Protective Effect of l‑Theanine on Cyclophosphamide-Induced Testicular Toxicity in Mice

l-Theanine is the most abundant
free amino acid present
in tea. Several tea components have been studied for their impact
on male fertility, but little is known about the effects of l-theanine. Cyclophosphamide (CP) is an antineoplastic and immunosuppressive
agent that reduces fertility in males. In the present study, we evaluated
the effect of l-theanine on CP-induced testicular toxicity
in male mice. A single dosage of 50 mg/kg saline or CP was administered
intraperitoneally over the course of 5 days. Mice were administered l-theanine (80 mg/kg) or saline by gavage for 30 days. Animals
were euthanized 24 h after the last l-theanine administration,
and the testes were removed for histopathological and transmission
electron microscopy analysis. Histological evaluation and transmission
electron microscopy showed that administration of l-theanine
alleviated CP-induced damage to the testicles, including spermatogonial
cells, epithelial cells, seminiferous tubules, and basement membrane.
An integrated proteomics and metabolomics investigation of testes
revealed that l-theanine therapy substantially affected the
quantity of 719 proteins (395 upregulated and 324 downregulated) and
196 metabolites (75 upregulated and 111 downregulated). The top three
enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for
these proteins and metabolites were purine metabolism, choline metabolism
in cancer, and arachidonic acid metabolism. This is the first study
to reveal the protective effect of l-theanine on CP-induced
testicular toxicity. l-Theanine could be a potential natural
active substance for resistance to the testis toxicity induced by
CP.