西咪替丁对低剂量率照射比格犬肝细胞凋亡的影响及其机制研究

摘 要 目的：研究西咪替丁对低剂量率照射比格犬肝细胞凋亡的影响及其机制。方法：将健康雄性比格犬随机分为正常对照组、模型对照组、阳性药物组（香菇多糖，21.33 mg/kg）和西咪替丁低、中、高剂量组（5.33、10.67、21.33 mg/kg），每组4只。除正常对照组外，其余各组比格犬均予60Co-γ射线（剂量率：0.040 8 mGy/min）累积照射23 d，各给药组于每日照射前口服相应药物1次。停止照射24 h后，采用TUNEL法检测各组比格犬肝细胞凋亡情况，并计算凋亡细胞百分比；采用免疫组化法检测其肝组织中凋亡相关蛋白[Bax、Bcl-2、胱天蛋白酶3（Caspase-3）、p53]的表达水平。结果：与正常对照组比较，模型对照组比格犬肝组织中凋亡细胞以及Bax、Caspase-3、p53阳性细胞均明显增加，凋亡细胞百分比以及Bax、Caspase-3、p53蛋白表达水平均显著升高；Bcl-2阳性细胞明显减少，其蛋白表达水平均显著降低（P<0.05或P<0.01）。与模型对照组比较，各给药组比格犬肝组织中上述阳性细胞均有不同程度的变化，其中各给药组凋亡细胞百分比和p53蛋白表达水平，阳性药物组和西咪替丁低、高剂量组Bax蛋白表达水平以及西咪替丁各剂量组Caspase-3蛋白表達水平均显著降低；西咪替丁各剂量组Bcl-2蛋白表达水平均显著升高；且西咪替丁中、高剂量组凋亡细胞百分比以及西咪替丁各剂量组Caspase-3蛋白表达水平均显著低于阳性对照组，西咪替丁低剂量组p53蛋白表达水平显著高于阳性药物组（P<0.05或P<0.01）。结论：西咪替丁可抑制低剂量率照射所致的比格犬肝细胞凋亡，对其具有一定的辐射保护作用。这种作用可能与上调Bcl-2蛋白的表达，下调Bax、Caspase-3、p53蛋白的表达有关。

关键词 西咪替丁；低剂量率辐射；肝脏；肝细胞凋亡；凋亡相关蛋白；比格犬；防辐射；机制

Effects of Cimetidine on Low Dose Rate Irradiation-induced Liver Cell Apoptosis in Beagle Dogs and Its Mechanism

WANG Qingrong，HE Ying，ZHAO Yining，SHEN Xiaong，LIU Yuming，LI Kexian，LUO Qun，CHEN Wei，HOU Dengyong（Dept. of Radiation Protection Medicine， Naval Medical Research Institute， Second Military Medical University， Shanghai 200433， China）

ABSTRACT OBJECTIVE： To study the effects of cimetidine on low dose rate irradiation-induced liver cell apoptosis in Beagle dogs. METHODS： Healthy male Beagle dogs were randomly divided into normal control group， model control group， positive drug group （lentinan， 21.33 mg/kg） and cimetidine low-dose， medium-dose and high-dose groups （5.33， 10.67， 21.33 mg/kg）， with 4 Beagle dogs each. Except for normal control group， other groups were given 60Co-γ accumulative irradiation （dosage rate： 0.040 8 mGy/min） for 23 d； the medication groups were given relevant medicine orally before irradiation， once a day. Twenty-four hours after stopping irradiation， TUNEL method was used to detect the apoptosis of liver cells in Beagle dogs. The percentage of apoptotic cells was calculated. The expression level of apoptosis-related proteins （Bax， Bcl-2， Caspase-3， p53） in liver tissue was detected by immunohistochemistry. RESULTS： Compared with normal control group， apoptotic cells and Bax， Caspase-3， p53 positive cells were increased significantly in liver tissue of Beagle dogs in model control group； the percentage of apoptotic cells， protein expression levels of Bax， Caspase-3 and p53 were increased significantly； Bcl-2 positive cells were decreased significantly， and its protein expression level was decreased significantly （P<0.05 or P<0.01）. Compared with model control group， above positive cells of liver tissue in Beagle dogs were changed to different extents in medication groups； the percentage of apoptotic cells and protein expression levels of p53 in medication groups， protein expression levels of Bax in positive drug group， cimetidine low-dose and high-dose groups as well as protein expression levels of Caspase-3 in cimetidine groups were decreased significantly； protein expression levels of Bcl-2 were increased significantly in cimetidine groups. The percentage of apoptotic cells in cimetidine medium-dose and high-dose groups as well as protein expression levels of Caspase-3 in cimetidine groups were all lower than positive control group. Protein expression level of p53 in cimetidine low-dose group was significantly higher than positive drug group （P<0.05 or P<0.01）. CONCLUSIONS： Cimetidine can inhibit the low dose rate irradiation-induced apoptosis of liver cells in Beagle dogs， and certainly protect liver cells against irradiation. The mechanism of it may be associated with up-regulating the protein expression of Bcl-2 and down-regulating the protein expression of Bax， Caspase-3 and p53 in liver cells.

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