Phospholipases A2 and inflammatory responses in the central nervous system

Phospholipases A2 (PLA2s) belong to a superfamily of enzymes responsible for hydrolyzing the sn-2 fatty acids of membrane phospholipids. These enzymes are known to play multiple roles for maintenance of membrane phospholipid homeostasis and for production of a variety of lipid mediators. Over 20 different types of PLA2s are present in the mammalian cells, and in snake and bee venom. Despite their common function in hydrolyzing fatty acids of phospholipids, they are diversely encoded by a number of genes and express proteins that are regulated by different mechanisms. Recent studies have focused on the group IV calcium-dependent cytosolic cPLA2, the group VI calcium-independent iPLA2, and the group II small molecule secretory sPLA2. In the central nervous system (CNS), these PLA2s are distributed among neurons and glial cells. Although the physiological role of these PLA2s in regulating neural cell function has not yet been clearly elucidated, there is increasing evidence for their involvement in receptor signaling and transcriptional pathways that link oxidative events to inflammatory responses that underline many neurodegenerative diseases. Recent studies also reveal an important role of cPLA2 in modulating neuronal excitatory functions, sPLA2 in the inflammatory responses, and iPLA2 with childhood neurologic disorders associated with brain iron accumulation. The goal for this review is to better understand the structure and function of these PLA2s and to highlight specific types of PLA2s and their cross-talk mechanisms in these inflammatory responses under physiological and pathological conditions in the CNS.

Secretory phospholipase A2 type III enhances alpha-secretase-dependent amyloid precursor protein processing through alterations in membrane fluidity

In the non-amyloidogenic pathway, amyloid precursor protein (APP) is cleaved by alpha-secretases to produce alpha-secretase-cleaved soluble APP (sAPP(alpha)) with neuroprotective and neurotrophic properties; therefore, enhancing the non-amyloidogenic pathway has been suggested as a potential pharmacological approach for the treatment of Alzheimer's disease. Here, we demonstrate the effects of type III secretory phospholipase A(2) (sPLA(2)-III) on sAPP(alpha) secretion. Exposing differentiated neuronal cells (SH-SY5Y cells and primary rat neurons) to sPLA(2)-III for 24 h increased sAPP(alpha) secretion and decreased levels of Abeta(1-42) in SH-SY5Y cells, and these changes were accompanied by increased membrane fluidity. We further tested whether sPLA(2)-III-enhanced sAPP(alpha) release is due in part to the production of its hydrolyzed products, including arachidonic acid (AA), palmitic acid (PA), and lysophosphatidylcholine (LPC). Addition of AA but neither PA nor LPC mimicked sPLA(2)-III-induced increases in sAPP(alpha) secretion and membrane fluidity. Treatment with sPLA(2)-III and AA increased accumulation of APP at the cell surface but did not alter total expressions of APP, alpha-secretases, and beta-site APP cleaving enzyme. Taken together, these results support the hypothesis that sPLA(2)-III enhances sAPP(alpha) secretion through its action to increase membrane fluidity and recruitment of APP at the cell surface.

Neuroprotective effects of a nanocrystal formulation of sPLA(2) inhibitor PX-18 in cerebral ischemia/reperfusion in gerbils

The group IIA secretory phospholipase A2 (sPLA(2)-IIA) has been studied extensively because of its involvement in inflammatory processes. Up-regulation of this enzyme has been shown in a number of neurodegenerative diseases including cerebral ischemia and Alzheimer's disease. PX-18 is a selective sPLA(2) inhibitor effective in reducing tissue damage resulting from myocardial infarction. However, its use as a neuroprotective agent has been hampered due to its low solubility. In this study, we test the possible neuroprotective effects of PX-18 formulated as a suspension of nanocrystals. Transient global cerebral ischemia was induced in gerbils by occlusion of both common carotid arteries for 5 min. Four days after ischemia/reperfusion (I/R), extensive delayed neuronal death, DNA damage, and increases in reactive astrocytes and microglial cells were observed in the hippocampal CA1 region. PX-18 nanocrystals (30 and 60 mg/kg body wt) and vehicle controls were injected i.p. immediately after I/R. PX-18 nanocrystal injection significantly reduced delayed neuronal death, DNA damage, as well as glial cell activation. These findings demonstrated the effective neuroprotection of PX-18 in the form of nanocrystal against I/R-induced neuronal damage. The results also suggest that nanocrystals hold promise as an effective strategy for the delivery of compounds with poor solubility that would otherwise be precluded from preclinical development.

First Report of Sooty Blotch and Flyspeck Caused by Species of Dissoconium, Mycosphaerella, and Peltaster on Hawthorn Fruit in China

Sooty blotch and flyspeck (SBFS), a disease complex comprised of as many as 30 putative species of fungi, occurs on the cuticle of pome fruits in moist production regions worldwide, inciting cosmetic damage that causes significant economic losses (1). Chinese hawthorn (Crataegus pinnatifida Bge.) is an economically important tree species in China. Its fruit are sold fresh or dried and are used as a culinary spice as well as an ingredient in Chinese traditional medicine. In October of 2007, Chinese hawthorn fruit exhibiting SBFS signs were sampled from supermarkets in Yangling, Shaanxi Province and Luoyang, Henan Province, China. Thalli directly from the hawthorn fruit were transferred onto potato dextrose agar (PDA) slants under a dissecting microscope and cultured at 22 ± 1°C in darkness. DNA was extracted from pure isolates and the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA (nrDNA) was amplified and sequenced using primers ITS-1F and ITS4 (3). Phylogenetic analysis of the ITS sequences revealed that the 35 isolates generated in this study included five species in three genera: Dissoconium sp. (18 isolates), Mycosphaerella sp. (5 isolates), and Peltaster sp. 1 (4 isolates), Peltaster sp. 2 (4 isolates), and Peltaster sp. 3 (4 isolates). To fulfill Koch's postulates and verify that these fungi could also infest apple fruit, two representative isolates of each putative species were inoculated onto mature intact hawthorn and apple (cv. Fuji) fruit that had been surface disinfested with 75% ethanol and allowed to dry. Inoculum was prepared by comminuting 1-month-old cultures growing on PDA into a suspension of mycelial fragments and conidia (10⁵ to ~10⁶ CFU/ml) in a blender with sterile deionized water (SDW). Each isolate was inoculated on three hawthorn and three apple fruit by using cotton swabs. As controls, two surface-disinfested hawthorn and apple fruit were swabbed with SDW. After the inoculated hawthorn and apple fruit had been incubated in a moist chamber at 22 ± 1°C for 1 month, all inoculated hawthorn and apple fruit exhibited SBFS signs similar to those of the original colonies on hawthorn fruit, but the controls did not. Reservoir hosts have been inferred to play an important role in SBFS by providing the fungi with overwintering habitat and inoculum for infestations on apple. Many reservoir hosts have been reported in the United States and Japan (2). To our knowledge, this is the first report of fungi in the SBFS complex on hawthorn fruit and the first confirmation that fungi growing on hawthorn fruit can produce SBFS signs on apple fruit. These results identify hawthorn as a potential inoculum source for SBFS in apple orchards. References: (1) J. C. Batzer et al. Mycologia 97:1283, 2005. (2) K. Hemnani et al. Phytopathology 98(suppl):S66, 2008. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

Amyloid beta-protein stimulates trafficking of cholesterol and caveolin-1 from the plasma membrane to the Golgi complex in mouse primary astrocytes

The Golgi complex plays a key role in cholesterol trafficking in cells. Our earlier study demonstrated amyloid beta-protein (Abeta) alters cholesterol distribution and abundance in the Golgi complex of astrocytes. We now test the hypothesis that the Abeta-induced increase in Golgi complex cholesterol is due to retrograde movement of the cholesterol carrier protein caveolin-1 from the cell plasma membrane to the Golgi complex in astrocytes. Results with mouse primary astrocytes indicated that Abeta(1-42)-induced increase in cholesterol and caveolin abundance in the Golgi complex was accompanied by a reduction in cholesterol and caveolin levels in the plasma membrane. Transfected rat astrocytes (DITNC1) with siRNA directed at caveolin-1 mRNA inhibited the Abeta(1-42)-induced redistribution of both cholesterol and caveolin from the plasma membrane to the Golgi complex. In astrocytes not treated with Abeta(1-42), suppression of caveolin-1 expression also significantly reduced cholesterol abundance in the Golgi complex, further demonstrating the role for caveolin in retrograde transport of cholesterol from the plasma membrane to the Golgi complex. Perturbation of this process by Abeta(1-42) could have consequences on membrane structure and cellular functions requiring optimal levels of cholesterol.

Involvement of oxidative pathways in cytokine-induced secretory phospholipase A2-IIA in astrocytes

Recent studies have suggested the involvement of secretory phospholipase A2-IIA (sPLA2-IIA) in neuroinflammatory diseases. Although sPLA2-IIA is transcriptionally induced through the NF-kappaB pathway by pro-inflammatory cytokines, whether this induction pathway is affected by other intracellular signaling pathways has not been investigated in detail. In this study, we demonstrated the induction of sPLA2-IIA mRNA and protein expression in astrocytes by cytokines and detected the protein in the culture medium after stimulation. We further investigated the effects of oxidative pathways and botanical antioxidants on the induction pathway and observed that IL-1beta-induced sPLA2-IIA mRNA expression in astrocytes is dependent on ERK1/2 and PI-3 kinase, but not p38 MAPK. In addition to apocynin, a known NADPH oxidase inhibitor, botanical antioxidants, such as resveratrol and epigallocatechin gallate, also inhibited IL-1beta-induced sPLA2-IIA mRNA expression. These compounds also suppressed IL-1beta-induced ERK1/2 activation and translocation of the NADPH oxidase subunit p67 phox from cytosol to membrane fraction. Taken together, these results support the involvement of reactive oxygen species from NADPH oxidase in cytokine induction of sPLA2-IIA in astrocytes and promote the use of botanical antioxidants as protective agents for inhibition of inflammatory responses in these cells.

Interleukin-1beta enhances nucleotide-induced and alpha-secretase-dependent amyloid precursor protein processing in rat primary cortical neurons via up-regulation of the P2Y(2) receptor

The heterologous expression and activation of the human P2Y(2) nucleotide receptor (P2Y(2)R) in human 1321N1 astrocytoma cells stimulates alpha-secretase-dependent cleavage of the amyloid precursor protein (APP), causing extracellular release of the non-amyloidogenic protein secreted amyloid precursor protein (sAPPalpha). To determine whether a similar response occurs in a neuronal cell, we analyzed whether P2Y(2)R-mediated production of sAPPalpha occurs in rat primary cortical neurons (rPCNs). In rPCNs, P2Y(2)R mRNA and receptor activity were virtually absent in quiescent cells, whereas overnight treatment with the pro-inflammatory cytokine interleukin-1beta (IL-1beta) up-regulated both P2Y(2)R mRNA expression and receptor activity by four-fold. The up-regulation of the P2Y(2)R was abrogated by pre-incubation with Bay 11-7085, an IkappaB-alpha phosphorylation inhibitor, which suggests that P2Y(2)R mRNA transcript levels are regulated through nuclear factor-kappa-B (NFkappaB) signaling. Furthermore, the P2Y(2)R agonist Uridine-5'-triphosphate (UTP) enhanced the release of sAPPalpha in rPCNs treated with IL-1beta or transfected with P2Y(2)R cDNA. UTP-induced release of sAPPalpha from rPCNs was completely inhibited by pre-treatment of the cells with the metalloproteinase inhibitor TACE inhibitor (TAPI-2) or the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, and was partially inhibited by the MAPK/extracellular signal-regulated kinase inhibitor U0126 and the protein kinase C inhibitor GF109203. These data suggest that P2Y(2)R-mediated release of sAPPalpha from cortical neurons is directly dependent on a disintegrin and metalloproteinase (ADAM) 10/17 and PI3K activity, whereas extracellular signal-regulated kinase 1/2 and PI3K activity may indirectly regulate APP processing. These results demonstrate that elevated levels of pro-inflammatory cytokines associated with neurodegenerative diseases, such as IL-1beta, can enhance non-amyloidogenic APP processing through up-regulation of the P2Y(2)R in neurons.

Amyloid-beta peptide induces temporal membrane biphasic changes in astrocytes through cytosolic phospholipase A2

Oligomeric amyloid-beta peptide (Abeta) is known to induce cytotoxic effects and to damage cell functions in Alzheimer's disease. However, mechanisms underlying the effects of Abeta on cell membranes have yet to be fully elucidated. In this study, Abeta 1-42 (Abeta(42)) was shown to cause a temporal biphasic change in membranes of astrocytic DITNC cells using fluorescence microscopy of Laurdan. Abeta(42) made astrocyte membranes became more molecularly-disordered within the first 30 min to 1 h, but gradually changed to more molecularly-ordered after 3 h. However, Abeta(42) caused artificial membranes of vesicles made of rat whole brain lipid extract to become more disordered only. The trend for more molecularly-ordered membranes in astrocytes induced by Abeta(42) was abrogated by either an NADPH oxidase inhibitor, apocynin, or an inhibitor of cytosolic phospholipase A(2) (cPLA(2)), but not by an inhibitor of calcium-independent PLA(2) (iPLA(2)). Apocynin also suppressed the increased production of superoxide anions (O(2)(-)) and phosphorylation of cPLA(2) induced by Abeta(42). In addition, hydrolyzed products of cPLA(2), arachidonic acid (AA), but not lysophosphatidylcholine (LPC) caused astrocyte membranes to become more molecularly-ordered. These results suggest (1) a direct interaction of Abeta(42) with cell membranes making them more molecularly-disordered, and (2) Abeta(42) also indirectly makes membranes become more molecularly-ordered by triggering the signaling pathway involving NADPH oxidase and cPLA(2) in astrocytes.

Botanical phenolics and brain health

The high demand for molecular oxygen, the enrichment of polyunsaturated fatty acids in membrane phospholipids, and the relatively low abundance of antioxidant defense enzymes are factors rendering cells in the central nervous system (CNS) particularly vulnerable to oxidative stress. Excess production of reactive oxygen species (ROS) in the brain has been implicated as a common underlying factor for the etiology of a number of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and stroke. While ROS are generated by enzymatic and nonenzymatic reactions in the mitochondria and cytoplasm under normal conditions, excessive production under pathological conditions is associated with activation of Ca(2+)-dependent enzymes including proteases, phospholipases, nucleases, and alterations of signaling pathways which subsequently lead to mitochondrial dysfunction, release of inflammatory factors, and apoptosis. In recent years, there is considerable interest to investigate antioxidative and anti-inflammatory effects of phenolic compounds from different botanical sources. In this review, we describe oxidative mechanisms associated with AD, PD, and stroke, and evaluate neuroprotective effects of phenolic compounds, such as resveratrol from grape and red wine, curcumin from turmeric, apocynin from Picrorhiza kurroa, and epi-gallocatechin from green tea. The main goal is to provide a better understanding of the mode of action of these compounds and assess their use as therapeutics to ameliorate age-related neurodegenerative diseases.

First Report of Anthracnose of Lycium barbarum Caused by Colletotrichum acutatum in China

Barbary wolfberry (Lycium barbarum, Solanaceae) is an important Chinese traditional medicine that is widely planted in northwestern China (6.7 × 10⁴ ha under cultivation, including Ningxia Hui Autonomous Region). After a recent, large increase in the planting area and density, anthracnose has become more damaging. In China, Colletotrichum gloeosporioides was assumed to be the sole causal agent of anthracnose on L. chinense (wolfberry) (3), whereas in Korea, C. dematium was reported to cause anthracnose on wolfberry (4). During the summer and autumn of 2007, 29 barbary wolfberry fruit samples were collected from three orchards in Zhongning County, Ningxia Hui Autonomous Region. Conidia were 8.5 to 16.5 × 2.5 to 4 μm and fusiform or pointed at one or both ends. Slow-growing colonies on potato dextrose agar were white to orange or pink; sclerotia and setae were absent. The morphological traits were identical to those of C. acutatum and clearly distinct from those of C. gloeosporioides (conidia cylindrical with both ends rounded, gray colony color) or C. dematium (conidia falcate, sclerotia and setae abundant) (2-4). Koch's postulates were performed to verify that the isolates were capable of causing anthracnose on wolfberry. Six wolfberry fruits were surface sterilized with 70% alcohol, allowed to dry 1 min, then wounded with a sterile needle, and dipped in 6 ml of spore suspension (1 × 10⁵ conidia/ml). Anthracnose symptoms were observed on inoculated fruit after 3 days, whereas control fruits inoculated with sterile water did not develop symptoms. The pathogenicity test was performed three times; in each trial, fungi reisolated from symptomatic tissue were morphologically identical to those that had been used as inoculum. Amplification of the internal transcribed spacer (ITS) region of rDNA with primers ITS1 and ITS4 resulted in bands of approximately 600 bp. The sequences of both isolates were compared with sequences deposited in the GenBank database and demonstrated 99% similarity to C. acutatum isolate DQ286123. PCR amplification of the ITS region was also carried out using species-specific primer CaInt2 in conjunction with the universal primer ITS4 (1). A DNA fragment of approximately 500 bp was amplified from all isolates, whereas no amplification products were obtained from reference cultures of C. gloeosporioides and C. dematium. To our knowledge, this is the first report of C. acutatum causing anthracnose on L. barbarum. References: (1) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996. (2) B. C. Sutton. Page 523 in: The Coelomycetes. Commonwealth Mycological Institute, Kew, Surrey, England, 1980. (3) X. M. Wang and J. Y. Li. Acta Mycol. Sinica 6:211, 1987. (4) S. H. Yu. Korean J. Plant Pathol. 2:31, 1986.

First Report of Bitter Rot Caused by Colletotrichum acutatum on Apple in China

Bitter rot of apple caused by Colletotrichum gloeosporioides was first reported in China in 1985 (3). In China, apples are grown on approximately 2 million ha, and bitter rot occurs in almost all production areas, with crop damage ranging from 30 to 70%. During the summer of 2007, fungi were isolated from apple fruit exhibiting bitter rot symptoms in 12 and 9 orchards in Shaanxi and Henan provinces, respectively, in China. Symptoms included 2- to 3-cm-diameter, sunken, brown lesions on the fruit surface that contained black, pinhead-size fruiting structures producing orange conidial masses under high humidity, similar to that of C. gloeosporioides. On potato dextrose agar (PDA), colonies were white, pale gray, or pale orange when grown at 25°C. Conidia were 8 to 16 × 2.5 to 4 μm, fusiform, pointed at one or both ends, one celled, thin walled, aseptate, and hyaline. Appressoria were 6.5 to 11 × 4.5 to 7.5 μm, clavate to circular, and light to dark brown. These characteristics matched published descriptions of C. acutatum (2). To confirm pathogenicity, three mature, healthy apples (cv. Fuji) were surface disinfested with 70% ethanol and then wounded with a sterile needle. After being inoculated with a spore suspension (1 × 10⁵ conidia/ml) prepared from a 2-week-old culture on PDA, these apples were sealed in a plastic bag and incubated at 25°C. Symptoms appeared 3 to 5 days after inoculation and began to enlarge 7 days later, forming lesions with fruiting structures. Under high humidity, cream-to-salmon pink spore masses were produced on lesions. As the lesions enlarged, the rot progressed to the core of the fruit in a V-shaped pattern. When the pathogen was reisolated from lesions of inoculated fruit onto PDA and incubated at 25°C, colony and conidial morphology were identical to those of the original isolates. Tests were performed three times with similar results. PCR with species-specific primer pair CaInt2/ITS4 (1) of genomic DNA from the isolates resulted in an amplification product of approximately 490 bp, which is specific for C. acutatum. The sequences exhibited 99% similarity with those of C. acutatum isolates AB273195 from GenBank. Approximately 20 of 103 symptomatic fruit from the field survey yielded fungal cultures whose morphology was consistent with that of C. acutatum, whereas the other cultures were C. gloeosporioides and Botryosphaeria dothidea. To our knowledge, this is the first report of bitter rot of apple caused by Colletotrichum acutatum in China. References: (1) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996. (2) B. C. Sutton. Page 523 in: The Coelomycetes. Commonwealth Mycological Institute, Kew, Surrey, England, 1980. (3) X. M. Wang. M.S. thesis. (In Chinese). College of Northwest Agriculture, Shaanxi Province, China, 1985.

Black Cohosh: Insights into its Mechanism(s) of Action

The Women's Health Initiative found that combination estrogen and progesterone hormone replacement therapy increases breast cancer and cardiovascular disease risk, which compelled many women to seek herbal alternatives such as black cohosh extract (BCE) to relieve their menopausal symptoms. While several clinical trials document the efficacy of BCE in alleviating menopausal symptoms, preclinical studies to determine how BCE works have yielded conflicting results. Part of this is because there is not a universally accepted method to standardize the dose of black cohosh triterpenes, the presumed active ingredients in the extract. Although the mechanism by which BCE relieves symptoms is unknown, several hypotheses have been proposed: it acts 1) as a selective estrogen receptor modulator, 2) through serotonergic pathways, 3) as an antioxidant, or 4) on inflammatory pathways. We found that while the most prominent triterpene in BCE, 23-epi-26-deoxyactein, suppresses cytokine-induced nitric oxide production in brain microglial cells, the whole BCE extract actually enhanced this pathway. A variety of activities have been reported for black cohosh and its compounds, but the absorption and tissue distribution of these compounds is unknown.

Black Cohosh: Insights into its Mechanism(s) of Action

The Women's Health Initiative found that combination estrogen and progesterone hormone replacement therapy increases breast cancer and cardiovascular disease risk, which compelled many women to seek herbal alternatives such as black cohosh extract (BCE) to relieve their menopausal symptoms. While several clinical trials document the efficacy of BCE in alleviating menopausal symptoms, preclinical studies to determine how BCE works have yielded conflicting results. Part of this is because there is not a universally accepted method to standardize the dose of black cohosh triterpenes, the presumed active ingredients in the extract. Although the mechanism by which BCE relieves symptoms is unknown, several hypotheses have been proposed: it acts 1) as a selective estrogen receptor modulator, 2) through serotonergic pathways, 3) as an antioxidant, or 4) on inflammatory pathways. We found that while the most prominent triterpene in BCE, 23-epi-26-deoxyactein, suppresses cytokine-induced nitric oxide production in brain microglial cells, the whole BCE extract actually enhanced this pathway. A variety of activities have been reported for black cohosh and its compounds, but the absorption and tissue distribution of these compounds is unknown.

Oral administration of grape polyphenol extract ameliorates cerebral ischemia/reperfusion-induced neuronal damage and behavioral deficits in gerbils: comparison of pre- and post-ischemic administration

Oxidative stress has been regarded as an important underlying cause for the delayed neuronal death (DND) after cerebral ischemia. In this study, the effects of short-term oral administration of grape polyphenol extract (GPE) on ischemia/reperfusion (I/R) injury in a gerbil global ischemia model were determined. Ischemia was induced by occlusion of the common carotid arteries for 5 min. GPE (30 mg/ml)-containing formula or formula without GPE was administered daily via gavage for 4 days prior to and/or for 4 days after I/R. I/R resulted in hyperlocomotion, extensive DND, oxidative and fragmented DNA damage, and an increase in reactive astrocytes and microglial cells in the hippocampal CA1 region. GPE administration for 4 days prior to I/R and for 4 days after I/R attenuated DND, DNA damage and glial cell activation. However, neuroprotection was more pronounced when GPE was administered for 4 days after I/R than when administered for 4 days prior to I/R. GPE administration after I/R attenuated I/R-induced hyperlocomotion. These findings indicate that oral GPE intake may confer protection against I/R injury and emphasize that early intervention may be an effective therapeutic measure for ameliorating brain injury in stroke.

Amyloid beta peptide and NMDA induce ROS from NADPH oxidase and AA release from cytosolic phospholipase A2 in cortical neurons

Increase in oxidative stress has been postulated to play an important role in the pathogenesis of a number of neurodegenerative diseases including Alzheimer's disease. There is evidence for involvement of amyloid-beta peptide (Abeta) in mediating the oxidative damage to neurons. Despite yet unknown mechanism, Abeta appears to exert action on the ionotropic glutamate receptors, especially the N-methyl-D-aspartic acid (NMDA) receptor subtypes. In this study, we showed that NMDA and oligomeric Abeta(1-42) could induce reactive oxygen species (ROS) production from cortical neurons through activation of NADPH oxidase. ROS derived from NADPH oxidase led to activation of extracellular signal-regulated kinase 1/2, phosphorylation of cytosolic phospholipase A(2)alpha (cPLA(2)alpha), and arachidonic acid (AA) release. In addition, Abeta(1-42)-induced AA release was inhibited by d(-)-2-amino-5-phosphonopentanoic acid and memantine, two different NMDA receptor antagonists, suggesting action of Abeta through the NMDA receptor. Besides serving as a precursor for eicosanoids, AA is also regarded as a retrograde messenger and plays a role in modulating synaptic plasticity. Other phospholipase A(2) products such as lysophospholipids can perturb membrane phospholipids. These results suggest an oxidative-degradative mechanism for oligomeric Abeta(1-42) to induce ROS production and stimulate AA release through the NMDA receptors. This novel mechanism may contribute to the oxidative stress hypothesis and synaptic failure that underline the pathogenesis of Alzheimer's disease.

Bioavailability of apocynin through its conversion to glycoconjugate but not to diapocynin

Apocynin (4-hydroxy-3-methoxyacetophenone) is a major active ingredient from the rhizomes of Picrorhiza kurroa, a botanical plant used as an herbal medicine for treatment of a number of inflammatory diseases. Recently, apocynin is regarded as a specific inhibitor for NADPH oxidase in cell and animal models. In vitro studies indicated conversion of apocynin to diapocynin in the presence of peroxidases, e.g., myloperoxidase, posing the possibility that diapocynin also contributes to the anti-oxidative action of apocynin. The objectives of this study are to examine the bioavailability of apocynin to plasma, liver and brain tissue after intraperitoneal (i.p.) injection, and to examine whether apocynin is converted to diapocynin in vivo. Diapocynin was chemically synthetized and characterized by NMR and IR. Apocynin (5mg/kg body wt) was injected i.p. to adult male Sprague-Dawley rats and plasma, liver and brain were collected at different times (30min, 1 and 2h) after injection. Samples were treated with beta-glucuronidase to hydrolyze the glycosyl linkage and analyzed by HPLC/MS. At 30min and 1h after injection, approximately 50% of apocynin was converted to its glycosyl derivative and was distributed in plasma, liver and brain. No diapocynin was detected in any samples. These results indicate rapid glycosylation of apocynin and its transport to blood and other organs but no apparent conversion to diapocynin in vivo.

An RFLP-Based Technique for Identifying Fungi in the Sooty Blotch and Flyspeck Complex on Apple

A restriction fragment length polymorphism (RFLP)-based technique was developed to identify members of the sooty blotch and flyspeck (SBFS) disease complex on apple because these fungi are difficult to identify using agar-plate isolation and morphological description. The method includes polymerase chain reaction (PCR) amplification of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) using a fungal-specific forward primer (ITS1-F) and an SBFS-specific reverse primer (Myc1-R), followed by digestion of the PCR product by the HaeIII restriction enzyme. When applied to previously identified isolates of 24 SBFS-causing species in nine genera, the PCR-RFLP assay produced 14 unique banding patterns. Different genera never shared the same RFLP pattern. To evaluate performance in vivo, the technique was applied to DNA extracted directly from SBFS colonies on apple fruit from three Iowa orchards. The primers amplified the rDNA of only SBFS fungi, with the exception of a Cladosporium sp.; however, its RFLP banding pattern was distinct from those of SBFS fungi. The majority (60%) of SBFS colonies in the in vivo trial were identified to genus by RFLP analysis. The PCR-RFLP assay greatly streamlined the identification process by minimizing the need for culturing, indicating its value as a tool for field studies of the SBFS complex.

Cyclooxygenase-2 inhibition improves amyloid-beta-mediated suppression of memory and synaptic plasticity

Non-steroidal anti-inflammatory agents (NSAIDs) are associated with a marked reduction in the risk of developing Alzheimer's disease, a form of dementia characterized by the accumulation of amyloid plaques containing the amyloid-beta protein (Abeta). Studies of the effects of NSAIDs upon the inflammatory response surrounding amyloid plaques and upon the generation of Abeta from the amyloid precursor protein (APP) have led to two proposed mechanisms by which NSAIDs may protect against Alzheimer's disease: one, the selective lowering of Abeta42 by a subset of NSAIDs; and two, the reduction of inflammation. Although Alzheimer's disease is a disorder of brain and synaptic function, the effects of NSAIDs on Abeta-mediated suppression of synaptic plasticity and memory function have never been reported. We therefore investigated how three different NSAIDs, chosen for their distinct effects on Abeta42 production and the inhibition of the cyclooxygenase (COX) isoenzymes, COX-1 and COX-2, affect memory function and synaptic plasticity. By focusing upon brain and synapse function, we made novel observations about the effects of NSAIDs on Abeta-mediated neural processes. Here we report that the selective inhibition of COX-2, but not COX-1, acutely prevented the suppression of hippocampal long-term plasticity (LTP) by Abeta. The non-selective NSAIDs, ibuprofen and naproxen, and a selective COX-2 inhibitor, MF-tricyclic, each restored memory function in Tg2576 mice over-expressing APP, and also blocked Abeta-mediated inhibition of LTP. There was no advantage of ibuprofen, a selective Abeta42-lowering agent (SALA), over the non-SALAs, naproxen and MF-tricyclic. The beneficial effects on memory did not depend upon lowered levels of Abeta42 or the inflammatory cytokines, tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta). Intriguingly, improved memory function was inversely related to prostaglandin E2 (PGE2) levels. Conversely, exogenous PGE2 prevented the restorative effects of COX-2 inhibitors on LTP. The data indicate that the inhibition of COX-2 blocks Abeta-mediated suppression of LTP and memory function, and that this block occurs independently of reductions in Abeta42 or decreases in inflammation. The results lead us to propose a third possible mechanism by which NSAIDs may protect against Alzheimer's disease, involving the blockade of a COX-2-mediated PGE2 response at synapses.

Ethanol preconditioning protects against ischemia/reperfusion-induced brain damage: role of NADPH oxidase-derived ROS

Ethanol preconditioning (EtOH-PC) refers to a phenomenon in which tissues are protected from the deleterious effects of ischemia/reperfusion (I/R) by prior ingestion of ethanol at low to moderate levels. In this study, we tested whether prior (24 h) administration of ethanol as a single bolus that produced a peak plasma concentration of 42-46 mg/dl in gerbils would offer protective effects against neuronal damage due to cerebral I/R. In addition, we also tested whether reactive oxygen species (ROS) derived from NADPH oxidase played a role as initiators of these putative protective effects. Groups of gerbils were administered either ethanol or the same volume of water by gavage 24 h before transient global cerebral ischemia induced by occlusion of both common carotid arteries for 5 min. In some experiments, apocynin, a specific inhibitor of NADPH oxidase, was administered (5 mg/kg body wt, i.p.) 10 min before ethanol administration. EtOH-PC ameliorated behavioral deficit induced by cerebral I/R and protected the brain against I/R-induced delayed neuronal death, neuronal and dendritic degeneration, oxidative DNA damage, and glial cell activation. These beneficial effects were attenuated by apocynin treatment coincident with ethanol administration. Ethanol ingestion was associated with translocation of the NADPH oxidase subunit p67(phox) from hippocampal cytosol fraction to membrane, increased NADPH oxidase activity in hippocampus within the first hour after gavage, and increased lipid peroxidation (4-hydroxy-2-nonenal) in plasma and hippocampus within the first 2 h after gavage. These effects were also inhibited by concomitant apocynin treatment. Our data are consistent with the hypothesis that antecedent ethanol ingestion at socially relevant levels induces neuroprotective effects in I/R by a mechanism that is triggered by ROS produced through NADPH oxidase. Our results further suggest the possibility that preconditioning with other pharmacological agents that induce a mild oxidative stress may have similar therapeutic value for suppressing stroke-mediated damage in brain.

First Report of Race 3 of Bipolaris zeicola on Corn in China

In Meixian County of Shaanxi Province, China, during the summer of 2002, mature corn plants in a field plot showed severe leaf spot symptoms. The lesions were narrow (3.5 to 18 mm long and 0.4 to 1.5 mm wide), grayish tan, and surrounded by a light- to dark-pigmented border. Leaves wilted when lesions coalesced. From 2002 to 2005, the disease was observed in other Shaanxi Province counties, including Yangling, Wugong, Qianxian, Longxian, and Qianyang, although in most cases, symptom development was less severe than it was in Meixian. Seven isolates from four counties were obtained by isolation from host tissue on potato dextrose agar (PDA), followed by single-spore culturing and incubation on PDA at 25°C in the dark for 7 days. Conidial suspensions were prepared from a single-spored culture on PDA plates. Pathogenicity tests were performed by spraying five corn seedlings (cv. Yuyu 22) at the three- to four-leaf stage in separate 10-cm-diameter pots with 10 ml of a conidial suspension (10⁶ spores per ml) per plant. Each of three isolates was used in separate inoculations that were performed in different weeks. Controls were sprayed with sterile distilled water only. Plants were covered with plastic bags for 48 h and incubated at 23 to 25°C in a chamber. One week after inoculation, leaves on all inoculated plants developed characteristic lesions, whereas untreated controls had no symptoms. The pathogen was reisolated from diseased leaves on PDA after surface sterilization with 2% NaOCl. On PDA, proliferation of conidia usually occurred on all sides of the conidiophore. Conidiophores were cylindrical, simple, smooth, septate, and straight to flexuous. Conidia were 49 to 89 μm long and 11 to 17 μm wide, with 3 to 10 distosepta, straight or moderately curved, dark or olivaceous brown, and the cells on the ends sometimes appeared paler than those in the middle. These characteristics match those of Bipolaris zeicola (Stout) Shoemaker. On the basis of the arbitrary primers selected by Jones et al. (1), random amplified polymorphic DNA (RAPD) analysis was used for species and physiological race determination. A single DNA fragment approximately 1.2 kb, which is characteristic of B. zeicola, was amplified from all seven isolates with arbitrary primer A20 (5'CTTGGATTC3'). Analysis of PCR products obtained with arbitrary primer A03 (5'AGTCAGCCAC3') showed that all seven isolates lacked 2,700- and 2,300-base bands, and therefore, sorted into B. zeicola race 3. On the basis of pathogenicity, morphology, and RAPD band patterns of primer A20, the fungus was confirmed as B. zeicola. The shape of leaf lesions and RAPD band patterns using primer A03 showed further that the pathogen was race 3 of B. zeicola. Bai et al. (2) reported race 1 and race 2 of B. zeicola in China, but to our knowledge, this is the first report of race 3 in China. References: (1) M. J. Jones and L. D. Dunkle. Phytopathology 83:366, 1993. (2) J. K. Bai et al. Acta Phytopathol. Sin. 12:61, 1982.

Exercise and diet induced weight loss improves measures of oxidative stress and insulin sensitivity in adults with characteristics of the metabolic syndrome

Obesity and insulin resistance (IR) increase the risk for coronary heart disease; however, much of this risk is not attributable to traditional risk factors. We sought to determine whether weight loss associated with supervised aerobic exercise beneficially alters biomarkers of oxidative stress and whether these alterations are associated with improvements in measures of insulin resistance. Twenty-five sedentary and overweight to obese [body mass index (BMI) = 33.0 +/- 0.8 kg/m(2)] individuals, with characteristics of the metabolic syndrome, participated in a 4- to 7-mo weight loss program that consisted of energy restriction (reduced by approximately 500 kcal/day) and supervised aerobic exercise (5 days/wk, 45 min/day at 60% Vo(2 max); approximately 375 kcal/day). IR and insulin sensitivity were assessed by the calculation of the homeostasis model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI), respectively. Oxidative stress was assessed by oxidized LDL (oxLDL), myeloperoxidase (MPO), and low- and high- density lipoprotein (LDL and HDL) lipid hydroperoxide concentrations in serum. Indexes for antioxidative status included apolipoprotein A1 (apoA1) concentrations and paraoxonase-1 (PON1) activity and protein concentrations. Exercise- and diet-induced weight loss ( approximately 10%) significantly (P < 0.05) increased insulin sensitivity and reduced IR, oxLDL, and LDL lipid hydroperoxides but did not alter HDL lipid hydroperoxides or MPO concentrations. Lifestyle modification impacted systemic antioxidative status by increasing apoA1 concentrations and reducing serum PON1 protein and activity. Changes in oxidative stress were not associated with alterations in HOMA or QUICKI. Diet- and exercise-induced weight loss ( approximately 10%) improves measures of insulin sensitivity and beneficially alters biomarkers of oxidative status.

Cytotoxicity of paraquat in microglial cells: Involvement of PKCdelta- and ERK1/2-dependent NADPH oxidase

Excess production of reactive oxygen species (ROS) is an important mechanism underlying the pathogenesis of a number of neurodegenerative diseases including Parkinson's disease (PD) which is characterized by a progressive loss of dopaminergic neurons in the substantia nigra. Exposure to paraquat, an herbicide with structure similar to the dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium (MPP+), has been shown to produce PD-like symptoms. Despite previous focus on the dopaminergic neurons and signaling pathways involved in their cell death, recent studies have implicated microglial cells as a major producer of ROS for damaging neighboring neurons. In this study, we examined the source of ROS and the underlying signaling pathway for paraquat-induced cytotoxicity to BV-2 microglial cells. Paraquat-induced ROS production (including superoxide anions) in BV-2 cells was accompanied by translocation of the p67phox cytosolic subunit of NADPH oxidase to the membrane. Paraquat-induced ROS production was inhibited by NADPH oxidase inhibitors, apocynin and diphenylene iodonium (DPI), but not the xanthine/xanthine oxidase inhibitor, allopurinol. Apocynin and DPI also rescued cells from paraquat-induced toxicity. The inhibitors for protein kinase C delta (PKCdelta) or extracellular signal-regulated kinases (ERK1/2) could partially attenuate paraquat-induced ROS production and cell death. Rottlerin, a selective PKCdelta inhibitor, also inhibited paraquat-induced translocation of p67phox. Taken together, this study demonstrates the involvement of ROS from NADPH oxidase in mediating paraquat cytotoxicity in BV-2 microglial cells and this process is mediated through PKCdelta- and ERK-dependent pathways.