The Impact of Pesticides - Academy Publish

count and morphology, as well as serum luteinizing hormone than wild-typeindividuals. In a cross-sectional study conducted by our group to evaluate the role ofPON1 Q192R polymorphism on the susceptibility to OP toxicity on semen qualityin 54 agricultural workers in southern Mexico exposed mainly to OP (i.e.methamidophos), Pérez-Herrera et al. (2008) observed a dose-dependentrelationship between OP exposure (as an exposure index) during 3 months beforesampling (as a reflect of the exposure to sperm cells during one spermatogeniccycle) and sperm quality parameters in workers carrying the PON1 192RRgenotype.Modulation of OP neurological effects by PON1 polymorphismsThe inhibition of acetylcholinesterase (AChE) activity through the phosphorylationof a serine residue in the active site is the most studied adverse effect of OPexposure, which causes severe cholinergic symptoms that may lead to death (Galloand Lawryk, 1991). Because of its function to deactivate the oxon of OP pesticides,PON1 has been associated with a protective role against OP neurotoxicity. Studiesconducted in English farmers mainly exposed to diazinon with ill health reported alower PON1 diazoxonase activity compared to a referent group, and the risk ofdeveloping health problems among exposed farmers was higher if carrying thePON1 192RR genotype (OR=3.7, 95%CI 1.2-11.5) compared to those who were192QQ homozygous (OR=1.1, 95%CI 0.5-2.1) after controlling for potential bias.Additionally, there was an increase risk in farmers carrying the 55LL genotype(OR=4.3, 95%CI 1.1-17.3) (Cherry et al., 2002; Povey et al., 2007). On the otherhand, studies were conducted in Gulf War veterans reporting symptoms ofneurological damage to determine if PON1 activity and genotype (PON1 L55M andQ192R polymorphisms) were related to these effects. Veterans were exposed tochemical agents including OP pesticides and nerve gases (Mackness et al., 2000;Hotopf et al., 2003). Significant lower PON1 activity toward paraoxon but nottoward diazoxon was observed in veterans, and this effect was not explained bydifferences in PON1 coding region polymorphisms. PON1 concentration was alsolower in veterans, which was again not dependent of PON1 genotype. Authorsconclude that a decreased capacity to detoxify OP pesticides may have contributedto the development of neurotoxicity in Gulf War veterans. Finally, Lee et al. (2003)performed a study in farmers from South Africa (n=100) and PON1 Q192Rpolymorphism resulted an independent predictor of chronic toxicity, subjectscarrying one or two 192Q alleles showed an increased risk (OR=2.9, 95%CI 1.7-6.9) of having anticholinesterase symptoms.PON1 in Parkinson’s and Alzheimer’s diseasesParkinson's disease is an idiopathic disorder of the dopaminergic nervous systemcharacterized by progressive tremor, bradykinesia, rigidity, and postural instability(Ruiz et al., 2011). It has been postulated that exogenous compounds, includingpesticides, might be involved in its etiology, and the relationship appears strongerfor the exposure to herbicides and insecticides after long term exposures. However,the evidence is not sufficient to conclude that such a relationship exists for anyparticular pesticide or combined pesticide or other exogenous toxicant exposure(Brown et al., 2006). Additionally, several genetic factors have been proposed asrisk factors for developing Parkinson's disease, and the association of PON1polymorphisms is the most studied genetic predisposition factor.A case-control study of Parkinson's disease conducted in a rural population ofCalifornia's Central Valley (351 cases and 363 controls) living close to areas withextensive agricultural pesticide application, especially OP (diazinon, chlorpyrifosAcademyPublish.org - The Impact of Pesticides66