Chloroquine inhibits autophagic flux by decreasing autophagosome-lysosome fusion

Structural and molecular modelling studies reveal a new mechanism of action of chloroquine and hydroxychloroquine against SARS-CoV-2 infection

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The COVID‐19 pandemic caused by SARS‐CoV‐2 poses a global health emergency.

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Promising results suggest that chloroquine could stop the spread of SARS‐CoV‐2.

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In-silico studies confirm the antiviral properties of chloroquine.

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New mechanism of action of chloroquine elucidated.

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Hydroxychloroquine is more potent than chloroquine.

The recent emergence of the novel pathogenic SARS-coronavirus 2 (SARS-CoV-2) is responsible for a worldwide pandemic. Given the global health emergency, drug repositioning is the most reliable option to design an efficient therapy for infected patients without delay. The first step of the viral replication cycle [i.e. attachment to the surface of respiratory cells, mediated by the spike (S) viral protein] offers several potential therapeutic targets. The S protein uses the angiotension-converting enzyme-2 (ACE-2) receptor for entry, but also sialic acids linked to host cell surface gangliosides. Using a combination of structural and molecular modelling approaches, this study showed that chloroquine (CLQ), one of the drugs currently under investigation for SARS-CoV-2 treatment, binds sialic acids and gangliosides with high affinity. A new type of ganglioside-binding domain at the tip of the N-terminal domain of the SARS-CoV-2 S protein was identified. This domain (111–158), which is fully conserved among clinical isolates worldwide, may improve attachment of the virus to lipid rafts and facilitate contact with the ACE-2 receptor. This study showed that, in the presence of CLQ [or its more active derivative, hydroxychloroquine (CLQ-OH)], the viral S protein is no longer able to bind gangliosides. The identification of this new mechanism of action of CLQ and CLQ-OH supports the use of these repositioned drugs to cure patients infected with SARS-CoV-2. The in-silico approaches used in this study might also be used to assess the efficiency of a broad range of repositioned and/or innovative drug candidates before clinical evaluation.

EI24 tethers endoplasmic reticulum and mitochondria to regulate autophagy flux

Etoposide-induced protein 2.4 (EI24), located on the endoplasmic reticulum (ER) membrane, has been proposed to be an essential autophagy protein. Specific ablation of EI24 in neuronal and liver tissues causes deficiency of autophagy flux. However, the molecular mechanism of the EI24-mediated autophagy process is still poorly understood. Like neurons and hepatic cells, pancreatic β cells are also secretory cells. Pancreatic β cells contain large amounts of ER and continuously synthesize and secrete insulin to maintain blood glucose homeostasis. Yet, the effect of EI24 on autophagy of pancreatic β cells has not been reported. Here, we show that the autophagy process is inhibited in EI24-deficient primary pancreatic β cells. Further mechanistic studies demonstrate that EI24 is enriched at the ER-mitochondria interface and that the C-terminal domain of EI24 is important for the integrity of the mitochondria-associated membrane (MAM) and autophagy flux. Overexpression of EI24, but not the EI24-ΔC mutant, can rescue MAM integrity and decrease the aggregation of p62 and LC3II in the EI24-deficient group. By mass spectrometry-based proteomics following immunoprecipitation, EI24 was found to interact with voltage-dependent anion channel 1 (VDAC1), inositol 1,4,5-trisphosphate receptor (IP3R), and the outer mitochondrial membrane chaperone GRP75. Knockout of EI24 impairs the interaction of IP3R with VDAC1, indicating that these proteins may form a quaternary complex to regulate MAM integrity and the autophagy process.

β2 -adrenoceptor activation improves skeletal muscle autophagy in neurogenic myopathy

β2 -adrenoceptor agonists improve autophagy and re-establish proteostasis in cardiac cells; therefore, suggesting autophagy as a downstream effector of β2 -adrenoceptor signaling pathway. Here, we used the pharmacological and genetic tools to determine the autophagy effect of sustained β2 -adrenoceptor activation in rodents with neurogenic myopathy, which display impaired skeletal muscle autophagic flux. Sustained β2 -adrenoceptor activation using Formoterol (10 μg kg-1  day-1 ), starting at the onset of neurogenic myopathy, prevents disruption of autophagic flux in skeletal muscle 14 days after sciatic nerve constriction. These changes are followed by reduction of the cytotoxic protein levels and increased skeletal muscle cross-sectional area and contractility properties. Of interest, sustained administration of Formoterol at lower concentration (1 μg kg-1  day-1 ) induces similar improvements in skeletal muscle autophagic flux and contractility properties in neurogenic myopathy, without affecting the cross-sectional area. Sustained pharmacological inhibition of autophagy using Chloroquine (50 mg kg-1  day-1 ) abolishes the beneficial effects of β2 -adrenoceptor activation on the skeletal muscle proteostasis and contractility properties in neurogenic myopathy. Further supporting an autophagy mechanism for β2 -adrenoceptor activation, skeletal muscle-specific deletion of ATG7 blunts the beneficial effects of β2 -adrenoceptor on skeletal muscle proteostasis and contractility properties in neurogenic myopathy in mice. These findings suggest autophagy as a critical downstream effector of β2 -adrenoceptor signaling pathway in skeletal muscle.

mTORC1-dependent protein synthesis and autophagy uncouple in the regulation of Apolipoprotein A-I expression

BACKGROUND

Apolipoprotein A-I (ApoA-I) is involved in reverse cholesterol transport as a major component of HDL, but also conveys anti-thrombotic, anti-oxidative, anti-inflammatory and immune-regulatory properties that are pertinent to its protective roles in cardiovascular, inflammatory and malignant pathologies. Despite the pleiotropy in ApoA-I functions, the regulation of intracellular ApoA-I levels remains poorly explored.

METHODS

HepG2 hepatoma cells and primary mouse hepatocytes were used as in vitro models to study the impact of genetic and chemical inhibitors of autophagy and the proteasome on ApoA-I by immunoblot, immunofluorescence and electron microscopy. Different growth conditions were implemented in conjunction with mTORC inhibitors to model the influence of nutrient scarcity versus sufficiency on ApoA-I regulation. Hepatic ApoA-I expression was also evaluated in high fat diet-fed mice displaying blockade in autophagy.

RESULTS

Under nutrient-rich conditions, basal ApoA-I levels in liver cells are sustained by the balancing act of autophagy and of mTORC1-dependent de novo protein synthesis. ApoA-I proteolysis occurs through a canonical autophagic pathway involving Beclin1 and ULK1 and the receptor protein p62/SQSTM1 that targets ApoA-I to autophagosomes. However, upon aminoacid insufficiency, suppression of ApoA-I synthesis prevails, rendering mTORC1 inactivation dispensable for autophagy-mediated ApoA-I proteolysis.

CONCLUSION

These data underscore the major contribution of post-transcriptional mechanisms to ApoA-I levels which differentially involve mTORC1-dependent signaling to protein synthesis and autophagy, depending on nutrient availability. Given the established role of ApoA-I in HDL-mediated reverse cholesterol transport, this mode of ApoA-I regulation may reflect a hepatocellular response to the organismal requirement for maintenance of cholesterol and lipid reserves under conditions of nutrient scarcity.

Autophagy Induced by Simian Retrovirus Infection Controls Viral Replication and Apoptosis of Jurkat T Lymphocytes

Autophagy and apoptosis are two important evolutionarily conserved host defense mechanisms against viral invasion and pathogenesis. However, the association between the two pathways during the viral infection of T lymphocytes remains to be elucidated. Simian type D retrovirus (SRV) is an etiological agent of fatal simian acquired immunodeficiency syndrome (SAIDS), which can display disease features that are similar to acquired immunodeficiency syndrome in humans. In this study, we demonstrate that infection with SRV-8, a newly isolated subtype of SRV, triggered both autophagic and apoptotic pathways in Jurkat T lymphocytes. Following infection with SRV-8, the autophagic proteins LC3 and p62/SQSTM1 interacted with procaspase-8, which might be responsible for the activation of the caspase-8/-3 cascade and apoptosis in SRV-8-infected Jurkat cells. Our findings indicate that autophagic responses to SRV infection of T lymphocytes promote the apoptosis of T lymphocytes, which, in turn, might be a potential pathogenetic mechanism for the loss of T lymphocytes during SRV infection.

Lysosomal Dysfunction and Autophagy Blockade Contribute to MDMA-Induced Neurotoxicity in SH-SY5Y Neuroblastoma Cells

Methylenedioxymethamphetamine (MDMA) is a psychostimulant with high abuse potential and severe neurotoxicity. According to our previous study, MDMA promotes autophagosome accumulation and contributes to cell death in cultured cortical and serotonergic neurons. However, the detailed mechanism underlying autophagy dysfunction remains unclear. Lysosomes play an important role in autophagic degradation. The present study aimed to examine the role of lysosomal function in autophagic flux in neuronal cultures exposed to MDMA. We showed that MDMA induced enlarged vesicles that accumulate in SH-SY5Y neuroblastoma cells. In addition, we demonstrated that MDMA stimulated dynamin-dependent but clathrin-independent endocytosis, which might contribute to vacuole expansion. Morphological and Western blot analyses revealed that MDMA induced lysosomal swelling, whereas the activity of the lysosomal hydrolytic enzymes cathepsin B and cathepsin D was decreased in SH-SY5Y and cultured cortical neurons, which might lead to autophagosome accumulation and autophagic degradation blockage. Intriguingly, inactivation of cathepsins B and D led to cell death and autophagy-lysosomal dysregulation, which mimicked MDMA-induced neurotoxicity. Consequently, impairment of lysosomal proteolysis and blockage of autophagy degradation contributed to MDMA-induced neurotoxicity in neuronal cultures.

Catabolic degradation of endothelial VEGFA via autophagy

Extracellular matrix-evoked angiostasis and autophagy within the tumor microenvironment represent two critical, but unconnected, functions of the small leucine-rich proteoglycan, decorin. Acting as a partial agonist of vascular endothelial growth factor 2 (VEGFR2), soluble decorin signals via the energy sensing protein, AMP-activated protein kinase (AMPK), in the autophagic degradation of intracellular vascular endothelial growth factor A (VEGFA). Here, we discovered that soluble decorin evokes intracellular catabolism of endothelial VEGFA that is mechanistically independent of mTOR, but requires an autophagic regulator, paternally expressed gene 3 (PEG3). We found that administration of autophagic inhibitors such as chloroquine or bafilomycin A1, or depletion of autophagy-related 5 (ATG5), results in accumulation of intracellular VEGFA, indicating that VEGFA is a basal autophagic substrate. Mechanistically, decorin increased the VEGFA clearance rate by augmenting autophagic flux, a process that required RAB24 member RAS oncogene family (RAB24), a small GTPase that facilitates the disposal of autophagic compartments. We validated these findings by demonstrating the physiological relevance of this process in vivo Mice starved for 48 h exhibited a sharp decrease in overall cardiac and aortic VEGFA that could be blocked by systemic chloroquine treatment. Thus, our findings reveal a unified mechanism for the metabolic control of endothelial VEGFA for autophagic clearance in response to decorin and canonical pro-autophagic stimuli. We posit that the VEGFR2/AMPK/PEG3 axis integrates the anti-angiogenic and pro-autophagic bioactivities of decorin as the molecular basis for tumorigenic suppression. These results support future therapeutic use of decorin as a next-generation protein therapy to combat cancer.

Role of uL3 in the Crosstalk between Nucleolar Stress and Autophagy in Colon Cancer Cells

The nucleolus is the site of ribosome biogenesis and has been recently described as important sensor for a variety of cellular stressors. In the last two decades, it has been largely demonstrated that many chemotherapeutics act by inhibiting early or late rRNA processing steps with consequent alteration of ribosome biogenesis and activation of nucleolar stress response. The overall result is cell cycle arrest and/or apoptotic cell death of cancer cells. Our previously data demonstrated that ribosomal protein uL3 is a key sensor of nucleolar stress activated by common chemotherapeutic agents in cancer cells lacking p53. We have also demonstrated that uL3 status is associated to chemoresistance; down-regulation of uL3 makes some chemotherapeutic drugs ineffective. Here, we demonstrate that in colon cancer cells, the uL3 status affects rRNA synthesis and processing with consequent activation of uL3-mediated nucleolar stress pathway. Transcriptome analysis of HCT 116^p53−/− cells expressing uL3 and of a cell sub line stably depleted of uL3 treated with Actinomycin D suggests a new extra-ribosomal role of uL3 in the regulation of autophagic process. By using confocal microscopy and Western blotting experiments, we demonstrated that uL3 acts as inhibitory factor of autophagic process; the absence of uL3 is associated to increase of autophagic flux and to chemoresistance. Furthermore, experiments conducted in presence of chloroquine, a known inhibitor of autophagy, indicate a role of uL3 in chloroquine-mediated inhibition of autophagy. On the basis of these results and our previous findings, we hypothesize that the absence of uL3 in cancer cells might inhibit cancer cell response to drug treatment through the activation of cytoprotective autophagy. The restoration of uL3 could enhance the activity of many drugs thanks to its pro-apoptotic and anti-autophagic activity.

The Second Generation Antibody-Drug Conjugate SYD985 Overcomes Resistances to T-DM1

Trastuzumab-emtansine (T-DM1) is an antibody-drug conjugate (ADC) approved for the treatment of HER2 (human epidermal growth factor receptor 2)-positive breast cancer. T-DM1 consists of trastuzumab covalently linked to the cytotoxic maytansinoid DM1 via a non-cleavable linker. Despite its efficacy, primary or acquired resistance frequently develops, particularly in advanced stages of the disease. Second generation ADCs targeting HER2 are meant to supersede T-DM1 by using a cleavable linker and a more potent payload with a different mechanism of action. To determine the effect of one of these novel ADCs, SYD985, on tumors resistant to T-DM1, we developed several patient-derived models of resistance to T-DM1. Characterization of these models showed that previously described mechanisms-HER2 downmodulation, impairment of lysosomal function and upregulation of drug efflux pumps-account for the resistances observed, arguing that mechanisms of resistance to T-DM1 are limited, and most of them have already been described. Importantly, SYD985 was effective in these models, showing that the resistance to first generation ADCs can be overcome with an improved design.

Microtubule disrupting agent-mediated inhibition of cancer cell growth is associated with blockade of autophagic flux and simultaneous induction of apoptosis

Objectives

Given that autophagy inhibition is a feasible way to enhance sensitivity of cancer cells towards chemotherapeutic agents, identifying potent autophagy inhibitor has obvious clinical relevance. Here, we investigated ability of TN‐16, a microtubule disrupting agent, on modulation of autophagic flux and its significance in promoting in vitro and in vivo cancer cell death.

Materials and methods

The effect of TN‐16 on cancer cell proliferation, cell division, autophagic process and apoptotic signalling was assessed by various biochemical (Western blot and SRB assay), morphological (TEM, SEM, confocal microscopy) and flowcytometric assays. In vivo anti‐tumour efficacy of TN‐16 was investigated in syngeneic mouse model of breast cancer.

Results

TN‐16 inhibited cancer cell proliferation by impairing late‐stage autophagy and induction of apoptosis. Inhibition of autophagic flux was demonstrated by accumulation of autophagy‐specific substrate p62 and lack of additional LC3‐II turnover in the presence of lysosomotropic agent. The effect was validated by confocal micrographs showing diminished autophagosome‐lysosome fusion. Further studies revealed that TN‐16–mediated inhibition of autophagic flux promotes apoptotic cell death. Consistent with in vitro data, results of our in vivo study revealed that TN‐16–mediated tumour growth suppression is associated with blockade of autophagic flux and enhanced apoptosis.

Conclusions

Our data signify that TN‐16 is a potent autophagy flux inhibitor and might be suitable for (pre‐) clinical use as standard inhibitor of autophagy with anti‐cancer activity.

Anticancer Effects of Antihypertensive L-Type Calcium Channel Blockers on Chemoresistant Lung Cancer Cells via Autophagy and Apoptosis

Purpose

Hypertension and cancer are frequently found comorbidity occurring in same individual. This study was intended to evaluate the anticancer effects of commonly used antihypertensive medications and chemotherapy on chemoresistant lung cancer cells.

Methods

Calcium channel blockers (CCBs), including Verapamil, Diltiazem, and Nifedipine, either alone or combined with docetaxel (DOC) or vincristine (VCR) were used to treat A549 lung adenocarcinoma chemoresistant sublines. Cell viability was determined by MTT assay, and colony formation assay was used to demonstrate the long-term effect of CCBs on proliferation of the sublines. Apoptosis was evaluated by Annexin V assay and autophagy intensity was quantitated from acidic vesicular organelle formation. Pan-caspase inhibitor, shATG5 interference and chloroquine were applied to study the roles of Verapamil on apoptosis and autophagy, with related proteins verified by Western blot analysis.

Results

Results show that 10 μM of Verapamil and Diltiazem, but not Nifedipine, differentially induce autophagy in DOC-resistant or VCR-resistant A549 cells, respectively. When CCBs are combined with DOC or VCR to treat the sublines, 10 μM of Verapamil induces autophagy more significantly than Diltiazem and Nifedipine, respectively, in DOC-resistant (54.91±0.76, 18.03±0.69, 7.05±0.30) or VCR-resistant A549 (32.41±1.04, 21.51±0.63, 7.14±0.24) cells. Inhibition of apoptosis by pan-caspase inhibitor partly reduced cell death indicates association of caspase-dependent cell death but with persistence of autophagy. Inhibition of autophagy by interfering ATG5 expression reduced c-PARP level and apoptotic cells suggest a pro-death role of autophagy. Chloroquine treatment enhanced autophagosome accumulation and cell death but with reduced c-PARP level suggests that mechanism of caspase-independent cell death also contributes to Verapamil/chemotherapy-induced anticancer effects. 

Conclusion

Verapamil combined with DOC or VCR induces chemoresistant lung cancer cells to death through autophagy burst and apoptosis more strongly than Diltiazem and Nifedipine. Administering Verapamil or Diltiazem individually with chemotherapy, but not Nifedipine, can be considered in lung cancer patients with hypertension.

Autophagy inhibition in 3T3-L1 adipocytes breaks the crosstalk with tumor cells by suppression of adipokine production

Several studies have revealed the functional importance of autophagy in both adipogenesis and carcinogenesis. Here, we investigated autophagy as a link between tumorigenesis and adipogenesis using 3T3-L1 cells, which have been shown to closely mimic the in vivo differentiation process. The relative levels of LC3-II/I showed that autophagy was the highest after 4–6 days of initiation of differentiation and it diminished thereafter. Furthermore, chloroquine (CQ), a late autophagy inhibitor, effectively inhibited adipogenic differentiation of 3T3-L1 cells, suggesting that autophagy may have a positive impact on adipogenic differentiation. Notably, real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis showed that CQ completely blocked the mRNA expression of three adipokines (adiponectin, leptin, and peroxisome proliferator-activated receptor-γ (PPARγ)), which increased proportionally to adipocyte differentiation. Using adipokine antibody arrays, we also found that among 38 adipokines examined, 6 adipokines were significantly differentially regulated in mature adipocytes compared to those in preadipocytes. A comparative analysis of adipokine production revealed that CQ-treated adipocytes displayed a profile similar to that of preadipocytes. Subsequently, CQ treatment significantly inhibited the migration capacity of v-Ha-ras-transformed cells in both 3T3-L1 adipocyte-conditioned medium and co-culture with 3T3-L1 using a transwell plate. Taken together, our results suggest that autophagy inhibition blocks the production of mediators relevant to the adipogenic process and may significantly contribute to reducing obesity-related cancer risk.

Inhibition of JNJ-26481585-mediated autophagy induces apoptosis via ROS activation and mitochondrial membrane potential disruption in neuroblastoma cells

Neuroblastoma (NB) is the common pediatric tumor of the sympathetic nervous system characterized by poor prognosis. Owing to the challenges such as high tumor heterogeneity, multidrug resistance, minimal residual disease, etc., there is an immediate need for exploring new therapeutic strategies and effective treatments for NB. Herein, in the current study, we explored the unexplored response of NB cells to the second-generation histone deacetylase inhibitor (HDACi) JNJ-26481585(JNJ) and the lysosomotropic agent, Chloroquine (CQ) alone and upon JNJ/CQ treatment as a plausible therapeutic. We identify that while JNJ alone induced autophagy in NB cells, JNJ/CQ treatment decreased the viability and proliferation of NB cells in vitro by switching from autophagy to apoptosis. Further we found that autophagy inhibition by CQ pre-treatment led to the generation of ROS and a decrease in the mitochondrial membrane potential (MMP) that subsequently caused caspase-3-mediated apoptotic cell death in NB cells. Corroborating the above observations, we found that the ROS scavenger N-acetylcysteine (NAC) countered caspase-3 activity and the cells were rescued from apoptosis. Finally, these observations establish that JNJ/CQ treatment resulted in cell death in NB cells by triggering the formation of ROS and disruption of MMP, suggesting that modulation of JNJ-induced autophagy by CQ represents a promising new therapeutic approach in NB.

Dissecting pharmacological effects of chloroquine in cancer treatment: interference with inflammatory signaling pathways

Chloroquines are 4-aminoquinoline-based drugs mainly used to treat malaria. At pharmacological concentrations, they have significant effects on tissue homeostasis, targeting diverse signaling pathways in mammalian cells. A key target pathway is autophagy, which regulates macromolecule turnover in the cell. In addition to affecting cellular metabolism and bioenergetic flow equilibrium, autophagy plays a pivotal role at the interface between inflammation and cancer progression. Chloroquines consequently have critical effects in tissue metabolic activity and importantly, in key functions of the immune system. In this article, we will review the work addressing the role of chloroquines in the homeostasis of mammalian tissue, and the potential strengths and weaknesses concerning their use in cancer therapy.

Long Term Pharmacological Perturbation of Autophagy in Mice: Are HCQ Injections a Relevant Choice?

Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved catabolic process whose loss-of-function has been linked to a growing list of pathologies. Knockout mouse models of key autophagy genes have been instrumental in the demonstration of the critical functions of autophagy, but they display early lethality, neurotoxicity and unwanted autophagy-independent phenotypes, limiting their applications for in vivo studies. To avoid problems encountered with autophagy-null transgenic mice, we investigated the possibility of disturbing autophagy pharmacologically in the long term. Hydroxychloroquine (HCQ) ip injections were done in juvenile and adult C57bl/6j mice, at range doses adapted from the human malaria prophylactic treatment. The impact on autophagy was assessed by western-blotting, and juvenile neurodevelopment and adult behaviours were evaluated for four months. Quite surprisingly, our results showed that HCQ treatment in conditions used in this study neither impacted autophagy in the long term in several tissues and organs nor altered neurodevelopment, adult behaviour and motor capabilities. Therefore, we recommend for future long-term in vivo studies of autophagy, to use genetic mouse models allowing conditional inhibition of selected Atg genes in appropriate lineage cells instead of HCQ treatment, until it could be successfully revisited using higher HCQ doses and/or frequencies with acceptable toxicity.

Autophagy in cancer: moving from understanding mechanism to improving therapy responses in patients

Autophagy allows for cellular material to be delivered to lysosomes for degradation resulting in basal or stress-induced turnover of cell components that provide energy and macromolecular precursors. These activities are thought to be particularly important in cancer where both tumor-promoting and tumor-inhibiting functions of autophagy have been described. Autophagy has also been intricately linked to apoptosis and programmed cell death, and understanding these interactions is becoming increasingly important in improving cancer therapy and patient outcomes. In this review, we consider how recent discoveries about how autophagy manipulation elicits its effects on cancer cell behavior can be leveraged to improve therapeutic responses.

Mitophagy contributes to alpha-tocopheryl succinate toxicity in GSNOR-deficient hepatocellular carcinoma

The downregulation of the denitrosylating enzyme S-nitrosoglutathione reductase (GSNOR, EC:1.1.1.284), is a feature of hepatocellular carcinoma (HCC). This condition causes mitochondrial rearrangements that sensitize these tumors to mitochondrial toxins, in particular to the mitochondrial complex II inhibitor alpha-tocopheryl succinate (αTOS). It has also been reported the GSNOR depletion impairs the selective degradation of mitochondria through mitophagy; however, if this contributes to GSNOR-deficient HCC cell sensitivity to αTOS and can be applied to anticancer therapies, is still not known. Here, we provide evidence that GSNOR-deficient HCC cells show defective mitophagy which contributes to αTOS toxicity. Mitophagy inhibition by Parkin (EC: 2.3.2.31) depletion enhances αTOS anticancer effects, thus suggesting that this drug could be effective in treating mitophagy-defective tumors.

A Curcumin Derivative Activates TFEB and Protects Against Parkinsonian Neurotoxicity in Vitro

TFEB (transcription factor EB), which is a master regulator of autophagy and lysosome biogenesis, is considered to be a new therapeutic target for Parkinson’s disease (PD). However, only several small-molecule TFEB activators have been discovered and their neuroprotective effects in PD are unclear. In this study, a curcumin derivative, named E4, was identified as a potent TFEB activator. Compound E4 promoted the translocation of TFEB from cytoplasm into nucleus, accompanied by enhanced autophagy and lysosomal biogenesis. Moreover, TFEB knockdown effectively attenuated E4-induced autophagy and lysosomal biogenesis. Mechanistically, E4-induced TFEB activation is mainly through AKT-MTORC1 inhibition. In the PD cell models, E4 promoted the degradation of α-synuclein and protected against the cytotoxicity of MPP⁺ (1-methyl-4-phenylpyridinium ion) in neuronal cells. Overall, the TFEB activator E4 deserves further study in animal models of neurodegenerative diseases, including PD.

A Review of Diatom Lipid Droplets

The dynamic nutrient availability and photon flux density of diatom habitats necessitate buffering capabilities in order to maintain metabolic homeostasis. This is accomplished by the biosynthesis and turnover of storage lipids, which are sequestered in lipid droplets (LDs). LDs are an organelle conserved among eukaryotes, composed of a neutral lipid core surrounded by a polar lipid monolayer. LDs shield the intracellular environment from the accumulation of hydrophobic compounds and function as a carbon and electron sink. These functions are implemented by interconnections with other intracellular systems, including photosynthesis and autophagy. Since diatom lipid production may be a promising objective for biotechnological exploitation, a deeper understanding of LDs may offer targets for metabolic engineering. In this review, we provide an overview of diatom LD biology and biotechnological potential.

Lysosomotropic drugs enhance pro-inflammatory responses to IL-1β in macrophages by inhibiting internalization of the IL-1 receptor

Interleukin (IL)-1 signaling leads to production of pro-inflammatory mediators and is regulated by receptor endocytosis. Lysosomotropic drugs have been linked to increased pro-inflammatory responses under sterile inflammatory conditions but the underlying mechanisms have not been fully elucidated. Here, we report that lysosomotropic drugs potentiate pro-inflammatory effects in response to IL-1β via a mechanism involving reactive oxygen species, p38 mitogen-activated protein kinase and reduced IL-1 receptor internalization. Chloroquine and hydroxychloroquine increased IL-1β-induced CXCL8 secretion in macrophages which was critically dependent on the lysosomotropic character and inhibition of macroautophagy but independent from the NLRP3 inflammasome. Co-stimulation with the autophagy inducer interferon gamma attenuated CXCL8 release. Other lysosomotropic drugs like bafilomycin A₁, fluoxetine and chlorpromazine but also the endocytosis inhibitor dynasore showed similar pro-inflammatory responses. Increased cell surface expression of IL-1 receptor suggests reduced receptor degradation in the presence of lysosomotropic drugs. Our findings provide new insights into a potentially crucial immunoregulatory mechanism in macrophages that may explain how lysosomotropic drugs drive sterile inflammation.

Pharmacological enhancement of TFEB-mediated autophagy alleviated neuronal death in oxidative stress-induced Parkinson's disease models

Autophagy, a conserved cellular degradation and recycling process, can be enhanced by nutrient depletion, oxidative stress or other harmful conditions to maintain cell survival. 6-Hydroxydopamine/ascorbic acid (6-OHDA/AA) is commonly used to induce experimental Parkinson’s disease (PD) lesions by causing oxidative damage to dopaminergic neurons. Activation of autophagy has been observed in the 6-OHDA-induced PD models. However, the mechanism and exact role of autophagy activation in 6-OHDA PD model remain inconclusive. In this study, we report that autophagy was triggered via mucolipin 1/calcium/calcineurin/TFEB (transcription factor EB) pathway upon oxidative stress induced by 6-OHDA/AA. Interestingly, overexpression of TFEB alleviated 6-OHDA/AA toxicity. Moreover, autophagy enhancers, Torin1 (an mTOR-dependent TFEB/autophagy enhancer) and curcumin analog C1 (a TFEB-dependent and mTOR-independent autophagy enhancer), significantly rescued 6-OHDA/AA-induced cell death in SH-SY5Y cells, iPSC-derived DA neurons and mice nigral DA neurons. The behavioral abnormality of 6-OHDA/AA-treated mice can also be rescued by Torin 1 or C1 administration. The protective effects of Torin 1 and C1 can be blocked by autophagy inhibitors like chloroquine (CQ) or by knocking down autophagy-related genes TFEB and ATG5. Taken together, this study supports that TFEB-mediated autophagy is a survival mechanism during oxidative stress and pharmacological enhancement of this process is a neuroprotective strategy against oxidative stress-associated PD lesions.

Mechanisms of action of hydroxychloroquine and chloroquine: implications for rheumatology

Despite widespread clinical use of antimalarial drugs such as hydroxychloroquine and chloroquine in the treatment of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and other inflammatory rheumatic diseases, insights into the mechanism of action of these drugs are still emerging. Hydroxychloroquine and chloroquine are weak bases and have a characteristic 'deep' volume of distribution and a half-life of around 50 days. These drugs interfere with lysosomal activity and autophagy, interact with membrane stability and alter signalling pathways and transcriptional activity, which can result in inhibition of cytokine production and modulation of certain co-stimulatory molecules. These modes of action, together with the drug's chemical properties, might explain the clinical efficacy and well-known adverse effects (such as retinopathy) of these drugs. The unknown dose-response relationships of these drugs and the lack of definitions of the minimum dose needed for clinical efficacy and what doses are toxic pose challenges to clinical practice. Further challenges include patient non-adherence and possible context-dependent variations in blood drug levels. Available mechanistic data give insights into the immunomodulatory potency of hydroxychloroquine and provide the rationale to search for more potent and/or selective inhibitors.

The novel proautophagy anticancer drug ABTL0812 potentiates chemotherapy in adenocarcinoma and squamous nonsmall cell lung cancer

Around 40% of newly diagnosed lung cancer patients are Stage IV, where the improvement of survival and reduction of disease-related adverse events is the main goal for oncologists. In this scenario, we present preclinical evidence supporting the use of ABTL0812 in combination with chemotherapy for treating advanced and metastatic Nonsmall cell lung adenocarcinomas (NSCLC) and squamous carcinomas. ABTL0812 is a new chemical entity, currently in Phase 1b/2a clinical trial for advanced squamous NSCLC in combination with paclitaxel and carboplatin (P/C), after successfully completing the first-in-human trial where it showed an excellent safety profile and signs of efficacy. We show here that ABTL0812 inhibits Akt/mTOR axis by inducing the overexpression of TRIB3 and activating autophagy in lung squamous carcinoma cell lines. Furthermore, treatment with ABTL0812 also induces AMPK activation and ROS accumulation. Moreover, combination of ABTL0812 with chemotherapy markedly increases the therapeutic effect of chemotherapy without increasing toxicity. We further show that combination of ABTL0812 and chemotherapy induces nonapoptotic cell death mediated by TRIB3 activation and autophagy induction. We also present preliminary clinical data indicating that TRIB3 could serve as a potential novel pharmacodynamic biomarker to monitor ABTL0812 activity administered alone or in combination with chemotherapy in squamous NSCLC patients. The safety profile of ABTL0812 and its good synergy with chemotherapy potentiate the therapeutic potential of current lines of treatment based on chemotherapy regimens, arising as a promising option for improving these patients therapeutic expectancy.

Mass spectrometry proteomics reveals a function for mammalian CALCOCO1 in MTOR-regulated selective autophagy

Macroautophagy/autophagy is suppressed by MTOR (mechanistic target of rapamycin kinase) and is an anticancer target under active investigation. Yet, MTOR-regulated autophagy remains incompletely mapped. We used proteomic profiling to identify proteins in the MTOR-autophagy axis. Wild-type (WT) mouse cell lines and cell lines lacking individual autophagy genes (Atg5 or Ulk1/Ulk2) were treated with an MTOR inhibitor to induce autophagy and cultured in media with either glucose or galactose. Mass spectrometry proteome profiling revealed an elevation of known autophagy proteins and candidates for new autophagy components, including CALCOCO1 (calcium binding and coiled-coil domain protein 1). We show that CALCOCO1 physically interacts with MAP1LC3C, a key protein in the machinery of autophagy. Genetic deletion of CALCOCO1 disrupted autophagy of the endoplasmic reticulum (reticulophagy). Together, these results reveal a role for CALCOCO1 in MTOR-regulated selective autophagy. More generally, the resource generated by this work provides a foundation for establishing links between the MTOR-autophagy axis and proteins not previously linked to this pathway. Abbreviations: ATG: autophagy-related; CALCOCO1: calcium binding and coiled-coil domain protein 1; CALCOCO2/NDP52: calcium binding and coiled-coil domain protein 2; CLIR: MAP1LC3C-interacting region; CQ: chloroquine; KO: knockout; LIR: MAP1LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; MLN: MLN0128 ATP-competitive MTOR kinase inhibitor; MTOR: mechanistic target of rapamycin kinase; reticulophagy: selective autophagy of the endoplasmic reticulum; TAX1BP1/CALCOCO3: TAX1 binding protein 1; ULK: unc 51-like autophagy activating kinase; WT: wild-type.

Combined EGFR and ROCK Inhibition in Triple-negative Breast Cancer Leads to Cell Death Via Impaired Autophagic Flux

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with very limited therapeutic options. We have recently shown that the combined inhibition of EGFR and ROCK in TNBC cells results in cell death, however, the underlying mechanisms remain unclear. To investigate this, here we applied a mass spectrometry-based proteomic approach to identify proteins altered on single and combination treatments. Our proteomic data revealed autophagy as the major molecular mechanism implicated in the cells' response to combinatorial treatment. We here show that EGFR inhibition by gefitinib treatment alone induces autophagy, a cellular recycling process that acts as a cytoprotective response for TNBC cells. However, combined inhibition of EGFR and ROCK leads to autophagy blockade and accumulation of autophagic vacuoles. Our data show impaired autophagosome clearance as a likely cause of antitumor activity. We propose that the inhibition of the autophagic flux on combinatorial treatment is attributed to the major cytoskeletal changes induced on ROCK inhibition, given the essential role the cytoskeleton plays throughout the various steps of the autophagy process.

AXL Targeting Abrogates Autophagic Flux and Induces Immunogenic Cell Death in Drug-Resistant Cancer Cells

INTRODUCTION

Acquired cancer therapy resistance evolves under selection pressure of immune surveillance and favors mechanisms that promote drug resistance through cell survival and immune evasion. AXL receptor tyrosine kinase is a mediator of cancer cell phenotypic plasticity and suppression of tumor immunity, and AXL expression is associated with drug resistance and diminished long-term survival in a wide range of malignancies, including NSCLC.

METHODS

We aimed to investigate the mechanisms underlying AXL-mediated acquired resistance to first- and third-generation small molecule EGFR tyrosine kinase inhibitors (EGFRi) in NSCLC.

RESULTS

We found that EGFRi resistance was mediated by up-regulation of AXL, and targeting AXL reduced reactivation of the MAPK pathway and blocked onset of acquired resistance to long-term EGFRi treatment in vivo. AXL-expressing EGFRi-resistant cells revealed phenotypic and cell signaling heterogeneity incompatible with a simple bypass signaling mechanism, and were characterized by an increased autophagic flux. AXL kinase inhibition by the small molecule inhibitor bemcentinib or siRNA mediated AXL gene silencing was reported to inhibit the autophagic flux in vitro, bemcentinib treatment blocked clonogenicity and induced immunogenic cell death in drug-resistant NSCLC in vitro, and abrogated the transcription of autophagy-associated genes in vivo. Furthermore, we found a positive correlation between AXL expression and autophagy-associated gene signatures in a large cohort of human NSCLC (n = 1018).

CONCLUSION

Our results indicate that AXL signaling supports a drug-resistant persister cell phenotype through a novel autophagy-dependent mechanism and reveals a unique immunogenic effect of AXL inhibition on drug-resistant NSCLC cells.

Exosome-transmitted miR-567 reverses trastuzumab resistance by inhibiting ATG5 in breast cancer

Trastuzumab is commonly used in the treatment of human epidermal growth factor receptor-2 positive (HER-2+) breast cancer, but its efficacy is often limited by the emergence of chemoresistance. Recent studies indicate that exosomes act as vehicles for exchange of genetic cargo between heterogeneous populations of tumor cells, engendering a transmitted drug resistance for cancer development and progression. However, the specific contribution of breast cancer-derived exosomes is poorly understood. In this study, publicly available expression profiling data from breast cancer and bioinformatics analyses were used to screen potential miRNAs in trastuzumab resistance. A series of gain- or loss-functional assays were performed to define the function of miR-567 and ATG5 in trastuzumab resistance and autophagy, both in vitro and in vivo. Our results showed that miR-567 was significantly decreased in trastuzumab-resistant patients compared with responding patients. Moreover, miR-567 was also downregulated in trastuzumab-resistant cells compared with parental cells. Overexpression of miR-567 reversed chemoresistance, whereas silence of miR-567 induced trastuzumab resistance, both in vitro and in vivo. In addition, enhanced miR-567 could be packaged into exosomes, incorporated into receipt cells, suppressing autophagy and reversed chemoresistance by targeting ATG5. To conclude, exosomal miR-567 plays a key role in reversing trastuzumab resistance via regulating autophagy, indicating it may be a promising therapeutic target and prognostic indicator for breast cancer patients.

Autophagy Inhibition Induces the Secretion of Macrophage Migration Inhibitory Factor (MIF) with Autocrine and Paracrine Effects on the Promotion of Malignancy in Breast Cancer

Breast cancer is the main cause of cancer-related death in women in the world. Because autophagy is a known survival pathway for cancer cells, its inhibition is currently being explored in clinical trials for treating several types of malignancies. In breast cancer, autophagy has been shown to be necessary for the survival of cancer cells from the triple negative subtype (TNBC), which has the worst prognosis among breast cancers and currently has limited therapeutic options. Autophagy has also been involved in the regulation of protein secretion and, of importance for this work, the inhibition of autophagy is known to promote the secretion of proinflammatory cytokines from distinct cell types. We found that the inhibition of autophagy in TNBC cell lines induced the secretion of the macrophage migration inhibitory factor (MIF), a pro-tumorigenic cytokine involved in breast cancer invasion and immunomodulation. MIF secretion was dependent on an increase in reactive oxygen species (ROS) induced by the inhibition of autophagy. Importantly, MIF secreted from autophagy-deficient cells increased the migration of cells not treated with autophagy inhibitors, indicating that autophagy inhibition in cancer cells promoted malignancy in neighboring cells through the release of secreted factors, and that a combinatorial approach should be evaluated for cancer therapy.

Zebrafish C-reactive protein isoforms inhibit SVCV replication by blocking autophagy through interactions with cell membrane cholesterol

In the present work, the mechanisms involved in the recently reported antiviral activity of zebrafish C-reactive protein-like protein (CRP1-7) against the spring viraemia of carp rhabdovirus (SVCV) in fish are explored. The results neither indicate blocking of the attachment or the binding step of the viral replication cycle nor suggest the direct inhibition of G protein fusion activity or the stimulation of the host’s interferon system. However, an antiviral state in the host is induced. Further results showed that the antiviral protection conferred by CRP1-7 was mainly due to the inhibition of autophagic processes. Thus, given the high affinity of CRPs for cholesterol and the recently described influence of the cholesterol balance in lipid rafts on autophagy, both methyl-β-cyclodextrin (a cholesterol-complexing agent) and 25-hydroxycholesterol (a cholesterol molecule with antiviral properties) were used to further describe CRP activity. All the tested compounds exerted antiviral activity by affecting autophagy in a similar manner. Further assays indicate that CRP reduces autophagy activity by initially disturbing the cholesterol ratios in the host cellular membranes, which in turn negatively affects the intracellular regulation of reactive oxygen species (ROS) and increases lysosomal pH as a consequence. Ultimately, here we propose that such pH changes exert an inhibitory direct effect on SVCV replication by disrupting the pH-dependent membrane-fusogenic ability of the viral glycoprotein G, which allows the release of the virus from endosomes into cytoplasm during its entry phase.

Mitochondrial Quality Control: Role in Cardiac Models of Lethal Ischemia-Reperfusion Injury

The current standard of care for acute myocardial infarction or 'heart attack' is timely restoration of blood flow to the ischemic region of the heart. While reperfusion is essential for the salvage of ischemic myocardium, re-introduction of blood flow paradoxically kills (rather than rescues) a population of previously ischemic cardiomyocytes-a phenomenon referred to as 'lethal myocardial ischemia-reperfusion (IR) injury'. There is long-standing and exhaustive evidence that mitochondria are at the nexus of lethal IR injury. However, during the past decade, the paradigm of mitochondria as mediators of IR-induced cardiomyocyte death has been expanded to include the highly orchestrated process of mitochondrial quality control. Our aims in this review are to: (1) briefly summarize the current understanding of the pathogenesis of IR injury, and (2) incorporating landmark data from a broad spectrum of models (including immortalized cells, primary cardiomyocytes and intact hearts), provide a critical discussion of the emerging concept that mitochondrial dynamics and mitophagy (the components of mitochondrial quality control) may contribute to the pathogenesis of cardiomyocyte death in the setting of ischemia-reperfusion.

HMGB1/RAGE axis mediates stress-induced RVLM neuroinflammation in mice via impairing mitophagy flux in microglia

Background

Microglial mediated neuroinflammation in the rostral ventrolateral medulla (RVLM) plays roles in the etiology of stress-induced hypertension (SIH). It was reported that autophagy influenced inflammation via immunophenotypic switching of microglia. High-mobility group box 1 (HMGB1) acts as a regulator of autophagy and initiates the production of proinflammatory cytokines (PICs), but the underlying mechanisms remain unclear.

Methods

The stressed mice were subjected to intermittent electric foot shocks plus noises administered for 2 h twice daily for 15 consecutive days. In mice, blood pressure (BP) and renal sympathetic nerve activity (RSNA) were monitored by noninvasive tail-cuff method and platinum-iridium electrodes placed respectively. Microinjection of siRNA-HMGB1 (siHMGB1) into the RVLM of mice to study the effect of HMGB1 on microglia M1 activation was done. mRFP-GFP-tandem fluorescent LC3 (tf-LC3) vectors were transfected into the RVLM to evaluate the process of autolysosome formation/autophagy flux. The expression of RAB7, lysosomal-associated membrane protein 1 (LAMP1), and lysosomal pH change were used to evaluate lysosomal function in microglia. Mitophagy was identified by transmission electron microscopic observation or by checking LC3 and MitoTracker colocalization under a confocal microscope.

Results

We showed chronic stress increased cytoplasmic translocations of HMGB1 and upregulation of its receptor RAGE expression in microglia. The mitochondria injury, oxidative stress, and M1 polarization were attenuated in the RVLM of stressed Cre-CX3CR1/RAGE^fl/fl mice. The HMGB1/RAGE axis increased at the early stage of stress-induced mitophagy flux while impairing the late stages of mitophagy flux in microglia, as revealed by decreased GFP fluorescence quenching of GFP-RFP-LC3-II puncta and decreased colocalization of lysosomes with mitochondria. The expressions of RAB7 and LAMP1 were decreased in the stressed microglia, while knockout of RAGE reversed these effects and caused an increase in acidity of lysosomes. siHMGB1 in the RVLM resulted in BP lowering and RSNA decreasing in SIH mice. When the autophagy inducer, rapamycin, is used to facilitate the mitophagy flux, this treatment results in attenuated NF-κB activation and reduced PIC release in exogenous disulfide HMGB1 (ds-HMGB1)-stimulated microglia.

Conclusions

Collectively, we demonstrated that inhibition of the HMGB1/RAGE axis activation led to increased stress-induced mitophagy flux, hence reducing the activity of microglia-mediated neuroinflammation and consequently reduced the sympathetic vasoconstriction drive in the RVLM.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1673-3) contains supplementary material, which is available to authorized users.

Genome-wide CRISPR screen identifies host dependency factors for influenza A virus infection

Host dependency factors that are required for influenza A virus infection may serve as therapeutic targets as the virus is less likely to bypass them under drug-mediated selection pressure. Previous attempts to identify host factors have produced largely divergent results, with few overlapping hits across different studies. Here, we perform a genome-wide CRISPR/Cas9 screen and devise a new approach, meta-analysis by information content (MAIC) to systematically combine our results with prior evidence for influenza host factors. MAIC out-performs other meta-analysis methods when using our CRISPR screen as validation data. We validate the host factors, WDR7, CCDC115 and TMEM199, demonstrating that these genes are essential for viral entry and regulation of V-type ATPase assembly. We also find that CMTR1, a human mRNA cap methyltransferase, is required for efficient viral cap snatching and regulation of a cell autonomous immune response, and provides synergistic protection with the influenza endonuclease inhibitor Xofluza.

Here, Li et al. perform a genome-wide CRISPR screen to identify host dependency factors for influenza A virus infection and show that the host mRNA cap methyltransferase CMTR1 is important for viral cap snatching and that it affects expression of antiviral genes.

Chloroquine differentially modulates coronary vasodilation in control and diabetic mice

BACKGROUND AND PURPOSE

Chloroquine is a traditional medicine to treat malaria. There is increasing evidence that chloroquine not only induces phagocytosis but regulates vascular tone. Few reports investigating the effect of chloroquine on vascular responsiveness of coronary arteries have been made. In this study, we examined how chloroquine affected endothelium-dependent relaxation in coronary arteries under normal and diabetic conditions.

EXPERIMENTAL APPROACH

We isolated coronary arteries from mice and examined endothelium-dependent relaxation (EDR). Human coronary endothelial cells and mouse coronary endothelial cells isolated from control and diabetic mouse (TALLYHO/Jng [TH] mice, a spontaneous type 2 diabetic mouse model) were used for the molecular biological or cytosolic NO and Ca²⁺ measurements.

KEY RESULTS

Chloroquine inhibited endothelium-derived NO-dependent relaxation but had negligible effect on endothelium-derived hyperpolarization (EDH)-dependent relaxation in coronary arteries of control mice. Chloroquine significantly decreased NO production in control human coronary endothelial cells partly by phosphorylating eNOS^Thr495 (an inhibitory phosphorylation site of eNOS) and attenuating the rise of cytosolic Ca²⁺ concentration after stimulation. EDR was significantly inhibited in diabetic mice in comparison to control mice. Interestingly, chloroquine enhanced EDR in diabetic coronary arteries by, specifically, increasing EDH-dependent relaxation due partly to its augmenting effect on gap junction activity in diabetic mouse coronary endothelial cells.

CONCLUSIONS AND IMPLICATIONS

These data indicate that chloroquine affects vascular relaxation differently under normal and diabetic conditions. Therefore, the patients' health condition such as coronary macrovascular or microvascular disease, with or without diabetes, must be taken account into the consideration when selecting chloroquine for the treatment of malaria.

miR-218 Inhibits Mitochondrial Clearance by Targeting PRKN E3 Ubiquitin Ligase

The selective elimination of dysfunctional mitochondria through mitophagy is crucial for preserving mitochondrial quality and cellular homeostasis. The most described mitophagy pathway is regulated by a positive ubiquitylation feedback loop in which the PINK1 (PTEN induced kinase 1) kinase phosphorylates both ubiquitin and the E3 ubiquitin ligase PRKN (Parkin RBR E3 ubiquitin ligase), also known as PARKIN. This event recruits PRKN to the mitochondria, thus amplifying ubiquitylation signal. Here we report that miR-218 targets PRKN and negatively regulates PINK1/PRKN-mediated mitophagy. Overexpression of miR-218 reduces PRKN mRNA levels, thus also reducing protein content and deregulating the E3 ubiquitin ligase action. In fact, following miR-218 overexpression, mitochondria result less ubiquitylated and the autophagy machinery fails to proceed with correct mitochondrial clearance. Since mitophagy defects are associated with various human diseases, these results qualify miR-218 as a promising therapeutic target for human diseases.

ROCK inhibitors upregulate the neuroprotective Parkin-mediated mitophagy pathway

The accumulation of damaged mitochondria causes the death of dopaminergic neurons. The Parkin-mediated mitophagy pathway functions to remove these mitochondria from cells. Targeting this pathway represents a therapeutic strategy for several neurodegenerative diseases, most notably Parkinson's disease. We describe a discovery pipeline to identify small molecules that increase Parkin recruitment to damaged mitochondria and ensuing mitophagy. We show that ROCK inhibitors promote the activity of this pathway by increasing the recruitment of HK2, a positive regulator of Parkin, to mitochondria. This leads to the increased targeting of mitochondria to lysosomes and removal of damaged mitochondria from cells. Furthermore, ROCK inhibitors demonstrate neuroprotective effects in flies subjected to paraquat, a parkinsonian toxin that induces mitochondrial damage. Importantly, parkin and rok are required for these effects, revealing a signaling axis which controls Parkin-mediated mitophagy that may be exploited for the development of Parkinson's disease therapeutics.

Tissue-infiltrating macrophages mediate an exosome-based metabolic reprogramming upon DNA damage

DNA damage and metabolic disorders are intimately linked with premature disease onset but the underlying mechanisms remain poorly understood. Here, we show that persistent DNA damage accumulation in tissue-infiltrating macrophages carrying an ERCC1-XPF DNA repair defect (Er1^F/−) triggers Golgi dispersal, dilation of endoplasmic reticulum, autophagy and exosome biogenesis leading to the secretion of extracellular vesicles (EVs) in vivo and ex vivo. Macrophage-derived EVs accumulate in Er1^F/− animal sera and are secreted in macrophage media after DNA damage. The Er1^F/− EV cargo is taken up by recipient cells leading to an increase in insulin-independent glucose transporter levels, enhanced cellular glucose uptake, higher cellular oxygen consumption rate and greater tolerance to glucose challenge in mice. We find that high glucose in EV-targeted cells triggers pro-inflammatory stimuli via mTOR activation. This, in turn, establishes chronic inflammation and tissue pathology in mice with important ramifications for DNA repair-deficient, progeroid syndromes and aging.

DNA damage is associated with metabolic disorders, but the mechanism in unclear. Here, the authors show that persistent DNA damage induced by lack of the endonuclease XPF-ERCC1 triggers extracellular vesicle biogenesis in tissue infiltrating macrophages, and that vesicle uptake stimulates glucose uptake in recipient cells, leading to increased inflammation.

Shikonin induces colorectal carcinoma cells apoptosis and autophagy by targeting galectin-1/JNK signaling axis

Colorectal carcinoma (CRC) is the third most common malignant tumor pathology worldwide. Despite progress in surgical procedures and therapy options, CRC is still a considerable cause of cancer-related mortality. In this study, we tested the antitumor effects of shikonin in CRC and tried to identify its potential mechanism. The potential target, molecular mechanism as well as in vitro and in vivo antitumor effects of shikonin in CRC cells were determined by an integrative protocol including quantitative proteomics, RT-PCR, western blotting, RNA interference and overexpression, apoptosis and autophagy assays, etc. Galectin-1 was a potential target of shikonin from the iTRAQ-based proteomic analysis in shikonin-treated SW620 cell. The overexpression and RNA silencing of galectin-1 in two CRC cells suggested that the shikonin sensitivity was correlation to galectin-1 levels. The ROS accumulation induced by shikonin was important to the formation of galectin-1 dimers. Dimer galectin-1 was found to be associated with the activation of JNK and downstream apoptosis or autophagy. Moreover, through functional in vitro studies, we showed that differences in galectin-1 level affected tumor cell proliferation, migration, and invasion. In summary, shikonin induced CRC cells apoptosis and autophagy by targeting galectin-1 and JNK signaling pathway both in vitro and in vivo, which suggested a potential novel therapy target for CRC.

Iron-Induced Apoptotic Cell Death and Autophagy Dysfunction in Human Neuroblastoma Cell Line SH-SY5Y

Iron accumulation plays a major role in neuronal cell death which has severe effects on mental health like neurodegenerative disorders. The present work aims to explore the involvement of molecular pathways involved in iron-mediated neuronal cell death using Ferric Ammonium Citrate (FAC) as a source of iron to treat neuroblastoma SH-SY5Y cells. In this study, it was found that cytotoxicity induced by iron treatment is highly correlated with enhanced intracellular reactive oxygen species (ROS) generation and loss of mitochondrial integrity. Appearance of early and late apoptotic cells with altered nuclear morphology and increased expression of effector proteins, i.e., cleaved Caspase 3 and cleaved PARP (Poly-ADP-ribose Polymerase), clearly confirmed iron-induced apoptotic cell deaths. Furthermore, excess accumulation of acidic vesicles and microtubule-associated protein 1 light chain 3 (LC3) puncta and LC3II/I expressions were observed. Simultaneously, ultrastructural studies of SH-SY5Y cells demonstrated the accumulation of a large number of autophagosomes, autophagic vacuolization, and swollen mitochondria which further confirmed the induction of autophagy concomitant with mitochondrial damage. Furthermore, increased incorporation of lysosome-specific dye, LysoTracker Deep Red, and the red fluorescence retention of LC3-GFP-RFP constructs indicates the incomplete autophagy or autophagy dysfunction due to altered lysosomal activity. Hence, the present work unveiled the interruption in autophagy progression caused by the plausible suppression of lysosomal activity due to iron treatment resulting in autophagic cell death in SH-SY5Y cell lines. In general, both apoptotic and autophagic pathways were prominent and each of the pathways played their prospective roles, in iron-mediated neuronal cell death.

Induction of immunogenic cell death in cancer cells by a photoactivated platinum(IV) prodrug

The platinum(_IV) prodrug trans,trans,trans-[Pt(N₃)₂(OH)₂(py)₂] (1) is stable and non-toxic in the dark, but potently cytotoxic to cancer cells when irradiated by visible light, including cisplatin-resistant cells. On irradiation with visible light, it generates reactive Pt(II) species which can attack DNA, and produces reactive oxygen species (ROS) and reactive nitrogen species (RNS) which exert unusual effects on biochemical pathways. We now show that its novel mechanism of action includes induction of immunogenic cell death (ICD). Treatment of cancer cells with 1 followed by photoirradiation with visible light induces calreticulin (CRT) expression at the surface of dying cancer cells. This is accompanied by release of high mobility group protein-1B (HMGB1) and the secretion of ATP. Autophagy appears to play a key role in this chemotherapeutically-stimulated ICD. The observed uneven distribution of ecto-CRT promotes phagocytosis, confirmed by the observation of engulfment of photoirradiated CT26 colorectal cancer cells treated with 1 by J774.A1 macrophages. The photoactivatable prodrug 1 has a unique mechanism of action which distinguishes it from other platinum drugs due to its immunomodulating properties, which may enhance its anticancer efficacy.

The changing landscape of SARS-CoV-2: Implications for the maternal-infant dyad

The COVID-19 pandemic represents the greatest challenge to date faced by the medical community in the 21st century. The rate of rapid dissemination, magnitude of viral contagiousness, person to person transmission at an asymptomatic phase of illness pose a unique and dangerous challenge for all patients, including neonatal and obstetric patients. Although scientific understanding of the pathophysiology of the disease, nature of transmission, and efficacy of mitigation strategies is growing, neither a cure or vaccine have been developed. While COVID-19 is primarily a disease of older patients, infection is now seen across all age demographics with reports of illness in pregnant patients and infants. Altered hormone status and predominance of Th-2 immune helper cells may result in increased predisposition to SARS-CoV-2. Case reports of pregnant patients demonstrate a clinical presentation comparable to non-pregnant adults, but evidence of vertical transmission to the fetus is controversial. Neonatal reports demonstrate an inconsistent and non-specific phenotype, and it is often difficult to separate COVID-19 from the underlying conditions of prematurity or bacterial infection. The development of international registries to enable risk profiling of COVID-19 positive pregnant mothers and/or their offspring may facilitate the development of enhanced mitigation strategies, medical treatments and effective vaccinations.

Apigenin induced autophagy and stimulated autophagic lipid degradation

Apigenin could induce autophagic lipid degradation by restoring the blocked autophagic flux in PA-induced HepG2 cells.

CHK2-FOXK axis promotes transcriptional control of autophagy programs

Autophagy is an evolutionarily conserved catabolic process, which plays a vital role in removing misfolded proteins and clearing damaged organelles to maintain internal environment homeostasis. Here, we uncovered the checkpoint kinase 2 (CHK2)-FOXK (FOXK1 and FOXK2) axis playing an important role in DNA damage-mediated autophagy at the transcriptional regulation layer. Mechanistically, following DNA damage, CHK2 phosphorylates FOXK and creates a 14-3-3γ binding site, which, in turn, traps FOXK proteins in the cytoplasm. Because FOXK functions as the transcription suppressor of ATGs, DNA damage-mediated FOXKs' cytoplasmic trapping induces autophagy. In addition, we found that a cancer-derived FOXK mutation induces FOXK hyperphosphorylation and enhances autophagy, resulting in chemoresistance. Cotreatment with cisplatin and chloroquine overcomes the chemoresistance caused by FOXK mutation. Overall, our study highlights a mechanism whereby DNA damage triggers autophagy by increasing autophagy genes via CHK2-FOXK-mediated transcriptional control, and misregulation of this pathway contributes to chemoresistance.

Spatial targeting of Bcl-2 on endoplasmic reticulum and mitochondria in cancer cells by lipid nanoparticles

The presence of the same proteins at different sub-cellular locations with completely different functions adds to the complexity of signalling pathways in cancer.

Autophagy Induction by HDAC Inhibitors Is Unlikely to be the Mechanism of Efficacy in Prevention of Retinal Degeneration Caused by P23H Rhodopsin

We previously found that valproic acid (VPA) and other histone deacetylase inhibitors (HDACis) ameliorate retinal degeneration (RD) caused by P23H rhodopsin in Xenopus laevis larvae and hypothesized that this may be due to enhancement of autophagy. Here we use X. laevis expressing an autophagy marker to assess effects of HDACis on autophagy. We also assess the effects of non-HDACi activators and inducers of autophagy on RD caused by P23H rhodopsin.

Multichannel DNA Sensor Array Fingerprints Cell States and Identifies Pharmacological Effectors of Catabolic Processes

Cells at disease onset are often associated with subtle changes in the expression level of a single or few molecular components, making traditionally used biomarker-driven clinical diagnosis a challenging task. We demonstrate here the design of a DNA nanosensor array with multichannel output that identifies the normal or pathological state of a cell based on the alteration of its global proteomic signature. Fluorophore-encoded single-stranded DNA (ssDNA) strands were coupled via supramolecular interaction with a surface-functionalized gold nanoparticle quencher to generate this integrated sensor array. In this design, ssDNA sequences exhibit dual roles, where they provide differential affinities with the receptor gold nanoparticle as well as act as transducer elements. The unique interaction mode of the analyte molecules disrupts the noncovalent supramolecular complexation, generating simultaneous multichannel fluorescence output to enable signature-based analyte identification via a linear discriminant analysis-based machine learning algorithm. Different cell types, particularly normal and cancerous cells, were effectively distinguished using their fluorescent fingerprints. Additionally, this DNA sensor array displayed excellent sensitivity to identify cellular alterations associated with chemical modulation of catabolic processes. Importantly, pharmacological effectors, which could modulate autophagic flux, have been effectively distinguished by generating responses from their global protein signatures. Taken together, these studies demonstrate that our multichannel DNA nanosensor is well suited for rapid identification of subtle changes in a complex mixture and thus can be readily expanded for point-of-care clinical diagnosis, high-throughput drug screening, or predicting the therapeutic outcome from a limited sample volume.