German cockroach extract induces matrix metalloproteinase 1 expression, leading to tight junction disruption in the airway epithelial cells

Abstract

Background: Cockroach exposure is a pivotal cause of asthma, and the barrier function of the airway epithelium was shown to be impaired in this disease. Tight junctions are intercellular structures, required for epithelial barrier function maintenance. Matrix metalloproteinases (MMPs) digest extracellular matrix components and are involved in asthma pathogenesis; MMP1 is a collagenase with a direct activity in the airway obstruction in asthmatics. Objective: To investigate the mechanisms of MMP1 expression by German cockroach extract (GCE) and whether MMP1 release alters cellular tight junctions in the airway epithelial cells. Methods: Human airway epithelial cells (H292) were treated with GCE. mRNA and protein levels were determined using real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Tight junction proteins were detected using immunofluorescence staining. Epithelial barrier function was measured by transepithelial electrical resistance (TEER). GM6001 as a potent MMP inhibitor, PD98059 as a MAPK/ERK kinase inhibitor, siRNAs against MMP1, ETS1, and SP1, and anti-TLR2 antibody were used as pre-treatments prior to the GCE stimulation. The levels of tight junction proteins and ERK phosphorylation were determined using western blotting. Results: GCE was shown to increase MMP1 expression, tight junction protein degradation, and decrease TEER. GM6001 treatment and transient cell transfection with MMP1 siRNA inhibited GCE-induced tight junction disruption. Additionally, transient transfection using ETS1/SP1-targeting siRNA and anti-TLR2 antibody pretreatment prevented MMP1 expression inhibition and tight junction degradation. PD98059 effectively blocked MMP1 release, ETS1/SP1 expression, and tight junction alteration. Conclusions: This study demonstrated that GCE treatment induces MMP1 expression, leading to tight junction disruption, and elucidated MMP1 transcriptional regulation in the airway epithelial cells. These findings may help develop novel therapeutic strategies for the treatment of airway diseases.