Molecular mechanisms of amyloidosis

Structural Differences in Aβ Amyloid Protofibrils and Fibrils Mapped by Hydrogen Exchange – Mass Spectrometry with On-line Proteolytic Fragmentation

We report here structural differences between Abeta(1-40) protofibrils and mature amyloid fibrils associated with Alzheimer's disease as determined using hydrogen-deuterium exchange-mass spectrometry (HX-MS) coupled with on-line proteolysis. Specifically, we have identified regions of the Abeta(1-40) peptide containing backbone amide hydrogen atoms that are protected from HX or exposed when this peptide is incorporated into protofibrils or amyloid fibrils formed in phosphate-buffered saline without stirring at 37 degrees C. Study of protofibrils was facilitated by use of the protofibril-stabilizing agent calmidazolium chloride. Our data clearly show that both the C-terminal segment 35-40 and the N-terminal segment 1-19 are highly exposed to HX in both fibrils and protofibrils. In contrast, the internal fragment 20-34 is highly protected from exchange in fibrils but much less so in protofibrils. The data suggest that the beta-sheet elements comprising the amyloid fibril are already present in protofibrils, but that they are expanded into some adjacent residues upon the formation of mature amyloid. The N-terminal approximately ten residues appear to be unstructured in both protofibrils and fibrils. The 20-30 segment of Abeta(1-40) is more ordered in fibrils than in protofibrils, suggesting that, if protofibrils are a mechanistic precursor of fibrils, the transition from protofibril to fibril involves substantial ordering of this region of the Abeta peptide.

Diagnostic accuracy of subcutaneous abdominal fat tissue aspiration for detecting systemic amyloidosis and its utility in clinical practice

OBJECTIVE

Aspiration of subcutaneous abdominal fat is a simple and fast method for detecting systemic amyloidosis; however, the sensitivity of this approach remains undetermined. The aim of this study was to assess the accuracy of fat tissue aspiration for detecting systemic amyloidosis and the utility of this method in clinical practice.

METHODS

All consecutive patients with established and suspected systemic amyloidosis who attended our tertiary referral hospital between 1994 and 2004 underwent aspiration of subcutaneous abdominal fat. Congo red-stained tissue was assessed quickly in a single smear in a routine manner by a single observer, and was also assessed thoroughly in 3 smears by 2 independent observers.

RESULTS

One hundred twenty patients with established systemic amyloidosis were studied (38 with AA amyloidosis, 70 with AL amyloidosis, and 12 with ATTR amyloidosis). Routine (quick) assessment was associated with a sensitivity of 80% (95% confidence interval [95% CI] 72-87%). Sensitivity increased to 93% (95% CI 87-97%) when 3 smears were thoroughly examined. The specificity of fat aspiration in 45 control subjects was 100% (95% CI 92-100%). One hundred sixty-two patients for whom there was a clinical suspicion of systemic amyloidosis were screened for amyloidosis by fat tissue aspiration and biopsy of at least 1 other tissue. In 69 (43%) of these 162 patients, a diagnosis of amyloidosis was established, and in 66 (96%) of these patients, the results of fat tissue aspiration were positive. The clinical utility of fat tissue aspiration was greater than that of biopsy of the rectum.

CONCLUSION

Subcutaneous abdominal fat aspiration is the preferred method for detecting systemic amyloidosis, with sensitivity of 80% associated with use of a routine approach. The use of a thorough assessment (3 fat smears, 2 observers) increased sensitivity to >90%. If the results of fat tissue aspiration are negative, the additional value of a subsequent biopsy of the rectum is negligible.

Identification of the core structure of lysozyme amyloid fibrils by proteolysis

Human lysozyme variants form amyloid fibrils in individuals suffering from a familial non-neuropathic systemic amyloidosis. In vitro, wild-type human and hen lysozyme, and the amyloidogenic mutants can be induced to form amyloid fibrils when incubated under appropriate conditions. In this study, fibrils of wild-type human lysozyme formed at low pH have been analyzed by a combination of limited proteolysis and Fourier-transform infrared (FTIR) spectroscopy, in order to map conformational features of the 130 residue chain of lysozyme when embedded in the amyloid aggregates. After digestion with pepsin at low pH, the lysozyme fibrils were found to be composed primarily of N and C-terminally truncated protein species encompassing residues 26-123 and 32-108, although a significant minority of molecules was found to be completely resistant to proteolysis under these conditions. FTIR spectra provide evidence that lysozyme fibrils contain extensive beta-sheet structure and a substantial element of non beta-sheet or random structure that is reduced significantly in the fibrils after digestion. The sequence 32-108 includes the beta-sheet and helix C of the native protein, previously found to be prone to unfold locally in human lysozyme and its pathogenic variants. Moreover, this core structure of the lysozyme fibrils encompasses the highly aggregation-prone region of the sequence recently identified in hen lysozyme. The present proteolytic data indicate that the region of the lysozyme molecule that unfolds and aggregates most readily corresponds to the most highly protease-resistant and thus highly structured region of the majority of mature amyloid fibrils. Overall, the data show that amyloid formation does not require the participation of the entire lysozyme chain. The majority of amyloid fibrils formed from lysozyme under the conditions used here contain a core structure involving some 50% of the polypeptide chain that is flanked by proteolytically accessible N and C-terminal regions.

Dangerous small B-cell clones

The detection of a monoclonal immunoglobulin in serum or urine usually raises concerns about the size of the underlying B-cell-derived clone and possible systemic effects caused by its expansion. However, a small clone can synthesize a very toxic protein, producing devastating systemic damage and protean clinical presentations. The resulting "monoclonal component-related diseases," although difficult to diagnose, may be progressive and even fatal. The monoclonal protein can aggregate and deposit systemically as occurs in light-chain amyloidosis, monoclonal immunoglobulin deposition disease, crystal-storing histiocytosis, and monoclonal cryoglobulinemia. Alternatively, some monoclonal proteins possess antibody activity toward autogenous antigens and cause chronic cold agglutinin disease, mixed cryoglobulinemia, and peripheral neuropathies. Other humoral mediators may contribute to neuropathy in variant disorders such as the POEMS (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes) syndrome. The clone synthesizing the noxious monoclonal proteins is often small, and sensitive techniques may be required to detect these immunoglobulins. A delay in diagnosis can allow irreversible organ damage and dramatically shorten survival. Prompt recognition of suggestive signs and symptoms should trigger a thorough diagnostic approach to reach the correct diagnosis quickly, because this is the key to effective therapy. Although the treatment of these conditions is not optimal, significant advances have been made, improving the duration and quality of life.

Immunohistochemical Classification of Amyloid in Surgical Pathology Revisited

We aimed to reassess the suitability of immunohistochemical classification of amyloid in surgical pathology. One hundred sixty-nine biopsies from 121 patients diagnosed with amyloid during the period from 1994 to 2004 were included. Amyloid was classified immunohistochemically, using antibodies directed against amyloid P-component, AA amyloid, apolipoprotein AI, fibrinogen, keratoepithelin, lactoferrin, lysozyme, beta2-microglobulin (beta2M), immunoglobulin-derived lambda-light and kappa-light chains, and transthyretin. Amyloid was most commonly present in biopsies from the hepatogastrointestinal tract. The deposits were classified immunohistochemically in 156 (92%) biopsies. In 13 biopsies of 12 patients, amyloid remained unclassified. AL amyloidosis was diagnosed in 76 (45%) biopsies and was further categorized into AL amyloid of kappa-light chain origin [32 (42%) biopsies] or lambda-light chain origin [20 (26%)]. In 24 (32%) biopsies, the amyloid deposits did not show unequivocal staining for lambda-light or kappa-light chain. However, these cases were categorized as "probably AL amyloid, not otherwise specified", because no other antibody showed unequivocal staining of the amyloid deposits. AA amyloidosis was diagnosed in 32, ATTR amyloidosis in 21, and AApoAI amyloidosis in 3 biopsies. Other types of amyloid included AKer and ALac amyloids each in 1, and ALys and ACal amyloids each in 2 biopsies. Abeta2M amyloid was not diagnosed in any case. Immunohistochemical classification of amyloid still poses problems. Although classification of AA, AApoAI, ALys, ALac, and ATTR amyloids is relatively straightforward, classification of AL amyloid and rare hereditary amyloidoses is a serious obstacle and sometimes even impossible when conclusive clinical information or additional protein biochemical or molecular biologic studies are not available.

AA amyloidosis in psoriatic arthritis

BACKGROUND

Amyloidosis is an extremely rare complication of psoriatic arthritis (PsA) and is associated with a poor prognosis. We report a case of amyloidosis secondary to severe PsA in a young patient and the course of his disease over a 13-year period of aggressive immunosuppression.

METHODS

Diagnosis of renal amyloidosis was made on biopsy: multi-agent immunosuppressive therapy was continued with stabilisation of renal function.

RESULTS

Marked deterioration in renal function subsequently occurred following a reduction in cyclosporin A (CyA) dose and repeat biopsy confirmed worsening amyloidosis.

CONCLUSION

This case report emphasises the need for aggressive control of the inflammatory response in secondary amyloidosis.

Multiple myeloma-associated AL amyloidosis: is a distinctive therapeutic approach warranted?

The natural history of multiple myeloma (MM) was revolutionized by the introduction of haematopoietic stem cell transplantation to the treatment armamentarium of this disease. Defined subgroups of MM patients (such as the elderly or dialysis-dependent) have required an individualized approach in order to minimize the transplant-related mortality. Little, however, is known about the management of 12-30% of MM patients with coexistent AL amyloidosis as the amyloidopathy is often overlooked and when recognized these patients commonly are excluded from clinical trials. While occult amyloidosis appears to have no impact on the toxicity and outcome of MM patients, the presence of symptomatic amyloidopathy clearly worsens their prognosis. Use of induction chemotherapy drugs that can cause further damage to the heart (Adriamycin), nervous system (Vincristine) or kidneys should be avoided as should lengthy delays in proceeding to autograft. Further, refining the transplant eligibility criteria for this subgroup of patients with co-existent amyloidopathy to include the number of organs involved and the degree of cardiac involvement (NYHA class, Troponins and NT-pro-BNP levels) along with melphalan dose-adjustment will minimize the treatment-related toxicity and mortality and possibly allow a reversal of the organ damage induced by the amyloidogenic light chain.

Interconverting Conformations of Variants of the Human Amyloidogenic Protein β2-Microglobulin Quantitatively Characterized by Dynamic Capillary Electrophoresis and Computer Simulation

Capillary electrophoretic separation profiles of cleaved variants of beta2-microglobulin (beta2m) reflect the conformational equilibria existing in solutions of these proteins. The characterization of these equilibria is of interest since beta2m is responsible for amyloid formation in dialysis-related amyloidosis and thus is able to attain alternative conformations that lead to irreversible aggregation and precipitation. In this study, we quantitate the increased conformational instability of cleaved beta2m by extracting rate constants and activation energies by simulating the experimental data using a unified theory for dynamic chromatography and dynamic electrophoresis. The results are correlated with the outcome of independent experiments based on mass spectrometric measurement of H/D exchange. This study illustrates that dynamic capillary electrophoresis is suitable for the investigation of the interconversion of protein conformations of amyloidogenic molecules and is not only restricted to ideal model compounds.

Myocardial sleeves of pulmonary veins and atrial fibrillation: a postmortem histopathological study of 100 subjects

Atrial fibrillation (AF) is triggered by ectopic beats originating from extensions of the left atrial myocardium over the pulmonary veins (PVs), so-called myocardial sleeves. A total of 100 hearts (393 PVs) obtained at autopsy were studied. Of these, 50 were from patients with chronic AF and 50 from controls in sinus rhythm. Out of a total of 393 PVs studied, a sleeve was present in 349 PVs (88.8%). The myocardial sleeves frequently harboured senile atrial amyloid and scarring. These two changes were evaluated semi-quantitatively (grade 0-3). Amyloidosis was found in 68% of all hearts and in 55% of all sleeves. It was more frequent in patients with AF (58.5%) than in those without (51.7%), however, without statistical significance (p values 0.948, 0.306, 0.166 and 1). Scarring was present in all 349 sleeves studied. It was significantly more severe in patients with AF (average grade 2.44) than in those without (average grade 2.00) (p values <0.001, <0.1, <0.05 and <0.01). In conclusion, amyloidosis and particularly scarring of the myocardial sleeves of the pulmonary veins, appear to be common in the elderly population as an arrhythmogenic substrate for AF.

Diagnostic performance of 123I-labeled serum amyloid P component scintigraphy in patients with amyloidosis

PURPOSE

To assess the diagnostic accuracy and additional information provided by 123I-labeled serum amyloid P component (SAP) scintigraphy in patients with systemic and localized amyloidosis.

SUBJECTS AND METHODS

123I-labeled human SAP was injected intravenously into 20 controls and 189 consecutive patients with histologically proven amyloidosis: of AA type in 60 cases, AL type in 80, hereditary ATTR type in 27, and localized amyloidosis in 22 cases. SAP scintigrams were obtained 24 hours after tracer injection and were analyzed for abnormal patterns of uptake. Sensitivity and specificity were determined, and scintigraphic findings were compared with clinical data.

RESULTS

Diagnostic sensitivity of SAP scintigraphy for systemic AA, AL, and ATTR amyloidosis was 90%, 90%, and 48% respectively, and specificity was 93%. The distribution of amyloid was less diverse in AA than in AL type. Myocardial uptake was not visualized in any patient. Splenic amyloid was very frequent (80%) in AA and AL type but rarely detected clinically (14%). Abnormal tracer uptake in the liver and kidneys correlated with disturbed liver function and proteinuria, respectively. Bone marrow uptake was specific for AL (21%) and was more frequent in AL kappa than AL lambda. Localized amyloid deposits were not imaged.

CONCLUSION

SAP scintigraphy is diagnostic of amyloid in most patients with AA and AL type but fewer with hereditary ATTR type, relating to differing distributions and burdens of amyloid in these disorders. It usually reveals more widespread organ involvement than is identified clinically, and certain distributions of amyloid are characteristic of particular fibril types.

Differential post-translational modifications of transthyretin in Alzheimer's disease: A study of the cerebral spinal fluid

Transthyretin (TTR) is a 55 kDa homotetrameric protein. TTR in the cerebral spinal fluid (CSF) is primarily synthesized by the choroid plexus. TTR can bind to the beta-amyloid peptide and a number of familial amyloidosis diseases (familial amyloid polyneuropathy) have been associated with its allele variants. In a transgenic mice model overexpression of TTR was positively correlated with a neuroprotective effect from the pathogenic APPsw mutation. TTR has a free reactive sulphydryl moiety located on the Cys(10) residue which has been implicated to undergo a variety of oxidation reactions. To examine the neuroprotective role of TTR, we investigated the conjugated forms of TTR with cysteine (Cys) and cysteinglycine (CsyGly) in the CSF of 39 probable Alzheimer's disease (AD)-affected subjects and in a cohort of subjects without cognitive impairment (27 subjects). Linear MALDI-TOF MS experiments were employed to obtain high-resolution protein profiling of TTR isoforms. Nano-LC-TANDEM MS combined with reflectron MALDI-TOF-MS was used to unequivocally assign the investigated TTR-conjugate signals. Our results indicate a differential distribution of TTR-Cys and TTR-CysGly adducts. Both oxidized forms of TTR are significantly less abundant in the AD group (p = 0.0001). The investigated population (66 subjects) was then diagnosed using the ratio of conjugated TTR to free TTR in each subject. A sensitivity >90% and a specificity >70% were derived from a receiver operating characteristic curve when the overall cohort is analysed by the TTR-Cys signals. This manuscript is the first report describing the presence of differential post-translational oxidations of TTR in the CSF of AD patients.

Micro-heterogeneity and aggregation in β2-microglobulin solutions: effects of temperature, pH, and conformational variant addition

We show that beta(2)-microglobulin solutions in physiological conditions contain a tiny fraction of aggregates, which can hardly be filtered out and tend to re-form spontaneously. At physiological pH the fractional amount and size distribution of the latter aggregates do not depend on temperature. Conversely, in the pH range typical of the peri-articular tissue acidosis that often occurs in hemodialysis, temperature increase leads to fast and irreversible growth of the aggregates. Quite similar, but strongly enhanced aggregation effects can be induced even in physiological conditions by adding a very small amount of DeltaN6, a naturally occurring truncated isoform of beta(2)-m known to promote fibrillogenesis.

Transmission of amyloidosis in offspring of mice with AApoAII amyloidosis

Pre-existing amyloid fibrils can induce further polymerization of endogenous precursor proteins in vivo. Thus, transmission of amyloid fibrils (AApoAII) may induce a conformational change in endogenous apolipoprotein A-II and accelerate amyloid deposition in mouse senile amyloidosis. To characterize transmissibility, we examined amyloidosis in the offspring of AApoAII-injected mother mice that possessed the amyloidogenic Apoa2(c) allele of the apolipoprotein A-II gene. At 4 months of age, amyloid deposits were detected in the intestines of offspring born from and nursed by amyloid fibril-injected mothers, with intensity of deposition increasing thereafter. No amyloid deposits were detected in the offspring of noninjected control mothers. Accelerated amyloidosis was also observed in offspring born from mothers without injection but nursed by amyloid fibril-injected mothers. However, this was not observed in offspring born from amyloid fibril-injected mothers but nursed by control mothers. This fostering excluded vertical transmission through the placenta, suggesting the presence of factors that accelerate amyloidosis during the nursing period. In addition, milk obtained from amyloid fibril-injected mothers induced AApoAII amyloidosis in young mice, and transmission electron microscopy detected noodle-like amyloid fibrils in milk of amyloid fibril-injected mothers. These results provide important insight into the etiology and pathogenesis of amyloid diseases.

[Systemic amyloidoses]

Amyloidoses are a heterogeneous group of diseases characterized by extracellular fibrillar protein deposits in the organs and tissues. These proteins are not biochemically related to each other, but share certain common characteristics, including apple green birefringence with polarized light after staining with Congo red, and beta-pleated sheet configuration through x-ray diffraction. Amyloid deposits may occur in many organs (systemic amyloidoses) or may affect a single tissue (localized or organ-specific amyloidoses). There are different classifications, but in this review the amyloidoses are organized by clinical symptoms, which are determined by the amyloid protein involved. Special attention is given to cutaneous and mucous membrane manifestations, which are often the first sign of the disease and are useful for early diagnosis, thus avoiding more aggressive procedures. The involvement of other organs is analyzed, as are the diagnosis, prognosis and treatment of systemic amyloidoses.

Nutritional status of outpatients with systemic immunoglobulin light-chain amyloidosis 1

BACKGROUND

Maintenance of a good nutritional status is associated with prolonged survival in many chronic diseases. To date, the nutritional status of outpatients with immunoglobulin light-chain (AL) amyloidosis has not been evaluated.

OBJECTIVE

The aims of this study were to obtain information regarding the nutritional status of AL amyloidosis outpatients and to investigate its prognostic role.

DESIGN

One hundred six consecutive patients with histologically confirmed AL amyloidosis were enrolled. Anthropometric, biochemical, and clinical variables were measured. The Kaplan-Meier method was used to calculate survival. A Cox proportional hazard model was constructed to evaluate the prognostic effect of the nutritional variables.

RESULTS

Unintentional weight loss (median: 11.3%; range: 2.6-34% of usual nonedematous body weight) was documented in 58 subjects (54.7%). Body mass index (BMI; in kg/m2) was <22 in 25 subjects (23.6%). Serum prealbumin was <200 mg/L (lower reference limit) in 26 patients (24.5%). A multivariate analysis showed that the percentage weight loss was significantly greater in patients with than in those without cardiac involvement (P = 0.03), and it also differed significantly by New York Heart Association class (P = 0.02) and Eastern Cooperative Oncology Group performance status (P = 0.001). Cardiac involvement (P = 0.008), hematologic response to therapy (P = 0.013), BMI (P = 0.001) and serum prealbumin (P = 0.001) were independent predictors of survival.

CONCLUSIONS

Malnutrition is a prominent clinical feature of patients with AL amyloidosis. Appropriate nutritional evaluation that comprises the easily measurable nutritional variables associated with survival should be an integral part of the clinical assessment of AL amyloidosis outpatients.

Evaluation of a new capillary zone electrophoresis system for the identification and typing of Bence Jones Protein

OBJECTIVES

Capillary electrophoresis has recently emerged as a new sensitive technique for the separation of urinary proteins. We evaluated a new method for Bence Jones Protein (BJP) detection and characterization on native urine samples by the Paragon CZE 2000 system. To avoid interference in electrophoretic separation, urine samples were preliminarily treated for the selective removal of interfering salt particles.

DESIGN AND METHODS

The evaluation was done on a total of 350 fresh 24-h urine samples. The salt particle removal consisted of a manual chromatographic separation, optimized in the course of our evaluation. Capillary zone urinary protein electrophoresis (CZ-UPE) was compared with conventional high-resolution electrophoresis on an agarose gel, while capillary immunosubtraction (CZU-IFE) was compared with agarose gel immunofixation.

RESULTS

After finding a consistent protein loss in eluates, the preanalytical treatment was optimized by changing sample dilution and eluate collection. The within- and between-run imprecision values for monoclonal peaks corresponding to BJP ranged from 0.4-12.2% to 3.3-6.3%, respectively. The detection limit for BJP, defined as the lowest measurable monoclonal peak on CZ-UPE, was 0.0012 g/L for kappa BJP and 0.0007 g/L for lambda BJP. CZ-UPE and CZU-IFE sensitivities were significantly lower in urine samples with a total protein level < or = 100 mg/L (67% and 78%, respectively) compared to those with total protein >100 mg/L (92% and 94%, respectively). Comparison between BJP measurements obtained from densitometric scanning with those from absorbance tracing showed a correlation coefficient of 0.994 and a bias of 29.8 mg/L.

CONCLUSIONS

Paragon CZE 2000 can be introduced in routine for screening and typing of BJP; in urine samples with a total protein level >100 mg/L, the performance is consistent with results from published validation studies on CZE applied to serum samples.

Amyloid in neurosurgical and neurological practice

The amyloidoses are a diverse group of diseases characterized by the deposition of specific proteins with distinct affinity to the dye Congo red, collectively called amyloid. The amyloidogenic proteins have acquired an abnormal, highly ordered, beta-pleated sheet configuration with a propensity to self-aggregate. The amyloid may be distributed in different organs with a remarkable diversity. Two broad categories of amyloidoses are recognised: The systemic (consisting of the primary or light chain form, the secondary or reactive form and the familial or hereditary form) and the localised that target specific organs. A tropism of amyloid proteins to the neural tissue produces certain patterns of central nervous system diseases: cerebral amyloid angiopathy, a substrate of spontaneous intracerebral haemorrhage; mature neuritic plaques found in Alzheimer disease and a subset of prion diseases; a topographically restricted accumulation of extracellular proteins giving rise to tumour-mimicking masses, the amyloidomas; and finally, spinal extradural amyloid collections that occasionally are found in the context of rheumatoid arthritis. In this review article we present original illustrative cases of amyloid diseases of the central nervous system that may be encountered in neurosurgical and neurological practice. Molecular aspects and clinical management problems are discussed.

Immunoaffinity chromatographic and immunoprecipitation methods combined with mass spectrometry for characterization of circulating transthyretin

Transthyretin (TTR) is a small serum protein that is involved in distinct phenotypes of amyloidosis with different tissue localization, age of onset, and rate of progression. Some types of TTR-amyloidosis (such as familial amyloid polyneuropathy) are associated with various amino acid point mutations, while cardiac amyloid myopathy may also be associated with precipitation of the wild-type molecules, e.g., in senile systemic amyloidosis. Because of the unsettled relationship between circulating and precipitated TTR we here explore on-line immunoaffinity (IA) chromatography-MS and immunoprecipitation (IP)-MS methods for characterizing the circulating TTR population in normal individuals and in patients with known TTR-amyloidosis. It was found necessary to reduce the samples, e.g., with DTT, prior to ESI-TOF-MS. This reversed oxidative modifications to sufficiently resolve the two mass peaks isolated from sera of heterozygous patients. A simple IP technique without the use of centrifugal filtration was found to be convenient for the assessment of the TTR population in serum as demonstrated for both normal and variant (the Met111Leu mutation) TTR. This approach also readily allowed the identification of oxidation, S-sulfation, and S-cysteinylation in unreduced samples, while these modifications were less well resolved in the on-line IA chromatography-MS approach.

Alanine scanning mutagenesis of Abeta(1-40) amyloid fibril stability

We describe here an alanine scanning mutational analysis of the Abeta(1-40) amyloid fibril monitored by fibril elongation thermodynamics derived from critical concentration values for fibril growth. Alanine replacement of most residues in the amyloid core region, residues 15-36, leads to destabilization of the elongation step, compared to wild-type, by about 1kcal/mol, consistent with a major role for hydrophobic packing in Abeta(1-40) fibril assembly. Where comparisons are possible, the destabilizing effects of Ala replacements are generally in very good agreement with the effects of Ala replacements of the same amino acid residues in an element of parallel beta-sheet in the small, globular protein Gbeta1. We utilize these Ala-WT DeltaDeltaG values to filter previously described Pro-WT DeltaDeltaG values, creating Pro-Ala DeltaDeltaG values that specifically assess the sensitivity of a sequence position, in the structural context of the Abeta fibril, to replacement by proline. The results provide a conservative view of the energetics of Abeta(1-40) fibril structure, indicating that positions 18-21, 25-26, and 32-33 within amyloid structure are particularly sensitive to the main-chain disrupting effects of Pro replacements. In contrast, residues 14-17, 22, 24, 27-31, and 34-39 are relatively insensitive to Pro replacements; most N-terminal residues were not tested. The results are discussed in terms of amyloid fibril structure and folding energetics, in particular focusing on how the data compare to those from other structural studies of Abeta(1-40) amyloid fibrils grown in phosphate-buffered saline at 37 degrees C under unstirred ("quiescent") conditions.

Seeking confidence in the diagnosis of systemic AL (Ig light-chain) amyloidosis: patients can have both monoclonal gammopathies and hereditary amyloid proteins

Investigators in the United Kingdom have shown that hereditary amyloidosis can be misdiagnosed as Ig light-chain (AL) amyloidosis because family history is an ineffective screen, and tissue staining used to type amyloid is unreliable. Misdiagnosis of AL can lead to inappropriate use of chemotherapy and failure to diagnose a hereditary disease. Over a 3-year period we sought to determine how often both possible sources of amyloidosis occurred in the same patient. We employed an algorithm based on established data and patterns of amyloidosis in order to focus the screening effort. Of 178 consecutive patients referred for amyloidosis, 54 were screened by polymerase chain reaction techniques with primers designed to detect transthyretin, apolipoprotein AI, apolipoprotein AII, fibrinogen Aalpha, and lysozyme variants. Three patients (6% of those screened and 2% of symptomatic patients) had both a monoclonal gammopathy and a hereditary variant. These results justify further study of screening for hereditary variants in patients with apparent AL, and highlight the need for practical techniques for identifying fibrils extracted from tissue.

Circulating amyloidogenic free light chains and serum N-terminal natriuretic peptide type B decrease simultaneously in association with improvement of survival in AL

N-terminal natriuretic peptide type B (NT-proBNP) is a marker of cardiac dysfunction in light chain amyloidosis (AL) and a powerful prognostic determinant. Serum NT-proBNP and circulating free light chains (FLCs) were measured at enrollment and after 3 cycles of chemotherapy in 51 patients with cardiac AL. In patients (n = 22, 43%) in whom FLCs decreased by more than 50% (hematologic response), NT-proBNP concentration decreased by a median of 48%, whereas in the remaining patients it increased by 47% (P = .01). The reduction of NT-proBNP was greater in patients (n = 9) in whom amyloidogenic FLCs disappeared at immunofixation (median 53%), than in the remaining responding patients (median 31%, P = .04). Left ventricular wall thickness decreased by at least 2 mm in 3 of 20 patients in whom NT-proBNP improved. Fifteen patients died. Thirteen of them, in whom NT-proBNP and FLCs did not improve, died after a median of 1.8 months. The decrease of FLCs translates into a simultaneous decrease of NT-proBNP and improved survival. Patients in whom chemotherapy fails to induce such a decrease are at risk of early death. Cardiac function in AL can rapidly improve due to a reduction of the circulating amyloidogenic precursor, despite the amount of cardiac amyloid deposits remaining apparently unaltered, as measured by echocardiography.

Oligomerization and aggregation of bovine pancreatic ribonuclease A: characteristic events observed by FTIR spectroscopy

Nonnative protein aggregation, which is a common feature in biotechnology, is also a clinical feature in more than 20 serious degenerative diseases. We studied the specific events of bovine pancreatic ribonuclease A thermal aggregation by a combination of second derivative infrared analysis and two-dimensional infrared correlation spectroscopy. By comparing the events that occur in reversible and irreversible thermal unfolding processes, certain events that were related to protein aggregation were characterized. Particularly, a band that appeared at high temperatures was assigned to the cross beta-structures in oligomers. The effect of pH, NaCl, and ethanol on ribonuclease A oligomerization as well as further aggregation induced by heat were studied and dissimilar effects of these additives were found. Basic pH and NaCl could accelerate the thermal aggregation but did not affect the formation of oligomers, whereas ethanol could increase both the aggregation rate and the population of oligomers. Our results suggested that the aggregation of RNase A might be initiated by hydrophobic interactions, controlled by oligomerization and mediated by electrostatic interactions. Moreover, the strategy of using second derivative and two-dimensional infrared analysis might provide a potential powerful tool to study the events that are directly related to the initiation of protein aggregation.

Absolute values of immunoglobulin free light chains are prognostic in patients with primary systemic amyloidosis undergoing peripheral blood stem cell transplantation

The immunoglobulin free light chain (FLC) is the precursor protein of amyloid in primary systemic amyloidosis (AL). Historically, the ability to monitor the amyloid protein precursor protein has been crude. We evaluated the utility of the FLC assay in a retrospective analysis of patients with AL undergoing peripheral blood stem cell transplantation (PBSCT). Ninety-three such patients had serial FLC measurements performed. The prognostic effects of the initial concentration and the extent of reduction of monoclonal FLC on survival were studied. There was a significantly higher risk of death in patients with higher baseline FLC (hazard ratio 2.6, P < .04). Baseline FLC correlated with serum cardiac troponin levels, and higher FLC levels were associated with more organs involved by amyloid, suggesting that high FLC levels may be associated with more advanced disease. The percent FLC reduction did not predict for survival, but the absolute level of FLC achieved after therapy did. Normalization of FLC level after PBSCT predicted for both organ response and complete hematologic response. Achievement of FLC response was a better predictor of survival than achievement of complete hematologic response or normalization of the FLC ratio. FLC measurements both before and after PBSCT are important predictors of patient outcome.

Scanning Cysteine Mutagenesis Analysis of Aβ-(1-40) Amyloid Fibrils

We describe here the use of cysteine substitution mutants in the Alzheimer disease amyloid plaque peptide Abeta-(1-40) to probe amyloid fibril structure and stabilization. In one approach, amyloid fibrils were grown from Cys mutant peptides under reducing conditions and then challenged with an alkylating agent to probe solvent accessibility of different residues in the fibril. In another approach, monomeric Cys mutants, either in the thiol form or modified with iodoacetic acid or methyl iodide, were grown into amyloid fibrils, and the equilibrium position at the end of the amyloid formation reaction was quantified by determining the concentration of monomeric Abeta. The DeltaG values of fibril elongation obtained were then compared in order to provide information on the environment of each residue side chain in the fibril. In general, Cys residues in the N and C termini of Abeta-(1-40) were not only accessible to alkylation in the fibril state but also, when modified in the monomeric state, did not greatly impact fibril stability; these observations were consistent with previous indications that these portions of the peptide are not part of the amyloid core. In contrast, residues 16-19 and 31-34 were not only uniformly inaccessible to alkylation in the fibril state, but their modification with the negatively charged carboxymethyl group in monomeric Abeta also destabilized fibril elongation, confirming other data showing that these segments are likely packed into a hydrophobic amyloid core. Residues 20, 30, and 35, flanking these implicated beta-sandwich regions, are accessible to alkylation in the fibril indicating a location in solvent exposed structure.

The search for disease-modifying drugs for neurodegenerative disorders

Neurodegenerative disorders (NDs) are a complex group of illnesses that possibly share common mechanisms. The onset and progression of NDs may depend upon genetic traits as well as complex interactions between individual genetic backgrounds and environmental factors. The exact role of the risk factors involved, and how they influence the onset and pacing of the disease, is not yet fully understood. Similarly, the relationship between the rate of neuronal death and clinical expression of the disease is a matter for discussion. The knowledge of the various molecules and mechanisms that accompany NDs as primary or secondary events is increasing steadily, but the distinction between their physiological and pathological roles is still uncertain. These premises highlight the difficulties underlying the design of disease modifying strategies. However, it is possible to identify several disease modifying strategies based on various approaches, including the targeting of putative causal elements or of general mechanisms of degeneration and reparative strategies. The purpose of this review is to examine the biological rationale behind attempted protective, restorative and therapeutic strategies.

Kinetics and Thermodynamics of Amyloid Assembly Using a High‐Performance Liquid Chromatography–Based Sedimentation Assay

Nonnative protein aggregation has been classically treated as an amorphous process occurring by colloidal coagulation kinetics and proceeding to an essentially irreversible endpoint often ascribed to a chaotic tangle of unfolded chains. However, some nonnative aggregates, particularly amyloid fibrils, exhibit ordered structures that appear to assemble according to ordered mechanisms. Some of these fibrils, as illustrated here with the Alzheimer's plaque peptide amyloid beta, assemble to an endpoint that is a dynamic equilibrium between monomers and fibrils exhibiting a characteristic equilibrium constant with an associated free energy of formation. Some fibrils, as illustrated here with the polyglutamine repeat sequences associated with Huntington's disease, assemble via highly regular mechanisms exhibiting nucleated growth polymerization kinetics. Here, we describe a series of linked methods for quantitative analysis of such aggregation kinetics and thermodynamics, focusing on a robust high-performance liquid chromatography (HPLC)-based sedimentation assay. An integrated group of protocols is provided for peptide disaggregation, setting up the HPLC sedimentation assay, the preparation of fibril seed stocks and determination of the average functional molecular weight of the fibrils, elongation and nucleation kinetics analysis, and the determination of the critical concentration describing the thermodynamic endpoint of fibril elongation.

Three cases of the nodular pulmonary amyloidosis with a longterm observation

Longterm observation with chest radiograph and computed tomography (CT) scan was performed for pulmonary amyloidosis. There are few reports of primary pulmonary amyloidosis with a longterm observation. We encountered three cases of nodular pulmonary amyloidosis observed by intermittent chest radiograph or CT for 5 years or more. The patients were a 54-year-old man, and 67- and 68-year old women. For diagnosis, transbronchial biopsy and percutaneous lung biopsy were performed. Amyloid nodules grew slowly and two cases showed findings of cavity and calcification.

Cathepsin protease activity modulates amyloid load in extracerebral amyloidosis

In cerebral amyloidoses, such as Alzheimer's disease, proteolytic processing of the precursor protein is a fundamental mechanism of the disease, since it generates the amyloid protein. However, the putative significance of proteases in extracerebral amyloidoses is less well defined. In this study, we investigated the biological significance of cathepsin (Cath) B, CathK, and CathL in the pathology and pathogenesis of extracerebral amyloidoses by using the murine model of reactive or secondary AA amyloidosis with three different cathepsin-deficient mouse strains. Extracerebral AA amyloid was induced by injecting amyloid-enhancing factor and silver nitrate into CathB(-/-), CathK(-/-), and CathL(-/-) mice. Wild-type mice served as a control. CathK(-/-) mice deposited over 90% more amyloid and CathL(-/-) mice 60% less amyloid than the control (p < 0.0001). The amyloid load in CathB(-/-) mice did not differ from that in wild-type mice. In vitro degradation experiments with recombinant human and murine serum amyloid A (SAA) 1.1 and CathK and CathL showed that CathL generates a large number of differently sized SAA cleavage products. One of these fragments spans the heparin/heparan sulphate binding site and the neutral cholesterol ester hydrolase activating region of SAA. CathK showed only endoproteolytic activity and did not generate any AA amyloid-like peptides. This study provides unequivocal evidence that proteases modulate amyloid load in extracerebral amyloidosis. CathL was identified as an amyloid-promoting and CathK as an amyloid-retarding cysteine protease. CathB may only modulate the primary structure of the amyloid peptide without affecting amyloid load.

Lysozyme amyloidosis: report of 4 cases and a review of the literature

Autosomal dominant hereditary amyloidosis represents not 1 disease but a group of diseases, each the result of mutations in a specific protein. The most common form is transthyretin amyloidosis, which has been recognized clinically for over 50 years as a familial polyneuropathy. Nonneuropathic amyloidoses (Ostertag type amyloidosis) include those due to abnormalities in lysozyme, fibrinogen Aalpha-chain, and apolipoprotein A-I and A-II. The role of lysozyme in amyloid-related human disorders was first described in 1993; to date, there have been only 9 publications describing this disorder, which is a nonneuropathic form of hereditary amyloidosis. Reported cases have involved 7 unrelated families. We describe here our own experience with 4 families suffering from lysozyme amyloidosis: the first had prominent renal manifestations with sicca syndrome, the second and third had prominent gastrointestinal symptoms, and the fourth had a dramatic bleeding event due to rupture of abdominal lymph nodes. To our knowledge, this last symptom has not been reported previously, but is reminiscent of the hepatic hemorrhage seen in a previously reported case of a patient with lysozyme amyloidosis. To characterize the manifestations of this disorder, we performed an exhaustive literature review.Although hereditary amyloidosis is thought to be a rare disease, it is probably not as rare as we think and may well be underdiagnosed. Moreover, some cases of lysozyme amyloidosis are probably confused with acquired monoclonal immunoglobulin light-chain (AL) amyloidosis, formerly known as primary amyloidosis, which is the most frequent type of amyloidosis. Because treatment for each type of amyloidosis is different, and because therapy directed at 1 type may worsen symptoms of the other types, it is important to determine precisely the nature of the amyloid protein. Thus, hereditary lysozyme amyloidosis should be considered in all patients with systemic amyloidosis, particularly in patients who present with renal, gastrointestinal, or bleeding complications without evidence of AL or AA (secondary) amyloidoses.

Noninvasive etiologic diagnosis of cardiac amyloidosis using 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid scintigraphy

OBJECTIVES

We investigated the diagnostic accuracy of 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) scintigraphy for differentiation of monoclonal immunoglobulin light-chain (AL) and transthyretin (TTR)-related cardiac amyloidosis.

BACKGROUND

Differential diagnosis between TTR-related and AL amyloidosis is often complex and time-consuming.

METHODS

Patients under routine observation with TTR-related/AL systemic amyloidosis and echocardiographic evidence of cardiac involvement were studied with 99mTc-DPD scintigraphy.

RESULTS

Patients with cardiac involvement of TTR-related (group A; n = 15) and AL (group B; n = 10) etiology were comparable for left ventricular mass and renal function. Heart and heart/whole-body tracer retention were significantly higher (p < 0.05) in group A as compared with group B and with 10 unaffected controls. At visual scoring, cardiac 99mTc-DPD uptake was present in all group A patients and absent in all group B patients; thus, using genotyping/immunohistochemistry as the reference technique, the accuracy of 99mTc-DPD scintigraphy for distinction of TTR-related and AL etiology was 100%. Cardiac 99mTc-DPD uptake was also absent among unaffected controls. Using echocardiography as the reference standard for recognition of cardiac involvement, sensitivity and specificity of scintigraphy were both 100% for group A patients; in group B, sensitivity was 0% and specificity was 100% (accuracy, 50%). Eleven patients with myocardial 99mTc-DPD uptake underwent 99mTc-methylene diphosphonate (99mTc-MDP) scintigraphy; all patients showed a 99mTc-MDP myocardial visual score of 0.

CONCLUSIONS

Etiology is a third major cause--in addition to type of organ-involved (soft-tissue/heart) and tracer type--of scintigraphic variability in cardiac amyloidosis. This is a highly relevant consideration for future studies. We conclude that 99mTc-DPD scintigraphy is a useful step in the workup of the differential diagnosis of TTR versus AL etiology in patients with documented cardiac amyloidosis.

Peripheral blood progenitor cell mobilization and collection in 42 patients with primary systemic amyloidosis

BACKGROUND

High-dose chemotherapy followed by an inoculum of autologous peripheral blood progenitor cells (PBPCs) can improve survival in patients affected with primary systemic amyloidosis (AL). It has been documented, however, that the morbidity and mortality of PBPC mobilization and collection in this setting are higher than in patients with other diseases. To minimize the mobilization and collection-related risks, we developed a multidisciplinary approach involving different specialists to manage AL patients with predominant heart and renal involvement.

STUDY DESIGN AND METHODS

We report our experience in 42 patients (23 men, 19 women; median age, 51.2 years; range, 28-68 years) with AL who underwent PBPC mobilization and collection. Twenty of the 42 patients (47.6%) had cardiac involvement and 35 of 42 (83.3%) renal involvement. Thirty-three patients (78.5%) were mobilized with granulocyte-colony-stimulating factor (G-CSF) alone (10 microg/kg) and 9 (21.4%) with cyclophosphamide (CTX) (3 g/m(2)) plus G-CSF (10 microg/kg).

RESULTS

The median number of collections per patient after either G-CSF or CTX plus G-CSF was 1.8 (range, 1-3). The median number of CD34+ cells collected in patients mobilized with G-CSF alone was 8.2 x 10(6) per kg (range, 1.35 x 10(6)-21.3 x 10(6)/kg) and in patients mobilized with CTX plus G-CSF it was 8.9 x 10(6) per kg (range, 5.5 x 10(6)-14.9 x 10(6)/kg). Forty of the 42 (95.2%) patients produced the minimum required CD34+ cell target dose (4 x 10(6)/kg). The overall rate of morbidity during the collections was 50 percent (21/42 patients): 18 patients (42.8%) had asymptomatic hypotension, 1 (2.4%) had symptomatic hypotension with nausea and vomiting, and 2 (4.7%) experienced a life-threatening hypotensive episode. There were no procedure-related deaths.

CONCLUSION

Our multidisciplinary approach was effective in limiting the serious side effects related to PBPC mobilization and collection in AL patients.

Clinical aspects of systemic amyloid diseases

Amyloidosis is a protein misfolding disorder in which soluble proteins aggregate as insoluble amyloid fibrils. Protein aggregates and amyloid fibrils cause functional and structural organ damage respectively. To date, at least 24 different proteins have been recognized as causative agents of amyloid diseases, localized or systemic. The two most common forms of systemic amyloidosis are light-chain (AL) amyloidosis and reactive AA amyloidosis due to chronic inflammatory diseases. beta(2)-microglobulin amyloidosis is a common complication associated with long-term hemodialysis. Hereditary systemic amyloidoses are a group of autosomal dominant disorders caused by mutations in the genes of several plasma proteins. Heterogeneity in clinical presentation, pattern of amyloid-related organ toxicity and rate of disease progression is observed among systemic amyloidoses. In particular, beta(2)-microglobulin presents unique clinical features compared to the other systemic forms. The phenotypic features of hereditary systemic amyloidoses may instead overlap those of the two more common forms of acquired amyloidoses mentioned above and therefore a correct diagnosis can not rely only on clinical grounds. Unequivocal identification of the deposited protein is essential in order to avoid misdiagnosis and inappropriate treatment. Amyloid deposits can be reabsorbed and organ dysfunction reversed if the concentration of the amyloidogenic protein is reduced or zeroed. At present, the most effective approach to treatment of the systemic amyloidoses involves shutting down, or substantially reducing the synthesis of the amyloid precursor, or, as in the case of beta(2)-microglobulin, promoting its clearance.

Interactions of charged ligands with β2-microglobulin conformers in affinity capillary electrophoresis

Alternative conformations of beta(2)-microglobulin (beta(2)m) are involved in its transformation from soluble monomeric precursor molecules to the insoluble polymeric material that constitutes beta(2)m amyloid. Accordingly, non-native conditions such as low pH or high ionic strength promote beta(2)m amyloid formation in vitro. The early events in these processes are not well known, partly because of the paucity of techniques available for the characterization of transient folding intermediates in proteins. We have used high-resolution separations in capillaries (capillary electrophoresis, CE) to resolve putative conformer fractions in native and structurally modified beta(2)m and to show the induction of alternatively folded beta(2)m under different experimental conditions. The conformer fractions are observed as distinct peaks in the separation profiles and thus it is possible to probe for the reactivity of these individual beta(2)m species with specific ligands that, upon binding, alter analyte mobility in affinity capillary electrophoresis experiments. Interactions were shown in this way for the negatively charged substances heparin, Congo red, and suramin, as well as for Cu(2+) ions. Marked differences in the binding behavior of the beta(2)m conformational variants compared with native beta(2)m could be demonstrated. This approach for conformer separation and binding characterization is a valuable starting point for the assessment of various ligand molecules, or analogues thereof, as agents capable of perturbing the mechanisms of fibril formation.

Imaging beta-amyloid fibrils in Alzheimer's disease: a critical analysis through simulation of amyloid fibril polymerization

The polymerization of beta-amyloid (A beta) peptides into fibrillary plaques is implicated, in part, in the pathogenesis of Alzheimer's disease. A beta molecular imaging probes (A beta-MIPs) have been introduced in an effort to quantify amyloid burden or load, in subjects afflicted with AD by invoking the classic PET receptor model for the quantitation of neuronal receptor density. In this communication, we explore conceptual differences between imaging the density of amyloid fibril polymers and neuronal receptors. We formulate a mathematical model for the polymerization of A beta with parameters that are mapped to biological modulators of fibrillogenesis and introduce a universal measure for amyloid load to accommodate various interactions of A beta-MIPs with fibrils. Subsequently, we hypothesize four A beta-MIPs and utilize the fibrillogenesis model to simulate PET tissue time activity curves (TACs). Given the unique nature of polymer growth and resulting PET TAC, the four probes report differing amyloid burdens for a given brain pathology, thus complicating the interpretation of PET images. In addition, we introduce the notion of an MIP's resolution, apparent maximal binding site concentration, optimal kinetic topology and its resolving power in characterizing the pathological progression of AD and the effectiveness of drug therapy. The concepts introduced in this work call for a new paradigm that goes beyond the classic parameters B(max) and K(D) to include binding characteristics to polymeric peptide aggregates such as amyloid fibrils, neurofibrillary tangles and prions.

Renal Apolipoprotein A-I Amyloidosis: A Rare and Usually Ignored Cause of Hereditary Tubulointerstitial Nephritis

Apolipoprotein A-I amyloidosis is a rare, late-onset, autosomal dominant condition characterized by systemic deposition of amyloid in tissues, the major clinical problems being related to renal, hepatic, and cardiac involvement. Described is the clinical and histologic picture of renal involvement as a result of apolipoprotein A-I amyloidosis in five families of Italian ancestry. In all of the affected family members, the disease was caused by the Leu75Pro heterozygous mutation in exon 4 of apolipoprotein A-I gene, as demonstrated by direct sequencing and RFLP analysis. Immunohistochemistry confirmed that amyloid deposits were specifically stained with an anti-apolipoprotein A-I antibody. The clinical phenotype was mainly characterized by a variable combination of kidney and liver disturbance. The occurrence of renal involvement seemed to be almost universal, although its severity varied greatly ranging from subclinical organ damage to overt, slowly progressive renal dysfunction. The renal presentation was consistent with a tubulointerstitial disease, as suggested by the findings of defective urine-concentrating capacity, moderate polyuria, negative urinalysis, and mild tubular proteinuria. Histology confirmed tubulointerstitial nephritis. Surprising, amyloid was restricted to nonglomerular regions and limited to the renal medulla. This location of apolipoprotein A-I amyloid differs sharply from other systemic amyloidoses that are mainly characterized by glomerular and vascular deposits. The tubulointerstitial nephritis as a result of hereditary apolipoprotein A-I amyloidosis is a rare disease and a challenging diagnosis to recognize. Patients who present with familial tubulointerstitial nephritis associated with liver disease require a high index of suspicion for apolipoprotein A-I amyloidosis.

Recent advances in blood-related proteomics

Blood is divided in two compartments, namely, plasma and cells. The latter contain red blood cells, leukocytes, and platelets. From a descriptive medical discipline, hematology has evolved towards a pioneering discipline where molecular biology has permitted the development of prognostic and diagnostic indicators for disease. The recent advance in MS and protein separation now allows similar progress in the analysis of proteins. Proteomics offers great promise for the study of proteins in plasma/serum, indeed a number of proteomics databases for plasma/serum have been established. This is a very complex body fluid containing lipids, carbohydrates, amino acids, vitamins, nucleic acids, hormones, and proteins. About 1500 different proteins have recently been identified, and a number of potential new markers of diseases have been characterized. Here, examples of the enormous promise of plasma/serum proteomic analysis for diagnostic/prognostic markers and information on disease mechanism are given. Within the blood are also a large number of different blood cell types that potentially hold similar information. Proteomics of red blood cells, until now, has not improved our knowledge of these cells, in contrast to the major progresses achieved while studying platelets and leukocytes. In the future, proteomics will change several aspects of hematology.

Influence of tissue fixation on the microextraction and identification of amyloid proteins

In surgical pathology, correct immunohistochemical identification of AL amyloidosis poses a particular problem. Immunostaining for lambda- or kappa-light chains is commonly encountered even in non-immunoglobulin-derived amyloidoses, which leads to a false-positive classification as AL amyloidosis. In this respect, microextraction of amyloid proteins from surgical pathology specimens and their subsequent biochemical characterization may prove useful in reaching the correct diagnosis. In this study, we investigated systematically the influence of fixation on the extraction of amyloid proteins from amyloid-containing tissue samples. Tissue samples were obtained from a patient with generalized AA amyloidosis and from a second patient with generalized AL amyloidosis. The samples were stored either unfixed or fixed in phosphate buffered 4% p-formaldehyde, methacarn, or Bouin for 3 days, 1 week, or 1 month. Thereafter, proteins were extracted according to the procedure of Layfield et al, separated by SDS-PAGE and subjected to Western blotting, using antibodies directed against AA amyloid and immunoglobulin-derived lambda-light chain. Following this procedure, a variety of differently sized AA amyloid or lambda-light chain immunoreactive protein bands were found in both patients, which is typical for amyloid proteins. Fixation time did not per se prohibit the extraction of these amyloid proteins from tissue samples, which remained detectable irrespective of fixation time. Although all three fixatives impaired the resolution of some, but not all, individual amyloid proteins, this procedure may help to confirm or reject a diagnosis of AL amyloidosis, because detection of several lambda- or kappa-light chain immunoreactive protein bands in the low-molecular-weight range (<20 kDa) is a common characteristic of their amyloid nature.

Sporadische zerebrale Amyloidangiopathie mit ischämischer Leukenzephalopathie und Mikroblutungen

We describe a 72-year-old patient with rapidly progressive dementia and a complex focal seizure. Magnetic resonance (MR) imaging revealed leukoencephalopathy with the involvement of the U-fibers as well as cortical and subcortical microbleeds. Brain biopsy confirmed the diagnosis of cerebral Abeta amyloid angiopathy (CAA). The presented case illustrates the significance of CAA as a cause of rapidly progressive dementia and leukoencephalopathy and points out the importance of T2-weighted MR imaging in the evaluation of dementia.

Histochemical and topo-optical investigations on tissue-isolated and in vitro amyloid fibrils

An improved microscopic slide preparation for staining of tissue-isolated and in vitro amyloid fibrils is described in detail. Specimens were prepared by slow drying of an amyloid fibril suspension on aminoalkyl-silanised glass slides underneath a coverglass. The purpose of this method is to obtain microscopically visible fibers. Polarization microscopy was performed on unstained fibers in different embedding media, on fibers stained with Congo red, toluidine blue, 1,9-dimethylmethylene blue, anisotropic PAS reaction and Sudan black. Results were identical in 8 tissue-isolated amyloid fibril preparations. The refractive index of amyloid was about 1.5, as expected for protein fibrils. Congo red-stained fibrils showed yellow or blue-green polarization colors, while staining with toluidine blue or 1,9-dimethylmethylene blue induced green or orange polarization colors. The latter dyes stained the fibrils even in buffers with low pH or high ionic strength, pointing to strong acidic groups like sulphates in amyloid. The anisotropic PAS reaction for selective demonstration of periodate reactive carbohydrates in tissue-isolated amyloid fibrils was positive. Thus, linearly ordered acidic groups and carbohydrate residues could be detected for the first time in tissue-isolated amyloid fibrils using an improved technique for microscopic slide preparation on one side and topo-optical reactions on the other.

Helix-Turn-Helix Peptides That Form α-Helical Fibrils: Turn Sequences Drive Fibril Structure

Models of apolipoprotein A-I (apo A-I), the main protein of high-density lipoprotein, predict that it contains 10 amphiphilic, alpha-helical segments connected by turns. We synthesized four peptides with two identical 18-residue, amphiphilic, alpha-helical segments (Anantharamaiah, G. M., et al. (1985) J. Biol. Chem. 260, 10248-10255) connected by putative turn sequences from apo A-I: (1) Ac-DWLKAFYDKVAEKLKEAFKVEPLRADWLKAFYDKVAEKLKEAF-NH2, (2) Ac-DWLKAFYDKVAEKLKEAFGLLPVLEDWLKAFYDKVAEKLKEAF-NH2, (3) Ac-DWLKAFYDKVAEKLKEAFKVQPYLDDWLKAFYDKVAEKLKEAF-NH2, and (4) Ac-DWLKAFYDKVAEKLKEAFNGGARLADWLKAFYDKVAEKLKEAF-NH2. Surprisingly, peptides 1-3 formed fibrils after incubation (37 degrees C, 10 mM sodium phosphate, pH 7.60), but in contrast to beta-sheet amyloid fibrils, these did not bind thioflavin T and they induced a blue shift in the spectrum of Congo red. CD (peptides 1-3) and FTIR (peptides 1 and 2) of the fibrils showed significant alpha-helical character. Synchrotron X-ray fiber diffraction on a magnetically aligned sample of 1 confirmed the alpha-helical character in the fibrils and indicated that the helical axes are oriented perpendicular to the fibril axis. In contrast, peptide 4, containing two Gly residues but no Pro in the turn, formed only a small amount of nonfibrillar precipitate after prolonged incubation. Peptide 4P (peptide 4 with a Pro in place of the central Ala) and peptide 5, containing a PEG block in lieu of the central turn, were similar to peptide 4 in not forming fibrils, possibly because the region linking the helices was unstructured. These studies indicate that varying turn sequences between longer amphiphilic alpha-helical segments can drive the structure of fibrils.

Lysozyme: A paradigmatic molecule for the investigation of protein structure, function and misfolding

BACKGROUND

The term amyloidosis encompasses a wide group of conditions characterised by the tissue deposition of autologous proteins assembled in homogeneous regularly spaced antiparallel beta strands. The mechanism by which the different proteins gain a conformation, allowing monomers to bind to each other to form the regular amyloid fibril, is under intensive investigation. The discovery that human lysozyme, a protein thoroughly structurally and functionally characterised, can form amyloid fibrils has offered unique opportunities to unveil the molecular mechanisms involved in amyloid formation. Four amyloidogenic mutations have been identified and an apparently non-amyloidogenic polymorphism has been recently described.

RESULTS AND CONCLUSIONS

Lysozyme is well characterised for structure, function, folding dynamics and metabolism and comparative studies are becoming available that highlight pathogenic differences between the wild-type and the amyloidogenic variants. The chemical structure of lysozyme in natural amyloid fibrils was characterised in high detail in the early cases, but it is still lacking in the cases most recently discovered. Amyloidogenic lysozymes represent a prototypic molecule for new pharmaceutical approaches in which the formation of amyloid fibrils is abrogated through a stabilisation of the precursor.

Transcriptomics applied to obesity and caloric restriction

Caloric restriction still remains the most efficient way to promote weight loss. Deciphering the molecular basis of adaptation to energy restriction is critical for the tailoring of new therapeutic strategies. This review focuses on the recent input of gene profiling on adipose tissue in obesity pathogenesis and on the new insights on adaptations occurring during very low caloric diet (VLCD) in humans. Hypocaloric diets improve a wide range of metabolic parameters including lipolytic efficiency, insulin sensitivity, and inflammatory profile. In the subcutaneous white adipose tissue (scWAT) the VLCD induced a decrease in the mRNA levels for the antilipolytic alpha2-adrenergic receptor associated with changes in catecholamine-induced adipocyte lipolytic capacity. The improvement in insulin sensitivity was not associated with a change in subcutaneous adipose tissue adiponectin gene expression or in its plasma level, suggesting that adiponectin is not involved in the regulation of VLCD-induced improvement of insulin sensitivity and that there is a small contribution of subcutaneous adipose tissue to plasma adiponectin levels. Pangenomic microarray studies in human scWAT revealed that a panel of inflammatory markers and acute phase reactants were over expressed in obese compared to lean subjects. Caloric restriction improved the inflammatory profile of obese subjects through a decrease of pro-inflammatory factors and an increase of anti-inflammatory molecules. These genes were mostly expressed in the stroma vascular fraction of the adipose tissue. Specific cell-type isolation and immunohistochemistry demonstrated that monocyte/macrophage lineage cells were responsible for the expression of both mRNA and protein inflammatory markers. The acute phase proteins serum amyloid A was highly expressed in mature adipocytes from obese subjects. Caloric restriction decreased both serum amyloid mRNA and circulating levels. Obesity now clearly appears as chronic low-grade inflammation state. Modulation of the inflammatory pathways may represent new therapeutic targets for the treatment of obesity-related complications.

Unexpectedly high incidence of visceral AA-amyloidosis in slaughtered cattle in Japan

Experimental mouse AA amyloidosis can be transmissible by dietary ingestion of amyloid fibrils and it is well known that AA amyloidosis occasionally develops in aged cattle. Bovine liver and intestine have conventionally been used in Oriental foods, and the incidence of visceral AA amyloidosis in slaughtered cattle was evaluated. Renal tissues from 302 aged cattle older than 4 years were obtained from a local abattoir. Amyloid deposition was microscopically examined and amyloid protein was immunochemically determined. Renal amyloid deposition was seen in 15 out of 302 cattle with no previous history of diseas, an incidence of 5.0%. Amyloid protein in these cattle was AA and they had pathological findings in their visceral organs on gross examination. The incidence of visceral AA amyloidosis in slaughtered cattle in this study was disturbingly high compared with those (0.4-2.7%) previously reported from Japan and other foreign countries. AA amyloidosis is a life-threatening complication in patients with chronic inflammatory diseases and these patients at risk should avoid ingesting food that may possibly contain AA amyloid fibrils. More detailed information on cattle amyloidosis is required to guarantee the safety of our food.

Weight loss regulates inflammation-related genes in white adipose tissue of obese subjects

Adipose tissue produces inflammation and immunity molecules suspected to be involved in obesity-related complications. The pattern of expression and the nutritional regulation of these molecules in humans are poorly understood. We analyzed the gene expression profiles of subcutaneous white adipose tissue from 29 obese subjects during very low calorie diet (VLCD) using cDNA microarray and reverse transcription quantitative PCR. The patterns of expression were compared with that of 17 non-obese subjects. We determined whether the regulated genes were expressed in adipocytes or stromavascular fraction cells. Gene expression profiling identified 100 inflammation-related transcripts that are regulated in obese individuals when eating a 28 day VLCD but not a 2 day VLCD. Cluster analysis showed that the pattern of gene expression in obese subjects after 28 day VLCD was closer to the profile of lean subjects than to the pattern of obese subjects before VLCD. Weight loss improves the inflammatory profile of obese subjects through a decrease of proinflammatory factors and an increase of anti-inflammatory molecules. The genes are expressed mostly in the stromavascular fraction of adipose tissue, which is shown to contain numerous macrophages. The beneficial effect of weight loss on obesity-related complications may be associated with the modification of the inflammatory profile in adipose tissue.