Studies of cell signaling in a reconstructed human epidermis exposed to sensitizers: IL-8 synthesis and release depend on EGFR activation

Abstract

Models of reconstructed human epidermis (RHE) holding proliferating and fully differentiated cultured keratinocytes allow in vitro investigation of early molecular and cellular epidermal events during the complex response of keratinocytes at the onset of allergic contact dermatitis (ACD) or sensitization. In this study, data collected on RHE exposed to well-characterized sensitizing chemicals, such as dinitrofluorobenzene, oxazolone, cinnamaldehyde and isoeugenol, revealed a transient expression of IL-8 mRNA in association with abundant IL-8 cell release. Investigations of keratinocyte signaling illustrate transient activation by tissue exposure to sensitizing chemicals of the epidermal growth factor receptor (EGFR). This activation of EGFR tyrosine kinase is involved in the expression and release of IL-8. The IL-8 release appears also to be partially dependent on p38 and ERK 1/2 MAPK activation. Moreover, data suggest that heparin-binding EGF-like growth factor (HB-EGF) expression and release induced after exposure of RHE to sensitizing chemicals are also under the control of EGFR tyrosine kinase activity, independently of the IL-8 expression and release. Mechanistic approach of keratinocyte responses in the context of RHE underlying regulation of expression and release of epidermal cytokines and growth factors after topical application of sensitizing chemicals is proposed to identify biomarkers which could then be analysed for in vitro toxicological screening of new or undefined compounds.

High-Glucose Environment Enhanced Oxidative Stress and Increased Interleukin-8 Secretion From Keratinocytes

“…(Fig. 1 C ) It has been reported that nuclear factor-κB (NF-κB), p38 MAPK, and ERK are involved in IL-8 secretion of keratinocytes (22,23). Since we had previously demonstrated that upregulation of NF-κB and p38 MAPK was not observed in high glucose–cultivated keratinocytes (21), we focused on ERK signaling.…”

HB-EGF, the Growth Factor that Accelerates Keratinocyte Migration, But Slows Proliferation

“…Thus, it appears that epidermal keratinocytes challenged by various alterations in their environment behave in a similar manner and exhibit stimulation of their endogenous expression of HB-EGF. This is concomitant with stimulation of the expression of other gene products, such as interleukin-8 after cholesterol depletion (Mathay et al, 2011) or exposure to sensitizing chemicals (Frankart et al, 2012), matrix metalloproteases 1 and 10 (Mathay et al, 2011;Stoll et al, 2012), and even more surprisingly, involucrin (Mathay et al, 2008;Giltaire et al, 2009;Mathay et al, 2011). Now, Stoll et al (2012) reveal that keratinocytes overexpressing HB-EGF are very likely triggered toward a motile, abnormally differentiated, but also poorly proliferative, phenotype.…”

Skin Irritation Testing beyond Tissue Viability: Fucoxanthin Effects on Inflammation, Homeostasis, and Metabolism

“…IL-1α activates the p38 MAPK pathway to increase the expression of HSPB1, which causes anti-apoptotic effects, possesses chaperone-like activity and refolds denatured proteins, and is cytoprotective against heat shock [35]. EGFR also increases the expression of IL-8 [39] and plays an essential role in re-epithelialization by increasing keratinocyte proliferation and cell migration in wounded skin [40]. The constant gene expressions of EGFR and HSPB1 substantiate the absence of damage from fucoxanthin, but does not explain the reduction in IL-6 and IL-8 gene expression.…”