Contribution of apoptosis in myocardial reperfusion injury and loss of cardioprotection in diabetes mellitus

Shuxuening Injection Inhibits Apoptosis and Reduces Myocardial Ischemia-Reperfusion Injury in Rats through PI3K/AKT Pathway

OBJECTIVE

To investigate the main components and potential mechanism of Shuxuening Injection (SXNI) in the treatment of myocardial ischemia-reperfusion injury (MIRI) through network pharmacology and in vivo research.

METHODS

The Traditional Chinese Medicine Systems Pharmacology (TCMSP) and PharmMapper databases were used to extract and evaluate the effective components of Ginkgo biloba leaves, the main component of SXNI. The Online Mendelian Inheritance in Man (OMIM) and GeneCards databases were searched for disease targets and obtain the drug target and disease target intersections. The active ingredient-target network was built using Cytoscape 3.9.1 software. The STRING database, Metascape online platform, and R language were used to obtain the key targets and signaling pathways of the anti-MIRI effects of SXNI. In order to verify the therapeutic effect of different concentrations of SXNI on MIRI in rats, 60 rats were first divided into 5 groups according to random number table method: the sham operation group, the model group, SXNI low-dose (3.68 mg/kg), medium-dose (7.35 mg/kg), and high-dose (14.7 mg/kg) groups, with 12 rats in each group. Then, another 60 rats were randomly divided into 5 groups: the sham operation group, the model group, SXNI group (14.7 mg/kg), SXNI+LY294002 group, and LY294002 group, with 12 rats in each group. The drug was then administered intraperitoneally at body weight for 14 days. The main biological processes were validated using in vivo testing. Evans blue/triphenyltetrazolium chloride (TTC) double staining, hematoxylin-eosin (HE) staining, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, enzyme-linked immunosorbent assay (ELISA), and Western blot analysis were used to investigate the efficacy and mechanism of SXNI in MIRI rats.

RESULTS

Eleven core targets and 30 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were selected. Among these, the phosphoinositide 3-kinase (PI3K)/ protein kinase B (AKT) pathway was closely related to SXNI treatment of MIRI. In vivo experiments showed that SXNI reduced the myocardial infarction area in the model group, improved rat heart pathological damage, and reduced the cardiomyocyte apoptosis rate (all P<0.01). After SXNI treatment, the p-PI3K/PI3K and p-AKT/AKT ratios as well as B-cell lymphoma-2 (Bcl-2) protein expression in cardiomyocytes were increased, while the Bax and cleaved caspase 3 protein expression levels were decreased (all P<0.05). LY294002 partially reversed the protective effect of SXNI on MIRI.

CONCLUSION

SXNI protects against MIRI by activating the PI3K/AKT signaling pathway.

CKLF1, transcriptionally activated by FOXC1, promotes hypoxia/reoxygenation‑induced oxidative stress and inflammation in H9c2 cells by NLRP3 inflammasome activation

Myocardial ischemia/reperfusion (I/R) injury is a clinical challenge in the treatment of ischemic heart disease. The present study aimed to establish a hypoxia/reoxygenation (H/R)-induced H9c2 cell model to explore the role and mechanism of chemokine-like factor 1 (CKLF1) in myocardial I/R injury. First, CKLF1 expression was measured in H/R-induced H9c2 cells by reverse transcription-quantitative PCR and western blotting. Subsequently, after CKLF1 silencing, cell viability and apoptosis were evaluated by Cell Counting Kit-8 assay and flow cytometry. In addition, 2,7-dichlorodihydrofluorescein diacetate staining was used to assess the levels of cellular reactive oxygen species. Additionally, the levels of superoxide dismutase, glutathione peroxidase and malondialdehyde, and the contents of inflammatory factors IL-6, IL-1β and TNF-α were detected using corresponding commercially available kits. Western blotting was used to examine the expression levels of proteins involved in the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome. The JASPAR database predicted that forkhead box protein C1 (FOXC1) would bind to the CKLF1 promoter region, and dual luciferase and chromatin immunoprecipitation assays were performed to verify it. Subsequently, FOXC1 overexpression and CKLF1 silencing were used to clarify the regulatory mechanism of FOXC1 on CKLF1 in H/R-induced H9c2 cells. The results revealed that CKLF1 expression was markedly enhanced in H/R-stimulated H9c2 cells. CKLF1 knockdown enhanced the viability and inhibited the apoptosis of H9c2 cells exposed to H/R. Moreover, the oxidative stress and inflammation induced by H/R were alleviated following CKLF1 silencing. CKLF1 knockdown also inhibited NLRP3 inflammasome activation. Furthermore, FOXC1 bound to the CKLF1 promoter region to upregulate CKLF1 expression, and FOXC1 overexpression alleviated the effects of CKLF1 knockdown on H9c2 cell damage induced by H/R via activation of the NLRP3 inflammasome. In conclusion, CKLF1 transcriptionally activated by FOXC1 may promote H/R-induced oxidative stress and inflammation in H9c2 cells via NLRP3 inflammasome activation.

Alpha-lipoic acid enhances ischemic postconditioning-mediated improvement of myocardial infarction and apoptosis in diabetic rats with ischemia/reperfusion injury

This work evaluated the combined effects of alpha-lipoic acid (ALA) and ischemic postconditioning (Post) on myocardial infarction and cell death in rats with chronic type-II diabetes following ischemia/reperfusion injury. The rats received a high-fat diet and were given one intraperitoneal injection of 35 mg/kg streptozotocin to induce chronic diabetes. They were then pretreated with ALA (100 mg/kg/day, orally) for 5 weeks before undergoing ischemia/reperfusion (I/R) insult. The hearts experienced 35 min regional ischemia through ligating the left anterior descending coronary artery, followed by 60 min reperfusion. The Post protocol involved 6 cycles of a 10/10 s algorithm, applied during the early stage of reperfusion. The use of Post alone did not significantly alter lactate dehydrogenase and infarct size levels, while ALA showed positive effects. Similar findings were observed for apoptotic changes with single treatments. However, the concurrent administration of ALA and Post significantly reduced the protein expressions of Bax, Bax/Bcl2, and cleaved caspase-3 while increasing Bcl2 expression. Additionally, the histopathological findings of the combined therapy were superior to those of single treatments. The concomitant use of ALA and Post effectively inhibited apoptosis, leading to cardiac recovery after I/R injury in diabetic conditions. This strategy could improve outcomes for preserving diabetic hearts following I/R insults.

The protective effects of Zhi-Gan-Cao-Tang against diabetic myocardial infarction injury and identification of its effective constituents

ETHNOPHARMACOLOGICAL RELEVANCE

Cardiovascular complications are highly prevalent in patients with diabetes. Zhi-Gan-Cao-Tang (ZGCT), a famous traditional Chinese medicine (TCM) prescription, can be used for the treatment of diabetes with cardiovascular disease complications. ZGCT is composed of nine Chinese herbs: the radix and rhizoma of Glycyrrhiza uralensis Fisch. (Gancao in Chinese, 12 g), the radix of Rehmannia glutinosa Libosch. (Dihuang in Chinese, 50 g), the radix and rhizoma of Panax ginseng C. A. Mey. (Renshen in Chinese, 6 g), the radix of Ophiopogon japonicus (L. f.) Ker-Gawl. (Maidong in Chinese, 10 g), the fructus of Ziziphus jujuba Mill. (Dazao in Chinese, 18 g), the fructus of Cannabis sativa L. (Maren in Chinese, 10 g), Donkey-hide gelatine (Ejiao in Chinese, 6 g), the ramulus of Cinnamomum cassia Presl (Guizhi in Chinese, 9 g), and the fresh rhizoma of Zingiber officinale Rosc. (Shengjiang in Chinese, 9 g). Many of these Chinese herbs are also used in other systems of medicine (Japan, India, European, etc.). However, the effects and effective constituents of ZGCT against diabetic cardiovascular disease remain unclear.

AIM OF THE STUDY

This study aimed to investigate the protective effect of ZGCT against diabetic myocardial infarction (DMI) injury in vivo and in vitro and to identify the effective constituents of ZGCT.

MATERIALS AND METHODS

The in vivo effect on DMI injury was evaluated in a DMI mouse model. The in vitro effect and effective constituent screening experiments were conducted in an H9c2 cardiomyocyte injury model induced by high glucose and hypoxia.

RESULTS

It was found that ZGCT significantly reduced myocardial infarction size and serum lactate dehydrogenase (LDH) levels in DMI mice. Myocardial histopathological experiments showed that ZGCT alleviated the disordered arrangement and fracture of muscle fibers and cell disappearance and reduced inflammatory cell infiltration. Cellular experiments showed that ZGCT inhibited cardiomyocyte apoptosis by decreasing the expression of the proapoptotic factor Bax. In addition, it inhibited inflammatory reactions by suppressing the activation of the IκBα/NF-κB pathway and the expression of iNOS. Eight constituents from six Chinese herbs in the recipe of ZGCT were found to enhance the viability of injured cardiomyocytes, and six effective constituents played protective roles through anti-apoptotic and/or anti-inflammatory activities. In addition, one of the effective constituents, glycyrrhizic acid, was verified in vivo to have cardioprotective effect on DMI mice.

CONCLUSIONS

The TCM prescription ZGCT protects against DMI by inhibiting cardiomyocyte apoptosis and reducing inflammatory reactions. Eight effective constituents of ZGCT were identified. This study provides a scientific basis for the clinical application of ZGCT and is valuable for quality marker research on this prescription.

Mechanistic correlation between mitochondrial permeability transition pores and mitochondrial ATP dependent potassium channels in ischemia reperfusion

Mitochondrial dysfunction is one of the fundamental causes of ischemia reperfusion (I/R) damage. I/R refers to the paradoxical progression of cellular dysfunction and death that occurs when blood flow is restored to previously ischemic tissues. I/R causes a significant rise in mitochondrial permeability resulting in the opening of mitochondrial permeability transition pores (MPTP). The MPTP are broad, nonspecific channels present in the inner mitochondrial membrane (IMM), and are known to mediate the deadly permeability alterations that trigger mitochondrial driven cell death. Protection from reperfusion injury occurs when long-term ischemia is accompanied by short-term ischemic episodes or inhibition of MPTP from opening via mitochondrial ATP dependent potassium (mitoK_ATP) channels. These channels located in the IMM, play an essential role in ischemia preconditioning (PC) and protect against cell death by blocking MPTP opening. This review primarily focuses on the interaction between the MPTP and mitoK_ATP along with their role in the I/R injury. This article also describes the molecular composition of the MPTP and mitoK_ATP in order to promote future knowledge and treatment of diverse I/R injuries in various organs.

Mn(III) Porphyrin, MnTnBuOE-2-PyP5+, Commonly Known as a Mimic of Superoxide Dismutase Enzyme, Protects Cardiomyocytes from Hypoxia/Reoxygenation Induced Injury via Reducing Oxidative Stress

Myocardial ischemia-reperfusion injury (I/R) causes damage to cardiomyocytes through oxidative stress and apoptosis. We investigated the cardioprotective effects of MnTnBuOE-2-PyP5+ (BMX-001), a superoxide dismutase mimic, in an in vitro model of I/R injury in H9c2 cardiomyocytes. We found that BMX-001 protected against hypoxia/reoxygenation (H/R)-induced oxidative stress, as evident by a significant reduction in intracellular and mitochondrial superoxide levels. BMX-001 pre-treatment also reduced H/R-induced cardiomyocyte apoptosis, as marked by a reduction in TUNEL-positive cells. We further demonstrated that BMX-001 pre-treatment significantly improved mitochondrial function, particularly O2 consumption, in mouse adult cardiomyocytes subjected to H/R. BMX-001 treatment also attenuated cardiolipin peroxidation, 4-hydroxynonenal (4-HNE) level, and 4-HNE adducted proteins following H/R injury. Finally, the pre-treatment with BMX-001 improved cell viability and lactate dehydrogenase (LDH) activity in H9c2 cells following H/R injury. Our findings suggest that BMX-001 has therapeutic potential as a cardioprotective agent against oxidative stress-induced H/R damage in H9c2 cardiomyocytes.

Metaflammation in glucolipid metabolic disorders: Pathogenesis and treatment

The public health issue of glucolipid metabolic disorders (GLMD) has grown significantly, posing a grave threat to human wellness. Its prevalence is rising yearly and tends to affect younger people. Metaflammation is an important mechanism regulating body metabolism. Through a complicated multi-organ crosstalk network involving numerous signaling pathways such as NLRP3/caspase-1/IL-1, NF-B, p38 MAPK, IL-6/STAT3, and PI3K/AKT, it influences systemic metabolic regulation. Numerous inflammatory mediators are essential for preserving metabolic balance, but more research is needed to determine how they contribute to the co-morbidities of numerous metabolic diseases. Whether controlling the inflammatory response can influence the progression of GLMD determines the therapeutic strategy for such diseases. This review thoroughly examines the role of metaflammation in GLMD and combs the research progress of related therapeutic approaches, including inflammatory factor-targeting drugs, traditional Chinese medicine (TCM), and exercise therapy. Multiple metabolic diseases, including diabetes, non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, and others, respond therapeutically to anti-inflammatory therapy on the whole. Moreover, we emphasize the value and open question of anti-inflammatory-based means for treating GLMD.

Semaglutide inhibits ischemia/reperfusion-induced cardiomyocyte apoptosis through activating PKG/PKCε/ERK1/2 pathway

Apoptosis is a major pathophysiological change following myocardial ischemia/reperfusion (I/R) injury. Glucagon-like peptide 1 (GLP-1) and its receptor GLP-1R are widely expressed in the cardiovascular system and GLP-1/GLP-1R activates the protein kinase G (PKG)-related signaling pathway. Therefore, this study tested whether semaglutide, a new GLP-1 analog, inhibits I/R injury-induced cardiomyocyte apoptosis by activating the PKG/PKCε/ERK1/2 pathway. We induced myocardial I/R injury in rats and hypoxia/reoxygenation (H/R) injury in H9C2 cells and detected the effects of semaglutide, a PKG analog (8-Br-cGMP), and a PKG inhibitor (KT-5823) on the PKG/PKCε/ERK1/2 pathway and cardiomyocyte apoptosis. We found that semaglutide upregulated GLP-1R levels, and both semaglutide and 8-Br-cGMP activated the PKG/PKCε/ERK1/2 pathway, inhibited myocardial infarction (MI), decreased hs-cTNT levels, increased NT-proBNP levels, and suppressed cardiomyocyte apoptosis in I/R rats and H/R H9C2 cells. However, KT-5823 exerted contrasting effects with semaglutide and 8-Br-cGMP, and KT-5823 weakened the cardioprotective effects of semaglutide. In conclusion, semaglutide inhibits I/R injury-induced cardiomyocyte apoptosis by activating the PKG/PKCε/ERK1/2 pathway. The beneficial effect of GLP-1/GLP-1R, involved in the activation of the PKG/PKCε/ERK1/2 pathway, may provide a novel treatment method for myocardial I/R injury.

Role of Oxidative Stress in Cardiac Dysfunction and Subcellular Defects Due to Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury is well-known to be associated with impaired cardiac function, massive arrhythmias, marked alterations in cardiac metabolism and irreversible ultrastructural changes in the heart. Two major mechanisms namely oxidative stress and intracellular Ca²⁺-overload are considered to explain I/R-induced injury to the heart. However, it is becoming apparent that oxidative stress is the most critical pathogenic factor because it produces myocardial abnormalities directly or indirectly for the occurrence of cardiac damage. Furthermore, I/R injury has been shown to generate oxidative stress by promoting the formation of different reactive oxygen species due to defects in mitochondrial function and depressions in both endogenous antioxidant levels as well as regulatory antioxidative defense systems. It has also been demonstrated to adversely affect a wide variety of metabolic pathways and targets in cardiomyocytes, various resident structures in myocardial interstitium, as well as circulating neutrophils and leukocytes. These I/R-induced alterations in addition to myocardial inflammation may cause cell death, fibrosis, inflammation, Ca²⁺-handling abnormalities, activation of proteases and phospholipases, as well as subcellular remodeling and depletion of energy stores in the heart. Analysis of results from isolated hearts perfused with or without some antioxidant treatments before subjecting to I/R injury has indicated that cardiac dysfunction is associated with the development of oxidative stress, intracellular Ca²⁺-overload and protease activation. In addition, changes in the sarcolemma and sarcoplasmic reticulum Ca²⁺-handling, mitochondrial oxidative phosphorylation as well as myofibrillar Ca²⁺-ATPase activities in I/R hearts were attenuated by pretreatment with antioxidants. The I/R-induced alterations in cardiac function were simulated upon perfusing the hearts with oxyradical generating system or oxidant. These observations support the view that oxidative stress may be intimately involved in inducing intracellular Ca²⁺-overload, protease activation, subcellular remodeling, and cardiac dysfunction as a consequence of I/R injury to the heart.

Preliminary evidence for the presence of multiple forms of cell death in diabetes cardiomyopathy

Diabetic mellitus (DM) is a common degenerative chronic metabolic disease often accompanied by severe cardiovascular complications (DCCs) as major causes of death in diabetic patients with diabetic cardiomyopathy (DCM) as the most common DCC. The metabolic disturbance in DCM generates the conditions/substrates and inducers/triggers and activates the signaling molecules and death executioners leading to cardiomyocyte death which accelerates the development of DCM and the degeneration of DCM to heart failure. Various forms of programmed active cell death including apoptosis, pyroptosis, autophagic cell death, autosis, necroptosis, ferroptosis and entosis have been identified and characterized in many types of cardiac disease. Evidence has also been obtained for the presence of multiple forms of cell death in DCM. Most importantly, published animal experiments have demonstrated that suppression of cardiomyocyte death of any forms yields tremendous protective effects on DCM. Herein, we provide the most updated data on the subject of cell death in DCM, critical analysis of published results focusing on the pathophysiological roles of cell death, and pertinent perspectives of future studies.

An Updated Insight Into Molecular Mechanism of Hydrogen Sulfide in Cardiomyopathy and Myocardial Ischemia/Reperfusion Injury Under Diabetes

Cardiovascular diseases are the most common complications of diabetes, and diabetic cardiomyopathy is a major cause of people death in diabetes. Molecular, transcriptional, animal, and clinical studies have discovered numerous therapeutic targets or drugs for diabetic cardiomyopathy. Within this, hydrogen sulfide (H₂S), an endogenous gasotransmitter alongside with nitric oxide (NO) and carbon monoxide (CO), is found to play a critical role in diabetic cardiomyopathy. Recently, the protective roles of H₂S in diabetic cardiomyopathy have attracted enormous attention. In addition, H₂S donors confer favorable effects in myocardial infarction, ischaemia-reperfusion injury, and heart failure under diabetic conditions. Further studies have disclosed that multiplex molecular mechanisms are responsible for the protective effects of H₂S against diabetes-elicited cardiac injury, such as anti-oxidative, anti-apoptotic, anti-inflammatory, and anti-necrotic properties. In this review, we will summarize the current findings on H₂S biology and pharmacology, especially focusing on the novel mechanisms of H₂S-based protection against diabetic cardiomyopathy. Also, the potential roles of H₂S in diabetes-aggravated ischaemia-reperfusion injury are discussed.

Propofol postconditioning ameliorates hypoxia/reoxygenation induced H9c2 cell apoptosis and autophagy via upregulating forkhead transcription factors under hyperglycemia

BACKGROUND

Administration of propofol, an intravenous anesthetic with antioxidant property, immediately at the onset of post-ischemic reperfusion (propofol postconditioning, P-PostC) has been shown to confer cardioprotection against ischemia-reperfusion injury, while the underlying mechanism remains incompletely understood. The FoxO transcription factors are reported to play critical roles in activating cardiomyocyte survival signaling throughout the process of cellular injuries induced by oxidative stress and are also involved in hypoxic postconditioning mediated neuroprotection, however, the role of FoxO in postconditioning mediated protection in the heart and in particular in high glucose condition is unknown.

METHODS

Rat heart-derived H9c2 cells were exposed to high glucose (HG) for 48 h (h), then subjected to hypoxia/reoxygenation (H/R, composed of 8 h of hypoxia followed by 12 h of reoxygenation) in the absence or presence of postconditioning with various concentrations of propofol (P-PostC) at the onset of reoxygenation. After having identified the optical concentration of propofol, H9c2 cells were subjected to H/R and P-PostC in the absence or presence of FoxO1 or FoxO3a gene silencing to explore their roles in P-PostC mediated protection against apoptotic and autophagic cell deaths under hyperglycemia.

RESULTS

The results showed that HG with or without H/R decreased cell viability, increased lactate dehydrogenase (LDH) leakage and the production of reactive oxygen species (ROS) in H9c2 cells, all of which were significantly reversed by propofol (P-PostC), especially at the concentration of 25 µmol/L (P25) (all P < 0.05, NC vs. HG; HG vs. HG + HR; HG + HR + P12.5 or HG + HR + P25 or HG + HR + P50 vs. HG + HR). Moreover, we found that propofol (P25) decreased H9c2 cells apoptosis and autophagy that were concomitant with increased FoxO1 and FoxO3a expression (all P < 0.05, HG + HR + P25 vs. HG + HR). The protective effects of propofol (P25) against H/R injury were reversed by silencing FoxO1 or FoxO3a (all P < 0.05, HG + HR + P25 vs. HG + HR + P25 + siRNA-1 or HG + HR + P25 + siRNA-5).

CONCLUSION

It is concluded that propofol postconditioning attenuated H9c2 cardiac cells apoptosis and autophagy induced by H/R injury through upregulating FoxO1 and FoxO3a under hyperglycemia.

Cardioprotective effects of co-administration of thymoquinone and ischemic postconditioning in diabetic rats

OBJECTIVES

Ischemia/reperfusion (I/R) is a leading cause of myocardial infarction (MI) injury, contributing to excess injury to cardiac tissues involved in inflammation, apoptosis, and oxidative stress. The present study was conducted to examine the effects of combined thymoquinone (TQ) with ischemic postconditioning (IPostC) therapy on apoptosis and inflammation due to I/R injury in diabetic rat hearts.

MATERIALS AND METHODS

A single dose injection of streptozotocin (STZ; 60 mg/kg) was administered to thirty-two Wistar male rats to induce diabetes. Hearts were fixed on a Langendorff setting and exposed to a 30 min regional ischemia subsequently to 60 min reperfusion. IPostC was induced at the onset of reperfusion by 3 cycles of 30 sec R/I. ELISA, Western blotting assay, and TUNEL staining were applied to assess the cardioprotective effect of IPostC and TQ against I/R injury in diabetic and non-diabetic rats.

RESULTS

Administration of TQ alone in non-diabetic isolated hearts significantly diminished CK-MB, TNF-α, IL-1β, and apoptosis and enhanced p-GSK-3β and Bcl-2 (P<0.05). Following administration of TQ, the cardioprotective effects of IPostC by elevating p-GSK-3β and Bcl-2 and alleviating apoptosis and inflammation were reestablished compared with non-IPostC diabetic hearts.

CONCLUSION

These results provide substantial evidence that co-administration of TQ plus IPostC can exert cardioprotective effects on diabetic myocardium during I/R damage by attenuating the inflammatory response and apoptosis.

Scutellarin alleviates type 2 diabetes (HFD/low dose STZ)-induced cardiac injury through modulation of oxidative stress, inflammation, apoptosis and fibrosis in mice

BACKGROUND

Diabetes is a serious global health concern which severely affected public health as well as socio-economic growth worldwide. Scutellarin (SCU), a bioactive flavonoid, is known for its efficacious action against a range of ailments including cardiovascular problems. The present study was conducted to find out possible protective effect and its associated mechanisms of SCU on experimental type 2 diabetes-induced cardiac injury.

METHODS

Type 2 diabetes was induced by treating animals with high fat diet for 4 weeks and a single intraperitoneal dose (35 mg/kg body weight) of streptozotocin and diabetic animals received SCU (10 or 20 mg/kg/day) for 6 weeks.

RESULTS

Scutellarin attenuated type 2 diabetes-induced hyperglycemia, bodyweight loss, hyperlipidaemia, cardiac functional damage with histopathological alterations and fibrosis. Scutellarin treatment to type 2 diabetic mice ameliorated oxidative stress, inflammatory status and apoptosis in heart. Furthermore, the underlying mechanisms for such mitigation of oxidative stress, inflammation and apoptosis in heart involved modulation of Nrf2/Keap1 pathway, TLR4/MyD88/NF-κB mediated inflammatory pathway and intrinsic (mitochondrial) apoptosis pathway, respectively.

CONCLUSIONS

The current findings suggest that SCU is effective in protecting type 2 diabetes-induced cardiac injury by attenuating oxidative stress and inflammatory responses and apoptosis, and it is also worth considering the efficacious potential of SCU to treat diabetic cardiomyopathy patients.

Peoniflorin Preconditioning Protects Against Myocardial Ischemia/Reperfusion Injury Through Inhibiting Myocardial Apoptosis: RISK Pathway Involved

Preconditioning with Peoniflorin, a component of traditional Chinese prescriptions, was proposed to be a potential strategy for cardioprotection against ischemia/reperfusion (I/R) injury. However, the cardioprotective effect of Peoniflorin preconditioning has not been thoroughly confirmed, and the underlying mechanism remains unclear. Here, we examined the cardioprotective effect and its mechanism of Peoniflorin preconditioning against myocardial I/R injury. Rats were subjected to 30 min of transient ischemia followed by 2 h of reperfusion with or without Peoniflorin (100 mg/kg) prior to reperfusion. Peoniflorin preconditioning significantly limited myocardial infarct size and reperfusion arrhythmias, as well as obviously attenuated the histomorphological and micromorphological damages induced by I/R injury. The reduced myocardial injury was also associated with the anti-apoptotic effect of Peoniflorin, as evidence by decreased TUNEL-positive cells, upregulation of BCL-2 expression, and downregulation of Bax and caspase-3 expression. In an effort to evaluate the mechanism responsible for the observed cardioprotective and anti-apoptotic effect, Western blot of phosphorylated protein was performed after 20 min of reperfusion. Results showed that Peoniflorin preconditioning activated both the Akt and ERK1/2 arm of the reperfusion injury salvage kinase (RISK) pathway. To further confirm this mechanism, the PI3K signaling inhibitor LY294002 and ERK1/2 signaling inhibitor PD98059 were administered in vivo. The cardioprotective and anti-apoptotic effects of Peoniflorin preconditioning were diminished but not abolished by pretreatment with LY294002 or PD98059. Taken together, these results indicate that Peoniflorin preconditioning protects the myocardial against I/R injury and inhibits myocardial apoptosis via the activation of the RISK pathway, highlighting the potential therapeutic effects of Peoniflorin on reducing myocardial I/R injury.

Knockdown of lncRNA Abhd11os attenuates myocardial ischemia/reperfusion injury by inhibiting apoptosis in cardiomyocytes

ABSTRACT

Long non-coding RNA (lncRNA) is one potential target for the treatment of various disorders. Here, we explored the role of Abhd11os in ischemia/reperfusion-induced myocardial injury, and preliminarily explored the regulatory mechanisms. Relative Abhd11os expression level was examined by qRT-PCR. Western blot was done to measure the expression of apoptotic-related proteins. CCK-8 assay and flow cytometry were performed to detect cell viability and apoptosis, respectively. ELISA assay was used to ensure the levels of LDH, CK, and cTnI in serum. Besides, the infarct sizes were confirmed by TTC and Evans blue staining. Apoptotic rate of cardiomyocytes in myocardial tissues was evaluated by TUNEL assay. Here, increased Abhd11os expression was found in rat myocardial ischemia/reperfusion injury (MIRI) model and hypoxia/reoxygenation (H/R)-treated cardiomyocytes. Subsequently, our data in vitro showed that upregulation of Abhd11os inhibited proliferation of cardiomyocytes, but promoted cell apoptosis. In animal experiments, myocardial infarct size in MIRI rats was reduced by Abhd11os knockdown. Moreover, downregulation of Abhd11os inhibited apoptosis of cardiomyocytes. Overall, our results revealed that knockdown of Abhd11os could notably attenuate H/R-induced myocardial injury through suppressing apoptosis of cardiomyocytes. These data suggest that Abhd11os may be a potential target for MIRI therapy.

Hinokinin alleviates high fat diet/streptozotocin-induced cardiac injury in mice through modulation in oxidative stress, inflammation and apoptosis

Type 2 diabetes, a global health concern has been considered as major risk factor for cardiovascular diseases. Hinokinin, an emerging bioactive lignin, is reported to show wide range of pharmacological activities. However, the protective role and mechanisms of Hinokinin against type 2 diabetes-mediated cardiotoxicity are still remains unknown. An experimental type 2 diabetic mice model was created by treating animals with high fat diet for four weeks and intraperitoneal injection of streptozotocin (35 mg/kg body weight). Post-type 2 diabetic induction, animals orally treated with Hinokinin (20 or 40 mg/kg body weight) for six weeks. The type 2 diabetic mice exhibited a rise in blood glucose level as well as glycated hemoglobin (HbA1c %), decrease in weekly body weights, decrease in food intake, reduction in absolute heart weight, fall in serum insulin level with altered lipid profile and cardiac functional damage. Diabetic mice treated with Hinokinin attenuated hyperglycemia, dyslipidemia and cardiac dysfunction. In addition, Hinokinin ameliorated histological alterations, fibrosis and glycated proteins in HFD/STZ-induced mice. Type 2 diabetic condition in mice exacerbated oxidative stress, inflammatory status and apoptosis. Hinokinin treatment significantly assuaged oxidative stress, inflammation and apoptosis and elevated antioxidant defenses in diabetic heart. The underlying mechanisms for such mitigation involved the modulation of Nrf2/Keap1/ARE pathway, MAPKs (JNK, p38 and ERK 1/2) and TLR4/MyD88/NF-κB mediated inflammatory pathways and mitochondrial-dependent (intrinsic) apoptosis pathway. In conclusion, the results of this study provided clear evidence that Hinokinin protects against HFD/STZ (type 2 diabetes)-induced cardiac injury by alleviating oxidative stress, inflammation and apoptosis.

Cardioprotective Effect of Echinatin Against Ischemia/Reperfusion Injury: Involvement of Hippo/Yes-Associated Protein Signaling

Background: Echinatin (Ech) has been reported to exert antioxidant and anti-inflammatory activities. In this study, we aimed to characterize the functional role of Ech in myocardial ischemic/reperfusion (MI/R) injury and elucidate its underlying mechanism of action.

Method: We established in vivo and in vitro models of MI/R injury to determine the effect of Ech on MI/R injury. Gene expression was examined using quantitative real-time polymerase chain reaction and western blotting. Myocardial infarction was assessed using tetrazolium chloride staining and the degree of myocardial injury was evaluated by measuring lactate dehydrogenase (LDH) and creatine kinase-myocardial band (CK-MB) levels. Cell apoptosis was detected using the terminal deoxynucleotidyl transfer-mediated dUTP nick end-labeling (TUNEL) assay. The viability of H9c2 cells was determined using Cell Counting Kit-8 assay.

Results: MI/R induced myocardial infarction, which was mitigated by Ech treatment. Moreover, Ech treatment resulted in a marked decline of LDH and CK-MB levels in the serum and myocardium of MI/R rats. Ech treatment also restrained cardiomyocyte apoptosis in vivo and in vitro, as evidenced by reduction in LDH release, the number of TUNEL-positive cells, and caspase-3 activity. Furthermore, Ech administration inhibited MI/R-induced activation of Hippo/Yes-associated protein signaling in vivo and in vitro, as indicated by inhibition of mammalian sterile 20-like protein kinase 1, large tumor suppressor one, and YAP phosphorylation and promotion of YAP nuclear translocation. However, silencing of YAP counteracted the protective effect of Ech on hypoxia/reoxygenation-induced myocardial injury in vitro.

Conclusion: Ech exerted its protective effect against MI/R injury at least partially by suppressing the Hippo/YAP signaling pathway, providing novel insights into the remission of MI/R injury.

The Protective Roles and Molecular Mechanisms of Troxerutin (Vitamin P4) for the Treatment of Chronic Diseases: A Mechanistic Review

Troxerutin (TRX), a semi-synthetic bioflavonoid derived from rutin, has been reported to exert several pharmacological effects including antioxidant, anti-inflammatory, antihyperlipidemic, and nephroprotective. However, the related molecular details and its mechanisms remain poorly understood. In the present review, we presented evidences from the diversity in vitro and in vivo studies on the therapeutic potential of TRX against neurodegenerative, diabetes, cancer and cardiovascular diseases with the purpose to find molecular pathways related to the treatment efficacy. TRX has a beneficial role in many diseases through multiple mechanisms including, increasing antioxidant enzymes and reducing oxidative damage, decreasing in proapoptotic proteins (APAF-1, BAX, caspases-9 and-3) and increasing the antiapoptotic BCL-2, increasing the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and downregulating the nuclear factor κB (NFκ). TRX also reduces acetylcholinesterase activity and upregulates phosphoinositide 3- kinase/Akt signaling pathway in Alzheimer's disease models. Natural products such as TRX may develop numerous and intracellular pathways at several steps in the treatment of many diseases. Molecular mechanisms of action are revealing novel, possible combinational beneficial approaches to treat multiple pathological conditions.

Implication of regulatory networks of long noncoding RNA/circular RNA-miRNA-mRNA in diabetic cardiovascular diseases

Diabetic cardiovascular diseases (DCVDs) are the most common complications of diabetes mellitus and are considered to be one of the most important threats to global health and an economic burden. Long noncoding RNA (lncRNA), circular RNA (circRNA), and miRNA are a novel group of noncoding RNAs that are involved in the regulation of various pathophysiological processes, including DCVDs. Interestingly, both lncRNA and circRNA can act as competing endogenous RNA of miRNA, thereby regulating the expression of the target mRNA by decoying or sponging the miRNA. In this review, we focus on the mechanistic, pathological and functional roles of lncRNA/circRNA-miRNA-mRNA networks in DCVDs and further discuss the potential implications for early detection, therapeutic intervention and prognostic evaluation.

Irisin Attenuates Myocardial Ischemia/Reperfusion Injury and Improves Mitochondrial Function Through AMPK Pathway in Diabetic Mice

Aims

Several recent reports have shown irisin protects the heart against ischemia/reperfusion injury. However, the effect of irisin on I/R injury in diabetic mice has not been described. The present study was designed to investigate the role of irisin in myocardial ischemia-reperfusion (MI/R) injury in diabetic mice.

Methods

A mouse model of diabetes was established by feeding wild type or gene-manipulated adult male mice with a high-fat diet. All the mice received intraperitoneal injection of irisin or PBS. Thirty minutes after injection, mice were subjected to 30 min of myocardial ischemia followed by 3h (for cell apoptosis and protein determination), 24 h (for infarct size and cardiac function).

Results

Knock-out of gene FNDC5 augmented MI/R injury in diabetic mice, while irisin treatment attenuated MI/R injury, improved cardiac function, cellular ATP biogenetics, mitochondria potential, and impaired mitochondrion-related cell death. More severely impaired AMPK pathway was observed in diabetic FNDC5^-/- mice received MI/R. Knock-out of gene AMPK blocks the beneficial effects of irisin on MI/R injury, cardiac function, cellular ATP biogenetics, mitochondria potential, and mitochondrion-related cell death.

Conclusions

Our present study demonstrated that irisin improves the mitochondria function and attenuates MI/R injury in diabetic mice through AMPK pathway.

Syringic acid mitigates myocardial ischemia reperfusion injury by activating the PI3K/Akt/GSK-3β signaling pathway

Syringic acid is an abundant phenolic acid compound that possesses anti-oxidant, anti-microbial, anti-inflammatory, and anti-endotoxic properties. However, the research of pretreatment with syringic acid against myocardial ischemia reperfusion is still limited. Thus, our research revealed the protective effect of syringic acid in the rat model with myocardial ischemia reperfusion injury. Histological analysis was performed by hematoxylin and eosin (H&E). The myocardial systolic function was detected by echocardiographic. Myocardial infarct size was measured by Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) double staining. The apoptosis index was recorded by Terminal deoxynucleotidyl transferase dUTP nick end labeling staining (TUNEL). The contents of creatine kinase MB (CK-MB) and lactate dehydrogenase (LDH) in the serum were determined by a commercial kit. The expression of the PI3K/Akt/GSK-3β signaling pathway-related molecules and apoptosis-associated indicators was detected by western blotting or real-time PCR. We found that pretreatment with syringic acid obviously increased the myocardial systolic function (LVEF and LVFS) and decreased the infarct size, the apoptosis index as well as the serum level of CK-MB and LDH. Meanwhile, syringic acid also remarkably augmented the contents of p-PI3K, p-Akt, p-GSK-3β, Bcl-2 and mitochondria cytochrome c. However, the expression of caspase-3, -9 and Bax significantly reduced. Interestingly, co-treatment with PI3K inhibitor of LY294002 counteracted those effects induced by syringic acid. In conclusion, pretreatment with syringic acid can mitigate myocardial ischemia reperfusion injury by inhibiting mitochondria-induced apoptosis which is regulated by the PI3K/Akt/GSK-3β signaling pathway.

Hyperosmotic stress promotes endoplasmic reticulum stress-dependent apoptosis in adult rat cardiac myocytes

In different pathological situations, cardiac cells undergo hyperosmotic stress and cell shrinkage. This change in cellular volume has been associated with contractile dysfunction and cell death. However, the intracellular mechanisms involved in hyperosmotic stress-induced cell death have not been investigated in depth in adult cardiac myocytes. Given that osmotic stress has been shown to promote endoplasmic reticulum stress (ERS), a recognized trigger for apoptosis, we examined whether hyperosmotic stress triggers ERS in adult cardiac myocytes and if so whether this mechanism mediates hyperosmotic stress-induced cell death. Adult rat cardiomyocytes cultured overnight in a hypertonic solution (HS) containing mannitol as the osmolite, showed increased expression of ERS markers, GRP78, CHOP and cleaved-Caspase-12, compared with myocytes in isotonic solution (IS), suggesting that hyperosmotic stress induces ERS. In addition, HS significantly reduced cell viability and increased TUNEL staining and the expression of active Caspase-3, indicative of apoptosis. These effects were prevented with the addition of the ERS inhibitor, 4-PBA, indicating that hyperosmotic stress-induced apoptosis is mediated by ERS. Hyperosmotic stress-induced apoptosis was also prevented when cells were cultured in the presence of a Ca²⁺-chelating agent (EGTA) or the CaMKII inhibitor (KN93), suggesting that hyperosmotic stress-induced ERS is mediated by a Ca²⁺ and CaMKII-dependent mechanism. Similar results were observed when hyperosmotic stress was induced using glucose as the osmolite. We conclude that hyperosmotic stress promotes ERS by a CaMKII-dependent mechanism leading to apoptosis of adult cardiomyocytes. More importantly, we demonstrate that hyperosmotic stress-triggered ERS contributes to hyperglycemia-induced cell death.

Diabetes aggravates renal ischemia and reperfusion injury in rats by exacerbating oxidative stress, inflammation, and apoptosis

Diabetic patients are more susceptible to renal ischemia/reperfusion (I/R) injury (RI/RI) and have a poor prognosis, but the underlying mechanism remains unclear. The present study aimed to examine whether diabetes could worsen acute kidney injury induced by I/R in rats and clarify its mechanism. Control and streptozotocin-induced diabetic rats were subjected to 45 min renal pedicle occlusion followed by 24 h reperfusion. Tert-butylhydroquinone (TBHQ, 16.7 mg/kg) was administrated intraperitoneally 3 times at intervals of 8 h before ischemia. Serum and kidneys were harvested after reperfusion to evaluate renal function and histological injury. Enzyme-linked immunosorbent assays were used to test pro-inflammatory cytokines. Terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labeling assays were used to detect apoptotic cells, and western blotting was performed to determine the expression of B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), and cleaved caspase-3, as well as oxidative stress and inflammation-related proteins, such as nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), Toll-like receptor 4 (TLR4), and nuclear factor-κB (NF-κB). Compared with control animals, diabetic rats undergoing I/R exhibited more severe tubular damage and renal dysfunction. Diabetes exacerbated oxidative stress, the inflammatory response, and apoptosis after renal I/R by enhancing TLR4/NF-κB signaling and blocking the Nrf2/HO-1 pathway. RI/RI in diabetic rats was attenuated by pretreatment with TBHQ (a Nrf2 agonist), which exerted anti-inflammatory and anti-apoptotic properties by inhibiting NF-κB signaling. These findings indicate that hyperglycemia exacerbates RI/RI by intensifying oxidative stress, inflammation, and apoptosis. Antioxidant pretreatment may alleviate RI/RI in diabetic patients.

The cystathionine γ-lyase/hydrogen sulfide pathway mediates the trimetazidine-induced protection of H9c2 cells against hypoxia/reoxygenation-induced apoptosis and oxidative stress

Objective:

Trimetazidine is a piperazine-derived metabolic agent. It exerts cardioprotective effects against myocardial ischemia/reperfusion (I/R) injury. In addition, studies confirm that the cystathionine γ-lyase (CSE)/hydrogen sulfide (H₂S) pathway serves a beneficent role in attenuating myocardial I/R injury. However, the underlying role of the CSE/H₂S pathway in the trimetazidine-induced protection against myocardial I/R injury remains elusive. Therefore, this study investigated whether trimetazidine ameliorates hypoxia/reoxygenation (H/R)-induced H9c2 cardiomyocyte injuries in an in vitro cell model of myocardial I/R injury, by enhancing the CSE/H₂S pathway.

Methods:

The H9c2 cell viability was determined with a cell counting Kit-8.

Results:

Trimetazidine significantly increased the cell viability and decreased lactate dehydrogenase (LDH) release in H/R-treated H9c2 cells. Additionally, trimetazidine increased the H₂S levels and the CSE mRNA and protein levels, promoting the CSE/H₂S pathway under H/R conditions. The inhibition of the CSE/H₂S pathway, induced by transfection with specific siRNA against human CSE (si-CSE), eliminated the trimetazidine-induced upregulation of cell viability, downregulation of LDH release, increase of caspase-3 activity and apoptosis regulator BAX expression, and the decrease of apoptosis regulator Bcl-2 expression, which suggests involvement of the CSE/H₂S pathway in trimetazidine-induced cardioprotection. Furthermore, trimetazidine mitigated the H/R-induced increase in reactive oxygen species production and NADPH oxidase 2 expression, and decrease in superoxide dismutase activity and glutathione level, in H9c2 cells. These effects were also reversed by si-CSE.

Conclusion:

This study revealed that the CSE/H₂S pathway mediates the trimetazidine-induced protection of H9c2 cardiomyocytes against H/R-induced damage by inhibiting apoptosis and oxidative stress.

Selective Inhibition of PKCβ2 Restores Ischemic Postconditioning-Mediated Cardioprotection by Modulating Autophagy in Diabetic Rats

Diabetic hearts are more susceptible to myocardial ischemia/reperfusion (I/R) injury and less sensitive to ischemic postconditioning (IPostC), but the underlying mechanisms remain unclear. PKCβ2 is preferentially overactivated in diabetic myocardium, in which autophagy status is abnormal. This study determined whether hyperglycemia-induced PKCβ2 activation resulted in autophagy abnormality and compromised IPostC cardioprotection in diabetes. We found that diabetic rats showed higher cardiac PKCβ2 activation and lower autophagy than control at baseline. However, myocardial I/R further increased PKCβ2 activation and promoted autophagy status in diabetic rats. IPostC significantly attenuated postischemic infarct size and CK-MB, accompanied with decreased PKCβ2 activation and autophagy in control but not in diabetic rats. Pretreatment with CGP53353, a selective inhibitor of PKCβ2, attenuated myocardial I/R-induced infarction and autophagy and restored IPostC-mediated cardioprotection in diabetes. Similarly, CGP53353 could restore hypoxic postconditioning (HPostC) protection against hypoxia reoxygenation- (HR-) induced injury evidenced by decreased LDH release and JC-1 monomeric cells and increased cell viability. These beneficial effects of CGP53353 were reversed by autophagy inducer rapamycin, but could be mimicked by autophagy inhibitor 3-MA. It is concluded that selective inhibition of PKCβ2 could attenuate myocardial I/R injury and restore IPostC-mediated cardioprotection possibly through modulating autophagy in diabetes.

Analyses of changes in myocardial long non-coding RNA and mRNA profiles after severe hemorrhagic shock and resuscitation via RNA sequencing in a rat model

Background

Ischemia–reperfusion injury has been proven to induce organ dysfunction and death, although the mechanism is not fully understood. Long non-coding RNAs (lncRNAs) have drawn wide attention with their important roles in the gene expression of some biological processes and diseases, including myocardial ischemia–reperfusion (I/R) injury. In this paper, a total of 26 Sprague–Dawley (SD) rats were randomized into two groups: sham and ischemia–reperfusion (I/R) injury. Hemorrhagic shock was induced by removing 45% of the estimated total blood volume followed by reinfusion of shed blood. High-throughput RNA sequencing was used to analyze differentially expressed (DE) lncRNAs and messenger RNAs (mRNAs) in the heart tissue 4 h after reperfusion. Myocardial function was also evaluated.

Results

After resuscitation, the decline of myocardial function of shocked animals, expressed by cardiac output, ejection fraction, and myocardial performance index (MPI), was significant (p < 0.05). DE lncRNAs and mRNAs were identified by absolute value of fold change ≥ 2 and the false discovery rate ≤ 0.001. In rats from the I/R injury group, 851 lncRNAs and 1015 mRNAs were significantly up-regulated while 1533 lncRNAs and 1702 m RNAs were significantly down-regulated when compared to the sham group. Among the DE lncRNAs, we found 12 location-associated with some known apoptosis-related protein-coding genes which were up-regulated or down-regulated accordingly, including STAT3 and Il1r1. Real time PCR assays confirmed that the expression levels of five location-associated lncRNAs (NONRATT006032.2, NONRATT006033.2, NONRATT006034.2, NONRATT006035.2 and NONRATT029969.2) and their location-associated mRNAs (STAT3 and Il1r1) in the rats from the I/R injury group were all significantly up-regulated versus the sham group.

Conclusions

The DE lncRNAs (NONRATT006032.2, NONRATT006033.2, NONRATT006034.2 and NONRATT006035.2) could be compatible with their role in myocardial protection by stimulating their co-located gene (STAT3) after hemorrhagic shock and resuscitation. The final prognosis of I/R injury might be regulated by different genes, which is regarded as a complex network.

Electronic supplementary material

The online version of this article (10.1186/s12867-018-0113-8) contains supplementary material, which is available to authorized users.

Experimental diabetes mellitus exacerbates ischemia/reperfusion-induced myocardial injury by promoting mitochondrial fission: Role of down-regulation of myocardial Sirt1 and subsequent Akt/Drp1 interaction

Diabetes mellitus (DM) has a negative impact on clinical outcomes for patients with myocardial infarction. The aim of the present study was to assess whether decreased myocardial levels of Sirtuin1 (Sirt1) contribute to the increased susceptibility of the diabetic myocardium to ischemia/reperfusion (I/R) injury. In vivo, myocardial levels of Sirt1 expression and activity were decreased in mice with STZ-induced DM. Increasing Sirt1 activity prevented the DM-induced exacerbation of myocardial mitochondrial fission, apoptosis and dysfunction elicited by I/R. In vitro, anoxia/reoxygenation (A/R) challenge of cardiomyocytes (CM) that were preconditioned with high glucose (HG-CM) resulted in an exacerbation of the A/R-induced mitochondrial fission, oxidant production and CM apoptosis; effects reversed by increasing Sirt1 protein/activity. Inhibition of Drp1 prevented the exacerbated CM mitochondrial fission and oxidant production after A/R challenge of HG-CM. Decreased Sirt1 in HG-CM was associated with decreased Akt phosphorylation. Inhibition of Akt had no effect on CM Sirt1 levels, but further increased Drp1 activation. Increasing Sirt1 levels prevented the decrease in Akt phosphorylation and Drp1 activation in A/R challenged HG-CM. In conclusion: our data indicate that the increased vulnerability of the diabetic myocardium to I/R-induced apoptosis/dysfunction is attributable, in part, to decreased myocardial Sirt1 activity which leads to a decrease in Akt activation, an increase in Drp1 activity, culminating in excessive mitochondrial fission and ROS production.

Protective effect of morin on myocardial ischemia‑reperfusion injury in rats

Morin, a natural flavonol, exhibits antioxidative, anti-inflammatory and anti-apoptotic effects in various pathological and physiological processes. However, whether morin exerts a protective effect on myocardial ischemia-reperfusion injury (MIRI) is unknown. The present study aimed to determine the effect of morin on MIRI in cultured cardiomyocytes and isolated rat hearts, and to additionally explore the underlying mechanism. The effect of morin on the viability, lactate dehydrogenase (LDH) activity and apoptosis of H9c2 cardiomyocytes subjected to hypoxia/reoxygenation, and cardiac function and infarct size of rat hearts following ischemia/reperfusion in an animal model were measured. Furthermore, the mitochondrial permeability transition pore (MPTP) opening, mitochondrial membrane potential (ΔΨm), and the change in the expression levels of B-cell lymphoma 2 (Bcl2)-associated X protein (Bax), Bcl-2 and mitochondrial apoptosis-associated proteins following MPTP opening were also detected. The results indicated that morin treatment significantly increased cell viability, decreased LDH activity and cell apoptosis, improved the recovery of cardiac function and decreased the myocardial infarct size. Furthermore, morin treatment markedly inhibited MPTP opening, prevented the decrease of ΔΨm, and decreased the expression of cytochrome c, apoptotic protease activating factor-1, caspase-9, caspase-3 and the Bax/Bcl-2 ratio. However, these beneficial effects were reversed by treatment with atractyloside, an MPTP opener. The present study demonstrated that morin may prevent MIRI by inhibiting MPTP opening and revealed the possible mechanism of the cardioprotection of morin and its acting target. It also provided an important theoretical basis for the research on drug interventions for MIRI in clinical applications.

Combination of Vildagliptin and Ischemic Postconditioning in Diabetic Hearts as a Working Strategy to Reduce Myocardial Reperfusion Injury by Restoring Mitochondrial Function and Autophagic Activity

Purpose: Diabetic hearts are resistant to cardioprotection by ischemic-postconditioning (IPostC). Protection of diabetic hearts and finding related interfering mechanisms would have clinical benefits. This study investigated the combination effects of vildagliptin (Vilda) and IPostC on cardioprotection and the levels of autophagy and mitochondrial function following myocardial ischemia/reperfusion (I/R) injury in type-II diabetic rats.

Methods: Diabetes was established by high fat diet/low dose of streptozotocin and lasted for 12 weeks. The diabetic rats received Vilda (6 mg/kg/day, orally) for one month before I/R. Myocardial regional ischemia was induced through the ligation of left coronary artery, and IPostC was applied immediately at the onset of reperfusion. The infarct size was assessed by a computerised planimetry and left ventricles samples were harvested for cardiac mitochondrial function studies (ROS production, membrane potential and staining) and western blotting was used for determination of autophagy markers.

Results: None of Vilda or IPostC but combination of them could significantly reduce the infarct size of diabetic hearts, comparing to control (P<0.001). IPostC could not significantly affect p62 expression level in diabetic hearts, but pre-treatment with Vilda alone (p<0.05) and in combination with IPostC (p<0.01) more significantly decreased p62 expression in comparison with corresponding control group. The expression of LC3B-II and LC3BII/LC3BI as well as mitochondrial ROS production were decreased significantly in treatment groups (p<0.001). Mitochondrial membrane depolarization was significantly higher and mitochondrial density was lower in untreated diabetic I/R hearts than treated groups (p<0.001). IPostC in combination with vildagliptin prevented the mitochondrial membrane depolarization and increased the mitochondrial content more potent than IPostC alone in diabetic hearts.

Conclusion: Combination of vildagliptin and IPostC in diabetic hearts was a well-working strategy to reduce myocardial I/R damages by restoring mitochondrial membrane potential and ROS production and modulating the autophagic activity in I/R hearts.

Annexin A5 reduces infarct size and improves cardiac function after myocardial ischemia-reperfusion injury by suppression of the cardiac inflammatory response

Annexin A5 (AnxA5) is known to have anti-inflammatory and anti-apoptotic properties. Inflammation and apoptosis are key processes in post-ischemic cardiac remodeling. In this study, we investigated the effect of AnxA5 on left ventricular (LV) function and remodeling three weeks after myocardial ischemia-reperfusion (MI-R) injury in hypercholesterolemic ApoE*3-Leiden mice. Using a mouse model for MI-R injury, we demonstrate AnxA5 treatment resulted in a 27% reduction of contrast-enhanced MRI assessed infarct size (IS). End-diastolic and end-systolic volumes were decreased by 22% and 38%, respectively. LV ejection fraction was increased by 29% in the AnxA5 group compared to vehicle. Following AnxA5 treatment LV fibrous content after three weeks was reduced by 42%, which was accompanied by an increase in LV wall thickness of the infarcted area by 17%. Two days and three weeks after MI-R injury the number of cardiac macrophages was significantly reduced in both the infarct area and border zones following AnxA5 treatment compared to vehicle treatment. Finally, we found that AnxA5 stimulation leads to a reduction of IL-6 production in bone-marrow derived macrophages in vitro. AnxA5 treatment attenuates the post-ischemic inflammatory response and ameliorates LV remodeling which improves cardiac function three weeks after MI-R injury in hypercholesterolemic ApoE*3-Leiden mice.

Signaling mediators modulated by cardioprotective interventions in healthy and diabetic myocardium with ischaemia-reperfusion injury

Ischaemic heart diseases are one of the major causes of death in the world. In most patients, ischaemic heart disease is coincident with other risk factors such as diabetes. Patients with diabetes are more prone to cardiac ischaemic dysfunctions including ischaemia-reperfusion injury. Ischaemic preconditioning, postconditioning and remote conditionings are reliable interventions to protect the myocardium against ischaemia-reperfusion injuries through activating various signaling pathways and intracellular mediators. Diabetes can disrupt the intracellular signaling cascades involved in these myocardial protections, and studies have revealed that cardioprotective effects of the conditioning interventions are diminished in the diabetic condition. The complex pathophysiology and poor prognosis of ischaemic heart disease among people with diabetes necessitate the investigation of the interaction of diabetes with ischaemia-reperfusion injury and cardioprotective mechanisms. Reducing the outcomes of ischaemia-reperfusion injury using targeted strategies would be particularly helpful in this population. In this study, we review the protective interventional signaling pathways and mediators which are activated by ischaemic conditioning strategies in healthy and diabetic myocardium with ischaemia-reperfusion injury.

Role of inducible nitric oxide synthase in myocardial ischemia-reperfusion injury in sleep-deprived rats

INTRODUCTION

REM sleep deprivation (SD) decreases tolerance of the rat heart to ischemia-reperfusion (IR) injury; the underlying mechanisms, however, are unknown. This study aimed at determining whether changes in iNOS, Bax, and Bcl-2 gene expression are involved in this detrimental effect.

METHOD

SD was induced by flowerpot technique for a period of 4 days. This method is simple and able to induce sleep fragmentation which occurs as one of the sleep disorder symptoms in clinical conditions. The hearts of control and SD rats were perfused in Langendorff apparatus and subjected to 30 min ischemia, followed by 90 min reperfusion. The hemodynamic parameters (left ventricular developed pressure (LVDP), and ± dp/dt), NOx (nitrite + nitrate) level, infarct size, and mRNA expression of iNOS, Bax, and Bcl-2 were measured after IR.

RESULTS

SD rats had lower recovery of post-ischemic LVDP (32.8 ± 2.5 vs. 51.5 ± 2.1 mmHg; P < 0.05), + dp/dt (1555 ± 66 vs. 1119.5 ± 87 mmHg/s; P < 0.05) and - dp/dt (1437 ± 65 vs. 888 ± 162 mmHg/s; P < 0.05). SD rats also had higher NOx levels (41.4 ± 3.1 vs. 22.4 ± 3.6 μmol/L; P < 0.05) and infarct size (64.3 ± 2.3 vs. 38.3 ± 1.6%; P < 0.05) after IR, which along with LVDP, ± dp/dt restored to near normal status in the presence of aminoguanidine, a selective iNOS inhibitor. Following IR, expression of iNOS and Bax increased and Bcl-2 decreased (502, 372, and 54%, respectively) in SD rats; whereas in the presence of aminoguanidine, expression of iNOS and Bax significantly decreased and Bcl-2 increased (165, 168, and 19%, respectively).

CONCLUSION

Higher expression of iNOS and subsequent increase in apoptosis in the hearts after IR may contribute to less tolerance to myocardial IR injury in SD rats.

NLRP3 Inflammasome Activation-Mediated Pyroptosis Aggravates Myocardial Ischemia/Reperfusion Injury in Diabetic Rats

The reactive oxygen species- (ROS-) induced nod-like receptor protein-3 (NLRP3) inflammasome triggers sterile inflammatory responses and pyroptosis, which is a proinflammatory form of programmed cell death initiated by the activation of inflammatory caspases. NLRP3 inflammasome activation plays an important role in myocardial ischemia/reperfusion (MI/R) injury. Our present study investigated whether diabetes aggravated MI/R injury through NLRP3 inflammasome-mediated pyroptosis. Type 1 diabetic rat model was established by intraperitoneal injection of streptozotocin (60 mg/kg). MI/R was induced by ligating the left anterior descending artery (LAD) for 30 minutes followed by 2 h reperfusion. H9C2 cardiomyocytes were exposed to high glucose (HG, 30 mM) conditions and hypoxia/reoxygenation (H/R) stimulation. The myocardial infarct size, CK-MB, and LDH release in the diabetic rats subjected to MI/R were significantly higher than those in the nondiabetic rats, accompanied with increased NLRP3 inflammasome activation and increased pyroptosis. Inhibition of inflammasome activation with BAY11-7082 significantly decreased the MI/R injury. In vitro studies showed similar effects, as BAY11-7082 or the ROS scavenger N-acetylcysteine, attenuated HG and H/R-induced H9C2 cell injury. In conclusion, hyperglycaemia-induced NLRP3 inflammasome activation may be a ROS-dependent process in pyroptotic cell death, and NLRP3 inflammasome-induced pyroptosis aggravates MI/R injury in diabetic rats.

Modulation of hippocampal gene expression of microRNA-146a/microRNA-155-nuclear factor-kappa B inflammatory signaling by troxerutin in healthy and diabetic rats

Objectives:

Inflammation plays a critical role in the progression of diabetic complications such as neurological disorders. Previous reports have indicated the memory-improving effect of troxerutin, in rat hippocampus, but the underlying mechanisms are unclear. Hence, we have investigated the effect of troxerutin pretreatment on gene expressions of inflammation-related microRNAs (miRs), miR-146a and miR-155, and nuclear factor-kappa B (NF-κB) signaling pathway in the hippocampus of healthy and diabetic rats.

Materials and Methods:

Wistar rats were randomly divided into four groups (control, control + troxerutin, diabetic, and diabetic + troxerutin). Diabetes was induced by a single i.p. injection of streptozotocin (50 mg/kg). Troxerutin (150 mg/kg) was orally administered in animals for 1 month. After 10 weeks of diabetes, animals were anesthetized and decapitated for the isolation of hippocampus. The expression of miR-146a and miR-155 and the messenger RNA (mRNA) expressions of NF-κB, interleukin-1 receptor-associated kinase-1 (IRAK-1), and tumor necrosis factor receptor-associated factor-6 (TRAF-6) were analyzed by real-time polymerase chain reaction.

Results:

Diabetes significantly increased hippocampal mRNA levels of NF-κB, IRAK-1, and TRAF-6 compared with nondiabetic rats (P < 0.05); however, pretreatment with troxerutin decreased them in both diabetic and nondiabetic animals, independent of its glycemic effect (P < 0.05). The expression levels of miR-146a and miR-155 were decreased in diabetic group as compared to the control (P < 0.01).

Conclusion:

These findings showed that troxerutin could inhibit the inflammatory NF-κB pathway in the hippocampus of diabetic rats, which may be due to the negative feedback loop regulated by miR-146a.

Chronic type-I diabetes could not impede the anti-inflammatory and anti-apoptotic effects of combined postconditioning with ischemia and cyclosporine A in myocardial reperfusion injury

It has been shown that diabetes modifies the myocardial responses to ischemia/reperfusion (I/R) and to cardioprotective agents. In this study, we aimed to investigate the effects of combined treatment with ischemic postconditioning (IPostC) and cyclosporine A (CsA) on inflammation and apoptosis of the diabetic myocardium injured by I/R. Eight weeks after induction of diabetes in Wistar rats, hearts were mounted on a Langendorff apparatus and were subsequently subjected to a 30-min regional ischemia followed by 45-min reperfusion. IPostC was induced at the onset of reperfusion, by 3 cycles of 30-s reperfusion/ischemia (R/I). The concentration of creatine kinase (CK), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 were determined; the levels of total and phosphorylated glycogen synthase kinase 3 beta (p-GSK3β) and B-cell lymphoma 2 (Bcl-2) were quantified by western blotting, and the rate of apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. Administration of either IPostC or CsA alone in nondiabetic animals significantly reduced CK, TNF-α, IL-1β, and IL-6 concentrations, increased the p-GSK3β and Bcl-2, and decreased the level of apoptosis (P < 0.05) but had no effect on diabetic hearts. However, in diabetic animals, after administration of CsA, the cardioprotective effects of IPostC in increasing the p-GSK3β and Bcl-2 and decreasing apoptosis and inflammation were restored in comparison with nonpostconditioned diabetic hearts. IPostC or CsA failed to affect apoptosis and inflammation and failed to protect the diabetic myocardium against I/R injury. However, combined administration of IPostC and CsA at reperfusion can protect the diabetic myocardium by decreasing the inflammatory response and apoptosis.

Cox-2 Inhibition Protects against Hypoxia/Reoxygenation-Induced Cardiomyocyte Apoptosis via Akt-Dependent Enhancement of iNOS Expression

The present study explored the potential causal link between ischemia-driven cyclooxygenase-2 (COX-2) expression and enhanced apoptosis during myocardial ischemia/reperfusion (I/R) by using H9C2 cardiomyocytes and primary rat cardiomyocytes subjected to hypoxia/reoxygenation (H/R). The results showed that H/R resulted in higher COX-2 expression than that of controls, which was prevented by pretreatment with Helenalin (NFκB specific inhibitor). Furthermore, pretreatment with NS398 (COX-2 specific inhibitor) significantly attenuated H/R-induced cell injury [lower lactate dehydrogenase (LDH) leakage and enhanced cell viability] and apoptosis (higher Bcl2 expression and lower level of cleaved caspases-3 and TUNEL-positive cells) in cardiomyocytes. The amelioration of posthypoxic apoptotic cell death was paralleled by significant attenuation of H/R-induced increases in proinflammatory cytokines [interleukin 6 (IL6) and tumor necrosis factor (TNFα)] and reactive oxygen species (ROS) production and by higher protein expression of phosphorylated Akt and inducible nitric oxide synthase (iNOS) and enhanced nitric oxide production. Moreover, the application of LY294002 (Akt-specific inhibitor) or 1400W (iNOS-selective inhibitor) cancelled the cellular protective effects of NS398. Findings from the current study suggest that activation of NFκB during cardiomyocyte H/R induces the expression of COX-2 and that higher COX-2 expression during H/R exacerbates cardiomyocyte H/R injury via mechanisms that involve cross talks among inflammation, ROS, and Akt/iNOS/NO signaling.

Remote ischaemic conditioning in the context of type 2 diabetes and neuropathy: the case for repeat application as a novel therapy for lower extremity ulceration

An emerging treatment modality for reducing damage caused by ischaemia–reperfusion injury is ischaemic conditioning. This technique induces short periods of ischaemia that have been found to protect against a more significant ischaemic insult. Remote ischaemic conditioning (RIC) can be administered more conveniently and safely, by inflation of a pneumatic blood pressure cuff to a suprasystolic pressure on a limb. Protection is then transferred to a remote organ via humoral and neural pathways. The diabetic state is particularly vulnerable to ischaemia–reperfusion injury, and ischaemia is a significant cause of many diabetic complications, including the diabetic foot. Despite this, studies utilising ischaemic conditioning and RIC in type 2 diabetes have often been disappointing. A newer strategy, repeat RIC, involves the repeated application of short periods of limb ischaemia over days or weeks. It has been demonstrated that this improves endothelial function, skin microcirculation, and modulates the systemic inflammatory response. Repeat RIC was recently shown to be beneficial for healing in lower extremity diabetic ulcers. This article summarises the mechanisms of RIC, and the impact that type 2 diabetes may have upon these, with the role of neural mechanisms in the context of diabetic neuropathy a focus. Repeat RIC may show more promise than RIC in type 2 diabetes, and its potential mechanisms and applications will also be explored. Considering the high costs, rates of chronicity and serious complications resulting from diabetic lower extremity ulceration, repeat RIC has the potential to be an effective novel advanced therapy for this condition.

Hyperglycemia Aggravates Hepatic Ischemia Reperfusion Injury by Inducing Chronic Oxidative Stress and Inflammation

Aim. To investigate whether hyperglycemia will aggravate hepatic ischemia reperfusion injury (HIRI) and the underlying mechanisms. Methods. Control and streptozotocin-induced diabetic Sprague-Dawley rats were subjected to partial hepatic ischemia reperfusion. Liver histology, transferase, inflammatory cytokines, and oxidative stress were assessed accordingly. Similarly, BRL-3A hepatocytes were subjected to hypoxia/reoxygenation (H/R) after high (25 mM) or low (5.5 mM) glucose culture. Cell viability, reactive oxygen species (ROS), and activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-κB) were determined. Results. Compared with control, diabetic rats presented more severe hepatic injury and increased hepatic inflammatory cytokines and oxidative stress. HIRI in diabetic rats could be ameliorated by pretreatment of N-acetyl-L-cysteine (NAC) or apocynin. Excessive ROS generation and consequent Nrf2 and NF-κB translocation were determined after high glucose exposure. NF-κB translocation and its downstream cytokines were further increased in high glucose cultured group after H/R. While proper regulation of Nrf2 to its downstream antioxidases was observed in low glucose cultured group, no further induction of Nrf2 pathway by H/R after high glucose culture was identified. Conclusion. Hyperglycemia aggravates HIRI, which might be attributed to chronic oxidative stress and inflammation and potential malfunction of antioxidative system.

Effect of ischemic postconditioning on myocardial protection in patients undergoing coronary artery bypass grafting surgery with cardiopulmonary bypass

INTRODUCTION

Reperfusion injury is a well-known phenomenon following restoration of the coronary circulation after coronary artery bypass grafting (CABG) that impairs myocardial function. In order to control the severity of this injury, we aimed to investigate the effect of a new conditioning strategy namely ischemic postconditioning (IPOC) along with controlled aortic root reperfusion (CARR) on myocardial protection in CABG surgery with cardiopulmonary bypass.

METHODS

In a doubled blind clinical trial study, 51 patients undergoing first-time elective CABG were randomly divided in three groups: CARR, IPOC, and combination of IPOC and CARR. At the end of procedure and just before aortic cross-clamp removal, reperfusion was started as following: In CARR-receiving groups, the reperfusion was started with low perfusion pressures for 10 minutes, and in IPOC-receiving groups, three cycles of 1 minute episodes of ischemia separated by 1 minute episodes of reperfusion was applied as postconditioning protocol. Left ventricular ejection fraction (EF) (by echocardiography), inotrope requirement index, and myocardial arrhythmias were measured up to 72 hours after operation.

RESULTS

Echocardiography revealed that the recovery of EF after operation in IPOC group was significantly higher than those of two other groups (P < 0.05). Inotropic support requirement was significantly lower in IPOC groups. In addition, the incidence of atrial and ventricular arrhythmias after opening of aortic clamp and in intensive care unit (ICU) as well as recovery time of cardiac rhythm upon reperfusion were lowered by administration of IPOC, as compared with CARR group.

CONCLUSION

The study suggests that IPOC may provide clinical benefits against reperfusion injury in patients undergoing CABG surgery and maintain the post ischemic left ventricular performance.

Enhanced vulnerability to tobacco use in persons with diabetes: A behavioral and neurobiological framework

Tobacco use significantly magnifies the negative health complications associated with diabetes. Although tobacco use is strongly discouraged in persons with diabetes, clinical evidence suggests that they often continue to smoke and have more difficulty quitting despite serious contraindications. Here, we suggest that a potential reason for enhanced vulnerability to tobacco use in persons with diabetes is greater rewarding effects of nicotine. This review summarizes pre-clinical evidence indicating that the rewarding effects of nicotine are enhanced in rodent models of type 1 and type 2 diabetes. We also provide a framework of neurobiological mechanisms that are posited to promote tobacco use in persons with diabetes. This framework suggests that diabetes induces a disruption in insulin signaling that leads to a suppression of dopamine systems in the mesolimbic reward pathway. Lastly, we consider the clinical implications of enhanced rewarding effects of nicotine that may promote tobacco use in persons with diabetes. The clinical efficacy of smoking cessation medications that enhance dopamine are important to consider, given that persons with diabetes may display disrupted dopaminergic mechanisms. Future work is needed to better understand the complex interaction of dopamine and insulin in order to develop better smoking cessation medications for persons with diabetes.

Involvement of inducible nitric oxide synthase in the loss of cardioprotection by ischemic postconditioning in hypothyroid rats

Cardioprotection by ischemic postconditioning (IPost) is negated in hypothyroidism; the underlying mechanisms however are unknown. This study aimed at determining whether changes in Bax, Bcl-2, eNOS, and iNOS gene expressions are involved in the negating effects of IPost against ischemia-reperfusion (IR) injury in hypothyroidism. The hearts from control and hypothyroid rats were perfused in Langendorff apparatus and exposed to 30 min ischemia, followed by 120 min reperfusion and IPost. In a subgroup of hypothyroid rats, ischemia duration was extended to 40 min. Hemodynamic parameters, infarct size, and gene expressions were measured. Compared to controls, hypothyroid rats with 30 min ischemia had higher recovery of post-ischemic LVDP and ± dp/dt, confirmed by decreased CK and LDH levels (187 ± 16 vs. 485 ± 41 and 191 ± 9 vs. 702 ± 48 U/L, respectively; p<0.05), decreased infarct size (6.7 ± 1.1 vs. 46.1 ± 1.7%; p<0.05), and a reduced DNA laddering pattern. Recovery of post-ischemic LVDP and ± dp/dt decreased and infarct size increased following extension of ischemia period in hypothyroid rats. IPost increased eNOS and Bcl-2 expression by 3.2-fold and 3.7-fold and decreased Bax and iNOS expression by 79% and 38%, respectively; it also reduced IR-induced DNA laddering pattern in controls, whereas no change was observed in hypothyroid rats, regardless of the ischemia period. In conclusion, hearts from hypothyroid rats were resistant to IR injury, partly due to the lower expression of iNOS and subsequent reduction in apoptosis after IR. In hypothyroid rats, IPost was not associated with further reduction in iNOS expression and failed to provide additional cardioprotection against ischemia.

Differential Effects of β-Blockers, Angiotensin II Receptor Blockers, and a Novel AT2R Agonist NP-6A4 on Stress Response of Nutrient-Starved Cardiovascular Cells

In order to determine differences in cardiovascular cell response during nutrient stress to different cardiovascular protective drugs, we investigated cell responses of serum starved mouse cardiomyocyte HL-1 cells and primary cultures of human coronary artery vascular smooth muscles (hCAVSMCs) to treatment with β-blockers (atenolol, metoprolol, carvedilol, nebivolol, 3μM each), AT1R blocker losartan (1μM) and AT2R agonists (CGP42112A and novel agonist NP-6A4, 300nM each). Treatment with nebivolol, carvedilol, metoprolol and atenolol suppressed Cell Index (CI) of serum-starved HL-1 cells (≤17%, ≤8%, ≤15% and ≤15% respectively) as measured by the Xcelligence Real-Time Cell Analyzer (RTCA). Conversely, CI was increased by Ang II (≥9.6%), CGP42112A (≥14%), and NP-6A4 (≥25%) respectively and this effect was blocked by AT2R antagonist PD123319, but not by AT1R antagonist losartan. Thus, the CI signature for each drug could be unique. MTS cell proliferation assay showed that NP-6A4, but not other drugs, increased viability (≥20%) of HL-1 and hCAVSMCs. Wheat Germ Agglutinin (WGA) staining showed that nebivolol was most effective in reducing cell sizes of HL-1 and hCAVSMCs. Myeloid Cell Leukemia 1 (MCL-1) is a protein critical for cardiovascular cell survival and implicated in cell adhesion. β-blockers significantly suppressed and NP-6A4 increased MCL-1 expression in HL-1 and hCAVSMCs as determined by immunofluorescence. Thus, reduction in cell size and/or MCL-1 expression might underlie β-blocker-induced reduction in CI of HL-1. Conversely, increase in cell viability and MCL-1 expression by NP-6A4 through AT2R could have resulted in NP-6A4 mediated increase in CI of HL-1. These data show for the first time that activation of the AT2R-MCL-1 axis by NP-6A4 in nutrient-stressed mouse and human cardiovascular cells (mouse HL-1 cells and primary cultures of hCAVSMCs) might underlie improved survival of cells treated by NP-6A4 compared to other drugs tested in this study.