Selective binding to transthyretin and tetramer stabilization in serum from patients with familial amyloidotic polyneuropathy by an iodinated diflunisal derivative.

In familial amyloidotic polyneuropathy, TTR (transthyretin) variants are deposited as amyloid fibrils. It is thought that this process involves TTR tetramer dissociation, which leads to partially unfolded monomers that aggregate and polymerize into amyloid fibrils. This process can be counteracted by stabilization of the tetramer. Several small compounds, such as diclofenac, diflunisal and flufenamic acid, have been reported to bind to TTR in vitro, in the T4 (thyroxine) binding channel that runs through the TTR tetramer, and consequently are considered to stabilize TTR. However, if these agents bind plasma proteins other than TTR, decreased drug availability will occur, compromising their use as therapeutic agents for TTR amyloidosis. In the present work, we compared the action of these compounds and of new derivatives designed to increase both selectivity of binding to TTR and inhibitory potency in relation to TTR amyloid fibril formation. We found two diflunisal derivatives that, in contrast with diclofenac, flufenamic acid and diflunisal, displaced T4 from TTR in plasma preferentially over binding to albumin and thyroxine binding globulin. The same diflunisal derivatives also had a stabilizing effect on TTR tetramers in plasma, as studied by isoelectric focusing of whole plasma under semi-denaturing conditions. In addition, by transmission electron microscopy, we demonstrated that, in contrast with other proposed TTR stabilizers (namely diclofenac, flufenamic acid and diflunisal), one of the diflunisal derivatives tested efficiently inhibited TTR aggregation. Taken together, our ex vivo and in vitro studies present evidence for the selectivity and efficiency of novel diflunisal derivates as TTR stabilizers and as inhibitors of fibril formation.

Comparative studies of two transthyretin variants with protective effects on familial amyloidotic polyneuropathy: TTR R104H and TTR T119M.

Recently, a new nonpathogenic transthyretin (TTR) variant-TTR R104H (TTR H104)-has been described in heterozygotic and compound heterozygotic individuals from a Japanese family with familial amyloidotic polyneuropathy (FAP). The compound heterozygotic individual, a carrier of TTR V30M (TTR M30) and TTR R104H (TTR M30/H104) presented a very mild form of FAP with slow progression of the disease. TTR and retinol binding protein (RBP) levels were found to be increased in serum from TTR H104 carriers. These characteristics are very similar to those found in compound heterozygotic carriers of TTR V30M-T119M (TTR M30/M119). To structurally compare these variants, we performed stability and thyroxine (T(4)) binding studies. TTR M30/H104 showed an increased resistance to dissociation into monomers similar to TTR M30/M119. This suggests that the His104 substitution has the same stabilizing effect on tetrameric TTR as the Met119 substitution. Concerning T(4) binding, TTR H104 presents a T(4) binding affinity lower than that of TTR M119, but still higher than normal TTR. However, TTR from the compound heterozygotic carrier of TTR M30/H104 presented a T(4) binding affinity lower than normal. The results indicate that the His 104 substitution induces structural alterations that increase the stability of the tetramer in compound heterozygotes for TTR M30 despite a lower affinity for T(4) binding. Thus, stability of TTR and binding affinity for T(4) may not be related. More detailed characterization of these variants is needed to clarify the structural alterations responsible for their increased stability.

Usefulness of MALDI/TOF mass spectrometry of immunoprecipitated serum variant transthyretin in the diagnosis of familial amyloid polyneuropathy.

A matrix-assisted laser desorption ionization/time-of-flight (MALDI/TOF) mass spectrometry (MS) system was used to detect variant transthyretin (TTR) in immunoprecipitated serum TTR molecules obtained from 6 patients with familial amyloid polyneuropathy (FAP) who were already proven not to have ATTR Val30Met. This simple and quick method showed six different patterns of mass spectra of TTR-related immunoprecipitates from these patients, and in each patient the clearly identified characteristic doublet-shaped ion peaks consisted of normal and variant TTR apart from each other peak with a mass difference between them. DNA sequencing confirmed that the patterns of variant TTR corresponded respectively to ATTR Val30Leu, ATTR Phe33Val, ATTR Asp38Ala, ATTR Ser50Arg, ATTR Ala97Gly and ATTR Ala97Ser. ATTR Asp38Ala and ATTR Ala97Ser are previously unknown variants of TTR leading to the development of FAP. ATTR Phe33Val was found in a Chinese FAP patient and ATTR Ala97Ser in a Taiwanese. Serum analysis using immunoprecipitation and MALDI/TOF MS system can provide useful information when investigating FAP patients with diverse types of variant TTR.

Familial amyloidotic polyneuropathy type 1 in Brazil is associated with the transthyretin Val30Met variant.

UNLABELLED: Familial amyloidotic polyneuropathy type 1 (FAP1) is an inherited systemic amyloidosis that is secondary to the deposition of transthyretin (TTR) variants in peripheral nerves and in certain visceral organs. More than 50 distinct mutations have already been described in the TTR gene. Yet, the most common mutation found worldwide is a substitution of valine for methionine in position 30 (Val30Met). Currently, the variants of TTR in Brazilian FAP1 patients remain largely unknown and the aim of this study was to analyze the frequency of the TTR Val30Met mutation in such Brazilian subjects. METHODS: Thirty-two FAP1 patients belonging to 24 different families were studied for the presence of Val30Met variant by PCR-RFLP. RESULTS: All Brazilian FAP1 subjects studied were positive for the TTR Val30Met variant. As expected, all of them were heterozygous for the mutation. CONCLUSION: TTR Val30Met mutation was the sole TTR variant found in Brazilian FAP1 patients in this cohort, and it was present even in those subjects without a clear history of Portuguese ancestry.

A novel compound heterozygote (FAP ATTR Arg104His/ATTR Val30Met) with high serum transthyretin (TTR) and retinol binding protein (RBP) levels.

A 64-year-old Japanese male suffering from very slowly progressive amyloidosis was studied by immunohistopathologic, mass spectrometric, and molecular genetic methods. After confirming the immunoreactivity of transthyretin (TTR) in the amyloid deposits using an anti-TTR polyclonal antibody, matrix-assisted laser desorption ionization/time-of-flight-mass spectrometry (MALDI/TOF-MS) was employed to look for the presence of variant TTR(s) in the serum. Two variant forms of TTR, one with a molecular weight 32 Da greater and another with a molecular weight 19 Da less than that of normal TTR encoded by the two respective alleles, were detected in this patient. Direct sequence analysis confirmed the presence of a double substitution: one at codon 30 from GTG (Val) to ATG (Met) and the other at codon 104 from CGC (Arg) to CAC (His) in the two alleles. MALDI/TOF-MS of the parents of the proband revealed that his father was a heterozygote of ATTR Arg104His and his mother was a heterozygote of ATTR Val30Met. The total TTR and retinol binding protein (RBP) concentrations in the serum samples of the proband were very high compared with those of FAP ATTR Val30Met patients and control subjects. We report here a new compound heterozygote in the TTR gene with familial amyloidotic polyneuropathy (FAP).

Partial-liver transplantation to treat familial amyloid polyneuropathy: follow-up of 11 patients.

BACKGROUND: Recently, liver transplantation has been used to treat patients with familial amyloid polyneuropathy (FAP). OBJECTIVE: To describe the clinical course of patients with FAP who received partial-liver transplantation from living donors. DESIGN: Case series. SETTING: University hospital in Matsumoto, Japan. PATIENTS: 11 patients with FAP who underwent partial-liver transplantation. The transthyretin gene abnormality in all 11 patients was the substitution of methionine for valine at position 30. INTERVENTION: Partial liver transplantation from living donors. MEASUREMENTS: Preoperative and follow-up (3 to 64 months) clinical data, including routine laboratory data, nerve conduction velocity tests, and sural nerve histology. RESULTS: All 7 patients who had severe gastrointestinal autonomic disorders or polyneuropathy localized to the lower limbs for less than 4 years showed improvement. Three of 4 patients with polyneuropathy involving both the upper and lower limbs had adverse outcomes, including two deaths. The preoperative duration of their illness was more than 6 years. These 3 patients also had marked decreases in creatinine clearance and nerve conduction velocities and severe loss of myelinated fibers in sural nerves. CONCLUSION: Preoperative clinical severity and duration of illness are associated with outcomes after liver transplantation for FAP.

Electrically neutral microheterogeneity of human plasma transthyretin (prealbumin) detected by isoelectric focusing in urea gradients.

Mutants of the human plasma transthyretin (TTR, prealbumin) have attracted interest due to their rather frequent association with the autosomal dominant disease familial amyloidotic polyneuropathy (FAP). Some three quarters of known TTR mutations produce electrically neutral amino acid substitutions undetectable via separation by charge. We have developed an electrophoretic procedure sensitive to differences in the stability of tetramers and monomers under partially denaturing conditions. The differential folding states were found to be fully reversible. Applying the procedure we found 14 electrically silent mutants of TTR among 2000 plasma samples from German donors. We demonstrate that the normal TTR monomer exists in different forms of variable stability and/or charge due to binding of sulfhydryls from plasma to the unique cysteine at position 10 of the primary structure as well as due to modification by treatment with an oxidant. We found that reduction of Cys10 increases the stability of the folded monomeric and tetrameric conformations. The conformational changes of TTR induced by isoelectric focusing in a urea gradient were found to be associated by a gain of three positive charge units. Using published crystallographic data we present structural sites in the TTR molecule which could explain the observed effects.

Unusual self-association properties of transthyretin Y114C related to familial amyloidotic polyneuropathy: effects on detection and quantification.

We performed biochemical and immunological examinations of heterozygotic carriers of the transthyretin (TTR) mutant Y114C associated with familial amyloidotic polyneuropathy (FAP). The total serum TTR levels in Y114C TTR carriers were extremely low when analyzed by single radial immunodiffusion (SRID), whereas by indirect enzyme-linked immunosorbent assay (ELISA) procedure, their total TTR concentrations were increased. Recombinant homozygotic Y114C TTR showed no immunoreactivity towards a TTR antibody when analyzed by SRID, whereas by the ELISA procedure presented the same degree of reactivity as that of normal TTR or isolated serum heterozygotic Y114C TTR. These results indicate that immunodifusion based techniques cannot properly determine TTR serum levels in Y114C carriers. Analyses of serum TTR of the Y114C TTR carriers by electrospray ionization mass spectrometry (ESI-MS) with the orifice corn voltage at 60 V revealed a small peak of the free Y114C TTR in addition to large TTR peaks of normal TTR. The levels of the free mutant TTR increased with the orifice corn voltage at 90 V. In contrast, increase in orifice voltage from 60 to 90 V produced a reduction in the level of normal TTR. The results suggest a different pattern of association between monomers in Y114C relative to normal TTR.

A simple and reliable method of detecting variant transthyretins by multidimensional liquid chromatography coupled to electrospray ionization mass spectrometry.

Transthyretin (TTR) variants cause amyloidosis. A method, originally reported by us, of detecting the variants by high performance liquid chromatography/electrospray ionization mass spectrometry (ESIMS) using materials precipitated with anti-TTR antiserum, has been successfully applied by several institutions. The method is simple and reliable, but some variants may not precipitate with the antiserum or may precipitate in different yields compared to normal TTR. Moreover, unidentified minor peaks were observed, which may have been derived from cross reactive materials. We have now devised a new procedure to overcome these problems. An anion exchange and reversed phase liquid chromatography system and ESI mass spectrometer were connected in a tandem fashion using a 6 port valve and a protein trap cartridge. The profile of ion peaks by the method was the same as that by MS with immunoprecipitates. The minor peaks were proved not to be derived from cross reactive materials, and the molecular species of these peaks were characterized. This method is faster than immunoprecipitation method and using no antibody is a great benefit. The method can be applied widely to the study various proteins, when antibodies are not available.

Familial Amyloidotic Polyneuropathy: domino liver transplantation.

BACKGROUND/AIMS: The primary cause of Familial Amyloidotic Polyneuropathy is a variant transthyretin gene on chromosome 18. Progressive polyneuropathy followed by fatal cardiac and renal failure commonly manifest during middle age. Within 10 years after onset of clinical symptoms, affected individuals usually die due to malnutrition or heart failure. Currently, liver transplantation is the only available therapeutic option. METHODS: We performed liver transplantation in two patients with Familial Amyloidotic Polyneuropathy carrying the transthyretin-30 mutant. Two patients aged more than 50 years received the two explanted amyloidotic livers. This procedure is called Domino liver transplantation. We report the outcome in the studied subjects and analyze the metabolic consequences of this procedure. RESULTS: We determined the serum half-life of transthyretin-30 as 2.25 days using daily monitoring of transthyretin-30 levels. An affected amyloidotic patient had an increased serum concentration of lipoprotein(a) of 78 mg/dl before transplantation. The tumor patient, who received the organ from this affected patient, developed an almost identical serum concentration of lipoprotein(a) after liver transplantation, confirming the liver as the primary site of synthesis of this lipoprotein. CONCLUSION: Once Domino liver transplantation has been performed, the impact of the liver-dependent metabolism of specific proteins of interest can be studied.

Variant transthyretin (TTR) amyloidosis in Argentina. Detection of the trait by electrospray ionization mass spectrometry of lyophilized TTR immunoprecipitate.

We have developed a quick and reliable diagnostic method for detecting variant forms of transthyretin (TTR); namely, centrifugal concentration followed by electrospray ionization mass spectrometry (ESI-MS). Argentinian patients from three families with neuropathic amyloidosis and their relatives were screened for mutated TTR by ESI-MS. In order to facilitate transportation, we investigated the impact storage had on lyophilized anti-TTR-antibody precipitates' mass spectra. For this investigation, plasma samples from three Swedish patients with known TTR amyloidosis were analysed. We detected identical, additional peaks corresponding to a variant form of TTR in 10 members of the families, and also in a lyophilized sample sent unfrozen by mail from Argentina. All except one symptomatic subject had additional peaks, the exception having undergone a liver transplantation for the disease. All patients were early onset cases, i.e. below 35 years of age, and family history suggests an aggressive, rapidly progressing disease. Lyophilized anti-TTR-antibody precipitates stored at room temperature for 1 week exhibited only minor differences compared with plasma samples stored at -70 degrees C. In a new Argentinian study on familial amyloidotic polyneuropathy, the variant TTR was quickly identified and typed by ESI-MS. To facilitate transportation, dry-frozen samples can be used and the quality of the spectra is similar to that of samples stored at -70 degrees C.

Liver transplantation for familial amyloid polyneuropathy.

Familiar Amyloid Polyneuropathy (FAP), an autosomal dominant inherited multisystemic disorder was first observed by Corino de Andrade, a Portuguese neurologist, in 1939. This disease of Portuguese origin was probably spread by fishermen, mainly to Sweden and Japan. It is characterized by a progressive peripheral polyneuropathy and autonomic neuropathy (erectile sexual disfunction, gastrointestinal disfunction, bladder dysfunction and cardio vascular disease) and malnutrition. There are neural and systemic amiloid deposits. Type I FAP, of Portuguese origin, is the most common variety. The amyloid protein is the variant transthyretin (TTR) in which methionine (MET) is a substitute for valine in position 30 (TTR MET 30). It is mainly produced by the liver (90%) and, in small amounts, by the choroidal plexus. Symptoms usually start in the 3rd and 4th decade of life and the patients usually die within 10-15 years. From the therapeutic options--plasmapheresis, immunoadsorption and liver transplantation; the latter seems to be the only one, which stops the production of TTR MET 30 in a permanent way, by means of the liver. The lack of any other effective therapy and the success of the first liver transplantation performed in Sweden arouse great hope. So far, around 300 patients have been transplanted all over the world. A hundred and thirty of them were transplanted in Portugal. A Kaplan Meier survival curve of the Portuguese patients shows a survival rate of 78% at 5 years. However, in spite of the progression of the disease being halted, the irreversibility of some neurological lesions seems to persist. This fact raises the problem of the timing of the transplantation. It seems that the patients should be transplanted as soon as the symptoms start, since mortality and severe morbidity seems to mainly involve those in whom symptomatic disease has lasted longer than six years. As the explanted liver is a morphologic normal liver, a sequential (domino) transplant has been carried out in 16 cases so far done--by one of the authors (ALF) on patients with either hepatocellular carcinoma or liver metastatic disease.

Familial amyloidotic polyneuropathy type I with extracellular superoxide dismutase mutation: a case report.

We report an autopsy case of familial amyloidotic polyneuropathy (FAP) Type I with mutations in both transthyretin (TTR) and extracellular superoxide dismutase (EC-SOD). This patient started to develop peripheral neuropathy at age 25, followed by cardiac, renal, and autonomic nervous system failure due to massive amyloid deposition. Thirteen years after the initial symptoms, he died of septic shock. Autopsy revealed suppurative peritonitis, multiple abscesses in the bile ducts and urinary tract, and more marked amyloid deposition than commonly seen in FAP. Amyloid deposition occurred in various organs and tissues, especially prominently around blood vessels and in interstitial tissues, and was demonstrated immunohistochemically to be composed of TTR but not amyloid A (AA) and not amyloid L (AL) proteins. The serum EC-SOD content of the patient was 10 fold higher than those seen often in other FAP patients and in healthy controls. Genetic analysis demonstrated the single amino acid substitutions in Val30Met TIR and Arg213Gly EC-SOD. Since these data suggest the dissociation of EC-SOD from the vascular wall, massive amyloid deposition in the present case may be related to increased oxidative stress in loco.

Adenoviral expression of murine serum amyloid A proteins to study amyloid fibrillogenesis.

Serum amyloid A (SAA) proteins are one of the most inducible acute-phase reactants and are precursors of secondary amyloidosis. In the mouse, SAA1 and SAA2 are induced in approximately equal quantities in response to amyloid induction models. These two isotypes differ in only 9 of 103 amino acid residues; however, only SAA2 is selectively deposited into amyloid fibrils. SAA expression in the CE/J mouse species is an exception in that gene duplication did not occur and the CE/J variant is a hybrid molecule sharing features of SAA1 and SAA2. However, even though it is more closely related to SAA2 it is not deposited as amyloid fibrils. We have developed an adenoviral vector system to overexpress SAA proteins in cell culture to determine the ability of these proteins to form amyloid fibrils, and to study the structural features in relation to amyloid formation. Both the SAA2 and CE/J SAA proteins were synthesized in large quantities and purified to homogeneity. Electron microscopic analysis of the SAA proteins revealed that the SAA2 protein was capable of forming amyloid fibrils, whereas the CE/J SAA was incapable. Radiolabelled SAAs were associated with normal or acute-phase high-density lipoproteins (HDLs); we examined them for their clearance from the circulation. In normal mice, SAA2 had a half-life of 70 min and CE/J SAA had a half-life of 120 min; however, in amyloid mice 50% of the SAA2 cleared in 55 min, compared with 135 min for the CE/J protein. When the SAA proteins were associated with acute-phase HDLs, SAA2 clearance was decreased to 60 min in normal mice compared with 30 min in amyloidogenic mice. Both normal and acute-phase HDLs were capable of depositing SAA2 into preformed amyloid fibrils, whereas the CE/J protein did not become associated with amyloid fibrils. This established approach opens the doors for large-scale SAA production and for the examination of specific amino acids involved in the fibrillogenic capability of the SAA2 molecule in vitro and in vivo.

Serum potassium concentrations after suxamethonium in patients with familial amyloid polyneuropathy type I.

BACKGROUND: Suxamethonium produces an abnormal increase in serum potassium in some neurological diseases and some authors have suggested that it is safer not to use this drug in patients with familial amyloid polyneuropathy (FAP). However, there are no data previously reported to support this hypothesis. The aim of this study was to evaluate the magnitude of the potassium increase produced by suxamethonium in FAP type I. METHOD: Twenty-one FAP Met 30 patients anaesthetised for liver transplantation were studied. Age was 34.9 +/- 6.9 years (mean +/- SD), time elapsed from first symptom 5.5 +/- 3.2 years and weight was 14 +/- 9% below ideal body weight. Anaesthesia was induced with thiopentone and low-dose fentanyl. Samples for blood gas and 5 min after 1 mg/kg of suxamethonium was given for tracheal intubation. RESULTS: Before induction serum potassium levels were 3.8 +/- 0.4 mmol/L. One minute after suxamethonium, values were 3.8 +/- 0.4 mmol/L and 5 min after 4.3 +/- 0.5 mmol/L. The maximal increase observed was 1.6 mmol/L (from 3.4 mmol/L to 5.0 mmol/L). CONCLUSION: The average increase in plasma potassium concentrations observed in FAP patients after suxamethonium was similar to the increase observed in a normal population by others. Our study can exclude the hypothesis that an anomalous increase in potassium would be a typical and frequent response to suxamethonium in FAP met 30 patients. However, we cannot exclude that a dangerous rise in serum potassium may exist in a certain percentage of FAP patients.

A trinucleotide deletion in the transthyretin gene (delta V 122) in a kindred with familial amyloidotic polyneuropathy.

A 63-year-old white man of Ecuadorian origin had a subarachnoid hemorrhage at age 57 followed by numbness and paresthesia in his lower extremities. He subsequently developed sexual impotence, alternating constipation and diarrhea, urinary frequency, and difficulty in walking. Rectal biopsy revealed amyloid deposits immunohistochemically reactive with antitransthyretin antisera. Direct DNA sequencing of the transthyretin gene of the patient showed a trinucleotide deletion in exon 4. This deletion resulted in the loss of one of two valines at position 121 or 122. DNA analysis on 11 family members at risk revealed four mutant gene carriers. Plasma transthyretin levels in the mutant gene carriers measured by nephelometry were very low. Peptide sequence analysis revealed that most of plasma transthyretin was normal with only a small amount of variant protein. This is the first report of a DNA deletion in the transthyretin gene. We speculate that the loss of valine in the carboxyl terminal region of the transthyretin monomer alters stability of the tetrameric protein, which leads to rapid clearance from the plasma and amyloid deposition in the tissue.