Hypoxia exacerbates cardiomyocyte injury via upregulation of Wnt3a and inhibition of Sirt3

SIRT3 regulates mitochondrial function: A promising star target for cardiovascular disease therapy

Dysregulation of mitochondrial homeostasis is common to all types of cardiovascular diseases. SIRT3 regulates apoptosis and autophagy, material and energy metabolism, mitochondrial oxidative stress, inflammation, and fibrosis. As an important mediator and node in the network of mechanisms, SIRT3 is essential to many activities. This review explains how SIRT3 regulates mitochondrial homeostasis and the tricarboxylic acid cycle to treat common cardiovascular diseases. A novel description of the impact of lifestyle factors on SIRT3 expression from the angles of nutrition, exercise, and temperature is provided.

Acetylation of aldehyde dehydrogenase ALDH1L2 regulates cellular redox balance and the chemosensitivity of colorectal cancer to 5-fluorouracil

Folate-mediated one-carbon metabolism (FOCM) is crucial in sustaining rapid proliferation and survival of cancer cells. The folate cycle depends on a series of key cellular enzymes, including aldehyde dehydrogenase 1 family member L2 (ALDH1L2) that is usually overexpressed in cancer cells, but the regulatory mechanism of ALDH1L2 remains undefined. In this study, we observed the significant overexpression of ALDH1L2 in colorectal cancer (CRC) tissues, which is associated with poor prognosis. Mechanistically, we identified that the acetylation of ALDH1L2 at the K70 site is an important regulatory mechanism inhibiting the enzymatic activity of ALDH1L2 and disturbing cellular redox balance. Moreover, we revealed that sirtuins 3 (SIRT3) directly binds and deacetylates ALDH1L2 to increase its activity. Interestingly, the chemotherapeutic agent 5-fluorouracil (5-Fu) inhibits the expression of SIRT3 and increases the acetylation levels of ALDH1L2 in colorectal cancer cells. 5-Fu-induced ALDH1L2 acetylation sufficiently inhibits its enzymatic activity and the production of NADPH and GSH, thereby leading to oxidative stress-induced apoptosis and suppressing tumor growth in mice. Furthermore, the K70Q mutant of ALDH1L2 sensitizes cancer cells to 5-Fu both in vitro and in vivo through perturbing cellular redox and serine metabolism. Our findings reveal an unknown 5-Fu-SIRT3-ALDH1L2 axis regulating redox homeostasis, and suggest that targeting ALDH1L2 is a promising therapeutic strategy to sensitize tumor cells to chemotherapeutic agents.

Cellular and molecular biology of sirtuins in cardiovascular disease

Sirtuins (SIRTs) are a nicotinic adenine dinucleotide (+) -dependent histone deacetylase that regulates critical signaling pathways in prokaryotes and eukaryotes. Studies have identified seven mammalian homologs of the yeast SIRT silencing message regulator 2, namely, SIRT1-SIRT7. Recent in vivo and in vitro studies have successfully demonstrated the involvement of SIRTs in key pathways for cell biological function in physiological and pathological processes of the cardiovascular system, including processes including cellular senescence, oxidative stress, apoptosis, DNA damage, and cellular metabolism. Emerging evidence has stimulated a significant evolution in preventing and treating cardiovascular disease (CVD). Here, we review the important roles of SIRTs for the regulatory pathways involved in the pathogenesis of cardiovascular diseases and their molecular targets, including novel protein post-translational modifications of succinylation. In addition, we summarize the agonists and inhibitors currently identified to target novel specific small molecules of SIRTs. A better understanding of the role of SIRTs in the biology of CVD opens new avenues for therapeutic intervention with great potential for preventing and treating CVD.

Peptidase Inhibitor 16 Attenuates Left Ventricular Injury and Remodeling After Myocardial Infarction by Inhibiting the HDAC1-Wnt3a-β-Catenin Signaling Axis

Background Myocardial infarction (MI) is a cardiovascular disease with high morbidity and mortality. PI16 (peptidase inhibitor 16), as a secreted protein, is highly expressed in heart diseases such as heart failure. However, the functional role of PI16 in MI is unknown. This study aimed to investigate the role of PI16 after MI and its underlying mechanisms. Methods and Results PI16 levels after MI were measured by enzyme-linked immunosorbent assay and immunofluorescence staining, which showed that PI16 was upregulated in the plasma of patients with acute MI and in the infarct zone of murine hearts. PI16 gain- and loss-of-function experiments were used to investigate the potential role of PI16 after MI. In vitro, PI16 overexpression inhibited oxygen-glucose deprivation-induced apoptosis in neonatal rat cardiomyocytes, whereas knockdown of PI16 exacerbated neonatal rat cardiomyocyte apoptosis. In vivo, left anterior descending coronary artery ligation was performed on PI16 transgenic mice, PI16 knockout mice, and their littermates. PI16 transgenic mice showed decreased cardiomyocyte apoptosis at 24 hours after MI and improved left ventricular remodeling at 28 days after MI. Conversely, PI16 knockout mice showed aggravated infract size and remodeling. Mechanistically, PI16 downregulated Wnt3a (wingless-type MMTV integration site family, member 3a)/β-catenin pathways, and the antiapoptotic role of PI16 was reversed by recombinant Wnt3a in oxygen-glucose deprivation-induced neonatal rat cardiomyocytes. PI16 also inhibited HDAC1 (class I histone deacetylase) expression, and overexpression HDAC1 abolished the inhibition of apoptosis and Wnt signaling of PI16. Conclusions In summary, PI16 protects against cardiomyocyte apoptosis and left ventricular remodeling after MI through the HDAC1-Wnt3a-β-catenin axis.

Identification of patient subtypes based on protein expression for prediction of heart failure after myocardial infarction

This study investigates the ability of high-throughput aptamer-based platform to identify circulating biomarkers able to predict occurrence of heart failure (HF), in blood samples collected during hospitalization of patients suffering from a first myocardial infarction (MI). REVE-1 (derivation) and REVE-2 (validation) cohorts included respectively 254 and 238 patients, followed up respectively 9 · 2 ± 4 · 8 and 7 · 6 ± 3 · 0 years. A blood sample collected during hospitalization was used for quantifying 4,668 proteins. Fifty proteins were significantly associated with long-term occurrence of HF with all-cause death as the competing event. k-means, an unsupervised clustering method, identified two groups of patients based on expression levels of the 50 proteins. Group 2 was significantly associated with a higher risk of HF in both cohorts. These results showed that a subset of 50 selected proteins quantified during hospitalization of MI patients is able to stratify and predict the long-term occurrence of HF.

LINC00936 exacerbated myocardial infarction progression via miR-4795-3p/Wnt3a signaling pathway based on biological and imaging methods

OBJECTIVE

LncRNAs show great potential in diagnosing and treating myocardial infarction (MI). Clarifying the mechanism of lncRNAs on MI is of great significance for the application of MI biomarkers. Therefore, this report intended to determine the role and mechanism of LINC00936 on MI by biological and imaging methods.

METHODS

Hypoxia H9C2 model was established by hypoxia treatment. Flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assay detected the apoptosis of H9C2. H2DCFDA staining and enzyme-linked immunosorbent assay (ELISA) was used to detect the reactive oxygen species (ROS) accumulation and Lactate dehydrogenase (LDH) contents, respectively. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect LINC00936, Wnt3a and miR-4795-3p levels. Western blot detected Wnt3a protein expression. Dual luciferase reporter assays detected the relationship of miR-4795-3p to LINC00936 or Wnt3a. Echocardiography analysis detected cardiac function. 2,3,5-Triphenyltetrazolium chloride (TTC) detected the infarct size. Masson staining detected the pathological changes.

RESULTS

LINC00936 level was elevated in the MI patients compared with the controls. Overexpression of LINC00936 promoted apoptosis and ROS accumulation in hypoxia H9C2 model and exacerbated MI progression in vivo. miR-4795-3p bound with LINC00936 in H9C2 cells and miR-4795-3p mimics inhibited apoptosis and ROS accumulation in hypoxia H9C2 model regulated by LINC00936. Wnt3a was targeted by miR-4795-3p and Wnt3a elevation promoted apoptosis and ROS accumulation in hypoxia H9C2 model.

CONCLUSION

In this report, we illustrated that LINC00936 exacerbated MI progression via the miR-4795-3p/Wnt3a signaling pathway based on biological and imaging methods. These findings might provide potential molecular target for the diagnosis and treatment of MI.

Emerging Roles of SIRT3 in Cardiac Metabolism

The heart is a highly metabolically active organ that predominantly utilizes fatty acids as an energy substrate. The heart also derives some part of its energy by oxidation of other substrates, including glucose, lactose, amino acids and ketones. The critical feature of cardiac pathology is metabolic remodeling and loss of metabolic flexibility. Sirtuin 3 (SIRT3) is one of the seven mammalian sirtuins (SIRT1 to SIRT7), with NAD⁺ dependent deacetylase activity. SIRT3 is expressed in high levels in healthy hearts but downregulated in the aged or diseased hearts. Experimental evidence shows that increasing SIRT3 levels or activity can ameliorate several cardiac pathologies. The primary deacetylation targets of SIRT3 are mitochondrial proteins, most of which are involved in energy metabolism. Thus, SIRT3 improves cardiac health by modulating cardiac energetics. In this review, we discuss the essential role of SIRT3 in regulating cardiac metabolism in the context of physiology and pathology. Specifically, we summarize the recent advancements that emphasize the critical role of SIRT3 as a master regulator of cardiac metabolism. We also present a comprehensive view of all known activators of SIRT3, and elaborate on their therapeutic potential to ameliorate energetic abnormalities in various cardiac pathologies.

Upregulation of Small Ubiquitin-Like Modifier 2 and Protein SUMOylation as a Cardioprotective Mechanism Against Myocardial Ischemia-Reperfusion Injury

Background: Small ubiquitin-like modifier (SUMO) proteins modify proteins through SUMOylation as an essential protein post-translational modification (PTM) for regulating redox status, inflammation, and cardiac fibrosis in myocardial infarction. This study aimed to investigate whether natural product puerarin could alleviate myocardial ischemia/reperfusion injury (MI-RI) by targeting protein SUMOylation. Methods: Mouse MI-RI model was induced by ligating the left anterior descending (LAD) coronary artery and subsequently treated with puerarin at the dose of 100 mg/kg. Rat cardiomyocyte H9c2 cells were challenged by hypoxia/reoxygenation and treated with puerarin at concentrations of 10, 20, and 40 μM. The infarction area of mouse hearts was assessed by 2% TTC staining. Cell damage was analyzed for the release of lactate dehydrogenase (LDH) in serum and cell culture medium. Western blot technique was employed to detect the expression of SUMO2, phospho-ERK, pro-inflammatory biomarker COX2, fibrosis index galectin-3, apoptosis-related protein cleaved PARP-1. The activation of the estrogen receptor (ER) pathway was assayed by the dual-luciferase reporter system. Results: The present study validated that puerarin effectively reduced myocardial infarct size and LDH release in the mouse MI-RI model. In the cell culture system, puerarin effectively decreased the release of LDH and the protein level of COX2, galectin-3, and cleaved PARP-1. Mechanistic studies revealed that puerarin increased the expression of SUMO2, SUMOylation of proteins and the activation of ER/ERK pathway in cardiomyocytes. ER, ERK and SUMO2 inhibitors attenuated the cardioprotective effects of puerarin. Conclusion: Puerarin may alleviate myocardial injury by promoting protein SUMOylation through ER/ERK/SUMO2-dependent mechanism.

Sirtuins-Mediated System-Level Regulation of Mammalian Tissues at the Interface between Metabolism and Cell Cycle: A Systematic Review

Sirtuins are a family of highly conserved NAD+-dependent proteins and this dependency links Sirtuins directly to metabolism. Sirtuins' activity has been shown to extend the lifespan of several organisms and mainly through the post-translational modification of their many target proteins, with deacetylation being the most common modification. The seven mammalian Sirtuins, SIRT1 through SIRT7, have been implicated in regulating physiological responses to metabolism and stress by acting as nutrient sensors, linking environmental and nutrient signals to mammalian metabolic homeostasis. Furthermore, mammalian Sirtuins have been implicated in playing major roles in mammalian pathophysiological conditions such as inflammation, obesity and cancer. Mammalian Sirtuins are expressed heterogeneously among different organs and tissues, and the same holds true for their substrates. Thus, the function of mammalian Sirtuins together with their substrates is expected to vary among tissues. Any therapy depending on Sirtuins could therefore have different local as well as systemic effects. Here, an introduction to processes relevant for the actions of Sirtuins, such as metabolism and cell cycle, will be followed by reasoning on the system-level function of Sirtuins and their substrates in different mammalian tissues. Their involvement in the healthy metabolism and metabolic disorders will be reviewed and critically discussed.