Overexpression of Bcl-xl protects septal neurons from prolonged hypoglycemia and from acute ischemia-like stress.
Overexpression of Bcl-xl, a member of the Bcl-2 protein family, is reported to protect from a variety of stresses involving delayed cell death. We tested the ability of Bcl-xl overexpression to protect primary cultures of embryonic rat septal neurons subjected to one of four different stresses: 6 h of combined oxygen-glucose deprivation, which produces rapid cell death, or a 24 h exposure to hypoglycemia, hyperglycemia, or 1mM 3-nitropropionic acid (an inhibitor of mitochondrial respiration), which results in a more slowly-developing death. Prior to the stress neurons were transiently transfected to overexpress either green fluorescent protein only or green fluorescent protein along with wild-type Bcl-xl. Immediately after oxygen-glucose deprivation, many neurons expressing green fluorescent protein only showed process blebbing and disintegration, with only 49% of the initial cells remaining intact with processes. Neurons expressing both green fluorescent protein and Bcl-xl showed less damage (68% intact post-stress, P<0.05). This result indicates that Bcl-xl's saving effects are not due solely to blocking delayed (apoptotic) death, because death following oxygen-glucose deprivation was rapid and was not accompanied by increased activation of caspase-3. Bcl-xl expression also significantly protected against the hypoglycemic stress (23% intact 24 h post-stress with green fluorescent protein only, compared with 70% with Bcl-xl and green fluorescent protein), but did not protect from hyperglycemia or 3-nitropropionic acid. Thus Bcl-xl does not protect against all forms of delayed death. Bcl-xl's protective effects may include blocking early damaging events, perhaps by increasing mitochondrial function in the face of low levels of energy substrates. Bcl-xl's protective effects may require an intact electron transport chain.
Panickar
K S
KS
Department of Physiology and Biophysics (R430), University of Miami Miller School of Medicine, PO Box 016430, Miami, FL 33101, USA. kpanickar@med.miami.edu
Nonner
D
D
Barrett
J N
JN
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000963:Antimetabolites; D002545:Brain Ischemia / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D003847:Deoxyglucose; D003952:Diagnostic Imaging; D005786:Gene Expression Regulation / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007003:Hypoglycemia / Q000139:chemically induced / Q000378:metabolism*; D002534:Hypoxia, Brain / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D009574:Nitro Compounds / Q000494:pharmacology; D011422:Propionates / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020665:Septum of Brain / Q000166:cytology / Q000378:metabolism*; D013312:Stress, Physiological / Q000378:metabolism*; D013385:Succinate Dehydrogenase / Q000378:metabolism; D014162:Transfection; D051020:bcl-X Protein / Q000096:biosynthesis* / Q000235:genetics
D000963:Antimetabolites; D009574:Nitro Compounds; D011422:Propionates; D051020:bcl-X Protein; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D003847:Deoxyglucose; D013385:Succinate Dehydrogenase; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; C015392:3-nitropropionic acid