Direct ENaC activation preserves capillary barrier function in pneumonia

The lectin-like domain of TNF, mimicked by the TIP peptide, reduces pulmonary edema in multiple animal models, as well as in a phase 2a clinical trial in patients with acute lung injury, leading to a clinical interest in the molecule. Our preliminary data demonstrate that the TIP peptide directly activates the epithelial sodium channel (ENaC) upon association with the second transmembrane domain of the crucial alpha subunit. The TIP peptide also protects microvascular endothelial cells from pneumolysin- and LPS- induced hyperpermeability, in a manner requiring ENaC expression in these cells. Our central hypothesis is that TIP peptide preserves complex formation of ENaC with PIP2 in the presence of LPS or pneumolysin, which in turn abrogates activation of the PC-PLC/PKC-alpha axis, involved in impairment of barrier function. Our main objectives are to: 1) demonstrate that TIP peptide can activate ENaC in human lung MVEC; 2) test the hypothesis that ENaC activation is crucial for the barrier-stabilizing effect of the lectin-like domain of TNF in pneumolysin/LPS-treated human lung endothelial monolayers and 3) to assess whether ENaC-alpha affects pneumolysin/LPS-induced barrier dysfunction in mice. Our expected outcomes include: 1) demonstration of a hitherto unknown role for ENaC in capillary barrier regulation during pneumonia, and 2) development of a novel therapy for pulmonary permeability edema. The impact of our project includes advancing understanding of TNF biology and optimizing a new therapy to improve the outcome of patients with pneumonia-associated pulmonary edema. (AHA Program: Scientist Development Grant)