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Astrocyte Swelling (astrocyte + swelling)
Selected AbstractsCalcium in the mechanism of ammonia-induced astrocyte swellingJOURNAL OF NEUROCHEMISTRY, Issue 2009Arumugam R. Jayakumar Abstract Brain edema, due largely to astrocyte swelling, is an important clinical problem in patients with acute liver failure. While mechanisms underlying astrocyte swelling in this condition are not fully understood, ammonia and associated oxidative/nitrosative stress appear to be involved. Mechanisms responsible for the increase in reactive oxygen/nitrogen species (RONS) and their role in ammonia-induced astrocyte swelling, however, are poorly understood. Recent studies have demonstrated a transient increase in intracellular Ca2+ in cultured astrocytes exposed to ammonia. As Ca2+ is a known inducer of RONS, we investigated potential mechanisms by which Ca2+ may be responsible for the production of RONS and cell swelling in cultured astrocytes after treatment with ammonia. Exposure of cultured astrocytes to ammonia (5 mM) increased the formation of free radicals, including nitric oxide, and such increase was significantly diminished by treatment with the Ca2+ chelator 1,2-bis-(o -aminophenoxy)-ethane- N,N,- N,,N, -tetraacetic acid tetraacetoxy-methyl ester (BAPTA). We then examined the activity of Ca2+ -dependent enzymes that are known to generate RONS and found that ammonia significantly increased the activities of NADPH oxidase (NOX), constitutive nitric oxide synthase (cNOS), and phospholipase A2 (PLA2) and such increases in activity were significantly diminished by BAPTA. Pre-treatment of cultures with 7-nitroindazole, apocyanin, and quinacrine, respective inhibitors of cNOS, NOX, and PLA2, all significantly diminished RONS production. Additionally, treatment of cultures with BAPTA or with inhibitors of cNOS, NOX, and PLA2 reduced ammonia-induced astrocyte swelling. These studies suggest that the ammonia-induced rise in intracellular Ca2+ activates free radical producing enzymes that ultimately contribute to the mechanism of astrocyte swelling. [source] Role of mitogen-activated protein kinases in the mechanism of oxidant-induced cell swelling in cultured astrocytesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 11 2010M. Moriyama Abstract Cytotoxic brain edema, usually a consequence of astrocyte swelling, is an important complication of stroke, traumatic brain injury, hepatic encephalopathy, and other neurological disorders. Although mechanisms underlying astrocyte swelling are not fully understood, oxidative stress (OS) has generally been considered an important factor in its pathogenesis. To better understand the mechanism(s) by which OS causes cell swelling, we examined the potential involvement of mitogen-activated protein kinases (MAPKs) in this process. Cultures exposed to theoxidant H2O2 (10, 25, 50 ,M) for different time periods (1,24 hr) significantly increased cell swelling in a triphasic manner. Swelling was initially observed at 10 min (peaking at 30 min), which was followed by cell shrinkage at 1 hr. A subsequent increase in cell volume occurred at approximately 6 hr, and the rise lasted for at least 24 hr. Cultures exposed to H2O2 caused the activation of MAPKs (ERK1/2, JNK and p38-MAPK), whereas inhibition of MAPKs diminished cell swelling induced by 10 and 25 ,M H2O2. These findings suggest that activation of MAPKs is an important factor in the mediation of astrocyte swelling following oxidative stress. © 2010 Wiley-Liss, Inc. [source] | ||||||||||