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Identification of early gene expression changes in primary cultured neurons treated with topoisomerase I poisons
Sharyn L Rossi1, Casey J Lumpkin2, Ashlee W Harris1
1Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA.
Abstract:
Topoisomerase 1 (TOP1) poisons like camptothecin (CPT) are currently used in cancer chemotherapy but these compounds can have damaging, off-target effects on neurons leading to cognitive, sensory and motor deficits. To understand the molecular basis for the enhanced sensitivity of neurons to CPT, we examined the effects of compounds that inhibit TOP1-CPT, actinomycin D (ActD) and β-lapachone (β-Lap)-on primary cultured rat motor (MN) and cortical (CN) neurons as well as fibroblasts. Neuronal cells expressed higher levels of Top1 mRNA than fibroblasts but transcript levels are reduced in all cell types after treatment with CPT. Microarray analysis was performed to identify differentially regulated transcripts in MNs in response to a brief exposure to CPT. Pathway analysis of the differentially expressed transcripts revealed activation of ERK and JNK signaling cascades in CPT-treated MNs. Immediate-early genes like Fos, Egr-1 and Gadd45b were upregulated in CPT-treated MNs. Fos mRNA levels were elevated in all cell types treated with CPT; Egr-1, Gadd45b and Dyrk3 transcript levels, however, increased in CPT-treated MNs and CNs but decreased in CPT-treated fibroblasts. These transcripts may represent new targets for the development of therapeutic agents that mitigate the off-target effects of chemotherapy on the nervous system.
Insights
Chemotherapy drugs targeting Topoisomerase 1 (TOP1) harm neurons. Researchers found specific genes (Fos, Egr-1, Gadd45b) are upregulated in neurons after TOP1 poison treatment, offering potential therapeutic targets.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Topoisomerase 1 (TOP1) poisons, like camptothecin (CPT), are used in cancer chemotherapy.
- These drugs can cause significant neurotoxicity, leading to sensory, cognitive, and motor deficits.
- The molecular mechanisms underlying neuronal hypersensitivity to CPT are not fully understood.
Purpose of the Study:
- To investigate the molecular basis for enhanced neuronal sensitivity to TOP1 inhibitors.
- To identify specific gene expression changes in neurons exposed to CPT.
- To explore potential therapeutic targets for mitigating chemotherapy-induced neurotoxicity.
Main Methods:
- Primary cultured rat motor neurons (MNs), cortical neurons (CNs), and fibroblasts were treated with CPT.
- Quantitative analysis of Top1 mRNA levels.
- Microarray analysis to identify differentially regulated transcripts in MNs.
- Pathway analysis of gene expression data.
Main Results:
- Neuronal cells exhibited higher basal Top1 mRNA levels than fibroblasts.
- CPT treatment reduced Top1 mRNA levels in all cell types.
- Microarray analysis revealed activation of ERK and JNK signaling pathways in CPT-treated MNs.
- Immediate-early genes (Fos, Egr-1, Gadd45b) were upregulated in CPT-treated MNs and CNs, but not fibroblasts (except Fos).
Conclusions:
- Specific immediate-early genes (Egr-1, Gadd45b, Dyrk3) are differentially regulated in neurons versus fibroblasts following CPT exposure.
- These differentially expressed transcripts represent potential therapeutic targets for reducing chemotherapy-induced neurotoxicity.
- Understanding these molecular pathways could lead to the development of neuroprotective strategies.
