Effect of Graphene and Graphene Oxide on Airway Barrier and Differential Phosphorylation of Proteins in Tight and Adherens Junction Pathways.

Sofie Van Den Broucke,Jeroen A J Vanoirbeek,Manosij Ghosh,Rita Derua,Peter H M Hoet

doi:10.3390/nano11051283

Sofie Van Den Broucke, Jeroen A J Vanoirbeek + Show 3 more

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https://doi.org/10.3390/nano11051283

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Journal: Nanomaterials	Publication Date: May 13, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: KU Leuven

Abstract

Via inhalation we are continuously exposed to environmental and occupational irritants which can induce adverse health effects, such as irritant-induced asthma (IIA). The airway epithelium forms the first barrier encountered by these agents. We investigated the effect of environmental and occupational irritants on the airway epithelial barrier in vitro. The airway epithelial barrier was mimicked using a coculture model, consisting of bronchial epithelial cells (16HBE) and monocytes (THP-1) seeded on the apical side of a permeable support, and human lung microvascular endothelial cells (HLMVEC) grown on the basal side. Upon exposure to graphene (G) and graphene oxide (GO) in a suspension with fetal calf serum (FCS), ammonium persulfate (AP), sodium persulfate (SP) and hypochlorite (ClO−), the transepithelial electrical resistance (TEER) and flux of fluorescent labelled dextran (FD4-flux), was determined. Exposure to graphene nanoparticles (GNPs) induced an immediate negative effect on the epithelial barrier, whereas ClO− only had a negative impact after 24 h of exposure. AP and SP did not affect the barrier properties. The tight junctions (TJ) network showed less connected zonula occludens 1 (ZO-1) and occludin staining in GNP-exposed cocultures. Functional analysis of the phosphoproteomic data indicated that proteins in the adherens junction (AJ) and TJ pathways showed an altered phosphorylation due to GNP exposure. To conclude, the negative effect of GNPs on the epithelial barrier can be explained by the slightly altered the TJ organization which could be caused by alterations in the phosphorylation level of proteins in the AJ and TJ pathway.

Highlights

The airway epithelium is located at the interface between the internal and external environment and plays an important role in host defense [1]
Intercellular junctional complexes consist of apically localized tight junctions (TJ) which regulate paracellular transport of ions and small molecules and establish an apical–lateral polarity, and the underlying adherens junctions (AJ) which are important for initiation and maintenance of cell–cell adhesion
In a large set of membrane-associated proteins, we found using phosphoproteomics that the proteins in the AJ and TJ pathways were significantly hypo- or hyperphosphorylated due to graphene nanoparticles (GNPs) exposure, which provides an explanation for the observed negative effect on the airway epithelial barrier

Summary

Introduction

The airway epithelium is located at the interface between the internal and external environment and plays an important role in host defense [1]. The airway epithelial cells are tightly connected and create a first barrier to the outside world. Intercellular junctions are dynamic structures that confer a loose structure when ions, solutes or immune cells have to pass the epithelial layer, yet establish an impenetrable fence to harmful agents [2,3]. Intercellular junctional complexes consist of apically localized tight junctions (TJ) which regulate paracellular transport of ions and small molecules and establish an apical–lateral polarity, and the underlying adherens junctions (AJ) which are important for initiation and maintenance of cell–cell adhesion. The principal proteins in Nanomaterials 2021, 11, 1283.

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