Abstract：
Diabetes leads to intestinal barrier dysfunction. 5-Hydroxytryptamine 4 receptor (5-HT4R) is distributed in the colonic mucosa, but little is known about the role of its activation in diabetes-evoked colonic barrier dysfunction. This study investigates whether activation of 5-HT4Rs on goblet cells (GCs) protects the colon from commensal bacterial translocation in diabetic mice. Expression of 5-HT4R detected inside the colonic epithelium by RNAscope in situ hybridization was further observed within the mucin 2 (MUC2)-immunoreactive GCs. In diabetic mice, neither 5-HT4R transcription nor protein levels were altered compared with those in nondiabetic mice. Bacterial translocation was characterized by 16S rRNA RNAscope in situ hybridization and manifested in both crypts and lamina propria of the colon in diabetic mice. Mucin production and MUC2 expression were significantly decreased in diabetic mice. Furthermore, the loss of mitochondrial cristae of GCs and the down-regulation of mitofilin, the core protein maintaining mitochondrial homeostasis, were observed in diabetic mice. Long-term treatment with 5-HT4R agonist in diabetic mice not only prevented bacterial penetration of the whole colonic mucosa but also promoted mucin production and MUC2 expression. Markedly, 5-HT4R agonist also restored the mitochondrial cristae of GCs and up-regulated mitofilin. However, co-administration of 5-HT4R antagonist abolished the effects of 5-HT4R agonist on diabetic mice. These findings indicate that 5-HT4R in colonic mucosa is an effective target for the treatment of diabetes-induced colonic mucous barrier dysfunction.
摘要：
糖尿病导致肠屏障功能障碍。5-羟色胺4受体（5-HT4R）分布在结肠粘膜，但对其激活在糖尿病诱发的结肠屏障功能障碍中的作用知之甚少。这项研究调查了5-HT4Rs在杯状细胞（GC）上的激活是否保护糖尿病小鼠的结肠免受共生细菌易位。在粘蛋白2（MUC2）免疫反应性GC中进一步观察到通过RNAscope原位杂交在结肠上皮内检测到的5-HT4R的表达。在糖尿病小鼠中，与非糖尿病小鼠相比，5-HT4R转录和蛋白质水平均未改变。细菌易位的特征是16SrRNARNAscope原位杂交，并在糖尿病小鼠的结肠隐窝和固有层中均有表现。糖尿病小鼠的粘蛋白产生和MUC2表达显著降低。此外，GCs线粒体cristae的丢失和mitofilin的下调，维持线粒体稳态的核心蛋白，在糖尿病小鼠中观察到。在糖尿病小鼠中使用5-HT4R激动剂的长期治疗不仅阻止了细菌对整个结肠粘膜的渗透，而且还促进了粘蛋白的产生和MUC2的表达。很明显，5-HT4R激动剂还恢复了GC的线粒体cr和上调的丝裂素。然而,共同施用5-HT4R拮抗剂消除了5-HT4R激动剂对糖尿病小鼠的作用。这些发现表明结肠粘膜中的5-HT4R是治疗糖尿病引起的结肠粘膜屏障功能障碍的有效靶标。
