Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
J Pharmacol Exp Ther. 2010 May;333(2):540-6. doi: 10.1124/jpet.109.164830. Epub 2010 Feb 1.
We previously reported that lysophosphatidic acid (LPA) initiates nerve injury-induced neuropathic pain and its underlying mechanisms. In addition, we recently demonstrated that intrathecal injection of LPA induces de novo LPA production through the action of autotaxin (ATX), which converts lysophosphatidylcholine to LPA. Here, we examined nerve injury-induced de novo LPA production by using a highly sensitive biological titration assay with B103 cells expressing LPA1 receptors. Nerve injury caused high levels of LPA production in the ipsilateral sides of the spinal dorsal horn and dorsal roots, but not in the dorsal root ganglion, spinal nerve, or sciatic nerve. Nerve injury-induced LPA production reached its maximum at 3 h after injury, followed by a rapid decline by 6 h. The LPA production was significantly attenuated in ATX heterozygous mutant mice, whereas the concentration and activity of ATX in cerebrospinal fluid were not affected by nerve injury. On the other hand, the activities of cytosolic phospholipase A2 (cPLA2) and calcium-independent phospholipase A2 (iPLA2) were enhanced, with peaks at 1 h after injury. Both de novo LPA production and neuropathic pain-like behaviors were substantially abolished by intrathecal injection of arachidonyl trifluoromethyl ketone, a mixed inhibitor of cPLA2 and iPLA2, or bromoenol lactone, an iPLA2 inhibitor, at 1 h after injury. However, administration of these inhibitors at 6 h after injury had no significant effect on neuropathic pain. These findings provide evidence that PLA2- and ATX-mediated de novo LPA production in the early phase is involved in nerve injury-induced neuropathic pain.
我们之前曾报道过,溶血磷脂酸(LPA)会引发神经损伤诱导的神经性疼痛及其潜在机制。此外,我们最近还证实,鞘内注射 LPA 通过自分泌酶(ATX)的作用诱导新的 LPA 产生,该酶将溶血磷脂酰胆碱转化为 LPA。在这里,我们使用表达 LPA1 受体的 B103 细胞的高度敏感的生物滴定测定法检查了神经损伤诱导的新产生的 LPA。神经损伤导致脊髓背角和背根的同侧侧方产生高水平的 LPA,但在背根神经节、脊神经或坐骨神经中则没有。神经损伤诱导的 LPA 产生在损伤后 3 小时达到最大值,随后在 6 小时迅速下降。在 ATX 杂合突变小鼠中,LPA 的产生明显减弱,而神经损伤对脑脊液中 ATX 的浓度和活性没有影响。另一方面,细胞质型 PLA2(cPLA2)和钙非依赖性 PLA2(iPLA2)的活性增强,在损伤后 1 小时达到峰值。鞘内注射 arachidonyl trifluoromethyl ketone(cPLA2 和 iPLA2 的混合抑制剂)或 bromoenol lactone(iPLA2 抑制剂),可在损伤后 1 小时基本上消除新产生的 LPA 和神经性疼痛样行为,但在损伤后 6 小时给予这些抑制剂则对神经性疼痛没有明显影响。这些发现提供了证据,表明在早期阶段 PLA2 和 ATX 介导的新产生的 LPA 参与了神经损伤诱导的神经性疼痛。