Efficacy of ulinastatin for improvement of cerebral resuscitation using therapeutic hypothermia in rats with cardiac arrest

Objective To investigate the efficacy of ulinastatin for improvement of cerebral resuscitation using therapeutic hypothermia(TH)in rats with cardiac arrest(CA). Methods Sixty pathogen-free healthy male Sprague-Dawley rats, weighing 280-320 g, were divided into 5 groups(n=12 each)using a random number table: sham operation group(group Sham); CA/cardiopulmonary resuscitation(CPR)group(group CA/CPR); group TH; ulinastatin group(group U); ulinastatin + TH group(group U+ TH). CA was induced through transesophageal cardiac pacing, and CPR was performed at 4 min of untreated arrest to establish CA/CPR model.In group TH, the rectal temperature was cooled down to 32-34 ℃ by rubbing the body surface with ethanol within 15 min starting from the time point immediately after restoration of spontaneous circulation(ROSC), and maintained at this level for 6 h. In group U, ulinastatin 100 000 U/kg was injected via the femoral vein immediately after ROSC.In group U+ TH, ulinastatin 100 000 U/kg was intravenously injected immediately after ROSC, and rectal cooling was then started.The neurological function was evaluated and scored at 24 and 72 h after ROSC.The rats were sacrificed after the neurological function was scored at 72 h after ROSC, and the hippocampi were removed for microscopic examination of pathological changes in hippocampal CA1 region and for determination of caspase-3 expression(by immunohistochemical staining and Western blot)and Bax and Bcl-2 expression(by Western blot)in hippocampal tissues.Bax/Bcl-2 ratio was calculated. Results Compared with group Sham, the neurological function score was significantly decreased, the expression of caspase-3 and Bax was up-regulated, the expression of Bcl-2 was down-regulated, and Bax/Bcl-2 ratio was increased after ROSC in group CA/CPR(P<0.05). Compared with group CA/CPR, the neurological function score was significantly increased at 24 and 72 h after ROSC in TH and U+ TH groups and at 24 h after ROSC in group U, caspase-3 expression was significantly down-regulated, Bcl-2 expression was up-regulated, and Bax/Bcl-2 ratio was decreased at 72 h after ROSC in TH, U and U+ TH groups, and the expression of Bax was significantly down-regulated in U and U+ TH groups(P<0.05). Compared with group TH or group U, the neurological function score was significantly increased at 24 h after ROSC, and the expression of caspase-3 was down-regulated and Bax/Bcl-2 ratio was decreased at 72 h after ROSC in group U+ TH(P<0.05). The pathological changes of hippocampal tissues were significantly mitigated in group U+ TH when compared with group TH or group U. Conclusion Ulinastatin can improve the efficacy of TH for cerebral resuscitation in rats with cardiac arrest, and the mechanism may be related to inhibition of neuronal apoptosis. Key words: Trypsin inhibitors; Hypothermia, induced; Heart arrest; Cardiopulmonary resuscitation; Brain