Enteropathogenic Escherichia coli Infection Inhibits Intestinal Ascorbic Acid Uptake via Dysregulation of Its Transporter Expression

Background EnteropathogenicEscherichia 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. Aims To investigate the effect of EPEC infection on intestinal AA uptake process and expression of both AA transporters. Methods We used two experimental models: human-derived intestinal epithelial Caco-2 cells and mice.C-14-AA uptake assay, Western blot, RT-qPCR, and promoter assay were performed. Results EPEC (WT) as well as Delta espFand Delta espG/G2mutant-infected Caco-2 cells showed markedly inhibited AA uptake, while other mutants (Delta escN,Delta espA,Delta espB, and Delta espD) 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. Conclusions These findings suggest that EPEC infection causes inhibition in AA uptake through a multifactorial dysregulation of SVCT1 and SVCT2 expression in intestinal epithelial cells.

Automated summary

EPEC infection inhibits intestinal absorption of ascorbic acid (AA) through a multifactorial dysregulation of SVCT1 and SVCT2 expression in intestinal epithelial cells. This study also found that microRNA regulators miR103a, miR141, and miR200a were upregulated significantly upon EPEC infection, and EPEC infection significantly decreased the expression of the accessory protein GRHPR which regulates SVCT1 function.