N-stearoyltyrosine protects primary neurons from Aβ-induced apoptosis through modulating mitogen-activated protein kinase activity

Lipopeptides as tools in catalysis, supramolecular, materials and medicinal chemistry

Lipopeptides are amphiphilic peptides in which an aliphatic chain is attached to either the C or N terminus of peptides. Their self-assembly - into micelles, vesicles, nanotubes, fibres or nanobelts - leads to applications in nanotechnology, catalysis or medicinal chemistry. Self-organization of lipopeptides is dependent on both the length of the lipid tail and the amino acid sequence, in which the chirality of the peptide sequence can be transmitted into the supramolecular species. This Review describes the use of lipopeptides to design synthetic advanced dynamic supramolecular systems, nanostructured materials or self-responsive delivery systems in the area of medical biotechnology. We examine the influence of external stimuli, the ability of lipopeptide-derived structures to adapt over time and their application as medicinal agents with antibacterial, antifungal, antiviral or anticancer activities. Finally, we discuss the catalytic efficiency of lipopeptides, with the aim of building minimal synthetic enzymes, and recent efforts to incorporate metals into lipopeptide assemblies.

How Can Insulin Resistance Cause Alzheimer's Disease?

Alzheimer's disease (AD) is a neurodegenerative disorder associated with cognitive decline. Despite worldwide efforts to find a cure, no proper treatment has been developed yet, and the only effective countermeasure is to prevent the disease progression by early diagnosis. The reason why new drug candidates fail to show therapeutic effects in clinical studies may be due to misunderstanding the cause of AD. Regarding the cause of AD, the most widely known is the amyloid cascade hypothesis, in which the deposition of amyloid beta and hyperphosphorylated tau is the cause. However, many new hypotheses were suggested. Among them, based on preclinical and clinical evidence supporting a connection between AD and diabetes, insulin resistance has been pointed out as an important factor in the development of AD. Therefore, by reviewing the pathophysiological background of brain metabolic insufficiency and insulin insufficiency leading to AD pathology, we will discuss how can insulin resistance cause AD.

Do We Have Viable Protective Strategies against Anesthesia-Induced Developmental Neurotoxicity?

Since its invention, general anesthesia has been an indispensable component of modern surgery. While traditionally considered safe and beneficial in many pathological settings, hundreds of preclinical studies in various animal species have raised concerns about the detrimental and long-lasting consequences that general anesthetics may cause to the developing brain. Clinical evidence of anesthetic neurotoxicity in humans continues to mount as we continue to contemplate how to move forward. Notwithstanding the alarming evidence, millions of children are being anesthetized each year, setting the stage for substantial healthcare burdens in the future. Hence, furthering our knowledge of the molecular underpinnings of anesthesia-induced developmental neurotoxicity is crucially important and should enable us to develop protective strategies so that currently available general anesthetics could be safely used during critical stages of brain development. In this mini-review, we provide a summary of select strategies with primary focus on the mechanisms of neuroprotection and potential for clinical applicability. First, we summarize a diverse group of chemicals with the emphasis on intracellular targets and signal-transduction pathways. We then discuss epigenetic and transgenerational effects of general anesthetics and potential remedies, and also anesthesia-sparing or anesthesia-delaying approaches. Finally, we present evidence of a novel class of anesthetics with a distinct mechanism of action and a promising safety profile.

N-stearoyl-l-Tyrosine inhibits the cell senescence and apoptosis induced by H2O2 in HEK293/Tau cells via the CB2 receptor

Although considerable energy and money have been spent trying to inhibit Aβ production and its related metabolic enzyme activities, there are still no drug treatments available to cure even slow for Alzheimer's disease. Therefore, tau protein has been focused recently as the new target for the treatment of Alzheimer's disease. The transfected human embryonic kidney 293 (HEK 293) cells with or without Tau 411 plasmid were used to evaluate the effect of tau protein on cell viability. H₂O₂ was added to simulate microenvironment of oxidative stress (OS) during aging. N-stearoyl-l-tyrosine (Nstyr), one of the synthesized N-arachidonoylethanolamide analogues was administrated in HEK293/Tau cells during H₂O₂ insults. Cellular senescence and tau aberrant modification appeared after tau transfection and aggravated by H₂O₂ insult which detected by β-galactosidase staining analysis and western blotting analysis. The level of expression of Bcl-2 and the result of FCAS analysis indicated the appearance of cellular apoptosis. The expression of prosenescence moleculars such as p16-Rb and P53 were induced by tau transfection in HEK293 cells. Both p16-Rb and p53 senescent molecules were inhibited by Nstyr. AM251 (1 μM; an antagonist of CB1 cannabinoid receptor) or AM630 (1 μM; an antagonist of CB2 cannabinoid receptor) was used to offset the anti-senescence effects afforded by NsTyr. The anti-senescence and anti-apoptosis effect of NsTyr was completely abolished by AM630. Meanwhile, transfection of siRNA_CB2 was used to further confirm the above experimental results and it came out the similar results compared with AM630. Taken together, our results suggest that oxidative stress aggravates cellular senescence and apoptosis in HEK293/Tau, which can be reversed by Nstyr via CB2 receptor.

Mitochondrial Ferritin Deletion Exacerbates β-Amyloid-Induced Neurotoxicity in Mice

Mitochondrial ferritin (FtMt) is a mitochondrial iron storage protein which protects mitochondria from iron-induced oxidative damage. Our previous studies indicate that FtMt attenuates β-amyloid- and 6-hydroxydopamine-induced neurotoxicity in SH-SY5Y cells. To explore the protective effects of FtMt on β-amyloid-induced memory impairment and neuronal apoptosis and the mechanisms involved, 10-month-old wild-type and Ftmt knockout mice were infused intracerebroventricularly (ICV) with Aβ_25–35 to establish an Alzheimer's disease model. Knockout of Ftmt significantly exacerbated Aβ_25–35-induced learning and memory impairment. The Bcl-2/Bax ratio in mouse hippocampi was decreased and the levels of cleaved caspase-3 and PARP were increased. The number of neuronal cells undergoing apoptosis in the hippocampus was also increased in Ftmt knockout mice. In addition, the levels of L-ferritin and FPN1 in the hippocampus were raised, and the expression of TfR1 was decreased. Increased MDA levels were also detected in Ftmt knockout mice treated with Aβ_25–35. In conclusion, this study demonstrated that the neurological impairment induced by Aβ_25–35 was exacerbated in Ftmt knockout mice and that this may relate to increased levels of oxidative stress.

Neuroprotective effects of phytosterols and flavonoids from Cirsium setidens and Aster scaber in human brain neuroblastoma SK-N-SH cells

AIMS

We investigated the neuroprotective effects and action mechanism of three major compounds [daucosterol (Dau), pectolinarin (Pec), and astragalin (Ast)] isolated from edible plants against H2O2-induced cell death of human brain neuroblastoma SK-N-SH cells.

MAIN METHODS

Cytotoxicity was determined by MTT and lactate dehydrogenase (LDH) assays. Apoptotic cell death was monitored by annexin V-FITC/PI double staining and by TUNEL assay. The formation of reactive oxygen species (ROS), expression of antioxidant enzymes and phosphorylation of mitogen-activated protein kinase (MAPK) were determined by 2,7-dichlorofluorescein diacetate (DCF-DA) assay, RT-PCR, and western blotting, respectively.

KEY FINDINGS

The ethyl acetate fractions from Cirsium setidens (CSEA) and Aster scaber (ASEA) showed neuroprotective effects in SK-N-SH cells. The phytochemicals were isolated from CSEA and ASEA and identified by spectral analyses, as β-sitosterol, Dau, Pec, Ast, or isoquercitrin. Pretreatment with Dau, Pec, or Ast showed protective effects against H2O2-induced cell death and inhibited ROS generation by oxidative stress. HO-1 mRNA and protein levels were increased by the presence of H2O2 and were further elevated by pretreatment with Dau and Ast. Dau pretreatment resulted in further increases of H2O2-induced enhancement in levels of CAT and SOD2. Pretreatment with Dau, Pec, and Ast inhibited phosphorylation of MAPK, such as extracellular protein regulated protein kinase, p38, and c-Jun N-terminal kinase by H2O2.

SIGNIFICANCE

Dau exerts its neuroprotective effects by down regulation of MAPK pathways and upregulation of the HO-1, CAT and SOD2 antioxidant genes and is associated with reduced oxidative stress in SK-N-SH cells.

Should development of Alzheimer's disease-specific intravenous immunoglobulin be considered?

Recent phase II and III studies with intravenous immunoglobulin (IVIG) in patients with Alzheimer's disease (AD) did not find evidence for the slowing of AD progression compared to placebo-treated patients, in contrast to encouraging results in pilot studies. An additional phase III trial is ongoing. If negative results are found, then further AD studies with IVIG are unlikely unless a manufacturer opts for a trial with high-dose IVIG, which would increase its anti-inflammatory effects but also the risk for adverse events. An alternative approach could be an AD-specific IVIG, supplementing IVIG with higher concentrations of selected antibodies purified from it or produced via recombinant polyclonal antibody technology. These antibodies could include those to amyloid-beta (Aβ, tau protein, inflammatory cytokines, complement activation proteins, and the receptor for advanced glycation end products. IgG fragment crystallizable (Fc) fragments containing terminal sialic acid could be added to increase anti-inflammatory effects. While this product might be more effective in slowing AD clinical progression than current IVIG, there are difficulties with this approach. Preclinical studies would be required to determine which of the antibodies of interest for supplementing current IVIG (for example, antibodies to phosphorylated or oligomeric tau) are actually present (and, therefore, available for purification) in IVIG, and the effects of the product in mouse models of AD. An Investigational New Drug application for an AD-specific IVIG would require United States Food and Drug Administration approval. If the drug would be found to benefit AD patients, meeting the increased demand for IVIG would be challenging.

Protective effects of EphB2 on Aβ1-42 oligomer-induced neurotoxicity and synaptic NMDA receptor signaling in hippocampal neurons

Alzheimer's disease (AD) is a neurodegenerative disorder characterized pathologically by the abnormal deposition of extracellular amyloid-β (Aβ) oligomers. However, the nature and precise mechanism of the toxicity of Aβ oligomers are not clearly understood. Aβ oligomers have been previously shown to cause a major loss of EphB2, a member of the EphB family of receptor tyrosine kinases. To determine the effect of EphB2 on Aβ oligomer-induced neurotoxicity and the underlying molecular mechanisms, we examined the EphB2 gene in cultured hippocampal neurons. Using a cellular model of AD, Aβ1-42 oligomers were confirmed to induce neurotoxicity in a time-dependent manner and result in a major decrease of EphB2. EphB2 overexpression could prevent the neurotoxicity of hippocampal neurons from exposure to Aβ1-42 oligomers for 1h. Further analysis revealed that EphB2 overexpression increased synaptic NR1 and NR2B expression in Aβ1-42 oligomer-treated neurons. Moreover, EphB2 overexpression prevented Aβ1-42 oligomer-induced downregulation of dephosphorylated p38 MAPK and phosphorylated CREB. Together, these results suggest that EphB2 is a factor which protects hippocampal neurons against the toxicity of Aβ1-42 oligomers, and we infer that the protection of EphB2 is achieved by increasing the synaptic NMDA receptor level and downstream p38 MAPK and CREB signaling in hippocampal neurons. This study provides new molecular insights into the neuroprotective effect of EphB2 and highlights its potential therapeutic role in the management of AD.

IMM-H004, a novel coumarin derivative compound, protects against amyloid beta-induced neurotoxicity through a mitochondrial-dependent pathway

We have investigated the effect of IMM-H004 (7-hydroxy-5-methoxy-4-methyl-3-(4-methylpiperazin-1-yl)-2H-chromen-2-one), a coumarin derivative, on the amyloid beta (Aβ)-induced neurotoxicity in primary culture cortical neurons and pheochromocytoma (PC12) cells. Our results showed that treatment with IMM-H004 markedly reduced the number of apoptotic cells after exposure to Aβ25-35 or Aβ1-42, determined by MTT, TUNEL staining and Flow cytometry. Further study indicated that IMM-H004 significantly inhibited Aβ-induced cytotoxicity and apoptosis by reversing Aβ-induced mitochondrial dysfunction, including MMP (mitochondrial membrane potential) decrease, reactive oxygen species production, and mitochondrial release of cytochrome c. IMM-H004 can regulate the interaction between Bax and Bcl-2, decreased levels of p53 and active caspase-3 protein induced by Aβ25-35. Furthermore, IMM-H004 also reduced translocation of AIF (apoptosis-inducing factor) induced by Aβ25-35. These results demonstrated that IMM-H004 was capable of protecting neuronal cells from Aβ-induced degeneration through a mitochondrial-dependent apoptotic pathway. The results of this study lend further credence to the notion that IMM-H004 is a 'multipotent therapeutic agrent' that reduces toxic levels of brain Aβ, and holds the potential to protect neuronal mitochondrial function in Alzheimer's disease.

N-stearoyl-L-tyrosine ameliorates sevoflurane induced neuroapoptosis via MEK/ERK1/2 MAPK signaling pathway in the developing brain

N-arachidonoylethanolamine (AEA) plays a crucial neuroprotective role in certain neurodegenerative diseases. Our recent studies suggested that AEA analog N-stearoyl-l-tyrosine (NsTyr) could protect neurons from apoptosis and improve hippocampus-dependent learning and memory deficits. The present study was designed to determine the neuroprotective effect of NsTyr on developmental sevoflurane neurotoxicity using primary hippocampal neuronal cultures and rat pups. We found that NsTyr could decrease cell viability and reduce apoptosis in sevoflurane treated neuronal cultures. In addition, NsTyr attenuated sevoflurane-induced apoptosis by modulating Caspase-3 and Bcl-2 in vivo. Moreover, sevoflurane exposure led to an inhibition of phospho-ERK1/2, which was rescued by NsTyr. Administration of U0126 (an inhibitor of MEK) abolished the neuroprotective effect of NsTyr on sevoflurane neurotoxicity both in vitro and in vivo. Finally, administration of NsTyr improved the learning and memory disorders induced by postnatal sevoflurane exposure without alteration in locomotor activity. These results indicated that AEA analog NsTyr protects developing brain against developmental sevoflurane neurotoxicity possibly through MEK/ERK1/2 MAPK signaling pathway.

Mitochondrial ferritin attenuates β-amyloid-induced neurotoxicity: reduction in oxidative damage through the Erk/P38 mitogen-activated protein kinase pathways

AIMS

Mitochondrial ferritin (MtFt), which was recently discovered, plays an important role in preventing neuronal damage in 6-hydroxydopamine-induced Parkinsonism by maintaining mitochondrial iron homeostasis. Disruption of iron regulation also plays a key role in the etiology of Alzheimer's disease (AD). To explore the potential neuroprotective roles of MtFt, rats and cells were treated with Aβ(25-35) to establish an AD model.

RESULTS

We report that knockdown of MtFt expression significantly enhanced Aβ(25-35)-induced neurotoxicity as shown by dysregulation of iron homeostasis, enhanced oxidative stress, and increased cell apoptosis. Opposite results were obtained when MtFt was overexpressed in SH-SY5Y cells prior to treatment with Aβ(25-35). Further, MtFt inhibited Aβ(25-35)-induced P38 mitogen-activated protein kinase and activated extracellular signal-regulated kinase (Erk) signaling.

INNOVATION

MtFt attenuated Aβ(25-35)-induced neurotoxicity and reduced oxidative damage through Erk/P38 kinase signaling.

CONCLUSION

Our results show a protective role of MtFt in AD and suggest that regulation of MtFt expression in neuronal cells may provide a new neuroprotective strategy for AD.

Neuroprotective effects of black soybean anthocyanins via inactivation of ASK1-JNK/p38 pathways and mobilization of cellular sialic acids

AIMS

To investigate neuroprotective effects of three major anthocyanins (cyanidin-3-O-glucoside, delphinidin-3-O-glucoside, and petunidin-3-O-glucoside) isolated from the black soybean (Glycine max L.) cv. Cheongja 3 seed coat against H(2)O(2)-induced cell death of human brain neuroblastoma SK-N-SH cells.

MAIN METHODS

Cell viability, reactive oxygen species (ROS) generation, production and expression of heme oxygenase (HO)-1 and inactivation of mitogen-activated protein (MAP) kinase cascades were determined by MTT assay, 2,7-dichlorofluorescein diacetate (DCF-DA) assay, reverse transcriptase polymerase chain reaction (RT-PCR), and western blotting, respectively.

KEY FINDINGS

Pretreatment with anthocyanins reduced the cytotoxicity of H(2)O(2) on SK-N-SH cells, dose-dependently reduced the intracellular ROS level and inactivated apoptosis signal-regulating kinase (ASK1, Thr845), p38, and c-Jun N-terminal kinase (JNK) proteins. The HO-1 and Neu1 mRNA levels were increased by H(2)O(2) (25 μM) and further elevated by the pretreatment with anthocyanins. Sialic acids added to the culture plates not only attenuated the cytotoxicity of H(2)O(2) (25 μM) but also reduced intracellular ROS level. These results suggest that Cheongja 3 black soybean seed coat anthocyanins have brain neuroprotective effects against oxidative stress (H(2)O(2)) by inhibiting the activation of ASK1-JNK/p38 pathways, scavenging ROS, stimulating the expression of HO-1 and, more interestingly, recruiting cellular free sialic acids through up-regulation of Neu1 sialidase gene expression.

SIGNIFICANCE

This is the first report indicating potent health benefits of black soybean seed coat anthocyanins in neuroprotection by triggering mobilization of cellular free sialic acid and utilizing it as an additional biological antioxidant in brain neural cells.

Intravenous immunoglobulin protects neurons against amyloid beta-peptide toxicity and ischemic stroke by attenuating multiple cell death pathways

Intravenous immunoglobulin (IVIg) preparations obtained by fractionating blood plasma, are increasingly being used increasingly as an effective therapeutic agent in treatment of several inflammatory diseases. Its use as a potential therapeutic agent for treatment of stroke and Alzheimer's disease has been proposed, but little is known about the neuroprotective mechanisms of IVIg. In this study, we investigated the effect of IVIg on downstream signaling pathways that are involved in neuronal cell death in experimental models of stroke and Alzheimer's disease. Treatment of cultured neurons with IVIg reduced simulated ischemia- and amyloid βpeptide (Aβ)-induced caspase 3 cleavage, and phosphorylation of the cell death-associated kinases p38MAPK, c-Jun NH2 -terminal kinase and p65, in vitro. Additionally, Aβ-induced accumulation of the lipid peroxidation product 4-hydroxynonenal was attenuated in neurons treated with IVIg. IVIg treatment also up-regulated the anti-apoptotic protein, Bcl2 in cortical neurons under ischemia-like conditions and exposure to Aβ. Treatment of mice with IVIg reduced neuronal cell loss, apoptosis and infarct size, and improved functional outcome in a model of focal ischemic stroke. Together, these results indicate that IVIg acts directly on neurons to protect them against ischemic stroke and Aβ-induced neuronal apoptosis by inhibiting cell death pathways and by elevating levels of the anti-apoptotic protein Bcl2.