title: Cigarette smoking represses expression of cytokine IL-12 and its regulator miR-21-An observational study in patients with coronary artery disease.
abstract: The heterodimer IL-12 is an inducer of Th1 responses and stimulates INFƴ production. Micro-RNA-21 (miR-21) is described as a key regulator of the pro-inflammatory response and has IL-12p35 mRNA as one of its main targets. The IL-12p40 1188A/C genetic variant located in 3'untranslated region (UTR), thus environmentally exposed, has further been reported to modify IL-12 levels. We have previously reported on the lowering effect of cigarette smoke on circulating IL-12 in patients with coronary artery disease (CAD).
  
  
  
  To explore if cigarette smoking affects IL-12p35, IL-12p40, INFƴ and miR-21 gene-expression and further modulates any effect of the IL-12p40 polymorphism on circulating IL-12 levels.
  
  
  
  The IL-12p40 1188A/C polymorphism was analyzed in 1001 stable CAD patients, of which 330 subjects were included for IL-12p35, IL-12p40 and INFƴ gene-expression analyses in circulating leukocytes and 200 were further selected for plasma miR-21 analysis. Smoking associated with lower expression of miR-21 and its target IL-12p35 mRNA (adjusted p<0.05, both) whereas the influence on INFƴ expression tended to be high-dose reliant (p = 0.057). The IL-12p40 CC genotype associated with elevated circulating IL-12 levels, however, when stratified according to smoking, only in the non-smoking group (adjusted p < 0.05). Although the markers were mainly downregulated in current smokers, their inter-correlations were potentiated.
  
  
  
  Smoking associated with reduced miR-21 gene-repression and the results can therefore not explain the previously observed reduction in circulating IL-12. Smoking attenuated the IL-12 pro-inflammatory axis in which the investigated IL-12p40 genetic variant may have different clinical impact in smokers vs non-smokers.
authors.affiliation: Center for Clinical Heart Research, Department of Cardiology, Oslo University Hospital, Ullevål, Norway; Center for Heart Failure Research, Oslo University Hospital, Norway; Faculty of Medicine, University of Oslo, Norway. Electronic address: trineoa@medisin.uio.no.
authors.forename: T B
authors.initials: TB
authors.lastname: Opstad
authors.affiliation: Department of Medical Biochemistry, Oslo University Hospital, Ullevål, Norway.
authors.forename: B S
authors.initials: BS
authors.lastname: Brusletto
authors.affiliation: Center for Clinical Heart Research, Department of Cardiology, Oslo University Hospital, Ullevål, Norway; Center for Heart Failure Research, Oslo University Hospital, Norway; Faculty of Medicine, University of Oslo, Norway.
authors.forename: H
authors.initials: H
authors.lastname: Arnesen
authors.affiliation: Center for Clinical Heart Research, Department of Cardiology, Oslo University Hospital, Ullevål, Norway; Center for Heart Failure Research, Oslo University Hospital, Norway.
authors.forename: A Å
authors.initials: AÅ
authors.lastname: Pettersen
authors.affiliation: Center for Clinical Heart Research, Department of Cardiology, Oslo University Hospital, Ullevål, Norway; Center for Heart Failure Research, Oslo University Hospital, Norway; Faculty of Medicine, University of Oslo, Norway.
authors.forename: I
authors.initials: I
authors.lastname: Seljeflot
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers; D000073865:Cigarette Smoking / Q000009:adverse effects; D003324:Coronary Artery Disease / Q000209:etiology* / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D005838:Genotype; D006801:Humans; D018664:Interleukin-12 / Q000235:genetics* / Q000378:metabolism; D008297:Male; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D011110:Polymorphism, Genetic
chemical_list: D015415:Biomarkers; D016207:Cytokines; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D018664:Interleukin-12
keywords: Cigarette smoking; Gene-expression; Genetic polymorphism; IL-12; INFƴ; MiR-21