Sanqi Oral Solution Mitigates Proteinuria in Rat Passive Heymann Nephritis and Blocks Podocyte Apoptosis via Nrf2/HO-1 Pathway

Idiopathic membranous nephropathy (IMN) is the most common pathological type in adult nephrotic syndrome where podocyte apoptosis was found to mediate the development of proteinuria. Sanqi oral solution (SQ), an effective Chinese herbal preparation clinically used in treatment of IMN for decades, plays an important role in reducing proteinuria, but the underlying mechanisms have not been fully elucidated yet. The current study tested the hypothesis that SQ directly lessens proteinuria in IMN by reducing podocyte apoptosis. To investigate the effects of SQ, we established the experimental passive Heymann nephritis (PHN) rat model induced by anti-Fx1A antiserum in vivo and doxorubicin hydrochloride (ADR)-injured apoptotic podocyte model in vitro. SQ intervention dramatically reduced the level of proteinuria, together with the rat anti-rabbit IgG antibodies, complement C3, and C5b-9 deposition in glomerulus of PHN rats, accompanied by an elevation of serum albumin. Protein expression of synaptopodin, marker of podocyte injury, restored after SQ administration, whereas the electron microscopic analysis indicated that fusion of foot processes, and the pachynsis of glomerular basement membrane was markedly diminished. Further studies showed that SQ treatment could significantly inhibit podocyte apoptosis in PHN rats and ADR-injured podocytes, and protein levels of Cleaved Caspase-3 or the ratio of Bax/Bcl-2 were significantly decreased with SQ treatment in vivo or in vitro. Moreover, we found that the nuclear factor erythroid 2–related factor-2/heme oxygenase 1 (Nrf2/HO-1) pathway mediated the anti-apoptosis effective of SQ in podocyte. Thus, SQ mitigates podocyte apoptosis and proteinuria in PHN rats via the Nrf2/HO-1 pathway.

Curcumin Improves the Renal Autophagy in Rat Experimental Membranous Nephropathy via Regulating the PI3K/AKT/mTOR and Nrf2/HO-1 Signaling Pathways

Membranous nephropathy (MN, also known as membranous glomerulopathy) is one of the many glomerular diseases causing nephrotic syndrome. The literature indicates that autophagy is associated with the homeostasis of podocytes in glomeruli. Curcumin, the main active component in turmeric, has drawn attention for its effective bioactivities against chronic kidney disease. The current study was aimed at assessing the effects of curcumin and exploring the underlying mechanism that mediates autophagy in an animal model of passive Heymann nephritis (PHN) in rats. Passive Heymann nephritis (PHN) was induced in male SD rats by intraperitoneal injection of anti-Fx1A serum. The rats were divided into 3 groups: control ( n = 10 , normal diet), model group ( n = 10 , 0.5% sodium carboxymethylcellulose), and curcumin ( n = 10 , 300 mg/kg/d). The kidney function and oxidative stress indicators were measured using commercial diagnostic kits, and the histomorphology of renal tissues was observed. The number of podocytes was measured by immunohistochemistry. Meanwhile, the autophagosomes in podocyte were analyzed by transmission electron microscopy and the immunofluorescence assay pointing to p62, an autophagic marker. Western blot analyzed the levels of apoptosis, autophagy, PI3K/AKT/mTOR, and Nrf2/HO-1 pathway-associated proteins. The total cholesterol (TC), triglycerides (TG), creatinine (Scr), blood urea nitrogen (BUN), urine volume, and urine albumin of PHN rats were significantly reduced by the administration of curcumin and attenuated renal histomorphological changes in model rats. Meanwhile, curcumin improved the oxidative stress response by decreasing MDA and increasing SOD, GSH, and CAT levels in the kidney of PHN rats. Furthermore, curcumin significantly ameliorated the podocyte loss, along with the fusion, and increased the autophagic vacuoles compared to the PHN control rats. In addition, curcumin downregulated the expression of Bax, Caspase-3, p62, PI3K, p-AKT, and p-mTOR proteins and upregulated the Bcl-2, beclin1, LC3, Nrf2, and HO-1 levels in this animal model. The results provide a scientific basis that curcumin could significantly alleviate the development of MN by inducing autophagy and alleviating renal oxidative stress through the PI3K/AKT/mTOR and Nrf2/HO-1 pathways.

Immunology of membranous nephropathy

Accounting for about 20 to 50% of cases of primary nephrotic syndrome, membranous nephropathy (MN) is the leading cause of nephrotic syndrome in adults. A rat model created nearly 60 years ago to research the primary MN disorder, Heymann nephritis, has provided us with a plethora of important information. Recently, our knowledge about MN has dramatically progressed. Heymann nephritis and human MN are now known to share a high degree of similarity in pathogenesis. This review summarizes our current understanding of MN pathogenesis while focusing particularly on the immunological aspects.

Membranous glomerulonephritis

It has been clear for several decades from comparison with the rodent model disease Heymann nephritis that membranous glomerulonephritis (MGN) is an immune condition in which antibodies, usually autoantibodies, bind to targets on the surface of podocytes. However, the antigen in Heymann nephritis, megalin, is not present on human podocytes. The first potential antigen was identified by studying rare examples of maternal alloimmunization, leading to congenital membranous nephropathy in the infant caused by antibodies to neutral endopeptidase. More recently, the target of autoantibody formation in most patients with primary MGN has been identified to be the phospholipase A2 receptor, PLA2R. Genome-wide association studies identify predisposing genetic loci at HLADQ and at the locus encoding the autoantigen itself. So antibodies to at least two different molecular targets can cause MGN, and it seems likely that there may be other targets in secondary types of MGN, and possibly haptenized or otherwise modified molecules are implicated in drug- and toxin-induced MGN. Once antibodies are fixed, animal models and human observations suggest that complement is involved in mediating tissue damage. However, immunoglobulin G4, not thought to fix complement, is the predominant isotype in human MGN, and the mechanisms are not fully unravelled. Podocyte injury is known to cause proteinuria. In MGN, antibody fixation or cell damage may stimulate production of extracellular matrix to account for the increased GBM thickness with ‘podocyte type’ basement membrane collagen isoforms, and ultimately cell death and glomerulosclerosis.

MORPHOFUNCTIONAL STATEOFKIDNEYS OF RATSAFTER INJECTIONOFPLACENTAL CRYOEXTRACT IN HEYMANN NEPHRITIS

Изучение иммунного механизма поражения почек на модели нефрита Хеймана (НХ), вызывающего изменения сосудов почечных клубочков, их морфологических и морфометрических показателей, представляют значительный интерес Цель работы: изучить влияние введения криоэкстракта аллогенной плаценты (КЭП) на функциональные и морфологические показатели почек при экспериментальном НХ. Материал и методы. Крысы-самцы 4-х месячного возраста были разделены на 3 группы: I – интактные; 2 – животные с моделью НХ; 3 – животные с моделью НХ, которым на 28 день после иммунизации 3 раза за неделю внутримышечно вводили КЭП. Животных 2-й и 3-й групп выводили из эксперимента на 45 и 60 сутки. Исследованы биохимические, функциональные и морфологические показатели почек на всех стадиях развития НХ и после введения КЭП. Результаты и их обсуждение. У животных 2 и 3 группы на 28-е сутки возрастало количество циркулирующих иммунных комплексов (ЦИК) в крови и иммунных депозитов на базальных мембранах клубочков, что сопровождалось нарушением их структуры и выделительной функции почек. Выявлены морфометрические различия в размерах клубочков в динамике НХ. Через 60 суток в ткани почек экспериментальных животных наблюдались признаки фокального мезангиального пролиферативного гломерулонефрита как при введении КЭП, так и без него. При введении КЭП отложения депозитов иммунных комплексов не обнаруживалось. Выводы: При НХ на 28 сутки отмечено возрастание ЦИК в крови, отложение депозитов иммунных комплексов на базальных мембранах капилляров клубочков, сужение их просвета и пролиферация мезангиоцитов, что сопровождалось нарушением выделительной функции почек. Введение КЭП нормализовывало функцію почек, снижало к 45 суткам уровни комплемента ЦИК до показателей нормы.