The Molecular Mechanism and Therapeutic Application of Autophagy for Urological Disease

Autophagy is a lysosomal degradation process known as autophagic flux, involving the engulfment of damaged proteins and organelles by double-membrane autophagosomes. It comprises microautophagy, chaperone-mediated autophagy (CMA), and macroautophagy. Macroautophagy consists of three stages: induction, autophagosome formation, and autolysosome formation. Atg8-family proteins are valuable for tracking autophagic structures and have been widely utilized for monitoring autophagy. The conversion of LC3 to its lipidated form, LC3-II, served as an indicator of autophagy. Autophagy is implicated in human pathophysiology, such as neurodegeneration, cancer, and immune disorders. Moreover, autophagy impacts urological diseases, such as interstitial cystitis /bladder pain syndrome (IC/BPS), ketamine-induced ulcerative cystitis (KIC), chemotherapy-induced cystitis (CIC), radiation cystitis (RC), erectile dysfunction (ED), bladder outlet obstruction (BOO), prostate cancer, bladder cancer, renal cancer, testicular cancer, and penile cancer. Autophagy plays a dual role in the management of urologic diseases, and the identification of potential biomarkers associated with autophagy is a crucial step towards a deeper understanding of its role in these diseases. Methods for monitoring autophagy include TEM, Western blot, immunofluorescence, flow cytometry, and genetic tools. Autophagosome and autolysosome structures are discerned via TEM. Western blot, immunofluorescence, northern blot, and RT-PCR assess protein/mRNA levels. Luciferase assay tracks flux; GFP-LC3 transgenic mice aid study. Knockdown methods (miRNA and RNAi) offer insights. This article extensively examines autophagy's molecular mechanism, pharmacological regulation, and therapeutic application involvement in urological diseases.

Pharmacotherapy developments in autophagy inhibitors for bladder cancer

INTRODUCTION

Autophagy is an intracellular process that plays a key role in the cellular homeostasis. Recently, it has been described as a potential therapeutic target in oncology, whether by activating or inhibiting its different cascades. Autophagy inhibitors interact with different molecular processes of the hallmarks of cancer.

AREAS COVERED

Multiple proteins of the autophagy cascade could be aimed by specific inhibitors in many tumors, notably bladder cancer. In fact, bladder cancer has been increasing in prevalence over the last decade, and resistance to conventional treatment has been extensively reported in the literature. Autophagy inhibitors in bladder cancer have been described in preclinical studies to increase the sensitivity of the tumor to chemotherapy and radiotherapy. This paper is a review of the literature, which selected randomized trials, cohort studies, and case-control studies documenting the relationship between autophagy inhibitors and bladder cancer treatment.

EXPERT OPINION

Autophagy is a promising pathway for cancer cell targeting that opens the horizons for a potential new therapeutic area in particular the multidisciplinary management of bladder cancer.

Energy metabolism disturbance in migraine: From a mitochondrial point of view

Migraine is a serious central nervous system disease with a high incidence rate. Its pathogenesis is very complex, which brings great difficulties for clinical treatment. Recently, many studies have revealed that mitochondrial dysfunction may play a key role in migraine, which affects the hyperosmotic of Ca²⁺, the excessive production of free radicals, the decrease of mitochondrial membrane potential, the imbalance of mPTP opening and closing, and the decrease of oxidative phosphorylation level, which leads to neuronal energy exhaustion and apoptosis, and finally lessens the pain threshold and migraine attack. This article mainly introduces cortical spreading depression, a pathogenesis of migraine, and then damages the related function of mitochondria, which leads to migraine. Oxidative phosphorylation and the tricarboxylic acid cycle are the main ways to provide energy for the body. 95 percent of the energy needed for cell survival is provided by the mitochondrial respiratory chain. At the same time, hypoxia can lead to cell death and migraine. The pathological opening of the mitochondrial permeability transition pore can promote the interaction between pro-apoptotic protein and mitochondrial, destroy the structure of mPTP, and further lead to cell death. The increase of mPTP permeability can promote the accumulation of reactive oxygen species, which leads to a series of changes in the expression of proteins related to energy metabolism. Both Nitric oxide and Calcitonin gene-related peptide are closely related to the attack of migraine. Recent studies have shown that changes in their contents can also affect the energy metabolism of the body, so this paper reviews the above mechanisms and discusses the mechanism of brain energy metabolism of migraine, to provide new strategies for the prevention and treatment of migraine and promote the development of individualized and accurate treatment of migraine.

Vacuolar proteases and autophagy in phytopathogenic fungi: A review

Autophagy (macroautophagy) is a survival and virulence mechanism of different eukaryotic pathogens. Autophagosomes sequester cytosolic material and organelles, then fuse with or enter into the vacuole or lysosome (the lytic compartment of most fungal/plant cells and many animal cells, respectively). Subsequent degradation of cargoes delivered to the vacuole via autophagy and endocytosis maintains cellular homeostasis and survival in conditions of stress, cellular differentiation, and development. PrA and PrB are vacuolar aspartyl and serine endoproteases, respectively, that participate in the autophagy of fungi and contribute to the pathogenicity of phytopathogens. Whereas the levels of vacuolar proteases are regulated by the expression of the genes encoding them (e.g., PEP4 for PrA and PRB1 for PrB), their activity is governed by endogenous inhibitors. The aim of the current contribution is to review the main characteristics, regulation, and role of vacuolar soluble endoproteases and Atg proteins in the process of autophagy and the pathogenesis of three fungal phytopathogens: Ustilago maydis, Magnaporthe oryzae, and Alternaria alternata. Aspartyl and serine proteases are known to participate in autophagy in these fungi by degrading autophagic bodies. However, the gene responsible for encoding the vacuolar serine protease of U. maydis has yet to be identified. Based on in silico analysis, this U. maydis gene is proposed to be orthologous to the Saccharomyces cerevisiae genes PRB1 and PBI2, known to encode the principal protease involved in the degradation of autophagic bodies and its inhibitor, respectively. In fungi that interact with plants, whether phytopathogenic or mycorrhizal, autophagy is a conserved cellular degradation process regulated through the TOR, PKA, and SNF1 pathways by ATG proteins and vacuolar proteases. Autophagy plays a preponderant role in the recycling of cell components as well as in the fungus-plant interaction.

Cornel Iridoid Glycoside and Its Effective Component Regulate ATPase Vps4A/JNK to Alleviate Autophagy Deficit with Autophagosome Accumulation

Improving autophagy-lysosome fusion has been considered a key method in the treatment of Alzheimer's disease (AD). Cornel iridoid glycoside (CIG) is extracted from Cornus officinalis and has been shown to promote the clearance of tau oligomers via the autophagy pathway. However, the mechanisms of CIG on autophagy deficits are not understood. Here, we found autophagy deficit and tau aggregation in the brains of P301S tau transgenic mice and MAPT cells edited using CRISPR-Cas9 technology. CIG decreased tau aggregation and alleviated autophagic markers involving the JNK/Beclin-1 signaling pathway which demonstrated CIG that might enhance lysosome formation by upregulating ATPase Vps4A expression. Knocking down VPS4A increased autophagosome accumulation and attenuated the effect of CIG on p62. In addition, CIG had no effect on tau oligomers but still inhibited the level of tau monomer in VPS4A knockout cells. The effective component (Sweroside, SWE) of CIG attenuated tau oligomers accumulation and increased Vps4A level but not CHMP2B. SWE could not change the level of tau oligomers in VPS4A knockout cells. In conclusion, CIG suppressed autophagosome accumulation by regulating the ATPase Vps4A/JNK. SWE is a core of active factors of CIG in Vps4A regulation. These findings suggest CIG may be a potential drug in AD treatment.

Construction of PIK3C3 Transgenic Pig and Its Pathogenesis of Liver Damage

As a member of the PIKs family, PIK3C3 participates in autophagy and plays a central role in liver function. Several studies demonstrated that the complete suppression of PIK3C3 in mammals can cause hepatomegaly and hepatosteatosis. However, the function of PIK3C3 overexpression on the liver and other organs is still unknown. In this study, we successfully generated PIK3C3 transgenic pigs through somatic cell nuclear transfer (SCNT) by designing a specific vector for the overexpression of PIK3C3. Plasmid identification was performed through enzyme digestion and transfected into the fetal fibroblasts derived from Diannan miniature pigs. After 2 weeks of culturing, six positive colonies obtained from a total of 14 cell colonies were identified through PCR. One positive cell line was selected as the donor cell line for SCNT for the construction of PIK3C3transgenic pigs. Thirty single blastocysts were collected and identified as PIK3C3 transgenic-positive blastocysts. Two surrogates became pregnant after transferring the reconstructed embryos into four surrogates. Fetal fibroblasts of PIK3C3-positive fetuses identified through PCR were used as donor cells for SCNT to generate PIK3C3 transgenic pigs. To further explore the function of PIK3C3 overexpression, genotyping and phenotyping of the fetuses and piglets obtained were performed by PCR, immunohistochemical, HE, and apoptosis staining. The results showed that inflammatory infiltration and vacuolar formation in hepatocytes and apoptotic cells, and the mRNA expression of NF-κB, TGF-β1, TLR4, TNF-α, and IL-6 significantly increased in the livers of PIK3C3 transgenic pigs when compared with wild-type (WT) pigs. Immunofluorescence staining showed that LC3B and LAMP-1-positive cells increased in the livers of PIK3C3 transgenic pigs. In the EBSS-induced autophagy of the porcine fibroblast cells (PFCs), the accumulated LC3II protein was cleared faster in PIK3C3 transgenic (PFCs) thanWT (PFCs). In conclusion, PIK3C3 overexpression promoted autophagy in the liver and associated molecular mechanisms related to the activation of ULK1, AMBR1, DRAM1, and MTOR, causing liver damage in pigs. Therefore, the construction of PIK3C3 transgenic pigs may provide a new experimental animal resource for liver diseases.

Scalp Acupuncture Attenuates Brain Damage After Intracerebral Hemorrhage Through Enhanced Mitophagy and Reduced Apoptosis in Rats

To study the effect of scalp acupuncture (SA) on the mitophagy signaling pathway in the caudate nucleus of Sprague-Dawley rats following intracerebral hemorrhage (ICH). An ICH model was established by injecting autologous arterial blood into the caudate nucleus in 200 male Sprague-Dawley rats, which were divided into five groups: sham, ICH, 3-methyladenine group (3-MA, 30 mg/kg), SA, and SA+3-MA. Animals were analyzed at 6 and 24 h as well as at 3 and 7 days. Composite neurological scale score was significantly higher in the SA group than in the ICH group. Transmission electron microscopy showed less structural damage and more autophagic vacuoles within brain in the SA group than in the ICH group. SA group showed higher levels of Beclin1, Parkin, PINK1, NIX protein, and a lower level of Caspase-9 in brain tissue. These animals consequently showed less neural cell apoptosis. Compared with the SA group, however, the neural function score and levels of mitophagy protein in the SA+3-MA group were decreased, neural cell apoptosis was increased with more severe structural damage, which suggested that 3-MA may antagonize the protective effect of SA on brain in rats with ICH. SA may mitigate the neurologic impairment after ICH by enhancing mitophagy and reducing apoptosis.

Toxic Feedback Loop Involving Iron, Reactive Oxygen Species, α-Synuclein and Neuromelanin in Parkinson's Disease and Intervention with Turmeric

Parkinson's disease (PD) is a movement disorder associated with severe loss of mainly dopaminergic neurons in the substantia nigra. Pathological hallmarks include Lewy bodies, and loss of neuromelanin, due to degeneration of neuromelanin-containing dopaminergic neurons. Despite being described over 200 years ago, the etiology of PD remains unknown. Here, we highlight the roles of reactive oxygen species (ROS), iron, alpha synuclein (α-syn) and neuromelanin in a toxic feedback loop culminating in neuronal death and spread of the disease. Dopaminergic neurons are particularly vulnerable due to decreased antioxidant concentration with aging, constant exposure to ROS and presence of neurotoxic compounds (e.g. ortho-quinones). ROS and iron increase each other's levels, creating a state of oxidative stress. α-Syn aggregation is influenced by ROS and iron but also increases ROS and iron via its induced mitochondrial dysfunction and ferric-reductase activity. Neuromelanin's binding affinity is affected by increased ROS and iron. Furthermore, during neuronal death, neuromelanin is degraded in the extracellular space, releasing its bound toxins. This cycle of events continues to neighboring neurons in the form of a toxic loop, causing PD pathology. The increase in ROS and iron may be an important target for therapies to disrupt this toxic loop, and therefore diets rich in certain 'nutraceuticals' may be beneficial. Turmeric is an attractive candidate, as it is known to have anti-oxidant and iron chelating properties. More studies are needed to test this theory and if validated, this would be a step towards development of lifestyle-based therapeutic modalities to complement existing PD treatments.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Treatment with the Ketone Body D-β-hydroxybutyrate Attenuates Autophagy Activated by NMDA and Reduces Excitotoxic Neuronal Damage in the Rat Striatum In Vivo

BACKGROUND

The ketone bodies (KB), β-hydroxybutyrate (BHB) and acetoacetate, have been proposed for the treatment of acute and chronic neurological disorders, however, the molecular mechanisms involved in KB protection are not well understood. KB can substitute for glucose and support mitochondrial metabolism increasing cell survival. We have reported that the D-isomer of BHB (D-BHB) stimulates autophagic degradation during glucose deprivation in cultured neurons increasing cell viability. Autophagy is a lysosomal degradation process of damaged proteins and organelles activated during nutrient deprivation to obtain building blocks and energy. However, impaired or excessive autophagy can contribute to neuronal death.

OBJECTIVE

The aim of the present study was to test whether D-BHB can preserve autophagic function in an in vivo model of excitotoxic damage induced by the administration of the glutamate receptor agonist, N-methyl-Daspartate (NMDA), in the rat striatum.

METHODS

D-BHB was administered through an intravenous injection followed by either an intraperitoneal injection (i.v+i.p) or a continuous epidural infusion (i.v+pump), or through a continuous infusion of D-BHB alone. Changes in the autophagy proteins ATG7, ATG5, BECLIN 1 (BECN1), LC3, Sequestrosome1/p62 (SQSTM1/ p62) and the lysosomal membrane protein LAMP2, were evaluated by immunoblot. The lesion volume was measured in cresyl violet-stained brain sections.

RESULTS

Autophagy is activated early after NMDA injection but autophagic degradation is impaired due to the cleavage of LAMP2. Twenty-four h after NMDA intrastriatal injection, the autophagic flux is re-established, but LAMP2 cleavage is still observed. The administration of D-BHB through the i.v+pump protocol reduced the content of autophagic proteins and the cleavage of LAMP2, suggesting decreased autophagosome formation and lysosomal membrane preservation, improving autophagic degradation. D-BHB also reduced brain injury. The i.v+i.p administration protocol and the infusion of D-BHB alone showed no effect on autophagy activation or degradation.

Autophagy Contributes to Oxidative Stress-Induced Apoptosis in Porcine Granulosa Cells

Oxidative stress-induced granulosa cell (GC) death is a major cause of follicular atresia. As the major types of programmed cell death, autophagy and apoptosis have been observed in response to H₂O₂-mediated oxidative stress and have been demonstrated to be responsible for porcine GC death. To date, however, the cellular reactions linking autophagy to the apoptosis of porcine GC under oxidative stress are still poorly understood. Porcine GC were treated with H₂O₂, and autophagic flux was examined by western blotting. Cell viability and cell death assays were performed after cotreatment of porcine GC with autophagy activator (rapamycin) or inhibitor (3-methyladenine, 3-MA) together with H₂O₂. We revealed that short exposure (1-3 h) of porcine GC to H₂O₂ dramatically increased autophagic flux (1.8- to 2.5-fold over that in the control), whereas 6-12 h prolonged treatment decreased autophagy but elevated the caspase-3 activity and GC apoptotic rate. Furthermore, we showed that pretreatment with rapamycin exacerbated H₂O₂-mediated cytotoxicity and caspase-3 activation but that 3-MA or siRNAs specific for Beclin 1 and Atg7 genes ameliorated H₂O₂-mediated GC apoptosis. Together, our results indicate that autophagy plays a pivotal role in H₂O₂-mediated porcine GC apoptosis. Importantly, we show that the early induction of autophagic flux contributes to oxidative stress-induced apoptosis in porcine GC. The results also suggest that regulating the autophagy response in porcine GC under oxidative stress might be a new strategy for abnormal follicular atresia.

Curative effect of xanthohumol supplementation during liver fluke-associated cholangiocarcinogenesis: Potential involvement of autophagy

Xanthohumol (XH), a plant flavonoid, was shown to attenuate cholangiocarcinoma (CCA) development induced by the liver fluke Opisthorchis viverrini (Ov) and N-dinitrosomethylamine (NDMA) in the hamster model. We investigated the possible involvement of autophagy, a self-degrading process dysregulated in cancer, in XH chemotherapeutic effect. During cholangiocarcinogenesis, the expression of LC3 (an autophagic marker) was increased in the precancerous stage and decreased in the cancerous stage. The XH-treated ON (Ov plus NDMA) group showed retarded progression of CCA along with increased expression of LC3. The possible relation between autophagy and cell death was investigated in cultured human CCA cells. XH induced apoptosis associated with reduced expression of BCL-2 and increased expression of BAX. In parallel, XH induced the autophagy flux, as testified by increased LC3-II and decreased p62, along with induction of BECLIN1 and Vps34. Inhibition of BECLIN1-dependent autophagy greatly limited XH toxicity in CCA cells. These data suggest that XH attenuates the development of CCA through overstimulation of autophagy which then precipitates apoptosis.

Neuroprotective Effects of Necrostatin-1 Against Oxidative Stress-Induced Cell Damage: an Involvement of Cathepsin D Inhibition

Necroptosis, a recently discovered form of non-apoptotic programmed cell death, can be implicated in many pathological conditions including neuronal cell death. Moreover, an inhibition of this process by necrostatin-1 (Nec-1) has been shown to be neuroprotective in in vitro and in vivo models of cerebral ischemia. However, the involvement of this type of cell death in oxidative stress–induced neuronal cell damage is less recognized. Therefore, we tested the effects of Nec-1, an inhibitor of necroptosis, in the model of hydrogen peroxide (H₂O₂)-induced cell damage in human neuroblastoma SH-SY5Y and murine hippocampal HT-22 cell lines. The data showed that Nec-1 (10–40 μM) attenuated the cell death induced by H₂O₂ in undifferentiated (UN-) and neuronal differentiated (RA-) SH-SY5Y cells with a higher efficacy in the former cell type. Moreover, Nec-1 partially reduced cell damage induced by 6-hydroxydopamine in UN- and RA-SH-SY5Y cells. The protective effect of Nec-1 was of similar magnitude as the effect of a caspase-3 inhibitor in both cell phenotypes and this effect were not potentiated after combined treatment. Furthermore, the non-specific apoptosis and necroptosis inhibitor curcumin augmented the beneficial effect of Nec-1 against H₂O₂-evoked cell damage albeit only in RA-SH-SY5Y cells. Next, it was found that the mechanisms of neuroprotective effect of Nec-1 against H₂O₂-induced cell damage in SH-SY5Y cells involved the inhibition of lysosomal protease, cathepsin D, but not caspase-3 or calpain activities. In HT-22 cells, Nec-1 was protective in two models of oxidative stress (H₂O₂ and glutamate) and that effect was blocked by a caspase inhibitor. Our data showed neuroprotective effects of the necroptosis inhibitor, Nec-1, against oxidative stress–induced cell damage and pointed to involvement of cathepsin D inhibition in the mechanism of its action. Moreover, a cell type–specific interplay between necroptosis and apoptosis has been demonstrated.

Hydroxyl Group Difference between Anthraquinone Derivatives Regulate Different Cell Death Pathways via Nucleo-Cytoplasmic Shuttling of p53

BACKGROUND

Despite a number of measures having been taken for cancer management, it is still the second leading cause of death worldwide. p53 is the protein principally being targeted for cancer treatment. Targeting p53 localization may be an effective strategy in chemotherapy as it controls major cell death pathways based on its cellular localization. Anthraquinones are bioactive compounds widely being considered as potential anticancer agents but their mechanism of action is yet to be explored. It has been shown that the number and position of hydroxyl groups within the different anthraquinones like Emodin and Chrysophanol reflects the number of intermolecular hydrogen bonds which affect its activity. Emodin contains an additional OH group at C-3, in comparison to Chrysophanol and may differentially regulate different cell death pathways in cancer cell.

OBJECTIVE

The present study was aimed to investigate the effect of two anthraquinones Emodin and Chrysophanol on induction of different cell death pathways in human lung cancer cells (A549 cell line) and whether single OH group difference between these compounds differentially regulate cell death pathways.

METHODS

The cytotoxic effect of Emodin and Chrysophanol was determined by the MTT assay. The expression of autophagy and apoptosis marker genes at mRNA and protein level after treatment was checked by the RT-PCR and Western Blot, respectively. For cellular localization of p53 after treatment, we performed immunofluorescence microscopy.

RESULTS

We observed that both compounds depicted a dose-dependent cytotoxic response in A549 cells which was in concurrence with the markers associated with oxidative stress such as an increase in ROS generation, decrease in MMP and DNA damage. We also observed that both compounds up-regulated the p53 expression where Emodin causes nuclear p53 localization, which leads to down-regulation in mTOR expression and induces autophagy while Chrysophanol inhibits p53 translocation into nucleus, up-regulates mTOR expression and inhibits autophagy.

CONCLUSION

From this study, it may be concluded that the structural difference of single hydroxyl group may switch the mechanism from one pathway to another which could be useful in the future to improve anticancer treatment and help in the development of new selective therapies.

Amino acid response by Halofuginone in Cancer cells triggers autophagy through proteasome degradation of mTOR

Background

In the event of amino acid starvation, the cell activates two main protective pathways: Amino Acid starvation Response (AAR), to inhibit global translation, and autophagy, to recover the essential substrates from degradation of redundant self-components. Whether and how AAR and autophagy (ATG) are cross-regulated and at which point the two regulatory pathways intersect remain unknown. Here, we provide experimental evidence that the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) specifically located at the lysosome level links the AAR with the autophagy pathway.

Methods

As an inducer of the AAR, we used halofuginone (HF), an alkaloid that binds to the prolyl-tRNA synthetase thus mimicking the unavailability of proline (PRO). Induction of AAR was determined assessing the phosphorylation of the eukaryotic translation initiation factor (eIF) 2α. Autophagy was monitored by assessing the processing and accumulation of microtubule-associated protein 1 light chain 3 isoform B (LC3B) and sequestosome-1 (p62/SQSTM1) levels. The activity of mTORC1 was monitored through assessment of the phosphorylation of mTOR, (rp)S6 and 4E-BP1. Global protein synthesis was determined by puromycin incorporation assay. mTORC1 presence on the membrane of the lysosomes was monitored by cell fractionation and mTOR expression was determined by immunoblotting.

Results

In three different types of human cancer cells (thyroid cancer WRO cells, ovarian cancer OAW-42 cells, and breast cancer MCF-7 cells), HF induced both the AAR and the autophagy pathways time-dependently. In WRO cells, which showed the strongest induction of autophagy and of AAR, global protein synthesis was little if any affected. Consistently, 4E-BP1 and (rp)S6 were phosphorylated. Concomitantly, mTOR expression and activation declined along with its detachment from the lysosomes and its degradation by the proteasome, and with the nuclear translocation of transcription factor EB (TFEB), a transcription factor of many ATG genes. The extra supplementation of proline rescued all these effects.

Conclusions

We demonstrate that the AAR and autophagy are mechanistically linked at the level of mTORC1, and that the lysosome is the central hub of the cross-talk between these two metabolic stress responses.

Edaravone inhibits autophagy after neuronal oxygen-glucose deprivation/recovery injury

PURPOSE OF THE STUDY

Edaravone is an oxygen free radical scavenger that is widely used to treat ischemic injury to the nervous system. This study investigated the effect of edaravone pretreatment on neurons subjected to oxygen-glucose deprivation/recovery (OGD/R) injury.

MATERIALS AND METHODS

Common neurons were subjected to oxygen and glucose deprivation for 1 h, followed by oxygen and glucose recovery for 0.5, 2, 6 and 12 h to establish the OGD/R model. Autophagy was assessed by electron microscope observation of autophagosomes, cell immunofluorescence, mRFP-GFP-LC3 virus cell fluorescence and western blotting analyses of the autophagy-related proteins. The findings showed that at OGD/R 2 h autophagy was high. Next, neurons were pretreated with different concentrations of edaravone (0, 5, 10, 25, 50 and 100 μM) before establishing the OGD/R model. Western blotting was used to analyze the expression of autophagy-related proteins. The CCK-8 assay was used to analyze cell viability after pretreatment with different concentrations of edaravone. Optimal inhibition of autophagy was achieved with the concentration of edaravone 50 μM. Neurons pretreated with 50 μM edaravone and established OGD/R model were analyzed for autophagy levels.

RESULTS

At every OGD/R time point autophagy was lower in neurons pretreated with edaravone than in those not pretreated with the drug. The difference was statistically significant without OGD/R 12 h.

CONCLUSIONS

Pretreatment with edaravone may reduce the level of autophagy in neurons subjected to OGD/R injury.

Trehalose inhibits H2O2-induced autophagic death in dopaminergic SH-SY5Y cells via mitigation of ROS-dependent endoplasmic reticulum stress and AMPK activation

Autophagy is a catabolic process to maintain intracellular homeostasis via removal of cytoplasmic macromolecules and damaged cellular organelles through lysosome-mediated degradation. Trehalose is often regarded as an autophagy inducer, but we reported previously that it could prevent ischemic insults-induced autophagic death in neurons. Thus, we further investigated in this study whether trehalose could protect human dopaminergic SH-SY5Y cells against H2O2-induced lethal autophagy. We found pretreatment with trehalose not only prevented H2O2-induced death in SH-SY5Y cells, but also reversed H2O2-induced upregulation of LC3II, Beclin1 and ATG5 and downregulation of p62. Then, we proved that either autophagy inhibitor 3MA or genetic knockdown of ATG5 prevented H2O2-triggered death in SH-SY5Y cells. These indicated that trehalose could inhibit H2O2-induced autophagic death in SH-SY5Y cells. Further, we found that trehalose inhibited H2O2-induced AMPK activation and endoplasmic reticulum (ER) stress. Moreover, inhibition of AMPK activation with compound C or alleviation of ER stress with chemical chaperone 4-PBA obviously attenuated H2O2-induced changes in autophagy-related proteins. Notably, we found that trehalose inhibited H2O2-induced increase of intracellular ROS and reduction in the activities of CAT and SOD. Consistently, our data revealed as well that mitigation of intracellular ROS levels with antioxidant NAC markedly attenuated H2O2-induced AMPK activation and ER stress. Therefore, we demonstrated in this study that trehalose prevented H2O2-induced autophagic death in SH-SY5Y cells via mitigation of ROS-dependent endoplasmic reticulum stress and AMPK activation.

Autophagy in cancer: a complex relationship

Macroautophagy is the process by which cells package and degrade cytosolic components, and recycle the breakdown products for future use. Since its initial description by Christian de Duve in the 1960s, significant progress has been made in understanding the mechanisms that underlie this vital cellular process and its specificity. Furthermore, macroautophagy is linked to pathologic conditions such as cancer and is being studied as a therapeutic target. In this review, we will explore the connections between autophagy and cancer, which are tumor- and context-dependent and include the tumor microenvironment. We will highlight the importance of tumor compartment-specific autophagy in both cancer aggressiveness and treatment.

Effect of varying hypoxia reoxygenation times on autophagy of cardiomyocytes

PURPOSE

To investigate the impact of different hypoxia reoxygenation (HR) times on autophagy of rat cardiomyocytes (H9C2).

METHODS

Rat cardiomyocytes were randomly divided into normal control group (group A), hypoxia group (group B), 2 h HR group (group C), 12 h HR group (group D), and 24 h HR group (group E). LC3 II/LC3 I was determined via western blotting, and cell viabilities of cardiomyocytes were measured using methyl thiazolyl tetrazolium (MTT) assay.

RESULTS

Cell viabilities in HR model groups were significantly lower than those of group A (P<0.05). LC3 II/LC3 I levels in groups B to D were significantly higher than those of group A (P<0.05), and group D showed the highest LC3 II/LC3 I levels. Cell viabilities in groups B to D were significantly lower than those of group A (P<0.05), with group D showing the lowest cell viabilities (P<0.05).

CONCLUSIONS

Hypoxia can induce autophagy in rat cardiomyocytes, which can be further activated by reoxygenation; most notable after 12 h. Hypoxia-induced cell injury can be aggravated by reoxygenation. The lowest cell viability was observed at 12 h after reoxygenation; however, cell viability can be recovered after 24 h.

Circular RNA GRB10 as a competitive endogenous RNA regulating nucleus pulposus cells death in degenerative intervertebral disk

Intervertebral disc degeneration (IDD) is an important factor leading to low back pain, but the underlying mechanisms remain poorly understood. Compared with normal nucleus pulposus (NP) tissues, the expression of circ-GRB10 was downregulated in IDD. Furthermore, overexpression of circ-GRB10 inhibited NP cell apoptosis. circ-GRB10 could sequester miR-328-5p, which could potentially lead to the upregulation of target genes related to cell proliferation via the ErbB pathway. In conclusion, the present study revealed that circ-GRB10/miR-328-5p/ERBB2 signaling pathway is involved in IDD development, suggesting that circ-GRB10 might be a novel therapeutic target for IDD.

Inhibition of autophagy initiation potentiates chemosensitivity in mesothelioma

The benefits of inhibiting autophagy in cancer are still controversial, with differences in outcome based on the type of tumor, the context and the particular stage of inhibition. Here, we investigated the impact of inhibiting autophagy at different stages on chemosensitivity using 3-dimensional (3D) models of mesothelioma, including ex vivo human tumor fragment spheroids. As shown by LC3B accumulation, we successfully inhibited autophagy using either an early stage ULK1/2 inhibitor (MRT 68921) or a late stage inhibitor (hydroxychloroquine). We found that inhibition of autophagy at the early stage, but not at late stage, potentiated chemosensitivity. This effect was seen only in those spheroids with high autophagy and active initiation at steady state. Inhibition of autophagy alone, at either early or late stage, did not cause cell death, showing that the inhibitors were non-toxic and that mesothelioma did not depend on autophagy at baseline, at least over 24 h. Using ATG13 puncta analysis, we found that autophagy initiation identified tumors that are more chemosensitive at baseline and after autophagy inhibition. Our results highlight a potential role of autophagy initiation in supporting mesothelioma cells during chemotherapy. Our work also highlights the importance of testing the inhibition of different stages in order to uncover the role of autophagy and the potential of its modulation in the treatment of cancer.

The metabolic cross-talk between epithelial cancer cells and stromal fibroblasts in ovarian cancer progression: Autophagy plays a role

Cancer and stromal cells, which include (cancer‐associated) fibroblasts, adipocytes, and immune cells, constitute a mixed cellular ecosystem that dynamically influences the behavior of each component, creating conditions that ultimately favor the emergence of malignant clones. Ovarian cancer cells release cytokines that recruit and activate stromal fibroblasts and immune cells, so perpetuating a state of inflammation in the stroma that hampers the immune response and facilitates cancer survival and propagation. Further, the stroma vasculature impacts the metabolism of the cells by providing or limiting the availability of oxygen and nutrients. Autophagy, a lysosomal catabolic process with homeostatic and prosurvival functions, influences the behavior of cancer cells, affecting a variety of processes such as the survival in metabolic harsh conditions, the invasive growth, the development of immune and chemo resistance, the maintenance of stem‐like properties, and dormancy. Further, autophagy is involved in the secretion and the signaling of promigratory cytokines. Cancer‐associated fibroblasts can influence the actual level of autophagy in ovarian cancer cells through the secretion of pro‐inflammatory cytokines and the release of autophagy‐derived metabolites and substrates. Interrupting the metabolic cross‐talk between cancer cells and cancer‐associated fibroblasts could be an effective therapeutic strategy to arrest the progression and prevent the relapse of ovarian cancer.

Non-thermal plasma induces a stress response in mesothelioma cells resulting in increased endocytosis, lysosome biogenesis and autophagy

Non-thermal plasma (NTP) is a potential new therapeutic modality for cancer. However, its mechanism of action remains unclear. Herein, we studied the effect of NTP on mesothelioma cells and fibroblasts to understand its anti-proliferative efficacy. Interestingly, NTP demonstrated greater selective anti-proliferative activity against mesothelioma cells relative to fibroblasts than cisplatin, which is used for mesothelioma treatment. The anti-proliferative effect of NTP was enhanced by pre-incubation with the cellular iron donor, ferric ammonium citrate (FAC), and inhibited by iron chelation using desferrioxamine (DFO). Three oxidative stress probes (CM-H2DCFDA, MitoSOX and C11-BODIPY) demonstrated reactive oxygen species (ROS) generation by NTP, which was inhibited by DFO. Moreover, NTP decreased transferrin receptor-1 and increased ferritin-H and -L chain expression that was correlated with decreased iron-regulatory protein expression and RNA-binding activity. This regulation was potentially due to increased intracellular iron in lysosomes, which was demonstrated via the Fe(II)-selective probe, HMRhoNox-M, and was consistent with autophagic-induction. Immunofluorescence using LysoTracker and Pepstatin A probes demonstrated increased cellular lysosome content, which was confirmed by elevated LAMP1 expression. The enhanced lysosomal biogenesis after NTP could be due to the observed increase in fluid-phase endocytosis and early endosome formation. These results suggest NTP acts as a stressor, which results in increased endocytosis, lysosome content and autophagy. In fact, NTP rapidly increased autophagosome formation, as judged by increased LC3B-II expression, which co-localized with LAMP1, indicating autophagolysosome formation. Autophagic-induction by NTP was confirmed using electron microscopy. In summary, NTP acts as a cellular stressor to rapidly induce fluid-phase endocytosis, lysosome biogenesis and autophagy.

Resveratrol protects neuronal-like cells expressing mutant Huntingtin from dopamine toxicity by rescuing ATG4-mediated autophagosome formation

Parkinsonian-like motor deficits in Huntington's Disease (HD) patients are associated with abnormal dopamine neurotransmission in the striatum. Dopamine metabolism leads to the formation of oxidized dopamine quinones that exacerbates mitochondrial dysfunction with production of reactive oxygen species (ROS) that eventually lead to neuronal cell death. We have previously shown that dopamine-induced oxidative stress triggers apoptotic cell death in dopaminergic neuroblastoma SH-SY5Y cells hyper-expressing the mutant polyQ Huntingtin (polyQ-Htt) protein. Dopamine toxicity was paralleled by impaired autophagy clearance of the polyQ-Htt aggregates. In this study, we found that Dopamine affects the stability and function of ATG4, a redox-sensitive cysteine-protein involved in the processing of LC3, a key step in the formation of autophagosomes. Resveratrol, a dietary polyphenol with anti-oxidant and pro-autophagic properties, has shown neuroprotective potential in HD. Yet the molecular mechanism through which Resveratrol can protect HD cells against DA is not known. Here, we show that Resveratrol prevents the generation of ROS, restores the level of ATG4, allows the lipidation of LC3, facilitates the degradation of polyQ-Htt aggregates and protects the cells from Dopamine toxicity. The present findings provide a mechanistic explanation of the neuroprotective activity of Resveratrol and support its inclusion in a therapeutic regimen to slow down HD progression.

Dopamine exacerbates mutant Huntingtin toxicity via oxidative-mediated inhibition of autophagy in SH-SY5Y neuroblastoma cells: Beneficial effects of anti-oxidant therapeutics

Neuronal cell death in Huntington's Disease (HD) is associated with the abnormal expansions of a polyglutamine (polyQ) tract in the huntingtin protein (Htt) at the N-terminus that causes the misfolding and aggregation of the mutated protein (mHtt). Autophagy-lysosomal degradation of Htt aggregates may protect the neurons in HD. HD patients eventually manifest parkinsonian-like symptoms, which underlie defects in the dopaminergic system. We hypothesized that dopamine (DA) exacerbates the toxicity in affected neurons by over-inducing an oxidative stress that negatively impinges on the autophagy clearance of mHtt and thus precipitating neuronal cell death. Here we show that the hyper-expression of mutant (>113/150) polyQ Htt is per se toxic to dopaminergic human neuroblastoma SH-SY5Y cells, and that DA exacerbates this toxicity leading to apoptosis and secondary necrosis. DA toxicity is mediated by ROS production (mainly anion superoxide) that elicits a block in the formation of autophagosomes. We found that the pre-incubation with N-Acetyl-l-Cysteine (a quinone reductase inducer) or Deferoxamine (an iron chelator) prevents the generation of ROS, restores the autophagy degradation of mHtt and preserves the cell viability in SH-SY5Y cells expressing the polyQ Htt and exposed to DA. The present findings suggest that DA-induced impairment of autophagy underlies the parkinsonism in HD patients. Our data provide a mechanistic explanation of the DA toxicity in dopaminergic neurons expressing the mHtt and support the use of anti-oxidative stress therapeutics to restore protective autophagy in order to slow down the neurodegeneration in HD patients.

Identification of Cofilin-1 Induces G0/G1 Arrest and Autophagy in Angiotensin-(1-7)-treated Human Aortic Endothelial Cells from iTRAQ Quantitative Proteomics

The angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis is a pathway that acts against the detrimental effects of the renin-angiotensin system. However, the effects of angiotensin-(1-7) on endothelial protein expression and the related phenotypes are unclear. We performed a duplicate of iTRAQ quantitative proteomic analysis on human aortic endothelial cells (HAECs) treated with angiotensin-(1-7) for 6 hours. Cofilin-1 was identified as a highly abundant candidate with consistent >30% coverage and >1.2-fold overexpression in the angiotensin-(1-7)-treated group. Gene ontology analysis showed that the "regulation_of_mitosis" was significantly altered, and cell cycle analysis indicated that the 6-hour angiotensin-(1-7) treatment significantly induced G0/G1 arrest. Knockdown of the cofilin-1 (CFL1) gene suggested the G0/G1 phase arrest was mediated by the modulation of p27 and the p21/Cyclin/CDK complex by Cofilin-1. Interestingly, quiescent HAECs escaped G0/G1 arrest upon angiotensin-(1-7) treatment for 24 hours, and angiotensin-(1-7) induced autophagy by upregulating Beclin-1 and microtubule-associated protein 1 light chain 3b-II expression, which was also attenuated by A779 pre-treatment and CFL1 knockdown. After pre-treatment with 3-methyladenine (3MA), treatment with angiotensin-(1-7) for 24 h induced significant G0/G1 phase arrest and apoptosis, suggesting a pro-survival role of autophagy in this context. In conclusion, Cofilin-1 plays a dominant role in angiotensin-(1-7)-induced G0/G1 arrest and autophagy to maintain cellular homeostasis in HAECs.

Parkinsonian toxin-induced oxidative stress inhibits basal autophagy in astrocytes via NQO2/quinone oxidoreductase 2: Implications for neuroprotection

Oxidative stress (OS) stimulates autophagy in different cellular systems, but it remains controversial if this rule can be generalized. We have analyzed the effect of chronic OS induced by the parkinsonian toxin paraquat (PQ) on autophagy in astrocytoma cells and primary astrocytes, which represent the first cellular target of neurotoxins in the brain. PQ decreased the basal levels of LC3-II and LC3-positive vesicles, and its colocalization with lysosomal markers, both in the absence and presence of chloroquine. This was paralleled by increased number and size of SQSTM1/p62 aggregates. Downregulation of autophagy was also observed in cells chronically exposed to hydrogen peroxide or nonlethal concentrations of PQ, and it was associated with a reduced astrocyte capability to protect dopaminergic cells from OS in co-cultures. Surprisingly, PQ treatment led to inhibition of MTOR, activation of MAPK8/JNK1 and MAPK1/ERK2-MAPK3/ERK1 and upregulation of BECN1/Beclin 1 expression, all signals typically correlating with induction of autophagy. Reduction of OS by NMDPEF, a specific NQO2 inhibitor, but not by N-acetylcysteine, abrogated the inhibitory effect of PQ and restored autophagic flux. Activation of NQO2 by PQ or menadione and genetic manipulation of its expression confirmed the role of this enzyme in the inhibitory action of PQ on autophagy. PQ did not induce NFE2L2/NRF2, but when it was co-administered with NMDPEF NFE2L2 activity was enhanced in a SQSTM1-independent fashion. Thus, a prolonged OS in astrocytes inhibits LC3 lipidation and impairs autophagosome formation and autophagic flux, in spite of concomitant activation of several pro-autophagic signals. These findings outline an unanticipated neuroprotective role of astrocyte autophagy and identify in NQO2 a novel pharmacological target for its positive modulation.

Novel Approaches to Apoptosis-Inducing Therapies

Induction of apoptotic programmed cell death is one of the underlying principles of most current cancer therapies. In this review, we discuss the limitations and drawbacks of this approach and identify three distinct, but overlapping strategies to avoid these difficulties and further enhance the efficacy of apoptosis-inducing therapies. We postulate that the application of multi-targeted small molecule inhibitor cocktails will reduce the risk of the cancer cell populations developing resistance towards therapy. Following from these considerations regarding population genetics and ecology, we advocate the reconsideration of therapeutic end points to maximise the benefits, in terms of quantity and quality of life, for the patients. Finally, combining both previous points, we also suggest an altered focus on the cellular and molecular targets of therapy, i.e. targeting the (cancer cells') interaction with the tumour microenvironment.

Signaling Pathway in Early Brain Injury after Subarachnoid Hemorrhage: News Update

The annual incidence of subarachnoid hemorrhage (SAH) caused by intracranial aneurysm rupture is approximately 10.5/10 million people in China, making SAH the third most frequently occurring hemorrhage of the intracranial type after cerebral embolism and hypertensive intracerebral hemorrhage. SAH caused by ruptured aneurysm leads to a mortality rate as high as 67 %, and, because of the sudden onset of this disease, approximately 12-15 % of patients die before they can receive effective treatment. Early brain injury (EBI) is the brain damage occurring within the first 72 h after SAH. Two-thirds of mortality caused by SAH occurs within 48 h, mainly as a result of EBI. With the development of molecular biology and medicine microscopy techniques, various signaling pathways involved in EBI after SAH have been revealed. Understanding these signaling pathways may help clinicians treat EBI after SAH and improve long-term prognosis of SAH patients. This chapter summarizes several important signaling pathways implicated in EBI caused by SAH.

Apelin-13 promotes cardiomyocyte hypertrophy via PI3K-Akt-ERK1/2-p70S6K and PI3K-induced autophagy

Apelin is highly expressed in rat left ventricular hypertrophy Sprague Dawley rat models, and it plays a crucial role in the cardiovascular system. The aim this study was to clarify whether apelin-13 promotes hypertrophy in H9c2 rat cardiomyocytes and to investigate its underlying mechanism. The cardiomyocyte hypertrophy was observed by measuring the diameter, volume, and protein content of H9c2 cells. The activation of autophagy was evaluated by observing the morphology of autophagosomes by transmission electron microscopy, observing the subcellular localization of LC3 by light microscopy, and detecting the membrane-associated form of LC3 by western blot analysis. The phosphatidylinositol 3-kinase (PI3K) signaling pathway was identified and the proteins expression was detected using western blot analysis. The results revealed that apelin-13 increased the diameter, volume, and protein content of H9c2 cells and promoted the phosphorylation of PI3K, Akt, ERK1/2, and p70S6K. Apelin-13 activated the PI3K-Akt-ERK1/2-p70S6K pathway. PI3K inhibitor LY294002, Akt inhibitor 1701-1, ERK1/2 inhibitor PD98059 attenuated the increase of the cell diameter, volume, protein content induced by apelin-13. Apelin-13 increased the autophagosomes and up-regulated the expressions of beclin 1 and LC3-II/I both transiently and stably. The autophagy inhibitor 3MA ameliorated the increase of cell diameter, volume, and protein content that were induced by apelin-13. These results suggested that apelin-13 promotes H9c2 rat cardiomyocyte hypertrophy via PI3K-Akt-ERK1/2-p70S6K and PI3K-induced autophagy.

Doxorubicin-induced necrosis is mediated by poly-(ADP-ribose) polymerase 1 (PARP1) but is independent of p53

Necrosis, unregulated cell death, is characterized by plasma membrane rupture as well as nuclear and cellular swelling. However, it has recently been reported that necrosis is a regulated form of cell death mediated by poly-(ADP-ribose) polymerase 1 (PARP1). PARP1 is thought to mediate necrosis by inducing DNA damage, although this remains unconfirmed. In this study, we examined the mechanisms of PARP1-mediated necrosis following doxorubicin (DOX)-induced DNA damage in human kidney proximal tubular (HK-2) cells. DOX initiated DNA damage response (DDR) and upregulated PARP1 and p53 expression, resulting in morphological changes similar to those observed during necrosis. Additionally, DOX induced mitochondrial hyper-activation, as evidenced by increased mitochondrial respiration and cytosolic ATP (cATP) production. However, DOX affected mitochondrial mass. DOX-induced DNA damage, cytosolic reactive oxygen species (cROS) generation, and mitochondrial hyper-activation decreased in cells with inhibited PARP1 expression, while generation of nitric oxide (NO) and mitochondrial ROS (mROS) remained unaffected. Moreover, DOX-induced DNA damage, cell cycle changes, and oxidative stress were not affected by p53 inhibition. These findings suggest that DNA damage induced necrosis through a PARP1-dependent and p53-independent pathway.

Effects of Inhibitors of Necroptosis and Autophagy on Morphofunctional Characteristics of the Myocardium during Static Cold Storage of Donor Rat Heart

Cardioprotective effects of necrostatin-1 (necroptosis inhibitor) and 3-methyladenine (autophagy inhibitor) were studied on the model of long-term cold preservation of rat heart. Addition of necrostatin-1 (490 nmol/liter) or 3-methyladenine (4.5 mmol/liter) to custodiol preserving solution reduced myocardial infarction size and improved left-ventricular function during reperfusion after 8-h preservation at 4°C. Inhibition of necroptosis and autophagy contributed to the cardioprotective effect under conditions of cold preservation of the donor heart.

Turmeric toxicity in A431 epidermoid cancer cells associates with autophagy degradation of anti-apoptotic and anti-autophagic p53 mutant

The keratinocyte-derived A431 Squamous Cell Carcinoma cells express the p53R273H mutant, which has been reported to inhibit apoptosis and autophagy. Here, we show that the crude extract of turmeric (Curcuma longa), similarly to its bioactive component Curcumin, could induce both apoptosis and autophagy in A431 cells, and these effects were concomitant with degradation of p53. Turmeric and curcumin also stimulated the activity of mTOR, which notoriously promotes cell growth and acts negatively on basal autophagy. Rapamycin-mediated inhibition of mTOR synergized with turmeric and curcumin in causing p53 degradation, increased the production of autophagosomes and exacerbated cell toxicity leading to cell necrosis. Small-interference mediated silencing of the autophagy proteins BECLIN 1 or ATG7 abrogated the induction of autophagy and largely rescued p53 stability in Turmeric-treated or Curcumin-treated cells, indicating that macroautophagy was mainly responsible for mutant p53 degradation. These data uncover a novel mechanism of turmeric and curcumin toxicity in chemoresistant cancer cells bearing mutant p53.

Hypoxia facilitates the survival of nucleus pulposus cells in serum deprivation by down-regulating excessive autophagy through restricting ROS generation

Nucleus pulposus (NP) cells reside in a hypoxic environment in vivo, while the mechanisms of how NP cells maintain survival under hypoxia are not clear. Autophagy is an important physiological response to hypoxia and implicated in the survival regulation in most types of cells. This study was designed to investigate the role of autophagy in the survival of NP cells under hypoxia. We found that appropriate autophagy activity was beneficial to the survival of NP cells in serum deprivation, while excessive autophagy led to death of the NP cells. Hypoxia facilitated the survival of NP cells in serum deprivation by down-regulating excessive autophagy. Hypoxia down-regulated the autophagy activity of NP cells through restricting the production of reactive oxygen species (ROS) and inactivating the AMPK/mTOR signaling pathway, and possibly through a pathway involving HIF-1α. We believed that understanding the autophagy response of NP cells to hypoxia and its role in cell survival had important clinical significance in the prevention and treatment of degenerative discogenic diseases.

3-MA Inhibits Autophagy and Favors Long-Term Integration of Grafted Gad67–GFP GABAergic Precursors in the Developing Neocortex by Preventing Apoptosis

In human neonates, immature GABAergic interneurons are markedly affected by an excitotoxic insult. While in adults the interest of cell transplantation has been demonstrated in several neurological disorders, few data are available regarding the immature brain. The low survival rate constitutes a strong limitation in the capacity of transplanted neurons to integrate the host tissue. Because i) autophagy is an adaptive process to energetic/nutrient deprivation essential for cell survival and ii) literature describes cross-talks between autophagy and apoptosis, we hypothesized that regulation of autophagy would represent an original strategy to favor long-term survival of GABAergic precursors grafted in the immature neocortex. Morphological, neurochemical, and functional data showed that in control conditions, few grafted Gad67-GFP precursors survived. The first hours following transplantation were a critical period with intense apoptosis. Experiments performed on E15.5 ganglionic eminences revealed that Gad67-GFP precursors were highly sensitive to autophagy. Rapamycin and 3-MA impacted on LC3 cleavage, LC3II translocation, and autophagosome formation. Quantification of Bax, mitochondrial integrity, caspase-3 cleavage, and caspase-3 immunolocalization and activity showed that 3-MA induced a significant decrease of Gad67-GFP precursor apoptosis. In vivo, 3-MA induced, within the first 24 h, a diffuse LC3 pattern of grafted Gad67-GFP precursors, an increase of precursors with neurites, a reduction of the density of caspase-3 immunoreactive cells. A twofold increase in the survival rate occurred 15 days after the graft. Surviving neurons were localized in the cortical layers II–IV, which were still immature when the transplantation was done. Altogether, these data indicate that inhibition of autophagy represents an original strategy to allow GABAergic interneurons to overpass the first critical hours following transplantation and to increase their long-term survival in mice neonates.

A critical evaluation of PI3K inhibition in Glioblastoma and Neuroblastoma therapy

Members of the PI3K/Akt/mTor signaling cascade are among the most frequently altered proteins in cancer, yet the therapeutic application of pharmacological inhibitors of this signaling network, either as monotherapy or in combination therapy (CT) has so far not been particularly successful. In this review we will focus on the role of PI3K/Akt/mTOR in two distinct tumors, Glioblastoma multiforme (GBM), an adult brain tumor which frequently exhibits PTEN inactivation, and Neuroblastoma (NB), a childhood malignancy that affects the central nervous system and does not harbor any classic alterations in PI3K/Akt signaling. We will argue that inhibitors of PI3K/Akt signaling can be components for potentially promising new CTs in both tumor entities, but further understanding of the signal cascade's complexity is essential for successful implementation of these CTs. Importantly, failure to do this might lead to severe adverse effects, such as treatment failure and enhanced therapy resistance.

A critical evaluation of PI3K inhibition in Glioblastoma and Neuroblastoma therapy

Members of the PI3K/Akt/mTor signaling cascade are among the most frequently altered proteins in cancer, yet the therapeutic application of pharmacological inhibitors of this signaling network, either as monotherapy or in combination therapy (CT) has so far not been particularly successful. In this review we will focus on the role of PI3K/Akt/mTOR in two distinct tumors, Glioblastoma multiforme (GBM), an adult brain tumor which frequently exhibits PTEN inactivation, and Neuroblastoma (NB), a childhood malignancy that affects the central nervous system and does not harbor any classic alterations in PI3K/Akt signaling. We will argue that inhibitors of PI3K/Akt signaling can be components for potentially promising new CTs in both tumor entities, but further understanding of the signal cascade's complexity is essential for successful implementation of these CTs. Importantly, failure to do this might lead to severe adverse effects, such as treatment failure and enhanced therapy resistance.

PTEN deficiency and mutant p53 confer glucose-addiction to thyroid cancer cells: impact of glucose depletion on cell proliferation, cell survival, autophagy and cell migration

Proliferating cancer cells oxidize glucose through the glycolytic pathway. Since this metabolism is less profitable in terms of ATP production, cancer cells consume large quantity of glucose, and those that experience insufficient blood supply become glucose-addicted. We have analyzed the response to glucose depletion in WRO and FTC133 follicular thyroid cancer cells, which differ in the expression of two key regulators of the glucose metabolism. WRO cells, which express wild type p53 and PTEN, showed a higher rate of cell proliferation and were much less sensitive to glucose-depletion than FTC133 cells, which are PTEN null and express mutant p53. Glucose depletion slowed-down the autophagy flux in FTC133 cells, not in WRO cells. In a wound-healing assay, WRO cells were shown to migrate faster than FTC133 cells. Glucose depletion slowed down the cell migration rate, and these effects were more evident in FTC133 cells. Genetic silencing of either wild-type PTEN or p53 in WRO cells resulted in increased uptake of glucose, whereas the ectopic expression of PTEN in FTC133 cells resulted in diminished glucose uptake. In conclusion, compared to WRO, FTC133 cells were higher glucose up-taker and consumer. These data do not support the general contention that cancer cells lacking PTEN or expressing the mutant p53R273H are more aggressive and prone to better face glucose depletion. We propose that concurrent PTEN deficiency and mutant p53 leads to a glucose-addiction state that renders the cancer cell more sensitive to glucose restriction. The present observation substantiates the view that glucose-restriction may be an adjuvant strategy to combat these tumours.

Oxidative stress, redox signaling, and autophagy: cell death versus survival

SIGNIFICANCE

The molecular machinery regulating autophagy has started becoming elucidated, and a number of studies have undertaken the task to determine the role of autophagy in cell fate determination within the context of human disease progression. Oxidative stress and redox signaling are also largely involved in the etiology of human diseases, where both survival and cell death signaling cascades have been reported to be modulated by reactive oxygen species (ROS) and reactive nitrogen species (RNS).

RECENT ADVANCES

To date, there is a good understanding of the signaling events regulating autophagy, as well as the signaling processes by which alterations in redox homeostasis are transduced to the activation/regulation of signaling cascades. However, very little is known about the molecular events linking them to the regulation of autophagy. This lack of information has hampered the understanding of the role of oxidative stress and autophagy in human disease progression.

CRITICAL ISSUES

In this review, we will focus on (i) the molecular mechanism by which ROS/RNS generation, redox signaling, and/or oxidative stress/damage alter autophagic flux rates; (ii) the role of autophagy as a cell death process or survival mechanism in response to oxidative stress; and (iii) alternative mechanisms by which autophagy-related signaling regulate mitochondrial function and antioxidant response.

FUTURE DIRECTIONS

Our research efforts should now focus on understanding the molecular basis of events by which autophagy is fine tuned by oxidation/reduction events. This knowledge will enable us to understand the mechanisms by which oxidative stress and autophagy regulate human diseases such as cancer and neurodegenerative disorders.

Single amino acid arginine deprivation triggers prosurvival autophagic response in ovarian carcinoma SKOV3

Autophagy is a process of cytosol-to-lysosome vesicle trafficking of cellular constituents for degradation and recycling of their building blocks. Autophagy becomes very important for cell viability under different stress conditions, in particular under amino acid limitation. In this report we demonstrate that single amino acid arginine deprivation triggers profound prosurvival autophagic response in cultured human ovarian cancer SKOV3 cells. In fact, a significant drop in viability of arginine-starved SKOV3 cells was observed when autophagy was inhibited by either coadministration of chloroquine or transcriptional silencing of the essential autophagy protein BECLIN 1. Enzymatic arginine deprivation is a novel anticancer therapy undergoing clinical trials. This therapy is considered nontoxic and selective, as it allows controlling the growth of malignant tumours deficient in arginine biosynthesis. We propose that arginine deprivation-based combinational treatments that include autophagy inhibitors (e.g., chloroquine) may produce a stronger anticancer effect as a second line therapy for a subset of chemoresistant ovarian cancers.

Epigenetic control of autophagy by microRNAs in ovarian cancer

Autophagy is a lysosomal-driven catabolic process that contributes to the preservation of cell homeostasis through the regular elimination of cellular damaged, aged, and redundant molecules and organelles. Autophagy plays dual opposite roles in cancer: on one hand it prevents carcinogenesis; on the other hand it confers an advantage to cancer cells to survive under prohibitive conditions. Autophagy has been implicated in ovarian cancer aggressiveness and in ovarian cancer cell chemoresistance and dormancy. Small noncoding microRNAs (miRNAs) regulate gene expression at posttranscriptional level, thus playing an important role in many aspects of cell pathophysiology, including cancerogenesis and cancer progression. Certain miRNAs have recently emerged as important epigenetic modulators of autophagy in cancer cells. The mRNA of several autophagy-related genes contains, in fact, the target sequence for miRNAs belonging to different families, with either oncosuppressive or oncogenic activities. MiRNA profiling studies have identified some miRNAs aberrantly expressed in ovarian cancer tissues that can impact autophagy. In addition, plasma and stroma cell-derived miRNAs in tumour-bearing patients can regulate the expression of relevant autophagy genes in cancer cells. The present review focuses on the potential implications of miRNAs regulating autophagy in ovarian cancer pathogenesis and progression.

Antagonism of tumoral prolactin receptor promotes autophagy-related cell death

Therapeutic upregulation of macroautophagy in cancer cells provides an alternative mechanism for cell death. Prolactin (PRL) and its receptor (PRLR) are considered attractive therapeutic targets because of their roles as growth factors in tumor growth and progression. We utilized G129R, an antagonist peptide of PRL, to block activity of the tumoral PRL/PRLR axis, which resulted in inhibition of tumor growth in orthotopic models of human ovarian cancer. Prolonged treatment with G129R induced the accumulation of redundant autolysosomes in 3D cancer spheroids, leading to a type II programmed cell death. This inducible autophagy was a noncanonical beclin-1-independent pathway and was sustained by an astrocytic phosphoprotein (PEA-15) and protein kinase C zeta interactome. Lower levels of tumoral PRL/PRLR in clinical samples were associated with longer patient survival. Our findings provide an understanding of the mechanisms of tumor growth inhibition through targeting PRL/PRLR and may have clinical implications.

Hypoxia causes autophagic stress and derangement of metabolic adaptation in a cell model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a fatal neurodegenerative disease that affects motor neurons. The recruitment of autophagy (macroautophagy) and mitochondrial dysfunction are documented in amyotrophic lateral sclerosis patients and experimental models expressing mutant forms of Cu, Zn superoxide dismutase (SOD1) protein, but their impact in the disease remains unclear. Hypoxia is a stress closely related to the disease in patients and mutant SOD1 mice; in individual cells, hypoxia activates autophagy and regulates mitochondrial metabolism as fundamental adaptive mechanisms. Our aim was to examine whether mutant SOD1 changed this response. Hypoxia (1% O2 for 22 h) caused greater loss of viability and more marked activation of caspase 3/7 in the motor neuronal NSC-34 cell line stably transfected with the G93A mutant human SOD1 (G93A-NSC) than in the one with the wild-type SOD1 (WT-NSC) or in untransfected NSC-34. In the G93A-NSC cells, there was a more marked accumulation of the LC3-II autophagy protein, attributable to autophagic stress; 3-methyladenine, which acts on initiation of autophagy, fully rescued G93A-NSC viability and reduced the activation of caspase 3/7 indicating this was a secondary event; the metabolic handling of hypoxia was inappropriate possibly contributing to the autophagic stress. Our findings evidentiate that the G93A mutation of SOD1 profoundly altered the adaptive metabolic response to hypoxia and this could increase the cell susceptibility to this stress. Hypoxia activates autophagy and modifies glycolysis and mitochondrial respiration as fundamental cell adaptive mechanisms. This stress is closely related to amyotrophic lateral sclerosis. The recruitment of autophagy and mitochondrial dysfunction are documented in patients and models expressing mutant Cu, Zn superoxide dismutase (SOD1) protein, but their impact in the disease remains unclear. G93ASOD1 cells were more susceptible to hypoxia than wild-type SOD1 cells and showed autophagic stress and inappropriate handling of energy metabolism. Defective adaptation to hypoxia may contribute to neurodegeneration.

Crosstalk between apoptosis and autophagy: molecular mechanisms and therapeutic strategies in cancer

Both apoptosis and autophagy are highly conserved processes that besides their role in the maintenance of the organismal and cellular homeostasis serve as a main target of tumor therapeutics. Although their important roles in the modulation of tumor therapeutic strategies have been widely reported, the molecular actions of both apoptosis and autophagy are counteracted by cancer protective mechanisms. While apoptosis is a tightly regulated process that is implicated in the removal of damaged or unwanted cells, autophagy is a cellular catabolic pathway that is involved in lysosomal degradation and recycling of proteins and organelles, and thereby is considered an important survival/protective mechanism for cancer cells in response to metabolic stress or chemotherapy. Although the relationship between autophagy and cell death is very complicated and has not been characterized in detail, the molecular mechanisms that control this relationship are considered to be a relevant target for the development of a therapeutic strategy for tumor treatment. In this review, we focus on the molecular mechanisms of apoptosis, autophagy, and those of the crosstalk between apoptosis and autophagy in order to provide insight into the molecular mechanisms that may be essential for the balance between cell survival and death as well as their role as targets for the development of novel therapeutic approaches.

Antitumour effect of sesquiterpene (+)-chabranol on four human cancer cell lines by inducing apoptosis and autophagy

OBJECTIVE

To investigate the effects and mechanisms of sesquiterpene (+)-chabranol on proliferation of a panel of four human tumour cell lines (BGC-823, SGC-7901, SSMC-7721 and HepG2).

METHODS

Cell viability was assessed using a standard methyltetrazolium assay; cell-cycle analysis of BGC-823 cells was performed by flow cytometry. Transmission electron microscopy (TEM) was used to examine the ultrastructure of BGC-823 cells exposed to (+)-chabranol. Apoptosis was investigated by evaluating DNA laddering, using gel electrophoresis.

RESULTS

(+)-Chabranol had a marked time- and concentration-dependent inhibitory effect on BGC-823 cell proliferation. The effect was less marked in SGC-7901, SSMC-7721 and HepG2 cells. Exposure of BGC-823 cells to (+)-chabranol arrested the cell cycle at G(1). Evidence of apoptosis and autophagy was observed by TEM; DNA laddering in BGC-823 cells supported the presence of apoptosis.

CONCLUSIONS

This study suggested that (+)-chabranol has antitumour activity against BGC-823 cells, and may exert its action by inhibition of proliferation and induction of apoptosis and autophagy. With further development, (+)-chabranol may represent a potential novel treatment for poorly differentiated gastric cancer.