RGD Reference Report - Characteristics of L-citrulline transport through blood-brain barrier in the brain capillary endothelial cell line (TR-BBB cells). - Rat Genome Database

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Characteristics of L-citrulline transport through blood-brain barrier in the brain capillary endothelial cell line (TR-BBB cells).

Authors: Lee, Kyeong-Eun  Kang, Young-Sook 
Citation: Lee KE and Kang YS, J Biomed Sci. 2017 May 10;24(1):28. doi: 10.1186/s12929-017-0336-x.
RGD ID: 30309939
Pubmed: PMID:28490336   (View Abstract at PubMed)
PMCID: PMC5424428   (View Article at PubMed Central)
DOI: DOI:10.1186/s12929-017-0336-x   (Journal Full-text)


BACKGROUND: L-Citrulline is a neutral amino acid and a major precursor of L-arginine in the nitric oxide (NO) cycle. Recently it has been reported that L-citrulline prevents neuronal cell death and protects cerebrovascular injury, therefore, L-citrulline may have a neuroprotective effect to improve cerebrovascular dysfunction. Therefore, we aimed to clarify the brain transport mechanism of L-citrulline through blood-brain barrier (BBB) using the conditionally immortalized rat brain capillary endothelial cell line (TR-BBB cells), as an in vitro model of the BBB.
METHODS: The uptake study of [14C] L-citrulline, quantitative real-time polymerase chain reaction (PCR) analysis, and rLAT1, system b0,+, and CAT1 small interfering RNA study were performed in TR-BBB cells.
RESULTS: The uptake of [14C] L-citrulline was a time-dependent, but ion-independent manner in TR-BBB cells. The transport process involved two saturable components with a Michaelis-Menten constant of 30.9 ± 1.0 μM (Km1) and 1.69 ± 0.43 mM (Km2). The uptake of [14C] L-citrulline in TR-BBB cells was significantly inhibited by neutral and cationic amino acids, but not by anionic amino acids. In addition, [14C]L-citrulline uptake in the cells was markedly inhibited by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), which is the inhibitor of the large neutral amino acid transporter 1 (LAT1), B0, B0,+ and harmaline, the inhibitor of system b0,+. Gabapentin and L-dopa as the substrates of LAT1 competitively inhibited the uptake of [14C] L-citrulline. IC50 values for L-dopa, gabapentin, L-phenylalanine and L-arginine were 501 μM, 223 μM, 68.9 μM and 33.4 mM, respectively. The expression of mRNA for LAT1 was predominantly increased 187-fold in comparison with that of system b0,+ in TR-BBB cells. In the studies of LAT1, system b0,+ and CAT1 knockdown via siRNA transfection into TR-BBB cells, the transcript level of LAT1 and [14C] L-citrulline uptake by LAT1 siRNA were significantly reduced compared with those by control siRNA in TR-BBB cells.
CONCLUSIONS: Our results suggest that transport of L-citrulline is mainly mediated by LAT1 in TR-BBB cells. Delivery strategy for LAT1-mediated transport and supply of L-citrulline to the brain may serve as therapeutic approaches to improve its neuroprotective effect in patients with cerebrovascular disease.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
amino acid import across plasma membrane involved_inIMP 30309939PMID:28490336ARUK-UCL 

Molecular Function
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
amino acid transmembrane transporter activity enablesIMP 30309939PMID:28490336ARUK-UCL 

Objects Annotated

Genes (Rattus norvegicus)
Slc7a5  (solute carrier family 7 member 5)


Additional Information