Rapamycin regulates the balance between�cardiomyocyte apoptosis and autophagy in chronic heart failure by inhibiting mTOR signaling

Abstract

The progressive loss of cardiomyocytes caused by cell death leads to cardiac dysfunction and heart failure (HF). Rapamycin has been shown to be cardioprotective in pressure-overloaded and ischemic heart diseases by regulating the mechanistic target of rapamycin (mTOR) signaling network. However, the impact of rapamycin on cardiomyocyte death in chronic HF remains undetermined. Therefore, in the current study we addressed this issue using a rat myocardial infarction (MI)-induced chronic HF model induced by ligating the coronary artery. Following surgery, rats were randomly divided into six groups, including the sham-, vehicle- and rapamycin-operated groups, at 8 or 12 weeks post-MI. A period of 4 weeks after MI induction, the rats were treated with rapamycin (1.4 mg-kg-day) or vehicle for 4 weeks. Cardiac function was determined using echocardiography, the rats were subsequently euthanized and myocardial tissues were harvested for histological and biochemical analyses. In the cell culture experiments with H9c2 rat cardiomyocytes, apoptosis was induced using angiotensin II (100 nM; 24 h). Cardiomyocyte apoptosis and autophagy were assessed via measuring apoptosis- and autophagy-associated proteins. The activities of mTOR complex 1 (mTORC1) and mTORC2 were evaluated using the phosphorylation states of ribosomal S6 protein and Akt, respectively. The activity of the endoplasmic reticulum (ER) stress pathway was determined using the levels of GRP78, caspase-12, phospho-JNK and DDIT3. Echocardiographic and histological measurements indicated that rapamycin treatment improved cardiac function and inhibited cardiac remodeling at 8 weeks post-MI. Additionally, rapamycin prevented cardiomyocyte apoptosis and promoted autophagy at 8 weeks post-MI. Rapamycin treatment for 4 weeks inhibited the mTOR and ER stress pathways. Furthermore, rapamycin prevented angiotensin II-induced H9c2 cell apoptosis and promoted autophagy by inhibiting the mTORC1 and ER stress pathways. These results demonstrated that rapamycin reduced cardiomyocyte apoptosis and promoted cardiomyocyte autophagy, by regulating the crosstalk between the mTOR and ER stress pathways in chronic HF.

Translation Regulation by eIF2α Phosphorylation and mTORC1 Signaling Pathways in Non-Communicable Diseases (NCDs)

“…Therefore, non-eIF4E-mediated mRNA translation plays a major role during ischemia, as most lymphangiogenic factors are translationally induced in hypoxic cardiomyocytes [208][209][210][211]. Finally, consistent with these findings, inhibition of mTORC1 by rapamycin was recently shown to be cardioprotective in pressure-overloaded and ischemic heart diseases, preventing cardiomyocyte apoptosis, and promoting autophagy in chronic heart failure [212].…”

Mitochondria as a therapeutic target for cardiac ischemia‑reperfusion injury (Review)

“…As an allosteric inhibitor of mTOR complex I (mTORC1), rapamycin plays a role in the suppression of cell growth and division, and has been used as an immunosuppressant drug, or for the treatment of cancer and in-stent restenosis in clinical practice. Rapamycin has also been shown to reduce cardiomyocyte hypertrophy in a mouse model of chronic ischemic injury and to inhibit cardiomyocyte apoptosis in vitro (angiotensin II-induced myocyte apoptosis model) and in vivo (MI-induced chronic heart failure rat model) ( 126 ).…”

Cardiac Aging: From Basic Research to Therapeutics

“…Therefore, it has been shown that enhancing autophagy can improve cardiac function and alleviate pathological changes associated with cardiac aging by removing dysfunctional organelles and misfolded proteins. For example, inhibiting Akt/mTORC1 signaling can enhance autophagy, thereby inhibiting cardiac aging [53]. The deletion of Rhoassociated coiled-coil-containing protein kinase (ROCK)1 and ROCK2 reduces cardiac fibrosis during cardiac aging by promoting age-related autophagy in mice [54].…”

“…The second complex is mTOR complex 2 (mTORC2), which is made up of mTOR, Rictor, βl, Sin1, PRR5/Protor-1, and DEPTOR and is insensitive to short-term rapamycin treatment [88]. There is growing evidence that mTOR signaling is activated in many diseases, including cancer [89], neurodegenerative disorders [90], obesity [91], chronic obstructive pulmonary disease [91,92], pulse arterial hypertension [93], and CVD [53].…”