An inhibitor role of Nrf2 in the regulation of myocardial senescence and dysfunction after myocardial infarction.

Cellular senescence, a process whereby cells enter a state of permanent growth arrest, appears to regulate cardiac pathological remodeling and dysfunction in response to various stresses including myocardial infarction (MI). However, the precise role as well as the underlying regulatory mechanism of cardiac cellular senescence in the ischemic heart disease remain to be further determined. Herein we report an inhibitory role of Nrf2, a key transcription factor of cellular defense, in regulating cardiac senescence in infarcted hearts as well as a therapeutic potential of targeting Nrf2-mediated suppression of cardiac senescence in the treatment of MI-induced cardiac dysfunction. MI was induced by left coronary artery ligation for 28 days in mice. Heart tissues from the infarct border zone were used for the analyses. The MI-induced cardiac dysfunction was associated with increased myocardial cell senescence, oxidative stress and apoptosis in adult wild type (WT) mice. In addition, a downregulated Nrf2 activity was associated with upregulated Keap1 levels and increased phosphorylation of JAK and FYN in the infarcted border zone heart tissues. Nrf2 Knockout (Nrf2-/-) enhanced the MI-induced myocardial, cardiac dysfunction and senescence. Qiliqiangxin (QLQX), a herbal medicine which could reverse the MI-induced suppression of Nrf2 activity, significantly inhibited the MI-induced cardiac senescence, apoptosis, and cardiac dysfunction in WT mice but not in Nrf2-/- mice. These results indicate that MI downregulates Nrf2 activity thus promoting oxidative stress to accelerate cellular senescence in the infarcted heart towards cardiac dysfunction and Nrf2 may be a drug target for suppressing the cellular senescence-associated pathologies in infarcted hearts.