Effects of glycogen synthase kinase-3β activity inhibition on cognitive, behavioral, and hippocampal ultrastructural deficits in adulthood associated with adolescent methamphetamine exposure

Objective

Glycogen synthase kinase-3β (GSK3β) has been implicated in the maintenance of synaptic plasticity, memory process, and psychostimulant-induced behavioral effects. Hyperactive GSK3β in the Cornu Ammonis 1 (CA1) subregion of the dorsal hippocampus (DHP) was associated with adolescent methamphetamine (METH) exposure-induced behavioral and cognitive deficits in adulthood. This study aimed to evaluate the possible therapeutic effects of GSK3β inhibition in adulthood on adolescent METH exposure-induced long-term neurobiological deficits.

Methods

Adolescent male mice were treated with METH from postnatal day (PND) 45-51. In adulthood, three intervention protocols (acute lithium chloride systemic administration, chronic lithium chloride systemic administration, and chronic SB216763 administration within CA1) were used for GSK3β activity inhibition. The effect of GSK3β intervention on cognition, behavior, and GSK3β activity and synaptic ultrastructure in the DHP CA1 subregion were detected in adulthood.

Results

In adulthood, all three interventions reduced adolescent METH exposure-induced hyperactivity (PND97), while only chronic systemic and chronic within CA1 administration ameliorated the induced impairments in spatial (PND99), social (PND101) and object (PND103) recognition memory. In addition, although three interventions reversed the aberrant GSK3β activity in the DHP CA1 subregion (PND104), only chronic systemic and chronic within CA1 administration rescued adolescent METH exposure-induced synaptic ultrastructure changes in the DHP CA1 subregion (PND104) in adulthood.

Conclusion

Rescuing synaptic ultrastructural abnormalities in the dHIP CA1 subregion by chronic administration of a GSK3β inhibitor may be a suitable therapeutic strategy for the treatment of behavioral and cognitive deficits in adulthood associated with adolescent METH abuse.

Cariporide Attenuates Doxorubicin-Induced Cardiotoxicity in Rats by Inhibiting Oxidative Stress, Inflammation and Apoptosis Partly Through Regulation of Akt/GSK-3β and Sirt1 Signaling Pathway

Background: Doxorubicin (DOX) is a potent chemotherapeutic agent with limited usage due to its cumulative cardiotoxicity. The Na⁺/H⁺ exchanger isoform 1 (NHE1) is a known regulator of oxidative stress, inflammation, and apoptosis. The present study was designed to investigate the possible protective effect of cariporide (CAR), a selective inhibitor of NHE1, against DOX-induced cardiotoxicity in rats.

Methods: Male Sprague-Dawley rats were intraperitoneally injected with DOX to induce cardiac toxicity and CAR was given orally for treatment. The injured H9c2 cell model was established by incubation with DOX in vitro. Echocardiography, as well as morphological and ultra-structural examination were performed to evaluate cardiac function and histopathological changes. The biochemical parameters were determined according to the manufacturer’s guideline of kits. ROS were assessed by using an immunofluorescence assay. The serum levels and mRNA expressions of inflammatory cytokines were measured by using ELISA or qRT-PCR. Cardiac cell apoptosis and H9c2 cell viability were tested by TUNEL or MTT method respectively. The protein expressions of Cleaved-Caspase-3, Bcl-2, Bax, Akt, GSK-3β, and Sirt1 were detected by western blot.

Results: Treatment with CAR protected against DOX-induced body weight changes, impairment of heart function, leakage of cardiac enzymes, and heart histopathological damage. In addition, CAR significantly attenuated oxidative stress and inhibited the levels and mRNA expressions of inflammatory cytokines (TNF-α, IL-6, IL-18, and IL-1β), which were increased by DOX treatment. Moreover, CAR significantly suppressed myocardial apoptosis and Cleaved-Caspase-3 protein expression induced by DOX, which was in agreement with the increased Bcl-2/Bax ratio. Also, DOX suppressed phosphorylation of Akt and GSK-3β, which was significantly reversed by administration of CAR. Furthermore, CAR treatment prevented DOX-induced down-regulation of Sirt1 at the protein level in vitro and in vivo. Finally, Sirt1 inhibitor reversed the protective effects of CAR, as evidenced by reduced cell viability and Sirt1 protein expression in vitro.

Conclusion: Taken together, we provide evidence for the first time in the current study that CAR exerts potent protective effects against DOX-induced cardiotoxicity in rats. This cardio-protective effect is attributed to suppressing oxidative stress, inflammation, and apoptosis, at least in part, through regulation of Akt/GSK-3β and Sirt1 signaling pathway, which has not been reported to date.

Serine mutations in overexpressed Hsp27 abrogate the protection against doxorubicin-induced p53-dependent cardiac apoptosis in mice

Small heat shock proteins (sHsps) protect the heart from chemotherapeutics-induced heart failure by inhibiting p53-dependent apoptosis. However, mechanism of such protection has not been elucidated yet. Here we test a hypothesis that serine phosphorylation of sHsps is essential to inhibit the doxorubicin-induced and p53-dependent apoptotic pathway. Three transgenic mice (TG) lines with cardiomyocyte-specific overexpression of human heat shock protein 27 (hHsp27), namely, wild-type [myosin heavy chain (MHC)-hHsp27], S82A single mutant [MHC-mut-hHsp27(S82A)], and trimutant [MHC-mut-hHsp27(S15A/S78A/S82A)] were generated. TG mice were treated with Dox (6 mg/kg body wt; once in a week; 4 wk) along with age-matched nontransgenic (non-TG) controls. The Dox-treated MHC-hHsp27 mice showed improved survival and cardiac function (both MRI and echocardiography) in terms of contractility [ejection fraction (%EF)] and left ventricular inner diameter (LVID) compared with the Dox-treated non-TG mice. However, both MHC-mut-hHsp27(S82A) and MHC-mut-hHsp27(S15A/S78A/S82A) mutants overexpressing TG mice did not show such a cardioprotection. Furthermore, transactivation of p53 was found to be attenuated only in Dox-treated MHC-hHsp27 mice-derived cardiomyocytes in vitro, as low p53 was detected in the nuclei, not in mutant hHsp27 overexpressing cardiomyocytes. Similarly, only in MHC-hHsp27 overexpressing cardiomyocytes, low Bax, higher mechanistic target of rapamycin (mTOR) phosphorylation, and low apoptotic poly(ADP-ribose) polymerase-1 (PARP-1) cleavage (89 kDa fragment) were detected. Pharmacological inhibition of p53 was more effective in mutant TG mice compared with MHC-hHsp27 mice. We conclude that phosphorylation of overexpressed Hsp27 at S82 and its association with p53 are essential for the cardioprotective effect of overexpressed Hsp27 against Dox-induced dilated cardiomyopathy. Only phosphorylated Hsp27 protects the heart by inhibiting p53 transactivation.NEW & NOTEWORTHY Requirement of serine phosphorylation in Hsp27 for cardioprotective effect against Dox is tested in various mutants overexpressing mice. Cardioprotective effect was found to be compromised in Hsp27 serine mutants overexpressed mice compared with wild-type overexpressing mice. These results indicate that cancer patients, who carry these mutations, may have higher risk of aggravated cardiomyopathy on treated with cardiotoxic chemotherapeutics such as doxorubicin.

Antioxidant Approach as a Cardioprotective Strategy in Chemotherapy-Induced Cardiotoxicity

Significance: Chemotherapy-induced cardiotoxicity (CTX) has been associated with redox signaling imbalance. In fact, redox reactions are crucial for normal heart physiology, whereas excessive oxidative stress can cause cardiomyocyte structural damage. Recent Advances: An antioxidant approach as a cardioprotective strategy in this setting has shown encouraging results in preventing anticancer drug-induced CTX. Critical Issues: In fact, traditional heart failure drugs as well as many other compounds and nonpharmacological strategies, with a partial effect in reducing oxidative stress, have been shown to counterbalance chemotherapy-induced CTX in this setting to some extent. Future Directions: Given the various pathways of toxicity involved in different chemotherapeutic schemes, interactions with redox balance need to be fine-tuned and a personalized cardioprotective approach seems to be required.

EPO and EPO-Receptor System as Potential Actionable Mechanism for the Protection of Brain and Heart in Refractory Epilepsy and SUDEP

The most important activity of erythropoietin (EPO) is the regulation of erythrocyte production by activation of the erythropoietin receptor (EPO-R), which triggers the activation of anti-apoptotic and proliferative responses of erythroid progenitor cells. Additionally, to erythropoietic EPO activity, an antiapoptotic effect has been described in a wide spectrum of tissues. EPO low levels are found in the central nervous system (CNS), while EPO-R is expressed in most CNS cell types. In spite of EPO-R high levels expressed during the hypoxicischemic brain, insufficient production of endogenous cerebral EPO could be the cause of determined circuit alterations that lead to the loss of specific neuronal populations. In the heart, high EPO-R expression in cardiac progenitor cells appears to contribute to myocardial regeneration under EPO stimulation. Several lines of evidence have linked EPO to an antiapoptotic role in CNS and in heart tissue. In this review, an antiapoptotic role of EPO/EPO-R system in both brain and heart under hypoxic conditions, such as epilepsy and sudden death (SUDEP) has been resumed. Additionally, their protective effects could be a new field of research and a novel therapeutic strategy for the early treatment of these conditions and avoid SUDEP.

PI3Kα Pathway Inhibition With Doxorubicin Treatment Results in Distinct Biventricular Atrophy and Remodeling With Right Ventricular Dysfunction

Background

Cancer therapies inhibiting PI3Kα (phosphoinositide 3‐kinase‐α)–dependent growth factor signaling, including trastuzumab inhibition of HER2 (Human Epidermal Growth Factor Receptor 2), can cause adverse effects on the heart. Direct inhibition of PI3Kα is now in clinical trials, but the effects of PI3Kα pathway inhibition on heart atrophy, remodeling, and function in the context of cancer therapy are not well understood.

Method and Results

Pharmacological PI3Kα inhibition and heart‐specific genetic deletion of p110α, the catalytic subunit of PI3Kα, was characterized in conjunction with anthracycline (doxorubicin) treatment in female murine models. Biventricular changes in heart morphological characteristics and function were analyzed, with molecular characterization of signaling pathways. Both PI3Kα inhibition and anthracycline therapy promoted heart atrophy and a combined effect of distinct right ventricular dilation, dysfunction, and cardiomyocyte remodeling in the absence of pulmonary arterial hypertension. Congruent findings of right ventricular dilation and dysfunction were seen with pharmacological and genetic suppression of PI3Kα signaling when combined with doxorubicin treatment. Increased p38 mitogen‐activated protein kinase activation was mechanistically linked to heart atrophy and correlated with right ventricular dysfunction in explanted failing human hearts.

Conclusions

The PI3Kα pathway promotes heart atrophy in mice. The right ventricle is specifically at risk for dilation and dysfunction in the setting of PI3K inhibition in conjunction with chemotherapy. Inhibition of p38 mitogen‐activated protein kinase is a proposed therapeutic target to minimize this mode of cardiotoxicity.

Effects of BCc1 nanoparticle and its mixture with doxorubicin on survival of murine 4T1 tumor model

Background: Our previous findings showed that BCc1, a nanoparticle designed based on nanochelating technology, can be considered a new anti-cancer nanoparticle if confirmed by complementary studies.

Goal: In the present study, we investigated the effects of the BCc1 nanoparticle alone on some gene expressions influencing the apoptosis pathway, and also the effect of the mixture of BCc1 nanoparticle and doxorubicin on survival.

Method: Using an in vitro study, the effects of the BCc1 nanoparticle on Bax, Bcl2, p53, Caspase7 and p21 gene expressions were assessed after a 24-h treatment using real-time PCR in MCF-7 and MEFs; in addition, using an in vivo study, 4T1 tumor-bearing female Balb/c mice were treated with different doses of the BCc1 nanoparticle and doxorubicin alone and together and then their mean and median survival was evaluated.

Result: The results showed that the BCc1 nanoparticle increased gene expressions of RB, p53, Caspase7, p21, and Bax and decreased gene expressions of Bcl2 in MCF-7 significantly, but no change was observed in MEFs expressions. The findings revealed that the BCc1 nanoparticle, when used orally, had the highest mean and median survival time. A mixture of a high dose of the BCc1 nanoparticle (1 mg/kg) and a low dose of doxorubicin (0.1 mg/kg) showed synergistic effects on enhanced life span, while doxorubicin dose was prescribed approximately 50 times less than the murine applicable dose (5 mg/kg).

Conclusion: Our results demonstrated that the BCc1 nanoparticle not only has the potential to become a novel nanomedicine for cancer therapy, but it can also provide the basis of a new medicine for cancer management when mixed with a lower applicable dose of doxorubicin.

Insights into Doxorubicin-induced Cardiotoxicity: Molecular Mechanisms, Preventive Strategies, and Early Monitoring

Doxorubicin (DOX) is one of the most effective anticancer drugs to treat various forms of cancers; however, its therapeutic utility is severely limited by its associated cardiotoxicity. Despite the enormous amount of research conducted in this area, the exact molecular mechanisms underlying DOX toxic effects on the heart are still an area that warrants further investigations. In this study, we reviewed literature to gather the best-known molecular pathways related to DOX-induced cardiotoxicity (DIC). They include mechanisms dependent on mitochondrial dysfunction such as DOX influence on the mitochondrial electron transport chain, redox cycling, oxidative stress, calcium dysregulation, and apoptosis pathways. Furthermore, we discuss the existing strategies to prevent and/or alleviate DIC along with various techniques available for therapeutic drug monitoring (TDM) in cancer patients treated with DOX. Finally, we propose a stepwise flowchart for TDM of DOX and present our perspective at curtailing this deleterious side effect of DOX.

Evaluation of selenium nanoparticles and doxorubicin effect against hepatocellular carcinoma rat model cytogenetic toxicity and DNA damage

The present study aimed to demonstrate the potent role of nanoselenium and Doxorubicin in retrogression of genotoxicity induced in hepatocellular carcinoma rat model by studying chromosomal aberration, micronuclei formation, DNA fragmentation as well as comet assay. Male rats hepatocellular carcinoma model were treated with Se-Nanoparticles, Doxurobicin (DOX) and the combination of both. The results revealed the protective effect of nanoselenium, Doxorubicin and their combination on bone marrow cytogenetic toxicity by decreasing chromosomal aberrations and micronuclei formation as well as their effects on rat's liver by decreasing DNA damage. Nevertheless, the treatment with nanoselenium either alone or in combination with Doxorubicin was more effective than treatment with doxorubicin alone.

HDL protects against doxorubicin-induced cardiotoxicity in a scavenger receptor class B type 1-, PI3K-, and Akt-dependent manner

Doxorubicin is a widely used chemotherapeutic with deleterious cardiotoxic side effects. HDL has been shown to protect cardiomyocytes in vitro against doxorubicin-induced apoptosis. Scavenger receptor class B type 1 (SR-B1), a high-affinity HDL receptor, mediates cytoprotective signaling by HDL through Akt. Here, we assessed whether increased HDL levels protect against doxorubicin-induced cardiotoxicity in vivo and in cardiomyocytes in culture and explored the intracellular signaling mechanisms involved, particularly the role of SR-B1. Transgenic mice with increased HDL levels through overexpression of human apolipoprotein A1 (apoA1^Tg/Tg) and wild-type mice (apoA1^+/+) with normal HDL levels were treated repeatedly with doxorubicin. After treatment, apoA1^+/+ mice displayed cardiac dysfunction, as evidenced by reduced left ventricular end-systolic pressure and +dP/d t, and histological analysis revealed cardiomyocyte atrophy and increased cardiomyocyte apoptosis after doxorubicin treatment. In contrast, apoA1^Tg/Tg mice were protected against doxorubicin-induced cardiac dysfunction and cardiomyocyte atrophy and apoptosis. When SR-B1 was knocked out, however, overexpression of apoA1 did not protect against doxorubicin-induced cardiotoxicity. Using primary neonatal mouse cardiomyocytes and human immortalized ventricular cardiomyocytes in combination with genetic knockout, inhibitors, or siRNA-mediated knockdown, we demonstrated that SR-B1 is required for HDL-mediated protection of cardiomyocytes against doxorubicin-induced apoptosis in vitro via a pathway involving phosphatidylinositol 3-kinase and Akt1/2. Our findings provide proof of concept that raising apoA1 to supraphysiological levels can dramatically protect against doxorubicin-induced cardiotoxicity via a pathway that is mediated by SR-B1 and involves Akt1/2 activation in cardiomyocytes. NEW & NOTEWORTHY We have identified an important role for the scavenger receptor class B type 1 in facilitating high-density lipoprotein-mediated protection of cardiomyocytes against stress-induced apoptosis and shown that increasing plasma high-density lipoprotein protects against the deleterious side effects of the chemotherapeutic and cardiotoxic drug doxorubicin.

Erythropoietin activates SIRT1 to protect human cardiomyocytes against doxorubicin-induced mitochondrial dysfunction and toxicity

The hormone erythropoietin (EPO) has been demonstrated to protect against chemotherapy drug doxorubicin (DOX)-induced cardiotoxicity, but the underlying mechanism remains obscure. We hypothesized that silent mating type information regulation 2 homolog 1 (SIRT1), an NAD⁺-dependent protein deacetylase that activates peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), plays a crucial role in regulating mitochondrial function and mediating the beneficial effect of EPO. Our study in human cardiomyocyte AC16 cells showed that DOX-induced cytotoxicity and mitochondrial dysfunction, as manifested by decreased mitochondrial DNA (mtDNA) copy number, mitochondrial membrane potential, and increased mitochondrial superoxide accumulation, can be mitigated by EPO pretreatment. EPO was found to upregulate SIRT1 activity and protein expression to reverse DOX-induced acetylation of PGC-1α and suppression of a suite of PGC-1α-activated genes involved in mitochondrial function and biogenesis, such as nuclear respiratory factor-1 (NRF1), mitochondrial transcription factor A (TFAM), citrate synthase (CS), superoxide dismutase 2 (SOD2), cytochrome c oxidase IV (COXIV), and voltage-dependent anion channel (VDAC). Silencing of SIRT1 via small RNA interference sensitized AC16 cells to DOX-induced cytotoxicity and reduction in mtDNA copy number. Although with SIRT1 silenced, EPO could reverse to some extent DOX-induced mitochondrial superoxide accumulation, loss of mitochondrial membrane potential and ATP depletion, it failed to normalize protein expression of PGC-1α and its downstream genes. Taken together, our results indicated that EPO may activate SIRT1 to enhance mitochondrial function and protect against DOX-induced cardiotoxicity.

Hydrogen sulfide protects H9c2 cardiac cells against doxorubicin-induced cytotoxicity through the PI3K/Akt/FoxO3a pathway

Doxorubicin (DOX) is an efficient drug used in cancer therapy that also produces reactive oxygen species (ROS) that induces severe cytotoxicity, which limits its clinical application. Hydrogen sulfide (H2S), a novel gasotransmitter, has been shown to exert cardioprotective effects. The present study aimed to determine whether exogenous H2S protects H9c2 cardiac cells against DOX-induced cytotoxicity and whether these protective effects are mediated through the PI3K/Akt/FoxO3a pathway. The H9c2 cardiac cells were exposed to 5 µM DOX for 24 h to establish a model of DOX-induced cardiotoxicity. The results showed that the treatment of H9c2 cardiac cells with sodium hydrosulfide (NaHS) for 30 min prior to DOX exposure markedly attenuated the phosphorylation of Akt and FoxO3a. Notably, pre-treatment of the H9c2 cells with NaHS significantly attenuated the nuclear localization of FoxO3a as well as the apoptosis of H9c2 cells induced by DOX. The treatment of H9c2 cells with N-acetyl-L-cysteine (NAC), a scavenger of ROS, prior to DOX exposure, also markedly increased the phosphorylation of Akt and FoxO3a which was inhibited by DOX alone. Furthermore, pre-treatment with LY294002, a selective inhibitor of PI3K/Akt, reversed the protective effect of H2S against DOX-induced injury of cardiomyocytes, as demonstrated by an increased number of apoptotic cells, a decrease in cell viability and the reduced phosphorylation of Akt and FoxO3a. These findings suggested that exogenous H2S attenuates DOX-induced cytotoxic effects in H9c2 cardiac cells through the PI3K/Akt/FoxO3a pathway.

Irx3 is required for postnatal maturation of the mouse ventricular conduction system

The ventricular conduction system (VCS) orchestrates the harmonious contraction in every heartbeat. Defects in the VCS are often associated with life-threatening arrhythmias and also promote adverse remodeling in heart disease. We have previously established that the Irx3 homeobox gene regulates rapid electrical propagation in the VCS by modulating the transcription of gap junction proteins Cx40 and Cx43. However, it is unknown whether other factors contribute to the conduction defects observed in Irx3 knockout (Irx3(-/-)) mice. In this study, we show that during the early postnatal period, Irx3(-/-) mice develop morphological defects in the VCS which are temporally dissociated from changes in gap junction expression. These morphological defects were accompanied with progressive changes in the cardiac electrocardiogram including right bundle branch block. Hypoplastic VCS was not associated with increased apoptosis of VCS cardiomyocytes but with a lack of recruitment and maturation of ventricular cardiomyocytes into the VCS. Computational analysis followed by functional verification revealed that Irx3 promotes VCS-enriched transcripts targeted by Nkx2.5 and/or Tbx5. Altogether, these results indicate that, in addition to ensuring the appropriate expression of gap junctional channels in the VCS, Irx3 is necessary for the postnatal maturation of the VCS, possibly via its interactions with Tbx5 and Nkx2.5.

Insulin Protects Cardiac Myocytes from Doxorubicin Toxicity by Sp1-Mediated Transactivation of Survivin

Insulin inhibits ischemia/reperfusion-induced myocardial apoptosis through the PI3K/Akt/mTOR pathway. Survivin is a key regulator of anti-apoptosis against doxorubicin-induced cardiotoxicity. Insulin increases survivin expression in cardiac myocytes to mediate cytoprotection. However, the mechanism by which survivin mediates the protective effect of insulin against doxorubicin-associated injury remains to be determined. In this study, we demonstrated that pretreatment of H9c2 cardiac myocytes with insulin resulted in a significant decrease in doxorubicin-induced apoptotic cell death by reducing cytochrome c release and caspase-3 activation. Doxorubicin-induced reduction of survivin mRNA and protein levels was also significantly perturbed by insulin pretreatment. Reducing survivin expression with survivin siRNA abrogated insulin-mediated inhibition of caspase-3 activation, suggesting that insulin signals to survivin inhibited caspase-3 activation. Interestingly, pretreatment of H9c2 cells with insulin or MG132, a proteasome inhibitor, inhibited doxorubicin-induced degradation of the transcription factor Sp1. ChIP assay showed that pretreatment with insulin inhibited doxorubicin-stimulated Sp1 dissociation from the survivin promoter. Finally using pharmacological inhibitors of the PI3K pathway, we showed that insulin-mediated activation of the PI3K/Akt/mTORC1 pathway prevented doxorubicin-induced proteasome-mediated degradation of Sp1. Taken together, insulin pretreatment confers a protective effect against doxorubicin-induced cardiotoxicity by promoting Sp1-mediated transactivation of survivin to inhibit apoptosis. Our study is the first to define a role for survivin in cellular protection by insulin against doxorubicin-associated injury and show that Sp1 is a critical factor in the transcriptional regulation of survivin.

Kv4.3-Encoded Fast Transient Outward Current Is Presented in Kv4.2 Knockout Mouse Cardiomyocytes

Gradients of the fast transient outward K⁺ current (I_to,f) contribute to heterogeneity of ventricular repolarization in a number of species. Cardiac I_to,f levels and gradients change notably with heart disease. Human cardiac I_to,f appears to be encoded by the Kv4.3 pore-forming α-subunit plus the auxiliary KChIP2 β-subunit while mouse cardiac I_to,f requires Kv4.2 and Kv4.3 α-subunits plus KChIP2. Regional differences in cardiac I_to,f are associated with expression differences in Kv4.2 and KChIP2. Although I_to,f was reported to be absent in mouse ventricular cardiomyocytes lacking the Kv4.2 gene (Kv4.2-/-) when short depolarizing voltage pulses were used to activate voltage-gated K⁺ currents, in the present study, we showed that the use of long depolarization steps revealed a heteropodatoxin-sensitive I_to,f (at ~40% of the wild-type levels). Immunohistological studies further demonstrated membrane expression of Kv4.3 in Kv4.2-/- cardiomyocytes. Transmural I_to,f gradients across the left ventricular wall were reduced by ~3.5-fold in Kv4.2-/- heart, compared to wild-type. The I_to,f gradient in Kv4.2-/- hearts was associated with gradients in KChIP2 mRNA expression while in wild-type there was also a gradient in Kv4.2 expression. In conclusion, we found that Kv4.3-based I_to,f exists in the absence of Kv4.2, although with a reduced transmural gradient. Kv4.2-/- mice may be a useful animal model for studying Kv4.3-based I_to,f as observed in humans.

Phosphatidylinositol-3,4,5-triphosphate and cellular signaling: implications for obesity and diabetes

Phosphatidylinositol-3,4,5-triphosphate (PtdIns(3,4,5)P₃) is one of the most important phosphoinositides and is capable of activating a wide range of proteins through its interaction with their specific binding domains. Localization and activation of these effector proteins regulate a number of cellular functions, including cell survival, proliferation, cytoskeletal rearrangement, intracellular vesicle trafficking, and cell metabolism. Phosphoinositides have been investigated as an important agonist-dependent second messenger in the regulation of diverse physiological events depending upon the phosphorylation status of their inositol group. Dysregulation in formation as well as metabolism of phosphoinositides is associated with various pathophysiological disorders such as inflammation, allergy, cardiovascular diseases, cancer, and metabolic diseases. Recent studies have demonstrated that the impaired metabolism of PtdIns(3,4,5)P₃ is a prime mediator of insulin resistance associated with various metabolic diseases including obesity and diabetes. This review examines the current status of the role of PtdIns(3,4,5)P₃ signaling in the regulation of various cellular functions and the implications of dysregulated PtdIns(3,4,5)P₃ signaling in obesity, diabetes, and their associated complications.

Erythropoietin, a novel versatile player regulating energy metabolism beyond the erythroid system

Erythropoietin (EPO), the required cytokine for promoting the proliferation and differentiation of erythroid cells to stimulate erythropoiesis, has been reported to act as a pleiotropic cytokine beyond hematopoietic system. The various activities of EPO are determined by the widespread distribution of its cell surface EPO receptor (EpoR) in multiple tissues including endothelial, neural, myoblasts, adipocytes and other cell types. EPO activity has been linked to angiogenesis, neuroprotection, cardioprotection, stress protection, anti-inflammation and especially the energy metabolism regulation that is recently revealed. The investigations of EPO activity in animals and the expression analysis of EpoR provide more insights on the potential of EPO in regulating energy metabolism and homeostasis. The findings of crosstalk between EPO and some important energy sensors and the regulation of EPO in the cellular respiration and mitochondrial function further provide molecular mechanisms for EPO activity in metabolic activity regulation. In this review, we will summarize the roles of EPO in energy metabolism regulation and the activity of EPO in tissues that are tightly associated with energy metabolism. We will also discuss the effects of EPO in regulating oxidative metabolism and mitochondrial function, the interactions between EPO and important energy regulation factors, and the protective role of EPO from stresses that are related to metabolism, providing a brief overview of previously less appreciated EPO biological function in energy metabolism and homeostasis.

Protection from oxidative and electrophilic stress in the Gsta4-null mouse heart

4-Hydroxynonenal (4-HNE) mediates many pathological effects of oxidative and electrophilic stress and signals to activate cytoprotective gene expression regulated by NF-E2-related factor 2 (Nrf2). By exhibiting very high levels of 4-HNE-conjugating activity, the murine glutathione transferase alpha 4 (GSTA4-4) helps regulate cellular 4-HNE levels. To examine the role of 4-HNE in vivo, we disrupted the murine Gsta4 gene. Gsta4-null mice exhibited no cardiac phenotype under normal conditions and no difference in cardiac 4-HNE level as compared to wild-type mice. We hypothesized that the Nrf2 pathway might contribute an important compensatory mechanism to remove excess cardiac 4-HNE in Gsta4-null mice. Cardiac nuclear extracts from Gsta4-null mice exhibited significantly higher Nrf2 binding to antioxidant response elements. We also observed responses in critical Nrf2 target gene products: elevated Sod2, Cat, and Akr1b7 mRNA levels and significant increases in both cardiac antioxidant and anti-electrophile enzyme activities. Gsta4-null mice were less sensitive and maintained normal cardiac function following chronic doxorubicin treatment, known to increase cardiac 4-HNE levels. Hence, in the absence of GSTA4-4 to modulate both physiological and pathological 4-HNE levels, the adaptive Nrf2 pathway may be primed to contribute to a preconditioned cardiac phenotype in the Gsta4-null mouse.

AMPK is involved in mediation of erythropoietin influence on metabolic activity and reactive oxygen species production in white adipocytes

Erythropoietin, discovered for its indispensable role during erythropoiesis, has been used in therapy for selected red blood cell disorders in erythropoietin-deficient patients. The biological activities of erythropoietin have been found in animal models to extend to non-erythroid tissues due to the expression of erythropoietin receptor. We previously demonstrated that erythropoietin promotes metabolic activity and white adipocytes browning to increase mitochondrial function and energy expenditure via peroxisome proliferator-activated receptor alpha and Sirtuin1. Here we report that AMP-activated protein kinase was activated by erythropoietin possibly via Ca(2+)/calmodulin-dependent protein kinase kinase in adipocytes as well as in white adipose tissue from diet induced obese mice. Erythropoietin increased cellular nicotinamide adenine dinucleotide via increased AMP-activated protein kinase activity, possibly leading to Sirtuin1 activation. AMP-activated protein kinase knock down reduced erythropoietin mediated increase in cellular oxidative function including the increased oxygen consumption rate, fatty acid utilization and induction of key metabolic genes. Under hypoxia, adipocytes were found to generate more reactive oxygen species, and erythropoietin reduced the reactive oxygen species and increased antioxidant gene expression, suggesting that erythropoietin may provide protection from oxidative stress in adipocytes. Erythropoietin also reversed increased nicotinamide adenine dinucleotide by hypoxia via increased AMP-activated protein kinase. Additionally, AMP-activated protein kinase is found to be involved in erythropoietin stimulated increase in oxygen consumption rate, fatty acid oxidation and mitochondrial gene expression. AMP-activated protein kinase knock down impaired erythropoietin stimulated increases in antioxidant gene expression. Collectively, our findings identify the AMP-activated protein kinase involvement in erythropoietin signaling in regulating adipocyte cellular redox status and metabolic activity.

Akt-mTOR Pathway Inhibits Apoptosis and Fibrosis in Doxorubicin-Induced Cardiotoxicity Following Embryonic Stem Cell Transplantation

Doxorubicin (DOX) is an effective chemotherapeutic drug used for the treatment of a variety of malignancies. Unfortunately, time and dose-dependent DOX therapy induces cardiotoxicity and heart failure. We previously reported that transplanted embryonic stem (ES) cells and the conditioned medium (CM) can repair and regenerate injured myocardium in acute DOX-induced cardiomyopathy (DIC). However, the effectiveness of ES cell and CM therapeutics has not been challenged in the chronic DIC model. To this end, the long-term impact of ES cells and CM on apoptosis, fibrosis, cytoplasmic vacuolization, oxidative stress, and their associated mediators were examined. Four weeks post-DIC, ES cells and CM-transplanted hearts showed a significant decrease in cardiac apoptotic nuclei, which was consequent to modulation of signaling molecules in the Akt pathway including PTEN, Akt, and mTOR. Cytoplasmic vacuolization was reduced following treatment with ES cells and CM, as was cardiac fibrosis, which was attributable to downregulation of MMP-9 activity. Oxidative stress, as evidenced by DHE staining and lipid peroxide concentration, was significantly diminished, and preservation of the antioxidant defense system was observed following CM and ES cell transplantation. In conclusion, our data suggest that transplanted ES cells and CM have long-term potentiation to significantly mitigate various adverse pathological mechanisms present in the injured chronic DIC heart.

Erythropoietin enhances mitochondrial biogenesis in cardiomyocytes exposed to chronic hypoxia through Akt/eNOS signalling pathway

Adaptation of cardiomyocytes to chronic hypoxia in cyanotic patients remains unclear. Mitochondrial biogenesis is enhanced in myocardium from cyanotic patients, which is possibly an adaptive response. Erythropoietin (EPO) in blood and its receptor (EPOR) on cardiomyocytes are upregulated by chronic hypoxia, suggesting that EPO-EPOR interaction is increased, which is inferred to positively regulate mitochondrial biogenesis through protein kinase B (Akt)/endothelial nitric oxide synthase (eNOS) signalling pathway. H9c2 cardiomyocytes were exposed to hypoxia (1% O(2)) for 1 week and treated with different doses of recombinant human erythropoietin (rhEPO). Mitochondrial number, mitochondrial DNA (mtDNA) copy number and peroxisome proliferator activated receptor gamma coactivator alpha (PGC-1α) mRNA expression increased in a dose-dependent manner induced by rhEPO. Akt and eNOS were significantly phosphorylated by rhEPO. Both blocking Akt with Wortmannin and silencing eNOS expression with shRNA plasmid decreased the mtDNA copy number and PGC-1α mRNA expression induced by rhEPO. Blocking Akt was associated with the decreased phosphorylation of Akt and eNOS. RNA interference led to a reduction in the total and phosphorylated proteins of eNOS. Thus EPO enhances mitochondrial biogenesis in cardiomyocytes exposed to chronic hypoxia, at least partly through Akt/eNOS signalling, which might be an adaptive mechanism of cardiomyocytes associated with the increased EPO-EPOR interaction in patients with cyanotic congenital heart disease (CCHD).

Hypoxia-inducible factor-1 alpha in the heart: a double agent?

Hypoxia-inducible factor (HIF) is a set of transcription factors that regulate the cellular response to hypoxia. There is a great body of evidence supporting the protective role of HIF-1α in cardiovascular pathophysiology, however, newer studies are hinting at a maladaptive and deleterious role of this transcription factor that merits further investigation. There is a general agreement, however, that HIF-mediated responses appear to differ under conditions of acute and chronic oxygen deprivation. The intensity and sustainability of HIF-1α activation are major determinants of whether the responses are pathological or beneficial. HIF activation is seen to be beneficial in the setting of acute myocardial ischemia and deleterious in chronic conditions. In this review, we will focus on recent insights into the role of HIF-1α in the heart and especially in the setting of ischemic heart disease.

Targeting erythropoietin for chronic neurodegenerative diseases

INTRODUCTION

Since erythropoietin (EPO) and EPO receptor (EPOR) are expressed in the central nervous system (CNS) beyond hematopoietic system, EPO illustrates a robust biological function in maintaining neuronal survival and regulating neurogenesis and may play a crucial role in neurodegenerative diseases.

AREAS COVERED

EPO is capable of modulating multiple cellular signal transduction pathways to promote neuronal survival and enhance the proliferation and differentiation of neuronal progenitor cells. Initially, EPO binds to EPOR to activate the Janus-tyrosine kinase 2 (Jak2) protein followed by modulation of protein kinase B (Akt), mammalian target of rapamycin, signal transducer and activators of transcription 5, mitogen-activated protein kinases, protein tyrosine phosphatases, Wnt1 and nuclear factor κB. As a result, EPO may actively prevent the progression of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, epilepsy, multiple sclerosis and motor neuron diseases.

EXPERT OPINION

Novel knowledge of the cell signaling pathways regulated by EPO in the CNS will allow us to establish the foundation for the development of therapeutic strategies against neurodegenerative diseases. Further investigation of the role of EPO in neurodegenerative diseases can not only formulate EPO as a therapeutic candidate, but also further identify novel therapeutic targets for these disorders.

Erythropoietin attenuates cardiac dysfunction in experimental sepsis in mice via activation of the β-common receptor

There is limited evidence that the tissue-protective effects of erythropoietin are mediated by a heterocomplex of the erythropoietin receptor and the β-common receptor (‘tissue-protective receptor’), which is pharmacologically distinct from the ‘classical’ erythropoietin receptor homodimer that is responsible for erythropoiesis. However, the role of the β-common receptor and/or erythropoietin in sepsis-induced cardiac dysfunction (a well known, serious complication of sepsis) is unknown. Here we report for the first time that the β-common receptor is essential for the improvements in the impaired systolic contractility afforded by erythropoietin in experimental sepsis. Cardiac function was assessed in vivo (echocardiography) and ex vivo (Langendorff-perfused heart) in wild-type and β-common receptor knockout mice, that were subjected to lipopolysaccharide (9 mg/kg body weight; young mice) for 16–18 hours or cecal ligation and puncture (aged mice) for 24 hours. Mice received erythropoietin (1000 IU/kg body weight) 1 hour after lipopolysaccharide or cecal ligation and puncture. Erythropoietin reduced the impaired systolic contractility (in vivo and ex vivo) caused by endotoxemia or sepsis in young as well as old wild-type mice in a β-common-receptor-dependent fashion. Activation by erythropoietin of the β-common receptor also resulted in the activation of well-known survival pathways (Akt and endothelial nitric oxide synthase) and inhibition of pro-inflammatory pathways (glycogen synthase kinase-3β, nuclear factor-κB and interleukin-1β). All the above pleiotropic effects of erythropoietin were lost in β-common receptor knockout mice. Erythropoietin attenuates the impaired systolic contractility associated with sepsis by activation of the β-common receptor, which, in turn, results in activation of survival pathways and inhibition of inflammation.

Over-expression of calpastatin aggravates cardiotoxicity induced by doxorubicin

AIMS

Doxorubicin causes damage to the heart, which may present as cardiomyopathy. However, the mechanisms by which doxorubicin induces cardiotoxicity remain not fully understood and no effective prevention for doxorubicin cardiomyopathy is available. Calpains, a family of calcium-dependent thiol-proteases, have been implicated in cardiovascular diseases. Their activities are tightly controlled by calpastatin. This study employed transgenic mice over-expressing calpastatin to investigate the role of calpain in doxorubicin-induced cardiotoxicity.

METHODS AND RESULTS

Doxorubicin treatment decreased calpain activities in cultured neonatal mouse cardiomyocytes and in vivo mouse hearts, which correlated with down-regulation of calpain-1 and calpain-2 proteins. Over-expression of calpastatin or incubation with pharmacological calpain inhibitors enhanced apoptosis in neonatal and adult cardiomyocytes induced by doxorubicin. In contrast, over-expression of calpain-2 but not calpain-1 attenuated doxorubicin-induced apoptosis in cardiomyocytes. The pro-apoptotic effects of calpain inhibition were associated with down-regulation of protein kinase B (AKT) protein and mRNA expression, and a concomitant reduction in glycogen synthase kinase-3beta (GSK-3β) phosphorylation (Ser9) in doxorubicin-treated cardiomyocytes. Blocking AKT further increased doxorubicin-induced cardiac injuries, suggesting the effects of calpain inhibition may be mediated by inactivating the AKT signalling. In an in vivo model of doxorubicin-induced cardiotoxicity, over-expression of calpastatin exacerbated myocardial dysfunction as assessed by echocardiography and haemodynamic measurement in transgenic mice 5 days after doxorubicin injection. The 5-day mortality was higher in transgenic mice (29.16%) compared with their wild-type littermates (8%) after doxorubicin treatment.

CONCLUSION

Over-expression of calpastatin enhances doxorubicin-induced cardiac injuries through calpain inhibition and thus, calpains may protect cardiomyocytes against doxorubicin-induced cardiotoxicity.

Role of phosphatidylinositol 3,4,5-trisphosphate in cell signaling

Many lipids present in cellular membranes are phosphorylated as part of signaling cascades and participate in the recruitment, localization, and activation of downstream protein effectors. Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) is one of the most important second messengers and is capable of interacting with a variety of proteins through specific PtdIns(3,4,5)P3 binding domains. Localization and activation of these effector proteins controls a myriad of cellular functions including cell survival, proliferation, cytoskeletal rearrangement, and gene expression. Aberrations in the production and metabolism of PtdIns(3,4,5)P3 have been implicated in many human diseases including cancer, diabetes, inflammation, and heart disease. This chapter provides an overview of the role of PtdIns(3,4,5)P3 in cellular regulation and the implications of PtdIns(3,4,5)P3 dysregulation in human diseases. Additionally, recent attempts at targeting PtdIns(3,4,5)P3 signaling via small molecule inhibitors are summarized.

Molecular pathogenesis of myocardial remodeling and new potential therapeutic targets in chronic heart failure

It is well known that the natural history of chronic heart failure (CHF),regardless of age and aetiology,is characterized by progressive cardiac dysfunction refractory to conventional cardiokinetic, diuretic and peripheral vasodilator therapy. Several previous studies, both in animals and humans, showed that the key pathogenetic element of CHF negative clinical evolution is constituted by myocardial remodeling. This is a complex pathologic process of ultrastructural rearrangement of the heart induced by various neuro-humoral factors released by cardiac fibrocells in response to biomechanical stress connected to chronic haemodynamic overload. Typical features of myocardial remodeling are represented by cardiomyocytes hypertrophy and apoptosis, extracellular matrix alterations, mesenchymal fibrotic and phlogistic processes and by cardiac gene expression modifications with fetal genetic program reactivation. In the last years, increasing knowledge of subtle molecular and cellular mechanisms involved in myocardial remodeling has led to the discovery of some new potential therapeutic targets capable of inducing its regression. In this paper our attention is focused on the possible use of antiapoptotic and antifibrotic agents, and on the fascinating perspectives offered by the development of myocardial gene therapy and, in particular, by myocardial regenerative therapy.

Embryonic stem cells improve cardiac function in Doxorubicin-induced cardiomyopathy mediated through multiple mechanisms

Doxorubicin (DOX) is an effective antineoplastic agent used for the treatment of a variety of cancers. Unfortunately, its use is limited as this drug induces cardiotoxicity and heart failure as a side effect. There is no report that describes whether transplanted embryonic stem (ES) cells or their conditioned medium (CM) in DOX-induced cardiomyopathy (DIC) can repair and regenerate myocardium. Therefore, we transplanted ES cells or CM in DIC to examine apoptosis, fibrosis, cytoplasmic vacuolization, and myofibrillar loss and their associated Akt and ERK pathway. Moreover, we also determined activation of endogenous c-kit(+ve) cardiac stem cells (CSCs), levels of HGF and IGF-1, growth factors required for c-kit cell activation, and their differentiation into cardiac myocytes, which also contributes in cardiac regeneration and improved heart function. We generated DIC in C57Bl/6 mice (cumulative dose of DOX 12 mg/kg body weight, IP), and animals were treated with ES cells, CM, or cell culture medium in controls. Two weeks post-DIC, ES cells or CM transplanted hearts showed a significant (p < 0.05) decrease in cardiac apoptotic nuclei and their regulation with Akt and ERK pathway. Cardiac fibrosis observed in the ES cell or CM groups was significantly less compared with DOX and cell culture medium groups (p < 0.05). Next, cytoplasmic vacuolization and myofibrillar loss was reduced (p < 0.05) following treatment with ES cells or CM. Moreover, our data also demonstrated increased levels of c-kit(+ve) CSCs in ES cells or CM hearts and differentiated cardiac myocytes from these CSCs, suggesting endogenous cardiac regeneration. Importantly, the levels of HFG and IGF-1 were significantly increased in ES cells or CM transplanted hearts. In conclusion, we reported that transplanted ES cells or CM in DIC hearts significantly decreases various adverse pathological mechanisms as well as enhances cardiac regeneration that effectively contributes to improved heart function.

Mitochondria death/survival signaling pathways in cardiotoxicity induced by anthracyclines and anticancer-targeted therapies

Anthracyclines remain the cornerstone of treatment in many malignancies but these agents have a cumulative dose relationship with cardiotoxicity. Development of cardiomyopathy and congestive heart failure induced by anthracyclines are typically dose-dependent, irreversible, and cumulative. Although past studies of cardiotoxicity have focused on anthracyclines, more recently interest has turned to anticancer drugs that target many proteins kinases, such as tyrosine kinases. An attractive model to explain the mechanism of this cardiotoxicity could be myocyte loss through cell death pathways. Inhibition of mitochondrial transition permeability is a valuable tool to prevent doxorubicin-induced cardiotoxicity. In response to anthracycline treatment, activation of several protein kinases, neuregulin/ErbB2 signaling, and transcriptional factors modify mitochondrial functions that determine cell death or survival through the modulation of mitochondrial membrane permeability. Cellular response to anthracyclines is also modulated by a myriad of transcriptional factors that influence cell fate. Several novel targeted chemotherapeutic agents have been associated with a small but worrying risk of left ventricular dysfunction. Agents such as trastuzumab and tyrosine kinase inhibitors can lead to cardiotoxicity that is fundamentally different from that caused by anthracyclines, whereas biological effects converge to the mitochondria as a critical target.

Creating a pro-survival and anti-inflammatory phenotype by modulation of acetylation in models of hemorrhagic and septic shock

Shock, regardless of etiology, is characterized by decreased tissue perfusion resulting in cell death, organ dysfunction, and poor survival. Current therapies largely focus on restoring tissue perfusion through resuscitation but have failed to address the specific cellular dysfunction caused by shock. Acetylation is rapidly emerging as a key mechanism that regulates the expression of numerous genes (epigenetic modulation through activation of nuclear histone proteins), as well as functions of multiple cytoplasmic proteins involved in key cellular functions such as cell survival, repair/healing, signaling, and proliferation. Cellular acetylation can be increased immediately through the administration of histone deacetylase inhibitors (HDACI). A series of studies have been performed using: (1) cultured cells; (2) single-organ ischemia-reperfusion injury models; (3) rodent models of lethal septic and hemorrhagic shock; (4) swine models of lethal hemorrhagic shock and multi-organ trauma; and (5) tissues from severely injured trauma patients, to fully characterize the changes in acetylation that occur following lethal insults and in response to treatment with HDACI. These data demonstrate that: (1) shock causes a decrease in acetylation of nuclear and cytoplasmic proteins; (2) hypoacetylation can be rapidly reversed through the administration of HDACI; (3) normalization of acetylation prevents cell death, decreases inflammation, attenuates activation of pro-apoptotic pathways, and augments pro-survival pathways; (4) the effect of HDACI significantly improves survival in lethal models of septic shock, hemorrhagic shock, and complex poly-trauma without need for conventional fluid resuscitation or blood transfusion; and (5) improvement in survival is not due to better resuscitation but due to an enhanced ability of cells to tolerate lethal insults.As different models of hemorrhagic or septic shock have specific strengths and limitations, this chapter will summarize our attempts to create "pro-survival and anti-inflammatory phenotype" in various models of hemorrhagic shock and septic shock.

Erythropoietin and Wnt1 govern pathways of mTOR, Apaf-1, and XIAP in inflammatory microglia

Inflammatory microglia modulate a host of cellular processes in the central nervous system that include neuronal survival, metabolic fluxes, foreign body exclusion, and cellular regeneration. Elucidation of the pathways that oversee microglial survival and integrity may offer new avenues for the treatment of neurodegenerative disorders. Here we demonstrate that erythropoietin (EPO), an emerging strategy for immune system modulation, prevents microglial early and late apoptotic injury during oxidant stress through Wnt1, a cysteine-rich glycosylated protein that modulates cellular development and survival. Loss of Wnt1 through blockade of Wnt1 signaling or through the gene silencing of Wnt1 eliminates the protective capacity of EPO. Furthermore, endogenous Wnt1 in microglia is vital to preserve microglial survival since loss of Wnt1 alone increases microglial injury during oxidative stress. Cellular protection by EPO and Wnt1 intersects at the level of protein kinase B (Akt1), the mammalian target of rapamycin (mTOR), and p70S6K, which are necessary to foster cytoprotection for microglia. Downstream from these pathways, EPO and Wnt1 control "anti-apoptotic" pathways of microglia through the modulation of mitochondrial membrane permeability, the release of cytochrome c, and the expression of apoptotic protease activating factor-1 (Apaf-1) and X-linked inhibitor of apoptosis protein (XIAP). These studies offer new insights for the development of innovative therapeutic strategies for neurodegenerative disorders that focus upon inflammatory microglia and novel signal transduction pathways.

Erythropoietin gene delivery using an arginine-grafted bioreducible polymer system

Erythropoietin (EPO) plays a key regulatory role in the formation of new red blood cells (RBCs). Erythropoietin may also have a role as a therapeutic agent to counteract ischemic injury in neural, cardiac and endothelial cells. One of the limitations preventing the therapeutic application of EPO is its short half-life. The goal of this study was to develop a gene delivery system for the prolonged and controlled release of EPO. The arginine grafted bioreducible polymer (ABP) and its PEGylated version, ABP-PEG10, were utilized to study the expression efficiency and therapeutic effectiveness of this erythropoietin gene delivery system in vitro. Poly(ethylene glycol) (PEG) modification of the ABP was employed to inhibit the particle aggregation resulting from the interactions between cationic polyplexes and the negatively charged proteins typically present in serum. Both the ABP and the ABP-PEG10 carriers demonstrated efficient transfection and long-term production of EPO in a variety of cell types. The expressed EPO protein stimulated hematopoietic progenitor cells to form significant numbers of cell colonies in vitro. These data confirm that this EPO gene delivery system using a bioreducible polymeric carrier, either ABP or ABP-PEG 10, merits further testing as a potential therapeutic modality for a variety of clinically important disease states.

Erythropoietin protects against doxorubicin-induced heart failure

The hormone erythropoietin (EPO) has been demonstrated to have cardioprotective properties. The present study investigates the role of EPO to prevent heart failure following cancer treatment with doxorubicin [adriamycin (AD)]. Male Wistar rats (150 ± 10 g) were treated with saline (vehicle control group); with EPO, subcutaneously at 1,000 IU/kg body wt, three times per week for 4 wk (EPO group); with adriamycin, intraperitoneally at 2.5 mg/kg body wt, three times per week for 2 wk (AD group); and with adriamycin and EPO (EPO-AD group). Echocardiographic measurements showed that EPO-AD treatment prevented the AD-induced decline in cardiac function. Each of the hearts was then exposed to ischemia and reperfusion during Langendorff perfusion. The percentage of recovery after ischemia-reperfusion was significantly greater in EPO-AD than the AD-treated group for left ventricular developed pressure, maximal increase in pressure, and rate pressure product. The level of oxidative stress was significantly higher in AD (5 μM for 24 h)-exposed isolated cardiomyocytes; EPO (5 U/ml for 48 h) treatment prevented this. EPO treatment also decreased AD-induced cardiomyocyte apoptosis, which was associated with the decrease in the Bax-to-Bcl2 ratio and caspase-3 activation. Immunostaining of myocardial tissue for CD31 showed a significant decrease in the number of capillaries in AD-treated animals. EPO-AD treatment restored the number of capillaries. In conclusion, EPO treatment effectively prevented AD-induced heart failure. The protective effect of EPO was associated with a decreased level of oxidative stress and apoptosis in cardiomyocytes as well as improved myocardial angiogenesis.

Myocardial AKT: the omnipresent nexus

One of the greatest examples of integrated signal transduction is revealed by examination of effects mediated by AKT kinase in myocardial biology. Positioned at the intersection of multiple afferent and efferent signals, AKT exemplifies a molecular sensing node that coordinates dynamic responses of the cell in literally every aspect of biological responses. The balanced and nuanced nature of homeostatic signaling is particularly essential within the myocardial context, where regulation of survival, energy production, contractility, and response to pathological stress all flow through the nexus of AKT activation or repression. Equally important, the loss of regulated AKT activity is primarily the cause or consequence of pathological conditions leading to remodeling of the heart and eventual decompensation. This review presents an overview compendium of the complex world of myocardial AKT biology gleaned from more than a decade of research. Summarization of the widespread influence that AKT exerts upon myocardial responses leaves no doubt that the participation of AKT in molecular signaling will need to be reckoned with as a seemingly omnipresent regulator of myocardial molecular biological responses.

Absence of thrombospondin-2 increases cardiomyocyte damage and matrix disruption in doxorubicin-induced cardiomyopathy

Clinical use of the antineoplastic agent doxorubicin (DOX) is limited by its cardiomyocyte toxicity. Attempts to decrease cardiomyocyte injury showed promising results in vitro, but failed to reduce the adverse effects of DOX in vivo, suggesting that other mechanisms contribute to its cardiotoxicity as well. Evidence that DOX also induces cardiac injury by compromising extracellular matrix integrity is lacking. The matricellular protein thrombospondin-2 (TSP-2) is known for its matrix-preserving function, and for modulating cellular function. Here, we investigated whether TSP-2 modulates the process of doxorubicin-induced cardiomyopathy (DOX-CMP). TSP-2-knockout (TSP-2-KO) and wild-type (WT) mice were treated with DOX (2 mg/kg/week) for 12 weeks to induce DOX-CMP. Mortality was significantly increased in TSP-2-KO compared to WT mice. Surviving DOX-treated TSP-2-KO mice had depressed cardiac function compared to WT animals, accompanied by increased cardiomyocyte apoptosis and matrix damage. Enhanced myocyte damage in the absence of TSP-2 was associated with impaired activation of the Akt signaling pathway in TSP-2-KO compared to WT. The absence of TSP-2, in vivo and in vitro, reduced Akt activation both under non-treated conditions and after DOX. Importantly, inhibition of Akt phosphorylation in cardiomyocytes significantly reduced TSP-2 expression, unveiling a unique feedback loop between Akt and TSP-2. Finally, enhanced matrix disruption in DOX-treated TSP-2-KO hearts went along with increased matrix metalloproteinase-2 levels. Taken together, this study is the first to provide evidence for the implication of the matrix element TSP-2 in protecting against DOX-induced cardiac injury and dysfunction.

Mechanisms of anthracycline cardiotoxicity and strategies to decrease cardiac damage

Anthracyclines are common chemotherapeutic agents used to treat many different types of cancer. Unfortunately, the use of anthracyclines is limited by their cardiotoxic effects, which may become manifest as late as 20 years from initial exposure. Studies in cells and animals suggest that the mechanism of anthracycline-induced cardiotoxicity (AIC) is multifactorial. Anthracyclines induce multiple forms of cellular injury by free radical production. In addition, anthracyclines alter nucleic acid biology by intercalation into DNA and modulate intracellular signaling, leading to cell death and the disruption of homeostatic processes such as sarcomere maintenance. In an effort to decrease AIC, many strategies have been tested, but no specific therapies are universally acknowledged to prevent or treat anthracycline-induced cardiac dysfunction. Newer imaging modalities and cardiac biomarkers may be useful in improving early detection of cardiac injury and dysfunction. As long as there is no cardiac-specific therapy for AIC, evidence suggests that high-risk patients will benefit from prophylactic treatment with neurohormonal blockade by angiotensin-converting enzyme inhibitors and beta-adrenergic receptor blockers.

Modulation of acetylation: creating a pro-survival and anti-inflammatory phenotype in lethal hemorrhagic and septic shock

Histone deacetylases (HDACs) play a key role in homeostasis of protein acetylation in histone and nonhistone proteins and in regulating fundamental cellular activities. In this paper we review and discuss intriguing recent developments in the use of histone deacetylase inhibitors (HDACIs) to combat some critical conditions in an animal model of hemorrhagic and septic shock. HDACIs have neuroprotective, cardioprotective, renal-protective, and anti-inflammatory properties; survival improvements have been significantly shown in these models. We discuss the targets and mechanisms underlying these effects of HDACIs and comment on the potential new clinical applications for these agents in the future. This paper highlights the emerging roles of HDACIs as acetylation modulators in models of hemorrhagic and septic shock and explains some contradictions encountered in previous studies.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

A fork in the path: Developing therapeutic inroads with FoxO proteins

Advances in clinical care for disorders involving any system of the body necessitates novel therapeutic strategies that can focus upon the modulation of cellular proliferation, metabolism, inflammation and longevity. In this respect, members of the mammalian forkhead transcription factors of the O class (FoxOs) that include FoxO1, FoxO3, FoxO4 and FoxO6 are increasingly being recognized as exciting prospects for multiple disorders. These transcription factors govern development, proliferation, survival and longevity during multiple cellular environments that can involve oxidative stress. Furthermore, these transcription factors are closely integrated with several novel signal transduction pathways, such as erythropoietin and Wnt proteins, that may influence the ability of FoxOs to act as a “double-edge sword” to sometimes promote cell survival, but at other times lead to cell injury. Here we discuss the fascinating but complex role of FoxOs during cellular injury and oxidative stress, progenitor cell development, fertility, angiogenesis, cardiovascular function, cellular metabolism and diabetes, cell longevity, immune surveillance and cancer.

Taking the heart failure battle inside the cell: small molecule targeting of Gβγ subunits

Heart failure (HF) is devastating disease with poor prognosis. Elevated sympathetic nervous system activity and outflow, leading to pathologic attenuation and desensitization of β-adrenergic receptors (β-ARs) signaling and responsiveness, are salient characteristic of HF progression. These pathologic effects on β-AR signaling and HF progression occur in part due to Gβγ-mediated signaling, including recruitment of receptor desensitizing kinases such as G-protein coupled receptor (GPCR) kinase 2 (GRK2) and phosphoinositide 3-kinase (PI3K), which subsequently phosphorylate agonist occupied GPCRs. Additionally, chronic GPCR signaling signals chronically dissociated Gβγ subunits to interact with multiple effector molecules that activate various signaling cascades involved in HF pathophysiology. Importantly, targeting Gβγ signaling with large peptide inhibitors has proven a promising therapeutic paradigm in the treatment of HF. We recently described an approach to identify small molecule Gβγ inhibitors that selectively block particular Gβγ functions by specifically targeting a Gβγ protein-protein interaction "hot spot." Here we describe their effects on Gβγ downstream signaling pathways, including their role in HF pathophysiology. We suggest a promising therapeutic role for small molecule inhibition of pathologic Gβγ signaling in the treatment of HF. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure."

Doxorubicin toxicity can be ameliorated during antioxidant L-carnitine supplementation

Doxorubicin is an antibiotic broadly used in treatment of different types of solid tumors. The present study investigates whether L-carnitine, antioxidant agent, can reduce the hepatic damage induced by doxorubicin. Male Wistar albino rats were divided into six groups: group 1 was intraperitoneal injected with normal saline for 10 consecutive days; group 2, 3 and 4 were injected every other day with doxorubicin (3 mg/kg, i.p.), to obtain treatments with cumulative doses of 6, 12 and 18 mg/kg. The fifth group was injected with L-carnitine (200 mg/kg, i.p.) for 10 consecutive days and the sixth group was received doxorubicin (18 mg/kg) and L-carnitine (200 mg/kg). High cumulative dose of doxorubicin (18 mg/kg) significantly increases the biochemical levels of alanine transaminase, alkaline phosphatase, total bilirubin, thiobarbituric acid reactive substances (TBARs), total nitrate/nitrite (NOx) p < 0.05 and decrease in glutathione (GSH ), superoxide dismutase (SOD), glutathione peroxidase (GSHP x), glutathione-s-transferase (GST), glutathione reductase (GR) and catalase (CAT) activity p < 0.05. The effect of doxorubicin on the activity of antioxidant genes was confirmed by real time PCR in which the expression levels of these genes in liver tissue were significantly decrease compared to control p < 0.05. Interestingly, L-carnitine supplementation completely reversed the biochemical and gene expression levels induced by doxorubicin to the control values. In conclusion, data from this study suggest that the reduction of antioxidant defense during doxorubicin administration resulted in hepatic injury could be prevented by L-carnitine supplementation by decreasing the oxidative stress and preserving both the activity and gene expression level of antioxidant enzymes.

Cardiac toxicity in breast cancer patients: from a fractional point of view to a global assessment

When focusing on heart disease, most available studies split the two different parts of the adjuvant treatment, i.e., systemic therapies and radiation therapy, making it difficult to implement efficient strategies for preventing treatment-induced cardiac toxicity. This paper reviews the current understanding of treatments-induced cardiac toxicity in a global approach. Many factors should be considered when assessing the cardiac hazard. Treatment-related risk factors include heart dose exposure, chemotherapy, targeted agents such as HER2 inhibitors, but also endocrine agents, or anesthetic procedure. Patients' characteristics should also be taken into account. Age, menopausal status, stress, previous history of cardiac disease, genetic profile, and body mass index could all impact on cardiac function after adjuvant therapies. Cardiac toxicity should not be analyzed as the consequence of a specific therapy, but should be considered as the result of additive or supra-additive toxicities. By this way, it will be possible to implement new strategies for preventing treatment-induced cardiac toxicity.

Endoplasmic reticulum protein targeting of phospholamban: a common role for an N-terminal di-arginine motif in ER retention?

BACKGROUND

Phospholamban (PLN) is an effective inhibitor of the sarco(endo)plasmic reticulum Ca(2+)-ATPase, which transports Ca(2+) into the SR lumen, leading to muscle relaxation. A mutation of PLN in which one of the di-arginine residues at positions 13 and 14 was deleted led to a severe, early onset dilated cardiomyopathy. Here we were interested in determining the cellular mechanisms involved in this disease-causing mutation.

METHODOLOGY/PRINCIPAL FINDING

Mutations deleting codons for either or both Arg13 or Arg14 resulted in the mislocalization of PLN from the ER. Our data show that PLN is recycled via the retrograde Golgi to ER membrane traffic pathway involving COP-I vesicles, since co-immunoprecipitation assays determined that COP I interactions are dependent on an intact di-arginine motif as PLN RDelta14 did not co-precipitate with COP I containing vesicles. Bioinformatic analysis determined that the di-arginine motif is present in the first 25 residues in a large number of all ER/SR Gene Ontology (GO) annotated proteins. Mutations in the di-arginine motif of the Sigma 1-type opioid receptor, the beta-subunit of the signal recognition particle receptor, and Sterol-O-acyltransferase, three proteins identified in our bioinformatic screen also caused mislocalization of these known ER-resident proteins.

CONCLUSION

We conclude that PLN is enriched in the ER due to COP I-mediated transport that is dependent on its intact di-arginine motif and that the N-terminal di-arginine motif may act as a general ER retrieval sequence.