Tetracycline and its analogues protect Caenorhabditis elegans from β amyloid-induced toxicity by targeting oligomers (original) (raw)
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Tetracycline prevents Aβ oligomer toxicity through an atypical supramolecular interaction
Org. Biomol. Chem., 2011
The antibiotic tetracycline was reported to possess an anti-amyloidogenic activity on a variety of amyloidogenic proteins both in in vitro and in vivo models. To unveil the mechanism of action of tetracycline on Ab1-40 and Ab1-42 at both molecular and supramolecular levels, we carried out a series of experiments using NMR spectroscopy, FTIR spectroscopy, dynamic laser light-scattering (DLS) and atomic force microscopy (AFM). Firstly we showed that the co-incubation of Ab1-42 oligomers with tetracycline hinders the toxicity towards N2a cell lines in a dose-dependent manner. Therefore, the nature of the interaction between the drug and Ab oligomers was investigated. To carry out NMR and FTIR studies we have prepared Ab peptide solutions containing assemblies ranging from monomers to large oligomers. Saturation transfer difference (STD) NMR experiments have shown that tetracycline did not interact with monomers at variance with oligomers. Noteworthy, in this latter case we observed that this interaction was very peculiar since the transfer of magnetization from Ab oligomers to tetracycline involved all drug protons. In addition, intermolecular cross-peaks between tetracycline and Ab were not observed in NOESY spectra, indicating the absence of a specific binding site and suggesting the occurrence of a supramolecular interaction. DLS and AFM studies supported this hypothesis since the co-dissolution of Ab peptides and tetracycline triggered the immediate formation of new aggregates that improved the solubility of Ab peptides, preventing in this way the progression of the amyloid cascade. Moreover, competitive NMR binding experiments showed for the first time that tetracycline competes with thioflavin T (ThT) in the binding to Ab peptides. Our data shed light on a novel mechanism of anti-amyloidogenic activity displayed by tetracycline, governed by hydrophobic and charge multiparticle interactions.
Effect of Phenolic Compounds Against Aβ Aggregation and Aβ-Induced Toxicity in Transgenic C. elegans
Neurochemical Research, 2012
Substantial evidence suggests that the aggregation of amyloid-b (Ab) peptide into fibrillar structures that is rich in b-sheets is implicated as the cause of Alzheimer's disease. Therefore, an attractive therapeutic strategy is to prevent or alter Ab aggregation. Phenolic compounds are natural substances that are composed of one or more aromatic phenolic rings and present in wine, tea, fruits, vegetables and a wide variety of plants. In this work, we investigated the effects of ferulic acid, morin, quercetin and gossypol against Ab aggregation. From the ThT and turbidity assays, it is observed that in addition to the fibril aggregate, another type of aggregate is formed in the presence of morin, quercetin, and gossypol. On the other hand, ferulic acid did not prevent fibril formation, but it did appear to reduce the average length of fibrils compared to Ab alone. To study the protective effects of phenolic compounds on Ab-induced toxicity, we utilized the nematode Caenorhabditis elegans (C. elegans) as an in vivo model organism, human Ab is expressed intracellularly in the body wall muscle. We found that exposure of Caenorhabditis elegans to ferulic acid give more protection against Ab toxicity than morin, quercetin and gossypol.
Expression of A2V-mutated Aβ in Caenorhabditis elegans results in oligomer formation and toxicity
Neurobiology of Disease, 2014
Although Alzheimer's disease (AD) is usually sporadic, in a small proportion of cases it is familial and can be linked to mutations in β-amyloid precursor protein (APP). Unlike the other genetic defects, the mutation [alanine-673→valine-673] (A673V) causes the disease only in the homozygous condition with enhanced amyloid β (Aβ) production and aggregation; heterozygous carriers remain unaffected. It is not clear how misfolding and aggregation of Aβ is affected in vivo by this mutation and whether this correlates with its toxic effects. No animal models over-expressing the A673V-APP gene or alanine-2-valine (A2V) mutated human Aβ protein are currently available. Using the invertebrate Caenorhabditis elegans, we generated the first transgenic animal model to express the human Aβ 1-40 wild-type (WT) in neurons or possess the A2V mutation (Aβ 1-40A2V ). Insertion of an Aβ-mutated gene into this nematode reproduced the homozygous state of the human pathology. Functional and biochemical characteristics found in the A2V strain were compared to those of transgenic C. elegans expressing Aβ 1-40WT . The expression of both WT and A2V Aβ 1-40 specifically reduced the nematode's lifespan, causing behavioral defects and neurotransmission impairment which were worse in A2V worms. Mutant animals were more resistant than WT to paralysis induced by the cholinergic agonist levamisole, indicating that the locomotor defect was specifically linked to postsynaptic dysfunctions. The toxicity caused by the mutated protein was associated with a high propensity to form oligomeric assemblies which accumulate in the neurons, suggesting this to be the central event involved in the postsynaptic damage and early onset of the disease in homozygous human A673V carriers.
Targeting Amyloid Aggregation: An Overview of Strategies and Mechanisms
International journal of molecular sciences, 2018
Amyloids result from the aggregation of a set of diverse proteins, due to either specific mutations or promoting intra- or extra-cellular conditions. Structurally, they are rich in intermolecular β-sheets and are the causative agents of several diseases, both neurodegenerative and systemic. It is believed that the most toxic species are small aggregates, referred to as oligomers, rather than the final fibrillar assemblies. Their mechanisms of toxicity are mostly mediated by aberrant interactions with the cell membranes, with resulting derangement of membrane-related functions. Much effort is being exerted in the search for natural antiamyloid agents, and/or in the development of synthetic molecules. Actually, it is well documented that the prevention of amyloid aggregation results in several cytoprotective effects. Here, we portray the state of the art in the field. Several natural compounds are effective antiamyloid agents, notably tetracyclines and polyphenols. They are generally ...
Pharmaceuticals/MDPI, 2023
Abstract: Chronic, low-grade inflammation has been implicated in aging and age-dependent conditions, including Alzheimer’s disease, cardiomyopathy, and cancer. One of the age-associated processes underlying chronic inflammation is protein aggregation, which is implicated in neuroinflammation and a broad spectrum of neurodegenerative diseases such as Alzheimer’s, Huntington’s, and Parkinson’s diseases. We screened a panel of bioactive thiadiazolidinones (TDZDs) from our in-house library for rescue of protein aggregation in human-cell and C. elegans models of neurodegeneration. Among the tested TDZD analogs, PNR886 and PNR962 were most effective, significantly reducing both the number and intensity of Alzheimer-like tau and amyloid aggregates in human cell culture models of pathogenic aggregation. A C. elegans strain expressing human Aβ1–42 in muscle, leading to AD-like amyloidopathy, developed fewer and smaller aggregates after PNR886 or PNR962 treatment. Moreover, age-progressive paralysis was reduced 90% by PNR886 and 75% by PNR962, and “healthspan” (the median duration of spontaneous motility) was extended 29% and 62%, respectively. These TDZD analogs also extended wild-type C. elegans lifespan by 15–30% (p < 0.001), placing them among the most effective life-extension drugs. Because the lead drug in this family, TDZD-8, inhibits GSK3β, we used molecular-dynamic tools to assess whether these analogs may also target GSK3β. In silico modeling predicted that PNR886 or PNR962 would bind to the same allosteric pocket of inactive GSK3β as TDZD-8, employing the same pharmacophore but attaching with greater avidity. PNR886 and PNR962 are thus compelling candidate drugs for treatment of tau- and amyloid-associated neurodegenerative diseases such as AD, potentially also reducing all-cause mortality.
Medicinal Chemistry Research, 2012
Genetic, biochemical, and pathological evidence supports that aggregation of amyloid-beta (Ab) peptide into fibrillar structures rich in beta-sheets is implicated as the cause of Alzheimer's disease. Therefore, an attractive therapeutic strategy is to prevent or alter amyloidbeta aggregation. In this work we examine the effects of the short D-peptides pgklvya, kklvffarrrra, and kklvffa on Ab aggregation in vitro and toxicity in vivo. These peptides are based on the central hydrophobic region of Ab (residues 16-20), which is believed to be crucial in Ab selfassociation. The effect of peptides on Ab aggregation was examined by circular dichroism spectroscopy, Thioflavin T fluorescence, and ANS binding assay. Transgenic Caenorhabditis elegans model was used to evaluate the pharmacological effect of D-peptides on Ab-initiated toxicity. The data suggested that D-peptides are very effective at inhibiting fibrillogenesis of Ab. Among the three peptides tested, only pgklvya and kklvffa improved survival in the transgenic C. elegans. The activity of these peptides correlates with their ability to inhibit Ab oligomerization. These suggest that D-peptides should be considered during future design of peptide-based inhibitors of amyloid deposition and toxicity.
Toxicity Inhibitors Protect Lipid Membranes from Disruption by Aβ42
ACS Chemical Neuroscience, 2015
Although the precise molecular factors linking amyloid β-protein (Aβ) to Alzheimer's disease (AD) have not been deciphered, interaction of Aβ with cellular membranes has an important role in the disease. However, most therapeutic strategies targeting Aβ have focused on interfering with Aβ self-assembly rather than with its membrane interactions. Here, we studied the impact of three toxicity inhibitors on membrane interactions of Aβ42, the longer form of Aβ, which is associated most strongly with AD. The inhibitors included the four-residue C-terminal fragment Aβ(39−42), the polyphenol (−)-epigallocatechin-3-gallate (EGCG), and the lysine-specific molecular tweezer, CLR01, all of which previously were shown to disrupt different steps in Aβ42 self-assembly. Biophysical experiments revealed that incubation of Aβ42 with each of the three modulators affected membrane interactions in a distinct manner. Interestingly, EGCG and CLR01 were found to have significant interaction with membranes themselves. However, membrane bilayer disruption was reduced when the compounds were preincubated with Aβ42, suggesting that binding of the assembly modulators to the peptide attenuated their membrane interactions. Importantly, our study reveals that even though the three tested compounds affect Aβ42 assembly differently, membrane interactions were significantly inhibited upon incubation of each compound with Aβ42, suggesting that preventing the interaction of Aβ42 with the membrane contributes substantially to inhibition of its toxicity by each compound. The data suggest that interference with membrane interactions is an important factor for Aβ42 toxicity inhibitors and should be taken into account in potential therapeutic strategies, in addition to disruption or remodeling of amyloid assembly.
Progress toward Alzheimer's disease treatment: Leveraging the Achilles' heel of Aβ oligomers?
Protein Science, 2020
After three decades of false hopes and failures, a pipeline of therapeutic drugs that target the actual root cause of Alzheimer's disease (AD) is now available. Challenging the old paradigm that focused on β‐amyloid peptide (Aβ) aggregation in amyloid plaques, these compounds are designed to prevent the neurotoxicity of Aβ oligomers that form Ca2+ permeable pores in the membranes of brain cells. By triggering an intracellular Ca2+ overdose, Aβ oligomers induce a cascade of neurotoxic events including oxidative stress, tau hyperphosphorylation, and neuronal loss. Targeting any post‐Ca2+ entry steps (e.g., tau) will not address the root cause of the disease. Thus, preventing Aβ oligomers formation and/or blocking their toxicity is by essence the best approach to stop any progression of AD. Three categories of anti‐oligomer compounds are already available: antibodies, synthetic peptides, and small drugs. Independent in silico‐based designs of a peptide (AmyP53) and a monoclonal ant...
Targeting the neurotoxic species in Alzheimer's disease: Inhibitors of Aβ oligomerization
The FASEB Journal
In the past two decades, a large body of evidence has established a causative role for the -amyloid peptide (A) in Alzheimer's disease (AD). However, recent debate has focused on whether amyloid fibrils or soluble oligomers of A are the main neurotoxic species that contribute to neurodegeneration and dementia. Considerable early evidence has indicated that amyloid fibrils are toxic, but some recent studies support the notion that A oligomers are the primary neurotoxins. While this crucial aspect of AD pathogenesis remains controversial, effective therapeutic strategies should ideally target both oligomeric and fibrillar species of A. Here, we describe the anti-amyloidogenic and neuroprotective actions of some di-and tri-substituted aromatic compounds. Inhibition of the formation of soluble A oligomers was monitored using a specific antibody-based assay that discriminates between A oligomers and monomers. Thioflavin T and electron microscopy were used to screen for inhibitors of fibril formation. Taken together, these results led to the identification of compounds that more effectively block A oligomerization than fibrillization. It is significant that such compounds completely blocked the neurotoxicity of A to rat hippocampal neurons in culture. These findings provide a basis for the development of novel small molecule A inhibitors with potential applications in AD.
PLoS ONE, 2013
The presence of amyloid aggregates of the 42 amino acid peptide of amyloid beta (Ab42) in the brain is the characteristic feature of Alzheimer's disease (AD). Amyloid beta (Ab deposition is also found in muscle fibers of individuals affected by inclusion body myositis (sIBM), a rare muscular degenerative disease affecting people over 50. Both conditions are presently lacking an effective therapeutic treatment. There is increasing evidence to suggest that natural polyphenols may prevent the formation of toxic amyloid aggregates; this applies also to oleuropein aglycone (OLE), the most abundant polyphenol in extra virgin olive oil, previously shown to hinder amylin and Ab aggregation. Here we evaluated the ability of OLE to interfere with Ab proteotoxicity in vivo by using the transgenic CL2006 and CL4176 strains of Caenorhabditis elegans, simplified models of AD and of sIBM, which express human Ab in the cytoplasm of body wall muscle cells. OLE-fed CL2006 worms displayed reduced Ab plaque deposition, less abundant toxic Ab oligomers, remarkably decreased paralysis and increased lifespan with respect to untreated animals. A protective effect was also observed in CL4176 worms but only when OLE was administered before the induction of the Ab transgene expression. These effects were specific, dose-related, and not mediated by the known polyphenolic anti-oxidant activity, suggesting that, in this model organism, OLE interferes with the Ab aggregation skipping the appearance of toxic species, as already shown in vitro for Ab42. Citation: Diomede L, Rigacci S, Romeo M, Stefani M, Salmona M (2013) Oleuropein Aglycone Protects Transgenic C. elegans Strains Expressing Ab42 by Reducing Plaque Load and Motor Deficit. PLoS ONE 8(3): e58893.