Parietal epithelial cells and podocytes in glomerular diseases

In recent years, it has become apparent that parietal epithelial cells (PECs) play an important role within the renal glomerulus, in particular in diseased conditions. In this review, we examine current knowledge about the role of PECs and their interactions with podocytes in development and under physiological conditions. A particular focus is on the crucial role of PECs and podocytes in two major glomerular disease entities. In rapidly progressive glomerulonephritis, PECs and podocytes proliferate and obstruct the tubular outlet, resulting in loss of the affected nephron. In focal and segmental glomerulosclerosis, PECs become activated and invade a segment of the glomerular tuft via an adhesion. From this entry site, activated PECs displace podocytes and deposit matrix. Thus, activated PECs are involved in inflammatory as well as degenerative glomerular diseases, which both can lead to irreversible loss of renal function.     

Regulation of phosphoinositide hydrolysis and cytosolic free calcium induced by endothelin in human glomerular epitheial cells

The regulation of the inositide signalling pathway and [Ca²⁺]_iby endothelin (ET) peptides was investigated in human glomerularepithelial cells in culture. Endothelin-1 and -2 induced anaccumulation of inositol phosphates in a time- and dose-dependentmanner. The baseline of [Ca²⁺]_i, in glomerular epithelial cellswas 109±2.8 nmol/l, n=60. Endothelin-l (ED₅₀: approx.3x10 mol/l) caused a rapid and transient rise in [²⁺]_i as detectedby fura-2 microfluorimetry studies. The endothelin-l-inducedinositol phosphate accumulation was inhibited by the selectiveET_A recep tor antagonist BQ123. Endothelin-3 and BQ3020, a selectiveET_B receptor agonist, showed no effect. The results suggestan ETA-mediated pathway. This study demonstrates an ET_A-mediatedtransmembrane signalling via phospholipase C with consecutiveelevation of inositol phosphates and intracellular calcium.Since endothelin peptides contribute to both normal renal functionand renal dysfunction, this study adds further knowledge onglomerular cell regulation.     

The interaction of glomerular mesangial cells and epithelial cells

The interaction of cells within the glomerulus plays an important role in the development and progression of glomerular disease. To investigate the interaction of glomerular mesangial cells (GMC) and epithelial cells (GEC), and mediator(s) of this interaction, we investigated the effect of Adriamycin (doxorubicin hydrochloride)-induced (ADR) rat GMC-conditioned medium (GMC-CM) on the incorporation of ³⁵S, ³H-leucine, and ³H-thymidine in normal rat GEC, as well as ³H-thymidine uptake by normal rat GMC in response to ADR-rat GEC-CM. In addition, changes in the responsiveness to interleukin-6 (IL-6) and the products of IL-6 were assessed in ADR-rat GMC. The results showed that: (1) GMC-CM of ADR-rat with heavy proteinuria stimulated GEC proliferation and the synthesis of sulfated compounds and protein, while the GEC-CM of ADR-rat from the same nephrotic period increased GMC proliferation; (2) the ADR-rat GMC had altered responsiveness to IL-6 and its products. The stimulation index results demonstrated the interaction of GMC and GEC in the ADR-induced rat model, and that this interaction related closely to the degree of proteinuria and was mediated by soluble products of the damaged glomerular cell. Received March 29, 1996; received in revised form July 1, 1997; accepted July 2, 1997     

Shiga toxin-1 affects nitric oxide production by human glomerular endothelial and mesangial cells

Acute renal failure hallmarks the pathogenesis of the epidemic form of hemolytic uremic syndrome (D+HUS), which is caused by E. coli strains that produce Shiga-like toxin (Stx). In this study, we investigated the influence of Stx-1 on nitric oxide (NO) production by human glomerular microvascular endothelial cells (GMVEC) and human mesangial cells. NO synthesis by human mesangial cells is in the micromolar range and that of GMVEC in the picomolar range. Stx-1 reduced NO production in non-stimulated GMVEC (5 nmol/l Stx-1 required) without inhibition of protein synthesis. In non-stimulated and TNFα-pretreated mesangial cells, NO production was reduced with a maximal reduction at 10 fmol/l shiga toxin. The cellular iNOS antigen content in mesangial cells was reduced in a concentration-dependent way (10 fmol/l-100 pmol/l), while partial inhibition of protein synthesis required 10 nmol/l Stx-1 in these cells. Our in vitro data suggest that Stx may reduce NO synthesis during the course of HUS development, contributing to the aggravation of the thrombotic microangiopathy and renal failure as observed in HUS.     

精甘天丝四肽对人肾小球系膜细胞肌动蛋白及凋亡的影响

观察精-甘-天-丝(RGDS)四肽对肾小球系膜细胞肌动蛋白及凋亡的影响,以探讨细胞外基质(ECM)-整合素-细胞骨架的相互作用机制。方法 共聚焦显微镜观察肾小球系膜细胞肌动蛋白微丝的变化;以流式细胞仪和DNA电泳方法检测细胞凋亡。结果 用RGDS肽处理2小时后,系膜细胞开始由梭形变为圆形或卵圆形,同时细胞质的肌动蛋白微丝亦由弥漫分布变为聚集成团,居于细胞质一侧,形成着边现象,这些细胞继而脱壁、悬浮于培养上清中,脱落细胞经碘化丙啶染色见细胞核固缩、破碎。至第10小时RGDS处理组的系膜细胞大都脱壁,脱落细胞的DNA电泳呈现梯形条带,流式细胞仪分析显示处理组系膜细胞中出现了低二倍体细胞群(A_0峰),证实处理组的脱落细胞发生了细胞凋亡。在实验观察期间对照组的系膜细胞始终呈贴壁状态生长,细胞质肌动蛋白微丝呈弥漫分布。结论 RGDS肽可以使肾小球系膜细胞细胞骨架肌动蛋白微丝分布异常,导致肾小球系膜细胞变形、脱壁和凋亡。     

缬沙坦对人肾系膜细胞清道夫受体表达的影响

目的 探讨缬沙坦对人肾小球系膜细胞（HMC）表达清道夫受体（SR）水平的影响。方法 应用流式细胞仪和逆转录-聚合酶链反应（RT-PCR）检测体外培养HMC在佛波酯（PMA）刺激后缬沙坦对HMCSR的mRNA的表达。结果 体外培养的HMC在PMA刺激下能大量表达SRmRNA，呈剂量依赖性，其基因序列测定结果与巨噬细胞所表达的SR完全相同。缬沙坦能抑制PMA诱导的HMCSR表达，且呈剂量及时间依赖性。结论 矍有表达SR的潜力，缬沙坦能明显抑制HMCSR在PMA诱导下的表达。这可能是其发挥治疗作用的机制之一。     

脂蛋白（a）对肾小球系膜细胞的作用

目的探讨脂蛋白（ａ）［Ｌｐ（ａ）］对肾小球系膜细胞（ＧＭＣ）的作用。方法将体外培养的系膜细胞，加脂蛋白（ａ）刺激后，测定细胞生长率和细胞上清中血小板活化因子（ＰＡＦ）、肿瘤坏死因子（ＴＮＦ）、乳酸脱氢酶（ＬＤＨ）及纤维连结蛋白（ＦＮ）水平，并以未经刺激者作对照。结果经脂蛋白（ａ）刺激４８小时，在终浓度５～２０ｍｇ／Ｌ时细胞生长率轻度增加，而在５０～４００ｍｇ／Ｌ时细胞生长率明显下降。刺激１８小时，细胞上清中ＰＡＦ的水平明显高于对照，且与脂蛋白（ａ）浓度呈明显正相关（ｒ＝０．９３７，Ｐ＜０．０１）；Ｌ９２９细胞的杀伤率有所增加，但未达５０％；ＬＤＨ的水平在脂蛋白（ａ）１００ｍｇ／Ｌ以下时有所增加；刺激１８、４８、７２小时后的细胞上清纤维连结蛋白均为阴性。结论脂蛋白（ａ）对系膜细胞体外增殖有低浓度轻度促进、高浓度抑制的双向作用，对细胞ＰＡＦ的产生具有浓度依赖的促进作用，并能增加细胞上清中ＬＤＨ及ＴＮＦ水平，因而可通过多种途径介导肾小球损伤。     

Identification of endothelin receptors in normal and hyperplasic human prostate tissues

Specific endothelin-1 (ET1) binding sites have been demonstrated in membranes derived from normal (NP) and benign hyperplasic (BPH) human prostate using an ¹²⁵I-ET1 binding assay. ¹²⁵I saturation experiments and Scatchard analysis demonstrated the existence of a homogeneous population of binding sites with high affinity (Kd_app) and density (B_max), respectively, 106 ± 15 pM and 1086 ± 399 fmol/mg protein for NP (n = 5) and 168 ± 26 pM and 964 ± 445 fmol/mg protein for BPH (n = 5). We demonstrated the presence of two subtypes of ET1 receptors, ETA and ETB, by means of the following ET1 competitors: ET2, ET3, and BQ123 (which is selective for the ETA receptor), and IRL1620 and sarafotoxine c (S6c) (which are selective for the ETB receptor). The displacement curves allowed us to conclude that the large majority (85%) of the ET1 receptors in normal and hyperplasic human prostate are of the A subtype. © 1996 Wiley-Liss, Inc.     

内皮素对人肾小球系膜细胞表达细胞粘附分子的影响

目的 探讨内皮素-1(ET1-1)对体外培养的人肾小球系膜细胞表达细胞间粘附分子-1(ICAM-1)和血管细胞粘附分子-1(VCAM-1)的调节作用。方法 利用Northern杂交技术和细胞ELISA方法分别从mRNA和蛋白质两个水平观察ICAW-1和VCAM-1的变化。结果 在正常培养条件下,人肾小球系膜细胞仅低水平表达一定量的ICAM-1、VCAM-1的mRNA和蛋白质;ET-1(10~(-7)mol)刺激后,这两种细胞粘附分子的mRNA表达迅速上调,且随后其相应蛋白质表达也显著增加并呈时间依赖性。结论 提示ET-1对粘附分子表达的促进作用可能在传小球疾病的发生中具有重要意义。     

Human mesangial cells synthesize interleukin 1 alpha but not interleukin 1 beta, interleukin 1 receptor antagonist, or tumour necrosis factor.

There is controversy over whether mesangial cells synthesize and release IL-1 and TNF, and many of the positive experiments were performed before specific reagents and molecular probes were available. Consequently we have stimulated human mesangial cells using protocols known to stimulate the synthesis of other cytokines. No mRNA for IL-1 beta or TNF could be detected in quiescent or proliferating mesangial cells irrespective of whether they had been exposed to cytokines or not. In contrast mRNA for IL-1 alpha was detected in cells stimulated with IL-1 beta 10 ng/ml or with TNF 500 ng/ml; IL-1 alpha was also detected in cell lysates from stimulated mesangial cells. We could not detect mRNA for IL-1 receptor antagonist in any of the cell preparations. These results suggest that mesangial cells are unlikely to be a major source of IL-1 beta or TNF.     

霉酚酸对小鼠肾小球系膜细胞增殖及分泌单核细胞趋化因子-1的影响

目的　探讨霉酚酸在体外对小鼠肾小球系膜细胞增殖及其分泌单核细胞趋化因子1的影响。方法　在小鼠肾小球系膜细胞的培养基中加入不同浓度的霉酚酸(0.1、1、5 及10μmol/L),培养24 h,采用四甲基偶氮唑盐掺入法,以酶联免疫检测仪测定各组570 nm波长的吸光度值,以计算肾小球系膜细胞的存活率;另在肾小球系膜细胞的培养基中加入不同浓度的霉酚酸(0、0.5及2.5μmol/L),并同时加入肿瘤坏死因子(20 ng/ml)、白细胞介素1β(2 ng/ml)及γ干扰素(10 ng/ml)刺激4 h,收集上清液,测定单核细胞趋化因子1浓度,并行淋巴细胞迁移实验。结果　培养基中加入霉酚酸者,肾小球系膜细胞的增殖受到明显的抑制,并呈剂量依赖性;在肿瘤坏死因子、白细胞介素1β及γ干扰素的刺激下,培养的肾小球系膜细胞分泌单核细胞趋化因子1 明显增加,加入霉酚酸后,能明显抑制单核细胞趋化因子1的分泌(P<0.01),并能抑制淋巴细胞的迁移。结论　霉酚酸在体外可以抑制肾小球系膜细胞的增殖及趋化性细胞因子的分泌,这为临床上研究慢性移植肾肾病的发生和发展提供实验依据。     

Discrepant effects of vasoconstrictors on the growth of early passaged cultured rat mesangial cells

Summary: Mesangial cell growth stimulation by endothelin (ET) and arginine vasopressin (AVP) has been reported, but only in studies using late (3 times) pasaged cells. In the present study, we examined the effects of ET, AVP and platelet activating factor (PAF) on the proliferation of early (<3 times) passaged cultured rat mesangial cells which maintained their original characteristics. Cell growth was estimated by [³H]-thymidine incorporation into DNA and by counting cell nuclei. After 48 h preincubation in minimal essential medium containing 0.5% fetal calf serum, ET-1 (1-100 nmol/L), AVP (100 pmol/L-1 μmol/L) or PAF (1–100 nmol/L) was added to the incubation medium. In contrast to studies using late passaged cells, ET-1 attenuated and AVP did not increase thymidine uptake (ET-1: 18.4% inhibition at 10 nmol/L) or cell counts in early passaged cells, while the growth stimulatory effects of these agents were reproduced in late passaged cells. Platelet activating factor showed definite stimulation of cell growth in both early and late passaged cells in a dose-dependent manner. These data strongly suggest that ET-1 attenuates, and AVP does not stimulate, the cell growth of original mesangial cells. the PAF-induced cell growth seems to be the constant feature of mesangial cells in vivo.     

TRPC1通道参与调节肾小球系膜细胞的收缩

目的探讨离体和在体情况下TRPC1通道是否参与肾小球系膜细胞的收缩。方法通过计算细胞表面积来观察肾小球系膜细胞的收缩情况。分别利用荧光标记的菊粉和对氨基马尿酸（PAH）的血浆清除率计算大鼠肾小球滤过率（GFR）和肾血浆流量。结果在肾小球系膜细胞的培养液中加入血管紧张素Ⅱ（AngⅡ）10min后，细胞表面积减少（37．2％±4．0％），系膜细胞的收缩反应可因TRPC1基因敲除而受到显著抑制（20．1％±3．0％）。给大鼠注射AngⅡ（1．7ng·min^-1·100g^-1BW）可引起GFR下降，注射TRPC1抗体（300μg／L）显著抑制AngⅡ引起GFR下降（P〈0．05）。但与TRPC1抗体相同浓度的免疫球蛋白，不能抑制AngⅡ引起的GFR下降。另外，TRPC1抗体不影响AngⅡ引起的血压改变和肾血流量的下降。结论本实验表明TRPC1通道在调节肾小球系膜细胞收缩功能方面发挥了重要的作用。     

Aldosterone induces CTGF in mesangial cells by activation of the glucocorticoid receptor.

BACKGROUND: Aldosterone contributes substantially to cardiac and renal injury by acting on target cells not involved in the regulation of salt and water balance. The profibrotic protein connective tissue growth factor (CTGF) has been identified as one of the target proteins of aldosterone. However, the molecular mechanisms of aldosterone-mediated CTGF induction have not been characterized. METHODS: Mesangial cells were treated with aldosterone or dexamethasone. CTGF expression was characterized at the mRNA and protein level. Translocation of the glucocorticoid receptor (GR) was detected by immunocytochemistry and by Western blotting. RESULTS: Aldosterone and dexamethasone induced CTGF at the mRNA and protein level in a time- and concentration-dependent manner. Specific antagonists of the mineralocorticoid receptor, spironolactone, canrenoate or eplerenone, did not inhibit CTGF induction. However, inhibition of the GR by RU486 prevented dexamethasone-as well as aldosterone-induced CTGF expression, indicating the importance of the GR in aldosterone-mediated regulation of CTGF. This notion was confirmed by translocation of the GR to the nucleus upon stimulation with aldosterone. CONCLUSIONS: CTGF is a functional target of aldosterone in mesangial cells, but aldosterone-induced CTGF gene expression is not directly mediated by the mineralocorticoid receptor.     

雷帕霉素对炎性反应状态下肾小球系膜细胞内脂质稳态的影响

Objective To investigate the effect of rapamycin on cholesterol homeostasis of glomerular mesangial cells and the underlying mechanism. Methods Glomerular mesangial cell line (HMCL) cells were cultured and divided into control group, IL-1β group and different concentration rapamycin groups. Intracellular cholesterol accumulation was observed and measured by oil O staining and HPLC. Real-time quantitative PCR and Western blot were used to detect the mRNA and protein expression of LDLR, PPARγ, LXRα, ABCA1 in HMCL after the treatment with IL-1β and rapamycin. Results Rapamycin had no significant influence on intracellular cholesterol concentration under normal condition. IL-1β significantly increased the intracellular cholesterol concentration by 143％ of control (P<0.05), and 10, 50, 100 ?滋g/L rapamycin could significantly inhibit the effect of IL-1β (87％, 116％, 96％ of control respectively, all P<0.05). Rapamycin could suppress the increased expression of LDLR caused by IL-1β on both mRNA and protein level in a dose-dependent manner（P<0.01）. Rapamycin dose-dependently up-regulated the reduced mRNA and protein expression of ABCA1, the decreased mRNA expression of PPARγ and LXRα induced by IL-1β as well (P<0.01）. Conclusion Rapamycin may contribute to the maintenance of intracellular cholesterol homeostasis in glomerular mesangial cells under inflammatory state by both reducing cholesterol uptake and promoting cholesterol efflux.