l-theanine, the unique constituent of tea, improves neuronal survivability by curtailing inflammatory responses in MPTP model of Parkinson's disease

Abstract

Discrete components of tea possess multitude of health advantages. Escalating evidence advocate a consequential association between habitual tea consumption and a subsided risk of Parkinson's disease (PD). l-theanine is a non-protein amino acid inherent in tea plants, which exhibits structural resemblance with glutamate, the copious excitatory neurotransmitter in brain. Neuromodulatory effects of l-theanine are evident from its competency in traversing the blood brain barrier, promoting a sense of calmness beyond enervation, and enhancing cognition and attention. Despite the multifarious reports on antioxidant properties of l-theanine and its potential to regulate brain neurotransmitter levels, it is obligatory to understand its exact contribution in ameliorating the pathophysiology of PD. In this study, MPTP-induced mouse model was established and PD-like symptoms were developed in test animals where an increasing dosage of l-theanine (5, 25, 50, 100 and 250 mg/kg) was intraperitoneally administered for 23 days. 50 and 100 mg/kg dosage of l-theanine alleviated motor impairment and specific non-motor symptoms in Parkinsonian mice. The dosage of 100 mg/kg of l-theanine also improved striatal dopamine and serotonin level and tyrosine-hydroxylase positive cell count in the substantia nigra. Most crucial finding of the study is the proficiency of l-theanine to diminish astroglial injury as well as nitric oxide synthesis, which suggests its possible credential to prevent neurodegeneration by virtue of its anti-inflammatory attribute.