Sodium-coupled neutral amino acid transporter 1 (SNAT1) modulates L-citrulline transport and nitric oxide (NO) signaling in piglet pulmonary arterial endothelial cells.
BACKGROUND
There is evidence that impairments in nitric oxide (NO) signaling contribute to chronic hypoxia-induced pulmonary hypertension. The L-arginine-NO precursor, L-citrulline, has been shown to ameliorate pulmonary hypertension. Sodium-coupled neutral amino acid transporters (SNATs) are involved in the transport of L-citrulline into pulmonary arterial endothelial cells (PAECs). The functional link between the SNATs, L-citrulline, and NO signaling has not yet been explored.


OBJECTIVE
We tested the hypothesis that changes in SNAT1 expression and transport function regulate NO production by modulating eNOS coupling in newborn piglet PAECs.


RESULTS
A silencing RNA (siRNA) technique was used to assess the contribution of SNAT1 to NO production and eNOS coupling (eNOS dimer-to-monomer ratios) in PAECs from newborn piglets cultured under normoxic and hypoxic conditions in the presence and absence of L-citrulline. SNAT1 siRNA reduced basal NO production in normoxic PAECs and prevented L-citrulline-induced elevations in NO production in both normoxic and hypoxic PAECs. SNAT1 siRNA reduced basal eNOS dimer-to-monomer ratios in normoxic PAECs and prevented L-citrulline-induced increases in eNOS dimer-to-monomer ratios in hypoxic PAECs.


CONCLUSIONS
SNAT1 mediated L-citrulline transport modulates eNOS coupling and thus regulates NO production in hypoxic PAECs from newborn piglets. Strategies that increase SNAT1-mediated transport and supply of L-citrulline may serve as novel therapeutic approaches to enhance NO production in patients with pulmonary vascular disease.
Dept. of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America ; Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee, United States of America.
Anna
A
Dikalova
Dept. of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America ; Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee, United States of America.
Angela
A
Fagiana
Dept of Pediatrics, Albert Einstein College of Medicine and the Children's Hospital at Montefiore, New York, New York, United States of America.
Judy L
JL
Aschner
Dept. of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America ; Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee, United States of America ; Vanderbilt Center for Molecular Toxicology, Nashville, Tennessee, United States of America.
Michael
M
Aschner
Division of Genetics and Metabolism, Children's National Medical Center, Washington, District of Columbia, United States of America.
Marshall
M
Summar
Dept. of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America ; Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, Tennessee, United States of America.
Candice D
CD
Fike
D026924:Amino Acid Transport System A / Q000502:physiology*; D000818:Animals; D001692:Biological Transport; D015687:Cell Hypoxia; D002478:Cells, Cultured; D002956:Citrulline / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000473:pathology; D006976:Hypertension, Pulmonary / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D011651:Pulmonary Artery / Q000473:pathology*; D015398:Signal Transduction; D013481:Superoxides / Q000378:metabolism; D034421:Sus scrofa
D026924:Amino Acid Transport System A; D013481:Superoxides; D002956:Citrulline; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III