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

Copper Metabolism and Cuproptosis: Molecular Mechanisms and Therapeutic Perspectives in Neurodegenerative Diseases

Copper is an essential trace element, and plays a vital role in numerous physiological processes within the human body. During normal metabolism, the human body maintains copper homeostasis. Copper deficiency or excess can adversely affect cellular function. Therefore, copper homeostasis is stringently regulated. Recent studies suggest that copper can trigger a specific form of cell death, namely, cuproptosis, which is triggered by excessive levels of intracellular copper. Cuproptosis induces the aggregation of mitochondrial lipoylated proteins, and the loss of iron-sulfur cluster proteins. In neurodegenerative diseases, the pathogenesis and progression of neurological disorders are linked to copper homeostasis. This review summarizes the advances in copper homeostasis and cuproptosis in the nervous system and neurodegenerative diseases. This offers research perspectives that provide new insights into the targeted treatment of neurodegenerative diseases based on cuproptosis.

Inflammation in Metal-Induced Neurological Disorders and Neurodegenerative Diseases

Essential metals play critical roles in maintaining human health as they participate in various physiological activities. Nonetheless, both excessive accumulation and deficiency of these metals may result in neurotoxicity secondary to neuroinflammation and the activation of microglia and astrocytes. Activation of these cells can promote the release of pro-inflammatory cytokines. It is well known that neuroinflammation plays a critical role in metal-induced neurotoxicity as well as the development of neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Initially seen as a defense mechanism, persistent inflammatory responses are now considered harmful. Astrocytes and microglia are key regulators of neuroinflammation in the central nervous system, and their excessive activation may induce sustained neuroinflammation. Therefore, in this review, we aim to emphasize the important role and molecular mechanisms underlying metal-induced neurotoxicity. Our objective is to raise the awareness on metal-induced neuroinflammation in neurological disorders. However, it is not only just neuroinflammation that different metals could induce; they can also cause harm to the nervous system through oxidative stress, apoptosis, and autophagy, to name a few. The primary pathophysiological mechanism by which these metals induce neurological disorders remains to be determined. In addition, given the various pathways through which individuals are exposed to metals, it is necessary to also consider the effects of co-exposure to multiple metals on neurological disorders.

Cuproptosis-related genes signature and validation of differential expression and the potential targeting drugs in temporal lobe epilepsy

Introduction: Temporal lobe epilepsy (TLE) is the most common subtype of epilepsy in adults and is characterized by neuronal loss, gliosis, and sprouting mossy fibers in the hippocampus. But the mechanism underlying neuronal loss has not been fully elucidated. A new programmed cell death, cuproptosis, has recently been discovered; however, its role in TLE is not clear. Methods: We first investigated the copper ion concentration in the hippocampus tissue. Then, using the Sample dataset and E-MTAB-3123 dataset, we analyzed the features of 12 cuproptosis-related genes in TLEs and controls using the bioinformatics tools. Then, the expression of the key cuproptosis genes were confirmed using real-time PCR and immunohistochemical staining (IHC). Finally, the Enrichr database was used to screen the small molecules and drugs targeting key cuproptosis genes in TLE. Results: The Sample dataset displayed four differentially expressed cuproptosis-related genes (DECRGs; LIPT1, GLS, PDHA1, and CDKN2A) while the E-MTAB-3123 dataset revealed seven DECRGs (LIPT1, DLD, FDX1, GLS, PDHB, PDHA1, and DLAT). Remarkably, only LIPT1 was uniformly upregulated in both datasets. Additionally, these DECRGs are implicated in the TCA cycle and pyruvate metabolism-both crucial for cell cuproptosis-as well as various immune cell infiltrations, especially macrophages and T cells, in the TLE hippocampus. Interestingly, DECRGs were linked to most infiltrating immune cells during TLE's acute phase, but this association considerably weakened in the latent phase. In the chronic phase, DECRGs were connected with several T-cell subclasses. Moreover, LIPT1, FDX1, DLD, and PDHB were related to TLE identification. PCR and IHC further confirmed LIPT1 and FDX1's upregulation in TLE compared to controls. Finally, using the Enrichr database, we found that chlorzoxazone and piperlongumine inhibited cell cuproptosis by targeting LIPT1, FDX1, DLD, and PDHB. Conclusion: Our findings suggest that cuproptosis is directly related to TLE. The signature of cuproptosis-related genes presents new clues for exploring the roles of neuronal death in TLE. Furthermore, LIPT1 and FDX1 appear as potential targets of neuronal cuproptosis for controlling TLE's seizures and progression.

The metal ion hypothesis of Alzheimer's disease and the anti-neuroinflammatory effect of metal chelators

Alzheimer's disease (AD), characterized by the β-amyloid protein (Aβ) deposition and tau hyperphosphorylation, is the most common dementia with uncertain etiology. The clinical trials of Aβ monoclonal antibody drugs have almost failed, giving rise to great attention on the other etiologic hypothesis regarding AD such as metal ions dysmetabolism and chronic neuroinflammation. Mounting evidence revealed that the metal ions (iron, copper, and zinc) were dysregulated in the susceptible brain regions of AD patients, which was highly associated with Aβ deposition, tau hyperphosphorylation, neuronal loss, as well as neuroinflammation. Further studies uncovered that iron, copper and zinc could not only enhance the production of Aβ but also directly bind to Aβ and tau to promote their aggregations. In addition, the accumulation of iron and copper could respectively promote ferroptosis and cuproptosis. Therefore, the metal ion chelators were recognized as promising agents for treating AD. This review comprehensively summarized the effects of metal ions on the Aβ dynamics and tau phosphorylation in the progression of AD. Furthermore, taking chronic neuroinflammation contributes to the progression of AD, we also provided a summary of the mechanisms concerning metal ions on neuroinflammation and highlighted the metal ion chelators may be potential agents to alleviate neuroinflammation under the condition of AD. Nevertheless, more investigations regarding metal ions on neuroinflammation should be taken into practice, and the effects of metal ion chelators on neuroinflammation should gain more attention. Running title: Metal chelators against neuroinflammation.

Exposure of aluminium to C6 glioma cells modulates molecular and functional neurotoxic markers

The risk of aluminium exposure to humans is very high as it may get into the human body through excessive dietary contaminants, inhalation of fine particulate matter, or through parenteral routes as a vaccine adjuvant and so forth. The increased level of aluminium in brain tissue has been shown to be associated with several neurodegenerative and neurotoxic adverse effects, including AD. However, the exact mechanism of aluminium-induced neurotoxicity is still unclear. Therefore, our study aimed to investigate the mechanism of neurotoxic and neurodegenerative effects through in vitro exposure of aluminium in rat glioma C6 cell line. The findings of our study have indicated that aluminium chloride exposure may lead to alteration in acetylcholine levels, increased oxidative imbalance and induction of molecular structural and functional markers of neuronal inflammation. This study also demonstrated that aluminium exposure may lead to the induction of caspase-3 along with apoptotic cell death and a significant increase in amyloid-beta and hyperphosphorylated tau levels in C6 cells. Thus, this study may provide a mechanistic understanding of the regulation of neuroinflammatory and neurodegenerative biomarkers due to aluminium exposure.

Current understanding of the interactions between metal ions and Apolipoprotein E in Alzheimer's disease

Alzheimer's disease (AD), the most common type of dementia in the elderly, is a chronic and progressive neurodegenerative disorder with no effective disease-modifying treatments to date. Studies have shown that an imbalance in brain metal ions, such as zinc, copper, and iron, is closely related to the onset and progression of AD. Many efforts have been made to understand metal-related mechanisms and therapeutic strategies for AD. Emerging evidence suggests that interactions of brain metal ions and apolipoprotein E (ApoE), which is the strongest genetic risk factor for late-onset AD, may be one of the mechanisms for neurodegeneration. Here, we summarize the key points regarding how metal ions and ApoE contribute to the pathogenesis of AD. We further describe the interactions between metal ions and ApoE in the brain and propose that their interactions play an important role in neuropathological alterations and cognitive decline in AD.

Chronic oral exposure of aluminum chloride in rat modulates molecular and functional neurotoxic markers relevant to Alzheimer's disease

Aluminum is an environmentally abundant potential neurotoxic agent that may result in oxidative damage to a range of cellular biomarkers. The potential sources of aluminum accumulation in body include drinking water, food, medicines, vaccines, and aluminum cookware utensils etc. The accumulation of aluminum in brain is reported to be associated with cholinergic dysfunction, oxidative stress and neuronal damage, that may ultimately cause Alzheimer's disease. Since chronic exposure of aluminum leads to its accumulation in brain, so this study was done by a long-term (24 weeks) low dose (20 mg/kg) oral exposure of aluminum chloride in rats. In this chronic model, we have evaluated the major hallmarks of Alzheimer's disease including amyloid beta (Aβ_1-42) and phosphorylated-tau (p231-tau) protein in brain tissue. Furthermore, we evaluated the level of acetyl cholinesterase activity, inflammatory cytokines such as TNF-α, IL-6 and IL-1β, and oxidative stress biomarkers in rat brain in this model. The neurobehavioral parameters were also assessed in animals by using spontaneous locomotor activity, passive avoidance, rotarod test and novel object recognition test to evaluate alteration in learning, memory and muscle co-ordination. We found that chronic oral exposure of aluminum chloride causes a significant increase in structural hallmarks such as Aβ_1-42 and p231-tau levels along with proinflammatory cytokines (TNF-α and IL-6), oxidative stress, and a decrease in antioxidant markers such as GSH and catalase. in the brain tissue. These biomarkers significantly affected neurobehavioral parameters in animals. This study provides a mechanistic understanding of chronic aluminum-induced neuronal toxicity in brain with relevance to Alzheimer's disease.

Microglia and Astrocytes in Alzheimer's Disease in the Context of the Aberrant Copper Homeostasis Hypothesis

Evidence of copper’s (Cu) involvement in Alzheimer’s disease (AD) is available, but information on Cu involvement in microglia and astrocytes during the course of AD has yet to be structurally discussed. This review deals with this matter in an attempt to provide an updated discussion on the role of reactive glia challenged by excess labile Cu in a wide picture that embraces all the major processes identified as playing a role in toxicity induced by an imbalance of Cu in AD.

Natural products attenuate PI3K/Akt/mTOR signaling pathway: A promising strategy in regulating neurodegeneration

BACKGROUND

As common, progressive, and chronic causes of disability and death, neurodegenerative diseases (NDDs) significantly threaten human health, while no effective treatment is available. Given the engagement of multiple dysregulated pathways in neurodegeneration, there is an imperative need to target the axis and provide effective/multi-target agents to tackle neurodegeneration. Recent studies have revealed the role of phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) in some diseases and natural products with therapeutic potentials.

PURPOSE

This is the first systematic and comprehensive review on the role of plant-derived secondary metabolites in managing and/or treating various neuronal disorders via the PI3K/Akt/mTOR signaling pathway.

STUDY DESIGN AND METHODS

A systematic and comprehensive review was done based on the PubMed, Scopus, Web of Science, and Cochrane electronic databases. Two independent investigators followed the PRISMA guidelines and included papers on PI3K/Akt/mTOR and interconnected pathways/mediators targeted by phytochemicals in NDDs.

RESULTS

Natural products are multi-target agents with diverse pharmacological and biological activities and rich sources for discovering and developing novel therapeutic agents. Accordingly, recent studies have shown increasing phytochemicals in combating Alzheimer's disease, aging, Parkinson's disease, brain/spinal cord damages, depression, and other neuronal-associated dysfunctions. Amongst the emerging targets in neurodegeneration, PI3K/Akt/mTOR is of great importance. Therefore, attenuation of these mediators would be a great step towards neuroprotection in such NDDs.

CONCLUSION

The application of plant-derived secondary metabolites in managing and/or treating various neuronal disorders through the PI3K/Akt/mTOR signaling pathway is a promising strategy towards neuroprotection.

Protective effect of surfactin on copper sulfate-induced inflammation, oxidative stress, and hepatic injury in zebrafish

Surfactin, an antibacterial peptide, produced by various Bacillus subtilis strains, have broad-spectrum antibacterial and immune-enhancing functions. In this study, we investigated the anti-inflammatory, antioxidant, and hepatoprotective effect of surfactin on zebrafish (Danio rerio) larvae following their exposure to copper sulfate (CuSO₄ ). The mature AB wild-type and a transgenic line of zebrafish larvae that expressed enhanced GFP (EGFP) named Tg (Lyz:EGFP) were exposed to 0, 20, 40, and 60 μg/mL surfactin after incubation with 3.2 μg/mL CuSO₄ for 2 h from 72 h postfertilization (hpf). Different endpoints, such as migration of GFP-labeled neutrophils, analysis of inflammatory cytokines and transaminases, markers of oxidation, expression of certain genes, and histological changes of liver, were studied to evaluate the function of surfactin. The protein expression levels of NF-κBp65, TNF-α, cyclooxygenase-2 (COX-2), and iNOS were determined in murine macrophage RAW 264.7 cells by western blotting. Our results show that surfactin reduced migration of neutrophils and relieved hepatic injury. In addition, surfactin reduced the index levels of inflammatory factors, oxidative stress response, and improved hepatic function. Surfactin also significantly inhibited the expression of IL-1β, IL-8, TNF-α, nitric oxide, NF-κBp65, COX-2, and iNOS, and increased the expression of IL-10. Thus, our results demonstrate that surfactin has anti-inflammatory, antioxidant, and hepatoprotective activities. Surfactin has potential as a novel inflammation and immune adjustment.

Bone marrow mesenchymal stem cells and their derived exosomes resolve doxorubicin-induced chemobrain: critical role of their miRNA cargo

Background

Doxorubicin (DOX), a widely used chemotherapeutic agent, can cause neurodegeneration in the brain, which leads to a condition known as chemobrain. In fact, chemobrain is a deteriorating condition which adversely affects the lives of cancer survivors. This study aimed to examine the potential therapeutic effects of bone marrow mesenchymal stem cells (BMSCs) and their derived exosomes (BMSCs-Exo) in DOX-induced chemobrain in rat models.

Methods

Chemobrain was induced by exposing rats to DOX (2 mg/kg, i.p) once weekly for 4 consecutive weeks. After 48 h of the last DOX dose, a subset of rats was supplied with either an intravenous injection of BMSCs (1 × 10⁶) or a single dose of 150 μg of BMSCs-Exo. Behavioral tests were conducted 7 days post injection. Rats were sacrificed after 14 days from BMSCs or BMSCs-Exo injection.

Results

BMSCs and BMSCs-Exo successfully restored DOX-induced cognitive and behavioral distortion. These actions were mediated via decreasing hippocampal neurodegeneration and neural demyelination through upregulating neural myelination factors (myelin%, Olig2, Opalin expression), neurotropic growth factors (BDNF, FGF-2), synaptic factors (synaptophysin), and fractalkine receptor expression (Cx3cr1). Halting neurodegeneration in DOX-induced chemobrain was achieved through epigenetic induction of key factors in Wnt/β-catenin and hedgehog signaling pathways mediated primarily by the most abundant secreted exosomal miRNAs (miR-21-5p, miR-125b-5p, miR-199a-3p, miR-24-3p, let-7a-5p). Moreover, BMSCs and BMSCs-Exo significantly abrogate the inflammatory state (IL-6, TNF-α), apoptotic state (BAX/Bcl2), astrocyte, and microglia activation (GFAP, IBA-1) in DOX-induced chemobrain with a significant increase in the antioxidant mediators (GSH, GPx, SOD activity).

Conclusions

BMSCs and their derived exosomes offer neuroprotection against DOX-induced chemobrain via genetic and epigenetic abrogation of hippocampal neurodegeneration through modulating Wnt/β-catenin and hedgehog signaling pathways and through reducing inflammatory, apoptotic, and oxidative stress state.

Graphical abstract

Proposed mechanisms of the protective effects of bone marrow stem cells (BMSCs) and their exosomes (BMSCs-Exo) in doxorubicin (DOX)-induced chemobrain. Blue arrows: induce. Red arrows: inhibit.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02384-9.

Copper Toxicity Links to Pathogenesis of Alzheimer's Disease and Therapeutics Approaches

Alzheimer's disease (AD) is an irreversible, age-related progressive neurological disorder, and the most common type of dementia in aged people. Neuropathological lesions of AD are neurofibrillary tangles (NFTs), and senile plaques comprise the accumulated amyloid-beta (Aβ), loaded with metal ions including Cu, Fe, or Zn. Some reports have identified metal dyshomeostasis as a neurotoxic factor of AD, among which Cu ions seem to be a central cationic metal in the formation of plaque and soluble oligomers, and have an essential role in the AD pathology. Cu-Aβ complex catalyzes the generation of reactive oxygen species (ROS) and results in oxidative damage. Several studies have indicated that oxidative stress plays a crucial role in the pathogenesis of AD. The connection of copper levels in AD is still ambiguous, as some researches indicate a Cu deficiency, while others show its higher content in AD, and therefore there is a need to increase and decrease its levels in animal models, respectively, to study which one is the cause. For more than twenty years, many in vitro studies have been devoted to identifying metals' roles in Aβ accumulation, oxidative damage, and neurotoxicity. Towards the end, a short review of the modern therapeutic approach in chelation therapy, with the main focus on Cu ions, is discussed. Despite the lack of strong proofs of clinical advantage so far, the conjecture that using a therapeutic metal chelator is an effective strategy for AD remains popular. However, some recent reports of genetic-regulating copper transporters in AD models have shed light on treating this refractory disease. This review aims to succinctly present a better understanding of Cu ions' current status in several AD features, and some conflicting reports are present herein.

Oxidative stress, apoptosis and inflammatory responses involved in copper-induced pulmonary toxicity in mice

At present, there are few studies focused on the relationship between copper (Cu) and oxidative stress, apoptosis, or inflammatory responses in animal and human lungs. This study was conducted to explore the effects of Cu on pulmonary oxidative stress, apoptosis and inflammatory responses in mice orally administered with 0 mg/kg (control), 10 mg/kg, 20 mg/kg, and 40 mg/kg of CuSO₄ for 42 days. The results showed that CuSO₄ increased ROS production, and MDA, 8-OHdG and NO contents as well as iNOS activities and mRNA expression levels. Meanwhile, CuSO₄ reduced the activities and mRNA expression levels of antioxidant enzymes (GSH-Px, CAT, and SOD) and GSH contents, and ASA and AHR abilities. Also, CuSO₄ induced apoptosis, which was accompanied by decreasing Bcl-2, Bcl-xL mRNA expression levels and protein expression levels, and increasing Bax, Bak, cleaved-caspase-3, cleaved-caspase-9 mRNA, and protein expression levels, and Bax/Bcl-2 ratio. Concurrently, CuSO₄ caused inflammation by increasing MPO activities and activating the NF-κB signalling pathway, and down-regulating the mRNA and protein expression levels of anti-inflammatory cytokines (IL-2, IL-4, IL-10). In conclusion, the abovementioned findings demonstrated that over 10 mg/kg CuSO₄ can cause oxidative stress, apoptosis, and inflammatory responses, which contribute to pulmonary lesions and dysfunction in mice.

Association between serum copper levels and prevalence of hyperuricemia: a cross-sectional study

Hyperuricemia has been recognized as a worldwide public health concern. This study was conducted to examine the association between serum copper (Cu) concentration and the prevalence of hyperuricemia in a middle-aged and elderly population. Serum Cu concentration was measured by Roche modular P800 using the PAESA method. Serum uric acid (UA) concentration was detected by a Beckman Coulter AU 5800. Presence of hyperuricemia was defined as serum UA ≥ 416 μmol/L for men and ≥360 μmol/L for women. The association between serum Cu concentration and the prevalence of hyperuricemia was evaluated by logistic regression. The prevalence of hyperuricemia was 17.6% (n = 6,212) in the present study. Relative to the lowest quintile, the age- and sex-adjusted odds ratios for hyperuricemia were 1.38 (95% CI: 1.12 to 1.70), 1.34 (95% CI: 1.07 to 1.66), and 1.53 (95% CI: 1.23 to 1.91) in the third, fourth, and fifth serum Cu concentration quintiles (P for trend < 0.001). Similar results were found both in men and women subgroups. None of the findings were materially altered after adjustment for additional potential confounders. In conclusion, in this population-based cross-sectional study, serum Cu concentration was positively associated with the prevalence of hyperuricemia.

Troxerutin downregulates C/EBP-β gene expression via modulating the IFNγ-ERK1/2 signaling pathway to ameliorate rotenone-induced retinal neurodegeneration

Troxerutin, a natural flavonoid guards against oxidative stress and apoptosis with a high capability of passing through the blood-brain barrier. Our aim was to investigate the role of troxerutin in experimentally induced retinal neurodegeneration by modulating the interferon-gamma (IFNγ)-extracellular signal-regulated kinases 1/2 (ERK1/2)-CCAAT enhancer-binding protein β (C/EBP-β) signaling pathway. Three groups of rats (10 each group) were included. Group I (control group), group II (rotenone treated group): the rats were injected subcutaneously with a single rotenone dosage of 3 mg/kg repeated every 48 hours for 60 days to trigger retinal neurodegeneration. Group III (troxerutin-treated group): rats received troxerutin (150 mg/kg/day) by oral gavage 1 hour before rotenone administration. A real-time polymerase chain reaction technique was applied to measure messenger RNA (mRNA) levels of retinal C/EBP-β. Enzyme-linked immunosorbent assay technique was utilized to assay tumor necrosis factor-α (TNF-α), IFNγ, and ERK1/2 levels. Finally, reactive oxygen species (ROS), as well as carbonylated protein (CP) levels, were assessed spectrophotometrically. Improved retinal neurodegeneration by downregulation of C/EBP-β mRNA gene expression, also caused a significant reduction of TNF-α, IFNγ, ERK1/2 as well as ROS and CP levels compared with the diseased group. These findings could hold promise for the usage of troxerutin as a protective agent against rotenone-induced retinal neurodegeneration.

Potential Role of Trace Elements (Al, Cu, Zn, and Se) in Multiple Sclerosis Physiopathology

Multiple sclerosis (MS) is an unpredictable disease of the central nervous system. The cause of MS is not known completely, and pathology is specified by involved demyelinated areas in the white and gray matter of the brain and spinal cord. Inflammation and peripheral tolerance breakdown due to Treg cell defects and/or effector cell resistance are present at all stages of the disease. Several invading peripheral immune cells are included in the process of the disease such as macrophages, CD8+ T cells, CD4+ T cells, B cells, and plasma cells. Trace elements are known as elements found in soil, plants, and living organisms in small quantities. Some of them (e.g., Al, Cu, Zn, Mn, and Se) are essential for the body's functions like catalysts in enzyme systems, energy metabolism, etc. Al toxicity and Cu, Zn, and Se toxicity and deficiency can affect the immune system and following neuron inflammation and degeneration. These processes may result in MS pathology. Of course, factors such as lifestyle, environment, and industrialization can affect levels of trace elements in the human body.

Acetylcholinesterase inhibitors in Alzheimer's disease influence Zinc and Copper homeostasis

BACKGROUND

Alzheimer's disease (AD) is the most common age-related neurodegenerative disease. An altered homeostasis of Zinc (Zn) and Copper (Cu), as well as a dysregulated expression of Zn-regulatory proteins have been previously described in AD. Acetylcholinesterase inhibitors (AChEI) are commonly used as AD treatment to improve cognitive function, but their effect on Zn homeostasis is still unexplored.

OBJECTIVES

The aims of this study were to define the metal dyshomeostasis in AD patients, to investigate AChEI influence on Zn homeostasis and inflammation, and to analyze the relationship between cognitive impairment at two-year follow-up and metal concentrations, considering AChEI use.

METHODS AND RESULTS

84 Healthy Elderly (HE) and 95 AD patients were enrolled (62 AchEI user and 33 AchEI naïve). HE showed similar plasma Zn and Cu concentrations and Cu/Zn ratio in comparison to AChEI users, but significantly higher Zn level, as well as lower Cu amount and Cu/Zn ratio than AChEI naïve patients. Moreover, AChEI users had increased Zn plasma level, reduced Cu amount, Cu/Zn ratio, and IL1β concentration and lower Zip2 lymphocytic expression vs. naïve patients. A multiple linear regression analysis showed that the MMSE score decline after two-year follow-up was reduced by AChEI therapy and was positively associated with plasma Zn decrease over time.

CONCLUSION

Our data revealed that AChEI use may affect peripheral Zn and Cu homeostasis in AD patients, decrease Cu/Zn ratio demonstrating a general reduction of inflammatory status in patients under AChEI treatment. Finally, AChEI influence on circulating Zn could be implicated in the drug-related slowdown of cognitive decline.

Metal Toxicity Links to Alzheimer's Disease and Neuroinflammation

As the median age of the population increases, the number of individuals with Alzheimer's disease (AD) and the associated socio-economic burden are predicted to worsen. While aging and inherent genetic predisposition play major roles in the onset of AD, lifestyle, physical fitness, medical condition, and social environment have emerged as relevant disease modifiers. These environmental risk factors can play a key role in accelerating or decelerating disease onset and progression. Among known environmental risk factors, chronic exposure to various metals has become more common among the public as the aggressive pace of anthropogenic activities releases excess amount of metals into the environment. As a result, we are exposed not only to essential metals, such as iron, copper, zinc and manganese, but also to toxic metals including lead, aluminum, and cadmium, which perturb metal homeostasis at the cellular and organismal levels. Herein, we review how these metals affect brain physiology and immunity, as well as their roles in the accumulation of toxic AD proteinaceous species (i.e., β-amyloid and tau). We also discuss studies that validate the disruption of immune-related pathways as an important mechanism of toxicity by which metals can contribute to AD. Our goal is to increase the awareness of metals as players in the onset and progression of AD.

Inflammatory cytokines expression in Wilson's disease

BACKGROUND

Wilson's disease (WD) is an autosomal recessive inherited disorder of copper (Cu) metabolism. Inflammation is a self-defensive reaction aimed at eliminating or neutralizing injurious stimuli, and restoring tissue integrity. Copper deposition may lead to inflammation in the organs and tissues of WD patients.

OBJECTIVE

The aim of this study was to compare the plasma levels of inflammatory cytokines in patients with WD and healthy group, and also to assess whether inflammatory cytokines affects the clinical manifestation of WD.

METHODS

Ninety-nine patients with WD and 32 controls were recruited for this study. Ray Biotech antibody microarray was used to detect the levels of plasma inflammatory cytokines.

RESULTS AND CONCLUSION

Our results showed significant increase in T helper (Th) 1 cells (IL-2, TNF-α, and TNF-β), Th2 cells (IL-5, IL-10, and IL-13), and Th17 (IL-23) (p < 0.05). Higher plasma Th 1 cells (IL-2, TNF-α, and TNF-β), Th 2 cells (IL-13), and Th 17 (TGF-β1, IL-23) levels were found in neurological patients compared with control groups (p < 0.01). Besides, we found Th 1 cells (TNF-α and TNF-β), Th 3 (TGF-β1), and Th 17 (IL-23) levels were significantly higher in hepatic and neurological patients (p < 0.05). In addition, the higher Th1 cells (IL-2, TNF-α, and TNF-β), Th2 cells (IL-13), and Th17 (TGF-β1, IL-23) and the course of WD were associated with the severity of the neurological symptoms for WD patients. Altogether, our results indicated that dysregulation of cytokines, mainly increased expression of cytokines and chemokines, occurred in WD patients.

Alterations of antioxidant indexes and inflammatory cytokine expression aggravated hepatocellular apoptosis through mitochondrial and death receptor-dependent pathways in Gallus gallus exposed to arsenic and copper

In this study, we sought to investigate the effects of sub-chronic exposure of arsenic (As) and copper (Cu) on oxidative stress, inflammatory response, and mitochondria and death receptor apoptosis pathways in chicken liver. Seventy-two 1-day-old male Hy-line chickens were treated with basal diet, 30 mg/kg arsenic trioxide (As₂O₃), or/and 300 mg/kg copper sulfate (CuSO₄) for 4, 8, and 12 weeks. Study revealed that exposure to As or/and Cu undermined the antioxidant function and increased lipid peroxidation. Worse yet, liver cell swollen, vacuolar degeneration, and inflammatory cell infiltration were accompanied by an increase of the nuclear factor-κB (NF-κB) and its downstream inflammation-related genes after exposure to As or/and Cu. Furthermore, mitochondria swollen and chromatin condensation were found in As and Cu groups, and hepatocyte nuclear membrane rupture and markedly increased (P < 0.01) apoptosis index were observed in As combined with Cu group. Meanwhile, the transcription and protein expression levels of Bcl-2-associated X protein (Bax), p53, cytochrome c (Cyt c), and caspase-3, 8, 9 were upregulated and B cell lymphoma-2 (Bcl-2) was downregulated in As, Cu, and As + Cu groups in the liver tissues (P < 0.05, P < 0.01). Our results indicated that exposure to As or/and Cu could lead to oxidative stress, inflammatory response, and tissue damage and aggravate hepatocellular apoptosis through mitochondrial and death receptor-dependent pathways in chicken liver. And As and Cu showed a possible synergistic relationship in liver damage.

Synergistic effect of copper and arsenic upon oxidative stress, inflammation and autophagy alterations in brain tissues of Gallus gallus

Arsenic or copper is one of the most highly toxic pollution that can cause dysfunction to brains, however, the exact mechanism remains unclear. The aim of the study is to investigate the mechanisms of arsenic or/and copper-induced oxidative stress, inflammation and autophagy in chicken brains and elucidate the interactions between arsenic and copper. A total of 72 1-day-old Hy-line chickens were divided into four groups (18 chickens per group) treated with 30mg/kg arsenic trioxide (As₂O₃) or/and 300mg/kg copper sulfate (CuSO₄) for 12weeks. Histological signs of inflammation were found in the cerebrum, cerebellum and brainstem exposure to arsenic or/and copper. The malondialdehyde (MDA) content were up-regulation, whereas oxidative damage parameters total antioxidant capacity (T-AOC), glutathione (GSH), the inhibition ability of hydroxyl radical (OH), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly decreased (P<0.05). The mRNA levels and protein expressions of inflammation markers, such as nuclear factor kappa B (NF-κB), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and prostaglandin E synthase (PTGEs) were significantly increased (P<0.05). The mRNA levels and protein expressions of autophagy markers including phosphatidylinositol 3-kinase (PI3K), Akt, autophagy-related gene 5 (ATG5), microtubule-associated protein light chains 3 (LC3), ATG4B, and Becline1 in different regions of brains were up-regulation (P<0.05), except the mammalian target of rapamycin complex (mTORC). In conclusion, we speculated that arsenic or copper could induce oxidative stress, inflammation and autophagy in chicken brains, and there may have a synergistic effect between copper and arsenic.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

DL0410, a novel dual cholinesterase inhibitor, protects mouse brains against Aβ-induced neuronal damage via the Akt/JNK signaling pathway

AIM

1,1'-([1,1'-Biphenyl]-4,4'-diyl)bis(3-(piperidin-1-yl)propan-1-one)dihydrochloride (DL0410) is a novel synthetic dual acetylcholinesterase (AChE)/butyrocholinesterase (BuChE) inhibitor, which has shown a potential therapeutic effect on Alzheimer's disease (AD). In this study we examined whether DL0410 produced neuroprotective effects in an AD cellular model and an Aβ1-42-induced amnesia mouse model.

METHODS

The in vitro inhibitory activities against AChE and BuChE were estimated using Ellman's assay. Copper-induced toxicity in APPsw-SY5Y cells was used as AD cellular model, the cell viability was assessed using MTS assay, and cell apoptosis was evaluated based on mitochondrial membrane potential detection. Aβ1-42-induced amnesia mouse model was made in male mice by injecting aggregated Aβ1-42 (2 μg in 2 μL 0.1% DMSO) into the right cerebral ventricle. Before and after Aβ1-42 injection, the mice were orally administered DL0410 (1, 3, 9 mg·kg-1·d-1) or rivastigmine (2 mg·kg-1·d-1) for 3 and 11 d, respectively. Memory impairments were examined using Morris water maze (MWM) test and passive avoidance test. The expression levels of APP, CREB, BDNF, JNK and Akt in the mouse brains were measured with either immunohistochemistry or Western blotting.

RESULTS

DL0410 exhibited in vitro inhibitory abilities against AChE and BuChE with IC50 values of 0.286±0.004 and 3.962±0.099 μmol/L, respectively, which were comparable to those of donepezil and rivastigmine. In APPsw-SY5Y cells, pretreatment with DL0410 (1, 3, and 10 μmol/L) decreased the phosphorylation of JNK and increased the phosphorylation of Akt, markedly decreased copper-stimulated Aβ1-42 production, reversed the loss of mitochondrial membrane potential, and dose-dependently increased the cell viability. In Aβ1-42-treated mice, DL0410 administration significantly ameliorated learning and memory deficits in MWM test and passive avoidance test. Furthermore, DL0410 administration markedly decreased Aβ1-40/42 deposits in mouse cerebral cortices, and significantly up-regulated neurotrophic CREB/BDNF. Meanwhile, Akt/JNK signaling pathway may play a key role in the neuroprotective effect of DL0410.

CONCLUSION

DL0410 ameliorates cognitive deficit and exerts neuronal protection in AD models, implicating this compound as a candidate drug for the prevention and therapy of AD.

Dietary high cholesterol and trace metals in the drinking water increase levels of ABCA1 in the rabbit hippocampus and temporal cortex

BACKGROUND

Cholesterol-fed rabbits have been documented to show increased amyloid-β (Aβ) deposits in the brain that can be exacerbated by the quality of drinking water especially if rabbits drink tap water or distilled water containing copper. One mechanism of cholesterol and Aβ clearance may be through the ATP-binding cassette transporter A1 (ABCA1).

OBJECTIVE AND METHODS

Using an ABCA1 antibody, we determined the number of ABCA1-immunopositive neurons in three areas of rabbit brain as a function of feeding 2% cholesterol and providing tap water, distilled water, or distilled water to which aluminum, copper, or zinc was added.

RESULTS

The number of neurons with ABCA1 immunoreactivity was increased significantly as a result of dietary cholesterol in the rabbit hippocampus and inferior and superior temporal cortex. The number of neurons with ABCA1 immunoreactivity was further increased in all three areas as a result of cholesterol-fed rabbits drinking tap water or distilled water with copper. Finally, cholesterol-fed rabbits that drank distilled water with aluminum also showed an increased number of ABCA1-immunopositive neurons in inferior and superior temporal cortex.

CONCLUSIONS

These data suggest that ABCA1 levels increase in parallel with previously documented increases in Aβ levels as a result of high dietary cholesterol and copper in the drinking water. Addition of aluminum to distilled water may have a similar effect in the temporal cortex. ABCA1 has been proposed as a means of clearing Aβ from the brain and manipulations that increase Aβ also result in an increase of clearance machinery.

Copper-induced alterations in rat brain depends on route of overload and basal copper levels

OBJECTIVES

Copper (Cu) is widely used in industry for the manufacture of a vast range of goods including Cu-intrauterine devices (IUDs), electronic products, agrochemicals, and many others. It is also one of the trace elements essential to human health in the right measure and is used as a parenteral supplement in patients unable to ingest food. Elevated Cu levels have been found in the plasma of women using Cu-IUDs and in farmers working with Cu-based pesticides. However, possible alterations due to Cu overload in the brain have been poorly studied. Therefore, the aim of this study was to investigate the effects of Cu administration on rat brain in Cu-sufficient and Cu-deficient animals fed on semi-synthetic diets with different doses of Cu (7 or 35 ppm).

METHODS

We aimed to investigate the effects of Cu administration using two routes of administration: oral and intraperitoneal (IP). Male Wistar rats were feeding (one month) a complete (7 ppm) or a deficient (traces) Cu diets subdivided into three categories oral-, intraperitoneal- (or both) supplemented with copper carbonate (7 to 35 ppm). Cu content in plasma, brain zones (cortex and hippocampus), antioxidant enzyme activities, and protease systems involved in programmed cell death were determined.

RESULTS

The results show that Cu levels and the concentration of Cu in plasma and brain were dose-dependent and administration route-dependent and demonstrated a prooxidative effect in plasma and brain homogenates. Oxidative stress biomarkers and antioxidative enzyme activity both increased under Cu overload, these effects being more noticeable when Cu was administered IP. Concomitantly, brain lipids from cortex and hippocampus were strongly modified, reflecting Cu-induced prooxidative damage. A significant increase in the activities of calpain (milli- and micro-) and caspase-3 activity also was observed as a function of dose and administration route.

CONCLUSION

The findings of this study could be important in evaluating the role of Cu in brain metabolism and neuronal survival.

Neuroinflammation and copper in Alzheimer's disease

Inflammation is the innate immune response to infection or tissue damage. Initiation of proinflammatory cascades in the central nervous system (CNS) occurs through recognition of danger associated molecular patterns by cognate immune receptors expressed on inflammatory cells and leads to rapid responses to remove the danger stimulus. The presence of activated microglia and astrocytes in the vicinity of amyloid plaques in the brains of Alzheimer's disease (AD) patients and mouse models implicates inflammation as a contributor to AD pathogenesis. Activated microglia play a critical role in amyloid clearance, but chronic deregulation of CNS inflammatory pathways results in secretion of neurotoxic mediators that ultimately contribute to neurodegeneration in AD. Copper (Cu) homeostasis is profoundly affected in AD, and accumulated extracellular Cu drives Aβ aggregation, while intracellular Cu deficiency limits bioavailable Cu required for CNS functions. This review presents an overview of inflammatory events that occur in AD in response to Aβ and highlights recent advances on the role of Cu in modulation of beneficial and detrimental inflammatory responses in AD.

Effects of Copper and/or Cholesterol Overload on Mitochondrial Function in a Rat Model of Incipient Neurodegeneration

Copper (Cu) and cholesterol (Cho) are both associated with neurodegenerative illnesses in humans and animals models. We studied the effect in Wistar rats of oral supplementation with trace amounts of Cu (3 ppm) and/or Cho (2%) in drinking water for 2 months. Increased amounts of nonceruloplasmin-bound Cu were observed in plasma and brain hippocampus together with a higher concentration of ceruloplasmin in plasma, cortex, and hippocampus. Cu, Cho, and the combined treatment Cu + Cho were able to induce a higher Cho/phospholipid ratio in mitochondrial membranes with a simultaneous decrease in glutathione content. The concentration of cardiolipin decreased and that of peroxidation products, conjugated dienes and lipoperoxides, increased. Treatments including Cho produced rigidization in both the outer and inner mitochondrial membranes with a simultaneous increase in permeability. No significant increase in Cyt C leakage to the cytosol was observed except in the case of cortex from rats treated with Cu and Cho nor were there any significant changes in caspase-3 activity and the Bax/Bcl2 ratio. However, the A β (1-42)/(1-40) ratio was higher in cortex and hippocampus. These findings suggest an incipient neurodegenerative process induced by Cu or Cho that might be potentiated by the association of the two supplements.

Role of copper and cholesterol association in the neurodegenerative process

Age is one of the main factors involved in the development of neurological illnesses, in particular, Alzheimer, and it is widely held that the rapid aging of the world population is accompanied by a rise in the prevalence and incidence of Alzheimer disease. However, evidence from recent decades indicates that Cu and Cho overload are emerging causative factors in neurodegeneration, a hypothesis that has been partially investigated in experimental models. The link between these two variables and the onset of Alzheimer disease has opened up interesting new possibilities requiring more in-depth analysis. The aim of the present study was therefore to investigate the effect of the association of Cu + Cho (CuCho) as a possible synergistic factor in the development of an Alzheimer-like pathology in Wistar rats. We measured total- and nonceruloplasmin-bound Cu and Cho (free and sterified) contents in plasma and brain zones (cortex and hippocampus), markers of oxidative stress damage, inflammation, and programmed cell death (caspase-3 and calpain isoforms). The ratio beta-amyloid (1-42)/(1-40) was determined in plasma and brain as neurodegenerative biomarker. An evaluation of visuospatial memory (Barnes maze test) was also performed. The results demonstrate the establishment of a prooxidative and proinflammatory environment after CuCho treatment, hallmarked by increased TBARS, protein carbonyls, and nitrite plus nitrate levels in plasma and brain zones (cortex and hippocampus) with a consequent increase in the activity of calpains and no significant changes in caspase-3. A simultaneous increase in the plasma Aβ1-42/Aβ1-40 ratio was found. Furthermore, a slight but noticeable change in visuospatial memory was observed in rats treated with CuCho. We conclude that our model could reflect an initial stage of neurodegeneration in which Cu and Cho interact with one another to exacerbate neurological damage.

Ursolic acid improves domoic acid-induced cognitive deficits in mice

Our previous findings suggest that mitochondrial dysfunction is the mechanism underlying cognitive deficits induced by domoic acid (DA). Ursolic acid (UA), a natural triterpenoid compound, possesses many important biological functions. Evidence shows that UA can activate PI3K/Akt signaling and suppress Forkhead box protein O1 (FoxO1) activity. FoxO1 is an important regulator of mitochondrial function. Here we investigate whether FoxO1 is involved in the oxidative stress-induced mitochondrial dysfunction in DA-treated mice and whether UA inhibits DA-induced mitochondrial dysfunction and cognitive deficits through regulating the PI3K/Akt and FoxO1 signaling pathways. Our results showed that FoxO1 knockdown reversed the mitochondrial abnormalities and cognitive deficits induced by DA in mice through decreasing HO-1 expression. Mechanistically, FoxO1 activation was associated with oxidative stress-induced JNK activation and decrease of Akt phosphorylation. Moreover, UA attenuated the mitochondrial dysfunction and cognitive deficits through promoting Akt phosphorylation and FoxO1 nuclear exclusion in the hippocampus of DA-treated mice. LY294002, an inhibitor of PI3K/Akt signaling, significantly decreased Akt phosphorylation in the hippocampus of DA/UA mice, which weakened UA actions. These results suggest that UA could be recommended as a possible candidate for the prevention and therapy of cognitive deficits in excitotoxic brain disorders.

Diphenyl diselenide prevents cortico-cerebral mitochondrial dysfunction and oxidative stress induced by hypercholesterolemia in LDL receptor knockout mice

Recent studies have indicated a causal link between high dietary cholesterol intake and brain oxidative stress. In particular, we have previously shown a positive correlation between elevated plasma cholesterol levels, cortico-cerebral oxidative stress and mitochondrial dysfunction in low density lipoprotein receptor knockout (LDLr(-/-)) mice, a mouse model of familial hypercholesterolemia. Here we show that the organoselenium compound diphenyl diselenide (PhSe)2 (1 mg/kg; o.g., once a day for 30 days) significantly blunted the cortico-cerebral oxidative stress and mitochondrial dysfunction induced by a hypercholesterolemic diet in LDLr(-/-) mice. (PhSe)2 effectively prevented the inhibition of complex I and II activities, significantly increased the reduced glutathione (GSH) content and reduced lipoperoxidation in the cerebral cortex of hypercholesterolemic LDLr(-/-) mice. Overall, (PhSe)2 may be a promising molecule to protect against hypercholesterolemia-induced effects on the central nervous system, in addition to its already demonstrated antiatherogenic effects.

Links between copper and cholesterol in Alzheimer's disease

Altered copper homeostasis and hypercholesterolemia have been identified independently as risk factors for Alzheimer's disease (AD). Abnormal copper and cholesterol metabolism are implicated in the genesis of amyloid plaques and neurofibrillary tangles (NFT), which are two key pathological signatures of AD. Amyloidogenic processing of a sub-population of amyloid precursor protein (APP) that produces Aβ occurs in cholesterol-rich lipid rafts in copper deficient AD brains. Co-localization of Aβ and a paradoxical high concentration of copper in lipid rafts fosters the formation of neurotoxic Aβ:copper complexes. These complexes can catalytically oxidize cholesterol to generate H₂O₂, oxysterols and other lipid peroxidation products that accumulate in brains of AD cases and transgenic mouse models. Tau, the core protein component of NFTs, is sensitive to interactions with copper and cholesterol, which trigger a cascade of hyperphosphorylation and aggregation preceding the generation of NFTs. Here we present an overview of copper and cholesterol metabolism in the brain, and how their integrated failure contributes to development of AD.

Small interfering RNA-mediated knockdown of protein kinase C zeta attenuates domoic acid-induced cognitive deficits in mice

Accumulated evidence indicates that domoic acid (DA)-induced excitatory neuronal injury is associated with excessive reactive oxygen species (ROS) production. Protein kinase C zeta (PKC-ζ)/nicotinamide adenine dinucleotide phosphate (NOX) signaling regulates ROS levels and is involved in various neurodegenerative disorders including excitoneurotoxicity. Our previous studies have demonstrated that ROS-induced activation of the stress-activated protein kinase/c-jun-N-terminal kinase (SAPK/JNK) pathway plays a key role in the pathogenesis of cognitive deficits induced by DA. However, the precise biological mechanisms underlying these effects are not well understood. In this study, we investigate whether the PKC-ζ mediates DA-induced cognitive deficits and further explored the potential molecular processes. DA treatment significantly increased the expression of PI3K p85α, and PKC-ζ in the hippocampus of mice, which promoted the p47phox phosphorylation and expression, enhanced NOX activity, and increased the levels of ROS and protein carbonyls. In turn, the abnormal ROS levels in the hippocampus of DA-treated mice activated SAPK/JNK pathway, decreased FoxO1 phosphorylation, stimulated the nuclear translocation of FoxO1, activated FasL/Fas signaling, and promoted the activation of caspase-8 and caspase-3, which resulted in neuron apoptosis and cognitive deficits in mice. However, PKC-ζ knockdown reversed these changes in mice. It was further demonstrated that FoxO1 was a downstream target of SAPK/JNK signaling by FoxO1 small interfering RNA and SP600125 (an inhibitor of SAPK/JNK pathway) treatment. Additionally, SP600125 treatment or FoxO1 knockdown also blocked FasL/Fas signaling-dependent apoptosis and improved DA-induced cognitive deficits in the hippocampus of mice. These results suggest that PKC-ζ could be a possible target for the prevention or treatment of cognitive deficits in excitotoxic and other brain disorders.

Purple sweet potato color attenuates domoic acid-induced cognitive deficits by promoting estrogen receptor-α-mediated mitochondrial biogenesis signaling in mice

Recent findings suggest that endoplasmic reticulum stress may be involved in the pathogenesis of domoic acid-induced neurodegeneration. Purple sweet potato color, a class of naturally occurring anthocyanins, has beneficial health and biological effects. Recent studies have also shown that anthocyanins have estrogenic activity and can enhance estrogen receptor-α expression. In this study, we evaluated the effect of purple sweet potato color on cognitive deficits induced by hippocampal mitochondrial dysfunction in domoic acid-treated mice and explored the potential mechanisms underlying this effect. Our results showed that the oral administration of purple sweet potato color to domoic acid-treated mice significantly improved their behavioral performance in a step-through passive avoidance task and a Morris water maze task. These improvements were mediated, at least in part, by a stimulation of estrogen receptor-α-mediated mitochondrial biogenesis signaling and by decreases in the expression of p47phox and gp91phox. Decreases in reactive oxygen species and protein carbonylation were also observed, along with a blockade of the endoplasmic reticulum stress pathway. Furthermore, purple sweet potato color significantly suppressed endoplasmic reticulum stress-induced apoptosis, which prevented neuron loss and restored the expression of memory-related proteins. However, knockdown of estrogen receptor-α using short hairpin RNA only partially blocked the neuroprotective effects of purple sweet potato color in the hippocampus of mice cotreated with purple sweet potato color and domoic acid, indicating that purple sweet potato color acts through multiple pathways. These results suggest that purple sweet potato color could be a possible candidate for the prevention and treatment of cognitive deficits in excitotoxic and other brain disorders.

Introduction and technical survey: protein aggregation and fibrillogenesis

In this chapter we provided the overall background to the subject of protein aggregation and fibrillogenesis in amyloidogenesis, with introduction and brief discussion of the various topics that are included with the coming chapters. The division of the book into basic science and clinical science sections enables correlation of the topics to be made. The many proteins and peptides that have currently been found to undergo fibrillogenesis are tabulated. A broad technical survey is made, to indicate the vast array of techniques currently available to study aspects of protein oligomerization, aggregation and fibrillogenesis. These are split into three groups and tabulated, as the microscopical techniques, the analytical and biophysical methods, and the biochemical and cellular techniques. A few techniques are discussed, but in most cases only a link to relevant recent literature is provided.

Ursolic acid improves high fat diet-induced cognitive impairments by blocking endoplasmic reticulum stress and IκB kinase β/nuclear factor-κB-mediated inflammatory pathways in mice

Evidence suggests that obesity-induced cognitive impairments are driven by in brain inflammatory responses and inflammation-mediated brain insulin resistance. Ursolic acid (UA), a triterpenoid compound, has many important biological functions, including antioxidant and anti-inflammatory activities. Here, we evaluated the effect of UA on cognitive impairment induced by a high-fat diet (HFD), and we explored the potential mechanisms mediating this effect. Results showed that UA administration significantly improved the behavioral performance of C57/BL6J mice fed a HFD in both the step-through test and the Morris water maze task. These results were associated with the inhibition of endoplasmic reticulum stress and IκB kinase β/nuclear factor-κB-mediated inflammatory signaling and the restoration of insulin signaling and phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. UA administration also increased memory-related protein expression in the hippocampus of mice given a HFD. However, the neuroprotective effects of UA were blocked by an intracerebroventricular (i.c.v.) injection of PI-103, a specific PI3K 110α inhibitor. These results suggest that UA may be a potent candidate for the prevention and treatment of cognitive deficits caused by type 2 diabetes.

Increases in β-amyloid protein in the hippocampus caused by diabetic metabolic disorder are blocked by minocycline through inhibition of NF-κB pathway activation

Activation of the NF-κB pathway plays an important role in the pathophysiology of Alzheimer's disease (AD), and blocking NF-κB pathway activation has been shown to attenuate cognitive impairment. Diabetic metabolic disorder contributes to β-amyloid protein (Aβ) generation. The goal of this study was to determine the effect of minocycline on Aβ generation and the NF-κB pathway in the hippocampus of diabetic rats and to elucidate the neuroprotective mechanisms of minocycline for the treatment of diabetic metabolic disorder. The diabetic rat model was established using a high-fat diet and an intraperitoneal injection of streptozocin (STZ). Behavioral tests showed that the capacity of learning and memory was significantly lower in diabetic rats. The levels of NF-κB, COX-2, iNOS, IL-1β and TNF-α after the STZ injection were significantly increased in the hippocampus. Significant increases in Aβ, BACE1, NF-κB, COX-2, iNOS, IL-1β and TNF-α were found in diabetic rats. The levels of Aβ, NF-κB, COX-2, iNOS, IL-1β and TNF-α were significantly decreased after minocycline administration; however, minocycline had no effect on BACE1 expression. In sum, diabetes contributes to the activation of the NF-κB pathway and upregulates BACE1 and Aβ. Minocycline downregulates Aβ in the hippocampus by inhibiting NF-κB pathway activation.

Copper modulation as a therapy for Alzheimer's disease?

The role of metals in the pathophysiology of Alzheimer's disease (AD) has gained considerable support in recent years, with both in vitro and in vivo data demonstrating that a mis-metabolism of metal ions, such as copper and zinc, may affect various cellular cascades that ultimately leads to the development and/or potentiation of AD. In this paper, we will provide an overview of the preclinical and clinical literature that specifically relates to attempts to affect the AD cascade by the modulation of brain copper levels. We will also detail our own novel animal data, where we treated APP/PS1 (7-8 months old) mice with either high copper (20 ppm in the drinking water), high cholesterol (2% supplement in the food) or a combination of both and then assessed β-amyloid (Aβ) burden (soluble and insoluble Aβ), APP levels and behavioural performance in the Morris water maze. These data support an interaction between copper/cholesterol and both Aβ and APP and further highlight the potential role of metal ion dyshomeostasis in AD.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

Mammalian target of rapamycin: hitting the bull's-eye for neurological disorders

The mammalian target of rapamycin (mTOR) and its associated cell signaling pathways have garnered significant attention for their roles in cell biology and oncology. Interestingly,the explosion of information in this field has linked mTOR to neurological diseases with promising initial studies. mTOR, a 289 kDa serine/threonine protein kinase, plays an important role in cell growth and proliferation and is activated through phosphorylation in response to growth factors, mitogens and hormones. Growth factors, amino acids, cellular nutrients and oxygen deficiency can downregulate mTOR activity. The function of mTOR signaling is mediated primarily through two mTOR complexes: mTORC1 and mTORC2. mTORC1 initiates cap-dependent protein translation, a rate-limiting step of protein synthesis, through the phosphorylation of the targets eukaryotic initiation factor 4E-binding protein 1 (4EBP1) and p70 ribosomal S6 kinase (p70S6K). In contrast, mTORC2 regulates development of the cytoskeleton and also controls cell survival. Although closely tied to tumorigenesis, mTOR and the downstream signaling pathways are significantly involved in the central nervous system (CNS) with synaptic plasticity, memory retention, neuroendocrine regulation associated with food intake and puberty and modulation of neuronal repair following injury. The signaling pathways of mTOR also are believed to be a significant component in a number of neurological diseases, such as Alzheimer disease, Parkinson disease and Huntington disease, tuberous sclerosis, neurofibromatosis, fragile X syndrome, epilepsy, traumatic brain injury and ischemic stroke. Here we describe the role of mTOR in the CNS and illustrate the potential for new strategies directed against neurological disorders.

Quercetin activates AMP-activated protein kinase by reducing PP2C expression protecting old mouse brain against high cholesterol-induced neurotoxicity

It is known that a high-cholesterol diet induces oxidative stress, inflammatory response, and beta-amyloid (Abeta) accumulation in mouse brain, resulting in neurodegenerative changes. Quercetin, a naturally occurring flavonoid, has been reported to possess numerous biological activities beneficial to health. Our previous studies have demonstrated that quercetin protects mouse brain against D-galactose-induced oxidative damage. Against this background, we evaluated the effect of quercetin on high-cholesterol-induced neurotoxicity in old mice and explored its potential mechanism. Our results showed that oral administration of quercetin significantly improved the behavioural performance of high-cholesterol-fed old mice in both a step-through test and the Morris water maze task. This is at least in part caused by decreasing ROS and protein carbonyl levels and restoring Cu--Zn superoxide dismutase (Cu, Zn-SOD) activity. Furthermore, quercetin also significantly activated the AMP-activated protein kinase (AMPK) via down-regulation of protein phosphatase 2C (PP2C), which reduced the integral optical density (IOD) of activated microglia cells and CD11b expression, down-regulated iNOS and cyclooxygenase-2 (COX-2) expression, and decreased IL-1beta, IL-6, and TNF-alpha expression in the brains of high-cholesterol-fed old mice through the suppression of NF-kappaB p65 nuclear translocation. Moreover, AMPK activation significantly increased 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and acetyl-CoA carboxylase (ACC) phosphorylation and reduced fatty acid synthase (FAS) expression in the brains of high-cholesterol-fed old mice, which reduced cholesterol levels, down-regulated cholesterol 24-hydroxylase (CYP46A1) and beta-amyloid converting enzyme 1 (BACE1) expression, decreased eukaryotic translation initiation factor 2alpha (eIF2alpha) phosphorylation, and lowered Abeta deposits. However, the neuroprotective effect of quercetin was weakened by intraperitoneal injection of compound C, an AMPK inhibitor. These results suggest that AMPK activated by quercetin may be a potential target to enhance the resistance of neurons to age-related diseases.

The effects of cholesterol on learning and memory

Cholesterol is vital to normal brain function including learning and memory but that involvement is as complex as the synthesis, metabolism and excretion of cholesterol itself. Dietary cholesterol influences learning tasks from water maze to fear conditioning even though cholesterol does not cross the blood brain barrier. Excess cholesterol has many consequences including peripheral pathology that can signal brain via cholesterol metabolites, pro-inflammatory mediators and antioxidant processes. Manipulations of cholesterol within the central nervous system through genetic, pharmacological, or metabolic means circumvent the blood brain barrier and affect learning and memory but often in animals already otherwise compromised. The human literature is no less complex. Cholesterol reduction using statins improves memory in some cases but not others. There is also controversy over statin use to alleviate memory problems in Alzheimer's disease. Correlations of cholesterol and cognitive function are mixed and association studies find some genetic polymorphisms are related to cognitive function but others are not. In sum, the field is in flux with a number of seemingly contradictory results and many complexities. Nevertheless, understanding cholesterol effects on learning and memory is too important to ignore.

Extremely low copper concentrations affect gene expression profiles of human prostate epithelial cell lines

Although cellular copper metabolism is tightly regulated through a variety of copper transport proteins and chaperones, disturbances in copper homeostasis are involved in several pathological disorders. The aim of this study was to evaluate the effects of extremely low copper concentrations on gene expression profiles of a line of human prostate epithelial cells (RWPE) which grows in the absence of fetal calf serum, a source of variable and unpredictable copper. Cells were exposed to copper(II) sulfate for 24h at concentrations varying from 10(-6) to 10(-17)M and untreated reference cells were exposed to the same volume of copper-free water. Relative gene expression variations between copper-treated and control cells were studied with microarray technology using the Whole Human Genome Array from Agilent. Microarray data demonstrated that copper added to the medium varied gene expression at all concentrations tested. Many genes belonging to functional gene families were modulated by copper, some dose-dependently. Amongst these genes metallothioneins (MT1A and MT2A) were over-expressed at all copper concentrations, MT1M was up-regulated between 10(-6) and 10(-9)M, while MT1B, MT1E, MT1G and MT1H were up-regulated between 10(-6) and 10(-14)M. The heat shock protein (HSP) gene family showed similar behavior: some HSP genes were constantly up-regulated by copper (HSP90Ad, HSP90B1 and HSPD1) and others only at higher concentrations (HSP90AB1 and HSPA8). Reverse-transcription-PCR analysis, performed on four different genes on five biological replicates for selected genes, on each copper concentration tested, confirmed the trend observed in microarray results. In conclusion, we unexpectedly observed a modulation of gene expression even at extremely diluted copper concentrations, similar to that induced by toxic concentrations, possibly as a result of very tight control of free copper(II) levels inside the cells.

Diabetes mellitus: channeling care through cellular discovery

Diabetes mellitus (DM) impacts a significant portion of the world's population and care for this disorder places an economic burden on the gross domestic product for any particular country. Furthermore, both Type 1 and Type 2 DM are becoming increasingly prevalent and there is increased incidence of impaired glucose tolerance in the young. The complications of DM are protean and can involve multiple systems throughout the body that are susceptible to the detrimental effects of oxidative stress and apoptotic cell injury. For these reasons, innovative strategies are necessary for the implementation of new treatments for DM that are generated through the further understanding of cellular pathways that govern the pathological consequences of DM. In particular, both the precursor for the coenzyme beta-nicotinamide adenine dinucleotide (NAD(+)), nicotinamide, and the growth factor erythropoietin offer novel platforms for drug discovery that involve cellular metabolic homeostasis and inflammatory cell control. Interestingly, these agents and their tightly associated pathways that consist of cell cycle regulation, protein kinase B, forkhead transcription factors, and Wnt signaling also function in a broader sense as biomarkers for disease onset and progression.