Laboratory of Experimental Immunology, Istituto Dermopatico dell'Immacolata-IDI-IRCCS, Rome, Italy.
Cell Death Dis. 2012 Jun 28;3(6):e334. doi: 10.1038/cddis.2012.69.
Because of their genetically determined capacity to respond to pro-inflammatory stimuli, keratinocytes have a crucial role in the pathogenesis of psoriasis. Upon IFN-γ and TNF-α exposure, psoriatic keratinocytes express exaggerated levels of inflammatory mediators, and show aberrant hyperproliferation and terminal differentiation. The thickening of psoriasic skin also results from a peculiar resistance of keratinocytes to cytokine-induced apoptosis. In this study, we investigated on the molecular mechanisms concurring to the resistance of psoriatic keratinocytes to cell death, focusing on the role having suppressor of cytokine signaling (SOCS)1 and SOCS3, two molecules abundantly expressed in IFN-γ/TNF-α-activated psoriatic keratinocytes, in sustaining anti-apoptotic pathways. We found that SOCS1 and SOCS3 suppress cytokine-induced apoptosis by sustaining the activation of the PI3K/AKT pathway in keratinocytes. The latter determines the activation of the anti-apoptotic NF-κB cascade and, in parallel, the inhibition of the pro-apoptotic BAD function in keratinocytes. For the first time, we report that phosphorylated AKT and phosphorylated BAD are strongly expressed in lesional psoriatic skin, compared with healthy or not lesional skin, and they strictly correlate to the high expression of SOCS1 and SOCS3 molecules in the psoriatic epidermis. Finally, the depletion of SOCS1 and SOCS3, as well as the chemical inactivation of PI3K activity in psoriatic keratinocytes, definitively unveils the role of PI3K/AKT cascade on the resistance of diseased keratinocytes to apoptosis.
由于其对促炎刺激物的基因决定的反应能力,角质形成细胞在银屑病的发病机制中起着至关重要的作用。在 IFN-γ 和 TNF-α 暴露下,银屑病角质形成细胞表达过度的炎症介质,并表现出异常的过度增殖和终末分化。银屑病皮肤的增厚也源于角质形成细胞对细胞因子诱导的凋亡的特殊抵抗。在这项研究中,我们研究了导致银屑病角质形成细胞抵抗细胞死亡的分子机制,重点研究了抑制细胞因子信号(SOCS)1 和 SOCS3 的作用,这两种分子在 IFN-γ/TNF-α 激活的银屑病角质形成细胞中大量表达,以维持抗凋亡途径。我们发现 SOCS1 和 SOCS3 通过维持角质形成细胞中 PI3K/AKT 通路的激活来抑制细胞因子诱导的凋亡。后者决定了抗凋亡 NF-κB 级联的激活,并且平行地抑制了角质形成细胞中促凋亡 BAD 的功能。我们首次报道,与健康或非病变皮肤相比,磷酸化 AKT 和磷酸化 BAD 在病变的银屑病皮肤中强烈表达,并且它们与银屑病表皮中 SOCS1 和 SOCS3 分子的高表达严格相关。最后,SOCS1 和 SOCS3 的耗竭以及在银屑病角质形成细胞中化学失活 PI3K 活性,明确揭示了 PI3K/AKT 级联在疾病角质形成细胞抵抗凋亡中的作用。