CFTR expression during cellular senescence

Background: Cystic fibrosis trans-membrane conductance regulator (CFTR) is a cAMP-modulated chloride/bicarbonate channel with different functions in various organs and tissues. CFTR expression get decreasing from embryogenesis to adult/elder age and recent evidences show that some CFTR-regulating microRNAs, i.e, miR-494, is up-regulated during cellular senescence. Cellular senescence is a permanent cell cycle arrest that can be induced in young cells by different stimuli such as the physiological shortening of telomeres, the activation of oncogenes as well as oxidative stress. Aims: To assess whether and how CFTR might be involved in cellular senescence. Methods: To induce premature senescence, IMR90 young cells (PDL34) were treated with 100 M diethylmaleate (DEM) for ten days. The over-expression and the silencing of CFTR in pre-senescent IMR90 cells and young IMR90 cells, respectively, were performed by lentiviral cell infection and cell counting. The CFTR and the microRNAs expression were assessed by Western Blot and RT-PCR analysis either in: i) IMR90 cells at different population doubling levels (PDL); ii) IMR90 cells at different days after DEM treatment. Results: We found that: a) the CFTR expression significantly decreased in IMR90 cells during replicative senescence and after DEM treatment in an inverse relationship with miR-494 expression; c) the over-expression of CFTR in IMR90 pre-senescent cells significantly accelerate cellular senescence, while, the silencing of CFTR significantly slowed the appearance of the senescent phenotype. Conclusions: Our preliminary data show that CFTR is physiologically down-regulated during cellular senescence and this may (at least partially) depend on the up-regulation of miR-494. The over-expression and the silencing of CFTR in IMR90 cells have important effects on their cell cycle. Furthermore, we are now validating such results on primary epithelial nasal cells from different subjects.