Carcinine ditrifluoroacetate

Quantification of Histamine and Carcinine in Drosophila melanogaster Tissues.[Pubmed:26765065]

ACS Chem Neurosci. 2016 Mar 16;7(3):407-14.

Histamine is a neurotransmitter crucial to the visual processing of Drosophila melanogaster. It is inactivated by metabolism to carcinine, a beta-alanyl derivative, and the same enzyme that controls that process also converts dopamine to N-beta-alanyl-dopamine. Direct detection of histamine and carcinine has not been reported in single Drosophila brains. Here, we quantify histamine, carcinine, dopamine, and N-beta-alanyl-dopamine in Drosophila tissues by capillary electrophoresis coupled to fast-scan cyclic voltammetry (CE-FSCV). Limits of detection were low, 4 +/- 1 pg for histamine, 10 +/- 4 pg for carcinine, 2.8 +/- 0.3 pg for dopamine, and 9 +/- 3 pg for N-beta-alanyl-dopamine. Tissue content was compared in the brain, eyes, and cuticle from wild-type (Canton S) and mutant (tan(3) and ebony(1)) strains. In tan(3) mutants, the enzyme that produces histamine from carcinine is nonfunctional, whereas in ebony(1) mutants, the enzyme that produces carcinine from histamine is nonfunctional. In all fly strains, the neurotransmitter content was highest in the eyes and there were no strain differences for tissue content in the cuticle. The main finding was that carcinine levels changed significantly in the mutant flies, whereas histamine levels did not. In particular, tan(3) flies had significantly higher carcinine levels in the eyes and brain than Canton S or ebony(1) flies. N-beta-Alanyl-dopamine was detected in tan(3) mutants but not in other strains. These results show the utility of CE-FSCV for sensitive detection of histamine and carcinine, which allows a better understanding of their content and metabolism in different types of tissues to be obtained.

Drosophila Vision Depends on Carcinine Uptake by an Organic Cation Transporter.[Pubmed:26923590]

Cell Rep. 2016 Mar 8;14(9):2076-2083.

Recycling of neurotransmitters is essential for sustained neuronal signaling, yet recycling pathways for various transmitters, including histamine, remain poorly understood. In the first visual ganglion (lamina) of Drosophila, photoreceptor-released histamine is taken up into perisynaptic glia, converted to carcinine, and delivered back to the photoreceptor for histamine regeneration. Here, we identify an organic cation transporter, CarT (carcinine transporter), that transports carcinine into photoreceptors during histamine recycling. CarT mediated in vitro uptake of carcinine. Deletion of the CarT gene caused an accumulation of carcinine in laminar glia accompanied by a reduction in histamine, resulting in abolished photoreceptor signal transmission and blindness in behavioral assays. These defects were rescued by expression of CarT cDNA in photoreceptors, and they were reproduced by photoreceptor-specific CarT knockdown. Our findings suggest a common role for the conserved family of CarT-like transporters in maintaining histamine homeostasis in both mammalian and fly brains.

The carcinine transporter CarT is required in Drosophila photoreceptor neurons to sustain histamine recycling.[Pubmed:26653853]

Elife. 2015 Dec 14;4:e10972.

Synaptic transmission from Drosophila photoreceptors to lamina neurons requires recycling of histamine neurotransmitter. Synaptic histamine is cleared by uptake into glia and conversion into carcinine, which functions as transport metabolite. How carcinine is transported from glia to photoreceptor neurons remains unclear. In a targeted RNAi screen for genes involved in this pathway, we identified carT, which encodes a member of the SLC22A transporter family. CarT expression in photoreceptors is necessary and sufficient for fly vision and behavior. Carcinine accumulates in the lamina of carT flies. Wild-type levels are restored by photoreceptor-specific expression of CarT, and endogenous tagging suggests CarT localizes to synaptic endings. Heterologous expression of CarT in S2 cells is sufficient for carcinine uptake, demonstrating the ability of CarT to utilize carcinine as a transport substrate. Together, our results demonstrate that CarT transports the histamine metabolite carcinine into photoreceptor neurons, thus contributing an essential step to the histamine-carcinine cycle.

Histamine Recycling Is Mediated by CarT, a Carcinine Transporter in Drosophila Photoreceptors.[Pubmed:26713872]

PLoS Genet. 2015 Dec 29;11(12):e1005764.

Histamine is an important chemical messenger that regulates multiple physiological processes in both vertebrate and invertebrate animals. Even so, how glial cells and neurons recycle histamine remains to be elucidated. Drosophila photoreceptor neurons use histamine as a neurotransmitter, and the released histamine is recycled through neighboring glia, where it is conjugated to beta-alanine to form carcinine. However, how carcinine is then returned to the photoreceptor remains unclear. In an mRNA-seq screen for photoreceptor cell-enriched transporters, we identified CG9317, an SLC22 transporter family protein, and named it CarT (Carcinine Transporter). S2 cells that express CarT are able to take up carcinine in vitro. In the compound eye, CarT is exclusively localized to photoreceptor terminals. Null mutations of cart alter the content of histamine and its metabolites. Moreover, null cart mutants are defective in photoreceptor synaptic transmission and lack phototaxis. These findings reveal that CarT is required for histamine recycling at histaminergic photoreceptors and provide evidence for a CarT-dependent neurotransmitter trafficking pathway between glial cells and photoreceptor terminals.

Pharmacological effects of carcinine on histaminergic neurons in the brain.[Pubmed:15466447]

Br J Pharmacol. 2004 Nov;143(5):573-80.

1 Carcinine (beta-alanyl histamine) is an imidazole dipeptide. The present study was designed to characterize the pharmacological effects of carcinine on histaminergic activity in the brain and on certain neurobehavior. 2 Carcinine was highly selective for the histamine H3 receptor over H1 or H2 receptor (Ki (microM)=0.2939+/-0.2188 vs 3621.2+/-583.9 or 365.3+/-232.8 microM, respectively). 3 Carcinine at a dose of 20 mg kg(-1) slightly increased histidine decarboxylase (HDC) activity in the cortex (from 0.186+/-0.069 to 0.227+/-0.009 pmol mg protein(-1) min(-1)). In addition, carcinine (10, 20, and 50 mg kg(-1)) significantly decreased histamine levels in mice brain. 4 Like thioperamide, a histamine H3 receptor antagonist, carcinine (20, 50 microM) significantly increased 5-HT release from mice cortex slices, but had no apparent effect on dopamine release. 5 Carcinine (20 mg kg(-1)) significantly inhibited pentylenetetrazole-induced kindling. This inhibition was completely reversed by (R)-alpha-methylhistamine, a representative H3 receptor agonist, and alpha-fluromethylhistidine, a selective HDC inhibitor. 6 Carcinine (20 mg kg(-1)) ameliorated the learning deficit induced by scopolamine. This amelioration was reversed by (R)-alpha-methylhistamine as evaluated by the passive avoidance test in mice. 7 Like thioperamide, carcinine dose-dependently increased mice locomotor activity in the open-field test. 8 The results of this study provide first and direct evidence that carcinine, as a novel histamine H3 receptor antagonist, plays an important role in histaminergic neurons activation and might be useful in the treatment of certain diseases, such as epilepsy, and locomotor or cognitive deficit.

L-carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) act as natural antioxidants with hydroxyl-radical-scavenging and lipid-peroxidase activities.[Pubmed:7998987]

Biochem J. 1994 Dec 1;304 ( Pt 2):509-16.

Carnosine (beta-alanyl-L-histidine) and carcinine (beta-alanylhistamine) are natural imidazole-containing compounds found in the non-protein fraction of mammalian tissues. Carcinine was synthesized by an original procedure and characterized. Both carnosine and carcinine (10-25 mM) are capable of inhibiting the catalysis of linoleic acid and phosphatidylcholine liposomal peroxidation (LPO) by the O2(-.)-dependent iron-ascorbate and lipid-peroxyl-radical-generating linoleic acid 13-monohydroperoxide (LOOH)-activated haemoglobin systems, as measured by thiobarbituric-acid-reactive substance. Carcinine and carnosine are good scavengers of OH. radicals, as detected by iron-dependent radical damage to the sugar deoxyribose. This suggests that carnosine and carcinine are able to scavenge free radicals or donate hydrogen ions. The iodometric, conjugated diene and t.l.c. assessments of lipid hydroperoxides (13-monohydroperoxide linoleic acid and phosphatidylcholine hydroperoxide) showed their efficient reduction and deactivation by carnosine and carcinine (10-25 mM) in the liberated and bound-to-artificial-bilayer states. This suggests that the peroxidase activity exceeded that susceptible to direct reduction with glutathione peroxidase. Imidazole, solutions of beta-alanine, or their mixtures with peptide moieties did not show antioxidant potential. Free L-histidine and especially histamine stimulated iron (II) salt-dependent LPO. Due to the combination of weak metal chelating (abolished by EDTA), OH. and lipid peroxyl radicals scavenging, reducing activities to liberated fatty acid and phospholipid hydroperoxides, carnosine and carcinine appear to be physiological antioxidants able to efficiently protect the lipid phase of biological membranes and aqueous environments.