Assessment of neurotoxicity: Use of glial fibrillary acidic protein as a biomarker
Neurotoxicology Division, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711. Biomedical and Environmental Sciences
(Impact Factor: 1.65).
Diverse neurotoxic insults result in proliferation and hypertrophy of astrocytes. The hallmark of this response is enhanced expression of the major intermediate filament protein of astrocytes, glial fibrillary acidic protein (GFAP). These observations suggest that GFAP may be a useful biomarker of neurotoxicity. To investigate this possibility, we administered prototype neurotoxicants to experimental animals and assessed the effects of these agents on the tissue content of GFAP, as determined by radioimmunoassay. A review of the background, design, and results of these experiments are presented in this paper. Our findings indicate that GFAP is a sensitive and specific biomarker of neurotoxicity.
Available from: PubMed Central
- "Representative results in Figure 2 show the GFAP expression in retinas at 2 weeks after intravitreal administration. The injection and the microspheres did not cause elevated expression of GFAP, which is a marker of retinal injury.20 "
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ABSTRACT: Poly(lactic-co-glycolic acid) (PLGA) and/or poly(lactic-acid) (PLA) microspheres are important drug delivery systems. This study investigated eye biocompatibility and safety of PLGA/PLA microspheres through intravitreal injection in rabbits. Normal New Zealand rabbits were randomly selected and received intravitreal administration of different doses (low, medium, or high) of PLGA/PLA microspheres and erythropoietin-loaded PLGA/PLA microspheres. The animals were clinically examined and sacrificed at 1, 2, 4, 8, and 12 weeks postadministration, and retinal tissues were prepared for analysis. Retinal reactions to the microspheres were evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end staining and glial fibrillary acidic protein immunohistochemistry. Retinal structure changes were assessed by hematoxylin and eosin staining and transmission electron microscopy. Finally, retinal function influences were explored by the electroretinography test. Terminal deoxynucleotidyl transferase-mediated dUTP nick end staining revealed no apoptotic cells in the injected retinas; immunohistochemistry did not detect any increased glial fibrillary acidic protein expression. Hematoxylin and eosin staining and transmission electron microscopy revealed no micro- or ultrastructure changes in the retinas at different time points postintravitreal injection. The electroretinography test showed no significant influence of scotopic or photopic amplitudes. The results demonstrated that PLGA/PLA microspheres did not cause retinal histological changes or functional damage and were biocompatible and safe enough for intravitreal injection in rabbits for controlled drug delivery.
Available from: In-Beom Kim
- "By immunohistochemistry with anti-GFAP, a reliable marker for profiling neurotoxicity [18, 19], we evaluated the degree of retinal injury according to the MNU injection in different doses. In control retinas, GFAP was expressed within end feet portion of Müller cells and astrocytes located in the ganglion cell layer (GCL) (Fig. 3A). "
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ABSTRACT: The retinal degeneration (RD) is a general cause of blindness. To study its pathophysiology and evaluate the effects of new therapeutic agents before clinical trials, it is essential to establish reliable and stable animal models. This study evaluated a RD animal model in which blindness was induced by N-methyl-N-nitrosourea (MNU), a potent retinotoxin leading to apoptosis of photoreceptors. MNU was applied to the Sprague-Dawley rats by a single intraperitoneal injection in different doses (40, 50, and 60 mg/kg). The retinal functions were examined at 1 week after MNU injection by electroretinogram (ERG). Afterwards, each retina was examined by hematoxylin and eosin stain and immunohistochemistry with anti-glial fibrillary acidic protein antibody. Upon MNU injection of 40, 50 and 60 mg/kg, the ERG amplitude of a-waves showed significant reductions of 7, 26, and 44%, respectively, when compared to that of normal a-waves. The b-wave amplitudes were about 89, 65, and 58% of normal b-waves in the response to scotopic light stimulus. At 1 week, 2 weeks, and 4 weeks after MNU injection (50 mg/kg), all scotopic ERG components decreased progressively. In addition, degeneration of retinal neurons was observed in a time- and dose-dependent manner after MNU injection. Taken together, functional reduction following RD induced by MNU correlates with morphological changes. Thus, this RD rat model may be a useful model to study its pathophysiology and to evaluate the effects of new therapeutic agents before clinical trials.
Available from: Haseeb Khan
- "Glial fibrillary acidic protein (GFAP) is the major intermediate filament protein of astrocytes and has been regarded as a sensitive and reliable indicator of reactive gliosis in response to noxious stimuli      . GFAP assays are useful to quantify dose-, time-, and regiondependent pattern of toxicant-induced astrogliosis  . "
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ABSTRACT: The sensitivity of capillary electrophoresis coupled with laser-induced fluorescence (CE-LIF) was compared with conventional agarose gel electrophoresis-ethidium bromide-UV method (AE-EUV) for detection and semi-quantitative determination of GFAP mRNA in mouse brain. GFAP expression was induced by the neurotoxin MPTP in C57BL mice. Serially diluted RNA samples (0.0003, 0.003, 0.03, 0.3, and 3 microg total RNA) were subjected to RT-PCR and analyzed by both procedures. The integrated pixel density (AE-EUV) and peak area (CE-LIF) were directly proportional to the amount of RNA. However, the observed high sensitivity of CE-LIF suggests its potential application for detection and semi-quantitative determination of low-abundance mRNA transcripts.
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