Interleukin-1beta and glutamate activate the NF-kappaB/Rel binding site from the regulatory region of the amyloid precursor protein gene in primary neuronal cultures

Kismet/CHD7/CHD8 and Amyloid Precursor Protein-like Regulate Synaptic Levels of Rab11 at the Drosophila Neuromuscular Junction

The transmembrane protein β-amyloid precursor protein (APP) is central to the pathophysiology of Alzheimer's disease (AD). The β-amyloid hypothesis posits that aberrant processing of APP forms neurotoxic β-amyloid aggregates, which lead to the cognitive impairments observed in AD. Although numerous additional factors contribute to AD, there is a need to better understand the synaptic function of APP. We have found that Drosophila APP-like (APPL) has both shared and non-shared roles at the synapse with Kismet (Kis), a chromatin helicase binding domain (CHD) protein. Kis is the homolog of CHD7 and CHD8, both of which are implicated in neurodevelopmental disorders including CHARGE Syndrome and autism spectrum disorders, respectively. Loss of function mutations in kis and animals expressing human APP and BACE in their central nervous system show reductions in the glutamate receptor subunit, GluRIIC, the GTPase Rab11, and the bone morphogenetic protein (BMP), pMad, at the Drosophila larval neuromuscular junction (NMJ). Similarly, processes like endocytosis, larval locomotion, and neurotransmission are deficient in these animals. Our pharmacological and epistasis experiments indicate that there is a functional relationship between Kis and APPL, but Kis does not regulate appl expression at the larval NMJ. Instead, Kis likely influences the synaptic localization of APPL, possibly by promoting rab11 transcription. These data identify a potential mechanistic connection between chromatin remodeling proteins and aberrant synaptic function in AD.

Molecular mechanisms underlying the effect of tooth shortening on memory dysfunction in Wistar male rat

OBJECTIVE

We investigated the effects of molar tooth shortening on the mRNA expression of the AβPP/BACE1, BDNF/TrkB, and Bax/Bcl-2 signaling pathways in the Wistar male rat hippocampal regions.

DESIGN

Four groups (n = 5 per group) of male Wistar rats (control, SRM (shortened right molar), SLM (shortened left molar), and SBM (shortened bilateral molar)) were used. RNA was isolated from the hippocampus and transformed into cDNA. Real-time quantitative PCR was used to evaluate the mRNA expression levels of AβPP, BACE1, Bax, Bcl-2, BDNF, and TrkB.

RESULTS

Differential mRNA expression was observed in rat groups. SBM significantly upregulated the AβPP, BACE1, and Bax mRNA expressions, whereas the expression levels of Bcl-2, BDNF, and TrkB were decreased. SRM and SLM approximately had the same effect on the expression enhancement of AβPP, BACE1, and Bax; however, SRM was more effective than SLM in increasing the expression of these genes.

CONCLUSIONS

Symmetrical molar teeth shortening affected the mRNA expression of AβPP and BACE1, which is related to learning and memory dysfunction.

Relationship between preoperative neutrophil-to-lymphocyte ratio and postoperative delirium: The PNDABLE and the PNDRFAP cohort studies

OBJECTIVES

In this study, the relationship between preoperative neutrophil-to-lymphocyte ratio (NLR) and Alzheimer-related biomarkers in cerebrospinal fluid (CSF) was investigated to determine whether high NLR is a potential risk factor for postoperative delirium (POD) and to evaluate its predictive efficacy.

METHODS

We selected 1000 patients from the perioperative neurocognitive disorder risk factor and prognosis (PNDRFAP) database and 999 patients from the perioperative neurocognitive disorder and biomarker lifestyle (PNDABLE) database. Patients in the PNDABLE database have been measured for Alzheimer-related biomarkers in CSF (Aβ40 , Aβ42 , P-tau, and tau protein). Mini-mental state examination was used to assess the preoperative mental status of patients. POD was diagnosed using the confusion assessment method and assessed for severity using the memorial delirium assessment scale. Logistic regression analysis was utilized to explore the association of preoperative NLR with POD. What's more, we also performed sensitivity analysis by adding corrected confounders, and the results were almost unchanged. Spearman's rank correlation was used to determine the associations between NLR and Alzheimer-related biomarkers. Mediation analyses with 10,000 bootstrapped iterations were used to explore the mediation effects. Finally, we use decision curves and the nomogram model to evaluate the efficacy of preoperative NLR in predicting POD; we also performed external validation using data from Qilu Hospital.

RESULT

Logistic regression results showed that an elevated preoperative NLR was a risk factor for the development of POD in patients (PNDRFAP: OR = 1.067, 95% CI 1.020-1.116; PNDABLE: OR = 1.182, 95% CI 1.048-1.335, p < .05). Spearman's rank correlation analysis showed a positive but weak correlation between NLR and P-tau/T-tau (R = .065). The mediating effect results indicate that NLR likely mediates the occurrence of POD through elevated tau protein levels (proportion: 47.47%). The results of the box plots showed statistically significant NLR and CSF biomarkers between the POD and non-POD (NPOD) groups (p < .05), with higher NLR, P-tau, and T-tau in the POD group than in the NPOD group. In contrast, the NPOD group had higher Aβ42 levels compared to the POD group. In addition, we used R package to plot the decision curve and nomogram both suggesting a good predictive effect of preoperative NLR on the occurrence of POD.

CONCLUSION

Elevated preoperative NLR levels may be a risk factor for POD and likely mediate the development of POD through elevated P-tau/T-tau levels.

Zinc and Central Nervous System Disorders

Zinc (Zn²⁺) is the second most abundant necessary trace element in the human body, exerting a critical role in many physiological processes such as cellular proliferation, transcription, apoptosis, growth, immunity, and wound healing. It is an essential catalyst ion for many enzymes and transcription factors. The maintenance of Zn²⁺ homeostasis is essential for the central nervous system, in which Zn²⁺ is abundantly distributed and accumulates in presynaptic vesicles. Synaptic Zn²⁺ is necessary for neural transmission, playing a pivotal role in neurogenesis, cognition, memory, and learning. Emerging data suggest that disruption of Zn²⁺ homeostasis is associated with several central nervous system disorders including Alzheimer's disease, depression, Parkinson's disease, multiple sclerosis, schizophrenia, epilepsy, and traumatic brain injury. Here, we reviewed the correlation between Zn²⁺ and these central nervous system disorders. The potential mechanisms were also included. We hope that this review can provide new clues for the prevention and treatment of nervous system disorders.

Deficiency of IKKβ in neurons ameliorates Alzheimer's disease pathology in APP- and tau-transgenic mice

In Alzheimer's disease (AD) brain, inflammatory activation regulates protein levels of amyloid-β-peptide (Aβ) and phosphorylated tau (p-tau), as well as neurodegeneration; however, the regulatory mechanisms remain unclear. We constructed APP- and tau-transgenic AD mice with deletion of IKKβ specifically in neurons, and observed that IKKβ deficiency reduced cerebral Aβ and p-tau, and modified inflammatory activation in both AD mice. However, neuronal deficiency of IKKβ decreased apoptosis and maintained synaptic proteins (e.g., PSD-95 and Munc18-1) in the brain and improved cognitive function only in APP-transgenic mice, but not in tau-transgenic mice. Additionally, IKKβ deficiency decreased BACE1 protein and activity in APP-transgenic mouse brain and cultured SH-SY5Y cells. IKKβ deficiency increased expression of PP2A catalytic subunit isoform A, an enzyme dephosphorylating cerebral p-tau, in the brain of tau-transgenic mice. Interestingly, deficiency of IKKβ in neurons enhanced autophagy as indicated by the increased ratio of LC3B-II/I in brains of both APP- and tau-transgenic mice. Thus, IKKβ deficiency in neurons ameliorates AD-associated pathology in APP- and tau-transgenic mice, perhaps by decreasing Aβ production, increasing p-tau dephosphorylation, and promoting autophagy-mediated degradation of BACE1 and p-tau aggregates in the brain. However, IKKβ deficiency differently protects neurons in APP- and tau-transgenic mice. Further studies are needed, particularly in the context of interaction between Aβ and p-tau, before IKKβ/NF-κB can be targeted for AD therapies.

Transcriptional and Post-Transcriptional Regulations of Amyloid-β Precursor Protein (APP) mRNA

Alzheimer’s disease (AD) is an age-associated neurodegenerative disorder characterized by progressive impairment of memory, thinking, behavior, and dementia. Based on ample evidence showing neurotoxicity of amyloid-β (Aβ) aggregates in AD, proteolytically derived from amyloid precursor protein (APP), it has been assumed that misfolding of Aβ plays a crucial role in the AD pathogenesis. Additionally, extra copies of the APP gene caused by chromosomal duplication in patients with Down syndrome can promote AD pathogenesis, indicating the pathological involvement of the APP gene dose in AD. Furthermore, increased APP expression due to locus duplication and promoter mutation of APP has been found in familial AD. Given this background, we aimed to summarize the mechanism underlying the upregulation of APP expression levels from a cutting-edge perspective. We first reviewed the literature relevant to this issue, specifically focusing on the transcriptional regulation of APP by transcription factors that bind to the promoter/enhancer regions. APP expression is also regulated by growth factors, cytokines, and hormone, such as androgen. We further evaluated the possible involvement of post-transcriptional regulators of APP in AD pathogenesis, such as RNA splicing factors. Indeed, alternative splicing isoforms of APP are proposed to be involved in the increased production of Aβ. Moreover, non-coding RNAs, including microRNAs, post-transcriptionally regulate the APP expression. Collectively, elucidation of the novel mechanisms underlying the upregulation of APP would lead to the development of clinical diagnosis and treatment of AD.

A High Neutrophil-to-Lymphocyte Ratio Predicts Higher Risk of Poststroke Cognitive Impairment: Development and Validation of a Clinical Prediction Model

Objective

Poststroke cognitive impairment (PSCI) is a serious complication of stroke. The neutrophil-to-lymphocyte ratio (NLR) is a marker of peripheral inflammation. The relationship between the NLR and PSCI is far from well studied, and the thesis of this study was to assess the predictive value of the NLR in patients with PSCI, and establish and verify the corresponding prediction model based on this relationship.

Methods

A total of 367 stroke patients were included in this study. Neutrophils, lymphocytes, and NLRs were measured at baseline, and clinical and neuropsychological assessments were conducted 3 months after stroke. The National Institutes of Health Scale (NIHSS) was used to assess the severity of stroke. A Chinese version of the Mini Mental State Examination (MMSE) was used for the assessment of cognitive function.

Results

After three months of follow-up, 87 (23.7%) patients were diagnosed with PSCI. The NLR was significantly higher in PSCI patients than in non-PSCI patients (P &lt; 0.001). Patient age, sex, body mass index, NIHSS scores, and high-density lipoprotein levels also differed in the univariate analysis. In the logistic regression analysis, the NLR was an independent risk factor associated with the patients with PSCI after adjustment for potential confounders (OR = 1.67, 95%CI: 1.21–2.29, P = 0.002). The nomogram based on patient sex, age, NIHSS score, and NLR had good predictive power with an AUC of 0.807. In the validation group, the AUC was 0.816.

Conclusion

An increased NLR at admission is associated with PSCI, and the model built with NLR as one of the predictors can increase prognostic information for the early detection of PSCI.

Essential Metals in the Brain and the Application of Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry for their Detection

Metals are natural component of the ecosystem present throughout the layers of atmosphere; their abundant expression in the brain indicates their importance in the central nervous system (CNS). Within the brain tissue, their distribution is highly compartmentalized, the pattern of which is determined by their primary roles. Bio-imaging of the brain to reveal spatial distribution of metals within specific regions has provided a unique understanding of brain biochemistry and architecture, linking both the structures and the functions through several metal mediated activities. Bioavailability of essential trace metal is needed for normal brain function. However, disrupted metal homeostasis can influence several biochemical pathways in different fields of metabolism and cause characteristic neurological disorders with a typical disease process usually linked with aberrant metal accumulations. In this review we give a brief overview of roles of key essential metals (Iron, Copper and Zinc) including their molecular mechanisms and bio-distribution in the brain as well as their possible involvement in the pathogenesis of related neurodegenerative diseases. In addition, we also reviewed recent applications of Laser Ablation Inductively Couple Plasma Mass Spectrophotometry (LA-ICP-MS) in the detection of both toxic and essential metal dyshomeostasis in neuroscience research and other related brain diseases.

Effects of quercetin-conjugated with superparamagnetic iron oxide nanoparticles on learning and memory improvement through targeting microRNAs/NF-κB pathway

Quercetin-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) have an ameliorative effect on diabetes-induced memory impairment. The current study aimed to compare the effect of quercetin (QC) and QCSPIONs on inflammation-related microRNAs and NF-κB signaling pathways in the hippocampus of diabetic rats. The expression levels of miR-146a, miR-9, NF-κB, and NF-κB-related downstream genes, including TNF-α, BACE1, AβPP, Bax, and Bcl-2 were measured using quantitative real-time PCR. To determine the NF-κB activity, immunohistochemical expression of NF-κB/p65 phosphorylation was employed. Computer simulated docking analysis also performed to find the QC target proteins involved in the NF-κB pathway. Results indicate that diabetes significantly upregulated the expression levels of miR-146a, miR-9, TNF-α, NF-κB, and subsequently AβPP, BACE1, and Bax. Expression analysis shows that QCSPIONs are more effective than pure QC in reducing the expression of miR-9. Interestingly, QCSPIONs reduce the pathological activity of NF-κB and subsequently normalize BACE1, AβPP, and the ratio of Bax/Bcl-2 expression better than pure QC. Comparative docking analyses also show the stronger binding affinity of QC to IKK and BACE1 proteins compared to specific inhibitors of each protein. In conclusion, our study suggests the potent efficacy of QCSPIONs as a promising drug delivery system in memory improvement through targeting the NF-κB pathway.

Crosstalk between obesity, diabetes, and alzheimer's disease: Introducing quercetin as an effective triple herbal medicine

Obesity and diabetes are the most common metabolic disorders, which are strongly related to Alzheimer's disease (AD) in aging. Diabetes and obesity can lead to the accumulation of amyloid plaques, neurofibrillary tangles (NFTs), and other symptoms of AD through several pathways, including insulin resistance, hyperglycemia, hyperinsulinemia, chronic inflammation, oxidative stress, adipokines dysregulation, and vascular impairment. Currently, the use of polyphenols has been expanded in animal models and in-vitro studies because of their comparatively negligible adverse effects. Among them, quercetin (QT) is one of the most abundant polyphenolic flavonoids, which is present in fruits and vegetables and displays many biological, health-promoting effects in a wide range of diseases. The low bioavailability and poor solubility of QT have also led researchers to make various QT-involved nanoparticles (NPs) to overcome these limitations. In this paper, we review significant molecular mechanisms induced by diabetes and obesity that increase AD pathogenesis. Then, we summarize in vitro, in vivo, and clinical evidence regarding the anti-Alzheimer, anti-diabetic and anti-obesity effects of QT. Finally, QT in pure and combination form using NPs has been suggested as a promising therapeutic agent for future studies.

NF-κB as a Key Mediator of Brain Inflammation in Alzheimer's Disease

Alzheimer's disease is the most common form of dementia. It is characterized by betaamyloid peptide fibrils which are extracellular deposition of a specific protein, accompanied by extensive neuroinflammation. Various studies show the presence of a number of inflammation markers in the AD brain: elevated inflammatory cytokines and chemokines, and an accumulation of activated microglia in the damaged regions. NF-κB is a family of redox sensitive transcriptional factors, and it is known that NF-κB has binding sites in the promoter region of the genes involved in amyloidogenesis and inflammation. Long-term use of non-steroidal anti-inflammatory drugs prevents progression of AD and delays its onset, suggesting that there is a close correlation between NF-κB and AD pathogenesis. This study aims to (1) assess the association between NF-κB activity and AD through discussion of a variety of experimental and clinical studies on AD and (2) review treatment strategies designed to treat or prevent AD with NF-κB inhibitors.

Gamma-oryzanol Prevents LPS-induced Brain Inflammation and Cognitive Impairment in Adult Mice

Background: Rice (Oryza sativa L.) is the main food source for more than half of humankind. Rice is rich in phytochemicals and antioxidants with several biological activities; among these compounds, the presence of γ-oryzanol is noteworthy. The present study aims to explore the effects of γ-oryzanol on cognitive performance in a mouse model of neuroinflammation and cognitive alterations. Methods: Mice received 100 mg/kg γ-oryzanol (ORY) or vehicle once daily for 21 consecutive days and were then exposed to an inflammatory stimulus elicited by lipopolysaccharide (LPS). A novel object recognition test and mRNA expression of antioxidant and neuroinflammatory markers in the hippocampus were evaluated. Results: ORY treatment was able to improve cognitive performance during the neuroinflammatory response. Furthermore, phase II antioxidant enzymes such as heme oxygenase-1 (HO-1) and NADPH-dehydrogenase-quinone-1 (NQO1) were upregulated in the hippocampi of ORY and ORY+LPS mice. Lastly, γ-oryzanol showed a strong anti-inflammatory action by downregulating inflammatory genes after LPS treatment. Conclusion: These results suggest that chronic consumption of γ-oryzanol can revert the LPS-induced cognitive and memory impairments by promoting hippocampal antioxidant and anti-inflammatory molecular responses.

GATA-4 regulates neuronal apoptosis after intracerebral hemorrhage via the NF-κB/Bax/Caspase-3 pathway both in vivo and in vitro

GATA-binding protein 4 (GATA-4)，a member of the GATA family of transcription factors, is expressed in the normal brain and participates in the neural inflammatory response and senescence. However, few studies have investigated whether GATA-4 is involved in the brain damage induced by intracerebral hemorrhage (ICH). The aim of this study was to investigate in vivo and in vitro the role of GATA-4 in ICH-induced secondary brain injury (SBI) and its potential underlying mechanisms. A rat model of ICH was established by autologous blood injection in vivo. In vitro, oxidized hemoglobin was applied to mimic the effects of ICH in neuronal culture. The function of GATA-4 and its mechanism of action after ICH were investigated using siRNA-mediated knockdown and plasmid-mediated overexpression techniques combined with immunofluorescence, western blot, and other molecular methods. It was found that the expression of GATA-4 was increased in the brain of rats after ICH, and its phosphorylation also increased correspondingly. Furthermore, knocking down the expression of GATA-4 led to a significant decrease in neurobehavioral scores and neuronal apoptosis, indicating that secondary brain damage was improved. Conversely, the overexpression of GATA-4 aggravated brain damage. Blockade of a critical phosphorylation site on the GATA-4 overexpression plasmid alleviated the exacerbated damage in vitro and in vivo. Moreover, GATA-4 promoted the activation of NF-κB, and increased the expression of Bax, and cysteine aspartate-specific protease 3 (caspase-3) in its cleaved form, causing neuronal apoptosis. In conclusion, the expression of GATA-4 was increased in the brain of rats after ICH. GATA-4 phosphorylation mediates the function of the protein in ICH-induced SBI. Neuronal apoptosis after ICH was mainly induced by NF-κB activation, which was promoted by GATA-4.

Effect of quercetin-conjugated superparamagnetic iron oxide nanoparticles on diabetes-induced learning and memory impairment in rats

Background

Diabetes mellitus plays a causative role in cognitive decline. Newly, neuroprotective effects of flavonoids have been widely investigated in neurodegenerative diseases. Quercetin (QC) is a phyto-derived bioactive flavone with numerous beneficial activities. However, its limited permeability to cross the blood–brain barrier, low oral bioavailability, poor aqueous solubility, and rapid gastrointestinal digestion lead to the administration of high dose of QC in clinical application.

Materials and methods

In order to overcome these limitations, we conjugated QC with superparamagnetic iron oxide nanoparticles (QCSPIONs) and supplemented streptozotocin-induced diabetic rats with it to improve diabetes-related memory impairment. In this regard, 40 rats were distributed into five groups with eight animals: control, diabetes, and diabetes treated with SPIONs, QC, and QCSPIONs. All treatments (at the dose of 25 mg/kg) were dissolved in deionized water and gavaged for 35 consecutive days.

Results

At the end of the study, QCSPIONs possessed significantly better efficacy than free QC on the improvement of memory performance. In the Morris water maze test, QCSPIONs compared to free QC reduced much better the escape latency over training trials (P<0.01) and increased the time spent in the target quadrant in probe trial (P<0.001). In the passive avoidance test, it increased step-through latency (P<0.05) and reduced the time spent in the dark compartment (P<0.01). In addition, both free QC and QCSPIONs were able to prevent the changes in body weight and decrease blood glucose levels in diabetic rats (P<0.05).

Conclusion

Overall, according to these results, we conclude that QC in the conjugated state with lower dose offers significantly higher potency in ameliorating diabetes-related memory impairment. Thus, this study offers an effective combined therapy for improving learning and memory.

The attenuating effects of 1,2,3,4,6 penta-O-galloyl-β-d-glucose on pro-inflammatory responses of LPS/IFNγ-activated BV-2 microglial cells through NFƙB and MAPK signaling pathways

BACKGROUND

Overactivated microglial cells exhibit chronic inflammatory response and can lead to the continuous production of pro-inflammatory cytokines, perpetuating inflammation, and ultimately resulting in neuronal injury. 1,2,3,4,6-Penta-O-Galloyl-β-d-Glucose (PGG), which is a naturally occurring polyphenolic compound, has exhibited anti-inflammatory effect through the inhibition of many cytokines in different experimental models, but its effect on activated microglia cells was never described. In the present study, we investigated PGG effect in proteins involved in the NFƙB and MAPK signaling pathways, which play a central role in inflammation through their ability to induce transcription of pro-inflammatory genes.

METHODS

PCR arrays and RT-PCR with individual primers were used to determine the effect of PGG on mRNA expression of genes involved in NFƙB and MAPK signaling pathways. Western blots were performed to confirm PCR results.

RESULTS

The data obtained showed that PGG modulated the expression of 5 genes from the NFƙB (BIRC3, CHUK, IRAK1, NFƙB1, NOD1) and 2 genes from MAPK signaling pathway (CDK2 and MYC) when tested in RT-PCR assays. Western blots confirmed the PCR results at the protein level, showing that PGG attenuated the expression of total and phosphorylated proteins (CDK2, CHUK, IRAK1, and NFƙB1) involved in NFƙB and MAPK signaling.

CONCLUSION

These findings show that PGG could modulate the expression of genes and proteins involved in the production of pro-inflammatory cytokines in microglia cells.

Integrated communications between cyclooxygenase-2 and Alzheimer's disease

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) are involved in the pathogenesis of Alzheimer's disease (AD), which is characterized by the accumulation of β-amyloid protein (Aβ) and tau hyperphosphorylation. However, the gaps in our knowledge of the roles of COX-2 and PGs in AD have not been filled. Here, we summarized the literature showing that COX-2 dysregulation obviously influences abnormal cleavage of β-amyloid precursor protein, aggregation and deposition of Aβ in β-amyloid plaques and the inclusion of phosphorylated tau in neurofibrillary tangles. Neuroinflammation, oxidative stress, synaptic plasticity, neurotoxicity, autophagy, and apoptosis have been assessed to elucidate the mechanisms of COX-2 regulation of AD. Notably, an imbalance of these factors ultimately produces cognitive decline. The current review substantiates our understanding of the mechanisms of COX-2-induced AD and establishes foundations for the design of feasible therapeutic strategies to treat AD.-Guan, P.-P., Wang, P. Integrated communications between cyclooxygenase-2 and Alzheimer's disease.

Amyloid precursor protein and amyloid precursor-like protein 2 in cancer

Amyloid precursor protein (APP) and its family members amyloid precursor-like protein 1 (APLP1) and amyloid precursor-like protein 2 (APLP2) are type 1 transmembrane glycoproteins that are highly conserved across species. The transcriptional regulation of APP and APLP2 is similar but not identical, and the cleavage of both proteins is regulated by phosphorylation. APP has been implicated in Alzheimer's disease causation, and in addition to its importance in neurology, APP is deregulated in cancer cells. APLP2 is likewise overexpressed in cancer cells, and APLP2 and APP are linked to increased tumor cell proliferation, migration, and invasion. In this present review, we discuss the unfolding account of these APP family members’ roles in cancer progression and metastasis.

Palmitic Acid-BSA enhances Amyloid-β production through GPR40-mediated dual pathways in neuronal cells: Involvement of the Akt/mTOR/HIF-1α and Akt/NF-κB pathways

The pathophysiological actions of fatty acids (FAs) on Alzheimer’s disease (AD), which are possibly mediated by genomic effects, are widely known; however, their non-genomic actions remain elusive. The aim of this study was to investigate the non-genomic mechanism of extra-cellular palmitic acid (PA) regulating beta-amyloid peptide (Aβ) production, which may provide a link between obesity and the occurrence of AD. In an obese mouse model, a high-fat diet (HFD) significantly increased the expression levels of APP and BACE1 as well as the AD pathology in the mouse brain. We further found that PA conjugated with bovine serum albumin (PA-BSA) increased the expression of APP and BACE1 and the production of Aβ through the G protein-coupled receptor 40 (GPR40) in SK-N-MC cells. PA-BSA coupling with GPR40 significantly induced Akt activation which is required for mTOR/p70S6K1-mediated HIF-1α expression and NF-κB phosphorylation facilitating the transcriptional activity of the APP and BACE1 genes. In addition, silencing of APP and BACE1 expression significantly decreased the production of Aβ in SK-N-MC cells treated with PA-BSA. In conclusion, these results show that extra-cellular PA coupled with GPR40 induces the expression of APP and BACE1 to facilitate Aβ production via the Akt-mTOR-HIF-1α and Akt-NF-κB pathways in SK-N-MC cells.

Neuroprotective Effects of Aged Garlic Extract on Cognitive Dysfunction and Neuroinflammation Induced by β-Amyloid in Rats

Neuroinflammation is pathological evidence of Alzheimer's disease (AD) that likely starts as a host defense response to the damaging effects of the β-amyloid (Aβ) deposits in the brain. The activation of microglia may promote the neurodegenerative process through the release of proinflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNFα), which may lead to neuronal damage and eventual death. Aged garlic extract (AGE) has been reported to have multiple biological activities, including anti-inflammatory effects. Therefore, the objective of this study was to investigate the effect of AGE on Aβ (1-42)-induced cognitive dysfunction and neuroinflammation. Adult male Wistar rats were given AGE (125, 250, and 500 mg/kg BW, body weight), orally administered, daily for 56 days. They were then injected with 1 μL of aggregated Aβ (1-42) into the lateral ventricles; bilaterally. Seven days later, their recognition memory was evaluated using a novel object recognition (NOR) test. Then the rats were sacrificed to investigate the alteration of microglia cells, IL-1β and TNFα in the cerebral cortex and hippocampus. The results indicated that AGE at doses of 250 and 500 mg/kg BW significantly improved short-term recognition memory in cognitively impaired rats. In addition, AGE significantly minimized the inflammatory response by reducing the activation of microglia and IL-1β to the levels found in the control, which is similar to the results found in Celebrex-treated rats. In conclusion, AGE may be useful for improving the short-term recognition memory and relieve the neuroinflammation in Aβ-induced rats.

Neuronal Gene Targets of NF-κB and Their Dysregulation in Alzheimer's Disease

Although, better known for its role in inflammation, the transcription factor nuclear factor kappa B (NF-κB) has more recently been implicated in synaptic plasticity, learning, and memory. This has been, in part, to the discovery of its localization not just in glia, cells that are integral to mediating the inflammatory process in the brain, but also neurons. Several effectors of neuronal NF-κB have been identified, including calcium, inflammatory cytokines (i.e., tumor necrosis factor alpha), and the induction of experimental paradigms thought to reflect learning and memory at the cellular level (i.e., long-term potentiation). NF-κB is also activated after learning and memory formation in vivo. In turn, activation of NF-κB can elicit either suppression or activation of other genes. Studies are only beginning to elucidate the multitude of neuronal gene targets of NF-κB in the normal brain, but research to date has confirmed targets involved in a wide array of cellular processes, including cell signaling and growth, neurotransmission, redox signaling, and gene regulation. Further, several lines of research confirm dysregulation of NF-κB in Alzheimer's disease (AD), a disorder characterized clinically by a profound deficit in the ability to form new memories. AD-related neuropathology includes the characteristic amyloid beta plaque formation and neurofibrillary tangles. Although, such neuropathological findings have been hypothesized to contribute to memory deficits in AD, research has identified perturbations at the cellular and synaptic level that occur even prior to more gross pathologies, including transcriptional dysregulation. Indeed, synaptic disturbances appear to be a significant correlate of cognitive deficits in AD. Given the more recently identified role for NF-κB in memory and synaptic transmission in the normal brain, the expansive network of gene targets of NF-κB, and its dysregulation in AD, a thorough understanding of NF-κB-related signaling in AD is warranted and may have important implications for uncovering treatments for the disease. This review aims to provide a comprehensive view of our current understanding of the gene targets of this transcription factor in neurons in the intact brain and provide an overview of studies investigating NF-κB signaling, including its downstream targets, in the AD brain as a means of uncovering the basic physiological mechanisms by which memory becomes fragile in the disease.

Investigation of one-lung ventilation postoperative cognitive dysfunction and regional cerebral oxygen saturation relations

OBJECTIVE

To explore the relationship of postoperative cognitive dysfunction (POCD) in one-lung ventilation (OLV) patients and regional cerebral oxygen saturation (rSO2).

METHODS

Twenty-nine male and twenty-one female cases of OLV received thoracic surgery, with American Standards Association (ASA) physical status being at Grades I-III. Neuropsychological tests were performed on the day before operation and 7 d after operation, and there was an intraoperative continuous monitoring of rSO2. The values of rSO2 before anesthesia induction (t1), at the beginning of OLV (t2), and at the time of OLV 30 min (t3), OLV 60 min (t4), the end of OLV (t5), and the end of surgery (t6) were recorded. The intraoperative average of rSO2 , the intraoperative minimum value of rSO2 (rSO(2, min)), and the reduced maximum percentage of rSO2 (rSO(2, %max)) when compared with the baseline value were calculated. The volume of blood loss, urine output, and the amount of fluid infusion was recorded.

RESULTS

A total of 14 patients (28%) in the 50 cases suffered from POCD. The values of mini-mental state examination (MMSE), the digit span and the digit symbol on the 7th day after the operation for POCD in OLV patients were found to be significantly lower than those before the operation (P<0.05). The values of MMSE and vocabulary fluency scores were significantly lower than those in the non-POCD group (P<0.05). The values of rSO2 in the POCD group of OLV patients at t2 and t3 and the values of rSO2 in the non-POCD group at t2 were found to be significantly higher than those at t1 (P<0.05). The values of rSO(2, %max) in the POCD group were significantly higher than those in the non-POCD group (P<0.05). When the value of rSO(2, %max) is more than 10.1%, it may act as an early warning index for cognitive function changes.

CONCLUSIONS

POCD after OLV may be associated with a decline in rSO2.

NFκB-inducing kinase inhibits NFκB activity specifically in neurons of the CNS

The control of NFκB in CNS neurons appears to differ from that in other cell types. Studies have reported induction of NFκB in neuronal cultures and immunostaining in vivo, but others have consistently detected little or no transcriptional activation by NFκB in brain neurons. To test if neurons lack some component of the signal transduction system for NFκB activation, we transfected cortical neurons with several members of this signaling system along with a luciferase-based NFκB-reporter plasmid; RelA was cotransfected in some conditions. No component of the NFκB pathway was permissive for endogenous NFκB activity, and none stimulated the activity of exogenous RelA. Surprisingly, however, the latter was inhibited by cotransfection of NFκB-inducing kinase (NIK). Fluorescence imaging of RelA indicated that co-expression of NIK sequestered RelA in the cytoplasm, similar to the effect of IκBα. NIK-knockout mice showed elevated expression of an NFκB-reporter construct in neurons in vivo. Cortical neurons cultured from NIK-knockout mice showed elevated expression of an NFκB-reporter transgene. Consistent with data from other cell types, a C-terminal fragment of NIK suppressed RelA activity in astrocytes as well as neurons. Therefore, the inhibitory ability of the NIK C-terminus was unbiased with regard to cell type. However, inhibition of NFκB by full-length NIK is a novel outcome that appears to be specific to CNS neurons. This has implications for unique aspects of transcription in the CNS, perhaps relevant to aspects of development, neuroplasticity, and neuroinflammation. Full-length NIK was found to inhibit (down arrow) transcriptional activation of NFκB in neurons, while it elevated (up arrow) activity in astrocytes. Deletion constructs corresponding to the N-terminus or C-terminus also inhibited NFκB in neurons, while only the C-terminus did so in astrocytes. One possible explanation is that the inhibition in neurons occurs via two different mechanisms, including the potential for a neuron-specific protein (e.g., one of the 14-3-3 class) to create a novel complex in neurons, whereas the C-terminus may interact directly with NFκB. [Structure of NIK is based on Liu J., Sudom A., Min X., Cao Z., Gao X., Ayres M., Lee F., Cao P., Johnstone S., Plotnikova O., Walker N., Chen G., and Wang Z. (2012) Structure of the nuclear factor κB-inducing kinase (NIK) kinase domain reveals a constitutively active conformation. J Biol Chem. 287, 27326-27334); N-terminal lobe is oriented at top].

Mitochondrial lysates induce inflammation and Alzheimer's disease-relevant changes in microglial and neuronal cells

Neuroinflammation occurs in Alzheimer's disease (AD). While AD genetic studies implicate inflammation-relevant genes and fibrillar amyloid-β protein promotes inflammation, our understanding of AD neuroinflammation nevertheless remains incomplete. In this study we hypothesized damage-associated molecular pattern (DAMP) molecules arising from mitochondria, intracellular organelles that resemble bacteria, could contribute to AD neuroinflammation. To preliminarily test this possibility, we exposed neuronal and microglial cell lines to enriched mitochondrial lysates. BV2 microglial cells treated with mitochondrial lysates showed decreased TREM2 mRNA, increased TNFα mRNA, increased MMP-8 mRNA, increased IL-8 mRNA, redistribution of NFκB to the nucleus, and increased p38 MAPK phosphorylation. SH-SY5Y neuronal cells treated with mitochondrial lysates showed increased TNFα mRNA, increased NFκB protein, decreased IκBα protein, increased AβPP mRNA, and increased AβPP protein. Enriched mitochondrial lysates from SH-SY5Y cells lacking detectable mitochondrial DNA (ρ0 cells) failed to induce any of these changes, while mtDNA obtained directly from mitochondria (but not PCR-amplified mtDNA) increased BV2 cell TNFα mRNA. These results indicate at least one mitochondrial-derived DAMP molecule, mtDNA, can induce inflammatory changes in microglial and neuronal cell lines. Our data are consistent with the hypothesis that a mitochondrial-derived DAMP molecule or molecules could contribute to AD neuroinflammation.

Magnesium ion influx reduces neuroinflammation in Aβ precursor protein/Presenilin 1 transgenic mice by suppressing the expression of interleukin-1β

Alzheimer's disease (AD) has been associated with magnesium ion (Mg²⁺) deficits and interleukin-1β (IL-1β) elevations in the serum or brains of AD patients. However, the mechanisms regulating IL-1β expression during Mg²⁺ dyshomeostasis in AD remain unknown. We herein studied the mechanism of IL-1β reduction using a recently developed compound, magnesium-L-threonate (MgT). Using human glioblastoma A172 and mouse brain D1A glial cells as an in vitro model system, we delineated the signaling pathways by which MgT suppressed the expression of IL-1β in glial cells. In detail, we found that MgT incubation stimulated the activity of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and peroxisome proliferator-activated receptor gamma (PPARγ) signaling pathways by phosphorylation, which resulted in IL-1β suppression. Simultaneous inhibition of the phosphorylation of ERK1/2 and PPARγ induced IL-1β upregulation in MgT-stimulated glial cells. In accordance with our in vitro data, the intracerebroventricular (i.c.v) injection of MgT into the ventricles of APP/PS1 transgenic mice and treatment of Aβ precursor protein (APP)/PS1 brain slices suppressed the mRNA and protein expression of IL-1β. These in vivo observations were further supported by the oral administration of MgT for 5 months. Importantly, Mg²⁺ influx into the ventricles of the mice blocked the effects of IL-1β or amyloid β-protein oligomers in the cerebrospinal fluid. This reduced the stimulation of IL-1β expression in the cerebral cortex of APP/PS1 transgenic mice, which potentially contributed to the inhibition of neuroinflammation.

Relationship between post-operative cognitive dysfunction and regional cerebral oxygen saturation and β-amyloid protein

OBJECTIVE

To investigate the relationship between post-operative cognitive dysfunction (POCD) and regional cerebral oxygen saturation (rSO2) and β-amyloid protein (Aβ) in patients undergoing laparoscopic pancreaticoduodenectomy.

METHODS

Fifty patients undergoing elective laparoscopic pancreaticoduodenectomy received five groups of neuropsychological tests 1 d pre-operatively and 7 d post-operatively, with continuous monitoring of rSO2 intra-operatively. Before anesthesia induction (t0), at the beginning of laparoscopy (t1), and at the time of pneumoperitoneum 120 min (t2), pneumoperitoneum 240 min (t3), pneumoperitoneum 480 min (t4), the end of pneumoperitoneum (t5), and 24 h after surgery, jugular venous blood was drawn respectively for the measurement of Aβ by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Twenty-one cases of the fifty patients suffered from POCD after operation. We found that the maximum percentage drop in rSO2 (rSO(2, %max)) was significantly higher in the POCD group than in the non-POCD group. The rSO(2, %max) value of over 10.2% might be a potential predictor of neurocognitive injury for those patients. In the POCD group, the plasma Aβ levels after 24 h were significantly higher than those of pre-operative values (P<0.01). After 24 h, levels of plasma Aβ in the POCD group were significantly higher than those in the non-POCD group (P<0.01).

CONCLUSIONS

The development of POCD in patients undergoing laparoscopic pancreaticoduodenectomy is associated with alterations of rSO2 and Aβ. Monitoring of rSO2 might be useful in the prediction of POCD, and Aβ might be used as a sensitive biochemical marker to predict the occurrence of POCD.

Transcriptional regulation and its misregulation in Alzheimer's disease

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder characterized by loss of memory and cognitive function. A key neuropathological event in AD is the accumulation of amyloid-β (Aβ) peptide. The production and clearance of Aβ in the brain are regulated by a large group of genes. The expression levels of these genes must be fine-tuned in the brain to keep Aβ at a balanced amount under physiological condition. Misregulation of AD genes has been found to either increase AD risk or accelerate the disease progression. In recent years, important progress has been made in uncovering the regulatory elements and transcriptional factors that guide the expression of these genes. In this review, we describe the mechanisms of transcriptional regulation for the known AD genes and the misregualtion that leads to AD susceptibility.

Sustained, neuron-specific IKK/NF-κB activation generates a selective neuroinflammatory response promoting local neurodegeneration with aging

Background

Increasing evidence indicates that neuroinflammation is a critical factor contributing to the progression of various neurodegenerative diseases. The IKK/NF-κB signalling system is a central regulator of inflammation, but it also affects neuronal survival and differentiation. A complex interplay between different CNS resident cells and infiltrating immune cells, which produce and respond to various inflammatory mediators, determines whether neuroinflammation is beneficial or detrimental. The IKK/NF-κB system is involved in both production of and responses to these mediators, although the precise contribution depends on the cell type as well as the cellular context, and is only partially understood. Here we investigated the specific contribution of neuronal IKK/NF-κB signalling on the regulation of neuroinflammatory processes and its consequences. To address this issue, we established and analysed a conditional gain-of-function mouse model that expresses a constitutively active allele of IKK2 in principal forebrain neurons (IKK2^nCA). Proinflammatory gene and growth factor expression, histopathology, microgliosis, astrogliosis, immune cell infiltration and spatial learning were assessed at different timepoints after persistent canonical IKK2/NF-κB activation.

Results

In contrast to other cell types and organ systems, chronic IKK2/NF-κB signalling in forebrain neurons of adult IKK2^nCA animals did not cause a full-blown inflammatory response including infiltration of immune cells. Instead, we found a selective inflammatory response in the dentate gyrus characterized by astrogliosis, microgliosis and Tnf-α upregulation. Furthermore, downregulation of the neurotrophic factor Bdnf correlated with a selective and progressive atrophy of the dentate gyrus and a decline in hippocampus-dependent spatial learning. Neuronal degeneration was associated with increased Fluoro-jade staining, but lacked activation of apoptosis. Remarkably, neuronal loss could be partially reversed when chronic IKK2/NF-κB signalling was turned off and Bdnf expression was restored.

Conclusion

Our results demonstrate that persistent IKK2/NF-κB signalling in forebrain neurons does not induce overall neuroinflammation, but elicits a selective inflammatory response in the dentate gyrus accompanied by decreased neuronal survival and impaired learning and memory. Our findings further suggest that chronic activation of neuronal IKK2/NF-κB signalling, possibly as a consequence of neuroinflammatory conditions, is able to induce apoptosis-independent neurodegeneration via paracrine suppression of Bdnf synthesis.

Zinc homeostasis and neurodegenerative disorders

Zinc is an essential trace element, whose importance to the function of the central nervous system (CNS) is increasingly being appreciated. Alterations in zinc dyshomeostasis has been suggested as a key factor in the development of several neuropsychiatric disorders. In the CNS, zinc occurs in two forms: the first being tightly bound to proteins and, secondly, the free, cytoplasmic, or extracellular form found in presynaptic vesicles. Under normal conditions, zinc released from the synaptic vesicles modulates both ionotropic and metabotropic post-synaptic receptors. While under clinical conditions such as traumatic brain injury, stroke or epilepsy, the excess influx of zinc into neurons has been found to result in neurotoxicity and damage to postsynaptic neurons. On the other hand, a growing body of evidence suggests that a deficiency, rather than an excess, of zinc leads to an increased risk for the development of neurological disorders. Indeed, zinc deficiency has been shown to affect neurogenesis and increase neuronal apoptosis, which can lead to learning and memory deficits. Altered zinc homeostasis is also suggested as a risk factor for depression, Alzheimer's disease (AD), aging, and other neurodegenerative disorders. Under normal CNS physiology, homeostatic controls are put in place to avoid the accumulation of excess zinc or its deficiency. This cellular zinc homeostasis results from the actions of a coordinated regulation effected by different proteins involved in the uptake, excretion and intracellular storage/trafficking of zinc. These proteins include membranous transporters (ZnT and Zip) and metallothioneins (MT) which control intracellular zinc levels. Interestingly, alterations in ZnT and MT have been recently reported in both aging and AD. This paper provides an overview of both clinical and experimental evidence that implicates a dysfunction in zinc homeostasis in the pathophysiology of depression, AD, and aging.

Minimal NF-κB activity in neurons

Nuclear factor-kappa B (NF-κB) is a ubiquitous transcription factor that regulates immune and cell-survival signaling pathways. NF-κB has been reported to be present in neurons wherein it reportedly responds to immune and toxic stimuli, glutamate, and synaptic activity. However, because the brain contains many cell types, assays specifically measuring neuronal NF-κB activity are difficult to perform and interpret. To address this, we compared NF-κB activity in cultures of primary neocortical neurons, mixed brain cells, and liver cells, employing Western blot of NF-κB subunits, electrophoretic mobility shift assay (EMSA) of nuclear κB DNA binding, reporter assay of κB DNA binding, immunofluorescence of the NF-κB subunit protein p65, quantitative real-time polymerase chain reaction (PCR) of NF-κB-regulated gene expression, and enzyme-linked immunosorbent assay (ELISA) of produced proteins. Assay of p65 showed its constitutive presence in cytoplasm and nucleus of neurons at levels significantly lower than in mixed brain or liver cells. EMSA and reporter assays showed that constitutive NF-κB activity was nearly absent in neurons. Induced activity was minimal--many fold lower than in other cell types, as measured by phosphorylation and degradation of the inhibitor IκBα, nuclear accumulation of p65, binding to κB DNA consensus sites, NF-κB reporting, or induction of NF-κB-responsive genes. The most efficacious activating stimuli for neurons were the pro-inflammatory cytokines tumor necrosis factor α (TNFα) and interleukin-beta (IL-β). Neuronal NF-κB was not responsive to glutamate in most assays, and it was also unresponsive to hydrogen peroxide, lipopolysaccharide, norepinephrine, ATP, phorbol ester, and nerve growth factor. The chemokine gene transcripts CCL2, CXCL1, and CXCL10 were strongly induced via NF-κB activation by TNFα in neurons, but many candidate responsive genes were not, including the neuroprotective genes SOD2 and Bcl-xL. Importantly, the level of induced neuronal NF-κB activity in response to TNFα or any other stimulus was lower than the level of constitutive activity in non-neuronal cells, calling into question the functional significance of neuronal NF-κB activity.

Inflammation and clinical presentation in neurodegenerative disease: a volatile relationship

A proposed immune mechanism that potentially modifies or exacerbates neurodegenerative disease presentation in older adults has received considerable attention in the past decade, with recent studies demonstrating a strong link between pro-inflammatory markers and neurodegeneration. The overarching aim of the following review is to synthesize recent research that supports a possible relationship between inflammation and clinical features of neurodegenerative diseases, including risk of development, cognitive and clinical correlates, and progression of the specified diseases. Specific emphasis is placed on providing a temporal context for the association between inflammation and neurodegeneration.

Clusterin in Alzheimer's disease

Clusterin, also known as apolipoprotein J, is a ubiquitous multifunctional glycoprotein. Following its identification in 1983, clusterin was found to be clearly increased in Alzheimer's disease (AD). Later research demonstrated that clusterin could bind amyloid-beta (Abeta) peptides and prevent fibril formation, a hallmark of AD pathology. In addition to preventing excessive inflammation, intracellular clusterin was found to reduce apoptosis and oxidative stress. Although early studies were inconclusive, two recent large-scale genome-wide association studies (GWAS) independently identified variants within the clusterin gene as risk factors for developing AD. This review focuses on the characteristics of clusterin and possible mechanisms of its relationship to AD.

Inhibitory effect of a tyrosine-fructose Maillard reaction product, 2,4-bis(p-hydroxyphenyl)-2-butenal on amyloid-β generation and inflammatory reactions via inhibition of NF-κB and STAT3 activation in cultured astrocytes and microglial BV-2 cells

BACKGROUND

Amyloidogenesis is linked to neuroinflammation. The tyrosine-fructose Maillard reaction product, 2,4-bis(p-hydroxyphenyl)-2-butenal, possesses anti-inflammatory properties in cultured macrophages, and in an arthritis animal model. Because astrocytes and microglia are responsible for amyloidogenesis and inflammatory reactions in the brain, we investigated the anti-inflammatory and anti-amyloidogenic effects of 2,4-bis(p-hydroxyphenyl)-2-butenal in lipopolysaccharide (LPS)-stimulated astrocytes and microglial BV-2 cells.

METHODS

Cultured astrocytes and microglial BV-2 cells were treated with LPS (1 μg/ml) for 24 h, in the presence (1, 2, 5 μM) or absence of 2,4-bis(p-hydroxyphenyl)-2-butenal, and harvested. We performed molecular biological analyses to determine the levels of inflammatory and amyloid-related proteins and molecules, cytokines, Aβ, and secretases activity. Nuclear factor-kappa B (NF-κB) DNA binding activity was determined using gel mobility shift assays.

RESULTS

We found that 2,4-bis(p-hydroxyphenyl)-2-butenal (1, 2, 5 μM) suppresses the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) as well as the production of nitric oxide (NO), reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) in LPS (1 μg/ml)-stimulated astrocytes and microglial BV-2 cells. Further, 2,4-bis(p-hydroxyphenyl)-2-butenal inhibited the transcriptional and DNA binding activity of NF-κB--a transcription factor that regulates genes involved in neuroinflammation and amyloidogenesis via inhibition of IκB degradation as well as nuclear translocation of p50 and p65. Consistent with the inhibitory effect on inflammatory reactions, 2,4-bis(p-hydroxyphenyl)-2-butenal inhibited LPS-elevated Aβ42 levels through attenuation of β- and γ-secretase activities. Moreover, studies using signal transducer and activator of transcription 3 (STAT3) siRNA and a pharmacological inhibitor showed that 2,4-bis(p-hydroxyphenyl)-2-butenal inhibits LPS-induced activation of STAT3.

CONCLUSIONS

These results indicate that 2,4-bis(p-hydroxyphenyl)-2-butenal inhibits neuroinflammatory reactions and amyloidogenesis through inhibition of NF-κB and STAT3 activation, and suggest that 2,4-bis(p-hydroxyphenyl)-2-butenal may be useful for the treatment of neuroinflammatory diseases like Alzheimer's disease.

Sensory stimuli induce nuclear translocation and phosphorylation of nuclear factor κ B in primary sensory neurons of mice

Nuclear factor kappa B (NF-κB) is a transcription factor, which is translocated to the nucleus when activated. Herein, we demonstrate immunohistochemically that electrical, chemical, and thermal stimuli, applied to the skin of mice, all induced nuclear translocation and phosphorylation of NF-κB in dorsal root ganglia (DRG) neurons. The latency of this response was short, with effects observable in as little as 3min following stimulation. Few nuclear phospho-NF-κB-positive neurons were observed in DRG innervating unstimulated regions. These results suggest somatosensory stimuli quickly induce NF-κB-mediated gene transcription in DRG, and phospho-NF-κB could be a suitable histological marker for activated DRG neurons.

Paeonol attenuates H₂O₂-induced NF-κB-associated amyloid precursor protein expression

Hydrogen peroxide (H₂O₂) has been shown to promote neurodegeneration by inducing the activation of nuclear factor-κB (NF-κB). In this study, NF-κB activation was induced by H₂O₂ in human neuroblastoma SH-SY5Y cells. Whether paeonol, one of the phenolic phytochemicals isolated from the Chinese herb Paeonia suffruticosa Andrews (MC), would attenuate the H₂O₂-induced NF-κB activity was investigated. Western blot results showed that paeonol inhibited the phosphorylation of IκB and the translocation of NF-κB into the nucleus. The ability of paeonol to reduce DNA binding ability and suppress the H₂O₂-induced NF-κB activation was confirmed by an electrophoretic mobility shift assay and a luciferase reporter assay. Using a microarray combined with gene set analysis, we found that the suppression of NF-κB was associated with mature T cell up-regulated genes, the c-jun N-terminal kinase pathway, and two hypoxia-related gene sets, including the hypoxia up-regulated gene set and hypoxia inducible factor 1 targets. Moreover, using network analysis to investigate genes that were altered by H₂O₂ and reversely regulated by paeonol, we found that NF-κB was the primary center of the network and amyloid precursor protein (APP) was the secondary center. Western blotting showed that paeonol inhibited APP at the protein level. In conclusion, our work suggests that paeonol down-regulates H₂O₂-induced NF-κB activity, as well as NF-κB-associated APP expression. Furthermore, the gene expression profile accompanying the suppression of NF-κB by paeonol was identified. The new gene set that can be targeted by paeonol provided a potential use for this drug and a possible pharmacological mechanism for other phenolic compounds that protect against oxidative-related injury.

Ischemic preconditioning mediates cyclooxygenase-2 expression via nuclear factor-kappa B activation in mixed cortical neuronal cultures

Nuclear factor-kappaB (NF-κB) activation occurs following ischemic preconditioning (IPC) in brain. However, the upstream signaling messengers and down-stream targets of NF-κB required for induction of IPC remain undefined. In a previous study, we demonstrated that epsilon protein kinase c (εPKC) was a key mediator of IPC in brain. Activation of εPKC induced cyclooygenase-2 (COX-2) expression and conferred ischemic tolerance in the neuronal and hippocampal slice models. Here, we hypothesized that IPC-mediated COX-2 expression was mediated by NF-κB. We tested this hypothesis in mixed cortical neuron/astrocyte cell cultures. To simulate IPC or ischemia, cell cultures were exposed to 1 or 4 h of oxygen-glucose deprivation, respectively. Our results demonstrated translocation of p65 and p50 subunits of NF-κB into nucleus following IPC or εPKC activation. NF-κB inhibition with pyrrolidine dithiocarbamate (10 μM) abolished IPC or εPKC activator-mediated neuroprotection indicating that NF-κB activation was involved in ischemic tolerance. In parallel studies, inhibition of either εPKC or the extracellular signal-regulated kinase (ERK 1/2) pathway reduced IPC-induced NF-κB activation. Finally, inhibition of NF-κB blocked IPC-induced COX-2 expression. In conclusion, we demonstrated that IPC-signaling cascade comprises εPKC activation→ERK1/2 activation→NF-κB translocation to nucleus→COX-2 expression resulting in neuroprotection in mixed neuronal culture.

APP expression, distribution and accumulation are altered by aluminum in a rodent model for Alzheimer's disease

Up-regulated expression of amyloid precursor protein (APP) occurs early in the cascade of events that leads to amyloid plaque formation in the human brain. APP gene up-regulation, mediated by activated NF-kappaB, is a response to stress from nM concentrations of aluminum ions, aluminum-disregulated iron ions, reactive-oxygen species, cytokines, and physical trauma. We examined in vivo effects of aluminum on APP in aged rats, obtained from previously-reported longitudinal studies, that chronically ingested aluminum in amounts equivalent to total dietary aluminum levels that Americans routinely ingest. These rats exhibited two outcomes: one group remained cognitively-intact, scoring as well on a memory-discrimination task in old age as in middle age. The other developed cognitive deterioration, obtaining significantly lower mean performance scores in old age than in middle age and exhibiting abnormal behaviors associated with dementia. We compared the expression, distribution and accumulation of APP in hippocampal and cortical tissue of these two rat groups. Compared to results from cognitively-intact rats, hippocampal and cortical tissue from the cognitively-deteriorated rats showed elevated APP gene expression, significantly more dense APP deposits in cytoplasm of neural cells, and APP-immunoreactive neurites that were swollen and varicose. This study shows aluminum routinely derived from chronic oral ingestion, that gradually accumulates in brain regions important for memory-processing, is sufficient to increase APP levels in neural cells of those regions. Aluminum may thus launch the cascade that results in the formation of amyloid plaques in human brain.

The comorbidity of HIV-associated neurocognitive disorders and Alzheimer's disease: a foreseeable medical challenge in post-HAART era

Although the introduction of highly active antiretroviral therapy (HAART) has led to a strong reduction of HIV-associated dementia (HAD) incidence, the prevalence of minor HIV-1-associated neurocognitive disorder (HAND) is rising among AIDS patients. HAART medication has shifted neuropathology from a subacute encephalitic condition to a subtle neurodegenerative process involving synaptic and dendritic degeneration, particularly of hippocampal neurons that are spared prior to HAART medication. Considerable neuroinflammation coupled with mononuclear phagocyte activation is present in HAART-medicated brains, particularly in the hippocampus. Accumulating evidence suggests that the resultant elevated secretion of pro-inflammatory cytokines such as interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta can increase amyloid-beta peptide (Abeta) generation and reduce Abeta clearance. Recent advancements in Alzheimer's disease (AD) research identified Abeta biogenesis and clearance venues that are potentially influenced by HIV viral infection, providing new insights into beta-amyloidosis segregation in HIV patients. Our study suggests enhanced beta-amyloidosis in ART-treated HAD and HIV-associated encephalitis brains and suppression of Abeta clearance by viral infection of human primary macrophages. A growing awareness of potential convergent mechanisms leading to neurodegeneration shared by HIV and Abeta points to a significant chance of comorbidity of AD and HAND in senile HIV patients, which calls for a need of basic studies.

Unique aspects of transcriptional regulation in neurons--nuances in NFkappaB and Sp1-related factors

The unique physiology and function of neurons create differences in their cellular physiology, including their regulation of gene expression. We began several years ago exploring the relationships between the NFκB transcription factor, neuronal survival, and glutamate receptor activation in telencephalic neurons. These studies led us to conclude that this population of cells is nearly incapable of activating the NFκB that is nonetheless expressed at reasonable levels. A subset of the κB cis elements are instead bound by members of the Sp1 family in neurons. Also surprising was our discovery that Sp1 itself, typically described as ubiquitous, is severely restricted in expression within forebrain neurons; Sp4 seems to be substituted during neuronal differentiation. These findings and their implications for neuronal differentiation – as well as potential dedifferentiation during degenerative processes – are discussed here.

Trace amounts of copper exacerbate beta amyloid-induced neurotoxicity in the cholesterol-fed mice through TNF-mediated inflammatory pathway

Evidence has been gathered to suggest that trace amounts of copper induce neurotoxicity by interaction with elevated cholesterol in diet. Step-through task and Morris water maze task were used to evaluate cognitive function in the animals. Although a 16-week copper treatment alone in mice showed no significant change in learning and memory performances, cholesterol treatment significantly induced learning and memory impairments, which could be exacerbated by the co-treatment with copper. Immunohistochemical studies revealed that trace amounts of copper further stimulated the amyloid precursor protein (APP) upregulation and contributed to amyloid beta-peptide (Abeta) deposition in the brain of cholesterol-fed mice. Western blot analysis showed that copper also increased the protein expression levels of tumor necrosis factor-alpha (TNF-alpha) and the degradation of IkappaB proteins in the brain of cholesterol-fed mice. Furthermore, increased production of high inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) expressions were detected in the hippocampus and cerebral cortex of copper and cholesterol co-treated mice by immunohistochemical analysis. These findings suggest that trace amounts of copper could induce APP upregulation, activate inflammatory pathway and exacerbate neurotoxicity in cholesterol-fed mice.

Tumor necrosis factor (TNF)-alpha persistently activates nuclear factor-kappaB signaling through the type 2 TNF receptor in chromaffin cells: implications for long-term regulation of neuropeptide gene expression in inflammation

Chromaffin cells of the adrenal medulla elaborate and secrete catecholamines and neuropeptides for hormonal and paracrine signaling in stress and during inflammation. We have recently documented the action of the cytokine TNF-alpha on neuropeptide secretion and biosynthesis in isolated bovine chromaffin cells. Here, we demonstrate that the type 2 TNF-alpha receptor (TNF-R2) mediates TNF-alpha signaling in chromaffin cells via activation of nuclear factor (NF)-kappaB. Microarray and suppression subtractive hybridization have been used to identify TNF-alpha target genes in addition to those encoding the neuropeptides galanin, vasoactive intestinal polypeptide, and secretogranin II in chromaffin cells. TNF-alpha, acting through the TNF-R2, causes an early up-regulation of NF-kappaB, long-lasting induction of the NF-kappaB target gene inhibitor kappaB (IkappaB), and persistent stimulation of other NF-kappaB-associated genes including mitogen-inducible gene-6 (MIG-6), which acts as an IkappaB signaling antagonist, and butyrate-induced transcript 1. Consistent with long-term activation of the NF-kappaB signaling pathway, delayed induction of neuropeptide gene transcription by TNF-alpha in chromaffin cells is blocked by an antagonist of NF-kappaB signaling. TNF-alpha-dependent signaling in neuroendocrine cells thus leads to a unique, persistent mode of NF-kappaB activation that features long-lasting transcription of both IkappaB and MIG-6, which may play a role in the long-lasting effects of TNF-alpha in regulating neuropeptide output from the adrenal, a potentially important feedback station for modulating long-term cytokine effects in inflammation.

The role of peroxisome proliferator-activated receptor-gamma (PPARgamma) in Alzheimer's disease: therapeutic implications

Alzheimer's disease is a complex neurodegenerative disorder, with aging, genetic and environmental factors contributing to its development and progression. The complexity of Alzheimer's disease presents substantial challenges for the development of new therapeutic agents. Alzheimer's disease is typified by pathological depositions of beta-amyloid peptides and neurofibrillary tangles within the diseased brain. It has also been demonstrated to be associated with a significant microglia-mediated inflammatory component, dysregulated lipid homeostasis and regional deficits in glucose metabolism within the brain. The peroxisome proliferator-activated receptor-gamma (PPARgamma) is a prototypical ligand-activated nuclear receptor that coordinates lipid, glucose and energy metabolism, and is found in elevated levels in the brains of individuals with Alzheimer's disease. A recently appreciated physiological function of this type of receptor is its ability to modulate inflammatory responses. In animal models of Alzheimer's disease, PPARgamma agonist treatment results in the reduction of amyloid plaque burden, reduced inflammation and reversal of disease-related behavioural impairment. In a recent phase II clinical trial, the use of the PPARgamma agonist rosiglitazone was associated with improved cognition and memory in patients with mild to moderate Alzheimer's disease. Thus, PPARgamma may act to modulate multiple pathophysiological mechanisms that contribute to Alzheimer's disease, and represents an attractive therapeutic target for the treatment of the disease.

Salsolinol, an endogenous neurotoxin, activates JNK and NF-kappaB signaling pathways in human neuroblastoma cells

Salsolinol, an endogenous neurotoxin, is known to be involved in the pathogenesis of Parkinson's disease (PD). In the present study, we have investigated the effects of salsolinol on the activation of two different signaling pathways that involve c-Jun N-terminal kinase (JNK), and nuclear factor-kappaB, (NF-kappaB) in human dopaminergic neuroblastoma SH-SY5Y cells. Salsolinol treatment caused upregulation in the levels of c-Jun and phosphorylated c-Jun. It also caused degradation of IkappaBalpha and translocated the active NF-kappaB into the nucleus. The binding activity of NF-kappaB to DNA was enhanced by salsolinol in a concentration dependent manner. Furthermore, salsolinol decreased the levels of the anti-apoptotic protein Bcl-2, and increased pro-apoptotic protein Bax, while enhancing the release of cytochrome-c from mitochondria. Mitochondrial complex-I activity was significantly decreased and reactive oxygen species (ROS) were increased in salsolinol treated cells. These results partly suggest that salsolinol-induced JNK and NF-kappaB signaling pathways may be involved in induction of apoptosis in human dopaminergic neurons, as seen in Parkinson's disease.

Genetics of inclusion-body myositis

Sporadic inclusion-body myositis (sIBM) is the most common acquired muscle disease in Caucasians over the age of 50 years. Pathologically it is marked by inflammatory, degenerative, and mitochondrial changes that interact in a yet-unknown way to cause progressive muscle degeneration and weakness. The cause of the disease is unknown, but it is thought to involve a complex interplay between environmental factors, genetic susceptibility, and aging. The strongest evidence for genetic susceptibility comes from studies of the major histocompatibility complex (MHC), where different combinations of alleles have been associated with sIBM in different ethnic groups. The rare occurrence of familial cases of inclusion-body myositis (fIBM) adds additional evidence for genetic susceptibility. Other candidate genes such as those encoding some of the proteins accumulating in muscle fibers have been investigated, with negative results. The increased understanding of related disorders, the hereditary inclusion-body myopathies (hIBM), may also provide clues to the underlying pathogenesis of sIBM, but to date there is no indication that the genes responsible for these conditions are involved in sIBM. This review summarizes current understanding of the contribution of genetic susceptibility factors to the development of sIBM.