Gastric aspiration, epithelial injury and chronic lung allograft rejection

Abstract

Introduction For patients with a variety of end stage lung diseases, lung transplantation has become an effective therapy. Chronic allograft rejection occurs in over 50% of patients 5 years post transplantation however. Although alloimmune-mediated injury directed against endothelial and epithelial structures were traditionally thought to be the major culprit, non-alloimmunologic inflammation after bile acid aspiration has been implicated in cystic fibrosis (CF) lung injury, after transplantation. Hypothesis Reflux with aspiration of bile acid is present in the lower airways of people with cystic fibrosis associated lung injury before and after transplantation. Bile acid challenge would cause cytoxicity and release of inflammatory mediators from patient derived primary epithelial cells (PBECs), before and after transplantation. Methods PBECs from lung transplantation patients, explanted CF patient cultures and a goblet cell line were used to perform proof of concept experiments. In these experiments the effect of individual primary and secondary bile acids, porcine pepsin, different patient derived gastric juices (whole or filtered and dialysed) samples and an artificial bile acid mixture were evaluated. Cell death, Interleukin 8 (IL-8), Interleukin 6 (IL-6) and Granulocyte Macrophage Colony Stumulating Factor (GMCSF) production were measured by Titer blue and multiplex ELISA. Results Epithelial cells can be cultured successfully from the bronchial brushings of lung transplant recipient, CF patient explanted lungs and a Goblet cell line. In work connected with this study my research group has demonstrated that the lungs of people with advanced CF lung disease removed at the time of transplantation contained significant levels of bile acids higher than expected based on normal serum levels. I therefore tested the effects of bile acids on PBECs from lung transplant and CF patients. Challengesof ≥10mol/l was associated with significant cell death. Potentially physiological challenges with 1, 5 and 10 mol/l bile acids led to a significant release of pro-neutrophilic cytokines from lung transplant PBECs and CF PBECs .The goblet cell line HT-29 MTX was resistant to bile acids. Conclusion Aspiration of bile acids in CF lungs before and after transplantation may cause cell damage and inflammation. This injury may benefit from medical and surgical treatments for reflux, which may benefit the lung allograft generally.