Biochemical analysis of glial fibrillary acidic protein as a quantitative approach to neurotoxicity assessment: advantages, disadvantages and application to the assessment of NMDA receptor antagonist-induced neurotoxicity.
Hypertrophy appears to be a universal response of astrocytes, a central nervous system (CNS) cell type, to all forms of brain injury. The hallmark of this response, often termed "reactive gliosis," is the enhanced expression of the major intermediate filament protein of astrocytes, glial fibrillary acidic protein (GFAP). Reactive gliosis traditionally has been examined qualitatively by immunohistochemistry of GFAP. But, the widespread availability of enzyme-linked immunosorbent assays (ELISAs) now makes it possible to quantify damage-induced expression of GFAP as a potential biomarker of diverse neurotoxic insults. To evaluate this possibility, we administered prototype neurotoxicants to experimental animals and then assessed the effects of these agents on the tissue content of GFAP, as determined by a recently developed sandwich ELISA. We found that assays of GFAP reveal dose-, time-, and region-dependent patterns of neural damage, often at toxicant dosages below those that cause light microscopic evidence of cell loss or damage. No false positives have been seen following exposure to a variety of pharmacological agents at therapeutic dosages. With respect to NMDA receptor antagonists, we find that MK-801 causes a large dose-dependent increase in GFAP that, within the cortex, appears to be restricted to the retrosplenial zone. Among the advantages of the CFAP-based approach re its simplicity, objectivity, cost and the fact that the assay can be automated. Among the disadvantages are the need to perform brain dissections and the requirement for a time-course analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
O'Callaghan
J P
JP
Neurotoxicology Division (MD-74B), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
D000818:Animals; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis / Q000378:metabolism*; D005911:Gliosis / Q000188:drug therapy; D006801:Humans; D009422:Nervous System Diseases / Q000139:chemically induced* / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*
D005904:Glial Fibrillary Acidic Protein; D016194:Receptors, N-Methyl-D-Aspartate