Project description:This SuperSeries is composed of the following subset Series: GSE32105: Expression data from mouse livers lacking STAT3 and RelA during pneumonia GSE35513: Expression data from mouse livers lacking NF-kappaB RelA (p65) during pneumonia GSE35514: Expression data from mouse livers lacking STAT3 during pneumonia GSE35515: Expression data from mouse livers expressing or lacking Cre recombinase during pneumonia Refer to individual Series
Project description:During bacterial pneumonia, alveolar epithelial cells are critical for maintaining gas exchange and providing antimicrobial as well as pro-immune properties. We previously demonstrated that leukemia inhibitory factor (LIF), an IL-6 family cytokine, is produced by type II alveolar epithelial cells (ATII) and is critical for tissue protection during bacterial pneumonia. However, the target cells and mechanisms of LIF-mediated protection remain unknown. Here, we demonstrate that antibody-induced LIF blockade remodels the lung epithelial transcriptome in association with increased apoptosis. Based on these data, we performed pneumonia studies using a novel mouse model in which LIFR (the unique receptor for LIF) is absent in lung epithelium. While LIFR was detected on the surface of epithelial cells, its absence only minimally contributed to tissue protection during pneumonia. Single-cell RNA-sequencing (scRNAseq) was conducted to identify adult murine lung cell types most prominently expressing LIFR, revealing endothelial cells, mesenchymal cells, and ATIIs as major sources of LIFR. Sequencing data indicated that ATII cells were significantly impacted as a result of pneumonia, with additional differences observed in response to LIF neutralization, including but not limited to gene programs related to cell death, injury, and inflammation. Overall, our data suggest that LIF signaling on epithelial cells alters responses in this cell type during pneumonia. However, our results also suggest separate and perhaps more prominent roles of LIFR in other cell types, such as endothelial cells or mesenchymal cells, which provide grounds for future investigation.
Project description:Rationale: Patients in the intensive care unit (ICU) are frequently exposed to unnecessary antibiotics. Markers of the host response to infection may aid pneumonia diagnosis and avoid antibiotic-induced complications. Objective: To assess the host response to suspected bacterial pneumonia through assessment of alveolar neutrophilia and transcriptomic profiling of alveolar macrophages. Methods: We determined the test characteristics of BAL neutrophilia for the diagnosis of bacterial pneumonia in 3 cohorts of mechanically ventilated patients. In one cohort, we also isolated alveolar macrophages from BAL fluid and used the transcriptome to identify signatures of bacterial pneumonia. Finally, we developed a humanized mouse model of Pseudomonas aeruginosa pneumonia to determine if pathogen-specific signatures can be identified in human alveolar macrophages. Measurements and Main Results: BAL neutrophilia was highly sensitive for bacterial pneumonia in both the retrospective (N = 851) and validation cohorts (N = 76 and N = 79) with a negative predictive value of over 90% when BAL neutrophil percentage was less than 50%. A transcriptional signature of bacterial pneumonia was present in both resident and recruited macrophages. Gene signatures from both cell types identified patients with bacterial pneumonia with test characteristics similar to BAL neutrophilia. Conclusions: A BAL neutrophil percentage of less than 50% is highly sensitive for bacterial pneumonia. Informative transcriptomic signatures can be generated from BAL fluid obtained during routine clinical care in the ICU. The identification of novel host response biomarkers is a promising approach to aid the diagnosis and treatment of pneumonia.
Project description:During influenza pneumonia, the alveolar epithelial cells of the lungs are targeted by influenza virus. The distal airway stem cells (DASCs) and proliferating alveolar type II (AT2) cells are reported to be putative lung repair cells. However, their relative spatial and temporal distribution is still unknown during influenza-induced acute lung injury. Here, we investigated the distribution of these cells, and concurrently performed global proteomic analysis of the infected lungs to elucidate and link the cellular and molecular events during influenza pneumonia recovery. BALB/c mice were infected with a sub-lethal dose of influenza H1N1 virus. From 5 to 25 days post-infection (dpi), mouse lungs were subjected to histopathologic and immunofluorescence analysis to probe for global distribution of lung repair cells (using P63 and KRT5 markers for DASCs; PCNA and SPC markers for AT2 cells). At 7 and 15 dpi, infected mouse lungs were also subjected to protein mass spectrometry for relative protein quantification. DASCs appeared only in the damaged area of the lung from 7 dpi onwards, reaching a peak at 21 dpi, and persisted at 25 dpi. However, no differentiation of DASCs to AT2 cells was observed by 25 dpi. In contrast, AT2 cells began proliferating from 7 dpi to replenish its population. Mass spectrometry and gene ontology analysis revealed prominent innate immune response at 7 dpi, which shifted towards adaptive immune responses by 15 dpi. Hence, proliferating AT2 cells but not DASCs contribute to AT2 cell regeneration following transition from innate to adaptive immune responses during the early phase of recovery from influenza pneumonia up to 25 dpi.