Fei Xie , Yoshinori Kitagawa , Hiroki Ogata , Shingo Yasuhara , Zerong You , J.A. Jeevendra Martyn
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引用次数: 0
Abstract
Background
Opioid activation of the microglia or macrophage Toll-like receptor 4 (TLR4) and associated inflammatory cytokine release are implicated in opioid-induced hyperalgesia and tolerance. The cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS-STING) signaling pathway, activated by double-stranded DNA including mitochondrial DNA (mtDNA), has emerged as another key mediator of inflammatory responses. This study tested the hypothesis that morphine induces immune inflammatory responses in microglia and macrophages involving TLR4 and cGAS-STING pathway.
Methods
BV2 microglia and Raw 264.7 (Raw) macrophage cells were exposed to morphine with and without a STING inhibitor (C176) for 6 h or TLR 4 inhibitor (TAK242) for 24 h. Western blotting and RT-qPCR analyses assessed TLR4, cGAS, STING, nuclear factor-kappa B (NF-κB), and pro-inflammatory cytokine expression. Morphine-induced mitochondria dysfunction was quantified by reactive oxygen species (ROS) release using MitoSOX, mtDNA release by immunofluorescence, and RT-qPCR. Polarization of BV2 and Raw cells was assessed by inducible nitric oxide (iNOS) and CD86 expression. The role of mtDNA on morphine-related inflammation was investigated by mtDNA depletion of the cells with ethidium bromide (EtBr) or cell transfection of mtDNA extracted from morphine-treated cells.
Results
Morphine significantly increased the expression of TLR4, cGAS, STING, p65 NF-κB, and cytokines (IL-6 and TNF-α) in BV2 and Raw cells. Morphine-induced mitochondrial dysfunction by increased ROS and mtDNA release; the increased iNOS and CD86 evidenced inflammatory M1-like phenotype polarization. TLR4 and STING inhibitors reduced morphine-induced cytokine release in both cell types. The transfection of mtDNA activated inflammatory signaling proteins, cytokine release, and polarization. Conversely, mtDNA depletion led to the reversal of these effects.
Conclusion
Morphine activates the cGAS-STING pathway in macrophage cell types. Inhibition of the STING pathway can be an additional method to overcome immune cell inflammation-related morphine tolerance and opioid-induced hyperalgesia.
期刊介绍:
The journal Cytokine has an open access mirror journal Cytokine: X, sharing the same aims and scope, editorial team, submission system and rigorous peer review.
* Devoted exclusively to the study of the molecular biology, genetics, biochemistry, immunology, genome-wide association studies, pathobiology, diagnostic and clinical applications of all known interleukins, hematopoietic factors, growth factors, cytotoxins, interferons, new cytokines, and chemokines, Cytokine provides comprehensive coverage of cytokines and their mechanisms of actions, 12 times a year by publishing original high quality refereed scientific papers from prominent investigators in both the academic and industrial sectors.
We will publish 3 major types of manuscripts:
1) Original manuscripts describing research results.
2) Basic and clinical reviews describing cytokine actions and regulation.
3) Short commentaries/perspectives on recently published aspects of cytokines, pathogenesis and clinical results.