Prevention of epigallocatechin gallate on decreasing expression of cardiac troponin-Ⅰ in aging mice hearts and its mechanism

Abstract:

Objective：To investigate whether epigallocatechin gallate（EGCG） could prevent the declining expression of cardiac tro－ponin Ⅰ（cTnⅠ） in aging mice hearts and to study its mechanism. Methods：Expression levels of cTnⅠ mRNA and protein were de－tected by using RT-PCR and Western blot assays in each age group（n=5）. A total of 32 C57 BL/6 female mice of 12 month old were randomly divided into the blank group，the EGCG low-dose group[EGCG-L，50 mg/（kg·d）]，the EGCG medium-dose group[EGCG-M，100 mg/（kg·d）] and the EGCG high-dose group[EGCG-H，200 mg/（kg·d）]. Mice from EGCG intervention groups were treated with EGCG by water for 6 months. The female mice at age of 3-month were chosen as the young group（n=8）. The cTnⅠ and HDAC1 mRNA expression were measured by RT-PCR. The protein level of cTnⅠ was determined by Western blot. The binding level of acetylated lysine 9 on histone H3（AcH3K9），HDAC1，transcription factors GATA4 and Mef2c near cTnⅠ’s promoter was identified by CHIP-Q-PCR. Results：During the aging process，both expressive levels of cTnⅠ mRNA and protein of 16-month-old mice[（0.913±0.150），（0.683±0.133）] began decreasing（P=0.002，P=0.003） when compared with 12-month-old mice[（1.483±0.226），（1.127±0.074）]. After EGCG intervention，the HDAC1 expression and the binding level in cTnⅠ’s promoter region in the EGCG-H group[（0.801±0.037），（0.225±0.153）] were lower than those in the blank group[（1.924±0.117），（0.963±0.105）]（P=0.000，P=0.000）. AcH3K9 levels in cTnⅠ’s promoter region and binding levels of GATA4 and Mef2c were （0.392±0.138），（0.404±0.150），（0.347±0.093），respectively. In the EGCG-H group，AcH3K9 levels（0.723±0.208），GATA4（1.051±0.239） and Mef2c（1.129±0.187） binding levels in the proximal promoter region of cTnⅠ gene were increased（P=0.014，P=0.000，P=0.000）. Expressive levels of cTnⅠ mRNA and protein in the EGCG-H group[（0.943±0.114），（1.034±0.058）] were higher than those in the blank group[（0.093±0.033），（0.619±0.179）]（P=0.000，P=0.007）. Conclusion：High dose EGCG can prevent the decline of cTnⅠ in aging mice by inhibiting HDAC1 and elevating AcH3K9.