Analysis for functional mechanism of peripheral neuropathy induced by anti-cancer drug Paclitaxel

紫杉醇诱导的疼痛性周围神经病变是一个主要的剂量限制因素。最近有报道称，巨噬细胞在紫杉醇治疗大鼠的背根神经节中积累，巨噬细胞的激活可能参与了神经病变的发生和发展。然而，巨噬细胞活化的机制尚不清楚。在本研究中，为了探索参与紫杉醇治疗大鼠背根神经节巨噬细胞活化机制的候选基因，我们建立了紫杉醇诱导的神经性疼痛模型大鼠，并通过微阵列分析了背根神经节基因表达的变化。在表达水平改变的基因中，我们重点关注了基质金属蛋白酶-3 （MMP-3, stromelysin-1）和巨噬细胞标志物CD163。RT-PCR结果显示，MMP-3和CD163在紫杉醇处理后的背根神经节中表达水平明显上调。免疫组化研究结果显示，大神经节神经元主要表达MMP-3，但雪旺细胞和巨噬细胞均未表达。这种MMP-3上调发生在巨噬细胞在背根神经节积聚之前。此外，重组MMP-3在体外诱导RAW264巨噬细胞活化。综上所述，我们认为MMP-3的上调及其引起的巨噬细胞激活可能是引发紫杉醇诱导的周围神经性疼痛的一系列反应的重要事件。

Paclitaxel-induced painful peripheral neuropathy is a major dose-limiting factor. Recently, it has been reported that macrophages accumulated in the dorsal root ganglion of paclitaxel-treated rats, and their activation is suggested to contribute to generation and development of the neuropathy. However, the mechanism for macrophage activation is still unknown. In this study, to explore candidate genes involved in the mechanism for macrophage activation in the dorsal root ganglion of paclitaxel-treated rats, we developed model rats for paclitaxel-induced neuropathic pain and performed a microarray assay to analyze the changes of gene expressions in the dorsal root ganglion. Among the genes with changed expression levels, we focused on matrix metalloproteinase-3 (MMP-3, stromelysin-1) and CD163, a macrophage marker. By RT-PCR, the expression levels of MMP-3 and CD163 were markedly up-regulated in paclitaxel-treated dorsal root ganglion. As a result of immunohistochemical study, large ganglion neurons, but neither Schwann cells nor macrophages, predominantly expressed MMP-3. This MMP-3 up-regulation occurred prior to macrophage accumulation in the dorsal root ganglion. In addition, recombinant MMP-3 led to the activation of RAW264 macrophages in vitro. Taken together, we suggested that the up-regulation of MMP-3 and following macrophage activation caused in the dorsal root ganglion might be a significant event to trigger a series of reactions developing paclitaxel-induced peripheral neuropathic pain.