Maki Takehiro, Arishima Kazuyoshi, Yamamoto Masako, Sakaue Motoharu
Neurol Res. 2015 Jan;37(1):30-4. doi: 10.1179/1743132814Y.0000000403. Epub 2014 Jun 16.
Brain-derived neurotrophic factor (BDNF) binds to its high-affinity binding receptor, tropomyosin-related kinase (Trk) B, and can induce neuronal differentiation and survival. BDNF also accelerates neuronal cell death in a glutamate-induced model; however, it has been unknown whether the mechanism involves TrkB. In the current study, to determine the role of TrkB in neuronal cell death, we investigated TrkB involvement in BDNF acceleration of glutamate-induced neuronal death.
A TrkB-stable transformant of rat neuroblastoma B35 (B35(TrkB)) cells was utilized to investigate whether TrkB is involved in BDNF acceleration of neuronal death. The cell viability of the B35(TrkB) cells was compared to that of mock vector-transgened B35 (B35(mock)) cells after treatment with/without BDNF and glutamate.
In both B35(TrkB) and B35(mock) cells, glutamate treatment decreased the cell viability. BDNF treatment further accelerated the decrease in the viability of B35(TrkB) cells, but not that in the viability of B35(mock) cells. At glutamate concentrations that did not significantly decrease cell viability, BDNF increased the cell viability of B35(TrkB), but not that of B35(mock). A mitogen-activated protein kinase (MAPK) inhibitor, U0126, suppressed BDNF's accelerating effect on cell death. Although B35 parental cells endogenously express other neurotrophin receptors such as TrkA, nerve growth factor β (a ligand of TrkA and p75(NTR)) could not influence the viability of B35(TrkB) or B35(mock) cells.
These results indicate that TrkB is an intermediator for the trophic and toxicity-exacerbating effects of BDNF against cell viabilities at non-cytotoxic and cytotoxic glutamate concentrations, respectively.
脑源性神经营养因子（BDNF）与其高亲和力结合受体原肌球蛋白相关激酶（Trk）B结合，可诱导神经元分化和存活。在谷氨酸诱导的模型中，BDNF也会加速神经元细胞死亡；然而，其机制是否涉及TrkB尚不清楚。在本研究中，为了确定TrkB在神经元细胞死亡中的作用，我们研究了TrkB在BDNF加速谷氨酸诱导的神经元死亡中的作用。
利用大鼠神经母细胞瘤B35（B35(TrkB)）细胞的TrkB稳定转化体，研究TrkB是否参与BDNF加速神经元死亡的过程。在用/不用BDNF和谷氨酸处理后，将B35(TrkB)细胞的细胞活力与空载体转基因B35（B35(mock)）细胞的细胞活力进行比较。
在B35(TrkB)和B35(mock)细胞中，谷氨酸处理均降低了细胞活力。BDNF处理进一步加速了B35(TrkB)细胞活力的下降，但未加速B35(mock)细胞活力的下降。在谷氨酸浓度未显著降低细胞活力时，BDNF增加了B35(TrkB)细胞的活力，但未增加B35(mock)细胞的活力。丝裂原活化蛋白激酶（MAPK）抑制剂U0126抑制了BDNF对细胞死亡的加速作用。尽管B35亲本细胞内源性表达其他神经营养因子受体，如TrkA，但神经生长因子β（TrkA和p75(NTR)的配体）不影响B35(TrkB)或B35(mock)细胞的活力。
这些结果表明，TrkB分别是BDNF在非细胞毒性和细胞毒性谷氨酸浓度下对细胞活力的营养作用和毒性加剧作用的介质。
