Autophagosome formation--the role of ULK1 and Beclin1-PI3KC3 complexes in setting the stage

Amyotrophic Lateral Sclerosis and Autophagy: Dysfunction and Therapeutic Targeting

Over the past 20 years, there has been a drastically increased understanding of the genetic basis of Amyotrophic Lateral Sclerosis. Despite the identification of more than 40 different ALS-causing mutations, the accumulation of neurotoxic misfolded proteins, inclusions, and aggregates within motor neurons is the main pathological hallmark in all cases of ALS. These protein aggregates are proposed to disrupt cellular processes and ultimately result in neurodegeneration. One of the main reasons implicated in the accumulation of protein aggregates may be defective autophagy, a highly conserved intracellular "clearance" system delivering misfolded proteins, aggregates, and damaged organelles to lysosomes for degradation. Autophagy is one of the primary stress response mechanisms activated in highly sensitive and specialised neurons following insult to ensure their survival. The upregulation of autophagy through pharmacological autophagy-inducing agents has largely been shown to reduce intracellular protein aggregate levels and disease phenotypes in different in vitro and in vivo models of neurodegenerative diseases. In this review, we explore the intriguing interface between ALS and autophagy, provide a most comprehensive summary of autophagy-targeted drugs that have been examined or are being developed as potential treatments for ALS to date, and discuss potential therapeutic strategies for targeting autophagy in ALS.

The mechanisms of arsenic-induced ovotoxicity, ultrastructural alterations, and autophagic related paths: An enduring developmental study in folliculogenesis of mice

Arsenic (As) exerts a wide range of adverse effects on biological systems, including the reproductive organs in males and females. However, the mechanisms of As-induced reproductive toxicity are mostly obscure. Recently, we showed that autophagy is an essential route for As₂O₃-induced reprotoxicity through the hypothalamic-pituitary-gonadal-sperm (HPG-S) axis in pubertal and matured F1-male mice. However, the role of autophagy in As₂O₃- induced ovarian toxicity is mostly unknown. Hence, this study aimed to elucidate the role of oxidative stress, mitochondrial impairment, and autophagic processes in the ovary of As-exposed female mice. For this purpose, mature female mice were challenged with 0, low (0.2), medium (2), and high (20 ppm) As₂O₃ from 35-days before mating till weaning their pups, and the F1- females from weaning until maturity. Then, all the mice were sacrificed, and oxidative stress parameters, mitochondrial indices, electron microscopic evaluation of the ovaries, expression of autophagic-related genes and proteins, and autophagosome formation were assessed. It was shown that medium and high As₂O₃ doses were a potent inducer of oxidative stress, mitochondrial dysfunction, and autophagy in the ovary of F1-generation. A dose-dependent increment in the gene expression of PDK₁, PI3K, TSC2, AMPK, ULK1, ATG13, Beclin1, ATG12, ATG5, LC3, P62, ATG3, ATG7, and p62, as well as protein expression of Beclin1, and LC3- I, II, was evident in the ovaries of the As-treated animals. Moreover, a dose-dependent decrease in the expression of mTOR and Bcl-2 genes, and mTOR protein was detected with increasing doses of As, suggesting that As treatment-induced autophagy. Along with a dose-dependent increase in the number of MDC-labeled autophagic vacuoles, transmission electron microscopy also confirmed more autophagosomes and injured mitochondria in medium and high As₂O₃ doses groups. As₂O₃ also negatively affected the mean body weight, litter size, organ coefficient, and stereological indices in female mice. Finally, in physiological conditions, arsenic trioxide (As₂O₃) leads to an increased level of autophagy in the oocyte when many oocytes were being lost. These findings indicated that an imbalance in the oxidant-antioxidant system, mitochondrial impairment, and the autophagic process, through inhibition of mTOR, dependent and independent pathways, and Bcl-2, as well as activation of AMPK/PI3K/Beclin1/LC3 routes, could play a pivotal role in As-induced reproductive toxicity through ovarian dysfunction in females.

Statins: Could an old friend help in the fight against COVID-19?

The COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has overwhelmed healthcare systems requiring the rapid development of treatments, at least, to reduce COVID-19 severity. Drug repurposing offers a fast track. Here, we discuss the potential beneficial effects of statins in COVID-19 patients based on evidence that they may target virus receptors, replication, degradation, and downstream responses in infected cells, addressing both basic research and epidemiological information. Briefly, statins could modulate virus entry, acting on the SARS-CoV-2 receptors, ACE2 and CD147, and/or lipid rafts engagement. Statins, by inducing autophagy activation, could regulate virus replication or degradation, exerting protective effects. The well-known anti-inflammatory properties of statins, by blocking several molecular mechanisms, including NF-κB and NLRP3 inflammasomes, could limit the "cytokine storm" in severe COVID-19 patients which is linked to fatal outcome. Finally, statin moderation of coagulation response activation may also contribute to improving COVID-19 outcomes. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Cardiac glycosides inhibit cancer through Na/K-ATPase-dependent cell death induction

Successful drug repurposing relies on the understanding of molecular mechanisms of the target compound. Cardiac glycosides have demonstrated potent anticancer activities; however, the pharmacological mechanisms underlying their anticancer effects remained elusive, which has restricted their further development in cancer treatment. A bottleneck is the lack of comprehensive understanding about genes and signaling pathways that are altered at the early stage of drug treatment, which is key to understand how they inhibit cancer. To address this issue, we first investigated the anticancer effects of a panel of 68 naturally isolated cardiac glycosides. Our results illustrate critical structure activity relationship of these compounds on cancer cell survival. We confirmed the anticancer effect of cardiac glycoside in mouse tumor xenografts. Through RNA sequencing, quantitative PCR and immunoblotting, we show that cardiac glycoside first activated autophagy and then induced apoptosis. Further activating autophagy by rapamycin or inhibiting apoptosis by caspase inhibitor mitigated cardiac glycoside-induced cell death, whereas inhibiting autophagy by RNA interference-mediated depletion of critical autophagy genes enhanced cell death. While depletion of Na/K-ATPase, the protein target of cardiac glycosides, by RNA interference inhibited both autophagy activation and apoptosis induction by cardiac glycoside, expression of human, but not rodent Na/K-ATPase, increased cell sensitivity to cardiac glycoside. In conclusion, our analyses reveal sequential activation of autophagy and apoptosis during early stages of cardiac glycoside treatment and indicate the importance of Na/K-ATPase in their anticancer effects.

NRBF2 is a RAB7 effector required for autophagosome maturation and mediates the association of APP-CTFs with active form of RAB7 for degradation

NRBF2 is a component of the class III phosphatidylinositol 3-kinase (PtdIns3K) complex. Our previous study has revealed its role in regulating ATG14-associated PtdIns3K activity for autophagosome initiation. In this study, we revealed an unknown mechanism by which NRBF2 modulates autophagosome maturation and APP-C-terminal fragment (CTF) degradation. Our data showed that NRBF2 localized at autolysosomes, and loss of NRBF2 impaired autophagosome maturation. Mechanistically, NRBF2 colocalizes with RAB7 and is required for generation of GTP-bound RAB7 by interacting with RAB7 GEF CCZ1-MON1A and maintaining the GEF activity. Specifically, NRBF2 regulates CCZ1-MON1A interaction with PI3KC3/VPS34 and CCZ1-associated PI3KC3 kinase activity, which are required for CCZ1-MON1A GEF activity. Finally, we showed that NRBF2 is involved in APP-CTF degradation and amyloid beta peptide production by maintaining the interaction between APP and the CCZ1-MON1A-RAB7 module to facilitate the maturation of APP-containing vesicles. Overall, our study revealed a pivotal role of NRBF2 as a new RAB7 effector in modulating autophagosome maturation, providing insight into the molecular mechanism of NRBF2-PtdIns3K in regulating RAB7 activity for macroautophagy/autophagy maturation and Alzheimer disease-associated protein degradation..Abbreviations: 3xTg AD, triple transgenic mouse for Alzheimer disease; Aβ, amyloid beta peptide; Aβ_1-40, amyloid beta peptide 1-40; Aβ_1-42, amyloid beta peptide 1-42; AD, Alzheimer disease; APP, amyloid beta precursor protein; APP-CTFs, APP C-terminal fragments; ATG, autophagy related; ATG5, autophagy related 5; ATG7, autophagy related 7; ATG14, autophagy related 14; CCD, coiled-coil domain; CCZ1, CCZ1 homolog, vacuolar protein trafficking and biogenesis associated; CHX, cycloheximide; CQ, chloroquine; DAPI, 4',6-diamidino-2-phenylindole; dCCD, delete CCD; dMIT, delete MIT; FYCO1, FYVE and coiled-coil domain autophagy adaptor 1; FYVE, Fab1, YGL023, Vps27, and EEA1; GAP, GTPase-activating protein; GDP, guanine diphosphate; GEF, guanine nucleotide exchange factor; GTP, guanine triphosphate; GTPase, guanosine triphosphatase; HOPS, homotypic fusion and vacuole protein sorting; ILVs, endosomal intralumenal vesicles; KD, knockdown; KO, knockout; LAMP1, lysosomal associated membrane protein 1; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MLVs, multilamellar vesicles; MON1A, MON1 homolog A, secretory trafficking associated; NRBF2, nuclear receptor binding factor 2; PtdIns3K, class III phosphatidylinositol 3-kinase; PtdIns3P, phosphatidylinositol-3-phosphate; RILP, Rab interacting lysosomal protein; SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62, sequestosome 1; UVRAG, UV radiation resistance associated; VPS, vacuolar protein sorting; WT, wild type.

Shikonin Inhibits Cancer Through P21 Upregulation and Apoptosis Induction

Shikonin is a natural naphthoquinone compound and has demonstrated potent anti-cancer activities; however, the underlying molecular mechanisms remained elusive. Here we report that Shikonin inhibited the growth of a wide range of human cancer cell lines, illustrating a broad anticancer effect. Mechanistically, we show that Shikonin arrested the cell cycle at the G2/M phase, inhibited the ERK-dependent cell growth signal, and induced cell death in both P53 wild type and mutant cancer cells, which collectively contributed to the growth inhibitory effect of Shikonin. A pan-apoptosis inhibitor largely suppressed Shikonin-induced cell death, suggesting an important role of apoptosis in this process. Intriguingly, Shikonin also activated autophagy and inhibition of autophagy by depleting critical autophagic genes further increased Shikonin-induced cell death, indicating a protective role of autophagy. In uncovering the molecular mechanisms underlying these effects of Shikonin, we found that Shikonin induced a robust upregulation of P21 independent of the P53 status, upregulated autophagy genes, as well as inhibited expression of genes required for cell growth. Using mouse tumor models, we confirmed the strong anticancer effect of Shikonin in vivo. Together, our data reveal a broad range of pharmacological functions of Shikonin, involving simultaneous growth inhibition, cell cycle arrest, autophagy activation and apoptosis induction through regulating expression of critical genes involved in these pathways. Our study may facilitate the development of Shikonin in cancer therapy as a single agent or in combination with other anticancer therapies.

Arsenic induces dysfunctional autophagy via dual regulation of mTOR pathway and Beclin1-Vps34/PI3K complex in MLTC-1 cells

Arsenic poisoning and induced potential lesion is a global concern. However, the exact mechanisms underlying its toxicity especially in male reproductive system still remain unclear. Hence, this study aimed to explore the roles of mTOR and Beclin1-Vps34/PI3K complex during As-induced-toxicity using Rapamycin (mTOR inhibitor), Beclin1 siRNA and 3-methyladenine (3-MA, Vps34/PI3K inhibitor) in testicular stromal cells. For this, mouse testis Leydig Tumor Cell lines (MLTC-1) were challenged with As₂O₃ (0, 3, 6 and 9 μM) exposure for 24 hs. Lyso-Tracker Red and Monodansylcadaverine (MDC) staining results depicted a significant accumulation of autophagosomes in MLTC-1 cells exposed to arsenic. Meanwhile, arsenic treatment up-regulated autophagic markers including LC3, Atg7, Beclin1 and Vps34 expressions, mTOR downstream autophagy related genes and the Beclin1-Vps34/PI3K complex associated members. Furthermore, silencing of Beclin1, and inhibition of Vps34/PI3K and mTOR altered the arsenic-induced autophagosomes formation. However, p62, the substrate protein of autophagy, was also up-regulated by arsenic administration independent on Beclin1-Vps34/PI3K complex. Altogether, our results revealed that arsenic exposure induced autophagosomes formation via regulation of the Beclin1-Vps34/PI3K complex and mTOR pathway; the blockage of autophagosomes degradation maybe due to impaired function of lysosomes. Thus, this study provides a novel mechanistic approach with respect to As-induced male reproductive toxicity.

Absence of Sac2/INPP5F enhances the phenotype of a Parkinson's disease mutation of synaptojanin 1

Extensive genetic studies have identified numerous genes whose mutations results on Parkinson’s disease (PD), including synaptojanin 1 (SJ1/Park20), a nerve terminal enriched protein that includes an inositol 4-phosphatase domain (Sac domain). In addition, many PD candidate genes have been identified by genome-wide association studies, but for most of these genes, the link to PD remains hypothetical. One such gene is Sac2/INPP5F, which, interestingly, also includes an inositol 4-phosphatase domain. While Sac2KO mice do not show obvious defects, we show a striking synthetic effect in mice of the KO of Sac2 and the Sac domain mutation of SJ1 found in PD patients. These findings support a synergistic role of SJ1 and Sac2 on a PI4P pool whose dysfunction results in PD.

Numerous genes whose mutations cause, or increase the risk of, Parkinson’s disease (PD) have been identified. An inactivating mutation (R258Q) in the Sac inositol phosphatase domain of synaptojanin 1 (SJ1/PARK20), a phosphoinositide phosphatase implicated in synaptic vesicle recycling, results in PD. The gene encoding Sac2/INPP5F, another Sac domain-containing protein, is located within a PD risk locus identified by genome-wide association studies. Knock-In mice carrying the SJ1 patient mutation (SJ1^RQKI) exhibit PD features, while Sac2 knockout mice (Sac2KO) do not have obvious neurologic defects. We report a “synthetic” effect of the SJ1 mutation and the KO of Sac2 in mice. Most mice with both mutations died perinatally. The occasional survivors had stunted growth, died within 3 wk, and showed abnormalities of striatal dopaminergic nerve terminals at an earlier stage than SJ1^RQKI mice. The abnormal accumulation of endocytic factors observed at synapses of cultured SJ1^RQKI neurons was more severe in double-mutant neurons. Our results suggest that SJ1 and Sac2 have partially overlapping functions and are consistent with a potential role of Sac2 as a PD risk gene.

BCL2L10/BECN1 modulates hepatoma cells autophagy by regulating PI3K/AKT signaling pathway

The aim of this study was to investigate BCL2L10 and BECN1 expression and their effect on autophagy in hepatocellular carcinoma (HCC). We found that BCL2L10 expression was low in hepatoma tissues and cells. Overexpression of BCL2L10 decreased the activity of hepatoma cells. To analyze autophagic flux, we monitored the formation of autophagic vesicles by fluorescence protein method. Autophagy-related protein LC3B-II was accumulated and P62 was decreased, which indicated that autophagy was induced by BECN1, while BCL2L10 could suppress this trend. Immunofluorescence assay showed that BCL2L10 and Beclin 1 were co-located in hepatoma cells. Immunoprecipitation showed that BCL2L10 could inhibit the autophagy of hepatoma cells by combining with Beclin 1. ELISA and co-immunoprecipitation suggested that the combination between BCL2L10 and Beclin 1 reduced the bond between Beclin 1 and PI3KC3. Based on Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, the PI3K/AKT signaling pathway was significantly upregulated in HCC. In conclusions, BCL2L10 had a low expression in HCC tissues and cells, which could release BECN1 to induce autophagy of hepatoma cells by downregulating PI3K/AKT signaling pathway.

A Review of ULK1-Mediated Autophagy in Drug Resistance of Cancer

The difficulty of early diagnosis and the development of drug resistance are two major barriers to the successful treatment of cancer. Autophagy plays a crucial role in several cellular functions, and its dysregulation is associated with both tumorigenesis and drug resistance. Unc-51-like kinase 1 (ULK1) is a serine/threonine kinase that participates in the initiation of autophagy. Many studies have indicated that compounds that directly or indirectly target ULK1 could be used for tumor therapy. However, reports of the therapeutic effects of these compounds have come to conflicting conclusions. In this work, we reviewed recent studies related to the effects of ULK1 on the regulation of autophagy and the development of drug resistance in cancers, with the aim of clarifying the mechanistic underpinnings of this therapeutic target.

Effect of arsenic and/or fluoride gestational exposure on renal autophagy in offspring mice

Both arsenic (As) and fluorine (F) are toxic substances widely found in the environment, which threaten to various organs of both human and animals, especially the kidney. In this study, to investigate the individual and combined effects of arsenic (15 mg/L As₂O₃(III)) and fluoride (100 mg/L NaF), arsenic (15 mg/L As₂O₃(III)) and fluoride-arsenic (15 mg/L As₂O₃(III)+100 mg/L NaF) on the renal autophagy during early life, a mouse model of gestationally exposed to As and/or F was established. The results showed that the mRNA expression levels of LC3, LC3I, LC3II, Beclin-1, ULK1, Atg13 and Atg14 were significantly increased with a concomitant decrease in mTOR and Bcl-2 up on individual exposure to As and F rather than in combined (As + F) exposure. In addition, the protein expression levels of LC3-II/LC3-I, Beclin-1, and LAMP1 were significantly increased with a concomitant decrease in mTOR and Bcl-2 in the mice subjected to individual exposure than the combined exposure. Based on the results, it was observed that renal tissue of mice was highly sensitive to F than As. Moreover, the toxicity of the combined (As + F) exposure was significantly lower than that of the individual exposure, which could be attributed due to the antagonism between As and F.

Autophagy in Astrocytes and its Implications in Neurodegeneration

Autophagy is a major degradation pathway where double-membrane vesicles called autophagosomes deliver cytoplasmic content to the lysosome. Increasing evidence suggests that autophagy dysfunction contributes to the pathogenesis of neurodegenerative diseases. In addition, misfolded proteins that accumulate in these diseases and constitute a common pathological hallmark are substrates for autophagic degradation. Astrocytes, a major type of glial cells, are emerging as a critical component in most neurodegenerative diseases. This review will summarize the recent efforts to investigate the role that autophagy plays in astrocytes in the context of neurodegenerative diseases. While the field has mostly focused on the implications of autophagy in neurons, autophagy may also be involved in the clearance of disease-related proteins in astrocytes as well as in maintaining astrocyte function, which could impact the cell autonomous and non-cell autonomous contribution of astrocytes to neurodegeneration.

Beclin 1 Complex and Neurodegenerative Disorders

Beclin1 is the mammalian orthologue of yeast Atg6/vacuolar protein sorting-30 (VPS30). Beclin1 interacts with various biological macromolecules like ATG14, BIF-1, NRBF2, RUBICON, UVRAG, AMBRA1, HMGB1, PINK1, and PARKIN. Such interactions promote Beclin1-PI3KC3 complex formation. Autophagy is blocked in apoptosis owing to the breakdown of Beclin1 by caspase whereas autophagy induction inhibits effector caspase degradation, therefore, blocks apoptosis. Thus, the Beclin1 is an essential biomolecular species for cross-regulation between autophagy and apoptosis. Various studies carried out in neurodegenerative animal models associated with aggregated proteins have confirmed that multifunctional Beclin1 protein is necessary for neuronal integrity. The role of Beclin1 protein has been investigated and was reported in various human neurodegeneration disorders. This chapter aims to provide an insight into the role of Beclin1 in the development of neurodegenerative disorders.

PINK1/Parkin in Neurodegenerative Disorders

PTEN-induced kinase 1 (PINK1), a mitochondrial serine/threonine-protein kinase encoded by the PINK1 gene, is thought to protect cells from stress-induced mitochondrial dysfunction. The activity of PINK1 facilitates the binding of Parkin protein with depolarized mitochondria to induce autophagy. Mutations of PINK1causes a type of autosomal recessive early-onset Parkinson's disease. Cell depends on the surveillance systems or mechanisms like protein quality control to handle the alterations in the proteins that are induced because of these mutations. These mutant proteins are found to be pathogenic and are reported to be related to various neurodegenerative disorders. This chapter focuses on the role of PINK1/Parkin in mitochondria quality control and its subsequent effect in neurodegeneration.

TLR9 in MAFLD and NASH: At the Intersection of Inflammation and Metabolism

Toll-Like Receptor 9 (TLR9) is an ancient receptor integral to the primordial functions of inflammation and metabolism. TLR9 functions to regulate homeostasis in a healthy system under acute stress. The literature supports that overactivation of TLR9 under the chronic stress of obesity is a critical driver of the pathogenesis of NASH and NASH-associated fibrosis. Research has focused on the core contributions of the parenchymal and non-parenchymal cells in the liver, adipose, and gut compartments. TLR9 is activated by endogenous circulating mitochondrial DNA (mtDNA). Chronically elevated circulating levels of mtDNA, caused by the stress of overnutrition, are observed in obesity, metabolic dysfunction-associated fatty liver disease (MAFLD), and NASH. Clinical evidence is supportive of TLR9 overactivation as a driver of disease. The role of TLR9 in metabolism and energy regulation may have an underappreciated contribution in the pathogenesis of NASH. Antagonism of TLR9 in NASH and NASH-associated fibrosis could be an effective therapeutic strategy to target both the inflammatory and metabolic components of such a complex disease.

Flavonoids from Apios americana Medikus Leaves Protect RAW264.7 Cells against Inflammation via Inhibition of MAPKs, Akt-mTOR Pathways, and Nfr2 Activation

Apios americana Medikus was once widely accepted as staple food in India for a long time, and the tuber of which possesses high nutrients. During the past decades, most of the research has focused on the biological activity in the tubers of Apios americana Medikus whereas the leaves were ignored. In this study, the Apios americana Medikus leaf extract (ALE) was obtained and seven compounds were identified. LPS-induced RAW264.7 cells were used to study the anti-inflammation activity of ALE. As expected, ALE reduced the secretion of nitric oxide (NO) and inflammatory cytokines via inhibition of NF-κB and MAPK signaling together with activation of Nrf2-Keap1 and FOXO pathways, as well as alleviating the oxidative stress and mitochondrial dysfunction. In addition, ALE could activate HMGB1-Beclin1 and Sirt1-FoxO1 pathways and inhibit the Akt-mTOR signaling pathway to activate autophagy, protecting RAW264.7 cells from inflammation. In summary, our results suggested that ALE might help activate the anti-inflammation system, resulting in the prevention of LPS-induced damage in RAW264.7 cells.

Establishment of canine macrophages stably expressing GFP-tagged canine LC3 protein for effectively detecting autophagy

Autophagy plays a crucial role in eliminating protein aggregates, damaged organelles and invading pathogens. Genetically engineered cell line stably expressing green fluorescent protein (GFP)-tagged microtubule-associated protein light chain 3 (LC3) is extensively used to test autophagy through observing GFP puncta formation in the cells by fluorescence imaging. However, canine LC3 (cLC3) gene has not been cloned, therefore, GFP-tagged canine LC3 (GFP-cLC3) detection system has not been established. To generate GFP-cLC3 stably expressing canine-derived macrophages, the cLC3 cDNA was first amplified by RT-PCR and inserted into pEGFP-C1 plasmid to create GFP-cLC3 gene fusion. This genetic element was then transducted into canine macrophages mediated by lentivirus vector to generate the canine macrophages stably expressing fusion protein. Results showed that the sequence of cLC3 cloned in this study is highly homologous with other animals (80-95% homology). Phenotypic and functional analysis of these engineered cells revealed that GFP-cLC3 was indeed stably expressed and rapamycin or starvation can effectively induce GFP puncta formation in the cells, indicative of autophagosome formation. These GFP-cLC3-expressing cells may thus be useful to study autophagy in canine.

Curcumin ameliorates dextran sulfate sodium-induced colitis in mice via regulation of autophagy and intestinal immunity

BACKGROUND/AIMS

Inflammatory bowel disease (IBD) is regarded as a kind of chronic and unspecific intestinal inflammatory disorder. Its exact pathogenesis has not been elucidated. Curcumin, as an herbal drug, has been used in the treatment of IBD due to its immunoregulation. Autophagy has been reported to play an important role in the mechanism of IBD. In the present study, we focused on the autophagic regulation role of curcumin in the murine model of dextran sulfate sodium (DSS)-induced colitis.

MATERIALS AND METHODS

We investigated the effects of curcumin on the progress of DSS-induced acute colitis in mice by evaluating the disease activity index (DAI) and histopathological score. Meanwhile, the mRNA and protein expression of autophagy-related key genes from colon tissues comprising autophagy-related 5 (ATG5), LC3-phosphatidylethanolamine conjugate (LC-3II), beclin-1, and B cell lymphoma 2 (bcl-2) was examined by quantitative reverse transcription polymerase chain reaction and Western blot. Furthermore, the mRNA and protein expression of cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL) 6, IL-10, and IL-17A, was examined. Autophagosome was also examined under transmission electron microscopy.

RESULTS

Both DAI and histopathological score increased in mice with DSS-induced colitis and obviously decreased after curcumin intervention. The expression levels of TNF-α, IL-6, IL-17, ATG5, LC-3II, and beclin-1 were significantly higher in mice with colitis than in normal ones, whereas those of IL-10 and bcl-2 decreased accordingly. However, curcumin intervention adjusted the expression level of those factors toward normal level. The number of autophagosome in the colon epithelia increased after DSS stimulation and decreased after curcumin administration.

CONCLUSION

Curcumin could prevent the development of DSS-induced colitis through the inhibition of excessive autophagy and regulation of following cytokine networks.

Autophagy is essential for the endothelial differentiation of breast cancer stem‑like cells

Blood vessels serve an important role in tumor growth and metastasis, and recent studies have shown that certain tumor cancer stem cells may differentiate into endothelial cells and contribute to angiogenesis. In the present study, vascular endothelial growth factor (VEGF) was used to induce endothelial differentiation of breast cancer stem‑like cells (BCSLCs), and methods including flow cytometry, western blotting and immunofluorescence were used to study the relationship between autophagy and the endothelial differentiation of BCSLCs. The results showed that BCSLCs could differentiate into endothelial cells under the induction of VEGF in vitro. Subsequently, the role of autophagy in the endothelial differentiation of BCSLCs was examined. Autophagic activity was measured during endothelial differentiation of BCSLCs, and the association between autophagy and endothelial differentiation was investigated using autophagy activators, autophagy inhibitors and autophagy related 5 (Atg5)‑knockdown BCSLCs. Autophagy was increased during endothelial differentiation of BCSLCs, and there was a positive association between autophagy and endothelial differentiation. The ability of cells to undergo endothelial differentiation was reduced in BCSLCs with Atg5 knockdown. Therefore, autophagy was essential for endothelial differentiation of BCSLCs, and the findings of the present study may highlight novel potential avenues for reducing angiogenesis and improving treatment of breast cancer.

Autophagy suppression enhances DNA damage and cell death upon treatment with PARP inhibitor Niraparib in laryngeal squamous cell carcinoma

Although poly (ADP-ribose) polymerase (PARP) inhibitors, as anti-tumor drugs targeting the DNA damage response (DDR), have been used for the therapy of various tumors, few researches reported their effect on laryngeal squamous cell carcinoma (LSCC). Here, we first discovered that the PARP-1/2 inhibitor Niraparib could simultaneously induce cell growth inhibition and autophagy in LSCC TU212 and TU686 cells. Niraparib decelerated cell cycle of LSCC by arresting G1 phase and preventing the cells from entering S phase. DNA lesions were also observed upon Niraparib treatment as evidenced by the accumulation of γH2AX and abatement of pRB expression. In addition, autophagy generation was confirmed by the observation of autophagosomes, LC3-positive autophagy-like vacuoles, and obvious conversion of LC3-I to LC3-II. Moreover, blocking autophagy enhanced Niraparib-induced growth inhibition and DNA lesions. Further studies suggested that autophagy suppression could obstruct the activation of checkpoint kinase 1 (Chk1) through elevating proteasomal activity and then impair the capacity of homologous recombination (HR), thereby improving the anti-LSCC efficiency of Niraparib. Collectively, these findings suggested that simultaneous targeting of Niraparib and autophagy might be a promising therapeutic schedule for LSCC in clinic.

Endosomes and Autophagy: Regulators of Pulmonary Endothelial Cell Homeostasis in Health and Disease

Significance: Alterations in oxidant/antioxidant balance injure pulmonary endothelial cells and are important in the pathogenesis of lung diseases, such as Acute Respiratory Distress Syndrome (ARDS), ischemia/reperfusion injury, pulmonary arterial hypertension (PAH), and emphysema. Recent Advances: The endosomal and autophagic pathways regulate cell homeostasis. Both pathways support recycling or degradation of macromolecules or organelles, targeted to endosomes or lysosomes, respectively. Thus, both processes promote cell survival. However, with environmental stress or injury, imbalance in endosomal and autophagic pathways may enhance macromolecular or organelle degradation, diminish biosynthetic processes, and cause cell death. Critical Issues: While the role of autophagy in cellular homeostasis in pulmonary disease has been investigated, the role of the endosome in the lung vasculature is less known. Furthermore, autophagy can either decrease or exacerbate endothelial injury, depending upon inciting insult and disease process. Future Directions: Diseases affecting the pulmonary endothelium, such as emphysema, ARDS, and PAH, are linked to altered endosomal or autophagic processing, leading to enhanced degradation of macromolecules and potential cell death. Efforts to target this imbalance have yielded limited success as treatments for lung injuries, which may be due to the complexity of both processes. It is possible that endosomal trafficking proteins, such as Rab GTPases and late endosomal/lysosomal adaptor, MAPK and MTOR activator 1, may be novel therapeutic targets. While endocytosis or autophagy have been linked to improved function of the pulmonary endothelium in vitro and in vivo, further studies are needed to identify targets for modulating cellular homeostasis in the lung.

Ubiquitin-mediated regulation of autophagy

Autophagy is a major degradation pathway that utilizes lysosome hydrolases to degrade cellular constituents and is often induced under cellular stress conditions to restore cell homeostasis. Another prime degradation pathway in the cells is ubiquitin-proteasome system (UPS), in which proteins tagged by certain types of polyubiquitin chains are selectively recognized and removed by proteasome. Although the two degradation pathways are operated independently with different sets of players, recent studies have revealed reciprocal cross talks between UPS and autophagy at multiple layers. In this review, we summarize the roles of protein ubiquitination and deubiquitination in controlling the initiation, execution, and termination of bulk autophagy as well as the role of ubiquitination in signaling certain types of selective autophagy. We also highlight how dysregulation of ubiquitin-mediated autophagy pathways is associated with a number of human diseases and the potential of targeting these pathways for disease intervention.

Therapeutic effects of JLX-001 on ischemic stroke by inducing autophagy via AMPK-ULK1 signaling pathway in rats

(3β,5α,16α,20S)-4,4,14-trimethyl-3,20-bis(methylamino)-9,19-cyclopregnan-16-ol-dihydrochloride (JLX-001), a structural analogue of cyclovirobuxine D (CVB-D), is a novel compound from synthesis. This study aims to confirm the therapeutic effects of JLX001 on ischemic stroke (IS) and research its induction of autophagy function via 5'-AMP-activated protein kinase (AMPK)-Human Serine/threonine-protein kinase (ULK1) signaling pathway activation. The therapeutic effects of JLX001 were evaluated by infarct sizes, brain edema, neurological scores and proportion of apoptotic neurons in Sprague-Dawley (SD) rats with middle cerebral artery occlusion/reperfusion (MCAO/R). The number of autophagosomes was obtained by transmission electron microscopy. The expression of LC3-II was measured by immunofluorescence. p-AMPK and activated ULK1 were detected by western blots. Results showed that JLX001 treatment markedly alleviated cerebral infarcts, edema, neurological scores and proportion of apoptotic neurons in MCAO/R rats. The number of autophagosomes was increased, accompanying with the increased expressions of LC3-II, p-AMPK and ULK1. In summary, JLX001 attenuates cerebral ischemia injury and the underlying mechanisms may relate to inducing autophagy via AMPK-ULK1 signaling pathway activation.

Intravesical delivery of rapamycin via folate-modified liposomes dispersed in thermo-reversible hydrogel

Purpose

To develop an intravesical instillation system for the treatment of bladder cancer, rapamycin (Rap) was encapsulated into liposomes and then homogeneously dispersed throughout a poloxamer 407 (P407)-based hydrogel.

Methods

Rap-loaded conventional liposomes (R-CL) and folate-modified liposomes (R-FL) were prepared using a film hydration method and pre-loading technique, and characterized by particle size, drug entrapment efficiency, and drug loading. The cellular uptake behavior in folate receptor-expressing bladder cancer cells was observed by flow cytometry and confocal laser scanning microscopy using a fluorescent probe. In vitro cytotoxic effects were evaluated using MTT assay, colony forming assay, and Western blot. For in vivo intravesical instillation, Rap-loaded liposomes were dispersed in P407-gel, generating R-CL/P407 and R-FL/P407. Gel-forming capacities and drug release were evaluated. Using the MBT2/Luc orthotopic bladder cancer mouse model, in vivo antitumor efficacy was evaluated according to regions of interest (ROI) measurement.

Results

R-CL and R-FL were successfully prepared, at approximately <160 nm, 42% entrapment efficiency, and 57 μg/mg drug loading. FL cellular uptake was enhanced over 2-fold than that of CL; folate receptor-mediated endocytosis was confirmed using a competitive assay with folic acid pretreatment. In vitro cytotoxic effects increased dose-dependently. Rap-loaded liposomes inhibited mTOR signaling and induced autophagy in urothelial carcinoma cells. With gelation time of <30 seconds and gel duration of >12 hrs, both R-CL/P407 and R-FL/P407 preparations transformed into gel immediately after instillation into the mouse bladder. Drug release from the liposomal gel was erosion controlled. In orthotopic bladder cancer mouse model, statistically significant differences in ROI values were found between R-CL/P407 and R-FL/P407 groups at day 11 (P=0.0273) and day 14 (P=0.0088), indicating the highest tumor growth inhibition by R-FL/P407.

Conclusion

Intravesical instillation of R-FL/P407 might represent a good candidate for bladder cancer treatment, owing to its enhanced retention and FR-targeting.

Depletion of NBR1 in urothelial carcinoma cells enhances rapamycin-induced apoptosis through impaired autophagy and mitochondrial dysfunction

Rapamycin is well-recognized in the clinical therapeutic intervention for patients with cancer by specifically targeting mammalian target of rapamycin (mTOR) kinase. Rapamycin regulates general autophagy to clear damaged cells. Previously, we identified increased expression of messenger RNA levels of NBR1 (the neighbor of BRCA1 gene; autophagy cargo receptor) in human urothelial cancer (URCa) cells, which were not exhibited in response to rapamycin treatment for cell growth inhibition. Autophagy plays an important role in cellular physiology and offers protection against chemotherapeutic agents as an adaptive response required for maintaining cellular energy. Here, we hypothesized that loss of NBR1 sensitizes human URCa cells to growth inhibition induced by rapamycin treatment, leading to interruption of protective autophagic activation. Also, the potential role of mitochondria in regulating autophagy was tested to clarify the mechanism by which rapamycin induces apoptosis in NBR1-knockdown URCa cells. NBR1-knockdown URCa cells exhibited enhanced sensitivity to rapamycin associated with the suppression of autophagosomal elongation and mitochondrial defects. Loss of NBR1 expression altered the cellular responses to rapamycin treatment, resulting in impaired ATP homeostasis and an increase in reactive oxygen species (ROS). Although rapamycin treatment-induced autophagy by adenosine monophosphate-activated protein kinase (AMPK) phosphorylation in NBR1-knockdown cells, it did not process the conjugated form of LC3B-II after activation by unc-51 like autophagy-activating kinase 1 (ULK1). NBR1-knockdown URCa cells exhibited rather profound mitochondrial dysfunctions in response to rapamycin treatment as evidenced by Δψm collapse, ATP depletion, ROS accumulation, and apoptosis activation. Therefore, our findings provide a rationale for rapamycin treatment of NBR1-knockdown human urothelial cancer through the regulation of autophagy and mitochondrial dysfunction by regulating the AMPK/mTOR signaling pathway, indicating that NBR1 can be a potential therapeutic target of human urothelial cancer.

Lipids and Lipid-Binding Proteins in Selective Autophagy

Eukaryotic cells have the capacity to degrade intracellular components through a lysosomal degradation pathway called macroautophagy (henceforth referred to as autophagy) in which superfluous or damaged cytosolic entities are engulfed and separated from the rest of the cell constituents into double membraned vesicles known as autophagosomes. Autophagosomes then fuse with endosomes and lysosomes, where cargo is broken down into basic building blocks that are released to the cytoplasm for the cell to reuse. Autophagic degradation can target either cytoplasmic material in bulk (non-selective autophagy) or particular cargo in what is called selective autophagy. Proper autophagic turnover requires the orchestrated participation of several players that need to be tightly and temporally coordinated. Whereas a large number of autophagy-related (ATG) proteins have been identified and their functions and regulation are starting to be understood, there is substantially less knowledge regarding the specific lipids constituting the autophagic membranes as well as their role in initiating, enabling or regulating the autophagic process. This review focuses on lipids and their corresponding binding proteins that are crucial in the process of selective autophagy.

ER-Targeted Beclin 1 Supports Autophagosome Biogenesis in the Absence of ULK1 and ULK2 Kinases

Autophagy transports cytoplasmic material and organelles to lysosomes for degradation and recycling. Beclin 1 forms a complex with several other autophagy proteins and functions in the initiation phase of autophagy, but the exact role of Beclin 1 subcellular localization in autophagy initiation is still unclear. In order to elucidate the role of Beclin 1 localization in autophagosome biogenesis, we generated constructs that target Beclin 1 to the endoplasmic reticulum (ER) or mitochondria. Our results confirmed the proper organelle-specific targeting of the engineered Beclin 1 constructs, and the proper formation of autophagy-regulatory Beclin 1 complexes. The ULK kinases are required for autophagy initiation upstream of Beclin 1, and autophagosome biogenesis is severely impaired in ULK1/ULK2 double knockout cells. We tested whether Beclin 1 targeting facilitated its ability to rescue autophagosome formation in ULK1/ULK2 double knockout cells. ER-targeted Beclin 1 was most effective in the rescue experiments, while mitochondria-targeted and non-targeted Beclin 1 also showed an ability to rescue, but with lower activity. However, none of the constructs was able to increase autophagic flux in the knockout cells. We also showed that wild type Beclin 1 was enriched on the ER during autophagy induction, and that ULK1/ULK2 facilitated the ER-enrichment of Beclin 1 under basal conditions. The results suggest that one of the functions of ULK kinases may be to enhance Beclin 1 recruitment to the ER to drive autophagosome formation.

Metabolic features and regulation in cell senescence

Organismal aging is accompanied by a host of progressive metabolic alterations and an accumulation of senescent cells, along with functional decline and the appearance of multiple diseases. This implies that the metabolic features of cell senescence may contribute to the organism’s metabolic changes and be closely linked to age-associated diseases, especially metabolic syndromes. However, there is no clear understanding of senescent metabolic characteristics. Here, we review key metabolic features and regulators of cellular senescence, focusing on mitochondrial dysfunction and anabolic deregulation, and their link to other senescence phenotypes and aging. We further discuss the mechanistic involvement of the metabolic regulators mTOR, AMPK, and GSK3, proposing them as key metabolic switches for modulating senescence.

Molecular determinants regulating selective binding of autophagy adapters and receptors to ATG8 proteins

Autophagy is an essential recycling and quality control pathway. Mammalian ATG8 proteins drive autophagosome formation and selective removal of protein aggregates and organelles by recruiting autophagy receptors and adaptors that contain a LC3-interacting region (LIR) motif. LIR motifs can be highly selective for ATG8 subfamily proteins (LC3s/GABARAPs), however the molecular determinants regulating these selective interactions remain elusive. Here we show that residues within the core LIR motif and adjacent C-terminal region as well as ATG8 subfamily-specific residues in the LIR docking site are critical for binding of receptors and adaptors to GABARAPs. Moreover, rendering GABARAP more LC3B-like impairs autophagy receptor degradation. Modulating LIR binding specificity of the centriolar satellite protein PCM1, implicated in autophagy and centrosomal function, alters its dynamics in cells. Our data provides new mechanistic insight into how selective binding of LIR motifs to GABARAPs is achieved, and elucidate the overlapping and distinct functions of ATG8 subfamily proteins.

Retracted: Long noncoding RNA MEG3 inhibits proliferation and migration but induces autophagy by regulation of Sirt7 and PI3K/AKT/mTOR pathway in glioma cells

Glioma is a common primary brain tumor with high mortality rate and poor prognosis. Long noncoding RNA maternally expressed gene 3 (MEG3) is a tumor suppressor in diverse cancer types. However, the role of MEG3 in glioma remains unclear. We aimed to explore the effects of MEG3 on U251 cells as well as the underlying mechanisms. U251 cells were stably transfected with different recombined plasmids to overexpress or silence MEG3. Effects of aberrantly expressed MEG3 on cell viability, migration, apoptosis, expressions of apoptosis-associated and autophagy-associated proteins, and phosphorylated levels of key kinases in the PI3K/AKT/mTOR pathway were all evaluated. Then, messenger RNA (mRNA) and protein expression of Sirt7 in cells abnormally expressing MEG3 were estimated. In addition, effects of abnormally expressed MEG3 and Sirt7 on U251 cells were determined to reveal the underlying mechanism of MEG3-associated modulation. Cell viability and migration were significantly reduced by MEG3 overexpression whereas cell apoptosis as well as Bax and cleaved caspase-3/-9 proteins were obviously induced. Beclin-1 and LC3-II/LC3-I were upregulated and p62 was downregulated in MEG3 overexpressed cells. In addition, the autophagy pharmacological inhibitor (3-methyladenine, 3-MA) affected the effect of MEG3 overexpression on cell proliferation. Furthermore, the phosphorylated levels of key kinases in the PI3K/AKT/mTOR pathway were all reduced by MEG3 overexpression. Sirt7 was positively regulated by MEG3 expression, and effects of MEG3 overexpression on U251 cells were ameliorated by Sirt7 silence. MEG3 suppressed cell proliferation and migration but promoted autophagy in U251 cells through positively regulating Sirt7, involving in the inhibition of the PI3K/AKT/mTOR pathway.

TEX264 Is an Endoplasmic Reticulum-Resident ATG8-Interacting Protein Critical for ER Remodeling during Nutrient Stress

Cells respond to nutrient stress by trafficking cytosolic contents to lysosomes for degradation via macroautophagy. The endoplasmic reticulum (ER) serves as an initiation site for autophagosomes and is also remodeled in response to nutrient stress through ER-phagy, a form of selective autophagy. Quantitative proteome analysis during nutrient stress identified an unstudied single-pass transmembrane ER protein, TEX264, as an ER-phagy receptor. TEX264 uses an LC3-interacting region (LIR) to traffic into ATG8-positive puncta that often initiate from three-way ER tubule junctions and subsequently fuse with lysosomes. Interaction and proximity biotinylation proteomics identified a cohort of autophagy regulatory proteins and cargo adaptors located near TEX264 in an LIR-dependent manner. Global proteomics and ER-phagy flux analysis revealed the stabilization of a cohort of ER proteins in TEX264^-/- cells during nutrient stress. This work reveals TEX264 as an unrecognized ER-phagy receptor that acts independently of other candidate ER-phagy receptors to remodel the ER during nutrient stress.

mTORC1-Regulated and HUWE1-Mediated WIPI2 Degradation Controls Autophagy Flux

mTORC1, the major homeostatic sensor and responder, regulates cell catabolism mainly by targeting autophagy. Here, we show that mTORC1 directly controls autophagosome formation via phosphorylation of WIPI2, a critical protein in isolation membrane growth and elongation. mTORC1 phosphorylates Ser395 of WIPI2, directing WIPI2 to interact specifically with the E3 ubiquitin ligase HUWE1 for ubiquitination and proteasomal degradation. Physiological or pharmacological inhibition of mTORC1 in cells promotes WIPI2 stabilization, autophagosome formation, and autophagic degradation. In mouse liver, fasting significantly increases the WIPI2 protein level, while silencing HUWE1 enhances autophagy, and introducing WIPI2 improves lipid clearance. Thus, regulation of the intracellular WIPI2 protein level by mTORC1 and HUWE1 is a key determinant of autophagy flux and may coordinate the initiation, progression, and completion of autophagy.

USP1 (ubiquitin specific peptidase 1) targets ULK1 and regulates its cellular compartmentalization and autophagy

ULK1 (unc-51 like autophagy activating kinase 1) is a core component at multiple steps of canonical macroautophagy/autophagy. The activity of ULK1 is tightly regulated by several post-translational modifications, including ubiquitination, yet the deubiquitinase (DUB) responsible for its reversible deubiquitination has not been described. Here, we identified USP1 (ubiquitin specific peptidase 1) as a key player in the modulation of ULK1 K63-linked deubiquitination. Moreover, both USP1 depletion and its chemical inhibition by pimozide are coupled to a reduction of ULK1 in Triton X-100 soluble cellular lysates, and its compartmentalization to a fraction that can be solubilized in 5 M urea. In USP1-depleted cells this fraction is also enriched in SQSTM1 (sequestosome 1), the aggresome marker HDAC6 (histone deacetylase 6), and the prototype of USP1 targets FANCD2 (FA complementation group D2). Consistently, in USP1-depleted and pimozide-treated cells, ULK1 forms protein aggregates enriched in SQSTM1, as detected by both immummunofluorescence and co-immunoprecipitation studies. Notably, depletion of USP1 inhibits canonical autophagic flux and promotes an alternative route leading to lysosomal-mediated degradation of SQSTM1. Our findings reveal a novel function of the USP1-ULK1 axis as a modulator of the switch between canonical and unconventional autophagy. Further, we provide the first evidence supporting the existence of a subset of breast tumors co-expressing ULK1 and MAP1LC3B (microtubule associated protein 1 light chain 3 beta) proteins. Because the USP1 inhibitor pimozide affects breast cancer cell growth, targeting USP1 in those tumors relying on autophagy for growth might prove to be a convenient therapeutic strategy. Abbreviations: ATG13: autophagy related 13; BECN1: beclin 1; BZ: bortezomib; CAPN1: calpain 1; DUB: deubiquitinase; FANCI: FA complementation group I; FANCD2: FA complementation group D2; FZR1: fizzy and cell division cycle 20 related 1; HDAC6: histone deacetylase 6; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; PMZ: pimozide; SH3GLB1: SH3 domain containing GRB2 like, endophilin B1; SQSTM1: sequestosome 1; TRAF6: TNF receptor associated factor 6; ULK1: unc-51 like autophagy activating kinase 1; USP1: ubiquitin specific peptidase 1; WDR48: WD repeat domain 48.

Suppressing glucose metabolism with epigallocatechin-3-gallate (EGCG) reduces breast cancer cell growth in preclinical models

Numerous studies propose that epigallocatechin-3-gallate (EGCG), an abundant polyphenol in green tea, has anti-cancer properties. However, its mechanism of action in breast cancer remains unclear. This study investigated the capacity of EGCG to suppress breast cancer cell growth in vitro and in vivo, characterizing the underlying mechanisms, focusing on the effect of EGCG on glucose metabolism. EGCG reduced breast cancer 4T1 cell growth in a concentration- (10-320 μM) and time- (12-48 h) dependent manner. EGCG induced breast cancer apoptotic cell death at 24 h, as evidenced by annexin V/PI, caspase 3, caspase 8 and caspase 9 activation. Furthermore, EGCG affected the expression of 16 apoptosis-related genes, and promoted mitochondrial depolarization. EGCG induced autophagy concentration-dependently in 4T1 cells by modulating the levels of the autophagy-related proteins Beclin1, ATG5 and LC3B. Moreover, EGCG affected glucose, lactate and ATP levels. Mechanistically, EGCG significantly inhibited the activities and mRNA levels of the glycolytic enzymes hexokinase (HK), phosphofructokinase (PFK), and lactic dehydrogenase (LDH), and to a lesser extent the activity of pyruvate kinase (PK). In addition, EGCG decreased the expression of hypoxia-inducible factor 1α (HIF1α) and glucose transporter 1 (GLUT1), critical players in regulating glycolysis. In vivo, EGCG reduced breast tumor weight in a dose-dependent manner, reduced glucose and lactic acid levels and reduced the expression of the vascular endothelial growth factor (VEGF). In conclusion, EGCG exerts an anti-tumor effect through the inhibition of key enzymes that participate in the glycolytic pathway and the suppression of glucose metabolism.

Apios americana Medikus tuber polysaccharide exerts anti-inflammatory effects by activating autophagy

The tubers of Apios americana Medikus possess high nutritional value and have been used as food in many countries for a long time. However, few researches have focused on the tuber polysaccharides. In the present study, a purified polysaccharide (ATP-1) was isolated with the average molecular weights of 12.16 kDa. ATP-1 significantly suppressed the release of nitric oxide (NO) and inflammatory cytokines from LPS-induced RAW 264.7 cells, as well as oxidative stress and mitochondrial dysfunction. Meanwhile, ATP-1 reduced oxidative damage via the NF-κB, MAPKs and Nrf2-Keap1 signaling pathways in RAW264.7 macrophages. Furthermore, autophagy was activated by HMGB1-Beclin1, Sirt1-FoxO1 and Akt-mTOR signaling pathways, leading to a relief of oxidative stress, mitochondrial dysfunction, inflammation and an expression enhancement of autophagy-related proteins, such as LC3, Beclin1, Atg4, Atg5, and Atg7. In summary, our results suggested that ATP-1 might help to activate the anti-inflammation system，resulting in prevention of LPS-induced damage in RAW264.7 cells.

Hallmarks of Aging: An Autophagic Perspective

Autophagy is a major protein turnover pathway by which cellular components are delivered into the lysosomes for degradation and recycling. This intracellular process is able to maintain cellular homeostasis under stress conditions, and its dysregulation could lead to the development of physiological alterations. The autophagic activity has been found to decrease with age, likely contributing to the accumulation of damaged macromolecules and organelles during aging. Interestingly, failure of the autophagic process has been reported to worsen aging-associated diseases, such as neurodegeneration or cancer, among others. Likewise, it has been proposed in different organisms that maintenance of a proper autophagic activity contributes to extending longevity. In this review, we discuss recent papers showing the impact of autophagy on cell activity and age-associated diseases, highlighting the relevance of this process to the hallmarks of aging. Thus, understanding how autophagy plays an important role in aging opens new avenues for the discovery of biochemical and pharmacological targets and the development of novel anti-aging therapeutic approaches.

The cellular stress response in hepatitis C virus infection: A balancing act to promote viral persistence and host cell survival

Oxidative- and endoplasmic reticulum (ER)-stress are common events during hepatitis C virus (HCV) infection and both regulate cell survival and determine clinical outcome. In response to intrinsic and extrinsic cellular stress, different adaptive mechanisms have evolved in hepatocytes to restore cellular homeostasis like the anti-oxidant response, the unfolded protein response (UPR) and the integrated stress response (ISR). In this review, we focus on the cellular stress response in the context of acute and chronic HCV infection. The mechanisms of induction and modulation of oxidative- and ER-stress are reviewed and analyzed from both perspectives: viral persistence and cell survival. Besides, we delve into the activation of the eIF2α/ATF4 pathway and selective autophagy induction; pathways involved in the elimination of harmful viral proteins after oxidative stress induction. For this, the negative role of autophagy upon HCV infection or negative regulation of viral replication is analyzed. Finally, we hypothesize that the cellular stress response in hepatocytes plays a major role for HCV control thus acting as an important host-factor for virus clearance during the early stages of HCV infection.

Rapamycin enhances growth inhibition on urothelial carcinoma cells through LKB1 deficiency-mediated mitochondrial dysregulation

Rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, has significant potential for application in the treatment of urothelial carcinoma (URCa) of the bladder. Previous studies have shown that regulation of the AMP-activated serine/threonine protein kinase (AMPK)-mTOR signaling pathway enhances apoptosis by inducing autophagy or mitophagy in bladder cancer. Alteration of liver kinase B1 (LKB1)-AMPK signaling leads to mitochondrial dysfunction and the accumulation of autophagy-related proteins as a result of mitophagy, resulting in enhanced cell sensitivity to drug treatments. Therefore, we hypothesized that LKB1 deficiency in URCa cells could lead to increased sensitivity to rapamycin by inducing mitochondrial defect-mediated mitophagy. To test this, we established stable LKBI-knockdown URCa cells and analyzed the effects of rapamycin on their growth. Rapamycin enhanced growth inhibition and apoptosis in stable LKB1-knockdown URCa cells and in a xenograft mouse model. In spite of the stable downregulation of LKB1 expression, rapamycin induced AMPK activation in URCa cells, causing loss of the mitochondrial membrane potential, ATP depletion, and ROS accumulation, indicating an alteration of mitochondrial biogenesis. Our findings suggest that the absence of LKB1 can be targeted to induce dysregulated mitochondrial biogenesis by rapamycin treatment in the design of novel therapeutic strategies for bladder cancer.

FSIP1 regulates autophagy in breast cancer

Fibrous sheath interacting protein 1 (FSIP1) is a cancer antigen expressed in the majority of breast cancer tissues and is associated with poor prognosis. However, the role of FSIP1 in the progression and drug sensitivity of triple-negative breast cancer (TNBC) has not been explored. Here, we show that FSIP1 deficiency by shRNA-mediated knockdown or CRISPR-Cas9-mediated knockout significantly inhibits the proliferation and invasion of TNBC cells and impairs chemotherapy-induced growth inhibition in vivo. Computational modeling predicted that FSIP1 binds to ULK1, and this was established by coimmunoprecipitation. FSIP1 deficiency promoted autophagy, enhanced AMP-activated protein kinase (AMPK) signaling, and decreased mechanistic target of rapamycin (mTOR) and Wnt/β-catenin activity. In contrast, knockdown of AMPK or inhibition of autophagy restored the sensitivity to chemotherapy drugs in TNBC cells. Our findings uncover a role of FSIP1 as well as mechanisms underlying FSIP1 action in drug sensitivity and may, therefore, aid in design of TNBC therapies.

EGb761 improves the cognitive function of elderly db/db-/- diabetic mice by regulating the beclin-1 and NF-κB signaling pathways

To assess whether EGb761 could protect elderly diabetic mice with cognitive disorders and explore the role of beclin-1-mediated autophagy in these protective effects. Two-month-old male db/db^-/- mice and wild-type C57/BL6 mice were randomly divided into six groups: db/db^-/- control, db/db^-/- 50 mg, db/db^-/- 100 mg, wild-type (WT) control, WT 50 mg, and WT 100 mg. EGb761 (50 mg/kg or 100 mg/kg of bodyweight) was given by gavage once a day for 1 month from the age of 6 months. Y-maze and social choice tests were performed at 8th months. The blood pressure was measured. The imaging changes in the brain were measured using magnetic resonance imaging (MRI). The expression and distribution of beclin-1, LC3, and NF-κB were detected using immunohistochemistry staining and western blotting. Ultrastructure alterations in the hippocampus were observed using transmission electron microscopy. Compared with WT mice, the learning ability, memory and overall cognitive function of db/db^-/- mice decreased (P < 0.05), and EGb761 could significantly improve the learning and memory function of db/db^-/- mice (P < 0.05). EGb761 significantly improved systolic blood pressure in db/db^-/- mice (P < 0.01). In addition, fMRI-bold showed a decline in the hippocampus of mice in the db/db^-/- group compared with WT. EGb761 could improve these above changes. Immunohistochemistry staining and western blotting confirmed that EGb761 significantly increased beclin-1 and reduced LC3-II/I levels in the brains of db/db^-/- mice (P < 0.05). NF-κB levels were obviously higher in the db/db^-/- group than that in the WT group, and EGb761 significantly reduced NF-κB levels in db/db^-/- mice (P < 0.05). There was a trend of increased autophagosomes in db/db^-/- mice, but EGb761 did not change obviously the number of autophagosomes. Compared with normal aged WT mice, aging db/db^-/- mice had more common complications of cerebral small vessel disease and cognitive dysfunction. EGb761 could significantly improve the cognitive function of aging db/db^-/- mice via a mechanism that may involve the regulation of beclin-1, LC3, and NF-κB.

HIF-1α/Beclin1-Mediated Autophagy Is Involved in Neuroprotection Induced by Hypoxic Preconditioning

Hypoxic preconditioning (HPC) exerts a protective effect against hypoxic/ischemic brain injury, and one mechanism explaining this effect may involve the upregulation of hypoxia-inducible factor-1 (HIF-1). Autophagy, an endogenous protective mechanism against hypoxic/ischemic injury, is correlated with the activation of the HIF-1α/Beclin1 signaling pathway. Based on previous studies, we hypothesize that the protective role of HPC may involve autophagy occurring via activation of the HIF-1α/Beclin1 signaling pathway. To test this hypothesis, we evaluated the effects of HPC on oxygen-glucose deprivation/reperfusion (OGD/R)-induced apoptosis and autophagy in SH-SY5Y cells. HPC significantly attenuated OGD/R-induced apoptosis, and this effect was suppressed by the autophagy inhibitor 3-methyladenine and mimicked by the autophagy agonist rapamycin. In control SH-SY5Y cells, HPC upregulated the expression of HIF-1α and downstream molecules such as BNIP3 and Beclin1. Additionally, HPC increased the LC3-II/LC3-I ratio and decreased p62 levels. The increase in the LC3-II/LC3-I ratio was inhibited by the HIF-1α inhibitor YC-1 or by Beclin1-short hairpin RNA (shRNA). In OGD/R-treated SH-SY5Y cells, HPC also upregulated the expression levels of HIF-1α, BNIP3, and Beclin1, as well as the LC3-II/LC3-I ratio. Furthermore, YC-1 or Beclin1-shRNA attenuated the HPC-mediated cell viability in OGD/R-treated cells. Taken together, our results demonstrate that HPC protects SH-SY5Y cells against OGD/R via HIF-1α/Beclin1-regulated autophagy.

Autophagy in Paracoccidioides brasiliensis under normal mycelia to yeast transition and under selective nutrient deprivation

Paracoccidioides spp. is a thermally dimorphic fungus endemic to Latin America and the etiological agent of paracoccidioidomycosis (PCM), a granulomatous disease acquired through fungal propagule inhalation by its mammalian host. The infection is established after successful mycelia to yeast transition in the host pulmonary alveoli. The challenging environment inside the host exposes the fungus to the need of adaptation in order to circumvent nutritional, thermal, oxidative, immunological and other stresses that can directly affect their survival. Considering that autophagy is a response to abrupt environmental changes and is induced by stress conditions, this study hypothesizes that this process might be crucially involved in the adaptation of Paracoccidioides spp. to the host and, therefore, it is essential for the proper establishment of the disease. By labelling autophagous vesicles with monodansylcadaverine, autophagy was observed as an early event in cells during the normal mycelium to yeast transition, as well as in yeast cells of P. brasiliensis under glucose deprivation, and under either rapamycin or 3-methyladenine (3-MA). Findings in this study demonstrated that autophagy is triggered in P. brasiliensis during the thermal-induced mycelium to yeast transition and by glucose-limited conditions in yeasts, both of which modulated by rapamycin or 3-MA. Certainly, further genetic and in vivo analyses are needed in order to finally address the contribution of autophagy for adaptation. Yet, our data propose that autophagy possibly plays an important role in Paracoccidioides brasiliensis virulence and pathogenicity.

Autophagic degradation of SQSTM1 inhibits ovarian cancer motility by decreasing DICER1 and AGO2 to induce MIRLET7A-3P

The relationship between macroautophagy/autophagy and miRNA in regulating cancer cell motility is not clearly delineated. Here, we found that induction of BECN1-dependent or -independent autophagy decreased ubiquitin-binding proteins SQSTM1/p62 and CALCOCO2/NDP52. Downregulation of SQSTM1 (but not CALCOCO2) led to a decrease of the miRNA-processing enzyme DICER1 and the miRNA effector AGO2. The autophagy-mediated reduction of levels of SQSTM1, DICER1 or AGO2 resulted in increased MIRLET7A-3P (but not MIRLET7A-5P or PRE-MIRLET7A miRNA) and suppressed ovarian cancer motility. The investigation of the MIRLET7A effects on cancer cell motility showed that synthetic MIRLET7A-3P (3 nM) inhibited, whereas MIRLET7A-5P (100 nM) increased cancer cell motility. Moreover, downregulation of MIRLET7A-3P with antisense of MIRLET7A-3P miRNA (MIRLET7A-3P inhibitor; 3 nM) reversed the nutrient depletion- and rVP1-mediated suppression of ovarian cancer cell motility. In addition, restoring SQSTM1, DICER1 and AGO2 with inhibition of autophagic degradation or overexpression of DICER1 and AGO2 reversed the autophagy-associated enhancement of MIRLET7A-3P and inhibition of motility. Examination of ovarian cancer tissue microarray further showed that the levels of SQSTM1, DICER1 and AGO2 in the tumor were higher than those in the non-tumor cells and negatively correlated with the levels of autophagy and MIRLET7A-3P. Our results demonstrated that induction of autophagy to decrease SQSTM1, DICER1 and AGO2 and increase MIRLET7A-3P is a potential therapeutic strategy for suppressing ovarian cancer cell motility. Abbreviations: ACTB: actin beta; AGO2: argonaute 2, RISC catalytic component; ATG: autophagy related; BCIP/NBT: 5-bromo-4-chloro-3-indolyl-phosphate/nitro blue tetrazolium; BECN1: beclin 1, autophagy related; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CQ: chloroquine; DICER1: dicer 1, ribonuclease III; EBSS: Earle balanced salt solution; FBS: fetal bovine serum; HGF: hepatocyte growth factor; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MIRLET7A: microRNA LET-7A: MIR16: microRNA 16; MIR29C: microRNA 29C; miRNA: microRNA; MMP: matrix metallopeptidase; PRE-MIRNA: precursor microRNA; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; RISC: RNA-induced silencing complex; rVP1: recombinant foot-and-mouth disease virus capsid protein VP1; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; WIPI: WD repeat domain, phosphoinositide interacting.

Autophagy upregulation as a possible mechanism of arsenic induced diabetes

The key features of type 2 diabetes mellitus (T2DM) caused by high fat diet (HFD) in combination with arsenic (As) exposure (pronounced glucose intolerance despite a significant decrease in insulin resistance) are different from those expected for T2DM. Autophagy has been considered as a possible link between insulin resistance and obesity. Therefore in this study, we utilized autophagy gene expression profiling via real-time RT-PCR array analysis in livers of NMRI mice exposed to an environmentally relevant and minimally cytotoxic concentration of arsenite (50 ppm) in drinking water while being fed with a HFD for 20 weeks. Out of 84 genes associated with autophagy under study, 21 genes were related to autophagy machinery components of which 13 genes were downregulated when HDF diet was applied. In this study, for the first time, it was shown that the exposure to arsenic in the livers of mice chronically fed with HFD along with increased oxidative stress resulted in the restoration of autophagy [upregulation of genes involved in the early phase of phagophore formation, phagophore expansion and autophagosome-lysosome linkage stages]. Considering the role of arsenic in the induction of autophagy; it can be argued that reduced insulin resistance in HFD - As induced diabetes may be mediated by autophagy upregulation.

Autophagy-Associated Shrinkage of the Hepatopancreas in Fasting Male Macrobrachium rosenbergii Is Rescued by Neuropeptide F

Invertebrate neuropeptide F-I (NPF-I), much alike its mammalian homolog neuropeptide Y, influences several physiological processes, including circadian rhythms, cortical excitability, stress response, and food intake behavior. Given the role of autophagy in the metabolic stress response, we investigated the effect of NPF-1 on autophagy during fasting and feeding conditions in the hepatopancreas and muscle tissues of the male giant freshwater prawn Macrobrachium rosenbergii. Starvation up-regulated the expression of the autophagy marker LC3 in both tissues. Yet, based on the relative levels of the autophagosome-associated LC3-II isoform and of its precursor LC3-I, the hepatopancreas was more responsive than the muscle to starvation-induced autophagy. Injection of NPF-I inhibited the autophagosome formation in the hepatopancreas of fasting prawns. Relative to the body weight, the muscle weight was not affected, while that of the hepatopancreas decreased upon starvation and NPF-1 treatment could largely prevent such weight loss. Thus, the hepatopancreas is the reserve organ for the nutrient homeostasis during starvation and NPF-I plays a crucial role in the balancing of energy expenditure and energy intake during starvation by modulating autophagy.

The programmed DNA elimination and formation of micronuclei in germ line cells of the natural hybridogenetic water frog Pelophylax esculentus

DNA elimination is a radical form of gene silencing and occurs both in somatic and germ cells. The programmed DNA elimination occurs during gametogenesis in interspecies hybrids that reproduce by hybridogenesis (stick insects, fishes, and amphibians) and concerns removal of whole genomes of one of the parental species and production of clonal gametes propagating the genome of the other species. The cellular mechanisms differ considerably in hybridogenetic insects and fishes but remains unknown in edible frogs Pelophylax esculentus, natural hybrids between Pelophylax lessonae and Pelophylax ridibundus. Here we report DNA elimination mechanism in early developing gonads of diploid and triploid hybrid frogs, studied by TEM, immunofluorescence, and cytochemistry. In gonocytes of both sexes (primary oogonia and prespermatogonia), micronuclei emerge as detached nuclear buds formed during interphase. We found depletion of nuclear pore complexes in micronuclear membrane and chromatin inactivation via heterochromatinization followed by degradation of micronuclei by autophagy. Micronuclei formation does not lead to apoptotic cell death showing that genome elimination is a physiological process. Chromatin elimination via micronuclei in P. esculentus is unique among hybridogenetic animals and contributes to broadening the knowledge about reproductive modes in animals.