Protein Kinase B/Akt Is Required for Complete Freund's Adjuvant-Induced Upregulation of Nav1.7 and Nav1.8 in Primary Sensory Neurons

  • Lingli Liang
    Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
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  • Longchang Fan
    Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland

    Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, PR China
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  • Bo Tao
    Undergraduate Program in Public Health Studies, Johns Hopkins University Zanvyl Krieger School of Arts and Sciences, Baltimore, Maryland
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  • Myron Yaster
    Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
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  • Yuan-Xiang Tao
    Address reprint requests to Yuan-Xiang Tao, MD, PhD, Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, 1721 East Madison St, 370 Ross, Baltimore, MD 21205.
    Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
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      Voltage-gated sodium channels (Nav) are essential for the generation and conduction of action potentials. Peripheral inflammation increases the expression of Nav1.7 and Nav1.8 in dorsal root ganglion (DRG) neurons, suggesting that they participate in the induction and maintenance of chronic inflammatory pain. However, how Nav1.7 and Nav1.8 are regulated in the DRG under inflammatory pain conditions remains unclear. Using a complete Freund's adjuvant (CFA)-induced chronic inflammatory pain model and Western blot analysis, we found that phosphorylated Akt (p-Akt) was significantly increased in the ipsilateral L4/5 DRGs of rats on days 3 and 7 after intraplantar CFA injection. Immunohistochemistry showed that the percentage of p-Akt-positive neurons in the DRG was also significantly increased in the ipsilateral L4/5 DRGs at these time points. Moreover, CFA injection increased the colocalization of p-Akt with Nav1.7 and Nav1.8 in L4/5 DRG neurons. Pretreatment of rats with an intrathecal injection of Akt inhibitor IV blocked CFA-induced thermal hyperalgesia and CFA-induced increases in Nav1.7 and Nav1.8 in the L4/5 DRGs on day 7 after CFA injection. Our findings suggest that the Akt pathway participates in inflammation-induced upregulation of Nav1.7 and Nav1.8 expression in DRG neurons. This participation might contribute to the maintenance of chronic inflammatory pain.


      This article presents that inhibition of Akt blocks CFA-induced thermal hyperalgesia and CFA-induced increases in dorsal root ganglion Nav1.7 and Nav1.8. These findings have potential implications for use of Akt inhibitors to prevent and/or treat persistent inflammatory pain.

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