Guan Le, Shi Xi, Tang Ying, Yan Yan, Chen Liang, Chen Yu, Gao Guangcheng, Lin Chun, Chen Aiqin
Fujian Provincial Key Laboratory of Brain Aging and Neurodegenerative Diseases, School of Basic Medical Sciences, Pain Research Institute, Fujian Medical University, Fuzhou, China.
Department of Medical Oncology, The First Affiliated Hospital of Fujian Medical University, Fuzhou, China.
Front Neurosci. 2022 May 6;16:843396. doi: 10.3389/fnins.2022.843396. eCollection 2022.
Patients with irritable bowel syndrome (IBS) experience not only enhanced visceral pain but also emotional comorbidities, such as anxiety and depression. Early life stress (ELS) is a high-risk for the development of IBS. Literatures have reported an important epigenetic modulation in sustaining extrinsic phenotypes. The amygdala is closely related to the regulation of visceral functions and emotional experiences. In this study, we hypothesized that ELS-induced reprogramming inappropriate adaptation of histone acetylation modification in the amygdala may result in visceral hypersensitivity and anxiety-like behaviors in ELS rats. To test this hypothesis, the model of ELS rats was established by neonatal colorectal dilatation (CRD). Visceral hypersensitivity was assessed based on the electromyography response of the abdominal external oblique muscle to CRD. Emotional comorbidities were examined using the elevated plus maze test, open field test, and sucrose preference test. Trichostatin A (TSA) and C646 were microinjected into the central amygdala (CeA) individually to investigate the effects of different levels of histone acetylation modification on visceral hypersensitivity and emotion. We found neonatal CRD resulted in visceral hypersensitivity and anxiety-like behaviors after adulthood. Inhibiting histone deacetylases (HDACs) in the CeA by TSA enhanced visceral sensitivity but did not affect anxiety-like behaviors, whereas inhibiting HAT by C646 attenuated visceral hypersensitivity in ELS rats. Interestingly, CeA treatment with TSA induced visceral sensitivity and anxiety-like behaviors in the control rats. Western blot showed that the expressions of acetylated 9 residue of Histone 3 (H3K9) and protein kinase C zeta type (PKMζ) were higher in the ELS rats compared to those of the controls. The administration of the PKMζ inhibitor ZIP into the CeA attenuated visceral hypersensitivity of ELS rats. Furthermore, the expression of amygdala PKMζ was enhanced by TSA treatment in control rats. Finally, western blot and immunofluorescence results indicated the decrease of HDAC1 and HDAC2 expressions, but not HDAC3 expression, contributed to the enhancement of histone acetylation in ELS rats. Our results support our hypothesis that amygdala-enhanced histone acetylation induced by stress in early life results in visceral hypersensitivity and anxiety-like behaviors in ELS rats, and reversing the abnormal epigenetic mechanisms may be crucial to relieve chronic symptoms in ELS rats.
肠易激综合征（IBS）患者不仅会经历内脏疼痛加剧，还会出现焦虑和抑郁等情绪共病。早年生活应激（ELS）是IBS发病的高危因素。文献报道了一种在维持外在表型中起重要作用的表观遗传调控。杏仁核与内脏功能调节和情绪体验密切相关。在本研究中，我们假设ELS诱导的杏仁核组蛋白乙酰化修饰的重编程不适当适应可能导致ELS大鼠出现内脏超敏反应和焦虑样行为。为了验证这一假设，通过新生大鼠结肠扩张（CRD）建立ELS大鼠模型。基于腹外斜肌对CRD的肌电图反应评估内脏超敏反应。使用高架十字迷宫试验、旷场试验和蔗糖偏好试验检测情绪共病情况。将曲古抑菌素A（TSA）和C646分别微量注射到中央杏仁核（CeA）中，以研究不同水平的组蛋白乙酰化修饰对内脏超敏反应和情绪的影响。我们发现新生大鼠CRD在成年后导致内脏超敏反应和焦虑样行为。TSA抑制CeA中的组蛋白去乙酰化酶（HDACs）可增强内脏敏感性，但不影响焦虑样行为，而C646抑制组蛋白乙酰转移酶（HAT）可减轻ELS大鼠的内脏超敏反应。有趣的是，用TSA处理CeA会在对照大鼠中诱导内脏敏感性和焦虑样行为。蛋白质印迹法显示，与对照组相比，ELS大鼠中组蛋白3第9位赖氨酸残基（H3K9）的乙酰化表达和蛋白激酶Cζ型（PKMζ）的表达更高。将PKMζ抑制剂ZIP注入CeA可减轻ELS大鼠的内脏超敏反应。此外，TSA处理可增强对照大鼠杏仁核PKMζ的表达。最后，蛋白质印迹法和免疫荧光结果表明，HDAC1和HDAC2表达的降低而非HDAC3表达的降低导致了ELS大鼠组蛋白乙酰化的增强。我们的结果支持了我们的假设，即早年生活应激诱导的杏仁核组蛋白乙酰化增强导致ELS大鼠出现内脏超敏反应和焦虑样行为，逆转异常的表观遗传机制可能对缓解ELS大鼠的慢性症状至关重要。
