Molecules and their functions in autophagy

ATG10S promotes IFNL1 expression and autophagic degradation of multiple viral proteins mediated by IFNL1

ATG10S is a newly discovered subtype of the autophagy protein ATG10. It promotes complete macroautophagy/autophagy, degrades multiple viral proteins, and increases the expression of type III interferons. Here, we aimed to investigate the mechanism of ATG10S cooperation with IFNL1 to degrade viral proteins from different viruses. Using western blot, immunoprecipitation (IP), tandem sensor RFP-GFP-LC3B and in situ proximity ligation assays, we showed that exogenous recombinant ATG10S protein (rHsATG10S) could enter into cells through clathrin, and ATG10S combined with ATG7 with IFNL1 assistance to facilitate ATG12-ATG5 conjugation, thereby contributing to the autophagosome formation in multiple cell lines containing different virions or viral proteins. The results of DNA IP and luciferase assays also showed that ATG10S was able to directly bind to a core motif (CAAGGG) within a binding site of transcription factor ZNF460 on the IFNL1 promoter, by which IFNL1 transcription was activated. These results clarified that ATG10S promoted autophagosome formation with the assistance of IFNL1 to ensure autophagy flux and autophagic degradation of multiple viral proteins and that ATG10S could also act as a novel transcription factor to promote IFNL1 gene expression. Importantly, this study further explored the antiviral mechanism of ATG10S interaction with type III interferon and provided a theoretical basis for the development of ATG10S into a new broad-spectrum antiviral protein drug.Abbreviation: ATG: autophagy related; ATG10S: the shorter isoform of autophagy-related 10; CC50: half cytotoxicity concentration; CCV: clathrin-coated transport vesicle; CLTC: clathrin heavy chain; CM: core motif; co-IP: co-immunoprecipitation; CPZ: chlorpromazine; ER: endoplasmic reticulum; HCV: hepatitis C virus; HBV: hepatitis B virus; HsCoV-OC43: Human coronavirus OC43; IFN: interferon; PLA: proximity ligation assay; rHsATG10S: recombinant human ATG10S protein; RLU: relative light unit; SQSTM1: sequestosome 1; ZNF: zinc finger protein.

The preventive and therapeutic role of Lactobacillus spp. in in vitro model of inflammation via affecting autophagy signaling pathway

BACKGROUND

Intestinal inflammation has various causes and leads to some inflammatory diseases, of which autophagy pathway dysfunction could be considered as one of them. Probiotics could have a positive effect on reducing inflammation by activating the autophagy pathway. To evaluate the precise effects of probiotics as preventive and therapeutic agents to control the symptoms of inflammatory diseases, we aimed to investigate the efficacy of Lactobacillus spp. in regulating the autophagy signaling pathway.

METHODS

A quantitative real-time polymerase chain reaction assay was used to analyze the expression of autophagy genes involved in the formation of phagophores, autophagosomes, and autolysosomes after exposing the HT-29 cell line to sonicated pathogens and adding Lactobacillus spp. before, after, and simultaneously with inflammation. A cytokine assay was also accomplished to evaluate the interleukin (IL)-6 and IL-1β level following the probiotic treatment.

RESULTS

Lactobacillus spp. generally increased autophagy gene expression and consumption of Lactobacillus spp. before, simultaneously, and after inflammation, ultimately leading to activate autophagy pathways. The proinflammatory cytokines including IL-6 and IL-1β decreased after probiotic treatment.

CONCLUSIONS

Our native probiotic Lactobacillus spp. showed beneficial effects on HT-29 cells by increasing autophagy gene expression and decreasing the proinflammatory cytokines production in all treatments. Therefore, this novel probiotic cocktail Lactobacillus spp. can prevent and treat inflammation-related diseases.

TMEM9 activates Rab9-dependent alternative autophagy through interaction with Beclin1

Transmembrane protein 9 (TMEM9) is a transmembrane protein that regulates lysosomal acidification by interacting with the v-type ATPase complex. However, the role of TMEM9 in the lysosome-dependent autophagy machinery has yet to be identified. In this study, we demonstrate that the lysosomal protein TMEM9, which is involved in vesicle acidification, regulates Rab9-dependent alternative autophagy through its interaction with Beclin1. The cytosolic domain of TMEM9 interacts with Beclin1 via its Bcl-2-binding domain. This interaction between TMEM9 and Beclin1 dissociates Bcl-2, an autophagy-inhibiting partner, from Beclin1, thereby activating LC3-independent and Rab9-dependent alternative autophagy. Late endosomal and lysosomal TMEM9 apparently colocalizes with Rab9 but not with LC3. Furthermore, we show that multiple glycosylation of TMEM9, essential for lysosomal localization, is essential for its interaction with Beclin1 and the activation of Rab9-dependent alternative autophagy. These findings reveal that TMEM9 recruits and activates the Beclin1 complex at the site of Rab9-dependent autophagosome to induce alternative autophagy.

The Roles of Endocytosis and Autophagy at the Cellular Level During Influenza Virus Infection: A Mini-Review

Acute respiratory infections contribute to morbidity and mortality worldwide. The common cause of this deadly disease is a virus, and one of the most commonly found is the influenza virus. Influenza viruses have several capabilities in infection, including utilizing the host's machinery to survive within cells and replicate safely. This review aims to examine the literature on how influenza viruses use host machinery, including endocytosis and autophagy, for their internalization and replication within cells. This review method involves a literature search by examining articles published in the PubMed and Scopus databases. The keywords used were "Endocytosis" OR "Autophagy" AND "Influenza Virus". Eighteen articles were included due to inclusion and exclusion criteria. GTPases switch, and V-ATPase plays a key role in the endocytic machinery hijacked by influenza viruses to enter host cells. On the other hand, LC3 and Atg5 facilitate influenza-induced apoptosis via the autophagic pathway. In conclusion, influenza viruses primarily use clathrin-mediated endocytosis to enter cells and avoid degradation during endosomal maturation by exiting endosomes for transfer to the nucleus for replication. It also uses autophagy to induce apoptosis to continue replication. The capability of the influenza viruses to hijack endocytosis and autophagy mechanisms could be critical points for further research. Therefore, we discuss how the influenza virus utilizes both endocytosis and autophagy and the approach for a new strategic therapy targeting those mechanisms.

Reduced circ_lrrc49 in trigeminal ganglion contributes to neuropathic pain in mice by downregulating Ist1 and impairing autophagy

Orofacial neuropathic pain is a common symptom induced by orofacial nerve injury caused by a range of trauma or dental and maxillofacial procedures but lacks effective treatment. Circular RNAs (circRNAs) participate in the regulatory processes of neuropathic pain. Nevertheless, the biological roles of circRNAs in orofacial neuropathic pain remain unexplored. In this study, circRNA sequencing and Real-time quantitative polymerase chain reaction (RT-qPCR) were carried out. Notably, a novel circRNA named circ_lrrc49 was identified to be downregulated following chronic constriction injury of the infraorbital nerve (CCI-ION) in mice on day 14. Subsequent RNA Antisense Purification (RAP)-mass spectrometry and RNA immunoprecipitation found a direct interaction between circ_lrrc49 and increased sodium tolerance 1 homolog (Ist1). Western blot (WB) identified decreased expression of Ist1 on day 14 post-CCI-ION. Considering the known relationship between Ist1 and autophagy, LC3-II and p62 were detected to be upregulated, and an accumulation of autophagosomes were observed at the same time point. Besides, the knockdown of circ_lrrc49 by small interfering RNA (siRNA) reduced Ist1 expression, increased LC3-II, p62 levels and autophagosomes amount, and evoked orofacial mechanical hypersensitivity, which could be counteracted by the Ist1 overexpression. Similarly, the knockdown of Ist1 by siRNA also increased LC3-II and p62 levels and evoked orofacial mechanical hypersensitivity without influence on circ_lrrc49. Moreover, autophagy activation by rapamycin alleviated orofacial mechanical hypersensitivity evoked by CCI-ION or circ_lrrc49 knockdown. In conclusion, our data revealed the existence of a circ_lrrc49/Ist1/autophagy signaling axis contributing to the progression of orofacial neuropathic pain. These discoveries reveal the intricate molecular processes that drive orofacial neuropathic pain and identify circ_lrrc49 as a promising target for potential therapeutic interventions.

Hydatid fluid from Echinococcus granulosus induces autophagy in dendritic cells and promotes polyfunctional T-cell responses

Parasites possess remarkable abilities to evade and manipulate the immune response of their hosts. Echinococcus granulosus is a parasitic tapeworm that causes cystic echinococcosis in animals and humans. The hydatid fluid released by the parasite is known to contain various immunomodulatory components that manipulate host´s defense mechanism. In this study, we focused on understanding the effect of hydatid fluid on dendritic cells and its impact on autophagy induction and subsequent T cell responses. Initially, we observed a marked downregulation of two C-type lectin receptors in the cell membrane, CLEC9A and CD205 and an increase in lysosomal activity, suggesting an active cellular response to hydatid fluid. Subsequently, we visualized ultrastructural changes in stimulated dendritic cells, revealing the presence of macroautophagy, characterized by the formation of autophagosomes, phagophores, and phagolysosomes in the cell cytoplasm. To further elucidate the underlying molecular mechanisms involved in hydatid fluid-induced autophagy, we analyzed the expression of autophagy-related genes in stimulated dendritic cells. Our results demonstrated a significant upregulation of beclin-1, atg16l1 and atg12, indicating the induction of autophagy machinery in response to hydatid fluid exposure. Additionally, using confocal microscopy, we observed an accumulation of LC3 in dendritic cell autophagosomes, confirming the activation of this catabolic pathway associated with antigen presentation. Finally, to evaluate the functional consequences of hydatid fluid-induced autophagy in DCs, we evaluated cytokine transcription in the splenocytes. Remarkably, a robust polyfunctional T cell response, with inhibition of Th2 profile, is characterized by an increase in the expression of il-6, il-10, il-12, tnf-α, ifn-γ and tgf-β genes. These findings suggest that hydatid fluid-induced autophagy in dendritic cells plays a crucial role in shaping the subsequent T cell responses, which is important for a better understanding of host-parasite interactions in cystic echinococcosis.

Norflurazon causes cell death and inhibits implantation-related genes in porcine trophectoderm and uterine luminal epithelial cells

Norflurazon, an inhibitor of carotenoid synthesis, is a pre-emergent herbicide that prevents growth of weeds. The norflurazon is known to hamper embryo development in non-mammals. However, specific toxic effects of norflurazon on mammalian maternal and fetal cells have not been elucidated. Thus, the hypothesis of this study is that norflurazon may influence the toxic effects between maternal and fetal cells during early pregnancy in pigs. We aimed to examine the toxic effects of norflurazon in porcine trophectoderm (Tr) and uterine luminal epithelium (LE) cells. Norflurazon, administered at 0, 20, 50 or 100 μM for 48 h was used to determine its effects on cell proliferation and cell-cycle arrest. For both uterine LE and Tr cell lines, norflurazone caused mitochondrial dysfunction by inhibiting mitochondrial respiration and ATP production, and down-regulated expression of mRNAs of mitochondrial complex genes. Norflurazon increased cell death by increasing intracellular calcium and regulating PI3K and MAPK cell signaling pathways, as well as endoplasmic reticulum (ER) stress, ER-mitochondrial contact, and autophagy-related target proteins. Norflurazone also inhibited expression of genes required for implantation of blastocysts, including SMAD2, SMAD4, and SPP1. These findings indicate that norflurazon may induce implantation failure in pigs and other mammals through adverse effects on both Tr and uterine LE cells.

Effects and mechanisms of Salmonella plasmid virulence gene spv on host-regulated cell death

Salmonella is responsible for the majority of food poisoning outbreaks around the world. Pathogenic Salmonella mostly carries a virulence plasmid that contains the Salmonella plasmid virulence gene (spv), a highly conserved sequence encoding effector proteins that can manipulate host cells. Intestinal epithelial cells are crucial components of the innate immune system, acting as the first barrier of defense against infection. When the barrier is breached, Salmonella encounters the underlying macrophages in lamina propria, triggering inflammation and engaging in combat with immune cells recruited by inflammatory factors. Host regulated cell death (RCD) provides a variety of means to fight against or favour Salmonella infection. However, Salmonella releases effector proteins to regulate RCD, evading host immune killing and neutralizing host antimicrobial effects. This review provides an overview of pathogen-host interactions in terms of (1) pathogenicity of Salmonella spv on intestinal epithelial cells and macrophages, (2) mechanisms of host RCD to limit or promote pathogenic Salmonella expansion, and (3) effects and mechanisms of Salmonella spv gene on host RCD.

L-Dopa decarboxylase modulates autophagy in hepatocytes and is implicated in dengue virus-caused inhibition of autophagy completion

The enzyme L-Dopa Decarboxylase (DDC) synthesizes the catecholamine dopamine and the indolamine serotonin. Apart from its role in the brain as a neurotransmitter biosynthetic enzyme, DDC has been detected also in the liver and other peripheral organs, where it is implicated in cell proliferation, apoptosis, and host-virus interactions. Dengue virus (DENV) suppresses DDC expression at the later stages of infection, during which DENV also inhibits autophagosome-lysosome fusion. As dopamine affects autophagy in neuronal cells, we investigated the possible association of DDC with autophagy in human hepatocytes and examined whether DDC mediates the relationship between DENV infection and autophagy. We performed DDC silencing/overexpression and evaluated autophagic markers upon induction of autophagy, or suppression of autophagosome-lysosome fusion. Our results showed that DDC favored the autophagic process, at least in part, through its biosynthetic function, while knockdown of DDC or inhibition of DDC enzymatic activity prevented autophagy completion. In turn, autophagy induction upregulated DDC, while autophagy reduction by chemical or genetic (ATG14L knockout) ways caused the opposite effect. This study also implicated DDC with the cellular energetic status, as DDC silencing reduced the oxidative phosphorylation activity of the cell. We also report that upon DDC silencing, the repressive effect of DENV on the completion of autophagy was enhanced, and the inhibition of autolysosome formation did not exert an additive effect on viral proliferation. These data unravel a novel role of DDC in the autophagic process and suggest that DENV downregulates DDC expression to inhibit the completion of autophagy, reinforcing the importance of this protein in viral infections.

Cellular stress responses as modulators of drug cytotoxicity in pharmacotherapy of glioblastoma

Despite the extensive efforts to find effective therapeutic strategies, glioblastoma (GBM) remains a therapeutic challenge with dismal prognosis of survival. Over the last decade the role of stress responses in GBM therapy has gained a great deal of attention, since depending on the duration and intensity of these cellular programs they can be cytoprotective or promote cancer cell death. As such, initiation of the UPR, autophagy or oxidative stress may either impede or facilitate drug-mediated cell killing. In this review, we summarize the mechanisms that regulate ER stress, autophagy, and oxidative stress during GBM development and progression to later discuss the involvement of these stress pathways in the response to different treatments. We also discuss how a precise understanding of the molecular mechanisms regulating stress responses evoked by different pharmacological agents could decisively contribute to the design of novel and more effective combinational treatments against brain malignancies.

Resolvin D1 Induces mTOR-independent and ATG5-dependent Autophagy in BV-2 Microglial Cells

OBJECTIVE

The activation state of microglia is known to occupy a central position in the pathophysiological process of cerebral inflammation. Autophagy is a catabolic process responsible for maintaining cellular homeostasis. In recent years, autophagy has been demonstrated to play an important role in neuroinflammation. Resolvin D1 (RvD1) is a promising therapeutic mediator that has been shown to exert substantial anti-inflammatory and proresolving activities. However, whether RvD1-mediated resolution of inflammation in microglia is related to autophagy regulation needs further investigation. The present study aimed to explore the effect of RvD1 on microglial autophagy and its corresponding pathways.

METHODS

Mouse microglial cells (BV-2) were cultured, treated with RvD1, and examined by Western blotting, confocal immunofluorescence microscopy, transmission electron microscopy, and flow cytometry.

RESULTS

RvD1 promoted autophagy in both BV-2 cells and mouse primary microglia by favoring the maturation of autophagosomes and their fusion with lysosomes. Importantly, RvD1 had no significant effect on the activation of mammalian target of rapamycin (mTOR) signaling. Furthermore, RvD1-induced mTOR-independent autophagy was confirmed by observing reduced cytoplasmic calcium levels and suppressed calcium/calmodulin-dependent protein kinase II (CaMK II) activation. Moreover, by downregulating ATG5, the increased phagocytic activity induced by RvD1 was demonstrated to be tightly controlled by ATG5-dependent autophagy.

CONCLUSION

The present work identified a previously unreported mechanism responsible for the role of RvD1 in microglial autophagy, highlighting its therapeutic potential against neuroinflammation.

Green tea catechin prevents oxidative stress-regulated autophagy and apoptosis signaling, and inhibits tenderness in postmortem bovine longissimus thoracis et lumborum muscle

Although green tea catechin has been reported to be an antioxidant and preservative in meat, the extent to which it affects the tenderization of bovine muscle remains largely unknown. This study seeks to evaluate the effect of catechin on the interplay between apoptosis and autophagy, and subsequently, the development of bovine muscle tenderness. The results indicate that catechin significantly alleviated oxidative stress. A concomitant reduction of autophagic markers LC3-II/LC3-I ratio, Beclin-1, and Atg7 levels were caused by catechin. Besides, aforementioned autophagy inhibition was further augmented by PI3K/Akt/mTOR activation. Additionally, catechin protected against mitochondrial dysfunction and inhibited mitochondria-dependent caspase apoptosis pathway. Furthermore, there was a reciprocal inhibition between autophagy and apoptosis. Ultimately, tenderness at 24 and 120 h, an increase in the gap between muscle fiber bundles, and disintegration of myofibrillar architectures were all inhibited by catechin. Therefore, despite alleviating oxidative stress, catechin may hamper tenderization pattern of postmortem bovine muscle.

DAP1 regulates osteoblast autophagy via the ATG16L1-LC3 axis in Graves' disease-induced osteoporosis

OBJECTIVE

This study aimed to uncover a critical protein and its mechanisms in modulating autophagy in Graves' disease (GD)-induced osteoporosis (OP).

METHODS

We discovered the target protein, death-associated protein 1 (DAP1), using bone proteomics analysis. Furthermore, genetic overexpression and knockdown (KD) of DAP1 in bone and MC3T3-E1 cells revealed DAP1 effects on autophagy and osteogenic markers, and autophagic vacuoles in cells were detected using transmission electron microscopy and the microtubule-associated protein 1 light chain 3 alpha (MAP1LC3/LC3) dual fluorescence system. An autophagy polymerase chain reaction (PCR) array kit was used to identify the key molecules associated with DAP1-regulated autophagy.

RESULTS

DAP1 levels were significantly higher in the bone tissue of GD mice and MC3T3-E1 cells treated with triiodothyronine (T3). DAP1 overexpression reduced LC3 lipidation, autophagic vacuoles, RUNX family transcription factor 2 (RUNX2), and osteocalcin (OCN) expression in MC3T3-E1 cells, whereas DAP1 KD reversed these changes. In vivo experiments revealed that GD mice with DAP1 KD had greater bone mass than control mice. DAP1-overexpressing (OE) cells had lower levels of phosphorylated autophagy-related 16-like 1 (ATG16L1) and LC3 lipidation, whereas DAP1-KD cells had higher levels.

CONCLUSIONS

DAP1 was found to be a critical regulator of autophagy homeostasis in GD mouse bone tissue and T3-treated osteoblasts because it negatively regulated autophagy and osteogenesis in osteoblasts via the ATG16L1-LC3 axis.

Wrinkled topography regulates osteogenesis via autophagy-mediated Wnt/β-catenin signaling pathway in MC3T3-E1 cells

OBJECTIVE

In this study, we aimed to evaluate the effects of different dimensional wrinkled in topography on the osteogenic differentiation of MC3T3-E1 cells and explored the underlying mechanisms.

DESIGN

Polydimethylsiloxane (PDMS) with a wrinkled topography was synthesized using an elastomer base and crosslinking while observing by atomic force microscopy. MC3T3-E1 proliferation was detected by Cell Counting Kit-8(CCK-8) assays and the cell morphology was determined by phalloidin staining. Osteogenetic genes expression levels were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting. In addition, Autophagy-related genes expression levels were evaluated by immunostaining and western blotting in MC3T3-E1 in order to assess the induction of autophagy.

RESULTS

In this experiment, the 0.7 µm amplitude and 3 µm wavelength (W3) group increased the expression of osteogenic markers, whereas the 4.3 µm amplitude and 27 µm wavelength (W27) group showed inhibition. Both the cytoplasm and the nucleus of β-catenin, compared with those of the Flat, W3 increased, whereas W27 decreased. At the same time, the autophagy was consistent with the influence of the topography on osteogenic differentiation. Moreover, using CQ or RAPA significantly inhibited or promoted autophagy, as well as partially decreasing or increasing osteogenesis, respectively. Infecting siRNA-β-catenin decreased the expression of RUNX2 and OSX in MC3T3-E1 cells both treated with CQ and RAPA.

CONCLUSIONS

Wrinkled topographies activated the autophagy-mediated Wnt/β-catenin signaling pathway and affected the osteogenic differentiation of MC3T3-E1 cells. The introduction of aligned topographies on biomaterial scaffolds could provide physical cues with which modulate MC3T3-E1 responses for bone engineering constructs.

Restored autophagy is protective against PAK3-induced cardiac dysfunction

Despite the development of clinical treatments, heart failure remains the leading cause of mortality. We observed that p21-activated kinase 3 (PAK3) was augmented in failing human and mouse hearts. Furthermore, mice with cardiac-specific PAK3 overexpression exhibited exacerbated pathological remodeling and deteriorated cardiac function. Myocardium with PAK3 overexpression displayed hypertrophic growth, excessive fibrosis, and aggravated apoptosis following isoprenaline stimulation as early as two days. Mechanistically, using cultured cardiomyocytes and human-relevant samples under distinct stimulations, we, for the first time, demonstrated that PAK3 acts as a suppressor of autophagy through hyper-activation of the mechanistic target of rapamycin complex 1 (mTORC1). Defective autophagy in the myocardium contributes to the progression of heart failure. More importantly, PAK3-provoked cardiac dysfunction was mitigated by administering an autophagic inducer. Our study illustrates a unique role of PAK3 in autophagy regulation and the therapeutic potential of targeting this axis for heart failure.

Silicon dioxide nanoparticles compromise decidualization via autophagy impairment to possibly cause embryo resorption

The wide application of silicon dioxide nanoparticles (SiO₂NPs) has raised concerns about their harmful effects on reproduction. The purpose of this research was to investigate the toxic effects and the possible mechanisms by which SiO₂NPs affect decidualization and pregnancy progression. We found that SiO₂NPs could inhibit decidualization, both in mice and in human endometrial stromal cells (HESCs). Embryo resorption was also evident in mice treated with SiO₂NPs. When HESCs were treated with SiO₂NPs, decidualization was inhibited and there was an increase in intracellular lysosomes and autophagosomes as well as the blockage of autophagic flux. Interestingly, a reduction of autophagosome accumulation via 3-methyladenine (3MA) significantly restored the decidualization of HESCs. In summary, our results indicate that SiO₂NPs can affect embryo survival by impairing decidualization through a dysfunctional autophagic process.

H3K27 acetylation activated-CCS regulates autophagy and apoptosis of lung cancer by alleviating oxidative stress

Copper chaperone for superoxide dismutase (CCS) is abnormally expressed in various human malignancies. However, the function and mechanism of CCS in lung cancer progression remain unclear. In the current study, CCS protein and mRNA levels were found to be increased in lung adenocarcinoma (LUAD) tissue and cell lines. Patients with higher CCS levels had a poorer prognosis. Decreasing the enrichment of histone H3 Lys27 acetylation (H3K27ac) by A-485 inhibited CCS expression. CCS depletion upregulated reactive oxygen species (ROS) levels, aggravated oxidative stress, inhibited autophagy, inhibited cell survival, and promoted apoptosis. The treatment of antioxidant N-Acetyl-L-cysteine (NAC) rescued these changes induced by CCS depletion. CCS also was found to be related to the immune infiltration of CD8 + T cells and regulatory T cells in LUAD. These data indicated that overexpression of CCS activated by H3K27 acetylation relieved oxidative stress, promoted autophagy, and inhibited apoptosis. CCS may be regarded as a potential therapeutic target for LUAD.

Co-Targeting the EGFR and PI3K/Akt Pathway to Overcome Therapeutic Resistance in Head and Neck Squamous Cell Carcinoma: What about Autophagy?

Resistance to EGFR-targeted therapy is a major obstacle on the road to effective treatment options for head and neck cancers. During the search for underlying mechanisms and regulators of this resistance, there were several indications that EGFR-targeted therapy resistance is (partially) mediated by aberrant signaling of the PI3K/Akt pathway. Genomic alterations in and/or overexpression of major components of the PI3K/Akt pathway are common in HNSCC tumors. Therefore, downstream effectors of the PI3K/Akt pathway serve as promising targets in the search for novel therapeutic strategies overcoming resistance to EGFR inhibitors. As both the EGFR/Ras/Raf/MAPK and the PI3K/Akt pathway are involved in autophagy, combinations of EGFR and PI3K/Akt pathway inhibitors can induce an autophagic response in tumor cells. This activation of autophagy can be seen as a "double-edge sword", depending on the cellular context. Autophagy is largely known as a cytoprotective mechanism, but it can also be a mechanism of programmed (autophagic) cell death. The activation of autophagy during anti-cancer treatment is, therefore, not necessarily a bad sign. However, in HNSCC, the role of therapy-induced autophagy as an anti-tumor mechanism is still largely unclear. Further research is warranted to understand the potential of combination treatments targeting both the EGFR and PI3K/Akt pathway.

Mechanism of autophagy induced by low concentrations of chlorantraniliprole in silk gland, Bombyx mori

Chlorantraniliprole (CAP) is widely used in the control of agricultural pests, and its residues can affect the formation of silkworm (Bombyx. mori) cocoon easily. To accurately evaluate the toxicity of CAP to silkworms and clarify the mechanism of its effect on silk gland function, we proposed a novel toxicity evaluation method based on the body weight changes after CAP exposure. We also analyzed the Ca²⁺-related ATPase activity, characterized energy metabolism and transcriptional changes about the autophagy key genes on the downstream signaling pathways. The results showed that after a low concentration of CAP exposed for 96 h, there were CAP residues in the silk glands of B. mori, the activities of Ca²⁺-ATPase and Ca²⁺-Mg²⁺-ATPase decreased significantly (P ≤ 0.01), and the activation of AMPK-related genes AMPK-α and AMPK-β were up-regulated by 6.39 ± 0.02-fold and 12.33 ± 1.06-fold, respectively, reaching a significant level (P ≤ 0.01)). In addition, the autophagy-related genes Atg1, Atg6, Atg5, Atg7, and Atg8 downstream AMPK were significantly up-regulated at 96 h (P ≤ 0.05). The results of immunohistochemistry and protein expression assay for autophagy marker Atg8 further confirmed the occurrence of autophagy. Overall, our results indicate that CAP exposure leads to autophagy in the silk gland of B. mori and affects their physiological functions, which provides guidance for the evaluation of toxicity of low concentration environmental CAP residues to insects.

Luteolin, a Potent Anticancer Compound: From Chemistry to Cellular Interactions and Synergetic Perspectives

Increasing rates of cancer incidence and the toxicity concerns of existing chemotherapeutic agents have intensified the research to explore more alternative routes to combat tumor. Luteolin, a flavone found in numerous fruits, vegetables, and herbs, has exhibited a number of biological activities, such as anticancer and anti-inflammatory. Luteolin inhibits tumor growth by targeting cellular processes such as apoptosis, cell-cycle progression, angiogenesis and migration. Mechanistically, luteolin causes cell death by downregulating Akt, PLK-1, cyclin-B1, cyclin-A, CDC-2, CDK-2, Bcl-2, and Bcl-xL, while upregulating BAX, caspase-3, and p21. It has also been reported to inhibit STAT3 signaling by the suppression of STAT3 activation and enhanced STAT3 protein degradation in various cancer cells. Therefore, extensive studies on the anticancer properties of luteolin reveal its promising role in chemoprevention. The present review describes all the possible cellular interactions of luteolin in cancer, along with its synergistic mode of action and nanodelivery insight.

FIP200 Methylation by SETD2 Prevents Trim21-Induced Degradation and Preserves Autophagy Initiation

FIP200, also known as RB1CC1, is a protein that assembles the autophagy initiation complex. Its post-translational modifications and degradation mechanisms are unclear. Upon autophagy activation, we find that FIP200 is methylated at lysine1133 (K1133) by methyltransferase SETD2. We identify the E3 ligase Trim21 to be responsible for FIP200 ubiquitination by targeting K1133, resulting in FIP200 degradation through the ubiquitin–proteasome system. SETD2-induced methylation blocks Trim21-mediated ubiquitination and degradation, preserving autophagy activity. SETD2 and Trim21 orchestrate FIP200 protein stability to achieve dynamic and precise control of autophagy flux.

Genetic Analysis of the ATG16L1 c.898A>G (p.T300A) Variant in Acute and Chronic Pancreatitis

OBJECTIVES

Human and animal studies suggest an important role of autophagy in the pathogenesis of pancreatitis. ATG16L1 (autophagy-related 16 like 1) is part of a protein complex that is involved in the formation of autophagosomes. The c.898A > G (p.T300A) variant of ATG16L1 is associated with Crohn disease. In this study, we analyzed ATG16L1 c.898A > G (p.T300A) for an association with pancreatitis.

METHODS

We genotyped 777 patients and 551 control subjects of German origin by melting curve analysis using fluorescence resonance energy transfer probes. The patient group included 429 patients with nonalcoholic chronic pancreatitis (CP), 141 patients with alcoholic CP, and 207 patients with acute pancreatitis (AP). We classified AP by severity according to the Atlanta symposium 1992.

RESULTS

Allele and genotype frequencies of ATG16L1 c.898A > G (p.T300A) did not differ significantly between patients and controls (G allele frequencies: nonalcoholic CP, 49.9%; alcoholic CP, 48.2%; AP, 49.5%; controls, 52.7%). We found no significant association with the severity of AP either.

CONCLUSIONS

Our data do not support a role of ATG16L1 c.898A > G (p.T300A) in the pathogenesis of AP or CP or an influence on the severity of AP.

Progress in preclinical studies of macrophage autophagy in the regulation of ALI/ARDS

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a critical clinical syndrome with high morbidity and mortality that poses a major challenge in critical care medicine. The development of ALI/ARDS involves excessive inflammatory response, and macrophage autophagy plays an important role in regulating the inflammatory response in ALI/ARDS. In this paper, we review the effects of autophagy in regulating macrophage function, discuss the roles of macrophage autophagy in ALI/ARDS, and highlight drugs and other interventions that can modulate macrophage autophagy in ALI/ARDS to improve the understanding of the mechanism of macrophage autophagy in ALI/ARDS and provide new ideas and further research directions for the treatment of ALI/ARDS.

Autophagy Balances Neuroinflammation in Alzheimer's Disease

Autophagy is a highly evolutionary conserved process that degrades cytosolic macromolecules or damaged organelles (e.g., mitochondria), as well as intracellular pathogens for energy and survival. Dysfunction of autophagy has been associated with the pathologies of Alzheimer's disease (AD), including Aβ plaques and neurofibrillary tangles. Recently, the presence of sustained immune response in the brain has been considered a new core pathology in AD. Accumulating evidence suggests that autophagy activation may suppress inflammation response through degrading inflammasomes or pro-inflammatory cytokines and improving immune system function in both clinical trials and preclinical studies. This review provides an overview of updated information on autophagy and inflammation and their potential mediators in AD. In summary, we believe that understanding the relationship between autophagy and inflammation will provide insightful knowledge for future therapeutic implications in AD.

HSF-1: Guardian of the Proteome Through Integration of Longevity Signals to the Proteostatic Network

Discoveries made in the nematode Caenorhabditis elegans revealed that aging is under genetic control. Since these transformative initial studies, C. elegans has become a premier model system for aging research. Critically, the genes, pathways, and processes that have fundamental roles in organismal aging are deeply conserved throughout evolution. This conservation has led to a wealth of knowledge regarding both the processes that influence aging and the identification of molecular and cellular hallmarks that play a causative role in the physiological decline of organisms. One key feature of age-associated decline is the failure of mechanisms that maintain proper function of the proteome (proteostasis). Here we highlight components of the proteostatic network that act to maintain the proteome and how this network integrates into major longevity signaling pathways. We focus in depth on the heat shock transcription factor 1 (HSF1), the central regulator of gene expression for proteins that maintain the cytosolic and nuclear proteomes, and a key effector of longevity signals.

Hormetic Heat Shock Enhances Autophagy through HSF1 in Retinal Pigment Epithelium Cells

To maintain homeostasis, cells have evolved stress-response pathways to cope with exogenous and endogenous stress factors. Diverse stresses at high doses may be detrimental, albeit low doses of stress, known as hormesis, can be beneficial. Upon exposure to stress, such as temperature rise, the conventional heat shock response (HSR) regulated by the heat shock transcription factor 1 (HSF1) facilitates refolding of misfolded proteins with the help of heat shock proteins (HSPs). However, the role and molecular mechanisms underlying the beneficial effects of HSR with other clearance processes, such as autophagy, remain poorly understood. In this study, human ARPE-19 cells, an in vitro model of retinal pigment epithelium, were treated with hormetic heat shock (HHS) and the autophagy expression profile was examined using quantitative PCR (qPCR), immunoblotting, immunoprecipitation, and immunofluorescence. We demonstrate that HHS enhances the expression of fundamental autophagy-associated genes in ARPE-19 cells through the activation of HSF1. HHS transiently increases the level of SQSTM1 and LC3B-II and activates autophagy. These findings reveal a role for autophagic HSF1-regulated functions and demonstrate the contribution of autophagy to hormesis in the HSR by improving proteostasis.

Poly(I:C) attenuates myocardial ischemia/reperfusion injury by restoring autophagic function

Polyinosinic-polycytidylic acid (poly(I:C)) is the agonist of Toll-like receptor 3 (TLR3), which participates in innate immune responses under the condition of myocardial ischemia/reperfusion injury (MIRI). It has been shown that poly(I:C) exhibited cardioprotective activities through the PI3K/Akt pathway, which is the main signal transduction pathway during autophagy. However, the precise mechanism by whether poly(I:C) regulates autophagy remains poorly understood. Thus, this study was designed to investigate the therapeutic effect of poly(I:C) against MIRI and the underlying pathway connection with autophagy. We demonstrated that 1.25 and 5 mg/kg poly(I:C) preconditioning significantly reduced myocardial infarct size and cardiac dysfunction. Moreover, poly(I:C) significantly promoted cell survival by restoring autophagy flux and then regulating it to an adequate level Increased autophagy protein Beclin1 and LC3II together with p62 degradation after additional chloroquine. In addition, mRFP-GFP-LC3 adenoviruses exhibited autophagy activity in neonatal rat cardiac myocytes (NRCMs). Mechanistically, poly(I:C) activated the PI3K/AKT/mTOR pathway to induce autophagy, which was abolished by LY294002 (PI3K antagonist), rapamycin (autophagy activator and mTOR inhibitor), or 3-methyladenine (autophagy inhibitor), suggesting either inhibition of the PI3K/Akt/mTOR pathway or autophagy activity interrupt the beneficial effect of poly(I:C) preconditioning. In conclusion, poly(I:C) promotes cardiomyocyte survival from ischemia/reperfusion injury by regulating autophagy via the PI3K/Akt/mTOR pathway.

Short-Term Autophagy Preconditioning Upregulates the Expression of COX2 and PGE2 and Alters the Immune Phenotype of Human Adipose-Derived Stem Cells In Vitro

Human adipose-derived stem cells (hASCs) are potent modulators of inflammation and promising candidates for the treatment of inflammatory and autoimmune diseases. Strategies to improve hASC survival and immunoregulation are active areas of investigation. Autophagy, a homeostatic and stress-induced degradative pathway, plays a crucial role in hASC paracrine signaling—a primary mechanism of therapeutic action. Therefore, induction of autophagy with rapamycin (Rapa), or inhibition with 3-methyladenine (3-MA), was examined as a preconditioning strategy to enhance therapeutic efficacy. Following preconditioning, both Rapa and 3-MA-treated hASCs demonstrated preservation of stemness, as well as upregulated transcription of cyclooxygenase-2 (COX2) and interleukin-6 (IL-6). Rapa-ASCs further upregulated TNFα-stimulated gene-6 (TSG-6) and interleukin-1 beta (IL-1β), indicating additional enhancement of immunomodulatory potential. Preconditioned cells were then stimulated with the inflammatory cytokine interferon-gamma (IFNγ) and assessed for immunomodulatory factor production. Rapa-pretreated cells, but not 3-MA-pretreated cells, further amplified COX2 and IL-6 transcripts following IFNγ exposure, and both groups upregulated secretion of prostaglandin-E2 (PGE2), the enzymatic product of COX2. These findings suggest that a 4-h Rapa preconditioning strategy may bestow the greatest improvement to hASC expression of cytokines known to promote tissue repair and regeneration and may hold promise for augmenting the therapeutic potential of hASCs for inflammation-driven pathological conditions.

Retinal Neuroprotective Effect of Mesenchymal Stem Cells Secretome Through Modulation of Oxidative Stress, Autophagy, and Programmed Cell Death

Purpose

Degenerative mechanisms of retinal neurodegenerative diseases (RND) share common cellular and molecular signalization pathways. Curative treatment does not exist and cell-based therapy, through the paracrine properties of mesenchymal stem cells (MSC), is a potential unspecific treatment for RND. This study aimed to evaluate the neuroprotective capability of human bone marrow (bm) MSC secretome and its potential to modulate retinal responses to neurodegeneration.

Methods

An in vitro model of spontaneous retinal neurodegeneration was used to compare three days of monocultured neuroretina (NR), NR cocultured with bmMSC, and NR cultured with bmMSC secretome. We evaluated retinal morphology markers (Lectin peanut agglutinin, rhodopsin, protein kinase C α isoform, neuronal-specific nuclear protein, glial fibrillary acidic protein, TdT-mediated dUTP nick-end labeling, and vimentin) and proteins involved in apoptosis (apoptosis-inductor factor, caspase-3), necroptosis (MLKL), and autophagy (p62). Besides, we analyzed the relative mRNA expression through qPCR of genes involved in apoptosis (BAX, BCL2, CASP3, CASP8, CASP9), necroptosis (MLKL, RIPK1, RIPK3), autophagy (ATG7, BCLIN1, LC3B, mTOR, SQSTM1), oxidative stress (COX2, CYBA, CYBB, GPX6, SOD1, TXN2, TXNRD1) and inflammation (IL1, IL6, IL10, TGFb1, TNFa).

Results

The bmMSC secretome preserves retinal morphology, limits pro-apoptotic- and pro-necroptotic-related gene and protein expression, modulates autophagy-related genes and proteins, and stimulates the activation of antioxidant-associated genes.

Conclusions

The neuroprotective ability of the bmMSC secretome is associated with activation of antioxidant machinery, modulation of autophagy, and inhibition of apoptosis and necroptosis during retinal degeneration. The neuroprotective effect of bmMSC secretomes in the presence/absence of MSC looks similar. Our current results reinforce the hypothesis that the human bmMSC secretome slows retinal neurodegeneration and may be a therapeutic option for treating RND.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Methylation silencing of ULK2 via epithelial-mesenchymal transition causes transformation to poorly differentiated gastric cancers

BACKGROUND

Diffuse-type gastric cancers (DGC) typically have a poor prognosis related to their invasion and metastasis, in which the epithelial-mesenchymal transition (EMT) is the initiation step. ULK2 plays a role in the autophagy initiation, which might provide a survival advantage in cancer cells. Although knock-down of ULK2 reportedly induces autophagy and EMT in a lung cancer cell line, the mechanism of EMT via the down-regulation of ULK2, as well as its clinical significance, remains yet unclear. The present study, therefore, aims at clarifying this mechanism and its clinical significance in gastric cancers.

METHODS

We examined ULK2 mRNA expression in gastric cancer tissues and normal gastric tissues of healthy people. The effects of knock-downed ULK2 were examined in two gastric cancer cells, which were investigated in terms of their gene expression changes by the mRNA microarray.

RESULTS

ULK2 was strongly expressed in intestinal-type cancers but was scarcely expressed in DGC by immunohistochemical staining. Furthermore, we found that ULK2 was methylated in DGC and was unmethylated in corresponding adjacent normal tissues. Then, we validated whether knock-down of ULK2 could induce autophagy, cell migration, and EMT in NUGC3 and MKN45 cells. Using mRNA microarray analysis, we confirmed that knock-down of ULK2 changed expressions of oncogenic genes associated with cell migration and EMT. Autophagy inhibitor suppressed cell migration and EMT induced by knock-down of ULK2 in NUGC3 and MKN45.

CONCLUSION

Methylation silencing of ULK2 could induce cell migration and EMT by means of autophagy induction, causing transformation to poorly differentiated cancers.

Polymorphisms in autophagy genes are genetic susceptibility factors in glioblastoma development

Background

Glioblastoma is the most aggressive and common malignant primary brain tumor in adults. Many genetic, epigenetic and genomic mutations have been identified in this tumor, but no driving cause has been identified yet for glioblastoma pathogenesis. Autophagy has proved to be deregulated in different diseases such as cancer where it has a dual role, acting as a tumor suppression mechanism during the first steps of tumor development and promoting cancer cells survival in stablished tumors.

Methods

Here, we aimed to assess the potential association between several candidate polymorphisms in autophagy genes (ATG2B rs3759601, ATG16L1 rs2241880, ATG10 rs1864183, ATG5 rs2245214, NOD2 rs2066844 and rs2066845) and glioblastoma susceptibility.

Results

Our results showed a significant correlation between ATG2B rs3759601, ATG10 rs1864183 and NOD2 rs2066844 variants and higher risk to suffer glioblastoma. In addition, the relationship between the different clinical features listed in glioblastoma patients and candidate gene polymorphisms was also investigated, finding that ATG10 rs1864183 might be a promising prognosis factor for this tumor.

Conclusions

This is the first report evaluating the role of different variants in autophagy genes in modulating glioblastoma risk and our results emphasize the importance of autophagy in glioblastoma development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09214-y.

Autophagy regulates differentiation of ovarian granulosa cells through degradation of WT1

Ovarian granulosa cells (GCs) proliferate and differentiate along with follicular growth, and this is indispensable for oocyte development and female fertility. Although the role of macroautophagy/autophagy in ovarian function has been reported, its contribution to the regulation of GC characteristics remains elusive. The siRNA-mediated knockdown of two key autophagy-related genes ATG5 and BECN1 and the autophagy inhibitor chloroquine were used to interfere with autophagy in GCs. Inhibition of autophagy both genetically and pharmacologically resulted in decreased expression of genes associated with GC differentiation, including CYP19A1/Aromatase and FSHR, as well as in reduced estradiol synthesis. Mechanistically, when autophagy was disrupted, the transcription factor WT1 accumulated in GCs due to its insufficient degradation by the autophagic pathway, and this inhibited GC differentiation. Finally, decreased expression of several autophagy-related genes, as well as reduced LC3-II:LC3-I and elevated SQSTM1/p62 protein levels, which are indications of decreased autophagy, were detected in GCs from biochemical premature ovarian insufficiency patients. In summary, our study reveals that autophagy regulates the differentiation of ovarian GCs by degrading WT1 and that insufficient autophagy might be involved in ovarian dysfunction.

Autophagy as a Therapeutic Target of Natural Products Enhancing Embryo Implantation

Infertility is an emerging health issue worldwide, and female infertility is intimately associated with embryo implantation failure. Embryo implantation is an essential process during the initiation of prenatal development. Recent studies have strongly suggested that autophagy in the endometrium is the most important factor for successful embryo implantation. In addition, several studies have reported the effects of various natural products on infertility improvement via the regulation of embryo implantation, embryo quality, and endometrial receptivity. However, it is unclear whether natural products can improve embryo implantation ability by regulating endometrial autophagy. Therefore, we performed a literature review of studies on endometrial autophagy, embryo implantation, natural products, and female infertility. Based on the information from these studies, this review suggests a new treatment strategy for female infertility by proposing natural products that have been proven to be safe and effective as endometrial autophagy regulators; additionally, we provide a comprehensive understanding of the relationship between the regulation of endometrial autophagy by natural products and female infertility, with an emphasis on embryo implantation.

Modulating autophagy by strontium-doped micro/nano rough titanium surface for promotion of osteogenesis and inhibition of osteoclastogenesis

Although it has been demonstrated that implant surfaces treated with strontium (Sr) promote osseointegration, the underlying intracellular mechanism remains unknown. Autophagy is a vital intracellular degradation mechanism that plays an essential role in maintaining bone homeostasis. Therefore, while designing implant biomaterials, it is critical to consider the autophagy mechanism. In this study, we fabricated Sr-doped micro/nano rough titanium implant surface by hydrothermal treatment (SLA+Sr). The in vitro results revealed that the SLA+Sr surface promoted osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) via autophagy activation. The SLA+Sr surface, on the other hand, inhibited osteoclast differentiation by downregulating autophagy. Additionally, in vivo, the SLA+Sr implant improved osseointegration, inhibited osteoclastogenesis, and upregulated autophagy levels in surrounding bone tissue cells. Our findings established a novel centralized mechanism by which SLA+Sr regulated osteogenesis and osteoclastogenesis during the osseointegration process through autophagy regulation. Moreover, endowing implants with the ability to modulate autophagy may be a promising strategy for enhancing implant osseointegration in the future translational medicine field.

Autophagy in Femoral Head Necrosis of Broilers Bone Metabolism Parameters and Autophagy-Related Gene Expression in Femoral Head Necrosis Induced by Glucocorticoid in Broilers

Objectives: In this study, the influence of methylprednisolone (MP) and 3-methyladenine (3-MA) on chondrocyte autophagy and bone quality were determined to investigate the mechanisms of femoral head necrosis in broilers.

Methods: Chickens were divided into four groups: control, MP, 3-MA, and 3-MA+MP groups. Blood and bone samples were collected for biochemistry assay and bone quality determination. Cartilage was separated from the femoral head for histopathological analysis and gene expression detection.

Results: The results indicated that MP treatment significantly affected blood levels of alkaline phosphatase, high-density lipoprotein, calcium, phosphorus, bone alkaline phosphatase, and osteocalcin in broilers. Additionally, MP treatment significantly increased blood levels of cholesterol, low-density lipoprotein, triglyceride, carboxy-terminal telopeptide of type-I collagen, and tartrate-resistant acid phosphatase 5. MP treatment also significantly decreased the levels of bone parameters compared with these values in controls, inhibited the expression of collagen-2, aggrecan, and mammalian target of rapamycin, and increased the expression of beclin1 and microtubule-associated protein 1 light chain 3, hypoxia-inducible factor 1 alpha, phosphoinositide 3-kinase, protein kinase B and autophagy-related gene 5 of the femoral head. Furthermore, following co-treatment with 3-MA and MP, 3-MA mitigated the effects of MP.

Conclusions: Our findings demonstrated that autophagy may be involved in the pathogenesis of femoral head necrosis induced by MP in broilers, and this study provides new treatment and prevention ideas for femoral head necrosis caused by glucocorticoids.

Unraveling and targeting RAS-driven metabolic signaling for therapeutic gain

RAS mutations are among the most frequent oncogenic drivers observed in human cancers. With a lack of available treatment options, RAS-mutant cancers account for many of the deadliest cancers in the United States. Recent studies established that altered metabolic requirements are a hallmark of cancer, and many of these alterations are driven by aberrant RAS signaling. Specifically, RAS-driven cancers are characterized by upregulated glycolysis, the differential channeling of glycolytic intermediates, upregulated nutrient scavenging pathways such as autophagy and macropinocytosis, and altered glutamine utilization and mitochondrial function. This unique metabolic landscape promotes tumorigenesis, proliferation, survival in nutrient deficient environments and confers resistance to conventional cytotoxic and targeted therapies. Emerging work demonstrates how these dependencies can be therapeutically exploited in vitro and in vivo with many metabolic inhibitors currently in clinical trials. This review aims to outline the unique metabolic requirements induced by aberrant RAS signaling and how these altered dependencies present opportunities for therapeutic intervention.

Interconnections among major forms of regulated cell death

As a basic biological phenomenon of cells, regulated cell death (RCD) has irreplaceable influence on the occurrence and development of many processes of life and diseases. RCD plays an important role in the stability of the homeostasis, the development of multiple systems and the evolution of organisms. Thus comprehensively understanding of RCD is undoubtedly helpful in the innovation of disease treatment. Recently, research on the underlying mechanisms of the major forms of RCD, such as apoptosis, autophagy, necroptosis, pyroptosis, paraptosis and neutrophils NETosis has made significant breakthroughs. In addition, the interconnections among them have attracted increasing attention from global scholars in the field of life sciences. Here, recent advances in RCD research field are discussed.

Gene Manipulation Protocols in Autophagy

Macroautophagy (referred to as autophagy hereafter) is a highly conserved catabolic process in eukaryotic cells. Autophagy is essential for cellular homeostasis through elimination and recycling of large cytoplasmic components, such as abnormal protein aggregates and damaged organelles, via lysosomal degradation. Since being originally identified by genetic screening in yeast, autophagy-related (ATG) genes have played a central role in autophagy research in different organisms, including plants, worms, flies, and mammals. Mouse models for monitoring autophagic activity or clarifying its biological functions have also been established. These mice are powerful tools to investigate roles of autophagy in vivo. Owing to the rapid technological advances in molecular biology, it is ever more efficient and simpler to manipulate autophagy-associated genes. Herein, we will introduce some commonly used approaches of gene silencing in mammalian cells, including CRIPSR/Cas9-mediated gene knockout and siRNA- and shRNA-mediated gene knockdown. We also summarized the common mouse models used for assessing autophagy. We hope to bring the researchers some useful information as they study autophagy.

Characterization of the effects of heat stress on autophagy induction in the pig oocyte

BACKGROUND

Heat stress (HS) occurs when body heat accumulation exceeds heat dissipation and is associated with swine seasonal infertility. HS contributes to compromised oocyte integrity and reduced embryo development. Autophagy is a potential mechanism for the oocyte to mitigate the detrimental effects of HS by recycling damaged cellular components.

METHODS

To characterize the effect of HS on autophagy in oocyte maturation, we utilized an in vitro maturation (IVM) system where oocytes underwent thermal neutral (TN) conditions throughout the entire maturation period (TN/TN), HS conditions during the first half of IVM (HS/TN), or HS conditions during the second half of IVM (TN/HS).

RESULTS

To determine the effect of HS on autophagy induction within the oocyte, we compared the relative abundance and localization of autophagy-related proteins. Heat stress treatment affected the abundance of two well described markers of autophagy induction: autophagy related gene 12 (ATG12) in complex with ATG5 and the cleaved form of microtubule-associated protein 1 light chain 3 beta (LC3B-II). The HS/TN IVM treatment increased the abundance of the ATG12-ATG5 complex and exacerbated the loss of LC3B-II in oocytes. The B-cell lymphoma 2 like 1 protein (BCL2L1) can inhibit autophagy or apoptosis through its interaction with either beclin1 (BECN1) or BCL2 associated X, apoptosis regulator (BAX), respectively. We detected colocalization of BCL2L1 with BAX but not BCL2L1 with BECN1, suggesting that apoptosis is inhibited under the HS/TN treatment but not autophagy. Interestingly, low doses of the autophagy inducer, rapamycin, increased oocyte maturation.

CONCLUSIONS

Our results here suggest that HS increases autophagy induction in the oocyte during IVM, and that artificial induction of autophagy increases the maturation rate of oocytes during IVM. These data support autophagy as a potential mechanism activated in the oocyte during HS to recycle damaged cellular components and maintain developmental competence.

Energy metabolism disorder mediated ammonia gas-induced autophagy via AMPK/mTOR/ULK1-Beclin1 pathway in chicken livers

Ammonia gas is a well-known environmental pollution gas, threatening human health. Ammonia gas is also one of the most harmful gases to livestock and poultry for many years. Many studies have demonstrated toxic effect of ammonia gas on animal health, such as eyes, respiratory system, and digestive system. However, the effect of ammonia gas toxicity on chicken livers and underlying molecular mechanism remains unclear. In this study, we selected chicken liver as research object and duplicated successfully ammonia gas poisoning model of chickens. 1-day-old Ross-308 broilers were randomly divided into the control group (the low ammonia gas group), and two treatment groups (the middle ammonia gas group and the high ammonia gas group) (3 replicates per group and 12 chickens per replicate). Ammonia gas concentration in the low ammonia gas group was ≤5 mg/m³ during day 1-42. Ammonia gas concentration in the middle group was set as 10 ± 0.5 mg/m³ during day 1-21, and 15 ± 0.5 mg/m³ during day 22-42). Ammonia gas concentration in the high ammonia gas group was set as 20 ± 0.5 mg/m³ during day 1-21, and 45 ± 0.5 mg/m³ during day 22-42. The ultrastructure of chicken livers was observed. The activities of four ATPases (Na⁺K⁺-ATPase, Mg⁺⁺-ATPase, Ca⁺⁺-ATPase, and Ca⁺⁺Mg⁺⁺-ATPase), the expression of twelve energy metabolism-related genes (HK1, HK2, PK, PFK, PDHX, CS, LDHA, LDHB, SDHA, SDHB, avUCP, and AMPK), as well as the expression of ten autophagy-related genes (PI3K, LC3I, LC3II, Beclin1, SQSTM1, mTOR, ULK1, ATG5, ATG12, and ATG13) were measured to explore the effect of ammonia gas on energy metabolism and autophagy in chicken livers. Our results showed that excess ammonia gas induced mitochondrial and autophagic damage in chicken liver tissue cells. Meanwhile, ATPases activities were inhibited and the expression of energy metabolism-related genes changed during ammonia gas treatment, meaning that excess ammonia gas caused energy metabolism disorder. Furthermore, ammonia gas exposure altered the expression of autophagy-related genes, suggesting that ammonia gas treatment caused autophagy in chicken livers. Moreover, ammonia gas-induced AMPK compensatory up-regulation activated autophagy process through inhibiting mTOR and promoting ULK1. In addition. there were dose-dependent and time-dependent effects on all detected indexes in ammonia gas-caused chicken liver cell damage. Taken together, AMPK/mTOR/ULK1-Beclin1 pathway participated in energy metabolism disorder-mediated autophagic injury caused by ammonia gas exposure in chicken livers.

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.

Exogenous Hydrogen Sulfide Plays an Important Role by Regulating Autophagy in Diabetic-Related Diseases

Autophagy is a vital cell mechanism which plays an important role in many physiological processes including clearing long-lived, accumulated and misfolded proteins, removing damaged organelles and regulating growth and aging. Autophagy also participates in a variety of biological functions, such as development, cell differentiation, resistance to pathogens and nutritional hunger. Recently, autophagy has been reported to be involved in diabetes, but the mechanism is not fully understood. Hydrogen sulfide (H₂S) is a colorless, water-soluble, flammable gas with the typical odor of rotten eggs, which has been known as a highly toxic gas for many years. However, it has been reported recently that H₂S, together with nitric oxide and carbon monoxide, is an important gas signal transduction molecule. H₂S has been reported to play a protective role in many diabetes-related diseases, but the mechanism is not fully clear. Recent studies indicate that H₂S plays an important role by regulating autophagy in many diseases including cancer, tissue fibrosis diseases and glycometabolic diseases; however, the related mechanism has not been fully studied. In this review, we summarize recent research on the role of H₂S in regulating autophagy in diabetic-related diseases to provide references for future related research.

Lysosome Depletion-Triggered Autophagy Impairment in Progressive Kidney Injury

Background

Macroautophagy (autophagy) is a cellular recycling process involving the destruction of damaged organelles and proteins in intracellular lysosomes for efficient nutrient reuse.

Summary

Impairment of the autophagy-lysosome pathway is tightly associated with multiple kidney diseases, such as diabetic nephropathy, proteinuric kidney disease, acute kidney injury, crystalline nephropathy, and drug- and heavy metal-induced renal injury. The impairment in the process of autophagic clearance may induce injury in renal intrinsic cells by activating the inflammasome, inducing cell cycle arrest, and cell death. The lysosome depletion may be a key mechanism triggering this process. In this review, we discuss this pathway and summarize the protective mechanisms for restoration of lysosome function and autophagic flux via the endosomal sorting complex required for transport (ESCRT) machinery, lysophagy, and transcription factor EB-mediated lysosome biogenesis.

Key Message

Further exploring mechanisms of ESCRT, lysophagy, and lysosome biogenesis may provide novel therapy strategies for the management of kidney diseases.

The Role of the Effects of Autophagy on NLRP3 Inflammasome in Inflammatory Nervous System Diseases

Autophagy is a stable self-sustaining process in eukaryotic cells. In this process, pathogens, abnormal proteins, and organelles are encapsulated by a bilayer membrane to form autophagosomes, which are then transferred to lysosomes for degradation. Autophagy is involved in many physiological and pathological processes. Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome, containing NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and pro-caspase-1, can activate caspase-1 to induce pyroptosis and lead to the maturation and secretion of interleukin-1 β (IL-1 β) and IL-18. NLRP3 inflammasome is related to many diseases. In recent years, autophagy has been reported to play a vital role by regulating the NLRP3 inflammasome in inflammatory nervous system diseases. However, the related mechanisms are not completely clarified. In this review, we sum up recent research about the role of the effects of autophagy on NLRP3 inflammasome in Alzheimer’s disease, chronic cerebral hypoperfusion, Parkinson’s disease, depression, cerebral ischemia/reperfusion injury, early brain injury after subarachnoid hemorrhage, and experimental autoimmune encephalomyelitis and analyzed the related mechanism to provide theoretical reference for the future research of inflammatory neurological diseases.

The Multifaceted Role of Autophagy in Endometrium Homeostasis and Disease

Autophagy is a conserved fundamental cellular process with a primary function of catabolizing harmful or surplus cellular contents such as protein aggregates, dysfunctional/long-lived organelles, intracellular pathogens, and storage nutrients. An increasing body of evidence reveals that basal autophagy is essential for maintaining endometrial homeostasis and mediating endometrial-specific functions, including menstrual cycle, embryo implantation, and decidualization. However, perturbed levels of autophagy can lead to severe endometrial pathologies, including endometriosis, endometrial hyperplasia, endometrial cancer, adenomyosis, and leiomyoma. This review highlights the most recent findings on the activity, regulation, and function of autophagy in endometrium physiology and pathology. Understanding the mechanistic roles of autophagy in endometrium homeostasis and disease is key to developing novel therapeutic strategies for endometrium-related infertility and malignancies.

Positively Correlated CD47 Activation and Autophagy in Umbilical Cord Blood-Derived Mesenchymal Stem Cells during Senescence

Autophagy plays a critical role in stem cell maintenance and is related to cell growth and cellular senescence. It is important to find a quality-control marker for predicting senescent cells. This study verified that CD47 could be a candidate to select efficient mesenchymal stem cells (MSCs) to enhance the therapeutic effects of stem cell therapy by analyzing the antibody surface array. CD47 expression was significantly decreased during the expansion of MSCs in vitro (p < 0.01), with decreased CD47 expression correlated with accelerated senescence phenotype, which affected cell growth. UCB-MSCs transfected with CD47 siRNA significantly triggered the downregulation of pRB and upregulation of pp38, which are senescence-related markers. Additionally, autophagy-related markers, ATG5, ATG12, Beclin1, and LC3B, revealed significant downregulation with CD47 siRNA transfection. Furthermore, autophagy flux following treatment with an autophagy inducer, rapamycin, has shown that CD47 is a key player in autophagy and senescence to maintain and regulate the growth of MSCs, suggesting that CD47 may be a critical key marker for the selection of effective stem cells in cell therapy.

Autophagy in Viral Development and Progression of Cancer

Autophagy is a complex degradative process by which eukaryotic cells capture cytoplasmic components for subsequent degradation through lysosomal hydrolases. Although this catabolic process can be triggered by a great variety of stimuli, action in cells varies according to cellular context. Autophagy has been previously linked to disease development modulation, including cancer. Autophagy helps suppress cancer cell advancement in tumor transformation early stages, while promoting proliferation and metastasis in advanced settings. Oncoviruses are a particular type of virus that directly contribute to cell transformation and tumor development. Extensive molecular studies have revealed complex ways in which autophagy can suppress or improve oncovirus fitness while still regulating viral replication and determining host cell fate. This review includes recent advances in autophagic cellular function and emphasizes its antagonistic role in cancer cells.

Autophagy in Viral Development and Progression of Cancer

Autophagy is a complex degradative process by which eukaryotic cells capture cytoplasmic components for subsequent degradation through lysosomal hydrolases. Although this catabolic process can be triggered by a great variety of stimuli, action in cells varies according to cellular context. Autophagy has been previously linked to disease development modulation, including cancer. Autophagy helps suppress cancer cell advancement in tumor transformation early stages, while promoting proliferation and metastasis in advanced settings. Oncoviruses are a particular type of virus that directly contribute to cell transformation and tumor development. Extensive molecular studies have revealed complex ways in which autophagy can suppress or improve oncovirus fitness while still regulating viral replication and determining host cell fate. This review includes recent advances in autophagic cellular function and emphasizes its antagonistic role in cancer cells.

Inhibition of HMGB1 Suppresses Hepatocellular Carcinoma Progression via HIPK2-Mediated Autophagic Degradation of ZEB1

Autophagy is a conserved catabolic process maintaining cellular homeostasis and reportedly plays a critical role in tumor progression. Accumulating data show that autophagic activity is inhibited in hepatocellular carcinoma. However, the underlying molecular basis of impaired autophagy in HCC remains unclear. In this study, we revealed that autophagic activity was suppressed by HMGB1 in a HIPK2-dependent way. Targeting HMGB1 could inhibit the degradation of HIPK2, as a result of which, autophagic degradation of ZEB1 was enhanced by reprogramming glucose metabolism/AMPK/mTOR axis. Moreover, we demonstrated that selectively degradation of ZEB1 was responsible for HCC growth inhibition in HMGB1 deficient cells. Lastly, we found the combination therapy of HMGB1 inhibitor and rapamycin achieved a better anti-HCC effect. These results demonstrate that impaired autophagy is controlled by HMGB1 and targeting HMGB1 could suppress HCC progression via HIPK2-mediated autophagic degradation of ZEB1.