title: Cigarette smoke enhances human rhinovirus-induced CXCL8 production via HuR-mediated mRNA stabilization in human airway epithelial cells.
abstract: BACKGROUND
  Human rhinovirus (HRV) triggers exacerbations of asthma and chronic obstructive pulmonary disease (COPD). Cigarette smoking is the leading risk factor for the development of COPD and 25% of asthmatics smoke. Smoking asthmatics have worse symptoms and more frequent hospitalizations compared to non-smoking asthmatics. The degree of neutrophil recruitment to the airways correlates with disease severity in COPD and during viral exacerbations of asthma. We have previously shown that HRV and cigarette smoke, in the form of cigarette smoke extract (CSE), each induce expression of the neutrophil chemoattractant and activator, CXCL8, in human airway epithelial cells. Additionally, we demonstrated that the combination of HRV and CSE induces expression of levels of CXCL8 that are at least additive relative to induction by each stimulus alone, and that enhancement of CXCL8 expression by HRV+CSE is regulated, at least in part, via mRNA stabilization. Here we further investigate the mechanisms by which HRV+CSE enhances CXCL8 expression.
  
  
  METHODS
  Primary human bronchial epithelial cells were cultured and treated with CSE alone, HRV alone or the combination of the two stimuli. Stabilizing/destabilizing proteins adenine/uridine-rich factor-1 (AUF-1), KH-type splicing regulatory protein (KHSRP) and human antigen R (HuR) were measured in cell lysates to determine expression levels following treatment. siRNA knockdown of each protein was used to assess their contribution to the induction of CXCL8 expression following treatment of cells with HRV and CSE.
  
  
  RESULTS
  We show that total expression of stabilizing/de-stabilizing proteins linked to CXCL8 regulation, including AUF-1, KHSRP and HuR, are not altered by CSE, HRV or the combination of the two stimuli. Importantly, however, siRNA-mediated knock-down of HuR, but not AUF-1 or KHSRP, abolishes the enhancement of CXCL8 by HRV+CSE. Data were analyzed using one-way ANOVA with student Newman-Keuls post hoc analysis and values of p≤ 0.05 were considered significant.
  
  
  CONCLUSIONS
  Induction of CXCL8 by the combination of HRV and CSE is regulated by mRNA stabilization involving HuR. Thus, targeting the HuR pathway may be an effective method of dampening CXCL8 production during HRV-induced exacerbations of lower airway disease, particularly in COPD patients and asthmatic patients who smoke.
authors.affiliation: Department of Physiology & Pharmacology, HRIC 4AC60, University of Calgary Faculty of Medicine, 3280 Hospital Drive N,W,, Calgary, AB T2N 4Z6, Canada. dproud@ucalgary.ca.
authors.forename: Magdalena H
authors.initials: MH
authors.lastname: Hudy
authors.forename: David
authors.initials: D
authors.lastname: Proud
mesh_terms: D001980:Bronchi / Q000378:metabolism* / Q000821:virology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D051959:ELAV Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism / Q000821:virology; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D016601:RNA-Binding Proteins / Q000378:metabolism; D012229:Rhinovirus / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D012906:Smoke / Q000009:adverse effects; D062789:Tobacco Products / Q000009:adverse effects; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D051959:ELAV Proteins; C000630986:HNRNPD protein, human; D000081035:Heterogeneous Nuclear Ribonucleoprotein D0; D034502:Heterogeneous-Nuclear Ribonucleoprotein D; D016209:Interleukin-8; C105789:KHSRP protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D012906:Smoke; D015534:Trans-Activators; D007770:L-Lactate Dehydrogenase