Neuroprotective actions of norepinephrine in neurological diseases.

Precise control of norepinephrine (NE) levels and NE-receptor interaction is crucial for proper function of the brain. Much evidence for this view comes from experimental studies that indicate an important role for NE in the pathophysiology and treatment of various conditions, including cognitive dysfunction, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and sleep disorders. NE provides neuroprotection against several types of insults in multiple ways. It abrogates oxidative stress, attenuates neuroinflammatory responses in neurons and glial cells, reduces neuronal and glial cell activity, promotes autophagy, and ameliorates apoptotic responses to a variety of insults. It is beneficial for the treatment of neurodegenerative diseases because it improves the generation of neurotrophic factors, promotes neuronal survival, and plays an important role in the regulation of adult neurogenesis. This review aims to present the evidence supporting a principal role for NE in neuroprotection, and molecular mechanisms of neuroprotection.

Reduction of advanced tau-mediated memory deficits by the MAP kinase p38γ.

Hyperphosphorylation of the neuronal tau protein contributes to Alzheimer's disease (AD) by promoting tau pathology and neuronal and cognitive deficits. In contrast, we have previously shown that site-specific tau phosphorylation can inhibit toxic signals induced by amyloid-ß (Aß) in mouse models. The post-synaptic mitogen-activated protein (MAP) kinase p38γ mediates this site-specific phosphorylation on tau at Threonine-205 (T205). Using a gene therapeutic approach, we draw on this neuroprotective mechanism to improve memory in two Aß-dependent mouse models of AD at stages when advanced memory deficits are present. Increasing activity of post-synaptic kinase p38γ that targets T205 in tau reduced memory deficits in symptomatic Aß-induced AD models. Reconstitution experiments with wildtype human tau or phosphorylation-deficient tauT205A showed that T205 modification is critical for downstream effects of p38γ that prevent memory impairment in APP-transgenic mice. Furthermore, genome editing of the T205 codon in the murine Mapt gene showed that this single side chain in endogenous tau critically modulates memory deficits in APP-transgenic Alzheimer's mice. Ablating the protective effect of p38γ activity by genetic p38γ deletion in a tau transgenic mouse model that expresses non-pathogenic tau rendered tau toxic and resulted in impaired memory function in the absence of human Aß. Thus, we propose that modulating neuronal p38γ activity serves as an intrinsic tau-dependent therapeutic approach to augment compromised cognition in advanced dementia.

Current anti-Alzheimer's disease effect of natural products and their principal targets.

Various bioactive substances isolated from natural products play a pivotal role in the prevention and cure of neurodegenerative diseases, such as Alzheimer's disease. Currently, there are many theories about the pathogenesis of this disease. In this review we discuss among them, the cholinergic hypotheses, the Aß toxicity hypothesis, and the tau dysfunction hypothesis. Multiple potential targets are a focus for the development of anti-AD drugs. There is an urgent need to develop more effective therapies to treat and delay the onset of the disease and to find safe and effective drugs. In this review, the recent progress of anti-AD effects and their principal targets are updated.

Nonsteroidal anti-inflammatory drugs attenuate amyloid-ß protein-induced actin cytoskeletal reorganization through Rho signaling modulation.

Amyloid-ß protein (Aß) neurotoxicity occurs along with the reorganization of the actin-cytoskeleton through the activation of the Rho GTPase pathway. In addition to the classical mode of action of the non-steroidal anti-inflammatory drugs (NSAIDs), indomethacin, and ibuprofen have Rho-inhibiting effects. In order to evaluate the role of the Rho GTPase pathway on Aß-induced neuronal death and on neuronal morphological modifications in the actin cytoskeleton, we explored the role of NSAIDS in human-differentiated neuroblastoma cells exposed to Aß. We found that Aß induced neurite retraction and promoted the formation of different actin-dependent structures such as stress fibers, filopodia, lamellipodia, and ruffles. In the presence of Aß, both NSAIDs prevented neurite collapse and formation of stress fibers without affecting the formation of filopodia and lamellipodia. Similar results were obtained when the downstream effector, Rho kinase inhibitor Y27632, was applied in the presence of Aß. These results demonstrate the potential benefits of the Rho-inhibiting NSAIDs in reducing Aß-induced effects on neuronal structural alterations.

SKN-1 is indispensable for protection against Aß-induced proteotoxicity by a selenopeptide derived from Cordyceps militaris.

Oxidative stress (OS) and disruption of proteostasis caused by aggregated proteins are the primary causes of cell death in various diseases. Selenopeptides have shown the potential to control OS and alleviate inflammatory damage, suggesting promising therapeutic applications. However, their potential function in inhibiting proteotoxicity is not yet fully understood. To address this gap in knowledge, this study aimed to investigate the effects and underlying mechanisms of the selenopeptide VPRKL(Se)M on amyloid ß protein (Aß) toxicity in transgenic Caenorhabditis elegans. The results revealed that supplementation with VPRKL(Se)M can alleviate Aß-induced toxic effects in the transgenic C. elegans model. Moreover, the addition of VPRKL(Se)M inhibited the Aß aggregates formation, reduced the reactive oxygen species (ROS) levels, and ameliorated the overall proteostasis. Importantly, we found that the inhibitory effects of VPRKL(Se)M on Aß toxicity and activation of the unfolded protein are dependent on skinhead-1 (SKN-1). These findings suggested that VPRKL(Se)M is a potential bioactive agent for modulating SKN-1, which subsequently improves proteostasis and reduces OS. Collectively, the findings from the current study suggests VPRKL(Se)M may play a critical role in preventing protein disorder and related diseases.

Indole-3 Carbinol and Diindolylmethane Mitigated ß-Amyloid-Induced Neurotoxicity and Acetylcholinesterase Enzyme Activity: In Silico, In Vitro, and Network Pharmacology Study.

Background: Alzheimer's disease (AD) is a neurodegenerative disease characterized by beta-amyloid (Aß) deposition and increased acetylcholinesterase (AchE) enzyme activities. Indole 3 carbinol (I3C) and diindolylmethane (DIM) are reported to have neuroprotective activities against various neurological diseases, including ischemic stroke, Parkinson's disease, neonatal asphyxia, depression, stress, neuroinflammation, and excitotoxicity, except for AD. In the present study, we have investigated the anti-AD effects of I3C and DIM. Methods: Docking and molecular dynamic studies against AchE enzyme and network pharmacological studies were conducted for I3C and DIM. I3C and DIM's neuroprotective effects against self and AchE-induced Aß aggregation were investigated. The neuroprotective effects of I3C and DIM against Aß-induced neurotoxicity were assessed in SH-S5Y5 cells by observing cell viability and ROS. Results: Docking studies against AchE enzyme with I3C and DIM show binding efficiency of -7.0 and -10.3, respectively, and molecular dynamics studies revealed a better interaction and stability between I3C and AchE and DIM and AchE. Network pharmacological studies indicated that I3C and DIM interacted with several proteins involved in the pathophysiology of AD. Further, I3C and DIM significantly inhibited the AchE (IC50: I3C (18.98 µM) and DIM (11.84 µM)) and self-induced Aß aggregation. Both compounds enhanced the viability of SH-S5Y5 cells that are exposed to Aß and reduced ROS. Further, I3C and DIM show equipotential neuroprotection when compared to donepezil. Conclusions: Our findings indicate that both I3C and DIM show anti-AD effects by inhibiting the Aß induced neurotoxicity and AchE activities.

Protein retention in the endoplasmic reticulum rescues Aß toxicity in Drosophila.

Amyloid ß (Aß) accumulation is a hallmark of Alzheimer's disease. In adult Drosophila brains, human Aß overexpression harms climbing and lifespan. It's uncertain whether Aß is intrinsically toxic or activates downstream neurodegeneration pathways. Our study uncovers a novel protective role against Aß toxicity: intra-endoplasmic reticulum (ER) protein accumulation with a focus on laminin and collagen subunits. Despite high Aß, laminin B1 (LanB1) overexpression robustly counters toxicity, suggesting a potential Aß resistance mechanism. Other laminin subunits and collagen IV also alleviate Aß toxicity; combining them with LanB1 augments the effect. Imaging reveals ER retention of LanB1 without altering Aß secretion. LanB1's rescue function operates independently of the IRE1α/XBP1 ER stress response. ER-targeted GFP overexpression also mitigates Aß toxicity, highlighting broader ER protein retention advantages. Proof-of-principle tests in murine hippocampal slices using mouse Lamb1 demonstrate ER retention in transduced cells, indicating a conserved mechanism. Though ER protein retention generally harms, it could paradoxically counter neuronal Aß toxicity, offering a new therapeutic avenue for Alzheimer's disease.

Cobalt nanoparticles induce mitochondrial damage and ß-amyloid toxicity via the generation of reactive oxygen species.

Exposure to cobalt nanoparticles (CoNPs) has been associated with neurodegenerative disorders, while the mitochondrial-associated mechanisms that mediate their neurotoxicity have yet to be fully characterized. In this study, we reported that CoNPs exposure reduced the survival and lifespan in the nematodes, Caenorhabditis elegans (C. elegans). Moreover, exposure to CoNPs aggravated the induction of paralysis and the aggregation of ß-amyloid (Aß). These effects were accompanied by reactive oxygen species (ROS) overproduction, ATP reduction as well as mitochondrial fragmentation. Dynamin-related protein 1 (drp-1) activation and ensuing mitochondrial fragmentation have been shown to be associated with CoNPs-reduced survival. In order to address the role of mitochondrial damage and ROS production in CoNPs-induced Aß toxicity, the mitochondrial reactive oxygen species scavenger mitoquinone (Mito Q) was used. Our results showed that Mito Q pretreatment alleviated CoNPs-induced ROS generation, rescuing mitochondrial dysfunction, thereby lessening the CoNPs-induced Aß toxicity. Taken together, we show for the first time, that increasing of ROS and the upregulation of drp-1 lead to CoNPs-induced Aß toxicity. Our novel findings provide in vivo evidence for the mechanisms of environmental toxicant-induced Aß toxicity, and can afford new modalities for the prevention and treatment of CoNPs-induced neurodegeneration.

Aesculin offers increased resistance against oxidative stress and protective effects against Aß-induced neurotoxicity in Caenorhabditis elegans.

Aesculin, a coumarin compound, is one of the major active ingredients of traditional Chinese herbal medicine Qinpi (Cortex Fraxini), which has been reported to exhibit antioxidative, anti-inflammatory and neuroprotective properties against oxidative stress and cellular apoptosis. However, the regulatory mechanisms remain poorly characterized in vivo. This research was performed to explore the underlying molecular mechanisms behind aesculin response conferring oxidative stress resistance, and the protective effects on amyloid-ß (Aß)-mediated neurotoxicity in Caenorhabditis elegans. Study indicated that aesculin plays the protective roles for C. elegans against oxidative stress and Aß-mediated neurotoxicity and reduces the elevated ROS and MDA contents through enhancement of antioxidant defenses. The KEGG pathway analysis suggested that the differentially expressed genes are mainly involved in longevity regulating pathway, and the nuclear translocation of DAF-16 and the RNAi of daf-16 and hsf-1 indicated that DAF-16 and HSF-1 play critical roles in integrating upstream signals and inducing the expressions of stress resistance-related genes. Furthermore, the up-regulated expressions of their target genes such as sod-3 and hsp-16.2 were confirmed in transgenic GFP reporter strains CF1553 and CL2070, respectively. These results indicated that the regulators DAF-16 and HSF-1 elevate the stress resistance of C. elegans by modulating stress-responsive genes. Further experiments revealed that aesculin is capable of suppressing Aß-induced oxidative stress and apoptosis and improves chemosensory behavior dysfunction in Aß-transgenic nematodes. In summary, this study suggested that aesculin offers increased resistance against oxidative stress and protective effects against Aß-induced neurotoxicity through activation of stress regulators DAF-16 and HSF-1 in nematodes.

Correlation between Sialylation Status and Cell Susceptibility to Amyloid Toxicity.

The interaction between the cell membrane and misfolded protein species plays a crucial role in the development of neurodegeneration. This study was designed to clarify the relationship between plasma membrane composition in terms of the differently linked sialic acid (Sia) content and cell susceptibility to toxic and misfolded Aß-42 peptides. The sialylation status in different cell lines was investigated by lectin histochemistry and confocal immunofluorescence and then correlated with the different propensities to bind amyloid fibrils and with the relative cell susceptibility to amyloid damage. This study reveals that expressions of Sias α2,3 and α2,6 linked to galactose/N-acetyl-galactosamine, and PolySia are positively correlated with Aß-42-induced cell toxicity. PolySia shows an early strong interaction with amyloid fibrils, favoring their binding to GM1 ganglioside containing α2,3 galactose-linked Sia and a loss of cell viability. Our findings demonstrate that cell lines with a prevailing plastic neuron-like phenotype and high monoSia and PolySia contents are highly susceptible to amyloid Aß-42 toxicity. This toxicity may involve a change in neuron metabolism and promote a compensative/protective increase in PolySia, which, in turn, could favor amyloid binding to GM1, thus exacerbating cell dysmetabolism and further amyloid aggregation.

Assembly of redox active metallo-enzymes and metallo-peptides on electrodes: Abiological constructs to probe natural processes.

Redox active metallo-proteins and metallo-peptides attached to self-assembled monolayers (SAM) of thiols on Au electrodes or constituting the SAM on Au electrodes can provide unique opportunities to investigate a range of complicated biological phenomena in controlled abiological constructs. In addition to conventional biochemical tools like site-directed mutagenesis, these constructs allow control over electron transfer (ET) processes, micro solvation (SAM design), folding/misfolding and orientation of these biological entities. This article presents a review of the work done by this group in creating abiological bio-inspired SAM on Au electrodes to probe several important biological processes where redox plays or might play a major role. These include stabilisation of different morphologies of Aß peptides and which allow investigation of the reactivity of their Cu/Zn/heme-bound forms, determination of both outer-sphere and inner-sphere reorganisation energies of cytochrome c along with deciphering the role of the fluxional methionine and finally creation of bio-chemical constructs of cytochrome c oxidase which not only reduce O2 selectively to H2O efficiently but also provide key insights in O2 reduction mechanism which has aided the development of efficient artificial catalysts.

Early Mitochondrial Fragmentation and Dysfunction in a Drosophila Model for Alzheimer's Disease.

Many different cellular systems and molecular processes become compromised in Alzheimer's disease (AD) including proteostasis, autophagy, inflammatory responses, synapse and neuronal circuitry, and mitochondrial function. We focused in this study on mitochondrial dysfunction owing to the toxic neuronal environment produced by expression of Aß42, and its relationship to other pathologies found in AD including increased neuronal apoptosis, plaque deposition, and memory impairment. Using super-resolution microscopy, we have assayed mitochondrial status in the three distinct neuronal compartments (somatic, dendritic, axonal) of mushroom body neurons of Drosophila expressing Aß42. The mushroom body neurons comprise a major center for olfactory memory formation in insects. We employed calcium imaging to measure mitochondrial function, immunohistochemical and staining techniques to measure apoptosis and plaque formation, and olfactory classical conditioning to measure learning. We found that mitochondria become fragmented at a very early age along with decreased function measured by mitochondrial calcium entry. Increased apoptosis and plaque deposition also occur early, yet interestingly, a learning impairment was found only after a much longer period of time-10 days, which is a large fraction of the fly's lifespan. This is similar to the pronounced delay between cellular pathologies and the emergence of a memory dysfunction in humans. Our studies are consistent with the model that mitochondrial dysfunction and/or other cellular pathologies emerge at an early age and lead to much later learning impairments. The results obtained further develop this Drosophila model as a useful in vivo system for probing the mechanisms by which Aß42 produces mitochondrial and other cellular toxicities that produce memory dysfunction.

The role of CREB and BDNF in neurobiology and treatment of Alzheimer's disease.

Alzheimer's disease (AD) is the most common form of dementia worldwide. ß-amyloid peptide (Aß) is currently assumed to be the main cause of synaptic dysfunction and cognitive impairments in AD, but the molecular signaling pathways underlying its neurotoxic consequences have not yet been completely explored. Additional investigations regarding these pathways will contribute to development of new therapeutic targets. In context, developing evidence suggest that Aß decreases brain-derived neurotrophic factor (BDNF) mostly by lowering phosphorylated cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) protein. In fact, it has been observed that brain or serum levels of BDNF appear to be beneficial markers for cognitive condition. In addition, the participation of transcription mediated by CREB has been widely analyzed in the memory process and AD development. Designing pharmacologic or genetic therapeutic approaches based on the targeting of CREB-BDNF signaling could be a promising treatment potential for AD. In this review, we summarize data demonstrating the role of CREB-BDNF signaling pathway in cognitive status and mediation of Aß toxicity in AD. Finally, we also focus on the developing intervention methods for improvement of cognitive decline in AD based on targeting of CREB-BDNF pathway.

G37V mutation of Aß42 induces a nontoxic ellipse-like aggregate: An in vitro and in silico study.

The glycine zipper motif at the C-terminus of the ß-amyloid (Aß) peptide have been shown to strongly influence the formation of neurotoxic aggregates. A previous study showed that the G37L mutation dramatically reduces the Aß toxicity in vivo and in vitro. However, the primary cause and mechanism of the glycine zipper motif on Aß properties remain unknown. To gain molecular insights into the impact of glycine zipper on Aß properties, we substituted the residue 37 of Glycine by Valine and studied the structural and biochemical properties of G37V mutation, Aß42(37V), by using in vitro and in silico approaches. Unlike G37L mutation, the G37V mutation reduced toxicity substantially but did not significantly accelerate the aggregation rate or change the content of secondary structures. Further TEM analyses showed that the G37V mutation formed an ellipse-like aggregate rather than a network-like fibril as wild type or G37L mutation of Aß42 form. This different aggregation morphology may be highly linked with the reduction of toxicity. To gain the insight for the different properties of Aß42(37V), we studied the structure of Aß42 and G37V mutation using the replica exchange molecular dynamics simulation. Our results demonstrate that although the overall secondary structure population is similar with Aß42 and Aß42(G37V), Aß42(G37V) shows an increase in the ß-turn and ß-hairpin at residues 36-37 and the flexibility of the Asp23-Lys28 salt bridge. These unique structural features may be the possible reason to account for the ellipse-like morphology.

Cranberry extract supplementation exerts preventive effects through alleviating Aß toxicity in Caenorhabditis elegans model of Alzheimer's disease.

Cranberry extract (CBE) rich in polyphenols are potent to delay paralysis induced by alleviating ß-amyloid (Aß) toxicity in C. elegans model of Alzheimer's disease (AD). In order to better apply CBE as an anti-AD agent efficiently, we sought to deterrmine whether preventive or therapeutic effect contributes more prominently toward CBE's anti-AD activity. As the level of Aß toxicity and memory health are two major pathological parameters in AD, in the present study, we compared the effects of CBE on Aß toxicity and memory health in the C. elegans AD model treated with preventive and therapeutic protocols. Our results revealed that CBE prominently showed the preventive efficacy, providing a basis for further investigation of these effects in mammals.

Nature of the neurotoxic membrane actions of amyloid-ß on hippocampal neurons in Alzheimer's disease.

The mechanism by which amyloid-ß (Aß) produces brain dysfunction in patients with Alzheimer's disease is largely unknown. According to previous studies, Aß might share perforating properties with gramicidin, a well-accepted membrane-disrupting peptide. Therefore, we hypothesize that the key steps leading to synaptotoxicity by Aß and gramicidin involve peptide aggregation, pore formation, and calcium dysregulation. Here, we show that Aß and gramicidin form aggregates enriched in ß-sheet structures using electron microscopy, and Thioflavin and Congo Red staining techniques. Also, we found that Aß and gramicidin display fairly similar actions in hippocampal cell membranes, i.e. inducing Ca(2+) entry and synaptoxicity characterized by the loss of synaptic proteins and a decrease in neuronal viability. These effects were not observed in a Ca(2+) free solution, indicating that both Aß and gramicidin induce neurotoxicity by a Ca(2+)-dependent mechanism. Using combined perforated patch clamp and imaging recordings, we found that only Aß produced a perforation that progressed from a small (Cl(-)-selective pore) to a larger perforation that allowed the entry of fluorescent molecules. Therefore, based on these results, we propose that the perforation at the plasma membrane by Aß is a dynamic process that is critical in producing neurotoxicity similar to that found in the brains of AD patients.

The central molecular clock is robust in the face of behavioural arrhythmia in a Drosophila model of Alzheimer's disease.

Circadian behavioural deficits, including sleep irregularity and restlessness in the evening, are a distressing early feature of Alzheimer's disease (AD). We have investigated these phenomena by studying the circadian behaviour of transgenic Drosophila expressing the amyloid beta peptide (Aß). We find that Aß expression results in an age-related loss of circadian behavioural rhythms despite ongoing normal molecular oscillations in the central clock neurons. Even in the absence of any behavioural correlate, the synchronised activity of the central clock remains protective, prolonging lifespan, in Aß flies just as it does in control flies. Confocal microscopy and bioluminescence measurements point to processes downstream of the molecular clock as the main site of Aß toxicity. In addition, there seems to be significant non-cell-autonomous Aß toxicity resulting in morphological and probably functional signalling deficits in central clock neurons.

Different effects of Alzheimer's peptide Aß(1-40) oligomers and fibrils on supported lipid membranes.

Beta-amyloid (1-40) is one of the two most abundant species of amyloid-beta peptides present as fibrils in the extracellular senile plaques in the brain of Alzheimer's patients. Recently, the molecular aggregates constituting the early stage of fibril formation, i.e., oligomers and protofibrils, have been investigated as the main responsible for amyloid-beta cytotoxic effect. The molecular mechanism leading to neurodegeneration is still under debate, and it is common opinion that it may reside in the interaction between amyloid species and the neural membrane. In this investigation Atomic Force Microscopy and spectroscopy have been used to understand how structural (and mechanical) properties of POPC/POPS lipid bilayers, simulating the phospholipid composition and negative net charge of neuritic cell membranes, are influenced by the interaction with Aß(1-40), in different stages of the peptide aggregation. Substantial differences in the damage caused to the lipid bilayers have been observed, confirming the toxic effect exerted especially by Aß(1-40) prefibrillar oligomers.

Dose-dependent improvements in learning and memory deficits in APPPS1-21 transgenic mice treated with the orally active Aß toxicity inhibitor SEN1500.

In the Alzheimer's disease (AD) brain, accumulation of Aß1-42 peptides is suggested to initiate a cascade of pathological events. To date, no treatments are available that can reverse or delay AD-related symptoms in patients. In the current study, we introduce a new Aß toxicity inhibitor, SEN1500, which in addition to its block effect on Aß1-42 toxicity in synaptophysin assays, can be administered orally and cross the blood-brain barrier without adverse effects in mice. In a different set of animals, APPPS1-21 mice were fed with three different doses of SEN1500 (1 mg/kg, 5 mg/kg and 20 mg/kg) for a period of 5 months. Cognition was assessed in a variety of behavioral tests (Morris water maze, social recognition, conditioned taste aversion and passive avoidance). Results suggest a positive effect on cognition with 20 mg/kg SEN1500 compared to control APPPS1-21 mice. However, no changes in soluble or insoluble Aß1-40 and Aß1-42 were detected in the brains of SEN1500-fed mice. SEN1500 also attenuated the effect of Aß1-42 on synaptophysin levels in mouse cortical neurons, which indicated that the compound blocked the synaptic toxicity of Aß1-42. In vitro and in vivo effects presented here suggest that SEN1500 could be an interesting AD therapeutic.