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Journal of Molecular Biology Jun 2024Autophagy is a cellular degradation pathway where double-membrane autophagosomes form de novo to engulf cytoplasmic material destined for lysosomal degradation. This... (Review)
Review
Autophagy is a cellular degradation pathway where double-membrane autophagosomes form de novo to engulf cytoplasmic material destined for lysosomal degradation. This process requires regulated membrane remodeling, beginning with the initial autophagosomal precursor and progressing to its elongation and maturation into a fully enclosed, fusion-capable vesicle. While the core protein machinery involved in autophagosome formation has been extensively studied over the past two decades, the role of phospholipids in this process has only recently been studied. This review focuses on the phospholipid composition of the phagophore membrane and the mechanisms that supply lipids to expand this unique organelle.
PubMed: 38944336
DOI: 10.1016/j.jmb.2024.168691 -
Cellular Signalling Jun 2024Silicosis, one of the occupational health illnesses is caused by inhalation of crystalline silica. Deposition of extracellular matrix and fibroblast proliferation in...
BACKGROUND AND OBJECTIVES
Silicosis, one of the occupational health illnesses is caused by inhalation of crystalline silica. Deposition of extracellular matrix and fibroblast proliferation in lungs are linked to silicosis development. Mitochondrial dysfunction plays critical role in some diseases, but how these processes progress and regulated in silicosis, remains limited. Detailed study of silica induced pulmonary fibrosis in mouse model, its progression and severity may be helpful in designing future therapeutic strategies.
METHODS
In present study, mice model of silicosis has been developed after repeated silica exposures which may closely resemble clinical symptoms of silicosis in human. In addition to efficiently mimicking the acute/chronic transformation processes of silicosis, this is practical and efficient in terms of time and output, which avoids mechanical injury to the upper respiratory tract due to surgical interventions. Sonicated sterile silica suspension (120 mg/kg) was administered through intranasal route thrice a week at regular intervals (21, 28 and 35 days).
RESULTS
Presence of minute to larger silicotic nodules in H&E-stained lung sections were observed in all silica induced model groups. Enhanced ECM deposition was noted in MT stained lung sections of silica exposure groups as compared to control which were confirmed by significantly higher MMP9 expression levels and hydroxyproline content in silica 35 days group. Increase in Reactive oxygen species (ROS), inflammatory cell recruitment mainly, neutrophils and macrophage were observed in all three silica exposure groups. Transmission electron microscopic analysis has confirmed presence of many aberrant shaped mitochondria (swollen, round shape) in 35 days model where autophagosomes were minimum. Western blot analysis of mitophagy and autophagy markers such as Pink1, Parkin, Cytochrome c, SQSTM1/p62, the ratio of light chain LC3B II/LC3B I was found higher in 21 and 28 days which were significantly reduced in 35 days silica model.
CONCLUSIONS
Higher MMP9 activity and MMP9 /TIMP1 ratio demonstrate excessive extracellular matrix damage and deposition in 35 days model. Significantly reduced expressions of autophagy and mitophagy markers have also confirmed progression in fibrosis severity and its association with repeated silica exposures in 35 days model group.
PubMed: 38944258
DOI: 10.1016/j.cellsig.2024.111272 -
Cell Death & Disease Jun 2024High basal autophagy and enhanced mitochondrial fission in triple-negative breast cancer (TNBC) cells support cell migration and promote plasticity of cancer cell...
High basal autophagy and enhanced mitochondrial fission in triple-negative breast cancer (TNBC) cells support cell migration and promote plasticity of cancer cell metabolism. Here, we suggest a novel combination therapy approach for the treatment of TNBC that targets Drp1-mediated mitochondrial fission and autophagy pathways. Hydrogen sulfide (HS) mediates a myriad of biological processes, including autophagy and mitochondrial function. In this study, we demonstrated that 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione (ADT-OH), one of the most widely utilized sustained-release HS donors, effectively suppresses metastasis of TNBC cells in the absence of proliferation inhibition in vitro and in vivo. ADT-OH treatment ameliorated autophagy flux by suppressing autophagosome formation and induced mitochondrial elongation through decreasing expression of dynamin-related protein 1 (Drp1) and increasing expression of mitochondrial fusion protein (Mfn2). At the same time, ADT-OH downregulated mitophagy flux and inhibited mitochondrial function, eventually leading to the inhibition of migration and invasion in TNBC cells. In vivo, intraperitoneal administration of ADT-OH revealed a potent anti-metastatic activity in three different animal models, the MDA-MB-231 orthotopic xenograft model, the 4T1-Luci orthotopic model and the 4T1-Luci tail vein metastasis model. However, ADT-OH has an extremely low water solubility, which is a significant barrier to its effectiveness. Thus, we demonstrated that the solubility of ADT-OH in water can be improved significantly by absorption with hydroxypropyl-β-cyclodextrin (CD). Remarkably, the obtained CD-ADT-OH demonstrated superior anti-cancer effect to ADT-OH in vivo. Altogether, this study describes a novel regulator of mammalian mitochondrial fission and autophagy, with potential utility as an experimental therapeutic agent for metastatic TNBC.
Topics: Triple Negative Breast Neoplasms; Mitochondrial Dynamics; Humans; Animals; Autophagy; Female; Cell Line, Tumor; Mice; Cell Movement; Mice, Nude; Thiones; Xenograft Model Antitumor Assays; Mice, Inbred BALB C; Mitochondria; Cell Proliferation; Neoplasm Metastasis; Hydrogen Sulfide; Dynamins; Thiophenes
PubMed: 38942765
DOI: 10.1038/s41419-024-06829-w -
Tissue & Cell Jun 2024Exposure to the neonicotinoid insecticide, imidacloprid (IMI), causes reproductive toxicity in mammals and reptiles. However, reports on the effects of IMI on the gonads...
Exposure to the neonicotinoid insecticide, imidacloprid (IMI), causes reproductive toxicity in mammals and reptiles. However, reports on the effects of IMI on the gonads in birds are grossly lacking. Therefore, this study investigated the effects of pubertal exposure to IMI on the histology, ultrastructure, as well as the cytoskeletal proteins, desmin, smooth muscle actin and vimentin, of the gonads of Japanese quail (Coturnix coturnix japonica). Quails were randomly divided into four groups at 5 weeks of age. The control group was given only distilled water, whereas, the other three experimental groups, IMI was administered by oral gavage at 1.55, 3.1, and 6.2 mg/kg, twice per week for 4 weeks. Exposure to IMI doses of 3.1 and 6.2 mg/kg caused dose-dependent histopathological changes in the ovary and testis. In the ovary, accumulation of lymphocytes, degenerative changes, and necrosis with granulocyte infiltrations were observed, while in the testis, distorted seminiferous tubules, germ cell sloughing, vacuolisations, apoptotic bodies, autophagosomes, and mitochondrial damage were detected. These changes were accompanied by a decreased number of primary follicles (P ≤ 0.05) in the ovary and a decrease (P ≤ 0.05) in the epithelial height, luminal, and tubular diameters of seminiferous tubules at the two higher dosages. In addition, IMI had a negative effect on the immunostaining intensity of desmin, smooth muscle actin, and vimentin in the ovarian and testicular tissue. In conclusion, exposure to IMI during puberty can lead to a range of histopathological alterations in the gonads of Japanese quails, which may ultimately result in infertility.
PubMed: 38941762
DOI: 10.1016/j.tice.2024.102450 -
Biochemistry Jun 2024Protein advanced glycation end products (AGEs) can be formed via nonenzymatic glycation and accumulated intracellularly to disrupt cellular homeostasis for protein...
Protein advanced glycation end products (AGEs) can be formed via nonenzymatic glycation and accumulated intracellularly to disrupt cellular homeostasis for protein clearance. Here, we investigated the formation particulars of intracellular protein AGEs and sought to elucidate the molecular events implicated in the impact of cellular clearance systems. The formation and accumulation of intracellular protein AGEs increased protein aggregation and protease resistance, potentially overwhelming the ubiquitin-proteasome system (UPS). At high levels of protein AGEs, the abundance of many E3 ligases decreased and the overall ubiquitination level was reduced, all of which indicated decreased UPS activity. On the other hand, autophagy activity was stimulated, as evidenced by the upregulation of autophagy marker LC3II and important proteins in autophagosome and autolysosome formation, as well as downregulation of mTOR. Understanding the functional impacts of intracellular protein AGEs on the UPS and autophagy could pave the way for the future development of pharmaceutical agents targeting AGE-related diseases.
PubMed: 38941592
DOI: 10.1021/acs.biochem.4c00250 -
Sheng Li Xue Bao : [Acta Physiologica... Jun 2024The purpose of the study was to investigate the mechanism of TFEB activator 1 (TA1) improving the autophagic degradation of oligomeric amyloid-β (oAβ) in microglia,...
The purpose of the study was to investigate the mechanism of TFEB activator 1 (TA1) improving the autophagic degradation of oligomeric amyloid-β (oAβ) in microglia, and to explore the therapeutic effect of TA1 on an in vitro model of microglia in Alzheimer's disease (AD). Primary microglia were exposed to 1 μmol/L oAβ for 0, 3, 12, and 24 h respectively to construct the in vitro model of microglia in AD. In order to explore the therapeutic effect of TA1, primary microglia were co-treated with 1 μmol/L oAβ and 1 μmol/L TA1 for 12 h. To determine the autophagy flux, the above cells were further treated with 100 nmol/L Bafilomycin A1 for 1 h before fixation. Fluorescent probes were used to detect the endocytosis or degradation of oAβ by microglia. The autophagic flux was determined by infection of lentivirus mCherry-EGFP-LC3. The nuclear TFEB intensity, the autophagosomes number, and the colocalization ratio of oAβ with lysosome-associated membrane protein 1 (LAMP1) or microtubule-associated protein light chain 3 (LC3), were detected by immunofluorescence assay. Expressions of autophagy-related-genes, including Lamp1, Atg5, and Map1lc3b, were detected by qRT-PCR. Results showed that prolonged oAβ exposure inhibited the endocytosis and degradation of oAβ by microglia. Meanwhile, the number of autophagosomes and autophagy flux in microglia decreased after 12 h of oAβ treatment. We further found that the nuclear expression of autophagy regulator TFEB decreased after 12 h of oAβ exposure, resulting in the decrease of autophagy genes, thus leading to the damage of autophagic degradation of oAβ. Therefore, long-term oAβ exposure was considered to construct the in vitro model of microglia in AD. After TA1 treatment, the nuclear expression of TFEB in cells was obviously upregulated. TA1 treatment upregulated the expressions of autophagy-related genes, leading to the recovery of autophagy flux. TA1 also recovered the endocytosis and degradation of oAβ by microglia. In conclusion, TA1 could improve oAβ clearance by microglia in AD by upregulating microglial TFEB-mediated autophagy, suggesting TA1 as a potential therapeutic drug for AD.
Topics: Microglia; Amyloid beta-Peptides; Autophagy; Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Alzheimer Disease; Cells, Cultured; Mice
PubMed: 38939931
DOI: No ID Found -
Molecular Therapy : the Journal of the... Jun 2024Galactosyl-ceramidase (GALC) is a ubiquitous lysosomal enzyme crucial for the correct myelination of the mammalian nervous system during early postnatal development....
Deficiency of galactosylceramidase in adult oligodendrocytes worsens the neurological deficits and shortens the survival during chronic experimental allergic encephalomyelitis.
Galactosyl-ceramidase (GALC) is a ubiquitous lysosomal enzyme crucial for the correct myelination of the mammalian nervous system during early postnatal development. However, the physiological consequence of GALC deficiency in the adult brain remains unknown. In this study, we found that mice with conditional ablation of GALC activity in post-myelinating oligodendrocytes were lethally sensitized when challenged with chronic experimental allergic encephalomyelitis (EAE), in contrast to the non-lethal dysmyelination observed in GALC-ablated mice without the EAE challenge. Mechanistically, we found a strong inflammatory demyelination without remyelination and an impaired fusion of lysosomes and autophagosomes with accumulation of myelin debris following a TFEB-dependent increase in the lysosomal autophagosome flux. These results indicate that the physiological impact of GALC deficiency is highly influenced by the cell context (oligodendroglial vs global expression), the presence of inflammation, and the developmental time when it happens (pre-myelination vs post-myelination). We conclude that GALC expression in adult oligodendrocytes is crucial for the maintenance of adult central myelin and to reduce vulnerability to additional demyelinating insults.
PubMed: 38937968
DOI: 10.1016/j.ymthe.2024.06.035 -
Journal of Diabetes and Its... Jun 2024Hyperglycemia-induced endothelial cell injury is one of the main causes of diabetic vasculopathy. Fat mass and obesity-associated protein (FTO) was the first RNA...
N6-methyladenosine demethylase fat mass and obesity-associated protein suppresses hyperglycemia-induced endothelial cell injury by inhibiting reactive oxygen species formation via autophagy promotion.
INTRODUCTION
Hyperglycemia-induced endothelial cell injury is one of the main causes of diabetic vasculopathy. Fat mass and obesity-associated protein (FTO) was the first RNA N6-methyladenosine (m6A) demethylase identified; it participates in the pathogenesis of diabetes. However, the role of FTO in hyperglycemia-induced vascular endothelial cell injury remains unclear.
MATERIALS AND METHODS
The effects of FTO on cellular m6A, autophagy, oxidative stress, proliferation, and cytotoxicity were explored in human umbilical vein endothelial cells (HUVECs) treated with high glucose (33.3 mmol/mL) after overexpression or pharmacological inhibition of FTO. MeRIP-qPCR and RNA stability assays were used to explore the molecular mechanisms by which FTO regulates autophagy.
RESULTS
High glucose treatment increased m6A levels and reduced FTO protein expression in HUVECs. Wild-type overexpression of FTO markedly inhibited reactive oxygen species generation by promoting autophagy, increasing endothelial cell proliferation, and decreasing the cytotoxicity of high glucose concentrations. The pharmacological inhibition of FTO showed the opposite results. Mechanistically, we identified Unc-51-like kinase 1 (ULK1), a gene responsible for autophagosome formation, as a downstream target of FTO-mediated m6A modification. FTO overexpression demethylated ULK1 mRNA and inhibited its degradation in an m6A-YTHDF2-dependent manner, leading to autophagy activation.
CONCLUSIONS
Our study demonstrates the functional importance of FTO-mediated m6A modification in alleviating endothelial cell injury under high glucose conditions and indicates that FTO may be a novel therapeutic target for diabetic vascular complications.
PubMed: 38935979
DOI: 10.1016/j.jdiacomp.2024.108801 -
Autophagy Jun 2024A multitude of cellular responses to intrinsic and extrinsic signals converge on macroautophagy/autophagy, a conserved catabolic process that degrades cytoplasmic...
A multitude of cellular responses to intrinsic and extrinsic signals converge on macroautophagy/autophagy, a conserved catabolic process that degrades cytoplasmic constituents and organelles in the lysosome, particularly during starvation or stress. In addition to protein degradation, autophagy is deeply interconnected with unconventional protein secretion and polarized sorting at multiple levels within eukaryotic cells. Secretory autophagy (SA) has been recognized as a novel mechanism in which autophagosomes fuse with the plasma membrane and actively participate in the secretion of a series of cytosolic proteins, ranging from tissue remodeling factors to inflammatory molecules of the IL1 family. SA is partially controlled by the glucocorticoid-responsive, HSP90 co-chaperone FKBP5 and members of the SNARE proteins, SEC22B, SNAP23, SNAP29, STX3 and STX4. SA deregulation is implicated in several inflammatory pathologies, including cancer, cell death and degeneration. However, the key molecular mechanisms governing SA and its regulation remain elusive, as does its role in neuroinflammation and neurodegeneration. To further characterize SA and pinpoint its involvement in neuroinflammatory processes, we studied SA-relevant protein interaction networks in mouse brain, microglia and human postmortem brain tissue from control subjects and Alzheimer disease cases. We demonstrate that SA regulates neuroinflammation-mediated neurodegeneration via SKA2 and FKBP5 signaling.
PubMed: 38934263
DOI: 10.1080/15548627.2024.2373675 -
Viruses Jun 2024Infectious spleen and kidney necrosis virus (ISKNV) infections can induce the process of host cellular autophagy but have rarely been identified within the molecular...
Infectious spleen and kidney necrosis virus (ISKNV) infections can induce the process of host cellular autophagy but have rarely been identified within the molecular autophagy signaling pathway. In the present study, we demonstrated that ISKNV induces ROS-mediated oxidative stress signals for the induction of 5'AMP-activated protein kinase/mechanistic target of rapamycin kinase (AMPK/mTOR)-mediated autophagy and upregulation of host antioxidant enzymes in fish GF-1 cells. We also examined ISKNV-induced oxidative stress, finding that reactive oxidative species (ROS) increased by 1.5-fold and 2.5-fold from day 2 to day 3, respectively, as assessed by the HDCFDA assay for tracing hydrogen peroxide (HO), which was blocked by NAC treatment in fish GF-1 cells. Furthermore, ISKNV infection was shown to trigger oxidative stress/Nrf2 signaling from day 1 to day 3; this event was then correlated with the upregulation of antioxidant enzymes such as Cu/ZnSOD and MnSOD and was blocked by the antioxidant NAC. Using an MDC assay, TEM analysis and autophagy marker LC3-II/I ratio, we found that ROS stress can regulate autophagosome formation within the induction of autophagy, which was inhibited by NAC treatment in GF-1 cells. Through signal analysis, we found that AMPK/mTOR flux was modulated through inhibition of mTOR and activation of AMPK, indicating phosphorylation levels of mTOR Ser 2448 and AMPK Thr 172 from day 1 to day 3; however, this process was reversed by NAC treatment, which also caused a reduction in virus titer (TCID) of up to 1000 times by day 3 in GF-1 cells. Thus, ISKNV-induced oxidative stress signaling is blocked by antioxidant NAC, which can also either suppress mTOR/AMPK autophagic signals or reduce viral replication. These findings may provide the basis for the creation of DNA control and treatment strategies.
Topics: Oxidative Stress; Autophagy; Virus Replication; Animals; TOR Serine-Threonine Kinases; Signal Transduction; Cell Line; AMP-Activated Protein Kinases; Antioxidants; Reactive Oxygen Species; NF-E2-Related Factor 2
PubMed: 38932206
DOI: 10.3390/v16060914