Targeted deletion of Puma attenuates cardiomyocyte death and improves cardiac function during ischemia-reperfusion

Regulation of optimized new Shengmai powder on cardiomyocyte apoptosis and ferroptosis in ischemic heart failure rats: The mediating role of phosphatidylinositol-3-kinase/protein kinase B/tumor protein 53 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Optimized New Shengmai Powder (ONSMP) is a sophisticated traditional Chinese medicinal formula renowned for bolstering vital energy, optimizing blood circulation, and mitigating fluid retention. After years of clinical application, ONSMP has shown a significant impact in improving myocardial injury and cardiac function and has a positive effect on treating heart failure. However, many unknowns exist about the molecular biological mechanisms of how ONSMP exerts its therapeutic effects, which require further research and exploration.

AIM OF THE STUDY

Exploring the potential molecular biological mechanisms by which ONSMP ameliorates cardiomyocyte apoptosis and ferroptosis in ischemic heart failure (IHF).

MATERIALS AND METHODS

First, we constructed a rat model of IHF by inducing acute myocardial infarction through surgery and using echocardiography, organ coefficients, markers of heart failure, antioxidant markers, and histopathological examination to assess the effects of ONSMP on cardiomyocyte apoptosis and ferroptosis in IHF rats. Next, we used bioinformatics analysis techniques to analyze the active components, signaling pathways, and core targets of ONSMP and calculated the interactions between core targets and corresponding elements. Finally, we detected the positive expression of apoptosis and ferroptosis markers and core indicators of signaling pathways by immunohistochemistry; detected the mean fluorescence intensity of core indicators of signaling pathways by immunofluorescence; detected the protein expression of signaling pathways and downstream effector molecules by western blotting; and detected the mRNA levels of p53 and downstream effector molecules by quantitative polymerase chain reaction.

RESULTS

ONSMP can activate the Ser83 site of ASK by promoting the phosphorylation of the PI3K/AKT axis, thereby inhibiting the MKK3/6-p38 axis and the MKK4/7-JNK axis signaling to reduce p53 expression, and can also directly target and inhibit the activity of p53, ultimately inhibiting p53-mediated mRNA and protein increases in PUMA, SAT1, PIG3, and TFR1, as well as mRNA and protein decreases in SLC7A11, thereby inhibiting cardiomyocyte apoptosis and ferroptosis, effectively improving cardiac function and ventricular remodeling in IHF rat models.

CONCLUSION

ONSMP can inhibit cardiomyocyte apoptosis and ferroptosis through the PI3K/AKT/p53 signaling pathway, delaying the development of IHF.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Docosahexaenoic Acid-Enhanced Autophagic Flux Improves Cardiac Dysfunction after Myocardial Infarction by Targeting the AMPK/mTOR Signaling Pathway

Background and Purpose. Docosahexaenoic acid (DHA) is a type of polyunsaturated fatty acid enriched in cod liver oil and seaweed. It is necessary for the human body and has important functions, such as antioxidation and antiatherosclerosis activities. Long-term oral administration of DHA or the use of DHA at the initial stage of ischemia can increase the level of autophagy and exert a protective effect on neurological functions related to cerebral infarction. However, the effect of DHA on myocardial injury and cardiac insufficiency after myocardial infarction (MI) is unknown. This study was aimed at exploring whether DHA plays a protective role in AMI and its specific molecular mechanism. Experimental Method. In vitro cardiomyocyte hypoxia and in vivo MI injury models were used to determine the role of DHA in MI. Hypoxic injury induced damage in cultured neonatal mouse cardiomyocytes (NMCs). The C57BL/6J mouse MI model was established by permanent ligation of the left anterior descending branch. Main Results. DHA improved the cardiomyocyte viability of NMCs induced by hypoxia injury and reduced cell necrosis. DHA reduced infarct size, improved heart function, and reduced the degree of myocardial fibrosis in mice after MI. In addition, DHA enhanced autophagy flux and reduced apoptosis in vitro and in vivo. In addition, we found that chloroquine, an autophagy inhibitor, blocked the protective effect of DHA on cardiomyocyte apoptosis and cardiac dysfunction, indicating that DHA exerts cardioprotective effects in part by promoting autophagy flux. We also observed that DHA enhanced autophagy flux by activating the AMPK/mTOR signaling pathway. Conclusions and Significance. In conclusion, our findings indicate for the first time that DHA improves MI-induced cardiac dysfunction by promoting AMPK/mTOR-mediated autophagic flux.

Dexmedetomidine attenuates ischemia and reperfusion-induced cardiomyocyte injury through p53 and forkhead box O3a (FOXO3a)/p53-upregulated modulator of apoptosis (PUMA) signaling signaling

Dexmedetomidine (DEX) has been reported to attenuate the ischemia and reperfusion (I/R) induced cardiomyocyte apoptosis. However, mechanisms underlying these protective effect remain to be fully elucidated. Cardiomyocyte apoptosis is associated with ischemic heart disease. Here we investigated the role of DEX in I/R -induced cardiomyocyte apoptosis. Mice and H9c2 cardiomyocyte cells were subjected to cardiomyocyte I/R injury and hypoxia/reoxygenation (H/R) injury, respectively. The roles and mechanisms of DEX on H9c2 cardiomyocyte cells and mice cardiomyocyte cells exposured to H/R or I/R injury were explored. The results showed that DEX attenuates H/R injury-induced H9c2 cell apoptosis and alleviated mitochondrial oxidative stress; it also reduced myocardial infarct size and protected the cardiac function following cardiomyocyte I/R injury. In addition, H/R and I/R injury increased p53 expression and forkhead box O3a (FOXO3a)/p53-upregulated modulator of apoptosis (PUMA) signaling in H9c2 cardiomyocyte cells and cardiomyocytes. Targeting p53 expression or FOXO3a/PUMA signaling inhibited cell apoptosis and protected against H/R injury in H9c2 cardiomyocyte cells and cardiomyocytes. Pretreatment with DEX reduced the H/R or I/R injury-induced activation of p53 expression and FOXO3a/PUMA signaling, and alleviated H/R or I/R injury-induced apoptosis and mitochondrial oxidative stress. Therefore, DEX could alleviate H/R- or I/R-induced cardiomyocytes injury by reducing cell apoptosis and blocking p53 expression and FOXO3a/PUMA signaling. Targeting p53 or/and FOXO3a/PUMA signaling could alleviate cardiomyocyte I/R injury.

Molecular Signaling to Preserve Mitochondrial Integrity against Ischemic Stress in the Heart: Rescue or Remove Mitochondria in Danger

Cardiovascular diseases are one of the leading causes of death and global health problems worldwide, and ischemic heart disease is the most common cause of heart failure (HF). The heart is a high-energy demanding organ, and myocardial energy reserves are limited. Mitochondria are the powerhouses of the cell, but under stress conditions, they become damaged, release necrotic and apoptotic factors, and contribute to cell death. Loss of cardiomyocytes plays a significant role in ischemic heart disease. In response to stress, protective signaling pathways are activated to limit mitochondrial deterioration and protect the heart. To prevent mitochondrial death pathways, damaged mitochondria are removed by mitochondrial autophagy (mitophagy). Mitochondrial quality control mediated by mitophagy is functionally linked to mitochondrial dynamics. This review provides a current understanding of the signaling mechanisms by which the integrity of mitochondria is preserved in the heart against ischemic stress.

Too much death can kill you: inhibiting intrinsic apoptosis to treat disease

Apoptotic cell death is implicated in both physiological and pathological processes. Since many types of cancerous cells intrinsically evade apoptotic elimination, induction of apoptosis has become an attractive and often necessary cancer therapeutic approach. Conversely, some cells are extremely sensitive to apoptotic stimuli leading to neurodegenerative disease and immune pathologies. However, due to several challenges, pharmacological inhibition of apoptosis is still only a recently emerging strategy to combat pathological cell loss. Here, we describe several key steps in the intrinsic (mitochondrial) apoptosis pathway that represent potential targets for inhibitors in disease contexts. We also discuss the mechanisms of action, advantages and limitations of small-molecule and peptide-based inhibitors that have been developed to date. These inhibitors serve as important research tools to dissect apoptotic signalling and may foster new treatments to reduce unwanted cell loss.

The role of P53 up-regulated modulator of apoptosis (PUMA) in ovarian development, cardiovascular and neurodegenerative diseases

P53 up-regulated modulator of apoptosis (PUMA), a pro-apoptotic BCL-2 homology 3 (BH3)-only member of the BCL-2 family, is a direct transcriptional target of P53 that elicits mitochondrial apoptosis under treatment with radiation and chemotherapy. It also induces excessive apoptosis in cardiovascular and/or neurodegenerative diseases. PUMA has been found to play a critical role in ovarian apoptosis. In the present paper, we review the progress of the study in PUMA over the past two decades in terms of its inducement and/or amplification of programmed cell death and describe recent updates to the understanding of both P53-dependent and P53-independent PUMA-mediated apoptotic pathways that are implicated in physiology and pathology, including the development of the ovary and cardiovascular and neurodegenerative diseases. We propose that PUMA may be a key regulator during ovary development, provide a model for PUMA-mediated apoptotic pathways, including intrinsic and extrinsic apoptotic pathways.

miR-22 protect PC12 from ischemia/reperfusion-induced injury by targeting p53 upregulated modulator of apoptosis (PUMA)

MicroRNAs have been implicated as critical regulatory molecules in many cerebrovascular diseases. Recent studies demonstrated miR-22 might provide a potential neuroprotective effect. However, the neuroprotective effect of miR-22 in ischemia/reperfusion (I/R) injury has not been thoroughly elucidated. In this study, the PC12 cells were subjected to 4 h oxygen and glucose deprivation (I) and 24 h reoxygenation (R). The PC12 cells were pre-transfected with miR-22 or anti-miR-22 or siRNA-mediated downregulation of p53-upregulated-modulator-of-apoptosis (PUMA)(PUMA siRNA) or their controls at 24 h prior to exposure to I/R. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot were employed to analyze mRNA and protein expression. PI and Annexin V assays and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay were used to quantify the rate of apoptosis. We found that miR-22 expression was significantly downregulated in the PC12 cells subjected to I/R. Loss of function of miR-22 increased PC12 apoptosis after I/R, and overexpression of miR-22 decreases PC12 apoptosis after I/R. PUMA protein was upregulated in the I/R group as compared with the sham group. The increased PUMA protein expression and apoptosis induced by I/R was reversed by transfection with PUMA siRNA. We concluded that I/R enhanced apoptosis and PUMA expression in PC12 cells via downregulation of miR-22. Enhanced miR-22 expression reversed both PUMA expression and apoptosis induced by I/R in PC12 cells. miR-22/PUMA axis has important implications for their clinical applications.

MicroRNA-221/222 Mediates ADSC-Exosome-Induced Cardioprotection Against Ischemia/Reperfusion by Targeting PUMA and ETS-1

Cardiovascular disease is a major health problem in industrialized and developing countries and is the leading cause of death and disability. Myocardial ischemia/reperfusion (I/R) causes cardiomyocyte damage such as apoptosis and hypertrophy. The purpose of this study was to investigate the effects of exosomes from adipose-derived stem cells (ADSC-Exo) on hearts from I/R mice and to explore the underlying mechanisms. ADSC-Exo significantly decreased I/R-induced cardiomyocyte apoptosis and hypertrophy, as detected by TdT-mediated dUTP nick end-labeling (TUNEL) and wheat germ agglutinin (WGA) staining, respectively. In addition, the expression of apoptosis-related proteins p-p53 and PUMA and hypertrophy-related proteins ETS-1 and ANP were significantly reduced in the cardiomyocytes of ADSC-Exo-treated I/R mice compared to those of control mice. Both PUMA and ETS-1 are reported to be target genes for miR-221/222. I/R operation significantly reduced miR-221/222 expression, while ADSC-Exo treatment increased miR-221/222 expression, as detected by RT-qPCR. We also observed that cardiac I/R operation markedly increased cell apoptosis and hypertrophy in miR-221/222 knockout (KO) mice, while ADSC-Exo reduced the effects of I/R operation. Furthermore, ADSC-Exo protected H9c2 cardiomyocytes from H₂O₂-induced damage by reducing apoptosis and hypertrophy in vitro. H₂O₂ treatment significantly reduced miR-221/222 expression, while ADSC-Exo treatment reversed this effect in H9c2 cells. ADSC-Exo treatment decreased H₂O₂-induced PUMA and ETS-1 expression. Compared with control treatment, I/R treatment significantly reduced p-AKT and increased p-p65, while ADSC-Exo and miR-221/222 mimics attenuated these effects. The AKT activator SC79 and p65 inhibitor Bay 11-7082 reduced H₂O₂-induced cell apoptosis and hypertrophy. Based on these findings, ADSC-Exo prevents cardiac I/R injury through the miR-221/miR-222/PUMA/ETS-1 pathway. Therefore, ADSC-Exo is an effective inhibitor of I/R-induced heart injury.

Copanlisib promotes growth inhibition and apoptosis by modulating the AKT/FoxO3a/PUMA axis in colorectal cancer

Colorectal cancer (CRC) is the type of cancer with the third highest incidence and is associated with high mortality and low 5-year survival rates. We observed that copanlisib, an inhibitor of PI3K (pan-class I phosphoinositide 3-kinase) that preferentially inhibits PI3Kδ and PI3Kα, impedes the growth of CRC cells by inducing apoptosis via PUMA. There was a marked increase in the expression of PUMA independent of p53 after treatment with copanlisib. The response of CRC cells to copanlisib could be predicted by PUMA expression. Copanlisib was found to induce PUMA expression through FoxO3a by directly binding to the PUMA promoter after inhibiting AKT signaling. PUMA deficiency mitigated the apoptosis induced by copanlisib. Caspase activation and mitochondrial dysfunction led to copanlisib resistance, as observed through a clonogenic assay, whereas enhanced expression of PUMA increased the copanlisib-induced susceptibility to apoptosis. Moreover, the antitumor effects of copanlisib were suppressed by a deficiency of PUMA in a xenograft model, and caspase activation and reduced apoptosis were also observed in vivo. Copanlisib-mediated chemosensitization seemed to involve the concurrent induction of PUMA expression via mechanisms that were both dependent and independent of p53. These observations indicate that apoptosis mediated by PUMA is crucial for the anticancer effects of copanlisib and that manipulation of PUMA may aid in enhancing anticancer activities.

Deletion of Microfibrillar-Associated Protein 4 Attenuates Left Ventricular Remodeling and Dysfunction in Heart Failure

Background

Cardiac remodeling predisposes individuals to heart failure if the burden is not solved, and heart failure is a growing cause of morbidity and mortality worldwide. The cardiac extracellular matrix not only provides structural support, but also is a core aspect of the myocardial response to various biomechanical stresses and heart failure. MFAP4 (microfibrillar‐associated protein 4) is an integrin ligand located in the extracellular matrix, whose biological functions in the heart remain poorly understood. In the current study we aimed to test the role of MFAP4 in cardiac remodeling.

Methods and Results

MFAP4‐deficient (MFAP4^−/−) and wild‐type mice were subjected to aortic banding surgery and isoproterenol to establish models of cardiac remodeling. We also evaluated the functional effects of MFAP4 on cardiac hypertrophy, fibrosis, and cardiac electrical remodeling. The expression of MFAP4 was increased in the animal cardiac remodeling models induced by pressure overload and isoproterenol. After challenge of 8 weeks of aortic banding or 2 weeks of intraperitoneal isoproterenol, MFAP4^−/− mice exhibited lower levels of cardiac fibrosis and fewer ventricular arrhythmias than wild‐type mice. However, there was no significant effect on cardiomyocyte hypertrophy. In addition, there was no significant difference in cardiac fibrosis severity, hypertrophy, or ventricular arrhythmia incidence between wild‐type‐sham and knockout‐sham mice.

Conclusions

These findings are the first to demonstrate that MFAP4 deficiency inhibits cardiac fibrosis and ventricular arrhythmias after challenge with 8 weeks of aortic banding or 2 weeks of intraperitoneal isoproterenol but does not significantly affect the hypertrophy response. In addition, MFAP4 deficiency had no significant effect on cardiac fibrosis, hypertrophy, or ventricular arrhythmia in the sham group in this study.

iNOS/NO is required for IRF1 activation in response to liver ischemia-reperfusion in mice

Background

Ischemia and reperfusion (I/R) induces cytokines, and up-regulates inducible nitric oxide synthase (iNOS), interferon regulatory factor-1(IRF1) and p53 up-regulated modulator of apoptosis (PUMA), which contribute to cell death and tissue injury. However, the mechanisms that I/R induces IRF1-PUMA through iNOS/NO is still unknown.

Methods

Ischemia was induced by occluding structures in the portal triad (hepatic artery, portal vein, and bile duct) to the left and median liver lobes for 60 min, and reperfusion was initiated by removal of the clamp. Induction of iNOS, IRF1 and PUMA in response to I/R were analyzed. I/R induced IRF1 and PUMA expression were compared between iNOS wild-type and iNOS knockout (KO) mice. Human iNOS gene transfected-cells were used to determine iNOS/NO signals targeting IRF1. To test whether HDAC2 was involved in the mediation of iNOS/NO-induced IRF1 transcriptional activities and its target gene (PUMA and p21) expression, NO donors were used in vitro and in vivo.

Results

IRF1 nuclear translocation and PUMA transcription elevation were markedly induced following I/R in the liver of iNOS wild-type mice compared with that in knock-out mice. Furthermore, I/R induced hepatic HDAC2 expression and activation, and decreased H3AcK9 expression in iNOS wild-type mice, but not in the knock-out mice. Mechanistically, over-expression of human iNOS gene increased IRF1 transcriptional activity and PUMA expression, while iNOS inhibitor L-NIL reversed these effects. Cytokine-induced PUMA through IRF1 was p53 dependent. IRF1 and p53 synergistically up-regulated PUMA expression. iNOS/NO-induced HDAC2 mediated histone H3 deacetylation and promoted IRF1 transcriptional activity. Moreover, treating the cells with romidepsin, an HDAC1/2 inhibitor decreased NO-induced IRF1 and PUMA expression.

Conclusions

This study demonstrates a novel mechanism that iNOS/NO is required for IRF1/PUMA signaling through a positive-feedback loop between iNOS and IRF1, in which HDAC2-mediated histone modification is involved to up-regulate IRF1 in response to I/R in mice.

CTCF inhibits endoplasmic reticulum stress and apoptosis in cardiomyocytes by upregulating RYR2 via inhibiting S100A1

AIMS

Pediatric heart failure is a common cardiovascular disease in clinical pediatrics. CCCTC-binding factor (CTCF), a novel transcriptional repressor, was reported to participate in the occurrence of various cardiovascular diseases. The present study focuses on exploring the effects of CTCF on tunicamycin (TM)-induced endoplasmic reticulum (ER) stress, and investigating the underlying mechanisms.

MATERIALS AND METHOD

Expression of CTCF in blood samples of heart failure children and TM-induced cardiomyocytes were evaluated by real-time quantitative PCR (RT-qPCR). Apoptotic rate of cardiomyocytes was detected by Annexin v assay. Western blotting and enzyme-linked immunosorbent assay (ELISA) were applied to examine the effect of CTCF on ER stress. Co-immunoprecipitation and western blotting were devoted to explore the mechanism by which CTCF contributes to ER stress.

KEY FINDINGS

We proved that CTCF was lowly expressed in blood samples of heart failure children and TM-induced cardiomyocytes, and overexpression of CTCF weaken the TM-induced ER stress. Using co-immunoprecipitation and protein blots, we demonstrated that CTCF upregulates RYR2 by inhibiting S100A1, thus mediating the PERK signaling pathway and regulating ER stress.

SIGNIFICANCE

Our data revealed that CTCF protects cardiomyocytes from ER stress through S100A1-RYR2 axis, and can be applied as a therapeutic target for the treatment of pediatric heart failure in future.

Targeting mitochondria for cardiovascular disorders: therapeutic potential and obstacles

A large body of evidence indicates that mitochondrial dysfunction has a major role in the pathogenesis of multiple cardiovascular disorders. Over the past 2 decades, extraordinary efforts have been focused on the development of agents that specifically target mitochondria for the treatment of cardiovascular disease. Despite such an intensive wave of investigation, no drugs specifically conceived to modulate mitochondrial functions are currently available for the clinical management of cardiovascular disease. In this Review, we discuss the therapeutic potential of targeting mitochondria in patients with cardiovascular disease, examine the obstacles that have restrained the development of mitochondria-targeting agents thus far, and identify strategies that might empower the full clinical potential of this approach.

Fundamental Mechanisms of Regulated Cell Death and Implications for Heart Disease

Twelve regulated cell death programs have been described. We review in detail the basic biology of nine including death receptor-mediated apoptosis, death receptor-mediated necrosis (necroptosis), mitochondrial-mediated apoptosis, mitochondrial-mediated necrosis, autophagy-dependent cell death, ferroptosis, pyroptosis, parthanatos, and immunogenic cell death. This is followed by a dissection of the roles of these cell death programs in the major cardiac syndromes: myocardial infarction and heart failure. The most important conclusion relevant to heart disease is that regulated forms of cardiomyocyte death play important roles in both myocardial infarction with reperfusion (ischemia/reperfusion) and heart failure. While a role for apoptosis in ischemia/reperfusion cannot be excluded, regulated forms of necrosis, through both death receptor and mitochondrial pathways, are critical. Ferroptosis and parthanatos are also likely important in ischemia/reperfusion, although it is unclear if these entities are functioning as independent death programs or as amplification mechanisms for necrotic cell death. Pyroptosis may also contribute to ischemia/reperfusion injury, but potentially through effects in non-cardiomyocytes. Cardiomyocyte loss through apoptosis and necrosis is also an important component in the pathogenesis of heart failure and is mediated by both death receptor and mitochondrial signaling. Roles for immunogenic cell death in cardiac disease remain to be defined but merit study in this era of immune checkpoint cancer therapy. Biology-based approaches to inhibit cell death in the various cardiac syndromes are also discussed.

Targeting MIAT reduces apoptosis of cardiomyocytes after ischemia/reperfusion injury

This study aims to investigate the role of targeting lncRNA myocardial infarction-associated transcript (MIAT) in protection against hypoxia/reoxygenation (H/R) injury in H9c2 cells in vitro and myocardial ischemia/reperfusion (I/R) injury in vivo by regulating expression of NF-kB and p53 upregulated modulator of apoptosis (PUMA). H9C2 cells were infected with lentivirus expressing the short-hairpin RNA direct against human MIAT gene (Lv-MIAT shRNA) or lentivirus expressing scrambled control (Lv-NC shRNA) or PUMA siRNA or p65 siRNA or their control siRNA respectively. Then the H9c2 cells were infected with Lv-shRNA to 2 hours of hypoxia (H) and 24 hour of reoxygenation (R). 100 ul of Lv-MIAT shRNA (1 × 10⁸ PFU) or Lv-NC shRNA was transfected into mouse hearts, then the hearts were subjected to I/R (1h/72 h). We discovered targeting MIAT remarkably enhanced H9c2 cell viability, decreased H/R-induced cell apoptosis and LDH leakage and significantly decreased I/R-induced myocardial infarct size, reduced myocardial apoptosis and enhanced the heart function. Targeting MIAT downregulated p65 nuclear translocation, NF-κB activity and anti-apoptotic protein cleaved-caspase-3, Bax, and upregulated anti-apoptotic protein Bcl-2 induced by H/R or I/R. Our study suggests that targeting MIAT may protect against H9c2 cardiomyoblasts H/R injury or myocardial I/R injury via inhibition of cell apoptosis, mediated by NF-κB and PUMA signal pathway.

Identification of differentially expressed genes and preliminary validations in cardiac pathological remodeling induced by transverse aortic constriction

Cardiac remodeling predisposes to heart failure if the burden is unresolved, and heart failure is an important cause of mortality in humans. The aim of the present study was to identify the key genes involved in cardiac pathological remodeling induced by pressure overload. Gene expression profiles of the GSE5500, GSE18224, GSE36074 and GSE56348 datasets were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs), defined as |log2FC|>1 (FC, fold change) and an adjusted P‑value of <0.05, were screened using the R software with the limma package. Gene ontology enrichment analysis was performed and a protein‑protein interaction (PPI) network of the DEGs was constructed. A cardiac remodeling model induced by transverse aortic constriction (TAC) was established. Furthermore, consistent DEGs were further validated using reverse transcription‑quantitative polymerase chain reaction (RT‑PCR) analysis, western blotting and immunohistochemistry in the ventricular tissue samples after TAC or sham operation. A total of 24 common DEGs were identified (23 significantly upregulated and 1 downregulated), of which 9 genes had been previously confirmed to be directly involved in cardiac remodeling. Hence, the level of expression of the other 15 genes was detected in subsequent studies via RT‑PCR. Based on the results of the PPI network analysis and RT‑PCR, we further detected the protein levels of Itgbl1 and Asporin, which were consistent with the results of bioinformatics analysis and RT‑PCR. The expression of Itgbl1, Aspn, Fstl1, Mfap5, Col8a1, Ltbp2, Mfap4, Pamr1, Cnksr1, Aqp8, Meox1, Gdf15 and Srpx was found to be upregulated in a mouse model of cardiac remodeling, while that of Retnla was downregulated. Therefore, the present study identified the key genes implicated in cardiac remodeling, aiming to provide new insight into the underlying mechanism.

Broken heart: A matter of the endoplasmic reticulum stress bad management?

Cardiovascular diseases are the number one cause of morbidity and mortality in the United States and worldwide. The induction of the endoplasmic reticulum (ER) stress, a result of a disruption in the ER homeostasis, was found to be highly associated with cardiovascular diseases such as hypertension, diabetes, ischemic heart diseases and heart failure. This review will discuss the latest literature on the different aspects of the involvement of the ER stress in cardiovascular complications and the potential of targeting the ER stress pathways as a new therapeutic approach for cardiovascular complications.

p53 Up-regulated Modulator of Apoptosis Induction Mediates Acetaminophen-Induced Necrosis and Liver Injury in Mice

Acetaminophen (APAP) overdose is one of the leading causes of hepatotoxicity and acute liver failure in the United States. Accumulating evidence suggests that hepatocyte necrosis plays a critical role in APAP-induced liver injury (AILI). However, the mechanisms of APAP-induced necrosis and liver injury are not fully understood. In this study, we found that p53 up-regulated modulator of apoptosis (PUMA), a B-cell lymphoma-2 (Bcl-2) homology domain 3 (BH3)-only Bcl-2 family member, was markedly induced by APAP in mouse livers and in isolated human and mouse hepatocytes. PUMA deficiency suppressed APAP-induced mitochondrial dysfunction and release of cell death factors from mitochondria, and protected against APAP-induced hepatocyte necrosis and liver injury in mice. PUMA induction by APAP was p53 independent, and required receptor-interacting protein kinase 1 (RIP1) and c-Jun N-terminal kinase (JNK) by transcriptional activation. Furthermore, a small-molecule PUMA inhibitor, administered after APAP treatment, mitigated APAP-induced hepatocyte necrosis and liver injury. Conclusion: Our results demonstrate that RIP1/JNK-dependent PUMA induction mediates AILI by promoting hepatocyte mitochondrial dysfunction and necrosis, and suggest that PUMA inhibition is useful for alleviating acute hepatotoxicity attributed to APAP overdose.

Gene expression changes in human iPSC-derived cardiomyocytes after X-ray irradiation

Purpose: Radiation-induced heart disease caused by cardiac exposure to ionizing radiation comprises a variety of cardiovascular effects. Research in this field has been hampered by limited availability of clinical samples and appropriate test models. In this study, we wanted to elucidate the molecular mechanisms underlying electrophysiological changes, which we have observed in a previous study. Materials and methods: We employed RNA deep-sequencing of human-induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) 48 h after 5 Gy X-ray irradiation. By comparison to public data from hiPSC-CMs and human myocardium, we verified the expression of cardiac-specific genes in hiPSC-CMs. Results were validated by qRT-PCR. Results: Differentially gene expression analysis identified 39 and 481 significantly up- and down-regulated genes after irradiation, respectively. Besides, a large fraction of genes associated with cell cycle processes, we identified genes implicated in cardiac calcium homeostasis (PDE3B), oxidative stress response (FDXR and SPATA18) and the etiology of cardiomyopathy (SGCD, BBC3 and GDF15). Conclusions: Notably, observed gene expression characteristics specific to hiPSC-CMs might be relevant regarding further investigations of the response to external stressors like radiation. The genes and biological processes highlighted in our study present promising starting points for functional follow-up studies for which hiPSC-CMs could pose an appropriate cell model when cell type specific peculiarities are taken into account.

Inhibiting aberrant p53-PUMA feedback loop activation attenuates ischaemia reperfusion-induced neuroapoptosis and neuroinflammation in rats by downregulating caspase 3 and the NF-κB cytokine pathway

Background

Ischaemia reperfusion (IR) induces multiple pathophysiological changes. In addition to its classical role in regulating tumourigenesis, the feedback loop formed by p53 and its driven target p53-upregulated modulator of apoptosis (PUMA) was recently demonstrated to be the common node tightly controlling various cellular responses during myocardial IR. However, the roles of the p53-PUMA feedback loop in the spinal cord remain unclear. This study aimed to elucidate the roles of p53-PUMA feedback interactions in the spinal cord after IR, specifically investigating their regulation of caspase 3-mediated apoptosis and nuclear factor (NF)-κB-mediated cytokine release.

Methods

SD rats subjected to 12 min of aortic arch occlusion served as IR models. Neurological assessment as well as p53 and PUMA mRNA and protein expression analyses were performed at 12-h intervals during a 48-h reperfusion period. The cellular distributions of p53 and PUMA were determined via double immunofluorescence staining. The effects of the p53-PUMA feedback loop on modulating hind-limb function; the number of TUNEL-positive cells; and protein levels of caspase 3, NF-κB and cytokines interleukin (IL)-1β and tumour necrosis factor (TNF)-α, were evaluated by intrathecal treatment with PUMA-specific or scramble siRNA and pifithrin (PFT)-α. Blood-spinal cord barrier (BSCB) breakdown was examined by Evans blue (EB) extravasation and water content analyses.

Results

IR induced significant behavioural deficits as demonstrated by deceased Tarlov scores, which displayed trends opposite those of PUMA and p53 protein and mRNA expression. Upregulated PUMA and p53 fluorescent labels were widely distributed in neurons, astrocytes and microglia. Injecting si-PUMA and PFT-α exerted significant anti-apoptosis effects as shown by the reduced number of TUNEL-positive cells, nuclear abnormalities and cleaved caspase 3 levels at 48 h post-IR. Additionally, p53 colocalized with NF-κB within the cell. Similarly, injecting si-PUMA and PFT-α exerted anti-inflammatory effects as shown by the decreased NF-κB translocation and release of IL-1β and TNF-α. Additionally, injecting si-PUMA and PFT-α preserved the BSCB integrity as determined by decreased EB extravasation and spinal water content. However, injecting si-Con did not induce any of the abovementioned effects.

Conclusions

Inhibition of aberrant p53-PUMA feedback loop activation by intrathecal treatment with si-PUMA and PFT-α prevented IR-induced neuroapoptosis, inflammatory responses and BSCB breakdown by inactivating caspase 3-mediated apoptosis and NF-κB-mediated cytokine release.

Rbm24, a target of p53, is necessary for proper expression of p53 and heart development

Activation of p53-dependent apoptosis is critical for tumor suppression but aberrant activation of p53 also leads to developmental defects and heart failure. Here, we found that Rbm24 RNA-binding protein, a target of p53, regulates p53 mRNA translation. Mechanistically, we found that through binding to p53 mRNA and interaction with translation initiation factor eIF4E, Rbm24 prevents eIF4E from binding to p53 mRNA and inhibits the assembly of translation initiation complex. Importantly, we showed that mice deficient in Rbm24 die in utero due to the endocardial cushion defect in the heart at least in part due to aberrant activation of p53-dependent apoptosis. We also showed that the heart developmental defect in Rbm24-null mice can be partially rescued by p53 deficiency through decreased apoptosis in the heart. Together, we postulate that the p53-Rbm24 loop is critical for the heart development and may be explored for mitigating congenital heart diseases and heart failure.

The CCR4-NOT deadenylase complex controls Atg7-dependent cell death and heart function

Shortening and removal of the polyadenylate [poly(A)] tail of mRNA, a process called deadenylation, is a key step in mRNA decay that is mediated through the CCR4-NOT (carbon catabolite repression 4-negative on TATA-less) complex. In our investigation of the regulation of mRNA deadenylation in the heart, we found that this complex was required to prevent cell death. Conditional deletion of the CCR4-NOT complex components Cnot1 or Cnot3 resulted in the formation of autophagic vacuoles and cardiomyocyte death, leading to lethal heart failure accompanied by long QT intervals. Cnot3 bound to and shortened the poly(A) tail of the mRNA encoding the key autophagy regulator Atg7. In Cnot3-depleted hearts, Atg7 expression was posttranscriptionally increased. Genetic ablation of Atg7, but not Atg5, increased survival and partially restored cardiac function of Cnot1 or Cnot3 knockout mice. We further showed that in Cnot3-depleted hearts, Atg7 interacted with p53 and modulated p53 activity to induce the expression of genes encoding cell death-promoting factors in cardiomyocytes, indicating that defects in deadenylation in the heart aberrantly activated Atg7 and p53 to promote cell death. Thus, mRNA deadenylation mediated by the CCR4-NOT complex is crucial to prevent Atg7-induced cell death and heart failure, suggesting a role for mRNA deadenylation in targeting autophagy genes to maintain normal cardiac homeostasis.

Rosmarinic acid attenuates cardiac fibrosis following long-term pressure overload via AMPKα/Smad3 signaling

Agonists of peroxisome proliferator-activated receptor gamma (PPAR-γ) can activate 5' AMP-activated protein kinase alpha (AMPKα) and exert cardioprotective effects. A previous study has demonstrated that rosmarinic acid (RA) can activate PPAR-γ, but its effect on cardiac remodeling remains largely unknown. Our study aimed to investigate the effect of RA on cardiac remodeling and to clarify the underlying mechanism. Mice were subjected to aortic banding to generate pressure overload induced cardiac remodeling and then were orally administered RA (100 mg/kg/day) for 7 weeks beginning 1 week after surgery. The morphological examination, echocardiography, and molecular markers were used to evaluate the effects of RA. To ascertain whether the beneficial effect of RA on cardiac fibrosis was mediated by AMPKα, AMPKα2 knockout mice were used. Neonatal rat cardiomyocytes and fibroblasts were separated and cultured to validate the protective effect of RA in vitro. RA-treated mice exhibited a similar hypertrophic response as mice without RA treatment, but had an attenuated fibrotic response and improved cardiac function after pressure overload. Activated AMPKα was essential for the anti-fibrotic effect of RA via inhibiting the phosphorylation and nuclear translocation of Smad3 in vivo and in vitro, and AMPKα deficiency abolished RA-mediated protective effects. Small interfering RNA against Ppar-γ (siPpar-γ) and GW9662, a specific antagonist of PPAR-γ, abolished RA-mediated AMPKα phosphorylation and alleviation of fibrotic response in vitro. RA attenuated cardiac fibrosis following long-term pressure overload via AMPKα/Smad3 signaling and PPAR-γ was required for the activation of AMPKα. RA might be a promising therapeutic agent against cardiac fibrosis.

Cardiac-specific ablation of the E3 ubiquitin ligase Mdm2 leads to oxidative stress, broad mitochondrial deficiency and early death

The maintenance of normal heart function requires proper control of protein turnover. The ubiquitin-proteasome system is a principal regulator of protein degradation. Mdm2 is the main E3 ubiquitin ligase for p53 in mitotic cells thereby regulating cellular growth, DNA repair, oxidative stress and apoptosis. However, which of these Mdm2-related activities are preserved in differentiated cardiomyocytes has yet to be determined. We sought to elucidate the role of Mdm2 in the control of normal heart function. We observed markedly reduced Mdm2 mRNA levels accompanied by highly elevated p53 protein expression in the hearts of wild type mice subjected to myocardial infarction or trans-aortic banding. Accordingly, we generated conditional cardiac-specific Mdm2 gene knockout (Mdm2^f/f;mcm) mice. In adulthood, Mdm2^f/f;mcm mice developed spontaneous cardiac hypertrophy, left ventricular dysfunction with early mortality post-tamoxifen. A decreased polyubiquitination of myocardial p53 was observed, leading to its stabilization and activation, in the absence of acute stress. In addition, transcriptomic analysis of Mdm2-deficient hearts revealed that there is an induction of E2f1 and c-Myc mRNA levels with reduced expression of the Pgc-1a/Ppara/Esrrb/g axis and Pink1. This was associated with a significant degree of cardiomyocyte apoptosis, and an inhibition of redox homeostasis and mitochondrial bioenergetics. All these processes are early, Mdm2-associated events and contribute to the development of pathological hypertrophy. Our genetic and biochemical data support a role for Mdm2 in cardiac growth control through the regulation of p53, the Pgc-1 family of transcriptional coactivators and the pivotal antioxidant Pink1.

Chronic Intermittent Hypobaric Hypoxia Improves Cardiac Function through Inhibition of Endoplasmic Reticulum Stress

We investigated the role of endoplasmic reticulum stress (ERS) in chronic intermittent hypobaric hypoxia (CIHH)-induced cardiac protection. Adult male Sprague-Dawley rats were exposed to CIHH treatment simulating 5000 m altitude for 28 days, 6 hours per day. The heart was isolated and perfused with Langendorff apparatus and subjected to 30-min ischemia followed by 60-min reperfusion. Cardiac function, infarct size, and lactate dehydrogenase (LDH) activity were assessed. Expression of ERS molecular chaperones (GRP78, CHOP and caspase-12) was assayed by western blot analysis. CIHH treatment improved the recovery of left ventricular function and decreased cardiac infarct size and activity of LDH after I/R compared to control rats. Furthermore, CIHH treatment inhibited over-expression of ERS-related factors including GRP78, CHOP and caspase-12. CIHH-induced cardioprotection and inhibition of ERS were eliminated by application of dithiothreitol, an ERS inducer, and chelerythrine, a protein kinase C (PKC) inhibitor. In conclusion CIHH treatment exerts cardiac protection against I/R injury through inhibition of ERS via PKC signaling pathway.

Impact of high cholesterol and endoplasmic reticulum stress on metabolic diseases: An updated mini-review

Endoplasmic reticulum (ER) is the major site of protein folding and calcium storage. Beside the role of ER in protein homeostasis, it controls the cholesterol production and lipid-membrane biosynthesis as well as surviving and cell death signaling mechanisms in the cell. It is well-documented that elevated plasma cholesterol induces adverse effects in cardiovascular diseases (CVDs), liver disorders, such as non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatosis hepatitis (NASH), and metabolic diseases which are associated with oxidative and ER stress. Recent animal model and human studies have showed high cholesterol and ER stress as an emerging factors involved in the development of many metabolic diseases. In this review, we will summarize the crucial effects of hypercholesterolemia and ER stress response in the pathogenesis of CVDs, NAFLD/NASH, diabetes and obesity which are major health problems in western countries.

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Endoplasmic reticulum stress involves in various metabolic disease development.

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Altered cholesterol metabolism is a well-documented inducer of ER stress.

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ER stress mediated apoptosis leads many cardiovascular disorders.

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UPR might lead NAFLD/NASH progression by enhancing inflammation and fibrosis.

Doxorubicin-induced chronic dilated cardiomyopathy-the apoptosis hypothesis revisited

The chemotherapeutic agent doxorubicin (DOX) has significantly increased survival rates of pediatric and adult cancer patients. However, 10% of pediatric cancer survivors will 10-20 years later develop severe dilated cardiomyopathy (DCM), whereby the exact molecular mechanisms of disease progression after this long latency time remain puzzling. We here revisit the hypothesis that elevated apoptosis signaling or its increased likelihood after DOX exposure can lead to an impairment of cardiac function and cause a cardiac dilation. Based on recent literature evidence, we first argue why a dilated phenotype can occur when little apoptosis is detected. We then review findings suggesting that mature cardiomyocytes are protected against DOX-induced apoptosis downstream, but not upstream of mitochondrial outer membrane permeabilisation (MOMP). This lack of MOMP induction is proposed to alter the metabolic phenotype, induce hypertrophic remodeling, and lead to functional cardiac impairment even in the absence of cardiomyocyte apoptosis. We discuss findings that DOX exposure can lead to increased sensitivity to further cardiomyocyte apoptosis, which may cause a gradual loss in cardiomyocytes over time and a compensatory hypertrophic remodeling after treatment, potentially explaining the long lag time in disease onset. We finally note similarities between DOX-exposed cardiomyocytes and apoptosis-primed cancer cells and propose computational system biology as a tool to predict patient individual DOX doses. In conclusion, combining recent findings in rodent hearts and cardiomyocytes exposed to DOX with insights from apoptosis signal transduction allowed us to obtain a molecularly deeper insight in this delayed and still enigmatic pathology of DCM.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

Mitochondrial Function, Biology, and Role in Disease: A Scientific Statement From the American Heart Association

Cardiovascular disease is a major leading cause of morbidity and mortality in the United States and elsewhere. Alterations in mitochondrial function are increasingly being recognized as a contributing factor in myocardial infarction and in patients presenting with cardiomyopathy. Recent understanding of the complex interaction of the mitochondria in regulating metabolism and cell death can provide novel insight and therapeutic targets. The purpose of this statement is to better define the potential role of mitochondria in the genesis of cardiovascular disease such as ischemia and heart failure. To accomplish this, we will define the key mitochondrial processes that play a role in cardiovascular disease that are potential targets for novel therapeutic interventions. This is an exciting time in mitochondrial research. The past decade has provided novel insight into the role of mitochondria function and their importance in complex diseases. This statement will define the key roles that mitochondria play in cardiovascular physiology and disease and provide insight into how mitochondrial defects can contribute to cardiovascular disease; it will also discuss potential biomarkers of mitochondrial disease and suggest potential novel therapeutic approaches.

Iron metabolism and regulation by neutrophil gelatinase-associated lipocalin in cardiomyopathy

Neutrophil gelatinase-associated lipocalin (NGAL) has recently become established as an important contributor to the pathophysiology of cardiovascular disease. Accordingly, it is now viewed as an attractive candidate as a biomarker for various disease states, and in particular has recently become regarded as one of the best diagnostic biomarkers available for acute kidney injury. Nevertheless, the precise physiological effects of NGAL on the heart and the significance of their alterations during the development of heart failure are only now beginning to be characterized. Furthermore, the mechanisms via which NGAL mediates its effects are unclear because there is no conventional receptor signalling pathway. Instead, previous work suggests that regulation of iron metabolism could represent an important mechanism of NGAL action, with wide-ranging consequences spanning metabolic and cardiovascular diseases to host defence against bacterial infection. In the present review, we summarize rapidly emerging evidence for the role of NGAL in regulating heart failure. In particular, we focus on iron transport as a mechanism of NGAL action and discuss this in the context of the existing strong associations between iron overload and iron deficiency with cardiomyopathy.

Abnormalities in Alternative Splicing of Apoptotic Genes and Cardiovascular Diseases

Apoptosis is required for normal heart development in the embryo, but has also been shown to be an important factor in the occurrence of heart disease. Alternative splicing of apoptotic genes is currently emerging as a diagnostic and therapeutic target for heart disease. This review addresses the involvement of abnormalities in alternative splicing of apoptotic genes in cardiac disorders including cardiomyopathy, myocardial ischemia and heart failure. Many pro-apoptotic members of the Bcl-2 family have alternatively spliced isoforms that lack important active domains. These isoforms can play a negative regulatory role by binding to and inhibiting the pro-apoptotic forms. Alternative splicing is observed to be increased in various cardiovascular diseases with the level of alternate transcripts increasing elevated in diseased hearts compared to healthy subjects. In many cases these isoforms appear to be the underlying cause of the disease, while in others they may be induced in response to cardiovascular pathologies. Regardless of this, the detection of alternate splicing events in the heart can serve as useful diagnostic or prognostic tools, while those splicing events that seem to play a causative role in cardiovascular disease make attractive future drug targets.

Mindin regulates vascular smooth muscle cell phenotype and prevents neointima formation

In the present study, using diverse in vitro and in vivo models, we revealed that mindin is a novel modulator of VSMC phenotype and neointima formation in an AKT-dependent manner in response to vascular injury.

Post-trauma administration of the pifithrin-α oxygen analog improves histological and functional outcomes after experimental traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Programmed death of neuronal cells plays a crucial role in acute and chronic neurodegeneration following TBI. The tumor suppressor protein p53, a transcription factor, has been recognized as an important regulator of apoptotic neuronal death. The p53 inactivator pifithrin-α (PFT-α) has been shown to be neuroprotective against stroke. A previous cellular study indicated that PFT-α oxygen analog (PFT-α (O)) is more stable and active than PFT-α. We aimed to investigate whether inhibition of p53 using PFT-α or PFT-α (O) would be a potential neuroprotective strategy for TBI. To evaluate whether these drugs protect against excitotoxicity in vitro, primary rat cortical cultures were challenged with glutamate (50mM) in the presence or absence of various concentrations of the p53 inhibitors PFT-α or PFT-α (O). Cell viability was estimated by LDH assay. In vivo, adult Sprague Dawley rats were subjected to controlled cortical impact (CCI, with 4m/s velocity, 2mm deformation). Five hours after injury, PFT-α or PFT-α (O) (2mg/kg, i.v.) was administered to animals. Sensory and motor functions were evaluated by behavioral tests at 24h after TBI. The p53-positive neurons were identified by double staining with cell-specific markers. Levels of mRNA encoding for p53-regulated genes (BAX, PUMA, Bcl-2 and p21) were measured by reverse transcription followed by real time-PCR from TBI animals without or with PFT-α/PFT-α (O) treatment. We found that PFT-α(O) (10 μM) enhanced neuronal survival against glutamate-induced cytotoxicity in vitro more effectively than PFT-α (10 μM). In vivo PFT-α (O) treatment enhanced functional recovery and decreased contusion volume at 24h post-injury. Neuroprotection by PFT-α (O) treatment also reduced p53-positive neurons in the cortical contusion region. In addition, p53-regulated PUMA mRNA levels at 8h were significantly reduced by PFT-α (O) administration after TBI. PFT-α (O) treatment also decreased phospho-p53 positive neurons in the cortical contusion region. Our data suggest that PFT-α (O) provided a significant reduction of cortical cell death and protected neurons from glutamate-induced excitotoxicity in vitro, as well as improved neurological functional outcome and reduced brain injury in vivo via anti-apoptotic mechanisms. The inhibition of p53-induced apoptosis by PFT-α (O) provides a useful tool to evaluate reversible apoptotic mechanisms and may develop into a novel therapeutic strategy for TBI.

Basic mechanisms in endoplasmic reticulum stress and relation to cardiovascular diseases

The folding process is an important step in protein synthesis for the functional shape or conformation of the protein. The endoplasmic reticulum (ER) is the main organelle for the correct folding procedure, which maintains the homeostasis of the organism. This process is normally well organized under unstressed conditions, whereas it may fail under oxidative and ER stress. The unfolded protein response (UPR) is a defense mechanism that removes the unfolded/misfolded proteins to prevent their accumulation, and two main degradation systems are involved in this defense, including the proteasome and autophagy. Cells decide which mechanism to use according to the type, severity, and duration of the stress. If the stress is too severe and in excess, the capacity of these degradation mechanisms, proteasomal degradation and autophagy, is not sufficient and the cell switches to apoptotic death. Because the accumulation of the improperly folded proteins leads to several diseases, it is important for the body to maintain this balance. Cardiovascular diseases are one of the important disorders related to failure of the UPR. Especially, protection mechanisms and the transition to apoptotic pathways have crucial roles in cardiac failure and should be highlighted in detailed studies to understand the mechanisms involved. This review is focused on the involvement of the proteasome, autophagy, and apoptosis in the UPR and the roles of these pathways in cardiovascular diseases.

Co-expression of POU4F2/Brn-3b with p53 may be important for controlling expression of pro-apoptotic genes in cardiomyocytes following ischaemic/hypoxic insults

Cardiomyocyte death following ischaemic/hypoxic injury causes irreversible damage to cardiac function and contributes to chronic diseases such as heart failure. Understanding the mechanisms associated with myocyte loss under these conditions can help to identify strategies to minimise/abrogate such detrimental effects. The p53 protein can induce apoptosis or cell cycle arrest, but effects on cell fate depend on interactions with other regulators such as POU4F2/Brn-3b (Brn-3b), which co-operates with p53 to increase the expression of pro-apoptotic genes. In contrast, the related POU4F1/Brn-3a (Brn-3a) blocks p53-mediated apoptosis but co-operates with p53 to enhance cell cycle arrest. In this study, we showed that permanent coronary artery ligation in mouse hearts, which induced apoptotic markers, activated caspase-3 and -8 and necroptosis markers; RIP-1 and -3 also increased Brn-3b and Brn-3a expression. However, Brn-3a was only detected in uninjured myocardium but not at the site of injury, whereas Brn-3b showed generalised increase, including within the infarct zone. Conversely, p53 was detected in the infarct zone and in some cells adjacent to the site of injury but not in uninjured myocardium. Co-localisation studies showed Brn-3a co-expression with p53 in cardiomyocytes adjacent to the infarct zone, whereas Brn-3b was co-localised with p53 in the infarct zone only. Increased Brn-3b and p53 correlated with elevated expression of pro-apoptotic target genes, Bax, Noxa and PUMA, whereas cleaved caspase-3 confirmed the presence of apoptotic cells within this region of the injured heart. Similarly, simulated ischaemia/reoxygenation (sI/R) injury in neonatal rat ventricular cardiomyocytes (NRVM) and heart derived H9c2 myoblasts increased Brn-3b, p53 as well as apoptotic genes, and this was associated with enhanced apoptosis. Furthermore, targeted reduction of Brn-3b using shRNA caused reduction in pro-apoptotic Bax and Noxa proteins, even though p53 expression remained intact, suggesting that Brn-3b is important for controlling the fate of the myocardium in the injured heart.

Lysine methyltransferase Smyd2 suppresses p53-dependent cardiomyocyte apoptosis

Apoptosis, or programmed cell death, is an essential physiological process for proper embryogenesis as well as for homeostasis during aging. In addition, apoptosis is one of the major mechanisms causing cell loss in pathophysiological conditions such as heart failure. Thus, inhibition of apoptosis is an important approach for preventive and therapeutic strategies. Here we show that the histone 3 lysine 4- and lysine 36-specific methyltransferase Smyd2 acts as an endogenous antagonistic player of p53-dependent cardiomyocyte apoptosis. Smyd2 protein levels were significantly decreased in cardiomyocytes upon cobalt chloride-induced apoptosis or myocardial infarction, while p53 expression was enhanced. siRNA-mediated knockdown of Smyd2 in cultured cardiomyocytes further enhanced cobalt chloride-induced cardiomyocyte apoptosis. In contrast, Smyd2 overexpression resulted in marked methylation of p53 and prevented its accumulation as well as apoptotic cell death in an Hsp90-independent manner. Moreover, overexpression, of Smyd2, but not Smyd2Y240F lacking a methyl transferase activity, significantly rescued CoCl2-induced apoptosis in H9c2 cardioblasts. Finally, Smyd2 cardiomyocyte-specific deletion in vivo promoted apoptotic cell death upon myocardial infarction, which correlated with enhanced expression of p53 and pro-apoptotic Bax. Collectively, our data indicate Smyd2 as a cardioprotective protein by methylating p53.

Unique transcriptional profile of sustained ligand-activated preconditioning in pre- and post-ischemic myocardium

Background

Opioidergic SLP (sustained ligand-activated preconditioning) induced by 3–5 days of opioid receptor (OR) agonism induces persistent protection against ischemia-reperfusion (I-R) injury in young and aged hearts, and is mechanistically distinct from conventional preconditioning responses. We thus applied unbiased gene-array interrogation to identify molecular effects of SLP in pre- and post-ischemic myocardium.

Methodology/Principal Findings

Male C57Bl/6 mice were implanted with 75 mg morphine or placebo pellets for 5 days. Resultant SLP did not modify cardiac function, and markedly reduced dysfunction and injury in perfused hearts subjected to 25 min ischemia/45 min reperfusion. Microarray analysis identified 14 up- and 86 down-regulated genes in normoxic hearts from SLP mice (≥1.3-fold change, FDR≤5%). Induced genes encoded sarcomeric/contractile proteins (Myh7, Mybpc3,Myom2,Des), natriuretic peptides (Nppa,Nppb) and stress-signaling elements (Csda,Ptgds). Highly repressed genes primarily encoded chemokines (Ccl2,Ccl4,Ccl7,Ccl9,Ccl13,Ccl3l3,Cxcl3), cytokines (Il1b,Il6,Tnf) and other proteins involved in inflammation/immunity (C3,Cd74,Cd83, Cd86,Hla-dbq1,Hla-drb1,Saa1,Selp,Serpina3), together with endoplasmic stress proteins (known: Dnajb1,Herpud1,Socs3; putative: Il6, Gadd45g,Rcan1) and transcriptional controllers (Egr2,Egr3, Fos,Hmox1,Nfkbid). Biological themes modified thus related to inflammation/immunity, together with cellular/cardiovascular movement and development. SLP also modified the transcriptional response to I-R (46 genes uniquely altered post-ischemia), which may influence later infarction/remodeling. This included up-regulated determinants of cellular resistance to oxidant (Mgst3,Gstm1,Gstm2) and other forms of stress (Xirp1,Ankrd1,Clu), and repression of stress-response genes (Hspa1a,Hspd1,Hsp90aa,Hsph1,Serpinh1) and Txnip.

Conclusions

Protection via SLP is associated with transcriptional repression of inflammation/immunity, up-regulation of sarcomeric elements and natriuretic peptides, and modulation of cell stress, growth and development, while conventional protective molecules are unaltered.

Deletion of MCL-1 causes lethal cardiac failure and mitochondrial dysfunction

MCL-1 is an essential BCL-2 family member that promotes the survival of multiple cellular lineages, but its role in cardiac muscle has remained unclear. Here, we report that cardiac-specific ablation of Mcl-1 results in a rapidly fatal, dilated cardiomyopathy manifested by a loss of cardiac contractility, abnormal mitochondria ultrastructure, and defective mitochondrial respiration. Strikingly, genetic ablation of both proapoptotic effectors (Bax and Bak) could largely rescue the lethality and impaired cardiac function induced by Mcl-1 deletion. However, while the overt consequences of Mcl-1 loss were obviated by combining with the loss of Bax and Bak, mitochondria from the Mcl-1-, Bax-, and Bak-deficient hearts still revealed mitochondrial ultrastructural abnormalities and displayed deficient mitochondrial respiration. Together, these data indicate that merely blocking cell death is insufficient to completely overcome the need for MCL-1 function in cardiomyocytes and suggest that in cardiac muscle, MCL-1 also facilitates normal mitochondrial function. These findings are important, as specific MCL-1-inhibiting therapeutics are being proposed to treat cancer cells and may result in unexpected cardiac toxicity.

A pre-microRNA-149 (miR-149) genetic variation affects miR-149 maturation and its ability to regulate the Puma protein in apoptosis

MicroRNAs (miRNAs) are small, single-stranded, noncoding RNAs that function as negative regulators of gene expression. They are transcribed from endogenous DNA and form hairpin structures (termed as pre-miRNAs) that are processed to form mature miRNAs. It remains largely unknown as to the molecular consequences of the natural genetic variation in pre-miRNAs. Here, we report that an A→G polymorphism (rs71428439) is located in Homo sapiens miR-149 stem-loop region. This polymorphism results in a change in the structure of the miR-149 precursor. Our results showed that the genotype distribution of this polymorphism in myocardial infarction cases was significantly different from that in the control subjects. We examined the biological significance of this polymorphism on the production of mature miR-149, and we observed that the G-allelic miR-149 precursor displayed a lower production of mature miR-149 compared with the A-allelic one. Further investigations disclosed that miR-149 could withstand mitochondrial fission and apoptosis through targeting the pro-apoptotic factor p53-up-regulated modulator of apoptosis (Puma). Enforced expression of miR-149 promoted cell survival, whereas knockdown of miR-149 rendered cells to be sensitive to apoptotic stimulation. Intriguingly, the A to G variation led pre-miR-149 to elicit an attenuated effect on the inhibition of mitochondrial fission and apoptosis. Finally, this polymorphism exerts its influence on cardiac function in the mouse model of myocardial infarction. These data suggest that this polymorphism in the miR-149 precursor may result in important phenotypic traits of myocardial infarction. Our findings warrant further investigations on the relationship between miR-149 polymorphism and myocardial infarction.

Cell death in the myocardium: my heart won't go on

Loss of cardiomyocytes plays a critical role in the pathogenesis of heart failure. With fewer myocytes, the heart is unable to sustain efficient contraction. Much attention has been focused on understanding mechanisms of cell death in myocytes with the ultimate goal being to reduce the extent of injury and improve function in the failing myocardium. Both necrosis and apoptosis contribute to loss of myocytes, and this loss of cells is a hallmark of cardiac pathologies, including ischemia/reperfusion, myocardial infarction, and heart failure. Apoptosis is a highly regulated process that is activated via death receptors in the plasma membrane or via permeabilization of the mitochondria. Necrosis is generally viewed as an uncontrolled process that leads to mitochondrial swelling, cell rupture, and subsequent inflammation. However, recent studies have uncovered a signaling pathway that mediates regulated necrosis or necroptosis. Mitochondria play an important role in both apoptosis and necrosis, and changes in their morphology can affect the cells' susceptibility to stress. This review focuses on the various modes of cell death in the myocardium and highlights how they contribute to loss of myocytes in response to stress.

Myocardial Ablation of G Protein-Coupled Receptor Kinase 2 (GRK2) Decreases Ischemia/Reperfusion Injury through an Anti-Intrinsic Apoptotic Pathway

Studies from our lab have shown that decreasing myocardial G protein–coupled receptor kinase 2 (GRK2) activity and expression can prevent heart failure progression after myocardial infarction. Since GRK2 appears to also act as a pro-death kinase in myocytes, we investigated the effect of cardiomyocyte-specific GRK2 ablation on the acute response to cardiac ischemia/reperfusion (I/R) injury. To do this we utilized two independent lines of GRK2 knockout (KO) mice where the GRK2 gene was deleted in only cardiomyocytes either constitutively at birth or in an inducible manner that occurred in adult mice prior to I/R. These GRK2 KO mice and appropriate control mice were subjected to a sham procedure or 30 min of myocardial ischemia via coronary artery ligation followed by 24 hrs reperfusion. Echocardiography and hemodynamic measurements showed significantly improved post-I/R cardiac function in both GRK2 KO lines, which correlated with smaller infarct sizes in GRK2 KO mice compared to controls. Moreover, there was significantly less TUNEL positive myocytes, less caspase-3, and -9 but not caspase-8 activities in GRK2 KO mice compared to control mice after I/R injury. Of note, we found that lowering cardiac GRK2 expression was associated with significantly lower cytosolic cytochrome C levels in both lines of GRK2 KO mice after I/R compared to corresponding control animals. Mechanistically, the anti-apoptotic effects of lowering GRK2 expression were accompanied by increased levels of Bcl-2, Bcl-xl, and increased activation of Akt after I/R injury. These findings were reproduced in vitro in cultured cardiomyocytes and GRK2 mRNA silencing. Therefore, lowering GRK2 expression in cardiomyocytes limits I/R-induced injury and improves post-ischemia recovery by decreasing myocyte apoptosis at least partially via Akt/Bcl-2 mediated mitochondrial protection and implicates mitochondrial-dependent actions, solidifying GRK2 as a pro-death kinase in the heart.

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

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

Mitochondria and mitophagy: the yin and yang of cell death control

Mitochondria are primarily responsible for providing the contracting cardiac myocyte with a continuous supply of ATP. However, mitochondria can rapidly change into death-promoting organelles. In response to changes in the intracellular environment, mitochondria become producers of excessive reactive oxygen species and release prodeath proteins, resulting in disrupted ATP synthesis and activation of cell death pathways. Interestingly, cells have developed a defense mechanism against aberrant mitochondria that can cause harm to the cell. This mechanism involves selective sequestration and subsequent degradation of the dysfunctional mitochondrion before it causes activation of cell death. Induction of mitochondrial autophagy, or mitophagy, results in selective clearance of damaged mitochondria in cells. In response to stress such as ischemia/reperfusion, prosurvival and prodeath pathways are concomitantly activated in cardiac myocytes. Thus, there is a delicate balance between life and death in the myocytes during stress, and the final outcome depends on the complex cross-talk between these pathways. Mitophagy functions as an early cardioprotective response, favoring adaptation to stress by removing damaged mitochondria. In contrast, increased oxidative stress and apoptotic proteases can inactivate mitophagy, allowing for the execution of cell death. Herein, we discuss the importance of mitochondria and mitophagy in cardiovascular health and disease and provide a review of our current understanding of how these processes are regulated.

Pifithrin-α enhances the survival of transplanted neural stem cells in stroke rats by inhibiting p53 nuclear translocation

AIMS

To examine a novel strategy to enhance the survival of grafted neural stem cells (NSCs) in stroke model.

METHODS

Using a cell counting kit-8 (CCK-8) and TUNEL assay to test the protective effects of p53 inhibitor, pifithrin-α (PFT-α), on oxygen glucose deprivation (OGD) in NSCs. We compared the effects of vehicle + NSCs and FFT-α + NSCs on the efficacy of transplantation in stroke rat model using behavioral analysis, immunohistochemistry, etc.

RESULTS

Pifithrin-α increased viability and decreased apoptosis in NSCs after OGD in vitro. By in vivo studies, we showed that the best recovery of neurological function in the stroke rats and the maximum survival of grafted NSCs were found in the PFT-α + NSCs group. Twelve hours after cell transplantation, p53 was localized to the nuclei of grafted NSCs in the vehicle + NSCs group but was primarily localized to the cytoplasm in the PFT-α + NSCs group. The p53-upregulated modulator of apoptosis (PUMA) was highly expressed among the grafted cells in the vehicle + NSCs group compared with that in the PFT-α + NSCs group.

CONCLUSION

Our results indicate that PFT-α enhances the survival of grafted NSCs through the inhibition of p53 translocation into the nucleus.

The changes of calretinin immunoreactivity in paraquat-induced nephrotoxic rats

Calcium-binding proteins are present in the kidneys: calbindin D-28k in the distal tubules and calretinin in the proximal tubules. Since paraquat causes degeneration in the brush border-bearing proximal tubule cells in rat kidneys, we investigated the changes of calretinin immunoreactivity in the proximal tubule cells of paraquat-induced nephrotoxicity in experimental male Sprague-Dawley rats following chitosan oligosaccharide pretreatment to investigate its protective properties. Paraquat (60 mg/kg) was administered intraperitoneally with or without chitosan oligosaccharide (500 mg/kg, p.o.) pretreatment. The changes on calretinin were compared with those of calbindin D-28k by immunohistochemistry and Western Blot analysis. Calretinin was immunolocalized on the apical surface of proximal tubule cells in the deeper cortex of normal kidney, and disappeared after paraquat administration with minor changes of calbindin D-28k immunoreactivity in the distal tubules and collecting ducts. Chitosan oligosaccharide pretreatment caused increased expression of calretinin and calbindin D-28k before paraquat injection and helped preserve proximal tubules after paraquat treatment. However, Western blot analysis on calretinin and calbindin D-28k could not explain the degeneration of the proximal tubule cells in paraquat-induced nephrotoxicity. These findings suggested that calretinin is a possible and more useful histopathological marker for proximal tubule cells in paraquat-induced nephrotoxic rats.