坐骨神经切断后背根神经节 A 、 B 细胞的不同凋亡反应： p75 神经营养因子受体的作用。

Different apoptotic reactions of dorsal root ganglion A- and B-cells after sciatic nerve axotomy: effect of p75 neurotrophin receptor.

机构信息

Department of Neurology, Aarhus University Hospital, DK-8000 Aarhus C, Denmark.

出版信息

Chin Med J (Engl). 2010 Oct;123(19):2695-700.

Abstract

BACKGROUND

By unbiased stereological methods, we have observed preferential dorsal root ganglion (DRG) B-cell loss in rodents after nerve injury, and caspase-3 activation and cell loss were related to the present of p75 receptor (p75(NTR)). We hypothesized that DRG B-cells express higher levels of pro-apoptotic proteins as compared to A-cells and the expressions of pro-apoptotic proteins can be reduced by depletion of p75(NTR). This study aimed to identify the p75(NTR) involved apoptotic pathway in DRG neurons after nerve injury.

METHODS

The p75(NTR) knockout mice (p75-/-) and wildtype Balb/C mice (p75+/+) were used in this study. The expressions of pro-apoptotic proteins, c-Jun-N-terminal kinase (JNK), c-jun and p38 in DRG were evaluated with immunohistochemistry 2 and 7 days following unilateral sciatic nerve transection. In addition, extra-cellular related kinase (ERK), a transducer of survival signals, was also tested with immunohistochemistry and Western blotting methods in these animal models.

RESULTS

Phosphorylated JNK (P-JNK) and phosphorylated p38 (P-p38) were mainly located in small B-cells, whereas phosphorylated c-jun (P-c-jun) was located in both A- and B-cells. Phosphorylated ERK (P-ERK) was located in both B-cells and satellite cells. Axotomy dramatically increased the expressions of P-JNK and P-c-jun (paired t-test), with no influence on the expressions of P-p38 and P-ERK. Furthermore, the increase of P-JNK in p75+/+ mice 2 days after nerve axotomy was approximately 2.2-folds of that in p75-/- mice (P = 0.001, unpaired t-test).

CONCLUSION

p75(NTR)-dependent JNK-caspase-3 pathway is involved in DRG B-cell loss after nerve injury and JNK is not the unique upstream of c-jun activation.

摘要

背景

通过无偏立体学方法，我们观察到在神经损伤后，啮齿动物的背根神经节（DRG）B 细胞优先丢失，并且 caspase-3 的激活和细胞丢失与 p75 受体（p75（NTR））的存在有关。我们假设 DRG B 细胞表达的促凋亡蛋白水平高于 A 细胞，并且通过耗尽 p75（NTR）可以减少促凋亡蛋白的表达。本研究旨在确定神经损伤后 DRG 神经元中 p75（NTR）参与的凋亡途径。

方法

本研究使用 p75（NTR）敲除小鼠（p75-/-）和野生型 Balb/C 小鼠（p75+/+）。用免疫组织化学方法检测单侧坐骨神经横断后 2 天和 7 天 DRG 中促凋亡蛋白 c-Jun-N-末端激酶（JNK）、c-jun 和 p38 的表达。此外，还通过免疫组织化学和 Western blot 方法检测这些动物模型中细胞外相关激酶（ERK），一种存活信号转导物。

结果

磷酸化 JNK（P-JNK）和磷酸化 p38（P-p38）主要位于小 B 细胞中，而磷酸化 c-jun（P-c-jun）则位于 A 细胞和 B 细胞中。磷酸化 ERK（P-ERK）位于 B 细胞和卫星细胞中。轴突切断术显著增加了 P-JNK 和 P-c-jun 的表达（配对 t 检验），但对 P-p38 和 P-ERK 的表达没有影响。此外，p75+/+ 小鼠神经轴突切断后 2 天 P-JNK 的增加约为 p75-/- 小鼠的 2.2 倍（P = 0.001，未配对 t 检验）。