Antiapoptotic cardioprotective effect of hypothermia treatment against oxidative stress injuries.
OBJECTIVE
The effect of hypothermia on cardiomyocyte injury induced by oxidative stress remains unclear. The authors investigated the effects of hypothermia on apoptosis and mitochondrial dysfunction in cardiomyocytes exposed to oxidative stress.


METHODS
Cardiomyocytes (H9c2) derived from embryonic rat heart cell culture were exposed to either normothermic (37 degrees C) or hypothermic (31 degrees C) environments before undergoing oxidative stress via treatment with hydrogen peroxide (H(2)O(2)). The degree of apoptosis was determined by annexin V and terminal deoxynucleotidyl transferase (TUNEL) staining. The amount of reactive oxygen species (ROS) was compared after H(2)O(2) exposure between normo- and hypothermic-pretreated groups. Mitochondrial dysfunction in both groups was measured by differential reductase activity and transmembrane potential (DeltaPsim).


RESULTS
Hydrogen peroxide induced significant apoptosis in both normothermic and hypothermic cardiomyocytes. Hypothermia ameliorated apoptosis as demonstrated by decreased annexin V staining (33 +/- 1% vs. 49 +/- 4%; p < 0.05) and TUNEL staining (27 +/- 17% vs. 80 +/-25%; p < 0.01). The amount of intracellular ROS increased after H(2)O(2) treatment and was higher in the hypothermic group than that in the normothermic group (237.9 +/- 31.0% vs. 146.6 +/- 20.6%; p < 0.05). In the hypothermic group, compared with the normothermic group, after H(2)O(2) treatment mitochondrial reductase activity was greater (72.0 +/- 17.9% vs. 27.0 +/- 13.3%; p < 0.01) and the mitochondria DeltaPsim was higher (101.0 +/- 22.6% vs. 69.7 +/- 12.9%; p < 0.05). Pretreatment of cardiomyocytes with the antioxidant ascorbic acid diminished the hypothermia-induced increase in intracellular ROS and prevented the beneficial effects of hypothermia on apoptosis and mitochondrial function.


CONCLUSIONS
Hypothermia at 31 degrees C can protect cardiomyocytes against oxidative stress-induced injury by decreasing apoptosis and mitochondrial dysfunction through intracellular ROS-dependent pathways.
Huang
Chien-Hua
CH
Department of Emergency Medicine, National Taiwan University Hospital Yun-Lin Branch, Yun-Lin County.
Chen
Huei-Wen
HW
Tsai
Min-Shan
MS
Hsu
Chiung-Yuan
CY
Peng
Ren-How
RH
Wang
Tzung-Dau
TD
Chang
Wei-Tien
WT
Chen
Wen-Jone
WJ
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D004195:Disease Models, Animal; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy; D006861:Hydrogen Peroxide; D007036:Hypothermia, Induced; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000502:physiology*; D018384:Oxidative Stress; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide