Induction by vasoactive intestinal peptide of interferon α/β synthesis in glial cells but not in neurons

Vasoactive intestinal peptide (VIP), a 28-aminoacid peptide, plays a multifunctional neuromodulatory role in both peripheral and central nervous systems. We have recently reported that VIP induces interferon (IFN) α/β synthesis in human colon adenocarcinoma cell line HT-29. It has been reported that VIP may counteract HIV-induced neuronal cell death; therefore, we postulated that the action of VIP may be mediated by a cascade regulation, involving the production of some cytokines such as IFN. Here we demonstrate that primary cultures of rat mesencephalic neurons and glial cells respond differently to VIP. Thus VIP enhanced 2′5′ oligoadenylate (2′5′A) synthetase activity and inhibited vesicula stomatitis virus multiplication in glial cultures only. However, both cell cultures had functional adenylate cyclase coupled receptors for VIP. The increase in 2′5′A synthetase activity in glial cultures reached a maximum with 10^?6M VIP and required cellular RNA and protein synthesis. Anti-IFN α/β, but not anti-IFN γ, antibodies abolished the induction of the antiviral and 2′5′A synthetase activities by VIP in rat glial-enriched cultures, suggesting that these inductions were mediated through IFN α/β synthesis. Moreover, VIP or poly (i).poly (C₁₂U) caused, in the glial cultures, the induction and secretion of an IFN of type α/β with a titer value of 16 and 32 units/ml respectively. In contrast, neither of these two substances was able to induce IFN synthesis in neurons, which were, however, sensitive to IFN α/β produced by VIP-treated glial cells. IFN produced by VIP in glial cells may therefore play an important role in defending the brain against viruses. © 1994 Wiley-Liss, Inc.     

Cross talk between PML and p53 during poliovirus infection: implications for antiviral defense

PML nuclear bodies (NBs) are dynamic intranuclear structures harboring numerous transiently or permanently localized proteins. PML, the NBs' organizer, is directly induced by interferon, and its expression is critical for antiviral host defense. We describe herein the molecular events following poliovirus infection that lead to PML-dependent p53 activation and protection against virus infection. Poliovirus infection induces PML phosphorylation through the extracellular signal-regulated kinase pathway, increases PML SUMOylation, and induces its transfer from the nucleoplasm to the nuclear matrix. These events result in the recruitment of p53 to PML NBs, p53 phosphorylation on Ser15, and activation of p53 target genes leading to the induction of apoptosis. Moreover, the knock-down of p53 by small interfering RNA results in higher poliovirus replication, suggesting that p53 participates in antiviral defense. This effect, which requires the presence of PML, is transient since poliovirus targets p53 by inducing its degradation in a proteasome- and MDM2-dependent manner. Our results provide evidence of how poliovirus counteracts p53 antiviral activity by regulating PML and NBs, thus leading to p53 degradation.     

Les cicadiaires vecteurs potentiels de phytopathogènes en vignoble tunisien (Hemiptera : Cicadomorpha : Fulgoromorpha)

Afin de connaître la faune des cicadiaires dans le vignoble tunisien, plusieurs collectes ont été réalisées. Ces prélèvements de 1109 spécimens, effectuées aussi bien sur la vigne que sur les adventices, au cours de l’année 2001, ont concerné plusieurs parcelles, dans les principales régions viticoles du pays : Rafraf, Baddar, Mraissa, Belli, Gobba et Bousalem. Trente espèces d’Hemiptera: Cicadomorpha et Fulgoromorpha, ont été collectées dont les espèces vectrices de phytoplasme et les espèces aux dégâts directs sur la vigne. 82,50% des espèces de cicadelles rencontrées en Tunisie sont signalées comme vecteurs de virus ou de phytoplasmes causant des maladies graves ou comme ravageurs directs des cultures. Les 17,49% restant ne jouent pas de rôle important sur les cultures.     

Computational Prediction of Candidate Proteins for S-Nitrosylation in Arabidopsis thaliana

Nitric oxide (NO) is an important signaling molecule that regulates many physiological processes in plants. One of the most important regulatory mechanisms of NO is S-nitrosylation—the covalent attachment of NO to cysteine residues. Although the involvement of cysteine S-nitrosylation in the regulation of protein functions is well established, its substrate specificity remains unknown. Identification of candidates for S-nitrosylation and their target cysteine residues is fundamental for studying the molecular mechanisms and regulatory roles of S-nitrosylation in plants. Several experimental methods that are based on the biotin switch have been developed to identify target proteins for S-nitrosylation. However, these methods have their limits. Thus, computational methods are attracting considerable attention for the identification of modification sites in proteins. Using GPS-SNO version 1.0, a recently developed S-nitrosylation site-prediction program, a set of 16,610 candidate proteins for S-nitrosylation containing 31,900 S-nitrosylation sites was isolated from the entire Arabidopsis proteome using the medium threshold. In the compartments “chloroplast,” “CUL4-RING ubiquitin ligase complex,” and “membrane” more than 70% of the proteins were identified as candidates for S-nitrosylation. The high number of identified candidates in the proteome reflects the importance of redox signaling in these compartments. An analysis of the functional distribution of the predicted candidates showed that proteins involved in signaling processes exhibited the highest prediction rate. In a set of 46 proteins, where 53 putative S-nitrosylation sites were already experimentally determined, the GPS-SNO program predicted 60 S-nitrosylation sites, but only 11 overlap with the results of the experimental approach. In general, a computer-assisted method for the prediction of targets for S-nitrosylation is a very good tool; however, further development, such as including the three dimensional structure of proteins in such analyses, would improve the identification of S-nitrosylation sites.     

Function of S-nitrosoglutathione reductase (GSNOR) in plant development and under biotic/abiotic stress

During the last decade, it was established that the class III alcohol dehydrogenase (ADH3) enzyme, also known as glutathione-dependent formaldehyde dehydrogenase (FALDH; EC 1.2.1.1), catalyzes the NADH-dependent reduction of S-nitrosoglutathione (GSNO) and therefore was also designated as GSNO reductase. This finding has opened new aspects in the metabolism of nitric oxide (NO) and NO-derived molecules where GSNO is a key component. In this article, current knowledge of the involvement and potential function of this enzyme during plant development and under biotic/abiotic stress is briefly reviewed.Key words: nitric oxide, nitrosative stress, S-nitrosoglutathione reductase     

Expression of the long form of human FLIP by retroviral gene transfer of hemopoietic stem cells exacerbates experimental autoimmune encephalomyelitis

Subsidence of inflammation and clinical recovery in experimental autoimmune encephalomyelitis (EAE) is postulated to involve apoptosis of inflammatory cells. To test this concept, we examined the effects of overexpressing the long form of human FLICE-inhibitory protein, a potent inhibitor of death receptor-mediated apoptosis, in myelin oligodendrocyte glycoprotein-induced EAE in DBA/1 mice. We found that overexpression of the long form of human FLICE-inhibitory protein by retroviral gene transfer of hemopoietic stem cells led to a clinically more severe EAE in these mice compared with control mice receiving the retroviral vector alone. The exacerbated disease was evident by an enhanced and prolonged inflammatory reaction in the CNS of these animals compared with control mice. The acute phase of EAE was characterized by a massive infiltration of macrophages and granulocytes and a simultaneous increase in TNF-alpha production in the CNS. In the chronic phase of the disease, there was a prolonged inflammatory response in the form of persistent CD4(+) T and B cells in the CNS and a peripheral Th1 cytokine bias caused by elevated levels of IFN-gamma and reduced levels of IL-4 in the spleen. Our findings demonstrate that death receptor-mediated apoptosis can be important in the pathogenesis of EAE and further emphasize the need for effective apoptotic elimination of inflammatory cells to achieve disease remission.     

Mechanical wounding induces a nitrosative stress by down-regulation of GSNO reductase and an increase in S-nitrosothiols in sunflower (Helianthus annuus) seedlings

Nitric oxide (NO) and related molecules such as peroxynitrite, S-nitrosoglutathione (GSNO), and nitrotyrosine, among others, are involved in physiological processes as well in the mechanisms of response to stress conditions. In sunflower seedlings exposed to five different adverse environmental conditions (low temperature, mechanical wounding, high light intensity, continuous light, and continuous darkness), key components of the metabolism of reactive nitrogen species (RNS) and reactive oxygen species (ROS), including the enzyme activities L-arginine-dependent nitric oxide synthase (NOS), S-nitrosogluthathione reductase (GSNOR), nitrate reductase (NR), catalase, and superoxide dismutase, the content of lipid hydroperoxide, hydrogen peroxide, S-nitrosothiols (SNOs), the cellular level of NO, GSNO, and GSNOR, and protein tyrosine nitration [nitrotyrosine (NO(2)-Tyr)] were analysed. Among the stress conditions studied, mechanical wounding was the only one that caused a down-regulation of NOS and GSNOR activities, which in turn provoked an accumulation of SNOs. The analyses of the cellular content of NO, GSNO, GSNOR, and NO(2)-Tyr by confocal laser scanning microscopy confirmed these biochemical data. Therefore, it is proposed that mechanical wounding triggers the accumulation of SNOs, specifically GSNO, due to a down-regulation of GSNOR activity, while NO(2)-Tyr increases. Consequently a process of nitrosative stress is induced in sunflower seedlings and SNOs constitute a new wound signal in plants.