Respiratory surfaces are exposed to billions of particulates and pathogens daily. A protective mucus barrier traps and eliminates them via mucociliary clearance (MCC)1,2. However, excessive mucus contributes to transient respiratory infections and to the pathogenesis of numerous respiratory diseases1. MUC5AC and MUC5B are evolutionarily conserved genes that encode structurally related mucin glycoproteins, the principal macromolecules in airway mucus1,3. Genetic variants are linked to diverse lung diseases4-6, but specific roles for MUC5AC and MUC5B in MCC, and the lasting effects of their inhibition, are unknown. Here we show that Muc5b (but not Muc5ac) is required for MCC, for controlling infections in the airways and middle ear, and for maintaining immune homeostasis in the lungs. Muc5b deficiency caused materials to accumulate in upper and lower airways. This defect led to chronic infection by multiple bacterial species, including Staphylococcus aureus, and to inflammation that failed to resolve normally7. Apoptotic macrophages accumulated, phagocytosis was impaired, and IL-23 production was reduced inMuc5b−/− mice. By contrast, in Muc5b transgenic (Tg) mice, macrophage functions improved. Existing dogma defines mucous phenotypes in asthma and chronic obstructive pulmonary disease (COPD) as driven by increased MUC5AC, with MUC5B levels either unaffected or increased in expectorated sputum1,8. However, in many patients, MUC5B production at airway surfaces decreases by as much as 90%9-11. By distinguishing a specific role for Muc5b in MCC, and by determining its impact on bacterial infections and inflammation in mice, our results provide a refined framework for designing targeted therapies to control mucin secretion and restore MCC.

BackgroundTumor cells produce various cytokines and chemokines that attract leukocytes. Leukocytes can amplify parenchymal innate immune responses, and have been shown to contribute to tumor promotion. Neutrophils are among the first cells to arrive at sites of inflammation, and the increased number of tumor-associated neutrophils is linked to poorer outcome in patients with lung cancer.ResultsWe have previously shown that COPD-like airway inflammation promotes lung cancer in a K-ras mutant mouse model of lung cancer (CC-LR). This was associated with severe lung neutrophilic influx due to the increased level of neutrophil chemoattractant, KC. To further study the role of neutrophils in lung tumorigenesis, we depleted neutrophils in CC-LR mice using an anti-neutrophil antibody. This resulted in a significant reduction in lung tumor number. We further selectively inhibited the main receptor for neutrophil chemo-attractant KC, CXCR2. Similarly, this resulted in suppression of neutrophil recruitment into the lung of CC-LR mice followed by significant tumor reduction. Neutrophil elastase (NE) is a potent elastolytic enzyme produced by neutrophils at the site of inflammation. We crossed the CC-LR mice with NE knock-out mice, and found that lack of NE significantly inhibits lung cancer development. These were associated with significant reduction in tumor cell proliferation and angiogenesis.ConclusionWe conclude that lung cancer promotion by inflammation is partly mediated by activation of the IL-8/CXCR2 pathway and subsequent recruitment of neutrophils and release of neutrophil elastase. This provides a baseline for future clinical trials using the IL-8/CXCR2 pathway or NE inhibitors in patients with lung cancer.

Nontypeable Haemophilus influenzae (NTHi) commonly colonizes the lower airways of patients with chronic obstructive pulmonary disease (COPD). Whether it contributes to COPD progression is unknown. Here, we determined which aspects of the COPD phenotype can be induced by repetitive exposure to NTHi products. Mice were exposed weekly to an aerosolized NTHi lysate, and inflammation was evaluated by measurement of cells and cytokines in bronchoalveolar lavage fluid (BALF) and immunohistochemical staining; structural changes were evaluated histochemically by periodic acid fluorescent Schiff's reagent, Masson's trichrome, and Picrosirius red staining; mucin gene expression was measured by quantitative RT-PCR; and the role of TNF-alpha was examined by transgenic airway overexpression and use of an inhibitory antibody. NTHi lysate induced rapid activation of NF-kappaB in airway cells and increases of inflammatory cytokines and neutrophils in BALF. Repetitive exposure induced infiltration of macrophages, CD8+ T cells, and B cells around airways and blood vessels, and collagen deposition in airway and alveolar walls, but airway mucin staining and gel-forming mucin transcripts were not increased. Transgenic overexpression of TNF-alpha caused BALF neutrophilia and inflammatory cell infiltration around airways, but not fibrosis, and TNF-alpha neutralization did not reduce BALF neutrophilia in response to NTHi lysate. In conclusion, NTHi products elicit airway inflammation in mice with a cellular and cytokine profile similar to that in COPD, and cause airway wall fibrosis but not mucous metaplasia. TNF-alpha is neither required for inflammatory cell recruitment nor sufficient for airway fibrosis. Colonization by NTHi may contribute to the pathogenesis of small airways disease in patients with COPD.

Some people remain healthier throughout life than others but the underlying reasons are poorly understood. Here we hypothesize this advantage is attributable in part to optimal immune resilience (IR), defined as the capacity to preserve and/or rapidly restore immune functions that promote disease resistance (immunocompetence) and control inflammation in infectious diseases as well as other causes of inflammatory stress. We gauge IR levels with two distinct peripheral blood metrics that quantify the balance between (i) CD8+ and CD4+ T-cell levels and (ii) gene expression signatures tracking longevity-associated immunocompetence and mortality-associated inflammation. Profiles of IR metrics in ~48,500 individuals collectively indicate that some persons resist degradation of IR both during aging and when challenged with varied inflammatory stressors. With this resistance, preservation of optimal IR tracked (i) a lower risk of HIV acquisition, AIDS development, symptomatic influenza infection, and recurrent skin cancer; (ii) survival during COVID-19 and sepsis; and (iii) longevity. IR degradation is potentially reversible by decreasing inflammatory stress. Overall, we show that optimal IR is a trait observed across the age spectrum, more common in females, and aligned with a specific immunocompetence-inflammation balance linked to favorable immunity-dependent health outcomes. IR metrics and mechanisms have utility both as biomarkers for measuring immune health and for improving health outcomes.

Chronic obstructive pulmonary disease (COPD), an inflammatory disease of the lung, is an independent risk factor for lung cancer. Lung tissues obtained from human smokers with COPD and lung cancer demonstrate hypoxia and up-regulated hypoxia inducible factor-1 (HIF-1). HIF-1 activation is the central mechanism for controlling the cellular response to hypoxia during inflammation and tumor development. These facts suggest a link between COPD-related airway inflammation, HIF-1, and lung cancer. We have previously established a mouse model of COPD-like airway inflammation that promotes lung cancer in a K-ras mutant mouse model (CC-LR). Here we show that tumors in the CC-LR model have significantly elevated levels of HIF-1α and HIF-1 activity. To determine the tumor-promoting functions of HIF-1 in CC-LR mice, the gene Hif1a which encodes HIF-1α and is required for HIF-1 activity, was disrupted in the lung epithelium of CC-LR animals. Airway epithelial specific HIF-1α deficient mice demonstrated significant reductions in lung surface tumor numbers, tumor angiogenesis, and tumor cell proliferation in the absence or presence of COPD-like airway inflammation. In addition, when CC-LR mice were bred with transgenic animals that overexpress a constitutively active mutant form of human HIF-1α in the airway epithelium, both COPD- and adenocarcinoma-like phenotypes were observed. HIF-1α overexpressing CC-LR mice had significant emphysema, and they also showed potentiated tumorigenesis, angiogenesis, and cell proliferation accompanied by an invasive metastatic phenotype. Our gain and loss of function studies support a key role for HIF-1α in the promotion of lung cancer by COPD-like inflammation.