title: Cellular uptake of lead in the blood-cerebrospinal fluid barrier: Novel roles of Connexin 43 hemichannel and its down-regulations via Erk phosphorylation.
abstract: As the structural basis of blood-cerebrospinal fluid barrier (BCB), epithelial cells in the choroid plexus (CP) are targets for lead (Pb). Pb is known to accumulate in the CP; however, the mechanism of Pb uptake in the choroidal epithelial cells remains unknown. Recently, hemichannels of Connexin 43 (Cx43), the most ubiquitously expressed gap junction proteins in the CP, were found to be important pathways for many substances. This study was designed to investigate the roles of Cx43 in Pb uptake in the epithelial cells. Autometallography was used to outline Pb's subcellular location, and the characteristics of Pb transport into CP cells, including concentration- and time-dependence were analyzed by atomic absorption spectroscopy. Knockdown/overexpression of Cx43 with transient siRNA/plasmids transfections before Pb exposure diminished/increased the Pb accumulation. In the Z310 cell-based doxycycline-inducible Cx43 expression cell line (iZCx43), doxycycline induced a significant increase (3-fold) in Pb uptake, corresponding to the increased Cx43 levels. Activation of Cx43 hemichannels by reduced serum conditions caused an increase of Pb concentrations. Cx43-induced Pb uptake was attenuated after blockage of Cx43 hemichannels with its inhibitor, carbenoxolone. Additionally, down-regulation of Cx43 protein levels by Pb exposure paralleled cellular Pb concentrations in the time study. Concomitantly, expressions of phosphor-Src and phosphor-Erk were both significantly increased by Pb. However, inactivation of Erk, not Src pathway, reversed Pb-induced downregulation of Cx43. Taken together, these data establish that Pb can accumulate in the BCB and validate the role of Cx43 hemichannel in Pb uptake and its regulations through Erk phosphorylation.
authors.affiliation: Department of Occupational and Environmental Health and the Ministry-of-Education's Key Laboratory of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Han
authors.initials: H
authors.lastname: Song
authors.affiliation: Department of Occupational and Environmental Health and the Ministry-of-Education's Key Laboratory of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Zheng
authors.affiliation: Department of Occupational and Environmental Health and the Ministry-of-Education's Key Laboratory of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Occupational and Environmental Health and the Ministry-of-Education's Key Laboratory of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Xue-Feng
authors.initials: XF
authors.lastname: Shen
authors.affiliation: Department of Occupational and Environmental Health and the Ministry-of-Education's Key Laboratory of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Zai-Hua
authors.initials: ZH
authors.lastname: Zhao
authors.affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Aschner
authors.affiliation: Department of Occupational and Environmental Health and the Ministry-of-Education's Key Laboratory of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an 710032, China. Electronic address: luowenj@fmmu.edu.cn.
authors.forename: Wen-Jing
authors.initials: WJ
authors.lastname: Luo
authors.affiliation: Department of Occupational and Environmental Health and the Ministry-of-Education's Key Laboratory of Hazard Assessment and Control in Special Operational Environment, School of Public Health, Fourth Military Medical University, Xi'an 710032, China. Electronic address: jy_chen@fmmu.edu.cn.
authors.forename: Jing-Yuan
authors.initials: JY
authors.lastname: Chen
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002831:Choroid Plexus / Q000187:drug effects / Q000378:metabolism*; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004318:Doxycycline; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007854:Lead / Q000097:blood / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics* / Q000633:toxicity; D008297:Male; D010766:Phosphorylation; D017207:Rats, Sprague-Dawley
chemical_list: D018031:Connexin 43; D007854:Lead; D048049:Extracellular Signal-Regulated MAP Kinases; D004318:Doxycycline
keywords: Choroid plexus; Connexin 43; Erk; Lead; Src; iZCx43