Autophagy Substrate Research Articles

Role of autophagy in resistance to ivermectin in Haemonchus contortus

Haemonchus contortus is a highly pathogenic gastrointestinal nematode that parasitizes the abomasum of cattle, sheep, and other ruminants. Long-term use of large quantities of ivermectin (IVM) to control H. contortus has resulted in the development of drug resistance. However, the mechanism of IVM resistance in H. contortus remains incompletely understood. Autophagy is involved in regulating drug resistance in some parasites. Previous omics sequencing of differentially expressed genes in drug-resistant strains of H. contortus revealed substantial enrichment of autophagy-related pathway. Therefore, autophagy was used as the entry point in this study to investigate its role in IVM resistance in H. contortus. Larval migration inhibition test, RT-qPCR, and transmission electron microscopy of IVM-susceptible and -resistant strains were performed. Results showed that the H. contortus-resistant strain had higher autophagy levels than the susceptible strain. After IVM treatment, the susceptible strain exhibited significant upregulation of the autophagy-related genes lgg-1, lgg-2, bec-1, lc3, and atg-18 and significant downregulation of the autophagy substrate sqst-1, along with an increased number of autolysosomes. Additionally, the autophagy inhibitor 3-MA reduced the resistance of the IVM-resistant H. contortus strain toward IVM after inhibiting autophagy, and the autophagy inducer urolithin A reduced the susceptibility of the IVM-susceptible H. contortus strain of IVM after activating its autophagy. These results demonstrate that IVM promotes autophagy in H. contortus and that autophagy is involved in regulating drug resistance in H. contortus. This study fills the knowledge gap regarding the role of autophagy in H. contortus drug resistance and provides a novel perspective on the study of drug resistance mechanisms in H. contortus.

New Toolset of Reporters Reveals That Glycogen Granules Are Neutral Substrates of Bulk Autophagy in Komagataella phaffii.

Glycogen, a branched polysaccharide organized into glycogen granules (GGs), is delivered from the cytoplasm to the lysosomes of hepatocytes by STBD1-driven selective autophagy (glycophagy). Recently, we developed Komagataella phaffii yeast as a simple model of GG autophagy and found that it proceeds non-selectively under nitrogen starvation conditions. However, another group, using Saccharomyces cerevisiae as a model, found that glycogen is a non-preferred cargo of nitrogen starvation-induced bulk autophagy. To clarify cargo characteristics of K. phaffii GGs, we used the same glycogen synthase-based reporter (Gsy1-GFP) of GG autophagy in K. phaffii as was used in S. cerevisiae. The K. phaffii Gsy1-GFP marked the GGs and reported on their autophagic degradation during nitrogen starvation, as expected. However, unlike in S. cerevisiae, glycogen synthase-marked GGs were delivered to the vacuole and degraded there with the same efficiency as a cytosolic glycogen synthase in glycogen-deficient cells, suggesting that glycogen is a neutral cargo of bulk autophagy in K. phaffii. We verified our findings with a new set of reporters based on the glycogen-binding CBM20 domain of human STBD1. The GFP-CBM20 and mCherry-CBM20 fusion proteins tagged GGs, reported about the autophagy of GGs, and confirmed that GGs in K. phaffii are neither preferred nor non-preferred substrates of bulk autophagy. They are its neutral substrates.

Effects of wheat-grain moxibustion on autophagy and endoplasmic reticulum stress in rats with cervical spondylotic radiculopathy

To observe the effects of wheat-grain moxibustion on autophagy and endoplasmic reticulum stress (ERS) in the spinal cord and nerve root tissues of rats with cervical spondylotic radiculopathy (CSR), and to explore the potential mechanisms by which wheat-grain moxibustion alleviates neuropathic pain in CSR. Forty-eight SPF-grade SD rats were randomly divided into a sham operation group, a model group, a wheat-grain moxibustion group, and a wheat-grain moxibustion + 3-methyladenine (3MA) group, with 12 rats in each group. The CSR model was established in the model group, the wheat-grain moxibustion group, and the wheat-grain moxibustion + 3MA group using the spinal canal insertion method. From the third day after successful modeling, the wheat-grain moxibustion group received wheat-grain moxibustion at "Dazhui" (GV 14), once daily, six cones each session. The wheat-grain moxibustion + 3MA group received intraperitoneal injection of 3MA (2.5 mg/kg), followed by the same wheat-grain moxibustion intervention as the wheat-grain moxibustion group. Interventions were performed once daily for seven consecutive days. The gait disturbance scores and peripheral nerve mechanical pain thresholds were observed before and after the intervention. Western blot was used to detect the expression of ERS apoptosis factors C/EBP-homologous protein (CHOP) and Caspase-12, as well as autophagy substrate P62 in spinal cord and nerve root tissues. Transmission electron microscopy was used to observe autophagosomes and cellular ultrastructure in spinal cord and nerve root tissues. After modeling, compared with the sham operation group, gait disturbance scores were increased (P<0.05) and peripheral nerve mechanical pain thresholds were decreased (P<0.05) in the model group, the wheat-grain moxibustion group, and the wheat-grain moxibustion + 3MA group. After intervention, compared with the sham operation group, gait disturbance scores were increased (P<0.05) and peripheral nerve mechanical pain thresholds were decreased (P<0.05) in the model group; compared with the model group, gait disturbance score was decreased (P<0.05) and peripheral nerve mechanical pain threshold was increased (P<0.05) in the wheat-grain moxibustion and the wheat-grain moxibustion + 3MA group; compared with the wheat-grain moxibustion + 3MA group, gait disturbance score was decreased (P<0.05) and peripheral nerve mechanical pain threshold was increased (P<0.05) in the wheat-grain moxibustion group. Compared with the sham operation group, the expression of CHOP and Caspase-12 proteins in spinal cord and nerve root tissues was increased in the model group (P<0.05); compared with the model group and the wheat-grain moxibustion + 3MA group, the expression of CHOP, Caspase-12, and P62 proteins in spinal cord and nerve root tissues was decreased in the wheat-grain moxibustion group (P<0.05). Compared with the model group and the wheat-grain moxibustion + 3MA group, the number of autophagosomes in spinal cord and nerve root tissues was increased in the wheat-grain moxibustion group, and the cellular ultrastructure was clear and intact, similar to the sham operation group. Wheat-grain moxibustion at "Dazhui" (GV 14) could effectively alleviate neuropathic pain in CSR model rats. The analgesic mechanism may be related to promoting autophagy, inhibiting ERS, reducing ERS-mediated apoptosis, and repairing damaged nerves.

Functional Relationships between L1CAM, LC3, ATG12, and Aβ.

Abnormal protein accumulations in the brain are linked to aging and the pathogenesis of dementia of various types, including Alzheimer's disease. These accumulations can be reduced by cell indigenous mechanisms. Among these is autophagy, whereby proteins are transferred to lysosomes for degradation. Autophagic dysfunction hampers the elimination of pathogenic protein aggregations that contribute to cell death. We had observed that the adhesion molecule L1 interacts with microtubule-associated protein 1 light-chain 3 (LC3), which is needed for autophagy substrate selection. L1 increases cell survival in an LC3-dependent manner via its extracellular LC3 interacting region (LIR). L1 also interacts with Aβ and reduces the Aβ plaque load in an AD model mouse. Based on these results, we investigated whether L1 could contribute to autophagy of aggregated Aβ and its clearance. We here show that L1 interacts with autophagy-related protein 12 (ATG12) via its LIR domain, whereas interaction with ubiquitin-binding protein p62/SQSTM1 does not depend on LIR. Aβ, bound to L1, is carried to the autophagosome leading to Aβ elimination. Showing that the mitophagy-related L1-70 fragment is ubiquitinated, we expect that the p62/SQSTM1 pathway also contributes to Aβ elimination. We propose that enhancing L1 functions may contribute to therapy in humans.

Autophagy, aging, and age-related neurodegeneration.

Autophagy is a conserved mechanism that degrades damaged or superfluous cellular contents and enables nutrient recycling under starvation conditions. Many neurodegeneration-associated proteins are autophagy substrates, and autophagy upregulation ameliorates disease in many animal models of neurodegeneration by enhancing the clearance of toxic proteins, proinflammatory molecules, and dysfunctional organelles. Autophagy inhibition also induces neuronal and glial senescence, a phenomenon that occurs with increasing age in non-diseased brains as well as in response to neurodegeneration-associated stresses. However, aging and many neurodegeneration-associated proteins and mutations impair autophagy. This creates a potentially detrimental feedback loop whereby the accumulation of these disease-associated proteins impairs their autophagic clearance, facilitating their further accumulation and aggregation. Thus, understanding how autophagy interacts with aging, senescence, and neurodegenerative diseases in a temporal, cellular, and genetic context is important for the future clinical application of autophagy-modulating therapies in aging and neurodegeneration.

Protective Proteolysis in Huntington's Disease: Unraveling the Role of Post-Translational Myristoylation of Huntingtin in Autophagy.

Huntington's disease (HD) is a devastating neurodegenerative disorder characterized by impaired motor function and cognitive decline, ultimately leading to death. HD is caused by a polyglutamine expansion in the N-terminal region of the huntingtin (HTT) protein, which is linked to decreased HTT turnover, increased HTT proteolysis, increased HTT aggregation, and subsequent neuronal death. In this review, we explore the mechanism of the protective effect of blocking HTT proteolysis at D586, which has been shown to rescue the HD phenotype in HD mouse models. Until recently, the mechanism remained unclear. Herein, we discuss how blocking HTT proteolysis at D586 promotes HTT turnover by correcting autophagy, and making HTT a better autophagy substrate, through post-translational myristoylation of HTT at G553.

Metformin Alleviates Inflammation and Induces Mitophagy in Human Retinal Pigment Epithelium Cells Suffering from Mitochondrial Damage.

Mitochondrial malfunction, excessive production of reactive oxygen species (ROS), deficient autophagy/mitophagy, and chronic inflammation are hallmarks of age-related macular degeneration (AMD). Metformin has been shown to activate mitophagy, alleviate inflammation, and lower the odds of developing AMD. Here, we explored the ability of metformin to activate mitophagy and alleviate inflammation in retinal pigment epithelium (RPE) cells. Human ARPE-19 cells were pre-treated with metformin for 1 h prior to exposure to antimycin A (10 µM), which induced mitochondrial damage. Cell viability, ROS production, and inflammatory cytokine production were measured, while autophagy/mitophagy proteins were studied using Western blotting and immunocytochemistry. Metformin pre-treatment reduced the levels of proinflammatory cytokines IL-6 and IL-8 to 42% and 65% compared to ARPE-19 cells exposed to antimycin A alone. Metformin reduced the accumulation of the autophagy substrate SQSTM1/p62 (43.9%) and the levels of LC3 I and II (51.6% and 48.6%, respectively) after antimycin A exposure. Metformin also increased the colocalization of LC3 with TOM20 1.5-fold, suggesting active mitophagy. Antimycin A exposure increased the production of mitochondrial ROS (226%), which was reduced by the metformin pre-treatment (84.5%). Collectively, metformin showed anti-inflammatory and antioxidative potential with mitophagy induction in human RPE cells suffering from mitochondrial damage.

Glutamine deprivation in glioblastoma stem cells triggers autophagic SIRT3 degradation to epigenetically restrict CD133 expression and stemness.

Glioblastoma multiforme (GBM) is a highly malignant brain tumor, and glioblastoma stem cells (GSCs) are the primary cause of GBM heterogeneity, invasiveness, and resistance to therapy. Sirtuin 3 (SIRT3) is mainly localized in the mitochondrial matrix and plays an important role in maintaining GSC stemness through cooperative interaction with the chaperone protein tumor necrosis factor receptor-associated protein 1 (TRAP1) to modulate mitochondrial respiration and oxidative stress. The present study aimed to further elucidate the specific mechanisms by which SIRT3 influences GSC stemness, including whether SIRT3 serves as an autophagy substrate and the mechanism of SIRT3 degradation. We first found that SIRT3 is enriched in CD133+ GSCs. Further experiments revealed that in addition to promoting mitochondrial respiration and reducing oxidative stress, SIRT3 maintains GSC stemness by epigenetically regulating CD133 expression via succinate. More importantly, we found that SIRT3 is degraded through the autophagy-lysosome pathway during GSC differentiation into GBM bulk tumor cells. GSCs are highly dependent on glutamine for survival, and in these cells, we found that glutamine deprivation triggers autophagic SIRT3 degradation to restrict CD133 expression, thereby disrupting the stemness of GSCs. Together our results reveal a novel mechanism by which SIRT3 regulates GSC stemness. We propose that glutamine restriction to trigger autophagic SIRT3 degradation offers a strategy to eliminate GSCs, which combined with other treatment methods may overcome GBM resistance to therapy as well as relapse.

Pseudoginsenoside-F11 reduces cognitive impairment and white matter injury in vascular dementia by alleviating autophagy-lysosomal pathway deficiency

BackgroundVascular dementia (VaD) resulting from chronic cerebral hypoperfusion (CCH) induces cognitive impairment and white matter injury (WMI). We previously found that CCH induces dysfunction of the autophagy-lysosomal pathway (ALP) in white matter (WM) of rats. Enhancing oligodendrocyte autophagy to counteract ALP deficiency is beneficial for cognitive recovery. Pseudogenoside-F11 (PF11), a saponin extracted from Panax quinquefolium l., provides neuroprotective benefits in many animal models of cerebral ischemia and dementia. PurposeTo investigate how PF11 affects cognitive deterioration in rats with VaD induced by two vessel occlusion (2VO), and to determine if PF11 regulates ALP dysfunction in WM. MethodsCCH-related VaD was induced in rats using the 2VO method. PF11 (6, 12, 24 mg/kg, intragastric administration) was given continuously for 4 weeks postoperatively. Behavioral tests related to cognitive function were performed on the 28th day following 2VO. Transmission electron microscopy, immunofluorescence, western blotting and Luxol fast blue staining were used to assess the WMI and the mechanism of action of PF11 in 2VO-induced VaD. ResultsPF11 (12 mg/kg) ameliorated 2VO-induced cognitive impairment. PF11 also alleviated WMI on the 28th day following 2VO, as characterized by reduction of neuronal axonal demyelination and axonal loss. Furthermore, PF11 prevented mature oligodendrocytes death by attenuating ALP deficiency in WM on the 14th day following 2VO, as manifested by enhancement of mechanistic target of rapamycin-mediated autophagy and lysosomal function, thereby reducing the aberrant accumulation of autophagy substrates and increasing the level of autophagosomes in WM. In addition, PF11 also prevented microglia and astrocytes from activating in WM on the 28th day following 2VO. ConclusionPF11 significantly ameliorates cognitive impairment and WMI, and the mechanism is at least partly related to lessening ALP dysfunction in WM by enhancing autophagy and reducing lysosomal defects in oligodendrocytes.

Follicular fluid HD-sevs-mir-128–3p is a key molecule in regulating bovine granulosa cells autophagy

Follicular fluid (FF) is rich in extracellular vesicles (EVs). EVs carries a variety of miRNA involved in regulating follicular development, the function of cells in follicles, primordial follicular formation, follicular recruitment and selection, follicular atresia, oocyte communication, granulosa cells (GCs) function and luteinization and other biological processes of follicular development. Previous studies in our laboratory have shown that bovine follicular fluid (bFF) high density-small extracellular vesicles (HD-sEVs)-miRNA was enriched in autophagy-related pathways. However, the mechanism of bFF EVs carrying miRNA regulating GCs autophagy is not clear. Thus, this study carried out a series of studies on the previous HD-sEVs sequencing data and miR-128–3p contained in bFF HD-sEVs. A total of 38 differentially expressed genes were detected by RNA-Seq after overexpression of miR-128–3p in bovine GCs (bGCs). Through cell transfection, Western blot (WB) and Immunofluorescence (IF), it was proved that overexpression of miR-128–3p could promote the expression of LC3 (microtubule-associated protein I light chain 3), inhibit p62, promote the number of autophagosome, promote the formation of autophagy lysosome and autophagy flow, and activate bGCs autophagy. MiR-128–3p inhibitor significantly inhibited the expression of LC3 and monodansylcadaverine (MDC) in bGCs, and promoted the expression of autophagy substrate p62, indicating that HD-sEVs-miR-128–3p could activate bGCs autophagy. In addition, through double luciferase assay, bioinformatics analysis, WB and RT-qPCR, it was concluded that bFF HD-sEVs-miR-128–3p could target TFEB (transcription factor EB) and FoxO4 (Forkhead box O4) and activate GCs autophagy.

Taenia solium cysticerci's extracellular vesicles Attenuate the AKT/mTORC1 pathway for Alleviating DSS-induced colitis in a murine model.

The excretory-secretory proteome plays a pivotal role in both intercellular communication during disease progression and immune escape mechanisms of various pathogens including cestode parasites like Taenia solium. The cysticerci of T. solium causes infection in the central nervous system known as neurocysticercosis (NCC), which affects a significant population in developing countries. Extracellular vesicles (EVs) are 30-150-nm-sized particles and constitute a significant part of the secretome. However, the role of EV in NCC pathogenesis remains undetermined. Here, for the first time, we report that EV from T. solium larvae is abundant in metabolites that can negatively regulate PI3K/AKT pathway, efficiently internalized by macrophages to induce AKT and mTOR degradation through auto-lysosomal route with a prominent increase in the ubiquitination of both proteins. This results in less ROS production and diminished bacterial killing capability among EV-treated macrophages. Due to this, both macro-autophagy and caspase-linked apoptosis are upregulated, with a reduction of the autophagy substrate sequestome 1. In summary, we report that T. solium EV from viable cysts attenuates the AKT-mTOR pathway thereby promoting apoptosis in macrophages, and this may exert immunosuppression during an early viable stage of the parasite in NCC, which is primarily asymptomatic. Further investigation on EV-mediated immune suppression revealed that the EV can protect the mice from DSS-induced colitis and improve colon architecture. These findings shed light on the previously unknown role of T. solium EV and the therapeutic role of their immune suppression potential.

Caki-1 Spheroids as a 3D Model for Studying Free Fatty Acid-Induced Proximal Tubule Lipotoxicity

Three-dimensional (3D) multicellular spheroid shows a biological complexity resembling native tissue in comparison to conventional monolayer cultures, making it a better model system to assess drug effcacy and cytotoxicity. The main aim of this study was to examine the usefulness of Caki-1, a human proximal tubule (PT) representative cell line, as a 3D model system for studying free fatty acid-induced PT lipotoxicity. Caki-1 spheroids were generated and maintained on ultra-low attachment plates and characterized regarding time-dependent changes in morphology and functionality. In optimal 3D culture conditions, Caki-1 cells formed well-defined large compact 3D spheroids with uniform morphology, good circularity, and increased diameter from days 2-10. There was no change when the spheroids were incubated with lipid-free bovine serum albumin (BSA, 0.5%) from day 6 to 10. Chronic exposure to palmitate (300 μM) resulted in dispersed and flattened spheroid morphology, with a larger number of dead cells in the peripheral layers and decreased spheroid core. Moreover, palmitate-treated spheroids showed a significant increase in caspase-3 activity at the external layers of the spheroids, suggesting that the detached cells underwent apoptosis. Simultaneous addition of oleate (200 μM) prevents palmitate-induced spheroid disintegration and cell death in Caki-1 3D culture. Mechanistically, palmitate triggered endoplasmic reticulum (ER) stress and autophagy dysfunction, as evidenced by significantly increased protein levels of ER stress markers AFT4 and CHOP, and autophagy substrate p62. Oleate upregulated adipose differentiation-related protein (ADRP, a lipid droplet-associated protein), and promoted lipid droplet formation in palmitate-treated Caki-1 cells. These results indicate that Caki-1 3D spheroids are a simple and reproducible in vitro system for lipotoxicity study. It can potentially be used for evaluating human renal proximal tubular toxicity and drug screening. NIH/NIGMS R16GM149499, NIH TL1DK136047. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Perinatal bisphenol S exposure exacerbates the oxidative burden and apoptosis in neonatal ovaries by suppressing the mTOR/autophagy axis

Bisphenol S (BPS) is an emerging environmental endocrine disruptor capable of crossing the placental barrier, resulting in widespread exposure to pregnant women due to its extensive usage. However, the impact of perinatal maternal exposure to BPS on reproductive health in offspring and the underlying molecular mechanism remain underexplored. In this study, gestational ICR mice were provided with drinking water containing 3.33 mg/L BPS to mimic possible human exposure in some countries. Results demonstrated that BPS accelerated the breakdown of germ-cell cysts and the assembly of primordial follicles in neonates, leading to oocyte over-loss. Furthermore, the expression levels of folliculogenesis-related genes (Kit, Nobox, Gdf9, Sohlh2, Kitl, Bmp15, Lhx8, Figla, and Tgfb1) decreased, thus compromising oocyte quality and disrupting early folliculogenesis dynamics. BPS also disrupted other aspects of offspring reproduction, including advancing puberty onset, disrupting the estrus cycle, and impairing fertility. Further investigation found that BPS exposure inhibited the activities and expression levels of antioxidant-related enzymes in neonatal ovaries, leading to the substantial accumulation of MDA and ROS. The increased oxidative burden exacerbated the intracellular apoptotic signaling, manifested by increased expression levels of pro-apoptotic markers (Bax, Caspase 3, and Caspase 9) and decreased expression levels of anti-apoptotic marker (Bcl2). Concurrently, BPS inhibited autophagy by increasing p-mTOR/mTOR and decreasing p-ULK1/ULK1, subsequently down-regulating autophagy flux-related biomarkers (LC3b/LC3a and Beclin-1) and impeding the degradation of autophagy substrate p62. However, the imbalanced crosstalk between autophagy, apoptosis and oxidative stress homeostasis was restored after rapamycin treatment. Collectively, the findings demonstrated that BPS exposure induced reproductive disorders in offspring by perturbing the mTOR/autophagy axis, and such autophagic dysfunction exacerbated redox imbalance and promoted excessive apoptosis. These results provide novel mechanistic insights into the role of autophagy in mitigating BPS-induced intergenerational reproductive dysfunction.

Combined light and electron microscopy (CLEM) to quantify methamphetamine-induced alpha-synuclein-related pathology

Methamphetamine (METH) produces a cytopathology, which is rather specific within catecholamine neurons both in vitro and ex vivo, in animal models and chronic METH abusers. This led some authors to postulate a sort of parallelism between METH cytopathology and cell damage in Parkinson’s disease (PD). In fact, METH increases and aggregates alpha-syn proto-fibrils along with producing spreading of alpha-syn. Although alpha-syn is considered to be the major component of aggregates and inclusions developing within diseased catecholamine neurons including classic Lewy body (LB), at present, no study provided a quantitative assessment of this protein in situ, neither following METH nor in LB occurring in PD. Similarly, no study addressed the quantitative comparison between occurrence of alpha-syn and other key proteins and no investigation measured the protein compared with non-protein structure within catecholamine cytopathology. Therefore, the present study addresses these issues using an oversimplified model consisting of a catecholamine cell line where the novel approach of combined light and electron microscopy (CLEM) was used measuring the amount of alpha-syn, which is lower compared with p62 or poly-ubiquitin within pathological cell domains. The scenario provided by electron microscopy reveals unexpected findings, which are similar to those recently described in the pathology of PD featuring packing of autophagosome-like vesicles and key proteins shuttling autophagy substrates. Remarkably, small seed-like areas, densely packed with p62 molecules attached to poly-ubiquitin within wide vesicular domains occurred. The present data shed new light about quantitative morphometry of catecholamine cell damage in PD and within the addicted brain.

Mitophagy as a potential mediator for the anti‐inflammatory effects of metformin in human retinal pigment epithelium cells

Aims/Purpose: Mitochondrial malfunction and subsequent excessive production of reactive oxygen species (ROS), deficient autophagy and chronic inflammation are associated with many age‐related diseases, including age‐related macular degeneration. In this study, we investigated metformin and its ability to activate mitophagy and alleviate inflammation in retinal pigment epithelium (RPE) cells upon induced mitochondrial damage.Methods: Experiments were conducted using the ARPE‐19 cell line. The cells were treated with 15 mM metformin (Met) for 1 h before adding 10 μM mitochondrial complex 3 inhibitor Antimycin A (Aa) for additional 2–24 h. The levels of proinflammatory cytokines IL‐6 and IL‐8 were measured using the enzyme‐linked immunosorbent assay (ELISA). The levels of the autophagy substrate SQSTM1/p62 and the autophagy marker LC3 were studied using the Western blot method. To further analyse mitophagy, LC3 and TOM20 colocalization was detected using immunofluorescence. Mitochondrial ROS production was assessed using MitoSOX CMXRos staining.Results: The production of proinflammatory cytokines IL‐6 and IL‐8 were increased by Aa exposure. Conversely, Met treatment significantly reduced the levels of IL‐6 and IL‐8. The autophagy substrate SQSTM1/p62 was accumulated in the cells after Aa treatment implying a blockage in the autophagic flux. Met treatment induced the clearance of SQSTM1/p62 and LC3 I and II at 6‐h time point. At 24‐h time point, Met treatment increased the amount of LC3 puncta/cell and colocalization of LC3 and TOM20 suggesting enhanced mitophagy in cells suffering mitochondrial damage induced by Aa. Aa treatment led to increased production of mitochondrial ROS which was decreased by Met treatment.Conclusions: Metformin has anti‐inflammatory and antioxidant properties in human RPE cells upon antimycin A exposure. Studies on autophagy markers suggest enhanced activation of autophagy, and mitophagy, upon metformin exposure, which could explain the detected positive effects on inflammation and oxidative stress.

Selective Autophagy Receptor NBR1 Retards Nucleus Pulposus Cell Senescence by Directing the Clearance of SRBD1.

Intervertebral disc degeneration (IDD) is a prevalent degenerative disorder that closely linked to aging. Numerous studies have indicated the crucial involvement of autophagy in the development of IDD. However, the non-selective nature of autophagy substrates poses great limitations on the application of autophagy-related medications. This study aims to enhance our comprehension of autophagy in the development of IDD and investigate a novel therapeutic approach from the perspective of selective autophagy receptor NBR1. Proteomics and immunoprecipitation and mass spectrometry analysis, combined with in vivo and in vitro experimental verification were performed. NBR1 is found to be reduced in IDD, and NBR1 retards cellular senescence and senescence-associated secretory phenotype (SASP) of nucleus pulposus cells (NPCs), primarily through its autophagy-dependent function. Mechanistically, NBR1 knockdown leads to the accumulation of S1 RNA-binding domain-containing protein 1 (SRBD1), which triggers cellular senescence via AKT1/p53 and RB/p16 pathways, and promotes SASP via NF-κβ pathway in NPCs. Our findings reveal the function and mechanism of selective autophagy receptor NBR1 in regulating NPCs senescence and degeneration. Targeting NBR1 to facilitate the clearance of detrimental substances holds the potential to provide novel insights for IDD treatment.

Knockdown of TXNIP alleviates gestational diabetes mellitus by activating autophagy to regulate cell proliferation and apoptosis in high glucose-treated trophoblasts

Dysregulated thioredoxin-interacting protein (TXNIP) has been observed in women with gestational diabetes mellitus (GDM), but the specific role of TXNIP in GDM and the underlying mechanism remain unclear. HTR-8/SVneo cells were treated with high glucose to mimic the injured trophoblasts of GDM. In vitro, TXNIP knockdown was performed by siRNA. RTqPCR was performed to determine the expression of the corresponding genes. Cell proliferation and apoptosis were measured using CCK-8, EdU and Annexin V/PI assays. The autophagosome number was assessed using transmission electron microscopy. The expression of the autophagy substrate sequestosome 1 (P62) was evaluated by immunofluorescence. Autophagy-related proteins, including P62, light chain 3 (LC3)-I, and LC3-II, were analysed by Western blotting. HTR-8/Svneo cells treated with high glucose demonstrated reduced proliferation, increased apoptosis, decreased autophagosome formation and overall decreased autophagy. However, knockdown of TXNIP reversed the effects of HG on HTR-8/Svneo cells. However, the effect of TXNIP knockdown on HG-treated HTR-8/Svneo cells was inhibited by 3-methyladenine (3-MA) (widely used as an inhibitor of autophagy). We concluded that knockdown of TXNIP has the potential to enhance the activity of high glucose-treated human trophoblasts through autophagic activation, thereby improving pregnancy outcomes in patients with GDM.

Enhancer-mediated FOXO3 expression promotes MSC adipogenic differentiation by activating autophagy

BackgroundMesenchymal stem cells (MSCs) are pluripotent stem cells capable of differentiating into osteocytes, adipocytes and chondrocytes. However, in osteoporosis, the balance of differentiation is tipped toward adipogenesis and the key mechanism is controversial. Researches have shown that, as upstream regulatory elements of gene expression, enhancers ar involved in the expression of identity genes. In this study, we identified enhancers-mediated gene FOXO3 promoting MSC adipogenic differentiation by activating autophagy. MethodsWe integrated data of RNA sequencing (RNA-seq), chromatin immunoprecipitation sequencing (ChIP-seq) and ATAC-sequencing (ATAC-seq) to find the identity gene FOXO3. The expression of FOXO3 protein, adipogenic transcription factors and the substrate of autophagy were measured by western blotting. The Oil Red O (ORO) staining was used to visualize the adipogenesis of MSCs. Immunohistochemistry was used to visualize the FOXO3 expression in adipocytes in bone marrow. Immunofluorescence was used to detect the expression of PPARγ and LC3B. ResultsDuring adipogenesis, enhancers redistribute to genes associated with adipogenic differentiation, among which we identified the pivotal identity gene FOXO3. FOXO3 could promote the expression of the adipogenic transcription factors PPARγ, CEBPα, and CEBPβ during adipogenic differentiation, while PPARγ, CEBPα, and CEBPβ could in turn bind to FOXO3 and continue to promote FOXO3 expression to form a positive feedback loop. Consistently elevated FOXO3 expression promotes autophagy by activating the PI3K-AKT pathway which mediates adipogenic differentiation. ConclusionsPivotal identity gene FOXO3 promotes autophagy by activating PI3K-AKT pathway, which provokes adipogenic differentiation of MSCs. Enhancer-regulated adipogenic identity gene FOXO3 could be an attractive treatment for osteoporosis.

CKLF induces microglial activation via triggering defective mitophagy and mitochondrial dysfunction

ABSTRACT Although microglial activation is induced by an increase in chemokines, the role of mitophagy in this process remains unclear. This study aimed to elucidate the role of microglial mitophagy in CKLF/CKLF1 (chemokine-like factor 1)-induced microglial activation and neuroinflammation, as well as the underlying molecular mechanisms following CKLF treatment. This study determined that CKLF, an inducible chemokine in the brain, leads to an increase in mitophagy markers, such as DNM1L, PINK1 (PTEN induced putative kinase 1), PRKN, and OPTN, along with a simultaneous increase in autophagosome formation, as evidenced by elevated levels of BECN1 and MAP1LC3B (microtubule-associated protein 1 light chain 3 beta)-II. However, SQSTM1, a substrate of autophagy, was also accumulated by CKLF treatment, suggesting that mitophagy flux was reduced and mitophagosomes accumulated. These findings were confirmed by transmission electron microscopy and confocal microscopy. The defective mitophagy observed in our study was caused by impaired lysosomal function, including mitophagosome-lysosome fusion, lysosome generation, and acidification, resulting in the accumulation of damaged mitochondria in microglial cells. Further analysis revealed that pharmacological blocking or gene-silencing of mitophagy inhibited CKLF-mediated microglial activation, as evidenced by the expression of the microglial marker AIF1 (allograft inflammatory factor 1) and the mRNA of proinflammatory cytokines (Tnf and Il6). Ultimately, defective mitophagy induced by CKLF results in microglial activation, as observed in the brains of adult mice. In summary, CKLF induces defective mitophagy, microglial activation, and inflammation, providing a potential approach for treating neuroinflammatory diseases. Abbreviation: 3-MA: 3-methyladenine; AIF1: allograft inflammatory factor 1; ANOVA: analysis of variance; BAF: bafilomycin A1; BSA: bovine serum albumin; CCCP: carbonyl cyanide m-chlorophenyl hydrazone; cGAMP: cyclic GMP-AMP; CGAS: cyclic GMP-AMP synthase; CKLF/CKLF1: chemokine-like factor 1; CNS: central nervous system; DMEM: Dulbecco’s Modified Eagle Medium; DNM1L: dynamin 1 like; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescence protein; IRF3: interferon regulatory factor 3; IgG: immunoglobulin G; LAMP1: lysosomal-associated membrane protein 1; LAPTM4A: lysosomal-associated protein transmembrane 4A; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; Mdivi-1: mitochondrial division inhibitor 1; mRFP: monomeric red fluorescent protein; mtDNA: mitochondrial DNA; MTORC1: mechanistic target of rapamycin kinase complex 1; OPTN: optineurin; PBS: phosphate-buffered saline; PCR: polymerase chain reaction; PINK1: PTEN induced putative kinase 1; PLL: poly-L-lysine; PRKN: parkin RBR E3 ubiquitin protein ligase; qPCR: quantitative polymerase chain reaction; ROS: reactive oxygen species; SQSTM1: sequestosome 1; TBK1: TANK-binding kinase 1; TFEB: transcription factor EB; VDAC: voltage-dependent anion channel

A Golgi‐Targeted Platinum Complex Plays a Dual Role in Autophagy Regulation for Highly Efficient Cancer Therapy

AbstractRegulating autophagy to control the homeostatic recycling process of cancer cells is a promising anticancer strategy. Golgi apparatus is a substrate of autophagy but the Golgi‐autophagy (Golgiphagy) mediated antitumor pathway is rarely reported. Herein, we have developed a novel Golgi‐targeted platinum (II) complex Pt3, which is ca. 20 times more cytotoxic to lung carcinoma than cisplatin and can completely eliminate tumors after intratumoral administration in vivo. Its nano‐encapsulated system for tail vein administration also features a good anti‐tumor effect. Mechanism studies indicate that Pt3 induces substantial Golgi stress, indicated by the fragmentation of Golgi structure, down‐regulation of Golgi proteins (GM130, GRASP65/55), loss of Golgi‐dependent transport and glycosylation. This triggers Golgiphagy but blocks the subsequent fusion of autophagosomes with lysosomes, that is a dual role in autophagy regulation, resulting in loss of proteostasis and apoptotic cell death. As far as we know, Pt3 is the first Golgi‐targeted Pt complex that can trigger Golgi stress‐mediated dual‐regulation of autophagic flux and autophagy‐apoptosis crosstalk for highly efficient cancer therapy.