Autophagy Contributes to Caspase-independent Macrophage Cell Death

Elucidating the mechanism of action of Isobavachalcone induced autophagy and apoptosis in non-small cell lung cancer by network pharmacology and experimental validation methods

BACKGROUND

Lung cancer is the leading cause of cancer deaths, and non-small cell lung cancer (NSCLC) accounts for the majority of lung cancer-related mortality. In recent years, there have been numerous treatments for non-small cell lung cancer, but the cure and survival rates are still extremely low. Isobavachalcone (IBC) belongs to the chalcone component of the traditional Chinese medicine Psoralea corylifolia L., and is a unique Protein kinase B (AKT) pathway inhibitor with significant anticancer effects. Previous studies have shown that IBC possess a variety of biological properties, including anti-cancer, anti-inflammatory, and antioxidant properties. This study focused on the use of network pharmacology analysis, molecular docking technology and experimental validation to elucidate the potential mechanisms of IBC for the treatment of NSCLC.

METHODS

Screening key genes and pathways of IBC action in NSCLC using network pharmacology. The IBC target genes were from The Encyclopedia of Traditional Chinese Medicine (ETCM) and BATMAN-TCM databases, the NSCLC target genes were from GeneCards, Online Mendelian Inheritance in Man (OMIM) and The Therapeutic Target database (TTD) databases, both of which were taken as intersecting genes for protein-protein interaction network analysis and enrichment analysis, and the binding energies of the compounds to the core targets were further verified by molecular docking. Cell lines in vitro experiments were then performed to further unravel the mechanism of IBC for NSCLC.

RESULTS

A total of 279 potential targets were retrieved by searching the intersection of IBC and NSCLC targets. Protein-protein interaction (PPI) network analysis indicated that 6 targets, including AKT1, RXRA, NCOA1, RXRB, RARA, PPARG were hub genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that IBC treatment of NSCLC mainly involves steroid binding, transcription factor activity, Pathways in cancer, cAMP signaling pathway, Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway. Among them, the AMPK signaling pathway, which contained the largest number of enriched genes, may play a greater role in the treatment of NSCLC. Then, the results of in vitro experiment indicated that IBC could inhibit proliferation of NSCLC cells and induce cell autophagy and apoptosis. The results also showed that IBC could increase the protein expression of AMPK and decrease the protein expression of AKT and mammalian target of rapamycin (mTOR), suggesting that IBC can treat NSCLC by inducing cellular autophagy and apoptosis as well as modulating AMPK and AKT signaling pathways.

CONCLUSIONS

In summary, this study provided a new insight into the protective mechanism of IBC against NSCLC through network pharmacology and experimental validation.

The Role of Autophagy in Vascular Endothelial Cell Health and Physiology

Autophagy is a highly conserved cellular recycling process which enables eukaryotes to maintain both cellular and overall homeostasis through the catabolic breakdown of intracellular components or the selective degradation of damaged organelles. In recent years, the importance of autophagy in vascular endothelial cells (ECs) has been increasingly recognized, and numerous studies have linked the dysregulation of autophagy to the development of endothelial dysfunction and vascular disease. Here, we provide an overview of the molecular mechanisms underlying autophagy in ECs and our current understanding of the roles of autophagy in vascular biology and review the implications of dysregulated autophagy for vascular disease. Finally, we summarize the current state of the research on compounds to modulate autophagy in ECs and identify challenges for their translation into clinical use.

Targeting Pro-Survival Autophagy Enhanced GSK-3β Inhibition-Induced Apoptosis and Retarded Proliferation in Bladder Cancer Cells

Advanced bladder cancer (BC) (local invasive and/or metastatic) is not curable even with cytotoxic chemotherapy, immune checkpoint inhibitors, and targeted treatment. Targeting GSK-3β is a promising novel approach in advanced BC. The induction of autophagy is a mechanism of secondary resistance to various anticancer treatments. Our objectives are to investigate the synergistic effects of GSK-3β in combination with autophagy inhibitors to evade GSK-3β drug resistance. Small molecule GSK-3β inhibitors and GSK-3β knockdown using siRNA promote the expression of autophagy-related proteins. We further investigated that GSK-3β inhibition induced the nucleus translocation of transcription factor EB (TFEB). Compared to the GSK-3β inhibition alone, its combination with chloroquine (an autophagy inhibitor) significantly reduced BC cell growth. These results suggest that targeting autophagy potentiates GSK-3β inhibition-induced apoptosis and retarded proliferation in BC cells.

Magnolol improves Alzheimer's disease-like pathologies and cognitive decline by promoting autophagy through activation of the AMPK/mTOR/ULK1 pathway

Alzheimer's disease (AD) is the most common neurodegenerative disease. Amyloid-β (Aβ) plaque deposition and apoptosis are main pathological features of AD. Autophagy plays an important role in clearing abnormal protein accumulation and inhibiting apoptosis; however, autophagy defects often occur from the early stages of AD. The serine/threonine AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/unc-51-like kinase 1/2 (ULK1/2) pathway serves as an energy sensor and is involved in autophagy activation. Furthermore, magnolol is an autophagy regulator, and has potential for AD therapy. We propose that magnolol can ameliorate AD pathologies and inhibit apoptosis by regulating autophagy through the AMPK/mTOR/ULK1 pathway. We examined cognitive function and AD-related pathologies in AD transgenic mice and the protective mechanism of magnolol by western blotting, flow cytometry, and a tandem mRFP-GFP-LC3 adenovirus assay in Aβ oligomer (AβO)-induced N2a and BV2 cell models. In our study, magnolol decreased amyloid pathology and ameliorated cognitive impairment in APP/PS1 mice. Moreover, magnolol inhibited apoptosis by downregulating cleaved-caspase-9 and Bax and upregulating Bcl-2 in APP/PS1 mice and AβO-induced cell models. Magnolol promoted autophagy by degrading p62/SQSTM1, and upregulating LC3II and Beclin-1 expression. Magnolol activated the AMPK/mTOR/ULK1 pathway by increasing phosphorylation of AMPK and ULK1 and decreasing mTOR phosphorylation in in vivo and in vitro AD models. AMPK inhibitor weakened the effects of magnolol in promoting autophagy and inhibiting apoptosis, and ULK1 knockdown weakened the effect of magnolol on AβO-induced apoptosis. These results indicate that magnolol inhibits apoptosis and improves AD-related pathologies by promoting autophagy through activation of the AMPK/mTOR/ULK1 pathway.

Molecular mechanisms behind ROS regulation in cancer: A balancing act between augmented tumorigenesis and cell apoptosis

ROS include hydroxyl radicals (HO^.), superoxide (O₂^..), and hydrogen peroxide (H₂O₂). ROS are typically produced under physiological conditions and play crucial roles in living organisms. It is known that ROS, which are created spontaneously by cells through aerobic metabolism in mitochondria, can have either a beneficial or detrimental influence on biological systems. Moderate levels of ROS can cause oxidative damage to proteins, DNA and lipids, which can aid in the pathogenesis of many disorders, including cancer. However, excessive concentrations of ROS can initiate programmed cell death in cancer. Presently, a variety of chemotherapeutic drugs and herbal agents are being investigated to induce ROS-mediated cell death in cancer. Therefore, preserving ROS homeostasis is essential for ensuring normal cell development and survival. On account of a significant association of ROS levels at various concentrations with carcinogenesis in a number of malignancies, further studies are needed to determine the underlying molecular mechanisms and develop the possibilities for intervening in these processes.

Chrysophanol-8-O-glucoside protects mice against acute liver injury by inhibiting autophagy in hepatic stellate cells and inflammatory response in liver-resident macrophages

Acute liver failure (ALF) is an unfavorable condition characterized by the rapid loss of liver function and high mortality. Chrysophanol-8-O-glucoside (CPOG) is an anthraquinone derivative isolated from rhubarb. This study aims to evaluate the protective effect of CPOG on lipopolysaccharide (LPS)/D-GalN-induced ALF and its underlying mechanisms. LPS/D-GalN-induced mice ALF model and LPS treatment model in RAW 264.7 and LX2 cells were established. It was found that CPOG ameliorated LPS/D-GalN-induced liver injury and improved mortality as indicated by Hematoxylin-eosin (H&E) staining. Molecularly, qPCR and ELISA results showed that CPOG alleviated LPS/D-GalN-induced release of alanine aminotransferase and aspartate transaminase and the secretion of TNF-α and IL-1β in vivo. LPS/D-GalN-induced intracellular ROS production was also attenuated by CPOG in liver tissue. Further, CPOG attenuated ROS generation and inhibited the expression of p-IκB and p-p65 as well as the expression of TNF-α and IL-1β stimulated by LPS in RAW 264.7 cells. In addition, CPOG alleviated LPS-induced up-regulation of LC3B, p62, ATG5 and Beclin1 by attenuating ROS production and inhibiting MAPK signaling in LX2 cells. Taken together, our data indicated that the CPOG protected against LPS/D-GalN-induced ALF by inhibiting oxidative stress, inflammation response and autophagy. These findings suggest that CPOG could be potential drug for the treatment of ALF in clinic.

Modified Titanium Dioxide as a Potential Visible-Light-Activated Photosensitizer for Bladder Cancer Treatment

Low oxygen concentration inside the tumor microenvironment represents a major barrier for photodynamic therapy of many malignant tumors, especially urothelial bladder cancer. In this context, titanium dioxide, which has a low cost and can generate high ROS levels regardless of local O₂ concentrations, could be a potential type of photosensitizer for treating this type of cancer. However, the use of UV can be a major disadvantage, since it promotes breakage of the chemical bonds of the DNA molecule on normal tissues. In the present study, we focused on the cytotoxic activities of a new material (Ti(OH)₄) capable of absorbing visible light and producing high amounts of ROS. We used the malignant bladder cell line MB49 to evaluate the effects of multiple concentrations of Ti(OH)₄ on the cytotoxicity, proliferation, migration, and production of ROS. In addition, the mechanisms of cell death were investigated using FACS, accumulation of lysosomal acid vacuoles, caspase-3 activity, and mitochondrial electrical potential assays. The results showed that exposure of Ti(OH)₄ to visible light stimulates the production of ROS and causes dose-dependent necrosis in tumor cells. Also, Ti(OH)₄ was capable of inhibiting the proliferation and migration of MB49 in low concentrations. An increase in the mitochondrial membrane potential associated with the accumulation of acid lysosomes and low caspase-3 activity suggests that type II cell death could be initiated by autophagic dysfunction mechanisms associated with high ROS production. In conclusion, the characteristics of Ti(OH)₄ make it a potential photosensitizer against bladder cancer.

Pan-Caspase Inhibitor zVAD Induces Necroptotic and Autophagic Cell Death in TLR3/4-Stimulated Macrophages

In addition to inducing apoptosis, caspase inhibition contributes to necroptosis and/or autophagy depending on the cell type and cellular context. In macrophages, necroptosis can be induced by co-treatment with Toll-like receptor (TLR) ligands (lipopolysaccharide [LPS] for TLR4 and polyinosinic-polycytidylic acid [poly I:C] for TLR3) and a cell-permeable pan-caspase inhibitor zVAD. Here, we elucidated the signaling pathways and molecular mechanisms of cell death. We showed that LPS/zVAD- and poly I:C/zVAD-induced cell death in bone marrow-derived macrophages (BMDMs) was inhibited by receptor-interacting protein kinase 1 (RIP1) inhibitor necrostatin-1 and autophagy inhibitor 3-methyladenine. Electron microscopic images displayed autophagosome/autolysosomes, and immunoblotting data revealed increased LC3II expression. Although zVAD did not affect LPS- or poly I:C-induced activation of IKK, JNK, and p38, it enhanced IRF3 and STAT1 activation as well as type I interferon (IFN) expression. In addition, zVAD inhibited ERK and Akt phosphorylation induced by LPS and poly I:C. Of note, zVAD-induced enhancement of the IRF3/IFN/STAT1 axis was abolished by necrostatin-1, while zVAD-induced inhibition of ERK and Akt was not. Our data further support the involvement of autocrine IFNs action in reactive oxygen species (ROS)-dependent necroptosis, LPS/zVAD-elicited ROS production was inhibited by necrostatin-1, neutralizing antibody of IFN receptor (IFNR) and JAK inhibitor AZD1480. Accordingly, both cell death and ROS production induced by TLR ligands plus zVAD were abrogated in STAT1 knockout macrophages. We conclude that enhanced TRIF-RIP1-dependent autocrine action of IFNβ, rather than inhibition of ERK or Akt, is involved in TLRs/zVAD-induced autophagic and necroptotic cell death via the JAK/STAT1/ROS pathway.

Autophagy Is Involved in Mesenchymal Stem Cell Death in Coculture with Chondrocytes

OBJECTIVE

Cartilage formation is stimulated in mixtures of chondrocytes and human adipose-derived mesenchymal stromal cells (MSCs) both in vitro and in vivo. During coculture, human MSCs perish. The goal of this study is to elucidate the mechanism by which adipose tissue-derived MSC cell death occurs in the presence of chondrocytes.

METHODS

Human primary chondrocytes were cocultured with human MSCs derived from 3 donors. The cells were cultured in monoculture or coculture (20% chondrocytes and 80% MSCs) in pellets (200,000 cells/pellet) for 7 days in chondrocyte proliferation media in hypoxia (2% O₂). RNA sequencing was performed to assess for differences in gene expression between monocultures or coculture. Immune fluorescence assays were performed to determine the presence of caspase-3, LC3B, and P62.

RESULTS

RNA sequencing revealed significant upregulation of >90 genes in the 3 cocultures when compared with monocultures. STRING analysis showed interconnections between >50 of these genes. Remarkably, 75% of these genes play a role in cell death pathways such as apoptosis and autophagy. Immunofluorescence shows a clear upregulation of the autophagic machinery with no substantial activation of the apoptotic pathway.

CONCLUSION

In cocultures of human MSCs with primary chondrocytes, autophagy is involved in the disappearance of MSCs. We propose that this sacrificial cell death may contribute to the trophic effects of MSCs on cartilage formation.

Reactive Oxygen Species (ROS) Regulates Different Types of Cell Death by Acting as a Rheostat

Reactive oxygen species (ROS) are essential for cellular signaling and response to stress. The level of ROS and the type of ROS determine the ability of cells to undergo cell death. Furthermore, dysregulation of the antioxidant pathways is associated with many diseases. It has become apparent that cell death can occur through different mechanisms leading to the classifications of different types of cell death such as apoptosis, ferroptosis, and necroptosis. ROS play essential roles in all forms of cell death, but it is only now coming into focus that ROS control and determine the type of cell death that occurs in any given cell. Indeed, ROS may act as a rheostat allowing different cell death mechanisms to be engaged and crosstalk with different cell death types. In this review, we will describe the ROS regulatory pathways and how they control different types of cell death under normal and disease states. We will also propose how ROS could provide a mechanism of crosstalk between cell death mechanisms and act as a rheostat determining the type of cell death.

Self Nano-Emulsifying Curcumin (SNEC30) attenuates arsenic-induced cell death in mice

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Sodium arsenite disrupts the histoarchitecture and cell morphology causing cell death in thymus and spleen of Swiss albino mice.

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Activation of apoptotic cell death occurred due to high level of ROS generation and increased promotion of autophagy upon arsenic insult.

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SNEC30 restored cellular architecture, reduced ROS generation and ameliorated autophagy-mediated cell death in the immune organs.

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This study clearly demonstrated anti-oxidative and anti-apoptotic properties of SNEC30 against NaAsO₂-induced in vivo immunotoxicity.

Several precedents have confirmed numerous infirmities caused by arsenic poisoning, including immune suppression and cancer. Exposure to arsenic leads to alterations of the cellular machinery and eventually cell death, depending on the dose and duration of exposure. Oxidative stress induced by arsenic is the major mechanism by which it inflicts cellular toxicity, challenging the survival-support - autophagy and culminating in apoptosis in the thymus and spleen of mice. Curcumin, a potent dietary anti-oxidant with known anti-apoptotic and anti-inflammatory properties, was assessed for therapeutic benefits. However, the major caveat of this polyphenol is its low water solubility and limited bioavailability. Therefore, Self Nano-Emulsifying Curcumin (SNEC30) was used to treat mice exposed to arsenic. When administered, SNEC30 effectively ameliorated the adverse effects of arsenic in mice, by restoring structural alterations and reducing ROS-mediated cell death, thereby endorsing the importance of nutraceuticals in counteracting heavy metal-induced cellular toxicity.

Angiotensin II and hypoxia induce autophagy in cardiomyocytes via activating specific protein kinase C subtypes

Background

The purpose of this study was to explore the role of protein kinase C (PKC) isozymes and reactive oxygen species (ROS) in hypoxia and angiotensin (Ang) II-induced autophagy.

Methods

Primary cardiomyocytes were isolated from Sprague-Dawley (SD) neonatal rats and cultured in hypoxia and/or Ang II conditions. Dihydroethidium fluorescence staining was used to detect the content of ROS. Cardiomyocyte autophagy was determined using Monodansylcadaverine fluorescence staining and Western blot. We also inhibited ROS production to explore the relationship between ROS and autophagy. ELISA was used to detect the contents of PKC δ and PKC ε. After inhibition of PKC δ activation and PKC ε expression by lentiviral siRNA, ROS content and autophagy of cultured cardiomyocytes were detected.

Results

Hypoxia and Ang II stimulation increased autophagy in cardiomyocytes, accompanied by increased intracellular ROS production. Inhibiting ROS following hypoxia or Ang II stimulation significantly suppressed autophagy in comparison with hypoxia or Ang II stimulation group. Inhibiting PKC δ significantly reduced ROS production and autophagy activity following hypoxia or accompanied with Ang II stimulation except Ang II stimulation alone. Knockdown of PKC ε notably decreased ROS production and autophagy in response to Ang II alone and in combination with hypoxia rather than hypoxia alone.

Conclusions

Both hypoxia and Ang II stimulation can induce autophagy in cardiomyocytes through increasing intracellular ROS. However, hypoxia and Ang II stimulation induced myocardial autophagy via PKC δ and PKC ε, respectively.

Lysosomal dysfunction and autophagy blockade contribute to autophagy-related cancer suppressing peptide-induced cytotoxic death of cervical cancer cells through the AMPK/mTOR pathway

Background

Autophagy is an intracellular process through which intracellular components are recycled in response to nutrient or growth factor deficiency to maintain homeostasis. We identified the peptide autophagy-related cancer-suppressing peptide (ARCSP), a potential antitumor peptide that disrupts intracellular homeostasis by blocking autophagic flux and causes cytotoxic death.

Methods

The proliferative ability of ARCSP-treated cervical cancer cells was examined by the CCK8, EdU, and colony formation assays. The TUNEL assay was used to detect apoptosis. Mitochondrial function was evaluated based on the mitochondrial membrane potential. Autophagic flux was detected by immunofluorescence and confocal microscopy. The autophagy-related proteins AMPK, Raptor, mTOR, p62, LC3B, atg7, Rab7, LAMP1, LAMP2, and cathepsin D were detected by Immunoblotting. The antitumor effect of ARCSP was explored in vivo by establishing a transplant tumor model in nude mice.

Results

The results demonstrated that ARCSP induced cell death and inhibited proliferation. ARCSP induced AMPK/mTOR activation, resulting in the accumulation of the proteins LC3B, p62 and Atg7. ARCSP also blocked autophagosome-lysosome fusion by inhibiting endosomal maturation and increasing the lysosomal pH. The accumulation of nonfused autophagosomes exacerbated cytotoxic death, whereas knocking down Atg7 reversed the cytotoxic death induced by ARCSP. ARCSP-treated cells exhibited increased cytotoxic death after cotreatment with an autophagy inhibitor (Chloroquine CQ). Furthermore, the tumors of ARCSP-treated nude mice were significantly smaller than those of untreated mice.

Conclusions

Our findings demonstrate that ARCSP, a novel lethal nonfused autophagosome inducer, might cause mitochondrial dysfunction and autophagy-related cytotoxic death and is thus a prospective agent for cancer therapy.

Artesunate reverses LPS tolerance by promoting ULK1-mediated autophagy through interference with the CaMKII-IP3R-CaMKKβ pathway

The progress of sepsis is increasingly recognized by the transition from early hyperinflammation to long term immunosuppression, which is characterized in innate immune cells by diminished responsiveness termed as lipopolysaccharide (LPS) tolerance. In this study, we investigated the ability of the antimalarial drug artesunate to reverse LPS tolerance and explored the underlying mechanisms. Initially, we detected a dramatic decline in autophagy accompanied by decreased cytokine production and impaired bacterial clearance by LPS tolerant macrophages. Then we demonstrated that artesunate restored cytokine production and enhanced bacterial clearance by inducing autophagy. Moreover, artesunate caused greater suppression of inhibitory phosphorylation than of activating phosphorylation of Unc-51 like autophagy activating kinase 1 (ULK1), a kinase that is essential for initiating autophagy through the inhibition of excessive AMP-activated protein kinase (AMPK) activation. This effect was shown to be achieved by suppression of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) phosphorylation, resulting in reduction of the inositol 1,4,5-triphate receptor (IP3R) dependent Ca²⁺ release from the endoplasmic reticulum (ER) and inhibiting the overactive CaMKKβ-AMPK cascade. Administration of artesunate also upregulated autophagy and reversed the tolerant status in LPS tolerant mice. In summary, our findings reveal a novel immunopharmacological action of artesunate to reverse LPS tolerance by restoring autophagy. Our results may also indicate the significance of autophagy induction for treating immunosuppression in sepsis.

Misaponin B Induces G2/M Arrest, Cytokinesis Failure and Impairs Autophagy

Saponins are a group of naturally occurring plant glycosides with the features of their strong foam-forming properties and multibiological effects such as antitumor activity. Though Misaponin B, one of the triterpenoid saponins from Madhuca longifolia, is known to have spermicidal and antioxidant activity, the other biological activities have been never reported so far. Thus, in the present study, the antitumor mechanism of Misaponin B was investigated in A549 and AsPC-1 cancer cells. Misaponin B exerted significant cytotoxicity in A549, H460, SKOV3, and AsPC-1 cancer cells. Among them, A549 and AsPC-1 cells were more susceptible to Misaponin B. Misaponin B induced G2/M arrest and cytokinesis failure and increased the expression of LC3B and p62 with autophagic vacuoles and GFP-LC3 punctae in A549 and AsPC-1 cells. Furthermore, Misaponin B suppressed autophagy flux in A549 cells transfected by GFP-mRFP-LC3 constructs by showing merged yellow color by autophagy flux assay. Overall, our findings provide evidences that Misaponin B induces G2M arrest and impairs autophagy in A549 and AsPC-1 cells.

Induction of autophagy protects human dental pulp cells from lipopolysaccharide-induced pyroptotic cell death

The NOD-like receptor protein 3/caspase-1 inflammasome can be activated in human dental pulp tissue and fibroblasts; however, the underlying mechanisms are poorly understood. In the present study, lipopolysaccharide (LPS) was used to treat dental pulp cells to establish an inflammation model. Cell viability was examined by sulforhodamine B assay. Interleukin (IL)-1β, caspase-1, microtubule-associated protein-1 light chain 3-II/I and p62 were determined by western blotting and ELISA. The phosphorylation (p-) levels of NF-κB and NF-κB inhibitor (IκB)α protein were observed by western blotting. The results demonstrated that LPS induced pyroptotic cell death in cultured dental pulp cells, which was supported by the increased levels of IL-1β, IL-18 and caspase-1. Rapamycin and 3-methyladenine (3-MA) were used to activate and inhibit autophagy, and it was observed that LPS increased autophagy and rapamycin reduced LPS-induced dental pulp cell pyroptosis. However, 3-MA aggravated LPS-induced dental pulp cell pyroptosis. In addition, LPS inhibited the expression of IκBα, but increased the expression of p-NF-κB. Compared with the LPS group, 3-MA further inhibited the expression of IκBα but promoted the expression of p-NF-κB. However, rapamycin produced the opposite results to LPS. Under LPS treatment, the NF-κB pathway inhibitor BAY11-7082 further enhanced the inhibitory effects of rapamycin, but inhibited the promoting effects of 3-MA on the protein expression levels of IL-1β and caspase-1. The results of the present study demonstrated that there is an important crosstalk between autophagy, pyroptosis and the NF-κB pathway, and that the modulation of pyroptosis in dental pulp cells may be a promising strategy to pulpitis therapy.

miRNA-344b-1-3p modulates the autophagy of NR8383 cells during Aspergillus fumigatus infection via TLR2

Autophagy serves a pivotal role in host defense during fungal infections, and the contribution by toll-like receptor 2 (TLR2) has been well demonstrated. It has been reported that microRNA-344a-1-3p (miR-344a-1-3p) can directly target TLR2. However, the expression of TLR2 significantly decreases during Aspergillus fumigatus infection. Therefore, the specific role of miR-344a-1-3p in the host defense against A. fumigatus infection remains to be elucidated. In the present study, A. fumigatus infection increased the expression of TLR2 and induced autophagy, which was indicated by increasing expression levels of autophagy-related protein 5 (ATG5), Beclin-1, light chain 3 (LC3)-1 and LC3-II, as measured by western blot analysis, and an increased number of GFP-LC3 puncta, as measured by fluorescence. Following transfection with miR-344a-1-3p mimics and/or TLR2, miR-344b-1-3p significantly inhibited the expression of TLR2, Beclin-1, ATG5, LC3-I and LC3-II, whereas the overexpression of TLR2 significantly attenuated the inhibitory effect on autophagy by miR-344b-1-3p. Collectively, these findings demonstrate that A. fumigatus can be controlled by the induction of autophagy following de-repression of the expression of TLR2, mediated by miR-344a-1-3p.

Parthenolide regulates oxidative stress-induced mitophagy and suppresses apoptosis through p53 signaling pathway in C2C12 myoblasts

Muscle redox disturbances and oxidative stress have emerged as a common pathogenetic mechanism and potential therapeutic intervention in some muscle diseases. Parthenolide (PTL), a sesquiterpene lactone found in large amounts in the leaves of feverfew, possesses anti-inflammatory, anti-migraine, and anticancer properties. Although PTL was reported to alleviate cancer cachexia and improve skeletal muscle characteristics in a cancer cachexia model, its actions on oxidative stress-induced damage in C2C12 myoblasts have not been reported and the regulatory mechanisms have not yet been defined. In our study, PTL attenuated H₂ O₂ -induced growth inhibition and morphological changes. Furthermore, PTL exhibited scavenging activity against reactive oxygen species and protected C2C12 cells from apoptosis in response to H₂ O₂ . Meanwhile, PTL suppressed collapse of the mitochondrial membrane potential, thereby contributing to normalizing H₂ O₂ -induced autophagy flux and mitophagy, correlating with inhibiting degradation of mitochondrial marker protein TIM23, the increase in LC3-II expression and the reduction of mitochondria DNA. Besides its protective effect on mitochondria, PTL also prevented H₂ O₂ -induced lysosomes damage in C2C12 cells. In addition, the phosphorylation of p53, cathepsin B, and Bax/Bcl-2 protein levels, and the translocation of Bax from the cytosol to mitochondria induced by H₂ O₂ in C2C12 cells was significantly reduced by PTL. In conclusion, PTL modulates oxidative stress-induced mitophagy and protects C2C12 myoblasts against apoptosis, suggesting a potential protective effect against oxidative stress-associated skeletal muscle diseases.

Recombinant human arginase I elicited immunosuppression in activated macrophages through inhibiting autophagy

Arginase I has been documented to impair T cell function and attenuate cellular immunity, however, there is little evidence to reveal the effect of arginase I on macrophage function. Recently, recombinant human arginase I (rhArg) has been developed for cancer therapy and is in clinical trial for hepatocellular carcinoma, whereas the potential immunosuppression induced by rhArg limited its therapeutic efficacy. To improve the clinical outcome of rhArg, addressing the immune suppression appears to be particularly important. In this study, we found that rhArg attenuated macrophage functions, including inhibiting macrophage cell proliferation, nitric oxide (NO) and reactive oxygen species (ROS) production, cytokine secretion, MHC-II surface expression, and phagocytosis, thereby inducing immunosuppression in lipopolysaccharides (LPS)/interferon-γ (IFN-γ)-activated macrophages. Notably, we observed that rhArg downregulated autophagy in activated macrophages. Moreover, application of trehalose (an autophagy inducer) significantly restored the impaired immune function in activated macrophages, suggesting the essential role of autophagy in rhArg-induced immunosuppression. To further illustrate the effect of autophagy in immunosuppression, we then observed the effect of 3-MA (an autophagy inhibitor) on the immune function of macrophages. As expected, inhibiting autophagy by 3-MA attenuated immune functions in activated macrophages. Collectively, this study elucidated that rhArg induced immunosuppression in activated macrophages via inhibiting autophagy, providing potential strategy to ameliorate the immune suppression which is of great significance to cancer therapy and facilitating the development of rhArg as a potential therapy for malignant carcinomas.

Inhibition of Autophagy Alleviates Cadmium-Induced Mouse Spleen and Human B Cells Apoptosis

Cadmium (Cd) is a toxic heavy metal that can accumulate and cause severe damage to many organs, such as liver, kidney, lung, etc. Cd also significantly suppresses immunity, however, the underlying mechanism involved in Cd-induced immunnotoxicity is still unclear. The present study indicated that semichronic Cd exposure (7 days) induced apoptotic damage of mouse spleen. In human Ramos B cells, Cd exposure also induced apoptosis, which was dependent on Cd-induced vacuole membrane protein 1 (VMP1) expression and autophagy. Cd-induced autophagy and apoptosis were abated when VMP1 expression was knockdown. In addition, Cd-induced VMP1 expression, autophagy, and apoptosis were dependent on the elevation of Ca2+ and reactive oxygen species (ROS). More important, Cd exposure also induced VMP1 expression and autophagy in mouse spleen tissue, and the intraperitoneal injection of the autophagy inhibitor chloroquine (CQ) into mice effectively reduced Cd-induced spleen apoptotic damage. Taken together, these results indicate Cd-induced autophagy, promotes apoptosis in immune cells, and inhibition of autophagy can alleviate Cd-induced spleen and immune cell apoptosis. This study might provide the groundwork for future studies on Cd-induced immunomodulatory effects and immune diseases.

Autophagy in pulmonary hypertension: Emerging roles and therapeutic implications

Autophagy is an important mechanism for cellular self-digestion and basal homeostasis. This gene- and modulator-regulated pathway is conserved in cells. Recently, several studies have shown that autophagic dysfunction is associated with pulmonary hypertension (PH). However, the relationship between autophagy and PH remains controversial. In this review, we mainly introduce the effects of autophagy-related genes and some regulatory molecules on PH and the relationship between autophagy and PH under the conditions of hypoxia, monocrotaline injection, thromboembolic stress, oxidative stress, and other drugs and toxins. The effects of other autophagy-related drugs, such as chloroquine, 3-methyladenine, rapamycin, and other potential therapeutic drugs and targets, in PH are also described.

Investigation of Morphological Features of Autophagy During Plant Programmed Cell Death

The investigation of autophagy particularly when observed during programmed cell death (PCD) is strongly based on the morphological features recorded with transmission electron microscope (TEM). Here we describe methods to induce and to inhibit autophagy in plants. Also some tips for obtaining better preservation of biological membranes, crucial for the investigation of autophagy, are provided together with information about plant autophagic mutants, use of antibodies and methods for 3D reconstruction of large membrane-bound objects that are commonly formed during autophagic processes leading to PCD in plants.

Lipoxin A4 receptor agonist BML-111 induces autophagy in alveolar macrophages and protects from acute lung injury by activating MAPK signaling

Background

Acute lung injury (ALI) is a life-threatening lung disease where alveolar macrophages (AMs) play a central role both in the early phase to initiate inflammatory responses and in the late phase to promote tissue repair. In this study, we examined whether BML-111, a lipoxin A4 receptor agonist, could alter the phenotypes of AM and thus present prophylactic benefits for ALI.

Methods

In vitro, isolated AMs were treated with lipopolysaccharide (LPS) to induce ALI. In response to BML-111 pre-treatment, apoptosis and autophagy of AMs were examined by flow cytometry, and by measuring biomarkers for each process. The potential involvement of MAPK1 and mTOR signaling pathway was analyzed. In vivo, an LPS-induced septic ALI model was established in rats and the preventative significance of BML-111 was assessed. On the cellular and molecular levels, the pro-inflammatory cytokines TNF-α and IL-6 from bronchoalveolar lavage were measured by ELISA, and the autophagy in AMs examined using Western blot.

Results

BML-111 inhibited apoptosis and induced autophagy of AMs in response to ALI inducer, LPS. The enhancement of autophagy was mediated through the suppression of MAPK1 and MAPK8 signaling, but independent of mTOR signaling. In vivo, BML-111 pre-treatment significantly alleviated LPS-induced ALI, which was associated with the reduction of apoptosis, the dampened production of pro-inflammatory cytokines in the lung tissue, as well as the increase of autophagy of AMs.

Conclusions

This study reveals the prophylactic significance of BML-111 in ALI and the underlying mechanism: by targeting the MAPK signaling but not mTOR pathway, BML-111 stimulates autophagy in AMs, attenuates the LPS-induced cell apoptosis, and promotes the resolution of ALI.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

Autophagy activation in circulating proangiogenic cells aggravates AKI in type I diabetes mellitus

Acute kidney injury (AKI) occurs frequently in hospitals worldwide, but the therapeutic options are limited. Diabetes mellitus (DM) affects more and more people around the globe. The disease worsens the prognosis of AKI even further. In recent years, cell-based therapies have increasingly been applied in experimental AKI. The aim of the study was to utilize two established autophagy inducers for pharmacological preconditioning of so-called proangiogenic cells (PACs) in PAC treatment of diabetic AKI. Insulin-dependent DM was induced in male C57/Bl6N mice by intraperitoneal injections of streptozotocine. Six weeks later, animals underwent bilateral renal ischemia for 45 min, followed by intravenous injections of either native or zVAD (benzyloxycarbonyl-Val-Ala-Asp-fluoro-methylketone)- or Z-Leu-Leu-Leu-al (MG132)-pretreated syngeneic murine PACs. Mice were analyzed 48 h (short term) and 6 wk (long term) later, respectively. DM worsened postischemic AKI, and PAC preconditioning with zVAD and MG132 resulted in a further decline of excretory kidney function. Injection of native PACs reduced fibrosis in nondiabetic mice, but cell preconditioning promoted interstitial matrix accumulation significantly. Both substances aggravated endothelial-to-mesenchymal transition (EndoMT) under diabetic conditions; these effects occurred either exclusively in the short (zVAD) or in the short and long term (MG132). Preconditioned cells stimulated the autophagocytic flux in intrarenal endothelial cells, and all experimental groups displayed increased endothelial abundances of senescence-associated β-galactosidase, a marker of premature cell senescence. Pharmacological autophagy activation may not serve as an effective strategy for improving PAC competence in diabetic AKI in general. On the contrary, several outcome parameters (excretory function, fibrosis, EndoMT) may even be worsened.

The Complex Link between Apoptosis and Autophagy: a Promising New Role for RB

Physiological processes, as autophagy, proliferation and apoptosis are affected during carcinogenesis. Restoring cellular sensitivity to apoptotic stimuli, such as the antineoplastic cocktails, has been explored as a strategy to eliminate cancer cells. Autophagy, a physiological process of recycling organelles and macromolecules can be deviated from homeostasis to support cancer cells survival, proliferation, escape from apoptosis, and therapy resistance. The relationship between autophagy and apoptosis is complex and many stimuli can induce both processes. Most chemotherapeutic agents induce autophagy and it is not clear whether and how this chemotherapy-induced autophagy might contribute to resistance to apoptosis. Here, we review current strategies to sensitize cancer cells by interfering with autophagy. Moreover, we discuss a new link between autophagy and apoptosis: the tumor suppressor retinoblastoma protein (RB). Inactivation of RB is one of the earliest and more frequent hallmarks of cancer transformation, known to control cell cycle progression and apoptosis. Therefore, understanding RB functions in controlling cell fate is essential for an effective translation of RB status in cancer samples to the clinical outcome.

The tumor-suppressor cholesterol metabolite, dendrogenin A, is a new class of LXR modulator activating lethal autophagy in cancers

Dendrogenin A (DDA) is a mammalian cholesterol metabolite recently identified that displays tumor suppressor properties. The discovery of DDA has revealed the existence in mammals of a new metabolic branch in the cholesterol pathway centered on 5,6α-epoxycholesterol and bridging cholesterol metabolism with histamine metabolism. Metabolic studies showed a drop in DDA levels in cancer cells and tumors compared to normal cells, suggesting a link between DDA metabolism deregulation and oncogenesis. Importantly, complementation of cancer cells with DDA induced 1) cancer cell re-differentiation, 2) blockade of 6-oxo-cholestan-3β,5α-diol (OCDO) production, an endogenous tumor promoter and 3) lethal autophagy in tumors. Importantly, by binding the liver X receptor (LXR), DDA activates the expression of genes controlling autophagy. These genes include NR4A1, NR4A3, LC3 and TFEB. The canonical LXR ligands 22(R)hydroxycholesterol, TO901317 and GW3965 did not induce these effects indicating that DDA delineates a new class of selective LXR modulator (SLiM). The induction of lethal autophagy by DDA was associated with the accumulation in cancer cells of lysosomes and of the pro-lysosomal cholesterol precursor zymostenol due to the inhibition of the 3β-hydroxysteroid-Δ⁸Δ⁷-isomerase enzyme (D8D7I). The anti-cancer efficacy of DDA was established on different mouse and human cancers such as breast cancers, melanoma and acute myeloid leukemia, including patient derived xenografts, and did not discriminate bulk cancer cells from cancer cell progenitors. Together these data highlight that the mammalian metabolite DDA is a promising anticancer compound with a broad range of anticancer applications. In addition, DDA and LXR are new actors in the transcriptional control of autophagy and DDA being a "first in line" driver of lethal autophagy in cancers via the LXR.

Nr4a1 plays a crucial modulatory role in Th1/Th17 cell responses and CNS autoimmunity

Nuclear receptor4 group A1 (Nr4a1), an orphan nuclear receptor, is down-regulated in peripheral blood mononuclear cells (MNCs) of individuals with multiple sclerosis (MS), and Nr4a1 deficiency results in severe experimental autoimmune encephalomyelitis (EAE), an animal model of MS, caused by increased macrophage infiltration into the central nervous system (CNS). However, the role of Nr4a1 in macrophage phenotype and T cell responses remains poorly understood. In the present study we show that macrophages/microglia of Nr4a1^-/- mice, which exhibited earlier onset and more severe clinical EAE, were polarized to an enhanced type 1 (M1) phenotype and produced higher levels of IL-12 and TNF-α than wild type mice. Significantly increased numbers of CD4⁺ T cells and frequency of CD4⁺IFN-γ⁺ and CD4⁺IL-17⁺ T cells were observed in the CNS and spleen of Nr4a1^-/- mice, with decreased percentages of apoptosis in CD4⁺ T cells. The percentages of CD4⁺Foxp3⁺ Treg cells in the CNS of Nr4a1^-/- mice were also reduced. Furthermore, purified CD4⁺ T cells from naïve Nr4a1^-/- mice exhibited enhanced Th1 and Th17 differentiation capacity, and MOG-reactive Th17 cells from Nr4a1^-/- mice adoptively transferred more severe EAE in recipient mice. Our results, for the first time, demonstrate that Nr4a1 not only induces Type 2 macrophages/microglia phenotype, but is also a critical inhibitory molecule for Th1/Th17 cell differentiation. This finding indicates that Nr4a1-related molecule(s) may have therapeutic potential in MS and likely other autoimmune disorders.

The Polyphenol Oleuropein Aglycone Modulates the PARP1-SIRT1 Interplay: An In Vitro and In Vivo Study

Poly(ADP-ribose) polymerase-1 (PARP1) activation contributes to the cascade of events initiated by amyloid-β (Aβ) peptide eventually leading to cell death in Alzheimer's disease brain. A significant accumulation of PAR polymers and increase of PARP1 expression were detected in the cortex at the early (3.5 months) and intermediate (6 months) stage of Aβ deposition in the TgCRND8 mouse model. Our previous data highlighted the beneficial effects of oleuropein aglycone (OLE), the main polyphenol found in the olive oil, against neurodegeneration both in cultured cells and in model organisms. Here we found that 8-week OLE treatment (50 mg/kg of diet) to 6-month-old TgCRND8 mice rescued to control values PARP1 activation and the levels of its product, PAR. In N2a neuroblastoma cells, PARP1 activation and PAR formation upon exposure to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were abolished by pretreatment for 24 h with either OLE (100μM) or PARP inhibitors. A significant reduction of the NAD+ content, compared to controls, was found in N2a cells exposed to MNNG (100μM) for 90 min; the latter was slightly attenuated by cell treatment for 24 h with PJ-34 or with OLE. In vitro and in vivo, the OLE-induced reduction of PARP1 activation was paralleled by the overexpression of Sirtuin1 (SIRT1), and, in vivo, by a decrease of NF-κB and the pro-apoptotic marker p53. In N2a cells, we also found that OLE potentiates the MNNG-induced increase of Beclin1 levels. In conclusion, our data show that OLE treatment counteracts neuronal damage through modulation of the PARP1-SIRT1 interplay.

Monotropein promotes angiogenesis and inhibits oxidative stress-induced autophagy in endothelial progenitor cells to accelerate wound healing

Attenuating oxidative stress‐induced damage and promoting endothelial progenitor cell (EPC) differentiation are critical for ischaemic injuries. We suggested monotropein (Mtp), a bioactive constituent used in traditional Chinese medicine, can inhibit oxidative stress‐induced mitochondrial dysfunction and stimulate bone marrow‐derived EPC (BM‐EPC) differentiation. Results showed Mtp significantly elevated migration and tube formation of BM‐EPCs and prevented tert‐butyl hydroperoxide (TBHP)‐induced programmed cell death through apoptosis and autophagy by reducing intracellular reactive oxygen species release and restoring mitochondrial membrane potential, which may be mediated viamTOR/p70S6K/4EBP1 and AMPK phosphorylation. Moreover, Mtp accelerated wound healing in rats, as indicated by reduced healing times, decreased macrophage infiltration and increased blood vessel formation. In summary, Mtp promoted mobilization and differentiation of BM‐EPCs and protected against apoptosis and autophagy by suppressing the AMPK/mTOR pathway, improving wound healing in vivo. This study revealed that Mtp is a potential therapeutic for endothelial injury‐related wounds.

Autophagy induces apoptosis and death of T lymphocytes in the spleen of pigs infected with CSFV

Lymphocyte depletion and immunosuppression are typical clinical characteristics of pigs infected with classical swine fever virus (CSFV). The apoptosis of virus-infected and bystander cells plays a role in the immunopathology of classical swine fever (CSF). Here, we offer the first evidence that autophagy is involved in apoptosis and death of T lymphocytes in the spleen of pigs infected with CSFV. Using immunohistochemical assays, we observed that more LC3II-positive cells appear in the T-cell zone of spleens. Spleen cell apoptosis was demonstrated using flow cytometry and TUNEL staining. Confocal immunofluorescence revealed that partial LC3II-positive cells were simultaneously TUNEL-positive. By cultivating spleen cells ex vivo, we demonstrated that the inhibition of autophagy by 3-MA treatment inhibited apoptosis and death of T lymphocytes caused by CSFV infection but did not have this effect  on B lymphocytes. Further observations demonstrated that uninfected cells in the spleen were also undergoing autophagy in vivo. In summary, these results linked autophagy with the apoptosis and cell death of splenic T cells, providing a new outlook to understand the mechanism of T lymphocyte depletion and immunosuppression during CSF.

Lutein Induces Autophagy via Beclin-1 Upregulation in IEC-6 Rat Intestinal Epithelial Cells

Lutein is a carotenoid with anti-oxidant properties. Autophagy, an evolutionarily conserved catabolic cellular pathway for coping with stress conditions, is responsive to reactive oxygen species (ROS) and degrades damaged organelles. We previously demonstrated that lutein can induce anti-oxidant enzymes to relieve methotrexate-induced ROS stress. We therefore hypothesized that lutein, which activates ROS-scavenging enzymes, can also induce autophagy for cell survival. In this study, we demonstrated that lutein treatment attenuated the reduction in cell viability caused by H2O2. Lutein dose-dependently induced the processing of microtubule-associated protein light chain 3 (LC3)-II, an autophagy marker protein, and accumulation of LC3-positive puncta in rat intestinal IEC-6 cells. Furthermore, (a) direct observation of autophagosome formation through transmission electron microscopy, (b) upregulation of autophagy-related genes including ATG4A, ATG5, ATG7, ATG12, and beclin-1 (BENC1), and (c) increased BECN1/Bcl-2 ratio confirmed the induction of autophagy by lutein. The results revealed that bafilomycin-A1-induced inhibition of autophagy reduced cell viability and increased apoptosis in lutein-treated cells, indicating a protective role of lutein-induced autophagy. Lutein treatment also activated adenosine monophosphate–activated protein kinase (AMPK), c-Jun N-terminal kinase (JNK), and p-38, but had no effects on the induction of extracellular signal-related kinase or inhibition of mTOR; however, the inhibition of activated AMPK, JNK, or p-38 did not attenuate lutein-induced autophagy. Finally, increased BECN1 expression levels were detected in lutein-treated cells, and BECN1 knockdown abolished autophagy induction. These results suggest that lutein-induced autophagy was mediated by the upregulation of BECN1 in IEC-6 cells. We are the first to demonstrate that lutein induces autophagy. Elevated autophagy in lutein-treated IEC-6 cells may have a protective role against various stresses, and this warrants further investigation.

A Vibrio vulnificus VvpM Induces IL-1β Production Coupled with Necrotic Macrophage Death via Distinct Spatial Targeting by ANXA2

An inflammatory form of phagocyte death evoked by the Gram-negative bacterium Vibrio (V.) vulnificus (WT) is one of hallmarks to promote their colonization, but the virulence factor and infectious mechanism involved in this process remain largely unknown. Here, we identified extracellular metalloprotease VvpM as a new virulence factor and investigated the molecular mechanism of VvpM which acts during the regulation of the inflammatory form of macrophage death and bacterial colonization. Mutation of the vvpM gene appeared to play major role in the prevention of IL-1β production due to V. vulnificus infection in macrophage. However, the recombinant protein (r) VvpM caused IL-1β production coupled with necrotic cell death, which is highly susceptible to the knockdown of annexin A2 (ANXA2) located in both membrane lipid and non-lipid rafts. In lipid rafts, rVvpM recruited NOX enzymes coupled with ANXA2 to facilitate the production of ROS responsible for the epigenetic and transcriptional regulation of NF-κB in the IL-1β promoter. rVvpM acting on non-lipid rafts increased LC3 puncta formation and autophagic flux, which are required for the mRNA expression of Atg5 involved in the autophagosome formation process. The autophagy activation caused by rVvpM induced NLRP3 inflammasome-dependent caspase-1 activation in the promoting of IL-1β production. In mouse models of V. vulnificus infection, the VvpM mutant failed to elevate the level of pro-inflammatory responses closely related to IL-1β production and prevented bacterial colonization. These findings delineate VvpM efficiently regulates two pathogenic pathways that stimulate NF-κB-dependent IL-1β production and autophagy-mediated NLRP3 inflammasome via distinct spatial targeting by ANXA2.

Vitexin confers HSF-1 mediated autophagic cell death by activating JNK and ApoL1 in colorectal carcinoma cells

Heat shock transcription factor-1 (HSF-1) guards the cancerous cells proteome against the alterations in protein homeostasis generated by their hostile tumor microenvironment. Contrasting with the classical induction of heat shock proteins, the pro-oncogenic activities of HSF-1 remains to be explored. Therefore, cancer's fragile proteostatic pathway governed by HSF-1 could be a potential therapeutic target and novel biomarker by natural compounds. Vitexin, a natural flavonoid has been documented as a potent anti-tumor agent on various cell lines. However, in the present study, when human colorectal carcinoma HCT-116 cells were exposed to vitexin, the induction of HSF-1 downstream target proteins, such as heat shock proteins were suppressed. We identified HSF-1 as a potential molecular target of vitexin that interact with DNA-binding domain of HSF-1, which inhibited HSF-1 oligomerization and activation (in silico). Consequently, HSF-1 hyperphosphorylation mediated by JNK operation causes transcriptional inactivation of HSF-1, and supported ROS-mediated autophagy induction. Interestingly, in HSF-1 immunoprecipitated and silenced HCT-116 cells, co-expression of apolipoprotein 1 (ApoL1) and JNK was observed which promoted the caspase independent autophagic cell death accompanied by p62 downregulation and increased LC3-I to LC3-II conversion. Finally, in vivo findings confirmed that vitexin suppressed tumor growth through activation of autophagic cascade in HCT-116 xenograft model. Taken together, our study insights a probable novel association between HSF-1 and ApoL-1 was established in this study, which supports HSF-1 as a potential target of vitexin to improve treatment outcome in colorectal cancer.

Adiponectin modulates oxidative stress-induced mitophagy and protects C2C12 myoblasts against apoptosis

Adiponectin (APN), also known as apM1, Acrp30, GBP28 and adipoQ, is a circulating hormone that is predominantly produced by adipose tissue. Many pharmacological studies have demonstrated that this protein possesses potent anti-diabetic, anti-atherogenic and anti-inflammatory properties. Although several studies have demonstrated the antioxidative activity of this protein, the regulatory mechanisms have not yet been defined in skeletal muscles. The aim of the present study was to examine the cytoprotective effects of APN against damage induced by oxidative stress in mouse-derived C2C12 myoblasts. APN attenuated H₂O₂-induced growth inhibition and exhibited scavenging activity against intracellular reactive oxygen species that were induced by H₂O₂. Furthermore, treating C2C12 cells with APN significantly induced heme oxygenase-1 (HO-1) and nuclear factor-erythroid 2 related factor 2 (Nrf2). APN also suppressed H₂O₂-induced mitophagy and partially inhibited the colocalization of mitochondria with autophagosomes/lysosomes, correlating with the expression of Pink1 and Parkin and mtDNA. Moreover, APN protected C2C12 myoblasts against oxidative stress-induced apoptosis. Furthermore, APN significantly reduced the mRNA and protein expression levels of Bax. These data suggest that APN has a moderate regulatory role in oxidative stress-induced mitophagy and suppresses apoptosis. These findings demonstrate the antioxidant potential of APN in oxidative stress-associated skeletal muscle diseases.

Nrf2 promotes progression of non-small cell lung cancer through activating autophagy

The transcription factor, NFE2-related factor 2 (Nrf2) and autophagy have been implicated in the oxidative-stress response during tumor evolution. However, few studies focus on crosstalk between Nrf2 and autophagy in cancer progression of non-small cell lung cancer (NSCLC). Herein, we evaluated the effect of Nrf2 on autophagy in NSCLC and their role in development of NSCLC. Effect of Nrf2 on overal survival (OS) of NSCLC patients were evaluated. Cell biological behaviors in response to Nrf2 were evaluated by MTT, colony formation assay and flow cytometry. Effect of 3-MA (a classical inhibitor of autophagy) on 95D-Nrf2 cells was also analyzed using flow cytometry. After up/down-regulating Nrf2 in NSCLC cell lines, expression of autophagy-related proteins were evaluated with western blot analysis. The results revealed that Nrf2 was an independent prognositc factor negtively associated with OS of NSCLC patients. Elevated Nrf2 expression promotes NSCLC progression, enhancing the escape of tumor cells from apoptosis in vivo and in vitro. Double staining with Annexin V-APC and 7-AAD showed that the proportions of apoptotic cells in 95D-Nrf2 cells were gradually increased after the addition of 3-MA. Importently, Nrf2 induced autophagosome formation and enhanced autophagic activity, which subsequently inhibits NSCLC cell apoptosis. In conclusion, our present study demonstrates that Nrf2 promotes progression of non-small cell lung cancer through activating autophagy. It provides novel insights into Nrf2-mediated of cell proliferation in NSCLC and may facilitate therapeutic development against NSCLC.

The roles of reactive oxygen species (ROS) and autophagy in the survival and death of leukemia cells

As a clonal disease of hematopoietic stem cells (HSCs), the etiology and pathogenesis of leukemia is not fully understood. Recent studies suggest that cellular homeostasis plays an essential role in maintaining the function of HSCs because dysregulation of cellular homeostasis is one of the major factors underlying the malignant transformation of HSCs. Reactive oxygen species (ROS) and autophagy, key factors regulating cellular homeostasis, are commonly observed in the human body. Autophagy can be induced by ROS through a variety of signaling pathways, and conversely inhibits ROS-induced damage to cells and tissues. ROS and autophagy coordinate to maintain cellular homeostasis. Previous studies have demonstrated that both of ROS and autophagy play important roles in the development of leukemia and are closely involved in drug resistance in leukemia. Interference with cellular homeostasis by promoting programmed leukemia cell death via ROS and autophagy has been verified to be an efficient technique in the treatment of leukemia. However, the critical roles of ROS and autophagy in the development of leukemia are largely unknown. In this review, we summarize the roles of ROS and autophagy in the pathogenesis of leukemia, which may allow the identification of novel targets and drugs for the treatment of leukemia based on the regulation of HSCs homeostasis through ROS and autophagy.

Immunomodulatory proteins FIP-gts and chloroquine induce caspase-independent cell death via autophagy for resensitizing cisplatin-resistant urothelial cancer cells

BACKGROUND

Chloroquine, a lysosomal inhibitor, is used for malaria, rheumatoid arthritis, and lupus erythematosus therapy. In our previous study, FIP-gts, an immunomodulatory protein from Ganoderma tsugae, inhibited cell viability in lung cancer cells and urothelial cancer cells. Urothelial carcinoma is the most common type of bladder cancer. Cisplatin resistance is an important issue in urothelial carcinoma therapy.

PURPOSE

The aim of this study is to investigate the effect of combination treatment with FIP-gts and chloroquine on cytotoxicity to resensitize the cisplatin-resistant cells.

METHODS

FIP-gts and chloroquine cytotoxicity were determined by evaluating CCK-8 assay. Cell death pathways, ROS and cell cycle arrested were analysed through flow cytometry and Western blot. ShRNA targeting to autophagy-related genes were tested to evaluate their autophagic cell death for resistant urothelial cells.

RESULTS

Using CCK-8 assay, chloroquine increased FIP-gts-induced cytotoxicity in parental and cisplatin-resistant urothelial cancer cell lines. On flow cytometry, chloroquine enhanced FIP-gts-mediated sub-G1 accumulation, annexin V positive signal and mitochondrial membrane potential loss. Caspase-3/PARP cascade and z-VAD-fmk were performed to prove that FIP-gts and chloroquine induced caspase-independent cell death. Using H2DCFDA staining and flow cytometry, FIP-gts and chloroquine did not induce ROS production. N-acetyl cysteine, a ROS scavenger, inhibited the cytotoxicity and LC3-II accumulation in FIP-gts and chloroquine-treated N/P cells. To elucidate the role of autophagy in caspase-independent cell death by FIP-gts and chloroquine, LC3 shRNA were used to inhibit autophagy in N/P cells. The capabilities of FIP-gts and chloroquine to induce cytotoxicity and sub-G1 phase accumulation were abolished in autophagy-defective cells. This is the first study to reveal the novel function of FIP-gts in triggering caspase-independent cell death in cisplatin-resistant urothelial cancer cells.

CONCLUSION

Chloroquine enhanced FIP-gts-induced autophagy dependent caspase-independent cell death via abundant autophagosome accumulation. Combination treatment with FIP-gts and chloroquine may provide a new strategy for urothelial cancer therapy.

Cloaked in ubiquitin, a killer hides in plain sight: the molecular regulation of RIPK1

In the past decade, studies have shown how instrumental programmed cell death (PCD) can be in innate and adaptive immune responses. PCD can be a means to maintain homeostasis, prevent or promote microbial pathogenesis, and drive autoimmune disease and inflammation. The molecular machinery regulating these cell death programs has been examined in detail, although there is still much to be explored. A master regulator of programmed cell death and innate immunity is receptor-interacting protein kinase 1 (RIPK1), which has been implicated in orchestrating various pathologies via the induction of apoptosis, necroptosis, and nuclear factor-κB-driven inflammation. These and other roles for RIPK1 have been reviewed elsewhere. In a reflection of the ability of tumor necrosis factor (TNF) to induce either survival or death response, this molecule in the TNF pathway can transduce either a survival or a death signal. The intrinsic killing capacity of RIPK1 is usually kept in check by the chains of ubiquitin, enabling it to serve in a prosurvival capacity. In this review, the intricate regulatory mechanisms responsible for restraining RIPK1 from killing are discussed primarily in the context of the TNF signaling pathway and how, when these mechanisms are disrupted, RIPK1 is free to unveil its program of cellular demise.

Reduction of polyethylenimine-coated iron oxide nanoparticles induced autophagy and cytotoxicity by lactosylation

Superparamagnetic iron oxide (SPIO) nanoparticles are excellent magnetic resonance contrast agents and surface engineering can expand their applications. When covered with amphiphilic alkyl-polyethyleneimine (PEI), the modified SPIO nanoparticles can be used as MRI visible gene/drug delivery carriers and cell tracking probes. However, the positively charged amines of PEI can also cause cytotoxicity and restricts their further applications. In this study, we used lactose to modify amphiphilic low molecular weight polyethylenimine (C12-PEI2K) at different lactosylation degree. It was found that the N-alkyl-PEI-lactobionic acid wrapped SPIO nanocomposites show better cell viability without compromising their labelling efficacy as well as MR imaging capability in RAW 264.7 cells, comparing to the unsubstituted ones. Besides, we found the PEI induced cell autophagy can be reduced via lactose modification, indicating the increased cell viability might rely on down-regulating autophagy. Thus, our findings provide a new approach to overcome the toxicity of PEI wrapped SPIO nanocomposites by lactose modification.

The Different Effects of Atorvastatin and Pravastatin on Cell Death and PARP Activity in Pancreatic NIT-1 Cells

Statins have been widely used drugs for lowering low-density lipoprotein and for preventing heart attack and stroke. However, the increased risk for developing diabetes during extended stain use and the molecular mechanisms remain unclear. The objective of this study was to elucidate the signaling pathway and biological function between necrosis and autophagy induced by atorvastatin (AS) and pravastatin (PS). Here we observed that atorvastatin (AS) can increase intracellular reactive oxygen species (ROS) and induce necrotic cell death and autophagy in NIT-1 cells, whereas pravastatin (PS) does not cause ROS and cell death but also induces autophagy. PARP1 exhibited a dual role in modulating necrosis and autophagy in AS- and PS-treated NIT-1 cells through RIP1-RIP3-MLKL pathway and PARP1-AMPK-mTOR pathway. Lastly, AS treatment induced mitochondrial morphology injury significantly more than PS treatment did. Thus, the PARP1 activation should be considered in the development of effective statin therapies for diabetes. Future studies may examine specific mechanisms and pathways in mitochondria, autophagy, and oxidative stress in vivo.

Role of autophagy in cisplatin-induced ototoxicity

OBJECTIVE

Hearing loss is a major side effect of cisplatin chemotherapy. Although cell death in cisplatin-induced ototoxicity is primarily caused by apoptosis, the exact mechanism behind the ototoxic effects of cisplatin is not fully understood. Autophagy is generally known as a pro-survival mechanism that protects cells under starvation or stress conditions. However, recent research has reported that autophagy plays a functional role in cell death also. This study aimed to investigate the role of autophagy in cisplatin-induced ototoxicity in an auditory cell line.

METHODS

Cultured HEI-OC1 cells were exposed to 30 μM cisplatin for 48 h, and cell viability was tested using MTT assays. To evaluate whether autophagy serves to cell death after cisplatin exposure, western blotting and immunofluorescence staining for LC3-II were performed. Markers of two autophagy-related pathways, mTOR and class III PI3K, were also investigated.

RESULTS

The formation of the autophagic protein LC3-II in response to 30 μM cisplatin increased with time. The early upregulation of autophagy exerted cytoprotective activity via the class III PI3K pathway. But later increase in autophagy induced cell death by suppressing the mTOR pathway.

CONCLUSION

Our results prove that autophagy could induce cell death during cisplatin-induced ototoxicity, and modulating the autophagic pathway might be another strategy against cisplatin-induced ototoxicity.

TAK1 inhibition-induced RIP1-dependent apoptosis in murine macrophages relies on constitutive TNF-α signaling and ROS production

Background

Transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) is a key regulator of signal cascades of TNF-α receptor and TLR4, and can induce NF-κB activation for preventing cell apoptosis and eliciting inflammation response.

Results

TAK1 inhibitor (TAKI) can decrease the cell viability of murine bone marrow-derived macrophages (BMDM), RAW264.7 and BV-2 cells, but not dermal microvascular endothelial cells, normal human epidermal keratinocytes, THP-1 monocytes, human retinal pigment epithelial cells, microglia CHME3 cells, and some cancer cell lines (CL1.0, HeLa and HCT116). In BMDM, TAKI-induced caspase activation and cell apoptosis were enhanced by lipopolysaccharide (LPS). Moreover, TAKI treatment increased the cytosolic and mitochondrial reactive oxygen species (ROS) production, and ROS scavengers NAC and BHA can inhibit cell death caused by TAKI. In addition, RIP1 inhibitor (necrostatin-1) can protect cells against TAKI-induced mitochondrial ROS production and cell apoptosis. We also observed the mitochondrial membrane potential loss after TAKI treatment and deterioration of oxygen consumption upon combination with LPS. Notably TNF-α neutralization antibody and inhibitor enbrel can decrease the cell death caused by TAKI.

Conclusions

TAKI-induced cytotoxicity is cell context specific, and apoptosis observed in macrophages is dependent on the constitutive autocrine action of TNF-α for RIP1 activation and ROS production.

Autophagy Mediates Astrocyte Death During Zinc-Potentiated Ischemia--Reperfusion Injury

Pathological release of excess zinc ions and the resultant increase in intracellular zinc has been implicated in ischemic brain cell death, although the underlying mechanisms are not fully understood. Since zinc promotes the formation of the autophagic signal, reactive oxygen species (ROS), and increases autophagy, a known mechanism of cell death, we hypothesized that autophagy is involved in zinc-induced hypoxic cell death. To study this hypothesis, we determined the effect of zinc on autophagy and ROS generation in C8-D1A astrocytes subjected to hypoxia and rexoygenation (H/R), simulating ischemic stroke. C8-D1A astrocytes subjected to 3-h hypoxia and 18-h reoxygenation exhibited dramatically increased autophagy and astrocyte cell death in the presence of 100 μM zinc. Pharmacological inhibition of autophagy decreased zinc-potentiated H/R-induced cell death, while scavenging ROS reduced both autophagy and cell death caused by zinc-potentiated H/R. These data indicate that zinc-potentiated increases in ROS lead to over-exuberant autophagy and increased cell death in H/R-treated astrocytes. Furthermore, our elucidation of this novel mechanism indicates that modulation of autophagy, ROS, and zinc levels may be useful targets in decreasing brain damage during stroke.

Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Infection Induced Apoptosis and Autophagy in Thymi of Infected Piglets

Previously, we demonstrated that the highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) HuN4 strain causes obvious thymic atrophy and thymocytes apoptosis in infected piglets after birth, which is more severe than that induced by classical PRRSV. In this study, we investigated apoptosis and autophagy in the thymus of piglets infected with the HP-PRRSV HuN4 strain, and found that both apoptosis and autophagy occurred in the thymus of piglets infected with HP-PRRSV. In addition to a few virus-infected cells, CD14⁺ cells, the main autophagic cells in the thymus were thymic epithelial cells. These findings demonstrated that HP-PRRSV induces apoptosis in bystander cells, and induces autophagy in both infected and bystander cells in the thymus of infected piglets. Herein, we first present new data on the thymic lesions induced by HP-PRRSV, and show that apoptosis and autophagy are key mechanisms involved in cell survival and determinants of the severity of thymic atrophy in infected piglets. Finally, future studies of the mechanism underlying immune responses are proposed based on our current understanding of PRRSV-host interactions.

Globular Adiponectin Causes Tolerance to LPS-Induced TNF-α Expression via Autophagy Induction in RAW 264.7 Macrophages: Involvement of SIRT1/FoxO3A Axis

Adiponectin, an adipokine predominantly produced from adipose tissue, exhibited potent anti-inflammatory properties. In particular, it inhibits production of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), in macrophages. Autophagy, an intracellular self-digestion process, has been recently shown to regulate inflammatory responses. In the present study, we investigated the role of autophagy induction in the suppression of Lipopolysaccharide (LPS) -induced TNF-α expression by globular adiponectin (gAcrp) and its potential mechanisms. Herein, we found that gAcrp treatment increased expression of genes related with autophagy, including Atg5 and microtubule-associated protein light chain (LC3B), induced autophagosome formation and autophagy flux in RAW 264.7 macrophages. Similar results were observed in primary macrophages isolated peritoneum of mice. Interestingly, inhibition of autophagy by pretreatment with Bafilomycin A1 or knocking down of LC3B gene restored suppression of TNF-α expression, tumor necrosis factor receptor- associated factor 6 (TRAF6) expression and p38MAPK phosphorylation by gAcrp, implying a critical role of autophagy induction in the development of tolerance to LPS-induced TNF-α expression by gAcrp. We also found that knocking-down of FoxO3A, a forkhead box O member of transcription factor, blocked gAcrp-induced expression of LC3II and Atg5. Moreover, gene silencing of Silent information regulator 1 (SIRT1) blocked both gAcrp-induced nuclear translocation of FoxO3A and LC3II expression. Finally, pretreatment with ROS inhibitors, prevented gAcrp-induced SIRT1 expression and further generated inhibitory effects on gAcrp-induced autophagy, indicating a role of ROS production in gAcrp-induced SIRT1 expression and subsequent autophagy induction. Taken together, these findings indicate that globular adiponectin suppresses LPS-induced TNF-α expression, at least in part, via autophagy activation. Furthermore, SIRT1-FoxO3A axis plays a crucial role in gAcrp-induced autophagy in macrophages.

Poly(ADP-ribose) in the bone: from oxidative stress signal to structural element

Contrary to common perception bone is a dynamic organ flexibly adapting to changes in mechanical loading by shifting the delicate balance between bone formation and bone resorption carried out by osteoblasts and osteoclasts, respectively. In the past decades numerous studies demonstrating production of reactive oxygen or nitrogen intermediates, effects of different antioxidants, and involvement of prototypical redox control mechanisms (Nrf2-Keap1, Steap4, FoxO, PAMM, caspase-2) have proven the central role of redox regulation in the bone. Poly(ADP-ribosyl)ation (PARylation), a NAD-dependent protein modification carried out by poly(ADP-ribose) polymerase (PARP) enzymes recently emerged as a new regulatory mechanism fine-tuning osteoblast differentiation and mineralization. Interestingly PARylation does not simply serve as a signaling mechanism during osteoblast differentiation but also couples it to osteoblast death. Even more strikingly, the poly(ADP-ribose) polymer likely released from succumbed cells at the terminal stage of differentiation is incorporated into the bone matrix representing the first structural role of this versatile biopolymer. Moreover, this new paradigm explains why and how osteodifferentiation and death of cells entering this pathway are closely coupled to each other. Here we review the role of reactive oxygen and nitrogen intermediates as well as PARylation in osteoblast and osteoclast differentiation, function, and cell death.