Pathogenesis Of Familial Amyloidotic Polyneuropathy Research Articles

Generation of familial amyloidotic polyneuropathy-specific induced pluripotent stem cells

Familial amyloidotic polyneuropathy (FAP) is a hereditary amyloidosis induced by amyloidogenic transthyretin (ATTR). Because most transthyretin (TTR) in serum is synthesized by the liver, liver transplantation (LT) is today the only treatment available to halt the progression of FAP, even though LT is associated with several problems. Despite the urgent need to develop alternatives to LT, the detailed pathogenesis of FAP is still unknown; also, no model fully represents the relevant processes in patients with FAP. The induction of induced pluripotent stem (iPS) cells has allowed development of pluripotent cells specific for patients and has led to useful models of human diseases. Because of the need for a tool to elucidate the molecular pathogenesis of FAP, in this study we sought to establish heterozygous ATTR mutant iPS cells, and were successful, by using a Sendai virus vector mixture containing four transcription factors (Oct3/4, Sox2, Klf4, and c-Myc) to reprogram dermal fibroblasts derived from FAP patients. Moreover, FAP-specific iPS cells had the potential to differentiate into hepatocyte-like cells and indeed expressed ATTR. FAP-specific iPS cells demonstrated the possibility of serving as a pathological tool that will contribute to understanding the pathogenesis of FAP and development of FAP treatments.

Effect of albumin on transthyretin and amyloidogenic transthyretin Val30Met disposition and tissue deposition in familial amyloidotic polyneuropathy

AimsTransthyretin (TTR)-related familial amyloidotic polyneuropathy (FAP) is characterized by the systemic accumulation of amyloid fibrils caused by amyloidogenic. Our previous studies demonstrated that albumin played a role in the inhibition of TTR amyloid-formation. The aim of this study was to evaluate the effect of albumin on TTR disposition and tissue deposition in vivo. Main methodsFor pharmacokinetic studies, recombinant wild-type TTR (rTTR) and recombinant amyloidogenic TTR Val30Met (rATTR V30M) were labeled with iodine and administered to Sprague–Dawley rats and analbuminemia rats (NAR: Nagase Analbuminemia Rats). The deposition of ATTR V30M was also analyzed by immunohistochemistry in the transgenic (Tg) rats possessing a human ATTR V30M gene (ATTR V30M Tg rats) and NAR possessing a human ATTR V30M gene (ATTR V30M Tg NAR). Key findingsThe presence of albumin had no effect on the tissue distribution of either rTTR or rATTR V30M. However, more ATTR V30M was deposited in the hearts, stomachs and small intestines of ATTR V30M Tg NAR rats, compared to ATTR V30M Tg rats. SignificanceAlthough the disposition of TTR and ATTR V30M was unaffected by the presence of albumin, the deposition of ATTR V30M in some organs was apparently increased in the absence of albumin compared to the presence of albumin. These results show that albumin would contribute to suppressing the tissue deposition of TTR in pathogenesis of FAP, but does not affect the disposition of TTR.

Focus on autonomic dysfunction in familial amyloidotic polyneuropathy (FAP)

It is well known that autonomic dysfunction in familial amyloidotic polyneuropathy (FAP) is the most serious problem, because it restricts the daily life of these patients. The detail mechanisms of the onset are not well understood in FAP and domino liver transplantation-induced amyloid neuropathy. As autonomic disturbances play an important role in the symptomatology of FAP, further studies of autonomic dysfunction in these patients may lead the pathogenesis of FAP. Autonomic dysfunction is often observed before sensory and motor nerve dysfunction in FAP. This can be attributed to the morphological characteristics of the nerves. Unmyelinated, small myelinated, and large myelinated fibers tend to become impaired in that order. Although the reasons of susceptibility to amyloid infiltration and injury are not known, studies of autopsied FAP patients have revealed heavy infiltration of amyloid in autonomic ganglions. Moreover, spinal ganglion and posterior loot of the spine had severe amyloid deposits than did the anterior root of the spine or the motor nerves. It is well known that autonomic dysfunction is the most serious problem, because it restricts the daily life of FAP patients. However, we have four major questions about autonomic dysfunction in clinical. In this manuscript, we discuss about the answers of these questions.

Loss of functional albumin triggers acceleration of transthyretin amyloid fibril formation in familial amyloidotic polyneuropathy

Transthyretin (TTR)-related familial amyloidotic polyneuropathy (FAP) is characterized by systemic accumulation of amyloid fibrils caused by a point mutation in the TTR gene. Despite the urgent need for alternative therapeutic strategies, the pathogenesis of FAP still remains elusive. In our study reported here, we focused on albumin, the most abundant protein in plasma, and described the role of albumin in the TTR amyloid-formation process. Patients with FAP evidenced significantly decreased serum albumin levels as the disease progressed. Biacore analysis showed that albumin had a binding affinity for TTR and exhibited higher affinity for TTR amyloid than native TTR. Albumin functioning as an antioxidant effectively suppressed TTR amyloid formation. In patients with FAP, albumin was significantly oxidized as the disease progressed. Moreover, loss of functional albumin accelerated TTR deposition in analbuminemic rats possessing a human variant TTR gene. Taken together, these results indicate that albumin may have an inhibitory role in the TTR amyloid-formation process.

SELDI-TOF Mass Spectrometry Evaluation of Variant Transthyretins for Diagnosis and Pathogenesis of Familial Amyloidotic Polyneuropathy

Mass spectrometric analyses are valuable for detection of transthyretin (TTR) variants, which cause familial amyloidotic polyneuropathy (FAP). However, those methods require an immunoprecipitation step with an anti-TTR antibody and are not suitable for quantitative detection. We investigated the usefulness of SELDI-TOF mass spectrometry (MS) without an immunoprecipitation step. We used ProteinChips with chromatographic capture formats to detect TTRs. We attempted to correlate the intensity of mixed samples of amyloidogenic TTR (ATTR) V30M to wild-type (WT) TTR. We analyzed the proportion of ATTR V30M in amyloid-laden cardiac tissues from FAP patients, and also evaluated samples from FAP patients with 16 other TTR mutations. Detection of ATTR required only 3 h of SELDI-TOF MS analysis. We determined that SELDI-TOF MS was suitable for quantitative detection of ATTR V30M and demonstrated that the proportion of ATTR V30M to WT TTR was 46.6% in amyloid-laden cardiac tissue from an FAP patient who died 10 years after liver transplantation. With this method, we identified 12 of 17 TTR variants. Small mass shifts and low concentrations of variants prevented ATTR detection. By changing the analytical conditions, we achieved detection of low concentrations of ATTR Y114C in serum. SELDI-TOF MS is a reliable tool for quantitative evaluation of TTR variants, in both tissue amyloid deposits and body fluids. This method is useful for the diagnosis and investigation of the pathogenesis of FAP.

Transthyretin and familial amyloidotic polyneuropathy

Familial amyloidotic polyneuropathy (FAP) is an inherited autosomal dominant disease that is commonly caused by accumulation of deposits of transthyretin (TTR) amyloid around peripheral nerves. The only effective treatment for FAP is liver transplantation. However, recent studies on TTR aggregation provide clues to the mechanism of the molecular pathogenesis of FAP and suggest new avenues for therapeutic intervention. It is increasingly recognized that there are common features of a number of protein-misfolding diseases that can lead to neurodegeneration. As for other amyloidogenic proteins, the most toxic forms of aggregated TTR are likely to be the low-molecular-mass diffusible species, and there is increasing evidence that this toxicity is mediated by disturbances in calcium homeostasis. This article reviews what is already known about the mechanism of TTR aggregation in FAP and describes how recent discoveries in other areas of amyloid research, particularly Alzheimer's disease, provide clues to the molecular pathogenesis of FAP.

Advanced glycation end product is implicated in amyloid‐related kidney complications

Background. Kidney failure is a common complication in familial amyloidotic polyneuropathy (FAP). It has been suggested that advanced glycation end products (AGEs) play an important role in the development and pathogenesis of FAP. Material and methods. To evaluate the impact of AGEs on FAP patients' kidney dysfunction, we measured AGE in serum and urine of 28 FAP patients and 18 healthy controls by AGE‐specific enzyme‐linked immunosorbent assay (ELISA). Immunohistochemistry utilizing antibodies to AGE and the receptor for AGE (RAGE) were used on kidney tissue from 3 FAP patients and 3 diabetic patients to disclose a correlation between amyloid deposits and AGE–RAGE. Results. The glomeruli of FAP patients were heavily deposited with amyloid and the glomerular size was enlarged. The space between Bowman's capsule and glomerulus was totally covered by the enlarged glomerulus. AGE and RAGE were deposited in glomeruli and tubuli and correlated with amyloid deposits. Decreased AGE levels in the liver‐transplanted FAP patients' serum compared with that of non‐transplanted patients were noted, and AGE concentration in serum tended to be higher in non‐transplanted FAP patients compared with normal control subjects. There were no differences in the AGE urine levels in FAP patients compared with controls. No correlation could be found between AGE in urine and serum compared with serum albumin, serum creatinine and creatinine clearance. Conclusions. The accumulation of AGE, RAGE and amyloid in the kidney of FAP patients suggests that these molecules play an important role in the origin and pathogenesis of renal failure in FAP patients.

Change in the age of onset in patients with familial amyloidotic polyneuropathy type I.

To investigate the influence of environmental factor(s) on the pathogenesis of familial amyloidotic polyneuropathy (FAP) type I, the age of onset in 33 FAP patients in the Arao district of Kumamoto Prefecture in Japan and in 20 of their ancestors to the 3rd prior generation was carefully examined. The age of onset in FAP patients progressively became younger. This tendency was more apparent in female FAP patients than in male patients. Since the pathogenesis of amyloid formation in FAP as well as other amyloidosis diseases is not still elucidated, this phenomenon may be of interest.

Genetic abnormalities and pathogenesis of familial amyloidotic polyneuropathy.

Familial amyloidotic polyneuropathy (FAP) is an autosomal inherited disease, characterized by extracellular amyloid deposits and by peripheral neuropathy. Amyloid fibrils derived from most types of FAP consist of variant transthyretin (TTR) with single amino acid substitutions, and methionine 30 TTR is the most common variant TTR. TTR is mainly produced in the liver and the choroid plexus. Biochemical and molecular biological techniques have been revealing the amyloidogenicity of variant TTR in vitro and in vivo using the transgenic mouse as a model. It will be important for the development of effective therapy to find out the factors, other than variant TTR, which affect amyloid deposition and define the tissue specificity of amyloid.

Role of variant prealbumin in the pathogenesis of familial amyloidotic polyneuropathy: Fate of normal and variant prealbumin in the circulation

According to recent studies on protein chemistry and genetic engineering, replacement of the Val 30 residue of prealbumin by methionine is believed to play a critical role in the formation of amyloid deposit and the pathogenesis of familial amyloidotic polyneuropathy (FAP). However, only limited information is available concerning the behavior of prealbumin in the circulation. To obtain the molecular insight into the mechanism of amyloid deposition, it is indispensable to know the fates of normal and variant prealbumin in vivo. Thus, the fates of prealbumin samples from normal and FAP patients were studied in normal rats as well as in animals that were challenged with acute inflammation induced by turpentine. The effect of in vitro photooxidation of prealbumin samples on their behavior was also examined in vivo. Kinetic analysis revealed no appreciable difference between prealbumin samples from normal and FAP patients. These results suggest that factors other than the rate of transfer of the variant form prealbumin from plasma to an extravascular compartment may play a critical role in the pathogenesis of amyloid deposition in FAP patients.

Molecular Genetics of Familial Amyloidotic Polyneuropathy

We established a diagnosis of familial amyloidotic polyneuropathy (FAP) based on DNA and demonstrated a direct link between prealbumin gene mutation and FAP. The individuals with FAP, so far examined, were heterozygous for the prealbumin gene, carrying one normal and one mutant gene. To investigate the molecular pathogenesis of FAP, we isolated a normal prealbumin gene (7 kb in length) and also a mutant prealbumin gene associated with FAP. We compared their nucleotide sequences and found that they matched except for a single-base substitution present in the second exon. In an effort to construct mouse model systems for the FAP, we developed strains of transgenic mice carrying human mutant prealbumin genes.

Generation of transgenic mice producing a human transthyretin variant: A possible mouse model for familial amyloidotic polyneuropathy

Type I familial amyloidotic polyneuropathy (FAP) results from the systemic deposition of a plasma transthyretin (TTR) variant with a Val----Met change at position 30. In an attempt to establish a model of this disease, we generated transgenic mice producing the variant TTR. A DNA fragment containing the mouse metallothionein-I promoter fused to the structural gene coding for the human TTR variant was microinjected into fertilized mouse eggs. Among 72 mice that developed from these eggs, ten carried the fusion gene and three of these showed significant concentrations of the variant TTR in their serum. These mice may be useful in elucidating the pathogenesis of FAP and in establishing a therapy for this intractable disorder.