proBDNF对大鼠后足切割疼痛的影响

目的 研究大鼠后足切割后proBDNF在脊髓和背根神经节的表达及注射proBDNF后大鼠的行为学变化.方法 ①16只大鼠随机分为切割组和对照组,切割组建立后足切割模型,取2组大鼠的脊髓和背根神经节行免疫荧光实验;②48只大鼠随机分为6组,每组8只,proBDNF腹腔注射大(Ⅰ组)、中(Ⅱ组)、小剂量组(Ⅲ组),鞘内注射组(Ⅳ组),足底注射组(Ⅴ组)和对照组(Ⅵ组).各组大鼠建立后足切割模型,均行缩足阈值测定.结果 ①切割后1 h大鼠背根神经节proBDNF的表达增强,脊髓proBDNF的表达没有明显变化;②Ⅰ组、Ⅱ组大鼠切割后大鼠右后足的机械痛阈明显高于Ⅲ组和Ⅵ组;Ⅳ组和Ⅴ组大鼠切割后大鼠右后足的机械痛阈与Ⅵ组相比无统计学意义.结论 proBDNF在转运至脊髓之前已经转变为成体BDNF或者与其受体结合,腹腔注射proBDNF具有明显的止痛效果,并且其止痛作用有封顶效应.     

BDNF前体蛋白在成年恒河猴中枢神经系统中的分布

采用免疫组织化学方法探讨脑源性神经营养因子前体蛋白(proBDNF)在成年恒河猴中枢神经系统(CNS)内的定位分布。结果显示:不同染色强度的proBDNF免疫阳性反应产物广泛分布于大脑皮质、海马、丘脑、小脑、中脑、脑桥、延髓和脊髓。神经元和胶质细胞的核染色明显,胞浆淡染,突起无染色。本研究结果表明在CNS的各个部位均存在proBDNF,提示proBDNF在猴的CNS广泛发挥作用。通过与文献报道的proBDNF在大鼠CNS的分布比较,发现proBDNF在不同物种之间的表达模式和作用可能存在差异;而与BDNF在成年猴脑中的分布进行比较,发现proBDNF在猴小脑的Purkinje细胞层及动眼神经核单独表达,提示proBDNF在这些部位可能发挥重要作用。本研究结果为探讨proBDNF在成年猴的分布及作用提供了重要的形态学资料。     

Spatial memory training modifies the expression of brain-derived neurotrophic factor tyrosine kinase receptors in young and aged rats

Aging leads to alterations in the function of the hippocampus, a brain structure largely involved in learning processes. This study aimed at examining the basal levels and the impact of a learning-associated task on brain-derived neurotrophic factor (BDNF), on BDNF full-length catalytic receptor (TrkB.FL) and on the truncated forms (TrkB.T1 and TrkB.T2) receptor expression (mRNA and protein) in the hippocampus of young (2-month-old) and aged (24-month-old) Wistar rats. Spatial memory was evaluated using a water-maze procedure involving visible and invisible platform location learning. Aged rats showed higher latencies during the first two training days but rapidly exhibited learning performances similar to patterns observed with young rats. Real-time PCR measurements showed that aged rats had significantly higher levels of trkB.FL mRNAs than young rats under basal conditions. In situ hybridization analysis indicated that the highest level of trkB.FL mRNA (mRNA encoding for TrkB.FL receptor) was noted in the dentate gyrus, and in the CA2 and CA3 hippocampal layers. In contrast, there was no marked difference in trkB.T1 signal in any hippocampal region. Training induced a significant reduction in trkB.FL mRNA levels solely in aged rats. In contrast, in young and aged rats, trkB.T2 mRNA levels were significantly increased after training. Measurements of proteins revealed that learning significantly increased TrkB.FL content in aged rats. Untrained aged rats presented higher levels of BDNF and brain-derived neurotrophic factor precursor (proBDNF) proteins than young rats. Training strongly increased precursor BDNF metabolism in young and aged rats, resulting in increased levels of proBDNF in the two groups but in old rats the mature BDNF level did not change. This study shows that Wistar rats present age-related differences in the levels of BDNF and TrkB isoforms and that spatial learning differentially modifies some of these parameters in the hippocampus.     

脑源性神经营养因子前体对阿尔茨海默病大鼠海马齿状回神经元增殖和分化的影响

目的 观察脑源性神经营养因子前体(pmBDNF)对阿尔茨海默病(AD)大鼠模型海马齿状回神经元增殖和分化的影响.方法 成功建立AD大鼠模型后,采用微量渗透泵连续14 d向右侧海马注射proBDNF、羊抗proBDNF抗体或正常羊血清,浓度均为1μg/μl,速度0.5μ/h,同时给予5-溴-2'-脱氧尿核苷(BrdU)50 ms/kg·体重腹腔注射,每日 2次,持续14 d.免疫组化染色并统计新生细胞数量;应用BrdU与微管相关蛋白Doublecortin抗体/抗胶质纤维酸性蛋白抗体免疫三标记法,鉴别BrdU阳性细胞的细胞类型.结果 proBDNF组BrdU阳性细胞数明显低于正常羊血清对照组,而抗proBDNF组则明显高于对照组.proBDNF组、抗proBDNF组以及对照组中各细胞类型的百分比差异无统计学意义.结论 proBDNF能够抑制AD大鼠海马齿状回的细胞增殖,而采用特异性抗proBDNF以拮抗内源性pwBDNF能够促进海马齿状回的细胞增殖,这一功能对于AD的治疗可能有重要的意义.     

脑源性神经营养因子前体的研究进展

神经营养因子是一种分泌性多肽类生长因子家族,参与神经系统的多种生理功能活动,研究发现成熟的脑源性神经营养因子与其前体分子具有不同的生物学活性,它们的受体以及介导的细胞内信号通路也大相径庭。本文对近年来关于脑源性神经营养因子前体分子的研究进展予以综述,着重讨论其体内分布、生物合成与分泌、生物学活性以及与疾病的联系。研究脑源性神经营养因子前体分子在生理和病理状态下的作用将对未来的药物开发和神经系统疾病的治疗具有重要的意义。     

Distinct signaling pathways of precursor BDNF and mature BDNF in cultured cerebellar granule neurons

Recent studies have focused on a distinctive contrast between bioactivities of precursor brain-derived neurotrophic factor (proBDNF) and mature BDNF (matBDNF). In this study, using a proteolytic cleavage-resistant proBDNF mutant (CR-proBDNF), signaling mechanisms underlying the proapoptotic effect of proBDNF and antiapoptotic effect of matBDNF on the low potassium (LK)-inducing cell death of cultured cerebellar granule neurons (CGNs) were analyzed. A time course study demonstrated that unlike matBDNF, CR-proBDNF failed to induce TrkB phosphorylation for up to 360 min. CR-proBDNF did not activate ERK-1, ERK-2 and Akt, which are involved in TrkB-induced cell survival signaling, while matBDNF activated these kinases. On the other hand treatment of CGNs with CR-proBDNF led to a rapid activation of Rac-GTPase and phosphorylation of JNK which are involved in p75^NTR-induced apoptosis. In addition, a JNK-specific inhibitor, SP600125, inhibited the CR-proBDNF-induced apoptosis but did not affect the antiapoptotic effect of matBDNF. CR-proBDNF treatment led to an earlier appearance of active caspase-3. In contrast, matBDNF dramatically postponed the appearance of active caspase-3. Not like other signaling molecules, activation of caspase-3 was conversely regulated by both CR-proBDNF and matBDNF. These results thus suggest that in CGNs proBDNF elicits apoptosis via activation of p75^NTR, Rac-GTPase, JNK, and caspase-3, while matBDNF signals cell survival via activation of TrkB, ERKs and Akt, and deactivation of caspase-3.