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Microvasc Res. 2018 Nov;120:29-35. doi: 10.1016/j.mvr.2018.05.010. Epub 2018 Jun 2.

l-Citrulline restores nitric oxide level and cellular uptake at the brain capillary endothelial cell line (TR-BBB cells) with glutamate cytotoxicity.

Author information

1
College of Pharmacy and Research Center for Cell Fate Control, Sookmyung Women's University, 100 Chungpa-ro 47-gil, Yongsan-gu, Seoul 04310, Republic of Korea.
2
College of Pharmacy and Research Center for Cell Fate Control, Sookmyung Women's University, 100 Chungpa-ro 47-gil, Yongsan-gu, Seoul 04310, Republic of Korea. Electronic address: yskang@sm.ac.kr.

Abstract

OBJECTIVE:

Glutamate excitotoxicity provokes neuronal cell damage and death, leading to collapse of the blood-brain barrier (BBB). Recently, it has been reported that l-citrulline, a neutral amino acid and a major precursor of l-arginine in the nitric oxide (NO) cycle, can prevent both neuronal cell death and cerebrovascular cell loss in brain ischemia. Therefore, the objective of this study was to investigate the effect of l-citrulline on glutamate cytotoxicity in the BBB using the conditionally immortalized rat brain capillary endothelial cell line (TR-BBB cells) as an in vitro model of the BBB.

METHODS:

Cell viability was determined using MTT assay. Cellular uptake of [14C] l-citrulline and expression levels of rat large neutral amino acid transporter 1 (rLAT1), endothelial nitric oxide synthase (eNOS), and inducible nitric oxide synthase (iNOS) at mRNA level were performed using quantitative real-time polymerase chain reaction (PCR) analysis. NO production from TR-BBB cells was measured using Griess reagents. All experiments were performed after treatment of TR-BBB cells with glutamate alone or co-treatment with l-citrulline, l-arginine, and/or taurine for 24 h.

RESULTS:

l-Citrulline treatment increased cell viability, [14C] l-citrulline uptake, and the mRNA levels of LAT1 and eNOS in TR-BBB cells treated with glutamate. However, iNOS mRNA expression was inhibited by l-citrulline. NO production and transcript level of iNOS were markedly increased by glutamate treatment alone. However, co-treatment with l-citrulline, taurine, or both l-citrulline and taurine decreased NO levels and mRNA levels of iNOS in TR-BBB cells treated with glutamate. In co-treatment of TR-BBB cells with l-arginine, a NO donor, and glutamate, NO levels were increased and expression levels of iNOS mRNA were similar compared to those in cells treated with glutamate alone.

CONCLUSION:

l-Citrulline can restore NO level and its cellular uptake in TR-BBB cells with glutamate cytotoxicity. Supplying l-citrulline at the BBB may provide neuroprotective effect to improve cerebrovascular dysfunction such as a brain ischemia.

KEYWORDS:

Blood-brain barrier (BBB); Endothelial nitric oxide synthase (eNOS); Glutamate; Inducible nitric oxide synthase (iNOS); Large neutral amino acid transporter 1 (LAT1); Nitric oxide (NO); l-Citrulline

PMID:
29870781
DOI:
10.1016/j.mvr.2018.05.010
[Indexed for MEDLINE]

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