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Gene Expression Study in WT and ATF4 KO embryonic neurons

ABSTRACT: Oxidative stress is pathogenic in neurological diseases including stroke. The identity of oxidative stress-inducible transcription factors and their role(s) in propagating the death cascade are poorly understood. Microarray analysis of neurons undergoing oxidative stress showed significant induction of prodeath genes. These genes have been shown to be regulated by the bZip transcription factor, ATF4. ATF4 protein localized to the promoter of a putative death gene in neurons in vitro and in vivo. Germline deletion of ATF4 in neurons resulted in a reduction in oxidative stress-induced gene expression and resistance to oxidative death. ATF4 knockout mice experienced significantly smaller infarcts and improved behavioral recovery as compared to wild-type mice subjected to the same reductions in blood flow in a rodent model of stroke. ATF4 modulates an early, upstream event in the death pathway, as resistance to oxidative death by ATF4 deletion was associated with decreased consumption of the antioxidant glutathione. Restoration of ATF4 protein in knockout neurons was sufficient to restore sensitivity to oxidative death and to reaccelerate loss of glutathione. Together, these findings establish ATF4 as a redox-regulated, pro-death transcriptional activator in the nervous system that propagates death responses to oxidative stress in vitro and to stroke in vivo. Keywords: ATF4, oxidative stress, gene expression, neuroprotection, stroke

ORGANISM(S): Mus musculus

PROVIDER: GSE10470 | GEO | 2008/03/01

SECONDARY ACCESSION(S): PRJNA108031

REPOSITORIES: GEO

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Project description:Cellular redox control is maintained by generation of reactive oxygen/nitrogen species balanced by activation of antioxidative pathways. Disruption of redox balance leads to oxidative stress, a central causative event in numerous diseases including heart failure. Redox control in the heart exposed to hemodynamic stress, however, remains to be fully elucidated. Here, we show that production of cardiomyocyte NADPH (nicotinamide adenine dinucleotide phosphate), a key factor in redox regulation, is decreased in pressure overload-induced heart failure. As a consequence, the level of reduced glutathione is downregulated, a change associated with cardiac cell death, fibrosis, and cardiomyopathy. We report that the pentose phosphate pathway (PPP) and mitochondrial serine/glycine/folate metabolic signaling, two major NADPH-generating pathways in the cytosol and mitochondria, respectively, are induced in the heart by pressure overload. We identify ATF4 (activating transcriptional factor 4) as an upstream transcription factor controlling the expression of multiple enzymes in these two pathways. Consistent with this, joint pathway analysis (JPA) of transcriptomic and metabolomic data reveals that ATF4 preferably controls oxidative stress and redox-related pathways. Overexpression of ATF4 in cardiomyocytes in culture leads to a significant increase in NADPH-producing enzymes whereas silencing of ATF4 decreases their expression. Further, stable isotope tracer experiments reveal that ATF4 overexpression in vitro strongly augments metabolic flux within these two pathways. In vivo, cardiomyocyte-specific deletion of ATF4 exacerbates cardiomyopathy in the setting of pressure overload and accelerates the development of heart failure, attributable, at least in part, to an inability to increase the expression of NADPH-generating enzymes. Taken together, our findings reveal that ATF4 plays a critical role in cardiac homeostasis under conditions of hemodynamic stress by governing both cytosolic and mitochondrial production of NADPH.

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Gene Expression Study in WT and ATF4 KO embryonic neurons

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