Drug Development in Conformational Diseases: A Novel Family of Chemical Chaperones that Bind and Stabilise Several Polymorphic Amyloid Structures

Amylovis-201 enhances physiological memory formation and rescues memory and hippocampal cell loss in a streptozotocin-induced Alzheimer's disease animal model

Alzheimer's disease is the most common neurodegenerative disease, and its treatment is lacking. In this work, we tested Amylovis-201, a naphthalene-derived compound, as a possible therapeutic candidate for the treatment of AD. For this purpose, we performed three experiments. In the first and third experiment, animals received a bilateral administration of streptozotocin and, starting 24 h after injection, a daily dose of Amylovis-201 (orally), for 17 days or for the whole time of the experiment respectively (28 days), after which learning and memory, as well as the number of hippocampal dentate gyrus cells, were assessed. In the second experiment, healthy animals received a single dose of Amylovis-201, 10 min or 5 h after the learning section to assess whether this substance could promote specific mechanisms involved in memory trace formation. Our data show that, administration of a single dose of Amylovis-201, 10 min after the end of training, but not at 5 h, produces a prolongation in memory duration, probably because it modulates specific mechanisms involved in memory trace consolidation. Furthermore, daily administration of Amylovis-201 to animals with bilateral intracerebroventricular injection of STZ produces a reduction in the loss of the hippocampus dentate gyrus cells and an improvement in spatial memory, probably because Amylovis-201 can interact with some of the protein kinases of the insulin signaling cascade, also involved in neural plasticity, and thereby halt or reverse some of the effects of STZ. Taking to account these results, Amylovis-201 is a good candidate for the therapeutic treatment of AD.

Design and synthesis of ruthenium complexes and their studies on the inhibition of amyloid β (1-42) peptide aggregation

Misfolding and protein aggregation have been linked to numerous human neurodegenerative disorders such as Alzheimer's, prions, and Parkinson's. Due to their interesting photophysical properties, ruthenium (Ru) complexes have received considerable attention in studying protein aggregation. In this study, we synthesized the novel Ru complexes ([Ru(p-cymene)Cl(L-1)][PF₆](Ru-1), and [Ru(p-cymene)Cl(L-2)][PF₆](Ru-2)) and investigated their inhibitory activity against the bovine serum albumin (BSA) aggregation and the Aβ_1-42 peptides amyloid formation. Several spectroscopic methods were used to characterize the complexes, and the molecular structure was determined by X-ray crystallography. Amyloid aggregation and inhibition activity were examined using the Thioflavin-T (ThT) assay, and secondary structures were analyzed by circular dichroism (CD) spectroscopy and transmission electron microscopy (TEM). The cell viability assay was carried out on the neuroblastoma cell line, revealing that the Ru-2 complex showed better protective effects against Aβ_1-42 peptide toxicity on neuro-2a cells than the Ru-1 complex. Molecular docking studies elucidate binding sites and interactions between the Ru-complexes and the Aβ_1-42 fibrils. The experimental studies revealed that these complexes significantly inhibited BSA aggregation and Aβ_1-42 amyloid fibril formation at 1:3 and 1:1 equimolar concentrations, respectively. Antioxidant assays demonstrated that these complexes act as antioxidants, protecting from amyloid-induced oxidative stress. Molecular docking studies with the monomeric Aβ_1-42 (PDB: 1IYT) show hydrophobic interaction, and both complexes bind preferably in the central region of the peptide and coordinate with two binding sites of the peptide. Hence, we suggest that the Ru-based complexes could be applied as a potential agent in metallopharmaceutical research against Alzheimer's disease.

Amyloid-like aggregation of bovine serum albumin at physiological temperature induced by cross-seeding effect of HEWL amyloid aggregates

BSA can form amyloid-like aggregates in vitro at 65 °C. Heterologous amyloid can proposedly cross-seed other protein's aggregation, however, general mechanisms and driving conditions remain to be vividly elucidated. Here, we examined if pre-formed HEWL amyloid can cross-seed the aggregation of BSA at physiological temperature, 37 °C, and whether the efficacy depends on the BSA conformation. We find that at pH 3.0, 37 °C where BSA manifests exposure of abundant hydrophobic patches, HEWL amyloid efficiently drives BSA into ThT-positive, sarkosyl-resistant, β-sheet rich amyloid-like aggregates exhibiting fibrils in TEM. On the contrary, HEWL amyloid fails to cross-seed the BSA aggregation at pH 7.0, 37 °C where BSA has largely internalized hydrophobic patches. Strikingly, human lysozyme amyloid could also cross-seed human serum albumin aggregation at pH 3.0, 37 °C. Thus, heterologous amyloid cross-seeding can help overcome the energy-barrier for aggregation of other proteins that, for any reason, may have perturbed and promiscuous structural conformation at physiological temperatures.

Protein misfolding, ER Stress and Chaperones: An approach to develop chaperone-based therapeutics for Alzheimer's Disease

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disorder with complex etiology that eventually leads to dementia. The main culprit of AD is the extracellular deposition of β-amyloid (Aβ) and intracellular neurofibrillary tangles. The protein conformational change and protein misfolding are the key events of AD pathophysiology, therefore endoplasmic reticulum (ER) stress is an apparent consequence. ER, stress-induced unfolded protein response (UPR) mediators (viz. PERK, IRE1, and ATF6) have been reported widely in the AD brain. Considering these factors, preventing proteins misfolding or aggregation of tau or amyloidogenic proteins appears to be the best approach to halt its pathogenesis. Therefore, therapies through chemical and pharmacological chaperones came to light as an alternative for the treatment of AD. Diverse studies have demonstrated 4-phenylbutyric acid (4-PBA) as a potential therapeutic agent in AD. The current review outlined the mechanism of protein misfolding, different etiological features behind the progression of AD, the significance of ER stress in AD, and the potential therapeutic role of different chaperones to counter AD. The study also highlights the gaps in current knowledge of the chaperones-based therapeutic approach and the possibility of developing chaperones as a potential therapeutic agent for AD treatment.

A new naphthalene derivative with anti-amyloidogenic activity as potential therapeutic agent for Alzheimer's disease

The aggregation of β-amyloid peptides is associated to neurodegeneration in Alzheimer's disease (AD) patients. Consequently, the inhibition of both oligomerization and fibrillation of β-amyloid peptides is considered a plausible therapeutic approach for AD. Herein, the synthesis of new naphthalene derivatives and their evaluation as anti-β-amyloidogenic agents are presented. Molecular dynamic simulations predicted the formation of thermodynamically stable complexes between the compounds, the Aβ_1-42 peptide and fibrils. In human microglia cells, these compounds inhibited the aggregation of Aβ_1-42 peptide. The lead compound 8 showed a high affinity to amyloid plaques in mice brain ex vivo assays and an adequate log P_oct/PBS value. Compound 8 also improved the cognitive function and decreased hippocampal β-amyloid burden in the brain of 3xTg-AD female mice. Altogether, our results suggest that 8 could be a novel therapeutic agent for AD.

Computational Insights into the Binding of Monolayer-Capped Gold Nanoparticles onto Amyloid-β Fibrils

Amyloids-β (Aβ) fibrils are involved in several neurodegenerative diseases. In this study, atomistic molecular dynamics simulations have been used to investigate how monolayer-protected gold nanoparticles interact with Aβ(1-40) and Aβ(1-42) fibrils. Our results show that small gold nanoparticles bind with the external side of amyloid-β fibrils that is involved in the fibrillation process. The binding affinity, studied for both kinds of fibrils as a function of the monolayer composition and the nanoparticle diameter, is modulated by hydrophobic interactions and ligand monolayer conformation. Our findings thus show that monolayer-protected nanoparticles are good candidates to prevent fibril aggregation and secondary nucleation or to deliver drugs to specific fibril regions.

Protein-conformational diseases in childhood: Naturally-occurring hIAPP amyloid-oligomers and early β-cell damage in obesity and diabetes

BACKGROUND AND AIMS

This is the first time that obesity and diabetes mellitus (DM) as protein conformational diseases (PCD) are reported in children and they are typically diagnosed too late, when β-cell damage is evident. Here we wanted to investigate the level of naturally-ocurring or real (not synthetic) oligomeric aggregates of the human islet amyloid polypeptide (hIAPP) that we called RIAO in sera of pediatric patients with obesity and diabetes. We aimed to reduce the gap between basic biomedical research, clinical practice-health decision making and to explore whether RIAO work as a potential biomarker of early β-cell damage.

MATERIALS AND METHODS

We performed a multicentric collaborative, cross-sectional, analytical, ambispective and blinded study; the RIAO from pretreated samples (PTS) of sera of 146 pediatric patients with obesity or DM and 16 healthy children, were isolated, measured by sound indirect ELISA with novel anti-hIAPP cytotoxic oligomers polyclonal antibody (MEX1). We carried out morphological and functional studied and cluster-clinical data driven analysis.

RESULTS

We demonstrated by western blot, Transmission Electron Microscopy and cell viability experiments that RIAO circulate in the blood and can be measured by ELISA; are elevated in serum of childhood obesity and diabetes; are neurotoxics and works as biomarkers of early β-cell failure. We explored the range of evidence-based medicine clusters that included the RIAO level, which allowed us to classify and stratify the obesity patients with high cardiometabolic risk.

CONCLUSIONS

RIAO level increases as the number of complications rises; RIAOs > 3.35 μg/ml is a predictor of changes in the current indicators of β-cell damage. We proposed a novel physio-pathological pathway and shows that PCD affect not only elderly patients but also children. Here we reduced the gap between basic biomedical research, clinical practice and health decision making.

Unpacking the aggregation-oligomerization-fibrillization process of naturally-occurring hIAPP amyloid oligomers isolated directly from sera of children with obesity or diabetes mellitus

The formation of amyloid oligomers and fibrils of the human islet amyloid polypeptide (hIAPP) has been linked with β- cell failure and death which causes the onset, progression, and comorbidities of diabetes. We begin to unpack the aggregation-oligomerization-fibrillization process of these oligomers taken from sera of pediatric patients. The naturally occurring or real hIAPP (not synthetic) amyloid oligomers (RIAO) were successfully isolated, we demonstrated the presence of homo (dodecamers, hexamers, and trimers) and hetero-RIAO, as well as several biophysical characterizations which allow us to learn from the real phenomenon taking place. We found that the aggregation/oligomerization process is active in the sera and showed that it happens very fast. The RIAO can form fibers and react with anti-hIAPP and anti-amyloid oligomers antibodies. Our results opens the epistemic horizon and reveal real differences between the four groups (Controls vs obesity, T1DM or T2DM) accelerating the process of understanding and discovering novel and more efficient prevention, diagnostic, transmission and therapeutic pathways.

Diabetes Drug Discovery: hIAPP1-37 Polymorphic Amyloid Structures as Novel Therapeutic Targets

Human islet amyloid peptide (hIAPP_1–37) aggregation is an early step in Diabetes Mellitus. We aimed to evaluate a family of pharmaco-chaperones to act as modulators that provide dynamic interventions and the multi-target capacity (native state, cytotoxic oligomers, protofilaments and fibrils of hIAPP_1–37) required to meet the treatment challenges of diabetes. We used a cross-functional approach that combines in silico and in vitro biochemical and biophysical methods to study the hIAPP_1–37 aggregation-oligomerization process as to reveal novel potential anti-diabetic drugs. The family of pharmaco-chaperones are modulators of the oligomerization and fibre formation of hIAPP_1–37. When they interact with the amino acid in the amyloid-like steric zipper zone, they inhibit and/or delay the aggregation-oligomerization pathway by binding and stabilizing several amyloid structures of hIAPP_1–37. Moreover, they can protect cerebellar granule cells (CGC) from the cytotoxicity produced by the hIAPP_1–37 oligomers. The modulation of proteostasis by the family of pharmaco-chaperones A–F is a promising potential approach to limit the onset and progression of diabetes and its comorbidities.

Amyloid Biomarkers in Conformational Diseases at Face Value: A Systematic Review

Conformational diseases represent a new aspect of proteomic medicine where diagnostic and therapeutic paradigms are evolving. In this context, the early biomarkers for target cell failure (neurons, β-cells, etc.) represent a challenge to translational medicine and play a multidimensional role as biomarkers and potential therapeutic targets. This systematic review, which follows the PICO and Prisma methods, analyses this new-fangled multidimensionality, its strengths and limitations, and presents the future possibilities it opens up. The nuclear diagnosis methods are immunoassays: ELISA, immunodot, western blot, etc., while the therapeutic approach is focused on pharmaco- and molecular chaperones.

Inhibition of Chaperonin GroEL by a Monomer of Ovine Prion Protein and Its Oligomeric Forms

The possibility of inhibition of chaperonin functional activity by amyloid proteins was studied. It was found that the ovine prion protein PrP as well as its oligomeric and fibrillar forms are capable of binding with the chaperonin GroEL. Besides, GroEL was shown to promote amyloid aggregation of the monomeric and oligomeric PrP as well as PrP fibrils. The monomeric PrP was shown to inhibit the GroEL-assisted reactivation of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The oligomers of PrP decelerate the GroEL-assisted reactivation of GAPDH, and PrP fibrils did not affect this process. The chaperonin GroEL is capable of interacting with GAPDH and different PrP forms simultaneously. A possible role of the inhibition of chaperonins by amyloid proteins in the misfolding of the enzymes involved in cell metabolism and in progression of neurodegenerative diseases of amyloid nature is discussed.

From the Evolution of Protein Sequences Able to Resist Self-Assembly to the Prediction of Aggregation Propensity

Folding of polypeptide chains into biologically active entities is an astonishingly complex process, determined by the nature and the sequence of residues emerging from ribosomes. While it has been long believed that evolution has pressed genomes so that specific sequences could adopt unique, functional three-dimensional folds, it is now clear that complex protein machineries act as quality control system and supervise folding. Notwithstanding that, events such as erroneous folding, partial folding, or misfolding are frequent during the life of a cell or a whole organism, and they can escape controls. One of the possible outcomes of this misbehavior is cross-β aggregation, a super secondary structure which represents the hallmark of self-assembled, well organized, and extremely ordered structures termed amyloid fibrils. What if evolution would have not taken into account such possibilities? Twenty years of research point toward the idea that, in fact, evolution has constantly supervised the risk of errors and minimized their impact. In this review we tried to survey the major findings in the amyloid field, trying to describe what the real pitfalls of protein folding are-from an evolutionary perspective-and how sequence and structural features have evolved to balance the need for perfect, dynamic, functionally efficient structures, and the detrimental effects implicit in the dangerous process of folding. We will discuss how the knowledge obtained from these studies has been employed to produce computational methods able to assess, predict, and discriminate the aggregation properties of protein sequences.