Budesonide Inhibits Intracellular Infection with Non-Typeable <b><i>Haemophilus influenzae</i></b> despite Its Anti-Inflammatory Effects in Respiratory Cells and Human Lung Tissue: A Role for p38 MAP Kinase

Abstract

Background: Inhaled corticosteroids (ICS) are widely used in the treatment of obstructive lung diseases. Recent data suggest a higher pneumonia risk in chronic obstructive pulmonary disease (COPD) patients treated with ICS. Objective: Since non-typeable Haemophilus influenzae (NTHi) is the most common pathogen associated with acute exacerbations of COPD, we investigated the effects of budesonide (BUD) on NTHi-induced inflammation and invasive infection. Methods: The alveolar epithelial cell line A549 and specimens of human lung tissue (HLT) were used in our experiments. Intracellular infection was determined by a lysis/culture assay of infected cells. Activated p38 mitogen-associated protein kinase (MAPK) was assessed using Western blotting and immunohistochemistry, expression of toll-like receptor 2 (TLR2) was determined by PCR, and CXCL-8 levels were measured using ELISA. Immunohistochemistry was used for detection of CXCL-8, platelet-activating factor receptor (PAF-R) and NTHi. Results: BUD significantly reduced CXCL-8 secretion in A549 cells and lung tissue infected with NTHi. Furthermore, BUD decreased the expression of PAF-R in HLT and A549 cells. In A549 cells and HLT, BUD inhibited intracellular infection and - synergistically with NTHi - increased the expression of TLR2 (in A549 cells). TLR2 stimulation did not influence the intracellular infection of A549 cells, but p38 MAPK inhibition resulted in a significant reduction of infection. Conclusion: The present study adds new insights into the effects of glucocorticoids on pulmonary host defence after NTHi infection. Although the inflammatory response to infection is suppressed by BUD, interestingly, the intracellular infection is also inhibited. This effect seems to depend on the inhibition of p38 MAPK - a key enzyme in many pro-inflammatory pathways - as well as of PAF-R expression.

Beyond communication

“…This positive effect is further supported by findings of others who demonstrated a decreased invasion of airway epithelial cells and lungs by S. pneumoniae and H. influenzae upon treatment with glucocorticoids [65,66]. These effects were dependent on a reduction of inflammation and consequently a reduced expression of platelet-activating factor receptor (PAF-R) [66]. PAF-R is important for the bacterial adhesion of certain airway pathogens, including S. pneumoniae and H. influenzae but not for other bacteria such as Klebsiella pneumonia.…”

“…So, together our findings implicate that treatment with these glucocorticoids and/or azithromycin has beneficial effects on inflammation (figure 1). This positive effect is further supported by findings of others who demonstrated a decreased invasion of airway epithelial cells and lungs by S. pneumoniae and H. influenzae upon treatment with glucocorticoids [65,66]. These effects were dependent on a reduction of inflammation and consequently a reduced expression of platelet-activating factor receptor (PAF-R) [66].…”

“…With regard to airway disease, it has been shown that the release of extracellular vesicles occurs by cells that are key players in the disease process and vesicles from different sources have been detected in bronchoalveolar lavage fluid [61,62]. The intrinsic properties that these vesicles exhibit, in vitro or in vivo upon instillation, indicates they can contribute to the pathogenesis of airway disease and acute airway inflammation [63][64][65][66][67]. It remains however highly complicated to comprehend the full extend as to which extracellular vesicles contribute to disease.…”

“…aminoglycosides). Generally, the peptides and the antibiotics that trigger the formation of membrane vesicles have been shown to be cell envelope-di-rected, to induce the SOS response (oxidative stress), to alter the LPS structure, or a combination of the above [66]. Therefore, they can trigger the vesicle formation by one of the three models described above (A: lipid asymmetry maintenance, B: extra-cytoplasmic stress responses or C: LPS modification).…”

Human lung ex vivo infection models

“…Nontypeable Haemophilus influenza (NTHI) infections, in particular newly acquired strains, may trigger infectionrelated exacerbation in COPD and recurrent infections may induce overall disease progression (Duell et al 2016). On using the NTHI strain Rd KW20 isolated from a COPD patient suffering from invasive pneumonia, Wagner et al (2015) noticed strong IL-8 induction in ex vivo infected human lungs; this was reduced in tissue pre-treated with the antiinflammatory drug budenoside. Interestingly, the steroid reduced not only the induction of IL-8; it furthermore reduced the presence of intracellular bacteria in the tissue by a hitherto unexplored mechanism.…”