Mutant Transthyretin Research Articles

Challenges in the approach to a patient with aortic stenosis and cardiac amyloidosis with ATTR mutation associated with negative scintigraphy - A case report

IntroductionCardiac amyloidosis (CA) poses significant diagnostic and therapeutic challenges. In this case report, we detail a patient with CA due to a rare transthyretin (CA-TTR) mutation, manifesting with negative myocardial scintigraphy and requiring genetic testing for diagnosis. The patient also had severe aortic stenosis (AS), necessitating discussion with a heart team to determine the optimal treatment strategy. Case reportA 70-year-old male with a family history of sudden death was previously diagnosed with third-degree atrioventricular block and treated with a pacemaker. He presented with worsening exertional dyspnoea, and examination revealed a third heart sound, a systolic murmur indicative of AS and bilateral muscular atrophy in the thenar region. Transthoracic echocardiography indicated severe AS and moderate left ventricular dysfunction, with images suggesting infiltrative disease. Pyrophosphate scintigraphy revealed no abnormal cardiac tracer uptake. Cardiac magnetic resonance imaging (MRI) revealed extensive, heterogeneous, subendocardial late gadolinium enhancement in both the atria and ventricles, which was consistent with CA. Genetic testing identified the Phe84Leu mutation in the TTR gene. Following heart team discussions, the patient underwent successful transcatheter aortic valve implantation (TAVI) and remained asymptomatic in follow-up, being monitored at an outpatient clinic specializing in CA and using tafamidis. DiscussionCA-TTR can be an autosomal dominant disease with variable penetrance involving abnormal amyloid protein deposition in tissues and can often be diagnosed noninvasively via myocardial scintigraphy. However, some TTR mutations do not affect scintigraphy results, necessitating genetic testing when clinical suspicion is high, potentially avoiding endomyocardial biopsy. Moreover, AS occurs in up to 16 % of TTR amyloidosis patients, with the conditions mutually exacerbating each other. Recent consensus suggests that TAVI reduces mortality in patients with severe AS and amyloidosis. ConclusionsVarious diagnostic algorithms emphasize the use of myocardial scintigraphy for suspected CA-TTR. Genetic testing is crucial when scintigraphy results are negative, but clinical suspicion remains high, potentially circumventing invasive procedures. Compared with medical management alone, TAVI has been shown to improve quality of life and survival in patients with concurrent severe AS and CA.

Water Plays Key Roles in Stabilities of Wild Type and Mutant Transthyretin Complexes.

Transthyretin (TTR), a 56 kDa homotetramer that is involved in the transport of thyroxine and retinol, has been linked to amyloidosis through disassembly of tetramers to form monomers, dimers, and trimers that then reassemble into higher order oligomers and/or fibrils. Hybrid TTR (hTTR) tetramers are found in heterozygous individuals that express both wild type TTR (wt-TTR) and mutant TTR (mTTR) forms of the protein, and these states display increased rates of amyloidosis. Here we monitor subunit exchange (SUE) reactions involving homomeric and mixed tetramers using high resolution native mass spectrometry (nMS). Our results show evidence that differences in TTR primary structure alter tetramer stabilities, and hTTR products can form spontaneously by SUE reactions. In addition, we find that solution temperature has strong effects on TTR tetramer stabilities and formation of SUE products. Lower temperatures promote formation of hTTR tetramers containing L55P and V30M subunits, whereas small effects on the formation of hTTR tetramers containing F87A and T119M subunits are observed. We hypothesize that the observed temperature dependent stabilities and subsequent SUE behavior are a result of perturbations to the network of "two kinds of water": hydrating and structure stabilizing water molecules (Spyrakis et al. J. Med. Chem. 2017, 60 (16), 6781-6827; Xu et al. Soft Matter 2012, 8, 324-336) that stabilize wt-TTR and mTTR tetramers. The results presented in this work illustrate the utility of high resolution nMS for studies of the structures, stabilities, and dynamics of protein complexes that directly influence SUE reactions.

Altered connectivity of central autonomic network: effects of dysautonomia in hereditary transthyretin amyloidosis with polyneuropathy

Background Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is a progressive fatal disorder caused by deposition of mutant transthyretin (TTR) amyloids mainly in the nerves and heart. Autonomic dysfunction is a major disabling manifestation, affecting 90% of patients with late-onset ATTRv-PN. The current study aimed to investigate brain functional alterations associated with dysautonomia due to peripheral autonomic nerve degeneration in ATTRv-PN. Methods Resting-state functional MRI data were acquired from 43 ATTRv-PN patients predominantly of A97S (p.A117S) genotype, and the functional connectivity of central autonomic regions was assessed. Results Compared with age-matched healthy controls, the ATTRv-PN patients exhibited (1) reduced functional connectivity of the central autonomic regions such as hypothalamus, amygdala, anterior insula, and middle cingulate cortex with brain areas of the limbic, frontal, and somatosensory systems, and (2) correlations of reduced functional autonomic connectivity with the severity of autonomic dysfunction especially orthostatic intolerance, decreased heart rate variability, and greater clinical disability. Conclusions Our findings provide evidence linking peripheral autonomic dysfunction with altered connectivity in the central autonomic network in ATTRv-PN.

RNA Interference Therapeutics for Hereditary Amyloidosis: A Narrative Review of Clinical Trial Outcomes and Future Directions.

Hereditary transthyretin amyloidosis (ATTR) is an autosomal dominant, life-threatening genetic disorder caused by a single-nucleotide variant in the transthyretin gene. This mutation leads to the misfolding and deposition of amyloid in various body organs. Both mutant and wild-type transthyretin contribute to the resulting polyneuropathy and cardiomyopathy, leading to significant sensorimotor disturbances and severe cardiac conditions such as heart failure and arrhythmias, thereby impacting quality of life. Despite several treatments, including orthotopic liver transplantation and transthyretin tetramer stabilizers, their limitations persisted until the introduction of RNA interference (RNAi). RNAi, a means to regulate mRNA stability and translation of targeted genes, has brought about significant changes in treatment strategies for ATTR with the introduction of patisiran in 2018. This study reviews patisiran, vutrisiran, inotersen, and eplontersen, developed for the treatment of ATTR. It provides an overview of the clinical trial outcomes, focusing mainly on quality of life, adverse reactions, and the future of RNAi-based therapies.

DON’T FORGET ABOUT CARDIAC AMYLOIDOSIS: WHEN RED FLAGS MATTER

Abstract Case Report A 78–year–old man came to our attention for worsening dyspnea, asthenia and frequent lipothymic episodes in the last few weeks. Nothing remarkable was reported in anamnesis except for periodic cardiological check–ups ascribed to hypertensive heart disease and moderate aortic stenosis. Other cardiovascular risk factors were obesity, previous smoking habits and dyslipidemia. A recent 24–hours ECG monitoring revealed slow permanent atrial fibrillation (AF) with 3–seconds pauses, frequent premature ventricular complexes (PVCs) and some PVCs couplets. On arrival, NT–proBNP was elevated (2952 pg/mL), while ECG showed AF with a heart rate of 50/m and low voltages in peripheral leads. Transthoracic echocardiogram revealed a biatrial dilatation, a severe left ventricular (LV) concentric hypertrophy with a preserved LV ejection fraction (EF) and a moderate aortic stenosis. In addition, a restrictive LV filling pattern, a decreased longitudinal myocardial contraction and an apical sparing of longitudinal strain were reported. Invasive coronary angiography was performed with evidence of normal coronary arteries. Given the echocardiographic suspicion of amyloidosis, a 99mTc–Hydroxymethylene diphosphonate (HMDP) scintigraphy was performed, showing a moderate cardiac uptake and an attenuated bone uptake (Perugini Score 2). Serum and urine immunofixation resulted negative. Genetic testing did not find any mutations in Transthyretin (TTR) gene. Therefore, the diagnosis of TTR wild–type amyloidosis was made. Before discharge, putting it all together, we opted to implant a leadless pacemaker in order to protect the patient from life–threatening bradyarrhythmias. Discussion Although it is currently considered rare, there is growing evidence that cardiac amyloidosis may be more common than once thought. First of all, it should be investigated in HFpEF–patients (heart failure with preserved EF) with LV hypertrophy. Despite several red flags (low QRS voltages, conduction disorders, elevated NT–proBNP, severe LV hypertrophy and aortic stenosis) and various medical consultations, our patient had to wait 4 years or more to be diagnosed with cardiac amyloidosis. Inevitably, a diagnostic delay means loss of time in treatment initiation. Earlier diagnosis would enable us to improve our patients’ survival and heart failure hospitalization. Awareness alone is not enough, we must be right on target too.

Characterization of Transthyretin Mutation G47V Associated with Hereditary Cardiac Amyloidosis

Introduction: Amyloidosis caused by TTR mutations (ATTRv) is a rare inherited and autosomal dominant disease. More than 150 mutants of TTR have been reported, whereas some of them remain to be investigated. Methods: A 52-year-old male presented with heart failure and clinically diagnosed ATTR cardiac amyloidosis (ATTR-CA) was recruited. Whole-exome sequencing (WES) was performed. Biochemical and biophysical experiments characterized protein stability using urea-mediated tryptophan fluorescence. Drug response was analyzed by fibril formation assay. Finally, tetramer TTR concentration in patient’s serum sample was measured by ultra-performance liquid chromatography (UPLC). Results: For the proband, WES revealed a mutation (c.200G>T; p.Gly67Val and referred to as G47V) in TTR gene. Biochemical and biophysical kinetics study showed that the thermodynamic stability of G47V-TTR (Cm = 2.4 m) was significantly lower than that of WT-TTR (Cm = 3.4 m) and comparable to that of L55P-TTR (Cm = 2.3 m), an early age-of-onset mutation. G47V:WT-TTR heterozygous tetramer kinetic stability (t1/2 = 1.4 h) was further compromised compared to that of the homozygous G47V-TTR (t1/2 = 3.1 h). Among three small molecule stabilizers, AG10 exhibited the best inhibition of the fibrillation of G47V-TTR homozygous protein. Using a UPLC assay, nearly 40% of TTR in this patient was calculated to be non-tetrameric. Conclusion: In this work, we reported a patient presented early onset of clinically typical ATTR-CA due to G47V-TTR mutation. Our work for the first time not only characterized the biochemical properties of G47V-TTR mutation, but also provided hints for the pathogenicity of this mutation.

Neuromuscular manifestations of wild type transthyretin amyloidosis: a review and single center's experience.

Transthyretin amyloidosis (ATTR) is a condition defined by accumulation of insoluble transthyretin amyloid deposits in multiple organs, especially in the peripheral nerve and heart muscle. ATTR may result from transthyretin mutations (variant ATTR or ATTRv) or may occur with normal transthyretin genotype (wild type ATTR or ATTRwt). ATTRwt was previously known as "senile amyloidosis" and causes cardiomyopathy which may lead to heart failure with a preserved ejection fraction, affecting predominantly elderly men. The exact prevalence of ATTRwt in the general population remains unclear, but its occurrence may be underestimated in women. It was observed that a proportion of ATTRwt cardiomyopathy patients may develop slowly progressing neuropathy that is milder and indolent in comparison with typical progressive neuropathy associated with ATTRv. Furthermore, the causality of neuropathy is often uncertain in patients with ATTRwt. Neuropathy symptoms, including distal sensory loss, unsteadiness and (neuropathic) pain are common in elderly patients with multiple potential causes, and as ATTRwt patients are typically older, relatively high prevalence of peripheral neuropathy is expected with frequent comorbidities. Relatively high prevalence of ATTRwt in elderly population contrasts few documented cases of neuropathy caused by ATTRwt, and there is uncertainty whether ATTRwt neuropathy is an infrequent occurrence or a significant manifestation of multisystemic ATTRwt. We review neurologic and musculoskeletal manifestations of ATTRwt and present clinical features of a single center cohort of ATTRwt patients with suspected peripheral neuropathy.

Characterization and natural history of different phenotypes in hereditary transthyretin amyloidosis: 40-year experience at a single Italian referral centre.

Hereditary transthyretin amyloidosis (ATTRv) is one of the leading aetiologies of systemic amyloidosis with more than 135 mutations described and a broad spectrum of clinical manifestations. We aimed to provide a systematic description of a population of individuals carrying pathogenic mutations of transthyretin (TTR) gene and to investigate the major clinical events during follow-up. This was an observational, retrospective, cohort study including consecutive patients with mutations of TTR gene, admitted to a tertiary referral centre in Bologna, Italy, between 1984 and 2022. Three hundred twenty-five patients were included: 106 asymptomatic carriers, 49 cardiac phenotype, 49 neurological phenotype, and 121 mixed phenotype. Twenty-two different mutations were found, with Ile68Leu (41.8%), Val30Met (19%), and Glu89Gln (10%) being the most common. After a median follow-up of 51 months, 111 patients (38.3%) died and 9 (11.5%) of the 78 asymptomatic carriers developed ATTRv. Carriers had a prognosis comparable with healthy population, while no significant differences were seen among the three phenotypes adjusted by age. Age at diagnosis, New York Heart Association class III, left ventricular ejection fraction, modified polyneuropathy disability score IV, and disease-modifying therapy were independently associated with survival. This study offers a wide and comprehensive overview of ATTRv from the point of view of a tertiary referral centre in Italy. Three main phenotypes can be identified (cardiac, neurological, and mixed) with specific clinical and instrumental features. Family screening programmes are essential to identify paucisymptomatic affected patients or unaffected carriers of the mutation, to be followed through the years. Lastly, disease-modifying therapy represents an evolving cornerstone of the management of ATTRv, with a great impact on mortality.

Disease-Modifying Drugs Extend Survival in Hereditary Transthyretin Amyloid Polyneuropathy.

Hereditary transthyretin (ATTRv) amyloidosis is a rare, fatal systemic disease, associated with polyneuropathy and cardiomyopathy, that is caused by mutant transthyretin (TTR). In addition to liver transplantation, several groundbreaking disease-modifying drugs (DMDs) such as tetrameric TTR stabilizers and TTR gene-silencing therapies have been developed for ATTRv amyloid polyneuropathy. They were based on a working hypothesis of the mechanisms of ATTRv amyloid formation. In this retrospective cohort study, we investigated survival of all 201 consecutive patients with ATTRv amyloidosis in our center. The effects of DMDs on survival improvements were significant not only in early-onset patients but also in late-onset patients. ANN NEUROL 2024;95:230-236.

Generation of two induced pluripotent stem cell lines from hereditary amyloidosis patients with polyneuropathy carrying heterozygous transthyretin (TTR) mutation

Hereditary transthyretin amyloidosis with polyneuropathy (ATTR-PN) results from specific TTR gene mutations. In this study, we generated two induced pluripotent stem cell (iPSC) lines derived from ATTR-PN patients with heterozygous TTR gene mutations (Ala97Ser and Phe64Leu). These iPSC lines exhibited normal morphology, karyotype, high pluripotency marker expression, and differentiation into cells representing all germ layers. The generation of these iPSC lines serve as a valuable tool for investigating the mechanisms of ATTR-PN across various cell types and facilitating patient-specific in vitro amyloidosis modeling.

Nerve pathology of microangiopathy and thromboinflammation in hereditary transthyretin amyloidosis.

Despite amyloid deposition as a hallmark of hereditary transthyretin amyloidosis (ATTRv) with polyneuropathy, this pathology could not completely account for nerve degeneration. ATTRv patients frequently have vasomotor symptoms, but microangiopathy hypothesis in ATTRv was not systemically clarified. This study examined the vascular pathology of sural nerves in ATTRv patients with transthyretin (TTR) mutation of p.Ala117Ser (TTR-A97S), focusing on morphometry and patterns of molecular expression in relation to nerve degeneration. We further applied human microvascular endothelial cell (HMEC-1) culture to examine the direct effect of TTR-A97S protein on endothelial cells. In ATTRv nerves, there was characteristic microangiopathy compared to controls: increased vessel wall thickness and decreased luminal area; both were correlated with the reduction of myelinated fiber density. Among the components of vascular wall, the area of collagen IV in ATTRv nerves was larger than that of controls. This finding was validated in a cell model of HMEC-1 culture in which the expression of collagen IV was upregulated after exposure to TTR-A97S. Apoptosis contributed to the endothelial cell degeneration of microvasculatures in ATTRv endoneurium. ATTRv showed prothrombotic status with intravascular fibrin deposition, which was correlated with (1) increased tissue factor and coagulation factor XIIIA and (2) reduced tissue plasminogen activator. This cascade led to intravascular thrombin deposition, which was colocalized with upregulated p-selectin and thrombomodulin, accompanied by complement deposition and macrophages infiltration, indicating thromboinflammation in ATTRv. Microangiopathy with thromboinflammation is characteristic of advanced-stage ATTRv nerves, which provides an add-on mechanism and therapeutic target for nerve degeneration.

Generation of two induced pluripotent stem cell lines from patients with cardiac amyloidosis carrying heterozygous transthyretin (TTR) mutation

Specific mutations in the TTR gene are responsible for the development of variant (hereditary) ATTR amyloidosis. Here, we generated two human induced pluripotent stem cell (iPSC) lines from patients diagnosed with Transthyretin Cardiac Amyloidosis (ATTR-CM) carrying heterozygous mutation in the TTR gene (i.e., p.Val30Met). The patient-derived iPSC lines showed expression of high levels of pluripotency markers, trilineage differentiation capacity, and normal karyotype. The generation of these iPSC lines represents a great tool for modeling patient-specific amyloidosis in vitro, allowing the investigation of the pathological mechanisms related to the disease in different cell types and tissues.

Electrocardiographic heterogeneity of patients with variant transthyretin amyloid cardiomyopathy: Genotype-phenotype correlations

BackgorundHereditary transthyretin(vATTR) cardiac amyloidosis has extremely different features according to the type of transthyretin(TTR) mutation. Data about electrocardiographic findings(ECG) in vATTR are limited and not informative of genotype correlation. Aim of this study is to analyze ECG characteristics and their correlation to clinical and echocardiographic aspects in patients with vATTR, focusing on different TTR mutations. Methods and resultsThis is a multicentric, retrospective, observational study performed in six Italian referral centres. We divided patients in two groups, according to the previously described phenotypic manifestations of the TTR mutation. Of 64 patients with vATTR, 23(36%) had prevalent cardiac(PC) TTR mutations and 41(64%) patients had a prevalent neurological(PN) TTR mutations. Patients with PC mutations were more frequently males and older, with advanced NAC staging. At baseline ECG, atrial fibrillation was more common in patients with PC, while pacemaker induced rhythm in PN mutations. PQ and QRS durations were longer and voltage to mass ratio was lower in PC mutations. Different TTR mutations tend to have distinctive ECG features. ConclusionsECG in vATTR is extremely heterogeneous and the specific mutations are associated with distinct instrumental and clinical features. The differences between PN and PC vATTR are only partially explained by the different degree of cardiac infiltration.

An 82-year-old woman with retinal vascular sheathing and vitreous hemorrhage.

This report describes a case of hereditary transthyretin amyloidosis in an 82-year-old woman who presented with bilateral retinal arteriolar vascular sheathing and vitreous hemorrhage in one eye. The patient underwent a full history, physical examination, genetic workup, and cardiac imaging to establish the diagnosis. Fundus photographs, optical coherence tomography, fluorescein angiography, and indocyanine green angiography were performed throughout the patient's treatment course. Fundus examination demonstrated segmental sheathing of the retinal arterioles, telangiectasias, and intraretinal hemorrhages in both eyes without neovascularization. Fluorescein angiography revealed delayed filling of the nasal retinal arterioles in the right eye with severe temporal nonperfusion and areas hyperfluorescent segmental sheathing in both eyes. Ocular coherence tomography demonstrated retinal vessels with hyperreflective thickened walls. Cardiac amyloid nuclear scan was consistent with transthyretin-mediated amyloidosis amyloid heart disease, and genetic testing confirmed a heterozygous pathogenic transthyretin mutation: c.290 C>A (p.Ser97Tyr) also known as Ser77Tyr. Amyloidosis should be considered in the differential of vasculitis and vitreous hemorrhage with or without significant vitreous opacities. Ophthalmologists aware of this diagnosis should complete a full review of systems with specific focus on cardiac history and symptoms of peripheral neuropathy when amyloidosis is in the differential.

P2 A RARE CASE OF MUTANT TRANSTHYRETIN CARDIAC AMYLOIDOSIS

Abstract A 65–year–old man with a history of multiple hospitalizations in the past 12 months for heart failure with preserved left ventricular ejection fraction (HFpEF) attended the emergency department for exertional dyspnea, peripheral edema, abdominal bloating, and weight gain. An ECG showed sinus bradycardia with first degree AV block, RBBB, and inferior pseudo–q. Blood tests showed NT–proBNP 8985 pg/ml, troponin hs–cTnI 106 ng/L. An echocardiogram demonstrated severe left ventricular hypertrophy, EF 50%, GLS –11% with apical sparing, and restrictive transmitral pattern, raising suspicion of infiltrative disease (Figure 1). A cardiac MRI corroborated the suspicion, showing altered gadolinium kinetics, diffuse subendocardial LGE, and increased native T1 and extracellular volume (Figure 2). A search for monoclonal components on serum and urine was negative. A bone tracer scintigraphy showed cardiac uptake (Perugini grade 2). A genetic test showed the presence of p.Ile88Leu (Ile68Leu) mutation in heterozygosity, so a non–biopsy diagnosis of mutant transthyretin cardiac amyloidosis (ATTRv) was posed. A thorough neurological evaluation did not document signs of amyloid neuropathy. The patient was then started on tafamidis therapy. Transthyretin cardiac amyloidosis (ATTR) is still an underdiagnosed but increasingly recognized condition, causing up to 13% of HFpEF cases. ATTR is caused by extracellular accumulation of amyloid substance resulting from transthyretin misfolding. In Italy ATTRv is rare and Ile68Leu is among the most frequent mutations, especially in the Tuscan–Emilian Apennines. Ile68Leu is usually associated with an almost exclusively cardiac phenotype, clinically indistinguishable from ATTR wild type, except for an earlier age of onset. Because effective treatments are available for ATTRv with cardiac and/or neurological involvement, it is important to suspect the diagnosis of ATTR in patients with HFpEF and to proceed with genetic testing to identify individuals with ATTRv.

Description of a Rare Compound Heterozygous Transthyretin Mutation Val30Met/Val122Ile Conferring Early Onset Hereditary Amyloidosis with Severe Features (P14-8.009)

<h3>Objective:</h3> To describe a case of hereditary amyloidosis with a rare compound heterozygous mutation that is not described in the literature. <h3>Background:</h3> Hereditary amyloidosis is a rare disease characterized by accumulation of amyloid deposits in tissue, causing end-organ failure. Most common manifestations include cardiomyopathy, nephropathy, and neuropathy. The transthyretin (TTR) is encoded on chromosome 18 and functions to transport thyroxine and retinol through blood and CSF. Mutations in TTR increase the amyloidogenic potential of the protein. TTR is inherited in an autosomal dominant fashion, and thus mutagenic carriers often have a strong family history of the associated diseases. There are over 100 characterized mutations of this gene. The vast majority of genetically proven cases are associated with missense mutations in a single codon. Compound heterozygotes are rarely reported in the literature. <h3>Design/Methods:</h3> N/A <h3>Results:</h3> A 40-year-old male with history of chronic diarrhea and anemia presents with two years of pedal edema, weight loss, dyspnea on exertion, and progressive limb weakness resulting in multiple falls. On cardiac evaluation he was found to have severe cardiomyopathy with increase LV thickness and evidence of amyloidosis on cardiac MRI. EMG demonstrated a severe sensorimotor polyneuropathy. Exam was notable for absent joint position sense resulting in gait dysfunction necessitating use of a cane. Subsequent endomyocardial biopsy revealed ATTR type amyloid deposition. Genetic evaluation demonstrated two separate pathogenic variants in TTR (Val30Met/Val122Ile). He was started on therapy with tafamidis and later transitioned to patisiran infusions with some symptomatic improvement. Genetic testing of family members was suggested however not yet completed. <h3>Conclusions:</h3> Compound heterozygous mutations in TTR are exceedingly rare, and this report presents a perhaps never before described case of an individual with both Val30Met and Val122Ile mutations resulting in early onset severe hereditary amyloidosis with multisystem involvement. <b>Disclosure:</b> Dr. Nardin has nothing to disclose. Dr. Traub has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alnylam. Dr. Traub has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Argenx. The institution of Dr. Traub has received research support from Alnylam Pharmaceuticals. The institution of Dr. Traub has received research support from Alexion. The institution of Dr. Traub has received research support from Muscular Dystrophy Association (MDA). The institution of Dr. Traub has received research support from Ionis.

TLR2 and 4 signaling pathways are altered in macrophages from V30M TTR mice with down-regulated expression of chemokines.

Hereditary amyloid transthyretin (ATTRv) amyloidosis is a fatal neurodegenerative disorder, first identified in Portugal. The most common transthyretin (TTR) mutation in ATTRv results from an exchange of a methionine for a valine at position 30 (V30M). ATTRv is characterized by the extracellular deposition of aggregates and fibrils of mutant forms of TTR, particularly in the nerves and ganglia of the peripheral nervous system (PNS). This phenotype is often accompanied by the lack of inflammatory infiltrates, despite the importance of macrophages in removal of TTR deposits in ATTRv patients. The mechanisms underlying this impairment of inflammatory responses in ATTRv patients are poorly understood. Here, we show a significant down-regulation in the expression of several chemokines by bone marrow-derived macrophages (BMDM) generated from V30M TTR mice upon stimulation with toll-like receptor 4 (TLR4) and TLR2 agonists. The phosphorylation of the MAP kinase p38, important for TLR4 and TLR2 signaling pathways, was also down-regulated in V30M macrophages, as compared with wild-type (WT) ones. The present study contributes with new insights to unravel the molecular mechanisms underlying the lack of inflammatory immune responses observed in ATTRv patients and may help in the development of new immune therapeutic strategies for the disease.

Identification of a novel transthyretin mutation D39Y in a cardiac amyloidosis patient and its biochemical characterizations.

Hereditary transthyretin cardiac amyloidosis (hATTR-CA) is a rare autosomal dominantly inherited disease caused by mutations in the transthyretin (TTR) gene. TTR mutations often cause the instability of transthyretin, production of misfolded proteins, and ultimately excessive deposition of insoluble amyloid fibrils in the myocardium, thereby leading to cardiac dysfunction. Herein, we report a novel transthyretin D39Y mutation in a Chinese family. We characterized the kinetic and thermodynamic stabilities of D39Y mutant TTR, revealing that TTR D39Y mutant was less stable than WT TTR and more stable than amyloidogenic mutation TTR L55P. Meanwhile, the only FDA approved drug Tafamidis showed satisfactory inhibitory effect toward ATTR amyloid formation and strong binding affinity in test tube revealed by isothermal titration calorimetry. Finally, we measured the well-folded tetrameric TTR concentration in patient's and his descents' blood serum using a previously reported UPLC-based assay. Notably, the tetramer concentrations gradually increased from symptomatic D39Y gene carrier father, to asymptomatic D39Y gene carrier daughter, and further to wild type daughter, suggesting the decrease in functional tetrameric TTR concentration may serve as an indicator for disease age of onset in D39Y gene carriers. The study described a Chinese family with hATTR-CA due to the TTR variant D39Y with its destabilizing effect in both kinetic and thermodynamic stabilities.

Structure restoration and aggregate inhibition of V30M mutant transthyretin protein by potential quinoline molecules

Transthyretin (TTR) is a tetrameric protein found in human plasma and cerebrospinal fluid that functions as a transporter of thyroxine (T4) and retinol. A mutation resulting in the substitution of valine to methionine at position 30 (V30M) is the most common mutation that destabilizes the tetramer structure of TTR protein resulting in a fatal neuropathy known as TTR amyloidosis. The V30M TTR-induced neuropathy can be inhibited through stabilization of the TTR tetramer by the binding of small molecules. We accessed the potential of in-house synthesized quinoline molecules to stabilize the V30M TTR structure and analyzed the impact of protein-ligand interactions through molecular docking, molecular dynamics (MD) simulations, steered MD, and umbrella sampling simulations. This study revealed that the binding of quinoline molecules reverted back the structural changes including the residual flexibility, changes in secondary structural elements, and also restored the alterations in the electrostatic surface potential induced by the V30M mutation. Further, the top-most 4G and 4R molecules were compared with an FDA-approved drug (Tafamidis) and a reference quinoline molecule 14C. Here, we intend to suggest that the quinoline molecules could revert the structural changes, cease tetramer dissociation, prevent abnormal oligomerization and therefore could be developed as an effective therapeutics against TTR amyloidosis.

826 NEW THERAPEUTIC PERSPECTIVES IN CARDIAC AMYLOIDOSIS

Abstract Man, 72 years old, smoker, hypertensive and dyslipidemic, came to our clinic suspected of heart disease with a hypertrophic phenotype. In anamnesis there was a recent hospitalization for heart failure in the course of undated atrial fibrillation. During hospitalization because of the presence of antero-septal and lateral QS complexes, a coronary disease was excluded by coronary angiography while the echocardiogram showed a left ventricle with moderate concentric wall thickening, LVEF 38% with a restrictive transmitral pattern. The patient was discharged on therapy with ramipril, bisoprolol, canrenone, furosemide and rivaroxaban with an electrical cardioversion program which had been subsequently ineffective. At the time of the first evaluation the patient was symptomatic of dyspnea in functional class NYHA III, he also reported in anamnesis a progressive reduction of exercise tolerance for about two years and a previous surgery for bilateral carpal tunnel syndrome 5 years earlier. The echocardiogram showed concentric parietal thickening in the presence of granular sparkling, apical sparing, thickening of the valvular apparatus and reduced GLS (- 12%) which led to a suspect of cardiac amyloidosis. To complete the diagnosis, the patient underwent: total-body bone scan with 99-Tc-DPD (Perugini score = 2); assay of serum kappa and lambda light chains (negative), serum and urinary immunofixation (negative), NT-proBNP (980 pg / mL) and a determination of troponin I (32 ng / L) which showed a picture of transthyretin cardiac amyloidosis. The genetic sampling confirmed the presence of the Ile68Leu transthyretin mutation and a neurological evaluation with electromyography ruled out a peripheral polyneuropathy. During follow-up the patient presented a worsening of clinical and instrumental pattern despite the progressive uptitration of diuretic therapy and the addition of metolazone with a simultaneous deterioration of left ventricular dysfunction (LVEF 30%) at echocardiogram. Therefore, the patient's case and possible therapeutic strategies were discussed collectively as it was not possible to access conventional therapies for cardiac amyloidosis with Tafamidis, Inotersen and Patisiran due to the contextual functional class NYHA&amp;gt; II and the absence of polyneuropathy, not it was possible to undertake biventricular resynchronization in the absence of intraventricular block or to implement therapy for heart failure with reduced ejection fraction due to intolerance. As a last option, implantation of a cardiac contractility modulation device (CCM) was proposed and performed via right subclavicular. At the successive follow-up after implantation, the patient showed a slight clinical and instrumental improvement and it was possible to reduce the diuretic dose, discontinuing metolazone. The echocardiogram also showed a slight increase in LVEF (35%). The long-term outpatient evaluation of the patient is currently underway with the aim of undertaking specific therapy with Tafamidis if the prescription criteria are met. Family screening has started. Conclusion the present clinical case represents an example of the application of alternative and potentially effective therapeutic strategies in patients with cardiac amyloidosis not susceptible to conventional pharmacological treatments.