Oncostatin M in Pulmonary Epithelial Barrier Dysfunction

Abstract

The lung mucosal epithelium is essential for gas exchange, and its breakdown can be fatal. Oncostatin M (OSM) is a member of the IL-6 family of cytokines. Previous studies have shown that OSM can regulate pulmonary epithelial barrier dysfunction in vitro, is a potent activator of the JAK/ STAT pathway and synergizes with pro-inflammatory cytokines (IL-1beta and TNF-alpha) in other systems. However, the role of the JAK/STAT signaling pathway and the effect of OSM co-stimulations with IL-1beta, TNF-alpha or IL-33 on barrier function are unclear. A standard adherent cell culture model of mouse embryonic fibroblasts (NIH3T3) was used to determine if OSM would combine with IL-33 to increase responses. Stimulation of NIH3T3 cells with IL-33 increased secretion of TIMP-1. When combined with OSM, IL-33 showed a trend toward increased TIMP-1 mRNA and significantly induced IL-33, which was associated with STAT3 activation. Since IL-24 was implicated in skin barrier dysfunction, IL-24 expression in transformed human bronchial epithelial (HBEC3-KT) cells was also examined. OSM stimulation increased IL-24 mRNA, however there were no differences in intracellular and secreted IL-24. TER and FITC-dextran passage in air-liquid interface (ALI) cultures of HBEC3-KT cells and normal human bronchial epithelial (NHBE) cells were used to determine the effect of cytokine stimulations on barrier function in vitro. NHBE cells were validated for barrier differentiation and OSM responsiveness (pSTAT3 elevation) at day 1 and 21 in culture. The transwell system was optimized for OSM stimulations and OSM dose-dependent barrier dysfunction was successfully reproduced. OSM co-stimulations with TNF-alpha or IL-1beta were completed to investigate the effects on barrier dysfunction. Only co-stimulation with TNF-alpha resulted in increased barrier dysfunction at low doses. These findings identify OSM as a potent disruptor of pulmonary epithelial barrier function correlating with STAT3 signaling pathway activation. Thus, OSM may contribute to barrier dysfunction during respiratory infections.