L-citrulline recycling in opossum internal anal sphincter relaxation by nonadrenergic, noncholinergic nerve stimulation

doi:10.1016/S0016-5085(97)70137-9

Gastroenterology

Volume 112, Issue 4, April 1997, Pages 1250-1259

https://doi.org/10.1016/S0016-5085(97)70137-9 Get rights and content

Abstract

BACKGROUND & AIMS: L-citrulline formed stoichiometrically along with nitric oxide (1:1) from L-arginine may be enzymatically converted to L- arginine. The possibility of L-citrulline recycling in the maintenance of nitrergic neurotransmission in the opossum internal anal sphincter (IAS) smooth muscle strips was investigated. METHODS: Responses to nonadrenergic, noncholinergic (NANC) nerve stimulation by electrical field stimulation (EFS) (either short-train or continuous stimulation) on the basal IAS tension were recorded before and after the NO synthase inhibitor N(omega)-nitro-L-arginine (L-NNA), L-NNA plus L-citrulline, or L-arginine. During continuous EFS, when the basal IAS tone after the initial relaxation had recovered to almost pre-EFS levels, the effects of L-citrulline or L-arginine were examined before and after L- glutamine, which is a putative blocker of L-citrulline uptake. RESULTS: Inhibition of NANC nerve-mediated IAS relaxation by L-NNA was reversed by L-citrulline as well as L-arginine. L-Citrulline and L-arginine caused concentration-dependent relaxation of the IAS tone recovered during the prolonged EFS. L-Glutamine blocked the responses of L- citrulline but not of L-arginine. Furthermore, L-glutamine increased the speed of recovery of IAS tone during continuous EFS. CONCLUSIONS: L- citrulline recycling may be responsible for the maintenance of IAS relaxation during frequent short-train and prolonged NANC nerve stimulation. (Gastroenterology 1997 Apr;112(4):1250-9)

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Cited by (14)

Role of the l-citrulline/l-arginine cycle in iNANC nerve-mediated nitric oxide production and airway smooth muscle relaxation in allergic asthma
2006, European Journal of Pharmacology
Nitric oxide synthase (NOS) converts l-arginine into nitric oxide (NO) and l-citrulline. In NO-producing cells, l-citrulline can be recycled to l-arginine in a two-step reaction involving argininosuccinate synthase (ASS) and -lyase (ASL). In guinea pig trachea, l-arginine is a limiting factor in neuronal nNOS-mediated airway smooth muscle relaxation upon inhibitory nonadrenergic noncholinergic (iNANC) nerve stimulation. Moreover, in a guinea pig model of asthma iNANC nerve-induced NO production and airway smooth muscle relaxation are impaired after the allergen-induced early asthmatic reaction, due to limitation of l-arginine. Using guinea pig tracheal preparations, we now investigated whether (i) the l-citrulline/l-arginine cycle is active in airway iNANC nerves and (ii) the NO deficiency after the early asthmatic reaction involves impaired l-citrulline recycling. Electrical field stimulation-induced relaxation was measured in tracheal open-rings precontracted with histamine. l-citrulline as well as the ASL inhibitor succinate did not affect electrical field stimulation-induced relaxation under basal conditions. However, reduced relaxation induced by a submaximal concentration of the NOS inhibitor N^ω-nitro-l-arginine was restored by l-citrulline, which was prevented by the additional presence of succinate or the ASS inhibitor α-methyl-d,l-aspartate. Remarkably, the impaired iNANC relaxation after the early asthmatic reaction was restored by l-citrulline. In conclusion, the l-citrulline/l-arginine cycle is operative in guinea pig iNANC nerves in the airways and may be effective under conditions of low l-arginine utilization by nNOS (caused by NOS inhibitors), and during reduced l-arginine availability after allergen challenge. Enzymatic dysfunction in the l-citrulline/l-arginine cycle appears not to be involved in the l-arginine limitation and reduced iNANC activity after the early asthmatic reaction.
L-Citrulline recycling by argininosuccinate synthetase and lyase in rat gastric fundus
2002, European Journal of Pharmacology
The aim of this study was to investigate in rat gastric fundus whether l-citrulline, the co-product in the nitric oxide (NO) biosynthesis catalyzed by neuronal nitric oxide synthase (nNOS), can be converted back to the nNOS substrate l-arginine. Immunohistochemistry showed that argininosuccinate synthetase and argininosuccinate lyase, that mediate transformation of l-citrulline to l-arginine in the ureum cycle in hepatocytes, co-localize with nNOS. In longitudinal smooth muscle strips, l-arginine as well as l-citrulline (10⁻³ M) was capable of completely respectively partially preventing the N^G-nitro-l-arginine methyl ester (l-NAME) (3×10⁻⁵ M)-induced inhibition of electrically induced nitrergic relaxations, whereas d-citrulline (10⁻³ M) was not. The l-citrulline-mediated prevention of the l-NAME-induced inhibition was reduced by l-glutamine (3×10⁻³ M), the putative l-citrulline uptake inhibitor, and by succinate, an argininosuccinate lyase inhibitor. The results demonstrate that the l-citrulline recycling mechanism is active in rat gastric fundus. Recycling of l-citrulline might play a role in providing sufficient amounts of nNOS substrate during long-lasting relaxations in gastric fundus after food intake.
Reduced arginine availability and nitric oxide production
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Coinduction of inducible nitric oxide synthase and arginine recycling enzymes in cytokine-stimulated PC12 cells and high output production of nitric oxide
2000, Molecular Brain Research
Citation Excerpt :
The cationic amino acid transporter (CAT)-2 gene is stimulated by cytokines and LPS in various cell types, including vascular smooth muscle cells [18], macrophages [5,26,43] and astrocytes [51]. On the other hand, the citrulline–NO cycle functions in cultured endothelial cells [22] and macrophages [56], and also in the peripheral nervous system including canine enteric neurons [47], opossum internal anal sphincter [41] and canine esophageal sphincter [42]. Furthermore, inducible NOS (iNOS) and AS are coinduced in activated murine macrophage-like RAW 264.7 cells [38], in cultured vascular smooth muscle cells [21], in activated macrophages of rat and mouse tissues in vivo [37,43], and in rodent and human pancreatic β-cells [16].
Nitric oxide (NO) is involved in many physiological and pathological processes in the brain. NO is synthesized from arginine by nitric oxide synthase (NOS), and the citrulline generated as a by-product can be recycled to arginine by argininosuccinate synthetase (AS) and argininosuccinate lyase (AL) via the citrulline–NO cycle. When neuronal PC12 cells differentiated with nerve growth factor were treated with interferon-γ (IFNγ) and tumor necrosis factor-α (TNFα), iNOS and AS mRNAs and proteins were markedly induced, with AL mRNA and protein being weakly induced. Cationic amino acid transporter-1 and -2 were not induced. IFNγ or TNFα alone was ineffective. A large amount of NO (190 μM NO₂⁻ plus NO₃⁻ in culture medium in 24 h) was produced from arginine by cytokine-stimulated cells, and arginine could be replaced by citrulline. iNOS induction and NO production were attenuated by dexamethasone and dibutyryl cAMP and even more strongly so when combined. Therefore, a large amount of NO is produced in cytokine-stimulated PC12 cells following to induction of iNOS and citrulline-arginine recycling is important for NO production.
Expression of citrulline-nitric oxide cycle in lipopolysaccharide and cytokine-stimulated rat astroglioma C6 cells
1999, Brain Research
Nitric oxide (NO) is involved in many physiological and pathological processes in the brain. NO is synthesized from arginine by nitric oxide synthase (NOS), with citrulline generated as a by-product of the reaction. Thus, citrulline can by recycled to arginine by argininosuccinate synthetase (AS) and argininosuccinate lyase (AL) via the citrulline–NO cycle. Rat astroglioma C6 cells were treated with bacterial lipopolysaccharide (LPS), interferon-γ (IFNγ) and tumor necrosis factor-α, and the expression of the enzymes of the citrulline–NO cycle was investigated by RNA blot and immunoblot analyses. NO production from arginine and citrulline was also assessed. iNOS mRNA and protein were induced 6–12 h after stimulation with LPS and cytokines and decreased at 24 h. AS mRNA increased up to 12 h and decreased at 24 h. AS protein increased gradually up to 48 h. On the other hand, AL mRNA remained unchanged by stimulation. NO production from arginine was enhanced by the treatment with LPS and cytokines. NO production was also observed when arginine was replaced by citrulline. These results indicate that NO production is enhanced in LPS- and cytokine-stimulated C6 cells due to induction of iNOS and that the citrulline–arginine recycling is important for NO production.
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