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L-Theanine Improves Immunity by Altering TH2/TH1 Cytokine Balance, Brain Neurotransmitters, and Expression of Phospholipase C in Rat Hearts

Chengjian Li, Haiou Tong, Qiongxian Yan, Shaoxun Tang, Xuefeng Han, Wenjun Xiao, Zhiliang Tan

(National Research Center of Engineering Technology for Utilization of Botanical Functional Ingredients from Botanicals, Provincial Co-Innovation Center for Utilization of Botanical Function Ingredients, Hunan Agricultural University, Changsha, Hunan, China (mainland))

Med Sci Monit 2016; 22:662-669

DOI: 10.12659/MSM.897077

Published: 2016-02-28

BACKGROUND: This study aimed to investigate the regulatory effects of L-theanine on secretion of immune cytokines, hormones, and neurotransmitters, and mRNA expression of phospholipase C (PLC) in rats, and to explore its regulatory mechanism in immune function.
MATERIAL AND METHODS: Sixty-four Sprague-Dawley rats received daily intragastric infusion of different doses of L-theanine solution [0, 50 (LT), 200 (MT), and 400 (HT) mg/kg BW]. Cytokines, immunoglobulins, and hormones in the serum, neurotransmitters, and mRNA expression of PLC in the relevant tissues were assayed.
RESULTS: L-theanine administration increased the splenic organ index and decreased the contents of ILs-4/6/10 and the ratio of IL-4/IFN-γ in the serum. High-dose L-theanine administration increased the levels of dopamine and 5-hydroxytryptamine in the pituitary and hippocampus, resulting in decrease in corticosterone level in the serum. L-theanine administration decreased the mRNA expressions of PLC isomers in the liver and PLC-γ1 and PLC-δ1 in the spleen. Interestingly, mRNA expressions of PLC-β1 in the spleen and PLC isomers mRNA in the heart were up-regulated by L-theanine administration.
CONCLUSIONS: Administration of 400 mg/kg BWL-theanine improved immune function of the rats by increasing the splenic weight, altering the Th2/Th1 cytokine balance, decreasing the corticosterone level in the serum, elevating dopamine and 5-hydroxytryptamine in the brain, and regulating the mRNA expression of PLC isomers in the heart.

Keywords: Cytokines - blood, Brain - metabolism, Animals, Female, Gene Expression Regulation, Enzymologic, Glutamates - pharmacology, Immunity - drug effects, Male, Myocardium - enzymology, Neurotransmitter Agents - metabolism, Organ Specificity - drug effects, Rats, Sprague-Dawley, Real-Time Polymerase Chain Reaction, Th1 Cells - immunology, Th2 Cells - immunology, Type C Phospholipases - metabolism