Roles and mechanisms of SUMOylation on key proteins in myocardial ischemia/reperfusion injury

Protective Role of (-)-Epicatechin on Trimethylamine-N-Oxide (TMAO)-Induced Cardiac Hypertrophy via SP1/SIRT1/SUMO1 Signaling Pathway

(-)-Epicatechin (EPI) is beneficial for cardiovascular health. Trimethylamine N-oxide (TMAO), a gut microbe-derived food metabolite, is strongly associated with the risk of cardiovascular diseases. However, the effects and underlying mechanisms of EPI on TMAO-induced cardiac hypertrophy remain unclear. This study aimed to determine whether EPI inhibits TMAO-induced cardiac hypertrophy. Plasma levels of TMAO in control participants and patients with cardiac hypertrophy were measured and analyzed. Male C57BL/6 mice were randomly divided into control group, TMAO group, EPI group and TMAO + EPI group. According to the groups assignments, mice received intraperitoneal (i.p.) injection of normal saline or i.p. injection of TMAO (150 mg/kg/day) for 14 days. The EPI group was given intragastric (i.g.) administration of EPI alone (1 mg/kg/day) for 21 days, and TMAO + EPI group received i.g. administration of EPI for 7 days before starting i.p. injection of TMAO, continuing until the end of the TMAO treatment. Histological analyses of the mice's hearts was accessed by H&E and Masson staining. In vitro, H9c2 cells were induced to hypertrophy by TMAO (10 µM) for 24 h and were pre-treated with or without EPI (10 µM) for 1 h. Protein level of cardiac hypertrophy markers and Sp1/SIRT1/SUMO1 pathway were determined by western blot. The plasma level of TMAO was 2.66 ± 1.59 μmol/L in patients with cardiac hypertrophy and 0.62 ± 0.30 μmol/L in control participants. EPI attenuated TMAO-induced hypertrophy in H9c2 cells. In vivo, TMAO induced cardiac hypertrophy and impaired the cardiac function of mice. Pathological staining showed that TMAO induced cardiac hypertrophy and collagen deposition in mice. EPI treatment improved the cardiac function, inhibited the myocardial hypertrophy induced by TMAO. EPI significantly attenuated the TMAO-induced upregulation of ANP and BNP and the downregulation of SP1, SIRT1 and SUMO1 in vivo and in vitro. EPI may suppress TMAO-induced cardiac hypertrophy by activating the Sp1/SIRT1/SUMO1 signaling pathway.

DJ-1: Potential target for treatment of myocardial ischemia-reperfusion injury

Ischemic heart disease (IHD) is a significant global health concern, resulting in high rates of mortality and disability among patients. Although coronary blood flow reperfusion is a key treatment for IHD, it often leads to acute myocardial ischemia-reperfusion injury (IRI). Current intervention strategies have limitations in providing adequate protection for the ischemic myocardium. DJ-1, originally known as a Parkinson's disease related protein, is a highly conserved cytoprotective protein. It is involved in enhancing mitochondrial function, scavenging reactive oxygen species (ROS), regulating autophagy, inhibiting apoptosis, modulating anaerobic metabolism, and exerting anti-inflammatory effects. DJ-1 is also required for protective strategies, such as ischemic preconditioning, ischemic postconditioning, remote ischemic preconditioning and pharmacological conditioning. Therefore, DJ-1 emerges as a potential target for the treatment of myocardial IRI. Our comprehensive review delves into its protective mechanisms in myocardial IRI and the structural foundations underlying its functions.

Renal protection after hemorrhagic shock in rats: Possible involvement of SUMOylation

Hemorrhagic shock (HS), a leading cause of preventable death, is characterized by severe blood loss and inadequate tissue perfusion. Reoxygenation of ischemic tissues exacerbates organ damage through ischemia-reperfusion injury. SUMOylation has been shown to protect neurons after stroke and is upregulated in response to cellular stress. However, the role of SUMOylation in organ protection after HS is unknown. This study aimed to investigate SUMOylation-mediated organ protection following HS. Male Wistar rats were subjected to HS (blood pressure of 40 ± 2 mmHg, for 90 min) followed by reperfusion. Blood, kidney, and liver samples were collected at various time points after reperfusion to assess organ damage and investigate the profile of SUMO1 and SUMO2/3 conjugation. In addition, human kidney cells (HK-2), treated with the SUMOylation inhibitor TAK-981 or overexpressing SUMO proteins, were subjected to oxygen and glucose deprivation to investigate the role of SUMOylation in hypoxia/reoxygenation injury. The animals presented progressive multiorgan dysfunction, except for the renal system, which showed improvement over time. Compared to the liver, the kidneys displayed distinct patterns in terms of oxidative stress, apoptosis activation, and tissue damage. The global level of SUMO2/3 in renal tissue was also distinct, suggesting a differential role. Pharmacological inhibition of SUMOylation reduced cell viability after hypoxia-reoxygenation damage, while overexpression of SUMO1 or SUMO2 protected the cells. These findings suggest that SUMOylation might play a critical role in cellular protection during ischemia-reperfusion injury in the kidneys, a role not observed in the liver. This difference potentially explains the renal resilience observed in HS animals when compared to other systems.

Protein modification in neurodegenerative diseases

Posttranslational modifications play a crucial role in governing cellular functions and protein behavior. Researchers have implicated dysregulated posttranslational modifications in protein misfolding, which results in cytotoxicity, particularly in neurodegenerative diseases such as Alzheimer disease, Parkinson disease, and Huntington disease. These aberrant posttranslational modifications cause proteins to gather in certain parts of the brain that are linked to the development of the diseases. This leads to neuronal dysfunction and the start of neurodegenerative disease symptoms. Cognitive decline and neurological impairments commonly manifest in neurodegenerative disease patients, underscoring the urgency of comprehending the posttranslational modifications' impact on protein function for targeted therapeutic interventions. This review elucidates the critical link between neurodegenerative diseases and specific posttranslational modifications, focusing on Tau, APP, α-synuclein, Huntingtin protein, Parkin, DJ-1, and Drp1. By delineating the prominent aberrant posttranslational modifications within Alzheimer disease, Parkinson disease, and Huntington disease, the review underscores the significance of understanding the interplay among these modifications. Emphasizing 10 key abnormal posttranslational modifications, this study aims to provide a comprehensive framework for investigating neurodegenerative diseases holistically. The insights presented herein shed light on potential therapeutic avenues aimed at modulating posttranslational modifications to mitigate protein aggregation and retard neurodegenerative disease progression.

Research progress on the protective effect of hormones and hormone drugs in myocardial ischemia-reperfusion injury

Ischemic heart disease (IHD) is a condition where the heart muscle does not receive enough blood flow, leading to cardiac dysfunction. Restoring blood flow to the coronary artery is an effective clinical therapy for myocardial ischemia. This strategy helps lower the size of the myocardial infarction and improves the prognosis of patients. Nevertheless, if the disrupted blood flow to the heart muscle is restored within a specific timeframe, it leads to more severe harm to the previously deprived heart tissue. This condition is referred to as myocardial ischemia/reperfusion injury (MIRI). Until now, there is a dearth of efficacious strategies to prevent and manage MIRI. Hormones are specialized substances that are produced directly into the circulation by endocrine organs or tissues in humans and animals, and they have particular effects on the body. Hormonal medications utilize human or animal hormones as their active components, encompassing sex hormones, adrenaline medications, thyroid hormone medications, and others. While several studies have examined the preventive properties of different endocrine hormones, such as estrogen and hormone analogs, on myocardial injury caused by ischemia-reperfusion, there are other hormone analogs whose mechanisms of action remain unexplained and whose safety cannot be assured. The current study is on hormones and hormone medications, elucidating the mechanism of hormone pharmaceuticals and emphasizing the cardioprotective effects of different endocrine hormones. It aims to provide guidance for the therapeutic use of drugs and offer direction for the examination of MIRI in clinical therapy.

Function and regulation of ubiquitin-like SUMO system in heart

The small ubiquitin-related modifier (SUMOylation) system is a conserved, reversible, post-translational protein modification pathway covalently attached to the lysine residues of proteins in eukaryotic cells, and SUMOylation is catalyzed by SUMO-specific activating enzyme (E1), binding enzyme (E2) and ligase (E3). Sentrin-specific proteases (SENPs) can cleave the isopeptide bond of a SUMO conjugate and catalyze the deSUMOylation reaction. SUMOylation can regulate the activity of proteins in many important cellular processes, including transcriptional regulation, cell cycle progression, signal transduction, DNA damage repair and protein stability. Biological experiments in vivo and in vitro have confirmed the key role of the SUMO conjugation/deconjugation system in energy metabolism, Ca2+ cycle homeostasis and protein quality control in cardiomyocytes. In this review, we summarized the research progress of the SUMO conjugation/deconjugation system and SUMOylation-mediated cardiac actions based on related studies published in recent years, and highlighted the further research areas to clarify the role of the SUMO system in the heart by using emerging technologies.

HypERlnc attenuates angiotensin II-induced cardiomyocyte hypertrophy via promoting SIRT1 SUMOylation-mediated activation of PGC-1α/PPARα pathway in AC16 cells

Cardiac hypertrophy is a well-established risk factor for cardiovascular mortality worldwide. According to a recent study, hypoxia-induced endoplasmic reticulum stress regulating long noncoding RNA (HypERlnc) is significantly reduced in the left ventricular myocardium of heart failure (HF) patients compared with healthy controls. However, the effect of HypERlnc on hypertrophy is unclear. In this study, the expression level of HypERlnc in serum of patients with chronic HF was analyzed. Moreover, the cardioprotective effect and mechanism of HypERlnc against cardiomyocyte hypertrophy were explored. Here, the level of HypERlnc expression was reduced in serum of patients with HF and in Angiotensin II (Ang II)-stimulated AC16 cells. HypERlnc overexpression could reduce cell size and inhibit expression of hypertrophy genes (ANP, BNP, and β-MHC) in the Ang II-induced cardiomyocyte hypertrophy. Meanwhile, HypERlnc could improve the Ang II-induced energy metabolism dysfunction and mitochondrial damage via upregulating PGC-1α/PPARα signaling pathway. Furthermore, it is found that SIRT1 SUMOylation mediated the HypERlnc-induced inhibition of cardiomyocyte hypertrophy and the improvement of energy metabolism. Taken together, this study suggests that HypERlnc suppresses cardiomyocyte hypertrophy and energy metabolism dysfunction via enhancing SUMOylation of SIRT1 protein. HypERlnc is a potential novel molecular target for preventing and treating pathological cardiac hypertrophy.

Small ubiquitin-related modifier (SUMO)ylation of SIRT1 mediates (-)-epicatechin inhibited- differentiation of cardiac fibroblasts into myofibroblasts

CONTEXT

(-)-Epicatechin (EPI) is a crucial substance involved in the protective effects of flavanol-rich foods. Previous studies have indicated EPI has a cardioprotective effect, but the molecular mechanisms in inhibition of cardiac fibrosis are unclear.

OBJECTIVE

We evaluated the effect of EPI in preventing cardiac fibrosis and the underlying molecular mechanism related to the SIRT1-SUMO1/AKT/GSK3β pathway.

MATERIALS AND METHODS

Cardiac fibrosis mice model was established with transaortic constriction (TAC). Male C57BL/6 mice were randomly separated into 4 groups. Mice received 1 mg/kg/day of EPI or vehicle orally for 4 weeks. The acutely isolated cardiac fibroblasts were induced to myofibroblasts with 1 µM angiotensin II (Ang II). The cardiac function was measured with the ultrasonic instrument. Histological analysis of mice's hearts was determined with H&E or Masson method. The protein level of fibrosis markers, SUMOylation of SIRT1, and AKT/GSK3β pathway were quantified by immunofluorescence and western blot.

RESULTS

EPI treatment (1 mg/kg/day) could reverse the TAC-induced decline in LVEF (TAC, 61.28% ± 1.33% vs. TAC + EPI, 74.00% ± 1.64%), LVFS (TAC, 28.16% ± 0.89% vs. TAC + EPI, 37.18% ± 1.29%). Meantime, we found that 10 µM EPI blocks Ang II-induced transformation of cardiac fibroblasts into myofibroblasts. The underlying mechanism of EPI-inhibited myofibroblasts transformation involves activation of SUMOylation of SIRT1 through SP1. Furthermore, SUMOylation of SIRT1 inhibited Ang II-induced fibrogenic effect via the AKT/GSK3β pathway.

CONCLUSION

EPI plays a protective effect on cardiac fibrosis by regulating the SUMO1-dependent modulation of SIRT1, which provides a theoretical basis for use in clinical therapies.

Integrated Bioinformatics and Validation of lncRNA-Mediated ceRNA Network in Myocardial Ischemia/Reperfusion Injury

Background

Myocardial ischemia/reperfusion (MI/R) injury is a common pathology in ischemia heart disease. Long noncoding RNAs (lncRNAs) are significant regulators related to many ischemia/reperfusion conditions. This study is aimed at exploring the molecule mechanism of lncRNA-mediated competing endogenous RNA (ceRNA) network in MI/R.

Methods

The dataset profiles of MI/R and normal tissues (GSE130217 and GSE124176) were obtained from the GEO database. Integrated bioinformatics were performed to screen out differentially expressed genes (DEGs). Thereafter, an lncRNA-mediated ceRNA network was constructed by the starBase database. The GO annotations and KEGG pathway analysis were conducted to study action mechanism and related pathways of DEGs in MI/R. A model of hypoxia/reoxygenation- (H/R-) treated HL-1 cell was performed to verify the expression of lncRNAs through qRT-PCR.

Results

2406 differentially expressed- (DE-) mRNAs, 70 DE-lncRNAs, and 156 DE-miRNAs were acquired. These DEGs were conducted to construct an lncRNA-mediated ceRNA network, and a subnetwork including lncRNA Xist/miRNA-133c/mRNA (Slc30a9) was screen out. The functional enrichment analyses revealed that the lncRNAs involved in the ceRNA network might functions in oxidative stress and calcium signaling pathway. The lncRNA Xist expression is reduced under H/R conditions, followed by the increased level of miRNA-133c, thus downregulating the expression of Slc30a9.

Conclusion

In sum, the identified ceRNA network which included the lncRNA Xist/miR-133c/Slc30a9 axis might contribute a better understanding to the pathogenesis and development of MI/R injury and offer a novel targeted therapy way.

SUMOylation of Nuclear γ-Actin by SUMO2 supports DNA Damage Repair against Myocardial Ischemia-Reperfusion Injury

Myocardial infarction triggers oxidative DNA damage, apoptosis and adverse cardiac remodeling in the heart. Small ubiquitin-like modifier (SUMO) proteins mediate post-translational SUMOylation of the cardiac proteins in response to oxidative stress signals. Upregulation of isoform SUMO2 could attenuate myocardial injury via increasing protein SUMOylation. The present study aimed to discover the identity and cardioprotective activities of SUMOylated proteins. A plasmid vector for expressing N-Strep-SUMO2 protein was generated and introduced into H9c2 rat cardiomyocytes. The SUMOylated proteins were isolated with Strep-Tactin^® agarose beads and identified by MALDI-TOF-MS technology. As a result, γ-actin was identified from a predominant protein band of ~42 kDa and verified by Western blotting. The roles of SUMO2 and γ-actin SUMOylation were subsequently determined in a mouse model of myocardial infarction induced by ligating left anterior descending coronary artery and H9c2 cells challenged by hypoxia-reoxygenation. In vitro lentiviral-mediated SUMO2 expression in H9c2 cells were used to explore the role of SUMOylation of γ-actin. SUMOylation of γ-actin by SUMO2 was proven to be a new cardioprotective mechanism from the following aspects: 1) SUMO2 overexpression reduced the number of TUNEL positive cells, the levels of 8-OHdG and p-γ-H2ax while promoted the nuclear deposition of γ-actin in mouse model and H9c2 cell model of myocardial infarction; 2) SUMO-2 silencing decreased the levels of nuclear γ-actin and SUMOylation while exacerbated DNA damage; 3) Mutated γ-actin (K⁶⁸R/K²⁸⁴R) void of SUMOylation sites failed to protect cardiomyocytes against hypoxia-reoxygenation challenge. The present study suggested that SUMO2 upregulation promoted DNA damage repair and attenuated myocardial injury via increasing SUMOylation of γ-actin in the cell nucleus.

SUMOylation of SIRT1 activating PGC-1α/PPARα pathway mediates the protective effect of LncRNA-MHRT in cardiac hypertrophy

Long noncoding RNA-Myosin heavy chain associated RNA transcript (LncRNA-MHRT) has been reported to prevent pathological cardiac hypertrophy. However, the underlying inhibition mechanism has not been fully elucidated. Further, whether MHRT inhibits hypertrophy by regulating post-translational modification of certain proteins remains unclear. Therefore, this study aims to find potential role of MHRT in inhibiting cardiac hypertrophy via regulating modification of certain proteins. Here, Angiotensin II (Ang II) -treated neonatal rat cardiomyocytes and transverse aortic constriction (TAC) mice were used to investigate the effect and mechanism of MHRT in cardiac hypertrophy in vitro and in vivo. Moreover, the regulatory effects of MHRT on SUMOylation of NAD-dependent protein deacetylase sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α)/peroxisome proliferator-activated receptor-α (PPARα), specificity protein 1 (SP1)/histone deacetylase 4 (HDAC4) pathway were investigated. Here, we found that MHRT improved heart function by attenuating pathological cardiac hypertrophy in vivo and in vitro. MHRT also promoted the SUMOylation of SIRT1 protein that activated PGC1-α/PPAR-α pathway. Furthermore, MHRT enhanced SUMOylation of SIRT1 by upregulating SP1/HDAC4. Our findings suggested that SUMOylation of SIRT1 could mediate the protective effect of MHRT in cardiac hypertrophy. The new regulatory pathway provides a potential new therapeutic target for pathological cardiac hypertrophy.

SUMOylation in peripheral tissues under low perfusion-related pathological states

SUMOylation is described as a posttranslational protein modification (PTM) that is involved in the pathophysiological processes underlying several conditions related to ischemia- and reperfusion-induced damage. Increasing evidence suggests that, under low oxygen levels, SUMOylation might be part of an endogenous mechanism, which is triggered by injury to protect cells within the central nervous system. However, the role of ischemia-induced SUMOylation in the periphery is still unclear. This article summarizes the results of recent studies regarding SUMOylation profiles in several diseases characterized by impaired blood flow to the cardiorenal, gastrointestinal, and respiratory systems. Our review shows that although ischemic injury per se does not always increase SUMOylation levels, as seen in strokes, it seems that in most cases the positive modulation of protein SUMOylation after peripheral ischemia might be a protective mechanism. This complex relationship warrants further investigation, as the role of SUMOylation during hypoxic conditions differs from organ to organ and is still not fully elucidated.

Estrogen inhibits endoplasmic reticulum stress and ameliorates myocardial ischemia/reperfusion injury in rats by upregulating SERCA2a

Background

The incidence of coronary heart disease (CHD) in premenopausal women is significantly lower than that of men of the same age, suggesting protective roles of estrogen for the cardiovascular system against CHD. This study aimed to confirm the protective effect of estrogen on myocardium during myocardial ischemia/reperfusion (MI/R) injury and explore the underlying mechanisms.

Methods

Neonatal rat cardiomyocytes and Sprague–Dawley rats were used in this study. Different groups were treated by bilateral ovariectomy, 17β-estradiol (E2), adenoviral infection, or siRNA transfection. The expression of sarcoplasmic reticulum Ca²⁺ ATPase pump (SERCA2a) and endoplasmic reticulum (ER) stress-related proteins were measured in each group to examine the effect of different E2 levels and determine the relationship between SERCA2a and ER stress. The cell apoptosis, myocardial infarction size, levels of apoptosis and serum cardiac troponin I, ejection fraction, calcium transient, and morphology changes of the myocardium and ER were examined to verify the effects of E2 on the myocardium.

Results

Bilateral ovariectomy resulted in reduced SERCA2a levels and more severe MI/R injury. E2 treatment increased SERCA2a expression. Both E2 treatment and exogenous SERCA2a overexpression decreased levels of ER stress-related proteins and alleviated myocardial damage. In contrast, SERCA2a knockdown exacerbated ER stress and myocardial damage. Addition of E2 after SERCA2a knockdown did not effectively inhibit ER stress or reduce myocardial injury.

Conclusions

Our data demonstrate that estrogen inhibits ER stress and attenuates MI/R injury by upregulating SERCA2a. These results provide a new potential target for therapeutic intervention and drug discovery in CHD.

Cardiac fibroblasts secrete exosome microRNA to suppress cardiomyocyte pyroptosis in myocardial ischemia/reperfusion injury

Molecular mechanisms underlying myocardial ischemia/reperfusion (MI/R) injury and effective strategies to treat MI/R injury are both in shortage. Although pyroptosis of cardiomyocytes and the protective role of cardiac fibroblasts (CFs) have been well recognized as targets to reduce MI/R injury and sudden cardiac death (SCD), the connection has not yet been established. Here, we showed that CFs protected cardiomyocytes against MI/R-induced injury through suppression of pyroptosis. A novel molecular mechanism underpinning this effect was further identified. Under hypoxia/reoxygenation condition, CFs were found to secrete exosomes, which contain increased level of microRNA-133a (miR-133a). These exosomes then delivered miR-133a into cardiomyocytes to target ELAVL1 and repressed cardiomyocyte pyroptosis. Based on this finding, we successfully developed a new strategy that used exosomes derived from CFs with overexpressed miR-133a to enhance the therapeutic outcomes for the MI/R injury. Overall, our results provide a novel molecular basis for understanding and treating MI/R injury, and our study also provides novel insight for the postmortem diagnosis of MI/R injury induced SCD by using exosome biomarker in forensic.

microRNA-124-3p attenuates myocardial injury in sepsis via modulating SP1/HDAC4/HIF-1α axis

Sepsis-induced cardiac dysfunction can lead to death in sepsis. In this case, we targeted to explore in detail the relative mechanism of microRNA (miR)-124-3p in sepsis-induced myocardial injury via the specific protein 1/histone deacetylase 4/hypoxia-inducing factor 1α (SP1/HDAC4/HIF-1α) axis. Septic rats were modeled by cecal ligation puncture while in vitro septic cardiomyocyte H9C2 were induced by lipopolysaccharide (LPS). miR-124-3p/SP1/HDAC4/HIF-1α expression levels in myocardial tissues of septic rats and LPS-treated H9C2 cells were measured. miR-124-3p overexpression and SP1 silencing assays were implemented on LPS-treated H9C2 cells to explore theirs actions in inflammation, oxidative stress and cell apoptosis. The interactions of miR-124-3p, SP1, and HDAC4 were testified. miR-124-3p was lowly expressed while SP1, HDAC4, and HIF-1α were highly expressed in sepsis. Upregulation of miR-124-3p ameliorated inflammation, oxidative stress, and apoptosis of LPS-treated H9C2 cells. Silencing SP1 improved LPS-induced damage to cardiomyocytes. miR-124-3p targeted SP1 and HDAC4 interacted with SP1. SP1 overexpression antagonized miR-124-3p upregulation-induced improvements in LPS-induced cardiomyocyte damage. This study illustrates that miR-124-3p improves myocardial injury in septic rats through targeted regulation of SP1 to mediate HDAC4/HIF-1α.

Activation of Nrf2 by Lithospermic Acid Ameliorates Myocardial Ischemia and Reperfusion Injury by Promoting Phosphorylation of AMP-Activated Protein Kinase α (AMPKα)

Background: As a plant-derived polycyclic phenolic carboxylic acid isolated from Salvia miltiorrhiza, lithospermic acid (LA) has been identified as the pharmacological management for neuroprotection and hepatoprotection. However, the role and mechanism of lithospermic acid in the pathological process of myocardial ischemia-reperfusion injury are not fully revealed. Methods: C57BL/6 mice were subjected to myocardial ischemia and reperfusion (MI/R) surgery and pretreated by LA (50 mg/kg, oral gavage) for six consecutive days before operation. The in vitro model of hypoxia reoxygenation (HR) was induced by hypoxia for 24 h and reoxygenation for 6 h in H9C2 cells, which were subsequently administrated with lithospermic acid (100 μM). Nrf2 siRNA and dorsomorphin (DM), an inhibitor of AMPKα, were used to explore the function of AMPKα/Nrf2 in LA-mediated effects. Results: LA pretreatment attenuates infarct area and decreases levels of TnT and CK-MB in plasm following MI/R surgery in mice. Echocardiography and hemodynamics indicate that LA suppresses MI/R-induced cardiac dysfunction. Moreover, LA ameliorates oxidative stress and cardiomyocytes apoptosis following MI/R operation or HR in vivo and in vitro. In terms of mechanism, LA selectively activates eNOS, simultaneously increases nuclear translocation and phosphorylation of Nrf2 and promotes Nrf2/HO-1 pathway in vivo and in vitro, while cardioprotection of LA is abolished by pharmacological inhibitor of AMPK or Nrf2 siRNA in H9C2 cells. Conclusion: LA protects against MI/R-induced cardiac injury by promoting eNOS and Nrf2/HO-1 signaling via phosphorylation of AMPKα.

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.

The Function of SUMOylation and Its Critical Roles in Cardiovascular Diseases and Potential Clinical Implications

Cardiovascular disease (CVD) is a common disease caused by many factors, including atherosclerosis, congenital heart disease, heart failure, and ischemic cardiomyopathy. CVD has been regarded as one of the most common diseases and has a severe impact on the life quality of patients. The main features of CVD include high morbidity and mortality, which seriously threaten human health. SUMO proteins covalently conjugate lysine residues with a large number of substrate proteins, and SUMOylation regulates the function of target proteins and participates in cellular activities. Under certain pathological conditions, SUMOylation of proteins related to cardiovascular development and function are greatly changed. Numerous studies have suggested that SUMOylation of substrates plays critical roles in normal cardiovascular development and function. We reviewed the research progress of SUMOylation in cardiovascular development and function, and the regulation of protein SUMOylation may be applied as a potential therapeutic strategy for CVD treatment.

SUMOylation as a Therapeutic Target for Myocardial Infarction

Myocardial infarction is a prevalent and life-threatening cardiovascular disease. The main goal of existing interventional therapies is to restore coronary reperfusion while few are designed to ameliorate the pathology of heart diseases via targeting the post-translational modifications of those critical proteins. Small ubiquitin-like modifier (SUMO) proteins are recently discovered to form a new type of protein post-translational modifications (PTM), known as SUMOylation. SUMOylation and deSUMOylation are dynamically balanced in the maintenance of various biological processes including cell division, DNA repair, epigenetic transcriptional regulation, and cellular metabolism. Importantly, SUMOylation plays a critical role in the regulation of cardiac functions and the pathology of cardiovascular diseases, especially in heart failure and myocardial infarction. This review summarizes the current understanding on the effects of SUMOylation and SUMOylated proteins in the pathophysiology of myocardial infarction and identifies the potential treatments against myocardial injury via targeting SUMO. Ultimately, this review recommends SUMOylation as a key therapeutic target for treating cardiovascular diseases.

STAT3 but Not STAT5 Contributes to the Protective Effect of Electroacupuncture Against Myocardial Ischemia/Reperfusion Injury in Mice

Electroacupuncture (EA) can help reduce infarct size and injury resulting from myocardial ischemia/reperfusion (I/R); however, the underlying molecular mechanism remains unknown. We previously reported that STAT5 plays a critical role in the cardioprotective effect of remote ischemic preconditioning (RIPC). Here, we assessed the effects of electroacupuncture pretreatment (EAP) on myocardial I/R injury in the presence and/or absence of Stat5 in mice and investigated whether EAP exerts its cardioprotective effects in a STAT5-dependent manner. Adult Stat5^fl/fl and Stat5-cKO mice were exposed to EAP at Neiguan (PC6) for 7 days before the induction of I/R injury by left anterior descending (LAD) coronary artery ligation. The myocardial infarct size (IS), area at risk, and apoptotic rate of cardiomyocytes were detected. RT-qPCR and western blotting were used to measure gene and protein expression, respectively, in homogenized heart tissues. RNA-seq was used to identify candidate genes and pathways. Our results showed that EAP decreased IS and the rate of cardiomyocyte apoptosis. We further found that STAT5 was activated by EAP in Stat5^fl/fl mice but not in Stat5-cKO mice, whereas the opposite was observed for STAT3. Following EAP, the levels of the antiapoptotic proteins Bcl-xL, Bcl-2, and p-AKT were increased in the presence of Stat5, while that of interleukin 10 (IL-10) was increased in both Stat5^fl/fl and Stat5-cKO. The gene expression profile in heart tissues was different between Stat5^fl/fl and the Stat5-cKO mice with EAP. Importantly, the top 30 DEGs under EAP in the Stat5-cKO mice were enriched in the IL-6/STAT3 signaling pathway. Our results revealed for the first time that the protective effect of EAP following myocardial I/R injury was attributable to, but not dependent on, STAT5. Additionally, we found that EAP could activate STAT3 signaling in the absence of the Stat5 gene, and could also activate antiapoptotic, survival, and anti-inflammatory signaling pathways.

HIF‑1α in myocardial ischemia‑reperfusion injury (Review)

Myocardial ischemia-reperfusion injury (MIRI) is a severe injury to the ischemic myocardium following the recovery of blood flow. Currently, there is no effective treatment for MIRI in clinical practice. Over the past two decades, biological studies of hypoxia and hypoxia-inducible factor-1α (HIF-1α) have notably improved understanding of oxygen homeostasis. HIF-1α is an oxygen-sensitive transcription factor that mediates adaptive metabolic responses to hypoxia and serves a pivotal role in MIRI. In particular, previous studies have demonstrated that HIF-1α improves mitochondrial function, decreases cellular oxidative stress, activates cardioprotective signaling pathways and downstream protective genes and interacts with non-coding RNAs. The present review summarizes the roles and associated mechanisms of action of HIF-1α in MIRI. In addition, HIF-1α-associated MIRI intervention, including natural compounds, exosomes, ischemic preconditioning and ischemic post-processing are presented. The present review provides evidence for the roles of HIF-1α activation in MIRI and supports its use as a therapeutic target.

Ferroptosis occurs in phase of reperfusion but not ischemia in rat heart following ischemia or ischemia/reperfusion

Ferroptosis is an iron-dependent regulated necrosis. This study aims to evaluate the contribution of ferroptosis to ischemia or reperfusion injury, and lay a basis for precise therapy of myocardial infarction. The Sprague-Dawley (SD) rat hearts were subjected to ischemia for different duration or the hearts were treated with 1 h-ischemia plus different duration of reperfusion. The myocardial injury was assessed by biochemical assays and hematoxylin & eosin (HE) staining. The ferroptosis was evaluated with the levels of acyl-CoA synthetase long-chain family member 4 (ACSL4), glutathione peroxidase 4 (GPX4), iron, and malondialdehyde. Iron chelator (deferoxamine) was applied to verify the contribution of ferroptosis to ischemia and reperfusion injury. The results showed that ischemic injury (infarction and CK release) was getting worse with the extension of ischemia, but no significant changes in ferroptosis indexes (ACSL4, GPX4, iron, and malondialdehyde) in cardiac tissues were observed. Differently, the levels of ACSL4, iron, and malondialdehyde were gradually elevated with the extension of reperfusion concomitant with a decrease of GPX4 level. In the ischemia-treated rat hearts, no significant changes in myocardial injury were observed in the presence of deferoxamine, while in the ischemia/reperfusion-treated rat hearts, myocardial injury was markedly attenuated in the presence of deferoxamine concomitant with a reduction of ferroptosis. Based on these observations, we conclude that ferroptosis occurs mainly in the phase of myocardial reperfusion but not ischemia. Thus, intervention of ferroptosis exerts beneficial effects on reperfusion injury but not ischemic injury, laying a basis for precise therapy for patients with myocardial infarction.

Post-translational modifications of EZH2 in cancer

Enhancer of zeste homolog 2 (EZH2), as a main component of Polycomb Repressive Complex 2, catalyzes histone H3K27me3 to silence its target gene expression. EZH2 upregulation results in cancer development and poor prognosis of cancer patients. Post-translational modifications (PTMs) are important biological events in cancer progression. PTMs regulate protein conformation and diversity functions. Recently, mounting studies have demonstrated that EZH2 stability, histone methyltransferase activity, localization, and binding partners can be regulated by PTMs, including phosphorylation, O-GlcNAcylation, acetylation, methylation and ubiquitination. However, the detailed molecular mechanisms of the EZH2-PTMs and whether other types of PTMs occur in EZH2 remain largely unclear. This review presents an overview of different roles of EZH2 modification and EZH2-PTMs crosstalk during tumorigenesis and cancer metastasis. We also discussed the therapeutic potential of targeting EZH2 modifications for cancer therapy.

Ginsenoside Re Treatment Attenuates Myocardial Hypoxia/Reoxygenation Injury by Inhibiting HIF-1α Ubiquitination

Previous studies have shown an attenuating effect of ginsenoside Re on myocardial injury induced by hypoxia/reoxygenation (H/R). However, the underlying mechanism remains unclear. This study was designed to determine the underlying mechanism by which ginsenoside Re protects from myocardial injury induced by H/R. HL-1 cells derived from AT-1 mouse atrial cardiomyocyte tumor line were divided into control, H/R, and H/R + ginsenoside Re groups. Cell viability was measured by CCK-8 assay. ATP levels were quantified by enzymatic assays. Signaling pathway was predicted by network pharmacology analyses and verified by luciferase assay and gene-silencing experiment. The relationship between ginsenoside Re and its target genes and proteins was analyzed by docking experiments, allosteric site analysis, real-time PCR, and ubiquitination and immunoprecipitation assays. Our results showed that ginsenoside Re treatment consistently increased HL-1 cell viability and significantly up-regulated ATP levels after H/R-induced injury. Network pharmacology analysis suggested that the effect of ginsenoside Re was associated with the regulation of the Hypoxia-inducing factor 1 (HIF-1) signaling pathway. Silencing of HIF-1α abrogated the effect of ginsenoside Re on HL-1 cell viability, which was restored by transfection with an HIF-1α-expressing plasmid. Results of the bioinformatics analysis suggested that ginsenoside Re docked at the binding interface between HIF-1α and the von Hippel-Lindau (VHL) E3 ubiquitin ligase, preventing VHL from binding HIF-1α, thereby inhibiting the ubiquitination of HIF-1α. To validate the results of the bioinformatics analysis, real-time PCR, ubiquitination and immunoprecipitation assays were performed. Compared with the mRNA expression levels of the H/R group, ginsenoside Re did not change expression of HIF-1α mRNA, while protein level of HIF-1α increased and that of HIF-1α[Ub]n decreased following ginsenoside Re treatment. Immunoprecipitation results showed that the amount of HIF-1α bound to VHL substantially decreased following ginsenoside Re treatment. In addition, ginsenoside Re treatment increased the expression of GLUT1 (glucose transporter 1) and REDD1 (regulated in development and DNA damage response 1), which are targets of HIF-1α and are critical for cell metabolism and viability. These results suggested that Ginsenoside Re treatment attenuated the myocardial injury induced by H/R, and the possible mechanism was associated with the inhibition of HIF-1α ubiquitination.

Knockdown of endogenous RNF4 exacerbates ischaemia-induced cardiomyocyte apoptosis in mice

RNF4, a poly‐SUMO‐specific E3 ubiquitin ligase, is associated with protein degradation, DNA damage repair and tumour progression. However, the effect of RNF4 in cardiomyocytes remains to be explored. Here, we identified the alteration of RNF4 from ischaemic hearts and oxidative stress‐induced apoptotic cardiomyocytes. Upon myocardial infarction (MI) or H₂O₂/ATO treatment, RNF4 increased rapidly and then decreased gradually. PML SUMOylation and PML nuclear body (PML‐NB) formation first enhanced and then degraded upon oxidative stress. Reactive oxygen species (ROS) inhibitor was able to attenuate the elevation of RNF4 expression and PML SUMOylation. PML overexpression and RNF4 knockdown by small interfering RNA (siRNA) enhanced PML SUMOylation, promoted p53 recruitment and activation and exacerbated H₂O₂/ATO‐induced cardiomyocyte apoptosis which could be partially reversed by knockdown of p53. In vivo, knockdown of endogenous RNF4 via in vivo adeno‐associated virus infection deteriorated post‐MI structure remodelling including more extensive interstitial fibrosis and severely fractured and disordered structure. Furthermore, knockdown of RNF4 worsened ischaemia‐induced cardiac dysfunction of MI models. Our results reveal a novel myocardial apoptosis regulation model that is composed of RNF4, PML and p53. The modulation of these proteins may provide a new approach to tackling cardiac ischaemia.

TANK-binding kinase 1 alleviates myocardial ischemia/reperfusion injury through regulating apoptotic pathway

Myocardial ischemia/reperfusion (MI/R) injury, a complicated pathophysiological process, is regulated by lots of signaling pathways. Here in our present study, we identified TANK-binding kinase 1 (TBK1), an IKK-related serine/threonine kinase, as a protective regulator in MI/R injury. Our results indicated that TBK1 was decreased in MI/R injury in mice. However, after overexpressing TBK1 through an intramyocardial injection of TBK1 adenovirus, TBK1 overexpression improved cardiac function detected by echocardiography, decreased infarct size detected by Evans Blue and TTC staining, reduced cardiomyocyte apoptosis measured by TUNEL staining and alleviated disruption of mitochondria and cardiac muscle fibers detected by TEM in response to MI/R injury. Consistently, TBK1 overexpression ameliorated mitochondrial oxygen consumption rate (OCR) in neonatal rat cardiomyocytes (NRCMs) in response to hypoxia/reoxygenation (H/R) injury. Mechanistically, TBK1 overexpression upregulated Bcl-2 (an anti-apoptotic protein) but downregulated Bax (a pro-apoptotic protein) in vivo and in vitro. Collectively, our findings uncovered a pivotal function of TBK1 in MI/R injury through regulating the levels of apoptotic proteins for the first time, which might represent a promising target in treating MI/R patients in the future.