Structural and biochemical studies of the aggregation of the amyloid-β peptide (Aβ) are important to understand the mechanisms of Alzheimer's disease, but research is complicated by aggregate inhomogeneity and instability. We previously engineered a hairpin form of Aβ called Aβcc, which forms stable protofibrils that do not convert into amyloid fibrils. Here we provide a detailed characterization of Aβ42 cc protofibrils. Like wild type Aβ they appear as smooth rod-like particles with a diameter of 3.1 (±0.2) nm and typical lengths in the range 60 to 220 nm when observed by atomic force microscopy. Non-perturbing analytical ultracentrifugation and nanoparticle tracking analyses are consistent with such rod-like protofibrils. Aβ42 cc protofibrils bind the ANS dye indicating that they, like other toxic protein aggregates, expose hydrophobic surface. Assays with the OC/A11 pair of oligomer specific antibodies put Aβ42 cc protofibrils into the same class of species as fibrillar oligomers of wild type Aβ. Aβ42 cc protofibrils may be used to extract binding proteins in biological fluids and apolipoprotein E is readily detected as a binder in human serum. Finally, Aβ42 cc protofibrils act to attenuate spontaneous synaptic activity in mouse hippocampal neurons. The experiments indicate considerable structural and chemical similarities between protofibrils formed by Aβ42 cc and aggregates of wild type Aβ42. We suggest that Aβ42 cc protofibrils may be used in research and applications that require stable preparations of protofibrillar Aβ.

Alzheimer’s disease (AD) is pathologically defined by the presence of fibrillar amyloid β (Aβ) peptide in extracellular senile plaques and tau filaments in intracellular neurofibrillary tangles. Extensive research has focused on understanding the assembly mechanisms and neurotoxic effects of Aβ during the last decades but still we only have a brief understanding of the disease associated biological processes. This review highlights the many other constituents that, beside Aβ, are accumulated in the plaques, with the focus on extracellular proteins. All living organisms rely on a delicate network of protein functionality. Deposition of significant amounts of certain proteins in insoluble inclusions will unquestionably lead to disturbances in the network, which may contribute to AD and copathology. This paper provide a comprehensive overview of extracellular proteins that have been shown to interact with Aβ and a discussion of their potential roles in AD pathology. Methods that can expand the knowledge about how the proteins are incorporated in plaques are described. Top-down methods to analyze post-mortem tissue and bottom-up approaches with the potential to provide molecular insights on the organization of plaque-like particles are compared. Finally, a network analysis of Aβ-interacting partners with enriched functional and structural key words is presented.

The progressive neurodegeneration in Alzheimer's disease is believed to be linked to the presence of prefibrillar aggregates of the amyloid-β (Aβ) peptide in the brain. The exact role of these aggregates in the disease pathology is, however, still an open question. Any mechanism by which oligomeric Aβ may cause damage to neuronal cells must, in one way or another, involve interactions with other molecules. Here, we identify proteins in human serum and cerebrospinal fluid that bind to stable protofibrils formed by an engineered variant of Aβ42 (Aβ42CC). We find that the protofibrils attract a substantial number of protein binding partners. Many of the 101 identified proteins are involved in lipid transport and metabolism, the complement system, or in hemostasis. Binding of representative proteins from all of these groups with micromolar affinity was confirmed using surface plasmon resonance. In addition, binding of apolipoprotein E to the protofibrils with nanomolar affinity was demonstrated. We also find that aggregation of Aβ enhances protein binding, as lower amounts of proteins bind monomeric Aβ. Proteins that bind to Aβ protofibrils might contribute to biological effects in which these aggregates are involved. Our results therefore suggest that an improved understanding of the mechanisms by which Aβ causes cytotoxicity and neurodegeneration might be gained from studies carried out in biologically relevant matrices in which Aβ-binding proteins are present.

Aggregation and deposition of misfolded amyloid  (A) peptide in the brain is central to Alzheimer's disease (AD). Oligomeric, protofibrillar and fibrillar forms of A are believed to be neurotoxic and cause neurodegeneration in AD, but the toxicity mechanisms are not well understood and may involve A-interacting molecular partners. In a previous study, we identified potential A42 protofibrillar-binding proteins in serum and cerebrospinal fluid (CSF) using an engineered version of A42 (A42CC) that forms protofibrils, but not fibrils. Here we studied binding of proteins to A42 fibrils in AD and non-AD CSF and compared these with protofibrillar A42CC-binding partners. A42 fibrils sequestered 2.4-fold more proteins than A42CC protofibrils. Proteins with selective binding to fibrillar aggregates with low nanomolar affinity were identified. We also found that protofibrillar and fibrillar A-binding proteins represent distinct functional categories. A42CC protofibrils triggered interactions with proteins involved in catalytic activities, like transferases and oxidoreductases, whilst A42 fibrils were more likely involved in binding to proteoglycans, growth factors and neuron-associated proteins, e.g., neurexin-1, -2 and -3. Interestingly, 10 brain-enriched proteins were identified among the fibril-binding proteins, whilst protofibrilextracted proteins had more general expression patterns. Both types of A aggregates bound several extracellular proteins. Additionally, we list a set of CSF proteins that might have potential to discriminate between AD and non-AD CSF samples. The results may be of relevance both for biomarker studies and for studies of A-related toxicity mechanisms.

Protofibrils of the 42 amino acids long amyloid-β peptide are transient pre-fibrillar intermediates in the process of peptide aggregation into amyloid plaques and are thought to play a critical role in the pathology of Alzheimer’s disease. Hence, there is a need for research reagents and potential diagnostic reagents for detection and imaging of such aggregates. Here we describe an in vitro selection of Affibody molecules that bind to protofibrils of Aβ42cc, which is a stable engineered mimic of wild type Aβ42 protofibrils. Several binders were identified that bind Aβ42cc protofibrils with low nanomolar affinities, and which also recognize wild type Aβ42 protofibrils. Dimeric head-to-tail fusion proteins with subnanomolar binding affinities, and very slow dissociation off-rates, were also constructed. A mapping of the chemical properties of the side chains onto the Affibody scaffold surface reveals three distinct adjacent surface areas of positively charged surface, nonpolar surface and a polar surface, which presumably match a corresponding surface epitope on the protofibrils. The results demonstrate that the engineered Aβ42cc is a suitable antigen for directed evolution of affinity reagents with specificity for wild type Aβ42 protofibrils.

Delonix regia (Fabaceae) leaf is used in folk medicine of Bangladesh for the treatment of diabetes, but so far no scientific study has been done which may support its use in traditional medicine. The present study was carried out to evaluate the possible glucose tolerance efficacy of methanolic extract of Delonix regia leaf using glucose-induced hyperglycemic mice. The extract at different doses was administered one hr prior to glucose administration and blood glucose level was measured after two hrs of glucose administration (p.o.) using glucose oxidase method. The statistical data indicated significant oral hypoglycemic activity on glucose-loaded mice at every dose. Maximum anti-hyperglycemic activity was showed at 400 mg/kg which was comparable to that of a standard drug, glibenclamide (10 mg/kg). The methanolic extract of leaf of Delonix regia had beneficial effects in reducing the elevated blood glucose level of hyperglycemic mice.

The deposition of proteins in the form of amyloid fibrils is closely associated with several serious diseases. The events that trigger the conversion from soluble functional proteins into insoluble amyloid are not fully understood. Many proteins that are not associated with disease can form amyloid with similar structural characteristics as the disease-associated fibrils, which highlights the potential risk of cross-seeding of disease amyloid by amyloid-like structures encountered in our surrounding. Of particular interest are common food proteins that can be transformed into amyloid under conditions similar to cooking. We here investigate cross-seeding of amyloid-β (Aβ), a peptide known to form amyloid during the development of Alzheimer’s disease, by 16 types of amyloid fibrils derived from food proteins or peptides. Kinetic studies using thioflavin T fluorescence as output show that none of the investigated protein fibrils accelerates the aggregation of Aβ. In at least two cases (hen egg lysozyme and oat protein isolate) we observe retardation of the aggregation, which appears to originate from interactions between the food protein seeds and Aβ in aggregated form. The results support the view that food-derived amyloid is not a risk factor for development of Aβ pathology and Alzheimer’s disease.

Abstract:Aim: Oral health problem is one of the major health problems during pregnancy in both developing and developed countries. This cross-sectional study was carried out to assess the oral health status of the pregnant women attended some selected mothers and children welfare centers (MCWCs) in Bangladesh. Methods: Data was collected by face-to-face interview and clinical examination with the help of a structured questionnaire and check list. Results: Half (50.0%) of the pregnant women was of 15 to 20 years old and their mean age was 22.28±4.22 years. Thirty eight percent (38.2%) of the women had primary education and 78.4% did not visit any dentist. Majority (93.1%) used tooth brush before breakfast and most (84.4%) of them had no information about oral hygiene care. Regarding oral health status, 87.3% had caries affected teeth and 94.1% had gingivitis. Presence of gingivitis and calculus were higher among the elder women (21-35 years) than the younger group (15-20 years) which was 92.2% among the housewives. Gingivitis was significantly higher among the women in low income group (95.7%) than the other income groups (X 2 = 5.80, p<0.05). Conclusion:The study findings recommended for provision of essential dental health services to the pregnant women for prevention and control of various dental health problems during pregnancy.