Neurotoxic mechanisms caused by the Alzheimer's disease-linked Swedish amyloid precursor protein mutation: oxidative stress, caspases, and the JNK pathway

Association between insulin and Nrf2 signalling pathway in Alzheimer's disease: A molecular landscape

Insulin, a well-known hormone, has been implicated as a regulator of blood glucose levels for almost a century now. Over the past few decades, the non-glycemic actions of insulin i.e. neuronal growth and proliferation have been extensively studied. In 2005, Dr. Suzanne de La Monte and her team reported that insulin might be involved in the pathogenesis of Alzheimer's Disease (AD) and thus coined a term "Type-3 diabetes" This hypothesis was supported by several subsequent studies. The nuclear factor erythroid 2- related factor 2 (Nrf2) triggers a cascade of events under the regulation of distinct mechanisms including protein stability, phosphorylation and nuclear cytoplasmic shuttling, finally leading to the protection against oxidative damage. The Nrf2 pathway has been investigated extensively in relevance to neurodegenerative disorders, particularly AD. Many studies have indicated a strong correlation between insulin and Nrf2 signalling pathways both in the periphery and the brainbut merely few of them have focused on elucidating their inter-connective role in AD. The present review emphasizes key molecular pathways that correlate the role of insulin with Nrf2 during AD. The review has also identified key unexplored areas that could be investigated in future to further establish the insulin and Nrf2 influence in AD.

JNK Activation in Alzheimer's Disease Is Driven by Amyloid β and Is Associated with Tau Pathology

c-Jun N-terminal kinase 3 (JNK3) is suggested to play a key role in neurodegenerative disorders, especially in Alzheimer's disease (AD). However, it remains unclear whether JNK or amyloid β (Aβ) appears first in the disease onset. Postmortem brain tissues from four dementia subtypes of patients (frontotemporal dementia, Lewy body dementia, vascular dementia, and AD) were used to measure activated JNK (pJNK) and Aβ levels. pJNK expression is significantly increased in AD; however, similar pJNK expression was found in other dementias. Furthermore, there was a significant correlation, co-localization, and direct interaction between pJNK expression and Aβ levels in AD. Significant increased levels of pJNK were also found in Tg2576 mice, a model of AD. In this line, Aβ₄₂ intracerebroventricular injection in wild-type mice was able to induce a significant elevation of pJNK levels. JNK3 overexpression, achieved by intrahippocampal injection of an adeno-associated viral vector expressing this protein, was enough to induce cognitive deficiencies and precipitate Tau aberrant misfolding in Tg2576 mice without accelerating amyloid pathology. JNK3 overexpression may therefore be triggered by increased Aβ. The latter, together with subsequent involvement of Tau pathology, may be underlying cognitive alterations in early stages of AD.

Role of Metal Cations of Copper, Iron, and Aluminum and Multifunctional Ligands in Alzheimer's Disease: Experimental and Computational Insights

Alzheimer's disease (AD) is the most common form of dementia, affecting millions of people around the world. Even though the causes of AD are not completely understood due to its multifactorial nature, some neuropathological hallmarks of its development have been related to the high concentration of some metal cations. These roles include the participation of these metal cations in the production of reactive oxygen species, which have been involved in neuronal damage. In order to avoid the increment in the oxidative stress, multifunctional ligands used to coordinate these metal cations have been proposed as a possible treatment to AD. In this review, we present the recent advances in experimental and computational works aiming to understand the role of two redox active and essential transition-metal cations (Cu and Fe) and one nonbiological metal (Al) and the recent proposals on the development of multifunctional ligands to stop or revert the damaging effects promoted by these metal cations.

Distinct effects of SDC3 and FGFRL1 on selective neurodegeneration in AD and PD

Alzheimer's disease (AD) and Parkinson's disease (PD) are age-dependent neurodegenerative disorders. There is a profound neuronal loss in the basal forebrain cholinergic system in AD and severe dopaminergic deficiency within the nigrostriatal pathway in PD. Swedish APP (APP_SWE ) and SNCA_A53T mutations promote Aβ generation and α-synuclein aggregation, respectively, and have been linked to the pathogenesis of AD and PD. However, the mechanisms underlying selective cholinergic and dopaminergic neurodegeneration in AD and PD are still unknown. We demonstrated that APP_SWE mutation enhanced Aβ generation and increased cell susceptibility to Aβ oligomer in cholinergic SN56 cells, whereas SNCA_A53T mutations promoted aggregates formation and potentiated mutant α-synuclein oligomer-induced cytotoxicity in MN9D cells. Furthermore, syndecan-3 (SDC3) and fibroblast growth factor receptor-like 1 (FGFRL1) genes were differentially expressed in SN56 and MN9D cells carrying APP_SWE or SNCA_A53T mutation. SDC3 and FGFRL1 proteins were preferentially expressed in the cholinergic nucleus and dopaminergic neurons of APP_SWE and SNCA_A53T mouse models, respectively. Finally, the knockdown of SDC3 and FGFRL1 attenuated oxidative stress-induced cell death in SN56-APP_SWE and MN9D-SNCAA53T cells. The results demonstrate that SDC3 and FGFRL1 mediated the specific effects of APP_SWE and SNCA_A53T on cholinergic and dopaminergic neurodegeneration in AD and PD, respectively. Our study suggests that SDC3 and FGFRL1 could be potential targets to alleviate the selective neurodegeneration in AD and PD.

The cellular model for Alzheimer's disease research: PC12 cells

Alzheimer's disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive decline and irreversible memory impairment. Currently, several studies have failed to fully elucidate AD's cellular and molecular mechanisms. For this purpose, research on related cellular models may propose potential predictive models for the drug development of AD. Therefore, many cells characterized by neuronal properties are widely used to mimic the pathological process of AD, such as PC12, SH-SY5Y, and N2a, especially the PC12 pheochromocytoma cell line. Thus, this review covers the most systematic essay that used PC12 cells to study AD. We depict the cellular source, culture condition, differentiation methods, transfection methods, drugs inducing AD, general approaches (evaluation methods and metrics), and in vitro cellular models used in parallel with PC12 cells.

Treponema denticola Induces Neuronal Apoptosis by Promoting Amyloid-β Accumulation in Mice

Background: Neuronal apoptosis is a major contributor to Alzheimer's disease (AD). Periodontitis is a significant risk factor for AD. The periodontal pathogens Porphyromonas gingivalis and Treponema denticola have been shown to initiate the hallmark pathologies and behavioral symptoms of AD. Studies have found that T. denticola infection induced Tau hyperphosphorylation and amyloid β accumulation in the hippocampi of mice. Aβ accumulation is closely associated with neuronal apoptosis. However, the roles of T. denticola in neuronal apoptosis remain unclear and its roles in AD pathology need further study. Objective: This study aimed to investigate whether oral infection with T. denticola induced alveolar bone loss and neuronal apoptosis in mice. Methods: C57BL/6 mice were orally administered with T. denticola, Micro-CT was employed to assess the alveolar bone resorption. Western blotting, quantitative PCR, and TUNEL staining were utilized to detect the apoptosis-associated changes in mouse hippocampi. N2a were co-cultured with T. denticola to verify in vivo results. Results: Mice infected with T. denticola exhibited more alveolar bone loss compared with the control mice. T. denticola oral infection induced neuronal apoptosis in hippocampi of mice. Consistent results of the apoptosis-associated protein expression were observed in N2a cells treated with T. denticola and Aβ_1-42 in vitro. However, the Aβ inhibitor reversed these results, suggesting that Aβ_1-42 mediates T. denticola infection-induced neuronal apoptosis. Conclusions: This study found that oral infected T. denticola caused alveolar bone loss, and induced neuronal apoptosis by promoting Aβ accumulation in mice, providing evidence for the link between periodontitis and AD.

c-Jun N-Terminal Kinases in Alzheimer's Disease: A Possible Target for the Modulation of the Earliest Alterations

Given the highly multifactorial origin of Alzheimer's disease (AD) neuropathology, disentangling and orderly knowing mechanisms involved in sporadic onset are arduous. Nevertheless, when the elements involved are dissected into smaller pieces, the task becomes more accessible. This review aimed to describe the link between c-Jun N-terminal Kinases (JNKs), master regulators of many cellular functions, and the early alterations of AD: synaptic loss and dysregulation of neuronal transport. Both processes have a role in the posterior cognitive decline observed in AD. The manuscript focuses on the molecular mechanisms of glutamatergic, GABA, and cholinergic synapses altered by the presence of amyloid-β aggregates and hyperphosphorylated tau, as well as on several consequences of the disruption of cellular processes linked to neuronal transport that is controlled by the JNK-JIP (c-jun NH2-terminal kinase (JNK)-interacting proteins (JIPs) complex, including the transport of AβPP or autophagosomes.

Alzheimer's Disease: A Molecular View of β-Amyloid Induced Morbific Events

Amyloid-β (Aβ) is a dynamic peptide of Alzheimer’s disease (AD) which accelerates the disease progression. At the cell membrane and cell compartments, the amyloid precursor protein (APP) undergoes amyloidogenic cleavage by β- and γ-secretases and engenders the Aβ. In addition, externally produced Aβ gets inside the cells by receptors mediated internalization. An elevated amount of Aβ yields spontaneous aggregation which causes organelles impairment. Aβ stimulates the hyperphosphorylation of tau protein via acceleration by several kinases. Aβ travels to the mitochondria and interacts with its functional complexes, which impairs the mitochondrial function leading to the activation of apoptotic signaling cascade. Aβ disrupts the Ca²⁺ and protein homeostasis of the endoplasmic reticulum (ER) and Golgi complex (GC) that promotes the organelle stress and inhibits its stress recovery machinery such as unfolded protein response (UPR) and ER-associated degradation (ERAD). At lysosome, Aβ precedes autophagy dysfunction upon interacting with autophagy molecules. Interestingly, Aβ act as a transcription regulator as well as inhibits telomerase activity. Both Aβ and p-tau interaction with neuronal and glial receptors elevate the inflammatory molecules and persuade inflammation. Here, we have expounded the Aβ mediated events in the cells and its cosmopolitan role on neurodegeneration, and the current clinical status of anti-amyloid therapy.

Identifying the Mechanisms and Molecular Targets of Yizhiqingxin Formula on Alzheimer's Disease: Coupling Network Pharmacology with GEO Database

Background

Yizhiqingxin formula (YZQX) is a promising formula for the treatment of Alzheimer’s disease (AD) with significant clinical effects. Here, we coupled a network pharmacology approach with the Gene Expression Omnibus (GEO) database to illustrate comprehensive mechanisms and screen for molecular targets of YZQX for AD treatment.

Methods

First, active ingredients of YZQX were screened for the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database with the absorption, distribution, metabolism, and excretion (ADME) parameters. Subsequently, putative targets of active ingredients were predicted using the DrugBank database. AD-related targets were retrieved by analyzing published microarray data (accession number GSE5281). Protein–protein interaction (PPI) networks of YZQX putative targets and AD-related targets were constructed visually and merged to identify candidate targets for YZQX against AD using Cytoscape 3.7.2 software. We performed gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis to further clarify the biological functions of the candidate targets. The gene-pathway network was established to filter for key target genes.

Results

Forty-three active ingredients were identified, and 193 putative target genes were predicted. Seven hundred and ten targets related to AD were screened with |log2 FC| > 1 and P < 0.05. Based on the PPI network, 110 target genes of YZQX against AD were identified. Moreover, 32 related pathways including the PI3K-Akt signaling pathway, MAPK signaling pathway, ubiquitin-mediated proteolysis, apoptosis and the NF-kappa B signaling pathway were significantly enriched. In the gene-pathway network, MAPK1, AKT1, TP53, MDM2, EGFR, RELA, SRC, GRB2, CUL1, and MYC targets are putative core genes for YZQX in AD treatment.

Conclusion

YZQX against AD may exert its neuroprotective effect via the PI3K-Akt signaling pathway, MAPK signaling pathway, and ubiquitin-mediated proteolysis. YZQX may be a promising drug that can be used in the treatment of AD.

Protective role of Apelin-13 on amyloid β25-35-induced memory deficit; Involvement of autophagy and apoptosis process

Alzheimer's disease (AD) by progressive neurodegenerative pattern is associated with autophagy stress which is suggested as a potential cause of amyloid β (Aβ) aggregation and neural loss. Apelin-13, a neuropeptide with modulatory effect on autophagy, has been shown the beneficial effects on neural cell injuries. We investigated the effect of Apelin-13 on Aβ-induced memory deficit as well as autophagy and apoptosis processes. We performed bilateral intra-CA1 injection of Aβ25-35 alone or in combination with Apelin-13. Spatial reference and working memory was evaluated using the Morris water maze (MWM) and Y-maze tests. Hippocampus was harvested on 2, 5, 10 and 21 days after Aβ injection. The light chain 3 (LC3II/I) ratio, histone deacetylase 6 (HDAC6) level, Caspase-3 cleavage, and mTOR phosphorylation were assessed using western blot technique. Intra-CA1 injection of Aβ caused impairment of working and spatial memory. We observed higher LC3II/I ratio, cleaved caspase-3 and lower HDAC6, and p-mTOR/mTOR ratio in Aβ-treated animals. Apelin-13 provided significant protection against the destructive effects of Aβ on working and spatial memory. Apelin-13 prevented the increase of LC3II/I ratio and cleaved caspase-3 on days 10 and 21 after injection of Aβ. It also limited the Aβ-induced reduction in HDAC6 expression. This implies that Apelin-13 has suppressed both autophagy and apoptosis. Our findings suggested that the neuroprotection of Apelin-13 may be in part related to autophagy and apoptosis inhibition via the mTOR signaling pathway. Apelin-13 may be a promising approach to improve memory impairment and potentially pave the way for new therapeutic plans in AD.

The Extracellular Protein, Transthyretin Is an Oxidative Stress Biomarker

The extracellular protein, transthyretin is responsible for the transport of thyroxin and retinol binding protein complex to the various parts of the body. In addition to this transport function, transthyretin has also been involved in cardiovascular malfunctions, polyneuropathy, psychological disorders, obesity and diabetes, etc. Recent developments have evidenced that transthyretin has been associated with many other biological functions that are directly or indirectly associated with the oxidative stress, the common hallmark for many human diseases. In this review, we have attempted to address that transthyretin is associated with oxidative stress and could be an important biomarker. Potential future perspectives have also been discussed.

A pilot study on the effect of lactoferrin on Alzheimer's disease pathological sequelae: Impact of the p-Akt/PTEN pathway

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases in which the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (PKB or Akt) pathway is deregulated in response to phosphatase and tensin homolog (PTEN) overexpression. Lactoferrin (LF), a multifunctional iron-binding glycoprotein, is involved in AD pathology; however, direct evidence of its impact upon AD remains unclear. To elucidate LF's role in AD, the possible protective mechanism post-LF administration for 3 months was investigated in AD patients by observing changes in the p-Akt/PTEN pathway. AD patients showed decreased serum acetylcholine (ACh), serotonin (5-HT), antioxidant and anti-inflammatory markers, and decreased expression of Akt in peripheral blood lymphocytes (PBL), as well as PI3K, and p-Akt levels in PBL lysate; all these parameters were significantly improved after daily LF administration for 3 months. Similarly, elevated serum amyloid β (Aβ) 42, cholesterol, oxidative stress markers, IL-6, heat shock protein (HSP) 90, caspase-3, and p-tau, as well as increased expression of tau, MAPK1 and PTEN in AD patients, were significantly reduced upon LF intake. Improvement in the aforementioned AD surrogate markers post-LF treatment was reflected in enhanced cognitive function assessed by the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-Cognitive Subscale 11-item (ADAS-COG 11) questionnaires as clinical endpoints. These results provide a basis for a possible protective mechanism of LF in AD through its ability to alleviate the AD pathological cascade and cognitive decline via modulation of the p-Akt/PTEN pathway, which affects the key players of inflammation and oxidative stress that are involved in AD pathology.

Mortal engines: Mitochondrial bioenergetics and dysfunction in neurodegenerative diseases

Mitochondria are best known for their role in ATP generation. However, studies over the past two decades have shown that mitochondria do much more than that. Mitochondria regulate both necrotic and apoptotic cell death pathways, they store and therefore coordinate cellular Ca²⁺ signaling, they generate and metabolize important building blocks, by-products and signaling molecules, and they also generate and are targets of free radical species that modulate many aspects of cell physiology and pathology. Most estimates suggest that although the brain makes up only 2 percent of body weight, utilizes about 20 percent of the body's total ATP. Thus, mitochondrial dysfunction greatly impacts brain functions and is indeed associated with numerous neurodegenerative diseases. Furthermore, a number of abnormal disease-associated proteins have been shown to interact directly with mitochondria, leading to mitochondrial dysfunction and subsequent neuronal cell death. Here, we discuss the role of mitochondrial dynamics impairment in the pathological processes associated with neurodegeneration and suggest that a therapy targeting mitochondrialdysfunction holds a great promise.

DHA Selectively Protects SAMP-8-Associated Cognitive Deficits Through Inhibition of JNK

A potential role of marine n-3 polyunsaturated fatty acids (ω-3 PUFAs) has been suggested in memory, learning, and cognitive processes. Therefore, ω-3 PUFAs might be a promising treatment option, albeit controversial, for Alzheimer's disease (AD). Among the different mechanisms that have been proposed as responsible for the beneficial effects of ω-3 PUFAs, inhibition of JNK stands as a particularly interesting candidate. In the present work, it has been studied whether the administration of two different PUFAs (docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)) and a DHA-derived specialized pro-resolving lipid mediator (MaR1) is able to reverse cognitive deficits in the senescence-accelerated mouse prone 8 (SAMP8) mouse model of sporadic AD. The novel object recognition test (NORT) test showed that recognition memory was significantly impaired in SAMP8 mice, as shown by a significantly decreased discrimination index that was reversed by MaR1 and DHA. In the retention phase of the Morris water maze (MWM) task, SAMP8 mice showed memory deficit that only DHA treatment was able to reverse. pJNK levels were significantly increased in the hippocampus of SAMP8 mice compared to SAMR1 mice, and only DHA treatment was able to significantly reverse these increased pJNK levels. Similar results were found when measuring c-Jun, the main JNK substrate. Consequently to the increases in tau phosphorylation after increased pJNK, it was checked that tau phosphorylation (PHF-1) was increased in SAMP mice, and this effect was reversed after DHA treatment. Altogether, DHA could represent a new approach for the treatment of AD through JNK inhibition.

An optimized method for enrichment of whole brain-derived extracellular vesicles reveals insight into neurodegenerative processes in a mouse model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the major cause of dementia that has increased dramatically in prevalence over the past several decades. Yet many questions still surround the etiology of AD. Recently, extracellular vesicles (EVs) that transport protein, lipid, and nucleic acids from cell to cell have been implicated in the clearance and propagation of misfolded proteins. Investigation of EVs in AD progression, and their potential diagnostic utility may contribute to understanding and treating AD. However, the challenges of isolating brain-derived EVs have in part hindered these studies.

NEW METHOD

Here, we provide an optimized method for the enrichment of brain-derived EVs by iodixanol floatation density gradient for mass spectrometry analysis.

RESULTS

We demonstrate the isolation of these vesicles and the enrichment of EV proteins compared to sedimentation gradient isolation of vesicles. Moreover, comparative proteomic analysis of brain-derived EVs from healthy and AD mouse brains revealed differences in vesicular content including proteins involved in aging, immune response, and oxidation-reduction maintenance. These changes provide insight into AD-associated neurodegeneration and potential biomarkers of AD. Comparison with existing methods: Recent techniques have used sedimentation sucrose gradients to isolate EVs from brain tissue. However, here we demonstrate the advantages of floatation iodixanol density gradient isolation of small EVs, and provide evidence of EV enrichment by electron microscopy, immunoblot analysis, and quantitative mass spectrometry.

CONCLUSIONS

Together these findings offer a rigorous technique for enriching whole tissue-derived EVs for downstream analyses, and application of this approach to uncovering molecular changes in AD progression and other neurological conditions.

Evaluation of neuropathological effects of a high-fat high-sucrose diet in middle-aged male C57BL6/J mice

Metabolic dysfunction related to diet-induced obesity has recently been linked to the pathogenesis of sporadic Alzheimer's disease (AD). However, the underlying mechanisms linking obesity and AD remain unclear. The purpose of this study was to examine early alterations in brain insulin signaling, inflammatory/stress markers, and energetic stress in a model of diet-induced obesity during middle age. Male C57BL/6J mice were randomized to either a control diet (AGE n = 12) or high-fat and sucrose diet (AGE-HFS n = 12) for 13-weeks from 20-weeks of age. Prefrontal cortex and hippocampal samples were collected at 20-weeks of age (BSL n = 11) and at 33-weeks of age (AGE and AGE-HFS). The HFS diet resulted in increased body weight (30%; P = 0.0001), increased %fat mass (28%; P = 0.0001), and decreased %lean mass (33%; P = 0.0001) compared to aged controls. In the prefrontal cortex, AGE-HFS resulted in increased 5' adenosine monophosphate - activated protein kinase (AMPK) phosphorylation (P = 0.045). In the hippocampus, AGE-HFS resulted in increased extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) phosphorylation and protein kinase B (Akt) serine473 and glycogen synthase kinase (GSK) phosphorylation (P < 0.05). Results from this study demonstrate that aging combined with a HFS diet results in increased inflammation (pERK and pJNK) and energetic stress (pAMPK) in the hippocampus and prefrontal cortex, respectively. Together these novel results provide important information for future targets in early AD pathogenesis.

Neuroprotective effects of N-acetyl cysteine on primary hippocampus neurons against hydrogen peroxide-induced injury are mediated via inhibition of mitogen-activated protein kinases signal transduction and antioxidative action

N-acetyl cysteine (NAC) has been extensively reported to exert neuroprotective effects on the central nervous system. Oxidative stress may contribute to the underlying mechanisms causing Alzheimer's disease (AD). The effect of NAC against oxidative stress injury was investigated in a cellular model of AD in the present study and the underlying mechanisms were revealed. The neuroprotective action of NAC (1, 10, 100 and 1,000 µmol/l) on a cellular model of AD [hydrogen peroxide (H2O2)‑induced (3, 30 and 300 µmol/l) toxicity in primary rat hippocampus neurons] demonstrated the underlying mechanisms. Cytotoxicity was measured using the MTT assay, and light microscopy and the dichloro-dihydro-fluorescein diacetate method were used to detect the reactive oxygen species (ROS) levels. Furthermore, the levels of mitogen-activated protein kinases (MAPKs) signal transduction and tau protein phosphorylation were measured via western blotting. NAC (100 µmol/l) protected hippocampus neurons against H2O2‑mediated toxicity, as evidenced by enhanced cell viability. Using MTT assay and light microscopy for the observation of cell death, NAC ameliorated cell viability, which was induced by H2O2 injury (P<0.05). NAC was found to mitigate the excessive production of ROS (P<0.05). Another mechanism involved in the neuroprotective action of NAC may be its ability to inhibit MAPK signal transduction following H2O2 exposure. In addition, NAC may protect cells against H2O2‑induced toxicity by attenuating increased tau phosphorylation. Thus, the protective ability of NAC is hypothesized to result from inhibition of oxidative stress and downregulation of MAPK signal transduction and tau phosphorylation.

Alzheimer's disease pathology and the unfolded protein response: prospective pathways and therapeutic targets

Many vital interdependent cellular functions including proteostasis, lipogenesis and Ca homeostasis are executed by the endoplasmic reticulum (ER). Exogenous insults can impair ER performance: this must be rapidly corrected or cell death will ensue. Protective adaptations can boost the functional capacity of the ER and form the basis of the unfolded protein response (UPR). Activated in response to the accumulation of misfolded proteins, the UPR can halt protein translation while increasing protein-handling chaperones and the degradation of erroneous proteins through a conserved three-tier molecular cascade. However, prolonged activation of the UPR can result in the maladaptation of the system, resulting in the activation of inflammatory and apoptotic effectors. Recently, UPR and its involvement in neurodegenerative disease has attracted much interest and numerous potentially 'drugable' points of crosstalk are now emerging. Here, we summarize the functions of the ER and UPR, and highlight evidence for its potential role in the pathogenesis of Alzheimer's disease, before discussing several key targets with therapeutic potential.

Battery of behavioral tests in mice to study postoperative delirium

Postoperative delirium is associated with increased morbidity, mortality and cost. However, its neuropathogenesis remains largely unknown, partially owing to lack of animal model(s). We therefore set out to employ a battery of behavior tests, including natural and learned behavior, in mice to determine the effects of laparotomy under isoflurane anesthesia (Anesthesia/Surgery) on these behaviors. The mice were tested at 24 hours before and at 6, 9 and 24 hours after the Anesthesia/Surgery. Composite Z scores were calculated. Cyclosporine A, an inhibitor of mitochondria permeability transient pore, was used to determine potential mitochondria-associated mechanisms of these behavioral changes. Anesthesia/Surgery selectively impaired behaviors, including latency to eat food in buried food test, freezing time and time spent in the center in open field test, and entries and duration in the novel arm of Y maze test, with acute onset and various timecourse. The composite Z scores quantitatively demonstrated the Anesthesia/Surgery-induced behavior impairment in mice. Cyclosporine A selectively ameliorated the Anesthesia/Surgery-induced reduction in ATP levels, the increases in latency to eat food, and the decreases in entries in the novel arm. These findings suggest that we could use a battery of behavior tests to establish a mouse model to study postoperative delirium.

Effects of grape seed proanthocyanidin on Alzheimer's disease in vitro and in vivo

Grape seed proanthocyanidin (GSPA) consists of catechin, epicatechin and epicatechin gallate, which are strong antioxidants that are beneficial to health and may attenuate or prevent Alzheimer's disease (AD). In the present study, the effects of GSPA on pheochromocytoma (PC12) cell viability were determined using cell counting kit-8 and lactate dehydrogenase (LDH) assays, whereas apoptosis and mitochondrial membrane potential (Ψm) were measured via flow cytometry analysis. The effect of GSPA administration on the behavior and memory of amyloid precursor protein (APP)/presenilin-1 (PS-1) double transgenic mice was assessed using a Morris water maze. APP Aβ peptides and tau hyperphosphorylation were examined by western blotting; whereas the expression levels of PS-1 were evaluated by reverse transcription-quantitative polymerase chain reaction and compared with pathological sections stained with hematoxylin-eosin and Congo red. Data from the in vitro experiments demonstrated that GSPA significantly alleviated Aβ25–35 cytotoxicity and LDH leakage ratio, inhibited apoptosis and increased Ψm. The findings from the in vivo experiments showed a significant enhancement in cognition and spatial memory ability, an improvement in the pathology of APP and tau protein and a decrease in PS-1 mRNA expression levels. Therefore, the results of the present study indicated that GSPA may be a novel therapeutic strategy for the treatment of AD or may, at the very least, improve the quality of life of patients with AD.

c-Jun N-terminal Kinase (JNK) Signaling as a Therapeutic Target for Alzheimer's Disease

c-Jun N-terminal kinases (JNKs) are a family of protein kinases that play a central role in stress signaling pathways implicated in gene expression, neuronal plasticity, regeneration, cell death, and regulation of cellular senescence. It has been shown that there is a JNK pathway activation after exposure to different stressing factors, including cytokines, growth factors, oxidative stress, unfolded protein response signals or Aβ peptides. Altogether, JNKs have become a focus of screening strategies searching for new therapeutic approaches to diabetes, cancer or liver diseases. In addition, activation of JNK has been identified as a key element responsible for the regulation of apoptosis signals and therefore, it is critical for pathological cell death associated with neurodegenerative diseases and, among them, with Alzheimer’s disease (AD). In addition, in vitro and in vivo studies have reported alterations of JNK pathways potentially associated with pathogenesis and neuronal death in AD. JNK’s, particularly JNK3, not only enhance Aβ production, moreover it plays a key role in the maturation and development of neurofibrillary tangles. This review aims to explain the rationale behind testing therapies based on inhibition of JNK signaling for AD in terms of current knowledge about the pathophysiology of the disease. Keeping in mind that JNK3 is specifically expressed in the brain and activated by stress-stimuli, it is possible to hypothesize that inhibition of JNK3 might be considered as a potential target for treating neurodegenerative mechanisms associated with AD.

Maslinic Acid Protected PC12 Cells Differentiated by Nerve Growth Factor against β-Amyloid-Induced Apoptosis

β-Amyloid peptide (Abeta) was used to induce apoptosis in PC12 cells differentiated by nerve growth factor, and the protective activities of maslinic acid (MA) at 2-16 μM were examined. Abeta treatment lowered Bcl-2 expression, raised Bax expression, and decreased cell viability. MA pretreatments decreased Bax expression, raised the Bcl-2/Bax ratio, and increased cell viability. MA pretreatments retained glutathione content and decreased subsequent Abeta-induced release of reactive oxygen species, tumor necrosis factor-α, interleukin (IL)-1β, and IL-6. Abeta treatment up-regulated protein expression of p47(phox), gp91(phox), mitogen-activated protein kinase, advanced glycation end product receptor (RAGE), and nuclear factor-κ B (NF-κB). MA pretreatments at 2-16 μM suppressed the expression of proteins including gp91(phox), p47(phox), p-p38, and NF-κB p65, at 4-16 μM down-regulated RAGE and NF-κB p50 expression, and at 8 and 16 μM reduced p-ERK1/2 expression. These novel findings suggest that maslinic acid is a potent compound against Abeta-induced cytotoxicity.

The carbonic anhydrase inhibitor methazolamide prevents amyloid beta-induced mitochondrial dysfunction and caspase activation protecting neuronal and glial cells in vitro and in the mouse brain

Mitochondrial dysfunction has been recognized as an early event in Alzheimer's disease (AD) pathology, preceding and inducing neurodegeneration and memory loss. The presence of cytochrome c (CytC) released from the mitochondria into the cytoplasm is often detected after acute or chronic neurodegenerative insults, including AD. The carbonic anhydrase inhibitor (CAI) methazolamide (MTZ) was identified among a library of drugs as an inhibitor of CytC release and proved to be neuroprotective in Huntington's disease and stroke models. Here, using neuronal and glial cell cultures, in addition to an acute model of amyloid beta (Aβ) toxicity, which replicates by intra-hippocampal injection the consequences of interstitial and cellular accumulation of Aβ, we analyzed the effects of MTZ on neuronal and glial degeneration induced by the Alzheimer's amyloid. MTZ prevented DNA fragmentation, CytC release and activation of caspase 9 and caspase 3 induced by Aβ in neuronal and glial cells in culture through the inhibition of mitochondrial hydrogen peroxide production. Moreover, intraperitoneal administration of MTZ prevented neurodegeneration induced by intra-hippocampal Aβ injection in the mouse brain and was effective at reducing caspase 3 activation in neurons and microglia in the area surrounding the injection site. Our results, delineating the molecular mechanism of action of MTZ against Aβ-mediated mitochondrial dysfunction and caspase activation, and demonstrating its efficiency in a model of acute amyloid-mediated toxicity, provide the first combined in vitro and in vivo evidence supporting the potential of a new therapy employing FDA-approved CAIs in AD.

Quantitative interaction proteomics of neurodegenerative disease proteins

Several proteins have been linked to neurodegenerative disorders (NDDs), but their molecular function is not completely understood. Here, we used quantitative interaction proteomics to identify binding partners of Amyloid beta precursor protein (APP) and Presenilin-1 (PSEN1) for Alzheimer’s disease (AD), Huntingtin (HTT) for Huntington’s disease, Parkin (PARK2) for Parkinson’s disease, and Ataxin-1 (ATXN1) for spinocerebellar ataxia type 1. Our network reveals common signatures of protein degradation and misfolding and recapitulates known biology. Toxicity modifier screens and comparison to genome-wide association studies show that interaction partners are significantly linked to disease phenotypes in vivo. Direct comparison of wild-type proteins and disease-associated variants identified binders involved in pathogenesis, highlighting the value of differential interactome mapping. Finally, we show that the mitochondrial protein LRPPRC interacts preferentially with an early-onset AD variant of APP. This interaction appears to induce mitochondrial dysfunction, which is an early phenotype of AD.

Hosp et al. show that quantitative interaction proteomics of neurodegenerative disease proteins captures interactions relevant to pathogenesis. Differential interactome mapping reveals preferential binding of the mitochondrial protein LRPPRC with an early-onset Alzheimer’s disease (AD) variant of APP, potentially contributing to mitochondrial dysfunction observed in AD.

Implication of Caspase-3 as a Common Therapeutic Target for Multineurodegenerative Disorders and Its Inhibition Using Nonpeptidyl Natural Compounds

Caspase-3 has been identified as a key mediator of neuronal apoptosis. The present study identifies caspase-3 as a common player involved in the regulation of multineurodegenerative disorders, namely, Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). The protein interaction network prepared using STRING database provides a strong evidence of caspase-3 interactions with the metabolic cascade of the said multineurodegenerative disorders, thus characterizing it as a potential therapeutic target for multiple neurodegenerative disorders. In silico molecular docking of selected nonpeptidyl natural compounds against caspase-3 exposed potent leads against this common therapeutic target. Rosmarinic acid and curcumin proved to be the most promising ligands (leads) mimicking the inhibitory action of peptidyl inhibitors with the highest Gold fitness scores 57.38 and 53.51, respectively. These results were in close agreement with the fitness score predicted using X-score, a consensus based scoring function to calculate the binding affinity. Nonpeptidyl inhibitors of caspase-3 identified in the present study expeditiously mimic the inhibitory action of the previously identified peptidyl inhibitors. Since, nonpeptidyl inhibitors are preferred drug candidates, hence, discovery of natural compounds as nonpeptidyl inhibitors is a significant transition towards feasible drug development for neurodegenerative disorders.

Nucleofection of rat pheochromocytoma PC-12 cells with human mutated beta-amyloid precursor protein gene (APP-sw) leads to reduced viability, autophagy-like process, and increased expression and secretion of beta amyloid

Pheochromocytoma PC-12 cells are immune to physiological stimuli directed to evoke programmed cell death. Besides, metabolic inhibitors are incapable of sensitizing PC-12 cells to extrinsic or intrinsic apoptosis unless they are used in toxic concentrations. Surprisingly, these cells become receptive to cell deletion after human APP-sw gene expression. We observed reduced cell viability in GFP vector + APP-sw-nucleofected cells (drop by 36%) but not in GFP vector - or GFP vector + APP-wt-nucleofected cells. Lower viability was accompanied by higher expression of Aβ 1-16 and elevated secretion of Aβ 1-40 (in average 53.58 pg/mL). At the ultrastructural level autophagy-like process was demonstrated to occur in APP-sw-nucleofected cells with numerous autophagosomes and multivesicular bodies but without autolysosomes. Human APP-sw gene is harmful to PC-12 cells and cells are additionally driven to incomplete autophagy-like process. When stimulated by TRAIL or nystatin, CLU protein expression accompanies early phase of autophagy.

Lysophosphatidylcholine increases the neurotoxicity of Alzheimer's amyloid β1-42 peptide: role of oligomer formation

Oligomer formation is considered as a critical process for the neurotoxic effects of Alzheimer's amyloid β (Aβ) peptide. Previously we have demonstrated that lysophosphatidylcholine (LPC) increases the oligomer formation of Aβ1-42, the major Aβ peptide found Alzheimer's disease (AD) lesions. In this study, we have investigated whether LPC affects the neurotoxic effects of Aβ1-42 in a neuronal cell line (A1) culture. Dimethyl thiazolyl diphenyl tetrazolium (MTT) assay revealed that up to 10μM concentration, LPC did not affect A1 cell viability. Aβ1-42 decreased the cell viability, and such effect was dose dependently enhanced by LPC. However, neither LPC nor Aβ1-42, alone or in combination increased lactate dehydrogenase (LDH) release from A1 cells after 24-h treatment. Terminal deoxynucleotidyl transferase dUTP-biotin nick-end-labeling (TUNEL) assay showed that LPC increased Aβ1-42-induced apoptotic cell number. To determine the underlying mechanisms, the proteins implicated in apoptosis pathways including Bcl-2- and caspase-family were analyzed by Western blotting. The results demonstrated that Aβ1-42 decreased Bcl-2 in A1 cells at 24h, whereas LPC had no effect at any time point. Both LPC and Aβ1-42 increased Bax level at 24h, and their combined stimulation showed a synergistic effect. Similar synergistic effect of LPC and Aβ1-42 on caspase9 activation was observed. Dot blot immunoassay and Western blotting showed that LPC augmented Aβ1-42 oligomer formation in cell culture medium. Removing LPC-induced early-formed Aβ1-42 oligomer from the culture medium by immunoprecipitation decreased active caspase9 level and neurotoxicity, as revealed by Western blotting and MTT assay. Furthermore, dihydroethidium (DHE) assay showed that Aβ1-42 increased reactive oxygen species level in A1 cells, such effect was further enhanced by LPC. Thus, our results demonstrated that LPC increased the oligomer formation process of Aβ1-42 peptide in culture condition, and consequently increased apoptotic neuronal death. Such process might be important for the pathogenesis of AD, and inhibition of LPC generation could be a therapeutic target for the disease.

Multiple pathogenic proteins implicated in neuronopathic Gaucher disease mice

Gaucher disease, a prevalent lysosomal storage disease (LSD), is caused by insufficient activity of acid β-glucosidase (GCase) and the resultant glucosylceramide (GC)/glucosylsphingosine (GS) accumulation in visceral organs (Type 1) and the central nervous system (Types 2 and 3). Recent clinical and genetic studies implicate a pathogenic link between Gaucher and neurodegenerative diseases. The aggregation and inclusion bodies of α-synuclein with ubiquitin are present in the brains of Gaucher disease patients and mouse models. Indirect evidence of β-amyloid pathology promoting α-synuclein fibrillation supports these pathogenic proteins as a common feature in neurodegenerative diseases. Here, multiple proteins are implicated in the pathogenesis of chronic neuronopathic Gaucher disease (nGD). Immunohistochemical and biochemical analyses showed significant amounts of β-amyloid and amyloid precursor protein (APP) aggregates in the cortex, hippocampus, stratum and substantia nigra of the nGD mice. APP aggregates were in neuronal cells and colocalized with α-synuclein signals. A majority of APP co-localized with the mitochondrial markers TOM40 and Cox IV; a small portion co-localized with the autophagy proteins, P62/LC3, and the lysosomal marker, LAMP1. In cultured wild-type brain cortical neural cells, the GCase-irreversible inhibitor, conduritol B epoxide (CBE), reproduced the APP/α-synuclein aggregation and the accumulation of GC/GS. Ultrastructural studies showed numerous larger-sized and electron-dense mitochondria in nGD cerebral cortical neural cells. Significant reductions of mitochondrial adenosine triphosphate production and oxygen consumption (28-40%) were detected in nGD brains and in CBE-treated neural cells. These studies implicate defective GCase function and GC/GS accumulation as risk factors for mitochondrial dysfunction and the multi-proteinopathies (α-synuclein-, APP- and Aβ-aggregates) in nGD.

Structure based molecular inhibition of Caspase-8 for treatment of multi-neurodegenerative diseases using known natural compounds

Neurodegenerative disorders are often associated with excessive neuronal apoptosis. It is well known that apoptosis is regulated by some intracellular proteases, such as, Caspases (cysteine-dependent, aspartate-specific proteases). In fact, Caspase-8 which is an initiator caspase, has been identified as a key mediator of neuronal apoptosis. In addition, Caspase-8 is found to be coupled with the regulation of various neurodegenerative disorders including Alzheimer׳s disease (AD), Parkinson׳s disease (PD), Huntington׳s Diseases (HD) and Dentatorubral Pallidoluysian Atrophy (DRPLA). Caspase-8 inhibition may provide an effective means of treatment for multiple neurodegenerative disorders. Therefore, the present study describes the molecular interaction of some selected natural compounds with known anti neurodegenerative properties with Caspase-8. Docking between Caspase-8 and each of these compounds (separately) was performed using 'Autodock4.2'. Out of all the selected compounds, rosmarinic acid and curcumin proved to be the most potent inhibitors of Caspase-8 with binding energy (ΔG) of -7.10 Kcal/mol and -7.08 Kcal/mol, respectively. However, further in vitro and in vivo studies are needed to validate the anti-neurodegenerative potential of these compounds.

Role of methylglyoxal in Alzheimer's disease

Alzheimer's disease is the most common and lethal neurodegenerative disorder. The major hallmarks of Alzheimer's disease are extracellular aggregation of amyloid β peptides and, the presence of intracellular neurofibrillary tangles formed by precipitation/aggregation of hyperphosphorylated tau protein. The etiology of Alzheimer's disease is multifactorial and a full understanding of its pathogenesis remains elusive. Some years ago, it has been suggested that glycation may contribute to both extensive protein cross-linking and oxidative stress in Alzheimer's disease. Glycation is an endogenous process that leads to the production of a class of compounds known as advanced glycation end products (AGEs). Interestingly, increased levels of AGEs have been observed in brains of Alzheimer's disease patients. Methylglyoxal, a reactive intermediate of cellular metabolism, is the most potent precursor of AGEs and is strictly correlated with an increase of oxidative stress in Alzheimer's disease. Many studies are showing that methylglyoxal and methylglyoxal-derived AGEs play a key role in the etiopathogenesis of Alzheimer's disease.

Arsenic induces reactive oxygen species-caused neuronal cell apoptosis through JNK/ERK-mediated mitochondria-dependent and GRP 78/CHOP-regulated pathways

Arsenic (As), a well-known high toxic metal, is an important environmental and industrial contaminant, and it induces oxidative stress, which causes many adverse health effects and diseases in humans, particularly in inorganic As (iAs) more harmful than organic As. Recently, epidemiological studies have suggested a possible relationship between iAs exposure and neurodegenerative disease development. However, the toxicological effects and underlying mechanisms of iAs-induced neuronal cell injuries are mostly unknown. The present study demonstrated that iAs significantly decreased cell viability and induced apoptosis in Neuro-2a cells. iAs also increased oxidative stress damage (production of malondialdehyde (MDA) and ROS, and reduction of Nrf2 and thioredoxin protein expression) and induced several features of mitochondria-dependent apoptotic signals, including: mitochondrial dysfunction, the activations of PARP and caspase cascades, and the increase in caspase-3 activity. Pretreatment with the antioxidant N-acetylcysteine (NAC) effectively reversed these iAs-induced responses. iAs also increased the phosphorylation of JNK and ERK1/2, but did not that p38-MAPK, in treated Neuro-2a cells. NAC and the specific JNK inhibitor (SP600125) and ERK1/2 inhibitor (PD98059) abrogated iAs-induced cell cytotoxicity, caspase-3/-7 activity, and JNK and ERK1/2 activation. Additionally, exposure of Neuro-2a cells to iAs triggered endoplasmic reticulum (ER) stress identified through several key molecules (GRP 78, CHOP, XBP-1, and caspase-12), which was prevented by NAC. Transfection with GRP 78- and CHOP-specific si-RNA dramatically suppressed GRP 78 and CHOP expression, respectively, and attenuated the activations of caspase-12, -7, and -3 in iAs-exposed cells. Therefore, these results indicate that iAs induces ROS causing neuronal cell death via both JNK/ERK-mediated mitochondria-dependent and GRP 78/CHOP-triggered apoptosis pathways.

Attenuation of oxidative damage-associated cognitive decline by Withania somnifera in rat model of streptozotocin-induced cognitive impairment

Oxidative stress is a critical contributing factor to age-related neurodegenerative disorders. Therefore, the inhibition of oxidative damage, responsible for chronic detrimental neurodegeneration, is an important strategy for neuroprotective therapy. Withania somnifera (WS) extract has been reported to have potent antioxidant and free radical quenching properties in various disease conditions. The present study evaluated the hypothesis that WS extract would reduce oxidative stress-associated neurodegeneration after intracerebroventricular injection of streptozotocin (ICV-STZ) in rats. To test this hypothesis, male Wistar rats were pretreated with WS extract at doses of 100, 200, and 300 mg/kg body weight once daily for 3 weeks. On day 22nd, the rats were infused bilaterally with ICV-STZ injection (3 mg/kg body weight) in normal saline while sham group received only saline. Two weeks after the lesioning, STZ-infused rats showed cognitive impairment in the Morris water maze test. The rats were sacrificed after 3 weeks of the lesioning for the estimation of the contents of lipid peroxidation, reduced glutathione, and activities of glutathione reductase, glutathione peroxidase, and catalase. Pretreatment with WS extract attenuated behavioral, biochemical, and histological alterations significantly in dose-dependent manner in the hippocampus and cerebral cortex of ICV-STZ-infused rats. These results suggest that WS affords a beneficial effect on cognitive deficit by ameliorating oxidative damage induced by streptozotocin in a model of cognitive impairment.

Pharmacophore modeling and docking studies on some nonpeptide-based caspase-3 inhibitors

Neurodegenerative disorders are major consequences of excessive apoptosis caused by a proteolytic enzyme known as caspase-3. Therefore, caspase-3 inhibition has become a validated therapeutic approach for neurodegenerative disorders. We performed pharmacophore modeling on some synthetic derivatives of caspase-3 inhibitors (pyrrolo[3,4-c]quinoline-1,3-diones) using PHASE 3.0. This resulted in the common pharmacophore hypothesis AAHRR.6 which might be responsible for the biological activity: two aromatic rings (R) mainly in the quinoline nucleus, one hydrophobic (H) group (CH₃), and two acceptor (A) groups (–C=O). After identifying a valid hypothesis, we also developed an atom-based 3D-QSAR model applying the PLS algorithm. The developed model was statistically robust (q² = 0.53; pred_r² = 0.80). Additionally, we have performed molecular docking studies, cross-validated our results, and gained a deeper insight into its molecular recognition process. Our developed model may serve as a query tool for future virtual screening and drug designing for this particular target.

The senescence hypothesis of disease progression in Alzheimer disease: an integrated matrix of disease pathways for FAD and SAD

Alzheimer disease (AD) is a progressive, neurodegenerative disease characterised in life by cognitive decline and behavioural symptoms and post-mortem by the neuropathological hallmarks including the microtubule-associated protein tau-reactive tangles and neuritic plaques and amyloid-beta-protein-reactive senile plaques. Greater than 95 % of AD cases are sporadic (SAD) with a late onset and <5 % of AD cases are familial (FAD) with an early onset. FAD is associated with various genetic mutations in the amyloid precursor protein (APP) and the presenilins (PS)1 and PS2. As yet, no disease pathway has been fully accepted and there are no treatments that prevent, stop or reverse the cognitive decline associated with AD. Here, we review and integrate available environmental and genetic evidence associated with all forms of AD. We present the senescence hypothesis of AD progression, suggesting that factors associated with AD can be seen as partial stressors within the matrix of signalling pathways that underlie cell survival and function. Senescence pathways are triggered when stressors exceed the cells ability to compensate for them. The APP proteolytic system has many interactions with pathways involved in programmed senescence and APP proteolysis can both respond to and be driven by senescence-associated signalling. Disease pathways associated with sporadic disease may be different to those involving familial genetic mutations. The interpretation we provide strongly points to senescence as an additional underlying causal process in dementia progression in both SAD and FAD via multiple disease pathways.

Adiponectin is protective against oxidative stress induced cytotoxicity in amyloid-beta neurotoxicity

Beta-amyloid (Aβ ) neurotoxicity is important in Alzheimer’s disease (AD) pathogenesis. Aβ neurotoxicity causes oxidative stress, inflammation and mitochondrial damage resulting in neuronal degeneration and death. Oxidative stress, inflammation and mitochondrial failure are also pathophysiological mechanisms of type 2 diabetes (T₂DM) which is characterized by insulin resistance. Interestingly, T₂DM increases risk to develop AD which is associated with reduced neuronal insulin sensitivity (central insulin resistance). We studied the potential protective effect of adiponectin (an adipokine with insulin-sensitizing, anti-inflammatory and anti-oxidant properties) against Aβ neurotoxicity in human neuroblastoma cells (SH-SY5Y) transfected with the Swedish amyloid precursor protein (Sw-APP) mutant, which overproduced Aβ with abnormal intracellular Aβ accumulation. Cytotoxicity was measured by assay for lactate dehydrogenase (LDH) released upon cell death and lysis. Our results revealed that Sw-APP transfected SH-SY5Y cells expressed both adiponectin receptor 1 and 2, and had increased AMP-activated protein kinase (AMPK) activation and enhanced nuclear factor-kappa B (NF-κB) activation compared to control empty-vector transfected SH-SY5Y cells. Importantly, adiponectin at physiological concentration of 10 µg/ml protected Sw-APP transfected SH-SY5Y cells against cytotoxicity under oxidative stress induced by hydrogen peroxide. This neuroprotective action of adiponectin against Aβ neurotoxicity-induced cytotoxicity under oxidative stress involved 1) AMPK activation mediated via the endosomal adaptor protein APPL1 (adaptor protein with phosphotyrosine binding, pleckstrin homology domains and leucine zipper motif) and possibly 2) suppression of NF-κB activation. This raises the possibility of novel therapies for AD such as adiponectin receptor agonists.

Chloroacetic acid induced neuronal cells death through oxidative stress-mediated p38-MAPK activation pathway regulated mitochondria-dependent apoptotic signals

Chloroacetic acid (CA), a toxic chlorinated analog of acetic acid, is widely used in chemical industries as an herbicide, detergent, and disinfectant, and chemical intermediates that are formed during the synthesis of various products. In addition, CA has been found as a by-product of chlorination disinfection of drinking water. However, there is little known about neurotoxic injuries of CA on the mammalian, the toxic effects and molecular mechanisms of CA-induced neuronal cell injury are mostly unknown. In this study, we examined the cytotoxicity of CA on cultured Neuro-2a cells and investigated the possible mechanisms of CA-induced neurotoxicity. Treatment of Neuro-2a cells with CA significantly reduced the number of viable cells (in a dose-dependent manner with a range from 0.1 to 3mM), increased the generation of ROS, and reduced the intracellular levels of glutathione depletion. CA also increased the number of sub-G1 hypodiploid cells; increased mitochondrial dysfunction (loss of MMP, cytochrome c release, and accompanied by Bcl-2 and Mcl-1 down-regulation and Bax up-regulation), and activated the caspase cascades activations, which displayed features of mitochondria-dependent apoptosis pathway. These CA-induced apoptosis-related signals were markedly prevented by the antioxidant N-acetylcysteine (NAC). Moreover, CA activated the JNK and p38-MAPK pathways, but did not that ERK1/2 pathway, in treated Neuro-2a cells. Pretreatment with NAC and specific p38-MAPK inhibitor (SB203580), but not JNK inhibitor (SP600125) effectively abrogated the phosphorylation of p38-MAPK and attenuated the apoptotic signals (including: decrease in cytotoxicity, caspase-3/-7 activation, the cytosolic cytochrome c release, and the reversed alteration of Bcl-2 and Bax mRNA) in CA-treated Neuro-2a cells. Taken together, these data suggest that oxidative stress-induced p38-MAPK activated pathway-regulated mitochondria-dependent apoptosis plays an important role in CA-caused neuronal cell death.

Pathological alteration in the choroid plexus of Alzheimer's disease: implication for new therapy approaches

Morphological alterations of choroid plexus in Alzheimer’s disease (AD) have been extensively investigated. These changes include epithelial atrophy, thickening of the basement membrane, and stroma fibrosis. As a result, synthesis, secretory, and transportation functions are significantly altered resulting in decreased cerebrospinal fluid (CSF) turnover. Recent studies discuss the potential impacts of these changes, including the possibility of reduced resistance to stress insults and slow clearance of toxic compounds from CSF with specific reference to the amyloid peptide. Here, we review new evidences for AD-related changes in the choroid plexus. The data suggest that the significantly altered functions of the choroid plexus contribute to the multiparametric pathogenesis of late-onset AD.

Successful transplantation of rat hearts subjected to extended cold preservation with a novel preservation solution

Since prolonged cold preservation of the heart deteriorates the outcome of heart transplantation, a more protective preservation solution is required. We therefore developed a new solution, named Dsol, and examined whether Dsol, in comparison to UW, could better inhibit myocardial injury resulting from prolonged cold preservation. Syngeneic heterotopic heart transplantation in Lewis rats was performed after cold preservation with UW or Dsol for 24 or 36 h. In addition to graft survival, myocardial injury, ATP content, and Ca(2+) -dependent proteases activity were assessed in the 24-h preservation group. The cytosolic Ca(2+) concentration of H9c2 cardiomyocytes after 24-h cold preservation was assessed. Dsol significantly improved 7-day graft survival after 36-h preservation. After 24-h preservation, Dsol was associated with significantly faster recovery of ATP content and less activation of calpain and caspase-3 after reperfusion. Dsol diminished graft injury significantly, as revealed by the lower levels of infarction, apoptosis, serum LDH and AST release, and graft fibrosis at 7-day. Dsol significantly inhibited Ca(2+) overload during cold preservation. Dsol inhibited myocardial injury and improved graft survival by suppressing Ca(2+) overload during the preservation and the activation of Ca(2+) -dependent proteases. Dsol is therefore considered a better alternative to UW to ameliorate the outcome of heart transplantation.

c-Jun N-terminal kinase induces axonal degeneration and limits motor recovery after spinal cord injury in mice

c-Jun N-terminal kinase (JNK) mediates neuronal death in response to stress and injury in the CNS and peripheral nervous system. Here, we show that JNK also regulates retrograde axonal degeneration (axonal dieback) after spinal cord injury (SCI) in mice. Activated phospho-JNK was highly expressed in damaged corticospinal tract (CST) axons after thoracic SCI by hemisection. Local administration of SP600125, a JNK inhibitor, prevented accumulation of amyloid-β precursor protein and retraction of the severed CST axons as well as preserved the axonal arbors rostral to the injury site. The treatment with SP600125 also improved functional recovery of the hindlimbs, assessed by Basso mouse scale open-field scores and the grid-walking test. In Jnk1(-/-) and Jnk3(-/-) mice, we observed prevention of axonal degeneration and enhancement of motor recovery after SCI. These results indicate that both JNK1 and JNK3 induce axonal degeneration and limit motor recovery after SCI. Thus, a JNK inhibitor may be a suitable therapeutic agent for SCI.

s-Allyl cysteine, s-ethyl cysteine, and s-propyl cysteine alleviate β-amyloid, glycative, and oxidative injury in brain of mice treated by D-galactose

The neuroprotective effects of s-allyl cysteine, s-ethyl cysteine, and s-propyl cysteine in D-galactose (DG)-treated mice were examined. DG treatment increased the formation of Aβ(1-40) and Aβ(1-42), enhanced mRNA expression of β-amyloid precursor protein (APP) and β-site APP cleavage enzyme 1 (BACE1), and reduced neprilysin expression in brain (P < 0.05); however, the intake of three test compounds significantly decreased the production of Aβ(1-40) and Aβ(1-42) and suppressed the expression of APP and BACE1 (P < 0.05). DG treatments declined brain protein kinase C (PKC) activity and mRNA expression (P < 0.05). Intake of test compounds significantly retained PKC activity, and the expression of PKC-α and PKC-γ (P < 0.05). DG treatments elevated brain activity and mRNA expression of aldose reductase (AR) and sorbitol dehydrogenase as well as increased brain levels of carboxymethyllysine (CML), pentosidine, sorbitol, and fructose (P < 0.05). Test compounds significantly lowered AR activity, AR expression, and CML and pentosidine levels (P < 0.05). DG treatments also significantly increased the formation of reactive oxygen species (ROS) and protein carbonyl and decreased the activity of glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (P < 0.05); however, the intake of test compounds in DG-treated mice significantly decreased ROS and protein carbonyl levels and restored brain GPX, SOD, and catalase activities (P < 0.05). These findings support that these compounds via their anti-Aβ, antiglycative, and antioxidative effects were potent agents against the progression of neurodegenerative disorders such as Alzheimer's disease.