Expression data from camptothecin-treated rat primary motor neurons

Topoisomerase 1 (TOP1) poisons like camptothecin (CPT), which are used as chemotherapeutic agents in cancer, elicit DNA damage in quiescient neurons. In this study, we examined the effects of CPT and actinomycin D (ActD) on neuronal cells. Motor (MNs) and cortical (CNs) neurons were more susceptible to the toxic effects of CPT and ActD than fibroblasts. MNs and CNs exhibited a delayed DNA damage response—increase in nuclear ¿-H2AX foci—relative to fibroblasts. Neuronal cells expressed higher levels of Top1 mRNA than fibroblasts which could explain their enhanced vulnerability to CPT and ActD toxicity. Microarray analysis was performed to identify differentially regulated transcripts in MNs treated with CPT for 2 hours. Many immediate-early genes including Fos and Egr-1 were upregulated in CPT-treated MNs. Fos mRNA levels were elevated in all cells types treated with CPT; Egr-1 transcript levels, however, were reduced in CPT-treated fibroblasts even though they were elevated in treated MNs and CNs. Pathway and network analysis of the differentially expressed transcripts revealed activation of ERK and JNK signaling cascades in CPT-treated MNs. In conclusion, MNs were more vulnerable than fibroblasts to the damaging effects of TOP1 poisons and they elicit a unique intracellular response to CPT treatment.拓扑异构酶1（Topoisomerase 1, TOP1）抑制剂类药物如喜树碱（camptothecin, CPT）作为癌症化疗用药，可诱导静息神经元产生DNA损伤。本研究考察了喜树碱与放线菌素D（actinomycin D, ActD）对神经元细胞的影响。运动神经元（Motor neurons, MNs）与皮层神经元（cortical neurons, CNs）对喜树碱及放线菌素D的毒性作用敏感性显著高于成纤维细胞。相较于成纤维细胞，运动神经元与皮层神经元表现出延迟的DNA损伤应答——细胞核内γ-H2AX焦点数量增加。神经元细胞的Top1 mRNA表达水平高于成纤维细胞，这或可解释其对喜树碱与放线菌素D毒性的易感性增强。本研究通过基因芯片分析（microarray analysis），鉴定了经喜树碱处理2小时的运动神经元中差异调控的转录本。经喜树碱处理的运动神经元中，包括Fos与Egr-1在内的多种即早基因表达上调。所有经喜树碱处理的细胞类型中，Fos mRNA水平均出现升高；但Egr-1转录本水平在经处理的成纤维细胞中却有所下调，而在处理后的运动神经元与皮层神经元中则呈上调趋势。对差异表达转录本进行通路与网络分析后发现，经喜树碱处理的运动神经元中激活了ERK与JNK信号级联反应。综上，运动神经元对拓扑异构酶1抑制剂类药物的损伤作用比成纤维细胞更为敏感，且其对喜树碱处理会产生独特的胞内应答。