Role of glycogen synthase kinase-3beta in cardioprotection

Inhibition of glycogen synthase kinase 3 beta ameliorates liver ischemia reperfusion injury by way of an interleukin-10-mediated immune regulatory mechanism

The ubiquitous serine/threonine kinase glycogen synthase kinase 3 beta (Gsk3β) differentially regulates macrophage Toll-like receptor (TLR)-triggered pro- and anti-inflammatory cytokine programs. This study was designed to determine the in vivo role and therapeutic potential of Gsk3β modulation in tissue inflammation and injury in a murine model of liver partial warm ischemia/reperfusion injury (IRI). As a constitutively activated liver kinase, Gsk3β became quickly inactivated (phosphorylated) following IR. The active Gsk3β, however, was essential for the development of IRI pathology, as administration of its specific inhibitor, SB216763, ameliorated the hepatocellular damage, evidenced by reduced serum alanine aminotransferase (sALT) levels and well-preserved liver architecture compared with controls. The liver protective effect of Gsk3β inhibition was dependent on an immune regulatory mechanism, rather than direct cytoprotection via mitochondria permeability transition pores (MPTP). Indeed: (1) coadministration of SB216763 and atractyloside (MPTP opener) failed to abrogate a local cytoprotective Gsk3β inhibition effect; (2) SB216763 selectively inhibited IR-triggered liver pro-inflammatory, but spared interleukin (IL)-10, gene induction programs; and (3) IL-10 neutralization restored liver inflammation and IRI in SB216763-treated mice. Gsk3β inactivation by IR was a self-regulatory mechanism in liver homeostasis, critically dependent on phosphoinositide 3 (PI3)-kinase activation, as administration of a PI3 kinase inhibitor, wortmannin, reduced Gsk3 phosphorylation and augmented liver damage. In vitro, IL-10 was critical for the suppression of pro-inflammatory gene programs by Gsk3 inhibition in bone marrow-derived macrophages in response to TLR4 stimulation.

CONCLUSION

Our novel findings document the key immune regulatory function of Gsk3β signaling in the pathophysiology of liver IRI, and provide a rationale to target Gsk3β as a refined therapeutic strategy to ameliorate liver IRI.

Potent Long-Term Cardioprotective Effects of Single Low-Dose Insulin-Like Growth Factor-1 Treatment Postmyocardial Infarction

Background—

Insulin-like growth factor-1 (IGF-1) is recognized as an important regulator of cardiac structure and cardiomyocyte homeostasis. The prosurvival and antiapoptotic effects of IGF-1 have been investigated in vitro and in rodent models of myocardial infarction (MI). However, the clinical application of IGF-1 has been hampered by dose-dependent side effects both acutely and during chronic administration. We hypothesized that single, low-dose IGF-1 (LD-IGF-1) administered locally and early in the reperfusion phase after acute MI in a large animal model would avoid significant side effects but would have prosurvival effects that would manifest in long-term structural and functional improvement after MI treatment.

Methods and Results—

Forty-four female Landrace pigs underwent intracoronary administration of LD-IGF-1 or saline 2 hours into the reperfusion phase of acute left anterior descending artery occlusion MI. In the area of infarction, IGF-1 receptor and signaling responses were activated at 30 minutes and cardiomyocyte cell death attenuated at 24 hours after LD-IGF-1 but not saline treatment. Hemodynamic and structural studies using pressure-volume loop, CT, and triphenyltetrazolium chloride analysis 2 months post-MI confirmed a marked reduction in infarct size, attenuation of wall thinning, and augmentation of wall motion in the LD-IGF-1-treated but not in the saline-treated animals. These regional structural benefits were associated with global reductions in left ventricular volumes and significant improvement in left ventricular systolic and diastolic function.

Conclusions—

One-time LD-IGF-1 effects potent acute myocardial salvage in a preclinical model of left anterior descending artery occlusive MI, extending to long-term benefits in MI size, wall structure, and function and underscoring its potential as an adjunctive therapeutic agent.

cAMP-guanine exchange factor protection from bile acid-induced hepatocyte apoptosis involves glycogen synthase kinase regulation of c-Jun NH2-terminal kinase

Cholestatic liver disorders are accompanied by the hepatic accumulation of cytotoxic bile acids that induce cell death. Increases in cAMP protect hepatocytes from bile acid-induced apoptosis by a cAMP-guanine exchange factor (cAMP-GEF)/phosphoinositide-3-kinase (PI3K)/Akt pathway. The aim of these studies was to identify the downstream substrate in this pathway and to determine at what level in the apoptotic cascade cytoprotection occurs. Since inhibitory phosphorylation of glycogen synthase kinase-3 (GSK) occurs downstream of PI3K/Akt and this phosphorylation has been implicated in cell survival, we conducted studies to determine whether GSK was downstream in cAMP-GEF/PI3K/Akt-mediated cytoprotection. Our results show that treatment of hepatocytes with the cAMP-GEF-specific analog, 4-(4-chlorophenylthio)-2'-O-methyladenosine-3',5'-cAMP, results in PI3K-dependent phosphorylation of GSK. Direct chemical inhibition of GSK in rat hepatocytes or human HUH7-NTCP cells with several structurally and functionally distinct inhibitors including bromoindirubin-3'-oxime (BIO), maleimides (SB216763, SB415286), thiadiazolidine derivatives, and LiCl attenuates apoptosis induced by glycochenodeoxycholate (GCDC). In addition, genetic silencing of the GSK β isoform with small interfering RNA attenuates GCDC apoptosis in HUH7-NTCP cells. Adenoviral inhibition of the Rap1 blocks both cAMP-GEF-mediated cytoprotection against GCDC-induced apoptosis and Akt/GSK3β phosphorylation. GCDC-induced phosphorylation of the proapoptotic kinase, c-Jun NH(2)-terminal kinase (JNK) is inhibited by GSK inhibition or cAMP-GEF activation. GCDC-induced apoptosis is accompanied by phosphorylation of the endoplasmic reticulum stress markers pIEF2α and IRE-1, and pretreatment with the cAMP-GEF analog or GSK inhibitors prevents this phosphorylation. Collectively, our results support the presence of a cAMP/cAMP-GEF/Rap1/PI3K/Akt/GSKβ survival pathway in hepatocytes that inhibits bile acid-induced JNK phosphorylation.

What makes the mitochondria a killer? Can we condition them to be less destructive?

Cardioprotection, such as preconditioning and postconditioning, has been shown to result in a significant reduction in cell death. Many of the signaling pathways activated by cardioprotection have been elucidated, but there is still a lack of understanding of the mechanisms by which these signaling pathways reduce cell death. Mitochondria have been reported to be an important player in many types of apoptotic and necrotic cell death. If mitochondria play an important role in cell death, then it seems reasonable to consider that cardioprotective mechanisms might act, at least in part, by opposing mitochondrial cell death pathways. One of the major mechanisms of cell death in ischemia-reperfusion is suggested to be the opening of a large conductance pore in the inner mitochondrial membrane, known as the mitochondrial permeability transition pore. Inhibition of this mitochondrial pore appears to be one of the major mechanisms by which cardioprotection reduces cell death. Cardioprotection activates a number of signaling pathways that reduce the level of triggers (reactive oxygen species and calcium) or enhances inhibitors of the mitochondrial permeability transition pore at the start of reperfusion. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.

Gα(i2)-mediated protection from ischaemic injury is modulated by endogenous RGS proteins in the mouse heart

AIMS

Regulator of G protein signalling (RGS) proteins act as molecular 'off switches' that terminate G protein signalling by catalyzing the hydrolysis of Gα-bound GTP to GDP. Many different Gα(i)-coupled receptors have been implicated in the cardioprotective effects of ischaemic preconditioning. However, the role of RGS proteins in modulating cardioprotection has not been previously investigated. We used mice that were homozygous (GS/GS) or heterozygous (GS/+) for a mutation in Gα(i2) rendering it RGS-insensitive (G184S) to determine whether interactions between endogenous RGS proteins and Gα(i2) modulate Gα(i)-mediated protection from ischaemic injury.

METHODS AND RESULTS

Langendorff-perfused mouse hearts were subjected to 30 min global ischaemia and 2 h reperfusion. Infarcts in GS/GS (14.5% of area at risk) and GS/+ (22.6% of AAR) hearts were significantly smaller than those of +/+ hearts (37.2% of AAR) and recovery of contractile function was significantly enhanced in GS/GS and GS/+ hearts compared with +/+ hearts. The cardioprotective phenotype was not reversed by wortmannin or U0126 but was reversed by 5-hydroxydecanoic acid and HMR 1098, indicating that RGS-insensitive Gα(i2) protects the heart through a mechanism that requires functional ATP-dependent potassium channels but does not require acute activation of extracellular-regulated kinase or Akt signalling pathways.

CONCLUSIONS

This is the first study to demonstrate that Gα(i2)-mediated cardioprotection is suppressed by RGS proteins. These data suggest that RGS proteins may provide novel therapeutic targets to protect the heart from ischaemic injury.

Clusterin protects H9c2 cardiomyocytes from oxidative stress-induced apoptosis via Akt/GSK-3β signaling pathway

Clusterin is a secretory glycoprotein, which is highly up-regulated in a variety of normal and injury tissues undergoing apoptosis including infarct region of the myocardium. Here, we report that clusterin protects H9c2 cardiomyocytes from H2O2-induced apoptosis by triggering the activation of Akt and GSK-3β. Treatment with H2O2 induces apoptosis of H9c2 cells by promoting caspase cleavage and cytochrome c release from mitochondria. However, co-treatment with clusterin reverses the induction of apoptotic signaling by H2O2, thereby recovers cell viability. The protective effect of clusterin on H2O2-induced apoptosis is impaired by PI3K inhibitor LY294002, which effectively suppresses clusterin-induced activation of Akt and GSK-3β. In addition, the protective effect of clusterin is independent on its receptor megalin, because inhibition of megalin has no effect on clusterin-mediated Akt/GSK-3β phosphoylation and H9c2 cell viability. Collectively, these results suggest that clusterin has a role protecting cardiomyocytes from oxidative stress and the Akt/GSK-3β signaling mediates anti-apoptotic effect of clusterin.

Neuronal calcium homeostasis and dysregulation

The calcium ion (Ca(2+)) is the main second messenger that helps to transmit depolarization status and synaptic activity to the biochemical machinery of a neuron. These features make Ca(2+) regulation a critical process in neurons, which have developed extensive and intricate Ca(2+) signaling pathways. High intensity Ca(2+) signaling necessitates high ATP consumption to restore basal (low) intracellular Ca(2+) levels after Ca(2+) influx through plasma membrane receptor and voltage-dependent ion channels. Ca(2+) influx may also lead to increased generation of mitochondrial reactive oxygen species (ROS). Impaired abilities of neurons to maintain cellular energy levels and to suppress ROS may impact Ca(2+) signaling during aging and in neurodegenerative disease processes. This review focuses on mitochondrial and endoplasmic reticulum Ca(2+) homeostasis and how they relate to synaptic Ca(2+) signaling processes, neuronal energy metabolism, and ROS generation. Also, the contribution of altered Ca(2+) signaling to neurodegeneration during aging will be considered. Advances in understanding the molecular regulation of Ca(2+) homeostasis and how it is perturbed in neurological disorders may lead to therapeutic strategies that modulate neuronal Ca(2+) signaling to enhance function and counteract disease processes.

Mechanisms of novel cardioprotective functions of CCN2/CTGF in myocardial ischemia-reperfusion injury

CCN2/connective tissue growth factor (CTGF), a CCN family matricellular protein repressed in healthy hearts after birth, is induced in heart failure of various etiologies. Multiple cellular and biological functions have been assigned to CCN2/CTGF depending on cellular context. However, the functions and mechanisms of action of CCN2/CTGF in the heart as well as its roles in cardiac physiology and pathophysiology remain unknown. Transgenic mice with cardiac-restricted overexpression of CTGF (Tg-CTGF) were generated and compared with nontransgenic littermate control (NLC) mice. Tg-CTGF mice displayed slightly lower cardiac mass and inconspicuous increase of myocardial collagen compared with NLC mice but no evidence of contractile dysfunction. Analysis of the myocardial transcriptome by DNA microarray revealed activation of several distinct gene programs in Tg-CTGF hearts involved in cardioprotection and growth inhibition. Indeed, Tg-CTGF mice subjected to ischemia-reperfusion injury by in situ transient occlusion of the left anterior descending coronary artery in vivo displayed reduced vulnerability with markedly diminished infarct size. These findings were recapitulated in isolated hearts perfused with recombinant human (h)CTGF before the ischemia-reperfusion procedure. Consistently, Tg-CTGF hearts, as well as isolated adult cardiac myocytes exposed to recombinant hCTGF, displayed enhanced phosphorylation and activity of the Akt/p70S6 kinase/GSK-3β salvage kinase pathway and induction of several genes with reported cardioprotective functions. Inhibition of Akt activities also prevented the cardioprotective phenotype of hearts from Tg-CTGF mice. This report provides novel evidence that CTGF confers cardioprotection by salvage phosphokinase signaling leading to inhibition of GSK-3β activities, activation of phospho-SMAD2, and reprogramming of gene expression.

Glucagon-like peptide-1-based therapies and cardiovascular disease: looking beyond glycaemic control

Type 2 diabetes mellitus is a well-established risk factor for cardiovascular disease (CVD). New therapeutic approaches have been developed recently based on the incretin phenomenon, such as the degradation-resistant incretin mimetic exenatide and the glucagon-like peptide-1 (GLP-1) analogue liraglutide, as well as the dipeptidyl dipeptidase (DPP)-4 inhibitors, such as sitagliptin, vildagliptin, saxagliptin, which increase the circulating bioactive GLP-1. GLP-1 exerts its glucose-regulatory action via stimulation of insulin secretion and glucagon suppression by a glucose-dependent way, as well as by weight loss via inhibition of gastric emptying and reduction of appetite and food intake. These actions are mediated through GLP-1 receptors (GLP-1Rs), although GLP-1R-independent pathways have been reported. Except for the pancreatic islets, GLP-1Rs are also present in several other tissues including central and peripheral nervous systems, gastrointestinal tract, heart and vasculature, suggesting a pleiotropic activity of GLP-1. Indeed, accumulating data from both animal and human studies suggest a beneficial effect of GLP-1 and its metabolites on myocardium, endothelium and vasculature, as well as potential anti-inflammatory and antiatherogenic actions. Growing lines of evidence have also confirmed these actions for exenatide and to a lesser extent for liraglutide and DPP-4 inhibitors compared with placebo or standard diabetes therapies. This suggests a potential cardioprotective effect beyond glucose control and weight loss. Whether these agents actually decrease CVD outcomes remains to be confirmed by large randomized placebo-controlled trials. This review discusses the role of GLP-1 on the cardiovascular system and addresses the impact of GLP-1-based therapies on CVD outcomes.

Altered fusion dynamics underlie unique morphological changes in mitochondria during hypoxia-reoxygenation stress

Functional states of mitochondria are often reflected in characteristic mitochondrial morphology. One of the most fundamental stress conditions, hypoxia-reoxygenation has been known to cause impaired mitochondrial function accompanied by structural abnormalities, but the underlying mechanisms need further investigation. Here, we monitored bioenergetics and mitochondrial fusion-fission in real time to determine how changes in mitochondrial dynamics contribute to structural abnormalities during hypoxia-reoxygenation. Hypoxia-reoxygenation resulted in the appearance of shorter mitochondria and a decrease in fusion activity. This fusion inhibition was a result of impaired ATP synthesis rather than Opa1 cleavage. A striking feature that appeared during hypoxia in glucose-free and during reoxygenation in glucose-containing medium was the formation of donut-shaped (toroidal) mitochondria. Donut formation was triggered by opening of the permeability transition pore or K(+) channels, which in turn caused mitochondrial swelling and partial detachment from the cytoskeleton. This then favored anomalous fusion events (autofusion and fusion at several sites among 2-3 mitochondria) to produce the characteristic donuts. Donuts effectively tolerate matrix volume increases and give rise to offspring that can regain ΔΨ(m). Thus, the metabolic stress during hypoxia-reoxygenation alters mitochondrial morphology by inducing distinct patterns of mitochondrial dynamics, which includes processes that could aid mitochondrial adaptation and functional recovery.

Platelet activating factor: the good and the bad in the ischemic/reperfused heart

The present review is focused on the dual role played by platelet-activating factor (PAF) in ischemia and reperfusion (I/R) injury of the heart. Although the involvement of PAF in the pathogenesis of myocardial reperfusion injury is well established, in the last few years it has emerged that very low concentrations of PAF exert cardioprotective effects, comparable to that afforded by ischemic preconditioning (IP). PAF is a potent phosphoglyceride involved in different pathophysiological conditions affecting the cardiovascular system, including the development of myocardial I/R injury. PAF is released from the I/R myocardium in concentrations (1-10 nmol/L) high enough to negatively modulate coronary circulation as well as electrical and contractile activities. PAF may act either directly, via generation of secondary mediators, or through the activation of inflammatory cells like platelets and polymorphonuclear neutrophils, which exacerbate postischemic myocardial injury. The effects of PAF are mediated through specific receptors (PAFRs) that belong to the superfamily of G protein-coupled receptors. Since cardiomyocytes not only produce PAF but also possess PAFRs, it is likely that PAF acts as an autocrine/paracrine mediator. Although the negative effects exerted by high concentrations of PAF are well established, several recent findings from our and other laboratories have demonstrated that very low concentrations (pmol/L) of PAF infused before ischemia induce cardioprotective effects similar to those afforded by IP, and that endogenous PAF production participates in the induction of IP itself. The IP-like action exerted by low concentrations of PAF is due to the activation/phosphorylation of kinases included in the reperfusion injury salvage kinase (RISK) pathway, such as protein kinase C, Akt/PkB and nitric oxide synthase. Together with the activation of mitochondrial K(ATP) channels, these events may allow prevention of mitochondrial permeability transition pores opening at reperfusion. Moreover, the nitric oxide-dependent S-nitrosylation of L-type Ca(2+) channels induced by PAF reduces intracellular Ca(2+) overload.

Reperfusion injury salvage kinase and survivor activating factor enhancement prosurvival signaling pathways in ischemic postconditioning: two sides of the same coin

The discovery of ischemic postconditioning (IPost) has rejuvenated the field of cardioprotection. As an interventional strategy to be applied at the onset of myocardial reperfusion, the transition of IPost from a bench-side curiosity to potential clinical therapy has been impressively rapid. Its existence also confirms the existence of lethal myocardial reperfusion injury in man, suggesting that 40%-50% of the final reperfused myocardial infarct may actually be due to myocardial reperfusion injury. Intensive analysis of the signal transduction pathways underlying IPost has identified similarities with the signaling pathways underlying its preischemic counterpart, ischemic preconditioning. In this article, the reperfusion injury salvage kinase pathway and the more recently described survivor activating factor enhancement pathway, two apparently distinct signaling pathways that actually interact to convey the IPost stimulus from the cell surface to the mitochondria, where many of the prosurvival and death signals appear to converge. The elucidation of the reperfusion signaling pathways underlying IPost may result in the identification of novel pharmacological targets for cardioprotection.

Blockade of electron transport during ischemia preserves bcl-2 and inhibits opening of the mitochondrial permeability transition pore

Myocardial ischemia damages the electron transport chain and augments cardiomyocyte death during reperfusion. To understand the relationship between ischemic mitochondrial damage and mitochondrial-driven cell death, the isolated perfused heart underwent global stop-flow ischemia with and without mitochondrial protection by reversible blockade of electron transport. Ischemic damage to electron transport depleted bcl-2 content and favored mitochondrial permeability transition (MPT). Reversible blockade of electron transport preserved bcl-2 content and attenuated calcium-stimulated mitochondrial swelling. Thus, the damaged electron transport chain leads to bcl-2 depletion and MPT opening. Chemical inhibition of bcl-2 with HA14-1 also dramatically increased mitochondrial swelling, augmented by exogenous H(2)O(2) stress, indicating that bcl-2 depleted mitochondria are poised to undergo MPT during the enhanced oxidative stress of reperfusion.

Volatile anesthetic post-treatment induces protection via inhibition of glycogen synthase kinase 3β in human neuron-like cells

Application of the volatile anesthetic isoflurane during the early phase of reperfusion reduces ischemic heart and brain injury (anesthetic post-conditioning). We hypothesize that inhibition of glycogen synthase kinase 3β (GSK3β), a protein whose activation can lead to cell death, participates in anesthetic post-conditioning-induced neuroprotection. SH-SY5Y cells, a human neuroblastoma cell line, were induced by retinoic acid to differentiate into terminal neuron-like cells. The cells were then subjected to a 1-h oxygen-glucose deprivation (OGD), a condition to simulate ischemia in vitro, and a 20-h simulated reperfusion. Isoflurane, sevoflurane or desflurane, three commonly used volatile anesthetics, were applied for 1 h during the early phase of simulated reperfusion. Cell injury was quantified by lactate dehydrogenase (LDH) release. Phospho-GSK3β at Ser9 and total GSK3β were quantified at 1 or 3 h after the OGD. OGD increased LDH release, suggesting that OGD induced cell injury. Post-treatment with isoflurane, sevoflurane or desflurane reduced this cell injury. This protection was apparent when 2% isoflurane was applied within 1 h after the onset of reperfusion. Isoflurane post-treatment also significantly increased the phosphorylation of GSK3β at Ser9 at 1 h after the OGD. GSK3β inhibitors reduced OGD and simulated reperfusion-induced LDH release. The combination of GSK3β inhibitors and isoflurane post-conditioning did not cause a greater protection than isoflurane post-conditioning alone. These results suggest that volatile anesthetic post-conditioning reduces OGD and simulated reperfusion-induced cell injury. Since phospho-GSK3β at Ser9 decreases GSK3β activity, our results suggest that volatile anesthetic post-conditioning in human neuron-like cells may be mediated by GSK3β inhibition.

Nuclear-encoded mitochondrial proteins and their role in cardioprotection

During myocardial ischemia/reperfusion, mitochondria are both a source and a target of injury. In cardioprotective maneuvers such as ischemic and pharmacological pre- and postconditioning mitochondria have a decisive role. Since about 99% of the mitochondrial proteins are encoded in the nucleus, deleterious and protective mitochondrial effects most likely comprise the import of cytosolic proteins. The present review therefore discusses the role of mitochondria in myocardial ischemia/reperfusion injury and protection from it, focusing on some cytosolic proteins, which are translocated into mitochondria before, during, or following ischemia/reperfusion. Both morphological and functional alterations are discussed at the level of the heart, the cardiomyocyte and/or the mitochondrion itself. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.

Hypertensive Hypertrophied Myocardium Is Vulnerable to Infarction and Refractory to Erythropoietin-Induced Protection

The objective of this study was to examine the hypothesis that hypertensive hypertrophy is vulnerable to infarction and defective in cytoprotective mechanisms by modification of intracellular signaling and mitochondrial proteins. Myocardial infarction was induced by 20-minute coronary occlusion/reperfusion in spontaneously hypertensive stroke-prone rats (SHR-SPs) and their controls (Wistar-Kyoto rats [WKYs]). Infarct size expressed as a percentage of area-at-risk was larger by 29% in SHR-SPs than in WKYs. Pretreatment with erythropoietin (EPO) significantly limited infarct size in WKYs but not in SHR-SPs. Ca 2+ retention capacity of mitochondria, an index of the threshold for opening of the mitochondrial permeability transition pore, on reperfusion was reduced in SHR-SPs compared with that in WKYs. Suppression of reactive oxygen species by N -(2-mercaptopropionyl)-glycine increased Ca 2+ retention capacity after reperfusion and limited infarct size in SHR-SPs to levels in WKYs. EPO induced phosphorylation of Akt, extracellular signal-related kinase, and glycogen synthase kinase-3β in the myocardium in both WKYs and SHR-SPs. EPO enhanced interaction of phospho-glycogen synthase kinase-3β and adenine nucleotide translocase on reperfusion in WKYs, although such an effect of EPO was not detected in SHR-SPs. The results suggest that enhanced opening of mitochondrial permeability transition pores by reactive oxygen species and modification of the signal downstream of phospho-glycogen synthase kinase-3β in the mitochondria underlie the increased vulnerability to infarction and the lack of anti-infarct tolerance by EPO, respectively, in hypertensive hypertrophied hearts.

Targeting GSK-3 family members in the heart: a very sharp double-edged sword

The GSK-3 family of serine/threonine kinases, which is comprised of two isoforms (α and β), was initially identified as a negative regulator of glycogen synthase, the rate limiting enzyme of glycogen synthesis [1,2]. In the 30 years since its initial discovery, the family has been reported to regulate a host of additional cellular processes and, consequently, disease states such as bipolar disorders, diabetes, inflammatory diseases, cancer, and neurodegenerative diseases including Alzheimer's Disease and Parkinson's Disease [3,4]. As a result, there has been intense interest on the part of the pharmaceutical industry in developing small molecule antagonists of GSK-3. Herein, we will review the roles played by GSK-3s in the heart, focusing primarily on recent studies that have employed global and tissue-specific gene deletion. We will highlight roles in various pathologic processes, including pressure overload and ischemic injury, focusing on some striking isoform-specific effects of the family. Due to space limitations and/or the relatively limited data in gene-targeted mice, we will not be addressing the family's roles in ischemic pre-conditioning or its many interactions with various pro- and anti-apoptotic factors. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure."

Roles of phospho-GSK-3β in myocardial protection afforded by activation of the mitochondrial K ATP channel

The aim of this study was to determine the roles of glycogen synthase kinase-3β (GSK-3β) in cardioprotection by activation of the mitochondrial ATP-sensitive K(+) channel (mK(ATP) channel). In isolated rat hearts, an mK(ATP) activator, diazoxide, and a GSK-3β inhibitor, SB216763, similarly limited infarct size and the combination of these agents did not afford further protection. The protection by pre-ischemic treatment with diazoxide was abolished by inhibition of protein kinase C-ε (PKC-ε) or phosphatidylinositol-3-kinase (PI3K) upon reperfusion. Infusion of a GSK-3β inhibitor (LiCl), but not diazoxide, during reperfusion limited infarct size. Inhibition of PKC-ε or PI3K did not affect the protection by LiCl. Diazoxide infusion alone did not induce GSK-3β phosphorylation. However, diazoxide infusion before ischemia increased mitochondrial phospho-GSK-3β level and reduced cyclophilin-D (CypD) binding to adenine nucleotide translocase (ANT) at 10 min after reperfusion. This diazoxide-induced GSK-3β phosphorylation was inhibited by blockade of the mK(ATP) channel before ischemia and by blockade of PKC-ε, PI3K or the adenosine A2b receptor at the time of reperfusion. Inhibition of GSK-3β by LiCl during reperfusion increased phospho-GSK-3β but had no significant effect on CypD-ANT binding. These results suggest that GSK-3β phosphorylation at the time of reperfusion by a PKC-ε, PI3K- and A2b receptor-dependent mechanism contributes to prevention of myocardial necrosis by pre-ischemic activation of the mK(ATP) channel. Inhibition of CypD-ANT interaction may contribute to mK(ATP)-induced myocardial protection, though it is not the sole mechanism of phospho-GSK-3β-mediated cytoprotection.

Elevated levels of activated NHE1 protect the myocardium and improve metabolism following ischemia/reperfusion injury

In the myocardium, the Na(+)/H(+) exchanger isoform 1 (NHE1) is a plasma membrane protein that regulates intracellular pH. Inhibition of NHE1 activity has been shown to be beneficial in cardiovascular disease. However, recent reports have suggested that elevation of NHE1 levels has beneficial effects in hearts subjected to ischemia/reperfusion. We determined if activated and non-activated NHE1 proteins have varying cardioprotective and metabolic effects with ischemia/reperfusion in the isolated perfused working mouse heart. We used transgenic mice hearts that specifically expressed wild type NHE1 (N-line) or activated NHE1 protein (K-line). Intact hearts 10-12 weeks of age were perfused under working conditions, with fatty acids and glucose present as substrates. Hearts were subjected to 30 min of aerobic perfusion, followed by 20 min of global no-flow ischemia and 40 min of aerobic reperfusion. We examined changes in contractility and substrate use and ATP levels. K-line hearts expressing activated NHE1, recovered to a much greater extent than N-line and control hearts recovering almost 75% of their preischemic function. In addition, K-line hearts had elevated fatty acid oxidation, increased glycolysis rates and elevated ATP levels relative to N-line mice or controls. An examination of kinase activation showed that there were no differences between controls and transgenics in ERK, p38, p90(rsk) or pGSK3β levels. The results demonstrate that elevated levels of NHE1 induce cardioprotection and alter cardiac metabolism. However, in the working heart model, with glucose and fatty acid as substrates, this required an activated NHE1 protein.

Cardioprotective PKG-independent NO signaling at reperfusion

Cell models of ischemic preconditioning (IPC) indicate nitric oxide (NO) is involved in protection accruing during reoxygenation but disagree whether it acts through PKG. Using a more relevant intact heart model, we studied isolated rabbit hearts subjected to 30-min coronary artery occlusion/120-min reperfusion. We previously found protection from PKG activator 8-(4-chlorophenylthio)-guanosine 3',5'-cyclic monophosphate (CPT-cGMP) at reperfusion was blocked by A(2b) adenosine receptor (A(2b)AR), ERK, or phosphatidylinositol 3-kinase (PI3-kinase) blockers. In this investigation A(2b)AR agonist BAY 60-6583 or CPT-cGMP at reperfusion reduced infarction comparably to IPC. Their protection was abrogated by N(ω)-nitro-l-arginine methyl ester (l-NAME), suggesting a PKG-independent NO synthase in IPC's mediator pathway downstream of PKG and A(2b)AR. NO donor S-nitroso-N-acetyl-d,l-penicillamine (SNAP) at reperfusion also protected. This protection was not blocked by PI3-kinase inhibitor wortmannin or ERK antagonist PD-98059, suggesting NO acted downstream of these kinases. Protection from SNAP was not affected by mitochondrial ATP-sensitive K(+) channel closer 5-hydroxydecanoate, PKC antagonist chelerythrine, reactive oxygen species scavenger N-2-mercaptopropionylglycine, or soluble guanylyl cyclase antagonist 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). Absence of ODQ effect indicated NO was acting independently of PKG. BAY 58-2667, a soluble guanylyl cyclase activator, was protective, and l-NAME blocked its infarct-sparing effect, indicating a second signaling event dependent on NO generation but independent of PKG. SB216763, a blocker of glycogen synthase kinase-3β (GSK-3β), decreased infarct size, and its infarct-sparing effect was not affected by l-NAME, suggesting GSK-3β acted downstream or independently of NO. Hence, NO signaling occurs in IPC's mediator pathway downstream of Akt and ERK, and its protection is independent of PKG.

Calcium-sensing receptor: a sensor and mediator of ischemic preconditioning in the heart

As a G protein-coupled receptor, the extracellular Ca(2+)-sensing receptor (CaSR) responds to changes not only in extracellular Ca(2+), but also to many other ligands. CaSR has been found to be expressed in the hearts and cardiovascular system. In this study, we confirmed that CaSR is expressed in mouse cardiomyocytes and showed that it is predominantly localized in caveolae. The goal of this study was to investigate whether CaSR plays a cardioprotective role in ischemic preconditioning (IPC). Hearts from C57BL/6J mice (male, 12-16 wk) were perfused in the Langendorff mode and subjected to the following treatments: 1) control perfusion; 2) perfusion with a specific CaSR antagonist, NPS2143; 3) IPC (four cycles of 5 min of global ischemia and 5 min of reperfusion); or 4) perfusion with NPS2143 before and during IPC. Following these treatments, hearts were subjected to 20 min of no-flow global ischemia and 120 min of reperfusion. Compared with control, IPC significantly improved postischemic left ventricular functional recovery and reduced infarct size. Although NPS2143 perfusion alone did not change the hemodynamic function and did not change the extent of postischemic injury, NPS2143 treatment abolished cardioprotection of IPC. Through immunoblot analysis, it was demonstrated that IPC significantly increased the levels of phosphorylated ERK1/2, AKT, and GSK-3β, which were also prevented by NPS2143 treatment. Taken together, the distribution of CaSR in caveolae along with NPS2143-blockade of IPC-induced cardioprotective signaling suggest that the activation of CaSR during IPC is cardioprotective by a process involving caveolae.

Mitochondrial reprogramming through cardiac oxygen sensors in ischaemic heart disease

Under hypoxic conditions, mitochondria can represent a threat to the cell because of their capacity to generate toxic reactive oxygen species (ROS). However, cardiomyocytes are equipped with an oxygen-sensing pathway that involves prolyl hydroxylase oxygen sensors and hypoxia-inducible factors (HIFs), which induces a tightly regulated programme to keep ischaemic mitochondrial activity under control. The aim of this review is to provide an update on the pathways leading to mitochondrial reprogramming, which occurs in the myocardium during ischaemia, with particular emphasis on those induced by HIF activation. We start by studying the mechanisms of mitochondrial damage during ischaemia and upon reperfusion, highlighting the importance of the formation of the mitochondrial permeability transition pore during reperfusion and its consequences for cardiomyocyte survival. Next, we analyse hypoxia-induced metabolic reprogramming through HIF and its important consequences for mitochondrial bioenergetics, as well as the phenomenon known as the hibernating myocardium. Subsequently, we examine the mechanisms underlying ischaemic preconditioning, focusing, in particular, on those that involve the HIF pathway, such as adenosine signalling, sub-lethal ROS generation, and nitric oxide production. Finally, the role of the mitochondrial uncoupling proteins in ischaemia tolerance is discussed.

A pore way to die: the role of mitochondria in reperfusion injury and cardioprotection

In addition to their normal physiological role in ATP production and metabolism, mitochondria exhibit a dark side mediated by the opening of a non-specific pore in the inner mitochondrial membrane. This mitochondrial permeability transition pore (MPTP) causes the mitochondria to breakdown rather than synthesize ATP and, if unrestrained, leads to necrotic cell death. The MPTP is opened in response to Ca2+ overload, especially when accompanied by oxidative stress, elevated phosphate concentration and adenine nucleotide depletion. These conditions are experienced by the heart and brain subjected to reperfusion after a period of ischaemia as may occur during treatment of a myocardial infarction or stroke and during heart surgery. In the present article, I review the properties, regulation and molecular composition of the MPTP. The evidence for the roles of CyP-D (cyclophilin D), the adenine nucleotide translocase and the phosphate carrier are summarized and other potential interactions with outer mitochondrial membrane proteins are discussed. I then review the evidence that MPTP opening mediates cardiac reperfusion injury and that MPTP inhibition is cardioprotective. Inhibition may involve direct pharmacological targeting of the MPTP, such as with cyclosporin A that binds to CyP-D, or indirect inhibition of MPTP opening such as with preconditioning protocols. These invoke complex signalling pathways to reduce oxidative stress and Ca2+ load. MPTP inhibition also protects against congestive heart failure in hypertensive animal models. Thus the MPTP is a very promising pharmacological target for clinical practice, especially once more specific drugs are developed.

Mitochondrially targeted anti-cancer agents

Cancer is an ever-increasing problem that is yet to be harnessed. Frequent mutations make this pathology very variable and, consequently, a considerable challenge. Intriguingly, mitochondria have recently emerged as novel targets for cancer therapy. A group of agents with anti-cancer activity that induce apoptosis by way of mitochondrial destabilisation, termed mitocans, have been a recent focus of research. Of these compounds, many are hydrophobic agents that associate with various sub-cellular organelles. Clearly, modification of such structures with mitochondria-targeting moieties, for example tagging them with lipophilic cations, would be expected to enhance their activity. This may be accomplished by the addition of triphenylphosphonium groups that direct such compounds to mitochondria, enhancing their activity. In this paper, we will review agents that possess anti-cancer activity by way of destabilizing mitochondria and their possible targets. We propose that mitochondrial targeting, in particular where the agent associates directly with the target, results in more specific and efficient anti-cancer drugs of potential high clinical relevance.

Glycogen synthase kinase-3 and p38 MAPK are required for opioid-induced microglia apoptosis

Opioids have been widely applied in clinics as one of the most potent pain relievers for centuries, but their abuse has deleterious physiological effects beyond addiction. We previously reported that opioids inhibit cell growth and trigger apoptosis in lymphocytes. However, the underlying mechanism by which microglia apoptosis in response to opioids is not yet known. In this study, we show that morphine induces microglia apoptosis and caspase-3 activation in an opioid-receptor dependent manner. Morphine decreased the levels of microglia phosphorylated Akt (p-Akt) and p-GSK-3β (glycogen synthase kinase-3 beta) in an opioid-receptor dependent manner. More interestingly, GSK-3β inhibitor SB216763 significantly increases morphine-induced apoptosis in both BV-2 microglia and mouse primary microglial cells. Moreover, co-treatment of microglia with SB216763 and morphine led to a significant synergistic effect on the level of phospho-p38 mitogen-activated protein kinase (MAPK). In addition, inhibition of p38 MAPK by its specific inhibitor SB203580 significantly inhibited morphine-induced apoptosis and caspase-3 activation. Taken together, our data clearly demonstrates that morphine-induced apoptosis in microglial cells, which is mediated via GSK-3β and p38 MAPK pathways.

Effect of pressure overload on cardioprotection via PI3K-Akt: comparison of postconditioning, insulin, and pressure unloading

BACKGROUND

Postconditioning (PC) and insulin exert cardioprotection by activating phosphatidylinositol-3 kinase (PI3K) signaling. Because pressure overload exacerbates ischemia-reperfusion (IR) injury, we tested the hypothesis that (i) pressure overload attenuates PC- and insulin-induced cardioprotection, an effect caused by reduced PI3K-Akt signaling and (ii) pressure unloading confers cardioprotection comparable to either PC or insulin.

METHODS

Infarct size (IS) and levels of relevant proteins (i.e., Akt, glycogen synthase kinase-3beta (GSK-3beta), 3'-phosphoinositide dependent kinase 1 (PDK1), phosphatase and tensin homolog on chromosome ten (PTEN)) were determined in hearts subjected to IR.

RESULTS

Pressure overload increased IS in association with changes in protein levels consistent with reduced PI3K-Akt signaling (i.e., ischemic reperfused vs. normoxic hearts). PC and insulin reduced IS but it was greater in hearts perfused at the higher, than the lower, pressure. Wortmannin (PI3K inhibitor) partially reversed PC-induced cardioprotection, with IS being greater in the high-pressure group. Pressure unloading during reperfusion caused the most marked reduction in IS whereas pressure loading abolished PC-induced cardioprotection. Nonetheless, the phospho-Akt/total Akt ratios and phospho-GSK-3beta levels were unaffected by perfusion pressure in insulin-treated or postconditioned hearts. Moreover, protein levels were similar in pressure-unloaded and pressure-loaded hearts.

CONCLUSIONS

Pressure overload reduces PI3K-Akt signaling following IR. However, a differential in PI3K-Akt signaling was not observed in ischemia-reperfused, insulin-treated, and postconditioned hearts, suggesting involvement of pathways other than PI3K-Akt for the effect of pressure on IS. Importantly, pressure unloading at reperfusion represents a novel and effective cardioprotective maneuver.

Ginsenoside Rb1 protects cardiomyocytes against CoCl2-induced apoptosis in neonatal rats by inhibiting mitochondria permeability transition pore opening

AIM

To investigate whether mitochondria permeability transition pore (mPTP) opening was involved in ginsenoside Rb1 (Gs-Rb1) induced anti-hypoxia effects in neonatal rat cardiomyocytes ex vivo.

METHODS

Cardiomyocytes were randomly divided into 7 groups: control group, hypoxia group (500 micromol/L CoCl(2)), Gs-Rb1 200 micromol/L group (CoCl(2) intervention+Gs-Rb1), wortmannin (PI3K inhibitor) 0.5 micromol/L group, wortmannin+Gs-Rb1 group, adenine 9-beta-D-arabinofuranoside (Ara A, AMPK inhibitor) 500 micromol/L group, and Ara A and Gs-Rb1 group. Apoptosis rate was determined by using flow cytometry. The opening of the transient mPTP was assessed by using co-loading with calcein AM and CoCl(2) in high conductance mode. Expression of GSK-3beta, cytochrome c, caspase-3 and poly (ADP-ribose) polymerase (PARP) was measured by using Western blotting. DeltaGSK-3beta was defined as the ratio of p-Ser9-GSK-3beta to total GSK-3beta.

RESULTS

CoCl(2) significantly stimulated mPTP opening and up-regulated the level of DeltaGSK-3beta. There was a statistically significant positive correlation between apoptosis rate and mPTP opening, between apoptosis rate and DeltaGSK-3beta, and between mPTP opening and DeltaGSK-3beta. Gs-Rb1 significantly inhibited mPTP opening induced by hypoxia (41.3%+/-2.0%, P<0.001) . Gs-Rb1 caused a 77.3%+/-3.2% reduction in the expression of GSK-3beta protein (P<0.001) and a significant increase of 1.182+/-0.007-fold (P=0.0001) in p-Ser9-GSK-3beta compared with control group. Wortmannin and Ara A significantly inhibited the effect of Gs-Rb1 on mPTP opening and DeltaGSK-3beta. Gs-Rb1 significantly decreased expression of cytochrome c (66.1%+/-1.7%, P=0.001), caspase-3 (56.5%+/-2.7%, P=0.001) and cleaved poly ADP-ribose polymerase (PARP) (57.9%+/-1.4%, P=0.001).

CONCLUSION

Gs-Rb1 exerted anti-hypoxia effect on neonatal rat cardiomyocytes by inhibiting GSK-3beta-mediated mPTP opening.

Role of the gap junction in ischemic preconditioning in the heart

The gap junction plays roles not only in electrical coupling of cardiomyocytes but also in intercellular transport of biologically active substances. Furthermore, the gap junction participates in decision making on cell survival versus cell death in various types of cells, and a part of reperfusion injury in the heart has been indicated to be gap junction mediated. The contribution of gap junction communication (GJC) and/or mitochondrial “hemichannels” to protective signaling during the trigger phase of ischemic preconditioning (IPC) is suggested by observations that IPC failed to protect the heart when GJC was blocked during IPC. Although ischemia suppresses both electrical and chemical GJC, chemical GJC persists for a considerable time after electrical GJC is lost. IPC facilitates the ischemia-induced suppression of chemical GJC, whereas IPC delays the reduction of electrical GJC after ischemia. The inhibition of GJC during sustained ischemia and reperfusion by GJC blockers mimics the effect of IPC on myocardial necrosis. IPC induces distinct effects on the interaction of connexin-43 with protein kinases, and the phosphorylation of connexin-43 at Ser368 by PKCε is a primary mechanism of inhibition of chemical GJC by IPC. Several lines of evidence support the notion that the modulation of GJC is a part of the mechanism of IPC-induced protection against myocardial necrosis and arrhythmias, though what percentage of IPC protection is attributable to the inhibition of GJC during ischemia-reperfusion still remains unclear.

The cardiomyocyte circadian clock: emerging roles in health and disease

Circadian misalignment has been implicated in the development of obesity, diabetes mellitus, and cardiovascular disease. Time-of-day-dependent synchronization of organisms with their environment is mediated by circadian clocks. This cell autonomous mechanism has been identified within all cardiovascular-relevant cell types, including cardiomyocytes. Recent molecular- and genetic-based studies suggest that the cardiomyocyte circadian clock influences multiple myocardial processes, including transcription, signaling, growth, metabolism, and contractile function. Following an appreciation of its physiological roles, the cardiomyocyte circadian clock has recently been linked to the pathogenesis of heart disease in response to adverse stresses, such as ischemia/reperfusion, in animal models. The purpose of this review is therefore to highlight recent advances regarding the roles of the cardiomyocyte circadian clock in both myocardial physiology and pathophysiology (ie, health and disease).

Signal transduction to the permeability transition pore

The permeability transition pore (PTP) is an inner mitochondrial membrane channel that has been thoroughly characterized functionally, yet remains an elusive molecular entity. The best characterized PTP-regulatory component, cyclophilin (CyP) D, is a matrix protein that favors pore opening. CyP inhibitors, CyP-D null animals, and in situ PTP readouts have established the role of PTP as an effector mechanism of cell death, and the growing definition of PTP signalling mechanisms. This review briefly covers the functional features of the PTP and the role played by its dysregulation in disease pathogenesis. Recent progress on PTP modulation by kinase/phosphatase signal transduction is discussed, with specific emphasis on hexokinase and on the Akt-ERK-GSK3 axis, which might modulate the PTP through CyP-D phosphorylation.

Cardioprotection by GSK-3 inhibition: role of enhanced glycogen synthesis and attenuation of calcium overload

AIMS

Glycogen synthase kinase-3 (GSK-3) is a multi-functional kinase that regulates signalling pathways affecting glycogen metabolism, protein synthesis, mitosis, and apoptosis. GSK-3 inhibition limits cardiac ischaemia-reperfusion (IR) injury, but mechanisms are not clearly defined. This study tested the hypothesis that acute GSK-3 inhibition stimulates glycogen synthesis, repartitions glucose away from glycolysis, reduces proton (H+) production from glucose metabolism, and attenuates intracellular Ca2+ (Ca2+(i)) overload.

METHODS AND RESULTS

In isolated perfused working rat hearts subjected to global ischaemia and reperfusion, the selective GSK-3 inhibitor, SB-216763 (SB, 3 micromol/L), when added either prior to ischaemia or at the onset of reperfusion, improved recovery of left-ventricular (LV) work. SB increased glycogen synthesis during reperfusion while glycolysis and H+ production were reduced. Rates of glucose and palmitate oxidation were improved by SB. Measurement of Ca2+(i) concentration by rapid acquisition indo-1 fluorescence imaging showed that SB, when added either prior to ischaemia or at the onset of reperfusion, reduced diastolic Ca2+(i) overload during reperfusion. In aerobic hearts depleted of glycogen by substrate-free perfusion to a level similar to that measured at the onset of reperfusion, SB accelerated glycogen synthesis and reduced glycolysis and H+ production independent of changes in LV work.

CONCLUSION

Our study indicates that reduction in H+ production by GSK-3 inhibition is an early and upstream event that lessens Ca2+(i) overload during ischaemia and early reperfusion independent of LV work which enhances the recovery of post-ischaemic LV function and that may ultimately contribute to previously observed reductions in cell death and infarction.

Endoplasmic reticulum stress in diabetic hearts abolishes erythropoietin-induced myocardial protection by impairment of phospho-glycogen synthase kinase-3beta-mediated suppression of mitochondrial permeability transition

OBJECTIVE

Alteration in endoplasmic reticulum (ER) stress in diabetic hearts and its effect on cytoprotective signaling are unclear. Here, we examine the hypothesis that ER stress in diabetic hearts impairs phospho-glycogen synthase kinase (GSK)-3beta-mediated suppression of mitochondrial permeability transition pore (mPTP) opening, compromising myocardial response to cytoprotective signaling.

RESEARCH DESIGN AND METHODS

A rat model of type 2 diabetes (OLETF) and its control (LETO) were treated with tauroursodeoxycholic acid (TUDCA) (100 mg . kg(-1) . day(-1) for 7 days), an ER stress modulator. Infarction was induced by 20-min coronary occlusion and 2-h reperfusion.

RESULTS

Levels of ER chaperones (GRP78 and GRP94) in the myocardium and level of nonphoshopho-GSK-3beta in the mitochondria were significantly higher in OLETF than in LETO rats. TUDCA normalized levels of GRP78 and GRP94 and mitochondrial GSK-3beta in OLETF rats. Administration of erythropoietin (EPO) induced phosphorylation of Akt and GSK-3beta and reduced infarct size (% risk area) from 47.4 +/- 5.2% to 23.9 +/- 3.5% in LETO hearts. However, neither phosphorylation of Akt and GSK-3beta nor infarct size limitation was induced by EPO in OLETF rats. The threshold for mPTP opening was significantly lower in mitochondria from EPO-treated OLETF rats than in those from EPO-treated LETO rats. TUDCA restored responses of GSK-3beta, mPTP opening threshold, and infarct size to EPO receptor activation in OLETF rats. There was a significant correlation between mPTP opening threshold and phospho-GSK-3beta-to-total GSK-3beta ratio in the mitochondrial fraction.

CONCLUSIONS

Disruption of protective signals leading to GSK-3beta phosphorylation and increase in mitochondrial GSK-3beta are dual mechanisms by which increased ER stress inhibits EPO-induced suppression of mPTP opening and cardioprotection in diabetic hearts.

Cardioprotection leads to novel changes in the mitochondrial proteome

It is proposed that ischemic preconditioning (PC) initiates signaling that converges on mitochondria and results in cardioprotection. The outcome of this signaling on mitochondrial enzyme complexes is yet to be understood. We therefore used proteomic methods to test the hypothesis that PC and pharmacological preconditioning similarly alter mitochondrial signaling complexes. Langendorff-perfused murine hearts were treated with the specific GSK-3 inhibitor AR-A014418 (GSK Inhib VIII) for 10 min or subjected to four cycles of 5-min ischemia-reperfusion (PC) before 20-min global ischemia and 120-min reperfusion. PC and GSK Inhib VIII both improved recovery of postischemic left ventricular developed pressure, decreased infarct size, and reduced lactate production during ischemia compared with their time-matched controls. We used proteomics to examine mitochondrial protein levels/posttranslational modifications that were common between PC and GSK Inhib VIII. Levels of cytochrome-c oxidase subunits Va and VIb, ATP synthase-coupling factor 6, and cytochrome b-c1 complex subunit 6 were increased while cytochrome c was decreased with PC and GSK Inhib VIII. Furthermore, the amount of cytochrome-c oxidase subunit VIb was found to be increased in PC and GSK Inhib VIII mitochondrial supercomplexes, which are comprised of complexes I, III, and IV. This result would suggest that changes in complex subunits associated with cardioprotection may affect supercomplex composition. Thus the ability of PC and GSK inhibition to alter the expression levels of electron transport complexes will have important implications for mitochondrial function.

Regulation and pharmacology of the mitochondrial permeability transition pore

The 'mitochondrial permeability transition', characterized by a sudden induced change of the inner mitochondrial membrane permeability for water as well as for small substances ( Collapse

Key Words

• adenine nucleotide translocator
• cyclophilin d
• mitochondrial voltage-dependent anion channel
• hexokinase
• creatine kinase
• mitochondrial peripheral benzodiazepine receptor
• bcl-2
• glycogen synthase kinase-3β

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MESH Headings

• Adenine Nucleotide Translocator 1/metabolism
• Animals
• Cardiovascular Agents/pharmacology
• Creatine Kinase, Mitochondrial Form/metabolism
• Peptidyl-Prolyl Isomerase F
• Cyclophilins/metabolism
• Hexokinase/metabolism
• Humans
• Lipid Metabolism
• Membrane Potential, Mitochondrial
• Mitochondria, Heart/drug effects
• Mitochondria, Heart/metabolism
• Mitochondrial Membrane Transport Proteins/chemistry
• Mitochondrial Membrane Transport Proteins/drug effects
• Mitochondrial Membrane Transport Proteins/genetics
• Mitochondrial Membrane Transport Proteins/metabolism
• Mitochondrial Permeability Transition Pore
• Myocardium/metabolism
• Phosphates/metabolism
• Receptors, GABA-A/metabolism
• Voltage-Dependent Anion Channels/metabolism

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Grants

• Intramural NIH HHS

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Affiliation(s)

Dmitry B. Zorov
Magdalena Juhaszova
Yael Yaniv
H. Bradley Nuss
Su Wang
Steven J. Sollott Laboratory of Cardiovascular Science, Gerontology Research Center, Box 13, Intramural Research Program, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224-6825, USA

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