Proteomic analysis of the Otoprotective effects of green tea extract on age-related hearing loss

Background: Age-related hearing loss (ARHL) is a very common complex disease that causes hearing deficits with age. ARHL seriously affects the cognition and quality of life for the elderly. An ideal method of treating or preventing ARHL is currently unavailable. Green tea and its active ingredients can reduce the risk of age-related diseases. Objective: This study aimed to evaluate the effect of green tea and its important active ingredients such as epigallocatechin gallate (EGCG) on ARHL, as well as to reveal the molecular mechanism underlying this effect. Methods: Green tea extract (GTE) along with EGCG was given to C57BL/6 J mice over a period of 9 months. The dosage of green tea extract used in this study corresponds to a human acceptable intake level and is within the known safety range. The impact on hearing was measured using the auditory brainstem response. Subsequently, 4D label-free proteomics was utilized to examine the expression of cochlear proteins in the GTE and 12 m groups. Differential protein expression was visualized through volcano plot analysis. Enrichment evaluations of GO and KEGG pathways were performed to uncover biological roles and molecular pathways. Furthermore, proteins within these differential expressions were analyzed using PPI network and VarElect analysis, enhancing the identification of key proteins based on scoring criteria. Results: GTE-treated mice had better hearing than control ones, whereas EGCG-treated mice had no significant improvement in hearing. GTE-treated mice also showed better cochlear tissue morphology, and less spiral ganglion neuron damage than control ones. 4D label-free proteomics were used to assess the proteomic patterns. A multitude of differentially expressed proteins (59) were identified in the cochlea of GTE-treated mice. Pathway analysis further indicated that these DE proteins were involved in the Cytosolic DNA-sensing pathway, spliceosome, Rap1 signaling, and metabolism process of various substances, such as taurine. Conclusions : Long-term GTE supplementation ameliorated ARHL in mice through various pathways, suggesting some drug targets for ARHL treatment. • ARHL, a common complex disease, causes age-related hearing loss, impairing cognition/life quality in elderly. • GTE-treated mice had better hearing vs controls; EGCG showed no improvement. • 4D label-free proteomics reveals that GTE improves age-related hearing loss by regulating metabolism.