Alveolar Epithelial Type II Cells Activate Alveolar Macrophages and Mitigate P. Aeruginosa Infection

Abstract

Although alveolar epithelial type II cells (AECII) perform substantial roles in the maintenance of alveolar integrity, the extent of their contributions to immune defense is poorly understood. Here, we demonstrate that AECII activates alveolar macrophages (AM) functions, such as phagocytosis using a conditioned medium from AECII infected by P. aeruginosa. AECII-derived chemokine MCP-1, a monocyte chemoattractant protein, was identified as a main factor in enhancing AM function. We proposed that the enhanced immune potency of AECII may play a critical role in alleviation of bacterial propagation and pneumonia. The ability of phagocytosis and superoxide release by AM was reduced by MCP-1 neutralizing antibodies. Furthermore, MCP-1−/− mice showed an increased bacterial burden under PAO1 and PAK infection vs. wt littermates. AM from MCP-1−/− mice also demonstrated less superoxide and impaired phagocytosis over the controls. In addition, AECII conditioned medium increased the host defense of airway in MCP-1−/− mice through the activation of AM function. Mechanistically, we found that Lyn mediated NFκB activation led to increased gene expression and secretion of MCP-1. Consequently Lyn−/− mice had reduced MCP-1 secretion and resulted in a decrease in superoxide and phagocytosis by AM. Collectively, our data indicate that AECII may serve as an immune booster for fighting bacterial infections, particularly in severe immunocompromised conditions.

Elevated Inflammatory Response in Caveolin-1-deficient Mice with Pseudomonas aeruginosa Infection Is Mediated by STAT3 Protein and Nuclear Factor κB (NF-κB)

“…For lung homogenates, excised lungs were ground in 500 l of PBS. 96-well plates (Corning Costar 9018) were coated with 100 l/well capture antibody in coating buffer and incubated overnight at 4°C (33). 100-l aliquots of serum samples were added to the coated microtiter wells.…”

“…Homogenized lung tissue in 62.5 mM Tris-HCl (pH ϭ 6.8) supplemented with Complete Mini protease inhibitor (Roche Diagnostics) in equal protein amounts was used in the assay. Duplicates were done for each sample and control (41).…”

“…Absorbance was read at 460 nm at 2-min intervals. Duplicates were done for each sample and control (41).…”

Type I CRISPR-Cas targets endogenous genes and regulates virulence to evade mammalian host immunity

“…Female C57BL/6J mice were obtained from the Jackson Laboratory [42], and tlr4 −/− mice in C57BL/6J background (originally from S Akira, Osaka University, Osaka, Japan) were kindly provided by Dr Jyotika Sharma (University of North Dakota). Mice were kept in a pathogen-free facility at the University of North Dakota.…”

“…Non-adherent cells were removed by washing with normal saline. Murine MLE-12 lung type II epithelial cells and MH-S AMs cells were obtained from American Type Culture Collection (Manassas, VA) and cultured following the manufacturer's instructions [42]. Human primary AMs from BALF samples were obtained through assistance by Dr Arvind Bansal at Altru Hospital.…”