Inhibition of the activity of poly (ADP-ribose) polymerase reduces heart ischaemia/reperfusion injury via suppressing JNK-mediated AIF translocation

c-Jun N-terminal kinase signaling in cellular senescence

Cellular senescence leads to decreased tissue regeneration and inflammation and is associated with diabetes, neurodegenerative diseases, and tumorigenesis. However, the mechanisms of cellular senescence are not fully understood. Emerging evidence has indicated that c-Jun N-terminal kinase (JNK) signaling is involved in the regulation of cellular senescence. JNK can downregulate hypoxia inducible factor-1α to accelerate hypoxia-induced neuronal cell senescence. The activation of JNK inhibits mTOR activity and triggers autophagy, which promotes cellular senescence. JNK can upregulate the expression of p53 and Bcl-2 and accelerates cancer cell senescence; however, this signaling also mediates the expression of amphiregulin and PD-LI to achieve cancer cell immune evasion and prevents their senescence. The activation of JNK further triggers forkhead box O expression and its target gene Jafrac1 to extend the lifespan of Drosophila. JNK can also upregulate the expression of DNA repair protein poly ADP-ribose polymerase 1 and heat shock protein to delay cellular senescence. This review discusses recent advances in understanding the function of JNK signaling in cellular senescence and includes a comprehensive analysis of the molecular mechanisms underlying JNK-mediated senescence evasion and oncogene-induced cellular senescence. We also summarize the research progress in anti-aging agents that target JNK signaling. This study will contribute to a better understanding of the molecular targets of cellular senescence and provides insights into anti-aging, which may be used to develop drugs for the treatment of aging-related diseases.

Cardioprotective Effects of a Selective c-Jun N-terminal Kinase Inhibitor in a Rat Model of Myocardial Infarction

Activation of c-Jun N-terminal kinases (JNKs) is involved in myocardial injury, left ventricular remodeling (LV), and heart failure (HF) after myocardial infarction (MI). The aim of this research was to evaluate the effects of a selective JNK inhibitor, 11H-indeno [1,2-b]quinoxalin-11-one oxime (IQ-1), on myocardial injury and acute myocardial ischemia/reperfusion (I/R) in adult male Wistar rats. Intraperitoneal administration of IQ-1 (25 mg/kg daily for 5 days) resulted in a significant decrease in myocardial infarct size on day 5 after MI. On day 60 after MI, a significant (2.6-fold) decrease in LV scar size, a 2.2-fold decrease in the size of the LV cavity, a 2.9-fold decrease in the area of mature connective tissue, and a 1.7-fold decrease in connective tissue in the interventricular septum were observed compared with the control group. The improved contractile function of the heart resulted in a significant (33%) increase in stroke size, a 40% increase in cardiac output, a 12% increase in LV systolic pressure, a 28% increase in the LV maximum rate of pressure rise, a 45% increase in the LV maximum rate of pressure drop, a 29% increase in the contractility index, a 14% increase in aortic pressure, a 2.7-fold decrease in LV end-diastolic pressure, and a 4.2-fold decrease in LV minimum pressure. We conclude that IQ-1 has cardioprotective activity and reduces the severity of HF after MI.

OUP accepted manuscript

Cardiovascular diseases (CVDs) arise from a complex interplay among genomic, proteomic, and metabolomic abnormalities. Emerging evidence has recently consolidated the presence of robust DNA damage in a variety of cardiovascular disorders. DNA damage triggers a series of cellular responses termed DNA damage response (DDR) including detection of DNA lesions, cell cycle arrest, DNA repair, cellular senescence, and apoptosis, in all organ systems including hearts and vasculature. Although transient DDR in response to temporary DNA damage can be beneficial for cardiovascular function, persistent activation of DDR promotes the onset and development of CVDs. Moreover, therapeutic interventions that target DNA damage and DDR have the potential to attenuate cardiovascular dysfunction and improve disease outcome. In this review, we will discuss molecular mechanisms of DNA damage and repair in the onset and development of CVDs, and explore how DDR in specific cardiac cell types contributes to CVDs. Moreover, we will highlight the latest advances regarding the potential therapeutic strategies targeting DNA damage signalling in CVDs.

Astragaloside IV enhances GATA-4 mediated myocardial protection effect in hypoxia/reoxygenation injured H9c2 cells

BACKGROUND AND AIM

The transcription factor GATA-4 plays an important role in myocardial protection. Astragaloside IV (Ast-IV) was reported with the effects on improving cardiac function after ischemia. In this study, we explored how Ast-IV interacts with GATA-4 to protect myocardial cells H9c2 against Hypoxia/Reoxygenation (H/R) stress.

METHODS AND RESULTS

H9c2 cells were cultured under the H/R condition. Various cell activity and morphology assays were used to assess the rates of apoptosis and autophagy. In these H/R injured H9c2 cells, increased apoptosis (P < 0.01) and autophagosome number (P < 0.01) were observed, and the addition of Ast-IV ameliorated this tendency. Mechanistically, we used the RT-qPCR and Western blot to evaluate the expressions of various molecules. The results showed that Ast-IV treatment upregulated gene expression of GATA-4 (P < 0.01) and the survival factors (Bcl-2, P < 0.05; p62, P < 0.01), but suppressed apoptosis and autophagy related genes (PARP, Caspase-3, Beclin-1, and LC3-II; All P < 0.01). Furthermore, overexpressing of GATA-4 by its agonist phenylephrine can also protect H/R injured H9c2 cells, and the addition of Ast-IV further enhanced this protection of GATA-4. In contrast, silencing GATA-4 expression abolished the H/R protection of Ast-IV, which demonstrated that the myocardial protection of Ast-IV is mediated by GATA-4. Lastly, along with GATA overexpression, enhanced interactions between Bcl-2 and Beclin-1 were detected by Chromatin immunoprecipitation (P < 0.01).

CONCLUSION

Ast-IV rescued the H/R injury induced apoptosis and autophagy in H9c2 cells. Ast-IV treatment can stimulate the overexpression of GATA-4, and further enhanced the myocardial protection effect of GATA-4.

Exendin-4 protects the hearts of rats from ischaemia/reperfusion injury by boosting antioxidant levels and inhibition of JNK/p66 Shc/NADPH axis

Exendin-4, a glucagon-like peptide-1 receptor agonist, was shown to protect against cardiac ischaemia/reperfusion (I/R) injury by suppressing oxidative stress. p⁶⁶ Shc, a pro-oxidant and an apoptotic protein, is activated in the infarcted left ventricles (LVs) after induction of I/R. This study investigated if the cardiac protective effect of Exendin-4 against I/R injury in rats involves inhibition of p⁶⁶ Shc and to determine the underlying mechanisms behind this. Adult male rats (n = 12/group) were divided into four groups as a sham, a sham + Exendin-4, an I/R, and an I/R + Exendin-4. Exendin-4 was administered to rats 7 days before the induction of I/R. Ischaemia was induced by ligating the left anterior descending (LAD) coronary artery for 40 minutes followed by reperfusion for 10 minutes. The infarct myocardium was used for further analysis. Exendin-4 significantly reduced infarct area (by 62%), preserved LV function and lowered serum levels of LDH and CK-MB in I/R-induced rats. Also, it significantly reduced LV levels of ROS and MDA and protein levels of cytochrome-c and cleaved caspase-3 but significantly increased levels of glutathione (GSH) and manganese superoxide dismutase (MnSOD) in LVs of I/R rats indicating antioxidant and anti-apoptotic effects. Furthermore, it inhibited JNK and p⁶⁶ Shc activation and downregulated protein levels of p⁶⁶ Shc and NADPH oxidase with no effect on protein levels/activity of p53 and PKCβII. Of note, Exendin-4 also increased GSH and MnSOD in LVs of control rats. In conclusion, Exendin-4 cardioprotective effect in I/R hearts is mediated mainly by antioxidant effect and inhibition of JNK/P⁶⁶ Shc/NADPH oxidase.

Melatonin Ameliorates MI-Induced Cardiac Remodeling and Apoptosis through a JNK/p53-Dependent Mechanism in Diabetes Mellitus

Diabetes mellitus, a worldwide health threat, is considered an independent risk factor for cardiovascular diseases. The overall cardiovascular risk of diabetes is similar to the one having one myocardial infarction (MI) attack although the precise impact of diabetes on MI-induced myocardial anomalies remains elusive. Given that mortality following MI is much greater in diabetic patients compared to nondiabetic patients, this study was designed to examine the effect of melatonin on MI injury-induced myocardial dysfunction in diabetes. Adult mice were made diabetic using high-fat feeding and streptozotocin (100 mg/kg body weight) prior to MI and were treated with melatonin (50 mg/kg/d, p.o.) for 4 weeks prior to assessment of cardiac geometry and function. The MI procedure in diabetes displayed overt changes in cardiac geometry (chamber dilation and interstitial fibrosis) and functional anomalies (reduced fractional shortening and cardiomyocyte contractile capacity) in association with elevated c-Jun N-terminal kinase (JNK) phosphorylation and p53 level. Melatonin treatment markedly attenuated cardiac dysfunction and myocardial fibrosis in post-MI diabetic mice. Furthermore, melatonin decreased JNK phosphorylation, reduced p53 levels, and suppressed apoptosis in hearts from the post-MI diabetic group. In vitro findings revealed that melatonin effectively counteracted high-glucose/high fat-hypoxia-induced cardiomyocyte apoptosis and contractile dysfunction through a JNK-mediated mechanism, the effects of which were impaired by the JNK activator anisomycin. In summary, our study suggests that melatonin protects against myocardial injury in post-MI mice with diabetes, which offers a new therapeutic strategy for the management of MI-induced cardiac injury in diabetes.

Poly (ADP-ribose) polymerase inhibition protects against myocardial ischaemia/reperfusion injury via suppressing mitophagy

Myocardial ischaemia/reperfusion (I/R) injury attenuates the beneficial effects of reperfusion therapy. Poly(ADP-ribose) polymerase (PARP) is overactivated during myocardial I/R injury. Mitophagy plays a critical role in the development of myocardial I/R injury. However, the effect of PARP activation on mitophagy in cardiomyocytes is unknown. In this study, we found that I/R induced PARP activation and mitophagy in mouse hearts. Poly(ADP-ribose) polymerase inhibition reduced the infarct size and suppressed mitophagy after myocardial I/R injury. In vitro, hypoxia/reoxygenation (H/R) activated PARP, promoted mitophagy and induced cell apoptosis in cardiomyocytes. Poly(ADP-ribose) polymerase inhibition suppressed H/R-induced mitophagy and cell apoptosis. Parkin knockdown with lentivirus vectors inhibited mitophagy and prevented cell apoptosis in H/R-treated cells. Poly(ADP-ribose) polymerase inhibition prevented the loss of the mitochondrial membrane potential (ΔΨm). Cyclosporin A maintained ΔΨm and suppressed mitophagy but FCCP reduced the effect of PARP inhibition on ΔΨm and promoted mitophagy, indicating the critical role of ΔΨm in H/R-induced mitophagy. Furthermore, reactive oxygen species (ROS) and poly(ADP-ribosylation) of CypD and TSPO might contribute to the regulation of ΔΨm by PARP. Our findings thus suggest that PARP inhibition protects against I/R-induced cell apoptosis by suppressing excessive mitophagy via the ΔΨm/Parkin pathway.

YB1 protects cardiac myocytes against H2O2‑induced injury via suppression of PIAS3 mRNA and phosphorylation of STAT3

Oxidative stress serves important roles in cardiac injury during the process of ischemia/reperfusion (I/R). Y-box protein 1 (YB1), a member of the highly conserved Y-box protein family, is closely associated with inflammation and stress responses by regulating gene transcription, RNA splicing and mRNA translation. However, the roles of YB1 in oxidative stress-induced myocardial-I/R (M-I/R) injury are unknown. The aim of the present study was to examine the effects of YB1 on H₂O₂-induced cardiomyocyte injury and its underlying mechanism. The results demonstrated that YB1 expression was upregulated during H₂O₂-induced myocardial injury. YB1 knockdown through transfection of small interfering RNA significantly aggravated cardiac cell apoptosis. Furthermore, YB1 knockdown significantly reversed the H₂O₂-mediated increase in phosphorylated signal transducer and activator of transcription (STAT)3, but did not affect the phosphorylation of P38, extracellular signal-regulated kinases 1/2, c-Jun N-terminal kinases, P65, Janus kinase 1 and 2 or STAT1. Moreover, protein co-immunoprecipitation and RNA-binding protein immunoprecipitation assays revealed that YB1 interacted with protein inhibitor of activated STAT 3 (PIAS3) mRNA but not its translated protein. YB1 overexpression may have promoted PIAS3 mRNA decay, decreasing PIAS3 protein levels, and therefore increased the levels of phosphorylated STAT3. Finally, YB1 knockdown, mediated by a lentivirus carrying YB1 targeted short hairpin RNA, significantly decreased left ventricle percentage fractional shortening and ejection fraction values, while increasing the infarct sizes in a rat model of M-I/R injury. These results demonstrated for the first time (to the best of our knowledge) that YB1 may protect cardiac myocytes against H₂O₂ or M-I/R-induced injury by binding to PIAS3 mRNA and resulting in the phosphorylation of STAT3.

Poly(ADP-ribose) Polymerase (PARP) and PARP Inhibitors: Mechanisms of Action and Role in Cardiovascular Disorders

Poly(ADP-ribosyl)ation is an immediate cellular repair response to DNA damage and is catalyzed primarily by poly(ADP-ribose)polymerase-1 (PARP1), which is the most abundant of the 18 different PARP isoforms and accounts for more than 90% of the catalytic activity of PARP in the cell nucleus. Upon detection of a DNA strand break, PARP1 binds to the DNA, cleaves nicotinamide adenine dinucleotide between nicotinamide and ribose and then modifies the DNA nuclear acceptor proteins by formation of a bond between the protein and the ADP-ribose residue. This generates ribosyl-ribosyl linkages that act as a signal for other DNA-repairing enzymes and DNA base repair. Extensive DNA breakage in cells results in excessive activation of PARP with resultant depletion of the cellular stores of nicotinamide adenine dinucleotide (NAD+) which slows the rate of glycolysis, mitochondrial electron transport, and ultimately ATP formation in these cells. This paper focuses on PARP in DNA repair in atherosclerosis, acute myocardial infarction/reperfusion injury, and congestive heart failure and the role of PARP inhibitors in combating the effects of excessive PARP activation in these diseases. Free oxygen radicals and nitrogen radicals in arteries contribute to disruption of the vascular endothelial glycocalyx, which increase the permeability of the endothelium to inflammatory cells and also low-density lipoproteins and the accumulation of lipid in the vascular intima. Mild inflammation and DNA damage within vascular cells promote PARP1 activation and DNA repair. Moderate DNA damage induces caspase-dependent PARP cleavage and vascular cell apoptosis. Severe DNA damage due to vascular inflammation causes excessive activation of PARP1. This causes endothelial cell depletion of NAD+ and ATP, downregulation of atheroprotective SIRT1, necrotic cell death, and ultimately atherosclerotic plaque disruption. Inhibition of PARP decreases vascular endothelial cell adhesion P-selectin and ICAM-1 molecules, inflammatory cells, pro-death caspase-3, and c-Jun N-terminal kinase (JNK) activation and upregulates prosurvival extracellular signal-regulated kinases and AKT, which decrease vascular cell apoptosis and necrosis and limit atherosclerosis and plaque disruption. In myocardial infarction with coronary occlusion then reperfusion, which occurs with coronary angioplasty or thrombolytic therapy, reperfusion injury occurs in as many as 31% of patients and is caused by inflammatory cells, free oxygen and nitrogen radicals, the rapid transcriptional activation of inflammatory cytokines, and the activation of PARP1. Inhibition of PARP attenuates neutrophil infiltration and inflammatory cytokine expression in the reperfused myocardium and preserves myocardial NAD+ and ATP. In addition, PARP inhibition increases the activation of myocyte survival enzymes protein kinase B (Akt) and protein kinase C epsilon (PKCε), and decreases the activity of myocardial ventricular remodeling enzymes PKCα/β, PKCζ/λ, and PKCδ. As a consequence, cardiomyocyte and vascular endothelial cell necrosis is decreased and myocardial contractility is preserved. In heart failure and circulatory shock in animal models, PARP inhibition significantly attenuates decreases in left ventricular systolic pressure, ventricular contractility and relaxation, stroke volume, and increases survival by limiting or preventing upregulation of adhesion molecules, proinflammatory cytokines, myocardial mononuclear cell infiltration, and PKCα/β and PKC λ/ζ. In this manner, PARP inhibition partially restores the myocardial concentrations of NAD+, limits ventricular remodeling and fibrosis, and prevents significant decreases in myocardial contractility. Based primarily on investigations in preclinical models of atherosclerosis, myocardial infarction, and heart failure, PARP inhibition appears to be beneficial in limiting or inhibiting cardiovascular dysfunction. These studies indicate that investigations of acute and chronic PARP inhibition are warranted in patients with atherosclerotic coronary artery disease.

Potential role of poly (ADP-ribose) polymerase in delayed cerebral vasospasm following subarachnoid hemorrhage in rats

Poly (ADP-ribose) polymerase (PARP) serves a key role in several neurological disorders, however, the specific role of PARP in delayed cerebral vasospasm (DCVS) following subarachnoid hemorrhage (SAH) remains unclear. The present study was conducted to clarify the possible mechanism of PARP in DCVS with the treatment of 3-aminobenzamide (3-AB), a PARP inhibitor. In the preliminary experiment, an internal carotid artery puncture SAH model, a cisterna magna double injection SAH model and prechiasmatic cistern single injection SAH model were compared with respect to mortality and neurobehavioral test results. The prechiasmatic cistern single injection SAH model was chosen to induce DCVS in the formal experiment. In the formal experiment, a total of 96 Sprague Dawley rats were randomly allocated into the sham group, the SAH group and the SAH+3-AB group and then each group was further subdivided into days 3, 5, 7 and 14 post-SAH subgroups (n=8 for each subgroup). The prechiasmatic cistern single injection SAH model was established to induce DCVS. Neurobehavioral testing and HE staining were conducted to evaluate the degree of cerebral vasospasm. PARP activity was assessed by ELISA and immunohistochemistry. An electrophoretic mobility shift assay was used to detect nuclear factor (NF)-κB DNA-binding activity. The expression of monocyte chemotactic protein 1 (MCP-1) and C-reactive protein (CRP) were measured by western blotting. Cerebral vasospasm occurred following SAH and became most severe on around day 7 post-SAH. NF-κB activity, PARP activity, the expression of MCP-1 and CRP exhibited a similar time course to cerebral vasospasm. Treatment with 3-AB alleviated the degree of cerebral vasospasm. NF-κB activity, PARP activity and the expression of MCP-1 and CRP were also suppressed by 3-AB treatment. In conclusion, PARP may serve an important role in regulating the inflammatory response and ultimately contribute to DCVS. Therefore 3-AB may be a potential therapeutic agent for DCVS.

c-Jun N-Terminal Kinases (JNKs) in Myocardial and Cerebral Ischemia/Reperfusion Injury

In this article, we review the literature regarding the role of c-Jun N-terminal kinases (JNKs) in cerebral and myocardial ischemia/reperfusion injury. Numerous studies demonstrate that JNK-mediated signaling pathways play an essential role in cerebral and myocardial ischemia/reperfusion injury. JNK-associated mechanisms are involved in preconditioning and post-conditioning of the heart and the brain. The literature and our own studies suggest that JNK inhibitors may exert cardioprotective and neuroprotective properties. The effects of modulating the JNK-depending pathways in the brain and the heart are reviewed. Cardioprotective and neuroprotective mechanisms of JNK inhibitors are discussed in detail including synthetic small molecule inhibitors (AS601245, SP600125, IQ-1S, and SR-3306), ion channel inhibitor GsMTx4, JNK-interacting proteins, inhibitors of mixed-lineage kinase (MLK) and MLK-interacting proteins, inhibitors of glutamate receptors, nitric oxide (NO) donors, and anesthetics. The role of JNKs in ischemia/reperfusion injury of the heart in diabetes mellitus is discussed in the context of comorbidities. According to reviewed literature, JNKs represent promising therapeutic targets for protection of the brain and the heart against ischemic stroke and myocardial infarction, respectively. However, different members of the JNK family exert diverse physiological properties which may not allow for systemic administration of non-specific JNK inhibitors for therapeutic purposes. Currently available candidate JNK inhibitors with high therapeutic potential are identified. The further search for selective JNK3 inhibitors remains an important task.

Ozone oxidative postconditioning inhibits oxidative stress and apoptosis in renal ischemia and reperfusion injury through inhibition of MAPK signaling pathway

Background

Ozone has been used as a curative agent for a variety of different diseases for over 150 years. In our previous study, we found that ozone oxidative preconditioning could alleviate renal damage induced by ischemia and reperfusion injury (I/R). Although this method had obvious protective effects in the reduction of I/R, its clinical application remains limited because this treatment must be commenced prior to the ischemic period, which is not practical in the clinic.

Purpose

In the present study, we investigated whether ozone oxidative postconditioning (OzoneOP) could attenuate renal I/R in vivo and in vitro, as well as the mechanisms underlying the effects of this treatment.

Methods

Sprague Dawley rats were subjected to right renal ischemia for 45 min and reperfusion for 24 h, or to sham operation with the left kidney removed, both with and without OzoneOP. In addition, normal rat kidney tubular epithelial cells (NRK-52E) were chosen to create a hypoxia–reoxygenation (H/R) model of 3 h hypoxia and 24 h reoxygenation processes, both with or without OzoneOP and mitogen-activated protein kinase (MAPK) inhibitors.

Results

Our results showed that OzoneOP significantly reversed apoptosis and the abnormal superoxide dismutase and malondialdehyde levels induced by I/R or H/R. OzoneOP also inhibited activation of the MAPK pathways both in vivo and in vitro, which resulted in significant protection against apoptosis and oxidative stress.

Conclusion

Our current data provide evidence that OzoneOP might serve as a potential therapy for renal I/R.

Poly(adenosine diphosphate-ribose) polymerase as therapeutic target: lessons learned from its inhibitors

Poly(ADP-ribose) polymerases are a family of DNA-dependent nuclear enzymes catalyzing the transfer of ADP-ribose moieties from cellular nicotinamide-adenine-dinucleotide to a variety of target proteins. Although they have been considered as resident nuclear elements of the DNA repair machinery, recent works revealed a more intricate physiologic role of poly(ADP-ribose) polymerases with numerous extranuclear activities. Indeed, poly(ADP-ribose) polymerases participate in fundamental cellular processes like chromatin remodelling, transcription or regulation of the cell-cycle. These new insight into the physiologic roles of poly(ADP-ribose) polymerases widens the range of human pathologies in which pharmacologic inhibition of these enzymes might have a therapeutic potential. Here, we overview our current knowledge on extranuclear functions of poly(ADP-ribose) polymerases with a particular focus on the mitochondrial ones and discuss potential fields of future clinical applications.

Indolylmaleimide Derivative IM-17 Shows Cardioprotective Effects in Ischemia-Reperfusion Injury

We previously developed IM-54 as a novel type of inhibitor of hydrogen-peroxide-induced necrotic cell death. Here, we examined its cell death inhibition profile. IM-54 was found to selectively inhibit oxidative stress-induced necrosis, but it did not inhibit apoptosis induced by various anticancer drugs or Fas ligand, or necroptosis. IM-17, an IM derivative having improved water-solubility and metabolic stability, was developed and confirmed to retain necrosis-inhibitory activity. IM-17 showed cardioprotective effects in an isolated rat heart model and an in vivo arrhythmia model, suggesting that IM derivatives may have therapeutic potential.

Melatonin protects diabetic heart against ischemia-reperfusion injury, role of membrane receptor-dependent cGMP-PKG activation

It has been demonstrated that the anti-oxidative and cardioprotective effects of melatonin are, at least in part, mediated by its membrane receptors. However, the direct downstream signaling remains unknown. We previously found that melatonin ameliorated myocardial ischemia-reperfusion (MI/R) injury in diabetic animals, although the underlying mechanisms are also incompletely understood. This study was designed to determine the role of melatonin membrane receptors in melatonin's cardioprotective actions against diabetic MI/R injury with a focus on cGMP and its downstream effector PKG. Streptozotocin-induced diabetic Sprague-Dawley rats and high-glucose medium-incubated H9c2 cardiomyoblasts were utilized to determine the effects of melatonin against MI/R injury. Melatonin treatment preserved cardiac function and reduced oxidative damage and apoptosis. Additionally, melatonin increased intracellular cGMP level, PKGIα expression, p-VASP/VASP ratio and further modulated myocardial Nrf-2-HO-1 and MAPK signaling. However, these effects were blunted by KT5823 (a selective inhibitor of PKG) or PKGIα siRNA except that intracellular cGMP level did not changed significantly. Additionally, our in vitro study showed that luzindole (a nonselective melatonin membrane receptor antagonist) or 4P-PDOT (a selective MT₂ receptor antagonist) not only blocked the cytoprotective effect of melatonin, but also attenuated the stimulatory effect of melatonin on cGMP-PKGIα signaling and its modulatory effect on Nrf-2-HO-1 and MAPK signaling. This study showed that melatonin ameliorated diabetic MI/R injury by modulating Nrf-2-HO-1 and MAPK signaling, thus reducing myocardial apoptosis and oxidative stress and preserving cardiac function. Importantly, melatonin membrane receptors (especially MT₂ receptor)-dependent cGMP-PKGIα signaling played a critical role in this process.

Olaparib protects cardiomyocytes against oxidative stress and improves graft contractility during the early phase after heart transplantation in rats

BACKGROUND AND PURPOSE

Olaparib, rucaparib and niraparib, potent inhibitors of poly(ADP-ribose) polymerase (PARP) are approved as anti-cancer drugs in humans. Considering the previously demonstrated role of PARP in various forms of acute and chronic myocardial injury, we tested the effects of olaparib in in-vitro models of oxidative stress in cardiomyocytes, and in an in vivo model of cardiac transplantation.

EXPERIMENTAL APPROACH

H9c2-embryonic rat heart-derived myoblasts pretreated with vehicle or olaparib (10μM) were challenged with either hydrogen peroxide (H₂ O₂ ) or with glucose oxidase (GOx, which generates H₂ O₂ in the tissue culture medium). Cell viability assays (MTT, lactate dehydrogenase) and Western blotting for PARP and its product, PAR was performed. Heterotopic heart transplantation was performed in Lewis rats; recipients were treated either with vehicle or olaparib (10 mg kg^-1 ). Left ventricular function of transplanted hearts was monitored via a Millar catheter. Multiple gene expression in the graft was measured by qPCR.

KEY RESULTS

Olaparib blocked autoPARylation of PARP1 and attenuated the rapid onset of death in H9c2 cells, induced by H₂ O₂ , but did not affect cell death following chronic, prolonged oxidative stress induced by GOx. In rats, after transplantation, left ventricular systolic and diastolic function were improved by olaparib. In the transplanted hearts, olaparib also reduced gene expression for c-jun, caspase-12, catalase, and NADPH oxidase-2.

CONCLUSIONS AND IMPLICATIONS

Olaparib protected cardiomyocytes against oxidative stress and improved graft contractility in a rat model of heart transplantation. These findings raise the possibility of repurposing this clinically approved oncology drug, to be used in heart transplantation.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Can crosstalk between DOR and PARP reduce oxidative stress mediated neurodegeneration?

The progressive loss of structure and function of neurons leads to neurodegenerative processes which become the causative reason for various neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD) etc. These diseases are multifactorial in nature but they have been seen to possess similar causative agents to a certain extent. Oxidative Stress (OS) has been identified as a major stressor and a mediator in most of these diseases. OS not only leads to the generation of free radical species but if persistent, can possibly lead to lipid peroxidation, protein damage, DNA damage, and cell death. Anti-oxidants are endogenously present in our body to tackle oxygen metabolites but their levels reduce greatly under continuous OS conditions. In such a case, dietary supplements to replenish the anti-oxidant levels in our body is a good way of treatment but it is very slow and may not be as effective in chronic stress conditions. Thus, there is a need for more effective mechanisms to attenuate OS. Two such mechanisms which can be considered are the activation of Delta opioid receptor (DOR) and Inhibition of Poly (ADP-ribose)-polymerase1 (PARP1), which have been suggested to protect neurons and increase neuronal cell survivability in both in-vitro and in-vivo disease models. Various signaling pathways have been highlighted to probably play a significant role in attenuating OS by the activation of DOR. It would be an interesting topic of investigation to see if one of the probable mechanisms by which DOR attenuates OS could be by modulation of PARP through a cascade of intracellular signaling reactions.

Rho-kinase signaling pathway promotes the expression of PARP to accelerate cardiomyocyte apoptosis in ischemia/reperfusion

It has been previously reported that Rho-kinase (ROCK) and poly ADP-ribose polymerase (PARP) serve critical roles in myocardial ischemia/reperfusion (I/R) injury. Studies have additionally demonstrated that the activation of ROCK and the expression of PARP are increased in I/R. However, the effect and mechanism of the two proteins remains to be fully elucidated in I/R. In addition, whether they can be influenced by each other is unclear. In the present study, it was demonstrated that ischemia followed by reperfusion resulted in a significant increase in ROCK and PARP. In addition, Y-27632 (ROCK inhibitor) and 3-aminobenzamide (3-AB; PARP inhibitor) pretreatment rescued myocardial infarction size and cardiomyocyte apoptosis. The inhibitory role of Y-27632 was observed to be superior to that of the 3-AB group. In addition, Y-27632 and 3-AB diminished extracellular signal-related kinase (ERK) phosphorylation and the production of tumor necrosis factor α and interleukin 6. Overall, the results of the present study suggested that the inhibition of ROCK leads to reduced myocardial infarction size and cardiomyocyte apoptosis via the PARP/ERK signaling pathway.

Delta Opioid Receptor and Peptide: A Dynamic Therapy for Stroke and Other Neurological Disorders

Research of the opioid system and its composite receptors and ligands has revealed its promise as a potential therapy for neurodegenerative diseases such as stroke and Parkinson's Disease. In particular, delta opioid receptors (DORs) have been elucidated as a therapeutically distinguished subset of opioid receptors and a compelling target for novel intervention techniques. Research is progressively shedding light on the underlying mechanism of DORs and has revealed two mechanisms of DOR neuroprotection; DORs function to maintain ionic homeostasis and also to trigger endogenous neuroprotective pathways. Delta opioid agonists such as (D-Ala2, D-Leu5) enkephalin (DADLE) have been shown to promote neuronal survival and decrease apoptosis, resulting in a substantial amount of research for its application as a neurological therapeutic. Most notably, DADLE has demonstrated significant potential to reduce cell death following ischemic events. Current research is working to reveal the complex mechanisms of DADLE's neuroprotective properties. Ultimately, our knowledge of the DOR receptors and agonists has made the opioid system a promising target for therapeutic intervention in many neurological disorders.

Deficiency of Parkinson's disease-related gene Fbxo7 is associated with impaired mitochondrial metabolism by PARP activation

The Parkinson's disease (PD)-related protein F-box only protein 7 (Fbxo7) is the substrate-recognition component of the Skp1-Cullin-F-box protein E3 ubiquitin ligase complex. We have recently shown that PD-associated mutations in Fbxo7 disrupt mitochondrial autophagy (mitophagy), suggesting a role for Fbxo7 in modulating mitochondrial homeostasis. Here we report that Fbxo7 deficiency is associated with reduced cellular NAD⁺ levels, which results in increased mitochondrial NADH redox index and impaired activity of complex I in the electron transport chain. Under these conditions of compromised respiration, mitochondrial membrane potential and ATP contents are reduced, and cytosolic reactive oxygen species (ROS) production is increased. ROS activates poly (ADP-ribose) polymerase (PARP) activity in Fbxo7-deficient cells. PARP inhibitor restores cellular NAD⁺ content and redox index and ATP pool, suggesting that PARP overactivation is cause of decreased complex I-driven respiration. These findings bring new insight into the mechanism of Fbxo7 deficiency, emphasising the importance of mitochondrial dysfunction in PD.

miR-7a/b attenuates post-myocardial infarction remodeling and protects H9c2 cardiomyoblast against hypoxia-induced apoptosis involving Sp1 and PARP-1

miRs (microRNAs, miRNAs) intricately regulate physiological and pathological processes. Although miR-7a/b protects against cardiomyocyte injury in ischemia/reperfusion injury, the function of miR-7a/b in myocardial infarction (MI)-induced cardiac remodeling remains unclear. Here, we sought to investigate the function of miR-7a/b in post-MI remodeling in a mouse model and to determine the underlying mechanisms involved. miR-7a/b overexpression improved cardiac function, attenuated cardiac remodeling and reduced fibrosis and apoptosis, whereas miR-7a/b silencing caused the opposite effects. Furthermore, miR-7a/b overexpression suppressed specific protein 1 (Sp1) and poly (ADP-ribose) polymerase (PARP-1) expression both in vivo and in vitro, and a luciferase reporter activity assay showed that miR-7a/b could directly bind to Sp1. Mithramycin, an inhibitor of the DNA binding activity of Sp1, effectively repressed PARP-1 and caspase-3, whereas knocking down miR-7a/b partially counteracted these beneficial effects. Additionally, an immunoprecipitation assay indicated that hypoxia triggered activation of the binding activity of Sp1 to the promoters of PARP-1 and caspase-3, which is abrogated by miR-7a/b. In summary, these findings identified miR-7a/b as protectors of cardiac remodeling and hypoxia-induced injury in H9c2 cardiomyoblasts involving Sp1 and PARP-1.

Complex role of nicotinamide adenine dinucleotide in the regulation of programmed cell death pathways

Over the past few years, a growing body of experimental observations has led to the identification of novel and alternative programs of regulated cell death. Recently, autophagic cell death and controlled forms of necrosis have emerged as major alternatives to apoptosis, the best characterized form of regulated cell demise. These recently identified, caspase-independent, forms of cell death appear to play a role in the response to several forms of stress, and their importance in different pathological conditions such as ischemia, infection and inflammation has been recognized. The functional link between cell metabolism and survival has also been the matter of recent studies. Nicotinamide adenine dinucleotide (NAD(+)) has gained particular interest due to its role in cell energetics, and as a substrate for several families of enzymes, comprising poly ADP-ribose polymerases (PARPs) and sirtuins, involved in numerous biological functions including cell survival and death. The recently uncovered diversity of cell death programs has led us to reevaluate the role of this important metabolite as a universal pro-survival factor, and to discuss the potential benefits and limitations of pharmacological approaches targeting NAD(+) metabolism.

Protection of rat intestinal epithelial cells from ischemia/reperfusion injury by (D-Ala2, D-Leu5)-enkephalin through inhibition of the MKK7-JNK signaling pathway

Previous studies have demonstrated that (D‑Ala2, D‑Leu5)‑enkephalin (DADLE) protects rats from hepatic ischemia/reperfusion (I/R) injury. In the present study, DADLE was also observed to alleviate IR‑induced intestinal epithelial cell injury in rats by inhibiting mitogen‑activated protein kinase kinase 7 (MKK7)‑c‑Jun N‑terminal kinase (JNK) pathway signaling. To investigate the protective effect of DADLE on hypoxia/reoxygenation injury in rat intestinal epithelial cells, rat intestinal epithelial cells were treated with different concentrations of DADLE, following which the cell survival rate was determined using a tetrazolium (MTT) colorimetric assay, and apoptosis was determined using flow cytometry. To confirm whether the protective effect of DADLE was due to its effect on MKK7‑JNK signaling, the phosphorylation levels of MKK7 and JNK were analyzed using western blot analysis following treatment with different concentrations of DADLE. The results demonstrated that, following treatment with DADLE, the survival rate of the rat intestinal cells subjected to I/R‑induced injury increased significantly and the apoptotic rate decreased in a concentration‑dependent manner. In addition, the levels of phosphorylated MKK7 and JNK decreased in a concentration‑dependent manner following treatment with DADLE. Silencing the gene expression of MKK7 using small interfering RNA prior to DADLE treatment resulted in a reduction in the protective effects of DADLE on the rat intestinal epithelial cells subjected to I/R injury. Collectively, the results of the present study demonstrated that the protective effects of DADLE in I/R injury in rat intestinal cells occurred through inhibition of the MKK7‑JNK pathway.

Identification through high-throughput screening of 4'-methoxyflavone and 3',4'-dimethoxyflavone as novel neuroprotective inhibitors of parthanatos

BACKGROUND AND PURPOSE

The current lack of disease-modifying therapeutics to manage neurological and neurodegenerative conditions justifies the development of more efficacious agents. One distinct pathway leading to neuronal death in these conditions and which represents a very promising and attractive therapeutic target is parthanatos, involving overactivation of PARP-1. We therefore sought to identify small molecules that could be neuroprotective by targeting the pathway.

EXPERIMENTAL APPROACH

Using HeLa cells, we developed and optimized an assay for high-throughput screening of about 5120 small molecules. Structure-activity relationship (SAR) study was carried out in HeLa and SH-SY5Y cells for molecules related to the initial active compound. The neuroprotective ability of each active compound was tested in cortical neuronal cultures.

KEY RESULTS

4'-Methoxyflavone (4MF) showed activity by preventing the decrease in cell viability of HeLa and SH-SY5Y cells caused by the DNA-alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), which induces parthanatos. A similar compound from the SAR study, 3',4'-dimethoxyflavone (DMF), also showed significant activity. Both compounds reduced the synthesis and accumulation of poly (ADP-ribose) polymer and protected cortical neurones against cell death induced by NMDA.

CONCLUSIONS AND IMPLICATIONS

Our data reveal additional neuroprotective members of the flavone class of flavonoids and show that methoxylation of the parent flavone structure at position 4' confers parthanatos-inhibiting activity while additional methoxylation at position 3', reported by others to improve metabolic stability, does not destroy the activity. These molecules may therefore serve as leads for the development of novel neurotherapeutics for the management of neurological and neurodegenerative conditions.

Crosstalk between mitogen-activated protein kinases and mitochondria in cardiac diseases: therapeutic perspectives

Cardiovascular diseases cause more mortality and morbidity worldwide than any other diseases. Although many intracellular signaling pathways influence cardiac physiology and pathology, the mitogen-activated protein kinase (MAPK) family has garnered significant attention because of its vast implications in signaling and crosstalk with other signaling networks. The extensively studied MAPKs ERK1/2, p38, JNK, and ERK5, demonstrate unique intracellular signaling mechanisms, responding to a myriad of mitogens and stressors and influencing the signaling of cardiac development, metabolism, performance, and pathogenesis. Definitive relationships between MAPK signaling and cardiac dysfunction remain elusive, despite 30 years of extensive clinical studies and basic research of various animal/cell models, severities of stress, and types of stimuli. Still, several studies have proven the importance of MAPK crosstalk with mitochondria, powerhouses of the cell that provide over 80% of ATP for normal cardiomyocyte function and play a crucial role in cell death. Although many questions remain unanswered, there exists enough evidence to consider the possibility of targeting MAPK-mitochondria interactions in the prevention and treatment of heart disease. The goal of this review is to integrate previous studies into a discussion of MAPKs and MAPK-mitochondria signaling in cardiac diseases, such as myocardial infarction (ischemia), hypertrophy and heart failure. A comprehensive understanding of relevant molecular mechanisms, as well as challenges for studies in this area, will facilitate the development of new pharmacological agents and genetic manipulations for therapy of cardiovascular diseases.

Ceramide in the molecular mechanisms of neuronal cell death. The role of sphingosine-1-phosphate

Ceramide and sphingosine-1-phosphate (S1P), two important bioactive sphingolipids, have been suggested as being key players in the pathology of Alzheimer’s disease in inflammation and cancer. However, their role in the molecular mechanisms of neuronal death has not been fully elucidated. Our study indicated that ceramide significantly enhanced the level of free radicals and decreased the viability of the human neuroblastoma cell line (SH-SY5Y) through inhibition of the prosurvival PI3-K/Akt pathway. Ceramide also decreased anti-apoptotic (Bcl-2) and increased pro-apoptotic (Bax, Hrk) mRNA/protein levels. Concomitantly, our study indicated that ceramide induced poly(ADP-ribose) polymerase-1 (PARP-1) activation and accumulation of poly(ADP-ribose) PAR, a signalling molecule involved in mitochondria-nucleus cross-talk and mitochondria integrity. Ceramide treatment significantly decreased the level of apoptosis-inducing factor (AIF) in the mitochondria. The PARP-1 inhibitor (PJ-34) prevented AIF release from the mitochondria. In addition, our data showed that exogenously added S1P increased the viability of SH-SY5Y through the S1P (1,3) receptor-dependent mechanism. It was also revealed that the S1P and PARP-1 inhibitor (PJ-34) decreased oxidative stress, gene expression of the pro-apoptotic Hrk protein and up-regulated the anti-apoptotic Bcl-2 protein. Our data demonstrate that neuronal cell death evoked by ceramide is regulated by PARP/PAR/AIF and by S1P receptor signalling. In summary, our results suggest that PARP-1 inhibitor(s) and modulators of sphingosine-1-phosphate receptor(s) should be considered in potential therapeutic strategies directed at neurodegenerative diseases.

Therapeutic applications of PARP inhibitors: anticancer therapy and beyond

The aim of this article is to describe the current and potential clinical translation of pharmacological inhibitors of poly(ADP-ribose) polymerase (PARP) for the therapy of various diseases. The first section of the present review summarizes the available preclinical and clinical data with PARP inhibitors in various forms of cancer. In this context, the role of PARP in single-strand DNA break repair is relevant, leading to replication-associated lesions that cannot be repaired if homologous recombination repair (HRR) is defective, and the synthetic lethality of PARP inhibitors in HRR-defective cancer. HRR defects are classically associated with BRCA1 and 2 mutations associated with familial breast and ovarian cancer, but there may be many other causes of HRR defects. Thus, PARP inhibitors may be the drugs of choice for BRCA mutant breast and ovarian cancers, and extend beyond these tumors if appropriate biomarkers can be developed to identify HRR defects. Multiple lines of preclinical data demonstrate that PARP inhibition increases cytotoxicity and tumor growth delay in combination with temozolomide, topoisomerase inhibitors and ionizing radiation. Both single agent and combination clinical trials are underway. The final part of the first section of the present review summarizes the current status of the various PARP inhibitors that are in various stages of clinical development. The second section of the present review summarizes the role of PARP in selected non-oncologic indications. In a number of severe, acute diseases (such as stroke, neurotrauma, circulatory shock and acute myocardial infarction) the clinical translatability of PARP inhibition is supported by multiple lines of preclinical data, as well as observational data demonstrating PARP activation in human tissue samples. In these disease indications, PARP overactivation due to oxidative and nitrative stress drives cell necrosis and pro-inflammatory gene expression, which contributes to disease pathology. Accordingly, multiple lines of preclinical data indicate the efficacy of PARP inhibitors to preserve viable tissue and to down-regulate inflammatory responses. As the clinical trials with PARP inhibitors in various forms of cancer progress, it is hoped that a second line of clinical investigations, aimed at testing of PARP inhibitors for various non-oncologic indications, will be initiated, as well.

Mechanisms of load dependency of myocardial ischemia reperfusion injury

Coronary artery disease and associated ischemic heart disease are prevalent disorders worldwide. Further, systemic hypertension is common and markedly increases the risk for heart disease. A common denominator of systemic hypertension of various etiologies is increased myocardial load/mechanical stress. Thus, it is likely that high pressure/mechanical stress attenuates the contribution of cardioprotective but accentuates the contribution of cardiotoxic pathways thereby exacerbating the outcome of an ischemia reperfusion insult to the heart. Critical events which contribute to cardiomyocyte injury in the ischemic-reperfused heart include cellular calcium overload and generation of reactive oxygen/nitrogen species which, in turn, promote the opening of the mitochondrial permeability transition pore, an important event in cell death. Increasing evidence also indicates that the myocardium is capable of mounting a robust inflammatory response which contributes importantly to tissue injury. On the other hand, cardioprotective maneuvers of ischemic preconditioning and postconditioning have led to identification of complex web of signaling pathways (e.g., reperfusion injury salvage kinase) which ultimately converge on the mitochondria to exert cytoprotection. The present review is intended to briefly describe mechanisms of cardiac ischemia reperfusion injury followed by a discussion of our work focused on how pressure/mechanical stress modulates endogenous cardiotoxic and cardioprotective mechanisms to ultimately exacerbate ischemia reperfusion injury.

Poly(ADP-ribose) polymerase 1 (PARP1) in atherosclerosis: from molecular mechanisms to therapeutic implications

Poly(ADP-ribosyl)ation reactions, carried out by poly(ADP-ribose) polymerases (PARPs/ARTDs), are reversible posttranslational modifications impacting on numerous cellular processes (e.g., DNA repair, transcription, metabolism, or immune functions). PARP1 (EC 2.4.2.30), the founding member of PARPs, is particularly important for drug development for its role in DNA repair, cell death, and transcription of proinflammatory genes. Recent studies have established a novel concept that PARP1 is critically involved in the formation and destabilization of atherosclerotic plaques in experimental animal models and in humans. Reduction of PARP1 activity by pharmacological or molecular approaches attenuates atherosclerotic plaque development and enhances plaque stability as well as promotes the regression of pre-established atherosclerotic plaques. Mechanistically, PARP1 inhibition significantly reduces monocyte differentiation, macrophage recruitment, Sirtuin 1 (SIRT1) inactivation, endothelial dysfunction, neointima formation, foam cell death, and inflammatory responses within plaques, all of which are central to the pathogenesis of atherosclerosis. This article presents an overview of the multiple roles and underlying mechanisms of PARP1 activation (poly(ADP-ribose) accumulation) in atherosclerosis and emphasizes the therapeutic potential of PARP1 inhibition in preventing or reversing atherosclerosis and its cardiovascular clinical sequalae.

Cellular NAD depletion and decline of SIRT1 activity play critical roles in PARP-1-mediated acute epileptic neuronal death in vitro

Intense poly(ADP-ribose) polymerase-1 (PARP-1) activation was implicated as a major cause of caspase-independent cell death in the hippocampal neuronal culture (HNC) model of acute acquired epilepsy (AE). The molecular mechanisms are quite complicated. The linkage among neuronal death, cellular nicotinamide adenine dinucleotide (NAD) levels, apoptosis-inducing factor (AIF) translocation, SIRT1 expression and activity were investigated here. The results showed that PARP-1 over-activation caused by Mg²⁺-free stimuli led to cellular NAD depletion which could block AIF translocation from mitochondria to nucleus and attenuate neuronal death. Also, SIRT1 deacetylase activity was reduced by Mg²⁺-free treatment, accompanied by elevated ratio of neuronal death, which could be rescued by NAD repletion. These data demonstrated that cellular NAD depletion and decline of SIRT1 activity play critical roles in PARP-1-mediated epileptic neuronal death in the HNC model of acute AE.

ROS-mediated PARP activity undermines mitochondrial function after permeability transition pore opening during myocardial ischemia-reperfusion

Background

Ischemia–reperfusion (I/R) studies have implicated oxidant stress, the mitochondrial permeability transition pore (mPTP), and poly(ADP‐ribose) polymerase (PARP) as contributing factors in myocardial cell death. However, the interdependence of these factors in the intact, blood‐perfused heart is not known. We therefore wanted to determine whether oxidant stress, mPTP opening, and PARP activity contribute to the same death pathway after myocardial I/R.

Methods and Results

A murine left anterior descending coronary artery (LAD) occlusion (30 minutes) and release (1 to 4 hours) model was employed. Experimental groups included controls and antioxidant‐treated, mPTP‐inhibited, or PARP‐inhibited hearts. Antioxidant treatment prevented oxidative damage, mPTP opening, ATP depletion, and PARP activity, placing oxidant stress as the proximal death trigger. Genetic deletion of cyclophilin D (CypD^−/−) prevented loss of total NAD⁺ and PARP activity, and mPTP‐mediated loss of mitochondrial function. Control hearts showed progressive mitochondrial depolarization and loss of ATP from 1.5 to 4 hours of reperfusion, but not outer mitochondrial membrane rupture. Neither genetic deletion of PARP‐1 nor its pharmacological inhibition prevented the initial mPTP‐mediated depolarization or loss of ATP, but PARP ablation did allow mitochondrial recovery by 4 hours of reperfusion.

Conclusions

These results indicate that oxidant stress, the mPTP, and PARP activity contribute to a single death pathway after I/R in the heart. PARP activation undermines cell survival by preventing mitochondrial recovery after mPTP opening early in reperfusion. This suggests that PARP‐mediated prolongation of mitochondrial depolarization contributes significantly to cell death via an energetic crisis rather than by mitochondrial outer membrane rupture.

Pretreatment of therapeutic cells with poly(ADP-ribose) polymerase inhibitor enhances their efficacy in an in vitro model of cell-based therapy in myocardial infarct

The potential of cell-based therapies in diseases involving ischemia-reperfusion is greatly hampered by the excessive loss of administered cells in the harsh and oxidative environment where these cells are supposed to act. Therefore, we investigated if inhibition of poly(ADP-ribose) polymerase (PARP) in the therapeutically added cells would lead to their increased viability and, subsequently, to an enhanced effect in an in vitro simulated ischemia-reperfusion (I-R) setting. Ischemic conditions were simulated by oxygen and glucose deprivation for 160 min using H9c2 rat cardiomyoblast cells. After 30 min of reperfusion, these cells received 4 types of treatments: no added cells (I-R model), fluorescently labeled (Vybrant DiD) therapeutic H9c2 cells with vehicle (H9c2) or PARP inhibitor (10 μM or 100 μM PJ34) pretreatment. We assessed viability (live, apoptotic and necrotic) of both ‘postischemic’ and therapeutic cells with flow cytometric analysis using calcein-AM/ethidium homodimer-2 fluorescent staining after 24 h of co-culture. Further measurements on necrosis and metabolic activity were performed using lactate dehydrogenase (LDH) release and resazurin based assays. The percentage of surviving therapeutic cells increased significantly with PARP inhibition (untreated, 52.02±5.01%; 10 μM PJ34, 63.38±4.50%; 100 μM PJ34, 64.99±3.47%). The percentage of necrotic cells decreased in a similar manner (untreated, 37.23±4.40%; 10 μM PJ34, 26.83±3.49%; 100 μM PJ34, 24.96±2.43%). Notably, the survival of the cells that suffered I-R injury was also significantly higher when treated with PARP-inhibited therapeutic cells (I-R model, 36.44±5.05%; H9c2, 42.81±5.11%; 10 μM PJ34, 52.07±5.80%; 100 μM PJ34, 54.95±5.55%), while necrosis was inhibited (I-R model, 43.64±4.00%; H9c2, 37.29±4.55%; 10 μM PJ34, 30.18±4.60%; 100 μM PJ34, 25.52±3.47%). In subsequent experiments, PARP inhibition decreased LDH-release of the observed combined cell population and enhanced the metabolic activity. Thus, our results suggest that pretreating the therapeutically added cells with a PARP inhibitor could be beneficial in the setting of cell-based therapies.

A dual role for poly(ADP-ribose) polymerase-1 during caspase-dependent apoptosis

2,3,5-Tris(glutathion-S-yl)hydroquinone (TGHQ), a metabolite of benzene, catalyzes the generation of reactive oxygen species (ROS) and caspase-dependent apoptosis in human promyelocytic leukemia (HL-60) cells. We now report that TGHQ induces severe DNA damage, as evidenced by DNA ladder formation and H2AX phosphorylation. The subsequent activation of the DNA nick sensor enzyme, poly(ADP-ribose) polymerase-1 (PARP-1), leads to the rapid depletion of ATP and NAD and the concomitant formation of poly(ADP-ribosylated) proteins (PARs). PJ-34 (a PARP-1 inhibitor) completely prevented the formation of PARs, partially attenuated TGHQ-mediated ATP depletion, but had little effect on NAD depletion. Intriguingly, although z-vad-fmk (a pan-caspase inhibitor) attenuated TGHQ-induced apoptosis, cotreatment with PJ-34 led to a further decrease in apoptosis, suggesting that PARP-1 participates in caspase-dependent apoptosis. Indeed, PARP-1 inhibition reduced TGHQ-induced caspase-3, -7, and -9 activation, at least partially by attenuating cytochrome c translocation from mitochondria to the cytoplasm. In contrast, PJ-34 potentiated TGHQ-induced caspase-8 activation, suggesting that PARP-1 plays a dual role in regulating TGHQ-induced apoptosis via opposing effects on the intrinsic (mitochondrial) and extrinsic (death-receptor) pathways. PARP-1 knockdown in HL-60 cells confirmed that PARP-1 participates in effector caspase activation. Finally, PJ-34 also inhibited TGHQ-induced apoptosis-inducing factor (AIF) nuclear translocation, but neither c-jun NH(2)-terminal kinase nor p38 MAPK (p38 mitogen-activated protein kinase) activation was required for AIF translocation. In summary, TGHQ-induced apoptosis of HL-60 cells is accompanied by PARP-1, caspase activation, and AIF nuclear translocation. TGHQ-induced apoptosis appears to primarily occur via engagement of the mitochondrial-mediated pathway in a process amenable to PARP inhibition. Residual cell death in the presence of PJ-34 is likely mediated via the extrinsic apoptotic pathway.

SP600125 inhibits Orthopoxviruses replication in a JNK1/2 -independent manner: Implication as a potential antipoxviral

The pharmacological inhibitor SP600125 [anthra(1,9-cd)pyrazol-6(2H)-one 1,9-pyrazoloanthrone] has been largely employed as a c-JUN N-terminal kinase (JNK1/2) inhibitor. In this study, we evaluated whether pretreatment with SP600125 was able to prevent Orthopoxviruses Vaccinia virus (VACV), Cowpox virus (CPXV) and modified Vaccinia virus Ankara (MVA) replication. We found that incubation with SP600125 not only blocked virus-stimulated JNK phosphorylation, but also, significantly reduced virus production. We observed 1-3 log decline in viral yield depending on the cell line infected (A31, BSC-40 or BHK-21). The reduction in viral yield correlated with a dramatic impact on virus morphogenesis progress, intracellular mature viruses (IMV) were barely detected. Despite the fact that SP600125 can act as an efficient anti-orthopoxviral compound, we also provide evidence that this antiviral effect is not specifically exerted through JNK1/2 inhibition. This conclusion is supported by the fact that viral titers measured after infections of JNK1/2 knockout cells were not altered as compared to those of wild-type cells. In contrast, a decline in viral titers was verified when the infection of KO cells was carried out in the presence of the pharmacological inhibitor. SP600125 has been the focus of recent studies that have evaluated its action on diverse viral infections including DNA viruses. Our data support the notion that SP600125 can be regarded as a potential antipoxviral compound.

Molecular and cellular pathways associated with chromosome 1p deletions during colon carcinogenesis

Chromosomal instability is a major pathway of sporadic colon carcinogenesis. Chromosome arm 1p appears to be one of the "hot spots" in the non-neoplastic mucosa that, when deleted, is associated with the initiation of carcinogenesis. Chromosome arm 1p contains genes associated with DNA repair, spindle checkpoint function, apoptosis, multiple microRNAs, the Wnt signaling pathway, tumor suppression, antioxidant activities, and defense against environmental toxins. Loss of 1p is dangerous since it would likely contribute to genomic instability leading to tumorigenesis. The 1p deletion-associated colon carcinogenesis pathways are reviewed at the molecular and cellular levels. Sporadic colon cancer is strongly linked to a high-fat/low-vegetable/low-micronutrient, Western-style diet. We also consider how selected dietary-related compounds (eg, excess hydrophobic bile acids, and low levels of folic acid, niacin, plant-derived antioxidants, and other modulatory compounds) might affect processes leading to chromosomal deletions, and to the molecular and cellular pathways specifically altered by chromosome 1p loss.

Mitogen-activated protein kinase signaling in the heart: angels versus demons in a heart-breaking tale

Among the myriad of intracellular signaling networks that govern the cardiac development and pathogenesis, mitogen-activated protein kinases (MAPKs) are prominent players that have been the focus of extensive investigations in the past decades. The four best characterized MAPK subfamilies, ERK1/2, JNK, p38, and ERK5, are the targets of pharmacological and genetic manipulations to uncover their roles in cardiac development, function, and diseases. However, information reported in the literature from these efforts has not yet resulted in a clear view about the roles of specific MAPK pathways in heart. Rather, controversies from contradictive results have led to a perception that MAPKs are ambiguous characters in heart with both protective and detrimental effects. The primary object of this review is to provide a comprehensive overview of the current progress, in an effort to highlight the areas where consensus is established verses the ones where controversy remains. MAPKs in cardiac development, cardiac hypertrophy, ischemia/reperfusion injury, and pathological remodeling are the main focuses of this review as these represent the most critical issues for evaluating MAPKs as viable targets of therapeutic development. The studies presented in this review will help to reveal the major challenges in the field and the limitations of current approaches and point to a critical need in future studies to gain better understanding of the fundamental mechanisms of MAPK function and regulation in the heart.

Therapeutic injection of PARP inhibitor INO-1001 preserves cardiac function in porcine myocardial ischemia and reperfusion without reducing infarct size

Pharmacological protection from myocardial reperfusion injury, despite plenty of approaches, has still not been realized in humans. We studied the putative infarct size (IS)-sparing capacity of poly(ADP-ribose)polymerase inhibitor, INO-1001, and focused on cardiac functional recovery during reperfusion. Male farm-bred Landrace pigs were subjected to 1-h left anterior descending coronary artery occlusion followed by 3 h of reperfusion (control). Infarct size was determined by triphenyltetrazolium chloride/Evans blue staining. Plasma markers of myocardial injury (troponin T, creatine kinase, lactate dehydrogenase) were determined upon protocol completion. Cardiac function was continuously assessed via pulmonary and femoral artery catheters. INO-1001 (1 mg/kg) was administered upon reperfusion in the treatment group. As a positive control, untreated pigs were subjected to ischemic preconditioning (10-min left anterior descending coronary artery occlusion followed by 15-min reperfusion before the intervention). Ischemic preconditioning reduced myocardial damage reflected by a smaller IS and lower plasma markers of myocardial injury. INO-1001 did not reduce IS but significantly improved functional recovery (increased stroke volume, cardiac index, and mixed venous oxygen saturation) during reperfusion compared with vehicle-treated control and ischemic preconditioning. Although we could not confirm the IS-sparing capacities of poly(ADP-ribose)polymerase inhibitor, INO-1001, the drug holds the potential of hemodynamic improvement during reperfusion.

Emerging anticancer therapeutic targets and the cardiovascular system: is there cause for concern?

The race for a cure to cancer continues, fueled by unprecedented discoveries of fundamental biology underlying carcinogenesis and tumorigenesis. The expansion of the target list and tools to approach them is moving the oncology community extraordinarily rapidly to clinical trials, bringing new hope for cancer patients. This effort is also propelling biological discoveries in cardiovascular research, because many of the targets being explored in cancer play fundamental roles in the heart and vasculature. The combined efforts of cardiovascular and cancer biologists, along with clinical investigators in these fields, will be needed to understand how to safely exploit these efforts. Here, we discuss a few of the many research foci in oncology where we believe such collaboration will be particularly important.

ERK-MAPK signaling opposes rho-kinase to reduce cardiomyocyte apoptosis in heart ischemic preconditioning

We and others have reported that Rho-kinase plays an important role in the pathogenesis of heart ischemia/reperfusion (I/R) injury. Studies have also demonstrated that the activation of Rho-kinase is reversed in ischemic preconditioning (IPC). However, the mechanisms by which Rho-kinase is increased in I/R and reversed in IPC are not thoroughly understood. In female Wistar rats, we created I/R by ligating the left anterior-descending branch of the coronary artery (LAD) for 30 min and releasing the ligature for 180 min. IPC rats underwent IPC (two cycles of 5-min ligation of the LAD and 5-min reflow) before I/R. IPC caused a significant increase in extracellular signal-regulated kinase (ERK)1/2 activity and reduced Rho-kinase activity and cardiomyocyte apoptosis (P<0.05 versus I/R). Administration of PD98059, an inhibitor of ERK-mitogen-activated protein kinase (MAPK), increased cardiomyocyte apoptosis, Caspase-3 activity and myocardial infarction size (P<0.05 versus IPC). Western-blot analysis showed that administration of PD98059 increased Rho-kinase activity. Treatment with fasudil, an inhibitor of Rho-kinase, reversed cell apoptosis caused by treatment with PD98059 in IPC. In addition, ROCK1 (Rho-kinase 1) may be the major Rho-kinase isoform that is opposed by ERK-MAPK signaling in IPC. These results indicate that ERK-MAPK signaling is required in IPC to oppose Rho-kinase activity in cardiomyocyte apoptosis in vivo.

BGP-15 inhibits caspase-independent programmed cell death in acetaminophen-induced liver injury

It has been recently shown that acute acetaminophen toxicity results in endoplasmic reticulum redox stress and an increase in cells with apoptotic phenotype in liver. Since activation of effector caspases was absent, the relevance of caspase-independent mechanisms in acetaminophen-induced programmed cell death was investigated. BGP-15, a drug with known protective actions in conditions involving redox imbalance, has been co-administered with a single sublethal dose of acetaminophen. Proapoptotic events and outcome of the injury were investigated. ER redox alterations and early ER-stress-related signaling events induced by acetaminophen, such as ER glutathione depletion, phosphorylation of eIF2alpha and JNK and induction of the transcription factor GADD153, were not counteracted by co-treatment with BGP-15. However, BGP-15 prevented AIF mitochondria-to-nucleus translocation and mitochondrial depolarization. BGP-15 co-treatment attenuated the rate of acetaminophen-induced cell death as assessed by apoptotic index and enzyme serum release. These results reaffirm that acute acetaminophen toxicity involves oxidative stress-induced caspase-independent cell death. In addition, pharmacological inhibition of AIF translocation may effectively protect against or at least delay acetaminophen-induced programmed cell death.

Role of apoptosis in cardiovascular disease

Apoptosis plays a key role in the pathogenesis in a variety of cardiovascular diseases due to loss of terminally differentiated cardiac myocytes. Cardiac myocytes undergoing apoptosis have been identified in tissue samples from patients suffering from myocardial infarction, diabetic cardiomyopathy, and end-stage congestive heart failure. Apoptosis is a highly regulated program of cell death and can be mediated by death receptors in the plasma membrane, as well as the mitochondria and the endoplasmic reticulum. The cell death program is activated in cardiac myocytes by various stressors including cytokines, increased oxidative stress and DNA damage. Many studies have demonstrated that inhibition of apoptosis is cardioprotective and can prevent the development of heart failure. This review provides a current overview of the evidence of apoptosis in cardiovascular diseases and discusses the molecular pathways involved in cardiac myocyte apoptosis.

Inhibition of the activity of Rho-kinase reduces cardiomyocyte apoptosis in heart ischemia/reperfusion via suppressing JNK-mediated AIF translocation

BACKGROUND

Recent studies have demonstrated that Rho-kinase has been proposed to play an important role in the pathogenesis of heart ischemia/reperfusion (I/R) injury. However, the mechanism of Rho-kinase mediated cardiomyocyte apoptosis in I/R is still not thoroughly understood.

METHOD

Studies were performed with female Wistar rats.

RESULTS

Ischemia followed by reperfusion caused a significant increase in Rho-kinase, c-Jun NH2-terminal kinase (JNK) and apoptosis-inducing factor (AIF) activity. Administration of fasudil, an inhibitor of Rho-kinase, decreased myocardial infarction size from 59.89+/-3.83% to 38.62+/-2.66% (P<0.05) and cell apoptosis from 32.78+/-5.1% to 17.05+/-4.2% (P<0.05). Western blot analysis showed that administration of fasudil reduced the activation of JNK and attenuated mitochondrial-nuclear translocation of AIF. Additionally, administration of SP600125, an inhibitor of JNK, attenuated mitochondrial-nuclear translocation of AIF.

CONCLUSION

The inhibition of Rho-kinase reduced cell apoptosis in I/R in vivo via suppression of JNK-mediated AIF translocation.