Acid sphingomyelinase deficiency contributes to resistance of scleroderma fibroblasts to Fas-mediated apoptosis

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• 作者：Glady Hazitha Samuel ; Stefania Lenna ; Andreea M. Bujor ; Robert Lafyatis ; Maria Trojanowska
• 关键词：Systemic sclerosis ; Myofibroblast ; Fas ligand ; Apoptosis ; Fibrosis
• 刊名：Journal of Dermatological Science
• 出版年：2012
• 出版时间：September, 2012
• 年：2012
• 卷：67
• 期：3
• 页码：166-172
• 全文大小：777 K

文摘

<h4 class=""h4"">Backgroundh4>Scleroderma (SSc) is characterized by excess production and deposition of extracellular matrix (ECM) proteins. Activated fibroblasts play a key role in fibrosis in SSc and are resistant to Fas-mediated apoptosis. Acid sphingomyelinase (ASMase), a major sphingolipid enzyme, plays an important role in the Fas-mediated apoptosis.<h4 class=""h4"">Objectiveh4>

We investigated whether dysregulation of ASMase contributes to Fas-mediated apoptosis resistance in SSc fibroblasts.<h4 class=""h4"">Methodsh4>

Fibroblasts were isolated from SSc patients and healthy controls. Western blot was performed to analyze protein levels and quantitative real time RT-PCR was used to determine mRNA expression. Cells were transiently transfected with siRNA oligos against ASMase or transduced with adenoviruses overexpressing ASMase. Apoptosis was induced using anti-Fas antibody (1 ¦Ìg/mL) and analyzed using caspase-3 antibody or Cell Death Detection ELISA.<h4 class=""h4"">Resultsh4>

SSc fibroblasts showed increased resistance to Fas-mediated apoptosis. ASMase expression was decreased in SSc fibroblasts and Transforming Growth Factor beta (TGF¦Â), the major fibrogenic cytokine involved in the pathogenesis of SSc, downregulated ASMase in normal fibroblasts. Forced expression of ASMase in SSc fibroblasts restored sensitivity of these cells to Fas-mediated apoptosis while blockade of ASMase was sufficient to induce partial resistance to Fas-induced apoptosis in normal fibroblasts. In addition, ASMase blockade decreased activity of protein phosphatase 2A (PP2A) through phosphorylation on Tyr³⁰⁷ and resulted in activation of extracellular regulated kinase 1/2 (Erk1/2) and protein kinase B (Akt/PKB).<h4 class=""h4"">Conclusionh4>

In conclusion, this study suggests that ASMase deficiency promotes apoptosis resistance and contributes to activation of profibrotic signaling in SSc fibroblasts.