Glycoxidative modification of AA amyloid deposits in renal tissue.

BACKGROUND: N(epsilon)-carboxymethyllysine (CML) is a product of the oxidative modification of glycated proteins, which damages proteins with ageing, diabetes, uraemia and Alzheimer's disease. In contrast, pyrraline is one of the advanced glycation end products, which is independent of oxidative processes. CML has been identified in beta-amyloid of Alzheimer's disease and beta(2)-microglobulin-associated amyloid. We investigated whether CML and pyrraline are formed in AA and AL amyloid of the kidney. METHOD: Renal specimens from 19 cases of AA amyloidosis and 14 cases of AL amyloidosis were investigated for immunolocalization of CML, pyrraline, collagen type IV and laminin in amyloid deposits. Renal biopsies of 10 age-matched cases with thin basement membrane disease and normal renal function were used as controls. The fractional areas of amyloid, CML, laminin and collagen IV in glomeruli and interstitium (%amyloid, %CML, %laminin and %collagen, respectively) were calculated using the point counting method. The correlation between these parameters was evaluated using Spearman's rank correlation test. RESULTS: CML colocalized with AA amyloid, but not AL amyloid, except in two cases of the latter with a long history of nephropathy exceeding 14 years. In contrast, pyrraline was not observed in either type of amyloid. Mean %CML in AA amyloid was significantly higher than %collagen and %laminin in glomeruli and interstitium, indicating that AA amyloid is modified by CML independent of colocalized extracellular matrix. %CML significantly correlated with %amyloid both in glomeruli and interstitium in AA amyloidosis. AL amyloid cases with a long history of nephropathy showed positive staining for CML in glomeruli and interstitium but no staining for collagen IV and laminin in amyloid deposits. CONCLUSION: CML modification may occur in amyloid deposits of AA amyloidosis, independent of extracellular matrix components. Glycoxidative modification may have a functional link to AA amyloid deposition in renal tissues.     

Familial amyloid polyneuropathy type I (Portuguese): distribution and characterization of renal amyloid deposits

Renal amyloidosis has been considered rare and late in the evolution of the transthyretin (TTR) familial amyloid polyneuropathy (FAP) of the Portuguese type (type I). Renal biopsy has been performed systematically in 14 patients with FAP type I before liver transplantation. In all patients, TTR Met30 mutation was shown. Seven had proteinuria or abnormal microalbuminuria, whereas seven others had no urinary abnormalities. All had renal amyloid deposition predominantly in the medulla. Glomerular and vascular involvement was more prominent in patients with urinary abnormalities. Patients with the most extensive renal lesions represented a subgroup with a low score of polyneuropathy disability, a high prevalence of nephropathy in the proband generation, or a late onset for relatives with nephropathy. Immunohistochemistry studies showed that the amyloid substance corresponded to transthyretin. We have shown that renal TTR-derived amyloid deposition is common in patients with FAP type I, even in the absence of urinary abnormalities. The clinical presentation of nephropathy is not a late occurrence in the disease.     

Retroperitoneal bleeding: Hidden culprit of acute renal failure

We report on a case of acute, anuric renal failure from bilateral ureteral obstruction due to retroperitoneal hematoma during anticoagulation therapy.     

Globular amyloid deposits isolated to the small bowel: a rare association with AL amyloidosis

We describe a 55-year-old man with isolated duodenal and jejunal amyloidosis producing rare endoscopic and histologic findings. The patient had no specific gastrointestinal complaints but underwent esophagogastroduodenoscopy and colonoscopy because of progressive microcytic anemia. Endoscopy revealed multiple polyps, some filiform and measuring up to 3 cm in length, in the duodenum and proximal jejunum. Microscopically, the polyps resulted from amyloid deposition, predominantly within the submucosa, but also focally involving muscularis mucosae and lamina propria. The amyloid formed multiple globular submucosal deposits with a lamellated appearance reminiscent of corpora amylacea; linear amyloid deposition was also present in a perivascular distribution and within the overlying mucosa. Immunophenotyping confirmed AL amyloidosis with lambda immunoglobulin light chain restriction. There was no clinical evidence of visceral amyloidosis. The source of lambda light chain production was unclear as bone marrow biopsy and multiple gastrointestinal biopsies revealed normal numbers of polyclonal plasma cells. Further, immunoglobulin-free light chain assay was normal, as were serum and urine protein electrophoreses with immunofixation. This endoscopic presentation of isolated small bowel polyposis is an uncommon association with AL amyloidosis and to our knowledge this represents the first case of globular gastrointestinal amyloidosis resulting from AL amyloid.     

Tendon thickening in dialysis-related joint arthritis is due to amyloid deposits at the surface of the tendon

Objectives

Beta-2-microglobulin (β2M) dialysis-related amyloidosis (DRA), a disabiliting joint disease, has been initially reported in patients under long-term dialysis. The incidence and prevalence has significantly decreased with the improvement in dialysis techniques. Here, we attempted to clarify the clinical and MRI features to improve the diagnosis.

Specific imaging of dialysis-related amyloid deposits using 131I-beta-2-microglobulin

Dialysis-related amyloidosis (DRA), characterized by its association with beta 2-microglobulin (beta 2m), has become a major concern in long-term hemodialysis patients. Hitherto the diagnosis was based on histological examinations of tissue obtained by biopsy or during surgery. In this preliminary study a new noninvasive diagnostic method was developed using the affinity of beta 2m for its derived fibrils. 3 patients on long-term hemodialysis for 10-16 years with biopsy-proven DRA and 1 patient on chronic hemodialysis for only 6 months were examined after intravenous injection of 131I-labelled beta 2m. Specific local accumulation of radioactivity was noted in the DRA patients after 48 h, persisting for further 96 h and corresponding to clinically or radiologically evident sites of amyloid deposition and to several other hitherto unsuspected sites. Examination of an excised amyloid tumor subsequent to in vivo labelling confirmed a highly specific accumulation of radioactivity in the amyloid tissue but not in control tissue. In the patient on chronic hemodialysis for only 6 months, no specific local accumulation was detected even after 1 week. These findings provide in vivo evidence in man that a specific uptake of circulating amyloid precursor molecules into deposits occurs and that this uptake may be used to radiolabel even small tissue infiltrates of amyloid. This method therefore may not only allow an objective, noninvasive detection of DRA but may also be used to obtain new pathophysiologic insights into amyloid formation in man, as well as permitting the evaluation of preventive therapeutic strategies in prospective studies on new patients.     

Demonstration of plasma proteinase inhibitors in beta 2-microglobulin amyloid deposits.

beta 2-microglobulin-related amyloidosis (A beta 2M) represents a frequent complication in long-term dialysis patients. Although the pathogenetic mechanism has yet to be fully understood, it is known that amyloid fibrils usually consist of intact molecules of beta 2-microglobulin (beta 2m). Plasma proteinase inhibitors (PPI) are a broad family of glycoproteins with the function of eliminating unwanted proteolysis of serine proteases. Their role in amyloidogenesis has become a subject of intense discussion, especially since the recent identification of alpha 1-antichymotrypsin in the beta-protein amyloid deposits of Alzheimer's disease. We evaluated immunohistochemically and biochemically the presence and distribution of several PPIs (alpha 1-proteinase inhibitor, alpha 1-antichymotrypsin, antithrombin III, alpha 2-macroglobulin and tissue inhibitor metalloproteinase) and amyloid P component in A beta 2M deposits in osteo-articular and visceral tissues from dialysis patients with amyloidosis, as well as two carpal tunnel synovia from non-dialysis patients and one Alzheimer's brain as controls. The immunohistochemical study demonstrated that all but one (anti-alpha 1-antichymotrypsin) of the PPI antibodies tested showed varying degrees of positive reaction against A beta 2M deposits. All the antibodies (including anti-alpha 1-antichymotrypsin) also reacted to some extent with other non-amyloid visceral and connective tissue elements diffusely and/or selectively. Among them, only the reaction of anti-amyloid P component had significantly distinctive localization to A beta 2M deposits, which were identified in adjacent serial sections by Congo red staining and immunohistochemical reaction against anti-beta 2m.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lysine-specific cleavage of beta 2-microglobulin in amyloid deposits associated with hemodialysis

Amyloid fibrils isolated from bone and carpal synovia of seven patients on long-term hemodialysis were further characterized biochemically. In addition, renal amyloid stones of three dialyzed patients were examined. All deposits and stones were of beta 2-microglobulin-origin (AB-amyloid) by immunohistochemical and immunochemical evaluation. Amyloid fibril extracts were dissolved in 80% formic acid and separated by high performance liquid chromatography in 60% formic acid and 20% 2-propanol. Three major retarded fractions with molecular weights of approximately 24, 12 and 7 to 10 kD were recovered. N-terminal amino acid sequence analysis documented beta 2-microglobulin (beta 2m) as the principal polypeptide in all investigated cases. In addition to proteins with intact N-termini, one fragment commencing with isoleucine in position 7 was found in osseous or synovial amyloid. In renal amyloid stones, one additional fragment was found beginning with serine in position 20. Generally, these data point to proteolytic cleavage carboxyterminal to a lysine residue and establish that not only intact beta 2m but also at least one beta 2m fragment is present in beta 2m-derived amyloid deposits of patients with long-term hemodialysis. The fragmentation pattern is consistent with the action of lysine-specific protease(s) and underscores a potentially important role of limited proteolysis in the pathogenesis of AB-amyloid deposits.     

Chronic humoral rejection: identification of antibody-mediated chronic renal allograft rejection by C4d deposits in peritubular capillaries

The pathogenesis of chronic renal allograft rejection (CR) remains obscure. The hypothesis that a subset of CR is mediated by antidonor antibody was tested by determining whether C4d is deposited in peritubular capillaries (PTC) and whether it correlates with circulating antidonor antibodies. All cases (from January 1, 1990, to July 31, 1999) that met histologic criteria for CR and had frozen tissue (28 biopsies, 10 nephrectomies) were included. Controls were renal allograft biopsies with chronic cyclosporine toxicity (n = 21) or nonspecific interstitial fibrosis (n = 10), and native kidneys with end-stage renal disease (n = 10) or chronic interstitial fibrosis (n = 5). Frozen sections were stained by two-color immunofluorescence for C4d, type IV collagen and Ulex europaeus agglutinin I. Antidonor HLA antibody was sought by panel-reactive antibody analysis and/or donor cross matching in sera within 7 wk of biopsy. Overall, 23 of 38 CR cases (61%) had PTC staining for C4d, compared with 1 of 46 (2%) of controls (P < 0.001). C4d in PTC was localized at the interface of endothelium and basement membrane. Most of the C4d-positive CR tested had antidonor HLA antibody (15 of 17; 88%); none of the C4d-negative CR tested (0 of 8) had antidonor antibody (P < 0.0002). The histology of C4d-positive CR was similar to C4d-negative CR, and 1-yr graft survival rates were 62% and 25%, respectively (P = 0.05). Since August 1998, five of six C4d-positive CR cases have been treated with mycophenolate mofetil +/- tacrolimus with a 100% 1-yr graft survival, versus 40% before August 1998 (P < 0.03). These data support the hypothesis that a substantial fraction of CR is mediated by antibody (immunologically active). C4d can be used to separate this group of CR from the nonspecific category of chronic allograft nephropathy and may have the potential to guide successful therapeutic intervention.     

Imaging of dialysis-related amyloid (AB-amyloid) deposits with 131I-beta 2-microglobulin

The diagnosis of dialysis-related amyloid (AB-amyloid) has been based usually on clinical and radiological criteria. Following the discovery that beta 2-microglobulin was the major protein of this amyloid, we isolated and radiolabelled uremic plasma beta 2-microglobulin. After intravenous injection, gamma-camera images of selected joint areas were obtained from 42 patients who were on regular hemodialysis therapy. Positive scans involving the shoulder, hip, knee and carpal regions were found in 13 of 14 patients treated for more than 10 years and 10 of 16 patients treated for 5 to 10 years. Patients treated for less time had negative scans. Specificity was indicated by negative scans in non-amyloid inflammatory lesions in control hemodialysis patients. Up to 48-fold tracer enrichment was detected in excised AB-amyloid containing tissue as compared to amyloid-free tissue. These findings suggest that circulating radiolabelled beta 2-microglobulin is taken up by the amyloid deposits. This method may non-invasively detect tissue infiltrates of amyloid. It may also permit prospective evaluation of the efficacy of prophylactic dialysis strategies which are designed to prevent or delay the onset of this complication of long-term dialysis.     

Interleukin-6: From identification of the cytokine to development of targeted treatments

Interleukin-6 (IL-6) was identified based on extensive research conducted simultaneously on a variety of topics ranging from hepatocyte production of acute-phase proteins to plasmacytoma growth. IL-6 is a cytokine produced by a broad array of cell types and can exert its effects on virtually all cells. IL-6 can induce cell signaling not only via the classic pathway involving the transmembrane receptor IL-6Rα (restricted cellular expression) associated with gp130 (ubiquitous and responsible for signal transmission), but also via the soluble receptor IL-6Rα, which binds to IL-6 and induces a signal mediated by the ubiquitous gp130 molecule (transsignaling). IL-6 is deregulated in many inflammatory and autoimmune diseases, including rheumatoid arthritis (RA). By virtue of its multiple effects, IL-6 is involved in the various phases of RA development, including the acute phase, immuno-inflammatory phase, and destructive phase. IL-6 has an impact on the many pathogenic factors identified in RA and, consequently, holds promise for targeted treatments. However, anti-IL-6 monoclonal antibodies evaluated as IL-6 antagonists, instead, increased the half-life of the cytokine. In contrast, monoclonal antibody (tocilizumab) to transmembrane and soluble IL-6Rα has been found effective in patients with RA. Tocilizumab is now indicated for the treatment of adults with RA who have failed at least one synthetic disease-modifying antirheumatic drug or TNFα antagonist.     

Effect of renal transplantation on the radiological signs of dialysis amyloid osteoarthropathy

We have assessed the fate of amyloid bone cysts after a successful renal transplantation in 5 patients who had been on dialysis for 7 to 15 years. The size of 34 cysts, typical of amyloid osteoarthropathy, was monitored on annual X-rays for 29 to 75 (mean 47) months after TP. In sharp contrast to their progression during dialysis, cysts did not increase in size and no new cysts appeared during follow-up. However, despite a successful graft, none of the 34 cysts regressed significantly. The stability of the bone cysts may reflect either the poor solubility of the beta 2-m amyloid deposits or the limited accessibility of bone deposits to lytic factors. A longer follow-up will perhaps be necessary to document a significant regression of the cysts. Strikingly, transplantation resulted within a few days in an almost complete relief of articular complaints; in the absence of evidence of amyloid regression, this probably reflects the anti-inflammatory effect of steroids.