The Effect of Global DNA Methylation on PDCD5 Expression in the PBMC of Occupational Chromate Exposed Workers

Effects of Sodium Chromate Exposure on Gene Expression Profiles of Primary Rat Hepatocytes (In Vitro)

Chromium exposure has adverse impacts on human health and the environment, whereas chromate-induced hepatotoxicity's detailed mechanism is still unclear. Therefore, the purpose of the current study was to reveal the crucial signaling pathways and genes linked to sodium chromate-induced hepatotoxicity. GSE19662, a gene expression microarray, was obtained from Gene Expression Omnibus (GEO). Six primary rat hepatocyte (PRH) samples from GSE19662 include sodium chromate-treated (n = 3) and the control PRH samples (n = 3). A total of 2,525 differentially expressed genes (DEGs) were obtained, especially 962, and 1,563 genes were up- and downregulated in sodium chromate-treated PRHs compared to the control. Gene ontology (GO) enrichment analysis suggested that those DEGs were involved in multiple biological processes, including the response to toxic substances, the positive regulation of apoptotic process, lipid and cholesterol metabolic process, and others. Signaling pathway enrichment analysis indicated that the DEGs were mainly enriched in MAPK, PI3K-Akt, PPAR, AMPK, cellular senescence, hepatitis B, fatty acid biosynthesis, etc. Moreover, many genes, including CYP2E1, CYP1A2, CYP2C13, CDK1, NDC80, and CCNB1, might contribute to sodium chromate-induced hepatotoxicity. Taken together, this study enhances our knowledge of the potential molecular mechanisms of sodium chromate-induced hepatotoxicity.

Association of environmental exposure to chromium with differential DNA methylation: An epigenome-wide study

Introduction: Previous studies have reported that chromium (Cr)-induced epigenetic alterations and DNA methylation play a vital role in the pathogenesis of diseases induced by chromium exposure. Epigenomic analyses have been limited and mainly focused on occupational chromium exposure; their findings are not generalizable to populations with environmental Cr exposure. Methods: We identified the differential methylation of genes and regions to elucidate the mechanisms of toxicity related to environmental chromium exposure. DNA methylation was measured in blood samples collected from individuals in Cr-contaminated (n = 10) and unexposed areas (n = 10) by using the Illumina Infinium HumanMethylation850K array. To evaluate the relationship between chromium levels in urine and CpG methylation at 850 thousand sites, we investigated differentially methylated positions (DMPs) and differentially methylated regions (DMRs) by using linear models and DMRcate method, respectively. The model was adjusted for biologically relevant variables and estimated cell-type compositions. Results: At the epigenome-wide level, we identified five CpGs [cg20690919 (p _{FDR =}0.006), cg00704664 (p _{FDR =}0.024), cg10809143 (p _{FDR =}0.043), cg27057652 (p _{FDR =}0.047), cg05390480 (p _{FDR =}0.024)] and one DMR (chr17: 19,648,718-19,648,972), annotated to ALDH3A1 genes (p < 0.05) as being significantly associated with log₂ transformed urinary chromium levels. Discussion: Environmental chromium exposure is associated with DNA methylation, and the significant DMPs and DMR being annotated to cause DNA damage and genomic instability were found in this work. Research involving larger samples is required to further explore the epigenetic effect of environmental chromium exposure on health outcomes through DNA methylation.