Presynaptic Mechanisms of Lead Neurotoxicity

铅神经毒性的突触前机制

• 批准号: 8292734
• 负责人: Tomas R Guilarte
• 金额: $ 53.07万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-04 至 2017-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8292734
• 关键词: Action Potentials; Address; Affect; Agonist; Animals; Aspartate; Brain; Brain Injuries; Brain-Derived Neurotrophic Factor; Calcium; Calcium Channel; Cells; Child; Chronic; Cognition; Cognitive; Collaborations; Data; Development; Dyes; Endocytosis; Environment; Environmental Risk Factor; Epigenetic Process; Exocytosis; Exposure to; Gene Expression; Glutamate Receptor; Goals; Hippocampus (Brain); Image; Impairment; In Vitro; Individual; Infusion procedures; Intervention; Intraventricular; Intraventricular Infusion; Laboratories; Laser Scanning Microscopy; Lead; Life; Long-Term Effects; Longevity; MAP Kinase Gene; Measures; Memory; Methods; Methyl-CpG-Binding Protein 2; Methylation; N-Methyl-D-Aspartate Receptors; Nervous system structure; Neurons; Phosphorylation; Phosphotransferases; Population; Presynaptic Terminals; Property; Proteins; Public Health; Rattus; Receptor Activation; Receptor Inhibition; Regulation; Relative (related person); Research; Research Personnel; Resources; Risk; Role; Running; Severities; Signal Transduction; Site; Slice; Synapses; Synapsin I; Synapsins; Synaptic Transmission; Synaptophysin; System; Testing; Therapeutic; Time; Tropomyosin; Vesicle; Work; brain volume; cognitive function; environmental enrichment for laboratory animals; experience; hippocampal pyramidal neuron; imaging modality; in vivo; lead exposure; lead ion; neurotoxicity; novel; novel therapeutics; patch clamp; postsynaptic; presynaptic; prevent; programs; promoter; protein B; protein expression; receptor; receptor function; synaptic function; synaptogenesis; transmission process; two-photon; vesicle-associated membrane protein; voltage

DESCRIPTION (provided by applicant): The severe nervous system developmental risks of early life exposure to lead (Pb2+) are well known. It is now becoming increasingly clear that much lower concentrations of Pb2+ can produce significant detrimental effects in children, heightening the need to understand the properties and extent of Pb2+ actions on the brain. Our laboratory has recently discovered that in vitro exposure to very low levels of Pb2+ produces long-term impairments in presynaptic transmitter release in cultured hippocampal neurons, and that these actions mimic those observed in animals lacking the trophic factor brain-derived neurotrophic factor (BDNF). We propose studies in hippocampal slices from rats exposed to low levels of Pb2+ during development to utilize 1) state-of- the-art two-photon imaging methods to assess long-term effects on presynaptic Ca2+ influx and vesicular transmitter release in intact synapses, and 2) whole-cell patch-clamp recording from CA1 pyramidal neurons to characterize the long-term effects of low level Pb2+ exposure on postsynaptic N-methyl-D-aspartate receptor (NMDAR)-gated currents. Our working hypothesis is that early Pb2+ exposure produces impairments in NMDAR function that leads to reduced BDNF synthesis and release and subsequent impairments of presynaptic transmission that are critical to normal cognitive function. One manipulation known to increase BDNF levels and release is an enriched environment. To test our hypothesis and identify potential methods of protecting the brain from developmental damage from Pb2+, we propose to 1) characterize the effects of low [Pb2+] exposure on BDNF gene expression, promoter methylation and TrkB receptor activation, and 2) test the ability of an enriched environment, exogenous intraventricular BDNF infusion or administration of the TrkB agonist 7,8-dihydroxyflavone to prevent Pb2+-induced long-term damage to NMDAR function and transmitter release. The research program we propose addresses the critical question of whether early developmental exposure to low-levels of Pb2+ than previously thought have long-term detrimental effects on brain function. These studies will provide novel information about Pb2+ effects on both presynaptic and postsynaptic mechanisms critical to cognition and memory storage. Further, we will examine novel therapeutic manipulations that elevate BDNF release and TrKB receptor activation in order to protect against the long-term detrimental effects of Pb2+ exposure. PUBLIC HEALTH RELEVANCE: It is well recognized that exposure to lead (Pb2+) causes severe effects to children's long-term cognitive function. New data indicates the concerning possibility that early exposure to much lower concentrations of Pb2+ produces significant detrimental effects that can be long-term, perhaps even life-long. In order to set rational limits and develop therapeutic strategies to this environmental risk to young children, we need to know much more about the scope of these low-level effects of Pb2+. New evidence suggests that very low levels of Pb2+ can lead to long-term impairments in presynaptic transmitter release, and that these effects may be due to impairment of N-methyl-d-aspartate glutamate receptor-dependent release of brain-derived neurotrophic factor (BDNF). The studies proposed in this application will extend these findings to intact synapses in brain slices, directly test ths working hypothesis about the mechanism of action of Pb2+ on transmitter release, and evaluate the potential of therapeutic manipulations to help protect children from such effects. The novel finding that exposure to low levels of Pb2+ can reduced BDNF levels in the brain has important implications to brain volume changes throughout the lifespan. It is likely that large populations o children being exposed to very low concentrations of Pb2+ have subtle but life-long cognitive and structural brain damage that only now it is beginning to be recognized. Thus, the need to understand the severity of this danger and the key mechanisms involved is critical to dealing with a Public Health threat of significant proportion.

描述（由申请人提供）：众所周知，严重的神经系统发育风险（PB2+）是众所周知的。现在越来越清楚的是，PB2+浓度较低会对儿童产生重大的有害影响，从而增加了了解PB2+作用对大脑的特性和程度的需求。我们的实验室最近发现，体外暴露于非常低的PB2+会在培养的海马神经元中产生突触前发射器释放的长期损害，并且这些动作模仿了缺乏营养因子脑源性神经植物营养因子（BDNF）的动物中观察到的动作。 We propose studies in hippocampal slices from rats exposed to low levels of Pb2+ during development to utilize 1) state-of- the-art two-photon imaging methods to assess long-term effects on presynaptic Ca2+ influx and vesicular transmitter release in intact synapses, and 2) whole-cell patch-clamp recording from CA1 pyramidal neurons to characterize the long-term effects of low level Pb2+突触后N-甲基-D-天冬氨酸受体（NMDAR）的电流暴露。我们的工作假设是，早期的PB2+暴露会导致NMDAR功能的损害，从而导致BDNF合成和释放以及随后的突触前传播的损害对正常认知功能至关重要。一种已知可以提高BDNF水平并释放的操纵是一个丰富的环境。为了检验我们的假设并确定保护大脑免受PB2+发育损害的潜在方法，我们建议1）表征低[Pb2+]暴露对BDNF基因表达，启动子甲基化和TRKB受体激活和TRKB受体激活和2）的影响的影响。 7,8-二氢氟氟酮可防止PB2+诱导的NMDAR功能和发射器释放的长期损害。我们提出的研究计划解决了一个关键问题，即早期发育暴露于低水平的PB2+是否比以前认为的对脑功能的长期有害影响。这些研究将提供有关PB2+对认知和记忆存储至关重要的突触前和突触后机制的新信息。此外，我们将研究新型的治疗操作，以提高BDNF释放和TRKB受体激活，以防止PB2+暴露的长期有害影响。 公共卫生相关性：众所周知，接触铅（PB2+）会对儿童的长期认知功能产生严重影响。新数据表明，早期暴露于较低浓度的PB2+会产生重大的有害影响，这可能是长期的，甚至可能终身。为了设定合理限制并为幼儿制定这种环境风险的治疗策略，我们需要更多地了解PB2+这些低级影响的范围。新的证据表明，非常低的PB2+会导致突触前发射器释放的长期损害，并且这些作用可能是由于N-甲基-D-天冬氨酸谷氨酸受体受体依赖性释放脑源性神经营养因子（BDNF）的损害所致。本应用中提出的研究将把这些发现扩展到脑切片中完整的突触，直接检验有关PB2+在发射机释放的作用机理的工作假设，并评估治疗性操纵的潜力，以帮助保护儿童免受此类影响。新的发现，暴露于低水平的PB2+可以降低大脑中的BDNF水平对整个寿命中的脑体积变化具有重要意义。大量人群可能会暴露于非常低浓度的PB2+的儿童具有微妙但终生的认知和结构性脑损伤，直到现在才开始被认识到。因此，了解这种危险的严重性以及所涉及的关键机制的需求对于应对大量比例的公共卫生威胁至关重要。