Expression of lymphotactin mRNA in experimental crescentic glomerulonephritis

Lymphotactin (LTN) is the sole member of C chemokine, the third subfamily of chemokines. LTN has been shown to be a chemoattractant specific for CD8⁺ cells and/or natural killer (NK) cells, and to be produced by CD8⁺ T cells, NK cells, and mast cells. However, there have been no reports describing its expression in clinical or experimental models of diseases so far. Since glomerular infiltration of CD8⁺ cells is prominent in an animal model of crescentic glomerulonephritis induced in WKY rats by an injection of anti-glomerular basement membrane antibody, we investigated the gene expression of LTN in this model. LTN mRNA was not detected in normal glomeruli but was detected at 0.5 h after the antibody injection, which detection preceded the infiltration of CD8⁺ cells. The expression of LTN mRNA peaked on day 3 and decreased thereafter. We next studied the expression of LTN mRNA in cultured glomerular and vascular cells, and found that glomerular mesangial and vascular endothelial cells could express LTN mRNA when stimulated with IL-1β. These results indicate that the gene expression of LTN is enhanced in the animal model of glomerulonephritis and that intrinsic renal cells are the potential source of the gene expression of LTN in the kidney.     

Protease-activated receptor-2 augments experimental crescentic glomerulonephritis

Protease-activated receptor-2 (PAR-2) is a cellular receptor expressed prominently on epithelial, mesangial, and endothelial cells in the kidney and on macrophages. PAR-2 is activated by serine proteases such as trypsin, tryptase, and coagulation factors VIIa and Xa. It induces pleiotropic effects including vasodilatation, increasing plasminogen activator inhibitor (PAI-1) expression, mesangial cell proliferation, and cytokine production by macrophages. The role of PAR-2 in renal inflammation was studied in antiglomerular basement membrane antibody-induced crescentic glomerulonephritis (CGN) using PAR-2-deficient (PAR-2(-/-)) mice and wild-type littermate controls. PAR-2(-/-) mice had reduced crescent formation, proteinuria, and serum creatinine compared with wild-type mice 21 days after initiation of CGN. Glomerular accumulation of CD4(+) T cells and macrophages and the number of proliferating cells in glomeruli were similar in both groups. Glomerular fibrin deposition was significantly reduced in PAR-2(-/-) mice, and this was associated with reduced renal plasminogen activator inhibitor expression and increased renal matrix-metalloprotinase-9 activity. These results demonstrate a proinflammatory role for PAR-2 in CGN that is independent of effects on glomerular leukocyte recruitment and mesangial cell proliferation. PAR-2-mediated augmentation of renal plasminogen activator inhibitor expression and inhibition of matrix-metalloprotinase-9 activity may contribute to increased glomerular fibrin accumulation and glomerular injury in CGN.     

Glomerular expression of cell-cycle-regulatory proteins in human crescentic glomerulonephritis

To elucidate the mechanism underlying crescentic formation, we assessed the phenotypic characterization and cell-cycle protein expression in human crescentic glomerulonephritis (CRGN). Kidney tissue specimens taken from CRGN patients (10 patients with pauci-immune type rapidly progressive glomerulonephritis (RPGN), 2 patients with Henoch-Schönlein purpura nephritis, and 1 patient with IgA nephropathy) were examined immunohistochemically. Most of the cellular components of the crescents expressed cytokeratin, whereas few cells expressed PHM-5. CD68-positive cells were minor components of cellular crescents, indicating that the major principal cellular component of the crescents is made up of cells with the parietal glomerular epithelial cell (PEC) phenotype. Additionally, serial section analysis revealed that Ki-67-positive cells in the crescents were frequently cyclin-A positive and Bcl-2 positive, but seldom cyclin-B₁ positive. Moreover, the expression of cyclin-dependent kinase inhibitor p27^Kip1 was low in the cellular crescents, despite being exclusively positive in podocytes within the same section. We concluded that the major component of the cellular crescents is made up of PECs and that apparent expression of cyclins and Bcl-2 and restrained expression of p27^Kip1 may be synergistically associated with the development of cellular crescents in human CRGN.     

The IL-27 receptor has biphasic effects in crescentic glomerulonephritis mediated through Th1 responses

Despite its initially defined role as a T-helper type 1 cell (Th1)-inducing cytokine, interleukin-27 (IL-27) has complex roles in vivo. The role of IL-27 receptor (IL-27R) was defined in experimental crescentic glomerulonephritis induced by a foreign antigen, sheep globulin, which is planted in glomeruli. This lesion is dependent on a Th1 effector cellular response. Twenty-one days after the administration of sheep anti-mouse glomerular basement membrane antibody, wild-type mice developed histologic and functional inflammatory renal injury. Injury was attenuated in the absence of IL-27R α chain (IL-27Rα), the unique component of the IL-27R complex. In contrast to the attenuated renal injury on day 21, Il27ra(-/-) mice exhibited enhanced systemic immune responses, including Th1 responses, with increased IL-2-dependent interferon-γ (IFN-γ) production. However, earlier in the development of the nephritogenic immune response, IFN-γ production was decreased, with reduced early immune responses translating into attenuated renal injury. Having demonstrated decreased early Th1 systemic immune responses, followed by enhanced nephritogenic Th1 immune responses, renal injury was studied at later time points. On days 28 and 35 after injection of the nephritogenic antigen, renal injury was enhanced in Il27ra(-/-) mice compared with wild-type mice in an at least partially IFN-γ-dependent manner. In Th1-dependent autoinflammatory lesions, IL-27Rα has a biphasic role in vivo, initially pathogenic, but ultimately playing a protective role by regulating immune responses and attenuating disease.     

The roles of T cells in experimental crescentic glomerulonephritis]

A crescentic glomerulonephritis (GN) model was induced by intravenous injection of rabbit anti-mouse glomerular basement membrane (GBM) antiserum and lipopolysaccharide (LPS) in BALB/c mice, heterozygous mice and nude mice respectively, in order to detect the T-cells effects on the development of crescentic GN. The immunofluorescence and morphological changes of glomeruli in different groups of animals were compared. Intense fluorescence (4+) of rabbit IgG could be found along the GBM in liner pattern in all the animals. Intense (3(+)-4+) mouse IgG was also found along the GBM in liner pattern in the normal and heterozygous mice, but could not be identified in the nude mice. The normal mice developed typical crescentic GN, characterized by serious degeneration and destruction of GBM, fibrin deposition and crescents formation, 3-6 weeks after the injection. The heterozygous mice only developed mild proliferation of the mesangial cells in the glomeruli but there was no glomerular lesion detected in the nude mice. It suggests that the glomerular immune damage requires the participation of functional T-cell.     

Podocyte expression of MHC class I and II and intercellular adhesion molecule-1 (ICAM-1) in experimental pauci-immune crescentic glomerulonephritis

We examined immunopathological changes of podocytes in vivo which, based on in vitro studies, are thought to be relevant for the pathogenesis of renal diseases. We investigated the alterations of podocytes in local inflammation in a recently developed model of pauci-immune necrotizing crescentic glomerulonephritis (NCGN) in the rat. Frozen and plastic embedded kidney sections at different time points of the disease were incubated with antibodies directed to MHC class I, MHC class II, ICAM-1 and to relevant cytokines. Strong glomerular expression of MHC class I. II and ICAM-1 was found within 4 days, and plastic embedded sections clearly demonstrated increased cell membrane staining of podocytes. Increased glomerular interferon-gamma (IFN-γ) was detected within 24 h of induction of NCGN. and IL-IβT and tumour necrosis factor-alpha (TNF-α) were found from day 4. The potency of these cytokines to induce adhesion molecules on podocytes was investigated on rat glomerular epithelial cells in vitro. By using IACS analysis and electron microscopical techniques, we found that the in vivo expression of MHC class I, II and ICAM-I by podocytes could in vivo be simulated by IFN-γ IFN-α weakly induced MHC class I. while IL-Iβ and TNF-α were ineffective. We hypothesize that podocytes in this in vivo model are important to maintain the local inflammatory process in the glomerulus by expression of relevant adhesion molecules and MHC molecules upon stimulation with specific cytokines.     

Modulation of inflammation by slit protein in vivo in experimental crescentic glomerulonephritis

A basic conservation of cell migration guidance mechanisms in the nervous and immune systems was proposed when Slit, known for its role in axon guidance, was found to inhibit chemokine-induced leukocyte chemotaxis in vitro. These studies examined the role of Slit2 in modulating inflammation in vivo. In a rat model of glomerulonephritis, endogenous glomerular Slit2 expression fell after disease induction, and its inhibition during the early disease period accelerated inflammation. Ex vivo glomerular leukocytes showed decreased chemokine and chemoattractant-induced chemotaxis in response to Slit2, suggesting an anti-inflammatory role for glomerular Slit2. In contrast to the effect of inhibition, glomerulonephritis was ameliorated by systemic Slit2 administration. Slit2 treatment improved disease histologically and also improved renal function when given early in the disease course. Leukocytes harvested from rats receiving Slit2 showed decreased monocyte chemoattractant protein-1 (MCP)-1-mediated migration, consistent with a peripheral Slit2 effect. In keeping with this functional alteration, Slit2-mediated inhibition of RAW264.7 cell chemotaxis was associated with decreased levels of active cdc42 and Rac1, implicating GTPases in leukocyte Slit2 signaling. These findings suggest a role for endogenous Slit2 in the inhibition of chemoattractant-mediated signals, demonstrate a potentially important anti-inflammatory effect for Slit2 in vivo, and provide further evidence for conserved mechanisms guiding the process of migration in distinct cell types.     

De Novo renal expression of macrophage migration inhibitory factor during the development of rat crescentic glomerulonephritis.

Macrophage migration inhibitory factor (MIF), a key mediator of the delayed-type hypersensitivity response, was originally thought to be produced by activated T cells. However, recent studies have found that MIF is produced in many cell types including monocytes/macrophages and anterior pituitary cells. The current study has examined MIF expression in normal and diseased kidney using in situ hybridization, immunohistochemistry, and Northern blotting. MIF mRNA and protein are constitutively expressed in normal kidney, being largely restricted to tubular epithelial cells and some glomerular visceral and parietal epithelial cells. During the development of rat anti-glomerular basement membrane glomerulonephritis, a model of macrophage-mediated renal injury, there was marked de novo expression of MIF by intrinsic kidney cells including endothelium and glomerular and tubular epithelial cells. Up-regulation of MIF expression correlated with macrophage accumulation within the glomerulus (P < 0.001) and tubulointerstitium (P < 0.001). Of significance, the accumulation of macrophages was exclusively localized to areas of strong MIF expression, contributing to focal glomerular and tubulointerstitial lesion formation. In addition, up-regulation of MIF expression by parietal epithelial cells was associated with macrophage accumulation within Bowman's space and crescent formation. Combined in situ hybridization and immunostaining also demonstrated MIF expression by macrophages, T cells, and fibroblast-like cells within renal lesions. In conclusion, these data provide the first demonstration that renal epithelial cells are a major source of MIF in both normal and diseased kidney. Furthermore, the up-regulation of MIF expression may play an important role in macrophage accumulation and progressive renal injury in rat crescentic glomerulonephritis.     

In situ expression of connective tissue growth factor in human crescentic glomerulonephritis

Connective tissue growth factor (CTGF) has recently been recognized as an important profibrotic factor and is up-regulated in various renal diseases with fibrosis. The present study describes the sequential localization of CTGF mRNA and its association with transforming growth factor (TGF)-1 in human crescentic glomerulonephritis (CRGN). Furthermore, we examined the phenotype of CTGF-expressing cells using serial section analysis. Kidney biopsy specimens from 18 CRGN patients were examined using in situ hybridization and immunohistochemistry. CTGF mRNA was expressed in the podocytes and parietal epithelial cells (PECs) in unaffected glomeruli. In addition, it was strongly expressed in the cellular and fibrocellular crescents, particularly in pseudotubule structures. Serial sections revealed that the majority of CTGF mRNA-positive cells in the crescents co-expressed the epithelial marker cytokeratin, but not a marker for macrophages. Moreover, TGF-1, its receptor TGF- receptor-I, and extracellular matrix molecules (collagen type I and fibronectin) were co-localized with CTGF mRNA-positive crescents. Our results suggest that CTGF is involved in extracellular matrix production in PECs and that it is one of the mediators promoting the scarring process in glomerular crescents.     

Cyr61上调人角质形成细胞表达IL-36α的实验研究

银屑病是多种炎症因子参与的慢性炎症性皮肤疾病,其中IL-1家族分子IL-36α与银屑病发生发展密切相关。在基因敲除小鼠研究中发现,当敲除IL-36α基因后,再用咪喹莫特制备小鼠银屑病样模型时,皮损和炎症都明显减轻。我们前期研究发现促炎因子Cyr61/CCN1能通过活化角质细胞、促进趋化因子产生而加剧银屑病发生,但其是否也参与IL-36α表达与调控则未见报道。本研究采用人永生化角质形成细胞(human immortalized keratinocytes cell line,HaCaT cell)在体外研究Cyr61对IL-36α表达的调控作用。结果发现Cyr61能显著上调HaCaT细胞表达IL-36α,而且呈剂量依赖性。进一步通过siRNA干扰技术下调HaCaT细胞中Cyr61的内源性表达,发现当Cyr61表达受抑制后,IL-36α表达也被有效抑制,表明Cyr61能够介导角质细胞表达IL-36α。已有报道表明TNF-α、IL-17和IL-22能够上调角质细胞表达IL-36α,因此我们还采用TNF-α、IL-17和IL-22特异性siRNA干扰这些炎症因子的内源性表达,观察Cyr61对IL-36α的作用。结果表明这些因子被干扰后并不影响Cyr61对IL-36α表达的影响,说明Cyr61能直接促进IL-36α表达。本研究的结果提示Cyr61/CCN1还可能通过上调IL-1家族分子IL-36α而参与银屑病发生。     

新月体型肾小球肾炎中肝X受体α的表达及意义

目的 探讨肝X受体α（LXRα）在大鼠新月体型肾小球肾炎（GN)的表达及意义。方法 7周龄Wistar Kyoto 雄性大鼠40只随机分为两组。其中20只静脉注射兔抗大鼠肾小球基底膜抗体构建新月体型肾小球肾炎模型,20只作为正常对照。于注射抗体后第3、7、14、28和49天分别测定24h尿蛋白;免疫组织化学法检测第3、14、28和49天肾炎组和对照组大鼠肾组织LXRα表达;Western blotting和实时定量 PCR检测第14天肾炎肾皮质LXRα蛋白和mRNA表达变化。结果 注射抗体后第14天尿蛋白达（167.03±42.50）mg/24h;新月体百分比达65%;肾炎大鼠肾小管上皮细胞核LXRα表达明显增加;肾炎组肾皮质LXRα蛋白表达明显高于同期对照组,但肾皮质 mRNA表达则未见上调。 结论 新月体型肾炎肾小管上皮细胞核LXRα蛋白表达增强,说明肾小管LXR通路参与此型肾炎的发病过程。     

IL-1 up-regulates the expression of cytokine receptors on a factor-dependent human hemopoietic cell line, TF-1

A factor-dependent human hemopoietic cell line, TF-1, requiresinterleukln 3 (IL-3) or granulocyte/acrophage colony-stimulatingfactor (GM-CSF) for its long-term growth. We have found thatIL-4, IL-5, and IL-6 also support the growth of TF-1 and thatIL-1 enhances the proliferative effect of these cytoklnes. Augmentationby IL-1 is associated with up-regulatlon of the receptors forIL-3, IL-5, GM-CSF, and erythropoietln (Epo). IL-1 increasedthe number of binding sites forIL-3 and Epo without changingtheir affinities. In contrast, IL-1 Increased the number ofhigh affinity binding sites forGM-CSF and IL-5, whereas thetotal number of binding sites was unchanged. Chemical crossllnkingexperiments Indicated that the receptors for IL-3, IL-5, andGM-CSF were composed of two components and that the molecularmasses of the larger components of these cytokine receptorswere quite similar (120 kd). The enhanced expression of thelarger components of theIL-3, IL-5, and GM-CSF receptors byIL-1 may be responsible for IL-1-induced up-regulation of thesereceptors. These observations are consistent with the modelthat the receptors for IL-3 and GM-CSF share a common component.     

Role of mesangial Factor V expression in crescent formation in rat experimental mesangioproliferative glomerulonephritis

It has been suggested that fibrin deposition participates in the development of crescents in active glomerulonephritis (GN). In human IgA nephropathy, which is a common form of mesangioproliferative GN (MsPGN), crescent formation is occasionally observed in active disease, leading to end-stage renal failure. Factor V is a membrane-bound potent cofactor for the conversion of prothrombin to thrombin by Factor Xa. An in vivo study was conducted to clarify the contribution of local fibrin production to crescent formation in MsPGN through mesangial Factor V expression. Wistar rats were injected intravenously with rabbit anti-rat thymocyte serum. Three days after injection, mesangiolysis with intense mesangial Factor V expression was observed and immunoelectron microscopy revealed fibrin localization in mesangiolytic lesions, which had spread into the glomerular basement membrane adjacent to the destroyed mesangium, accompanied by clots in Bowman's space. Marked glomerular fibrin deposition, together with its deposition in Bowman's space and cellular crescent formation, was noted with mesangial proliferation on day 8. Specific bands for Factor V mRNA were also detected from isolated glomeruli. Fibrin deposition and cellular crescent formation were significantly suppressed by treatment with anti-Factor V antibody. These results suggest that local fibrin production, following mesangial Factor V expression, together with mesangiolysis that spreads to the adjacent glomerular basement membrane, plays a role in crescent formation in MsPGN.     

肠-肾轴在新月体肾炎发病机制中的研究进展

新月体肾炎(CreGN)是最凶险的肾小球肾炎,常常导致终末期肾病.免疫机制是其发病和决定预后最重要的因素.近年来,肠道和肠道菌群在包括CreGN在内的多种肾脏病中作用受到关注,其中"肠-肾轴"通过肠道菌群、肠源性免疫细胞等途径会直接影响全身和肾脏免疫应答及相关病理生理机制.