Amyloid-β peptide on sialyl-Lewis(X)-selectin-mediated membrane tether mechanics at the cerebral endothelial cell surface

Increased deposition of amyloid-β peptide (Aβ) at the cerebral endothelial cell (CEC) surface has been implicated in enhancement of transmigration of monocytes across the brain blood barrier (BBB) in Alzheimer's disease (AD). In this study, quantitative immunofluorescence microscopy (QIM) and atomic force microscopy (AFM) with cantilevers biofunctionalized by sialyl-Lewis(x) (sLe(x)) were employed to investigate Aβ-altered mechanics of membrane tethers formed by bonding between sLe(x) and p-selectin at the CEC surface, the initial mechanical step governing the transmigration of monocytes. QIM results indicated the ability for Aβ to increase p-selectin expression at the cell surface and promote actin polymerization in both bEND3 cells (immortalized mouse CECs) and human primary CECs. AFM data also showed the ability for Aβ to increase cell stiffness and adhesion probability in bEND3 cells. On the contrary, Aβ lowered the overall force of membrane tether formation (Fmtf ), and produced a bimodal population of Fmtf , suggesting subcellular mechanical alterations in membrane tethering. The lower Fmtf population was similar to the results obtained from cells treated with an F-actin-disrupting drug, latrunculin A. Indeed, AFM results also showed that both Aβ and latrunculin A decreased membrane stiffness, suggesting a lower membrane-cytoskeleton adhesion, a factor resulting in lower Fmtf . In addition, these cerebral endothelial alterations induced by Aβ were abrogated by lovastatin, consistent with its anti-inflammatory effects. In sum, these results demonstrated the ability for Aβ to enhance p-selectin expression at the CEC surface and induce cytoskeleton reorganization, which in turn, resulted in changes in membrane-cytoskeleton adhesion and membrane tethering, mechanical factors important in transmigration of monocytes through the BBB.

Etiology of Moldy Core, Core Browning, and Core Rot of Fuji Apple in China

'Fuji' apple fruit were collected in Shaanxi Province, China, and 186 fungal isolates were obtained from the fruit core region. Fungi were isolated from fruit with symptomless core regions, as well as from the core regions of fruit showing browning, typical moldy core, or core rot. Based on phylogenetic and morphological analysis, all fungi were identified to species. Pathogenicity was determined by cutting apple fruit into halves and daubing spore suspensions containing 1 × 10⁴ up to 1 × 10⁸ spores/ml on the carpel in the core region. Pathogenicity varied significantly among genera, with Alternaria and Cladosporium spp. causing core browning at lower spore concentrations and moldy core at higher spore concentrations. Combinations of pathogens initiated more browning and moldy core than the pathogens applied alone. Epicoccum and Phoma spp. predominated in dry core rot, whereas primarily Trichothecium but also Fusarium and Penicillium spp. caused wet core rot. Core browning was introduced as a new type of core symptom, along with moldy core, dry core rot, and wet core rot. Alternaria alternata, A. tenuissima, A. arborescens, Cladosporium cladosporioides, and C. tenuissimum were the main pathogens causing core browning and moldy core.

Magnolia polyphenols attenuate oxidative and inflammatory responses in neurons and microglial cells

Background

The bark of magnolia has been used in Oriental medicine to treat a variety of remedies, including some neurological disorders. Magnolol (Mag) and honokiol (Hon) are isomers of polyphenolic compounds from the bark of Magnolia officinalis, and have been identified as major active components exhibiting anti-oxidative, anti-inflammatory, and neuroprotective effects. In this study, we investigate the ability of these isomers to suppress oxidative stress in neurons stimulated by the ionotropic glutamate receptor agonist N-methyl-D-aspartate (NMDA) and oxidative and inflammatory responses in microglial cells activated by interferon-γ (IFNγ) and lipopolysaccharide (LPS). We also attempt to elucidate the mechanism and signaling pathways involved in cytokine-induced production of reactive oxygen species (ROS) in microglial cells.

Methods

Dihydroethidium (DHE) was used to assay superoxide production in neurons, while CM-H2DCF-DA was used to test for ROS production in murine (BV-2) and rat (HAPI) immortalized microglial cells. NADPH oxidase inhibitors (for example, diphenyleneiodonium (DPI), AEBSF, and apocynin) and immunocytochemistry targeting p47phox and gp91phox were used to assess the involvement of NADPH oxidase. Western blotting was used to assess iNOS and ERK1/2 expression, and the Griess reaction protocol was employed to determine nitric oxide (NO) concentration.

Results

Exposure of Hon and Mag (1–10 μM) to neurons for 24 h did not alter neuronal viability, but both compounds (10 μM) inhibited NMDA-stimulated superoxide production, a pathway known to involve NADPH oxidase. In microglial cells, Hon and Mag inhibited IFNγ±LPS-induced iNOS expression, NO, and ROS production. Studies with inhibitors and immunocytochemical assay further demonstrated the important role of IFNγ activating the NADPH oxidase through the p-ERK-dependent pathway. Hon and, to a lesser extent, Mag inhibited IFNγ-induced p-ERK1/2 and its downstream pathway for ROS and NO production.

Conclusion

This study highlights the important role of NADPH oxidase in mediating oxidative stress in neurons and microglial cells and has unveiled the role of IFNγ in stimulating the MAPK/ERK1/2 signaling pathway for activation of NADPH oxidase in microglial cells. Hon and Mag offer anti-oxidative or anti-inflammatory effects, at least in part, through suppressing IFNγ-induced p-ERK1/2 and its downstream pathway.

Enzymic hydrolysis of arachidonoyl-phospholipids by rat brain synaptosomes

Rat brain synaptosomes prelabeled with [(14)C]arachidonoyl-phospholipids were used to study the characteristic properties of acyl hydrolases for different phospholipids. Incubation of the prelabeled synaptosomes at 37 degrees C resulted in a time-dependent decrease of label from phosphatidylcholines (PC) and phosphatidylinositols (PI) and a concomitant increase in label in the free fatty acid fraction, but not diacylglycerols (DG). Phosphatidylserines (PS) also showed a decrease in radioactivity, but little change was observed for phosphatidylethanolamines (PE). At pH 7.4, the release of labeled arachidonate from PI was Ca(2+)-dependent, but that from PS and approx 50% of that from PC was not. The hydrolysis of PC was greatest at pH 7.4, but Ca(2+)-dependent hydrolysis of PI was active from pH 5.5 to 8.5. All detergents tested severely inhibited the release of labeled arachidonate, but in the presence of Ca(2+) and deoxycholate or taurocholate, a large portion of PI was converted to DG through activation of the PI-phosphodiesterase. Different effects on the phospholipid hydrolysis were observed with different phospholipase A(2) inhibitors. Mepacrine (1 mM) inhibited the Ca(2+)-dependent hydrolysis of PI but not PC, whereas dibucaine (1 mM) inhibited PC hydrolysis by 40% but did not affect PI. p-Bromophenacyl bromide (1 mM) dissolved in dimethylsulfoxide (DMSO) only partially inhibited (about 40%) the hydrolysis of PI and PC. The preferential hydrolysis of PI and PC by endogenous phospholipid acyl hydrolase correlates well with the observation that these same two lyso-phospholipids are also preferred by the acyltransferase for the reacylation process.

The fatty acid and aldehyde composition of the major phospholipids of mouse brain

Phospholipid classes were separated from mouse brain lipid extracts by preparative thin-layer chromatography (TLC). Methyl esters were prepared from the intact phospholipids by direct transesterification at room temperature in the presence of silica gel by using 0.5M: NaOH-methanol in order to prevent interference by aldehydes or derivatives. Dimethyl acetal derivatives of phosphoglyceride alkenyl ethers (alkenyl moiety with a double bond in 1,2-position relative to oxygen linkage) were prepared, using 5% concentrated HCl in methanol, followed by preparative TLC for isolation.The major phospholipids present were ethanolamine phosphoglycerides (EPG) 39.8%, choline phosphoglycerides (CPG) 39.7%, serine phosphoglycerides (SPG) 15.0%, and sphingomyelin (Sph) 5.4%. One-fifth of the total phospholipids (PL) were in the form of plasmalogens, mainly EPG. Choline and serine plasmalogens were present in trace quantities. The major aldehyde components of the plasmalogens were 16ratio0, 18ratio0, and 18ratio1.The EPG were rich in long-chain poly-unsaturated fatty acids, including 28.8% of 22ratio6 and 17.0% of 20ratio4, but contained only 7.2% of 16ratio0. In contrast, the CPG contained 39.6% of 16ratio0, and 31.0% of 18ratio1 with a small content of polyunsaturated fatty acids. The SPG exhibited a still different pattern containing 38.2% of 18ratio0, 23.2% of 18ratio1, 24.3% of 22ratio6, 2.9% of 16ratio0, and 3.8% of 20ratio4.

Inhibition of MMP-9 by a selective gelatinase inhibitor protects neurovasculature from embolic focal cerebral ischemia

Background

Cerebral ischemia has been shown to induce activation of matrix metalloproteinases (MMPs), particularly MMP-9, which is associated with impairment of the neurovasculature, resulting in blood–brain barrier breakdown, hemorrhage and neurodegeneration. We previously reported that the thiirane inhibitor SB-3CT, which is selective for gelatinases (MMP-2 and −9), could antagonize neuronal apoptosis after transient focal cerebral ischemia.

Results

Here, we used a fibrin-rich clot to occlude the middle cerebral artery (MCA) and assessed the effects of SB-3CT on the neurovasculature. Results show that neurobehavioral deficits and infarct volumes induced by embolic ischemia are comparable to those induced by the filament-occluded transient MCA model. Confocal microscopy indicated embolus-blocked brain microvasculature and neuronal cell death. Post-ischemic SB-3CT treatment attenuated infarct volume, ameliorated neurobehavioral outcomes, and antagonized the increases in levels of proform and activated MMP-9. Embolic ischemia caused degradation of the neurovascular matrix component laminin and tight-junction protein ZO-1, contraction of pericytes, and loss of lectin-positive brain microvessels. Despite the presence of the embolus, SB-3CT mitigated these outcomes and reduced hemorrhagic volumes. Interestingly, SB-3CT treatment for seven days protected against neuronal laminin degradation and protected neurons from ischemic cell death.

Conclusion

These results demonstrate considerable promise for the thiirane class of selective gelatinase inhibitors as potential therapeutic agents in stroke therapy.

Nucleotides released from Aβ₁₋₄₂ -treated microglial cells increase cell migration and Aβ₁₋₄₂ uptake through P2Y₂ receptor activation

Amyloid β-protein (Aβ) deposits in brains of Alzheimer's disease patients generate proinflammatory cytokines and chemokines that recruit microglial cells to phagocytose Aβ. Nucleotides released from apoptotic cells activate P2Y(2) receptors (P2Y(2) Rs) in macrophages to promote clearance of dead cells. In this study, we investigated the role of P2Y(2) Rs in the phagocytosis and clearance of Aβ. Treatment of mouse primary microglial cells with fibrillar (fAβ(1-42) ) and oligomeric (oAβ(1-42) ) Aβ(1-42) aggregation solutions caused a rapid release of ATP (maximum after 10 min). Furthermore, fAβ(1-42) and oAβ(1-42) treatment for 24 h caused an increase in P2Y(2) R gene expression. Treatment with fAβ(1-42) and oAβ(1-42) aggregation solutions increased the motility of neighboring microglial cells, a response inhibited by pre-treatment with apyrase, an enzyme that hydrolyzes nucleotides. The P2Y(2) R agonists ATP and UTP caused significant uptake of Aβ(1-42) by microglial cells within 30 min, which reached a maximum within 1 h, but did not increase Aβ(1-42) uptake by primary microglial cells isolated from P2Y(2) R(-/-) mice. Inhibitors of α(v) integrins, Src and Rac decreased UTP-induced Aβ(1-42) uptake, suggesting that these previously identified components of the P2Y(2) R signaling pathway play a role in Aβ phagocytosis by microglial cells. Finally, we found that UTP treatment enhances Aβ(1-42) degradation by microglial cells, but not in cells isolated from P2Y(2) R(-/-) mice. Taken together, our findings suggest that P2Y(2) Rs can activate microglial cells to enhance Aβ clearance and highlight the P2Y(2) R as a therapeutic target in Alzheimer's disease.

AP-2β regulates amyloid beta-protein stimulation of apolipoprotein E transcription in astrocytes

Two key players involved in Alzheimer's disease (AD) are amyloid beta protein (Aβ) and apolipoprotein E (apoE). Aβ increases apoE protein levels in astrocytes which is associated with cholesterol trafficking, neuroinflammatory responses and Aβ clearance. The mechanism for the increase in apoE protein abundance is not understood. Based on different lines of evidence, we propose that the beta-adrenergic receptor (βAR), cAMP and the transcription factor activator protein-2 (AP-2) are contributors to the Aβ-induced increase in apoE abundance. This hypothesis was tested in mouse primary astrocytes and in cells transfected with an apoE promoter fragment with binding sites for AP-2. Aβ(42) induced a time-dependent increase in apoE mRNA and protein levels which were significantly inhibited by βAR antagonists. A novel finding was that Aβ incubation significantly reduced AP-2α levels and significantly increased AP-2β levels in the nuclear fraction. The impact of Aβ-induced translocation of AP-2 into the nucleus was demonstrated in cells expressing AP-2 and incubated with Aβ(42). AP-2 expressing cells had enhanced activation of the apoE promoter region containing AP-2 binding sites in contrast to AP-2 deficient cells. The transcriptional upregulation of apoE expression by Aβ(42) may be a neuroprotective response to Aβ-induced cytotoxicity, consistent with apoE's role in cytoprotection.

Stroke, angiogenesis and phytochemicals

Stroke, or brain attack, is the third leading cause of death and the leading cause of adult disability worldwide. There is a great demand for intervention therapy. Unfortunately, although more than 700 drugs that target neuroprotection showed beneficial effects in preclinical animal studies, none of them proved efficacious in treating stroke patients. There is recent interest in understanding mechanism for post-ischemic angiogenesis in the penumbra area, and correlation of the extent of angiogenesis with survival in stroke patients. It is postulated that besides replenishing oxygen and nutrients to ischemic tissue, angiogenesis may play a crucial role in neural protection and tissue recovery. Consequently, therapeutic agents to promote angiogenesis and formation of new vessels after stroke can offer promising approach. Several large population epidemiological and clinical studies have revealed a reciprocal relationship between intake of phytochemicals and incidence of stroke. However, the detailed cellular and molecular mechanisms leading to these beneficial effects remain to be elucidated. In this article, we review the current knowledge on phytochemicals and post-ischemic angiogenesis, and discuss the possibility of a combinatorial treatment, including neuroprotection, angiogenesis, neurogenesis, and phytochemicals regimen for stroke.

The neuroprotective effects of apocynin

The recognition of health benefits of phytomedicines and herbal supplements lead to an increased interest to understand the cellular and molecular basis of their biological activities. Apocynin (4-hydroxy-3-methoxy-acetophenone) is a constituent of the Himalayan medicinal herb Picrorhiza kurroa which is regarded as an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase, a superoxide-producing enzyme. NADPH oxidase appears to be especially important in the modulation of redox-sensitive signaling pathways and also has been implicated in neuronal dysfunction and degeneration, and neuroinflammmation in diseases ranging from stroke, Alzheimer's and Parkinson's diseases to psychiatric disorders. In this review, we aim to give an overview of current literature on the neuroprotective effects of apocynin in the prevention and treatment of neurodegenerative disorders. Particular attention is given to in vivo studies.

Role of Aβ-receptor for advanced glycation endproducts interaction in oxidative stress and cytosolic phospholipase A₂ activation in astrocytes and cerebral endothelial cells

Blood-brain barrier (BBB) dysfunctions have been implicated in the progression of Alzheimer's disease. Cerebral endothelial cells (CECs) and astrocytes are the main cell components of the BBB. Although amyloid-β oligomers (Aβ₄₂) have been reported to mediate oxidative damage to the CECs and astrocytes and trigger the downstream mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway, the cell surface binding site for Aβ₄₂ and exact sequence of these events have yet to be elucidated. In this study, the receptor for advanced glycation endproducts (RAGE) was postulated to function as a signal transducing cell surface receptor for Aβ₄₂ to induce reactive oxygen species (ROS) generation from NADPH oxidase and trigger downstream pathways for the phosphorylation of extracellular signal-regulated kinases (ERK1/2) and cytosolic phospholipase A₂ (cPLA₂). We found that Aβ₄₂ competed with the anti-RAGE antibody (Ab(RAGE)) to bind to RAGE on the surfaces of CECs and primary astrocytes. In addition, Ab(RAGE) abrogate Aβ₄₂-induced ROS production and the colocalization between the cytosolic (p47-phox) and membrane (gp91-phox) subunits of NADPH oxidase in both cell types. Ab(RAGE) as well as NADPH oxidase inhibitor and ROS scavenger suppressed Aβ₄₂-induced ERK1/2 and cPLA₂ phosphorylation in CECs. At the same time, only Ab(RAGE), but neither NADPH oxidase inhibitor nor ROS scavenger, inhibited the ERK1/2 pathway and cPLA₂ phosphorylation in primary astrocytes. Therefore, this study demonstrates that NADPH oxidase complex assembly and ROS production are not required for Aβ₄₂ binding to RAGE at astrocytic surface leading to sequential phosphorylation of ERK1/2 and cPLA₂, and suggests the presence of two different RAGE-dependent downstream pathways in the CECs and astrocytes.

Pro-inflammatory cytokines and lipopolysaccharide induce changes in cell morphology, and upregulation of ERK1/2, iNOS and sPLA₂-IIA expression in astrocytes and microglia

Background

Activation of glial cells, including astrocytes and microglia, has been implicated in the inflammatory responses underlying brain injury and neurodegenerative diseases including Alzheimer's and Parkinson's diseases. Although cultured astrocytes and microglia are capable of responding to pro-inflammatory cytokines and lipopolysaccharide (LPS) in the induction and release of inflammatory factors, no detailed analysis has been carried out to compare the induction of iNOS and sPLA2-IIA. In this study, we investigated the effects of cytokines (TNF-alpha, IL-1beta, and IFN-gamma) and LPS + IFN-gamma to induce temporal changes in cell morphology and induction of p-ERK1/2, iNOS and sPLA₂-IIA expression in immortalized rat (HAPI) and mouse (BV-2) microglial cells, immortalized rat astrocytes (DITNC), and primary microglia and astrocytes.

Methods/Results

Cytokines (TNF-alpha, IL-1beta, and IFN-gamma) and LPS + IFN-gamma induced a time-dependent increase in fine processes (filopodia) in microglial cells but not in astrocytes. Filopodia production was attributed to IFN-gamma and was dependent on ERK1/2 activation. Cytokines induced an early (15 min) and a delayed phase (1 ~ 4 h) increase in p-ERK1/2 expression in microglial cells, and the delayed phase increase corresponded to the increase in filopodia production. In general, microglial cells are more active in responding to cytokines and LPS than astrocytes in the induction of NO. Although IFN-gamma and LPS could individually induce NO, additive production was observed when IFN-gamma was added together with LPS. On the other hand, while TNF-alpha, IL-1beta, and LPS could individually induce sPLA₂-IIA mRNA and protein expression, this induction process does not require IFN-gamma. Interestingly, neither rat immortalized nor primary microglial cells were capable of responding to cytokines and LPS in the induction of sPLA2-IIA expression.

Conclusion

These results demonstrated the utility of BV-2 and HAPI cells as models for investigation on cytokine and LPS induction of iNOS, and DITNC astrocytes for induction of sPLA2-IIA. In addition, results further demonstrated that cytokine-induced sPLA2-IIA is attributed mainly to astrocytes and not microglial cells.

Spatial learning and memory impairment and increased locomotion in a transgenic amyloid precursor protein mouse model of Alzheimer's disease

This study provides an examination of spatial learning and a behavioral assessment of irritability and locomotion in TgCRND8 mice, an amyloid precursor protein transgenic model of Alzheimer's disease. Performance was assessed using the Barnes maze, the touch escape test, and an open-field test. While past research focused primarily on 2-5-month-old TgCRND8 mice, the present study used an older age cohort (9-month-old female mice), in addition to a 4-month-old cohort of both transgenic (Tg) and wildtype female mice. Both younger and older Tg mice displayed poor spatial learning in the Barnes maze task compared to their wildtype littermates, as demonstrated by significantly longer latencies and more errors both during acquisition and at a 2-week retest. No differences in irritability were found between Tg and control mice in the younger cohort; however, older Tg mice displayed significantly higher irritability compared with wildtype littermates, as measured by the touch escape test. Additionally, Tg mice of both age cohorts showed increased locomotion and slowed habituation during a 60-min open-field test over 3 days of testing. These results demonstrate that TgCRND8 mice show significant deficits in spatial and nonspatial behavioral tasks at advanced stages of amyloid pathology.

Phospholipases A2 and neural membrane dynamics: implications for Alzheimer's disease

Phospholipases A(2) (PLA(2)s) are essential enzymes in cells. They are not only responsible for maintaining the structural organization of cell membranes, but also play a pivotal role in the regulation of cell functions. Activation of PLA(2) s results in the release of fatty acids and lysophospholipids, products that are lipid mediators and compounds capable of altering membrane microdomains and physical properties. Although not fully understood, recent studies have linked aberrant PLA(2) activity to oxidative signaling pathways involving NADPH oxidase that underlie the pathophysiology of a number of neurodegenerative diseases. In this paper, we review studies describing the involvement of cytosolic PLA(2) in oxidative signaling pathways leading to neuronal impairment and activation of glial cell inflammatory responses. In addition, this review also includes information on the role of cytosolic PLA(2) and exogenous secretory PLA(2) on membrane physical properties, dynamics, and membrane proteins. Unraveling the mechanisms that regulate specific types of PLA(2)s and their effects on membrane dynamics are important prerequisites towards understanding their roles in the pathophysiology of Alzheimer's disease, and in the development of novel therapeutics to retard progression of the disease.

Low energy laser light (632.8 nm) suppresses amyloid-β peptide-induced oxidative and inflammatory responses in astrocytes

Oxidative stress and inflammation are important processes in the progression of Alzheimer's disease (AD). Recent studies have implicated the role of amyloid β-peptides (Aβ) in mediating these processes. In astrocytes, oligomeric Aβ induces the assembly of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complexes resulting in its activation to produce anionic superoxide. Aβ also promotes production of pro-inflammatory factors in astrocytes. Since low energy laser has previously been reported to attenuate oxidative stress and inflammation in biological systems, the objective of this study was to examine whether this type of laser light was able to abrogate the oxidative and inflammatory responses induced by Aβ. Primary rat astrocytes were exposed to Helium-Neon laser (λ=632.8 nm), followed by the treatment with oligomeric Aβ. Primary rat astrocytes were used to measure Aβ-induced production of superoxide anions using fluorescence microscopy of dihydroethidium (DHE), assembly of NADPH oxidase subunits by the colocalization between the cytosolic p47(phox) subunit and the membrane gp91(phox) subunit using fluorescent confocal microscopy, phosphorylation of cytosolic phospholipase A(2) cPLA(2) and expressions of pro-inflammatory factors including interleukin-1β (IL-1β) and inducible nitric-oxide synthase (iNOS) using Western blot Analysis. Our data showed that laser light at 632.8 nm suppressed Aβ-induced superoxide production, colocalization between NADPH oxidase gp91(phox) and p47(phox) subunits, phosphorylation of cPLA(2,) and the expressions of IL-1β and iNOS in primary astrocytes. We demonstrated for the first time that 632.8 nm laser was capable of suppressing cellular pathways of oxidative stress and inflammatory responses critical in the pathogenesis in AD. This study should prove to provide the groundwork for further investigations for the potential use of laser therapy as a treatment for AD.

Specific disruption of astrocytic Ca2+ signaling pathway in vivo by adeno-associated viral transduction

Astrocytes are the predominant glial-cell type in the CNS and they are known to play an active role in modulating neuronal function. Since many of the same molecules including G-protein coupled receptors (GPCRs) are expressed in both neurons and astrocytes, in vivo pharmacological manipulations to target astrocytes lack specificity. In this study, we investigated the effect of Pleckstrin Homology (PH) domain of Phospholipase C (PLC)-like protein p130 (p130PH) on Ca(2+) signaling in astrocytes in vivo. We used the serotype 2/5 recombinant adeno-associated virus (rAAV2/5) vectors to introduce p130PH fused with a tagged protein monomer red fluorescent protein at the N-terminal (i.e., transgene mRFP-p130PH). In order to selectively disrupt the Ca(2+) signaling pathway in astrocytes, the transgene was driven by a novel astrocyte-specific promoter gfaABC(1)D. Our results show that mRFP-p130PH is exclusively expressed in astrocytes with a high efficiency and a stable expression level. In vivo imaging using two-photon microscopy demonstrated reduced Ca(2+) signal in transduced astrocytes in response to ATP stimulation. As Ca(2+) signaling is a characteristic form of cellular excitability in astrocytes that can mediate chemical transmitter release and contribute to neuronal excitotoxicity, the current study provides an in vivo approach to better understand Ca(2+)-dependent gliotransmission and its involvement in glia-related diseases.

Altered microglial copper homeostasis in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by progressive neurodegeneration associated with the aggregation and deposition of β-amyloid (Aβ(40) and Aβ(42) ) peptide in senile plaques. Recent studies suggest that copper may play an important role in AD pathology. Copper concentrations are elevated in amyloid plaques and copper binds with high affinity to the Aβ peptide and promotes Aβ oligomerization and neurotoxicity. Despite this connection between copper and AD, it is unknown whether the expression of proteins involved in regulating copper homeostasis is altered in this disorder. In this study, we demonstrate that the copper transporting P-type ATPase, ATP7A, is highly expressed in activated microglial cells that are specifically clustered around amyloid plaques in the TgCRND8 mouse model of AD. Using a cultured microglial cell line, ATP7A expression was found to be increased by the pro-inflammatory cytokine interferon-gamma, but not by TNF-α or IL-1β. Interferon-gamma also elicited marked changes in copper homeostasis, including copper-dependent trafficking of ATP7A from the Golgi to cytoplasmic vesicles, increased copper uptake and elevated expression of the CTR1 copper importer. These findings suggest that pro-inflammatory conditions associated with AD cause marked changes in microglial copper trafficking, which may underlie the changes in copper homeostasis in AD. It is concluded that copper sequestration by microglia may provide a neuroprotective mechanism in AD.

Simvastatin stimulates production of the antiapoptotic protein Bcl-2 via endothelin-1 and NFATc3 in SH-SY5Y cells

The use of statins for the prevention or treatment of different neurodegenerative diseases has generated considerable interest albeit with some controversy. Mechanisms of statin-induced neuroprotection are not well understood. Recently, we reported that simvastatin stimulated neuronal gene expression and protein levels of the major antiapoptotic protein Bcl-2 in vivo and in vitro; suppression of Bcl-2 in SH-SY5Y cells reduced simvastatin neuroprotection; effects were independent of cholesterol and other products of the 3-hydroxy-3-methylglutaryl-CoA reductase pathway. Endothelin-1 (ET-1) can increase Bcl-2 abundance via the transcription factor nuclear factor of activated thymocytes (NFATc), and simvastatin was reported to increase ET-1 gene expression. We tested the hypothesis that simvastatin stimulation of Bcl-2 involves up-regulation of ET-1 and binding of NFATc to Bcl-2 promoter sites in SH-SY5Y human neuroblastoma cells. Simvastatin increased both intracellular and secreted ET-1 protein levels. Exogenous ET-1 increased Bcl-2 protein abundance, which was inhibited by ET-1 receptor antagonists. Simvastatin increased translocation of NFATc3 to the nucleus while reducing nuclear NFATc1 and having no effect on NFATc4. Endothelin-1 also increased NFATc3 levels in the nucleus, and this increase was inhibited by ET-1 receptor antagonists. Treatment of cells with simvastatin stimulated binding of NFATc3 to the Bcl-2 promoter. We report novel findings showing that up-regulation of Bcl-2 by simvastatin involves ET-1 and the transcription factor NFATc3. Discovering how statins can selectively alter a specific NFATc isoform that leads to an increase in an antiapoptotic protein will provide a new approach to understanding statin-induced neuroprotection and conditions outside the brain in which apoptosis contributes to pathophysiology.

P2Y2 nucleotide receptor-mediated responses in brain cells

Acute inflammation is important for tissue repair; however, chronic inflammation contributes to neurodegeneration in Alzheimer's disease (AD) and occurs when glial cells undergo prolonged activation. In the brain, stress or damage causes the release of nucleotides and activation of the G(q) protein-coupled P2Y(2) nucleotide receptor subtype (P2Y(2)R) leading to pro-inflammatory responses that can protect neurons from injury, including the stimulation and recruitment of glial cells. P2Y(2)R activation induces the phosphorylation of the epidermal growth factor receptor (EGFR), a response dependent upon the presence of a SH3 binding domain in the intracellular C terminus of the P2Y(2)R that promotes Src binding and transactivation of EGFR, a pathway that regulates the proliferation of cortical astrocytes. Other studies indicate that P2Y(2)R activation increases astrocyte migration. P2Y(2)R activation by UTP increases the expression in astrocytes of alpha(V)beta(3/5) integrins that bind directly to the P2Y(2)R via an Arg-Gly-Asp (RGD) motif in the first extracellular loop of the P2Y(2)R, an interaction required for G(o) and G(12) protein-dependent astrocyte migration. In rat primary cortical neurons (rPCNs) P2Y(2)R expression is increased by stimulation with interleukin-1beta (IL-1beta), a pro-inflammatory cytokine whose levels are elevated in AD, in part due to nucleotide-stimulated release from glial cells. Other results indicate that oligomeric beta-amyloid peptide (Abeta(1-42)), a contributor to AD, increases nucleotide release from astrocytes, which would serve to activate upregulated P2Y(2)Rs in neurons. Data with rPCNs suggest that P2Y(2)R upregulation by IL-1beta and subsequent activation by UTP are neuroprotective, since this increases the non-amyloidogenic cleavage of amyloid precursor protein. Furthermore, activation of IL-1beta-upregulated P2Y(2)Rs in rPCNs increases the phosphorylation of cofilin, a cytoskeletal protein that stabilizes neurite outgrowths. Thus, activation of pro-inflammatory P2Y(2)Rs in glial cells can promote neuroprotective responses, suggesting that P2Y(2)Rs represent a novel pharmacological target in neurodegenerative and other pro-inflammatory diseases.

Resveratrol as a therapeutic agent for neurodegenerative diseases

Excess production of reactive oxygen species in the brain has been implicated as a common underlying risk factor for the pathogenesis of a number of neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and stroke. In recent years, there is considerable interest concerning investigation of antioxidative and anti-inflammatory effects of phenolic compounds from different botanical sources. In this review, we first describe oxidative mechanisms associated with stroke, AD, and PD, and subsequently, we place emphasis on recent studies implicating neuroprotective effects of resveratrol, a polyphenolic compound derived from grapes and red wine. These studies show that the beneficial effects of resveratrol are not only limited to its antioxidant and anti-inflammatory action but also include activation of sirtuin 1 (SIRT1) and vitagenes, which can prevent the deleterious effects triggered by oxidative stress. In fact, SIRT1 activation by resveratrol is gaining importance in the development of innovative treatment strategies for stroke and other neurodegenerative disorders. The goal here is to provide a better understanding of the mode of action of resveratrol and its possible use as a potential therapeutic agent to ameliorate stroke damage as well as other age-related neurodegenerative disorders.