High dose everolimus promotes a pro-inflammatory phenotype and facilitates the epithelial to mesenchymal transition of primary bronchial epithelial cells isolated from cystic fibrosis patients.

Background: Lung transplantation is still the best therapeutic option for cystic fibrosis (CF) patients, but, unfortunately, immunosuppressive therapies, often employed at high dosages to avoid acute rejection, may induce severe complications. In particular, patients treated with high dose of mammalian target of rapamycin inhibitors (mTOR-Is) may experience lung fibrosis (including bronchiolitis obliterans-organizing pneumonia). Although epithelial to mesenchymal transition (EMT) of airway cells has a central role in this process, the complete biological machinery is not completely clarified.Methods: In order to improve our knowledge on this process, primary bronchial epithelial cells carrying F508del mutation were treated with 5 and 100 nM everolimus (EVE) for 24 hours. Subsequently, RNA was hybridized to the Human HT-12 v3 Expression BeadChip (Illumina). Real-Time PCR was, then, used to validate microarray results and to measure major EMT biomarkers. Trans-epithelial resistance was measured by Millicell-ERS ohmmeter.Results: High dosage EVE induced a significant up-regulation of 42 genes and a down-regulation of 12 genes. After pathway analysis by Gene Set Enrichment Analysis and Ingenuity Pathway Analysis, we found that most of them were implicated in the pro-inflammatory pathway. Real-Time PCR validated these results and revealed that, in addition to pro-inflammatory genes (IL-1α, IL-8, Pim-1 Oncogene), EVE at high dosage was able to up-regulate major EMT biomarkers (such as: alpha-smooth muscle actin, connective tissue growth factor and metalloproteinase 12). In lung, EMT is the convergence point between inflammation and the progression of fibrotic damage. Additionally, EVE at this dosage reduced the trans-epithelial resistance (altering tight junction strength). In contrast, lower EVE did not trigger similar effects.Conclusions: We demonstrated that high dose EVE may trigger a pro-inflammatory/fibrotic biological machinery in bronchial epithelial cells from CF patients. Our results, although obtained in vitro, suggest that solid organ transplant recipients affected by CF should be treated with the lowest possible dose of mTOR inhibitors to minimize/avoid the onset and development of lung complications. In vivo studies might be useful to confirm our hypothesis.