Alterations in hexose, amino acid and peptide transporter expression in intestinal epithelial cells during Nippostrongylus brasiliensis infection in the rat

Abstract

Infection with the nematode Nippostrongylus brasiliensis induces various types of cytological alterations in the intestinal villus epithelium. The aim of this study was to analyse the expression of hexose, peptide and amino acid transporters in the small intestinal epithelium after infection. Brown-Norway rats were infected with 2000 N. brasiliensis L3 larvae and villus epithelial cells were isolated at various time points after infection. Expression of hexose transporters Na +/glucose cotransporter SGLT1 and glucose transporter GLUT-1, -2 and -5, a peptide transporter (PepT1) and an amino acid transporter (LAT2) was examined by reverse transcription-PCR, Western blotting or immunohistochemistry. Semi-quantitative reverse transcription-PCR studies of separated jejunal epithelial cells showed that expression levels of GLUT5, PepT1 and LAT2 were significantly decreased 7 and 14 days after infection, while these changes were not observed in the ileal epithelium. Although the apical surface glucose transporter SGLT1 showed no significant alteration in mRNA expression, Western blotting analyses of jejunal epithelial cell lysate showed a marked decrease. Contrary to SGLT1, GLUT5, PepT1 and LAT2, expression of GLUT1, which is essential in maintaining high rates of glucose influx, was significantly up-regulated in the jejunal epithelium 7 and 14 days after infection in reverse transcription-PCR as in Western blotting analyses. Immunohistochemical studies showed that GLUT1 immunoreactivity was localised to the basolateral membrane of intestinal epithelial cells 7 days after infection. These results show that N. brasiliensis infection results in an increase in GLUT1 and a decrease in various hexose, amino acid and peptide transporter expression in jejunal epithelial cells. Up-regulation of GLUT1 might be a compensatory response in injured epithelial cells.