The Journal of Neuroscience, November 26, 2008, 28(48):12775-12787; doi:10.1523/JNEUROSCI.3512-08.2008
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Cellular/Molecular
Interleukin-18-Mediated Microglia/Astrocyte Interaction in the Spinal Cord Enhances Neuropathic Pain Processing after Nerve Injury
Kan Miyoshi,1
Koichi Obata,1
Takashi Kondo,1
Haruki Okamura,2 and
Koichi Noguchi1
1Department of Anatomy and Neuroscience and 2Laboratory of Host Defenses, Institute for Advanced Medical Sciences, Hyogo College of Medicine, Hyogo 663-8501, Japan
Correspondence should be addressed to Dr. Koichi Noguchi, Department of Anatomy and Neuroscience, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan. Email: noguchi{at}hyo-med.ac.jp
Interleukin (IL)-18 is an important regulator of innate and acquired immune responses. Here we show that both the IL-18 and IL-18 receptor (IL-18R), which are induced in spinal dorsal horn, are crucial for tactile allodynia after nerve injury. Nerve injury induced a striking increase in IL-18 and IL-18R expression in the dorsal horn, and IL-18 and IL-18R were upregulated in hyperactive microglia and astrocytes, respectively. The functional inhibition of IL-18 signaling pathways suppressed injury-induced tactile allodynia and decreased the phosphorylation of nuclear factor
B in spinal astrocytes and the induction of astroglial markers. Conversely, intrathecal injection of IL-18 induced behavioral, morphological, and biochemical changes similar to those observed after nerve injury. Our results indicate that IL-18-mediated microglia/astrocyte interactions in the spinal cord have a substantial role in the generation of tactile allodynia. Thus, blocking IL-18 signaling in glial cells might provide a fruitful strategy for treating neuropathic pain.
Key words: microglia; astrocytes; neuropathic pain; IL-18; MAPK; NF
B
Received July 25, 2008;
revised Oct. 3, 2008;
accepted Oct. 9, 2008.
Correspondence should be addressed to Dr. Koichi Noguchi, Department of Anatomy and Neuroscience, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan. Email: noguchi{at}hyo-med.ac.jp
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