Bcl-xL gene transfer inhibits Bax translocation and prolongs cardiac cold preservation time in rats

Mitochondrion-targeted carboxymethyl chitosan hybrid nanoparticles loaded with Coenzyme Q10 protect cardiac grafts against cold ischaemia‒reperfusion injury in heart transplantation

BACKGROUND

Heart transplantation (HT) has been approved as an optimal therapeutic regimen for patients with terminal-stage cardiac failure. However, cold ischaemia‒reperfusion (I/R) injury remains an unavoidable and outstanding challenge, which is a major factor in early graft dysfunction and an obstacle to long-term survival in HT. Cold I/R injury induces cardiac graft injury by promoting mitochondrial dysfunction and augmenting free radical production and inflammatory responses. We therefore designed a mitochondrion-targeted nanocarrier loaded with Coenzyme Q10 (CoQ10) (CoQ10@TNPs) for treatment of cold I/R injury after cardiac graft in a murine heterotopic cardiac transplantation model.

METHODS

Hybrid nanoparticles composed of CaCO3/CaP/biotinylated-carboxymethylchitosan (CaCO3/CaP/BCMC) were synthesized using the coprecipitation method, and the mitochondria-targeting tetrapeptide SS31 was incorporated onto the surface of the hybrid nanoparticles through biotin-avidin interactions. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis were used for characterisation. In vitro, the hypoxia-reoxygenation model of H9c2 cells was employed to replicate in vivo cold I/R injury and treated with CoQ10@TNPs. The impact of CoQ10@TNPs on H9c2 cell injury was assessed by analysis of oxidative damage and apoptosis. In vivo, donor hearts (DHs) were perfused with preservation solution containing CoQ10@TNPs and stored in vitro at 4 °C for 12 h. The DHs were heterotopically transplanted and analysed for graft function, oxidative damage, apoptosis, and inflammatory markers 1 day post-transplantation.

RESULTS

CoQ10@TNPs were successfully synthesized and delivered CoQ10 to the mitochondria of the cold ischaemic myocardium. In vitro experiments demonstrated that CoQ10@TNPs was taken up by H9c2 cells at 4 °C and localized within the mitochondria, thus ameliorating oxidative stress damage and mitochondrial injury in cold I/R injury. In vivo experiments showed that CoQ10@TNPs accumulated in DH tissue at 4 °C, localized within the mitochondria during cold storage and improved cardiac graft function by attenuating mitochondrial oxidative injury and inflammation.

CONCLUSIONS

CoQ10@TNPs can precisely deliver CoQ10 to the mitochondria of cold I/R-injured cardiomyocytes to effectively eliminate mitochondrial reactive oxygen species (mtROS), thus reducing oxidative injury and inflammatory reactions in cold I/R-injured graft tissues and finally improving heart graft function. Thus, CoQ10@TNPs offer an effective approach for safeguarding cardiac grafts against extended periods of cold ischaemia, emphasizing the therapeutic potential in mitigating cold I/R injury during HT. These findings present an opportunity to enhance existing results following HT and broaden the range of viable grafts for transplantation.

A Review of Chinese Herbal Medicine for the Treatment of Chronic Heart Failure

Heart failure is one of the major causes of mortality worldwide and it is the end stage of sev-eral cardiovascular diseases. Traditional Chinese medicine has been used in the management of heart failure for a long time. Only until recently, well-designed clinical trials have been put into practice to study the efficacies of Chinese herbs. Extensive studies have also been carried out to explore the under-lying mechanisms of pharmaceutical actions of Chinese herbs. In this study, we will summarize the frequently used Chinese herbs, formulae and patent Chinese drugs in treating patients with heart failure and review published clinical evaluations of Chinese herbs in treating cardiovascular diseases. The mechanisms by which Chinese herbs exert cardio-protective effects will also be reviewed. In the end, we will point out the limitations of current studies and challenges facing modernization of traditional Chi-nese medicine.

Participation of GATA-3 in regulation of bone healing through transcriptional upregulation of bcl-xL expression

We have previously demonstrated the expression of GATA-DNA-binding protein (GATA)-3, a transcription factor, in osteoblasts and have verified its function in transducing cell survival signaling. This translational study was further designed to evaluate the roles of GATA-3 in regulating bone healing and to explore its possible mechanisms. A metaphyseal bone defect was created in the left femurs of male ICR mice. Analysis by micro-computed topography showed that the bone volume, trabecular bone number and trabecular thickness were augmented and that the trabecular pattern factor decreased. Interestingly, immunohistological analyses showed specific expression of GATA-3 in the defect area. In addition, colocalized expression of GATA-3 and alkaline phosphatase was observed at the wound site. As the fracture healed, the amounts of phosphorylated and non-phosphorylated GATA-3 concurrently increased. Separately, GATA-3 mRNA was induced during bone healing, and, levels of Runx2 mRNA and protein were also increased. The results of confocal microscopy and co-immunoprecipitation showed an association between nuclear GATA-3 and Runx2 in the area of insult. In parallel with fracture healing, Bcl-XL mRNA was significantly triggered. A bioinformatic search revealed the existence of a GATA-3-specific DNA-binding element in the promoter region of the bcl-xL gene. Analysis by chromatin immunoprecipitation assays further demonstrated transactivation activity by which GATA-3 regulated bcl-xL gene expression. Therefore, this study shows that GATA-3 participates in the healing of bone fractures via regulating bcl-xL gene expression, owing to its association with Runx2. In the clinic, GATA-3 may be used as a biomarker for diagnoses/prognoses or as a therapeutic target for bone diseases, such as bone fractures.

Development and Evaluation of Heartbeat: A Machine Perfusion Heart Preservation System

Static cold storage is accompanied with a partial safe ischemic interval for donor hearts. In this current study, a machine perfusion system was built to provide a better preservation for the donor heart and assessment for myocardial function. Chinese mini-swine (weight 30-35 kg, n = 16) were randomly divided into HTK, Celsior, and Heartbeat groups. All donor hearts were respectively preserved for 8 hours under static cold storage or machine perfusion. The perfusion solution is aimed to maintain its homeostasis based on monitoring the Heartbeat group. The ultrastructure of myocardium suggests better myocardial protection in the Heartbeat group compared with HTK or Celsior-preserved hearts. The myocardial and coronary artery structural and functional integrity was evaluated by immunofluorescence and Western blots in the Heartbeat. In the Heartbeat group, donor hearts maintained a high adenosine triphosphate level. Bcl-2 and Beclin-1 protein demonstrates high expression in the Celsior group. The Heartbeat system can be used to preserve donor hearts, and it could guarantee the myocardial and endothelial function of hearts during machine perfusion. Translating Heartbeat into clinical practice, it is such as to impact on donor heart preservation for cardiac transplantation.

mDia1 regulates breast cancer invasion by controlling membrane type 1-matrix metalloproteinase localization

Mammalian diaphanous-related formin 1 (mDia1) expression has been linked with progression of malignant cancers in various tissues. However, the precise molecular mechanism underlying mDia1-mediated invasion in cancer cells has not been fully elucidated. In this study, we found that mDia1 is upregulated in invasive breast cancer cells. Knockdown of mDia1 in invasive breast cancer profoundly reduced invasive activity by controlling cellular localization of membrane type 1-matrix metalloproteinase (MT1-MMP) through interaction with microtubule tracks. Gene silencing and ectopic expression of the active form of mDia1 showed that mDia1 plays a key role in the intracellular trafficking of MT1-MMP to the plasma membrane through microtubules. We also demonstrated that highly invasive breast cancer cells possessed invasive activity in a 3D culture system, which was significantly reduced upon silencing mDia1 or MT1-MMP. Furthermore, mDia1-deficient cells cultured in 3D matrix showed impaired expression of the cancer stem cell marker genes, CD44 and CD133. Collectively, our findings suggest that regulation of cellular trafficking and microtubule-mediated localization of MT1-MMP by mDia1 is likely important in breast cancer invasion through the expression of cancer stem cell genes.

Effect of Temperature Downshift on the Transcriptomic Responses of Chinese Hamster Ovary Cells Using Recombinant Human Tissue Plasminogen Activator Production Culture

Recombinant proteins are widely used as biopharmaceuticals, but their production by mammalian cell culture is expensive. Hence, improvement of bioprocess productivity is greatly needed. A temperature downshift (TDS) from 37°C to 28–34°C is an effective strategy to expand the productive life period of cells and increase their productivity (q_p). Here, TDS in Chinese hamster ovary (CHO) cell cultures, initially grown at 37°C and switched to 30°C during the exponential growth phase, resulted in a 1.6-fold increase in the q_p of recombinant human tissue plasminogen activator (rh-tPA). The transcriptomic response using next-generation sequencing (NGS) was assessed to characterize the cellular behavior associated with TDS. A total of 416 (q > 0.8) and 3,472 (q > 0.9) differentially expressed transcripts, with more than a 1.6-fold change at 24 and 48 h post TDS, respectively, were observed in cultures with TDS compared to those at constant 37°C. In agreement with the extended cell survival resulting from TDS, transcripts related to cell growth arrest that controlled cell proliferation without the activation of the DNA damage response, were differentially expressed. Most upregulated genes were related to energy metabolism in mitochondria, mitochondrial biogenesis, central metabolism, and avoidance of apoptotic cell death. The gene coding for rh-tPA was not differentially expressed, but fluctuations were detected in the transcripts encoding proteins involved in the secretory machinery, particularly in glycosylation. Through NGS the dynamic processes caused by TDS were assessed in this biological system.

The mitochondria-targeted anti-oxidant MitoQ decreases ischemia-reperfusion injury in a murine syngeneic heart transplant model

Background

Free radical production and mitochondrial dysfunction during cardiac graft reperfusion is a major factor in post-transplant ischemia-reperfusion (IR) injury, an important underlying cause of primary graft dysfunction. We therefore assessed the efficacy of the mitochondria-targeted anti-oxidant MitoQ in reducing IR injury in a murine heterotopic cardiac transplant model.

Methods

Hearts from C57BL/6 donor mice were flushed with storage solution alone, solution containing the anti-oxidant MitoQ, or solution containing the non–anti-oxidant decyltriphenylphosphonium control and exposed to short (30 minutes) or prolonged (4 hour) cold preservation before transplantation. Grafts were transplanted into C57BL/6 recipients and analyzed for mitochondrial reactive oxygen species production, oxidative damage, serum troponin, beating score, and inflammatory markers 120 minutes or 24 hours post-transplant.

Results

MitoQ was taken up by the heart during cold storage. Prolonged cold preservation of donor hearts before IR increased IR injury (troponin I, beating score) and mitochondrial reactive oxygen species, mitochondrial DNA damage, protein carbonyls, and pro-inflammatory cytokine release 24 hours after transplant. Administration of MitoQ to the donor heart in the storage solution protected against this IR injury by blocking graft oxidative damage and dampening the early pro-inflammatory response in the recipient.

Conclusions

IR after heart transplantation results in mitochondrial oxidative damage that is potentiated by cold ischemia. Supplementing donor graft perfusion with the anti-oxidant MitoQ before transplantation should be studied further to reduce IR-related free radical production, the innate immune response to IR injury, and subsequent donor cardiac injury.

Bcl-xL Genetic Modification Enhanced the Therapeutic Efficacy of Mesenchymal Stem Cell Transplantation in the Treatment of Heart Infarction

Objectives. Low survival rate of mesenchymal stem cells (MSCs) severely limited the therapeutic efficacy of cell therapy in the treatment of myocardial infarction (MI). Bcl-xL genetic modification might enhance MSC survival after transplantation. Methods. Adult rat bone marrow MSCs were modified with human Bcl-xL gene (hBcl-xL-MSCs) or empty vector (vector-MSCs). MSC apoptosis and paracrine secretions were characterized using flow cytometry, TUNEL, and ELISA in vitro. In vivo, randomized adult rats with MI received myocardial injections of one of the three reagents: hBcl-xL-MSCs, vector-MSCs, or culture medium. Histochemistry, TUNEL, and echocardiography were carried out to evaluate cell engraftment, apoptosis, angiogenesis, scar formation, and cardiac functional recovery. Results. In vitro, cell apoptosis decreased 43%, and vascular endothelial growth factor (VEGF), insulin-like growth factor-1 (IGF-1), and plate-derived growth factor (PDGF) increased 1.5-, 0.7-, and 1.2-fold, respectively, in hBcl-xL-MSCs versus wild type and vector-MSCs. In vivo, cell apoptosis decreased 40% and 26% in hBcl-xL-MSC group versus medium and vector-MSC group, respectively. Similar results were observed in cell engraftment, angiogenesis, scar formation, and cardiac functional recovery. Conclusions. Genetic modification of MSCs with hBcl-xL gene could be an intriguing strategy to improve the therapeutic efficacy of cell therapy in the treatment of heart infarction.

The study of the intercellular trafficking of the fusion proteins of herpes simplex virus protein VP22

BACKGROUND

Genetic modifications can improve the therapeutic efficacy of mesenchymal stem cell (MSC) transplantation in myocardial infarction. However, so far, the efficiency of MSC modification is very low. Seeking for a more efficient way of MSC modification, we investigated the possibility of employing the intercellular trafficking capacity of the herpes simplex virus type-1 tegument protein VP22 on the enhancement of MSC modification.

METHODS

Plasmids pVP22-myc, pVP22-EGFP, pEGFP-VP22, pVP22-hBcl-xL and phBcl-xL-VP22 were constructed for the expressions of the myc-tagged VP22 and the fusion proteins VP22-EGFP, EGFP-VP22, VP22-hBcl-xL and hBcl-xL-VP22. MSCs were isolated from rat bone marrow and the surface markers were identified by Flowcytometry. COS-1 cells were transfected with the above plasmids and co-cultured with untransfected MSCs, the intercellular transportations of the constructed proteins were studied by immunofluorescence. The solubility of VP22-hBcl-xL and hBcl-xL-VP22 was analyzed by Western blot.

RESULTS

VP22-myc could be expressed in and spread between COS-1 cells, which indicates the validity of our VP22 expression construct. Flowcytometry analysis revealed that the isolated MSCs were CD29, CD44, and CD90 positive and were negative for the hematopoietic markers, CD34 and CD45. The co-culturing and immunofluorescence assay showed that VP22-myc, VP22-EGFP and EGFP-VP22 could traffic between COS-1 cells and MSCs, while the evidence of intercellular transportation of VP22-hBcl-xL and hBcl-xL-VP22 was not detected. Western blot analysis showed that VP22-hBcl-xL and hBcl-xL-VP22 were both insoluble in the cell lysate suggesting interactions of the fusion proteins with other cellular components.

CONCLUSIONS

The intercellular trafficking of VP22-myc, VP22-EGFP and EGFP-VP22 between COS-1 cells and MSCs presents an intriguing prospect in the therapeutic application of VP22 as a delivery vehicle which enhances genetic modifications of MSCs. However, VP22-hBcl-xL and hBcl-xL-VP22 failed to spread between cells, which are due to the insolubility of the fusion protein incurred by interactions with other cellular components.

Gr-1+CD11b+ myeloid cells efficiently home to site of injury after intravenous administration and enhance diabetic wound healing by neoangiogenesis

Vascularization is an important factor that affects diabetic wound healing. There is increasing evidence that myeloid cell lineages play a role in neovascularization. In this study, the efficiency of Gr-1+CD11b+ myeloid cells to home to the site of injury and enhance diabetic wound healing by neoangiogenesis after intravenous administration was investigated. Gr-1+CD11b+ myeloid cells were injected into tail vein after establishment of dorsal window chamber, hindlimb ischaemia and ear-punch injury in diabetic or non-diabetic mice. The Gr-1+CD11b+ myeloid cells efficiently homed to the site of injury after intravenous administration and increased neoangiogenesis. The chemokine receptor type 4 (CXCR4) is robustly expressed by Gr-1+CD11b+ myeloid cells. Inhibition of CXCR4 decreases the homing ability of Gr-1+CD11b+ myeloid cells to the site of injury, which indicates that the CXCR4/SDF-1 axis plays an important role in the homing of Gr-1+CD11b+ myeloid cells to the site of injury. In addition, Gr-1+CD11b+ myeloid cells were found to improve blood flow recovery of ischaemic limb and enhance wound healing in diabetic mice by neoangiogenesis after intravenous administration. Taken together, the results of this study suggest that Gr-1+CD11b+ myeloid cells may serve as a potential cell therapy for diabetic wound healing.

Genomics of liver transplant injury and regeneration

While improved surgical techniques, post-operative care, and immunosuppression regimens have reduced morbidity and mortality associated with orthotopic liver transplantation (OLT), further improvement of outcomes requires personalized treatment and a better understanding of genomic mechanisms involved. Gene expression profiles of ischemia/reperfusion (I/R) injury, regeneration, and rejection, may suggest mechanisms for development of better predictive tools and treatments. The liver is unique in its regenerative potential, recovering lost mass and function after injury from ischemia, resection, and rejection. I/R injury, an inevitable consequence of perfusion cessation, cold storage, and reperfusion, is regulated by the interaction of the immune system, inflammatory cytokines, and reduced microcirculatory blood flow in the liver. Rejection, a common post-operative complication, is mediated by the recipient's immune system through T-cell-dependent responses activating proinflammatory and apoptotic pathways. Characterizing distinctive gene expression signatures for these events can identify therapies to reduce injury, promote regeneration, and improve outcomes. While certain markers of liver injury and regeneration have been observed in animals, many of these are unverified in human studies. Further investigation of these genomic signatures and mechanisms through new technology offers promise, but continues to pose a significant challenge. An overview of the current fund of knowledge in this area is reviewed.

Treatment with bone morphogenetic protein 2 limits infarct size after myocardial infarction in mice

Various strategies have been devised to reduce the clinical consequences of myocardial infarction, including acute medical care, revascularization, stem cell transplantations, and more recently, prevention of cardiomyocyte cell death. Activation of embryonic signaling pathways is a particularly interesting option to complement these strategies and to improve the functional performance and survival rate of cardiomyocytes. Here, we have concentrated on bone morphogenetic protein 2 (BMP-2), which induces ectopic formation of beating cardiomyocytes during development in the mesoderm and protects neonatal cardiomyocytes from ischemia-reperfusion injury. In a mouse model of acute myocardial infarction, an i.v. injection of BMP-2 reduced infarct size in mice when given after left anterior descending artery ligation. Mice treated with BMP-2 are characterized by a reduced rate of apoptotic cardiomyocytes both in the border zone of the infarcts and in the remote myocardium. In vitro, BMP-2 increases the frequency of spontaneously beating neonatal cardiomyocytes and the contractile performance under electrical pacing at 2 Hz, preserves cellular adenosine triphosphate stores, and decreases the rate of apoptosis despite the increased workload. In addition, BMP-2 specifically induced phosphorylation of Smad1/5/8 proteins and protected adult cardiomyocytes from long-lasting hypoxia-induced cellular damage and oxidative stress without activation of the cardiodepressant transforming growth factor-β pathway. Our data suggest that BMP-2 treatment may have considerable therapeutic potential in individuals with acute and chronic myocardial ischemia by improving the contractility of cardiomyocytes and preventing cardiomyocyte cell death.

Apoptosis and autophagy contribute to gender difference in cardiac ischemia-reperfusion induced injury in rats

AIMS

Gender difference in cardiac ischemia-reperfusion (IR) induced injury has been reported in animal models. However, a large-scale clinical trial found an increase in cardiovascular incidents in women with hormone replacement therapy. The present study is aimed to explore possible mechanisms of gender difference in cardiac IR induced injury.

MAIN METHODS

Male and female Sprague-Dawley rats were subjected to a 30-min coronary arterial occlusion followed by reperfusion. The infarct size and apoptotic cell number at 24h after reperfusion were significantly lower in female rats than in male rats.

KEY FINDINGS

Male rats expressed higher anti-apoptotic protein Bcl2 levels compared with female rats under physiological conditions. However, levels of Bcl2 were reduced significantly after IR in male rats but not in, female rats. Levels of pro-apoptotic protein, Bax and phospho-p38, showed similar under physiological conditions. In response to IR expression of Bax was markedly reduced in female rats but not in male rats, and expression of phospho-p38 was significantly increased in male rats but not in female rats. In addition, female rats showed marked increase of autophagy marker, ratio of LC3B to LC3A, while male rats significantly decreased the ratio in response to IR.

SIGNIFICANCE

Gender difference in IR injury is due to the different regulation of anti-apoptotic protein, pro-apoptotic protein and autophagy protein levels in male rats and levels in female rats. Our results provide better understanding of sex differences in cardiac IR injury.

Mitochondrial membrane permeabilization and cell death during myocardial infarction: roles of calcium and reactive oxygen species

Excess generation of reactive oxygen species (ROS) and cytosolic calcium accumulation play major roles in the initiation of programmed cell death during acute myocardial infarction. Cell death may include necrosis, apoptosis and autophagy, and combinations thereof. During ischemia, calcium handling between the sarcoplasmic reticulum and myofilament is disrupted and calcium is diverted to the mitochondria causing swelling. Reperfusion, while essential for survival, reactivates energy transduction and contractility and causes the release of ROS and additional ionic imbalance. During acute ischemia-reperfusion, the principal death pathways are programmed necrosis and apoptosis through the intrinsic pathway, initiated by the opening of the mitochondrial permeability transition pore and outer mitochondrial membrane permeabilization, respectively. Despite intense investigation, the mechanisms of action and modes of regulation of mitochondrial membrane permeabilization are incompletely understood. Extrinsic apoptosis, necroptosis and autophagy may also contribute to ischemia-reperfusion injury. In this review, the roles of dysregulated calcium and ROS and the contributions of Bcl-2 proteins, as well as mitochondrial morphology in promoting mitochondrial membrane permeability change and the ensuing cell death during myocardial infarction are discussed.

Real time measurement of myocardial oxygen dynamics during cardiac ischemia-reperfusion of rats

Because oxygen plays a critical role in the pathophysiology of myocardial injury during subsequent reperfusion, as well as ischemia, the accurate measurement of myocardial oxygen tension is crucial for the assessment of myocardial viability by ischemia-reperfusion (IR) injury. Therefore, we utilized a sol-gel derived electrochemical oxygen microsensor to monitor changes in oxygen tension during myocardial ischemia-reperfusion. We also analyzed differences in oxygen tension recovery in post-ischemic myocardium depending on ischemic time to investigate the correlation between recovery parameters for oxygen tension and the severity of IR injury. An oxygen sensor was built using a xerogel-modified platinum microsensor and a coiled Ag/AgCl reference electrode. Rat hearts were randomly divided into 5 groups: control (0 min ischemia), I-10 (10 min ischemia), I-20 (20 min ischemia), I-30 (30 min ischemia), and I-40 (40 min ischemia) groups (n = 3 per group, respectively). After the induction of ischemia, reperfusion was performed for 60 min. As soon as the ischemia was initiated, oxygen tension rapidly declined to near zero levels. When reperfusion was initiated, the changes in oxygen tension depended on ischemic time. The normalized peak level of oxygen tension during the reperfusion episode was 188 ± 27 in group I-10, 120 ± 24 in group I-20, 12.5 ± 10.6 in group I-30, and 1.24 ± 1.09 in group I-40 (p < 0.001, n = 3, respectively). After 60 min of reperfusion, the normalized restoration level was 129 ± 30 in group I-10, 88 ± 4 in group I-20, 3.40 ± 4.82 in group I-30, and 0.99 ± 0.94 in group I-40 (p < 0.001, n = 3, respectively). The maximum and restoration values of oxygen tension in groups I-30 and I-40 after reperfusion were lower than pre-ischemic values. In particular, oxygen tension in the I-40 group was not recovered at all. These results were also demonstrated by TTC staining. We suggest that these recovery parameters could be utilized as an index of tissue injury and severity of ischemia. Therefore, quantitative measurements of oxygen tension dynamics in the myocardium would be helpful for evaluation of the cardioprotective effects of therapeutic treatments such as drug administration.

Impaired cardioprotective function of transplantation of mesenchymal stem cells from patients with diabetes mellitus to rats with experimentally induced myocardial infarction

Background

Diabetes mellitus (DM) exacerbates coronary artery disease (CAD) morbidity and mortality. Mesenchymal stem cells (MSCs) play an important therapeutic role in myocardial ischemic injury. However, little is known about changes in the cardioprotective characteristics of MSCs from patients with DM.

Methods

Sternal bone marrow aspirates were taken at the time of coronary artery bypass graft surgery. The morphology and growth characteristics of hMSCs were observed in passage 3. Differences in gene expression profiling were measured by Affymetrix GeneChipHuman Genome U133 Plus 2.0 Arrays. Forty two adult male rats with experimentally CAD were randomized into three groups. MSCs from patients with CAD+DM or CAD were injected into the infarcted myocardium. Control animals received culture medium. Echocardiography, TUNEL, immunohistochemistry and Western-blot analysis were performed 4 weeks after transplantation.

Results

Growth curves showed that proliferation of hMSCs in the CAD+DM group was significantly lower than in the CAD group. Nine transcripts of genes related to apoptosis containing Bcl-2 were found to differentiate the two groups. Transplantation of hMSCs in the infarcted border zone improved cardiac function, but DM partly impaired this effect. Similar results were observed from TUNEL, immunohistochemistry and Western-blot analysis.

Conclusions

hMSCs from patients with CAD+DM and CAD alone both have proliferative properties. Transplantation of hMSCs ameliorate heart function, but proliferative ability and myocardial protection decrease significantly in MSCs obtained from patients with CAD+DM compared with cultures from patients with CAD alone, possibly as a result of differences in Bcl-2 protein expression and reduced anti-apoptosis.

Prevention of acute kidney injury by tauroursodeoxycholic acid in rat and cell culture models

BACKGROUND

Acute kidney injury (AKI) has grave short- and long-term consequences. Often the onset of AKI is predictable, such as following surgery that compromises blood flow to the kidney. Even in such situations, present therapies cannot prevent AKI. As apoptosis is a major form of cell death following AKI, we determined the efficacy and mechanisms of action of tauroursodeoxycholic acid (TUDCA), a molecule with potent anti-apoptotic and pro-survival properties, in prevention of AKI in rat and cell culture models. TUDCA is particularly attractive from a translational standpoint, as it has a proven safety record in animals and humans.

METHODOLOGY/PRINCIPAL FINDINGS

We chose an ischemia-reperfusion model in rats to simulate AKI in native kidneys, and a human kidney cell culture model to simulate AKI associated with cryopreservation in transplanted kidneys. TUDCA significantly ameliorated AKI in the test models due to inhibition of the mitochondrial pathway of apoptosis and upregulation of survival pathways.

CONCLUSIONS

This study sets the stage for testing TUDCA in future clinical trials for prevention of AKI, an area that needs urgent attention due to lack of effective therapies.

Successful transplantation of rat hearts subjected to extended cold preservation with a novel preservation solution

Since prolonged cold preservation of the heart deteriorates the outcome of heart transplantation, a more protective preservation solution is required. We therefore developed a new solution, named Dsol, and examined whether Dsol, in comparison to UW, could better inhibit myocardial injury resulting from prolonged cold preservation. Syngeneic heterotopic heart transplantation in Lewis rats was performed after cold preservation with UW or Dsol for 24 or 36 h. In addition to graft survival, myocardial injury, ATP content, and Ca(2+) -dependent proteases activity were assessed in the 24-h preservation group. The cytosolic Ca(2+) concentration of H9c2 cardiomyocytes after 24-h cold preservation was assessed. Dsol significantly improved 7-day graft survival after 36-h preservation. After 24-h preservation, Dsol was associated with significantly faster recovery of ATP content and less activation of calpain and caspase-3 after reperfusion. Dsol diminished graft injury significantly, as revealed by the lower levels of infarction, apoptosis, serum LDH and AST release, and graft fibrosis at 7-day. Dsol significantly inhibited Ca(2+) overload during cold preservation. Dsol inhibited myocardial injury and improved graft survival by suppressing Ca(2+) overload during the preservation and the activation of Ca(2+) -dependent proteases. Dsol is therefore considered a better alternative to UW to ameliorate the outcome of heart transplantation.

Alternatively spliced tissue factor and full-length tissue factor protect cardiomyocytes against TNF-α-induced apoptosis

Tissue Factor (TF) is expressed in various cell types of the heart, such as cardiomyocytes. In addition to its role in the initiation of blood coagulation, the TF:FVIIa complex protects cells from apoptosis. There are two isoforms of Tissue Factor (TF): "full length" (fl)TF--an integral membrane protein, and alternatively spliced (as)TF--a protein that lacks a transmembrane domain and can thus be secreted in a soluble form. Whether asTF or flTF affects apoptosis of cardiomyocytes is unknown. In this study, we examined whether asTF or flTF protects murine cardiomyocytes from TNF-α-induced apoptosis. We used murine cardiomyocytic HL-1 cells and primary murine embryonic cardiomyocytes that overexpressed either murine asTF or murine flTF, and stimulated them with TNF-α to initiate cell death. Apoptosis was assessed by annexin-V assay, propidium iodide assay, as well as activation of caspase-3 and -9. In addition, signaling via integrins, Akt, NFκB and Erk1/2, and gene-expression of Bcl-2 family members were analyzed. We here report that overexpression of asTF reduced phosphatidylserine exposure upon TNF-α-stimulation. asTF overexpression led to an increased expression and phosphorylation of Akt, as well as up-regulation of the anti-apoptotic protein Bcl-x(L). The anti-apoptotic effects of asTF overexpression were mediated via α(V)β(3)/Akt/NFκB signaling and were dependent on Bcl-x(L) expression in HL-1 cells. The anti-apoptotic activity of asTF was also observed using primary cardiomyocytes. Analogous yet less pronounced anti-apoptotic sequelae were observed due to overexpression of flTF. Importantly, cardiomyocytes deficient in TF exhibited increased apoptosis compared to wild type cells. We propose that asTF and flTF protect cardiomyocytes against TNF-α-induced apoptosis via activation of specific signaling pathways, and up-regulation of anti-apoptotic members of the Bcl-2 protein family.

Dexamethasone induces transcriptional activation of Bcl-xL gene and inhibits cardiac injury by myocardial ischemia

Psychological or physical stress causes an elevation of glucocorticoids in the circulating system. Glucocorticoids regulate a variety of physiological functions, from energy metabolism and biochemical homeostasis to immune response. Synthetic steroids are among the most prescribed drugs for immune suppression and chemotherapy. While glucocorticoids are best known for inducing apoptosis in a number of cell types, we have found that corticosteroids at stress relevant levels protect cardiomyocytes from apoptosis. Current study addresses whether glucocorticoids inhibit cardiac injury in vivo. Adult male C57BL6 mice were administered with dexamethasone (20mg/kg, i.p.) or vehicle control 20 h prior to left anterior descending coronary artery occlusion surgery. Myocardial infarction was measured by triphenyl tetrazoliumchloride staining in tissue slices and by levels of cardiac Troponin (cTn I) in the blood. Treatment of dexamethasone markedly reduced infarct size (19.6 ± 4.3%, vs. 29.2 ± 4.9%, p<0.01) and cTn I level in the blood (3.83 ± 0.66 ng/ml vs. 5.62 ± 0.37 ng/ml, p<0.01). In studying the mechanism of such protection, we found that dexamethasone induces the expression of Bcl-xL gene in the myocardium. With cardiomyocytes in culture, glucocorticoids increased transcription of Bcl-xL gene as evidenced by Bcl-xL mRNA increase and promoter activation. The glucocorticoid receptor antagonist mifepristone prevented dexamethasone from inducing cardiac protection or Bcl-xL expression. Our data suggest that activation of glucocorticoid receptor can prevent cardiac injury through transcriptional activation of Bcl-xL gene.

Heat shock protein 90 mediates anti-apoptotic effect of diazoxide by preventing the cleavage of Bid in hypothermic preservation rat hearts

BACKGROUND

Successful organ preservation is the premise for clinical organ transplantation. The present study investigated whether heat shock protein 90 (Hsp90) is important in the anti-apoptotic effect of diazoxide in hypothermic preservation rat hearts.

METHODS

Isolated rat hearts were preserved in Celsior solution, with or without diazoxide, for 3 to 9 hours, followed by 60 minutes of reperfusion. Cell apoptosis was assessed by terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling. The left ventricular developed pressure (LVDP) was recorded. Expression of Hsp90 protein and cleavage of Bid were detected by Western blot and polymerase chain reaction.

RESULTS

After hypothermic preservation for 3 to 9 hours, the LVDP recovery rate significantly decreased and cardiomyocyte apoptosis index increased in a time-dependent manner. When compared with the 9-hour preservation group, Celsior solution supplemented with diazoxide significantly enhanced the LVDP recovery rate and decreased the apoptosis index. The cleavage of Bid increased after 9 hours of hypothermic preservation, which was inhibited by Celsior solution supplemented with diazoxide. Hypothermic preservation of rat hearts for 9 hours decreased the expression of Hsp90, whereas diazoxide supplementation significantly increased the expression of Hsp90. The Hsp90 inhibitor 17-allylamino-17-demethoxy-geldanamycin inhibited the diazoxide-induced decrease in cleavage of Bid, improvement of cardiac function, and decrease of apoptosis. Hsp90 inhibitor had no effect on the diazoxide-induced increase of total Cx43 protein expression in hearts preserved 9 hours, but inhibited the diazoxide-induced increase of mitochondrial Cx43 protein level.

CONCLUSION

Hsp90 might mediate diazoxide-induced cardioprotection against apoptosis in hypothermic preservation heart by preventing the cleavage of Bid.

GATA-3 transduces survival signals in osteoblasts through upregulation of bcl-x(L) gene expression

GATA-3, a transcription factor, participates in regulating cell development, proliferation, and death. This study was aimed at evaluating the roles of GATA-3 in protecting osteoblasts against oxidative stress-induced apoptotic insults and their possible mechanisms. Pretreatment with nitric oxide (NO) for 24 hours protected osteoblasts, prepared from neonatal rat calvaria, against oxidative stress-induced apoptotic insults. Such protection involved enhancement of Bcl-X(L) messenger mRNA and protein syntheses and the translocation of this antiapoptotic protein from the cytoplasm to mitochondria. GATA-3 was detected in rat osteoblasts, and GATA-3-specific DNA-binding elements exist in the promoter region of the bcl-x(L) gene. NO preconditioning attenuated oxidative stress-caused suppression of GATA-3 mRNA and protein synthesis and the translocation of this transcription factor from the cytoplasm to nuclei. Application of GATA-3 small interfering siRNA into osteoblasts decreased the levels of this transcription factor and simultaneously inhibited Bcl-X(L) mRNA synthesis. Pretreatment with NO lowered the oxidative stress-caused alteration in the binding of GATA-3 to its specific DNA motifs. Oxidative stress-inhibited Runx2 mRNA expression, but NO preconditioning decreased such inhibition. NO pretreatment time-dependently enhanced the association of GATA-3 with Runx2. Knocking down the translation of GATA-3 using RNA interference significantly decreased the protection of NO preconditioning against oxidative stress-induced alterations of cell morphologies, DNA fragmentation, and cell apoptosis. In comparison, overexpression of GATA-3 could promote NO preconditioning-involved Bcl-X(L) expression and cell survival. Therefore, this study shows that GATA-3 plays critical roles in mediating survival signals in osteoblasts, possibly through upregulating bcl-x(L) gene expression.

Runx2-mediated bcl-2 gene expression contributes to nitric oxide protection against hydrogen peroxide-induced osteoblast apoptosis

Nitric oxide (NO) can regulate osteoblast activities. This study was aimed to evaluate the protective effects of pretreatment with sodium nitroprusside (SNP) as a source of NO on hydrogen peroxide-induced osteoblast insults and its possible mechanisms. Exposure of human osteosarcoma MG63 cells to hydrogen peroxide significantly increased cellular oxidative stress, but decreased ALP activity and cell viability, inducing cell apoptosis. Pretreatment with 0.3 mM SNP significantly lowered hydrogen peroxide-induced cell insults. Treatment of human MG63 cells with hydrogen peroxide inhibited Bcl-2 mRNA and protein production, but pretreatment with 0.3 mM SNP significantly ameliorated such inhibition. Sequentially, hydrogen peroxide decreased the mitochondrial membrane potential, but increased the levels of cytochrome c and caspase-3 activity. Pretreatment with 0.3 mM SNP significantly lowered such alterations. Exposure to hydrogen peroxide decreased Runx2 mRNA and protein syntheses. However, pretreatment with 0.3 mM SNP significantly lowered the suppressive effects. Runx2 knockdown using RNA interference inhibited Bcl-2 mRNA production in human MG63 cells. Protection of pretreatment with 0.3 mM SNP against hydrogen peroxide-induced alterations in ALP activity, caspase-3 activity, apoptotic cells, and cell viability were also alleviated after administration of Runx2 small interference RNA. Thus, this study shows that pretreatment with 0.3 mM SNP can protect human MG63 cells from hydrogen peroxide-induced apoptotic insults possibly via Runx2-involved regulation of bcl-2 gene expression.

Anti-inflammatory treatment strategies for ischemia/reperfusion injury in transplantation

Inflammatory reactions in the graft have a pivotal influence on acute as well as long-term graft function. The main reasons for an inflammatory reaction of the graft tissue are rejection episodes, infections as well as ischemia/reperfusion (I/R) injury. The latter is of particular interest as it affects every solid organ during the process of transplantation. I/R injury impairs acute as well as long-term graft function and is associated with an increased number of acute rejection episodes that again affect long-term graft outcome.

I/R injury is the result of ATP depletion during prolonged hypoxia. Further tissue damage results from the reperfusion of the tissue after the ischemic insult. Adaptive cellular responses activate the innate immune system with its Toll-like receptors and the complement system as well as the adaptive immune system. This results in a profound inflammatory tissue reaction with immune cells infiltrating the tissue. The damage is mediated by various cytokines, chemokines, adhesion molecules, and compounds of the extracellular matrix. The expression of these factors is regulated by specific transcription factors with NF-κB being one of the key modulators of inflammation.

Strategies to prevent or treat I/R injury include blockade of cytokines/chemokines, adhesion molecules, NF-κB, specific MAP kinases, metalloproteinases, induction of protective genes, and modulation of the innate immune system. Furthermore, preconditioning of the donor is an area of intense research. Here pharmacological treatment as well as new additives to conventional cold storage solutions have been analyzed together with new techniques for the perfusion of grafts, or methods of normothermic storage that would avoid the problem of cold damage and graft ischemia.

However, the number of clinical trials in the field of I/R injury is limited as compared to the large body of experimental knowledge that accumulated during recent years in the field of I/R injury. Future activities in the treatment of I/R injury should focus on the translation of experimental protocols into clinical trials in order to reduce I/R injury and, thus, improve short- as well as long-term graft outcome.

Polymerized placenta hemoglobin attenuates ischemia/reperfusion injury and restores the nitroso-redox balance in isolated rat heart

Ischemia/reperfusion (I/R) injury mainly caused by oxidative stress plays a major role in cardiac damage. The extent of the I/R injury is also an important factor that determines the function of a transplanted heart. This study first examined whether hemoglobin-based oxygen carriers (HBOCs) could protect isolated rat heart from I/R injury and then elucidated the underlying mechanism. Using the Langendorff model, isolated Sprague-Dawley rat hearts were arrested and stored at 4 degrees C for 8 h and then reperfused for 2 h. Compared with St. Thomas' solution (STS) and rat self blood in STS, polymerized placenta hemoglobin (PolyPHb) in STS greatly improved heart contraction and decreased infarction size. The extent of myocardial apoptosis was also significantly decreased, which was related to reduced iNOS-derived nitric oxide production, increased protein ratio of Bcl-2/Bax, and reduced caspase-3 activity and cleavage level. Furthermore, PolyPHb in STS did not increase malondialdehyde, peroxynitrite, or mitochondrial hydrogen peroxide formation, but greatly elevated superoxide dismutase activity and preserved mitochondrial ATP synthesis, which served to maintain redox homeostasis in I/R heart. In conclusion, our results demonstrate that HBOCs protected isolated heart from I/R injury and this protection was associated with attenuation of NO-mediated myocardial apoptosis and restoration of the nitroso-redox balance.

Posttransplant ischemia-reperfusion injury in transplanted heart is prevented by a minibody to the fifth component of complement

BACKGROUND

Complement activation has been implicated in the development of posttransplant ischemia-reperfusion (I/R) which is responsible for the delayed function of 20% to 30% of grafts. C5a and the terminal complement complex (TCC) are the complement activation products mainly involved in tissue injury caused by I/R.

METHODS

To control activation of the terminal step of the complement activation pathways, we used a neutralizing minibody to C5 containing a human single-chain fragment variable (scFv) linked to the hinge region, CH2, and CH3 domains of rat IgG1.

RESULTS

The minibody acts on C5 inhibiting the release of C5a and the assembly of TCC and depletes circulating C5 in Sprague-Dawley rats with a therapeutic activity of 4 hr. Administration of the minibody to rats 30 min before heart allotransplantation prevented tissue deposition of TCC, apoptosis, and necrosis of the graft and increase in the levels of serum creatine phosphokinase and tumor necrosis factor-alpha observed in control transplanted rats.

CONCLUSIONS

These data suggest that an anti-C5 therapy is effective in preventing graft injury caused by I/R. A minibody containing the human scFv linked to the hinge region and the CH2 and CH3 domains of human IgG1 is ready for use in clinical transplantation.

Propofol limits rat myocardial ischemia and reperfusion injury with an associated reduction in apoptotic cell death in vivo

Propofol, a rapidly acting, short duration, intravenous hypnotic anesthetic induction agent, is often used in clinical situations where myocardial ischemia/ reperfusion (I/R) injury is a threat. The aim of the present study was to evaluate the protective effect of propofol on myocardial I/R injury in rat due to apoptosis. Myocardial I/R injury were induced by occluding the left anterior descending (LAD) coronary artery for 25 min followed by either 2 h or 6 h reperfusion. Apoptosis was evaluated by Western blot analysis (Bcl-2, Bax expression), DNA strand breaks, TUNEL analysis and measuring myocardial caspase-3 activity. Propofol significantly reduced infarct size and improved I/R-induced myocardial contractile dysfunction by improving left ventricular diastolic pressure and positive and negative maximal values of the first derivative (+dp/dt) of left ventricular pressure. Propofol increased Bcl-2/Bax expression ratio and decreased caspase-3 activity in I/R rat hearts, which resulted in reduction of myocardial apoptosis as evidenced by TUNEL analysis and DNA laddering experiments. In an in vitro study, propofol increased H9c2 cell viability against oxidative stress induced by glucose oxidase (GOX) in a dose-dependent manner. These data suggest propofol limits I/R injury with an associated reduction in apoptotic cell death in vivo.

Does white wine qualify for French paradox? Comparison of the cardioprotective effects of red and white wines and their constituents: resveratrol, tyrosol, and hydroxytyrosol

It is generally believed that the French paradox is related to the consumption of red wine and not other varieties of wine, including white wine or champagne. Some recent studies have indicated that white wine could also be as cardioprotective as red wine. The present investigation compares the cardioprotective abilities of red wine, white wine, and their principal cardioprotective constituents. Different groups of rats were gavaged with red wine, white wine, resveratrol, tyrosol, and hydroxytyrosol. Red wine and its constituent resveratrol and white wine and its constituents tyrosol and hydroxytyrosol all showed different degrees of cardioprotection as evidenced by their abilities to improve postischemic ventricular performance, reduce myocardial infarct size and cardiomyocyte apoptosis, and reduce peroxide formation. It was discovered in this study that although each of the wines and their components increased the enzymatic activities of the mitochondrial complex (I-IV) and citrate synthase, which play very important roles in oxidative phosphorylation and ATP synthesis, some of the groups were more complex-specific in inducing the activity compared to the other groups. Cardioprotective ability was further confirmed by increased expression of phospho-Akt, Bcl-2, eNOS, iNOS, COX-1, COX-2, Trx-1, Trx-2, and HO-1. The results of this study suggest that white wine can provide cardioprotection similar to red wine if it is rich in tyrosol and hydroxytyrosol.

Anti-Apoptotic Effect of Magnolol in Myocardial Ischemia and Reperfusion Injury Requires Extracellular Signal-Regulated Kinase1/2 Pathways in RatIn Vivo

Magnolol, an active component extracted from Magnolia officinalis, has been reported to have protective effect on ischemia and reperfusion (I/R)-induced injury in experimental animals. The aim of the present investigation was to further evaluate the mechanism(s) by which magnolol reduces I/R-induced myocardial injury in rats in vivo. Under anesthesia, left anterior descending (LAD) coronary artery was occluded for 30 min followed by reperfusion for 24 h (for infarct size and cardiac function analysis). In some experiments, reperfusion was limited to 1 h or 6 h for analysis of biochemical and molecular events. Magnolol and DMSO solution (vehicle) were injected intra-peritoneally 1 h prior to I/R insult. The infarct size was measured by TTC technique and heart function was monitored by Millar Catheter. Apoptosis related events such as p-ERK, p-Bad, Bcl-xl and cytochrome c expression were evaluated by Western blot analysis and myocardial caspase-3 activity was also measured. Magnolol (10 mg/kg) reduced infarct size by 50% ( P < 0.01 versus vehicle), and also improved I/R-induced myocardial dysfunction. Left ventricular systolic pressure and positive and negative maximal values of the first derivative of left ventricular pressure (dP/dt) were significantly improved in magnolol-treated rats. Magnolol increased the expression of phosphor ERK and Bad which resulted in inhibition of myocardial apoptosis as evidenced by TUNEL analysis and DNA laddering experiments. Application of PD 98059, a selective MEK1/2 inhibitor, strongly antagonized the effect of magnolol. Taken together, we concluded that magnolol inhibits apoptosis through enhancing the activation of ERK1/2 and modulation of the Bcl-xl proteins which brings about reduction of infarct size and improvement of cardiac function in I/R-induced injury.

Research progress in anti-apoptosis gene Bcl-xL

Apoptosis is a physiological process that an organism selectively eliminates cells that are no longer needed, or have been damaged, or are dangerous. Bcl-xL, an important member of the Bcl-2 family that plays indispensable roles in regulating cell survival and apoptosis, is frequently over-expressed in various kinds of human cancers. The inhibition of this molecule is associated with decreased tumorigenesis and resistance to conventional chemotherapy. This article briefly reviews some progresses in the study of Bcl-xL in the past few years.

Hsp27 inhibits Bax activation and apoptosis via a phosphatidylinositol 3-kinase-dependent mechanism

Hsp27 inhibits mitochondrial injury and apoptosis in both normal and cancer cells by an unknown mechanism. To test the hypothesis that Hsp27 decreases apoptosis by inhibiting Bax, Hsp27 expression was manipulated in renal epithelial cells before transient metabolic stress, an insult that activates Bax, induces mitochondrial injury, and causes apoptosis. Compared with control, enhanced Hsp27 expression inhibited conformational Bax activation, oligomerization, and translocation to mitochondria, reduced the leakage of both cytochrome c and apoptosis-inducing factor, and significantly improved cell survival by >50% after stress. In contrast, Hsp27 down-regulation using RNA-mediated interference promoted Bax activation, increased Bax translocation, and reduced cell survival after stress. Immunoprecipitation did not detect Hsp27-Bax interaction before, during, or after stress, suggesting that Hsp27 indirectly inhibits Bax. During stress, Hsp27 expression prevented the inactivation of Akt, a pro-survival kinase, and increased the interaction between Akt and Bax, an Akt substrate. In contrast, Hsp27 RNA-mediated interference promoted Akt inactivation during stress. Hsp27 up- or down-regulation markedly altered the activity of phosphatidylinositol 3-kinase (PI3-kinase), a major regulator of Akt. Furthermore, distinct PI3-kinase inhibitors completely abrogated the protective effect of Hsp27 expression on Akt activation, Bax inactivation, and cell survival. These data show that Hsp27 antagonizes Bax-mediated mitochondrial injury and apoptosis by promoting Akt activation via a PI3-kinase-dependent mechanism.

Cardiomyocyte death and renewal in the normal and diseased heart

During post-natal maturation of the mammalian heart, proliferation of cardiomyocytes essentially ceases as cardiomyocytes withdraw from the cell cycle and develop blocks at the G0/G1 and G2/M transition phases of the cell cycle. As a result, the response of the myocardium to acute stress is limited to various forms of cardiomyocyte injury, which can be modified by preconditioning and reperfusion, whereas the response to chronic stress is dominated by cardiomyocyte hypertrophy and myocardial remodeling. Acute myocardial ischemia leads to injury and death of cardiomyocytes and nonmyocytic stromal cells by oncosis and apoptosis, and possibly by a hybrid form of cell death involving both pathways in the same ischemic cardiomyocytes. There is increasing evidence for a slow, ongoing turnover of cardiomyocytes in the normal heart involving death of cardiomyocytes and generation of new cardiomyocytes. This process appears to be accelerated and quantitatively increased as part of myocardial remodeling. Cardiomyocyte loss involves apoptosis, autophagy, and oncosis, which can occur simultaneously and involve different individual cardiomyocytes in the same heart undergoing remodeling. Mitotic figures in myocytic cells probably represent maturing progeny of stem cells in most cases. Mitosis of mature cardiomyocytes that have reentered the cell cycle appears to be a rare event. Thus, cardiomyocyte renewal likely is mediated primarily by endogenous cardiac stem cells and possibly by blood-born stem cells, but this biological phenomenon is limited in capacity. As a consequence, persistent stress leads to ongoing remodeling in which cardiomyocyte death exceeds cardiomyocyte renewal, resulting in progressive heart failure. Intense investigation currently is focused on cell-based therapies aimed at retarding cardiomyocyte death and promoting myocardial repair and possibly regeneration. Alteration of pathological remodeling holds promise for prevention and treatment of heart failure, which is currently a major cause of morbidity and mortality and a major public health problem. However, a deeper understanding of the fundamental biological processes is needed in order to make lasting advances in clinical therapeutics in the field.

In vivo activation of peroxisome proliferator-activated receptor-delta protects the heart from ischemia/reperfusion injury in Zucker fatty rats

Peroxisome proliferator-activated receptor (PPAR)-delta is a transcription factor that belongs to the PPAR family. PPAR-delta is abundantly expressed in the heart, and its role in the heart is largely unknown. We tested whether pharmacological activation of PPAR-delta protects the heart from ischemia/reperfusion (I/R) injury in male Zucker fatty rats, a rodent model of obesity and dyslipidemia. A highly selective PPAR-delta agonist, [4-[[[2-[3-fluoro-4-(trifluoromethyl)phenyl]-4-methyl-5-thiazolyl]methyl] thio]-2-methylphenoxy]acetic acid (GW0742), was administered for 7 days at 10 mg/kg/day (p.o., once a day). Ischemic injury was produced by occlusion of the left anterior descending artery for 30 min followed by reperfusion for up to 24 h. Treatment with GW0742 reduced serum levels of cardiac troponin-I and infarct size by 63% (p < 0.01) and 32% (p < 0.01), respectively, and improved left ventricular function. Treatment with GW0742 up-regulated gene expression involved in cardiac fatty acid oxidation, increased fat use in the heart, and reduced serum levels of free fatty acids. The enhanced cardiac expression of interleukin (IL)-6, IL-8, intercellular adhesion molecule-1, and monocyte chemoattractant protein-1 induced by I/R were significantly attenuated by GW0742. Treatment with GW0742 also reduced apoptotic cardiomyocytes by 34% and cardiac caspase-3 activity by 61% (both p < 0.01 versus vehicle). GW0742 differentially regulated Bcl family members, favoring cell survival, and attenuated I/R-induced cardiac mitochondrial damage. In addition, GW0742 treatment augmented the cardiac Akt signaling pathway, as reflected by enhanced phospho-3-phosphoinositide-dependent kinase-1 and p-Akt. The results indicate that activation of PPAR-delta protected the heart from I/R injury in Zucker fatty rats, and multiple mechanisms including amelioration of lipotoxicity, anti-inflammation, and up-regulation of prosurvival signaling contribute together to the cardioprotection.

The interplay between pro-death and pro-survival signaling pathways in myocardial ischemia/reperfusion injury: apoptosis meets autophagy

INTRODUCTION

Programmed cell death of cardiac myocytes occurs following a bout of ischemia/reperfusion (I/R), which results in reduced function of the heart. Numerous studies, including in vivo, have shown that cell death occurs via necrosis and apoptosis following I/R. Recently, autophagy has emerged as a powerful mediator of programmed cell death, either opposing or enhancing apoptosis, or acting as an alternative form of programmed cell death distinct from apoptosis.

AIM

Here we review the apoptotic and autophagic signaling pathways, their influences on each other, and we discuss the relevance of autophagy in the heart.

Tanshinone IIA protects cardiac myocytes against oxidative stress-triggered damage and apoptosis

Tanshinone IIA (tan), a derivative of phenanthrenequinone, is one of the key components of Salvia miltiorrhiza Bunge. Previous reports showed that tan inhibited the apoptosis of cultured PC12 cells induced by serum withdrawal or ethanol. However, whether tan has a cardioprotective effect against apoptosis remains unknown. In this study, we investigated the effects of tan on cardiac myocyte apoptosis induced both by in vitro incubation of neonatal rat ventricular myocytes with H(2)O(2) and by in vivo occlusion followed by reperfusion of the left anterior descending coronary artery in adult rats. In vitro, as revealed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) assay, treatment with tan prior to H(2)O(2) exposure significantly increased cell viability. Tan also markedly inhibited H(2)O(2)-induced cardiomyocyte apoptosis, as detected by ladder-pattern fragmentation of genomic DNA, chromatin condensation, and hypodioloid DNA content. In vivo, tan significantly inhibited ischemia/reperfusion-induced cardiomyocyte apoptosis by attenuating morphological changes and reducing the percentage of terminal transferase dUTP nick end-labeling (TUNEL)-positive myocytes and caspase-3 cleavage. These effects of tan were associated with an increased ratio of Bcl-2 to Bax protein in cardiomyocytes, an elevation of serum superoxide dismutase (SOD) activity and a decrease in serum malondialdehyde (MDA) level. Taken together, these data for the first time provide convincing evidence that tan protects cardiac myocytes against oxidative stress-induced apoptosis. The in vivo protection is mediated by increased scavenging of oxygen free radicals, prevention of lipid peroxidation and upregulation of the Bcl-2/Bax ratio.

Structure-function analysis of the interaction between Bax and the cytomegalovirus-encoded protein vMIA

The viral mitochondrial inhibitor of apoptosis (vMIA) encoded by the human cytomegalovirus exerts cytopathic effects and neutralizes the proapoptotic endogenous Bcl-2 family member Bax by recruiting it to mitochondria, inducing its oligomerization and membrane insertion. Using a combination of computational modeling and mutational analyses, we addressed the structure-function relationship of the molecular interaction between the protein Bax and the viral antiapoptotic protein vMIA. We propose a model in which vMIA exhibits an overall fold similar to Bcl-X(L). In contrast to Bcl-X(L), however, this predicted conformation of vMIA does not bind to the BH3 domain of Bax and rather engages in electrostatic interactions that involve a stretch of amino acids between the BH3 and BH2 domains of Bax and an alpha-helical domain located within the previously defined Bax-binding domain of vMIA, between the putative BH1-like and BH2-like domains. According to this model, vMIA is likely to bind Bax preferentially in its membrane-inserted conformation. The capacity of vMIA to cause fragmentation of the mitochondrial network and disorganization of the actin cytoskeleton is independent of its Bax-binding function. We found that Delta131-147 vMIA mutant, which lacks both the Bax-binding function and cell-death suppression but has intact mitochondria-targeting capacity, is similar to vMIA in its ability to disrupt the mitochondrial network and to disorganize the actin cytoskeleton. vMIADelta131-147 is a dominant-negative inhibitor of the antiapoptotic function of wild-type vMIA. Our experiments with vMIADelta131-147 suggest that vMIA forms homo-oligomers, which may engage in cooperative and/or multivalent interactions with Bax, leading to its functional neutralization.

Use of diffusion tensor imaging to predict myocardial viability after warm global ischemia: possible avenue for use of non-beating donor hearts

BACKGROUND

The assessment of myocardial viability after global warm ischemia (WI) but before reperfusion is challenging. We hypothesized that fractional anisotropy (FA), a magnetic resonance imaging (MRI) parameter of water diffusion that characterizes cellular integrity within tissues, provides a rapid and useful method for evaluating the viability of hearts after WI.

METHODS

Dog hearts were exposed to 60 minutes of WI after exanguination, explanted and preserved in a cold, non-beating state for 6 hours, using continuous perfusion (CP) or static cold storage (CS). Toward the end of preservation, a global FA assessment, acquired using MRI, was compared with analyses obtained from myocardial biopsies that included adenosine triphosphate (ATP), endothelin-1 (ET-1) and caspase-3 levels, light microscopy and tetrazolium staining. Functional recovery was analyzed after restoration of blood flow on a non-working Langendorff preparation.

RESULTS

FA measured at the end of CP showed strong correlations with all parameters of functional recovery (developed pressure, R = 0.60; dP/dt, R = 0.96; -dP/dt, R = 0.96). Although FA also correlated with tissue levels of ATP, ET-1 and caspase-3 (R = 0.77, -0.84, -0.64), recovery of myocardial function did not correlate with these markers or any other conventional analyses of myocardial injury (troponin I, changes on light microscopy or tetrazolium staining).

CONCLUSIONS

FA, an MRI-based parameter that indicates cellular integrity, was found to reflect better myocardial ATP stores, less induction of ET-1 and caspase-3 and improved functional recovery of hearts after global WI. As a clinically applicable tool capable of rapidly differentiating reversible from lethal injury, diffusion tensor imaging may prove useful in the eventual adoption of non-beating donor hearts for transplantation.

Upregulation of Bcl-2 proteins during the transition to pressure overload-induced heart failure

BACKGROUND

Cardiomyocyte apoptosis is implicated in the pathogenesis of heart failure and mitochondria play an important role in this mode of cell death. In this study, activity of the Bcl-2 family of mitochondrial apoptotic proteins and their regulator (p53) were assessed during the transition to heart failure.

METHODS

Ten adult male sheep were banded with a variable aortic constriction device. This was progressively inflated to increase left ventricular (LV) afterload. The sheep were monitored echocardiographically, measuring LV Mass Index (LVMI), diastolic LV Internal Diameter (LVIDd) and Fractional Shortening (FS). Serial LV endomyocardial biopsies were obtained, to measure expression of p53 and Bcl-2 family proteins by Western blotting.

RESULTS

Over the first 3-4 weeks, the sheep developed hypertrophy (LVMI 79.5+/-4.6 vs. 44.0+/-3.0 g/m2, p<0.01), followed by gradual LV dilatation (LVIDd 4.23+/-0.08 vs. 3.39+/-0.07 cm, p<0.01). Ventricular function remained stable until 7-8 weeks post banding, when there was significant deterioration (FS 18.3+/-2.4 vs. 46.9+/-2.6%, p<0.01), associated with clinical heart failure. Upregulation of the Bax/Bcl-2 ratio, associated with increased levels of p53, was demonstrated in each of the echocardiographically defined stages (LV hypertrophy, LV dilatation and LV failure). In parallel, significantly higher levels of anti-apoptotic protein (Bcl-xL) was associated with LV dilatation and failure.

CONCLUSIONS

Upregulation of Bax/Bcl-2 ratio occurs during the transition to heart failure and in particular with the initial hypertrophic response. Increase in expression of the anti-apoptotic protein Bcl-xL suggests possible concomitant compensatory mechanisms being activated during the transition to heart failure.

Enhancing Macroautophagy Protects against Ischemia/Reperfusion Injury in Cardiac Myocytes

Cardiac myocytes undergo programmed cell death as a result of ischemia/reperfusion (I/R). One feature of I/R injury is the increased presence of autophagosomes. However, to date it is not known whether macroautophagy functions as a protective pathway, contributes to programmed cell death, or is an irrelevant event during cardiac I/R injury. We employed simulated I/R of cardiac HL-1 cells as an in vitro model of I/R injury to the heart. To assess macroautophagy, we quantified autophagosome generation and degradation (autophagic flux), as determined by steady-state levels of autophagosomes in relation to lysosomal inhibitor-mediated accumulation of autophagosomes. We found that I/R impaired both formation and downstream lysosomal degradation of autophagosomes. Overexpression of Beclin1 enhanced autophagic flux following I/R and significantly reduced activation of pro-apoptotic Bax, whereas RNA interference knockdown of Beclin1 increased Bax activation. Bcl-2 and Bcl-x(L) were protective against I/R injury, and expression of a Beclin1 Bcl-2/-x(L) binding domain mutant resulted in decreased autophagic flux and did not protect against I/R injury. Overexpression of Atg5, a component of the autophagosomal machinery downstream of Beclin1, did not affect cellular injury, whereas expression of a dominant negative mutant of Atg5 increased cellular injury. These results demonstrate that autophagic flux is impaired at the level of both induction and degradation and that enhancing autophagy constitutes a powerful and previously uncharacterized protective mechanism against I/R injury to the heart cell.