Wei Zheng - US grants

DESCRIPTION (provided by applicant): The recent addition of a manganese (Mn)-containing antiknock compound methylcyclo-pentadienyl Mn tricarbonyl (MMT) to the US gasoline supply has raised a great concern about the health risks associated with a potential increase in the environmental levels of Mn. Both environmental and occupational exposures to (Mn) result in neurodegenerative symptoms resembling Parkinson's disease. However, the mechanisms underlying Mn neurotoxicity remain unknown. Our recent results show that in vivo and in vitro exposures to Mn alter both systemic and subcellular Fe status. While the former facilitates influx of Fe from the blood circulation to the cerebral spinal fluid (CSF), the latter promotes cellular Fe overload. We also found that accumulation of Mn in the choroid plexus, a tissue where blood-CSF barrier resides, enhances the density of transferrin receptor (TfR) mRNA, which has 3' binding IRE (iron responsive element) loops receptive to [4Fe-4S] cluster-containing iron regulatory protein-1 (IRP-1, or cytosolic aconitase). These findings have led us to propose that the mechanism by which Mn causes abnormal Fe metabolism is likely via its interaction with IRP-1 and the subsequent overexpression of TfR. The events, in turn, expedite Fe transport at the brain barrier systems and aggravate Fe accumulation in neuronal cells. Thus, we hypothesize in this proposal that accumulation of Mn in the choroid plexus alters Fe regulatory mechanisms in the blood-CSF barrier and thereby disturbs Fe homeostasis in the CSF, which may contribute to Mn-induced neurodegenerative Parkinsonism. Our research goals are to better understand the mechanism of Mn-induced Parkinsonism and in so doing identify and prevent environmental causes of neurodegenerative diseases. Our specific aims are (1) to test the working hypothesis that Mn exposure alters the Fe regulatory mechanism in the choroid plexus, leading to a distorted Fe status in the CSF. We will define the dose and time response relationship of Mn exposure and Fe in CSF, blood, and choroid plexus, examine the activity of IRP-1, and determine the expression of TfR in blood-CSF barrier and selected brain areas; (2) to test the working hypothesis that Mn-facilitated transport of Fe at the blood-CSF barrier is directed toward the CSF and quantitatively is more significant than transport by the blood-brain barrier. We will use in vitro transport models to determine the direction and magnitude of Fe fluxes at two major brain barriers and to investigate if blocking of cellular trafficking of TfR antagonizes Mn-augmented unidirectional transport of Fe; and (3) to test the working hypothesis that alteration by Mn of cellular Fe regulation takes place at the level of mRNA expression, but not at the level of transcriptional modulation of genomic DNA. We will deterrnine the effect of Mn on RNA binding capability of IRP-1 and pertinent expression of TfR, examine if Mn inhibits degradation of TfR mRNA, and study cellular ferritin status in both barriers. In addition, we will study the effect of Mn on the RNA binding capability of a newly discovered IRP which regulates the synthesis of an [Fe-S] subunit of Complex-I.

DESCRIPTION (provided by applicant) Conference support: This application is for support of part of a 3 day International workshop on choroid plexus research. The cerebral choroid plexuses (CP) are the major sites of the blood-cerebrospinal fluid barrier and their importance in brain health and disease are becoming increasingly recognized as new data emerges on the role of the choroid plexus in neuroprotection, acting as a barrier to systemic toxics, synthesizing proteins and hormones essential to brain health, and participating in endocrine and immunological function activity in the central nervous system throughout the lifespan. The home disciplines of researchers active in the field are diverse, and include those in toxicology, pharmacology, endocrinology, physiology and molecular biology. The primary goal of this workshop is to act as a focus for those groups specifically activity in CP research, who would not otherwise have a natural meeting "home." This workshop builds upon the first meeting held in France, and the continuing dissemination of CP research via the CP website which developed from that meeting. The second international workshop on choroid plexus research will be held at King's College London in the United Kingdom from 12th- 14th April 2003. The participants are drawn widely from international research on CP, and given the emerging nature of the topic, we aim to include all those interested in or actively pursing CP research including established researchers, experienced groups who are new to this field, and encourage young researchers undertaking doctoral and postdoctoral studies. The board topic to be covered are: 1) New insight into Choroid plexus structure and CSF section; 2) The role of the choroid plexus in brain health and disease; 3) Choroid plexus function in brain protection; 4) Choroid Plexus as a route for compounding transport and access to brain.

DESCRIPTION (provided by applicant): Brain is well protected against blood-borne xenobiotics (drugs, nutrients, and toxins) by two major barriers, i.e., blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barrier (BCB). The BCB, whose surface area is about one-half of the BBB, is located in brain ventricles and functions to produce CSF and transport xenobiotics between blood and CSF. We have recently established a novel immortalized choroidal epithelial cell line, named Z310 cell line. This ceil line possesses the essential morphology of the parent primary cells and, upon growing on a semipermeable membrane, forms a monolayer that restricts the free movement of paracellular leakage marker, [14C]sucrose. While the tightness of the cell monolayer, as measured by trans-epithelial electrical resistance (TEER) or paracellular leakage of [14C]sucrose, remains to be improved, we are convinced that this cell line shows a great promise as a unique in vitro blood-brain barrier transport system, as there has been no such brain cell-derived transport model in the current neurotoxicology and neuropharmacology research field. To create this novel system, we hypothesize that the tightness of the monolayer of Z310 epithelial cells can be improved by alteration of the chemical components of the culture media, by induction and promotion of tight junction assembly, and/or by genetic modulation of the expression of tight junction proteins. Thus, our specific aims are to reduce the paracellular permeability of the Z310 barrier model by modifying the culture medium components, such as using serum-free or astrocyte-conditioned culture media, to improve the tightness of the barrier structure by application of tight-junction inducing agents in cell culture medium, and to knock-in the specific gene fragments that encode the proteins or regulatory proteins associated with tight junctions in existing Z310 cells. We further design a series of experiments to validate this model system. The studies proposed in this application, if successful despite the notable risk, will lead to the creation of a novel in vitro blood-brain/CSF model for transport study of materials into brain and should have significant impact on pharmacological and toxicological investigation of CNS transport of drugs and toxicants, CNS drug development, and etiological research of brain diseases.

[unreadable] DESCRIPTION (provided by applicant): Altered brain iron (Fe) homeostasis has been shown in idiopathic Parkinson's disease (IPD) and in manganese (Mn)-induced Parkinsonism. The current proposal continues the central theme of our long-time research goal, i.e., to explore the role of brain barrier systems in metal-induced neurotoxicities. Divalent metal transporter-1 (DMT1) and metal transport protein-1 (MTP1) are two newly discovered metal transporters and function to transport metals across the cell membrane. In the Progress Report, we have demonstrated the presence of DMT1 and MTP1 in the choroid plexus, where the blood-cerebrospinal fluid (CSF) barrier (BCB) is located. We have also observed that Mn exposure increases DMT1 expression and mobilizes subcellular MTP1 in the BCB epithelia. However, the questions as to where the DMT1 and MTP1 are subcellularly co-localized in the BCB, how they function in concert to respond to divalent-metal fluxes on both sides of the BCB, by what mechanism Mn exposure alters the expression and function of both transporters, and how the dysregulation of DMT1 and MTP1 in the BCB by Mn exposure affects brain homeostasis of Fe and Mn, remain mysterious. Thus, to understand the structural functionality of DMT1 and MTP1 in the brain barrier and their dysfunction-associated neuronal disorders, we hypothesize that the altered expression of DMT1 and MTP1 in the choroid plexus following Mn exposure contributes to Mn- induced Fe metabolism disorder in the CSF. Our specific aims are: (1) to explore whether DMT1 and MTP1 control the direction of Fe transport at the BCB by investigating the subcellular location of DMT1 and MTP1 in choroidal epithelia, by blocking or inducing DMT1 and MTP1 expression to determine the direction of Fe and Mn transport at BCB, and by using siRNA technique to silence the genes encoding DMT1 and MTP1 to investigate Fe and Mn uptake and transport kinetics under DMT1 or MTP1 knock-down conditions; (2) to explore whether in vivo chronic Mn exposure distorts the expression of DMT1 and MTP1 in the BCB and selected regional blood-brain barrier and leads to increased fluxes of Fe between the blood and CSF, by using a rat chronic Mn exposure model and by a ventriculo-cisternal perfusion technique; and (3) to explore whether Mn exposure interferes the binding of iron-regulatory proteins to mRNAs of DMT1 and MTP1, since the stem-loop structure exists in 3'-untranslated regions (UTR) and 5'-UTR in DMT1 and MTP1 mRNA, respectively. Studies proposed in this application will define the inter-relationship between DMT1 and MTP1 in the BCB with regard to their subcellular locations, roles in transport of divalent metals at the BCB, and their regulation as affected by Mn exposure; will provide insight into the molecular mechanism by which Mn affects divalent Fe transport by brain barriers; and will ultimately provide a better understanding of Fe dysfunction-related neuronal diseases such as IPD. [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Accumulation of beta-amyloid (A2) in brain extracellular fluids is the key event in the amyloid cascade leading to neuronal cell damage in the etiology of Alzheimer's disease (AD). Our preliminary data suggest that the choroid plexus sequesters A2 from the cerebrospinal fluid (CSF). The choroid plexus, as the tissue constituting the blood-CSF barrier, is also known to accumulate toxic metal lead (Pb) based on both human and animal studies. More recently, we found that acute in vivo Pb exposure increases A2 deposition in this tissue. Thus, this exploratory research proposal is designed to test the hypothesis that exposure to Pb results in an accumulation of beta-amyloids in the choroid plexus as well as in brain tissues;this may occur as a result of Pb alteration of beta-amyloid clearance by the choroid plexus by affecting beta-amyloid transport and/or enzymatic degradation in this tissue. Several techniques unique to the blood-brain barrier research such as in vitro two-chamber Transwell trans-epithelial model, in situ brain perfusion and in situ ventriculo-cisternal perfusion, along with transgenic mice that over-express A2, will be used to test the research hypothesis. The study proposed in this application will explore novel pathways of A2 clearance from brain extracellular fluids and will define the role of Pb exposure in these processes. Potential discovery of A2 transporters and metabolic regulatory mechanisms in the choroid plexus will help develop novel strategies for treatment and prevention of Alzheimer's disease. PUBLIC HEALTH RELEVANCE This study will explore novel pathways of A2 clearance from brain extracellular fluids and will define the role of Pb exposure in these processes. Results of this study will provide clues as to whether exposure to toxic metal lead (Pb) in the general population may contribute to the AD etiology. Potential discovery of A2 transporters and metabolic regulatory mechanism in the choroid plexus will help develop novel strategies for treatment and prevention of Alzheimer's disease.

DESCRIPTION (provided by applicant): The Xi'an International Neurotoxicology Conference (XINC) is a joint conference of the 13th International Neurotoxicology Association Biennial Meeting (INA-13) and 11th International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health (NEUREOH-11). The XINC will convene between June 5-9, 2011 in Xi'an Jian-Guo Hotel and Conference Center in Downtown Xi'an, China. The theme of the conference is "Neurotoxicity and Neurodegeneration: Local Effect and Global Impact". The overall objective of the conference is to bring together worldwide experts from academia, industry, government and non-government organizations to discuss new advances, in order to identify research gaps, and to define future research needs in the environmental and occupational causes of neurotoxicity and neurodegeneration. With the meeting venue taking place in the world largest developing country, the XINC will provide a unique opportunity to examine the real environmental and occupational issues resulting from rapid industrial development. The joint conference will discuss these outcomes within the context of numerous neurodegenerative disorders, with emphasis on genetics, molecular and cellular mechanisms of neurodegeneration (Theme 1), exposure, regulation, and risk assessment of neurotoxicities (Theme 2), advances in diagnosis, treatment and prevention of neurotoxicities (Theme 3), behavioral neurotoxicity testing (Theme 4), and neurotoxicological epidemiology (Theme 5). The health relevance of this conference is highly significant in that the discussions and presentations will define the major questions that require experimental resolution in areas that affect human neurological heath. PUBLIC HEALTH RELEVANCE: Worldwide experts in neurotoxicology specializing in environmental and occupational exposure will meet in Xi'an, China, between June 5-9, 2011, to discuss the issues related to chemical- induced neurotoxicity and neurodegeneration. The meeting will help to identify and develop novel strategies for diagnosis, treatment and prevention of neurological disorders.

Abstract:   Accumulation of beta?amyloid (A?) in brain extracellular parenchyma and fluid is the key event in the amyloid cascade leading to neuronal cell damage in the etiology of Alzheimer's disease (AD). The blood?brain barrier (BBB) between the blood and brain interstitial fluid and the blood-CSF barrier (BCB) between the blood and cerebrospinal fluid (CSF) play an important role in maintaining the homeostasis of A? in brain extracellular milieu. Since the brain barrier systems are the known targets of Pb toxicity, it is quite possible that Pb toxicity on brain barriers may affect the critical processes in brain barrier systems that regulate A? transport and metabolism. Thus, the central hypothesis to be tested in this study is that exposure to Pb damages the brain barrier systems, which compromises the clearance and eventually increases the leakage of A? at the BBB and BCB, facilitates the physiochemical reactions between A? and Pb ions, ultimately leading to an increased formation of amyloid plaques in both brains and blood vessels. To test this hypothesis, we have designed three sets of specific aims. In aim 1, we will use the state?of?the?art dynamic contrast? enhanced computed tomography (DCE?CT) to quantify the real?time brain regional blood flow, blood volume, and BBB permeability before and after Pb exposure in Tg?APP mice which overexpress A? and have the detectable amyloid plaques in brain as well as WT mice. We will also characterize the shift of fibril A? deposits from the brain's capillary vessels to its parenchyma as a result of Pb exposure in a dose?time dependent fashion. We will focus on expressions of two transporters, RAGE and LRP?1, in the BBB treated with Pb. The experiments in Aim 2 will focus on the role of two A? transporters, i.e., lipoprotein receptor protein?1 (LRP1) and advanced glycation end products (RAGE) in mediating A? transport by mainly the BCB, and how Pb exposure may affect the direction of A? transport across the BCB. Finally, in Aim 3, we will use synchrotron X?ray fluorescence (XRF) imaging technique coupled with immunohistochemistry to co? localize Pb with amyloidal aggregates and K X?ray fluorescence (KXRF) technique quantify real?time Pb concentrations in bone (PbBn) and to establish the association between PbBn and amyloid aggregation in brain and blood vessels after Pb exposure at different doses and time. These studies will establish a novel concept that the brain barriers play a key role in regulating Pb?induced brain A? oligomers and plaques as well as in blood vessels. We will also establish the relationship between Pb exposure and permeability changes of brain barriers to A? fluxes and provide clues as to whether chronic Pb exposure and changes in cerebral vascular permeability contribute to AD pathogenesis and development. The research will help develop the novel strategies for diagnosis, treatment and prevention of AD.    PHS 398/2590 (Rev. 06/09) Page 1 Continuation Format Page

Principal Investigator: Zheng, W. 1 The 13th Biennial Conference of the Int?l Society for Trace Element Research in Humans Project Summary The 13th Biennial Conference of International Society for Trace Element Research in Humans (ISTERH) will convene in Prama Sanur Beach Hotel in Bali, Indonesia, September 22-26, 2019. The theme of this ISTERH-2019 conference emphasizes ?Systemic Impact of Trace Elements on Human Health and Diseases: Nutrition, Toxicity, and Beyond?. The overall objective of the Conference is to bring together worldwide experts from academia, industry, government and non-government organizations to discuss new advances, to identify research gaps, and to define future research needs in one of the long-lasting research areas, i.e., the health and harmful impact of trace elements on humans. The Conference will explore the current state of research and discovery on the molecular and cellular mechanisms of beneficial and harmful effects of trace elements, mammalian and non- mammalian models for metal?s health research, in vitro models to assess developmental metal toxicity, as well as observations from human cohort metal studies. Moreover, the Conference will discuss the beneficial implication of trace elements on the body systems, consequential changes, as well as broader worldwide environmental health preventions and internationally occupational safety promotion. With the meeting venue taking place in a developing country Indonesia, the ISTERH-2019 will provide a unique opportunity to examine the metal nutrition- and exposure-related issues resulting from rapid industrial development. The Conference invited 10 world-renowned scholars as the plenary-speakers whose presentations are open to all meeting attendees. There will be 12 symposia that are arranged in the parallel sessions to meet the specific interests of diverse audience. The Conference also plans one student oral presentation session, with the purpose to propel research and education in the international community, foster career development of promising young scientists entering the field, promote collaborative research and learning experience with an international scope, and provide state- of-the-art information for students and post/doc fellows.