Cellular uptake of lead in the blood-cerebrospinal fluid barrier

Novel roles of Connexin 43 hemichannel and its down-regulations via Erk phosphorylation

Han Song, Gang Zheng, Yang Liu, Xue Feng Shen, Zai Hua Zhao, Michael Aschner, Wen Jing Luo, Jing Yuan Chen

Research output: Contribution to journalArticle

7 Citations (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)1-11
Number of pages11
JournalToxicology and Applied Pharmacology
Volume297
DOIs
StatePublished - Apr 15 2016

Fingerprint

Cerebrospinal fluid
Connexin 43
Phosphorylation
Cerebrospinal Fluid
Blood
Down-Regulation
Choroid Plexus
Doxycycline
Epithelial Cells
Phosphors
Lead
Carbenoxolone
Atomic spectroscopy
Time and motion study
Connexins
Time and Motion Studies
Absorption spectroscopy
Small Interfering RNA
Transfection
Spectrum Analysis

Keywords

  • Choroid plexus
  • Connexin 43
  • Erk
  • IZCx43
  • Lead
  • Src

ASJC Scopus subject areas

  • Pharmacology
  • Toxicology

Cite this

Cellular uptake of lead in the blood-cerebrospinal fluid barrier : Novel roles of Connexin 43 hemichannel and its down-regulations via Erk phosphorylation. / Song, Han; Zheng, Gang; Liu, Yang; Shen, Xue Feng; Zhao, Zai Hua; Aschner, Michael; Luo, Wen Jing; Chen, Jing Yuan.

In: Toxicology and Applied Pharmacology, Vol. 297, 15.04.2016, p. 1-11.

Research output: Contribution to journalArticle

Song, Han ; Zheng, Gang ; Liu, Yang ; Shen, Xue Feng ; Zhao, Zai Hua ; Aschner, Michael ; Luo, Wen Jing ; Chen, Jing Yuan. / Cellular uptake of lead in the blood-cerebrospinal fluid barrier : Novel roles of Connexin 43 hemichannel and its down-regulations via Erk phosphorylation. In: Toxicology and Applied Pharmacology. 2016 ; Vol. 297. pp. 1-11.
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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.",
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AU - Shen, Xue Feng

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