系膜来源的肿瘤坏死因子-α激活肾小管上皮细胞：IgA肾病中的肾小球-肾小管通讯

Activation of tubular epithelial cells by mesangial-derived TNF-alpha: glomerulotubular communication in IgA nephropathy.

作者信息

Chan Loretta Y Y, Leung Joseph C K, Tsang Anita W L, Tang Sydney C W, Lai Kar Neng

机构信息

Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong.

出版信息

Kidney Int. 2005 Feb;67(2):602-12. doi: 10.1111/j.1523-1755.2005.67116.x.

DOI:10.1111/j.1523-1755.2005.67116.x

PMID:15673307

Abstract

BACKGROUND

IgA nephropathy (IgAN), characterized by mesangial IgA deposition, runs a variable clinical course with tubulointerstitial damage and renal failure in no less than 30% of patients. Histologically, IgA is rarely detected in renal tubules. The direct toxicity by IgA on renal tubules remains uncertain. We hypothesize that mediators released from human mesangial cells (HMC) triggered by IgA deposition may lead to activation of proximal tubular epithelial cells (PTEC).

METHODS

The binding of IgA to PTEC or HMC was assessed by flow cytometry. IgA-HMC medium was prepared by collecting the spent medium in which growth arrested HMC were incubated with IgA isolated from patients with IgAN, healthy control subjects, or other nephritic control patients. PTEC was cultured with the IgA-HMC medium in the presence or absence of neutralizing antibodies to TNF-alpha, IL-1beta, TGF-beta, or PDGF. Gene expression and protein synthesis of TNF-alpha, MIF, or ICAM-1 by PTEC were determined by RT-PCR and ELISA, respectively.

RESULTS

The binding of IgA isolated from patients with IgAN to PTEC was increased when compared to binding of IgA from healthy control subjects (P < 0.005). However, the binding to PTEC was less than one tenth that of HMC in IgAN. The binding to PTEC was not mediated through known IgA receptors, as shown by competitive binding assays and gene expression of the receptors. Despite the in vitro binding, PTEC cultured with isolated IgA exhibited no increased cell proliferation or enhanced synthesis of TNF-alpha, MIF, or sICAM-1. However, when PTEC were cultured with IgA-HMC medium prepared from IgAN patients, there was enhanced proliferation of PTEC (P < 0.001) and increased synthesis of TNF-alpha, MIF, and sICAM-1 when compared with PTEC cultured with IgA-HMC medium from control subjects (P < 0.001). The synthesis of MIF and sICAM-1 by PTEC cultured with IgA-HMC medium was reduced by neutralizing antibodies to TNF-alpha (P < 0.001) but not by neutralizing antibodies to IL-1beta, TGF-beta, or PDGF.

CONCLUSION

Our finding implicates that TNF-alpha released from the mesangium after IgA deposition activates renal tubular cells. The glomerulotubular communication could play an important role in the pathogenesis of tubulointerstitial damage in IgAN.

摘要

背景

IgA 肾病（IgAN）以系膜 IgA 沉积为特征，临床病程多变，至少 30%的患者会出现肾小管间质损伤和肾衰竭。组织学上，很少在肾小管中检测到 IgA。IgA 对肾小管的直接毒性尚不确定。我们推测，IgA 沉积触发人系膜细胞（HMC）释放的介质可能导致近端肾小管上皮细胞（PTEC）活化。

方法

通过流式细胞术评估 IgA 与 PTEC 或 HMC 的结合。IgA-HMC 培养基的制备方法是收集生长停滞的 HMC 与从 IgAN 患者、健康对照者或其他肾病对照患者分离的 IgA 一起孵育后的上清培养基。在存在或不存在针对 TNF-α、IL-1β、TGF-β 或 PDGF 的中和抗体的情况下，用 IgA-HMC 培养基培养 PTEC。分别通过 RT-PCR 和 ELISA 测定 PTEC 中 TNF-α、MIF 或 ICAM-1 的基因表达和蛋白质合成。

结果

与健康对照者的 IgA 相比，IgAN 患者分离的 IgA 与 PTEC 的结合增加（P < 0.005）。然而，在 IgAN 中，与 PTEC 的结合不到与 HMC 结合的十分之一。竞争结合试验和受体基因表达表明，与 PTEC 的结合不是通过已知的 IgA 受体介导的。尽管存在体外结合，但用分离的 IgA 培养的 PTEC 未表现出细胞增殖增加或 TNF-α、MIF 或 sICAM-1 的合成增强。然而，当用 IgAN 患者制备的 IgA-HMC 培养基培养 PTEC 时，与用对照受试者的 IgA-HMC 培养基培养的 PTEC 相比，PTEC 的增殖增强（P < 0.001），TNF-α、MIF 和 sICAM-1 的合成增加（P < 0.001）。用 IgA-HMC 培养基培养的 PTEC 合成 MIF 和 sICAM-1 的量可被抗 TNF-α 中和抗体降低（P < 0.001），但不能被抗 IL-1β、TGF-β 或 PDGF 中和抗体降低。