title: Carbon monoxide modulates apoptosis by reinforcing oxidative metabolism in astrocytes: role of Bcl-2.
abstract: Modulation of cerebral cell metabolism for improving the outcome of hypoxia-ischemia and reperfusion is a strategy yet to be explored. Because carbon monoxide (CO) is known to prevent cerebral cell death; herein the role of CO in the modulation of astrocytic metabolism, in particular, at the level of mitochondria was investigated. Low concentrations of CO partially inhibited oxidative stress-induced apoptosis in astrocytes, by preventing caspase-3 activation, mitochondrial potential depolarization, and plasmatic membrane permeability. CO exposure enhanced intracellular ATP generation, which was accompanied by an increase on specific oxygen consumption, a decrease on lactate production, and a reduction of glucose use, indicating an improvement of oxidative phosphorylation. Accordingly, CO increased cytochrome c oxidase (COX) enzymatic specific activity and stimulated mitochondrial biogenesis. In astrocytes, COX interacts with Bcl-2, which was verified by immunoprecipitation; this interaction is superior after 24 h of CO treatment. Furthermore, CO enhanced Bcl-2 expression in astrocytes. By silencing Bcl-2 expression with siRNA transfection, CO effects in astrocytes were prevented, namely: (i) inhibition of apoptosis, (ii) increase on ATP generation, (iii) stimulation of COX activity, and (iv) mitochondrial biogenesis. Thus, Bcl-2 expression is crucial for CO modulation of oxidative metabolism and for conferring cytoprotection. In conclusion, CO protects astrocytes against oxidative stress-induced apoptosis by improving metabolism functioning, particularly mitochondrial oxidative phosphorylation.
authors.affiliation: Instituto de Biologia Experimental e Tecnológica, Apartado 12, 2781-901 Oeiras, Portugal.
authors.forename: Ana S
authors.initials: AS
authors.lastname: Almeida
authors.forename: Cláudia S F
authors.initials: CS
authors.lastname: Queiroga
authors.forename: Marcos F Q
authors.initials: MF
authors.lastname: Sousa
authors.forename: Paula M
authors.initials: PM
authors.lastname: Alves
authors.forename: Helena L A
authors.initials: HL
authors.lastname: Vieira
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001253:Astrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D002248:Carbon Monoxide / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects*; D003576:Electron Transport Complex IV / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010085:Oxidative Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D015427:Reperfusion Injury / Q000473:pathology
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D002248:Carbon Monoxide; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV