ovalbumin and Pneumonia--Bacterial

The Th17 cytokines interleukin-17A (IL-17A), IL-17F, and IL-22 are critical for the lung immune response to a variety of bacterial pathogens, including Klebsiella pneumoniae. Th2 cytokine expression in the airways is a characteristic feature of asthma and allergic airway inflammation. The Th2 cytokines IL-4 and IL-13 diminish ex vivo and in vivo IL-17A protein expression by Th17 cells. To determine the effect of IL-4 and IL-13 on IL-17-dependent lung immune responses to acute bacterial infection, we developed a combined model in which allergic airway inflammation and lung IL-4 and IL-13 expression were induced by ovalbumin sensitization and challenge prior to acute lung infection with K. pneumoniae. We hypothesized that preexisting allergic airway inflammation decreases lung IL-17A expression and airway neutrophil recruitment in response to acute K. pneumoniae infection and thereby increases the lung K. pneumoniae burden. As hypothesized, we found that allergic airway inflammation decreased the number of K. pneumoniae-induced airway neutrophils and lung IL-17A, IL-17F, and IL-22 expression. Despite the marked reduction in postinfection airway neutrophilia and lung expression of Th17 cytokines, allergic airway inflammation significantly decreased the lung K. pneumoniae burden and postinfection mortality. We showed that the decreased lung K. pneumoniae burden was independent of IL-4, IL-5, and IL-17A and partially dependent on IL-13 and STAT6. Additionally, we demonstrated that the decreased lung K. pneumoniae burden associated with allergic airway inflammation was both neutrophil and CCL8 dependent. These findings suggest a novel role for CCL8 in lung antibacterial immunity against K. pneumoniae and suggest new mechanisms of orchestrating lung antibacterial immunity.

Topics: Animals; Chemokine CCL8; Eosinophils; Female; Hypersensitivity; Inflammation; Interleukins; Klebsiella Infections; Klebsiella pneumoniae; Lung; Mice; Mice, Inbred BALB C; Neutrophils; Ovalbumin; Pneumonia, Bacterial

Somatostatin released from activated capsaicin-sensitive afferents of the lung inhibits inflammation and related bronchial hyperreactivity presumably via somatostatin 4 receptors (sst(4)). The aim of this study was to examine the effects of TT-232, a heptapeptide sst(4)/sst(1) receptor agonist and J-2156, a high affinity sst(4) receptor-selective peptidomimetic agonist in airway inflammation models. Acute pneumonitis was evoked by intranasal lipopolysaccharide 24 h before measurement. Chronic inflammation was induced by ovalbumin inhalation on days 28, 29 and 30 after i.p. sensitization on days 1 and 14. Semiquantitative histopathological scoring was based on perivascular/peribronchial oedema, neutrophil/macrophage infiltration, goblet cell hyperplasia in the acute model and eosinophil infiltration, mucosal oedema, mucus production and epithelial cell damage in chronic inflammation. Myeloperoxidase activity of the lung was measured spectrophotometrically to quantify granulocyte accumulation and the broncoalveolar lavage fluid was analysed by flow cytometry. Carbachol-induced bronchoconstriction was assessed by unrestrained whole body plethysmography and its calculated indicator, enhanced pause (Penh) was determined. TT-232 and J-2156 induced similar inhibition on granulocyte recruitment and histopathological changes in both models, although macrophage infiltration in LPS-induced inflammation was unaltered by either compounds. Both agonists diminished inflammatory airway hyperresponsiveness. Since their single administration after the development of the inflammatory reactions also inhibited carbachol-induced bronchoconstriction, somatostatin sst(4) receptor activation on bronchial smooth muscle cells is likely to be involved in their anti-hyperreactivity effect. These results suggest that stable, somatostatin sst(4) receptor-selective agonists could be potential candidates for the development of a completely novel group of anti-inflammatory drugs for the treatment of airway inflammation and hyperresponsiveness.

Topics: Animals; Anti-Inflammatory Agents; Asthma; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Bronchoconstrictor Agents; Butanes; Carbachol; Cells, Cultured; Female; Interleukin-1beta; Lipopolysaccharides; Lung; Macrophages, Peritoneal; Membrane Proteins; Mice; Mice, Inbred BALB C; Naphthalenes; Ovalbumin; Peptides, Cyclic; Pneumonia, Bacterial; Receptors, Somatostatin; Respiratory System Agents; Somatostatin; Sulfones; Tetradecanoylphorbol Acetate; Time Factors

The innate immune system of the lung is a multicomponent host defense system and in addition has an instructing role in regulating the quality and quantity of the adaptive immune response. When the interaction between innate and adaptive immunity is disturbed, pathological conditions such as asthma can develop. It was the aim of the study to investigate the effect of the allergic inflammation of the lung on the innate host defense during bacterial infection. Human bronchial epithelial cells were preincubated with Th2 cytokines and infected with Pseudomonas aeruginosa. The effect of the Th2 cytokines on the mRNA levels of antimicrobial peptides and the antimicrobial activity of HBEC was determined. To investigate the influence of an allergic inflammation on pulmonary host defense in vivo, mice sensitized and challenged with OVA were infected with P. aeruginosa, and the number of viable bacteria in the lungs was determined together with markers of inflammation like cytokines and antimicrobial peptides. Exposure of airway epithelial cells to Th2 cytokines resulted in a significantly decreased antimicrobial activity of the cells and in suppressed mRNA levels of the antimicrobial peptide human beta-defensin 2. Furthermore, mice with allergic airway inflammation had significantly more viable bacteria in their lungs after infection. This was consistent with reduced levels of proinflammatory cytokines and of the antimicrobial peptide cathelin-related antimicrobial peptide. These results show that an allergic airway inflammation suppresses the innate antimicrobial host defense. The adaptive immune system modulates the functions of the pulmonary innate immune system.

Topics: Allergens; Animals; Antimicrobial Cationic Peptides; Cell Line; Cytokines; Female; Humans; Immunity, Innate; Immunosuppression Therapy; Inflammation; Lung; Mice; Mice, Inbred BALB C; Ovalbumin; Pneumonia, Bacterial; Pseudomonas aeruginosa; Respiratory Hypersensitivity; Respiratory Mucosa; Th2 Cells