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High-density lipoprotein protects cardiomyocytes from oxidative stress via the PI3K/mTOR signaling pathway.

ABSTRACT: Low levels of plasma high-density lipoprotein (HDL) cholesterol are associated with an increased risk of heart failure, regardless of the presence or absence of coronary artery disease. However, the direct effects of HDL on failing myocardium have not been fully elucidated. We found that HDL treatment resulted in improved cell viability in H9c2 cardiomyocytes under oxidative stress. This cardioprotective effect of HDL was regulated via the phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway. mTOR signaling promotes cell survival through the inactivation of the BCL2-associated agonist of cell death via phosphorylation of ribosomal protein S6 kinase. Modulation of cardiac PI3K/mTOR signaling by HDL could represent a novel therapeutic strategy for heart failure.

SUBMITTER: Nagao M

PROVIDER: S-EPMC5586351 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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High-density lipoprotein protects cardiomyocytes from oxidative stress via the PI3K/mTOR signaling pathway.

Nagao Manabu M Toh Ryuji R Irino Yasuhiro Y Nakajima Hideto H Oshita Toshihiko T Tsuda Shigeyasu S Hara Tetsuya T Shinohara Masakazu M Ishida Tatsuro T Hirata Ken-Ichi KI

FEBS open bio 20170814 9

Low levels of plasma high-density lipoprotein (HDL) cholesterol are associated with an increased risk of heart failure, regardless of the presence or absence of coronary artery disease. However, the direct effects of HDL on failing myocardium have not been fully elucidated. We found that HDL treatment resulted in improved cell viability in H9c2 cardiomyocytes under oxidative stress. This cardioprotective effect of HDL was regulated via the phosphatidylinositol 3-kinase (PI3K)/mammalian target of ...[more]

PMID: 28904868

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Project description:Background:Diabetic cardiomyopathy (DCM), which is associated with many pathological processes, commonly occurs when advanced glycation end products (AGEs) are present. ?-carotene (BC) is a well-known vitamin A precursor that is found in many fruits and vegetables. BC can reduce the risk of cancer and cardiovascular disease. This study aimed to investigate the effect of BC on AGE-induced myocardial injury in vitro. Methods:Cell viability test was used to select 40 µM concentrations of BC to treat AGE-induced H2c9 cells. The cell apoptosis was detected by flow cytometry. Western blotting was used to measure the protein expression levels of Bcl-2-associated X protein (Bax), B-cell lymphoma-2 (Bcl-2), cleaved caspase-3, activating transcription factor 4 (ATF4), glucose-regulated protein 78 (GRP78), CCAAT/enhancer-binding protein homologous protein (CHOP), beclin 1, p62,microtubule-associated protein 1 light chain 3 (LC3), phosphorylated PI3K (p-PI3K), phosphorylated Akt (p-AKT), and phosphorylated mTOR (p-mTOR). Enzyme-linked immunosorbent assay (ELISA) was performed to measure the levels of lactate dehydrogenase (LDH) and cardiac troponin-1 (cTn-I). Reactive oxygen species (ROS) was detected by flow cytometry. The levels of malondialdehyde (MDA), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) were used to determine MDA kits, SOD assay kit and GSH-Px kit, respectively. Results:BC significantly inhibited AGE-induced cell death and apoptosis in H9c2 cells. BC had a suppressive effect on intracellular ROS production and antioxidative enzyme reduction. Moreover, BC decreased hyperactive endoplasmic reticulum (ER) stress and autophagy in H9c2 cells. Furthermore, BC exerted a cardioprotective effect in AGE-induced H9c2 cells via the activation of the PI3K/Akt/mTOR signaling pathway. Conclusions:BC exhibited a cardioprotective effect AGE-induced apoptosis. Our study provides a foundation for further study into the potential value of BC for treating DCM or other heart diseases.

Project description:Autophagy is a cellular self-digestion process that mediates protein quality control and serves to protect against neurodegenerative disorders, infections, inflammatory diseases and cancer. Current evidence suggests that autophagy can selectively remove damaged organelles such as the mitochondria. Mitochondria-induced oxidative stress has been shown to play a major role in a wide range of pathologies in several organs, including the heart. Few studies have investigated whether enhanced autophagy can offer protection against mitochondrially-generated oxidative stress. We induced mitochondrial stress in cardiomyocytes using antimycin A (AMA), which increased mitochondrial superoxide generation, decreased mitochondrial membrane potential and depressed cellular respiration. In addition, AMA augmented nuclear DNA oxidation and cell death in cardiomyocytes. Interestingly, although oxidative stress has been proposed to induce autophagy, treatment with AMA did not result in stimulation of autophagy or mitophagy in cardiomyocytes. Our results showed that the MTOR inhibitor rapamycin induced autophagy, promoted mitochondrial clearance and protected cardiomyocytes from the cytotoxic effects of AMA, as assessed by apoptotic marker activation and viability assays in both mouse atrial HL-1 cardiomyocytes and human ventricular AC16 cells. Importantly, rapamycin improved mitochondrial function, as determined by cellular respiration, mitochondrial membrane potential and morphology analysis. Furthermore, autophagy induction by rapamycin suppressed the accumulation of ubiquitinylated proteins induced by AMA. Inhibition of rapamycin-induced autophagy by pharmacological or genetic interventions attenuated the cytoprotective effects of rapamycin against AMA. We propose that rapamycin offers cytoprotection against oxidative stress by a combined approach of removing dysfunctional mitochondria as well as by degrading damaged, ubiquitinated proteins. We conclude that autophagy induction by rapamycin could be utilized as a potential therapeutic strategy against oxidative stress-mediated damage in cardiomyocytes.

Dataset Information

High-density lipoprotein protects cardiomyocytes from oxidative stress via the PI3K/mTOR signaling pathway.

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High-density lipoprotein protects cardiomyocytes from oxidative stress via the PI3K/mTOR signaling pathway.

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