Protective Effect of Hypothermia in Delayed Astrocyte Death after Transient Histotoxic Hypoxia in Vitro

Kim, Myung Hee; Shin, Baek Hyo; Lee, Sang Eun

Abstract

BACKGROUND: It is well known that neuronal degeneration can occur after a brief deprivation of energy source. To investigate whether glial astrocyte can induce a phenomenon of delayed cell death after transient energy loss and to see how different are the effects of nifedipine, lidocaine, carnosine and hypothermia on delayed toxicity in astrocyte.
METHODS
Human astrocytoma cells (U1242MG) were used in this study. To assess the astrocyte survival during post-ischemic period after transient histotoxic hypoxia, 3-[4,5-dimethylthiazol-2yl]-2,5, diphenyl tetrazolium bromide (MTT) test was used. Compared to MTT test, tryphan blue test was also used to demonstrate membrane damage of affected cells. Studies on intracellular calcium dynamics during ischemic and post-ischemic period were carried out with fluo-3 and flow cytometry system.
RESULTS
The percentage survival of astrocyte during post-ischemic period was decreasing with time. Calcium channel blocker nifedipine, sodium and calcium channel blocker lidocaine and free radical scavenger carnosine could not prevent post-ischemic cell damage. But, hypothermia was only an effective method in ameliorating post-ischemic cell death. Intracellular calcium increase during ischemia and post-ischemia was dependent on extracellular calcium influx.
CONCLUSIONS
Only hypothermia was effective in reducing astrocyte death during post-ischemia after transient energy depletion. Intracellular calcium alterations during post-ischemia was from extracellular space.