骨癌痛小鼠脊髓谷氨酸转运体GLAST表达下调

The expression of glutamate transporters （GLAST） protein downregulate in spine in bone cancer mice

目的观察谷氨酸转运体GLAST在骨癌痛小鼠脊髓中表达的变化。方法35只C3H／HeJ小鼠随机分为2组：骨癌痛组（Ca组，n=30）和假手术组（Sham组，n=5）。Ca组小鼠是将含2×10^5个NCTC2472细胞的20μl的最小必需培养基注入右股骨远端骨髓腔中制备癌痛模型。Sham组是不注射NCTC2472细胞，余操作同于骨癌痛组。Ca组小鼠注射肿瘤细胞后1d、3d、7d、10d、14d、21d观察小鼠的机械缩足阈值（MWT）和热辐射缩足反射潜伏期（PWL），并于注射肿瘤细胞前、注射后7d、14d、21d进行X线检查评估股骨破坏程度。Ca组分别于肿瘤细胞后1d、3d、7d、10d、14d、21d检测行为学实验后处死小鼠取右侧腰段脊髓，Sham组直接取右侧腰段脊髓，采用Western blot方法测定GLAST在脊髓的蛋白表达。结果Ca组小鼠在接种肿瘤细胞后第7天MWT显著降低，低于术前的基础值（P〈0．05），持续下降至第21天；接种后第14天PWL显著降低，低于术前的基础值（P〈0．05），持续下降至第21天。Ca组小鼠第7天的X线片仅见股骨远端有小的病灶，第14天骨质破坏增多，到第21天骨破坏进一步加重，骨质破坏范围加大，有骨质缺损或骨折出现。Ca组小鼠接种肿瘤细胞后第10天脊髓GLAST蛋白含量开始减少，第14天明显减少，持续降低至术后21d（P〈0．01）。结论骨癌痛小鼠脊髓的谷氨酸转运体GLAST的蛋白表达下降，提示脊髓谷氨酸转运体GLAST参与骨癌痛的形成。

Objective To investigate the expression of glutamate transporter （GLAST） in spine in bone cancer mice. Methods 35 mice were randomly assigned into bone cancer pain model group （Ca group） （n = 30） and sham group （n = 5 ）. The bone cancer pain model was made by injecting 2×10^5 NCTC 2472 cells suspended in 20 μl of a minimal essential medium to the medullary cavity of the right distal femur. The sham group was only injected 20 μl medium without NCTC 2472 cells. Mechanical withdraw threshold （MWT） and paw withdrawal latencies （PWL） to radiant heat stimulation of Ca group were measured pre-injection and on the 1st,3rd, 7th,10th,14th,21st day after injection. The development of the bone tumor and structural damage in the bone were assessed by X-ray scan pre-injection and on the 7th,14th,21st day. Mice were decapitated after the behavior test in the time point of 1 st,3rd,7th,10th, 14th ,21 st day and the right lumbar spinal cord enlargement was removed. The right lumbar spinal cord enlargement of the sham group was removed directly. The expression of glutamate transporters in the spine were studied by Western blot. Results The MWT of the right foot of Ca group decreased significantly on day 7 compared with that before inoculation procedure （ P 〈 0.05 ） and continued to decrease until 21st day after innoeulation procedures. The PWL of the right foot of Ca group decreased on days 14 significantly compared with that before inoculation procedure （P 〈 0. 05） and continued to decrease until 21st day after innoculation procedures. The X-ray scan of the femur showed small pits of destruction in the distal of the bone on the 7th day and increased pitted appearance on the 14th day. Bone loss increased and displaced skeletal fracture appeared on the 21st day. The expression of the protein content of GLAST decreased from day 10 and decreased significantly by day 14 and continuously decreased till day 21 （P 〈 0.01 ）. Conclusion Downregulation of spinal glutamate transporter was involved in the forming of bone cancer pain.