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Shvachiy L, Geraldes V, Amaro-Leal Â, Rocha I. Persistent Effects on Cardiorespiratory and Nervous Systems Induced by Long-Term Lead Exposure: Results from a Longitudinal Study. Neurotox Res 2020; 37:857-870. [PMID: 31997153 DOI: 10.1007/s12640-020-00162-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 01/06/2020] [Accepted: 01/08/2020] [Indexed: 02/06/2023]
Abstract
Long-term lead (Pb) exposure alters the normal development of the nervous system and physiology. It affects multiple organ systems, causing hypertension, cardiorespiratory dysfunction, being a well-known neurotoxin, inducing changes in neurogenesis, neurodegeneration, and glial cells. However, studies of the developmental effects of lead and its outcomes throughout life are lacking. Determine morphofunctional, behavioral, and cognitive developmental effects of long-term lead exposure at three different ages. Wistar rats were exposed to a Pb-acetate solution from fetal period until adulthood and compared to a non-exposed control group. General behavior and cognitive skills were evaluated by behavioral tests and physiological data and cardiorespiratory reflexes measured. Neurodegeneration, neuroinflammation, and synaptic activity were assessed by immunohistochemistry. Lead exposure caused long-lasting anxiety-like behavior and strong long-term memory impairment without changes in locomotor and exploratory activity. Hypertension was observed at all time points, concomitant with baroreflex impairment and increased chemoreflex sensitivity. Persistent neuroinflammation, transient synaptic overexcitation without neurodegeneration was observed. Long-term Pb exposure, since fetal period, causes long-lasting anxiety-like behavior, concomitant with hypertension, without general motor skills impairment. Synaptic overexcitation, reactive astrogliosis, and microgliosis could underlie behavioral and long-term memory changes, which might have been caused during developmental phases and consolidated during adulthood. Also, alterations observed in the cardiorespiratory reflexes can explain persistent hypertension. This longitudinal study identifies and characterizes lead toxicity nature and magnitude, important to devise and test potential interventions to attenuate the long-term harmful effects of lead on the nervous and cardiovascular systems.
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Affiliation(s)
- Liana Shvachiy
- Centro Cardiovascular da Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Av Prof Egas Moniz, 1649-028, Lisbon, Portugal
| | - Vera Geraldes
- Centro Cardiovascular da Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Av Prof Egas Moniz, 1649-028, Lisbon, Portugal.
| | - Ângela Amaro-Leal
- Centro Cardiovascular da Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Av Prof Egas Moniz, 1649-028, Lisbon, Portugal
| | - Isabel Rocha
- Centro Cardiovascular da Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Av Prof Egas Moniz, 1649-028, Lisbon, Portugal
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Intermittent low-level lead exposure provokes anxiety, hypertension, autonomic dysfunction and neuroinflammation. Neurotoxicology 2018; 69:307-319. [PMID: 30098355 DOI: 10.1016/j.neuro.2018.08.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/31/2018] [Accepted: 08/04/2018] [Indexed: 01/14/2023]
Abstract
BACKGROUND Exposures to lead (Pb) during developmental phases can alter the normal course of development, with lifelong health consequences. Permanent Pb exposure leads to behavioral changes, cognitive impairment, sympathoexcitation, tachycardia, hypertension and autonomic dysfunction. However, the effects of an intermittent lead exposure are not yet studied. This pattern of exposure has been recently increasing due to migrations, implementation of school exchange programs and/or residential changes. OBJECTIVE To determine and compare lead effects on mammal's behavior and physiology, using a rat model of intermittent and permanent Pb exposures. METHODS Fetuses were intermittently (PbI) or permanently (PbP) exposed to water containing lead acetate (0.2% w/v) throughout life until adulthood (28 weeks of age). A control group (CTL) without any exposure to lead was also used. Anxiety was assessed by elevated plus maze (EPM) and locomotor activity and exploration by open field test (OFT). Blood pressure (BP), electrocardiogram (ECG), heart rate (HR), respiratory frequency (RF), sympathetic and parasympathetic activity and baro- and chemoreceptor reflex profiles were evaluated. Immunohistochemistry protocol for the assessment of neuroinflammation, neuronal loss (NeuN), gliosis and synaptic alterations (Iba-1, GFAP, Syn), were performed at the hippocampus. One-way ANOVA with Tukey's multiple comparison between means were used (significance p < 0.05) for statistical analysis. RESULTS The intermittent lead exposure produced a significant increase in diastolic and mean BP values, concomitant with a tendency to sympathetic overactivity (estimated by increased low-frequency power) and without significant changes in systolic BP, HR and RF. A chemoreceptor hypersensitivity and a baroreflex impairment were also observed, however, less pronounced when compared to the permanent exposure. Regarding behavioral changes, both lead exposure profiles showed an anxiety-like behavior without changes in locomotor and exploratory activity. Increase in GFAP and Iba-1 positive cells, without changes in NeuN positive cells were found in both exposed groups. Syn staining suffered a significant decrease in PbI group and a significant increase in PbP group. CONCLUSION This study is the first to show that developmental Pb exposure since fetal period can cause lasting impairments in physiological parameters. The intermittent lead exposure causes adverse health effects, i.e, hypertension, increased respiratory frequency and chemoreflex sensitivity, baroreflex impairment, anxiety, decreased synaptic activity, neuroinflammation and reactive gliosis, in some ways similar to a permanent exposure, however some are lower-grade, due to the shorter duration of exposure. This study brings new insights on the environmental factors that influence autonomic and cardiovascular systems during development, which can help in creating public policy strategies to prevent and control the adverse effects of Pb toxicity.
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Cong X, Xu X, Xu L, Li M, Xu C, Qin Q, Huo X. Elevated biomarkers of sympatho-adrenomedullary activity linked to e-waste air pollutant exposure in preschool children. ENVIRONMENT INTERNATIONAL 2018; 115:117-126. [PMID: 29558634 DOI: 10.1016/j.envint.2018.03.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/06/2018] [Accepted: 03/08/2018] [Indexed: 02/07/2023]
Abstract
Air pollution is a risk factor for cardiovascular disease (CVD), and cardiovascular regulatory changes in childhood contribute to the development and progression of cardiovascular events at older ages. The aim of the study was to investigate the effect of air pollutant exposure on the child sympatho-adrenomedullary (SAM) system, which plays a vital role in regulating and controlling the cardiovascular system. Two plasma biomarkers (plasma epinephrine and norepinephrine) of SAM activity and heart rate were measured in preschool children (n = 228) living in Guiyu, and native (n = 104) and non-native children (n = 91) living in a reference area (Haojiang) for >1 year. Air pollution data, over the 4-months before the health examination, was also collected. Environmental PM2.5, PM10, SO2, NO2 and CO, plasma norepinephrine and heart rate of the e-waste recycling area were significantly higher than for the non-e-waste recycling area. However, there was no difference in plasma norepinephrine and heart rate between native children living in the non-e-waste recycling area and non-native children living in the non-e-waste recycling area. PM2.5, PM10, SO2 and NO2 data, over the 30-day and the 4-month average of pollution before the health examination, showed a positive association with plasma norepinephrine level. PM2.5, PM10, SO2, NO2 and CO concentrations, over the 24 h of the day of the health examination, the 3 previous 24-hour periods before the health examination, and the 24 h after the health examination, were related to increase in heart rate. At the same time, plasma norepinephrine and heart rate on children in the high air pollution level group (≤50-m radius of family-run workshops) were higher than those in the low air pollution level group. Our results suggest that air pollution exposure in e-waste recycling areas could result in an increase in heart rate and plasma norepinephrine, implying e-waste air pollutant exposure impairs the SAM system in children.
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Affiliation(s)
- Xiaowei Cong
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, Guangdong, China
| | - Xijin Xu
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, Guangdong, China; Department of Cell Biology and Genetics, Shantou University Medical College, Shantou 515041, Guangdong, China.
| | - Long Xu
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, Guangdong, China
| | - Minghui Li
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, Guangdong, China
| | - Cheng Xu
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, Guangdong, China
| | - Qilin Qin
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangzhou and Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 510632, Guangdong, China
| | - Xia Huo
- Laboratory of Environmental Medicine and Developmental Toxicology, Guangzhou and Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 510632, Guangdong, China.
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Geraldes V, Carvalho M, Goncalves-Rosa N, Tavares C, Laranjo S, Rocha I. Lead toxicity promotes autonomic dysfunction with increased chemoreceptor sensitivity. Neurotoxicology 2016; 54:170-177. [PMID: 27133440 DOI: 10.1016/j.neuro.2016.04.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 04/11/2016] [Accepted: 04/26/2016] [Indexed: 02/07/2023]
Abstract
Mortality and morbidity by toxic metals is an important issue of occupational health. Lead is an ubiquitous heavy metal in our environment despite having no physiological role in biological systems. Being an homeostatic controller is expected that the autonomic nervous system would show a degree of impairment in lead toxicity. In fact, sympathoexcitation associated to high blood pressure and tachypnea has been described together with baroreflex dysfunction. However, the mechanisms underlying the autonomic dysfunction and the interplay between baro- and chemoreflex are not yet fully clarified. The angiotensinogenic PVN-NTS axis (paraventricular nucleus of the hypothalamus - nucleus tractus solitarius axis) is a particularly important neuronal pathway that could be responsible for the autonomic dysfunction and the cardiorespiratory impairment in lead toxicity. Within the current work, we addressed in vivo, baro- and chemoreceptor reflex behaviour, before and after central angiotensin inhibition, in order to better understand the cardiorespiratory autonomic mechanisms underlying the toxic effects of long-term lead exposure. For that, arterial pressure, heart rate, respiratory rate, sympathetic and parasympathetic activity and baro- and chemoreceptor reflex profiles of anaesthetized young adult rats exposed to lead, from foetal period to adulthood, were evaluated. Results showed increased chemosensitivity together with baroreceptor reflex impairment, sympathetic over-excitation, hypertension and tachypnea. Chemosensitivity and sympathetic overexcitation were reversed towards normality values by NTS treatment with A-779, an angiotensin (1-7) antagonist. No parasympathetic changes were observed before and after A-799 treatment. In conclusion, angiotensin (1-7) at NTS level is involved in the autonomic dysfunction observed in lead toxicity. The increased sensitivity of chemoreceptor reflex expresses the clear impairment of autonomic outflow to the cardiovascular and respiratory systems induced by putative persistent, long duration, alert reaction evoked by the long term exposure to lead toxic effects. The present study brings new insights on the central mechanisms implicated in the autonomic dysfunction induced by lead exposure which are relevant for the development of additional therapeutic options to tackle lead toxicity symptoms.
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Affiliation(s)
- Vera Geraldes
- Institute of Physiology, Faculty of Medicine of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal; Cardiovascular Centre of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal
| | - Mafalda Carvalho
- Cardiovascular Centre of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal
| | - Nataniel Goncalves-Rosa
- Institute of Physiology, Faculty of Medicine of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal; Cardiovascular Centre of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal
| | - Cristiano Tavares
- Institute of Physiology, Faculty of Medicine of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal; Cardiovascular Centre of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal
| | - Sérgio Laranjo
- Cardiovascular Centre of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal
| | - Isabel Rocha
- Institute of Physiology, Faculty of Medicine of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal; Cardiovascular Centre of the University of Lisbon, Av. Prof Egas Moniz, 1649-028 Lisbon, Portugal.
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Analytical evidence of heterogeneous lead accumulation in the hypothalamic defence area and nucleus tractus solitarius. Neurotoxicology 2014; 44:91-7. [DOI: 10.1016/j.neuro.2014.05.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 03/25/2014] [Accepted: 05/07/2014] [Indexed: 01/17/2023]
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Guimarães D, Carvalho ML, Geraldes V, Rocha I, Alves LC, Santos JP. Lead in liver and kidney of exposed rats: aging accumulation study. J Trace Elem Med Biol 2012; 26:285-90. [PMID: 22683051 DOI: 10.1016/j.jtemb.2012.02.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 11/22/2011] [Accepted: 02/17/2012] [Indexed: 11/18/2022]
Abstract
The concentration of lead in liver and kidneys of Wistar rats, fed with lead since fetal period in relation to their age and to a control group, was determined. A group of rats was exposed to lead acetate (n=30) in drinking water and the other group was exposed to normal water (n=20). Samples were collected from rats aging between 1 and 11 months and were analyzed by Energy Dispersive X-ray Fluorescence (EDXRF) without any chemical preparation. The EDXRF results were assessed by the PIXE (Proton Induced X-ray Emission) technique. The formaldehyde used to preserve the samples was also analyzed by ETAAS (Electro-Thermal Atomic Absorption Spectrometry) in order to verify if there was any loss of lead from the samples to the formaldehyde. We found that the loss was not significant (<2%). Concerning the mean values of the lead concentration measured in the contaminated soft tissues, in liver they range from 6 to 22μgg(-1), and in kidneys from 44 to 79μgg(-1). The control rats show, in general, values below the EDXRF detection limit (2μgg(-1)). The ratio kidney/liver ranges from 2 to 10 and is strongly positively correlated with the age of the animals. A Spearman correlation matrix to investigate the correlation between elemental concentrations and the dependence of these concentrations with age showed that there is a strong positive correlation with age for lead in the liver but not in the kidney. The correlation matrix showed also that the concentration of lead in these two soft tissues is not correlated. The lead accumulation in liver is made by different plateaus that strongly decrease with age. It was verified the existence of two levels of accumulation in kidney, not very highlighted, which might be indicative of a maximum accumulation level for lead in kidney.
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Affiliation(s)
- Diana Guimarães
- Centro de Física Atómica, CFA, Departamento de Física, FCT, Universidade Nova de Lisboa, Portugal.
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Guimarães D, Carvalho ML, Geraldes V, Rocha I, Santos JP. Study of lead accumulation in bones of Wistar rats by X-ray fluorescence analysis: aging effect. Metallomics 2012; 4:66-71. [DOI: 10.1039/c1mt00149c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Struzyńska L. A glutamatergic component of lead toxicity in adult brain: the role of astrocytic glutamate transporters. Neurochem Int 2009; 55:151-6. [PMID: 19428820 DOI: 10.1016/j.neuint.2009.01.025] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 01/20/2009] [Accepted: 01/21/2009] [Indexed: 11/28/2022]
Abstract
Astroglial cells have a variety of roles in the central nervous system (CNS), providing a homeostasis for the proper functioning of neuronal cells. The classical view concerning the supportive role of astroglia towards associated neurons has to be extended. A great number of new evidences suggest that astrocytes interact closely with neurons being involved in the active control of neuronal activity and metabolism, forming with pre- and postsynaptic nerve terminals a tripartite synapse. Astrocytes control many aspects of brain function. Regulation of extracellular glutamate concentration, potentially neurotoxic neurotransmitter, is fundamental. Glial glutamate transporters system is of importance in protection against glutamate excitotoxicity and antioxidant defence system which is glutathione. When astrocytes fail to function properly, they influence the degree of neuronal damage. Thus, astrocytes are involved to a very great extent into numerous brain pathologies, including toxicity of heavy metals, like lead (Pb). Under pathological conditions they appear to express two opposite features: they are neuroprotective (until they can) or deleterious for neurons and may participate in neuronal damage. The very well known affinity of Pb to astroglia and the changes in glutamatergic transmission upon Pb toxicity, led us to discuss the role of astroglia and astrocytic glutamate transporters in the neurotoxicity of this metal. Our observations are viewed against a background of other results.
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Affiliation(s)
- Lidia Struzyńska
- Department of Neurochemistry, Laboratory of Pathoneurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.
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Verstraeten SV, Aimo L, Oteiza PI. Aluminium and lead: molecular mechanisms of brain toxicity. Arch Toxicol 2008; 82:789-802. [DOI: 10.1007/s00204-008-0345-3] [Citation(s) in RCA: 333] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 07/15/2008] [Indexed: 10/21/2022]
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Jiang YM, Long LL, Zhu XY, Zheng H, Fu X, Ou SY, Wei DL, Zhou HL, Zheng W. Evidence for altered hippocampal volume and brain metabolites in workers occupationally exposed to lead: a study by magnetic resonance imaging and (1)H magnetic resonance spectroscopy. Toxicol Lett 2008; 181:118-25. [PMID: 18692119 DOI: 10.1016/j.toxlet.2008.07.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/05/2008] [Accepted: 07/05/2008] [Indexed: 11/28/2022]
Abstract
Environmental and occupational exposure to lead (Pb) remains to be a major public health issue. The purpose of this cross-sectional study was to use non-invasive magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy ((1)H MRS) techniques to investigate whether chronic exposure to Pb in an occupational setting altered brain structure and function of Pb-exposed workers. The Pb-exposed group consisted of 15 workers recruited from either a Pb-smelting factory or a Pb-battery manufacturer. The control group had 19 healthy volunteers who had no history of Pb exposure in working environment or at home. The average airborne Pb concentrations in fume and dust were 0.43 and 0.44 mg/m(3), respectively, in the smeltery, and 0.10 and 1.06 mg/m(3), respectively, in the Pb battery workshop. The average blood Pb concentrations (BPb) in Pb-exposed and control workers were 63.5 and 8.7 microg/dL, respectively. The MRI examination showed that brain hippocampal volume among Pb-exposed workers was significantly diminished in comparison to age-matched control subjects (p < 0.01), although the extent of this reduction was relatively small (5-6% of the control values). Linear regression analyses revealed significant inverse associations between BPb and the decreased hippocampal volume on both sides of brain hemisphere. Among five brain metabolites investigated by MRS, i.e., N-acetyl-aspartate (NAA), creatine (Cr), choline (Cho), inosine (mI), glutamate/glutamine (Glx) and lipids (Lip), a significant decrease in NAA/Cr ratio (7% of controls, p < 0.05) and a remarkable increase in Lip/Cr ratio (40%, p < 0.01) were observed in the brains of Pb-exposed workers as compared to controls. Furthermore, the increased Lip/Cr ratio was significantly associated with BPb (r = 0.46, p < 0.01). Taken together, this study suggests that occupational exposure to Pb may cause subtle structural and functional alteration in human brains. The MRI and MRS brain imaging techniques can be used as the non-invasive means to evaluate Pb-induced neurotoxicity.
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Affiliation(s)
- Yue-Ming Jiang
- Department of Occupational Health and Toxicology, Guangxi Medical University, Nanning, Guangxi, China
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Kidd S, Anderson D, Schneider J. Postnatal lead exposure alters expression of forebrain p75 and TrkA nerve growth factor receptors. Brain Res 2008; 1195:113-9. [DOI: 10.1016/j.brainres.2007.12.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 12/05/2007] [Accepted: 12/05/2007] [Indexed: 11/25/2022]
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12
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Wang HL, Chen XT, Luo L, Lou ZY, Wang S, Chen JT, Wang M, Sun LG, Ruan DY. Reparatory effects of nicotine on NMDA receptor-mediated synaptic plasticity in the hippocampal CA1 region of chronically lead-exposed rats. Eur J Neurosci 2006; 23:1111-9. [PMID: 16553775 DOI: 10.1111/j.1460-9568.2006.04645.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Activation of neuronal nicotinic acetylcholine receptors (nAChRs) modulates the induction of long-term potentiation (LTP): a possible cellular mechanism of learning. To investigate the effect of nicotine on synaptic plasticity in chronically lead-exposed rats, field excitatory postsynaptic potentials and paired-pulse facilitation (PPF) were recorded in the CA1 area of hippocampal slices from chronically lead-exposed 23-30-day-old rats. The results showed the following. (1) Nicotine (1 microm) facilitated the induction of LTP in CA1 by a weak tetanic stimulation (100 Hz, 20 pulses), which does not by itself produce LTP in lead-exposed rats. This effect was significantly suppressed by mecamylamine, a nicotinic antagonist, suggesting that the facilitation of LTP was through nAChRs. (2) The nicotine-facilitated LTP was blocked by dihydro-beta-erythroidine (DHbetaE), a non-alpha7 nAChR antagonist, whereas long-term depression (LTD) was produced by the combination of nicotine and methyllycaconitine, a alpha7-nAChR antagonist. This type of LTD was blocked by DHbetaE. This suggested that several nAChR subtypes were involved in the nicotine-facilitated synaptic plasticity. (3) Nicotine enhanced PPF in the hippocampal CA1 region, and the nicotine-facilitated LTP in lead-exposed rats was blocked by either d-(-)-2-amino-5-phosphonopentanoic acid, the N-methyl-d-aspartate (NMDA) receptor antagonist, or picrotoxin, an antagonist of gamma-aminobutyric acid(A) receptors. We suggest that nicotine-facilitated synaptic plasticity was due to the activation of NMDARs by disinhibition of pyramidal cells through presynaptic nAChRs. This may represent the cellular basis of nicotine-facilitated cognitive enhancement observed in chronically lead-exposed rats.
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Affiliation(s)
- Hui-Li Wang
- Department of Neurobiology and Biophysics, School of Life Science and Institute of Polar Environment, University of Science & Technology of China, Hefei, Anhui
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Zhang J, Wang XF, Lu ZB, Liu NQ, Zhao BL. The effects of meso-2,3-dimercaptosuccinic acid and oligomeric procyanidins on acute lead neurotoxicity in rat hippocampus. Free Radic Biol Med 2004; 37:1037-50. [PMID: 15336320 DOI: 10.1016/j.freeradbiomed.2004.06.037] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2004] [Revised: 05/24/2004] [Accepted: 06/24/2004] [Indexed: 01/03/2023]
Abstract
Oxidative stress is considered to be a mechanism involved in lead neurotoxicity. Apoptosis is also thought to relate to lead neurotoxicity. The present study, focused on the hippocampus, was designed to investigate the two possible mechanisms involved in lead neurotoxicity and the potential protective effects of 2,3-dimercaptosuccinic acid (DMSA) and oligomeric procyanidins (OPC). It was proved that reactive oxygen species and oxidative damage were implicated in the induction of apoptosis induced by lead in the hippocampus. Administration of DMSA attenuated the oxidative stress and apoptosis in addition to having strong chelating and lead-removing capacity. OPC alone had antioxidant protective effects in the hippocampus but no removing capacity for lead in vivo despite showing higher affinity and stronger chelating ability for Pb(2+) than DMSA in vitro. It is suggested that OPC chelates Pb(2+) but does not discharge it from the body and even accumulates Pb(2+) in some organs. At the same time, a reasonable deduction can also be made that the complex of OPC-Pb(2+) prevents or at least weakens the neurotoxicity of Pb(2+). Whether this complex displays toxicity over a long time span should be studied further.
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Affiliation(s)
- Jie Zhang
- Laboratory of Visual Information Processing, Center for Brain and Cognitive Sciences, Institute of Biophysics, Academia Sinica, Beijing 100101 China
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Braga MFM, Pereira EFR, Mike A, Albuquerque EX. Pb2+ via protein kinase C inhibits nicotinic cholinergic modulation of synaptic transmission in the hippocampus. J Pharmacol Exp Ther 2004; 311:700-10. [PMID: 15226386 DOI: 10.1124/jpet.104.070466] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study was designed to investigate the effects of Pb(2+) on modulation of synaptic transmission by nicotinic receptors (nAChRs) in the rat hippocampus. To this end, inhibitory and excitatory postsynaptic currents (IPSCs and EPSCs, respectively) were recorded by means of the whole-cell mode of the patch-clamp technique from rat hippocampal neurons in culture. Acetylcholine (ACh, 1 mM; 1-s pulses) triggered GABA release via activation of alpha4beta2* and alpha7* nAChRs. It also triggered glutamate release via activation of alpha7* nAChRs. Pb(2+) (0.1 and 1 microM) blocked ACh-triggered transmitter release. Blockade by Pb(2+) of ACh-triggered IPSCs was partially reversible upon washing of the neurons. In contrast, even after 30- to 60-min washing, there was no reversibility of Pb(2+)-induced blockade of ACh-triggered EPSCs. The effects of Pb(2+) on GABA release triggered by activation of alpha7* and alpha4beta2* nACRs were mimicked by the protein kinase C (PKC) activator phorbol-12-myristate-13-acetate (1 microM) and blocked by the indolocarbazole Go 7874 (50 nM) and the bisindolylmaleimide Ro-31-8425 (150 nM), which are selective PKC inhibitors. After washing of fully functional neuronal networks that had been exposed for 5 min to Pb(2+), the irreversible inhibition by Pb(2+) of ACh-triggered glutamate release was partially overridden by a disinhibitory mechanism that is likely to involve alpha4beta2* nAChR activation in interneurons that synapse onto other interneurons synapsing onto pyramidal neurons. Long-lasting inhibition of alpha7* nAChR modulation of synaptic transmission may contribute to the persistent cognitive impairment that results from childhood Pb(2+) intoxication.
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Affiliation(s)
- Maria F M Braga
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, 655 West Baltimore St., Baltimore, MD 21201, USA
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Zhou M, Suszkiw JB. Nicotine attenuates spatial learning deficits induced in the rat by perinatal lead exposure. Brain Res 2004; 999:142-7. [PMID: 14746932 DOI: 10.1016/j.brainres.2003.10.068] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Maternally lead (Pb)-exposed, juvenile rats exhibit significant deficits in spatial reference memory acquisition and working memory performance in the Morris water maze (MWM). Acute systemic application of nicotine reverses these deficits without affecting behavioral performance of the age-matched, lead-unexposed control animals. These results suggest that nicotinic agonist treatments can ameliorate learning and memory impairments, presumably by compensating for deficient nicotinic function in developmentally lead-exposed animals.
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MESH Headings
- Animals
- Animals, Newborn
- Brain/drug effects
- Brain/pathology
- Brain/physiopathology
- Disease Models, Animal
- Female
- Lead Poisoning, Nervous System, Childhood/drug therapy
- Lead Poisoning, Nervous System, Childhood/physiopathology
- Maze Learning/drug effects
- Maze Learning/physiology
- Memory Disorders/chemically induced
- Memory Disorders/drug therapy
- Memory Disorders/physiopathology
- Memory, Short-Term/drug effects
- Memory, Short-Term/physiology
- Nicotine/pharmacology
- Nicotine/therapeutic use
- Nicotinic Agonists/pharmacology
- Nicotinic Agonists/therapeutic use
- Pregnancy
- Prenatal Exposure Delayed Effects
- Rats
- Reaction Time/drug effects
- Reaction Time/physiology
- Receptors, Nicotinic/drug effects
- Receptors, Nicotinic/physiology
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Affiliation(s)
- Mingfu Zhou
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, P.O. Box 670576, Cincinnati, OH 45267-0576, USA
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16
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Meng XM, Ruan DY, Kang LD, Zhu DM, She JQ, Luo L, Zheng Y, Li XH. Age-related morphological impairments in the rat hippocampus following developmental lead exposure: an MRI, LM and EM study. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2003; 13:187-197. [PMID: 21782654 DOI: 10.1016/s1382-6689(02)00159-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2002] [Accepted: 12/10/2002] [Indexed: 05/31/2023]
Abstract
Lead is one of the most common neurotoxic metals present in our environment. Chronic developmental lead exposure is known to be associated with cognitive dysfunction in children. Functional and morphological impairment of the rat brain has also been reported in the hippocampus (Hi) following developmental lead exposure. The present study was carried out to further investigate age-related morphological impairments in the rat Hi following developmental lead exposure with three methods: (1) magnetic resonance imaging (MRI); (2) light microscopy (LM); and (3) electron microscopy (EM) techniques. Neonatal Wistar rats were exposed to lead from parturition to weaning via milk of dams drinking a 0.2% lead acetate solution. Age-related morphological alternations were investigated in the Hi of lead-exposed rats at various postnatal ages: postnatal day (PND) 17, 30 and 90. The MRI signal intensities (SIs) in the left, right, superior and inferior hippocampal regions of control and lead-exposed rats were analyzed. Compared with controls, the SIs of the four hippocampal regions of interest were significantly increased in lead-exposed rats at PND 17, 30 and 90. Moreover, the lead-induced impairment of the Hi showed an age-related decline and a specific topographical pattern. The impairment of inferior hippocampal regions was more severe than that of superior regions in lead-exposed rats at PND 17 and 30, while no significant difference of SIs was observed between left and right hippocampal regions in the three age groups, and between superior and inferior regions in the PND 90 lead-exposed rats. The LM observations indicated that the morphological injury of hippocampal neurons in lead-exposed rats was also age-related. The EM observations revealed that the endoplasmic reticular, Golgi complex and mitochondria of hippocampal CA1 and dentate gyrus neurons in lead-exposed rats were damaged. These results demonstrate that lead-induced morphological impairments of the rat Hi follow a specific age- and site-related pattern.
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Affiliation(s)
- Xiao-Mei Meng
- School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China
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17
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Bouton CM, Hossain MA, Frelin LP, Laterra J, Pevsner J. Microarray analysis of differential gene expression in lead-exposed astrocytes. Toxicol Appl Pharmacol 2001; 176:34-53. [PMID: 11578147 DOI: 10.1006/taap.2001.9274] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The toxic metal lead is a widespread environmental health hazard that can adversely affect human health. In an effort to better understand the cellular and molecular consequences of lead exposure, we have employed cDNA microarrays to analyze the effects of acute lead exposure on large-scale gene expression patterns in immortalized rat astrocytes. Our studies identified many genes previously reported to be differentially regulated by lead exposure. Additionally, we have identified novel putative targets of lead-mediated toxicity, including members of the family of calcium/phospholipid binding annexins, the angiogenesis-inducing thrombospondins, collagens, and tRNA synthetases. We demonstrate the ability to distinguish lead-exposed samples from control or sodium samples solely on the basis of large-scale gene expression patterns using two complementary clustering methods. We have confirmed the altered expression of candidate genes and their encoded proteins by RT-PCR and Western blotting, respectively. Finally, we show that the calcium-dependent phospholipid binding protein annexin A5, initially identified as a differentially regulated gene by our microarray analysis, is directly bound and activated by nanomolar concentrations of lead. We conclude that microarray technology is an effective tool for the identification of lead-induced patterns of gene expression and molecular targets of lead.
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Affiliation(s)
- C M Bouton
- Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland 21205, USA
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18
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Tian X, Sun X, Suszkiw JB. Upregulation of tyrosine hydroxylase and downregulation of choline acetyltransferase in lead-exposed PC12 cells: the role of PKC activation. Toxicol Appl Pharmacol 2000; 167:246-52. [PMID: 10986016 DOI: 10.1006/taap.2000.8996] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of lead (Pb) on the expression of tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) were compared in relation to Pb-activation of cPKC in the PC12 cells. Exposure to 0.53 microM Pb (0.1094 ppm) increased TH but reduced ChAT activity and mRNA levels. The increase of TH activity was detectable as early as 0.5 h of exposure, reached a maximum 150% of control after 2 h, and then diminished to a steady state 135% of control between 12 and 48 h of exposure. The decrease of ChAT activity was first detectable after 2 h of Pb exposure, reached a 45% reduction after 6 h, and remained stable thereafter through 48 h of exposure. PKC activity increased 200% after 2 h and then reverted to control levels by 48 h of Pb exposure. The increase of TH activity after 2 h but not 48 h of exposure exceeded that of its mRNA. PKC inhibitor Rö32-0342 suppressed TH activity increase after 2 h of Pb exposure by 80% without affecting TH mRNA. The decrease of ChAT activity correlated with the reductions in steady-state ChAT mRNA levels at 2 and 48 h of Pb exposure and Rö32-0342 had no effect on the Pb-induced decrease of either ChAT activity or mRNA. These results demonstrate that Pb alters TH and ChAT expression in PC12 cells in a reciprocal manner, i.e., upregulates the former but downregulates the latter. PKC is not involved in Pb-induced downregulation of ChAT but does mediate the early phase of Pb-induced augmentation of TH activity, presumably through postranslational modification (phosphorylation) of the enzyme. However, this effect is short-lived due to downregulation of PKC in the course of prolonged (48 h) Pb exposure. It is concluded that, in the course of prolonged exposure, both upregulation of TH and downregulation of ChAT reflect primarily the effects of Pb at the level of gene expression through mechanisms that are not related to Pb activation of PKC.
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Affiliation(s)
- X Tian
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0576, USA
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19
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Zhou M, Tian X, Suszkiw JB. Developmental stage-dependent protective effect of NGF against lead cholinotoxicity in the rat septum. Brain Res 2000; 866:268-73. [PMID: 10825503 DOI: 10.1016/s0006-8993(00)02265-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The ability of nerve growth factor (NGF) to ameliorate developmental cholinotoxicity of inorganic lead (Pb) for the septal neurons was investigated by making intracerebroventricular injections of single doses of 30 microg 2.5S NGF into maternally lead-exposed suckling rats on postnatal days P2, P4, P11, or P18. Administration of NGF on P4 or later induced septal choline acetyltransferase (ChAT) activity to the same relative extent in both Pb-exposed as in control rats but failed to reverse the net reductions of ChAT activity induced by Pb. In contrast, injection of NGF at P2 completely restored ChAT activity in Pb-exposed pups to control levels by preventing the loss of ChAT-immunoreactive cells in the septum. It is concluded that although NGF retains the capacity to upregulate ChAT throughout the period of Pb exposure, it protects against the Pb-induced loss of septal cholinergic neurons only when applied within the critical period of Pb-vulnerability between postnatal days 2 and 4.
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Affiliation(s)
- M Zhou
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0576, USA
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20
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Adhami VM, Husain R, Agarwal AK, Seth PK. Intrahippocampal cholinergic-rich transplants restore lead-induced deficits: a preliminary study in rats. Neurotoxicol Teratol 2000; 22:41-53. [PMID: 10642113 DOI: 10.1016/s0892-0362(99)00047-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In the present study restorative potential of fetal cholinergic rich cell suspensions in ameliorating cognitive deficits in rats perinatally exposed to lead was studied. Lactating dams with 1-day old litters were given 0.2% (w/v) lead acetate in drinking water throughout lactation from postnatal day (PND) 1 to PND21 at the end of which the treatment was stopped and the animals were weaned. On PND42 lead exposed rats were given bilateral, intrahippocampal, cholinergic rich fetal neural transplants (approximately 60,000 cells per site) and subsequently assessed 3 and 6 months posttransplantation. Control animals (Sham operated and transplanted) were also run in parallel. Lead exposed rats exhibited a decreased learning ability and locomotor activity. A significant decrease in the levels of acetylcholinesterase and sodium potassium ATPase Na+,K+-ATPase activity was observed in hippocampal region of lead exposed rats. The levels of lead were increased by fivefold in the hippocampal region of lead exposed rats. Transplantation showed marginal improvement in the above impairments at 3 months which were more marked at 6 months. Lead levels at 6 months were not significantly higher in lead exposed rats as compared with the control. Results confirm previous findings that fetal neural transplants help in restoring the lost functional deficits and demonstrate their restorative potential in case of lead induced deficits.
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Affiliation(s)
- V M Adhami
- Developmental Toxicology Division, Industrial Toxicology Research Centre, Luckno, India
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21
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Audesirk T, Pedersen C, Audesirk G, Kern M. Low levels of inorganic lead noncompetitively inhibit mu-calpain. Toxicology 1998; 131:169-74. [PMID: 9928631 DOI: 10.1016/s0300-483x(98)00127-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Calpain is a ubiquitous calcium-dependent cysteine protease, whose cytoskeletal protein substrates suggest that it may be important in neuronal differentiation. Lead (Pb2+) is known to substitute for Ca2+ in a variety of intracellular processes, and interferes with the development of hippocampal neurons in vitro. We found that free Pb2+ at 1 nM does not activate calpain in the absence of Ca2+. Pb2+ inhibited the activity of calpain; the degree of calpain inhibition was dependent on an interaction between concentrations of both Ca2+ and Pb2+. In the presence of 1 microM free Ca2+, 10 pM free Pb2+ reduced calpain activity, but in the presence of 100 microM free Ca2+, 1 nM free Pb2+ failed to inhibit calpain. This provides evidence that Pb2+ competes for the Ca2+ binding sites on calpain. In the presence of 40 microM free Ca2+, 1 nM free Pb2+ significantly reduces Vmax without altering Km, suggesting that Pb2+ acts as a noncompetitive inhibitor of calpain. Inhibition of calpain is one mechanism by which Pb2+ may interfere with neuronal development.
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Affiliation(s)
- T Audesirk
- Department of Biology, University of Colorado at Denver, 80217-3364, USA.
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22
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Bourjeily N, Suszkiw JB. Developmental cholinotoxicity of lead: loss of septal cholinergic neurons and long-term changes in cholinergic innervation of the hippocampus in perinatally lead-exposed rats. Brain Res 1997; 771:319-28. [PMID: 9401752 DOI: 10.1016/s0006-8993(97)00828-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effects of perinatal lead exposure on choline acetyltransferase-immunoreactive (ChAT-IR) cell counts in the medial septum and AChE-positive fiber counts in the hippocampus were examined in relation to changes in cholinergic markers in the septohippocampal pathway of the rat. Maternal exposure to 0.2% lead acetate in drinking water from gestational day 16 through weaning at post-natal day 21 (P21) induced in the offspring a 30% reduction in septal ChAT activity and a 20% reduction in ChAT-IR cell profile counts in the medial septum/vertical diagonal band (MS/vDB). These changes were seen as early as P7, persisted through 2 months post-exposure (P81), and were followed by recovery of ChAT activity but not the ChAT-IR cell numbers, at 3 months post-exposure (P112). The loss of ChAT activity and ChAT-IR neurons in the septum was temporally associated with a reduction of ChAT activity (30%), hemicholinium-3 (HC-3) binding (40%), and AChE-positive fiber counts (13-15%) in the hippocampus. The hippocampal ChAT activity and AChE-positive fiber counts returned to control levels by P112 whereas HC-3 binding was restored to normal levels by P200. These results indicate that perinatal, low-level lead exposure induces loss of septohippocampal cholinergic projection neurons in neonate animals, resulting in a deficit in hippocampal cholinergic innervation that persists into young adulthood. The disruption of cholinergic septohippocampal system may be an important factor in lasting cognitive impairments associated with early Pb exposure.
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Affiliation(s)
- N Bourjeily
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, OH 45267-0576, USA
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23
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Cory-Slechta DA, Garcia-Osuna M, Greenamyre JT. Lead-induced changes in NMDA receptor complex binding: correlations with learning accuracy and with sensitivity to learning impairments caused by MK-801 and NMDA administration. Behav Brain Res 1997; 85:161-74. [PMID: 9105573 DOI: 10.1016/s0166-4328(96)00174-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This study sought to further evaluate potential mechanistic relationships between Pb-induced alterations in glutamate neurotransmission and behavioral toxicity. It examined correlations between Pb-induced changes in [3H]MK-801 and [3H]CGP-39653 binding sites in 4 different brain regions (frontal cortex, dentate gyrus, CA1 and striatum) and (1) changes in learning accuracy on a multiple repeated acquisition and performance schedule, and (2) sensitivity to the accuracy-impairing effects of MK-801 and NMDA on this learning baseline. All data were obtained from a single population of rats that had been chronically exposed from weaning to 0, 50 or 250 ppm Pb acetate in drinking water and demonstrated selective learning impairments and altered sensitivity to the effects of MK-801 and NMDA on learning accuracy. Pb exposure decreased MK-801 binding and possibly increased CGP-39653 binding, effects statistically significant in some brain regions, but generally exhibiting similar trends across regions. At 0 ppm, higher levels, particularly of MK-801 binding, were associated with higher accuracy levels in the learning paradigm and with greater decrements in learning accuracy following MK-801 or NMDA administration. These linear correlations were negated and in some cases even reversed by 50 and 250 ppm Pb, an effect that might be attributable to an alteration of NMDA receptor complex subunit composition and thus, ligand binding. Of the 4 brain regions examined, striatal MK-801 binding proved to be the best predictor of learning accuracy levels. These data provide additional support for an involvement of the NMDA receptor complex in Pb-induced learning impairments. The fact that these effects were noted most frequently in striatum also raises the possibility that dopamine-glutamatergic interactions contribute to Pb's effects.
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Affiliation(s)
- D A Cory-Slechta
- Department of Neurobiology and Anatomy, University of Rochester, School of Medicine and Dentistry, NY 14642, USA.
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24
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Sun X, Tian X, Suszkiw JB. Reduction of vesicular acetylcholine transporter mRNA in the rat septum following lead exposure. Neuroreport 1997; 8:891-4. [PMID: 9141059 DOI: 10.1097/00001756-199703030-00015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have previously observed that maternal exposure to lead (Pb) results in a reduction of levels of mRNA coding for cholineacetyltransferase (ChAT) in the septum of developing rat without affecting the dams. Here we report that Pb similarly affects the expression of vesicular acetylcholine transporter (VAChT) mRNA in the rat septum. In close agreement with the time course of ChAT mRNA expression, septal VAChT mRNA levels increased from 30% at postnatal day 7 to 78% and 100% of adult levels at days 14 and 21, respectively. Maternal exposure to 0.2% lead acetate in drinking water from gestational day 16 resulted in an approximately 30% reduction of VAChT in 7 and 21-day-old rat pups without affecting VAChT mRNA levels in the dams. These results indicate a developmental stage-dependent interference by Pb with ChAT/VAChT gene expression in the rat septum.
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Affiliation(s)
- X Sun
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, OH 45267-0576, USA
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