c-Jun N-terminal kinase activation by nitrobenzoxadiazoles leads to late-stage autophagy inhibition

Overexpression of Glutathione S-Transferases in Human Diseases: Drug Targets and Therapeutic Implications

Glutathione S-transferases (GSTs) are a major class of phase II metabolic enzymes. Besides their essential role in detoxification, GSTs also exert diverse biological activities in the occurrence and development of various diseases. In the past few decades, much research interest has been paid to exploring the mechanisms of GST overexpression in tumor drug resistance. Correspondingly, many GST inhibitors have been developed and applied, solely or in combination with chemotherapeutic drugs, for the treatment of multi-drug resistant tumors. Moreover, novel roles of GSTs in other diseases, such as pulmonary fibrosis and neurodegenerative diseases, have been recognized in recent years, although the exact regulatory mechanisms remain to be elucidated. This review, firstly summarizes the roles of GSTs and their overexpression in the above-mentioned diseases with emphasis on the modulation of cell signaling pathways and protein functions. Secondly, specific GST inhibitors currently in pre-clinical development and in clinical stages are inventoried. Lastly, applications of GST inhibitors in targeting cell signaling pathways and intracellular biological processes are discussed, and the potential for disease treatment is prospected. Taken together, this review is expected to provide new insights into the interconnection between GST overexpression and human diseases, which may assist future drug discovery targeting GSTs.

Autophagy Modulation as a Potential Therapeutic Strategy in Osteosarcoma: Current Insights and Future Perspectives

Autophagy, the process that enables the recycling and degradation of cellular components, is essential for homeostasis, which occurs in response to various types of stress. Autophagy plays an important role in the genesis and evolution of osteosarcoma (OS). The conventional treatment of OS has limitations and is not always effective at controlling the disease. Therefore, numerous researchers have analyzed how controlling autophagy could be used as a treatment or strategy to reverse resistance to therapy in OS. They highlight how the inhibition of autophagy improves the efficacy of chemotherapeutic treatments and how the promotion of autophagy could prove positive in OS therapy. The modulation of autophagy can also be directed against OS stem cells, improving treatment efficacy and preventing cancer recurrence. Despite promising findings, future studies are needed to elucidate the molecular mechanisms of autophagy and its relationship to OS, as well as the mechanisms underlying the functioning of autophagic modulators. Careful evaluation is required as autophagy modulation may have adverse effects on normal cells, and the optimization of autophagic modulators for use as drugs in OS is imperative.

Impacts of autophagy on the formation of organelle-free zone during the lens development

The thorough degeneration of organelles in the core of the lens is certainly a hallmark event during the lens development. Organelles degradation in the terminal differentiation process of lens fiber cells to form an organelle-free zone is critical for lens maturation and transparency. Several mechanisms have been proposed to expand our understanding of lens organelles degradation, including apoptotic pathways, the participation of ribozyme, proteolytic enzyme and phospholipase A and acyltransferase, and the newly discovered roles for autophagy. Autophagy is a lysosome-dependent degradation reaction during which the "useless" cellular components are degraded and recycled. These cellular components, such as incorrectly folded proteins, damaged organelles and other macromolecules, are first engulfed by the autophagosome before being further delivered to lysosomes for degradation. Although autophagy has been recognized involving in organelle degradation of the lens, the detailed functions remain to be discovered. Recent advances have revealed that autophagy not only plays a vital role in the intracellular quality control of the lens but is also involved in the degradation of nonnuclear organelles in the process of lens fiber cell differentiation. Herein, we first review the potential mechanisms of organelle-free zone formation, then discuss the roles of autophagy in intracellular quality control and cataract formation, and finally substantially summarize the potential involvement of autophagy in the development of organelle-free zone formation.

Upregulation of the EGFR/MEK1/MAPK1/2 signaling axis as a mechanism of resistance to antiestrogen‑induced BimEL dependent apoptosis in ER+ breast cancer cells

The epidermal growth factor receptor (EGFR) is commonly upregulated in multiple cancer types, including breast cancer. In the present study, evidence is provided in support of the premise that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitates the escape of breast cancer cells from BimEL‑dependent apoptosis, conferring resistance to therapy. This conclusion is based on the findings that ectopic BimEL cDNA overexpression and confocal imaging studies confirm the pro‑apoptotic role of BimEL in ERα expressing breast cancer cells and that upregulated EGFR/MEK1/MAPK1/2 signaling blocks BimEL pro‑apoptotic action in an antiestrogen‑resistant breast cancer cell model. In addition, the present study identified a pro‑survival role for autophagy in antiestrogen resistance while EGFR inhibitor studies demonstrated that a significant percentage of antiestrogen‑resistant breast cancer cells survive EGFR targeting by pro‑survival autophagy. These pre‑clinical studies establish the possibility that targeting both the MEK1/MAPK1/2 signaling axis and pro‑survival autophagy may be required to eradicate breast cancer cell survival and prevent the development of antiestrogen resistance following hormone treatments. The present study uniquely identified EGFR upregulation as one of the mechanisms breast cancer cells utilize to evade the cytotoxic effects of antiestrogens mediated through BimEL‑dependent apoptosis.

TNF Receptor Associated Factor 2 (TRAF2) Signaling in Cancer

Simple Summary

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) is an intracellular adapter protein with E3 ligase activity, which interacts with a plethora of other signaling proteins, including plasma membrane receptors, kinases, phosphatases, other E3 ligases, and deubiquitinases. TRAF2 is involved in various cancer-relevant cellular processes, such as the activation of transcription factors of the NFκB family, stimulation of mitogen-activated protein (MAP) kinase cascades, endoplasmic reticulum (ER) stress signaling, autophagy, and the control of cell death programs. In a context-dependent manner, TRAF2 promotes tumor development but it can also act as a tumor suppressor. Based on a general description, how TRAF2 in concert with TRAF2-interacting proteins and other TRAF proteins act at the molecular level is discussed for its importance for tumor development and its potential usefulness as a therapeutic target in cancer therapy.

Abstract

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) has been originally identified as a protein interacting with TNF receptor 2 (TNFR2) but also binds to several other receptors of the TNF receptor superfamily (TNFRSF). TRAF2, often in concert with other members of the TRAF protein family, is involved in the activation of the classical NFκB pathway and the stimulation of various mitogen-activated protein (MAP) kinase cascades by TNFRSF receptors (TNFRs), but is also required to inhibit the alternative NFκB pathway. TRAF2 has also been implicated in endoplasmic reticulum (ER) stress signaling, the regulation of autophagy, and the control of cell death programs. TRAF2 fulfills its functions by acting as a scaffold, bringing together the E3 ligase cellular inhibitor of apoptosis-1 (cIAP1) and cIAP2 with their substrates and various regulatory proteins, e.g., deubiquitinases. Furthermore, TRAF2 can act as an E3 ligase by help of its N-terminal really interesting new gene (RING) domain. The finding that TRAF2 (but also several other members of the TRAF family) interacts with the latent membrane protein 1 (LMP1) oncogene of the Epstein–Barr virus (EBV) indicated early on that TRAF2 could play a role in the oncogenesis of B-cell malignancies and EBV-associated non-keratinizing nasopharyngeal carcinoma (NPC). TRAF2 can also act as an oncogene in solid tumors, e.g., in colon cancer by promoting Wnt/β-catenin signaling. Moreover, tumor cell-expressed TRAF2 has been identified as a major factor-limiting cancer cell killing by cytotoxic T-cells after immune checkpoint blockade. However, TRAF2 can also be context-dependent as a tumor suppressor, presumably by virtue of its inhibitory effect on the alternative NFκB pathway. For example, inactivating mutations of TRAF2 have been associated with tumor development, e.g., in multiple myeloma and mantle cell lymphoma. In this review, we summarize the various TRAF2-related signaling pathways and their relevance for the oncogenic and tumor suppressive activities of TRAF2. Particularly, we discuss currently emerging concepts to target TRAF2 for therapeutic purposes.

Anti-influenza A virus activity and structure-activity relationship of a series of nitrobenzoxadiazole derivatives

Influenza viruses represent a major threat to human health and are responsible for seasonal epidemics, along with pandemics. Currently, few therapeutic options are available, with most drugs being at risk of the insurgence of resistant strains. Hence, novel approaches targeting less explored pathways are urgently needed. In this work, we assayed a library of nitrobenzoxadiazole derivatives against the influenza virus A/Puerto Rico/8/34 H1N1 (PR8) strain. We identified three promising 4-thioether substituted nitrobenzoxadiazoles (12, 17, and 25) that were able to inhibit viral replication at low micromolar concentrations in two different infected cell lines using a haemagglutination assay. We further assessed these molecules using an In-Cell Western assay, which confirmed their potency in the low micromolar range. Among the three molecules, 12 and 25 displayed the most favourable profile of activity and selectivity and were selected as hit compounds for future optimisation studies.

Discovery of 6-(7-Nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol Derivatives as Glutathione Transferase Inhibitors with Favorable Selectivity and Tolerated Toxicity

Glutathione transferase (GST P1-1) is a potential target for anticancer drugs. In this work, a series of 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX) derivatives as GST P1-1 inhibitors were designed, synthesized, and evaluated for their biological activity. Among the target compounds, 4n showed more selective inhibition toward GST P1-1 and GST M2-2, better water solubility, and more potent anticancer activities toward all the tested cancer cells (except for HOS) than its parent molecule. Detailed biological studies on the effect of 4n toward 143b cells revealed that 4n could arrest the cell cycle at the G2 phase and induced cell apoptosis in a dose-dependent manner. Like NBDHEX, 4n displayed good pharmacokinetic characteristics. An in vivo study on 143b xenograft models demonstrated that 4n could significantly reduce tumor growth in a dose-dependent manner, showing stronger antitumor activity than NBDHEX. Thus, 4n deserves to be further investigated as a potential antitumor agent for cancer therapy.

Paeonol derivative-6 attenuates inflammation by activating ZEB2 in acute liver injury

Paeonol is a natural phenolic compound and isolated as an active ingredient from Moutan Cortex. Paeonol derivative-6 (DPF-6) is a derivative of paeonol improved in water solubility and bioavailability. Previous studies have reported that paeonol possesses a variety of pharmacological activities, such as antioxidant and anti-inflammatory properties. Moreover, we have previously verified that DPF-6 has anti-inflammatory effects. However, the role and fundamental mechanism of DPF-6 in acute liver injury (ALI) was still unclear. In this study, we indicated that DPF-6 inhibited inflammation and the expression of TNF-α, IL-6 and IL-1β in liver tissues and LPS-mediated L-02 cells, concomitant with the upregulated expression of ZEB2. More importantly, it was demonstrated that overexpression of ZEB2 inhibited the expression level of TNF-α, IL-6 and IL-1β in LPS-mediated L-02 cells. In contrast, knockdown of ZEB2 increased the expression level of TNF-α, IL-6 and IL-1β in LPS-mediated L-02 cells. Further studies showed that ZEB2 inhibited the inflammation cytokine secretion via JNK signaling pathway in L-02 cells. Taken together, all the above results indicate that DPF-6 increased the expression of ZEB2, consequently inhibited inflammation cytokine secretion through JNK signaling pathway, which may be utilized as a potential anti-inflammation monomeric compound in the treatment of ALI.

In Vitro and in Vivo Efficacy of NBDHEX on Gefitinib-resistant Human Non-small Cell Lung Cancer

Gefitinib, a first-generation EGFR tyrosine kinase inhibitor (EGFR-TKI), is recommended for treatment of non-small cell lung cancer (NSCLC) patients who harbor activating EGFR mutations. However, the tumors of most patients initially sensitive to gefitinib will develop resistance within several months of therapy. Drug resistance is a major obstacle to NSCLC treatment. The novel glutathione transferase P1 (GSTPi) inhibitor 6-(7-nitro-2, 1, 3-benzoxadiazol-4-ylthio) hexanol (NBDHEX) has recently been shown to be active against tumors. In this study, we investigated the in vitro and in vivo efficacy of NBDHEX against NSCLC. Treatment with NBDHEX inhibited GSTpi enzymatic activity and promoted apoptosis of gefinitb-resistant NSCLC cells. Moreover, NBDHEX reduced tumor growth in mice. These findings indicated that NBDHEX is a good candidate for treatment of NSCLC patients, and that NBDHEX offers a new approach to cancer therapy.

Cilostazol alleviate nicotine induced cardiomyocytes hypertrophy through modulation of autophagy by CTSB/ROS/p38MAPK/JNK feedback loop

Nicotine is proved to be an important factor for cardiac hypertrophy. Autophagy is important cell recycling system involved in the regulation of cardiac hypertrophy. Cilostazol, which is often used in the management of peripheral vascular disease. However, the effects of cilostazol on nicotine induced autophagy and cardiac hypertrophy are unclear. Here, we aim to determine the role and molecular mechanism of cilostazol in alleviating nicotine-induced cardiomyocytes hypertrophy through modulating autophagy and the underlying mechanisms. Our results clarified that nicotine stimulation caused cardiomyocytes hypertrophy and autophagy flux impairment significantly in neonatal rat ventricular myocytes (NRVMs), which were evidenced by augments of LC3-II and p62 levels, and impaired autophagosomes clearance. Interestingly, cathepsin B (CTSB) activity decreased dramatically after stimulation with nicotine in NRVMs, which was crucial for substrate degradation in the late stage of autophagy process, and cilostazol could reverse this effect dramatically. Intracellular ROS levels were increased significantly after nicotine exposure. Meanwhile, p38MAPK and JNK were activated after nicotine treatment. By using ROS scavenger N-acetyl-cysteine (NAC) could reverse the effects of nicotine by down-regulation the phosphorylation of p38MAPK and JNK pathways, and pretreatment of specific inhibitors of p38MAPK and JNK could restore the autophagy impairment and cardiomyocytes hypertrophy induced by nicotine. Moreover, CTSB activity of lysosome regained after the treatment with cilostazol. Cilostazol also inhibited the ROS accumulation and the activation of p38MAPK and JNK, which providing novel connection between lysosome CTSB and ROS/p38MAPK/JNK related oxidative stress pathway. This is the first demonstration that cilostazol could alleviate nicotine induced cardiomyocytes hypertrophy through restoration of autophagy flux by activation of CTSB and inhibiting ROS/p38/JNK pathway, exhibiting a feedback loop on regulation of autophagy and cardiomyocytes hypertrophy.

FK866 attenuates sepsis-induced acute lung injury through c-jun-N-terminal kinase (JNK)-dependent autophagy

AIMS

Increasing evidence indicates that FK866, a specific noncompetitive nicotinamide phosphoribosyl transferase inhibitor, exhibits a protective effect on acute lung injury (ALI). Autophagy plays a pivotal role in sepsis-induced ALI. However, the contribution of autophagy and the underlying mechanism by which FK866-confered lung protection remains elusive. Herein, we aimed to study whether FK866 could alleviate sepsis-induced ALI via the JNK-dependent autophagy.

MAIN METHODS

Male C57BL/6 mice were subjected to cecal ligation and puncture (CLP) to establish the polymicrobial sepsis mice model, and treated with FK866 (10 mg/kg) at 24, 12 and 0.5 h before the CLP procedure. The lung protective effects were measured by lung histopathology, tissue edema, vascular leakage, inflammation infiltration, autophagy-related protein expression and JNK activity. A549 cells were stimulated with LPS (1000 ng/ml) to generate the ALI cell model, and pretreated with FK866 or SP600125 for 30 min to measure the autophagy-related protein expression and JNK activity.

KEY FINDINGS

Our results demonstrated that FK866 reduced lung injury score, tissue edema, vascular leakage, and inflammatory infiltration, and upregulated autophagy. The protective effect of autophagy conferred by FK866 on ALI was further clarified by using 3-methyladenine (3MA) and rapamycin. Additionally, the activity of JNK was suppressed by FK866, and inhibition of JNK promoted autophagy and showed a benefit effect.

SIGNIFICANCE

Our study indicates that FK866 protects against sepsis-induced ALI by induction of JNK-dependent autophagy. This may provide new insights into the functional mechanism of NAMPT inhibition in sepsis-induced ALI.

Effects of Glutathione Transferase-Targeting Nitrobenzoxadiazole Compounds in Relation to PD-L1 Status in Human Melanoma Cells

BACKGROUND

PD-L1 is a membrane protein with inhibitory effects on immune responses, whose expression has been correlated with high aggressiveness and the propensity of melanoma to metastasize. The nitrobenzoxadiazole (NBD) NBDHEX and its analog MC3181 are endowed with strong antitumor activity towards melanoma and a significant ability to reduce its adhesion and invasiveness. Therefore, we investigated whether PD-L1 status could affect cell sensitivity to the cytotoxic effects of NBDs. We then evaluated the effects of NBDHEX on PD-L1 expression and autophagy in melanoma cells. We used the BRAF-mutated A375 melanoma cell line and an A375 variant population enriched for PD-L1+ cells as a model. The cytotoxic effects of NBDs were evaluated in comparison to those of the BRAF inhibitor vemurafenib and the autophagy inhibitor chloroquine.

METHODS

The effect of NBDHEX on autophagy was determined by measuring LC3-II and p62 protein levels by Western blot. The cytotoxic activity of the compounds was evaluated by sulforhodamine B assay. PD-L1 expression and plasma membrane localization were analyzed by FACS and Western blot analysis.

RESULTS

NBDHEX behaves as a late-autophagy inhibitor in A375 melanoma cells, as previously found in other tumor cell lines. NBDHEX and MC3181 showed strong and comparable cytotoxic activity in both parental and PD-L1+ A375 cells, with IC50 values in the sub-micromolar range. Conversely, cells sorted for high PD-L1 expression had lower sensitivity to both the BRAF inhibitor vemurafenib and the autophagy inhibitor chloroquine. NBDHEX treatment did not change the total expression and cell surface localization of PD-L1 in both parental and PD-L1+ A375 cells.

CONCLUSIONS

Our data suggest that NBDs may represent a promising treatment strategy for melanoma with elevated PD-L1 expression.

Sirt3 promotes sensitivity to sunitinib-induced cardiotoxicity via inhibition of GTSP1/JNK/autophagy pathway in vivo and in vitro

Sunitinib malate is a multi-targeted tyrosine kinase inhibitor used extensively for treatment of human tumors. However, cardiovascular adverse effects of sunitinib limit its clinical use. It is pivotal to elucidate molecular targets that mediate sunitinib-induced cardiotoxicity. Sirtuin 3 (Sirt3) is an effective mitochondrial deacetylase that has been reported to regulate sensitivity of different types of cells to chemotherapies, but roles of Sirt3 in sunitinib-induced cardiotoxicity have not been investigated. In the present study, we established wild type, Sirt3-knockout, and Sirt3-overexpressing mouse models of sunitinib (40 mg kg^-1 day^-1 for 28 days)-induced cardiotoxicity and examined cardiovascular functions and pathological changes. We further cultured wild type, Sirt3-knockout, and Sirt3-overexpressing primary mouse cardiac pericytes and analyzed sunitinib (10 μMol for 48 h)-induced alterations in cellular viability, cell death processes, and molecular pathways. Our results show that sunitinib predominantly induced hypertension, left ventricular systolic dysfunction, and cardiac pericyte death accompanied with upregulation of Sirt3 in cardiac pericytes, and these cardiotoxicities were significantly attenuated in Sirt3-knockout mice, but aggravated in Sirt3-overexpressing mice. Mechanistically, sunitinib induced cardiac pericyte death through inhibition of GSTP1/JNK/autophagy pathway and Sirt3 interacted with and inhibited GSTP1, further inhibiting the pathway and aggravating sunitinib-induced pericyte death. Conclusively, we demonstrate that Sirt3 promotes sensitivity to sunitinib-induced cardiotoxicity via GSTP1/JNK/autophagy pathway. Our results suggest Sirt3 might be a potential target for developing cardioprotective therapies for sunitinib-receiving patients.

Glutathione S-transferase π: a potential role in antitumor therapy

Glutathione S-transferase π (GSTπ) is a Phase II metabolic enzyme that is an important facilitator of cellular detoxification. Traditional dogma asserts that GSTπ functions to catalyze glutathione (GSH)-substrate conjunction to preserve the macromolecule upon exposure to oxidative stress, thus defending cells against various toxic compounds. Over the past 20 years, abnormal GSTπ expression has been linked to the occurrence of tumor resistance to chemotherapy drugs, demonstrating that this enzyme possesses functions beyond metabolism. This revelation reveals exciting possibilities in the realm of drug discovery, as GSTπ inhibitors and its prodrugs offer a feasible strategy in designing anticancer drugs with the primary purpose of reversing tumor resistance. In connection with the authors' current research, we provide a review on the biological function of GSTπ and current developments in GSTπ-targeting drugs, as well as the prospects of future strategies.

Role of the MAPK/cJun NH2-terminal kinase signaling pathway in starvation-induced autophagy

Autophagy is required for cellular homeostasis and can determine cell viability in response to stress. It is established that MTOR is a master regulator of starvation-induced macroautophagy/autophagy, but recent studies have also implicated an essential role for the MAPK8/cJun NH₂-terminal kinase 1 signal transduction pathway. We found that MAPK8/JNK1 and MAPK9/JNK2 were not required for autophagy caused by starvation or MTOR inhibition in murine fibroblasts and epithelial cells. These data demonstrate that MAPK8/9 has no required role in starvation-induced autophagy. We conclude that the role of MAPK8/9 in autophagy may be context-dependent and more complex than previously considered.

Abbreviations: AKT: thymoma viral proto-oncogene;ALB: albumin; ATG4: autophagy related 4; BCL2: B cell leukemia/lymphoma 2; BECN1: beclin 1, autophagy related; BNIP3: BCL2/adenovirus E1B interacting protein 3; CQ: chloroquine diphosphate; DMEM: Dulbecco’s modified Eagle’s medium; EDTA: ethylenediaminetetraacetic acid; EBSS: Earle’s balanced salt solution; FBS: fetal bovine serum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; HRAS: Harvey rat sarcoma virus oncogene; IgG: Immunoglobulin G; MAPK3/ERK1: mitogen-activated protein kinase 3; MAPK8/JNK1: mitogen-activated protein kinase 8; MAPK9/JNK2: mitogen-activated protein kinase 9; MAPK10/JNK3: mitogen-activated protein kinase 10; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MEFs: mouse embryonic fibroblasts; MTOR: mechanistic target of rapamycin kinase; RPS6KB1/p70: ribosomal protein S6 kinase, polypeptide 1; PPARA: peroxisome proliferator activated receptor alpha; SEM: standard error of the mean; SQSTM1/p62: sequestosome 1; TORC1: target of rapamycin complex 1; TORC2: target of rapamycin complex 2; TRP53: transforming related protein 53; TUBA: tubulin alpha; UV: ultraviolet; WT: wild-type

6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio) hexanol: a promising new anticancer compound

The 7-nitro-2,1,3-nitrobenzoxadiazole (NBD) derivatives are a series of compounds containing the NBD scaffold that are not glutathione (GSH) peptidomimetics, and result in a strong inhibition of glutathione S-transferases (GSTs). Growing evidences highlight their pivotal roles and outstanding anticancer activity in different tumor models. In particular, 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio) hexanol (NBDHEX) is extensively studied, which is a very efficient inhibitor of GSTP1-1. It triggers apoptosis in several tumor cell lines and this cytotoxic activity is observed at micro and submicromolar concentrations. Importantly, studies have shown that NBDHEX acts as an anticancer drug by inhibiting GSTs catalytic activity, avoiding inconvenience of the inhibitor extrusion from the cell by specific pumps and disrupting the interaction between the GSTP1-1 and key signaling effectors. Additionally, some researchers also have discovered that NBDHEX can act as late-phase autophagy inhibitor, which opens new opportunities to fully exploit its therapeutic potential. In this review, we summarize the advantages, anticancer mechanisms, and analogs of this compound, which will establish the basis on the usage of NBDHEX in clinical applications in future.

A Dual Role of P53 in Regulating Colistin-Induced Autophagy in PC-12 Cells

This study aimed to investigate the mechanism of p53 in regulating colistin-induced autophagy in PC-12 cells. Importantly, cells were treated with 125 μg/ml colistin for 12 and 24 h after transfection with p53 siRNA or recombinant plasmid. The hallmarks of autophagy and apoptosis were examined by real-time PCR and western blot, fluorescence/immunofluorescence microscopy, and electron microscopy. The results showed that silencing of p53 leads to down-regulation of Atg5 and beclin1 for 12 h while up-regulation at 24 h and up-regulation of p62 noted. The ratio of LC3-II/I and autophagic vacuoles were significantly increased at 24 h, but autophagy flux was blocked. The cleavage of caspase3 and PARP (poly ADP-ribose polymerase) were enhanced, while PC-12-sip53 cells exposed to 3-MA showed down-regulation of apoptosis. By contrast, the expression of autophagy-related genes and protein reduced in p53 overexpressing cells following a time dependent manner. Meanwhile, there was an increase in the expression of activated caspase3 and PARP, condensed and fragmented nuclei were evident. Conclusively, the data supported that silencing of p53 promotes impaired autophagy, which acts as a pro-apoptotic induction factor in PC-12 cells treated with colistin for 24 h, and overexpression of p53 inhibits autophagy and accelerates apoptosis. Hence, it has been suggested that p53 could not act as a neuro-protective target in colistin-induced neurotoxicity.

FK866 attenuates acute hepatic failure through c-jun-N-terminal kinase (JNK)-dependent autophagy

FK866 exhibits a protective effect on D-galactosamine (GaIN)/lipopolysaccharide (LPS) and concanavalin A (ConA)-induced acute liver failure (ALF), but the mechanism by which FK866 affords this benefit has not yet been elucidated. Autophagy has a protective effect on acute liver injury. However, the contribution of autophagy to FK866-conferred hepatoprotection is still unclear. This study aimed to investigate whether FK866 could attenuate GaIN/LPS and ConA-induced ALF through c-jun-N-terminal kinase (JNK)-dependent autophagy. In vivo, Mice were pretreated with FK866 at 24, 12, and 0.5 h before treatment with GaIN/LPS and ConA. 3-methyladenine (3MA) or rapamycin were used to determine the role of autophagy in FK866-conferred hepatoprotection. In primary hepatocytes, autophagy was inhibited by 3MA or autophagy-related protein 7 (Atg7) small interfering RNA (siRNA). JNK was suppressed by SP600125 or Jnk siRNA. FK866 alleviated hepatotoxicity and increased autophagy while decreased JNK activation. Suppression of autophagy abolished the FK866-conferred protection. Inhibition of JNK increased autophagy and exhibited strongly protective effect. Collectively, FK866 could ameliorate GaIN/LPS and ConA-induced ALF through induction of autophagy while suppression of JNK. These findings suggest that FK866 acts as a simple and applicable preconditioning intervention to protect against ALF; autophagy and JNK may also provide therapeutic targets for ALF treatment.

Autophagy as a potential target for sarcoma treatment

Autophagy is a constitutively active, evolutionary conserved, catabolic process for maintaining homeostasis in cellular stress responses and cell survival. Although its mechanism has not been fully illustrated, recent work on autophagy in various types of sarcomas has demonstrated that autophagy exerts an important role in sarcoma cell growth and proliferation, in pro-survival response to therapies and stresses, and in therapeutic resistance of sarcoma. Thus, the autophagic process is being seen as a possibly novel therapeutic target of sarcoma. Additionally, some co-regulators of autophagy have also been investigated as promising biomarkers for the diagnosis and prognosis of sarcoma. In this review, we summarize contemporary advances in the role of autophagy in sarcoma and discuss the potential of autophagy as a new target for sarcoma treatment.

Silencing Livin induces apoptotic and autophagic cell death, increasing chemotherapeutic sensitivity to cisplatin of renal carcinoma cells

Renal cell carcinoma (RCC) accounts for 3 % of all adult malignancies and is the most lethal urological cancer. Livin is a member of the inhibitor of apoptosis protein (IAP) family, which is associated with tumor resistance to radiotherapy and chemotherapy. Clinical data also showed that patients with high tumor grades and stages have higher expression levels of Livin in RCC cells. Autophagy is a survival mechanism activated in response to nutrient deprivation. A possible role of Livin in the autophagy of RCC cells has not been investigated; therefore, this pioneer study was carried out. Livin was silenced in RCC cells (slow virus infection [SVI]-shLivin cells) by lentiviral transfection. Then, mRNA and protein expression levels in the transfected cells were assessed by quantitative fluorescence PCR and Western blotting, respectively. In addition, acridine orange staining and electron microscopy were used to assess autophagy in SVI-shLivin cells. The cisplatin IC50 values for RCC cells were measured by the CCK8 assay. Potent antitumor activities were observed in xenograft mouse models generated with Livin-silenced RCC cells in terms of delayed tumor onset and suppressed tumor growth. These results suggested that Livin silencing could increase the chemotherapeutic sensitivity of RCC cells to cisplatin and induce autophagic cell death. A possible mechanism of Bcl-2 and Akt pathway involvement was discussed specifically in this study. Overall, Livin silencing induces apoptotic and autophagic cell death and increases chemotherapeutic sensitivity of RCC cells to cisplatin.

Bexarotene targets autophagy and is protective against thromboembolic stroke in aged mice with tauopathy

Stroke is a highly debilitating, often fatal disorder for which current therapies are suitable for only a minor fraction of patients. Discovery of novel, effective therapies is hampered by the fact that advanced age, primary age-related tauopathy or comorbidities typical to several types of dementing diseases are usually not taken into account in preclinical studies, which predominantly use young, healthy rodents. Here we investigated for the first time the neuroprotective potential of bexarotene, an FDA-approved agent, in a co-morbidity model of stroke that combines high age and tauopathy with thromboembolic cerebral ischemia. Following thromboembolic stroke bexarotene enhanced autophagy in the ischemic brain concomitantly with a reduction in lesion volume and amelioration of behavioral deficits in aged transgenic mice expressing the human P301L-Tau mutation. In in vitro studies bexarotene increased the expression of autophagy markers and reduced autophagic flux in neuronal cells expressing P301L-Tau. Bexarotene also restored mitochondrial respiration deficits in P301L-Tau neurons. These newly described actions of bexarotene add to the growing amount of compelling data showing that bexarotene is a potent neuroprotective agent, and identify a novel autophagy-modulating effect of bexarotene.