u-0126 and Alzheimer-Disease

Amyloid-β (Aβ) produces neurotoxicity in the brain and causes neuronal death, but the endogenous defense mechanism that is activated on Aβ insult is less well known. Here we found that acute Aβ increases the expression of PIAS1 and Mcl-1 via activation of MAPK/ERK, and Aβ induction of PIAS1 enhances HDAC1 SUMOylation in rat hippocampus. Knockdown of PIAS1 decreases endogenous HDAC1 SUMOylation and blocks Aβ induction of Mcl-1. Sumoylated HDAC1 reduces it association with CREB, increases CREB binding to the Mcl-1 promoter and mediates Aβ induction of Mcl-1 expression. Transduction of SUMO-modified lenti-HDAC1 vector to the hippocampus of APP/PS1 mice rescues spatial learning and memory deficit and long-term potentiation impairment in APP/PS1 mice. It also reduces the amount of amyloid plaque and the number of apoptotic cells in CA1 area of APP/PS1 mice. Meanwhile, HDAC1 SUMOylation decreases HDAC1 binding to the neprilysin promoter. These results together reveal an important role of HDAC1 SUMOylation as a naturally occurring defense mechanism protecting against Aβ toxicity and provide an alternative therapeutic strategy against AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Apoptosis; Butadienes; Disease Models, Animal; Epigenesis, Genetic; Gene Expression; HEK293 Cells; Hippocampus; Histone Deacetylase 1; Humans; Male; Mice; Mice, Transgenic; Neuroprotection; Nitriles; Protein Binding; Protein Inhibitors of Activated STAT; Rats; Rats, Sprague-Dawley; RNA Interference; Sumoylation

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Apoptosis; Butadienes; Caspase 3; Cells, Cultured; Cerebral Cortex; Extracellular Signal-Regulated MAP Kinases; Male; Memory Disorders; Mitochondria; Nerve Degeneration; Neurons; Nitriles; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats, Sprague-Dawley; Saponins; Synapses; tau Proteins

Elevated levels of reactive carbonyl species such as methylglyoxal triggers carbonyl stress and activates a series of inflammatory responses leading to accelerated vascular damage. Carbonyl stress is implicated in conditions and diseases like aging, diabetes mellitus, Alzheimer's disease and cardiovascular diseases. Our aim was to examine the effects of methylglyoxal on human hCMEC/D3 brain endothelial cells and search for protective molecules to prevent endothelial damage.. Methylglyoxal-induced modification of albumin was tested in a cell-free assay. Endothelial cell viability was monitored by impedance measurement in real-time. The following compounds were tested in cell-free and viability assays: β-alanine, all-trans-retinoic acid, aminoguanidine, ascorbic acid, L-carnosine, GW-3333, indapamide, piracetam, γ-tocopherol, U0126, verapamil. Barrier function of brain endothelial monolayers was characterized by permeability measurements and visualized by immunohistochemistry for β-catenin. mRNA expression level of 60 selected blood-brain barrier-related genes in hCMEC/D3 cells was investigated by a custom Taqman gene array.. Methylglyoxal treatment significantly elevated protein modification, exerted toxicity, reduced barrier integrity, increased permeability for markers FITC-dextran and albumin and caused higher production of reactive oxygen species in hCMEC/D3 endothelial cells. Changes in the mRNA expression of 30 genes coding tight junction proteins, transporters and enzymes were observed in methylglyoxal-treated hCMEC/D3 cells. From the tested 11 compounds only all-trans-retinoic acid, an antioxidant and antiglycation agent, U0126, a MAP/ERK kinase inhibitor and aminoguanidine attenuated methylglyoxal-induced damage in hCMEC/D3 cells.. All-trans-retinoic acid and inhibition of the MAP/ERK signaling pathway may be protective in carbonyl stress induced brain endothelial damage.

Topics: Alzheimer Disease; Antioxidants; beta Catenin; Blood-Brain Barrier; Butadienes; Cell Line; Cell Survival; Endothelial Cells; Endothelium, Vascular; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Guanidines; Humans; MAP Kinase Signaling System; Nitriles; Pyruvaldehyde; Reactive Oxygen Species; Signal Transduction; Tight Junction Proteins; Tretinoin

Amyloid-β (Aβ) and tau are the pathogenic hallmarks in Alzheimer's disease (AD). Aβ oligomers are considered the actual toxic entities, and the toxicity relies on the presence of tau. Recently, Aβ oligomers have been shown to specifically interact with cellular prion protein (PrP(C)) where the role of PrP(C) in AD is still not fully understood. To investigate the downstream mechanism of PrP(C) and Aβ oligomer interaction and their possible relationships to tau, we examined tau expression in human neuroblastoma BE(2)-C cells transfected with murine PrP(C) and studied the effect under Aβ oligomer treatment. By Western blotting, we found that PrP(C) overexpression down-regulated tau protein and Aβ oligomer binding alleviated the tau reduction induced by wild type but not M128V PrP(C), the high AD risk polymorphic allele in human prion gene. PrP(C) lacking the Aβ oligomer binding site was incapable of rescuing the level of tau reduction. Quantitative RT-PCR showed the PrP(C) effect was attributed to tau reduction at the transcription level. Treatment with Fyn pathway inhibitors, Fyn kinase inhibitor PP2 and MEK inhibitor U0126, reversed the PrP(C)-induced tau reduction and Aβ oligomer treatment modulated Fyn kinase activity. The results suggested Fyn pathway regulated Aβ-PrP(C)-tau signaling. Overall, our results demonstrated that PrP(C) down-regulated tau via the Fyn pathway and the effect can be regulated by Aβ oligomers. Our study facilitated the understanding of molecular mechanisms among PrP(C), tau, and Aβ oligomers.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Butadienes; Cell Line, Tumor; Down-Regulation; Humans; MAP Kinase Signaling System; Mice; Mutation, Missense; Nitriles; Peptide Fragments; Point Mutation; Proto-Oncogene Proteins c-fyn; PrPC Proteins; Pyrimidines; Real-Time Polymerase Chain Reaction; Recombinant Fusion Proteins; RNA, Messenger; Signal Transduction; tau Proteins

In the present study, we examined the effects of intracerebroventricular administration of extracellular signal-regulated protein kinase- (ERK) and p38-specific inhibitors, U0126 and PD169316, respectively, on apoptosis induced by amyloid beta (Aβ) in rats. To investigate the effects of these compounds, we evaluated intracellular signalling pathways of apoptosis, as well as inflammatory and antioxidant pathways, 7 and 20 days after Aβ injection. We found that caspase-3 and Bax/Bcl-2 ratio, two hallmarks of apoptosis, were significantly decreased in the rats pre-treated with U0126 and PD169316, 7 days after Aβ injection. This observation was in agreement with the results of immunostaining analysis of the hippocampus that showed decreased levels of terminal transferase dUTP nick end labelling positive cells in the hippocampus of U0126 and PD169316 pre-treated rats, compared with the Aβ-injected group. We also chased the changes in the levels of calpain-2 and caspase-12, two ER factors, in the Aβ-injected and treatment groups. Decreased levels of calpain-2 and caspase-12 in U0126 and PD169316 pre-treated rats confirmed the protective effects of these inhibitors. Furthermore, we studied the effect of two stress-sensing transcription factors, nuclear-related factor-2 (Nrf2) and nuclear factor-кB (NF-кB), in Aβ-injected as wells as U0126 and PD169316 pre-treated rats. U0126 and PD169316 activated Nrf2 and suppressed NF-кB pathways, 7 days after Aβ injection. These antioxidant and inflammatory pathways restored to the vehicle level within 20 days. Taken together, our findings reinforce and extend the notion of the potential neuroprotective role of ERK and/or p38 inhibitors against the neuronal toxicity induced by Aβ.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Apoptosis; Blotting, Western; Butadienes; Disease Models, Animal; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Hippocampus; Imidazoles; In Situ Nick-End Labeling; Injections, Intraventricular; Male; MAP Kinase Signaling System; NF-E2-Related Factor 2; NF-kappa B; Nitriles; p38 Mitogen-Activated Protein Kinases; Rats; Rats, Wistar

Lipid and protein tyrosine phosphatase, phosphatase and tension homologue (PTEN), is a widely known negative regulator of insulin/phosphoinositide 3-kinase signaling. Down-regulation of PTEN is thus widely documented to ameliorate insulin resistance in peripheral tissues such as skeletal muscle and adipose. However, not much is known about its exact role in neuronal insulin signaling and insulin resistance. Moreover, alterations of PTEN in neuronal systems have led to discovery of several unexpected outcomes, including in the neurodegenerative disorder Alzheimer's disease (AD), which is increasingly being recognized as a brain-specific form of diabetes. In addition, contrary to expectations, its neuron-specific deletion in mice resulted in development of diet-sensitive obesity. The present study shows that PTEN, paradoxically, positively regulates neuronal insulin signaling and glucose uptake. Its down-regulation exacerbates neuronal insulin resistance. The positive role of PTEN in neuronal insulin signaling is likely due to its protein phosphatase actions, which prevents the activation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK), the kinases critically involved in neuronal energy impairment and neurodegeneration. Results suggest that PTEN acting through FAK, the direct protein substrate of PTEN, prevents ERK activation. Our findings provide an explanation for unexpected outcomes reported earlier with PTEN alterations in neuronal systems and also suggest a novel molecular pathway linking neuronal insulin resistance and AD, the two pathophysiological states demonstrated to be closely linked.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Butadienes; Cell Line, Tumor; Deoxyglucose; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Focal Adhesion Kinase 1; Gene Knockdown Techniques; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Inositol Polyphosphate 5-Phosphatases; Insulin; Insulin Resistance; MAP Kinase Signaling System; Mice; Neurons; Nitriles; Phosphatidylinositol 3-Kinases; Phosphatidylinositols; Phosphoric Monoester Hydrolases; Phosphorylation; Primary Cell Culture; Protein Processing, Post-Translational; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; RNA Interference

1. Deposition of β-amyloid (Aβ) peptide is a defining pathological hallmark of Alzheimer's disease (AD) and is involved in memory impairment. Evidence suggests that activation of an extracellular signal-regulated kinase (ERK) pathway is related to Aβ accumulation. Thus, the aim of the present study was to investigate the effects of an ERK inhibitor (U0126) on amyloidogenesis and cognitive function in Tg2576 mice. 2. Tg2576 mice were injected with U0126 (20 mg/kg, i.p.) or vehicle (1% dimethyl sulphoxide in sterile saline) once a day for 7 days and then cognitive function was assessed by the Morris water maze test and passive avoidance test. In addition, immunostaining, western blot analysis, ELISA and enzyme activity assays were used to examine the degree of Aβ deposition in the brains of Tg2576 mice. 3. Our results showed that U0126 attenuated memory impairment and inhibited Aβ deposition in the brains of Tg2576 mice. Further experiments revealed that the inhibition of Aβ deposition by U0126 was due to a reduction in β-secretase and amyloid precursor protein expression in the brains of U0126-treated Tg2576 mice. 4. These results suggest that the ERK pathway is associated with Aβ accumulation and consequent memory dysfunction in Tg2576 mice and that inhibition of the ERK pathway may be an appropriate intervention in the treatment of AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Aspartic Acid Endopeptidases; Brain; Butadienes; Cognition Disorders; Extracellular Signal-Regulated MAP Kinases; Female; Memory Disorders; Mice; Mice, Transgenic; Nitriles

Berberine (BER), the major alkaloidal component of Rhizoma coptidis, has multiple pharmacological effects including inhibition of acetylcholinesterase, reduction of cholesterol and glucose levels, anti-inflammatory, neuroprotective and neurotrophic effects. It has also been demonstrated that BER can reduce the production of beta-amyloid40/42, which plays a critical and primary role in the pathogenesis of Alzheimer's disease. However, the mechanism by which it accomplishes this remains unclear.. Here, we report that BER could not only significantly decrease the production of beta-amyloid40/42 and the expression of beta-secretase (BACE), but was also able to activate the extracellular signal-regulated kinase1/2 (ERK1/2) pathway in a dose- and time-dependent manner in HEK293 cells stably transfected with APP695 containing the Swedish mutation. We also find that U0126, an antagonist of the ERK1/2 pathway, could abolish (1) the activation activity of BER on the ERK1/2 pathway and (2) the inhibition activity of BER on the production of beta-amyloid40/42 and the expression of BACE.. Our data indicate that BER decreases the production of beta-amyloid40/42 by inhibiting the expression of BACE via activation of the ERK1/2 pathway.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Berberine; Butadienes; Down-Regulation; HEK293 Cells; Humans; Neuroprotective Agents; Nitriles; Peptide Fragments; Time Factors

Although apolipoprotein (apo) E is synthesized in the brain primarily by astrocytes, neurons in the central nervous system express apoE, albeit at lower levels than astrocytes, in response to various physiological and pathological conditions, including excitotoxic stress. To investigate how apoE expression is regulated in neurons, we transfected Neuro-2a cells with a 17-kilobase human apoE genomic DNA construct encoding apoE3 or apoE4 along with upstream and downstream regulatory elements. The baseline expression of apoE was low. However, conditioned medium from an astrocytic cell line (C6) or from apoE-null mouse primary astrocytes increased the expression of both isoforms by 3-4-fold at the mRNA level and by 4-10-fold at the protein level. These findings suggest that astrocytes secrete a factor or factors that regulate apoE expression in neuronal cells. The increased expression of apoE was almost completely abolished by incubating neurons with U0126, an inhibitor of extracellular signal-regulated kinase (Erk), suggesting that the Erk pathway controls astroglial regulation of apoE expression in neuronal cells. Human neuronal precursor NT2/D1 cells expressed apoE constitutively; however, after treatment of these cells with retinoic acid to induce differentiation, apoE expression diminished. Cultured mouse primary cortical and hippocampal neurons also expressed low levels of apoE. Astrocyte-conditioned medium rapidly up-regulated apoE expression in fully differentiated NT2 neurons and in cultured mouse primary cortical and hippocampal neurons. Thus, neuronal expression of apoE is regulated by a diffusible factor or factors released from astrocytes, and this regulation depends on the activity of the Erk kinase pathway in neurons.

Topics: Alzheimer Disease; Animals; Apolipoproteins E; Astrocytes; Blotting, Western; Butadienes; Cell Line, Tumor; Cells, Cultured; Culture Media, Conditioned; Enzyme Inhibitors; Gene Expression Regulation; Hippocampus; Humans; Immunohistochemistry; Mice; Mitogen-Activated Protein Kinases; Models, Biological; Models, Genetic; Neuroglia; Neurons; Nitriles; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Up-Regulation

In this paper we show that exposure of a rat brain synaptosome fraction to the amyloid beta peptide fragment betaA(25-35), but not the inverted peptide betaA(35-25), stimulated production of reactive oxygen species (ROS) in a concentration- and time-dependent manner. The ROS formation was attenuated by the tyrosine kinase inhibitor genistein, the mitogen-activated protein kinase inhibitor U0126, and the phospholipase A2 (PLA2) inhibitor 7,7-dimethyl-(5Z,8Z)-eicosadienoic acid. This strongly suggests that betaA(25-35) stimulated ROS production through an extracellular signal-regulated kinase-PLA2-dependent pathway. The interaction between these enzymes and their possible involvement in free radical formation in Alzheimer's disease are discussed.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Brain; Butadienes; Enzyme Inhibitors; Fatty Acids, Unsaturated; Genistein; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Nitriles; Peptide Fragments; Phospholipases A; Phospholipases A2; Rats; Reactive Oxygen Species; Spectrometry, Fluorescence; Synaptosomes