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Biomedical subjects

Giuseppe Remuzzi

Publications and source records attributed to Giuseppe Remuzzi.

At least 91 records · Page 5Linked to original sources

Hemolytic uremic syndrome: a fatal outcome after kidney and liver transplantation performed to correct factor h gene mutation.

Factor H-associated hemolytic uremic syndrome (HUS) is a genetic form of thrombotic microangiopathy characterized by deficient factor H (HF-1) levels/activity and uncontrolled complement activation. The disorder mostly leads to end-stage renal disease and often recurs after kidney transplantation. We previously demonstrated that in a child with HF-1-associated HUS a simultaneous kidney and liver transplantation restored the defective HF-1 with no recurrence of the disease in the transplanted kidney. Here we describe a second childhood case of HF-1-associated HUS treated by combined kidney and liver transplant and complicated by a fatal, primary non-function of the liver graft. Graft hypoperfusion during surgery triggered ischemia/reperfusion changes and complement activation. Conceivably, as a result of defective complement regulatory potential, massive shedding of vascular heparan sulfates was documented in the transplanted liver. This might have impaired the physiological thromboresistance of vascular endothelium ending with widespread microvascular thrombosis and infarction. This case indicates that more fundamental research is needed before combined liver and kidney transplant is considered an option for children with HF-1-associated HUS.

Complement Activation↗

Transplantation tolerance. A complex scenario awaiting clinical applicability.

Organ transplantation is now firmly established as the therapy of choice for end-stage organ failure. Specific immunological tolerance of transplant recipients towards their foreign organ or tissue grafts is a goal that has been sought by transplant biologists for almost 50 years following the original description of the phenomenon in experimental animals by Medawar and colleagues. Since that time, a wealth of experimental data has accumulated relating to strategies for extending allograft survival and function. Recent studies have shed new light on the molecular and cellular basis of transplant rejection and have better defined the mechanisms of allograft tolerance with particular emphasis on a role for regulatory T cells. Still, the question remains of how near we are to the day when long-term tolerance of engrafted organs or tissues will be a clinical reality. Recently, clinical trials to explore pilot tolerance protocols in humans have been initiated under the auspices of the Immune Tolerance Network (www.immunetolerance.org). In this review we will highlight the promise and challenges of making transplantation tolerance a clinical reality.

Animals↗

Hyperuricemia in kidney transplantation.

Hyperuricemia is a common problem among renal transplant recipients. Its prevalence is clearly attributable to cyclosporine (CsA) use, although individual patients may have other risk factors as well. CsA lowers the urinary clearance of uric acid. The specific mechanism for this is unknown, but may involve alteration in tubular transport. Hyperuricemia may add on to several other factors in contributing to progressive deterioration of graft function and ultimately graft loss. The therapy of hyperuricemia may be particularly challenging in transplant patients.

Chronic Disease↗

Complement activation: the missing link between ADAMTS-13 deficiency and microvascular thrombosis of thrombotic microangiopathies.

Endothelial injury is the central factor in the events leading to thrombotic microangiopathy (TMA); however, the mechanisms involved are not fully understood. Here we investigate the role of neutrophils (PMNs) and of complement activation in inducing microvascular damage and loss of thromboresistance in TMA associated with ADAMTS-13 deficiency. PMNs isolated during the acute phase of the disease released excessive amounts of reactive-oxygen species (ROS), N-derived oxidants and proteinases and induced damage and thromboresistance loss in human microvascular endothelial cell line (HMEC-1) ex vivo. Endothelial cytotoxicity and thromboresistance loss was also induced by TMA serum. Complement-derived products were responsible for the above effects: in fact, TMA serum caused C3 and Membrane Attack Complex (MAC) deposition on HMEC-1 and its cytotoxic effect was abolished by complement inhibition. TMA serum caused surface expression of P-selectin on HMEC-1 which may promote PMN adhesion and resulted in increased PMN cytotoxicity, indicating that complement may have a role in PMN activation. In addition, TMA serum stimulated control PMNs to release ROS and proteinases, and to cause endothelial cell cytotoxicity. All of the above effects were abrogated by complement inactivation. These data document for the first time that complement-initiated PMN activation and endothelial injury may have a crucial role in microvascular thrombosis of TMA associated with ADAMTS-13 deficiency.

ADAM Proteins↗

Inhibition of the renin-angiotensin system and cardio-renal protection: focus on losartan and angiotensin receptor blockade.

Angiotensin II plays a central role in the pathogenesis and progression of proteinuric nephropathies and related cardiovascular complications. Losartan is a selective non-peptide angiotensin Type 1-receptor blocker (ARB) with unique uricosuric effect, not shared by other ARBs. Losartan has demonstrated renoprotective effects in animals and humans with diabetic and non-diabetic renal diseases similar to those of angiotensin-converting enzyme inhibitors, with a lower incidence of dry cough and angioneurotic oedema. A reduced incidence of cerebrovascular events and diabetes has been reported in hypertensive patients with left ventricular hypertrophy on losartan therapy compared with patients treated with atenolol. Whether ARBs have superior cardioprotective effects, compared with other blood pressure medications, is still unknown. Combined angiotensin-converting enzyme inhibitor and ARB therapy improves renal outcomes in non-diabetic nephropathies more than single drug renin-angiotensin system inhibition. Whether this also applies to diabetic nephropathy and related cardiovascular outcomes is still unknown.

Adrenergic beta-Antagonists↗

Emerging drugs for diabetic nephropathy.

There is an increasing number of patients with diabetes mellitus in many countries. Diabetic kidney disease, one of its microvascular complications, is also increasing markedly and has become a major cause of end stage renal disease worldwide. Intervention for preventing and delaying the development and progression of diabetic kidney disease is not only a medical concern, but also a social issue. Despite extensive efforts, however, medical interventions thus far are not effective enough to prevent the progression of the disease and the development of end stage renal disease. This justifies attempts to develop novel therapeutic approaches for diabetic nephropathy. Recent insights on its pathogenesis and progression have suggested new targets for the specific treatment of this disease. They include aldosterone, aldose reductase, arachidonic acid metabolites, growth factors, advanced glycosylation end-products, peroxisome proliferator-activated receptors and endothelin. Several other biochemical mediators have been targeted in experimental animal models with the goal to prevent diabetic nephropathy progression, but translation to clinics of these experimental achievements are still limited or lacking.

Animals↗

Dual blockade of the renin-angiotensin system: the ultimate treatment for renal protection?

The prevalence of chronic renal diseases is increasing worldwide. There is a great need to identify therapies that arrest disease progression to end-stage renal failure. Inhibition of the renin-angiotensin system both by angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists is probably the best therapeutic option available. Several large, multicenter studies have indeed shown a significant reduction in the risk for doubling baseline serum creatinine or progression toward end-stage renal failure in patients who do and do not have diabetes and have chronic nephropathies that are treated with angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists. However, the number of patients who reach end-stage renal failure is still considerably high. Significant reduction of the incidence of ESRD is likely to be achieved in the near future for chronic nephropathies, provided that the degree of renoprotection can be improved. This goal may be attainable with a more complex strategy than with a single or dual pharmacologic intervention on the renin-angiotensin system. Strict control of BP and protein excretion rate, lowering of blood lipids, tight glucose control for individuals with diabetes, and lifestyle changes form part of the future multimodal protocol for treatment of patients with chronic nephropathies.

Angiotensin-Converting Enzyme Inhibitors↗

Angiotensin-converting enzyme inhibition and renal protection in nondiabetic patients: the data of the meta-analyses.

ESRD represents a major health problem. The number of patients who enter kidney replacement programs has increased at an average of 7% per year in the past 10 yr. A large number of experimental and clinical studies have demonstrated that chronic nephropathies share common pathogenic mechanisms that contribute to renal disease progression, even independent of the original cause. Clinical studies found a significant correlation between the extent of urinary protein excretion and the rate of GFR decline in both diabetic and nondiabetic chronic nephropathies. Randomized trials, in particular the Ramipril Efficacy In Nephropathy (REIN) study, also showed that treatments that reduce proteinuria (namely angiotensin-converting enzyme [ACE] inhibitors) are renoprotective and limit progression to ESRD. Meta-analyses of randomized clinical trials also evaluated the role of proteinuria and of ACE inhibition therapy in chronic renal disease progression. Their findings were consistent with those of the REIN study and confirmed in larger series of patients the predictive value of proteinuria and the renoprotective effect of proteinuria reduction by ACE inhibition therapy. Thus, the meta-analyses may confirm and extend previous findings generated by randomized clinical trials. Conceivably, well-designed studies in properly selected and carefully monitored patients who are at increased risk continue to be the best approach to test novel hypotheses. The meta-analyses, however, represent a valuable tool to evaluate the consistency and generalizability of trial results to larger cohorts of patients.

Angiotensin-Converting Enzyme Inhibitors↗

Preventing microalbuminuria in type 2 diabetes.

BACKGROUND: The multicenter double-blind, randomized Bergamo Nephrologic Diabetes Complications Trial (BENEDICT) was designed to assess whether angiotensin-converting-enzyme inhibitors and non-dihydropyridine calcium-channel blockers, alone or in combination, prevent microalbuminuria in subjects with hypertension, type 2 diabetes mellitus, and normal urinary albumin excretion. METHODS: We studied 1204 subjects, who were randomly assigned to receive at least three years of treatment with trandolapril (at a dose of 2 mg per day) plus verapamil (sustained-release formulation, 180 mg per day), trandolapril alone (2 mg per day), verapamil alone (sustained-release formulation, 240 mg per day), or placebo. The target blood pressure was 120/80 mm Hg. The primary end point was the development of persistent microalbuminuria (overnight albumin excretion, > or =20 microg per minute at two consecutive visits). RESULTS: The primary outcome was reached in 5.7 percent of the subjects receiving trandolapril plus verapamil, 6.0 percent of the subjects receiving trandolapril, 11.9 percent of the subjects receiving verapamil, and 10.0 percent of control subjects receiving placebo. The estimated acceleration factor (which quantifies the effect of one treatment relative to another in accelerating or slowing disease progression) adjusted for predefined baseline characteristics was 0.39 for the comparison between verapamil plus trandolapril and placebo (P=0.01), 0.47 for the comparison between trandolapril and placebo (P=0.01), and 0.83 for the comparison between verapamil and placebo (P=0.54). Trandolapril plus verapamil and trandolapril alone delayed the onset of microalbuminuria by factors of 2.6 and 2.1, respectively. Serious adverse events were similar in all treatment groups. CONCLUSIONS: In subjects with type 2 diabetes and hypertension but with normoalbuminuria, the use of trandolapril plus verapamil and trandolapril alone decreased the incidence of microalbuminuria to a similar extent. The effect of verapamil alone was similar to that of placebo.

Adult↗

Albuminuria, a therapeutic target for cardiovascular protection in type 2 diabetic patients with nephropathy.

BACKGROUND: Albuminuria is an established risk marker for both cardiovascular and renal outcomes. Albuminuria can be reduced with drugs that block the renin-angiotensin system (RAS). We questioned whether the short-term drug-induced change in albuminuria would predict the long-term cardioprotective efficacy of RAS intervention. METHODS AND RESULTS: We analyzed data from Reduction in Endpoints in Non-insulin dependent diabetes mellitus with the Angiotensin II Antagonist Losartan (RENAAL), a double-blind, randomized trial in 1513 type 2 diabetic patients with nephropathy, focusing on the relationship between the prespecified cardiovascular end point (composite) or hospitalization for heart failure and baseline or reduction in albuminuria. Patients with high baseline albuminuria (> or =3 g/g creatinine) had a 1.92-fold (95% CI, 1.54 to 2.38) higher risk for the cardiovascular end point and a 2.70-fold (95% CI, 1.94 to 3.75) higher risk for heart failure compared with patients with low albuminuria (<1.5 g/g). Among all available baseline risk markers, albuminuria was the strongest predictor of cardiovascular outcome. The association between albuminuria and cardiovascular outcome was driven by those patients who also had a renal event. Modeling of the initial 6-month change in risk parameters showed that albuminuria reduction was the only predictor for cardiovascular outcome: 18% reduction in cardiovascular risk for every 50% reduction in albuminuria and a 27% reduction in heart failure risk for every 50% reduction in albuminuria. CONCLUSIONS: Albuminuria is an important factor predicting cardiovascular risk in patients with type 2 diabetic nephropathy. Reducing albuminuria in the first 6 months appears to afford cardiovascular protection in these patients.

Aged↗

A comparative prospective study of two available solutions for kidney and liver preservation.

BACKGROUND: Viaspan (University of Wisconsin [UW]) solution is the gold standard for abdominal organ preservation. Celsior (CEL) is an extracellular-type, low-potassium, low-viscosity solution, initially used for heart and lung preservation. We have performed a prospective multicenter study to compare the role of these cold-storage solutions on kidney and liver recovery after transplantation. PATIENTS AND METHODS: From March 15, 2000 to December 31, 2001, 441 (172 CEL and 269 UW) renal transplants (RT) and 175 (79 CEL and 96 UW) liver transplants (LT) were included in the study. RESULTS: Perfusate volume used was significantly lower in the UW group, being 4,732 +/- 796 mL versus 5,826 + 834 mL in the CEL group (P < 0.001). In LT, median total bilirubin serum levels were significantly higher at 5 and 7 posttransplant days in the UW group (90.6 and 92.3 micromol/L, respectively) as compared with CEL (51.3 and 63.4 micromol/L, respectively). After LT, primary nonfunction (PNF) rates in the CEL and UW groups were 3.8% and 4.2% (P = NS) respectively, with 1-year graft and patient survival being 83.3% versus 85.4% (P = NS) and 89.9% versus 90.6% (P = NS). After RT, delayed graft function (DGF) rates were 23.2% and 22.7% (P = NS), respectively; PNF rates were 1.9% and 1.7% (P = NS) respectively, with 1-year graft and patient survival being 92.3% versus 94.2% (P = NS) and 99.4% versus 97.7% (P = NS). CONCLUSIONS: CEL solution was shown to be as effective as UW in both liver and kidney preservation. In LT patients, biliary function recovery is significantly better in the CEL group. CEL solution represents an efficacious option in multiorgan harvesting.

Adenosine↗

Favorable effect of cotransfection with TGF-beta and CTLA4Ig of the donor kidney on allograft survival.

BACKGROUND/AIMS: Gene transfer of viral interleukin 10 (vIL-10) or transforming growth factor beta (TGF-beta) successfully prolonged liver and heart graft survival. Here we assessed whether injection of adenovirus (Ad) coding vIL-10 (AdvIL-10) or TGF-beta3 (AdTGF-beta3) prolonged kidney allograft survival. Since we previously demonstrated that transfection of the donor kidney with CTLA4Ig significantly prolonged allograft survival, we also evaluated the effect of a combined injection of AdvIL-10 or AdTGF-beta3 with the AdCTLA4Ig. METHODS: Adenoviral vectors or saline were ex vivo injected into the renal artery of Brown Norway (RT.1n) donor kidneys subsequently grafted into Lewis (RT.1(l)) rats. Graft survival, transgene expression, graft cell infiltration, and histological changes were assessed. RESULTS: Allografts of saline or Ad-beta-galactosidase controls were promptly rejected (mean survival time +/- SE 7.6 +/- 0.2 and 7.8 +/- 0.3 days, respectively). AdvIL-10 significantly prolonged survival only in 2 out of 9 animals (23.2 +/- 9.9 days), with vIL-10 expression detected on day 4. Survival was prolonged in 1 out of 5 animals by AdTGF-beta3 (14.4 +/- 5.3 days) despite the fact that the transgene was still observed after 14 days. While the combined injection of AdvIL-10 with AdCTLA4Ig did not protect the kidney from rejection (17.4 +/- 4.6 days), AdTGF-beta3 added to AdCTLA4Ig consistently prolonged the allograft lifespan in all animals (70.6 +/- 39.6 days), inducing indefinite survival in 1 animal which showed long-term gene expression and T cells hyporesponsive to alloantigens. CONCLUSION: Overexpression of AdTGF-beta3 concomitant with the blockade of the CD28/B7 pathway by AdCTLA4Ig induces strong immunosuppression that occasionally allows the acceptance of a fully major histocompatibility complex mismatched renal graft.

Abatacept↗

L-arginine depletion in preeclampsia orients nitric oxide synthase toward oxidant species.

Less nitric oxide (NO)-dependent vasodilation and excess formation of reactive oxygen species could explain poor placenta perfusion in preeclampsia, but the pathways involved are unknown. We tested the hypothesis that reduced NO activity and increased oxidative stress in preeclamptic placenta is related to a low bioavailability of l-arginine. Placental endothelial NO synthase (ecNOS) expression (by immunoperoxidase) and activity (by diaphorase and [(3)H]L-citrulline formation) were comparable in normotensive pregnancy and in preeclampsia, whereas nitrotyrosine staining, a marker of peroxynitrite, was stronger in preeclamptic villi, confirming previously reported data. Oxidative tissue damage was documented in preeclamptic villi by strong 4-hydroxynonenal-lysine staining (by immunoperoxidase), which closely colocalized with nitrotyrosine. Concentration of the NO precursor l-arginine (by HPLC) in umbilical blood and in villous tissue was lower in preeclampsia than in normotensive pregnancy. This was not caused by a defective l-arginine transport, because gene expression of the CAT-1, 4F2hc, and LAT-1 cationic amino acid transporters (by real-time reverse-transcription polymerase chain reaction [RT-PCR]) was normal. Instead, gene expression (by real-time RT-PCR) and protein tissue content (by immunoperoxidase and Western blot) of arginase II-the enzyme that degrades arginine to ornithine-were higher in preeclamptic villi than in normotensive pregnancy. These results provide a biochemical explanation for defective NO activity and increased oxidative stress in preeclamptic placenta. In normal placenta, adequate concentration of l-arginine orients ecNOS toward NO. In preeclampsia, a lower than normal l-arginine concentration caused by arginase II overexpression redirects ecNOS toward peroxynitrite.

Adult↗

Changes in glomerular perm-selectivity induced by angiotensin II imply podocyte dysfunction and slit diaphragm protein rearrangement.

Molecular mechanisms governing the loss of glomerular membrane perm selectivity during progression of proteinuric kidney diseases are so far poorly defined. Discovery of the proteins of the podocyte slit diaphragm, including the nephrin-CD2AP-podocin complex, has represented a major breakthrough in understanding the crucial role of the glomerular epithelial layer in the pathogenesis of proteinuria in human congenital disorders. A number of studies have tried to address the role of nephrin in acquired proteinuric disorders with conflicting results. In human diabetic nephropathy a defect of nephrin gene and protein expression has been consistently reported, which translates in profound changes of filtration slit ultrastructural architecture. The exclusive effect of angiotensin II inhibitors of restoring deficient nephrin expression in proteinuric diseases underlines a close interaction between angiotensin II and podocyte proteins and indicates a fresh way to look at the renoprotective properties of these molecules.

Angiotensin II↗

Platelet dysfunction in renal failure.

Patients with end-stage renal disease suffer from complex hemostatic disorders. Uremic patients show a bleeding diathesis that is mainly due to abnormalities of primary hemostasis; in particular, platelet dysfunction and impaired platelet-vessel wall interaction. However, despite decreased platelet function, these patients have a high prevalence of cardiovascular and thrombotic complications. Platelet dysfunction in uremic patients is partially due to uremic toxins present in circulating blood. Dialysis improves platelet abnormalities and reduces, but does not eliminate, the risk of hemorrhage. Hemodialysis can even contribute to the bleeding through the continuous platelet activation induced by the interaction between blood and artificial surfaces. Thrombocytopenia, glomerular thrombosis, and thrombi in small arteries and glomerular capillaries are common pathological features in many renal diseases. Platelets are also involved directly in the pathogenesis of glomerular diseases through a variety of mechanisms, including release of active molecules, by enhancing immune complex deposition, and by altering glomerular permeability.

Blood Platelet Disorders↗

Cellular responses to protein overload: key event in renal disease progression.

PURPOSE OF REVIEW: Insight into the mechanisms underlying the progression of chronic proteinuric nephropathies has attracted the interest of the renal community in the last two decades. Systemic hypertension, proteinuria, cytokines and growth factors, and reactive oxygen species have all been implicated. Reviewed here are the determinants of tubulointerstitial injury; the focus is on protein ultrafiltration and reabsorption, which ultimately contribute, by activating fibrogenic mechanisms in tubular cells, to renal scarring. RECENT FINDINGS: Protein overloading of proximal tubular cells--a well-documented consequence of exuberant protein ultrafiltration--differentially regulates transcription of NF-kappaB-dependent and NF-kappa-B-independent genes. This forms endothelin-1, cytokines and chemokines; all of these, being secreted toward the basolateral compartment of tubular epithelial cells, foster local recruitment of mononuclear cells. Autocrine pathways of activation of tubular epithelial cells contribute to interstitial injury and fibrosis. Albumin endocytosis in proximal tubular cells triggers events that include protein kinase C-dependent generation of reactive oxygen species, nuclear translocation of NF-kappaB, and activation of mitogen-activated protein kinase. In-vivo evidence that proteinuria activates transcription factors, including NF-kappaB, and overexpression of chemokine and fibrogenic cytokines is also available. SUMMARY: Proteinuria incites a multitude of inflammatory and fibrogenic mediators, all of which contribute to renal scarring. Specific antagonism of multiple injurious pathways might help to arrest, or even reverse, the progression of renal damage.

Animals↗