BECN1 Overexpression Research Articles

Salvianolate injection ameliorates cardiomyopathy by regulating autophagic flux through miR-30a/becn1 axis in zebrafish.

Salvianolate is a compound mainly composed of salvia magnesium acetate, which is extracted from the Chinese herb Salvia miltiorrhiza. In recent years, salvianolate injection has been widely used in the treatment of cardiovascular diseases, but the mechanism of how it can alleviate cardiotoxicity remains unclear. The cardiac injury model was constructed by treatment with doxorubicin (Dox) or azithromycin (Azi) in zebrafish larvae. Heart phenotype, heart rate, and cardiomyocyte apoptosis were observed in the study. RNA-seq analysis was used to explore the underlying mechanism of salvianolate treatment. Moreover, cardiomyocyte autophagy was assessed by in situ imaging. In addition, the miR-30a/becn1 axis regulation by salvianolate was further investigated. Salvianolate treatment reduced the proportion of pericardial edema, recovered heart rate, and inhibited cardiomyocyte apoptosis in Dox/Azi-administered zebrafish larvae. Mechanistically, salvianolate regulated the lysosomal pathway and promoted autophagic flux in zebrafish cardiomyocytes. The expression level of becn1 was increased in Dox-induced myocardial tissue injury after salvianolate administration; overexpression of becn1 in cardiomyocytes alleviated the Dox/Azi-induced cardiac injury and promoted autophagic flux in cardiomyocytes, while becn1 knockdown blocked the effects of salvianolate. In addition, miR-30a, negatively regulated by salvianolate, partially inhibited the cardiac amelioration of salvianolate by targeting becn1directly. This study has proved that salvianolate reduces cardiomyopathy by regulating autophagic flux through the miR-30a/becn1 axis in zebrafish and is a potential drug for adjunctive Dox/Azi therapy.

Mechanism of Drug Resistance to First-Line Chemotherapeutics Mediated by TXNDC17 in Neuroblastomas.

The prognosis of high-risk neuroblastomas (NB) that are resistant to first-line induction chemotherapy is relatively poor. This study explored the mechanism of resistance to first-line chemotherapeutics mediated by TXNDC17 and its potential solutions in NB. The genetic and clinical data of patients with NB were obtained from the Therapeutically Applicable Research to Generate Effective Treatments dataset. TXNDC17 and BECN1 expressions in NB cells were up- and downregulated by transfection with plasmids and shRNA, respectively. Autophagy-related proteins were detected by western blot. Cell viability was determined using cell proliferation and toxicity experiments. Apoptotic cells were detected using flow cytometry. Overall, 1076 pediatric and adolescent patients with NB were enrolled in this study. The 10-year overall survival (OS) rates and event-free survival (EFS) rates for the patients with a mutation of BECN1 were 37.4 ± 9.1% and 34.5 ± 8.8%, respectively. For patients with a mutation of TXNDC17, the 10-year OS and EFS were 41.4 ± 5.9% and 24.3 ± 5.1%, respectively, which were significantly lower than those in the unaltered group. The overexpression of BECN1 and TXNDC17 reduced NB sensitivity to cisplatin (DDP), etoposide (VP16), and cyclophosphamide (CTX). Autophagy mediated by BECN1 was regulated by TXNDC17, and this process was involved in the resistance to DDP, VP16, and CTX in NB. Suberoylanilide hydroxamic acid (SAHA) can enhance the sensitivity and apoptosis of NB cells to chemotherapeutics by inhibiting TXNDC17, ultimately decreasing autophagy-mediated chemoresistance. Acquired resistance to first-line chemotherapeutics was associated with autophagy mediated by BECN1 and regulated by TXNDC17, which can be reversed by SAHA.

BECN1 regulates FADD/RIPK1/Caspase-8 complex formation via RIPK1 ubiquitination by downregulating OTUD1 in MI/R induced myocyte apoptosis

BackgroundCardiomyocyte apoptosis plays a vital role in myocardial ischemia–reperfusion (MI/R) injury; however, the role of beclin1 (BECN1) remains unclear. This study aimed at revealing the function of BECN1 during cardiomyocyte apoptosis after MI/R injury. MethodsIn vivo, TTC and Evan's blue double staining was applied to verify the gross morphological alteration in both wild type (WT) mice and BECN1 transgene mice (BECN1-TG), and TUNEL staining and western blot were adopted to evaluate the cardiomyocyte apoptosis. In vitro, a hypoxia/reoxygenation (H/R) model was established in H9c2 cells to simulate MI/R injury. Proteomics analysis was preformed to verify if apoptosis occurs in the H/R cellular model. And apoptosis factors, RIPK1, Caspase-1, Caspase-3, and cleaved Caspase-3, were investigated using western bolting. In addition, the mRNA level were verified using RT-PCR. To further investigate the protein interactions small interfering RNA and lentiviral transfection were used. To continue investigate the protein interactions, immunofluorescence and coimmunoprecipitation were applied. ResultsMorphologically, BECN1 significantly attenuated the apoptosis from TTC-Evan's staining, TUNEL, and cardiac tissue western blot. After H/R, a RIPK1-induced complex (complex II) containing RIPK1, Caspase-8, and FADD was formed. Thereafter, cleaved Caspase-3 was activated, and myocyte apoptosis occurred. However, BECN1 decreased the expression of RIPK1, Caspase-8, and FADD. Nevertheless, BECN1 overexpression increased RIPK1 ubiquitination before apoptosis by inhibiting OTUD1. ConclusionsBECN1 regulates FADD/RIPK1/Caspase-8 complex formation via RIPK1 ubiquitination by downregulating OTUD1 in C-Caspase-3-induced myocyte apoptosis after MI/R injury. Therefore, BECN1 can function as a cardioprotective candidate.

Lipopolysaccharide inhibits osteoblast formation and receptor activator of nuclear factor-κB ligand degradation via autophagy inhibition.

Lipopolysaccharide (LPS) and Receptor Activator of Nuclear Factor-κB Ligand (RANKL) are the two important factors causing bone loss, which is an important pathogenesis for osteoporosis. However, the relationship between LPS and RANKL is not yet clear. LPS can be involved in the weakened osteoblast formation as an autophagy regulator, and osteoblasts and their precursors are the source cells for RANKL production. Our study aimed to explore the relationship between autophagy changes and RANKL production during LPS-regulated osteoblasts. Our results showed that LPS inhibited autophagy (LC3 conversion and autophagosome formation) and enhanced the protein and mRNA expression of RANKL in MC3T3-E1 osteoblast precursor line. Autophagy upregulation with Rapamycin over BECN1 overexpression rescued LPS-inhibited osteoblast formation and -promoted RANKL protein production in MC3T3-E1 cells. In vivo experiments supported that damaged bone mass, bone microstructure, osteoblastic activity (ALP and P1NP production by ELISA assays) and enhanced RANKL production by LPS administration were partially rescued by Rapamycin application. In conclusion, LPS can inhibit autophagy in osteoblast precursors, thereby inhibiting osteoblast formation and RANKL autophagic degradation.

Effect of BECN1 Expression on Proliferation and Invasion of Human Myeloma Cell Line RPMI-8226

To investigate the effect of BECN1 expression on proliferation and invasion of human multiple myeloma (MM) cell line RPMI-8226. RPMI-8226 cells were cultured in vitro, the recombinant plasmid pcDNA3.1-BECN1 was constructed and transfected into RPMI-8226 cells, then the cells were divided into three groups: control group, negative transfection group and BECN1 transfection group. The expression of BECN1 mRNA in cells of each group was detected by real-time fluorescent quantitative polymerase chain reaction (qRT-PCR); the effect of BECN1 overexpression on cell proliferation inhibition rate was detected by cell counting kit 8 (CCK-8); the effect of BECN1 overexpression on the colony formation rate was detected by plate cloning assay; the effect of BECN1 overexpression on cell invasion was detected by Transwell assay; the effects of BECN1 overexpression on the expression of cell proliferation, invasion and autophagy-related proteins were detected by Western blot. The expression of BECN1 mRNA in BECN1 transfection group was significantly higher than that in control group and negative transfection group (P<0.05); the inhibition rate of cell proliferation and the expression of autophagy-related proteins Beclin1, Atg5 and invasion-related protein E-cadherin in BECN1 transfection group were significantly higher than those in control group and negative transfection group; the colony formation rate, invasion number and the expression of proliferation-related proteins CyclinD1, β-catenin and invasion-related protein N-cadherin were significantly lower than those in control group and negative transfection group (P<0.05). Overexpression of BECN1 can inhibit the proliferation and invasion of human MM cells RPMI-8226, which may be a potential research target of MM.

TXNDC17 protein overexpression in uterine papillary serous carcinoma is associated with clinicopathological characteristics and prognosis

Objective: To analyze clinicopathological characteristics of patients with uterine papillary serous carcinoma (UPSC) in China, and investigate roles of TXNDC17 protein in UPSC clinicopathological characteristics and prognosis. Methods: Fifty-five patients with UPSC treated in Women's Hospital School of Medicine Zhejiang University from 2003 to 2016 were analysed retrospectively. Immunohistochemistry (IHC) were performed to TXNDC17 and BECN1 (Beclin 1 protein, a key regulator of autophagy) protein expression respectively. Kaplan-Meier was used to calculate the cumulative survival rate, Log-rank test was performed to compare the difference in cumulative survival rate among patients with different clinicopathological characteristics, and Cox regression model was used to analyze the related between TXNDC17 expression and prognosis of UPSC patients. Results: The median age of the 55 UPSC patients was 63(49, 79) years, 43.6%(24/55) with late stages (stage Ⅲ/Ⅳ), and 32.7 % (18/55) exhibiting more than half of myometrium invasion were enrolled. Notably, 28 (50.9%) patients had TXNDC17 protein overexpression, and associated with BECN1 overexpression(P=0.023). Besides, co-expression of TXNDC17 and BECN1 occurred at an advanced stage and deep myometrial invasion (P=0.013,0.009). The cumulative survival rate of TXNDC17 overexpression(37.4% vs 91.5%),FIGO Ⅲ/Ⅳ stage(44.1% vs 70.1%), deep myometrium invasion(36.1% vs 75.4%) and BECN1 overexpression(0 vs 83.0%)patients was low (P<0.05). The multivariate proportional hazards model revealed that myometrial invasion and TXNDC17 overexpression were associated with prognosis of UPSC patients. Conclusions: This study shows that TXNDC17 overexpression is associate with poor survival in UPSC patients. Co-expression of TXNDC17 and BECN1 shows characteristics of advanced stages and deep myometrial invasion. TXNDC17 may be a potential predictor or target in UPSC therapeutics..

Beclin-1 overexpression regulates NLRP3 activation by promoting TNFAIP3 in microvascular injury following myocardial reperfusion

Innate immune response contributes significantly to ischemia reperfusion (I/R) injury. Targeting innate immunity seems to be a promising method for protecting the microvascular injury in ST-elevation myocardial infarction (STEMI) patients following myocardial I/R injury (MI/R). NLRP3 inflammasome is a central part of the innate immune system involved in the pathophysiological process of MI/R. However, the mechanisms regulating NLRP3 activation are yet to be clarified. Recently, autophagy has been related to the regulation of NLRP3 activation. Thus, how Beclin-1/Becn1 overexpression influences NLRP3 activation in microvascular endothelial cells (CMECs) after MI/R is yet to be investigated. The present study showed that Becn1 overexpression exhibits a significant increase in NLRP3 and IL-1β in CMEC responses to MI/R. Interestingly, Becn1 overexpression promoted TNFAIP3 expression, which restricted NLRP3 activation in vitro and in vivo. The current study also showed that inflammatory cells (CD68) and B (CDB220) lymphocytes were decreased in transgenic mice with overexpression of Beclin-1 (BECN1-Tg) in the spleen and heart. These findings highlighted Becn1 as a prospective target for treating NLRP3 mediated microvascular injury following MI/R.

The Regulation of ROS- and BECN1-Mediated Autophagy by Human Telomerase Reverse Transcriptase in Glioblastoma.

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor with high morbidity and mortality. Human telomerase reverse transcriptase (hTERT), the catalytic subunit of human telomerase, is overexpressed in most cancers including GBM. It is well known that hTERT can compensate telomere shortening to immortalize cells. However, in addition to the canonical function, hTERT has the roles beyond canonical telomere maintenance. To further understand the effects of hTERT on glioblastoma progression, we investigated the role of hTERT in regulating autophagy—a conserved pathway, by which cells deliver cellular organic material and impaired organelles to the lysosomes for degradation and recycle these cargos to produce energy under a stressful condition. Our results showed that downregulation of hTERT impaired autophagy levels by suppressing BECN1/beclin-1 and induced an increase of reactive oxygen species (ROS), which resulted in cell death ultimately. On the contrary, overexpression of BECN1 or treating cells with the antioxidant N-acetylcysteine (NAC) could restore the survival of hTERT knockdown cells. Our study will provide an additional basis of telomerase-targeting therapy for future clinical anticancer treatment.

The Roles of Beclin 1 Expression in Gastric Cancer: A Marker for Carcinogenesis, Aggressive Behaviors and Favorable Prognosis, and a Target of Gene Therapy.

Beclin 1 is encoded by Becn1, and plays a role in tumorigenesis, neurodegeneration, apoptosis and autophagy. Here, the aggressive phenotypes and relevant proteins were examined after Beclin 1 expression was altered in gastric cancer cells. We also observed the effects of Beclin 1 on gastric carcinogenesis using Becn1 knockout mice. Finally, clinicopathological significances of Beclin 1 expression were analyzed using meta- and bioinformatics analyses. Becn1 overexpression was found to inhibit proliferation, glucose metabolism, migration and invasion of gastric cancer cells, whereas its knockdown caused the opposite effects. Beclin 1 suppressed the tumor growth by decreasing proliferation and increasing apoptosis. The heterozygous abrogation of Becn1 in gastric pit, parietal and chief cells could not cause any epithelial lesion. Beclin 1-mediated chemoresistance was closely linked to the autophagy, Bax underexpression, and the overexpression of Bcl-2, LRP1, MDR1, and ING5. Bioinformatics analysis showed higher Becn1 mRNA expression in intestinal- than diffuse-type carcinomas (P<0.05), and in male than female gastric cancer patients (P<0.05). Becn1 hyperexpression was positively associated with both overall and progression-free survival rates of the cancer patients (P<0.05). Meta-analysis showed that down-regulated Beclin 1 expression in gastric cancer was positively with lymph node metastasis, TNM staging, dedifferentiation and poor prognosis (P<0.05). Becn1-related signal pathways in gastric cancer included prostate, lung, renal, colorectal, endometrial and thyroid cancers, glioma, and leukemia, the metabolism of amino acid, lipid and sugar, and some signal pathways of insulin, MAPK, TRL, VEGF, JAK-STAT, chemokine, p53, lysosome, peroxidome and ubiquitin-mediated protein degradation (P<0.05). These suggested that Beclin 1 might be considered as a potential marker of gastric carcinogenesis, aggressiveness and prognostic prediction, and as a target of gene therapy in gastric cancer.

Impact of differential and time-dependent autophagy activation on therapeutic efficacy in a model of Huntington disease

ABSTRACT Activation of macroautophagy/autophagy, a key mechanism involved in the degradation and removal of aggregated proteins, can successfully reverse Huntington disease phenotypes in various model systems. How neuronal autophagy impairments need to be considered in Huntington disease progression to achieve a therapeutic effect is currently not known. In this study, we used a mouse model of HTT (huntingtin) protein aggregation to investigate how different methods and timing of autophagy activation influence the efficacy of autophagy-activating treatment in vivo. We found that overexpression of human TFEB, a master regulator of autophagy, did not decrease mutant HTT aggregation. On the other hand, Becn1 overexpression, an autophagic regulator that plays a key role in autophagosome formation, partially cleared mutant HTT aggregates and restored neuronal pathology, but only when administered early in the disease progression. When Becn1 was administered at a later stage, when prominent mutant HTT accumulation and autophagy impairments have occurred, Becn1 overexpression did not rescue the mutant HTT-associated phenotypes. Together, these results demonstrate that the targets used to activate autophagy, as well as the timing of autophagy activation, are crucial for achieving efficient therapeutic effects.Abbreviations: AAV: adeno-associated viral vectors; ACTB: actin beta; BECN1: beclin 1, autophagy related; DAPI: 4ʹ,6-diamidino-2-phenylindole; GO: gene ontology; HD: Huntington disease; HTT: huntingtin; ICQ: Li’s intensity correlation quotient; IHC: immunohistochemistry; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; mHTT: mutant huntingtin; PCA: principal component analysis; PPP1R1B/DARPP-32: protein phosphatase 1 regulatory inhibitor subunit 1B; SQSTM1: sequestosome 1; TFEB: transcription factor EB; WB: western blot; WT: wild-type.

EHMT2/G9a Inhibits Aortic Smooth Muscle Cell Death by Suppressing Autophagy Activation.

Although EHMT2 (also known as G9a) plays a critical role in several kinds of cancers and cardiac remodeling, its function in vascular smooth muscle cells (VSMCs) remains unknown. In the present study, we revealed a novel function of EHMT2 in regulating autophagic cell death (ACD) of VSMC. Inhibition of EHMT2 by BIX01294 or knockdown of EHMT2 resulted in reduced VSMC numbers which were independent of proliferation and apoptosis. Interestingly, EHMT2 protein levels were significantly decreased in VSMCs treated with autophagic inducers. Moreover, more autophagic vacuoles and accumulated LC3II were detected in VSMCs treated with BIX01294 or lenti-shEHMT2 than their counterparts. Furthermore, we found that EHMT2 inhibited the ACD of VSMCs by suppressing autophagosome formation. Mechanistically, the pro-autophagic effect elicited by EHMT2 inhibition was associated with SQSTM1 and BECN1 overexpression. Moreover, these detrimental effects were largely nullified by SQSTM1 or BECN1 knockdown. More importantly, similar results were observed in primary human aortic VSMCs. Overall, these findings suggest that EHMT2 functions as a crucial negative regulator of ACD via decreasing SQSTM1 or BECN1 expression and that EHMT2 could be a potent therapeutic target for cardiovascular diseases (e.g., aortic dissection).

Puerarin inhibits the osteoclastogenesis by inhibiting RANKL-dependent and \u2013independent autophagic responses

BackgroundPuerarin exerts therapeutic effect on osteoporosis due to its inhibitory effect on the formation of osteoclasts. Puerarin is also widely established as an autophagy inhibitor. The study aimed to investigate the significance of autophagy in Puerarin-treated osteoclast formation.MethodsOsteoclast precursors (OCPs) derived from bone marrow-derived macrophages (BMMs) were treated with Puerarin along with RANKL or without RANKL, and then the autophagic parameters of OCPs (including autophagic proteins, LC3 transformation, autophagosome or LC3-puncta) were observed through Western Blotting, Transmission Electron Microscopy and Immunofluorescence assays. Next, after using overexpression vectors of autophagic genes (Atg7, Atg5 and BECN1) to alter autophagy activity, OCP proliferation was measured by Ethynyl deoxyuridine (EdU) assays and Cell Counting Kit-8 (CCK-8) kit, and osteoclast differentiation was assessed by Tartrate-resistant acid phosphatase (TRAP) staining.ResultsThe results showed that Puerarin could directly inhibit the autophagy and proliferation of OCPs. Importantly, overexpression of autophagic genes Atg5, Atg7 and BECN1 reversed Puerarin-inhibited OCP autophagy and proliferation. What’s more, RANKL could promote the autography of OCPs, which was recovered by Puerarin treatment. Interestingly, different from single-Puerarin treatment, we found that in the presence of RANKL, only BECN1 overexpression significantly reversed Puerarin-inhibited osteoclast differentiation and OCP autophagy.ConclusionIn conclusion, Puerarin could inhibit the OCP autophagy in the presence or absence of RANKL, which blocked the OCP proliferation and osteoclast differentiation respectively. Moreover, BECN1 plays an essential role in Puerarin-inhibited osteoclastogenesis. Our study provides potential clue to further complete the intrinsic mechanism of Puerarin in treating osteoporosis.

BECN1 promotes the migration of NSCLC cells through regulating the ubiquitination of Vimentin

ABSTRACTBECN1/Beclin1 is one of the key proteins in autophagy regulation. However, the biological functions of BECN1 in non-small cell lung cancer (NSCLC) were obscure. Here, we found that neither BECN1 knockdown nor overexpression affected the proliferation of NSCLC cells. Surprisingly, BECN1 overexpression increased cell migration and knocking down BECN1 significantly reduced the migratory ability of NSCLC cells. We further demonstrated that BECN1 could interact with Vimentin and affected its K48-linked ubiquitination. What’s more, BECN1 could also interact with ubiquitin-specific peptidase 14 (USP14), the key de-ubiquitinase of Vimentin, and regulated USP14 mediated de-ubiquitination of Vimentin. Thus, our studies revealed an oncosupportive role of BECN1 in the migration of NSCLC cells through regulating the ubiquitination of Vimentin.

Tumor Sidedness and Enriched Gene Groups for Efficacy of First-line Cetuximab Treatment in Metastatic Colorectal Cancer.

Molecular differences in tumor locations may contribute to the sidedness-specific response to cetuximab in metastatic colorectal cancer (mCRC). We investigated genes associated with the response to cetuximab treatment depending on tumor sidedness. Our study included 77 patients with mCRC (13/63, right/left) with KRAS exon 2 wild-type tumors from phase II trials of first-line therapy with cetuximab. Expression levels of 2,551 genes were measured in tissue samples by HTG EdgeSeq Oncology Biomarker Panel. Univariate Cox regression analysis using log2 values of counts per million (CPM) was conducted in each sidedness to assess associations with clinical outcomes, and to define the optimal cut-off point for clinically significant genes. In addition, a gene set enrichment analysis (GSEA) was performed to identify significant gene pathways in each sidedness. Sixty-nine patients were assessable for gene expression data. Overexpression of BECN1 [log2(CPM) ≥ 6.8] was associated with favorable survival, regardless of tumor sidedness. High expression of NOTCH1 [log2(CPM) ≥ 7.5] predicted significantly longer progression-free survival (PFS; median 14.7 vs. 11.1 months, HR 0.43, P = 0.01) and overall survival (OS; median 42.8 vs. 26.5 months, HR 0.35, P = 0.01) in left side but not in right side. The GSEA showed that regulation of DNA replication gene set correlated with favorable survival in the left, whereas the subcellular component and leukocyte migration gene sets were associated with good survival in the right. In conclusion, genes contributing to the efficacy of cetuximab treatment may differ according to the sidedness in mCRC. NOTCH1 may potentially discriminate favorable responders to cetuximab in patients with left-sided tumors.

Nano-sized Al2O3 particle-induced autophagy reduces osteolysis in aseptic loosening of total hip arthroplasty by negative feedback regulation of RANKL expression in fibroblasts

Aseptic loosening is mainly caused by wear debris generated by friction that can increase the expression of receptor activation of nuclear factor (NF)-κB (RANKL). RANKL has been shown to support the differentiation and maturation of osteoclasts. Although autophagy is a key metabolic pathway for maintaining the metabolic homeostasis of cells, no study has determined whether autophagy induced by Al2O3 particles is involved in the pathogenesis of aseptic loosening. The aim of this study was to evaluate RANKL levels in patients experiencing aseptic loosening after total hip arthroplasty (THA) and hip osteoarthritis (hOA) and to consequently clarify the relationship between RANKL and LC3II expression. We determined the levels of RANKL and autophagy in fibroblasts treated with Al2O3 particles in vitro while using shBECN-1 interference lentivirus vectors to block the autophagy pathway and BECN-1 overexpression lentivirus vectors to promote autophagy. We established a novel rat model of femoral head replacement and analyzed the effects of Al2O3 particles on autophagy levels and RANKL expression in synovial tissues in vivo. The RANKL levels in the revision total hip arthroplasty (rTHA) group were higher than those in the hOA group. In patients with rTHA with a ceramic interface, LC3II expression was high, whereas RANKL expression was low. The in vitro results showed that Al2O3 particles promoted fibroblast autophagy in a time- and dose-dependent manner and that RANKL expression was negatively correlated with autophagy. The in vivo results further confirmed these findings. Al2O3 particles induced fibroblast autophagy, which reduced RANKL expression. Decreasing the autophagy level promoted osteolysis and aseptic prosthetic loosening, whereas increasing the autophagy level reversed this trend.

Mir30c Is Involved in Diabetic Cardiomyopathy through Regulation of Cardiac Autophagy via BECN1.

Multiple factors have been shown to promote the progression of diabetic cardiomyopathy. A link has previously been found between Mir30 and autophagy in cancer cells and in the heart, but the role of Mir30 in diabetic heart has not been studied. Using in vitro and in vivo approaches, we found that the depletion of Mir30c and induction of BECN1 enhanced autophagy in diabetic (db/db) hearts and in cardiomyocytes treated with the fatty acid palmitate. We verified that Mir30c repressed BECN1 expression by direct binding to the BECN1 3′ UTRs. Mir30c overexpression inhibited the induction of BECN1 and subsequent autophagy in diabetic hearts and improved cardiac function and structure in diabetic mice. However, these effects were abrogated by BECN1 overexpression. Similarly, Mir30c knockdown resulted in increased BECN1 levels and autophagic flux, aggravating cardiac abnormalities. We also show that SP1, an important transcriptional factor in energy metabolism regulation, is a key upstream activator of Mir30c that binds the promoter region of Mir30c. Our findings indicate that downregulation of Mir30c and subsequent activation of BECN1 promotes autophagy, contributing to the pathogenesis of diabetic cardiomyopathy. This observation suggests a theoretical ground for developing microRNA-based therapeutics against diabetic cardiomyopathy by inhibiting autophagy.

HMGB1 is involved in autophagy inhibition caused by SNCA/α-synuclein overexpression

SNCA/α-synuclein and its rare mutations are considered as the culprit proteins in Parkinson disease (PD). Wild-type (WT) SNCA has been shown to impair macroautophagy in mammalian cells and in transgenic mice. In this study, we monitored the dynamic changes in autophagy process and confirmed that overexpression of both WT and SNCAA53T inhibits autophagy in PC12 cells in a time-dependent manner. Furthermore, we showed that SNCA binds to both cytosolic and nuclear high mobility group box 1 (HMGB1), impairs the cytosolic translocation of HMGB1, blocks HMGB1-BECN1 binding, and strengthens BECN1-BCL2 binding. Deregulation of these molecular events by SNCA overexpression leads to autophagy inhibition. Overexpression of BECN1 restores autophagy and promotes the clearance of SNCA. siRNA knockdown of Hmgb1 inhibits basal autophagy and abolishes the inhibitory effect of SNCA on autophagy while overexpression of HMGB1 restores autophagy. Corynoxine B, a natural autophagy inducer, restores the deficient cytosolic translocation of HMGB1 and autophagy in cells overexpressing SNCA, which may be attributed to its ability to block SNCA-HMGB1 interaction. Based on these findings, we propose that SNCA-induced impairment of autophagy occurs, in part, through HMGB1, which may provide a potential therapeutic target for PD.

Suppression of autophagy is protective in high glucose-induced cardiomyocyte injury

Hyperglycemia is linked to increased heart failure among diabetic patients. However, the mechanisms that mediate hyperglycemia-induced cardiac damage remain poorly understood. Autophagy is a cellular degradation pathway that plays important roles in cellular homeostasis. Autophagic activity is altered in the diabetic heart, but its functional role has been unclear. In this study, we determined if mimicking hyperglycemia in cultured cardiomyocytes from neonatal rats and adult mice could affect autophagic activity and myocyte viability. High glucose (17 or 30 mM) reduced autophagic flux compared with normal glucose (5.5 mM) as indicated by the difference in protein levels of LC3-II (microtubule-associated protein 1 light chain 3 form II) or the changes of punctate fluorescence patterns of GFP-LC3 and mRFP-LC3 in the absence and presence of the lysosomal inhibitor bafilomycin A1. Unexpectedly, the inhibited autophagy turned out to be an adaptive response that functioned to limit high glucose cardiotoxicity. Indeed, suppression of autophagy by 3-methyladenine or short hairpin RNA-mediated silencing of the Becn1 or Atg7 gene attenuated high glucose-induced cardiomyocyte death. Conversely, upregulation of autophagy with rapamycin or overexpression of Becn1 or Atg7 predisposed cardiomyocytes to high glucose toxicity. Mechanistically, the high glucose-induced inhibition of autophagy was mediated at least partly by increased mTOR signaling that likely inactivated ULK1 through phosphorylation at serine 467. Together, these findings demonstrate that high glucose inhibits autophagy, which is a beneficial adaptive response that protects cardiomyocytes against high glucose toxicity. Future studies are warranted to determine if autophagy plays a similar role in diabetic heart in vivo.

Abstract C45: Inhibition of antiapoptotic BCL2 members facilitates interferon regulatory factor-1 (IRF1) mediated prodeath signaling in breast cancer cells

Abstract Antiestrogens (AEs) have long been a standard treatment for estrogen receptor-positive (ER+) breast cancer patients. However, antiestrogen resistance, either de novo or acquired, is a major hurdle for effective therapy in breast cancer patients. To address this, the underlying mechanisms of antiestrogen resistance must be understood. Antiestrogens are known to induce apoptosis in sensitive breast cancer cells. The tumor suppressor gene interferon regulatory factor-1 (IRF1) plays a key role in signaling to proapoptotic BH3 only BCL2 (B-cell lymphoma 2) family members (i.e., BIK, PUMA, and BMF). In an attempt to understand IRF1-mediated signaling in AE sensitivity, AE-sensitive and -resistant breast cancer cells were made to overexpress IRF1 or a dominant negative IRF1 (dnIRF1; lacks the transactivation domain of IRF1 but retains the DNA-binding domain). We found that IRF1 regulates the transcription of proapoptotic BIK, BMF, and PUMA, which are necessary to induce apoptosis in AE-sensitive cells. Conversely, AE-resistant breast cancer cells have low IRF1 expression and increased levels of antiapoptotic BCL2 and BCLW. Previous work by our group showed that the inflammatory cytokine IFNγ can be used to induce IRF1 expression in AE-resistant cells, and restores the responsiveness of these cells to fulvestrant (Faslodex; ICI 182,780) through BH3-mediated apoptosis, suggesting a key role of IRF1 in endocrine-resistant breast cancer. We also discovered that the pan BCL2 inhibitor GX15-070 (obatoclax) significantly reduces cell proliferation and, in combination with fulvestrant or tamoxifen, results in a synergistic inhibition of cell growth in AE-resistant breast cancer cells. Treatment with obatoclax in AE-resistant cells results in a reduction in Beclin1 (BECN1) protein levels with a corresponding increase in cleaved caspase-7, indicating a possible role of autophagy and apoptosis in GX15-070-induced cell death. Moreover, overexpression of BECN1 in AE-resistant cells enhances obatoclax-mediated cell death. Collectively, our data demonstrate that a combination of obatoclax and an antiestrogen increases the levels of free BH3 domain proteins, thus facilitating mitochondrial dysfunction, and rendering breast cancer cells more susceptible to tumor cell death by IRF1-mediated signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr C45.

Autophagy patterns and prognosis in uveal melanomas

Autophagy is a self-degradation mechanism by which cells recycle their own cytoplasmic constituents. It has been claimed that, under certain conditions, such a process may be associated with tumor progression. In this study, the autophagic activity was investigated in a series of 99 uveal melanomas after immunohistochemical staining for the autophagy-associated proteins MAP1LC3A and BECN1, most commonly known as LC3A and Beclin 1, respectively. These were assessed in parallel with the hypoxia-inducible factor 1α (HIF1A) and its downstream protein lactate dehydrogenase 5 (composed by five LDHA subunits). Increased autophagic reactivity, detected by MAP1LC3A or BECN1, was associated with intense pigmentation and tumor hypoxia. Uveal melanomas with extensive overexpression of BECN1 or those with underexpression of this protein were associated with the worst prognosis, but the former manifested metastases much earlier than the latter; only 58% of patients with extensive BECN1 overexpression were alive at 4 years, compared with 80% of patients with underexpressed patterns. It is concluded that autophagy is commonly upregulated in uveal melanomas, and may be associated with hypoxia and intense pigmentation. There is a strong association between extensive BECN1 overexpression and early metastases/poor prognosis, and between underexpression of this protein and late metastases/better prognosis.