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Fulltext The role of autophagy-related proteins in the pathogenesis of neuromyelitis optica spectrum disorders

Guo HL, Shen XR, Liang XT, Li LZ

Bioengineered, 2022 Jun;13(6):14329-14338.
PMID: 36694421 DOI: 10.1080/21655979.2022.2084273

This study aimed to investigate the expression of autophagy-related proteins in a mouse model of neuromyelitis optica (NMO). Mice were assigned to one of four groups: an animal experimental model group (NMO-EAE group, given with exogenous IL-17A), Interleukin-17 monoclonal antibody intervention group (NMO-EAE_0IL17inb), No exogenous interleukin-17 enhanced immune intervention group (NMO-EAE_0IL17), and a control group. Behavioral scores were assessed in each group, and the protein expressions of sequestosome 1 (P62), Beclin-1, the mammalian target of rapamycin (mTOR), phosphoinositide 3-kinase (PI3K-I), and LC3II/LC3I were detected using Western blotting. In the NMO-EAE_0IL17 group, the expression of Beclin-1 decreased, the LC3II/LC3I ratio was lower, and the expressions of P62, mTOR, and PI3K-I increased; after administration of IL-17A inhibitor into the brain tissue, however, the expression of Beclin-1 increased significantly, along with the LC3II/LC3I ratio, while the expressions of P62, mTOR and PI3K-I protein decreased significantly. In terms of behavioral scores, the scores of optic neuritis and myelitis were more serious, onset occurred earlier and the progress was faster, after the administration of IL-17A. In the mechanism of NMO animal model, IL-17A may regulate autophagy and affect the disease process through the activation of the PI3K-mTOR signaling pathway.

Matched MeSH terms: Beclin-1/metabolism
Autophagy inhibition suppresses Newcastle disease virus-induced cell death by inhibiting viral replication in human breast cancer cells

Rozilah MI, Yusoff K, Chia SL, Ismail S

Virology, 2024 Feb;590:109957.
PMID: 38100982 DOI: 10.1016/j.virol.2023.109957

Newcastle disease virus (NDV) is an oncolytic virus which selectively replicates in cancer cells without harming normal cells. Autophagy is a cellular mechanism that breaks down unused cytoplasmic constituents into nutrients. In previous studies, autophagy enhanced NDV-induced oncolysis in lung cancer and glioma cells. However, the effect of autophagy inhibition on NDV-induced oncolysis in breast cancer cells remains unknown. This study aimed to examine the effect of autophagy inhibition on NDV-induced oncolysis in human breast cancer cells, MCF7. To inhibit autophagy, we knocked down the expression of the autophagy protein beclin-1 (BECN1) by short interfering RNA (siRNA). The cells were infected with the recombinant NDV strain AF2240 expressing green fluorescent protein. We found that NDV induced autophagy and knockdown of BECN1 significantly reduced the NDV-induced autophagy in MCF7 cells. Importantly, BECN1 knockdown significantly suppressed cell death by inhibiting viral replication, as observed at 24 h post infection. Overall, our data suggest that autophagy inhibition may not be a suitable strategy to enhance NDV oncolytic efficacy against breast cancer.

Matched MeSH terms: Beclin-1/metabolism
Fulltext The apoptotic effect of 1'S-1'-Acetoxychavicol Acetate (ACA) enhanced by inhibition of non-canonical autophagy in human non-small cell lung cancer cells

Sok SP, Arshad NM, Azmi MN, Awang K, Ozpolat B, Hasima Nagoor N

PLoS One, 2017;12(2):e0171329.
PMID: 28158287 DOI: 10.1371/journal.pone.0171329

Autophagy plays a role in deciding the fate of cells by inducing either survival or death. 1'S-1-acetoxychavicol acetate (ACA) is a phenylpropanoid isolated from rhizomes of Alpinia conchigera and has been reported previously on its apoptotic effects on various cancers. However, the effect of ACA on autophagy remains ambiguous. The aims of this study were to investigate the autophagy-inducing ability of ACA in human non-small cell lung cancer (NSCLC), and to determine its role as pro-survival or pro-death mechanism. Cell viability assay was conducted using MTT. The effect of autophagy was assessed by acridine orange staining, GFP-LC3 punctate formation assay, and protein level were analysed using western blot. Annexin V-FITC/PI staining was performed to detect percentage of cells undergoing apoptosis by using flow cytometry. ACA inhibits the cell viability and induced formation of cytoplasmic vacuoles in NSCLC cells. Acidic vesicular organelles and GFP-LC3 punctate formation were increased in response to ACA exposure in A549 and SK-LU-1 cell lines; implying occurrence of autophagy. In western blot, accumulation of LC3-II accompanied by degradation of p62 was observed, which further confirmed the full flux of autophagy induction by ACA. The reduction of Beclin-1 upon ACA treatment indicated the Beclin-1-independent autophagy pathway. An early autophagy inhibitor, 3-methyaldenine (3-MA), failed to suppress the autophagy triggered by ACA; validating the existence of Beclin-1-independent autophagy. Silencing of LC3-II using short interfering RNA (siRNA) abolished the autophagy effects, enhancing the cytotoxicity of ACA through apoptosis. This proposed ACA triggered a pro-survival autophagy in NSCLC cells. Consistently, co-treatment with lysosomal inhibitor, chloroquine (CQ), exerted a synergistic effect resulting in apoptosis. Our findings suggested ACA induced pro-survival autophagy through Beclin-1-independent pathway in NSCLC. Hence, targeting autophagy pathway using autophagy inhibitor such as CQ represented a novel promising approach to potentiate the cytotoxicity of ACA through apoptosis in NSCLC.

Matched MeSH terms: Beclin-1/metabolism
Panduratin A induces protective autophagy in melanoma via the AMPK and mTOR pathway

Lai SL, Mustafa MR, Wong PF

Phytomedicine, 2018 Mar 15;42:144-151.
PMID: 29655680 DOI: 10.1016/j.phymed.2018.03.027

BACKGROUND: Targeting autophagy is emerging as a promising strategy in cancer therapeutics in recent years. Autophagy can be modulated to drive cancer cell deaths that are notoriously resistant to apoptotic-inducing drugs. In addition, autophagy has been implicated as a prosurvival mechanism in mediating cancer chemoresistance. Our previous study has demonstrated that Panduratin A (PA), a plant-derived active compound exploits ER-stress-mediated apoptosis as its cytotoxic mechanism on melanoma.
PURPOSE: Our previous proteomics analysis revealed that treatment with PA resulted in the upregulation of an autophagy marker, LC3B in melanoma cells. Therefore, the present study sought to investigate the role of PA-induced autophagy in melanoma cells.
METHODS: Transmission electron microscopy was performed for examination of autophagic ultra-structures in PA-treated A375 cells. Cytoplasmic LC3B and p62/SQSMT1 punctate structures were detected using immunofluorescene staining. Expression levels of LC3B II, p62/SQSMT1, ATG 12, Beclin 1, phospho S6 (ser235/236), phospho AMPK (Thr172) and cleaved PARP were evaluated by western blotting.
RESULTS: Autophagosomes, autolysosomes and punctuates of LC3 proteins could be observed in PA-treated A375 cells. PA-induced autophagy in A375 melanoma cells was found to be mediated through the inhibition of mTOR signaling and activation of AMPK pathway. Furthermore, we showed that PA-induced apoptosis was increased in the presence of an autophagy inhibitor, signifying the cytoprotective effect of PA-induced autophagy in melanoma cells.
CONCLUSION: Taken together, results from the present study suggest that the inhibition of autophagy by targeting mTOR and AMPK could potentiate the cytotoxicity effects of PA on melanoma cells.

Matched MeSH terms: Beclin-1/metabolism
Umbilical Cord Mesenchymal Stem Cells Conditioned Medium Promotes Aβ25-35 phagocytosis by Modulating Autophagy and Aβ-Degrading Enzymes in BV2 Cells

Xu Z, Nan W, Zhang X, Sun Y, Yang J, Lu K, et al.

J Mol Neurosci, 2018 Jun;65(2):222-233.
PMID: 29845511 DOI: 10.1007/s12031-018-1075-5

Mesenchymal stem cell (MSC) therapy is a promising prospect for the treatment of Alzheimer's disease (AD); however, the underlying mechanisms by which MSCs mediate positive effects are still unclear. We speculated that MSCs mediate microglial autophagy and enhance the clearance of Aβ. To test this hypothesis, we cultured BV2 microglial cells with umbilical cord mesenchymal stem cells conditioned medium (ucMSCs-CM) in the presence or absence of Aβ25-35 oligomers. We investigated BV2 cell proliferation, cell death, and Aβ25-35 phagocytosis as well as protein expression levels of LC3, Beclin-1, p62, insulin-degrading enzyme (IDE), and neprilysin (Nep) with western blotting. The results showed that ucMSCs-CM inhibited the proliferation and decreased cell death of BV2 cells induced by Aβ25-35. ucMSCs-CM also promoted the phagocytosis of Aβ25-35 by BV2 cells and changed the expression of autophagy-related proteins LC3, Beclin-1, and p62. Treatment also upregulated the expression of Aβ-degrading enzymes IDE and Nep. Furthermore, the culture medium in BV2 cells with Aβ25-35 and ucMSCs-CM prevented neuronal cell SH-SY5Y from cell death compared to control medium without ucMSCs-CM. Altogether, these data suggested that ucMSCs-CM protect microglial and neuronal cells from Aβ25-35-induced cell death and promote Aβ phagocytosis by modulating autophagy and enhancing the expression of Aβ-degrading enzymes in microglia.

Matched MeSH terms: Beclin-1/metabolism
Fulltext Differential regulation of cell death pathways by the microenvironment correlates with chemoresistance and survival in leukaemia

Qattan MY, Bakker EY, Rajendran R, Chen DW, Saha V, Liu J, et al.

PLoS One, 2017;12(6):e0178606.
PMID: 28582465 DOI: 10.1371/journal.pone.0178606

Glucocorticoids (GCs) and topoisomerase II inhibitors are used to treat acute lymphoblastic leukaemia (ALL) as they induce death in lymphoid cells through the glucocorticoid receptor (GR) and p53 respectively. Mechanisms underlying ALL cell death and the contribution of the bone marrow microenvironment to drug response/resistance remain unclear. The role of the microenvironment and the identification of chemoresistance determinants were studied by transcriptomic analysis in ALL cells treated with Dexamethasone (Dex), and Etoposide (Etop) grown in the presence or absence of bone marrow conditioned media (CM). The necroptotic (RIPK1) and the apoptotic (caspase-8/3) markers were downregulated by CM, whereas the inhibitory effects of chemotherapy on the autophagy marker Beclin-1 (BECN1) were reduced suggesting CM exerts cytoprotective effects. GCs upregulated the RIPK1 ubiquitinating factor BIRC3 (cIAP2), in GC-sensitive (CEM-C7-14) but not in resistant (CEM-C1-15) cells. In addition, CM selectively affected GR phosphorylation in a site and cell-specific manner. GR is recruited to RIPK1, BECN1 and BIRC3 promoters in the sensitive but not in the resistant cells with phosphorylated GR forms being generally less recruited in the presence of hormone. FACS analysis and caspase-8 assays demonstrated that CM promoted a pro-survival trend. High molecular weight proteins reacting with the RIPK1 antibody were modified upon incubation with the BIRC3 inhibitor AT406 in CEM-C7-14 cells suggesting that they represent ubiquitinated forms of RIPK1. Our data suggest that there is a correlation between microenvironment-induced ALL proliferation and altered response to chemotherapy.

Matched MeSH terms: Beclin-1/metabolism