Effect of Bcl-x(L) overexpression on reactive oxygen species, intracellular calcium, and mitochondrial membrane potential following injury in astrocytes.
Many studies have demonstrated the protective effects of Bcl-x(L) against both apoptotic and necrotic cell death, but the mode of action of Bcl-x(L) remains unclear. This work analyzed effects of Bcl-x(L) overexpression on cellular levels of reactive oxygen species (ROS), intracellular calcium ([Ca(2+)](i)), and mitochondrial membrane potential (DeltaPsi(m)) in cultured mouse primary astrocytes after exposure to glucose deprivation (GD) or hydrogen peroxide (H(2)O(2)). Upon exposure to GD or H(2)O(2), uninfected and Lac-Z-expressing astrocytes showed an immediate, rapid increase in ROS accumulation that was slowed and or reduced by Bcl-x(L). Changes in DeltaPsi(m) in response to the two insults differed. H(2)O(2) induced a decrease in DeltaPsi(m) that was initially greater in Bcl-x(L) cells, but then held stable. DeltaPsi(m) in control and Lac-Z-expressing cells initially declined more slowly, but after about 20 min showed rapid deterioration. Five hours of GD caused mitochondrial membrane hyperpolarization followed by a decrease in DeltaPsi(m,) which was not observed with Bcl-x(L) overexpression. Bcl-x(L) failed to inhibit the calcium dysregulation seen in control cells exposed to 400 microM H(2)O(2), but still improved cell survival. There was no increase in [Ca(2+)](i) with 5 h of GD. These data thus dissociate the effect of Bcl-x(L) on calcium homeostasis from effects on ROS, DeltaPsi(m,) and for H(2)O(2) exposure, cell survival.
Ouyang
Yi-Bing
YB
Department of Anesthesia, Stanford University School of Medicine, Stanford, CA 94305, USA.
Carriedo
Sean G
SG
Giffard
Rona G
RG
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D017930:Genes, Reporter; D005947:Glucose / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000633:toxicity; D007425:Intracellular Membranes / Q000502:physiology*; D007763:Lac Operon; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D051020:bcl-X Protein
C494812:Bcl2l1 protein, mouse; D009419:Nerve Tissue Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; D051020:bcl-X Protein; D006861:Hydrogen Peroxide; D005947:Glucose; D002118:Calcium