RESUMO
Klebsiella pneumoniae (KP) is an extracellular Gram-negative bacterium that causes infections in the lower respiratory and urinary tracts and the bloodstream. STAT1 is a master transcription factor that acts to maintain T cell quiescence under homeostatic conditions. Although STAT1 helps defend against systemic spread of acute KP intrapulmonary infection, whether STAT1 regulation of T cell homeostasis impacts pulmonary host defense during acute bacterial infection and injury is less clear. Using a clinical KP respiratory isolate and a pneumonia mouse model, we found that STAT1 deficiency led to an early neutrophil-dominant transcriptional profile and neutrophil recruitment in the lung preceding widespread bacterial dissemination and lung injury development. Yet, myeloid cell STAT1 was dispensable for control of KP proliferation and dissemination, because myeloid cell-specific STAT1-deficient (LysMCre/WT;Stat1fl/fl) mice showed bacterial burden in the lung, liver, and kidney similar to that of their wild-type littermates. Surprisingly, IL-17-producing CD4+ T cells infiltrated Stat1-/- murine lungs early during KP infection. The increase in Th17 cells in the lung was not due to preexisting immunity against KP and was consistent with circulating rather than tissue-resident CD4+ T cells. However, blocking global IL-17 signaling with anti-IL-17RC administration led to increased proliferation and dissemination of KP, suggesting that IL-17 provided by other innate immune cells is essential in defense against KP. Contrastingly, depletion of CD4+ T cells reduced Stat1-/- murine lung bacterial burden, indicating that early CD4+ T cell activation in the setting of global STAT1 deficiency is pathogenic. Altogether, our findings suggest that STAT1 employs myeloid cell-extrinsic mechanisms to regulate neutrophil responses and provides protection against invasive KP by restricting nonspecific CD4+ T cell activation and immunopathology in the lung.
Assuntos
Infecções por Klebsiella , Neutrófilos , Fator de Transcrição STAT1 , Animais , Camundongos , Interleucina-17 , Klebsiella pneumoniae , Pulmão/microbiologia , Células Mieloides , Neutrófilos/imunologia , Fator de Transcrição STAT1/metabolismo , Infecções por Klebsiella/imunologiaRESUMO
The lack of techniques for noninvasive imaging of inflammation has challenged precision medicine management of acute respiratory distress syndrome (ARDS). Here, we determined the potential of positron emission tomography (PET) of chemokine-like receptor-1 (CMKLR1) to monitor lung inflammation in a murine model of lipopolysaccharide-induced injury. Lung uptake of a CMKLR1-targeting radiotracer, [64Cu]NODAGA-CG34, was significantly increased in lipopolysaccharide-induced injury, correlated with the expression of multiple inflammatory markers, and reduced by dexamethasone treatment. Monocyte-derived macrophages, followed by interstitial macrophages and monocytes were the major CMKLR1-expressing leukocytes contributing to the increased tracer uptake throughout the first week of lipopolysaccharide-induced injury. The clinical relevance of CMKLR1 as a biomarker of lung inflammation in ARDS was confirmed using single-nuclei RNA-sequencing datasets which showed significant increases in CMKLR1 expression among transcriptionally distinct subsets of lung monocytes and macrophages in COVID-19 patients vs. controls. CMKLR1-targeted PET is a promising strategy to monitor the dynamics of lung inflammation and response to anti-inflammatory treatment in ARDS.
Assuntos
Lesão Pulmonar Aguda , COVID-19 , Síndrome do Desconforto Respiratório , Humanos , Camundongos , Animais , Lipopolissacarídeos/toxicidade , Lesão Pulmonar Aguda/induzido quimicamente , Lesão Pulmonar Aguda/diagnóstico por imagem , Lesão Pulmonar Aguda/metabolismo , Pulmão/diagnóstico por imagem , Pulmão/metabolismo , Quimiocinas/metabolismo , Síndrome do Desconforto Respiratório/diagnóstico por imagem , Imagem Molecular , Receptores de QuimiocinasRESUMO
Thrombocytopenia is associated with worse outcomes in patients with acute respiratory distress syndrome, which is most commonly caused by infection and marked by alveolar-capillary barrier disruption. However, the mechanisms by which platelets protect the lung alveolar-capillary barrier during infectious injury remain unclear. We found that natively thrombocytopenic Mpl -/- mice deficient in the thrombopoietin receptor sustain severe lung injury marked by alveolar barrier disruption and hemorrhagic pneumonia with early mortality following acute intrapulmonary Pseudomonas aeruginosa (PA) infection; barrier disruption was attenuated by platelet reconstitution. Although PA infection was associated with a brisk neutrophil influx, depletion of airspace neutrophils failed to substantially mitigate PA-triggered alveolar barrier disruption in Mpl -/- mice. Rather, PA cell-free supernatant was sufficient to induce lung epithelial cell apoptosis in vitro and in vivo and alveolar barrier disruption in both platelet-depleted mice and Mpl -/- mice in vivo. Cell-free supernatant from PA with genetic deletion of the type 2 secretion system, but not the type 3 secretion system, mitigated lung epithelial cell death in vitro and lung injury in Mpl -/- mice. Moreover, platelet releasates reduced poly (ADP ribose) polymerase cleavage and lung injury in Mpl -/- mice, and boiling of platelet releasates, but not apyrase treatment, abrogated PA supernatant-induced lung epithelial cell cytotoxicity in vitro. These findings indicate that while neutrophil airspace influx does not potentiate infectious lung injury in the thrombocytopenic host, platelets and their factors protect against severe pulmonary complications from pathogen-secreted virulence factors that promote host cell death even in the absence of overt infection.