A pathogenic role for tumor necrosis factor-related apoptosis-inducing ligand in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a life-threatening inflammatory respiratory disorder, often induced by cigarette smoke (CS) exposure. The development of effective therapies is impaired by a lack of understanding of the underlining mechanisms. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine with inflammatory and apoptotic properties. We interrogated a mouse model of CS-induced experimental COPD and human tissues to identify a novel role for TRAIL in COPD pathogenesis. CS exposure of wild-type mice increased TRAIL and its receptor messenger RNA (mRNA) expression and protein levels, as well as the number of TRAIL(+)CD11b(+) monocytes in the lung. TRAIL and its receptor mRNA were also increased in human COPD. CS-exposed TRAIL-deficient mice had decreased pulmonary inflammation, pro-inflammatory mediators, emphysema-like alveolar enlargement, and improved lung function. TRAIL-deficient mice also developed spontaneous small airway changes with increased epithelial cell thickness and collagen deposition, independent of CS exposure. Importantly, therapeutic neutralization of TRAIL, after the establishment of early-stage experimental COPD, reduced pulmonary inflammation, emphysema-like alveolar enlargement, and small airway changes. These data provide further evidence for TRAIL being a pivotal inflammatory factor in respiratory diseases, and the first preclinical evidence to suggest that therapeutic agents that target TRAIL may be effective in COPD therapy.

Elevated IL-33 expression is associated with pediatric eosinophilic esophagitis, and exogenous IL-33 promotes eosinophilic esophagitis development in mice.

We tested whether the T helper (Th) type 2 (Th2) cell agonist and allergenic ligand IL-33 was associated with eosinophilic esophagitis (EoE) development in a pediatric cohort and whether IL-33 protein could induce disease symptoms in mice. Biopsies from EoE patients or controls were used to measure IL-33 mRNA and protein expression. Increased expression of IL-33 mRNA was found in the esophageal mucosa in EoE. IL-33 protein was detected in cells negative for CD45, mast cells, and epithelial cell markers near blood vessels. Circulating levels of IL-33 were not increased. The time course for IL-33 gene expression was quantified in an established Aspergillus fumigatus allergen mouse model of EoE. Because IL-33 induction was transient in this model and chronicity of IL-33 expression has been demonstrated in humans, naive mice were treated with recombinant IL-33 for 1 wk and esophageal pathology was evaluated. IL-33 application produced changes consistent with phenotypically early EoE, including transmural eosinophilia, mucosal hyperproliferation, and upregulation of eosinophilic genes and chemokines. Th2 cytokines, including IL-13, along with innate lymphoid cell group 2, Th1/17, and M2 macrophage marker genes, were increased after IL-33 application. IL-33-induced eosinophilia was ablated in IL-13 null mice. In addition, IL-33 induced a profound inhibition of the regulatory T cell gene signature. We conclude that IL-33 gene expression is associated with pediatric EoE development and that application of recombinant protein in mice phenocopies the early clinical phase of the human disease in an IL-13-dependent manner. IL-33 inhibition of esophageal regulatory T cell function may induce loss of antigenic tolerance, thereby providing a mechanistic rationale for EoE development.

Tumor necrosis factor-related apoptosis-inducing ligand translates neonatal respiratory infection into chronic lung disease.

Respiratory infections in early life can lead to chronic respiratory disease. Chlamydia infections are common causes of respiratory disease, particularly pneumonia in neonates, and are linked to permanent reductions in pulmonary function and the induction of asthma. However, the immune responses that protect against early-life infection and the mechanisms that lead to chronic lung disease are incompletely understood. Here we identify novel roles for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in promoting Chlamydia respiratory infection-induced pathology in early life, and subsequent chronic lung disease. By infecting TRAIL-deficient neonatal mice and using neutralizing antibodies against this factor and its receptors in wild-type mice, we demonstrate that TRAIL is critical in promoting infection-induced histopathology, inflammation, and mucus hypersecretion, as well as subsequent alveolar enlargement and impaired lung function. This suggests that therapeutic agents that target TRAIL or its receptors may be effective treatments for early-life respiratory infections and associated chronic lung disease.