Blocking angiotensin II ameliorates proteinuria and glomerular lesions in progressive mesangioproliferative glomerulonephritis.
BACKGROUND: The renin-angiotensin system is thought to be involved in the progression of glomerulonephritis (GN) into end-stage renal failure (ESRF) because of the observed renoprotective effects of angiotensin-converting enzyme inhibitors (ACEIs). However, ACEIs have pharmacological effects other than ACE inhibition that may help lower blood pressure and preserve glomerular structure. We previously reported a new animal model of progressive glomerulosclerosis induced by a single intravenous injection of an anti-Thy-1 monoclonal antibody, MoAb 1-22-3, in uninephrectomized rats. Using this new model of progressive GN, we examined the hypothesis that ACEIs prevent the progression to ESRF by modulating the effects of angiotensin II (Ang II) on the production of transforming growth factor-beta (TGF-beta) and extracellular matrix components. METHODS: We studied the effect of an ACEI (cilazapril) and an Ang II type 1 receptor antagonist (candesartan) on the clinical features and morphological lesions in the rat model previously reported. After 10 weeks of treatment with equihypotensive doses of cilazapril, cilazapril plus Hoe 140 (a bradykinin receptor B2 antagonist), candesartan, and hydralazine, we examined systolic blood pressure, urinary protein excretion, creatinine clearance, the glomerulosclerosis index, and the tubulointerstitial lesion index. We performed a semiquantitative evaluation of glomerular immunostaining for TGF-beta and collagen types I and III by immunofluorescence study and of these cortical mRNA levels by Northern blot analysis. RESULTS: Untreated rats developed massive proteinuria, renal dysfunction, and severe glomerular and tubulointerstitial injury, whereas uninephrectomized control rats did not. There was a significant increase in the levels of glomerular protein and cortical mRNA for TGF-beta and collagen types I and III in untreated rats. Cilazapril and candesartan prevented massive proteinuria, increased creatinine clearance, and ameliorated glomerular and tubulointerstitial injury. These drugs also reduced levels of glomerular protein and cortical mRNA for TGF-beta and collagen types I and III. Hoe 140 failed to blunt the renoprotective effect of cilazapril. Hydralazine did not exhibit a renoprotective effect. CONCLUSION: These results indicate that ACEIs prevent the progression to ESRF by modulating the effects of Ang II via Ang II type 1 receptor on the production of TGF-beta and collagen types I and III, as well as on intrarenal hemodynamics, but not by either increasing bradykinin activity or reducing blood pressure in this rat model of mesangial proliferative GN. (+info)
Lysophosphatidic acid and mesangial cells: implications for renal diseases.
The last decade has witnessed a phenomenal increase in our understanding of the biological role of lysophosphatidic acid (LPA) and has led to an appreciation of this critical serum-derived growth factor released from platelets. We herein summarize recent observations that collectively support the hypothesis that LPA may play a key role in the pathogenesis of initiation and progression of proliferative glomerulonephritis. LPA synergistically stimulates mesangial cell proliferation in combination with platelet-derived growth factor in primary culture. The mechanism of co-mitogenesis is likely to be mediated by the prolonged activation of mitogen-activated protein kinase which is stimulated by platelet-derived growth factor and LPA through different mechanisms. LPA contracts cultured mesangial cells and has properties in common with other pressor molecules including mobilization of intracellular Ca2+ and promotion of Ca2+ entry through dihydropyridine-sensitive calcium channels. LPA receptor mRNA has been identified in isolated glomeruli dissected from renal biopsy samples of patients with IgA nephropathy. All of these facts have led us to postulate that LPA is produced within glomeruli and that LPA's mitogenic as well as haemodynamic action contribute to the pathological process of mesangial proliferative glomerulonephritis. The possible production of LPA as an autocrine factor from mesangial cells themselves has also been discussed. (+info)
Detection of urinary macrophages expressing the CD16 (Fc gamma RIII) molecule: a novel marker of acute inflammatory glomerular injury.
BACKGROUND: The CD16 antigen is the Fc gamma receptor III. CD14+CD16+ cells are proinflammatory monocytes/macrophages (Mo/M phi) that constitute a minor population in the peripheral blood of healthy individuals. Little is known about the expression of CD16 antigen on Mo/M phi in glomerulonephritis. METHODS: Flow cytometric analyses were performed on urine and blood samples obtained from 209 patients with various renal diseases. Patients variously suffered from rapidly progressive crescentic glomerulonephritis (RPGN), membranoproliferative glomerulonephritis (MPGN), postinfectious acute glomerulonephritis (AGN), Henoch-Schonlein purpura nephritis (HSPN), IgA nephropathy (IgAN), membranous nephropathy (MN), minimal change nephrotic syndrome (MCNS), lupus nephritis (LN), acute interstitial nephritis, hereditary nephropathy, idiopathic renal hematuria (IRH), and renal stone. RESULTS: The CD16+ M phi population of cells was present in the urine of hematuria-positive patients with proliferative glomerulonephritis, including AGN, IgAN, RPGN, MPGN, and LN with acute inflammatory lesions, such as endocapillary proliferation, tuft necrosis, and cellular crescents. In contrast, the urinary CD16+ M phi population was negligible in hematuria-positive patients with nonproliferative renal disease, including hereditary nephropathy, IRH, and renal stone and also in patients with proliferative glomerulonephritis lacking acute inflammatory lesions. Total urinary M phi of these patients were much less than those of patients having proliferative glomerulonephritis with acute inflammatory lesions. Transient expansion of the CD16+ M phi population in urine was observed during the acute exacerbation of urinary abnormalities, whereas the disappearance of CD16+ M phi closely preceded the amelioration of urinary abnormalities in patients with proliferative glomerulonephritis. In 38 of the 98 patients positive for CD16+ M phi population in urine, the CD16+ Mo population was negligible in peripheral blood. Immunohistochemically, CD16+ M phi were present in the glomeruli of active proliferative glomerulonephritis, whereas such cells were absent in inactive proliferative glomerulonephritis or nonproliferative glomerular diseases. CONCLUSION: CD16+ M phi may be effector cells involved in the acute inflammation common to all types of proliferative glomerulonephritis. Furthermore, the detection of CD16+ M phi in urine, as well as urinary M phi counts, may serve as a useful indicator of the active stage of proliferative glomerulonephritis. (+info)
Thrombospondin peptides are potent inhibitors of mesangial and glomerular endothelial cell proliferation in vitro and in vivo.
BACKGROUND: Thrombospondin 1 (TSP1), a multifunctional, matricellular glycoprotein, is expressed de novo in many inflammatory disease processes, including glomerular disease. Short peptide fragments derived from the type I properdin repeats of the TSP1 molecule mimic anti-angiogenic and/or transforming growth factor-beta (TGF-beta)-activating properties of the whole TSP1 glycoprotein. We investigated the effects of D-reverse peptides derived from the type I domain of TSP1 in experimental mesangial proliferative glomerulonephritis in the rat (anti-Thy1 model), as well as their effects on cultured mesangial and glomerular endothelial cells. METHODS: Effects of TSP peptides on proliferation of mesangial or glomerular endothelial cells in culture after growth arrest or growth factor stimulation (fibroblast growth factor-2, platelet-derived growth factor-BB, 10% fetal calf serum) were measured by [3H]thymidine incorporation assay. Adhesion of rat mesangial cells (MCs) to a TSP-peptide matrix was assayed using an attachment-hexosaminidase assay. TSP peptides were intraperitoneally injected daily in rats that had received an intravenous injection of polyclonal anti-Thy1 antibody to induce mesangial proliferative glomerulonephritis. On biopsies from days 2, 5, and 8 of anti-Thy1 disease, mesangial and glomerular endothelial proliferation, matrix expansion, mesangial activation, and microaneurysm formation were assessed. Functional parameters such as blood pressure and proteinuria were also measured. RESULTS: An 18-amino acid peptide (type I peptide) with anti-angiogenic and TGF-beta-activating sequences decreased mesangial and glomerular endothelial cell proliferation in vitro and in vivo and reduced microaneurysm formation and proteinuria in experimental glomerulonephritis. Analogues lacking the TGF-beta-activating sequence mimicked most effects of the type I peptide. The mechanism of action of these peptides may include antagonism of fibroblast growth factor-2 and alteration of MC adhesion. The TGF-beta-activating sequence alone did not have significant effects on mesangial or glomerular endothelial cells in vitro or in experimental kidney disease in vivo. CONCLUSION: Peptides from TSP1 may be promising therapeutics in treating glomerular disease with mesangial and endothelial cell injury. (+info)
Role of intron 1 in smooth muscle alpha-actin transcriptional regulation in activated mesangial cells in vivo.
BACKGROUND: The activation of glomerular mesangial cells is one of the early, important features of progressive glomerular disease. Smooth muscle alpha-actin (SMalphaA) is an excellent marker of activated mesangial cells. However, the mechanisms of SMalphaA regulation are only available from in vitro investigation. METHODS: We examined in vivo promoter analysis of the SMalphaA gene-utilizing transgenic mice harboring different promoter regions of the SMalphaA gene fused to chloramphenicol acetyl transferase (CAT). CAT activities were tested in primary cultured mesangial cells and in glomerular legions of Habu venom glomerulonephritis. RESULTS: The DNA sequence -891 to +3828, which contains exon 1, intron 1, and the first 14 bp of exon 2 in addition to the 5'-flanking sequence of the SMalphaA gene, induced high levels of transcription in activated mesangial cells in in vivo habu venom glomerulonephritis and in cultured mesangial cells derived from transgenic mice. The DNA region -891 to -124 was a positive element in mesangial cells derived from transgenic mice. Deletions (3316 or 137 bp) in intron 1 reduced transcription to undetectable levels. The 137 bp sequence is highly conserved among several species, containing one CArG box element, which is one of the key motifs for transcriptional activation of contractile-related proteins. In vitro transfection analysis failed to demonstrate these positive effects of intron 1 and region -891 to -124. Conclusions. In vivo promoter analysis of the SMalphaA gene provided new information about the transcriptional regulation of SMalphaA in activated mesangial cells. The DNA region -891 to -124 has a positive effect on SMalphaA transcription in cultured mesangial cells. The intron 1 region (+1088 to +1224) plays a pivotal role in SMalphaA transcription in activated mesangial cells in vivo. Further analysis of this conserved region in intron 1, including the CArG motif, will be of great value in understanding the molecular mechanisms of mesangial activation. (+info)
Hepatitis C virus-associated glomerular disease in patients with human immunodeficiency virus coinfection.
Chronic infection with hepatitis C virus (HCV) has been linked to the development of glomerular disease. HCV infection is highly prevalent among intravenous drug users, a population that is also at risk for HIV coinfection. This study reports the clinical-pathologic features and outcome of HCV-associated glomerular disease (HCV-GD) in 14 patients with HIV coinfection. All were intravenous drug users and all but one were African-Americans. Renal presentations included renal insufficiency, microscopic hematuria with active urine sediment, hypertension, and nephrotic syndrome or nephrotic-range proteinuria without hypercholesterolemia. Hypocomplementemia and cryoglobulinemia were present in 46 and 33% of patients, respectively. The predominant renal biopsy findings were membranoproliferative glomerulonephritis type 1 or type 3 (Burkholder subtype) in 79% of patients and membranous glomerulopathy with atypical features in 21% (including overlap with collapsing glomerulopathy in one patient). The clinical course was characterized by rapid progression to renal failure requiring dialysis. The overall morbidity and mortality were high with median time of 5.8 mo to dialysis or death. Although most patients died in renal failure, cause of death was primarily attributable to long-term immunosuppression and advanced AIDS. Patients with AIDS had shorter survival than those without (median survival time of 6.1 mo versus 45.9 mo, log-rank test P = 0.02). Only two patients were alive with stable renal function at follow-up of 28.5 mo. In patients with HCV-GD, coinfection with HIV leads to an aggressive form of renal disease that can be easily confused with HIV-associated nephropathy. Although hypocomplementemia, cryoglobulinemia, and more prominent hypertension and microscopic hematuria may provide clues to the presence of HCV-GD, renal biopsy is essential to differentiate HCV-GD from HIV-associated nephropathy. (+info)
Hyperimmunoglobulin E syndrome associated with nephrotic syndrome.
A 21-year-old man was admitted to Kure National Hospital with nephrotic syndrome in September 1996. He had suffered from an intractable pruritic skin rash and recurrent subcutaneous abscesses caused by the hyperimmunoglobulin E syndrome since the age of 18 months. Renal biopsy gave a diagnosis of membranoproliferative glomerulonephritis. Steroid therapy decreased urinary protein loss and hypoproteinemia, and his pruritic skin rash was improved. Patients with hyperimmunoglobulin E syndrome have a defective immune response, especially to Staphylococcus aureus infection. Continuous antigen stimulation may have caused this patient's renal histological damage as in immune complex glomerulonephritis. (+info)
Prediction in idiopathic membranous nephropathy.
BACKGROUND: Results of the prognosis of idiopathic membranous nephropathy are conflictive and prevent an effective risk stratification. These conflicts are explained in part by insufficient consideration of methodological principles for prognostic research. This cohort study is aimed at identifying clinical predictors for risk stratification while paying particular attention to methodology. METHODS: We studied 120 patients with idiopathic membranous nephropathy. Baseline data were extracted at the time of diagnostic renal biopsy, and patients were followed prospectively. Predictors were identified for the end points end-stage renal failure (ESRF) and ESRF or death. RESULTS: From the 120 patients followed for a median of five years (1 to 24 years), 19% developed end-stage renal failure or deterioration of renal function. Proteinuria of more than 3.5 g/day persisted in 34%, and 47% were in complete or partial remission. The Kaplan-Meier estimated probability of renal survival was 91 +/- 3% at five years and 75 +/- 6% at ten years. The predictors for the primary outcome, ESRF, identified in a Cox proportional hazards model, were histological stage (Ehrenreich-Churg) III-IV (hazard ratio 5.3, CI 1.9 to 15.0, P = 0.002) and nephrotic syndrome (hazard ratio 7.9, CI 1.1 to 61.5, P = 0.04); the predictors for the secondary outcome, ESRF or patient death, were histological stage III-IV (hazard ratio 2.8, CI 1.3 to 6.0, P = 0.008), nephrotic syndrome (hazard ratio 3.0, CI 1.1 to 8.0, P = 0.003) and comorbidity (hazard ratio 2.8, CI 1.3 to 5.9, P = 0.007). Nephrotic syndrome and histological stage III-IV allowed the demarcation of the high-risk group from the remaining patients (P < 0.0001). CONCLUSION: Histological stage, nephrotic syndrome, and comorbidity predict end-stage renal failure or death in idiopathic membranous nephropathy. Identification of the high-risk group at the time of diagnostic renal biopsy will permit appropriate treatment to be targeted to the patients who might benefit the most from the therapy in future clinical trials. (+info)