Altered levels of oxidation and phospholipase C isozyme expression in the brains of theanine-administered rats.

Previously, we revealed that theanine, a green tea component, induced phospholipase C (PLC)-beta1 and -gamma1, stress-responsible molecules, in primary cultured rat cerebral cortical neurons, suggesting its protective effect on oxidative stress in neurons. In this study, we investigated whether the same favorable effect occurs in vivo. On the oral administration of theanine (10 mmol (1.74 g)/kg, once a day) to rats via gastric intubation for 2 weeks, there was no change in the weight of the body or the cerebral cortex (Cx), cerebellum (Cb), or hippocampus (Hip) in the brain. On assessment of oxidation levels in the brain with thiobarbiturate reactive substances as a marker, the levels were found to be 20% lower in the Cx of theanine-treated rats than in that of control ones. The protein expression levels of PLC-beta1 and -gamma1 were significantly increased in the Cx on theanine administration and the same tendency was observed in the Cb, but not the Hip. In addition, the protein expression level of PLC-delta1, which plays an opposite role to the other two isozymes, was not affected in any brain regions on theanine administration. Overall, it was demonstrated that theanine is a safe compound and its repeated oral administration reduces oxidation levels in the brain, especially the Cx, by increasing PLC-beta1 and -gamma1 protein expression, suggesting its favorable effect on the brain in vivo.