Department I, Institute of Anatomy and Cell Biology, Ludwig-Maximilians-Universität (LMU) Munich, Munich, Germany.
Department of Dermatology, University Medical Center Tübingen, Eberhard Karls University, Tübingen, Germany.
Front Immunol. 2019 Apr 17;10:770. doi: 10.3389/fimmu.2019.00770. eCollection 2019.
Pemphigus is an autoimmune blistering disease targeting the desmosomal proteins desmoglein (Dsg) 1 and Dsg3. Recently, a genetic variant of the Suppression of tumorigenicity 18 (ST18) promoter was reported to cause ST18 up-regulation, associated with pemphigus vulgaris (PV)-IgG-mediated increase in cytokine secretion and more prominent loss of keratinocyte cohesion. Here we tested the effects of PV-IgG and the pathogenic pemphigus mouse anti-Dsg3 antibody AK23 on cytokine secretion and ERK activity in human keratinocytes dependent on ST18 expression. Without ST18 overexpression, both PV-IgG and AK23 induced loss of keratinocyte cohesion which was accompanied by prominent fragmentation of Dsg3 immunostaining along cell borders. In contrast, release of pro-inflammatory cytokines such as IL-1α, IL-6, TNFα, and IFN-γ was not altered significantly in both HaCaT and primary NHEK cells. These experiments indicate that cytokine expression is not strictly required for loss of keratinocyte cohesion. Upon ST18 overexpression, fragmentation of cell monolayers increased significantly in response to autoantibody incubation. Furthermore, production of IL-1α and IL-6 was enhanced in some experiments but not in others whereas release of TNF-α dropped significantly upon PV-IgG application in both EV- and ST18-transfected HaCaT cells. Additionally, in NHEK, application of PV-IgG but not of AK23 significantly increased ERK activity. In contrast, ST18 overexpression in HaCaT cells augmented ERK activation in response to both c-IgG and AK23 but not PV-IgG. Because inhibition of ERK by U0126 abolished PV-IgG- and AK23-induced loss of cell cohesion in ST18-expressing cells, we conclude that autoantibody-induced ERK activation was relevant in this scenario. In summary, similar to the situation in PV patients carrying ST18 polymorphism, overexpression of ST18 enhanced keratinocyte susceptibility to autoantibody-induced loss of cell adhesion, which may be caused in part by enhanced ERK signaling.
天疱疮是一种自身免疫性水疱病，靶向桥粒蛋白桥粒芯糖蛋白 1（Dsg）1 和 Dsg3。最近，有报道称 Suppression of tumorigenicity 18（ST18）启动子的遗传变异可导致 ST18 上调，与天疱疮寻常型（PV）-IgG 介导的细胞因子分泌增加和更明显的角质形成细胞黏附丧失相关。在这里，我们检测了 PV-IgG 和致病性天疱疮抗 Dsg3 抗体 AK23 在依赖于 ST18 表达的情况下对人角质形成细胞细胞因子分泌和 ERK 活性的影响。在没有 ST18 过表达的情况下，PV-IgG 和 AK23 均诱导角质形成细胞黏附丧失，这伴随着 Dsg3 免疫染色沿着细胞边界的明显碎片化。相比之下，PV-IgG 和 AK23 在 HaCaT 和原代 NHEK 细胞中均未显著改变促炎细胞因子（如 IL-1α、IL-6、TNFα 和 IFN-γ）的释放。这些实验表明，细胞因子表达对于角质形成细胞黏附丧失不是严格必需的。在 ST18 过表达的情况下，细胞单层的碎片化在孵育自身抗体时显著增加。此外，在一些实验中增强了 IL-1α 和 IL-6 的产生，但在其他实验中没有，而在 EV 和 ST18 转染的 HaCaT 细胞中，PV-IgG 应用后 TNF-α 的释放显著下降。此外，在 NHEK 中，PV-IgG 的应用但不是 AK23 的应用显著增加了 ERK 活性。相比之下，在 HaCaT 细胞中 ST18 的过表达增强了对 c-IgG 和 AK23 的 ERK 激活，但对 PV-IgG 没有。由于 U0126 抑制 ERK 消除了 ST18 表达细胞中 PV-IgG 和 AK23 诱导的细胞黏附丧失，我们得出结论，自身抗体诱导的 ERK 激活在此情况下是相关的。总之，与携带 ST18 多态性的 PV 患者的情况类似，ST18 的过表达增强了角质形成细胞对自身抗体诱导的细胞黏附丧失的易感性，这可能部分是由增强的 ERK 信号引起的。
