAR-Wt and SPAR-Mut (S1328) were constructed for transfection Assays. Results MM exposure declined the density and length of dendritic spines, and dendrite branches in dose-effect relationship in hippocampal neurons. And the mushroom and thin spines were decreased. Simultaneously, the Snk expression were up-regulated accompanying with the down-regulation of SPAR expression. Similar to what observed in the hippocampal neurons, the synaptic morphology analysis of NGF-differentiated PC12 cells showed their neurite length and tip end numbers were declined in dose-effect relationship after MM exposure, which accompanied with the up-regulation of Snk and the down-regulation of SPAR. Snk agonist aggravated these impairment, whereas, Snk knockdown and SPAR overexpression attenuated the changes of neurite outgrowth. In addition, SPAR-Mut (S1328) overexpression performed a better reversion than SPAR-Wt overexpression in the changes of neurite outgrowth induced by MM-exposure. Conclusion These results indicated that combined exposure to low doses MM disturbed the synaptic homeostasis, and Snk-SPAR pathway might be a novel target to prevent MM induced neurotoxicity.

1373 Time sequence of oxidative stress in neurodegenerative brain after long-term lead exposure in rats

Introduction A large number of studies have shown that the developmental neurotoxicity induced by lead is related to oxidative injury, meanwhile, oxidative stress is among the most common mechanisms of neurodegeneration. However, few studies have explored the role of oxidative stress in age-related cognitive impairment caused by prolonged lead exposure and oxidative stress. Methods In the present study, rats were exposed to low-level lead from the embryonic stage to old age. Dynamic changes in neurodegeneration, endoplasmic reticulum (ER) stress, and oxidative stress in brains during postnatal weeks 3, 41 and 70 (PNW3, PNW41 and PNW70, respectively) were investigated. Results Lead exposure resulted in neurodegeneration in PNW70 rats based on magnetic resonance imaging (MRI) scans and thionine stain analysis. Amyloid precursor protein (APP) and tau mRNA expression in PNW41 and PNW70 brains increased in a time- and dose-dependent manner. APP and Tau protein levels significantly increased with lead exposure at PNW3 and PNW70. Mechanistically, the expression of the ER stress protein glucose-regulated protein 78 (GRP78) was higher in the presence of lead than in normal controls, which was associated with high levels of 8-hydroxy-2’-deoxyguanosine (8-OHdG) in brain tissues after lead exposure in PNW3 and PNW70, their changes were like as APP and tau protein that were a u- or j-shaped curve with time of lead exposure. Conclusion Our findings suggest that the neurodegenerative injuries induced by lead exposure may be mediated by ER and oxidative stresses, and there is a critical period for prevention or intervention AD in early life and later life, however middle-aged people at the latent stage of neurodegenerative process should not be ignored.

Lead, cadmium, arsenic, and mercury combined exposure disrupted synaptic homeostasis through activating the Snk-SPAR pathway

Lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) are among the leading toxic agents detected in the environment, and they have also been detected simultaneously in blood, serum, and urine samples of the general population. Meanwhile early neurologic effects and multiple interactions of Pb, Cd, As, and Hg had been found in children from environmentally polluted area. However, the current studies of these four metals were mostly limited to the interactions between any two metals, whereas the interaction characteristics between any three and four metals were rarely studied. In our study, we firstly explored the characteristics of the neurotoxic interactions among these four elements in nerve cells with factorial designs. The results showed that Pb+Cd+As+Hg co-exposure had a synergistic neurotoxic effect that was more severe than that induced by any two or three metals, when their individual metals were at human environmental exposure (in the blood of U.S. population) relevant levels and below no observed adverse effect levels (NOAELs). Therefore, Pb+Cd+As+Hg co-exposure at human environmental exposure relevant levels were further selected to examine synaptic homeostasis as the cellular and molecular foundation of learning and memory. We reported for the first time that Pb+Cd+As+Hg co-exposure induced dose-dependent decreases of the dendritic lengths and branching, as well as spine density and mature phenotype in primary hippocampal neurons, and the stimulated neurite outgrowths in NGF-differentiated PC12 cells. And the above synaptic homeostasis disruption was associated with serum induced kinase (Snk)-spine associated Rap GTPase activating protein (SPAR) pathway. Our study suggests that human environmental Pb, Cd, As, and Hg co-exposure has the potential to evoke synergistic neurotoxicity even if their individual metals are below NOAELs, which reinforces the need to control and regulate potential sources of metal contamination.

dbMDEGA: a database for meta-analysis of differentially expressed genes in autism spectrum disorder

BackgroundAutism spectrum disorders (ASD) are hereditary, heterogeneous and biologically complex neurodevelopmental disorders. Individual studies on gene expression in ASD cannot provide clear consensus conclusions. Therefore, a systematic review to synthesize the current findings from brain tissues and a search tool to share the meta-analysis results are urgently needed.MethodsHere, we conducted a meta-analysis of brain gene expression profiles in the current reported human ASD expression datasets (with 84 frozen male cortex samples, 17 female cortex samples, 32 cerebellum samples and 4 formalin fixed samples) and knock-out mouse ASD model expression datasets (with 80 collective brain samples). Then, we applied R language software and developed an interactive shared and updated database (dbMDEGA) displaying the results of meta-analysis of data from ASD studies regarding differentially expressed genes (DEGs) in the brain.ResultsThis database, dbMDEGA (https://dbmdega.shinyapps.io/dbMDEGA/), is a publicly available web-portal for manual annotation and visualization of DEGs in the brain from data from ASD studies. This database uniquely presents meta-analysis values and homologous forest plots of DEGs in brain tissues. Gene entries are annotated with meta-values, statistical values and forest plots of DEGs in brain samples. This database aims to provide searchable meta-analysis results based on the current reported brain gene expression datasets of ASD to help detect candidate genes underlying this disorder.ConclusionThis new analytical tool may provide valuable assistance in the discovery of DEGs and the elucidation of the molecular pathogenicity of ASD. This database model may be replicated to study other disorders.