Superfund Research Program
Role of Paraoxonases (PONs) in Modulating Cadmium and Manganese Neurotoxicity
Final Progress Reports
Year: 2016 2014
Data from a mouse model study of the effects of PON1 genetic variability on the ability of a mother to protect a fetus from exposure to chlorpyrifos oxon were analyzed and published. The study showed that PON1 status (plasma activity and amino acid present at position 192 of the PON1) determined the ability of the dam to protect her fetuses from a dermal exposure to chlorpyrifos oxon. These experiments emphasize the importance of Dr. Furlong and his research team's earlier study on the genetic variability of PON1 status in farmworker mothers and their babies where a large variability in PON1 status was observed. The progress on developing biomarker protocols for mass spectrometric (MS) determining OP exposures was significant. Red cell acylpeptide hydrolase (APH) was shown to be an improved biomarker for exposure to the oxon forms of chlorpyrifos and diazoxon with the added advantages of a much longer half-life of the OP adducted protein compared with butyrylcholinesterase (BChE) (33d vs. 11d) and a significantly increased sensitivity of OP adduct determination. The MS analysis of modified biomarker proteins from dried blood spots will change the field of exposure analysis by eliminating the requirement for a pre-exposure activity measurement and facilitating sample collection, shipping and storage. Antibodies to the active site peptide of RBC acetylcholinesterase (AChE) were raised and used to generate a rapid immunomagnetic bead protocol for the single step purification of the active site peptide of AChE as an additional biomarker of OP exposure with a 33d half-life and an advantage of simplifying identification of the OP of exposure. A similar protocol was developed for monocyte carboxylesterase 1 (CES1). These protocols and recombinant 15N-labeled APH have been provided to the CDC as part of the research team's collaboration. The data for exposure risk related to PON1 status is shared with the WA State Health Department and with the EPA. MS analysis of PON3 in plasma will facilitate their development of protocols for quantifying protein levels of PONs 1, 2 and 3 in the clinical laboratory. The MPTP exposure experiments related to PON2 status and Parkinson's disease are being changed to exposure to manganese or cadmium as they do not pose excessive risk of adverse health effects in personnel from MPTP exposure. Researchers have also continued their studies on the expression and function of PON2 in the CNS. In collaboration with Dr. Elsmorth (Yale University), they have determined that a gender difference exists in PON2 expression in non-human primates, with females having a significantly higher level of PON2 protein. In addition, they are continuing their studies on the developmental expression of PON2. In monkey brain they have found that PON2 protein levels increase prenatally, reach a peak in infant monkeys (27-days) and then decline in juvenile (~2 years), young adult (5-7 years), and old (21-30 years) monkeys.