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Shiga toxin 2 reduces complement inhibitor CD59 expression on human renal tubular epithelial and glomerular endothelial cells.

发布于：2013年6月13日    文字：【大】【中】【小】

Infect Immun. 2013 May 20. [Epub ahead of print]

Shiga toxin 2 reduces complement inhibitor CD59 expression on human renal tubular epithelial and glomerular endothelial cells.

Ehrlenbach S, Rosales A, Posch W, Wilflingseder D, Hermann M, Brockmeyer J, Karch H, Satchell SC, Würzner R, Orth-H?ller D.

Source

Division of Hygiene and Medical Microbiology, Innsbruck Medical University, 6020 Innsbruck, Austria.

Abstract

Infections with enterohemorrhagic Escherichia coli (EHEC) are a primary cause of hemolytic uremic syndrome (HUS). Recently, Shiga toxin 2 (Stx2), the major virulence factor of EHEC, was reported to interact with complement, implying that the latter is involved in the pathogenesis of EHEC-induced HUS. The aim of the present study was to investigate the effect of Stx2 on the expression of membrane-bound complement regulators CD46, CD55 and CD59 on proximal tubular epithelial (HK-2) and glomerular endothelial (GEnC) cells, derived from human kidney cells that are involved in HUS. Incubation with Stx2 did not influence the amount of CD46 and CD55 on the surface of HK-2 and GEnC cells, as determined by FACS. In contrast, CD59 was significantly reduced by half on GEnC cells, but less pronounced on HK-2 cells. With increasing amounts of Stx2 reduction of CD59 also reached significance in HK-2 cells. ELISA analyses showed that CD59 was not present in supernatant of Stx2-treated cells, implying that CD59 reduction was not caused by cleavage from the cell surface. In fact, RT-qPCR analyses showed downregulation of CD59 mRNA as likely reason for CD59 cell surface reduction. In addition, a significant increase in terminal complement complex deposition on HK-2 cells was observed after treatment with Stx2, as possible consequence of CD59 downregulation. In summary, Stx2 downregulates CD59 on mRNA and protein levels on tubular epithelial and glomerular endothelial cells, which likely contributes to complement activation and kidney destruction in EHEC-associated HUS.

志贺毒素2降低人肾小管上皮细胞及肾小球内皮细胞上补体抑制因子CD59的表达

肠出血性大肠杆菌(EHEC)感染是HUS的主要病因。最近有报道认为志贺毒素2(Stx2, EHEC的主要毒力因子)可以与补体相互作用，提示补体系统也可能参与到了EHEC导致的HUS的发病机制中。这个研究的目的在于阐明Stx2对近端肾小管上皮细胞(HK-2)和肾小球内皮细胞(GEnC)上膜结合的补体调节分子，包括CD46，CD55 和 CD59的表达。这两种细胞是肾脏固有细胞，且在HUS发生时被累及。HK-2 和 GEnC与Stx2共孵育后用荧光活化细胞分选法检测，CD46和CD55的表达不受影响。但CD59表达量在GEnC降低一半，在HK-2降低不明显。当Stx2剂量增大时，CD59在HK-2上表达可显著降低。ELISA法无法检测到与Stx-2共孵育的细胞上清中CD59的表达。提示细胞膜上CD59表达降低不是由于细胞表面的分子剪切。实际上，实时定量PCR检测显示CD59mRNA表达降低，这可能是胞膜上CD59降低的原因。HK-2与Stx2共孵育后，其胞膜上补体终末复合物沉积增加，这可能是CD59表达降低之后的效应。总之，Stx-2在mRNA和蛋白水平上影响了人肾小管上皮细胞及肾小球内皮细胞CD59的表达，这可能与EHEC相关HUS中补体激活和肾脏损伤相关。