The potential of lumbrokinase and serratiopeptidase for the degradation of Aβ 1-42 peptide - an in vitro and in silico approach

BACKGROUND

Alzheimer's disease (AD) is diagnosed with the deposition of insoluble β-amyloid (Aβ) peptides in the neuropil of the brain leading to dementia. The extracellular deposition of the fibrillar Aβ peptide on the neurons is known as senile plaques. Therefore, Aβ degradation and clearance from the human body is a promising therapeutic approach in the medication of AD.

METHODS

In the current study, the enzyme lumbrokinase (LK) was extracted and purified from earthworm and its activity was utilized toward Aβ 1-42 amyloids degradation in vitro alongside with an additional enzyme serratiopeptidase (SP) considering nattokinase (NK) as a standard.

RESULTS

The output of this study revealed that preformed Aβ 1-42 amyloids was disintegrated by both LK and SP, as demonstrated from fluorescence assay using Thioflavin T dye. In addition, dynamic light scattering study revealed the lower size of the preformed fibrils Aβ 1-42 at various time intervals after incubation with the enzymes LK and SP. Furthermore, in silico approach showed high affinity thermodynamically favorable interaction of LK as well as SP toward Aβ 1-42 amyloid. Finally, the toxicity of degraded preformed Aβ 1-42 amyloid was assessed by MTT assay which showed reduced toxicity of enzyme treated Aβ 1-42 amyloid compared to only Aβ 1-42 amyloid.

CONCLUSION

The findings of the present study indicated that LK and SP, not only had Aβ 1-42 amyloid degrading potential, but also could reduce the toxicity which can make them a suitable drug candidate for AD. Furthermore, the in vivo studies are needed to be executed in future.

Effect of total flavonoids of Dracocephalum moldavica L. On neuroinflammation in Alzheimer's disease model amyloid-β (Aβ1-42)-peptide-induced astrocyte activation

One of the main pathological features noted in Alzheimer's disease (AD) is the presence of plagues of aggregated β-amyloid (Aβ1-42)-peptides. Excess deposition of amyloid-β oligomers (AβO) are known to promote neuroinflammation. Sequentially, following neuroinflammation astrocytes become activated with cellular characteristics to initiate activated astrocytes. The purpose of this study was to determine whether total flavonoids derived from Dracocephalum moldavica L. (TFDM) inhibited Aβ1-42-induced damage attributed to activated C8-D1A astrocytes. Western blotting and ELISA were used to determine the expression of glial fibrillary acidic protein (GFAP), and complement C3 to establish the activation status of astrocytes following induction from exposure to Aβ1-42. Data demonstrated that stimulation of C8-D1A astrocytes by treatment with 40 μM Aβ1-42 for 24 hr produced significant elevation in protein expression and protein levels of acidic protein (GFAP) and complement C3 accompanied by increased expression and levels of inflammatory cytokines. Treatment with TFDM or the clinically employed drug donepezil in AD therapy reduced production of inflammatory cytokines, and toxicity initiated following activation of C8-D1A astrocytes following exposure to Aβ1-42. Therefore, TFDM similar to donepezil inhibited inflammatory secretion in reactive astrocytes, suggesting that TFDM may be considered as a potential compound to be utilized in AD therapy.

Alternative Renin-Angiotensin System

The renin-angiotensin system is the most important peptide hormone system in the regulation of cardiovascular homeostasis. Its classical arm consists of the enzymes, renin, and angiotensin-converting enzyme, generating angiotensin II from angiotensinogen, which activates its AT1 receptor, thereby increasing blood pressure, retaining salt and water, and inducing cardiovascular hypertrophy and fibrosis. However, angiotensin II can also activate a second receptor, the AT2 receptor. Moreover, the removal of the C-terminal phenylalanine from angiotensin II by ACE2 (angiotensin-converting enzyme 2) yields angiotensin-(1-7), and this peptide interacts with its receptor Mas. When the aminoterminal Asp of angiotensin-(1-7) is decarboxylated, alamandine is generated, which activates the Mas-related G-protein-coupled receptor D, MrgD (Mas-related G-protein-coupled receptor type D). Since Mas, MrgD, and the AT2 receptor have opposing effects to the classical AT1 receptor, they and the enzymes and peptides activating them are called the alternative or protective arm of the renin-angiotensin system. This review will cover the historical aspects and the current standing of this recent addition to the biology of the renin-angiotensin system.

Identification of Factor XIII β-Sandwich Residues Mediating Glutamine Substrate Binding and Activation Peptide Cleavage

BACKGROUND

 Factor XIII (FXIII) forms covalent crosslinks across plasma and cellular substrates and has roles in hemostasis, wound healing, and bone metabolism. FXIII activity is implicated in venous thromboembolism (VTE) and is a target for developing pharmaceuticals, which requires understanding FXIII - substrate interactions. Previous studies proposed the β-sandwich domain of the FXIII A subunit (FXIII-A) exhibits substrate recognition sites.

MATERIAL AND METHODS

 Recombinant FXIII-A proteins (WT, K156E, F157L, R158Q/E, R171Q, and R174E) were generated to identify FXIII-A residues mediating substrate recognition. Proteolytic (FXIII-A*) and non-proteolytic (FXIII-A°) forms were analyzed for activation and crosslinking activities toward physiological substrates using SDS-PAGE and MALDI-TOF MS.

RESULTS

 All FXIII-A* variants displayed reduced crosslinking abilities compared to WT for Fbg αC (233 - 425), fibrin, and actin. FXIII-A* WT activity was greater than A°, suggesting the binding site is more exposed in FXIII-A*. With Fbg αC (233 - 425), FXIII-A* variants R158Q/E, R171Q, and R174E exhibited decreased activities approaching those of FXIII-A°. However, with a peptide substrate, FXIII-A* WT and variants showed similar crosslinking suggesting the recognition site is distant from the catalytic site. Surprisingly, FXIII-A R158E and R171Q displayed slower thrombin activation than WT, potentially due to loss of crucial H-bonding with neighboring activation peptide (AP) residues.

CONCLUSION

 In conclusion, FXIII-A residues K156, F157, R158, R171, and R174 are part of a binding site for physiological substrates [fibrin (α and γ) and actin]. Moreover, R158 and R171 control AP cleavage during thrombin activation. These investigations provide new molecular details on FXIII - substrate interactions that control crosslinking abilities.

Pretreatment with Liposome-Encapsulated Shrimp Shell Extract Attenuated Neuronal Damage and Death in Aβ1-42-Induced Memory Deficits in Rats

The accumulation of amyloid-beta (Aβ) peptides is a crucial factor in the neuronal degeneration of Alzheimer's disease (AD). The current study investigated the underlying neuroprotective mechanisms of shrimp shell extract (SSE) and liposome-encapsulated SSE (SSE/L) against Aβ1-42-induced neuronal damage and death in rats. Intracerebroventricular infusion of Aβ1-42 effectively induced memory decline, as observed in a reduction of the rat's discriminating ability in the novel object recognition and novel object location tasks. Oral pretreatment with 100 mg/kg of SSE demonstrated no preventive effect on the memory decline induced by Aβ1-42 infusion. However, treatment with SSE/L 100 mg/kg BW effectively attenuated memory deficits in both behavioral assessments following two and four weeks after Aβ1-42 infusion. Moreover, SSE/L exerted neuroprotective effects by reducing lipid peroxidation and increasing Nrf2/HO-1 expression. There was a significant decrease in Iba1 and GFAP (biomarkers of microglia and astrocyte activity, respectively), as well as a decrease in the levels of NF-κB expression and the inflammatory cytokines TNF-α and IL-6 in the cortical and hippocampal tissues. Treatment with SSE/L also reduced the pro-apoptotic proteins Bax and cleaved caspase-3 while raising the anti-apoptotic protein Bcl2. In addition, the beneficial effects of SSE/L were along with the effects of a positive control commercial astaxanthin (AST). The findings of this study indicated that SSE/L provided neuroprotective effects on Aβ1-42-induced AD rats by ameliorating oxidative stress, neuroinflammation and apoptotic cell death. Therefore, SSE/L might be employed to prevent and mitigate Aβ accumulation-induced neurotoxicity in AD.

Novel photocatalytic carbon dots: efficiently inhibiting amyloid aggregation and quickly disaggregating amyloid aggregates

Amyloid aggregation is implicated in the pathogenesis of various neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD). It is critical to develop high-performance drugs to combat amyloid-related diseases. Most identified nanomaterials exhibit limited biocompatibility and therapeutic efficacy. In this work, we used a solvent-free carbonization process to prepare new photo-responsive carbon nanodots (CNDs). The surface of the CNDs is densely packed with chemical groups. CNDs with large, conjugated domains can interact with proteins through π-π stacking and hydrophobic interactions. Furthermore, CNDs possess the ability to generate singlet oxygen species (1O2) and can be used to oxidize amyloid. The hydrophobic interaction and photo-oxidation can both influence amyloid aggregation and disaggregation. Thioflavin T (ThT) fluorescence analysis and circular dichroism (CD) spectroscopy indicate that CNDs can block the transition of amyloid from an α-helix structure to a β-sheet structure. CNDs demonstrate efficacy in alleviating cytotoxicity induced by Aβ42 and exhibit promising blood-brain barrier (BBB) permeability. CNDs have small size, low biotoxicity, good fluorescence and photocatalytic properties, and provide new ideas for the diagnosis and treatment of amyloid-related diseases.

[Age-dependent expression of HSP90 in the hippocampus of APP/PS1 mice]

The present study aims to observe the change in expression of heat shock protein 90 (HSP90) along with amyloid-β (Aβ) and phosphorylated Tau (p-Tau) protein levels in the hippocampus tissue of Alzheimer's disease (AD) transgenic animal model with age. APP/PS1 transgenic mice at age of 6-, 9- and 12-month and C57BL/6J mice of the same age were used. The cognitive abilities of these animals were evaluated using a Morris water maze. Western blot or immunohistochemistry was used to detect the expressions of HSP90 and Aβ1-42, as well as the phosphorylation levels of Tau protein in the hippocampus. The hsp90 mRNA levels and the morphology and number of cells in the hippocampus were detected with real-time quantitative polymerase chain reaction (qRT-PCR) and Nissl staining, respectively. The results showed that compared with C57BL/6J mice of the same age, HSP90 and hsp90 mRNA expression were decreased (P < 0.05 or P < 0.01), while Aβ1-42 and p-Tau protein levels were increased (P < 0.05 or P < 0.01) in the hippocampal tissue of APP/PS1 transgenic mice. Meanwhile, the decrease in HSP90 and hsp90 mRNA expression (P < 0.05 or P < 0.01), the increase in Aβ1-42 and p-Tau levels (P < 0.01 or P < 0.05) in hippocampal tissue and the reduction in behavioral ability showed a progressive development with the advancing of age in the APP/PS1 transgenic mice. In conclusion, in the hippocampal tissue of APP/PS1 mice, the decrease in HSP90 expression and the increase in Aβ1-42 and p-Tau levels together with the decline of their cognitive ability are age-dependent.

Deciphering S100B Allosteric Signaling: The Role of a Peptide Target, TRTK-12, as an Ensemble Modulator

Allostery is an essential biological phenomenon in which perturbation at one site in a biomolecule elicits a functional response at a distal location(s). It is integral to biological processes, such as cellular signaling, metabolism, and transcription regulation. Understanding allostery is also crucial for rational drug discovery. In this work, we focus on an allosteric S100B protein that belongs to the S100 class of EF-hand Ca2+-binding proteins. The Ca2+-binding affinity of S100B is modulated allosterically by TRTK-12 peptide binding 25 Å away from the Ca2+-binding site. We investigated S100B allostery by carrying out nuclear magnetic resonance (NMR) measurements along with microsecond-long molecular dynamics (MD) simulations on S100B/Ca2+ with/without TRTK-12 at different NaCl salt concentrations. NMR HSQC results show that TRTK-12 reorganizes how S100B/Ca2+ responds to different salt concentrations at both orthosteric and allosteric sites. The MD data suggest that TRTK-12 breaks the dynamic aromatic and hydrogen-bond interactions (not observed in X-ray crystallographic structures) between the hinge/helix and Ca2+-binding EF-hand loop of the two subunits in the homodimeric protein. This triggers rearrangement in the protein network architectures and leads to allosteric communication. Finally, computational studies of S100B at distinct ionic strengths suggest that ligand-bound species are more robust to the changing environment relative to the S100B/Ca2+ complex.

Improving Anti-HIV activity and pharmacokinetics of enfuvirtide (T20) by modification with oligomannose

Dendritic cells (DCs) play a pivotal role in controlling HIV-1 infections of CD4+ T cells. DC-SIGN, which is expressed on the surface of DCs, efficiently captures HIV-1 virions by binding to the highly mannosylated membrane protein, gp120, and then the DCs transport the virus to target T cells in lymphoid organs. This study explored the modification of T20, a peptide inhibitor of HIV-1 fusion, by conjugation of the N-terminus with varying sizes of oligomannose, which are DC-SIGN-specific carbohydrates, aiming to create dual-targeting HIV inhibitors. Mechanistic studies indicated the dual-target binding of the conjugates. Antiviral assays demonstrated that N-terminal mannosylation of T20 resulted in increased inhibition of the viral infection of TZM-b1 cells (EC50 = 0.3-0.8 vs. 1.4 nM). Pentamannosylated T20 (M5-T20) exhibited a stronger inhibitory effect on virus entry into DC-SIGN+ 293T cells compared with T20 (67% vs. 50% inhibition at 500 μM). M5-T20 displayed an extended half-life in rats relative to T20 (T1/2: 8.56 vs. 1.64 h, respectively). These conjugates represent a potential new treatment for HIV infections with improved antiviral activity and pharmacokinetics, and this strategy may prove useful in developing dual-target inhibitors for other pathogens that require DC-SIGN involvement for infection.

Futoquinol improves Aβ25-35-induced memory impairment in mice by inhibiting the activation of p38MAPK through the glycolysis pathway and regulating the composition of the gut microbiota

Futoquinol (Fut) is a compound extracted from Piper kadsura that has a nerve cell protection effect. However, it is unclear whether Fut has protective effects in Alzheimer's disease (AD). In this study, we aimed to explore the therapeutic effect of Fut in AD and its underlying mechanism. UPLC-MS/MS method was performed to quantify Fut in the hippocampus of mice brain. The cognition ability, neuronal and mitochondria damage, and levels of Aβ1-42, Aβ1-40, p-Tau, oxidative stress, apoptosis, immune cells, and inflammatory factors were measured in Aβ25-35-induced mice. The content of bacterial meta-geometry was predicted in the microbial composition based on 16S rDNA. The protein levels of HK II, p-p38MAPK, and p38MAPK were detected. PC-12 cells were cultured in vitro, and glucose was added to activate glycolysis to further explore the mechanism of action of Fut intervention in AD. Fut improved the memory and learning ability of Aβ25-35 mice, and reduced neuronal damage and the deposition of Aβ and Tau proteins. Moreover, Fut reduced mitochondrial damage, the levels of oxidative stress, apoptosis, and inflammatory factors. Fut significantly inhibited the expression of HK II and p-p38MAPK proteins. The in vitro experiment showed that p38MAPK was activated and Fut action inhibited after adding 10 mM glucose. Fut might inhibit the activation of p38MAPK through the glycolysis pathway, thereby reducing oxidative stress, apoptosis, and inflammatory factors and improving Aβ25-35-induced memory impairment in mice. These data provide pharmacological rationale for Fut in the treatment of AD.

Molecular recognition and binding between human plasminogen Kringle 5 and α-chain of human complement component C3b by frontal chromatography and dynamics simulation

The binding and molecular recognition between α-chain of human complement C3b (α-chain of C3b) and human plasminogen Kringle 5 (Kringle 5) were studied and explored by frontal chromatography and dynamics simulation in the combination of bio-specific technologies. The specific interaction between the α-chain of C3b and Kringle 5 was initially confirmed by ligand blot and ELISA (Kd = 4.243×10-6 L/mol). Furthermore, the binding determination conducted via frontal chromatography showed that the presence of a single binding site between them, with the binding constant of 2.98 × 105 L/mol. Then the molecular recognition by dynamics simulation and molecular docking showed that there were 9 and 13 amino acid residues respective in the Kringle 5 and α-chain of C3b directly implicated in the binding and the main stabilizing forces were electrostatic force (-55.99 ± 11.82 kcal/mol) and Van der Waals forces (-42.70 ± 3.45 kcal/mol). Additionally, a loop structure (65-71) in Kringle 5 underwent a conformational change from a random structure to an α-helix and a loop structure (417-425) in α-chain of C3b was closer to the molecular center, both of them were more conducive to the binding between them. Meanwhile, the involvement of the lysine binding site of Kringle 5 played an important role in the binding process. In addition, the erythrocyte-antibody complement rosette assay substantiated that the presence of Kringle 5 hindered the transportation of α-chain of C3b to antigen-antibody complex in a dose-dependent manner. These findings collectively indicated that the α-chain of C3b is very likely a receptor protein for Kringle 5, which provides a methodology for other similar investigations and valuable insights into expansion of the pharmacological effects and potential application of Kringle 5 in immune-related diseases.

Blockage of metallothionein synthesis via adrenaline β receptor activation invalidates dehydroeffusol-mediated prevention of amyloid β1-42 toxicity

Dehydroeffusol, a major phenanthrene in Juncus effusus, protects neurodegeneration induced by intracellular Zn2+ ferried by extracellular amyloid β1-42 (Aβ1-42). Here we focused on adrenaline β receptor activation and the induction of metallothioneins (MTs), intracellular Zn2+-binding proteins to test the protective mechanism of dehydroeffusol. Isoproterenol, an agonist of adrenergic β receptors elevated the level of MTs in the dentate granule cell layer 1 day after intracerebroventricular (ICV) injection. When Aβ1-42 was injected 1 day after isoproterenol injection, pre-injection of isoproterenol protected Aβ1-42 toxicity via reducing the increase in intracellular Zn2+ after ICV injection of Aβ1-42. On the basis of the effect of increased MTs by isoproterenol, dehydroeffusol (15 mg/kg body weight) was orally administered to mice once a day for 2 days. On day later, dehydroeffusol elevated the level of MTs and prevented Aβ1-42 toxicity via reducing Aβ1-42-mediated increase in intracellular Zn2+. In contrast, propranolol, an antagonist of adrenergic β receptors reduced the level of MTs increased by dehydroeffusol, resulting in invalidating the preventive effect of dehydroeffusol on Aβ1-42 toxicity. The present study indicates that blockage of MT synthesis via adrenaline β receptor activation invalidates dehydroeffusol-mediated prevention of Aβ1-42 toxicity. It is likely that MT synthesis via adrenaline β receptor activation is beneficial to neuroprotection and that oral intake of dehydroeffusol preventively serves against the Aβ1-42 toxicity.

Edge Substitution Effects of Histidine Tautomerization Behaviors on the Structural Properties and Aggregation Properties of Aβ(1-42) Mature Fibril

Histidine behaviors play critical roles in folding and misfolding processes due to the changes in net charge and the various N/N-H orientations on imidazole rings. However, the effect of histidine tautomerization (HIE (Nε-H, ε) and HID (Nδ-H, δ) states) behaviors on the edge chain of Aβ mature fibrils remains inadequately understood, which is critical for finding a strategy to disturb fibril elongation and growth. In the current study, eight independent molecular dynamics simulations were conducted to investigate such impacts on the structural and aggregation properties. Our results from three different binding models revealed that the binding contributions of edge substitution effects are primarily located between chains 1 and 2. Histidine states significantly influence the secondary structure of each domain. Further analysis confirmed that the C1_H6//C1_E11 intrachain interaction is essential in maintaining the internal stability of chain 1, while the C1_H13//C2_H13 and C1_H14//C2_H13 interchain interactions are critical in maintaining the interchain stability of the fibril structure. Our subsequent analysis revealed that the current edge substitution leads to the loss of the C1_H13//C1_E11 intrachain and C1_H13//C2_H14 interchain interactions. The N-terminal regularity was significantly directly influenced by histidine states, particularly by the residue of C1_H13. Our study provides valuable insights into the effect of histidine behaviors on the edge chain of Aβ mature fibril, advancing our understanding of the histidine behavior hypothesis in misfolding diseases.

Extracellular Vesicles Slow Down Aβ(1-42) Aggregation by Interfering with the Amyloid Fibril Elongation Step

Formation of amyloid-β (Aβ) fibrils is a central pathogenic feature of Alzheimer's disease. Cell-secreted extracellular vesicles (EVs) have been suggested as disease modulators, although their exact roles and relations to Aβ pathology remain unclear. We combined kinetics assays and biophysical analyses to explore how small (<220 nm) EVs from neuronal and non-neuronal human cell lines affected the aggregation of the disease-associated Aβ variant Aβ(1-42) into amyloid fibrils. Using thioflavin-T monitored kinetics and seeding assays, we found that EVs reduced Aβ(1-42) aggregation by inhibiting fibril elongation. Morphological analyses revealed this to result in the formation of short fibril fragments with increased thicknesses and less apparent twists. We suggest that EVs may have protective roles by reducing Aβ(1-42) amyloid loads, but also note that the formation of small amyloid fragments could be problematic from a neurotoxicity perspective. EVs may therefore have double-edged roles in the regulation of Aβ pathology in Alzheimer's disease.

Investigating the functionalization of liposomes with NFL-TBS. 40-63 peptide as a promising drug delivery system

The NFL-peptide was discovered almost 20 years ago, and its targeting properties were assessed alone or in combination with lipid nanocapsules (LNC), magnetic porous silicon nanorods, or gold nanoparticles. Results highlighted a better targeting of cancer cells, in particular glioblastoma and pancreas cancer. Considering the large use of liposomes (LPs) as an hydrophilic drug delivery system, this study explored the possibility to functionalize liposomes with three different sequences of NFL-peptides: native (NFL-peptide), biotinylated (BIOT-NFL) and coupled to fluorescein (FAM-NFL). Dynamic Light Scattering (DLS) complemented by cryo-electron microscopy (CEM) showed a peculiar ultrastructural arrangement between NFL-peptides and liposomes. Based on this architectural interaction, we investigated the biological contribution of these peptides in LPs-DiD glioblastoma cellular uptake. Flow cytometry complemented by confocal microscopy experiments demonstrated a consequent and systematic increased uptake of LPs-DiD into F98 cells when their surface was decorated with NFL-peptides. The intra-cellular distribution of these liposomes via an organelle tracker indicated the presence of LPs-DiD in lysosomes after 4 h. Based on the properties of this NFL-peptide, we showed in this work the crucial role of NFL peptide as an effective and promising actor to potentiate nanoparticles entry in glioblastoma cell lines.

Impact of nanoplastics on Alzheimer 's disease: Enhanced amyloid-β peptide aggregation and augmented neurotoxicity

Nanoplastics, widely existing in the environment and organisms, have been proven to cross the blood-brain barrier, increasing the incidence of neurodegenerative diseases like Alzheimer's disease (AD). However, current studies mainly focus on the neurotoxicity of nanoplastics themselves, neglecting their synergistic effects with other biomolecules and the resulting neurotoxicity. Amyloid β peptide (Aβ), which triggers neurotoxicity through its self-aggregation, is the paramount pathogenic protein in AD. Here, employing polystyrene nanoparticles (PS) as a model for nanoplastics, we reveal that 100 pM PS nanoparticles significantly accelerate the nucleation rate of two Aβ subtypes (Aβ40 and Aβ42) at low concentrations, promoting the formation of more Aβ oligomers and leading to evident neurotoxicity. The hydrophobic surface of PS facilitates the interaction of hydrophobic fragments between Aβ monomers, responsible for the augmented neurotoxicity. This work provides consequential insights into the modulatory impact of low-dose PS on Aβ aggregation and the ensuing neurotoxicity, presenting a valuable foundation for future research on the intricate interplay between environmental toxins and brain diseases.

Luteoloside inhibits Aβ1-42 fibrillogenesis, disintegrates preformed fibrils, and alleviates amyloid-induced cytotoxicity

Abnormal aggregation and fibrillogenesis of amyloid-β protein (Aβ) can cause Alzheimer's disease (AD). Thus, the discovery of effective drugs that inhibit Aβ fibrillogenesis in the brain is crucial for the treatment of AD. Luteoloside, as one of the polyphenolic compounds, is found to have a certain therapeutic effect on nervous system diseases. However, it remains unknown whether luteoloside is a potential drug for treating AD by modulating Aβ aggregation pathway. In this study, we performed diverse biophysical and biochemical methods to explore the inhibition of luteoloside on Aβ1-42 which is linked to AD. The results demonstrated that luteoloside efficiently prevented amyloid oligomerization and cross-β-sheet formation, reduced the rate of amyloid growth and the length of amyloid fibrils in a dose-dependent manner. Moreover, luteoloside was able to influence aggregation and conformation of Aβ1-42 during different fiber-forming phases, and it could disintegrate already preformed fibrils of Aβ1-42 and convert them into nontoxic aggregates. Furthermore, luteoloside protected cells from amyloid-induced cytotoxicity and hemolysis, and attenuated the level of reactive oxygen species (ROS). The molecular docking study showed that luteoloside interacted with Aβ1-42 mainly via Conventional Hydrogen Bond, Carbon Hydrogen Bond, Pi-Pi T-shaped, Pi-Alkyl and Pi-Anion, thereby possibly preventing it from forming the aggregates. These observations indicate that luteoloside, a natural anti-oxidant molecule, may be applicable as an effective inhibitor of Aβ, and promote further exploration of the therapeutic strategy against AD.

Signaling pathways and genetics of brain Renin angiotensin system in psychiatric disorders: State of the art

Along the conventional pathways, Renin-angiotensin system (RAS) plays a key role in the physiology of the CNS and pathogenesis of psychiatric diseases. RAS is a complex regulatory pathway which is composed of several peptides and receptors and comprises two counter-regulatory axes. The classical (ACE1/AngII/AT1 receptor) axis and the contemporary (ACE2/Ang (1-7)/Mas receptor) axis. The genes coding for elements of both axes have been broadly studied. Numerous functional polymorphisms on components of RAS have been identified to serve as informative disease and treatment markers. This review summarizes the role of each peptide and receptor in the pathophysiology of psychiatric disorders (depression, bipolar disorders and schizophrenia), followed by a concise look at the role of genetic polymorphism of the RAS in the pathophysiology of these disorders.

RNA and the RNA-binding protein FUS act in concert to prevent TDP-43 spatial segregation

FUS and TDP-43 are two self-adhesive aggregation-prone mRNA-binding proteins whose pathological mutations have been linked to neurodegeneration. While TDP-43 and FUS form reversible mRNA-rich compartments in the nucleus, pathological mutations promote their respective cytoplasmic aggregation in neurons with no apparent link between the two proteins except their intertwined function in mRNA processing. By combining analyses in cellular context and at high resolution in vitro, we unraveled that TDP-43 is specifically recruited in FUS assemblies to form TDP-43-rich subcompartments but without reciprocity. The presence of mRNA provides an additional scaffold to promote the mixing between TDP-43 and FUS. Accordingly, we also found that the pathological truncated form of TDP-43, TDP-25, which has an impaired RNA-binding ability, no longer mixes with FUS. Together, these results suggest that the binding of FUS along nascent mRNAs enables TDP-43, which is highly aggregation-prone, to mix with FUS phase to form mRNA-rich subcompartments. A functional link between FUS and TDP-43 may explain their common implication in amyotrophic lateral sclerosis.

Regulation of the apico-basolateral trafficking polarity of the homologous copper-ATPases ATP7A and ATP7B

The homologous P-type copper-ATPases (Cu-ATPases) ATP7A and ATP7B are the key regulators of copper homeostasis in mammalian cells. In polarized epithelia, upon copper treatment, ATP7A and ATP7B traffic from the trans-Golgi network (TGN) to basolateral and apical membranes, respectively. We characterized the sorting pathways of Cu-ATPases between TGN and the plasma membrane and identified the machinery involved. ATP7A and ATP7B reside on distinct domains of TGN in limiting copper conditions, and in high copper, ATP7A traffics to basolateral membrane, whereas ATP7B traverses common recycling, apical sorting and apical recycling endosomes en route to apical membrane. Mass spectrometry identified regulatory partners of ATP7A and ATP7B that include the adaptor protein-1 complex. Upon knocking out pan-AP-1, sorting of both Cu-ATPases is disrupted. ATP7A loses its trafficking polarity and localizes on both apical and basolateral surfaces in high copper. By contrast, ATP7B loses TGN retention but retained its trafficking polarity to the apical domain, which became copper independent. Using isoform-specific knockouts, we found that the AP-1A complex provides directionality and TGN retention for both Cu-ATPases, whereas the AP-1B complex governs copper-independent trafficking of ATP7B solely. Trafficking phenotypes of Wilson disease-causing ATP7B mutants that disrupts putative ATP7B-AP1 interaction further substantiates the role of AP-1 in apical sorting of ATP7B.

Chicken Muscle-Derived ACE2-Upregulating Peptide VVHPKESF Reduces Blood Pressure Associated with the ACE2/Ang (1-7)/MasR Axis in Spontaneously Hypertensive Rats

SCOPE

This study aims to investigate the antihypertensive effect of four chicken muscle-derived angiotensin (Ang)-converting enzymes (ACE)-regulating peptides: Val-Arg-Pro (VRP, ACE inhibition), Leu-Lys-Tyr and Val-Arg-Tyr (LKY and VRY, ACE inhibition and ACE2 upregulation), and Val-Val-His-Pro-Lys-Glu-Ser-Phe (VVHPKESF [V-F], ACE2 upregulation) in spontaneously hypertensive rats.

METHODS AND RESULTS

Rats (12-14 weeks old) are grouped: 1) untreated, 2) VRP, 3) LKY, 4) VRY, and 5) V-F. Blood pressure (BP) is monitored using implantable telemetry technology. Over 18-day oral administration of 15 mg kg-1 body weight (BW) per day, only peptide V-F significantly (p < 0.05) reduces BP, decreases circulating Ang II, and increases ACE2 and Ang (1-7) levels, and enhances aortic expressions of ACE2 and Mas receptor (MasR). Peptide V-F also attenuates vascular inflammation (TNFα, MCP-1, IL-1α, IL-15, and cyclooxygenase 2 [COX2]) and vascular oxidative stress (nitrotyrosine). The gastrointestinal (GI)-degraded fragment of peptide V-F, Val-Val-His-Pro-Lys (VVHPK), is also an ACE2-upregulating peptide. Peptides VRP, LKY, and VRY do not reduce BP, possibly due to low bioavailability or other unknown reasons.

CONCLUSIONS

Peptide V-F is the first ACE2-upregulating peptide, purified and fractionated from food proteins based on in vitro ACE2 upregulation, that reduces BP associated with the activation of ACE2/Ang (1-7)/MasR axis; the N-terminal moiety VVHPK may be responsible for the antihypertensive effect of V-F.

Development of a Python-based electron ionization mass spectrometry amino acid and peptide fragment prediction model

The increased fragmentation caused by harsher ionization methods used during mass spectrometry such as electron ionization can make interpreting the mass spectra of peptides difficult. Therefore, the development of tools to aid in this spectral analysis is important in utilizing these harsher ionization methods to study peptides, as these tools may be more accessible to some researchers. We have compiled fragmentation mechanisms described in the literature, confirmed them experimentally, and used them to create a Python-based fragment prediction model for peptides analyzed under direct exposure probe electron ionization mass spectrometry. This initial model has been tested using single amino acids as well as targeted libraries of short peptides. It was found that the model does well in predicting fragments of peptides composed of amino acids for which the model is well-defined, but several cases where additional mechanistic information needs to be incorporated have been identified.

Cryo-EM structures of lipidic fibrils of amyloid-β (1-40)

Alzheimer's disease (AD) is a progressive and incurable neurodegenerative disease characterized by the extracellular deposition of amyloid plaques. Investigation into the composition of these plaques revealed a high amount of amyloid-β (Aβ) fibrils and a high concentration of lipids, suggesting that fibril-lipid interactions may also be relevant for the pathogenesis of AD. Therefore, we grew Aβ40 fibrils in the presence of lipid vesicles and determined their structure by cryo-electron microscopy (cryo-EM) to high resolution. The fold of the major polymorph is similar to the structure of brain-seeded fibrils reported previously. The majority of the lipids are bound to the fibrils, as we show by cryo-EM and NMR spectroscopy. This apparent lipid extraction from vesicles observed here in vitro provides structural insights into potentially disease-relevant fibril-lipid interactions.

The structure of tyrosine-10 favors ionic conductance of Alzheimer's disease-associated full-length amyloid-β channels

Amyloid β (Aβ) ion channels destabilize cellular ionic homeostasis, which contributes to neurotoxicity in Alzheimer's disease. The relative roles of various Aβ isoforms are poorly understood. We use bilayer electrophysiology, AFM imaging, circular dichroism, FTIR and fluorescence spectroscopy to characterize channel activities of four most prevalent Aβ peptides, Aβ1-42, Aβ1-40, and their pyroglutamylated forms (AβpE3-42, AβpE3-40) and correlate them with the peptides' structural features. Solvent-induced fluorescence splitting of tyrosine-10 is discovered and used to assess the sequestration from the solvent and membrane insertion. Aβ1-42 effectively embeds in lipid membranes, contains large fraction of β-sheet in a β-barrel-like structure, forms multi-subunit pores in membranes, and displays well-defined ion channel features. In contrast, the other peptides are partially solvent-exposed, contain minimal β-sheet structure, form less-ordered assemblies, and produce irregular ionic currents. These findings illuminate the structural basis of Aβ neurotoxicity through membrane permeabilization and may help develop therapies that target Aβ-membrane interactions.

Modulation of Aβ 16-22 aggregation by glucose

The self-assembly of amyloid-beta (Aβ) peptides into fibrillar structures in the brain is a signature of Alzheimer's disease. Recent studies have reported correlations between Alzheimer's disease and type-2 diabetes. Structurally, hyperglycemia induces covalent protein crosslinkings by advanced glycation end products (AGE), which can affect the stability of Aβ oligomers. In this work, we leverage physics-based coarse-grained molecular simulations to probe alternate thermodynamic pathways that affect peptide aggregation propensities at varying concentrations of glucose molecules. Similar to previous experimental reports, our simulations show a glucose concentration-dependent increase in Aβ aggregation rates, without changes in the overall secondary structure content. We discovered that glucose molecules prefer partitioning onto the aggregate-water interface at a specific orientation, resulting in a loss of molecular rotational entropy. This effectively hastens the aggregation rates, as peptide self-assembly can reduce the available surface area for peptide-glucose interactions. This work introduces a new thermodynamic-driven pathway, beyond chemical cross-linking, that can modulate Aβ aggregation.

Helical sulfonyl-γ-AApeptides modulating Aβ oligomerization and cytotoxicity by recognizing Aβ helix

In contrast to prevalent strategies which make use of β-sheet mimetics to block Aβ fibrillar growth, in this study, we designed a series of sulfonyl-γ-AApeptide helices that targeted the crucial α-helix domain of Aβ13-26 and stabilized Aβ conformation to avoid forming the neurotoxic Aβ oligomeric β-sheets. Biophysical assays such as amyloid kinetics and TEM demonstrated that the Aβ oligomerization and fibrillation could be greatly prevented and even reversed in the presence of sulfonyl-γ-AApeptides in a sequence-specific and dose-dependent manner. The studies based on circular dichroism, Two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) spectra unambiguously suggested that the sulfonyl-γ-AApeptide Ab-6 could bind to the central region of Aβ42 and induce α-helix conformation in Aβ. Additionally, Electrospray ionisation-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS) was employed to rule out a colloidal mechanism of inhibitor and clearly supported the capability of Ab-6 for inhibiting the formation of Aβ aggregated forms. Furthermore, Ab-6 could rescue neuroblastoma cells by eradicating Aβ-mediated cytotoxicity even in the presence of pre-formed Aβ aggregates. The confocal microscopy demonstrated that Ab-6 could still specifically bind Aβ42 and colocalize into mitochondria in the cellular environment, suggesting the rescue of cell viability might be due to the protection of mitochondrial function otherwise impaired by Aβ42 aggregation. Taken together, our studies indicated that sulfonyl-γ-AApeptides as helical peptidomimetics could direct Aβ into the off-pathway helical secondary structure, thereby preventing the formation of Aβ oligomerization, fibrillation and rescuing Aβ induced cell cytotoxicity.

Identification of potential aggregation hotspots on Aβ42 fibrils blocked by the anti-amyloid chaperone-like BRICHOS domain

Protein misfolding can generate toxic intermediates, which underlies several devastating diseases, such as Alzheimer's disease (AD). The surface of AD-associated amyloid-β peptide (Aβ) fibrils has been suggested to act as a catalyzer for self-replication and generation of potentially toxic species. Specifically tailored molecular chaperones, such as the BRICHOS protein domain, were shown to bind to amyloid fibrils and break this autocatalytic cycle. Here, we identify a site on the Aβ42 fibril surface, consisting of three C-terminal β-strands and particularly the solvent-exposed β-strand stretching from residues 26-28, which is efficiently sensed by a designed variant of Bri2 BRICHOS. Remarkably, while only a low amount of BRICHOS binds to Aβ42 fibrils, fibril-catalyzed nucleation processes are effectively prevented, suggesting that the identified site acts as a catalytic aggregation hotspot, which can specifically be blocked by BRICHOS. Hence, these findings provide an understanding how toxic nucleation events can be targeted by molecular chaperones.

ATP7A-dependent copper sequestration contributes to termination of β-CATENIN signaling during early adipogenesis

OBJECTIVES

Adipocyte fate determination is tightly regulated by extrinsic signaling pathways and intrinsic metabolic and morphologic changes that maintain adipose tissue function. Copper (Cu) homeostasis is required for the normal metabolism of mature adipocytes, whereas the role of Cu in adipogenesis is unclear.

METHODS

To determine the role of Cu is adipocytes differentiation, we used 3T3-L1 adipocytes, immunocytochemistry, X-ray fluorescence, mass-spectrometry, pharmacological treatments, and manipulations of copper levels.

RESULTS

In differentiating 3T3-L1 cells, adipogenic stimuli trigger the upregulation and trafficking of the Cu transporter Atp7a, thus causing Cu redistribution from the cytosol to vesicles. Disrupting Cu homeostasis by the deletion of Atp7a results in Cu elevation and inhibition of adipogenesis. The upregulation of C/EBPβ, an initial step of adipogenesis, is not affected in Atp7a-/- cells, whereas the subsequent upregulation of PPARγ is inhibited. Comparison of changes in the Atp7a-/- and wild type cells proteomes during early adipogenesis revealed stabilization of β-catenin, a negative regulator of adipogenesis. Cu chelation, or overexpression of the Cu transporter ATP7B in Atp7a-/- cells, restored β-catenin down-regulation and intracellular targeting.

CONCLUSIONS

Cu buffering during early adipogenesis contributes to termination of β-catenin signaling. Abnormal upregulation of β-catenin was also observed in vivo in the livers of Atp7b-/- mice, which accumulate Cu, suggesting a tissue-independent crosstalk between Cu homeostasis and the Wnt/β-catenin pathway. These results point to a new regulatory role of Cu in adipocytes and contribute to better understanding of human disorders of Cu misbalance.

Antihypertensive treatment of end-stage renal disease patients on hemodialysis does not alter circulating ACE and ACE2 activity and angiotensin peptides

Cardiovascular diseases (CVD) are the main causes of death in hemodialysis patients, representing a public health challenge. We investigated the effect of different antihypertensive treatments on circulating levels of renin-angiotensin system (RAS) components in end-stage renal disease (ESRD) patients on hemodialysis. ESRD patients were grouped following the prescribed antihypertensive drugs: ß-blocker, ß-blocker+ACEi and ß-blocker+AT1R blocker. ESDR patients under no antihypertensive drug treatment were used as controls. Blood samples were collected before hemodialysis sessions. Enzymatic activities of the angiotensin-converting enzymes ACE and ACE2 were measured through fluorescence assays and plasma concentrations of the peptides Angiotensin II (Ang II) and Angiotensin-(1-7) [Ang-(1-7)] were quantified using mass spectrometry (LC-MS/MS). ACE activity was decreased only in the ß-blocker+ACEi group compared to the ß-blocker+AT1R, while ACE2 activity did not change according to the antihypertensive treatment. Both Ang II and Ang-(1-7) levels also did not change according to the antihypertensive treatment. We concluded that the treatment of ESRD patients on hemodialysis with different antihypertensive drugs do not alter the circulating levels of RAS components.

CCR5 regulates Aβ1-42-induced learning and memory deficits in mice

C-C chemokine receptor 5 (CCR5) is a chemokine receptor involved in immune responses and a co-receptor for HIV infection. Recently, CCR5 has also been reported to play a role in synaptic plasticity, learning and memory, and cognitive deficits associated with normal aging, traumatic brain injury (TBI), and HIV-associated neurocognitive disorder (HAND). In contrast, the role of CCR5 in cognitive deficits associated with other disorders, including Alzheimer's disease (AD), is much less understood. Studies have reported an increase in expression of CCR5 or its ligands in both AD patients and AD rodent models, suggesting a correlation between AD and CCR5 expression. However, whether blocking CCR5 in specific brain regions, such as the hippocampus, could improve memory deficits in AD mouse models is unknown. To study the potential causal role of CCR5 in cognitive deficits in AD, we injected soluble Aβ1-42 or a control (Aβ42-1) oligomers in the dorsal CA1 region of the hippocampus and found that Aβ1-42 injection resulted in severe memory impairment in the object place recognition (OPR) and novel object recognition (NOR) tests. Aβ1-42 injection caused an increase in Ccr5, Ccl3, and Ccl4 in the dorsal hippocampus, and the expression levels of CCR5 and its ligands remained elevated at 2 weeks after Aβ1-42 injection. Knocking down Ccr5 in the CA1 region of dorsal hippocampus reversed the increase in microglia number and size in dorsal CA1 and rescued memory deficits. These results indicate that CCR5 plays an important role in modulating Aβ1-42-induced learning and memory deficits, and suggest that CCR5 antagonists may serve as a potential treatment to improve cognitive deficits associated with AD.

Stabilization and Reduced Cytotoxicity of Amyloid Beta Aggregates in the Presence of Catechol Neurotransmitters

Oligomeric aggregates of the amyloid-beta (Aβ) peptide have been implicated as the toxic species for Alzheimer's disease by contributing to oxidative cytotoxicity and physical disruption in cell membranes in the brain. Recent evidence points to the ability of the catecholamine neurotransmitter dopamine in the presence of copper ions to both stabilize oligomers and decrease the toxic effects of these oligomers. Based on these results, physical characterization of aggregates and subsequent cell studies with a neuroblastoma line were performed that show both dopamine and the related neurotransmitter, norepinephrine, can stabilize oligomers and decrease toxicity of Aβ aggregates without copper present. To investigate this reduction of toxicity, structural characterization of oligomers in the presence of neurotransmitters was compared to aggregates formed with Aβ alone. Gel electrophoresis and transmission electron microscopy show higher levels of oligomers in the presence of dopamine and norepinephrine, yet the oligomer structure is largely amorphous. Aβ aggregated alone forms the predicted highly organized fibrillar species, with increased levels of dityrosine covalent linkages, which are largely absent in the presence of the neurotransmitters. A proposed mechanism for the observed decrease in cell death by Aβ in the presence of dopamine and norepinephrine suggests the neurotransmitters both block the formation of organized oligomer structures and dityrosine stabilizing linkages while also behaving as antioxidants, providing a dual mechanism for increased cell viability.

Re-Engineering Therapeutic Anti-Aβ Monoclonal Antibody to Target Amyloid Light Chain

Amyloidosis involves the deposition of misfolded proteins. Even though it is caused by different pathogenic mechanisms, in aggregate, it shares similar features. Here, we tested and confirmed a hypothesis that an amyloid antibody can be engineered by a few mutations to target a different species. Amyloid light chain (AL) and β-amyloid peptide (Aβ) are two therapeutic targets that are implicated in amyloid light chain amyloidosis and Alzheimer's disease, respectively. Though crenezumab, an anti-Aβ antibody, is currently unsuccessful, we chose it as a model to computationally design and prepare crenezumab variants, aiming to discover a novel antibody with high affinity to AL fibrils and to establish a technology platform for repurposing amyloid monoclonal antibodies. We successfully re-engineered crenezumab to bind both Aβ42 oligomers and AL fibrils with high binding affinities. It is capable of reversing Aβ42-oligomers-induced cytotoxicity, decreasing the formation of AL fibrils, and alleviating AL-fibrils-induced cytotoxicity in vitro. Our research demonstrated that an amyloid antibody could be engineered by a few mutations to bind new amyloid sequences, providing an efficient way to reposition a therapeutic antibody to target different amyloid diseases.

Searching for EGF Fragments Recreating the Outer Sphere of the Growth Factor Involved in Receptor Interactions

The aims of this study were to determine whether it is possible to use peptide microarrays obtained using the SPOT technique (immobilized on cellulose) and specific polyclonal antibodies to select fragments that reconstruct the outer sphere of proteins and to ascertain whether the selected peptide fragments can be useful in the study of their protein-protein and/or peptide-protein interactions. Using this approach, epidermal growth factor (EGF) fragments responsible for the interaction with the EGF receptor were searched. A library of EGF fragments immobilized on cellulose was obtained using triazine condensing reagents. Experiments on the interactions with EGFR confirmed the high affinity of the selected peptide fragments. Biological tests on cells showed the lack of cytotoxicity of the EGF fragments. Selected EGF fragments can be used in various areas of medicine.

Detection of Femtomolar Amyloid-β Peptides for Early-Stage Identification of Alzheimer's Amyloid-β Aggregation with Functionalized Gold Nanoparticles

Progressive amyloid-β (Aβ) fibrillar aggregates have long been considered as the pathogenesis of Alzheimer's disease (AD). Biocompatible and stable cysteine-Aβ peptide-conjugated gold nanoparticles (Cys-Aβ@AuNP) are demonstrated as suitable materials for detecting subfemtomolar Aβ peptides in human plasma. Incubation with Aβ peptides causes the Cys-Aβ@AuNP to aggregate and changes its absorption spectra. The spectral change is especially apparent and noticeable when detecting subfemtomolar Aβ peptides, and the aggregates contain only two or three AuNPs. Cys-Aβ@AuNP can also be used to identify early-stage Aβ oligomerization, which is not possible using the conventional method, in which the fluorescence of thioflavin-T is measured. The ability to detect Aβ oligomerization can facilitate therapeutics for AD. In addition, the binding of Aβ peptides by Cys-Aβ@AuNP in combination with centrifugation redirects the conventional Aβ aggregation pathway and can effectively inhibit the formation of toxic Aβ oligomers or fibrils. Therefore, the proposed Cys-Aβ@AuNP can also be used to develop effective therapeutic agents to inhibit Aβ aggregation. The results obtained in this study are expected to open revolutionary ways to both detect and inhibit Aβ aggregation at an early stage.

miR-277 targets the proapoptotic gene-hid to ameliorate Aβ42-mediated neurodegeneration in Alzheimer's model

Alzheimer's disease (AD), an age-related progressive neurodegenerative disorder, exhibits reduced cognitive function with no cure to date. One of the reasons for AD is the accumulation of Amyloid-beta 42 (Aβ42) plaque(s) that trigger aberrant gene expression and signaling, which results in neuronal cell death by an unknown mechanism(s). Misexpression of human Aβ42 in the developing retina of Drosophila exhibits AD-like neuropathology. Small non-coding RNAs, microRNAs (miRNAs), post-transcriptionally regulate the expression of their target genes and thereby regulate different signaling pathways. In a forward genetic screen, we identified miR-277 (human ortholog is hsa-miR-3660) as a genetic modifier of Aβ42-mediated neurodegeneration. Loss-of-function of miR-277 enhances the Aβ42-mediated neurodegeneration. Whereas gain-of-function of miR-277 in the GMR > Aβ42 background downregulates cell death to maintain the number of neurons and thereby restores the retinal axonal targeting defects indicating the functional rescue. In addition, gain-of-function of miR-277 rescues the eclosion- and climbing assays defects observed in GMR > Aβ42 background. Thus, gain-of-function of miR-277 rescues both structurally as well as functionally the Aβ42-mediated neurodegeneration. Furthermore, we identified head involution defective (hid), an evolutionarily conserved proapoptotic gene, as one of the targets of miR-277 and validated these results using luciferase- and qPCR -assays. In the GMR > Aβ42 background, the gain-of-function of miR-277 results in the reduction of hid transcript levels to one-third of its levels as compared to GMR > Aβ42 background alone. Here, we provide a novel molecular mechanism where miR-277 targets and downregulates proapoptotic gene, hid, transcript levels to rescue Aβ42-mediated neurodegeneration by blocking cell death. These studies shed light on molecular mechanism(s) that mediate cell death response following Aβ42 accumulation seen in neurodegenerative disorders in humans and provide new therapeutic targets for neurodegeneration.

Roles of Apigenin and Nepetin in the Assembly Behavior and Cytotoxicity of Prion Neuropeptide PrP106-126

Development of potential inhibitors to prevent prion protein (PrP) fibrillation is a therapeutic strategy for prion diseases. The prion neuropeptide PrP106-126, a research model of abnormal PrP (PrPSc), presents similar physicochemical and biochemical characters to PrPSc, which is also a target of potential inhibitors against prion deposition. Many flavones have antioxidant, anti-inflammatory, and antibacterial properties, and they are applied in treating prion disorder and other amyloidosis as well. However, the inhibition mechanism of flavones on PrP106-126 fibrillation is still unclear. In the current work, apigenin and nepetin were used to suppress the aggregation of PrP106-126 and to alleviate the peptide-induced cytotoxicity. The results showed that apigenin and nepetin impeded the fibril formation of PrP106-126 and depolymerized the preformed fibrils. They were bound to PrP106-126 predominantly by hydrophobic and hydrogen bonding interactions. In addition, both flavones upregulated cell viability and decreased membrane leakage through reducing peptide oligomerization. The differences in inhibition and cell protection between the two small molecules were presumably attributed to the substitution of hydroxyl and methoxy groups in nepetin, which demonstrated the significant structure-function relationship of flavones with prion neuropeptide and the prospect of flavonoids as drug candidates against prion diseases.

A Chronic Increase in Blood-Brain Barrier Permeability Facilitates Intraneuronal Deposition of Exogenous Bloodborne Amyloid-Beta1-42 Peptide in the Brain and Leads to Alzheimer's Disease-Relevant Cognitive Changes in a Mouse Model

Background

Increased blood-brain barrier (BBB) permeability and amyloid-β (Aβ) peptides (especially Aβ1-42) (Aβ42) have been linked to Alzheimer's disease (AD) pathogenesis, but the nature of their involvement in AD-related neuropathological changes leading to cognitive changes remains poorly understood.

Objective

To test the hypothesis that chronic extravasation of bloodborne Aβ42 peptide and brain-reactive autoantibodies and their entry into the brain parenchyma via a permeable BBB contribute to AD-related pathological changes and cognitive changes in a mouse model.

Methods

The BBB was rendered chronically permeable through repeated injections of Pertussis toxin (PT), and soluble monomeric, fluorescein isothiocyanate (FITC)-labeled or unlabeled Aβ42 was injected into the tail-vein of 10-month-old male CD1 mice at designated intervals spanning ∼3 months. Acquisition of learned behaviors and long-term retention were assessed via a battery of cognitive and behavioral tests and linked to neuropathological changes.

Results

Mice injected with both PT and Aβ42 demonstrated a preferential deficit in the capacity for long-term retention and an increased susceptibility to interference in selective attention compared to mice exposed to PT or saline only. Immunohistochemical analyses revealed increased BBB permeability and entry of bloodborne Aβ42 and immunoglobulin G (IgG) into the brain parenchyma, selective neuronal binding of IgG and neuronal accumulation of Aβ42 in animals injected with both PT and Aβ42 compared to controls.

Conclusion

Results highlight the potential synergistic role of BBB compromise and the influx of bloodborne Aβ42 into the brain in both the initiation and progression of neuropathologic and cognitive changes associated with AD.

Targeting the Renin-Angiotensin System (RAS) for Neuropsychiatric Disorders

BACKGROUND

Neuropsychiatric disorders, such as mood disorders, schizophrenia, and Alzheimer's disease (AD) and related dementias, are associated to significant morbidity and mortality worldwide. The pathophysiological mechanisms of neuropsychiatric disorders remain to be fully elucidated, which has hampered the development of effective therapies. The Renin Angiotensin System (RAS) is classically viewed as a key regulator of cardiovascular and renal homeostasis. The discovery that RAS components are expressed in the brain pointed out a potential role for this system in central nervous system (CNS) pathologies. The understanding of RAS involvement in the pathogenesis of neuropsychiatric disorders may contribute to identifying novel therapeutic targets.

AIMS

We aim to report current experimental and clinical evidence on the role of RAS in physiology and pathophysiology of mood disorders, schizophrenia, AD and related dementias. We also aim to discuss bottlenecks and future perspectives that can foster the development of new related therapeutic strategies.

CONCLUSION

The available evidence supports positive therapeutic effects for neuropsychiatric disorders with the inhibition/antagonism of the ACE/Ang II/AT1 receptor axis or the activation of the ACE2/Ang-(1-7)/Mas receptor axis. Most of this evidence comes from pre-clinical studies and clinical studies lag much behind, hampering a potential translation into clinical practice.

Synergetic effect of matrine on the catalytic scFv antibody HS72 in vitro and in mice with Alzheimer disease pathology

Single-chain variable fragment (scFv) HS72 is a catalytic antibody that specifically degrades amyloid β-protein 1-42 (Aβ42) aggregates in vitro or reduces the level or burden of Aβ42 deposits/plaques in the brains of mice with Alzheimer disease pathology. Its efficacy has been shown in protecting neural cells in vitro and improving the morphology of the cell population in the brain of mice with AD pathology (AD mice). Matrine (Mat) is a natural product capable of binding to Aβ42 or its aggregates and blocking their neurotoxicity at concentrations of at least 10 μM or greater. However, this study revealed a synergistic effect of Mat on the catalytic effect of HS72 at low concentrations (0.01-2.5 μM). This is evidenced by the fact that Mat synergistically enhances HS72's ability to degrade Aβ42 aggregates and protect neural cells (SH-SY5Y and HT22 cells, and brain cells of AD mice). The molecular docking models and characterization of Mat's action both indicated that the mechanism of Mat's synergistic impact on HS72 catalysis is to increase the turnover number (or molecular activity) of HS72 by enhancing the catalytic power of the HS72's catalytic groups and encouraging the release of the degradation products (Aβ fragments). The study's results suggest a natural synergy between Mat-like small molecules and the catalytic anti-oligomeric Aβ42 antibody HS72, enabling more effective reduction or removal of Aβ42 aggregates or plaques than the antibody alone. These findings provide novel insights into the effectiveness of anti-oligomeric Aβ42 antibodies in AD immunotherapy.

GDP dissociation inhibitor 1 (GDI1) attenuates β-amyloid-induced neurotoxicity in Alzheimer's diseases

OBJECTIVE

β-Amyloid (Aβ) induced neurotoxicity is an implicated mechanism in Alzheimer's disease (AD). This study focused on the role of GDP dissociation inhibitor 1 (GDI1) in Aβ-induced neurotoxicity.

METHODS

Data from the GEO database for AD-related datasets GSE140829, GSE63061, GSE36980, and GSE60360 were downloaded and identified common differentially expressed genes (coDEGs). The mRNA levels of GDI1 in the serum of AD patients were analyzed by RT-qPCR. ROC curve evaluated the diagnostic value. Aβ25-35 induced SH-SY5Y cells to construct an AD cell model. CCK-8, flow cytometry, and ELISA assay were used to analyze cell viability, apoptosis, and concentrations of inflammatory factors. KEGG enrichment was employed to analyze the signal pathway of targets from GDI1 in the AD.

RESULTS

The GEO database identifies coDEGs including GDI1. GDI1 is generally elevated in serum from AD patients as well as in Aβ-induced SH-SY5Y cells. GDI1 has 77.97% sensitivity and 84.44% specificity to identify AD patients from controls. Aβ induced decreased cell viability, increased apoptosis, and promoted over-secretion of inflammatory cytokines, but they were all partially weakened by reduced GDI1. What's more, the GDI1 interacting gene and AD target gene were co-enriched on Endocytosis and MAPK signaling pathway.

CONCLUSION

Elevated GDI1 is a potential diagnostic biomarker for AD and that inhibition of GDI1 attenuates Aβ-induced neurotoxicity in AD. Our study offers new horizons for AD treatment.

Neuroprotective Effects of Ferrostatin and Necrostatin Against Entorhinal Amyloidopathy-Induced Electrophysiological Alterations Mediated by voltage-gated Ca2+ Channels in the Dentate Gyrus Granular Cells

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is the main form of dementia. Abnormal deposition of amyloid-beta (Aβ) peptides in neurons and synapses cause neuronal loss and cognitive deficits. We have previously reported that ferroptosis and necroptosis were implicated in Aβ25-35 neurotoxicity, and their specific inhibitors had attenuating effects on cognitive impairment induced by Aβ25-35 neurotoxicity. Here, we aimed to examine the impact of ferroptosis and necroptosis inhibition following the Aβ25-35 neurotoxicity on the neuronal excitability of dentate gyrus (DG) and the possible involvement of voltage-gated Ca2+ channels in their effects. After inducing Aβ25-35 neurotoxicity, electrophysiological alterations in the intrinsic properties and excitability were recorded by the whole-cell patch-clamp under current-clamp condition. Voltage-clamp recordings were also performed to shed light on the involvement of calcium channel currents. Aβ25-35 neurotoxicity induced a considerable reduction in input resistance (Rin), accompanied by a profoundly decreased excitability and a reduction in the amplitude of voltage-gated calcium channel currents in the DG granule cells. However, three days of administration of either ferrostatin-1 (Fer-1), a ferroptosis inhibitor, or Necrostatin-1 (Nec-1), a necroptosis inhibitor, in the entorhinal cortex could almost preserve the normal excitability and the Ca2+ currents. In conclusion, these findings suggest that ferroptosis and necroptosis involvement in EC amyloidopathy could be a potential candidate to prevent the suppressive effect of Aβ on the Ca2+ channel current and neuronal function, which might take place in neurons during the development of AD.

Ganglioside Micelles Affect Amyloid β Aggregation by Coassembly

Amyloid β peptide (Aβ) is the crucial protein component of extracellular plaques in Alzheimer's disease. The plaques also contain gangliosides lipids, which are abundant in membranes of neuronal cells and in cell-derived vesicles and exosomes. When present at concentrations above its critical micelle concentration (cmc), gangliosides can occur as mixed micelles. Here, we study the coassembly of the ganglioside GM1 and the Aβ peptides Aβ40 and 42 by means of microfluidic diffusional sizing, confocal microscopy, and cryogenic transmission electron microscopy. We also study the effects of lipid-peptide interactions on the amyloid aggregation process by fluorescence spectroscopy. Our results reveal coassembly of GM1 lipids with both Aβ monomers and Aβ fibrils. The results of the nonseeded kinetics experiments show that Aβ40 aggregation is delayed with increasing GM1 concentration, while that of Aβ42 is accelerated. In seeded aggregation reactions, the addition of GM1 leads to a retardation of the aggregation process of both peptides. Thus, while the effect on nucleation differs between the two peptides, GM1 may inhibit the elongation of both types of fibrils. These results shed light on glycolipid-peptide interactions that may play an important role in Alzheimer's pathology.

Beta-Amyloid Enhances Vessel Formation in Organotypic Brain Slices Connected to Microcontact Prints

In Alzheimer's disease, the blood-brain barrier breakdown, blood vessel damage and re-organization are early events. Deposits of the small toxic peptide beta-amyloid (Aβ) cause the formation of extracellular plaques and accumulate in vessels disrupting the blood flow but may also play a role in blood clotting. In the present study, we aim to explore the impact of Aβ on the migration of endothelial cells and subsequent vessel formation. We use organotypic brain slices of postnatal day 10 wildtype mice (C57BL/6) and connect them to small microcontact prints (µCPs) of collagen. Our data show that laminin-positive endothelial cells migrate onto collagen µCPs, but without any vessel formation after 4 weeks. When the µCPs are loaded with human Aβ40, (aggregated) human Aβ42 and mouse Aβ42 peptides, the number and migration distance of endothelial cells are significantly reduced, but with a more pronounced subsequent vessel formation. The vessel formation is verified by zonula occludens (ZO)-1 and -2 stainings and confocal microscopy. In addition, the vessel formation is accompanied by a stronger GFAP-positive astroglial formation. Finally, we show that vessels can grow towards convergence when two opposed slices are connected via microcontact-printed lanes. In conclusion, our data show that Aβ promotes vessel formation, and organotypic brain slices connected to collagen µCPs provide a potent tool to study vessel formation.

Angiotensin-Converting Enzyme 2 (ACE2) Signaling in Pulmonary Arterial Hypertension: Underpinning Mechanisms and Potential Targeting Strategies

Pulmonary arterial hypertension (PAH) is a debilitating progressive disease characterized by excessive pulmonary vasoconstriction and abnormal vascular remodeling processes that lead to right-ventricular heart failure and, ultimately, death. Although our understanding of its pathophysiology has advanced and several treatment modalities are currently available for the management of PAH patients, none are curative and the prognosis remains poor. Therefore, further research is required to decipher the molecular mechanisms associated with PAH. Angiotensin-converting enzyme 2 (ACE2) plays an important role through its vasoprotective functions in cardiopulmonary homeostasis, and accumulating preclinical and clinical evidence shows that the upregulation of the ACE2/Angiotensin-(1-7)/MAS1 proto-oncogene, G protein-coupled receptor (Mas 1 receptor) signaling axis is implicated in the pathophysiology of PAH. Herein, we highlight the molecular mechanisms of ACE2 signaling in PAH and discuss its potential as a therapeutic target.

Effect of Terahertz Waves on the Structure of the Aβ42 Monomer, Dimer, and Protofibril: Insights from Molecular Dynamics Simulations

Amyloid-β (Aβ) and its assemblies play important roles in the pathogenesis of Alzheimer's disease (AD). Recent studies conducted by experimental and computational researchers have extensively explored the structure, assembly, and influence of biomolecules and cell membranes on Aβ. However, the impact of terahertz waves on the structures of Aβ monomers and aggregates remains largely unexplored. In this study, we systematically investigate the molecular mechanisms by which terahertz waves affect the structure of the Aβ42 monomer, dimer, and tetramer through all-atom molecular dynamics (MD) simulations. Our findings indicate that terahertz waves at a specific frequency (42.55 THz) can enhance intramolecular and intermolecular interactions in the Aβ42 monomer and dimer, respectively, by resonating with the symmetric stretching mode of the -COO- groups and the symmetric bending/stretching mode of -CH3 groups. Consequently, the β-structure content of the Aβ42 monomer is greatly increased, and the binding energy between the monomers in the Aβ42 dimer is significantly enhanced. Additionally, our observations suggest that terahertz waves can mildly stabilize the structure of tetrameric protofibrils by enhancing the interactions among peripheral peptides. Furthermore, we also investigated the effect of the frequency of terahertz waves on the structure of Aβ42. The present study contributes to a better understanding of the impact of external fields on the biobehavior of Aβ42 peptides and may shed some light on the potential risks associated with electromagnetic field radiation.

Small Molecules N-Phenylbenzofuran-2-carboxamide and N-Phenylbenzo[b]thiophene-2-carboxamide Promote Beta-Amyloid (Aβ42) Aggregation and Mitigate Neurotoxicity

This study reports the unusual ability of small molecules N-phenylbenzofuran-2-carboxamide (7a) and N-phenylbenzo[b]thiophene-2-carboxamide (7b) to promote and accelerate Aβ42 aggregation. In the in vitro aggregation kinetic assays, 7a was able to demonstrate rapid increases in Aβ42 fibrillogenesis ranging from 1.5- to 4.7-fold when tested at 1, 5, 10, and 25 μM compared to Aβ42-alone control. Similarly, compound 7b also exhibited 2.9- to 4.3-fold increases in Aβ42 fibrillogenesis at the concentration range tested. Electron microscopy studies at 1, 5, 10, and 25 μM also demonstrate the ability of compounds 7a and 7b to promote and accelerate Aβ42 aggregation with the formation of long, elongated fibril structures. Both 7a and 7b were not toxic to HT22 hippocampal neuronal cells and strikingly were able to prevent Aβ42-induced cytotoxicity in HT22 hippocampal neuronal cells (cell viability ∼74%) compared to the Aβ42-treated group (cell viability ∼20%). Fluorescence imaging studies using BioTracker 490 green, Hoeschst 33342, and the amyloid binding dye ProteoStat further demonstrate the ability of 7a and 7b to promote Aβ42 fibrillogenesis and prevent Aβ42-induced cytotoxicity to HT22 hippocampal neuronal cells. Computational modeling studies suggest that both 7a and 7b can interact with the Aβ42 oligomer and pentamers and have the potential to modulate the self-assembly pathways. The 8-anilino-1-naphthalenesulfonic acid (ANS) dye binding assay also demonstrates the ability of 7a and 7b to expose the hydrophobic surface of Aβ42 to the solvent surface that promotes self-assembly and rapid fibrillogenesis. These studies demonstrate the unique ability of small molecules 7a and 7b to alter the self-assembly and misfolding pathways of Aβ42 by promoting the formation of nontoxic aggregates. These findings have direct implications in the discovery and development of novel small-molecule-based chemical and pharmacological tools to study the Aβ42 aggregation mechanisms, and in the design of novel antiamyloid therapies to treat Alzheimer's disease.

Hederagenin Upregulates PTPN1 Expression in Aβ-Stimulated Neuronal Cells, Exerting Anti-Oxidative Stress and Anti-Apoptotic Activities

Alzheimer's disease (AD) is a prevalently neurodegenerative disease characterized by neuronal damage which is associated with amyloid-β (Aβ) accumulation. Hederagenin is a triterpenoid saponin, exerting anti-apoptotic, anti-oxidative, anti-inflammatory, anti-tumoral, and neuroprotective activities. However, its role in AD progression is still obscure. The aim of this study was to explore the influences of hederagenin on Aβ-caused neuronal injury in vitro. Neuronal cells were treated with Aβ25-35 (Aβ) to establish a cellular model of AD. Cell viability was assessed using cell counting kit-8 (CCK-8). Oxidative stress was evaluated by detecting reactive oxygen species (ROS) generation and superoxide dismutase (SOD) activity. Apoptosis was investigated using TUNEL staining and caspase-3 activity assays. Protein tyrosine phosphatase nonreceptor type 1 (PTPN1) was screened by bioinformatics analysis. Protein levels of PTPN1 and protein kinase B (Akt) were measured by western blotting. Hederagenin (2.5, 5, and 10 μM) alone did not affect viability of neuronal cells, but relieved Aβ-induced viability reduction. Hederagenin mitigated Aβ-induced increase in ROS accumulation and decrease in SOD activity. Hederagenin attenuated Aβ-induced increase in apoptotic rate and caspase-3 activity. PTPN1 was screened as a target of hederagenin against AD by bioinformatics analysis. Hederagenin treatment resisted Aβ-induced decrease in PTPN1 mRNA and protein levels in neuronal cells. PTPN1 silencing attenuated the suppressive functions of hederagenin in Aβ-stimulated oxidative stress and apoptosis. Hederagenin mitigated Aβ-induced Akt signaling inactivation by upregulating PTPN1 expression. In conclusion, hederagenin attenuates oxidative stress and apoptosis in neuronal cells stimulated with Aβ by promoting PTPN1/Akt signaling activation.

Impact of N-terminal pro-B-type natriuretic peptide and related inflammatory biomarkers on periodontal treatment outcomes in patients with periodontitis: An explorative human randomized-controlled clinical trial

BACKGROUND

N-terminal portion of the B-type natriuretic propeptide (NT-proBNP) has potentially been shown to play an important role in the development of periodontitis and cardiovascular disease (CVD). This study evaluated the efficacy of periodontal treatment on NT-proBNP and related CVD biomarkers and explored whether subjects harboring high NT-proBNP at baseline showed increased clinical benefits with the non-surgical periodontal treatment performed with full-mouth scaling and root planing (FM-SRP) at 6-month follow-up.

METHODS

Forty-eight patients with stage III periodontitis were randomized to receive minimal standard oral care (SOC) (n = 24) or FM-SRP (n = 24) protocol. Clinical periodontal parameters (probing depth, clinical attachment loss, bleeding on probing), serum NT-proBNP, α1-antitrypsin, C-reactive protein (hs-CRP), endothelial cell-specific molecule-1 (ECM-1), and neutrophil gelatinase-associated lipocalin (NGAL) concentrations were assessed at baseline and at 1-, 3-, and 6- month follow-up.

RESULTS

At 6 months, FM-SRP was more effective than SOC in reducing periodontal parameters and mean proportions of NT-proBNP (p = 0.004), hs-CRP (p = 0.003), α1-antitrypsin (p = 0.012), ECM-1 (p = 0.014), and NGAL (p = 0.045). At 6-month follow-up, the reduced NT-proBNP, α1-antitrypsin, hs-CRP, ECM-1, and NGAL levels were significantly correlated with the extent of periodontitis (p < 0.05). Furthermore, the analysis of variance analysis evidenced that, at 6-month follow-up, FM-SRP significantly impacted the reduction of NT-proBNP, hs-CRP, ECM-1, and NGAL. Moreover, high levels of NT-proBNP, hs-CRP, ECM-1, and NGAL at baseline significantly influenced the efficacy of periodontal treatment positively.

CONCLUSION

In this study, FM-SRP was more effective than SOC in reducing clinical variables and NT-proBNP levels, although subjects who harbored high NT-proBNP concentrations at baseline showed greater clinical benefits of periodontal treatment at 6-month follow-up.

Sterol-activated amyloid beta fibril formation

The metabolic processes that link Alzheimer's disease (AD) to elevated cholesterol levels in the brain are not fully defined. Amyloid beta (Aβ) plaque accumulation is believed to begin decades prior to symptoms and to contribute significantly to the disease. Cholesterol and its metabolites accelerate plaque formation through as-yet-undefined mechanisms. Here, the mechanism of cholesterol (CH) and cholesterol 3-sulfate (CS) induced acceleration of Aβ42 fibril formation is examined in quantitative ligand binding, Aβ42 fibril polymerization, and molecular dynamics studies. Equilibrium and pre-steady-state binding studies reveal that monomeric Aβ42•ligand complexes form and dissociate rapidly relative to oligomerization, that the ligand/peptide stoichiometry is 1-to-1, and that the peptide is likely saturated in vivo. Analysis of Aβ42 polymerization progress curves demonstrates that ligands accelerate polymer synthesis by catalyzing the conversion of peptide monomers into dimers that nucleate the polymerization reaction. Nucleation is accelerated ∼49-fold by CH, and ∼13,000-fold by CS - a minor CH metabolite. Polymerization kinetic models predict that at presumed disease-relevant CS and CH concentrations, approximately half of the polymerization nuclei will contain CS, small oligomers of neurotoxic dimensions (∼12-mers) will contain substantial CS, and fibril-formation lag times will decrease 13-fold relative to unliganded Aβ42. Molecular dynamics models, which quantitatively predict all experimental findings, indicate that the acceleration mechanism is rooted in ligand-induced stabilization of the peptide in non-helical conformations that readily form polymerization nuclei.

The interplay between copper metabolism and microbes: in perspective of host copper-dependent ATPases ATP7A/B

Copper, a vital element in various physiological processes, is transported from the gastrointestinal tract to tissues and cells through diverse copper transporters. Among these transporters, ATP7A and ATP7B play significant roles in regulating systemic copper metabolism and exhibit precise regulation in their intracellular trafficking. These transporters undergo dynamic shuttling between the trans-Golgi network (TGN) and the plasma membrane via the endocytic recycling mechanism, which involves the retromer and other associated factors. Interestingly, the antimicrobial attribute of copper implies a potential connection between microbial infection and copper metabolism. Several microbes, including Salmonella enterica, Cryptococcus, Influenza A virus (IAV) and Zika virus (ZIKV) have been observed to impact the regulatory mechanisms of ATP7A/B, either directly or indirectly, as a means of survival. This review summarizes the key features and trafficking mechanisms of the copper transporters ATP7A/B, and examines the intricate interplay between microbes and copper metabolism. Ultimately, it highlights how microbes can perturb copper homeostasis through interactions with host factors, offering valuable insights into the mechanistic aspects of host-microbe interactions.