Oxidative stress is found in amyloid deposits in systemic amyloidosis

Transthyretin Amyloidosis: Role of oxidative stress and the beneficial implications of antioxidants and nutraceutical supplementation

Transthyretin (ATTR) amyloidosis constitutes a spectrum of debilitating neurodegenerative diseases instigated by systemic extracellular deposition of partially unfolded/aggregated aberrant transthyretin. The homotetrameric protein, TTR, is abundant in the plasma, and to a lesser extent the cerebrospinal fluid. Rate-limiting tetramer dissociation of the native protein is regarded as the critical step in the formation of morphologically heterogenous toxic aggregates and the onset of clinical manifestations such as polyneuropathy, cardiomyopathy, disturbances in motor and autonomic functions. Over the past few decades there has been increasing evidence suggesting that in addition to destabilization in TTR tetramer structure, oxidative stress may also play an important role in the pathogenesis of ATTR amyloidosis. In this review, an update on the impact of oxidative stress in TTR amyloidogenesis as well as TTR aggregate-mediated pathologies is discussed. The counteracting effects of antioxidants and nutraceutical agents explored in the treatment of ATTR amyloidosis based on recent evidence is also critically examined. The insights unveiled could further strengthen current understanding of the mechanisms underlying ATTR amyloidosis as well as extend the range of strategies for effective management of ATTR amyloidoses.

Oxidative Stress in Transthyretin-Mediated Amyloidosis: An Exploratory Study

Transthyretin-mediated amyloidosis (ATTR) is a systemic disease with protein precipitation in many tissues, mainly the peripheral nerve and heart. Both genetic (ATTRv, "v" for variant) and wild-type (ATTRwt) forms are known. Beyond the steric encumbrance, precipitated transthyretin seems to have a toxic effect. In this study carried out in men, we recruited 15 ATTRv patients, 7 ATTRv asymptomatic carriers, 14 ATTRwt patients and 10 young and 13 old healthy controls to evaluate the oxidative stress using FORD (Free Oxygen Radicals Defense) and FORT (Free Oxygen Radicals Test) analyses. ATTRv patients showed reduced FORD compared to ATTRwt and ATTRv asymptomatic carriers. FORD independently predicted the disease stage, with the early stages characterized by the highest consumption. These findings suggest a role for oxidative stress in the early stages of ATTRv.

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.

Urinary Transthyretin as a Biomarker in ATTRv Val50Met Amyloidosis

Transthyretin (TTR), the precursor protein for amyloidogenic TTR (ATTR) amyloidosis, forms tetramers and escapes glomerular filtration by binding with thyroxine and retinol-binding protein. However, variant TTRs are unstable as tetramers, so monomeric TTR has become the precursor protein of amyloid deposits, via protein misfolding. The aim of the study was to evaluate the utility of urinary TTR in the diagnosis of ATTRv amyloidosis. Urinary samples from healthy volunteers, ATTRv V50M amyloidosis patients, and asymptomatic carriers of the ATTRv V50M gene were analysed using ELISA. To analyse the different forms of TTR secreted to the urine, we performed Western blotting and mass spectrometry. Urinary TTR concentrations were significantly higher in the ATTRv V50M amyloidosis patients than they were in the healthy volunteers and asymptomatic carriers of the gene. Although the TTR concentrations were negligible in the healthy volunteers, they were correlated with disease progression and urinary albumin concentrations in the ATTRv V50M amyloidosis patients. The Western blotting and mass spectrometry revealed the presence of monomeric wild-type and variant TTRs in the urine. Urinary TTR concentrations may become a more sensitive biomarker of ATTRv progression than albumin.

Santalol Isomers Inhibit Transthyretin Amyloidogenesis and Associated Pathologies in Caenorhabditis elegans

Transthyretin (TTR) is a homotetrameric protein found in human serum and is implicated in fatal inherited amyloidoses. Destabilization of native TTR confirmation resulting from mutation, environmental changes, and aging causes polymerization and amyloid fibril formation. Although several small molecules have been reported to stabilize the native state and inhibit TTR aggregation, prolonged use can cause serious side effects. Therefore, pharmacologically enhancing the degradation of TTR aggregates and kinetically stabilizing the native tetrameric structure with bioactive molecule(s) could be a viable therapeutic strategy to hinder the advancement of TTR amyloidoses. In this context, here we demonstrated α- and β-santalol, natural sesquiterpenes from sandalwood, as a potent TTR aggregation inhibitor and native state stabilizer using combined in vitro, in silico, and in vivo experiments. We found that α- and β-santalol synergize to reduce wild-type (WT) and Val30Met (V30M) mutant TTR aggregates in novel C. elegans strains expressing TTR fragments fused with a green fluorescent protein in body wall muscle cells. α- and β-Santalol extend the lifespan and healthspan of C. elegans strains carrying TTR_WT::EGFP and TTR_V30M::EGFP transgene by activating the SKN-1/Nrf2, autophagy, and proteasome. Moreover, α- and β-santalol directly interacted with TTR and reduced the flexibility of the thyroxine-binding cavity and homotetramer interface, which in turn increases stability and prevents the dissociation of the TTR tetramer. These data indicate that α- and β-santalol are the strong natural therapeutic intervention against TTR-associated amyloid diseases.

Anti-Inflammatory, Antioxidant, and Anti-Atherosclerotic Effects of Natural Supplements on Patients with FMF-Related AA Amyloidosis: A Non-Randomized 24-Week Open-Label Interventional Study

We aimed to evaluate the effect of a combination of natural products on parameters related to inflammation, endothelial dysfunction, and oxidative stress in a cohort of familial Mediterranean fever (FMF) patients with Serum Amyloid A amyloidosis, in a non-randomized, 24-week open-label interventional study. Morinda citrifolia (anti-atherosclerotic-AAL), omega-3 (anti-inflammatory-AIC), and extract with Alaskan blueberry (antioxidant-AOL) were given to patients with FMF-related biopsy-proven AA amyloidosis. Patients were >18 years and had proteinuria (>3500 mg/day) but a normal estimated glomerular filtration rate (eGFR). Arterial flow-mediated dilatation (FMD), carotid intima media thickness (CIMT), and serum biomarkers asymmetric dimethylarginine (ADMA), high sensitivity C-reactive protein (hs-CRP), pentraxin (PTX3), malondialdehyde (MDA), Cu/Zn-superoxide dismutase (Cu/Zn-SOD), and glutathione peroxidase (GSH-Px) were studied at baseline and after 24 weeks of treatment. A total of 67 FMF-related amyloidosis patients (52 male (77.6%); median age 36 years (range 21−66)) were enrolled. At the end of a 24-week treatment period with AAL, AIC, and AOL combination therapy, ADMA, MDA, PTX3, hsCRP, cholesterol, and proteinuria were significantly decreased compared to baseline, while CuZn-SOD, GSH-Px, and FMD levels were significantly increased. Changes in inflammatory markers PTX3, and hsCRP were negatively correlated with FMD change, and positively correlated with decreases in proteinuria, ADMA, MDA, cholesterol, and CIMT. Treatment with AAL, AIC and AOL combination for 24 weeks were significantly associated with reduction in inflammatory markers, improved endothelial functions, and oxidative state. Efficient control of these three mechanisms can have long term cardiovascular and renal benefits for patients with AA amyloidosis.

Metabolomics analysis for diagnosis and biomarker discovery of transthyretin amyloidosis

Untargeted metabolomics is a well-established technique and a powerful tool to find potential plasma biomarkers for early diagnosing hereditary transthyretin amyloidosis. Hereditary transthyretin amyloidosis (ATTRv) is a disabling and fatal disease with different clinical features such as polyneuropathy, cardiomyopathy, different gastrointestinal symptoms and renal failure. Plasma specimens collected from 27 patients with ATTRv (ATTRV30M), 26 asymptomatic TTRV30M carriers and 26 control individuals were subjected to gas chromatography (GC)- and liquid chromatography (LC)-mass spectrometry (MS)-based metabolomics analysis. Partial least squares discriminant and univariate analysis was used to analyse the data. The models constructed by Partial least squares-discriminant analysis (PLS-DA) could clearly discriminate ATTRV30M patients from controls and asymptomatic TTRV30M carriers. In total, 24 plasma metabolites (VIP > 1.0 and p < .05) were significantly altered in ATTRV30M patient group (6 increased and 18 decreased). Eleven of these distinguished the ATTRV30M group from both controls and TTRV30M carriers. Plasma metabolomics analysis revealed marked changes in several pathways in patients with ATTRV30M amyloidosis. Statistical analysis identified a panel of biomarkers that could effectively separate controls/TTRV30M carriers from ATTRV30M patients. These biomarkers can potentially be used to diagnose patients at an early stage of the disease.

Serum high-density lipoprotein cholesterol serves as a prognostic marker for light-chain cardiac amyloidosis

BACKGROUND

Oxidative stress and inflammation are central in the pathophysiology of light-chain amyloid cardiomyopathy (AL-CM). High-density lipoprotein cholesterol (HDLC) is an antioxidant and acts as an anti-inflammatory regulator. In this study, the prognostic value of serum HDL-C was explored in AL-CM.

METHOD

In this prospective single-center study, two hundred consecutive patients with biopsy-confirmed light-chain amyloidosis (AL) and cardiac involvement were enrolled. Patients were classified into low or normal serum HDL-C groups (HDL-C < 40 mg/dL and HDL-C ≥ 40 mg/dL, respectively). Univariate and multivariate Cox models were used to identify predictors of survival. Kaplan-Meier analysis was performed to compare survival between patients with low or normal serum HDL-C.

RESULTS

Patients with low serum HDL-C were more likely to present with higher levels of cardiac troponin-T (123.4 ng/L vs. 79.1 ng/L, p = 0.026) and higher levels of N-terminal pro-B-type natriuretic peptide (9146 pg/mL vs. 4945 pg/mL, p = 0.011). Patients were followed for a median follow-up period of 19 months, in which 118 (59%) patients died. The median overall survival times for patients with low or normal serum HDL-C were 7 and 16 months, respectively (p = 0.002). Multivariate analysis demonstrated that serum HDL-C (HR 0.984, 95% CI 0.973-0.994, p = 0.003) was independently associated with prognosis, after adjusting for nephrotic syndrome, hepatic involvement, nutritional state, renal function, SBP, DBP, serum uric acid, total cholesterol, Mayo AL 2004 stage, and treatment with chemotherapy.

CONCLUSIONS

HDL-C is a novel serum biomarker for disease severity and prognosis in light-chain cardiac amyloidosis.

Suppression of Mouse AApoAII Amyloidosis Progression by Daily Supplementation with Oxidative Stress Inhibitors

Amyloidosis is a group of diseases characterized by protein misfolding and aggregation to form amyloid fibrils and subsequent deposition within various tissues. Previous studies have indicated that amyloidosis is often associated with oxidative stress. However, it is not clear whether oxidative stress is involved in the progression of amyloidosis. We administered the oxidative stress inhibitors tempol and apocynin via drinking water to the R1.P1-Apoa2^c mouse strain induced to develop mouse apolipoprotein A-II (AApoAII) amyloidosis and found that treatment with oxidative stress inhibitors led to reduction in AApoAII amyloidosis progression compared to an untreated group after 12 weeks, especially in the skin, stomach, and liver. There was no effect on ApoA-II plasma levels or expression of Apoa2 mRNA. Detection of the lipid peroxidation markers 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA) revealed that the antioxidative effects of the treatments were most obvious in the skin, stomach, and liver, which contained higher levels of basal oxidative stress. Moreover, the unfolded protein response was reduced in the liver and was associated with a decrease in oxidative stress and amyloid deposition. These results suggest that antioxidants can suppress the progression of AApoAII amyloid deposition in the improved microenvironment of tissues and that the effect may be related to the levels of oxidative stress in local tissues. This finding provides insights for antioxidative stress treatment strategies for amyloidosis.

Development of transgenic Caenorhabditis elegans expressing human transthyretin as a model for drug screening

Familial amyloid polyneuropathy is a hereditary systemic amyloidosis caused by a mutation in the transthyretin (TTR) gene. Amyloid deposits in tissues of patients contain not only full-length TTR but also C-terminal TTR fragments. However, in vivo models to evaluate the pathogenicity of TTR fragments have not yet been developed. Here, we generated transgenic Caenorhabditis elegans strains expressing several types of TTR fragments or full-length TTR fused to enhanced green fluorescent protein in the body wall muscle cells and analyzed the phenotypes of the worms. The transgenic strain expressing residues 81-127 of TTR, which included the β-strands F and H, formed aggregates and caused defective worm motility and a significantly shortened lifespan compared with other strains. These findings suggest that the C-terminal fragments of TTR may contribute to cytotoxicity of TTR amyloidosis in vivo. By using this C. elegans model system, we found that (-)-epigallocatechin-3-gallate, a major polyphenol in green tea, significantly inhibited the formation of aggregates, the defective motility, and the shortened lifespan caused by residues 81-127 of TTR. These results suggest that our newly developed C. elegans model system will be useful for in vivo pathological analyses of TTR amyloidosis as well as drug screening.

Inhibitory effect of propolis on the development of AA amyloidosis

In the several types of amyloidoses, participation of oxidative stresses in the pathogenesis and the effect of antioxidants on amyloidosis have been reported. Meanwhile, the relationship between oxidative stresses and pathogenesis of amyloid A (AA) amyloidosis is still unclear. In this study, we used an antioxidant, Brazilian propolis, to investigate the inhibitory effects on AA amyloidosis. The results showed that AA deposition was inhibited by administration of propolis. Increased expression of antioxidant markers was detected in molecular biological examinations of mice treated with propolis. Although serum amyloid A (SAA) levels were strongly correlated with the immunoreactive area of AA deposits in the control group, the correlation was weaker in the propolis-treated groups. In addition, there were no changes in SAA levels between the control group and the propolis-treated groups. The results indicate that propolis, an antioxidant, may induce inhibitory effects against AA amyloidosis.

mtDNA copy number associated with age of onset in familial amyloid polyneuropathy

BACKGROUND

Transthyretin-related familial amyloid polyneuropathy (TTR-FAP Val30Met) shows a wide variation in age-at-onset (AO) between generations and genders, as in Portuguese families, where women display a later onset and a larger anticipation (>10 years). Mitochondrial DNA (mtDNA) copy number was assessed to clarify whether it has a modifier effect on AO variability in Portuguese patients.

METHODS

The mtDNA copy number of 262 samples (175 Val30Met TTR carriers and 87 controls (proven Val30Val)) was quantified by quantitative real-time PCR. Statistical analysis was performed using IBM SPSS V.23 software.

RESULTS

This study shows that Val30Met TTR carriers have a significantly higher (p<0.001) mean mtDNA copy number than controls. Furthermore, the highest mtDNA copy number mean was observed in early-onset patients (AO <40 years). Importantly, early-onset offspring showed a significant increase (p=0.002) in the mtDNA copy number, when compared with their late AO parents.

CONCLUSIONS

The present findings suggest, for the first time, that mtDNA copy number may be associated with earlier events and may therefore be further explored as a potential biomarker for follow-up of TTR-FAP Val30Met carriers.

C1q ablation exacerbates amyloid deposition: A study in a transgenic mouse model of ATTRV30M amyloid neuropathy

ATTRV30M amyloid neuropathy is a lethal autosomal dominant sensorimotor and autonomic neuropathy, caused by deposition of amyloid fibrils composed of aberrant transthyretin (TTR). Ages of onset and penetrance exhibit great variability and genetic factors have been implicated. Complement activation co-localizes with amyloid deposits in amyloidotic neuropathy and is possibly involved in the kinetics of amyloidogenesis. A candidate gene approach has recently identified C1q polymorphisms to correlate with disease onset in a Cypriot cohort of patients with ATTRV30M amyloid neuropathy. In the current study we use a double transgenic mouse model of ATTRV30M amyloid neuropathy in which C1q is ablated to elucidate further a possible modifier role for C1q. Amyloid deposition is found to be increased by 60% in the absence of C1q. Significant up regulation is also recorded in apoptotic and cellular stress markers reflecting extracellular toxicity of pre-fibrillar and fibrillar TTR. Our data further indicate that in the absence of C1q there is marked reduction of macrophages in association with amyloid deposits and thus less effective phagocytosis of TTR.

4-Hydroxy-nonenal-A Bioactive Lipid Peroxidation Product

This review on recent research advances of the lipid peroxidation product 4-hydroxy-nonenal (HNE) has four major topics: I. the formation of HNE in various organs and tissues, II. the diverse biochemical reactions with Michael adduct formation as the most prominent one, III. the endogenous targets of HNE, primarily peptides and proteins (here the mechanisms of covalent adduct formation are described and the (patho-) physiological consequences discussed), and IV. the metabolism of HNE leading to a great number of degradation products, some of which are excreted in urine and may serve as non-invasive biomarkers of oxidative stress.

Redox proteomics gives insights into the role of oxidative stress in alkaptonuria

Alkaptonuria (AKU) is an ultra-rare metabolic disorder of the catabolic pathway of tyrosine and phenylalanine that has been poorly characterized at molecular level. As a genetic disease, AKU is present at birth, but its most severe manifestations are delayed due to the deposition of a dark-brown pigment (ochronosis) in connective tissues. The reasons for such a delayed manifestation have not been clarified yet, though several lines of evidence suggest that the metabolite accumulated in AKU sufferers (homogentisic acid) is prone to auto-oxidation and induction of oxidative stress. The clarification of the pathophysiological molecular mechanisms of AKU would allow a better understanding of the disease, help find a cure for AKU and provide a model for more common rheumatic diseases. With this aim, we have shown how proteomics and redox proteomics might successfully overcome the difficulties of studying a rare disease such as AKU and the limitations of the hitherto adopted approaches.

Loss of gastric interstitial cells of Cajal in patients with hereditary transthyretin amyloidosis

BACKGROUND

Hereditary transthyretin (TTR) amyloidosis is a systemic neuropathic disorder caused by TTR gene mutations. Gastrointestinal complications are common and the underlying mechanisms remain unclear. The interstitial cells of Cajal (ICC) function as pacemaker cells in the gastrointestinal tract and are important for gastrointestinal motility. The aim of this study was to investigate the densities of gastric ICC and nerves in patients with TTR amyloidosis compared to non-amyloidosis controls.

METHODS

Antral wall autopsy specimens from 11 Japanese ATTR V30M patients and 10 controls were analyzed with immunohistochemistry and computerized analysis. Antibodies to c-Kit and TMEM16A were used to assess ICC and an antibody to PGP 9.5 was used to assess nervous tissue. The study was approved by a Japanese ethical committee.

RESULTS

The densities of c-Kit-immunoreactive (IR) ICC were significantly lower in the circular and longitudinal muscle layers of patients compared to controls (p = 0.004 for both). Equivalent results were found for TMEM16A-IR ICC. There were no significant differences in PGP 9.5-IR cells in the circular or longitudinal muscle layers between patients and controls (p = 0.173 and 0.099, respectively).

CONCLUSIONS

A loss of gastrointestinal ICC may be an important factor for the digestive disturbances in hereditary TTR amyloidosis.

Age-related oxidative modifications of transthyretin modulate its amyloidogenicity

The transthyretin amyloidoses are diseases of protein misfolding characterized by the extracellular deposition of fibrils and other aggregates of the homotetrameric protein transthyretin (TTR) in peripheral nerves, heart, and other tissues. Age is the major risk factor for the development of these diseases. We hypothesized that an age-associated increase in the level of protein oxidation could be involved in the onset of the senile forms of the TTR amyloidoses. To test this hypothesis, we have produced and characterized relevant age-related oxidative modifications of the wild type (WT) and the Val122Ile (V122I) TTR variant, both involved in cardiac TTR deposition in the elderly. Our studies show that methionine/cysteine-oxidized TTR and carbonylated TTR from either the WT or the V122I variant are thermodynamically less stable than their nonoxidized counterparts. Moreover, carbonylated WT and carbonylated V122I TTR have a stronger propensity to form aggregates and fibrils than WT and V122I TTR, respectively, at physiologically attainable pH values. It is well-known that TTR tetramer dissociation, the limiting step for aggregation and amyloid fibril formation, can be prevented by small molecules that bind the TTR tetramer interface. Here, we report that carbonylated WT TTR is less amenable to resveratrol-mediated tetramer stabilization than WT TTR. All the oxidized forms of TTR tested are cytotoxic to a human cardiomyocyte cell line known to be a target for cardiac-specific TTR variants. Overall, these studies demonstrate that age-related oxidative modifications of TTR can contribute to the onset of the senile forms of the TTR amyloidoses.

Inhibitory effect of α-tocopherol on methylmercury-induced oxidative steress

OBJECTIVES

The present study investigated the involvement of oxidative stress in the degeneration of the cerebellum during methylmercury (MeHg) intoxication and the protective effect of α-tocopherol (Vit E) against MeHg toxicity.

METHODS

After 5 mg/kg of MeHg was administered to Wistar rats for 12 consecutive days, the cerebellum were examined histopathologically. In addition, the same amount of MeHg was administered to 3 different groups of Wistar rats: rats with a Vit E-deficient diet, rats fed 150 mg/kg of Vit E for 20 consecutive days after initial MeHg administration, and rats with an ordinary diet.

RESULTS

Positive immunoreactivity against anti-hydroxynonenal (HNE), a marker of lipid peroxidation, was observed in the cerebellum after MeHg administration. Levels of thiobarbituric acid reactive substance (TBARS), another marker of lipid peroxidation, and those of protein carbonyl, a biomarker for protein oxidation, increased after MeHg administration. In the rats with MeHg and a Vit E-deficient diet, mortality and prevalence of piloerection significantly increased, and in the rats with MeHg and Vit E, mortality, piloerection, retracted and crossed hind leg, and ataxic gait significantly decreased, compared with the rats with MeHg alone. The levels of NO(2) (-) and NO(3) (-) in the serum significantly increased in the rats with MeHg alone 14 days after the initial MeHg administration, but were significantly suppressed by Vit E administration.

CONCLUSIONS

Oxidative stress, especially lipid peroxidation, may play an important role in the cerebellar degeneration process during MeHg intoxication and Vit E may play a protective role against MeHg toxicity as an effective antioxidant.

Protective role of clusterin in preserving endothelial function in AL amyloidosis

Misfolded immunoglobulin light chain proteins (LC) in light chain amyloidosis (AL) are toxic to vascular tissues. We tested the hypothesis that chaperone protein clusterin preserves endothelial function and cell survival during LC exposure.

METHODS

LC (20 μg/mL) were given to human aortic endothelial cells (EC) for 24-h and clusterin protein/gene expression and secretion were measured. DNA fragmentation was measured with/without recombinant clusterin (Clu, 300 ng/mL). Adipose arterioles (non-AL subjects) were tested for dilator responses to acetylcholine/papaverine at baseline and after 1-h of LC ± Clu.

RESULTS

LC reduced EC clusterin secretion, protein and gene expression while increasing DNA fragmentation. Clu attenuated LC-induced DNA fragmentation and restored dilator response to acetylcholine (logEC50: control -7.05 ± 0.2, LC + Clu -6.53 ± 0.4, LC -4.28 ± 0.7, p < 0.05 versus control, LC + Clu).

CONCLUSIONS

LC induced endothelial cell death and dysfunction while reducing clusterin protein/gene expression and secretion. Exogenous clusterin attenuated LC toxicity. This represents a new pathobiologic mechanism and therapeutic target for AL amyloidosis.

Transthyretin aggregates induce production of reactive nitrogen species

BACKGROUND AND OBJECTIVE

Misfolded and aggregated transthyretins (agTTR) contribute to neurodegenerative amyloid diseases such as familial amyloid polyneuropathy and senile systemic amyloidosis. The neurotoxicity mechanisms of agTTR, however, are not well understood. In the current study, the possible contribution of reactive nitrogen species (RNS) to such mechanisms was investigated by examining agTTR-mediated changes in cellular RNS levels.

METHODS AND RESULTS

The production of RNS was assessed through nitrate and nitrite assays in two human cell lines after exposure to agTTR (2.4 µM pre-aggregation concentration). In both epidermoid (A431) and schwannoma (sNF94.3) cell lines, agTTR induced significant increases in RNS (p < 0.05 relative to the same concentration of normal TTR, or no-TTR controls). Redox modulators such as apocynin (1-(4-hydroxy-3-methoxy-phenyl)ethanone) and L-NMMA (N(G)-monomethyl-L-arginine) were tested for their effects on RNS production. These modulators decreased RNS production in both cell lines; although the effects of L-NMMA were statistically significant only in the schwannoma cells. Moreover, cells treated with agTTR exhibited decreases in metabolic activity relative to TTR- or non-TTR-treated cells (p < 0.05) as assessed by reduction of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide).

CONCLUSION

The results provide novel evidence for involvement of RNS in pro-oxidative effects of agTTR in two different human cell lines, and show that agTTR can induce more generalized changes in cellular metabolic activity.

Human microvascular dysfunction and apoptotic injury induced by AL amyloidosis light chain proteins

Light chain amyloidosis (AL) involves overproduction of amyloidogenic light chain proteins (LC) leading to heart failure, yet the mechanisms underlying tissue toxicity remain unknown. We hypothesized that LC induces endothelial dysfunction in non-AL human microvasculature and apoptotic injury in human coronary artery endothelial cells (HCAECs). Adipose arterioles (n = 34, 50 ± 3 yr) and atrial coronary arterioles (n = 19, 68 ± 2 yr) from non-AL subjects were cannulated. Adipose arteriole dilator responses to acetylcholine/papaverine were measured at baseline and 1 h exposure to LC (20 μg/ml) from biopsy-proven AL subjects (57 ± 11 yr) without and with antioxidant cotreatment. Coronary arteriole dilation to bradykinin/papaverine was measured post-LC exposure. HCAECs were exposed to 1 or 24 h of LC. LC reduced dilation to acetylcholine (10(-4) M: 41.6 ± 7 vs. 85.8 ± 2.2% control, P < 0.001) and papaverine (81.4 ± 4.6 vs. 94.8 ± 1.3% control, P < 0.01) in adipose arterioles and to bradykinin (10(-6) M: 68.6 ± 6.2 vs. 90.9 ± 1.6% control, P < 0.001) but not papaverine in coronary arterioles. There was an increase in superoxide and peroxynitrite in arterioles treated with LC. Adipose arteriole dilation was restored by cotreatment with polyethylene glycol-superoxide dismutase and tetrahydrobiopterin but only partially restored by mitoquinone (mitochondria-targeted antioxidant) and gp91ds-tat (NADPH oxidase inhibitor). HCAECs exposed to LC showed reduced NO and increased superoxide, peroxynitrite, annexin-V, and propidium iodide compared with control. Brief exposure to physiological amounts of LC induced endothelial dysfunction in human adipose and coronary arterioles and increased apoptotic injury in coronary artery endothelial cells likely as a result of oxidative stress, reduced NO bioavailability, and peroxynitrite production. Microvascular dysfunction and injury is a novel mechanism underlying AL pathobiology and is a potential target for therapy.

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

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

A possible role for miRNA silencing in disease phenotype variation in Swedish transthyretin V30M carriers

Background

Familial amyloidosis with polyneuropathy (FAP) is an autosomal dominant disease caused by transthyretin (TTR) mutations, of which V30M (TTR c.148G > A, p.Val50Met, "Val30Met") is the most common. Swedish V30M carriers display later age at onset and lower penetrance compared to other populations.

Methods

In the study, 130 Swedish V30M carriers (32 early, 30 late onset and 68 asymptomatic carriers) and 50 controls, 23 French symptomatic V30M carriers and 29 controls and 18 Japanese symptomatic V30M carriers and 29 controls were included. We aimed to identify additional genetic factors in the TTR gene and its surrounding region that could have an impact on phenotype.

Results

We identified three SNPs (rs71383038, rs3794885 and rs62093482) with a significant difference in allele frequency between Swedish V30M carriers and controls. The two Swedish V30M homozygous patients present in the study also displayed homozygosity for the CA10 (rs71383038), A (rs3794885) and T (rs62093482) alleles in these SNPs. Hence, these alleles are present on the Swedish V30M haplotype. Of these, rs62093482 is located in the 3'UTR of TTR gene and thus more interesting since SNPs in the 3'UTR can affect gene expression levels by modifying microRNA (miRNA) targeting activity. miRNA target predictions revealed four potential miRNAs with predicted targets unique for the polymorphic allele.

Conclusions

Our results are the first to show the presence of a 3'UTR polymorphism on the V30M haplotype in Swedish carriers, which can serve as a miRNA binding site potentially leading to down-regulated expression from the mutated TTR allele. This finding may be related to the low penetrance and high age at onset of the disease observed in the Swedish patient population.

Systemic and microvascular oxidative stress induced by light chain amyloidosis

Light chain amyloidosis (AL) is a plasma cell dyscrasia associated with production of amyloidogenic immunoglobulin light chains (LC). Despite its often fatal course, the mechanism of injury remains unknown. We tested the hypothesis that AL is associated with oxidative stress by comparing serum protein carbonyl (a marker of protein oxidation and oxidative stress) in AL subjects (n=23, 60 ± 11 years) vs. controls (n=9, 54 ± 2 years); we also measured superoxide production (n=11) and dilator response to sodium nitroprusside (SNP, n=6) in isolated non-AL human adipose arterioles exposed to LC (20 μg/mL) purified from AL subjects for 1 h vs. control. Protein carbonyl was higher in AL patients (0.19 ± 0.04 vs. 0.003 ± 0.003 nmol/mg control, p=0.002). Post-exposure to LC proteins, arteriole superoxide was higher (1.89 ± 0.36 times control, p=0.03) with impaired dilation to SNP (10(-4) M, 54 ± 6 vs. 86 ± 4%, p=0.01, logEC50 -3.7 ± 0.2 vs. -6.7 ± 0.6, p=0.002). AL is associated with systemic oxidative stress and brief acute exposure to AL light chain proteins induces oxidative stress and microvascular dysfunction in human adipose arterioles. This novel mechanism of injury may be important in AL pathophysiology.

Prognostic implication of late gadolinium enhancement on cardiac MRI in light chain (AL) amyloidosis on long term follow up

Background

Light chain amyloidosis (AL) is a rare plasma cell dyscrasia associated with poor survival especially in the setting of heart failure. Late gadolinium enhancement (LGE) on cardiac MRI was recently found to correlate with myocardial amyloid deposition but the prognostic role is not established. The aim is to determine the prognostic significance of LGE in AL by comparing long term survival of AL patients with and without LGE.

Methods

Twenty nine consecutive patients (14 females; 62 ± 11 years) with biopsy-proven AL undergoing cardiac MRI with gadolinium as part of AL workup were included. Survival was prospectively followed 29 months (median) following MRI and compared between those with and without LGE by Kaplan-Meier and log-rank analyses.

Results

LGE was positive in 23 subjects (79%) and negative in 6 (21%). Left ventricular ejection fraction was 66 ± 17% in LGE-positive and 69 ± 12% in LGE-negative patients (p = 0.8). Overall 1-year mortality was 36%. On follow-up, 14/23 LGE-positive and none of LGE-negative patients died (log rank p = 0.0061). Presenting New York Heart Association heart failure class was also associated with poor survival (p = 0.0059). Survival between two LGE groups stratified by heart failure class still showed a significant difference by a stratified log-rank test (p = 0.04).

Conclusion

Late gadolinium enhancement is common and is associated with poor long-term survival in light chain amyloidosis, even after adjustment for heart failure class presentation. The prognostic significance of late gadolinium enhancement in this disease may be useful in patient risk-stratification.

Transthyretin forms amyloid fibrils at physiological pH with ultrasonication

In transthyretin (TTR)-related amyloidosis, wild-type TTR (WT-TTR), as well as mutated TTRs play important roles in the pathogenesis of senile systemic amyloidosis and familial amyloidotic polyneuropathy. However, WT-TTR usually forms stable tetramers at physiological pH, and the mechanism of such fibril formation under physiological conditions remains to be elucidated. In this study, we demonstrated WT-TTR amyloid fibril formation at physiological pH with ultrasonication. Cross-linked SDS-PAGE and circular dichroism revealed that ultrasonication induced both tetrameric TTR dissociation and monomeric TTR denaturation. These results indicate that extremely low pH is not an essential condition for TTR amyloid fibril formation if TTR is degenerated in such conditions. In addition, this method allows analysis of accelerator factors or inhibitory agents in TTR amyloid fibril formation at neutral pH.

Mitochondrial haplogroup is associated with the phenotype of familial amyloidosis with polyneuropathy in Swedish and French patients

Familial amyloidotic polyneuropathy (FAP) is a monogenic disease caused by mutations in the transthyretin (TTR) gene. The phenotype of the most common TTR mutation, V30M, varies within and between populations. Oxidative stress and protein misfolding are cellular processes involved in the development of FAP. Because the mitochondria are important for both these processes, we investigated if mitochondrial haplogroups are related to age at onset of the disease in Swedish and French FAP patients. Mitochondrial haplogroup analysis was performed on 25 early-onset (below 40 years) and 29 late-onset (above 51 years) Swedish FAP patients. DNA from 249 Swedish individuals served as controls. In addition, 6 early-onset and 17 late-onset French FAP patients were examined with 25 French controls. The haplogroup distribution among late-onset Swedish and French cases was similar to that found in the general populations, whereas among early-onset cases a different haplogroup distribution was seen. The relatively rare haplogroup K was significantly more common among early-onset cases. Our findings substantiate the suggestion that a genetic component, still to be found, affecting mitochondrial function has an impact on the amyloid generating process in transthyretin amyloidosis.

Heterogeneity of penetrance in familial amyloid polyneuropathy, ATTR Val30Met, in the Swedish population

Transthyretin (TTR) familial amyloid polyneuropathies (FAP) are autosomal dominant devastating afflictions. They were first described in Portugal, later in Japan and Sweden and are now recognized worldwide. The TTR Val30Met mutation is the most common, and depending on the geographic origin, a wide variation in age at onset of the disease is observed. In Europe, northern Sweden is the second most prevalent area of the disease, and a late age of onset of 56 years has been reported. The present study aims to estimate the penetrance in TTR Val30Met Swedish families. Genealogical investigations, clinical data and genotyping were obtained in 77 TTR-Val30Met Swedish families. The penetrance in Val30Met carriers and variation within the endemic area, according to gender and transmitting parents were calculated by a newly developed bias-free method. The penetrance estimates were low, i.e. 1.7% and 22% at age 30 and 60 years, respectively, and far from complete (69%) by age 90 years. Differences between Piteå and Skellefteå regions were observed. Moreover, penetrance was significantly higher when the mutation was inherited from the mother than from the father. The low penetrance observed in TTR FAP kindreds and its variations is important information for the genetic counseling and treatment of Swedish FAP patients and their families.

Activation of the heat shock response in familial amyloidotic polyneuropathy

The heat shock proteins (Hsps) have been implicated in a variety of neurodegenerative diseases in which the underlying pathology is protein aggregation. Here, we studied the heat shock response in familial amyloidotic polyneuropathy (FAP), a neurodegenerative disease caused by aggregation and extracellular tissue deposition of mutated transthyretin (TTR). We observed greater expression of Hsp27 and Hsp70 related to the presence of extracellular TTR aggregates in human FAP nerve, skin, and salivary gland biopsies than in normal controls. Transthyretin aggregates did not colocalize with Hsp, suggesting that extracellular TTR tissue deposits induce an intracellular stress response. Moreover, the heat shock transcription factor 1 was upregulated and localized to nuclei in affected tissues. Transgenic mice expressing the V30M mutant form of TTR similarly showed the presence of TTR deposits, induced activation of heat shock transcription factor 1, and increased synthesis of Hsp. Furthermore, the addition of toxic TTR aggregates to cultures of human and rodent neuroblastoma cell lines induced upregulation of Hsp70 and Hsp27. Taken together, these novel findings suggest new avenues for research on pathogenic mechanisms in FAP and identify the heat shock response as a potential pharmacologic treatment target for FAP.

Multi-elemental analysis of serum and amyloid fibrils in familial amyloid polyneuropathy patients

There is accumulating evidence of the involvement of biological metal imbalance in the progression of amyloid diseases such as Alzheimer's, Parkinson's and prion diseases. However, the mineral status in patients affected with familial amyloidotic polyneuropathy (FAP) has not been investigated. It is the aim of this study to determine the metal concentrations in the serum and in the transthyretin (TTR) amyloid fibrils of FAP amyloidogenic TTR (ATTR) V30M patients. Multi-elemental analysis of 17 metals by high-resolution inductively coupled plasma mass spectrometry (ICP-MS) revealed a significant decrease of the metals Fe, Cu, Zn, Cs and Ba in the serum of FAP patients (mean age 38.5 +/- 8.3 years; duration of disease 4 +/- 2.6 years) in comparison with that of healthy individuals (mean age 36.2 +/- 9.2 years). On the other hand, these metals, except Cs, were found at high levels in the amyloid fibrils of FAP patients (mean age 55.8 +/- 9.2; duration of disease 6.5 +/- 1.3 years) compared with other metals. These findings firstly suggest that the mineral status could be a candidate factor, which participates in the wide spectrum of clinical pictures of FAP patients.

Liver mitochondrial function in familial amyloidotic polyneuropathy

The objective of the present study was to analyze hepatic mitochondrial function in patients with familial amyloidotic polyneuropathy (FAP) undergoing cadaveric donor orthotopic liver transplantation. From February 2005 to May 2007, eight patients with FAP, ranging in age from 34 to 41 years and with Model for End-Stage Liver Disease scores ranging from 24 to 29. Underwent orthotopic transplantation using a liver from a deceased donor by the piggyback method. Immediately before beginning the recipient hepatectomy in a patient with FAP, a biopsy was obtained for analysis of mitochondrial function (FAP group). The control group consisted of 15 patients undergoing hepatic surgery to treat small tumors of the liver. Mitochondrial respiration was determined on the basis of oxygen consumption by energized mitochondria using a polarographic method. The membrane potential of the mitochondria was determined spectrofluorometrically. Data were analyzed statistically by the Mann-Whitney test, with the level of significance set at 5%. State 3 and 4 values, respiratory control ratio, and membrane potential were 47 +/- 8 versus 28 +/- 10 natoms O/min/mg protein (P < .05); 14 +/- 3 vs 17 +/- 7 nat.O/min/mg.prot.mit. (P > .05); 3.6 +/- .5 vs 1.7 +/- 0.7 (P < .05); and 135 +/- 5.2 vs 135 +/- 6 mV (P > .05) for control versus FAP patients, respectively, demonstrating a decreased energy status of the liver in FAP.

Biomarkers in the assessment of therapies for familial amyloidotic polyneuropathy

The identification of specific biomarkers provides opportunities to develop early diagnostic parameters, monitor disease progression, and test drug efficiency in clinical trials. We previously demonstrated that in familial amyloidotic polyneuropathy (FAP) related to the abnormal extracellular tissue deposition of mutant transthyretin (TTR), inflammatory and apoptotic pathways are triggered in the presymptomatic stages of the disease, when nonfibrillar TTR deposits are present. In the present work, to better define biomarkers for future assessment of prophylactic and therapeutic drugs in the treatment of FAP, we extended the search for oxidative stress and apoptotic biomarkers to clinical samples and animal models presenting nonfibrillar and fibrillar TTR. We found that lipid peroxidation measured by hydroxynonenal, oxidative DNA damage measured by 8-hydroxy-2'-deoxyguanosine, and cellular redox homeostasis measured by glutaredoxin 1 were consistently increased in biopsy specimens from FAP patients and in tissues from transgenic mouse models presenting nonfibrillar TTR deposition. Death-receptor Fas, caspase-8, and Bax were also found to be increased, indicative of the involvement of death receptors in the observed apoptosis process. Removal of TTR deposition by an immunization protocol resulted in significant decreases of the selected markers we describe, corroborating the relationship between TTR deposition, oxidative stress, and apoptosis. Taken together, our results provide a robust biomarker profile for initial experimental animal studies and clinical trials to assess the application of the selected markers in therapies aimed at removal and/or inhibition of TTR polymerization.

Role of aggregated medin in the pathogenesis of thoracic aortic aneurysm and dissection

The pathogenesis of sporadic thoracic aortic aneurysm and dissection, which may lead to rupture of the aorta, remains largely unknown. Amyloid deposits, formed from the medin peptide, are very prevalent in the media of the thoracic aorta. We have studied the occurrence of medin-derived amyloid in specimens from patients with thoracic aortic aneurysm, aortic dissection type A and normal dimensioned aorta. Surprisingly, the amount of amyloid was significantly lower in the aneurysm and dissection groups (0.63+/-0.13 and 0.36+/-0.24 amyloid particles per mm2, respectively) compared to the control material (2.37+/-0.58). However, focal medin immunoreactivity not associated with amyloid was found more conspicuously in the media of the two diseased groups. Recent amyloid research indicates that prefibrillar oligomeric aggregates, rather than mature amyloid fibrils, are toxic to the surrounding cells. The non-amyloid medin immunoreactivity observed may represent such toxic oligomers. This is supported by the fact that aggregated medin induced death of aortic smooth muscle cells in vitro. In addition, cells incubated together with medin increased the production of matrix metalloproteinase-2, a protease that degrades elastin and collagen and subsequently weakens the vessel wall. We therefore propose that medin oligomers are involved in the degeneration process of sporadic thoracic aortic aneurysm and dissection.

Autonomic Peripheral Neuropathy

Most generalized peripheral polyneuropathies are accompanied by clinical or subclinical autonomic dysfunction. There is a group of peripheral neuropathies in which the small or unmyelinated fibers are selectively targeted. In these neuropathies, autonomic dysfunction is the most prominent manifestation. The features associated with an autonomic neuropathy include impairment of cardiovascular, gastrointestinal, urogenital, thermoregulatory, sudomotor, and pupillomotor autonomic function.

Liver transplantation and new therapeutic approaches for familial amyloidotic polyneuropathy (FAP)

Liver transplantation has been considered as a promising therapy to halt the progression of clinical symptoms in familial amyloidotic polyneuropathy (FAP) because most transthyretin (TTR) is produced by the liver. In addition, domino liver transplantation using an FAP patient's liver has been performed because of a shortage of donor livers. However, because the use of liver transplantation as therapy for FAP has given rise to several problems, an alternative treatment is needed. We have tried several other approaches. Recent studies suggested that certain metal ions affect amyloidogenesis. Among metal ions tested in an in vitro amyloid formation study, Cr3+ increased stability of both normal and mutant TTR tetramers and suppressed TTR amyloidogenesis induced by low pH. Our findings indicate that Cr3+ acts to suppress TTR amyloidogenesis. BSB, a Congo red derivative that binds to amyloid fibrils in FAP as well as to those in senile plaques in Alzheimer's disease, effectively suppressed TTR amyloid formation in vitro. BSB may thus be useful for preventing amyloid formation. Free radical scavenger therapy was also tried in FAP patients but yielded no conclusive results. Immunization for transgenic mice having the ATTR V30M gene using ATTR Y78P resulted in suppression of amyloid deposits. Finally, an RNA/DNA chimera and single-stranded oligonucleotides (SSOs) were tested in vitro and in vivo in an attempt to repair the amyloidogenic TTR gene in the liver and retina. On the basis of results achieved so far, SSO is a promising tool for gene therapy.

The effect of ethanol-induced CYP2E1 on proteasome activity: the role of 4-hydroxynonenal

Previous studies have shown that the induction of P450 cytochrome 2E1 (CYP2E1) is associated with the loss of proteasomal activities. To correlate the loss of proteasomal activity with CYP2E1 induction, ethanol was fed intragastrically for 1, 3, 7, and 15 days. The maximum induction of CYP2E1 (3.5-fold) occurred after 15 days of ethanol feeding. However, there was no significant decrease in the 26 S chymotrypsin-like and trypsin-like activity over this period of time. When ethanol was given to rats for 1 month, CYP2E1 was significantly induced, and the proteasomal activity was significantly decreased. These results indicate that proteasomal activity was not directly affected by ethanol or CYP2E1 induction. Since 4-hydroxynonenal (4-HNE) concentration was significantly increased at 1 month of ethanol feeding, it was suspected that 4-HNE adduct formation with proteasome subunits could be the mechanism of proteasome inhibition. Using an antibody to 4-HNE adducted proteins in Western blot analysis of the 26 S proteasome fraction isolated from the liver of alcohol fed rats, one extra band appeared around 44 kDa. When the antibody to an ATPase Rpt4 was used to stain the stripped membrane, the same band that was detected with the 4-HNE antibody was detected with the Rpt4 antibody. An adduct of 4-HNE formed with the Rpt4 subunit of 26 S could impede the association of 19 S and 20 S and thus account for the observed decrease of proteasomal activity.