title: Endothelium-Derived 5-Methoxytryptophan Protects Endothelial Barrier Function by Blocking p38 MAPK Activation.
abstract: The endothelial junction is tightly controlled to restrict the passage of blood cells and solutes. Disruption of endothelial barrier function by bacterial endotoxins, cytokines or growth factors results in inflammation and vascular damage leading to vascular diseases. We have identified 5-methoxytryptophan (5-MTP) as an anti-inflammatory factor by metabolomic analysis of conditioned medium of human fibroblasts. Here we postulated that endothelial cells release 5-MTP to protect the barrier function. Conditioned medium of human umbilical vein endothelial cells (HUVECs) prevented endothelial hyperpermeability and VE-cadherin downregulation induced by VEGF, LPS and cytokines. We analyzed the metabolomic profile of HUVEC conditioned medium and detected 5-MTP but not melatonin, serotonin or their catabolites, which was confirmed by enzyme-linked immunosorbent assay. Addition of synthetic pure 5-MTP preserved VE-cadherin and maintained barrier function despite challenge with pro-inflammatory mediators. Tryptophan hydroxylase-1, an enzyme required for 5-MTP biosynthesis, was downregulated in HUVECs by pro-inflammatory mediators and it was accompanied by reduction of 5-MTP. 5-MTP protected VE-cadherin and prevented endothelial hyperpermeability by blocking p38 MAPK activation. A chemical inhibitor of p38 MAPK, SB202190, exhibited a similar protective effect as 5-MTP. To determine whether 5-MTP prevents vascular hyperpermeability in vivo, we evaluated the effect of 5-MTP administration on LPS-induced murine microvascular permeability with Evans blue. 5-MTP significantly prevented Evans blue dye leakage. Our findings indicate that 5-MTP is a new class of endothelium-derived molecules which protects endothelial barrier function by blocking p38 MAPK.
authors.affiliation: Metabolomic Medicine Research Center, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Chu
authors.affiliation: Institute of Cellular and System Medicine, National Health Research Institutes, Zhunan, Taiwan.|Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Yi-Fu
authors.initials: YF
authors.lastname: Wang
authors.affiliation: Metabolomic Medicine Research Center, China Medical University Hospital, Taichung, Taiwan.|Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan.
authors.forename: Huei-Hsuan
authors.initials: HH
authors.lastname: Cheng
authors.affiliation: Metabolomic Medicine Research Center, China Medical University Hospital, Taichung, Taiwan.|Institute of Cellular and System Medicine, National Health Research Institutes, Zhunan, Taiwan.|Graduate Institute of Basic Medical Science, China Medical University, Taichung, Taiwan.
authors.forename: Cheng-Chin
authors.initials: CC
authors.lastname: Kuo
authors.affiliation: Metabolomic Medicine Research Center, China Medical University Hospital, Taichung, Taiwan.|Institute of Cellular and System Medicine, National Health Research Institutes, Zhunan, Taiwan.|Graduate Institute of Basic Medical Science, China Medical University, Taichung, Taiwan.|Department of Medical Sciences and Institute of Biotechnology National TsingHua University, Hsinchu, Taiwan.
authors.forename: Kenneth K
authors.initials: KK
authors.lastname: Wu
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020011:Protective Agents / Q000494:pharmacology*; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D000099152:Cadherin 5
chemical_list: D015703:Antigens, CD; D015820:Cadherins; D017077:Culture Media, Conditioned; D020011:Protective Agents; D014364:Tryptophan; D048051:p38 Mitogen-Activated Protein Kinases; D000099152:Cadherin 5; C027986:5-methoxytryptophan