Frequency of disease-associated and other nuclear autoantibodies in patients of the German Network for Systemic Scleroderma: correlation with characteristic clinical features.

INTRODUCTION: In the present study, we analysed in detail nuclear autoantibodies and their associations in systemic sclerosis (SSc) patients included in the German Network for Systemic Scleroderma Registry. METHODS: Sera of 863 patients were analysed according to a standardised protocol including immunofluorescence, immunoprecipitation, line immunoassay and immunodiffusion. RESULTS: Antinuclear antibodies (ANA) were detected in 94.2% of patients. In 81.6%, at least one of the autoantibodies highly associated with SSc or with overlap syndromes with scleroderma features was detected, that is, anti-centromere (35.9%) or anti-topoisomerase I (30.1%), followed in markedly lower frequency by antibodies to PM-Scl (4.9%), U1-ribonucleoprotein (U1-RNP) (4.8%), RNA polymerases (RNAPs) (3.8%), fibrillarin (1.4%), Ku (1.2%), aminoacyl-transfer RNA synthetases (0.5%), To (0.2%) and U11-RNP (0.1%). We found that the simultaneous presence of SSc-associated autoantibodies was rare (1.6%). Furthermore, additional autoantibodies were detected in 55.4% of the patients with SSc, of which anti-Ro/anti-La, anti-mitochondrial and anti-p25/p23 antibodies were most frequent. The coexistence of SSc-associated and other autoantibodies was common (43% of patients). SSc-associated autoantibodies disclosed characteristic associations with clinical features of patients, some of which were previously not acknowledged. CONCLUSIONS: This study shows that five autoantigens (that is, centromere, topoisomerase I, PM-Scl, U1-RNP and RNAP) detected more than 95% of the known SSc-associated antibody responses in ANA-positive SSc patients and characterise around 79% of all SSc patients in a central European cohort. These data confirm and extend previous data underlining the central role of the determination of ANAs in defining the diagnosis, subset allocation and prognosis of SSc patients.

Effect of different synthetic membranes on laboratory parameters and survival in chronic haemodialysis patients.

Background. A number of studies suggested that the type of dialysis membrane is associated with differences in long-term outcome of patients undergoing haemodialysis, both in terms of morbidity and mortality. In the majority of dialysis units, synthetic membranes are being used. However, no studies are available so far for comparison between different biocompatible membranes. Therefore, we studied the influence of high- and low-flux polysulphone membranes (PS) in comparison with polymethylmethacrylate (PMMA) membranes on mortality and morbidity on the basis of various laboratory parameters. Methods. In a cohort study, data of 260 consecutive haemodialysis patients entering our dialysis unit in the years 2003-07 were collected, comparing 435 PS patient-years and 85 PMMA patient-years. PMMA membranes (n = 33) were used for those patients who did not tolerate (e.g. for pruritus) PS membranes (n = 227). Low-flux dialysers (n = 233) were compared with high-flux (n = 37). Laboratory values were evaluated by unpaired t-test, and mortality was evaluated by log-rank test and Cox regression analysis adjusted for age, diabetes and laboratory parameters. Results. Patients in our dialysis unit had a high cardiovascular risk as demonstrated by a proportion of 63% of peripheral arterial disease. Despite this, cumulative survival was almost 60% after 5 years on dialysis. It was slightly but not significantly higher in patients on PMMA (68%) compared with PS dialysers (54%) and on high-flux (61%) versus low-flux membranes (54%). After accounting for the confounding effect of age and diabetes in the multivariate Cox regression analysis, there was no impact of the membranes used (high- or low-flux, PMMA or PS) on survival. Only age at the onset of dialysis showed a significant influence on survival (P ≤ 0.001). Independent predictors of mortality in all patients in the multivariate Cox regression analysis were age, haemoglobin, leucocytes, C-reactive protein (CRP) and creatinine. Laboratory parameters between the high- and low- flux groups were not different. PS-treated patients showed significantly (P ≤ 0.05) higher values for leucocytes, thrombocytes, ferritin, and CRP and lower values for haemoglobin, transferrin, creatinine, uric acid, creatine kinase (CK), and sodium than PMMA-treated patients. Irrespective of the membrane used, in deceased patients, the following laboratory values were higher than for patients alive: leucocytes, thrombocytes, ferritin and CRP; the following were lower: haemoglobin, iron, total protein, urea, creatinine, uric acid and CK. Conclusions. The data of 260 severely ill haemodialysis patients showed a slightly, but not significantly, reduced mortality in patients treated with PMMA membranes in comparison with PS and with high-flux membranes compared with low-flux. High- or low-flux membranes exhibited no difference in laboratory values. However, in PMMA patients, laboratory data with respect to inflammation, anaemia and nutrition were significantly improved compared with the PS group. A similarly positive laboratory pattern was seen in patients alive compared with patients deceased with both membrane types. The favourable effect of PMMA membranes may be explained by the reduced activation of catabolic components and inflammation, which, in turn, would result in an improved nutrition and better response to recombinant human erythropoietin.

High frequency of corticosteroid and immunosuppressive therapy in patients with systemic sclerosis despite limited evidence for efficacy.

INTRODUCTION: In systemic sclerosis (SSc) little evidence for the effectiveness of anti-inflammatory and immunosuppressive therapy exists. The objective of this study was to determine the extent to which SSc patients are treated with corticosteroids and immunosuppressive agents. METHODS: Data on duration and dosage of corticosteroids and on the type of immunosuppressive agent were analyzed from 1,729 patients who were registered in the German Network for Systemic Scleroderma (DNSS). RESULTS: A total 41.3% of all registered SSc patients was treated with corticosteroids. Corticosteroid use was reported in 49.1% of patients with diffuse cutaneous SSc and 31.3% of patients with limited cutaneous SSc (P < 0.0001). Among patients with overlap disease characteristics, 63.5% received corticosteroids (P < 0.0001 vs. limited cutaneous SSc). A total 16.1% of the patients received corticosteroids with a daily dose >or= 15 mg prednisone equivalent. Immunosuppressive therapy was prescribed in 35.8% of patients. Again, among those patients with overlap symptoms, a much higher proportion (64.1%) was treated with immunosuppressive agents, compared with 46.4% of those with diffuse cutaneous SSc sclerosis and 22.2% of those with limited cutaneous SSc (P < 0.0001). The most commonly prescribed drugs were methotrexate (30.5%), cyclophosphamide (22.2%), azathioprine (21.8%) and (hydroxy)chloroquine (7.2%). The use of these compounds varied significantly between medical subspecialties. CONCLUSIONS: Despite limited evidence for the effectiveness of corticosteroids and immunosuppressive agents in SSc, these potentially harmful drugs are frequently prescribed to patients with all forms of SSc. Therefore, this study indicates the need to develop and communicate adequate treatment recommendations.

mTOR regulates vascular smooth muscle cell differentiation from human bone marrow-derived mesenchymal progenitors.

OBJECTIVE: Vascular smooth muscle cells (VSMCs) and circulating mesenchymal progenitor cells (MSCs) with a VSMC phenotype contribute to neointima formation and lumen loss after angioplasty and during allograft arteriosclerosis. We hypothesized that phosphoinositol-Akt-mammalian target of rapamycin-p70S6 kinase (PI3K/Akt/mTOR/p70S6K) pathway activation regulates VSMC differentiation from MSCs. METHODS AND RESULTS: We studied effects of PI3K/Akt/mTOR signaling on phenotypic modulation of MSC and VSMC marker expression, including L-type Ca(2+) channels. Phosphorylation of Akt and p70S6K featured downregulation of VSMC markers in dedifferentiated MSCs. mTOR inhibition with rapamycin at below pharmacological concentrations blocked p70S6K phosphorylation and induced a differentiated contractile phenotype with smooth muscle (sm)-calponin, sm-alpha-actin, and SM protein 22-alpha (SM22alpha) expression. The PI3K inhibitor Ly294002 abolished Akt and p70S6K phosphorylation and reversed the dedifferentiated phenotype via induction of sm-calponin, sm-alpha-actin, SM22alpha, and myosin light chain kinase. Rapamycin acted antiproliferative without impairing MSC viability. In VSMCs, rapamycin increased a homing chemokine for MSCs, stromal cell-derived factor-1-alpha, at mRNA and protein levels. The CXCR4-mediated MSC migration toward conditioned medium of rapamycin-treated VSMCs was enhanced. CONCLUSIONS: We describe novel pleiotropic effects of rapamycin at very low concentrations that stabilized differentiated contractile VSMCs from MSCs in addition to exerting antiproliferative and enhanced homing effects.

Nephroprotective effect of the HMG-CoA-reductase inhibitor cerivastatin in a mouse model of progressive renal fibrosis in Alport syndrome.

BACKGROUND: Alport syndrome is caused by mutations in genes encoding for the alpha3, alpha4 or alpha5 chain of type IV collagen leading to excessive production of fibrotic tissue and end-stage renal failure. HMG-CoA-reductase-inhibitors exhibit pleiotropic effects by which they modulate the production of connective tissue. The aim of this study was to examine the anti-fibrotic effect of the HMG-CoA-reductase-inhibitor, cerivastatin, in COL4A3 knockout mice, an animal model of Alport syndrome with progressive renal fibrosis. METHODS: Forty homozygous COL4A3 knockout mice received cerivastatin, starting 28 or 49 days after birth. Mice were sacrificed at day 52 or 66 after birth. Immunohistochemistry against laminin and fibronectin was performed. Inflammatory cell infiltration was determined by F4/80- and CD3-staining. Myofibroblasts were identified by an alpha-smooth muscle actin staining. Expression of the profibrotic cytokines, TGF-beta1 and CTGF, were determined by immunoblot. RESULTS: The lifespan of treated COL4A3 knockout mice was increased by 28% compared with untreated animals (71+/-6 vs 91+/-9 days, P<0.01). Early cerivastatin treatment reduced cholesterol levels (113+/-13 vs 141+/-19 mmol/l in untreated animals, P<0.05) and serum urea (164 vs 235 mmol/l, day 66, P<0.05). Treatment also decreased proteinuria (5.5 vs 12 g/l at day 66, P<0.05). Deposition of laminin and fibronectin, expression of TGF-beta and CTGF was reduced. Infiltration of T-cells and macrophages as well as myofibroblasts appeared to be reduced in kidneys from cerivastatin-treated mice. CONCLUSION: Cerivastatin prolongs the lifespan of COL4A3 knockout mice, reduces proteinuria and delays uraemia. These effects are associated with decreased renal fibrosis and a reduction of inflammatory cell infiltration.

Rho/Rho kinase pathway regulates maintenance of the differentiated tubular epithelial cell phenotype on laminin-1.

BACKGROUND: Maintenance of a polarized tubular epithelium by appropriate intracellular signaling and extracellular matrix is critical both in normal renal function as well as in acute and chronic tubular injury. We examined the hypothesis that maintenance of a differentiated epithelial phenotype on the basement membrane glycoprotein laminin-1 is controlled by the Rho/Rho kinase pathway. METHODS: Using the tubular epithelial cell lines LLC-PK1 and MDCK which were cultured on laminin-1 vs. collagen IV, we analyzed cell morphology and motility (cohort migration assay) as well as expression of differentiation and dedifferentiation markers (immunofluorescence microscopy). RESULTS: Cohort migration of LLC-PK1 cells was significantly slowed down on laminin-1 (10.7 +/- 2.2 m.u. (migratory units)) compared with collagen IV (16.6 +/- 2.3 m.u.; BSA control: 2.8 +/- 2.5 m.u.). Inhibition of the Rho/Rho kinase pathway by C3 exotoxin (1 mug/ml) or the Rho kinase inhibitor Y27632 (10 microM) significantly augmented cohort migration on laminin-1 (14.5 +/- 1.4 and 16.0 +/- 1.8 m.u. vs. 10.7 +/- 2.2 m.u.). In parallel to the increased migratory activity, inhibition of the Rho/Rho kinase pathway resulted in a more mesenchymal phenotype of LLC-PK1 cells on laminin-1 with increased formation of lamellopodia and filopodia, distinct loss of focal contacts and stress fibers, upregulation of the dedifferentiation marker vimentin, and loss of cell-cell contacts with translocation of beta-catenin from the adherens junctions to the cytosol and nucleus. Similarly, cohort migration of MDCK cells was retarded on laminin-1 when compared with collagen IV, and addition of the Rho kinase inhibitor Y27632 resulted in enhanced motility and a change in cell morphology. CONCLUSION: The study demonstrates that the Rho/Rho kinase pathway is required to maintain a non-migratory epithelial phenotype of cultured renal tubular LLC-PK1 and MDCK cells on the basement membrane glycoprotein laminin-1.

Nephroprotection by antifibrotic and anti-inflammatory effects of the vasopeptidase inhibitor AVE7688.

BACKGROUND: Chronic renal disease substantially increases the risk of cardiovascular events and death. Vasopeptidase inhibitors are known to show a strong antihypertensive effect. In the present study, we investigated the nephroprotective potential of the vasopeptidase inhibitor AVE7688 beyond its antihypertensive effects in a mouse model of progressive renal fibrosis. METHODS: COL4A3 -/- mice received 25 mg AVE7688 per kg body weight. Treatment was initiated in week 4 (early) and week 7 (late). Eight mice per group were sacrificed after 7.5 or 9.5 weeks, and serum levels of urea, systemic blood pressure, and proteinuria were measured. Renal tissue was investigated by routine histology, electron microscopy, immunohistochemistry, and Western blotting. Lifespan until death from renal fibrosis was monitored. RESULTS: Lifespan of treated mice increased by 143% (early therapy) and by 53% (late therapy) compared to untreated animals (172 +/- 19 vs. 109 +/- 15 vs. 71 +/- 6 days, P < 0.01). Untreated COL4A3 -/- mice did not develop severe hypertension (mean systolic blood pressure 116 +/- 14 vs. 111 +/- 9 mm Hg in wild-type mice), and both therapies mildly reduced systemic blood pressure (107 +/- 13 and 105 +/- 14 mm Hg, data not significant). AVE7688 decreased proteinuria from 12 +/- 3 g/L in untreated mice to 2 +/- 1 g/L (early) and to 4 +/- 1 g/L (late therapy, P < 0.05), as well as serum-urea from 247 +/- 27 to 57 +/- 10 and to 105 +/- 20 mmol/L (P < 0.05). Extent of fibrosis, inflammation, and profibrotic cytokines was reduced by AVE7688 therapy. CONCLUSION: The results indicate a strong nephroprotective effect of the vasopeptidase inhibitor in this animal model of progressive renal fibrosis. Besides the antihypertensive action of AVE7688, its antifibrotic, anti-inflammatory, and antiproteinuric effects demonstrated in the present study may serve as an important therapeutic option for chronic inflammatory and fibrotic diseases in man.

[The Jo-1 Syndrome--immunological findings and clinical manifestations]. / Das Jo-1-Syndrom und seine klinischen Manifestationen.

El The Jo-1 syndrome is an autoimmune disease which is characterized by the presence of autoantibodies against the Jo-1 antigen. The designation Jo-1 is derived from the name of the first patient (John P.) who was tested positive for this antibody. This patient suffered from polymyositis and fibrosing alveolitis. The Jo-1 antigen was identified as histidyl-transfer-RNA synthetase present in the cytosol. The Jo-1 syndrome is a member of a family of autoimmune diseases, called anti-synthetase syndromes. These syndromes are characterized by autoantibodies directed against aminoacyl-transfer-RNA synthetases. The etiology of the Jo-1 syndrome is unknown. The most frequent clinical manifestation is myositis, which may present as polymyositis or dermatomyositis. In addition to muscle involvement, interstitial lung disease is frequently found and critical for the prognosis. Furthermore, symptoms of other autoimmune disorders such as polyarthritis may occur. Similar to polymyositis and dermatomyositis, the Jo-1 syndrome may present as myositis overlap syndrome. In these cases, antibodies against U1-RNP are detected. The Jo-1 syndrome responds to treatment with corticosteroids and, if necessary, azathioprine, methotrexate or cyclophosphamide. The clinical manifestations of the Jo-1 syndrome are illustrated by two clinical cases.

[Successful treatment of a severe case of idiopathic pulmonary fibrosis with rapamycin]. / Erfolgreiche Rapamycin--Therapie bei idiopathischer pulmonaler Fibrose (IPF) im Präfinalstadium.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a progressive chronic disorder of the lower respiratory tract. The main clinical feature is a progressive shortness of breath, particularly on exercise. An overproduction and deposition of collagen and a proliferation of mesenchymal cells are the histopathologic characteristics. Rapamycin is an immunosuppressive agent with antiproliferative effects on mesenchymal cells including fibroblasts. It was this rationale that prompted the authors to administer rapamycin in a case of rapidly progressive IPF. CASE REPORT: In a 73-year-old female with a 2-month history of IPF, treatment with steroids and interferon gamma-1b did not improve the detrimental clinical course. Treatment with rapamycin was started; subsequently, clinical condition and objective findings improved markedly within weeks. She is now under treatment for 18 months. CONCLUSION: The authors presume that partial remission is related to rapamycin which may be effective in blocking the progressive fibrosis and increased collagen synthesis thought to be pathophysiologically relevant in this disease. Further studies have to show whether rapamycin may be a treatment option in idiopathic pulmonary fibrosis.

Differential regulation of smooth muscle markers in human bone marrow-derived mesenchymal stem cells.

OBJECTIVE: To study smooth-muscle differentiation and de-differentiation of human bone marrow-derived mesenchymal stem cells (MSCs), which have been shown to enter the circulation and to contribute to vascular repair and atherosclerosis. DESIGN: Human MSCs from bone marrow were cultured with 20% fetal calf serum (FCS) or with 10% FCS and various concentrations of dimethyl sulfoxide (DMSO). Expression of smooth muscle markers was determined by Western blot analysis and immunofluorescence. For signalling studies, involvement of the mammalian target of rapamycin (mTOR) pathway was tested by treatment with rapamycin. RESULTS: MSCs cultured with 20% FCS acquired a smooth muscle-like appearance and expressed the smooth muscle (sm) markers sm-alpha-actin, desmin, sm-calponin and myosin light chain kinase (MLCK). DMSO induced a spindle-like morphology with marked reduction of stress fibers. As judged by Western blot analysis, treatment with 2.5% DMSO strongly downregulated expression of sm-calponin (-85%), short MLCK (-98%) and sm-alpha-actin expression (-51%). Reduced calponin expression was detected by day 2 of treatment with 0.5-2.5% DMSO. After withdrawal of DMSO, MSCs regained high expression of sm-calponin. Treatment with 6 nmol/l rapamycin partly antagonized the effect of DMSO, indicating the involvement of mTOR in regulation of the smooth muscle phenotype of MSCs. CONCLUSIONS: DMSO strongly downregulates the smooth muscle markers sm-calponin, short MLCK and sm-alpha-actin in human MSCs, indicating a transition from a smooth muscle-like phenotype to an undifferentiated state by an mTOR-dependent mechanism. Regulating the phenotype of human MSCs may be of relevance for novel therapeutic approaches in atherosclerosis and intimal hyperplasia after vascular injury.

Antifibrotic, nephroprotective potential of ACE inhibitor vs AT1 antagonist in a murine model of renal fibrosis.

BACKGROUND: Several studies have shown antifibrotic effects of angiotensin converting enzyme (ACE) inhibitors as well as of angiotensin receptor 1 (AT1) antagonists, however, prospective trials with clinical end points comparing these effects do not exist. COL4A3-/- mice develop a non-hypertensive progressive renal fibrosis. We used this animal model to compare the potential of ACE inhibitor vs AT1 antagonist to prevent renal fibrosis irrespective of blood pressure-dependent involvement by the renin system. METHODS: COL4A3-/- mice were treated with placebo, ramipril or candesartan. Blood pressure, proteinuria, serum urea and lifespan were monitored. Renal matrix was characterized by immuno-histochemistry, light and electron microscopy. Further biochemical analysis was provided using cDNA microarray and western blot techniques. RESULTS: Untreated mice died of renal failure after 71+/-6 days. Ramipril and candesartan both delayed onset and reduced the extent of proteinuria. Both had minor effects on blood pressure and postponed onset of uraemia. Ramipril increased lifespan by 111% to 150+/-21 days (P<0.01), whereas candesartan resulted in only a 38% prolongation to 98+/-16 days (P<0.01). Ramipril reduced glomerular and tubulo-interstitial fibrosis and numbers of activated fibroblasts to a greater extent than candesartan. Microarray and western blot analysis revealed a higher antifibrotic potential of ramipril in terms of downregulation of TGFbeta, connective tissue growth factor, metalloproteinases and extracellular matrix proteins. CONCLUSIONS: The results indicate an antifibrotic, nephroprotective effect of ACE inhibitors and AT1 antagonists in an animal model of progressive renal fibrosis. The greater antifibrotic effect of ramipril at the maximal therapeutic doses employed may not be explained by different antiproteinuric or blood pressure lowering properties, but by-in contrast to candesartan-its ability to hinder the proinflammatory, profibrotic activation of the angiotensin receptor 2.

[Glomerular-type proteinuria in hantavirus nephritis]. / Glomeruläre Proteinurie bei Hantavirus-Nephritis.

BACKGROUND: Infection with hantavirus of the Puumala type is known to cause severe illness, fever, loin pain and impaired vision. Tubulointerstitial nephritis leads to acute renal failure. CASE REPORTS: In four patients presenting with hantavirus infection and acute renal failure, proteinuria was analyzed by microelectrophoresis to explore possible causes of renal protein loss in hantavirus nephritis. The patients (three men, one woman) presented with a short history of fever, headache, loin pain and acute renal failure (enlarged kidneys in ultrasonography, serum creatinine 7.7/3.4/3.2/7.8 mg/dl, urinary protein excretion 1.7/0.5/1.5/9.0 g/l, IgM antibodies against hantavirus positive in all patients, subtype Puumala). Microelectrophoresis of the urine revealed a major fraction of higher molecular weight proteins such as transferrin and immunoglobulins indicating unselective glomerular-type proteinuria in all four patients. In three renal biopsy specimens obtained, morphology of glomeruli and vasculature was normal as judged by light microscopy. The tubulointerstitium exhibited interstitial hemorrhage and round-cell infiltrates. After 2 weeks, renal function had completely recovered in all patients and no persistent proteinuria developed. CONCLUSION: Hantavirus nephritis may lead to glomerular-type proteinuria. Glomerular morphology may be normal and proteinuria may cease within 2 weeks indicating a transient lesion of the glomerular filtration barrier. Transiently increased glomerular permeability may be caused by an immunologic response to virus infection.

Preemptive ramipril therapy delays renal failure and reduces renal fibrosis in COL4A3-knockout mice with Alport syndrome.

BACKGROUND: Alport syndrome (AS) is a common hereditary cause of end-stage renal failure in adolescence due to defects in type IV collagen genes. Molecular genetics allows early diagnosis, however, no preventive strategy can be offered. Using the COL4A3 -/- mouse, an animal model for human AS, we evaluated therapy with ramipril in mice. METHODS: One hundred and twenty-two Alport-mice were treated with 10 mg/kg/day ramipril added to drinking water. Proteinuria, serum-urea and lifespan were monitored. Renal matrix was characterized by immunohistochemistry, light- and electron microscopy, and Western blot. RESULTS: Untreated COL4A3 -/- mice died from renal failure after 71 +/- 6 days. Early therapy starting at four weeks of age and continuing to death delayed onset and reduced the extent of proteinuria. Uremia was postponed by three weeks in treated animals. Lifespan increased by more than 100% to 150 +/- 21 days (P < 0.01). In parallel, decreased deposition of extracellular matrix and lessened interstitial fibrosis as well as reduced amounts of renal transforming growth factor-beta1 (TGF-beta1) could be demonstrated. Late therapy starting at seven weeks decreased proteinuria, however, lifespan did not increase significantly. CONCLUSIONS: The results indicate an antiproteinuric and antifibrotic nephroprotective effect of ramipril in COL4A3 -/- mice is mediated by down-regulation of TGF-beta1. This effect in mice is enhanced by initiation of therapy during pre-symptomatic disease. The data in COL4A3 -/- mice as an animal-model for Alport syndrome suggest that ramipril might as well delay renal failure in humans with AS. Early diagnosis and preemptive treatment also may be crucial in humans.

P2 receptor antagonist PPADS inhibits mesangial cell proliferation in experimental mesangial proliferative glomerulonephritis.

BACKGROUND: Although extracellular nucleotides have been shown to confer mitogenic effects in cultured rat mesangial cells through activation of purinergic P2 receptors (P2Y receptors), thus far the in vivo relevance of these findings is unclear. Virtually all cells and in particular the dense granules of platelets contain high levels of nucleotides that are released upon cell injury or platelet aggregation. In experimental mesangial proliferative glomerulonephritis in the rat (anti-Thy1 model), mesangiolysis and glomerular platelet aggregation are followed by a pronounced mesangial cell (MC) proliferative response leading to glomerular hypercellularity. Therefore, we examined the role of extracellular nucleotides and their corresponding receptors in nucleotide-stimulated cultured mesangial cells and in inflammatory glomerular disease using the P2 receptor antagonist PPADS. METHODS: The effects of PPADS on nucleotide- or fetal calf serum (FCS)-stimulated proliferation of cultured MC were measured by cell counting and [3H]thymidine incorporation assay. After induction of the anti-Thy1 model, rats received injections of the P2-receptor antagonist PPADS at different doses (15, 30, 60 mg/kg BW). Proliferating mesangial and non-mesangial cells, mesangial cell activation, matrix accumulation, influx of inflammatory cells, mesangiolysis, microaneurysm formation, and renal functional parameters were assessed during anti-Thy1 disease. P2Y-mRNA and protein expression was assessed using RT-PCR and real time PCR, Northern blot analysis, in situ hybridization, and immunohistochemistry. RESULTS: In cultured mesangial cells, PPADS inhibited nucleotide, but not FCS-stimulated proliferation in a dose-dependent manner. In the anti-Thy1 model, PPADS specifically and dose-dependently reduced early (day 3), but not late (day 8), glomerular mesangial cell proliferation as well as phenotypic activation of the mesangium and slightly matrix expansion. While no consistent effect was obtained in regard to the degree of mesangiolysis, influx of inflammatory cells, proteinuria or blood pressure, PPADS treatment increased serum creatinine and urea in anti-Thy1 rats. P2Y receptor expression (P2Y2 and P2Y6) was detected in cultured MC and isolated glomeruli, and demonstrated a transient marked increase during anti-Thy1 disease. CONCLUSION: These data strongly suggest an in vivo role for extracellular nucleotides in mediating early MC proliferation after MC injury.