Dialysis-related amyloidosis

Mass spectrometry-based proteomic analysis of proteins adsorbed by hexadecyl-immobilized cellulose bead column for the treatment of dialysis-related amyloidosis

BACKGROUND

Dialysis-related amyloidosis (DRA) is a severe complication in end-stage kidney disease (ESKD) patients undergoing long-term dialysis treatment, characterized by the deposition of β2-microglobulin-related amyloids (Aβ2M amyloid). To inhibit DRA progression, hexadecyl-immobilized cellulose bead (HICB) columns are employed to adsorb circulating β2-microglobulin (β2M). However, it is possible that the HICB also adsorbs other molecules involved in amyloidogenesis.

METHODS

We enrolled 14 ESKD patients using HICB columns for DRA treatment; proteins were extracted from HICBs following treatment and identified using liquid chromatography-linked mass spectrometry. We measured the removal rate of these proteins and examined the effect of those molecules on Aβ2M amyloid fibril formation in vitro.

RESULTS

We identified 200 proteins adsorbed by HICBs. Of these, 21 were also detected in the amyloid deposits in the carpal tunnels of patients with DRA. After passing through the HICB column and hemodialyzer, the serum levels of proteins such as β2M, lysozyme, angiogenin, complement factor D and matrix Gla protein were reduced. These proteins acted in the Aβ2M amyloid fibril formation.

CONCLUSIONS

HICBs adsorbed diverse proteins in ESKD patients with DRA, including those detected in amyloid lesions. Direct hemoperfusion utilizing HICBs may play a role in acting Aβ2M amyloidogenesis by reducing the amyloid-related proteins.

Broken but not beaten: Challenge of reducing the amyloids pathogenicity by degradation

BACKGROUND

The accumulation of ordered protein aggregates, amyloid fibrils, accompanies various neurodegenerative diseases (such as Parkinson's, Huntington's, Alzheimer's, etc.) and causes a wide range of systemic and local amyloidoses (such as insulin, hemodialysis amyloidosis, etc.). Such pathologies are usually diagnosed when the disease is already irreversible and a large amount of amyloid plaques have accumulated. In recent years, new drugs aimed at reducing amyloid levels have been actively developed. However, although clinical trials have demonstrated a reduction in amyloid plaque size with these drugs, their effect on disease progression has been controversial and associated with significant side effects, the reasons of which are not fully understood.

AIM OF REVIEW

The purpose of this review is to summarize extensive array of data on the effect of exogenous and endogenous factors (physico-mechanical effects, chemical effects of low molecular weight compounds, macromolecules and their complexes) on the structure and pathogenicity of mature amyloids for proposing future directions of the development of effective and safe anti-amyloid therapeutics.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Our analysis show that destruction of amyloids is in most cases incomplete and degradation products often retain the properties of amyloids (including high and sometimes higher than fibrils, cytotoxicity), accelerate amyloidogenesis and promote the propagation of amyloids between cells. Probably, the appearance of protein aggregates, polymorphic in structure and properties (such as amorphous aggregates, fibril fragments, amyloid oligomers, etc.), formed because of uncontrolled degradation of amyloids, may be one of the reasons for the ambiguous effectiveness and serious side effects of the anti-amyloid drugs. This means that all medications that are supposed to be used both for degradation and slow down the fibrillogenesis must first be tested on mature fibrils: the mechanism of drug action and cytotoxic, seeding, and infectious activity of the degradation products must be analyzed.

Impact on change in serum beta 2 microglobulin by combination therapy of peritoneal dialysis and hemodialysis: a 12-month preliminary observational study

Background

In the Japanese guidelines on combination peritoneal dialysis (PD) and hemodialysis (HD) therapy, patients with serum beta 2 microglobulin (β2MG) levels less than 30 mg/L are recommended. And PD patients with β2MG more than 30 mg/L are considered to transfer to the PD + HD combination therapy. However, the resultant changes in serum β2MG levels by the introduction of PD + HD combination therapy and the factors influencing the change have not clearly elucidated.

Methods

We retrospectively studied 11 PD patients (mean age 56.4 ± 12.9 years, 10 males) with baseline β2MG levels > 30 mg/L with respect to changes in β2MG and its related factors for 12 months after the introduction of combination therapy of PD plus once a week HD (4 h) using a high-performance dialyzer. Laboratory data including hemoglobin, albumin, C-reactive protein, blood urea nitrogen, creatinine, and the patients’ demographic profiles, and HD-related factors, such as Kt/V and blood flow rate, were assessed.

Results

Serum β2MG levels decreased statistically significantly after the introduction of combination therapy: from 36.7 ± 6.7 mg/L at 0 months, to 33.4 ± 6.1 mg/L at 3 months (p = 0.030, compared to baseline), 32.9 ± 4.5 mg/L at 6 months (p = 0.009), and 33.3 ± 5.3 mg/L at 12 months (p = 0.023), respectively. However, only 27–36% patients achieved target β2MG levels of < 30 mg/L during the observation period. Regarding influencing factors, serum albumin levels, blood flow rates of HD, residual renal function and baseline β2MG were associated with a decrease in serum β2MG levels on univariate analysis. In multivariate analysis, serum albumin at 3 and 12 months correlated significantly with Δβ2MG (β =  − 0.990, p = 0.032 at 3 months, β =  − 0.551, p = 0.033 at 12 months). Urine volume at 12 months correlated significantly with Δβ2MG (β = 0.507, p = 0.019).

Conclusions

Combination therapy of PD and HD might reduce serum β2MG levels, but with marginal efficacy. Our preliminary data indicate that the combination therapy of PD and once weekly HD is not sufficient to significantly decrease serum β2MG levels. Additional HD prescriptions, such as increase in blood flow rate and hemodiafiltration, need to be tested in order to improve β2MG levels in these patients.

Spatiotemporal organisation of protein processing in the kidney

The kidney regulates plasma protein levels by eliminating them from the circulation. Proteins filtered by glomeruli are endocytosed and degraded in the proximal tubule and defects in this process result in tubular proteinuria, an important clinical biomarker. However, the spatiotemporal organization of renal protein metabolism in vivo was previously unclear. Here, using functional probes and intravital microscopy, we track the fate of filtered proteins in real time in living mice, and map specialized processing to tubular structures with singular value decomposition analysis and three-dimensional electron microscopy. We reveal that degradation of proteins requires sequential, coordinated activity of distinct tubular sub-segments, each adapted to specific tasks. Moreover, we leverage this approach to pinpoint the nature of endo-lysosomal disorders in disease models, and show that compensatory uptake in later regions of the proximal tubule limits urinary protein loss. This means that measurement of proteinuria likely underestimates severity of endocytotic defects in patients.

Polesel et al. visualize plasma protein filtration, uptake and metabolism in the kidneys of living mice in real-time. They reveal coordinated activity of different specialized tubular segments, with major compensatory adaptations occurring in disease states.

Carpal tunnel release under wide awake local anesthesia with no tourniquet in hemodialysis patients with arteriovenous shunt

INTRODUCTION

Long-term hemodialysis patients experience many hand diseases caused by dialysis-related amyloidosis (DRA), with carpal tunnel syndrome (CTS) being the most common. For the patients with arteriovenous (AV) shunt, surgical decompression remains challenging because of the contraindications of a tourniquet. A technique called wide-awake local anesthesia with no tourniquet (WALANT), in which epinephrine provides hemostasis instead of the tourniquet, can be a good option for hemodialysis patients. The purpose of this study was to assess the prevalence of CTS and related factors in hemodialysis patients, and to establish the efficacy and safety of WALANT on hemodialysis patients with AV shunt.

MATERIALS AND METHODS

This prospective study included 275 hemodialysis patients between March 2013 and July 2019. 43 patients were diagnosed with CTS, involving surgical treatment on 70 wrists. We performed mini-open carpal tunnel release using WALANT on the AV shunt arm (defined as the WALANT group), while using lidocaine and a tourniquet on the arm without an AV shunt (defined as the tourniquet group). The operative time, surgical field bleeding (blood loss and hemostasis score), surgical pain (injection pain and tourniquet pain), outcomes, complications, and satisfaction were compared between the two groups.

RESULTS

The incidence of CTS in hemodialysis patients was 15.6%. Longer dialysis durations were related to higher proportions of patients with CTS. There was no significant difference in blood loss (p=0.184) and hemostasis score (p=0.165) between the two groups. Clinical symptoms improved in all patients, and there were no severe complications. The WALANT group had a significantly longer preparation time of approximately 20minutes, but they had low injection pain and no tourniquet pain. There was also no significant difference in terms of satisfaction levels (p=0.212).

DISCUSSION

CTS is a very common disease among hemodialysis patients. WALANT provided sufficient hemostasis without a tourniquet, despite the patients' high bleeding tendency. The technique also had the advantages of low injection pain, no tourniquet pain, and no major complications. In this respect, WALANT can be a good choice for hemodialysis patients with AV shunt.

LEVEL OF EVIDENCE

II.

Application study of infrared free-electron lasers towards the development of amyloidosis therapy

Amyloidosis is known to be caused by the deposition of amyloid fibrils into various biological tissues; effective treatments for the disease are little established today. An infrared free-electron laser (IR-FEL) is an accelerator-based picosecond-pulse laser having tunable infrared wavelengths. In the current study, the irradiation effect of an IR-FEL was tested on an 11-residue peptide (NFLNCYVSGFH) fibril from β2-microglobulin (β2M) with the aim of applying IR-FELs to amyloidosis therapy. Infrared microspectroscopy (IRM) and scanning electron microscopy showed that a fibril of β2M peptide was clearly dissociated by IR-FEL at 6.1 µm (amide I) accompanied by a decrease of the β-sheet and an increase of the α-helix. No dissociative process was recognized at 6.5 µm (amide II) as well as at 5.0 µm (non-specific wavelength). Equilibrium molecular dynamics simulations indicated that the α-helix can exist stably and the probability of forming interchain hydrogen bonds associated with the internal asparagine residue (N4) is notably reduced compared with other amino acids after the β-sheet is dissociated by amide I specific irradiation. This result implies that N4 plays a key role for recombination of hydrogen bonds in the dissociation of the β2M fibril. In addition, the β-sheet was disrupted at temperatures higher than 340 K while the α-helix did not appear even though the fibril was heated up to 363 K as revealed by IRM. The current study gives solid evidence for the laser-mediated conversion from β-sheet to α-helix in amyloid fibrils at the molecular level.

Investigation of D76N β2-Microglobulin Using Protein Footprinting and Structural Mass Spectrometry

NMR studies and X-ray crystallography have shown that the structures of the 99-residue amyloidogenic protein β₂-microglobulin (β₂m) and its more aggregation-prone variant, D76N, are indistinguishable, and hence, the reason for the striking difference in their aggregation propensities remains elusive. Here, we have employed two protein footprinting methods, hydrogen-deuterium exchange (HDX) and fast photochemical oxidation of proteins (FPOP), in conjunction with ion mobility-mass spectrometry, to probe the differences in conformational dynamics of the two proteins. Using HDX-MS, a clear difference in HDX protection is observed between these two proteins in the E-F loop (residues 70-77) which contains the D76N substitution, with a significantly higher deuterium uptake being observed in the variant protein. Conversely, following FPOP-MS only minimal differences in the level of oxidation between the two proteins are observed in the E-F loop region, suggesting only modest side-chain movements in that area. Together the HDX-MS and FPOP-MS data suggest that a tangible perturbation to the hydrogen-bonding network in the E-F loop has taken place in the D76N variant and furthermore illustrate the benefit of using multiple complementary footprinting methods to address subtle, but possibly biologically important, differences between highly similar proteins.

A history of uraemic toxicity and of the European Uraemic Toxin Work Group (EUTox)

The uraemic syndrome is a complex clinical picture developing in the advanced stages of chronic kidney disease, resulting in a myriad of complications and a high early mortality. This picture is to a significant extent defined by retention of metabolites and peptides that with a preserved kidney function are excreted or degraded by the kidneys. In as far as those solutes have a negative biological/biochemical impact, they are called uraemic toxins. Here, we describe the historical evolution of the scientific knowledge about uraemic toxins and the role played in this process by the European Uraemic Toxin Work Group (EUTox) during the last two decades. The earliest knowledge about a uraemic toxin goes back to the early 17th century when the existence of what would later be named as urea was recognized. It took about two further centuries to better define the role of urea and its link to kidney failure, and one more century to identify the relevance of post-translational modifications caused by urea such as carbamoylation. The knowledge progressively extended, especially from 1980 on, by the identification of more and more toxins and their adverse biological/biochemical impact. Progress of knowledge was paralleled and impacted by evolution of dialysis strategies. The last two decades, when insights grew exponentially, coincide with the foundation and activity of EUTox. In the final section, we summarize the role and accomplishments of EUTox and the part it is likely to play in future action, which should be organized around focus points like biomarker and potential target identification, intestinal generation, toxicity mechanisms and their correction, kidney and extracorporeal removal, patient-oriented outcomes and toxin characteristics in acute kidney injury and transplantation.

High Peritoneal Clearance of Small Molecules Did Not Provide Low Serum β2–Microglobulin Concentrations in Peritoneal Dialysis Patients

Objective

Although early reports demonstrated that serum β2-microglobulin (s-β2m) concentrations in patients on peritoneal dialysis (PD) were lower than those in patients on hemodialysis (HD), more recent studies demonstrated lower s-β2m concentrations in HD patients treated mainly with high-flux synthetic membranes. We therefore compared s-β2m concentrations between patients on PD and on HD, and also analyzed the relationship between s-β2m concentrations and other parameters in patients on PD.

Patients and Methods

We investigated 24 patients who had been undergoing PD [11 on continuous ambulatory peritoneal dialysis, 13 on continuous cycling peritoneal dialysis] for 4.3 ± 2.7 years, and 24 patients who had been undergoing HD with high-flux synthetic membranes for 6.1 ± 3.2 years. Concentrations of s-β2m in the PD patients were compared to concentrations in the HD patients. In patients on PD, we also analyzed the relationship between s-β2m concentration and other parameters, including residual renal function, total weekly Kt/V urea, total weekly creatinine clearance (CCr), and dialysis schedules.

Results

We found no significant difference in s-β2m concentrations between the PD and HD patients (33.6 ± 10.4 mg/L vs 30.3 ± 10.5 mg/L respectively). Concentrations of s-β2m in PD patients rose with PD duration and were significantly inversely correlated with residual renal function ( r = –0.71, p < 0.0001). Unexpectedly, concentrations of s-β2m in anuric PD patients rose as peritoneal CCr increased. And most of the patients with high s-β2m levels fell into the high or high-average transport categories according to a peritoneal equilibration test.

Conclusions

Concentrations of s-β2m in patients on PD did not differ significantly from concentrations in HD patients who were using high-flux synthetic membranes. The contribution of residual renal function to removal of β2m was more important than the contribution of peritoneal clearance. High peritoneal clearance of small molecules did not result in low s-β2m concentrations, especially in anuric patients with accelerated peritoneal permeability.

Destructive Spondyloarthropathy in a Patient on Continuous Ambulatory Peritoneal Dialysis for 13 Years

Since 1984 there have been reports of a destructive spondyloarthropathy occurring in patients on long-term hemodialysis. The primary abnormality appears to be an accumulation of β2-microglobulin, which is not adequately removed by dialysis, and forms amyloid deposits in articular and periarticular tissues. We report a case of this disease in a patient treated only by peritoneal dialysis. While this form of treatment may delay the development of arthropathy, as compared to hemodialysis, it does not prevent it. An increasing incidence of this disorder may be expected, since increasing numbers of patients have been on long-term peritoneal dialysis.

Epidemiological survey and risk factor analysis of dialysis-related amyloidosis including destructive spondyloarthropathy, dialysis amyloid arthropathy, and carpal tunnel syndrome

The RDT population, initially at 215 patients, exceeded 300,000 in 2011, with a total of 329,609 patients at the end of December 2016. In our Institute, the number of patients with destructive spondylosis is increasing with the increase in the number of dialysis patients in Japan. We had 14 Cases in the 1990s, and then 82 cases in the 2000s and have already had 131 cases in the 2010s. The purpose of this study was to investigate the incidence of dialysis-related amyloidosis (DRA) such as destructive spondyloarthropathy (DSA), dialysis amyloid arthropathy (DAA), and carpal tunnel syndrome (CTS). In addition, another purpose was to examine the risk factors of the DRA. DAA made its own assessment on radiographs based on stage. Survey items were patient's basic data, laboratory data and X-ray view. Patient's basic data included such as sex, age, height, and weight and RDT-related factors such as kidney disease that led to RDT, age at start of RDT, RDT history, medical history (past and present), and history of surgery. The frequency of DRA was examined by medical history and radiological examination in 199 dialysis patients who obtained informed consent. The patients were divided into two groups according to the presence or absence of DRA, and risk factors of DRA were investigated from the medical history, basic data of patients, and blood tests. Of the 199 patients on regular dialysis therapy, 41 (20.6%) showed DRA. Based on the X-ray images, 21 patients (10.6%) showed DSA, while 22 patients (11.1%) showed DAA. Sixteen patients (8.0%) had CTS, determined through a history of surgery. Regarding overlap of conditions, 14 had both DSA and DAA, 3 had both DSA and CTS, and 2 had both DAA and CTS. There were statistically significant differences between the two groups in the cause of disease in Chronic glomerulonephritis and Diabetic Nephropathy, age at the start of RDT, period of RDT, body weight, blood platelet count, and blood Ca level. When multivariate analysis was performed on these items, statistical differences were recognized only during the dialysis period. In conclusion, long dialysis period was a risk factor for DRA.

Hemodialysis-associated soft tissue amyloidomas of the chest and abdominal wall

Amyloidoma is a highly unusual presentation of amyloidosis in tumoral or nodular form. Isolated soft tissue amyloidomas in individuals with end-stage renal disease on chronic hemodialysis is exceedingly rare, particularly in the era of advanced dialysis technologies. We report the case of a 55-year-old male with end-stage renal disease due to autosomal-dominant polycystic kidney disease, on HD for over 30 years, who was found to have soft-tissue, dialysis-related (β₂ -microglobulin) amyloidomas (DRA). He presented with painful, palpable masses within the thoracic and abdominal walls. Serum β₂ -microglobulin level was only mildly elevated at 24.9 mg/L. Biopsy confirmed amyloidosis with positivity for Congo Red staining and apple-green birefringence under polarized light. Amyloid subtyping with immunohistochemistry showed positive β₂ -microglobulin staining within the deposits. Conservative therapy involving pain management and close monitoring resulted in eventual improvement in symptoms and thus proved to be a viable option for treatment.

Positron Emission Tomography Can Support the Diagnosis of Dialysis-Related Amyloidosis

BACKGROUND

The improvements in dialysis have not eliminated long-term problems, including dialysis-related amyloidosis (DRA), caused by Beta-2 microglobulin deposition. Several types of scintigraphy have been tested to detect DRA, none entered the clinical practice. Aim of the study was to assess the potential of PET-FDG scan in the diagnosis of DRA.

METHODS

Forty-six dialysis patients with at least one PET scan (72 scans) were selected out 162 patients treated in 2016-2018. Subjective global assessment (SGA), malnutrition inflammation score (A), Charlson Comorbidity Index (CCI), were assessed at time of scan; 218 age-matched cases with normal kidney function were selected as controls. PET scans were read in duplicate. Carpal tunnel syndrome was considered a proxy for DRA. A composite "amyloid score" score considered each dialysis year = 1 point; carpal tunnel-DRA = 5 points per site. Logistic regression, ROC curves and a prediction model were built.

RESULTS

The prevalence of positive PET was 43.5% in dialysis, 5% in controls (p < 0.0001). PET was positive in 14/15 (93.3%) scans in patients with carpal tunnel. PET sensitivity for detecting DRA was 95% (specificity 64%). Carpal tunnel was related to dialysis vintage and MIS. A positive PET scan was significantly associated with dialysis vintage, MIS and amyloid score. A prediction model to explain PET positivity combined clinical score and MIS, allowing for an AUC of 0.906 (CI: 0.813-0.962; p < 0.001).

CONCLUSIONS

PET-FDG may identify DRA, and may be useful in detecting cases in which inflammation favours B2M deposition. This finding, needing large-scale confirmation, could open new perspectives in the study of DRA.

A new era for understanding amyloid structures and disease

The aggregation of proteins into amyloid fibrils and their deposition into plaques and intracellular inclusions is the hallmark of amyloid disease. The accumulation and deposition of amyloid fibrils, collectively known as amyloidosis, is associated with many pathological conditions that can be associated with ageing, such as Alzheimer disease, Parkinson disease, type II diabetes and dialysis-related amyloidosis. However, elucidation of the atomic structure of amyloid fibrils formed from their intact protein precursors and how fibril formation relates to disease has remained elusive. Recent advances in structural biology techniques, including cryo-electron microscopy and solid-state NMR spectroscopy, have finally broken this impasse. The first near-atomic-resolution structures of amyloid fibrils formed in vitro, seeded from plaque material and analysed directly ex vivo are now available. The results reveal cross-β structures that are far more intricate than anticipated. Here, we describe these structures, highlighting their similarities and differences, and the basis for their toxicity. We discuss how amyloid structure may affect the ability of fibrils to spread to different sites in the cell and between organisms in a prion-like manner, along with their roles in disease. These molecular insights will aid in understanding the development and spread of amyloid diseases and are inspiring new strategies for therapeutic intervention.

Structural Analysis of a Trimer of β2-Microgloblin Fragment by Molecular Dynamics Simulations

A peptide β₂-m_21-31, which is a fragment from residue 21 to residue 31 of β₂-microgloblin, is experimentally known to self-assemble and form amyloid fibrils. In order to understand the mechanism of amyloid fibril formations, we applied the replica-exchange molecular dynamics method to the system consisting of three fragments of β₂-m_21-31. From the analyses on the temperature dependence, we found that there is a clear phase transition temperature in which the peptides aggregate with each other. Moreover, we found by the free energy analyses that there are two major stable states: One of them is like amyloid fibrils and the other is amorphous aggregates.

Comparing Hydrogen Deuterium Exchange and Fast Photochemical Oxidation of Proteins: a Structural Characterisation of Wild-Type and ΔN6 β2-Microglobulin

Hydrogen deuterium exchange (HDX) coupled to mass spectrometry (MS) is a well-established technique employed in the field of structural MS to probe the solvent accessibility, dynamics and hydrogen bonding of backbone amides in proteins. By contrast, fast photochemical oxidation of proteins (FPOP) uses hydroxyl radicals, liberated from the photolysis of hydrogen peroxide, to covalently label solvent accessible amino acid side chains on the microsecond-millisecond timescale. Here, we use these two techniques to study the structural and dynamical differences between the protein β₂-microglobulin (β₂m) and its amyloidogenic truncation variant, ΔN6. We show that HDX and FPOP highlight structural/dynamical differences in regions of the proteins, localised to the region surrounding the N-terminal truncation. Further, we demonstrate that, with carefully optimised LC-MS conditions, FPOP data can probe solvent accessibility at the sub-amino acid level, and that these data can be interpreted meaningfully to gain more detailed understanding of the local environment and orientation of the side chains in protein structures. Graphical Abstract ᅟ.

A New Treatment for Dialysis-Related Amyloidosis with β 2-Microglobulin Adsorbent Column

Dialysis-related amyloidosis (DRA) is characterized by the presence of β 2-microglobulin (β 2-m) in the plasma. In order to eliminate β 2-m from the circulating blood, the β 2-m selective adsorbent for direct hemoperfusion (DHP) was developed. A DHP column (BM-01), containing 350 ml of the adsorbent, was subjected to clinical trials. The column was connected with a PAN (AN69) membrane dialyzer in series and used 3 times a week for 1 week (11 patients), 4 weeks (5 patients), 6 months (1 patient) and 12 months (2 patients). The percent reduction (%) of β 2-m was for 16 patients (for 1 or 4 weeks), more than 65, and for 3 patients (for more than 6 months), 76.5 ± 4.9, 73.5 ± 5.7, 72.2 ± 6.2. At the end of each session, β 2-m plasma levels were found to be below 10 mg/L, with 3.4 mg/L being the lowest. The total amounts of β 2-m removed were 172.5 ± 22.3, 257.0 ± 75.6, 157.6 ± 32.2 and 429.8 mg/session at max. Two out of these three patients had a favorable effect on joint symptoms and ocular fundus. It can be concluded that this selective adsorption therapy may delay the progression of DRA, and is worth considering for wide application.

Pathological Hip Fracture Due to Amyloidosis Occurring after Successful Renal Transplantation. A Case Report

A fifty-six year old man who had been on haemodialysis for a total of seventeen years sustained a pathological fracture of the femoral neck six months after successful renal transplantation. Multiple cystic lesions were present in both hips and a bone specimen from the fracture site confirmed amyloid deposition on immunohistochemical staining. Renal transplantation may prevent further deposition of amyloid but the long-term complications of dialysis-related amyloidosis may still occur.

Atypical familial Mediterranean fever developed in a long-term hemodialysis patient

Familial Mediterranean Fever (FMF) is usually an autosomal recessive autoinflammatory disease characterized by recurrent attacks of fever and serositis. FMF develops before the age of 20 years in 90% of patients. It has intervals of 1 week to several years between attacks, which leads to renal dysfunction-amyloidosis. We report a case of atypical FMF that developed in a long-term hemodialysis patient. A 65-year-old Japanese female undergoing hemodialysis for 32 years was referred to our hospital with a fever of unknown origin (FUO) following cervical laminoplasty. The fever occurred as recurrent attacks accompanied by oligoarthralgia of the left hip and knee. We suspected FMF because of recurrent self-limited febrile attacks, although the patient showed atypical clinical features such as late-onset and highly frequent attacks. After receiving treatment, she achieved a complete response to colchicine. Therefore, a diagnosis of FMF was made based on the Tel-Hashomer criteria, which was confirmed by genetic testing. The case suggests that FMF may be of note in long-term hemodialysis patients developing FUO.

Persistent fever and destructive arthritis caused by dialysis-related amyloidosis: A case report

RATIONALE

Dialysis-related amyloidosis (DRA) can present rheumatic manifestations in patients on long-term hemodialysis. Typical articular symptoms with DRA involve carpal-tunnel syndrome, effusion in large joints, spondyloarthropathy, or cystic bone lesions, which are usually with non-inflammatory processes.

PATIENT CONCERNS

A 64-year-old man on hemodialysis for >30 years was admitted because of intermittent fever, polyarthritis, and elevated serum C-reactive protein (CRP) level, which was continuous for 2 years. Several antibiotics were ineffective for 3 months before his admission. On physical examination, joint swelling was observed at bilateral wrists, knees, ankles, and hip joints. Laboratory tests revealed elevation of serum inflammatory markers and β2-microglobulin (β2-MG). Synovial fluid showed predominant infiltration of polymorphonuclear leukocytes and the increase of β2-MG level.

DIAGNOSIS

Significant deposition of β2-MG with inflammatory cell infiltration was found in biopsied samples from synovium, skin, and ileum.

INTERVENTIONS

We decided to switch to the hemodialysis column with membrane that can effectively absorb β2-MG in circulation.

OUTCOMES

The relief of symptoms and a decrease of CRP level by changing the membrane lead to the final diagnosis of DRA.

LESSONS

Our case demonstrates that DRA arthropathy can be inflammatory and destructive, and also develop systemic inflammatory signs and symptoms. In such cases, aggressive absorption of β2-MG in circulation might help the amelioration of symptoms.

Surgical Management for Destructive Atlantoaxial Spondyloarthropathy in Long-Term Hemodialysis Patients

BACKGROUND

Atlantoaxial spondyloarthropathy most often results from rheumatoid arthritis, cancer metastasis, or basilar invagination. Dialysis-related spondyloarthropathy is a rare cause of spinal deformity and cervical myelopathy at the atlantoaxial joint. We report 2 patients on long-term hemodialysis who presented with atlantoaxial spondyloarthropathy.

CASE DESCRIPTION

Two patients with end-stage renal failure presented with a history of progressively worsening neck pain, motion limitation, and gait disturbance. In both patients, radiologic findings showed a bone-destroying soft tissue mass lateral to C1 and C2, compressing the spinal cord and causing atlantoaxial instability. We performed a C1 laminectomy and C12 transarticular screw fixation and biopsied the osteolytic mass. The neck pain, hand numbness, and gait disturbance improved.

CONCLUSIONS

Although the surgical management of these patients involves many challenges, appropriate decompression and fusion surgery is an effective treatment option.

Endocytosed 2-Microglobulin Amyloid Fibrils Induce Necrosis and Apoptosis of Rabbit Synovial Fibroblasts by Disrupting Endosomal/Lysosomal Membranes: A Novel Mechanism on the Cytotoxicity of Amyloid Fibrils

Dialysis-related amyloidosis is a major complication in long-term hemodialysis patients. In dialysis-related amyloidosis, β2-microglobulin (β2-m) amyloid fibrils deposit in the osteoarticular tissue, leading to carpal tunnel syndrome and destructive arthropathy with cystic bone lesions, but the mechanism by which these amyloid fibrils destruct bone and joint tissue is not fully understood. In this study, we assessed the cytotoxic effect of β2-m amyloid fibrils on the cultured rabbit synovial fibroblasts. Under light microscopy, the cells treated with amyloid fibrils exhibited both necrotic and apoptotic changes, while the cells treated with β2-m monomers and vehicle buffer exhibited no morphological changes. As compared to β2-m monomers and vehicle buffer, β2-m amyloid fibrils significantly reduced cellular viability as measured by the lactate dehydrogenase release assay and the 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay and significantly increased the percentage of apoptotic cells as measured by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling method. β2-m amyloid fibrils added to the medium adhered to cell surfaces, but did not disrupt artificial plasma membranes as measured by the liposome dye release assay. Interestingly, when the cells were incubated with amyloid fibrils for several hours, many endosomes/lysosomes filled with amyloid fibrils were observed under confocal laser microscopy and electron microscopy, Moreover, some endosomal/lysosomal membranes were disrupted by intravesicular fibrils, leading to the leakage of the fibrils into the cytosol and adjacent to mitochondria. Inhibition of actin-dependent endocytosis by cytochalasin D attenuated the toxicity of amyloid fibrils. These results suggest that endocytosed β2-m amyloid fibrils induce necrosis and apoptosis by disrupting endosomal/lysosomal membranes, and this novel mechanism on the cytotoxicity of amyloid fibrils is described.

Significance of the decreased risk of dialysis-related amyloidosis now proven by results from Japanese nationwide surveys in 1998 and 2010

BACKGROUND

Although dialysis technology greatly improved in recent years, it remained unclear whether those improvements helped decrease the incidence of dialysis-related amyloidosis (DRA). Accordingly, we retrospectively compared the incidence of first-time carpal tunnel surgery (CTS)-as proxy for DRA onset-in two cohorts of chronic hemodialysis patients, with the second cohort studied after dialysis methods (especially dialyzate quality control) had greatly improved.

METHODS

We used the 1998 and 2010 Japan Renal Data Registries to compare crude risk of first-time CTS the following year. After adjusting for patient background and laboratory data, odds ratios (ORs) for CTS in the whole cohorts and the populations matched by propensity score (PS) for hemodialysis and hemodiafiltration were calculated at a 95% confidence interval.

RESULTS

Of note, 2 02 726 patients were analyzed. In the 1998 cohort, 1.77% experienced first-time CTS compared with 1.30% of the 2010 cohort (P < 0.001); with 2010 as referent, the adjusted 1998 OR was 2.22 (1.68-2.95). Both crude risks and adjusted ORs were analyzed by dialysis vintage, age, pre-dialysis β2-microglobulin (β2m) and β2m clearance, risk of CTS trending 1.5-2.0 higher in 1998 than 2010. The reduction was most prominent in patients with longer dialysis vintage, patients who were younger, and those with lower pre-dialysis β2m levels. Similar results were obtained by PS-matched analysis. We also found that β2m clearance >80% may reduce risk of CTS.

CONCLUSIONS

The incidence of first-time CTS as proxy for DRA decreased significantly from 1998 to 2010. Several factors may have contributed to this decrease, including improved dialysis methods.

Imaging Findings and Evaluation of Metabolic Bone Disease

Bone is a dynamic organ of the endoskeleton, playing an important role in structural integrity, mineral reservoirs, blood production, coagulation, and immunity. Metabolic bone disease encompasses a broad spectrum of inherited and acquired disorders that disrupt the normal homeostasis of bone formation and resorption. For patients affected by these processes, radiologic imaging plays a central role in diagnosis, monitoring treatment, and risk stratification. Radiologists should be familiar with the diseases, intimately aware of the imaging findings, and possessive of multimodality expertise to wisely guide the best practice of medicine. The purpose of this paper is to review the imaging features and characteristics of the most common types of metabolic bone disease with highlights of clinically relevant information so that readers can better generate appropriate differential diagnoses and recommendations. For this review, a thorough literature search for the most up-to-date information was performed on several key types of metabolic bone disease: osteoporosis, osteomalacia, rickets, scurvy, renal osteodystrophy, hyperparathyroidism, Paget’s disease, osteogenesis imperfecta, acromegaly, and osteopetrosis. Although they all affect the bone, these diseases have both shared characteristic features that can be discerned through imaging.

Impact of advanced dialysis technology on the prevalence of dialysis-related amyloidosis in long-term maintenance dialysis patients

Dialysis-related amyloidosis (DRA) is a unique type of amyloidosis (beta-2 microglobulin) predominantly in end-stage renal disease. Its clinical manifestations add to increased morbidity and reduced quality of life. There seems to be a relative risk reduction in DRA manifestations when hemodialysis (HD) patients are treated with advanced HD technology, but changes of the course of DRA are uncertain. The aim of our investigation was to evaluate the prevalence and severity of carpal tunnel syndrome (CTS) in long-term dialysis patients receiving either conventional or high-flux, online-produced ultrapure dialysis fluid. The cross-sectional study included 147 HD patients (at least 10 years). The definitive diagnosis of CTS was made histologically or by the coexistence of CTS with other radiological DRA manifestations (bone cysts, arthropathies). The two HD patient groups did not differ significantly in age at start of HD, gender, major co-morbid diseases, anuria, and dialysis vintage. The conventional HD group had significantly higher circulating beta-2 microglobulin and C-reactive protein (CRP) levels. The prevalence of DRA was 68% for the conventional HD group and 28% for the advanced HD group. Duration of dialysis treatment was the only significant risk factor for the development of clinical DRA manifestations in both study groups, but CTS, bone cysts, or arthropathies occurred significantly earlier in conventional HD patients. The prevalence and severity of DRA have decreased with advances in dialysis technology during the last two decades, although its occurrence is simply delayed.

Various musculoskeletal manifestations of chronic renal insufficiency

Musculoskeletal manifestations in chronic renal insufficiency are caused by complex bone metabolism alterations, now described under the umbrella term of chronic kidney disease mineral- and bone-related disorder (CKD-MBD), as well as iatrogenic processes related to renal replacement treatment. Radiological imaging remains the mainstay of disease assessment. This review aims to illustrate the radiological features of CKD-MBD, such as secondary hyperparathyroidism, osteomalacia, adynamic bone disease, soft-tissue calcifications; as well as features associated with renal replacement therapy, such as aluminium toxicity, secondary amyloidosis, destructive spondyloarthropathy, haemodialysis-related erosive arthropathy, tendon rupture, osteonecrosis, and infection.

Amyloidomas of soft parts: diagnosis by fine-needle aspiration

A tumoral mass of amyloid (amyloidoma) arising in the soft tissues of the distal extremities is exceedingly unusual, and applying the fine-needle aspiration (FNA) biopsy technique to specifically diagnose this condition is even more infrequent. Herein, we report an example of two separate amyloidomas arising in the right calf of an otherwise asymptomatic elderly man who was referred to the sarcoma clinic because these masses clinically and radiographically simulated a malignant neoplasm. The fine-needle aspirate yielded amorphous, acellular, dense blue material on Romanowsky-stained smears and smudgy acellular cyanophilic material on Papanicolaou-stained smears. The aspirate procured cell-block contained hyalinized eosinophilic acellular material on H&E stain that was Congo-red positive and displayed yellow-green birefringence with polarization. Unlike prior assertions to the contrary, a diagnosis of amyloidoma is possible using FNA cytopathology even in patients without a known underlying amyloidogenic disorder.

Ubiquitous amyloids

The common view of amyloids and prion proteins is that they are associated with many currently incurable diseases and present a great danger to an organism. This danger comes from the fact that not only prion proteins, but also the infectious form(s) of amyloids, as it has been shown recently, are able to transmit the disease. On the other hand, organisms take advantage of the strength and durability of specific forms of amyloids. Such forms do not spread any disease. Also, in nanotechnology there is a constantly growing need to employ amyloid fibrils in many industrial applications. With increasing knowledge about amyloids and prion proteins we are aware that the amyloidal state is inherent to any protein, making the problem of amyloid formation a central one in aging-related diseases. However, the “good” amyloids can be beneficial and even necessary for our health. Furthermore, because of their mechanical properties, the amyloids are of great interest to engineers.

Currents concepts on the immunopathology of amyloidosis

Amyloidosis is defined as the extracellular accumulation at systemic or organ-specific level of insoluble low molecular weight protein fibrils manifesting a beta pleated sheet configuration and a characteristic staining pattern. Several different types of proteins may lead to this phenomenon, and amyloidosis is defined by the biochemical nature of the protein in the deposits and further classified according to whether the deposits are localized or systemic, acquired or inherited, and by the resulting clinical phenotype. Amyloidosis includes subtypes such as light chain, associated with serum amyloid A protein, heritable and familial forms, dialysis-related disease, and organ-specific conditions. The pathogenesis and clinical features of these clinical and pathological entities will be critically discussed in this review article.

Amyloidogenic regions and interaction surfaces overlap in globular proteins related to conformational diseases

Protein aggregation underlies a wide range of human disorders. The polypeptides involved in these pathologies might be intrinsically unstructured or display a defined 3D-structure. Little is known about how globular proteins aggregate into toxic assemblies under physiological conditions, where they display an initially folded conformation. Protein aggregation is, however, always initiated by the establishment of anomalous protein-protein interactions. Therefore, in the present work, we have explored the extent to which protein interaction surfaces and aggregation-prone regions overlap in globular proteins associated with conformational diseases. Computational analysis of the native complexes formed by these proteins shows that aggregation-prone regions do frequently overlap with protein interfaces. The spatial coincidence of interaction sites and aggregating regions suggests that the formation of functional complexes and the aggregation of their individual subunits might compete in the cell. Accordingly, single mutations affecting complex interface or stability usually result in the formation of toxic aggregates. It is suggested that the stabilization of existing interfaces in multimeric proteins or the formation of new complexes in monomeric polypeptides might become effective strategies to prevent disease-linked aggregation of globular proteins.

The aggregation of proteins in tissues is associated with the pathogenesis of more than 40 human diseases. The polypeptides underlying disorders such as Alzheimer's and Parkinson's are devoid of any regular structure, whereas the polypeptides causing familial amyotrophic lateral sclerosis or nonneuropathic systemic amyloidosis correspond to globular proteins. Little is known about the mechanism by which globular proteins under physiological conditions aggregate from their initially folded and soluble conformations. Interestingly, several of these pathogenic proteins display quaternary structure or are bound to other proteins in their physiological context. In the present work, we show that protein-protein interaction surfaces and regions with high aggregation propensity significantly overlap in these polypeptides. This suggests that the formation of native complexes and self-aggregation reactions probably compete in the cell, explaining why point mutations affecting the interface or the stability of the protein complex lead in many cases to the formation of toxic aggregates. This study proposes general strategies to fight against diseases associated with the deposition of globular polypeptides.

Molecular pathogenesis of protein misfolding diseases: pathological molecular environments versus quality control systems against misfolded proteins

Diverse human diseases, including various neurodegenerative disorders and amyloidoses, are thought to result from the misfolding and aggregation of disease-causative proteins, and thus are collectively called protein misfolding diseases. Natively folded disease-causative proteins generally undergo a beta-sheet conformational transition through an energetically unfavourable process, and further polymerize into amyloid fibrils. In the case of beta(2)-microglobulin-related amyloidosis, an extracellular protein misfolding disease, many kinds of biological molecules including glycosaminoglycans, proteoglycans and lipids partially unfold beta(2)-microglobulin and catalyse its subsequent nucleus formation. After amyloid fibrils are formed, these biological molecules stabilize the beta(2)-microglobulin fibrils. In the polyglutamine neurodegenerative diseases, an intracellular protein misfolding disease, molecular chaperones as well as the ubiquitin-proteasome and autophagy-lysosome protein degradation systems, which are called the protein quality control systems, strictly regulate protein misfolding, aggregation and disease progression. A family of extracellular chaperones also binds to misfolded proteins and inhibit amyloid fibril formation in the extracellular space. Protein misfolding and aggregation may be an ideal therapeutic target for protein misfolding diseases in general.