Blockade of ATP-sensitive potassium channels prevents myocardial preconditioning in dogs

Profiles of sulfonylurea use in Diabetes Mellitus type 2: an analysis of clinical practice over the last 10 years

AIMS

Describing the evolution over time in the use of sulfonylureas (SUs) and the characteristics of patients at first prescription and at interruption of treatment with SUs.

METHODS

Retrospective evaluation of data from the Italian Association of Diabetologists (AMD) Annals registry (2010-2020), about T2D patients who started treatment with SUs. The longitudinal probability of remaining on SUs was estimated by Kaplan Meier survival curves.

RESULTS

SU prescription decreased from 30.7 % (2010) to 12.9 % (2020). Patients started on SU were 68.2 ± 11.2 years old, mostly males (55.5 %), with diabetes duration = 10.1 ± 8.3 years, BMI = 29.7 ± 5.5 kg/m2, and HbA1c = 8.3 ± 1.7 % [67 mmol/mol]. After one year, the probability of staying on SU was 85.4 %, 75.9 % after two years, 68.2 % after 3 years, 56.6 % after 5 years. Patients who discontinued SUs had higher BMI and HbA1c, were younger, more often males and treated with insulin. Over time, the percentage of subjects switched to metformin, DPP4i, SGLT2i, and GLP1RA increased, whereas use of glinides, glitazones, acarbose and insulin declined.

CONCLUSIONS

These data suggest a consensus, slowly, but increasingly aligning with the current National indications of dismissing SUs for the treatment of T2D. The new drugs for diabetes should represent a preferable choice in all patients who do not have specific contraindications.

Initial Despair and Current Hope of Identifying a Clinically Useful Treatment of Myocardial Reperfusion Injury: Insights Derived from Studies of Platelet P2Y12 Antagonists and Interference with Inflammation and NLRP3 Assembly

Myocardial necrosis following the successful reperfusion of a coronary artery occluded by thrombus in a patient presenting with ST-elevation myocardial infarction (STEMI) continues to be a serious problem, despite the multiple attempts to attenuate the necrosis with agents that have shown promise in pre-clinical investigations. Possible reasons include confounding clinical risk factors, the delayed application of protective agents, poorly designed pre-clinical investigations, the possible effects of routinely administered agents that might unknowingly already have protected the myocardium or that might have blocked protection, and the biological differences of the myocardium in humans and experimental animals. A better understanding of the pathobiology of myocardial infarction is needed to stem this reperfusion injury. P2Y12 receptor antagonists minimize platelet aggregation and are currently part of the standard treatment to prevent thrombus formation and propagation in STEMI protocols. Serendipitously, these P2Y12 antagonists also dramatically attenuate reperfusion injury in experimental animals and are presumed to provide a similar protection in STEMI patients. However, additional protective agents are needed to further diminish reperfusion injury. It is possible to achieve additive protection if the added intervention protects by a mechanism different from that of P2Y12 antagonists. Inflammation is now recognized to be a critical factor in the complex intracellular response to ischemia and reperfusion that leads to tissue necrosis. Interference with cardiomyocyte inflammasome assembly and activation has shown great promise in attenuating reperfusion injury in pre-clinical animal models. And the blockade of the executioner protease caspase-1, indeed, supplements the protection already seen after the administration of P2Y12 antagonists. Importantly, protective interventions must be applied in the first minutes of reperfusion, if protection is to be achieved. The promise of such a combination of protective strategies provides hope that the successful attenuation of reperfusion injury is attainable.

The involvement of soluble epoxide hydrolase in the development of cardiovascular diseases through epoxyeicosatrienoic acids

Arachidonic acid (AA) has three main metabolic pathways: the cycloxygenases (COXs) pathway, the lipoxygenases (LOXs) pathway, and the cytochrome P450s (CYPs) pathway. AA produces epoxyeicosatrienoic acids (EETs) through the CYPs pathway. EETs are very unstable in vivo and can be degraded in seconds to minutes. EETs have multiple degradation pathways, but are mainly degraded in the presence of soluble epoxide hydrolase (sEH). sEH is an enzyme of bifunctional nature, and current research focuses on the activity of its C-terminal epoxide hydrolase (sEH-H), which hydrolyzes the EETs to the corresponding inactive or low activity diol. Previous studies have reported that EETs have cardiovascular protective effects, and the activity of sEH-H plays a role by degrading EETs and inhibiting their protective effects. The activity of sEH-H plays a different role in different cells, such as inhibiting endothelial cell proliferation and migration, but promoting vascular smooth muscle cell proliferation and migration. Therefore, it is of interest whether the activity of sEH-H is involved in the initiation and progression of cardiovascular diseases by affecting the function of different cells through EETs.

Sevoflurane-mediated modulation of oxidative myocardial injury

Introduction

Volatile anesthetics offer protection when administered throughout an ischemic injury. We examined how volatile anesthetics modulate the cardiac myocytic injury associated with hydrogen peroxide.

Methods

Forty-eight Long-Evans rats were divided into four groups depending on the treatment: none (CONT), Glibenclamide (GLB); Sevoflurane (SEV); or GLB+SEV. Each group was further divided into two, one of which was exposed to hydrogen peroxide (H2O2). Oral GLB was administered 48 hours before myocardial isolation. All rats were anesthetized by intraperitoneal injection of Ketamine, and the hearts were harvested after heparinization. Cardiomyocytes were isolated using a combination of mechanical mincing and enzymatic digestion. After isolation, the aliquots of cells were exposed to H2O2 and FeSO4 for 30 minutes. The cell suspensions were then bubbled for 10 minutes with 100% oxygen and 1.5% SEV if appropriate. Apoptosis was detected by fluorescein-bound annexin-V (ANX-V), necrosis by propidium iodide, and ELISA assessed caspase-3 activity in all groups.

Results

There was an increase in apoptosis, necrosis, and caspase-3 activity in the cells following exposure to hydrogen peroxide. SEV reduced the rate of cell necrosis and apoptosis. Pretreatment with GLB did not alter the effects of SEV. Similarly, caspase-3 activity did not change with GLB, although SEV administration reduced this enzymatic activity in response to hydrogen peroxide.

Conclusion

In this oxidant injury model, we demonstrated that incubating isolated cardiomyocytes with SEV profoundly diminished H2O2-induced apoptotic and necrotic cells compared to their CONTs. These results support the hypothesis that KATP channels are not the sole mediators associated with anesthetic preconditioning.

Multitargeting in cardioprotection: An example of biaromatic compounds

A multitarget drug design approach is actively developing in modern medicinal chemistry and pharmacology, especially with regard to multifactorial diseases such as cardiovascular diseases, cancer, and neurodegenerative diseases. A detailed study of many well-known drugs developed within the single-target approach also often reveals additional mechanisms of their real pharmacological action. One of the multitarget drug design approaches can be the identification of the basic pharmacophore models corresponding to a wide range of the required target ligands. Among such models in the group of cardioprotectors is the linked biaromatic system. This review develops the concept of a "basic pharmacophore" using the biaromatic pharmacophore of cardioprotectors as an example. It presents an analysis of possible biological targets for compounds corresponding to the biaromatic pharmacophore and an analysis of the spectrum of biological targets for the five most known and most studied cardioprotective drugs corresponding to this model, and their involvement in the biological effects of these drugs.

The RISK pathway leading to mitochondria and cardioprotection: how everything started

Ischaemic heart disease, which often manifests clinically as myocardial infarction (MI), remains a major cause of mortality worldwide. Despite the development of effective pre-clinical cardioprotective therapies, clinical translation has been disappointing. Nevertheless, the 'reperfusion injury salvage kinase' (RISK) pathway appears to be a promising target for cardioprotection. This pathway is crucial for the induction of cardioprotection by numerous pharmacological and non-pharmacological interventions, such as ischaemic conditioning. An important component of the cardioprotective effects of the RISK pathway involves the prevention of mitochondrial permeability transition pore (MPTP) opening and subsequent cardiac cell death. Here, we will review the historical perspective of the RISK pathway and focus on its interaction with mitochondria in the setting of cardioprotection.

Internal translation of Gja1 (Connexin43) to produce GJA1-20k: Implications for arrhythmia and ischemic-preconditioning

Internal translation is a form of post-translation modification as it produces different proteins from one mRNA molecule by beginning translation at a methionine coding triplet downstream of the first methionine. Internal translation can eliminate domains of proteins that otherwise restrict movement or activity, thereby creating profound functional diversity. Connexin43 (Cx43), encoded by the gene Gja1, is the main gap junction protein necessary for propagating action potentials between adjacent cardiomyocytes. Gja1 can be internally translated to produce a peptide 20 kD in length named GJA1-20k. This review focuses on the role of GJA1-20k in maintaining cardiac electrical rhythm as well as in ischemic preconditioning (IPC). Connexin43 is the only ion channel we are aware that has been reported to be subject to internal translation. We expect many other ion channels also undergo internal translation. The exploration of post-translational modification of ion channels, and in particular of internal translation, has the potential to greatly increase our understanding of both canonical and non-canonical ion channel biology.

Glycaemic Control in Patients Undergoing Percutaneous Coronary Intervention: What Is the Role for the Novel Antidiabetic Agents? A Comprehensive Review of Basic Science and Clinical Data

Coronary artery disease (CAD) remains one of the most important causes of morbidity and mortality worldwide, and revascularization through percutaneous coronary interventions (PCI) significantly improves survival. In this setting, poor glycaemic control, regardless of diabetes, has been associated with increased incidence of peri-procedural and long-term complications and worse prognosis. Novel antidiabetic agents have represented a paradigm shift in managing patients with diabetes and cardiovascular diseases. However, limited data are reported so far in patients undergoing coronary stenting. This review intends to provide an overview of the biological mechanisms underlying hyperglycaemia-induced vascular damage and the contrasting actions of new antidiabetic drugs. We summarize existing evidence on the effects of these drugs in the setting of PCI, addressing pre-clinical and clinical studies and drug-drug interactions with antiplatelet agents, thus highlighting new opportunities for optimal long-term management of these patients.

Modification of Ischemia/Reperfusion-Induced Alterations in Subcellular Organelles by Ischemic Preconditioning

It is now well established that ischemia/reperfusion (I/R) injury is associated with the compromised recovery of cardiac contractile function. Such an adverse effect of I/R injury in the heart is attributed to the development of oxidative stress and intracellular Ca²⁺-overload, which are known to induce remodeling of subcellular organelles such as sarcolemma, sarcoplasmic reticulum, mitochondria and myofibrils. However, repeated episodes of brief periods of ischemia followed by reperfusion or ischemic preconditioning (IP) have been shown to improve cardiac function and exert cardioprotective actions against the adverse effects of prolonged I/R injury. This protective action of IP in attenuating myocardial damage and subcellular remodeling is likely to be due to marked reductions in the occurrence of oxidative stress and intracellular Ca²⁺-overload in cardiomyocytes. In addition, the beneficial actions of IP have been attributed to the depression of proteolytic activities and inflammatory levels of cytokines as well as the activation of the nuclear factor erythroid factor 2-mediated signal transduction pathway. Accordingly, this review is intended to describe some of the changes in subcellular organelles, which are induced in cardiomyocytes by I/R for the occurrence of oxidative stress and intracellular Ca²⁺-overload and highlight some of the mechanisms for explaining the cardioprotective effects of IP.

Interactions between remote ischemic conditioning and post-stroke sleep regulation

Sleep disturbances are common in patients with stroke, and sleep quality has a critical role in the onset and outcome of stroke. Poor sleep exacerbates neurological injury, impedes nerve regeneration, and elicits serious complications. Thus, exploring a therapy suitable for patients with stroke and sleep disturbances is imperative. As a multi-targeted nonpharmacological intervention, remote ischemic conditioning can reduce the ischemic size of the brain, improve the functional outcome of stroke, and increase sleep duration. Preclinical/clinical evidence showed that this method can inhibit the inflammatory response, mediate the signal transductions of adenosine, activate the efferents of the vagal nerve, and reset the circadian clocks, all of which are involved in sleep regulation. In particular, cytokines tumor necrosis factor α (TNFα) and adenosine are sleep factors, and electrical vagal nerve stimulation can improve insomnia. On the basis of the common mechanisms of remote ischemic conditioning and sleep regulation, a causal relationship was proposed between remote ischemic conditioning and post-stroke sleep quality.

The modifying effects of adiposity on the cardiovascular safety of sulphonylureas

AIMS

To determine whether adiposity modified the effect on the cardiovascular safety of sulphonylureas as a first-line therapy compared with metformin among patients with type 2 diabetes.

MATERIALS AND METHODS

Using the UK Clinical Practice Research Datalink, we conducted a cohort study among 13 862 new sulphonylurea users matched on body mass index (BMI) and propensity score, in a 1:1 ratio, to new metformin users between April 1, 1998 and December 31, 2016. Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) of major adverse cardiovascular events (MACE), individual components of MACE (myocardial infarction [MI], ischaemic stroke, cardiovascular mortality), and all-cause mortality, comparing use of sulphonylureas with use of metformin, overall and within BMI categories (≤24.9 kg/m² , 25.0-29.9 kg/m² , ≥30 kg/m² ).

RESULTS

Compared with metformin, sulphonylureas were not associated with an increased risk of MACE either overall (HR 1.08, 95% CI 0.94-1.23) or by BMI category. Similar findings were observed for MI and ischaemic stroke. By contrast, sulphonylureas were associated with an increased risk of cardiovascular mortality (HR 1.24, 95% CI 1.04-1.48), primarily among obese patients (HR 1.52, 95% CI 1.08-2.13), and not among normal-weight patients (HR 1.00, 95% CI 0.72-1.39; P-interaction 0.21). Similar results were observed for all-cause mortality (HR 1.47, 95% CI 1.32-1.62), where an increased risk was observed among obese patients (HR 1.83, 95% CI 1.49-2.25), but not normal-weight patients (HR 1.18, 95% CI 0.99-1.42; P-interaction: 0.006).

CONCLUSION

The findings of this study suggest that adiposity may have a modifying effect on the association between sulphonylureas and cardiovascular and all-cause mortality compared with metformin.

Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy

Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.

Influence of cardiometabolic comorbidities on myocardial function, infarction, and cardioprotection: Role of cardiac redox signaling

The morbidity and mortality from cardiovascular diseases (CVD) remain high. Metabolic diseases such as obesity, hyperlipidemia, diabetes mellitus (DM), non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) as well as hypertension are the most common comorbidities in patients with CVD. These comorbidities result in increased myocardial oxidative stress, mainly from increased activity of nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, mitochondria as well as downregulation of antioxidant defense systems. Oxidative and nitrosative stress play an important role in ischemia/reperfusion injury and may account for increased susceptibility of the myocardium to infarction and myocardial dysfunction in the presence of the comorbidities. Thus, while early reperfusion represents the most favorable therapeutic strategy to prevent ischemia/reperfusion injury, redox therapeutic strategies may provide additive benefits, especially in patients with heart failure. While oxidative and nitrosative stress are harmful, controlled release of reactive oxygen species is however important for cardioprotective signaling. In this review we summarize the current data on the effect of hypertension and major cardiometabolic comorbidities such as obesity, hyperlipidemia, DM, NAFLD/NASH on cardiac redox homeostasis as well as on ischemia/reperfusion injury and cardioprotection. We also review and discuss the therapeutic interventions that may restore the redox imbalance in the diseased myocardium in the presence of these comorbidities.

Novel cholesterol-dependent regulation of cardiac KATP subunit expression revealed using histone deacetylase inhibitors

We recently discovered that the histone deacetylase inhibitor, trichostatin A (TSA), increases expression of the sulfonylurea receptor 2 (SUR2; Abcc9) subunit of the ATP-sensitive K+ (KATP ) channel in HL-1 cardiomyocytes. Interestingly, the increase in SUR2 was abolished with exogenous cholesterol, suggesting that cholesterol may regulate channel expression. In the present study, we tested the hypothesis that TSA increases SUR2 by depleting cholesterol and activating the sterol response element binding protein (SREBP) family of transcription factors. Treatment of HL-1 cardiomyocytes with TSA (30 ng/ml) caused a time-dependent increase in SUR2 mRNA expression that correlates with the time course of cholesterol depletion assessed by filipin staining. Consistent with the cholesterol-dependent regulation of SREBP increasing SUR2 mRNA expression, we observe a significant increase in SREBP cleavage and translocation to the nucleus following TSA treatment that is inhibited by exogenous cholesterol. Further supporting the role of SREBP in mediating the effect of TSA on KATP subunit expression, SREBP1 significantly increased luciferase reporter gene expression driven by the upstream SUR2 promoter. Lastly, HL-1 cardiomyocytes treated with the SREBP inhibitor PF429242 significantly suppresses the effect of TSA on SUR2 gene expression. These results demonstrate that SREBP is an important regulator of KATP channel expression and suggest a novel method by which hypercholesterolemia may exert negative effects on the cardiovascular system, namely, by suppressing expression of the KATP channel.

Clinical Approach to Assessment and Amelioration of Atherosclerotic Vascular Disease in Diabetes

Atherosclerotic cardiovascular disease is increased on average 2-3-fold in people with diabetes as compared to their non-diabetic counterparts and is the major cause of the increased morbidity and mortality in this disease. There is however heterogeneity in cardiovascular risk between individuals based on demographic, cardiometabolic and clinical risk factors in the setting of hyperglycemia, insulin resistance and obesity that needs to be taken into consideration in planning preventive interventions. Randomized clinical trials of agents or procedures used for amelioration of augmented CVD risk in diabetes have been pivotal in providing evidenced-based treatments. Improvement in hyperglycemia in both type 1 and type 2 diabetes is considered to be central in the prevention of microvascular and macrovascular complications although selected antihyperglycemic agents have demonstrated beneficial as well as possible deleterious off-target effects. Lowering low density lipoprotein cholesterol, treating hypertension and stopping smoking each play important roles in preventing cardiovascular disease in diabetes as they do in the general population and low dose aspirin is overall beneficial in high risk individuals. Hypertriglyceridemia may represent another important marker for augmented cardiovascular risk in diabetes and newer agents targeting dyslipidemia appear promising. The fall in cardiovascular events over the past two decades offers hope that modern intervention strategies as well as novel approaches such as those targeting inflammation may contribute to a continued reduction of cardiovascular disease in people with diabetes.

Chloride channel blocker IAA-94 increases myocardial infarction by reducing calcium retention capacity of the cardiac mitochondria

Indanyloxyacetic acid-94 (IAA-94), an intracellular chloride channel blocker, is shown to ablate cardioprotection rendered by ischemic preconditioning (IPC), N (6)-2-(4-aminophenyl) ethyladenosine or the PKC activator phorbol 12-myristate 13-acetate and cyclosporin A (CsA) in both ex-vivo and in-vivo ischemia-reperfusion (IR) injury. Thus signifying the role of the IAA-94 sensitive chloride channels in mediating cardio-protection upon IR injury. Although IAA-94 sensitive chloride currents are recorded in cardiac mitoplast, there is still a lack of understanding of the mechanism by which IAA-94 increases myocardial infarction (MI) by IR injury. Mitochondria are the key arbitrators of cell life and death pathways. Both oxidative stress and calcium overload in the mitochondria, elicit pathways resulting in the opening of mitochondrial permeability transition pore (mPTP) leading to cell death. Therefore, in this study we explored the role of IAA-94 in MI and in maintaining calcium retention capacity (CRC) of cardiac mitochondria after IR. IAA-94 inhibited the CRC of the isolated cardiac mitochondria in a concentration-dependent manner as measured spectrofluorimetrically using calcium green-5 N. Interestingly, IAA-94 did not change the mitochondrial membrane potential. Further, CsA a blocker of mPTP opening could not override the effect of IAA-94. We also showed for the first time that IAA-94 perfusion after ischemic event augments MI by reducing the CRC of mitochondria. To conclude, our results demonstrate that the mechanism of IAA-94 mediated cardio-deleterious effects is via modulating the mitochondria CRC, thereby playing a role in mPTP opening. These findings highlight new pharmacological targets, which can mediate cardioprotection from IR injury.

Sulfonylureas as initial treatment for type 2 diabetes and the risk of adverse cardiovascular events: A population-based cohort study

AIMS

Sulfonylureas are recommended as second-line treatment in the management of type 2 diabetes. However, they are still commonly used also as first-line treatment instead of metformin. Given the controversial cardiovascular safety of sulfonylureas, we aimed to determine if their use as first-line treatment is associated with adverse cardiovascular events among patients with newly treated type 2 diabetes compared with metformin.

METHODS

We conducted a population-based cohort study of patients with newly treated type 2 diabetes using the UK's Clinical Practice Research Datalink. Initiators of metformin and sulfonylurea monotherapy were matched on high-dimensional propensity score, and Cox proportional hazards models were used to compare the rate of cardiovascular events (myocardial infarction, ischaemic stroke, cardiovascular death, and all-cause mortality) with sulfonylureas vs metformin.

RESULTS

Our cohort included 94 750 patients initiating treatment for type 2 diabetes, 17 612 on a sulfonylurea and 77 138 on metformin. After matching, sulfonylurea monotherapy, compared with metformin monotherapy, was not associated with an increased risk of myocardial infarction (hazard ratio [HR]: 1.04, 95% confidence interval [CI]: 0.85-1.25) but was associated with increased risks of ischaemic stroke (HR: 1.25, 95% CI: 1.002-1.56), cardiovascular death (HR: 1.25, 95% CI: 1.06-1.47), and all-cause mortality (HR: 1.60, 95% CI: 1.45-1.76). This represents an additional 2.0 ischaemic strokes, 3.5 cardiovascular deaths, and 21.4 all-cause deaths per 1,000 patients per year with sulfonylureas.

CONCLUSIONS

Initiating treatment of type 2 diabetes with a sulfonylurea rather than metformin is associated with higher rates of ischaemic stroke, cardiovascular death, and all-cause mortality.

Clinical significance of chronic myocardial ischemia in coronary artery disease patients

Myocardial ischemia is considered the cornerstone of the treatment of patients with coronary artery disease (CAD). Although the deleterious effects of myocardial infarction, the maximum expression of ischemia, have been extensively studied and described, the clinical effects of chronic, documented myocardial ischemia are not completely clarified. The first studies that compared therapies for coronary disease focused on the presence of anatomical features and assessed ischemia based on the interpretation of the findings of obstructive atherosclerotic lesions. They suggested that revascularization interventions did not confer any clinical advantage over medical therapy (MT), in terms of cardiac or overall death. Other retrospective studies that were dedicated to assessing the impact of documented stress-induced ischemia on cardiovascular outcomes have suggested a prognostic impact of chronic ischemia. However, this has been questioned in recent studies. Moreover, the previous understanding that chronic ischemia could lead to worsening of ventricular function was not confirmed in a recent study. Thus, the prognostic significance of stress-induced ischemia has been questioned. Regarding treatment options, although some previous analyses have suggested that interventional therapies would reduce cardiovascular events in CAD patients with documented ischemia, recent post-hoc studies and metanalysis have shown distinct results. In this review article, the authors discuss myocardial ischemia, the different responses of the myocardium to ischemic insults, ischemic preconditioning, and the main findings of recent studies about the clinical aspects and treatment of patients with chronic, documented myocardial ischemia.

An overview of protective strategies against ischemia/reperfusion injury: The role of hyperbaric oxygen preconditioning

INTRODUCTION

Ischemia/reperfusion (I/R) injury, such as myocardial infarction, stroke, and peripheral vascular disease, has been recognized as the most frequent causes of devastating disorders and death currently. Protective effect of various preconditioning stimuli, including hyperbaric oxygen (HBO), has been proposed in the management of I/R.

METHODS

In this study, we searched and reviewed up-to-date published papers to explore the pathophysiology of I/R injury and to understand the mechanisms underlying the protective effect of HBO as conditioning strategy.

RESULTS

Animal study and clinic observation support the notion that HBO therapy and conditioning provide beneficial effect against the deleterious effects of postischemic reperfusion. Several explanations have been proposed. The first likely mechanism may be that HBO counteracts hypoxia and reduces I/R injury by improving oxygen delivery to an area with diminished blood flow. Secondly, by reducing hypoxia-ischemia, HBO reduces all the pathological events as a consequence of hypoxia, including tissue edema, increased affective area permeability, postischemia derangement of tissue metabolism, and inflammation. Thirdly, HBO may directly affect cell apoptosis, signal transduction, and gene expression in those that are sensitive to oxygen or hypoxia. HBO provides a reservoir of oxygen at cellular level not only carried by blood, but also by diffusion from the interstitial tissue where it reaches high concentration that may last for several hours, improves endothelial function and rheology, and decreases local inflammation and edema.

CONCLUSION

Evidence suggests the benefits of HBO when used as a preconditioning stimulus in the setting of I/R injury. Translating the beneficial effects of HBO into current practice requires, as for the "conditioning strategies", a thorough consideration of risk factors, comorbidities, and comedications that could interfere with HBO-related protection.

Protein complexes as psychiatric and neurological drug targets

The need for improved medications for psychiatric and neurological disorders is clear. Difficulties in finding such drugs demands that all strategic means be utilized for their invention. The discovery of forebrain specific AMPA receptor antagonists, which selectively block the specific combinations of principal and auxiliary subunits present in forebrain regions but spare targets in the cerebellum, was recently disclosed. This discovery raised the possibility that other auxiliary protein systems could be utilized to help identify new medicines. Discussion of the TARP-dependent AMPA receptor antagonists has been presented elsewhere. Here we review the diversity of protein complexes of neurotransmitter receptors in the nervous system to highlight the broad range of protein/protein drug targets. We briefly outline the structural basis of protein complexes as drug targets for G-protein-coupled receptors, voltage-gated ion channels, and ligand-gated ion channels. This review highlights heterodimers, subunit-specific receptor constructions, multiple signaling pathways, and auxiliary proteins with an emphasis on the later. We conclude that the use of auxiliary proteins in chemical compound screening could enhance the detection of specific, targeted drug searches and lead to novel and improved medicines for psychiatric and neurological disorders.

Acute Myocardial Infarction, Cardioprotection, and Muse Cells

Acute myocardial infarction (AMI) is a common cause of morbidity and mortality worldwide. Severe MI leads to heart failure due to a marked loss of functional cardiomyocytes. First-line treatment for AMI is to reperfuse the occluded coronary artery by PCI as soon as possible. Besides PCI, there are several therapies to reduce the infarct size and improve the cardiac function and remodeling. These are drug therapies such as pharmacological pre- and postconditioning, cytokine therapies, and stem cell therapies. None of these therapies have been clinically developed as a standard treatment for AMI. Among many cell sources for stem cell therapies, the Muse cell is an endogenous non-tumorigenic pluripotent stem cell, which is able to differentiate into cells of all three germ layers from a single cell, suggesting that the Muse cell is a potential cell source for regenerative medicine. Endogenous Muse cell dynamics in the acute phase plays an important role in the prognosis of AMI patients; AMI patients with a higher number of Muse cells in the peripheral blood in the acute phase show more favorable improvement of the cardiac function and remodeling in the chronic phase, suggesting their innate reparative function for the heart. Intravenously administered exogenous Muse cells engrafted preferentially and efficiently to infarct border areas via the S1P-S1PR2 axis and differentiated spontaneously into working cardiomyocytes and vessels, showed paracrine effects, markedly reduced the myocardial infarct size, and delivered long-lasting improvement of the cardiac function and remodeling for 6 months. These findings suggest that Muse cells are reparative stem cells, and thus their clinical application is warranted.

Stem cell transplantation therapy for multifaceted therapeutic benefits after stroke

One of the exciting advances in modern medicine and life science is cell-based neurovascular regeneration of damaged brain tissues and repair of neuronal structures. The progress in stem cell biology and creation of adult induced pluripotent stem (iPS) cells has significantly improved basic and pre-clinical research in disease mechanisms and generated enthusiasm for potential applications in the treatment of central nervous system (CNS) diseases including stroke. Endogenous neural stem cells and cultured stem cells are capable of self-renewal and give rise to virtually all types of cells essential for the makeup of neuronal structures. Meanwhile, stem cells and neural progenitor cells are well-known for their potential for trophic support after transplantation into the ischemic brain. Thus, stem cell-based therapies provide an attractive future for protecting and repairing damaged brain tissues after injury and in various disease states. Moreover, basic research on naïve and differentiated stem cells including iPS cells has markedly improved our understanding of cellular and molecular mechanisms of neurological disorders, and provides a platform for the discovery of novel drug targets. The latest advances indicate that combinatorial approaches using cell based therapy with additional treatments such as protective reagents, preconditioning strategies and rehabilitation therapy can significantly improve therapeutic benefits. In this review, we will discuss the characteristics of cell therapy in different ischemic models and the application of stem cells and progenitor cells as regenerative medicine for the treatment of stroke.

Hearts lacking plasma membrane KATP channels display changes in basal aerobic metabolic substrate preference and AMPK activity

Cardiac ATP-sensitive K+ (KATP) channels couple changes in cellular metabolism to membrane excitability and are activated during metabolic stress, although under basal aerobic conditions, KATP channels are thought to be predominately closed. Despite intense research into the roles of KATP channels during metabolic stress, their contribution to aerobic basal cardiac metabolism has not been previously investigated. Hearts from Kir6.2+/+ and Kir6.2−/− mice were perfused in working mode, and rates of glycolysis, fatty acid oxidation, and glucose oxidation were measured. Changes in activation/expression of proteins regulating metabolism were probed by Western blot analysis. Despite cardiac mechanical function and metabolic efficiency being similar in both groups, hearts from Kir6.2−/− mice displayed an approximately twofold increase in fatty acid oxidation and a 0.45-fold reduction in glycolytic rates but similar glucose oxidation rates compared with hearts from Kir6.2+/+ mice. Kir6.2−/− hearts also possessed elevated levels of activated AMP-activated protein kinase (AMPK), higher glycogen content, and reduced mitochondrial density. Moreover, activation of AMPK by isoproterenol or diazoxide was significantly blunted in Kir6.2−/− hearts. These data indicate that KATP channel ablation alters aerobic basal cardiac metabolism. The observed increase in fatty acid oxidation and decreased glycolysis before any metabolic insult may contribute to the poor recovery observed in Kir6.2−/− hearts in response to exercise or ischemia-reperfusion injury. Therefore, KATP channels may play an important role in the regulation of cardiac metabolism through AMPK signaling.

NEW & NOTEWORTHY In this study, we show that genetic ablation of plasma membrane ATP-sensitive K+ channels results in pronounced changes in cardiac metabolic substrate preference and AMP-activated protein kinase activity. These results suggest that ATP-sensitive K+ channels may play a novel role in regulating metabolism in addition to their well-documented effects on ionic homeostasis during periods of stress.

Ischaemic preconditioning - Current knowledge and potential future applications after 30 years of experience

Ischaemic preconditioning (IPC) phenomenon has been known for thirty years. During that time several studies showed that IPC provided by brief ischaemic and reperfusion episodes prior to longer ischaemia can bestow a protective effect to both preconditioned and also remote organs. IPC affecting remote organs is called remote ischaemic preconditioning. Initially, most IPC studies were focused on enhancing myocardial resistance to subsequent ischaemia and reperfusion injury. However, preconditioning was found to be a universal phenomenon and was observed in various organs and tissues including the heart, liver, brain, retina, kidney, skeletal muscles and intestine. Currently, there are a lot of simultaneous studies are underway aiming at finding out whether IPC can be helpful in protecting these organs. The mechanism of local and remote IPC is complex and not well known. Several triggers, intracellular pathways and effectors, humoral, neural and induced by genetic changes may be considered potential pathways in the protective activity of local and remote IPC. Local and remote IPC mechanism may potentially serve as heart protection during cardiac surgery and may limit the infarct size of the myocardium, can be a strategy for preventing the development of acute kidney injury development and liver damage during transplantation, may protect the brain against ischaemic injury. In addition, the method is safe, non-invasive, cheap and easily applicable. The main purpose of this review article is to present new advances which would help to understand the potential mechanism of IPC. It also discusses both its potential applications and utility in clinical settings.

Pro- and Antiarrhythmic Actions of Sulfonylureas: Mechanistic and Clinical Evidence

Sulfonylureas are the most commonly used second-line drug class for treating type 2 diabetes mellitus (T2DM). While the cardiovascular safety of sulfonylureas has been examined in several trials and nonrandomized studies, little is known of their specific effects on sudden cardiac arrest (SCA) and related serious arrhythmic outcomes. This knowledge gap is striking, because persons with DM are at increased risk of SCA. In this review, we explore the influence of sulfonylureas on the risk of serious arrhythmias, with specific foci on ischemic preconditioning, cardiac excitability, and serious hypoglycemia as putative mechanisms. Elucidating the relationship between individual sulfonylureas and serious arrhythmias is critical, especially as the diabetes epidemic intensifies and SCA incidence increases in persons with diabetes.

Ubiquinol-cytochrome c reductase core protein 1 may be involved in delayed cardioprotection from preconditioning induced by diazoxide

This study aimed to use long-term diazoxide treatment to establish a loss-of-cardioprotection model and then perform proteomics analysis to explore which proteins of mitochondrial inner membrane (MIM) are potentially involved in delayed cardioprotection. Rats received 1 to 8 weeks of diazoxide treatments (20 mg•kg-1•d-1) to establish a loss-of-cardioprotection model in different groups. Detection of serum cTnI levels and cell apoptosis assays in heart tissue were performed. Then, rats MIM after 0, 4 and 6 weeks of diazoxide treatment was isolated and proteomics analysis was performed. An invitro model of H9C2 cells was performed to explore the effects of targeted protein on delayed cardioprotection. The effect of delayed cardioprotection by diazoxide preconditioning disappeared when diazoxide treatments were given for six weeks or longer. Ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) was identified in the proteomics analysis. UQCRC1 expression was upregulated by diazoxide treatment in H9C2 cells, and UQCRC1 down-regulation could increase the lactate dehydrogenase release and apoptosis rate after injury induced by oxygen glucose deprivation. These results showed that UQCRC1 might contribute to the loss-of-cardioprotection model induced by long-term diazoxide treatment and play a role in delayed cardioprotection.

Myocardial protection with Glucose-Insulin-Potassium infusion during adult cardiac surgery

Background & Objective:

Recent meta-analysis reports have called for more randomized trials to evaluate the effectiveness of GIK solution in patients of cardiac surgery. So this study was conducted to evaluate the effectiveness of Glucose-insulin-potassium (GIK) solutions in non-diabetic patients undergoing coronary artery bypass grafting.

Methods:

A total number of one hundred and sixty (160) patients were randomized into two equal groups; GIK Group and non-GIK group. In GIK group, 5% dextrose containing 70 IU/L regular insulin and 70 meq/L of potassium was administered. The infusion was started at a rate of 30 ml/hour after induction of anesthesia and before the start of cardiopulmonary bypass. The infusion was started again after removal of aortic cross clamp and was continued for six hours after the operation.

Results:

In early post-operative period, peak CKMB levels were high in non-GIK group 48.50±19.79 IU/L versus 33.40±14.69 IU/L in GIK group (p-value <0.001). There was no statistically significant difference in requirements of inotropic support between the groups. The mean duration of inotropic support in GIK group was only 5.50±6.88 hours in GIK group and 8.64±7.74 hours in non-GIK group (p-value 0.008). Mean ventilation time in GIK group was 5.06±2.39 hours versus 6.55±3.58 hours in non-GIK group (p-value 0.002). Similarly, ICU stay period was also shorter in GIK group (p-value 0.01). We did not found any detrimental effect of GIK infusion on non-cardiac complications e.g. renal, pulmonary and neurologic complications.

Conclusion:

Glucose-insulin-potassium (GIK) infusion has a beneficial role in myocardial protection and is associated with better post-operative outcomes without increasing the risk of non-cardiac complications.

Review: Sulphonylureas and cardiovascular risk: facts and controversies

Cardiovascular complications are the principal cause of death in type 2 diabetes. The importance of glycaemic control in preventing cardiovascular complications has been demonstrated. However, some oral antidiabetic agents and especially some sulphonylureas (SU) have been accused of having a deleterious effect on cardiovascular risk. A retrospective analysis of the administrative database of Saskatchewan Health for 5,795 subjects, identified by their first-ever dispensation for an oral antidiabetic agent, suggests that a higher exposure to SUs was associated with increased mortality. Nevertheless, the effects of SUs on cardiac ATP-sensitive potassium channels in experimental studies vary between agents and studies, so that the clinical relevance of this phenomenon is unclear. Moreover, 11 years of follow-up of patients randomised to glibenclamide or chlorpropamide in the United Kingdom Prospective Diabetes Study demonstrated no adverse effects on a range of cardiovascular end points. Despite SU structural differences and differences in binding to cardiac SU receptors, the clinical evidence base does not support the selection of one sulphonylurea over another on the basis of ischaemic preconditioning, possibly because ischaemic preconditioning may be blunted or absent in diabetes. The main objective remains the prevention or delay of diabetic complications through improvement of glycaemic control together with other cardiovascular risk factors.

Myocardial Preconditioning: Characteristics, Mechanisms, and Clinical Applications

Perioperative myocardial ischemia and dysfunction re main prevalent after cardiac surgery despite the use of conventional measures to provide myocardial protec tion. Myocardial preconditioning is a powerful, endog enously regulated means of myocardial protection that may also have some clinical usage for patients undergo ing cardiac surgical procedures. The paradoxical con cept of using ischemia as a stimulus for myocardial protection has been studied extensively in animals and humans. The specific characteristics and constituents of preconditioning have been well identified. The mecha nism remains to be completely elucidated due to differ ences among species and experimental models. Some pharmacologic agents are capable of mimicking the classic mechanism of ischemic preconditioning. Pharma cologic and ischemic preconditioning may have signifi cant clinical use and therapeutic efficacy as a means of providing myocardial protection during cardiac surgery, especially in procedures that do not use cardioplegia and cardiopulmonary bypass, such as minimally inva sive coronary artery bypass grafting. This article re views the characteristics, mechanisms, potential clini cal applications, and therapeutic efficacy of myocardial preconditioning.

Amiodarone Offsets the Cardioprotective Effects of Ischaemic Preconditioning against Ischaemia/Reperfusion Injury

Both ischaemic preconditioning (IPC) and amiodarone protect against myocardial ischaemia. We examined whether a combination of IPC and amiodarone demonstrated an additive protective effect in isolated rat hearts ( n = 40). The controls (group I) were subjected to ischaemia/reperfusion injury; group II was subjected to cycles of IPC prior to ischaemia/reperfusion injury; group III was subjected to ischaemia in the presence of amiodarone (10−10 mol/l); and group IV was subjected to IPC followed by ischaemia in the presence of amiodarone (10−10 mol/l). Amiodarone produced the best preserved left ventricular end-systolic pressure and dP/dtmax, less developed ventricular stiffness, the shortest arrhythmia duration, and the smallest infarct size among the groups. All of the myocardial protective effects against ischaemia/reperfusion injury were diminished or abolished when IPC and amiodarone were applied sequentially.

Mitochondria-Targeted Antioxidants: Future Perspectives in Kidney Ischemia Reperfusion Injury

Kidney ischemia/reperfusion injury emerges in various clinical settings as a great problem complicating the course and outcome. Ischemia/reperfusion injury is still an unsolved puzzle with a great diversity of investigational approaches, putting the focus on oxidative stress and mitochondria. Mitochondria are both sources and targets of ROS. They participate in initiation and progression of kidney ischemia/reperfusion injury linking oxidative stress, inflammation, and cell death. The dependence of kidney proximal tubule cells on oxidative mitochondrial metabolism makes them particularly prone to harmful effects of mitochondrial damage. The administration of antioxidants has been used as a way to prevent and treat kidney ischemia/reperfusion injury for a long time. Recently a new method based on mitochondria-targeted antioxidants has become the focus of interest. Here we review the current status of results achieved in numerous studies investigating these novel compounds in ischemia/reperfusion injury which specifically target mitochondria such as MitoQ, Szeto-Schiller (SS) peptides (Bendavia), SkQ1 and SkQR1, and superoxide dismutase mimics. Based on the favorable results obtained in the studies that have examined myocardial ischemia/reperfusion injury, ongoing clinical trials investigate the efficacy of some novel therapeutics in preventing myocardial infarct. This also implies future strategies in preventing kidney ischemia/reperfusion injury.

Succinate metabolism: a new therapeutic target for myocardial reperfusion injury

Myocardial ischaemia/reperfusion (IR) injury is a major cause of death worldwide and remains a disease for which current clinical therapies are strikingly deficient. While the production of mitochondrial reactive oxygen species (ROS) is a critical driver of tissue damage upon reperfusion, the precise mechanisms underlying ROS production have remained elusive. More recently, it has been demonstrated that a specific metabolic mechanism occurs during ischaemia that underlies elevated ROS at reperfusion, suggesting a unifying model as to why so many different compounds have been found to be cardioprotective against IR injury. This review will discuss the role of the citric acid cycle intermediate succinate in IR pathology focusing on the mechanism by which this metabolite accumulates during ischaemia and how it can drive ROS production at Complex I via reverse electron transport. We will then examine the potential for manipulating succinate accumulation and metabolism during IR injury in order to protect the heart against IR damage and discuss targets for novel therapeutics designed to reduce reperfusion injury in patients.

Plasticity of sarcolemmal KATP channel surface expression: relevance during ischemia and ischemic preconditioning

Myocardial ischemia remains the primary cause of morbidity and mortality in the United States. Ischemic preconditioning (IPC) is a powerful form of endogenous protection against myocardial infarction. We studied alterations in KATP channels surface density as a potential mechanism of the protection of IPC. Using cardiac-specific knockout of Kir6.2 subunits, we demonstrated an essential role for sarcolemmal KATP channels in the infarct-limiting effect of IPC in the mouse heart. With biochemical membrane fractionation, we demonstrated that sarcolemmal KATP channel subunits are distributed both to the sarcolemma and intracellular endosomal compartments. Global ischemia causes a loss of sarcolemmal KATP channel subunit distribution and internalization to endosomal compartments. Ischemia-induced internalization of KATP channels was prevented by CaMKII inhibition. KATP channel subcellular redistribution was also observed with immunohistochemistry. Ischemic preconditioning before the index ischemia reduced not only the infarct size but also prevented KATP channel internalization. Furthermore, not only did adenosine mimic IPC by preventing infarct size, but it also prevented ischemia-induced KATP channel internalization via a PKC-mediated pathway. We show that preventing endocytosis with dynasore reduced both KATP channel internalization and strongly mitigated infarct development. Our data demonstrate that plasticity of KATP channel surface expression must be considered as a potentially important mechanism of the protective effects of IPC and adenosine.

Modulation of Cardiac Potassium Current by Neural Tone and Ischemia

The cardiac action potential is generated by intricate flows of ions across myocyte cell membranes in a coordinated fashion to control myocardial contraction and the heart rhythm. Modulation of the flow of these ions in response to a variety of stimuli results in changes to the action potential. Abnormal or altered ion currents can result in cardiac arrhythmias. Abnormalities of autonomic regulation of potassium current play a role in the genesis of cardiac arrhythmias, and alterations in acetylcholine-activated potassium channels may play a key role in atrial fibrillation. Ischemia is another important modulator of cardiac cellular electrophysiology.

KATP Channels in the Cardiovascular System

KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.

Isosteviol Sensitizes sarcKATP Channels towards Pinacidil and Potentiates Mitochondrial Uncoupling of Diazoxide in Guinea Pig Ventricular Myocytes

K_ATP channel is an important mediator or factor in physiological and pathological metabolic pathway. Activation of K_ATP channel has been identified to be a critical step in the cardioprotective mechanism against IR injury. On the other hand, desensitization of the channel to its opener or the metabolic ligand ATP in pathological conditions, like cardiac hypertrophy, would decrease the adaption of myocardium to metabolic stress and is a disadvantage for drug therapy. Isosteviol, obtained by acid hydrolysis of stevioside, has been demonstrated to play a cardioprotective role against diseases of cardiovascular system, like anti-IR injury, antihypertension, antihyperglycemia, and so forth. The present study investigated the effect of isosteviol (STV) on sarcK_ATP channel current induced by pinacidil and mitochondrial flavoprotein oxidation induced by diazoxide. Our results showed that preincubating cells with STV not only increased the current amplitude and activating rate of sarcK_ATP channels induced by pinacidil but also potentiated diazoxide-elicited oxidation of flavoprotein in mitochondria.

Mitochondrial reactive oxygen species at the heart of the matter: new therapeutic approaches for cardiovascular diseases

Reactive oxygen species (ROS) have been implicated in a variety of age-related diseases, including multiple cardiovascular disorders. However, translation of ROS scavengers (antioxidants) into the clinic has not been successful. These antioxidants grossly reduce total levels of cellular ROS including ROS that participate in physiological signaling. In this review, we challenge the traditional antioxidant therapeutic approach that targets ROS directly with novel approaches that improve mitochondrial functions to more effectively treat cardiovascular diseases.

Role of Trimetazidine in Ischemic Preconditioning in Patients With Symptomatic Coronary Artery Disease

Ischemic preconditioning (IP) is a powerful cardioprotective cellular mechanism that has been related to the "warm-up phenomenon" or "walk-through" angina, and has been documented through the use of sequential exercise tests (ETs). It is known that several drugs, for example, cromokalim, pinacidil, adenosine, and nicorandil, can interfere with the cellular pathways of IP. The purpose of this article is to report the effect of the anti-ischemic agent trimetazidine (TMZ) on IP in symptomatic coronary artery disease (CAD) patients.We conducted a prospective study evaluating IP by the analysis of ischemic parameters in 2 sequential ETs. In phase I, without TMZ, patients underwent ET1 and ET2 with a 30-minute interval between them. In phase II, after 1 week of TMZ 35 mg twice daily, all patients underwent 2 consecutive ETs (ET3 and ET4). IP was considered present when the time to 1.0-mm segment ST on electrocardiogram deviation (T-1.0 mm) and rate pressure product (RPP) were greater in the second of 2 tests. The improvement in T-1.0 mm and RPP were compared in the 2 phases: without TMZ and after 1-week TMZ to assess the action of such drug in myocardial protective mechanisms. ETs were analyzed by 2 independent cardiologists.From 135 CAD patients screened, 96 met inclusion criteria and 62 completed the study protocol. Forty patients manifested IP by demonstrating an improvement in T-1.0 mm in ET2 compared with ET1, without the use of any drugs (phase I). In phase II, after 1-week TMZ, 26 patients (65%) did not show any incremental result in ischemic parameters in ET4 compared with ET3. Furthermore, of these patients, 8 (20%) had IP blockage.In this study, TMZ did not add any benefit to IP in patients with stable symptomatic CAD.

Cardiovascular safety of sulphonylureas: over 40 years of continuous controversy without an answer

More than 40 years after publication of the University Group Diabetes Program trial, the cardiovascular safety of sulphonylureas is still contentious. Although several hypotheses linking sulphonylureas to adverse cardiovascular effects exist, none provide conclusive evidence. Adding to the controversy, current clinical trials and observational studies provide inconsistent, and sometimes conflicting, evidence for the cardiovascular effects of sulphonylureas. Overall, observational evidence suggests that an increased risk of adverse cardiovascular outcomes is associated with sulphonylureas; however, these data may be subject to residual confounding and bias. Although evidence from randomized controlled trials has suggested a neutral effect, the majority of these studies were not specifically designed to assess the effect of sulphonylureas on adverse cardiovascular event risk. Current ongoing large clinical trials may provide some clarity on the cardiovascular safety of sulphonylureas, but the results are not expected for several years. With the continued uncertainties concerning the cardiovascular safety of all antidiabetic drugs, a clear answer with regard to sulphonylureas is warranted. The objectives of the present article were to provide an overview of the controversy surrounding sulphonylurea-related cardiovascular effects, to discuss the limitations of the current literature, and to provide recommendations for future studies aiming to elucidate the true relationship between sulphonylureas and adverse cardiovascular effects in people with type 2 diabetes.

Effects of Pogostemon cablin Blanco extract on hypoxia induced rabbit cardiomyocyte injury

Background:

Pogostemonis Herba, the dried aerial part of Pogostemon cablin Blanco, is a well-known materia medica in Asia that is widely used for syndrome of gastrointestinal dysfunctions.

Objective:

This study was undertaken to examine whether Pogostemon cablin extract (PCe) might have any beneficial effect on hypoxia induced rabbit cardiomyocyte injury.

Materials and Methods:

Isolated cardiomyocytes were divided into three groups and the changes of cell viability in cardiomyocytes of hypoxic and hypoxia/reoxygenation group were determined. The effect of PCe on reactive oxygen species (ROS) generation, intracellular formation of ROS was also measured by monitoring the 2’,7’-dichlorofluorescein fluorescence.

Results:

PCe effectively protected the cells against both the hypoxia and reoxygenation induced injury, and the protective effect of PCe is not mediated by interaction with adenosine triphosphate-sensitive K⁺ channels. In the presence of PCe, production of ROS under chemical hypoxia was remarkably reduced which suggests that PCe might exert its effect as a ROS scavenger.

Conclusion:

The present study provides clear evidence for the beneficial effect of PCe on cardiomyocyte injury during hypoxia or reoxygenation following prolonged hypoxia.

Signalling pathways and mechanisms of protection in pre- and postconditioning: historical perspective and lessons for the future

Ischaemic pre- and postconditioning are potent cardioprotective interventions that spare ischaemic myocardium and decrease infarct size after periods of myocardial ischaemia/reperfusion. They are dependent on complex signalling pathways involving ligands released from ischaemic myocardium, G-protein-linked receptors, membrane growth factor receptors, phospholipids, signalling kinases, NO, PKC and PKG, mitochondrial ATP-sensitive potassium channels, reactive oxygen species, TNF-α and sphingosine-1-phosphate. The final effector is probably the mitochondrial permeability transition pore and the signalling produces protection by preventing pore formation. Many investigators have worked to produce a roadmap of this signalling with the hope that it would reveal where one could intervene to therapeutically protect patients with acute myocardial infarction whose hearts are being reperfused. However, attempts to date to show efficacy of such an intervention in large clinical trials have been unsuccessful. Reasons for this inability to translate successes in the experimental laboratory to the clinical arena are evaluated in this review. It is suggested that all patients with acute coronary syndromes currently presenting to the hospital and being treated with platelet P2Y12 receptor antagonists, the current standard of care, are indeed already benefiting from protection from the conditioning pathways outlined earlier. If that proves to be the case, then future attempts to further decrease infarction will have to rely on interventions which protect by a different mechanism.

Caveolins in cardioprotection - translatability and mechanisms

Translation of preclinical treatments for ischaemia-reperfusion injury into clinical therapies has been limited by a number of factors. This review will focus on a single mode of cardiac protection related to a membrane scaffolding protein, caveolin, which regulates protective signalling as well as myocyte ultrastructure in the setting of ischaemic stress. Factors that have limited the clinical translation of protection will be considered specifically in terms of signalling and structural defects. The potential of caveolin to overcome barriers to protection with the ultimate hope of clinical translation will be discussed.

Mortality risk among sulfonylureas: a systematic review and network meta-analysis

BACKGROUND

Sulfonylureas are common second-line options for management of type 2 diabetes; however, they are associated with a higher risk of cardiovascular events compared with other antidiabetic drugs. Since tissue selectivity and risk of hypoglycaemia differ among sulfonylureas, we aimed to assess whether mortality and the risk of cardiovascular events also varies.

METHODS

We searched Medline and Embase from inception to June 11, 2014, to identify controlled studies reporting the risk of all-cause mortality, cardiovascular-related mortality, or myocardial infarction for at least two sulfonylureas. We examined differences in cardiovascular event risk among sulfonylureas with random effects models for direct pairwise comparisons and network meta-analyses to incorporate direct and indirect data.

FINDINGS

14 970 (9%) of 167 327 patients in 18 studies died: 841 (4%) of 19 334 gliclazide users, 5482 (11%) of 49 389 glimepiride users, 2106 (15%) of 14 464 glipizide users, 5296 (7%) of 77 169 glibenclamide users, 1066 (17%) of 6187 tolbutamide users, and 179 (23%) of 784 chlorpropamide users. Inconsistency was low for the network meta-analysis of all-cause mortality, and the relative risk of death compared with glibenclamide was 0·65 (95% credible interval 0·53-0·79) for gliclazide, 0·83 (0·68-1·00) for glimepiride, 0·98 (0·80-1·19) for glipizide, 1·13 (0·90-1·42) for tolbutamide, and 1·34 (0·98-1·86) for chlorpropamide. Similar associations were noted for cardiovascular-related mortality: the relative risk compared with glibenclamide was 0·60 (95% credible interval 0·45-0·84) for gliclazide, 0·79 (0·57-1·11) for glimepiride, 1·01 (0·72-1·43) for glipizide, 1·11 (0·79-1·55) for tolbutamide, and 1·45 (0·88-2·44) for chlorpropamide.

INTERPRETATION

Gliclazide and glimepiride were associated with a lower risk of all-cause and cardiovascular-related mortality compared with glibenclamide. Clinicians should consider possible differences in risk of mortality when selecting a sulfonylurea.

FUNDING

None.

Cardioprotection acquired through exercise: the role of ischemic preconditioning

A great bulk of evidence supports the concept that regular exercise training can reduce the incidence of coronary events and increase survival chances after myocardial infarction. These exercise-induced beneficial effects on the myocardium are reached by means of the reduction of several risk factors relating to cardiovascular disease, such as high cholesterol, hypertension, obesity etc. Furthermore, it has been demonstrated that exercise can reproduce the "ischemic preconditioning" (IP), which refers to the capacity of short periods of ischemia to render the myocardium more resistant to subsequent ischemic insult and to limit infarct size during prolonged ischemia. However, IP is a complex phenomenon which, along with infarct size reduction, can also provide protection against arrhythmia and myocardial stunning due to ischemia-reperfusion. Several clues demonstrate that preconditioning may be directly induced by exercise, thus inducing a protective phenotype at the heart level without the necessity of causing ischemia. Exercise appears to act as a physiological stress that induces beneficial myocardial adaptive responses at cellular level. The purpose of the present paper is to review the latest data on the role played by exercise in triggering myocardial preconditioning.

PO2 cycling reduces diaphragm fatigue by attenuating ROS formation

Prolonged muscle exposure to low PO₂ conditions may cause oxidative stress resulting in severe muscular injuries. We hypothesize that PO₂ cycling preconditioning, which involves brief cycles of diaphragmatic muscle exposure to a low oxygen level (40 Torr) followed by a high oxygen level (550 Torr), can reduce intracellular reactive oxygen species (ROS) as well as attenuate muscle fatigue in mouse diaphragm under low PO₂. Accordingly, dihydrofluorescein (a fluorescent probe) was used to monitor muscular ROS production in real time with confocal microscopy during a lower PO₂ condition. In the control group with no PO₂ cycling, intracellular ROS formation did not appear during the first 15 min of the low PO₂ period. However, after 20 min of low PO₂, ROS levels increased significantly by ∼30% compared to baseline, and this increase continued until the end of the 30 min low PO₂ condition. Conversely, muscles treated with PO₂ cycling showed a complete absence of enhanced fluorescence emission throughout the entire low PO₂ period. Furthermore, PO₂ cycling-treated diaphragm exhibited increased fatigue resistance during prolonged low PO₂ period compared to control. Thus, our data suggest that PO₂ cycling mitigates diaphragm fatigue during prolonged low PO₂. Although the exact mechanism for this protection remains to be elucidated, it is likely that through limiting excessive ROS levels, PO₂ cycling initiates ROS-related antioxidant defenses.

An electrocardiographic sign of ischemic preconditioning

Ischemic preconditioning is a form of intrinsic cardioprotection where an episode of sublethal ischemia protects against subsequent episodes of ischemia. Identifying a clinical biomarker of preconditioning could have important clinical implications, and prior work has focused on the electrocardiographic ST segment. However, the electrophysiology biomarker of preconditioning is increased action potential duration (APD) shortening with subsequent ischemic episodes, and APD shortening should primarily alter the T wave, not the ST segment. We translated findings from simulations to canine to patient models of preconditioning to test the hypothesis that the combination of increased [delta (Δ)] T wave amplitude with decreased ST segment elevation characterizes preconditioning. In simulations, decreased APD caused increased T wave amplitude with minimal ST segment elevation. In contrast, decreased action potential amplitude increased ST segment elevation significantly. In a canine model of preconditioning (9 mongrel dogs undergoing 4 ischemia-reperfusion episodes), ST segment amplitude increased more than T wave amplitude during the first ischemic episode [ΔT/ΔST slope = 0.81, 95% confidence interval (CI) 0.46-1.15]; however, during subsequent ischemic episodes the T wave increased significantly more than the ST segment (ΔT/ΔST slope = 2.43, CI 2.07-2.80) (P < 0.001 for interaction of occlusions 2 vs. 1). A similar result was observed in patients (9 patients undergoing 2 consecutive prolonged occlusions during elective percutaneous coronary intervention), with an increase in slope of ΔT/ΔST of 0.13 (CI -0.15 to 0.42) in the first occlusion to 1.02 (CI 0.31-1.73) in the second occlusion (P = 0.02). This integrated analysis of the T wave and ST segment goes beyond the standard approach to only analyze ST elevation, and detects cellular electrophysiology changes of preconditioning.