Suchergebnisse

Cognitive capacities decline with age, an event accompanied by the altered transcription of synaptic plasticity genes. Here, we show that the transcriptional induction of Bdnf by a mnemonic stimulus is impaired in aged hippocampal neurons. Mechanistically, this defect is due to reduced NMDA receptor (NMDAR)-mediated activation of CaMKII. Decreased NMDAR signaling prevents changes associated with activation at specific Bdnf promoters, including displacement of histone deacetylase 4, recruitment of the histone acetyltransferase CBP, increased H3K27 acetylation, and reduced H3K27 trimethylation. The decrease in NMDA-CaMKII signaling arises from constitutive reduction of synaptic cholesterol that occurs with normal aging. Increasing the levels of neuronal cholesterol in aged neurons in vitro, ex vivo, and in vivo restored NMDA-induced Bdnf expression and chromatin remodeling. Furthermore, pharmacological prevention of age-associated cholesterol reduction rescued signaling and cognitive deficits of aged mice. Thus, reducing hippocampal cholesterol loss may represent a therapeutic approach to reverse cognitive decline during aging. ; Spanish Ministry of Science and Spanish Ministry of Economy and Competitiveness grants SAF2010-14906 and SAF2013-45392 to C.G.D., by Spanish grants SAF2009-09129 and AGL2014-56464 to C.V., and by a Flemish government FWO grant G.0D76.14 to D.B. M.G.M. is a career investigator from the Argentine National Research Council/Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) ; Peer Reviewed

Ischemic stroke is an acute vascular event that compromises neuronal viability, and identification of the pathophysiological mechanisms is critical for its correct management. Ischemia produces increased nitric oxide synthesis to recover blood flow but also induces a free radical burst. Nitric oxide and superoxide anion react to generate peroxynitrite that nitrates tyrosines. We found that fibrinogen nitrotyrosination was detected in plasma after the initiation of ischemic stroke in human patients. Electron microscopy and protein intrinsic fluorescence showed that in vitro nitrotyrosination of fibrinogen affected its structure. Thromboelastography showed that initially fibrinogen nitrotyrosination retarded clot formation but later made the clot more resistant to fibrinolysis. This result was independent of any effect on thrombin production. Immunofluorescence analysis of affected human brain areas also showed that both fibrinogen and nitrotyrosinated fibrinogen spread into the brain parenchyma after ischemic stroke. Therefore, we assayed the toxicity of fibrinogen and nitrotyrosinated fibrinogen in a human neuroblastoma cell line. For that purpose we measured the activity of caspase-3, a key enzyme in the apoptotic pathway, and cell survival. We found that nitrotyrosinated fibrinogen induced higher activation of caspase 3. Accordingly, cell survival assays showed a more neurotoxic effect of nitrotyrosinated fibrinogen at all concentrations tested. In summary, nitrotyrosinated fibrinogen would be of pathophysiological interest in ischemic stroke due to both its impact on hemostasis - it impairs thrombolysis, the main target in stroke treatments - and its neurotoxicity that would contribute to the death of the brain tissue surrounding the infarcted area. ; This work was supported by the Spanish Ministry of Science and Innovation (SAF2012-38140; SAF 2009-10365); Fondo de Investigación Sanitaria (FIS PI13/00408, FIS PI13/00864, CP04-00112, PS09/00664 and Red HERACLESRD12/0042/0014, RD12/0042/0016 and RD12/0042/0020); FEDER Funds; Generalitat de Catalunya (SGR09-1369); and Fundació la Marató de TV3 (100310). Dr. A.M. Galán belongs to the Miguel Servet stabilization program of the Spanish Government's ISCIII research institute and "Direcció d'Estratègia i Coordinació del Departament de Salut" of the Generalitat de Catalunya.