Department of Medicine, University of California Irvine, Irvine, CA, 92697, USA.
Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA, 95616, USA.
Dig Dis Sci. 2021 Jul;66(7):2250-2260. doi: 10.1007/s10620-020-06389-x. Epub 2020 Jun 17.
Enteropathogenic Escherichia coli (EPEC) infection causes prolonged, watery diarrhea leading to morbidity and mortality. Although EPEC infection impacts nutrient transporter function and expression in intestinal epithelial cells, the effects of EPEC infection on intestinal absorption of ascorbic acid (AA) have not yet been investigated.
To investigate the effect of EPEC infection on intestinal AA uptake process and expression of both AA transporters.
We used two experimental models: human-derived intestinal epithelial Caco-2 cells and mice. C-AA uptake assay, Western blot, RT-qPCR, and promoter assay were performed.
EPEC (WT) as well as ΔespF and ΔespG/G2 mutant-infected Caco-2 cells showed markedly inhibited AA uptake, while other mutants (ΔescN, ΔespA, ΔespB, and ΔespD) did not affect AA uptake. Infection also reduced protein and mRNA expression levels for both hSVCT1 and hSVCT2. EPEC-infected mice showed marked inhibitory effect on AA uptake and decreased protein and mRNA expression levels for both mSVCT1 and mSVCT2 in jejunum and colon. MicroRNA regulators of SVCT1 and SVCT2 (miR103a, miR141, and miR200a) were upregulated significantly upon EPEC infection in both Caco-2 and mouse jejunum and colon. In addition, expression of the accessory protein glyoxalate reductase/hydroxypyruvate reductase (GRHPR), which regulates SVCT1 function, was markedly decreased by EPEC infection in both models.
These findings suggest that EPEC infection causes inhibition in AA uptake through a multifactorial dysregulation of SVCT1 and SVCT2 expression in intestinal epithelial cells.
肠致病性大肠杆菌（EPEC）感染可导致长期的水样腹泻，从而导致发病率和死亡率。尽管 EPEC 感染会影响肠道上皮细胞中的营养转运蛋白功能和表达，但 EPEC 感染对肠道吸收抗坏血酸（AA）的影响尚未得到研究。
研究 EPEC 感染对肠道 AA 摄取过程和 AA 转运蛋白表达的影响。
我们使用了两种实验模型：人源肠道上皮细胞 Caco-2 细胞和小鼠。进行 C-AA 摄取测定、Western blot、RT-qPCR 和启动子测定。
EPEC（WT）以及 ΔespF 和 ΔespG/G2 突变体感染的 Caco-2 细胞表现出明显的 AA 摄取抑制，而其他突变体（ΔescN、ΔespA、ΔespB 和 ΔespD）则不影响 AA 摄取。感染还降低了 hSVCT1 和 hSVCT2 的蛋白和 mRNA 表达水平。EPEC 感染的小鼠表现出明显的 AA 摄取抑制作用，并降低了空肠和结肠中 mSVCT1 和 mSVCT2 的蛋白和 mRNA 表达水平。SVCT1 和 SVCT2 的 microRNA 调节剂（miR103a、miR141 和 miR200a）在 Caco-2 和小鼠空肠和结肠中 EPEC 感染后显著上调。此外，在两种模型中，辅助蛋白乙醛酸还原酶/羟丙酮酸还原酶（GRHPR）的表达显著降低，而 GRHPR 调节 SVCT1 的功能。
这些发现表明，EPEC 感染通过肠道上皮细胞中 SVCT1 和 SVCT2 表达的多因素失调导致 AA 摄取抑制。
