42 CFTR Mediates Enteric Bacterial Translocation Post Severe Burn via ERK and Inflammatory Signaling

Abstract

Abstract Introduction This research was to investigate the role of cystic fibrosis transmembrane conductance regulator (CFTR) in mediating enteric bacterial translocation (EBT) post severe burn as well as the signaling pathways involved. Methods A hypoxia treatment model of Caco-2 in vitro and a 30% TBSA full-thickness dermal burn mice model in vivo were established to explore the effect of major burn injury on intestinal epithelial barrier and the expression of CFTR and tight junction proteins. In addition, the DF508 mice (mice with F508del CFTR gene mutation) were used to analyze bacterial counts in extraintestinal organs and the expression of ZO-1, OCLN and E-cadherin. And CFTR specific inhibitor or down-regulation of CFTR in Caco-2 cells were used to explore the effect of CFTR on tight junction of intestinal cells. Furthermore, in the models above, MAPK pathway and inflammatory factors were detected to explore the mechanism. Finally, Vitamin D3 was used to pretreat mice before severe burn or Caco-2 cells before hypoxia. Bacterial counts in extraintestinal organs and the expression of CFTR, ZO-1, OCLN and P-ERK as well as the concentrations of inflammatory factors were detected. Results Our data showed a decrease of CFTR, concomitant with activation of ERK signaling, elevation of inflammatory factors (TNF-α, IL-1β and IL-8) and declined expression of ZO-1, occludin and E-cadherin, and a cellular mislocation of ZO-1 and OCLN post hypoxia. Furthermore, either administration of CFTR specific inhibitor or down-regulation of CFTR caused similar alterations as hypoxia did. Ileum of DF508 -/- and +/- mice exhibited increased inflammation, declined ZO-1, occludin and E-cadherin and EBT compared to +/+ mice. Moreover, vitamin D3 could reverse the junctional damage induced by hypoxia, thus preventing occurrence of EBT, possibly via up-regulating CFTR. Conclusions CFTR/ERK/inflammatory factors signaling was critical in modulating intestinal epithelial junction, accordingly regulating EBT. Vitamin D3 can protect intestinal epithelial barrier after severe burn, which may be associated with the up-regulation of CFTR, the inhibition of ERK pathway and decreased pro-inflammatory cytokine. Applicability of Research to Practice This research may be used in practice in the future to regulate the metabolism after severe burns.