Dithranol and Dimethylfumarate Suppress the Interferon-γ-Induced Up-Regulation of Cytokeratin 17 as a Putative Psoriasis Autoantigen in vitro

Abstract

In psoriasis an etiopathogenetic vicious circle has been hypothesized in which disease manifestation is triggered by skin-specific autoantigen structures. Autoreactive T cells are supposed to mediate inflammation and hyperproliferation in the epidermopapillary compartment, positively feeding back the expression and accessibility of decisive antigen structures. Recently an epitope within cytokeratin 17 (K17) has been described as such a putative psoriasis autoantigen, which is moreover known to be up-regulated under the influence of proinflammatory interferon-γ (IFN-γ), which is abundantly detected in psoriatic plaques. The present study proposes an in vitro model for this presumptive IFN-γ/K17 autoimmune loop, i.e. the incubation of hyperproliferative human HaCaT keratinocytes with 25 U IFN-γ/ml for 72 h. This treatment led to a significant up-regulation of K17 protein expression (≧300%) measured by flow immunocytometry as compared to the untreated control (100%, p ≤ 0.05). Preincubation with a subcytotoxic and antiproliferative dithranol concentration as low as 0.3 µM for 2 h prior to the IFN-γ exposure resulted in a K17 expression that was significantly lower than the IFN-γ-induced K17 expression reference level. The IFN-γ-induced K17 expression was also significantly lowered by coincubation with a subcytotoxic and nonantiproliferative concentration of 3 µM dimethylfumarate. The data indicate for dithranol and dimethylfumarate that a part of their antipsoriatic mode of action may be related to a direct down-regulation of putative psoriasis autoantigen structures.

Interferon-γ-Dependent in vitro Model for the Putative Keratin 17 Autoimmune Loop in Psoriasis: Exploration of Pharmaco- and Gene-Therapeutic Effects

“…In the cell culture model of human HaCaT keratinocytes, we investigated by immunoflow cytometry to what extent K17 as a putative psoriasis major autoantigen might be induced on the protein level by cytokines other than IFN-Á known to be crucially involved in the psoriatic disease mechanisms [16][17][18][19]. Such an induction was not detectable for IL-1·, IL-1ß, IL-6, IL-8 and IL-18, but for TNF-· and TGF-·, however only when used in relatively high concentrations of 1,000 and 610 ng/ml, respectively.…”

“…This procedure was performed as previously described [19]. Briefly, 1 day after plating, subconfluent HaCaT keratinocytes were incubated with IFN-Á at a concentration of 25 U/ml for 72 h. Harvested cells were washed twice with PBS, fixed with 4% paraformaldehyde for 7 min and washed again.…”

“…Given these data, we have recently proposed the existence of an IFN-Á/K17 autoimmune loop [19]. The highly attractive feature of this autoimmune loop concept is based upon the pivotal assumption that the degree of K17 autoantigen expression is directly and positively correlated with the degree of inflammation and IFN-Á activity in the tissue micromilieu in terms of a positive feedback mechanism or a so-called vicious circle.…”

Effect of the Active Fraction of Flos Daturae on IFN-γ Induced Apoptosis in Immortalized Human Epidermal Keratinocyte Cells (HaCAT)

“…In previous dermatopathologic research, it has been shown that IFN-can induce apoptosis in HaCAT cells in vitro [19] and increase the expression of K17, which makes it a globally acceptable mimic model of psoriasis [8,19]. In the present study, we evaluated the IFN-induced of apoptosis in HaCAT cells and the expression of K17, both in the presence and the absence of AF-FD.…”

“…It has been shown that IFN-can increase the expression of K17 in a human keratinocyte cell line (HaCAT) [6,7]. Some authors used an IFN-/K17 loop to explain the positive feedback mechanism between IFN-activity and K17 expression in psoriasis [8].…”