Alleviation of chronic TBI through modulation of calcium signaling

项目摘要：慢性创伤性脑损伤引起的生长激素缺乏症很常见 在伊拉克和阿富汗战争的退伍军人中。这种情况的发生是由于 下丘脑-垂体轴(HPA)功能障碍导致生长激素(GH)水平下降，从而导致 由于医疗、心理和精神方面的后果，对他们的生活质量产生重大影响。《GH》 在大多数情况下，创伤后GHD的替代治疗并不能产生预期的临床结果。 对HPA功能障碍的体征和症状的分析表明，GH分泌的妥协可能是 这是下丘脑上游信号缺陷的结果。因此，我们建议恢复下丘脑- 脑外伤后存活的垂体前叶细胞分泌内源性生长激素对神经的趋性刺激 (生长激素)，导致脑损伤神经元的轴突再生。虽然细胞内钙离子 [Ca~(2+)]_i是调节激素释放的离子通道，负责[Ca~(2+)]_i升高 生长激素在垂体促生长激素细胞中的释放尚不清楚。我们正在进行的研究已经发现，激活 瞬时受体电位经典3(TRPC3)是一种钙离子内流通道，促进囊泡相关的可溶性 N-乙基马来酰亚胺敏感因子附着蛋白受体(SNARE)蛋白复合体相互作用，这是 这是荷尔蒙释放所必需的。此外，TRPC3的阻断显著减弱了[Ca~(2+)]i的内流，即 对生长激素分泌和轴突再生至关重要。因此，我们的中心假设是激动剂的激活 脑垂体细胞中TRPC3的表达触发钙离子内流，导致生长激素分泌增加，这将有助于 再生邻近HPA区受损的轴突。我们建议研究以下两个目标 利用已建立的受控皮质撞击(CCI)致脑损伤小鼠模型：(1)表征 从下丘脑功能恢复看TRPC3在调节GH分泌中的作用 以及(2)确定TRPC3激活刺激脑损伤后轴突再生。 并研究增强TRPC3表达/激活的“概念证据” 改善慢性神经行为异常。我们将进行一系列行为测试，如莫里斯 水迷宫记忆和光束行走测试评估感觉运动协调和运动学习 将这种行为与大脑神经化学联系起来。本研究的结果将：i)找到小说 TRPC3诱导的GH分泌对轴突生长和再生至关重要的机制可用作 发现潜在新治疗选择的工具；ii)阐明生长激素分泌的分子发病机制 在慢性脑损伤后；以及iii)帮助规划和执行未来的调查，以改善和管理脑损伤- 导致退伍军人和平民出现GHD和神经行为异常。

Project Summary: Growth hormone deficiency (GHD) due to chronic traumatic brain injury (TBI) is common among the veterans from the wars in Iraq and Afghanistan. Such condition develops as a result of hypothalamic-pituitary axis (HPA) dysfunction leading to reduced growth hormone (GH) levels, which pose a significant impact on their quality of life due to medical, psychological, and psychiatric consequences. The GH replacement therapy in post-traumatic GHD, in most cases, do not produce the desired clinical outcome. Analysis of the signs and symptoms of HPA dysfunction suggests that compromise in GH secretion may be as a result of defective upstream hypothalamic signaling. Thus, we propose to restore the hypothalamic- neurotropic stimulation by endogenous GH secretion from the surviving (post-TBI) anterior pituitary cells (somatotrophs), leading to axonal regeneration of TBI-damaged neurons. Although intracellular calcium ion (Ca2+) concentration ([Ca2+]i) can regulate hormone release, the ion channel responsible for increasing [Ca2+]i the GH release in pituitary somatotrophs is unknown. Our ongoing studies have identified that activation of Transient Receptor Potential Canonical 3 (TRPC3), a Ca2+ influx channel, facilitates vesicle-associated soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein complex interactions, which is necessary for hormonal release. Moreover, disruption of TRPC3 markedly attenuated [Ca2+]i entry, which is essential for GH secretion and axonal regeneration. Thus, our central hypothesis is that the agonist activation of TRPC3 in pituitary cells triggers Ca2+ entry, resulting in enhanced GH secretion, which will help to regenerate those damaged axons in the adjacent HPA region. We propose to study the following two Aims using an established controlled cortical impact (CCI)-induced injury mouse model of TBI: (1) Characterization of the role of TRPC3 in regulating GH secretion by examining the functional restoration of hypothalamic neurotropic connections in TBI; and (2) Determine that TRPC3 activation stimulates axonal regeneration in TBI-damaged neurons and examine a “proof of concept” that augmenting TRPC3 expression/activation ameliorates chronic neurobehavioral abnormalities. We will perform a series of behavioral tests such as Morris water maze for memory and beam walk test to assess sensorimotor coordination and motor learning for correlating the behavior with brain neurochemistry. The results of the present study will: i) find the novel mechanism of TRPC3-induced GH secretion essential for axonal growth and regeneration that can be used as a tool to identify potential new therapeutic options; ii) elucidate the molecular pathogenesis of GH secretion following chronic TBI; and iii) help to plan and execute future investigations to improve and manage TBI- induced GHD and neurobehavioral abnormalities in both veterans and civilians.