Anti-inflammatory Effects of Antibacterials on Bronchial Epithelial Cells
Abstract and Background
Background: Human Bronchial epithelial cells (hu-BEC) have been claimed to play a significant role in the pathogenesis of chronic inflammatory airway diseases like COPD. In this context IL-8 and GM-CSF have been shown to be key cytokines. Some antibiotics which are routinely used to treat lower respiratory tract infections have been shown to exert additional immunomodulatory or anti-inflammatory effects. We investigated whether these effects can also be detected in hu-BEC.
Methods: Hu-BEC obtained from patients undergoing lung resections were transferred to air-liquid-interface (ALI) culture. These cultures were incubated with cefuroxime (CXM, 10–62.5 mg/l), azithromycin (AZM, 0.1–1.5 mg/l), levofloxacin (LVX, 1–8 mg/l) and moxifloxacin (MXF, 1–16 mg/l). The spontaneous and TNF-α (10 ng/ml) induced expression and release of IL-8 and GM-CSF were measured using PCR and ELISA in the absence or presence of these antibiotics.
Results: The spontaneous IL-8 and GM-CSF release was significantly reduced with MXF (8 mg/l) by 37 ± 20% and 45 ± 31%, respectively (both p < 0.01). IL-8 release in TNF-α stimulated hu-BEC decreased by 16 ± 8% (p < 0.05) with AZM (1.5 mg/l). With MXF a concentration dependent decrease of IL-8 release was noted up to 39 ± 7% (p < 0.05). GM-CSF release from TNF-α stimulated hu-BEC was maximally decreased by 35 ± 24% (p < 0.01) with MXF (4 mg/l).
Conclusion: Using ALI cultures of hu-BEC we observed differential effects of antibiotics on spontaneous and TNF-α induced cytokine release. Our data suggest that MXF and AZM, beyond bactericidal effects, may attenuate the inflammatory process mediated by hu-BEC.
Antimicrobial agents of different classes - e.g. betalactames, quinolones, and macrolides - are standard of care in the treatment of respiratory tract infections. In addition to their antimicrobial activity some of these antibiotics, especially macrolides and fluoroquinolones, have immunomodulatory effects. These anti-inflammatory or immunomodulatory capabilities have been demonstrated in human cells, cell lines, and in animal experiments.
Due to intracellular accumulation of macrolides and quinolones in lung cells and in alveolar macrophages a targeted modulation of the inflammatory reaction could be of additional therapeutic benefit by attenuation of the inflammatory process in lower respiratory tract infection (LRTI) as well as in chronic non-infectious airway diseases like COPD.
Airway epithelial cells have been shown to be of crucial importance in the pathogenesis of inflammatory airway diseases. In addition to antimicrobial activities, macrolides directly affect pulmonary host defence like the neutrophil activation and the immune cell function. These effects are mediated by an alteration of cytokine and chemokine release, as has been demonstrated in vitro and ex vivo. Moreover, macrolides like azithromycin are already clinically used in chronic respiratory diseases like diffuse panbronchiolitis (DPB), cystic fibrosis despite they have no antimicrobial activity against Pseudomonas aeruginosa. A beneficial effect on bacterial virulence factors by inhibiting quorum-sensing, a mechanism of bacterial communication, is described for macrolides and quinolones as well.
Additionally, immunomodulatory effects of macrolides are used in bronchiolitis obliterans syndrom after bone marrow transplantation and lung transplantation which are diseases without infectious background. There are many studies, which elucidated the immunomodulatory effects of macrolides in human cells. However, the underlying intracellular mechanisms of immunomodulation by macrolides are not completely understood yet.
Similarly to macrolides, immunomodulatory effects have been shown for fluorquinolones in a variety of cells of the immune system and in lung epithelial cells. These effects were especially pronounced in fluorquinolones with a cyclopropyl-moiety at position N1 like ciprofloxacin and moxifloxacin. Moreover, expression of pro-inflammatory cytokines in human monocytes is suppressed by moxifloxacin in vitro and in vivo in an animal model of inflammation. Beside the modulation of cytokine release from cells of the immune system it has been shown, that quinolones reduce pro-inflammatory activities of respiratory epithelial cell lines, thus potentially influencing pulmonary host defence.
Therefore, we investigated the modulation of cytokine release from primary human bronchial epithelial cells in air-liquid interface culture by different antibiotics.