A new amyloidogenic transthyretin variant (Val122Ala) found in a compound heterozygous patient

Molecular simulation probes the potency of resveratrol in regulating the toxic aggregation of mutant V30M TTR fibrils in Transthyretin mediated amyloidosis

Transthyretin (TTR) mediated amyloidosis is a highly ruinous illness that affects various organs by aggravating the deposition of misfolded or mutated TTR protein aggregates in tissues. Hence, hindering the formation of TTR amyloid aggregates could be a key strategy in finding an effective cure towards the aggravating disorder. In this analysis, we examined the subversive nature of point mutation, V30M, in TTR that promotes amyloidogenicity using discrete molecular dynamics (DMD) simulations. Besides, we probed the association of naturally occurring polyphenols: EGCG (a proven anti TTR aggregation agent as positive control), resveratrol and curcumin in mitigating the pathogenic repercussions of mutant TTR. Results from the computational studies endorsed that the resveratrol constitutes a restorative potential to subjugate TTR mediated amyloidosis, besides EGCG. Hence, this study could be a reminiscent aspect in understanding the inhibitory role of key polyphenols against the mutant TTR aggregates, which could be an aid towards structure-based drug design in the upcoming research era on familial amyloid disorders.

Ocular Involvement in Hereditary Amyloidosis

The term amyloidosis describes a group of rare diseases caused by protein conformation abnormalities resulting in extracellular deposition and accumulation of insoluble fibrillar aggregates. So far, 36 amyloid precursor proteins have been identified, and each one is responsible for a specific disease entity. Transthyretin amyloidosis (ATTRv) is one of the most common forms of systemic and ocular amyloidosis, due to the deposition of transthyretin (TTR), which is a transport protein mainly synthesized in the liver but also in the retinal pigment epithelial cells. ATTRv amyloidosis may be misdiagnosed with several other conditions, resulting in a significant diagnostic delay. Gelsolin and keratoepithelin are other proteins that, when mutated, are responsible for a systemic amyloid disease with significant ocular manifestations that not infrequently appear before systemic involvement. The main signs of ocular amyloid deposition are in the cornea, irido-corneal angle and vitreous, causing complications related to vasculopathy and neuropathy at the local level. This review aims at describing the main biochemical, histopathological and clinical features of systemic amyloidosis associated with eye involvement, with particular emphasis on the inherited forms. We discuss currently available treatments, focusing on ocular involvement and specific ophthalmologic management and highlighting the importance of a prompt treatment for the potential sight-threatening complications derived from amyloid deposition in ocular tissues.

Amyloidosis and Ocular Involvement: an Overview

Purpose: To describe the ophthalmic manifestations of amyloidosis and the corresponding therapeutic measures.Methods: The 178 patients included in the study had different types of amyloidosis, diagnosed at a single internal medicine institution (Bari, Italy). To provide a comprehensive review of the types of amyloidosis that can be associated with ocular involvement, the images and clinical descriptions of patients with amyloidosis structurally related to gelsolin, keratoepithelin and lactoferrin were obtained in collaborations with the ophthalmology departments of hospitals in Mainz (Germany) and Helsinki (Finland).Results: Overall, ocular morbidity was detected in 41 of the 178 patients with amyloidosis (23%). AL amyloidosis was diagnosed in 18 patients with systemic disease, 3 with multiple myeloma, and 11 with localized amyloidosis. AA amyloidosis was detected in 2 patients with rheumatoid arthritis and 3 with Behçet syndrome, and transthyretin amyloidosis in 4 patients. The treatment of AL amyloidosis is based on chemotherapy to suppress the production of amyloidogenic L-chains and on surgical excision of orbital or conjunctival masses. AA amyloidosis is managed by targeting the underlying condition. Vitreous opacities and additional findings of ocular involvement in patients with transthyretin amyloidosis indicate the need for pars plana vitrectomy. Gelsolin amyloidosis, characterized by lattice corneal amyloidosis and polyneuropathy, results in recurrent keratitis and corneal scarring, such that keratoplasty is inevitable. In patients with lattice corneal dystrophies associated with amyloid deposits of keratoepithelin fragments, corneal transparency is compromised by deposits of congophilic material in the subepithelial layer and deep corneal stroma. Patients with established corneal opacities are treated by corneal transplantation, but the prognosis is poor because recurrent corneal deposits are possible after surgery. In patients with gelatinous drop-like dystrophy, the amyloid fibrils that accumulate beneath the corneal epithelium consist of lactoferrin and can severely impair visual acuity. Keratoplasty and its variants are performed for visual rehabilitation.Conclusion: A routine ophthalmic follow-up is recommended for all patients with established or suspected amyloidosis, independent of the biochemical type of the amyloid. Close collaboration between the ophthalmologist and the internist will facilitate a more precise diagnosis of ocular involvement in amyloidosis and allow the multidisciplinary management of these patients.Abbreviations: CD: corneal dystrophy; CLA: corneal lattice amyloidosis; CNS: central nervous system; CT: computed tomography; FAP: familial amyloidotic polyneuropathy; GDLCD: gelatinous drop-like corneal dystrophy; GLN: gelsolin; LCD: lattice corneal dystrophy; MRI: magnetic resonance imaging; OLT: orthotopic liver transplantation; TEM: transmission electron microscopy; TGFBI: transforming growth factor β induced; TTR: transthyretin.

A rare variant of transthyretin-related amyloidosis associated with exclusive cardiomyopathy in a Hong Kong Chinese patient

Hereditary transthyretin-related amyloidosis (ATTR, MIM #105210), also previously known as familial amyloidotic polyneuropathy, is one of the most life-threatening types of amyloidosis. ATTR is inherited in autosomal dominant mode with variable penetrance. If untreated, it is a relentless and lethal disease. Patients typically present with polyneuropathy, carpal tunnel syndrome, autonomic insufficiency, cardiomyopathy, and gastrointestinal features, occasionally accompanied by vitreous opacities and renal insufficiency. Frequency of transthyretin (TTR)-related cardiac amyloidosis amongst Chinese populations is unknown. We report here a 63-year-old Chinese man suffering from TTR-related cardiac amyloidosis presented with exclusive cardiomyopathy. He had no other systemic involvement and no significant family history. Echocardiography revealed severe global myocardial impairment and left ventricular ejection fraction of 35%. Serum kappa-to-lambda ratio was normal. Genetic test detected a heterozygous TTR variant, NM_000371.3:c.425T > C p.(Val142Ala). To our knowledge, this is the first case of TTR-related cardiac amyloidosis caused by p.Val142Ala mutation reported in Asian patient. <Learning objective: This case highlights the importance to exclude transthyretin-related cardiac amyloidosis as a cause of extensive cardiomyopathy, despite the late disease onset and lack of systemic amyloidosis. High clinical suspicion and genetic testing is the key for early diagnosis.>.

Circulating matrix metalloproteinases and tissue inhibitors of metalloproteinases in cardiac amyloidosis

BACKGROUND

Cardiac amyloidosis due to amyloid fibril deposition in the heart results in cardiomyopathy (CMP) with heart failure (HF) and/or conduction disturbances. Immunoglobulin light chain-related CMP (AL-CMP) features rapidly progressive HF with an extremely poor prognosis compared with a CMP due to the deposition of mutant (ATTR) amyloidosis or wild-type (senile systemic amyloidosis, SSA) transthyretin (TTR) proteins. Amyloid fibril deposition disrupts the myocardial extracellular matrix (ECM) homeostasis, which is partly regulated by matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). We therefore tested the hypothesis that circulating levels of MMPs and TIMPs in patients with AL-CMP and TTR-related CMP (TTR-CMP) are dissimilar and indicative of cardiac amyloid disease type.

METHODS AND RESULTS

Fifty AL-CMP patients were compared with 50 TTR-CMP patients (composed of 38 SSA and 12 ATTR patients). Clinical and laboratory evaluations including echocardiography were performed at the initial visit to our center and analyzed. Serum MMP-2, MMP-9, TIMP-1, and TIMP-2 levels were determined by ELISA. Compared with TTR-CMP patients, AL-CMP patients had higher levels of brain natriuretic peptide (BNP), troponin I (TnI), MMP-2, TIMP-1, and MMP-2/TIMP-2 ratio, despite less left ventricular (LV) hypertrophy and better preserved LV ejection fraction. Mortality was worse in AL-CMP patients than in TTR-CMP patients (log-rank P<0.01). MMP-2/TIMP-2 plus BNP and TnI showed the highest discriminative ability for distinguishing AL-CMP from TTR-CMP. Female sex (HR, 2.343; P=0.049) and BNP (HR, 1.041; P<0.01) were predictors for mortality for all patients with cardiac amyloidoses. Only BNP was a predictor of death in AL-CMP patients (HR, 1.090; P<0.01). There were no prognostic factors for all-cause death in TTR-CMP patients.

CONCLUSIONS

Circulating concentrations of MMPs and TIMPs may be useful in differentiating patients with AL-CMP from those with TTR-CMP, resulting in earlier diagnostic vigilance, and may add prognostic information. In addition to an elevated BNP level, female sex increased the risk of death in patients with cardiac amyloidoses.

Matrix metalloproteinases and their tissue inhibitors in cardiac amyloidosis: relationship to structural, functional myocardial changes and to light chain amyloid deposition

BACKGROUND

Cardiac amyloidosis is characterized by amyloid infiltration resulting in extracellular matrix disruption. Amyloid cardiomyopathy due to immunoglobulin light chain protein (AL-CMP) deposition has an accelerated clinical course and a worse prognosis compared with non-light chain cardiac amyloidoses (ie, forms associated with wild-type or mutated transthyretin [TTR]). We therefore tested the hypothesis that determinants of proteolytic activity of the extracellular matrix, the matrix metalloproteinases (MMPs), and their tissue inhibitors (TIMPs) would have distinct patterns and contribute to the pathogenesis of AL-CMP versus TTR-related amyloidosis.

METHODS AND RESULTS

We studied 40 patients with systemic amyloidosis: 10 AL-CMP patients, 20 patients with TTR-associated forms of cardiac amyloidosis, ie, senile systemic amyloidosis (involving wild-type TTR) or mutant TTR, and 10 patients with AL amyloidosis without cardiac involvement. Serum MMP-2 and -9, TIMP-1, -2, and -4, brain natriuretic peptide values, and echocardiography were determined. AL-CMP and TTR-related amyloidosis groups had similar degrees of increased left ventricular wall thickness. However, brain natriuretic peptide, MMP-9, and TIMP-1 levels were distinctly elevated accompanied by marked diastolic dysfunction in the AL-CMP group versus no or minimal increases in the TTR-related amyloidosis group. Brain natriuretic peptide, MMPs, and TIMPs were not correlated with the degree of left ventricular wall thickness but were correlated to each other and to measures of diastolic dysfunction. Immunostaining of human endomyocardial biopsies showed diffuse expression of MMP-9 and TIMP-1 in AL-CMP and limited expression in TTR-related amyloidosis hearts.

CONCLUSIONS

Despite comparable left ventricular wall thickness with TTR-related cardiac amyloidosis, AL-CMP patients have higher brain natriuretic peptide, MMPs, and TIMPs, which correlated with diastolic dysfunction. These findings suggest a relationship between light chains and extracellular matrix proteolytic activation that may play an important role in the functional and clinical manifestations of AL-CMP, distinct from the other non-light chain cardiac amyloidoses.

Detection and characterization of variant and modified structures of proteins in blood and tissues by mass spectrometry

Some variant proteins cause diseases, and some diseases result in increases of proteins with abnormally modified structures. The detection, characterization, and estimation of the relative amounts of protein variants and abnormally modified proteins are important for clinical diagnosis and for elucidation of the mechanisms of the pathogenesis of diseases. Analysis of the covalent structures of proteins using matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography-electrospray ionization MS (LC-ESI-MS), which had been developed by the early 1990s, have largely replaced analyses by conventional protein chemistry. Here, we review the detection and characterization of hemoglobin variants, HbA1c measurement, detection of carbohydrate-deficient transferrin, and identification of variants of transthyretin (TTR) and Cu/Zn-superoxide dismutase (SOD-1) using soft ionization MS. We also propose the diagnostic application of the signals of modified forms of TTR, that is, S-sulfonated TTR and S-homocysteinyl TTR. The relative peak height ratio of the abnormal/normal components gives valuable information about the instability of variants and enables the detection of unstable Hb subunits or thalassemia heterozygotes. We found unique modified structures of TTR that suggested changes in amyloid fibrils.

Transthyretin mutations in hyperthyroxinemia and amyloid diseases

Over 80 different disease-causing mutations in transthyretin (TTR) have been reported. The vast majority are inherited in an autosomal dominant manner and are related to amyloid deposition, affecting predominantly peripheral nerve and/or the heart. A small portion of TTR mutations are apparently non-amyloidogenic. Among these are mutations responsible for hyperthyroxinemia, presenting high affinity for thyroxine (a TTR ligand). Compound heterozygotic individuals for TTR mutants have been described; noteworthy is the clinically protective effect exerted by a non-pathogenic over a pathogenic mutation. Current TTR mutations and their significance are briefly reviewed here.

Postmortem findings in two familial amyloidosis patients with transthyretin variant Asp38Ala

Postmortem findings in 2 familial amyloidosis patients with the transthyretin variant (ATTR), Asp38Ala, are described Both showed cardiac failure, and progressive peripheral and autonomic neuropathy and died at the ages 82 and 57, respectively. TTR immunoreactive amyloid deposition was observed to be extensive in the myocardium, peripheral nerves, sympathetic ganglia and gastrointestinal tract. The pulmonary parenchyma was also diffusely involved, but renal glomeruli, follicular tissues of the thyroid, and the leptomeninges and subarachnoidal vessels of the central nervous system showed little deposition. The latter findings are not usually seen in the patients with ATTR Val30Met, the most common form of familial amyloidosis. Additionally, the clinicopathological findings of familial amyloidosis with ATTR Asp38Ala seem to vary in the different individuals.

Application of multishot acquisition in Fourier transform mass spectrometry

A new method of ion injection and trapping is discussed wherein ions are accumulated over several laser shots in the FT-ICR cell prior to detection. This allows accumulation of ion signal without accumulating noise so that the signal/noise ratio is much improved provided that the "space-charge" limit of the total number of ions in the cell is not exceeded. "In-cell" ion accumulation allows selected ion accumulation by simply sweeping unwanted ions out of the cell prior to subsequent ion trapping events and also allows shifted ion accumulations to correct for time-of-flight distortions in the ion abundance distributions.

Excretory plugs from the choroid plexus in the cerebrospinal fluid of dogs with neurological disease: possible role in the formation of corpora arenacea

Cytological specimens of cerebrospinal fluid (CSF) from 13 (6.5%) of 200 dogs with various neurological diseases contained excretory plugs (EPs) originating from choroid plexus cells (ChPCs). The presence of EPs was not related to age, breed or sex, or to any particular neurological disease. EPs, which ranged from 3 to 25 microm in diameter, had a sharp outline and contained granular material. Many such bodies were also found within ChPCs of dogs without neurological disease, which were examined to determine the origin of EPs. The results suggest that EPs found in the CSF are excretory products originating in a small population of ChPCs, and that when they reach a certain size they are eliminated into the CSF. It is possible that they serve as cores around which corpora arenacea ("brain sand") are subsequently formed.

Impact of age and amyloidosis on thiol conjugation of transthyretin in hereditary transthyretin amyloidosis

Variant forms and post-translational modifications of transthyretin (TTR) can be identified by electrospray ionisation mass spectrometry (ESI-MS). The aim of the present study was to investigate thiol conjugation of transthyretin and it's relation to age and symptomatic amyloid disease in different populations of variant TTR carriers. Plasma samples from 70 individuals from Denmark, Argentina, Sweden and Japan, with 2 different TTR mutations were analysed. The percentage cysteine (Cys) conjugated wild and variant TTR were calculated from the corresponding peaks of the spectra, and multiple regression analysis was employed to disclose relationships between age, symptomatic amyloid disease and origin. Age, origin and presence of symptomatic disease, were found to be independent factors related to transthyretin conjugation. A higher percentage of conjugated to unconjugated TTR was disclosed in symptomatic, but not in asymptomatic carriers. In summary: Thiol conjugation of TTR is dependent on age and presence of symptomatic amyloid disease. Furthermore, it varies between different populations. Variant TTR is more susceptible to thiol conjugation than the wild type. Post-translational factors may be related to amyloid formation and/or toxicity.