The cardioprotective effect of postconditioning is mediated by ARC through inhibiting mitochondrial apoptotic pathway

Nucleolar protein 3 promotes proliferation of bladder cancer cells through the PI3K-Akt pathway

Nucleolar protein 3 (NOL3), as a markedly increased protein across a range of tumors, has been well acknowledged that plays an anti-apoptotic role in malignancies, while some novel impacts of NOL3 on metastasis and chemoresistance are demonstrated recently. In this study, we uncover another role of NOL3 on promoting proliferation in bladder cancer (BLCA). The reduction of NOL3 significantly inhibited cell proliferation, and we detected the stable cell cycle arrest after knockdown of NOL3 in two-type BLCA cell lines. Mechanistically, we present the first evidence that the PI3K/Akt pathway was considerably inhibited with the decrease of NOL3 in BLCA cell lines. In addition, LY294002, a PI3K inhibitor, rescued NOL3 overexpression-mediated activation of the PI3K/Akt axis and the depression of proliferation in BLCA cell lines. In conclusion, our study suggests that NOL3 is upregulated in BLCA cells and promotes proliferation via the PI3K/Akt pathway, indicating that NOL3 may be a potential therapeutic target for BLCA.

A double-edged sword: role of apoptosis repressor with caspase recruitment domain (ARC) in tumorigenesis and ischaemia/reperfusion (I/R) injury

Apoptosis repressor with caspase recruitment domain (ARC) acts as a potent and multifunctional inhibitor of apoptosis, which is mainly expressed in postmitotic cells, including cardiomyocytes. ARC is special for its N-terminal caspase recruitment domain and caspase recruitment domain. Due to the powerful inhibition of apoptosis, ARC is mainly reported to act as a cardioprotective factor during ischaemia‒reperfusion (I/R) injury, preventing cardiomyocytes from being devastated by various catastrophes, including oxidative stress, calcium overload, and mitochondrial dysfunction in the circulatory system. However, recent studies have found that ARC also plays a potential regulatory role in tumorigenesis especially in colorectal cancer and renal cell carcinomas, through multiple apoptosis-associated pathways, which remains to be explored in further studies. Therefore, ARC regulates the body and maintains the balance of physiological activities with its interesting duplex. This review summarizes the current research progress of ARC in the field of tumorigenesis and ischaemia/reperfusion injury, to provide overall research status and new possibilities for researchers.

Preparation and pharmacological effects of minor ginsenoside nanoparticles: a review

Ginseng (Panax ginseng) is a perennial herbaceous plant belonging to Panax genus of Araliaceae. Ginsenosides are a kind of important compounds in ginseng and minor ginsenosides are secondary metabolic derivatives of ginsenosides. Studies have shown that minor ginsenosides have many pharmacological effects, such as antioxidant, anti-tumor, anti-platelet aggregation, and neuroprotective effects. However, the therapeutic effects of minor ginsenosides are limited due to poor solubility in water, short half-life, and poor targeting accuracy. In recent years, to improve the application efficiency, the research on the nanocrystallization of minor ginsenosides have attracted extensive attention from researchers. This review focuses on the classification, preparation methods, pharmacological effects, and action mechanisms of minor ginsenoside nanoparticles, as well as existing problems and future direction of relevant research, which provides a reference for the in-depth research of minor ginsenoside nanoparticles.

Role of apoptosis repressor with caspase recruitment domain (ARC) in cell death and cardiovascular disease

Apoptosis repressor with caspase recruitment domain (ARC) is a highly effective and multifunctional inhibitor of apoptosis that is mainly expressed in postmitotic cells such as cardiomyocytes and skeletal muscle cells. ARC contains a C-terminal region rich in proline and glutamic acid residues and an N-terminal caspase recruitment domain (CARD). The CARD is originally described as a protein-binding motif that interacts with caspase through a CARD-CARD interaction. Initially, the inhibitory effect of ARC was only found in apoptosis, however, it was later found that ARC also played a regulatory role in other types of cell death. As a powerful cardioprotective factor, ARC can protect the heart by inhibiting the death of cardiomyocytes in various ways. ARC can reduce the cardiomyocyte apoptotic response to various stresses and injuries, including extrinsic apoptosis induced by death receptor ligands, cellular Ca2+ homeostasis and the dysregulation of endoplasmic reticulum (ER) stress, oxidative stress and hypoxia. In addition, changes in ARC transcription and translation levels in the heart can cause a series of physiological and pathological changes, and ARC can also perform corresponding functions through interactions with other molecules. Although there has been much research on ARC, the functional redundancy among proteins shows that ARC still has much research value. This review summarizes the molecular characteristics of ARC, its roles in the various death modes in cardiomyocytes and the roles of ARC in cardiac pathophysiology. This article also describes the potential therapeutic effect and research prospects of ARC.

Expression profiling of some Acute Myeloid Leukemia - associated markers to assess their diagnostic / prognostic potential

Investigating the etiological causes of acute myeloid leukemia (AML) at the molecular level should help in identifying targets and strategies that would increase the efficacy of the current management regimens. Some genes may act as molecular diagnostics, of these ASXL1 and PHF6 are involved in regulation of gene expression, and BAX , and ARC, are pro- and anti-apoptotic molecules, respectively. In this study, peripheral blood samples were collected from 54 recently diagnosed AML patients in addition to 20 healthy individuals (the control group). Cellular RNA was extracted from all the samples and were subjected to quantitative analysis of the transcript levels of the four selected markers. Our data showed a significant elevation in the expression levels of PHF6 and ARC in AML patients, when compared to the controls (77.8% and 83.3%, respectively). On the other hand, ASXL1 and BAX exhibited increase, to a lesser extent, in the expression levels of the AML patients (52% and 55.6%, respectively). Our study also showed that the expression levels of ARC and PHF6 exhibited a concomitant increase and this could be correlated with poor prognosis of the cases. Thus, we can suggest these markers as reliable prognostic markers for prediction of AML outcomes.

ARC Is a Critical Protector against Inflammatory Bowel Disease (IBD) and IBD-Associated Colorectal Tumorigenesis

The key functional molecules involved in inflammatory bowel disease (IBD) and IBD-induced colorectal tumorigenesis remain unclear. In this study, we found that the apoptosis repressor with caspase recruitment domain (ARC) protein plays critical roles in IBD. ARC-deficient mice exhibited substantially higher susceptibility to dextran sulfate sodium (DSS)-induced IBD compared with wild-type mice. The inflammatory burden induced in ARC-deficient conditions was inversely correlated with CCL5 and CXCL5 levels in immune cells, especially CD4-positive T cells. Pathologically, ARC expression in immune cells was significantly decreased in clinical biopsy specimens from patients with IBD compared with normal subjects. In addition, ARC levels inversely correlated with CCL5 and CXCL5 levels in human biopsy specimens. ARC interacted with TNF receptor associated factor (TRAF) 6, regulating ubiquitination of TRAF6, which was associated with NF-κB signaling. Importantly, we identified a novel ubiquitination site at lysine 461, which was critical in the function of ARC in IBD. ARC played a critical role in IBD and IBD-associated colon cancer in a bone marrow transplantation model and azoxymethane/DSS-induced colitis cancer mouse models. Overall, these findings reveal that ARC is critically involved in the maintenance of intestinal homeostasis and protection against IBD through its ubiquitination of TRAF6 and subsequent modulation of NF-κB activation in T cells. SIGNIFICANCE: This study uncovers a crucial role of ARC in the immune system and IBD, giving rise to a novel strategy for IBD and IBD-associated colon cancer therapy.

Valproic acid attenuates global cerebral ischemia/reperfusion injury in gerbils via anti-pyroptosis pathways

Ischemic stroke is the third most common cause of death and the leading cause of disability worldwide in adults. The antiepileptic drug valproic acid (VPA) was reported to protect cerebral ischemia/reperfusion injury. However, the action mechanism of VPA in cerebral ischemia/reperfusion injury has not been fully understood. We explored the action mechanism of VPA in vivo and in vitro. Gerbils were subjected to transient global cerebral ischemic-reperfusion injury, and hippocampal neuron injury was treated with oxygen-glucose deprivation in vitro. Morris water maze test was performed to evaluate the cognitive dysfunction. Histopathological examinations and western blot were performed to evaluate the pyroptosis of neurons. The results showed that VPA attenuated the cognitive dysfunction, pyroptosis of the gerbils suffer from ischemic-reperfusion injury and decreased hippocampal neurons pyroptosis induced by oxygen-glucose deprivation in vitro. In addition, western blot and real-time PCR analysis revealed that VPA modulated the protein expression of apoptosis repressor with caspase recruitment domain (ARC), caspase-1 and IL-1β/IL-18. Our results suggested that VPA alleviated ischemic/reperfusion injury-mediated neuronal impairment by anti-pyroptotic effects.

Role of JNK signalling pathway and platelet‑lymphocyte aggregates in myocardial ischemia‑reperfusion injury and the cardioprotective effect of ischemic postconditioning in rats

In myocardial ischemia‑reperfusion injury (MIRI), increased activity of the c‑Jun N‑terminal kinase (JNK) pathway and the activation of platelets that leads to the formation of platelet‑leukocyte aggregates (PLAs) have been observed. It was hypothesized that ischemic postconditioning in MIRI exerts cardioprotective effects by altering JNK activity, which in turn leads to reduced PLA levels. A total of 60 rats were randomly divided into 6 groups (n=10 for each group): i) Control; ii) ischemia‑reperfusion injury alone; iii) ischemia‑reperfusion with postconditioning (PostC group), iv) treatment with the JNK inhibitor‑SP600125; v) postC and treatment with anisomycin; and vi) treatment with the JNK activator‑anisomycin. Subsequently, the levels of PLA, infarct size, myocardial injury markers (creatinine kinase‑muscle/brain and troponin I) and were measured. Western blotting was used to determine the protein expression of phosphorylated‑JNK. MIRI led to increased myocardial infarct size that was associated with raised troponin I and creatine kinase‑muscle/brain. At different time points of MIRI, the level of PLA gradually increased. Compared with the injury‑reperfusion group, the level of PLA in the PostC and Inhibitor‑JNK groups was significantly reduced at 60 min and 3 h following reperfusion. MIRI was able to increase the expression of phosphorylated JNK. These effects were significantly reduced by ischemic postC or by treatment with SP600125. By contrast, the addition of anisomycin attenuated these protective effects. JNK is a critical mediator of MIRI. Ischemic postC can reduce the level of PLA during reperfusion by inhibiting the phosphorylation of JNK MAPK, thereby reducing MIRI. Pharmacological inhibition and activation of JNK can improve and reduce cardioprotective effects, respectively. These results explained the mechanism of the cardioprotection of postC and provided novel insight and target for the therapeutic strategy of MIRI.

Blockade of RBP-J-Mediated Notch Signaling Pathway Exacerbates Cardiac Remodeling after Infarction by Increasing Apoptosis in Mice

Background

Ischemic heart disease (IHD) is the major cause of death in patients with cardiovascular disease. Cardiac remodeling is a common pathological change following myocardial infarction (MI), and cardiomyocyte apoptosis plays a key role in this change. Transcription factor recombination signal-binding protein-J (RBP-J)-mediated Notch signaling pathway has been implicated in several inherited cardiovascular diseases, including aortic valve diseases, but whether the RBP-J-mediated Notch signaling pathway plays a role in cardiomyocyte apoptosis after MI is unclear.

Method

We crossed RBP-J^fl/fl mice and Myh6-Cre/Esr1 transgenic mice to delete RBP-J in vivo and to partly inhibit the canonical Notch signaling pathway. MI was induced in mice by permanent ligation of the left anterior descending coronary artery followed by the knockout of RBP-J. Cardiac function and morphology were assessed by echocardiography and histological analysis 4 weeks after infarction. In addition, the expression and regulation of apoptosis-related molecules were examined by real time PCR and western blot.

Results

RBP-J knockout decreased the survival rate and deteriorated post-MI remodeling and function in mice, and this effect was associated with increased cardiomyocyte apoptosis. The potential mechanisms might be related to the downregulated expression of bcl-2, upregulated expression of bax, and cleaved-caspase 3 to exacerbate cardiomyocyte apoptosis.

Conclusion

These findings show that the RBP-J-mediated Notch signaling pathway in cardiomyocytes limits ventricular remodeling and improves cardiac function after MI. The RBP-J-mediated Notch signaling pathway has a protective role in cardiomyocyte apoptosis following cardiac injury.

Mitochondria in Cardiac Postconditioning

Mitochondria play a pivotal role in cardioprotection. Here we report some fundamental studies which considered the role of mitochondrial components (connexin 43, mitochondrial KATP channels and mitochondrial permeability transition pore) in postconditioning cardioprotection. We briefly discuss the role of mitochondria, reactive oxygen species and gaseous molecules in postconditioning. Also the effects of anesthetics-used as cardioprotective substances-is briefly considered in the context of postconditioning. The role of mitochondrial postconditioning signaling in determining the limitation of cell death is underpinned. Issues in clinical translation are briefly considered. The aim of the present mini-review is to discuss in a historical perspective the role of main mitochondria mechanisms in cardiac postconditioning.

Status of Therapeutic Gene Transfer to Treat Cardiovascular Disease in Dogs and Cats

Gene therapy is a procedure resulting in the transfer of a gene into an individual's cells to treat a disease. One goal of gene transfer is to express a functional gene when the endogenous gene is inactive. However, because heart failure is a complex disease characterized by multiple abnormalities at the cellular level, an alternate gene delivery approach is to alter myocardial protein levels to improve function. This article discusses background information on gene delivery, including packaging, administration, and a brief discussion of some of the candidate transgenes likely to alter the progression of naturally occurring heart disease in dogs and cats.

Role of microRNA-130a in myocardial hypoxia/reoxygenation injury

The aim of this study was to investigate the role of microRNA (miR)-130a in the pathogenesis of myocardial hypoxia/reoxygenation (H/R) injury. Primary rat cardiomyocytes were cultured and subjected to H/R treatment. Reverse transcription-quantitative polymerase chain reaction was performed to detect the levels of miR-130a, western blot analysis was used to determine the expression of various proteins, and CCK-8 assay was performed to determine cell viability. In addition, flow cytometry was used to assess apoptosis. The cell viability was significantly decreased and the apoptosis rate was significantly increased in H/R-treated primary cardiomyocytes, and the expression level of miR-130a was also elevated in these model cells. Transfection with miR-130a inhibitor significantly elevated the cell viability and reduced the apoptosis rate in H/R-treated cardiomyocytes. Bioinformatics analysis indicated that autophagy-related gene 14 (ATG14) is the target for miR-130a, which was confirmed by dual-luciferase reporter assay and western blot analysis. When the H/R model cells were co-transfected with miR-130a inhibitor and small interfering RNA against ATG14, the cell viability was significantly reduced and the apoptosis rate was significantly elevated, compared with that of cells transfected with miR-130a inhibitor alone. miR-130a inhibitor transfection significantly elevated the levels of ATG14 and phosphorylated (p-)Beclin 1, increased the LC3II/LC3I ratio, and decreased the expression levels of P62 and cleaved caspase-3, while the co-transfection of miR-130a inhibitor and siR-ATG14 attenuated these effects in H/R-induced primary cardiomyocytes. These results indicate that miR-130a is involved in H/R-induced injuries in primary cardiomyocytes, and that the inhibition of miR-130a increases the levels of ATG14 and p-Beclin 1, thereby increasing autophagy and inhibiting apoptosis in these cells.

Apoptosis repressor with caspase recruitment domain enhances survival and promotes osteogenic differentiation of human osteoblast cells under Zoledronate treatment

Zoledronate is one of the most potent nitrogen-containing bisphosphonates which has been demonstrated to result in osteoblast apoptosis and impact osteogenic differentiation in vitro. This effect of Zoledronate on osteoblasts may partially explain bisphosphonate-associated osteonecrosis of the jaw, a serious complication associated with treatment with bisphosphonates. Apoptosis repressor with caspase recruitment domain (ARC) is a multifunctional inhibitor of apoptosis that is physiologically expressed predominantly in post-mitotic cells such as cardiomyocytes, neurons and skeletal muscle cells. However, its effect on human osteoblasts remains unclear. The current study aimed to investigate the effects of ARC on human osteoblasts under the treatment of high concentrations of Zoledronate. ARC-overexpressed human osteoblasts were established and were exposed to Zoledronate with different concentrations (0, 1 and 5 µM) in vitro. Cell numbers were detected using the MTT assay, and flow cytometry was used to identity cell apoptosis. Alkaline phosphatase staining, quantitative analysis and ectopic osteogenesis in nude mice were used to evaluate the osteogenic differentiation of ARC-overexpressed osteoblasts. It was observed that ARC is able to reverse the inhibitory effect of Zoldronate on osteoblasts. ARC is additionally able to promote osteogenic differentiation of osteoblasts and inhibit their apoptosis. These observations suggest a critical role for ARC in the regulation of human osteoblasts under Zoledronate treatment.

Myofibrillogenesis regulator-1 attenuated hypoxia/reoxygenation-induced apoptosis by inhibiting the PERK/Nrf2 pathway in neonatal rat cardiomyocytes

The purpose of this study was to investigate the role of myofibrillogenesis regulator-1 (MR-1) in cardiomyocyte apoptosis induced by hypoxia/reoxygenation (H/R), through protein kinase R-like ER kinase (PERK)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. To address this aim, an H/R model of neonatal rat cardiomyocytes was used. MR-1 was overexpressed using an adenoviral vector system and knocked down using MR-1 specific siRNA. Apoptosis was assessed by using Annexin V/PI double staining, terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling assay, and the Bcl-2/Bax ratio. Western blotting was used to detect the protein levels of MR-1, glucose-regulated protein 78 (GRP78), total and phosphorylated PERK, Nrf2, activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), Bcl-2 and Bax. Immunofluorescence staining was used to assess the subcellular location of Nrf2. We found that H/R induced significant apoptosis in neonatal rat cardiomyocytes. MR-1 overexpression attenuated H/R-induced apoptosis, decreased GRP78 (P < 0.01) and CHOP expression (P < 0.05), and increased the Bcl-2/Bax ratio (P < 0.01). MR-1 overexpression suppressed H/R-induced PERK phosphorylation, Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). While MR-1 knockdown aggravated H/R-induced apoptosis, increased expression of GRP78 and CHOP (P < 0.05), and decreased the Bcl-2/Bax ratio (P < 0.01). MR-1 knockdown significantly increased H/R-induced PERK phosphorylation (P < 0.05), Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). These findings suggest that MR-1 alleviates H/R-induced cardiomyocyte apoptosis through inhibition of the PERK/Nrf2 pathway.

Pharmacological postconditioning with lactic acid and hydrogen rich saline alleviates myocardial reperfusion injury in rats

This study investigated whether pharmacological postconditioning with lactic acid and hydrogen rich saline can provide benefits similar to that of mechanical postconditioning. To our knowledge, this is the first therapeutic study to investigate the co-administration of lactic acid and hydrogen. SD rats were randomly divided into 6 groups: Sham, R/I, M-Post, Lac, Hyd, and Lac + Hyd. The left coronary artery was occluded for 45 min. Blood was withdrawn from the right atrium to measure pH. The rats were sacrificed at different time points to measure mitochondrial absorbance, infarct size, serum markers and apoptotic index. Rats in Lac + Hyd group had similar blood pH and ROS levels when compared to the M-Post group. Additionally, the infarct area was reduced to the same extent in Lac + Hyd and M-Post groups with a similar trends observed for serum markers of myocardial injury and apoptotic index. Although the level of P-ERK in Lac + Hyd group was lower, P-p38/JNK, TNFα, Caspase-8, mitochondrial absorbance and Cyt-c were all similar in Lac + Hyd and M-Post groups. The Lac and Hyd groups were able to partially mimic this protective role. These data suggested that pharmacological postconditioning with lactic acid and hydrogen rich saline nearly replicates the benefits of mechanical postconditioning.

Apoptosis repressor with caspase recruitment domain is regulated by MAPK/PI3K and confers drug resistance and survival advantage to AML

The apoptosis repressor with caspase recruitment domain (ARC) protein is known to suppress both intrinsic and extrinsic apoptosis. We previously reported that ARC expression is a strong, independent adverse prognostic factor in acute myeloid leukemia (AML). Here, we investigated the regulation and role of ARC in AML. ARC expression is upregulated in AML cells co-cultured with bone marrow-derived mesenchymal stromal cells (MSCs) and suppressed by inhibition of MAPK and PI3K signaling. AML patient samples with RAS mutations (N = 64) expressed significantly higher levels of ARC than samples without RAS mutations (N = 371) (P = 0.016). ARC overexpression protected and ARC knockdown sensitized AML cells to cytarabine and to agents that selectively induce intrinsic (ABT-737) or extrinsic (TNF-related apoptosis inducing ligand) apoptosis. NOD-SCID mice harboring ARC-overexpressing KG-1 cells had significantly shorter survival than mice injected with control cells (median 84 vs 111 days) and significantly fewer leukemia cells were present when NOD/SCID IL2Rγ null mice were injected with ARC knockdown as compared to control Molm13 cells (P = 0.005 and 0.03 at 2 and 3 weeks, respectively). Together, these findings demonstrate that MSCs regulate ARC in AML through activation of MAPK and PI3K signaling pathways. ARC confers drug resistance and survival advantage to AML in vitro and in vivo, suggesting ARC as a novel target in AML therapy.

Post-conditioning with gradually increased reperfusion provides better cardioprotection in rats

BACKGROUND

Rapid and complete reperfusion has been widely adopted in the treatment of patients with acute myocardial infarction (AMI), but this process sometimes can cause severe reperfusion injury. This study aimed to investigate different patterns of post-conditioning in acute myocardial ischemia-reperfusion injury, and to detect the role of mitogen activated protein kinase (MAPK) during the injury.

METHODS

RATS WERE RANDOMLY DIVIDED INTO FIVE GROUPS: sham group, reperfusion injury (R/ I) group, gradually decreased reperfusion group (GDR group, 30/10-25/15-15/25-10/30 seconds of reperfusion/ischemia), equal reperfusion group (ER group, 20/20 seconds reperfusion/ischemia, 4 cycles), and gradually increased reperfusion group (GIR group, 10/30-15/25-25/15-30/10 seconds of reperfusion/ischemia). Acute myocardial infarction and ischemic post-conditioning models were established in the rats. Six hours after reperfusion, 3 rats from each group were sacrificed and myocardial tissues were taken to measure the expressions of phosphorylation of extracellular signal-regulated protein kinase (P-ERK), phosphorylated c-Jun N-terminal kinase (P-JNK), mitogen-activated protein kinase p38 (p38 MAPK), tumor necrosis factor-α (TNF-α), caspases-8 in the myocardial tissue, and cytochrome c in the cytosol using Western blot. Hemodynamics was measured at 24 hours after reperfusion, the blood was drawn for the determination of cardiac enzymes, and the heart tissue was collected for the measurement of apoptosis using TUNEL. One-way analysis of variance and the Q test were employed to determine differences in individual variables between the 5 groups.

RESULTS

Three post-conditioning patterns were found to provide cardioprotection (P<0.05) compared with R/I without postconditioning. GIR provided the best cardioprotection effect, followed by ER and then GDR. Apoptotic index and serum marker levels were reduced more significantly in GIR than in ER (P<0.05). The enhanced cardioprotection provided by GIR was accompanied with significantly increased levels of P-ERK 1/2 (1.82±0.22 vs. 1.54±0.32, P<0.05), and lower levels of p-JNK, p38 MAPK, TNF-α, caspase-8, caspase-9 and cytochrome in the cytoplasm (P<0.05), compared with ER. The infarct size was smaller in the GIR group than in the ER group, but this difference was not significant (16.30%±5.22% vs. 20.57%±6.32%, P<0.05). All the measured variables were improved more significantly in the GIR group than in the GDR group (P<0.05).

CONCLUSION

Gradually increased reperfusion in post-conditioning could attenuate reperfusion injury more significantly than routine method, thereby the MAPK pathway plays an important role in this process.

Catestatin increases the expression of anti-apoptotic and pro-angiogenetic factors in the post-ischemic hypertrophied heart of SHR

Background

In the presence of comorbidities the effectiveness of many cardioprotective strategies is blunted. The goal of this study was to assess in a hypertensive rat model if the early reperfusion with anti-hypertensive and pro-angiogenic Chromogranin A-derived peptide, Catestatin (CST:hCgA_352–372; CST-Post), protects the heart via Reperfusion-Injury-Salvage-Kinases (RISK)-pathway activation, limiting infarct-size and apoptosis, and promoting angiogenetic factors (e.g., hypoxia inducible factor, HIF-1α, and endothelial nitric oxide synthase, eNOS, expression).

Methods and Results

The effects of CST-Post on infarct-size, apoptosis and pro-angiogenetic factors were studied in isolated hearts of spontaneously hypertensive rats (SHR), which underwent the following protocols: (a) 30-min ischemia and 120-min reperfusion (I/R); (b) 30-min ischemia and 20-min reperfusion (I/R-short), both with and without CST-Post (75 nM for 20-min at the beginning of reperfusion). In unprotected Wistar-Kyoto hearts, used as normal counterpart, infarct-size resulted smaller than in SHR. CST-Post reduced significantly infarct-size and improved post-ischemic cardiac function in both strains. After 20-min reperfusion, CST-Post induced S-nitrosylation of calcium channels and phosphorylation of RISK-pathway in WKY and SHR hearts. Yet specific inhibitors of the RISK pathway blocked the CST-Post protective effects against infarct in the 120-min reperfusion groups. Moreover, apoptosis (evaluated by TUNEL, ARC and cleaved caspase) was reduced by CST-Post. Importantly, CST-Post increased expression of pro-angiogenetic factors (i.e., HIF-1α and eNOS expression) after two-hour reperfusion.

Conclusions

CST-Post limits reperfusion damages and reverses the hypertension-induced increase of I/R susceptibility. Moreover, CST-Post triggers antiapoptotic and pro-angiogenetic factors suggesting that CST-Post can be used as an anti-maladaptive remodeling treatment.

Mechanisms involved in attenuated cardio-protective role of ischemic preconditioning in metabolic disorders

Myocardial infarction is a pathological state which occurs due to severe abrogation of the blood supply (ischemia) to a part of heart, which can cause myocardial damage. The short intermittent cycles of sub-lethal ischemia and reperfusion has shown to improve the tolerance of the myocardium against subsequent prolonged ischemia/reperfusion (I/R)-induced injury, which is known as ischemic preconditioning (IPC). Although, IPC-induced cardioprotection is well demonstrated in various species, including human beings, accumulated evidence clearly suggests critical abrogation of the beneficial effects of IPC in diabetes mellitus, hyperlipidemia and hyperhomocysteinemia. Various factors are involved in the attenuation of the cardioprotective effect of preconditioning, such as the reduced release of calcitonin gene-related peptide (CGRP), the over-expression of glycogen synthase kinase-3β (GSK-3β) and phosphatase and tensin homolog (PTEN), impairment of mito-KATP channels, the consequent opening of mitochondrial permeability transition pore (MPTP), etc. In this review, we have critically discussed the various signaling pathways involved in abrogated preconditioning in chronic diabetes mellitus, hyperlipidemia and hyperhomocysteinemia. We have also focused on the involvement of PTEN in abrogated preconditioning and the significance of PTEN inhibitors.

Notch 1 signalling inhibits cardiomyocyte apoptosis in ischaemic postconditioning

AIM

Recent studies have demonstrated that Notch signalling pathway is an important mediator of cardiac repair and regeneration after myocardial infarction. However, the mechanism by which Notch signalling pathway is mediating cardioprotection after ischaemic postconditioning (IPost) is still not understood thoroughly. The aim of the present study was to investigate the mechanism by which Notch signalling pathway mediated the cardioprotection effect after IPost.

METHODS

Rat heart-derived H9c2 cells were randomly divided into six groups as follows: Control group, hypoxia/reoxygenation group (H/R), H/R+N1ICD group, H-post group, H-post+Notch-1miRNA group, and Mock group. We used pcDNA3.1-Myc-His plasmid and RNA interference (RNAi) to activate/inhibit the expression of Notch-1 in H9c2 cell lines. The Bcl-2, Bax genes and proteins were assessed by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and Western blot analysis. The effects of Notch 1 signalling on cell survival, proliferation and apoptosis were detected by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) and flow cytometry analysis, respectively. Furthermore, Notch 1 signalling induced the disruption of mitochondrial membrane potential, thus leading to the activation of caspase-9/-3 measured using the colorimetric activity assay.

RESULTS

We found Notch 1 signalling reduced cardiomyocyte apoptosis in IPost through regulating the expression of Bcl-2, Bax and activation of caspase-9 and -3. We found that after transfected with pcDNA3.1-Myc-His plasmid, activation of the Notch 1 gene effectively promoted cell proliferation and inhibited apoptosis. The Notch 1 upregulation was accompanied by an upregulation of Bcl-2 and a downregulation of Bax. In addition, a paralled increase in caspase-9/-3 activities was observed. These effects were blunted by transfected with Notch-1 miRNA in the H9c2 cells.

CONCLUSION

Notch 1 signalling has a cardioprotection effect, which may result from cardiomyocyte apoptosis, by means of regulating the expression of cell apoptosis inhibiting proteins Bcl-2, Bax and the activation of caspase-9 and -3.

An improved postconditioning algorithm: gradually increased reperfusion provides improved cardioprotection in rats

The aim of the present study was to investigate whether a gradually increasing reperfusion algorithm, in which the brief reperfusion was lengthened as the duration of each reperfusion/reocclusion cycle remained fixed, enhances cardioprotection. Rats were randomized into 5 groups: the sham, reperfusion injury (R/I), gradually decreased reperfusion (GDR; 30/10‑25/15‑15/25‑10/30 sec of reperfusion/reocclusion), equal reperfusion (ER; 4 20/20‑sec reperfusion/reocclusion cycles) and gradually increased reperfusion (GIR; 10/30‑15/25‑25/15‑30/10 sec of reperfusion/reocclusion). The rats were sacrificed to measure serum markers, apoptotic indices and infarct size. Western blot analyses were used to analyze the expression of molecules involved in important signaling pathways. All the three postconditioning patterns were found to provide cardioprotection (P<0.05 compared with the R/I group). GIR provided optimum cardioprotection, followed by ER and then GDR. Apoptotic index and serum marker levels were significantly reduced in the GIR compared with the ER group (P<0.05). The enhanced cardioprotection provided by GIR was accompanied by significantly increased levels of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and Bcl‑2, as well as lower levels of p38/c‑Jun N‑terminal kinase (JNK) phosphorylation, tumor necrosis factor α (TNFα), caspase‑8, Bax, caspase‑9 and cytochrome c (Cyt‑c) in the cytoplasm of rats (P<0.05, all compared with ER). The infarct size in the rats of the GIR group was also smaller compared with that in the rats of the ER group, but this difference was not significant (16.30±5.22 vs. 20.57±6.32%, P>0.05). All the variables measured in the present study were significantly improved in the GIR group compared with the GDR group (P<0.05). In conclusion, the association between brief reperfusion and reocclusion is an important factor in postconditioning algorithms. Additionally, GIR results in improved cardioprotection compared with that achieved by the remaining algorithms examined.

MicroRNA-15a/b are up-regulated in response to myocardial ischemia/reperfusion injury

Objective

Several studies have indicated that miR-15a, miR-15b and miR-16 may be the important regulators of apoptosis. Since attenuate apoptosis could protect myocardium and reduce infarction size, the present study was aimed to find out whether these miRNAs participate in regulating myocardial ischemia reperfusion (I/R) injury.

Methods

Apoptosis in mice hearts subjected to I/R was detected by TUNEL assay in vivo, while flow cytometry analysis followed by Annexin V/PI double stain in vitro was used to detect apoptosis in cultured cardiomyocytes which were subjected to hypoxia/reoxygenation (H/R). Taqman real-time quantitative PCR was used to confirm whether miR-15a/15b/16 were involved in the regulation of cardiac I/R and H/R.

Results

Compared to those of the controls, I/R or H/R induced apoptosis of cardiomyocytes was significantly increased both in vivo (24.4% ± 9.4% vs. 2.2% ± 1.9%, P < 0.01, n = 5) and in vitro (14.12% ± 0.92% vs. 2.22% ± 0.08%). The expression of miR-15a and miR-15b, but not miR-16, was increased in the mice I/R model, and the results were consistent in the H/R model.

Conclusions

Our data indicate miR-15 and miR-15b are up-regulated in response to cardiac I/R injury, therefore, down-regulation of miR-15a/b may be a promising strategy to reduce myocardial apoptosis induced by cardiac I/R injury.

Hydrogen sulfide protects cardiomyocytes from myocardial ischemia-reperfusion injury by enhancing phosphorylation of apoptosis repressor with caspase recruitment domain

Hydrogen sulfide (H(2)S) displays an anti-apoptotic activity against myocardial ischemia reperfusion (MIR). Apoptosis repressor with caspase recruitment domain (ARC) is constitutively expressed in the heart and inhibits cell apoptosis when it is phosphorylated. Here, we investigated whether H(2)S could inhibit apoptosis by affecting ARC phosphorylation using cultured rat cardiomyocytes and a rat model of MIR. Primary cardiomyocytes were prepared from hearts of newborn rats and were pre-incubated with NaHS, a donor of H(2)S, for 60 min. Cardiomyocytes were subjected to hypoxia for 4 h, followed by reoxygenation for 2 h. The hypoxia and subsequent reoxygenation (H/R) significantly induced cell apoptosis, increased expression levels of Fas and FasL proteins, enhanced release of cytochrome c from mitochondria, and elevated caspase-3 activity, while H/R reduced ARC phosphorylation and increased the activity of calcineurin that dephosphorylates ARC. Pre-incubation with NaHS significantly attenuated the above effects through promoting ARC phosphorylation by reducing calcineurin activity and by increasing the activity of protein kinase casein kinase II (CK2) that phosphorylates ARC. In fact, TBB, a specific inhibitor of CK2, abolished the effects of NaHS. In rats undergoing MIR, NaHS significantly reduced the myocardial infarct size, cell apoptosis, calcineurin activity, and the expression levels of Fas, FasL and cleaved caspase-3 proteins, while NaHS increased ARC phosphorylation. In contrast, DL-propargylglycine, an inhibitor of cystathionine γ-lyase, the main enzyme for H(2)S production in hearts, showed opposite effects to NaHS. The results indicate that H(2)S inhibits apoptosis of cardiomyocytes induced by MIR through enhancing ARC phosphorylation.

Apoptosis repressor with caspase recruitment domain, a multifunctional modulator of cell death

Apoptosis repressor with caspase recruitment domain (ARC) is a highly potent and multifunctional inhibitor of apoptosis that is physiologically expressed predominantly in post-mitotic cells such as cardiomyocytes, skeletal muscle cells and neurons. ARC was also found to be up-regulated in many forms of malignant tumours. ARC impairs the cellular apoptotic responsiveness to a wide range of stresses and insults, including extrinsic apoptosis initiation via death receptor ligands, dysregulation of cellular Ca²⁺ homeostasis and endoplasmatic reticulum (ER) stress, genotoxic drugs, ionizing radiation, oxidative stress and hypoxia. ARC is subject to both transcriptional and post-translational regulation and exhibits its function through a multitude of molecular interactions with upstream transducers of apoptosis signals. This review summarizes, structures and comments on the published knowledge regarding ARC and its roles in modulating apoptotic cell death responsiveness in physiological and pathophysiological contexts.

Role of miR-1 and miR-133a in myocardial ischemic postconditioning

Background

Ischemic postconditioning (IPost) has aroused much attention since 2003 when it was firstly reported. The role of microRNAs (miRNAs or miRs) in IPost has rarely been reported. The present study was undertaken to investigate whether miRNAs were involved in the protective effect of IPost against myocardial ischemia-reperfusion (IR) injury and the probable mechanisms involved.

Methods

Thirty SD rats weighing 250-300 g were equally randomized to three groups: Control group, where the rats were treated with thoracotomy only; IR group, where the rats were treated with ischemia for 60 min and reperfusion for 180 min; and IPost group, where the rats were treated with 3 cycles of transient IR just before reperfusion. The extent of myocardial infarction, LDH and CK activities were measured immediately after treatment. Myocardial apoptosis was detected by TUNEL assay. The myocardial tissue was collected after IR or IPost stimulation to evaluate the miRNAs expression level by miRNA-microarray and quantitative real-time RT-PCR. Real-time PCR was conducted to identify changes in mRNA expression of apoptosis-related genes such as Bcl-2, Bax and Caspase-9 (CASP9), and Western blot was used to compare the protein expression level of CASP9 in the three groups. The miRNA mimics and anti-miRNA oligonucleotides (AMO) were transferred into the cultured neonatal cardiomyocytes and myocardium before they were treated with IR. The effect of miRNAs on apoptosis was determined by flow cytometry and TUNEL assay. CASP9, as one of the candidate target of miR-133a, was compared during IR after the miR-133a mimic or AMO-133a was transferred into the myocardium.

Results

IPost reduced the IR-induced infarct size of the left ventricle, and decreased CK and LDH levels. TUNEL assay showed that myocardial apoptosis was attenuated by IPost compared with IR. MiRNA-microarray and RT-PCR showed that myocardial-specific miR-1 and miR-133a were down-regulated by IR, and up-regulated by IPost compared with IR. Furthermore, IPost up-regulated the mRNA expression of Bcl-2, down-regulated that of Bax and CASP9. Western blot showed that IPost also down-regulated the CASP9 protein expression compared with IR. The results of flow cytometry and TUNEL assay showed that up-regulation of miR-1 and miR-133a decreased apoptosis of cardiomyocytes. MiR-133a mimic down-regulated CASP9 protein expression and attenuated IR-induced apoptosis.

Conclusion

MiRNAs are associated with the protective effect of IPost against myocardial IR injury. IPost can up-regulate miR-1 and miR-133a, and decrease apoptosis of cardiomyocyte. Myocardial-specific miR-1 and miR-133a may play an important role in IPost protection by regulating apoptosis-related genes. MiR-133a may attenuate apoptosis of myocardiocytes by targeting CASP9.

The multidimensional physiological responses to postconditioning

Reperfusion is the definitive treatment to reduce infarct size and other manifestations of postischemic injury. However, reperfusion contributes to postischemic injury, and, therefore, reperfusion therapies do not achieve the optimal salvage of myocardium. Other tissues as well undergo injury after reperfusion, notably, the coronary vascular endothelium. Postconditioning has been shown to have salubrious effects on different tissue types within the heart (cardiomyocytes, endothelium) and to protect against various pathologic processes, including necrosis, apoptosis, contractile dysfunction, arrhythmias, and microvascular injury or "no-reflow." The mechanisms by which postconditioning alters the pathophysiology of reperfusion injury is exceedingly complex and involves physiological mechanisms (e.g., delaying re-alkalinization of tissue pH, triggering release of autacoids, and opening and closing of various channels) and molecular mechanisms (activation of kinases) that affect cellular and subcellular targets or effectors. The physiologic responses to postconditioning are not isolated or mutually exclusive, but are interactive, with one response affecting another in an integrated manner. This integrated response on multiple targets differs from the monotherapy approach by drugs that have failed to reduce reperfusion injury on a consistent basis and may underlie the efficacy of this therapeutic approach across species and in human trials.

Mitochondria in postconditioning

Several signal transduction pathways are activated by cardioprotective stimuli, including ischemic or pharmacological postconditioning. These pathways converge on a common target, the mitochondria, and cardioprotection by postconditioning is associated with preserved mitochondrial function after ischemia/reperfusion. The present review discusses the role of mitochondria in cardioprotection, especially the involvement of ATP-dependent potassium channels, reactive oxygen species, and the mitochondrial permeability transition pore, and focuses on the effects of postconditioning on mitochondrial function (i.e., their oxygen consumption and calcium retention capacity). The contribution of mitochondria to loss of protection by postconditioning in diseased or aged myocardium is also addressed.

Expression of ARC (apoptosis repressor with caspase recruitment domain), an antiapoptotic protein, is strongly prognostic in AML

Regulators of apoptosis in acute myeloid leukemia (AML) have been extensively studied and are considered excellent therapeutic targets. Apoptosis repressor with caspase recruitment domain (ARC), an antiapoptotic protein originally found to be involved in apoptosis of cardiac cells, was recently demonstrated to be overexpressed in several solid tumors. To assess its importance in AML, we profiled ARC expression in 511 newly diagnosed AML patients using a validated robust reverse-phase protein array and correlated ARC levels with clinical outcomes. ARC was variably expressed in samples from patients with AML. ARC level was not associated with cytogenetic groups or with FLT-3 mutation status. However, patients with low or medium ARC protein levels had significantly better outcomes than those with high ARC levels: longer overall survival (median, 53.9 or 61.6 vs 38.9 weeks, P = .0015) and longer remission duration (median, 97.6 or 44.7 vs 31.1 weeks, P = .0007). Multivariate analysis indicated that ARC was a statistically significant independent predictor of survival in AML (P = .00013). Inhibition of ARC promoted apoptosis and sensitized cytosine arabinoside-induced apoptosis in OCI-AML3 cells. These results suggest that ARC expression levels are highly prognostic in AML and that ARC is a potential therapeutic target in AML.

Phosphorylation of ARC is a critical element in the antiapoptotic effect of anesthetic preconditioning

BACKGROUND

Transient exposure to volatile anesthetics before cardiac ischemia/reperfusion (I/R), termed anesthetic preconditioning, limits myocardial injury and inhibits apoptosis. Apoptosis repressor with caspase recruitment domain (ARC) is a novel protein that has been demonstrated to protect cardiomyocytes from apoptosis induced by I/R and is regulated by phosphorylation. We therefore hypothesized that the antiapoptotic effect of anesthetic preconditioning is, in part, mediated by phosphorylation of ARC.

METHODS

In the experiments we used a perfused rat heart model of sevoflurane anesthetic preconditioning and I/R. In addition to measures of left ventricular function, phosphorylation of ARC was measured with and without anesthetic preconditioning. Because the phosphorylation status of ARC is determined by calcineurin and protein kinase CK2, the role of ARC was defined by measuring calcineurin activity and using the calcineurin inhibitor FK506 and the ARC phosphorylation inhibitor 4,5,6,7-tetrabromobenzotrizole (TBB).

RESULTS

I/R without anesthetic preconditioning increased calcineurin and reduced ARC phosphorylation levels, whereas anesthetic preconditioning significantly improved functional recovery, decreased ischemic injury, limited the increase in calcineurin activity, increased the phosphorylation level of ARC, reduced cytochrome c release, and blocked the increase in caspase-8 after I/R. The effects of anesthetic preconditioning were mirrored by FK506 and abolished by TBB.

CONCLUSION

This study has identified a novel cardiac pathway in which anesthetic preconditioning prevents the increase in calcineurin after I/R, resulting in increased phosphorylated ARC and decreased markers of apoptosis.

Mitochondrial fission leads to Smac/DIABLO release quenched by ARC

Apoptosis plays a critical role for the development of a variety of cardiac diseases. Cardiomyocytes are enriched in mitochondria, while mitochondrial fission can regulate apoptosis. The molecular mechanism governing cardiomyocyte apoptosis remain to be fully elucidated. Our results showed that Smac/DIABLO is necessary for apoptosis in cardiomyocytes, and it is released from mitochondria into cytosol in response to apoptotic stimulation. Smac/DIABLO release is a consequence of mitochondrial fission mediated by dynamin-related protein-1 (Drp1). Upon release Smac/DIABLO binds to X-linked inhibitor of apoptosis protein (XIAP), resulting in the activation of caspase-9 and caspase-3. Their activation is a prerequisite for the initiation of apoptosis because the administration of z-LEHD-fmk and z-DQMD-fmk, two relatively specific inhibitors for caspase-9, and caspase-3, respectively, could significantly attenuate apoptosis. Smac/DIABLO release could not be blocked by these caspase inhibitors, indicating that it is an event upstream of caspase activation. ARC (apoptosis repressor with caspase recruitment domain), an abundantly expressed apoptotic repressor in cardiomyocytes, could inhibit mitochondrial fission and Smac/DIABLO release. Our data reveal that Smac/DIABLO is a target of ARC in counteracting apoptosis.

Neuroprotection induced in vitro by ischemic preconditioning and postconditioning: modulation of apoptosis and PI3K-Akt pathways

Preconditioning and postconditioning are mild ischemic exposures before or after severe injurious ischemia, respectively, that elicit endogenous neuroprotective responses. Molecular mechanisms of neuroprotection through preconditioning and postconditioning are not completely understood. Here we optimized the in vitro oxygen and glucose deprivation (OGD) models of preconditioning and postconditioning in primary cortical neuron cultures that allow the studies of the corresponding molecular mechanisms of neuroprotection. We found that the cortical cells preconditioned with a single 45-min OGD treatment administered 24 h prior to injurious 2 h OGD were robustly protected after both 3 h and 16 h of reperfusion. For the postconditioning treatment, we found that three cycles of 15 min OGD followed by 15 min reperfusion, applied immediately after injurious 2 h OGD and prior to complete reperfusion, resulted in effective neuroprotection at both 3 h and 16 h of reperfusion. Using real-time RT-PCR arrays focused on genes of the apoptosis and PI3K-Akt pathways, we found that injurious OGD mainly induced apoptosis-related and repressed PI3K-Akt pathway-related genes after either 3 h or 16 h of reperfusion. Preconditioning treatment resulted in the activation of both pro-survival and anti-apoptotic pathways after 3 h of reperfusion and mainly anti-apoptotic pathway after 16 h of reperfusion. In contrast, the activation of PI3K-Akt pathway mainly contributed to the neuroprotective effect by the postconditioning treatment after 3 h of reperfusion, but differential gene expression likely contributed minimally, if at all, to the neuroprotection observed after 16 h of reperfusion. Among the novel markers of neuroprotection, Nol3 gene upregulation was observed after 3 h of reperfusion following either preconditioning or postconditioning treatments and after 16 h of reperfusion following preconditioning treatment.

Ischemic post-conditioning reduces infarct size of the in vivo rat heart: role of PI3-K, mTOR, GSK-3beta, and apoptosis

Post-conditioning by repetitive cycles of reperfusion/ischemia after prolonged ischemia protects the heart from infarction. The objectives of this study were: Are kinases (PI3-kinase, mTOR, and GSK-3beta) involved in the signaling pathway of post-conditioning? Does post-conditioning result in a diminished necrosis or apoptosis? In open chest rats the infarct size was determined after 30 min of regional ischemia and 30 min of reperfusion using propidium iodide and microspheres. Post-conditioning was performed by three cycles of 30 s reperfusion and reocclusion each, immediately upon reperfusion. PI3-kinase and mTOR were blocked using wortmannin (0.6 mg/kg) or rapamycin (0.25 mg/kg), respectively. The phosphorylation of GSK-3beta and p70S6K was determined with phospho-specific antibodies. TUNEL staining and detection of apoptosis-inducing factor (AIF) were used for the determination of apoptosis. Control hearts had an infarct size of 49 +/- 3%, while post-conditioning significantly reduced it to 29 +/- 3% (P < 0.01). Wortmannin as well as rapamycin completely blocked the infarct size reduction of post-conditioning (51 +/- 2% and 54 +/- 5%, respectively). Western blot analysis revealed that post-conditioning increased the phosphorylation of GSK-3beta by 2.3 times (P < 0.01), and this increase could be blocked by wortmannin, a PI3-kinase inhibitor. Although rapamycin blocked the infarct size reduction, phosphorylation of p70S6K was not increased in post-conditioned hearts. After 2 h of reperfusion, the post-conditioned hearts had significantly fewer TUNEL-positive nuclei (35 %) compared to control hearts (53%; P < 0.001). AIF was equally reduced in post-conditioned rat hearts (P < 0.05 vs. control). Infarct size reduction by ischemic post-conditioning of the in vivo rat heart is PI3-kinase dependent and involves mTOR. Furthermore, GSK-3beta, which is thought to be a regulator of the mPTP, is part of the signaling pathway of post-conditioning. Finally, apoptosis was inhibited by post-conditioning, which was shown by two independent methods. The role of apoptosis and/or autophagy in post-conditioning has to be further elucidated to find therapeutic targets to protect the heart from the consequences of acute myocardial infarction.