Induction of ER stress in response to oxygen-glucose deprivation of cortical cultures involves the activation of the PERK and IRE-1 pathways and of caspase-12

Disturbance of calcium homeostasis and accumulation of misfolded proteins in the endoplasmic reticulum (ER) are considered contributory components of cell death after ischemia. However, the signal-transducing events that are activated by ER stress after cerebral ischemia are incompletely understood. In this study, we show that caspase-12 and the PERK and IRE pathways are activated following oxygen-glucose deprivation (OGD) of mixed cortical cultures or neonatal hypoxia–ischemia (HI). Activation of PERK led to a transient phosphorylation of eIF2α, an increase in ATF4 levels and the induction of gadd34 (a subunit of an eIF2α-directed phosphatase). Interestingly, the upregulation of ATF4 did not lead to an increase in the levels of CHOP. Additionally, IRE1 activation was mediated by the increase in the processed form of xbp1, which would be responsible for the observed expression of edem2 and the increased levels of the chaperones GRP78 and GRP94. We were also able to detect caspase-12 proteolysis after HI or OGD. Processing of procaspase-12 was mediated by NMDA receptor and calpain activation. Moreover, our data suggest that caspase-12 activation is independent of the unfolded protein response activated by ER stress

Genes associated with pro-apoptotic and protective mechanisms are affected differently on exposure of neuronal cell cultures to arsenite. No indication for endoplasmic reticulum stress despite activation of grp78 and gadd153 expression

Copyright 2002 Elsevier Science B.V. All rights reserved.The effect of arsenite exposure on cell viability, protein synthesis, energy metabolism and the expression of genes coding for cytoplasmic (hsp70) and endoplasmic reticulum (ER; gadd153, grp78, grp94) stress proteins was investigated in primary neuronal cell cultures. Furthermore, signs of ER stress were evaluated by investigating xbpl mRNA processing. Arsenite levels of 30 and 100 muM induced severe cell injury. Protein synthesis was reduced to below 20% of control in cultures exposed to 30 and 100 muM arsenite for I h, and it remained markedly suppressed until 24 h of exposure. Arsenite induced a transient inhibition of energy metabolism after I h of exposure, but energy state recovered completely after 3 h. Arsenite exposure affected the expression and translation of genes coding for HSP70 and GRP78, GRP94, GADD153 to different extents. While hsp70 mRNA levels rose drastically, approximally 550-fold after 6 h exposure, HSP70 protein levels did not change over the first 6 h., On the other hand, gadd153 mRNA levels rose only approximately 14-fold after 6 h exposure, while GADD153 protein levels were markedly increased after 3 and 6 h exposure. HSP70 protein levels were markedly increased and GADD153 protein levels decreased to almost control levels in cultures left in arsenite solution for 24 h, i.e. when only a small fraction of cells had escaped arsenite toxicity. Arsenite exposure of neurons thus induced an imbalance between pro-apoptotic and survival-activating pathways. Despite the marked increase in gadd153 mRNA levels, we did not observe signs of xbpl processing in arsenite exposed cultures, indicating that arsenite did not produce ER stress

Renouvellement de la prose néo-hellénique par la revue "Makedonikes Imeres" ("Jours de Macédoine"), Thessalonique, 1932-1939 (étude d'un mouvement moderniste)

Autour de la revue Jours de Macédoine ( a , 1932-1939) et de son inspirateur, le critique et écrivain Pétros Spandonidis, s'est créé à Thessalonique le mouvement moderniste le plus conséquent qu'ait connu la Grèce dans le domaine de la prose d'imagination, principalement illustré par les romans lyriques de Yorgos Délios et de Stélios Xéfloudas, les récits extravagants d'Alkiviadis Yannopoulos et les écrits expérimentaux de Yorgos Thémélis et de Nikos Gavriil Pentzikis. Quels ont été, saisis à travers l'œuvre collective de cette revue et de la pléiade de prosateurs qui l'ont animée, les enjeux et les modalités d'une " modernisation " ( g ) de la littérature de langue grecque dans l'entre-deux guerres ? Répondre à cette question, c'est sortir du cadre étroit d'une hypothétique " École de Thessalonique ". C'est, d'abord, décrire l'émergence dans le champ littéraire grec d'une ville nouvellement intégrée à la nation, concomitante à un projet de renaissance culturelle basé sur l'acclimatation de l'actualité des lettres européennes, singulièrement des lettres françaises perspective dans laquelle doit s'inscrire la question débattue du " monologue intérieur ". C'est, ensuite, confronter cette ambition à la réception effective de grands, et de moins grands, textes du début du vingtième siècle, à leur appropriation par les écrivains thessaloniciens, véritables auteurs-lecteurs, ainsi qu'à la redéfinition du statut de leurs propres œuvres en fonction, cette fois, des lecteurs-auteurs qu'ils ont appelés de leurs vœux et qu'ils ont postulés par leur écriture : ce en quoi consiste essentiellement la modernité du groupement littéraire des Jours de Macédoine, et son apport le plus remarquable au renouvellement de la prose néo-hellénique.The most important modernistic movement ever known in Greece in the field of prose fiction, mainly illustrated by Yorgos Delios's and Stelios Xefloudas's lyrical novels, Alkiviadis Yannopoulos's extravagant stories and Nikos Gavriil Pentzikis's or Yorgos Themelis's experimental texts, rose around the Thessalonician review Macedonian Days ( a , 1932-1939) and its instigator Petros Spandonidis, a critic and a writer. Which were the stakes and the modalities of a modernisation ( g ) in Greek literature between the two world wars, perceived in the collective work of this review and of the prose writers who where its very spirit? Answering this question means getting out the narrow framework of a hypothetical School of Thessalonica . It first means describing the spring in the Greek literary field of a city newly integrated to the nation, concomitantly to a project of cultural rebirth based on the adaptation of the contemporary European, particularly French, criticism and literary experimentation a prospect which must take into account the debated question of interior monologue . It then means confronting this ambition to the actual reception of major, and minor, literary works of the early twentieth century, and to their appropriation by Thessalonician writers as real authors-readers, as well as redefining their own works status now according to the readers-authors whom they wished for and whom they instituted in their writings: a basis on which the modernity of the Macedonian Days group and its most remarkable contribution to the revival of Neo-Hellenic prose essentially lies.PARIS-Bibl.Langues Orientales (751072101) / SudocSudocFranceF

Mechanisms underlying irreversible shut down of translation in transient focal cerebral ischemia in mouse brain

© 2003 The American Heart Association, Inc

Mechanisms underlying suppression of protein synthesis induced by transient focal cerebral ischemia in mouse brain

Transient global cerebral ischemia triggers suppression of the initiation step of protein synthesis, a process which is controlled by endoplasmic reticulum (ER) function. ER function has been shown to be disturbed after transient cerebral ischemia, as indicated by an activation of the ER-resident eIF2? kinase PERK. In this study, we investigated ischemia-induced changes in protein levels and phosphorylation states of the initiation factors eIF2?, eIF2Bvar epsilon, and eIF4G1 and of p70 S6 kinase, proteins playing a central role in the control of the initiation of translation. Transient focal cerebral ischemia was induced in mice by occlusion of the left middle cerebral artery. Transient ischemia caused a long-lasting suppression of global protein synthesis. eIF2? was transiently phosphorylated after ischemia, peaking at 1–3 h of recovery. eIF2Bvar epsilon and p70 S6 kinase were completely dephosphorylated during ischemia and phosphorylation did not recover completely following reperfusion. In addition, eIF2Bvar epsilon, eIF4G1, and p70 S6 kinase protein levels decreased progressively with increasing recirculation time. Thus, several different processes contributed to ischemia-induced suppression of the initiation of protein synthesis: a long-lasting dephosphorylation of eIF2Bvar epsilon and p70 S6K starting during ischemia, a transient phosphorylation of eIF2? during early reperfusion, and a marked decrease of eIF2Bvar epsilon, eIF4G1, and p70 S6K protein levels starting during vascular occlusion (eIF4G1). Study of the mechanisms underlying ischemia-induced suppression of the initiation step of translation will help to elucidate the role of protein synthesis inhibition in the development of neuronal cell injury triggered by transient cerebral ischemia

Phosphorylation state, solubility, and activity of calcium/calmodulin-dependent protein kinase II alpha in transient focal ischemia in mouse brain

Copyright KLUWER ACADEMIC/PLENUM PUBLDuring and after middle cerebral artery occlusion in mice, CaMKIIalpha protein was irreversibly translocated from the soluble to the Triton X-100-nonsoluble fraction. This decrease in solubility had a strong effect on activity: CaMKIIalpha was almost completely inactivated after being translocated. Results from solubilization experiments suggest that different mechanisms underlie the conversion of CaMKIIalpha protein from a soluble to a detergent nonsoluble form in ischemic as opposite to nonischemic tissue. Analysis of the phosphorylation state of CaMKIIalpha revealed that in the total homogenate and the Triton X-100-nonsoluble fraction, CaMKIIalpha phosphorylated at only one site was the dominant phosphorylated form, whereas in the soluble fraction CaMKII phosphorylated at two sites was the predominant phosphorylated species. Investigation of the mechanisms underlying ischemia-induced changes in the solubility of CaMKIIalpha could help to elucidate processes triggered by transient focal cerebral ischemia that lead to neuronal cell injury