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Biomedical subjects

Giuseppe Remuzzi

Publications and source records attributed to Giuseppe Remuzzi.

At least 19 recordsLinked to original sources
PubMed2007

Hemolytic uremic syndrome: a factor H mutation (E1172Stop) causes defective complement control at the surface of endothelial cells.

Defective complement regulation results in hemolytic uremic syndrome (HUS), a disease that is characterized by microangiopathy, thrombocytopenia, and acute renal failure and that causes endothelial cell damage. For characterization of how defective complement regulation relates to the pathophysiology, the role of the complement regulator factor H and also of a mutant factor H protein was studied on the surface of human umbilical vein endothelial cells. The mutant 145-kD factor H protein was purified to homogeneity, from plasma of a patient with HUS, who is heterozygous for a factor H gene mutation G3587T, which introduces a stop codon at position 1172. Functional analyses show that the lack of the most C-terminal domain short consensus repeats 20 severely affected recognition functions (i.e., binding to heparin, C3b, C3d, and the surface of endothelial cells). Wild-type factor H as well as the mutant protein formed dimers in solution as shown by cross-linking studies and mass spectroscopy. When assayed in fluid phase, the complement regulatory activity of the mutant protein was normal and comparable to wild-type factor H. However, on the surface of endothelial cells, the mutant factor H protein showed severely reduced regulatory activities and lacked protective functions. Similarly, with the use of sheep erythrocytes, the mutant protein lacked the protective activity and caused increased hemolysis when it was added to factor H-depleted plasma. This study shows how a mutation that affects the C-terminal region of the factor H protein leads to defective complement control on cell surfaces and damage to endothelial cells in patients with HUS. These effects explain how mutant factor H causes defective complement control and in HUS-particularly under condition of inflammation and complement activation-causes endothelial cell damage.

Cells, Cultured↗
PubMed2007

The interactive Factor H-atypical hemolytic uremic syndrome mutation database and website: update and integration of membrane cofactor protein and Factor I mutations with structural models.

Atypical hemolytic uremic syndrome (aHUS) is a disease of hemolytic anemia, thrombocytopenia, and renal failure associated with defective alternative pathway (AP) complement control. Previously, we presented a database (www.FH-HUS.org) focusing on aHUS mutations in the Factor H gene (CFH). Here, new aHUS mutations are reported for the complement regulatory proteins Factor H (FH), Factor I (FI), and membrane cofactor protein (MCP). Additional mutations or polymorphisms within CFH have been associated with membranoproliferative glomerulonephritis (MPGN) and age-related macular degeneration (AMD). Accordingly, the database now includes substitutions that predispose to aHUS, MPGN, and AMD. For this, structural models for the domains in MCP and FI were developed using homology modeling. With this new database, patients with mutations in more than one gene can be displayed and interpreted in a coherent manner. The database also includes SNP polymorphisms in CFH, MCP, and IF. There are now a total of 167 genetic alterations, including 100 in CFH, 43 in MCP, and 24 in IF. The mutations characterize clinical outcomes that vary from several AMD-associated polymorphisms to those associated with aHUS, MPGN, or FI deficiency. A consensus short complement regulator (SCR) domain structure facilitated the interpretations of aHUS mutations. Specific locations within this consensus domain often correlate with the occurrence of clinical phenotypes. The AMD Tyr402His polymorphism is structurally located at a hotspot for several aHUS mutations. The database emphasizes the causative role of the alternative pathway of complement in disease and provides a repository of knowledge to assist future diagnosis and novel therapeutic approaches.

Amino Acid Sequence↗
PubMed2006

Impact of blood pressure control and angiotensin-converting enzyme inhibitor therapy on new-onset microalbuminuria in type 2 diabetes: a post hoc analysis of the BENEDICT trial.

For assessment of the independent renoprotective effect of BP control and angiotensin-converting enzyme inhibitor (ACEi) therapy, the relationships of baseline BP, BP reduction, and follow-up BP with the incidence of persistent microalbuminuria were evaluated in 1204 hypertensive patients who had type 2 diabetes and normoalbuminuria and were included in the BErgamo Nephrologic Diabetic Complications Trial (BENEDICT) study and were randomly assigned to 3.6 yr of treatment with the ACEi trandolapril (2 mg/d), the nondihydropyridine calcium channel blocker (ndCCB) verapamil SR (240 mg/d), their fixed combination Veratran (trandolapril 2 mg/d plus verapamil SR 180 mg/d), or placebo, plus other antihypertensive medications targeted at systolic/diastolic BP <130/80 mmHg. Follow-up (from month 3 to study end) systolic, diastolic, mean, and pulse BP and their reductions versus baseline--but not baseline BP--independently predicted (P < 0.001) the risk for microalbuminuria. In patients with follow-up BP above medians, ACEi significantly reduced the risk for microalbuminuria to levels that were observed among patients with BP below medians, regardless of ACEi treatment. The same trend was observed among patients with BP reductions below medians. ndCCB therapy did not independently affect microalbuminuria. Patients who were on Veratran had lower BP and less frequently received diuretics, beta blockers, or dihydropyridine dCCB. In hypertensive, normoalbuminuric patients with type 2 diabetes, BP reduction and ACEi therapy both independently may prevent microalbuminuria. ACEi therapy is particularly effective when BP is poorly controlled, whereas ndCCB therapy is ineffective at any level of achieved BP. As compared with trandolapril, Veratran may help with achievement of target BP with less need for concomitant antihypertensive medications.

Albuminuria↗
PubMed2006

How does proteinuria cause progressive renal damage?

The possibility that proteinuria may accelerate kidney disease progression to end-stage renal failure has received support from the results of increasing numbers of experimental and clinical studies. Evidence indicating that this process occurs through multiple pathways, including induction of tubular chemokine expression and complement activation that lead to inflammatory cell infiltration in the interstitium and sustained fibrogenesis, is reviewed. Macrophages are prominent in the interstitial inflammatory infiltrate. This cell type mediates progression of renal injury to the extent that macrophage numbers in renal biopsy predict renal survival in patients with chronic renal disease. Chemoattractants and adhesive molecules for inflammatory cells are upregulated by excess ultrafiltered protein load of proximal tubular cells via activation of NF-kappaB-dependent and NF-kappaB-independent pathways. This mechanism is a potential target for therapeutic approaches, as shown by beneficial effects of manipulations with inhibitory molecules of NF-kappaB activation or of chemokine receptors in experimental studies. Targeting complement synthesis or activation in proximal tubule might offer novel therapeutic opportunities. Finally, proximal tubular cell receptors for uptake of plasma proteins that are under investigation may provide activation signals on excess tubular protein handling.

Cells, Cultured↗
PubMed2006

Beneficial effect of TGFbeta antagonism in treating diabetic nephropathy depends on when treatment is started.

BACKGROUND: In diabetic rats with maximal activation of RAS induced by uninephrectomy, late treatment with anti-TGFbeta antibody limited renal injury only when combined with ACE inhibitor. We investigated whether in a two-kidney diabetic model the time at which treatment started predicted the response to TGFbeta antagonist. METHODS: 27 weeks after streptozotocin injection, animals had mild proteinuria and were randomized to receive irrelevant antibody, anti-TGFbeta antibody (1D11) or enalapril till 52 weeks (early treatment). The effect of agents alone or combined was also evaluated at the time of overt proteinuria (late treatment, 52-61 weeks). RESULTS: When given early, 1D11 displayed marked antihypertensive and antiproteinuric effects. Glomerulosclerosis was reduced to the extent that a remarkable percentage of glomeruli without sclerosis appeared after treatment. Podocyte number was normalized. Renoprotection of 1D11 was comparable to enalapril. Despite control of blood pressure, in late treatment single agents did not reduce proteinuria significantly. Glomerulosclerosis and podocyte loss were partially limited by 1D11 or enalapril, but full protection was achieved by combination. CONCLUSIONS: Renoprotective effect of TGFbeta antagonism crucially depends on the time at which treatment started. Effectiveness of early treatment with 1D11 would indicate that TGFbeta is a major mediator of damage in early diabetes. To tackle the renal damage in the phase of advanced disease, a combined treatment with ACE inhibitor is needed.

Albuminuria↗
PubMed2006

Implications of the initial mutations in membrane cofactor protein (MCP; CD46) leading to atypical hemolytic uremic syndrome.

The hemolytic uremic syndrome is characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia and acute renal failure. There are two general types. One occurs in epidemic form and is diarrheal associated (D+HUS). It has a good prognosis. The second is a rare form known as atypical (aHUS), which may be familial or sporadic, and has a poor prognosis. aHUS is increasingly recognized to be a disease of defective complement regulation, particularly cofactor activity. Mutations in membrane cofactor protein (MCP; CD46) that predispose to the development of aHUS were first identified in 2003. MCP is a membrane-bound complement regulator that acts as a cofactor for the factor I-mediated cleavage of C3b and C4b deposited on host cells. More than 20 different mutations in MCP have now been identified in patients with aHUS. Many of these mutants have been functionally characterized and have helped to define the pathogenic mechanisms leading to aHUS development. Over 75% of the reported mutations cause a reduction in MCP expression, due to homozygous, compound heterozygous or heterozygous mutations. This deficiency of MCP leads to inadequate control of complement activation on endothelial cells after an initiating injury. The remaining MCP mutants are expressed, but demonstrate reduced ligand (C3b/C4b) binding capacity and cofactor activity of MCP. MCP mutations in aHUS demonstrate incomplete penetrance, indicating that additional genetic and environmental factors are required to manifest disease. MCP mutants as a cause of aHUS have a favorable clinical outcome in comparison to patients with factor H (CFH) or factor I (IF) mutations. In 90% of the renal transplants performed in patients with MCP-HUS, there has been no recurrence of the primary disease, whilst >50% of factor I or factor H deficient patients have had a prompt recurrence. This highlights the importance of defining and characterizing the underlying genetic defects in patients with aHUS.

Haplotypes↗
PubMed2006

Transcriptional regulation of nephrin gene by peroxisome proliferator-activated receptor-gamma agonist: molecular mechanism of the antiproteinuric effect of pioglitazone.

The renoprotective potential of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist pioglitazone was explored in an immune model of progressive nephropathy, passive Heymann nephritis (PHN), compared with that of an angiotensin II receptor antagonist, taken as standard therapy for renoprotection. PHN rats received orally vehicle, pioglitazone (10 mg/kg twice daily), or candesartan (1 mg/kg twice daily) from months 2 to 8. Pioglitazone reduced proteinuria as effectively as candesartan and limited renal functional and structural changes. Kidneys from untreated PHN rats showed lower nephrin mRNA and protein than controls, both restored by pioglitazone. The effect was seen both early and late during the course of the disease. Whether the antiproteinuric effect of pioglitazone could be due to its effect on nephrin gene transcription also was investigated. HK-2 cells were transfected with plasmids that harbor the luciferase gene under portions (2-kb or 325-bp) of human nephrin gene promoter that contain putative peroxisome proliferator-responsive elements (PPRE) and incubated with pioglitazone (10 muM). Transcriptional activity of luciferase gene was highly increased by pioglitazone, with the strongest expression achieved with the 325-bp fragment. Increase in luciferase activity was prevented by bisphenol A diglycidyl ether, a PPAR-gamma synthetic antagonist. Electrophoretic mobility shift assay experiments showed a direct interaction of PPAR/retinoid X receptor heterodimers to PPRE present in the enhancer region of the nephrin promoter. In conclusion, pioglitazone exerts an antiproteinuric effect in immune-mediated glomerulonephritis as angiotensin II receptor antagonist does. Enhancement of nephrin gene transcription through specific PPRE in its promoter discloses a novel mechanism of renoprotection for PPAR-gamma agonists.

Angiotensin Receptor Antagonists↗
PubMed2006

Adeno-associated virus-mediated CTLA4Ig gene transfer protects MHC-mismatched renal allografts from chronic rejection.

Short-term results of renal transplantation have improved considerably in the past 20 yr; however, similar improvements in long-term outcome have not been achieved. The primary cause of late graft loss is chronic rejection that might be treated by gene therapeutic approaches. Ideally, one would like to impair locally the contact between transplant antigen and the host immune system without compromising the generalized immune competence of the recipient. This can be achieved by local expression of the therapeutic protein in the site of interest using gene therapy. Here it is shown that chronic allograft rejection can be prevented effectively by local delivery of recombinant adeno-associated virus (AAV) vectors that encode the CTLA4Ig immunosuppressant protein to the donor kidney in a fully MHC-mismatched rat strain combination. AAV CTLA4Ig prevented progressive proteinuria and protected transplant kidneys from renal structural injury. A population of anergic T cells with regulatory activity, which eventually were responsible for the induction of tolerance, were found in recipient lymph nodes and in the graft as long as 120 d after transplantation. These data indicate that AAV-mediated CTLA4Ig gene transfer to donor graft represents a promising tool to prevent the onset of chronic rejection and circumvent the unwanted systemic adverse effects of the administration of immunomodulatory protein.

Abatacept↗
PubMed2006

Genetics of HUS: the impact of MCP, CFH, and IF mutations on clinical presentation, response to treatment, and outcome.

Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy with manifestations of hemolytic anemia, thrombocytopenia, and renal impairment. Genetic studies have shown that mutations in complement regulatory proteins predispose to non-Shiga toxin-associated HUS (non-Stx-HUS). We undertook genetic analysis on membrane cofactor protein (MCP), complement factor H (CFH), and factor I (IF) in 156 patients with non-Stx-HUS. Fourteen, 11, and 5 new mutational events were found in MCP, CFH, and IF, respectively. Mutation frequencies were 12.8%, 30.1%, and 4.5% for MCP, CFH, and IF, respectively. MCP mutations resulted in either reduced protein expression or impaired C3b binding capability. MCP-mutated patients had a better prognosis than CFH-mutated and nonmutated patients. In MCP-mutated patients, plasma treatment did not impact the outcome significantly: remission was achieved in around 90% of both plasma-treated and plasma-untreated acute episodes. Kidney transplantation outcome was favorable in patients with MCP mutations, whereas the outcome was poor in patients with CFH and IF mutations due to disease recurrence. This study documents that the presentation, the response to therapy, and the outcome of the disease are influenced by the genotype. Hopefully this will translate into improved management and therapy of patients and will provide the way to design tailored treatments.

Blood Component Transfusion↗
PubMed2006

Biocompatibility and function of microencapsulated pancreatic islets.

Encapsulation of pancreatic islets in alginate is used to protect against xenogenic rejection in different animal models. In this study, several factors, including differences in alginate composition, the presence or absence of xenogenic islet tissue and a transient immunosuppression, were investigated in a model of bovine islet transplantation in rats. A pure alginate with predominantly guluronic acid (Manugel) and an ultrapure low viscosity guluronic acid alginate (UP-LVG) were used. When microcapsules of Manugel or UP-LVG containing 16,000 bovine islet equivalents were transplanted in diabetic rats, we observed normoglycemia for 8.3+/-0.7 (range 6-12 days) and 7.5+/-0.2 days (range 7-8 days) on average, respectively. To ameliorate immunoprotection of alginate microcapsules we repeated the same experiments using transient immunosuppressive therapy. Low doses of cyclosporin A (CyA) administered for 18 days after implantation increased the time in normoglycemia, which averaged 27+/-3 days (range 8-55 days) in Manugel capsules while in UP-LVG capsules it averaged 18+/-8 days (range 3-39 days). The surface of recovered capsules showed less capsules free of overgrowth in Manugel with respect to UP-LVG alginate. These data were comparable with those observed in empty microcapsules similarly implanted, indicating that the capsular overgrowth was not promoted by the presence of xenogenic islet tissue. In recovered Manugel capsules the percentage of capsules without fibrotic overgrowth was higher than that observed without CyA. The same observation was made in empty capsules. These observations indicate that a combination of a highly purified alginate and short-term immunosuppression prolong islet function in a model of xenotransplantation.

Alginates↗
PubMed2006

Long-term outcome of renal transplantation from older donors.

BACKGROUND: Long-term survival of kidney grafts from older donors is inferior to that of grafts from younger donors. We sought to determine whether selecting older kidneys according to their histologic characteristics before implantation would positively influence long-term outcome. METHODS: In a prospective cohort study, we assessed outcomes among 62 patients who received one or two histologically evaluated kidneys from donors older than 60 years of age. These outcomes were compared with outcomes among 248 matched recipients of single kidney grafts that had not been histologically evaluated and were either from donors 60 years of age or younger (124 positive-reference recipients who, according to available data, were expected to have an optimal outcome) or from those older than 60 years (124 negative-reference recipients, expected to have a worse outcome). The primary end point was graft survival. RESULTS: During a median period of 23 months, 4 recipients (6 percent) of histologically evaluated kidneys progressed to dialysis, as compared with 7 positive-reference recipients (6 percent) and 29 negative-reference recipients (23 percent). Graft survival in recipients of histologically evaluated kidneys did not differ significantly from that of grafts in positive-reference recipients but was superior to that of grafts in negative-reference recipients (hazard ratio for graft failure in the negative-reference recipients relative to the recipients of histologically evaluated kidneys, 3.68; 95 percent confidence interval, 1.29 to 10.52; P=0.02). The performance of preimplantation histologic evaluation predicted better survival both in the whole study group (P=0.02) and among recipients of kidneys from older donors (P=0.01). CONCLUSIONS: The long-term survival of single or dual kidney grafts from donors older than 60 years of age is excellent, provided that the grafts are evaluated histologically before implantation. This approach may help to expand the donor-organ pool for kidney transplantation.

Age Factors↗