Sun Pengcheng, Feng Shijian, Guan Qiunong, Adomat Hans, Barbour Sean, Gleave Martin E, Nguan Christopher Y C, Xu Wanhai, Du Caigan
Department of Urologic Sciences, University of British Columbia, Vancouver, BC V6H 3Z6, Canada.
Department of Gynecology and Obstetrics, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, People's Republic of China.
J Inflamm Res. 2020 Nov 24;13:969-983. doi: 10.2147/JIR.S285985. eCollection 2020.
Membranous nephropathy (MN) is a specific entity of glomerulonephritis, and its glomerular inflammation is characterized by the deposition of immune complexes in the glomerular basement membrane and proteinuria. However, the molecular mechanisms underlying the glomerular inflammation of MN are not fully understood. This study was designed to investigate the role of clusterin (CLU) in the development of MN using a mouse model of cationic bovine serum albumin (cBSA)-induced MN.
Both wild-type C57BL/6j (WT) and CLU-knockout C57BL/6j (CLU-KO) mice were immunized with cBSA. The kidney function was determined by the levels of serum creatinine (SCr), blood urea nitrogen (BUN) and urinary protein. MN and glomerular deposits of CLU, complement C3 and immunoglobulins (Igs) were determined by histological analyses. Serum proteins were analyzed by the enzyme-linked immunosorbent assay, Western blot and liquid chromatography-mass spectrometry.
Here, we showed that after cBSA immunization, SCr and proteinuria were increased in CLU-KO mice but not in WT mice. Similarly, severe glomerular atrophy and mesangial expansion along with C3 deposit were only found in the kidneys of CLU-KO mice but not in WT mice. However, there were no differences of serum IgG and complement 3 levels between CLU-KO and WT mice. In the serum of WT mice, CLU bound to anti-cBSA IgG, complements (eg, C8), proteinase/protease inhibitors and antioxidative proteins to form a complex, and incubation with WT serum reduced the complement-dependent lysis of podocytes in cultures.
Our data suggest that a CLU deficiency induces cBSA-initiated glomerular inflammation of MN in a disease-resistant strain of mice, suggesting an anti-glomerular inflammatory function of CLU in the resistance to MN development. This function may be at least in part due to the formation of CLU-anti-cBSA Igs complex that prevents glomerular inflammation or injury in the disease-resistant mice.
膜性肾病（MN）是肾小球肾炎的一种特殊类型，其肾小球炎症的特征是免疫复合物在肾小球基底膜沉积及蛋白尿。然而，MN肾小球炎症的分子机制尚未完全明确。本研究旨在利用阳离子牛血清白蛋白（cBSA）诱导的MN小鼠模型，探讨簇集素（CLU）在MN发病过程中的作用。
野生型C57BL/6j（WT）小鼠和CLU基因敲除的C57BL/6j（CLU-KO）小鼠均用cBSA免疫。通过血清肌酐（SCr）、血尿素氮（BUN）水平及尿蛋白含量来测定肾功能。通过组织学分析确定MN以及CLU、补体C3和免疫球蛋白（Igs）的肾小球沉积情况。采用酶联免疫吸附测定、蛋白质印迹法和液相色谱-质谱分析法对血清蛋白进行分析。
在此，我们发现cBSA免疫后，CLU-KO小鼠的SCr和蛋白尿增加，而WT小鼠未出现此现象。同样，严重的肾小球萎缩和系膜扩张以及C3沉积仅在CLU-KO小鼠肾脏中发现，WT小鼠肾脏中未出现。然而，CLU-KO小鼠和WT小鼠的血清IgG和补体3水平并无差异。在WT小鼠血清中，CLU与抗cBSA IgG、补体（如C8）、蛋白酶/蛋白酶抑制剂及抗氧化蛋白结合形成复合物，用WT血清孵育可降低培养的足细胞的补体依赖性裂解。
我们的数据表明，在一种抗病品系小鼠中，CLU缺乏会诱导cBSA引发的MN肾小球炎症，提示CLU在抵抗MN发生发展中具有抗肾小球炎症功能。该功能可能至少部分归因于CLU-抗cBSA Igs复合物的形成，其可预防抗病小鼠的肾小球炎症或损伤。
