Abstract
Infection plays a significant role in the relapse of chronic rhinosinusitis (CRS), however, the role of primary human nasal epithelial cells (HNECs) in this process is largely unknown. Here, we determined the effect of Toll-like receptor (TLR) agonists and inflammatory cytokines on mucosal barrier integrity and immune response of HNECs. TLR 1–9 agonists and inflammatory cytokines were applied to submerged and/or air-liquid interface (ALI) cultures of HNECs from CRS patients and controls for 24 hours. Interleukin-6 (IL-6) protein levels were determined by ELISA. Mucosal barrier integrity was measured via Transepithelial Electrical Resistance and passage of fluorescently-labelled dextrans. IL-1β and IFN- γ significantly increased IL-6 production in HNECs derived from CRS patients and controls, however, a dose-dependent effect was observed in CRS-derived HNECs only. Stimulation with Poly (I:C) LMW induced a 15 to 17 fold increase in IL-6 production by HNEC-ALI control cells (p < 0.05) and HNEC-ALI-CRS cells (p = 0.004) whilst a 2.5 fold increase was observed in CRS HNEC submerged cultures. Priming of cells with Poly (I:C) LMW reduced subsequent IL-6 secretion upon stimulation with TLR 2–4 agonists. Poly (I:C) LMW exerts a potent pro-inflammatory effect on HNECs and reduces a subsequent immune activation by TLR agonists.
Highlights
The sinonasal mucosa has been widely recognised as protecting the host from invasion by harmful environmental toxins and micro-organisms by forming a structural barrier
Different concentrations of Tumour Necrosis Factor-α (TNF-α), Interferon-γ (IFN-γ), Interleukin-1β (IL-1β) and the Th17 cytokines IL-17, IL-22, and IL-26 were applied to the basal chamber of human nasal epithelial cells (HNECs)-air-liquid interface (ALI) monolayers derived from non-chronic rhinosinusitis (CRS) control patients (n = 5, 3 males, 2 females aged 30–50 years) and CRSwNP patients (n = 5, all males aged 45–65 years, 3 were diagnosed with grass-pollen allergy and 4 with asthma) for 24 hours followed by measuring secreted IL-6 protein levels using Enzyme-Linked Immunosorbent Assay (ELISA)
Whilst IFN-γ and IL-1β significantly induced the release of IL-6 from both patient groups, IL-6 protein levels were significantly higher upon stimulation with 100 ng/ml IFN- γ (42 pg/ml vs 13 pg/ml in CRSwNP patients and non-CRS controls respectively, P = 0.017) and with 10 ng/ml IL-1β (98 pg/ ml vs 13 pg/ml in CRSwNP patients and non-CRS controls respectively, P = 0.025) in monolayers derived from CRSwNP patients, than control patients
Summary
The sinonasal mucosa has been widely recognised as protecting the host from invasion by harmful environmental toxins and micro-organisms by forming a structural barrier. The role of the airway mucosa in raising and shaping an immune response to different environmental insults has been extensively described and different model systems have been developed These include ex vivo mucosal explant models that have been shown to have a robust response to bacterial triggers[3,4]. It has been previously established that HNECs are better suited than airway epithelial cell lines to study barrier structure and function and immune responses[7] It is not clear whether HNECs grown at ALI have a different response to immune stimulation compared to submerged HNECs, and whether cells derived from patients suffering from chronic airway inflammation respond differently from cells derived from control patients. This study compares immune responses of submerged and ALI-grown HNECs derived from patients affected by chronic rhinosinusitis and control patients and defines the immune triggers and conditions needed to induce robust immune activation in those cells
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