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

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,21.33mg/kg)和西咪替丁低、中、高剂量组(5.33、10.67、21.33mg/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 8mgy/min)累积照射23d,各给药组于每日照射前口服相应药物1次。停止照射24h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蛋白表达水平均显著降低;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。

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

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-γaccumulative 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.