Objective: To investigate the mechanisms that mediate the neuroprotective effect of the intestinal microbial metabolite sodium butyrate (NaB) in a mouse model of Parkinson's disease (PD) via the gut-brain axis.
Methods: Thirty-nine 7-week-old male C57BL/6J mice were randomized equally into control group, PD model group, and NaB treatment group. In the latter two groups, PD models were established by intraperitoneal injection of 30 mg/kg 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) once daily for 5 consecutive days, and normal saline was injected in the control group. After modeling, the mice received daily gavage of NaB (300 mg/kg) or an equal volume of saline for 14 days. Behavioral tests were carried out to assess the changes in motor function of the mice, and Western blotting was performed to detect the expressions of tyrosine hydroxylase (TH) and α-synuclein (α-syn) in the striatum and nuclear factor-κB (NF-κB), tumor necrosis factor (TNF-α), interleukin 6 (IL-6), and the tight junction proteins ZO-1, Occludin, and Claudinin the colon. HE staining was used to observe inflammatory cell infiltration in the colon of the mice. RNA sequencing analysis was performed to identify the differentially expressed genes in mouse colon tissues, and their expressions were verified using qRT-PCR and Western blotting.
Results: The mouse models of PD with NaB treatment showed significantly increased movement speed and pulling strength of the limbs with obviously upregulated expressions of TH, Occludin, and Claudin and downregulated expressions of α-syn, NF-κB, TNF-α, and IL-6 (all P < 0.05). HE staining showed that NaB treatment significantly ameliorated inflammatory cell infiltration in the colon of the PD mice. RNA sequencing suggested that Bmal1 gene probably mediated the neuroprotective effect of NaB in PD mice (P < 0.05).
Conclusion: NaB can improve motor dysfunction, reduce dopaminergic neuron loss in the striatum, and ameliorate colonic inflammation in PD mice possibly through a mechanism involving Bmal1.
目的: 探究肠道微生物代谢产物丁酸钠（NaB）通过肠-脑轴对帕金森病（PD）小鼠发挥神经保护作用及其潜在机制。
方法: 39只7周龄雄性C57BL/6J小鼠随机均分为对照组（NC）、模型组（PD）和NaB治疗组（NaB），13只/组。除NC组小鼠注射等体积生理盐水外，其余各组连续5 d腹腔注射1-甲基-4-苯基-1，2，3，6-四氢吡啶［MPTP，30 mg/（kg·d）］建立亚急性PD模型。造模完成后NaB组连续灌胃NaB［300 mg/（kg·d）］治疗14 d，其余两组小鼠灌胃等体积的生理盐水。治疗结束后进行行为学实验检测小鼠的运动功能。Western blot分别检测小鼠纹状体中酪氨酸羟化酶（TH）、α-突触核蛋白（α-syn）的表达和结肠中促炎因子核因子κB（NF-κB）、肿瘤坏死因子（TNF-α）、白介素6（IL-6）以及紧密连接蛋白ZO-1、occludin、claudin的表达。通过HE染色观察小鼠结肠的炎性浸润。RNA测序分析筛选出小鼠结肠组织的差异基因。
结果: 行为学实验结果显示，NaB治疗可提高PD小鼠的运动速度（P<0.01）以及四肢拉力（P<0.05）。Western blot结果显示，NaB上调PD小鼠纹状体中TH（P<0.01）和下调α-syn（P<0.05）的表达，NaB上调PD小鼠结肠组织中的Occludin和Claudin的表达（P<0.05），下调了NF-κB、TNF-α和IL-6的表达（P<0.05）。HE染色结果显示，NaB改善PD小鼠结肠的炎性浸润。结肠RNA测序结果显示，节律基因Bmal1可能介导了NaB对PD小鼠的神经保护作用（P<0.05）。总结 NaB改善PD小鼠的运动障碍，减少纹状体的多巴胺能神经元的丢失，并改善PD小鼠的结肠炎症，其机制可能与Bmal1有关。
Keywords: Bmal1; Parkinson's disease; gut-brain axis; sodium butyrate.