摘要
大多数哺乳动物中枢神经系统疾病发生后神经细胞轴突受到损伤,由于受损的神经细胞促进轴突再生的能力有限,同时胶质疤痕的生成以及抑制性营养因子的释放,导致受损神经细胞轴突难以再生。为研究注射用脑蛋白水解物(Ⅱ)[cerebroprotein hydrolysate for injection (II),CBL]对神经细胞轴突再生的影响及其潜在的分子机制,采用免疫荧光染色检测小鼠脑神经瘤细胞(Neuro-2a)和小鼠原代皮层神经细胞的轴突长度;通过蛋白免疫印迹法检测Neuro-2a细胞和小鼠原代皮层神经细胞内磷酸化TrkB蛋白的表达水平。结果显示:CBL可以促进Neuro-2a细胞和小鼠原代皮层神经细胞的轴突再生,上调神经细胞内TrkB的磷酸化水平;5 μg/mL的CBL作用于神经细胞1 h,可以显著升高神经细胞内TrkB磷酸化水平。研究结果表明:CBL可以促进神经细胞轴突再生以及升高TrkB磷酸化水平,提示CBL促进神经细胞轴突再生的作用可能与激活TrkB信号通路有关。
神经元和神经元之间的轴突连接对于维持神经系统的功能十分重要,在中枢神经系统中,多发性硬
注射用脑蛋白水解物(Ⅱ)[cerebroprotein hydrolysate for injection (Ⅱ),CBL]是猪脑蛋白经酶水解而产生的富含多种氨基酸和小分子生物活性多肽的混合物,作用于神经系统,促进神经元的存活,具有神经营养和神经保护的作
本文研究了CBL对神经细胞轴突再生的作用,阐述了CBL的作用机制,发现CBL可能是通过激活TrkB信号通路发挥作用,研究结果为进一步提高CBL药物临床应用提供理论指导。
注射用脑蛋白水解物(Ⅱ)(CBL,国药准字H20051230,规格:30.5 mg,无菌冻干粉,内含约16种游离氨基酸和不同长度的多肽,以及适宜辅料,广东隆赋药业股份有限公司);MEM培养基、DMEM/F12培养基、青链霉素(美国Gibco公司);Neurobasal培养基、B27添加剂、胰酶、Hoechst 33342(美国Invitrogen公司);DNA酶、多聚赖氨酸(美国Sigma公司);胎牛血清(美国Clark公司);Hank's平衡盐缓冲溶液(美国赛默飞世尔公司);RIPA细胞裂解液(上海碧云天生物技术有限公司);BCA蛋白浓度测定试剂盒(美国Thermo公司);牛血清白蛋白(BSA,南京生兴生物科技有限公司);上样缓冲液(美国Bio-Rad公司);Alexa Fluor 633羊抗鼠IgG(H + L)抗体、p-TrkB(Tyr706)抗体(美国Affinity Biosciences公司);β-actin抗体(武汉爱博泰克公司);TUBB3抗体、TrkB抗体(美国Proteintech公司);山羊血清(北京索莱宝公司);Triton-100(上海生工生物工程有限公司);其他试剂均为市售分析纯。
FV3000型激光共聚焦显微镜(日本Olympus公司);Operetta Phenix高内涵荧光成像系统(美国PerkinElmer公司);BT25S电子分析天平(德国Sartorius公司);BB15型CO2细胞培养箱(美国Thermo公司);垂直凝胶电泳仪、Gel DOC XR凝胶成像仪(美国Bio-Rad公司);冷冻离心机(美国Thermo公司)。
如先前报道所
根据文献报
将Neuro-2a细胞用含10% FBS的MEM培养基于37 ℃、5% CO2的细胞孵箱中培养,每隔24小时换液。当细胞达到80%~90%融合度后用0.25%胰酶消化,制成单细胞悬液备用。
对细胞进行相应的处理后,弃掉细胞培养基,用预冷的PBS溶液洗涤3次,加入含蛋白酶及磷酸酶抑制剂的RIPA裂解液,转移至新的1.5 mL 离心管,用BCA蛋白试剂盒检测蛋白浓度,加入适量的上样缓冲液后,在95 ℃的金属浴中加热10 min,使蛋白变性。每个泳道加入同等质量的蛋白进行SDS-PAGE电泳。电泳结束后转至PVDF膜,随后用5% BSA溶液封闭60 min;加入5% BSA溶液稀释的一抗溶液(p-TrkB、TrkB、β-actin),4 ℃孵育过夜。用TBST缓冲液洗涤5次后用HRP偶联的山羊抗兔二抗(1∶10 000)室温孵育1 h。随后用ECL化学发光液孵育2 min,使用凝胶成像系统分析。用Image J软件分析图像灰度,以目的蛋白和其内参蛋白β-actin的光密度值做比值,作为目的蛋白的相对表达量,实验重复3次。
将Neuro-2a细胞、小鼠原代神经细胞接种于共聚焦小皿中,在37 ℃、5% CO2的细胞孵箱培养24 h,加入不同质量浓度(1 μg/mL、5 μg/mL)的CBL生理盐水溶液,对照孔加入相应体积的生理盐水,分别于24 h、48 h及72 h弃去小皿中的培养液,用预冷的PBS溶液洗涤3次;加入4%多聚甲醛固定30 min,用PBS洗涤3次;加入5%山羊血清溶液,室温孵育1 h;弃掉5%山羊血清溶液后,加入5%山羊血清稀释后的TUBB3一抗,4 ℃孵育12 h;用PBS溶液洗涤3次,然后用5%山羊血清稀释后的羊抗鼠IgG二抗溶液,室温避光孵育1 h;最后加入Hoechst 33342染液,采用激光扫描共聚焦显微观察并拍照保存,采用Image J软件对图像进行分析。
将Neuro-2a细胞接种在培养皿中,根据文献报

Figure 1 Effect of cerebroprotein hydrolysate for injection (II) (CBL) on axon regeneration of Neuro-2a cells incubated with low serum
A: Representative immunofluorescence staining for the TUBB3 (red) in Neuro-2a cells treated with different concentrations of CBL for 24 h, 48 h and 72 h after low serum culture, scale bar =100 μm; B: Axon length of Neuro-2a cells was measured by Image J software; C: Percentage of the axon of cells was counted by Image J software ()
为了探索CBL对小鼠原代神经细胞轴突再生的作用,将不同浓度的CBL分别处理小鼠原代皮层神经细胞,通过免疫荧光染色检测小鼠原代皮层神经细胞中轴突长度及有轴突细胞的比例。结果如

Figure 2 Effect of CBL on axon regeneration of mouse primary cortical neuronal cells
A: Representative immunofluorescence staining for the TUBB3 (red) and Hoechst (blue) in mouse primary cortical neuronal cells treated with different concentrations of CBL for 24 h, 48 h and 72 h, scale bar =100 μm; B: Axon length of mouse primary cortical neuronal cells was measured by Image J software; C: Percentage of the axon of cells was counted by Image J software ()
为了研究CBL对Neuro-2a细胞轴突再生的作用机制,给予Neuro-2a细胞5 μg/mL的CBL分别处理15 min、30 min及1,3,6,9,12 h,通过Western blot 检测CBL对Neuro-2a细胞TrkB磷酸化水平的影响。结果如

Figure 3 Effect of CBL on the phosphorylation of TrkB at different time points in Neuro-2a cells
A: Neuro-2a cells were treated with CBL (5 μg/mL) at the different time points, and the expression of p-TrkB and total TrkB were detected by Western blot; B: Quantitative measurement of the ratio of p-TrkB/TrkB expression by Image J software ()
为了研究CBL质量浓度与Neuro-2a细胞p-TrkB表达水平是否存在相关性,用0.2、1、5 μg/mL的CBL溶液处理Neuro-2a细胞1 h,通过Western blot检测不同质量浓度的CBL对Neuro-2a细胞内TrkB磷酸化水平的影响。结果如

Figure 4 Effect of CBL on the phosphorylation of TrkB in different concentrations in Neuro-2a cells
A: Neuro-2a cells were treated with different concentrations of CBL for 1 h, and the expression of p-TrkB and total TrkB were detected by Western blot; B: Quantitative measurement of the ratio of p-TrkB/TrkB expression by Image J software ()
上述结果表明,当CBL质量浓度为5 μg/mL、作用于Neuro-2a细胞1 h时,Neuro-2a细胞的TrkB磷酸化水平最高。
为了确定CBL对小鼠原代皮层神经细胞是否也存在这样的机制,用5 μg/mL的CBL处理小鼠原代皮层神经细胞15 min、30 min、1 h、3 h及6 h,通过Western blot 检测小鼠原代皮层神经细胞中TrkB磷酸化水平的变化。结果如

Figure 5 Effect of CBL on the phosphorylation of TrkB at different time points in mouse primary cortical neuronal cells
A: Mouse primary cortical neuronal cells were treated with CBL (5 μg/mL) at the different time points, and the expression of p-TrkB and total TrkB were detected by Western blot; B: Quantitative measurement of the ratio of p-TrkB/TrkB expression by Image J software ()
为了研究CBL质量浓度与小鼠原代皮层神经细胞TrkB磷酸化水平是否存在相关性,用不同浓度的CBL溶液处理小鼠原代皮层神经细胞1 h,用Western blot检测小鼠原代皮层神经细胞中TrkB的磷酸化水平。结果如

Figure 6 Effect of CBL on the phosphorylation of TrkB in different concentrations in mouse primary cortical neuronal cells
A: Mouse primary cortical neuronal cells were treated with different concentrations of CBL for 1 h, and the expression of p-TrkB and total TrkB were detected by Western blot; B: Quantitative measurement of the ratio of p-TrkB/TrkB expression by Image J software ()
上述结果表明,当CBL质量浓度为5 μg/mL,作用于小鼠原代皮层神经细胞1 h时,CBL能够显著上调细胞内TrkB的磷酸化水平,可能通过激活TrkB信号通路促进神经元轴突再生。
中枢神经系统损伤后,通过轴突再生促进中枢神经系统的恢复,但由于自身再生能力差,以及微环境中的抑制因子,导致轴突再生失败,无法修复损伤的中枢神经系统。有研究表明,脑蛋白水解物可以促进突触的再
原肌球蛋白相关激酶(tropomyosin related kinase,Trk)受体是酪氨酸激酶受体家族的一种,包括TrkA、TrkB和TrkC共3种亚
轴突再生的机制尚不清晰,可能涉及到多个神经递质和细胞受体,但与TrkB的关系密切。Zheng
CBL是复合物,成分较为复杂,含有多种氨基酸和小分子多肽。本研究只是证明了CBL可以促进神经细胞轴突再生,无法确定其真正的有效成分。有研究表明,CBL中的有效成分为小分子多肽,发挥着神经营养因子的作用。因此,需要进一步确定CBL中与TrkB结合的多肽,确定CBL中促进神经细胞轴突再生的有效成分,以明确CBL临床发挥药效的有效成分。
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