BACKGROUND: Researches suggest that cascade reaction of cysteine protease mediated by caspase-12 can cause apoptosis after cerebral ischemia/reperfusion injury; however, nerve growth factor (NGF) can reduce apoptosis through inhibiting activation of that reaction. OBJECTIVE: To observe the effect of NGF on the expression of caspase-12 in brain tissue of rabbits with cerebral ischemia/reperfusion injury, and elucidate the protective mechanism of NGF on neural apoptosis induced by cerebral ischemia/reperfusion injury.DESIGN: Randomized controlled animal study.SETTING: Department of Image, Second Hospital, Hebei Medical University. MATERIALS: A total of 26 healthy New Zealand rabbits, of clean grade, aged 4.5-5 months, weighing (2.6±0.2) kg, were selected in this study. Reagents: NGF (Xiamen Beida Zhilu Biotechnology Co., Ltd.); caspase-12 (Santa Cruz Biotechnology Company, USA, clone number: SC-12395); caspase-3 (Santa Cruz Biotechnology Company, USA, clone number: SC-7272); biotin-antibody Ⅱ and ABC compound (Wuhan Boster Company); in situ end-labeling (ISEL, Beijing Zhongshan Company). METHODS: The experiment was carried out in the Laboratories of Nerve Molecule Image Science and Neurology of the Second Hospital of Hebei Medical University from May to August 2005. ① All animals were randomly divided into three groups. Ischemia/reperfusion (I/R) group (n=10): Left middle cerebral artery (MCA) was blocked for 2 hours and then blooded for 2 hours in order to establish focal cerebral ischemia/reperfusion models. Sham operation group (n=6): Cork was inserted with 3 cm in depth, and then pulled to common carotid artery. Other procedures were as the same as those in ischemia/reperfusion group. Treatment group (n=10): After modeling, 400 AU (16 μg/L) NGF was inserted into cerebral infarction focus immediately. ② Brain tissue was taken out from left ischemia/reperfusion area at 3 days after operation in sham operation group and at 3 days after reperfusion in other two groups. In addition, contents of caspase-12 and caspase-3 were measured with immunohistochemical technique; mean absorbency (A value) was compared with image analytic system; apoptosis rate and apoptosis quantity of nerves in ischemia/reperfusion area were detected with flow cytometry and DNA TdT-mediated biotinylated-dUTP nick end labeling method. ③ Measurement data were compared with one-way analysis of variance among groups and with q test every two groups. MAIN OUTCOME MEASURES: Expressions of caspase-12 and caspase-3 and apoptosis in cerebral ischemia/reperfusion area in the 3 groups. RESULTS: All 26 rabbits were involved in the final analysis. ① Expressions of caspase-12 and caspase-3: Expression of caspase-12 was 0.36±0.02 in I/R group and 0.13±0.03 in treatment group; expression of caspase-3 was 0.49±0.05 and 0.27±0.06, respectively. Both of them were higher than those in sham operation group (0.07±0.02, 0.09±0.03, P < 0.01), and expressions of two proteases were lower in treatment group than those in I/R group (P < 0.01). There were significant differences of expression of caspase between I/R group and treatment group as compared with that in sham operation group; meanwhile, there were significant differences between treatment group and I/R group. ② Apoptosis: Apoptosis rate was (20.2±1.3)% in I/R group and (7.7±0.8)% in treatment group; apoptosis quantity was (32.8±2.6), (7.6±1.5)/high sight, respectively. Both of them were higher and more than those in sham operation group [(4.8 ±0.4)%, (0.7±0.2) /high sight, P < 0.01]. Apoptosis rate and apoptosis quantity were lower and less in treatment group than those in I/R group (P < 0.01). There was significant difference between I/R group and treatment group as compared with sham operation group, and there was significant difference between treatment group and I/R group. CONCLUSION: NGF can decrease the number of apoptotic cells of the cerebral ischemia/reperfusion and inhibit the caspase cascade reaction induced by caspase-12, which is one of the protective mechanisms of NGF. BACKGROUND: Researches suggest that cascade reaction of cysteine ​​protease mediated by caspase-12 can cause apoptosis after cerebral ischemia / reperfusion injury; however, nerve growth factor (NGF) can reduce apoptosis through inhibiting activation of that reaction. OBJECTIVE: To observe the effect of NGF on the expression of caspase-12 in brain tissue of rabbits with cerebral ischemia / reperfusion injury, and elucidate the protective mechanism of NGF on neural apoptosis induced by cerebral ischemia / reperfusion injury. DESIGN: Randomized controlled animal study. SETTING: Department of Image , MATERIALS: A total of 26 healthy New Zealand rabbits, of clean grade, aged 4.5-5 months, weighing (2.6 ± 0.2) kg, were selected in this study. Reagents: NGF (Xiamen Beida Zhilu (Santa Cruz Biotechnology Company, USA, clone number: SC-7272); biotin-anti METHODS: The experiment was carried out in the Laboratories of Nerve Molecule Image Science and Neurology of the Second Hospital of Hebei Medical University from Ischemia / reperfusion (I / R) group (n = 10): Left middle cerebral artery (MCA) was blocked for 2 hours and then blocks for 2 hours in order to establish focal cerebral ischemia / reperfusion models. Sham operation group (n = 6): Cork was inserted with 3 cm in depth, and then pulled to common carotid artery. group (n = 10): After modeling, 400 AU (16 μg / L) NGF was inserted into cerebral infarction focus immediately. ② Brain tissue was taken out from left ischemia / reperfusion area at 3 days after operation in sham operation group and at 3 days after reperfusion in other tw o groups. In addition, contents of caspase-12 and caspase-3 were measured with immunohistochemical technique; mean absorbency (A value) was compared with image analytic system; apoptosis rate and apoptosis quantity of nerves in ischemia / reperfusion area were detected with flow cytometry and DNA TdT-mediated biotinylated-dUTP nick end labeling method. ③ Measurement data were compared with one-way analysis of variance among groups and with q test every two groups. MAIN OUTCOME MEASURES: Expressions of caspase-12 and caspase-3 and apoptosis in Expressions of caspase-12 and caspase-3: Expression of caspase-12 was 0.36 ± 0.02 in I / R group and 0.13 ± 0.03 in treatment group; expression of caspase-3 was 0.49 ± 0.05 and 0.27 ± 0.06, respectively. Both of them were higher than those in sham operation group (0.07 ± 0.02, 0.09 ± 0.03, P <0.01), and expressions of two proteases were lower in t There were significant differences of expression of caspase between I / R group and treatment group as compared with that in sham operation group; meanwhile, there were significant differences between treatment group and Apoptosis: Apoptosis rate was (20.2 ± 1.3)% in I / R group and (7.7 ± 0.8)% in treatment group; Apoptosis quantity was (32.8 ± 2.6), (7.6 ± 1.5) / high sight , respectively. Both of them were higher and more than those in sham operation group [(4.8 ± 0.4)%, (0.7 ± 0.2) / high sight, P <0.01]. Apoptosis rate and apoptosis were lower and less in treatment group There was a significant difference between I / R group and treatment group as compared with sham operation group, and there was significant difference between treatment group and I / R group. CONCLUSION: NGF can decrease the number of apoptotic cells of the cerebral ischemia / reperfusion and inhibit the caspase cascade reac tion induced by caspase-12, which is one of the protective mechanisms of NGF.