Intrinsic Renal Cells Research Articles

Signaling danger: toll-like receptors and their potential roles in kidney disease.

Toll-like receptors (TLR) are an emerging family of receptors that recognize pathogen-associated molecular patterns and promote the activation of leukocytes and intrinsic renal cells. Ligands of the TLR include exogenous microbial components such as LPS (TLR4), lipoproteins and peptidoglycans (TLR1, -2, -6), viral RNA (TLR3), bacterial and viral unmethylated cytosin-guanosin dinucleotide (CpG)-DNA (TLR9), and endogenous molecules including heat-shock proteins and extracellular matrix molecules. Upon stimulation, TLR induce expression of inflammatory cytokines or costimulatory molecules via the MyD88-dependent and MyD88-independent signaling pathways shared with the interleukin-1 receptors. TLR are differentially expressed on leukocyte subsets and non-immune cells and appear to regulate important aspects of innate and adaptive immune responses. Tubular epithelial cells are among the non-immune cells that express TLR1, -2, -3, -4, and -6, suggesting that these TLR might contribute to the activation of immune responses in tubulointerstitial injury (e.g., bacterial pyelonephritis, sepsis, and transplant nephropathy). In addition, TLR9 has been shown to be involved in antigen-induced immune complex glomerulonephritis and lupus nephritis by regulating humoral and cellular immune responses. TLR are evolutionary conserved regulators of innate and adaptive immune responses. It is likely that TLR are involved in many if not all types of renal inflammation. Here the authors provide an overview on the biology of TLR, summarize the present data on their expression in the kidney, and provide an outlook for the potential roles of TLR in kidney disease.

Renal expression of matrix metalloproteinases in human ANCA-associated glomerulonephritis.

Expression of matrix metalloproteinases (MMPs) by infiltrating and intrinsic renal cells is increased in inflammatory conditions, and may correlate with disease activity of glomerulonephritis. We analysed renal expression of MMPs, tissue inhibitor of metalloproteinase-1 (TIMP-1) and markers of neutrophil and monocyte infiltration in renal biopsies of patients with active anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis. Immunohistochemical expression of MMP-2, -3, -9, TIMP-1, the neutrophil- and monocyte-derived MMP activators cathepsin G, neutrophil elastase and myeloperoxidase (MPO), and the monocyte marker CD14 was determined in renal biopsies of active proteinase 3 (PR3)-ANCA (n = 7) and MPO-ANCA (n = 6) associated glomerulonephritis, and in normal renal tissue (n = 4). Double labelling experiments of MMPs and TIMP-1 were performed with MPO and CD68, labelling neutrophils and macrophages. MMP-2-, MMP-3-, MMP-9- and TIMP-1-positive cells were detected in ANCA-associated glomerulonephritis in glomeruli with active inflammation (cellular crescents or fibrinoid necrosis), only occasionally in normal appearing glomeruli, and not in sclerotic glomeruli and positive cells were found in the tubulo-interstitium. MMPs and TIMP-1 were expressed predominantly by MPO-and CD68-positive cells. In normal renal tissue, no expression was detected, with the exception of weak mesangial staining for MMP-2. In ANCA-associated glomerulonephritis, glomerular MMP-2, -9 and TIMP-1 correlated with glomerular cathepsin G expression, while the number of MMP-9-expressing cells per glomerulus correlated with the percentage of crescentic glomeruli. Tubulo-interstitial expression of MMPs correlated with all markers of neutrophil and monocyte infiltration, and interstitial MMP-9 and TIMP-1 expression correlated with renal function at the time of renal biopsy. Expression of glomerular and interstitial MMP-2, -3, -9 and TIMP-1 is increased in active ANCA-associated glomerulonephritis and correlates with inflammatory activity.

P38 Mitogen-activated protein kinase activation and cell localization in human glomerulonephritis: correlation with renal injury.

Activation of the p38 mitogen-activated protein kinase (MAPK) signal transduction pathway plays an important role in the inflammatory response. It was postulated that p38 MAPK is important in the pathogenesis of human glomerulonephritis and contributes to the development of renal injury. p38 MAPK activation was examined by immunodetection for dual phosphorylated p38 (p-p38) in normal human kidney and 77 renal biopsy specimens encompassing a wide spectrum of glomerulonephritides. In normal kidney, p-p38 immunostaining was restricted to the nuclei of a small number of podocytes, parietal epithelial cells, and tubular cells. There was a dramatic increase in the number of p-p38-positive cells in glomeruli and tubules in nonproliferative and proliferative glomerulonephritis and a substantial increase in the number of interstitial p-p38-positive cells in proliferative glomerulonephritis. Double immunostaining identified p38 activation in intrinsic renal cells (podocytes and endothelial and tubular cells), infiltrating macrophage and neutrophils, and myofibroblasts. Renal failure correlated with the number of p-p38-positive glomerular, tubular, and interstitial cells. Proteinuria correlated with the number of p-p38-positive tubular and interstitial cells and the number of p-p38-positive podocytes in nonproliferative glomerulonephritis. Furthermore, glomerular p38 activation correlated with segmental proliferative and necrotic lesions, and interstitial p38 activation correlated with the degree of interstitial inflammation. In conclusion, activation of p38 MAPK in intrinsic renal cells and infiltrating leukocytes correlated with renal dysfunction and histopathology, suggesting an important pathogenic role for p38 MAPK activation in human glomerulonephritis.

Transgene of MIF induces podocyte injury and progressive mesangial sclerosis in the mouse kidney

Recent evidence suggests that macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that plays a pathogenic role in glomerulonephritis. Renal expression of MIF is up-regulated in infiltrating and intrinsic renal cells, which include glomerular epithelial cells. The aim of the current study was to further clarify the role of MIF produced by podocytes in the process of renal disease. We generated transgenic mice carrying a murine MIF cDNA driven by cytomegalovirus enhancer and beta-actin/beta-globin promoter, a hybrid promoter transactivated in podocytes in vivo. MIF expression was markedly up-regulated in podocytes in neonatal and adult transgenic kidneys. A longitudinal study of the MIF transgenic mice demonstrated a progressive matrix increase in mesangium accompanied by collagen IV accumulation, representing no significant glomerular cell hypercellularity. The glomeruli in transgenic kidney were not accompanied by influx of macrophages and T cells at the early stage of disease progression. Although a significant number of the mice showing higher expression of MIF died from renal failure at 8 weeks, most of them survived with significant proteinuria and progressive renal failure. Podocytes of transgenic mice frequently underwent characteristic ultrastructural changes, such as cell flattening, contracted foot processes, and villous transformation. In addition, immunohistochemical expression of synaptopodin, an actin-associated protein distributed in differentiated podocyte foot process, was significantly attenuated in transgenic kidney. Our results indicate that podocyte-expressed MIF could induce an injury of podocytes themselves, thereby accelerating the progression of glomerulosclerosis and leading to end-stage renal failure.

Antifibrotic effect of the Chinese herbs, Astragalus mongholicus and Angelica sinensis, in a rat model of chronic puromycin aminonucleoside nephrosis

Nephrotic syndrome has long been treated in China with two herbs, Astragalus mongholicus and Angelica sinensis, which may have antifibrotic effects. Methods: Rats with chronic puromycin-induced nephrosis were treated with Astragalus and Angelica 3 mL/d (n=7) or enalapril 10 mg/kg/d (n=7). Normal control rats (n=7) received saline rather than puromycin, and an untreated control group (n=7) received puromycin but no treatment. After 12 weeks, stained sections of the glomerulus and tubulointerstitium were evaluated for injury. Immunohistochemistry staining measured extracellular matrix components, transforming growth factor-β1 (TGFβ1), osteopontin, ED-1-positive cells, and α-actin. TGFâ1 mRNA was assessed by in situ hybridization. Renin, ACE activity, angiotensin, and aldosterone were measured by radioimmunoassay or colorimetry. In the untreated rats, chronic renal injury progressed to marked fibrosis at 12 weeks. Astragalus and Angelica significantly reduced deterioration of renal function and histologic damage. Expressions of type III and IV collagen, fibronectin, and laminin also decreased significantly. This anti-fibrotic effect was similar to that of enalapril. The herbs had no effect on the renin-angiotensin system but did reduce the number of ED-1-positive, and α-actin positive cells and expression of osteopontin compared to untreated controls. The combination of Astragalus and Angelica retarded the progression of renal fibrosis and deterioration of renal function with comparable effects of enalapril .These effects were not caused by blocking the intrarenal renin-angiotensin system, but associated with suppression of the overexpression of TGFâ 1 and osteopontin, reduction of infiltrating macrophages, and less activation of renal intrinsic cells.

Plasticity of kidney cells: Role in kidney remodeling and scarring

The progression of renal scarring and the associated loss of function remains one of the main challenges in nephrology. Until recently, the glomerular and tubulointerstitial scarring processes were thought to involve primarily interactions between infiltrating inflammatory cells and resident renal cells culminating in loss of renal cells and their replacement by extracellular collagenous matrix (ECM). This review focuses on new aspects of renal response to injury and remodeling. Emphasis is on the plasticity of renal cells with the capacity of both glomerular and tubular cells to assume a range of phenotypes during the remodeling process. Both glomerular and tubular epithelial cells regress to primitive/embryonic mesenchymal phenotype in response to injury. This reverse embryogenesis is a key step in renal healing and scarring. In addition to the plasticity of intrinsic renal cells, it is becoming apparent that renal remodeling in health and disease involves the migration of progenitor hematopoietic stem cells into the kidneys. These cells assume various glomerular and tubular epithelial phenotype. They are also involved in the evolution of lesions toward healing or scarring. A better understanding of some of these key events in renal remodeling and their mediators may open the way to new interventions based on their manipulations and aimed at favoring renal healing and preventing scarring.

The involvement of advanced glycation endproducts (AGEs) in renal injury of diabetic glomerulosclerosis: association with phenotypic change in renal cells and infiltration of immune cells.

Glycation of proteins is regarded as one of the major causes of the progression of diabetic nephropathy (DN) and of the phenotypic changes in glomerular mesangial cells (MC) and the cellular infiltration that occurs in MC from DN. It thus is very important to study the interrelationships and interaction between these causes. The localization of advanced glycation endproducts (AGEs), cytoskeletal proteins, and immune cell infiltration was evaluated by immunohistochemical study in patients with DN. N(Epsilon)-(carboxymethyl)lysine (CML), Alpha-smooth muscle actin (SMA), and low-molecular-weight caldesmon (L-CLD) were localized in the mesangial area in DN. The intensity of mesangial SMA and L-CLD expression was significantly correlated with the index of diabetic glomerulosclerosis (IDGS), while the expression of pentosidine was correlated with the IDGS and with 24-h urinary protein. Pentosidine was localized in glomerular basement membrane (GBM) only in DN and had a significant correlation with the mesangial expression of SMA and L-CLD. Pyrraline deposition on the tubular basement membrane, and the expression of SMA and L-CLD, and the infiltration of immune cells were observed in interstitial areas in DN. The intensity of L-CLD expression had a close relationship with pyrraline deposition and immune cell infiltration. The expression of SMA and L-CLD in interstitial areas was significantly correlated with the percent interstitial volume. AGEs are involved in renal injury in DN, and their effect is, at least in part, exercised via phenotypic changes in intrinsic renal cells and by the infiltration of immune cells.

Intrinsic renal cells are the major source of tumor necrosis factor contributing to renal injury in murine crescentic glomerulonephritis.

Macrophages are prominent participants in crescentic glomerulonephritis (GN) and have been suggested to be the major source of TNF in this cell-mediated form of glomerular inflammation. Intrinsic renal cells also have the capacity to produce TNF. For dissecting the contribution of local versus bone marrow (BM)-derived TNF in inflammatory renal injury, TNF chimeric mice were created by transplanting normal wild-type (WT) BM into irradiated TNF-deficient recipients (WT-->TNF-/- chimeras) and vice versa (TNF-/- -->WT chimeras). A model of crescentic GN induced by an intravenous injection of sheep anti-murine glomerular basement membrane antibody was studied in WT mice, mice with complete TNF deficiency (TNF-/-), and chimeric mice. Crescentic GN was attenuated in TNF-/- mice with fewer crescents (crescents, 13.7 +/- 1.7% of glomeruli) and reduced functional indices of renal injury (serum creatinine, 15.2 +/- 0.8 micromol/L). Similar protection (crescents, 14.3 +/- 1.9% of glomeruli; serum creatinine, 18.9 +/- 1.1 micromol/L) was observed in chimeric mice with intact BM but absent renal-derived TNF (WT-->TNF-/- chimeras), suggesting a minor contribution of infiltrating leukocytes to TNF-mediated renal injury. Chimeric mice with TNF-deficient leukocytes but intact intrinsic renal cell-derived TNF (crescents, 20.5 +/- 2.0% of glomeruli; serum creatinine, 21.6 +/- 1.4 micromol/L) developed similar crescentic GN to WT mice (crescents, 22.3 +/- 1.4% of glomeruli; serum creatinine, 24.8 +/- 1.9 micromol/L). Cutaneous delayed-type hypersensitivity after subdermal challenge with the nephritogenic antigen was attenuated in the absence of BM cell-derived TNF but unaffected in WT-->TNF-/- chimeric mice. These studies suggest that intrinsic renal cells are the major cellular source of TNF contributing to inflammatory injury in crescentic GN.

Interferon-gamma induces macrophage migration inhibitory factor synthesis and secretion by tubular epithelial cells.

Macrophage migration inhibitory factor (MIF) promotes macrophage accumulation and leucocyte activation during inflammation. Macrophage migration inhibitory factor is upregulated in intrinsic renal cells in many types of kidney diseases, and has a pathogenic role in rat crescentic nephritis. However, little is known about the factors that regulate the production and secretion of MIF in kidney cells. In this study, we evaluated whether interferon-gamma (IFN-gamma), a cytokine implicated in the development of kidney disease and a potent inducer of MIF production in macrophages, could promote MIF synthesis and secretion from renal tubular epithelial cells. Northern blot analysis detected constitutive expression of MIF mRNA in rat tubular epithelial cells (NRK52E), which increased twofold after a 6-h stimulation with IFN-gamma. Macrophage migration inhibitory factor protein was found only in the cytoplasm of NRK52E cells. Following IFN-gamma stimulation, intracellular MIF in NRK52E cells was rapidly secreted with a maximal reduction of 50% after 20 min, which returned to normal levels after 2-4 h. Rapid secretion of MIF in response to IFN-gamma was also seen in rat mesangial cells. These findings indicate that IFN-gamma induces rapid secretion of MIF by tubular epithelial cells, and suggest that this may be an important mechanism leading to inflammatory cell accumulation and activation during kidney disease.

The role of chemokines and chemokine receptors in progressive renal diseases

Chemokines are members of a growing family of chemotactic cytokines, which induce recruitment of select leukocyte subpopulations. Additionally, they can activate leukocyte effector functions, are involved in the balance between proliferation and apoptosis, modulate angiogenesis, and regulate fibroblast functions. Most intrinsic renal cells can express chemokines on stimulation in vitro. Induction of chemokines and infiltration of chemokine receptor-bearing cells has been shown in a variety of animal models of renal diseases, as well as in human diseases and allograft rejection. This overview gives a short introduction into chemokines and current aspects of their role in progressive human kidney diseases. Am J Kidney Dis 41(S1):S15-S18. © 2003 by the National Kidney Foundation, Inc.

Bacterial CpG-DNA aggravates immune complex glomerulonephritis: role of TLR9-mediated expression of chemokines and chemokine receptors.

Immune complex glomerulonephritis (GN) often deteriorates during infection with viruses and bacteria that, in contrast to mammals, have DNA that contains many unmethylated CpG motifs. Balb/c mice with horse apoferritin-induced GN (HAF-GN) were treated with either saline, CpG-oligodeoxynucleotides (ODN), or control GpC-ODN. Only CpG-ODN exacerbated HAF-GN with an increase of glomerular macrophages, which was associated with massive albuminuria and increased renal MCP-1/CCL2, RANTES/CCL5, CCR1, CCR2, and CCR5 mRNA expression. CpG-ODN induced a Th1 response as indicated by serum anti-HAF IgG(2a) titers, mesangial IgG(2a) deposits, and splenocyte IFN-gamma secretion. Messenger RNA for the CpG-DNA receptor Toll-like reeptor 9 (TLR9) was present in kidneys with HAF-GN but not in normal kidneys. The source of TLR9 mRNA in HAF-GN could be infiltrating macrophages or intrinsic renal cells, e.g., mesangial cells; but, in vitro, only murine J774 macrophages expressed TLR9. In J774 cells, CpG-ODN induced the chemokines MCP-1/CCL2 and RANTES/CCL5 and the chemokine receptors CCR1 and CCR5. It is concluded that CpG-DNA can aggravate preexisting GN via a shift toward a Th1 response but also by a novel pathway involving TLR9-mediated chemokine and chemokine receptor expression by macrophages, which may contribute to the enhanced glomerular macrophage recruitment and activation. This mechanism may be relevant during infection-triggered exacerbation of human immune-complex GN and other immune-mediated diseases in general.

Nephrotoxic nephritis is mediated by Fcγ receptors on circulating leukocytes and not intrinsic renal cells

There is evidence that mesangial cells express Fcgamma receptors in vitro, but the in vivo relevance of this is not known. FcRgamma-/- mice lack the gamma chain signaling subunit and therefore do not express the activator Fcgamma receptors (FcgammaRI and FcgammaRIII) or the high affinity IgE receptor, FcepsilonRI. FcRgamma-/- mice were protected from renal inflammation following the induction of accelerated nephrotoxic nephritis using sheep anti-mouse glomerular basement membrane anti-serum in mice sensitized to sheep IgG. In order to test whether Fcgamma receptors had a role on intrinsic renal cells during nephritis, bone marrow cells were transplanted between wild-type (WT) mice and mice with a gene-targeted deletion of FcRgamma. Donor marrow reconstitution was confirmed by flow cytometric analysis of peripheral blood for FcgammaRIII, and the susceptibility of the transplanted mice to accelerated nephrotoxic nephritis was tested. Following the induction of nephrotoxic nephritis, FcRgamma-/- mice transplanted with WT bone marrow developed as much renal disease as WT mice transplanted with WT bone marrow. In contrast, WT mice transplanted with FcRgamma-/- marrow were completely protected from glomerular crescents, thrombosis, albuminuria and renal impairment, as were FcRgamma-/- mice transplanted with FcRgamma-/- marrow. Mice with FcRgamma-/- marrow had prolonged survival, but by day 28 after nephrotoxic serum injection they had developed mesangial hypercellularity and a macrophage influx caused by non-FcRgamma dependent mechanisms. Despite previous evidence that mesangial cells express Fcgamma receptors in vitro, they have no role in an FcRgamma-dependent model of glomerulonephritis in vivo.

Roles of SLC/CCL21 and CCR7 in human kidney for mesangial proliferation, migration, apoptosis, and tissue homeostasis.

The release of chemokines by intrinsic renal cells is an important mechanism for the regulation of leukocyte trafficking during renal inflammation. The expression of chemokine receptors by intrinsic renal cells such as mesangial cells (MC) suggests an expanded role for chemokine-chemokine receptor biology in local immunomodulation and potentially glomerular homeostasis. By immunohistochemistry we found the chemokine receptor CCR7 expressed in a mesangial pattern while the CCR7 ligand SLC/CCL21 showed a podocyte-specific expression. CCR7 expression was further characterized by RT-PCR, RNase protection assays, and FACS analysis of cultured human MC, and was found to be constitutively present. Real-time PCR of microdissected glomeruli confirmed the expression of SLC/CCL21. A functional role for CCR7 was demonstrated for human MC migration and proliferation. A protective effect of SLC/CCL21 was shown for MC survival in Fas Ab-induced apoptosis. Finally, "wound healing" was enhanced in the presence of SLC/CCL21 in an in vitro injury model. The constitutive glomerular expression of CCR7 and its ligand SLC/CCL21 in adjacent cell types of the human kidney suggests novel biological functions of this chemokine/chemokine receptor pair and a potential role in processes involved in glomerular homeostasis and regeneration.

IFN-gamma production by intrinsic renal cells and bone marrow-derived cells is required for full expression of crescentic glomerulonephritis in mice.

The contribution of IFN-gamma from bone marrow (BM) and non-BM-derived cells to glomerular and cutaneous delayed-type hypersensitivity (DTH) was studied in mice. Chimeric IFN-gamma mice (IFN-gamma(+/+) BM chimera), in which IFN-gamma production was restricted to BM-derived cells, were created by transplanting normal C57BL/6 (wild-type (WT)) BM into irradiated IFN-gamma-deficient mice. BM IFN-gamma-deficient chimeric mice (IFN-gamma(-/-) BM chimera) were created by transplanting WT mice with IFN-gamma-deficient BM. WT and sham chimeric mice (WT mice transplanted with WT BM) developed crescentic glomerulonephritis (GN) with features of DTH (including glomerular T cell and macrophage infiltration) in response to an Ag planted in their glomeruli and skin DTH following subdermal Ag challenge. IFN-gamma-deficient mice showed significant protection from crescentic GN and reduced cutaneous DTH. IFN-gamma(+/+) BM chimeric and IFN-gamma(-/-) BM chimeric mice showed similar attenuation of crescentic GN as IFN-gamma-deficient mice, whereas cutaneous DTH was reduced only in IFN-gamma(-/-) BM chimeras. In crescentic GN, IFN-gamma was expressed by tubular cells and occasional glomerular cells and was colocalized with infiltrating CD8(+) T cells, but not with CD4(+) T cells or macrophages. Renal MHC class II expression was reduced in IFN-gamma(+/+) BM chimeric mice and was more severely reduced in IFN-gamma-deficient mice and IFN-gamma(-/-) BM chimeric mice. These studies show that IFN-gamma expression by both BM-derived cells and intrinsic renal cells is required for the development of crescentic GN, but IFN-gamma production by resident cells is not essential for the development of cutaneous DTH.

Targeting growth factors to the kidney: myth or reality?

Growth factors and cytokines play a crucial role in the progression of renal diseases. A growing body of evidence has been obtained from experimental studies, suggesting that manipulation of the activity of growth factors and cytokines is a potential form of therapy for renal diseases. To preserve the renal function structure in progressive renal diseases, this approach is achieved by inhibition of apoptosis of renal intrinsic cells and by decrease in the fibrotic signal. Inhibition of transforming growth factor beta, platelet-derived growth factor, interleukin-1 and tumor necrosis factor alpha, and supplementation of hepatocyte growth factor, vascular endothelial growth factor and bone morphogenic protein-7 may be beneficial. Recent progress in therapeutic implements including humanized antibodies, chimeric soluble receptors, aptamers, antisense oligonucleotides, and gene therapy allow us to target the causal molecules. Administration of a combination of growth factors and cytokines is a potential therapeutic approach. Targeting signal transduction molecules and their co-factors and regulators is another possibility because the signals from various growth factors use a common pathway. Thus, targeting growth factors and cytokines in renal diseases could be a promising therapeutic approach.

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-1beta. 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.

An Essential Role of Angiotensin II Receptor Type 1a in Recipient Kidney, Not in Transplanted Peripheral Blood Leukocytes, in Progressive Immune-Mediated Renal Injury

Despite an intensive effort of elucidating the pathogenic role of angiotensin II (AII) in immune-mediated renal injury, the precise mechanisms are poorly understood. In the present study, we examined the site of AII action, peripheral blood leukocytes or resident renal cells, in immune-mediated renal injury using AII type 1a receptor (AT1a)-deficient homozygous (AT1a −/−) mice and wild-type (AT1a +/+) mice. The AT1a −/− mice showed delayed-type hypersensitivity similar to that of the AT1a +/+ mice, suggesting that the lack of AT1a does not impair a Th1-type cellular immune response of peripheral blood leukocytes involved in immune-mediated renal injury. We then generated the radiation bone marrow chimera mice, WA and AW, which have transplanted peripheral blood leukocytes from the AT1a +/+ and AT1a −/− mice into the AT1a −/− and AT1a +/+ mice, respectively. As controls, WW and AA, the AT1a +/+ and AT1a −/− mice given bone marrow cells from the AT1a +/+ and AT1a −/− mice, respectively, were generated. Seven days after induction of antiglomerular basement membrane nephritis, glomerulosclerosis observed in the WW mice was markedly ameliorated in the WA mice, but not in the AW mice. In addition, the recruitment of monocytes/macrophages and the expressions of monocyte chemoattractant protein-1 and intercellular adhesion molecule-1 in the glomeruli of the AW and WW mice was evident, but such significant phenotypes were not seen in the WA and AA mice, showing a marked amelioration of renal injury dependent on the host AT1a genotype. These results demonstrate an essential role of AT1a in intrinsic renal cells for progressive immune-mediated renal injury and indicate a beneficial effect of blocking the renin-angiotensin system in the treatment of such diseases.

Interleukin-12 from intrinsic cells is an effector of renal injury in crescentic glomerulonephritis.

Interleukin-12 (IL-12) directs the cognate nephritogenic T helper type 1 responses that initiate renal injury in murine crescentic glomerulonephritis (GN). The recent demonstration of IL-12 production by intrinsic renal cells, including mesangial and proximal tubular cells, raises the possibility that IL-12 from nonimmune cells may contribute to inflammatory renal injury. To address this possibility, the development of sheep anti-mouse glomerular basement membrane globulin-induced crescentic GN was studied in C57BL/6 wild-type (WT), IL-12-deficient (IL-12 -/-), and IL-12 "chimeric" mice. IL-12 chimeric mice were produced by transplantation of WT bone marrow into IL-12 -/- mice to restore IL-12 production by immune cells, while leaving them deficient in renal IL-12 production. WT and "sham" chimeric mice (normal bone marrow transplanted into WT mice) developed crescentic GN with glomerular T-cell and macrophage recruitment and impaired renal function (elevated proteinuria and serum creatinine) 10 d after initiation of GN. IL-12 -/- mice showed significant protection from GN. Chimeric IL-12 mice showed significant attenuation of crescent formation, glomerular T-cell and macrophage accumulation, and renal impairment, compared with WT and sham chimeric mice, but were not protected to the same extent as IL-12 -/- mice. IL-12 chimeric mice showed no attenuation of their systemic cognate immune response to the nephritogenic antigen (sheep globulin), indicated by antigen-specific circulating antibody and cutaneous delayed-type hypersensitivity. These studies indicate that IL-12 produced by non-bone marrow derived intrinsic renal cells contributes to immune renal injury. They provide the first in vivo demonstration of a proinflammatory role for an intrinsic renal cell-derived cytokine in renal inflammation.

Urinary tract obstruction.

Angiotensin II plays a pivotal role in the progression of renal diseases, including obstructive nephropathy. Increasing levels of angiotensin II in obstructive nephropathy upregulate the expression of several factors: transforming growth factor-beta1 (TGF-beta1), tumor necrosis factor-alpha (TNF-alpha), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF-1), osteopontin, vascular cell adhesion molecule-1 (VCAM-1), nuclear factor-kappaB (NF-kappaB), monocyte chemoattractant peptide-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and CD14 among others. Local production of TGF-beta, by intrinsic renal cells or by macrophages invading the kidney, is a key mediator of renal fibrosis. Activation of TGF-beta stimulates endothelin production. Endothelin, in turn, is a potent stimulus for fibrogenesis. Oxidative stress, fueled in part by angiotensin II, upregulates the expression of adhesion molecules, chemoattractant compounds and cytokines. Sustained obstructive nephropathy leads to apoptosis of tubular epithelial cells. Several factors and genes involved in apoptosis have been described. Nuclear factor kappa-B is involved in the transcriptional regulation of genes present in several organs, including the kidney. NF-kappaB is activated in the setting of ureteral obstruction. Administration of angiotensin-converting enzyme (ACE) inhibitors decreased significantly the activation of NF-kappaB in the obstructed kidney. Studies in neonatal rats indicate that chronic ureteral obstruction decreases the expression of epidermal growth factor (EGF). Replacement of this factor decreased apoptosis and reduced the expression of vimentin, clusterin, and TGF-beta. The administration of IGF-1 also lessened the tubular and interstitial pathology in the setting of ureteral obstruction. A spectrum of urinary tract malformations have been described. The utility of certain markers such as fetal serum beta(2) microglobulin as a predictor of postnatal renal function in bilateral uropathies has been described. A number of pharmacologic interventions that ameliorate the increased expansion of the interstitial volume, decrease the expression of TGF-beta, and down-regulate the production of extracellular matrix and the infiltration of the interstitium by macrophages have been described. Drugs used include ACE inhibitors, administration of arginine, administration of osteogenic protein-1, Pirferidone, and so on. It is likely that in the next decade advances in genetic manipulations and new drug therapies may forestall the development of fibrosis in the setting of urinary tract obstruction.

Expression of the chemokine monocyte chemoattractant protein-1 and its receptor chemokine receptor 2 in human crescentic glomerulonephritis.

Crescents are morphologic manifestations of severe glomerular injury. Several chemokines and their receptors have been demonstrated to be involved in animal models of crescentic glomerulonephritis (cGN) and are potential targets for therapeutic interventions. Therefore, the expression of monocyte chemoattractant protein-1 (MCP-1), its receptor chemokine receptor 2B (CCR2B), and CCR5 in human cGN was studied. MCP-1 and CCR2B mRNA expression was evaluated, by in situ hybridization, in serial sections of 23 renal biopsies from patients with cGN. T cells, macrophages, and CCR5-expressing cells were examined by immunohistochemical analysis. MCP-1 mRNA was expressed by cells in crescents, parietal epithelium, and tubular epithelium, as well as by infiltrating leukocytes in the tubulointerstitium. The expression of CCR2B mRNA was observed in cells in glomeruli and crescents and in infiltrating leukocytes in the tubulointerstitium. CCR2B mRNA expression could not be clearly localized to intrinsic renal cells; evidence that most of the CCR2B-expressing cells were leukocytes is provided. CD3-positive T cells formed the major part of the interstitial cell infiltrates but were rare within the glomerular tufts. CD68-positive macrophages constituted a major population of infiltrating cells in crescents and contributed significantly to the interstitial infiltrates. The number of glomerular macrophages was associated with the number of MCP-1- and CCR2B-positive glomerular cells. Expression of CCR2B was significantly correlated with interstitial CD3-positive T cells. CCR5 expression was restricted to infiltrating leukocytes and was correlated quantitatively and by localization with interstitial CD3-positive T cells and CD68-positive macrophages. These first morphologic data on the distribution of CCR2-positive cells in human cGN suggest differential effects of chemokines and their receptors on the distribution of infiltrating leukocytes in different compartments of the kidney.