title: Calcium-sensing receptor (CaSR)-mediated anti-inflammatory effects of L-amino acids in intestinal epithelial cells.
abstract: Calcium-sensing receptor (CaSR) plays an essential role in sensing nutrients and monitoring ion balance in the human gut. However, no discovery of CaSR-mediated anti-inflammatory effect of l-amino acids (l-AAs) on the gut system has been reported. The aim of this study is to screen and identify the anti-inflammatory activity of various l-AAs in intestinal epithelial cells (IECs) and stepwise illustrate a possible molecular mechanism for anti-inflammation. We used Caco-2 and HT-29 cell lines to evaluate the anti-inflammatory activity of l-AAs and revealed that l-tryptophan (l-Trp) and l-valine (l-Val) have strong anti-inflammatory activity consistent in both cell lines. l-Trp treatment (5 mM) reduced TNF-α-induced IL-8 secretion from HT-29 or Caco-2 cells to about 50 or 40%, respectively. l-Trp also significantly inhibited the expression of phosphorylation of JNK or IκBα to around 50% in HT-29 cells. However, the above inhibitory effects of l-Trp on inflammatory responses in TNF-α-induced HT-29 cells were abrogated by NPS-2143. The result of CaSR antagonist NPS-2143 pretreatment study suggests l-Trp exerts anti-inflammatory effects on IECs through CaSR activation. The involvement of β-arrestin2 was then found to block tumor necrosis factor (TNF)-α-induced signaling pathways after CaSR activated by l-Trp. These results validate a novel mechanism underlying CaSR agonistic l-AAs exerting anti-inflammatory effects on human intestinal epithelia.
authors.affiliation: Department of Food Science, University of Guelph , Guelph, Ontario N1G 2W1, Canada.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Mine
authors.affiliation: Department of Food Science, University of Guelph , Guelph, Ontario N1G 2W1, Canada.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000596:Amino Acids / Q000276:immunology*; D018938:Caco-2 Cells; D004847:Epithelial Cells / Q000276:immunology*; D006801:Humans; D016209:Interleukin-8 / Q000276:immunology; D007413:Intestinal Mucosa / Q000276:immunology; D007422:Intestines / Q000166:cytology / Q000276:immunology*; D044169:Receptors, Calcium-Sensing / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: D000596:Amino Acids; D016209:Interleukin-8; D044169:Receptors, Calcium-Sensing; D014409:Tumor Necrosis Factor-alpha
keywords: amino acids (AAs); anti-inflammatory activity; calcium-sensing receptor (CaSR); chronic inflammation; intestinal epithelial cells