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

Renin-Angiotensin System Antagonism Protects the Diabetic Heart from Ischemia/Reperfusion Injury in Variable Hyperglycemia Duration Settings by a Glucose Transporter Type 4-Mediated Pathway

BACKGROUND

Diabetes mellitus (DM) is a risk factor for cardiovascular diseases, specifically, the ischemic heart diseases (IHD). The renin-angiotensin system (RAS) affects the heart directly and indirectly. However, its role in the protection of the heart against I/R injury is not completely understood. The aim of the current study was to evaluate the efficacy of the angiotensin-converting enzyme (ACE) inhibitor and Angiotensin II receptor (AT1R) blocker or a combination thereof in protection of the heart from I/R injury.

METHODS

Hearts isolated from adult male Wistar rats (n = 8) were subjected to high glucose levels; acute hyperglycemia or streptozotocin (STZ)-induced diabetes were used in this study. Hearts were subjected to I/R injury, treated with Captopril, an ACE inhibitor; Losartan, an AT1R antagonist; or a combination thereof. Hemodynamics data were measured using a suitable software for that purpose. Additionally, infarct size was evaluated using 2,3,5-Triphenyltetrazolium chloride (TTC) staining. The levels of apoptosis markers (caspase-3 and -8), antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), nitric oxide synthase (eNOS), and glucose transporter type 4 (GLUT-4) protein levels were evaluated by Western blotting. Pro-inflammatory and anti-inflammatory cytokines levels were evaluated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Captopril and Losartan alone or in combination abolished the effect of I/R injury in hearts subjected to acute hyperglycemia or STZ-induced diabetes. There was a significant (p < 0.05) recovery in hemodynamics, infarct size, and apoptosis markers following the treatment with Captopril, Losartan, or their combination. Treatment with Captopril, Losartan, or their combination significantly (p < 0.05) reduced pro-inflammatory cytokines and increased GLUT-4 protein levels.

CONCLUSIONS

The blockade of the RAS system protected the diabetic heart from I/R injury. This protection followed a pathway that utilizes GLUT-4 to decrease the apoptosis markers, pro-inflammatory cytokines, and to increase the anti-inflammatory cytokines. This protection seems to employ a pathway which is not involving ERK1/2 and eNOS.

DNA damage response signaling: A common link between cancer and cardiovascular diseases

DNA damage response (DDR) signaling ensures genomic and proteomic homeostasis to maintain a healthy genome. Dysregulation either in the form of down- or upregulation in the DDR pathways correlates with various pathophysiological states, including cancer and cardiovascular diseases (CVDs). Impaired DDR is studied as a signature mechanism for cancer; however, it also plays a role in ischemia-reperfusion injury (IRI), inflammation, cardiovascular function, and aging, demonstrating a complex and intriguing relationship between cancer and pathophysiology of CVDs. Accordingly, there are increasing number of reports indicating higher incidences of CVDs in cancer patients. In the present review, we thoroughly discuss (1) different DDR pathways, (2) the functional cross talk among different DDR mechanisms, (3) the role of DDR in cancer, (4) the commonalities and differences of DDR between cancer and CVDs, (5) the role of DDR in pathophysiology of CVDs, (6) interventional strategies for targeting genomic instability in CVDs, and (7) future perspective.

Protective effect of ischaemic postconditioning combined with nicorandil on myocardial ischaemia‒reperfusion injury in diabetic rats

BACKGROUND

The diabetic heart exhibits a high sensitivity to ischaemia/reperfusion (I/R) injury. Diabetes mellitus (DM) can affect the efficacy of cardioprotective interventions and reduce the therapeutic potential of existing treatment options. This study aimed to investigate the feasibility of shifting from monotherapy to combination therapy in diabetic myocardial I/R injury.

METHODS

6-8 week rats were randomized into 10 groups: sham, I/R, ischaemia postconditioning (I-Post), nicorandil (Nic), combination therapy (I-Post + Nic), DM sham, DM I/R, DM I-Post, DM Nic and DM I-Post + Nic. The extent of myocardial injury was clarified by measuring CK-MB and NO levels in plasma, ROS content in myocardial tissues, and TTC/Evans Blue staining to assess the area of myocardial infarction. Pathological staining of cardiac tissue sections were performed to clarify the structural changes in myocardial histopathology. Finally, Western blotting was performed to detect the phosphorylation levels of some key proteins in the PI3K/Akt signalling pathway in myocardial tissues.

RESULTS

We confirms that myocardial injury in diabetic I/R rats remained at a high level after treatment with I-Post or nicorandil alone. I-Post combined with nicorandil showed better therapeutic effects in diabetic I/R rats, and the combined treatment further reduced the area of myocardial injury in diabetic I/R rats compared with I-Post or nicorandil treatment alone (P < 0.001), as well as the levels of the myocardial injury markers CK-MB and ROS (P < 0.001); it also significantly increased plasma NO levels. Pathological staining also showed that diabetic rats benefited significantly from the combination therapy. Further mechanistic studies confirmed this finding. The protein phosphorylation levels of PI3K/Akt signalling pathway in the heart tissue of diabetic I/R rats were significantly higher after the combination treatment than after one treatment alone (all P < 0.05).

CONCLUSION

I-Post combined with nicorandil treatment maintains effective cardioprotection against diabetic myocardial I/R injury by activating the PI3K/Akt signalling pathway.

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

Risk Factors of Ischemia Reperfusion Injury After PCI in Patients with Acute ST-Segment Elevation Myocardial Infarction and its Influence on Prognosis

Purpose

To explore the risk factors of ischemia reperfusion injury (IRI) after percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction (STEMI) and its influence on prognosis.

Methods

The clinical data of 80 patients with STMEI undergoing PCI in our hospital from June 2020 to June 2021 were collected. According to whether IRI occurred after PCI, STMEI patients were divided into IRI group and non-IRI group. The basic information, clinical characteristics, examination parameters and other data of all patients were collected, and the prognosis of the two groups was observed. Risk factors were analyzed by fitting binary Logistic regression model. The survival prognosis was analyzed by Kaplan-Meier survival curve.

Results

Logistic regression analysis showed that type 2 diabetes mellitus (T2DM), pre-hospital delay time (PHD) and door-to-balloon expansion time (DTB) were the influencing factors of IRI in patients with STMEI (p < 0.05). MACE occurred in 11 cases (32.35%) in the IRI group and 13 cases (28.26%) in the non-IRI group. Log-rank test showed p = 0.503, indicating no statistically significant difference.

Conclusion

T2DM, PHD and DTB were the influencing factors of IRI in patients with STMEI, and IRI will not reduce the prognosis of patients.

Pretreatment with Nicotinamide Mononucleotide Increases the Effect of Ischemic-Postconditioning on Cardioprotection and Mitochondrial Function Following ex vivo Myocardial Reperfusion Injury in Aged Rats

The present study aims to evaluate the combined effect of ischemic-postconditioning (IPostC) and nicotinamide mononucleotide (NMN) on cardioprotection and mitochondrial function in aged rats subjected to myocardial ischemia-reperfusion (IR) injury. Sixty aged Wistar rats were randomly divided into 5 groups (n=12), including sham, control, NMN, IPostC, and NMN+IPostC. Regional ischemia was induced by 30-min occlusion of the left anterior descending coronary artery (LAD) followed by 60-min reperfusion. IPostC was applied at the onset of reperfusion, by 6 cycles of 10-s reperfusion/ischemia. NMN (100 mg/kg) was intraperitoneally injected every other day for 28 days before IR. Myocardial hemodynamics and infarct size (IS) were measured, and the left ventricles samples were harvested to assess cardiac mitochondrial function. The results showed that all treatments reduced lactate dehydrogenase release compared to those of the control group. IPostC alone failed to reduce IS and myocardial function. However, NMN and combined therapy could significantly improve myocardial function and decrease the IS compared to the control animals. Moreover, the effects of combined therapy on the decrease of IS, mitochondrial reactive oxygen species (ROS), and improvement of mitochondrial membrane potential (MMP) were greater than those of alone treatments. These results demonstrated that cardioprotection by combined therapy with NMN+IPostC was superior to individual treatments, and pretreatment of aged rats with NMN was able to correct the failure of IPostC in protecting the hearts of aged rats against IR injury.

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.

The roles of signaling pathways in cardiac regeneration

In recent years, knowledge of cardiac regeneration mechanisms has dramatically expanded. Regeneration can replace lost parts of organs, common among animal species. The heart is commonly considered an organ with terminal development, which has no reparability potential during post-natal life; however, some intrinsic regeneration capacity has been reported for cardiac muscle, which opens novel avenues in cardiovascular disease treatment. Different endogenous mechanisms were studied for cardiac repairing and regeneration in recent decades. Survival, proliferation, inflammation, angiogenesis, cell-cell communication, cardiomyogenesis, and anti-aging pathways are the most important mechanisms that have been studied in this regard. Several in vitro and animal model studies focused on proliferation induction for cardiac regeneration reported promising results. These studies have mainly focused on promoting proliferation signaling pathways and demonstrated various signaling pathways such as Wnt, PI3K/Akt, IGF-1, TGF-β, Hippo, and VEGF signaling cardiac regeneration. Therefore, in this review, we intended to discuss the connection between different critical signaling pathways in cardiac repair and regeneration.

The potentials of distinct functions of autophagy to be targeted for attenuation of myocardial ischemia/reperfusion injury in preclinical studies: an up-to-date review

Despite remarkable advances in our knowledge about the function of autophagy in myocardial ischemia/reperfusion (I/R) injury, the debate continues over whether autophagy is protective or deleterious in cardiac I/R. Due to the complexity of autophagy signaling, autophagy can play a dual role in the pathological processes of myocardial I/R injury. Thus, more researches are needed to shed light on the complex roles of autophagy in cardioprotection for the future clinical development. Such researches can lead to the finding of new therapeutic strategies for improving cardiac I/R outcomes in patients. Several preclinical studies have targeted autophagy flux as a beneficial strategy against myocardial I/R injury. In this review, we aimed to discuss the complex contribution of autophagy in myocardial I/R injury, as well as the therapeutic agents that have been shown to be useful in reducing myocardial I/R injury by targeting autophagy. For this reason, we provided an updated summary of the data from in vivo, ex vivo, and in vitro experimental studies about the therapeutic agents that exert positive effects against myocardial I/R injury by modulating autophagy flux. By addressing these valuable studies, we try to provide a motivation for the promising hypothesis of "autophagy modulation as a therapeutic strategy against cardiac I/R" in the future clinical studies.

Modulation of autophagy as the target of mesenchymal stem cells-derived conditioned medium in rat model of myocardial ischemia/reperfusion injury

Human amniotic membrane mesenchymal stem cells-derived conditioned medium (hAM-MSCs-CM) has positive effects against myocardial ischemia/reperfusion (MI/R) injury. However, it needs further investigations how hAM-MSCs-CM leads to the cell survival under MI/R via modulation of autophagy. The purpose of this study is investigating the effects of hAM-MSCs-CM in a rat model of MI/R injury by focusing on the role of autophagy as one of its possible mechanisms. Male Wistar rats (44 rats, 175-200 g) were randomly divided into four groups: Sham, MI/R, culture media-receiving and conditioned medium-receiving. MI/R was induced by 30 min of left anterior descending coronary artery ligation. After 15 min reperfusion, culture media or hAM-MSCs-CM (150 μl) were injected intramyocardially. At the end of the experiment, CK-MB, autophagy markers, phosphorylated and total forms of mTOR and ULK1, cardiac function and fibrosis were measured. hAM-MSCs-CM significantly decreased CK-MB levels (P < 0.0001), and also the mRNA levels of Beclin1 (P < 0.0001), LC3 (P = 0.012) and p62 (P = 0.003). In addition, hAM-MSCs-CM significantly reduced Beclin1, LC3II/LC3I and p62 protein levels (P < 0.0001), and increased p-mTOR/mTOR (P = 0.022) and p-ULK1/ULK1 (P < 0.0001) expressions. Moreover, hAM-MSCs-CM improved cardiac function and decreased fibrosis (P < 0.0001). This study showed cardioprotective effects of hAM-MSCs-CM against MI/R injury through modulation of autophagy via mTOR/ULK1 pathway. Based on these findings, it can be concluded that hAM-MSCs-CM can be offered as an attractive candidate for attenuation of MI/R injury in future, but needs further investigations.

Role of Oxidative DNA Damage and Repair in Atrial Fibrillation and Ischemic Heart Disease

Atrial fibrillation (AF) and ischemic heart disease (IHD) represent the two most common clinical cardiac diseases, characterized by angina, arrhythmia, myocardial damage, and cardiac dysfunction, significantly contributing to cardiovascular morbidity and mortality and posing a heavy socio-economic burden on society worldwide. Current treatments of these two diseases are mainly symptomatic and lack efficacy. There is thus an urgent need to develop novel therapies based on the underlying pathophysiological mechanisms. Emerging evidence indicates that oxidative DNA damage might be a major underlying mechanism that promotes a variety of cardiac diseases, including AF and IHD. Antioxidants, nicotinamide adenine dinucleotide (NAD⁺) boosters, and enzymes involved in oxidative DNA repair processes have been shown to attenuate oxidative damage to DNA, making them potential therapeutic targets for AF and IHD. In this review, we first summarize the main molecular mechanisms responsible for oxidative DNA damage and repair both in nuclei and mitochondria, then describe the effects of oxidative DNA damage on the development of AF and IHD, and finally discuss potential targets for oxidative DNA repair-based therapeutic approaches for these two cardiac diseases.

Combination of ellagic acid and trans-cinnamaldehyde alleviates aging-induced cognitive impairment via modulation of mitochondrial function and inflammatory and apoptotic mediators in the prefrontal cortex of aged rats

Cognitive impairments are associated with advancing age. Trans-cinnamaldehyde (CIN) and ellagic acid (ELA) have multiplex activities to reduce various age-related cognitive disorders. In this study, we investigated the effects of these compounds separately or in combination on the cognitive outcomes, mitochondrial function, and inflammatory and apoptotic mediators in aged male Wistar rats. Thirty-two old (22 months old) and eight young (5 months old) rats were randomly allocated to five groups of young control, aged control, ELA-aged, CIN-aged, and ELA + CIN-aged. ELA (15 mg/kg, orally) and CIN (50 mg/kg, intraperitoneally) separately or in combination were administered for 1 month in aged animals. Spatial memory and cognitive activity were evaluated by the Barnes maze and novel object recognition tests. Mitochondrial function (its reactive oxygen species [ROS], mitochondrial membrane potential and ATP level), pro-inflammatory cytokines such as interleukin (IL)-1β and IL-6 and pro-apoptotic caspase 3 and Bax, and anti-apoptotic Bcl2 levels and their ratio were assessed in the prefrontal cortex. Behavioral results revealed that CIN separately or in combination with ELA significantly alleviates aging-induced memory impairment. Moreover, co-administration of agents effectively decreased inflammatory cytokines, cleaved-caspase 3, Bax and Bax/Bcl2 levels, mitochondrial ROS production, and mitochondrial membrane depolarization and increased Bcl2 and ATP level as compared with untreated aged control rats. Combination therapy was greater than those of individual treatments in all parameters. Therefore, combination therapy with CIN and ELA improved aging-induced cognitive impairment through anti-inflammatory, anti-apoptotic, and mitochondrial-boosting effects in aged rats.

Effects of cyclosporin A pre-treatment combined with etomidate post-treatment on lung injury induced by limb ischemia-reperfusion in rats

OBJECTIVES

To investigate the influence of cyclosporin A (CsA) pre-treatment and etomidate (ETO) post-treatment on lung injury induced by limb ischemia-reperfusion (I/R) in rats.

METHODS

Rats were randomly divided into five groups: sham, I/R, I/R+CsA, I/R+ETO, and I/R+CsA+ETO. Limb I/R lung injury was established by bilateral clamping of the femoral arteries for 2 hours. Following reperfusion for 3 hours, blood gas analysis was performed. Pathological changes were assessed using immunohistochemistry. The apoptosis index (AI) and wet/dry weight ratio (W/D) were calculated. Levels of Fas protein and FasL mRNA were assessed by western blotting and RT-PCR, respectively. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β were detected by ELISA.

RESULTS

I/R resulted in decreased PaO2 but increased AI, W/D, Fas, FasL mRNA, TNF-α and IL-1β. Scattered punctate apoptosis and necrosis were observed by immunohistochemistry. Compared with the I/R group, the I/R+ETO and I/R+CsA groups showed increased SpO2, decreased AI, W/D, Fas, FasL mRNA, TNF-α and IL-1β, and decreased numbers of apoptotic and necrotic cells. Combined treatment with CsA+ETO resulted in more dramatic changes in these parameters.

CONCLUSIONS

ETO post-treatment and CsA pretreatment reduced lung injury induced by limb I/R in rats. The mechanism may be related to synergistic inhibition of Fas/FasL signaling.

Vildagliptin reduces myocardial ischemia-induced arrhythmogenesis via modulating inflammatory responses and promoting expression of genes regulating mitochondrial biogenesis in rats with type-II diabetes

PURPOSE

Fatal arrhythmias are one of the main manifestations of ischemic heart disease in diabetic patients. Here, we investigated the effect of pretreatment with vildagliptin on myocardial arrhythmias, inflammatory responses, and expression of genes regulating mitochondrial biogenesis following cardiac ischemic injury in type II diabetic male Wistar rats.

METHODS

Chronic diabetes was modeled by a high-fat diet and low-dose streptozotocin method and lasted for 12 weeks. Vildagliptin (6 mg/dl) was orally administered during the last 4 weeks of the diabetic period. Then, rats' hearts (n = 8/each group) were immediately isolated and transferred to the Langendorff apparatus, in which left anterior descending coronary artery was tightened for 35 min to induce regional ischemia. Electrocardiography was continuously recorded and myocardial arrhythmias were interpreted according to the Lambeth Convention. Inflammatory cytokines in left ventricular samples were measured using ELISA kits, and gene expression was assayed using real-time PCR.

RESULTS

Diabetic groups showed increased incidence and duration of ventricular fibrillation (VF) than controls (P < 0.05). Pretreatment of diabetic rats with vildagliptin resulted in a significant decrease in number, duration, and severity of premature ventricular complexes (PVC), tachycardia (VT), and VF during ischemia, compared to non-treated diabetic group (P < 0.05). Additionally, vildagliptin significantly increased the expression of genes PGC-1α, SIRT-1, and NRF-2 and reduced the levels of myeloperoxidase, creatine kinase release, and myocardial content of TNF-α and IL-1β in nondiabetic and diabetic rats as compared to corresponding controls (P < 0.01-0.05).

CONCLUSION

Vildagliptin preconditioning reduced the occurrence and severity of fatal ventricular arrhythmias induced by myocardial ischemia in type II diabetic rats through increased activity of mitochondrial biogenesis-regulating genes and reduction of inflammatory reactions.

Pretreatment with vildagliptin boosts ischemic-postconditioning effects on cardioprotection and expression profile of genes regulating autophagy and mitochondrial fission/fusion in diabetic heart with reperfusion injury

The burden of myocardial ischemia/reperfusion (IR) injury is 2-3-folds higher in diabetic patients, so protecting diabetic hearts is clinically important. Here, we investigated the effect of combinational therapy with vildagliptin and ischemic postconditioning (IPostC) on cardioprotection and the expression of genes regulating autophagy and mitochondrial function in diabetic hearts with IR injury. Type 2 diabetes was induced through high-fat diet and streptozotocin protocol in Wistar rats. Vildagliptin was orally administered to diabetic rats 5 weeks before IR injury. Myocardial-IR injury was modeled by ligation of left the coronary artery for 30 min followed by 60-min reperfusion, on a Langendorff-perfusion system. IPostC was applied at early reperfusion as 6 alternative cycles of 10-s reperfusion/ischemia. Creatine-kinase levels were measured spectrometrically, and infarct size was evaluated by TTC staining method. Left ventricles were harvested for assessing the expression levels of autophagy and mitochondrial-related genes using real-time PCR. Induction of diabetes significantly increased creatine-kinase release in comparison to healthy rats, and all treatments significantly reduced the release of enzyme toward control levels (P < 0.05). Only the combination therapy (IPostC + vildagliptin) could significantly reduce the infarct size of diabetic hearts as compared to untreated diabetic-IR group (P < 0.01). The levels of autophagy genes LC3 and p62 were significantly higher in diabetic groups than healthy ones. Induction of IR injury in diabetic hearts enhanced mitochondrial fission (drp-1) and reduced mitochondrial fusion (mfn1 and mfn2) genes. IPostC alone had no significant effect on the gene expression and vildagliptin alone could only affect LC3-II and mfn2 expressions. Nevertheless, administration of combination therapy significantly reduced the expression of both autophagy genes and increased both LC3-II/I and mfn2/1 ratios as compared with diabetic-IR hearts (P < 0.01-0.05). Application of this combination therapy could overcome the diabetes-induced failure of cardioprotection by individual treatments and improve mitochondrial dynamic and autophagy flux.

Nicotinamide adenine dinucleotide emerges as a therapeutic target in aging and ischemic conditions

Nicotinamide adenine dinucleotide (NAD⁺) has been described as central coenzyme of redox reactions and is a key regulator of stress resistance and longevity. Aging is a multifactorial and irreversible process that is characterized by a gradual diminution in physiological functions in an organism over time, leading to development of age-associated pathologies and eventually increasing the probability of death. Ischemia is the lack of nutritive blood flow that causes damage and mortality that mostly occurs in various organs during aging. During the process of aging and related ischemic conditions, NAD⁺ levels decline and lead to nuclear and mitochondrial dysfunctions, resulting in age-related pathologies. The majority of studies have shown that restoring of NAD⁺ using supplementation with intermediates such as nicotinamide mononucleotide and nicotinamide riboside can be a valuable strategy for recovery of ischemic injury and age-associated defects. This review summarizes the molecular mechanisms responsible for the reduction in NAD⁺ levels during ischemic disorders and aging, as well as a particular focus is given to the recent progress in the understanding of NAD⁺ precursor's effects on aging and ischemia.

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.

Anti-arrhythmogenic and anti-inflammatory effects of troxerutin in ischemia/reperfusion injury of diabetic myocardium

INTRODUCTION

Medicinal plants are increasingly used in the treatment of cardiovascular diseases due to their multifaceted properties. This study was designed to investigate anti-arrhythmic and anti-inflammatory potentials of the natural bioflavonoid, troxerutin (TXR) in myocardial ischemia/reperfusion (I/R) injury in diabetic rats.

METHODS

Male Wistar rats were randomly divided into 4 groups (control, control + TXR [150 mg/kg, daily], diabetic, and diabetic + TXR). Type-1 diabetes was induced by an intraperitoneal injection of streptozotocin (50 mg/kg) and lasted for 10 weeks. After mounting on the Langendorff apparatus, isolated hearts in all groups received a normal Krebs-Henseleit solution for 20 min of stabilization period, followed by 30 min of regional ischemia through ligation of the left anterior descending coronary artery, and 60 min of full reperfusion. During the experiment, the electrocardiograms were recorded and the arrhythmias [number, duration and incidence of premature ventricular complexes (PVC), ventricular tachycardia (VT), ventricular fibrillation (VF), and arrhythmia score] during I/R phases were assessed based on the Lambeth Convention. Ischemic left ventricular samples were used to determine the activities of lactate dehydrogenase (LDH), interleukin-1beta (IL-1β), and tumor necrosis factor (TNF-α).

RESULTS

The arrhythmias induced by I/R were not significantly changed in diabetic group as compared to the control group. However, pretreatment with TXR significantly reduced the number of PVC and duration and incidence of VF in ischemic phase in comparison to the untreated animals (P < 0.05). In addition, the duration, and incidence of most arrhythmias during reperfusion phase were significantly declined by TXR administration in both control and diabetic groups (P < 0.05). Pretreatment of rats with TXR significantly reduced myocardial inflammatory cytokines TNF-α and IL-1β levels after I/R insult in diabetic as well as control hearts (P < 0.05).

CONCLUSION

Preconditioning with TXR could provide cardioprotection by anti-arrhythmic and anti-inflammatory effects against I/R injury in rat hearts. This effect of TXR can introduce this material as a protective agent in cardiovascular diseases.

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.

Changes in mitochondrial properties may contribute to enhanced resistance to ischemia-reperfusion injury in the diabetic rat heart

Diabetes mellitus, besides having deleterious effects, induces cardiac adaptation that may reduce the heart's susceptibility to ischemia-reperfusion (IR) injury. This study aimed to investigate whether changes in mitochondrial properties are involved in the mechanisms of increased resistance of the diabetic heart to IR. Adult male Wistar rats were made diabetic by a single dose of streptozotocin (65 mg·kg^-1, i.p.), and on the day 8, Langendorff-perfused hearts were subjected to 30 min global ischemia and 40 min reperfusion. Baseline preischemic parameters in the diabetic hearts did not differ markedly from those in the nondiabetic controls, except for lower left ventricular developed pressure, higher mitochondrial membrane fluidity, and protein levels of manganese superoxide dismutase. On the other hand, diabetic hearts showed significantly better post-IR functional restoration and reduced arrhythmogenesis associated with lower reactive oxygen species production as compared with healthy controls. IR decreased membrane fluidity in both experimental groups; however, it led to a complete recovery of mitochondrial Mg²⁺-ATPase activity in diabetics in contrast to its reduction in nondiabetics. These findings indicate that the heart may become adapted to diabetes-induced alterations that might increase its tolerance to an ischemic insult. Preserved mitochondrial function might play a role in the mechanisms of the heart's resistance to IR injury in diabetics.

Effects of prostaglandin E1 on reperfusion injury patients: A meta-analysis of randomized controlled trials

BACKGROUND

Prostaglandin E1 (PGE1) is widely used as a pretreatment for myocardial reperfusion injury in animal experiments. However, the cardioprotective effects of PGE1 in patients have not been established. We performed a meta-analysis to investigate whether PGE1 is cardioprotective, based on the reduction of correlative reperfusion injury events (CRIE), major adverse cardiac events (MACE), and biomarker release in patients with ischemia reperfusion injury.

METHODS

The Medline, EMBASE, and Cochrane databases were searched for randomized clinical trials confirming the effects of PGE1. Two investigators independently selected suitable trials, assessed trial quality, and extracted data.

RESULTS

Six studies in patients undergoing percutaneous coronary intervention (4 studies) and cardiac surgery (2 studies), comprising a total of 445 patients, were included in this review. The results showed that PGE1 reduced the incidence of CRIE (relative ratio 0.4 [95% confidence interval 0.43, 0.95]), the incidence of MACE (0.35 [0.17, 0.70]), and the level of troponin T (standardized mean difference 20.28 [20.47, 20.09]), creatine kinase-MB (-1.74 [-3.21, - 0.27]), interleukin-6 (-1.37 [-2.69, - 0.04]), and interleukin-8 (-2.05 [-2.75, - 1.34]).

CONCLUSION

PGE1 may have beneficial effects on myocardial reperfusion injury in the clinic.