The heat shock response modulates transthyretin deposition in the peripheral and autonomic nervous systems

Emerging Roles for Dendritic Cells in Heart Failure

The field of cardio-immunology has emerged from discoveries that define roles for innate and adaptive immune responses associated with myocardial inflammation and heart failure. Dendritic cells (DCs) comprise an important cellular compartment that contributes to systemic immune surveillance at the junction of innate and adaptive immunity. Once described as a singular immune subset, we now appreciate that DCs consist of a heterogeneous pool of subpopulations, each with distinct effector functions that can uniquely regulate the acute and chronic inflammatory response. Nevertheless, the cardiovascular-specific context involving DCs in negotiating the biological response to myocardial injury is not well understood. Herein, we review our current understanding of the role of DCs in cardiac inflammation and heart failure, including gaps in knowledge and clinical relevance.

Current Evidence Supporting the Role of Immune Response in ATTRv Amyloidosis

Hereditary transthyretin (ATTRv) amyloidosis with polyneuropathy, also known as familial amyloid polyneuropathy (FAP), represents a progressive, heterogeneous, severe, and multisystemic disease caused by pathogenic variants in the TTR gene. This autosomal-dominant neurogenetic disorder has an adult onset with variable penetrance and an inconstant phenotype, even among subjects carrying the same mutation. Historically, ATTRv amyloidosis has been viewed as a non-inflammatory disease, mainly due to the absence of any mononuclear cell infiltration in ex vivo tissues; nevertheless, a role of inflammation in its pathogenesis has been recently highlighted. The immune response may be involved in the development and progression of the disease. Fibrillary TTR species bind to the receptor for advanced glycation end products (RAGE), probably activating the nuclear factor κB (NF-κB) pathway. Moreover, peripheral blood levels of several cytokines, including interferon (IFN)-gamma, IFN-alpha, IL-6, IL-7, and IL-33, are altered in the course of the disease. This review summarizes the current evidence supporting the role of the immune response in ATTRv amyloidosis, from the pathological mechanisms to the possible therapeutic implications.

Decreased expression of S100A8/A9 in V30M related ATTRv amyloidosis

INTRODUCTION

Hereditary Transthyretin Amyloidosis is a rare, progressive and life-threatening systemic disease with predominant peripheral and autonomic nervous system involvement caused by mutation of the transthyretin protein. The most common TTR mutation regarding to ATTRv is a substitution of a Methionine for a Valine at position 30 that predisposes TTR to form aggregates and fibrils.

METHODS

S100A8 protein levels were measured in plasma samples from ATTRV30M patients and healthy donors. Additionally, S100A8/9 levels were measured in Schwann cells after incubation with human WT or V30M TTR. Moreover, bone marrow derived macrophages of either genetic background were generated and the expression of S100A8/9 was measured in response to toll like receptors agonists.

RESULTS

S100A8/A9 mRNA levels are decreased in HSF V30M mice as compared with the WT. Moreover, S100A8 protein levels were found downregulated in plasma samples from ATTRV30M patients. Furthermore, we provide evidence for a dysregulated S100 expression by Schwann cells in response to TTRV30M and by mutated macrophages in response to toll like receptors agonists.

CONCLUSION

The presence of TTRV30M impacts S100 expression, possibly contributing to the impaired immune activation of Schwann cells in nerves from ATTRV30M patients. This may be linked to the diminished immune cellular infiltration in these nerves, contributing in this way for the neuronal dysfunction present in the disease.

Cellular environment of TTR deposits in an animal model of ATTR—Cardiomyopathy

Introduction: Cardiac amyloidoses are the most fatal manifestation of systemic amyloidoses. It is believed the number of cases to be greatly underestimated mostly due to misdiagnosis. Particularly, the involvement of TTR V30M in the heart of ATTRV30M amyloidosis has not been completely understood specifically in terms of implicated cellular pathways, heart function and cardiac physiology. In the present work we proposed to characterize TTR V30M cardiac involvement particularly at the tissue cellular level in a mouse model.

Methods: HSF ± hTTR V30M mice, a model that expresses human TTRV30M in a Ttr null background, widely used for the characterization and modulation of neurological features of ATTRV30M amyloidosis was used. SDS-PAGE of cardiac homogenates followed by Western blot was performed. Immunohistochemistry and double immunofluorescence analyses were carried out to determine TTR deposition pattern and sub-localization.

Results: Western blots were able to detect TTR in its monomeric state at ∼14 kDa. Immunofluorescent images showed TTR was found mostly in the intercellular spaces. Blood contamination was excluded by CD31 staining. Tissues were Congo Red negative. Upon TTR and macrophages (CD68) staining in the cardiac tissue a clear tendency of macrophage convergence to the tissue regions where TTR was more abundant was observed. Moreover, in some instances it was possible to detect co-localization of both fluorophores. Cardiac fibroblasts were stained with PDGFr-alpha, and here the co-localization was not so evident although there was some degree of co-occurrence. The hearts of transgenic mice revealed higher content of Galectin-3.

Conclusion: This animal model and associated features observed as result of cardiac TTR deposition provide a promising and invaluable research tool for a better understanding of the implicated pathways that lead to the lethality associated to TTR cardiac amyloidosis. New therapeutic strategies can be tested and ultimately this will lead to improved treatment alternatives capable of increasing patient’s quality of life and life expectancy and, hopefully to eradicate a condition that is silently spreading worldwide.

Human transthyretin gene expression is markedly increased in repair Schwann cells in an in vitro model of hereditary transthyretin amyloidosis

Hereditary transthyretin (TTR) amyloidosis (ATTRv) is characterized by TTR amyloid deposition in the peripheral nervous system. It remains unknown why variant TTR preferentially deposits in the peripheral nerves and dorsal root ganglia. We previously detected low levels of TTR expression in Schwann cells and established an immortalized Schwann cell line, TgS1, derived from a mouse model of ATTRv amyloidosis expressing the variant TTR gene. In the present study, the expression of TTR and Schwann cell marker genes was investigated in TgS1 cells by quantitative RT-PCR. TTR gene expression was markedly upregulated in TgS1 cells incubated in non-growth medium-Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum. The expression levels of c-Jun, Gdnf and Sox2 were increased, while Mpz was downregulated, suggesting that TgS1 cells exhibit a repair Schwann cell-like phenotype in the non-growth medium. Western blot analysis revealed that TTR protein was produced and secreted by the TgS1 cells. Furthermore, downregulation of Hsf1 with siRNA induced TTR aggregates in the TgS1 cells. These findings indicate that TTR expression is markedly increased in repair Schwann cells, likely to promote axonal regeneration. Therefore, aged dysfunctional repair Schwann cells may cause the deposition of variant TTR aggregates in the nerves of patients with ATTRv.

Molecular Tweezers: Supramolecular Hosts with Broad-Spectrum Biological Applications

Lysine-selective molecular tweezers (MTs) are supramolecular host molecules displaying a remarkably broad spectrum of biologic activities. MTs act as inhibitors of the self-assembly and toxicity of amyloidogenic proteins using a unique mechanism. They destroy viral membranes and inhibit infection by enveloped viruses, such as HIV-1 and SARS-CoV-2, by mechanisms unrelated to their action on protein self-assembly. They also disrupt biofilm of Gram-positive bacteria. The efficacy and safety of MTs have been demonstrated in vitro, in cell culture, and in vivo, suggesting that these versatile compounds are attractive therapeutic candidates for various diseases, infections, and injuries. A lead compound called CLR01 has been shown to inhibit the aggregation of various amyloidogenic proteins, facilitate their clearance in vivo, prevent infection by multiple viruses, display potent anti-biofilm activity, and have a high safety margin in animal models. The inhibitory effect of CLR01 against amyloidogenic proteins is highly specific to abnormal self-assembly of amyloidogenic proteins with no disruption of normal mammalian biologic processes at the doses needed for inhibition. Therapeutic effects of CLR01 have been demonstrated in animal models of proteinopathies, lysosomal-storage diseases, and spinal-cord injury. Here we review the activity and mechanisms of action of these intriguing compounds and discuss future research directions. SIGNIFICANCE STATEMENT: Molecular tweezers are supramolecular host molecules with broad biological applications, including inhibition of abnormal protein aggregation, facilitation of lysosomal clearance of toxic aggregates, disruption of viral membranes, and interference of biofilm formation by Gram-positive bacteria. This review discusses the molecular and cellular mechanisms of action of the molecular tweezers, including the discovery of distinct mechanisms acting in vitro and in vivo, and the application of these compounds in multiple preclinical disease models.

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.

Amyloid Formation by Globular Proteins: The Need to Narrow the Gap Between in Vitro and in Vivo Mechanisms

The globular to fibrillar transition of proteins represents a key pathogenic event in the development of amyloid diseases. Although systemic amyloidoses share the common characteristic of amyloid deposition in the extracellular matrix, they are clinically heterogeneous as the affected organs may vary. The observation that precursors of amyloid fibrils derived from circulating globular plasma proteins led to huge efforts in trying to elucidate the structural events determining the protein metamorphosis from their globular to fibrillar state. Whereas the process of metamorphosis has inspired poets and writers from Ovid to Kafka, protein metamorphism is a more recent concept. It is an ideal metaphor in biochemistry for studying the protein folding paradigm and investigating determinants of folding dynamics. Although we have learned how to transform both normal and pathogenic globular proteins into fibrillar polymers in vitro, the events occurring in vivo, are far more complex and yet to be explained. A major gap still exists between in vivo and in vitro models of fibrillogenesis as the biological complexity of the disease in living organisms cannot be reproduced at the same extent in the test tube. Reviewing the major scientific attempts to monitor the amyloidogenic metamorphosis of globular proteins in systems of increasing complexity, from cell culture to human tissues, may help to bridge the gap between the experimental models and the actual pathological events in patients.

The Expression of Chemokines Is Downregulated in a Pre-Clinical Model of TTR V30M Amyloidosis

Inflammation is a hallmark of several neurodegenerative disorders including hereditary amyloidogenic transthyretin amyloidosis (ATTRv). ATTRv is an autosomal dominant neurodegenerative disorder with extracellular deposition of mutant transthyretin (TTR) aggregates and fibrils, particularly in nerves and ganglia of the peripheral nervous system. Nerve biopsies from ATTRv patients show increased cytokine production, but interestingly no immune inflammatory cellular infiltrate is observed around TTR aggregates. Here we show that as compared to Wild Type (WT) animals, the expression of several chemokines is highly downregulated in the peripheral nervous system of a mouse model of the disease. Interestingly, we found that stimulation of mouse Schwann cells (SCs) with WT TTR results in the secretion of several chemokines, a process that is mediated by toll-like receptor 4 (TLR4). In contrast, the secretion of all tested chemokines is compromised upon stimulation of SCs with mutant TTR (V30M), suggesting that V30M TTR fails to activate TLR4 signaling. Altogether, our data shed light into a previously unappreciated mechanism linking TTR activation of SCs and possibly underlying the lack of inflammatory response observed in the peripheral nervous system of ATTRv patients.

Myocardial ischaemia reperfusion injury and cardioprotection in the presence of sensory neuropathy: Therapeutic options

During the last decades, mortality from acute myocardial infarction has been dramatically reduced. However, the incidence of post-infarction heart failure is still increasing. Cardioprotection by ischaemic conditioning had been discovered more than three decades ago. Its clinical translation, however, is still an unmet need. This is mainly due to the disrupted cardioprotective signalling pathways in the presence of different cardiovascular risk factors, co-morbidities and the medication being taken. Sensory neuropathy is one of the co-morbidities that has been shown to interfere with cardioprotection. In the present review, we summarize the diverse aetiology of sensory neuropathies and the mechanisms by which these neuropathies may interfere with ischaemic heart disease and cardioprotective signalling. Finally, we suggest future therapeutic options targeting both ischaemic heart and sensory neuropathy simultaneously. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Contributions of Animal Models to the Mechanisms and Therapies of Transthyretin Amyloidosis

Transthyretin amyloidosis (ATTR amyloidosis) is a fatal systemic disease caused by amyloid deposits of misfolded transthyretin, leading to familial amyloid polyneuropathy and/or cardiomyopathy, or a rare oculoleptomeningeal amyloidosis. A good model system that mimic the disease phenotype is crucial for the development of drugs and treatments for this devastating degenerative disorder. The present models using fruit flies, worms, rodents, non-human primates and induced pluripotent stem cells have helped researchers understand important disease-related mechanisms and test potential therapeutic options. However, the challenge of creating an ideal model still looms, for these models did not recapitulates all symptoms, particularly neurological presentation, of ATTR amyloidosis. Recently, knock-in techniques was used to generate two humanized ATTR mouse models, leading to amyloid deposition in the nerves and neuropathic manifestation in these models. This review gives a recent update on the milestone, progress, and challenges in developing different models for ATTR amyloidosis research.

MMP-14 overexpression correlates with the neurodegenerative process in familial amyloidotic polyneuropathy

Levels of matrix metalloproteases (MMPs) can be differentially regulated in response to injury or neurological diseases. For instance, it is known that selective and short-term inhibition of MMP-14, a membrane-type 1 MMP, accelerates axon regeneration. Because axon growth and regeneration is impaired in familial amyloidotic polyneuropathy (FAP), a neurodegenerative disorder characterized by misfolding and deposition of mutant transthyretin (TTR) in the peripheral nervous system (PNS), we presently investigated the expression levels and the potential role for MMP-14 in this condition. By using cell culture studies, a mouse model of disease and human clinical samples, we observed that MMP-14: (i) is overexpressed in FAP nerves, correlating with TTR deposition; (ii) is upregulated in sciatic nerves from a preclinical transgenic mouse model, increasing with TTR deposition; (iii) levels in the PNS and plasma are rescued upon treatment of mice with anakinra or TTR siRNA, drugs acting over the IL-1 signaling pathway or TTR liver synthesis, respectively; (iv) increases in Schwann cells upon incubation with amyloid-like aggregates; and, finally, (v) is increased in plasma of FAP patients, correlating with disease progression. These results highlight the relevance of MMP-14 in the pathophysiology of FAP, suggesting not only a potential role for this molecule as a novel biomarker for therapy follow up, but also as a new potential therapeutic target.

Summary: MMP-14 overexpression correlates with familial amyloidotic polyneuropathy disease and progression, as determined using mouse models and human samples. TTR gene silencing in the preclinical model decreases MMP-14 plasma levels.

Amyloid deposition in a mouse model humanized at the transthyretin and retinol-binding protein 4 loci

Familial amyloidotic polyneuropathy is an autosomal dominant disorder caused by a point mutation in the transthyretin (TTR) gene. The process of TTR amyloidogenesis begins with rate-limiting dissociation of the TTR tetramer. Thus, the TTR stabilizers, such as Tafamidis and Diflunisal, are now in clinical trials. Mouse models will be useful to testing the efficacy of these drugs. Although several mouse models have been generated, they all express mouse Rbp4. Thus, human TTR associates with mouse RBP4, resulting in different kinetic and thermodynamic stability profiles of TTR tetramers. To overcome this problem, we previously produced humanized mouse strains at both the TTR and Rbp4 loci (Ttr ^hTTRVal30 , Ttr ^hTTRMet30 , and Rbp4 ^hRBP4 ). By mating these mice, we produced double-humanized mouse strains, Ttr ^{hTTRVal30/hTTRVal30} :Rbp4 ^hRBP4/hRBP4 and Ttr ^{hTTRVal30/Met30} :Rbp4 ^hRBP4/hRBP4 . We used conventional transgenic mouse strains on a wild-type (Ttr ^+/+ :Tg[6.0hTTRMet30]) or knockout Ttr background (Ttr^-/-:Tg[6.0hTTRMet30]) as reference strains. The double-humanized mouse showed 1/25 of serum hTTR and 1/40 of serum hRBP4 levels. However, amyloid deposition was more pronounced in Ttr ^{hTTRVal30/Met30} :Rbp4 ^hRBP4/hRBP4 than in conventional transgenic mouse strains. In addition, a similar amount of amyloid deposition was also observed in Ttr ^{hTTRVal30/ hTTRVal30} :Rbp4 ^{hRBP4/ hRBP4} mice that carried the wild-type human TTR gene. Furthermore, amyloid deposition was first observed in the sciatic nerve without any additional genetic change. In all strains, anti-TTR antibody-positive deposits were found in earlier age and at higher percentage than amyloid fibril deposition. In double-humanized mice, gel filtration analysis of serum revealed that most hTTR was free of hRBP4, suggesting importance of free TTR for amyloid deposition.

Sensory nerve degeneration in a mouse model mimicking early manifestations of familial amyloid polyneuropathy due to transthyretin Ala97Ser

AIMS

Sensory nerve degeneration and consequent abnormal sensations are the earliest and most prevalent manifestations of familial amyloid polyneuropathy (FAP) due to amyloidogenic transthyretin (TTR). FAP is a relentlessly progressive degenerative disease of the peripheral nervous system. However, there is a lack of mouse models to replicate the early neuropathic manifestations of FAP.

METHODS

We established human TTR knock-in mice by replacing one allele of the mouse Ttr locus with human wild-type TTR (hTTR^wt ) or human TTR with the A97S mutation (hTTR^A97S ). Given the late onset of neuropathic manifestations in A97S-FAP, we investigated nerve pathology, physiology, and behavioural tests in these mice at two age points: the adult group (8 - 56 weeks) and the ageing group (> 104 weeks).

RESULTS

In the adult group, nerve profiles, neurophysiology and behaviour were similar between hTTR^wt and hTTR^A97S mice. By contrast, ageing hTTR^A97S mice showed small fibre neuropathy with decreased intraepidermal nerve fibre density and behavioural signs of mechanical allodynia. Furthermore, significant reductions in sural nerve myelinated nerve fibre density and sensory nerve action potential amplitudes in these mice indicated degeneration of large sensory fibres. The unaffected motor nerve physiology replicated the early symptoms of FAP patients, that is, sensory nerves were more vulnerable to mutant TTR than motor nerves.

CONCLUSIONS

These results demonstrate that the hTTR^A97S mouse model develops sensory nerve pathology and corresponding physiology mimicking A97S-FAP and provides a platform to develop new therapies for the early stage of A97S-FAP.

Using Molecular Tweezers to Remodel Abnormal Protein Self-Assembly and Inhibit the Toxicity of Amyloidogenic Proteins

Molecular tweezers (MTs) are broad-spectrum inhibitors of abnormal protein self-assembly, which act by binding selectively to lysine and arginine residues. Through this unique mechanism of action, MTs inhibit formation of toxic oligomers and aggregates. Their efficacy and safety have been demonstrated in vitro, in cell culture, and in animal models. Here, we discuss the application of MTs in diverse in vitro and in vivo systems, the experimental details, the scope of their use, and the limitations of the approach. We also consider methods for administration of MTs in animal models to measure efficacy, pharmacokinetic, and pharmacodynamic parameters in proteinopathies.

Differential expression of Cathepsin E in transthyretin amyloidosis: from neuropathology to the immune system

Background

Increasing evidence supports a key role for inflammation in the neurodegenerative process of familial amyloidotic polyneuropathy (FAP). While there seems to be an overactivation of the neuronal interleukin-1 signaling pathway, the immune response is apparently compromised in FAP. Accordingly, little immune cell infiltration is observed around pre-fibrillar or fibrillar amyloid deposits, with the underlying mechanism for this phenomenon remaining poorly understood. Cathepsin E (CtsE) is an important intermediate for antigen presentation and chemotaxis, but its role in the pathogenesis of FAP disease remains unknown.

Methods

In this study, we used both mouse primary macrophages and in vivo studies based on transgenic models of FAP and human samples to characterize CtsE expression in different physiological systems.

Results

We show that CtsE is critically decreased in bone marrow-derived macrophages from a FAP mouse model, possibly contributing for cell function impairment. Compromised levels of CtsE were also found in injured nerves of transgenic mice and, most importantly, in naïve peripheral nerves, sensory ganglia, murine stomach, and sural nerve biopsies derived from FAP patients. Expression of CtsE in tissues was associated with transthyretin (TTR) deposition and differentially regulated accordingly with the physiological system under study. Preventing deposition with a TTR small interfering RNA rescued CtsE in the peripheral nervous system (PNS). In contrast, the expression of CtsE increased in splenic cells (mainly monocytes) or peritoneal macrophages, indicating a differential macrophage phenotype.

Conclusion

Altogether, our data highlights the potential of CtsE as a novel FAP biomarker and a possible modulator for innate immune cell chemotaxis to the disease most affected tissues—the peripheral nerve and the gastrointestinal tract.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0891-9) contains supplementary material, which is available to authorized users.

Overexpression of Protocadherin-10 in Transthyretin-Related Familial Amyloidotic Polyneuropathy

Overwhelming data suggest that oncogenic and neurodegenerative pathways share several altered cellular responses to insults such as oxidative stress, extracellular matrix remodeling, inflammation, or cell dyscommunication. Protocadherin-10 (Pcdh10) is an adhesion molecule found to protect against tumorigenesis and essential for axonal elongation and actin dynamics during development. Here, by using genome microarrays we identified for the first time Pcdh10 up-regulation in tissues from transgenic mouse models, cultured Schwann cells, and human samples from a familial form of peripheral neuropathy (familial amyloidotic polyneuropathy). Familial amyloidotic polyneuropathy is characterized by poor functional recovery and impaired nerve regenerative response after misfolding and deposition in the peripheral nervous system of mutant transthyretin. Not only increased transcriptional and translational Pcdh10 levels occurred in axons and Schwann cells of nerves with deposited transthyretin aggregates but the pattern also extended to associated cues of axon guidance like neuropilin-1 and F-actin. These findings suggest that Pcdh10 may influence subcellular actin cytoskeletal organization and axon-axon interactions in the course of familial amyloidotic polyneuropathy. Moreover, when preventing nonfibrillar transthyretin deposition with anakinra or transthyretin siRNA, Pcdh10 protein levels were reduced, highlighting its potential as a novel disease biomarker. Whether Pcdh10 overexpression in familial amyloidotic polyneuropathy represents a protective or deleterious response, enhancing survival or promoting cell death will need further investigation.

Efficiency of silencing RNA for removal of transthyretin V30M in a TTR leptomeningeal animal model

Some TTR mutants target the central nervous system (CNS). Familial amyloid polyneuropathy (FAP) with leptomeningeal involvement has been described in 9% of transthyretin (TTR) mutations and in valine for methionine at position 30 (V30M) patients. These individuals present dementia, ataxia, brain hemorrhages and focal neurological episodes (FNEs). FNEs occurred also in V30M FAP patients with longer disease duration, who have undergone liver transplant to remove the source of plasma mutant TTR as a form of treatment. It is thus to expect that as better treatments for FAP emerge and prolong survival, meningeal-vascular CNS deposition will increase and need special therapies. Recently, we detected TTR meningeal-vascular deposition in a V30M TTR transgenic mouse model, opening new avenues of research to investigate selective treatments of this condition. Since pre-clinical studies with TTR siRNA therapeutics were shown to promote clearance of TTR non-fibrillar deposits in several organs and tissues, we investigated its effect on TTR meningeal-vascular deposition. We show that systemically administered TTR siRNA promoted TTR clearance in the extracellular matrix of meninges and brain blood vessels. Surprisingly, despite the striking decline of blood TTR, cerebrospinal fluid TTR levels were unaffected. Though this is reassuring because siRNA will not interfere with the neuroprotective role of TTR in the CNS, it raises new questions on therapeutical approaches for CNS ATTR.

Molecular tweezers for lysine and arginine - powerful inhibitors of pathologic protein aggregation

Molecular tweezers represent the first class of artificial receptor molecules that have made the way from a supramolecular host to a drug candidate with promising results in animal tests. Due to their unique structure, only lysine and arginine are well complexed with exquisite selectivity by a threading mechanism, which unites electrostatic, hydrophobic and dispersive attraction. However, tweezer design must avoid self-dimerization, self-inclusion and external guest binding. Moderate affinities of molecular tweezers towards sterically well accessible basic amino acids with fast on and off rates protect normal proteins from potential interference with their biological function. However, the early stages of abnormal Aβ, α-synuclein, and TTR assembly are redirected upon tweezer binding towards the generation of amorphous non-toxic materials that can be degraded by the intracellular and extracellular clearance mechanisms. Thus, specific host-guest chemistry between aggregation-prone proteins and lysine/arginine binders rescues cell viability and restores animal health in models of AD, PD, and TTR amyloidosis.

Tissue remodeling after interference RNA mediated knockdown of transthyretin in a familial amyloidotic polyneuropathy mouse model

Transthyretin (TTR) deposition in the peripheral nervous system is the hallmark of familial amyloidotic polyneuropathy (FAP). Currently, liver transplantation is the only available treatment to halt the progression of clinical symptoms; however, due to the limitations of this procedure, development of alternative therapeutic strategies is of utmost importance. In this regard, interference RNA (RNAi) targeting TTR is currently in phase III clinical development. To dissect molecular changes occurring in dorsal root ganglia (DRG) upon RNAi-mediated knockdown of TTR, we treated both chronically and acutely an FAP mouse model, in different stages of disease. Our data show that inhibition of TTR expression by the liver with RNAi reverse TTR deposition in DRG, decrease matrix metalloproteinase-2 (MMP-2) protein levels in plasma, inhibit Mmp-2 gene expression and downregulate MMP-9 activity in DRG, indicating extracellular matrix remodeling. Furthermore, protein levels of MMP-2 were found upregulated in plasma samples from FAP patients indicating that MMP-2 might be a novel potential biomarker for FAP diagnosis. Collectively, our data show that silencing TTR liver synthesis in vivo can modulate TTR-induced pathology in the peripheral nervous system and highlight the potential of MMP-2 as a novel disease biomarker.

Preclinical evaluation of RNAi as a treatment for transthyretin-mediated amyloidosis

ATTR amyloidosis is a systemic, debilitating and fatal disease caused by transthyretin (TTR) amyloid accumulation. RNA interference (RNAi) is a clinically validated technology that may be a promising approach to the treatment of ATTR amyloidosis. The vast majority of TTR, the soluble precursor of TTR amyloid, is expressed and synthesized in the liver. RNAi technology enables robust hepatic gene silencing, the goal of which would be to reduce systemic levels of TTR and mitigate many of the clinical manifestations of ATTR that arise from hepatic TTR expression. To test this hypothesis, TTR-targeting siRNAs were evaluated in a murine model of hereditary ATTR amyloidosis. RNAi-mediated silencing of hepatic TTR expression inhibited TTR deposition and facilitated regression of existing TTR deposits in pathologically relevant tissues. Further, the extent of deposit regression correlated with the level of RNAi-mediated knockdown. In comparison to the TTR stabilizer, tafamidis, RNAi-mediated TTR knockdown led to greater regression of TTR deposits across a broader range of affected tissues. Together, the data presented herein support the therapeutic hypothesis behind TTR lowering and highlight the potential of RNAi in the treatment of patients afflicted with ATTR amyloidosis.

Curcumin: A multi-target disease-modifying agent for late-stage transthyretin amyloidosis

Transthyretin amyloidoses encompass a variety of acquired and hereditary diseases triggered by systemic extracellular accumulation of toxic transthyretin aggregates and fibrils, particularly in the peripheral nervous system. Since transthyretin amyloidoses are typically complex progressive disorders, therapeutic approaches aiming multiple molecular targets simultaneously, might improve therapy efficacy and treatment outcome. In this study, we evaluate the protective effect of physiologically achievable doses of curcumin on the cytotoxicity induced by transthyretin oligomers in vitro by showing reduction of caspase-3 activity and the levels of endoplasmic reticulum-resident chaperone binding immunoglobulin protein. When given to an aged Familial Amyloidotic Polyneuropathy mouse model, curcumin not only reduced transthyretin aggregates deposition and toxicity in both gastrointestinal tract and dorsal root ganglia but also remodeled congophilic amyloid material in tissues. In addition, curcumin enhanced internalization, intracellular transport and degradation of transthyretin oligomers by primary macrophages from aged Familial Amyloidotic Polyneuropathy transgenic mice, suggesting an impaired activation of naïve phagocytic cells exposed to transthyretin toxic intermediate species. Overall, our results clearly support curcumin or optimized derivatives as promising multi-target disease-modifying agent for late-stage transthyretin amyloidosis.

Micro-proteomics with iterative data analysis: Proteome analysis in C. elegans at the single worm level

Proteomics studies typically analyze proteins at a population level, using extracts prepared from tens of thousands to millions of cells. The resulting measurements correspond to average values across the cell population and can mask considerable variation in protein expression and function between individual cells or organisms. Here, we report the development of micro‐proteomics for the analysis of Caenorhabditis elegans, a eukaryote composed of 959 somatic cells and ∼1500 germ cells, measuring the worm proteome at a single organism level to a depth of ∼3000 proteins. This includes detection of proteins across a wide dynamic range of expression levels (>6 orders of magnitude), including many chromatin‐associated factors involved in chromosome structure and gene regulation. We apply the micro‐proteomics workflow to measure the global proteome response to heat‐shock in individual nematodes. This shows variation between individual animals in the magnitude of proteome response following heat‐shock, including variable induction of heat‐shock proteins. The micro‐proteomics pipeline thus facilitates the investigation of stochastic variation in protein expression between individuals within an isogenic population of C. elegans. All data described in this study are available online via the Encyclopedia of Proteome Dynamics (http://www.peptracker.com/epd), an open access, searchable database resource.

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.

Interleukin-1 signaling pathway as a therapeutic target in transthyretin amyloidosis

INTRODUCTION

Inflammation is a key pathological hallmark of several neurodegenerative disorders including Alzheimer's disease, Parkinson's disease and familial amyloidotic polyneuropathy (FAP). Among all inflammatory cytokines associated with FAP, IL-1β, in particular, has been implicated in playing a key pathogenic role. In the present study, we sought to investigate whether blocking IL-1β signaling provides disease-modifying benefits in an FAP mouse model.

METHODS

We assessed the effect of chronic administration of Anakinra, an IL-1 antagonist, on FAP pathogenesis in vivo, using real-time polymerase chain reaction (qPCR), semi-quantitative immunohistochemistry (SQ-IHC), western blot and nerve morphometric analyses.

RESULTS

We found that treatment with Anakinra prevents transthyretin (TTR) extracellular deposition in sciatic nerve, protecting unmyelinated nerve fibers from aggregate-induced degeneration. Moreover, Anakinra administration significantly suppressed IL-1 signaling pathway and inhibited apoptosis and nitrative stress.

CONCLUSIONS

The present work highlights the relevance of the IL-1 signaling pathway in the pathophysiology of FAP. Our results bring to light the importance of non-amyloid targets in the therapeutic strategies for this disorder. Thus, we propose the use of Anakinra as a potential therapeutic agent for TTR-related amyloidosis.

The systemic amyloid precursor transthyretin (TTR) behaves as a neuronal stress protein regulated by HSF1 in SH-SY5Y human neuroblastoma cells and APP23 Alzheimer's disease model mice

Increased neuronal synthesis of transthyretin (TTR) may favorably impact on Alzheimer's disease (AD) because TTR has been shown to inhibit Aβ aggregation and detoxify cell-damaging conformers. The mechanism whereby hippocampal and cortical neurons from AD patients and APP23 AD model mice produce more TTR is unknown. We now show that TTR expression in SH-SY5Y human neuroblastoma cells, primary hippocampal neurons and the hippocampus of APP23 mice, is significantly enhanced by heat shock factor 1 (HSF1). Chromatin immunoprecipitation (ChIP) assays demonstrated occupation of TTR promoter heat shock elements by HSF1 in APP23 hippocampi, primary murine hippocampal neurons, and SH-SY5Y cells, but not in mouse liver, cultured human hepatoma (HepG2) cells, or AC16 cultured human cardiomyocytes. Treating SH-SY5Y human neuroblastoma cells with heat shock or the HSF1 stimulator celastrol increased TTR transcription in parallel with that of HSP40, HSP70, and HSP90. With both treatments, ChIP showed increased occupancy of heat shock elements in the TTR promoter by HSF1. In vivo celastrol increased the HSF1 ChIP signal in hippocampus but not in liver. Transfection of a human HSF1 construct into SH-SY5Y cells increased TTR transcription and protein production, which could be blocked by shHSF1 antisense. The effect is neuron specific. In cultured HepG2 cells, HSF1 was either suppressive or had no effect on TTR expression confirming the differential effects of HSF1 on TTR transcription in different cell types.

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.

Induced pluripotent stem cell modeling of multisystemic, hereditary transthyretin amyloidosis

Familial transthyretin amyloidosis (ATTR) is an autosomal-dominant protein-folding disorder caused by over 100 distinct mutations in the transthyretin (TTR) gene. In ATTR, protein secreted from the liver aggregates and forms fibrils in target organs, chiefly the heart and peripheral nervous system, highlighting the need for a model capable of recapitulating the multisystem complexity of this clinically variable disease. Here, we describe the directed differentiation of ATTR patient-specific iPSCs into hepatocytes that produce mutant TTR, and the cardiomyocytes and neurons normally targeted in the disease. We demonstrate that iPSC-derived neuronal and cardiac cells display oxidative stress and an increased level of cell death when exposed to mutant TTR produced by the patient-matched iPSC-derived hepatocytes, recapitulating essential aspects of the disease in vitro. Furthermore, small molecule stabilizers of TTR show efficacy in this model, validating this iPSC-based, patient-specific in vitro system as a platform for testing therapeutic strategies.

Hsf-1 affects podocyte markers NPHS1, NPHS2 and WT1 in a transgenic mouse model of TTRVal30Met-related amyloidosis

INTRODUCTION

Familial amyloid polyneuropathy is characterized by transthyretin (TTR) deposition in various tissues, including the kidneys. While deposition induces organ dysfunction, renal involvement in TTR-related amyloidosis could manifest from proteinuria to end-stage kidney failure. As proteinuria is considered result of glomerular filtration barrier injury we investigated whether TTR deposition affects either glomerular basement membrane (GBM) or podocytes.

MATERIALS AND METHODS

Immunohistochemistry, immunoblot and gene expression studies for nephrin, podocin and WT1 were run on renal tissue from human-TTRV30M transgenic mice hemizygous or homozygous for heat shock factor one (Hsf-1). Transmission electron microscopy was used for evaluation of podocyte foot process width (PFW) and GBM thickness in Hsf-1 hemizygous mice with or without TTRV30M or amyloid deposition.

RESULTS

Glomeruli of hsf-1 hemizygous transgenic mice showed lower nephrin and podocin protein levels but an increased podocyte number when compared to Hsf-1 homozygous transgenic mice. Nephrin, podocin and WT1 gene expression levels were unaffected by the Hsf-1 carrier status. TTRV30M deposition was associated with increased PFW and GBM thickness.

CONCLUSIONS

Under the effect of Hsf-1 hemizygosity, TTRV30M deposition has deleterious effects on GBM thickness, PFW and slit diaphragm composition, without affecting nephrin and podocin gene expression.

Fibroblasts endocytose and degrade transthyretin aggregates in transthyretin-related amyloidosis

Transthyretin (TTR)-related amyloidosis is a fatal disorder characterized by systemic extracellular deposition of TTR amyloid fibrils. Mutations in the TTR gene cause an autosomal dominant form of the disease-familial amyloidotic polyneuropathy (FAP). Wild-type (WT) TTR can also form amyloid fibrils in elderly patients with senile systemic amyloidosis. Regression of amyloid deposits in FAP patients who undergo liver transplantation to remove the main source of mutant TTR suggests the existence of mechanisms for the clearance of TTR deposits from the extracellular matrix (ECM), but the precise mechanisms are largely unknown. Because fibroblasts are abundant, playing a central role in the maintenance of the ECM and because the skin is one of the major sites of soluble TTR catabolism, in the present study, we analyzed their role in clearance of TTR aggregates. In vitro studies with a fibroblast cell line revealed that fibroblasts endocytosed and degraded aggregated TTR. Subcutaneous injection of soluble and aggregated TTR into WT mice showed internalization and clearance over time by both fibroblasts and macrophages. Immunohistochemical studies of skin biopsies from V30M patients, asymptomatic carriers, recipients of domino FAP livers as well as transgenic mice for human V30M showed intracellular TTR immunoreactivity in fibroblasts and macrophages that increased with clinical status and with age in transgenic mice. Overall, the present in vitro and in vivo data show that fibroblasts endocytose and degrade TTR aggregates. The function or dysfunction of TTR clearance by fibroblasts may have important implications for the development, progression, and regression of TTR deposition in the ECM.

Modulators of amyloid protein aggregation and toxicity: EGCG and CLR01

Abnormal protein folding and self-assembly causes over 30 cureless human diseases for which no disease-modifying therapies are available. The common side to all these diseases is formation of aberrant toxic protein oligomers and amyloid fibrils. Both types of assemblies are drug targets, yet each presents major challenges to drug design, discovery, and development. In this review, we focus on two small molecules that inhibit formation of toxic amyloid protein assemblies — the green-tea derivative (−)-epigallocatechin-3-gallate (EGCG), which was identified through a combination of epidemiologic data and a compound library screen, and the molecular tweezer CLR01, whose inhibitory activity was discovered in our group based on rational reasoning, and subsequently confirmed experimentally. Both compounds act in a manner that is not specific to one particular protein and thus are useful against a multitude of amyloidogenic proteins, yet they act via distinct putative mechanisms. CLR01 disrupts protein aggregation through specific binding to lysine residues, whereas the mechanisms underlying the activity of EGCG are only recently beginning to unveil. We discuss current in vitro and, where available, in vivo literature related to EGCG and CLR01’s effects on amyloid β-protein, α-synuclein, transthyretin, islet amyloid polypeptide, and calcitonin. We also describe the toxicity, pharmacokinetics, and mechanism of action of each compound.

The proteome response to amyloid protein expression in vivo

Protein misfolding disorders such as Alzheimer, Parkinson and transthyretin amyloidosis are characterized by the formation of protein amyloid deposits. Although the nature and location of the aggregated proteins varies between different diseases, they all share similar molecular pathways of protein unfolding, aggregation and amyloid deposition. Most effects of these proteins are likely to occur at the proteome level, a virtually unexplored reality. To investigate the effects of an amyloid protein expression on the cellular proteome, we created a yeast expression system using human transthyretin (TTR) as a model amyloidogenic protein. We used Saccharomyces cerevisiae, a living test tube, to express native TTR (non-amyloidogenic) and the amyloidogenic TTR variant L55P, the later forming aggregates when expressed in yeast. Differential proteome changes were quantitatively analyzed by 2D-differential in gel electrophoresis (2D-DIGE). We show that the expression of the amyloidogenic TTR-L55P causes a metabolic shift towards energy production, increased superoxide dismutase expression as well as of several molecular chaperones involved in protein refolding. Among these chaperones, members of the HSP70 family and the peptidyl-prolyl-cis-trans isomerase (PPIase) were identified. The latter is highly relevant considering that it was previously found to be a TTR interacting partner in the plasma of ATTR patients but not in healthy or asymptomatic subjects. The small ubiquitin-like modifier (SUMO) expression is also increased. Our findings suggest that refolding and degradation pathways are activated, causing an increased demand of energetic resources, thus the metabolic shift. Additionally, oxidative stress appears to be a consequence of the amyloidogenic process, posing an enhanced threat to cell survival.

Natural polyphenols as modulators of TTR amyloidogenesis: in vitro and in vivo evidences towards therapy

Several natural polyphenols have been reported to act on different amyloidogenic proteins inhibiting amyloid formation therefore we decided to test their effect on transthyretin (TTR) amyloid formation. We found that epigallocatechin-3-gallate (EGCG), curcumin and nordihydroguaiaretic acid (NDGA) bind to TTR and modulate its amyloidogenicity, in vitro, although through different mechanisms of action. Based on these in vitro studies, we decided to test EGCG in vivo using mice models for familial amyloidotic polyneuropathy (FAP). Therefore, we performed a subchronic administration of EGCG to mice, for 6 weeks. Next, we assessed the effects of EGCG treatment by immunohistochemistry (IHC) and western blot analysis of mice tissues. The results obtained demonstrate that EGCG inhibits TTR aggregates deposition in about 50% along the gastrointestinal (GI) tract and peripheral nervous system (PNS) and lowered the levels of several FAP associated biomarkers. Furthermore, treatment of old FAP mice with EGCG resulted not only in the decrease of nonfibrillar TTR deposition but also in the disaggregation of congophilic amyloid deposits. The dual effect as inhibitor of aggregation and as disruptor of amyloid together with its low toxicity indicates that EGCG presents a therapeutic application in FAP.

Why are some amyloidoses systemic? Does hepatic "chaperoning at a distance" prevent cardiac deposition in a transgenic model of human senile systemic (transthyretin) amyloidosis?

In the human systemic amyloidoses caused by mutant or wild-type transthyretin (TTR), deposition occurs at a distance from the site of synthesis. The TTR synthesized and secreted by the hepatocyte circulates in plasma, then deposits in target tissues far from the producing cell, a pattern reproduced in mice transgenic for multiple copies of the human wild-type TTR gene. By 2 yr of age, half of the transgenic males show cardiac deposition resembling human senile systemic amyloidosis. However, as early as 3 mo of age, when there are no deposits, cardiac gene transcription differs from that of nontransgenic littermates, primarily in the expression of a large number of genes associated with inflammation and the immune response. At 24 mo, the hearts with histologically proven TTR deposits show expression of stress response genes, exuberant mitochondrial gene transcription, and increased expression of genes associated with apoptosis, relative to the hearts without TTR deposition. These 24-mo-old hearts with TTR deposits also show a decrease in transcription of inflammatory genes relative to that in the younger transgenic mice. After 2 yr of expressing large amounts of human TTR, the livers of the transgenic mice without cardiac deposition display chaperone gene expression and evidence of an activated unfolded protein response, while the livers of animals with cardiac TTR deposition display neither, showing increased transcription of interferon-responsive inflammatory genes and those encoding an antioxidant response. With time, in animals with cardiac deposition, it appears that hepatic proteostatic capacity is diminished, exposing the heart to a greater load of misfolded TTR with subsequent extracellular deposition. Hence systemic (cardiac) TTR deposition may be the direct result of the diminution in the distant chaperoning capacity of the liver related to age or long-standing exposure to misfolded TTR, or both.

Epigallocatechin-3-gallate as a potential therapeutic drug for TTR-related amyloidosis: "in vivo" evidence from FAP mice models

BACKGROUND

Familial amyloidotic polyneuropathy (FAP) is a neurodegenerative disease caused by the extracellular deposition of mutant transthyretin (TTR), with special involvement of the peripheral nervous system (PNS). Currently, hepatic transplantation is considered the most efficient therapy to halt the progression of clinical symptoms in FAP since more than 95% of TTR is produced by the liver. However, less invasive and more reliable therapeutic approaches have been proposed for FAP therapy, namely based on drugs acting as inhibitors of amyloid formation or as amyloid disruptors. We have recently reported that epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea, is able to inhibit TTR aggregation and fibril formation, "in vitro" and in a cellular system, and is also able to disrupt pre-formed amyloid fibrils "in vitro".

METHODOLOGY AND PRINCIPAL FINDINGS

In the present study, we assessed the effect of EGCG subchronic administration on TTR amyloidogenesis "in vivo", using well characterized animal models for FAP. Semiquantitative immunohistochemistry (SQ-IHC) and Western blot analysis of mice tissues after treatment demonstrated that EGCG inhibits TTR toxic aggregates deposition in about 50% along the gastrointestinal tract (GI) and peripheral nervous system (PNS). Moreover EGCG treatment considerably lowered levels of several biomarkers associated with non-fibrillar TTR deposition, namely endoplasmic reticulum (ER)-stress, protein oxidation and apoptosis markers. Treatment of old FAP mice with EGCG resulted not only in the decrease of non-fibrillar TTR deposition but also in disaggregation of amyloid deposits. Consistently, matrix metalloproteinase (MMP)-9 and serum amyloid P component (SAP), both markers of amyloid deposition, were also found reduced in treated old FAP mice.

CONCLUSIONS AND SIGNIFICANCE

The dual effect of EGCG both as TTR aggregation inhibitor and amyloid fibril disruptor together with the high tolerability and low toxicity of EGCG in humans, point towards the potential use of this compound, or optimized derivatives, in the treatment of TTR-related amyloidoses.

CSF transthyretin neuroprotection in a mouse model of brain ischemia

Brain injury caused by ischemia is a major cause of human mortality and physical/cognitive disability worldwide. Experimentally, brain ischemia can be induced surgically by permanent middle cerebral artery occlusion. Using this model, we studied the influence of transthyretin in ischemic stroke. Transthyretin (TTR) is normally responsible for the transport of thyroid hormones and retinol in the blood and CSF. We found that TTR null mice (TTR(-/-) ) did not show significant differences in cortical infarction 24 h after permanent middle cerebral artery occlusion compared with TTR(+/+) control littermates. However, TTR null mice, heterozygous for the heat-shock transcription factor 1 (TTR(-/-) HSF1(+/-) mice), which compromised the stress response, showed a significant increase in cortical infarction, cerebral edema and the microglial-leukocyte response compared with TTR(+/+) HSF1(+/-) mice. Unexpectedly, we observed novel TTR distribution throughout the infarct, localized to disintegrated β-tubulin III(+) neurons and cell debris. Specific elimination of TTR synthesis in the liver by RNAi had no effect on TTR distribution in the infarct, indicating that the observed TTR infiltration derived from CSF and not from the serum. This finding is corroborated by results from 'in situ' hybridization and real time PCR that excluded the presence of transthyretin mRNA in the infarct and peri-infarct areas. Our data suggest that in conditions of a compromised heat-shock response, CSF TTR contributes to control neuronal cell death, edema and inflammation, thereby influencing the survival of endangered neurons in cerebral ischemia.

αB-crystallin (HspB5) in familial amyloidotic polyneuropathy

The small heat shock protein αB-crystallin (HspB5) is known to be overexpressed in several neurodegenerative disorders. In familial amyloidotic polyneuropathy (FAP), a neurodegenerative disorder characterized by extracellular deposition of mutated transthyretin (TTR), activation of heat shock factor 1 -HSF1- by extracellular TTR deposition has been shown as well as induction of the expression of heat shock proteins, HSP27 and HSP70. Here we investigate the expression of αB-crystallin in FAP. We first detected αB-crystallin in aggregates extracted from tissues of both FAP patients and transgenic mice for the human V30M mutant TTR; however, subsequent studies by confocal fluorescence microscopy did not confirm the association of αB-crystallin with TTR aggregates; thus the presence of αB-crystallin in aggregate extracts might derive from the extraction procedure. Increased levels of αB-crystallin were observed by immunohistochemistry in human FAP skin, as compared to normal skin. Furthermore, skin, stomach and dorsal root ganglia from V30M transgenic mice showed increased expression of αB-crystallin as compared to controls without deposition. A human neuroblastoma cell line incubated with TTR aggregates displayed increased expression of αB-crystallin. Overall, these results show that extracellular TTR deposits induce an intracellular response of αB-crystallin. This small heat shock protein (HSP), which is important for anti-apoptotic and chaperone properties, may have a protective role in FAP.

Synergy of combined doxycycline/TUDCA treatment in lowering Transthyretin deposition and associated biomarkers: studies in FAP mouse models

Familial Amyloidotic Polyneuropathy (FAP) is a disorder characterized by the extracellular deposition of fibrillar Transthyretin (TTR) amyloid, with a special involvement of the peripheral nerve. We had previously shown that doxycycline administered for 3 months at 40 mg/Kg/ml in the drinking water, was capable of removing TTR amyloid deposits present in stomachs of old TTR-V30M transgenic mice; the removal was accompanied by a decrease in extracellular matrix remodeling proteins that accompany fibrillar deposition, but not of non-fibrillar TTR deposition and/or markers associated with pre-fibrillar deposits. On the other hand, Tauroursodeoxycholic acid (TUDCA), a biliary acid, administrated to the same mouse model was shown to be effective at lowering deposited non-fibrillar TTR, as well as the levels of markers associated with pre-fibrillar TTR, but only at young ages.

In the present work we evaluated different doxycycline administration schemes, including different periods of treatment, different dosages and different FAP TTR V30M animal models. Evaluation included CR staining, immunohistochemistry for TTR, metalloproteinase 9 (MMP-9) and serum amyloid P component (SAP). We determined that a minimum period of 15 days of treatment with a 8 mg/Kg/day dosage resulted in fibril removal. The possibility of intermittent treatments was also assessed and a maximum period of 15 days of suspension was determined to maintain tissues amyloid-free. Combined cycled doxycycline and TUDCA administration to mice with amyloid deposition, using two different concentrations of both drugs, was more effective than either individual doxycycline or TUDCA, in significantly lowering TTR deposition and associated tissue markers. The observed synergistic effect of doxycycline/TUDCA in the range of human tolerable quantities, in the transgenic TTR mice models prompts their application in FAP, particularly in the early stages of disease.

Animal models of human amyloidoses: are transgenic mice worth the time and trouble?

The amyloidoses are the prototype gain of toxic function protein misfolding diseases. As such, several naturally occurring animal models and their inducible variants provided some of the first insights into these disorders of protein aggregation. With greater analytic knowledge and the increasing flexibility of transgenic and gene knockout technology, new models have been generated allowing the interrogation of phenomena that have not been approachable in more reductionist systems, i.e. behavioral readouts in the neurodegenerative diseases, interactions among organ systems in the transthyretin amyloidoses and taking pre-clinical therapeutic trials beyond cell culture. The current review describes the features of both transgenic and non-transgenic models and discusses issues that appear to be unresolved even when viewed in their organismal context.