Kshirsagar Sudhir, Binder Elisabeth, Riedl Magdalena, Wechselberger Gottfried, Steichen Elisabeth, Edelbauer Monika
Innsbruck Medical University, Innsbruck, Austria.
Arthritis Rheum. 2013 Nov;65(11):2996-3006. doi: 10.1002/art.38089.
The breakdown of peripheral tolerance mechanisms is central to the pathogenesis of systemic lupus erythematosus (SLE). Although true Treg cells in patients with SLE exhibit intact suppressive activity, Teff cells are resistant to suppression. The underlying mechanisms are incompletely understood. This study was undertaken to examine the Akt signaling pathway and molecules that may alter its activity in T cells in lupus patients.
The Akt pathway and its regulators were analyzed in Teff and Treg cells from children with lupus nephritis and controls using flow cytometry and real-time quantitative polymerase chain reaction. T cell proliferation was assessed by analysis of 5,6-carboxyfluorescein succinimidyl ester dilution.
CD4+CD45RA-FoxP3(low) and FoxP3- Teff cells from children with lupus nephritis expressed high levels of activated Akt, resulting in the down-regulation of the proapoptotic protein Bim and an enhanced proliferative response. The induction of tumor necrosis factor receptor-associated factor 6 (TRAF6) was impaired, and TRAF6 levels inversely correlated with Akt activity. Although the expression of OX40 was enhanced on Teff cells from children with lupus nephritis compared to controls, OX40 stimulation failed to significantly increase TRAF6 expression in cells from patients, in contrast to those from healthy controls, but resulted in further increased Akt activation that was reversed by blockade of OX40 signaling. Moreover, inhibition of Akt signaling markedly decreased the proliferation of Teff cells from lupus patients.
Our findings indicate that hyperactivation of the Akt pathway in Teff cells from children with lupus nephritis is associated with reduced induction of TRAF6 and up-regulation of OX40, which may cause Teff cell resistance to Treg cell-mediated suppression.
外周耐受机制的破坏是系统性红斑狼疮（SLE）发病机制的核心。虽然SLE患者真正的调节性T细胞（Treg）表现出完整的抑制活性，但效应性T细胞（Teff）对抑制具有抗性。其潜在机制尚未完全了解。本研究旨在研究Akt信号通路以及可能改变狼疮患者T细胞中其活性的分子。
使用流式细胞术和实时定量聚合酶链反应分析狼疮性肾炎患儿和对照组的Teff和Treg细胞中的Akt信号通路及其调节因子。通过分析5,6-羧基荧光素琥珀酰亚胺酯稀释来评估T细胞增殖。
狼疮性肾炎患儿的CD4 + CD45RA - FoxP3（低）和FoxP3 - Teff细胞表达高水平的活化Akt，导致促凋亡蛋白Bim下调和增殖反应增强。肿瘤坏死因子受体相关因子6（TRAF6）的诱导受损，并且TRAF6水平与Akt活性呈负相关。与对照组相比，狼疮性肾炎患儿的Teff细胞上OX40的表达增强，但是与健康对照者的细胞相比，OX40刺激未能显著增加患者细胞中TRAF6的表达，而是导致Akt活化进一步增加，而这种增加可通过阻断OX40信号来逆转。此外，抑制Akt信号显著降低了狼疮患者Teff细胞的增殖。
我们的研究结果表明，狼疮性肾炎患儿的Teff细胞中Akt信号通路的过度活化与TRAF6诱导减少和OX40上调有关，这可能导致Teff细胞对Treg细胞介导的抑制产生抗性。
