Glutamine Transporter ASCT2 Was Down-Regulated in Ischemic Injured Human Intestinal Epithelial Cells and Reversed by Epidermal Growth Factor

Abstract

Background: Clinically, nutrition support has been an important component of the care of the hypoperfusion traumatized patient who is unable to accept complete volitional nutrition. However, enterocyte transport function during states of intestinal hypoperfusion remains unclear. Glutamine is essential for the viability and growth of intestine epithelial cells, and the Na⁺-dependent neutral amino acid transporter ASCT2 is thought to mainly mediate glutamine transport. This study aims to quantify the change of glutamine transporter ASCT2 expression in ischemic injured Caco-2 cell lines and the regulatory action of epidermal growth factor (EGF) on glutamine transport and its transporter. Methods: Cells were cultured under ischemic conditions for 2 hours. After ischemia was performed, Caco-2 cells were incubated with or without EGF (100 μg/mL) for 0–8 hours. Then we studied the cell membrane l-glutamine transport, the expression of ASCT2 protein, and mRNA. Results: After ischemia was performed, Caco-2 cell membrane glutamine transport decreased significantly (p< .01), and the expression of ASCT2 proteins decreased significantly compared with control (p < .01). Under ischemic conditions, expression of ASCT2 mRNA was down-regulated by a real-time polymerase chain reaction (PCR) method. After EGF incubation for 1–2 hours, the proteins and mRNA of ASCT2 were reversed to normal levels (p > .05). Conclusions: In ischemic injured Caco-2 cells, ASCT2 protein expression and mRNA transcription were involved in the down-regulation of Na⁺-dependent glutamine transport. The decrease of glutamine transport and its transporter under ischemic conditions could be reversed by EGF action. These findings may help in the choice of the nutrition support manner and clinical therapy of ischemia-damaged intestinal epithelial cells.

In this in vitro study, l-glutamine transport and its transporter ASCT2 were found to be significantly decreased in ischemic injured Caco-2 cells. After epidermal growth factor (100 μg/mL) incubation for 1–2 hours, the down-regulation of l-glutamine transport and expression of ASCT2 were reversed.

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