Browsing by Author "Almeida, Zaida L."
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- Morphological and Molecular Profiling of Amyloid-β Species in Alzheimer’s PathogenesisPublication . Almeida, Zaida L.; Vaz, Daniela C.; Brito, Rui M. M.Alzheimer’s disease (AD) is the most common form of dementia around the world (~ 65%). Here, we portray the neuropathology of AD, biomarkers, and classifcation of amyloid plaques (difuse, non-cored, dense core, compact). Tau pathology and its involvement with Aβ plaques and cell death are discussed. Amyloid cascade hypotheses, aggregation mechanisms, and molecular species formed in vitro and in vivo (on- and of-pathways) are described. Aβ42/Aβ40 monomers, dimers, trimers, Aβ‐derived difusible ligands, globulomers, dodecamers, amylospheroids, amorphous aggregates, protofbrils, fbrils, and plaques are characterized (structure, size, morphology, solubility, toxicity, mechanistic steps). An update on AD-approved drugs by regulatory agencies, along with new Aβ-based therapies, is presented. Beyond prescribing Aβ plaque disruptors, cholinergic agonists, or NMDA receptor antagonists, other therapeutic strategies (RNAi, glutaminyl cyclase inhibitors, monoclonal antibodies, secretase modulators, Aβ aggregation inhibitors, and anti-amyloid vaccines) are already under clinical trials. New drug discovery approaches based on “designed multiple ligands”, “hybrid molecules”, or “multitarget-directed ligands” are also being put forward and may contribute to tackling this highly debilitating and fatal form of human dementia.
- A New Folding Kinetic Mechanism for Human Transthyretin and the Influence of the Amyloidogenic V30M MutationPublication . Jesus, Catarina S. H.; Almeida, Zaida L.; Vaz, Daniela C.; Faria, Tiago Q.; Brito, Rui M. M.Protein aggregation into insoluble amyloid fibrils is the hallmark of several neurodegenerative diseases, chief among them Alzheimer’s and Parkinson’s. Although caused by different proteins, these pathologies share some basic molecular mechanisms with familial amyloidotic polyneuropathy (FAP), a rare hereditary neuropathy caused by amyloid formation and deposition by transthyretin (TTR) in the peripheral and autonomic nervous systems. Among the amyloidogenic TTR mutations known, V30M-TTR is the most common in FAP. TTR amyloidogenesis (ATTR) is triggered by tetramer dissociation, followed by partial unfolding and aggregation of the low conformational stability monomers formed. Thus, tetramer dissociation kinetics, monomer conformational stability and competition between refolding and aggregation pathways do play a critical role in ATTR. Here, we propose a new model to analyze the refolding kinetics of WT-TTR and V30M-TTR, showing that at pH and protein concentrations close to physiological, a two-step mechanism with a unimolecular first step followed by a second-order second step adjusts well to the experimental data. Interestingly, although sharing the same kinetic mechanism, V30M-TTR refolds at a much slower rate than WT-TTR, a feature that may favor the formation of transient species leading to kinetic partition into amyloidogenic pathways and, thus, significantly increasing the probability of amyloid formation in vivo.
- Oligomerization Profile of Human Transthyretin Variants with Distinct AmyloidogenicityPublication . Frangolho, Ana; Correia, Bruno E.; Vaz, Daniela C.; Almeida, Zaida L.; Brito, Rui M. M.One of the molecular hallmarks of amyloidoses is ordered protein aggregation involving the initial formation of soluble protein oligomers that eventually grow into insoluble fibrils. The identification and characterization of molecular species critical for amyloid fibril formation and disease development have been the focus of intense analysis in the literature. Here, using photo-induced cross-linking of unmodified proteins (PICUP), we studied the early stages of oligomerization of human transthyretin (TTR), a plasma protein involved in amyloid diseases (ATTR amyloidosis) with multiple clinical manifestations. Upon comparison, the oligomerization processes of wild-type TTR (TTRwt) and several TTR variants (TTRV30M, TTRL55P, and TTRT119M) clearly show distinct oligomerization kinetics for the amyloidogenic variants but a similar oligomerization mechanism. The oligomerization kinetics of the TTR amyloidogenic variants under analysis showed a good correlation with their amyloidogenic potential, with the most amyloidogenic variants aggregating faster (TTRL55P > TTRV30M > TTRwt). Moreover, the early stage oligomerization mechanism for these variants involves stepwise addition of monomeric units to the growing oligomer. A completely different behavior was observed for the nonamyloidogenic TTRT119M variant, which does not form oligomers in the same acidic conditions and even for longer incubation times. Thorough characterization of the initial steps of TTR oligomerization is critical for better understanding the origin of ATTR cytotoxicity and developing novel therapeutic strategies for the treatment of ATTR amyloidosis.
- Preserving and hydrogel-matrixing the bioactive properties of aromatic medicinal halophytic herbs from the coastline of the Iberian PeninsulaPublication . Parracho, Tiago; Cruz, Pedro F.; Peralta, Claúdia C.; Silva, Cândida G.; Campos, Maria Jorge; Neves, Marta; Cordeiro, Rachel; Trindade, Daniela; Moura, Carla; Almeida, Zaida L.; Pereira, Cidália D.; Guimarães, Carla; Brito, Rui M. M.; Guerra, Mauro; Reboredo, Fernando; Veríssimo, Paula; Vaz, Daniela C.; Santos Ribeiro, VâniaEdible wild plants are part of the ethnobotanic heritage of a certain geographical area and are important sources of essential oils, antioxidants, minerals, and special flavours. Corema album (Portuguese crowberry), Crithmum maritimum (sea fennel), Eryngium maritimum (sea holly), Helichrysum italicum (curry plant) and Otanthus maritimus (cottonweed) wildly flourish along the sandy dunes of the coast of the Iberian Peninsula. These plants are locally known for their beneficial properties, with important value for food, cosmetics and/or medicinal applications. Hence, leaves of these endemic species were collected at four different locations and submitted to different preserving treatments (oven-drying, freezing, and freeze-drying). Acetonic extracts of the different plants submitted to the different post-harvesting treatments were analysed regarding their antioxidant capacities and phenolic contents. Plant extracts were also analysed by diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY-NMR). In general, freeze-drying was the best method of preserving plant minerals, antioxidants (~4 mgVCEAC/g fw) and polyphenols (~5 mgGAE/g fw). Minerals were quantified via energy-dispersive X-ray fluorescence spectrometry, and despite their location, all plants were rich in Ca, Cl, K, S and P. Hierarchical clustering and principal component analyses (PCA) pointed towards chemical/metabolic proximity between taxonomic families. Alginate hydrogels loaded with 0.1 % and 0.2 % (w/v) of extracts presented homogenous surface properties by scanning electron microscopy, good mechanical tensile strength (~30 MPa) and antibacterial activity against S. aureus. Edible alginate hydrogels enriched with plant extracts hold great nutraceutical potential to be used as natural preservatives for food coating and packaging or as sources of bioactive compounds for biomedical applications.
- Retention of minerals, antioxidants, pigments, and glucosinolates by broccoli florets and green bean pods boiled in alkaline, neutral and acidic watersPublication . Ribeiro, Vânia S.; Cruz, Pedro F.; Almeida, Zaida L.; Silva, Cândida G.; Silva, Maria Isabel; Silva, Inês S.; Santos, Liliana R.; Santos, Marta T.; Guimarães, Carla; Brito, Rui M.M.; Guerra, Mauro; Reboredo, Fernando; Pereira, Cidália D.; Vaz, Daniela C.Given the poor palatability and chewability of crude green bean pods (Phaseolus vulgaris) and broccoli florets (Brassica oleracea var. italica Plenck) these vegetables are generally microwaved, steamed or water boiled. Hence, here, we evaluated the contents of minerals, antioxidants, phenolics, glucosinolates, pigments, colour, texture and flavour of water-boiling broccoli and green bean pods, with four mineral waters with variable composition and pH. Plant matrices were characterized by High Resolution Magic-Angle Spinning (HR-MAS) and plant extracts were analysed by pseudo-2D Diffusion-ordered nuclear magnetic resonance (NMR) spectroscopy. Mineral waters ranging from acidic to neutral and alkaline were used and the colour properties (lightness, greenness/yellowness, colour saturation and hue angles), minerals and bioactive contents retained by the vegetables were compared to microwaved and steamed material. Boiling bean pods for 5 min extracted more polyphenols and antioxidants, particularly with more acidic waters, than 5 min of microwaving or steaming. However, even if boiling broccoli with more acidic water could better preserve glucosinolates, the food material presented lower retention of pigments and poor palatability. Cooking with more alkaline water increased mineral retention and broccoli greenness, also leading to highest scores in “colour”, “texture”, and “flavour”. Hence, samples cooked in more alkaline water presented higher acceptability.
- Transthyretin mutagenesis: impact on amyloidogenesis and diseasePublication . Almeida, Zaida L.; Vaz, Daniela C.; Brito, Rui M. M.Transthyretin (TTR), a homotetrameric protein found in plasma, cerebrospinal fluid, and the eye, plays a pivotal role in the onset of several amyloid diseases with high morbidity and mortality. Protein aggregation and fibril formation by wild-type TTR and its natural more amyloidogenic variants are hallmarks of ATTRwt and ATTRv amyloidosis, respectively. The formation of soluble amyloid aggregates and the accumulation of insoluble amyloid fibrils and deposits in multiple tissues can lead to organ dysfunction and cell death. The most frequent manifestations of ATTR are polyneuropathies and cardiomyopathies. However, clinical manifestations such as carpal tunnel syndrome, leptomeningeal, and ocular amyloidosis, among several others may also occur. This review provides an up-to-date listing of all single amino-acid mutations in TTR known to date. Of approximately 220 single-point mutations, 93% are considered pathogenic. Aspartic acid is the residue mutated with the highest frequency, whereas tryptophan is highly conserved. “Hot spot” mutation regions are mainly assigned to β-strands B, C, and D. This manuscript also reviews the protein aggregation models that have been proposed for TTR amyloid fibril formation and the transient conformational states that convert native TTR into aggregation-prone molecular species. Finally, it compiles the various in vitro TTR aggregation protocols currently in use for research and drug development purposes. In short, this article reviews and discusses TTR mutagenesis and amyloidogenesis, and their implications in disease onset.