Choose Delicately and Reuse Adequately: The Newly Revealed Process of Autophagy

Autophagy in Ovarian Follicular Development and Atresia

Autophagy is a mechanism that exists in all eukaryotes under a variety of physiological and pathological conditions. In the mammalian ovaries, less than 1% of follicles ovulate, whereas the remaining 99% undergo follicular atresia. Autophagy and apoptosis have been previously found to be involved in the regulation of both primordial follicular development as well as atresia. The relationship between autophagy, follicular development, and atresia have been summarized in this review with the aim to obtain a more comprehensive understanding of the role played by autophagy in follicular development and atresia.

Upregulation of autophagy by Ginsenoside Rg2 in MCF-7 cells

Autophagy is a major intracellular degradation process that plays an important role in cell survival, stress responses, nutrient sensing and development. Our previous studies have shown that Rg2, a triterpenoid saponin contained in ginseng, protects cells against UVB-induced genotoxicity by increasing DNA repair, in possible association with modulation of protein levels involved in p53 pathway. In this study, we determined an upregulation of autophagy by Rg2. Rg2 treatment for 24 h in MCF-7, a breast cancer cell, did not show cytotoxicity up to 200 μM. Rg2 also upregulated the level of p-p53, p-AMPK, p-ACC, Atg-7 and LC3-II and decreased the level of p62 in concentration-dependent manners. We also determined the level of p53, AMPK, p62, Atg-7 and LC3 after UVB exposure and subsequent incubation in growth medium for 24 h. UVB increased the level of p-p53, p-AMPK, p-ACC and decreased the levels of p62, Atg-7 and LC3-II. Interestingly, Rg2 treatment for 24 h after UVB exposure increased the levels of p-p53, p-AMPK, p-ACC, Atg-7 and LC3-II and decreased the level of cyclobutane pyrimidine dimer, a UVB-induced DNA damage in concentration-dependent manners. All these results suggest that Rg2 increased autophagy and decreased UVB-induced DNA damage, in possible association with the modulation of protein levels in p53- and autophagic pathways.

Inhibition of silkworm vacuolar-type ATPase activity by its inhibitor Bafilomycin A1 induces caspase-dependent apoptosis in an embryonic cell line of silkworm

Vacuolar-type ATPase (V-ATPase) is a type of hydrogen ion transporter located in the vesicular membrane-like system, which mediates active transport and intracellular acidification in various compartments. In mammals, V-ATPase has been reported to play a key role in cell proliferation and apoptosis. The studies of V-ATPase in silkworm mainly focus on the acidification regulation of midgut and silk gland and immune resistance. However, there are few reports about the function of silkworm V-ATPase on cell proliferation, autophagy, and apoptosis. Thus, the function of V-ATPase in a cell line of Bombyx mori (BmE) was investigated by treating the cell line with bafilomycin A1, a specific inhibitor of V-ATPase. Cell counting kit 8 (CCK8) and flow cytometry analysis showed that bafilomycin A1 treatment decreased the cell proliferation activity, affected the cell cycle progression and induced cell apoptosis. LysoTracker Red staining showed that the target of bafilomycin A1 is lysosome. The expression of all autophagy-related genes ( BmATG5, BmATG6, and BmATG8) decreased, indicating that cell autophagy was inhibited. The analysis of the apoptosis pathway demonstrated that inhibiting the activity of V-ATPase of BmE cells could promote mitochondria to release cytochrome C, inhibit the expression of BmIAP, and activate the caspase cascade to induce apoptosis. All these findings systematically illustrate the effects of V-ATPase on the proliferation, autophagy, and apoptosis in BmE cells, and provide new ideas and a theoretical basis for further study on the function of V-ATPase in BmE.

Protein imbalance in the development of skeletal muscle wasting in tumour-bearing mice

BACKGROUND

Cancer cachexia occurs in approximately 80% of cancer patients and is a key contributor to cancer-related death. The mechanisms controlling development of tumour-induced muscle wasting are not fully elucidated. Specifically, the progression and development of cancer cachexia are underexplored. Therefore, we examined skeletal muscle protein turnover throughout the development of cancer cachexia in tumour-bearing mice.

METHODS

Lewis lung carcinoma (LLC) was injected into the hind flank of C57BL6/J mice at 8 weeks age with tumour allowed to develop for 1, 2, 3, or 4 weeks and compared with PBS injected control. Muscle size was measured by cross-sectional area analysis of haematoxylin and eosin stained tibialis anterior muscle. ² H₂ O was used to assess protein synthesis throughout the development of cancer cachexia. Immunoblot and RT-qPCR were used to measure regulators of protein turnover. TUNEL staining was utilized to measure apoptotic nuclei. LLC conditioned media (LCM) treatment of C2C12 myotubes was used to analyse cancer cachexia in vitro.

RESULTS

Muscle cross-sectional area decreased ~40% 4 weeks following tumour implantation. Myogenic signalling was suppressed in tumour-bearing mice as soon as 1 week following tumour implantation, including lower mRNA contents of Pax7, MyoD, CyclinD1, and Myogenin, when compared with control animals. AchRδ and AchRε mRNA contents were down-regulated by ~50% 3 weeks following tumour implantation. Mixed fractional synthesis rate protein synthesis was ~40% lower in 4 week tumour-bearing mice when compared with PBS controls. Protein ubiquitination was elevated by ~50% 4 weeks after tumour implantation. Moreover, there was an increase in autophagy machinery after 4 weeks of tumour growth. Finally, ERK and p38 MAPK phosphorylations were fourfold and threefold greater than control muscle 4 weeks following tumour implantation, respectively. Inhibition of p38 MAPK, but not ERK MAPK, in vitro partially rescued LCM-induced loss of myotube diameter.

CONCLUSIONS

Our findings work towards understanding the pathophysiological signalling in skeletal muscle in the initial development of cancer cachexia. Shortly following the onset of the tumour-bearing state alterations in myogenic regulatory factors are apparent, suggesting early onset alterations in the capacity for myogenic induction. Cancer cachexia presents with a combination of a loss of protein synthesis and increased markers of protein breakdown, specifically in the ubiquitin-proteasome system. Also, p38 MAPK may be a potential therapeutic target to combat cancer cachexia via a p38-FOX01-atrogene-ubiquitin-proteasome mechanism.

Impaired Mitophagy of Nucleated Erythroid Cells Leads to Anemia in Patients with Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal stem cell disorders characterized by cytopenia and dysplasia. Anemia is the most common symptom in patients with MDS. Mitophagy and mitochondrial dysfunction might be involved in the development of MDS. In this study, we investigated the change of mitophagy in erythroid precursors in MDS patients. We found that NIX-mediated mitophagy was impaired in bone marrow nucleated red blood cells (NRBC) of MDS patients, associated with an increased amount of damaged mitochondria and increased ROS level which might lead to apoptosis and ineffective erythropoiesis. The results showed that the amount of mitochondria in GlycoA⁺ NRBC positively correlated with the count of ring sideroblasts in bone marrow samples. Meanwhile, the level of autophagy-associated marker LC3B in GlycoA⁺ NRBC had a positive correlation with hemoglobin (Hb) levels, and the amount of mitochondria in GlycoA⁺ NRBC had a negative correlation with Hb levels in high-risk MDS patients. Our results indicated that mitophagy might involve the pathogenesis of anemia associated with MDS. Autophagy might be a novel target in treatments of MDS patients.

Anti-apoptotic effects of autophagy via ROS regulation in microtubule-targeted and PDGF-stimulated vascular smooth muscle cells

Autophagy has been studied as a therapeutic strategy for cardiovascular diseases. However, insufficient studies have been reported concerning the influence of vascular smooth muscle cells (VSMCs) through autophagy regulation. The aim of the present study was to determine the effects of VSMCs on the regulation of autophagy under in vitro conditions similar to vascular status of the equipped microtubule target agent-eluting stent and increased release of platelet-derived growth factor-BB (PDGF-BB). Cell viability and proliferation were measured using MTT and cell counting assays. Immunofluorescence using an anti-α-tubulin antibody was performed to determine microtubule dynamic formation. Cell apoptosis was measured by cleavage of caspase-3 using western blot analysis, and by nuclear fragmentation using a fluorescence assay. Autophagy activity was assessed by microtubule-associated protein light chain 3-II (LC-II) using western blot analysis. Levels of intracellular reactive oxygen species (ROS) were measured using H₂DCFDA. The proliferation and viability of VSMCs were inhibited by microtubule regulation. Additionally, microtubule-regulated and PDGF-BB-stimulated VSMCs increased the cleavage of caspase-3 more than only the microtubule-regulated condition, similar to that of LC3-II, implying autophagy. Inhibitory autophagy of microtubule-regulated and PDGF-BB-stimulated VSMCs resulted in low viability. However, enhancement of autophagy maintained survival through the reduction of ROS. These results suggest that the apoptosis of conditioned VSMCs is decreased by the blocking generation of ROS via the promotion of autophagy, and proliferation is also inhibited. Thus, promoting autophagy as a therapeutic target for vascular restenosis and atherosclerosis may be a good strategy.

Dissecting the molecular pathophysiology of drug-induced liver injury

Drug-induced liver injury (DILI) has become a major topic in the field of Hepatology and Gastroenterology. DILI can be clinically divided into three phenotypes: hepatocytic, cholestatic and mixed. Although the clinical manifestations of DILI are variable and the pathogenesis complicated, recent insights using improved preclinical models, have allowed a better understanding of the mechanisms that trigger liver damage. In this review, we will discuss the pathophysiological mechanisms underlying DILI. The toxicity of the drug eventually induces hepatocellular damage through multiple molecular pathways, including direct hepatic toxicity and innate and adaptive immune responses. Drugs or their metabolites, such as the common analgesic, acetaminophen, can cause direct hepatic toxicity through accumulation of reactive oxygen species and mitochondrial dysfunction. The innate and adaptive immune responses play also a very important role in the occurrence of idiosyncratic DILI. Furthermore, we examine common forms of hepatocyte death and their association with the activation of specific signaling pathways.

Diverse roles of mitochondria in ischemic stroke

Stroke is the leading cause of adult disability and mortality in most developing and developed countries. The current best practices for patients with acute ischemic stroke include intravenous tissue plasminogen activator and endovascular thrombectomy for large-vessel occlusion to improve clinical outcomes. However, only a limited portion of patients receive thrombolytic therapy or endovascular treatment because the therapeutic time window after ischemic stroke is narrow. To address the current shortage of stroke management approaches, it is critical to identify new potential therapeutic targets. The mitochondrion is an often overlooked target for the clinical treatment of stroke. Early studies of mitochondria focused on their bioenergetic role; however, these organelles are now known to be important in a wide range of cellular functions and signaling events. This review aims to summarize the current knowledge on the mitochondrial molecular mechanisms underlying cerebral ischemia and involved in reactive oxygen species generation and scavenging, electron transport chain dysfunction, apoptosis, mitochondrial dynamics and biogenesis, and inflammation. A better understanding of the roles of mitochondria in ischemia-related neuronal death and protection may provide a rationale for the development of innovative therapeutic regimens for ischemic stroke and other stroke syndromes.

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Review of current treatment of ischemic stroke indicates deficiency in the contemporary methods.

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Discuss the mitochondrial ROS-related signaling that affect neuronal fate after ischemic stroke.

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Mechanisms of mitochondrial dynamics and mitophagy could be pivotal for ischemic stroke.

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Inhibiting mitochondrion-induced inflammatory response is a potential treatment for ischemic stroke.

mTORC2 (Rictor) in Alzheimer's Disease and Reversal of Amyloid-β Expression-Induced Insulin Resistance and Toxicity in Rat Primary Cortical Neurons

Mammalian target of rapamycin complex 1 (mTORC1), a nutrient sensor and central controller of cell growth and proliferation, is altered in various models of Alzheimer's disease (AD). Even less studied or understood in AD is mammalian target of rapamycin complex 2 (mTORC2) that influences cellular metabolism, in part through the regulations of Akt/PKB and SGK. Dysregulation of insulin/PI3K/Akt signaling is another important feature of AD pathogenesis. We found that both total mTORC1 and C2 protein levels and individual C1 and C2 enzymatic activities were decreased in human AD brain samples. In two rodent AD models, mTORC1 and C2 activities were also decreased. In a neuronal culture model of AD characterized by accumulation of cellular amyloid-β (Aβ)42, mTORC1 activity was reduced. Autophagic vesicles and markers were correspondingly increased and new protein synthesis was inhibited, consistent with mTORC1 hypofunction. Interestingly, mTORC2 activity in neural culture seemed resistant to the effects of intracellular amyloid. In various cell lines, Aβ expression provoked insulin resistance, characterized by inhibition of stimulated Akt phosphorylation, and an increase in negative mTORC1 regular, p-AMPK, itself a nutrient sensor. Rapamycin decreased phospho-mTOR and to lesser degree p-Rictor. This further suppression of mTORC1 activity protected cells from Aβ-induced toxicity and insulin resistance. More striking, Rictor over-expression fully reversed the Aβ-effects on primary neuronal cultures. Finally, using in vitro assay, Rictor protein addition completely overcame oligomeric Aβ-induced inhibition of the PDK-Akt activation step. We conclude that striking a new balance by restoring mTORC2 abundance and/or inhibition of mTORC1 has therapeutic potential in AD.

Intraflagellar transporter protein 140 (IFT140), a component of IFT-A complex, is essential for male fertility and spermiogenesis in mice

Intraflagellar transport (IFT) is a conserved mechanism essential for the assembly and maintenance of most eukaryotic cilia and flagella. However, little is known about its role in sperm flagella formation and male fertility. IFT140 is a component of IFT-A complex. In mouse, it is highly expressed in the testis. Ift140 gene was inactivated specifically in mouse spermatocytes/spermatids. The mutant mice did not show any gross abnormalities, but all were infertile and associated with significantly reduced sperm number and motility. Multiple sperm morphological abnormalities were discovered, including amorphous heads, short/bent flagella and swollen tail tips, as well as vesicles along the flagella due to spermiogenesis defects. The epididymides contained round bodies of cytoplasm derived from the sloughing of the cytoplasmic lobes and residual bodies. Knockout of Ift140 did not significantly affect testicular expression levels of selective IFT components but localization of IFT27 and IFT88, two components of IFT-B complex, was changed. Our findings demonstrate that IFT140 is a key regulator for male fertility and normal spermiogenesis in mice. It not only plays a role in sperm flagella assembling, but is also involved in critical assembly of proteins that interface between the germ cell plasma and the Sertoli cell.

Inhibition of autophagy modulates astaxanthin and total fatty acid biosynthesis in Chlorella zofingiensis under nitrogen starvation

The present study showed that inhibition of autophagy significantly increased cellular levels of reactive oxygen species in Chlorella zofingiensis under nitrogen starvation. This was accompanied with increased expression of PSY, and enhanced accumulation of astaxanthin after 48h of cultivation. Nevertheless, the proportion of astaxanthin in secondary carotenoids remained unchanged. Meanwhile, the expression level of ACCase was also elevated in the 3-MA-treated cells compared to the control despite a >20% lower content of fatty acid in the former than the latter. This phenomenon might be due to inhibition of recycling of cellular components by 3-MA and suggests the potential involvement of post-transcriptional regulation in fatty acid biosynthesis. In summary, our work has been the first to report a potentially important role of autophagy in fatty acid and astaxanthin accumulation in C. zofingiensis under stress conditions. The findings might provide valuable insights to guide further research in this area.

ATD: a comprehensive bioinformatics resource for deciphering the association of autophagy and diseases

Autophagy is the natural, regulated, destructive mechanism of the eukaryotes cell that disassembles unnecessary or dysfunctional components. In recent years, the association between autophagy and diseases has attracted more and more attention, but our understanding of the molecular mechanism about the association in the system perspective is limited and ambiguous. Hence, we developed the comprehensive bioinformatics resource Autophagy To Disease (ATD, http://auto2disease.nwsuaflmz.com) to archive autophagy-associated diseases. This resource provides bioinformatics annotation system about genes and chemicals about autophagy and human diseases by extracting results from previous studies with text mining technology. Based on the big data from ATD, we found that some classes of disease tend to be related with autophagy, including respiratory disease, cancer, urogenital disease and digestive system disease. We also found that some classes of autophagy-related diseases have a strong association among each other and constitute modules. Furthermore, we extracted the autophagy-disease-related genes (ADGs) from ATD and provided a novel algorithm Optimized Random Forest with Label model to predict potential ADGs. This bioinformatics annotation system about autophagy and human diseases may provide a basic resource for the further detection of the molecular mechanisms of autophagy pathway to disease.

Proteomic investigation of effects of hydroxysafflor yellow A in oxidized low-density lipoprotein-induced endothelial injury

Oxidized low-density lipoprotein (ox-LDL)-induced vascular endothelial damage is a key event in early atherosclerosis. Safflower has been used to treat atherosclerotic heart disease in China for many years, but its molecular basis remains unclear. Hydroxysafflor yellow A (HSYA) is the main active ingredient of aqueous safflower extract. We identified the proteins involved in HSYA activity against ox-LDL-induced endothelial injury using isobaric tags for relative and absolute quantification-coupled two-dimensional liquid chromatography–tandem mass spectrometry. HSYA (1, 5, or 25 μM) alleviated ox-LDL-induced endothelial damage in a dose-dependent manner. We quantitated approximately 2700 protein species, of which 77 were differentially expressed following HSYA treatment. Most protein changes were related to structural molecules, metabolic enzymes, and proteins involved in signal transduction. Several differentially expressed proteins were further validated by western blot analysis. We also analysed the role of the mitochondrial membranous voltage-dependent anion-selective channel protein 2 (VDAC2) in HSYA treatment using small interfering RNA. VDAC2 functioned as a downstream anti-apoptosis effector during HSYA treatment of ox-LDL-induced endothelial impairment. These results further our understanding of the mechanisms responsible for the effects of HSYA.

Autophagy in osteoarthritis

Osteoarthritis is characterized by continuous degeneration of articular cartilage resulting in disability. The death of chondrocytes and the loss of the extracellular matrix are the central peculiarities in cartilage degeneration during osteoarthritis pathogenesis. Autophagy is an essential cellular homeostasis mechanism whereby cellular organelles and macromolecules are recycled to maintain cellular metabolism. Autophagy is reported to be cytoprotective effects for articular cartilage, and osteoarthritis is associated with decreased autophagy. While autophagy is known to be cytoprotective to chondrocytes, its role may vary with differing stages and models of osteoarthritis. Therefore, more in-depth studies on autophagy are needed to determine its impact on cell survival and death in articular cartilage under various in vitro and in vivo conditions. Application of autophagy on osteoarthritis therapeutics will be possible after a profound understanding is established on the role of autophagy in osteoarthritis pathogenesis.

Autophagy, its mechanisms and regulation: Implications in neurodegenerative diseases

Autophagy is a major regulatory cellular mechanism which gives the cell an ability to cope with some of the destructive events that normally occur within a metabolically living cell. This is done by maintaining the cellular homeostasis, clearance of damaged organelles and proteins and recycling necessary molecules like amino acids and fatty acids. There is a wide array of factors that influence autophagy in the state of health and disease. Disruption of these mechanisms may not only give rise to several autophagy-related disease, but also it can occur as the result of intracellular changes induced during disease pathogenesis causing exacerbation of the disease. Our knowledge is increasing regarding the role of autophagy and its mechanisms in the pathogenesis of various neurodegenerative diseases such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, Huntington's disease and Amyotrophic lateral sclerosis. Indeed, getting to know about the pathways of autophagy and its regulation can provide the basis for designing therapeutic interventions. In the present paper, we review the pathways of autophagy, its regulation and the possible autophagy-targeting interventions for the treatment of neurodegenerative disorders.

Silver nanoparticles induce lysosomal-autophagic defects and decreased expression of transcription factor EB in A549 human lung adenocarcinoma cells

Although silver nanoparticles (AgNPs) are widely used in consumer and medical products, the mechanism by which AgNPs cause pulmonary damage is unclear. AgNPs are incorporated into cells and processed via the autophagy pathway. We examined the effects of AgNP exposure on autophagic flux and expression of transcription factor EB (TFEB) in A549 lung adenocarcinoma cells. In cells exposed to citrate-coated 60-nm AgNPs, confocal laser microscopic examination showed a decrease in the LysoTracker fluorescence signal and an increase in that of Cyto-ID, indicating lysosomal pH alkalization and autophagosome formation, respectively. The proteins p62 and microtubule-associated protein light chain 3B-II (LC3B-II) are both degraded by autophagy, and their levels increased depending on AgNP dose. Furthermore, AgNP-induced increase in LC3B-II was not enhanced by treatment with the autophagic inhibitor bafilomycin A1. TFEB mRNA levels, and protein levels in cytosolic and nuclear fractions, were suppressed by exposure to AgNPs, suggesting transcriptional inhibition of TFEB expression. Overexpression of TFEB did not suppress AgNP-induced LC3B-II accumulation and cellular damage, indicating that impairment of autophagic flux and cellular damage by AgNPs might not be primarily caused by reduced TFEB expression. The present study suggests that AgNP-induced lysosomal dysfunction plays a principal role in the autophagic flux defect.

Autophagy protects auditory hair cells against neomycin-induced damage

Aminoglycosides are toxic to sensory hair cells (HCs). Macroautophagy/autophagy is an essential and highly conserved self-digestion pathway that plays important roles in the maintenance of cellular function and viability under stress. However, the role of autophagy in aminoglycoside-induced HC injury is unknown. Here, we first found that autophagy activity was significantly increased, including enhanced autophagosome-lysosome fusion, in both cochlear HCs and HEI-OC-1 cells after neomycin or gentamicin injury, suggesting that autophagy might be correlated with aminoglycoside-induced cell death. We then used rapamycin, an autophagy activator, to increase the autophagy activity and found that the ROS levels, apoptosis, and cell death were significantly decreased after neomycin or gentamicin injury. In contrast, treatment with the autophagy inhibitor 3-methyladenine (3-MA) or knockdown of autophagy-related (ATG) proteins resulted in reduced autophagy activity and significantly increased ROS levels, apoptosis, and cell death after neomycin or gentamicin injury. Finally, after neomycin injury, the antioxidant N-acetylcysteine could successfully prevent the increased apoptosis and HC loss induced by 3-MA treatment or ATG knockdown, suggesting that autophagy protects against neomycin-induced HC damage by inhibiting oxidative stress. We also found that the dysfunctional mitochondria were not eliminated by selective autophagy (mitophagy) in HEI-OC-1 cells after neomycin treatment, suggesting that autophagy might not directly target the damaged mitochondria for degradation. This study demonstrates that moderate ROS levels can promote autophagy to recycle damaged cellular constituents and maintain cellular homeostasis, while the induction of autophagy can inhibit apoptosis and protect the HCs by suppressing ROS accumulation after aminoglycoside injury.

A fully coupled space-time multiscale modeling framework for predicting tumor growth

Most biological systems encountered in living organisms involve highly complex heterogeneous multi-component structures that exhibit different physical, chemical, and biological behavior at different spatial and temporal scales. The development of predictive mathematical and computational models of multiscale events in such systems is a major challenge in contemporary computational biomechanics, particularly the development of models of growing tumors in humans. The aim of this study is to develop a general framework for tumor growth prediction by considering major biological events at tissue, cellular, and subcellular scales. The key to developing such multiscale models is how to bridge spatial and temporal scales that range from 10^-3 to 10³ mm in space and from 10^-6 to 10⁷ s in time. In this paper, a fully coupled space-time multiscale framework for modeling tumor growth is developed. The framework consists of a tissue scale model, a model of cellular activities, and a subcellular transduction signaling pathway model. The tissue, cellular, and subcellular models in this framework are solved using partial differential equations for tissue growth, agent-based model for cellular events, and ordinary differential equations for signaling transduction pathway as a network at subcellular scale. The model is calibrated using experimental observations. Moreover, this model is biologically-driven from a signaling pathway, volumetrically-consistent between cellular and tissue scale in terms of tumor volume evolution in time, and a biophysically-sound tissue model that satisfies all conservation laws. The results show that the model is capable of predicting major characteristics of tumor growth such as the morphological instability, growth patterns of different cell phenotypes, compact regions of the higher cell density at the tumor region, and the reduction of growth rate due to drug delivery. The predicted treatment outcomes show a reduction in proliferation at different rates in response to different drug dosages. Moreover, the results of several 3D applications to tumor growth and the evolution of cellular and subcellular events are presented.

Mechanisms of Tanshinone II a inhibits malignant melanoma development through blocking autophagy signal transduction in A375 cell

Background

Malignant melanoma (MM) is one of the high degree of malignancy and early prone to blood and lymph node metastasis. There is not cured for MM. Tan II A has been reported to reduce cancer cell proliferation. But the mechanism by which Tan II A inhibited melanoma growth are not well characterized. We sought to explore the possible mechanism by which Tan II A regulated cell proliferation through autophagy signaling pathway in A375 cells.

Methods

We tested the effects of Tan II A on melanoma A375, MV3, M14, and other human cell lines including Hacat and HUVEC cells in cell culture model. Cell proliferation was assessed by using methyl thiazol tetrazolium (MTT) assay. Cell migration ability melanoma A375 was monitored by using cell scratch assay. Transwell chamber experimental was performed to assess the effect of Tan II A on A375 melanoma cell invasion ability. The autophagy body was examined by using flow cytometry. The expression of autophagy-associated protein beclin-1 and microtubule-associated protein 1 light chain 3(LC3)-II, as well as phosphatidylinositol 3-kinase(PI3K)、protein kinase B (Akt)、mammalian target of rapamycin (mTOR)、p70S6K1 signaling pathways were detected by using Western blotting. The effects of Tan II A on tumor progression was also examined in melanoma A375 induced tumor in mouse model.

Results

We found that Tan IIA inhibited melanoma A375, MV3, and M14 cell proliferation in dose and time dependent manner. Tan II A reduced CXCL12-induced A375 cell invasive ability and migration in a dose dependent manner. Tan IIA promoted autophagic body production and increased autophagy-associated protein beclin-1 and LC3-II expression in A375 cells. However, Tan IIA reduced the phosphorylation of PI3K, P-AKT, P-mTOR, and P-p7036k1. We also confirmed that Tan II A reduced melanoma A375 induced tumor volume and weight in mouse model.

Conclusions

We concluded that Tan II A reduced A375 cells proliferation by activation of autophagy production, blocked PI3K- Akt – mTOR - p70S6K1 signaling pathway, increased autophagic related gene beclin-1, LC3-II protein expressions and induced autophagocytosis. Tan II A inhibited melanoma A375 induced tumor development in mouse model.

UCP2 attenuates apoptosis of tubular epithelial cells in renal ischemia-reperfusion injury

Uncoupling protein-2 (UCP2) plays critical roles in energy metabolism and cell survival. Previous investigations showed that UCP2 regulated the production of extracellular matrix and renal fibrosis. However, little is known about UCP2 in acute kidney injury (AKI). Here, we used Ucp2 knockout mice to investigate the role of UCP2 in an AKI model generated by renal ischemia-reperfusion (I/R) injury. The Ucp2 global knockout mice were born and grew normally without kidney histological abnormality or renal dysfunction. Compared with littermates, deletion of Ucp2 exacerbated I/R-induced AKI whereas increase of UCP2 by conjugated linoleic acid (CLA) attenuated I/R injury. Tubular cell apoptosis and autophagy were induced by I/R. After injury, more tubular cell apoptosis and less autophagy were identified in the kidneys of knockout mice compared with their littermates, and less apoptosis and more autophagy were observed in mice fed with CLA. In vitro rotenone, an inhibitor of electron transport chain complex I, was applied to induce energy depletion in cultured tubular epithelial cells. As expected, rotenone-recovery (R/R) treatment induced tubular cell apoptosis and autophagy. UCP2 plasmid transfection reduced cell apoptosis and facilitated autophagy after R/R treatment, whereas UCP2 small interfering RNA (siRNA) transfection sensitized cell apoptosis but reduced autophagy induced by R/R treatment. Interference of autophagy by treatment with autophagy inhibitor 3-methyladenine or autophagy initiation protein Beclin-1 siRNA transfection resulted in tubular cell apoptosis. Thus UCP2 attenuates I/R-induced AKI, probably by reducing cell apoptosis through protection of autophagy.

Pyrethrum-extract induced autophagy in insect cells: A new target?

Pyrethrum extract (PY) is a natural insecticide that is extensively used across the world, and its insecticidal activity is attributed to the presence of six active esters known as pyrethrins. PY targets the nervous systems of insects by delaying the closure of voltage-gated sodium ion channels in the nerve cells. However, limited information is available regarding the toxicity and detailed mechanisms of PY activity. This study is aimed at understanding the toxicity effect and the underlying mechanisms of PY in cellular level, which have not yet been investigated on the non-nervous system of insects. Results of the MTT assay showed that the viability of Sf9 cells was inhibited by PY in a time- and concentration-dependent manner, and observation under a microscope revealed accumulation of intracellular vacuoles. Monodansylcadaverine staining analysis and transmission electron microscope images revealed typical autophagic morphological changes in PY-treated Sf9 cells. Autophagy-related proteins such as LC3, p62, and beclin-1 were detected using by Western blotting. Protein expression levels of LC3-II and beclin-1 were upregulated while that of p62 was markedly downregulated in a dose-dependent manner upon the PY treatment in Sf9 cells. In conclusion, these results indicate that PY could induce autophagy in the non-nervous system of insects which may contribute to its insecticidal mechanism.

PPAR-γ Agonists As Antineoplastic Agents in Cancers with Dysregulated IGF Axis

It is now widely accepted that insulin resistance and compensatory hyperinsulinemia are associated to increased cancer incidence and mortality. Moreover, cancer development and progression as well as cancer resistance to traditional anticancer therapies are often linked to a deregulation/overactivation of the insulin-like growth factor (IGF) axis, which involves the autocrine/paracrine production of IGFs (IGF-I and IGF-II) and overexpression of their cognate receptors [IGF-I receptor, IGF-insulin receptor (IR), and IR]. Recently, new drugs targeting various IGF axis components have been developed. However, these drugs have several limitations including the occurrence of insulin resistance and compensatory hyperinsulinemia, which, in turn, may affect cancer cell growth and survival. Therefore, new therapeutic approaches are needed. In this regard, the pleiotropic effects of peroxisome proliferator activated receptor (PPAR)-γ agonists may have promising applications in cancer prevention and therapy. Indeed, activation of PPAR-γ by thiazolidinediones (TZDs) or other agonists may inhibit cell growth and proliferation by lowering circulating insulin and affecting key pathways of the Insulin/IGF axis, such as PI3K/mTOR, MAPK, and GSK3-β/Wnt/β-catenin cascades, which regulate cancer cell survival, cell reprogramming, and differentiation. In light of these evidences, TZDs and other PPAR-γ agonists may be exploited as potential preventive and therapeutic agents in tumors addicted to the activation of IGF axis or occurring in hyperinsulinemic patients. Unfortunately, clinical trials using PPAR-γ agonists as antineoplastic agents have reached conflicting results, possibly because they have not selected tumors with overactivated insulin/IGF-I axis or occurring in hyperinsulinemic patients. In conclusion, the use of PPAR-γ agonists in combined therapies of IGF-driven malignancies looks promising but requires future developments.

Tazarotene-Induced Gene 1 Enhanced Cervical Cell Autophagy through Transmembrane Protein 192

Tazarotene-induced gene 1 (TIG1) is a retinoic acid-inducible protein that is considered a putative tumor suppressor. The expression of TIG1 is decreased in malignant prostate carcinoma or poorly differentiated colorectal adenocarcinoma, but TIG1 is present in benign or well-differentiated tumors. Ectopic TIG1 expression led to suppression of growth in cancer cells. However, the function of TIG1 in cell differentiation is still unknown. Using a yeast two-hybrid system, we found that transmembrane protein 192 (TMEM192) interacted with TIG1. We also found that both TIG1A and TIG1B isoforms interacted and co-localized with TMEM192 in HtTA cervical cancer cells. The expression of TIG1 induced the expression of autophagy-related proteins, including Beclin-1 and LC-3B. The silencing of TMEM192 reduced the TIG1-mediated upregulation of autophagic activity. Furthermore, silencing of either TIG1 or TMEM192 led to alleviation of the upregulation of autophagy induced by all-trans retinoic acid. Our results demonstrate that the expression of TIG1 leads to cell autophagy through TMEM192. Our study also suggests that TIG1 and TMEM192 play an important role in the all-trans retinoic acid-mediated upregulation of autophagic activity.

FK506, an Immunosuppressive Drug, Induces Autophagy by Binding to the V-ATPase Catalytic Subunit A in Neuronal Cells

The drug FK506 (tacrolimus, fujimycin) exerts its immunosuppressive effects by regulating the nuclear factor of the activated T-cell (NFAT) family of transcription factors. However, FK506 also exhibits neuroprotective effects, but its direct target proteins that mediate these effects have not been determined. To identify the target proteins responsible for FK506's neuroprotective effects, the drug affinity responsive target stability (DARTS) method was performed using label-free FK506, and LC-MS/MS analysis of the FK506-treated proteome was also performed. Using DARTS and LC-MS/MS analyses in combination with reference studies, V-ATPase catalytic subunit A (ATP6V1A) was identified as a new target protein of FK506. The biological relevance of ATP6V1A in mediating the neuroprotective effects of FK506 was validated by analyzing FK506 activity with respect to autophagy via acridine orange staining and transcription factor EB (TFEB) translocation assay. These analyses demonstrated that the binding of FK506 with ATP6V1A induces autophagy by activating the translocation of TFEB from the cytosol into the nucleus. Because autophagy has been identified as a mechanism for treating neurodegenerative diseases and because we have demonstrated that FK506 induces autophagy, this study demonstrates that FK506 is a possible new therapy for treating neurodegenerative diseases.

Production of Human ATG Proteins for Lipidation Assays

Humans express several orthologs of yeast Atg8, in the LC3 and GABARAP families, which play crucial roles in autophagy through their covalent ligation to lipids, typically phosphatidylethanolamine (PE), in a process known as lipidation. Lipidation of LC3 and GABARAP regulates numerous facets of the autophagy process, including regulating expansion of the phagophore membrane, recruiting selected cargoes for degradation, and providing an autophagosome membrane-bound platform mediating dynamic interactions with other regulatory proteins. LC3 and GABARAP are families of related ubiquitin-like proteins (UBLs) (referred to here collectively as LC3/GABARAP), and their lipidation involves a divergent UBL conjugation cascade including ATG7, ATG3, and ATG12~ATG5-ATG16L1 acting as E1, E2, and E3 enzymes, respectively. ATG7 initiates LC3/GABARAP conjugation by catalyzing their C-terminal adenylation and conjugation to the catalytic cysteine of ATG3. Ultimately, the ATG12~ATG5-ATG16L1 complex catalyzes LC3/GABARAP ligation to a primary amino group on PE or other acceptor lipids. This chapter describes methods for expressing and purifying human LC3 or GABARAP, ATG7, ATG3, and the ATG12~ATG5-ATG16L1 complex for in vitro studies of LC3/GABARAP lipidation.

Whole-Organism Transcriptomic Analysis Provides Mechanistic Insight into the Acute Toxicity of Emamectin Benzoate in Daphnia magna

Emamectin benzoate (EMB) is an antisea lice chemical widely used in the aquaculture that may also unintentionally affect nontarget crustaceans in the environment. Although the adverse effects of this compound are well documented in various species, the full modes of action (MoAs) are still not well characterized. The current study was therefore conducted to characterize the MoAs of EMB and link perturbations of key toxicological pathways to adverse effects in the model freshwater crustacean Daphnia magna. Effects on molting and survival were determined after 48 h exposure to EMB, whereas global transcriptional changes and the ecdysone receptor (EcR) binding potency was determined to characterize the MoA. The results showed that the molting frequency and survival of D. magna decreased in a concentration-dependent manner, and the observed changes could not be attributed to direct interactions with the EcR. Major MoAs such as activation of glutamate-gated chloride channels and gamma-aminobutyric acid signaling, disruption of neuroendocrine regulation of molting, perturbation of energy homeostasis, suppression of DNA repair and induction of programmed cell death were observed by transcriptional analysis and successfully linked to the adverse effects. This study has demonstrated that acute exposure to intermediate and high pM levels of EMB may pose hazards to nontarget crustaceans in the aquatic environment.

Intraflagellar transport protein IFT20 is essential for male fertility and spermiogenesis in mice

Intraflagellar transport (IFT) is a conserved mechanism thought to be essential for the assembly and maintenance of cilia and flagella. However, little is known about its role in mammalian sperm flagella formation. To fill this gap, we disrupted the Ift20 gene in male germ cells. Homozygous mutant mice were infertile with significantly reduced sperm counts and motility. In addition, abnormally shaped elongating spermatid heads and bulbous round spermatids were found in the lumen of the seminiferous tubules. Electron microscopy revealed increased cytoplasmic vesicles, fiber-like structures, abnormal accumulation of mitochondria and a decrease in mature lysosomes. The few developed sperm had disrupted axonemes and some retained cytoplasmic lobe components on the flagella. ODF2 and SPAG16L, two sperm flagella proteins failed to be incorporated into sperm tails of the mutant mice, and in the germ cells, both were assembled into complexes with lighter density in the absence of IFT20. Disrupting IFT20 did not significantly change expression levels of IFT88, a component of IFT-B complex, and IFT140, a component of IFT-A complex. Even though the expression level of an autophagy core protein that associates with IFT20, ATG16, was reduced in the testis of the Ift20 mutant mice, expression levels of other major autophagy markers, including LC3 and ubiquitin were not changed. Our studies suggest that IFT20 is essential for male fertility and spermiogenesis in mice, and its major function is to transport cargo proteins for sperm flagella formation. It also appears to be involved in removing excess cytoplasmic components.

Discovery of Fluoromethylketone-Based Peptidomimetics as Covalent ATG4B (Autophagin-1) Inhibitors

ATG4B or autophagin-1 is a cysteine protease that cleaves ATG8 family proteins. ATG4B plays essential roles in the autophagosome formation and the autophagy pathway. Herein we disclose the design and structural modifications of a series of fluoromethylketone (FMK)-based peptidomimetics as highly potent ATG4B inhibitors. Their structure-activity relationship (SAR) and protease selectivity are also discussed.

Polymorphisms in ERAP1 and ERAP2 are shared by Caninae and segregate within and between random- and pure-breeds of dogs

Specific polymorphisms in the endoplasmic reticulum amino peptidase genes ERAP1 and ERAP2, when present with certain MHC class receptor types, have been associated with increased risk for specific cancers, infectious diseases and autoimmune disorders in humans. This increased risk has been linked to distinct polymorphisms in both ERAPs and MHC class I receptors that affect the way cell-generated peptides are screened for antigenicity. The incidence of cancer, infectious disease and autoimmune disorders differ greatly among pure breeds of dogs as it does in humans and it is possible that this heightened susceptibility is also due to specific polymorphisms in ERAP1 and ERAP2. In order to determine if such polymorphisms exist, the ERAP1 and ERAP2 genes of 10 dogs of nine diverse breeds were sequenced and SNPs causing synonymous or non-synonymous amino acid changes, deletions or insertions were identified. Eight ERAP1 and 10 ERAP2 SNPs were used to create a Sequenom MassARRAY iPLEX based test panel which defined 24 ERAP1, 36 ERAP2 and 128 ERAP1/2 haplotypes. The prevalence of these haplotypes was then measured among dog, wolf, coyote, jackal and red fox populations. Some haplotypes were species specific, while others were shared across species, especially between dog, wolf, coyote and jackal. The prevalence of these haplotypes was then compared among various canid populations, and in particular between various populations of random- and pure-bred dogs. Human-directed positive selection has led to loss of ERAP diversity and segregation of certain haplotypes among various dog breeds. A phylogenetic tree generated from 45 of the most common ERAP1/2 haplotypes demonstrated three distinct clades, all of which were rooted with haplotypes either shared among species or specific to contemporary dogs, coyote and wolf.

Enhanced mitochondrial glutamine anaplerosis suppresses pancreatic cancer growth through autophagy inhibition

Cancer cells use precursors derived from tricarboxylic acid (TCA) cycle to support their unlimited growth. However, continuous export of TCA cycle intermediates results in the defect of mitochondrial integrity. Mitochondria glutamine metabolism plays an essential role for the maintenance of mitochondrial functions and its biosynthetic roles by refilling the mitochondrial carbon pool. Here we report that human pancreatic ductal adenocarcinoma (PDAC) cells have a distinct dependence on mitochondrial glutamine metabolism. Whereas glutamine flux into mitochondria contributes to proliferation of most cancer cells, enhanced glutamine anaplerosis results in a pronounced suppression of PDAC growth. A cell membrane permeable α-ketoglutarate analog or overexpression of glutamate dehydrogenase lead to decreased proliferation and increased apoptotic cell death in PDAC cells but not other cancer cells. We found that enhanced glutamine anaplerosis inhibits autophagy, required for tumorigenic growth of PDAC, by activating mammalian TORC1. Together, our results reveal that glutamine anaplerosis is a crucial regulator of growth and survival of PDAC cells, which may provide novel therapeutic approaches to treat these cancers.

Insights into APC/C: from cellular function to diseases and therapeutics

Anaphase-promoting complex/cyclosome (APC/C) is a multifunctional ubiquitin-protein ligase that targets different substrates for ubiquitylation and therefore regulates a variety of cellular processes such as cell division, differentiation, genome stability, energy metabolism, cell death, autophagy as well as carcinogenesis. Activity of APC/C is principally governed by two WD-40 domain proteins, Cdc20 and Cdh1, in and beyond cell cycle. In the past decade, the results based on numerous biochemical, 3D structural, mouse genetic and small molecule inhibitor studies have largely attracted our attention into the emerging role of APC/C and its regulation in biological function, human diseases and potential therapeutics. This review will aim to summarize some recently reported insights into APC/C in regulating cellular function, connection of its dysfunction with human diseases and its implication of therapeutics.

Finding Ponce de Leon's Pill: Challenges in Screening for Anti-Aging Molecules

Aging is characterized by the progressive accumulation of degenerative changes, culminating in impaired function and increased probability of death. It is the major risk factor for many human pathologies - including cancer, type 2 diabetes, and cardiovascular and neurodegenerative diseases - and consequently exerts an enormous social and economic toll. The major goal of aging research is to develop interventions that can delay the onset of multiple age-related diseases and prolong healthy lifespan (healthspan). The observation that enhanced longevity and health can be achieved in model organisms by dietary restriction or simple genetic manipulations has prompted the hunt for chemical compounds that can increase lifespan. Most of the pathways that modulate the rate of aging in mammals have homologs in yeast, flies, and worms, suggesting that initial screening to identify such pharmacological interventions may be possible using invertebrate models. In recent years, several compounds have been identified that can extend lifespan in invertebrates, and even in rodents. Here, we summarize the strategies employed, and the progress made, in identifying compounds capable of extending lifespan in organisms ranging from invertebrates to mice and discuss the formidable challenges in translating this work to human therapies.

Rap2B GTPase: structure, functions, and regulation

Rap2B GTPase, a member of Ras-related protein superfamily, was first discovered from a platelet cDNA library in the early 1990s. Since then, it has been reported to play an important role in regulating cellular processes including cytoskeletal organization, cell growth, and proliferation. It can be stimulated and suppressed by a wide range of external and internal inducers, circulating between GTP-bound active state and GDP-bound inactive state. Increasing focus on Ras signaling pathway reveals critical effects of Rap2B on tumorigenesis. In particular, Rap2B behaves in a p53-dependent manner in regulation of apoptosis and migration. Apart from being an oncogenic activator, Rap2B has been found to participate in many other physiological events via diverse downstream effectors. In this review, we present recent studies on the structure, regulation, and multiple biological functions of Rap2B, shedding light on its potential status in treatment of cancer as well as other diseases.

Salmonella plasmid virulence gene spvB enhances bacterial virulence by inhibiting autophagy in a zebrafish infection model

Salmonella enterica serovar typhimurium (S. typhimurium) is a facultative intracellular pathogen that can cause gastroenteritis and systemic infection in a wide range of hosts. Salmonella plasmid virulence gene spvB is closely related to bacterial virulence in different cells and animal models, and the encoded protein acts as an intracellular toxin required for ADP-ribosyl transferase activity. However, until now there is no report about the pathogenecity of spvB gene on zebrafish. Due to the outstanding advantages of zebrafish in analyzing bacteria-host interactions, a S. typhimurium infected zebrafish model was set up here to study the effect of spvB on autophagy and intestinal pathogenesis in vivo. We found that spvB gene could decrease the LD50 of S. typhimurium, and the strain carrying spvB promoted bacterial proliferation and aggravated the intestinal damage manifested by the narrowed intestines, fallen microvilli, blurred epithelium cell structure and infiltration of inflammatory cells. Results demonstrated the enhanced virulence induced by spvB in zebrafish. In spvB-mutant strain infected zebrafish, the levels of Lc3 turnover and Beclin1 expression increased, and the double-membraned autophagosome structures were observed, suggesting that spvB can inhibit autophagy activity. In summary, our results indicate that S. typhimurium strain containing spvB displays more virulence, triggering an increase in bacterial survival and intestine injuries by suppressing autophagy for the first time. This model provides novel insights into the role of Salmonella plasmid virulence gene in bacterial pathogenesis, and can help to further elucidate the relationship between bacteria and host immune response.

Reactive oxygen species-initiated autophagy opposes aldosterone-induced podocyte injury

Evidence has demonstrated that aldosterone (Aldo) is involved in the development and progression of chronic kidney diseases. The purpose of the present study was to investigate the role of autophagy in Aldo-induced podocyte damage and the underlying mechanism. Mouse podocytes were treated with Aldo in the presence or absence of 3-methyladenine and N-acetylcysteine. Cell apoptosis was investigated by detecting annexin V conjugates, apoptotic bodies, caspase-3 activity, and alterations of the podocyte protein nephrin. Autophagy was evaluated by measuring the expressions of light chain 3, p62, beclin-1, and autophagy-related gene 5. Aldo (10^-7 mol/l) induced podocyte apoptosis, autophagy, and downregulation of nephrin protein in a time-dependent manner. Aldo-induced apoptosis was further promoted by the inhibition of autophagy via 3-methyladenine and autophagy-related gene 5 small interfering RNA pretreatment. Moreover, Aldo time dependently increased ROS generation, and H₂O₂ (10^-4 mol/l) application remarkably elevated podocyte autophagy. After treatment with N-acetylcysteine, the autophagy induced by Aldo or H₂O₂ was markedly attenuated, suggesting a key role of ROS in mediating autophagy formation in podocytes. Inhibition of ROS could also lessen Aldo-induced podocyte injury. Taken together, our findings suggest that ROS-triggered autophagy played a protective role against Aldo-induced podocyte injury, and targeting autophagy in podocytes may represent a new therapeutic strategy for the treatment of podocytopathy.