The intestinal crypt stem cells in the gut have a high growth potential and radiosensitivity that is dose-dependently reduced by carbon-ion irradiation, and intestinal death occurs by the arrest of epithelial cells supply in high-dose areas. Therefore, the development of intestinal radioprotection methods may contribute to more effective and less harmful carbon-ion radiotherapy. We have demonstrated that N-methyl-D-aspartate (NMDA) receptor antagonists reduce radiation-induced intestinal injury and that the activation of NMDA receptors significantly increased 24 hours after irradiation. In this study, we investigated the association with amino acid concentration that activates NMDA receptors in intestinal injury in irradiated mice. To investigate changes in amino acid concentration in mouse small intestine by carbon ion irradiation, we developed the HPLC method for the determination of six amino acids and related compounds—glycine (Gly), serine (Ser), aspartic acid (Asp), glutamic acid (Glu), taurine (Tau), and γ-aminobutyric acid (GABA). C3H/He female mice were abdominally irradiated with carbon ion at doses of 9 Gy (20 keV/μm, 290 MeV/u, accelerated by Heavy-Ion Medical Accelerator in Chiba synchrotron at National Institute of Radiological Sciences, Japan). After carbon-ion irradiation, the concentration of Tau significantly decreased with time. Tau, a sulfur-containing amino acid-related compound, has been reported to have a radioprotective effect. Therefore, the decrease in Tau concentration was inferred to be a decrease in radioprotective ability in the mouse’s intestine. On the contrary, the concentration of Glu significantly increased with time dependence by the irradiation. These results suggested that the increase in glutamate concentration after irradiation induces the activation of NMDA receptors; thus, radiation-induced intestinal injuries could be suppressed by NMDA receptor antagonists as radioprotective agents after carbon-ion irradiation.

1. T. Kamada, “Outline of Heavy Ion Radiotherapy,” in Proc. 2nd Int. Symp. Heavy-Ion Radiotherapy and Adv. Technology, Tokyo, Japan, 2016, pp. 1 – 4.
   Retrieved from: http://www.nirs.qst.go.jp/rd/reports/proceedings/pdf/2nd_International_Symposium_2016.pdf
   Retrieved on: Feb. 01, 2017
2. Y. Yoshida et al., “Evaluation of therapeutic gain for fractionated carbon-ion radiotherapy using the tumor growth delay and crypt survival assays,” Radiother. Oncol.,vol. 117, no. 2, pp. 351 – 357, Nov. 2015.
   DOI: 10.1016/j.radonc.2015.09.027
   PMid: 26454348
3. T. Ohno, “Particle radiotherapy with carbon ion beams,” EPMA J., vol. 4, no. 1, 9, Mar. 2013.
   DOI: 10.1186/1878-5085-4-9
   PMid: 23497542
   PMCid: PMC3598788
4. A. Dubois, R. I. Walker, “Prospects for Management of Gastrointestinal Injury Associated with the Acute Radiation Syndrome,” Gastroenterology , vol. 95, no. 2, pp. 500 – 507, Aug. 1988.
   Retrieved from: http://www.sciencedirect.com/science/article/pii/0016508588905124
   Retrieved on: Feb. 01, 2017
5. M. M. Bismar, F. A. Sinicrope, “Radiation enteritis,” Curr. Gastroenterol. Rep. , vol. 4, no. 5, pp. 361 – 365, Oct. 2002.
   DOI: 10.1007/s11894-002-0005-3
   PMid: 12228037
6. C. G. Rousseaux, “A Review of Glutamate Receptors I: Current Understanding of Their Biology,” J. Toxicol. Pathol., vol. 21, no. 1, pp. 25 – 51, Apr. 2008.
   DOI: 10.1293/tox.21.25
7. S. F. Traynelis et al., “Glutamate Receptor Ion Channels: Structure, Regulation, and Function,” Pharmacol. Rev.,vol. 62, no. 3, pp. 405 – 496, Sep. 2010.
   DOI: 10.1124/pr.109.002451
   PMid: 20716669
   PMCid: PMC2964903
8. K. G. Dickman, J. G. Youssef, S. M. Mathew, S. I. Said, “Ionotropic Glutamate Receptors in Lungs and Airways,” Am. J. Respir. Cell Mol., vol. 30, no. 2, pp. 139 – 144,
   Feb. 2004.
   DOI: 10.1165/rcmb.2003-0177OC
   PMid: 12855408
9. J. W. Olney, “Excitotoxic Amino Acids and Neuropsychiatric Disorders,” Annu. Rev. Pharmacol. Toxicol. , vol. 30, pp. 47 – 71, Apr. 1990.
   DOI: 10.1146/annurev.pa.30.040190.000403
   PMid: 2188577
10. D. W. Choi, “Excitotoxic cell death,” J. Neurobiol., vol. 23, no. 9, pp. 1261 – 1276, Nov. 1992.
    DOI: 10.1002/neu.480230915
    PMid: 1361523
11. Y. M. Lu, H. Z. Yin, J. Chiang, J. H. Weiss, “Ca²⁺-Permeable AMPA/Kainate and NMDA Channels: High Rate of Ca ²⁺ Influx Underlies Potent Induction of Injury,” J. Neurosci., vol. 16, no. 17, pp. 5457 – 5465, Sep. 1996.
    Retrieved from: http://www.jneurosci.org/content/jneuro/16/17/5457.full.pdf
    Retrieved on: Feb. 01, 2017
12. C. G. Rousseaux, “A Review of Glutamate Receptors II: Pathophysiology and Pathology,” J. Toxicol. Pathol., vol. 21, no. 3, pp. 133 – 173, Oct. 2008.
    DOI: 10.1293/tox.21.133
13. L. Tenneti, D. M. D`Emilia, C. M. Troy, S. A. Lipton, “Role of Caspases in N-Methyl-D-Aspartate-Induced Apoptosis in Cerebrocortical Neurons,” J. Neurochem., vol. 71, no. 3, pp. 946 – 959, Sep. 1998.
    DOI: 10.1046/j.1471-4159.1998.71030946.x
    PMid: 9721720
14. J. A. McRoberts et al., “Role of peripheral N-methyl-D-aspartate (NMDA) receptors in visceral nociception in rats,” Gastroenterology, vol. 120, no. 7, pp. 1737 – 1748, Jun. 2001.
    DOI: 10.1053/gast.2001.24848
    PMid: 11375955
15. H. Chen et al., “Identification of a homocysteine receptor in the peripheral endothelium and its role in proliferation,” J. Vasc. Surg., vol. 41, no. 5, pp. 853 – 860, May. 2005.
    DOI: 10.1016/j.jvs.2005.02.021
    PMid: 15886671
16. H. Wang, R. J. Liu, R. X. Zhang, J. T. Qiao, “Peripheral NMDA receptors contribute to activation of nociceptors: a c-fos expression study in rats,” Neurosci. Lett., vol. 221, no. 2-3, pp. 101 – 104, Jan. 1997.
    DOI: 10.1016/S0304-3940(96)13299-7
    PMid: 9121674
17. C. G. Parsons, “NMDA receptors as targets for drug action in neuropathic pain,” Eur. J. Pharmacol., vol. 429, no. 1-3, pp. 71 – 78, Oct. 2001.
    DOI: 10.1016/S0014-2999(01)01307-3
    PMid: 11698028
18. A. B. Petrenko, T. Yamakura, H. Baba, K. Shimoji, “The role of N-methyl-D-aspartate (NMDA) receptors in pain: a review,” Anesth Analg , vol. 97,no. 4, pp. 1108 – 1116, Oct. 2003.
    DOI: 10.1213/01.ANE.0000081061.12235.55
    PMid: 14500166
19. W. Rzeski, L. Turski, C. Ikonomidou, “Glutamate antagonists limit tumor growth,” PNAS USA, vol. 98, no. 11, pp. 6372 – 6377, May 2001.
    DOI: 10.1073/pnas.091113598
    PMid: 11331750
    PMCid: PMC33475
20. M. Ohgami et al., “Effect of N-methyl-D-aspartate receptors antagonist on radiation-induced gut injuries in mice,” in Proc. 5th Int. Conf. Radiation and Applications in Various Fields of Research (RAD 2017) , Budva, Montenegro, 2017, pp. 6 – 10.
    DOI: 10.21175/RadProc.2017.02
21. M. J. Niciu, B. Kelmendi, G. Sanacora, “Overview of glutamatergic neurotransmission in the nervous system,” Pharmacol. Biochem. Behav ., vol. 100, no. 4, pp. 656 – 664, Feb. 2012.
    DOI: 10.1016/j.pbb.2011.08.008
    PMid: 21889952
    PMCid: PMC3253893
22. T. Yamashita et al., “Effect of Radiation on the Expression of Taurine Transporter in the Intestine of Mouse,” Adv. Exp. Med. Biol., vol. 975, part 2, pp. 729 – 740, 2017.
    DOI: 10.1007/978-94-024-1079-2_57
    PMid: 28849495
23. X. Wu et al., “Determination of amino acid neurotransmitters in rat hippocampi by HPLC-UV using NBD-F as a derivative,” Biomed. Chromatogr ., vol. 28, no. 4, pp. 459 – 462, Apr. 2014.
    DOI: 10.1002/bmc.3062
    PMid: 24132719
24. Xue-Jiao Zhao et al., “Simultaneous determination of five amino acid neurotransmitters in rat and porcine blood and brain by two-dimensional liquid chromatography,” J. Chromatgr. B, vol. 1163, 122507, Jan. 2021.
    DOI: 10.1016/j.jchromb.2020.122507
    PMid: 33387860
25. K. Hamase et al., “Regional distribution and postnatal changes of D-amino acids in rat brain,” Biochim. Biophys. Acta Gen. Subj., vol. 1334, no. 2-3, pp. 214 – 222, Mar. 1997.
    DOI: 10.1016/s0304-4165(96)00095-5
    PMid: 9101716
26. A. Furusho et al., “Development of a Highly-Sensitive Two-Dimensional HPLC System with Narrowbore Reversed-Phase and Microbore Enantioselective Columns and Application to the Chiral Amino Acid Analysis of the Mammalian Brain,” Chromatography, vol. 39, no. 2, pp. 83 – 90, Apr. 2018.
    DOI: 10.15583/jpchrom.2018.007
27. E. Bonfoco, D. Krainc, M. Ankarcrona, P. Nicotera, S. A. Lipton, “Apoptosis and necrosis: Two distinct events induced, respectively, by mild and intense insults with N-methyl-D-aspartate or nitric oxide/superoxide in cortical cell cultures,” PNAS USA, vol. 92, no. 16, pp. 7162 – 7166, Aug. 1995.
    DOI: 10.1073/pnas.92.16.7162
    PMid: 7638161
    PMCid: PMC41299