Epithelial cell death markers in bronchoalveolar lavage correlate with chronic lung allograft dysfunction subtypes and survival in lung transplant recipients-a single-center retrospective cohort study.

Chronic lung allograft dysfunction (CLAD) remains the leading cause of late death after lung transplantation. Epithelial injury is thought to be a key event in the pathogenesis of CLAD. M30 and M65 are fragments of cytokeratin-18 released specifically during epithelial cell apoptosis and total cell death, respectively. We investigated whether M30 and M65 levels in bronchoalveolar lavage (BAL) correlate with CLAD subtypes: restrictive allograft syndrome (RAS) versus bronchiolitis obliterans syndrome (BOS). BALs were obtained from 26 patients with established CLAD (10 RAS, 16 BOS) and 19 long-term CLAD-free controls. Samples with concurrent infection or acute rejection were excluded. Protein levels were measured by ELISA. Variables were compared using Kruskal-Wallis, Mann-Whitney U test and Chi-squared tests. Association of M30 and M65 levels with post-CLAD survival was assessed using a Cox PH models. M65 levels were significantly higher in RAS compared to BOS and long-term CLAD-free controls and correlated with worse post-CLAD survival. Lung epithelial cell death is enhanced in patients with RAS. Detection of BAL M65 may be used to differentiate CLAD subtypes and as a prognostic marker in patients with established CLAD. Understanding the role of epithelial cell death in CLAD pathogenesis may help identify new therapeutic targets to improve outcome.

Lipopolysaccharide-Mediated Induction of Concurrent IL-1ß and IL-23 Expression in THP-1 Cells Exhibits Differential Requirements for Caspase-1 and Cathepsin B Activity.

The inflammasome is a multimeric protein complex required for interleukin (IL)-1ß production. Upon lipopolysaccharide (LPS) triggering of toll-like receptor (TLR)-4 and subsequent ATP signaling, the NOD-like receptor containing-pyrin domain 3 (NLRP3) inflammasome is activated to cleave pro-caspase-1 into caspase-1, allowing the secretion of IL-1ß. IL-1ß is known to function with IL-23 in the regulation of IL-17-producing CD4(+) T cells, Th17 cells, in adaptive immunity. Recently, studies have shown that IL-1ß and IL-23 together activate IL-17-producing innate lymphoid cells, demonstrating that the pair may exhibit additional effects on cell differentiation. Using an in vitro model of bacterial infection, LPS treatment of human monocytic cells, we investigated the molecular mechanisms involved in the co-expression of IL-1ß and IL-23. We found that IL-1ß is partially required for optimal LPS-induced IL-23 production. We also found that IL-23 production was partially dependent on ATP signaling via the P2X7 receptor, whereas IL-1ß production required this signaling. Furthermore, we identified a novel role for cathepsin B activity in IL-23 production. Taken together, this study identifies differential requirements for the co-expression of IL-1ß and IL-23. Due to their similar roles in Th17 differentiation, characterization of the regulatory mechanisms for LPS-induced IL-1ß and IL-23 may reveal novel information into the pathology of the inflammatory response particularly during bacterial infection.