Ischemic preconditioning or heat shock pretreatment ameliorates neuronal apoptosis following hypothermic circulatory arrest.
OBJECTIVE
Hypothermic circulatory arrest has been widely used in complex cardiac and aortic surgery. Stroke and/or neurologic injury can occur after prolonged hypothermic circulatory arrest, possibly due to apoptosis. Ischemic preconditioning has been widely used as a neuroprotective tool, but its application in neuronal injury under hypothermic circulatory arrest has never been studied.


METHODS
Forty male New Zealand white rabbits were placed on closed-chest cardiopulmonary bypass, subjected to hypothermic circulatory arrest, and rewarmed to normothermia. Experimental groups were treated with heat shock or ischemic preconditioning before hypothermic circulatory arrest. Hippocampal CA1 neurons were analyzed histopathologically. Apoptosis was confirmed by TUNEL assay and Western blot analysis, and serum S-100beta levels, c-Fos and Bcl-2 antibodies, and caspase-3 and heat shock protein 70 levels were measured.


RESULTS
After 2-hour hypothermic circulatory arrest and 4-hour reperfusion, apoptosis was observed in hippocampal CA1 neurons with elevation of serum S-100beta levels, which could be ameliorated by ischemic preconditioning or heat shock manipulations. TUNEL-positive nuclear expression of caspase-3 increased after hypothermic circulatory arrest (3.08% +/- 0.71%, P <.001) and was diminished with ischemic preconditioning (1.61% +/- 0.42%) and heat shock (1.72% +/- 0.38%) manipulations. Ischemic preconditioning or heat shock manipulations produced diverse patterns of heat shock protein 70, c-Fos, and Bcl-2 protein expression, suggesting that these manipulations provide neuroprotection via different pathways.


CONCLUSIONS
Ischemic preconditioning and heat shock can attenuate hippocampal CA1 neuronal apoptosis after prolonged hypothermic circulatory arrest under cardiopulmonary bypass. The expression of heat shock protein 70 may not play a major role in the first window of ischemic preconditioning-induced neuroprotection.
Yeh
Chi-Hsiao
CH
Division of Thoracic and Cardiovascular Surgery, Chang Gung Memorial Hospital, 222 Mai-Chin Road, Keelung, Taiwan 204. yehcc1@cgmh.org.tw
Wang
Yao-Chang
YC
Wu
Yi-Cheng
YC
Lin
Yu-Min
YM
Lin
Pyng Jing
PJ
D000818:Animals; D017209:Apoptosis; D001921:Brain / Q000473:pathology*; D001923:Brain Chemistry; D053148:Caspase 3; D020169:Caspases / Q000032:analysis; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis; D006324:Heart Arrest, Induced; D018869:Heat-Shock Response; D007036:Hypothermia, Induced; D019194:Ischemic Preconditioning; D008297:Male; D009414:Nerve Growth Factors; D009474:Neurons / Q000473:pathology*; D011817:Rabbits; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000097:blood
D018840:HSP70 Heat-Shock Proteins; D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; D053148:Caspase 3; D020169:Caspases