Epithelial membrane antigen in normal and proteinuric glomeruli and in damaged proximal tubules

Epithelial membrane antigen was detected in normal glomeruli by a polyclonal antiserum to the antigen and by the monoclonal antibodies Ca 1, DAKO-EMA and HMFG 2, but not HMFG 1, using an indirect immunoperoxidase method. The antigen was in the form of a thin ring or collar at the junction of glomerulus and tubule. In a series of 47 renal biopsies from patients with proteinuria, the antigen could still be seen in glomeruli, provided that there were adequate numbers of glomeruli in the sections. The main object of study was the glomerular tip lesion, in which tip adhesions were seen to be just adjacent to the patch of epithelial membrane antigen. This suggested that the antigen may be important in pathogenesis of the lesion. Normal proximal tubules did not express epithelial membrane antigen but it was detected on the luminal border of acutely damaged proximal tubules. Thus the distribution of epithelial membrane antigen in the kidney is more complex than was previously thought.     

肾病综合征患儿红细胞及肾小球阴电荷的变化

用Ａｌｃｉａｎ蓝染色法及电子计算机图象分析处理胶样铁染色肾脏标本，分别测定了肾病综合征患儿红细胞阴电荷及肾小球多阴离子含量，并分析了两种生物膜电荷变化的关系。结果表明：肾病时红细胞阴电荷量明显下降，且与疾病的活动情况有关；肾病时肾小球多阴离子量也显著下降，并与红细胞阴电荷的变化平行。在肾病患者未发现不同病理及临床类型间两种生物膜电荷量有显著差别。     

Functional endothelin 1 receptors on human glomerular podocytes and mesangial cells.

To determine if endothelin 1 (Et1) receptors are present in human glomeruli, and which glomerular cells possess these receptors, 125I Et1 binding to isolated glomeruli and cultured glomerular mesangial and epithelial cells was studied. The latter were identified as podocytes. We demonstrated that Et1 binds specifically and reversibly to isolated human glomeruli and to cultured glomerular mesangial and epithelial cells. Scatchard analysis of competitive inhibition of 125I Et1 binding gave the following results (m +/- SEM, n = 3): isolated glomeruli, Kd = 4.2 +/- 2.1 x 10(-10) M, Bmax = 8.1 +/- 1.2 x 10(10) sites/mg protein; mesangial cells, Kd = 5.2 +/- 1.5 x 10(-10) M, Bmax = 1.87 +/- 0.49 x 10(4) sites/cell; epithelial cells, Kd = 7.2 +/- 1.5 x 10(-10) M, Bmax = 2.46 +/- 0.15 x 10(4) sites/cell. These receptors seem to be functional, since in both mesangial and epithelial cells Et1 induces a rapid and transient increase in intracellular [Ca2+]i. All these results indicate that Et1 may regulate glomerular filtration rate through an autocrine-paracrine pathway on mesangial cells and on podocytes.     

Glomerular basement membrane thinning in adults: clinicopathological correlations of a new diagnostic approach.

We have studied glomerular basal laminar thickness in biopsy material, using a simple technique involving 16 selected measurements per case. Twenty-nine biopsied cases of adult glomerular haematuria were examined together with 'diseased' controls represented by a variety of glomerulopathies including minimal-change disease and IgA nephropathy. 'Normal' control populations were provided by 13 patients with acute-onset renal failure of non-glomerular origin and nine patients undergoing nephrectomy. Analysis of groups determined by the presence or absence of haematuria, the degree of proteinuria and presence or absence of a diagnostically characteristic immunofluorescence pattern showed that the nine patients with haematuria and proteinuria of less than 200 mg/24 h represented a distinct subpopulation with a mean membrane thickness of 225 nm compared to the control mean of 343 nm (P less than 0.0001). All members of this subpopulation had mean values below an arbitrary cut-off value of 270 nm. Within other specific disease categories, sporadic cases had mean membrane thicknesses below this critical value, indicative of an overlap of pathologies. On short-term follow-up there is no evidence that the 'pure' thin-membrane population are subject to any deterioration in renal function. It is of further interest that eight of nine thin-membrane 'syndrome' cases were O Rh positive. This finding may provide a starting point for investigation of a specific genetic defect.     

Cytokines, T cells and proliferative glomerulonephritis

SUMMARY: The glomerulus, by virtue of its functional role as a filter, is vulnerable to injury in the context of inflammatory responses, with the potential involvement of a number of different inflammatory processes. Recent work has provided insights into the role of T cells in proliferative glomerulonephritis, particularly in determining patterns of injury and outcomes in cresentic forms of glomerulonephritis. Experimental models have shown that in proliferative glomerulonephritis, cytokines play important roles both in determining T helper cell phenotype (particularly in the context of T helper cell 1 responses) and (from T cell themselves) in activating effectors of injury. Conversely, some cytokines regulate T cell responses to limit injury. There is an emerging role in other areas of the inflammatory response for cytokines traditionally thought to be involved predominantly in the injurious T cell response. These include regulatory T cells, the interaction between resident renal cells and leukocytes and the development of renal fibrosis. Cytokine-based therapies are entering clinical practice in other diseases. However, a number of challenges and questions remain to be answered before translating basic understanding into clinical practice in immune glomerular injury.     

知母皂苷元通过AMPK-mTOR-ULK1途径抑制肾小球系膜基质合成和激活自噬治疗糖尿病肾病的研究

目的探究知母皂苷元基于AMPK-mTOR-ULK1途径对糖尿病肾病大鼠的干预作用。方法将40只SD大鼠随机分为对照组、模型组、知母皂苷元低剂量组、知母皂苷元高剂量组和二甲双胍组,每组8只。除对照组外,其余组采用高脂饲料饲喂联合链脲佐菌素(STZ)诱导建立糖尿病模型。知母皂苷元低、高剂量组大鼠分别灌胃20 mg/(kg·d)和60 mg/(kg·d)知母皂苷元,二甲双胍组灌胃500 mg/(kg·d)二甲双胍,其余组灌胃等量生理盐水,连续8周。检测各组大鼠血糖、24 h尿蛋白、尿素氮、肌酐水平,HE染色和PAS染色观察大鼠肾脏病理组织学变化,检测肾组织中α-SMA表达情况和Ⅰ型胶原、Ⅳ型胶原、纤维连接蛋白含量,Western blot法检测肾组织中Beclin-1、LC3、AMPK、p-AMPK、mTOR、p-mTOR、ULK1和p-ULK1表达量。结果与对照组比较,模型组大鼠血糖、24 h尿蛋白、尿素氮、肌酐水平和肾重/体重均显著增高(P均<0.05);肾脏组织结构紊乱,肾小球基底膜增厚;肾小球体积、系膜基质面积、α-SMA阳性面积和Ⅰ型胶原、Ⅳ型胶原、纤维连接蛋白含量及p-mTOR/mTOR表达量均显著升高(P均<0.05),Beclin-1、LC3-Ⅱ/LC3-Ⅰ、p-AMPK/AMPK、p-ULK1/ULK1表达量均显著降低(P均<0.05)。与模型组比较,二甲双胍组大鼠血糖和知母皂苷元低剂量组、知母皂苷元高剂量组、二甲双胍组大鼠24 h尿蛋白、尿素氮、肌酐水平和肾重/体重均显著降低(P均<0.05);肾脏病理组织学变化得到明显改善;肾小球体积、系膜基质面积、α-SMA阳性面积和Ⅰ型胶原、Ⅳ型胶原、纤维连接蛋白含量及p-mTOR/mTOR表达量均显著降低(P均<0.05),Beclin-1、LC3-Ⅱ/LC3-Ⅰ、p-AMPK/AMPK、p-ULK1/ULK1表达量均显著增高(P均<0.05)。结论知母皂苷元可通过AMPK-mTOR-ULK1途径抑制肾小球系膜基质合成和激活自噬改善大鼠糖尿病肾病。     

Sorbinil does not prevent galactose-induced glomerular capillary basement membrane thickening in the rat

Summary We investigated the role of the polyol pathway in the pathogenesis of glomerular basement membrane thickening in galactosaemic rats, an animal model that develops basement membrane lesions comparable to those of human diabetic subjects. Normotensive Wistar-Kyoto rats fed a 30% galactose diet for nine months developed significant glomerular basement membrane thickening by comparison with rats on a control test diet (p=0.008). However, addition of an aldose reductase inhibitor, sorbinil (250 mg/kg diet), to the galactose diet did not prevent the increase in glomerular basement membrane thickness. Furthermore, by using a quantitative electron microscopic immunogold technique, we examined biochemical alterations in the composition of glomerular basement membranes in this animal model. The labelling density (comparable to relative concentration) of collagen type IV in thickened glomerular basement membranes of galactosaemic animals was significantly increased by comparison to those of control rats (p=0.015). However, there was no significant difference in labelling densities of laminin and heparan sulfate proteoglycan core protein of these animals. Thus, our results indicate that an increase in glomerular basement membrane thickness accompanied by an increase in the labelling density of collagen type IV occurs in the galactosaemic rats, but this thickening is not prevented by sorbinil at the dose used in this experiment. Our study raises the strong possibility that glomerular basement membrane thickening in galactosaemic rats may not be due to excessive polyol pathway activity.     

New insights into human minimal change disease: lessons from animal models

The pathogenesis of minimal change disease (MCD), considered to be the simplest form of nephrotic syndrome, has been one of the major unsolved mysteries in kidney disease. In this review, recent landmark studies that have led to the unraveling of MCD are discussed. A recent study now explains the molecular basis of major clinical and morphologic changes in MCD. Overproduction of angiopoietin-like 4 (ANGPTL4) in podocytes in MCD causes binding of ANGPTL4 to the glomerular basement membrane, development of nephrotic-range selective proteinuria, diffuse effacement of foot processes, and loss of glomerular basement membrane charge, but is not associated with changes shown by light microscopy in the glomerular and tubulointerstitial compartments. At least some of this ability of ANGPTL4 to induce proteinuria is linked to a deficiency of sialic acid residues because oral supplementation with sialic acid precursor N-acetyl-d-mannosamine improves sialylation of podocyte-secreted ANGPTL4 and significantly decreases proteinuria. Animal models of MCD, recent advances in potential biomarkers, and studies of upstream factors that may initiate glomerular changes also are discussed. In summary, recent progress in understanding MCD is likely to influence the diagnosis and treatment of MCD in the near future.