Macroautophagy: the key ingredient to a healthy diet?

Modulating autophagy and mitophagy as a promising therapeutic approach in neurodegenerative disorders

The high prevalence of neurodegenerative diseases has become a major public health challenge and is associated with a tremendous burden on individuals, society and federal governments worldwide. Protein misfolding and aggregation are the major pathological hallmarks of several neurodegenerative disorders. The cells have evolved several regulatory mechanisms to deal with aberrant protein folding, namely the classical ubiquitin pathway, where ubiquitination of protein aggregates marks their degradation via lysosome and the novel autophagy or mitophagy pathways. Autophagy is a catabolic process in eukaryotic cells that allows the lysosome to recycle the cell's own contents, such as organelles and proteins, known as autophagic cargo. Their most significant role is to keep cells alive in distressed situations. Mitophagy is also crucial for reducing abnormal protein aggregation and increasing organelle clearance and partly accounts for maintaining cellular homeostasis. Furthermore, substantial data indicate that any disruption in these homeostatic mechanisms leads to the emergence of several age-associated metabolic and neurodegenerative diseases. So, targeting autophagy and mitophagy might be a potential therapeutic strategy for a variety of health conditions.

ConA-Coated Liposomes as a System to Delivery β-Lapachone to Breast Cancer Cells

BACKGROUND

Target treatment using site-specific nanosystems is a hot topic for treating several diseases, especially cancer.

OBJECTIVE

The study was set out to develop site-specific liposomes using ConcanavalinA (ConA) to target β-lapachone(β-lap) to human breast cancer cells.

METHODS

Liposomes were prepared and characterized according to diameter size, zeta potential, ConA conjugation(%), and β-lap encapsulation efficiency (%). Isothermal Titration Calorimetry evaluated the binding energy between the biomolecules, which compose the liposomes. ConA avidity was assessed before and after conjugation. Cytotoxicity was evaluated, and fluorescence microscopy was performed to investigate the influence of ConA influenced on MCF-7 uptake.

RESULTS

Uncoated and ConA-coated liposomes presented size, and zeta potential values from 97.46 ± 2.01 to 152.23 ± 2.73nm, and -6.83 ± 0.28 to -17.23 ±0.64mV, respectively. Both ConA conjugation and β-lap encapsulation efficiency were approximately 100%. The favorable and spontaneous process confirmed the binding between ConA and the lipid. Hemagglutination assay confirmed ConA avidity once Lipo-ConA and Lipo-PEG-ConA were able to hemagglutinate the red blood cells at 128-1 and 256-1, respectively. Lipo-ConA was not cytotoxic, and the site-specific liposomes presented the highest toxicity. ConA-coated liposomes were more internalized by MCF7 than uncoated liposomes.

CONCLUSION

Therefore, the presence of ConA on the surface of liposomes influenced MCF7 uptake, suggesting that it could be used as a promising site-specific system to target β-lap to cancer cells.

Pumpkin Seed Extracts Inhibit Proliferation and Induce Autophagy in PC-3 Androgen Insensitive Prostate Cancer Cells

Pumpkin seed is a rich source of polyphenols and other bioactive compounds that may act as chemopreventive agents against cancer. In this study, five different extracts of pumpkin seeds were evaluated for their ability to affect proliferation and autophagy on PC-3 prostate cancer cells. All extracts (water [W], methanolic, acetone, ethylacetate, and polar lipid [PL]) inhibited cell proliferation in a dose-dependent manner. Treatment of cells with the PL extract increased cell distribution in the S phase, whereas PL and W extracts induced autophagy significantly. Moreover, PL extract induced a remarkable increase of glutathione and oxidized glutathione levels, whereas nitrite and hydrogen peroxide levels were not altered. In conclusion, pumpkin seed extracts affect PC-3 cell viability, oxidative parameters, and autophagic mechanism, thus demonstrating their potential pharmacological use.

ROS and metabolomics-mediated autophagy in rat's testicular tissue alter after exercise training; Evidence for exercise intensity and outcomes

AIMS

Oxidative damage and altered metabolic reactions are suspected to initiate the autophagy. The exercise training significantly impacts testicular antioxidant and metabolic potentials. However, the underlying mechanism(s) that the exercise-induced alterations can affect the autophagy markers remained unknown. This study explored the effect of exercise training on antioxidant and metabolic statuses of testicular tissue and uncovered the possible cross-link between these statuses and autophagy-inducers expression.

MAIN METHODS

Wistar rats were divided into sedentary control, low (LICT), moderate (MICT), and high (HICT) intensity continuous training groups. Following 8 weeks of training, the testicular total antioxidant capacity (TAC), total oxidant status (TOS), glutathione (GSH), and NADP⁺/NADPH as oxidative biomarkers along with intracytoplasmic carbohydrate and lipid droplet patterns, lactate dehydrogenase (LDH) activity, and lactate as metabolic elements were assessed. Finally, the autophagy-inducers expression and sperm count were examined.

KEY FINDINGS

With no significant impact on the oxidative biomarkers and metabolic elements, the LICT and MICT groups exhibited statistically unremarkable (p < 0.05) impacts on spermatogenesis differentiation, spermiogenesis ratio, and sperm count while increased the autophagy-inducers expression. Reversely, the HICT group, simultaneous with suppressing the antioxidant biomarkers (TAC↓, GSH↓, TOS↑, NADP⁺/NADPH↑), significantly (p < 0.05) reduced the testicular LDH activity and lactate level, changed the intracytoplasmic carbohydrate and lipid droplet's pattern, and amplified the classical autophagy-inducers p62, Beclin-1, autophagy-related gene (ATG)-7, and light chain 3 (LC3)-II/I expression.

SIGNIFICANCE

The autophagy-inducers overexpression has occurred after HICT induction, most probably to eliminate the oxidative damage cargoes, while increased to maintain the metabolic homeostasis in the LICT and MICT groups.

Changes in expression of the autophagy-related genes microtubule-associated protein 1 light chain 3β and autophagy related 7 in skeletal muscle of fattening Japanese Black cattle: a pilot study

Objective

Autophagy is a bulk degradation system for intracellular proteins which contributes to skeletal muscle homeostasis, according to previous studies in humans and rodents. However, there is a lack of information on the physiological role of autophagy in the skeletal muscle of meat animals. This study was planned as a pilot study to investigate changes in expression of two major autophagy-related genes, microtubule-associated protein 1 light chain 3β (MAP1LC3B) and autophagy related 7 (ATG7) in fattening beef cattle, and to compare them with skeletal muscle growth.

Methods

Six castrated Japanese Black cattle (initial body weight: 503±20 kg) were enrolled in this study and fattened for 7 months. Three skeletal muscles, M. longissimus, M. gluteus medius, and M. semimembranosus, were collected by needle biopsy three times during the observation period, and mRNA levels of MAP1LC3B and ATG7 were determined by quantitative reverse-transcription polymerase chain reaction. The expression levels of genes associated with the ubiquitin-proteasome system, another proteolytic mechanism, were also analyzed for comparison with autophagy-related genes. In addition, ultrasonic scanning was repeatedly performed to measure M. longissimus area as an index of muscle growth.

Results

Our results showed that both MAP1LC3B and ATG7 expression increased over the observation period in all three skeletal muscles. Interestingly, the increase in expression of these two genes in M. longissimus was highly correlated with ultrasonic M. longissimus area and body weight. On the other hand, the expression of genes associated with the ubiquitin-proteasome system was unchanged during the same period.

Conclusion

These findings suggest that autophagy plays an important role in the growth of skeletal muscle of fattening beef cattle and imply that autophagic activity affects meat productivity.

Role of Choline in the Modulation of Degenerative Processes: In Vivo and In Vitro Studies

The purpose of the present study was to examine the nutraceutical potential of choline as an added value to its well-known brain nutrient role. Several toxicity, antitoxicity, genotoxicity, antigenotoxicity, and longevity endpoints were checked in the somatic mutation and recombination test in in vivo Drosophila animal model. Cytotoxicity in human leukemia-60 cell line (HL-60) promyelocytic and NIH3T3 mouse fibroblast cells, proapoptotic DNA fragmentation, comet assay, methylation status, and macroautophagy (MA) activity were tested in in vitro assays. Choline is not only safe but it is also able to protect against the DNA damage caused by an oxidative genotoxin. Moreover, it improves the life extension in the animal model. The in vitro results show that it is able to exhibit genetic damage against leukemia HL-60 cells. Single-strand breaks in DNA are observed at the molecular level in treatments with choline, although only a significant hypermethylation on the long interspersed elements-1 and a hypomethylation on the satellite-alpha DNA repetitive DNA sequences of HL-60 cells at the lowest concentration (0.447 mM) were observed. Besides, choline decreased MA at the lower assayed concentration and the MA response to topoisomerase inhibitor (etoposide) is maintained in the presence of treatment with 0.22 mM choline. Taking into account the hopeful results obtained in the in vivo and in vitro assays, choline could be proposed as a substance with an important nutraceutical value for different purposes.

ACTP: A webserver for predicting potential targets and relevant pathways of autophagy-modulating compounds

Autophagy (macroautophagy) is well known as an evolutionarily conserved lysosomal degradation process for long-lived proteins and damaged organelles. Recently, accumulating evidence has revealed a series of small-molecule compounds that may activate or inhibit autophagy for therapeutic potential on human diseases. However, targeting autophagy for drug discovery still remains in its infancy. In this study, we developed a webserver called Autophagic Compound-Target Prediction (ACTP) (http://actp.liu-lab.com/) that could predict autophagic targets and relevant pathways for a given compound. The flexible docking of submitted small-molecule compound (s) to potential autophagic targets could be performed by backend reverse docking. The webpage would return structure-based scores and relevant pathways for each predicted target. Thus, these results provide a basis for the rapid prediction of potential targets/pathways of possible autophagy-activating or autophagy-inhibiting compounds without labor-intensive experiments. Moreover, ACTP will be helpful to shed light on identifying more novel autophagy-activating or autophagy-inhibiting compounds for future therapeutic implications.

Histone deacetylase 8 as a novel therapeutic target in oral squamous cell carcinoma

The overexpression of histone deacetylases (HDACs) has been observed in many cancers and inhibition of specific HDAC has emerged as a new target for cancer therapy. The present study examined the expression of HDAC8 and the inhibitory effect of HDAC8 in oral squamous cell carcinoma (OSCC). The expression of HDAC8 was measured in human OSCC tissues and OSCC cell lines using immunohistochemistry and immunoblotting. HDAC8 was knocked down in OSCC cells by transfection with HDAC8 siRNAs and cell proliferation was quantified. Apoptosis and autophagy were measured using flow cytometry and immunoblotting. HDAC8 were overexpressed in OSCC tissues and OSCC cells, mainly localized in the cytoplasm. HDAC8 siRNAs effectively reduced the level of HDAC8 expression and HDAC8 silencing significantly inhibited the proliferation of OSCC cells. HDAC8 knockdown induced apoptotic cell death through caspases activation and pro-survival autophagy in OSCC cells. Combination with HDAC silencing and autophagy inhibition enhanced cell death by increasing apoptosis in OSCC cells. This study suggests that inhibition of HDAC8 might become a novel therapeutic strategy for OSCC.

Rottlerin-induced autophagy leads to apoptosis in bladder cancer cells

It has been well-established that apoptosis contributes to cancer cell death; however, the role of autophagy in cancer cell death remains unclear. The aim of the present study was to investigate the effects of rottlerin, a traditional Indian medicine, on cell growth inhibition and autophagy in EJ human bladder carcinoma cells in vitro. Cell viability, measured by MTT assay, was found to be suppressed in a dose- and time-dependent manner. In addition, apoptosis was significantly increased in cells treated with rottlerin, as indicated by increased annexin V-fluorescein isothiocyanate/propidium iodide staining and changes in the cell cycle distribution that indicated blockage at G1 phase. Rottlerin treatment also enhanced the activation of autophagy, with increased expression of microtubule-associated protein 1 light chain 3 (LC3)-II and the appearance of autophagosomes. The increased level of LC3-II and autophagosomes suggests that autophagy may contribute to apoptosis in these cells. In addition, no apparent alterations in the levels of pro-caspase-3, cleaved caspase-3, total poly (ADP ribose) polymerase (PARP) and cleaved-PARP were observed in cells treated with rottlerin, which indicates that caspases may not serve a key role during the process of apoptosis induced by rottlerin. Therefore, the results of the present study indicate that rottlerin promotes apoptosis and arrests the cell cycle in EJ cells, which may be caused by autophagy activation.

Arginine Supplementation Recovered the IFN-γ-Mediated Decrease in Milk Protein and Fat Synthesis by Inhibiting the GCN2/eIF2α Pathway, Which Induces Autophagy in Primary Bovine Mammary Epithelial Cells

During the lactation cycle of the bovine mammary gland, autophagy is induced in bovine mammary epithelial cells (BMECs) as a cellular homeostasis and survival mechanism. Interferon gamma (IFN-γ) is an important antiproliferative and apoptogenic factor that has been shown to induce autophagy in multiple cell lines in vitro. However, it remains unclear whether IFN-γ can induce autophagy and whether autophagy affects milk synthesis in BMECs. To understand whether IFN-γ affects milk synthesis, we isolated and purified primary BMECs and investigated the effect of IFN-γ on milk synthesis in primary BMECs in vitro. The results showed that IFN-γ significantly inhibits milk synthesis and that autophagy was clearly induced in primary BMECs in vitro within 24 h. Interestingly, autophagy was observed following IFN-γ treatment, and the inhibition of autophagy can improve milk protein and milk fat synthesis. Conversely, upregulation of autophagy decreased milk synthesis. Furthermore, mechanistic analysis confirmed that IFN-γ mediated autophagy by depleting arginine and inhibiting the general control nonderepressible-2 kinase (GCN2)/eukaryotic initiation factor 2α (eIF2α) signaling pathway in BMECs. Then, it was found that arginine supplementation could attenuate IFN-γ-induced autophagy and recover milk synthesis to some extent. These findings may not only provide a novel measure for preventing the IFN-γ-induced decrease in milk quality but also a useful therapeutic approach for IFN-γ-associated breast diseases in other animals and humans.

Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide-based glioblastoma chemotherapy

Temozolomide (TMZ), an alkylating agent, is recommended as the initial treatment for high-grade glioblastoma. TMZ is widely used, but its short half-life and the frequency of tumor resistance limit its therapeutic efficacy. In the present study, the anticancer effect of vitamin D (VD) combined with TMZ upon glioblastoma was determined, and the underlying mechanism of this effect was identified. Through cell viability, clonogenic and wound healing assays, the current study demonstrated that treatment of a C6 glioblastoma cell line with TMZ and VD resulted in significantly increased in vitro antitumor effects compared with either VD or TMZ alone. Autophagy, hypothesized to be the dominant mechanism underlying TMZ-based tumor cell death, was maximally activated in TMZ and VD co-treated C6 cells. This was demonstrated by ultrastructural observations of autophagosomes, increased size and number of microtubule-associated protein 1 light chain 3 (LC3) puncta and increased conversion of LC3-I to LC3-II. However, the extent of apoptosis was not significantly different between cells treated with TMZ and VD and those treated with TMZ alone. Addition of the autophagy inhibitor 3-methyladenine markedly inhibited the anticancer effect of TMZ and VD treatment, indicating that the chemosensitizing effect of VD in TMZ-based glioblastoma therapy is generated through enhancement of cytotoxic autophagy. TMZ and VD co-treatment also significantly inhibited tumor progression and prolonged survival duration in rat glioblastoma orthotopic xenograft models when compared with TMZ treatment alone. These in vivo results are concordant with the aforementioned in vitro results, together revealing that the combined use of TMZ and VD exerts synergistic antitumor effects on rat models of glioblastoma and may represent an effective therapeutic strategy.

Cell death and tissue reorganization in Rhynchosciara americana (Sciaridae: Diptera) metamorphosis and their relation to molting hormone titers

Programmed cell death (PCD) is a focal topic for understanding processes underlying metamorphosis in insects, especially so in holometabolous orders. During adult morphogenesis it allows for the elimination of larva-specific tissues and the reorganization of others for their functionalities in adult life. In Rhynchosciara, this PCD process could be classified as autophagic cell death, yet the expression of apoptosis-related genes and certain morphological aspects suggest that processes, autophagy and apoptosis may be involved. Aiming to reveal the morphological changes that salivary gland and fat body cells undergo during metamorphosis we conducted microscopy analyses to detect chromatin condensation and fragmentation, as well as alterations in the cytoplasm of late pupal tissues of Rhynchosciara americana. Transmission electron microscopy and confocal microscopy revealed cells in variable stages of death. By analyzing the morphological structure of the salivary gland we observed the presence of cells with autophagic vacuoles and apoptotic bodies and DNA fragmentation was confirmed with the TUNEL assay in salivary gland. The reorganization of fat body occurs with discrete detection of cell death by TUNEL assay. However, both salivary gland histolysis and fat body reorganization occur under control of the hormone ecdysone.

Oleanolic acid inhibits proliferation and invasiveness of Kras-transformed cells via autophagy

Oleanolic acid (OA) has been widely studied because of its pleiotropic therapeutic and preventive effect on various diseases. However, the mechanisms of OA's action are still not clear yet, especially its suppressing effect on transformed cells. In this work, we found that OA induced autophagy in normal tissue-derived cells without cytotoxicity. OA-induced autophagy was shown to decrease the proliferation of KRAS-transformed normal cells and to impair their invasion and anchorage-independent growth. Interrupting autophagy rescued OA's effect on the transformed cells. Mouse model experiments also demonstrated that OA suppressed the growth of KRAS-transformed breast epithelial cell MCF10A-derived tumor xenograft by inducing autophagy. Finally, we identified that OA induced autophagy in normal cells by inhibiting the activation of Akt/mTOR/S6K signaling. In conclusions, we found that OA treatment permitted normal cells to undergo autophagy. The induced autophagy was required for OA to prevent or delay the growth of transformed normal cells.

Autophagy triggered by magnolol derivative negatively regulates angiogenesis

Angiogenesis has a key role in the tumor progression and metastasis; targeting endothelial cell proliferation has emerged as a promising therapeutic strategy for the prevention of cancer. Previous studies have revealed a complex association between the process of angiogenesis and autophagy and its outcome on tumorigenesis. Autophagy, also known as type-II cell death, has been identified as an alternative way of cell killing in apoptotic-resistant cancer cells. However, its involvement in chemoresistance and tumor promotion is also well known. In this study, we used a derivate of natural product magnolol (Ery5), a potent autophagy inducer, to study the association between the autophagy and angiogenesis in both in vitro and in vivo model system. We found that the robust autophagy triggered by Ery5, inhibited angiogenesis and caused cell death independent of the apoptosis in human umbilical cord vein endothelial cells and PC-3 cells. Ery5 induced autophagy effectively inhibited cell proliferation, migration, invasion and tube formation. We further demonstrated that Ery5-mediated autophagy and subsequent inhibition of angiogenesis was reversed when autophagy was inhibited through 3-methyl adenine and knocking down of key autophagy proteins ATG7 and microtubule-associated protein light chain 3. While evaluating the negative regulation of autophagy on angiogenesis, it was interesting to find that angiogenic environment produced by the treatment of VEGF and CoCl2 remarkably downregulated the autophagy and autophagic cell death induced by Ery5. These studies, while disclosing the vital role of autophagy in the regulation of angiogenesis, also suggest that the potent modulators of autophagy can lead to the development of effective therapeutics in apoptosis-resistant cancer.

A systems biology analysis of autophagy in cancer therapy

Autophagy, which degrades redundant or damaged cellular constituents, is intricately relevant to a variety of human diseases, most notably cancer. Autophagy exerts distinct effects on cancer initiation and progression, due to the intrinsic overlapping of autophagic and cancer signalling pathways. However, due to the complexity of cancer as a systemic disease, the fate of cancer cells is not decided by any one signalling pathway. Numerous autophagic inter-connectivity and cross-talk pathways need to be further clarified at a systems level. In this review, we propose a systems biology perspective for the comprehensive analysis of the autophagy-cancer network, focusing on systems biology analysis in autophagy and cancer therapy. Together, these analyses may not only improve our understanding on autophagy-cancer relationships, but also facilitate cancer drug discovery.

Fenugreek extract as an inducer of cellular death via autophagy in human T lymphoma Jurkat cells

Background

Drugs used both in classical chemotherapy and the more recent targeted therapy do not have cancer cell specificity and, hence, cause severe systemic side effects. Tumors also develop resistance to such drugs due to heterogeneity of cell types and clonal selection. Several traditional dietary ingredients from plants, on the other hand, have been shown to act on multiple targets/pathways, and may overcome drug resistance. The dietary agents are safe and readily available. However, application of plant components for cancer treatment/prevention requires better understanding of anticancer functions and elucidation of their mechanisms of action. The current study focuses on the anticancer properties of fenugreek, a herb with proven anti-diabetic, antitumor and immune-stimulating functions.

Method

Jurkat cells were incubated with 30 to 1500 μg/mL concentrations of 50% ethanolic extract of dry fenugreek seeds and were followed for changes in viability (trypan blue assay), morphology (microscopic examination) and autophagic marker LC3 transcript level (RT-PCR).

Results

Incubation of Jurkat cells with fenugreek extract at concentrations ranging from 30 to 1500 μg/mL for up to 3 days resulted in cell death in a dose- and time-dependent manner. Jurkat cell death was preceded by the appearance of multiple large vacuoles, which coincided with transcriptional up-regulation of LC3. GC-MS analysis of fenugreek extract indicated the presence of several compounds with anticancer properties, including gingerol (4.82%), cedrene (2.91%), zingerone (16.5%), vanillin (1.52%) and eugenol (1.25%).

Conclusions

Distinct morphological changes involving appearance of large vacuoles, membrane disintegration and increased expression of LC3 transcripts indicated that fenugreek extract induced autophagy and autophagy-associated death of Jurkat cells. In addition to the already known apoptotic activation, induction of autophagy may be an additional mechanism underlying the anticancer properties of fenugreek. This is the first report showing fenugreek as an inducer of autophagy in human cells and further work is needed to define the various intermediates of the autophagic pathway.

Honeybees and cell lines as models of DNA methylation and aging in response to diet

DNA methylation patterns change as individuals grow older, and DNA methylation appears susceptible to modification by the diet. Thus DNA methylation may be a mechanism through which diet can affect aging and longevity. We propose that effects on DNA methylation also contribute to the extension in lifespan observed in response to dietary restriction. Relationships between diet-induced changes in DNA methylation and parallel effects on aging and/or lifespan could, of course, be purely associative. Proof of these ideas requires experimental model systems in which it is possible to manipulate genome methylation status and to measure effects on aging and/or lifespan. Commonly-used short-lived and genetically-malleable metazoan species, such as Caenorhabditis elegans and Drosophila, are not suitable for such studies; the C. elegans genome is not methylated, and DNA methylation in Drosophila is dissimilar from mammalian DNA methylation, occurring at cytosines at sites other than in CpG sequences. The honeybee provides a potentially unique and tractable model for such studies. Female larval development into the long-lived queen phenotype or short-lived worker is determined purely by diet (royal jelly) through an effect on DNA methylation, and honeybee DNA methylation mirrors that of the mammalian genome. Mammalian cell lines and biochemical approaches offer complementary tools to address specific components of hypotheses relating to effects of diet on aging through DNA methylation in a more targeted manner. Our studies using mammalian cell lines are revealing effects of Sirt1 on DNA methylation, and indicate that Sirt1 and resveratrol affect the expression of different sets of genes.

Targeting autophagic pathways for cancer drug discovery

Autophagy, an evolutionarily conserved lysosomal degradation process, has drawn an increasing amount of attention in recent years for its role in a variety of human diseases, such as cancer. Notably, autophagy plays an important role in regulating several survival and death signaling pathways that determine cell fate in cancer. To date, substantial evidence has demonstrated that some key autophagic mediators, such as autophagy-related genes (ATGs), PI3K, mTOR, p53, and Beclin-1, may play crucial roles in modulating autophagic activity in cancer initiation and progression. Because autophagy-modulating agents such as rapamycin and chloroquine have already been used clinically to treat cancer, it is conceivable that targeting autophagic pathways may provide a new opportunity for discovery and development of more novel cancer therapeutics. With a deeper understanding of the regulatory mechanisms governing autophagy, we will have a better opportunity to facilitate the exploitation of autophagy as a target for therapeutic intervention in cancer. This review discusses the current status of targeting autophagic pathways as a potential cancer therapy.

Autophagy and cancer

Basal autophagy plays a critical role in maintaining cellular homeostasis and genomic integrity by degrading aged or malfunctioning organelles and damaged or misfolded proteins. However, autophagy also plays a complicated role in tumorigenesis and treatment responsiveness. It can be tumor-suppressing during the early stages of tumorigenesis (i.e., it is an anti-tumor mechanism), as reduced autophagy is found in tumor cells and may be associated with malignant transformation. In this case, induction of autophagy would seem to be beneficial for cancer prevention. In established tumors, however, autophagy can be tumor- promoting (i.e., it is a pro-tumor mechanism), and cancer cells can use enhanced autophagy to survive under metabolic and therapeutic stress. The pharmacological and/or genetic inhibition of autophagy was recently shown to sensitize cancer cells to the lethal effects of various cancer therapies, including chemotherapy, radiotherapy and targeted therapies, suggesting that suppression of the autophagic pathway may represent a valuable sensitizing strategy for cancer treatments. In contrast, excessive stimulation of autophagy may also provide a therapeutic strategy for treating resistant cancer cells having high apoptotic thresholds. In order for us to develop successful autophagy- modulating strategies against cancer, we need to better understand how the roles of autophagy differ depending on the tumor stage, cell type and/or genetic factors, and we need to determine how specific pathways of autophagy are activated or inhibited by the various anti-cancer therapies.

Translational evidence that impaired autophagy contributes to arterial ageing

Ageing causes arterial endothelial dysfunction that increases the risk of cardiovascular diseases (CVD), but the underlying mechanisms are incompletely understood. The aim of the present study was to determine the role of autophagy, the cellular process of recycling damaged biomolecules, in endothelial dysfunction with ageing. In older humans, expression of autophagy markers in arterial endothelial cells was impaired by ∼50% (P <0.05) and was associated with an ∼30% (P <0.05) reduction in arterial endothelium-dependent dilatation (EDD). Similarly, in C57BL/6 control mice ageing was associated with an ∼40% decrease (P <0.05) in arterial markers of autophagy and an ∼25% reduction (P <0.05) in EDD. In both humans and mice, impaired EDD was mediated by reduced nitric oxide (NO) bioavailability and was associated with increased oxidative stress and inflammation (P <0.05). In old mice, treatment with the autophagy-enhancing agent trehalose restored expression of autophagy markers, rescued NO-mediated EDD by reducing oxidative stress, and normalized inflammatory cytokine expression. In cultured endothelial cells, inhibition of autophagy increased oxidative stress and reduced NO production, whereas trehalose enhanced NO production via an autophagy-dependent mechanism. These results provide the first evidence that autophagy is impaired with ageing in vascular tissues. Our findings also suggest that autophagy preserves arterial endothelial function by reducing oxidative stress and inflammation and increasing NO bioavailability. Autophagy-enhancing strategies may therefore have therapeutic efficacy for ameliorating age-associated arterial dysfunction and preventing CVD.

Autophagy and cancer cell metabolism

Autophagy is a catabolic process involving lysosomal turnover of proteins and organelles for maintenance of cellular homeostasis and mitigation of metabolic stress. Autophagy defects are linked to diseases, such as liver failure, neurodegeneration, inflammatory bowel disease, aging and cancer. The role of autophagy in tumorigenesis is complex and likely context-dependent. Human breast, ovarian and prostate cancers have allelic deletions of the essential autophagy regulator BECN1 and Becn1(+/-) and other autophagy-deficient transgenic mice are tumor-prone, whereas tumors with constitutive Ras activation, including human pancreatic cancers, upregulate basal autophagy and are commonly addicted to this pathway for survival and growth; furthermore, autophagy suppression by Fip200 deletion compromises PyMT-induced mammary tumorigenesis. The double-edged sword function of autophagy in cancer has been attributed to both cell- and non-cell-autonomous mechanisms, as autophagy defects promote cancer progression in association with oxidative and ER stress, DNA damage accumulation, genomic instability and persistence of inflammation, while functional autophagy enables cancer cell survival under stress and likely contributes to treatment resistance. In this review, we will focus on the intimate link between autophagy and cancer cell metabolism, a topic of growing interest in recent years, which has been recognized as highly clinically relevant and has become the focus of intense investigation in translational cancer research. Many tumor-associated conditions, including intermittent oxygen and nutrient deprivation, oxidative stress, fast growth and cell death suppression, modulate, in parallel and in interconnected ways, both cellular metabolism and autophagy to enable cancer cells to rapidly adapt to environmental stressors, maintain uncontrolled proliferation and evade the toxic effects of radiation and/or chemotherapy. Elucidating the interplay between autophagy and tumor cell metabolism will provide unique opportunities to identify new therapeutic targets and develop synthetically lethal treatment strategies that preferentially target cancer cells, while sparing normal tissues.

Concanavalin A: a potential anti-neoplastic agent targeting apoptosis, autophagy and anti-angiogenesis for cancer therapeutics

Concanavalin A (ConA), a Ca(2+)/Mn(2+)-dependent and mannose/glucose-binding legume lectin, has drawn a rising attention for its remarkable anti-proliferative and anti-tumor activities to a variety of cancer cells. ConA induces programmed cell death via mitochondria-mediated, P73-Foxo1a-Bim apoptosis and BNIP3-mediated mitochondrial autophagy. Through IKK-NF-κB-COX-2, SHP-2-MEK-1-ERK, and SHP-2-Ras-ERK anti-angiogenic pathways, ConA would inhibit cancer cell survival. In addition, ConA stimulates cell immunity and generates an immune memory, resisting to the same genotypic tumor. These biological findings shed light on new perspectives of ConA as a potential anti-neoplastic agent targeting apoptosis, autophagy and anti-angiogenesis in pre-clinical or clinical trials for cancer therapeutics.

Autophagy in heart disease: a strong hypothesis for an untouched metabolic reserve

Autophagy is a conserved catabolic process for long-lived proteins and organelles and is primarily responsible for nonspecific degradation of redundant or faulty cell components. Although autophagy has been described as the cell's major adaptive strategy in response to metabolic challenges, its influence on the cell's energy profile is poorly understood. In the myocardium, autophagy is active at basal levels and is crucial for maintaining its contractile function. Defects in the autophagic machinery cause cardiac dysfunction and heart failure. In this paper we propose that (1) autophagy contributes significantly to the metabolic balance sheet of the heart. (2) Increased autophagy contributes to an improved myocardial energy profile through changing the cardiac substrate preference. (3) Substrates generated through autophagy give rise to an alternative for ATP production with an oxygen-sparing effect. These elements identify autophagy in a new context of myocardial metabolic interregulation, which we discuss in the settings of myocardial infarction, heart failure and the diabetic heart. It is hoped that the hypothesis presented can lead to new insights aimed at exploiting autophagy to improve existing metabolic-based therapy in heart disease.

At the core of survival: autophagy delays the onset of both apoptotic and necrotic cell death in a model of ischemic cell injury

Ischemic cell injury leads to cell death. Three main morphologies have been described: apoptosis, cell death with autophagy and necrosis. Their inherent dynamic nature, a point of no return (PONR) and molecular overlap have been stressed. The relationship between a defined cell death type and the severity of injury remains unclear. The functional role of autophagy and its effects on cell death onset is largely unknown. In this study we report a differential induction of cell death, which is dependent on the severity and duration of an ischemic insult. We show that mild ischemia leads to the induction of autophagy and apoptosis, while moderate or severe ischemia induces both apoptotic and necrotic cell death without increased autophagy. The autophagic response during mild injury was associated with an ATP surge. Real-time imaging and Fluorescence Resonance Energy Transfer (FRET) revealed that increased autophagy delays the PONR of both apoptosis and necrosis significantly. Blocking autophagy shifted PONR to an earlier point in time. Our results suggest that autophagic activity directly alters intracellular metabolic parameters, responsible for maintaining mitochondrial membrane potential and cellular membrane integrity. A similar treatment also improved functional recovery in the perfused rat heart. Taken together, we demonstrate a novel finding: autophagy is implicated only in mild injury and positions the PONR in cell death.

Targeting the autophagy pathway for cancer chemoprevention

Autophagy is crucial for maintaining cellular homeostasis, coping with metabolic stress, and limiting oxidative damage. Several autophagy-deficient or knockout models show increased tumor incidence, implicating autophagy as a tumor suppressor. Autophagy is involved in multiple processes that may curb transformation, including the control of oncogene-induced senescence (OIS), which can limit progression to full malignancy, and efficient antigen presentation, which is crucial for immune cell recognition and elimination of nascent cancer cells. Activation of the autophagy pathway may therefore hold promise as a chemoprevention strategy. Caloric restriction, bioactive dietary compounds, or specific pharmacological activators of the autophagy pathway are all possible avenues to explore in harnessing the autophagy pathway in cancer prevention.

Dietary patterns, risk and prognosis of breast cancer

Survival in women diagnosed with early-stage, invasive breast cancer has improved dramatically in the past 10–15 years. This is largely due to the use of pharmacological therapies targeting a reduction in estrogen action and exposure. Women diagnosed with breast cancer often alter their eating behavior towards healthier food choices in an attempt to improve their survival and their overall health and well being. Mounting interest in the role of diet to modify breast cancer survival and/or comorbidity and mortality has led researchers to evaluate the effects of differential dietary patterns on this disease. Current findings suggest a possible, but inconsistent, benefit of a prudent, vegetable-rich, low-fat/high-vegetable eating pattern on disease-free survival, but the results to date are limited by strong treatment effectiveness and low overall recurrence rates. It is more likely this prudent eating pattern will improve non-breast cancer mortality (e.g., cardiovascular disease) compared with a Western dietary pattern. Efforts to educate women diagnosed with breast cancer to consume a diet lower in total and saturated fat, higher in vegetables and fiber, and which results in mild to modest weight loss among overweight/obese women is sensible in light of the high survivability of breast cancer and need to direct attention to comorbidities that likely increase as a consequence of treatment and treatment-related weight gain and sedentary behavior. Additional research is needed to address the importance of diet in the breast cancer patient, particularly in relation to the effect of select dietary patterns on factors that influence individual recurrence risk (e.g., hormone levels, drug metabolism and oxidative stress), as well as factors that influence non-breast cancer morbidity risk and causes of death in the survivor population.

The regulation of aging: does autophagy underlie longevity?

The accumulation of cellular damage is a feature common to all aging cells and leads to decreased ability of the organism to survive. The overall rate at which damage accumulates is influenced by conserved metabolic factors (longevity pathways and regulatory proteins) that control lifespan through adjusting mechanisms for maintenance and repair. Autophagy, the major catabolic process of eukaryotic cells that degrades and recycles damaged macromolecules and organelles, is implicated in aging and in the incidence of diverse age-related pathologies. Recent evidence has revealed that autophagic activity is required for lifespan extension in various long-lived mutant organisms, and that numerous autophagy-related genes or proteins are directly regulated by longevity pathways. These findings support the emerging view that autophagy is a central regulatory mechanism for aging in diverse eukaryotic species.

Plant lectins: potential antineoplastic drugs from bench to clinic

Plant lectins, carbohydrate-binding proteins distributed widely in a variety of plant species, have drawn a rising attention for cancer biologists due to their remarkable anti-tumour properties. In this review, we present a brief outline of the up-to-date advances of plant lectins in elucidating their complex anti-cancer mechanisms implicated in apoptosis and autophagy. In addition, we further discuss the pre-clinical and clinical studies of plant lectins for their potential therapeutic applications. In conclusion, these inspiring findings would open a new perspective for plant lectins as potential antineoplastic drugs from bench to clinic.