Genomic And Proteomic Studies On Arsenic Toxicity

Abstract

be positively correlated with their respective intracellular ROS level, which is consistent with the significant variation found in ND3 gene among the exposed individuals. In addition, the extent of potentially damaging variants in arsenic-exposed individuals had significant positive correlation to the degree of G0/G1 cell cycle arrest.In the context of understanding the underlying molecular mechanisms that render a person susceptible to arsenic toxicity it was imperative to look for the differentially expressed proteins (a) among the arsenic exposed and unexposed individuals, and (b) among the arsenic exposed individuals with and without skin lesion. To address this problem, plasma samples from 40 individuals expose to arsenic (20 symptomatic, 20 asymptomatic) and 20 unexposed individuals were taken as discovery cohort and subjected to iTRAQ followed by mass spectrometry analysis. A replicative cohort comprising of total 30 individuals (10 symptomatic, 10 asymptomatic and 10 unexposed) were also similarly subjected to iTRAQ based protein quantitation. A total of 103 proteins were identified to be differentially expressed among the three groups in both the discovery and replicative cohorts. The proteins thus identified were enriched in several biological processes like apoptosis, cellular adhesion,endothelial processes, immune responses, etc. defined by Gene Ontology terms and determined by online free software Genecodi(http://genecodis.cnb.csic.es/). Further, OMIM analysis revealed that defects in genes like APOE and DSG1 lead to skin lesion. The “skin lesion phenotype” caused due to defects in DSG1 is very similar to the type of skin lesion caused by arsenicosis. To check whether genetic defect of this gene is actually related to arsenic induced skin lesion, the entire DSG1 gene along with its regulatory regions were screened in 25 symptomatic and 25 asymptomatic individuals. In this pilot study no significant change was observed in the DSG1 gene. Interestingly, APOE isoforms have been recently reported to be associated with cardiovascular disease in the arsenic exposed individuals of Taiwan. When the APOE isoforms as well as the promoter SNPs were determined in our population of arsenic exposed individuals (100 symptomatics and 100 asymptomatics) significant association was observed. Further, DSG1, DAPK3 and APOE, found to be differentially expressed by iTRAQ, were validated by Western Blot in individual plasma samples