Overexpression of Nrdp1 in the heart exacerbates doxorubicin-induced cardiac dysfunction in mice

The E3 ubiquitin ligases regulate inflammation in cardiovascular diseases

Accumulating evidence has illustrated that the E3 ubiquitin ligases critically participate in the development and progression of cardiovascular diseases. Dysregulation of E3 ubiquitin ligases exacerbates cardiovascular diseases. Blockade or activation of E3 ubiquitin ligases mitigates cardiovascular performance. Therefore, in this review, we mainly introduced the critical role and underlying molecular mechanisms of E3 ubiquitin ligase NEDD4 family in governing the initiation and progression of cardiovascular diseases, including ITCH, WWP1, WWP2, Smurf1, Smurf2, Nedd4-1 and Nedd4-2. Moreover, the functions and molecular insights of other E3 ubiquitin ligases, such as F-box proteins, in cardiovascular disease development and malignant progression are described. Furthermore, we illustrate several compounds that alter the expression of E3 ubiquitin ligases to alleviate cardiovascular diseases. Therefore, modulation of E3 ubiquitin ligases could be a novel and promising strategy for improvement of therapeutic efficacy of deteriorative cardiovascular diseases.

Molecular mechanisms of anthracycline induced cardiotoxicity: Zebrafish come into play

Anthracyclines are among the most potent chemotherapeutics; however, cardiotoxicity significantly restricts their use. Indeed, anthracycline-induced cardiotoxicity (AIC) fares among the worst types of cardiomyopathy, and may only slowly and partially respond to standard heart failure therapies including β-blockers and ACE inhibitors. No therapy specifically designed to treat anthracycline cardiomyopathy at present, and neither is it known if any such strategy could be developed. To address this gap and to elucidate the molecular basis of AIC with a therapeutic goal in mind, zebrafish has been introduced as an in vivo vertebrate model about a decade ago. Here, we first review our current understanding of the basic molecular and biochemical mechanisms of AIC, and then the contribution of zebrafish to the AIC field. We summarize the generation of embryonic zebrafish AIC models (eAIC) and their use for chemical screening and assessment of genetic modifiers, and then the generation of adult zebrafish AIC models (aAIC) and their use for discovering genetic modifiers via forward mutagenesis screening, deciphering spatial-temporal-specific mechanisms of modifier genes, and prioritizing therapeutic compounds via chemical genetic tools. Several therapeutic target genes and related therapies have emerged, including a retinoic acid (RA)-based therapy for the early phase of AIC and an autophagy-based therapy that, for the first time, is able to reverse cardiac dysfunction in the late phase of AIC. We conclude that zebrafish is becoming an important in vivo model that would accelerate both mechanistic studies and therapeutic development of AIC.

Insights on the molecular targets of cardiotoxicity induced by anticancer drugs: A systematic review based on proteomic findings

Several anticancer agents have been associated with cardiac toxic effects. The currently proposed mechanisms to explain cardiotoxicity differ among anticancer agents, but in fact, the specific modulation is not completely elucidated. Thus, this systematic review aims to provide an integrative perspective of the molecular mechanisms underlying the toxicity of anticancer agents on heart muscle while using a high-throughput technology, mass spectrometry (MS)-based proteomics. A literature search using PubMed database led to the selection of 27 studies, of which 13 reported results exclusively on animal models, 13 on cardiomyocyte-derived cell lines and only one included both animal and a cardiomyocyte line. The reported anticancer agents were the proteasome inhibitor carfilzomib, the anthracyclines daunorubicin, doxorubicin, epirubicin and idarubicin, the antimicrotubule agent docetaxel, the alkylating agent melphalan, the anthracenedione mitoxantrone, the tyrosine kinase inhibitors (TKIs) erlotinib, lapatinib, sorafenib and sunitinib, and the monoclonal antibody trastuzumab. Regarding the MS-based proteomic approaches, electrophoretic separation using two-dimensional (2D) gels coupled with tandem MS (MS/MS) and liquid chromatography-MS/MS (LC-MS/MS) were the most common. Overall, the studies highlighted 1826 differentially expressed proteins across 116 biological processes. Most of them were grouped in larger processes and critically analyzed in the present review. The selection of studies using proteomics on heart muscle allowed to obtain information about the anticancer therapy-induced modulation of numerous proteins in this tissue and to establish connections that have been disregarded in other studies. This systematic review provides interesting points for a comprehensive understanding of the cellular cardiotoxicity mechanisms of different anticancer drugs.

Understanding Anthracycline Cardiotoxicity From Mitochondrial Aspect

Anthracyclines, such as doxorubicin, represent one group of chemotherapy drugs with the most cardiotoxicity. Despite that anthracyclines are capable of treating assorted solid tumors and hematological malignancies, the side effect of inducing cardiac dysfunction has hampered their clinical use. Currently, the mechanism underlying anthracycline cardiotoxicity remains obscure. Increasing evidence points to mitochondria, the energy factory of cardiomyocytes, as a major target of anthracyclines. In this review, we will summarize recent findings about mitochondrial mechanism during anthracycline cardiotoxicity. In particular, we will focus on the following aspects: 1) the traditional view about anthracycline-induced reactive oxygen species (ROS), which is produced by mitochondria, but in turn causes mitochondrial injury. 2) Mitochondrial iron-overload and ferroptosis during anthracycline cardiotoxicity. 3) Autophagy, mitophagy and mitochondrial dynamics during anthracycline cardiotoxicity. 4) Anthracycline-induced disruption of cardiac metabolism.

atg7-Based Autophagy Activation Reverses Doxorubicin-Induced Cardiotoxicity

[Figure: see text].

The Interplay Between Autophagy and Senescence in Anthracycline Cardiotoxicity

PURPOSE OF REVIEW

Doxorubicin (DOXO) is a highly effective chemotherapeutic drug employed for the treatment of a wide spectrum of cancers, spanning from solid tumours to haematopoietic malignancies. However, its clinical use is hampered by severe and dose-dependent cardiac side effects that ultimately lead to heart failure (HF).

RECENT FINDINGS

Mitochondrial dysfunction and oxidative stress are well-established mechanisms of DOXO-induced cardiotoxicity, although recent evidence suggests that deregulation of other biological processes, like autophagy, could be involved. It is increasingly recognized that autophagy deregulation is intimately interconnected with the initiation of detrimental cellular responses, including autosis and senescence, raising the possibility of using autophagy modulators as well as senolytics and senomorphics for preventing DOXO cardiotoxicity. This review aims at providing an overview of the signalling pathways that are common to autophagy and senescence, with a special focus on how the relationship between these two processes is deregulated in response to cardiotoxic treatments. Finally, we will discuss the potential therapeutic utility of drugs modulating autophagy and/or senescence for counteracting DOXO cardiotoxicity.

Role of the Nrdp1 in Brain Injury Induced by Chronic Intermittent Hypoxia in Rats via Regulating the Protein Levels of ErbB3

Obstructive sleep apnea syndrome (OSAS) is known as a repeated obstruction of the upper airway during sleep, leading to generalized hypoxia episodes and associated with cardiovascular and cerebrovascular diseases. We mainly explored the role of neuregulin receptor degradation protein-1 (Nrdp1, also known as FLRF) in brain injury induced by chronic intermittent hypoxia (CIH) in rats. Wistar rats were randomly divided into 4 groups (n = 12 per group), including the sham + adeno-associated virus-NC (AAV-NC) group, the sham + AAV-siNrdp1 group, the IH-4w (intermittent hypoxia for 4 weeks) + AAV-NC group, and the IH-4w + AAV-siNrdp1 group. Morphologic changes in brain tissue were observed by hematoxylin and eosin (HE) staining. Apoptosis in the hippocampus was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining. Spatial learning and memory were assessed by the Morris water maze test. The expression of Nrdp1 mRNA and protein in the hippocampus was detected by qualitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. The concentration of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in serum was detected via enzyme-linked immunosorbent assay (ELISA) kits. Nrdp1 expression was increased after intermittent hypoxia exposure over time. Western blotting and H&E results showed that pathological changes of hippocampus neurons in chronic intermittent hypoxia rat were diminished by shNrdp1. Western blotting and TUNEL staining showed that apoptotic cells in the hippocampus of CIH rats were decreased by shNrdp1. The Morris water maze results proved that shNrdp1 improved spatial learning performance of chronic intermittent hypoxia rats. ELISA kits results showed that CIH-induced inflammatory response was decreased by shNrdp1. Western blotting and qRT-PCR results showed protein expression of ErbB3 in the hippocampus of CIH rats. Nrdp1 could regulate ErbB3 protein levels in brain-injured rats with CIH, which demonstrates that Nrdp1 is a potential therapeutic target in the cognition deficits associated with OSAS.

Nrdp1 increases neuron apoptosis via downregulation of Bruce following intracerebral haemorrhage

Background

Neuregulin receptor degradation protein-1 (Nrdp1) is an E3 ubiquitin ligase that plays an important role in regulating cell growth, apoptosis and oxidative stress. However, the data regarding its expression and exact mechanism in neuronal injury following ICH has not been well identified.

Methods

In this study, primary cortical neurons from C57BL/6 mice were subjected to erythrocyte lysates. Nrdp1 expression, cell apoptosis, caspase-3 and BRUCE levels were detected. In addition, inflammatory response, brain edema, and neurological injury in ICH mice were also assessed.

Results

We found that the expression of Nrdp1 was significantly increased in neuron cells accompanied by up-regulation of active caspase-3 and decreased expression of BRUCE (an inhibitor of apoptosis protein). However, inhibiting Nrdp1 levels of neurons reduced caspase-3 activity but induced up-regulation of BRUCE. In vivo, inhibiting Nrdp1 levels increased pro-inflammatory cytokines, brain edema, and neurological injury following ICH.

Conclusions

Taken together, the data suggested that Nrdp1 might play a crucial role in neuronal apoptosis via inhibiting BRUCE following ICH.

Carvedilol (CAR) combined with carnosic acid (CAA) attenuates doxorubicin-induced cardiotoxicity by suppressing excessive oxidative stress, inflammation, apoptosis and autophagy

Doxorubicin (DOX) is a wide spectrum antitumor drug. However, its clinical application is limited due to the cardiotoxicity. Carvedilol (CAR) is a β-blocker used to treat high blood pressure and heart failure. Accordingly, supplementation with natural antioxidants or plant extracts exerts protective effects against various injury in vivo. Carnosic acid (CAA), the principal constituent of rosemary, has various biological activities, including antioxidant, antitumor, and anti-inflammatory. Here, heart injury mouse model was established using DOX (20 mg/kg) in vivo. And cardiac muscle cell line of H9C2 was subjected to 0.5 μM of DOX for 24 h in vitro. Then, the protective effects of CAA and CAR alone, or the two in combination on DOX-induced cardiotoxicity in vivo and in vitro were explored. The results indicated that both CAA and CAR, when used alone, were moderately effective in attenuating DOX-induced cardiotoxicity. The combination of two drugs functioned synergistically to ameliorate cardiac injury caused by DOX, as evidenced by the significantly reduced collagen accumulation and improved dysfunction of heart. CAA and CAR exhibited stronger anti-oxidative role in DOX-treated mice partly by augmenting the expression and activities of the anti-oxidative enzymes. In addition, inflammatory response was significantly suppressed by the two in combination, proved by the decreased pro-inflammatory cytokines (COX2, TNF-α, IL-6, IL-1β and IL-18), which was associated with the inactivation of nuclear factor κB (NF-κB). Furthermore, DOX-stirred apoptosis and autophagy were dramatically attenuated by the co-treatments of CAA and CAR through down-regulating cleaved Caspase-3 and LC3B signaling pathways. The effects of CAA and CAR combination against cardiotoxicity were observed in H9C2 cells with DOX stimulation. Our findings above suggested that the use of CAR and CAA in combination could be expected to have synergistic efficacy and significant potential against cardiotoxicity induced by DOX.

Nrdp1 Increases Ischemia Induced Primary Rat Cerebral Cortical Neurons and Pheochromocytoma Cells Apoptosis Via Downregulation of HIF-1α Protein

Neuregulin receptor degradation protein-1 (Nrdp1) is an E3 ubiquitin ligase that targets proteins for degradation and regulates cell growth, apoptosis and oxidative stress in various cell types. We have previously shown that Nrdp1 is implicated in ischemic cardiomyocyte death. In this study, we investigated the change of Nrdp1 expression in ischemic neurons and its role in ischemic neuronal injury. Primary rat cerebral cortical neurons and pheochromocytoma (PC12) cells were infected with adenoviral constructs expressing Nrdp1 gene or its siRNA before exposing to oxygen-glucose deprivation (OGD) treatment. Our data showed that Nrdp1 was upregulated in ischemic brain tissue 3 h after middle cerebral artery occlusion (MCAO) and in OGD-treated neurons. Of note, Nrdp1 overexpression by Ad-Nrdp1 enhanced OGD-induced neuron apoptosis, while knockdown of Nrdp1 with siRNA attenuated this effect, implicating a role of Nrdp1 in ischemic neuron injury. Moreover, Nrdp1 upregulation is accompanied by increased protein ubiquitylation and decreased protein levels of ubiquitin-specific protease 8 (USP8) in OGD-treated neurons, which led to a suppressed interaction between USP8 and HIF-1α and subsequently a reduction in HIF-1α protein accumulation in neurons under OGD conditions. In conclusion, our data support an important role of Nrdp1 upregulation in ischemic neuronal death, and suppressing the interaction between USP8 and HIF-1α and consequently the hypoxic adaptive response of neurons may account for this detrimental effect.

Transcriptional Effects of E3 Ligase Nrdp1 on Hypertrophy in Neonatal Rat Cardiomyocytes by Microarray and Integrated Gene Network Analysis

Objective: Neuregulin receptor degradation protein-1 (Nrdp1) is a novel E3 ubiquitin ligase, and we have previously shown that overexpression of Nrdp1 increased cardiomyocyte injury. However, the role of Nrdp1 in myocardial hypertrophy is unclear. In the present study, we clarified the molecular mechanisms of angiotensin II (Ang II)-induced cardiomyocyte hypertrophy regulated by Nrdp1 based on genome-wide transcriptional analysis. Methods: Neonatal rat cardiomyocytes were infected with adenoviruses containing green fluorescent protein (Ad-GFP) or wild-type Nrdp1 (Ad-Nrdp1), and then treated with Ang II for 36 h. Detection of differentially expressed genes was achieved with an Affymetrix Rat Gene 2.0 Array and Cluster and Java TreeView software. Results and Conclusion: Microarray data analysis demonstrated that Nrdp1 overexpression affected the expression of 12,140 mRNA genes in Ang II-induced cardiomyocyte hypertrophy, including the upregulation of 12,044 and the downregulation of 96. Gene ontology and globe signal transduction network analysis showed that Nrdp1 affected the expression of many genes related to stimulus response, the cell receptor pathway, and cell growth. Pathway network analysis identified myocardial metabolism, DNA replication, and the cell cycle as the most important pathways targeted by Nrdp1. lncRNA-mRNA coexpression network analysis showed that two core lncRNAs, NONRATT057160 and NONRATT054243, were involved in cardiomyotrophy regulated by Nrdp1 in cardiomyocytes. Taken together, these data provide compelling clues for further exploration of the function of Nrdp1 in heart disease.

Microarray and Co-expression Network Analysis of Genes Associated with Acute Doxorubicin Cardiomyopathy in Mice

Clinical use of doxorubicin (DOX) in cancer therapy is limited by its dose-dependent cardiotoxicity. But molecular mechanisms underlying this phenomenon have not been well defined. This study was to investigate the effect of DOX on the changes of global genomics in hearts. Acute cardiotoxicity was induced by giving C57BL/6J mice a single intraperitoneal injection of DOX (15 mg/kg). Cardiac function and apoptosis were monitored using echocardiography and TUNEL assay at days 1, 3 and 5. Myocardial glucose and ATP levels were measured. Microarray assays were used to screen gene expression profiles in the hearts at day 5, and the results were confirmed with qPCR analysis. DOX administration caused decreased cardiac function, increased cardiomyocyte apoptosis and decreased glucose and ATP levels. Microarrays showed 747 up-regulated genes and 438 down-regulated genes involved in seven main functional categories. Among them, metabolic pathway was the most affected by DOX. Several key genes, including 2,3-bisphosphoglycerate mutase (Bpgm), hexokinase 2, pyruvate dehydrogenase kinase, isoenzyme 4 and fructose-2,6-bisphosphate 2-phosphatase, are closely related to glucose metabolism. Gene co-expression networks suggested the core role of Bpgm in DOX cardiomyopathy. These results obtained in mice were further confirmed in cultured cardiomyocytes. In conclusion, genes involved in glucose metabolism, especially Bpgm, may play a central role in the pathogenesis of DOX-induced cardiotoxicity.

The ER structural protein Rtn4A stabilizes and enhances signaling through the receptor tyrosine kinase ErbB3

ErbB3 and ErbB4 are receptor tyrosine kinases that are activated by the neuregulin (NRG) family of growth factors. These receptors govern various developmental processes, and their dysregulation contributes to several human disease states. The abundance of ErbB3 and ErbB4, and thus signaling through these receptors, is limited by the E3 ubiquitin ligase Nrdp1, which targets ErbB3 and ErbB4 for degradation. Reticulons are proteins that influence the morphology of the endoplasmic reticulum (ER) by promoting the formation of tubules, a response of cells to some stressors. We found that the ER structural protein reticulon 4A (Rtn4A, also known as Nogo-A) increased ErbB3 abundance and proliferative signaling by suppressing Nrdp1 function. Rtn4A interacted with Nrdp1 and stabilized ErbB3 in an Nrdp1-dependent manner. Rtn4A overexpression induced the redistribution of Nrdp1 from a cytosolic or perinuclear localization to ER tubules. Rtn4A knockdown in human breast tumor cells decreased ErbB3 abundance, NRG-stimulated signaling, and cellular proliferation and migration. Because proteins destined for the plasma membrane are primarily synthesized in the sheet portions of the ER, our observations suggest that Rtn4A counteracts the Nrdp1-mediated degradation of ErbB3 by sequestering the ubiquitin ligase into ER tubules. The involvement of a reticulon suggests a molecular link between ER structure and the sensitivity of cells to receptor tyrosine kinase-mediated survival signals at the cell surface.

Doxorubicin Blocks Cardiomyocyte Autophagic Flux by Inhibiting Lysosome Acidification

BACKGROUND

The clinical use of doxorubicin is limited by cardiotoxicity. Histopathological changes include interstitial myocardial fibrosis and the appearance of vacuolated cardiomyocytes. Whereas dysregulation of autophagy in the myocardium has been implicated in a variety of cardiovascular diseases, the role of autophagy in doxorubicin cardiomyopathy remains poorly defined.

METHODS AND RESULTS

Most models of doxorubicin cardiotoxicity involve intraperitoneal injection of high-dose drug, which elicits lethargy, anorexia, weight loss, and peritoneal fibrosis, all of which confound the interpretation of autophagy. Given this, we first established a model that provokes modest and progressive cardiotoxicity without constitutional symptoms, reminiscent of the effects seen in patients. We report that doxorubicin blocks cardiomyocyte autophagic flux in vivo and in cardiomyocytes in culture. This block was accompanied by robust accumulation of undegraded autolysosomes. We go on to localize the site of block as a defect in lysosome acidification. To test the functional relevance of doxorubicin-triggered autolysosome accumulation, we studied animals with diminished autophagic activity resulting from haploinsufficiency for Beclin 1. Beclin 1(+/-) mice exposed to doxorubicin were protected in terms of structural and functional changes within the myocardium. Conversely, animals overexpressing Beclin 1 manifested an amplified cardiotoxic response.

CONCLUSIONS

Doxorubicin blocks autophagic flux in cardiomyocytes by impairing lysosome acidification and lysosomal function. Reducing autophagy initiation protects against doxorubicin cardiotoxicity.

Chemical Endoplasmic Reticulum Chaperone Alleviates Doxorubicin-Induced Cardiac Dysfunction

RATIONALE

Doxorubicin is an effective chemotherapeutic agent for cancer, but its use is often limited by cardiotoxicity. Doxorubicin causes endoplasmic reticulum (ER) dilation in cardiomyocytes, and we have demonstrated that ER stress plays important roles in the pathophysiology of heart failure.

OBJECTIVE

We evaluated the role of ER stress in doxorubicin-induced cardiotoxicity and examined whether the chemical ER chaperone could prevent doxorubicin-induced cardiac dysfunction.

METHODS AND RESULTS

We confirmed that doxorubicin caused ER dilation in mouse hearts, indicating that doxorubicin may affect ER function. Doxorubicin activated an ER transmembrane stress sensor, activating transcription factor 6, in cultured cardiomyocytes and mouse hearts. However, doxorubicin suppressed the expression of genes downstream of activating transcription factor 6, including X-box binding protein 1. The decreased levels of X-box binding protein 1 resulted in a failure to induce the expression of the ER chaperone glucose-regulated protein 78 which plays a major role in adaptive responses to ER stress. In addition, doxorubicin activated caspase-12, an ER membrane-resident apoptotic molecule, which can lead to cardiomyocyte apoptosis and cardiac dysfunction. Cardiac-specific overexpression of glucose-regulated protein 78 by adeno-associated virus 9 or the administration of the chemical ER chaperone 4-phenylbutyrate attenuated caspase-12 cleavage, and alleviated cardiac apoptosis and dysfunction induced by doxorubicin.

CONCLUSIONS

Doxorubicin activated the ER stress-initiated apoptotic response without inducing the ER chaperone glucose-regulated protein 78, further augmenting ER stress in mouse hearts. Cardiac-specific overexpression of glucose-regulated protein 78 or the administration of the chemical ER chaperone alleviated the cardiac dysfunction induced by doxorubicin and may facilitate the safe use of doxorubicin for cancer treatment.

Circulating E3 ligases are novel and sensitive biomarkers for diagnosis of acute myocardial infarction

Ubiquitin ligase (E3) is a decisive element of the ubiquitin-proteasome system (UPS), which is the main pathway for intracellular protein turnover. Recently, circulating E3 ligases have been increasingly considered as cancer biomarkers. In the present study, we aimed to determine if cardiac-specific E3 ligases in circulation can serve as novel predictors for early diagnosis of acute myocardial infarction (AMI). By screening and verifying their tissue expression patterns with microarray and real-time PCR analysis, six of 261 E3 ligases, including cardiac-specific Rnf207 and cardiac- and muscle-enriched Fbxo32/atrogin-1, Trim54/MuRF3, Trim63/MuRF1, Kbtbd10/KLHL41, Asb11 and Asb2 in mouse heart, were selected for the present study. In the AMI rats, the levels of five E3 ligases including Rnf207, Fbxo32, Trim54, Trim63 and Kbtbd10 in the plasma were significantly increased compared with control animals. Especially, the plasma levels of Rnf207 was markedly increased at 1 h, peaked at 3 h and decreased at 6-24 h after ligation. Further evaluation of E3 ligases in AMI patients confirmed that plasma Rnf207 level increased significantly compared with that in healthy people and patients without AMI, and showed a similar time course to that in AMI rats. Simultaneously, plasma level of cardiac troponin I (cTnI) was measured by ELISA assays. Finally, receiver operating characteristic (ROC) curve analysis indicated that Rnf207 showed a similar sensitivity and specificity to the classic biomarker troponin I for diagnosis of AMI. Increased cardiac-specific E3 ligase Rnf207 in plasma may be a novel and sensitive biomarkers for AMI in humans.

Nrdp1 is Associated with Neuronal Apoptosis in Lipopolysaccharide-Induced Neuroinflammation

Neuregulin receptor degradation protein-1 (Nrdp1), a kind of ring finger E3 ubiquitin ligase, is expressed in several adult tissues, including the heart, testis, prostate and brain. Studies of this molecule have demonstrated its great importance in regulating cell growth, apoptosis and oxidative stress in various cell types. However, information regarding its expression and possible function in the central nervous system is still limited. In this study, we performed a neuroinflammation model by lipopolysaccharide (LPS) lateral ventral injection in adult rats. It was found that the expression of Nrdp1 was significantly increased in cerebral cortex after LPS injection. Immunofluorescence indicated that Nrdp1 was located in the neurons, but not astrocytes or microglia. Furthermore, there was a concomitant up-regulation of active caspase-3 and decreased expression of BRUCE (an inhibitor of apoptosis protein). In addition, decreasing Nrdp1 levels by RNA interference in cortical primary neurons reduced active caspase-3 expression but induced up-regulation of BRUCE. Collectively, all these results suggested that Nrdp1 might play a role in neuronal apoptosis by reducing the expression of BRUCE in neuroinflammation after LPS injection.

Lower expression of Nrdp1 in human glioma contributes tumor progression by reducing apoptosis

Ubiquitin ligase Nrdp1 (neuregulin receptor degradation protein 1) plays important roles in multiple physiological process because it can ubiquitinate various substrates such as ErbB3, BRUCE, MyD88, C/EBPβ, and Parkin, and so forth. In addition to the physiological function, it was also found to be involved in tumor progression. It has been shown that loss of Nrdp1 enhances breast cancer cell growth. Up to now, the role of Nrdp1 in glioma has not been elucidated. Here, we reported that Nrdp1 as well as cleaved caspase 3 was lower expressed in human glioma tissues comparing with the nontumorous. And then we found that the expression of Nrdp1 and cleaved caspase 3 was increased in the treatment of Temozolomide (TMZ), a drug for glioma chemotherapy. Further investigation indicated that transient transfection of Nrdp1 significantly promoted cell apoptosis by aggravating the degradation of BRUCE and activation of caspase 3. In addition, overexpression of Nrdp1 augmented TMZ induced apoptosis by evaluating the degradation of BRUCE and the activation of caspase 3, while silencing of Nrdp1 reduced the sensitivity to the TMZ by inhibiting the degradation of BRUCE and the activation of caspase 3 in human glioma cells. These observations show that Nrdp1 is a pro-apoptotic protein in human glioma and lower expression of Nrdp1 in human glioma may promote tumor progression by reducing apoptosis, suggesting that Nrdp1 may be an important regulator in the development of human glioma.

The tell-tale heart: molecular and cellular responses to childhood anthracycline exposure

Since the modern era of cancer chemotherapy that began in the mid-1940s, survival rates for children afflicted with cancer have steadily improved from 10% to current rates that approach 80% (60). Unfortunately, many long-term survivors of pediatric cancer develop chemotherapy-related health effects; 25% are afflicted with a severe or life-threatening medical condition, with cardiovascular disease being a primary risk (96). Childhood cancer survivors have markedly elevated incidences of stroke, congestive heart failure (CHF), coronary artery disease, and valvular disease (96). Their cardiac mortality is 8.2 times higher than expected (93). Anthracyclines are a key component of most curative chemotherapeutic regimens used in pediatric cancer, and approximately half of all childhood cancer patients are exposed to them (78). Numerous epidemiologic and observational studies have linked childhood anthracycline exposure to an increased risk of developing cardiomyopathy and CHF, often decades after treatment. The acute toxic effects of anthracyclines on cardiomyocytes are well described; however, myocardial tissue is comprised of additional resident cell types, and events occurring in the cardiomyocyte do not fully explain the pathological processes leading to late cardiomyopathy and CHF. This review will summarize the current literature regarding the cellular and molecular responses to anthracyclines, with an important emphasis on nonmyocyte cardiac cell types as well as those that mediate the myocardial injury response.

Protein quality control in the endoplasmic reticulum

THE TOPOLOGICAL BARRIERS DEFINED BY BIOLOGICAL MEMBRANES ARE NOT IMPERMEABLE: from small solutes to intact proteins, specialized transport and translocation mechanisms adjust to the cell's needs. Here, we review the removal of unwanted proteins from the endoplasmic reticulum (ER) and emphasize the need to extend observations from tissue culture models and simple eukaryotes to studies in whole animals. The variation in protein production and composition that characterizes different cell types and tissues requires tailor-made solutions to exert proper control over both protein synthesis and breakdown. The ER is an organelle essential to achieve and maintain such homeostasis.

Nrf2 deficiency exaggerates doxorubicin-induced cardiotoxicity and cardiac dysfunction

The anticancer therapy of doxorubicin (Dox) has been limited by its acute and chronic cardiotoxicity. In addition to a causative role of oxidative stress, autophagy appears to play an important role in the regulation of Dox-induced cardiotoxicity. However, the underlying mechanisms remain unclear. Accordingly, we explored a role of nuclear factor erythroid-2 related factor 2 (Nrf2) in Dox-induced cardiomyopathy with a focus on myocardial oxidative stress and autophagic activity. In wild type (WT) mice, a single intraperitoneal injection of 25 mg/kg Dox rapidly induced cardiomyocyte necrosis and cardiac dysfunction, which were associated with oxidative stress, impaired autophagy, and accumulated polyubiquitinated protein aggregates. However, these Dox-induced adverse effects were exaggerated in Nrf2 knockout (Nrf2(-/-)) mice. In cultured cardiomyocytes, overexpression of Nrf2 increased the steady levels of LC3-II, ameliorated Dox-induced impairment of autophagic flux and accumulation of ubiquitinated protein aggregates, and suppressed Dox-induced cytotoxicity, whereas knockdown of Nrf2 exerted opposite effects. Moreover, the exaggerated adverse effects in Dox-intoxicated Nrf2 depleted cardiomyocytes were dramatically attenuated by forced activation of autophagy via overexpression of autophagy related gene 5 (Atg5). Thus, these results suggest that Nrf2 is likely an endogenous suppressor of Dox-induced cardiotoxicity by controlling both oxidative stress and autophagy in the heart.

Oligomerization of the Nrdp1 E3 ubiquitin ligase is necessary for efficient autoubiquitination but not ErbB3 ubiquitination

Overexpression of the ErbB3 receptor tyrosine kinase protein in breast and other cancers contributes to tumor malignancy and therapeutic resistance. The RBCC/TRIM family RING finger E3 ubiquitin ligase Nrdp1 mediates the ubiquitination of ErbB3 in normal mammary epithelial cells to facilitate receptor degradation and suppress steady-state receptor levels. Post-transcriptional loss of Nrdp1 in patient breast tumors allows ErbB3 overexpression and receptor contribution to tumor progression, and elevated lability through autoubiquitination contributes to the observed loss of Nrdp1 in tumors relative to normal tissue. To begin to understand the mechanisms underlying Nrdp1 protein self-regulation through lability, we investigated the structural determinants required for efficient autoubiquitination and ErbB3 ubiquitination. Using mutagenesis, chemical cross-linking, size exclusion chromatography, and native polyacrylamide gel electrophoresis, we demonstrate that Nrdp1 self-associates into a stable oligomeric complex in cells. Deletion of its coiled-coil domain abrogates oligomerization but does not affect Nrdp1-mediated ErbB3 ubiquitination or degradation. On the other hand, the presence of the coiled-coil domain is necessary for efficient Nrdp1 autoubiquitination via a trans mechanism, indicating that Nrdp1 ubiquitination of its various targets is functionally separable. Finally, a GFP fusion of the coiled-coil domain stabilizes Nrdp1 and potentiates ErbB3 ubiquitination and degradation. These observations point to a model whereby the coiled-coil domain plays a key role in regulating Nrdp1 lability by promoting its assembly into an oligomeric complex, and raise the possibility that inhibition of ligase oligomerization via its coiled-coil domain could be of therapeutic benefit to breast cancer patients by restoring Nrdp1 protein.

Desacyl ghrelin prevents doxorubicin-induced myocardial fibrosis and apoptosis via the GHSR-independent pathway

Doxorubicin is an effective chemotherapeutic agent used to treat malignancies, but it causes cardiomyopathy. Preliminary evidence suggests that desacyl ghrelin might have protective effects on doxorubicin cardiotoxicity. This study examined the cellular effects of desacyl ghrelin on myocardial fibrosis and apoptosis in a doxorubicin cardiomyopathy experimental model. Adult C57BL/6 mice received an intraperitoneal injection of doxorubicin to induce cardiomyopathy, followed by 4-day treatment of saline (control) or desacyl ghrelin with or without [d-Lys3]-GHRP-6 (a growth hormone secretagogue receptor or GHSR1a antagonist). Ventricular structural and functional parameters were evaluated by transthoracic echocardiography. Molecular and cellular measurements were performed in ventricular muscle to examine myocardial fibrosis and apoptosis. Cardiac dysfunction was induced by doxorubicin, as indicated by significant decreases in ventricular fractional shortening and ejection fraction. This doxorubicin-induced cardiac dysfunction was prevented by the treatment of desacyl ghrelin no matter with or without the presence of [d-Lys3]-GHRP-6. Doxorubicin induced fibrosis (accumulated collagen deposition and increased CTGF), activated apoptosis (increased TUNEL index, apoptotic DNA fragmentation, and caspase-3 activity and decreased Bcl-2/Bax ratio), and suppressed phosphorylation status of prosurvival signals (ERK1/2 and Akt) in ventricular muscles. All these molecular and cellular alterations induced by doxorubicin were not found in the animals treated with desacyl ghrelin. Notably, the changes in the major markers of apoptosis, fibrosis, and Akt phosphorylation were found to be similar in the animals following the treatment of desacyl ghrelin with and without GHSR antagonist [d-Lys3]-GHRP-6. These findings demonstrate clearly that desacyl ghrelin protects the cardiomyocytes against the doxorubicin-induced cardiomyopathy by preventing the activation of cardiac fibrosis and apoptosis, and the effects are probably mediated through GHSR-independent mechanism.

Doxorubicin has in vivo toxicological effects on ex vivo cultured mesenchymal stem cells

Doxorubicin (dox) is an effective chemotherapeutic agent that leads to cardiotoxicity. An alternative treatment for dox-cardiotoxicity is autologous mesenchymal stem cells (MSCs) transplantation. It remains unclear if dox has deleterious effects on MSCs from subjects under chemotherapy, therefore this study aimed to evaluate dox in vivo toxicological effects on ex vivo cultured MSCs, inferring whether autologous transplantation may be an alternative treatment in patients who are exposed to the drug. Wistar rats received either dox or saline. Following treatments, animals were sacrificed and bone marrow MSCs were isolated, characterized for cell surface markers and assessed according to their viability, alkaline phosphatase production, and proliferation kinetics. Moreover, MSCs were primed to cardiac differentiation and troponin T and connexin 43 expressions were evaluated. Compared to control, undifferentiated MSCs from dox group kept the pattern for surface marker and had similar viability results. In contrast, they showed lower alkaline phosphatase production, proliferation rate, and connexin 43 expression. Primed MSCs from dox group showed lower troponin T levels. It was demonstrated a toxic effect of dox in host MSCs. This result renders the possibility of autologous MSCs transplantation to treat dox-cardiotoxicity, which could be a non-suitable option for subjects receiving such antineoplastic agent.

Cardiomyocyte autophagy and cancer chemotherapy

Autophagy, an evolutionally conserved process of controlled cellular cannibalization, plays a vital role in cardiac physiology. Perturbations in cardiomyocyte autophagy contribute to the pathogenesis of a wide range of cardiac diseases, many of which culminate in heart failure. With recent advances in cancer chemotherapy and consequent improvements in cancer survival, drug-induced toxicity to the heart has assumed greater importance. As a number of prominent cellular pathways are critical to the survival of both tumor cells and heart cells, it comes as little surprise that therapies targeting those pathways have consequences in both tissues. Little is known presently about cardiomyocyte autophagy, a prominent cellular response to stress, in the setting of chemotherapy, but preliminary evidence suggests an important and context-dependent role. Dissecting the role of autophagy in "onco-cardiology" will likely yield insights into mechanisms underlying cardiomyopathy and may lead to novel means to protect the myocardium from chemotherapy-induced injury. This article is part of a Special Issue entitled "Protein Quality Control, the Ubiquitin Proteasome System, and Autophagy".

Role for granulocyte colony stimulating factor in angiotensin II-induced neutrophil recruitment and cardiac fibrosis in mice

BACKGROUND

Granulocyte colony stimulating factor (G-CSF) is a key mediator of neutrophil infiltration and is profibrotic in the liver, lung, and infarcted heart, but its roles in angiotensin II (Ang II)-induced hypertension and cardiac remodeling have not been fully determined. Thus, we sought to investigate the causal relation of G-CSF to neutrophil recruitment and cardiac fibrosis in C57BL/6J mice.

METHODS

Hypertension and cardiac fibrosis were induced in wild-type (WT) mice receiving continuous infusion of Ang II (1,500ng/kg/min). After 7 days, heart sections were stained with hematoxylin and eosin, Masson's trichrome, and immunohistochemistry. The mRNA expression of cytokines was detected by real-time polymerase chain reaction analysis. The protein levels were measured by Western blot analysis.

RESULTS

After Ang II infusion, myocardial G-CSF expression was significantly elevated in the hearts. Moreover, WT mice exhibited increased blood pressure, marked neutrophil accumulation, proinflammatory cytokine expression, reactive oxygen species production, and cardiac fibrosis after 7 days of Ang II infusion. However, administration of anti-G-CSF neutralizing antibody, but not with control immunoglobulin G, significantly attenuated these effects. In addition, neutralizing G-CSF antibody reversed Ang II-induced activation of ERK1/2, STAT3, and AKT signaling pathways in the hearts.

CONCLUSIONS

This study demonstrates that G-CSF plays a critical role in hypertension and cardiac fibrosis and targeting this cytokine may be a novel therapeutic strategy to ameliorate hypertensive heart disease.

Cardioprotective effects of fish omega-3 fatty acids on doxorubicin-induced cardiotoxicity in rats

The aim of this study was to investigate the protective effects of fish omega-3 (n-3) fatty acids on doxorubicin (DOX)-induced acute cardiotoxicity. A total of 24 rats were divided into three groups: control, DOX-treated, and DOX treated with fish n-3 fatty acids. Control group received 0.4 ml/kg/day of saline intragastrically. The rats in the fish n-3 fatty acid-pretreated group were given 400 mg/kg/day fish n-3 fatty acids for 30 days by intragastric intubation. To induce acute cardiotoxicity, DOX (30 mg/kg) was injected intraperitoneally by a single dose and the rats were killed after 48 h. DOX treatment caused severe damage in heart tissues. Disorganization of myocardial muscle fibers, myofibrillar loss, and cardiotoxic myocardial fibers with cytoplasmic vacuoles were seen. Fish n-3 fatty acid-treated rats showed an improved histological appearance in the DOX-treated group. Our data indicate a significant reduction in the activity of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling in cardiomyocytes of the DOX-treated group with fish n-3 fatty acids therapy. The DOX-treated with fish n-3 fatty acids group showed a significant decrease in malondialdehyde levels, and an increase in superoxide dismutase and glutathione peroxidase activities in comparison with the DOX-treated group. This study showed that fish n-3 fatty acids may be a suitable cardioprotector against acute toxic effects of DOX.

Transcriptional effects of E3 ligase atrogin-1/MAFbx on apoptosis, hypertrophy and inflammation in neonatal rat cardiomyocytes

Atrogin-1/MAFbx is an ubiquitin E3 ligase that regulates myocardial structure and function through the ubiquitin-dependent protein modification. However, little is known about the effect of atrogin-1 activation on the gene expression changes in cardiomyocytes. Neonatal rat cardiomyocytes were infected with adenovirus atrogin-1 (Ad-atrogin-1) or GFP control (Ad-GFP) for 24 hours. The gene expression profiles were compared with microarray analysis. 314 genes were identified as differentially expressed by overexpression of atrogin-1, of which 222 were up-regulated and 92 were down-regulated. Atrogin-1 overexpression significantly modulated the expression of genes in 30 main functional categories, most genes clustered around the regulation of cell death, proliferation, inflammation, metabolism and cardiomyoctye structure and function. Moreover, overexpression of atrogin-1 significantly inhibited cardiomyocyte survival, hypertrophy and inflammation under basal condition or in response to lipopolysaccharide (LPS). In contrast, knockdown of atrogin-1 by siRNA had opposite effects. The mechanisms underlying these effects were associated with inhibition of MAPK (ERK1/2, JNK1/2 and p38) and NF-κB signaling pathways. In conclusion, the present microarray analysis reveals previously unappreciated atrogin-1 regulation of genes that could contribute to the effects of atrogin-1 on cardiomyocyte survival, hypertrophy and inflammation in response to endotoxin, and may provide novel insight into how atrogin-1 modulates the programming of cardiac muscle gene expression.

Doxorubicin Cardiotoxicity and Cardiac Function Improvement After Stem Cell Therapy Diagnosed by Strain Echocardiography

Doxorubicin (Dox) is one of the most effective chemotherapeutic agents; however, it causes dose-dependent cardiotoxicity. Evaluation of left ventricular function relies on measurements based on M-mode echocardiography. A new technique based on quantification of myocardial motion and deformation, strain echocardiography, has been showed promising profile for early detection of cardiac dysfunction. Different therapy strategies, such as flavonoid plant extracts and stem cells, have been investigated to improve heart function in toxic cardiomyopathy. This work aimed to assess early cardiac function improvement after treatments with either flavonoid extract from Camellia sinensis or mesenchymal stem cells in Dox cardiotoxicity using strain echocardiography. Twenty Wistar rats were randomly assigned to four groups. They received water (control, Dox, Dox + stem cells) or 100 mg/kg C. sinensis extract (Dox + C. sinensis) via gavage, daily, for four weeks. Animals also received saline (control) or 5 mg/kg doxorubicin (Dox, Dox + C. sinensis, Dox + stem cells) via intraperitoneal injection, weekly, for four weeks. Stem cells were injected (3 × 10⁶ cells) through tail vein prior the beginning of the experiment (Dox + stem cells). Animals were evaluated by hematological, electrocardiography, echocardiography, and histopathological examinations. Dox cardiotoxicity was only diagnosed with strain echocardiography, detecting a decrease in ventricular function. C. sinensis extract did not prevent ventricular dysfunction induced by Dox. However, strain echocardiography examination revealed that Dox cardiotoxicity was significantly suppressed in rats treated with stem cells. In conclusion, strain echocardiography was able to detect precocity signs of heart failure and stem cell therapy showed cardioprotection effect against Dox cardiotoxicity.

Carboxyl terminus of heat shock protein 70-interacting protein inhibits angiotensin II-induced cardiac remodeling

BACKGROUND

The carboxyl terminus of heat shock protein 70-interacting protein (CHIP), an E3 ligase/chaperone, was found to protect cardiomyocytes against apoptosis induced by ischemic injury; however, the functional role of CHIP in remodeling induced by angiotensin II (Ang II) remains unclear.

METHODS

We generated CHIP-overexpressed transgenic (TG) mice infused with Ang II (1,500 ng/kg/min) or saline for days or small interfering RNA (siRNA) knockdown of neonatal rat cardiomyocytes. Heart sections were stained with hematoxylin and eosin, Masson trichrome, TdT-mediated dUTP nick-end labeling (TUNEL) staining, and immunohistochemistry, and the levels of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK) were measured by western blot analysis.

RESULTS

Seven days after Ang II infusion, cardiac-specific overexpression of CHIP significantly enhanced cardiac contractile performance in mice and attenuated cardiac apoptosis, fibrosis, and inflammation: the number of TUNEL-positive cells, fibrotic areas, macrophage infiltration, and the expression of interleukin-1β (IL-1β), IL-6, monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule-1 (ICAM-1) in heart tissues were decreased as compared with wild-type (WT) mice (all P < 0.05). In contrast, CHIP siRNA knockdown markedly increased Ang II-induced apoptosis and the expression of proinflammatory cytokines, as compared with siRNA control. The mechanisms underlying these beneficial actions were associated with CHIP-mediated inhibition of NF-κB and MAPK (p38 and JNK) pathways.

CONCLUSIONS

CHIP plays an important role in regulating Ang II-triggered hypertensive cardiac apoptosis, inflammation, and fibrosis.