Mechanism of leukotriene D4 inhibition of Na-alanine cotransport in intestinal epithelial cells.
In a rabbit model of chronic intestinal inflammation, we previously demonstrated inhibition of neutral Na-amino acid cotransport. The mechanism of the inhibition was secondary to a decrease in the affinity for amino acid rather than the number of cotransporters. Since leukotriene (LT)D4 is known to be elevated in enterocytes during chronic intestinal inflammation, we used rat intestinal epithelial cell (IEC-18) monolayers to determine the mechanism of regulation of Na-alanine cotransport (alanine, serine, cysteine transporter 1: ASCT1) by LTD4. Na-alanine cotransport was inhibited by LTD4 in IEC-18 cells. The mechanism of inhibition of ASCT1 (solute carrier, SLC1A4) by LTD4 is secondary to a decrease in the affinity of the cotransporter for alanine without a significant change in cotransporter numbers and is not secondary to an alteration in the Na+ extruding capacity of the cells. Real-time quantitative PCR and Western blot analysis results indicate that ASCT1 message and protein levels are also unchanged in LTD4-treated IEC-18 cells. These results indicate that LTD4 inhibits Na-dependent neutral amino acid cotransport in IEC. The mechanism of inhibition is secondary to a decrease in the affinity for alanine, which is identical to that seen in villus cells from the chronically inflamed rabbit small intestine, where LTD4 levels are significantly increased.
Talukder
Jamilur R
JR
Section of Digestive Diseases, Department of Medicine, West Virginia University, Morgantown, WV 26506, USA.
Kekuda
Ramesh
R
Saha
Prosenjit
P
Sundaram
Uma
U
D026921:Amino Acid Transport Systems, Neutral / Q000037:antagonists & inhibitors*; D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000166:cytology*; D007700:Kinetics; D020024:Leukotriene Antagonists / Q000494:pharmacology; D017998:Leukotriene D4 / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D018077:Receptors, Leukotriene / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013379:Substrate Specificity; D027981:Symporters / Q000037:antagonists & inhibitors*
D026921:Amino Acid Transport Systems, Neutral; D020024:Leukotriene Antagonists; D011804:Quinolines; D018077:Receptors, Leukotriene; D027981:Symporters; C052168:sodium-alanine cotransporter; C049740:alpha-pentyl-3-(2-quinolinylmethoxy)benzenemethanol; D017998:Leukotriene D4; D000254:Sodium-Potassium-Exchanging ATPase; C083169:leukotriene D4 receptor