Mini reviewHuman PON1, a biomarker of risk of disease and exposure
Section snippets
Early studies
In 1953, Aldridge divided esterases into two categories, those that catalytically hydrolyzed organophosphate substrates (A-esterases) and those that were inhibited by organophosphates (B-esterases) [1]. Plasma paraoxonase 1 (PON1) is an A-esterase. Studies in the 1960s and 1970s demonstrated that PON1 activity was polymorphically distributed in human populations and the frequency of the low activity phenotype varied among populations of different ethnic origins. These studies are summarized in
Diseases associated with PON1 variability
In recent years, there have been approximately 500 papers published related to the association or lack of association of PON1 with specific diseases (PubMed searches). The largest number of studies has been carried out on vascular disease. Other diseases studied for their possible association with genetic variability in PON1 include Parkinson disease (PD), amyotrophic lateral sclerosis (ALS), kidney disease, eye diseases, systemic lupus erythematosus, abdominal aortic aneurysms, asthma, chronic
PON1 status as a possible indicator of defects in the modulation of oxidative stress
Several recent studies have suggested linkage between Parkinson disease (PD) and genetic variability in the PON region of chromosome 7 [48], [49], [50], [51], while others have not [52], [53], [54], [55]. Based on our knowledge of the importance of PON1 status in risk of disease or exposure, we felt that it would be important to carry out a PON1 status analysis on a sizeable cohort of patients with PD. We expected to find lower PON1 levels in PD patients compared with control subjects as we had
PONs and quorum sensing
Ozer et al. reported that all three PONs hydrolyzed the quorum sensing factor of Pseudomonas aeruginosa N-(3-oxododecanoyl)-L- homoserine lactone (3OC12-HSL) [59]. Exposure experiments with PON1−/− mice were inconclusive in demonstrating a protective effect for PON1 due to the abilities of PON2 and PON3 to inactivate 3OC12-HSL [59]. Experiments with PON2−/− mice were more convincing with respect to demonstrating a protective role of PON2 against P. aeruginosa infection [60]. The ability of PON1
PON1 as a potential therapeutic
Our early studies [22], [23] following those of Main [20] indicated that it would be possible to use PON1 purified from human plasma to treat cases of CPF/CPO and DZ/DZO exposure, with the PON1R192 alloform being the best choice of alloforms, since it hydrolyzes both CPO and DZO efficiently [24]. However, it will be necessary to engineer recombinant human PON1 for higher catalytic efficiency for use in treating exposure to OPs hydrolyzed with low catalytic efficiency [24], [62], [63].
To test
Immunolocalization of the PON family of enzymes
Circulating PON1 is synthesized in the liver [13], [68] and the secreted PON1 circulates in plasma tightly bound to HDL [68], using its unprocessed hydrophobic signal sequence as an anchor into the lipoprotein particles [13], [69]. Some authors have reported PON1 protein expression in kidney and aorta [70], [71]. Immunolocalization of PON1 has been described in nearly all the tissues of mice [72]. Specifically, PON1 was found in nearly all the studied epithelia, such as chondrocytes,
Summary
The many studies carried out on the PON family of enzymes have provided convincing evidence for the protective role of PON1 in modulating exposures to CPO/CPF and DZO/DZ, but not in modulating exposure to PS/PO or nerve agents. To protect against the latter OPs, PON1 will need to be engineered for increased catalytic efficiency. All three PONs appear to be important in modulating oxidative stress and protecting against vascular disease and perhaps other diseases that result from deficiencies in
Conflict of interest
The authors declare that there are no conflicts of interest.
Acknowledgements
This work was supported by the grants from the NIH (ES04696, ES09883; ES07033; ES09601, HL67406, R01 NS065070, P50 NS062684) and the Department of Veterans Affairs (Merit Review Award). JM was supported by a Beatriu de Pinós postdoctoral fellowship (2008 BP A 00166) from Comissionat per a Universitats i Recerca del Departament d’Innovació, Universitats i Empresa, Catalunya Spain.
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