Roles of Lung Epithelium in Neutrophil Recruitment during Pneumococcal Pneumonia

Abstract

Epithelial cells line the respiratory tract and interface with the external world. Epithelial cells contribute to pulmonary inflammation, but specific epithelial roles have proven difficult to define. To discover unique epithelial activities that influence immunity during infection, we generated mice with nuclear factor-κB RelA mutated throughout all epithelial cells of the lung and coupled this approach with epithelial cell isolation from infected and uninfected lungs for cell-specific analyses of gene induction. The RelA mutant mice appeared normal basally, but in response to pneumococcus in the lungs they were unable to rapidly recruit neutrophils to the air spaces. Epithelial cells expressed multiple neutrophil-stimulating cytokines during pneumonia, all of which depended on RelA. Cytokine expression by nonepithelial cells was unaltered by the epithelial mutation of RelA. Epithelial cells were the predominant sources of CXCL5 and granulocyte-macrophage colony-stimulating factor (GM-CSF), whereas nonepithelial cells were major sources for other neutrophil-activating cytokines. Epithelial RelA mutation decreased whole lung levels of CXCL5 and GM-CSF during pneumococcal pneumonia, whereas lung levels of other neutrophil-recruiting factors were unaffected. Defective neutrophil recruitment in epithelial mutant mice could be rescued by administration of CXCL5 or GM-CSF. These results reveal a specialized immune function for the pulmonary epithelium, the induction of CXCL5 and GM-CSF, to accelerate neutrophil recruitment in the infected lung.

Lung inflammation promotes metastasis through neutrophil protease-mediated degradation of Tsp-1

“…LPS-induced acute lung injury is marked by increased neutrophil influx and up-regulation of proinflammatory cytokines. Similar phenotypes are observed in other lung inflammatory conditions, including asthma (6), chronic obstructive pulmonary disease (7), and pneumonia (8,9). LPS-mediated lung inflammation is associated with breast and colon cancer metastasis to the lungs (10)(11)(12).…”

Activated β2 Integrins Restrict Neutrophil Recruitment during Murine Acute Pseudomonal Pneumonia

“…Neutropenic human patients (39,40) and laboratory mice (36,41,42) have enhanced susceptibility to pseudomonal pneumonia. Inefficient rapid, early neutrophil recruitment, even when corrected within 24 hours, resulted in 10-fold more bacteria in the airspaces at 48 hours in a murine model of pneumococcal pneumonia (43). Potentiating the early phase of neutrophil recruitment may represent a therapeutic approach in the age of antibiotic resistance.…”

Expression of Piwi protein MIWI2 defines a distinct population of multiciliated cells

“…Specific cell sources of Miwi2 expression were interrogated in mice infected with S. pneumoniae using a previously described protocol for isolating purified cell populations recovered from whole lung enzymatic digests and bronchoalveolar lavage fluid (3,16 ized in the cytoplasm, and restricted to airway cells ( Figure 1E). To determine whether the increase in Miwi2 mRNA correlated with increased MIWI2 protein expression, tissue sections isolated from uninfected or infected lungs were quantitatively compared, and demonstrated that the number of MIWI2-positive cells was significantly increased as a result of infection ( Figure 1F).…”

“…-cells from whole lung digests contain the major pulmonary epithelial subtypes, including club cells, multiciliated cells, and type I and II pneumocytes (16). We evaluated lung sections by immunohistochemistry to determine the cell type and anatomic location of MIWI2 protein expression in the lungs.…”

“…Lung digestion. Lung digests for isolation of epithelial cells were performed using elastase, as previously described (3,16). Briefly, after euthanasia, lungs were perfused with 10 ml HBSS via the right ventricle through the pulmonary artery.…”