The good, the bad and the autophagosome: exploring unanswered questions of autophagy-dependent cell death

Isowalsuranolide targets TrxR1/2 and triggers lysosomal biogenesis and autophagy via the p53-TFEB/TFE3 axis

The lysosome is transformed from a major degradative site to a dynamic regulator of cellular homeostasis. Cancer cells with altered redox environments could be exploited as potential targets for cancer therapy. The thioredoxin (Trx) system, which includes thioredoxin reductases (TrxRs), is a promising target for cancer drug development. Here, by identifying the natural product isowalsuranolide (Hdy-7), we showed that lysosomal biogenesis and autophagy are elicited by Hdy-7 via the inhibition of TrxRs. The attenuation of cellular TrxR activity led to the accumulation of ROS, which are indispensable for p53 activation and subsequent lysosomal biogenesis mediated by the transcription factor TFEB/TFE3. Knockdown of TrxR1/2 led to activation of TFEB/TFE3, thereafter increasing lysosomal biogenesis. Treatment with the ROS scavenger NAC or knockdown of p53 or SESN2 led to attenuation of the nuclear translocation of TFEB/TFE3, lysosomal biogenesis, and autophagic flux, suggesting that the TrxR1/2-p53-TFEB/TFE3 axis plays a role in maintaining lysosomal homeostasis under stress conditions other than starvation. Surprisingly, pharmacological inhibition or genetic ablation of autophagy prevented Hdy-7-induced cell death, suggesting that Hdy-7-induced autophagy is detrimental to cancer cells. Our study revealed that Hdy-7 induces ROS-mediated lysosomal biogenesis and retards cell growth by targeting TrxR1/2. This study highlights the lysosome as a regulatory hub for cellular homeostasis and as an attractive therapeutic target for a variety of lysosome-related diseases, including cancer.

Lysophosphatidylcholine promoting α-Synuclein aggregation in Parkinson's disease: disrupting GCase glycosylation and lysosomal α-Synuclein degradation

In Parkinson's Disease (PD), elevated serum lysophosphatidylcholine (LPC) levels correlate with disease progression. However, the mechanisms by which abnormal LPC elevation contributes to PD-related neurotoxicity remain poorly understood. This study aims to investigate the pathogenic role of LPC in dopaminergic neuronal damage and elucidates its underlying mechanisms. Our results showed LPC induces α-synuclein aggregation, exacerbating cognitive dysfunction. LPC activates Cleaved-Caspase3 via the orphan receptor GPR35-ERK signaling pathway, inhibits GRASP65 expression, and disrupts the polarized structure of the Golgi apparatus. This disruption impairs glycosylation and function of glucocerebrosidase (GCase), preventing its transport to lysosomes and leading to glucosylceramide (GlcCer) accumulation, a scaffold for α-synuclein aggregation. LPC also disrupts the autophagolysosomal pathway and lysosomal acidification, exacerbating toxic α-synuclein accumulation. Restoring GCase glycosylation, limiting GlcCer synthesis, or blocking ERK signaling mitigates these effects. This study highlights LPC's role in promoting α-synuclein aggregation and autophagolysosomal dysfunction, advancing our understanding of PD pathology.

FOXS1, frequently inactivated by promoter methylation, inhibited colorectal cancer cell growth by promoting TGFBI degradation through autophagy-lysosome pathway

INTRODUCTION

Tumor suppressor gene (TSG) inactivation by epigenetic modifications contributes to the carcinogenesis and progression of colorectal cancer (CRC). Expression profiling and CpG methylomics revealed that a forkhead-box transcriptional factor, FOXS1, is downregulated and methylated in CRC.

OBJECTIVES

To assess the biological functions and underlying mechanisms of FOXS1 in colorectal cancer.

METHODS

Public databases, semi-quantitative RT-PCR, immunohistochemistry, MSP, and BGS were used to analyze FOXS1 expression and promoter methylation in CRC. Stable FOXS1-overexpressing or knockdown cell lines were established. Cell growth, colony formation, flow cytometry, GFP-LC3 puncta detection, Ad-mCherry-GFP-LC3B, qPCR, in vivo subcutaneous tumor model, RNA-seq, western blotting, immunofluorescence, Co-IP assays, and protein stability analysis were performed to investigate the underlying molecular mechanisms of FOXS1.

RESULTS

In CRC, FOXS1 was frequently downregulated due to promoter CpG methylation, acting as an independent prognostic marker. Moreover, FOXS1 exerts inhibitory effects on the growth of CRC cells in vitro and in vivo, while concurrently promoting CRC cell autophagy. Intriguingly, we found that FOXS1 interacted with transforming growth factor beta induced (TGFBI) and FOXS1 promoted TGFBI degradation through the autophagy-lysosome pathway rather than the ubiquitin-proteasome system. FOXS1 was also found to facilitate the interaction between TGFBI and lysosomal associated membrane protein 2A (LAMP2A), leading to the translocation of TGFBI into lysosomes for degradation. Additionally, FOXS1 regulates AKT phosphorylation and FOXO3a nuclear translocation, promoting the transcription of autophagy-related genes downstream of FOXO3a. Restoration of TGFBI expression reversed the suppressive effect exerted by FOXS1 on the growth of colorectal cancer cells.

CONCLUSION

FOXS1 functions as a tumor suppressor that is methylated in CRC and promotes the lysosomal degradation of TGFBI, regulates cell growth and promotes autophagy in CRC through the TGFBI/AKT/FOXO3a signaling pathway. These findings indicate that FOXS1 exhibits potential as a promising biomarker and therapeutic target for colorectal cancer.

Autosis: a new form of cell death in myocardial ischemia-reperfusion injury

Cardiomyocytes undergo a variety of cell death events during myocardial ischemia‒reperfusion injury (MIRI). Understanding the causes of cardiomyocyte mortality is critical for the prevention and treatment of MIRI. Among the various types of cell death, autosis is a recently identified type of autophagic cell death with distinct morphological and chemical characteristics. Autosis can be attenuated by autophagy inhibitors but not reversed by apoptosis or necrosis inhibitors. In recent years, it has been shown that during the late phase of reperfusion, autosis is activated, which exacerbates myocardial injury. This article describes the characteristics of autosis, autophagic cell death, and the relationship between autophagic cell death and autosis; reviews the mechanism of autosis in MIRI; and discusses its clinical significance.

Let's talk about flux: the rising potential of autophagy rate measurements in disease

Macroautophagy/autophagy is increasingly implicated in a variety of diseases, making it an attractive therapeutic target. However, many aspects of autophagy are not fully understood and its impact on many diseases remains debatable and context-specific. The lack of systematic and dynamic measurements in these cases is a key reason for this ambiguity. In recent years, Loos et al. 2014 and Beesabathuni et al. 2022 developed methods to quantitatively measure autophagy holistically. In this commentary, we pose some of the unresolved biological questions regarding autophagy and consider how quantitative measurements may address them. While the applications are ever-expanding, we provide specific use cases in cancer, virus infection, and mechanistic screening. We address how the rate measurements themselves are central to developing cancer therapies and present ways in which these tools can be leveraged to dissect the complexities of virus-autophagy interactions. Screening methods can be combined with rate measurements to mechanistically decipher the labyrinth of autophagy regulation in cancer and virus infection. Taken together, these approaches have the potential to illuminate the underlying mechanisms of various diseases.Abbreviation MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; R1: rate of autophagosome formation; R2: rate of autophagosome-lysosome fusion; R3: rate of autolysosome turnover.

Plasma SQSTM1/p62 act as a biomarker for steroid-induced osteonecrosis of the femoral head

Autophagy is closely associated with the onset and progression of steroid-induced osteonecrosis of the femoral head (SIONFH). SQSTM1/p62 is an important indicator of autophagic activity. The aim of this study was to investigate the role of SQSTM1/p62 in the development of SIONFH. From May 2021 through November 2021, 36 patients diagnosed with SIONFH and 36 healthy controls were recruited for this study. Evaluations included imaging and pathologic assessment of clinical bone tissue, location and level of SQSTM1/p62 expression, plasma SQSTM1/p62 levels, and receiver operating characteristic (ROC) curves. We observed that the expression level of SQSTM1/p62 in bone samples decreased with the Association Research Circulation Osseous (ARCO) phase. Plasma SQSTM1/p62 levels were significantly higher in the SIONFH group compared to healthy controls. Plasma SQSTM1/p62 levels were higher in pre-crash patients than in post-crash patients, and lower plasma SQSTM1/p62 levels were associated with elevated ARCO stage. Plasma SQSTM1/p62 may represent a potential biomarker for different stages during SIONFH. Lower plasma SQSTM1/p62 levels indicate an advanced stage of SIONFH. This study provides new clues for early diagnosis of SIONFH.

Role of autophagy in modulating tumor cell radiosensitivity: Exploring pharmacological interventions for glioblastoma multiforme treatment

Autophagy is an innate cellular process characterized by self-digestion, wherein cells degrade or recycle aged proteins, misfolded proteins, and damaged organelles via lysosomal pathways. Its crucial role in maintaining cellular homeostasis, ensuring development and survival is well established. In the context of cancer therapy, autophagy's importance is firmly recognized, given its critical impact on treatment efficacy. Following radiotherapy, several factors can modulate autophagy including parameters related to radiation type and delivery methods. The concomitant use of chemotherapy with radiotherapy further influences autophagy, potentially either enhancing radiosensitivity or promoting radioresistance. This review article discusses some pharmacological agents and drugs capable of modulating autophagy levels in conjunction with radiation in tumor cells, with a focus on those identified as potential radiosensitizers in glioblastoma multiforme treatment.

The synergistic mechanisms of propofol with cisplatin or doxorubicin in human ovarian cancer cells

BACKGROUND

Most ovarian cancer cases are diagnosed at an advanced stage, leading to poor outcomes and a relatively low 5-year survival rate. While tumor resection in the early stages can be highly effective, recurrence following primary treatment remains a significant cause of mortality. Propofol is a commonly used intravenous anesthetic agent in cancer resection surgery. Previous research has shown that propofol anesthesia was associated with improved survival in patients undergoing elective surgery for epithelial ovarian cancer. However, the underlying antitumor mechanisms are not yet fully understood.

METHODS

This study aimed to uncover the antitumor properties of propofol alone and combined with cisplatin or doxorubicin, in human SKOV3 and OVCAR3 ovarian cancer cells. We applied flowcytometry analysis for mitochondrial membrane potential, apoptosis, and autophagy, colony formation, migration, and western blotting analysis.

RESULTS

Given that chemotherapy is a primary clinical approach for managing advanced and recurrent ovarian cancer, it is essential to address the limitations of current chemotherapy, particularly in the use of cisplatin and doxorubicin, which are often constrained by their side effects and the development of resistance. First of all, propofol acted synergistically with cisplatin and doxorubicin in SKOV3 cells. Moreover, our data further showed that propofol suppressed colony formation, disrupted mitochondrial membrane potential, and induced apoptosis and autophagy in SKOV3 and OVCAR3 cells. Finally, the effects of combined propofol with cisplatin or doxorubicin on mitochondrial membrane potential, apoptosis, autophagy, and epithelial-mesenchymal transition were different in SKOV3 and OVCAR3 cells, depending on the p53 status.

CONCLUSION

In summary, repurposing propofol could provide novel insights into the existing chemotherapy strategies for ovarian cancer. It holds promise for overcoming resistance to cisplatin or doxorubicin and may potentially reduce the required chemotherapy dosages and associated side effects, thus improving treatment outcomes.

Types of cell death and their relations to host immunological pathways

Various immune pathways have been identified in the host, including TH1, TH2, TH3, TH9, TH17, TH22, TH1-like, and THαβ immune reactions. While TH2 and TH9 responses primarily target multicellular parasites, host immune pathways directed against viruses, intracellular microorganisms (such as bacteria, protozoa, and fungi), and extracellular microorganisms can employ programmed cell death mechanisms to initiate immune responses or execute effective strategies for pathogen elimination. The types of programmed cell death involved include apoptosis, autophagy, pyroptosis, ferroptosis, necroptosis, and NETosis. Specifically, apoptosis is associated with host anti-virus eradicable THαβ immunity, autophagy with host anti-virus tolerable TH3 immunity, pyroptosis with host anti-intracellular microorganism eradicable TH1 immunity, ferroptosis with host anti-intracellular microorganism tolerable TH1-like immunity, necroptosis with host anti-extracellular microorganism eradicable TH22 immunity, and NETosis with host anti-extracellular microorganism tolerable TH17 immunity.

Yixin-Fumai granules modulate autophagy through the PI3K/AKT/FOXO pathway and lead to amelioration of aging mice with sick sinus syndrome

OBJECTIVE

By employing network pharmacology alongside molecular docking techniques, we can delve into the intricate workings of Yixin-Fumai granules (YXFMs) and their impact on sick sinus syndrome (SSS) within wrinkles mice. Specifically, we aim to understand how YXFMs enhance autophagy through the PI3K/AKT/FOXO path.

METHODS

The active ingredients and medicinal uses of Ginseng, ligusticum wallichii, Ophiopogon, Schisandra, salvia, and astragalus were compiled using the BATMAN-TCM database. We also used Genecards, OMIM, and Disgenet files to identify the disease goals. A hierarchical diagram of "disease-drug-key targets" was generated using the Cytoscape programs. In addition, we established a target protein interaction (PPI) network using the STRING database. Then, the Cluster Profiler R package was used to conduct GO functional enrichment evaluation and KEGG pathway enrichment analyses of the targets. Based on the PPI system, we chose the top communicating targets and substances over molecular docking. In vivo studies were performed to validate these selections further. The mouse model was induced to study the damaged sinoatrial node (SAN) in mice with lower heart rates due to age-related changes. Electrocardiogram and Masson staining assessments were performed to obtain the results. The transmission electron microscope was used to assess the autophagy level of SAN cells. Western blot was employed to analyze the impact of YXFMs on protein expression in the PI3K/AKT/FOXO signaling process throughout SSS therapy in aging mice.

RESULTS

One hundred forty-two active ingredients, 1858 targets, 1226 disease targets, and 266 intersection targets were obtained. The key targets of the PPI network encompassed TP53, AKT1, CTNNB1, INS, and TNF, among others. According to GO functional analysis, the mechanism underlying YXFMs in SSS treatment may primarily be associated with the control of ion transport across membranes, cardiac contraction, regulation of blood circulation, and other biological processes. Based on the results of KEGG pathway enrichment analysis, it was determined that they were mainly enriched in multiple pathways of signaling such as the PI3K-Akt signaling route, MAPK signaling process, AGE-RAGE signaling path, FOXO signaling path, HIF-1 signaling process, and several other paths. Molecular docking demonstrated that five compounds had excellent binding to the key candidate target proteins AKT1 and INS. Through the in vivo studies, we noticed notable effects when administering YXFMs. These effects included the suppression of aging-induced SSS, a decrease in the R-R interval, a rise in heart rate, a reduction in fibrosis, a boost in the autophagy process level, and a spike in the levels of expression of key protein molecules in the PI3K/AKT/FOXO signaling path.

CONCLUSION

This research has made preliminary predictions about the potential of YXFMs in treating SSS. It suggests that YXFMs may have the ability to target key proteins and critical paths associated with the condition. Further testing has been conducted to discover new findings and evidence of ideas for tackling SSS triggered by aging.

Dysregulated dendritic cells in sepsis: functional impairment and regulated cell death

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Studies have indicated that immune dysfunction plays a central role in the pathogenesis of sepsis. Dendritic cells (DCs) play a crucial role in the emergence of immune dysfunction in sepsis. The major manifestations of DCs in the septic state are abnormal functions and depletion in numbers, which are linked to higher mortality and vulnerability to secondary infections in sepsis. Apoptosis is the most widely studied pathway of number reduction in DCs. In the past few years, there has been a surge in studies focusing on regulated cell death (RCD). This emerging field encompasses various forms of cell death, such as necroptosis, pyroptosis, ferroptosis, and autophagy-dependent cell death (ADCD). Regulation of DC's RCD can serve as a possible therapeutic focus for the treatment of sepsis. Throughout time, numerous tactics have been devised and effectively implemented to improve abnormal immune response during sepsis progression, including modifying the functions of DCs and inhibiting DC cell death. In this review, we provide an overview of the functional impairment and RCD of DCs in septic states. Also, we highlight recent advances in targeting DCs to regulate host immune response following septic challenge.

Unraveling the intriguing interplay: Exploring the role of lncRNAs in caspase-independent cell death

Cell death plays a crucial role in various physiological and pathological processes. Until recently, programmed cell death was mainly attributed to caspase-dependent apoptosis. However, emerging evidence suggests that caspase-independent cell death (CICD) mechanisms also contribute significantly to cellular demise. We and others have reported and functionally characterized numerous long noncoding RNAs (lncRNAs) that modulate caspase-dependent apoptotic pathways potentially in a pathway-dependent manner. However, the interplay between lncRNAs and CICD pathways has not been comprehensively documented. One major reason for this is that most CICD pathways have been recently discovered with some being partially characterized at the molecular level. In this review, we discuss the emerging evidence that implicates specific lncRNAs in the regulation and execution of CICD. We summarize the diverse mechanisms through which lncRNAs modulate different forms of CICD, including ferroptosis, necroptosis, cuproptosis, and others. Furthermore, we highlight the intricate regulatory networks involving lncRNAs, protein-coding genes, and signaling pathways that orchestrate CICD in health and disease. Understanding the molecular mechanisms and functional implications of lncRNAs in CICD may unravel novel therapeutic targets and diagnostic tools for various diseases, paving the way for innovative strategies in disease management and personalized medicine. This article is categorized under: RNA in Disease and Development > RNA in Disease.

Regulated cell death and its role in Alzheimer's disease and amyotrophic lateral sclerosis

Despite considerable research efforts, it is still not clear which mechanisms underlie neuronal cell death in neurodegenerative diseases. During the last 20 years, multiple pathways have been identified that can execute regulated cell death (RCD). Among these RCD pathways, apoptosis, necroptosis, pyroptosis, ferroptosis, autophagy-related cell death, and lysosome-dependent cell death have been intensively investigated. Although RCD consists of numerous individual pathways, multiple common proteins have been identified that allow shifting from one cell death pathway to another. Another layer of complexity is added by mechanisms such as the endosomal machinery, able to regulate the activation of some RCD pathways, preventing cell death. In addition, restricted axonal degeneration and synaptic pruning can occur as a result of RCD activation without loss of the cell body. RCD plays a complex role in neurodegenerative processes, varying across different disorders. It has been shown that RCD is differentially involved in Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS), among the most common neurodegenerative diseases. In AD, neuronal loss is associated with the activation of not only necroptosis, but also pyroptosis. In ALS, on the other hand, motor neuron death is not linked to canonical necroptosis, whereas pyroptosis pathway activation is seen in white matter microglia. Despite these differences in the activation of RCD pathways in AD and ALS, the accumulation of protein aggregates immunoreactive for p62/SQSTM1 (sequestosome 1) is a common event in both diseases and many other neurodegenerative disorders. In this review, we describe the major RCD pathways with clear activation in AD and ALS, the main interactions between these pathways, as well as their differential and similar involvement in these disorders. Finally, we will discuss targeting RCD as an innovative therapeutic concept for neurodegenerative diseases, such as AD and ALS. Considering that the execution of RCD or "cellular suicide" represents the final stage in neurodegeneration, it seems crucial to prevent neuronal death in patients by targeting RCD. This would offer valuable time to address upstream events in the pathological cascade by keeping the neurons alive.

Exosomal miR-126-3p: Potential protection against vascular damage by regulating the SLC7A5/mTOR Signalling pathway in human umbilical vein endothelial cells

Systemic sclerosis (SSc) is a chronic autoimmune connective tissue disease. Vascular damage is one of the important features of SSc, which affects the progression and prognosis of the disease. MiR-126-3p is an important microRNA (miRNA) that regulates vascular structure and function, which can be transported through exosomes. However, the role of miR-126-3p in vascular damage in SSc is still unclear. Therefore, we focused on the connection between miR-126-3p and vascular damage in SSc, as well as investigated the potential role of miR-126-3p in vascular damage in SSc. First, this study successfully extracted extracellular vesicles from clinical plasma samples and characterized the exosomes within them. Then, we predicted and screened the target pathway mammalian/mechanistic target of rapamycin (mTOR) and the target gene SLC7A5 of miR-126-3p through online databases. Next, we constructed SSc mice for in vivo studies. The results showed that the expression of miR-126-3p was decreased in the plasma exosomes, while the SLC7A5 expression, autophagy, and lipid peroxidation were increased in the aorta. Luciferase reporter gene assays demonstrated that miR-126-3p can bind to SLC7A5, resulting in a decrease in its expression. In vitro experiments have shown that exosomal miR-126-3p can be internalized by human umbilical vein endothelial cells (HUVECs). The miR-126-3p group exhibited enhanced cell viability and tube formation ability, along with increased expression of the vascular formation marker CD31. Additionally, miR-126-3p downregulated the protein expression of SLC7A5 and LC3 in HUVECs, while upregulating the protein expression of mTOR, P62, PPARγ, and CPT-1. However, the effects of miR-126-3p on HUVECs were counteracted by mTOR inhibitors and enhanced by mTOR activators. The results indicated that exosomal miR-126-3p has the potential to protect against vascular injury in SSc by regulating the SLC7A5/mTOR signalling pathway in HUVECs.

Natural products targeting macroautophagy signaling in hepatocellular carcinoma therapy: Recent evidence and perspectives

Hepatocellular carcinoma (HCC), presently the second leading cause of global cancer-related mortality, continues to pose significant challenges in the realm of medical oncology, impacting both clinical drug selection and mechanistic research. Recent investigations have unveiled autophagy-related signaling as a promising avenue for HCC treatment. A growing body of research has highlighted the pivotal role of autophagy-modulating natural products in inhibiting HCC progression. In this context, we provide a concise overview of the fundamental autophagy mechanism and delineate the involvement of autophagic signaling pathways in HCC development. Additionally, we review pertinent studies demonstrating how natural products regulate autophagy to mitigate HCC. Our findings indicate that natural products exhibit cytotoxic effects through the induction of excessive autophagy, simultaneously impeding HCC cell proliferation by autophagy inhibition, thereby depriving HCC cells of essential energy. These effects have been associated with various signaling pathways, including PI3K/AKT, MAPK, AMPK, Wnt/β-catenin, Beclin-1, and ferroautophagy. These results underscore the considerable therapeutic potential of natural products in HCC treatment. However, it is important to note that the present study did not establish definitive thresholds for autophagy induction or inhibition by natural products. Further research in this domain is imperative to gain comprehensive insights into the dual role of autophagy, equipping us with a better understanding of this double-edged sword in HCC management.

The lipid basis of cell death and autophagy

ABBREVIATIONS

ACSL: acyl-CoA synthetase long chain family; DISC: death-inducing signaling complex; DAMPs: danger/damage-associated molecular patterns; Dtgn: dispersed trans-Golgi network; FAR1: fatty acyl-CoA reductase 1; GPX4: glutathione peroxidase 4; LPCAT3: lysophosphatidylcholine acyltransferase 3; LPS: lipopolysaccharide; MUFAs: monounsaturated fatty acids; MOMP: mitochondrial outer membrane permeabilization; MLKL, mixed lineage kinase domain like pseudokinase; oxPAPC: oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine; OxPCs: oxidized phosphatidylcholines; PUFAs: polyunsaturated fatty acids; POR: cytochrome p450 oxidoreductase; PUFAs: polyunsaturated fatty acids; RCD: regulated cell death; RIPK1: receptor interacting serine/threonine kinase 1; SPHK1: sphingosine kinase 1; SOAT1: sterol O-acyltransferase 1; SCP2: sterol carrier protein 2; SFAs: saturated fatty acids; SLC47A1: solute carrier family 47 member 1; SCD: stearoyl-CoA desaturase; VLCFA: very long chain fatty acids.

5-ALA localises to the autophagy compartment and increases its fluorescence upon autophagy enhancement through caloric restriction and spermidine treatment in human glioblastoma

Glioblastoma Multiforme (GBM) is the most invasive and prevalent Central Nervous System (CNS) malignancy. It is characterised by diffuse infiltrative growth and metabolic dysregulation that impairs the extent of surgical resection (EoR), contributing to its poor prognosis. 5-Aminolevulinic acid (5-ALA) fluorescence-guided surgical resection (FGR) takes advantage of the preferential generation of 5-ALA-derived fluorescence signal in glioma cells, thereby improving visualisation and enhancing the EoR. However, despite 5-ALA FGR is a widely used technique in the surgical management of malignant gliomas, the infiltrative tumour margins usually show only vague or no visible fluorescence and thus a significant amount of residual tumour tissue may hence remain in the resection cavity, subsequently driving tumour recurrence. To investigate the molecular mechanisms that govern the preferential accumulation of 5-ALA in glioma cells, we investigated the precise subcellular localisation of 5-ALA signal using Correlative Light and Electron Microscopy (CLEM) and colocalisation analyses in U118MG glioma cells. Our results revealed strong 5-ALA signal localisation in the autophagy compartment - specifically autolysosomes and lysosomes. Flow cytometry was employed to investigate whether autophagy enhancement through spermidine treatment (SPD) or nutrient deprivation/caloric restriction (CR) would enhance 5-ALA fluorescence signal generation. Indeed, SPD, CR and a combination of SPD/CR treatment significantly increased 5-ALA signal intensity, with a most robust increase in signal intensity observed in the combination treatment of SPD/CR. When using 3-D glioma spheroids to assess the effect of 5-ALA on cellular ultrastructure, we demonstrate that 5-ALA exposure leads to cytoplasmic disruption, vacuolarisation and large-scale mitophagy induction. These findings not only suggest a critical role for the autophagy compartment in 5-ALA engagement and signal generation but also point towards a novel and practically feasible approach to enhance 5-ALA fluorescence signal intensity. The findings may highlight that indeed autophagy control may serve as a promising avenue to promote an improved resection and GBM prognosis.

Autophagy-modulating biomembrane nanostructures: A robust anticancer weapon by modulating the inner and outer cancer environment

Recently, biomembrane nanostructures, such as liposomes, cell membrane-coated nanostructures, and exosomes, have demonstrated promising anticancer therapeutic effects. These nanostructures possess remarkable biocompatibility, multifunctionality, and low toxicity. However, their therapeutic efficacy is impeded by chemoresistance and radiotherapy resistance, which are closely associated with autophagy. Modulating autophagy could enhance the therapeutic sensitivity and effectiveness of these biomembrane nanostructures by influencing the immune system and the cancer microenvironment. For instance, autophagy can regulate the immunogenic cell death of cancer cells, antigen presentation of dendritic cells, and macrophage polarization, thereby activating the inflammatory response in the cancer microenvironment. Furthermore, combining autophagy-regulating drugs or genes with biomembrane nanostructures can exploit the targeting and long-term circulation properties of these nanostructures, leading to increased drug accumulation in cancer cells. This review explores the role of autophagy in carcinogenesis, cancer progression, metastasis, cancer immune responses, and resistance to treatment. Additionally, it highlights recent research advancements in the synergistic anticancer effects achieved through autophagy regulation by biomembrane nanostructures. The review also discusses the prospects and challenges associated with the future clinical translation of these innovative treatment strategies. In summary, these findings provide valuable insights into autophagy, autophagy-modulating biomembrane-based nanostructures, and the underlying molecular mechanisms, thereby facilitating the development of promising cancer therapeutics.

The beneficial role of autophagy in multiple sclerosis: Yes or No?

Multiple sclerosis (MS) is a chronic progressive demyelinating disease of the central nervous system (CNS) due to an increase of abnormal peripherally auto-reactive T lymphocytes which elicit autoimmunity. The main pathophysiology of MS is myelin sheath damage by immune cells and a defect in the generation of myelin by oligodendrocytes. Macroautophagy/autophagy is a critical degradation process that eliminates dysfunctional or superfluous cellular components. Autophagy has the property of a double-edged sword in MS in that it may have both beneficial and detrimental effects on MS neuropathology. Therefore, this review illustrates the protective and harmful effects of autophagy with regard to this disease. Autophagy prevents the progression of MS by reducing oxidative stress and inflammatory disorders. In contrast, over-activated autophagy is associated with the progression of MS neuropathology and in this case the use of autophagy inhibitors may alleviate the pathogenesis of MS. Furthermore, autophagy provokes the activation of different immune and supporting cells that play an intricate role in the pathogenesis of MS. Autophagy functions in the modulation of MS neuropathology by regulating cell proliferation related to demyelination and remyelination. Autophagy enhances remyelination by increasing the activity of oligodendrocytes, and astrocytes. However, autophagy induces demyelination by activating microglia and T cells. In conclusion, specific autophagic activators of oligodendrocytes, and astrocytes, and specific autophagic inhibitors of dendritic cells (DCs), microglia and T cells induce protective effects against the pathogenesis of MS.Abbreviations: ALS: amyotrophic lateral sclerosis; APCs: antigen-presenting cells; BBB: blood-brain barrier; CSF: cerebrospinal fluid; CNS: central nervous system; DCs: dendritic cells; EAE: experimental autoimmune encephalomyelitis; ER: endoplasmic reticulum; LAP: LC3-associated phagocytosis; MS: multiple sclerosis; NCA: non-canonical autophagy; OCBs: oligoclonal bands; PBMCs: peripheral blood mononuclear cells; PD: Parkinson disease; ROS: reactive oxygen species; UPR: unfolded protein response.

Effect of ATG8 or SAC1 deficiency on the cell proliferation and lifespan of the long-lived PMT1 deficiency yeast cells

Autophagy is pivotal in maintaining intracellular homeostasis, which involves various biological processes, including cellular senescence and lifespan modulation. Being an important member of the protein O-mannosyltransferase (PMT) family of enzymes, Pmt1p deficiency can significantly extend the replicative lifespan (RLS) of yeast cells through an endoplasmic reticulum (ER) unfolded protein response (UPR) pathway, which is participated in protein homeostasis. Nevertheless, the mechanisms that Pmt1p regulates the lifespan of yeast cells still need to be explored. In this study, we found that the long-lived PMT1 deficiency strain (pmt1Δ) elevated the expression levels of most autophagy-related genes, the expression levels of total GFP-Atg8 fusion protein and free GFP protein compared with wild-type yeast strain (BY4742). Moreover, the long-lived pmt1Δ strain showed the greater dot-signal accumulation from GFP-Atg8 fusion protein in the vacuole lumen through a confocal microscope. However, deficiency of SAC1 or ATG8, two essential components of the autophagy process, decreased the cell proliferation ability of the long-lived pmt1Δ yeast cells, and prevented the lifespan extension. In addition, our findings demonstrated that overexpression of ATG8 had no potential effect on the RLS of the pmt1Δ yeast cells, and the maintained incubation of minimal synthetic medium lacking nitrogen (SD-N medium as starvation-induced autophagy) inhibited the cell proliferation ability of the pmt1Δ yeast cells with the culture time, and blocked the lifespan extension, especially in the SD-N medium cultured for 15 days. Our results suggest that the long-lived pmt1Δ strain enhances the basal autophagy activity, while deficiency of SAC1 or ATG8 decreases the cell proliferation ability and shortens the RLS of the long-lived pmt1Δ yeast cells. Moreover, the maintained starvation-induced autophagy impairs extension of the long-lived pmt1Δ yeast cells, and even leads to the cell death.

Interplay of energy metabolism and autophagy

Macroautophagy/autophagy, is widely recognized for its crucial role in enabling cell survival and maintaining cellular energy homeostasis during starvation or energy stress. Its regulation is intricately linked to cellular energy status. In this review, covering yeast, mammals, and plants, we aim to provide a comprehensive overview of the understanding of the roles and mechanisms of carbon- or glucose-deprivation related autophagy, showing how cells effectively respond to such challenges for survival. Further investigation is needed to determine the specific degraded substrates by autophagy during glucose or energy deprivation and the diverse roles and mechanisms during varying durations of energy starvation.Abbreviations: ADP: adenosine diphosphate; AMP: adenosine monophosphate; AMPK: AMP-activated protein kinase; ATG: autophagy related; ATP: adenosine triphosphate; ER: endoplasmic reticulum; ESCRT: endosomal sorting complex required for transport; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GD: glucose deprivation; GFP: green fluorescent protein; GTPases: guanosine triphosphatases; HK2: hexokinase 2; K phaffii: Komagataella phaffii; LD: lipid droplet; MAP1LC3/LC3: microtubule-associated protein1 light chain 3; MAPK: mitogen-activated protein kinase; Mec1: mitosis entry checkpoint 1; MTOR: mechanistic target of rapamycin kinase; NAD (+): nicotinamide adenine dinucleotide; OGD: oxygen and glucose deprivation; PAS: phagophore assembly site; PCD: programmed cell death; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; ROS: reactive oxygen species; S. cerevisiae: Saccharomyces cerevisiae; SIRT1: sirtuin 1; Snf1: sucrose non-fermenting 1; STK11/LKB1: serine/threonine kinase 11; TFEB: transcription factor EB; TORC1: target of rapamycin complex 1; ULK1: unc-51 like kinase 1; Vps27: vacuolar protein sorting 27; Vps4: vacuolar protein sorting 4.

Differential induction of C6 glioma apoptosis and autophagy by 3β-hydroxysteroid-indolamine conjugates

In a previous work, we reported the synthesis of four novel indole steroids and their effect on rat C6 glioma proliferation in vitro. The steroid derived from dehydroepiandrosterone and tryptamine (IS-1) was the most active (52 % inhibition at 10 µM), followed by one of the epimers derived from pregnenolone and tryptamine (IS-3, 36 % inhibition at 10 µM). By contrast, the steroid derived from estrone and tryptamine (IS-2) showed negligible activity at 10 µM. No necrosis, increase in intracellular calcium or ROS levels was observed. In this work, the effect of compounds on C6 glioma apoptosis and autophagy is examined by fluorimetry and fluorescent microscopy. The IS-3 epimers disrupt the mitochondrial membrane potential and induce apoptosis in vitro moderately whereas IS-1 and IS-2 do not. However, IS-1 produces a large increase in monodansylcadaverine-positive autophagic vesicles over 24 h. The antiproliferative effect of indole steroids is ameliorated by autophagy inhibitor hydroxychloroquine, suggesting an autophagy-dependent mechanism of cell death.

Making a good egg: human oocyte health, aging, and in vitro development

Mammalian eggs (oocytes) are formed during fetal life and establish associations with somatic cells to form primordial follicles that create a store of germ cells (the primordial pool). The size of this pool is influenced by key events during the formation of germ cells and by factors that influence the subsequent activation of follicle growth. These regulatory pathways must ensure that the reserve of oocytes within primordial follicles in humans lasts for up to 50 years, yet only approximately 0.1% will ever be ovulated with the rest undergoing degeneration. This review outlines the mechanisms and regulatory pathways that govern the processes of oocyte and follicle formation and later growth, within the ovarian stroma, through to ovulation with particular reference to human oocytes/follicles. In addition, the effects of aging on female reproductive capacity through changes in oocyte number and quality are emphasized, with both the cellular mechanisms and clinical implications discussed. Finally, the details of current developments in culture systems that support all stages of follicle growth to generate mature oocytes in vitro and emerging prospects for making new oocytes from stem cells are outlined.

Acid sphingomyelinase mediates ferroptosis induced by high glucose via autophagic degradation of GPX4 in type 2 diabetic osteoporosis

BACKGROUND

Ferroptosis has been implicated in the pathological process of type 2 diabetic osteoporosis (T2DOP), although the specific underlying mechanisms remain largely unknown. This study aimed to clarify the role and possible mechanism of acid sphingomyelinase (ASM)-mediated osteoblast ferroptosis in T2DOP.

METHODS

We treated hFob1.19 cells with normal glucose (NG) and different concentrations of high glucose (HG, 26.25 mM, 35 mM, or 43.75 mM) for 48 h. We then measured cell viability and osteogenic function, quantified ferroptosis and autophagy levels, and measured the levels of ASM and ceramide in the cells. To further investigate the specific mechanism, we examined these indicators by knocking down ASM expression, hydroxychloroquine (HCQ) treatment, or N-acetylcysteine (NAC) treatment. Moreover, a T2DOP rat model was induced and microcomputed tomography was used to observe the bone microstructure. We also evaluated the serum levels of iron metabolism-associated factors, ceramide and lipid peroxidation (LPO) and measured the expression of ASM, LC3 and GPX4 in bone tissues.

RESULTS

HG inhibited the viability and osteogenic function of osteoblasts by inducing ferroptosis in a concentration-dependent manner. Furthermore, the expression of ASM and ceramide and autophagy levels were increased by HG treatment, and these factors were required for the HG-induced reactive oxygen species (ROS) generation and LPO. Similarly, inhibiting intracellular ROS also reduced HG-induced ASM activation and autophagy. ASM-mediated activation of autophagy was crucial for HG-induced degradation of GPX4, and inhibiting ASM improved osteogenic function by decreasing HG-induced autophagy, GPX4 degradation, LPO and subsequent ferroptosis. We also found that inhibiting ASM could alleviated ferroptosis and autophagy and improved osteogenic function in a T2DOP rat model.

CONCLUSION

ASM-mediated autophagy activation induces osteoblast ferroptosis under HG conditions through the degradation of GPX4, providing a novel mechanistic insight into the treatment and prevention of T2DOP.

Cogs in the autophagic machine-equipped to combat dementia-prone neurodegenerative diseases

Neurodegenerative diseases are often characterized by hydrophobic inclusion bodies, and it may be the case that the aggregate-prone proteins that comprise these inclusion bodies are in fact the cause of neurotoxicity. Indeed, the appearance of protein aggregates leads to a proteostatic imbalance that causes various interruptions in physiological cellular processes, including lysosomal and mitochondrial dysfunction, as well as break down in calcium homeostasis. Oftentimes the approach to counteract proteotoxicity is taken to merely upregulate autophagy, measured by an increase in autophagosomes, without a deeper assessment of contributors toward effective turnover through autophagy. There are various ways in which autophagy is regulated ranging from the mammalian target of rapamycin (mTOR) to acetylation status of proteins. Healthy mitochondria and the intracellular energetic charge they preserve are key for the acidification status of lysosomes and thus ensuring effective clearance of components through the autophagy pathway. Both mitochondria and lysosomes have been shown to bear functional protein complexes that aid in the regulation of autophagy. Indeed, it may be the case that minimizing the proteins associated with the respective neurodegenerative pathology may be of greater importance than addressing molecularly their resulting inclusion bodies. It is in this context that this review will dissect the autophagy signaling pathway, its control and the manner in which it is molecularly and functionally connected with the mitochondrial and lysosomal system, as well as provide a summary of the role of autophagy dysfunction in driving neurodegenerative disease as a means to better position the potential of rapamycin-mediated bioactivities to control autophagy favorably.

Autophagy deficiency protects against ocular hypertension and neurodegeneration in experimental and spontanous glaucoma mouse models

Glaucoma is a group of diseases that leads to chronic degeneration of retinal ganglion cell (RGC) axons and progressive loss of RGCs, resulting in vision loss. While aging and elevated intraocular pressure (IOP) have been identified as the main contributing factors to glaucoma, the molecular mechanisms and signaling pathways triggering RGC death and axonal degeneration are not fully understood. Previous studies in our laboratory found that overactivation of autophagy in DBA/2J::GFP-LC3 mice led to RGC death and optic nerve degeneration with glaucomatous IOP elevation. We found similar findings in aging GFP-LC3 mice subjected to chronic IOP elevation. Here, we further investigated the impact of autophagy deficiency on autophagy-deficient DBA/2J-Atg4bko and DBA/2J-Atg4b+/- mice, generated in our laboratory via CRISPR/Cas9 technology; as well as in Atg4bko mice subjected to the experimental TGFβ2 chronic ocular hypertensive model. Our data shows that, in contrast to DBA/2J and DBA/2J-Atg4b+/- littermates, DBA/2J-Atg4bko mice do not develop glaucomatous IOP elevation. Atg4b deficiency also protected against glaucomatous IOP elevation in the experimental TGFβ2 chronic ocular hypertensive model. Atg4 deletion did not compromise RGC or optic nerve survival in Atg4bko mice. Moreover, our results indicate a protective role of autophagy deficiency against RGC death and ON atrophy in the hypertensive DBA/2J-Atg4b+/- mice. Together, our data suggests a pathogenic role of autophagy activation in ocular hypertension and glaucoma.

Beyond apoptosis: evidence of other regulated cell death pathways in the ovary throughout development and life

BACKGROUND

Regulated cell death is a fundamental component of numerous physiological processes; spanning from organogenesis in utero, to normal cell turnover during adulthood, as well as the elimination of infected or damaged cells throughout life. Quality control through regulation of cell death pathways is particularly important in the germline, which is responsible for the generation of offspring. Women are born with their entire supply of germ cells, housed in functional units known as follicles. Follicles contain an oocyte, as well as specialized somatic granulosa cells essential for oocyte survival. Follicle loss-via regulated cell death-occurs throughout follicle development and life, and can be accelerated following exposure to various environmental and lifestyle factors. It is thought that the elimination of damaged follicles is necessary to ensure that only the best quality oocytes are available for reproduction.

OBJECTIVE AND RATIONALE

Understanding the precise factors involved in triggering and executing follicle death is crucial to uncovering how follicle endowment is initially determined, as well as how follicle number is maintained throughout puberty, reproductive life, and ovarian ageing in women. Apoptosis is established as essential for ovarian homeostasis at all stages of development and life. However, involvement of other cell death pathways in the ovary is less established. This review aims to summarize the most recent literature on cell death regulators in the ovary, with a particular focus on non-apoptotic pathways and their functions throughout the discrete stages of ovarian development and reproductive life.

SEARCH METHODS

Comprehensive literature searches were carried out using PubMed and Google Scholar for human, animal, and cellular studies published until August 2022 using the following search terms: oogenesis, follicle formation, follicle atresia, oocyte loss, oocyte apoptosis, regulated cell death in the ovary, non-apoptotic cell death in the ovary, premature ovarian insufficiency, primordial follicles, oocyte quality control, granulosa cell death, autophagy in the ovary, autophagy in oocytes, necroptosis in the ovary, necroptosis in oocytes, pyroptosis in the ovary, pyroptosis in oocytes, parthanatos in the ovary, and parthanatos in oocytes.

OUTCOMES

Numerous regulated cell death pathways operate in mammalian cells, including apoptosis, autophagic cell death, necroptosis, and pyroptosis. However, our understanding of the distinct cell death mediators in each ovarian cell type and follicle class across the different stages of life remains the source of ongoing investigation. Here, we highlight recent evidence for the contribution of non-apoptotic pathways to ovarian development and function. In particular, we discuss the involvement of autophagy during follicle formation and the role of autophagic cell death, necroptosis, pyroptosis, and parthanatos during follicle atresia, particularly in response to physiological stressors (e.g. oxidative stress).

WIDER IMPLICATIONS

Improved knowledge of the roles of each regulated cell death pathway in the ovary is vital for understanding ovarian development, as well as maintenance of ovarian function throughout the lifespan. This information is pertinent not only to our understanding of endocrine health, reproductive health, and fertility in women but also to enable identification of novel fertility preservation targets.

Lower dose of metformin combined with artesunate induced autophagy-dependent apoptosis of glioblastoma by activating ROS-AMPK-mTOR axis

Glioblastoma multiform (GBM), one of the most common, aggressive primary brain tumours, demonstrates resistance to radiotherapy and chemotherapy after surgical resection and treatment failure. Metformin (MET) has been shown to suppress the proliferative capacity and invasion ability of GBM cells by activating AMPK and inhibiting mTOR, but the effective dose exceeded the maximum tolerated dose. Artesunate (ART) can exert certain anti-tumour effects by activating the AMPK-mTOR axis and inducing autophagy in tumour cells. Therefore, this study investigated the effects of MET combined with ART combination therapy on autophagy and apoptosis in GBM cells. MET combined with ART treatment effectively suppressed the viability, mono-cloning ability, migration and invasion capacities, as well as metastatic ability of GBM cells. The underlying mechanism involved modulation of the ROS-AMPK-mTOR axis, which was confirmed using 3-methyladenine and rapamycin to inhibit or promote the effects of MET combined with ART, respectively. The study findings suggest that MET used in combination with ART can induce autophagy-dependent apoptosis in GBM cells by activating the ROS-AMPK-mTOR pathway, providing a potential new treatment for GBM.

Advances in tumor nanotechnology: theragnostic implications in tumors via targeting regulated cell death

Cell death constitutes an indispensable part of the organismal balance in the human body. Generally, cell death includes regulated cell death (RCD) and accidental cell death (ACD), reflecting the intricately molecule-dependent process and the uncontrolled response, respectively. Furthermore, diverse RCD pathways correlate with multiple diseases, such as tumors and neurodegenerative diseases. Meanwhile, with the development of precision medicine, novel nano-based materials have gradually been applied in the clinical diagnosis and treatment of tumor patients. As the carrier, organic, inorganic, and biomimetic nanomaterials could facilitate the distribution, improve solubility and bioavailability, enhance biocompatibility and decrease the toxicity of drugs in the body, therefore, benefiting tumor patients with better survival outcomes and quality of life. In terms of the most studied cell death pathways, such as apoptosis, necroptosis, and pyroptosis, plenty of studies have explored specific types of nanomaterials targeting the molecules and signals in these pathways. However, no attempt was made to display diverse nanomaterials targeting different RCD pathways comprehensively. In this review, we elaborate on the potential mechanisms of RCD, including intrinsic and extrinsic apoptosis, necroptosis, ferroptosis, pyroptosis, autophagy-dependent cell death, and other cell death pathways together with corresponding nanomaterials. The thorough presentation of RCD pathways and diverse nano-based materials may provide a wider cellular and molecular landscape of tumor diagnosis and treatments.

PCK1 activates oncogenic autophagy via down-regulation Serine phosphorylation of UBAP2L and antagonizes colorectal cancer growth

Phosphoenolpyruvate carboxykinase 1 (PCK1) is the rate-limiting enzyme in gluconeogenesis. PCK1 is considered an anti-oncogene in several human cancers. In this study, we aimed to determine the functions of PCK1 in colorectal cancer (CRC). PCK1 expression in CRC tissues was tested by western blot and immunohistochemistry analyses and associations of PCK1 level with clinicopathological characteristics and disease survival evaluated. Further, we studied the effect of PCK1 on CRC cell proliferation and the underlying mechanisms. Our results show that PCK1 is expressed at significantly lower levels in CRC than in control tissues. High PCK1 expression was correlated with smaller tumor diameter and less bowel wall invasion (T stage). Overexpression and knockdown experiments demonstrated that PCK1 inhibits CRC cell growth both in vitro and in vivo. Mechanistically, PCK1 antagonizes CRC growth via inactivating UBAP2L phosphorylation at serine 454 and enhancing autophagy. Overall, our findings reveal a novel molecular mechanism involving PCK1 and autophagy, and highlight PCK1 as a promising candidate therapeutic target in CRC.

Endoplasmic reticulum stress regulates autophagic response that is involved in Saikosaponin a-induced liver cell damage

Saikosaponin a (Ssa) is an active ingredient of the Chinese herbal plant Radix Bupleuri (RB) and has severe hepatotoxicity. However, biomolecular mechanisms involved in Ssa-induced hepatotoxicity are not yet entirely clear. Previous studies reported that Ssd (an isomer of Ssa) as a sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) inhibitor can induce autophagy in apoptotic defective cells, leading to autophagy-dependent cell death. Therefore, we speculate that endoplasmic reticulum (ER) stress and autophagy may also play an important role in Ssa-induced hepatocyte death. This study aimed to explore the connection between ER stress and autophagy and Ssa-induced hepatotoxicity. Experiments in vitro showed that the cell viability of L-02 cells in the Ssa treatment group decreased, the level of autophagy marker LC3-II/LC3-I and Beclin1 increased, the level of p62 decreased, the colocalization of autophagosome and lysosome increased, and the cell viability was significantly increased after the application of autophagy inhibitors 3-MA. In addition, SSa can induce ER stress in L-02 cells in vitro. Further studies demonstrated that SSa activated the PERK/eIF2α/ATF4/CHOP pathway, IRE1-TRAF2 pathway, ATF6 pathway, and AMPK/mTOR pathway associated with ER stress. Application of ER stress inhibitors 4-PBA can significantly down-regulate the level of autophagy and improve cell viability. Results of in vivo experiments showed that treatment with 150 and 300 mg/kg Ssa significantly elevated the liver/body weight ratio and caused histological injury in mice liver. Furthermore, Ssa treatment induced significantly downregulated p62 expression but upregulated LC3-II, CHOP, and GRP78 expression in mice livers. Taken together, our results showed that SSa can activate endoplasmic reticulum stress, promote toxic autophagy, and then induce cell death. We revealed an alternative mechanism involving autophagy and ERs, by which Ssa induced hepatotoxicity.

Oleoylethanolamide alleviates hyperlipidaemia-mediated vascular calcification via attenuating mitochondrial DNA stress triggered autophagy-dependent ferroptosis by activating PPARα

Vascular calcification, a prevalent pathological alteration in metabolic syndromes, is tightly related with cardiometabolic risk events. Ferroptosis, a newly iron-dependent programmed cell death, induced by palmitic acid (PA), the major saturated free fatty acid in hyperlipidemia, is a vital mechanism of vascular calcification. Recent studies reported that ferroptosis is a distinctive type of cell death dependent on autophagy, with the lipotoxicity of PA on cell viability being closely linked with autophagy. Oleoylethanolamide (OEA), an endogenous bioactive mediator of lipid homeostasis, exerts vascular protection against intimal calcification, atherosclerosis; however, its beneficial effect on vascular smooth muscle cell (VSMC)-associated medial calcification has not been investigated. Our aim was to characterize the effect of OEA on vascular calcification and ferroptosis of VSMCs under hyperlipidaemia/PA exposure. In vivo, vascular calcification model was induced in rats by high-fat diet and vitamin D3 plus nicotine; in vitro, VSMCs ferroptosis was induced by PA or plus β-glycerophosphate mimicking vascular calcification. The calcium deposition in hyperlipidaemia-mediated rat thoracic aortas, the PA-induced ferroptosis and subsequent calcium deposition in VSMCs, were suppressed by OEA treatment. Additionally, CGAS-STING1-induced ferritinophagy, the main molecular mechanism of PA-triggered ferroptosis of VSMCs, was activated by mitochondrial DNA damage; however, early administration of OEA alleviated these phenomena. Intriguingly, overexpression of peroxisome proliferator activated receptor alpha (PPARα) contributed to a decrease in PA-induced ferroptosis, whereas PPARɑ knockdown inhibited the OEA-mediated anti-ferroptotic effects. Collectively, our study demonstrated that OEA serves as a prospective candidate for the prevention and treatment of vascular calcification in metabolic abnormality syndromes.

Transcription factor EB as a key molecular factor in human health and its implication in diseases

Transcription factor EB, as a component of the microphthalmia family of transcription factors, has been demonstrated to be a key controller of autophagy-lysosomal biogenesis. Transcription factor EB is activated by stressors such as nutrition and deprivation of growth factors, hypoxia, lysosomal stress, and mitochondrial injury. To achieve the ultimate functional state, it is controlled in a variety of modes, such as in its rate of transcription, post-transcriptional control, and post-translational alterations. Due to its versatile role in numerous signaling pathways, including the Wnt, calcium, AKT, and mammalian target of rapamycin complex 1 signaling pathways, transcription factor EB-originally identified to be an oncogene-is now well acknowledged as a regulator of a wide range of physiological systems, including autophagy-lysosomal biogenesis, response to stress, metabolism, and energy homeostasis. The well-known and recently identified roles of transcription factor EB suggest that this protein might play a central role in signaling networks in a number of non-communicable illnesses, such as cancer, cardiovascular disorders, drug resistance mechanisms, immunological disease, and tissue growth. The important developments in transcription factor EB research since its first description are described in this review. This review helps to advance transcription factor EB from fundamental research into therapeutic and regenerative applications by shedding light on how important a role it plays in human health and disease at the molecular level.

Apoptosis, Proliferation, and Autophagy Are Involved in Local Anesthetic-Induced Cytotoxicity of Human Breast Cancer Cells

Breast cancer accounts for almost one quarter of all female cancers worldwide, and more than 90% of those who are diagnosed with breast cancer undergo mastectomy or breast conservation surgery. Local anesthetics effectively inhibit the invasion of cancer cells at concentrations that are used in surgical procedures. The limited treatment options for triple-negative breast cancer (TNBC) demonstrate unmet clinical needs. In this study, four local anesthetics, lidocaine, levobupivacaine, bupivacaine, and ropivacaine, were applied to two breast tumor cell types, TNBC MDA-MB-231 cells and triple-positive breast cancer BT-474 cells. In addition to the induction of apoptosis and the suppression of the cellular proliferation rate, the four local anesthetics decreased the levels of reactive oxygen species and increased the autophagy elongation indicator in both cell types. Our combination index analysis with doxorubicin showed that ropivacaine had a synergistic effect on the two cell types, and lidocaine had a synergistic effect only in MDA-MB-231 cells; the others had no synergistic effects on doxorubicin. Lidocaine contributed significantly to the formation of autophagolysosomes in a dose-dependent manner in MDA-MB-231 cells but not in BT-474 cells. Our study demonstrated that the four local anesthetics can reduce tumor growth and proliferation and promote apoptosis and autophagy.

The role of autophagic cell death in cardiac disease

Cardiomyocytes undergo various forms of cell death during heart disease such as myocardial infarction and heart failure. Understanding the mechanisms of cell death in cardiomyocytes is one of the most fundamental issues in the treatment of heart failure. Among the several kinds of cell death mechanisms, this review will focus on autophagy-related cardiomyocyte cell death. Although autophagy plays an essential role in mediating cellular quality control mechanisms for cell survival, dysregulation of autophagy can cause cell death, referred to as autophagy-dependent cell death or type II programmed cell death. The recent discovery of autosis as a modality of autophagy-dependent cell death with unique morphological and biochemical features has allowed us to broaden our understanding of the mechanistic role of autophagy in cell death. Here, we discuss autophagy-dependent cardiomyocyte cell death, including autosis, in pathophysiological conditions of the heart.

Proton-coupled monocarboxylate transporters in cancer: From metabolic crosstalk, immunosuppression and anti-apoptosis to clinical applications

The Warburg effect is known as the hyperactive glycolysis that provides the energy needed for rapid growth and proliferation in most tumor cells even under the condition of sufficient oxygen. This metabolic pattern can lead to a large accumulation of lactic acid and intracellular acidification, which can affect the growth of tumor cells and lead to cell death. Proton-coupled monocarboxylate transporters (MCTs) belong to the SLC16A gene family, which consists of 14 members. MCT1-4 promotes the passive transport of monocarboxylate (e.g., lactate, pyruvate, and ketone bodies) and proton transport across membranes. MCT1-4-mediated lactate shuttling between glycolytic tumor cells or cancer-associated fibroblasts and oxidative tumor cells plays an important role in the metabolic reprogramming of energy, lipids, and amino acids and maintains the survival of tumor cells. In addition, MCT-mediated lactate signaling can promote tumor angiogenesis, immune suppression and multidrug resistance, migration and metastasis, and ferroptosis resistance and autophagy, which is conducive to the development of tumor cells and avoid death. Although there are certain challenges, the study of targeted drugs against these transporters shows great promise and may form new anticancer treatment options.

Hyperthermia and doxorubicin release by Fol-LSMO nanoparticles induce apoptosis and autophagy in breast cancer cells

Background: Studies on the anticancer effects of lanthanum strontium manganese oxide (LSMO) nanoparticles (NPs)-mediated hyperthermia at cellular and molecular levels are scarce. Materials & methods: LSMO NPs conjugated with folic acid (Fol-LSMO NPs) were synthesized, followed by doxorubicin-loading (DoxFol-LSMO NPs), and their effects on breast cancer cells were investigated. Results: Hyperthermia (45°C) and combination treatments exhibited the highest (∼95%) anticancer activity with increased oxidative stress. The involvement of intrinsic mitochondria-mediated apoptotic pathway and induction of autophagy was noted. Cellular and molecular evidence confirmed the crosstalk between apoptosis and autophagy, involving Beclin1, Bcl2 and Caspase-3 genes with free reactive oxygen species presence. Conclusion: The study confirmed hyperthermia and doxorubicin release by Fol-LSMO NPs induces apoptosis and autophagy in breast cancer cells.

Preclinical investigation of artesunate as a therapeutic agent for hepatocellular carcinoma via impairment of glucosylceramidase-mediated autophagic degradation

Artesunate (ART) has been indicated as a candidate drug for hepatocellular carcinoma (HCC). Glucosylceramidase (GBA) is required for autophagic degradation. Whether ART regulates autophagic flux by targeting GBA in HCC remains to be defined. Herein, our data demonstrated that the dramatic overexpression of GBA was significantly associated with aggressive progression and short overall survival times in HCC. Subsequent experiments revealed an association between autophagic activity and GBA expression in clinical HCC samples, tumor tissues from a rat model of inflammation-induced HCC and an orthotopic mouse model, and human HCC cell lines. Interestingly, probe labeling identified GBA as an ART target, which was further verified by both a glutathione-S-transferase pulldown assay and surface plasmon resonance analysis. The elevated protein expression of LC3B, the increased numbers of GFP-LC3B puncta and double-membrane vacuoles, and the enhanced expression of SQSTM1/p62 indicated that the degradation of autophagosomes in HCC cells was inhibited by ART treatment. Both the in vitro and in vivo data revealed that autophagosome accumulation through targeting of GBA was responsible for the anti-HCC effects of ART. In summary, this preclinical study identified GBA as one of the direct targets of ART, which may have promising potential to inhibit lysosomal autophagy for HCC therapy.

Confirmation that the malaria drug artesunate targets a key enzyme overexpressed in aggressive liver cancer suggests it may be a novel therapeutic option for the disease. High levels of an enzyme called glucosylceramidase (GBA) are associated with poor prognosis in liver cancer, according to research conducted by Yanqiong Zhang and Na Lin at the Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, and co-workers. In experiments on rat and mouse models and human cell lines, the team demonstrated that high GBA levels over activated autophagic flux, accelerated the rate at which cellular material may be degraded and recycled in balanced, healthy cells. This disturbance enables liver cancer to progress. The researchers found that artesunate can suppress GBA expression levels and restore normal autophagic flux, boosting the drug’s anticancer activity.

ZNF143 regulates autophagic flux to alleviate myocardial ischemia/reperfusion injury through Raptor

The exact role of autophagy in myocardial ischemia/reperfusion (I/R) injury is still controversial. Excessive or insufficient autophagy may lead to cell death. Therefore, how to regulate autophagic balance during myocardial ischemia/reperfusion is critical to the treatment of myocardial I/R injury. Raptor is an mTOR regulatory related protein and closely related to the induction of autophagy. ZNF143 is widely expressed in various cells and acts as a transcription factor, which is involved in the regulation of autophagy, cell growth and development. In this study, we aimed to explore the mechanism by which ZNF143 regulated autophagy in myocardial I/R injury and the relationship between ZNF143 and Raptor. In our results, we found that ZNF143 expression was down-regulated in myocardial I/R. Inhibition of ZNF143 expression further enhanced autophagy and restored the deficiency of autophagic flux caused by myocardial I/R, subsequently alleviating myocardial I/R injury. On the other hand, overexpression of ZNF143 up-regulated Raptor expression and reduced autophagic activity, consequently exacerbating myocardial I/R injury. Taken together, our study revealed that ZNF143 might be a key target of the regulation of autophagy and a novel therapeutic target of myocardial I/R injury.

Past, present, and future perspectives of transcription factor EB (TFEB): mechanisms of regulation and association with disease

Transcription factor EB (TFEB), a member of the MiT/TFE family of basic helix-loop-helix leucine zipper transcription factors, is an established central regulator of the autophagy/lysosomal-to-nucleus signaling pathway. Originally described as an oncogene, TFEB is now widely known as a regulator of various processes, such as energy homeostasis, stress response, metabolism, and autophagy-lysosomal biogenesis because of its extensive involvement in various signaling pathways, such as mTORC1, Wnt, calcium, and AKT signaling pathways. TFEB is also implicated in various human diseases, such as lysosomal storage disorders, neurodegenerative diseases, cancers, and metabolic disorders. In this review, we present an overview of the major advances in TFEB research over the past 30 years, since its description in 1990. This review also discusses the recently discovered regulatory mechanisms of TFEB and their implications for human diseases. We also summarize the moonlighting functions of TFEB and discuss future research directions and unanswered questions in the field. Overall, this review provides insight into our understanding of TFEB as a major molecular player in human health, which will take us one step closer to promoting TFEB from basic research into clinical and regenerative applications.

MiR-21 modulates proliferation and apoptosis of human airway smooth muscle cells by regulating autophagy via PARP-1/AMPK/mTOR signalling pathway

Superfluous human airway smooth muscle (HASM) cell proliferation is an important pathological feature of airway remodelling in asthma. This study aimed to determine whether miR-21 is involved in the regulation of HASM cell survival. Overexpressed miR-21 inhibited HASM cell apoptosis and autophagy and promoted proliferation, whereas a miR-21 inhibitor exerted the opposite effects (P < 0.05). Overexpressed poly (ADP-ribose) polymerase-1 (PARP-1) promoted apoptosis and inhibited proliferation of HASM cells (P < 0.05). Dual-luciferase assays confirmed that miR-21 directly targeted poly (ADP-ribose) polymerase-1 (PARP-1) mRNA (P < 0.05). Silencing PARP-1 based on miR-21 downregulation mimicked the role of 3-methyladenine (3-MA), an autophagy inhibitor (P < 0.05). Overexpressed PARP-1 reversed the effects of miR-21 on HASM cells, somewhat dependently on PARP-1-induced enhanced autophagy, which we elucidated by 3-MA block (P < 0.05). MicroRNA-21 mimics reduced AMPK and increased mTOR signalling by downregulating PARP-1, and a miR-21 inhibitor exerted the opposite effects (P < 0.05). Collectively, miR-21 inhibitor could upregulate PARP-1 in HASM cells to promote autophagy and thus inhibit proliferation and promote apoptosis that might be mediated by the AMPK/mTOR signalling pathway.

Neuronal Death Mechanisms and Therapeutic Strategy in Ischemic Stroke

Ischemic stroke caused by intracranial vascular occlusion has become increasingly prevalent with considerable mortality and disability, which gravely burdens the global economy. Current relatively effective clinical treatments are limited to intravenous alteplase and thrombectomy. Even so, patients still benefit little due to the short therapeutic window and the risk of ischemia/reperfusion injury. It is therefore urgent to figure out the neuronal death mechanisms following ischemic stroke in order to develop new neuroprotective strategies. Regarding the pathogenesis, multiple pathological events trigger the activation of cell death pathways. Particular attention should be devoted to excitotoxicity, oxidative stress, and inflammatory responses. Thus, in this article, we first review the principal mechanisms underlying neuronal death mediated by these significant events, such as intrinsic and extrinsic apoptosis, ferroptosis, parthanatos, pyroptosis, necroptosis, and autophagic cell death. Then, we further discuss the possibility of interventions targeting these pathological events and summarize the present pharmacological achievements.

Parthenolide and Its Soluble Analogues: Multitasking Compounds with Antitumor Properties

Due to its chemical properties and multiple molecular effects on different tumor cell types, the sesquiterpene lactone parthenolide (PN) can be considered an effective drug with significant potential in cancer therapy. PN has been shown to induce either classic apoptosis or alternative caspase-independent forms of cell death in many tumor models. The therapeutical potential of PN has been increased by chemical design and synthesis of more soluble analogues including dimethylaminoparthenolide (DMAPT). This review focuses on the molecular mechanisms of both PN and analogues action in tumor models, highlighting their effects on gene expression, signal transduction and execution of different types of cell death. Recent findings indicate that these compounds not only inhibit prosurvival transcriptional factors such as NF-κB and STATs but can also determine the activation of specific death pathways, increasing intracellular reactive oxygen species (ROS) production and modifications of Bcl-2 family members. An intriguing property of these compounds is its specific targeting of cancer stem cells. The unusual actions of PN and its analogues make these agents good candidates for molecular targeted cancer therapy.

The regulation, function, and role of lipophagy, a form of selective autophagy, in metabolic disorders

Autophagy is a conserved method of quality control in which cytoplasmic contents are degraded via lysosomes. Lipophagy, a form of selective autophagy and a novel type of lipid metabolism, has recently received much attention. Lipophagy is defined as the autophagic degradation of intracellular lipid droplets (LDs). Although much remains unknown, lipophagy appears to play a significant role in many organisms, cell types, metabolic states, and diseases. It participates in the regulation of intracellular lipid storage, intracellular free lipid levels (e.g., fatty acids), and energy balance. However, it remains unclear how intracellular lipids regulate autophagy. Impaired lipophagy can cause cells to become sensitive to death stimuli and may be responsible for the onset of a variety of diseases, including nonalcoholic fatty liver disease and metabolic syndrome. Like autophagy, the role of lipophagy in cancer is poorly understood, although analysis of specific autophagy receptors has helped to expand the diversity of chemotherapeutic targets. These studies have stimulated increasing interest in the role of lipophagy in the pathogenesis and treatment of cancer and other human diseases.

The complexity of biological control systems: An autophagy case study

Autophagy and YAP1-WWTR1/TAZ signalling are tightly linked in a complex control system of forward and feedback pathways which determine different cellular outcomes in differing cell types at different time-points after perturbations. Here we extend our previous experimental and modelling approaches to consider two possibilities. First, we have performed additional mathematical modelling to explore how the autophagy-YAP1 crosstalk may be controlled by posttranslational modifications of components of the pathways. Second, since analogous contrasting results have also been reported for autophagy as a regulator of other transduction pathways engaged in tumorigenesis (Wnt/β-catenin, TGF-β/Smads, NF-kB or XIAP/cIAPs), we have considered if such discrepancies may be explicable through situations involving competing pathways and feedback loops in different cell types, analogous to the autophagy-YAP/TAZ situation. Since distinct posttranslational modifications dominate those pathways in distinct cells, these need to be understood to enable appropriate cell type-specific therapeutic strategies for cancers and other diseases.

A Balance Between Autophagy and Other Cell Death Modalities in Cancer

Autophagy is an intracellular self-digestive process involved in catabolic degradation of damaged proteins, and organelles, and the elimination of cellular pathogens. Initially, autophagy was considered as a prosurvival mechanism, but the following insights shed light on its prodeath function. Nowadays, autophagy is established as a crucial player in the development of various diseases through interaction with other molecular pathways within a cell. Additionally, disturbance in autophagy is one of the main pathological alterations that lead to resistance of cancer cells to treatment. These autophagy-related pathologies gave rise to the development of new therapeutic drugs. Here, we summarize the current knowledge on the autophagic role in disease pathogenesis, particularly in cancer, and the interplay between autophagy and other cell death modalities in order to combat cancer.

Cell Survival and Cell Death at the Intersection of Autophagy and Apoptosis: Implications for Current and Future Cancer Therapeutics

Autophagy and apoptosis are functionally distinct mechanisms for cytoplasmic and cellular turnover. While these two pathways are distinct, they can also regulate each other, and central components of the apoptosis or autophagy pathway regulate both processes directly. Furthermore, several upstream stress-inducing signaling pathways can influence both autophagy and apoptosis. The crosstalk between autophagy and apoptosis has an integral role in pathological processes, including those related to cancer, homeostasis, and aging. Apoptosis is a form of programmed cell death, tightly regulated by various cellular and biochemical mechanisms, some of which have been the focus of drug discovery efforts targeting cancer therapeutics. Autophagy is a cellular degradation pathway whereby cells recycle macromolecules and organelles to generate energy when subjected to stress. Autophagy can act as either a prodeath or a prosurvival process and is both tissue and microenvironment specific. In this review we describe five groups of proteins that are integral to the apoptosis pathway and discuss their role in regulating autophagy. We highlight several apoptosis-inducing small molecules and biologics that have been developed and advanced into the clinic and discuss their effects on autophagy. For the most part, these apoptosis-inducing compounds appear to elevate autophagy activity. Under certain circumstances autophagy demonstrates cytoprotective functions and is overactivated in response to chemo- or radiotherapy which can lead to drug resistance, representing a clinical obstacle for successful cancer treatment. Thus, targeting the autophagy pathway in combination with apoptosis-inducing compounds may be a promising strategy for cancer therapy.

Extracellular vesicle-associated small heat shock proteins as therapeutic agents in neurodegenerative diseases and beyond

Increasing evidence points towards using extracellular vesicles (EVs) as a therapeutic strategy in neurodegenerative diseases such as multiple sclerosis, Parkinson's, and Alzheimer's disease. EVs are nanosized carriers that play an essential role in intercellular communication and cellular homeostasis by transporting an active molecular cargo, including a large variety of proteins. Recent publications demonstrate that small heat shock proteins (HSPBs) exhibit a beneficial role in neurodegenerative diseases. Moreover, it is defined that HSPBs target the autophagy and the apoptosis pathway, playing a prominent role in chaperone activity and cell survival. This review elaborates on the therapeutic potential of EVs and HSPBs, in particular HSPB1 and HSPB8, in neurodegenerative diseases. We conclude that EVs and HSPBs positively influence neuroinflammation, central nervous system (CNS) repair, and protein aggregation in CNS disorders. Moreover, we propose the use of HSPB-loaded EVs as advanced nanocarriers for the future development of neurodegenerative disease therapies.

Inhibition of Autophagy Promotes Hemistepsin A-Induced Apoptosis via Reactive Oxygen Species-Mediated AMPK-Dependent Signaling in Human Prostate Cancer Cells

Chemotherapy is an essential strategy for cancer treatment. On the other hand, consistent exposure to chemotherapeutic drugs induces chemo-resistance in cancer cells through a variety of mechanisms. Therefore, it is important to develop a new drug inhibiting chemo-resistance. Although hemistepsin A (HsA) is known to have anti-tumor effects, the molecular mechanisms of HsA-mediated cell death are unclear. Accordingly, this study examined whether HsA could induce apoptosis in aggressive prostate cancer cells, along with its underlying mechanism. Using HsA on two prostate cancer cell lines, PC-3 and LNCaP cells, the cell analysis and in vivo xenograft model were assayed. In this study, HsA induced apoptosis and autophagy in PC-3 cells. HsA-mediated ROS production attenuated HsA-induced apoptosis and autophagy after treatment with N-acetyl-L-cysteine (NAC), a ROS scavenger. Moreover, autophagy inhibition by 3-MA or CQ is involved in accelerating the apoptosis induced by HsA. Furthermore, we showed the anti-tumor effects of HsA in mice, as assessed by the reduced growth of the xenografted tumors. In conclusion, HsA induced apoptosis and ROS generation, which were blocked by protective autophagy signaling.

The roles of GTPase-activating proteins in regulated cell death and tumor immunity

GTPase-activating protein (GAP) is a negative regulator of GTPase protein that is thought to promote the conversion of the active GTPase-GTP form to the GTPase-GDP form. Based on its ability to regulate GTPase proteins and other domains, GAPs are directly or indirectly involved in various cell requirement processes. We reviewed the existing evidence of GAPs regulating regulated cell death (RCD), mainly apoptosis and autophagy, as well as some novel RCDs, with particular attention to their association in diseases, especially cancer. We also considered that GAPs could affect tumor immunity and attempted to link GAPs, RCD and tumor immunity. A deeper understanding of the GAPs for regulating these processes could lead to the discovery of new therapeutic targets to avoid pathologic cell loss or to mediate cancer cell death.