Monitoring Autophagy Flux and Activity: Principles and Applications

Zinc oxide nanoparticles induces cell death and consequently leading to incomplete neural tube closure through oxidative stress during embryogenesis

The implementation of Zinc oxide nanoparticles (ZnO NPs) raises concerns regarding their potential toxic effects on human health. Although more and more researches have confirmed the toxic effects of ZnO NPs, limited attention has been given to their impact on the early embryonic nervous system. This study aimed to explore the impact of exposure to ZnO NPs on early neurogenesis and explore its underlying mechanisms. We conducted experiments here to confirm the hypothesis that exposure to ZnO NPs causes neural tube defects in early embryonic development. We first used mouse and chicken embryos to confirm that ZnO NPs and the Zn2+ they release are able to penetrate the placental barrier, influence fetal growth and result in incomplete neural tube closure. Using SH-SY5Y cells, we determined that ZnO NPs-induced incomplete neural tube closure was caused by activation of various cell death modes, including ferroptosis, apoptosis and autophagy. Moreover, dissolved Zn2+ played a role in triggering widespread cell death. ZnO NPs were accumulated within mitochondria after entering cells, damaging mitochondrial function and resulting in the over production of reactive oxygen species, ultimately inducing cellular oxidative stress. The N-acetylcysteine (NAC) exhibits significant efficacy in mitigating cellular oxidative stress, thereby alleviating the cytotoxicity and neurotoxicity brought about by ZnO NPs. These findings indicated that the exposure of ZnO NPs in early embryonic development can induce cell death through oxidative stress, resulting in a reduced number of cells involved in early neural tube closure and ultimately resulting in incomplete neural tube closure during embryo development. The findings of this study could raise public awareness regarding the potential risks associated with the exposure and use of ZnO NPs in early pregnancy.

Synthesis of metformin-derived fluorescent quantum dots: uptake, cytotoxicity, and inhibition in human breast cancer cells through autophagy pathway

BACKGROUND

Breast cancer remains a challenge for physicians. Metformin, an antidiabetic drug, show promising anticancer properties against cancers. An emerging quantum dot (QD) material improves therapeutic agents' anticancer and imaging properties. QD are nano-sized particles with extreme application in nanotechnology captured by cells and accumulated inside cells, suggesting bioimaging and effective anticancer outcomes. In this study, a simple one-pot hydrothermal method was used to synthesize fluorescent metformin-derived carbon dots (M-CDs) and then investigated the cytotoxic effects and imaging features on two human breast cancer cell lines including, MCF-7 and MDA-MB-231 cells.

RESULTS

Results showed that M-CDs profoundly decreased the viability of both cancer cells. IC50 values showed that M-CDs were more cytotoxic than metformin either 24-48 h post-treatment. Cancer cells uptake M-CDs successfully, which causes morphological changes in cells and increased levels of intracellular ROS. The number of Oil Red O-positive cells and the expression of caspase-3 protein were increased in M-CDs treated cells. Authophagic factors including, AMPK, mTOR, and P62 were down-regulated, while p-AMPK, Becline-1, LC3 I, and LC3 II were up-regulated in M-CDs treated cells. Finally, M-CDs caused a decrease in the wound healing rate of cells.

CONCLUSIONS

For the first, M-CDs were synthesized by simple one-pot hydrothermal treatment without further purification. M-CDs inhibited both breast cancer cells through modulating autophagy signalling.

Mitigation of experimental ER stress and diabetes mellitus induced peripheral neuropathy by autophagy promoter, 6-BIO

Neuropathy occurs due to damage to the peripheral/central nervous system either due to injury, disease, or drug usage. Increased endoplasmic reticulum (ER) stress is observed in neuropathy. ER stress also leads to a block in autophagy amplifying neuropathic pain. 6-Bromoindirubin-3'-oxime (6-BIO) is an inhibitor of GSK-3β which suppresses mTOR activity thereby increasing autophagy. Tunicamycin (TM)-mediated ER stress and diabetic rat models were used to elucidate the role of ER stress and autophagy in mitigation of neuropathic pain by 6-BIO. Pain was assessed by behavioral studies in ER stressed/diabetic rats having neuropathy. Western blotting, RT-PCR, and fluorescence microscopy were used to assess the level of autophagy and ER stress after TM and 6-BIO treatment in SH-SY5Y neurons. Intraplantar injection of TM in rats led to peripheral neuropathy which was reduced upon 6-BIO injection. 6-BIO also reduced pain in animals exhibiting diabetic peripheral neuropathy. Modulation in the markers of autophagy (p-mTOR, LC-3, and SQSTM1/p62) shows that 6-BIO induces autophagolysosome formation post TM treatment. Concomitantly, 6-BIO reduces ER stress and c-Fos expression-a neuronal activity and pain marker. Alleviation of pain by the inhibition of ER stress and increased formation of autolysosomes by 6-BIO can be harnessed for treating peripheral neuropathy.

FoxO1 silencing in Atp7b-/- neural stem cells attenuates high copper-induced apoptosis via regulation of autophagy

Wilson disease (WD) is a severely autosomal genetic disorder triggered by dysregulated copper metabolism. Autophagy and apoptosis share common modulators that process cellular death. Emerging evidences suggest that Forkhead Box O1 over-expression (FoxO1-OE) aggravates abnormal autophagy and apoptosis to induce neuronal injury. However, the underlying mechanisms remain undetermined. Herein, the aim of this study was to investigate how regulating FoxO1 affects cellular autophagy and apoptosis to attenuate neuronal injury in a well-established WD cell model, the high concentration copper sulfate (CuSO4, HC)-triggered Atp7b-/- (Knockout, KO) neural stem cell (NSC) lines. The FoxO1-OE plasmid, or siRNA-FoxO1 (siFoxO1) plasmid, or empty vector plasmid was stably transfected with recombinant lentiviral vectors into HC-induced Atp7b-/- NSCs. Toxic effects of excess deposited copper on wild-type (WT), Atp7b-/- WD mouse hippocampal NSCs were tested by Cell Counting Kit-8 (CCK-8). Subsequently, the FoxO1 expression was evaluated by immunofluorescence (IF) assay, western blot (WB) and quantitative real-time polymerase chain reaction (qRT-PCR) analysis. Meanwhile, the cell autophagy and apoptosis were evaluated by flow cytometry (FC), TUNEL staining, 2,7-dichlorofluorescein diacetate (DCFH-DA), JC-1, WB, and qRT-PCR. The current study demonstrated a strong rise in FoxO1 levels in HC-treated Atp7b-/- NSCs, accompanied with dysregulated autophagy and hyperactive apoptosis. Also, it was observed that cell viability was significantly decreased with the over-expressed FoxO1 in HC-treated Atp7b-/- WD model. As intended, silencing FoxO1 effectively inhibited abnormal autophagy in HC-treated Atp7b-/- NSCs, as depicted by a decline in LC3II/I, Beclin-1, ATG3, ATG7, ATG13, and ATG16, whereas simultaneously increasing P62. In addition, silencing FoxO1 suppressed apoptosis via diminishing oxidative stress (OS), and mitochondrial dysfunction in HC-induced Atp7b-/- NSCs. Collectively, these results clearly demonstrate the silencing FoxO1 has the neuroprotective role of suppressing aberrant cellular autophagy and apoptosis, which efficiently attenuates neuronal injury in WD.

Sialyltransferase ST3GAL6 silencing reduces α2,3-sialylated glycans to regulate autophagy by decreasing HSPB8-BAG3 in the brain with hepatic encephalopathy

End-stage liver diseases, such as cirrhosis and liver cancer caused by hepatitis B, are often combined with hepatic encephalopathy (HE); ammonia poisoning is posited as one of its main pathogenesis mechanisms. Ammonia is closely related to autophagy, but the molecular mechanism of ammonia's regulatory effect on autophagy in HE remains unclear. Sialylation is an essential form of glycosylation. In the nervous system, abnormal sialylation affects various physiological processes, such as neural development and synapse formation. ST3 β‍-galactoside α2,‍3-sialyltransferase 6 (ST3GAL6) is one of the significant glycosyltransferases responsible for adding α2,3-linked sialic acid to substrates and generating glycan structures. We found that the expression of ST3GAL6 was upregulated in the brains of mice with HE and in astrocytes after ammonia induction, and the expression levels of α2,3-sialylated glycans and autophagy-related proteins microtubule-associated protein light chain 3 (LC3) and Beclin-1 were upregulated in ammonia-induced astrocytes. These findings suggest that ST3GAL6 is related to autophagy in HE. Therefore, we aimed to determine the regulatory relationship between ST3GAL6 and autophagy. We found that silencing ST3GAL6 and blocking or degrading α2,3-sialylated glycans by way of Maackia amurensis lectin-II (MAL-II) and neuraminidase can inhibit autophagy. In addition, silencing the expression of ST3GAL6 can downregulate the expression of heat shock protein β8 (HSPB8) and Bcl2-associated athanogene 3 (BAG3). Notably, the overexpression of HSPB8 partially restored the reduced autophagy levels caused by silencing ST3GAL6 expression. Our results indicate that ST3GAL6 regulates autophagy through the HSPB8-BAG3 complex.

Cryptomphalus aspersa Egg Extract Protects against Human Stem Cell Stress-Induced Premature Senescence

Cellular senescence is a tightly regulated pathophysiologic process and is caused by replicative exhaustion or external stressors. Since naturally derived bioactive compounds with anti-ageing properties have recently captured scientific interest, we analysed the anti-ageing and antioxidant efficacy of Cryptomphalus aspersa egg extract (CAEE). Its effects on stemness, wound-healing properties, antioxidant defense mechanisms, and DNA damage repair ability of Human Wharton's jelly mesenchymal stem cells (WJ-MSCs) were analysed. Our results revealed that CAEE fortifies WJ-MSCs stemness, which possibly ameliorates their wound-healing ability. Additionally, we show that CAEE possesses a strong antioxidant capacity as demonstrated by the elevation of the levels of the basic antioxidant molecule, GSH, and the induction of the NRF2, a major antioxidant regulator. In addition, CAEE alleviated cells' oxidative stress and therefore prevented stress-induced premature senescence (SIPS). Furthermore, we demonstrated that the prevention of SIPS could be mediated via the extract's ability to induce autophagy, as indicated by the elevation of the protein levels of all basic autophagic molecules and the increase in formation of autophagolysosomes in CAEE-treated WJ-MSCs. Moreover, CAEE-treated cells exhibited decreased Caveolin-1 levels. We propose that Cryptomphalus aspersa egg extract comprises bioactive compounds that can demonstrate strong antioxidant/anti-ageing effects by regulating the Caveolin-1-autophagy-senescence molecular axis.

FTO-mediated autophagy inhibition promotes non-small cell lung cancer progression by reducing the stability of SESN2 mRNA

The role of fat mass and obesity-associated protein (FTO), an N6-methyladenosine (m6A) demethylase, in non-small cell lung cancer (NSCLC) has recently received widespread attention. However the underlying mechanisms of FTO-mediated autophagy regulation in NSCLC progression remain elusive. In this study, we found that FTO was significantly upregulated in NSCLC, and downregulation of FTO suppressed the growth, invasion and migration of NSCLC cells by inducing autophagy. FTO knockdown resulted in elevated m6A levels in NSCLC cells. Methylated RNA immunoprecipitation sequencing showed that sestrin 2 (SESN2) was involved in m6A regulation during autophagy in NSCLC cells. Interestingly, m6A modifications in exon 9 of SESN2 regulated its stability. FTO deficiency promoted the binding of insulin-like growth factor 2 mRNA-binding protein 1 to SESN2 mRNA, enhancing its stability and elevating its protein expression. FTO inhibited autophagic flux by downregulating SESN2, thereby promoting the growth, invasion and migration of NSCLC cells. Besides, the mechanism by which FTO blocked SESN2-mediated autophagy activation was associated with the AMPK-mTOR signaling pathway. Taken together, these findings uncover an essential role of the FTO-autophagy-SESN2 axis in NSCLC progression.

USP13 Cooperates with MARCH8 to Inhibit Antiviral Signaling by Targeting MAVS for Autophagic Degradation in Teleost

Mitochondrial antiviral signaling protein (MAVS), as a central adapter protein in retinoic acid-inducible gene I-like receptor signaling, is indispensable for innate antiviral immunity. Yet, the molecular mechanisms modulating the stability of MAVS are not fully understood in low vertebrates. In this study, we report that the deubiquitinase ubiquitin-specific protease 13 (USP13) acts as a negative regulator of antiviral immunity by targeting MAVS for selective autophagic degradation in teleost fish. USP13 is induced by RNA virus or polyinosinic:polycytidylic acid stimulation and acts as a negative regulator to potentiate viral replication in fish cells. Mechanistically, USP13 functions as a scaffold to enhance the interaction between MAVS and the E3 ubiquitin ligase MARCH8, thus promoting MARCH8 to catalyze MAVS through K27-linked polyubiquitination for selective autophagic degradation. Taken together, to our knowledge, our study demonstrates a novel mechanism by which viruses evade host antiviral immunity via USP13 in fish and provides a new idea for mammalian innate antiviral immunity.

THSD1 Suppresses Autophagy-Mediated Focal Adhesion Turnover by Modulating the FAK-Beclin 1 Pathway

Focal adhesions (FAs) play a crucial role in cell spreading and adhesion, and their autophagic degradation is an emerging area of interest. This study investigates the role of Thrombospondin Type 1 Domain-Containing Protein 1 (THSD1) in regulating autophagy and FA stability in brain endothelial cells, shedding light on its potential implications for cerebrovascular diseases. Our research reveals a physical interaction between THSD1 and FAs. Depletion of THSD1 significantly reduces FA numbers, impairing cell spreading and adhesion. The loss of THSD1 also induces autophagy independently of changes in mTOR and AMPK activation, implying that THSD1 primarily governs FA dynamics rather than serving as a global regulator of nutrient and energy status. Mechanistically, THSD1 negatively regulates Beclin 1, a central autophagy regulator, at FAs through interactions with focal adhesion kinase (FAK). THSD1 inactivation diminishes FAK activity and relieves its inhibitory phosphorylation on Beclin 1. This, in turn, promotes the complex formation between Beclin 1 and ATG14, a critical event for the activation of the autophagy cascade. In summary, our findings identify THSD1 as a novel regulator of autophagy that degrades FAs in brain endothelial cells. This underscores the distinctive nature of THSD1-mediated, cargo-directed autophagy and its potential relevance to vascular diseases due to the loss of endothelial FAs. Investigating the underlying mechanisms of THSD1-mediated pathways holds promise for discovering novel therapeutic targets in vascular diseases.

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

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

The Role of BNIP3 and Blocked Autophagy Flux in Arsenic-Induced Oxidative Stress-Induced Liver Injury in Rats

Arsenic is a widely distributed environmental toxic substance in nature. Chronic arsenic exposure can cause permanent damage to the liver, resulting in the death of poisoned patients. However, the mechanism of liver damage caused by arsenic poisoning is yet unclear. Here, four different concentrations of sodium arsenite (NaAsO2) (0 mg/L (control group), 25 mg/L, 50 mg/L, and 100 mg/L group)were established to induce liver injury in rats. Taking this into account, the relationship and potential mechanisms of oxidative stress, Bcl-2/adenovirus E1B-19-kDa-interacting protein 3 (BNIP3), and inhibition of autophagy flux in liver injury caused by arsenic poisoning were studied. The results indicated that long-term exposure to NaAsO2 could induce oxidative stress, leading to high expression of BNIP3, thereby impaired autophagy flux, and ultimately resulting in liver damage. This research provides an important basis for future research on liver damage caused by chronic arsenic exposure and prevention and treatment with BNIP3 as the target.

Pelargonic acid vanillylamide alleviates hepatic autophagy and ER stress in hepatic steatosis model

Pelargonic acid vanillylamide (PAVA) has been shown to reduce hepatic lipid accumulation in an obese rat model, however the underlying mechanism responsible for regulating lipid metabolism remains unclear. This study investigated the molecular mechanisms invoked by PAVA in regulating lipogenesis, autophagy, and endoplasmic reticulum (ER) stress in obese rats. Male Sprague-Dawley rats were fed on a diet consisting of 65.26% fat (16 weeks) and HepG2 cells were incubated with 200 μM oleic acid (OA) plus 100 μM palmitic acid (PA) for 48 h. These treatments resulted in a steatosis model. PAVA was shown to reduce fat deposition in hepatocytes in HepG2 by reducing lipotoxicity, the triglyceride content, the expression of sterol regulatory element binding protein 1c (SREBP-1c) and fatty acid synthase (FASN). PAVA also significantly reduced the calcium level and the expression of calpain 2 and upregulated the expression of Atg7 in comparison to the HFD group. In addition, PAVA was shown to significantly decrease the expression of autophagy pathway-related proteins including LC3 and p62. Treatment with PAVA (1 mg/day) reduced the expressions of ER stress markers Bip, ATF6 (p50), p-IRE1/IRE1, p-eIF2α/eIF2α, pJNK, CHOP and cleaved CASP12. In conclusion, PAVA ameliorated obesity induced hepatic steatosis by attenuating defective autophagy and ER stress pathways.

MAT as a promising therapeutic strategy against triple-negative breast cancer via inhibiting PI3K/AKT pathway

Triple-negative breast cancer (TNBC), a highly aggressive and heterogeneous subtype of breast cancer, lacks effective treatment options. Sophora flavescens Aiton, a Chinese medicinal plant, is often used in traditional Chinese medicine to treat cancer. Matrine (MAT) is an alkaloid extracted from Sophora flavescens. It has good anticancer effects, and thus can be explored as a new therapeutic agent in TNBC research. We performed bioinformatics analysis to analyze the differentially expressed genes between normal breast tissues and TNBC tissues, and comprehensive network pharmacology analyses. The activity and invasion ability of TNBC cells treated with MAT were analyzed. Apoptosis and cell cycle progression were determined using cytometry. We used Monodansylcadaverine (MDC) staining to determine the condition of autophagosomes. Finally, the expression levels of the key target proteins of the PI3K/AKT pathway were determined using western blotting. The proliferation and invasion ability of MDA-MB-231 and MDA-MB-468 can be effectively inhibited by MAT. The results of flow cytometry indicated that MAT arrested the TNBC cell cycle and induced apoptosis. In addition, we confirmed that MAT inhibited the expression of BCL-2 while up-regulating the expression of cleaved caspase-3. Moreover, enhanced intensity of MDC staining and high LC3-II expression were observed, which confirmed that MAT induced autophagy in TNBC cells. Western blotting showed that MAT inhibited the PI3K/AKT pathway and downregulated the expressions of PI3K, AKT, p-AKT, and PGK1. This study provides feasible methods, which include bioinformatics analysis and in vitro experiments, for the identification of compounds with anti-TNBC properties. MAT inhibited the PI3K/AKT signaling pathway, arrested cell cycle, as well as promoted cell apoptosis and autophagy. These experiments provide evidence for the anti-TNBC effect of MAT and identified potential targets against TNBC.

Excessive Protein Accumulation and Impaired Autophagy in the Hippocampus of Angelman Syndrome Modeled in Mice

BACKGROUND

Angelman syndrome (AS), a neurodevelopmental disorder caused by abnormalities of the 15q11.2-q13.1 chromosome region, is characterized by impairment of cognitive and motor functions, sleep problems, and seizures. How the genetic defects of AS produce these neurological symptoms is unclear. Mice modeling AS (AS mice) accumulate activity-regulated cytoskeleton-associated protein (ARC/ARG3.1), a neuronal immediate early gene (IEG) critical for synaptic plasticity. This accumulation suggests an altered protein metabolism.

METHODS

Focusing on the dorsal hippocampus (dHC), a brain region critical for memory formation and cognitive functions, we assessed levels and tissue distribution of IEGs, de novo protein synthesis, and markers of protein synthesis, endosomes, autophagy, and synaptic functions in AS mice at baseline and following learning. We also tested autophagic flux and memory retention following autophagy-promoting treatment.

RESULTS

AS dHC exhibited accumulation of IEGs ARC, FOS, and EGR1; autophagy proteins MLP3B, SQSTM1, and LAMP1; and reduction of the endosomal protein RAB5A. AS dHC also had increased levels of de novo protein synthesis, impaired autophagic flux with accumulation of autophagosome, and altered synaptic protein levels. Contextual fear conditioning significantly increased levels of IEGs and autophagy proteins, de novo protein synthesis, and autophagic flux in the dHC of normal mice, but not in AS mice. Enhancing autophagy in the dHC alleviated AS-related memory and autophagic flux impairments.

CONCLUSIONS

A major biological deficit of AS brain is a defective protein metabolism, particularly that dynamically regulated by learning, resulting in stalled autophagy and accumulation of neuronal proteins. Activating autophagy ameliorates AS cognitive impairments and dHC protein accumulation.

A mitochondrial iron-responsive pathway regulated by DELE1

The heme-regulated kinase HRI is activated under heme/iron deficient conditions; however, the underlying molecular mechanism is incompletely understood. Here, we show that iron-deficiency-induced HRI activation requires the mitochondrial protein DELE1. Notably, mitochondrial import of DELE1 and its subsequent protein stability are regulated by iron availability. Under steady-state conditions, DELE1 is degraded by the mitochondrial matrix-resident protease LONP1 soon after mitochondrial import. Upon iron chelation, DELE1 import is arrested, thereby stabilizing DELE1 on the mitochondrial surface to activate the HRI-mediated integrated stress response (ISR). Ablation of this DELE1-HRI-ISR pathway in an erythroid cell model enhances cell death under iron-limited conditions, suggesting a cell-protective role for this pathway in iron-demanding cell lineages. Our findings highlight mitochondrial import regulation of DELE1 as the core component of a previously unrecognized mitochondrial iron responsive pathway that elicits stress signaling following perturbation of iron homeostasis.

Deregulation of mTORC1-TFEB axis in human iPSC model of GBA1-associated Parkinson's disease

Mutations in the GBA1 gene are the single most frequent genetic risk factor for Parkinson's disease (PD). Neurodegenerative changes in GBA1-associated PD have been linked to the defective lysosomal clearance of autophagic substrates and aggregate-prone proteins. To elucidate novel mechanisms contributing to proteinopathy in PD, we investigated the effect of GBA1 mutations on the transcription factor EB (TFEB), the master regulator of the autophagy-lysosomal pathway (ALP). Using PD patients' induced-pluripotent stem cells (iPSCs), we examined TFEB activity and regulation of the ALP in dopaminergic neuronal cultures generated from iPSC lines harboring heterozygous GBA1 mutations and the CRISPR/Cas9-corrected isogenic controls. Our data showed a significant decrease in TFEB transcriptional activity and attenuated expression of many genes in the CLEAR network in GBA1 mutant neurons, but not in the isogenic gene-corrected cells. In PD neurons, we also detected increased activity of the mammalian target of rapamycin complex1 (mTORC1), the main upstream negative regulator of TFEB. Increased mTORC1 activity resulted in excess TFEB phosphorylation and decreased nuclear translocation. Pharmacological mTOR inhibition restored TFEB activity, decreased ER stress and reduced α-synuclein accumulation, indicating improvement of neuronal protiostasis. Moreover, treatment with the lipid substrate reducing compound Genz-123346, decreased mTORC1 activity and increased TFEB expression in the mutant neurons, suggesting that mTORC1-TFEB alterations are linked to the lipid substrate accumulation. Our study unveils a new mechanism contributing to PD susceptibility by GBA1 mutations in which deregulation of the mTORC1-TFEB axis mediates ALP dysfunction and subsequent proteinopathy. It also indicates that pharmacological restoration of TFEB activity could be a promising therapeutic approach in GBA1-associated neurodegeneration.

Digested Cinnamon (Cinnamomum verum J. Presl) Bark Extract Modulates Claudin-2 Gene Expression and Protein Levels under TNFα/IL-1β Inflammatory Stimulus

Epigenetic changes, host-gut microbiota interactions, and environmental factors contribute to inflammatory bowel disease (IBD) onset and progression. A healthy lifestyle may help to slow down the chronic or remitting/relapsing intestinal tract inflammation characteristic of IBD. In this scenario, the employment of a nutritional strategy to prevent the onset or supplement disease therapies included functional food consumption. Its formulation consists of the addition of a phytoextract enriched in bioactive molecules. A good candidate as an ingredient is the Cinnamon verum aqueous extract. Indeed, this extract, subjected to a process of gastrointestinal digestion simulation (INFOGEST), exhibits beneficial antioxidant and anti-inflammatory properties in an in vitro model of the inflamed intestinal barrier. Here, we deepen the study of the mechanisms related to the effect of digested cinnamon extract pre-treatment, showing a correlation between transepithelial electrical resistance (TEER) decrement and alterations in claudin-2 expression under Tumor necrosis factor-α/Interleukin-1β (TNF-α/IL-1) β cytokine administration. Our results show that pre-treatment with cinnamon extract prevents TEER loss by claudin-2 protein level regulation, influencing both gene transcription and autophagy-mediated degradation. Hence, cinnamon polyphenols and their metabolites probably work as mediators in gene regulation and receptor/pathway activation, leading to an adaptive response against renewed insults.

Effects of Prunus Tomentosa Thumb Total Flavones on adjuvant arthritis in rats and regulation of autophagy

BACKGROUND

Rheumatoid arthritis (RA) is a slow in taking effect systemic autoimmune disease. Prunus Tomentosa Thumb Total Flavones (PTTTF) has anti-inflammatory and antioxidant properties.

OBJECTIVE

The purpose of this study is to the PTTTF on adjuvant arthritis (AA) in rats and to explore the mechanism of autophagy.

METHODS

Adjuvant arthritis model was established in rats. The cyclooxygenase 1 (COX-1) and cyclooxygenase 2 (COX-2), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-17 (IL-17), tumor necrosis factor (TNF-α) of rat synovial tissue were determined by RT-PCR. The histopathological varieties of knee joints in AA rats were observed by HE staining. The expressions of autophagy-related proteins ATG5, ATG7, ATG12, Beclin1, Lc3II and Bcl-2 in rat synovial tissue were determined by Western Blotting.

RESULTS

PTTTF (50, 100, 200 mg/kg) significantly inhibited inflammation in rats (P< 0.01). PTTTF significantly inhibited inflammatory factor COX in rat synovial tissue. COX-2, IL-1β, IL-6, IL-17, TNF-α expression (P< 0.05); PTTTF can significantly improve the pathological damage of rat knee joint PTTTF and can significantly inhibited the expression of autophagy-related proteins in rat synovium (P< 0.05 ).

CONCLUSION

PTTTF can inhibit adjuvant arthritis in rats and can inhibit the expression of autophagy-related proteins ATG5, ATG7, ATG12, Beclin1, Lc3II and Bcl-2.

Impaired Autophagy in Krabbe Disease: The Role of BCL2 and Beclin-1 Phosphorylation

Autophagic impairment was identified in many lysosomal storage diseases and adult neurodegenerative diseases. It seems that this defect could be directly related to the appearance of a neurodegenerative phenotype and could contribute to worsen metabolite accumulation and lysosomal distress. Thus, autophagy is becoming a promising target for supportive therapies. Autophagy alterations were recently identified also in Krabbe disease. Krabbe disease is characterized by extensive demyelination and dysmyelination and it is due to the genetic loss of function of the lysosomal enzyme galactocerebrosidase (GALC). This enzyme leads to the accumulation of galactosylceramide, psychosine, and secondary substrates such as lactosylceramide. In this paper, we induced autophagy through starvation and examined the cellular response occurring in fibroblasts isolated from patients. We demonstrated that the inhibitory AKT-mediated phosphorylation of beclin-1 and the BCL2-beclin-1 complex concur to reduce autophagosomes formation in response to starvation. These events were not dependent on the accumulation of psychosine, which was previously identified as a possible player in autophagic impairment in Krabbe disease. We believe that these data could better elucidate the capability of response to autophagic stimuli in Krabbe disease, in order to identify possible molecules able to stimulate the process.

Methylmercury drives lipid droplet formation and adipokine expression during the late stages of adipocyte differentiation in 3T3-L1 cells

Chronic exposure to methylmercury (MeHg) is positively associated with obesity and metabolic syndromes. However, the effect of MeHg on adipogenesis has not been thoroughly investigated. This study investigated the effects of continuous exposure to 0.5 µM MeHg on adipocyte differentiation in 3T3-L1 cells. Oil Red O staining and triglycerides (TG) assays demonstrated that MeHg enhanced the TG content in 3T3-L1 cells. MeHg enhanced the mRNA and protein expression of adipocyte differentiation markers including peroxisome proliferator-activated receptor γ, adiponectin, and fatty acid-binding protein, and their expression levels were prominent during the late stages (days 6-8) after the induction of differentiation. In addition, 0.5 µM MeHg promoted the expression of autophagy-related genes, including light chain 3 B-II and p62, after induction of differentiation. Treatment of 3T3-L1 cells with chloroquine (CQ), an autophagy inhibitor, during the early stages (days 0-2) after induction of differentiation inhibited cellular lipid accumulation in the presence of 0.5 µM MeHg. However, treatment with CQ during the late stages (days 6-8) had little effect on the MeHg-induced increase in TG content and the expression of adipocyte differentiation markers. Although the underlying mechanisms in the late stages remain to be completely elucidated, but the present data suggest that autophagy and other mechanisms play critical roles in adipogenesis during MeHg-induced differentiation. Collectively, our results suggest that continuous exposure to MeHg induces TG accumulation and expression of genes related to adipogenesis, especially during the late stages of 3T3-L1 differentiation, which may contribute to an improved understanding of MeHg-induced adipogenesis.

CTB-targeted protocells enhance ability of lanthionine ketenamine analogs to induce autophagy in motor neuron-like cells

Impaired autophagy, a cellular digestion process that eliminates proteins and damaged organelles, has been implicated in neurodegenerative diseases, including motor neuron disorders. Motor neuron targeted upregulation of autophagy may serve as a promising therapeutic approach. Lanthionine ketenamine (LK), an amino acid metabolite found in mammalian brain tissue, activates autophagy in neuronal cell lines. We hypothesized that analogs of LK can be targeted to motor neurons using nanoparticles to improve autophagy flux. Using a mouse motor neuron-like hybrid cell line (NSC-34), we tested the effect of three different LK analogs on autophagy modulation, either alone or loaded in nanoparticles. For fluorescence visualization of autophagy flux, we used a mCherry-GFP-LC3 plasmid reporter. We also evaluated protein expression changes in LC3-II/LC3-I ratio obtained by western blot, as well as presence of autophagic vacuoles per cell obtained by electron microscopy. Delivering LK analogs with targeted nanoparticles significantly enhanced autophagy flux in differentiated motor neuron-like cells compared to LK analogs alone, suggesting the need of a delivery vehicle to enhance their efficacy. In conclusion, LK analogs loaded in nanoparticles targeting motor neurons constitute a promising treatment option to induce autophagy flux, which may serve to mitigate motor neuron degeneration/loss and preserve motor function in motor neuron disease.

The FACT-targeted drug CBL0137 enhances the effects of rituximab to inhibit B-cell non-Hodgkin's lymphoma tumor growth by promoting apoptosis and autophagy

BACKGROUND

Aggressive B-cell non-Hodgkin's lymphoma (B-NHL) patients often develop drug resistance and tumor recurrence after conventional immunochemotherapy, for which new treatments are needed.

METHODS

We investigated the antitumor effects of CBL0137. In vitro, cell proliferation was assessed by CCK-8 and colony formation assay. Flow cytometry was performed to analyze cell cycle progression, apoptosis, mitochondrial depolarization, and reactive oxygen species (ROS) production. Autophagy was detected by transmission electron microscopy and mGFP-RFP-LC3 assay, while western blotting was employed to detect proteins involved in apoptosis and autophagy. RNA-sequencing was conducted to analyze the transcription perturbation after CBL0137 treatment in B-NHL cell lines. Finally, the efficacy and safety of CBL0137, rituximab, and their combination were tested in vivo.

RESULTS

CBL0137, a small molecule anticancer agent that has significant antitumor effects in B-NHL. CBL0137 sequesters the FACT (facilitates chromatin transcription) complex from chromatin to produce cytotoxic effects in B-NHL cells. In addition, we discovered novel anticancer mechanisms of CBL0137. CBL0137 inhibited human B-NHL cell proliferation by inducing cell cycle arrest in S phase via the c-MYC/p53/p21 pathway. Furthermore, CBL0137 triggers ROS generation and induces apoptosis and autophagy in B-NHL cells through the ROS-mediated PI3K/Akt/mTOR and MAPK signaling pathways. Notably, a combination of CBL0137 and rituximab significantly suppressed B-NHL tumor growth in subcutaneous models, consistent with results at the cellular level in vitro.

CONCLUSIONS

CBL0137 has potential as a novel approach for aggressive B-NHL, and its combination with rituximab can provide new therapeutic options for patients with aggressive B-NHL. Video Abstract.

Seeing Neurodegeneration in a New Light Using Genetically Encoded Fluorescent Biosensors and iPSCs

Neurodegenerative diseases present a progressive loss of neuronal structure and function, leading to cell death and irrecoverable brain atrophy. Most have disease-modifying therapies, in part because the mechanisms of neurodegeneration are yet to be defined, preventing the development of targeted therapies. To overcome this, there is a need for tools that enable a quantitative assessment of how cellular mechanisms and diverse environmental conditions contribute to disease. One such tool is genetically encodable fluorescent biosensors (GEFBs), engineered constructs encoding proteins with novel functions capable of sensing spatiotemporal changes in specific pathways, enzyme functions, or metabolite levels. GEFB technology therefore presents a plethora of unique sensing capabilities that, when coupled with induced pluripotent stem cells (iPSCs), present a powerful tool for exploring disease mechanisms and identifying novel therapeutics. In this review, we discuss different GEFBs relevant to neurodegenerative disease and how they can be used with iPSCs to illuminate unresolved questions about causes and risks for neurodegenerative disease.

Mechanistic Insights and Potential Therapeutic Approaches in PolyQ Diseases via Autophagy

Polyglutamine diseases are a group of congenital neurodegenerative diseases categorized with genomic abnormalities in the expansion of CAG triplet repeats in coding regions of specific disease-related genes. Protein aggregates are the toxic hallmark for polyQ diseases and initiate neuronal death. Autophagy is a catabolic process that aids in the removal of damaged organelles or toxic protein aggregates, a process required to maintain cellular homeostasis that has the potential to fight against neurodegenerative diseases, but this pathway gets affected under diseased conditions, as there is a direct impact on autophagy-related gene expression. The increase in the accumulation of autophagy vesicles reported in neurodegenerative diseases was due to an increase in autophagy or may have been due to a decrease in autophagy flux. These reports suggested that there is a contribution of autophagy in the pathology of diseases and regulation in the process of autophagy. It was demonstrated in various disease models of polyQ diseases that autophagy upregulation by using modulators can enhance the dissolution of toxic aggregates and delay disease progression. In this review, interaction of the autophagy pathway with polyQ diseases was analyzed, and a therapeutic approach with autophagy inducing drugs was established for disease pathogenesis.

Live-Cell High-Throughput Screen for Monitoring Autophagy Flux

Autophagy is a cellular process implicated in the renewal of cellular components and the maintenance of cellular hemostasis and therefore associated with various types of diseases. In addition, autophagy belongs to the stress response pathways and is frequently activated by chemical compounds harboring characteristics of cell toxicity. High-throughput screens analyzing autophagy flux are therefore applied in both, the field of compound identification for targeting autophagy and compound characterization for analyzing compound toxicity. In this chapter, we describe a live-cell, fluorescent-based, high-throughput screening method in 384-well format for the fast and accurate measurement of autophagy flux over time suitable for academic research, pharmacological applications, and drug discovery.

Atg8-PE protein-based in vitro biochemical approaches to autophagy studies

Macroautophagy/autophagy is an evolutionarily conserved intracellular degradation pathway that maintains cellular homeostasis. Over the past two decades, a series of scientific breakthroughs have helped explain autophagy-related molecular mechanisms and physiological functions. This tremendous progress continues to depend largely on powerful research methods, specifically, various autophagy marker Atg8-PE protein-based methods for studying membrane dynamics and monitoring autophagic activity. Recently, several biochemical approaches have been successfully developed to produce the lipidated protein Atg8-PE or its mimics in vitro, including enzyme-mediated reconstitution systems, chemically defined reconstitution systems, cell-free lipidation systems and protein chemical synthesis. These approaches have contributed important insights into the mechanisms underlying Atg8-mediated membrane dynamics and protein-protein interactions, creating a new perspective in autophagy studies. In this review, we comprehensively summarize Atg8-PE protein-based in vitro biochemical approaches and recent advances to facilitate a better understanding of autophagy mechanisms. In addition, we highlight the advantages and disadvantages of various Atg8-PE protein-based approaches to provide general guidance for their use in studying autophagy.Abbreviations: ATG: autophagy related; ATP: adenosine triphosphate; COPII: coat protein complex II; DGS-NTA: 1,2-dioleoyl-sn-glycero-3-[(N-(5-amino-1-carboxypentyl)iminodiacetic acid)succinyl] (nickel salt); DPPE: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine; DSPE: 1,2-distearoyl-sn-glycero-3-phosphoethanolamine; E. coli: Escherichia coli; EPL: expressed protein ligation; ERGIC: ER-Golgi intermediate compartment; GABARAP: GABA type A receptor-associated protein; GABARAPL1: GABA type A receptor associated protein like 1; GABARAPL2: GABA type A receptor associated protein like 2; GFP: green fluorescent protein; GUVs: giant unilamellar vesicles; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MBP: maltose binding protein; MEFs: mouse embryonic fibroblasts; MESNa: 2-mercaptoethanesulfonic acid sodium salt; NCL: native chemical ligation; NTA: nitrilotriacetic acid; PE: phosphatidylethanolamine; PS: phosphatidylserine; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; SPPS: solid-phase peptide synthesis; TEV: tobacco etch virus; WT: wild-type.

Molecular Mechanism and Regulation of Autophagy and Its Potential Role in Epilepsy

Autophagy is an evolutionally conserved degradation mechanism for maintaining cell homeostasis whereby cytoplasmic components are wrapped in autophagosomes and subsequently delivered to lysosomes for degradation. This process requires the concerted actions of multiple autophagy-related proteins and accessory regulators. In neurons, autophagy is dynamically regulated in different compartments including soma, axons, and dendrites. It determines the turnover of selected materials in a spatiotemporal control manner, which facilitates the formation of specialized neuronal functions. It is not surprising, therefore, that dysfunctional autophagy occurs in epilepsy, mainly caused by an imbalance between excitation and inhibition in the brain. In recent years, much attention has been focused on how autophagy may cause the development of epilepsy. In this article, we overview the historical landmarks and distinct types of autophagy, recent progress in the core machinery and regulation of autophagy, and biological roles of autophagy in homeostatic maintenance of neuronal structures and functions, with a particular focus on synaptic plasticity. We also discuss the relevance of autophagy mechanisms to the pathophysiology of epileptogenesis.

Mn(II) Quinoline Complex (4QMn) Restores Proteostasis and Reduces Toxicity in Experimental Models of Huntington's Disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder, of the so-called minority diseases, due to its low prevalence. It is caused by an abnormally long track of glutamines (polyQs) in mutant huntingtin (mHtt), which makes the protein toxic and prone to aggregation. Many pathways of clearance of badly-folded proteins are disrupted in neurons of patients with HD. In this work, we show that one Mn(II) quinone complex (4QMn), designed to work as an artificial superoxide dismutase, is able to activate both the ubiquitin-proteasome system and the autophagy pathway in vitro and in vivo models of HD. Activation of these pathways degrades mHtt and other protein-containing polyQs, which restores proteostasis in these models. Hence, we propose 4QMn as a potential drug to develop a therapy to treat HD.

Enhanced Delivery of Rose Bengal by Amino Acids Starvation and Exosomes Inhibition in Human Astrocytoma Cells to Potentiate Anticancer Photodynamic Therapy Effects

Photodynamic therapy (PDT) is a promising anticancer strategy based on the light energy stimulation of photosensitizers (PS) molecules within a malignant cell. Among a multitude of recently challenged PS, Rose bengal (RB) has been already reported as an inducer of cytotoxicity in different tumor cells. However, RB displays a low penetration capability across cell membranes. We have therefore developed a short-term amino acids starvation protocol that significantly increases RB uptake in human astrocytoma cells compared to normal rat astrocytes. Following induced starvation uptake, RB is released outside cells by the exocytosis of extracellular vesicles (EVs). Thus, we have introduced a specific pharmacological treatment, based on the GW4869 exosomes inhibitor, to interfere with RB extracellular release. These combined treatments allow significantly reduced nanomolar amounts of administered RB and a decrease in the time interval required for PDT stimulation. The overall conditions affected astrocytoma viability through the activation of apoptotic pathways. In conclusion, we have developed for the first time a combined scheme to simultaneously increase the RB uptake in human astrocytoma cells, reduce the extracellular release of the drug by EVs, and improve the effectiveness of PDT-based treatments. Importantly, this strategy might be a valuable approach to efficiently deliver other PS or chemotherapeutic drugs in tumor cells.

NNK from tobacco smoking enhances pancreatic cancer cell stemness and chemoresistance by creating a β2AR-Akt feedback loop that activates autophagy

Low responsiveness to chemotherapy is an important cause of poor prognosis in pancreatic cancer. Smoking is a high-risk factor for pancreatic cancer and cancer resistance to gemcitabine; however, the underlying mechanisms remain unclear. 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the main metabolite of tobacco burning and has been shown to be associated with cancer development and chemoresistance. However, in pancreatic cancer, its mechanism remains poorly understood. In this study, we found that NNK promoted stemness and gemcitabine resistance in pancreatic cancer cell lines. Moreover, NNK increased autophagy and elevated the expression levels of the autophagy-related markers autophagy-related gene 5 (ATG5), autophagy-related gene 7 (ATG7), and Beclin1. Furthermore, the results showed that NNK-promoted stemness and gemcitabine resistance was partially dependent on the role of NNK in cell autophagy, which is mediated by the β2-adrenergic receptor (β2AR)-Akt axis. Finally, we proved that NNK intervention could not only activate β2AR, but also increase its expression, making β2AR and Akt form a feedback loop. Overall, these findings show that the NNK-induced β2AR-Akt feedback loop promotes stemness and gemcitabine resistance in pancreatic cancer cells.

Rhein induces changes in the lysosomal compartment of HeLa cells

Rhein is an anthraquinone found in Rheum palmatum, used in Chinese medicine. Due to potential anticancer properties, the study assessed its effect on the lysosomal compartment, which indirectly influences cell death. The experiment was performed on HeLa cells by treating them with rhein at concentrations of 100-300 µM. LC3-II protein and caspase 3/7 activity, level of apoptosis, the concentration of reactive oxide species (ROS), and mitochondrial potential (Δψm) were evaluated by the cytometric method. To evaluate the permeability of the lysosomal membrane (LMP), staining with acridine orange and the assessment of activity of cathepsin D and L in the lysosomal and extralysosomal fractions were used. Cell viability was assessed by -(3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) (MTT) and neutral red (NR) assays. Changes in cells were also demonstrated at the level of electron, optical, confocal, and fluorescence microscopy. Inhibition of autophagy was done using chloroquine. Rhein-induced degradation processes were confirmed by an increase in the number of primary lysosomes, autophagosomes, and autolysosomes. At high concentrations, rhein caused the generation of ROS, which induced LMP expressed by quenching of acridine orange fluorescence. These results correlated with a reduction of lysosomes, as visualized in graphical modeling, with the decreased uptake of NR by lysosomes, and increased activity of cathepsin D and L in the extralysosomal fraction. The studies also showed an increase in the activity of caspase 3/7 and a decrease in the expression of Bcl-2 protein, indicative of rhein-stimulated apoptosis. At the same time, we demonstrated that preincubation of cells with chloroquine inhibited rhein-induced autophagy and contributed to increased cytotoxicity to HeLa cells. Rhein also induced DNA damage and led to cycle arrest in the S phase. Our results indicate that rhein, by inducing changes in the lysosomal compartment, indirectly affects apoptosis of HeLa cells and in combination with autophagy inhibitors may be an effective form of anticancer therapy.

Inhibition of autophagy with expression of NADPH oxidase subunit p22phox in preneoplastic lesions in a high-fat diet and streptozotocin-related hepatocarcinogenesis rat model

To study the effects of autophagy inducer carbamazepine (CBZ) in a high-fat diet (HFD)/streptozotocin (STZ)-related early hepatocarcinogenesis model, we determined autophagic flux by immunohistochemical analysis of autophagy marker expression in preneoplastic liver foci and compared that with the expression of the NADPH oxidase subunit. Male F344 rats were fed a basal diet or HFD and subjected to two-stage hepatocarcinogenesis; diabetes mellitus was induced via STZ administration. Several STZ-treated, HFD-fed rats were administered CBZ (a total of five doses every one or two days) at week 7 and 8. STZ-treated, HFD-fed rats decreased β cells in the islet of Langerhans and increased adipophilin-positive lipid droplets in the liver; moreover, they had a larger area of glutathione S-transferase placental form-immunopositive preneoplastic liver foci, which was associated with inhibition of autophagy and induction of the NADPH oxidase subunit, as demonstrated by increased immunohistochemical expression of an autophagosome receptor marker microtubule-associated protein light chain 3 (LC3)-binding protein p62, and of an NADPH oxidase subunit p22phox in the preneoplastic foci. An increased trend of an autophagy phagophore marker LC3 in preneoplastic foci was also detected. CBZ administration could induce autophagy and impair p22phox expression, as shown by altered expression of autophagy regulators (Atg5, Atg6, Lamp1, Lamp2, and Lc3), NADPH oxidase subunits (P22phox and P67phox), and antioxidant enzymes Gpx1 and Gpx2. These results suggest that inhibition of autophagy and induction of p22phox might contribute to HFD/STZ-related early hepatocarcinogenesis in rats; however, the effects of CBZ administration on the STZ/HFD-increased preneoplastic foci were marginal in this study.

Porcine Epidemic Diarrhea Virus Infection Induces Autophagosome Formation but Inhibits Autolysosome Formation during Replication

In this study, we investigated the correlation between the mechanism involved in porcine epidemic diarrhea virus (PEDV) replication and autophagic flux. In this study, we found that as PEDV replicated, production of LC3-II was significantly induced up to 24 h post-infection (hpi). Interestingly, although there was significant production of LC3-II, greater p62 accumulation was simultaneously found. Pretreatment with rapamycin significantly induced PEDV replication, but autolysosome formation was reduced. These results were confirmed by the evaluation of ATG5/ATG12 and LAMP1/LAMP2. Taken together, we conclude that PEDV infection induces autophagosome formation but inhibits autolysosome formation during replication.

Revisited role of TRAF2 and TRAF2 C-terminal domain in endoplasmic reticulum stress-induced autophagy in HAP1 leukemia cells

The scaffold protein Tumor Necrosis Factor Receptor-Associated Factor 2 (TRAF2) has been reported to play a key role in the endoplasmic reticulum (ER) stress-induced activation of c-Jun N-terminal Kinase (JNK) and hence autophagy. Autophagy is a highly conserved catabolic process, whose dysregulation is involved in the pathogenesis of various human diseases, including cancer. We investigated the involvement of TRAF2 in autophagy regulation in the human leukemic HAP1 cell line, under both basal and ER stress conditions. In TRAF2-knockout HAP1 cell line (KO), the basal autophagic flux was higher than in the parental cell line (WT). Moreover, tunicamycin-induced ER stress stimulated JNK activation and autophagy both in WT and KO HAP1. On the other hand, re-expression of a TRAF2 C-terminal fragment (residues ,310-501), in a TRAF2-KO cellular background, rendered HAP1 cells unable to activate both JNK and autophagy upon ER stress induction. Of note, this apparent dominant negative effect of the C-terminal fragment was observed even in the absence of the endogenous, full-length TRAF2 molecule. Furthermore, the expression of the C-terminal fragment resulted in both protein kinase B (AKT) pathway activation and increased resistance to the toxic effects induced by prolonged ER stress conditions. These findings indicate that TRAF2 is dispensable for the activation of both JNK and autophagy in HAP1 cells, while the TRAF2 C-terminal domain may play an autonomous role in regulating the cellular response to ER stress.

Cancer-Related Intracellular Signalling Pathways Activated by DOXorubicin/Cyclodextrin-Graphene-Based Nanomaterials

In the last decade, nanotechnological progress has generated new opportunities to improve the safety and efficacy of conventional anticancer therapies. Compared with other carriers, graphene nanoplatforms possess numerous tunable functionalities for the loading of multiple bioactive compounds, although their biocompatibility is still a debated concern. Recently, we have investigated the modulation of genes involved in cancer-associated canonical pathways induced by graphene engineered with cyclodextrins (GCD). Here, we investigated the GCD impact on cells safety, the HEp-2 responsiveness to Doxorubicin (DOX) and the cancer-related intracellular signalling pathways modulated by over time exposure to DOX loaded on GCD (GCD@DOX). Our studies evidenced that both DOX and GCD@DOX induced p53 and p21 signalling resulting in G₀/G₁ cell cycle arrest. A genotoxic behaviour of DOX was reported via detection of CDK (T14/Y15) activation and reduction of Wee-1 expression. Similarly, we found a cleavage of PARP by DOX within 72 h of exposure. Conversely, GCD@DOX induced a late cleavage of PARP, which could be indicative of less toxic effect due to controlled release of the drug from the GCD nanocarrier. Finally, the induction of the autophagy process supports the potential recycling of DOX with the consequent limitation of its toxic effects. Together, these findings demonstrate that GCD@DOX is a biocompatible drug delivery system able to evade chemoresistance and doxorubicin toxicity.

Molecular Mechanistic Pathways Targeted by Natural Antioxidants in the Prevention and Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) is the progressive loss of renal function and the leading cause of end-stage renal disease (ESRD). Despite optimal therapy, many patients progress to ESRD and require dialysis or transplantation. The pathogenesis of CKD involves inflammation, kidney fibrosis, and blunted renal cellular antioxidant capacity. In this review, we have focused on in vitro and in vivo experimental and clinical studies undertaken to investigate the mechanistic pathways by which these compounds exert their effects against the progression of CKD, particularly diabetic nephropathy and kidney fibrosis. The accumulated and collected data from preclinical and clinical studies revealed that these plants/bioactive compounds could activate autophagy, increase mitochondrial bioenergetics and prevent mitochondrial dysfunction, act as modulators of signaling pathways involved in inflammation, oxidative stress, and renal fibrosis. The main pathways targeted by these compounds include the canonical nuclear factor kappa B (NF-κB), canonical transforming growth factor-beta (TGF-β), autophagy, and Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid factor 2-related factor 2 (Nrf2)/antioxidant response element (ARE). This review presented an updated overview of the potential benefits of these antioxidants and new strategies to treat or reduce CKD progression, although the limitations related to the traditional formulation, lack of standardization, side effects, and safety.

A Novel Method of Mouse RPE Explant Culture and Effective Introduction of Transgenes Using Adenoviral Transduction for In Vitro Studies in AMD

Degeneration of retinal pigment epithelium (RPE) is one of the most critical phenotypic changes of age-related macular degeneration (AMD), the leading cause of vision loss in the elderly. While cultured polarized RPE cells with original properties are valuable in in vitro models to study RPE biology and the consequences of genetic and/or pharmacological manipulations, the procedure to establish mouse primary PRE cell culture or pluripotent stem cell-derived RPE cells is time-consuming and yields a limited number of cells. Thus, establishing a mouse in situ RPE culture system is highly desirable. Here we describe a novel and efficient method for RPE explant culture that allows for obtaining biologically relevant RPE cells in situ. These RPE explants (herein referred to as RPE flatmounts) are viable in culture for at least 7 days, can be efficiently transduced with adenoviral constructs, and/or treated with a variety of drugs/chemicals followed by downstream analysis of the signaling pathways/biological processes of interest, such as assessment of the autophagy flux, inflammatory response, and receptor tyrosine kinases stimulation. This method of RPE explant culture is highly beneficial for pharmacological and mechanistic studies in the field of RPE biology and AMD research.

Melibiose Confers a Neuroprotection against Cerebral Ischemia/Reperfusion Injury by Ameliorating Autophagy Flux via Facilitation of TFEB Nuclear Translocation in Neurons

Autophagic/lysosomal dysfunction is a critical pathogenesis of neuronal injury after ischemic stroke. Trehalose has been validated to restore the impaired autophagy flux by boosting transcription factor EB (TFEB) nuclear translocation, but orally administrated trehalose can be greatly digested by intestinal trehalase before entering into brain. Melibiose (MEL), an analogue of trehalose, may thoroughly exert its pharmacological effects through oral administration due to absence of intestinal melibiase. The present study was to investigate whether melibiose could also confer a neuroprotection by the similar pharmacological mechanism as trehalose did after ischemic stroke. The rats were pretreated with melibiose for 7 days before middle cerebral artery occlusion (MCAO) surgery. Twenty-four hours following MCAO/reperfusion, the cytoplasmic and nuclear TFEB, and the proteins in autophagic/lysosomal pathway at the penumbra were detected by western blot and immunofluorescence, respectively. Meanwhile, the neurological deficit, neuron survival, and infarct volume were assessed to evaluate the therapeutic outcomes. The results showed that the neurological injury was significantly mitigated in MCAO+MEL group, compared with that in MCAO group. Meanwhile, nuclear TFEB expression in neurons at the penumbra was significantly promoted by melibiose. Moreover, melibiose treatment markedly enhanced autophagy flux, as reflected by the reinforced lysosomal capacity and reduced autophagic substrates. Furthermore, the melibiose-elicited neuroprotection was prominently counteracted by lysosomal inhibitor Bafilomycin A1 (Baf-A1). Contrarily, reinforcement of lysosomal capacity with EN6 further improved the neurological performance upon melibiose treatment. Our data suggests that melibiose-augmented neuroprotection may be achieved by ameliorating autophagy flux via facilitation of TFEB nuclear translocation in neurons after ischemic stroke.

Glucagon-Like Peptide-1 Receptor Agonist Ameliorates 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine (MPTP) Neurotoxicity Through Enhancing Mitophagy Flux and Reducing α-Synuclein and Oxidative Stress

Parkinson disease (PD) is the second most common neurodegenerative disease without known disease modification therapy to slow down disease progression. This disease has pathological features of Lewy bodies with α-synuclein aggregation being the major component and selective dopaminergic neuronal loss over the substantia nigra. Although the exact etiology is still unknown, mitochondrial dysfunction has been shown to be central in PD pathophysiology. Type 2 diabetes mellitus has recently been connected to PD, and anti-diabetic drugs, such as glucagon-like peptide-1 receptor agonists (GLP-1RAs), have been shown to possess neuroprotective effects in PD animal models. The GLP-1RA liraglutide is currently under a phase 2 clinical trial to measure its effect on motor and non-motor symptoms in PD patients. In this study, we used an acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD to test the possible mechanism of the GLP-1RA liraglutide in the pathogenesis of PD. We show that the neurobehavioral and motor dysfunction caused by the mitochondrial complex I inhibitor, MPTP, can be partially reversed by liraglutide. The GLP-1RA can protect mice from apoptosis of substantia nigra neurons induced by MPTP. MPTP treatment led to imbalanced mitochondrial fusion and fission dynamics, altered mitochondrial morphology, impeded autophagy flux, increased α-synuclein accumulation, and elevated oxidative stress. Specifically, the normalizing of mitochondrial fusion-fission dynamic-related proteins and enhancement of autophagy flux after administration of liraglutide is associated with improving neuronal survival. This suggests that GLP-1RAs may provide potential beneficial effects for PD caused by mitochondrial dysfunction through improvement of mitochondrial morphology balance and enhancing damaged organelle degradation.

Bifidobacterium longum subsp. infantis YB0411 Inhibits Adipogenesis in 3T3-L1 Pre-adipocytes and Reduces High-Fat-Diet-Induced Obesity in Mice

Although the health benefits of probiotics have been widely known for decades, there has still been limited use of probiotic bacteria in anti-obesity therapy. Herein, we demonstrated the role of Bifidobacterium longum subsp. infantis YB0411 (YB, which was selected by an in vitro adipogenesis assay) in adipogenic differentiation in 3T3-L1 pre-adipocytes. We observed that YB-treatment effectively reduced triglyceride accumulation and the expression of CCAAT/enhancer-binding protein α, β, and δ (C/EBPα, C/EBPβ, and C/EBPδ), peroxisome proliferator-activated receptor γ (PPARγ), fatty acid-binding protein 4 (aP2), and acetyl-CoA carboxylase (ACC). YB-treatment also reduced the levels of core autophagic markers (p62 and LC3B) in 3T3-L1 pre-adipocytes. Small-interfering-RNA-mediated knockdown and competitive-chemical-inhibition assays showed that AMP-activated protein kinase (AMPK) commenced the anti-adipogenic effect of YB. In addition, YB supplement markedly reduced body weight and fat accretion in mice with high-fat-diet-induced obesity. Our findings suggest that YB may be used as a potential probiotic candidate to ameliorate obesity.

Mechanistic insights into the protective effects of chlorogenic acid against indomethacin-induced gastric ulcer in rats: Modulation of the cross talk between autophagy and apoptosis signaling

BACKGROUND

This study aimed to investigate the gastroprotective effect of chlorogenic acid (CGA) against Indomethacin (IND)-induced gastric ulcer (GU) in rats and its underlying mechanism, especially through autophagic and apoptotic pathways.

METHODS

Seventy-five rats were divided into five groups; control, IND (50 mg/kg, p.o.), CGA (100 mg/kg, p.o., 14 days), IND pretreated with CGA (50 mg/kg or 100 mg/kg, p.o., 14 days). The stomach tissues were examined to calculate the ulcer index and analyze markers of autophagy (beclin-1, LC3-II/LC3-I and p62), lysosomal function (cathepsin-D) and apoptosis (Bcl-2, Bax and caspase-3), along with expression of Akt/mTOR pathway using western blot or ELISA techniques. In addition, viability of gastric mucosal cells was detected by flowcytometry. Structural changes were assessed histologically, while autophagic and apoptotic changes of gastric mucosa were observed by transmission electron microscopy.

RESULTS

CGA exhibited a dose-dependent gastroprotective effect by reversing IND-induced accumulation of autophagic vacuoles, significant reduction in beclin-1, LC3-II/LC3-I, and p62 levels, and down-regulation of p-Akt/p-mTOR expression. CGA100 also restored normal autolysosomal function by modulation of cathepsin-D levels. Furthermore, pretreatment with CGA100 was significantly associated with an increase in antiapoptotic protein Bcl-2 along with a decrease in proapoptotic Bax and caspase-3 proteins in such a way that impairs IND-induced apoptosis. This was confirmed by CGA-induced significant decrease in annexin V⁺ cells.

CONCLUSIONS

The natural compound CGA offers a novel gastroprotective intervention against IND-induced GU through restoration of normal autophagic flux, impairment of apoptosis in a crosstalk mechanism mediated by Akt/mTOR pathway reactivation, and alleviation of IND-induced lysosomal dysfunction.

Monitoring autophagy using super-resolution structured illumination and direct stochastic optical reconstruction microscopy

Autophagy is a major protein degradation pathway responsible for the removal of primarily long-lived and misfolded proteins, contributing to cellular homeostasis. Autophagy dysfunction has been associated with the onset of various human pathologies. Visualizing key proteins that govern autophagy pathway activity, the molecular machinery and cargo is essential to elucidate roles and mechanisms of autophagy function. Although multiple fluorescence-based microscopy approaches exist to assess autophagy, the limit of resolution associated with light microscopy makes precise intracellular protein localization, interaction and molecular distribution challenging. Here we describe a detailed protocol for both super-resolution structured illumination microscopy (SR-SIM) as well as direct stochastic optical reconstruction microscopy (dSTORM) for the visualization of key proteins associated with the autophagy molecular machinery and cargo. The presented method enables to achieve increased resolving power to assess localization and molecular density profiles, typically not achievable with standard confocal or wide field fluorescence microcopy.

Bnip3 interacts with vimentin, an intermediate filament protein, and regulates autophagy of hepatic stellate cells

Bnip3, which is regulated by Hif-1 in cells under oxygen deprivation, is a death related protein associated with autophagy and apoptosis. Hif-1 was reported to regulate autophagy to activate hepatic stellate cells (HSCs), while the specific molecular mechanism is vague. The possible mechanism of Hif-1 regulating autophagy of HSCs via Bnip3 was explored in this study. Bnip3 was detected in fibrotic liver tissues from humans and mice. Hif-1 was inhibited by chemical inhibitor and Bnip3 was detected in activated HSCs. The co-localization of Bnip3 and LC3B was captured by confocal microscopy and autophagic flow was assessed in Bnip3 siRNA transfected cells. Bnip3 interacted proteins were screened with mass spectrometry. The interaction of Bnip3 and vimentin was detected with co-immunoprecipitation and confocal microscopy. The results showed that Bnip3 was increased in fibrotic liver tissues and activated HSCs. Hif-1 inhibition suppressed Bnip3 expression in activated HSCs. Bnip3 was partially co-localized with autophagosomes and Bnip3 inhibition suppessed autophagy in activated HSCs. Bnip3 interacted with vimentin and Bnip3 expression was inhibited as vimentin was inhibited in activated HSCs. Conclusively, this study indicated that Bnip3 promoted autophagy and activation of HSCs, via interacting with vimentin, an intermediate filament protein with highly abundant expression in HSCs.