title: Modulation of intestinal folate absorption by erythropoietin in vitro.
abstract: Besides the direct stimulation of erythropoiesis, erythropoietin (EPO) therapy in renal anemia may also play a regulatory role in maintaining the homeostasis of hematopoietic nutrients. It has been reported that EPO can stimulate intestinal iron absorption. However, the involvement of EPO in intestinal folate absorption remains elusive. The objective of this study was to investigate the effect of EPO on intestinal transport of folate in vitro and to elucidate the possible mechanism(s) involved in this regulation. Transport assays of folic acid were performed in Caco-2 monolayers treated with EPO. The effect of EPO on the expression of transporters involved in the folate absorption was investigated. The possible involvement of three main EPO signaling pathways, the janus protein tyrosine kinase 2 (JAK-2) pathway, extracellular signal regulated kinases (ERK) pathway, and phosphatidylinositol 3 kinase/Akt (PI3K/Akt) pathway, in the transporter regulation was explored. The absorptive flux (apical to basolateral) of folic acid was enhanced by EPO treatment in a dose-dependent manner, which was companied with the significant up-regulation of reduced folate carrier (RFC) and apical proton coupled folate transporter (PCFT). The efflux (basolaterial to apical) of folic acid was enhanced only by the high dose of EPO treatment, which was associated with the significant up-regulation of apical multidrug resistance-associated protein 2 (MRP2). The expression levels of all of these transporters were up-regulated by EPO treatment in a dose- and time-dependent manner. Transporter expression in response to blocking EPO induced activation of JAK-2, ERK, and PI3K/Akt was changed to a different extent. As a conclusion, intestinal folate absorption was enhanced by EPO treatment in vitro. Our findings provided direct evidence to establish the correlation between EPO and folate homeostasis.
authors.affiliation: State Key Laboratory of Genetic Engineering, Department of Biochemistry, School of Life Sciences, Fudan University , Handan Road 220, Shanghai, China.
authors.forename: Junkai
authors.initials: J
authors.lastname: Yan
authors.forename: Guiying
authors.initials: G
authors.lastname: Jin
authors.forename: Lisha
authors.initials: L
authors.lastname: Du
authors.forename: Qing
authors.initials: Q
authors.lastname: Yang
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D000068817:Epoetin Alfa; D004921:Erythropoietin / Q000494:pharmacology*; D005492:Folic Acid / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D053614:Janus Kinase 2 / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000068817:Epoetin Alfa; D004921:Erythropoietin; D005492:Folic Acid; D053614:Janus Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D011994:Recombinant Proteins; C000715087:ABCC2 protein, human; C507924:JAK2 protein, human; C535150:MAPK1 protein, human