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A7178 - The Role of Beta-Catenin/CREB Binding Protein (CBP) - Dependent Signalling in Airway Epithelial Barrier Function and CCL20 Release
Author Block: V. Kuchibhotla1, D. A. Knight2, M. C. Nawijn1, I. H. Heijink1; 1Pathology and Medical Biology, GRIAC Research Institute, University Medical Center Groningen, University of Groningen, Groningen, Netherlands, 2Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia.
RATIONALE The integrity of airway epithelium in asthma patients is often disrupted with the loss of cell-cell contact molecule E-cadherin. The airway epithelium in asthma displays impaired reconstitution of barrier function and re-differentiation upon environmental insults, such as house dust mite (HDM) allergens, while pro-inflammatory activity such as release of chemokine (C-C motif) ligand 20 (CCL20) is enhanced. Loss of E-cadherin and subsequent release of beta-catenin can activate two divergent gene expression programs through interaction with co-activators CREB binding protein (CBP) or p300, inducing cell migration, proliferation and maintaining the cells in undifferentiated state, or differentiation respectively. We hypothesise that blocking the binding of beta-catenin to CBP by a small molecule inhibitor ICG-001, restores the barrier function and attenuates the release of CCL20 upon damage in airway epithelium.
METHODS The effect of ICG-001 was studied on epithelial barrier function and CCL20 release in the human bronchial epithelial cell line 16HBE14o- and primary bronchial epithelial cells (PBECs) derived from tracheobronchial tissue of healthy donors using electric cell-substrate impedance sensing (ECIS) and ELISA, in the presence and absence of HDM as well as Ca2+-ATPase inhibitor thapsigargin to mimic HDM-induced Ca2+-dependent signalling.
RESULTS The presence of ICG-001 significantly increased epithelial barrier function in 16HBE14o- cells and a similar trend was observed in PBECs. In 16HBE14o- cells, both HDM and thapsigargin induced a transient reduction in epithelial barrier function, with a more robust effect of thapsigargin. ICG-001 significantly improved the restoration of barrier function upon damage by thapsigargin. Both HDM and thapsigargin induced the release of CCL20 after 24 hours in 16HBE14o- cells, which was significantly decreased by ICG-001. ICG-001 did not have an effect on the mRNA expression of CCL20 at 6 hours and 24 hours, suggesting that it inhibits the release of CCL20 through a post-translational mechanism. ICG-001 also significantly attenuated the release of CCL20 in PBECs, thus validating the relevance of our findings.
CONCLUSIONS Our data show that inhibition of the beta-catenin/CBP signalling attenuates Ca+2-signalling mediated barrier dysfunction and CCL20 release after HDM exposure in human bronchial epithelial cells. Thus, ICG-001 may protect against allergen-induced barrier dysfunction, impaired differentiation and increased pro-inflammatory activity as observed in the airway epithelium of asthma patients. Further research is needed to elucidate the molecular mechanisms involved. Together, interference of beta-catenin/CBP signalling may constitute a novel treatment strategy aimed at the restoration of immunological mucosal barrier in asthma.