Neuregulin-1 Attenuates Doxorubicin-induced Autophagy in Neonatal Rat Cardiomyocytes:

RGS11-CaMKII complex mediated redox control attenuates chemotherapy-induced cardiac fibrosis

Dose limiting cardiotoxicity remains a major limiting factor in the clinical use of several cancer chemotherapeutics including anthracyclines and the antimetabolite 5-fluorouracil (5-FU). Prior work has demonstrated that chemotherapeutics increase expression of R7 family regulator of G protein signaling (RGS) protein-binding partner Gβ5, which drives myocyte cytotoxicity. However, though several R7 family members are expressed in heart, the exact role of each protein in chemotherapy driven heart damage remains unclear. Here, we demonstrate that RGS11, downregulated in the human heart following chemotherapy exposure, possesses potent anti-apoptotic actions, in direct opposition to the actions of fellow R7 family member RGS6. RGS11 forms a direct complex with the apoptotic kinase CaMKII and stress responsive transcription factor ATF3 and acts to counterbalance the ability of CaMKII and ATF3 to trigger oxidative stress, mitochondrial dysfunction, cell death, and release of the cardiokine neuregulin-1 (NRG1), which mediates pathological intercommunication between myocytes and endothelial cells. Doxorubicin triggers RGS11 depletion in the murine myocardium, and cardiac-specific OE of RGS11 decreases doxorubicin-induced fibrosis, myocyte hypertrophy, apoptosis, oxidative stress, and cell loss and aids in the maintenance of left ventricular function. Conversely, RGS11 knockdown in heart promotes cardiac fibrosis associated with CaMKII activation and ATF3/NRG1 induction. Indeed, inhibition of CaMKII largely prevents the fibrotic remodeling resulting from cardiac RGS11 depletion underscoring the functional importance of the RGS11-CaMKII interaction in the pathogenesis of cardiac fibrosis. These data describe an entirely new role for RGS11 in heart and identify RGS11 as a potential new target for amelioration of chemotherapy-induced cardiotoxicity.

Neuregulin-1, a potential therapeutic target for cardiac repair

NRG1 (Neuregulin-1) is an effective cardiomyocyte proliferator, secreted and released by endothelial vascular cells, and affects the cardiovascular system. It plays a major role in heart growth, proliferation, differentiation, apoptosis, and other cardiovascular processes. Numerous experiments have shown that NRG1 can repair the heart in the pathophysiology of atherosclerosis, myocardial infarction, ischemia reperfusion, heart failure, cardiomyopathy and other cardiovascular diseases. NRG1 can connect related signaling pathways through the NRG1/ErbB pathway, which form signal cascades to improve the myocardial microenvironment, such as regulating cardiac inflammation, oxidative stress, necrotic apoptosis. Here, we summarize recent research advances on the molecular mechanisms of NRG1, elucidate the contribution of NRG1 to cardiovascular disease, discuss therapeutic approaches targeting NRG1 associated with cardiovascular disease, and highlight areas for future research.

A Transgenic Mouse Model of Eccentric Left Ventricular Hypertrophy With Preserved Ejection Fraction Exhibits Alterations in the Autophagy-Lysosomal Pathway

The ubiquitin-proteasome system (UPS) and the autophagy-lysosomal pathway (ALP) are the main proteolytic systems involved in cellular homeostasis. Since cardiomyocytes, as terminally differentiated cells, lack the ability to share damaged proteins with their daughter cells, they are especially reliant on these protein degradation systems for their proper function. Alterations of the UPS and ALP have been reported in a wide range of cardiac diseases, including cardiomyopathies. In this study, we determined whether the UPS and ALP are altered in a mouse model of eccentric left ventricular (LV) hypertrophy expressing both cyclin T1 and Gαq under the control of the cardiac-specific α-myosin heavy chain promoter (double transgenic; DTG). Compared to wild-type (WT) littermates, DTG mice showed higher end-diastolic (ED) LV wall thicknesses and diameter with preserved ejection fraction (EF). The cardiomyopathic phenotype was further confirmed by an upregulation of the fetal gene program and genes associated with fibrosis as well as a downregulation of genes involved in Ca²⁺ handling. Likewise, higher NT-proBNP levels were detected in DTG mice. Investigation of the UPS showed elevated steady-state levels of (poly)ubiquitinated proteins without alterations of all proteasomal activities in DTG mice. Evaluation of ALP key marker revealed a mixed pattern with higher protein levels of microtubule-associated protein 1 light chain 3 beta (LC3)-I and lysosomal-associated membrane protein-2, lower protein levels of beclin-1 and FYVE and coiled-coil domain-containing protein 1 (FYCO1) and unchanged protein levels of p62/SQSTM1 in DTG mice when compared to WT. At transcriptional level, a > 1.2-fold expression was observed for Erbb2, Hdac6, Lamp2, Nrg1, and Sqstm1, while a < 0.8-fold expression was revealed for Fyco1 in DTG mice. The results related to the ALP suggested overall a repression of the ALP during the initiation process, but an induction of the ALP at the level of autophagosome-lysosome fusion and the delivery of ubiquitinated cargo to the ALP for degradation.

Neuregulin 4 alleviates hepatic steatosis via activating AMPK/mTOR-mediated autophagy in aged mice fed a high fat diet

Neuregulin 4 (Nrg4) is a brown fat-enriched endocrine factor that exerts beneficial metabolic effects on insulin resistance and hepatic steatosis. Autophagy is a mechanism that is essential for preventing hepatic steatosis. The aim of this study was to explore whether Nrg4 ameliorates hepatic steatosis by inducing autophagy. Aged C57BL/6 mice were maintained on a high fat diet with or without Nrg4 intervention for 3 months. Lipid accumulation in the liver was investigated. Autophagy related protein levels along with related signaling pathways that regulate autophagy were evaluated. In addition, the effects of Nrg4 on autophagy were also determined in cultured L-02 cells. Nrg4 decreased high-fat induced intrahepatic lipid content both in vivo and in vitro. Autophagy level in the liver also decreased in obese mice and Nrg4 intervention reactivated autophagy. Further, Nrg4 intervention was found to have activated autophagy via the adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway. Moreover, when the AMPK/mTOR pathway was suppressed or autophagy was inhibited, the beneficial effects of Nrg4 intervention on hepatic steatosis were diminished. These results indicated that Nrg4 intervention attenuated hepatic steatosis by promoting autophagy in the liver of aged obese mice. Additionally, Nrg4 induced autophagy via the AMPK/mTOR signaling pathway.

Development and validation of a nomogram with an autophagy-related gene signature for predicting survival in patients with glioblastoma

Glioblastoma (GBM) is the most common brain tumor with significant morbidity and mortality. Autophagy plays a vital role in GBM development and progression. We aimed to establish an autophagy-related multigene expression signature for individualized prognosis prediction in patients with GBM. Differentially expressed autophagy-related genes (DE-ATGs) in GBM and normal samples were screened using TCGA. Univariate and multivariate Cox regression analyses were performed on DE-ATGs to identify the optimal prognosis-related genes. Consequently, NRG1 (HR=1.142, P=0.008), ITGA3 (HR=1.149, P=0.043), and MAP1LC3A (HR=1.308, P=0.014) were selected to establish the prognostic risk score model and validated in the CGGA validation cohort. GSEA revealed that these genes were mainly enriched in cancer- and autophagy-related KEGG pathways. Kaplan-Meier survival analysis demonstrated that patients with high risk scores had significantly poorer overall survival (OS, log-rank P= 6.955×10^-5). The autophagy signature was identified as an independent prognostic factor. Finally, a prognostic nomogram including the autophagy signature, age, pharmacotherapy, radiotherapy, and IDH mutation status was constructed, and TCGA/CGGA-based calibration plots indicated its excellent predictive performance. The autophagy-related three-gene risk score model could be a prognostic biomarker and suggest therapeutic targets for GBM. The prognostic nomogram could assist individualized survival prediction and improve treatment strategies.

NH4Cl treatment prevents doxorubicin-induced myocardial dysfunction in vivo

AIMS

Improvements in cancer treatment have significantly extended the lifespan of patients. However, due to the adverse effects of cancer treatment, cancer survivors are at increased risk of cardiovascular complications. Doxorubicin is a widely used spectrum antitumor drug, but the life-threatening side-effect of cardiotoxicity limits its clinical application. Ammonium chloride (NH₄Cl), as a heteropolar compound with pH value regulation, can cause intracellular alkalization and metabolic acidosis thus effecting enzymatic activity and influencing the process of biological system. The underlying effect of NH₄CL in DOX-induced cardiomyocyte apoptosis and hypertrophy in mice has never been reported before.

MAIN METHODS

This study we used DOX to induce cardiac remodeling and dysfunction in mice. Myocardial histology was performed using HE staining. Myocardial cell size was measured by wheat germ agglutinin (WGA) staining. Echocardiographic evaluation of cardiac function, qPCR detection of the mRNA expression of cardiac hypertrophy and inflammation markers. Apoptosis was detected by TUNEL method. Transmission electron microscopy (TEM) was used to detect autophagy.

KEY FINDINGS

We found that NH₄CL effectively improved DOX-induced cardiomyocyte apoptosis and cardiac dysfunction in mice. Our results showed that NH₄CL significantly improved DOX-induced contractile dysfunction, inflammation, apoptosis and autophagy in mice.

SIGNIFICANCE

Our results indicate that NH₄CL is effective in improving DOX-induced cardiac dysfunction and remodeling. It may therefore be a therapeutic entry point to limit doxorubicin-mediated adverse cardiac reactions.

Correlation of circulating pro-angiogenic miRNAs with cardiotoxicity induced by epirubicin/cyclophosphamide followed by docetaxel in patients with breast cancer

OBJECTIVE

This study aimed to evaluate predictive value of 14 pro-angiogenic miRNAs for cardiotoxicity induced by epirubicin/cyclophosphamide follow by docetaxel (EC-D) in breast cancer (BC) patients.

METHODS

Three hundred and sixty-three BC patients receiving EC-D neoadjuvant chemotherapy were consecutively enrolled in this prospective cohort study. Peripheral blood sample was obtained from each patient, and plasma was separated. The expressions of 14 pro-angiogenic miRNAs, cardiac troponin I (cTnI) and N-terminal pro brain natriuretic peptide (NT-proBNP) were evaluated. Left ventricular ejection fraction (LVEF) level at C0, the end of 4 cycles of EC chemotherapy (C4), the end of 4 cycles of docetaxel treatment (C8), 3rd months (M3), 6th months (M6), 9th months (M9) and 12th months (M12) after surgery were assessed.

RESULTS

LVEF decreased at C4, C8, M3, M6, M9 and M12 compared with C0, and the total cardiotoxicity incidence was 5.2%. Additionally, the levels of let-7f, miR-17-5p, miR-20a, miR-126, miR-210 and miR-378 were reduced in cardiotoxicity patients. Multivariate logistic regression revealed that miR-17-5p and miR-20a were independently predictive factors for less cardiotoxicity. Receiver operating characteristics (ROC) curve displayed a satisfactory predictive value for lower cardiotoxicity risk with area under curve (AUC) of 0.842 of the combination of the miR-17-5p and miR-20a expressions. In addition, let-7f,miR-126, miR-210 and miR-378 levels negatively correlated with cTnI expression, and let-7f and miR-130a expressions reversely correlated with NT-proBNP level.CONLUSIONS: miR-17-5p and miR-20a could be served as biomarkers for lower cardiotoxicity induced by EC-D neoadjuvant chemotherapy in BC patients.

Doxorubicin-induced death in tumour cells and cardiomyocytes: is autophagy the key to improving future clinical outcomes?

Objectives

Doxorubicin, a commonly used frontline chemotherapeutic agent for cancer, is not without side-effects. The original thinking that the drug causes necrosis in tumours has largely given way to its link with apoptosis over the past two decades.

Key findings

More recently, major biomarkers such as AMPK, p53 and Bcl-2 have been identified as important to apoptosis induction by doxorubicin. It is Bcl-2 and its interaction with Beclin-1 that has refocussed research attention on doxorubicin, albeit this time for its ability to induce autophagy. Autophagy can be either anticancerous or procancerous however, so it is critical that the reasons for which cancer cells undergo this type of cell biological event be clearly identified for future exploitation.

Summary

Taking a step back from treating patients with large doses of doxorubicin, which causes toxicity to the heart amongst other organs, and further research with this drug's molecular signalling in not only neoplastic but normal cells, may indeed redefine the way doxorubicin is used clinically and potentially lead to better neoplastic disease management.