Study of cell responses after lipid raft disruption by cholesterol depletion in epidermal keratinocytes

Abstract

The skin assumes a fascinating protection role by producing a barrier between the environment and the organism. This barrier, formed by the differentiation of epidermal keratinocytes, is vital for the organism as the skin is constantly exposed to external aggressions. In this study, we investigated the relevance of membrane cholesterol and lipid rafts in normal epidermal keratinocytes by extracting cholesterol with methyl-beta-cyclodextrin. Actually, the scientific interest in plasma membranes has strongly increased since the discovery that cholesterol-enriched membrane microdomains domains, lipid rafts, are directly involved in cell signaling. Our study identifies the heparin-binding EGF-like growth factor (HB-EGF) as a major actor after lipid raft disruption, HB-EGF is also shown to be expressed in wound-healing skin after burn injury. Parallelisms in the keratinocyte’s response to lipid raft disruption or to oxidative stress incited the investigation potential oxidative stress-mediated effects in cholesterol-depleted cells, but our results clearly demonstrate that lipid raft disruption does not initiate oxidative stress mechanisms. An unbiased microarray approach was then chosen to determine major actors, functions and pathways. HB-EGF, interleukin-8, urokinase-like plasminogen activator and its receptor are identified among the major transcriptional targets in lipid raft-disrupted keratinocytes. Moreover, bioinformatics analysis of differentially regulated genes permitted to establish a potential link with atopic dermatitis, an inflammatory skin disease. This hypothesis was investigated, and confirmed, in skin biopsies of atopic dermatitis patients. Thus, our study contributes to a better understanding of lipid raft biology and suggests that the functioning of keratinocyte lipid rafts could be compromised in atopic dermatitis.

Date of Award	8 Jul 2010
Original language	English
Awarding Institution	University of Namur
Supervisor	Yves Poumay (Supervisor), Catherine Lambert (President), Florence Debacq-Chainiaux (Jury), Eric Depiereux (Jury), Alain Colige (Jury), Arjen F. Nikkels (Jury) & Mark Pittelkow (Jury)