The Basic Biology of Aging at the University of Washington
Clement Furlong, Ph.D.

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Email: clem@u.washington.edu

The research efforts of Dr. Furlong’s laboratory are concerned with the interplay of genetics and the environment, including risk reduction through bioremediation, and the effect of polymorphisms of antioxidant enzymes, especially paraoxonase, on age-related diseases. Other interests include the development of biosensors for biomedical and environmental applications and the development of protein-producing bioreactors. One focus of this work is Alzheimer’s disease. Other GAATG faculty with whom Dr. Furlong has collaborated include Drs. Disteche, Kavanagh, Kukull, LeBoeuf, and Martin.

High density lipoprotein particles have esterases/lactonases associated with them. One of these enzymes (paraoxonase or PON1) has been purified to homogeneity. Amino acid sequence was used to design probes for isolating first the cDNAs that encode paraoxonase (PON1), then the genomic sequence from YAC clones. The initial efforts were aimed at understanding the role of this enzyme in protecting against poisoning by organophosphorus compounds that are hydrolyzed (inactivated) by PON1. Development of a mouse model has provided an excellent understanding of the role of the genetics of PON1 in the detoxication of the active forms of the insecticides diazinon and chlorpyrifos (Dursban).

While this work was in progress, it became clear from the work of other investigators that the physiological role of PON1 is protecting against vascular disease by metabolizing oxidized, bioactive lipid molecules. The assays that we developed for the insecticide research turned out to be very useful for studying the association of PON1 genetics with vascular disease. In a recent paper (Jarvik et al., 2000), we showed that low levels of PON1 are a risk factor for carotid artery disease. This paper also provides what we believe to be the best current approach for evaluating an individual's PON1 status with respect to susceptibility to vascular disease. Other studies have provided information on promoter polymorphisms that contribute to determining the levels of PON1 in an individual's serum.

More recently, other research groups have noted the importance of PON3 in the metabolism of oxidized lipids. PON3 has been difficult to purify from human plasma. A recent advance in our laboratory, the expression of active human and rabbit PON1's in E. coli, has provided a new avenue for examining the biochemical properties of the PON family of enzymes.

We anticipate that we will be able to express both PON3 and PON2 as enzymatically active proteins in the E. coli system, facilitating the understanding of their role in protecting against vascular disease. While PONs 1 & 3 are found mostly on HDL, PON2 appears to be ubiquitously expressed and may be important as a general antioxidant in other tissues, including the brain. Understanding the biochemical properties and regulation of the entire family of PON enzymes will provide a new approach for understanding the interplay of the PON anti-oxidant systems with susceptibility to diseases affected by oxidative stress (e.g., Alzheimer's disease and Parkinson's disease) and the free radical theory of aging.

Dr. Furlong is Research Professor of Medicine and Genetics and holds grants in Structure and Function of the Human PON1 Polymorphism, Advanced Surface Plasmon Resonance Sensors, and Fate of Human Paraoxonase, among others.

Selected Relevant Publications
Shih DM, Gu L, Xia YR, Navab M, Li WF, Hama S, Castellani LW, Furlong CE, Costa LG, Fogelman AM, Lusis AJ. Mice lacking serum paraoxonase are susceptible to organophosphate toxicity and atherosclerosis. Nature 394:284-287, 1998.

Furlong, C.E., W.-F. Li, L.G. Costa, R.J. Richter, D.M. Shih and A.J. Lusis. Genetically determined susceptibility to organophosphorus insecticides and nerve agents: developing a mouse model for the human PON1 polymorphism. Neurotoxicology 19:645-650, 1998.

Costa, LG, Li WF, Richter RJ, Shih DM, Lusis A, Furlong CE. The role of paraoxonase (PON1) in the detoxication of organophosphates and its human polymorphism. Chem-Biol Interactions 119-120:439-444, 1999.

Richter RJ, Furlong, CE. Determination of paraoxonase (PON1) status requires more than genotyping. Pharmacogenetics 9:745-753, 1999.

Brophy VH, Jarvik GP, Richter RJ, Rozek LS, Schellenberg GD, Furlong CE. Analysis of paraoxonase (PON1) L55M status requires both genotype and phenotype. Pharmacogenetics 10:453-460, 2000.

Furlong CE, Li WF, Richter RJ, Shih DM, Lusis AJ, Alleva E, Costa LG. Genetic and temporal determinants of pesticide sensitivity: role of paraoxonase (PON1). Neurotoxicology 21:91-100, 2000.

Jarvik GP, Rozek LS, Brophy VH, Hatsukami TS, Richter RJ, Schellenberg GD, Furlong CE. Paraoxonase (PON1) phenotype is a better predictor of vascular disease than is PON1(192) or PON1(55) genotype. Arterioscler Thromb Vasc Biol 20:2441-2447, 2000.

Li WF, Costa LG, Richter RJ, Hagen T, Shih DM, Tward A, Lusis AJ, Furlong CE. Catalytic efficiency determines the in-vivo efficacy of PON1 for detoxifying organophosphorus compounds. Pharmacogenetics 10:767-779, 2000.

Brophy VH, Hastings MD, Clendenning JB, Richter RJ, Jarvik GP, Furlong CE. Polymorphisms in the human paraoxonase (PON1) promoter. Pharmacogenetics 11:77-84, 2001.

Brophy VH, Jampsa RL, Clendenning JB, McKinstry LA, Jarvik GP, Furlong CE. Effects of 5' regulatory-region polymorphisms on paraoxonase-gene (PON1) expression. Am J Hum Genet 68:1428-1436, 2001.