Staphylococcus aureus Enterotoxin B Disrupts Nasal Epithelial Barrier Integrity via TLR2 Activation

Background: Staphylococcus aureus colonization and release of enterotoxin B (SEB) has been shown to contribute to the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP), but the pathogenic mechanisms are largely unknown. Methods: We investigated the effect of SEB on nasal epithelial function in vitro on primary polyp and nasal epithelial cells of patients with CRSwNP and healthy controls respectively, and in vivo in a mouse model by measuring epithelial integrity and tight junction expression. The involvement of TLR2 signaling was studied in vitro by using TLR2 monoclonal antibodies and in vivo in tlr2-/- transgenic mice. Findings: We found that in vitro stimulation with SEB decreased polyp epithelial integrity by reducing occludin and ZO-1 protein expression. This impaired barrier function was associated with elevated expression of epithelial TLR2 and antagonizing TLR2 triggering prevented SEB-induced barrier disruption in vitro. In wild type mice, SEB applied in the nose increased mucosal permeability and decreased occludin and ZO-1 mRNA expression, whereas tlr2-/- mice had an intact mucosal barrier and normal tight junction expression after SEB exposure. Furthermore, in vitro SEB stimulation resulted in epithelial production of IL-6, IL-8 and TNF, which was prevented when TLR2 triggering was antagonized. Interpretation: Our results indicate that SEB impairs epithelial barrier function in CRSwNP via TLR2 activation. Interfering with TLR2 activation may provide a way to avoid the pathophysiological consequences of S. aureus colonization in CRSwNP. Funding Statement: The author’s laboratories are supported by grants from the Belgian Federal Government (IUAP P7/30), IWT (TBM project 130260) and the research council of the KU Leuven (GOA 14/011). PWH, RS and DMB are recipients of a senior researcher fellowship from the Fund of Scientific Research (FWO), Flanders, Belgium. BS is currently a Postdoctoral Fellow of the Fund for Scientific Research Flanders (FWO). Declaration of Interests: The authors declare no competing interest related to this work. Ethics Approval Statement: All experiments were approved by the Medical Ethical Committee of the University Hospitals Leuven. Murine experiments were approved by the Ethical Committee for Animal Research at the KU Leuven.