The Beneficial Effects of Combining Anti-Aβ Antibody NP106 and Curcumin Analog TML-6 on the Treatment of Alzheimer’s Disease in APP/PS1 Mice

Alzheimer’s disease (AD) is a progressive neurodegenerative disease with a multifactorial etiology. A multitarget treatment that modulates multifaceted biological functions might be more effective than a single-target approach. Here, the therapeutic efficacy of combination treatment using anti-Aβ antibody NP106 and curcumin analog TML-6 versus monotherapy was investigated in an APP/PS1 mouse model of AD. Our data demonstrate that both combination treatment and monotherapy attenuated brain Aβ and improved the nesting behavioral deficit to varying degrees. Importantly, the combination treatment group had the lowest Aβ levels, and insoluble forms of Aβ were reduced most effectively. The nesting performance of APP/PS1 mice receiving combination treatment was better than that of other APP/PS1 groups. Further findings indicate that enhanced microglial Aβ phagocytosis and lower levels of proinflammatory cytokines were concurrent with the aforementioned effects of NP106 in combination with TML-6. Intriguingly, combination treatment also normalized the gut microbiota of APP/PS1 mice to levels resembling the wild-type control. Taken together, combination treatment outperformed NP106 or TML-6 monotherapy in ameliorating Aβ pathology and the nesting behavioral deficit in APP/PS1 mice. The superior effect might result from a more potent modulation of microglial function, cerebral inflammation, and the gut microbiota. This innovative treatment paradigm confers a new avenue to develop more efficacious AD treatments.     

Characterization of a Mouse Model of Alzheimer’s Disease Expressing Aβ4-42 and Human Mutant Tau

The relationship between the two most prominent neuropathological hallmarks of Alzheimer’s Disease (AD), extracellular amyloid-β (Aβ) deposits and intracellular accumulation of hyperphosphorylated tau in neurofibrillary tangles (NFT), remains at present not fully understood. A large body of evidence places Aβ upstream in the cascade of pathological events, triggering NFTs formation and the subsequent neuron loss. Extracellular Aβ deposits were indeed causative of an increased tau phosphorylation and accumulation in several transgenic models but the contribution of soluble Aβ peptides is still controversial. Among the different Aβ variants, the N-terminally truncated peptide Aβ_4–42 is among the most abundant. To understand whether soluble Aβ_4–42 peptides impact the onset or extent of tau pathology, we have crossed the homozygous Tg4–42 mouse model of AD, exclusively expressing Aβ_4–42 peptides, with the PS19 (P301S) tau transgenic model. Behavioral assessment showed that the resulting double-transgenic line presented a partial worsening of motor performance and spatial memory deficits in the aged group. While an increased loss of distal CA1 pyramidal neurons was detected in young mice, no significant alterations in hippocampal tau phosphorylation were observed in immunohistochemical analyses.     

CK1δ-Derived Peptides as Novel Tools Inhibiting the Interactions between CK1δ and APP695 to Modulate the Pathogenic Metabolism of APP

Alzheimer’s disease (AD) is the major cause of dementia, and affected individuals suffer from severe cognitive, mental, and functional impairment. Histologically, AD brains are basically characterized by the presence of amyloid plaques and neurofibrillary tangles. Previous reports demonstrated that protein kinase CK1δ influences the metabolism of amyloid precursor protein (APP) by inducing the generation of amyloid-β (Aβ), finally contributing to the formation of amyloid plaques and neuronal cell death. We therefore considered CK1δ as a promising therapeutic target and suggested an innovative strategy for the treatment of AD based on peptide therapeutics specifically modulating the interaction between CK1δ and APP. Initially, CK1δ-derived peptides manipulating the interactions between CK1δ and APP695 were identified by interaction and phosphorylation analysis in vitro. Selected peptides subsequently proved their potential to penetrate cells without inducing cytotoxic effects. Finally, for at least two of the tested CK1δ-derived peptides, a reduction in Aβ levels and amyloid plaque formation could be successfully demonstrated in a complex cell culture model for AD. Consequently, the presented results provide new insights into the interactions of CK1δ and APP695 while also serving as a promising starting point for further development of novel and highly innovative pharmacological tools for the treatment of AD.     

Circulating Insulin-Like Growth Factor I is Involved in the Effect of High Fat Diet on Peripheral Amyloid β Clearance

Obesity is a risk factor for Alzheimer’s disease (AD), but underlying mechanisms are not clear. We analyzed peripheral clearance of amyloid β (Aβ) in overweight mice because its systemic elimination may impact brain Aβ load, a major landmark of AD pathology. We also analyzed whether circulating insulin-like growth factor I (IGF-I) intervenes in the effects of overweight as this growth factor modulates brain Aβ clearance and is increased in the serum of overweight mice. Overweight mice showed increased Aβ accumulation by the liver, the major site of elimination of systemic Aβ, but unaltered brain Aβ levels. We also found that Aβ accumulation by hepatocytes is stimulated by IGF-I, and that mice with low serum IGF-I levels show reduced liver Aβ accumulation—ameliorated by IGF-I administration, and unchanged brain Aβ levels. In the brain, IGF-I favored the association of its receptor (IGF-IR) with the Aβ precursor protein (APP), and at the same time, stimulated non-amyloidogenic processing of APP in astrocytes, as indicated by an increased sAPPα/sAPPβ ratio after IGF-I treatment. Since serum IGF-I enters into the brain in an activity-dependent manner, we analyzed in overweight mice the effect of brain activation by environmental enrichment (EE) on brain IGF-IR phosphorylation and its association to APP, as a readout of IGF-I activity. After EE, significantly reduced brain IGF-IR phosphorylation and APP/IGF-IR association were found in overweight mice as compared to lean controls. Collectively, these results indicate that a high-fat diet influences peripheral clearance of Aβ without affecting brain Aβ load. Increased serum IGF-I likely contributes to enhanced peripheral Aβ clearance in overweight mice, without affecting brain Aβ load probably because its brain entrance is reduced.     

TGF-β1 Protection against Aβ1–42-Induced Neuroinflammation and Neurodegeneration in Rats

Transforming growth factor (TGF)-β1, a cytokine that can be expressed in the brain, is a key regulator of the brain’s responses to injury and inflammation. Alzheimer’s disease (AD), the most common neurodegenerative disorder, involves inflammatory processes in the brain in addition to the hallmarks, amyloid-β (Aβ) plaques and neurofibrillary tangles. Recently, we have shown that T-helper (Th) 17 cells, a subpopulation of CD4⁺ T-cells with high proinflammation, also participate in the brain inflammatory process of AD. However, it is poorly known whether TGF-β1 ameliorates the lymphocyte-mediated neuroinflammation and, thereby, alleviates neurodegeneration in AD. Herein, we administered TGF-β1 via the intracerebroventricle (ICV) in AD model rats, by Aβ_1–42 injection in both sides of the hippocampus, to show the neuroprotection of TGF-β1. The TGF-β1 administration after the Aβ_1–42 injection ameliorated cognitive deficit and neuronal loss and apoptosis, reduced amyloid precursor protein (APP) expression, elevated protein phosphatase (PP)2A expression, attenuated glial activation and alleviated the imbalance of the pro-inflammatory/anti-inflammatory responses of T-lymphocytes, compared to the Aβ_1–42 injection alone. These findings demonstrate that TGF-β1 provides protection against AD neurodegeneration and suggest that the TGF-β1 neuroprotection is implemented by the alleviation of glial and T-cell-mediated neuroinflammation.     

The Antithrombotic Agent Pterostilbene Interferes with Integrin αIIbβ3-Mediated Inside-Out and Outside-In Signals in Human Platelets

Platelets play a crucial role in the physiology of primary hemostasis and pathological processes such as arterial thrombosis; thus, developing a therapeutic target that prevents platelet activation can reduce arterial thrombosis. Pterostilbene (PTE) has remarkable pharmacological activities, including anticancer and neuroprotection. Few studies have reported the effects of pterostilbene on platelet activation. Thus, we examined the inhibitory mechanisms of pterostilbene in human platelets and its role in vascular thrombosis prevention in mice. At low concentrations (2–8 μM), pterostilbene strongly inhibited collagen-induced platelet aggregation. Furthermore, pterostilbene markedly diminished Lyn, Fyn, and Syk phosphorylation and hydroxyl radical formation stimulated by collagen. Moreover, PTE directly hindered integrin α_IIbβ₃ activation through interfering with PAC-1 binding stimulated by collagen. In addition, pterostilbene affected integrin α_IIbβ₃-mediated outside-in signaling, such as integrin β₃, Src, and FAK phosphorylation, and reduced the number of adherent platelets and the single platelet spreading area on immobilized fibrinogen as well as thrombin-stimulated fibrin clot retraction. Furthermore, pterostilbene substantially prolonged the occlusion time of thrombotic platelet plug formation in mice. This study demonstrated that pterostilbene exhibits a strong activity against platelet activation through the inhibition of integrin α_IIbβ₃-mediated inside-out and outside-in signaling, suggesting that pterostilbene can serve as a therapeutic agent for thromboembolic disorders.     

Impact of Amyloid-β on Platelet Mitochondrial Function and Platelet–Mediated Amyloid Aggregation in Alzheimer’s Disease

Background: Alzheimer’s disease (AD) is characterized by an accumulation of amyloid β (Aβ) peptides in the brain and mitochondrial dysfunction. Platelet activation is enhanced in AD and platelets contribute to AD pathology by their ability to facilitate soluble Aβ to form Aβ aggregates. Thus, anti-platelet therapy reduces the formation of cerebral amyloid angiopathy in AD transgenic mice. Platelet mitochondrial dysfunction plays a regulatory role in thrombotic response, but its significance in AD is unknown and explored herein. Methods: The effects of Aβ-mediated mitochondrial dysfunction in platelets were investigated in vitro. Results: Aβ40 stimulation of human platelets led to elevated reactive oxygen species (ROS) and superoxide production, while reduced mitochondrial membrane potential and oxygen consumption rate. Enhanced mitochondrial dysfunction triggered platelet-mediated Aβ40 aggregate formation through GPVI-mediated ROS production, leading to enhanced integrin αII_bβ₃ activation during synergistic stimulation from ADP and Aβ40. Aβ40 aggregate formation of human and murine (APP23) platelets were comparable to controls and could be reduced by the antioxidant vitamin C. Conclusions: Mitochondrial dysfunction contributes to platelet-mediated Aβ aggregate formation and might be a promising target to limit platelet activation exaggerated pathological manifestations in AD.     

The Role of Melatonin on Behavioral Changes and Concomitant Oxidative Stress in icvAβ1-42 Rat Model with Pinealectomy

One of the pathological hallmarks of Alzheimer’s disease (AD) associated with its progression that contributes to β-amyloid (Aβ) generation is oxidative stress (OS). Clinical data suggest that melatonin is a potent antioxidant that might be effective in the adjunctive therapy of this neurodegenerative disease. The present study aimed to explore the role of melatonin on behavioral changes and markers of OS in three rat models, namely, pinealectomy (pin) model of melatonin deficit, intracerebroventricular (icv)Aβ_1-42 model of AD, and combination of both pin and Aβ_1-42 model (pin+icvAβ_1-42). The chronic injection with vehicle/melatonin (50 mg/kg, i.p. for 40 days) started on the same day of sham/pin and icv vehicle/Aβ_1-42 infusion procedures. Anxiety in the open field and the elevated plus-maze test and cognitive responses in the object recognition test were tested between the 30th–35th day after the surgical procedures. Markers of OS in the frontal cortex (FC) and hippocampus were detected by the ELISA method. Melatonin treatment corrected the exacerbated anxiety response only in the pin+icvAβ_1-42 model while it alleviated the cognitive impairment in the three models. Pinealectomy disturbed the antioxidant system via enhanced SOD activity and decreased GSH levels both in the FC and hippocampus. The Aβ_1-42 model decreased the SOD activity in the FC and elevated the MDA level in the two brain structures. The pin+icvAβ_1-42 model impaired the antioxidant system and elevated lipid peroxidation. Melatonin supplementation restored only the elevated MDA level of icvAβ_1-42 and pin+icvAβ_1-42 model in the hippocampus. In conclusion, our study reveals that the pin+icvAβ_1-42 rat model triggers more pronounced anxiety and alterations in markers of OS that may be associated with melatonin deficit concomitant to icvAβ_1-42-induced AD pathology.     

Specific Mutations in Aph1 Cause γ-Secretase Activation

Amyloid beta peptides (Aβs) are generated from amyloid precursor protein (APP) through multiple cleavage steps mediated by γ-secretase, including endoproteolysis and carboxypeptidase-like trimming. The generation of neurotoxic Aβ42/43 species is enhanced by familial Alzheimer’s disease (FAD) mutations within the catalytic subunit of γ-secretase, presenilin 1 (PS1). FAD mutations of PS1 cause partial loss-of-function and decrease the cleavage activity. Activating mutations, which have the opposite effect of FAD mutations, are important for studying Aβ production. Aph1 is a regulatory subunit of γ-secretase; it is presumed to function as a scaffold of the complex. In this study, we identified Aph1 mutations that are active in the absence of nicastrin (NCT) using a yeast γ-secretase assay. We analyzed these Aph1 mutations in the presence of NCT; we found that the L30F/T164A mutation is activating. When introduced in mouse embryonic fibroblasts, the mutation enhanced cleavage. The Aph1 mutants produced more short and long Aβs than did the wild-type Aph1, without an apparent modulatory function. The mutants did not change the amount of γ-secretase complex, suggesting that L30F/T164A enhances catalytic activity. Our results provide insights into the regulatory function of Aph1 in γ-secretase activity.     

New Therapeutic Targets for Hepatic Fibrosis in the Integrin Family, α8β1 and α11β1, Induced Specifically on Activated Stellate Cells

A huge effort has been devoted to developing drugs targeting integrins over 30 years, because of the primary roles of integrins in the cell-matrix milieu. Five αv-containing integrins, in the 24 family members, have been a central target of fibrosis. Currently, a small molecule against αvβ1 is undergoing a clinical trial for NASH-associated fibrosis as a rare agent aiming at fibrogenesis. Latent TGFβ activation, a distinct talent of αv-integrins, has been intriguing as a therapeutic target. None of the αv-integrin inhibitors, however, has been in the clinical market. αv-integrins commonly recognize an Arg-Gly-Asp (RGD) sequence, and thus the pharmacophore of inhibitors for the 5-integrins is based on the same RGD structure. The RGD preference of the integrins, at the same time, dilutes ligand specificity, as the 5-integrins share ligands containing RGD sequence such as fibronectin. With the inherent little specificity in both drugs and targets, “disease specificity” has become less important for the inhibitors than blocking as many αv-integrins. In fact, an almighty inhibitor for αv-integrins, pan-αv, was in a clinical trial. On the contrary, approved integrin inhibitors are all specific to target integrins, which are expressed in a cell-type specific manner: αIIbβ3 on platelets, α4β1, α4β7 and αLβ2 on leukocytes. Herein, “disease specific” integrins would serve as attractive targets. α8β1 and α11β1 are selectively expressed in hepatic stellate cells (HSCs) and distinctively induced upon culture activation. The exceptional specificity to activated HSCs reflects a rather “pathology specific” nature of these new integrins. The monoclonal antibodies against α8β1 and α11β1 in preclinical examinations may illuminate the road to the first medical agents.     

Synthesis of Reactive Sulfur Species in Cultured Vascular Endothelial Cells after Exposure to TGF-β1: Induction of Cystathionine γ-Lyase and Cystathionine β-Synthase Expression Mediated by the ALK5-Smad2/3/4 and ALK5-Smad2/3-ATF4 Pathways

Transforming growth factor-β₁ (TGF-β₁) occurs at high levels at damage sites of vascular endothelial cell layers and regulates the functions of vascular endothelial cells. Reactive sulfur species (RSS), such as cysteine persulfide, glutathione persulfide, and hydrogen persulfide, are cytoprotective factors against electrophiles such as reactive oxygen species and heavy metals. Previously, we reported that sodium trisulfide, a sulfane sulfur donor, promotes vascular endothelial cell proliferation. The objective of the present study was to clarify the regulation and significance of RSS synthesis in vascular endothelial cells after exposure to TGF-β₁. Bovine aortic endothelial cells in a culture system were treated with TGF-β₁ to assess the expression of intracellular RSS, the effect of RSS on cell proliferation in the presence of TGF-β₁, induction of RSS-producing enzymes by TGF-β₁, and intracellular signal pathways that mediate this induction. The results suggest that TGF-β₁ increased intracellular RSS levels to modulate its inhibitory effect on proliferation. The increased production of RSS, probably high-molecular-mass RSS, was due to the induction of cystathionine γ-lyase and cystathionine β-synthase, which are RSS-producing enzymes, and the induction was mediated by the ALK5-Smad2/3/4 and ALK5-Smad2/3-ATF4 pathways in vascular endothelial cells. TGF-β₁ regulates vascular endothelial cell functions such as proliferation and fibrinolytic activity; intracellular high-molecular-mass RSS, which are increased by TGF-β₁, may modulate the regulation activity in vascular endothelial cells.     

The Effects of Aβ1-42 Binding to the SARS-CoV-2 Spike Protein S1 Subunit and Angiotensin-Converting Enzyme 2

Increasing evidence suggests that elderly people with dementia are vulnerable to the development of severe coronavirus disease 2019 (COVID-19). In Alzheimer’s disease (AD), the major form of dementia, β-amyloid (Aβ) levels in the blood are increased; however, the impact of elevated Aβ levels on the progression of COVID-19 remains largely unknown. Here, our findings demonstrate that Aβ_1-42, but not Aβ_1-40, bound to various viral proteins with a preferentially high affinity for the spike protein S1 subunit (S1) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the viral receptor, angiotensin-converting enzyme 2 (ACE2). These bindings were mainly through the C-terminal residues of Aβ_1-42. Furthermore, Aβ_1-42 strengthened the binding of the S1 of SARS-CoV-2 to ACE2 and increased the viral entry and production of IL-6 in a SARS-CoV-2 pseudovirus infection model. Intriguingly, data from a surrogate mouse model with intravenous inoculation of Aβ_1-42 show that the clearance of Aβ_1-42 in the blood was dampened in the presence of the extracellular domain of the spike protein trimers of SARS-CoV-2, whose effects can be prevented by a novel anti-Aβ antibody. In conclusion, these findings suggest that the binding of Aβ_1-42 to the S1 of SARS-CoV-2 and ACE2 may have a negative impact on the course and severity of SARS-CoV-2 infection. Further investigations are warranted to elucidate the underlying mechanisms and examine whether reducing the level of Aβ_1-42 in the blood is beneficial to the fight against COVID-19 and AD.     

Serotonin Promotes Serum Albumin Interaction with the Monomeric Amyloid β Peptide

Prevention of amyloid β peptide (Aβ) deposition via facilitation of Aβ binding to its natural depot, human serum albumin (HSA), is a promising approach to preclude Alzheimer’s disease (AD) onset and progression. Previously, we demonstrated the ability of natural HSA ligands, fatty acids, to improve the affinity of this protein to monomeric Aβ by a factor of 3 (BBRC, 510(2), 248–253). Using plasmon resonance spectroscopy, we show here that another HSA ligand related to AD pathogenesis, serotonin (SRO), increases the affinity of the Aβ monomer to HSA by a factor of 7/17 for Aβ₄₀/Aβ₄₂, respectively. Meanwhile, the structurally homologous SRO precursor, tryptophan (TRP), does not affect HSA’s affinity to monomeric Aβ, despite slowdown of the association and dissociation processes. Crosslinking with glutaraldehyde and dynamic light scattering experiments reveal that, compared with the TRP-induced effects, SRO binding causes more marked changes in the quaternary structure of HSA. Furthermore, molecular docking reveals distinct structural differences between SRO/TRP complexes with HSA. The disintegration of the serotonergic system during AD pathogenesis may contribute to Aβ release from HSA in the central nervous system due to impairment of the SRO-mediated Aβ trapping by HSA.     

Binding of Amyloid β(1–42)-Calmodulin Complexes to Plasma Membrane Lipid Rafts in Cerebellar Granule Neurons Alters Resting Cytosolic Calcium Homeostasis

Lipid rafts are a primary target in studies of amyloid β (Aβ) cytotoxicity in neurons. Exogenous Aβ peptides bind to lipid rafts, which in turn play a key role in Aβ uptake, leading to the formation of neurotoxic intracellular Aβ aggregates. On the other hand, dysregulation of intracellular calcium homeostasis in neurons has been observed in Alzheimer’s disease (AD). In a previous work, we showed that Aβ(1–42), the prevalent Aβ peptide found in the amyloid plaques of AD patients, binds with high affinity to purified calmodulin (CaM), with a dissociation constant ≈1 nM. In this work, to experimentally assess the Aβ(1–42) binding capacity to intracellular CaM, we used primary cultures of mature cerebellar granule neurons (CGN) as a neuronal model. Our results showed a large complexation of submicromolar concentrations of Aβ(1–42) dimers by CaM in CGN, up to 120 ± 13 picomoles of Aβ(1–42) /2.5 × 10⁶ cells. Using fluorescence microscopy imaging, we showed an extensive co-localization of CaM and Aβ(1–42) in lipid rafts in CGN stained with up to 100 picomoles of Aβ(1–42)-HiLyteTM-Fluor555 monomers. Intracellular Aβ(1–42) concentration in this range was achieved by 2 h incubation of CGN with 2 μM Aβ(1–42), and this treatment lowered the resting cytosolic calcium of mature CGN in partially depolarizing 25 mM potassium medium. We conclude that the primary cause of the resting cytosolic calcium decrease is the inhibition of L-type calcium channels of CGN by Aβ(1–42) dimers, whose activity is inhibited by CaM:Aβ(1–42) complexes bound to lipid rafts.     

Ionic Environment Affects Biomolecular Interactions of Amyloid-β: SPR Biosensor Study

In early stages of Alzheimer’s disease (AD), amyloid beta (Aβ) accumulates in the mitochondrial matrix and interacts with mitochondrial proteins, such as cyclophilin D (cypD) and 17β-hydroxysteroid dehydrogenase 10 (17β-HSD10). Multiple processes associated with AD such as increased production or oligomerization of Aβ affect these interactions and disbalance the equilibrium between the biomolecules, which contributes to mitochondrial dysfunction. Here, we investigate the effect of the ionic environment on the interactions of Aβ (Aβ_1–40, Aβ_1–42) with cypD and 17β-HSD10 using a surface plasmon resonance (SPR) biosensor. We show that changes in concentrations of K⁺ and Mg²⁺ significantly affect the interactions and may increase the binding efficiency between the biomolecules by up to 35% and 65% for the interactions with Aβ_1–40 and Aβ_1–42, respectively, in comparison with the physiological state. We also demonstrate that while the binding of Aβ_1–40 to cypD and 17β-HSD10 takes place preferentially around the physiological concentrations of ions, decreased concentrations of K⁺ and increased concentrations of Mg²⁺ promote the interaction of both mitochondrial proteins with Aβ_1–42. These results suggest that the ionic environment represents an important factor that should be considered in the investigation of biomolecular interactions taking place in the mitochondrial matrix under physiological as well as AD-associated conditions.     

Live Cell FRET Imaging Reveals Amyloid β-Peptide Oligomerization in Hippocampal Neurons

Amyloid β-peptide (Aβ) oligomerization is believed to contribute to the neuronal dysfunction in Alzheimer disease (AD). Despite decades of research, many details of Aβ oligomerization in neurons still need to be revealed. Förster resonance energy transfer (FRET) is a simple but effective way to study molecular interactions. Here, we used a confocal microscope with a sensitive Airyscan detector for FRET detection. By live cell FRET imaging, we detected Aβ42 oligomerization in primary neurons. The neurons were incubated with fluorescently labeled Aβ42 in the cell culture medium for 24 h. Aβ42 were internalized and oligomerized in the lysosomes/late endosomes in a concentration-dependent manner. Both the cellular uptake and intracellular oligomerization of Aβ42 were significantly higher than for Aβ40. These findings provide a better understanding of Aβ42 oligomerization in neurons.     

Cytotoxic Aβ Protofilaments Are Generated in the Process of Aβ Fibril Disaggregation

Significant research on Alzheimer’s disease (AD) has demonstrated that amyloid β (Aβ) oligomers are toxic molecules against neural cells. Thus, determining the generation mechanism of toxic Aβ oligomers is crucial for understanding AD pathogenesis. Aβ fibrils were reported to be disaggregated by treatment with small compounds, such as epigallocatechin gallate (EGCG) and dopamine (DA), and a loss of fibril shape and decrease in cytotoxicity were observed. However, the characteristics of intermediate products during the fibril disaggregation process are poorly understood. In this study, we found that cytotoxic Aβ aggregates are generated during a moderate disaggregation process of Aβ fibrils. A cytotoxicity assay revealed that Aβ fibrils incubated with a low concentration of EGCG and DA showed higher cytotoxicity than Aβ fibrils alone. Atomic force microscopy imaging and circular dichroism spectrometry showed that short and narrow protofilaments, which were highly stable in the β-sheet structure, were abundant in these moderately disaggregated samples. These results indicate that toxic Aβ protofilaments are generated during disaggregation from amyloid fibrils, suggesting that disaggregation of Aβ fibrils by small compounds may be one of the possible mechanisms for the generation of toxic Aβ aggregates in the brain.     

Oligomeric and Fibrillar Species of Aβ42 Diversely Affect Human Neural Stem Cells

Amyloid-β 42 peptide (Aβ_1-42 (Aβ42)) is well-known for its involvement in the development of Alzheimer’s disease (AD). Aβ42 accumulates and aggregates in fibers that precipitate in the form of plaques in the brain causing toxicity; however, like other forms of Aβ peptide, the role of these peptides remains unclear. Here we analyze and compare the effects of oligomeric and fibrillary Aβ42 peptide on the biology (cell death, proliferative rate, and cell fate specification) of differentiating human neural stem cells (hNS1 cell line). By using the hNS1 cells we found that, at high concentrations, oligomeric and fibrillary Aβ42 peptides provoke apoptotic cellular death and damage of DNA in these cells, but Aβ42 fibrils have the strongest effect. The data also show that both oligomeric and fibrillar Aβ42 peptides decrease cellular proliferation but Aβ42 oligomers have the greatest effect. Finally, both, oligomers and fibrils favor gliogenesis and neurogenesis in hNS1 cells, although, in this case, the effect is more prominent in oligomers. All together the findings of this study may contribute to a better understanding of the molecular mechanisms involved in the pathology of AD and to the development of human neural stem cell-based therapies for AD treatment.     

Biphasic α2β1 Integrin Expression in Breast Cancer Metastasis to Bone

Integrins participate in the pathogenesis and progression of tumors at many stages during the metastatic cascade. However, current evidence for the role of integrins in breast cancer progression is contradictory and seems to be dependent on tumor stage, differentiation status, and microenvironmental influences. While some studies suggest that loss of α2β1 enhances cancer metastasis, other studies suggest that this integrin is pro-tumorigenic. However, few studies have looked at α2β1 in the context of bone metastasis. In this study, we aimed to understand the role of α2β1 integrin in breast cancer metastasis to bone. To address this, we utilized in vivo models of breast cancer metastasis to bone using MDA-MB-231 cells transfected with an α2 expression plasmid (MDA-OEα2). MDA cells overexpressing the α2 integrin subunit had increased primary tumor growth and dissemination to bone but had no change in tumor establishment and bone destruction. Further in vitro analysis revealed that tumors in the bone have decreased α2β1 expression and increased osteolytic signaling compared to primary tumors. Taken together, these data suggest an inverse correlation between α2β1 expression and bone-metastatic potential. Inhibiting α2β1 expression may be beneficial to limit the expansion of primary tumors but could be harmful once tumors have established in bone.