Cytokines induce tight junction disassembly in airway cells via an EGFR-dependent MAPK/ERK1/2-pathway

Abstract

Epithelial barrier permeability is altered in inflammatory respiratory disorders by a variety of noxious agents through modifications of the epithelial cell structure that possibly involve tight junction (TJ) organization. To evaluate in vitro whether pro-inflammatory cytokines involved in the pathogenesis of respiratory disorders could alter TJ organization and epithelial barrier integrity, and to characterize the signal transduction pathway involved Calu-3 airway epithelial cells were exposed to TNF-a, IL-4 and IFN-g to assess changes in: (a) TJ assembly, that is, occludin and zonula occludens (ZO)-1 expression and localization, evaluated by confocal microscopy; (b) apoptotic activity, quantified using terminal transferase deoxyuridine triphosphate nick-end labeling staining; (c) epithelial barrier integrity, detected as transmembrane electrical resistance and expressed as G T values; (d) epidermal growth factor receptor (EGFR)-dependent mitogenactivated protein (MAP) kinase (MAPK)/extracellular signal-regulated kinases (ERK)1/2 phosphorylation, assessed by western blotting. Exposure to cytokines for 48 h induced a noticeable downregulation of the TJ transmembrane proteins. The degree ZO-1 and occludin colocalization was 62±2% in control cultures and significantly decreased in the presence of TNF-a (47 ± 3%), IL-4 (43 ± 1%) and INF-g (35 ± 3%). Although no apoptosis induction was detected following exposure to cytokines, changes in the epithelial barrier integrity were observed, with a significant enhancement in paracellular conductance. G T values were, respectively, 1.030 ± 0.0, 1.300 ± 0.04, 1.260 ± 0.020 and 2.220 ± 0.015 (mS/cm 2 ) Â 1000 in control cultures and in those exposed to TNF-a, IFN-g and IL-4. The involvement of EGFR-dependent MAPK/ERK1/2 signaling pathway in cytokine-induced damage was demonstrated by a significant increase in threonine/tyrosine phosphorylation of ERK1/2, already detectable after 5 min incubation. All these cytokine-induced changes were markedly prevented when Calu-3 cells were cultured in the presence of an EGFR inhibitor (AG1478, 1 mM) or a MAP kinase inhibitor (U0126, 25 mM). In conclusion, cytokine-induced epithelial injury includes TJ disassembly and epithelial barrier permeability alteration and involves the EGFR-dependent MAPK/ERK1/2 signaling pathway.

rpS6 regulates blood-testis barrier dynamics via its effects on MMP-9 mediated by Akt signaling

“…S2A,B). This observation is consistent with earlier findings that the activation of Erk1/2 is involved in the disruption of the epithelial tight junction barrier by downregulating tight junction proteins (Petecchia et al, 2012;Samak et al, 2011). Collectively, these data support the notion that overexpression of wild-type or active rpS6 leads to a downregulation of p-Akt, resulting in the activation of Raf-MER-Erk signaling that upregulates MMP-9.…”

A Gut Microbial Metabolite of Linoleic Acid, 10-Hydroxy-cis-12-octadecenoic Acid, Ameliorates Intestinal Epithelial Barrier Impairment Partially via GPR40-MEK-ERK Pathway

“…TNF-␣ activates MAPK and NF-B to induce inflammatory cytokines and chemokines such as IL-8, triggers inflammatory responses, and leads to changes in the expression of TJ-related molecules; for example, it increases MLCK expression and decreases ZO-1 expression through activation of p38 (42)(43)(44)(45). In this study, the pretreatment of HYA normalized the expression of occludin, ZO-1, and MLCK in Caco-2 cells (Fig.…”

Vascular Endothelial Tight Junctions and Barrier Function Are Disrupted by 15(S)-Hydroxyeicosatetraenoic Acid Partly via Protein Kinase Cϵ-mediated Zona Occludens-1 Phosphorylation at Threonine 770/772

“…studies from other laboratories have reported that MAPKs might play a role in the disruption of TJs via mediating phosphorylation of TJ proteins in response to external cues in epithelial cells (34,35). Therefore, to investigate the upstream mechanisms of ZO-1 phosphorylation by 15(S)-HETE, we tested the role of MAPKs.…”