| Genotoxicants Target Distinct Molecular Networks in Neonatal Neurons Glen E. Kisby,1 Antoinette Olivas,1 Melissa Standley,2 Xinfang Lu,2 Patrick Pattee,2 Jean O’Malley,2 Xiaorong Li,1 Juan Muniz,1 and Srinavasa R. Nagalla2 1Center for Research on Occupational and Environmental Toxicology (CROET), Oregon Health & Science University, Portland, Oregon; 2Department of Pediatrics, School of Medicine, Oregon Health & Science University, Portland, Oregon Abstract
Background: Exposure of the brain to environmental agents during critical periods of neuronal development is considered a key factor underlying many neurologic disorders. Objectives: In this study we examined the influence of genotoxicants on cerebellar function during early development by measuring global gene expression changes. Methods: We measured global gene expression in immature cerebellar neurons (i.e., granule cells) after treatment with two distinct alkylating agents, methylazoxymethanol (MAM) and nitrogen mustard (HN2) . Granule cell cultures were treated for 24 hr with MAM (10–1,000 µM) or HN2 (0.1–20 µM) and examined for cell viability, DNA damage, and markers of apoptosis. Results: Neuronal viability was significantly reduced (p < 0.01) at concentrations > 500 µM for MAM and > 1.0 µM for HN2 ; this correlated with an increase in both DNA damage and markers of apoptosis. Neuronal cultures treated with sublethal concentrations of MAM (100 µM) or HN2 (1.0 µM) were then examined for gene expression using large-scale mouse cDNA microarrays (27,648) . Gene expression results revealed that a) global gene expression was predominantly up-regulated by both genotoxicants ; b) the number of down-regulated genes was approximately 3-fold greater for HN2 than for MAM ; and c) distinct classes of molecules were influenced by MAM (i.e, neuronal differentiation, the stress and immune response, and signal transduction) and HN2 (i.e, protein synthesis and apoptosis) . Conclusions: These studies demonstrate that individual genotoxicants induce distinct gene expression signatures. Further study of these molecular networks may explain the variable response of the developing brain to different types of environmental genotoxicants. Key words: cerebellum, DNA damage, granule cell, HN2, MAM, methylazoxymethanol, nitrogen mustard. Environ Health Perspect 114:1703–1712 (2006) . doi:10.1289/ehp.9073 available via http://dx.doi.org/ [Online 7 September 2006]
Address correspondence to S. Nagalla, Department of Pediatrics, School of Medicine, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239 USA. Telephone: (503) 494-1928. Fax: (503) 494-4821. E-mail: nagallas@ohsu.edu Supplemental Material is available online (http://www.ehponline.org/docs/2006/9073/suppl.pdf) . Supported by National Institutes of Health (NIH) grant 5P42-ES10338-02 (National Institute of Environmental Health Sciences’ Toxicogenomics Consortium) and, in part, by NIH grant ES10338-02 and Department of Defense grant DAMD17-98-1-8625. The authors declare they have no competing financial interests. Received 3 February 2006 ; accepted 7 September 2006.
The full version of this article is available for free in HTML or PDF formats. |
