Resistance exercise upregulates Irisin expression and suppresses myocardial fibrosis following myocardial infarction via activating AMPK-Sirt1 and inactivating TGFß1-Smad2/3.

AIM: To reveal the contribution of Irisin in the beneficial effects of resistance exercise on myocardial fibrosis (MF) and cardiac function in the mice with myocardial infarction (MI). METHODS: The MI model was built by ligating the left anterior descending coronary artery in Fndc5 knockout mice (Fndc5-/-). Resistance exercise was started one week after surgery and continued for four weeks. In addition, H2O2, AICAR, recombinant human Irisin protein (rhIRISIN), and Sirt1 shRNA lentivirus (LV-Sirt1 shRNA) were used to intervene primary isolated cardiac fibroblasts (CFs). MF was observed through Masson staining, and apoptosis was assessed using TUNEL staining. MDA and T-SOD contents were detected by biochemical kits. The expression of proteins and genes was detected by Western blotting and RT-qPCR. RESULTS: Resistance exercise increased Fndc5 mRNA level, inhibited the activation of TGFß1-TGFßR2-Smad2/3 pathway, activated AMPK-Sirt1 pathway, reduced the levels of oxidative stress, apoptosis, and MF in the infarcted heart, and promoted cardiac function. However, Fndc5 knockout attenuated the protective effects of resistance exercise on the MI heart. Results of the in vitro experiments showed that AICAR and rhIRISIN intervention activated the AMPK-Sirt1 pathway and inactivated the TGFß1-Smad2/3 pathway, and promoted apoptosis in H2O2-treated CFs. Notably, these effects of rhIRISIN intervention, except for the TGFßR2 expression, were attenuated by LV-Sirt1 shRNA. CONCLUSION: Resistance exercise upregulates Fndc5 expression, activates AMPK-Sirt1 pathway, inhibits the activation of TGFß1-Smad2/3 pathway, attenuates MF, and promotes cardiac function after MI.

Knockdown of PKMYT1 is associated with autophagy inhibition and apoptosis induction and suppresses tumor progression in hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is a cancerous tumor that ranks as the third leading cause of cancer death across the globe. Protein kinase membrane-associated tyrosine/threonine kinase 1 (PKMYT1) is overexpressed in many cancer types, including HCC, but the potential mechanism and biological function of PKMYT1 are not fully understood. MATERIALS AND METHODS: The expression level of PKMYT1 was detected in human HCC tissues and adjacent tissues. We then established HCC cell lines with PKMYT1 knockdown and observed proliferation, migration, autophagy, apoptosis in cell lines and tumor growth in a nude mouse model. To investigate the underlying mechanism by which PKMYT1 regulates autophagy and apoptosis, RNA sequencing was performed in HCC-LM3 cells with and without PKMYT1 knockdown. RESULTS: Here, we observed that human HCC tissues had higher expression of PKMYT1 than adjacent tissues. Overexpression of PKMYT1 was closely associated with poor prognosis in HCC patients. PKMYT1 knockdown inhibited the proliferative potential and migration of HCC cell lines. We also found that downregulation of PKMYT1 inhibited autophagy and induced apoptosis. RNA sequencing analysis showed that the MAPK and PI3K-AKT pathways, which have been reported to affect autophagy and apoptosis, may be regulated after PKMYT1 knockdown by KEGG pathway enrichment analysis. Furthermore, we identified that knockdown of PKMYT1 attenuated the phosphorylation levels of p38 MAPK, ERK and PI3K/Akt/mTOR, which might mediate autophagy inhibition and apoptosis induction via these signaling pathways to inhibit the development of HCC. CONCLUSION: Our study suggests that PKMYT1 functions as an oncogene and may be a new target for HCC treatment.

Irisin and ALCAT1 mediated aerobic exercise-alleviated oxidative stress and apoptosis in skeletal muscle of mice with myocardial infarction.

Skeletal muscle in patients with heart failure (HF) exhibits altered structure, function and metabolism. Myocardial infarction (MI) is the most common cause of HF. Oxidative stress and cell apoptosis are involved in the pathophysiology of MI/HF-induced skeletal muscle atrophy. It is well recognized that aerobic exercise (AE) could prevent skeletal muscle atrophy after MI, but the underlying mechanism and molecular targets are still not fully clarified. In this study, Fndc5-/- and Alcat1-/- mice were used to establish the MI model and subjected to six weeks of moderate-intensity AE. C2C12 cells were treated with H2O2 and recombinant human Irisin (rhIrisin), or transduced with a lentiviral vector to mediate the overexpression of ALCAT1 (LV-Alcat1). Results showed that MI reduced Irisin expression and antioxidant capacity of skeletal muscle, increased ALCAT1 expression, induced protein degradation and cell apoptosis, which were partly reversed by AE; Knockout of Fndc5 further aggravated MI-induced oxidative stress and cell apoptosis in skeletal muscle, and partly weakened the beneficial effects of AE. In contrast, knockout of Alcat1 reduced MI-induced oxidative stress and cell apoptosis and strengthened the beneficial effects of AE. rhIrisin and AICAR intervention inhibited ALCAT1 expression, oxidative stress and cell apoptosis, which induced by H2O2 or LV-Alcat1 in C2C12 cells. These findings reveal that AE could alleviate the levels of oxidative stress and apoptosis in skeletal muscle following MI, partly via up-regulating Irisin and inhibiting ALCAT1 expression.

Role of Chitinase-3-like Protein 1 in Cardioprotection and Angiogenesis by Post-Infarction Exercise Training.

Chitinase-3-like protein 1 (CHI3L1) is a myokine involving tissue remodeling and inflammatory processes. CHI3L1 and its receptor protease-activated receptor 2 (PAR2) are induced by exercise in skeletal muscles. However, it remains unknown if CHI3L1/PAR2 signaling also mediates exercise-induced cardioprotection after myocardial infarction. Twenty-four adult male rats were divided into three groups (n = 8/group), receiving: (1) a sham operation; (2) permanent ligation of left anterior descending coronary artery; and (3) post-MI exercise training with one-week adaptive treadmill exercise for seven days followed by four weeks of aerobic exercise. Left ventricular systolic and end-diastolic pressure indices were measured and cardiac fibrosis, and angiogenesis were examined. Furthermore, HUVEC cells were treated in vitro with AMPK agonist-AICAR (a putative pharmacological memetic of exercise), recombinant human CHI3L1, PAR2 receptor blocker (AZ3451), and PI3K inhibitor (LY294002), respectively. We found that post-MI exercise significantly upregulated CHI3L1, PAR2, pPI3K/PI3K, pAKT/AKT, pERK/ERK, improved cardiac function, and diminished fibrosis. AICAR increased HUVEC tubules formation and upregulated CHI3L1 and PAR2 and these changes were attenuated by PAR2 blocker. In conclusion, post-MI exercise training can effectively activate CHI3L1/PAR2 signaling, which led to the improved myocardial function and enhanced cardiac angiogenesis in the infarcted heart.

Aerobic exercise alleviates oxidative stress-induced apoptosis in kidneys of myocardial infarction mice by inhibiting ALCAT1 and activating FNDC5/Irisin signaling pathway.

Aerobic exercise involves in ameliorating kidney injury, but the underlying mechanisms are not fully clarified. In this study, we elucidated the potential mechanisms of aerobic exercise in ameliorating kidney injury following myocardial infarction (MI). In vivo, wildtype and alcat1 knockout mice were used to establish the MI model, and subjected to six-week moderate-intensity aerobic exercise. In vitro, Normal Rat Kidney (NRK) cells treated with H2O2 and recombinant human Irisin (rhIrisin) were used for exploring potential mechanisms. Our results showed that Irisin expression was up-regulated by aerobic exercise in kidneys after MI, while ALCAT1 was reduced. In alcat1 knockout mice, we found that ALCAT1 involved in the progressions of oxidative stress and apoptosis in impaired kidney tissues of MI mice, but aerobic exercise reversed these changes. Furthermore, in vitro, we observed that Irisin inhibited both H2O2-treatment or overexpression of alcat1-induced oxidative stress and apoptosis in NRK cells, partially via AMPK-Sirt1-PGC-1α pathway. These findings reveal that aerobic exercise participates in alleviating the levels of oxidative stress and apoptosis in impaired kidney tissues following MI, partially via activating FNDC5/Irisin-AMPK-Sirt1-PGC-1α signaling pathway and inhibiting ALCAT1 expression.

Gain of function mutant p53 protein activates AKT through the Rac1 signaling to promote tumorigenesis.

Tumor suppressor p53 is the most frequently mutated gene in human cancer. Mutant p53 (mutp53) not only loses the tumor suppressive activity of wild type p53, but often gains new oncogenic activities to promote tumorigenesis, defined as mutp53 gain of function (GOF). While the concept of mutp53 GOF is well-established, its underlying mechanism is not well-understood. AKT has been suggested to be activated by mutp53 and contribute to mutp53 GOF, but its underlying mechanism is unclear. In this study, we found that the activation of the Rac1 signaling by mutp53 mediates the promoting effect of mutp53 on AKT activation. Blocking Rac1 signaling by RNAi or a Rac1 inhibitor can inhibit AKT activation by mutp53. Importantly, targeting Rac1/AKT can greatly compromise mutp53 GOF in tumorigenesis. Results from this study uncover a new mechanism for AKT activation in tumors, and reveal that activation of AKT by mutp53 via the Rac1 signaling contributes to mutp53 GOF in tumorigenesis. More importantly, this study provides Rac1 and AKT as potential targets for therapy in tumors containing mutp53.

Up-regulation of Thioredoxin 1 by aerobic exercise training attenuates endoplasmic reticulum stress and cardiomyocyte apoptosis following myocardial infarction.

Exercise training (ET) has been reported to reduce oxidative stress and endoplasmic reticulum (ER) stress in the heart following myocardial infarction (MI). Thioredoxin 1 (Trx1) plays a protective role in the infarcted heart. However, whether Trx1 regulates ER stress of the infarcted heart and participates in ET-induced cardiac protective effects are still not well known. In this work, H9c2 cells were treated with hydrogen peroxide (H2O2) and recombinant human Trx1 protein (TXN), meanwhile, adult male C57B6L mice were used to establish the MI model, and subjected to a six-week aerobic exercise training (AET) with or without the injection of Trx1 inhibitor, PX-12. Results showed that H2O2 significantly increased reactive oxygen species (ROS) level and the expression of TXNIP, CHOP and cleaved caspase12, induced cell apoptosis; TXN intervention reduced ROS level and the expression of CHOP and cleaved caspase12, and inhibited cell apoptosis in H2O2-treated H9c2 cells. Furthermore, AET up-regulated endogenous Trx1 protein expression and down-regulated TXNIP expression, restored ROS level and the expression of ER stress-related proteins, inhibited cell apoptosis as well as improved cardiac fibrosis and heart function in mice after MI. PX-12 partly inhibited the AET-induced beneficial effects in the infarcted heart. This study demonstrates that Trx1 attenuates ER stress-induced cell apoptosis, and AET reduces MI-induced ROS overproduction, ER stress and cell apoptosis partly through up-regulating of Trx1 expression in mice with MI.