Equilibrative nucleoside transporter 1 expression is downregulated by hypoxia in human umbilical vein endothelium.
Reduced oxygen level (hypoxia) induces endothelial dysfunction and release of the endogenous nucleoside adenosine. Human umbilical vein endothelium (HUVEC) function in an environment with 3% to 5% O2 and exhibit efficient adenosine membrane transport via human equilibrative nucleoside transporters 1 (hENT1). We studied whether adenosine transport and hENT1 expression are altered by hypoxia in HUVEC. Hypoxia (0 to 24 hours, 2% and 1% O2) reduced maximal hENT1-adenosine transport velocity (V(max)) and maximal nitrobenzylthionosine (NBMPR, a high-affinity hENT1 protein ligand) binding, but increased extracellular adenosine concentration. Hypoxia also reduced hENT1 protein and mRNA levels, effects unaltered by N(omega)-nitro-l-arginine methyl ester (l-NAME, nitric oxide synthase [NOS] inhibitor) or PD-98059 (inhibitor of mitogen-activated protein kinase kinase 1 and 2 [MEK1/2]). Hypoxia reduced endothelial NOS (eNOS) activity and eNOS phosphorylation at Ser(1177), but increased eNOS protein level. Hypoxia increased (1 to 3 hours), but reduced (24 hours) p42/44(mapk) phosphorylation. Thus, hypoxia-increased extracellular adenosine may result from reduced hENT1-adenosine transport in HUVEC. Hypoxia effect seems not to involve NO, but p42/44(mapk) may be required for the relatively rapid effect (1 to 3 hours) of hypoxia. These results could be important in diseases where the fetus is exposed to intrauterine environments poor in oxygen, such as intrauterine growth restriction, or where adenosine transport is altered, such as gestational diabetes.
Casanello
Paola
P
Cellular and Molecular Physiology Laboratory, School of Medicine, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile.
Torres
Alberto
A
Sanhueza
Felipe
F
González
Marcelo
M
Farías
Marcelo
M
Gallardo
Victoria
V
Pastor-Anglada
Marçal
M
San Martín
Rody
R
Sobrevia
Luis
L
D000241:Adenosine / Q000378:metabolism; D001692:Biological Transport; D015687:Cell Hypoxia; D002478:Cells, Cultured; D015536:Down-Regulation; D042783:Endothelial Cells / Q000378:metabolism*; D033721:Equilibrative Nucleoside Transporter 1 / Q000235:genetics* / Q000502:physiology; D033722:Equilibrative-Nucleoside Transporter 2 / Q000502:physiology; D005317:Fetal Growth Retardation / Q000209:etiology; D005786:Gene Expression Regulation; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D013868:Thioinosine / Q000031:analogs & derivatives / Q000378:metabolism; D014471:Umbilical Veins / Q000378:metabolism
D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; D012333:RNA, Messenger; C438649:SLC29A1 protein, human; C438654:SLC29A2 protein, human; D009569:Nitric Oxide; D013868:Thioinosine; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C001789:4-nitrobenzylthioinosine; D000241:Adenosine