Role of p62/SQSTM1 beyond autophagy: a lesson learned from drug-induced toxicity in vitro

Alpha-ketoglutarate promotes anxiety, activates autophagy, and suppresses antioxidant enzymes in the cerebral cortex of female mice on cafeteria diet

Alpha-ketoglutarate (AKG), an intermediate of the tricarboxylic acid cycle, has been found to mitigate oxidative stress and inflammation. In turn, a cafeteria diet (CD), an obesogenic diet, is often associated with oxidative stress and inflammation. This study aimed to determine whether AKG can level the effects of CD on animal behavior, oxidative stress markers, glycolytic flow, and autophagy in the mouse cerebral cortex. Female C57BL/6 J mice were divided into two groups and fed either a standard diet or a CD for eight weeks. For the next four weeks, each group continued to be fed the previous diet; however, half of the individuals within each group received drinking water with 1 % AKG. Using an open field test, we found that the combination of CD and AKG promoted the development of anxiety signs. Both CD and AKG decreased the exploratory behavior of mice, with a significant additive effect in the combined diet. On diets supplemented with AKG, animals produced fewer fecal boli, a measure of emotionality. On all experimental diets, mice had lower activities of antioxidant and related enzymes, with no significant differences in the activities of glycolytic enzymes. The AKG-supplemented diet induced the transcription of autophagy-related genes and targets of the forkhead box O factor, involved in the regulation of carbohydrate metabolism. Transcriptional changes induced by AKG were partly abrogated by the CD. These findings suggest that AKG, particularly when combined with CD, may modulate behavioral responses and oxidative stress intensity in the brain by altering key metabolic and autophagic pathways.

Cleavage of SQSTM1/p62 by the Zika virus protease NS2B3 prevents autophagic degradation of viral NS3 and NS5 proteins

Macroautophagy/autophagy plays a crucial role in inhibiting viral replication and regulating the host's immune response. The autophagy receptor SQSTM1/p62 (sequestosome 1) restricts viral replication by directing specific viral proteins to phagophores for degradation. In this study, we investigate the reciprocal relationship between Zika virus (ZIKV) and selective autophagy mediated by SQSTM1/p62. We show that NS2B3 protease encoded by ZIKV cleaves human SQSTM1/p62 at arginine 265 (R265). This cleavage also occurs with endogenous SQSTM1 in ZIKV-infected cells. Furthermore, overexpression of SQSTM1 inhibits ZIKV replication in A549 cells, while its absence increases viral titer. We have also shown that SQSTM1 impedes ZIKV replication by interacting with NS3 and NS5 and directing them to autophagic degradation, and that NS2B3-mediated cleavage could potentially alter this antiviral function of SQSTM1. Taken together, our study highlights the role of SQSTM1-mediated selective autophagy in the host's antiviral defense against ZIKV and uncovers potential viral evasion strategies that exploit the host's autophagic machinery to ensure successful infection.Abbreviation: Cas9: CRISPR-associated protein 9; Co-IP: co-immunoprecipitation; CRISPR: clustered regularly interspaced short palindromic repeats; DENV: dengue virus; GFP: green fluorescent protein; IFA: indirect immunofluorescence assay; KIR: KEAP1-interacting region; KO: knockout; LIR: MAP1LC3/LC3-interacting region; mAb: monoclonal antibody; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; pAb: polyclonal antibody; PB1: Phox/BEM1 domain; R265A, a SQSTM1 construct with the arginine (R) residue at position 265 replaced with glutamic acid (A); SQSTM1: sequestosome 1; SQSTM1-C, C-terminal fragment of SQSTM1; SQSTM1-N, N-terminal fragment of SQSTM1; SVV: Seneca Valley virus; TAX1BP1: Tax1 binding protein 1; TBD: TRAF6-binding domain; TCID50: 50% tissue culture infective dose; UBA: ubiquitin-associated domain; Ub: ubiquitin; WT: wild type; ZIKV: Zika virus; ZZ: ZZ-type zinc finger domain.

Dipsacoside B Attenuates Atherosclerosis by Promoting Autophagy to Inhibit Macrophage Lipid Accumulation

Atherosclerosis is a chronic inflammatory disease characterized by lipid accumulation and foam cell formation in the arterial wall. Promoting macrophage autophagy has emerged as a promising therapeutic strategy against atherosclerosis. Dipsacoside B (DB) is an oleanane-type pentacyclic triterpenoid saponin extracted from Lonicerae flos with potential anti-atherosclerotic properties. In this study, we investigated the effects of DB on atherosclerosis progression in ApoE-/- mice fed a high-fat diet and explored the underlying mechanisms in oxidized low-density lipoprotein (ox-LDL)-induced foam cells. DB treatment significantly reduced atherosclerotic lesion size, improved plaque stability, and regulated lipid metabolism without impairing liver and kidney function in ApoE-/- mice. In vitro studies revealed that DB dose-dependently inhibited ox-LDL internalization and intracellular lipid accumulation in RAW264.7 macrophages. Mechanistically, DB induced autophagy, as evidenced by increased autophagosome formation and upregulated expression of autophagy markers LC3-II and p62 both in vivo and in vitro. Inhibition of autophagy by chloroquine abolished the antiatherosclerotic and pro-autophagic effects of DB. Furthermore, DB treatment increased LC3-II and p62 mRNA levels, suggesting transcriptional regulation of autophagy. Collectively, our findings demonstrate that DB exerts anti-atherosclerotic effects by inhibiting foam cell formation via autophagy induction, providing new insights into the pharmacological actions of DB and its potential as a therapeutic agent against atherosclerosis.

DDIT3/CHOP promotes LPS/ATP-induced pyroptosis in osteoblasts via mitophagy inhibition

Inflammatory environments can trigger endoplasmic reticulum (ER) stress and lead to pyroptosis in various tissues and cells, including liver, brain, and immune cells. As a key factor of ER stress, DNA damage-inducible transcript 3 (DDIT3)/CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) is upregulated in osteoblasts during inflammatory stimulation. DDIT3/CHOP may therefore regulate osteoblast pyroptosis in inflammatory conditions. During this investigation, we found that lipopolysaccharides (LPS)/adenosine 5'-triphosphate (ATP) stimulation in vitro induced osteoblasts to undergo pyroptosis, and the expression of DDIT3/CHOP was increased during this process. The overexpression of DDIT3/CHOP further promoted osteoblast pyroptosis as evidenced by the increased expression of the inflammasome NLR family pyrin domain containing 3 (NLRP3) and ratios of caspase-1 p20/caspase-1 and cleaved gasdermin D (GSDMD)/GSDMD. To explore the specific mechanism of this effect, we found through fluorescence imaging and Western blot analysis that LPS/ATP stimulation promoted PTEN-induced kinase 1 (PINK1)/E3 ubiquitin-protein ligase parkin (Parkin)-mediated mitophagy in osteoblasts, and this alteration was suppressed by the DDIT3/CHOP overexpression, resulting in increased ratio of pyroptosis compared with the control groups. The impact of DDIT3/CHOP on pyroptosis in osteoblasts was reversed by the application of carbonyl cyanide 3-chlorophenylhydrazone (CCCP), a specific mitophagy agonist. Therefore, our data demonstrated that DDIT3/CHOP promotes osteoblast pyroptosis by inhibiting PINK1/Parkin-mediated mitophagy in an inflammatory environment.

Cypermethrin induces endoplasmic reticulum stress and autophagy, leads to testicular dysfunction

Cypermethrin is a pyrethroid insecticide that is used to control insects and protect crops. However, pesticide residues and their possible toxicity to non-target animals such as mammals are concerning. Although cypermethrin reduces testosterone levels, the molecular mechanisms involved, particularly those regarding endoplasmic reticulum (ER) stress and autophagy regulation, have not yet been fully elucidated. In this study, we demonstrated testicular toxicity of cypermethrin in mouse Leydig (TM3) and Sertoli (TM4) cells. Cypermethrin suppresses TM3 and TM4 cell proliferation and induces apoptosis. Moreover, it interrupted calcium homeostasis in intracellular organelles and dissipated mitochondrial membrane polarization in mouse testicular cells. Moreover, we verified the accumulation of Sqstm1/p62 protein in the mitochondria of cypermethrin-treated TM3 and TM4 cells. Furthermore, we confirmed that cypermethrin activated autophagy and the ER stress pathway in a time-dependent manner in both cell types. Finally, we determined that cypermethrin downregulated testicular function-related genes, steroidogenesis, and spermatogenesis in mouse testis cells. Therefore, we conclude that cypermethrin regulates autophagy and ER stress, leading to testicular dysfunction.

N-terminal acetylation shields proteins from degradation and promotes age-dependent motility and longevity

Most eukaryotic proteins are N-terminally acetylated, but the functional impact on a global scale has remained obscure. Using genome-wide CRISPR knockout screens in human cells, we reveal a strong genetic dependency between a major N-terminal acetyltransferase and specific ubiquitin ligases. Biochemical analyses uncover that both the ubiquitin ligase complex UBR4-KCMF1 and the acetyltransferase NatC recognize proteins bearing an unacetylated N-terminal methionine followed by a hydrophobic residue. NatC KO-induced protein degradation and phenotypes are reversed by UBR knockdown, demonstrating the central cellular role of this interplay. We reveal that loss of Drosophila NatC is associated with male sterility, reduced longevity, and age-dependent loss of motility due to developmental muscle defects. Remarkably, muscle-specific overexpression of UbcE2M, one of the proteins targeted for NatC KO-mediated degradation, suppresses defects of NatC deletion. In conclusion, NatC-mediated N-terminal acetylation acts as a protective mechanism against protein degradation, which is relevant for increased longevity and motility.

The sequestosome 1 protein: therapeutic vulnerabilities in ovarian cancer

Ovarian cancer (OC) is the most deadly tumor that may develop in a woman's reproductive system. It is also one of the most common causes of death among those who have been diagnosed with cancer in women. An adapter protein known as sequestosome 1(SQSTM1) or p62 is primarily responsible for the transportation, degradation, and destruction of a wide variety of proteins. This adapter protein works in conjunction with the autophagy process as well as the ubiquitin proteasome degradation pathway. In addition, the ability of SQSTM1 to interact with multiple binding partners link SQSTM1 to various pathways in the context of antioxidant defense system and inflammation. In this review, we outline the processes underlying the control that SQSTM1 has on these pathways and how their dysregulation contributes to the development of OC. At the final, the therapeutic approaches based on SQSTM1 targeting have been discussed.

Maltol attenuates polystyrene nanoplastic-induced enterotoxicity by promoting AMPK/mTOR/TFEB-mediated autophagy and modulating gut microbiota

The production and application of nanoplastics has been increased during decades, and the enterotoxicity caused by their bioaccumulation has attracted vast attention. Maltol was proved to exert a protective effect on gut damage induced by carbon tetrachloride and cisplatin, indicating its confrontation with nanoplastics-induced intestinal toxicity. To explore the ameliorative effects of maltol on polystyrene nanoplastics (PS)-mediated enterotoxicity and the underlying mechanism, the mice were exposed to PS (100 mg/kg), combining with or without the treatment of maltol treatment at 50 and 100 mg/kg. We found PS exposure caused intestinal barrier damage and enterocyte apoptosis, while lysosomal dysfunction and autophagic substrate degradation arrest in enterocytes of mice were also observed. In addition, PS exacerbated the disturbance of the intestinal microbial community, affected the abundance of lysosome and apoptosis-related bacterial genes, and decreased the number of known short-chain fatty acid (SCFA) producing bacteria. However, those alterations were improved by the maltol treatment. Maltol also protected the human intestinal Caco-2 cells from PS-induce damages. Mechanistic studies showed maltol promoted TFEB nuclear translocation through the AMPK/mTOR signaling pathway to restore lysosomal function and reduce autophagy dependent apoptosis. The findings in the present work might help to elucidate the potential molecular mechanisms of PS-induced enterotoxicity. For the first time to our knowledge, the protective effect of maltol on PS-induced intestinal injury was studied from multiple perspectives, which provided a potential therapeutic approach for diseases caused by environmental pollution.

Endocrine-disrupting chemical exposure augments neutrophilic inflammation in severe asthma through the autophagy pathway

Corticosteroid resistance, progressive lung function decline, and frequent asthma exacerbations are the hallmarks of neutrophilic asthma (NA). However, the potential contributors and their mechanisms of NA aggravation have not yet been fully clarified. This study was conducted to assess the precise mechanism and inflammatory effects of endocrine-disrupting chemicals using mono-n-butyl phthalate (MnBP) on an NA model. BALB/c mice from normal control and LPS/OVA-induced NA groups were treated with or without MnBP. The effects of MnBP on the airway epithelial cells (AECs), macrophages (Mφ), and neutrophils were investigated in vitro and in vivo. NA mice exposed to MnBP had significantly increased airway hyperresponsiveness, total and neutrophil cell counts in the bronchoalveolar lavage fluid, and the percentage of M1Mφ in the lung tissues compared to those non-exposed to MnBP. In in vitro study, MnBP induced the human neutrophil activation to release neutrophil DNA extracellular traps, Mφ polarizing toward M1Mφ, and AEC damage. Treatment with hydroxychloroquine (an autophagy inhibitor) reduced the effects of MnBP in vivo and in vitro. The results of our study suggest that MnBP exposure may increase the risk of neutrophilic inflammation in severe asthma and autophagy pathway-targeted therapeutics can help control MnBP-induced harmful effects in asthma.

Apoptotic and autophagic cell death induced in cervical cancer cells by a dual specific oncolytic adenovirus

OBJECTIVE

Oncolytic adenoviruses are capable of exerting anticancer effects via a variety of mechanisms, including apoptosis and autophagy. In the present study, the dual-specific antitumor oncolytic adenovirus, Ad-Apoptin-hTERT-E1a (ATV), was used to infect cervical cancer cell lines to test its antitumor effects.

METHODS

To explore the use of apoptin in tumor gene therapy, a recombinant adenovirus ATV expressing the apoptin protein was assessed to determine its lethal and growth-inhibitory effects on human cervical cancer cell line (HeLa) cells in vitro . Nonapoptotic autophagy of HeLa cells infected with ATV was assessed by examining the cell morphology, development of acidic vesicular organelles and the conversion of microtubule-associated protein 1 light chain 3 (LC3) from its cytoplasmic to autophagosomal membrane form. Using gene silencing (knockdown of LC3 and Belin-1), autophagy-associated molecules (e.g. ATG5, ATG12 and ULK1) were monitored by real-time PCR and western blot.

RESULTS

A series of experiments demonstrated that ATV could significantly induce apoptosis and autophagy in cervical cancer cells, and provided evidence that ATV not only induced apoptosis but also autophagy and ATG5, ATG12 and ULK1 related pathways were not entirely dependent on LC3 and Beclin-1.

CONCLUSION

These results indicate that ATV may have a potential application in tumor gene therapy.

Environmental microplastic accumulation exacerbates liver ischemia-reperfusion injury in rat: Protective effects of melatonin

Ischemia-reperfusion (IR) injury is an inevitable complication of liver transplantation and partial hepatectomy. Although the hazards of environmental microplastics (EMPs) have been well explored, data underlying their impact on IR-induced hepatotoxicity and how to alleviate these damages remain largely undefined. In this study, the involvement of melatonin (MT) in modulating EMPs toxicity in the liver undergoing ischemia-reperfusion injury was investigated. Male Wistar rats were exposed to MPs for 7 days and then subjected to 1 h of partial warm ischemia (70 %) followed by 24 h of reperfusion. We analyzed some parameters as the oxidative stress, the stability of cytoskeleton as well as inflammation, and autophagy. Our data suggested that EMPs elicited liver injury in ischemic animals. Data revealed several histological alterations caused by EMP and IRI, including cellular disorientation, cell necrosis, and microvacuolar steatosis, as well as inflammatory cell infiltration. EMPs increased blood transaminase (AST and ALT) and oxidative stress levels in the ischemic liver. In addition, RT-qPCR, immunofluorescence, and western blot analyses highlighted an increased expression of α-tubulin, IL-18, NFkB, and LC3. However, the ability of MT to reduce MPs and IRI toxicity was consistent with a significant decrease in the evaluated markers. The combined data not only document that melatonin is an effective agent to protect against hepatic IRI but also reduces cellular dysfunction caused by EMPs.

p62/SQSTM1 indirectly mediates remote multipotent mesenchymal cells and rescues bone loss and bone marrow integrity in ovariectomized rats

Intramuscular administration of p62/SQSTM1 (sequestosome1)-encoding plasmid demonstrated an anticancer effect in rodent models and dogs as well as a high safety profile and the first evidence of clinical benefits in humans. Also, an anti-inflammatory effect of the plasmid was reported in several rodent disease models. Yet, the mechanisms of action for the p62 plasmid remain unknown. Here, we tested a hypothesis that the p62-plasmid can act through the modulation of bone marrow multipotent mesenchymal cells (MSCs). We demonstrated that a p62 plasmid can affect MSCs indirectly by stimulating p62-transfected cells to secrete an active ingredient(s) sensed by untransfected MSCs. When we transfected MSCs with the p62-plasmid, collected their supernatant, and added it to an untransfected MSCs culture, it switched the differentiation state and prompt osteogenic responses of the untransfected MSCs. According to an accepted viewpoint, ovariectomy leads to bone pathology via dysregulation of MSCs, and restoring the MSC homeostasis would restore ovariectomy-induced bone damage. To validate our in vitro observations in a clinically relevant in vivo model, we administered the p62 plasmid to ovariectomized rats. It partially reversed bone loss and notably reduced adipogenesis with concurrent reestablishing of the MSC subpopulation pool within the bone marrow. Overall, our study suggests that remote modulation of progenitor MSCs via administering a p62-encoding plasmid may constitute a mechanism for its previously reported effects and presents a feasible disease-preventing and/or therapeutic strategy.

Alpha-lipoic acid inhibits sodium arsenite-mediated autophagic death of rat insulinoma cells

AIM

To investigate the protective effect of α-lipoic acid on sodium arsenite (NaAsO₂) induced INS-1 cells injury and its mechanism.

METHODS

The cell viability was measured by CCK-8 assay. The autophagosomes was observed under transmission electron microscopy. The autophagosomes in cells transfected with green fluorescent protein microtubule-associated protein light chain 3 (GFP-LC3) plasmids were observed under a laser scanning con-focal microscope. The expression of LC3-II, P62, PI3K, and mTOR proteins in INS-1 cells treated with a combination of chloroquine (CQ, autophagy inhibitor) and NaAsO₂ were detected by Western blot assay. The expression of LC3-II, P62, PI3K, and mTOR proteins were detected in INS-1 cells treated with a combination of rapamycin (autophagy inducer, mTOR inhibitor) and α-LA.

RESULTS

The cytotoxicity induced by NaAsO₂ was reversed by α-LA, and the viability of NaAsO₂-treated INS-1 cells increased. α-LA pretreatment decreased the autophagosome accumulation induced by NaAsO_2. α-LA also reduced the fluorescence spot aggregation of GFP-LC3 in INS-1 cells exposed to NaAsO₂ as observed under a laser scanning con-focal microscope. α-LA inhibited NaAsO₂ induced autophagy by up-regulating PI3K and mTOR and down-regulating LC3-II and P62. CQ inhibited NaAsO₂ induced autophagy by up-regulating PI3K, mTOR, P62 and down-regulating LC3-II. α-LA inhibited rapamycin-induced autophagy by up-regulating PI3K, mTOR and P62 and down-regulating LC3-II. The results showed that NaAsO₂ could induce autophagy activation in INS-1 cells. The α-LA may inhibit autophagy activation by regulating the PI3K/mTOR pathway.

CONCLUSION

The data indicated that α-LA might inhibit the NaAsO₂-induced autophagic death of INS-1 cells by regulating the PI3K/mTOR pathway.

A functional role for Serum Amyloid A in the molecular regulation of autophagy in breast cancer

It has been established that the acute phase protein, Serum amyloid A (SAA), which is usually synthesized by the liver, is also synthesized by cancer cells and cancer-associated cells in the tumor microenvironment. SAA also activates modulators of autophagy, such as the PI3K/Akt and MAPK signaling pathways. However, the role of SAA in autophagy in breast cancer still remains to be elucidated. The aim of this study was to investigate the role of SAA in the regulation of signaling pathways and autophagy in in vitro and in vivo models of breast cancer. The MDA-MB-231 and MCF7 cell lines were transiently transfected to overexpress SAA1. A tumor-bearing SAA1/2 knockout mouse model was also utilized in this study. SAA1 overexpression activated ERK signaling in the MDA-MB-231 cells, downregulated the PI3K pathway protein, PKB/Akt, in the MCF7 cell line, while SAA1/2 knockout also inhibited Akt. Furthermore, SAA1 overexpression in vitro downregulated autophagy, while the expression of SQSTM1/p62 was increased in the MCF7 cells, and SAA1/2 knockout induced autophagy in vivo. SAA overexpression in the MDA-MB-231 and MCF7 cells resulted in an increase in cell viability and increased the expression of the proliferation marker, MCM2, in the MCF7 cells. Furthermore, knockout of SAA1/2 resulted in an altered inflammatory profile, evident in the decrease of plasma IL-1β, IL-6 and IL-10, while increasing the plasma levels of MCP-1 and TNF-α. Lastly, SAA1/2 knockout promoted resistance to apoptosis and necrosis through the regulation of autophagy. SAA thus regulates autophagy in breast cancer cells to promote tumorigenesis.

Autophagic event and metabolomic disorders unveil cellular toxicity of environmental microplastics on marine polychaete Hediste diversicolor

Although the hazards of microplastics (MPs) have been quite well explored, the aberrant metabolism and the involvement of the autophagy pathway as an adverse response to environmental MPs in benthic organisms are still unclear. The present work aims to assess the impact of different environmental MPs collected from the south coast of the Mediterranean Sea, composed by polyethylene (PE), polyethylene vinyl acetate (PEVA), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and polyamide (PA) on the metabolome and proteome of the marine polychaete Hediste diversicolor. As a result, all the microplastic types were detected with Raman microspectroscopy in polychaetes tissues, causing cytoskeleton damage and induced autophagy pathway manifested by immunohistochemical labeling of specific targeted proteins, through Tubulin (Tub), Microtubule-associated protein light chain 3 (LC3), and p62 (also named Sequestosome 1). Metabolomics was conducted to further investigate the metabolic alterations induced by the environmental MPs-mixture in polychaetes. A total of 28 metabolites were differentially expressed between control and MPs-treated polychaetes, which showed elevated levels of amino acids, glucose, ATP/ADP, osmolytes, glutathione, choline and phosphocholine, and reduced concentration of aspartate. These novel findings extend our understanding given the toxicity of environmental microplastics and unravel their underlying mechanisms.

Mitochondrial stress response in drug-induced liver injury

Drug-induced liver injury (DILI) caused by the ingestion of medications, herbs, chemicals or dietary supplements, is a clinically widespread health problem. The underlying mechanism of DILI is the formation of reactive metabolites, which trigger mitochondrial oxidative stress and the opening of mitochondrial permeability transition (MPT) pores through direct toxicity or immune response, leading to cell inflammation, apoptosis, and necrosis. Traditionally, mitochondria play an indispensable role in maintaining the physiological and biochemical functions of cells by producing ATP and mediating intracellular signal transduction; drugs can typically stimulate the mitochondria and, in the case of sustained stress, can eventually cause impairment of mitochondrial function and metabolic activity. Meanwhile, the mitochondrial stress response, as an adaptive protective mechanism, occurs when mitochondrial homeostasis is threatened. In this review, we summarize the relevant frontier researches of the protective effects of mitochondrial stress response in DILI as well as the potential related mechanisms, thus providing some thoughts for the clinical treatment of DILI.

Canidin-3-glucoside prevents nano-plastics induced toxicity via activating autophagy and promoting discharge

Increasing attention has been brought to microplastics pollution recently, while emerging evidences indicate that nano-plastics degraded from microplastics are more of research significance owing to stronger toxicity. However, there is little study focused on the prevention of nano-plastics induced toxicity until now. Canidin-3-glucoside (C3G), a natural anthocyanin proved to possess multiple functions like antioxidant and intestinal tissue protection. Thus, we proposed whether C3G could act as a molecular weapon against nano-plastics induced toxicity. In Caco2 cell and Caenorhabditis elegans (C. elegans) models, we found that polystyrene (PS) nano-plastics exposure resulted in physiological toxicity and oxidative damage, which could be restored by C3G. More significantly in Caco2 cells, we observed that autophagy was activated via Sirt1-Foxo1 signaling pathway to attenuate PS induced toxicity after C3G intervention and further verified by adding autophagy inhibitor 3-Methyladenine (3-MA). Meanwhile, PS co-localization with lysosomes was observed, indicating the encapsulation and degradation of PS. In C. elegans, by detecting LGG-1/LC3 expression in GFP-targeted LGG-1 report gene (LGG-1:GFP) labeled transgenic DA2123 strain, the co-localization of LGG-1:GFP with PS was found as well, means that autophagy is involved in C3G's beneficial effects. Furthermore, we were surprised to find that C3G could promote the discharge of PS from N2 nematodes, which reduces PS toxicity more directly.

The autophagic response to Staphylococcus aureus provides an intracellular niche in neutrophils

Staphylococcus aureus is a major human pathogen causing multiple pathologies, from cutaneous lesions to life-threatening sepsis. Although neutrophils contribute to immunity against S. aureus, multiple lines of evidence suggest that these phagocytes can provide an intracellular niche for staphylococcal dissemination. However, the mechanism of neutrophil subversion by intracellular S. aureus remains unknown. Targeting of intracellular pathogens by macroautophagy/autophagy is recognized as an important component of host innate immunity, but whether autophagy is beneficial or detrimental to S. aureus-infected hosts remains controversial. Here, using larval zebrafish, we showed that the autophagy marker Lc3 rapidly decorates S. aureus following engulfment by macrophages and neutrophils. Upon phagocytosis by neutrophils, Lc3-positive, non-acidified spacious phagosomes are formed. This response is dependent on phagocyte NADPH oxidase as both cyba/p22phox knockdown and diphenyleneiodonium (DPI) treatment inhibited Lc3 decoration of phagosomes. Importantly, NADPH oxidase inhibition diverted neutrophil S. aureus processing into tight acidified vesicles, which resulted in increased host resistance to the infection. Some intracellular bacteria within neutrophils were also tagged by Sqstm1/p62-GFP fusion protein and loss of Sqstm1 impaired host defense. Together, we have shown that intracellular handling of S. aureus by neutrophils is best explained by Lc3-associated phagocytosis (LAP), which appears to provide an intracellular niche for bacterial pathogenesis, while the selective autophagy receptor Sqstm1 is host-protective. The antagonistic roles of LAP and Sqstm1-mediated pathways in S. aureus-infected neutrophils may explain the conflicting reports relating to anti-staphylococcal autophagy and provide new insights for therapeutic strategies against antimicrobial-resistant Staphylococci.Abbreviations: ATG: autophagy related; CFU: colony-forming units; CMV: cytomegalovirus; Cyba/P22phox: cytochrome b-245, alpha polypeptide; DMSO: dimethyl sulfoxide; DPI: diphenyleneiodonium; EGFP: enhanced green fluorescent protein; GFP: green fluorescent protein; hpf: hours post-fertilization; hpi: hours post-infection; Irf8: interferon regulatory factor 8; LAP: LC3-associated phagocytosis; lyz: lysozyme; LWT: london wild type; Map1lc3/Lc3: microtubule-associated protein 1 light chain 3; NADPH oxidase: nicotinamide adenine dinucleotide phosphate oxidase; RFP: red fluorescent protein; ROS: reactive oxygen species; RT-PCR: reverse transcriptase polymerase chain reaction; Sqstm1/p62: sequestosome 1; Tg: transgenic; TSA: tyramide signal amplification.

Molecular Action of Polyphenols in Leukaemia and Their Therapeutic Potential

Leukaemia is a malignant disease of the blood. Current treatments for leukaemia are associated with serious side-effects. Plant-derived polyphenols have been identified as potent anti-cancer agents and have been shown to work synergistically with standard chemotherapy agents in leukaemia cell lines. Polyphenols have multiple mechanisms of action and have been reported to decrease cell proliferation, arrest cell cycle and induce apoptosis via the activation of caspase (3, 8 and 9); the loss of mitochondrial membrane potential and the release of cytochrome c. Polyphenols have been shown to suppress activation of transcription factors, including NF-kB and STAT3. Furthermore, polyphenols have pro-oxidant properties, with increasing evidence that polyphenols inhibit the antioxidant activity of glutathione, causing oxidative DNA damage. Polyphenols also induce autophagy-driven cancer cell death and regulate multidrug resistance proteins, and thus may be able to reverse resistance to chemotherapy agents. This review examines the molecular mechanism of action of polyphenols and discusses their potential therapeutic targets. Here, we discuss the pharmacological properties of polyphenols, including their anti-inflammatory, antioxidant, anti-proliferative, and anti-tumour activities, and suggest that polyphenols are potent natural agents that can be useful therapeutically; and discuss why data on bioavailability, toxicity and metabolism are essential to evaluate their clinical use.

Epidemiology of Drug- and Herb-Induced Liver Injury Assessed for Causality Using the Updated RUCAM in Two Hospitals from China

Drug- and herb-induced liver injury (DILI and HILI) is an increasingly common and serious condition. Here, data for DILI and HILI patients from two large tertiary hospitals were retrospectively analyzed. Patient characteristics, causes and severity of DILI and HILI, the correlation between expression of p62 and the severity of DILI and HILI, treatment of DILI and HILI, and the prognostic factors of DILI and HILI were studied. A total of 82 patients with DILI and HILI were recruited for the study. Most patients presented with hepatocellular injury, followed by cholestatic injury and mixed injury. Our results indicate that traditional Chinese medicine or herbal and dietary supplements were the prevalent causal agents of HILI, which was characterized by higher frequencies of hepatocellular injury. Expression of p62 in the liver correlated with the severity of DILI and HILI. Improvements in the results of the liver enzymatic tests correlated with alanine transaminase (ALT) levels upon the first diagnosis of DILI and HILI and with the hepatocellular type of DILI and HILI. In conclusion, we provide an epidemiological assessment of DILI and HILI based on causality using the updated RUCAM on patients from two hospitals in China. ALT levels at first diagnosis and the hepatocellular type of injury may be prognostic factors of DILI and HILI.

Chlamydia trachomatis induces autophagy by p62 in HeLa cell

Chlamydia trachomatis is the most common bacterial pathogen causing sexually transmitted diseases. C. trachomatis infection is closely related to the development of cervical cancer, studies have shown that C. trachomatis can induce host cell autophagy. The autophagy related gene p62 plays an important role in the process of autophagy. To further understand the role of autophagy-associated gene p62 in autophagy of HeLa cells induced by C. trachomatis, p62-silencing cell line, HeLa229-shp62, and control cell line, HeLa229-shNC, were constructed, and a C. trachomatis-infected cell model was established. The autophagosome and C. trachomatis inclusions were observed under electron microscope. The autophagy level of C. trachomatis-infected HeLa cells was detected by Western blot. The results suggested that knockdown of p62 affected neither C. trachomatis infection of HeLa cells nor the initiation of C. trachomatis-induced autophagy, but at 48 h post C. trachomatis infection, autophagy levels were significantly inhibited in p62 silencing host cells. The study demonstrated the important role of p62 in the autophagy induced by C. trachomatis in HeLa cells, which could provide data support and theoretical basis for exploring the pathogenesis and prevention of C. trachomatis.

DIM-C-pPhtBu induces lysosomal dysfunction and unfolded protein response - mediated cell death via excessive mitophagy

Despite technological advances in cancer treatment, the survival rate of patients with head and neck cancer (HNC) has not improved significantly. Many studies have shown that endoplasmic reticulum (ER) stress-related signals are associated with mitochondrial damage and that these signals determine whether cells maintain homeostasis or activate cell death programs. The unfolded protein response (UPR) is regulated by ER membrane proteins such as double-stranded RNA-activated protein kinase R(PKR)-like ER kinase (PERK), which directly activate transcription of chaperones or genes that function in redox homeostasis, protein secretion, or cell death programs. In this study, we focused on the role of mitophagy and ER stress-mediated cell death induced by DIM-C-pPhtBu in HNC cancer. We found that DIM-C-pPhtBu, a compound that activates ER stress in many cancers, induced lysosomal dysfunction, excessive mitophagy, and cell death in HNC cells. Moreover, DIM-C-pPhtBu strongly inhibited HNC progression in a xenograft model by altering mitophagy related protein expression. Taken together, the results demonstrate that DIM-C-pPhtBu induces excessive mitophagy and eventually UPR-mediated cell death in HNC cells, suggesting that new anti-cancer drugs could be developed based on the connection between mitophagy and cancer cell death.

The flavonoids of Sophora flavescens exerts anti-inflammatory activity via promoting autophagy of Bacillus Calmette-Guérin-stimulated macrophages

Tuberculosis (TB), a highly infectious air-borne disease, has remained a global health problem. Conventional treatment and preventions such as antibiotics and Bacilli Calmette-Guerin (BCG) vaccine can be unreliable. In view of the increasing prevalence of anti-TB drug resistance, adjunctive therapy may be necessary to shorten the recovery time. We have previously shown that flavonoids in the medicinal herb Sophora flavescens exhibit anti-inflammatory and bactericidal activities. The aim of this study was to investigate the molecular and cellular characteristics of flavonoids of S. flavescens (FSF) in BCG-stimulated macrophages for assessing their roles in anti-inflammation and autophagy. Mouse alveolar macrophage (MH-S) cell line and primary mouse peritoneal macrophages were stimulated in vitro with heat-inactivated BCG and treated with FSF, with or without autophagy inhibitor Bafilomycin A1 (BafA1). Gene expression was analyzed using quantitative PCR, and cytokine/chemokine release was analyzed by Milliplex assay and ELISA. Autophagy-related proteins were quantified by Western blot and flow cytometry, and autophagolysosomes were detected using fluorescence microscopy. In both MH-S cell line and mouse peritoneal macrophages stimulated by heat-inactivated BCG, FSF was found to up-regulate autophagy-related proteins microtubule-associated protein 1A/1B-light chain 3 (LC3) and protein 62 (p62), and suppress the induced proinflammatory cytokine TNF-α, CCL5, and IL-6. FSF actively modulates immune processes through suppressing BCG-mediated inflammation by promoting autophagy in MH-S cells and mouse peritoneal macrophages. We suggest that FSF may be useful as an adjunctive therapeutic agent for TB infection by modulating cell survival through autophagy and reducing inflammation.

Synthesis and in vitro anti-bladder cancer activity evaluation of quinazolinyl-arylurea derivatives

Based on the structural modification of molecular-targeted agent sorafenib, a series of quinazolinyl-arylurea derivatives were synthesized and evaluated for their anti-proliferative activities against six human cancer cell lines. Compared with other cell lines tested, T24 was more sensitive to most compounds. Compound 7j exhibited the best profile with lower IC₅₀ value and favorable selectivity. In this study, we focused on 7j-induced death forms of T24 cells and tried to elucidate the reason for its potent proliferative inhibitory activity. Compound 7j treatment could trigger three different cell death forms including apoptosis, ferroptosis, and autophagy; which form would occur depended on the concentrations and incubation time of 7j: (1) Lower concentrations within the initial 8 h of 7j treatment led to apoptosis-dependent death. (2) Ferroptosis and autophagy occurred in the case of higher concentrations combining with extended incubation time through effectively regulating the Sxc^-/GPx4/ROS and PI3K/Akt/mTOR/ULK1 pathways, respectively. (3) The above death forms were closely associated with intracellular ROS generation and decreased mitochondrial membrane potential induced by 7j. In molecular docking and structure-activity relationship analyses, 7j could bind well to the active site of the corresponding receptor glutathione peroxidase 4 (GPx4). Compound 7j could be a promising lead for molecular-targeted anti-bladder cancer agents' discovery.

A Systems Toxicology Approach for the Prediction of Kidney Toxicity and Its Mechanisms In Vitro

The failure to predict kidney toxicity of new chemical entities early in the development process before they reach humans remains a critical issue. Here, we used primary human kidney cells and applied a systems biology approach that combines multidimensional datasets and machine learning to identify biomarkers that not only predict nephrotoxic compounds but also provide hints toward their mechanism of toxicity. Gene expression and high-content imaging-derived phenotypical data from 46 diverse kidney toxicants were analyzed using Random Forest machine learning. Imaging features capturing changes in cell morphology and nucleus texture along with mRNA levels of HMOX1 and SQSTM1 were identified as the most powerful predictors of toxicity. These biomarkers were validated by their ability to accurately predict kidney toxicity of four out of six candidate therapeutics that exhibited toxicity only in late stage preclinical/clinical studies. Network analysis of similarities in toxic phenotypes was performed based on live-cell high-content image analysis at seven time points. Using compounds with known mechanism as reference, we could infer potential mechanisms of toxicity of candidate therapeutics. In summary, we report an approach to generate a multidimensional biomarker panel for mechanistic de-risking and prediction of kidney toxicity in in vitro for new therapeutic candidates and chemical entities.

Autophagy Promotes Duck Tembusu Virus Replication by Suppressing p62/SQSTM1-Mediated Innate Immune Responses In Vitro

Duck Tembusu virus (DTMUV) has recently appeared in ducks in China and the key cellular determiners for DTMUV replication in host cells remain unknown. Autophagy is an evolutionarily conserved cellular process that has been reported to facilitate flavivirus replication. In this study, we utilized primary duck embryo fibroblast (DEF) as the cell model and found that DTMUV infection triggered LC3-II increase and polyubiquitin-binding protein sequestosome 1 (p62) decrease, confirming that complete autophagy occurred in DEF cells. The induction of autophagy by pharmacological treatment increased DTMUV replication in DEF cells, whereas the inhibition of autophagy with pharmacological treatments or RNA interference decreased DTMUV replication. Inhibiting autophagy enhanced the activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and interferon regulatory factor 7 (IRF7) pathways and increased the p62 protein level in DTMUV-infected cells. We further found that the overexpression of p62 decreased DTMUV replication and inhibited the activation of the NF-κB and IRF7 pathways, and changes in the NF-κB and IRF7 pathways were consistent with the level of phosphorylated TANK-binding kinase 1 (p-TBK1). Opposite results were found in p62 knockdown cells. In summary, we found that autophagy-mediated p62 degradation acted as a new strategy for DTMUV to evade host innate immunity.

Role of autophagy in alcohol and drug-induced liver injury

Alcohol-related liver disease (ALD) and drug-induced liver injury (DILI) are common causes of severe liver disease, and successful treatments are lacking. Autophagy plays a protective role in both ALD and DILI by selectively removing damaged mitochondria (mitophagy), lipid droplets (lipophagy), protein aggregates and adducts in hepatocytes. Autophagy also protects against ALD by degrading interferon regulatory factor 1 (IRF1) and damaged mitochondria in hepatic macrophages. Specifically, we will discuss selective autophagy for removal of damaged mitochondria and lipid droplets in hepatocytes and autophagy-mediated degradation of IRF1 in hepatic macrophages as protective mechanisms against alcohol-induced liver injury and steatosis. In addition, selective autophagy for removal of damaged mitochondria and protein adducts for protection against DILI is discussed in this review. Development of new therapeutics for ALD and DILI is greatly needed, and selective autophagy pathways may provide promising targets. Drug and alcohol effects on autophagy regulation as well as protective mechanisms of autophagy against DILI and ALD are highlighted in this review.

The ICP0 Protein of Herpes Simplex Virus 1 (HSV-1) Downregulates Major Autophagy Adaptor Proteins Sequestosome 1 and Optineurin during the Early Stages of HSV-1 Infection

Herpes simplex virus 1 (HSV-1) infects mucosal epithelial cells and establishes lifelong infections in sensory neurons. Following reactivation, the virus is transferred anterograde to the initial site of infection or to sites innervated by infected neurons, causing vesicular lesions. Upon immunosuppression, frequent HSV-1 reactivation can cause severe diseases, such as blindness and encephalitis. Autophagy is a process whereby cell components are recycled, but it also serves as a defense mechanism against pathogens. HSV-1 is known to combat autophagy through the functions of the γ₁34.5 protein, which prevents formation of the autophagophore by binding to Beclin 1, a key factor involved in the elongation of the isolation membrane, and by redirecting the protein phosphatase 1α (PP1α) to dephosphorylate the translation initiation factor 2α (eIF2α) to prevent host translational shutoff. Other viral proteins that counteract innate immunity negatively impact autophagy. Here, we present a novel strategy of HSV-1 to evade the host through the downregulation of the autophagy adaptor protein sequestosome (p62/SQSTM1) and of the mitophagy adaptor optineurin (OPTN). This down-modulation occurs during the early steps of the infection. We also found that infected cell protein 0 (ICP0) of the virus mediates the down-modulation of the two autophagy adaptors in a mechanism independent of its E3 ubiquitin ligase activity. Cells depleted of either p62 or OPTN were able to mount greater antiviral responses, whereas cells expressing exogenous p62 displayed decreased virus yields. We conclude that downregulation of p62/SQSTM1 and OPTN is a viral strategy to counteract the host.IMPORTANCE Autophagy is a homeostatic mechanism of cells to recycle components, as well as a defense mechanism to get rid of pathogens. Strategies that HSV-1 has developed to counteract autophagy have been described and involve inhibition of autophagosome formation or indirect mechanisms. Here, we present a novel mechanism that involves downregulation of two major autophagy adaptor proteins, sequestosome 1 (p62/SQSTM1) and optineurin (OPTN). These findings generate the question of why the virus targets two major autophagy adaptors if it has mechanisms to block autophagosome formation. P62/SQSTM1 and OPTN proteins have pleiotropic functions, including regulation of innate immunity, inflammation, protein sorting, and chromatin remodeling. The decrease in virus yields in the presence of exogenous p62/SQSTM1 suggests that these adaptors have an antiviral function. Thus, HSV-1 may have developed multiple strategies to incapacitate autophagy to ensure replication. Alternatively, the virus may target another antiviral function of these proteins.

Autophagy contributes to BMP type 2 receptor degradation and development of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterised by an increase in mean pulmonary arterial pressure which almost invariably leads to right heart failure and premature death. More than 70% of familial PAH and 20% of idiopathic PAH patients carry heterozygous mutations in the bone morphogenetic protein (BMP) type 2 receptor (BMPR2). However, the incomplete penetrance of BMPR2 mutations suggests that other genetic and environmental factors contribute to the disease. In the current study, we investigate the contribution of autophagy in the degradation of BMPR2 in pulmonary vascular cells. We demonstrate that endogenous BMPR2 is degraded through the lysosome in primary human pulmonary artery endothelial (PAECs) and smooth muscle cells (PASMCs): two cell types that play a key role in the pathology of the disease. By means of an elegant HaloTag system, we show that a block in lysosomal degradation leads to increased levels of BMPR2 at the plasma membrane. In addition, pharmacological or genetic manipulations of autophagy allow us to conclude that autophagy activation contributes to BMPR2 degradation. It has to be further investigated whether the role of autophagy in the degradation of BMPR2 is direct or through the modulation of the endocytic pathway. Interestingly, using an iPSC-derived endothelial cell model, our findings indicate that BMPR2 heterozygosity alone is sufficient to cause an increased autophagic flux. Besides BMPR2 heterozygosity, pro-inflammatory cytokines also contribute to an augmented autophagy in lung vascular cells. Furthermore, we demonstrate an increase in microtubule-associated protein 1 light chain 3 beta (MAP1LC3B) levels in lung sections from PAH induced in rats. Accordingly, pulmonary microvascular endothelial cells (MVECs) from end-stage idiopathic PAH patients present an elevated autophagic flux. Our findings support a model in which an increased autophagic flux in PAH patients contributes to a greater decrease in BMPR2 levels. Altogether, this study sheds light on the basic mechanisms of BMPR2 degradation and highlights a crucial role for autophagy in PAH. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Sicilian Litchi Fruit Extracts Induce Autophagy versus Apoptosis Switch in Human Colon Cancer Cells

Litchi chinensis Sonnerat is a tropical tree whose fruits contain significant amounts of bioactive polyphenols. Litchi cultivation has recently spread in Sicily where the climate conditions are particularly favorable for this crop. Recent findings have shown that Litchi extracts display anti-tumor and pro-apoptotic effects in vitro, but the precise underlying mechanisms have not been fully elucidated. In this study, we report for the first time the effects of Sicilian litchi fruit extracts on colon cancer cells. The results indicated that litchi exocarp, mesocarp and endocarp fractions reduce the viability and clonogenic growth of HT29 cells. These effects were due to cell cycle arrest in the G2/M phase followed by caspase-dependent cell death. Interestingly, litchi exocarp and endocarp triggered a precocious autophagic response (16–24 h), which was accompanied by an increase in the level of autophagy related 1/autophagy activating kinase 1 (ATG1/ULK1), beclin-1, microtubule associated protein 1 light chain 3 (LC3)-II and p62 proteins. Autophagy inhibition by bafilomycin A1 or beclin-1 silencing increased cell death, thus suggesting that autophagy was initially triggered as a pro-survival response. Significant effects of Litchi extracts were also observed in other colon cancer cells, including HCT116 and Caco-2 cells. On the other hand, differentiated Caco-2 cells, a model of human enterocytes, appeared to be insensitive to the extracts at the same treatment conditions. High-Performance Liquid Chromatography–Electrospray Ionization-Quadrupole-Time-Of-Flight HPLC/ESI/Q-TOF evidenced the presence of some polyphenolic compounds, specifically in exocarp and endocarp extracts, that can account for the observed biological effects. The results obtained suggest a potential therapeutic efficacy of polyphenolic compounds purified from Sicilian Litchi fractions for the treatment of colon cancer. Moreover, our findings indicate that modulation of autophagy can represent a tool to improve the effectiveness of these agents and potentiate the anti-tumor response of colon cancer cells.

Role of p62/SQSTM1 beyond autophagy: a lesson learned from drug-induced toxicity in vitro

BACKGROUND AND PURPOSE

SQSTM1/p62 is a multifunctional, stress-induced, scaffold protein involved in multiple cellular processes including autophagic clearance, regulation of inflammatory responses and redox homeostasis. Its altered function has been associated with different human pathologies, such as neurodegenerative, metabolic and bone diseases (down-regulation), and cancerogenesis (up-regulation). However, its role in the off-target effects of clinically used drugs is still not understood.

EXPERIMENTAL APPROACH

We evaluated the expression of p62 in cultured Hep3B cells and their derived ρ° cells (lacking mitochondria), along with markers of autophagy and mitochondrial dysfunction. The effects of efavirenz were compared with those of known pharmacological stressors, rotenone, thapsigargin and CCCP, and we also used transient silencing with siRNA and p62 overexpression. Western blotting, quantRT-PCR and fluorescence microscopy were used to assay these effects and their underlying mechanisms.

KEY RESULTS

In Hep3B cells, efavirenz augmented p62 protein content, an effect not observed in the corresponding ρ° cells. p62 up-regulation followed enhanced SQSTM1 expression mediated through the transcription factor CHOP/DDIT3, while other well-known regulators (NF-kB and Nrf2) were not involved. Inhibition of autophagy with 3MA or with transient silencing of Atg5 did not affect SQSTM1 expression in efavirenz-treated cells while p62 overexpression ameliorated the deleterious effect of efavirenz on cell viability.

CONCLUSION AND IMPLICATIONS

In our model, p62 exerted a specific, autophagy-independent role and protected against efavirenz-induced mitochondrial ROS generation and activation of the NLRP3 inflammasome. These findings add to the multifunctional nature of p62 and may help to understand the off-target effects of clinically useful drugs.