title: Exposure to metal-rich particulate matter modifies the expression of candidate microRNAs in peripheral blood leukocytes.
abstract: BACKGROUND
  Altered patterns of gene expression mediate the effects of particulate matter (PM) on human health, but mechanisms through which PM modifies gene expression are largely undetermined. MicroRNAs (miRNAs) are highly conserved, noncoding small RNAs that regulate the expression of broad gene networks at the posttranscriptional level.
  
  
  OBJECTIVE
  We evaluated the effects of exposure to PM and PM metal components on candidate miRNAs (miR-222, miR-21, and miR-146a) related with oxidative stress and inflammatory processes in 63 workers at an electric-furnace steel plant.
  
  
  METHODS
  We measured miR-222, miR-21, and miR-146a expression in blood leukocyte RNA on the first day of a workweek (baseline) and after 3 days of work (postexposure). Relative expression of miRNAs was measured by real-time polymerase chain reaction. We measured blood oxidative stress (8-hydroxyguanine) and estimated individual exposures to PM1 (< 1 microm in aerodynamic diameter), PM10 (< 10 microm in aerodynamic diameter), coarse PM (PM10 minus PM1), and PM metal components (chromium, lead, cadmium, arsenic, nickel, manganese) between the baseline and postexposure measurements.
  
  
  RESULTS
  Expression of miR-222 and miR-21 (using the 2-DeltaDeltaCT method) was significantly increased in postexposure samples (miR-222: baseline = 0.68 +/- 3.41, postexposure = 2.16 +/- 2.25, p = 0.002; miR-21: baseline = 4.10 +/- 3.04, postexposure = 4.66 +/- 2.63, p = 0.05). In postexposure samples, miR-222 expression was positively correlated with lead exposure (beta = 0.41, p = 0.02), whereas miR-21 expression was associated with blood 8-hydroxyguanine (beta = 0.11, p = 0.03) but not with individual PM size fractions or metal components. Postexposure expression of miR-146a was not significantly different from baseline (baseline = 0.61 +/- 2.42, postexposure = 1.90 +/- 3.94, p = 0.19) but was negatively correlated with exposure to lead (beta = -0.51, p = 0.011) and cadmium (beta = -0.42, p = 0.04).
  
  
  CONCLUSIONS
  Changes in miRNA expression may represent a novel mechanism mediating responses to PM and its metal components.
authors.affiliation: Department of Environmental and Occupational Health, Università degli Studi di Milano and IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Center of Molecular and Genetic Epidemiology, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Bollati
authors.forename: Barbara
authors.initials: B
authors.lastname: Marinelli
authors.forename: Pietro
authors.initials: P
authors.lastname: Apostoli
authors.forename: Matteo
authors.initials: M
authors.lastname: Bonzini
authors.forename: Francesco
authors.initials: F
authors.lastname: Nordio
authors.forename: Mirjam
authors.initials: M
authors.lastname: Hoxha
authors.forename: Valeria
authors.initials: V
authors.lastname: Pegoraro
authors.forename: Valeria
authors.initials: V
authors.lastname: Motta
authors.forename: Letizia
authors.initials: L
authors.lastname: Tarantini
authors.forename: Laura
authors.initials: L
authors.lastname: Cantone
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.forename: Pier Alberto
authors.initials: PA
authors.lastname: Bertazzi
authors.forename: Andrea
authors.initials: A
authors.lastname: Baccarelli
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000328:Adult; D019175:DNA Methylation / Q000187:drug effects*; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000032:analysis; D006801:Humans; D007558:Italy; D008297:Male; D008669:Metallurgy; D019216:Metals, Heavy / Q000737:chemistry / Q000633:toxicity*; D035683:MicroRNAs / Q000235:genetics; D008875:Middle Aged; D016273:Occupational Exposure / Q000032:analysis*; D052638:Particulate Matter / Q000737:chemistry / Q000633:toxicity*; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D019216:Metals, Heavy; D035683:MicroRNAs; D052638:Particulate Matter; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine