ORIGINAL ARTICLE: Interferon (IFN)- gamma is a main mediator of keratinocyte (HaCaT) apoptosis and contributes to autocrine IFN- gamma and tumour necrosis factor- alpha production

• Published in: British journal of dermatology (1951) Vol. 152; no. 6; pp. 1134 - 1142
• Main Authors: Konur, A, Schulz, U, Eissner, G, Andreesen, R, Holler, E
• Format: Journal Article
• Language: English
• Published: 01-06-2005
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1111/j.1365-2133.2005.06508.x

Background: Apoptosis of keratinocytes or intestinal epithelial cells is an important pathophysiological mechanism of organ damage during acute graft-versus-host disease. Objectives: To analyse in detail the mediators and their mutual interaction leading to keratinocyte apoptosis. Methods: Experiments were performed using a keratinocyte cell line (HaCaT) and human skin explant cultures. Results: Supernatants (SN) of major histocompatibility complex nonmatched mixed lymphocyte cultures (MLCs) induced apoptosis in HaCaT cells and also in keratinocytes from skin biopsies. Although both interferon (IFN)- gamma and Fas ligand (FasL) were detected in MLC-SN by enzyme-linked immunosorbent assay, the apoptosis-inducing capacity could be fully abrogated by neutralization of IFN- gamma , but not by neutralization of FasL. Recombinant (r) IFN- gamma induced HaCaT keratinocyte apoptosis in a dose- and time-dependent manner. Induction of HaCaT apoptosis by rFasL alone was induced only at higher doses than present in MLC-SN, but apoptosis was dramatically enhanced in the presence of rIFN- gamma . Further synergistic effects with IFN- gamma in the induction of apoptosis were also observed with agonistic antitumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) receptor 2 antibody, soluble TRAIL and TNF- alpha . However, in contrast to FasL and TRAIL, TNF- alpha alone did not induce HaCaT apoptosis. Interleukin-1 beta and lipopolysaccharide did not enhance the apoptosis-inducing effect of IFN- gamma . Beside its apoptosis-inducing capacity in HaCaT cells, rIFN- gamma also induced autocrine IFN- gamma production, and combined treatment with IFN- gamma and TNF- alpha induced autocrine TNF- alpha production. Neutralization of autocrine IFN- gamma protected HaCaT cells from apoptosis. Conclusions: Taken together, our data suggest a central role for IFN- gamma in HaCaT keratinocyte apoptosis but also show the importance of co-acting mediators such as TNF- alpha , TRAIL and FasL, which potentiate the effect of paracrine and autocrine IFN- gamma and TNF- alpha release.