Department of Nephrology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China.
Nephrology (Carlton). 2010 Feb;15(1):63-74. doi: 10.1111/j.1440-1797.2009.01152.x.
SUMMARY AT A GLANCE Patients with MCD and FSGS had significant changes in the expression of several EMT-related urinary proteins through activation ERK1/2 and p38 signaling pathways. Further studies to explore the molecular mechanisms behind the distinct clinical features of different types of nephrotic syndrome are warranted.
Proteinuria plays an important role in the progression of tubulointerstitial fibrosis, but the mechanism for the differential renal damage induced by proteinuria is unknown. This study examined the effects of urinary proteins from patients with idiopathic minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) on several epithelial-mesenchymal transition (EMT)-related marker proteins in cultured proximal tubular HK-2 cells.
Urinary proteins from MCD and FSGS patients were extracted by ultrafiltration and incubated with HK-2 cells; the expression of the cytokeratin-18, alpha-smooth muscle actin (alpha-SMA) and vimentin were assessed. p38 and extracellular regulated kinase (ERK) activation were measured by western blotting, and SB203580 (a p38 inhibitor) and PD98059 (an ERK1/2 inhibitor) were used to inhibit their activation.
It was observed that urinary proteins from FSGS patients more significantly induced the expression of alpha-SMA and vimentin and reduced cytokeratin-18 expression than those from MCD patients in HK-2 cells. Both ERK1/2 and p38 were activated by urinary proteins from MCD or FSGS patients. Pretreatment of the cells with SB203580 or PD98059 abolished the effect of urinary proteins from FSGS patients on the expression of alpha-SMA, vimentin and cytokeratin-18, while only SB203580 elicited this effect when cells were treated with urinary proteins from MCD patients.
The urinary proteins from MCD and FSGS patients induced significant changes of EMT-related proteins through activation of distinct mitogen-activated protein kinase-related signalling pathways. Quality of proteinuria may play an important role in determining the severity and progression of tubular injury associated with different kidney diseases.
蛋白尿在肾小管间质纤维化的进展中起重要作用，但蛋白尿引起不同类型肾病综合征肾损伤差异的机制尚不清楚。本研究探讨了特发性微小病变病（MCD）和局灶节段性肾小球硬化症（FSGS）患者尿液蛋白对培养的人近端肾小管 HK-2 细胞几种上皮-间充质转化（EMT）相关标志物蛋白的影响。
超滤法提取 MCD 和 FSGS 患者尿液蛋白，孵育 HK-2 细胞，检测细胞角蛋白 18、α-平滑肌肌动蛋白（α-SMA）和波形蛋白的表达。Western blot 法检测 p38 和细胞外调节激酶（ERK）的激活，并用 p38 抑制剂 SB203580 和 ERK1/2 抑制剂 PD98059 抑制其激活。
与 MCD 患者尿液蛋白相比，FSGS 患者尿液蛋白更显著地诱导 HK-2 细胞中 α-SMA 和波形蛋白的表达，降低细胞角蛋白 18 的表达。MCD 或 FSGS 患者尿液蛋白均可激活 ERK1/2 和 p38。细胞用 SB203580 或 PD98059 预处理可消除 FSGS 患者尿液蛋白对 α-SMA、波形蛋白和细胞角蛋白 18 表达的影响，而仅用 SB203580 预处理时，MCD 患者尿液蛋白对其有此作用。
MCD 和 FSGS 患者的尿液蛋白通过激活不同的丝裂原活化蛋白激酶相关信号通路，诱导 EMT 相关蛋白发生显著变化。蛋白尿的质量可能在决定不同肾脏疾病相关肾小管损伤的严重程度和进展中起重要作用。
