title: Monomethylarsonous acid inhibited endogenous cholesterol biosynthesis in human skin fibroblasts.
abstract: Human exposure to arsenic in drinking water is a widespread public health concern, and such exposure is known to be associated with many human diseases. The detailed molecular mechanisms about how arsenic species contribute to the adverse human health effects, however, remain incompletely understood. Monomethylarsonous acid [MMA(III)] is a highly toxic and stable metabolite of inorganic arsenic. To exploit the mechanisms through which MMA(III) exerts its cytotoxic effect, we adopted a quantitative proteomic approach, by coupling stable isotope labeling by amino acids in cell culture (SILAC) with LC-MS/MS analysis, to examine the variation in the entire proteome of GM00637 human skin fibroblasts following acute MMA(III) exposure. Among the ~6500 unique proteins quantified, ~300 displayed significant changes in expression after exposure with 2 μM MMA(III) for 24 h. Subsequent analysis revealed the perturbation of de novo cholesterol biosynthesis, selenoprotein synthesis and Nrf2 pathways evoked by MMA(III) exposure. Particularly, MMA(III) treatment resulted in considerable down-regulation of several enzymes involved in cholesterol biosynthesis. In addition, real-time PCR analysis showed reduced mRNA levels of select genes in this pathway. Furthermore, MMA(III) exposure contributed to a distinct decline in cellular cholesterol content and significant growth inhibition of multiple cell lines, both of which could be restored by supplementation of cholesterol to the culture media. Collectively, the present study demonstrated that the cytotoxicity of MMA(III) may arise, at least in part, from the down-regulation of cholesterol biosynthesis enzymes and the resultant decrease of cellular cholesterol content.
authors.affiliation: Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521-0403, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
authors.affiliation: Department of Chemistry, University of California, Riverside, CA 92521-0403, United States.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521-0403, United States; Department of Chemistry, University of California, Riverside, CA 92521-0403, United States. Electronic address: yinsheng.wang@ucr.edu.
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D018929:Cell Culture Techniques; D002460:Cell Line; D002470:Cell Survival; D002784:Cholesterol / Q000096:biosynthesis*; D015536:Down-Regulation / Q000187:drug effects; D004794:Enzyme Repression / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D015386:Hazardous Substances / Q000633:toxicity*; D006801:Humans; D009942:Organometallic Compounds / Q000633:toxicity*; D016133:Polymerase Chain Reaction; D040901:Proteomics; D012333:RNA, Messenger; D051140:Selenoproteins / Q000096:biosynthesis; D012867:Skin / Q000187:drug effects* / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D015386:Hazardous Substances; D009942:Organometallic Compounds; D012333:RNA, Messenger; D051140:Selenoproteins; C406082:monomethylarsonous acid; D002784:Cholesterol
keywords: De novo cholesterol biosynthesis; FASP; Monomethylarsonous acid; Quantitative proteomics; SILAC