Giovanni M. Frascà

Genome-wide association study identifies susceptibility loci for IgA nephropathy

We carried out a genome-wide association study of IgA nephropathy, a major cause of kidney failure worldwide. We studied 1,194 cases and 902 controls of Chinese Han ancestry, with targeted follow up in Chinese and European cohorts comprising 1,950 cases and 1,920 controls. We identified three independent loci in the major histocompatibility complex, as well as a common deletion of CFHR1 and CFHR3 at chromosome 1q32 and a locus at chromosome 22q12 that each surpassed genome-wide significance (P values for association between 1.59 × 10−26 and 4.84 × 10−9 and minor allele odds ratios of 0.63–0.80). These five loci explain 4–7% of the disease variance and up to a tenfold variation in interindividual risk. Many of the alleles that protect against IgA nephropathy impart increased risk for other autoimmune or infectious diseases, and IgA nephropathy risk allele frequencies closely parallel the variation in disease prevalence among Asian, European and African populations, suggesting complex selective pressures.

IgA nephropathy, the most common cause of glomerulonephritis, is linked to 6q22–23

End-stage renal disease (ESRD) is a major public health problem, affecting 1 in 1,000 individuals and with an annual death rate of 20% despite dialysis treatment. IgA nephropathy (IgAN) is the most common form of glomerulonephritis, a principal cause of ESRD worldwide; it affects up to 1.3% of the population and its pathogenesis is unknown. Kidneys of people with IgAN show deposits of IgA-containing immune complexes with proliferation of the glomerular mesangium (Fig. 1). Typical clinical features include onset before age 40 with haematuria and proteinuria (blood and protein in the urine), and episodes of gross haematuria following mucosal infections are common; 30% of patients develop progressive renal failure. Although not generally considered a hereditary disease, striking ethnic variation in prevalence and familial clustering, along with subclinical renal abnormalities among relatives of IgAN cases, have suggested a heretofore undefined genetic component. By genome-wide analysis of linkage in 30 multiplex IgAN kindreds, we demonstrate linkage of IgAN to 6q22–23 under a dominant model of transmission with incomplete penetrance, with a lod score of 5.6 and 60% of kindreds linked. These findings for the first time indicate the existence of a locus with large effect on development of IgAN and identify the chromosomal location of this disease gene.

The molecular basis of lecithin:cholesterol acyltransferase deficiency syndromes: a comprehensive study of molecular and biochemical findings in 13 unrelated Italian families.

Objective—To better understand the role of lecithin:cholesterol acyltransferase (LCAT) in lipoprotein metabolism through the genetic and biochemical characterization of families carrying mutations in the LCAT gene. Methods and Results—Thirteen families carrying 17 different mutations in the LCAT gene were identified by Lipid Clinics and Departments of Nephrology throughout Italy. DNA analysis of 82 family members identified 15 carriers of 2 mutant LCAT alleles, 11 with familial LCAT deficiency (FLD) and 4 with fish-eye disease (FED). Forty-four individuals carried 1 mutant LCAT allele, and 23 had a normal genotype. Plasma unesterified cholesterol, unesterified/total cholesterol ratio, triglycerides, very-low-density lipoprotein cholesterol, and pre-&bgr; high-density lipoprotein (LDL) were elevated, and high-density lipoprotein (HDL) cholesterol, apolipoprotein A-I, apolipoprotein A-II, apolipoprotein B, LpA-I, LpA-I:A-II, cholesterol esterification rate, LCAT activity and concentration, and LDL and HDL3 particle size were reduced in a gene–dose-dependent manner in carriers of mutant LCAT alleles. No differences were found in the lipid/lipoprotein profile of FLD and FED cases, except for higher plasma unesterified cholesterol and unesterified/total cholesterol ratio in the former. Conclusion—In a large series of subjects carrying mutations in the LCAT gene, the inheritance of a mutated LCAT genotype causes a gene–dose-dependent alteration in the plasma lipid/lipoprotein profile, which is remarkably similar between subjects classified as FLD or FED.

Plasma exchange treatment improves prognosis of antineutrophil cytoplasmic antibody-associated crescentic glomerulonephritis: a case-control study in 26 patients from a single center.

Abstract:  Twenty‐six patients with Antineutrophil cytoplasmic antibody (ANCA)‐associated crescentic glomerulonephritis (GN) were divided into two groups according to the acute phase treatment: drug therapy consisting of steroids and oral cyclophosphamide plus a plasma exchange (PE) course (group A, 13 patients) or drug therapy alone (group B, 13 patients). Group A patients had a more severe clinical picture and higher serum creatinine than group B (12.7 ± 6.9 vs. 8.5 ± 5.3 mg%); nine patients from group A (69%) and five from group B (38%) required dialysis. At follow up (mean 35 months) all patients treated with PE were alive; four of them were in end‐stage renal disease. Among group B patients, three (23%) died in the acute phase; 6 (46%) needed renal replacement therapy at follow up. Of the dialysis‐dependent patients, five out of nine from group A were free of dialysis, while in group B two out of five patients had died, two had entered a regular dialysis treatment and one had received a cadaver graft. These data suggest  that  PE  may  significantly  improve  the  prognosis of patients with ANCA‐associated crescentic GN even if they are  not  dialysis‐dependent  at  the  time  of diagnosis.

Effect of a New Antithrombotic Agent (Defibrotide) in Acute Renal Failure Due to Thrombotic Microangiopathy

8 patients with thrombotic microangiopathy were treated with a new antithrombotic agent, defibrotide. This drug displays considerable fibrinolytic and antithrombotic activity, and induces generation and release of a prostacyclin-like substance from vascular tissue. At admission all patients presented severe renal involvement and coagulation abnormalities. Neurological manifestations were present in 6. Defibrotide administration was followed by recovery of renal function in 6, disappearance of neurological symptoms and coagulation abnormalities in all patients. The use of defibrotide was not associated with side effects. On the basis of the results obtained in these patients, we suggest that defibrotide might be considered as a valuable drug in the management of patients with thrombotic microangiopathy.

A new antithrombotic agent in the treatment of acute renal failure due to hemolytic-uremic syndrome and thrombotic thrombocytopenic purpura

Prof. Vittorio Bonomini, Department of Nephrology, St Orsola University Hospital, Via Massarenti 9, I-40138 Bologna (Italy) Dear Sir, The hemolytic-uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) share many common features including microangiopathic hemolytic anemia, thrombocytopenia, and renal involvement. Prolonged anuria, severe hypertension and marked neurological manifestations are signs of poor prognosis for both the recovery of renal function and patient’s survival. The etiology and pathogenesis of the two conditions are still unclear. It has been suggested [1] that a process of intravascular coagulation plays a role in the development of renal lesions, and thrombotic lesions are seen in the glomeruli and vessels up to the arcuate arteries. These findings have prompted numerous therapeutic attempts using heparin, urokinase, streptokinase, and platelet aggregation inhibitors, but the efficacy of these approaches is difficult to assess. On the other hand such therapies are not without considerable morbidity and mortality. Recent studies [2] suggest the hypothesis that a deficiency of plasma factor(s), which normally modulate vascular PGL· synthesis and release, have some role in the pathogenesis of HUS and TTP. In the last year we treated 5 patients (3 children and 2 adults) affected by HUS or TTP with a new antithrombotic agent (Defibrotide). This drug is a polydeoxyribonu-cleotide [3], extracted from mammalian organs, which has been demonstrated to increase the generation of PGI, from vascular tissue, and displays considerable fibrino-lytic and antithrombotic activity. Clotting investigations did not indicate that Defibrotide has any significant heparin-like activity. All patients were anuric on admission. Serum creati-nine ranged from 5.3 to 8.7 mg/dl; platelet count was low (from 11,000/mm3 to 35,000/mm3); circulating fibrin degradation products (FDP) were found to be raised in all patients. Severe neurological involvement was present in 3 of them. All patients required dialysis treatment. Defibrotide was administered by intravenous infusion at a dosage of 10 mg/kg/day. Treatment was started 16–28 h after admission, and was continued for an average of 14 days (range from 9 to 21). All patients showed a rapid decrease of circulating FDP associated with an increase in platelet count. Diuresis increased and serum creati-nine concentration decreased in 4 patients, with a complete recovery of renal function within 12–47 days. In the 5th patient, who presented severe neurological involvement and hypertension at the admission, Defibrotide administration was followed by a rapid disappearance of neurological manifestations, and normalization of

Renal Transplantation in Patients with Microscopic Polyarteritis and Antimyeloperoxidase Antibodies: Report of Three Cases

This paper reports on 3 patients on renal dialysis for crescentic glomerulonephritis associated with microscopic polyarteritis (MPA) and antineutrophil cytoplasmic autoantibodies specific for myeloperoxidase (MPO-ANCAs). They successfully underwent renal transplantation from a cadaver donor 6-63 months after the onset of the disease, despite the persistence of antibodies at high titer. A triple immunosuppressive regimen including steroids, cyclosporin and azathioprine was used. One patient underwent transplantectomy for surgical complications 3 months later, while the serum creatinine was 2.0 mg/dl (178 mu mol/l): the remainder have a well-functioning graft after 21 and 38 months, no clinical sign of disease recurrence, and a MPO titer within the normal range. We conclude that MPA patients can undergo renal transplantation even if ANCAs persist at a high titer in the circulation.

Search for genetic association between IgA nephropathy and candidate genes selected by function or by gene mapping at loci IGAN2 and IGAN3

BACKGROUND IgA nephropathy (IgAN) is not generally considered a hereditary disease, even though extensive evidence suggests an undefined genetic influence. Linkage analysis identified a number of genome regions that could contain variations linked to IgAN. METHODS In this case-control association study, genes possibly involved in the development of IgAN were investigated. DNA samples from 460 North Italian patients with IgAN and 444 controls were collected. Candidate genes were selected based on their possible functional involvement (6 genes) or because of their location within linkage-identified genomic regions IGAN2 and IGAN3 (5 and 13 genes within chromosome 4q26-31 and 17q12-22, respectively). One hundred and ninety-two tag and functional single-nucleotide polymorphisms (SNPs) were typed with Veracode GoldenGate technology (Illumina). RESULTS C1GALT1 showed an association with IgAN (rs1008898: P = 0.0019 and rs7790522: P = 0.0049). Associations were found when the population was stratified by gender (C1GALT1, CD300LG, GRN, ITGA2B, ITGB3 in males and C1GALT1, TRPC3, B4GALNT2 in females) and by age (TLR4, ITGB3 in patients aged <27 years). Furthermore, rs7873784 in TLR4 showed an association with proteinuria (G allele: P = 0.0091; GG genotype: P = 0.0077). CONCLUSIONS Age and gender are likely to evidence distinct immunological and inflammatory reactions leading to individual susceptibility to IgAN. Overall, a genetic predisposition to sporadic IgAN was found. We might hypothesize that C1GALT1 and TLR4 polymorphisms influence the risk to develop IgAN and proteinuria, respectively.

Effect of a plasma sodium biofeedback system applied to HFR on the intradialytic cardiovascular stability. Results from a randomized controlled study

Background Intradialytic hypotension (IDH) is still a major clinical problem for haemodialysis (HD) patients. Haemodiafiltration (HDF) has been shown to be able to reduce the incidence of IDH. Methods Fifty patients were enrolled in a prospective, randomized, crossover international study focussed on a variant of traditional HDF, haemofiltration with endogenous reinfusion (HFR). After a 1-month run-in period on HFR, the patients were randomized to two treatments of 2 months duration: HFR (Period A) or HFR-Aequilibrium (Period B), followed by a 1-month HFR wash-out period and then switched to the other treatment. HFR-Aequilibrium (HFR-Aeq) is an evolution of the haemofiltration with endogenous reinfusion (HFR) dialysis therapy, with dialysate sodium concentration and ultrafiltration rate profiles elaborated by an automated procedure. The primary end point was the frequency of IDH. Results Symptomatic hypotension episodes were significantly lower on HFR-Aeq versus HFR (23 ± 3 versus 31 ± 4% of sessions, respectively, P l= l0.03), as was the per cent of clinical interventions (17 ± 3% of sessions with almost one intervention on HFR-Aeq versus 22 ± 2% on HFR, P <0.01). In a post-hoc analysis, the effect of HFR-Aeq was greater on more unstable patients (35 ± 3% of sessions with hypotension on HFR-Aeq versus 71 ± 3% on HFR, P <0.001). No clinical or biochemical signs of Na/water overload were registered during the treatment with HFR-Aeq. Conclusions HFR-Aeq, a profiled dialysis supported by the Natrium sensor for the pre-dialysis Na+ measure, can significantly reduce the burden of IDH. This could have an important impact in every day dialysis practice.

Searching for IgA nephropathy candidate genes: genetic studies combined with high throughput innovative investigations.

Idiopathic IgA Nephropathy (IgAN) is the most common biopsy-proven glomerulonephritis worldwide. All races with the exception of Blacks and Indians are involved. Families with two or more relatives affected by IgAN may be observed in 15-20% of pedigrees of IgAN patients. Genome wide linkage study has been considered the most promising approach to identify IgAN susceptibility genes. Therefore, some European investigators constituted the European IgAN Consortium which was initially funded by the European Union. Data from linkage analysis studies, family association studies and case-control association studies are reported. To date, the Consortium has identified two loci (located on chromosomes 4q26-31 and 17q12-22), in addition to the previous study which described the first IgAN locus on chromosome 6q22-23. The functional mapping of genes involved in the disease proceeds from the identification of susceptibility loci identified by linkage analysis (step 1) to the isolation of candidate genes within gene disease-susceptibility loci, after obtaining information by microarray analysis carried out on peripheral leukocytes and renal tissue samples (step 2). Then, the process will proceed from the design of RNA interferenceagents against selected genes (step 3) to the application of systematically tested effect of RNA agents on functional cellular assay (step 4). The above combined high-throughput technologies will give information on the pathogenic mechanisms of IgAN. In addition, these data may indicate potential targets for screening, prevention and early diagnosis of the disease and more appropriate and effective treatment.