Transthyretin Leu12Pro is associated with systemic, neuropathic and leptomeningeal amyloidosis

Pathogenesis, manifestations, diagnosis, and management of CNS complications in hereditary ATTR amyloidosis

The clinical efficacy of transthyretin (TTR) tetramer stabilisers and TTR gene silencers in addition to liver transplantation has been established for hereditary ATTR (ATTRv) amyloidosis. Accordingly, non-central nervous system (CNS) systemic amyloidosis manifestations, such as peripheral neuropathy and cardiomyopathy, are now being overcome. However, emerging disease-modifying therapeutics have limited effects on CNS amyloidosis since they target the blood-circulating TTR produced in the liver, and not the cerebral spinal fluid (CSF) TTR synthesised in the choroid plexus. CNS involvement is therefore becoming the most common and severe complication in patients with ATTRv amyloidosis, including transient focal neurologic episodes, haemorrhagic and ischaemic stroke, cognitive decline, and cranial nerve dysfunction. Pathologically, extensive amyloid depositions are observable in the leptomeninges and leptomeningeal vessels, which are in direct contact with the CSF. Amyloid positron emission tomography is a useful biomarker for the early detection and treatment evaluation of early-onset ATTRv amyloidosis with the V30M (p.V50M) variant. Treatment-wise, blood-brain barrier-permeable stabilisers, intrathecal injection of silencers, and monoclonal antibodies against misfolded TTR and/or ATTR amyloid may potentially ameliorate CNS ATTR amyloidosis. The development of novel imaging/CSF biomarkers and disease-modifying therapies are the greatest unmet medical need in ATTRv amyloidosis and require further clinical trials.

Cognitive manifestations and brain integrity in hereditary transthyretin amyloidosis: a systematic review

BACKGROUND

Central Nervous System involvement in hereditary transthyretin amyloidosis (ATTRv) is present in liver transplanted patients with longstanding ATTRV30M amyloidosis, and in some rarer variants. The pathophysiology of brain involvement and its relationship with cognitive disturbances is unknown. This systematic review summarized the literature on brain and cognitive involvement in ATTRv amyloidosis and aimed to elucidate the reasons for such involvement.

METHODS

The literature search was performed using the following databases: Medline/PubMed, Embase via Elsevier, Scopus, and Web of Science. Two assessors independently screened titles and abstracts, examined full texts, extracted data, and assessed the risk of bias. The risk of bias assessment was carried out using the JBI critical appraisal tools. This review included studies that applied any neuroimaging exam or cognitive assessment in humans with genetic confirmation of any TTR mutation.

RESULTS

59 studies met the inclusion criteria. Overall, the studies were of good quality. 57 studies reported at least one brain MRI technique. Only six studies reported a formal neuropsychological assessment. The studies included 1218 ATTRv patients (mean 45.7 ± 11.8 years) and 169 asymptomatic TTR variant carriers (mean 30.6 ± 7.5 years). The most common TTR variant was V30M (n = 936), followed by V122I (n = 74). 42.4% of ATTRv patients presented abnormalities in the neuroimaging exam and 19.7% presented cognitive dysfunction.

CONCLUSION

Based on the available evidence, brain involvement and cognitive symptoms can be present in ATTRv amyloidosis. Further research should explore the relationship of these symptoms with other complications (autonomic and cardiologic).

Hereditary leptomeningeal transthyretin amyloidosis with heterozygous TTR mutation: a case report and literature review

OBJECTIVE

This study aimed to characterize the clinical and neuroimaging features of hereditary leptomeningeal transthyretin amyloidosis (hATTR-LA), a dominant inheritance disorder caused by a heterozygous TTR gene mutation.

METHODS

A comprehensive retrospective evaluation was conducted, incorporating detailed clinical records, multimodal neuroimaging findings, and a systematic review of the literature to contextualize the observations.

RESULTS

The patient was a 55-year-old male who presented with chronic central nervous system symptoms, including sensory-motor peripheral neuropathy and progressive visual impairment. Cerebrospinal fluid analysis revealed elevated protein levels. Neuroimaging showed progressive leptomeningeal hyperdensity on CT and characteristic linear thickening with enhancement of the leptomeninges on MRI, involving both cerebral and spinal regions. Genetic testing confirmed the diagnosis by identifying a heterozygous c.265T > C (p.Y89H) pathogenic variant in exon 3 of the TTR gene, classified as pathogenic according to ACMG guidelines.

CONCLUSION

Multimodal imaging provides valuable, non-invasive insights for diagnosing hATTR-LA, enhancing diagnostic accuracy and informing clinical management of this rare condition.

Transthyretin mutagenesis: impact on amyloidogenesis and disease

Transthyretin (TTR), a homotetrameric protein found in plasma, cerebrospinal fluid, and the eye, plays a pivotal role in the onset of several amyloid diseases with high morbidity and mortality. Protein aggregation and fibril formation by wild-type TTR and its natural more amyloidogenic variants are hallmarks of ATTRwt and ATTRv amyloidosis, respectively. The formation of soluble amyloid aggregates and the accumulation of insoluble amyloid fibrils and deposits in multiple tissues can lead to organ dysfunction and cell death. The most frequent manifestations of ATTR are polyneuropathies and cardiomyopathies. However, clinical manifestations such as carpal tunnel syndrome, leptomeningeal, and ocular amyloidosis, among several others may also occur. This review provides an up-to-date listing of all single amino-acid mutations in TTR known to date. Of approximately 220 single-point mutations, 93% are considered pathogenic. Aspartic acid is the residue mutated with the highest frequency, whereas tryptophan is highly conserved. "Hot spot" mutation regions are mainly assigned to β-strands B, C, and D. This manuscript also reviews the protein aggregation models that have been proposed for TTR amyloid fibril formation and the transient conformational states that convert native TTR into aggregation-prone molecular species. Finally, it compiles the various in vitro TTR aggregation protocols currently in use for research and drug development purposes. In short, this article reviews and discusses TTR mutagenesis and amyloidogenesis, and their implications in disease onset.

Development of Benziodarone Analogues with Enhanced Potency for Selective Binding to Transthyretin in Human Plasma

Transthyretin amyloidosis is a fatal disorder caused by transthyretin amyloid aggregation. Stabilizing the native structure of transthyretin is an effective approach to inhibit amyloid aggregation. To develop kinetic stabilizers of transthyretin, it is crucial to explore compounds that selectively bind to transthyretin in plasma. Our recent findings demonstrated that the uricosuric agent benziodarone selectively binds to transthyretin in plasma. Here, we report the development of benziodarone analogues with enhanced potency for selective binding to transthyretin in plasma compared to benziodarone. These analogues featured substituents of chlorine, bromine, iodine, a methyl group, or a trifluoromethyl group, at the 4-position of the benzofuran ring. X-ray crystal structure analysis revealed that CH···O hydrogen bonds and a halogen bond are important for the binding of the compounds to the thyroxine-binding sites. The bioavailability of benziodarone analogues with 4-Br, 4-Cl, or 4-CH3 was comparable to that of tafamidis, a current therapeutic agent for transthyretin amyloidosis.

Hereditary transthyretin amyloidosis: a comprehensive review with a focus on peripheral neuropathy

Amyloidoses represent a group of diseases characterized by the pathological accumulation in the extracellular area of insoluble misfolded protein material called "amyloid". The damage to the tissue organization and the direct toxicity of the amyloidogenic substrates induce progressive dysfunctions in the organs involved. They are usually multisystem diseases involving several vital organs, such as the peripheral nerves, heart, kidneys, gastrointestinal tract, liver, skin, and eyes. Transthyretin amyloidosis (ATTR) is related to abnormalities of transthyretin (TTR), a protein that acts as a transporter of thyroxine and retinol and is produced predominantly in the liver. ATTR is classified as hereditary (ATTRv) and wild type (ATTRwt). ATTRv is a severe systemic disease of adults caused by mutations in the TTR gene and transmitted in an autosomal dominant manner with incomplete penetrance. Some pathogenic variants in TTR are preferentially associated with a neurological phenotype (progressive peripheral sensorimotor polyneuropathy); others are more frequently associated with restrictive heart failure. However, many mutations express a mixed phenotype with neurological and cardiological involvement. ATTRv is now a treatable disease. A timely and definite diagnosis is essential in view of the availability of effective therapies that have revolutionized the management of affected patients. The purpose of this review is to familiarize the clinician with the disease and with the correct diagnostic pathways in order to obtain an early diagnosis and, consequently, the possibility of an adequate treatment.

Clinical considerations in early-onset cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is an important cerebral small vessel disease associated with brain haemorrhage and cognitive change. The commonest form, sporadic amyloid-β CAA, usually affects people in mid- to later life. However, early-onset forms, though uncommon, are increasingly recognized and may result from genetic or iatrogenic causes that warrant specific and focused investigation and management. In this review, we firstly describe the causes of early-onset CAA, including monogenic causes of amyloid-β CAA (APP missense mutations and copy number variants; mutations of PSEN1 and PSEN2) and non-amyloid-β CAA (associated with ITM2B, CST3, GSN, PRNP and TTR mutations), and other unusual sporadic and acquired causes including the newly-recognized iatrogenic subtype. We then provide a structured approach for investigating early-onset CAA, and highlight important management considerations. Improving awareness of these unusual forms of CAA amongst healthcare professionals is essential for facilitating their prompt diagnosis, and an understanding of their underlying pathophysiology may have implications for more common, late-onset, forms of the disease.

Psychosis Caused by a Somatic Condition: How to Make the Diagnosis? A Systematic Literature Review

BACKGROUND

First episode of psychosis (FEP) is a clinical condition that usually occurs during adolescence or early adulthood and is often a sign of a future psychiatric disease. However, these symptoms are not specific, and psychosis can be caused by a physical disease in at least 5% of cases. Timely detection of these diseases, the first signs of which may appear in childhood, is of particular importance, as a curable treatment exists in most cases. However, there is no consensus in academic societies to offer recommendations for a comprehensive medical assessment to eliminate somatic causes.

METHODS

We conducted a systematic literature search using a two-fold research strategy to: (1) identify physical diseases that can be differentially diagnosed for psychosis; and (2) determine the paraclinical exams allowing us to exclude these pathologies.

RESULTS

We identified 85 articles describing the autoimmune, metabolic, neurologic, infectious, and genetic differential diagnoses of psychosis. Clinical presentations are described, and a complete list of laboratory and imaging features required to identify and confirm these diseases is provided.

CONCLUSION

This systematic review shows that most differential diagnoses of psychosis should be considered in the case of a FEP and could be identified by providing a systematic checkup with a laboratory test that includes ammonemia, antinuclear and anti-NMDA antibodies, and HIV testing; brain magnetic resonance imaging and lumbar puncture should be considered according to the clinical presentation. Genetic research could be of interest to patients presenting with physical or developmental symptoms associated with psychiatric manifestations.

Benziodarone and 6-hydroxybenziodarone are potent and selective inhibitors of transthyretin amyloidogenesis

Transthyretin amyloidosis is a progressive systemic disorder that is caused by the amyloid deposition of transthyretin in various organs. Stabilization of the native transthyretin is an effective strategy for the treatment of transthyretin amyloidosis. In this study we demonstrate that the clinically used uricosuric agent benziodarone is highly effective to stabilize the tetrameric structure of transthyretin. An acid-induced aggregation assay showed that benziodarone had strong inhibitory activity similar to that of tafamidis, which is currently used as a therapeutic agent for transthyretin amyloidosis. Moreover, a possible metabolite, 6-hydroxybenziodarone, retained the strong amyloid inhibitory activity of benziodarone. An ex vivo competitive binding assay using a fluorogenic probe showed that benziodarone and 6-hydroxybenziodarone were highly potent for selective binding to transthyretin in human plasma. An X-ray crystal structure analysis revealed that the halogenated hydroxyphenyl ring was located at the entrance of the thyroxine binding channel of transthyretin and that the benzofuran ring was located in the inner channel. These studies suggest that benziodarone and 6-hydroxybenziodarone would potentially be effective against transthyretin amyloidosis.

Cardiac transplantation in transthyretin amyloid cardiomyopathy: Outcomes from three decades of tertiary center experience

Aims

Transthyretin cardiac amyloidosis (ATTR-CM) is a progressive and fatal cardiomyopathy. Treatment options in patients with advanced ATTR-CM are limited to cardiac transplantation (CT). Despite case series demonstrating comparable outcomes with CT between patients with ATTR-CM and non-amyloid cardiomyopathies, ATTR-CM is considered to be a contraindication to CT in some centers, partly due to a perceived risk of amyloid recurrence in the allograft. We report long-term outcomes of CT in ATTR-CM at two tertiary centers.

Materials and methods and Results

We retrospectively evaluated ATTR-CM patients across two tertiary centers who underwent transplantation between 1990 and 2020. Pre-transplantation characteristics were determined and outcomes were compared with a cohort of non-transplanted ATTR-CM patients. Fourteen (12 male, 2 female) patients with ATTR-CM underwent CT including 11 with wild-type ATTR-CM and 3 with variant ATTR-CM (ATTRv). Median age at CT was 62 years and median follow up post-CT was 66 months. One, three, and five-year survival was 100, 92, and 90%, respectively and the longest surviving patient was Censored > 19 years post CT. No patients had recurrence of amyloid in the cardiac allograft. Four patients died, including one with ATTRv-CM from complications of leptomeningeal amyloidosis. Survival among the cohort of patients who underwent CT was significantly prolonged compared to UK patients with ATTR-CM generally (p < 0.001) including those diagnosed under age 65 years (p = 0.008) or with early stage cardiomyopathy (p < 0.001).

Conclusion

CT is well-tolerated, restores functional capacity and improves prognosis in ATTR-CM. The risk of amyloid recurrence in the cardiac allograft appears to be low.

Chlorinated Naringenin Analogues as Potential Inhibitors of Transthyretin Amyloidogenesis

Misfolding and aggregation of transthyretin are implicated in the fatal systemic disease known as transthyretin amyloidosis. Here, we report the development of a naringenin derivative bearing two chlorine atoms that will be efficacious for preventing aggregation of transthyretin in the eye. The amyloid inhibitory activity of the naringenin derivative was as strong as that of tafamidis, which is the first therapeutic agent targeting transthyretin in the plasma. X-ray crystal structures of the compounds in complex with transthyretin demonstrated that the naringenin derivative with one chlorine bound to the thyroxine-binding site of transthyretin in the forward mode and that the derivative with two chlorines bound to it in the reverse mode. An ex vivo competitive binding assay showed that naringenin derivatives exhibited more potent binding than tafamidis in the plasma. Furthermore, an in vivo pharmacokinetic study demonstrated that the dichlorinated derivative was significantly delivered to the eye.

The yeast molecular chaperone, Hsp104, influences transthyretin aggregate formation

Patients with the fatal disorder Transthyretin Amyloidosis (ATTR) experience polyneuropathy through the progressive destruction of peripheral nervous tissue. In these patients, the transthyretin (TTR) protein dissociates from its functional tetrameric structure, misfolds, and aggregates into extracellular amyloid deposits that are associated with disease progression. These aggregates form large fibrillar structures as well as shorter oligomeric aggregates that are suspected to be cytotoxic. Several studies have shown that these extracellular TTR aggregates enter the cell and accumulate intracellularly, which is associated with increased proteostasis response. However, there are limited experimental models to study how proteostasis influences internalized TTR aggregates. Here, we use a humanized yeast system to recapitulate intracellular TTR aggregating protein in vivo. The yeast molecular chaperone Hsp104 is a disaggregase that has been shown to fragment amyloidogenic aggregates associated with certain yeast prions and reduce protein aggregation associated with human neurogenerative diseases. In yeast, we found that TTR forms both SDS-resistant oligomers and SDS-sensitive large molecular weight complexes. In actively dividing cultures, Hsp104 has no impact on oligomeric or large aggregate populations, yet overexpression of Hsp104 is loosely associated with an increase in overall aggregate size. Interestingly, a potentiating mutation in the middle domain of Hsp104 consistently results in an increase in overall TTR aggregate size. These data suggest a novel approach to aggregate management, where the Hsp104 variant shifts aggregate populations away from toxic oligomeric species to more inert larger aggregates. In aged cultures Hsp104 overexpression has no impact on TTR aggregation profiles suggesting that these chaperone approaches to shift aggregate populations are not effective with age, possibly due to proteostasis decline.

Surgically treated intradural spinal manifestation of hereditary amyloidogenic transthyretin amyloidosis - A case report and scoping review of the literature

Introduction

Hereditary transthyretin amyloidosis (ATTRv) is an autosomal-dominant disorder, where a TTR mutations lead to amyloid fibril deposits in tissues and consecutively alter organ function. ATTRv is a multisystemic disorder with a heterogeneous clinical presentation. Spinal leptomeningeal depositions are described only scarcely in the literature.

Research question

We present a rare case of surgically treated intradural, extra-medullary amyloidosis with respective clinical, diagnostic and surgical features to raise awareness of this rare entity.

Material and methods

Clinical, radiological and operative characteristics were retrieved from the electronical patient management system. Additionally, a scoping literature review on leptomeningeal spinal manifestations of ATTRv was performed.

Results

A 45-year-old man with a known ATTRv presented with gait disturbance and paresis of the lower extremities. He had been treated with the siRNA therapeutical Patisiran for 13 months under which his symptoms worsened. An MRI of the spine revealed spinal cord compression with myelopathy at the level of T2 with anterior dislocation of the spinal cord due to an intradural, extramedullary lesion. A laminectomy and opening of the dura with a complete resection of the lesion was performed. The histological examination of the biopsy showed amyloid deposits. At six-month follow-up the patient showed complete normalization of the paresis, gait, sensory and urinary disturbances and resumed his work.

Discussion and conclusion

Spinal leptomeningeal deposition of amyloid is a rare occurrence within the framework of ATTRv. Micro-neurosurgical complete resection of the lesion is feasible in patients with preoperative myelopathic symptoms and resulted in complete symptom relief in this case.

An Exploratory Study of Cognitive Involvement in Hereditary Transthyretin Amyloidosis

OBJECTIVES

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis is an autosomal dominant disorder caused by mutations of the transthyretin (TTR) gene. The mutant ATTRv protein causes a systemic accumulation of amyloid fibrils in various organs. TTR is an important protein in the central nervous system physiology for the maintenance of normal cognitive process during aging, amidated neuropeptide processing, and nerve regeneration. The neuroprotective effect of transthyretin has been widely documented in animal models. Cognitive consequences of the mutant TTR in hereditary ATTRv amyloidosis patients remain still to be elucidated. We designed this study to investigate the cognitive involvement in ATTRv amyloidosis.

METHODS

Detailed neuropsychological tests and cranial MRIs were performed. Biomarkers including amyloid beta 1-42, total tau, and phosphorylated tau were investigated in the cerebrospinal fluid samples.

RESULTS

Median age of the cohort was 52 years (ranges 34-72). Neuropsychological assessment results were compatible with impaired executive functions (in all patients except one with only bilateral carpal tunnel syndrome, long-term visual and long-term verbal memory (severe in four patients and moderate in one). Visuospatial judgment and perception were impaired in six. Mean cerebrospinal fluid Aβ1-42 (pg/ml) was 878.0 ± 249.5 in patients with cortical atrophyin MRI whereas 1210.0 ± 45.9 in patients without any cortical atrophy. Cranial MRI showed cortical atrophy in six patients (6/10).

CONCLUSION

Our data showed the significance of the TTR protein in cognitive functions and highlighted the importance of the close follow-up of cognitive functions in ATTRv amyloidosis patients.

CNS Involvement in Hereditary Transthyretin Amyloidosis

Hereditary transthyretin amyloidosis (ATTRv amyloidosis) is predominantly a disease of the peripheral nerves, heart, kidney and eye. CNS involvement has been a marginal issue in research and the clinical setting, until recently. Growing evidence shows that leptomeningeal amyloid accumulation is frequent and present from early stages of ATTRv amyloidosis. Several recent studies show CNS symptoms arise as a common late complication in patients with the V30M mutation, after at least 14 years of symptomatic peripheral nerve disease. Conversely, in non-V30M patients, there are several descriptions, mostly case reports, of patients presenting with severe phenotypes of ocular and CNS dysfunction (oculoleptomeningeal amyloidosis), with little systemic involvement. This phenotype is found in rare families worldwide, associated with at least 14 mutations.In both patients with late and early onset CNS dysfunction, symptoms include transient focal neurological episodes, haemorrhagic and ischemic stroke, cognitive decline and cranial nerve dysfunction. Pathologically, there is severe amyloid deposition in the leptomeninges and cerebral amyloid angiopathy of leptomeningeal and penetrating vessels. These amyloid aggregates are formed mostly by CSF produced TTR and seem resistant to the available ATTRv therapies that increase the stability or reduce the production of plasma TTR. This indicates that CNS involvement will become a meaningful issue in patient management in upcoming years.

Current Review of Leptomeningeal Amyloidosis Associated With Transthyretin Mutations

INTRODUCTION

Leptomeningeal amyloidosis (LA) represents a rare subtype of familial transthyretin (TTR) amyloidosis, characterized by deposition of amyloid in cranial and spinal leptomeninges. Of >120 TTR mutations identified, few have been associated with LA.

CASE REPORT

A 27-year-old male presented with a 2-year history of progressive symptoms including cognitive decline and right-sided weakness and numbness. Cerebrospinal fluid (CSF) analyses demonstrated high protein level. Gadolinium-enhanced magnetic resonance imaging (MRI) revealed extensive leptomeningeal enhancement over the surface of the brain and spinal cord. Pathologic analyses revealed a TTR mutation c.113A>G (p.D38G).

REVIEW SUMMARY

Fifteen mutations and genotype-phenotype correlation of 72 LA patients have been summarized to provide an overview of LA associated with transthyretin mutations. The mean age of clinical onset was 44.9 years and the neurological symptoms primarily included cognitive impairment, headache, ataxia seizures and hearing, visual loss. CSF analysis showed elevated high CSF protein level and MRI revealed extensive leptomeningeal enhancement.

CONCLUSION

Clinicians should be aware of this rare form of familial transthyretin amyloidosis as well as its typical MRI enhancement and high CSF protein. The important role of biopsy, genetic testing and the potential early diagnosis value of contrast MRI were suggested. Early recognition of these characteristics is important to provide misdiagnosis and shorten the time before correct diagnosis. These findings expand the phenotypic spectrum of TTR gene and have implications for the diagnosis, treatment, and systematic study of LA.

Inhibitory activities of anthraquinone and xanthone derivatives against transthyretin amyloidogenesis

Transthyretin is a tetrameric protein which functions as a transporter of thyroxine and retinol-binding protein. Misfolding and amyloid aggregation of transthyretin are known to cause wild-type and hereditary transthyretin amyloidosis. Stabilization of the transthyretin tetramer by low molecular weight compounds is an efficacious strategy to inhibit the aggregation pathway in the amyloidosis. Here, we investigated the inhibitory activities of anthraquinone and xanthone derivatives against amyloid aggregation, and found that xanthone-2-carboxylic acid with one chlorine or methyl group has strong inhibitory activity comparable with that of diflunisal, which is one of the best known stabilizers of transthyretin. X-ray crystallographic structures of transthyretin in complex with the compounds revealed that the introduction of chlorine, which is buried in a hydrophobic region, is important for the strong inhibitory effect of the stabilizer against amyloidogenesis. An in vitro absorption, distribution, metabolism and elimination (ADME) study and in vivo pharmacokinetic study demonstrated that the compounds have drug-like features, suggesting that they have potential as therapeutic agents to stabilize transthyretin.

Amyloidosis in Heart Failure

PURPOSE

Amyloidosis represents an increasingly recognized but still frequently missed cause of heart failure. In the light of many effective therapies for light chain (AL) amyloidosis and promising new treatment options for transthyretin (ATTR) amyloidosis, awareness among caregivers needs to be raised to screen for amyloidosis as an important and potentially treatable differential diagnosis. This review outlines the diversity of cardiac amyloidosis, its relation to heart failure, the diagnostic algorithm, and therapeutic considerations that should be applied depending on the underlying type of amyloidosis.

RECENT FINDINGS

Non-biopsy diagnosis is feasible in ATTR amyloidosis in the absence of a monoclonal component resulting in higher detection rates of cardiac ATTR amyloidosis. Biomarker-guided staging systems have been updated to facilitate risk stratification according to currently available biomarkers independent of regional differences, but have not yet prospectively been tested. Novel therapies for hereditary and wild-type ATTR amyloidosis are increasingly available. The complex treatment options for AL amyloidosis are improving continuously, resulting in better survival and quality of life. Mortality in advanced cardiac amyloidosis remains high, underlining the importance of early diagnosis and treatment initiation. Cardiac amyloidosis is characterized by etiologic and clinical heterogeneity resulting in a frequently delayed diagnosis and an inappropriately high mortality risk. New treatment options for this hitherto partially untreatable condition have become and will become available, but raise challenges regarding their implementation. Referral to specialized centers providing access to extensive and targeted diagnostic investigations and treatment initiation may help to face these challenges.

Top Common Differentially Expressed Genes in the Epileptogenic Nucleus of Two Strains of Rodents Susceptible to Audiogenic Seizures: WAR and GASH/Sal

The Wistar Audiogenic Rat (WAR) and the Genetic Audiogenic Seizure Hamster from Salamanca (GASH/Sal) strains are audiogenic epilepsy models, in which seizures are triggered by acoustic stimulation. These strains were developed by selective reproduction and have a genetic background with minimal or no variation. In the current study, we evaluated the transcriptome of the inferior colliculus, the epileptogenic nucleus, of both audiogenic models, in order to get insights into common molecular aspects associated to their epileptic phenotype. Based on GASH/Sal RNA-Seq and WAR microarray data, we performed a comparative analysis that includes selection and functional annotation of differentially regulated genes in each model, transcriptional evaluation by quantitative reverse transcription PCR of common genes identified in both transcriptomes and immunohistochemistry. The microarray data revealed 71 genes with differential expression in WAR, and the RNA-Seq data revealed 64 genes in GASH/Sal, showing common genes in both models. Analysis of transcripts showed that Egr3 was overexpressed in WAR and GASH/Sal after audiogenic seizures. The Npy, Rgs2, Ttr, and Abcb1a genes presented the same transcriptional profile in the WAR, being overexpressed in the naïve and stimulated WAR in relation to their controls. Npy appeared overexpressed only in the naïve GASH/Sal compared to its control, while Rgs2 and Ttr genes appeared overexpressed in naïve GASH/Sal and overexpressed after audiogenic seizure. No statistical difference was observed in the expression of Abcb1a in the GASH/Sal model. Compared to control animals, the immunohistochemical analysis of the inferior colliculus showed an increased immunoreactivity for NPY, RGS2, and TTR in both audiogenic models. Our data suggest that WAR and GASH/Sal strains have a difference in the timing of gene expression after seizure, in which GASH/Sal seems to respond more quickly. The transcriptional profile of the Npy, Rgs2, and Ttr genes under free-seizure conditions in both audiogenic models indicates an intrinsic expression already established in the strains. Our findings suggest that these genes may be causing small changes in different biological processes involved in seizure occurrence and response, and indirectly contributing to the susceptibility of the WAR and GASH/Sal models to audiogenic seizures.

The Amyloid-Tau-Neuroinflammation Axis in the Context of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is typified by the cerebrovascular deposition of amyloid. Currently, there is no clear understanding of the mechanisms underlying the contribution of CAA to neurodegeneration. Despite the fact that CAA is highly associated with the accumulation of Aβ, other types of amyloids have been shown to associate with the vasculature. Interestingly, in many cases, vascular amyloidosis has been associated with an active immune response and perivascular deposition of hyperphosphorylated tau. Despite the fact that in Alzheimer’s disease (AD) a major focus of research has been the understanding of the connection between parenchymal amyloid plaques, tau aggregates in the form of neurofibrillary tangles (NFTs), and immune activation, the contribution of tau and neuroinflammation to neurodegeneration associated with CAA remains understudied. In this review, we discussed the existing evidence regarding the amyloid diversity in CAA and its relation to tau pathology and immune response, as well as the possible contribution of molecular and cellular mechanisms, previously associated with parenchymal amyloid in AD and AD-related dementias, to the pathogenesis of CAA. The detailed understanding of the “amyloid-tau-neuroinflammation” axis in the context of CAA could open the opportunity to develop therapeutic interventions for dementias associated with CAA that are currently being proposed for AD and AD-related dementias.

Pharyngo-laryngeal involvement in systemic amyloidosis with cardiac involvement: a prospective observational study

Background: Systemic amyloidosis with cardiac involvement (CA) is a severe disease caused by the aggregation of misfolded proteins infiltrating organs and tissues and leading to their dysfunction. No study has yet focused on potential pharyngo-laryngeal impairments associated to CA. Our objective was to define its prevalence and describe pharyngo-laryngeal involvement patterns in a population with CA (light chain: AL, wild-type transthyretin: ATTRwt, variant transthyretin: ATTRv). Methods: Consecutive patients with a confirmed diagnosis of CA were prospectively investigated for pharyngo-laryngeal involvement. This included questionnaires on symptoms of dysphonia/dysphagia and quality of life Voice Handicap Index (VHI). In cases of dysphonia, a nasofibroscopy was performed to evaluate potential laryngeal organic lesions of amyloid infiltration and induced laryngeal dysfunction (mobility, glottic air leak). In cases of dysphagia, Video Endoscopy Swallowing Study (VESS) was performed to evaluate the presence of hypopharyngeal pooling at rest and during swallowing and the time of swallowing 80 ml of water. Results: Ninety-five CA patients were enrolled, of whom 19 were ATTRv, 36 AL and 40 ATTRwt. Their mean age was 73.8 ± 9.2 years and the sex ratio was 2.6 in favor of men. Dysphagia was reported in 17% of the patients and 40% had more specific oropharyngeal symptoms (food sticking, regurgitation, change in dietary habits), preceding the CA diagnosis by 7 (0-24) months. Recent weight loss was reported in 60% of the patients (mean loss of 10 ± 6.3 kg). VESS showed functional swallowing impairment in only 4 patients without any macroscopic organic lesion. Dysphonia was reported in 36% of the patients (44% and 47% in AL and ATTRv sub-groups, respectively) of whom 40% had functional or organic laryngeal abnormality (14% of vocal fold mobility dysfunction and 26% of abnormal mucosa) without any macroscopic-specific lesions of amyloid infiltration in these patients. Conclusions: This prospective study suggests, for the first time, that amyloid associated with CA could infiltrate the various anatomical structures of the pharyngo-larynx, responsible for functional impairment and potential nutritional depletion and poor quality of life.

Association between hearing loss and hereditary ATTR amyloidosis

Background: Hereditary transthyretin (TTR) related amyloidosis (ATTRv) is a life-threatening condition, which can potentially affect all organs. The objective was to identify the hearing status of patients with cardiac ATTRv and describe their audiological pattern. Methods: Nineteen patients with confirmed diagnosis of ATTRv cardiac amyloidosis (CA) underwent otoscopy and audiological tests, including pure tone and speech audiometry. Results: 74% were male, with a mean age of 72 ± 1.8 years. The main mutations were Val122Ile (n = 7) and Val30Met (n = 6). Objective hearing loss was detected in 17 patients (89%), whereas only 37% complained of hearing loss. ATTRv patients presented a different audiometric profile compared to patients of the same age with presbycusis: a higher prevalence and worse hearing thresholds compared to age-related expectations (ISO). Hearing loss affected all frequencies with, unexpectedly, mixed or conductive hearing loss (35%). According to the type of mutation, there was an increased rate of sensorineural or mixed/conductive hearing loss. Conclusions: the present study indicates that hearing loss is more prevalent and worse in patients with ATTRv amyloidosis than in the general population, while mostly clinically under-estimated. It suggests that ATTRv deposits could infiltrate the various anatomical structures of the inner and mild ear.

Orthostatic hypotension in hereditary transthyretin amyloidosis: epidemiology, diagnosis and management

Purpose

Neurogenic orthostatic hypotension is a prominent and disabling manifestation of autonomic dysfunction in patients with hereditary transthyretin (TTR) amyloidosis affecting an estimated 40–60% of patients, and reducing their quality of life. We reviewed the epidemiology and pathophysiology of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis, summarize non-pharmacologic and pharmacological treatment strategies and discuss the impact of novel disease-modifying treatments such as transthyretin stabilizers (diflunisal, tafamidis) and RNA interference agents (patisiran, inotersen).

Methods

Literature review.

Results

Orthostatic hypotension in patients with hereditary transthyretin amyloidosis can be a consequence of heart failure due to amyloid cardiomyopathy or volume depletion due to diarrhea or drug effects. When none of these circumstances are apparent, orthostatic hypotension is usually neurogenic, i.e., caused by impaired norepinephrine release from sympathetic postganglionic neurons, because of neuronal amyloid fibril deposition.

Conclusions

When recognized, neurogenic orthostatic hypotension can be treated. Discontinuation of potentially aggravating medications, patient education and non-pharmacologic approaches should be applied first. Droxidopa (Northera^®), a synthetic norepinephrine precursor, has shown efficacy in controlled trials of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis and is now approved in the US and Asia. Although they may be useful to ameliorate autonomic dysfunction in hereditary TTR amyloidosis, the impact of disease-modifying treatments on neurogenic orthostatic hypotension is still uninvestigated.

Familial Amyloid Polyneuropathy

Transthyretin-related familial amyloid polyneuropathy (TTR-FAP) is a life-threatening disease caused by the accumulation of amyloidogenic transthyretin (TTR) protein in tissues. Mutations in TTR gene destabilize TTR protein to misfold from its native tetramer form to amyloidogenic monomer form. In endemic countries, TTR-FAP presents with length-dependent small fiber neuropathy, however in non-endemic countries clinical features can be highly variable. Genetic testing for TTR gene is mandatory for the diagnosis. Demonstrating amyloid deposits in tissues may be necessary for distinguishing symptomatic patients from asymptomatic carriers. Routine follow-up should include a wide range of tests to demonstrate systemic involvement. In recent years, treatment of TTR-FAP has significantly improved with new therapeutic approaches. TTR stabilizers and TTR-gene silencing drugs prevent the progression of the disease. Monoclonal antibodies that target amyloid deposits are currently under development. Early initiation of the treatment is important for better functional outcome.

Resting regional brain activity correlates of verbal learning deficit in major depressive disorder

Memory deficits are reported in major depressive disorder (MDD). Prefrontal cortical and mesiotemporal cortical (MTC)/subcortical regions are involved in the Buschke Selective Reminding Task (SRT), a verbal list-learning task. To determine whether depression-related changes in resting brain metabolism explain (in part) the deficits in SRT performance found in MDD, statistical correlation maps were calculated between SRT total recall score (TR) and relative regional cerebral metabolic rate for glucose (rCMRglu), measured by [¹⁸F]-flourodeoxyglucose (FDG) positron emission tomography (PET), in unmedicated, depressed MDD patients (N = 29). Subsequently, to explore hypothesized loss of top-down control in MDD, we compared the correlations between rCMRglu of SRT-relevant regions of the dorsolateral prefrontal cortex (dlPFC) and amygdala in a larger cohort of MDD (N = 60; 29 inclusive) versus healthy controls (HC) (N = 43). SRT performance of patients is on average 0.5 standard deviation below published normative mean. TR and rCMRglu positively correlate in bilateral dorsomedial PFC, dlPFC, dorsal anterior cingulate; negatively correlate in bilateral MTC/subcortical regions, and cerebellum. rCMRglu in dlPFC correlates negatively with that in amygdala in HC but not in MDD. Depression-related changes present in FDG-PET measured resting brain activity may be in part responsible for memory deficit found in MDD.

Cerebrovascular disorders associated with genetic lesions

Cerebrovascular disorders are underlain by perturbations in cerebral blood flow and abnormalities in blood vessel structure. Here, we provide an overview of the current knowledge of select cerebrovascular disorders that are associated with genetic lesions and connect genomic findings with analyses aiming to elucidate the cellular and molecular mechanisms of disease pathogenesis. We argue that a mechanistic understanding of genetic (familial) forms of cerebrovascular disease is a prerequisite for the development of rational therapeutic approaches, and has wider implications for treatment of sporadic (non-familial) forms, which are usually more common.

The identification of a transthyretin variant p.D38G in a Chinese family with early-onset leptomeningeal amyloidosis

Familial amyloid polyneuropathies (FAPs) are life-threatening, autosomal dominant diseases resulting, in most instances, from transthyretin gene (TTR) variants. A small number of TTR variants lead to leptomeningeal amyloidosis (LA), which is a rare FAP subtype with late-onset central nervous system (CNS) impairment symptoms. Previous studies suggest that LA's CNS selectivity was due to complete endoplasmic reticulum-associated degradation of highly destabilized mutants in peripheral tissues. LA's later age at onset (AAO) was due to lower choroid plexus secretory efficacy. This study reports on a family with LA, including six symptomatic and three presymptomatic members. The LA diagnosis was confirmed by leptomeningeal enhancement on contrast MRI, elevated cerebrospinal fluid protein levels, and positive Congo red staining. The predominant symptoms included headaches, dizziness, vomiting, hallucinations, and cognitive impairments which associated with obstructive hydrocephalus. The TTR p.D38G variant with the lowest secretory efficacy was identified as the genetic cause by whole exome sequencing. The family had a statistically significantly earlier mean AAO of 31.3 ± 7.4 (p = 0.001). These uncommon phenotypes indicate unknown factors influencing the progress of CNS impairment via TTR mutants. Medical imaging examinations suggest the potential early diagnosis value of contrast MRI and the importance of ependyma involvement in LA. LA genetic and clinical data were reviewed and summarized. These findings expand the FAPs' phenotypic spectrum and are valuable in FAP diagnosis, treatment, and further research.

Current and future treatment of amyloid diseases

There are more than 30 human proteins whose aggregation appears to cause degenerative maladies referred to as amyloid diseases or amyloidoses. These disorders are named after the characteristic cross-β-sheet amyloid fibrils that accumulate systemically or are localized to specific organs. In most cases, current treatment is limited to symptomatic approaches and thus disease-modifying therapies are needed. Alzheimer's disease is a neurodegenerative disorder with extracellular amyloid β-peptide (Aβ) fibrils and intracellular tau neurofibrillary tangles as pathological hallmarks. Numerous clinical trials have been conducted with passive and active immunotherapy, and small molecules to inhibit Aβ formation and aggregation or to enhance Aβ clearance; so far such clinical trials have been unsuccessful. Novel strategies are therefore required and here we will discuss the possibility of utilizing the chaperone BRICHOS to prevent Aβ aggregation and toxicity. Type 2 diabetes mellitus is symptomatically treated with insulin. However, the underlying pathology is linked to the aggregation and progressive accumulation of islet amyloid polypeptide as fibrils and oligomers, which are cytotoxic. Several compounds have been shown to inhibit islet amyloid aggregation and cytotoxicity in vitro. Future animal studies and clinical trials have to be conducted to determine their efficacy in vivo. The transthyretin (TTR) amyloidoses are a group of systemic degenerative diseases compromising multiple organ systems, caused by TTR aggregation. Liver transplantation decreases the generation of misfolded TTR and improves the quality of life for a subgroup of this patient population. Compounds that stabilize the natively folded, nonamyloidogenic, tetrameric conformation of TTR have been developed and the drug tafamidis is available as a promising treatment.

Cerebral amyloid angiopathy in posttransplant patients with hereditary ATTR amyloidosis

OBJECTIVE

To investigate the prevalence and clinical features of posttransplant CNS symptoms in patients with hereditary ATTR amyloidosis and their Pittsburgh compound B (PiB)-PET imaging correlates.

METHODS

We monitored prevalence and type of CNS symptoms in 53 consecutive posttransplant patients with hereditary ATTR amyloidosis. (11)C-PiB-PET was performed in 15 patients with various disease durations. We also analyzed pathologic and biochemical characteristics of ATTR amyloid deposition in the brain of a posttransplant patient.

RESULTS

Transient focal neurologic episodes (TFNEs) attributed to ATTR-type cerebral amyloid angiopathy (CAA) were found in 11.3% of posttransplant hereditary ATTR amyloidosis patients. TFNE occurred on average 16.8 years after onset of the disease. Patients with longer duration of illness (≥10 years) showed increased (11)C-PiB retention in the brain. The (11)C-PiB accumulation pattern in hereditary ATTR amyloidosis was unique and different from those in Alzheimer disease or Aβ-type CAA. In the autopsy case, ATTR amyloid deposition was mainly localized to leptomeningeal vessels and leptomeninges of the brain. Amyloid fibrils in the brain were almost completely composed of variant transthyretin (TTR).

CONCLUSIONS

TFNE due to ATTR-type CAA occurred frequently in posttransplant patients with long disease durations. (11)C-PiB-PET is a useful diagnostic tool for ATTR-type CAA. ATTR amyloid deposition in the CNS, as measured by PiB-PET, was detected approximately 10 years before onset of TFNE.

Comparative gene expression study of the vestibular organ of the Igf1 deficient mouse using whole-transcript arrays

The auditory and vestibular organs form the inner ear and have a common developmental origin. Insulin like growth factor 1 (IGF-1) has a central role in the development of the cochlea and maintenance of hearing. Its deficiency causes sensorineural hearing loss in man and mice. During chicken early development, IGF-1 modulates neurogenesis of the cochleovestibular ganglion but no further studies have been conducted to explore the potential role of IGF-1 in the vestibular system. In this study we have compared the whole transcriptome of the vestibular organ from wild type and Igf1(-/-) mice at different developmental and postnatal times. RNA was prepared from E18.5, P15 and P90 vestibular organs of Igf1(-/-) and Igf1(+/+) mice and the transcriptome analysed in triplicates using Affymetrix(®) Mouse Gene 1.1 ST Array Plates. These plates are whole-transcript arrays that include probes to measure both messenger (mRNA) and long intergenic non-coding RNA transcripts (lincRNA), with a coverage of over 28 thousand coding transcripts and over 7 thousands non-coding transcripts. Given the complexity of the data we used two different methods VSN-RMA and mmBGX to analyse and compare the data. This is to better evaluate the number of false positives and to quantify uncertainty of low signals. We identified a number of differentially expressed genes that we described using functional analysis and validated using RT-qPCR. The morphology of the vestibular organ did not show differences between genotypes and no evident alterations were observed in the vestibular sensory areas of the null mice. However, well-defined cellular alterations were found in the vestibular neurons with respect their number and size. Although these mice did not show a dramatic vestibular phenotype, we conducted a functional analysis on differentially expressed genes between genotypes and across time. This was with the aim to identify new pathways that are involved in the development of the vestibular organ as well as pathways that maybe affected by the lack of IGF-1 and be associated to the morphological changes of the vestibular neurons that we observed in the Igf1(-/-) mice.

Neuropathologic analysis of Tyr69His TTR variant meningovascular amyloidosis with dementia

Transthyretin/TTR gene mutations usually cause systemic amyloidotic diseases. Few TTR variants preferentially affect the central nervous system, manifesting as oculoleptomeningeal amyloidosis. Patients with TTR meningovascular amyloidosis often show dementia, however the neuropathologic features of dementia in these cases have not been elucidated. We report the neuropathologic findings from a brain autopsy of a 72-year-old man with the rare Tyr69His (Y69H) TTR gene variant, dementia and ataxia. Severe amyloid deposits were observed in the leptomeninges and in a subpial and subependymal distribution. Mass spectrometry analysis demonstrated that the amyloid deposits were comprised of over 80 % of the variant TTR. TTR was undetectable by mass spectrometry in the neocortex subjacent to the subpial amyloid deposits. Subpial TTR amyloid deposits were associated with brisk superficial reactive gliosis and siderosis in the neocortex and cerebellar cortex. Subependymal TTR amyloid deposits were associated with subjacent myelin pallor in the hippocampal outflow tract structures including the alveus, fimbria and fornix. Phospho-tau immunostains demonstrated transentorhinal-stage neurofibrillary degeneration (Braak stage II) which, in the absence of neocortical amyloid-beta and neuritic plaques, was indicative of primary age-related tauopathy (PART). However, distinctive phospho-tau aggregates were observed subjacent to the subpial TTR amyloid deposits in all regions of the neocortex, including the primary motor and striate cortices, suggesting a potential link between TTR amyloid and neocortical tauopathy. Our report reveals novel insights into the potential neuropathologic substrates of dementia in variant TTR amyloidosis that need to be investigated in larger autopsy series.

CNS involvement in V30M transthyretin amyloidosis: clinical, neuropathological and biochemical findings

OBJECTIVES

Since liver transplant (LT) was introduced to treat patients with familial amyloid polyneuropathy carrying the V30M mutation (ATTR-V30M), ocular and cardiac complications have developed. Long-term central nervous system (CNS) involvement was not investigated. Our goals were to: (1) identify and characterise focal neurological episodes (FNEs) due to CNS dysfunction in ATTR-V30M patients; (2) characterise neuropathological features and temporal profile of CNS transthyretin amyloidosis.

METHODS

We monitored the presence and type of FNEs in 87 consecutive ATTR-V30M and 35 non-ATTR LT patients. FNEs were investigated with CT scan, EEG and extensive neurovascular workup. MRI studies were not performed because all patients had cardiac pacemakers as part of the LT protocol. We characterised transthyretin amyloid deposition in the brains of seven ATTR-V30M patients, dead 3-13 years after polyneuropathy onset.

RESULTS

FNEs occurred in 31% (27/87) of ATTR-V30M and in 5.7% (2/35) of the non-ATTR transplanted patients (OR=7.0, 95% CI 1.5 to 33.5). FNEs occurred on average 14.6 years after disease onset (95% CI 13.3 to 16.0) in ATTR-V30M patients, which is beyond the life expectancy of non-transplanted ATTR-V30M patients (10.9, 95% CI 10.5 to 11.3). ATTR-V30M patients with FNEs had longer disease duration (OR=1.24; 95% CI 1.07 to 1.43), renal dysfunction (OR=4.65; 95% CI 1.20 to 18.05) and were men (OR=3.57; 95% CI 1.02 to 12.30). CNS transthyretin amyloidosis was already present 3 years after polyneuropathy onset and progressed from the meninges and its vessels towards meningocortical vessels and the superficial brain parenchyma, as disease duration increased.

CONCLUSIONS

Our findings indicate that CNS clinical involvement occurs in ATTR-V30M patients regardless of LT. Longer disease duration after LT can provide the necessary time for transthyretin amyloidosis to progress until it becomes clinically relevant. Highly sensitive imaging methods are needed to identify and monitor brain ATTR. Disease modifying therapies should consider brain TTR as a target.

Oculoleptomeningeal Amyloidosis associated with transthyretin Leu12Pro in an African patient

Oculoleptomeningeal amyloidosis is a rare manifestation of hereditary transthyretin (TTR) amyloidosis. Here, we present the first case of leptomeningeal amyloidosis associated with the TTR variant Leu12Pro mutation in an African patient. A 43-year-old right-handed Nigerian man was referred to our centre with rapidly progressive neurological decline. He presented initially with weight loss, confusion, fatigue, and urinary and erectile dysfunction. He then suffered recurrent episodes of slurred speech with right-sided weakness. He went on to develop hearing difficulties and painless paraesthesia. Neurological examination revealed horizontal gaze-evoked nystagmus, brisk jaw jerk, increased tone, brisk reflexes throughout and bilateral heel-shin ataxia. Magnetic resonance imaging showed extensive leptomeningeal enhancement. Cerebrospinal fluid analysis showed a raised protein of 6.4 g/dl. Nerve conduction studies showed an axonal neuropathy. Echocardiography was characteristic of cardiac amyloid. TTR gene sequencing showed that he was heterozygous for the leucine 12 proline mutation. Meningeal and brain biopsy confirmed widespread amyloid angiopathy. TTR amyloidosis is a rare cause of leptomeningeal enhancement, but should be considered if there is evidence of peripheral or autonomic neuropathy with cardiac or ocular involvement. The relationship between different TTR mutations and clinical phenotype, disease course, and response to treatment remains unclear.

Glial cells in familial amyloidotic polyneuropathy

INTRODUCTION

Transthyretin V30M mutation is the most common variant leading to Familial Amyloidotic Polyneuropathy. In this genetic disorder, Transthyretin accumulates preferentially in the extracellular matrix of peripheral and autonomic nervous systems leading to cell death and dysfunction. Thus, knowledge regarding important biological systems for Transthyretin clearance might unravel novel insights into Familial Amyloidotic Polyneuropathy pathophysiology. Herein, our aim was to evaluate the ability of glial cells from peripheral and autonomic nervous systems in Transthyretin uptake and degradation. We assessed the role of glial cells in Familial Amyloidotic Polyneuropathy pathogenesis with real-time polymerase chain reaction, immunohistochemistry, interference RNA and confocal microscopy.

RESULTS

Histological examination revealed that Schwann cells and satellite cells, from an Familial Amyloidotic Polyneuropathy mouse model, internalize and degrade non-fibrillar Transthyretin. Immunohistochemical studies of human nerve biopsies from V30M patients and disease controls showed intracellular Transthyretin immunoreactivity in Schwann cells, corroborating animal data. Additionally, we found Transthyretin expression in colon of this Familial Amyloidotic Polyneuropathy mouse model, probably being synthesized by satellite cells of the myenteric plexus.

CONCLUSIONS

Glial cells from the peripheral and autonomic nervous systems are able to internalize Transthyretin. Overall, these findings bring to light the closest relationship between Transthyretin burden and clearance from the nervous system extracellular milieu.

Molecular tweezers targeting transthyretin amyloidosis

Transthyretin (TTR) amyloidoses comprise a wide spectrum of acquired and hereditary diseases triggered by extracellular deposition of toxic TTR aggregates in various organs. Despite recent advances regarding the elucidation of the molecular mechanisms underlying TTR misfolding and pathogenic self-assembly, there is still no effective therapy for treatment of these fatal disorders. Recently, the "molecular tweezers", CLR01, has been reported to inhibit self-assembly and toxicity of different amyloidogenic proteins in vitro, including TTR, by interfering with hydrophobic and electrostatic interactions known to play an important role in the aggregation process. In addition, CLR01 showed therapeutic effects in animal models of Alzheimer's disease and Parkinson's disease. Here, we assessed the ability of CLR01 to modulate TTR misfolding and aggregation in cell culture and in an animal model. In cell culture assays we found that CLR01 inhibited TTR oligomerization in the conditioned medium and alleviated TTR-induced neurotoxicity by redirecting TTR aggregation into the formation of innocuous assemblies. To determine whether CLR01 was effective in vivo, we tested the compound in mice expressing TTR V30M, a model of familial amyloidotic polyneuropathy, which recapitulates the main pathological features of the human disease. Immunohistochemical and Western blot analyses showed a significant decrease in TTR burden in the gastrointestinal tract and the peripheral nervous system in mice treated with CLR01, with a concomitant reduction in aggregate-induced endoplasmic reticulum stress response, protein oxidation, and apoptosis. Taken together, our preclinical data suggest that CLR01 is a promising lead compound for development of innovative, disease-modifying therapy for TTR amyloidosis.

Transthyretin Ala36Pro mutation in a Chinese pedigree of familial transthyretin amyloidosis with elevated vitreous and serum vascular endothelial growth factor

The familial transthyretin (TTR) amyloidosis (FTA) demonstrates variable penetrance of clinical features associated with mutations in the plasma thyroid hormone-binding protein TTR gene. The purpose of this study was to assess the ocular features, to analyze vitreous and serum vascular endothelial growth factor (VEGF) levels, and to identify the genetic defect in a Chinese family with TTR FTA. The pedigree of interest was a three-generation family with eleven members. The primary ocular signs were vitreous opacities, beginning from the third or fourth decade, accompanied by retinal vasculitis, hemorrhages, and widespread pinpoint deposits in the peripheral retina. Two patients underwent vitrectomy with marked improvement of visual acuity postoperatively. Vitreous and serum samples for VEGF were analyzed with an enzyme-linked immunosorbent assay (ELISA). Forty-eight healthy adult volunteers were enrolled as a control group for the analysis of serum VEGF. Eight subjects who underwent vitrectomy for a macular epiretinal membrane or macular hole were enrolled as control for the analysis of vitreous VEGF. Both serum and vitreous VEGF levels of patients were raised compared to that of controls. Venous blood was collected from family members and the genomic DNA was extracted. All exons and exon-intron boundaries of the TTR gene were sequenced. A previously-described pathogenic transversion in exon 2 (c.G106C, p.Ala36Pro) was identified. Within this family eight individuals were confirmed as affected. In conclusion, a Chinese family with TTR Ala36Pro associated FTA is characterized by early ocular involvement. Widespread pinpoint lesions indicate RPE lesions caused by TTR deposition. FTA is associated with increased VEGF levels, both in serum and vitreous.

Transthyretin familial amyloid polyneuropathy

TTR FAP is characterized by phenotypic and genotypic heterogeneity. The severity of polyneuropathy along with autonomic dysfunction and heart involvement makes it a life-threatening disease. This protein is mainly produced by the liver. Molecular genetic testing is essential in the diagnostic strategy. TTR-Val30Met is the most frequent substitution, resulting in a guanine to cytosine mutation in exon 2 of the gene. It is virtually the only variant detected in Portugal, Brazil, and Sweden. By contrast, as many as 30 different TTR variants are reported in Japan and in other European countries. A less severe phenotype with late onset has been reported. Diagnosis should be performed as early as possible since upcoming pharmacological therapeutic approaches are now available, in addition to liver transplantation.

Amyloid neuropathies

Peripheral neuropathy is a common complication of many of the systemic amyloidoses. Although the cause of neuropathy is not entirely clear, it is likely related to amyloid deposition within the nerve. This may lead to focal, multifocal, or diffuse neuropathies involving sensory, motor and/or autonomic fibers. The presenting symptoms depend on the distribution of nerves affected. One of the most common phenotypes is sensorimotor polyneuropathy, which is characterized by symptoms of neuropathic pain, numbness, and in advanced cases weakness. Symptoms begin in the feet and ultimately progress to the proximal legs and hands. The most common focal neuropathy is a median neuropathy at the wrist, clinically known as carpal tunnel syndrome. Carpal tunnel symptoms may include pain and sensory disturbances in the lateral palm and fingers; hand weakness may ensue if the focal neuropathy is severe. Autonomic neuropathy may affect a variety of organ systems such as the cardiovascular, gastrointestinal, and genitourinary systems. Symptoms may be non-specific making the diagnosis of autonomic neuropathy more difficult to identify. However, it is important to recognize and distinguish autonomic neuropathy from diseases of the end-organs themselves. This article reviews the inherited and acquired amyloidoses that affect the peripheral nervous system including familial amyloid polyneuropathy, and primary, secondary and senile amyloidosis. We emphasize the clinical presentation of the neurologic aspects of these diseases, physical examination findings, appropriate diagnostic evaluation, treatment and prognosis.

Familial amyloid polyneuropathy

Familial amyloid polyneuropathies (FAPs) are a group of life-threatening multisystem disorders transmitted as an autosomal dominant trait. Nerve lesions are induced by deposits of amyloid fibrils, most commonly due to mutated transthyretin (TTR). Less often the precursor of amyloidosis is mutant apolipoprotein A-1 or gelsolin. The first identified cause of FAP-the TTR Val30Met mutation-is still the most common of more than 100 amyloidogenic point mutations identified worldwide. The penetrance and age at onset of FAP among people carrying the same mutation vary between countries. The symptomatology and clinical course of FAP can be highly variable. TTR FAP typically causes a nerve length-dependent polyneuropathy that starts in the feet with loss of temperature and pain sensations, along with life-threatening autonomic dysfunction leading to cachexia and death within 10 years on average. TTR is synthesised mainly in the liver, and liver transplantation seems to have a favourable effect on the course of neuropathy, but not on cardiac or eye lesions. Oral administration of tafamidis meglumine, which prevents misfolding and deposition of mutated TTR, is under evaluation in patients with TTR FAP. In future, patients with FAP might benefit from gene therapy; however, genetic counselling is recommended for the prevention of all types of FAP.

The hemorrhage caused by sporadic-type cerebral amyloid angiopathy occurs primarily in the cerebral sulci

We examined a solitary hematoma in a patient with sporadic cerebral amyloid angiopathy (CAA). The hematoma affected the middle frontal sulcus, cerebral cortex (CC) and subcortical frontal white matter (sfWM). We embedded the hematoma in four paraffin blocks, each of which was cut serially into 6-µm-thick sections. The first section and every 18th section from each block were subjected to Elastica-Goldner (E-G) staining, and the distribution and diameter of the ruptured blood vessels (rBVs) were examined. The rBVs were then marked on diagrams representing each E-G-stained section. The present study yielded the following important findings: (i), early- and recently ruptured Aβ-positive arteries were present mainly in the intrasulcal hematoma (ISH), rather than in the CC; (ii) many early-ruptured arteries in the ISH were larger in diameter than those in the CC; and (iii) ruptures of the cortical arteries, even near the cortical surface, did not occur so frequently and the ruptured vessels were small in size. We concluded that in patients with subcortical hematoma caused by sporadic-type CAA, successive rupturse of the meningeal vessels, mainly arteries, occur in the cerebral sulcus initially, followed by formation of an ISH and development of a fresh hemorrhagic or anemic infarct in the CC surrounding the ISH, the latter in most cases then extending into the brain parenchyma through the necrotic CC at the depth of the sulcus, finally creating a secondary hematoma in the subcortical white matter.

Familial amyloidotic polyneuropathy with muscle, vitreous, leptomeningeal, and cardiac involvement: phenotypic, pathological, and MRI description

Familial amyloidotic polyneuropathy (FAN type 1) is a rare systemic disease that causes severe and disabling peripheral neuropathy. We describe the phenotypic, radiological, and pathological characteristics of a patient with familial amyloid polyneuropathy type 1 who had evidence of motor-sensory-autonomic neuropathy, ocular vitreous deposits, diffuse leptomeningeal involvement, and hypertrophic cardiomyopathy. Muscle involvement, an infrequently reported feature, was also observed. Early recognition of the disease has significant therapeutic implications.

The neuromuscular manifestations of amyloidosis

Amyloidosis is a systemic disease that may be acquired or hereditary and which results in the deposition of amyloid fibrils in a variety of tissues causing their progressive dysfunction. Although the clinical presentation often is dominated by cardiac or renal failure, peripheral neuropathy may be a significant or the initial manifestation, resulting in presentation to the neurologist. Diagnosis often is challenging and may require multiple diagnostic procedures, including more than one biopsy. Acquired and hereditary amyloidosis can be definitively distinguished from one another only by immunohistochemical staining or molecular genetic testing. Treatment remains a challenge, although chemotherapy and autologous stem cell transplantation offer hope for those with primary systemic amyloidosis, whereas liver transplantation is effective for some forms of hereditary amyloid neuropathy. Much less commonly, myopathy may be a clinically significant manifestation of amyloidosis.

Suppression of choroid plexus transthyretin levels by antisense oligonucleotide treatment

Leptomeningeal amyloidosis associated with mutations in transthyretin (TTR) is a rare but fatal form of amyloidosis. Dementia and intracerebral haemorrhage are prominent features of this disease for which no specific therapy is known. In previous studies, we have shown that antisense oligonucleotides (ASOs) specific for human TTR could inhibit hepatic synthesis of TTR in mice transgenic for a human amyloid-associated TTR and may offer a medical means of treating systemic TTR amyloidosis. Parenteral administration of TTR-specific ASO, however, had no effect on the expression of TTR by the choroid plexus, which is believed to be the source of the amyloid protein in patients who have leptomeningeal amyloidosis. In the present study, mice transgenic for the human TTR amyloid-associated mutation Ile84Ser were treated by administration of TTR-specific ASO (50 microg or 75 microg per day) via an osmotic pump into the cerebral ventricular system over a 4-week period. Intraventricular administration of TTR-specific ASO significantly reduced choroid human TTR mRNA levels, and these findings correlated with decreased TTR in choroid plexus epithelial cells as demonstrated by immunohistochemistry. Suppression of choroid TTR expression by intraventricular administered ASO may offer a medical means of treating leptomeningeal amyloidosis.

White matter disorders with autosomal dominant heredity: a review with personal clinical case studies and their MRI findings

BACKGROUND

Leukoencephalopathies are a heterogeneous group of severe encephalopathy syndromes with myelin, axonal or vascular pathology, typically with extensive white matter lesions on MRI T2-FSE and/or -FLAIR sequences.

OBJECTIVES

This review is restricted to leukoencephalopathies with onset in adult age and a dominant inheritance. These diseases are generally severe and often lethal and present with an exacerbating or insidiously progressive course.

MATERIAL AND METHODS

The focus is on four syndromes with pure leukoencephalopathies, however, leukoencephalopathies with associated clinical features are included.

RESULTS

T2 weighted MR imaging often show features common for leukoencephalopathies, yet shows distinguishing features in transthyretin amyloidosis.

CONCLUSION

The diagnosis within the group of leukoencephalopathies thus characterized by MRI relies mainly upon clinical and genetic analysis. The differential diagnosis against treatable leukoencephalopathies is increasingly relevant.

Liver transplantation and combined liver-heart transplantation in patients with familial amyloid polyneuropathy: a single-center experience

Liver transplantation (LT) is the only curative option for patients with familial amyloid polyneuropathy (FAP) at present. Twenty patients with FAP underwent LT between May 1998 and June 2007. Transthyretin mutations included predominantly the Val30Met mutation but also 10 other mutations. Seven patients received a pacemaker prior to LT, and because of impairment of mechanical cardiac function, 4 combined heart-liver transplants were performed, 1 simultaneously and 3 sequentially. The first patient, who underwent simultaneous transplantation, died. Seven patients died after LT, with 5 dying within the first year after transplantation. The causes of death were cardiac complications (4 patients), infections (2 patients), and malnutrition (1 patient). One-year survival was 75.0%, and 5-year survival was 64.2%. Gly47Glu and Leu12Pro mutations showed an aggressive clinical manifestation: 2 patients with the Gly47Glu mutation, the youngest patients of all the non-Val30Met patients, suffered from severe cardiac symptoms leading to death despite LT. Two siblings with the Leu12Pro mutation, who presented only with grand mal seizures, died after LT because of sepsis. In conclusion, the clinical course in patients with FAP is very variable. Cardiac symptoms occurred predominantly in patients with non-Val30Met mutations and prompted combined heart-liver transplantation in 4 patients. Although early LT in Val30Met is indicated in order to halt the typical symptoms of polyneuropathy, additional complications occurring predominantly with other mutations may prevail and lead to life-threatening complications or a fatal outcome. Combined heart-liver transplantation should be considered in patients with restrictive cardiomyopathy.

Familial amyloid polyneuropathy: a clinico-pathologic study

In familial amyloid polyneuropathy (FAP), destruction of nerve fibres is related to accumulation of mutated transthyretin (mTTR) derived amyloid deposits (AD) in the endoneurium. Liver transplantation (LT), which removes the main source of mTTR, does not prevent deterioration of the clinical condition in all recipients.

MATERIAL AND METHODS

We evaluated the distribution of AD in the central and peripheral nervous system in order to better understand the pathophysiology of FAP and the potential role of lesions of nerve blood vessels and of mTTR released by choroid plexuses (CP). Forty nerve biopsy specimens and 3 autopsy cases, including 7 patients who underwent liver transplantation, all from patients with symptomatic FAP and DNA mutation of the TTR gene, were included.

RESULTS

Patients were ranged into three categories: MORPHOLOGICAL CHANGES: Amyloid predominated around endoneurial capillaries in 37 patients, with occlusion/destruction of endoneurial capillaries in 15 nerves at late stages of the disease. Post-mortem examination showed amyloid in choroid plexuses and perivascular spaces in the brain and around blood vessels penetrating the endoneurium, following arachnoid and connective tissue septae. Destruction of endoneurial blood vessels is a late event in the natural course of FAP. Morphological findings were similar in patients who underwent liver transplantation and in those who did not. The distribution of amyloid in areas communicating with the subarachnoid space suggests that mutated TTR released in the CSF may move to the endoneurial fluid and accumulate in peripheral nerves, accounting for lack of efficacy of liver transplantation in some individuals.