氯胺酮对N-甲基-D-天冬氨酸诱导大鼠脊髓背角星形胶质细胞损伤的作用

背景氯胺酮是临床常用的静脉全麻药,静脉或硬脊膜外腔用药都有镇痛作用,它是N-甲基-D-天冬氨酸受体非竞争性拮抗剂,可拮抗兴奋性氨基酸的毒性作用.目的观察氯胺酮对N-甲基-D-天冬氨酸受体过度激活诱导大鼠脊髓背角星形胶质细胞凋亡的影响,探讨其可能的作用机制.设计随机对照观察.单位郧阳医学院附属太和医院麻醉科.材料实验于2003-09/2005-01在郧阳医学院基础医学研究所细胞生物学实验室完成.由武汉大学动物实验中心提供新生两三天Wistar大鼠.方法取Wistar大鼠T11～L6脊髓背角星形胶质细胞原代纯化培养.胶质纤维酸性蛋白鉴定星形胶质细胞纯度达98%后用于实验.将培养细胞24孔板随机分为6组(每组9份)①对照组加Hanks液50μL.②N-甲基-D-天冬氨酸组加药浓度为100μmol/L.③氯胺酮组加药浓度为1 mmol/L.④100μmol/L N-甲基-D-天冬氨酸+0.1 mmol/L氯胺酮组.⑤100μmol/L N-甲基-D-天冬氨酸+0.5 mmol/L氯胺酮组.⑥100 μmol/L N-甲基-D-天冬氨酸+1mmol/L氯胺酮组.1 mmol/L氯胺酮为临床镇痛剂量.培养24 h后检测超氧化物歧化酶活性和丙二醛含量,免疫细胞化学观察Bcl-2蛋白和形态学变化,流式细胞仪检测星形胶质细胞凋亡率.主要观察指标①Bcl-2蛋白免疫组织化学苏木精-伊红复染细胞着色及形态学变化.②流式细胞仪检测星形胶质细胞凋亡率.③丙二醛含量和超氧化物歧化酶活性变化.结果①Bcl-2平均吸光度值(A)作为半定量测量Bcl-2蛋白表达水平100 μmol/L N-甲基-D-天冬氨酸组低于对照组,差异显著分别为0.054±0.021,0.108±0.039,P＜0.01],100 μmol/L N-甲基-D-天冬氨酸+1 mmol/L氯胺酮组高于100 μmol/L N-甲基-D-天冬氨酸组,差异显著分别为0.148±0.045,0.054±0.021,P＜0.01].②流式细胞仪检测星形胶质细胞凋亡率100 μmol/L N-甲基-D-天冬氨酸组高于对照组,差异显著分别为(25.26±6.13)%,(5.66±2.24)%,P＜0.01],100μmol/LN-甲基-D-天冬氨酸+1 mmol/L氯胺酮组低于100 μmol/L N-甲基-D-天冬氨酸组,差异显著分别为(24.41±4.82)%,(25.26±6.13)%,P＜0.01].③丙二醛含量和超氧化物歧化酶活性变化100 μmol/L N-甲基-D-天冬氨酸使星形胶质细胞内丙二醛含量显著升高,而超氧化物歧化酶活性明显降低;1 mmol/L氯胺酮明显降低丙二醛含量,显著增强超氧化物歧化酶活性,该效应在临床镇痛剂量以内有明显量效关系,与N-甲基-D-天冬氨酸组相比差异显著(P＜0.01).1 mmol/L氯胺酮组与对照组相比、100μmol/L N-甲基-D-天冬氨酸+0.1 mmol/L氯胺酮组与N-甲基-D-天冬氨酸组相比差异均无显著性.结论N-甲基-D-天冬氨酸受体过度激活可诱导大鼠脊髓背角星形胶质细胞大量凋亡,适量氯胺酮显著抑制细胞凋亡,其机制可能增强星形胶质细胞Bcl-2蛋白表达,同时抑制自由基的产生和增强超氧化物歧化酶活性.

Influence of ketamine on astrocyte damage in spinal dorsal horn of rats induced by N-methyl-D-aspartic acid

BACKGROUND: Ketamine is a kind of frequently used general venous anesthesia drug in clinic, and the medication in vein or epidural cavum has analgesic effect. It is N-methyl-D-aspartic acid (NMDA) receptor noncompetitive antagonist, which can inhibit toxic effect of excitatory amino acids.OBJECTIVE: To observe effect of ketamine on apoptosis of dorsal horn astrocytes of spinal cord of rats induced by NMDA receptor over activation and explore its possible mechanism of action.DESIGN: Randomized controlled observation.SETTING: Department of Anesthesiology, Taihe Hospital Affiliated to Yunyang Medical College.MATERIALS: The experiment was conducted at Cell Biology Laboratory,Institute of Basic Medical Sciences, Yunyang Medical College between September 2003 and January 2005. Neonatal Wistar rats of two or three days were provided by Animal Experimental Center of Wuhan University. METHODS: Primary astrocytes in dorsal horn of T11-L6 spinal cord of Wistar rats were purified and cultured. Astrocytes were used in the experiment when its purity coefficient reached 98% assessed by gial fibrillary acidic protein. The cultured cells in 24-well plates were divided randomly into 6 groups (9 portions in each group): ①50 μL Hanks liquor was added into the control group. ②Amount of 100μmol/L was added into the NMDA group. ③Amount of 1 mmol/L was added into the ketamine group. ④100μmol/L NMDA + 0.1 mmol/L ketamine group. ⑤100 μmol/L NMDA + 0.5 mmol/L ketamine group. ⑥100μmol/L NMDA + 1 mmol/L ke tamine group. 1 mmol/L ketamine was clinical antalgic dosage. Activity of superoxide dismutase (SOD) and content of malondialdehyde (MDA) were examined after 24-hour culture. Content of Bcl-2 protein and change of morphology were observed with immunocytochemistry. Apoptosis of astrocytes was measured with flow cytometry. MAIN OUTCOME MEASURES: ① Counterstain cell staining and changes of morphology of Bcl-2 protein with immunohistochemical method and hematoxylin-esoin staining (HE). ②Apoptosis of astrocytes was detected with flow cytometry. ③Content of MDA and activity of SOD.RESULTS: ①Mean absorbance (A) of Bcl-2 as expression of Bcl-2 protein measured semiquantitatively: It was lower in the 100μmoL/L NMDA group than the control group, which had significant difference 0.054±0.021,0.108±0.039, respectively, P＜0.01]. It was higher in the 100 μmol/L NMDA + 1 mmol/L ketamine group than the 100 μmol/L NMDA group,which had significant difference 0.148±0.045, 0.054±0.021, respectively,P ＜ 0.01]. ②Apoptosis of astrocytes detected with flow cytometry: It was higher in the 100μmol/L NMDA group than the control group, which had significant difference (25.26±6.13)%, (5.66±2.24)%, respectively, P＜0.01].It was lower in the 100μmol/L NMDA + 1 mmol/L ketamine group than in the 100μmol/L NMDA group, which had significant difference(24.41±4.82)%, (25.26±6.13)%, respectively, P＜0.01]. ③Content of MDA and activity of SOD: 100 μmol/L NMDA made the content of MDA in astrocytes obviously increase , while the activity of SOD markedly decrease. 1 mmol/L ketamine remarkably decreased the content of MDA, distinctly increased the activity of SOD. This effectiveness had evidently dosage-effect relationship in clinical antalgic dosage, which had obviously difference as compared with that of the NMDA group (P ＜ 0.01 ). The differences between the 1 mmol/L ketamine group and the control group as well as between the 100 μmol/L NMDA + 0.1 mmol/L ketamine group and the NMDA group had insignificant difference.CONCLUSION: NMDA receptor over activation can induce apoptosis of a great number of astrocytes in spinal dorsal horn of rats. Suitable ketamine dramatically inhibits apoptosis, and its mechanism can enhance the expressionof Bcl-2 protein of astrocytes, at the same time inhibit the production of free radical and reinforce the activity of SOD.