Luteolin improves contractile function and attenuates apoptosis following ischemia-reperfusion in adult rat cardiomyocytes

Natural Bioproducts with Epigenetic Properties for Treating Cardiovascular Disorders

Cardiovascular disorders (CVDs) are the leading cause of mortality worldwide, highlighting an urgent need for innovative therapeutic strategies. Recent advancements highlight the potential of naturally derived bioproducts with epigenetic properties to offer protection against CVDs. These compounds act on key epigenetic mechanisms, DNA methylation, histone modifications, and non-coding RNA regulation to modulate gene expression essential for cardiovascular health. This review explores the effects of various bioproducts, such as polyphenols, flavonoids, and other natural extracts, on these epigenetic modifications and their potential benefits in preventing and managing CVDs. We discuss recent discoveries and clinical applications, providing insights into the epigenetic regulatory mechanisms of these compounds as potential epidrugs, naturally derived agents with promising therapeutic prospects in epigenetic therapy for CVDs.

Flavonoids as therapeutics for myocardial ischemia-reperfusion injury: a comprehensive review on preclinical studies

Ischemic heart disease is the most prevalent cause of death worldwide affecting both the gender of all age groups. The high mortality rate is due to damage of myocardial tissue that emanates at the time of myocardial ischemia and re-oxygenation, thus averting reperfusion injury is recognized as a potential way to reduce acute cardiac injury and subsequent mortality. Flavonoids are polyphenol derivatives of plant origin and empirical shreds of evidence substantiate their numerous activities such as antioxidant, anti-inflammatory, anti-apoptotic, and anti-thrombotic activity, leading to their role in cardio protection. Recent investigations have unveiled the capacity of flavonoids to impede pivotal regulatory enzymes, signaling molecules, and transcription factors that orchestrate the mediators participating in the inflammatory cascade. The present comprehensive review, dwells on the preclinical studies on the effectiveness of flavonoids from the year 2007 to 2023, for the prevention and therapeutics for myocardial ischemia-reperfusion injury.

Molecular mechanisms of flavonoids in myocardial ischemia reperfusion injury: Evidence from in-vitro and in-vivo studies

OBJECTIVES

Flavonoids are polyphenolic compounds found in a wide range of foods, including fruits, vegetables, tea plants, and other natural products. They have been mainly classified as flavanols, flavonols, flavones, isoflavones, flavanones, and flavanonols. In this comprehensive review, we will discuss preclinical pieces of evidence on the potential of flavonoids for the prevention/treatment of myocardial ischemia-reperfusion (IR) injury.

KEY FINDINGS

In-vitro and in-vivo studies have shown that flavonoids play an important role in preventing ischemic heart disease (IHD). They possess strong anti-oxidant, anti-inflammatory, anti-bacterial, anti-thrombotic, anti-apoptotic, and anti-carcinogenic activities. In addition, at a molecular level, flavonoids also modulate various pathways like MAPK, NFκB etc. to confer beneficial effects.

SUMMARY

The current review of flavonoids in myocardial ischemia-reperfusion injury furnishes updated information that could drive future research. The in-vitro and in-vivo experiments have demonstrated various favourable pharmacological properties of flavonoids. This review provides valuable information to conduct clinical studies, validating the safety aspects of flavonoids in the clinical domain.

The recent advance and prospect of natural source compounds for the treatment of heart failure

Heart failure is a continuously developing syndrome of cardiac insufficiency caused by diseases, which becomes a major disease endangering human health as well as one of the main causes of death in patients with cardiovascular diseases. The occurrence of heart failure is related to hemodynamic abnormalities, neuroendocrine hormones, myocardial damage, myocardial remodeling etc, lead to the clinical manifestations including dyspnea, fatigue and fluid retention with complex pathophysiological mechanisms. Currently available drugs such as cardiac glycoside, diuretic, angiotensin-converting enzyme inhibitor, vasodilator and β receptor blocker etc are widely used for the treatment of heart failure. In particular, natural products and related active ingredients have the characteristics of mild efficacy, low toxicity, multi-target comprehensive efficacy, and have obvious advantages in restoring cardiac function, reducing energy disorder and improving quality of life. In this review, we mainly focus on the recent advance including mechanisms and active ingredients of natural products for the treatment of heart failure, which will provide the inspiration for the development of more potent clinical drugs against heart failure.

Luteolin Pretreatment Ameliorates Myocardial Ischemia/Reperfusion Injury by lncRNA-JPX/miR-146b Axis

Background

In the present study, we aimed to find out whether luteolin (Lut) pretreatment could ameliorate myocardial ischemia/reperfusion (I/R) injury by regulating the lncRNA just proximal to XIST (JPX)/microRNA-146b (miR-146b) axis.

Methods

We established the models in vitro (HL-1 cells) and in vivo (C57BL/6J mice) to certify the protection mechanism of Lut pretreatment on myocardial I/R injury. Dual luciferase reporter gene assay was utilized for validating that JPX could bind to miR-146b. JPX and miR-146b expression levels were determined by RT-qPCR. Western blot was utilized to examine apoptosis-related protein expression levels, including cleaved caspase-9, caspase-9, cleaved caspase-3, caspase-3, Bcl-2, Bax, and BAG-1. Apoptosis was analyzed by Annexin V-APC/7-AAD dualstaining, Hoechst 33342 staining, as well as flow cytometry. Animal echocardiography was used to measure cardiac function (ejection fraction (EF) and fractional shortening (FS) indicators).

Results

miR-146b was demonstrated to bind and recognize the JPX sequence site by dual luciferase reporter gene assay. The expression level of miR-146b was corroborated to be enhanced by H/R using RT-qPCR (P < 0.001 vs. Con). Moreover, JPX could reduce the expression of miR-146b, whereas inhibiting JPX could reverse the alteration (P < 0.001 vs. H/R, respectively). Western blot analysis demonstrated that Lut pretreatment increased BAG-1 expression level and Bcl-2/Bax ratio, but diminished the ratio of cleaved caspase 9/caspase 9 and cleaved caspase 3/caspase 3 (P < 0.001 vs. H/R, respectively). Moreover, the cell apoptosis change trend, measured by Annexin V-APC/7-AAD dualstaining, Hoechst 33342 staining, along with flow cytometry, was consistent with that of apoptosis-related proteins. Furthermore, pretreatment with Lut improved cardiac function (EF and FS) (P < 0.001 vs. I/R, respectively), as indicated in animal echocardiography.

Conclusion

Our results demonstrated that in vitro and in vivo, Lut pretreatment inhibited apoptosis via the JPX/miR-146b axis, ultimately improving myocardial I/R injury.

SENP2-mediated SERCA2a deSUMOylation increases calcium overload in cardiomyocytes to aggravate myocardial ischemia/reperfusion injury

BACKGROUND

Sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) is a key protein that maintains myocardial Ca 2+ homeostasis. The present study aimed to investigate the mechanism underlying the SERCA2a-SUMOylation (small ubiquitin-like modifier) process after ischemia/reperfusion injury (I/RI) in vitro and in vivo .

METHODS

Calcium transient and systolic/diastolic function of cardiomyocytes isolated from Serca2a knockout (KO) and wild-type mice with I/RI were compared. SUMO-relevant protein expression and localization were detected by quantitative real-time PCR (RT-qPCR), Western blotting, and immunofluorescence in vitro and in vivo . Serca2a-SUMOylation, infarct size, and cardiac function of Senp1 or Senp2 overexpressed/suppressed adenovirus infected cardiomyocytes, were detected by immunoprecipitation, triphenyltetrazolium chloride (TTC)-Evans blue staining, and echocardiography respectively.

RESULTS

The results showed that the changes of Fura-2 fluorescence intensity and contraction amplitude of cardiomyocytes decreased in the I/RI groups and were further reduced in the Serca2a KO + I/RI groups. Senp1 and Senp2 messenger ribose nucleic acid (mRNA) and protein expression levels in vivo and in cardiomyocytes were highest at 6 h and declined at 12 h after I/RI. However, the highest levels in HL-1 cells were recorded at 12 h. Senp2 expression increased in the cytoplasm, unlike that of Senp1. Inhibition of Senp2 protein reversed the I/RI-induced Serca2a-SUMOylation decline, reduced the infarction area, and improved cardiac function, while inhibition of Senp1 protein could not restore the above indicators.

CONCLUSION

I/RI activated Senp1 and Senp2 protein expression, which promoted Serca2a-deSUMOylation, while inhibition of Senp2 expression reversed Serca2a-SUMOylation and improved cardiac function.

Baicalein and luteolin inhibit ischemia/reperfusion-induced ferroptosis in rat cardiomyocytes

BACKGROUND

Ischemia/reperfusion (I/R) is associated with severe cellular damage and death. Ferroptosis, a new form of regulated cell death caused by the accumulation of iron-mediated lipid peroxidation, has been found in several diseases including I/R injury, which was reported to be suppressed by flavonoids. Baicalein (BAI) and luteolin (Lut) are flavonoids and were shown to reduce the myocardial I/R injury. BAI was found to suppress ferroptosis in cancer cells via reducing reactive oxygen species (ROS) generation. However, the anti-ferroptosis effect of Lut on ferroptosis has not been reported. This study aimed to investigate whether ferroptosis reduction contributes to the BAI- and Lut-protected cardiomyocytes.

METHODS

This research used erastin, RSL3, and Fe-SP to induce ferroptosis. Cell viability was examined using MTT assay. Annexin V-FITC, CM-H₂DCFDA, and Phen Green SK diacetate (PGSK) fluorescent intensity were detected to analyze apoptotsis, ROS levels, and Fe²⁺ concentrations, respectively. qPCR and Western blot analysis were conducted to detect the levels of mRNA and protein, respectively.

RESULTS

Our data show that BAI and Lut protected cardiomyocytes against ferroptosis caused by ferroptosis inducers and I/R. Moreover, both BAI and Lut decreased ROS and malondialdehyde (MDA) generation and the protein levels of ferroptosis markers, and restored Glutathione peroxidase 4 (GPX4) protein levels in cardiomyocytes reduced by ferroptosis inducers. BAI and Lut reduced the I/R-induced myocardium infarction and decreased the levels of Acsl4 and Ptgs2 mRNA.

CONCLUSIONS

BAI and Lut could protect the cardiomyocytes against the I/R-induced ferroptosis via suppressing accumulation of ROS and MDA.

Mechanism Repositioning Based on Integrative Pharmacology: Anti-Inflammatory Effect of Safflower in Myocardial Ischemia–Reperfusion Injury

Safflower (Carthamus tinctorius. L) possesses anti-tumor, anti-thrombotic, anti-oxidative, immunoregulatory, and cardio-cerebral protective effects. It is used clinically for the treatment of cardio-cerebrovascular disease in China. This study aimed to investigate the effects and mechanisms of action of safflower extract on myocardial ischemia–reperfusion (MIR) injury in a left anterior descending (LAD)-ligated model based on integrative pharmacology study and ultra-performance liquid chromatography–quadrupole time-of-flight-tandem mass spectrometer (UPLC-QTOF-MS/MS). Safflower (62.5, 125, 250 mg/kg) was administered immediately before reperfusion. Triphenyl tetrazolium chloride (TTC)/Evans blue, echocardiography, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, lactate dehydrogenase (LDH) ability, and superoxide dismutase (SOD) levels were determined after 24 h of reperfusion. Chemical components were obtained using UPLC-QTOF-MS/MS. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting were used to analyze mRNA and protein levels, respectively. Safflower dose-dependently reduced myocardial infarct size, improved cardiac function, decreased LDH levels, and increased SOD levels in C57/BL6 mice. A total of 11 key components and 31 hub targets were filtered based on the network analysis. Comprehensive analysis indicated that safflower alleviated inflammatory effects by downregulating the expression of NFκB1, IL-6, IL-1β, IL-18, TNFα, and MCP-1 and upregulating NFκBia, and markedly increased the expression of phosphorylated PI3K, AKT, PKC, and ERK/2, HIF1α, VEGFA, and BCL2, and decreased the level of BAX and phosphorylated p65. Safflower shows a significant cardioprotective effect by activating multiple inflammation-related signaling pathways, including the NFκB, HIF-1α, MAPK, TNF, and PI3K/AKT signaling pathways. These findings provide valuable insights into the clinical applications of safflower.

Application Potential of Luteolin in the Treatment of Viral Pneumonia

Aim of the Review. This study aims to summarize the therapeutic effect of luteolin on the pathogenesis of viral pneumonia, explore its absorption and metabolism in the human body, evaluate the possibility of luteolin as a drug to treat viral pneumonia, and provide a reference for future research. Materials and Methods. We searched MEDLINE/PubMed, Web of Science, China National Knowledge Infrastructure, and Google Scholar and collected research on luteolin in the treatment of viral pneumonia and related diseases since 2003. Then, we summarized the efficacy and potential of luteolin in directly inhibiting viral activity, limiting inflammatory storms, reducing pulmonary inflammation, and treating pneumonia complications. Results and Conclusion. Luteolin has the potential to treat viral pneumonia in multiple ways. Luteolin has a direct inhibitory effect on coronavirus, influenza virus, and respiratory syncytial virus. Luteolin can alleviate the inflammatory factor storm induced by multiple factors by inhibiting the function of macrophages or mast cells. Luteolin can reduce pulmonary inflammation, pulmonary edema, or pulmonary fibrosis induced by multiple factors. In addition, viral pneumonia may cause multisystem complications, while luteolin has extensive protective effects on the gastrointestinal system, cardiovascular system, and nervous system. However, due to the first-pass metabolism mediated by phase II enzymes, the bioavailability of oral luteolin is low. The bioavailability of luteolin can be improved, and its potential value can be further developed by changing the dosage form or route of administration.

Exploration of Luteolin as Potential Anti-COVID-19 Agent: Molecular Docking, Molecular Dynamic Simulation, ADMET and DFT Analysis

Background:

Coronavirus disease-2019 (COVID-19) has recently emerged as a pandemic respiratory disease with mild to severe pneumonia symptoms. No clinical antiviral agent is available so far. However, several repurposing drugs and vaccines are being given to individuals or in clinical trials against SARS-CoV-2

Objective:

The aim of this study is to uncover the potential effects of Luteolin (Lut) as an inhibitor of SARS-CoV2 encoded proteins via utilizing computational tools.

Method:

Molecular modelling to unfold the anti-SARS-CoV2 potential of Lut along with reference drugs namely remdesivir and nafamostat was performed by the use of molecular docking, molecular dynamic (MD) simulation, absorption, distribution, metabolism, excretion, toxicity (ADMET) and density functional theory (DFT) methods against the five different SARS-CoV-2 encoded key proteins and one human receptor protein. The chemical reactivity of Luteolin is done through prediction of HOMO-LUMO gap energy and other chemical descriptors analysis.

Results:

In the present study, Lut binds effectively in the binding pockets of spike glycoprotein (6VSB), ADP phosphatase of NSP3 (6W02), and RNA dependent RNA polymerase (7AAP) protein receptors with significant values of docking scores -7.00, -7.25, and -6.46 respectively as compared to reference drugs remdesivir and nafamostat.

Conclusion::

Thus, Lut can act as a therapeutic agent and is orally safe for human consumption as predicted by molecular modelling against SARS-CoV-2 in the treatment of COVID-19.

Cardioprotective Effects and Possible Mechanisms of Luteolin for Myocardial Ischemia-Reperfusion Injury: A Systematic Review and Meta-Analysis of Preclinical Evidence

Background

At present, effective clinical therapies for myocardial ischemia-reperfusion injury (MIRI) are lacking. We investigated if luteolin conferred cardioprotective effects against MIRI and elucidated the potential underlying mechanisms.

Method

Four databases were searched for preclinical studies of luteolin for the treatment of MIRI. The primary outcomes were myocardial infarct size (IS) and intracardiac hemodynamics. The second outcomes were representative indicators of apoptosis, oxidative stress, and inflammatory. The Stata and RevMan software packages were utilized for data analysis.

Results

Luteolin administration was confirmed to reduce IS and ameliorate hemodynamics as compared to the control groups (p &lt; 0.01). IS had decreased by 2.50%, 2.14%, 2.54% in three subgroups. Amelioration of hemodynamics was apparent in two different myocardial infarct models (model of left anterior descending branch ligation and model of global heart ischemia), as left ventricular systolic pressure improved by 21.62 and 35.40 mmHg respectively, left ventricular end-diastolic pressure decreased by 7.79 and 4.73 mmHg respectively, maximum rate of left ventricular pressure rise increased by 737.48 and 750.47 mmHg/s respectively, and maximum rate of left ventricular pressure decrease increased by 605.66 and 790.64 mmHg/s respectively. Apoptosis of cardiomyocytes also significantly decreased, as indicated by thelevels of MDA, an oxidative stress product, and expression of the inflammatory factor TNF-α (p &lt; 0.001).

Conclusion

Pooling of the data demonstrated that luteolin exerts cardioprotective effects against MIRI through different signaling pathways. As possible mechanisms, luteolin exerts anti-apoptosis, anti-oxidation, and anti-inflammation effects against MIRI.

Luteolin Protects Cardiomyocytes Cells against Lipopolysaccharide-Induced Apoptosis and Inflammatory Damage by Modulating Nlrp3

PURPOSE

In this article, we aimed to investigate the influences of luteolin on inflammatory injury to cardiomyocytes induced by lipopolysaccharide (LPS).

MATERIALS AND METHODS

H9c2 cells were pretreated with different concentrations of luteolin (10, 20, and 50 µM) for 12 h and then stimulated with 10 µg/mL LPS or no LPS for 6 h. Cell viability was detected by CCK-8 assay. Cell apoptosis was determined by flow cytometry. QRT-PCR and Western blotting were utilized to examine mRNA and protein levels. ELISA was used to determine the levels of monocyte chemoattractant protein-1, tumor necrosis factor-alpha, interleukin (IL)-6, IL-1β, and IL-18 in cell supernatants among different groups of H9c2 cells. Immunofluorescence was applied to evaluate reactive oxygen species formation in H9c2 cells. M-mode images of echocardiography, the ejection fraction test, fractional shortening test, end-systolic volume test, and end-diastolic volume test of mouse heart function were obtained by ultrasonic electrocardiogram.

RESULTS

Luteolin could alleviate inflammatory damage and inflammatory factor expression among LPS-induced H9c2 cells. Additionally, we found that luteolin decreased LPS-stimulated inflammatory damage in H9c2 cells by down-regulating NOD-like receptor family pyrin domain containing 3 (Nlrp3). Luteolin also improved myocardial function in mice treated with LPS and reduced myocardial relaxation. Luteolin reversed myocardial histological abnormalities in mice and reduced inflammation and cardiomyocyte apoptosis. Additionally, luteolin inhibited oxidative stress-mediated myocardial and systemic tissue damage in mice. Finally, luteolin reduced LPS-induced inflammatory damage in mouse cardiomyocytes by down-regulating Nlrp3.

CONCLUSION

We found that luteolin could reduce inflammatory damage to cardiomyocytes induced by LPS by down-regulating Nlrp3.

SHP-1/STAT3 Interaction Is Related to Luteolin-Induced Myocardial Ischemia Protection

Prevention and management of myocardial ischemia/reperfusion (I/R) injury is a key step in coronary heart disease surgery. Luteolin is a falconoid compound that has an antioxidant effect, but its mechanism in I/R injury in vivo and in vitro is still under explored. This study attempted to reveal the role of luteolin (Lut) in I/R through mediation of the Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1)/Signal transducer and activator of transcription 3 (STAT3) pathway. To establish I/R rat models, the left anterior descending artery (LAD) was ligated for 30 min and re-perfused for 1 h in Lut-pretreated or nude rats. Comparisons between infarct area, cardiac dysfunction, and myocardial cell death and inflammatory reaction were performed in I/R-induced rats. Hypoxia/reoxygenation (H/R) cell models were established by stimulating H9c2 cells with 95% nitrogen and 5% carbon dioxide. Simultaneously, H/R-related cell death and inflammatory reactions were investigated following Lut treatment. The target protein of Lut was identified using western blotting. Pro-inflammatory cytokines were also measured in serum or Lut-pretreated cell culture medium. The results revealed that compared with the I/R group, Lut treatment could significantly decrease myocardial infarction (MI) area, increase left ventricular ejection fraction (LVEF), and decrease cell death and pro-inflammatory cytokines in the serum. Decreased apoptosis and inflammatory cytokines were also observed in H/R cells after Lut treatment. Lut treatment downregulated SHP-1 expression and subsequently upregulated STAT3 phosphorylation in both I/R rat heart tissue and H9c2 cells. The findings of the current study suggest that Lut can protect the heart and reduce MI area, cell apoptosis rate, and inflammatory level in I/R models.

Modulations of Cardiac Functions and Pathogenesis by Reactive Oxygen Species and Natural Antioxidants

Homeostasis in the level of reactive oxygen species (ROS) in cardiac myocytes plays a critical role in regulating their physiological functions. Disturbance of balance between generation and removal of ROS is a major cause of cardiac myocyte remodeling, dysfunction, and failure. Cardiac myocytes possess several ROS-producing pathways, such as mitochondrial electron transport chain, NADPH oxidases, and nitric oxide synthases, and have endogenous antioxidation mechanisms. Cardiac Ca²⁺-signaling toolkit proteins, as well as mitochondrial functions, are largely modulated by ROS under physiological and pathological conditions, thereby producing alterations in contraction, membrane conductivity, cell metabolism and cell growth and death. Mechanical stresses under hypertension, post-myocardial infarction, heart failure, and valve diseases are the main causes for stress-induced cardiac remodeling and functional failure, which are associated with ROS-induced pathogenesis. Experimental evidence demonstrates that many cardioprotective natural antioxidants, enriched in foods or herbs, exert beneficial effects on cardiac functions (Ca²⁺ signal, contractility and rhythm), myocytes remodeling, inflammation and death in pathological hearts. The review may provide knowledge and insight into the modulation of cardiac pathogenesis by ROS and natural antioxidants.

Luteolin attenuates sepsis‑induced myocardial injury by enhancing autophagy in mice

Sepsis-induced cardiomyopathy (SIC) is a complication of severe sepsis and septic shock characterized by an invertible myocardial depression. This study sought to explore the potential effects and mechanism of luteolin, a flavonoid polyphenolic compound, in lipopolysaccharide (LPS)-induced myocardial injury. Experimental mice were randomly allocated into 3 groups (25 mice in each group): The control group (NC), the LPS group (LPS) and the LPS + luteolin group (LPS + Lut). Before the SIC model was induced, luteolin was dissolved in DMSO and injected intraperitoneally for 10 days into LPS + Lut group mice. NC group and LPS group mice received an equal volume of DMSO for 10 days. On day 11, the animal model of sepsis-induced cardiac dysfunction was induced by intraperitoneal injection of LPS. A total of 12 h after LPS injection, measurements and comparisons were made among the groups. Luteolin administration improved cardiac function, attenuated the inflammatory response, alleviated mitochondrial injury, decreased oxidative stress, inhibited cardiac apoptosis and enhanced autophagy. In addition, luteolin significantly decreased the phosphorylation of AMP-activated protein kinase (AMPK) in septic heart tissue. The protective effect of luteolin was abolished by 3-methyladenine (an autophagy inhibitor) and dorsomorphin (compound C, an AMPK inhibitor), as evidenced by decreased autophagic activity, destabilized mitochondrial membrane potential and increased apoptosis in LPS-treated cardiomyocytes, but was mimicked by 5-aminoimidazole-4-carboxamide ribonucleotide (an AMPK activator), suggesting that luteolin attenuates LPS-induced myocardial injury by increasing autophagy through AMPK activation. Luteolin may be a promising therapeutic agent for treating SIC.

Hydrogen-rich saline alleviates inflammation and apoptosis in myocardial I/R injury via PINK-mediated autophagy

Ischemia/reperfusion (I/R)-induced inflammatory reaction is one of the most important elements in myocardial I/R injury. In addition, autophagy serves an important role in normal cardiac homeostasis, and obstructions to the autophagy process lead to severe consequences for the heart. Hydrogen exerts an effective therapeutic role in numerous diseases associated with I/R injury via its anti-inflammation, anti-apoptosis and anti-oxidative properties. Therefore, the present study investigated the effect of hydrogen on the myocardial inflammation response and apoptosis in myocardial ischemic/reperfusion (MI/R) injury, and further explored the mechanism of PTEN-induced kinase 1 (PINK1)/Parkin-induced mitophagy in the protection of hydrogen on MI/R injury. MI/R injury was performed by surgical ligation of the left coronary artery in vivo and H9C2 cell injury was performed by hypoxia/reoxygenation (H/R) in vitro. Hydrogen-rich saline was administered twice through intraperitoneal injection at a daily dose of 10 ml/kg following the operation in the in vivo model, and hydrogen-rich medium culture was used for cells instead of normal medium in vitro. The infarction size of hearts, the levels of creati-nine kinase-muscle/brain (CK-MB) and cardiac troponin I (cTnI), cardiac function, cell viability and lactate dehydrogenase (LDH) release, levels of cytokines, apoptosis and the expression of autophagy-associated proteins were detected in the different treatment groups in vivo and in vitro. The results demonstrated that treatment with hydrogen improved the myocardial infarction size of hearts, cardiac function, apoptosis and cytokine release following MI/R in rats. In vitro, hydrogen improved cell viability and LDH release following hypoxia/reoxygenation in myocardial cells. In addition, it was demonstrated that hydrogen exerted an anti-inflammatory and anti-apoptotic effect in myocardial cells induced by H/R via PINK1/Parkin mediated autophagy. These results suggested that hydrogen-rich saline alleviated the inflammation response and apoptosis induced by MI/R or H/R in vivo or in vitro, and that hydrogen-rich saline contributed to the increased expression of proteins associated with autophagy. In summary, the present study indicated that treatment with hydrogen-rich saline improved the inflammatory response and apoptosis in MI/R via PINK1/Parkin-mediated mitophagy.

The Falconoid Luteolin Mitigates the Myocardial Inflammatory Response Induced by High-Carbohydrate/High-Fat Diet in Wistar Rats

Luteolin is a major component of many medicinal plants and traditional medicines. The current study aims at testing its protective effect against high-carbohydrate/high-fat (HCHF) diet-induced cardiac dysfunction in rats. Male Wistar rats were divided into six groups as follows: control group that received standard rat chow, group received HCHF diet (~ 30% carbohydrate and 42% fat) daily for 16 weeks, and four groups received HCHF diet concurrently with luteolin (10, 25, 50 or 100 mg/kg; 10% w/v suspension in 0.9% NaCl) daily from the first week by oral gavage. Body weight was measured weekly. At the end of the study, histopathological examinations of stained heart sections were carried out. Lipid profile, oxidative stress, and cardiac function biomarkers were measured. Furthermore, neurohumoral mediators and inflammatory cytokines (TNF-α, IL-18) were assigned. Results showed a significant improvement in cardiac function, tissue integrity, and a decrease in the compensatory neurohumoral mediators by luteolin 50 and 100 mg/kg. In addition, a significant (P < 0.05) decrease in collagen deposition, fibrosis percentage, lipid peroxidation, and inflammatory cells (macrophages and lymphocytes) infiltration was observed. Tested doses of luteolin decreased lipid peroxidation and elevated the endogenous antioxidant biomarkers (reduced glutathione and superoxide dismutase) significantly (P < 0.05). Finally, luteolin decreased TNF-α and IL-18 (P < 0.001) in a dose-dependent manner. It can be concluded that luteolin has a cardioprotective effect against HCHF diet-induced myocardial inflammation through antioxidant anti-inflammatory mechanisms.

Luteolin ameliorates rat myocardial ischaemia-reperfusion injury through activation of peroxiredoxin II

BACKGROUND AND PURPOSE

Antioxidants provide a promising therapeutic effect for the cardiovascular disease. Luteolin, a polyphenolic bioflavonoid, is known to confer cardioprotection, although the underlying mechanisms, especially the role of luteolin on the antioxidant enzymes, such as the peroxiredoxin family, remain unknown.

EXPERIMENTAL APPROACH

We measured the effects of luteolin on myocardial ischaemia/reperfusion (MI/R) injury in vivo (Sprague-Dawley rats) and in vitro, together with the underlying mechanisms, with a focus on signalling by peroxiredoxins. H9c2 cells were used to assess the changes in peroxiredoxins and the other antioxidant enzymes. Oxidative stress, cardiac function, LDH release, ROS and infarct size were also assayed.

KEY RESULTS

Luteolin exerted significant cardioprotective effects in vivo and in vitro via improving cardiac function, increasing the expression of anti-apoptotic protein Bcl-2 and decreasing the pro-apoptotic protein Bax and active caspases 3 and 9, associated with MI/R. Mechanistically, luteolin markedly enhanced expression of peroxiredoxin II, without significant effects on other forms of peroxiredoxin, catalase or SOD1. Molecular docking showed that luteolin could indeed bind to the enzymic active pocket of peroxiredoxin II. Furthermore, down-regulation of peroxiredoxin II by peroxiredoxin II-antisense, administered by adenovirus infection of H9c2 cardiomyocytes, and inhibition of peroxiredoxin II in vivo significantly reversed the cardioprotective effects of luteolin.

CONCLUSIONS AND IMPLICATIONS

Our findings, for the first time, demonstrate that luteolin protects against MI/R injury through promoting signalling through the endogenous antioxidant enzyme, peroxiredoxin II, indicating the important beneficial role of this antioxidant system in the heart.

Combination of Luteolin and Solifenacin Improves Urinary Dysfunction Induced by Diabetic Cystopathy in Rats

Background

The purpose of the present study was to assess the effect of luteolin and solifenacin on diabetic cystopathy (DCP) and to investigate the mechanism of action. A novel link between the overexpression of c-Kit in the bladder and voiding dysfunction was identified in rats with DCP.

Material/Methods

A rat model of DCP was successfully established by intraperitoneal injection of streptozotocin and a diet high in glucose and lipids, and animals were treated with luteolin and solifenacin. The effect of luteolin and solifenacin on urinary dysfunction in DCP rats was investigated by assessing bladder pressure and performing a volume test. The protein levels of c-Kit, stem cell factor (SCF), p110, and phosphorylated p110 in the bladder were detected by Western blot analysis and immunohistochemical staining.

Results

In DCP rats, the protein levels of c-Kit, SCF and phosphorylated p110 in the bladder were significantly increased. However, oral treatment of DCP rats with luteolin combined with solifenacin resulted in effective improvement of overactive bladder and reduced the protein expression of c-Kit, SCF, and phosphorylated p110. Moreover, the effect of luteolin combined with solifenacin on maximum voiding pressure and residual urine volume was improved compared to that of luteolin alone.

Conclusions

Luteolin improved overactive bladder in DCP rats, which may be due to SCF/c-kit inhibition, as well as the downregulation of the phosphoinositide-3 kinase signaling pathway. Moreover, solifenacin enhanced the potential pharmacological effect of luteolin in the treatment of DCP.

Effects of luteolin on regulatory proteins and enzymes for myocyte calcium circulation in hypothermic preserved rat heart

Heart transplantation has been applied in the clinic as an optimal solution for patients with end stage cardiac failure for a number of years. However, hypothermic preservation of the heart remains limited to 4–6 h and calcium accumulation over time is an important factor resulting in cell death. To provide longer and safer storage for donor hearts, it was demonstrated in our previous study that luteolin, a traditional Chinese medicine used to treat cardiovascular diseases, inhibits cell death and L-type calcium currents during hypothermic preservation. In the current study, the protective role of luteolin in modulating cardiomyocyte calcium cycling was further investigated. Intracellular calcium overload has already been implicated in hypothermia-induced dysfunction of cardiomyocytes. University of Wisconsin (UW) solution supplemented with 7.5, 15 or 30 µmol/l luteolin was used to preserve fresh isolated cardiomyocytes at 4°C. The results demonstrated that all three doses of luteolin supplementation attenuated calcium overload over a 6 h preservation period. Luteolin also suppressed the accumulation of important regulatory proteins and enzymes for cardiomyocyte calcium circulation, mitochondria Ca²⁺ uniporter and calmodulin, which are normally induced by cold storage in UW solution. Protein Kinase A activity was also suppressed in cardiomyocytes preserved in luteolin supplemented UW solution, while Ca²⁺-Mg²⁺-ATPase activity was increased. The results demonstrated that luteolin confers a cardioprotective effect through inhibiting the changes of calcium regulators during cold storage and therefore ameliorates Ca²⁺ overload in rat cardiomyocytes.

Luteolin: A Flavonoid that Has Multiple Cardio-Protective Effects and Its Molecular Mechanisms

Cardiovascular disease (CVD) has become the leading cause of morbidity and mortality worldwide. A well-monitored diet with a sufficient intake of fruits and vegetables has been confirmed as a primary prevention of CVD. Plant constituents such as flavonoids have been shown to confer healthy benefits. Luteolin (Lut), a kind of flavonoid, possesses anti-oxidative, anti-tumor, and anti-inflammatory properties. Recent scientific literature has reported the cardiac protective effects of Lut in vitro and in vivo. Therefore, the aim of this review is to provide an update and detailed overview with cardio-protective molecular mechanisms of Lut with a focus on multiple intrinsic and extrinsic effectors. We further explore how these mechanisms participate in ischemia/reperfusion (I/R) injury, heart failure (HF) and atherosclerosis (AS). A proper understanding of the cardiovascular protective effects and the relative mechanisms of Lut may provide the possibility of new drug design and development for CVD. With the previous studies mainly focused on basic research, we need to advance the prospects of its further clinical utilization against CVD, large prospective clinical trials of Lut are needed to observe its therapeutic effects on patients with I/R injury, HF and AS, especially on the effective therapeutic dosage, and safety of long-term administration.

Luteolin Enhances Sarcoplasmic Reticulum Ca2+-ATPase Activity through p38 MAPK Signaling thus Improving Rat Cardiac Function after Ischemia/Reperfusion

Background/Aims: A major challenge for current therapeutic strategies against ischemia/reperfusion (I/R) is the lack of effective drugs. Considering luteolin enhances the activity of sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) to improve the systolic/diastolic function of rat hearts and cardiomyocytes during the I/R process, we studied the regulatory function of the p38 MAPK pathway in this protective mechanism. Methods: Isolated cardiomyocytes and perfused hearts were separately divided into five groups and used to investigate I/R. The phosphorylation of p38 and phospholamban (p-PLB), the levels and activity of SERCA2a and the levels of proteins related to apoptosis were measured. Apoptotic cells were assessed using the TUNEL assay. Single-cell shortening, Ca2+ transients, and the decay of the mitochondrial membrane potential (Δψm) were detected. Results: The p38 MAPK pathway was activated during the I/R process, and inhibiting it with SB203580 promoted p-PLB, which enhanced the activity of SERCA2a and relieved the calcium overload to promote the recovery of the Δψm and reduce cardiomyocyte apoptosis in I/R. Luteolin also suppressed the activation of the p38 MAPK pathway and showed cardioprotective effects during I/R injury. Conclusions: We conclude that luteolin enhances SERCA2a activity to improve systolic/diastolic function during I/R in rat hearts and cardiomyocytes by attenuating the inhibitive effects of the p38 pathway on p-PLB.

Systems Pharmacology Dissection of the Integrated Treatment for Cardiovascular and Gastrointestinal Disorders by Traditional Chinese Medicine

Though cardiovascular diseases (CVDs) and gastrointestinal disorders (GIDs) are different diseases associated with different organs, they are highly correlated clinically. Importantly, in Traditional Chinese Medicine (TCM), similar treatment strategies have been applied in both diseases. However, the etiological mechanisms underlying them remain unclear. Here, an integrated systems pharmacology approach is presented for illustrating the molecular correlations between CVDs and GIDs. Firstly, we identified pairs of genes that are associated with CVDs and GIDs and found that these genes are functionally related. Then, the association between 115 heart meridian (HM) herbs and 163 stomach meridian (SM) herbs and their combination application in Chinese patent medicine was investigated, implying that both CVDs and GIDs can be treated by the same strategy. Exemplified by a classical formula Sanhe Decoration (SHD) treating chronic gastritis, we applied systems-based analysis to introduce a drug-target-pathway-organ network that clarifies mechanisms of different diseases being treated by the same strategy. The results indicate that SHD regulated several pathological processes involved in both CVDs and GIDs. We experimentally confirmed the predictions implied by the effect of SHD for myocardial ischemia. The systems pharmacology suggests a novel integrated strategy for rational drug development for complex associated diseases.

Luteolin Prevents H2O2-Induced Apoptosis in H9C2 Cells through Modulating Akt-P53/Mdm2 Signaling Pathway

Introduction. Luteolin, a falconoid compound in many Chinese herbs and formula, plays important roles in cardiovascular diseases. The underlying mechanism of luteolin remains to be further elaborated. Methods. A model of hydrogen peroxide- (H₂O₂-) induced H9C2 cells apoptosis was established. Cell viabilities were examined with an MTT assay. 2′,7′-Dichlorofluorescin diacetate (DCFH-DA) and flow cytometry were used to detect ROS level and apoptosis rate, respectively. The expressions of signaling proteins related to apoptosis were analyzed by western blot and mRNA levels were detected by real-time polymerase chain reaction (PCR). Quercetin was applied as positive drug. Results. Incubation with various concentrations of H₂O₂ (0, 50, 100, and 200 μM) for 1 h caused dose-dependent loss of cell viability and 100 μM H₂O₂ reduced the cell viability to approximately 50%. Treatments with luteolin and quercetin protected cells from H₂O₂-induced cytotoxicity and reduced cellular ROS level and apoptosis rate. Moreover, luteolin could downregulate the expressions of Bax, caspase-8, cleaved-caspase-3, and p53 in apoptotic signaling pathway. Further study showed that the expressions of Akt, Bcl-2, and Mdm2 were upregulated by luteolin. Conclusion. Luteolin protects H9C2 cells from H₂O₂-induced apoptosis. The protective and antiapoptotic effects of luteolin could be mediated by regulating the Akt-P53/Mdm2 apoptotic pathway.

Antioxidative effect of luteolin pretreatment on simulated ischemia/reperfusion injury in cardiomyocyte and perfused rat heart

OBJECTIVE

To investigate the antioxidative effect and mechanism of luteolin on rat cardiomyocytes and isolated hearts followed by simulated ischemia/reperfusion (SI/R) injury.

METHODS

The left ventricular cardiomyocytes and the isolated hearts from adult rats were subjected to SI/R injury. The experiment groups included control, SI/R, luteolin + SI/R (Lut + SI/R), vitamin E (Vit E) + SI/R, and LY294002 + luteolin + SI/R (LY + Lut + SI/R) groups. Cell viability, shortening amplitude, lactate dehydrogenase (LDH) release, superoxide dismutase (SOD) activity, the production of reactive oxygen species (ROS) and malondialdehyde (MDA), expression levels of Akt, phosphorylated Akt, NOX2 (gp91phox), NOX2 mRNA, mitogen-activated protein kinase (p38 MAPK) and phosphorylated p38MAPK were all measured after 3-h simulated ischemia and 2-h simulated reperfusion procedure in cardiomyocytes. Vit E was used as a standard control. The contractile function of isolated hearts was further observed after they were subjected to 30-min global ischemia and 120-min reperfusion.

RESULTS

Pretreatment with 8-μmol/L luteolin substantially increased cell viability and shortening amplitude, while reducing evidence of oxidative stress-induced damage in the cells. In addition, the expression of NOX2, NOX2 mRNA and phosphorylation of p38MAPK were all downregulated. Furthermore, pretreatment with 40-μmol/L luteolin improved the recovery of myocardial contractile function following SI/R-induced injury, and luteolin markedly increased phosphorylation of Akt. However, all of the above effects were partially inhibited by the phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002.

CONCLUSIONS

Luteolin prevents SI/R-induced myocardial damage by reducing oxidative stress-induced injury in isolated rat hearts and cardiomyocytes, and the cardioprotection induced by luteolin was partially mediated by the PI3K/Akt pathway.

Luteolin Inhibits Ischemia/Reperfusion-Induced Myocardial Injury in Rats via Downregulation of microRNA-208b-3p

BACKGROUND

Luteolin (LUT), a kind of flavonoid which is extracted from a variety of diets, has been reported to convey protective effects of various diseases. Recent researches have suggested that LUT can carry out cardioprotective effects during ischemia/reperfusion (I/R). However, there have no reports on whether LUT can exert protective effects against myocardial I/R injury through the actions of specific microRNAs (miRs). The purpose of this study was to determine which miRs and target genes LUT exerted such function through.

METHODS

Expression of various miRs in perfused rat hearts was detected using a gene chip. Target genes were predicted with TargetScan, MiRDB and MiRanda. Anoxia/reoxygenation was used to simulate I/R. Cells were transfected by miR-208b-3p mimic, inhibitor and small interfering RNA of Ets1 (avian erythroblastosis virus E26 (v ets) oncogene homolog 1). MiR-208b-3p and Ets1 mRNA were quantified by real-time quantitative polymerase chain reaction. The percentage of apoptotic cells was detected by annexin V-fluorescein isothiocyanate/propidium iodide dyeing and flow cytometry. The protein expression levels of cleaved caspase-3, Bcl-2, Bax, and Ets1 were examined by western blot analysis. A luciferase reporter assay was used to verify the combination between miR-208b-3p and the 3'-untranslated region of Ets1.

RESULTS

LUT pretreatment reduced miR-208b-3p expression in myocardial tissue, as compared to the I/R group. And LUT decreased miR-208b-3p expression and apoptosis caused by I/R. However, overexpression of miR-208b-3p further aggravated the changes caused by I/R and blocked all the effects of LUT. Knockdown of miR-208b-3p expression also attenuated apoptosis, while knockdown of Ets1 promoted apoptosis. Further, the luciferase reporter assay showed that miR-208b-3p could inhibit Ets1 expression.

CONCLUSION

LUT pretreatment conveys anti-apoptotic effects after myocardial I/R injury by decreasing miR-208b-3p and increasing Ets1 expression levels.

Luteolin Exerts Cardioprotective Effects through Improving Sarcoplasmic Reticulum Ca(2+)-ATPase Activity in Rats during Ischemia/Reperfusion In Vivo

The flavonoid luteolin exists in many types of fruits, vegetables, and medicinal herbs. Our previous studies have demonstrated that luteolin reduced ischemia/reperfusion (I/R) injury in vitro, which was related with sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2a) activity. However, the effects of luteolin on SERCA2a activity during I/R in vivo remain unclear. To investigate whether luteolin exerts cardioprotective effects and to monitor changes in SERCA2a expression and activity levels in vivo during I/R, we created a myocardial I/R rat model by ligating the coronary artery. We demonstrated that luteolin could reduce the myocardial infarct size, lactate dehydrogenase release, and apoptosis during I/R injury in vivo. Furthermore, we found that luteolin inhibited the I/R-induced decrease in SERCA2a activity in vivo. However, neither I/R nor luteolin altered SERCA2a expression levels in myocardiocytes. Moreover, the PI3K/Akt signaling pathway played a vital role in this mechanism. In conclusion, the present study has confirmed for the first time that luteolin yields cardioprotective effects against I/R injury by inhibiting the I/R-induced decrease in SERCA2a activity partially via the PI3K/Akt signaling pathway in vivo, independent of SERCA2a protein level regulation. SERCA2a activity presents a novel biomarker to assess the progress of I/R injury in experimental research and clinical applications.

Luteolin alleviates post-infarction cardiac dysfunction by up-regulating autophagy through Mst1 inhibition

Myocardial infarction (MI), which is characterized by chamber dilation and LV dysfunction, is associated with substantially higher mortality. We investigated the effects and underlying mechanisms of Luteolin on post‐infarction cardiac dysfunction. Myocardial infarction was constructed by left anterior descending coronary artery ligation. In vitro, cultured neonatal cardiomyocytes subjected to simulated MI were used to probe mechanism. Luteolin significantly improved cardiac function, decreased cardiac enzyme and inflammatory cytokines release after MI. Enhanced autophagic flux as indicated by more autophagosomes puncta, less accumulation of aggresomes and P62 in the neonatal cardiomyocytes after hypoxia was observed in the Luteolin pre‐treatment group. Western blot analysis also demonstrated that Luteolin up‐regulated autophagy in the cardiomyocytes subjected to simulated MI injury. Furthermore, Luteolin increased mitochondrial membrane potential, adenosine triphosphate content, citrate synthase activity and complexes I/II/III/IV/V activities in the cardiomyocytes subjected to simulated MI injury. Interestingly, mammalian sterile 20‐like kinase 1 (Mst1) knockout abolished the protective effects of Luteolin administration. Luteolin enhances cardiac function, reduces cardiac enzyme and inflammatory markers release after MI. The protective effects of Luteolin are associated with up‐regulation of autophagy and improvement of mitochondrial biogenesis through Mst1 inhibition.

Luteolin Inhibits Angiotensin II-Stimulated VSMC Proliferation and Migration through Downregulation of Akt Phosphorylation

Luteolin is a naturally occurring flavonoid found in many plants that possesses cardioprotective properties. The purpose of this study was to elucidate the effect of luteolin on vascular smooth muscle cells (VSMCs) proliferation and migration induced by Angiotensin II (Ang II) and to investigate the mechanism(s) of action of this compound. Rat VSMCs were cultured in vitro, and the proliferation and migration of these cells following Ang II stimulation were monitored. Different doses of luteolin were added to VSMC cultures, and the proliferation and migration rate were observed by MTT and Transwell chamber assays, respectively. In addition, the expressions of p-Akt (308), p-Akt (473), and proliferative cell nuclear antigen (PCNA) in VSMCs were monitored by Western blotting. This study demonstrated that luteolin has an inhibitory effect on Ang II-induced VSMC proliferation and migration. Further, the levels of p-Akt (308), p-Akt (473), and PCNA were reduced in VSMCs treated with both Ang II and luteolin compared to VSMCs treated with only Ang II. These findings strongly suggest that luteolin inhibits Ang II-stimulated proliferation and migration of VSMCs, which is partially due to downregulation of the Akt signaling pathway.

Protection by the NO-Donor SNAP and BNP against Hypoxia/Reoxygenation in Rat Engineered Heart Tissue

In vitro assays could replace animal experiments in drug screening and disease modeling, but have shortcomings in terms of functional readout. Force-generating engineered heart tissues (EHT) provide simple automated measurements of contractile function. Here we evaluated the response of EHTs to hypoxia/reoxygenation (H/R) and the effect of known cardiocytoprotective molecules. EHTs from neonatal rat heart cells were incubated for 24 h in EHT medium. Then they were subjected to 180 min hypoxia (93% N₂, 7% CO₂) and 120 min reoxygenation (40% O₂, 53% N₂, 7% CO₂), change of medium and additional follow-up of 48 h. Time-matched controls (40% O₂, 53% N₂, 7% CO₂) were run for comparison. The following conditions were applied during H/R: fresh EHT medium (positive control), the NO-donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 10^-7, 10^-6, 10^-5 M) or the guanylate cyclase activator brain type natriuretic peptide (BNP, 10^-9, 10^-8, 10^-7 M). Frequency and force of contraction were repeatedly monitored over the entire experiment, pH, troponin I (cTnI), lactate dehydrogenase (LDH) and glucose concentrations measured in EHT medium. Beating activity of EHTs in 24 h-medium ceased during hypoxia, partially recovered during reoxygenation and reached time-control values during follow-up. H/R was accompanied by a small increase in LDH and non-significant increase in cTnI. In fresh medium, some EHTs continued beating during hypoxia and all EHTs recovered faster during reoxygenation. SNAP and BNP showed small but significant protective effects during reoxygenation. EHTs are applicable to test potential cardioprotective compounds in vitro, monitoring functional and biochemical endpoints, which otherwise could be only measured by using in vivo or ex vivo heart preparations. The sensitivity of the model needs improvement.

Flavonoids and mitochondrial pharmacology: A new paradigm for cardioprotection

Acute myocardial ischemia is one of the major causes of illness and of deaths in Western society; therefore the definition of the signaling pathways involved in the cardioprotection represents a challenging goal in order to discover novel pharmacological approaches. In this regard, a number of epidemiologic studies demonstrate a relationship between intake of flavonoid-rich foods and reduction of cardiovascular risk factors and mortality. Moreover, numerous experimental studies have examined flavonoid-induced cardioprotective effects on several animal models of myocardial ischemia/reperfusion. As concerns the mechanisms of action, although the antioxidant effect of flavonoids has been long thought to be a crucial factor accounting for cardioprotection, mitochondrial pathways (ion channels, protein kinases, etc.) are presently emerging as specific pharmacological targets more relevantly involved in the anti-ischemic effects of some flavonoids. Since these pharmacodynamic features seem to be poorly considered, this review examines the mitochondrial role in the cardioprotective mechanisms of some members of this phytochemical class, by describing the biological pathways and reporting an overview of the most important experimental evidence in this field.

Cardioprotective effects of luteolin on ischemia/reperfusion injury in diabetic rats are modulated by eNOS and the mitochondrial permeability transition pathway

Myocardial ischemia/reperfusion (I/R) injury in diabetes is associated with oxidative stress, endothelial nitric oxide synthase (eNOS) dysfunction, and mitochondrial collapse, whereas luteolin is known to protect the cardiovascular system against diabetes and I/R injury. Here, we investigated whether luteolin pretreatment diminishes myocardial I/R injury in diabetic rats by affecting eNOS and the mitochondrial permeability transition pore (mPTP). After diabetic rats were produced by streptozotocin treatment (65 mg/kg) for 3 weeks, luteolin (100 mg·kg·d) or L-NAME (25 mg·kg·d) was administered intragastrically for 2 weeks. Hearts were then isolated and subjected to 30 minutes of global ischemia followed by 120 minutes of reperfusion. Pretreatment with luteolin significantly improved left ventricular function and coronary flow throughout reperfusion, increased cardiac tissue viability and manganese superoxide dismutase (MnSOD) activity, and reduced coronary lactate dehydrogenase release, and the myocardial malonaldehyde level in diabetic I/R rat hearts. All these improving effects of luteolin were significantly attenuated by L-NAME. Luteolin also significantly upregulated eNOS expression in diabetic rat hearts after I/R. Ca-induced mPTP opening and mitochondrial inner membrane potential reduction were significantly inhibited in ventricular myocytes isolated from luteolin-treated diabetic rats, and this effect was attenuated by L-NAME. These findings indicate that luteolin protects the diabetic heart against I/R injury by upregulating the myocardial eNOS pathway, and downstream effects include the enhancement of MnSOD and inhibition of mPTP.

Ischemic postconditioning inhibits apoptosis in an in vitro proximal tubular cell model

Ischemia-reperfusion is a common injury of clinical ischemic disease and surgical lesions. Ischemic postconditioning (IPO) improves the ability of organs subjected to ischemia to tolerate injury. However, renal IPO studies have been based on animal models. In order to gain insights into IPO-induced alterations at the cellular level, an in vitro model for IPO was designed using the rat proximal tubular cell line NRK-52E. This model was established by placing NRK-52E cells in ischemic conditions for 3 h, then exposing cells to three cycles of reperfusion for 10 min and finally to ischemic conditions for 10 min (postconditioning). The cells were cultured further in reperfusion conditions for 3, 6, 12 and 24 h. Flow cytometry and Hoechst were used to assess apoptosis. The protein expression of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, cleaved caspase-3 and caspase-8 were analyzed by western blotting. The results demonstrated that apoptosis occurred in cells subjected to ischemia/reperfusion (I/R) alone or with postconditioning following reperfusion for 24 h. Cells subjected to I/R demonstrated increased expression of Bax, cleaved caspase-3 and caspase-8 at the end of reperfusion. However, the levels of Bax, cleaved caspase-3 and caspase-8 were significantly attenuated in cells, which had undergone IPO. In conclusion, apoptosis was observed in cells subjected to 3 h of ischemia-reperfusion injury and IPO was able to inhibit this apoptosis. IPO inhibited apoptosis by inhibiting the caspase pathway thereby exerting protective effects.

Luteolin inhibits ROS-activated MAPK pathway in myocardial ischemia/reperfusion injury

AIMS

Luteolin is a falconoid compound that has an antioxidant effect, but its contribution to ROS-activated MAPK pathways in ischemia/reperfusion injury is seldom reported. Here, we have confirmed that it exhibits an antioxidant effect in myocardial ischemia/reperfusion injury (MIRI) by inhibiting ROS-activated MAPK pathways.

MAIN METHODS

We exposed rat hearts into the left anterior descending coronary artery (LAD) ligation for 30min followed by 1h of reperfusion. Observations were carried out using electrocardiography; detection of hemodynamic parameters; and testing levels of lactate dehydrogenase (LDH), creatine kinase (CK), total superoxide dismutase (T-SOD), and malondialdehyde (MDA). Mitogen-activated protein kinase (MAPK) pathway was measured by western blot and transmission electron microscopy was applied to observe the myocardial ultrastructure. Rat H9c2 cell in 95% N2 and 5% CO2 stimulated the MIRI. Oxidation system mRNA levels were measured by real-time PCR; mitochondrial membrane potential and apoptosis were measured by confocal microscopy and flow cytometry; western blot analysis was used to assay caspase-3, -8, and -9 and MAPK pathway protein expression; the MAPK pathway was inhibited using SB203580 (p38 MAPK inhibitor) and SP600125 (c-Jun NH2-terminal kinase inhibitor) before H9c2 cells were exposed to hypoxia/reoxygenation injury to show the modulation of the changes in ROS generation, cell viability and apoptosis.

KEY FINDINGS

In vivo, luteolin can ameliorate the impaired mitochondrial morphology, regulating the MAPK pathway to protect MIRI. In vitro, luteolin can affect the oxidation system, mitochondrial membrane potential and MAPK pathway to anti-apoptosis.

SIGNIFICANCE

These results reveal a ROS-MAPK mediated mechanism and mitochondrial pathway through which luteolin can protect myocardial ischemia/reperfusion injury.

Anti-oxidant and anti-apoptotic effects of luteolin on mice peritoneal macrophages stimulated by angiotensin II

PURPOSE

Luteolin, a plant flavonoid, can be found in a variety of plants and possesses anti-tumorigenic, anti-mutagenic, anti-oxidant and anti-inflammatory properties. However, the protective effects of luteolin on mice peritoneal macrophages stimulated by Angiotensin II (Ang II) have not been fully elucidated.

METHODS AND RESULTS

Mice peritoneal macrophages were confirmed to be strongly positive for the macrophage marker CD68. Cell viability was tested after cells were pretreated with different concentrations of luteolin (6.25, 12.5 and 25μM) and stimulated by Ang II. Luteolin not only significantly increased the viability of macrophages in the presence of Ang II, but also decreased the apoptotic rate, up-regulated Bcl-2 expression, and down-regulated Bax expression, thereby raising the ratio of Bcl-2 to Bax. In addition, luteolin pretreatment significantly increased the activity of SOD and reduced the levels of malondialdehyde (MDA), which was up-regulated in the presence of Ang II. This protective effect was also seen with Vitamin E (VitE) pretreatment, which was used as a standard control in this study.

CONCLUSIONS

These data clearly demonstrate that luteolin suppresses Ang II-directed oxidative stress and apoptosis on mice peritoneal macrophages.

Lentiviral-mediated overexpression of Akt1 reduces anoxia-reoxygenation injury in cardiomyocytes

Activated PI3K/Akt signalling exerts a protective effect after myocardial ischemia by phosphorylating various substrates; however, the precise mechanism by which this occurs remains to be elucidated. We have constructed the recombinant lentiviral vector pLVX-Akt1-EGFP- 3FLAG (LV-Akt1) to determine the efficiency of LV-Akt1 infection, explore the protective role of Akt1, and investigate the possible mechanism by which Akt1 signalling acts during anoxia/reoxygenation (A/R) of cardiomyocytes in primary culture. Akt1 gene transfection increased cardiomyocyte pulsation, reduced cell mortality, and decreased the concentration of lactate dehydrogenase (LDH) in myocardial cells supernatants. Akt1 transfection increased the levels of intracellular p-Akt, enhanced the expression of the anti-apoptosis protein Bcl-2, and reduced that of the apoptosis protein Bax (thereby increasing the Bcl-2/Bax ratio), and caused some increase in hypoxia-inducible factor1α (HIF-1α) and vascular endothelial growth factor (VEGF) expression after A/R. The protective role of Akt1 was partly suppressed by adding a phosphoinositide 3-kinase/Akt inhibitor (LY294002). In conclusion, LV-Akt1 was successfully constructed and neonatal rat cardiomyocytes were transfected efficiently. Akt1 overexpression significantly reduced A/R injury in cardiomyocytes, and this could be related to its effects on various targets of the PI3K/Akt signalling pathway, such as Bcl-2, Bax, HIF-1α and VEGF.

ERK/PP1a/PLB/SERCA2a and JNK pathways are involved in luteolin-mediated protection of rat hearts and cardiomyocytes following ischemia/reperfusion

Luteolin has long been used in traditional Chinese medicine for treatment of various diseases. Recent studies have suggested that administration of luteolin yields cardioprotective effects during ischemia/reperfusion (I/R) in rats. However, the precise mechanisms of this action remain unclear. The aim of this study is to confirm that luteolin-mediated extracellular signal regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) pathways are responsible for their cardioprotective effects during I/R. Wistar rats were divided into the following groups: (i) DMSO group (DMSO); (ii) I/R group (I/R); (iii) luteolin+I/R group (Lut+I/R); (iv) ERK1/2 inhibitor PD98059+I/R group (PD+I/R); (v) PD98059+luteolin+I/R group (PD+Lut+I/R); and (vi) JNK inhibitor SP600125+I/R group (SP+I/R). The following properties were measured: contractile function of isolated heart and cardiomyocytes; infarct size; the release of lactate dehydrogenase (LDH); the percentage of apoptotic cells; the expression levels of Bcl-2 and Bax; and phosphorylation status of ERK1/2, JNK, type 1 protein phosphatase (PP1a), phospholamban (PLB) and sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2a). Our data showed that pretreatment with luteolin or SP600125 significantly improved the contraction of the isolated heart and cardiomyocytes, reduced infarct size and LDH activity, decreased the rate of apoptosis and increased the Bcl-2/Bax ratio. However, pretreatment with PD98059 alone before I/R had no effect on the above indexes. Further, these consequences of luteolin pretreatment were abrogated by co-administration of PD98059. We also found that pretreatment with PD98059 caused a significant increase in JNK expression, and SP600125 could cause ERK1/2 activation during I/R. In addition, we are the first to demonstrate that luteolin affects PP1a expression, which results in the up-regulation of the PLB, thereby relieving its inhibition of SERCA2a. These results showed that luteolin improves cardiomyocyte contractile function after I/R injury by an ERK1/2-PP1a-PLB-SERCA2a-mediated mechanism independent of JNK signaling pathway.

Inhibitory effects and mechanisms of luteolin on proliferation and migration of vascular smooth muscle cells

Atherosclerosis (AS) is a complicated progress, involving many types of cells. Although the exact mechanisms of progression of atherosclerosis are uncertain, the balance of vascular smooth muscle cells (VSMCs) proliferation and apoptosis appears to play a pivotal role in the pathogenesis and progression of atherosclerosis, and much discussion has been undertaken to elucidate the detailed mechanisms, relevant gene expression and transduction pathways. Drug treatment has focused on ameliorating atherosclerosis. Some researchers have indicated that inhibiting VSMCs proliferation is involved in attenuating atherosclerosis. Luteolin is a kind of flavonoids naturally occurring in many plants and possesses beneficial effects on cardiovascular diseases. Luteolin can reduce VSMCs’ proliferation and migration and this reduction is stimulated by several factors. The aim of this review is to summarize the existing inhibitory effects and mechanisms of luteolin on proliferation and migration of VSMCs, and consider whether luteolin may be a potential candidate for preventing and treating atherosclerosis.

Targeting cell signaling and apoptotic pathways by luteolin: cardioprotective role in rat cardiomyocytes following ischemia/reperfusion

Myocardial ischemia often results in damaged heart structure and function, which can be restored through ischemia/reperfusion (I/R) in most cases. However, I/R can exacerbate myocardial ischemia reperfusion injury (IRI). Luteolin, a widely distributed flavonoid, a member of a group of naturally occurring polyphenolic compounds found in many fruits, vegetables and medicinal herbs, has been reported to exhibit anti-inflammatory, antioxidant and anti-carcinogenic activities. In recent years, luteolin has been shown to play an important role in the cardioprotection of IRI. However, its role and mechanism in cardioprotection against IRI has not been clearly elucidated with respect to the apoptosis pathway. The purpose of this paper is to review luteolin's anti-apoptotic role and mechanism following I/R in rats, and indicate luteolin as a potential candidate for preventing and treating cardiovascular diseases.

Flavones induce neutrophil apoptosis by down-regulation of Mcl-1 via a proteasomal-dependent pathway

Neutrophil apoptosis and subsequent nonphlogistic clearance by surrounding phagocytes are key to the successful resolution of neutrophilic inflammation, with dysregulated apoptosis reported in multiple human inflammatory diseases. Enhancing neutrophil apoptosis has proresolution and anti-inflammatory effects in preclinical models of inflammation. Here we investigate the ability of the flavones apigenin, luteolin, and wogonin to induce neutrophil apoptosis in vitro and resolve neutrophilic inflammation in vivo. Human neutrophil apoptosis was assessed morphologically and by flow cytometry following incubation with apigenin, luteolin, and wogonin. All three flavones induced time- and concentration-dependent neutrophil apoptosis (apigenin, EC₅₀=12.2 μM; luteolin, EC₅₀=14.6 μM; and wogonin, EC₅₀=28.9 μM). Induction of apoptosis was caspase dependent, as it was blocked by the broad-spectrum caspase inhibitor Q-VD-OPh and was associated with both caspase-3 and caspase-9 activation. Flavone-induced apoptosis was preceded by down-regulation of the prosurvival protein Mcl-1, with proteasomal inhibition preventing flavone-induced Mcl-1 down-regulation and apoptosis. The flavones abrogated the survival effects of mediators that prolong neutrophil life span, including lipoteichoic acid, peptidoglycan, dexamethasone, and granulocyte-macrophage colony stimulating factor, by driving apoptosis. Furthermore, wogonin enhanced resolution of established neutrophilic inflammation in a zebrafish model of sterile tissue injury. Wogonin-induced resolution was dependent on apoptosis in vivo as it was blocked by caspase inhibition. Our data show that the flavones induce neutrophil apoptosis and have potential as neutrophil apoptosis-inducing anti-inflammatory, proresolution agents.—Lucas, C. D., Allen, K. C., Dorward, D. A., Hoodless, L. J., Melrose, L. A., Marwick, J. A., Tucker, C. S., Haslett, C., Duffin, R., Rossi, A. G. Flavones induce neutrophil apoptosis by down-regulation of Mcl-1 via a proteasomal-dependent pathway.

Luteolin limits infarct size and improves cardiac function after myocardium ischemia/reperfusion injury in diabetic rats

Background

The present study was to investigate the effects and mechanism of Luteolin on myocardial infarct size, cardiac function and cardiomyocyte apoptosis in diabetic rats with myocardial ischemia/reperfusion (I/R) injury.

Methodology/Principal Findings

Diabetic rats underwent 30 minutes of ischemia followed by 3 h of reperfusion. Animals were pretreated with or without Luteolin before coronary artery ligation. The severity of myocardial I/R induced LDH release, arrhythmia, infarct size, cardiac function impairment, cardiomyocyte apoptosis were compared. Western blot analysis was performed to elucidate the target proteins of Luteolin. The inflammatory cytokine production were also examined in ischemic myocardium underwent I/R injury. Our results revealed that Luteolin administration significantly reduced LDH release, decreased the incidence of arrhythmia, attenuated myocardial infarct size, enhanced left ventricular ejection fraction and decreased myocardial apoptotic death compared with I/R group. Western blot analysis showed that Luteolin treatment up-regulated anti-apoptotic proteins FGFR2 and LIF expression, increased BAD phosphorylation while decreased the ratio of Bax to Bcl-2. Luteolin treatment also inhibited MPO expression and inflammatory cytokine production including IL-6, IL-1a and TNF-a. Moreover, co-administration of wortmannin and Luteolin abolished the beneficial effects of Luteolin.

Conclusions/Significance

This study indicates that Luteolin preserves cardiac function, reduces infarct size and cardiomyocyte apoptotic rate after I/R injury in diabetic rats. Luteolin exerts its action by up-regulating of anti-apoptotic proteins FGFR2 and LIF expression, activating PI3K/Akt pathway while increasing BAD phosphorylation and decreasing ratio of Bax to Bcl-2.