The interface targeting hnRNPA2B1 regulates the repression of transthyretin against human retinal microvascular endothelial cells in high-glucose environment.

BACKGROUND: The interaction between transthyretin (TTR) and heterogeneous nuclear ribonucleoprotein (hnRNP)A2B1 is involved in the neovascularization of human retinal microvascular endothelial cells (hRECs) under hyperglycemic conditions. However, whether the TTR-hnRNPA2B1 interface can be altered and how this protein-protein interaction and associated downstream pathways are regulated is unclear. METHODS: We performed homologous sequential analysis and binding energy assays using Discovery Studio and designed substitution targeting three fragments of the interface (fragment 1: aa 34-39, -RKAADD-; fragment 2, aa 61-68, -EEEFVEGI-; and fragment 3, aa 96-102, -TANDSGP-) to disrupt or stabilize the TTR-hnRNPA2B1 complex and were subjected to Co-immunoprecipitation analysis. To investigate the effect of TTR-hnRNPA2B1 interface alterations on the physiological properties of hRECs, we performed CCK-8, EdU, migration, wound healing and tube formation assays. To study the downstream genes, we performed qRT-PCR and western blot. RESULTS: Nineteen TTR substitutions were recombinantly expressed in soluble form, results indicated that reducing the binding energy stabilized the TTR-hnRNPA2B1, while increasing the binding energy had the opposite effect. The native TTR significantly prohibited the proliferation, DNA synthesis, migration and tube formation capacities of hRECs, while fragment 1 always reduced these effects. However, the I68R and D99R substitutions in fragments 2 and 3, respectively, increased the inhibitory effect of TTR. Furthermore, our qRT-PCR and western blot results showed that the expression and protein levels of STAT-4, miR-223-3p and FBXW7 were also regulated by the alteration of the TTR-hnRNPA2B1 interface. CONCLUSION: This work suggests that the formation of the TTR-hnRNPA2B1 complex plays vital role in hyperglycemia, and modification of this interface regulates the TTR-mediated inhibition of hREC neovascularization via the STAT-4/miR-223-3p/FBXW7 pathway. This mechanism could have important implications for diabetic retinopathy treatment.

The serum protein transthyretin as a platform for dimerization and tetramerization of antibodies and Fab fragments to enable target clustering.

Transthyretin (TTR) is an abundant homotetrameric serum protein and was selected here for engineering higher-valency molecules because of its compact size, simple structure, and natural propensity to tetramerize. To demonstrate this utility, we fused TTR to the C terminus of conatumumab, an antibody that targets tumor necrosis factor-related apoptosis-inducing ligand receptor 2, as heavy chains to form antibody dimers and Fab heavy chains to form Fab tetramers. Moreover, we used constant heavy domain 3 heterodimerization substitutions to create TTR-mediated conatumumab tetramers. The conatumumab-TTR fusions displayed substantially enhanced potency in cell-based assays, as well as in murine tumor xenograft models. We conclude that antibody-TTR fusions may provide a powerful platform for multimerizing antibody and Fab fragments to enhance the capabilities of human therapeutics that benefit from target clustering and higher-order antigen-binding valency.

Transthyretin affects the proliferation and migration of human retinal microvascular endothelial cells in hyperglycemia via hnRNPA2B1.

Transthyretin (TTR) has been proved to repress neovascularization in diabetic retinopathy environment by regulating the molecules in and downstream of the STAT-4/miR-223-3p/FBXW7 signal pathway; however, the details of its direct targets are still not well understood. The interaction between TTR and a target in nucleus of human retinal microvascular endothelial cells (hRECs), heterogeneous nuclear ribonucleoprotein (hnRNP) A2B1, was screened by immunoprecipitation (IP) and mass spectrum (MS), and it was further confirmed by co-immunoprecipitation (co-IP). Regarding ZDOCK analysis using Discovery Studio, the interface and potential binding sites between TTR and hnRNPA2B1 were simulated; mutants were designed in these regions and five soluble ones were recombinantly expressed and prepared; the interaction between TTR and hnRNPA2B1 were disrupted by several mutated residues. In addition, for several mutated TTRs, the inhibition activities against the proliferation, migration and tube formation of hRECs were absent in vitro. Following the disruption of TTR-hnRNPA2B1, the molecules in and downstream of STAT-4/miR-223-3p/FBXW7 signal pathway, including STAT-4, miR-223-3p, FBXW7 p-Akt and Notch1 could not be regulated by TTR mutants; therefore, a TTR-hnRNPA2B1/STAT-4/miR-223-3p/FBXW7 was proposed. In conclusion, this work suggested that TTR should play a physiological role in diabetic environment by the direct binding with hnRNPA2B1, and it provided a theoretical basis for clinical diagnosis, therapy and further application.

Transthyretin Stimulates Tumor Growth through Regulation of Tumor, Immune, and Endothelial Cells.

Early detection of lung cancer offers an important opportunity to decrease mortality while it is still treatable and curable. Thirteen secretory proteins that are Stat3 downstream gene products were identified as a panel of biomarkers for lung cancer detection in human sera. This panel of biomarkers potentially differentiates different types of lung cancer for classification. Among them, the transthyretin (TTR) concentration was highly increased in human serum of lung cancer patients. TTR concentration was also induced in the serum, bronchoalveolar lavage fluid, alveolar type II epithelial cells, and alveolar myeloid cells of the CCSP-rtTA/(tetO)7-Stat3C lung tumor mouse model. Recombinant TTR stimulated lung tumor cell proliferation and growth, which were mediated by activation of mitogenic and oncogenic molecules. TTR possesses cytokine functions to stimulate myeloid cell differentiation, which are known to play roles in tumor environment. Further analyses showed that TTR treatment enhanced the reactive oxygen species production in myeloid cells and enabled them to become functional myeloid-derived suppressive cells. TTR demonstrated a great influence on a wide spectrum of endothelial cell functions to control tumor and immune cell migration and infiltration. TTR-treated endothelial cells suppressed T cell proliferation. Taken together, these 13 Stat3 downstream inducible secretory protein biomarkers potentially can be used for lung cancer diagnosis, classification, and as clinical targets for lung cancer personalized treatment if their expression levels are increased in a given lung cancer patient in the blood.

Inhibition of curli assembly and Escherichia coli biofilm formation by the human systemic amyloid precursor transthyretin.

During biofilm formation, Escherichia coli and other Enterobacteriaceae produce an extracellular matrix consisting of curli amyloid fibers and cellulose. The precursor of curli fibers is the amyloidogenic protein CsgA. The human systemic amyloid precursor protein transthyretin (TTR) is known to inhibit amyloid-ß (Aß) aggregation in vitro and suppress the Alzheimer's-like phenotypes in a transgenic mouse model of Aß deposition. We hypothesized that TTR might have broad antiamyloid activity because the biophysical properties of amyloids are largely conserved across species and kingdoms. Here, we report that both human WT tetrameric TTR (WT-TTR) and its engineered nontetramer-forming monomer (M-TTR, F87M/L110M) inhibit CsgA amyloid formation in vitro, with M-TTR being the more efficient inhibitor. Preincubation of WT-TTR with small molecules that occupy the T4 binding site eliminated the inhibitory capacity of the tetramer; however, they did not significantly compromise the ability of M-TTR to inhibit CsgA amyloidogenesis. TTR also inhibited amyloid-dependent biofilm formation in two different bacterial species with no apparent bactericidal or bacteriostatic effects. These discoveries suggest that TTR is an effective antibiofilm agent that could potentiate antibiotic efficacy in infections associated with significant biofilm formation.

Neuropathy Associated with Systemic Amyloidosis.

Peripheral neuropathy occurs in the setting of both hereditary and acquired amyloidosis. The most common form of hereditary amyloidosis is caused by 1 of 140 mutations in the transthyretin (TTR) gene, which can lead to neuropathic hereditary transthyretin amyloidosis (hATTR; previously referred to as transthyretin familial amyloid polyneuropathy), whereas acquired immunoglobulin light chain (AL) amyloidosis is the most common acquired form. Patients typically present with a sensorimotor polyneuropathy, focal neuropathy such as carpal tunnel syndrome, or autonomic neuropathy. When neuropathy is the sole or dominant presenting symptom, the diagnosis is commonly delayed. With the advent of new drug therapies for AL amyloidosis and hATTR amyloidosis, including proteasome inhibitors, TTR silencers, and TTR protein stabilizers, the neurologist is uniquely positioned to diagnose neurologic manifestations of systemic amyloidosis, leading to earlier disease identification and treatment. This article reviews the epidemiology, clinical presentations, pathophysiology, diagnostic workup, and treatment of neuropathy in the setting of amyloidosis.

A biomimetic approach for enhancing the in vivo half-life of peptides.

The tremendous therapeutic potential of peptides has not yet been realized, mainly owing to their short in vivo half-life. Although conjugation to macromolecules has been a mainstay approach for enhancing protein half-life, the steric hindrance of macromolecules often harms the binding of peptides to target receptors, compromising the in vivo efficacy. Here we report a new strategy for enhancing the in vivo half-life of peptides without compromising their potency. Our approach involves endowing peptides with a small molecule that binds reversibly to the serum protein transthyretin. Although there are a few molecules that bind albumin reversibly, we are unaware of designed small molecules that reversibly bind other serum proteins and are used for half-life extension in vivo. We show here that our strategy was effective in enhancing the half-life of an agonist for GnRH receptor while maintaining its binding affinity, which was translated into superior in vivo efficacy.

Cytotoxic Effects of Transthyretin Aggregates in an Epidermoid Cell Line.

OBJECTIVE: Skin amyloid deposits can occur as part of systemic amyloidoses including those involving misfolded- aggregated transthyretins (agTTR). Pathological effects of agTTR on the skin are not well understood. The main objective of the current study was to examine the toxicity of agTTR upon a human keratinocyte cell line. METHODS: Cells were analyzed for indicators of oxidative stress after treatment with normal soluble TTR or the same pre-aggregation concentration of agTTR. Hydrogen peroxide production was analyzed as an indicator for the involvement of reactive oxygen species. RESULTS: Treatment of cells with agTTR significantly increased hydrogen peroxide production (p < 0.05 vs. controls). Glutathione (GSH) and catalase were analyzed as indicators of endogenous cellular antioxidant activity. Treatment of cells with agTTR resulted in significant decreases in both catalase activity and GSH levels (p < 0.05 vs. controls). CONCLUSION: agTTR disrupts redox balance and induces oxidative stress in these epidermoid cells.

Transthyretin represses neovascularization in diabetic retinopathy.

PURPOSE: The apoptosis of human umbilical vein endothelial cells has been reportedly induced by the protein transthyretin (TTR). In human ocular tissue, TTR is generally considered to be secreted mainly by retinal pigment epithelial cells (hRPECs); however, whether TTR affects the development of neovascularization in diabetic retinopathy (DR) remains unclear. METHODS: Natural and simulated DR media were used to culture human retinal microvascular endothelial cells (hRECs). Hyperglycemia was simulated by increasing the glucose concentration from 5.5 mM up to 25 mM, while hypoxia was induced with 200 µM CoCl2. To understand the effects of TTR on hRECs, cell proliferation was investigated under natural and DR conditions. Overexpression of TTR, an in vitro wound-healing assay, and a tube formation assay were employed to study the repression of TTR on hRECs. Real-time fluorescence quantitative PCR (qRT-PCR) was used to study the mRNA levels of DR-related genes, such as Tie2, VEGFR1, VEGFR2, Angpt1, and Angpt2. RESULTS: The proliferation of hRECs was significantly decreased in the simulated hyperglycemic and hypoxic DR environments. The cells were further repressed by added exogenous or endogenous TTR only under hyperglycemic conditions. The in vitro migration and tube formation processes of the hRECs were inhibited with TTR; furthermore, in the hyperglycemia and hyperglycemia/hypoxia environments, the levels of Tie2 and Angpt1 mRNA were enhanced with exogenous TTR, while those of VEGFR1, VEGFR2, and Angpt1 were repressed. CONCLUSIONS: In hyperglycemia, the proliferation, migration, and neovascularization of hRECs were significantly inhibited by TTR. The key genes for DR neovascularization, including Tie2, VEGFR1, VEGFR2, Angpt1, and Angpt2, were regulated by TTR. Under DR conditions, TTR significantly represses neovascularization by inhibiting the proliferation, migration and tube formation of hRECs.

Effects of transthyretin on thyroxine and ß-amyloid removal from cerebrospinal fluid in mice.

Transthyretin (TTR) is a binding protein for the thyroid hormone thyroxine (T4 ), retinol and ß-amyloid peptide. TTR aids the transfer of T4 from the blood to the cerebrospinal fluid (CSF), but also prevents T4 loss from the blood-CSF barrier. It is, however, unclear whether TTR affects the clearance of ß-amyloid from the CSF. This study aimed to investigate roles of TTR in ß-amyloid and T4 efflux from the CSF. Eight-week-old 129sv male mice were anaesthetized and their lateral ventricles were cannulated. Mice were infused with artificial CSF containing (125) I-T4 /(3) H-mannitol, or (125) I-Aß40/(3) H-inulin, in the presence or absence of TTR. Mice were decapitated at 2, 4, 8, 16, 24 minutes after injection. The whole brain was then removed and divided into different regions. The radioactivities in the brain were determined by liquid scintillation counting. At baseline, the net uptake of (125) I-T4 into the brain was significantly higher than that of (125) I-Aß40, and the half time for efflux was shorter ((125) I-T4 , 5.16; (3) H-mannitol, 7.44; (125) I-Aß40, 8.34; (3) H-inulin, 10.78 minutes). The presence of TTR increased the half time for efflux of (125) I-T4 efflux, and caused a noticeable increase in the uptake of (125) I-T4 and (125) I-Aß40 in the choroid plexus, whilst uptakes of (3) H-mannitol and (3) H-inulin remained similar to control experiments. This study indicates that thyroxine and amyloid peptide effuse from the CSF using different transporters. TTR binds to thyroxine and amyloid peptide to prevent the loss of thyroxine from the brain and redistribute amyloid peptide to the choroid plexus.

[Effects of transthyretin on biological behavior of retinal pigment epithelial cells and retinal microvascular epithelial cells].

Objective: To explore the effects of transthyretin (TTR) on biological behavior of retinal pigment epithelial cells (RPECs) and retinal microvascular epithelial cells (RMVECs). Methods: RPECs were cultured with exogenous TTR to explore the effect of TTR on the proliferation of RPECs. The expression of TTR of RPECs was silenced by TTR specific small interfering RNA and the expression of TTR was detected by using Western blotting to identify the efficacy of TTR silence. The level of vascular endothelial growth factor (VEGF) massage RNA was detected by using RT-PCR to identify the interaction between VEGF and TTR. The different proliferation and migration abilities of RMVECs with different expressions of TTR were measured by transwell system. Results: MTT assay showed that RPECs with 0 µmol/L TTR glowed faster than with 4 µmol/L TTR (t=18.08, P<0.0001). The expression level of TTR was decreased in the small interfering RNA group as compared with the negative control group (P<0.05). RT-PCR assay showed no differential expression of VEGF after the silencing of TTR (P>0.05). The transwell assay showed RMVECs with the silence of TTR proliferated more slowly than RMVECs without the treatment (t=4.901, P=0.0012), and also migrated more slowly (t=4.213, P=0.0029). Conclusions: TTR can inhibit the proliferation of RPECs and promote the proliferation and migration of RMVECs without the help of VEGF, the mechanism of which may be worth further study. (Chin J Ophthalmol, 2016, 52: 856-860).

Transthyretin suppresses the toxicity of oligomers formed by misfolded proteins in vitro.

Although human transthyretin (TTR) is associated with systemic amyloidoses, an anti-amyloidogenic effect that prevents Aß fibril formation in vitro and in animal models has been observed. Here we studied the ability of three different types of TTR, namely human tetramers (hTTR), mouse tetramers (muTTR) and an engineered monomer of the human protein (M-TTR), to suppress the toxicity of oligomers formed by two different amyloidogenic peptides/proteins (HypF-N and Aß42). muTTR is the most stable homotetramer, hTTR can dissociate into partially unfolded monomers, whereas M-TTR maintains a monomeric state. Preformed toxic HypF-N and Aß42 oligomers were incubated in the presence of each TTR then added to cell culture media. hTTR, and to a greater extent M-TTR, were found to protect human neuroblastoma cells and rat primary neurons against oligomer-induced toxicity, whereas muTTR had no protective effect. The thioflavin T assay and site-directed labeling experiments using pyrene ruled out disaggregation and structural reorganization within the discrete oligomers following incubation with TTRs, while confocal microscopy, SDS-PAGE, and intrinsic fluorescence measurements indicated tight binding between oligomers and hTTR, particularly M-TTR. Moreover, atomic force microscopy (AFM), light scattering and turbidimetry analyses indicated that larger assemblies of oligomers are formed in the presence of M-TTR and, to a lesser extent, with hTTR. Overall, the data suggest a generic capacity of TTR to efficiently neutralize the toxicity of oligomers formed by misfolded proteins and reveal that such neutralization occurs through a mechanism of TTR-mediated assembly of protein oligomers into larger species, with an efficiency that correlates inversely with TTR tetramer stability.

In vitro screening of per- and polyfluorinated substances (PFAS) for interference with seven thyroid hormone system targets across nine assays.

The US Environmental Protection Agency is evaluating the ecological and toxicological effects of per- and polyfluorinated chemicals. A number of perfluorinated chemicals have been shown to impact the thyroid axis in vivo suggesting that the thyroid hormone system is a target of these chemicals. The objective of this study was to evaluate the activity of 136 perfluorinated chemicals at seven key molecular initiating events (MIE) within the thyroid axis using nine in vitro assays. The potential MIE targets investigated are Human Iodothyronine Deiodinase 1 (hDIO1), Human Iodothyronine Deiodinase 2 (hDIO2), Human Iodothyronine Deiodinase 3 (hDIO3), Xenopus Iodothyronine Deiodinase (xDIO3); Human Iodotyrosine Deiodinase (hIYD), Xenopus Iodotyrosine Deiodinase (xIYD), Human Thyroid Peroxidase (hTPO); and the serum binding proteins Human Transthyretin (hTTR) and Human Thyroxine Binding Globulin (hTBG). Of the 136 PFAS chemicals tested, 85 had sufficient activity to produce a half-maximal effect concentration (EC50) in at least one of the nine assays. In general, most of these PFAS chemicals did not have strong potency towards the seven MIEs examined, apart from transthyretin binding, for which several PFAS had potency similar to the respective model inhibitor. These data sets identify potentially active PFAS chemicals to prioritize for further testing in orthogonal in vitro assays and at higher levels of biological organization to evaluate their capacity for altering the thyroid hormone system and causing potential adverse health and ecological effects.

Bioaccumulation and thyroid endcrione disruption of 2-ethylhexyl diphenyl phosphate at environmental concentration in zebrafish larvae.

2-ethylhexyl diphenyl phosphate (EHDPP) strongly binds to transthyretin (TTR) and affects the expression of genes involved in the thyroid hormone (TH) pathway in vitro. However, it is still unknown whether EHDPP induces endocrine disruption of THs in vivo. In this study, zebrafish (Danio rerio) embryos (< 2 h post-fertilization (hpf)) were exposed to environmentally relevant concentrations of EHDPP (0, 0.1, 1, 10, and 100 µg·L-1) for 120 h. EHDPP was detected in 120 hpf larvae at concentrations of 0.06, 0.15, 3.71, and 59.77 µg·g-1 dry weight in the 0.1, 1, 10, and 100 µg·L-1 exposure groups, respectively. Zebrafish development and growth were inhibited by EHDPP, as indicated by the increased malformation rate, decreased survival rate, and shortened body length. Exposure to lower concentrations of EHDPP (0.1 and 1 µg·L-1) significantly decreased the whole-body thyroxine (T4) and triiodothyronine (T3) levels and altered the expressions of genes and proteins involved in the hypothalamic-pituitary-thyroid axis. Downregulation of genes related to TH synthesis (nis and tg) and TH metabolism (dio1 and dio2) may be partially responsible for the decreased T4 and T3 levels, respectively. EHDPP exposure also significantly increased the transcription of genes involved in thyroid development (nkx2.1 and pax8), which may stimulate the growth of thyroid primordium to compensate for hypothyroidism. Moreover, EHDPP exposure significantly decreased the gene and protein expression of the transport protein transthyretin (TTR) in a concentration-dependent manner, suggesting a significant inhibitory effect of EHDPP on TTR. Molecular docking results showed that EHDPP and T4 partly share the same mode of action of binding to the TTR protein, which might result in decreased T4 transport due to the binding of EHDPP to the TTR protein. Taken together, our findings indicate that EHDPP can cause TH disruption in zebrafish and help elucidate the mechanisms underlying EHDPP toxicity.

Neurotoxicity and memory deficits induced by soluble low-molecular-weight amyloid-ß1-42 oligomers are revealed in vivo by using a novel animal model.

Neuronal and synaptic degeneration are the best pathological correlates for memory decline in Alzheimer's disease (AD). Although the accumulation of soluble low-molecular-weight amyloid-ß (Aß) oligomers has been suggested to trigger neurodegeneration in AD, animal models overexpressing or infused with Aß lack neuronal loss at the onset of memory deficits. Using a novel in vivo approach, we found that repeated hippocampal injections of small soluble Aß(1-42) oligomers in awake, freely moving mice were able to induce marked neuronal loss, tau hyperphosphorylation, and deficits in hippocampus-dependent memory. The neurotoxicity of small Aß(1-42) species was observed in vivo as well as in vitro in association with increased caspase-3 activity and reduced levels of the NMDA receptor subunit NR2B. We found that the sequestering agent transthyretin is able to bind the toxic Aß(1-42) species and attenuated the loss of neurons and memory deficits. Our novel mouse model provides evidence that small, soluble Aß(1-42) oligomers are able to induce extensive neuronal loss in vivo and initiate a cascade of events that mimic the key neuropathological hallmarks of AD.

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.

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.

Effects of taurine on metal cations, transthyretin and LRP-1 in a rat model of Alzheimer's disease.

BACKGROUND: Researches on diagnosis and treatment of Alzheimer's disease, the most common type of dementia, are still ongoing. Taurine is frequently used in Alzheimer's disease models due to its protective effects. Metal cation dyshomeostasis is an important etiological factor for Alzheimer's disease. Transthyretin protein is thought to act as a transporter for the Aß protein that accumulates in the brain and is eliminated in the liver and kidneys via the LRP-1 receptor. However, the effect of taurine on this mechanisms is not fully known. METHODS: 30 male rats, aged 28 ± 4 months, were divided into 5 groups (n = 6) as follows: control group, sham group, Aß 1-42 group, taurine group and taurine+Aß 1-42 group. Oral taurine pre-supplementation was given as 1000 mg/kg-body weight/day for 6 weeks to taurine and taurine+Aß 1-42 groups. RESULTS: Plasma copper, heart transthyretin and Aß 1-42, brain and kidney LRP-1 levels were found to be decreased in the Aß 1-42 group. Brain transthyretin was higher in taurine+Aß 1-42 group and brain Aß 1-42 was higher in Aß 1-42 and taurine+Aß 1-42 groups. CONCLUSION: Taurine pre-supplementation maintained cardiac transthyretin levels, decreased cardiac Aß 1-42 levels and increased brain and kidney LRP-1 levels. Taurine may have a potential to be used as a protective agent for aged people at high risk for Alzheimer's disease.

The goitrogenic efficiency of thioamides in a marine teleost, sea bream (Sparus auratus).

Studies on the role of thyroid hormones (THs) in teleost fish physiology have deployed the synthetic goitrogens, methimazol (MMI), propilthiouracil (PTU) and thiourea (TU) that are used to treat human hyperthyroidism. However, the action of the goitrogens, MMI, PTU and TU at different levels of the hypothalamic-pituitary-thyroid (HPT) axis in teleosts is largely unknown. The central importance of the hypothalamus and pituitary in a number of endocrine regulated systems and the cross-talk that occurs between different endocrine axes makes it pertinent to characterize the effects of MMI, PTU and TU, on several endpoints of the thyroid system. The marine teleost, sea bream (Sparus auratus) was exposed to MMI, PTU and TU (1mg/kg wet weight per day), via the diet for 21days. Radioimmunoassays (RIA) of plasma THs and ELISA of the TH carrier transthyretin (TTR) revealed that MMI was the only chemical that significantly reduced plasma TH levels (p<0.05), although both MMI and PTU significantly (p<0.05) reduced plasma levels of circulating TTR (p<0.05). Histological analysis of the thyroid tissue revealed modifications in thyrocyte activity that explain the reduced circulating levels of THs. MMI also significantly (p<0.05) up-regulated transcript abundance of liver deiodinase 1 and 2 while significantly (p<0.05) decreasing TRß expression in the pituitary, all hallmarks of HPT axis action of goitrogens in vertebrates. The results indicate that in the sea bream MMI is the most effective goitrogen followed by PTU and that TU (1mg/kg wet weight for 21days) failed to have a goitrogenic effect. The study highlights the non-uniform effect of goitrogens on the thyroid axis of sea bream and provides the basis for future studies of thyroid disrupting pollutants.