We have previously shown that Na+-coupled neutral
amino acid transporter 1 (SNAT1) modulates
nitric oxide (NO) production in pulmonary arterial endothelial cells (PAECs) from newborn piglets. Specifically, the ability to increase NO production in response to the
l-arginine-NO precursor l-
citrulline is dependent on SNAT1 expression. Elucidating factors that regulate SNAT1 expression in PAECs could provide new insights and therapeutic targets relevant to NO production. Our major goals were to determine if
reactive oxygen species (ROS) modulate SNAT1 expression in PAECs from newborn piglets and to evaluate the role of
NADPH oxidase 1 (NOX1) and uncoupled endothelial
NO synthase, enzymatic sources of ROS, in
hypoxia-induced increases in SNAT1 expression. Treatment with either H2O2 or
xanthine plus
xanthine oxidase increased SNAT1 expression in PAECs from newborn piglets cultured under normoxic conditions.
Hypoxia-induced increases in SNAT1 expression were inhibited by treatments with the ROS-removing agents
catalase and
superoxide dismutase, NOX1
siRNA, and the
NO synthase inhibitor
NG-nitro-l-arginine methyl ester. Both tetrahydropbiopterin (BH4) and l-
citrulline, two
therapies that decrease ROS by recoupling endothelial
NO synthase, reduced the
hypoxia-induced increase in SNAT1 expression. BH4 and l-
citrulline treatment improved NO production in hypoxic PAECs despite a reduction in SNAT1 expression. In conclusion, SNAT1 expression is modulated by ROS in PAECs from newborn piglets. However, ROS-mediated decreases in SNAT1 expression per se do not implicate a reduction in NO production. Although SNAT1 may be critical to l-
citrulline-induced increases in NO production,
therapies designed to alter SNAT1 expression may not lead to a concordant change in NO production. NEW & NOTEWORTHY Na+-coupled neutral
amino acid transporter 1 (SNAT1) modulates
nitric oxide (NO) production in piglet pulmonary arterial endothelial cells. Factors that regulate SNAT1 expression in pulmonary arterial endothelial cells are unclear. Here, we show that ROS-reducing strategies inhibit
hypoxia-induced increases in SNAT1 expression. l-
Citrulline and tetrahydropbiopterin decrease SNAT1 expression but increase NO production. Although SNAT1 is modulated by ROS, changes in SNAT1 expression may not cause a concordant change in NO production.