Abstract
BackgroundMicroglial cells become rapidly activated through interaction with pathogens, and their persistent activation is associated with the production and secretion of various pro-inflammatory genes, cytokines, and chemokines, which may initiate or amplify neurodegenerative diseases. Bromodomain and extraterminal domain (BET) proteins are a group of epigenetic regulators that associate with acetylated histones and facilitate the transcription of target genes. A novel synthetic BET inhibitor, JQ1, was proven to exert immunosuppressive activities by inhibiting the expression of IL-6 and Tnf-α in macrophages. However, a genome-wide search for JQ1 molecular targets is largely unexplored in microglia.MethodsThe present study was aimed at evaluating the anti-inflammatory function and underlying genes targeted by JQ1 in lipopolysaccharide (LPS)-stimulated BV-2 microglial cells using two transcriptomic techniques: global transcriptomic biological duplicate RNA sequencing and quantitative real-time PCR. Associated biological pathways and functional gene ontology were also evaluated.ResultsWith a cutoff value of P ≤ 0.01 and fold change ≥1.5 log2, the expression level of 214 and 301 genes, including pro-inflammatory cytokine, chemokine, and transcription factors, was found to be upregulated in BV-2 cells stimulated with LPS for 2 and 4 h, respectively. Among these annotated genes, we found that JQ1 selectively reduced the expression of 78 and 118 genes (P ≤ 0.01, and fold change ≥ 1.5, respectively). Importantly, these inflammatory genes were not affected by JQ1 treatment alone. Furthermore, we confirmed that JQ1 reduced the expression of key inflammation- and immunity-related genes as well as cytokines/chemokines in the supernatants of LPS-treated primary microglial cells isolated from 3-day-old ICR mice. Utilizing functional group analysis, the genes affected by JQ1 were classified into four categories related to biological regulation, immune system processes, and response to stimuli. Moreover, the biological pathways and functional genomics obtained in this study may facilitate the suppression of different key inflammatory genes through JQ1-treated BV-2 microglial cells.ConclusionsThese unprecedented results suggest the BET inhibitor JQ1 as a candidate for the prevention or therapeutic treatment of inflammation-mediated neurodegenerative diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-015-0260-5) contains supplementary material, which is available to authorized users.
Highlights
Microglia, a type of glial cell, are resident macrophages of the brain and spinal cord, acting as primary effector cells and regularly participating in host defense and immune surveillance in the brain
Microglial cells become rapidly activated in response to infection, inflammation, or injury, and their activation is associated with the production and secretion of a variety of compounds such as cytotoxic molecules, including reactive oxygen species (ROS), nitric oxide (NO) and prostaglandin E2 (PGE2), and a variety of proinflammatory cytokines, including interleukin Il-1β, Il-6, and tumor necrosis factor alpha (Tnf-α) [2]
Gene-induction patterns in LPS-stimulated BV-2 microglial cells We began our study by examining the timing of gene activation induced by LPS by performing an expression analysis of BV-2 microglial cells treated with LPS (10 ng/mL) for 10 min to 24 h and compared the results with the expression in untreated cells under normal culture conditions
Summary
A type of glial cell, are resident macrophages of the brain and spinal cord, acting as primary effector cells and regularly participating in host defense and immune surveillance in the brain. These cells play an important role in the brain’s innate immunity and neuronal homeostasis as well as in neuroinflammatory pathologies [1]. Microglial activation is considered a protective mechanism involved in the clearance of pathogen infection and in regulating tissue repair and recovery, excessive or persistent activation as an uncontrolled immune response stimulates and increases the production of neurotoxic pro-inflammatory mediators and causes neuroinflammation as well as neuronal injury [3]. A genome-wide search for JQ1 molecular targets is largely unexplored in microglia
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