title: Systems biology approaches for toxicology.
abstract: Systems biology/toxicology involves the iterative and integrative study of perturbations by chemicals and other stressors of gene and protein expression that are linked firmly to toxicological outcome. In this review, the value of systems biology to enhance the understanding of complex biological processes such as neurodegeneration in the developing brain is explored. Exposure of the developing mammal to NMDA (N-methyl-D-aspartate) receptor antagonists perturbs the endogenous NMDA receptor system and results in enhanced neuronal cell death. It is proposed that continuous blockade of NMDA receptors in the developing brain by NMDA antagonists such as ketamine (a dissociative anesthetic) causes a compensatory up-regulation of NMDA receptors, which makes the neurons bearing these receptors subsequently more vulnerable (e.g. after ketamine washout), to the excitotoxic effects of endogenous glutamate: the up-regulation of NMDA receptors allows for the accumulation of toxic levels of intracellular Ca(2+) under normal physiological conditions. Systems biology, as applied to toxicology, provides a framework in which information can be arranged in the form of a biological model. In our ketamine model, for example, blockade of NMDA receptor up-regulation by the co-administration of antisense oligonucleotides that specifically target NMDA receptor NR1 subunit mRNA, dramatically diminishes ketamine-induced cell death. Preliminary gene expression data support the role of apoptosis as a mode of action of ketamine-induced neurotoxicity. In addition, ketamine-induced cell death is also prevented by the inhibition of NF-kappaB translocation into the nucleus. This process is known to respond to changes in the redox state of the cytoplasm and has been shown to respond to NMDA-induced cellular stress. Although comprehensive gene expression/proteomic studies and mathematical modeling remain to be carried out, biological models have been established in an iterative manner to allow for the confirmation of biological pathways underlying NMDA antagonist-induced cell death in the developing nonhuman primate and rodent. Published in 2007 John Wiley & Sons, Ltd.
authors.affiliation: National Center for Toxicological Research, U S Food and Drug Administration, Jefferson, Arkansas 72079-9502, USA. william.slikker@fda.hhs.gov
authors.forename: William
authors.initials: W
authors.lastname: Slikker
authors.forename: Merle G
authors.initials: MG
authors.lastname: Paule
authors.forename: Linnzi K M
authors.initials: LK
authors.lastname: Wright
authors.forename: Tucker A
authors.initials: TA
authors.lastname: Patterson
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006801:Humans; D008954:Models, Biological; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D049490:Systems Biology / Q000379:methods*; D014116:Toxicology / Q000379:methods*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate