[Neuroprotective effect and mechanisms of hypothermia in neonatal rat cerebral hypoxic-ischemic damages].
OBJECTIVE
Recent studies suggest that hypothermia may be a potential treatment for perinatal hypoxic-ischemic (HI) brain damage. But the mechanisms of this effect are not well known. In the present study, the protective effect of systemic hypothermia as well as effect on apoptosis and associated biochemical events were investigated on neonatal rats with HI brain damage.


METHODS
Seven-day-old Wistar rats were subjected to left carotid artery ligation and hypoxia was persisted for 60 min. Immediately at the end of hypoxia, the animals were maintained either at 36 degrees C or 30 degrees C for 10 h at random. Caspase-2, 3 activity in brain homogenate was detected with Western blotting at 24 h post-HI (n = 8 for each group). Immunoactivity of microtubule-associated protein-2 (MAP-2), active caspase-3, apoptosis inducing factor (AIF) and oligonucleotide hairpin probe staining were detected at 72 h post-HI. The infarct volume, neuronal loss in CA(1) sector of hippocampus as well as brain injury scoring were calculated according to MAP-2 staining and hematoxylin and eosin staining.


RESULTS
Caspase-2, 3 activities were much higher in the normothermia group [(27.7 +/- 14.7), (94.9 +/- 53.1) pmol/(min.mg protein)] at 24 h post-HI than those of hypothermia [(7.9 +/- 3.4), (21.1 +/- 18.7) pmol/(min.mg protein)] and normal control groups [(7.6 +/- 0.7), (12.9 +/- 0.5) pmol/(min x mg protein)] (P < 0.01). The activities were not significantly different between hypothermia group and normal control group. Western blotting showed that caspase-3 activation process was blocked by hypothermia. The number of active caspase-3 and AIF positive cells in the cortex of ipsilateral hemisphere was much higher in the normothermia group (median: 148.5; 22/field) than that of hypothermia group (median: 48.5; 9/field) (P < 0.05). The number of apoptotic cells as judged by oligonucleotide hairpin probe labeling was much higher in normothermia group (median: 144/field) than that of hypothermia group (median: 133/field) (P < 0.05). The brain injury scoring, infarct volume and neuronal loss in CA(1) area of hippocampus were much less in the hypothermia group [10.4 +/- 2.9; 40.5 +/- 34.8)mm(3); 25.7 +/- 11.5] than that of normothermia group [14.2 +/- 3.5; (73.9 +/- 22.4) mm(3); 37.4 +/- 10.6, P < 0.05].


CONCLUSIONS
Systemic hypothermia for 10 h after hypoxia-ischemia seemed to be effective in reducing brain damage and the mechanism is associated with alteration of apoptotic pathway.
Zhu
Chang-lian
CL
Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China.
Wang
Xiao-yang
XY
Cheng
Xiu-yong
XY
Qiu
Lin
L
Hu
Sheng-hai
SH
Yang
Jing-li
JL
Xu
Fa-lin
FL
D000818:Animals; D000831:Animals, Newborn; D051033:Apoptosis Inducing Factor; D015153:Blotting, Western; D001921:Brain / Q000098:blood supply / Q000503:physiopathology*; D053148:Caspase 3; D020169:Caspases / Q000032:analysis; D005260:Female; D005420:Flavoproteins / Q000032:analysis; D007036:Hypothermia, Induced; D020925:Hypoxia-Ischemia, Brain / Q000201:enzymology / Q000378:metabolism* / Q000517:prevention & control; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
C494831:Aifm1 protein, rat; D051033:Apoptosis Inducing Factor; D005420:Flavoproteins; D008565:Membrane Proteins; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases