Terminal complement inhibitor eculizumab in atypical hemolytic-uremic syndrome.

BACKGROUND: Atypical hemolytic-uremic syndrome is a genetic, life-threatening, chronic disease of complement-mediated thrombotic microangiopathy. Plasma exchange or infusion may transiently maintain normal levels of hematologic measures but does not treat the underlying systemic disease. METHODS: We conducted two prospective phase 2 trials in which patients with atypical hemolytic-uremic syndrome who were 12 years of age or older received eculizumab for 26 weeks and during long-term extension phases. Patients with low platelet counts and renal damage (in trial 1) and those with renal damage but no decrease in the platelet count of more than 25% for at least 8 weeks during plasma exchange or infusion (in trial 2) were recruited. The primary end points included a change in the platelet count (in trial 1) and thrombotic microangiopathy event-free status (no decrease in the platelet count of >25%, no plasma exchange or infusion, and no initiation of dialysis) (in trial 2). RESULTS: A total of 37 patients (17 in trial 1 and 20 in trial 2) received eculizumab for a median of 64 and 62 weeks, respectively. Eculizumab resulted in increases in the platelet count; in trial 1, the mean increase in the count from baseline to week 26 was 73×10(9) per liter (P<0.001). In trial 2, 80% of the patients had thrombotic microangiopathy event-free status. Eculizumab was associated with significant improvement in all secondary end points, with continuous, time-dependent increases in the estimated glomerular filtration rate (GFR). In trial 1, dialysis was discontinued in 4 of 5 patients. Earlier intervention with eculizumab was associated with significantly greater improvement in the estimated GFR. Eculizumab was also associated with improvement in health-related quality of life. No cumulative toxicity of therapy or serious infection-related adverse events, including meningococcal infections, were observed through the extension period. CONCLUSIONS: Eculizumab inhibited complement-mediated thrombotic microangiopathy and was associated with significant time-dependent improvement in renal function in patients with atypical hemolytic-uremic syndrome. (Funded by Alexion Pharmaceuticals; C08-002 ClinicalTrials.gov numbers, NCT00844545 [adults] and NCT00844844 [adolescents]; C08-003 ClinicalTrials.gov numbers, NCT00838513 [adults] and NCT00844428 [adolescents]).

Long-term sustainability of hand hygiene improvements in the hemodialysis setting.

PURPOSE: In a previous observational intervention study, we achieved a more than 100 % increase in overall hand hygiene (HH) compliance in the hemodialysis setting by increasing the number of hand rubs (HR) performed and concomitantly optimizing HH standard operating procedures (SOPs). SOPs were mainly aimed at reducing the number of avoidable opportunities due to a less than perfect workflow. However, the long-term sustainability of this successful intervention was not evaluated. The present study was carried out to evaluate the long-term effects of our previous successful intervention. METHODS: We conducted a follow-up observational study 1 year after the first intervention study in the same hemodialysis unit to assess the sustainability. No HH-related interventions were performed in the 1 year between studies. The main outcome was HH compliance, and the secondary outcome was opportunities per hemodialysis procedure. RESULTS: A total of 1,574 opportunities for HH and 871 hand rubs (HR) were observed during the follow-up observational study. Overall, compliance was 55 %, which was significantly than that at the end of the first study (62 %; p < 0.0001), but significantly higher than that at the start and mid-term phases of the first study (37 and 49 %, p < 0.0001). Both the decrease in HH opportunities and the increase in HR were sustained over the course of this observational study. The number of avoidable opportunities in the present study was similar to that at the end of the previous study. Thus, in 320 opportunities (20 %), gloves were worn instead of HR performed, representing 46 % of all missed HR. CONCLUSIONS: Despite a decrease in HH compliance compared to the last postintervention period, a multifaceted intervention focusing on standardization and workflow optimization resulted in a sustained improvement in HH. We therefore propose that standardization of the hemodialysis workflow aimed at improving HH is a promising avenue for improving the quality of patient care and outcome.

CCN3 is a novel endogenous PDGF-regulated inhibitor of glomerular cell proliferation.

CCN proteins affect cell proliferation, migration, attachment, and differentiation. We identified CCN3 as a suppressed gene following platelet-derived growth factor (PDGF)-BB or -DD stimulation in a cDNA-array analysis of mesangial cells. In vitro growth-arrested mesangial cells overexpressed and secreted CCN3, whereas the addition of the recombinant protein inhibited cell growth. Induction of mesangial cell proliferation by PDGF-BB or the specific PDGF beta-receptor ligand PDGF-DD led to downregulation of CCN3 mRNA, confirming the array study. Specific PDGF alpha-receptor ligands had no effect. CCN3 protein was found in arterial smooth muscle cells, the medullary interstitium, and occasional podocytes in the healthy rat kidney. Glomerular CCN3 was low prior to mesangial proliferation but increased as glomerular cell proliferation subsided during mesangioproliferative glomerulonephritis (GN). Inhibition of PDGF-B in mesangioproliferative disease led to overexpression of glomerular CCN3 mRNA. CCN3 localized mostly to podocytes in human glomeruli, but this expression varied widely in different human glomerulonephritides. Glomerular cell proliferation negatively correlated with CCN3 expression in necrotizing GN. Our study identifies CCN3 as an endogenous inhibitor of mesangial cell growth and a modulator of PDGF-induced mitogenesis.

Sticky platelet syndrome: an underrecognized cause of graft dysfunction and thromboembolic complications in renal transplant recipients.

Sticky platelet syndrome (SPS) leads to hyperaggregabilty of platelets in response to physiologic stimuli. In this report we describe three patients with clinical symptoms of SPS after renal transplantation. The first patient developed an infarction of her transplant kidney with additional, subsequent renal microinfarctions. The second patient suffered multiple strokes and deep vein thrombosis with episodes of pulmonary embolism and ischemic bowel disease due to colonic microinfarctions. The third patient experienced a long episode of unexplained respiratory and graft dysfunction immediately after transplantation until therapy for SPS was initiated, at which point symptoms resolved quickly. Kidney transplant recipients with SPS may be at increased risk of developing thrombosis, given that most immunosuppressive drugs are known to induce either endothelial cell damage or augment platelet aggregation. All patients awaiting renal transplantation should be screened for a history of thrombosis and, if appropriate, tested for SPS. Affected patients should receive dose-adjusted acetylsalicylic acid.

Present and future therapy options in IgA-nephropathy.

Over the last 5 years the evidence base for therapeutic approaches in patients at risk for progressive IgA-nephropathy (IgAN) has markedly improved. In addition to several studies with low power, two randomized controlled trials suggest that in patients with preserved renal function, i.e. a GFR above 70 ml/min, corticosteroid-therapy can effectively prevent the development of progressive renal failure, whereas in patients with already impaired renal function, combination therapy consisting of cyclophosphamide, azathioprine and corticosteroids was effective. However, so far no study has firmly established that such immunosuppressive therapy is indeed superior to aggressive supportive therapy as it is available nowadays, i.e. high dose ACE-inhibitors and/or angiotensin-II receptor blockers, smoking cessation etc. It therefore appears prudent to first institute such supportive therapy and to limit immunosuppressive therapy to those patients, who maintain a proteinuria above 1 g/day or exhibit a progressive decline of GFR despite optimal supportive measures. Based on pathogenetic insights derived from experimental studies, antagonism of platelet-derived growth factor-B or -D provides an attractive and possibly more specific therapeutical alternative to immunosuppression. While clinical studies testing this new approach are about to start, the development of other novel therapeutic approaches is greatly hampered by the lack of sufficient animal models of IgAN. In this respect a recently described primate model of IgAN offers some hope for the future.

Inhibition of the renin-angiotensin system ameliorates genetically determined hyperinsulinemia.

This study was performed in order to assess the potentially different effects of the angiotensin-converting enzyme inhibitor captopril and of the angiotensin II receptor antagonist irbesartan on the metabolic syndrome in an animal model. Male NZO/BL6 F1 mice were treated with captopril, irbesartan, or placebo for 10 months: Control animals treated with placebo developed a metabolic syndrome with obesity (55.5+/-6.3 g), hypertension (146+/-10 mm Hg), hyperinsulinemia (7.2+/-5.7 ng/ml), hypercholesterolemia (5.1+/-0.7 mmol/l), cardiac hypertrophy (269+/-44 mg) and atherosclerotic plaques in the ascending aorta (3.6+/-1.5 microm(2)). Treatment with angiotensin-converting enzyme inhibitor or angiotensin II receptor antagonist significantly (p<0.001) reduces hypertension (73+/-5 and 78+/-11 mm Hg), cardiac hypertrophy (203+/-26 and 202+/-18 mg) and atherosclerosis (2.2+/-0.9 and 1.8+/-0.8 microm(2)). In addition, they prevented the development of obesity (42.2+/-3.5 and 38.3+/-2.8 g) and hyperinsulinemia (3.6+/-1.5 and 1.8+/-0.4 ng/ml). In conclusion, long-term treatment with an angiotensin-converting enzyme inhibitor or an angiotensin II receptor antagonist can ameliorate obesity and hyperinsulinemia in a genetically determined mouse model.

Expression of chemokines and chemokine receptors during human renal transplant rejection.

Infiltration of renal allografts by leukocytes is a hallmark of acute transplant rejection. Chemokines attract leukocytes bearing specific chemokine receptors, and the specific leukocyte chemokine receptor phenotype is associated with types of immune responses, ie, T helper subtype 1 (Th1; CXC chemokine receptor 3 [CXCR3], CC chemokine receptor 5 [CCR5]) versus Th2 (CCR3, CCR4, CCR8). We studied the expression of the chemokine monocyte chemoattractant protein-1 and the chemokine receptors CCR2B and CXCR4 messenger RNA (mRNA) by in situ hybridization, as well as the chemokine receptors Duffy antigen receptor for chemokines (DARC) and CCR5 protein by immunohistochemistry in renal biopsy specimens with acute cellular rejection (n = 12) and acute vascular rejection (n = 8), transplant nephrectomy specimens (n = 6), and normal areas of tumor nephrectomy specimens (n = 5). CC chemokines and CC chemokine receptor mRNA expression were evaluated by ribonuclease protection assay in specimens from four transplant nephrectomies and one tumor nephrectomy. Upregulation of mRNAs for the chemokines, interferon-inducible protein-10 (IP-10); regulated on activation normal T-cell expressed and secreted; macrophage inflammatory protein-1alpha (MIP-1alpha); MIP-1beta; and lymphotactin, as well as the chemokine receptors, CCR2 and CCR5, were documented during allograft rejection. CCR1 mRNA was detectable in both allografts and controls, but CCR3 and CCR8 were absent. The number of CXCR4, CCR5, and CCR2B mRNAs expressing leukocytes and DARC-positive vessels increased during rejection episodes. CXCR4 mRNA was the most widely expressed. Leukocytes in diffuse interstitial infiltrates were mainly CCR5 positive, but in areas in which leukocytes formed nodular aggregates of infiltrating cells, the number of CCR5-positive cells was low. Instead, leukocytes in these nodular aggregates mainly expressed CXCR4. DARC was expressed on peritubular capillaries, where it was upregulated in areas of interstitial infiltration. Induction of chemokines during renal allograft rejection is accompanied by infiltration of leukocytes bearing the respective chemokine receptors. The upregulation of the CXCR3 ligand IP-10, as well as CCR5 and its ligands, in the absence of CCR3 and CCR8 is indicative that renal allograft rejection is primarily the result of a Th1-type immune response.

Differential expression of cyclin-dependent kinase inhibitors in human glomerular disease: role in podocyte proliferation and maturation.

BACKGROUND: Normal human podocytes are terminally differentiated and quiescent cells. It is not known why podocytes fail to proliferate in response to most forms of injury. Proliferation is regulated by cell cycle proteins and their inhibitors. The Cip/Kip family of cyclin-dependent kinase (CDK) inhibitors (p21, p27, p57) in general prevent proliferation by inhibiting cyclin-CDK complexes. In the current study, we determined the expression and possible role of specific CDK inhibitors in podocyte proliferation in human disease characterized by podocyte injury. METHODS: Immunostaining was performed for the CDK inhibitors p21, p27, and p57 and the proliferation marker Ki-67 on renal biopsies from patients with minimal change disease (MCD; N = 6), membranous glomerulopathy (MGN; N = 19), cellular variant of focal segmental glomerulosclerosis (FSGS; N = 12), collapsing glomerulopathy (CG; N = 9), and HIV-associated nephropathy (HIVAN; N = 16). Adult nephrectomy specimens without evidence of glomerular disease served as controls (N = 9). RESULTS: Normal quiescent podocytes express p27 and p57, but not p21. In diseases without podocyte proliferation (MCD, MGN), p21, p27, and p57 expression did not change. In contrast, there was a uniform decrease in p27 and p57 immunostaining in diseases with podocyte proliferation (cellular FSGS, CG, and HIVAN). This was accompanied by the de novo expression of p21 in podocytes. CONCLUSIONS: Our results show that podocyte quiescence may require the presence of the CDK inhibitors p27 and p57. In human glomerular diseases, a decrease in p27 and p57 may be permissive for the altered proliferative podocyte phenotype. p21 may have a multifactorial role in podocyte cell cycle regulation.

Rapid shift from virally infected cells to germinal center-retained virus after HIV-2 infection of macaques.

Lymphoid tissues are the primary target during the initial virus dissemination that occurs in HIV-1-infected individuals. Recent advances in antiretroviral therapy and techniques to monitor virus load in humans have demonstrated that the early stages of viral infection and host response are major determinants of the outcome of individual infections. Relatively little is known about immunopathogenic events occurring during the acute phase of HIV infection. We analyzed viral dissemination within lymphoid tissues by in situ hybridization and by combined immunohistochemistry/in situ hybridization during the acute infection phase (12 hours to 28 days) in pig-tailed macaques (Macaca nemestrina), challenged intravenously with a virulent strain of HIV-2, HIV-2(287). Two stages in viral dissemination were clearly evident within the first 28 days after HIV-2(287) infection. First, a massive increase in individual HIV-2-infected cells, mostly CD3+ T lymphocytes and a smaller percentage of macrophages and interdigitating dendritic cells, was identified within lymph nodes which peaked on the 10th day after HIV-2 infection. A shift of HIV-2 distribution was demonstrable between day 10 and day 14 after HIV-2 infection. Coincident with a marked reduction in individual HIV-2 RNA+ cells by day 14 postinfection, there was a dramatic increase in germinal center-associated HIV-2 RNA. High concentrations of HIV-2 RNA persisted in germinal centers in all animals by days 21 and 28 postinfection. Thus, HIV-2 appears to go through an initial, highly disseminated cellular phase followed by localization in the follicular dendritic cell network with relatively few infected cells. In this nonhuman primate model of HIV-associated immunopathogenesis, using a virus derived from a human pathogen, we identified a significant shift in the pattern of HIV-2 localization within a narrow time frame (day 10 to day 14). This shift in virus localization and behavior indicates that there may be a discrete but remarkably narrow window for therapeutic interventions that interrupt this stage in the natural course of HIV infection. Reproducibility and the accelerated time course of disease development make this model an excellent candidate for such intervention studies.

Osteopontin expression in human crescentic glomerulonephritis.

UNLABELLED: Osteopontin expression in human crescentic glomerulonephritis. BACKGROUND: Osteopontin is a molecule with diverse biological functions, including cell adhesion, migration, and signaling. The expression of osteopontin has been demonstrated in a number of models of renal injury in association with accumulations of monocyte/macrophages, including recent reports of osteopontin expression in glomerular crescents in a rat model of anti-glomerular basement membrane glomerulonephritis. METHODS: Glomerular expression of osteopontin in biopsies of human crescentic glomerulonephritis (N = 25), IgA nephropathy with crescents (N = 2), and diffuse proliferative lupus glomerulonephropathy with crescents (N = 1) was studied by immunohistochemistry, in situ hybridization, and combined immunohistochemistry/in situ hybridization. Additionally, antibodies to cell-specific phenotypic markers were used to identify cellular components of the glomerular crescent, which express osteopontin protein and mRNA. RESULTS: All of the crescents present in the biopsies studied contained a significant number of cells that expressed osteopontin protein and mRNA, demonstrated by immunohistochemistry and in situ hybridization, respectively. Using replicate tissue sections and combined immunohistochemistry/in situ hybridization, we showed that the majority of the strongly osteopontin-positive cells are monocyte/macrophages. In addition to the very strong and cell-associated localization, a weaker and more diffuse pattern of osteopontin protein and mRNA expression could be seen in a number of crescents. None of the osteopontin mRNA-expressing cells could be identified as parietal epithelial cells, CD3-positive T cells, or alpha-smooth muscle actin-positive myofibroblasts. Interstitial monocyte/macrophages did not express osteopontin, except when located in a periglomerular inflammatory infiltrate. CONCLUSIONS: Macrophages present in the human glomerular crescent express osteopontin protein and mRNA at a high level. This expression supports a role for osteopontin in the formation and progression of the crescentic lesion via chemotactic and signaling properties of the molecule.

Expression of decorin, biglycan, and collagen type I in human renal fibrosing disease.

BACKGROUND: The extracellular matrix proteoglycans decorin and biglycan may have a pathogenic role in renal fibrosing disease via regulation of the activity of growth factors, such as transforming growth factor-beta, and effects on collagen type I fibrillogenesis. The expression of decorin and biglycan in human glomerular diseases characterized by mesangial sclerosis is unknown. METHODS: Decorin, biglycan, and collagen type I were localized immunohistochemically in human renal biopsy cases of amyloidosis (N = 18), diabetic nephropathy (N = 11), fibrillary glomerulonephritis (N = 5), immunotactoid glomerulopathy (N = 5), light-chain deposition disease (N = 4), idiopathic mesangial sclerosis (N = 4), and nephrosclerosis (N = 6), and in morphologically normal tissues obtained from tumor nephrectomies (N = 8). Decorin and biglycan mRNA synthesis was evaluated by in situ hybridization. RESULTS: Decorin and biglycan protein were not identified in normal glomeruli. Decorin accumulated in amyloid deposits, but not in deposits of fibrillary glomerulonephritis or immunotactoid glomerulopathy. Biglycan weakly accumulated in amyloid deposits, and both decorin and biglycan weakly stained mesangial nodules in cases of morphologically advanced light-chain deposition disease and diabetic nephropathy. In all analyzed cases, irrespective of the underlying disease, decorin and biglycan accumulated in glomeruli in areas of fibrous organization of the urinary space and in areas of tubulointerstitial fibrosis. Biglycan, but not decorin, accumulated in the neointima of arteriosclerotic blood vessels. Decorin and biglycan mRNA synthesis was detected at sites of proteoglycan accumulation in glomeruli, interstitium, and neointima. Collagen type I colocalized with decorin and biglycan deposits. CONCLUSIONS: Differences in extracellular matrix proteoglycan composition may be diagnostically useful in distinguishing morphologically similar diseases. Distinct patterns of proteoglycan expression may be related to modulation of specific growth factor activity in different glomerular diseases.

VEGF(165) mediates glomerular endothelial repair.

VEGF(165), the most abundant isoform in man, is an angiogenic cytokine that also regulates vascular permeability. Its function in the renal glomerulus, where it is expressed in visceral epithelial and mesangial cells, is unknown. To assess the role of VEGF(165) in glomerular disease, we administered a novel antagonist - a high-affinity, nuclease-resistant RNA aptamer coupled to 40-kDa polyethylene glycol (PEG) - to normal rats and to rats with mesangioproliferative nephritis, passive Heymann nephritis (PHN), or puromycin aminonucleoside nephrosis (PAN). In normal rats, antagonism of VEGF(165) for 21 days failed to induce glomerular pathology or proteinuria. In rats with mesangioproliferative nephritis, the VEGF(165) aptamer (but not a sequence-scrambled control RNA or PEG alone) led to a reduction of glomerular endothelial regeneration and an increase in endothelial cell death, provoking an 8-fold increase in the frequency of glomerular microaneurysms by day 6. In contrast, early leukocyte influx and the proliferation, activation, and matrix accumulation of mesangial cells were not affected in these rats. In rats with PHN or PAN, administration of the VEGF(165) aptamer did not influence the course of proteinuria using various dosages and administration routes. These data identify VEGF(165) as a factor of central importance for endothelial cell survival and repair in glomerular disease, and point to a potentially novel way to influence the course of glomerular diseases characterized by endothelial cell damage, such as various glomerulonephritides, thrombotic microangiopathies, or renal transplant rejection.

Localization of fibroblast growth factor-2 (basic FGF) and FGF receptor-1 in adult human kidney.

BACKGROUND: The expression pattern of fibroblast growth factor-2 (FGF-2; basic FGF), a pleiotrophic growth factor, as well as one of its receptors (FGFR1), in the kidney is highly controversial. METHODS: Using an approach that combines multiple antibodies for immunohistochemistry and correlative in situ hybridization, we assessed the intrarenal expression of both FGF-2 and FGFR1 in 13 specimens of adult kidney removed during tumor nephrectomy. RESULTS: The FGF-2 expression pattern in the kidneys as detected by immunohistochemistry was variable and depended on the antibody used. The most consistent expression of FGF-2 protein was demonstrated in glomerular parietal epithelial cells, tubular cells (mainly of the distal nephron), as well as arterial endothelial cells. These locations also corresponded to areas of FGF-2 mRNA expression. Additionally, by immunohistochemistry, FGF-2 protein was detected in arterial smooth muscle cells and occasional podocytes. The expression of FGFR1 protein and mRNA was most consistently present in tubular cells of the distal nephron and in vascular smooth muscle cells. In situ hybridization, but not immunohistochemistry, also suggested FGFR1 expression in cells that could not be precisely identified within the glomerular tuft as well as some interstitial cells. CONCLUSION: These data suggest potential autocrine and paracrine pathways within the FGF-2 system, particularly within the vascular walls and in the distal nephron, and thereby provide information for further mechanistic understanding of the role of the FGF-2 system in human renal disease.

Thrombotic microangiopathy in the HIV-2-infected macaque.

Thrombotic microangiopathy (TMA) has been increasingly reported in human immunodeficiency virus (HIV)-infected humans over the past decade. The pathogenesis is unknown. We prospectively analyzed the renal pathology and function of 27 pigtailed macaques (Macaca nemestrina), infected intravenously with a virulent HIV-2 strain, HIV-2(287), in addition to that of four uninfected control macaques. Necropsies were performed between 12 hours and 28 days after infection. HIV-2 antigen was detectable in peripheral blood mononuclear cell (PBMC) cocultures in all animals after 10 days of HIV-2 infection; a rapid decline in CD4(+) PBMC (<350/microliter) was seen in five of six animals 21 days and 28 days after infection. No macaque developed features of clinical AIDS. Typical lesions of human HIV-associated nephropathy were undetectable. Six of the 27 HIV-2-infected macaques demonstrated both histological TMA lesions (thrombi in glomerular capillary loops and small arteries, mesangiolysis) and ultrastructural lesions (mesangiolysis, subendothelial lucency, platelet thrombi in glomerular capillary lumina). Extrarenal thrombi were detected in the gastrointestinal and adrenal microvasculature of macaques that had developed renal TMA. None of the control animals demonstrated features of renal TMA at necropsy. In a retrospective analysis of kidneys obtained from 39 additional macaques infected with HIV-2(287), seven cases demonstrated TMA. In situ hybridization showed no detectable HIV-2 RNA in kidney sections of 65/66 HIV-2-infected macaques, including all 13 TMA cases. Expression of the chemokine receptor CXCR4, the putative coreceptor for HIV-2(287), was absent in intrinsic renal cells in all HIV-2-infected macaques. The HIV-2-infected macaque may be a useful model of human HIV-associated TMA. Our data do not support a role of direct HIV-2 infection of intrinsic renal cells as an underlying mechanism.

Chemokine receptor (CCR5) expression in human kidneys and in the HIV infected macaque.

BACKGROUND: The chemokine receptor, CCR5, has been identified as an essential co-receptor with CD4, which permits entry of human immunodeficiency virus (HIV) into mammalian cells. This receptor may also mediate leukocyte and parenchymal responses to injury by virtue of its binding to locally released chemokines such as RANTES, MIP-1 alpha and MIP-1 beta during inflammation. The localization of CCR5 in human or primate kidney is unknown. In this study we sought to identify sites of CCR5 synthesis through localization of mRNA coding for this peptide. METHODS: CCR5 cDNA cloned into an expression vector was transcribed into a 1.1 Kb antisense riboprobe that was utilized for in situ hybridization (ISH) and Northern blotting studies. RESULTS: Northern analysis demonstrated positive hybridization for CCR5 mRNA in total RNA isolated from allograft nephrectomy tissue with features of severe transplant rejection as well as in kidney tissue with focal interstitial nephritis. No comparable hybridization signal was achieved with human kidney tissue uninvolved by disease. CCR5 mRNA was not identified in intrinsic renal cell types by ISH in normal human (N = 6), normal macaque kidney (N = 5), in kidneys from macaques with established infection by HIV-2 (N = 9), kidneys from macaques infected with HIV-1 (N = 4), nor in kidneys from SIV-infected macaques (N = 5). CCR5 was identified by ISH in human kidneys with features of interstitial nephritis (N = 3) and in rejected human allograft kidneys (N = 14). The expression of CCR5 was restricted to infiltrating mononuclear leukocytes at sites of chronic tubulointerstitial injury and at sites of vascular and interestitial rejection, respectively. CONCLUSIONS: Understanding the localization of CCR5 as well as other chemokine receptors may help us understand how specificity in leukocyte trafficking is achieved in renal inflammatory processes such as allograft rejection and interstitial nephritis. They provide additional evidence that chemokines may be critical mediators of leukocyte trafficking in renal allograft rejection. These findings may account in part for the difficulty in demonstrating HIV infection of renal cells in human HIV infection, since these cells appear to lack constitutive expression of an essential co-receptor needed for viral entry.

Chemokine receptor (CXCR4) mRNA-expressing leukocytes are increased in human renal allograft rejection.

BACKGROUND: Mononuclear cell infiltration is a common feature of cell-mediated renal transplant rejection. Chemokines and their corresponding receptors likely play a central role in directing specific classes of leukocytes to graft sites during rejection. Localization of chemokine receptors may help us understand how specificity in leukocyte trafficking is achieved in renal inflammatory processes. The localization of the chemokine receptor CXCR4 in human kidney and in renal transplant rejection is unknown. METHODS: We generated a riboprobe specific for the detection of CXCR4 mRNA by in situ hybridization to evaluate cellular sites of synthesis of this receptor in native human kidneys (n=11) and in human allograft nephrectomies with features of severe rejection (n=14). RESULTS: By in situ hybridization, CXCR4 mRNA expression is undetectable in intrinsic glomerular, tubular, and renovascular cells in native kidneys. When renal interstitial inflammation is present, CXCR4 mRNA expression is localized to a large fraction of infiltrating leukocytes. Large numbers of CXCR4-expressing cells are detected in cell-mediated renal allograft rejection. Double immunolabeling for CD3 antigen identified a large fraction of infiltrating CXCR4 mRNA-expressing cells as T lymphocytes. CXCR4 mRNA-expressing cells were frequently seen in neointimal lesions of vascular rejection in allograft nephrectomies. CXCR4 mRNA expression was identified in infiltrating neointimal T lymphocytes, but not smooth muscle cells by immunolabeling. CONCLUSIONS: We demonstrate the involvement of CXCR4 mRNA-expressing infiltrating cells in human renal interstitial and vascular allograft rejection. Signaling via the CXCR4 receptor may be one mechanism by which chemokines mediate leukocyte trafficking in renal allograft rejection.

Improved survival and amelioration of nephrotoxic nephritis in intercellular adhesion molecule-1 knockout mice.

Intercellular adhesion molecule-1 (ICAM-1) expression is upregulated in nephrotoxic nephritis, a model of human rapidly progressive glomerulonephritis. To evaluate the pathogenetic relevance of ICAM-1 in this model, nephrotoxic nephritis was induced in ICAM-1 knockout mice and genetic controls. Mice were preimmunized with rabbit IgG in complete Freund's adjuvant. Seven days later they received rabbit anti-mouse glomerular basement membrane IgG. The early humoral immune responses (levels of circulating mouse anti-rabbit IgG, glomerular deposition of rabbit and mouse IgG and mouse C3c) were not altered in ICAM-1 knockout mice. During 28 d of follow-up, 3 of 19 control nephritic mice and 0 of 16 ICAM-1 knockout mice died. Proteinuria was high in nephritic control mice (means 10 to 12 mg/24 h at all time points investigated) and significantly reduced in nephritic ICAM-1 knockout mice (means <4.4 mg). Mean serum creatinine rose from 29 micromol/L at day -7 to 48 micromol/L (day 28) in nephritic control mice. This increase in serum creatinine was significantly lower in ICAM-1 knockout mice: 27 (day -7) and 36 micromol/L (day 28). Histologic analysis at day 28 revealed that ICAM-1 deficiency in nephrotoxic nephritis mice led to significantly reduced glomerular crescent formation (2+/-3% in ICAM-1 knockout mice versus 13+/-8% in nephritic controls) and tubulointerstitial injury (score 0.4+/-0.4 versus 2.0+/-1.1). By immunohistochemistry, ICAM-1 deficiency in nephritic mice led to significantly reduced (peri-)glomerular and/or interstitial macrophage influx, alpha-smooth muscle actin expression, and type IV collagen accumulation. These data indicate that ICAM-1 is a central mediator of glomerular and tubulointerstitial injury in murine nephrotoxic nephritis.