Autophagy: A Druggable Process

Autophagy modulation in cancer therapy: Challenges coexist with opportunities

Autophagy, a crucial intracellular degradation process facilitated by lysosomes, plays a pivotal role in maintaining cellular homeostasis. The elucidation of autophagy key genes and signaling pathways has significantly advanced our understanding of this process and has led to the exploration of autophagy as a promising therapeutic approach. This review comprehensively assesses the latest developments in small molecule modulators targeting autophagy. Moreover, the review delves into the most recent strategies for drug discovery, specifically focusing on selective agents that exploit autophagosomes and lysosomes for targeted protein degradation. Additionally, this article highlights the prevailing challenges and outlines potential future advancements in the field. By amalgamating the cutting-edge knowledge in the field, we aim to offer valuable insights and references for the anti-cancer drug development of autophagy-targeted therapies, thus contributing to the advancement of novel therapeutic interventions.

Impaired reprogramming of the autophagy flux in maturing dendritic cells from crohn disease patients with core autophagy gene-related polymorphisms

Crohn disease (CD) is an inflammatory bowel disease whose pathogenesis involves inappropriate immune responses toward gut microbiota on genetically predisposed backgrounds. Notably, CD is associated with single-nucleotide polymorphisms affecting several genes involved in macroautophagy/autophagy, the catabolic process that ensures the degradation and recycling of cytosolic components and microorganisms. In a clinical translation perspective, monitoring the autophagic activity of CD patients will require some knowledge on the intrinsic functional status of autophagy. Here, we focused on monocyte-derived dendritic cells (DCs) to characterize the intrinsic quantitative features of the autophagy flux. Starting with DCs from healthy donors, we documented a reprogramming of the steady state flux during the transition from the immature to mature status: both the autophagosome pool size and the flux were diminished at the mature stage while the autophagosome turnover remained stable. At the cohort level, DCs from CD patients were comparable to control in term of autophagy flux reprogramming capacity. However, the homozygous presence of ATG16L1 rs2241880 A>G (T300A) and ULK1 rs12303764 (G/T) polymorphisms abolished the capacity of CD patient DCs to reprogram their autophagy flux during maturation. This effect was not seen in the case of CD patients heterozygous for these polymorphisms, revealing a gene dose dependency effect. In contrast, the NOD2 rs2066844 c.2104C>T (R702W) polymorphism did not alter the flux reprogramming capacity of DCs. The data, opening new clinical translation perspectives, indicate that polymorphisms affecting autophagy-related genes can differentially influence the capacity of DCs to reprogram their steady state autophagy flux when exposed to proinflammatory challenges.Abbreviation: BAFA1: bafilomycin A1, CD: Crohn disease; DC: dendritic cells; HD: healthy donor; iDCs: immature DCs; IL: interleukin; J: autophagosome flux; LPS: lipopolysaccharide; MHC: major histocompatibility complex; nA: autophagosome pool size; SNPs: single-nucleotide polymorphisms; PCA: principal component analysis; TLR: toll like receptor; τ: transition time; TNF: tumor necrosis factor.

Enhancing Therapeutic Efficacy in Cancer Treatment: Integrating Nanomedicine with Autophagy Inhibition Strategies

The complicated stepwise lysosomal degradation process known as autophagy is in charge of destroying and eliminating damaged organelles and defective cytoplasmic components. This mechanism promotes metabolic adaptability and nutrition recycling. Autophagy functions as a quality control mechanism in cells that support homeostasis and redox balance under normal circumstances. However, the role of autophagy in cancer is controversial because, mostly depending on the stage of the tumor, it may either suppress or support the disease. While autophagy delays the onset of tumors and slows the dissemination of cancer in the early stages of tumorigenesis, numerous studies demonstrate that autophagy promotes the development and spread of tumors as well as the evolution and development of resistance to several anticancer drugs in advanced cancer stages. In this Review, we primarily emphasize the therapeutic role of autophagy inhibition in improving the treatment of multiple cancers and give a broad overview of how its inhibition modulates cancer responses. There have been various attempts to inhibit autophagy, including the use of autophagy inhibitor drugs, gene silencing therapy (RNA interference), and nanoparticles. In this Review, all these topics are thoroughly covered and illustrated by recent studies and field investigations.

Inhibition of CSPG-PTPσ Activates Autophagy Flux and Lysosome Fusion, Aids Axon and Synaptic Reorganization in Spinal Cord Injury

Chondroitin sulfate proteoglycans (CSPGs) and proteoglycan receptor protein tyrosine phosphatase σ (PTPσ) play a critical role in the pathology of spinal cord injury (SCI). CSPGs can be induced by autophagy inhibition in astrocyte. However, CSPG's impact on autophagy and its role in SCI is still unknown. We investigate intracellular sigma peptide (ISP) targeting PTPσ, its effects on autophagy, and synaptic reorganization in SCI. We found that ISP increased the level of autophagosome marker LC3B-II/I and decreased autophagosome degradation marker p62 in SCI, suggesting activated autophagy flux. ISP restored autophagosome-lysosome fusion-related protein syntaxin 17 (STX17) and lysosome-associated membrane protein 2 (LAMP2), indicating activated autophagosome-lysosome fusion. ISP increased pre-synaptic marker synaptophysin (SYN) and postsynaptic density protein-95 (PSD-95) expression and improved excitatory synapse marker vesicular glutamate transporter 1 (VGLUT1) and SYN in SCI, suggesting improved synaptic reorganization. ISP promoted axon marker neurofilament and growth-related GAP-43 expression in SCI. ISP rescued a preserved number of motor neurons and improved neurobehavioral recovery after SCI. Our study extended the CSPG-PTPσ inhibition role in activating autophagy flux, axon and synaptic reorganization, and functional recovery in SCI.

Mechanisms and implications of podocyte autophagy in chronic kidney disease

Autophagy is a protective mechanism through which cells degrade and recycle proteins and organelles to maintain cellular homeostasis and integrity. An accumulating body of evidence underscores the significant impact of dysregulated autophagy on podocyte injury in chronic kidney disease (CKD). In this review, we provide a comprehensive overview of the diverse types of autophagy and their regulation in cellular homeostasis, with a specific emphasis on podocytes. Furthermore, we discuss recent findings that focus on the functional role of different types of autophagy during podocyte injury in chronic kidney disease. The intricate interplay between different types of autophagy and podocyte health requires further research, which is critical for understanding the pathogenesis of CKD and developing targeted therapeutic interventions.

Tumor biomarkers for diagnosis, prognosis and targeted therapy

Tumor biomarkers, the substances which are produced by tumors or the body's responses to tumors during tumorigenesis and progression, have been demonstrated to possess critical and encouraging value in screening and early diagnosis, prognosis prediction, recurrence detection, and therapeutic efficacy monitoring of cancers. Over the past decades, continuous progress has been made in exploring and discovering novel, sensitive, specific, and accurate tumor biomarkers, which has significantly promoted personalized medicine and improved the outcomes of cancer patients, especially advances in molecular biology technologies developed for the detection of tumor biomarkers. Herein, we summarize the discovery and development of tumor biomarkers, including the history of tumor biomarkers, the conventional and innovative technologies used for biomarker discovery and detection, the classification of tumor biomarkers based on tissue origins, and the application of tumor biomarkers in clinical cancer management. In particular, we highlight the recent advancements in biomarker-based anticancer-targeted therapies which are emerging as breakthroughs and promising cancer therapeutic strategies. We also discuss limitations and challenges that need to be addressed and provide insights and perspectives to turn challenges into opportunities in this field. Collectively, the discovery and application of multiple tumor biomarkers emphasized in this review may provide guidance on improved precision medicine, broaden horizons in future research directions, and expedite the clinical classification of cancer patients according to their molecular biomarkers rather than organs of origin.

Microglial Dysfunction in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental disorder with onset in childhood. The molecular mechanisms underlying ASD have not yet been elucidated completely. Evidence has emerged to support a link between microglial dysfunction and the etiology of ASD. This review summarizes current research on microglial dysfunction in neuroinflammation and synaptic pruning, which are associated with altered transcriptomes and autophagy in ASD. Dysbiosis of gut microbiota in ASD and its correlation with microglial dysfunction are also addressed.

DADS Inhibits the Proliferation of MDCC-MSB-1 Cells by Inducing Autophagy via the MEK/ERK Signalling Pathway

Diallyl disulfide (DADS) is effective at suppressing tumour cell growth and proliferation. This study verified the morphology and growth activity of MDCC-MSB-1 cells by using an MTT assay to detect the effect of DADS on the proliferation of MDCC-MSB-1 cells and a CCK8 assay to detect the effect of DADS on the viability and proliferation of MDCC-MSB-1 cells. We found that the viability and proliferation of MDCC-MSB-1 cells decreased with increasing DADS concentrations. MDC staining and Western blotting were used to analyse autophagy, the associated protein LC3 and the MEK/ERK pathway proteins MEK and ERK and to investigate changes in cellular autophagy based on cell morphology and molecular biology. With increasing concentrations of DADS, MDCC-MSB-1 cell autophagy increased in a gradient manner. Additionally, the conversion of the autophagy marker protein LC3-I increased with increasing drug concentrations, and the relative expression of LC3-II steadily increased, as did the expression of key protein components of the MEK/ERK signalling pathway, including P-MEK1/2 and P-ERK1/2. These results suggest that DADS induces autophagy through the MEK/ERK pathway, thereby inhibiting the proliferation of MDCC-MSB-1 cells.

Embelin: A multifaceted anticancer agent with translational potential in targeting tumor progression and metastasis

Embelin, a natural para-benzoquinone product, is derived from plants of the Embelia genus, particularly Embelia ribes Burm.f. A staple in traditional medicinal formulations for centuries, Embelin's pharmacological actions are attributed to the hydroxyl benzoquinone present in its structure. Its therapeutic potential is bolstered by unique physical and chemical properties. Recently, Embelin, recognized as a non-peptidic, cell-permeable small inhibitor of the X-linked inhibitor of apoptosis protein (XIAP), has garnered significant attention for its anticancer activity. It demonstrates various anticancer mechanisms, such as apoptosis induction, cell cycle arrest, and autophagy, in different cancer types. Additionally, Embelin modulates several signal transduction pathways, including NF-κB, PI3Kinase/AKT, and STAT3, effectively inhibiting the proliferation of diverse cancer cell lines. This literature review illuminates the anticancer potential of Embelin, detailing its mechanisms of action and prospective clinical applications, based on relevant scientific literature from the past decade sourced from various electronic databases. See also the Graphical abstract(Fig. 1).

Interactive mechanism between connexin43 and Cd-induced autophagic flux blockage and gap junctional intercellular communication dysfunction in rat hepatocytes

Cadmium (Cd) is a significant environmental contaminant known for its potential hepatotoxic effects. However, the precise mechanisms underlying Cd-induced hepatotoxicity have yet to be fully understood. Therefore, the purpose of this study was to investigate the dynamic role of connexin 43 (Cx43) in response to Cd exposure, particularly its impact on gap junctional intercellular communication (GJIC) and autophagy in hepatocytes. To establish an in vitro model of Cd-induced hepatocyte injury, the Buffalo rat liver 3A cell line (BRL3A) was utilized.In order to elucidate the mechanism by which Cx43 influences Cd-induced hepatocyte toxic injury, inhibitors of Cx43 (Dynasore) and P-Cx43 (Ro318220) were employed in the model. The findings revealed that inhibiting Cx43 and its phosphorylation further compromised GJIC function, exacerbating the impairment, while also intensifying the blockage of autophagic flux. To gain further insight into the role of Cx43, siRNA was utilized to knock down Cx43 expression, yielding similar results. The down-regulation of Cx43 expression was found to worsen the morphological damage induced by cadmium exposure, diminish the cell proliferation capacity of BRL3A cells, and exacerbate the disruption of GJIC and autophagic flow caused by Cd.These findings suggest that Cx43 may serve as a potential therapeutic target for the treatment of liver damage resulting from Cd exposure. By targeting Cx43, it may be possible to mitigate the adverse effects of Cd on hepatocytes.

Immune aging - A mechanism in autoimmune disease

Evidence is emerging that the process of immune aging is a mechanism leading to autoimmunity. Over lifetime, the immune system adapts to profound changes in hematopoiesis and lymphogenesis, and progressively restructures in face of an ever-expanding exposome. Older adults fail to generate adequate immune responses against microbial infections and tumors, but accumulate aged T cells, B cells and myeloid cells. Age-associated B cells are highly efficient in autoantibody production. T-cell aging promotes the accrual of end-differentiated effector T cells with potent cytotoxic and pro-inflammatory abilities and myeloid cell aging supports a low grade, sterile and chronic inflammatory state (inflammaging). In pre-disposed individuals, immune aging can lead to frank autoimmune disease, manifesting with chronic inflammation and irreversible tissue damage. Emerging data support the concept that autoimmunity results from aging-induced failure of fundamental cellular processes in immune effector cells: genomic instability, loss of mitochondrial fitness, failing proteostasis, dwindling lysosomal degradation and inefficient autophagy. Here, we have reviewed the evidence that malfunctional mitochondria, disabled lysosomes and stressed endoplasmic reticula induce pathogenic T cells and macrophages that drive two autoimmune diseases, rheumatoid arthritis (RA) and giant cell arteritis (GCA). Recognizing immune aging as a risk factor for autoimmunity will open new avenues of immunomodulatory therapy, including the repair of malfunctioning mitochondria and lysosomes.

Pharmacotherapy developments in autophagy inhibitors for bladder cancer

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

TFEB is a central regulator of the aging process and age-related diseases

Old age is associated with a greater burden of disease, including neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease, as well as other chronic diseases. Coincidentally, popular lifestyle interventions, such as caloric restriction, intermittent fasting, and regular exercise, in addition to pharmacological interventions intended to protect against age-related diseases, induce transcription factor EB (TFEB) and autophagy. In this review, we summarize emerging discoveries that point to TFEB activity affecting the hallmarks of aging, including inhibiting DNA damage and epigenetic modifications, inducing autophagy and cell clearance to promote proteostasis, regulating mitochondrial quality control, linking nutrient-sensing to energy metabolism, regulating pro- and anti-inflammatory pathways, inhibiting senescence and promoting cell regenerative capacity. Furthermore, the therapeutic impact of TFEB activation on normal aging and tissue-specific disease development is assessed in the contexts of neurodegeneration and neuroplasticity, stem cell differentiation, immune responses, muscle energy adaptation, adipose tissue browning, hepatic functions, bone remodeling, and cancer. Safe and effective strategies of activating TFEB hold promise as a therapeutic strategy for multiple age-associated diseases and for extending lifespan.

Targeting NEDD8-activating enzyme for cancer therapy: developments, clinical trials, challenges and future research directions

NEDDylation, a post-translational modification through three-step enzymatic cascades, plays crucial roles in the regulation of diverse biological processes. NEDD8-activating enzyme (NAE) as the only activation enzyme in the NEDDylation modification has become an attractive target to develop anticancer drugs. To date, numerous inhibitors or agonists targeting NAE have been developed. Among them, covalent NAE inhibitors such as MLN4924 and TAS4464 currently entered into clinical trials for cancer therapy, particularly for hematological tumors. This review explains the relationships between NEDDylation and cancers, structural characteristics of NAE and multistep mechanisms of NEDD8 activation by NAE. In addition, the potential approaches to discover NAE inhibitors and detailed pharmacological mechanisms of NAE inhibitors in the clinical stage are explored in depth. Importantly, we reasonably investigate the challenges of NAE inhibitors for cancer therapy and possible development directions of NAE-targeting drugs in the future.

Role and clinical implication of autophagy in COVID-19

The ongoing coronavirus disease 2019 (COVID-19) pandemic constitutes a serious public health concern worldwide. Currently, more than 6 million deaths have occurred despite drastic containment measures, and this number is still increasing. Currently, no standard therapies for COVID-19 are available, which necessitates identifying effective preventive and therapeutic agents against COVID-19. However, developing new drugs and vaccines is a time-consuming process, and therefore, repurposing the existing drugs or redeveloping related targets seems to be the best strategy to develop effective therapeutics against COVID-19. Autophagy, a multistep lysosomal degradation pathway contributing to nutrient recycling and metabolic adaptation, is involved in the initiation and progression of numerous diseases as a part of an immune response. The key role of autophagy in antiviral immunity has been extensively studied. Moreover, autophagy can directly eliminate intracellular microorganisms by selective autophagy, that is, "xenophagy." However, viruses have acquired diverse strategies to exploit autophagy for their infection and replication. This review aims to trigger the interest in the field of autophagy as an antiviral target for viral pathogens (with an emphasis on COVID-19). We base this hypothesis on summarizing the classification and structure of coronaviruses as well as the process of SARS-CoV-2 infection and replication; providing the common understanding of autophagy; reviewing interactions between the mechanisms of viral entry/replication and the autophagy pathways; and discussing the current state of clinical trials of autophagy-modifying drugs in the treatment of SARS-CoV-2 infection. We anticipate that this review will contribute to the rapid development of therapeutics and vaccines against COVID-19.

Role of macrophage autophagy in postoperative pain and inflammation in mice

BACKGROUND

Postoperative pain and inflammation are significant complications following surgery. Strategies that aim to prevent excessive inflammation without hampering natural wound-healing are required for the management of postoperative pain and inflammation. However, the knowledge of the mechanisms and target pathways involved in these processes is lacking. Recent studies have revealed that autophagy in macrophages sequesters pro-inflammatory mediators, and it is therefore being recognized as a crucial process involved in regulating inflammation. In this study, we tested the hypothesis that autophagy in macrophages plays protective roles against postoperative pain and inflammation and investigated the underlying mechanisms.

METHODS

Postoperative pain was induced by plantar incision under isoflurane anesthesia in mice lacking macrophage autophagy (Atg5flox/flox LysMCre +) and their control littermates (Atg5flox/flox). Mechanical and thermal pain sensitivity, changes in weight distribution, spontaneous locomotor activity, tissue inflammation, and body weight were assessed at baseline and 1, 3, and 7 days after surgery. Monocyte/macrophage infiltration at the surgical site and inflammatory mediator expression levels were evaluated.

RESULTS

Atg5flox/flox LysMCre + mice compared with the control mice exhibited lower mechanical and thermal pain thresholds and surgical/non-surgical hindlimb weight-bearing ratios. The augmented neurobehavioral symptoms observed in the Atg5flox/flox LysMCre + mice were associated with more severe paw inflammation, higher pro-inflammatory mediator mRNA expression, and more monocytes/macrophages at the surgical site.

CONCLUSION

The lack of macrophage autophagy augmented postoperative pain and inflammation, which were accompanied by enhanced pro-inflammatory cytokine secretion and surgical-site monocyte/macrophage infiltration. Macrophage autophagy plays a protective role in postoperative pain and inflammation and can be a novel therapeutic target.

In Vitro Cytotoxic Effect of Aqueous Extracts from Leaves and Rhizomes of the Seagrass Posidonia oceanica (L.) Delile on HepG2 Liver Cancer Cells: Focus on Autophagy and Apoptosis

Aqueous extracts from Posidonia oceanica's green and brown (beached) leaves and rhizomes were prepared, submitted to phenolic compound and proteomic analysis, and examined for their potential cytotoxic effect on HepG2 liver cancer cells in culture. The chosen endpoints related to survival and death were cell viability and locomotory behavior, cell-cycle analysis, apoptosis and autophagy, mitochondrial membrane polarization, and cell redox state. Here, we show that 24 h exposure to both green-leaf- and rhizome-derived extracts decreased tumor cell number in a dose-response manner, with a mean half maximal inhibitory concentration (IC₅₀) estimated at 83 and 11.5 μg of dry extract/mL, respectively. Exposure to the IC₅₀ of the extracts appeared to inhibit cell motility and long-term cell replicating capacity, with a more pronounced effect exerted by the rhizome-derived preparation. The underlying death-promoting mechanisms identified involved the down-regulation of autophagy, the onset of apoptosis, the decrease in the generation of reactive oxygen species, and the dissipation of mitochondrial transmembrane potential, although, at the molecular level, the two extracts appeared to elicit partially differentiating effects, conceivably due to their diverse composition. In conclusion, P. oceanica extracts merit further investigation to develop novel promising prevention and/or treatment agents, as well as beneficial supplements for the formulation of functional foods and food-packaging material with antioxidant and anticancer properties.

Pharmacological Targeting of Bcl-2 Induces Caspase 3-Mediated Cleavage of HDAC6 and Regulates the Autophagy Process in Colorectal Cancer

Compound 6d, a spiroindoline compound, exhibits antiproliferative capability against cancer cell lines. However, the exact underlying mechanism of this compound-mediated inhibitory capability remains unclear. Here, we showed that compound 6d is an inhibitor of Bcl-2, which suppresses CRC growth by inducing caspase 3-mediated intrinsic apoptosis of mitochondria. Regarding the underlying mechanism, we identified HDAC6 as a direct substrate for caspase 3, and caspase 3 activation induced by compound 6d directly cleaves HDAC6 into two fragments. Moreover, the cleavage site was located at D1088 in the DMAD-S motif HDAC6. Apoptosis stimulated by compound 6d promoted autophagy initiation by inhibiting interaction between Bcl-2 and Beclin 1, while it led to the accumulation of ubiquitinated proteins and the reduction of autophagic flux. Collectively, our findings reveal that the Bcl-2-caspase 3-HDAC6 cascade is a crucial regulatory pathway of autophagy and identify compound 6d as a novel lead compound for disrupting the balance between apoptosis and autophagy.

The role of autophagy and ferroptosis in sensorineural hearing loss

Hearing loss has become a common sensory defect in humans. Because of the limited regenerative ability of mammalian cochlear hair cells (HCs), HC damage (caused by ototoxic drugs, aging, and noise) is the main risk factor of hearing loss. However, how HCs can be protected from these risk factors remains to be investigated. Autophagy is a process by which damaged cytoplasmic components are sequestered into lysosomes for degradation. Ferroptosis is a novel form of non-apoptotic regulated cell death involving intracellular iron overloading and iron-dependent lipid peroxide accumulation. Recent studies have confirmed that autophagy is associated with ferroptosis, and their crosstalk may be the potential therapeutic target for hearing loss. In this review, we provide an overview of the mechanisms of ferroptosis and autophagy as well as their relationship with HC damage, which may provide insights for a new future in the protection of HCs.

New Visions on Natural Products and Cancer Therapy: Autophagy and Related Regulatory Pathways

Macroautophagy (autophagy) has been a highly conserved process throughout evolution and allows cells to degrade aggregated/misfolded proteins, dysfunctional or superfluous organelles and damaged macromolecules, in order to recycle them for biosynthetic and/or energetic purposes to preserve cellular homeostasis and health. Changes in autophagy are indeed correlated with several pathological disorders such as neurodegenerative and cardiovascular diseases, infections, cancer and inflammatory diseases. Conversely, autophagy controls both apoptosis and the unfolded protein response (UPR) in the cells. Therefore, any changes in the autophagy pathway will affect both the UPR and apoptosis. Recent evidence has shown that several natural products can modulate (induce or inhibit) the autophagy pathway. Natural products may target different regulatory components of the autophagy pathway, including specific kinases or phosphatases. In this review, we evaluated ~100 natural compounds and plant species and their impact on different types of cancers via the autophagy pathway. We also discuss the impact of these compounds on the UPR and apoptosis via the autophagy pathway. A multitude of preclinical findings have shown the function of botanicals in regulating cell autophagy and its potential impact on cancer therapy; however, the number of related clinical trials to date remains low. In this regard, further pre-clinical and clinical studies are warranted to better clarify the utility of natural compounds and their modulatory effects on autophagy, as fine-tuning of autophagy could be translated into therapeutic applications for several cancers.

Melatonin Attenuates Ischemic-like Cell Injury by Promoting Autophagosome Maturation via the Sirt1/FoxO1/Rab7 Axis in Hippocampal HT22 Cells and in Organotypic Cultures

Dysfunctional autophagy is linked to neuronal damage in ischemia/reperfusion injury. The Ras-related protein 7 (Rab7), a member of the Rab family of small GTPases, appears crucial for the progression of the autophagic flux, and its activity is strictly interconnected with the histone deacetylase Silent information regulator 1 (Sirt1) and transcription factor Forkhead box class O1 (FoxO1). The present study assessed the neuroprotective role of melatonin in the modulation of the Sirt1/FoxO1/Rab7 axis in HT22 cells and organotypic hippocampal cultures exposed to oxygen-glucose deprivation followed by reoxygenation (OGD/R). The results showed that melatonin re-established physiological levels of autophagy and reduced propidium iodide-positive cells, speeding up autophagosome (AP) maturation and increasing lysosomal activity. Our study revealed that melatonin modulates autophagic pathways, increasing the expression of both Rab7 and FoxO1 and restoring the Sirt1 expression affected by OGD/R. In addition, the Sirt1 inhibitor EX-527 significantly reduced Rab7, Sirt1, and FoxO1 expression, as well as autolysosomes formation, and blocked the neuroprotective effect of melatonin. Overall, our findings provide, for the first time, new insights into the neuroprotective role of melatonin against ischemic injury through the activation of the Sirt1/FoxO1/Rab7 axis.

An autophagy-associated lncRNAs model for predicting the survival in non-small cell lung cancer patients

Long non-coding RNAs (lncRNAs) can influence the proliferation, autophagy, and apoptosis of non-small cell lung cancer (NSCLC). LncRNAs also emerge as valuable prognostic factors for NSCLC patients. Consequently, we set out to discover more autophagy-associated lncRNAs. We acquired autophagy-associated genes and information on lncRNAs from The Cancer Genome Atlas database (TCGA), and the Human Autophagy Database (HADb). Then, the prognostic prediction signature was constructed through using co-expression and Cox regression analysis. The signature was constructed including 7 autophagy-associated lncRNAs (ABALON, NKILA, LINC00941, AL161431.1, AL691432.2, AC020765.2, MMP2-AS1). After that, we used univariate and multivariate Cox regression analysis to calculate the risk score. The survival analysis and ROC curve analysis confirmed good performances of the signature. GSEA indicated that the high-risk group was principally enriched in the adherens junction pathway. In addition, biological experiments showed that ABALON promoted the proliferation, metastasis and autophagy levels of NSCLC cells. These findings demonstrate that the risk signature consisting of 7 autophagy-associated lncRNAs accurately predicts the prognosis of NSCLC patients and should be investigated for potential therapeutic targets in clinic.

Autophagy regulates transforming growth factor β signaling and receptor trafficking

Transforming growth factor beta (TGFβ) stimulates tumorigenesis by inducing epithelial to mesenchymal transition (EMT) and cell migration. TGFβ signaling is regulated by the endocytosis of cell surface receptors and their subcellular trafficking into the endo-lysosomal system. Here we investigated how autophagy, a cellular quality control network that delivers material to lysosomes, regulates TGFβ signaling pathways that induce EMT and cell migration. We impaired autophagy in non-small cell lung cancer cells using chloroquine, spautin-1, ULK-101, or small interfering RNA (siRNA) targeting autophagy-related gene (ATG)5 and ATG7 and observed that inhibiting autophagy results in a decrease in TGFβ1-dependent EMT transcription factor and cell marker expression, as well as attenuated stress fiber formation and cell migration. This correlated with decreased internalization of cell surface TGFβ receptors and their trafficking to early/late endosomal and lysosomal compartments. The effects of autophagy inhibition on TGFβ signaling were investigated by Smad2/Smad3 phosphorylation and cellular localization using western blotting, subcellular fractionation, and immunofluorescence microscopy. We observed that inhibiting autophagy decreased the amount and timeframe of Smad2/Smad3 signaling. Taken together, our results suggest that inhibiting autophagy attenuates pro-tumorigenic TGFβ signaling by regulating receptor trafficking, resulting in impaired Smad2/Smad3 phosphorylation and nuclear accumulation.

Anticancer activity of β-Lapachone derivatives on human leukemic cell lines

β-lapachone is a 1,2-naphthoquinone of great therapeutic interest that induces cell death by autophagy and apoptosis in tumor cells due to oxidative stress increasing. However, its high toxicity in healthy tissues limits its clinical use, which stimulates the planning and synthesis of more selective analogs. The aim of this study was to investigate the cytotoxic activity of three thiosemicarbazones derived from β-lapachone (BV2, BV3 and BV5) in leukemia cells. Cytotoxicity tests were performed on tumor cells (HL-60, K562, K562-Lucena and MOLT-4) and normal peripheral blood mononuclear cells (PBMCs). Subsequently, the mode of action of compounds was accessed by optical microscopy, transmission electron microscopy or fluorescence microscopy. Flow cytometry analysis was performed to investigate apoptosis induction, cell cycle, DNA fragmentation and mitochondrial depolarization. All derivatives inhibited tumor cell growth after 72 h (IC₅₀ < 10 μM to all cell lines, including the resistant K562-Lucena) with less toxic effects in PBMC cells, being BV3 the most selective compound with selective index (SI) of 275 for HL-60; SI of 40 to K562; SI of 10 for MOLT-4 and SI of 50 to K562-Lucena compared to β-lapachone with SI of 18 to HL-60, SI of 3.7 to K562; SI of 2.4 to MOLT-4 and SI of 0.9 to K562-Lucena. In addition, the K562 or MOLT-4 cells treated with BV3 showed characteristics of both apoptosis and autophagy cell death, mainly by autophagy. These results demonstrate the potent cytotoxic effect of thiosemicarbazones derived from β-lapachone as promising anticancer drugs candidates, encouraging the continuity of in vivo tests.

Endothelial Autophagy in Coronary Microvascular Dysfunction and Cardiovascular Disease

Coronary microvascular dysfunction (CMD) refers to a subset of structural and/or functional disorders of coronary microcirculation that lead to impaired coronary blood flow and eventually myocardial ischemia. Amid the growing knowledge of the pathophysiological mechanisms and the development of advanced tools for assessment, CMD has emerged as a prevalent cause of a broad spectrum of cardiovascular diseases (CVDs), including obstructive and nonobstructive coronary artery disease, diabetic cardiomyopathy, and heart failure with preserved ejection fraction. Of note, the endothelium exerts vital functions in regulating coronary microvascular and cardiac function. Importantly, insufficient or uncontrolled activation of endothelial autophagy facilitates the pathogenesis of CMD in diverse CVDs. Here, we review the progress in understanding the pathophysiological mechanisms of autophagy in coronary endothelial cells and discuss their potential role in CMD and CVDs.

Autophagy modulation by irbesartan mitigates the pulmonary fibrotic alterations in bleomycin challenged rats: Comparative study with rapamycin

AIMS

In pulmonary fibrosis, autophagy handles the maintenance of alveolar epithelial cells, prevents epithelial-mesenchymal transition (EMT), and controls collagen turnover. The mammalian target of rapamycin (mTOR) and its translational-dependent proteins are essential regulators of autophagy. Irbesartan (IRB) has earlier ameliorative effects in experimental pulmonary fibrosis. The current study aimed to explore therapeutic autophagy-modulated pulmonary fibrotic changes by IRB versus rapamycin (RAPA) in bleomycin (BLM)-challenged rats.

MATERIALS AND METHODS

A single intratracheal BLM dose at day (0), IRB in different doses (10, 20, and 40 mg/kg) or RAPA (2.5 mg/kg) was given daily for 14 continuous days.

KEY FINDINGS

IRB significantly diminished the fibrotic lung scores. Pulmonary levels of transforming growth factor (TGF)-β1 and hydroxyproline exhibited marked attenuation in IRB (40 mg/kg)-treated rats compared to other treated groups. IRB (40 mg/kg) was not significantly different from RAPA. It downregulated the fibrotic lung phosphorylated mammalian target of rapamycin (p-mTOR) levels and augmented lung Unc-51-like autophagy activating kinase 1 (ULK1), LC3-I and LC3-II more than IRB (10 and 20 mg/kg)-treated fibrotic groups.

SIGNIFICANCE

Autophagic effects via the mTOR signalling pathway may play a role in IRB's antifibrotic effects. Consideration of IRB as a therapeutic antifibrotic agent in pulmonary fibrosis needs further experimental and clinical long-term validation, especially in comorbid with primary hypertension, heart failure, and diabetic renal insults.

Glucolipotoxicity induces endothelial cell dysfunction by activating autophagy and inhibiting autophagic flow

OBJECTIVES

This study aims to determine the role and mechanism of autophagy in endothelial cell dysfunction by glucolipotoxicity.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with high glucose and high palmitic acid. The number of autophagosomes was evaluated by monodansylcadaverine (MDC) staining and transmission electron microscopy (TEM). The expression of autophagy-related proteins (LC3 and P62) was assessed by Western blotting. Capillary tube-like formation was evaluated on Matrigel. Reactive oxygen species (ROS) production was detected by DCFH-DA. Cell apoptosis was measured by Hoechst 33258 staining and flow cytometry. Phosphorylation of AMPK, mTOR, and ULK1 was also analyzed by Western blotting.

RESULTS

We found that glucolipotoxicity induced autophagy initiation and hindered autophagosomes degradation. Moreover, glucolipotoxicity increased the production of intracellular ROS, decreased the ability of tubular formation, and increased cell apoptosis. However, endothelial cell dysfunction was alleviated by 3-methyladenine, an early-stage autophagy inhibitor. Additionally, glucolipotoxicity promoted the phosphorylation of AMPK and ULK1 and inhibited the phosphorylation of mTOR.

CONCLUSIONS

Glucolipotoxicity initiates autophagy through the AMPK/mTOR/ULK1 signaling pathway and inhibits autophagic flow, leading to the accumulation of autophagosomes, thereby inducing apoptosis and impairing endothelial cell function.

SGLT2 Inhibitors as the Most Promising Influencers on the Outcome of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD), the most frequent liver disease in the Western world, is a common hepatic manifestation of metabolic syndrome (MetS). A specific cure has not yet been identified, and its treatment is currently based on risk factor therapy. Given that the initial accumulation of triglycerides in the liver parenchyma, in the presence of inflammatory processes, mitochondrial dysfunction, lipotoxicity, glucotoxicity, and oxidative stress, can evolve into non-alcoholic steatohepatitis (NASH). The main goal is to identify the factors contributing to this evolution because, once established, untreated NASH can progress through fibrosis to cirrhosis and, ultimately, be complicated by hepatocellular carcinoma (HCC). Several drugs have been tested in clinical trials for use as specific therapy for NAFLD; most of them are molecules used to cure type 2 diabetes mellitus (T2DM), which is one of the main risk factors for NAFLD. Among the most studied is pioglitazone, either alone or in combination with vitamin E, glucagon-like peptide-1 (GLP-1) receptor agonists, dipeptidyl peptidase-4 (DPP-4) inhibitors. Actually, the most promising category seems to be sodium-glucose cotransporter (SGLT2) inhibitors. Their action is carried out by inhibiting glucose reabsorption in the proximal renal tubule, leading to its increased excretion in urine and decreased levels in plasma. Experimental studies in animal models have suggested that SGLT2 inhibitors may have beneficial modulatory effects on NAFLD/NASH, and several trials in patients have proven their beneficial effects on liver enzymes, BMI, blood lipids, blood glucose, and insulin resistance in NAFLD patients, thus creating strong expectations for their possible use in preventing the evolution of liver damage in these patients. We will review the main pathogenetic mechanisms, diagnostic modalities, and recent therapies of NAFLD, with particular attention to the use of SGLT2 inhibitors.

Pathophysiological mechanisms leading to muscle loss in chronic kidney disease

Loss of muscle proteins is a deleterious consequence of chronic kidney disease (CKD) that causes a decrease in muscle strength and function, and can lead to a reduction in quality of life and increased risk of morbidity and mortality. The effectiveness of current treatment strategies in preventing or reversing muscle protein losses is limited. The limitations largely stem from the systemic nature of diseases such as CKD, which stimulate skeletal muscle protein degradation pathways while simultaneously activating mechanisms that impair muscle protein synthesis and repair. Stimuli that initiate muscle protein loss include metabolic acidosis, insulin and IGF1 resistance, changes in hormones, cytokines, inflammatory processes and decreased appetite. A growing body of evidence suggests that signalling molecules secreted from muscle can enter the circulation and subsequently interact with recipient organs, including the kidneys, while conversely, pathological events in the kidney can adversely influence protein metabolism in skeletal muscle, demonstrating the existence of crosstalk between kidney and muscle. Together, these signals, whether direct or indirect, induce changes in the levels of regulatory and effector proteins via alterations in mRNAs, microRNAs and chromatin epigenetic responses. Advances in our understanding of the signals and processes that mediate muscle loss in CKD and other muscle wasting conditions will support the future development of therapeutic strategies to reduce muscle loss.

Cholesterol-enriched membrane micro-domaindeficiency induces doxorubicin resistancevia promoting autophagy in breast cancer

Drug resistance has become one of the largest challenges for cancer chemotherapies. Under certain conditions, cancer cells hijack autophagy to cope with therapeutic stress, which largely undermines the chemo-therapeutic efficacy. Currently, biomarkers indicative of autophagy-derived drug resistance remain largely inclusive. Here, we report a novel role of lipid rafts/cholesterol-enriched membrane micro-domains (CEMMs) in autophagosome biogenesis and doxorubicin resistance in breast tumors. We showed that CEMMs are required for the interaction of VAMP3 with syntaxin 6 (STX6, a cholesterol-binding SNARE protein). Upon disruption of CEMM, VAMP3 is released from STX6, resulting in the trafficking of ATG16L1-containing vesicles to recycling endosomes and subsequent autophagosome biogenesis. Furthermore, we found that CEMM marker CAV1 is decreased in breast cancer patients and that the CEMM deficiency-induced autophagy is related to doxorubicin resistance, which is overcome by autophagy inhibition. Taken together, we propose a novel model whereby CEMMs in recycling endosomes support the VAMP3 and STX6 interaction and function as barriers to limit the activity of VAMP3 in autophagic vesicle fusion, thus CEMM deficiency promotes autophagosome biogenesis and doxorubicin resistance in breast tumors.

High fat diet-induced obesity leads to depressive and anxiety-like behaviors in mice via AMPK/mTOR-mediated autophagy

Depression is one of the most common mental illnesses in modern society. In recent years, several studies show that there are disturbances in lipid metabolism in depressed patients. High-fat diet may lead to anxiety and depression, but the mechanisms involved remain unclear. In our study, we found that 8 weeks of high-fat feeding effectively induced metabolic disorders, including obesity and hyperlipidemia in mice. Interestingly, the mice also showed depressive and anxiety-like behaviors. We further found activated microglia and astrocyte, increased neuroinflammation, decreased autophagy and BDNF levels in mice after high-fat feeding. Besides, high-fat feeding can also inhibit AMPK phosphorylation and induce mTOR phosphorylation. After treating with the mTOR inhibitor rapamycin, autophagy and BDNF levels were elevated. The number of activated microglia and astrocyte, and pro-inflammation levels were reduced. Besides, rapamycin can also reduce the body weight and serum lipid level in high fat feeding mice. Depressive and anxiety-like behaviors were also ameliorated to some extent after rapamycin treatment. In summary, these results suggest that high-fat diet-induced obesity may lead to depressive and anxiety-like behaviors in mice by inhibiting AMPK phosphorylation and promoting mTOR shift to phosphorylation to inhibit autophagy. Therefore, improving lipid metabolism or enhancing autophagy through the AMPK/mTOR pathway could be potential targets for the treatment of obesity depression.

Macroautophagy and aging: The impact of cellular recycling on health and longevity

Aging is associated with many deleterious changes at the cellular level, including the accumulation of potentially toxic components that can have devastating effects on health. A key protective mechanism to this end is the cellular recycling process called autophagy. During autophagy, damaged or surplus cellular components are delivered to acidic vesicles called lysosomes, that secure degradation and recycling of the components. Numerous links between autophagy and aging exist. Autophagy declines with age, and increasing evidence suggests that this reduction plays important roles in both physiological aging and the development of age-associated disorders. Studies in pharmacologically and genetically manipulated model organisms indicate that defects in autophagy promote age-related diseases, and conversely, that enhancement of autophagy has beneficial effects on both healthspan and lifespan. Here, we review our current understanding of the role of autophagy in different physiological processes and their molecular links with aging and age-related diseases. We also highlight some recent advances in the field that could accelerate the development of autophagy-based therapeutic interventions.

The New Role of Sirtuin1 in Human Osteoarthritis Chondrocytes by Regulating Autophagy

OBJECTIVE

The aim of this study is to investigate the role of Sirtuin1 (Sirt1) in the regulation of autophagy for human osteoarthritis (OA) chondrocytes.

DESIGN

All cartilage samples were collected from human donors, including young group, aged group, and OA group. Primary chondrocytes were isolated and cultured with Sirt1 activator or inhibitor. Sirt1 expression in cartilage tissue and chondrocytes was evaluated, and the deacetylation activity of Sirt1 was determined. The alteration of autophagy activity after upregulating or downregulating Sirt1 was detected. Chondrocytes were treated with autophagy activator and inhibitor, and then the protein level of Sirt1 was examined. The interactions between Sirt1 and autophagy-related proteins Atg7, microtubule associated protein 1 light chain 3 (LC3), and Beclin-1 were determined by using immunoprecipitation.

RESULTS

The assay of articular cartilage revealed that the expression of Sirt1 might be age-related: highly expressed in of younger people, and respectively decreased in the elderly people and OA patients. In vitro study was also validated this result. Further study confirmed that higher levels of Sirt1 significantly increased autophagy in aged chondrocytes, while the lower expression of Sirt1 reduced autophagy in young chondrocytes. Of note, the high levels of Sirt1 reduced autophagy in OA chondrocytes. When the chondrocytes were treated with autophagy activator or inhibitor, we found the expression of Sirt1 was not affected. In addition, we found that Sirt1 could interact with Atg7.

CONCLUSION

These results suggest that Sirt1 in human chondrocytes regulates autophagy by interacting with autophagy related Atg7, and Sirt1 may become a more important target in OA treatment.

Recent advances in understanding the role of proteostasis

Maintenance of a functional proteome is achieved through the mechanism of proteostasis that involves precise coordination between molecular machineries assisting a protein from its conception to demise. Although each organelle within a cell has its own set of proteostasis machinery, inter-organellar communication and cell non-autonomous signaling bring forth the multidimensional nature of the proteostasis network. Exposure to extrinsic and intrinsic stressors can challenge the proteostasis network, leading to the accumulation of aberrant proteins or a decline in the proteostasis components, as seen during aging and in several diseases. Here, we summarize recent advances in understanding the role of proteostasis and its regulation in aging and disease, including monogenetic and infectious diseases. We highlight some of the emerging as well as unresolved questions in proteostasis that need to be addressed to overcome pathologies associated with damaged proteins and to promote healthy aging.

Targeting Autophagy with Natural Products as a Potential Therapeutic Approach for Cancer

Macro-autophagy (autophagy) is a highly conserved eukaryotic intracellular process of self-digestion caused by lysosomes on demand, which is upregulated as a survival strategy upon exposure to various stressors, such as metabolic insults, cytotoxic drugs, and alcohol abuse. Paradoxically, autophagy dysfunction also contributes to cancer and aging. It is well known that regulating autophagy by targeting specific regulatory molecules in its machinery can modulate multiple disease processes. Therefore, autophagy represents a significant pharmacological target for drug development and therapeutic interventions in various diseases, including cancers. According to the framework of autophagy, the suppression or induction of autophagy can exert therapeutic properties through the promotion of cell death or cell survival, which are the two main events targeted by cancer therapies. Remarkably, natural products have attracted attention in the anticancer drug discovery field, because they are biologically friendly and have potential therapeutic effects. In this review, we summarize the up-to-date knowledge regarding natural products that can modulate autophagy in various cancers. These findings will provide a new position to exploit more natural compounds as potential novel anticancer drugs and will lead to a better understanding of molecular pathways by targeting the various autophagy stages of upcoming cancer therapeutics.

An alcoholic extract of Thuja orientalis L. leaves inhibits autophagy by specifically targeting pro-autophagy PIK3C3/VPS34 complex

Autophagy is a lysosome-dependent degradation program to maintain cellular homeostasis in response to a variety of stressful conditions, such as long-lived or non-functional subcellular organelles, protein aggregates, nutrient limitation, and virus/bacteria infection. Accordingly, dysregulation of autophagy is closely associated with many human pathophysiological conditions, such as neurodegenerative diseases, aging, and cancer, and autophagy is highlighted as an important therapeutic target for these human diseases. In autophagy process, PIK3C3/VPS34 complex plays important roles in autophagosome biogenesis. Accumulating evidences that inhibition of PIK3C3/VPS34 complex successfully blocks autophagy make the complex as an attractive target for the development of autophagy-specific inhibitors. However, considering that various forms of PIK3C3/VPS34 complex exist and they are involved in many different cellular functions, the targeting of the pro-autophagy PIK3C3/VPS34 complex is required to specifically inhibit autophagy. To identify autophagy inhibitors targeting the pro-autophagy complex, we have performed the screening of a customized natural product library consisting of 35 herbal extracts which are widely used in the oriental medicine as anti-inflammation and/or anti-tumor reagents. We discovered that an alcoholic extract of Thuja orientalis L. leaves inhibits pro-autophagy complex formation by disrupting the interaction between autophagy-specific factor, ATG14L, and the complex core unit Vps34-Beclin 1 in vitro. Also, it inhibits the nutrient starvation induced autophagy and diminished pro-autophagy PIK3C3/VPS34 complex containing either ATG14L or UVRAG in several cell lines. Our results strongly suggest that Thuja orientalis L. leave extract functions as an autophagy-specific inhibitor not decreasing the complex activity nor the protein level, but preventing protein-protein interaction between autophagy-specific factor (ATG14L and UVRAG) and PIK3C3/VPS34 complex core unit, Vps34-Beclin 1, thereby specifically depleting the pro-autophagy complex to inhibit autophagy.

MicroRNA-205-5p targets E2F1 to promote autophagy and inhibit pulmonary fibrosis in silicosis through impairing SKP2-mediated Beclin1 ubiquitination

Silicosis is an occupational disease characterized by extensive pulmonary fibrosis, and the underlying pathological process remains uncertain. Herein, we explored the molecular mechanism by which microRNA‐205‐5p (miR‐205‐5p) affects the autophagy of alveolar macrophages (AMs) and pulmonary fibrosis in mice with silicosis through the E2F transcription factor 1 (E2F1)/S‐phase kinase‐associated protein 2 (SKP2)/Beclin1 axis. Alveolar macrophages (MH‐S cells) were exposed to crystalline silica (CS) to develop an in vitro model, and mice were treated with CS to establish an in vivo model. Decreased Beclin1 and increased SKP2 and E2F1 were identified in mice with silicosis. We silenced or overexpressed miR‐205‐5p, E2F1, SKP2 and Beclin1 to investigate their potential roles in pulmonary fibrosis in vivo and autophagy in vitro. Recombinant adenovirus mRFP‐GFP‐LC3 was transduced into the MH‐S cells to assay autophagic flow. Knocking down Beclin1 promoted pulmonary fibrosis and suppressed the autophagy. Co‐immunoprecipitation and ubiquitination assays suggested that SKP2 induced K48‐linked ubiquitination of Beclin1. Furthermore, chromatin immunoprecipitation‐PCR revealed the site where E2F1 bound to the SKP2 promoter between 1638 bp and 1645 bp. As shown by dual‐luciferase reporter gene assay, the transfection with miR‐205‐5p mimic inhibited the luciferase activity of the wild‐type E2F1 3′untranslated region, suggesting that miR‐205‐5p targeted E2F1. Additionally, miR‐205‐5p overexpression increased autophagy and reduced the pulmonary fibrosis, while overexpression of E2F1 or SKP2 or inhibition of Beclin1 could annul this effect. The current study elucidated that miR‐205‐5p targeted E2F1, thereby inhibiting SKP2‐mediated Beclin1 ubiquitination to promote macrophage autophagy and inhibit pulmonary fibrosis in mice with silicosis.

Overexpression of lncRNA SLC26A4-AS1 inhibits papillary thyroid carcinoma progression through recruiting ETS1 to promote ITPR1-mediated autophagy

Papillary thyroid carcinoma (PTC), accounting for approximately 85% cases of thyroid cancer, is a common endocrine tumour with a relatively low mortality but an alarmingly high rate of recurrence or persistence. Long non‐coding RNAs (lncRNAs) is emerging as a critical player modulating diverse cellular mechanisms correlated with the progression of various cancers, including PTC. Herein, we aimed to investigate the role of lncRNA SLC26A4‐AS1 in regulating autophagy and tumour growth during PTC progression. Initially, ITPR1 was identified by bioinformatics analysis as a differentially expressed gene. Then, Western blot and RT‐qPCR were conducted to determine the expression of ITPR1 and SLC26A4‐AS1 in PTC tissues and cells, both of which were found to be poorly expressed in PTC tissues and cells. Then, we constructed ITPR1‐overexpressing cells and revealed that ITPR1 overexpression could trigger the autophagy of PTC cells. Further, we performed a series of gain‐ and loss‐of function experiments. The results suggested that silencing of SLC26A4‐AS1 led to declined ITPR1 level, up‐regulation of ETS1 promoted ITPR1 expression, and either ETS1 knockdown or autophagy inhibitor Bafilomycin A1 could mitigate the promoting effects of SLC26A4‐AS1 overexpression on PTC cell autophagy. In vivo experiments also revealed that SLC26A4‐AS1 overexpression suppressed PTC tumour growth. In conclusion, our study elucidated that SLC26A4‐AS1 overexpression promoted ITPR1 expression through recruiting ETS1 and thereby promotes autophagy, alleviating PTC progression. These finding provides insight into novel target therapy for the clinical treatment of PTC.

Novel Approaches of Dysregulating Lysosome Functions in Cancer Cells by Specific Drugs and Its Nanoformulations: A Smart Approach of Modern Therapeutics

The smart strategy of cancer cells to bypass the caspase-dependent apoptotic pathway has led to the discovery of novel anti-cancer approaches including the targeting of lysosomes. Recent discoveries observed that lysosomes perform far beyond just recycling of cellular waste, as these organelles are metabolically very active and mediate several signalling pathways to sense the cellular metabolic status. These organelles also play a significant role in mediating the immune system functions. Thus, direct or indirect lysosome-targeting with different drugs can be considered a novel therapeutic approach in different disease including cancer. Recently, some anticancer lysosomotropic drugs (eg, nortriptyline, siramesine, desipramine) and their nanoformulations have been engineered to specifically accumulate within these organelles. These drugs can enhance lysosome membrane permeabilization (LMP) or disrupt the activity of resident enzymes and protein complexes, like v-ATPase and mTORC1. Other anticancer drugs like doxorubicin, quinacrine, chloroquine and DQ661 have also been used which act through multi-target points. In addition, autophagy inhibitors, ferroptosis inducers and fluorescent probes have also been used as novel theranostic agents. Several lysosome-specific drug nanoformulations like mixed charge and peptide conjugated gold nanoparticles (AuNPs), Au-ZnO hybrid NPs, TPP-PEG-biotin NPs, octadecyl-rhodamine-B and cationic liposomes, etc. have been synthesized by diverse methods. These nanoformulations can target cathepsins, glucose-regulated protein 78, or other lysosome specific proteins in different cancers. The specific targeting of cancer cell lysosomes with drug nanoformulations is quite recent and faces tremendous challenges like toxicity concerns to normal tissues, which may be resolved in future research. The anticancer applications of these nanoformulations have led them up to various stages of clinical trials. Here in this review article, we present the recent updates about the lysosome ultrastructure, its cross-talk with other organelles, and the novel strategies of targeting this organelle in tumor cells as a recent innovative approach of cancer management.

Spatio-Temporal Autophagy Tracking with a Cell-Permeable, Water-Soluble, Peptide-Based, Autophagic Vesicle-Targeted Sensor

Autophagy is an essential cellular degradation process. Impaired autophagy has been linked to multiple disorders, including cancer and neurodegeneration. Tracking the autophagic flux in living cells will provide mechanistic insights into autophagy and will allow rapid screening of autophagy modulators as potential therapeutics. Imaging autophagy to track the autophagic flux demands a cell-permeable probe that can specifically target autophagic vesicles and report on the extent of autophagy. Existing fluorescent protein-based probes for imaging autophagy target autophagic vesicles but are cell-impermeable and degrade with the progress of autophagy resulting in ambiguous information on the later stages of autophagy. Although small-molecule-based autophagy probes can be cell-permeable, they are mostly water-insoluble and often target lysosomes instead of autophagic vesicles leading to incomplete evidence of the early stages of the process. Hence, there is a major gap in the ability to link the imaging data obtained by applying fluorescent sensors to the real extent of autophagy in living cells. To address these challenges, we have combined the desirable features of targetability and cell permeability to develop a novel water-soluble, cell-permeable, visible-light excitable, peptide-based, fluorescent sensor, HCFP, for imaging autophagy and tracking the autophagic flux. The probe readily enters living cells within 30 min of incubation, distinctly targets autophagic vesicles, and spatio-temporally tracks the entire autophagy pathway in living cells via a ratiometric pH-sensitive detection scheme. The salient features of the probe combining targetability with cell permeability should provide an edge in high-throughput screening of autophagy modulators by tracking autophagy live.

Role and mechanisms of autophagy in lung metabolism and repair

Mammalian lungs are metabolically active organs that frequently encounter environmental insults. Stress responses elicit protective autophagy in epithelial barrier cells and the supportive niche. Autophagy promotes the recycling of damaged intracellular organelles, denatured proteins, and other biological macromolecules for reuse as components required for lung cell survival. Autophagy, usually induced by metabolic defects, regulates cellular metabolism. Autophagy is a major adaptive response that protects cells and organisms from injury. Endogenous region-specific stem/progenitor cell populations are found in lung tissue, which are responsible for epithelial repair after lung damage. Additionally, glucose and fatty acid metabolism is altered in lung stem/progenitor cells in response to injury-related lung fibrosis. Autophagy deregulation has been observed to be involved in the development and progression of other respiratory diseases. This review explores the role and mechanisms of autophagy in regulating lung metabolism and epithelial repair.

LC3-associated phagocytosis protects against inflammation and liver fibrosis via immunoreceptor inhibitory signaling

Sustained hepatic and systemic inflammation, particularly originating from monocytes/macrophages, is a driving force for fibrosis progression to end-stage cirrhosis and underlies the development of multiorgan failure. Reprogramming monocyte/macrophage phenotype has emerged as a strategy to limit inflammation during chronic liver injury. Here, we report that LC3-associated phagocytosis (LAP), a noncanonical form of autophagy, protects against hepatic and systemic inflammation during chronic liver injury in rodents, with beneficial antifibrogenic effects. LAP is enhanced in blood and liver monocytes from patients with fibrosis and cirrhosis. Pharmacological inhibition of LAP components in human monocytes from patients with cirrhosis or genetic disruption of LAP in mice with chronic liver injury exacerbates both the inflammatory signature in isolated human monocytes and the hepatic inflammatory profile in mice, resulting in enhanced liver fibrosis. Mechanistically, patients with cirrhosis showed increased monocyte expression of Fc fragment of IgG receptor IIA (FcγRIIA) and enhanced engulfment of immunoglobulin G in LC3⁺ phagosomes that triggers an FcγRIIA/Src homology region 2 domain-containing phosphatase-1 (SHP-1) inhibitory immunoreceptor tyrosine-based activation motif (ITAMi) anti-inflammatory pathway. Mice overexpressing human FcγRIIA in myeloid cells show enhanced LAP in response to chronic liver injury and resistance to inflammation and liver fibrosis. Activation of LAP is lost in monocytes from patients with multiorgan failure and restored by specifically targeting ITAMi signaling with anti-FcγRIIA F(ab')₂ fragments, or with intravenous immunoglobulin (IVIg). These data suggest the existence of an ITAMi-mediated mechanism by which LAP might protect against inflammation. Sustaining LAP may open therapeutic perspectives for patients with chronic liver disease.

Puerarin Restores Autophagosome-Lysosome Fusion to Alleviate Cadmium-Induced Autophagy Blockade via Restoring the Expression of Rab7 in Hepatocytes

Autophagic dysfunction is one of the main mechanisms by which the environmental pollutant cadmium (Cd) induces cell injury. Puerarin (Pue, a monomeric Chinese herbal medicine extract) has been reported to alleviate Cd-induced cell injury by regulating autophagy pathways; however, its detailed mechanisms are unclear. In the present study, to investigate the detailed mechanisms by which Pue targets autophagy to alleviate Cd hepatotoxicity, alpha mouse liver 12 (AML12) cells were used to construct a model of Cd-induced hepatocyte injury in vitro. First, the protective effect of Pue on Cd-induced cell injury was confirmed by changes in cell proliferation, cell morphology, and cell ultrastructure. Next, we found that Pue activated autophagy and mitigated Cd-induced autophagy blockade. In this process, the lysosome was further activated and the lysosomal degradation capacity was strengthened. We also found that Pue restored the autophagosome-lysosome fusion and the expression of Rab7 in Cd-exposed hepatocytes. However, the fusion of autophagosomes with lysosomes and autophagic flux were inhibited after knocking down Rab7, and were further inhibited after combined treatment with Cd. In addition, after knocking down Rab7, the protective effects of Pue on restoring autophagosome-lysosome fusion and alleviating autophagy blockade in Cd-exposed cells were inhibited. In conclusion, Pue-mediated alleviation of Cd-induced hepatocyte injury was related to the activation of autophagy and the alleviation of autophagy blockade. Pue also restored the fusion of autophagosomes and lysosomes by restoring the protein expression of Rab7, thereby alleviating Cd-induced autophagy blockade in hepatocytes.

Dendrobium officinale polysaccharide triggers mitochondrial disorder to induce colon cancer cell death via ROS-AMPK-autophagy pathway

The homeostasis between mitochondrial function and autophagy is crucial to the physiological activity of cancer cells, and its mechanism is conducive to the development of anti-tumor drugs. Here, we aimed to explore the effect and mechanism of Dendrobium officinale polysaccharide (DOP) on colon cancer cell line CT26. Our data showed that DOP significantly inhibited the proliferation of CT26 cells and elevated autophagy level. Moreover, DOP disrupted mitochondrial function through increasing reactive oxygen species (ROS) and reducing mitochondrial membrane potential (MMP), thereby impairing ATP biosynthesis, which activated AMPK/mTOR autophagy signaling. Intriguingly, the further experiments demonstrated that DOP-induced cytotoxicity, excessive autophagy and mitochondrial dysfunction were reversed after CT26 cells pretreated with antioxidant (N-acetyl-l-cysteine). Herein, these findings implied that DOP-induced mitochondrial dysfunction and cytotoxic autophagy repressed the propagation of CT26 cells via ROS-ATP-AMPK signaling, providing a new opinion for the study of antineoplastic drugs.

Molecular regulation of autophagy in a pro-inflammatory tumour microenvironment: New insight into the role of serum amyloid A

Chronic inflammation, systemic or local, plays a vital role in tumour progression and metastasis. Dysregulation of key physiological processes such as autophagy elicit unfavourable immune responses to induce chronic inflammation. Cytokines, growth factors and acute phase proteins present in the tumour microenvironment regulate inflammatory responses and alter crosstalk between various signalling pathways involved in the progression of cancer. Serum amyloid A (SAA) is a key acute phase protein secreted by the liver during the acute phase response (APR) following infection or injury. However, cancer and cancer-associated cells produce SAA, which when present in high levels in the tumour microenvironment contributes to cancer initiation, progression and metastasis. SAA can activate several signalling pathways such as the PI3K and MAPK pathways, which are also known modulators of the intracellular degradation process, autophagy. Autophagy can be regarded as having a double edged sword effect in cancer. Its dysregulation can induce malignant transformation through metabolic stress which manifests as oxidative stress, endoplasmic reticulum (ER) stress and DNA damage. On the other hand, autophagy can promote cancer survival during metabolic stress, hypoxia and senescence. Autophagy has been utilised to promote the efficiency of chemotherapeutic agents and can either be inhibited or induced to improve treatment outcomes. This review aims to address the known mechanisms that regulate autophagy as well as illustrating the role of SAA in modulating these pathways and its clinical implications for cancer therapy.

Auto-ubiquitination of NEDD4-1 Recruits USP13 to Facilitate Autophagy through Deubiquitinating VPS34

The class III phosphoinositide 3-kinase vacuolar protein sorting 34 (VPS34) is a core protein of autophagy initiation, yet the regulatory mechanisms responsible for its stringent control remain poorly understood. Here, we report that the E3 ubiquitin ligase NEDD4-1 promotes the autophagy flux by targeting VPS34. NEDD4-1 undergoes lysine 29 (K29)-linked auto-ubiquitination at K1279 and serves as a scaffold for recruiting the ubiquitin-specific protease 13 (USP13) to form an NEDD4-1-USP13 deubiquitination complex, which subsequently stabilizes VPS34 to promote autophagy through removing the K48-linked poly-ubiquitin chains from VPS34 at K419. Knockout of either NEDD4-1 or USP13 increased K48-linked ubiquitination and degradation of VPS34, thus attenuating the formation of the autophagosome. Our results identify an essential role for NEDD4-1 in regulating autophagy, which provides molecular insights into the mechanisms by which ubiquitination regulates autophagy flux.

Molecular Mechanism of Autophagy and Its Regulation by Cannabinoids in Cancer

Simple Summary

This review examines the complex function of autophagy in malignancy and explores its regulation by cannabinoids in different cancers. Autophagy is an important process in the maintenance of cellular homeostasis, through the degradation and recycling of cytoplasmic constituents. The action of autophagy is highly dependent on tumour stage and type and the receptors with which ligands interact. Cannabinoids are growingly being acknowledged for their anticancer activities and are known to stimulate several mechanisms such as apoptosis and autophagy. Better understanding the mechanism of action behind autophagy and its regulation by cannabinoids will allow the development of novel cancer therapeutics.

Abstract

Autophagy is a “self-degradation” process whereby malfunctioned cytoplasmic constituents and protein aggregates are engulfed by a vesicle called the autophagosome, and subsequently degraded by the lysosome. Autophagy plays a crucial role in sustaining protein homeostasis and can be an alternative source of energy under detrimental circumstances. Studies have demonstrated a paradoxical function for autophagy in cancer, displaying both tumour suppressive and tumour promotive roles. In early phases of tumour development autophagy promotes cancer cell death. In later phases, autophagy enables cancer cells to survive and withstand therapy. Cannabinoids, which are derivatives of the Cannabis sativa L. plant, have shown to be associated with autophagy induction in cells. There is an emerging interest in studying the signalling pathways involved in cannabinoid-induced autophagy and their potential application in anticancer therapies. In this review, the molecular mechanisms involved in the autophagy degradation process will be discussed. This review also highlights a role for autophagy in cancer progression, with cannabinoid-induced autophagy presenting a novel strategy for anticancer therapy.

Prodigiosin Sensitizes Sensitive and Resistant Urothelial Carcinoma Cells to Cisplatin Treatment

Cisplatin-based treatment is the standard of care therapy for urothelial carcinomas. However, complex cisplatin resistance mechanisms limit the success of this approach. Both apoptosis and autophagy have been shown to contribute to this resistance. Prodigiosin, a secondary metabolite from various bacteria, exerts different biological activities including the modulation of these two cellular stress response pathways. We analyzed the effect of prodigiosin on protein levels of different autophagy- and apoptosis-related proteins in cisplatin-sensitive and -resistant urothelial carcinoma cells (UCCs). Furthermore, we investigated the effect on cell viability of prodigiosin alone or in combination with cisplatin. We made use of four different pairs of cisplatin-sensitive and -resistant UCCs. We found that prodigiosin blocked autophagy in UCCs and re-sensitized cisplatin-resistant cells to apoptotic cell death. Furthermore, we found that prodigiosin is a potent anticancer agent with nanomolar IC50 values in all tested UCCs. In combination studies, we observed that prodigiosin sensitized both cisplatin-sensitive and -resistant urothelial carcinoma cell lines to cisplatin treatment with synergistic effects in most tested cell lines. These effects of prodigiosin are at least partially mediated by altering lysosomal function, since we detected reduced activities of cathepsin B and L. We propose that prodigiosin is a promising candidate for the therapy of cisplatin-resistant urothelial carcinomas, either as a single agent or in combinatory therapeutic approaches.