Adenoviral-mediated gene transfer restores plasma ADAMTS13 antigen and activity in ADAMTS13 knockout mice

ADAMTS13 is a plasma metalloprotease that regulates the size of the von Willebrand factor (VWF) multimers. Genetic or acquired deficiency of ADAMTS13 causes thrombotic thrombocytopenic purpura (TTP) in humans. Plasma infusion is the treatment of choice for patients with congenital ADAMTS13 deficiency. However, this practice exposes patients to the risk of infections, allergies and fluid volume overload. The search for alternative treatments is required. Here, we tested the ability of systemically administered adenovirus encoding human ADAMTS13 to restore the deficient protein in the circulation of Adamts13(-/-) mice. Injection of the adenovirus efficiently transduced the liver, kidney, lung, heart and spleen, resulting in the secretion of ADAMTS13 into plasma. A reduced area of thrombi was observed when blood from Ad-ADAMTS13-treated mice was perfused over a collagen-coated surface in a parallel plate flow chamber compared with blood of Ad-betaGal-treated controls. The secreted ADAMTS13 protein was functionally active even after 2 months from injection. The data provide the proof of principle for developing a novel therapy for the correction of ADAMTS13 deficiency in patients with hereditary TTP.

Imatinib ameliorates renal disease and survival in murine lupus autoimmune disease

Platelet-derived growth factor (PDGF) has been proved to play an important role in progressive glomerular disease of systemic lupus. The present study investigated the tyrosine kinase inhibitor of PDGF receptor, imatinib, as a novel therapeutic approach for the cure of lupus nephritis in New Zealand Black/White (NZB/W)F1 hybrid mice with established disease. Two groups of NZB/W mice (N=30 each group), starting at 5 months of age, were given by gavage vehicle or imatinib (50 mg/kg b.i.d). Fifteen mice for each group were used for the survival study. The remaining were killed at 8 months. Imatinib significantly (P=0.0022) ameliorated animal survival with respect to vehicle. The drug significantly delayed the onset of proteinuria (% proteinuric mice, 7 and 8 months: 33 and 47 vs vehicle, 80 and 87, P<0.05) and limited the impairment of renal function. Imatinib protected the kidney against glomerular hypercellularity and deposits, tubulointerstitial damage, and accumulation of F4/80-positive mononuclear cells and alpha-smooth actin-positive myofibroblasts. The abnormal transforming growth factor-beta mRNA expression in kidneys of lupus mice was reduced by imatinib. In conclusion, findings of amelioration of animal survival and renal manifestations in NZB/W lupus mice with established disease by imatinib suggests the possibility to explore whether imatinib may function as steroid-sparing drug in human lupus nephritis.

Angiotensin-converting enzyme inhibition prevents glomerular-tubule disconnection and atrophy in passive Heymann nephritis, an effect not observed with a calcium antagonist

In proteinuric nephropathies tubular atrophy leads to glomerular-tubule disconnection through an unknown mechanism. Here we studied whether proteinuria promoted glomerular-tubule disconnection in individual nephrons and whether this phenomenon was prevented by an angiotensin-converting enzyme (ACE) inhibitor. Passive Heymann nephritis (PHN) and control rats were studied at 4 and 8 months. Two additional groups of PHN rats received lisinopril (40 mg/L) or a calcium channel blocker (lacidipine, 3 mg/kg) from day 7 after surgery to 8 months. At sacrifice, kidneys were serially sectioned to identify glomerular- tubule abnormalities in individual nephrons and changes in interstitial volume. In PHN rats, the time-dependent increase in proteinuria was paralleled by tubular atrophy leading to glomerular-tubule disconnection and interstitial volume enlargement. Marked apoptosis was invariably found in atrophic tubules in contrast to the absent or very mild terminal dUTP nick-end labeling staining in tubules normally connected to glomeruli in PHN animals. Treatment with an ACE inhibitor prevented hypertension, proteinuria, the formation of atrophic tubuli, glomerular-tubule disconnection and limited the fractional interstitial volume expansion. Although lacidipine limited hypertension, it did not reduce proteinuria or prevent tubular atrophy and disconnection. Multivariate analysis showed that the appearance of atubular glomeruli and the increase in interstitial volume were better predicted by proteinuria than blood pressure. This study suggests that ACE inhibitors effectively prevent glomerular-tubule disconnection possibly by their ability of reducing proteinuria, which in turn favors proximal tubular cell apoptosis. Agents that only reduced hypertension but not proteinuria do not affect tubular behavior.

Mycophenolate mofetil combined with a cyclooxygenase-2 inhibitor ameliorates murine lupus nephritis

BACKGROUND

Approaches to the treatment of lupus nephritis include immunosuppressants associated with anti-inflammatory drugs, mainly steroids, which, however, cause major side effects. Mycophenolate mofetil (MMF) has been described as being less toxic than conventional immunosuppressants, and it was effective in preventing progressive nephritis in lupus mice. Our study evaluated the therapeutic effect of MMF in NZB/W F1 hybrid mice with established disease. We also examined the combination of MMF with a selective cyclooxygenase-2 (COX-2) inhibitor, DFU, based on previous findings of excessive renal production of COX-2-derived thromboxane A2 (TXA2) in lupus nephritis.

METHODS

Four groups of NZB/W mice (N = 30 each group), starting at five months of age, were given daily by gavage the following: vehicle, MMF 60 mg/kg, DFU 3 mg/kg, or MMF + DFU. Fifteen mice for each group were used for the survival studies, and the remaining mice were sacrificed at nine months.

RESULTS

MMF or DFU alone partially delayed the onset of proteinuria compared with vehicle. Combined therapy was significantly (P < 0.05) more effective than single drugs. Animal survival was partially ameliorated by MMF and significantly improved by the drug combination in comparison with the vehicle (P = 0.005) and DFU alone (P < 0.03). At nine months, serum blood urea nitrogen (BUN) levels were lower in all of the treated groups than in the vehicle group. Renal damage was also limited, but to a greater extent in mice given the combined therapy. In untreated mice, renal COX-2 mRNA expression was up-regulated, and generation of TXB(2), the stable breakdown product of TXA(2), increased. DFU prevented the abnormal renal TXB(2) production, confirming the COX-2 origin of this eicosanoid, whereas renal 6-keto-PGF(1 alpha) and prostaglandin E(2) (PGE(2)) were not affected substantially.

CONCLUSIONS

These results offer a strong case for exploring the possibility that in humans MMF combined with COX-2 inhibitors has a role in the treatment options for lupus nephritis. This combined drug therapy may be at least as effective as steroids but without the obvious nephrotoxicity of the latter.

Protein traffic activates NF-kB gene signaling and promotes MCP-1-dependent interstitial inflammation

Mononuclear cells accumulate in the renal interstitium and contribute to renal injury in proteinuric nephropathies. Angiotensin-converting enzyme (ACE) inhibitors reduce protein trafficking and also lessen renal structural and functional damage. Many proinflammatory genes, including monocyte chemoattractant protein-1 (MCP-1), a chemoattractant for monocytes and T lymphocytes, are transcriptionally regulated by nuclear factor-kappa B (NF-kB). We aimed to study NF-kB activation and MCP-1 expression over time in two models of progressive proteinuric nephropathies (5/6 nephrectomy and passive Heymann nephritis [PHN]) and evaluate the effect of antiproteinuric therapy with an ACE inhibitor on these factors. In both models, increased urinary protein excretion over time was associated with a remarkable increase in NF-kB activity, which was almost completely suppressed by reducing proteinuria with lisinopril. NF-kB activation was paralleled by upregulation of MCP-1 messenger RNA and interstitial accumulation of ED-1-positive monocytes/macrophages and CD8-positive T cells. Lisinopril inhibited MCP-1 upregulation and limited interstitial inflammation. In a group of PHN rats with advanced disease and severe proteinuria, a dose of lisinopril high enough to inhibit renal ACE activity failed to reduce proteinuria and also did not limit NF-kB activation, which was sustained over time, along with MCP-1 gene overexpression and interstitial inflammation. These data suggest that NF-kB is activated in the presence of increased protein traffic, enhancing the nuclear transcription of the MCP-1 gene with potent chemotactic and inflammatory properties. This mechanism may help explain the long-term renal toxicity of filtered proteins.

17beta-estradiol corrects hemostasis in uremic rats by limiting vascular expression of nitric oxide synthases

Conjugated estrogens shorten the prolonged bleeding time in uremic patients and are similarly effective in a rat model of uremia. We have previously demonstrated that the shortening effect of a conjugated estrogen mixture or 17beta-estradiol on bleeding time was abolished by the nitric oxide (NO) precursor L-arginine, suggesting that the effect of these drugs on hemostasis in uremia might be mediated by changes in the NO synthetic pathway. The present study investigated the biochemical mechanism(s) by which conjugated estrogens limit the excessive formation of NO. 17beta-estradiol (0.6 mg/kg), given to rats made uremic by reduction of renal mass, significantly reduced bleeding time within 24 h and completely normalized plasma concentrations of the NO metabolites, nitrites and nitrates, and of NO synthase (NOS) catalytic activity, determined by NADPH-diaphorase staining in the thoracic aorta. Endothelial NOS (ecNOS) and inducible NOS (iNOS) immunoperoxidase staining in the endothelium of uremic aortas of untreated rats was significantly more intense than in control rats, while in uremic rats receiving 17beta-estradiol staining was comparable to controls. Thus 17beta-estradiol corrected the prolonged bleeding time of uremic rats and fully normalized the formation of NO by reducing the expression of ecNOS and iNOS in vascular endothelium. These results provide a possible biochemical explanation of the well-known effect of estrogens on primary hemostasis in uremia, in experimental animals and humans.

Angiotensin-converting enzyme inhibition prevents loss of glomerular hydraulic permeability in passive heymann nephritis

We used morphometric techniques and theoretical analysis to investigate structural and functional changes of the glomerular membrane that develop in passive Heymann nephritis (PHN), an experimental model of human membranous glomerulopathy The effect of angiotensin-converting enzyme (ACE) inhibition on the above parameters was also investigated to explore the mechanisms by which this treatment exerts functional and structural protection at the renal tissue level. Morphometric analysis of glomerular capillary by light and electron microscopy was performed in normal control rats and in rats injected with rabbit anti-Fx 1A antibody, 12 months after induction of PHN. A group of PHN rats treated with lisinopril during the observation period was also investigated. Glomerular capillary architecture was not significantly altered in PHN rats, thus glomerular volume and capillary lumen volume were comparable with normal controls; only mesangial volume was significantly elevated in PHN rats. Glomerular membrane structure was significantly affected by PHN: the thickness of the glomerular basement membrane (GBM) increased, and the frequency of epithelial filtration slits decreased. Electron-dense deposits in the subepithelial space of the GBM were estimated to occupy more than 20% of the GBM area. Theoretical analysis of glomerular hydraulic permeability allowed us to predict that, after these structural changes, the permeability of the GBM and the epithelial layer significantly decreased, with an average reduction in the ultrafiltration coefficient (Kf) of approximately 43%. ACE inhibition limited mesangial expansion and prevented changes of glomerular epithelial cells (filtration slit frequency) but not GBM thickening. Immune deposits within the GBM were only partially prevented by lisinopril. A selective effect on epithelial permeability was calculated in lisinopril-treated rats, and a partial preservation of Kf reduction was observed. These results suggest that structural changes of the GBM and epithelial cells that develop in PHN are responsible for the reduced filtration capacity observed in this model. ACE inhibition only partially prevented immune-deposits in the GBM and favorably affected epithelial cell structure. These selective effects on glomerular podocytes may contribute to preserve water and macromolecule permeability of the glomerular capillary wall in this immunologic model of kidney disease.

Combining an antiproteinuric approach with mycophenolate mofetil fully suppresses progressive nephropathy of experimental animals

Chronic renal diseases progress to organ insufficiency, which may require replacement therapy within one to three decades even independently of the type of initial insults. In the majority of cases, the degrees of proteinuria and interstitial leukocyte infiltration and scarring are strictly correlated with the rate of disease progression. This study tests the hypothesis that excess intrarenal protein traffic may cause lymphocyte-dependent interstitial injury that, while not fully controlled by antiproteinuric therapy, can be further inhibited by concomitant immunosuppression. A primarily nonimmune model was used to reproduce progressive renal disease due to a critical loss of nephron mass. Angiotensin-converting enzyme (ACE) inhibitor limited proteinuria, interstitial inflammation, MHC class II antigen expression, and severe lesions. Combined treatment with ACE inhibitor and a specific antilymphocyte agent, mycophenolate mofetil, dramatically attenuated macrophage and T cell infiltration, MHC-class II overexpression, dendritic cells, and all manifestations of the disease. Evidence of lymphocyte-mediated renal injury in the setting of excess protein traffic provides the basis for combining ACE inhibition and immunosuppression to halt progression of proteinuric kidney disease and minimize the need for dialysis or transplantation.

Antiproteinuric therapy while preventing the abnormal protein traffic in proximal tubule abrogates protein- and complement-dependent interstitial inflammation in experimental renal disease

In proteinuric glomerulopathies, the excess traffic of proteins into the renal tubule is a candidate trigger of interstitial inflammatory and immune events leading to progressive injury, and a key target for the renoprotective action of antiproteinuric drugs. Among proteins trafficked to the proximal tubule, the third component of complement (C3) can be activated locally and contribute to inflammation at sites of protein reabsorption. Experiments were performed in rats with renal mass reduction (RMR, 5/6 nephrectomy) with the following aims: (1) to study Ig (IgG) and complement deposition in proximal tubules, and interstitial macrophage infiltration and MHC class II expression at intervals after surgery by double immunofluorescence analysis; (2) to assess whether lisinopril (angiotensin-converting enzyme inhibitor [ACEi], 25 mg/L in the drinking water, from either day 1 or day 7) limited IgG and C3 accumulation and interstitial inflammation at day 30. In 7-d remnant kidneys, intracellular staining for both IgG and C3 was detectable in proximal tubules in focal areas; C3 was restricted to IgG-positive tubular cells, and there were no interstitial ED-1 macrophage and MHC II-positive cellular infiltrates. In 14-d and 30-d remnant kidneys, proximal tubular IgG and C3 staining was associated with the appearance of interstitial infiltrates that preferentially localized to areas of tubules positive for both proteins. RMR rats given ACEi had no or limited increases in levels of urinary protein excretion, tubular IgG, and C3 reactivity, and interstitial cellular infiltrates in kidneys at 30 d, even when ACEi was started from day 7 after surgery. These findings document that (1) in RMR, IgG and C3 accumulation in proximal tubular cells is followed by leukocyte infiltration and MHC II overexpression in the adjacent interstitium; (2) ACEi while preventing proteinuria limits both tubular accumulation of IgG and C3 and interstitial inflammation. The data suggest that ACE inhibition can be renoprotective by limiting the early abnormal protein traffic in proximal tubule and consequent deleterious effects of excess protein reabsorption, including the accumulation and local activation of complement as well as the induction of chemokines and endothelin genes known to promote interstitial inflammation and fibrosis.

Renoprotection by nitric oxide donor and lisinopril in the remnant kidney model

Previous studies showed a renoprotective effect of l-arginine in experimental uremia. Whether this was caused by an increased nitric oxide (NO) release or depended on l-arginine per se is not clear. Here, we evaluated whether chronic administration of an NO donor, molsidomine, controlled systemic blood pressure and renal disease progression and prolonged survival in rats with renal mass reduction (RMR). Rats with RMR received the following daily in the drinking water: group 1 (n = 21), no specific therapy (vehicle); group 2 (n = 12), molsidomine, 120 mg/L; group 3 (n = 9), lisinopril, 25 mg/L; and group 4 (n = 12), reserpine, 5 mg/L, hydralazine, 80 mg/L, and hydrochlorothiazide, 25 mg/L, from day 21 after surgery, when rats had hypertension and proteinuria, until the death of the vehicle-treated rats. Molsidomine normalized systemic hypertension, only partially reduced proteinuria and serum creatinine levels, but significantly prolonged animal survival, particularly in the early stage of the disease. Lisinopril at a similar systemic blood pressure was even better than molsidomine in limiting proteinuria, preserving renal function, and prolonging survival, but triple therapy, despite being effective on blood pressure, offered no renoprotection or prolonged survival. Endothelin-1 (ET-1) levels, formed in excessive amounts by the kidneys of these animals, were reduced by molsidomine and lisinopril, but not by triple therapy. The prolongation of survival by NO donor could be attributed to its effect of reducing ET levels, which in turn may limit the smooth muscle cell proliferation and matrix accumulation responsible for organ and, especially, myocardial fibrosis in uremia.

Experimental Goodpasture's syndrome in Wistar-Kyoto rats immunized with alpha3 chain of type IV collagen

BACKGROUND

Glomerulonephritis and lung hemorrhage of autoimmune Goodpasture syndrome develop due to immune reactions against epitope(s) of the non-collagenous (NC1) domain of alpha3-chain of type IV collagen [alpha3(IV) NC1]. Whether thymic mechanisms have a role in the loss of tolerance to the Goodpasture epitope has not been established. We studied the renal and pulmonary effects of immunization with different forms (monomer, dimer, or hexamer) of alpha3(IV) NC1 collagen in Wistar-Kyoto (WKY) rats, and assessed whether the intrathymic inoculation of the antigen may protect against anti-GBM disease.

METHODS

WKY rats were immunized with bovine alpha3(IV) monomer, dimer, or hexamer, or with alpha3(IV) NC1 synthetic peptide. Renal function, kidney and lung immunohistology, and circulating and tissue bound antibodies to type IV collagen chains were analyzed. Effects of intrathymic inoculation of antigen on subsequent disease induction were analyzed in WKY rats given alpha3(IV) NC1 dimer or GBM preparation intrathymically 48 hours before immunization.

RESULTS

Proteinuria, linear IgG deposition in GBM, and crescentic glomerulonephritis developed in WKY rats immunized with alpha3(IV) NC1 dimer or hexamer. Lesions were dose-dependent upon injections of 10 to 100 microgram dimer. The alpha3(IV) NC1 monomer induced less severe proteinuria and no crescents. Pulmonary hemorrhage was detectable in 35% of rats immunized with 25 to 100 microgram alpha3(IV) NC1 dimer; alpha3(IV) synthetic peptide (36 carboxyl terminal) did not induce disease. Rats injected intrathymically with up to 100 microgram alpha3(IV) NC1 dimer or with GBM 48 hours before immunization were not protected against subsequent development of proteinuria and glomerulonephritis.

CONCLUSIONS

These findings document that glomerulonephritis and lung hemorrhage can be elicited in WKY rats by immunization with alpha3(IV) NC1. Failure of the intrathymic inoculation of antigen to prevent disease suggests that immunological tolerance cannot be achieved by this intervention, in contrast to other autoimmune conditions, and may imply independent roles for cellular and humoral nephritogenic pathways in anti-GBM nephritis.

Renoprotective effect of contemporary blocking of angiotensin II and endothelin-1 in rats with membranous nephropathy

BACKGROUND

We previously showed that chronic administration of an angiotensin converting enzyme (ACE) inhibitor to rats with passive Heymann nephritis (PHN), a model of membranous nephropathy with proteinuria and increased renal synthesis of endothelin-1 (ET-1), reduces urinary proteins and partially limits the exaggerated ET-1 renal synthesis. Here we compared the effect of an ETA receptor antagonist and an ACE-inhibitor given as single therapies with a combination of the two drugs in uninephrectomized PHN rats.

METHODS

PHN was induced with a single i.v. injection of rabbit anti-Fx1A antibody in 40 male Sprague Dawley rats. To accelerate the onset of renal damage rats underwent uninephrectomy seven days later and were subsequently treated until eight months with the ETA receptor antagonist LU-135252 (50 mg/kg b.i.d. p.o.) or the ACE-inhibitor trandolapril (1 mg/kg in the drinking water) or the combination of the two drugs.

RESULTS

Either LU-135252 or trandolapril given alone prevented the increase in systolic blood pressure (SBP). Combined therapy was even more effective than single drugs. While LU-135252 and trandolapril reduced proteinuria by 23 to 25%, the drug combination resulted in 45% lowering of urinary proteins. Serum creatinine was significantly decreased by the combination, but not by the single drugs. Glomerulosclerosis and tubulointerstitial damage were more reduced by combined therapy than by LU-135252 or trandolapril alone.

CONCLUSIONS

These data suggest that contemporary blocking angiotensin II (Ang II) and ET-1 in an accelerated model of PHN had an additive renoprotective effect than single blocking Ang II or ET-1 and would represent a therapeutic advantage for renal disease patients who do not completely respond to ACE inhibitors.

In progressive nephropathies, overload of tubular cells with filtered proteins translates glomerular permeability dysfunction into cellular signals of interstitial inflammation

Progression to end-stage renal failure is the final common pathway of many forms of glomerular disease, independent of the type of initial insult. Progressive glomerulopathies have in common persistently high levels of urinary protein excretion and tubulointerstitial lesions at biopsy. Among the cellular mechanisms that may determine progression regardless of etiology, the traffic of excess proteins filtered from glomerulus in renal tubule may have functional importance by initiating interstitial inflammation in the early phase of parenchymal injury. This study analyzes the time course and sites of protein accumulation and interstitial cellular infiltration in two different models of proteinuric nephropathies. In remnant kidneys after 5/6 renal mass ablation, albumin and IgG accumulation by proximal tubular cells was visualized in the early stage, preceding interstitial infiltration of MHC-II-positive cells and macrophages. By double-staining, infiltrates developed at or near tubules containing intracellular IgG or luminal casts. This relationship persisted thereafter despite more irregular distribution of infiltrate. Similar patterns were found in an immune model (passive Heymann nephritis), indicating that the interstitial inflammatory reaction develops at the sites of protein overload, regardless of the type of glomerular injury. Osteopontin was detectable in cells of proximal tubules congested with protein in both models at sites of interstitial infiltration, and by virtue of its chemoattractive action this is likely mediator of a proximal tubule-dependent inflammatory pathway in response to protein load. Protein overload of tubules is a key candidate process translating glomerular protein leakage into cellular signals of interstitial inflammation. Mechanisms underlying the proinflammatory response of tubular cells to protein challenge in diseased kidney should be explored, as well as ways of limiting protein reabsorption/deposition to prevent consequent inflammation and progressive disease.

Pharmacologic control of angiotensin II ameliorates renal disease while reducing renal TGF-beta in experimental mesangioproliferative glomerulonephritis

We evaluated the effect of blocking angiotensin II (AngII) on the development of proteinuria and glomerular injury in antithymocyte serum (ATS) glomerulonephritis. Disease was induced in Sprague-Dawley rats by a single intravenous injection of rabbit ATS. Three groups of rats were considered: group 1 (n = 13), ATS rats with no therapy; group 2 (n = 13), ATS rats treated with angiotensin-converting enzyme inhibitor (40 mg/L lisinopril in the drinking water); and group 3 (n = 13), ATS rats treated with AngII receptor antagonist (50 mg/L L-158,809 in the drinking water). Treatment started 3 hours after ATS injection and lasted 4 days. An additional group of control rats (group 4, n = 13) received preimmune serum. At day 4, ATS rats developed proteinuria (46+/-5 mg/d v control 12+/-1 mg/d; P < 0.01), which was prevented by both lisinopril and L-158,809 (14+/-0.2 mg/d and 15+/-1.6 mg/d, respectively, P < 0.01 v ATS). Systolic blood pressure was comparable in ATS rats and in controls (119+/-4 mm Hg v 120+/-2 mm Hg). Systolic blood pressure values were significantly decreased after either lisinopril or L-158,809 (104+/-3 mm Hg and 101+/-5 mm Hg, respectively; P < 0.01 v ATS). Serum creatinine levels were similar in all groups. Quantitation of proliferating cells and macrophages by analysis of proliferating cell nuclear antigen-positive and ED1-positive cells/glomerular cross-section showed a marked increase in proliferating cell nuclear antigen-positive cells in glomeruli of ATS rats over controls (12.6+/-0.5 cells/glomerular cross-section v 1.9+/-0.2 cells/glomerular cross-section; P < 0.01), which was significantly (P < 0.01) prevented by both treatments (lisinopril, 5.7+/-1.0 cells/glomerular cross-section; L-158,809, 4.8+/-1.5 cells/glomerular cross-section). The increase in ED1-positive cells (10+/-0.7 cells/glomerular cross-section v controls, 1.8+/-0.2 cells/glomerular cross-section; P < 0.01) was also significantly (P < 0.01) reduced by lisinopril and L-158,809 (4.1+/-0.7 cells/glomerular cross-sections and 2.6+/-0.6 cells/glomerular cross-section, respectively). Blocking of AngII activity prevented almost completely the formation of microaneurysms in ATS rats (percent of glomeruli with microaneurysms: ATS, 11.5%+/-3.5%; ATS + lisinopril, 0.4%+/-0.2%; ATS + L-158,809, 0.8%+/-0.8%; controls, 0%). Because AngII is a potent inducer of renal transforming growth factor-beta (TGF-beta), a cytokine involved in the regulation of cell proliferation, matrix deposition, and monocyte migration (which is overexpressed in the kidney of ATS rats), we then evaluated the effect of AngII inhibitors on renal gene expression of TGF-beta1 and on urinary TGF-beta1. TGF-beta1 mRNA levels in kidneys of ATS rats were 3.6-fold higher than those of controls and were reduced by 46% and 32% after treatment with lisinopril and L-158,809, respectively. Urinary TGF-beta1 excretion increased in ATS (37.3+/-6.0 ng/d v controls, 13.8+/-3.4 ng/d; P< 0.01) but was normalized by lisinopril and L-158,809 (7.6+/-1.9 ng/d and 6.4+/-0.4 ng/d, respectively; P < 0.01). Thus, in ATS, blocking AngII synthesis prevents proteinuria and reduces glomerular cell proliferation and inflammatory cell infiltration, possibly by reducing excessive renal TGF-beta synthesis. These findings may be relevant for future strategies in the treatment of human mesangioproliferative glomerulonephritis.

Bindarit retards renal disease and prolongs survival in murine lupus autoimmune disease

As an alternative to classical immunosuppressants in experimental lupus nephritis, we looked at bindarit, 2-methyl-2-[[1-phenylmethyl)-1H-indazol-3-y1]methoxy]propanoic acid, a novel molecule devoid of immunosuppressive effects, which selectively reduces chronic inflammation in rat adjuvant arthritis. Two groups of NZB/W mice (N = 55 for each group) were given bindarit, (50 mg/kg/day p.o.) or vehicle starting at 2 months of age. Mice were sacrificed at 2, 6, 8 and 10 months or used for survival studies. Bindarit delayed the onset of proteinuria (% proteinuric mice, bindarit vs. vehicle, 6 months: 0 vs. 33% and 8 months: 7% vs. 60%, P < 0.005; 10 months: 53% vs. 80%) and significantly (P < 0.05) protected from renal function impairment (serum BUN, bindarit vs. vehicle: 8 months, 30 +/- 3 vs. 127 +/- 42; 10 months, 53 +/-5 vs. 140 +/- 37 mg/dl). Appearance of anti-DNA antibodies was retarded and survival significantly (P < 0.0001) prolonged by bindarit (% survival, bindarit vs. vehicle: 8 months, 100% vs. 80%; 10 months, 87% vs. 40%; 12 months, 27% vs. 20%). Bindarit significantly limited glomerular hypercellularity, interstitial inflammation and tubular damage. Renal expression of monocyte chemoattractant protein (MCP-1) mRNA (Northern blot) markedly increased (7 - 12-fold in 8- 10-month-old mice vs. 2-month-old) during the progression of nephritis in association with mononuclear cell infiltration. Bindarit completely prevented MCP-1 up-regulation. In another series of experiments, bindarit (0.25% and 0.5% medicated diet, N = 16 for each group) when started at 4.5 months of age in NZB/W mice improved survival in respect to untreated mice (N = 17) in a dose-dependent manner (% survival: 8 months, 94% and 100%, respectively, vs. 47%; 10 months, 75% and 100% vs. 35%; 12 months, 31% and 75% vs. 12%). Survival was even more prolonged when bindarit (0.5% medicated diet) was combined with a low dose of methylprednisolone (1.5 mg/kg i.p.), which that only partially modifies proteinuria and survival of lupus mice, in an additional group of animals (N = 16). Thus, at 14.5 months when all mice given bindarit alone died, 50% of mice on combined therapy were still alive (P < 0.023). Studies are needed to establish whether bindarit may function as a steroid sparing drug in human lupus.

Angiotensin II blockade limits tubular protein overreabsorption and the consequent upregulation of endothelin 1 gene in experimental membranous nephropathy

Proteinuric renal diseases are associated with excessive renal synthesis of endothelin 1 (ET-1) either in experimental animals or humans. This has been interpreted as an upregulation of ET-1 gene in proximal tubular cells secondary to overreabsorption of an unusual amount of filtered proteins. Here we used a model of chronic proteinuria, passive Heymann nephritis (PHN), to localize the structure of the kidney responsible for excessive ET-1 expression and synthesis and to clarify whether drugs that reduce glomerular protein trafficking modified the distribution of ET-1 mRNA and the corresponding peptide in the kidney. PHN was induced in Sprague-Dawley rats after injection of rabbit anti-Fx1A antibody. Group 1 (n = 5) was untreated, group 2 (n = 5) was given daily the angiotensin-converting enzyme inhibitor lisinopril (40 mg/l) plus the angiotensin II receptor antagonist L-158,809 (50 mg/l) from day 7--when rats were already proteinuric--to month 12. An additional group of normal rats (n = 5) was used as controls. Urinary excretion of ET-1 was significantly increased in PHN rats as compared with controls and normalized by the treatment. By in situ hybridization a weak signal for ET-1 mRNA was detectable in glomeruli, distal tubular segments, and proximal tubules of control kidneys. By contrast, a strong labeling was found in the kidneys of rats with PHN which was mainly localized to proximal tubules and renal interstitium. The pattern of renal ET-1-like immunoreactivity was remarkably consistent with ET-1 mRNA expression. In animals with PHN given the angiotensin II blocking therapy, the urinary excretion of proteins normalized, and the structural integrity of the kidney was well preserved. In the kidney tissue taken from these animals, both ET-1 mRNA and protein staining were quite comparable to controls. These data suggest a link between excessive protein tubular reabsorption and enhanced renal ET-1 in chronic nephropathies and provide a novel explanation for the renoprotective effect in vivo of drugs that, by blocking the biological activity of angiotensin II, reduce glomerular protein traffic and possible deleterious effects of excessive tubular protein overloading.

Time course and localization of endothelin-1 gene expression in a model of renal disease progression

Experimental and human proteinuric glomerulopathies are associated with tubulo-interstitial injury that correlates with the decline of renal function even better than glomerular lesions do. Mechanism(s) leading to tubulo-interstitial damage are unknown. It has been proposed that excessive reabsorption of filtered proteins activates renal cells to produce vasoactive and inflammatory molecules including endothelin-1. The aim of the present study was twofold: we first evaluated the cellular origin of excessive renal endothelin-1 production in the renal mass reduction model and then related endothelin-1 distribution to the development of kidney lesions. Four groups of renal mass reduction (n = 15) and four groups of control rats (n = 5) were studied at 7, 14, 21, and 28 days after surgery. Urinary proteins in renal mass reduction rats were comparable with controls at day 7 but became significantly higher thereafter. Renal mass reduction rats first developed tubulo-interstitial changes, which were already evident at day 14 in the majority of them. At 28 days, renal mass reduction rats also developed glomerulosclerosis. A parallel increase of renal endothelin-1 gene expression and synthesis of the corresponding peptide in renal mass reduction rats versus controls was observed from day 14. Nonradioactive in situ hybridization confirmed a pattern of endothelin-1 mRNA consistent with the distribution of lesions. At day 14, endothelin-1 staining was stronger in renal mass reduction than in control kidneys and mainly localized to the cytoplasm of tubular cells, whereas glomeruli were negative. At day 28, endothelin-1 expression further increased in renal mass reduction rats as compared with controls, and the staining was apparent also in glomeruli. Thus, in renal mass reduction, a progressive up-regulation of endothelin-1 occurs during the development of renal injury, that first involves the tubules and, only in a subsequent phase, the glomeruli.

Renal and systemic nitric oxide synthesis in rats with renal mass reduction

In rats undergoing renal mass reduction (RMR) oral supplementation with the nitric oxide (NO) precursor L-arginine increases glomerular filtration rate and ameliorates signs of glomerular injury, suggesting that chronic renal failure in the rats is a condition of low NO formation in the kidney. On the contrary, data are available that in the systemic circulation of uremics, both rats and human beings, NO is formed in excessive amounts and may contribute to platelet dysfunction and bleeding tendency, well-known complications of uremia. The present study was designed to clarify the pathophysiology of renal and systemic NO synthesis in uremia. We showed that renal ex vivo NO generation, measured as the conversion of [3H] L-arginine to [3H] L-citrulline, was lower than normal in RMR rats, seven days after surgery, and progressively worsened with time in close correlation with signs of renal injury. Consistent with these results, urinary excretion of the stable NO metabolites, NO2-/NO3-, significantly decreased in rats with RMR. To go deeper into the cellular origin and biochemical nature of this abnormality we used two histochemical approaches that could locate either NO synthase (NOS) catalytic activity (NADPH-diaphorase) or NOS isoenzyme expression (immunoperoxidase). NADPH-diaphorase documented a progressive loss of renal NOS activity in RMR rats that co-localized with a strong progressive decrease of inducible NOS isoenzyme (iNOS) immunostaining. At variance with iNOS, endothelial cell NOS (ecNOS) staining was rather comparable in RMR and control kidneys. At variance to the kidney, in the systemic circulation of RMR rats the synthesis of NO increased as reflected by higher than normal plasma NO2-/NO3- concentrations. High systemic NO likely derives from vessels as documented by the increased NOS activity and higher expression of both iNOS and ecNOS in the aorta of RMR rats. Up-regulation of systemic NO synthesis might be an early defense mechanism against hypertension of uremia. On the other hand, more NO available to circulating cells may sustain the bleeding tendency, a well-known complication of uremia.

Mycophenolate mofetil limits renal damage and prolongs life in murine lupus autoimmune disease

Classical immunosuppressants like cyclophosphamide give excellent results in human lupus nephritis. However, they augment malignancies and viral infections. Here we investigated the effect of the new immunosuppressant agent, mycophenolate mofetil (MMF), in New Zealand Black x New Zealand White (NZBxW) F1 hybrid mice, a model of genetically determined immune complex disease that mimics systemic lupus in humans. MMF has a selective antiproliferative effect on T- and B-lymphocytes, inhibits antibody formation and blocks the glycosylation of lymphocyte glycoproteins involved in the adhesion of leukocytes to endothelial cells. Two groups of NZBxW mice were used: group 1 (N = 20) given daily MMF (60 mg/kg p.o.) and group 2 (N = 15) given daily vehicle alone. Treatment started at three months of age and lasted until the death of the animals. Results showed that percentage of proteinuric mice was significantly reduced by MMF treatment and serum BUN levels were also lower than vehicle. MMF had a suppressive effect on autoantibody production and protected animals from leukopenia and anemia. Life survival of MMF treated lupus mice was significantly improved in respect to untreated animals. Thus, MMF delayed renal function deterioration and prolonged life survival in murine lupus nephritis. MMF has been already recognized as reasonably well tolerated in renal transplant patients and despite its gastrointestinal toxicity its overall safety profile appears superior to azathioprine. Human studies are needed to establish whether MMF may function as a steroid-sparing drug in lupus nephritis.

Renal expression of monocyte chemoattractant protein-1 in lupus autoimmune mice

Mononuclear cell infiltration in glomeruli and renal interstitium is a prominent feature of some types of glomerulonephritis, including lupus nephritis. The mechanism(s) underlying monocyte influx into the kidney is not fully understood. Recently, monocyte chemoattractant protein-1 (MCP-1) has been identified as a chemotactic factor involved in the recruitment of monocytes/macrophages in the glomeruli of rats with mesangioproliferative as well as anti-glomerular basement membrane glomerulonephritis. In the study presented here, renal MCP-1 mRNA expression in New Zealand Black x New Zealand White (NZB/W) F1 mice, a model of genetically determined immune complex disease that mimics systemic lupus in humans, was investigated. Northern blot analysis revealed a single 0.7 kb MCP-1 transcript of very low intensity in kidneys from 2-month-old NZB/W mice that had not yet developed proteinuria nor renal damage. Message levels, which increased markedly with the progression of nephritis and in association with mononuclear cell infiltration, were 10- and 15- fold higher in 8-10-month-old mice than in 2-month-old mice. By in situ hybridization, increased expression of MCP-1 mRNA was demonstrated in glomeruli and, even more striking, in tubular epithelial cells. Western blot analysis demonstrated increased expression of MCP-1 protein in kidneys of 10-month-old NZB/W mice, consistent with MCP-1 mRNA data. When NZB/W mice were treated with cyclophosphamide up to 12 months of age, expression of MCP-1 in the renal tissue remained low, the influx of inflammatory cells did not appear, and glomerular and tubular structures remained well preserved. These data suggest that elevated MCP-1 might act as a signal for inflammatory cells to infiltrate the kidney in lupus nephritis.

The renoprotective properties of angiotensin-converting enzyme inhibitors in a chronic model of membranous nephropathy are solely due to the inhibition of angiotensin II: evidence based on comparative studies with a receptor antagonist

In several models of renal disease progression, angiotensin-converting enzyme (ACE) inhibitors reduced proteinuria and limited glomerulosclerosis, which suggested that reduction of renal angiotensin II (Ang II) activity is crucial for the preservation of glomerular structure and function. However, it cannot be ruled out that other hormonal systems, including inhibition of the bradykinin breakdown, also play a role. We compared the effects of chronic treatment with the ACE inhibitor lisinopril with those of a specific Ang II receptor antagonist, L-158,809, on proteinuria and renal injury in passive Heymann nephritis (PHN), a model of immune renal disease that closely resembles human membranous nephropathy, with long-lasting proteinuria followed by tubulointerstitial damage and glomerulosclerosis. Passive Heymann nephritis was induced with 0.5 mL/100 g of rabbit anti-Fx1A antibody in 24 male Sprague-Dawley rats. The animals were divided into three groups of eight rats each, and were given the following in the drinking water on a daily basis: lisinopril (40 mg/L), L-158,809 (50 mg/L), or no therapy. Treatment started at day 7 (proteinuria was already present) and lasted 12 months. Eight normal rats were used as controls. Untreated PHN rats developed hypertension, while rats with PHN given lisinopril or L-158,809 all had systolic blood pressure values even lower than those of normal rats. Urinary protein excretion progressively increased with time in untreated PHN rats, who developed tubulointerstitial damage and glomerulosclerosis. Both lisinopril and L-158,809 exhibited a potent antiproteinuric effect and preserved glomerular and tubular structural integrity at a similar extent. Renal gene expression of transforming growth factor-beta and extracellular matrix proteins was also effectively reduced by the two treatments. These results indicate that ACE inhibitors and Ang II receptor antagonists are equally effective in preventing renal injury in PHN and suggest that the renoprotective effects of ACE inhibitors in this model are solely due to inhibition of Ang II.

A study of low-nutrient diets used for aging studies in the rat

The effects of diets of low caloric value on rats used in aging studies were investigated. Groups of 85 Sprague-Dawley rats were fed ad libitum from 3 months of age on three different diets containing 8 or 10 Megajoule (MJ) of metabolizable energy and 80 or 100 g of crude protein/kg. Body weights, food consumption, and morphological and biochemical parameters were monitored throughout life. Kidneys were examined histologically. Rats given the diet with highest energy and protein ate less food, attained greater weights, and had larger abdominal fat deposits than those on the lower energy diets. They had a raised proteinuria, and nearly half developed glomerulosclerosis and tubulo-interstitial damage by 26 months. There was no significant difference in mortality between the groups, and no other serious abnormalities were observed. It is concluded that rats can be maintained into old age with no signs of nutritional inadequacy on diets with lower energy and protein contents than those in general use.

Passive Heymann nephritis: evidence that angiotensin-converting enzyme inhibition reduces proteinuria and retards renal structural injury

In nonimmunological models of renal damage, abnormal traffic of proteins through the glomerular capillary is one of the possible causes of renal disease progression. Here we investigated whether in a model of immune-mediated glomerulonephritis long-lasting proteinuria resulted in renal structural damage and whether chronic treatment with perindopril, an angiotensin-converting enzyme (ACE) inhibitor, lowered proteinuria and retarded disease progression. Passive Heymann nephritis (PHN), a model of human membranous nephropathy, was induced with 0.5 ml/100 g of rabbit anti-Fx1 A antibody in 26 male Sprague-Dawley rats. Animals were then divided into two groups of 13 rats each, given daily vehicle or perindopril (1 mg/kg p.o). Treatment started at day 7 when proteinuria was already present and lasted 12 months. An additional group of normal rats was used as control. Renal biopsies were taken at months 8 and 12. Untreated PHN rats showed a significant increase in systolic blood pressure starting from month 8, that was normalized by perindopril administration. Urinary protein excretion progressively increased with time in untreated PHN rats that developed focal and segmental glomerulosclerosis and tubulointerstitial damage. Perindopril significantly reduced proteinuria and limited glomerular and tubulointerstitial injury. Urinary excretion of endothelin-1 (ET-1) and transforming growth factor-beta 1 (TGF-beta 1), two major mediators of renal damage in other models of glomerulonephritis, increased with time in PHN but only the former correlated with the degree of glomerulosclerosis. The effect of perindopril on proteinuria and renal structural damage was associated with a significant reduction in urinary ET-1 but not TGF-beta 1, suggesting that ET-1 may be an important determinant of disease progression in experimental membranous nephropathy.

Blocking both type A and B endothelin receptors in the kidney attenuates renal injury and prolongs survival in rats with remnant kidney

Renal disease progression in the rat is associated with a time-dependent upregulation of renal endothelin-1 (ET-1) gene expression and synthesis. We have previously demonstrated that endothelin A receptor subtype (ETA) blockade in rats with remnant kidney reduced signs of disease activity, suggesting that ET-1 exerts part of its deleterious effects on the kidney through ETA. No data are available so far on the role of ETB receptor in progressive renal injury. We first studied renal ETA and ETB receptor gene expression in rats with remnant kidney on days 7, 30, and 120 after the surgical procedure. While renal expression of ETA was unaffected, ETB receptor gene was significantly upregulated with time in rats with remnant kidney, being 3.5-fold and sixfold higher than shamoperated rats at days 30 and 120. We also evaluated whether bosentan, a nonpeptidic ETA and ETB receptor antagonist, offered better protection against renal disease progression than reported for ETA-selective blockers and whether it improved survival in animals with renal ablation. Two groups of rats with renal mass reduction (n = 11 each) were given bosentan 100 mg/kg/d orally or its vehicle (carboxymethyl cellulose) beginning day 7 after the surgical procedure and were followed until the death of the vehicle-treated animals. Sham-operated animals comprised the control group. Bosentan partially prevented increases in blood pressure and proteinuria, but had a remarkable protective effect on renal function and significantly prolonged animal survival. These data suggest that blocking both renal ETA and ETB receptors might have major implications in the treatment of human progressive nephropathies.

A specific endothelin subtype A receptor antagonist protects against injury in renal disease progression

We have recently reported that renal preproendothelin-1 gene is up-regulated in rats with renal mass reduction (RMR) and that time-dependent increase in urinary excretion of the corresponding peptide correlates with renal disease progression. Here we evaluated whether a specific endothelin subtype A (ETA) receptor antagonist, FR139317, reduced signs of disease activity in this model. Two groups of rats were given FR139317 or its vehicle (saline) from day 7 to day 60 after the surgical procedure. Sham-operated animals were the control group. Blood pressure, urinary protein excretion and serum creatinine were evaluated at days 0, 7 (before FR139317 or saline administration), 30, 45 and 60. At sacrifice, histological evaluation of renal tissue was performed. The results showed that ETA receptor blocker reduced the abnormal permeability to proteins, limited glomerular injury and prevented renal function deterioration thus confirming the working hypothesis. These findings suggest that this class of compounds may eventually prove useful in the treatment of human progressive nephropathies.

Renal endothelin gene expression is increased in remnant kidney and correlates with disease progression

We previously demonstrated that urinary endothelin excretion is increased in rats with extensive renal mass reduction, a model of progressive renal disease. Here we explored whether the increased urinary endothelin in this model were due to induction of renal pre-pro-endothelin-1 gene and whether changes in endothelin synthetic pathway correlated with the development of glomerulosclerosis. Four groups of rats with renal mass reduction and four groups of sham-operated control rats were studied 7, 30, 60 and 120 days after the surgical procedure. Urinary protein excretion in renal mass ablation animals did not differ from controls at seven days, but was already significantly elevated (P < 0.01) 30 days after surgery. Then proteinuria progressively increased in rats with remnant kidney at values above 400 mg/day at day 120. Serum creatinine concentration also progressively increased with time in renal mass ablation rats, unlike sham-operated animals, and values were significantly different (P < 0.01) at each of the points considered. Rats with renal mass reduction, unlike sham-operated animals, developed focal glomerulosclerosis that affected 8% of glomeruli at day 30, and 24% of glomeruli at day 120. Seven days after renal mass reduction renal pre-pro-endothelin-1 (pre-pro ET) mRNA was comparable to that of sham-operated rats, while a 2.5-, 5- and fourfold increase in 2.3 Kb pre-proET-1 transcript was observed at 30, 60 and 120 days, respectively. Urinary excretion of endothelin was significantly elevated (P < 0.01) in rats with renal mass reduction with respect to sham-operated rats, starting from 30 days after surgery and increased further thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Verotoxin glycolipid receptors determine the localization of microangiopathic process in rabbits given verotoxin-1

Infection with verotoxin-producing Escherichia coli has been implicated in the cause of hemolytic-uremic syndrome. Cases of thrombotic thrombocytopenic purpura and verotoxin infections have been also described. In this study we sought to determine the following: (1) whether verotoxin induces microvascular lesions in the rabbit, (2) the organ distribution of such lesions, and (3) the distribution of verotoxin glycolipid receptors in the various organs. Rabbits challenged with verotoxin-1 purified from E. coli O157:H7 had anorexia, lethargia, and limb paralysis; renal function, however, was normal. Central nervous system lesions found included pericellular and perivascular edema, focal hemorrhage, vascular lesions, and severe alterations of Purkinje cells. Histologic changes were also seen in the colon, with mucosal and submucosal edema and hemorrhage, and in the lung, with interstitial fibrosis and focal lymphohistiocitic infiltration. No lesions were detected in kidney, heart, liver, and spleen. Screening of various tissues for the presence of the verotoxin receptors revealed galabiosyl ceramide in the central nervous system and globotriosyl ceramide in the gastrointestinal tract, lung, and spleen. No receptors for verotoxin were found in the heart, liver, and kidney. These results indicate that organ localization of the disease in rabbits is dependent on the distribution of verotoxin receptors.

Renal protective effect of angiotensin-converting enzyme inhibition in aging rats

Aging in rats with intact kidneys is associated with changes in selective glomerular permeability to macromolecules resulting in proteinuria and progressive glomerular sclerosis. We have previously reported that angiotensin-converting enzyme (ACE) inhibition in Munich Wistar Fromter/Ztm (MWF/Ztm) rats resulted in a significant reduction of proteinuria, in respect to untreated animals, and that treated animals were protected against the development of glomerular sclerotic lesions. The present study was designed to establish whether ACE inhibition protects against glomerular injury in male Sprague-Dawley rats, which develop spontaneous proteinuria and glomerulosclerosis with age. The effect of ACE inhibition was tested when proteinuria was already present. Four-month treatment with the ACE inhibitor perindopril prevented the increase in systolic blood pressure, compared with vehicle-treated animals, and significantly decreased urinary protein excretion of aging rats. Partial protection of the development of glomerular sclerosis was also observed.

L-arginine, the precursor of nitric oxide, abolishes the effect of estrogens on bleeding time in experimental uremia

We have reported previously that conjugated estrogens that are effective in shortening the prolonged bleeding time in uremic patients are also effective on bleeding time in a rat model of uremia. Using such a rat model we have recently demonstrated that nitric oxide (NO), an endothelium-derived vasodilator, is involved in mediating the bleeding tendency of uremia. With the present study we wanted to investigate whether conjugated estrogen mixture or its active component, 17 beta-estradiol, reduce uremic bleeding by interfering with the NO pathway. Our results showed that the shortening effect of conjugated estrogen and 17 beta-estradiol on bleeding time of uremic rats was completely reversed by giving the animals the NO precursor L-arginine, but not D-arginine, which is not a precursor of NO. Dexamethasone which at variance to progesterone inhibits the process of induction of NO-forming enzyme, shortened the prolonged bleeding time of uremic rats within 4 hours from injection. This effect was eliminated by L-arginine but not D-arginine administration. The glucocorticoid receptor antagonist cortexolone prevented the shortening of bleeding time induced by dexamethasone, suggesting that a receptor-mediated mechanism is involved in the hemostatic effect of dexamethasone as previously reported for estrogens. Unlike conjugated estrogens and dexamethasone, progesterone had no effect on bleeding time. All these findings would indicate that the effect of estrogens and dexamethasone on primary hemostasis in uremia might be mediated by changes in NO synthetic pathway.

Role of endothelium-derived nitric oxide in the bleeding tendency of uremia

Endothelium-derived relaxing factor, now identified as nitric oxide (NO), is a labile humoral agent formed by vascular endothelial cells from L-arginine. NO mediates the action of substances that induce endothelium-dependent relaxation and plays a role in regulating blood pressure. In this study we investigated whether NO is involved in the pathogenesis of the bleeding tendency associated with renal failure. Rats with extensive surgical ablation of renal mass develop renal insufficiency due to progressive glomerulosclerosis. Like uremic humans, rats with renal mass reduction and uremia have a bleeding tendency that manifests itself by a prolonged bleeding time. We found that N-monomethyl-L-arginine (L-NMMA), a specific inhibitor of NO formation from L-arginine, completely normalized bleeding time when given to uremic rats. L-NMMA injection also increased ex vivo platelet adhesion but did not affect ex vivo platelet aggregation induced by adenosine diphosphate, arachidonic acid, and calcium ionophore A23187. The shortening effect of L-NMMA on bleeding time was completely reversed by giving the animals the NO precursor L-arginine, but not D-arginine, which is not a precursor of NO. It thus appears that NO is a mediator of the bleeding tendency of uremia.

Thromboxane synthesis inhibition increases renal prostacyclin and prevents renal disease progression in rats with remnant kidney

Previous studies have demonstrated that inhibition of thromboxane A2-dependent platelet aggregation by the thromboxane A2 synthase inhibitor, OKY 1581, ameliorated the progressive kidney disease of rats with subtotal renal ablation. OKY 1581 also decreased the excessive renal thromboxane A2 synthesis and lowered systemic blood pressure. In the same model, a low dose aspirin and a specific thromboxane A2 receptor antagonist failed to influence proteinuria, glomerulosclerosis, and hypertension, thus excluding a role for either platelet or renal thromboxane A2 in renal disease progression. The aims of this study were to establish (1) whether a thromboxane A2 synthase inhibitor different from OKY 1581 could retard the progression of glomerular disease in rats with remnant kidney and (2) whether this effect was associated with an increase in renal synthesis of the vasodilatory prostacyclin. Treatment of rats with renal mass ablation with FCE 22178 (100 mg/kg by gavage and 200 mg/kg in the drinking water) for 35 days starting 10 days after surgical ablation was associated with an improvement in renal function in comparison with rats receiving the vehicle alone. Proteinuria was significantly lower, and rats were partially protected from the development of glomerulosclerosis. Systolic blood pressure was significantly lower than in animals given the vehicle. Urinary thromboxane B2 excretion was significantly decreased, and urinary 6-keto-prostaglandin F1 alpha increased in respect to vehicle-treated rats. We conclude that FCE 22178 limits glomerular injury in rats with remnant kidney.

Oral zeranol shortens the prolonged bleeding time of uremic rats

Intravenous conjugated estrogens reduce the prolonged bleeding time in uremic patients and in a rat model of uremia. However, estrogens have major side effects related to their hormonal activity. We investigated whether a beta-resorcylic acid lactone, zeranol (a compound with close spatial similarity to estrogens but with a weak estrogenic activity), improves primary hemostasis in uremic rats and whether the effect is mediated by estrogen receptors. The results showed that single oral administration of zeranol significantly (P less than 0.01) shortened the bleeding time of uremic rats, 20 mg/kg being the minimum effective dose. This effect was long-lasting (72 hours). The dose of 30 mg/kg zeranol reproduced the pattern observed after 20 mg/kg but bleeding time values were still significantly (P less than 0.01) shortened 96 hours after the administration. No changes in hematocrit, platelet and leukocyte count, and serum creatinine were detected after zeranol administration. When uremic rats were pre-treated orally with two estrogen receptor antagonists, tamoxifen and clomiphene (3 mg/kg), zeranol did not shorten the bleeding time, thus suggesting that the hemostatic effect of zeranol was due to an estrogen receptor-mediated mechanisms. These results might have important future implications for the management of uremic bleeding in humans.

Tissue plasminogen activator therapy of rabbit nephrotoxic nephritis

To study the efficacy of tissue plasminogen activator (PA) therapy to prevent deteriorating renal function in experimental proliferative glomerulonephritis we used a model of nephrotoxic nephritis induced in rabbits by injection of antiglomerular basement membrane antiserum. Saline or recombinant tissue plasminogen activator (rt-PA, 1.3 mg/kg body weight) was infused daily for 7 days starting from day 7 after the injection of antiglomerular basement membrane antiserum when the disease had been already triggered. Animals were killed on day 14. Rabbits given saline had abundant deposits of fibrin and crescents in about 67% of glomeruli. rt-PA significantly protected animals from glomerular fibrin deposition and crescent formation with respect to saline-treated animals. Renal function measured as creatinine clearance was dramatically impaired in rabbits given saline. Treatment with rt-PA ameliorated the renal function impairment of nephrotoxic nephritis. rt-PA did not produce a systemic fibrinolytic state as indicated by alpha 2-antiplasmin level measurement. These results suggest that tissue PA may have important implications in preventing renal function deterioration in humans with crescentic glomerulonephritis and fibrin depositions.

17 beta-estradiol is the most active component of the conjugated estrogen mixture active on uremic bleeding by a receptor mechanism

We have reported previously that a mixture of conjugated estrogens which is effective in shortening the prolonged bleeding time in uremic patients is also effective on bleeding time in a rat model of uremia. With the present study we took advantage from such a rat model of chronic uremia and decided to identify the component(s) of the conjugated estrogen mixture responsible for shortening the bleeding time. Moreover, we wanted to clarify whether estrogen effect on primary hemostasis is due to a receptor mechanism and can be neutralized by specific estrogen receptor antagonists such as tamoxifen or clomiphene. Both estrone sulfate and 17 beta-estradiol, but not equilin, were effective in shortening the prolonged bleeding time of uremic rats. 17 beta-Estradiol was the most active component of the mixture, reproducing the time course of bleeding time shortening of the entire mixture (effect lasting 48 hr). The effect of estrone sulfate injection lasted only 24 hr. Tamoxifen and clomiphene pretreatment prevented the shortening of bleeding time induced by conjugated estrogen mixture and its active components. These findings indicate that 17 beta-estradiol is the key compound of the conjugated estrogen mixture effective on bleeding time shortening and that the effect of estrogens on primary hemostasis is mediated by a receptor mechanism.

Renal handling of aspirin in the rat

Aspirin (ASA), in addition to blocking platelet cyclooxygenase, thus preventing thromboxane A2 formation, can also block renal cyclooxygenase thus inhibiting the renal synthesis of vasodilatory prostaglandins (PGs) which can induce renal function deterioration. The purpose of the present study was to clarify the pharmacological basis of the inhibitory effect of ASA on renal cell cyclooxygenase in the rat. ASA was given to rats either i.v. or p.o. at doses ranging from 10 to 200 mg/kg. After both i.v. and p.o. administration ASA was rapidly detected in plasma as intact molecule. The kinetics were of a dose-dependent type with a disproportionate increase in plasma level increasing the dose. Plasma salicylic acid (SA) concentrations peaked after ASA with a precursor product relationship. ASA levels in kidney homogenates were also determined after i.v. and p.o. ASA. Whereas after i.v. administration ASA was detected in the kidney as intact molecule, no ASA was detected in the kidney after p.o. administration. SA was measurable in the kidney after both i.v. and p.o. ASA with a time course which paralleled the plasma concentrations. Results of isolated kidneys perfused with a medium containing ASA and of kidney homogenates exposed to ASA "in vitro" indicate that ASA is rapidly converted to SA by kidney tissue enzymes. After ASA hydrolysis SA accumulates in the kidney and may protect renal cyclooxygenase from the inhibitor effect of ASA.

Tumor necrosis factor induces glomerular damage in the rabbit

Tumor necrosis factor (TNF) is a polypeptide hormone produced by activated macrophages detectable in the circulation of experimental animals given endotoxin. Recent evidence strongly suggests that many of the deleterious effects of endotoxin in experimental animals are mediated by TNF. Because endotoxemia in experimental animals and humans is associated with glomerular damage the present investigation was designed to establish whether TNF directly induces glomerular functional and structural changes. Twenty-three rabbits were given human recombinant TNF at the doses of 0.08, 0.8, and 8.0 micrograms/kg/h as a continuous 5-hour intravenous infusion. Animals were killed at the end of the infusion. All rabbits given 0.8 and 8.0 micrograms/kg/h TNF developed anemia (Ht value decrease at 5 hours: 0.8 microgram/kg/h, 15%; 8.0 micrograms/kg/h, 16%); leukopenia (leukocyte count decrease at 5 hours: 0.8 micrograms/kg/h, 47%; 8.0 micrograms/kg/h, 59%); thrombocytopenia (platelet count decrease at 5 hours; 0.8 micrograms/kg/h, 45%; 8.0 micrograms/kg/h, 57%). Rabbits given 8.0 micrograms/kg/h also had renal failure (serum creatinine from 1.02 +/- 0.15 to 1.64 +/- 0.34 mg/dl). By light microscopy only occasional polymorphonuclear leukocytes in the glomerular capillaries were detectable in rabbits infused with 0.08 micrograms/kg/h TNF, whereas with 0.8 micrograms/kg/h TNF the presence of inflammatory cells in the glomerular capillaries was the prominent finding. With 8.0 micrograms/kg/h TNF beside leukocyte accumulation, fibrin was detected in the glomerular capillary lumens of two of eight animals. Electron microscopy found dose-dependent glomerular endothelial cell damage in animals given TNF with fibrinlike material in the capillary lumens. Glomerular changes induced by TNF were remarkably similar to those previously found in animals given endotoxin. Thus, TNF is likely to be the mediator of endotoxin-induced glomerular damage and can be regarded as a new mediator of macrophage-dependent damage in glomerulonephritis.

Sequence of glomerular changes in experimental endotoxemia: a possible model of hemolytic uremic syndrome

Glomerular morphological changes produced by 5-hour intravenous infusion of endotoxin (40 micrograms/kg/h) were studied in 57 rabbits. During endotoxin infusion all animals developed signs of endotoxemia, anemia, and transient leukopenia and thrombocytopenia. Acute renal failure also developed in all animals. By light microscopy a marked polymorphonuclear cell infiltration was the prominent finding within 1 h from the beginning of the infusion. At hour 5 fibrin deposits and thrombi were detected in most animals. The abnormalities were reversible. By electron microscopy endothelial damage was detected few minutes after the beginning of endotoxin infusion followed by leukocyte and platelet infiltration in glomerular capillaries. Fibrin appeared at hour 5 as free strands into the lumens or in large clumps along the luminal surface of endothelial layer. Occasionally, occlusive fibrin thrombi were seen. At hour 48 only mild endothelial damage was seen, associated with few polymorphonuclear cells in the glomerular capillary lumens. These results document the sequence of renal changes in the best available animal model of hemolytic uremic syndrome. Beside endothelial damage, leukocyte infiltration in glomerular capillaries is a prominent finding suggesting a role of inflammatory cells in the development of microvascular thrombosis.