Investigating the regulatory role of ORMDL3 in airway barrier dysfunction using in vivo and in vitro models

Abstract

The airway epithelium (AE) is the main protective barrier between the host and external environmental factors causing asthma. Allergens or pathogens induce AE dysfunction, including epithelial permeability alteration, trans-epithelial electrical resistance (TEER) reduction, upregulation of inflammatory mediators and downregulation of junctional complex molecules. Orosomucoid-like protein isoform 3 (ORMDL3), a gene closely associated with childhood onset asthma, is involved in airway inflammation and remodeling. It was hypothesized that ORMDL3 plays an important role in regulating AE barrier function. In vivo [chronic asthma induced by ovalbumin-respiratory syncytial virus (OVA-RSV)] in mice) and in vitro (human bronchial epithelial cells and 16HBE cells) models were used to assess ORMDL3′s role in AE function regulation, evaluating paracellular permeability, TEER and the expression levels of junctional complex molecules. The effects of ORMDL3 on the extracellular signal-regulated protein kinase (ERK) pathway were determined. In mice with OVA-RSV induced chronic asthma, ORMDL3 and sphingosine kinase 1 (SPHK1) were upregulated whereas the junction related proteins Claudin-18 and E-cadherin were downregulated. Overexpression of ORMDL3 resulted in decreased TEER, downregulation of junctional complex molecules and induced epithelial permeability. In contrast, ORMDL3 inhibition showed the opposite effects. In 16HBE cells, ORMDL3 overexpression induced SPHK1 distribution and activity, while SPHK1 inhibition resulted in increased TEER upon administration of an ORMDL3 agonist or ORMDL3 overexpression. In addition, ERK activation occurred downstream of SPHK1 activation in 16HBE cells. High levels of ORMDL3 result in damaged AE barrier function by inducing the SPHK1/ERK pathway.

The Degradation of Airway Epithelial Tight Junctions in Asthma Under High Airway Pressure Is Probably Mediated by Piezo-1

“…Occludin and ZO-1 were detected as they play an indispensable role in regulating barrier tightness and a critical role in the establishment of airway belt-like TJs, respectively ( Furuse, 2010 ; Matter and Balda, 2014 ). Claudin-18, a lung-specific claudin that is highly associated with airway epithelial barrier dysfunction in asthma, was also detected ( Sweerus et al, 2017 ; Yang et al, 2019 ). To further assess whether the disruption in occludin, ZO-1, and claudin-18 occurred because of additional pressure exposure, we first investigated cellular occludin, ZO-1, and claudin-18 by western blot assay.…”

Epithelial barriers in allergy and asthma

“…90 Yang et al 91 showed that high levels of ORMDL3 attenuated claudin 17 and E-cadherin protein levels in vitro on primary bronchial and 16HBE bronchial epithelial cells, and in an asthma mouse model, whereas inhibition of ORMLD3 reconstituted epithelial barrier integrity. 91 This process was mediated via the activation of sphingosine kinase 1 and ERK, which are involved in TJ disruption. 92 The genetic signature cannot only explain the increasing incidence and prevalence of airway diseases.…”

The Role of Defective Epithelial Barriers in Allergic Lung Disease and Asthma Development

“…Soluble isoform, IL-1RL1-a or sST2, acts as a decoy receptor by sequestering IL-33, thereby inhibiting IL1RL1-b/IL-33 signaling, which could be used as a biomarker or target for pharmacological intervention. 133,134 Orosomucoid-like 3 (ORMDL3), was shown to play an important role in regulating epithelial barrier function in allergic asthma, [135][136][137] rhinovirus infection 138,139 and by inducing the p-ERK/MMP-9 pathway to promote pathological airway remodeling in patients with asthma. 140 SMAD3 is an essential signal transducer in TGF-β signaling, which is elevated in airway epithelial cells of some asthmatics 141,142 and is involved in the response of bronchial epithelial cells to viral infection.…”