• Makoto Tsuda, Shigeo Hasegawa, and Kazuhide Inoue.
• Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Higashi, Fukuoka, Japan.
• J. Neurochem. 2007 Nov 1;103(4):1408-16.

AbstractActivation of P2X(3) and P2X(2/3) receptors (P2X(3)R/P2X(2/3)R), ionotropic ATP receptor subtypes, in primary sensory neurons is involved in neuropathic pain, a debilitating chronic pain that occurs after peripheral nerve injury. However, the underlying mechanisms remain unknown. We investigated the role of cytosolic phospholipase A(2) (cPLA(2)) as a downstream molecule that mediates the P2X(3)R/P2X(2/3)R-dependent neuropathic pain. We found that applying ATP to cultured dorsal root ganglion (DRG) neurons increased the level of Ser505-phosphorylated cPLA(2) and caused translocation of Ser505-phosphorylated cPLA(2) to the plasma membrane. The ATP-induced cPLA(2) activation was inhibited by a selective antagonist of P2X(3)R/P2X(2/3)R and by a selective inhibitor of cPLA(2). In the DRG in vivo, the number of cPLA(2)-activated neurons was strikingly increased after peripheral nerve injury but not after peripheral inflammation produced by complete Freund's adjuvant. Pharmacological blockade of P2X(3)R/P2X(2/3)R reversed the nerve injury-induced cPLA(2) activation in DRG neurons. Moreover, administering the cPLA(2) inhibitor near the DRG suppressed nerve injury-induced tactile allodynia, a hallmark of neuropathic pain. Our results suggest that P2X(3)R/P2X(2/3)R-dependent cPLA(2) activity in primary sensory neurons is a key event in neuropathic pain and that cPLA(2) might be a potential target for treating neuropathic pain.

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