Autophagy modulation as a potential therapeutic target for diverse diseases

Investigating the Role of Spermidine in a Model System of Alzheimer’s Disease Using Correlative Microscopy and Super-resolution Techniques

Background: Spermidine has recently received major attention for its potential therapeutic benefits in the context of neurodegeneration, cancer, and aging. However, it is unclear whether concentration dependencies of spermidine exist, to differentially enhance autophagic flux. Moreover, the relationship between low or high autophagy activity relative to basal neuronal autophagy flux and subsequent protein clearance as well as cellular toxicity has remained largely unclear.

Methods: Here, we used high-resolution imaging and biochemical techniques to investigate the effects of a low and of a high concentration of spermidine on autophagic flux, neuronal toxicity, and protein clearance in in vitro models of paraquat (PQ) induced neuronal toxicity and amyloid precursor protein (APP) overexpression, as well as in an in vivo model of PQ-induced rodent brain injury.

Results: Our results reveal that spermidine induces autophagic flux in a concentration-dependent manner, however the detectable change in the autophagy response critically depends on the specificity and sensitivity of the method employed. By using correlative imaging techniques through Super-Resolution Structured Illumination Microscopy (SR-SIM) and Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), we demonstrate that spermidine at a low concentration induces autophagosome formation capable of large volume clearance. In addition, we provide evidence of distinct, context-dependent protective roles of spermidine in models of Alzheimer’s disease. In an in vitro environment, a low concentration of spermidine protected against PQ-induced toxicity, while both low and high concentrations provided protection against cytotoxicity induced by APP overexpression. In the in vivo scenario, we demonstrate brain region-specific susceptibility to PQ-induced neuronal toxicity, with the hippocampus being highly susceptible compared to the cortex. Regardless of this, spermidine administered at both low and high dosages protected against paraquat-induced toxicity.

Conclusions: Taken together, our results demonstrate that firstly, administration of spermidine may present a favourable therapeutic strategy for the treatment of Alzheimer’s disease and secondly, that concentration and dosage-dependent precision autophagy flux screening may be more critical for optimal autophagy and cell death control than previously thought.

Infection Dynamics of ATG8 in Leishmania: Balancing Autophagy for Therapeutics

In many regions of the world, Leishmaniasis is a cause of substantial mortality and ailment. Due to impediment in available treatment, development of novel and effective treatments is indispensable. Significance of autophagy has been accentuated in infectious disease as well as in Leishmaniasis, and it is having capability to be manifested as a therapeutic target. By evincing autophagy as a novel therapeutic regime, this study emphasized on the critical role of ATG4.1-ATG8 and ATG5-ATG12 complexes in Leishmania species. The objective here was to identify ATG8 as a potential therapeutic target in Leishmania. R71T, P56E, R18P are the significant mutations which shows detrimental effect on ATG8 while Arg276, Arg73, Cys75 of ATG4.1 and Val88, Pro89, Glu116, Asn117, and Gly120 are interacting residues of ATG8. Along with this, we also bring into spotlight an enticing role of Thiabendazole derivatives that interferes with the survival mechanisms by targeting ATG8. Further, the study claims that thiabendazole can be a potential drug candidate to target autophagy process in the infectious disease Leishmaniasis.

Autophagy Modulation in Aggresome Formation: Emerging Implications and Treatments of Alzheimer's Disease

Alzheimer's disease (AD) is one of the most prevailing neurodegenerative diseases in the world, which is characterized by memory dysfunction and the formation of tau and amyloid β (Aβ) aggregates in multiple brain regions, including the hippocampus and cortex. The formation of senile plaques involving tau hyperphosphorylation, fibrillar Aβ, and neurofibrillary tangles (NFTs) is used as a pathological marker of AD and eventually produces aggregation or misfolded protein. Importantly, it has been found that the failure to degrade these aggregate-prone proteins leads to pathological consequences, such as synaptic impairment, cytotoxicity, neuronal atrophy, and memory deficits associated with AD. Recently, increasing evidence has suggested that the autophagy pathway plays a role as a central cellular protection system to prevent the toxicity induced by aggregation or misfolded proteins. Moreover, it has also been revealed that AD-related protein aggresomes could be selectively degraded by autophagosome and lysosomal fusion through the autophagy pathway, which is known as aggrephagy. Therefore, the regulation of autophagy serve as a useful approach to modulate the formation of aggresomes associated with AD. This review focuses on the recent improvements in the application of natural compounds and small molecules as a potential therapeutic approach for AD prevention and treatment via aggrephagy.

Enhancing autophagy in Alzheimer's disease through drug repositioning

Alzheimer's disease (AD) is one of the biggest human health threats due to increases in aging of the global population. Unfortunately, drugs for treating AD have been largely ineffective. Interestingly, downregulation of macroautophagy (autophagy) plays an essential role in AD pathogenesis. Therefore, targeting autophagy has drawn considerable attention as a therapeutic approach for the treatment of AD. However, developing new therapeutics is time-consuming and requires huge investments. One of the strategies currently under consideration for many diseases is "drug repositioning" or "drug repurposing". In this comprehensive review, we have provided an overview of the impact of autophagy on AD pathophysiology, reviewed the therapeutics that upregulate autophagy and are currently used in the treatment of other diseases, including cancers, and evaluated their repurposing as a possible treatment option for AD. In addition, we discussed the potential of applying nano-drug delivery to neurodegenerative diseases, such as AD, to overcome the challenge of crossing the blood brain barrier and specifically target molecules/pathways of interest with minimal side effects.

Incomplete autophagy: Trouble is a friend

Incomplete autophagy is an impaired self-eating process of intracellular macromolecules and organelles in which accumulated autophagosomes do not fuse with lysosomes for degradation, resulting in the blockage of autophagic flux. In this review, we summarized the literature over the past decade describing incomplete autophagy, and found that different from the double-edged sword effect of general autophagy on promoting cell survival or death, incomplete autophagy plays a crucial role in disrupting cellular homeostasis, and promotes only cell death. What matters is that incomplete autophagy is closely relevant to the pathogenesis and progression of various human diseases, which, meanwhile, intimately linking to the pharmacologic and toxicologic effects of several compounds. Here, we comprehensively reviewed the latest progress of incomplete autophagy on molecular mechanisms and signaling pathways. Moreover, implications of incomplete autophagy for pharmacotherapy are also discussed, which has great relevance for our understanding of the distinctive role of incomplete autophagy in cellular physiology and disease. Consequently, targeting incomplete autophagy may contribute to the development of novel generation therapeutic agents for diverse human diseases.

LncRNA small nucleolar RNA host gene 5 inhibits trophoblast autophagy in preeclampsia by targeting microRNA-31-5p and promoting the transcription of secreted protein acidic and rich in cysteine

Preeclampsia (PE) is a pregnancy-related complication. Dysregulation of long non-coding RNAs (lncRNAs) contributes to the pathogenesis of PE. The current study sought to investigate the effect of lncRNA small nucleolar RNA host gene 5 (SNHG5) on trophoblast autophagy in PE. A PE mouse model was established, followed by detection of parameters such as blood pressure, proteinuria, triglycerides, total cholesterol, low-density lipoprotein, and high-density lipoprotein, observation of alterations of mouse placenta and kidney, and detection of B-cell chronic lymphocytic leukemia/lymphoma-2, Bcl-2-associated X protein, and SNHG5 expression patterns. The expressions of LC3, Beclin-1, and p62 in the placenta of PE mice were detected. Moreover, the SNHG5 expression was downregulated in the established HTR-8/SVneo trophoblast model, followed by evaluation of cell proliferation, apoptosis, and autophagy. After combination treatment with 3-MA (an autophagy inhibitor) and si-SNHG5, the behaviors of HTR-8/SVneo cells were observed. The binding relations between SNHG5 and miR-31-5p, and miR-31-5p and SPARC were verified. The expressions of miR-31-5p and SPARC in the placenta of mice and trophoblasts were determined. Our results demonstrated a poor expression of lncRNA SNHG5 in PE mice. SNHG5 overexpression reduced the PE phenotype and tissue damage in mice. SNHG5 silencing reduced the proliferation, migration, and invasion of trophoblasts, but elevated apoptosis and autophagy. SNHG5 sponged miR-31-5p to promote SPARC transcription. Additionally, miR-31-5p knockdown or 3-MA treatment reverted the stimulative effect of SNHG5 silencing on trophoblast autophagy. Collectively, our study demonstrated that lncRNA SNHG5 alleviated the PE phenotype and inhibited trophoblast autophagy by sponging miR-31-5p and promoting SPARC transcription.

Autophagy Agents in Clinical Trials for Cancer Therapy: A Brief Review

Autophagy has been of novel interest since it was first demonstrated to have effect in Burkitt's lymphoma. Since that time, the autophagy agents chloroquine and hydroxychloroquine have become the only FDA (Food and Drug Administration)-approved autophagy inhibitors. While not approved for cancer therapy, there are ongoing clinical trials to evaluate their safety and efficacy. Pevonedistat has emerged as a novel inhibitor through the neddylation pathway and is an autophagy activator. This paper summarizes and presents current clinical trials for hydroxychloroquine (HCQ), chloroquine (CQ), and Pevonedistat for the clinician.

Towards targeting of shared mechanisms of cancer metastasis and therapy resistance

Resistance to therapeutic treatment and metastatic progression jointly determine a fatal outcome of cancer. Cancer metastasis and therapeutic resistance are traditionally studied as separate fields using non-overlapping strategies. However, emerging evidence, including from in vivo imaging and in vitro organotypic culture, now suggests that both programmes cooperate and reinforce each other in the invasion niche and persist upon metastatic evasion. As a consequence, cancer cell subpopulations exhibiting metastatic invasion undergo multistep reprogramming that - beyond migration signalling - supports repair programmes, anti-apoptosis processes, metabolic adaptation, stemness and survival. Shared metastasis and therapy resistance signalling are mediated by multiple mechanisms, such as engagement of integrins and other context receptors, cell-cell communication, stress responses and metabolic reprogramming, which cooperate with effects elicited by autocrine and paracrine chemokine and growth factor cues present in the activated tumour microenvironment. These signals empower metastatic cells to cope with therapeutic assault and survive. Identifying nodes shared in metastasis and therapy resistance signalling networks should offer new opportunities to improve anticancer therapy beyond current strategies, to eliminate both nodular lesions and cells in metastatic transit.

Mechanisms tailoring the expression of heat shock proteins to proteostasis challenges

All cells possess an internal stress response to cope with environmental and pathophysiological challenges. Upon stress, cells reprogram their molecular functions to activate a survival mechanism known as the heat shock response, which mediates the rapid induction of molecular chaperones such as the heat shock proteins (HSPs). This potent production overcomes the general suppression of gene expression and results in high levels of HSPs to subsequently refold or degrade misfolded proteins. Once the damage or stress is repaired or removed, cells terminate the production of HSPs and resume regular functions. Thus, fulfillment of the stress response requires swift and robust coordination between stress response activation and completion that is determined by the status of the cell. In recent years, single-cell fluorescence microscopy techniques have begun to be used in unravelling HSP-gene expression pathways, from DNA transcription to mRNA degradation. In this review, we will address the molecular mechanisms in different organisms and cell types that coordinate the expression of HSPs with signaling networks that act to reprogram gene transcription, mRNA translation, and decay and ensure protein quality control.

Autophagy in Virus Infection: A Race between Host Immune Response and Viral Antagonism

Virus-infected cells trigger a robust innate immune response and facilitate virus replication. Here, we review the role of autophagy in virus infection, focusing on both pro-viral and anti-viral host responses using a select group of viruses. Autophagy is a cellular degradation pathway operated at the basal level to maintain homeostasis and is induced by external stimuli for specific functions. The degradative function of autophagy is considered a cellular anti-viral immune response. However, autophagy is a double-edged sword in viral infection; viruses often benefit from it, and the infected cells can also use it to inhibit viral replication. In addition to viral regulation, autophagy pathway proteins also function in autophagy-independent manners to regulate immune responses. Since viruses have co-evolved with hosts, they have developed ways to evade the anti-viral autophagic responses of the cells. Some of these mechanisms are also covered in our review. Lastly, we conclude with the thought that autophagy can be targeted for therapeutic interventions against viral diseases.

Role of Bisphenol A in Autophagy Modulation: Understanding the Molecular Concepts and Therapeutic Options

Abstract:

Bisphenol A (4,4′-isopropylidenediphenol) is an organic compound, commonly used in the plastic bottles, packaging containers, beverages and resin industry. The adverse effects of bisphenol A were studied in various systems of the body. Autophagy is a lysosomal degradation process meant for the regeneration of new cells. The role of bisphenol A on autophagy modulation in the pathogenesis of diseases is still debatable. Few research studies showed that bisphenol A-induced adverse effects were associated with autophagy dysregulation, while few showed the activation of autophagy by bisphenol A. Such contrasting views make the subject more interesting and debatable. In the present review, we discuss the different steps of autophagy, genes involved, and the effect of bisphenol A in autophagy modulation on different systems of the body. We also discuss the methods for monitoring autophagy and the roles of drugs such as chloroquine, verteporfin, and rapamycin in autophagy. Proper understanding of the role of bisphenol A in the modulation of autophagy may be important for future treatment and drug discovery.

Current Status of Autophagy Enhancers in Metabolic Disorders and Other Diseases

Autophagy is pivotal in the maintenance of organelle function and intracellular nutrient balance. Besides the role of autophagy in the homeostasis and physiology of the individual tissues and whole organism in vivo, dysregulated autophagy has been incriminated in the pathogenesis of a variety of diseases including metabolic diseases, neurodegenerative diseases, cardiovascular diseases, inflammatory or immunological disorders, cancer and aging. Search for autophagy modulators has been widely conducted to amend dysregulation of autophagy or pharmacologically modulate autophagy in those diseases. Current data support the view that autophagy modulation could be a new modality for treatment of metabolic syndrome associated with lipid overload, human-type diabetes characterized by deposition of islet amyloid or other diseases including neurodegenerative diseases, infection and cardiovascular diseases. While clinically available bona fide autophagy modulators have not been developed yet, it is expected that on-going investigation will lead to the development of authentic autophagy modulators that can be safely administered to patients in the near future and will open a new horizon for treatment of incurable or difficult diseases.

The Role of Decorin Proteoglycan in Mitophagy

Proteoglycans are emerging as critical regulators of intracellular catabolism. This rise in prominence has transformed our basic understanding and alerted us to the existence of non-canonical pathways, independent of nutrient deprivation, that potently control the autophagy downstream of a cell surface receptor. As a member of the small leucine-rich proteoglycan gene family, decorin has single-handedly pioneered the connection between extracellular matrix signaling and autophagy regulation. Soluble decorin evokes protracted endothelial cell autophagy via Peg3 and breast carcinoma cell mitophagy via mitostatin by interacting with VEGFR2 or the MET receptor tyrosine kinase, respectively. In this paper, we give a mechanistic perspective of the vital factors underlying the nutrient-independent, SLRP-dependent programs utilized for autophagic and/or mitophagic progression in breast cancer. Future protein therapies based on decorin (or fellow proteoglycan members) will represent a quantum leap forward in transforming autophagic progression into a powerful tool to control intracellular cell catabolism from the outside.

Plasmodium Circumsporozoite Protein Enhances the Efficacy of Gefitinib in Lung Adenocarcinoma Cells by Inhibiting Autophagy via Proteasomal Degradation of LC3B

Background: Almost all lung adenocarcinoma (LUAD) patients with EGFR mutant will develop resistance to EGFR-TKIs, which limit the long-term clinical application of these agents. Accumulating evidence shows one of the main reasons for resistance to EGFR-TKIs is induction of autophagy in tumor cells. Our previous study found that circumsporozoite protein (CSP) in Plasmodium can suppress autophagy in host hepatocytes. However, it is unknown whether CSP-mediated inhibition of autophagy could improve the anti-tumor effect of EGFR-TKIs. Methods: We constructed A549 and H1975 cell lines with stable overexpression of CSP (OE-CSP cells). CCK-8, Lactate Dehydrogenase (LDH), flow cytometry, and colony analysis were performed to observe the effect of CSP overexpression on cell viability, apoptosis rate, and colony formation ratio. The sensitizing effect of CSP on gefitinib was evaluated in vivo using a subcutaneous tumor model in nude mice and immunohistochemical assay. The role of CSP in regulation of autophagy was investigated by laser confocal microscopy assay and western blotting. A transcriptome sequencing assay and real-time polymerase chain reaction were used to determine the levels of mRNA for autophagy-related proteins. Cycloheximide (CHX), MG132, TAK-243, and immunoprecipitation assays were used to detect and confirm proteasomal degradation of LC3B. Results: OE-CSP A549 and H1975 cells were more sensitive to gefitinib, demonstrating significant amounts of apoptosis and decreased viability. In the OE-CSP group, autophagy was significantly inhibited, and there was a decrease in LC3B protein after exposure to gefitinib. Cell viability and colony formed ability were recovered when OE-CSP cells were exposed to rapamycin. In nude mice with xenografts of LUAD cells, inhibition of autophagy by CSP resulted in suppression of cell growth, and more marked apoptosis during exposure to gefitinib. CSP promoted ubiquitin-proteasome degradation of LC3B, leading to inhibition of autophagy in LUAD cells after treatment with gefitinib. When LUAD cells were treated with ubiquitin activating enzyme inhibitor TAK-243, cell viability, apoptosis, and growth were comparable between the OE-CSP group and a control group both in vivo and in vitro. Conclusion: CSP can inhibit gefitinib-induced autophagy via proteasomal degradation of LC3B, which suggests that CSP could be used as an autophagy inhibitor to sensitize EGFR-TKIs.

The dual roles of autophagy and the GPCRs-mediating autophagy signaling pathway after cerebral ischemic stroke

Ischemic stroke, caused by a lack of blood supply in brain tissues, is the third leading cause of human death and disability worldwide, and usually results in sensory and motor dysfunction, cognitive impairment, and in severe cases, even death. Autophagy is a highly conserved lysosome-dependent process in which eukaryotic cells removal misfolded proteins and damaged organelles in cytoplasm, which is critical for energy metabolism, organelle renewal, and maintenance of intracellular homeostasis. Increasing evidence suggests that autophagy plays important roles in pathophysiological mechanisms under ischemic conditions. However, there are still controversies about whether autophagy plays a neuroprotective or damaging role after ischemia. G-protein-coupled receptors (GPCRs), one of the largest protein receptor superfamilies in mammals, play crucial roles in various physiological and pathological processes. Statistics show that GPCRs are the targets of about one-fifth of drugs known in the world, predicting potential values as targets for drug research. Studies have demonstrated that nutritional deprivation can directly or indirectly activate GPCRs, mediating a series of downstream biological processes, including autophagy. It can be concluded that there are interactions between autophagy and GPCRs signaling pathway, which provides research evidence for regulating GPCRs-mediated autophagy. This review aims to systematically discuss the underlying mechanism and dual roles of autophagy in cerebral ischemia, and describe the GPCRs-mediated autophagy, hoping to probe promising therapeutic targets for ischemic stroke through in-depth exploration of the GPCRs-mediated autophagy signaling pathway.

Effects of Prolonged Intermittent Fasting Model on Energy Metabolism and Mitochondrial Functions in Neurons

Background:

Calorie restriction (CR) during daily nutrition has been shown to affect the prognosis of many chronic diseases such as metabolic syndrome, diabetes, and aging. As an alternative nutrition model, prolonged intermittent fasting (PF) in humans is defined by the absence of food for more than 12 h. In our previous human studies, CR and PF models were compared and it was concluded that the two models might have differences in signal transduction mechanisms. We have investigated the effects of these models on neurons at the molecular level in this study.

Methods:

Neurons (SH-SY5Y) were incubated with normal medium (N), calorie-restricted medium (CR), fasting medium (PF), and glucose-free medium (G0) for 16 h. Simultaneously, ketone (beta-hydroxybutyrate; bOHB) was added to other experiment flasks containing the same media. Concentrations of lactate, lactate dehydrogenase (LDH), bOHB, and glucose were measured to demonstrate the changes in the energy metabolism together with the mitochondrial functions of cells. Citrate synthase activity and flow cytometric mitochondrial functions were investigated.

Results:

At the end of incubations, lactate and LDH levels were decreased and mitochondrial activity was increased in all ketone-added groups (P < .01) regardless of the glucose concentration in the environment. In the fasting model, these differences were more prominent.

Conclusion:

Our results demonstrated that neurons use ketones regardless of the amount of glucose, and bOHB-treated cells had positive changes in mitochondrial function. We conclude that the presence of bOHB might reverse neuron damage and that exogenous ketone treatment may be beneficial in the treatment of neurological diseases in the future.

Remote Ischemic Conditioning: A Potential Treatment for Chronic Cerebral Hypoperfusion

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is a clinical syndrome, which is characterized by significantly decreased cerebral blood flow (CBF). CCH is a common consequence of cerebrovascular and cardiovascular diseases and the elderly. CCH results in a series of pathological damages, increasing cell death, autophagy dysfunction, amyloid β (Aβ) peptide accumulation, blood-brain barrier (BBB) disruption, and endothelial damage, which are found in CCH models. In addition, CCH is a prominent risk factor of cognitive impairment, such as vascular dementia, and CCH contributes to the occurrence and development of Alzheimer's disease. Therefore, the treatment of patients with CCH is of great value. It has been confirmed that remote ischemic conditioning (RIC) is a safe, promising treatment for acute and chronic cerebrovascular diseases. RIC significantly increases CBF in both CCH models and patients, inhibits neuronal apoptosis, reduces Aβ deposition, protects BBB integrity and endothelial function, alleviates neuroinflammation, improves cognitive impairment, and exerts neuroprotection.

SUMMARY

With the development of animal models, the pathophysiological mechanisms of CCH and RIC are increasingly revealed. Key Messages: We discuss the mechanisms related to hypoperfusion in the brain and explore the potential treatment of RIC for CCH to promote its transformation and application in humans.

STAT3 exerts pro-tumor and anti-autophagy roles in cervical cancer

Background

STAT3 plays an important role in cervical cancer. LC3B, the most potential molecular biomarker of autophagy that may promote or inhibit cancer progression, can be downregulated by STAT3. However the role of STAT3 in the autophagy of cervical cancer remains unclear.

Purpose

This study aimed to evaluate the relationship between STAT3 and LC3B in protein level, and verify whether STAT3 promotes proliferation, migration and plate colony formation by inhibiting autophagy of cervical cancer cells through bcl2-beclin1 axis.

Results

STAT3 was overexpressed in cervical cancer tissues, and negatively correlated with the expression level of LC3B. STAT3 knockout or knockdown significantly increased the autophagy level and decreased proliferation, migration, plate colony formation and subcutaneous tumorigenesis of cervical cancer cells in vitro and in vivo. STAT3 is known to mediate autophagy through Bcl2-Beclin1 complex. Bcl2 was positively whereas Beclin1 negatively correlated with STAT3 expression, indicating that Bcl2-Beclin1 complex involved in this transition.

Conclusion

STAT3 may upregulate the autophagy level of cervical cancer cells through the Bcl2-Beclin1 axis. This indicates that STAT3 may be an important prognostic and therapeutic target for cervical cancer.

Mitochondrial quality control in stroke: From the mechanisms to therapeutic potentials

Mitochondrial damage is a critical contributor to stroke‐induced injury, and mitochondrial quality control (MQC) is the cornerstone of restoring mitochondrial homeostasis and plays an indispensable role in alleviating pathological process of stroke. Mitochondria quality control promotes neuronal survival via various adaptive responses for preserving mitochondria structure, morphology, quantity and function. The processes of mitochondrial fission and fusion allow for damaged mitochondria to be segregated and facilitate the equilibration of mitochondrial components such as DNA, proteins and metabolites. The process of mitophagy is responsible for the degradation and recycling of damaged mitochondria. This review aims to offer a synopsis of the molecular mechanisms involved in MQC for recapitulating our current understanding of the complex role that MQC plays in the progression of stroke. Speculating on the prospect that targeted manipulation of MQC mechanisms may be exploited for the rationale design of novel therapeutic interventions in the ischaemic stroke and haemorrhagic stroke. In the review, we highlight the potential of MQC as therapeutic targets for stroke treatment and provide valuable insights for clinical strategies.

Neuroprotective Effects of Resveratrol in In vivo and In vitro Experimental Models of Parkinson's Disease: a Systematic Review

Parkinson's disease (PD) is currently the second most common neurodegenerative disease, being characterized by motor and non-motor symptoms. The therapeutic options available for its treatment are limited, do not slow the progression of the disease, and have serious side effects. For this reason, many studies have sought to find compounds with neuroprotective properties that bring additional benefits to current therapy. In this context, resveratrol is a phenolic compound, found in many plant species, capable of crossing the blood-brain barrier and having multiple biological properties. Experimental studies in vitro and in vivo have shown that it can prevent or slow the progression of a variety of diseases, including PD. In this systematic review, we summarize the effects of resveratrol in experimental in vivo and in vitro models of PD and discuss the molecular mechanisms involved in its action. The bibliographic search was performed in the databases of PubMed, Web of Science, SciELO, and Google Scholar, and based on the inclusion criteria, 41 articles were selected and discussed. Most of the included studies have demonstrated neuroprotective effects of resveratrol. In general, resveratrol prevented behavioral and/or neurological disorders, improved antioxidant defenses, reduced neuroinflammatory processes, and inhibited apoptosis. In summary, this systematic review offers important scientific evidence of neuroprotective effects of resveratrol in PD and also provide valuable information about its mechanism of action that can support future clinical studies.

Biological Functions and Therapeutic Potential of Autophagy in Spinal Cord Injury

Autophagy is an evolutionarily conserved lysosomal degradation pathway that maintains metabolism and homeostasis by eliminating protein aggregates and damaged organelles. Many studies have reported that autophagy plays an important role in spinal cord injury (SCI). However, the spatiotemporal patterns of autophagy activation after traumatic SCI are contradictory. Most studies show that the activation of autophagy and inhibition of apoptosis have neuroprotective effects on traumatic SCI. However, reports demonstrate that autophagy is strongly associated with distal neuronal death and the impaired functional recovery following traumatic SCI. This article introduces SCI pathophysiology, the physiology and mechanism of autophagy, and our current review on its role in traumatic SCI. We also discuss the interaction between autophagy and apoptosis and the therapeutic effect of activating or inhibiting autophagy in promoting functional recovery. Thus, we aim to provide a theoretical basis for the biological therapy of SCI.

Mechanistic Insight on Autophagy Modulated Molecular Pathways in Cerebral Ischemic Injury: From Preclinical to Clinical Perspective

Cerebral ischemia is one of the most devastating brain injuries and a primary cause of acquired and persistent disability worldwide. Despite ongoing therapeutic interventions at both the experimental and clinical levels, options for stroke-related brain injury are still limited. Several evidence suggests that autophagy is triggered in response to cerebral ischemia, therefore targeting autophagy-related signaling pathways can provide a new direction for the therapeutic implications in the ischemic injury. Autophagy is a highly conserved lysosomal-dependent pathway that degrades and recycles damaged or non-essential cellular components to maintain neuronal homeostasis. But, whether autophagy activation promotes cell survival against ischemic injury or, on the contrary, causes neuronal death is still under debate. We performed an extensive literature search from PubMed, Bentham and Elsevier for various aspects related to molecular mechanisms and pathobiology involved in autophagy and several pre-clinical studies justifiable further in the clinical trials. Autophagy modulates various downstream molecular cascades, i.e., mTOR, NF-κB, HIF-1, PPAR-γ, MAPK, UPR, and ROS pathways in cerebral ischemic injury. In this review, the various approaches and their implementation in the translational research in ischemic injury into practices has been covered. It will assist researchers in finding a way to cross the unbridgeable chasm between the pre-clinical and clinical studies.

Targeting regulated cell death in tumor nanomedicines

Nanomedicines hold great potential in anticancer therapy by modulating the biodistribution of nanomaterials and initiating targeted oxidative stress damage, but they are also limited by the inherent self-protection mechanism and the evolutionary treatment resistance of cancer cells. New emerging explorations of regulated cell death (RCD), including processes related to autophagy, ferroptosis, pyroptosis, and necroptosis, substantially contribute to the augmented therapeutic efficiency of tumors by increasing the sensitivity of cancer cells to apoptosis. Herein, paradigmatic studies of RCD-mediated synergistic tumor nanotherapeutics are introduced, such as regulating autophagy-enhanced photodynamic therapy (PDT), targeting ferroptosis-sensitized sonodynamic therapy (SDT), inducing necroptosis-augmented photothermal therapy (PTT), and initiating pyroptosis-collaborative chemodynamic therapy (CDT), and the coordination mechanisms are discussed in detail. Multiangle analyses addressing the present challenges and upcoming prospects of RCD-based nanomedicines have also been highlighted and prospected for their further strengthening and the broadening of their application scope. It is believed that up-and-coming coadjutant therapeutic methodologies based on RCDs will considerably impact precision nanomedicine for cancer.

Autophagy Dysfunction as a Phenotypic Readout in hiPSC-Derived Neuronal Cell Models of Neurodegenerative Diseases

Autophagy is an evolutionarily conserved catabolic pathway for the degradation of cytoplasmic constituents in eukaryotic cells. It is the primary disposal route for selective removal of undesirable cellular materials like aggregation-prone proteins and damaged organelles for maintaining cellular homeostasis, and for bulk degradation of intracellular macromolecules and recycling the breakdown products for providing energy homeostasis during starvation. These functions of autophagy are attributed to cellular survival and thus pertinent for human health; however, malfunction of this process is detrimental to the cells, particularly for post-mitotic neurons. Thus, basal autophagy is vital for maintaining neuronal homeostasis, whereas autophagy dysfunction contributes to neurodegeneration. Defective autophagy has been demonstrated in several neurodegenerative diseases wherein pharmacological induction of autophagy is beneficial in many of these disease models. Elucidating the mechanisms underlying defective autophagy is imperative for the development of therapies targeting this process. Disease-affected human neuronal cells can be established from patient-derived human induced pluripotent stem cells (hiPSCs) that provide a clinically relevant platform for studying disease mechanisms and drug discovery. Thus, modeling autophagy dysfunction as a phenotypic readout in patient-derived neurons provides a more direct platform for investigating the mechanisms underlying defective autophagy and evaluating the therapeutic efficacy of autophagy inducers. Toward this, several hiPSC-derived neuronal cell models of neurodegenerative diseases have been employed. In this review, we highlight the key methodologies pertaining to hiPSC maintenance and neuronal differentiation, and studying autophagy at an endogenous level in hiPSC-derived neuronal cells.

Cell death mechanisms induced by synergistic effects of halofuginone and artemisinin in colorectal cancer cells

Our previous study found that the combination of halofuginone (HF) and artemisinin (ATS) synergistically arrest colorectal cancer (CRC) cells at the G1/G0 phase of the cell cycle; however, it remains unclear whether HF-ATS induces cell death. Here we report that HF-ATS synergistically induced caspase-dependent apoptosis in CRC cells. Specifically, both in vitro and in vivo experiments showed that HF or HF-ATS induces apoptosis via activation of caspase-9 and caspase-8 while only caspase-9 is involved in ATS-induced apoptosis. Furthermore, we found HF or HF-ATS induces autophagy; ATS can't induce autophagy until caspase-9 is blocked. Further analyzing the crosstalk between autophagic and caspase activation in CRC cells, we found autophagy is essential for activation of caspase-8, and ATS switches to activate capase-8 via induction of autophagy when caspase-9 is inhibited. When apoptosis is totally blocked, HF-ATS switches to induce autophagic cell death. This scenario was then confirmed in studies of chemoresistance CRC cells with defective apoptosis. Our results indicate that HF-ATS induces cell death via interaction between apoptosis and autophagy in CRC cells. These results highlight the value of continued investigation into the potential use of this combination in cancer therapy.

Plumbagin triggers redox-mediated autophagy through the LC3B protein in human papillomavirus-positive cervical cancer cells

INTRODUCTION

In this study, we analyzed the effect of plumbagin (PL) on cultured SiHa cervical cancer cells using fluorescence microscopy and flow cytometry techniques to identify the mode of cell death and to elucidate whether cells die through apoptosis or non-apoptosis.

MATERIAL AND METHODS

The cell death was analyzed using MTT assay. The cellular morphological changes were assessed using acridine orange/ethidium bromide dual staining. DNA damage and cell cycle progression were analyzed using a comet assay and flow cytometry respectively.

RESULTS

Morphological and cytological features revealed that PL induced autophagic cell death in cancer cells. The results of a cell cycle analysis indicated that the proportion of cells in sub-G0 phase increased. Translocation of LC-3B protein from the cytoplasm to the autophagosome was found in 31% of PL-treated cells, suggesting that PL provoked autophagic cell death. In this study, it was observed that plumbagin treatment caused cleavage of DNA in SiHa cancer cells, and morphological analysis provided very strong evidence supporting the occurrence of autophagic cell death as a result of plumbagin treatment.

CONCLUSIONS

In addition, a Cytoscape-based protein-PL interaction network analysis provided very strong evidence in support of the specific mode of cell death in the context of autophagy, which has also been one of the desired endpoints in human papillomavirus-positive cervical cancer therapy and apoptotic cell death-resistant cancer treatment. Thus, this study is the first to test PL against the SiHa cervical cancer cell line, providing leads for further testing on non-apoptotic cell death for application in cervical cancer management.

How autophagy controls the intestinal epithelial barrier

Macroautophagy/autophagy is a cellular catabolic process that results in lysosome-mediated recycling of organelles and protein aggregates, as well as the destruction of intracellular pathogens. Its role in the maintenance of the intestinal epithelium is of particular interest, as several autophagy-related genes have been associated with intestinal disease. Autophagy and its regulatory mechanisms are involved in both homeostasis and repair of the intestine, supporting intestinal barrier function in response to cellular stress through tight junction regulation and protection from cell death. Furthermore, a clear role has emerged for autophagy not only in secretory cells but also in intestinal stem cells, where it affects their metabolism, as well as their proliferative and regenerative capacity. Here, we review the physiological role of autophagy in the context of intestinal epithelial maintenance and how genetic mutations affecting autophagy contribute to the development of intestinal disease.Abbreviations: AKT1S1: AKT1 substrate 1; AMBRA1: autophagy and beclin 1 regulator 1; AMPK: AMP-activated protein kinase; APC: APC regulator of WNT signaling pathway; ATF6: activating transcription factor 6; ATG: autophagy related; atg16l1[ΔIEC] mice: mice with a specific deletion of Atg16l1 in intestinal epithelial cells; ATP: adenosine triphosphate; BECN1: beclin 1; bsk/Jnk: basket; CADPR: cyclic ADP ribose; CALCOCO2: calcium binding and coiled-coil domain 2; CASP3: caspase 3; CD: Crohn disease; CDH1/E-cadherin: cadherin 1; CF: cystic fibrosis; CFTR: CF transmembrane conductance regulator; CGAS: cyclic GMP-AMP synthase; CLDN2: claudin 2; CoPEC: colibactin-producing E. coli; CRC: colorectal cancer; CYP1A1: cytochrome P450 family 1 subfamily A member 1; DC: dendritic cell; DDIT3: DNA damage inducible transcript 3; DEPTOR: DEP domain containing MTOR interacting protein; DSS: dextran sulfate sodium; EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; EIF2A: eukaryotic translation initiation factor 2A; EIF2AK3: eukaryotic translation initiation factor 2 alpha kinase 3; EIF2AK4/GCN2: eukaryotic translation initiation factor 2 alpha kinase 4; ER: endoplasmic reticulum; ERN1: endoplasmic reticulum to nucleus signaling 1; GABARAP: GABA type A receptor-associated protein; HMGB1: high mobility group box 1; HSPA5/GRP78: heat shock protein family A (Hsp70) member 5; IBD: inflammatory bowel disease; IEC: intestinal epithelial cell; IFN: interferon; IFNG/IFNγ:interferon gamma; IL: interleukin; IRGM: immunity related GTPase M; ISC: intestinal stem cell; LGR5: leucine rich repeat containing G protein-coupled receptor 5; LRRK2: leucine rich repeat kinase 2; MAP1LC3A/LC3: microtubule associated protein 1 light chain 3 alpha; MAPK/JNK: mitogen-activated protein kinase; MAPK14/p38 MAPK: mitogen-activated protein kinase 14; MAPKAP1: MAPK associated protein 1; MAVS: mitochondrial antiviral signaling protein; miRNA: microRNA; MLKL: mixed lineage kinase domain like pseudokinase; MLST8: MTOR associated protein, LST8 homolog; MNV: murine norovirus; MTOR: mechanistic target of rapamycin kinase; NBR1: NBR1 autophagy cargo receptor; NLRP: NLR family pyrin domain containing; NOD: nucleotide binding oligomerization domain containing; NRBF2: nuclear receptor binding factor 2; OPTN: optineurin; OXPHOS: oxidative phosphorylation; P: phosphorylation; Patj: PATJ crumbs cell polarity complex component; PE: phosphatidyl-ethanolamine; PI3K: phosphoinositide 3-kinase; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; PPARG: peroxisome proliferator activated receptor gamma; PRR5: proline rich 5; PRR5L: proline rich 5 like; PtdIns3K: phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol 3-phosphate; RB1CC1/FIP200: RB1 inducible coiled-coil 1; RER: rough endoplasmic reticulum; RHEB: Ras homolog, MTORC1 binding; RICTOR: RPTOR independent companion of MTOR complex 2; RIPK1: receptor interacting serine/threonine kinase 1; ROS: reactive oxygen species; RPTOR: regulatory associated protein of MTOR complex 1; RPS6KB1: ribosomal protein S6 kinase B1; SH3GLB1: SH3 domain containing GRB2 like, endophilin B1; SNP: single-nucleotide polymorphism; SQSTM1: sequestosome 1; STAT3: signal transducer and activator of transcription 3; STING1: stimulator of interferon response cGAMP interactor 1; TA: transit-amplifying; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3; TGM2: transglutaminase 2; TJ: tight junction; TJP1/ZO1: tight junction protein 1; TNBS: 2,4,6-trinitrobenzene sulfonic acid; TNF/TNFα: tumor necrosis factor; Tor: target of rapamycin; TRAF: TNF receptor associated factor; TRIM11: tripartite motif containing 11; TRP53: transformation related protein 53; TSC: TSC complex subunit; Ub: ubiquitin; UC: ulcerative colitis; ULK1: unc-51 like autophagy activating kinase 1; USO1/p115: USO1 vesicle transport factor; UVRAG: UV radiation resistance associated; WIPI: WD repeat domain, phosphoinositide interacting; WNT: WNT family member; XBP1: X-box binding protein 1; ZFYVE1/DFCP1: zinc finger FYVE-type containing 1.

Impacts of MicroRNAs Induced by the Gut Microbiome on Regulating the Development of Colorectal Cancer

Although a dysfunctional gut microbiome is strongly linked to colorectal cancer (CRC), our knowledge of the mediators between CRC and the microbiome is limited. MicroRNAs (miRNAs) affect critical cellular processes, such as apoptosis, proliferation, and differentiation, and contribute to the regulation of CRC progression. Increasingly, studies found that miRNAs can significantly mediate bidirectional interactions between the host and the microbiome. Notably, miRNA expression is regulated by the gut microbiome, which subsequently affects the host transcriptome, thereby influencing the development of CRC. This study typically focuses on the specific functions of the microbiome in CRC and their effect on CRC-related miRNA production and reviews the role of several bacteria on miRNA, including Fusobacterium nucleatum, Escherichia coli, enterotoxigenic Bacteroides fragilis, and Faecalibacterium prausnitzii. Based on the important roles of miRNAs and the gut microbiome in CRC, strategies for modulating miRNA expression and regulating the gut microbiome composition need to be applied, such as bioactive dietary components and fecal microorganism transplantation.

Nelfinavir Induces Cytotoxicity towards High-Grade Serous Ovarian Cancer Cells, Involving Induction of the Unfolded Protein Response, Modulation of Protein Synthesis, DNA Damage, Lysosomal Impairment, and Potentiation of Toxicity Caused by Proteasome Inhibition

Simple Summary

High-grade serous ovarian cancer (HGSOC) accounts for 70% of all ovarian-cancer-related deaths. Mainstay treatment with platinum-based drugs following surgery results in favorable outcomes in the majority of patients; however, in >80% of cases, the disease relapses with eventual drug resistance. As such, urgent development of improved alternative therapies is necessary for HGSOC patients with lower life expectancy. Rapid repurposing of market available drugs for cancer therapy is a cost-effective alternative to bypass the decade-long traditional drug development pipeline. Among potential drug-repurposing candidates, nelfinavir (NFV)—an anti-infective agent to treat acquired immunodeficiency syndrome (AIDS)—has shown anti-cancer effects against diverse cancers; however, its remedial benefits against HGSOC are unknown. In this study, we explored how NFV targets HGSOC cells obtained from patients at platinum-sensitive and -resistant stages. We observed beneficial efficacy elicited by NFV against HGSOC in both disease conditions through multiple mechanistic avenues, suggesting positive drug-repurposing prospects.

Abstract

High-grade serous ovarian cancer (HGSOC) is a significant cause of mortality among women worldwide. Traditional treatment consists of platinum-based therapy; however, rapid development of platinum resistance contributes to lower life expectancy, warranting newer therapies to supplement the current platinum-based protocol. Repurposing market-available drugs as cancer therapeutics is a cost- and time-effective way to avail new therapies to drug-resistant patients. The anti-HIV agent nelfinavir (NFV) has shown promising toxicity against various cancers; however, its role against HGSOC is unknown. Here, we studied the effect of NFV against HGSOC cells obtained from patients along disease progression and carrying different sensitivities to platinum. NFV triggered, independently of platinum sensitivity, a dose-dependent reduction in the HGSOC cell number and viability, and a parallel increase in hypo-diploid DNA content. Moreover, a dose-dependent reduction in clonogenic survival of cells escaping the acute toxicity was indicative of long-term residual damage. In addition, dose- and time-dependent phosphorylation of H2AX indicated NFV-mediated DNA damage, which was associated with decreased survival and proliferation signals driven by the AKT and ERK pathways. NFV also mediated a dose-dependent increase in endoplasmic reticulum stress-related molecules associated with long-term inhibition of protein synthesis and concurrent cell death; such events were accompanied by a proapoptotic environment, signaled by increased phospho-eIF2α, ATF4, and CHOP, increased Bax/Bcl-2 ratio, and cleaved executer caspase-7. Finally, we show that NFV potentiates the short-term cell cycle arrest and long-term toxicity caused by the proteasome inhibitor bortezomib. Overall, our in vitro study demonstrates that NFV can therapeutically target HGSOC cells of differential platinum sensitivities via several mechanisms, suggesting its prospective repurposing benefit considering its good safety profile.

Regulated cell death: discovery, features and implications for neurodegenerative diseases

Regulated cell death (RCD) is a ubiquitous process in living organisms that is essential for tissue homeostasis or to restore biological balance under stress. Over the decades, various forms of RCD have been reported and are increasingly being found to involve in human pathologies and clinical outcomes. We focus on five high-profile forms of RCD, including apoptosis, pyroptosis, autophagy-dependent cell death, necroptosis and ferroptosis. Cumulative evidence supports that not only they have different features and various pathways, but also there are extensive cross-talks between modes of cell death. As the understanding of RCD pathway in evolution, development, physiology and disease continues to improve. Here we review an updated classification of RCD on the discovery and features of processes. The prominent focus will be placed on key mechanisms of RCD and its critical role in neurodegenerative disease. Video abstract.

The Autophagy Inhibitor Chloroquine, Alone or in Combination with mTOR Inhibitors, Displays Anti-Tumor Effects in In Vitro and In Vivo Lung Carcinoid Models

Simple Summary

Neuroendocrine neoplasms of the lung (lung carcinoids) are often diagnosed when they are not surgically curable, and treatment options are limited. One of the approved options for treating inoperable tumors is everolimus, an mTOR inhibitor. Activation of mTOR inhibits autophagy, which is a cell survival mechanism; everolimus may paradoxically encourage cancer cell survival via stimulation of autophagy. Chloroquine, a known antimalarial compound, inhibits autophagy. Our research is focused on the hypothesis that autophagy plays a key role in the development of tumor resistance to everolimus, and that chloroquine addition to an mTOR inhibitor increases their inhibitory effect on tumor growth. In this study, we examined the effects of chloroquine alone or in combination with mTOR inhibitors on lung neuroendocrine tumor models (cell lines and mice). We have shown that chloroquine alone suppresses tumor cells’ viability and proliferation and increases their cytotoxicity and apoptosis; these effects are augmented when chloroquine is added to mTOR inhibitors. Apparently, chloroquine suppresses tumor cell growth in lung neuroendocrine neoplasms models, potentiating the effects of the mTOR inhibitors, and implying that more research is warranted to unravel its possible role in the clinical setting, in patients with advanced lung neuroendocrine neoplasms.

Abstract

(1) Background: Neuroendocrine neoplasms of the lung (LNENs, lung carcinoids) are often diagnosed at an advanced stage when they are not surgically curable, and treatment options are limited. One of the approved options for treating inoperable tumors is everolimus—an mTOR inhibitor (mTORi). Activation of mTOR, among many other effects, inhibits autophagy, which is a cell survival mechanism in general, and in tumor cells in particular. Everolimus may paradoxically encourage cancer cell survival. In practice, the drug inhibits tumor development. Chloroquine (CQ) is a known antimalarial compound that inhibits autophagy. Our research is focused on the hypothesis that autophagy plays a key role in the development of tumor resistance to mTORi, and that the addition of autophagy inhibitors to mTORi exerts a synergistic effect on suppressing tumor cell proliferation. We have recently demonstrated that the combination of CQ with different mTORi increases their potency compared with mTORi alone in both in vitro and in vivo models of pancreatic NENs. In this study, we examined the effects of CQ and mTORi on in vitro and in vivo LNEN models. Aims: Testing the effects of CQ together with mTORi on cell proliferation, apoptosis, and autophagy in in vitro and in vivo LNEN models. (2) Methods: The NCI-H727 LNEN cells were treated with CQ ± mTORi. Cells’ viability and proliferation were measured using XTT and Ki-67 FACS staining. The effects of the treatments on the mTOR pathway and autophagy were examined using Western blotting. Cytotoxicity was measured using a cytotoxicity kit; apoptosis was measured by PI FACS staining and Western blotting. We further established an LNEN subcutaneous murine xenograft model and evaluated the effects of the drugs on tumor growth. (3) Results: CQ alone suppressed LNEN cells’ viability and proliferation and increased their cytotoxicity and apoptosis; these effects were augmented when CQ was added to an mTORi. We also showed the possible mechanisms for these results: on the one hand we could see a decrease in P62 levels and the absence of LC3-II (both inversely related to autophagy) following treatment with the mTORi, and on the other hand we could demonstrate an increase in their levels when CQ was added. The effect was less apparent in the murine xenograft model. (4) Conclusions: By inhibiting autophagy and inducing apoptosis, CQ suppresses tumor cell growth in LNENs. CQ potentiates mTORi effects, implying that further studies are needed in order to elucidate its possible role in tumor inhibition in patients with LNENs.

Autophagy-Lysosomal Pathway as Potential Therapeutic Target in Parkinson's Disease

Cellular quality control systems have gained much attention in recent decades. Among these, autophagy is a natural self-preservation mechanism that continuously eliminates toxic cellular components and acts as an anti-ageing process. It is vital for cell survival and to preserve homeostasis. Several cell-type-dependent canonical or non-canonical autophagy pathways have been reported showing varying degrees of selectivity with regard to the substrates targeted. Here, we provide an updated review of the autophagy machinery and discuss the role of various forms of autophagy in neurodegenerative diseases, with a particular focus on Parkinson's disease. We describe recent findings that have led to the proposal of therapeutic strategies targeting autophagy to alter the course of Parkinson's disease progression.

Prodigiosin inhibits cholangiocarcinoma cell proliferation and induces apoptosis via suppressing SNAREs-dependent autophagy

Background

Prodigiosin (PG), a natural red pigment produced by numerous bacterial species, has been a eye-catching research point in recent years for its anticancer activity. However, the role of PG in the cancer biology of cholangiocarcinoma (CCA) remains vague.

Methods

The proliferation of CCA cells was detected by Cell Counting Kit-8(CCK-8), Colony formation assay and 5-ethynyl-2′-deoxyuridine (EdU) assay. Cell apoptosis was evaluated by flow cytometry assay and western blot assay. The effects of PG or SNAREs on cell autophagy were measured by autophagy flux assay and western blot assay. Xenograft mouse models were used to assess the role of PG in CCA cells in vivo.

Results

PG could inhibit the proliferation and viability of CCA cells in a concentration- and time-dependent manner via suppressing the late stage of autophagy. Mechanistically, PG inhibits the fusion of autophagosomes and lysosomes by blocking STX17 and SNAP29, components of soluble N-ethyl-maleimide-sensitive factor attachment protein receptors (SNAREs)complex. When STX17 and SNAP29 were overexpressed, the inhibitory effect of PG on CCA cells autophagy was relieved. In addition, PG showed obvious inhibitory effects on cancer cell viability but no toxic effects on organs in xenotransplantation models.

Conclusion

Taken together, our results demonstrated that PG inhibits CCA cell proliferation via suppressing SNAREs-dependent autophagy, implying that PG could be a potential chemotherapy drug for advanced CCA.

The effect of paclitaxel on apoptosis, autophagy and mitotic catastrophe in AGS cells

Paclitaxel is an anti-microtubule agent that has been shown to induce cell death in gastric cancer. However, the detailed mechanism of action is unclear. In this study, we reveal that the paclitaxel-induced cell death mechanism involves mitotic catastrophe, autophagy and apoptosis in AGS cells. Paclitaxel induced intrinsic apoptosis by activating caspase-3, caspase-9 and PARP. In addition, the significant increase in autophagy marker LC3B-II, together with Atg5, class III PI3K and Beclin-1, and the down-regulation of p62 following paclitaxel treatment verified that paclitaxel induced autophagy. Further experiments showed that paclitaxel caused mitotic catastrophe, cell cycle arrest of the accumulated multinucleated giant cells at the G2/M phase and induction of cell death in 24 h. Within 48 h, the arrested multinucleated cells escaped mitosis by decreasing cell division regulatory proteins and triggered cell death. Cells treated with paclitaxel for 48 h were grown in fresh medium for 24 h and checked for CDC2, CDC25C and lamin B1 protein expressions. These proteins had decreased significantly, indicating that the remaining cells became senescent. In conclusion, it is suggested that paclitaxel-induced mitotic catastrophe is an integral part of the cell death mechanism, in addition to apoptosis and autophagy, in AGS cells.

Downregulation of AMPK dependent FOXO3 and TFEB involves in the inhibition of autophagy in diabetic cataract

PURPOSE

Autophagy plays a crucial role in intracellular quality control of crystalline lens and AMPK has regulatory effect on autophagy. However, whether AMPK regulated autophagy is involved in diabetic cataract (DC) progression remains unknown. This study aims to investigate the AMPK-FOXO3 and AMPK-TFEB induced autophagy activity in DC patients.

MATERIALS AND METHODS

First, anterior capsule specimens from DC and age-related cataract (ARC) patients were obtained to compare the expression difference of autophagy-related genes. The phosphorylation levels of AMPK, AKT, and mTOR and the expression of FOXO3 and TFEB were measured. Then, human lens epithelial cells (LECs, SRA 01/04) were cultured with 30 mM or 5.5 mM glucose, and AMPK activator (AICAR) and inhibitor (Compound C) were applied to further investigate the regulatory role of AMPK on autophagy.

RESULTS

Compared with ARC patients, the expression of autophagy-related genes ATG5, FYCO1, ATG8, ATG12, Beclin1, and ULK1 in anterior capsules LECs of DC patients were significantly down-regulated. Meanwhile, AMPK and AMPK-dependent transcription factors, FOXO3 and TFEB were also inhibited. Similar results were found in high glucose (HG) treated SRA 01/04 model. Notably, this down-regulation of autophagy activity was rescued by AICAR in vitro, which was manifested by inhibition of AKT and mTOR phosphorylation and up-regulation of FOXO3, TFEB, Beclin1 and LC3B-II expression.

CONCLUSIONS

Down-regulation of AMPK-FOXO3 and AMPK-TFEB induced autophagy activity was found in both LECs of anterior capsule from DC patients and SRA 01/04 cells under HG condition, which may be the underlying mechanism of DC formation. Thus, targeting AMPK-induced autophagy may be a potential therapeutic approach for diabetic cataract.

Autophagy and gastrointestinal cancers: the behind the scenes role of long non-coding RNAs in initiation, progression, and treatment resistance

Gastrointestinal (GI) cancers comprise a heterogeneous group of complex disorders that affect different organs, including esophagus, stomach, gallbladder, liver, biliary tract, pancreas, small intestine, colon, rectum, and anus. Recently, an explosion in nucleic acid-based technologies has led to the discovery of long non-coding RNAs (lncRNAs) that have been found to possess unique regulatory functions. This class of RNAs is >200 nucleotides in length, and is characterized by their lack of protein coding. LncRNAs exert regulatory effects in GI cancer development by affecting different functions such as the proliferation and metastasis of cancer cells, apoptosis, glycolysis and angiogenesis. Over the past few decades, considerable evidence has revealed the important role of autophagy in both GI cancer progression and suppression. In addition, recent studies have confirmed a significant correlation between lncRNAs and the regulation of autophagy. In this review, we summarize how lncRNAs play a behind the scenes role in the pathogenesis of GI cancers through regulation of autophagy.

Library Screening to Identify Highly-Effective Autophagy Inhibitors for Improving Photothermal Cancer Therapy

The small molecular inhibitor-associated downregulation of autophagy can remarkably enhance the efficiency of photothermal cancer therapy. To identify a more effective autophagy inhibitor, we screened a library of 20 compounds and found chloroquine, hydroxychloroquine, dauricine, and daurisoline were more efficient than the others to improve the photothermal killing of cancer cells. Interestingly, the four agents all disturb the autophagosome formation and fusion process, indicating it is a promising target to enhance cancer therapeutic efficiency. Among the four agents, daurisoline was identified to be the most efficient one. It reduced the viability of cancer cells treated by low-energy photothermal therapy from 86.27% to 32.92%. Finally, the combination treatment mediated by nanodrugs loaded with daurisoline and indocyanine green was more efficient than the individual modalities, resulting in complete inhibition of tumor growth. The study gives new inspiration to autophagy modulation-associated photothermal therapy and other therapeutic modalities for cancer treatment.

mTOR-mediated phosphorylation of VAMP8 and SCFD1 regulates autophagosome maturation

The mammalian target of rapamycin (mTORC1) has been shown to regulate autophagy at different steps. However, how mTORC1 regulates the N-ethylmaleimide-sensitive protein receptor (SNARE) complex remains elusive. Here we show that mTORC1 inhibits formation of the SNARE complex (STX17-SNAP29-VAMP8) by phosphorylating VAMP8, thereby blocking autophagosome-lysosome fusion. A VAMP8 phosphorylation mimic mutant is unable to promote autophagosome-lysosome fusion in vitro. Furthermore, we identify SCFD1, a Sec1/Munc18-like protein, that localizes to the autolysosome and is required for SNARE complex formation and autophagosome-lysosome fusion. VAMP8 promotes SCFD1 recruitment to autolysosomes when dephosphorylated. Consistently, phosphorylated VAMP8 or SCFD1 depletion inhibits autophagosome-lysosome fusion, and expression of phosphomimic VAMP8 leads to increased lipid droplet accumulation when expressed in mouse liver. Thus, our study supports that mTORC1-mediated phosphorylation of VAMP8 blocks SCFD1 recruitment, thereby inhibiting STX17-SNAP29-VAMP8 complex formation and autophagosome-lysosome fusion.

Autophagy relies on coordinated fusion of organelle membranes, although the interplay between the regulatory machinery is not well studied. Here, the authors show that SNARE complex formation is inhibited by mTORC1 phosphorylation of VAMP8, which prevents autophagosome-lysosome fusion.

Pimavanserin: A Novel Autophagy Modulator for Pancreatic Cancer Treatment

Pancreatic tumors exhibit high basal autophagy compared to that of other cancers. Several studies including those from our laboratory reported that enhanced autophagy leads to apoptosis in cancer cells. In this study, we evaluated the autophagy and apoptosis inducing effects of Pimavanserin tartrate (PVT). Autophagic effects of PVT were determined by Acridine Orange assay and Transmission Electron Microscopy analysis. Clinical significance of ULK1 in normal and pancreatic cancer patients was evaluated by R2 and GEPIA cancer genomic databases. Modulation of proteins in autophagy signaling was assessed by Western blotting and Immunofluorescence. Apoptotic effects of PVT was evaluated by Annexin-V/APC assay. Subcutaneous xenograft pancreatic tumor model was used to evaluate the autophagy-mediated apoptotic effects of PVT in vivo. Autophagy was induced upon PVT treatment in pancreatic ducal adenocarcinoma (PDAC) cells. Pancreatic cancer patients exhibit reduced levels of autophagy initiator gene, ULK1, which correlated with reduced patient survival. Interestingly, PVT induced the expression of autophagy markers ULK1, FIP200, Atg101, Beclin-1, Atg5, LC3A/B, and cleavage of caspase-3, an indicator of apoptosis in several PDAC cells. ULK1 agonist LYN-1604 enhanced the autophagic and apoptotic effects of PVT. On the other hand, autophagy inhibitors chloroquine and bafilomycin blocked the autophagic and apoptotic effects of PVT in PDAC cells. Notably, chloroquine abrogated the growth suppressive effects of PVT by 25% in BxPC3 tumor xenografts in nude mice. Collectively, our results indicate that PVT mediated pancreatic tumor growth suppression was associated with induction of autophagy mediated apoptosis.

Targeting UPR branches, a potential strategy for enhancing efficacy of cancer chemotherapy

Cancer cells are often exposed to cell intrinsic stresses and environmental perturbations that may lead to accumulation of unfolded and/or misfolded proteins in the lumen of endoplasmic reticulum (ER), a cellular condition known as ER stress. In response to ER stress, the cells elicit an adaptive process called unfolded protein response (UPR) to cope with the stress, supporting cellular homeostasis and survival. The ER stress sensors inositol requiring protein 1α (IRE1α), eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3, also called PERK), and activating transcription factor 6 (ATF6) constitute the three branches of UPR to resolve ER stress. IRE1α, PERK, and ATF6 play an important role in tumor cell growth and survival. They are also involved in chemotherapy resistance of cancers. These have generated widespread interest in targeting these UPR branches for cancer treatment. In this review, we provide an overview of the role of IRE1α, PERK, and ATF6 in cancer progression and drug resistance and we summarize the research advances in targeting these UPR branches to enhance the efficacy of chemotherapy of cancers.

The ubiquitin ligation machinery in the defense against bacterial pathogens

The ubiquitin system is an important part of the host cellular defense program during bacterial infection. This is in particular evident for a number of bacteria including Salmonella Typhimurium and Mycobacterium tuberculosis which—inventively as part of their invasion strategy or accidentally upon rupture of seized host endomembranes—become exposed to the host cytosol. Ubiquitylation is involved in the detection and clearance of these bacteria as well as in the activation of innate immune and inflammatory signaling. Remarkably, all these defense responses seem to emanate from a dense layer of ubiquitin which coats the invading pathogens. In this review, we focus on the diverse group of host cell E3 ubiquitin ligases that help to tailor this ubiquitin coat. In particular, we address how the divergent ubiquitin conjugation mechanisms of these ligases contribute to the complexity of the anti‐bacterial coating and the recruitment of different ubiquitin‐binding effectors. We also discuss the activation and coordination of the different E3 ligases and which strategies bacteria evolved to evade the activities of the host ubiquitin system.

Treatment-Free Remission in Chronic Myeloid Leukemia and New Approaches by Targeting Leukemia Stem Cells

The therapeutic landscape for chronic myeloid leukemia (CML) has improved significantly with the approval of tyrosine kinase inhibitors (TKIs) for therapeutic use. Most patients with optimal responses to TKIs can have a normal life expectancy. Treatment-free remission (TFR) after discontinuing TKI has increasingly become a new goal for CML treatment. However, TKI only "control" CML, and relapse after discontinuation has become a key factor hindering patient access to attempt TFR. In this study, we reviewed studies on TKI discontinuation, including both first and second-generation TKI. We also reviewed predictors of relapse, new monitoring methods, and strategies targeting leukemic stem cells.

p62/SQSTM1-induced caspase-8 aggresomes are essential for ionizing radiation-mediated apoptosis

The autophagy–lysosome pathway and apoptosis constitute vital determinants of cell fate and engage in a complex interplay in both physiological and pathological conditions. Central to this interplay is the archetypal autophagic cargo adaptor p62/SQSTM1/Sequestosome-1 which mediates both cell survival and endoplasmic reticulum stress-induced apoptosis via aggregation of ubiquitinated caspase-8. Here, we investigated the role of p62-mediated apoptosis in head and neck squamous cell carcinoma (HNSCC), which can be divided into two groups based on human papillomavirus (HPV) infection status. We show that increased autophagic flux and defective apoptosis are associated with radioresistance in HPV(-) HNSCC, whereas HPV(+) HNSCC fail to induce autophagic flux and readily undergo apoptotic cell death upon radiation treatments. The degree of radioresistance and tumor progression of HPV(-) HNSCC respectively correlated with autophagic activity and cytosolic levels of p62. Pharmacological activation of the p62-ZZ domain using small molecule ligands sensitized radioresistant HPV(-) HNSCC cells to ionizing radiation by facilitating p62 self-polymerization and sequestration of cargoes leading to apoptosis. The self-polymerizing activity of p62 was identified as the essential mechanism by which ubiquitinated caspase-8 is sequestered into aggresome-like structures, without which irradiation fails to induce apoptosis in HNSCC. Our results suggest that harnessing p62-dependent sequestration of ubiquitinated caspase-8 provides a novel therapeutic avenue in patients with radioresistant tumors.

Functions of the (pro)renin receptor (Atp6ap2) at molecular and system levels: pathological implications in hypertension, renal and brain development, inflammation, and fibrosis

The (pro)renin receptor [(P)RR, Atp6ap2] was initially discovered as a membrane-bound binding partner of prorenin and renin. A soluble (P)RR has additional paracrine effects and is involved in metabolic syndrome and kidney damage. Meanwhile it is clear that most of the effects of the (P)RR are independent of prorenin. In the kidney, (P)RR plays an important role in renal dysfunction by activating proinflammatory and profibrotic molecules. In the brain, (P)RR is expressed in cardiovascular regulatory nuclei and is linked to hypertension. (P)RR is known to be an essential component of the v-ATPase as a key accessory protein and plays an important role in kidney, brain and heart via regulating the pH of the extracellular space and intracellular compartments. V-ATPase and (P)RR together act on WNT and mTOR signalling pathways, which are responsible for cellular homeostasis and autophagy. (P)RR through its role in v-ATPase assembly and function is also important for fast recycling endocytosis by megalin. In the kidney, megalin together with v-ATPase and (P)RR is crucial for endocytic uptake of components of the RAS and their intracellular processing. In the brain, (P)RR, v-ATPases and megalin are important regulators both during development and in the adult. All three proteins are associated with diseases such as XLMR, XMRE, X-linked parkinsonism and epilepsy, cognitive disorders with Parkinsonism, spasticity, intellectual disability, and Alzheimer's Disease which are characterized by impaired neuronal function and/or neuronal loss. The present review focusses on the relevant effects of Atp6ap2 without assigning them necessarily to the RAS. Mechanistically, many effects can be well explained by the role of Atp6ap2 for v-ATPase assembly and function. Furthermore, application of a soluble (P)RR analogue as new therapeutic option is discussed.

Gossypol, a novel modulator of VCP, induces autophagic degradation of mutant huntingtin by promoting the formation of VCP/p97-LC3-mHTT complex

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by toxic aggregates of mutant huntingtin protein (mHTT) in the brain. Decreasing mHTT is a potential strategy for therapeutic purpose of HD. Valosin-containing protein (VCP/p97) is a crucial regulator of proteostasis, which regulates the degradation of damaged protein through proteasome and autophagy pathway. Since VCP has been implicated in pathogenesis of HD as well as other neurodegenerative diseases, small molecules that specifically regulate the activity of VCP may be of therapeutic benefits for HD patients. In this study we established a high-throughput screening biochemical assay for VCP ATPase activity measurement and identified gossypol, a clinical approved drug in China, as a novel modulator of VCP. Gossypol acetate dose-dependently inhibited the enzymatic activity of VCP in vitro with IC₅₀ of 6.53±0.6 μM. We further demonstrated that gossypol directly bound to the interface between the N and D1 domains of VCP. Gossypol acetate treatment not only lowered mHTT levels and rescued HD-relevant phenotypes in HD patient iPS-derived Q47 striatal neurons and HD knock-in mouse striatal cells, but also improved motor function deficits in both Drosophila and mouse HD models. Taken together, gossypol acetate acted through a gain-of-function way to induce the formation of VCP-LC3-mHTT ternary complex, triggering autophagic degradation of mHTT. This study reveals a new strategy for treatment of HD and raises the possibility that an existing drug can be repurposed as a new treatment of neurodegenerative diseases.

Engineering Chameleon Prodrug Nanovesicles to Increase Antigen Presentation and Inhibit PD-L1 Expression for Circumventing Immune Resistance of Cancer

Immune evasion is the major obstacle for T-cell-based cancer immunotherapy. The insufficient expression of the tumor-rejection antigen causes the intrinsic immune resistance and high expression of programmed death ligand 1 (PD-L1) induced by interferon gamma (IFN-γ), which accounts for the inducible immune resistance. To deal with both the intrinsic and inducible immune resistance of cancer, a multifunctional prodrug nanovesicle is sequentially developed. It is first sorted out that doxycycline (Doxy) efficiently inhibits autophagy of the tumor cells, and increases the surface level of major histocompatibility complex class I (MHC-I). Then, chameleon-inspired prodrug nanovesicles are engineered for tumor-targeted delivery of Doxy. The prodrug nanovesicles integrating a sheddable poly(ethylene glycol) shell and CRGDK ligand are kept stable during blood circulation, while exposing the targeting ligand in the tumor, which significantly inhibits autophagy, elicits MHC-I expression, increases tumor antigen presentation, recruits more tumor-infiltrating T lymphocytes, and suppresses FN-γ-induced intratumoral PD-L1 expression. After a proof of concept for overcoming intrinsic and inducible immune evasion, the prodrug nanovesicles are applied to validate the efficacy of cancer immunotherapy in two tumor-bearing mouse models. This research thus provides a novel targeting strategy for reducing tumor immune resistance and potentiating tumor immunotherapy.