The effects of quercetin protect cardiomyocytes from A/R injury is related to its capability to increasing expression and activity of PKCε protein

Role of dysregulated ferroptosis‑related genes in cardiomyocyte ischemia‑reperfusion injury: Experimental verification and bioinformatics analysis

Acute myocardial infarction is a life-threatening condition with high mortality and complication rates. Although myocardial reperfusion can preserve ischemic myocardial tissue, it frequently exacerbates tissue injury, a phenomenon known as ischemia-reperfusion injury (IRI). However, the underlying pathological mechanisms of IRI remain to be completely understood. Ferroptosis is a novel type of regulated cell death that is associated with various pathological conditions, including angiocardiopathy. The purpose of this article was to elucidate the possible mechanistic role of ferroptosis in IRI through bioinformatics analysis and experimental validation. Healthy and IRI heart samples were screened for differentially expressed ferroptosis-related genes and functional enrichment analysis was performed to determine the potential crosstalk and pathways involved. A protein-protein interaction network was established for IRI, and 10 hub genes that regulate ferroptosis, including HIF1A, EGFR, HMOX1, and ATF3 were identified. In vitro, an anoxia/reoxygenation (A/R) injury model was established using H9c2 cardiomyoblasts to validate the bioinformatics analysis results, and extensive ferroptosis was detected. A total of 4 key hub genes and 3 key miRNAs were also validated. It was found that IRI was related to the aberrant infiltration of immune cells and the small-molecule drugs that may protect against IRI by preventing ferroptosis were identified. These results provide novel insights into the role of ferroptosis in IRI, which can help identify novel therapeutic targets.

Resveratrol and beyond: The Effect of Natural Polyphenols on the Cardiovascular System: A Narrative Review

Cardiovascular diseases (CVDs) are among the leading causes of morbidity and mortality worldwide. Unhealthy dietary habits have clearly been shown to contribute to the development of CVDs. Beyond the primary nutrients, a healthy diet is also rich in plant-derived compounds. Natural polyphenols, found in fruits, vegetables, and red wine, have a clear role in improving cardiovascular health. In this review, we strive to summarize the results of the relevant pre-clinical and clinical trials that focused on some of the most important natural polyphenols, such as resveratrol and relevant flavonoids. In addition, we aim to identify their common sources, biosynthesis, and describe their mechanism of action including their regulatory effect on signal transduction pathways. Finally, we provide scientific evidence regarding the cardiovascular benefits of moderate, long-term red wine consumption.

Puerarin activates adaptive autophagy and protects the myocardium against doxorubicin-induced cardiotoxicity via the 14–3-3γ/PKCε pathway

Doxorubicin (Dox)-induced cardiotoxicity (DIC) seriously threatens the health of related patients. Studies have confirmed that 14-3-3γ and protein kinase C epsilon (PKCε) are the endogenous protective proteins. Puerarin (Pue) is a bioactive ingredient isolated from the root of Pueraria lobata. It possesses many pharmacological properties, which have been widely used in treating and adjuvant therapy of cardiovascular diseases. In the study, we intended to explore the effects and mechanism of Pue pretreatment to protect the myocardium against DIC injury. Adult mice and H9c2 cells were pretreated with Pue, and the injury model was made with Dox. Results showed that Pue pretreatment alleviated DIC injury, as revealed by increased cell viability, decreased LDH activity and apoptosis, inhibited excess oxidative stress, maintained mitochondrial function and energy metabolism, and improved myocardial function. Furthermore, Pue pretreatment upregulated 14-3-3γ expression, interacted with PKCε, phosphorylated and impelled migration to mitochondria, activated adaptive autophagy, and protected the myocardium. However, pAD/14-3-3γ-shRNA or εV1-2 (a PKCε activity inhibitor) or 3-methyladenine (an autophagy inhibitor) could weaken the above effects of Pue pretreatment. Together, Pue pretreatment could activate adaptive autophagy by the 14-3-3γ/PKCε pathway and protect the myocardium against DIC injury.

Combating Ischemia-Reperfusion Injury with Micronutrients and Natural Compounds during Solid Organ Transplantation: Data of Clinical Trials and Lessons of Preclinical Findings

Although extended donor criteria grafts bear a higher risk of complications such as graft dysfunction, the exceeding demand requires to extent the pool of potential donors. The risk of complications is highly associated with ischemia-reperfusion injury, a condition characterized by high loads of oxidative stress exceeding antioxidative defense mechanisms. The antioxidative properties, along with other beneficial effects like anti-inflammatory, antiapoptotic or antiarrhythmic effects of several micronutrients and natural compounds, have recently emerged increasing research interest resulting in various preclinical and clinical studies. Preclinical studies reported about ameliorated oxidative stress and inflammatory status, resulting in improved graft survival. Although the majority of clinical studies confirmed these results, reporting about improved recovery and superior organ function, others failed to do so. Yet, only a limited number of micronutrients and natural compounds have been investigated in a (large) clinical trial. Despite some ambiguous clinical results and modest clinical data availability, the vast majority of convincing animal and in vitro data, along with low cost and easy availability, encourage the conductance of future clinical trials. These should implement insights gained from animal data.

Therapeutic Potential of Quercetin to Alleviate Endothelial Dysfunction in Age-Related Cardiovascular Diseases

The vascular endothelium occupies a catalog of functions that contribute to the homeostasis of the cardiovascular system. It is a physically active barrier between circulating blood and tissue, a regulator of the vascular tone, a biochemical processor and a modulator of coagulation, inflammation, and immunity. Given these essential roles, it comes to no surprise that endothelial dysfunction is prodromal to chronic age-related diseases of the heart and arteries, globally termed cardiovascular diseases (CVD). An example would be ischemic heart disease (IHD), which is the main cause of death from CVD. We have made phenomenal advances in treating CVD, but the aging endothelium, as it senesces, always seems to out-run the benefits of medical and surgical therapies. Remarkably, many epidemiological studies have detected a correlation between a flavonoid-rich diet and a lower incidence of mortality from CVD. Quercetin, a member of the flavonoid class, is a natural compound ubiquitously found in various food sources such as fruits, vegetables, seeds, nuts, and wine. It has been reported to have a wide range of health promoting effects and has gained significant attention over the years. A growing body of evidence suggests quercetin could lower the risk of IHD by mitigating endothelial dysfunction and its risk factors, such as hypertension, atherosclerosis, accumulation of senescent endothelial cells, and endothelial-mesenchymal transition (EndoMT). In this review, we will explore these pathophysiological cascades and their interrelation with endothelial dysfunction. We will then present the scientific evidence to quercetin's anti-atherosclerotic, anti-hypertensive, senolytic, and anti-EndoMT effects. Finally, we will discuss the prospect for its clinical use in alleviating myocardial ischemic injuries in IHD.

Protective Mechanisms of Quercetin Against Myocardial Ischemia Reperfusion Injury

Quercetin has attracted more attention in recent years due to its protective role against ischemia/reperfusion injury. Quercetin can alleviate oxidative stress injury through the inhibition of NADPH oxidase and xanthine oxidase, blockage of the Fenton reaction, and scavenging of reactive oxygen species. Quercetin can also exert anti-inflammatory and anti-apoptotic effects by reducing the response to inflammatory factors and inhibiting cell apoptosis. Moreover, it can induce vasodilation effects through the inhibition of endothelin-1 receptors, the enhancement of NO stimulation and the activation of the large-conductance calcium-activated potassium channels. Finally, Quercetin can also antagonize the calcium overload. These multifaceted activities of Quercetin make it a potential therapeutic alternative for the treatment of ischemia/reperfusion injury.

Potential Implications of Quercetin and its Derivatives in Cardioprotection

Quercetin (QCT) is a natural polyphenolic compound enriched in human food, mainly in vegetables, fruits and berries. QCT and its main derivatives, such as rhamnetin, rutin, hyperoside, etc., have been documented to possess many beneficial effects in the human body including their positive effects in the cardiovascular system. However, clinical implications of QCT and its derivatives are still rare. In the current paper we provide a complex picture of the most recent knowledge on the effects of QCT and its derivatives in different types of cardiac injury, mainly in ischemia-reperfusion (I/R) injury of the heart, but also in other pathologies such as anthracycline-induced cardiotoxicity or oxidative stress-induced cardiac injury, documented in in vitro and ex vivo, as well as in in vivo experimental models of cardiac injury. Moreover, we focus on cardiac effects of QCT in presence of metabolic comorbidities in addition to cardiovascular disease (CVD). Finally, we provide a short summary of clinical studies focused on cardiac effects of QCT. In general, it seems that QCT and its metabolites exert strong cardioprotective effects in a wide range of experimental models of cardiac injury, likely via their antioxidant, anti-inflammatory and molecular pathways-modulating properties; however, ageing and presence of lifestyle-related comorbidities may confound their beneficial effects in heart disease. On the other hand, due to very limited number of clinical trials focused on cardiac effects of QCT and its derivatives, clinical data are inconclusive. Thus, additional well-designed human studies including a high enough number of patients testing different concentrations of QCT are needed to reveal real therapeutic potential of QCT in CVD. Finally, several negative or controversial effects of QCT in the heart have been reported, and this should be also taken into consideration in QCT-based approaches aimed to treat CVD in humans.

Quercetin protects the vascular endothelium against iron overload damages via ROS/ADMA/DDAHⅡ/eNOS/NO pathway

The aberrant accumulation of iron causes vascular endothelium damage, which is thought to be associated with excess reactive oxygen species (ROS) generation. Quercetin (Que), as a flavonoid, has a certain ability to scavenge free radicals. Therefore, we aimed to explore the protective mechanism of Que on iron overload induced HUVECs injury focused on ROS/ADMA/DDAHⅡ/eNOS/NO pathway. In this study, HUVECs was treated with 50 μM iron dextran and 20 μM Que for 48 h. We found that Que attenuated the damages induced by iron, as evidenced by decreased ROS generation, increased DDAHⅡexpression and activity, reduced ADMA level, increased NO content and p-eNOS/eNOS ratio, and eventually caused a decrease in apoptosis. After addition of pAD/DDAHⅡ-shRNA, the effects of Que mentioned above were reversed. Meanwhile, iron overload induced mitochondrial oxidative stress, reduced mitochondrial membrane potential and increased mitochondrial permeability transition pores (mPTP) opening, which were also partially alleviated by Que. In addition, L-arginine (L-Arg), a ADMA competition substrate, ciclosporin A (CsA), a mPTP blocking agent, and edaravone (Eda), a free radical scavenger, were used as positive control reagents. The effects of Que were similar to that of L-Arg, CsA and Eda treatment. These results illustrated that Que could attenuate iron overload induced HUVECs mitochondrial dysfunction via ROS/ADMA/DDAHⅡ/eNOS/NO pathway.

Quercetin protects cardiomyocytes against doxorubicin-induced toxicity by suppressing oxidative stress and improving mitochondrial function via 14-3-3γ

Cardiotoxicity limits the clinical applications of doxorubicin (Dox), which mechanism might be excess generation of intracellular ROS. Quercetin (Que) is a flavonoid that possesses anti-oxidative activities, exerts myocardial protection. We hypothesized that the cardioprotection against Dox injury of Que involved 14-3-3γ, and mitochondria. To investigate the hypothesis, we treated primary cardiomyocytes with Dox and determined the effects of Que pretreatment with or without 14-3-3γ knockdown. We analyzed various cellular and molecular indexes. Our data showed that Que attenuated Dox-induced toxicity in cardiomyocytes by upregulating 14-3-3γ expression. Que pretreatment increased cell viability, SOD, catalase, and GPx activities, GSH levels, MMP and the GSH/GSSG ratio; decreased LDH and caspase-3 activities, MDA and ROS levels, mPTP opening and the percentage of apoptotic cells. However, Que's cardioprotection were attenuated by knocking down 14-3-3γ expression using pAD/14-3-3γ-shRNA. In conclusion, Que protects cardiomyocytes against Dox injury by suppressing oxidative stress and improving mitochondrial function via 14-3-3γ.

Tanshinone IIA Pretreatment Protects H9c2 Cells against Anoxia/Reoxygenation Injury: Involvement of the Translocation of Bcl-2 to Mitochondria Mediated by 14-3-3η

Tanshinone IIA is an important component that is isolated from danshen (Salvia miltiorrhiza), which is known to be beneficial for cardiovascular health. In this study, we determined the effects of Tanshinone IIA and its underlying mechanisms of action in an anoxia/reoxygenation (A/R) cell line model. Prior to inducing A/R injury, rat cardiomyocyte-derived cell line H9c2 was stimulated with 8 μM of Tanshinone IIA for 48 hours. When compared with the A/R group, the Tanshinone IIA treatment significantly increased cell viability and decreased lactate dehydrogenase activity. Tanshinone IIA upregulated 14-3-3η expression and facilitated Bcl-2 translocation to the mitochondrial outer membrane, which bound with voltage-dependent anion channel 1. In addition, pretreatment with Tanshinone IIA reduced the generation of reactive oxygen species and cytochrome c release, inactivated caspase-3, prevented mitochondrial permeability transition pore opening, and reduced the percentage of apoptotic cells. Moreover, treatment with Tanshinone IIA reduced the level of malondialdehyde, thereby increasing the activity of superoxide dismutase and glutathione peroxidase. Silencing the expression of 14-3-3η by adenovirus blocked the above-mentioned results. These novel findings showed that pretreatment with Tanshinone IIA alleviated H9c2 cell damage against A/R injury and was associated with upregulation of 14-3-3η, thereby facilitating Bcl-2 translocation to the mitochondrial outer membrane and preventing mitochondrial permeability transition pore opening, decreasing cytochrome c release, preventing caspase-3 activation, and restraining apoptosis.

Therapeutic potential of quercetin as a cardiovascular agent

Flavonoids are integral components of various vegetation and in foods; consequently, they represent an inevitable part of the diet. Historical and epidemiological proof recommend that diet plans consisting of flavonoids such as quercetin have positive health benefits, especially on the heart. Flavonoids have been proven to be active against hypertension, inflammation, diabetes and vascular diseases. Quercetin exhibits significant heart related benefits as inhibition of LDL oxidation, endothelium-independent vasodilator effects, reduction of adhesion molecules and other inflammatory markers, the protective effect on nitric oxide and endothelial function under conditions of oxidative stress, prevention of neuronal oxidative and inflammatory damage and platelet antiaggregant effects. Searching for experimental evidence to validate the cardioprotective effects of quercetin, we review here the recent detailed in vivo studies. Quercetin and its derivatives lead to an enhancement in heart features, indicating the prospective for quercetin to be used therapeutically in the treatment of cardiac diseases. Several evidence-based studies suggest mechanisms to observe cardiovascular diseases such as aging effects, hypertension, angiotensin-converting enzyme activity and endothelial-dependent and independent functions. Different animal models including human are also used to elucidate the in vivo role of quercetin in cardiovascular diseases. The role of quercetin and its derivatives may go beyond their existence in food and has potential as a lead molecule in drug development programs.

On the causes and consequences of the uncoupler-like effects of quercetin and dehydrosilybin in H9c2 cells

Quercetin and dehydrosilybin are polyphenols which are known to behave like uncouplers of respiration in isolated mitochondria. Here we investigated whether the effect is conserved in whole cells. Following short term incubation, neither compound uncouples mitochondrial respiration in whole H9c2 cells below 50μM. However, following hypoxia, or long term incubation, leak (state IV with oligomycin) oxygen consumption is increased by quercetin. Both compounds partially protected complex I respiration, but not complex II in H9c2 cells following hypoxia. In a permeabilised H9c2 cell model, the increase in leak respiration caused by quercetin is lowered by increased [ADP] and is increased by adenine nucleotide transporter inhibitor, atractyloside, but not bongkrekic acid. Both quercetin and dehydrosilybin dissipate mitochondrial membrane potential in whole cells. In the case of quercetin, the effect is potentiated post hypoxia. Genetically encoded Ca++ sensors, targeted to the mitochondria, enabled the use of fluorescence microscopy to show that quercetin decreased mitochondrial [Ca++] while dehydrosilybin did not. Likewise, quercetin decreases accumulation of [Ca++] in mitochondria following hypoxia. Fluorescent probes were used to show that both compounds decrease plasma membrane potential and increase cytosolic [Ca++]. We conclude that the uncoupler-like effects of these polyphenols are attenuated in whole cells compared to isolated mitochondria, but downstream effects are nevertheless apparent. Results suggest that the effect of quercetin observed in whole and permeabilised cells may originate in the mitochondria, while the mechanism of action of cardioprotection by dehydrosilybin may be less dependent on mitochondrial uncoupling than originally thought. Rather, protective effects may originate due to interactions at the plasma membrane.

Protective Effects of Isorhamnetin on Cardiomyocytes Against Anoxia/Reoxygenation-induced Injury Is Mediated by SIRT1

It has been reported that apoptosis plays a very important role on anoxia/reoxygenation (A/R)-induced injury, and human silent information regulator type 1 (SIRT1) can inhibit the apoptosis of cardiomyocytes. It has been proved that isorhamnetin (IsoRN), 3'-O-methyl-quecetin, can protect the cardiomyocytes, but the mechanism is still not clear. The aim of the study was to explore whether the protective effects of IsoRN on the cardiomyocytes against the A/R-induced injury are mediated by SIRT1. The effects of IsoRN on cardioprotection against A/R injury in neonatal rat cardiomyocytes were monitored by cell viability, the levels of mitochondrial membrane potential (Δψm), apoptosis, and intracellular reactive oxygen species (ROS), the levels of lactate dehydrogenase (LDH), creatine phosphokinase (CPK) and mitochondrial permeability transition pores (mPTP). The effects on protein expression were measured by western blot assay. The results showed that IsoRN can reduce A/R-induced injury by decreasing the level of lactate dehydrogenase and creatine phosphokinase release from the cardiomyocytes, increasing cell viability and expression of SIRT1, reducing the generation of reactive oxygen species, inhibiting opening of mitochondrial permeability transition pores and loss of Δψm and activation of caspase-3, and decreasing the release of cytochrome c, and reducing apoptosis. In addition, sirtinol, a SIRT1 inhibitor, drastically reduced the protective effects of IsoRN on cardioprotective effects in cardiomocytes. In conclusion, we firstly demonstrated that SIRT1 may be involved in the protective effects of IsoRN on cardiomocytes against the A/R-induced injury.

Luteolin, quercetin, genistein and quercetagetin inhibit the effects of lipopolysaccharide obtained from Porphyromonas gingivalis in H9c2 cardiomyoblasts

Background

One of the microorganisms from dental plaque associated with severe inflammatory responses in infectious endocarditis is Porphyromonas gingivalis. It is a Gram-negative bacteria harvested from chronic periodontitis patients. Lipopolysaccharide (LPS) obtained from P. gingivalis promotes the expressions of interleukin-1 (IL-1), IL-6 and tumor necrosis factor alpha (TNF-α). Flavonoids are thought to participate in processes that control inflammation, such as the expression of cyclooxygenase-2 (COX-2).

Methods

We investigated the effects of luteolin, quercetin, genistein and quercetagetin on cardiomyoblasts treated with LPS alone or in combination with following inhibitors p38 (SB203580), ERK (PD98059), JNK (SP600125) and PKC (Calphostin C) for 1 h. The kinase activation and COX-2 expression levels were determined at the gene and protein levels.

Results

These flavonoids are considered to inhibit the activation of mitogen-activated protein kinase (MAPK) and the degradation of inhibitor of kappa B-alpha (IκB-α). They also play a role in COX-2 expression.

Conclusion

We conclude that the tested flavonoids inhibit inflammatory responses induced by LPS in H9c2 cells.

Effects of Polyphenols on Oxidative Stress-Mediated Injury in Cardiomyocytes

Cardiovascular diseases are the main cause of mortality and morbidity in the world. Hypertension, ischemia/reperfusion, diabetes and anti-cancer drugs contribute to heart failure through oxidative and nitrosative stresses which cause cardiomyocytes nuclear and mitochondrial DNA damage, denaturation of intracellular proteins, lipid peroxidation and inflammation. Oxidative or nitrosative stress-mediated injury lead to cardiomyocytes apoptosis or necrosis. The reactive oxygen (ROS) and nitrogen species (RNS) concentration is dependent on their production and on the expression and activity of anti-oxidant enzymes. Polyphenols are a large group of natural compounds ubiquitously expressed in plants, and epidemiological studies have shown associations between a diet rich in polyphenols and the prevention of various ROS-mediated human diseases. Polyphenols reduce cardiomyocytes damage, necrosis, apoptosis, infarct size and improve cardiac function by decreasing oxidative stress-induced production of ROS or RNS. These effects are achieved by the ability of polyphenols to modulate the expression and activity of anti-oxidant enzymes and several signaling pathways involved in cells survival. This report reviews current knowledge on the potential anti-oxidative effects of polyphenols to control the cardiotoxicity induced by ROS and RNS stress.

Comparison of quercetin and resveratrol in the prevention of injury due to testicular torsion/detorsion in rats

Quercetin (QE) and resveratrol (RSV) are powerful antioxidants with the potential to protect the testes against ischemia/reperfusion (I/R) injury. We compared their effects in testicular torsion/detorsion (T/D) in adult rats. Twenty-four male Wistar rats were divided into four groups: sham (group A), T/D (group B), T/D treated with QE (group C), and T/D treated with RSV (group D). QE (20 mg kg⁻¹) and RSV (20 mg kg⁻¹) were injected intra-peritoneally at 60 min of torsion. After 90 min of surgically induced torsion, the testicular cord was restored to its anatomical position. Twenty-four hour after torsion, blood and tissue samples were obtained for further examination. Testicular tissue malondialdehyde (MDA) and nitric oxide (NO) levels and serum total oxidant status (TOS) were higher in group B than in group A (P < 0.05). Group A had higher serum total antioxidant status (TAS) than group B. (P < 0.05) QE and RSV significantly lowered MDA, NO, and TOS levels and TAS consumption (P < 0.05). QE reduced the MDA and TOS levels more than RSV (P < 0.05), but their effects on NO reduction and TAS consumption were similar (P > 0.05). Group A had normal testicular architecture (grade 1). Groups C (mean grade 2.60) and D (mean grade 3.00) had lower testicular injury grades than group B (mean grade 3.45) (P < 0.05). Group C had lower testicular injury grade than group D (P < 0.05). Treatment with QE and RSV protects against I/R injury after testicular T/D. QE may exhibit better function than RSV at the doses tested in this study.

A new flavonoid glycoside (APG) isolated from Clematis tangutica attenuates myocardial ischemia/reperfusion injury via activating PKCε signaling

Clematis tangutica has been shown to be beneficial for the heart; however, the mechanism of this effectremains unknown. Apigenin-7-O-β-D-(-6″-p-coumaroyl)-glucopyranoside (APG) is a new flavonoid glycoside isolated from Clematis tangutica. This study investigates the effects of APG on myocardial ischemia/reperfusion (IR) injury (IRI). An IRI model of primary myocardial cells and mice was used in this study. Compared with the IR group, APG preconditioning is protective against IRI in primary myocardial cells and in mice hearts in a dose-dependent manner. The cardioprotective mechanisms of APG may involve a significant PKCε translocation into the mitochondria and an activation of the Nrf2/HO-1 pathway, which respectively suppressesmitochondrial oxidative stress and inhibits apoptosis. In addition, PKCε-targeted siRNA and a PKCε specialized inhibitor (ε-V1-2) were used to inhibit PKCε expression and activity. The inhibition of PKCε reversed the cardioprotective effect of APG, with an inhibition of Nrf2/HO-1 activation and increased mitochondrial oxidative stress and cardiomyocyte apoptosis. In conclusion, PKCε activation plays an important role in the cardioprotective effects of APG. PKCε activation induced by APG preconditioning reduces mitochondrial oxidative stress and promotes Nrf2/HO-1-mediated anti-apoptosis signaling.

Sasanquasaponin promotes cellular chloride efflux and elicits cardioprotection via the PKCε pathway

Sasanquasaponin (SQS) is an active component of Camellia oleifera Abel. A recent study by our group demonstrated that SQS was able to inhibit ischemia/reperfusion‑induced elevation of the intracellular chloride ion concentration ([Cl‑]i) and exerted cardioprotective effects; however, the underlying intracellular signal transduction mechanisms have yet to be elucidated. As protein kinase C ε (PKCε) is able to mediate Cl‑ homeostasis, the present study investigated its possible involvement in the effects of SQS on cardiomyocytes subjected to ischemia/reperfusion injury. Cardiomyocytes were pre‑treated with or without SQS or SQS plus εV1‑2, a selective PKCε inhibitor, followed by simulated ischemia/reperfusion (sI/R). The effects on cell viability, PKCε phosphorylation levels, [Cl‑]i, mitochondrial membrane potential and reactive oxygen species (ROS) production were assessed using an MTS assay, western blot analysis, colorimetric assays and flow cytometry. The results revealed that treatment with SQS prior to sI/R increased the viability of cardiomyocytes, and efficiently attenuated lactate dehydrogenase and creatine phosphokinase release induced by sI/R. In addition, SQS promoted PKCε phosphorylation and inhibited sI/R‑induced elevation of [Cl‑]i, paralleled by the attenuation of mitochondrial membrane potential loss and ROS generation. However, when the cardiomyocytes were treated with εV1‑2 prior to SQS pre‑conditioning, the cardioprotection induced by SQS was reduced and the inhibitory effects of SQS on sI/R‑induced elevation of [Cl‑]i, production of ROS and loss of mitochondrial membrane potential were also attenuated. These findings indicated that SQS may inhibit sI/R‑induced elevation of [Cl‑]i through the PKCε signaling pathway to elicit cardioprotection in cultured cardiomyocytes.

Naringin protects against anoxia/reoxygenation-induced apoptosis in H9c2 cells via the Nrf2 signaling pathway

Naringin (Nar) is a major and active flavanone glycoside derivative of several citrus species. The antioxidant properties of Nar have an important function in its cardioprotective effects in various models. However, the effects of Nar on Nrf2 activation and the expression of its downstream genes in myocardial cells are yet to be elucidated. This study was designed to investigate the protective effects of Nar against anoxia/reoxygenation (A/R)-induced injury in H9c2 cells and determine its effects on the activity of Nrf2 and the expression of phase II antioxidant enzymes. H9c2 cells were pretreated with Nar for 6 h before exposure to A/R. A/R treatment severely injured the H9c2 cells, which was accompanied by apoptosis. Nar also suppressed the A/R-induced mitochondrial membrane depolarization and caspase-3 activation. Nar pretreatment significantly reduced the apoptotic rate by enhancing the endogenous anti-oxidative activity of superoxide dismutase, glutathione peroxidase, and catalase, thereby inhibiting intracellular reactive oxygen species generation. Moreover, the presence of Nar alone in H9c2 cells increased the nuclear translocation of Nrf2 in a dose- and time-dependent manner, as well as consistently increased the protein levels of heme oxygenase (HO-1) and glutamate cysteine ligase (GCLC). Nar increased the phosphorylation of ERK1/2, PKCδ, and AKT. However, the Nar-mediated Nrf2 activation and cardioprotection were abolished through the genetic silencing of Nrf2 by siRNA and partially inhibited by specific inhibitors of ERK1/2, PKCδ, and AKT. Therefore, Nar provided cardioprotection by inducing the phosphorylation of ERK1/2, PKCδ, and AKT, which subsequently activated Nrf2 and its downstream genes.

Quercetin attenuates cardiomyocyte apoptosis via inhibition of JNK and p38 mitogen-activated protein kinase signaling pathways

Quercetin (Que), a plant-derived flavonoid, possesses various biological functions. Moreover, Que exerts multiple beneficial actions in treatment of cardiovascular diseases and there are an inverse association between Que intakes and occurrence and development of various cardiovascular diseases. Some researchers have inferred that the mechanisms of Que to protect cardiomyocytes from ischemia/reperfusion (I/R) injury may be involved in modulation of intracellular signal pathways and regulation of proteins expression in vivo. The current study investigated whether Que has any protective effects on cardiomyocytes from hypoxia/reoxygenation (H/R) in vitro and its potential cardioprotective mechanisms. The cell viability of Que on H9c2 cardiomyoblast cells was assessed by MTT. Apoptosis was evaluated by both Hoechst33342 staining and Flow cytometric analysis (FACS). Furthermore, the effect of Que, SP600125 (JNK inhibitor) and SB203580 (p38 inhibitor) on mitogen-activated protein kinases (MAPKs) and the expression of apoptosis related proteins (Bcl-2, Bax and caspase-3) was determined by Western blotting. MTT assays showed that pretreatment with Que could increase the viability of H9c2 cardiomyocytes that suffered H/R. Both Hoechst33342 staining and FACS confirmed that Que could remarkably suppress the H/R-induced apoptotic cardiomyocytes. In addition, Que significantly alleviated H/R-induced the phosphorylation of JNK and p38, which further increased Bcl-2 expression and inhibited the activation of Bax and caspase-3 directly or indirectly. In summary, our results imply that Que can induce cardioprotection by inhibition of JNK and p38 mitogen-activated protein kinase signaling pathways and modulate the expression of Bcl-2 and Bax proteins that provides a new experimental foundation for myocardial ischemia disease therapy.

The effects of bioactive compounds from plant foods on mitochondrial function: a focus on apoptotic mechanisms

Mitochondria are essential organelles for cellular integrity and functionality maintenance and their imparement is implicated in the development of a wide range of diseases, including metabolic, cardiovascular, degenerative and hyperproliferative pathologies. The identification of different compounds able to interact with mitochondria for therapeutic purposes is currently becoming of primary importance. Indeed, it is well known that foods, particularly those of vegetable origin, present several constituents with beneficial effects on health. This review summarizes and updates the most recent findings concerning the mechanisms through which different dietary compounds from plant foods affect mitochondria functionality in healthy and pathological in vitro and in vivo models, paying particular attention to the pathways involved in mitochondrial biogenesis and apoptosis.