Feng Jing, Hibberd Tim J, Luo Jialie, Yang Pu, Xie Zili, Travis Lee, Spencer Nick J, Hu Hongzhen
Center for the Study of Itch and Sensory Disorders, Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, United States.
Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
Front Cell Neurosci. 2022 Mar 3;16:799717. doi: 10.3389/fncel.2022.799717. eCollection 2022.
How the enteric nervous system determines the pacing and propagation direction of neurogenic contractions along the colon remains largely unknown. We used a chemogenetic strategy to ablate enteric neurons expressing calretinin (CAL). Mice expressing human diphtheria toxin receptor (DTR) in CAL neurons were generated by crossing mice with -dependent mice. Immunohistochemical analysis revealed treatment with diphtheria toxin incurred a 42% reduction in counts of Hu-expressing colonic myenteric neurons ( = 0.036), and 57% loss of CAL neurons (comprising ∼25% of all Hu neurons; = 0.004) compared to control. As proportions of Hu-expressing neurons, CAL neurons that contained nitric oxide synthase (NOS) were relatively spared (control: 15 ± 2%, CAL-DTR: 13 ± 1%; = 0.145), while calretinin neurons lacking NOS were significantly reduced (control: 26 ± 2%, CAL-DTR: 18 ± 5%; = 0.010). Colonic length and pellet sizes were significantly reduced without overt inflammation or changes in ganglionic density. Interestingly, colonic motor complexes (CMCs) persisted with increased frequency (mid-colon interval 111 ± 19 vs. 189 ± 24 s, CAL-DTR vs. control, respectively, < 0.001), decreased contraction size (mid-colon AUC 26 ± 24 vs. 59 ± 13 gram/seconds, CAL-DTR vs. control, respectively, < 0.001), and lacked preferential anterograde migration ( < 0.001). The functional effects of modest calretinin neuron ablation, particularly increased neurogenic motor activity frequencies, differ from models that incur general enteric neuron loss, and suggest calretinin neurons may contribute to pacing, force, and polarity of CMCs in the large bowel.
肠神经系统如何决定神经源性收缩沿结肠的起搏和传播方向在很大程度上仍然未知。我们采用化学遗传学策略来消融表达钙视网膜蛋白（CAL）的肠神经元。通过将小鼠与依赖小鼠杂交，产生了在CAL神经元中表达人白喉毒素受体（DTR）的小鼠。免疫组织化学分析显示，与对照组相比，用白喉毒素处理后，表达Hu的结肠肌间神经元数量减少了42%（P = 0.036），CAL神经元减少了57%（占所有Hu神经元的约25%；P = 0.004）。作为表达Hu的神经元比例，含有一氧化氮合酶（NOS）的CAL神经元相对保留（对照组：15±2%，CAL-DTR组：13±1%；P = 0.145），而缺乏NOS的钙视网膜蛋白神经元显著减少（对照组：26±2%，CAL-DTR组：18±5%；P = 0.010）。结肠长度和粪便颗粒大小显著减小，且无明显炎症或神经节密度变化。有趣的是，结肠运动复合体（CMC）持续存在，频率增加（结肠中部间隔分别为111±19秒和189±24秒，CAL-DTR组与对照组相比，P < 0.001），收缩幅度减小（结肠中部曲线下面积分别为26±24和59±13克/秒，CAL-DTR组与对照组相比，P < 0.001），并且缺乏优先的顺行迁移（P < 0.001）。适度消融钙视网膜蛋白神经元的功能效应，特别是神经源性运动活动频率增加，与导致一般肠神经元丢失的模型不同，提示钙视网膜蛋白神经元可能有助于大肠中CMC的起搏、力量和极性。
