Background: 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.
Methods: 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.
Results: 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.
Conclusion: 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.



中文翻译：

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凝聚素缺乏使 C57BL/6j 小鼠易患阳离子牛血清白蛋白诱导的肾小球炎症

背景：膜性肾病（Membranous nephropathy，MN）是一种特殊的肾小球肾炎，其肾小球炎症的特点是免疫复合物在肾小球基底膜沉积和蛋白尿。然而，MN 肾小球炎症的分子机制尚不完全清楚。本研究旨在使用阳离子牛血清白蛋白 (cBSA) 诱导的 MN 小鼠模型研究凝聚素 (CLU) 在 MN 发展中的作用。
方法：用 cBSA 免疫野生型 C57BL/6j (WT) 和 CLU 敲除 C57BL/6j (CLU-KO) 小鼠。肾功能由血清肌酐（SCr）、血尿素氮（BUN）和尿蛋白水平确定。通过组织学分析确定 CLU、补体 C3 和免疫球蛋白 (Igs) 的 MN 和肾小球沉积物。通过酶联免疫吸附测定、蛋白质印迹和液相色谱-质谱法分析血清蛋白。
结果：在这里，我们发现在 cBSA 免疫后，CLU-KO 小鼠的 SCr 和蛋白尿增加，而 WT 小鼠则没有。同样，仅在 CLU-KO 小鼠的肾脏中发现了严重的肾小球萎缩和系膜扩张以及 C3 沉积，但在 WT 小鼠中未发现。然而，CLU-KO 和 WT 小鼠之间的血清 IgG 和补体 3 水平没有差异。在 WT 小鼠的血清中，CLU 与抗 cBSA IgG、补体（例如 C8）、蛋白酶/蛋白酶抑制剂和抗氧化蛋白结合形成复合物，并且与 WT 血清孵育减少了培养物中足细胞的补体依赖性裂解。
结论：我们的数据表明，CLU 缺乏会在抗病小鼠品系中诱导 cBSA 引发的 MN 肾小球炎症，这表明 CLU 在抵抗 MN 发展中具有抗肾小球炎症功能。这种功能可能至少部分是由于形成了 CLU-抗 cBSA Igs 复合物，该复合物可防止抗病小鼠的肾小球炎症或损伤。