Publication Date

2007

Document Type

Thesis

Committee Members

David Cool (Advisor)

Degree Name

Master of Science (MS)

Abstract

Sarin is an organophosphorus (OP) ester chemical warfare agent (CWA) that has been used in past terrorist attacks. It remains a threat today because of its ease of manufacture and dispersal. Sarin acts by irreversibly inactivating acetylcholinesterase and interfering with neurotransmission by allowing acetylcholine to build up at neuro-effector junctions, where it continuously elicits a response. Symptoms of sarin toxicity include seizures, hypersecretions, respiratory distress and death in extreme cases. Previous studies on OP poisoning indicate that sarin exposure causes neurodegeneration and neuroinflammation in conjunction with seizure activity. In order to determine the mode of neuronal death and the extent of neuroinflammation induced by sarin exposure, C57Bl/6J mice were first dosed s.c. with 1.5 mg/kg cresylbenzodioxaphosphorin oxide (CBDP) to inhibit the large amount of carboxylesterase found in rodents. One hour later, mice were dosed with 24 ug/kg sarin, a dose which produces approximately 17% lethality. One group of mice was also dosed with 1.7 mg/kg 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, which has been shown by others to decrease different types of neuronal injury. Mice were sacrificed at times ranging from four hours to ten days after sarin administration and left or right brain hemispheres were collected and frozen in isopentane for histological examination. To detect DNA fragmentation, 10um-thick sections were TUNEL-stained using the NeuroTACS II in situ apoptosis detection kit. Activated caspase-3 and interleukin-1beta (IL-1beta) were detected by immunohistochemistry to determine whether apoptotic cell death and neuroinflammation were occurring. Manual cell counts were performed on micrographs of dentate gyrus and CA1 regions of hippocampus, amygdala and piriform cortex in NIH Image. Statistically significant TUNEL labeling was observed at various time points in all brain regions except CA1 hippocampus. Significant increases in caspase-3 staining were observed only in piriform cortex and CA1 hippocampus at 24 hours and four days post-sarin injection, respectively. IL-1beta expression was significantly increased in CA1 hippocampus at four days after sarin injection and in all brain regions except piriform cortex at ten days after sarin exposure. Neither TUNEL nor caspase-3 labeling were significantly decreased with 8-OH-DPAT treatment. The amygdala and dentate gyrus regions showed significant decreases in IL-1beta expression after 8-OH-DPAT treatment. Statistically non-significant upward trends over time in TUNEL labeling and IL-1beta expression were observed. In contrast, caspase-3 expression exhibited a gradual, non-significant decrease at later time points. These trends may be indicative of a decreasing role played by apoptotic cell death and an increasing or persisting role for oncotic cell death and inflammation in sarin neurotoxicity.

Page Count

75

Department or Program

Department of Pharmacology and Toxicology

Year Degree Awarded

2007

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