Insulin-like growth factor-1 prevents loss of electrochemical gradient in cardiac muscle mitochondria via activation of PI 3 kinase/Akt pathway

Therapeutic Targets for DOX-Induced Cardiomyopathy: Role of Apoptosis vs. Ferroptosis

Doxorubicin (DOX) is the most widely used anthracycline anticancer agent; however, its cardiotoxicity limits its clinical efficacy. Numerous studies have elucidated the mechanisms underlying DOX-induced cardiotoxicity, wherein apoptosis has been reported as the most common final step leading to cardiomyocyte death. However, in the past two years, the involvement of ferroptosis, a novel programmed cell death, has been proposed. The purpose of this review is to summarize the historical background that led to each form of cell death, focusing on DOX-induced cardiotoxicity and the molecular mechanisms that trigger each form of cell death. Furthermore, based on this understanding, possible therapeutic strategies to prevent DOX cardiotoxicity are outlined. DNA damage, oxidative stress, intracellular signaling, transcription factors, epigenetic regulators, autophagy, and metabolic inflammation are important factors in the molecular mechanisms of DOX-induced cardiomyocyte apoptosis. Conversely, the accumulation of lipid peroxides, iron ion accumulation, and decreased expression of glutathione and glutathione peroxidase 4 are important in ferroptosis. In both cascades, the mitochondria are an important site of DOX cardiotoxicity. The last part of this review focuses on the significance of the disruption of mitochondrial homeostasis in DOX cardiotoxicity.

Benazepril hydrochloride protects against doxorubicin cardiotoxicity by regulating the PI3K/Akt pathway

Doxorubicin (DOX) stimulates the generation of reactive oxygen species, thereby impairing mitochondrial functions. Angiotensin-converting enzyme inhibitors (ACEIs) have been identified to exhibit protective effects on cardiovascular diseases. The present study aimed to test the hypothesis that an ACEI benazepril hydrochloride (HCl) may protect against DOX-induced cardiotoxicity. The DOX injury model was established using rat embryonic cardiac myoblast cells (H9c2 cell line) treated with DOX in vitro. H9c2 cells were treated with benazepril-HCl, DOX or a mixture of DOX and benazepril-HCl to measure the activities of myocardial enzymes including lactate dehydrogenase (LDH), superoxide dismutase, catalase and glutathione peroxidase, in addition to the concentration of malondialdehyde in the culture medium. Cells without any treatment were used as a control. DOX treatment increased the levels of activity of myocardial enzymes in H9c2 cells compared with those in the untreated control cells. Additionally, co-treatment with benazepril-HCl significantly reduced the levels of apoptosis occurring due to DOX-mediated cellular damage. The mechanistic experiment revealed that pretreatment with benazepril-HCl counteracted the DOX-induced oxidative stress and suppressed the activation of apoptosis via the PI3K/Akt signaling pathway. By contrast, an Akt inhibitor (MK2206) inhibited the protective effects of benazepril-HCl against DOX-induced H9c2 cell injury, as revealed by increased LDH release in H9c2 cells. These results suggested that benazepril-HCl may potentially be administered as an adjuvant for DOX in long-term clinical use.

Soluble factors released by dedifferentiated fat cells reduce the functional activity of iPS cell-derived cardiomyocytes

Interactions between tissues such as epicardial adipose (EAT), and myocardial tissues is important in the pathogenesis of heart failure. Changes in adipose tissues in obesity or diabetes impair preadipocyte differentiation. Furthermore, proinflammatory cytokine secretion is higher in preadipocytes than in mature adipocytes in diabetes and obesity. However, how undifferentiated cells committed to the adipose lineage directly influence cardiomyocytes is not yet understood. We used human-derived dedifferentiated fat (DFAT) cells as models of undifferentiated cells committed to an adipose lineage. Here, we evaluated the effects of soluble factor interactions in indirect cocultures of DFAT cells and induced pluripotent stem cell-derived cardiomyocytes. Our RNA sequencing findings showed that these interactions were predominantly inflammatory responses. Furthermore, proinflammatory cytokines secreted by DFAT cells reduced myocardial functions such as contraction frequency and catecholamine sensitivity, and simultaneously increased apoptosis, decreased antioxidative stress tolerance, and reduced oxygen consumption rates in cardiomyocytes. These adverse effects might be attributable to monocyte chemoattractant protein-1, chemokine (C-X-C motif) ligands 1 (CXCL1), and 12, granulocyte colony-stimulating factor, interleukins 6 and 8, macrophage migration inhibitory factor (MIF), and plasminogen activator inhibitor 1-A among the proinflammatory mediators secreted by DFAT cells. Our results could be useful for understanding the pathogenesis of EAT-related heart failure in terms of the involvement of undifferentiated cells committed to the adipose lineage. Furthermore, we suggest the importance of focusing on surrounding adipose tissues as a strategy with which to maximize the survival and function of transplanted stem cell-derived cardiomyocytes.

Effects of doxorubicin-induced cardiotoxicity on cardiac mitochondrial dynamics and mitochondrial function: Insights for future interventions

Anthracyclines is an effective chemotherapeutic treatment used for many types of cancer. However, high cumulative dosage of anthracyclines leads to cardiac toxicity and heart failure. Dysregulation of mitochondrial dynamics and function are major pathways driving this toxicity. Several pharmacological and non‐pharmacological interventions aiming to attenuate cardiac toxicity by targeting mitochondrial dynamics and function have shown beneficial effects in cell and animal models. However, in clinical practice, there is currently no standard therapy for the prevention of anthracycline‐induced cardiotoxicity. This review summarizes current reports on the impact of anthracyclines on cardiac mitochondrial dynamics and mitochondrial function and potential interventions targeting these pathways. The roles of mitochondrial dynamics and mitochondrial function in the development of anthracycline‐induced cardiotoxicity should provide insights in devising novel strategies to attenuate the cardiac toxicity induced by anthracyclines.

IL-20 promotes hypoxia/reoxygenation-induced mitochondrial dysfunction and apoptosis in cardiomyocytes by upregulating oxidative stress by activating the PKC/NADPH oxidase pathway

Acute myocardial infarction (AMI) is the maximum critical cardiovascular event and causes high morbidity and mortality worldwide. The ischemia and reperfusion that occur in AMI cause apoptosis and cellular dysfunction in cardiomyocytes. IL-20, an IL-10 family member, is involved in various inflammatory diseases. Therefore, we sought to elucidate the role of IL-20 in the infarcted heart following ischemia/reperfusion (I/R) injury. We found that IL-20 and its receptors, IL-20R1 and IL-20R2, were increased in H2C2 cardiomyoblast cells and ventricular tissues subjected to hypoxia/reoxygenation (H/R) stimulation. The presence of IL-20 further inhibited the cell viability of H9C2 cells and primary cardiomyocytes. Our results suggested that IL-20 elicited an increase in Ca²⁺ and activation of the PKC/NADPH oxidase pathway, leading to the elevation of oxidase stress and downregulation of AKT. Furthermore, we demonstrated that IL-20 was able to mediate H/R-induced apoptosis via PKC/NADPH oxidase/AKT signaling. Our findings implied that IL-20 was responsive to H/R stress in vitro and in rat hearts undergoing I/R injury, and this upregulation of IL-20 may contribute to the apoptosis of cardiomyocytes.

Mesenchymal Stem Cell Therapy for Doxorubicin-Induced Cardiomyopathy: Potential Mechanisms, Governing Factors, and Implications of the Heart Stem Cell Debate

Over the past decades, researchers have reported several mechanisms for doxorubicin (DOX)-induced cardiomyopathy, including oxidative stress, inflammation, and apoptosis. Another mechanism that has been suggested is that DOX interferes with the cell cycle and induces oxidative stress in C-kit+ cells (commonly known as cardiac progenitor cells), reducing their regenerative capacity. Cardiac regeneration through enhancing the regenerative capacity of these cells or administration of other stem cells types has been the axis of several studies over the past 20 years. Several experiments revealed that local or systemic injections with mesenchymal stem cells (MSCs) were associated with significantly improved cardiac function, ameliorated inflammatory response, and reduced myocardial fibrosis. They also showed that several factors can affect the outcome of MSC treatment for DOX cardiomyopathy, including the MSC type, dose, route, and timing of administration. However, there is growing evidence that the C-kit+ cells do not have a cardiac regenerative potential in the adult mammalian heart. Similarly, the protective mechanisms of MSCs against DOX-induced cardiomyopathy are not likely to include direct differentiation into cardiomyocytes and probably occur through paracrine secretion, antioxidant and anti-inflammatory effects. Better understanding of the involved mechanisms and the factors governing the outcomes of MSCs therapy are essential before moving to clinical application in patients with DOX-induced cardiomyopathy.

Umbilical cord blood-mesenchymal stem cells and carvedilol reduce doxorubicin- induced cardiotoxicity: Possible role of insulin-like growth factor-1

In this study, we tried to demonstrate the effects of adding human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) to carvedilol in improving the doxorubicin- induced cardiotoxicity in rats. Rats were randomly divided into four groups: group 1: control group, group 2: doxorubicin untreated group, group 3: rats injected with doxorubicin and received carvedilol, and group 4: rats injected with doxorubicin and received carvedilol and stem cell-treated. Electrocardiography (ECG) was performed to assess cardiac function after animals were sacrificed. Cardiac muscle sections were examined histologically using H&E, Masson trichrome and immunohistochemically using caspase 3 immunostaining. The morphometric and statistical analysis was performed. Levels of malondialdehyde (MDA), superoxide dismutase (SOD), insulin-like growth factor (IGF-1), and vascular endothelial growth factor (VEGF) were measured. We concluded that combination of hUCB-MSCs and carvedilol markedly improves histological and immunohistochemical structure of cardiac muscle fibers and restores cardiac function in doxorubicin- induced cardiotoxicity in rats.

Low culture temperature inhibits myogenic differentiation through mitochondrial activity

A previous study by our group reported that mouse and human myoblasts fail to express myogenin and to fuse into multi-nucleate myotubes when cultured at low temperature, such as 30°C, but that this activity is rescued by adding IGF-I and vitamin C to the culture medium. In the present study, we examined mitochondrial activity as a target of the inhibitory effects of the low culture temperature. It has been suggested that mitochondria regulate myogenesis. By using a mouse myoblast cell line C2C12, we demonstrate that the expression of cytochrome c oxidase subunit I (COX I), which is encoded in mitochondrial genome, increases during myogenic differentiation at the normal culture temperature (38°C), but that this up-regulation is inhibited at 30°C. The mitochondrial membrane potential also decreased at 30°C compared to the culture at 38°C. However, IGF-I and vitamin C rescued both COX I expression and mitochondrial membrane potential at 30°C as promoting muscle differentiation. We also find that the rescue of mitochondrial activity by IGF-I and vitamin C at 30°C occurred after the myogenin expression, which suggests that myogenin regulates mitochondrial function during myogenesis. We suggest that our low temperature-culture system may be suitable for use in studying the detailed mechanism of myogenin-related phenomena during myogenesis.

Curcumin protects rat liver from streptozotocin-induced diabetic pathophysiology by counteracting reactive oxygen species and inhibiting the activation of p53 and MAPKs mediated stress response pathways

Curcumin (CUR) is a highly pleiotropic molecule and possesses anti-inflammatory, hypoglycemic, antioxidative, wound-healing and antimicrobial activities. The present study was carried out to investigate whether CUR plays any beneficial role in streptozotocin (STZ) induced hepatic pathophysiology in diabetic rats. STZ exposure increased hepatic damage associated serum markers (ALT, ALP and LDH) as well as NO production in the liver tissue. Moreover, the same exposure enhanced ROS generation and lipid peroxidation; reduced GSH levels and antioxidant enzyme activities. Hyperglycemia induced hepatic pathophysiology also activated stress response pathways (involving phosphorylation of p38, ERK1/2 MAPKs and p53) and reduced mitochondrial membrane potential which in turn led to cellular apoptosis as evidenced from increased hepatic DNA fragmentation as well as FACS analysis. However, treatment with CUR effectively counteracts diabetes-induced, oxidative stress mediated hepatic damage and could act as a therapeutic in lessening liver dysfunction in diabetic subjects.

The effect of recombinant human growth hormone and insulin-like growth factor-1 on the mitochondrial function and viability of peripheral blood mononuclear cells in vitro

This study investigated whether the putative physiological benefits induced by growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are countered at supra-physiological concentrations because of an augmentation in the production of mitochondrial-derived free radicals with a subsequent increase in oxidative damage, compromising mitochondrial function. To test this hypothesis, peripheral blood mononuclear cells were incubated for 4 h with either recombinant human GH (rhGH) (range = 0.25-100 μg/L) or recombinant IGF-1 (rIGF-1) (range = 100-600 μg/L) and along with control samples were subsequently analyzed by flow cytometry for the determination of cellular viability, mitochondrial membrane potential (Δψm), mitochondrial superoxide (O2(-)) generation, and mitochondrial permeability transition pore (mtPTP) activity. Results showed levels of mitochondrial O2(-) generation to be significantly reduced compared with control samples (lymphocytes: 21.5 ± 1.6 AU; monocytes: 230.2 ± 9.8 AU) following rhGH treatment at both concentrations of 5 μg/L (13.5 ± 1.3 AU, P ≤ 0.05) and 10 μg/L (12.3 ± 1.5 AU, P ≤ 0.05) in lymphocytes and at 10 μg/L (153.4 ± 11.4 AU, P ≤ 0.05) in monocytes. However, no significant effect was found at either higher rhGH concentrations or following treatment with any concentration of rIGF-1. In addition, neither of the 2 hormones had any significant effect on Δψm, mtPTP activity, or on cellular viability. In conclusion, physiological concentrations of rhGH elicited a protective cellular effect through the reduction of oxidative free radicals within mitochondria. This antioxidant effect was diminished at supra-physiological concentrations but not to a level that would elicit disruption of mitochondrial function.

Lutein inhibits the migration of retinal pigment epithelial cells via cytosolic and mitochondrial Akt pathways (lutein inhibits RPE cells migration)

During the course of proliferative vitreoretinopathy (PVR), the retinal pigment epithelium (RPE) cells will de-differentiate, proliferate, and migrate onto the surfaces of the sensory retina. Several studies have shown that platelet-derived growth factor (PDGF) can induce migration of RPE cells via an Akt-related pathway. In this study, the effect of lutein on PDGF-BB-induced RPE cells migration was examined using transwell migration assays and Western blot analyses. We found that both phosphorylation of Akt and mitochondrial translocation of Akt in RPE cells induced by PDGF-BB stimulation were suppressed by lutein. Furthermore, the increased migration observed in RPE cells with overexpressed mitochondrial Akt could also be suppressed by lutein. Our results demonstrate that lutein can inhibit PDGF-BB induced RPE cells migration through the inhibition of both cytoplasmic and mitochondrial Akt activation.

Exercise training enhanced SIRT1 longevity signaling replaces the IGF1 survival pathway to attenuate aging-induced rat heart apoptosis

Cardiovascular disease is the second leading cause of death (9.1 %) in Taiwan. Heart function deteriorates with age at a rate of 1 % per year. As society ages, we must study the serious problem of cardiovascular disease. SIRT1 regulates important cellular processes, including anti-apoptosis, neuronal protection, cellular senescence, aging, and longevity. In our previous studies, rats with obesity, high blood pressure, and diabetes exhibiting slowed myocardial performance and induced cell apoptosis were reversed via sports training through IGF1 survival signaling compensation. This study designed a set of experiments with rats, in aging and exercise groups, to identify changes in myocardial cell signaling transduction pathways. Three groups of three different aged rats, 3, 12, and 18 months old, were randomly divided into aging groups (C3, A12, and A18) and exercise groups (E3, AE12, and AE18). The exercise training consisted of swimming five times a week with gradual increases from the first week from 20 to 60 min for 12 weeks. After the sports training process was completed, tissue sections were taken to observe cell organization (hematoxylin and eosin (H&E) stain) and apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays) and to observe any changes in the myocardial tissues and proteins (Western blotting). The experimental results show that cardiomyocyte apoptotic pathway protein expression increased with age in the aging groups (C3, A12, and A18), with improvement in the exercise group (E3, AE12, and AE18). However, the expression of the pro-survival p-Akt protein decreased significantly with age and reduced performance. The IGF1R/PI3K/Akt survival pathway in the heart of young rats can indeed be increased through exercise training. As rats age, this pathway loses its original function, even with increasing upstream IGF1. However, levels of SIRT1 and its downstream target PGC-1α were found to increase with age and compensatory performance. Moreover, exercise training enhanced the SIRT longevity pathway compensation instead of IGF1 survival signaling to improve cardiomyocyte survival.

The effects of silencing of PI3K p85α on 5-FU-induced colorectal cancer cells apoptosis

Colorectal cancer is the third most common malignancy worldwide. 5-fluorouracil (5-FU) is the commonly used chemotherapeutic agent, however, more patients develop resistance. Phosphatidylinositol 3-kinases (PI3Ks) play a crucial role in a wide range of cellular processes associated with malignant behavior including cell growth, migration, and survival. In this study, we show increased expression of PI3K p85α during the progression of colorectal cancer. Silencing of PI3K p85α in colorectal cancer cells increased disruption of mitochondrial membrane potential and enhanced 5-FU-induced apoptosis. Furthermore, PI3K p85α-depletion results in activated expression of apoptosis-associated genes Bcl-6, Bim, and Bax. Our results suggest that knockdown of PI3K p85α is a potential therapeutic strategy in the treatment of colorectal cancer.

Mitochondrial respiratory chain complex I is inactivated by NADPH oxidase Nox4

ROS (reactive oxygen species) generated by NADPH oxidases play an important role in cellular signal transduction regulating cell proliferation, survival and differentiation. Nox4 (NADPH oxidase 4) induces cellular senescence in human endothelial cells; however, intracellular targets for Nox4 remained elusive. In the present study, we show that Nox4 induces mitochondrial dysfunction in human endothelial cells. Nox4 depletion induced alterations in mitochondrial morphology, stabilized mitochondrial membrane potential and decreased production of H(2)O(2) in mitochondria. High-resolution respirometry in permeabilized cells combined with native PAGE demonstrated that Nox4 specifically inhibits the activity of mitochondrial electron transport chain complex I, and this was associated with a decreased concentration of complex I subunits. These data suggest a new pathway by which sustained Nox4 activity decreases mitochondrial function.

Oxidative stress due to radiation in CD34(+) hematopoietic progenitor cells: protection by IGF-1

Radiation exerts direct as well as indirect effects on DNA through the generation of reactive oxygen species (ROS). Irradiated hematopoietic progenitor cells (HPCs) experience DNA strand breaks, favoring genetic instability, due to ROS generation. Our aim was to study the effect of a range of radiation doses in HPCs and the possible protective mechanisms activated by insulin-like growth factor-1 (IGF-1). ROS generation was evaluated, in the presence or absence of IGF-1 in liquid cultures of human HPCs-CD34(+) irradiated with 1-, 2- and 5-Gy X-rays, using a flow cytometry assay. Manganese superoxide dismutase (MnSOD) expression was studied by western blot analysis and visualized by an immunofluorescence assay. Apoptosis was estimated using the following assays: Annexin-V assay, DNA degradation assay, BCL-2/BAX mRNA and protein levels and caspase-9 protein immunofluorescence visualization. Viability and clonogenic potential were studied in irradiated HPCs. The generation of superoxide anion radicals at an early and a late time point was increased, while the hydrogen peroxide generation at a late time point was stable. IGF-1 presence further enhanced the radiation-induced increase of MnSOD at 24 h post irradiation. IGF-1 inhibited the mitochondria-mediated pathway of apoptosis by regulating the m-RNA and protein expression of BAX, BCL-2 and the BCL-2/BAX ratio and by decreasing caspase-9 protein expression. IGF-1 presence in culture media of irradiated cells restored the clonogenic capacity and the viability of HPCs as well. In conclusion, IGF-1 protects HPCs-CD34(+) from radiation effects, by eliminating the oxidative microenvironment through the enhancement of MnSOD activation and by regulating the mitochondria-mediated pathway of apoptosis.

The effects of ginsenoside Rb1 on JNK in oxidative injury in cardiomyocytes

Reactive oxygen species (ROS) can induce oxidative injury via iron interactions (i.e. Fenton chemistry and hydroxyl radical formation). Our prior work suggested that American ginseng berry extract and ginsenoside Re were highly cardioprotective against oxidant stress. To extend this study, we evaluated the protective effect of protopanaxadiol-type ginsenoside Rb1 (gRb1) on H(2)O(2)-induced oxidative injury in cardiomyocytes and explored the ROS-mediated intracellular signaling mechanism. Cultured embryonic chick cardiomyocytes (4-5 day) were used. Cell death was assessed by propidium iodide and lactate dehydrogenase release. Pretreatment with gRb1 (0.01, 0.1, or 1 μM) for 2 h and concurrent treatment with H(2)O(2) (0.5 mM) for 2 h resulted in a dose-dependent reduction of cell death, 36.6 ± 2.9% (n = 12, p < 0.05), 30.5 ± 5.1% (n = 12, p < 0.05) and 28.6 ± 3.1% (n = 12, p < 0.01) respectively, compared to H(2)O(2)-exposed cells (48.2 ± 3.3%, n = 12). This cardioprotective effect of gRb1 was associated with attenuated intracellular ROS generation as measured by 6-carboxy-2', 7'-dichlorodihydrofluorescein diacetate, preserved the mitochondrial membrane potential as determined using JC-1. In the ESR study, gRb1 exhibited the scavenging DPPH and hydroxyl radical activities. Furthermore, our data showed the increased JNK phosphorylation (p-JNK) in H(2)O(2)-exposed cells was suppressed by the pretreatment with gRb 1 (1 μM) (p < 0.01). Co-treatment of gRb1 with a specific inhibitor of JNK SP600125 (10 μM) further reduced the p-JNK and enhanced the cell survival after H(2)O(2) exposure. Collectively, our results suggest that gRb1 conferred cardioprotection that was mediated via attenuating ROS and suppressing ROS-induced JNK activation.

Low serum IGF-1 is a risk factor for cardiac allograft vasculopathy in cardiac transplant recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) has an incidence of 43% at 8 years after heart transplantation with extremely limited treatment options and unclear pathogenesis. CAV constitutes a significant complication that limits the long-term survival of heart recipients. Insulin-like growth factor-1 (IGF-1) is associated with different cardiovascular diseases; however, its role in CAV pathogenesis remains unknown.

METHODS

Serum samples of 10 matched recipients with CAV and 10 with no-CAV were initially screened with a protein array. Subsequently, IGF-1- and IGF-binding protein-3 (IGFBP-3) were analyzed using enzyme-linked immunosorbent assay in 44 randomly selected CAV and 50 no-CAV patients at two time points.

RESULTS

The initial screening showed that IGF-1 and IGFBP-3 are differentially expressed in CAV compared with no-CAV patients (P=0.037 and P<0.0001, respectively). Subsequent enzyme-linked immunosorbent assay analyses indicated that serum IGF-1 protein concentrations were significantly lower in CAV patients (159.7±114 ng/mL) as compared with no-CAV patients (234.1±136 ng/mL; P=0.02). Serum IGFBP-3 protein concentrations were significantly lower in CAV (0.46±0.37 mg/L) as compared with no-CAV patients (1.03±0.73 mg/L; P=0.04). Multivariate logistic regression analyses showed that IGF-1 (odds ratio, 0.89; P=0.04) and IGFBP-3 (odds ratio, 0.09; P=0.03) are independent risk factors for CAV.

CONCLUSION

Low IGF-1 and IGFPB-3 serum concentrations are associated with CAV. The assessment of serum IGF-1 and IGFPB-3 might be beneficial in identifying cardiac allograft recipients who are prone to develop CAV. Moreover, IGF-1 might be a useful therapy that could protect cardiac allografts against CAV.

Kaempferol protects against doxorubicin-induced cardiotoxicity in vivo and in vitro

The long-term clinical usefulness of doxorubicin (DOX), an anthracycline with potent antitumor activity, is limited by DOX-induced cardiotoxicity. Kaempferol, one of the most common dietary flavonoids, is known to have anti-apoptotic, anti-oxidative, and anti-inflammatory properties. The current study aimed to investigate the possible protective effect of kaempferol against DOX-induced cardiotoxicity and the underlying mechanisms. Rats were intraperitoneally (i.p.) treated with DOX (3 mg/kg) every other day for a cumulative dose of 9 mg/kg. After 28 days, DOX caused retarded body and heart growth, oxidative stress, apoptotic damage, mitochondrial dysfunction, and Bcl-2 expression disturbance. In contrast, kaempferol pretreatment (10 mg/kg i.p. before DOX administration) attenuated the DOX-induced apoptotic damage in heart tissues. In vitro studies also indicated that kaempferol may have used the mitochondrion-dependent pathway to counteract the DOX-induced cardiotoxicity. This counteraction was achieved by inhibiting p53 expression and its binding to the promoter region of the Bax proapoptotic gene, but not to the Bcl-2 antiapoptotic gene. Kaempferol also effectively suppressed DOX-induced extracellular signal-regulated kinase (ERK) 1/2 activation, but had no effect on p38 and JNK. Therefore, kaempferol protected against DOX-induced cardiotoxicity, at least, partially, by inhibiting the activation of p53-mediated, mitochondrion-dependent apoptotic signaling, and by being involved in an ERK-dependent mitogen-activated protein kinase pathway. These findings elucidated the potential of kaempferol as a promising reagent for treating DOX-induced cardiotoxicity, and may have implications in the long-term clinical usefulness of DOX.

Mitochondrial Akt-regulated mitochondrial apoptosis signaling in cardiac muscle cells

We recently reported translocation and activation of Akt in cardiac mitochondria. This study was to determine whether activation of Akt in mitochondria could inhibit apoptosis of cardiac muscle cells. Insulin stimulation induced translocation of phosphorylated Akt to the mitochondria in primary cardiomyocytes. A mitochondria-targeted constitutively active Akt was overexpressed via adenoviral vector and inhibited efflux of cytochrome c and apoptosis-inducing factor from mitochondria to cytosol and partially prevented loss of mitochondria cross-membrane electrochemical gradient. Activation of caspase 3 was suppressed in the cardiomyocytes transduced with mitochondria-targeted active Akt, whereas a mitochondria-targeted dominant negative Akt enhanced activation of caspase 3. Terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling assay showed that mitochondrial activation of Akt significantly reduced the number of apoptotic cells. When the endogenous Akt was abolished by LY294002, the antiapoptotic actions of mitochondrial Akt remained effective. These experiments suggested that mitochondrial Akt suppressed apoptosis signaling independent of cytosolic Akt in cardiac muscle cells.

Propofol ameliorates doxorubicin-induced oxidative stress and cellular apoptosis in rat cardiomyocytes

BACKGROUND

Propofol is an anesthetic with pluripotent cytoprotective properties against various extrinsic insults. This study was designed to examine whether this agent could also ameliorate the infamous toxicity of doxorubicin, a widely-used chemotherapeutic agent against a variety of cancer diseases, on myocardial cells.

METHODS

Cultured neonatal rat cardiomyocytes were administrated with vehicle, doxorubicin (1μM), propofol (1μM), or propofol plus doxorubicin (given 1h post propofol). After 24h, cells were harvested and specific analyses regarding oxidative/nitrative stress and cellular apoptosis were conducted.

RESULTS

Trypan blue exclusion and MTT assays disclosed that viability of cardiomyocytes was significantly reduced by doxorubicin. Contents of reactive oxygen and nitrogen species were increased and antioxidant enzymes SOD1, SOD2, and GPx were decreased in these doxorubicin-treated cells. Mitochondrial dehydrogenase activity and membrane potential were also depressed, along with activation of key effectors downstream of mitochondrion-dependent apoptotic signaling. Besides, abundance of p53 was elevated and cleavage of PKC-δ was induced in these myocardial cells. In contrast, all of the above oxidative, nitrative and pro-apoptotic events could be suppressed by propofol pretreatment.

CONCLUSIONS

Propofol could extensively counteract oxidative/nitrative and multiple apoptotic effects of doxorubicin in the heart; hence, this anesthetic may serve as an adjuvant agent to assuage the untoward cardiac effects of doxorubicin in clinical application.

The protective role of arjunolic acid against doxorubicin induced intracellular ROS dependent JNK-p38 and p53-mediated cardiac apoptosis

In spite of tremendous demand for the development and implementation of effective therapeutic strategies, limitations are still associated with doxorubicin-induced cardiotoxicity. Arjunolic acid (AA) has been shown to possess a multitude of biological functions. The purpose of the present study was to explore whether AA plays any protective role against doxorubicin-induced cardiotoxicity; and if so, what molecular mechanism it utilizes for its protective action. In rat cardiomyocytes, doxorubicin administration activated the proapoptotic p53, p38 and JNK MAPKs, Bax translocation, disrupted mitochondrial membrane potential, precipitated mitochondrion mediated caspase-dependent apoptotic signalling and reduced viability of cardiomyocytes. Doxorubicin exposure increases dichlorofluorescein (DCF) intensity corresponding to the intracellular H(2)O(2) generation in myocytes; catalase (CAT) treatment, however, reduced this intensity and preserves cell viability. Intracellular H(2)O(2) thus produced now activates the p38-JNK and p53-mediated pathways. CAT treatment also markedly decreased the doxorubicin-mediated activation of p38 and JNK, suggesting that H(2)O(2) is involved in the activation of MAPKs. Blockage of p53 and p38-JNK by pharmacological inhibitors also suppressed the doxorubicin-induced apoptosis with the concomitant inhibition of anti-apoptotic Bcl-2 family proteins. AA treatment ameliorates nearly all of these apoptotic actions of doxorubicin and preserves cell viability. Similarly, rats treated with doxorubicin displayed retarded growth of body and heart as well as elevated apoptotic indices in heart tissue, whereas AA treatment effectively neutralised all these doxorubicin-induced cardiac-abnormalities. Combining all, our results suggest that doxorubicin induces cardiac apoptosis via the activation of JNK-p38 and p53-mediated signalling pathways, where H(2)O(2) acts as the mediators of these pathways. AA can effectively and extensively counteract this action of doxorubicin, and may potentially protect the heart and cardiomyocytes from the severe doxorubicin-induced cardiovascular burden.

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.

Hepatotoxicity of di-(2-ethylhexyl)phthalate is attributed to calcium aggravation, ROS-mediated mitochondrial depolarization, and ERK/NF-κB pathway activation

Di-(2-ethylhexyl)phthalate (DEHP) is a widely used plasticizer found in a variety of polyvinyl chloride medical products. Although DEHP-induced cytotoxicity and apoptosis are well studied in various cell types, the precise mechanisms are not well understood so far. This study, aimed at going beyond the toxicology approach, focuses on the molecular mechanisms through which DEHP causes hepatotoxicity. We show that DEHP induces apoptotic cell death in a dose-dependent manner, as proven by an increase in annexin V-positively stained cells, DAPI/PI staining, and immunofluorescence studies. The DEHP-induced decrease in cell viability was significantly inhibited by adding catalase (CAT), but CAT treatment did not suppress the DEHP-stimulated calcium flux in the hepatocytes, whereas BAPTA-AM significantly reduced the DEHP-stimulated DCF intensity. These results demonstrate that DEHP increases the intracellular calcium level, which mediates the generation of H(2)O(2) in hepatocytes. Investigating cell-signaling mechanisms, we found that DEHP induced apoptotic cell death by mitochondrial-dependent caspase-3 activation and PARP cleavage. These changes due to DEHP exposure were associated with increased IKK and NF-κB phosphorylation. Preexposure of hepatocytes to an IKK inhibitor (PS-1145) prevented DEHP-induced caspase-3 and PARP cleavage. DEHP also markedly increased the activity of ERK1/2 MAPK. Pretreatment with the ERK inhibitor PD98059 attenuated NF-κB and IKK phosphorylation, indicating that ERK MAPK is mainly involved in DEHP-induced NF-κB activation. These results, for the first time, reveal that DEHP induces apoptosis in hepatocytes via the activation of the ERK/NF-κB signaling pathway, in which calcium ions and hydrogen peroxide act as the pivotal mediators of the apoptotic signaling.

Mechanisms of anthracycline cardiac injury: can we identify strategies for cardioprotection?

Anthracycline antibiotics have saved the lives of many cancer victims in the 50 plus years since their discovery. A major limitation of their use is the dose-limiting cardiotoxicity. Efforts focusing on understanding the biochemical basis for anthracycline cardiac effects have provided several strategies currently in clinical use: limit dose exposure, encapsulate anthracyclines in liposomes to reduce myocardial uptake, administer concurrently with the iron chelator dexrazoxane to reduce free iron-catalyzed reactive oxygen species formation; and modify anthracycline structure in an effort to reduce myocardial toxicity. Despite these efforts, anthracycline-induced heart failure continues to occur with consequences for both morbidity and mortality. Our inability to predict and prevent anthracycline cardiotoxicity is, in part, due to the fact that the molecular and cellular mechanisms remain controversial and incompletely understood. Studies examining the effects of anthracyclines in cardiac myocytes in vitro and small animals in vivo have demonstrated several forms of cardiac injury, and it remains unclear how these translate to the clinical setting. Given the clinical evidence that myocyte death occurs after anthracycline exposure in the form of elevations in serum troponin, myocyte cell death seems to be a probable mechanism for anthracycline-induced cardiac injury. Other mechanisms of myocyte injury include the development of cellular "sarcopenia" characterized by disruption of normal sarcomere structure. Anthracyclines suppress expression of several cardiac transcription factors, and this may play a role in the development of myocyte death as well as sarcopenia. Degradation of the giant myofilament protein titin may represent an important proximal step that leads to accelerated myofilament degradation. An interesting interaction has been noted clinically between anthracyclines and newer cancer therapies that target the erbB2 receptor tyrosine kinase. There is now evidence that erbB2 signaling in response to the ligand neuregulin regulates anthracycline uptake into cells via the multidrug-resistance protein. Therefore, up-regulation of cardiac neuregulin signaling may be one strategy to limit myocardial anthracycline injury. Moreover, assessing an individual's risk for anthracycline injury may be improved by having some measure of endogenous activity of this and other myocardial protective signals.

Grape seed proanthocyanidins ameliorate Doxorubicin-induced cardiotoxicity

Doxorubicin (Dox) is one of the most widely used and successful chemotherapeutic antitumor drugs. Its clinical application is highly limited due to its cumulative dose-related cardiotoxicity. Proposed mechanisms include the generation of reactive oxygen species (ROS)-mediated oxidative stress. Therefore, reducing oxidative stress should be protective against Dox-induced cardiotoxicity. To determine whether antioxidant, grape seed proanthocyanidin extract (GSPE) attenuates Dox-induced ROS generation and protects cardiomyocytes from Dox-induced oxidant injury, cultured primary cardiomyocytes were treated with doxorubicin (Dox, 10 microM) alone or GSPE (50 microg/ml) with Dox (10 microM) for 24 hours. Dox increased intracellular ROS production as measured by 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, induced significant cell death as assessed by propidium iodide, and declined the redox ratio of reduced glutathione (GSH)/oxidized glutathione (GSSG) and disrupted mitochondrial membrane potential as determined by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethlbenzimidazole-carbocyanide iodine (JC-1). Analysis of agarose gel electrophoresis revealed Dox-induced nuclear DNA damage with the ladder like fragmentation. GSPE treatment suppressed those alterations. Electron Spin Resonance (ESR) spectroscopy data also showed that GSPE strongly scavenged hydroxyl radical, superoxide and DPPH radicals. Together, these findings indicate that GSPE in combination with Dox has protective effect against Dox-induced toxicity in cardiomyocytes, which may be in part attributed to its antioxidative activity. Importantly, flow cytometric analysis demonstrated that co-treatment of Dox and GSPE did not decrease the proliferation-inhibitory effect of Dox in MCF-7 human breast carcinoma cells. Thus, GSPE may be a promising adjuvant to prevent cardiotoxicity without interfering with antineoplastic activity during chemotherapeutic treatment with Dox.

PHLPP-1 negatively regulates Akt activity and survival in the heart

RATIONALE

The recently discovered PHLPP-1 (PH domain leucine-rich repeat protein phosphatase-1) selectively dephosphorylates Akt at Ser473 and terminates Akt signaling in cancer cells. The regulatory role of PHLPP-1 in the heart has not been considered.

OBJECTIVE

To test the hypothesis that blockade/inhibition of PHLPP-1 could constitute a novel way to enhance Akt signals and provide cardioprotection.

METHODS AND RESULTS

PHLPP-1 is expressed in neonatal rat ventricular myocytes (NRVMs) and in adult mouse ventricular myocytes (AMVMs). PHLPP-1 knockdown by small interfering RNA significantly enhances phosphorylation of Akt (p-Akt) at Ser473, but not at Thr308, in NRVMs stimulated with leukemia inhibitory factor (LIF). The increased phosphorylation is accompanied by greater Akt catalytic activity. PHLPP-1 knockdown enhances LIF-mediated cardioprotection against doxorubicin and also protects cardiomyocytes against H(2)O(2). Direct Akt effects at mitochondria have been implicated in cardioprotection and mitochondria/cytosol fractionation revealed a significant enrichment of PHLPP-1 at mitochondria. The ability of PHLPP-1 knockdown to potentiate LIF-mediated increases in p-Akt at mitochondria and an accompanying increase in mitochondrial hexokinase-II was demonstrated. We generated PHLPP-1 knockout (KO) mice and demonstrate that AMVMs isolated from KO mice show potentiated p-Akt at Ser473 in response to agonists. When isolated perfused hearts are subjected to ischemia/reperfusion, p-Akt in whole-heart homogenates and in the mitochondrial fraction is significantly increased. Additionally in PHLPP-1 KO hearts, the increase in p-Akt elicited by ischemia/reperfusion is potentiated and, concomitantly, infarct size is significantly reduced.

CONCLUSIONS

These results implicate PHLPP-1 as an endogenous negative regulator of Akt activity and cell survival in the heart.

Human umbilical cord blood derived stem cells repair doxorubicin-induced pathological cardiac hypertrophy in mice

In the present study, we investigated the cardiomyogenic potential of human umbilical cord blood (hUCB)-derived stem cells and whether stem cell treatment repairs the pathological hypertrophy induced by doxorubicin (DOX) in cultured neonatal rat cardiomyocytes (NRCM) and in mouse hearts. hUCB, which were labeled with cell tracker dye, were co-cultured with isolated NRCM in vitro. After 48h of incubation, the red stained hUCB cells (30%) contracted rhythmically and synchronously (physical examination). These differentiated hUCB also expressed cardiac specific alpha-actinin and showed diffused expression of connexin 43 and N-cadherin, thereby suggesting a tight electrical coupling among hUCB cells and myocytes. When co-cultured, hUCB also reversed the pathological effects induced by DOX in NRCM and in mice as seen by RT-PCR, immunoblot analysis and immunocytochemistry. hUCB migrated and integrated into the hearts of mice that were treated with DOX after intravenous injection and reversed the expression of pathological hypertrophic markers induced by DOX in mice. Further, we observed a shift from pathological hypertrophy towards physiological hypertrophy by hUCB in DOX-challenged mice. hUCB treatment in mice decreased DOX-induced increase of heart weight to body mass ratio and fibrosis. Taken together, these findings suggest the potential therapeutic use of hUCB in reversing heart failure conditions.

Lyn-mediated mitochondrial tyrosine phosphorylation is required to preserve mitochondrial integrity in early liver regeneration

Functional alterations in mitochondria such as overproduction of ROS (reactive oxygen species) and overloading of calcium, with subsequent change in the membrane potential, are traditionally regarded as pro-apoptotic conditions. Although such events occur in the early phases of LR (liver regeneration) after two-thirds PH (partial hepatectomy), hepatocytes do not undergo apoptosis but continue to proliferate until the mass of the liver is restored. The aim of the present study was to establish whether tyrosine phosphorylation, an emerging mechanism of regulation of mitochondrial function, participates in the response to liver injury following PH and is involved in contrasting mitochondrial pro-apoptotic signalling. Mitochondrial tyrosine phosphorylation, negligible in the quiescent liver, was detected in the early phases of LR with a trend similar to the events heralding mitochondrial apoptosis and was attributed to the tyrosine kinase Lyn, a member of the Src family. Lyn was shown to accumulate in an active form in the mitochondrial intermembrane space, where it was found to be associated with a multiprotein complex. Our results highlight a role for tyrosine phosphorylation in accompanying, and ultimately counteracting, mitochondrial events otherwise leading to apoptosis, hence conveying information required to preserve the mitochondrial integrity during LR.

Mitochondrial integrity: preservation through Akt/Pim-1 kinase signaling in the cardiomyocyte

The central role of mitochondria as mediators of cell survival is indisputable and gathering increasing attention as a focal point for interventional strategies to mitigate apoptotic cell death in the wake of cardiomyopathic injury. A legacy of signal transduction studies has proven that mitochondrial integrity can be enhanced by kinases involved in cell survival. Among the many survival signaling cascades under investigation, the wide-ranging impact of Akt upon mitochondrial biology is well known. However, despite years of investigation, emerging research continues to reveal new mechanisms governing the protective effects of Akt signaling in the context of cardiomyocyte mitochondria. This review focuses on two emerging pathways that mediate preservation of mitochondrial function downstream of Akt: hexokinase and Pim-1 kinase.

Atrogin-1, MuRF1, and FoXO, as well as phosphorylated GSK-3beta and 4E-BP1 are reduced in skeletal muscle of chronic spinal cord-injured patients

Chronic complete spinal cord injury (SCI) is associated with severe skeletal muscle atrophy as well several atrophy and physical-inactivity-related comorbidity factors such as diabetes, obesity, lipid disorders, and cardiovascular diseases. Intracellular mechanisms associated with chronic complete SCI-related muscle atrophy are not well understood, and thus their characterization may assist with developing strategies to reduce the risk of comorbidity factors. Therefore, the aim of this study was to determine whether there was an increase in catabolic signaling targets, such as atrogin-1, muscle ring finger-1 (MuRF1), forkhead transcription factor (FoXO), and myostatin, and decreases in anabolic signaling targets, such as insulin-like growth factor (IGF), v-akt murine thymoma viral oncogene (Akt), glycogen synthase kinase-beta (GSK-3beta), mammalian target of rapamycin (mTOR), eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and p70(s6kinase) in chronic complete SCI patients. In SCI patients, when compared with controls, there was a significant reduction in mRNA levels of atrogin-1 (59%; P < 0.05), MuRF1 (55%; P < 0.05), and myostatin (46%; P < 0.01), and in protein levels of FoXO1 (72%; P < 0.05), FoXO3a (60%; P < 0.05), and atrogin-1 (36%; P < 0.05). Decreases in the protein levels of IGF-1 (48%; P < 0.001) and phosphorylated GSK-3beta (54%; P < 0.05), 4E-BP1 (48%; P < 0.05), and p70(s6kinase) (60%; P = 0.1) were also observed, the latter three in an Akt- and mTOR-independent manner. Reductions in atrogin-1, MuRF1, FoXO, and myostatin suggest the existence of an internal mechanism aimed at reducing further loss of muscle proteins during chronic SCI. The downregulation of signaling proteins that regulate anabolism, such as IGF, GSK-3beta, and 4E-BP1, would reduce the ability to increase protein synthesis rates.

Nuclear and mitochondrial signalling Akts in cardiomyocytes

Biological actions resulting from phosphoinositide synthesis trigger multiple downstream signalling cascades by recruiting proteins with pleckstrin homology domains, including phosphoinositide-dependent kinase-1 and protein kinase B (also known as Akt). Retrospectively, more attention has been focused on the plasma membrane-associated interactions of these molecules and resulting cytoplasmic target activation. The complex biological activities exerted by Akt activation suggest, however, that more subtle and complex subcellular control mechanisms are involved. This review examines the regulation of Akt activity from the perspective of subcellular compartmentalization and focuses specifically upon the actions of Akt activation downstream from phosphoinositide synthesis that influence cell biology by altering nuclear signalling leading to Pim-1 kinase induction as well as hexokinase phosphorylation that, together with Akt, serves to preserve mitochondrial integrity.

Akt mediated mitochondrial protection in the heart: metabolic and survival pathways to the rescue

Cardiomyocyte death is now recognized as a critical factor in the development of heart disease. Mitochondria are not only responsible for energy production to ensure that cardiac output meets the body's energy demands, but they serve as critical integrators of cell survival signals. Numerous stressors are known to induce cell death by necrosis and/or apoptosis mediated through mitochondrial dysregulation. Anti- and pro-apoptotic Bcl-2 family proteins regulate apoptosis by controlling mitochondrial outer membrane permeability, whereas opening of the mitochondrial permeability transition pore (PT-pore) induces large amplitude permeability of the inner membrane and consequent rupture of the outer membrane. Akt is one of the best described survival kinases activated by receptor ligands and its activation preserves mitochondrial integrity and protects cardiomyocytes against necrotic and apoptotic death. The mechanisms responsible for Akt-mediated mitochondrial protection have not been fully elucidated. There is, however, accumulating evidence that multiple Akt target molecules, recruited through both transcriptional and post-transcriptional mechanisms, directly impinge upon and protect mitochondria. In this review we discuss mechanisms by which Akt activation can effect changes at the mitochondria that protect cardiomyocytes and attenuate pathophysiological responses of the heart.

Insulin stimulates Akt translocation to mitochondria: implications on dysregulation of mitochondrial oxidative phosphorylation in diabetic myocardium

Mitochondrial oxidative phosphorylation is the major source of energy in cardiac muscle. In the streptozotocin-induced diabetic (STZ-DM) mice, myocardial oxidative phosphorylation was perturbated and oxidative phosphorylation complex V (ATP synthase) activity was significantly reduced. To determine the independent effects of hyperglycemia and insulin deficiency on the changes of myocardial complex V, we used phlorizin (Ph) to normalize blood glucose in the diabetic mice. Ph treatment did not improve myocardial complex V activity in the STZ-DM mice, whereas insulin treatment normalized myocardial complex V activity in the diabetic mice. Therefore, the reduction of complex V activity was caused by insulin deficiency and not by hyperglycemia in STZ-DM myocardium. Acute insulin stimulation induced phosphorylation of Akt and translocation of Akt to mitochondria in myocardium. Translocation of phospho-Akt to mitochondria was enhanced in the STZ-DM mice and was blunted in the diet-induced diabetic mice. In parallel, insulin activation of complex V was enhanced in the STZ-DM myocardium and suppressed in the diet-induced diabetic myocardium. In vivo inhibition of Akt blocked insulin stimulation of phospho-Akt translocation and blunted activation of complex V. Insulin-activated Akt translocation to mitochondria in cardiac muscle is a novel paradigm that may have important implications on myocardial bioenergetics.

Heat shock protein 20 interacting with phosphorylated Akt reduces doxorubicin-triggered oxidative stress and cardiotoxicity

Doxorubicin (DOX) is a widely used antitumor drug, but its application is limited because of its cardiotoxic side effects. Heat shock protein (Hsp)20 has been recently shown to protect cardiomyocytes against apoptosis, induced by ischemia/reperfusion injury or by prolonged beta-agonist stimulation. However, it is not clear whether Hsp20 would exert similar protective effects against DOX-induced cardiac injury. Actually, DOX treatment was associated with downregulation of Hsp20 in the heart. To elucidate the role of Hsp20 in DOX-triggered cardiac toxicity, Hsp20 was first overexpressed ex vivo by adenovirus-mediated gene delivery. Increased Hsp20 levels conferred higher resistance to DOX-induced cell death, compared to green fluorescent protein control. Furthermore, cardiac-specific overexpression of Hsp20 in vivo significantly ameliorated acute DOX-triggered cardiomyocyte apoptosis and animal mortality. Hsp20 transgenic mice also showed improved cardiac function and prolonged survival after chronic administration of DOX. The mechanisms underlying these beneficial effects were associated with preserved Akt phosphorylation/activity and attenuation of DOX-induced oxidative stress. Coimmunoprecipitation studies revealed an interaction between Hsp20 and phosphorylated Akt. Accordingly, BAD phosphorylation was preserved, and cleaved caspase-3 was decreased in DOX-treated Hsp20 transgenic hearts, consistent with the antiapoptotic effects of Hsp20. Parallel ex vivo experiments showed that either infection with a dominant-negative Akt adenovirus or preincubation of cardiomyocytes with the phosphatidylinositol 3-kinase inhibitors significantly attenuated the protective effects of Hsp20. Taken together, our findings indicate that overexpression of Hsp20 inhibits DOX-triggered cardiac injury, and these beneficial effects appear to be dependent on Akt activation. Thus, Hsp20 may constitute a new therapeutic target in ameliorating the cardiotoxic effects of DOX treatment in cancer patients.

Ginkgo biloba extract 761 reduces doxorubicin-induced apoptotic damage in rat hearts and neonatal cardiomyocytes

AIMS

The objective of this study was to investigate whether a cytoprotective herb-derived agent, Ginkgo biloba extract (EGb) 761, could have a beneficial effect on doxorubicin-induced cardiac toxicity in vitro and in vivo.

METHODS AND RESULTS

Primary cultured neonatal rat cardiomyocytes were treated with the vehicle, doxorubicin (1 microM), EGb761 (25 microg/mL), or EGb761 plus doxorubicin. After 24 h, doxorubicin upregulated p53 mRNA expression, disturbed Bcl-2 family protein balance, disrupted mitochondrial membrane potential, precipitated mitochondrion-dependent apoptotic signalling, induced apoptotic cell death, and reduced viability of cardiomyocytes, whereas EGb761 pretreatment suppressed all the actions of doxorubicin. Similarly, rats treated with doxorubicin [3 mg/kg intraperitoneally (i.p.) three doses every other day] displayed retarded growth of body and heart as well as elevated apoptotic indexes in heart tissue at both 7 and 28 days after exposure, whereas EGb761 pretreatment (5 mg/kg i.p. 1 day before each dose of doxorubicin) effectively neutralized the aforementioned gross and cellular adverse effects of doxorubicin.

CONCLUSION

Doxorubicin impairs viability of cardiomyocytes at least partially by activating the p53-mediated, mitochondrion-dependent apoptotic signalling. EGb761 can effectively and extensively counteract this action of doxorubicin, and may potentially protect the heart from the severe toxicity of doxorubicin.

Protection by doxycycline against doxorubicin-induced oxidative stress and apoptosis in mouse testes

Spermatogenic cells constitute one of the body tissues that are susceptible to doxorubicin-induced oxidative stress and apoptosis. To explore whether doxorubicin toxicity to these male germ cells could be prevented by adjuvant medication, this study was designed to examine the possible ameliorating action of doxycycline, an antibiotic with anti-oxidant property, on doxorubicin-induced oxidative and apoptotic effects in mouse testes. Male mice at 5-week of age were treated with vehicles, doxorubicin alone (3 mg/kg, i.p. every other day for 3 doses), doxycycline alone (2.5 mg/kg, i.p. every other day for 3 doses), or doxycycline plus doxorubicin (each dose given 1 day post-doxycycline). After 28 days, mice treated with doxorubicin alone displayed smaller body and testicular weights, reduced sperm counts, impaired spermatogenic capability (scarcer spermatids and spermatocytes), increased oxidative stress (malondialdehyde levels), decreased anti-oxidant activity (superoxide dismutase and glutathione peroxidase), and elevated apoptotic indexes (upregulation of Bax and Bad, downregulation of Bcl-2 and Bcl-xL, release of cytochrome c from mitochondria to cytosol, activation of caspase-3, and increase of cleaved caspase-3 abundance and TUNEL positive cells), while doxycycline pretreatment could effectively prevent nearly all of these abnormalities. These results provide firm evidence that doxycycline pretreatment would offset the oxidative and apoptotic impact imposed by doxorubicin, and imply doxycycline to be a promising adjuvant agent that may attenuate the toxicity of doxorubicin on testicular tissues in clinical practice.

Pleiotropic effects of PI-3' kinase/Akt signaling in human hepatoma cell proliferation and drug-induced apoptosis

IGF-II and type I-IGF receptor (IGF-IR) gene expression is increased in primary liver tumors, and transgenic mice overexpressing IGF-II in the liver develop hepatocellular carcinoma (HCC) spontaneously, suggesting that alterations of IGF-IR signaling in vivo may play a role in the auto/paracrine control of hepatocarcinogenesis. We have addressed the contribution of PI-3'K/Akt signaling on the proliferation of HepG2 human hepatoma cells and on their protection against doxorubicin-induced apoptosis. Both basal HepG2 cell DNA replication and that stimulated by IGF-IR signaling were inhibited by the specific PI-3'K inhibitor Ly294002 (Ly). In the former case, PI-3'K signaling overcame cell cycle arrest in G1 via increased cyclin D1 protein and decreased p27kip1 gene expression. Doxorubicin treatment induced apoptosis in HepG2 cells and was concomitant with the proteolytic cleavage of Akt-1 and -2. Drug-induced apoptosis was reversed by IGF-I and this effect was (i) dependent on Akt-1 and -2 phosphorylation and (ii) accompanied by the inhibition of initiator caspase-9 activity, suggesting that IGF-IR signaling interferes with mitochondria-dependent apoptosis. Accordingly, Ly enhanced doxorubicin-induced apoptosis and suppressed its reversal by IGF-I. Altogether, the data emphasize the crucial role of PI-3'K/Akt signaling (i) in basal as well as IGF-IR-stimulated HepG2 cell proliferation and (ii) in controlling both doxorubicin-induced apoptosis (e.g., drug-induced cleavage of Akt) and its reversal by IGF-I (protection against apoptosis parallels the extent of Akt phosphorylation). They suggest that targeting Akt activity or downstream Akt effectors (e.g., GSK3-beta, FOXO transcription factors) may help define novel therapeutic strategies of increased efficacy in the treatment of HCC-bearing patients.

Mitochondrial involvement in IGF-1 induced protection of cardiomyocytes against hypoxia/reoxygenation injury

Studies in animal models of myocardial ischemia-reperfusion revealed that the administration of insulin-like growth factor (IGF-1) can provide substantial cardioprotective effect. However, the mechanisms by which IGF-1 prevents myocardial ischemia-reperfusion injury are not fully understood. This study addresses whether mitochondrial bioenergetic pathways are involved in the cardioprotective effects of IGF-1. Single cardiomyocytes from adult rats were incubated in the absence or presence of IGF-1 for 60 min and subjected to 60 min hypoxia followed by 30 min reoxygenation at 37 degrees C. Mitochondrial function was evaluated by assessment of enzyme activities of oxidative phosphorylation and Krebs cycle pathways. Hypoxia/reoxygenation (HR) caused significant inhibition of mitochondrial respiratory complex IV and V activities and of the Krebs cycle enzyme citrate synthase, whereas pretreatment with IGF-1 maintained enzyme activities in myocytes at or near control levels. Mitochondrial membrane potential, evaluated with JC-1 staining, was significantly higher in IGF-1 + HR- treated myocytes than in HR alone, with levels similar to those found in normal control cardiomyocytes. In addition, IGF-1 reduced both HR-induced lactate dehydrogenase (LDH) release and malondialdehyde production (an indicator of lipid peroxidation) in cardiomyocytes. These results suggest that IGF-1 protects cardiomyocytes from HR injury via stabilizing mitochondria and reducing reactive oxidative species (ROS) damage.

IGF-I mediated survival pathways in normal and malignant cells

The type-I and -II insulin-like growth factors (IGF-I, II) are now established as survival- or proliferation-factors in many in vitro systems. Of note IGFs provide trophic support for multiple cell types or organ cultures explanted from various species, and delay the onset of programmed cell death (apoptosis) through the mitochondrial (intrinsic pathway) or by antagonizing activation of cytotoxic cytokine signaling (extrinsic pathway). In some instances, IGFs protect against other forms of death such as necrosis or autophagy. The effect of IGFs on cell survival appears to be context specific, being determined both by the cell origin (tissue specific) and the cellular stress that induces loss of cellular viability. In many human cancers, there is a strong association with dysregulated IGF signaling, and this association has been extensively reviewed recently. IGF-regulation is also disrupted in childhood cancers as a consequence of chromosomal translocations. IGFs are implicated also in acute renal failure, traumatic injury to brain tissue, and cardiac disease. This article focuses on the role of IGFs and their cellular signaling pathways that provide survival signals in stressed cells.

Cyclic and characteristic expression of phosphorylated Akt in human endometrium and decidual cells in vivo and in vitro

BACKGROUND

Akt is activated by phosphorylation and plays an important role in cell survival and maintenance of structure.

METHODS

We investigated whether phosphorylated Akt was characteristically expressed in human endometrium in vivo and whether insulin-like growth factor-I (IGF-I) can activate Akt using cultured decidualized human stromal cells in vitro, using immunohistochemistry and Western blotting analysis.

RESULTS

The levels of phosphorylated Akt protein increased markedly in the decidual tissues from ectopic pregnancy. The expression of phosphorylated Akt protein in stromal cells increased with the decidualization. The decidual cells showed strong cytoplasmic staining for phosphorylated Akt. However, cultured decidualized human stromal cells diminished phosphorylated Akt expression compared to control cells. IGF-I administration to decidualized human stromal cells significantly recovered pAkt expression. The effect of IGF-I on decidualized human stromal cells was blocked by an inhibitor of phosphatidylinositol-3 kinase (PI3K) (LY294,002). These results suggest that IGF-I may activate Akt via PI3K in human endometrium and decidua. The expression of phosphorylated Akt in stromal cells was only detected in the functional layer, where tissue remodelling occurs during menstruation or implantation.

CONCLUSIONS

Akt activation may be involved in cell survival and extracellular matrix remodelling in human endometrium and decidua.

Ca2+ Dysregulation Induces Mitochondrial Depolarization and Apoptosis

We previously reported that constitutively activated Galpha(q) (Q209L) expression in cardiomyocytes induces apoptosis through opening of the mitochondrial permeability transition pore. We assessed the hypothesis that disturbances in Ca(2+) handling linked Galpha(q) activity to apoptosis because resting Ca(2+) levels were significantly increased prior to development of apoptosis. Treating cells with EGTA lowered Ca(2+) and blocked both loss of mitochondrial membrane potential (an indicator of permeability transition pore opening) and apoptosis (assessed by DNA fragmentation). When cytosolic Ca(2+) and mitochondrial membrane potential were simultaneously measured by confocal microscopy, sarcoplasmic reticulum (SR)-driven slow Ca(2+) oscillations (time-to-peak approximately 4 s) were observed in Q209L-expressing cells. These oscillations were seen to transition into sustained increases in cytosolic Ca(2+), directly paralleled by loss of mitochondrial membrane potential. Ca(2+) transients generated by caffeine-induced release of SR Ca(2+) were greatly prolonged in Q209L-expressing cells, suggesting a decreased ability to extrude Ca(2+). Indeed, the Na(+)/Ca(2+) exchanger (NCX), which removes Ca(2+) from the cell, was markedly down-regulated at the mRNA and protein levels. Adenoviral NCX expression normalized cytosolic Ca(2+) levels and prevented DNA fragmentation in cells expressing Q209L. Interestingly, constitutively activated Akt, which rescues cells from Q209L-induced apoptosis, prevented the decrease in NCX expression, normalized cytosolic Ca(2+) levels and spontaneous Ca(2+) oscillations, shortened caffeine-induced Ca(2+) transients, and prevented loss of the mitochondrial membrane potential. Our findings demonstrate that NCX down-regulation and consequent increases in cytosolic and SR Ca(2+) can lead to Ca(2+) overloading-induced loss of mitochondrial membrane potential and suggest that recovery of Ca(2+) dysregulation is a target of Akt-mediated protection.

Angiogenic growth factors and/or cellular therapy for myocardial regeneration: A comparative study

BACKGROUND

Locally delivered angiogenic growth factors and cell implantation have been proposed for patients with myocardial infarcts without a possibility of percutaneous or surgical revascularization. The goal of this study was to compare the effects of these techniques in an experimental model of myocardial infarct.

METHODS

Left ventricular myocardial infarction was created in 27 sheep by ligation of 2 coronary arteries. Three weeks after creation of the infarct, animals were randomized into 4 groups. In group 1, sheep received a culture medium injection to the infarct area (control group); group 2 underwent autologous myoblast implantation; group 3 received vascular endothelial growth factor; and group 4 received injection of both vascular endothelial growth factor and myoblasts. Evaluation included serum troponin IC levels, echocardiography (2-dimensional and color kinesis), and immunohistologic studies for quantitative analysis of capillaries (3 months after surgery).

RESULTS

Four animals died of refractory ventricular fibrillation during myocardial infarction; 2 died after surgery because of stroke and 2 because of infections. Serum troponin increased to 45.6 +/- 4.7 ng/mL at postinfarction day 2. Echocardiography at 3 months showed a significant limitation of left ventricular dilation in the cell group (57 +/- 11.1 mL) and in the cell plus vascular endothelial growth factor group (58.6 +/- 6.6 mL: control group, 74.4 +/- 11.2 mL; vascular endothelial growth factor group, 68.1 +/- 3.4 mL). Color kinesis echography showed important improvements of regional fractional area change in the cell group (from 13.6% +/- 0.8% to 21.1% +/- 1.5%) and in the cell plus vascular endothelial growth factor group (from 12.8% +/- 0.9% to 18.7% +/- 2.3%). The number of capillaries increased in the peri-infarct region of the vascular endothelial growth factor group (1036 +/- 75: control group, 785 +/- 31; cell group, 830 +/- 75; cell plus vascular endothelial growth factor group, 831 +/- 83).

CONCLUSIONS

In the cell therapy groups, regional ventricular contractility improved and heart dilatation was limited compared with either vascular endothelial growth factor or control; thus, postischemic remodeling was reduced. Angiogenesis was demonstrated in the vascular endothelial growth factor group, without improvement of ventricular function and remodeling. To improve local conditions for cell survival, further studies are warranted on prevascularization of myocardial scars with angiogenic therapy.