Cocaine-mediated induction of microglial activation involves the ER stress-TLR2 axis.

Publisher: BioMed Central Country of Publication: England NLM ID: 101222974 Publication Model: Electronic Cited Medium: Internet ISSN: 1742-2094 (Electronic) Linking ISSN: 17422094 NLM ISO Abbreviation: J Neuroinflammation Subsets: MEDLINE

Original Publication: [London] : BioMed Central, c2004-

Cocaine/*pharmacology ; Dopamine Uptake Inhibitors/*pharmacology ; Endoplasmic Reticulum Stress/*drug effects ; Microglia/*drug effects ; Signal Transduction/*drug effects ; Toll-Like Receptor 2/*metabolism ; Up-Regulation/*drug effects; Animals ; Animals, Newborn ; Cells, Cultured ; Chemokine CCL2/genetics ; Chemokine CCL2/metabolism ; Cytokines/metabolism ; Macrophage Activation/drug effects ; Male ; Mice ; Mice, Inbred C57BL ; RNA, Small Interfering/genetics ; RNA, Small Interfering/metabolism ; Reactive Oxygen Species/metabolism ; Time Factors ; Tumor Necrosis Factor-alpha/genetics ; Tumor Necrosis Factor-alpha/metabolism

Background: Neuroinflammation associated with advanced human immunodeficiency virus (HIV)-1 infection is often exacerbated by chronic cocaine abuse. Cocaine exposure has been demonstrated to mediate up-regulation of inflammatory mediators in in vitro cultures of microglia. The molecular mechanisms involved in this process, however, remain poorly understood. In this study, we sought to explore the underlying signaling pathways involved in cocaine-mediated activation of microglial cells.
Methods: BV2 microglial cells were exposed to cocaine and assessed for toll-like receptor (TLR2) expression by quantitative polymerase chain reaction (qPCR), western blot, flow cytometry, and immunofluorescence staining. The mRNA and protein levels of cytokines (TNFα, IL-6, MCP-1) were detected by qPCR and ELISA, respectively; level of reactive oxygen species (ROS) production was examined by the Image-iT LIVE Green ROS detection kit; activation of endoplasmic reticulum (ER)-stress pathways were detected by western blot. Chromatin immunoprecipitation (ChIP) assay was employed to discern the binding of activating transcription factor 4 (ATF4) with the TLR2 promoter. Immunoprecipitation followed by western blotting with tyrosine antibody was used to determine phosphorylation of TLR2. Cocaine-mediated up-regulation of TLR2 expression and microglial activation was validated in cocaine-injected mice.
Results: Exposure of microglial cells to cocaine resulted in increased expression of TLR2 with a concomitant induction of microglial activation. Furthermore, this effect was mediated by NADPH oxidase-mediated rapid accumulation of ROS with downstream activation of the ER-stress pathways as evidenced by the fact that cocaine exposure led to up-regulation of pPERK/peIF2α/ATF4 and TLR2. The novel role of ATF4 in the regulation of TLR2 expression was confirmed using genetic and pharmacological approaches.
Conclusions: xThe current study demonstrates that cocaine-mediated activation of microglia involves up-regulation of TLR2 through the ROS-ER stress-ATF4-TLR2 axis. Understanding the mechanism(s) involved in cocaine-mediated up-regulation of ROS-ER stress/TLR2 expression and microglial activation could have implications for the development of potential therapeutic targets aimed at resolving neuroinflammation in cocaine abusers.

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R21 DA033614 United States DA NIDA NIH HHS; DA036157 United States DA NIDA NIH HHS; DA033614 United States DA NIDA NIH HHS; R01 DA035203 United States DA NIDA NIH HHS; DA035203 United States DA NIDA NIH HHS; R01 DA036157 United States DA NIDA NIH HHS; P30 GM103509 United States GM NIGMS NIH HHS; DA033150 United States DA NIDA NIH HHS; R01 DA033150 United States DA NIDA NIH HHS

0 (Ccl2 protein, rat)
0 (Chemokine CCL2)
0 (Cytokines)
0 (Dopamine Uptake Inhibitors)
0 (RNA, Small Interfering)
0 (Reactive Oxygen Species)
0 (Toll-Like Receptor 2)
0 (Tumor Necrosis Factor-alpha)
I5Y540LHVR (Cocaine)

Date Created: 20160211 Date Completed: 20161005 Latest Revision: 20181113

20221213

PMC4748483

10.1186/s12974-016-0501-2

26860188