Induction of CXC chemokines in A549 airway epithelial cells by trypsin and staphylococcal proteases − a possible route for neutrophilic inflammation in chronic rhinosinusitis

Abstract

While various microorganisms have been recovered from patients with chronic rhinosinusitis, the inflammatory impact of virulence factors, in particular proteases from Staphylococcus aureus and coagulase negative staphylococci on the nasal epithelium, has not yet been investigated. Expression of CXC chemokines was determined in the epithelium of patients with chronic rhinosinusitis by immunohistochemistry. In a cell culture system of A549 respiratory epithelial cells, chemokine levels were quantified by enzyme-linked immunosorbent assay (ELISA) after stimulation with supernatants originating from three different staphylococcal strains or with trypsin, representing a serine protease. Inhibition experiments were performed with prednisolone, with the serine protease inhibitor 4-(2-aminoethyl)-benzenesulphonylfluoride (AEBSF) and with the nuclear transcription factor (NF)-κΒ inhibitor (2E)-3-[[4-(1,1-dimethylethyl)phenyl]sulphonyl]-2-propenenitrite (BAY) 11–7085. Electromobility shift assays (EMSA) were used to demonstrate NF-κB-dependent protein synthesis. CXC chemokines interleukin (IL)-8, growth-related oncogene alpha (GRO-α) and granulocyte chemotactic protein-2 (GCP-2) were expressed in the patients’ epithelium whereas epithelial cell-derived neutrophil attractant 78 (ENA-78) was rarely detected. In A549 cells, chemokines IL-8, ENA-78 and GRO-α but not GCP-2 were induced by trypsin and almost equal levels were induced by staphylococcal supernatants. IL-8, GRO-α and ENA-78 synthesis was suppressed almost completely by AEBSF and BAY 11–7085, whereas prednisolone reduced chemokine levels differentially dependent on the supernatant added. CXC chemokines were detectable in the epithelium of patients with chronic rhinosinusitis. Staphylococcal serine proteases induced CXC chemokines in A549 cells, probably by the activation of proteases activated receptors, and thus might potentially be involved in neutrophilic inflammation in chronic sinusitis.