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Final Progress Reports: University of Washington: Paraoxonases: Biomarkers of Susceptibility to Environmentally-Induced Diseases

Superfund Research Program

Paraoxonases: Biomarkers of Susceptibility to Environmentally-Induced Diseases

Project Leader: Lucio G. Costa
Grant Number: P42ES004696
Funding Period: 2000 - 2009
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Final Progress Reports

Year:   2008  2005 

A major breakthrough was the successful expression of active recombinant human PON1 in Escherichia coli. The expression of recombinant human PON1 (rHuPON1) in E.coli provides a system in which PON1 can be engineered to achieve a catalytic efficiency sufficient to protect against specific OP exposures. The naturally occurring PON1R192 alloform, and an engineered variant with increased efficiency for OP hydrolysis (PON1K192) were expressed, purified and characterized. The rHuPON1K192, when injected into PON1 -/- mice had a long half life and was nontoxic. Most importantly, it protected PON1 -/- mice from the acute toxicity of the OP diazoxon (DZO).

Another important achievement was the development of a new method to determine PON1 status. After screening more than 70 nontoxic compounds under different assay conditions (variation of salt concentrations and pH), Dr. Costa’s research group finally found that measuring the hydrolysis of phenylacetate (PA) at high (2 M) salt, and of 4-(chloromethyl) phenylacetate (CMPA) at low salt, provided the best resolution of functional PON1 phenotypes. Both the old assay (with DZO/PO) and the new assay (with PA/CMPA) provide a clear resolution of the three functional PON1192 phenotypes.

Progress has been made also with regard to PON2 and its potential role as an antioxidant in brain tissue. PON2 protein was identified in hippocampus, cerebellum, cerebral cortex and liver of PON2 (+/+) mice but not in the same tissues from PON2 (-/-) mice. PON2 protein was also identified in cerebellar granule neurons, hippocampal neurons and cerbral cortical neurons from PON2 (+/+) mice, and was expressed at higher levels in neurons than in astrocytes from these three brain areas. Initial results suggest that the expression of PON2 may provide some degree of protection toward the toxicity of compounds eliciting oxidative stress.

Dr. Costa’s research group completed their investigation on the role of PON1 in modulating the toxicity of mixtures of OP compounds. They also continued their work investigating the role of PON1 polymorphisms in Parkinson’s disease

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