Data_Sheet_1_Long-Term Effect of Post-traumatic Stress in Adolescence on Dendrite Development and H3K9me2/BDNF Expression in Male Rat Hippocampus and Prefrontal Cortex.pdf

Exposure to a harsh environment in early life increases in the risk of post-traumatic stress disorder (PTSD) of an individual. Brain derived neurotrophic factor (BDNF) plays an important role in neurodevelopment in developmental stages. Both chronic and traumatic stresses induce a decrease in the level of BDNF and reduce neural plasticity, which is linked to the pathogenesis of PTSD. Also, studies have shown that stress alters the epigenetic marker H3K9me2, which can bind to the promoter region of the Bdnf gene and reduce BDNF protein level. However, the long-term effects of traumatic stress during adolescence on H3K9me2, BDNF expression and dendrite development are not well-known. The present study established a model of PTSD in adolescent rats using an inescapable foot shock (IFS) procedure. Anxiety-like behaviors, social interaction behavior and memory function were assessed by the open field test, elevated plus maze test, three-chamber sociability test and Morris water maze test. In addition, neuronal development and H3K9me2/BDNF expression in hippocampus (HIP) and prefrontal cortex (PFC) were evaluated by Golgi staining, western blotting, qRT-PCR analysis and CHIP-qPCR analysis. Additionally, the Unc0642, a small molecule inhibitor of histone methyltransferase (EHMT2) was used for intervention. The results showed that the IFS procedure induced the PTSD-like behaviors in rats, resulted in fewer dendrite branches and shorter dendrite length in CA1 of HIP and PFC, increased H3K9me2 level and decreased BDNF expression in HIP and PFC. Also, although all the changes can persist to adulthood, Unc0642 administration relieved most of alterations. Our study suggests that traumatic stress in adolescence leads to immediate and long-term mental disorders, neuronal morphological changes, lower BDNF level and increased H3K9me2 level in the HIP and PFC, indicating that H3K9me2/BDNF dysfunction plays a key role in pathogenesis of PTSD.

生命早期暴露于恶劣环境会增加个体罹患创伤后应激障碍（post-traumatic stress disorder, PTSD）的风险。脑源性神经营养因子（Brain derived neurotrophic factor, BDNF）在发育阶段的神经发育中发挥重要作用。慢性应激与创伤性应激均可降低BDNF水平并削弱神经可塑性，这与PTSD的发病机制密切相关。此外，已有研究表明，应激会改变表观遗传标记组蛋白H3赖氨酸9二甲基化（H3K9me2），后者可结合至Bdnf基因的启动子区域，进而降低BDNF蛋白的表达水平。然而，青春期创伤性应激对H3K9me2、BDNF表达以及树突发育的长期影响尚不清楚。
本研究采用不可逃避足底电击（inescapable foot shock, IFS）范式构建青春期大鼠PTSD模型。通过旷场实验、高架十字迷宫实验、三箱社交实验以及莫里斯水迷宫实验，分别评估大鼠的焦虑样行为、社交互动行为与记忆功能。此外，通过高尔基染色、蛋白质免疫印迹（Western Blotting）、实时定量荧光聚合酶链反应（qRT-PCR）以及染色质免疫沉淀-实时定量PCR（CHIP-qPCR）分析，检测海马体（HIP）与前额叶皮层（PFC）内的神经元发育情况以及H3K9me2/BDNF的表达水平。本研究还使用组蛋白甲基转移酶（EHMT2）的小分子抑制剂Unc0642进行干预。
结果显示，IFS范式可诱导大鼠出现PTSD样行为，导致海马CA1区与前额叶皮层的树突分支减少、树突长度缩短；同时升高海马体与前额叶皮层内的H3K9me2水平，并降低BDNF的表达。上述所有变化均可持续至成年阶段，而Unc0642给药可缓解大部分异常改变。
本研究表明，青春期创伤性应激会引发即时与长期的精神障碍、神经元形态学改变，降低海马体与前额叶皮层内的BDNF水平并升高H3K9me2水平，提示H3K9me2/BDNF功能异常在PTSD的发病机制中发挥关键作用。