Il-17A contributes to maintenance of pulmonary homeostasis in a murine model of cigarette smoke-induced emphysema.

Smoking is the main risk factor for the development of the chronic obstructive pulmonary disease (COPD) in Western countries. Recent studies suggest that IL-17A and Th17 cells play a role in the pathogenesis of COPD. We used a murine model of chronic cigarette smoke (CS) exposure to explore the contribution of IL-17A to CS-induced lung damage and loss of pulmonary function. Histology and morphometry showed that IL-17A deficiency spontaneously resulted in a loss of lung structure under basal conditions. Even though inflammatory markers [IL-1ß and granulocyte colony-stimulating factor (G-CSF)] were decreased in IL-17A-deficient mice (IL-17A(-/-)) exposed to CS compared with wild-type (WT) mice, IL-17A(-/-) mice were per se not protected from CS-induced emphysematous disease. Assessment of pulmonary function showed that IL-17A(-/-) mice were partially protected from CS-induced changes in total lung capacity. However, the respiratory elastance decreased and respiratory compliance increased in IL-17A(-/-) mice after exposure to CS. Morphometry revealed destruction of lung tissue in CS-exposed IL-17A(-/-) mice similar to WT mice. The expression of elastin was decreased in air-exposed IL-17A(-/-) mice and in CS-exposed WT and IL-17A(-/-) mice. Thus, in the present model of sterile CS-exposure, IL-17A contributes to normal lung homeostasis and does not mediate CS-induced loss of lung structure and pulmonary function.

Cigarette smoke-promoted acquisition of bacterial pathogens in the upper respiratory tract leads to enhanced inflammation in mice.

BACKGROUND: Bacterial colonization and recurrent infections of the respiratory tract contribute to the progression of chronic obstructive pulmonary disease (COPD). There is evidence that exacerbations of COPD are provoked by new bacterial strains acquired from the environment. Using a murine model of colonization, we examined whether chronic exposure to cigarette smoke (CS) promotes nasopharyngeal colonization with typical lung pathogens and whether colonization is linked to inflammation in the respiratory tract. METHODS: C57BL/6 N mice were chronically exposed to CS. The upper airways of mice were colonized with nontypeable Haemophilus influenzae (NTHi) or Streptococcus pneumoniae. Bacterial colonization was determined in the upper respiratory tract and lung tissue. Inflammatory cells and cytokines were determined in lavage fluids. RT-PCR was performed for inflammatory mediators. RESULTS: Chronic CS exposure resulted in significantly increased numbers of viable NTHi in the upper airways, whereas NTHi only marginally colonized air-exposed mice. Colonization with S. pneumoniae was enhanced in the upper respiratory tract of CS-exposed mice and was accompanied by increased translocation of S. pneumoniae into the lung. Bacterial colonization levels were associated with increased concentrations of inflammatory mediators and the number of immune cells in lavage fluids of the upper respiratory tract and the lung. Phagocytosis activity was reduced in whole blood granulocytes and monocytes of CS-exposed mice. CONCLUSIONS: These findings demonstrate that exposure to CS impacts the ability of the host to control bacterial colonization of the upper airways, resulting in enhanced inflammation and susceptibility of the host to pathogens migrating into the lung.

FOXO transcription factors regulate innate immune mechanisms in respiratory epithelial cells.

Bacterial pathogens are a leading cause of lung infections and contribute to acute exacerbations in patients with chronic respiratory diseases. The innate immune system of the respiratory tract controls and prevents colonization of the lung with bacterial pathogens. Forkhead box transcription factor family O (FOXO) transcription factors are key regulators of cellular metabolism, proliferation, and stress resistance. In this study, our aim was to investigate the role of FOXO transcription factors in innate immune functions of respiratory epithelial cells. We show that bacterial pathogens potently activate FOXO transcription factors in cultured human respiratory epithelial cells in vitro. Infection of mice with bacterial pathogens resulted in the activation of FOXO transcription factors in alveolar and bronchial epithelial cells in vivo. Active FOXO was also detectable in human bronchial tissue obtained from subjects with different infection-related lung diseases. Small interfering RNA-mediated knockdown of FOXO in bronchial epithelial cells resulted in reduced expression of factors of the innate immune system such as antimicrobial peptides and proinflammatory cytokines, both under basal conditions and upon infection. FOXO deficiency further affected internalization of Haemophilus influenzae in bronchial epithelial cells. Finally, we show that TLR3 activates innate immune responses in a FOXO-dependent manner. In conclusion, FOXO transcription factors are involved in the cellular responses to bacterial stimuli and act as central regulators of innate immune functions in respiratory epithelial cells.

Moxifloxacin modulates inflammation during murine pneumonia.

BACKGROUND: Moxifloxacin is a synthetic antibacterial agent belonging to the fluoroquinolone family. The antimicrobial activity of quinolones against Gram-positive and Gram-negative bacteria is based on their ability to inhibit topoisomerases. Quinolones are described to have immunomodulatory features in addition to their antimicrobial activities. It was the goal of this study to examine whether a short term treatment with moxifloxacin modulates the inflammation during a subsequently induced bacterial infection in an animal model. METHODS: Mice were treated with moxifloxacin or saline for two consecutive days and were subsequently intranasally infected with viable or heat-inactivated bacterial pathogens (Streptococcus pneumoniae, Pseudomonas aeruginosa) for 6 and 24 hours. Measurements of cytokines in the lungs and plasma were performed. Alveolar cells were determined in bronchoalveolar lavage fluits. RESULTS: The inflammation was increased after the inoculation of viable bacteria compared to inactivated bacteria. Numbers of total immune cells and neutrophils and concentrations of inflammatory mediators (e.g. KC, IL-1ß, IL-17A) were significantly reduced in lungs of moxifloxacin-treated mice infected with inactivated and viable bacterial pathogens as compared to infected control mice. Plasma concentrations of inflammatory mediators were significantly reduced in moxifloxacin-treated mice. Immunohistochemistry showed a stronger infiltrate of TNF-α-expressing cells into lungs of saline-treated mice infected with viable P. aeruginosa as compared to moxifloxacin-treated mice. CONCLUSIONS: These data show that in this pneumonia model moxifloxacin has anti-inflammatory properties beyond its antibacterial activity.

An easy-to-perform protocol for culturing primary murine lung tumor cells as organoids.

Cancer research involves significant animal consumption and suffering. Tumor cells can be differentiated in vitro into three-dimensional organoids that resemble the primary tumor. In basic cancer research, however, tumor organoids are usually only used alongside animal experiments. We have established an easy-to-perform protocol that allows to culture KRAS-driven lung tumor cells as organoids for extended periods of time. Like the corresponding tumors in mice, the organoids produce surfactant protein C but no markers of airway epithelial cells (e.g. SCGB1A1, KRT5). The organoids can be passaged as single cell suspensions. Our organoid model contributes to replace animal experiments with cell culture systems and can be used for drug testing or functional studies in cancer research.

IL-17C-mediated innate inflammation decreases the response to PD-1 blockade in a model of Kras-driven lung cancer.

Chronic obstructive pulmonary disease (COPD) is associated with neutrophilic lung inflammation and CD8 T cell exhaustion and is an important risk factor for the development of non-small cell lung cancer (NSCLC). The clinical response to programmed cell death-1 (PD-1) blockade in NSCLC patients is variable and likely affected by a coexisting COPD. The pro-inflammatory cytokine interleukin-17C (IL-17C) promotes lung inflammation and is present in human lung tumors. Here, we used a Kras-driven lung cancer model to examine the function of IL-17C in inflammation-promoted tumor growth. Genetic ablation of Il-17c resulted in a decreased recruitment of inflammatory cells into the tumor microenvironment, a decreased expression of tumor-promoting cytokines (e.g. interleukin-6 (IL-6)), and a reduced tumor proliferation in the presence of Haemophilus influenzae- (NTHi) induced COPD-like lung inflammation. Chronic COPD-like inflammation was associated with the expression of PD-1 in CD8 lymphocytes and the membrane expression of the programmed death ligand (PD-L1) independent of IL-17C. Tumor growth was decreased in Il-17c deficient mice but not in wildtype mice after anti-PD-1 treatment. Our results suggest that strategies targeting innate immune mechanisms, such as blocking of IL-17C, may improve the response to anti-PD-1 treatment in lung cancer patients.

Hypoxia and the hypoxia-regulated transcription factor HIF-1α suppress the host defence of airway epithelial cells.

Chronic diseases of the respiratory tract, such as cystic fibrosis, are associated with mucosal and systemic hypoxia. Innate immune functions of airway epithelial cells are required to prevent and control infections of the lung parenchyma. The transcription factor hypoxia-inducible factor 1α (HIF-1α) regulates cellular adaptation to low oxygen conditions. Here, we show that hypoxia and HIF-1α regulate innate immune mechanisms of cultured human bronchial epithelial cells (HBECs). Exposure of primary HBECs to hypoxia or the prolyl hydroxylase inhibitor dimethyloxaloylglycine (DMOG) resulted in a significantly decreased expression of inflammatory mediators (IL-6, IFN-γ-induced protein 10) in response to ligands for TLRs (flagellin, polyI:C) and Pseudomonas aeruginosa, whereas the expression of inflammatory mediators was not affected by hypoxia or DMOG in the absence of microbial factors. Small interfering RNA-mediated knockdown of HIF-1α in HBECs and in the bronchial epithelial cell line Calu-3 resulted in increased expression of inflammatory mediators. The inflammatory response was decreased in lungs of mice stimulated with inactivated P. aeruginosa under hypoxia. These data suggest that hypoxia suppresses the innate immune response of airway epithelial cells via HIF-1α.

Subacute effects of the brominated flame retardants hexabromocyclododecane and tetrabromobisphenol A on hepatic cytochrome P450 levels in rats.

The brominated flame retardants tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are found in the environment, e.g., in sediments and organisms, in food items, human blood samples and mother's milk. In this study, the effects of both compounds on rat hepatic cytochrome P450 (CYP) levels and activities were investigated. Juvenile/young male and female Wistar rats were treated orally with various doses via the feed (TBBPA) or by gavage (HBCD). After 28 days of treatment the animals were sacrificed and hepatic mRNA and microsomes were isolated. HBCD treatment led to a significant induction of CYP2B1 mRNA, CYP2B1/2B2 protein and 7-pentoxyresorufin O-depentylase (PROD) activity suggesting a phenobarbital-type of induction. Furthermore, a significant increase in CYP3A1/3A3 mRNA, CYP3A1 protein, and luciferin benzylether debenzylase (LBD) activity was found, being more pronounced in females than in males. The effect on CYP3A1/3A3 mRNA was significant in female rats at a daily dose of 3.0mg/kg body weight and above. HBCD exhibited no effects on CYP1A2 mRNA, CYP1A1/1A2 protein, or microsomal 7-ethoxyresorufin O-deethylase (EROD) activity suggesting lack of activation of the aryl hydrocarbon receptor. No significant effects on any of the parameters measured were obtained with TBBPA. Our findings suggest that oral exposure to HBCD induces drug-metabolising enzymes in rats probably via the CAR/PXR signalling pathway. Induction of CYPs and co-regulated enzymes of phase II of drug metabolism may affect homeostasis of endogenous substrates including steroid and thyroid hormones.