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Cystic fibrosis (CF) is due to mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which cause a massively proinflammatory phenotype in the CF airway. The chemical basis of the inflammation is hyperproduction of interleukin-8 (IL-8) by CF airway epithelial cells, based on both an intrinsic mutation-dependent mechanism and by infection. In infection-free, cultured CF lung epithelial cells, high levels of the microRNA (miR), miR-155, is responsible for hyperexpression of IL-8. However, whether infection-induced IL-8 expression in CF cells is also mediated by miR-155 is not known. We have hypothesized that miR-155 might be a general mediator of enhanced IL-8 expression in CF cells, either in response to other cytokine/chemokine mediators of inflammation, or after exposure to infectious agents. Here we find that a reduction in miR-155 accompanies suppression of IL-8 by either the anti-inflammatory cytokine IL-10 or by inhibition of ambient IL-1β with a neutralizing antibody. However, attempts to elevate IL-8 levels with either intact bacteria [viz. a mucoid strain of Pseudomonas aeruginosa (PA)], or lipopolysaccharide were unable to elevate miR-155 above its intrinsically high level in the absence of these agents. Instead, in response to PA infection, the CF cells modestly suppress the expression of miR-155, and express a novel set of miRs, including miR-215. We find that ex vivo CF lung epithelial cells also express high levels of both miR-155 and miR-215. The predicted module of infection-induced mRNA targets focuses on activation of the NFκB-signaling pathway, and on the proapoptotic p53-signaling pathway. We interpret these data to suggest that that CF lung epithelial cells respond to PA or bacterial cell products with a novel miR program that may carry with it serious challenges to survival.

(2016) RPTOR, a novel target of miR-155, elicits a fibrotic phenotype of cystic fibrosis lung epithelium by upregulating CTGF, RNA Biology, 13:9, 837-847, DOI: 10.1080/15476286.2016 ABSTRACTCystic fibrosis (CF) is an autosomal recessive disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, the most frequent of which is F508del-CFTR. CF is characterized by excessive secretion of pro-inflammatory mediators into the airway lumen, inducing a highly inflammatory cellular phenotype. This process triggers fibrosis, causing airway destruction and leading to high morbidity and mortality. We previously reported that miR-155 is upregulated in CF lung epithelial cells, but the molecular mechanisms by which miR-155 affects the disease phenotype is not understood. Here we report that RPTOR (regulatory associated protein of mTOR, complex 1) is a novel target of miR-155 in CF lung epithelial cells. The suppression of RPTOR expression and subsequent activation of TGF-b signaling resulted in the induction of fibrosis by elevating connective tissue growth factor (CTGF) abundance in CF lung epithelial cells. Thus, we propose that miR-155 might regulate fibrosis of CF lungs through the increased CTGF expression, highlighting its potential value in CF therapy.

more efficiently than human hepatocytes and results in lower overall transduction as compared to human clinical samples. Thus, while these models can serve as a surrogate to assess the activity of gene therapy constructs against functions of normal human liver, the doses required for optimal activity may be modestly higher than required in the human clinical setting. 146.Regulation of Inflammation in Cystic Fibrosis Lung Epithelial Cells by miR-155