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- Forsberg, Sofi, 1980-
(författare)
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Human Epidermal Growth Factor Receptors and Biological Effects of HER-directed Molecules on Skin Epithelialization
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human skin forms a biologically active barrier and maintains vital protective functions through continuous regeneration of cells within its outermost layer, the epidermis. In healthy skin, renewal of epithelial cells is a tightly regulated process in which the epidermal growth factor receptor (EGFR or HER1) and its various ligands are involved. The biological role of other EGFR family members (HER2–4) in normal and diseased human skin has gained less interest. The purpose of this work was to investigate the expression and contribution of different HERs in cultured epidermis and psoriatic skin. Epidermal regeneration was studied by fluorescence imaging of a skin explant model exposed to anti-psoriatic drugs, HER ligands or HER-blocking molecules. EGFR, HER2 and HER3 were all markedly expressed with an in vivo-like immunostaining pattern in cultured neoepidermis, whereas only low amounts of HER4 were detected at protein and mRNA levels. Re-epithelialization was associated with receptor activation. Application of HER-selective tyrosine kinase inhibitors and monoclonal antibodies reduced the proliferative activity, receptor phosphorylation and radial outgrowth from normal skin explants. Similar anti-dynamic effects were obtained with HER kinase inhibition of neoepidermis generated from psoriatic skin. Among the HER receptors, EGFR seemed to be the dominant subtype during epithelialization in vitro although HER2 and HER3 were also involved. HER2 probably functioned as a co-receptor for the kinase-deficient HER3 in neoepidermis. In vivo, expression of HER4 mRNA was detected in normal and uninvolved psoriatic skin but was virtually absent in lesional skin, a potentially important finding for HER signalling in psoriasis. This thesis demonstrates the utility of combined dynamic and biochemical analyses of re-epithelialization and highlights the role of EGFR and other HERs for epidermal growth. It also underscores the potential of HER-directed inhibition to control hyperproliferative states of the epidermis.
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| 2. |
- Lirvall, Margareta
(författare)
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Dynamics and gene expression of growth factor receptors in human cultured skin cells : Effects of UV radiation and calcium on EGF- and PDGF-receptors
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Growth factors transmit biological signals for the stimulation of cell growth and their stimulation may be involved in turnourigenesis. It is therefore of great importance to understand growth factor receptor reactions in response to stimuli such as calcium depletion or ultraviolet radiation, which normal human cells are invariably exposed to during their growth cycle. We have studied human skin cells i.e. fibroblasts, lceratinocytes and melanocytes and their growth factor receptor expression on the surface of cells, reactions in the plane of the cell membrane, intracellular trafficlcing, and gene expression after exposure to their ligand, serum, UVB radiation and calcium depletion. We have used Fluorescence recovery after photo bleaching (FRAP) to assess receptor characteristics in cell membranes, confocal laser scanning microscopy to visualize receptor internalization, Ratio imaging for calcium studies, Northern blot for detection of the gene for the epidermal growth factor receptor (EGF-R) and flow cytometry for cell surface receptor determination. Platelet-derived growth factor receptors (PDGF-R) and EGF-R were studied since they affect cell proliferation and viability.Our results showed that the addition of PDGF increased receptor mobility characteristics in normal fibroblasts, also "starvation" of cells increased their receptor mobility. We could show that changes in both intra-and extracellular free Ca2+ influence the mobility characteristics of PDGF-ß2 receptors. We have demonstrated that the three celltypes display different basal EGF-R mobility characteristics. After UVB irradiation mobility characteristics increased in all cell types but with differences in diffusion coefficients or mobile fractions. Addition of antioxidant enzymes, catalase and superoxide dismutase, prior to UVB irradiated cells abolished the UY-induced receptor mobility changes. We have shown that a single physiologic dose ofUVB radiation alters the intracellular EGF-R distribution and intracellular transport in melanocytes. It also significantly alters the melanocyte phenotype. We were able to detect a constitutive EGF-R gene expression and showed that UVB-radiation induces a time-dependent induction in EGF-R mRNA in melanocytes. Human melanocytes express EGF-R on their cell surface and UVR induces time dependent changes in the number of receptors but the number of receptors does not correlate with the level of UV-induced EGF-R gene expression.It is concluded that UV-radiation, growth factors and calcium, ubiquitous constituents of every day life, all having tremendous effects in vivo, also affect human cells in vitro in parameters studied that are of importance for proliferation, survival and tumourigenesis.
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