Guidelines for the use and interpretation of assays for monitoring autophagy

Down-regulation of autophagy proteins is associated with higher mTOR expression in the placenta of pregnant women with preeclampsia

Autophagy is a lysosomal degradation pathway that removes protein aggregates and damaged organelles maintaining cellular integrity. It seems to be essential for cell survival during stress, starvation, hypoxia, and consequently to the placenta implantation and development. Preeclampsia (PE) is a multisystemic disorder characterized by the onset of hypertension associated or not with proteinuria and other maternal complications. Considering that the placenta seems to play an important role in the pathogenesis of PE, the objective of the present study was to evaluate protein levels of light chain protein (LC3), beclin-1, and the mammalian target of rapamycin (mTOR) in the placenta of pregnant women with PE. Placental tissues collected from 20 women with PE and 20 normotensive (NT) pregnant women were evaluated for LC3, beclin-1, and mTOR expression by qPCR and immunohistochemistry. The mRNA for LC3 and beclin-1 were significantly lower, while mTOR gene expression was significantly higher in the placenta of pregnant women with PE than in the NT group. Placentas of PE women showed significantly decreased protein expression of LC3-II and beclin-1, whereas mTOR was significantly increased compared with the NT pregnant women. There was a negative correlation between protein expression of mTOR and LC3-II in the placental tissue of PE women. In conclusion, the results showed autophagy deficiency suggesting that failure in this degradation process may contribute to the pathogenesis of PE; however, new studies involving cross-talk between autophagy and inflammatory molecular mechanisms might help to better understand the autophagy process in this obstetric pathology.

Age-related changes in tau and autophagy in human brain in the absence of neurodegeneration

Tau becomes abnormally hyper-phosphorylated and aggregated in tauopathies like Alzheimers disease (AD). As age is the greatest risk factor for developing AD, it is important to understand how tau protein itself, and the pathways implicated in its turnover, change during aging. We investigated age-related changes in total and phosphorylated tau in brain samples from two cohorts of cognitively normal individuals spanning 19-74 years, without overt neurodegeneration. One cohort utilised resected tissue and the other used post-mortem tissue. Total soluble tau levels declined with age in both cohorts. Phosphorylated tau was undetectable in the post-mortem tissue but was clearly evident in the resected tissue and did not undergo significant age-related change. To ascertain if the decline in soluble tau was correlated with age-related changes in autophagy, three markers of autophagy were tested but only two appeared to increase with age and the third was unchanged. This implies that in individuals who do not develop neurodegeneration, there is an age-related reduction in soluble tau which could potentially be due to age-related changes in autophagy. Thus, to explore how an age-related increase in autophagy might influence tau-mediated dysfunctions in vivo, autophagy was enhanced in a Drosophila model and all age-related tau phenotypes were significantly ameliorated. These data shed light on age-related physiological changes in proteins implicated in AD and highlights the need to study pathways that may be responsible for these changes. It also demonstrates the therapeutic potential of interventions that upregulate turnover of aggregate-prone proteins during aging.

Phosphocholine cytidylyltransferase MoPct1 is crucial for vegetative growth, conidiation, and appressorium-mediated plant infection by Magnaporthe oryzae

Phosphatidylcholine (PC) plays crucial biological roles in eukaryotic cells. In Saccharomyces cerevisiae, apart from phosphatidylethanolamine (PE) methylation pathway, PC is also synthesized via CDP-choline pathway. Phosphocholine cytidylyltransferase Pct1 is the rate-limiting enzyme to catalyze the conversion from phosphocholine to CDP-choline in this pathway. Here, we report the identification and functional characterization of an ortholog of the budding yeast PCT1 in Magnaporthe oryzae, named MoPCT1. Targeted gene deletion mutants of MoPCT1 were impaired in vegetative growth, conidiation, appressorium turgor accumulation and cell wall integrity. Also, the mutants were severely compromised in appressorium-mediated penetration, infectious growth and pathogenicity. Western blot analysis revealed that cell autophagy was activated by the deletion of MoPCT1 under nutrient-rich conditions. Moreover, we found several key genes in PE methylation pathway, such as MoCHO2, MoOPI3, and MoPSD2, were significantly up-regulated in the ΔMopct1 mutants, indicating that a pronounced compensation effect exists between the two PC biosynthesis pathways in M. oryzae. Interestingly, in the ΔMopct1 mutants, histone H3 was hypermethylated and expression levels of several methionine cycling-related genes were significantly up-regulated, suggesting that MoPCT1 is involved in histone H3 methylation and methionine metabolism. Taken together, we conclude that the phosphocholine cytidylyltransferase coding gene MoPCT1 plays important roles in vegetative growth, conidiation and appressorium-mediated plant infection by M. oryzae.

A functional genetic screen for metabolic proteins unveils GART and the de novo purine biosynthetic pathway as novel targets for the treatment of luminal A ERα expressing primary and metastatic invasive ductal carcinoma

Targeting tumor cell metabolism is a new frontier in cancer management. Thus, metabolic pathway inhibitors could be used as anti-estrogen receptor α (ERα) breast cancer (BC) drugs. Here, the interplay among metabolic enzyme(s), the ERα levels and cell proliferation was studied. siRNA-based screen directed against different metabolic proteins in MCF10a, MCF-7 and MCF-7 cells genetically resistant to endocrine therapy (ET) drugs and metabolomic analyses in numerous BC cell lines unveil that the inhibition of GART, a key enzyme in the purine de novo biosynthetic pathway, induces ERα degradation and prevent BC cell proliferation. We report here that a reduced GART expression correlates with a longer relapse-free-survival (RFS) in women with ERα-positive BCs. ERα-expressing luminal A invasive ductal carcinomas (IDCs) are sensitive to GART inhibition and GART expression is increased in receptor-positive IDCs of high grade and stage and plays a role in the development of ET resistance. Accordingly, GART inhibition reduces ERα stability and cell proliferation in IDC luminal A cells where it deregulates 17β-estradiol (E2):ERα signaling to cell proliferation. Moreover, the GART inhibitor lometrexol (LMX) and drugs approved for clinical treatment of primary and metastatic BC (4OH-tamoxifen and the CDK4/CDK6 inhibitors) exert synergic antiproliferative effects in BC cells. In conclusion, GART inhibition by LMX or other inhibitors of the de novo purine biosynthetic pathway could be a novel effective strategy for the treatment of primary and metastatic BCs.

A high-concentrate diet induces inflammatory injury via regulating Ca2+/CaMKKβ-mediated autophagy in mammary gland tissue of dairy cows

Introduction

Calmodulin-dependent protein kinase β (CaMKKβ) is closely related to Ca²⁺ concentration. An increase in Ca²⁺ concentration in the cytoplasm activates CaMKKβ, and activated CaMKKβ affects the activities of AMPK and mTOR and induces autophagy. A high-concentrate diet leads to Ca²⁺ disorder in mammary gland tissue.

Objectives

Therefore, this study mainly investigated the induction of mammary gland tissue autophagy by a high-concentrate diet and the specific mechanism of lipopolysaccharide (LPS)-induced autophagy in bovine mammary epithelial cells (BMECs).

Material and Methods

Twelve mid-lactation Holstein dairy cows were fed with a 40% concentrate diet (LC) and a 60% concentrate diet (HC) for 3 weeks. At the end of the trial, rumen fluid, lacteal vein blood, and mammary gland tissue were collected. The results showed that the HC diet significantly decreased rumen fluid pH, with a pH lower than 5.6 for more than 3 h, indicating successfully induction of subacute rumen acidosis (SARA). The mechanism of LPS-induced autophagy in BMECs was studied in vitro. First, the cells were divided into a Ctrl group and LPS group to study the effects of LPS on the concentration of Ca²⁺ and autophagy in BMECs. Then, cells were pretreated with an AMPK inhibitor (compound C) or CaMKKβ inhibitor (STO-609) to investigate whether the CaMKKβ-AMPK signaling pathway is involved in LPS-induced BMEC autophagy.

Results

The HC diet increased the concentration of Ca²⁺ in mammary gland tissue and pro-inflammatory factors in plasma. The HC diet also significantly increased the expression of CaMKKβ, AMPK, and autophagy-related proteins, resulting in mammary gland tissue injury. In vitro cell experiments showed that LPS increased intracellular Ca²⁺ concentration and upregulated protein expression of CaMKKβ, AMPK, and autophagy-related proteins. Compound C pretreatment decreased the expression of proteins related to autophagy and inflammation. In addition, STO-609 pretreatment not only reversed LPS-induced BMECs autophagy but also inhibited the protein expression of AMPK, thereby alleviating the inflammatory response in BMECs. These results suggest that inhibition of the Ca²⁺/CaMKKβ-AMPK signaling pathway reduces LPS-induced autophagy, thereby alleviating inflammatory injury of BMECs.

Conclusion

Therefore, SARA may increase the expression of CaMKKβ by increasing Ca²⁺ levels and activate autophagy through the AMPK signaling pathway, thereby inducing inflammatory injury in mammary gland tissue of dairy cows.

Inhibition of a malaria host-pathogen interaction by a computationally designed inhibitor

Malaria is a substantial global health burden with 229 million cases in 2019 and 450,000 deaths annually. Plasmodium vivax is the most widespread malaria-causing parasite putting 2.5 billion people at risk of infection. P. vivax has a dormant liver stage and therefore can exist for long periods undetected. Its blood-stage can cause severe reactions and hospitalization. Few treatment and detection options are available for this pathogen. A unique characteristic of P. vivax is that it depends on the Duffy antigen/receptor for chemokines (DARC) on the surface of host red blood cells for invasion. P. vivax employs the Duffy binding protein (DBP) to bind to DARC. We first de novo designed a three helical bundle scaffolding database which was screened via protease digestions for stability. Protease-resistant scaffolds highlighted thresholds for stability, which we utilized for selecting DARC mimetics that we subsequentially designed through grafting and redesign of these scaffolds. The optimized design small helical protein disrupts the DBP:DARC interaction. The inhibitor blocks the receptor binding site on DBP and thus forms a strong foundation for a therapeutic that will inhibit reticulocyte infection and prevent the pathogenesis of P. vivax malaria.

Autophagic flux is impaired in the brain tissue of Tay-Sachs disease mouse model

Tay-Sachs disease is a lethal lysosomal storage disorder caused by mutations in the HexA gene encoding the α subunit of the lysosomal β-hexosaminidase enzyme (HEXA). Abnormal GM2 ganglioside accumulation causes progressive deterioration in the central nervous system in Tay-Sachs patients. Hexa-/- mouse model failed to display abnormal phenotype. Recently, our group generated Hexa-/-Neu3-/- mouse showed severe neuropathological indications similar to Tay-Sachs patients. Despite excessive GM2 ganglioside accumulation in the brain and visceral organs, the regulation of autophagy has not been clarified yet in the Tay-Sachs disease mouse model. Therefore, we investigated distinct steps of autophagic flux using markers including LC3 and p62 in four different brain regions from the Hexa-/-Neu3-/- mice model of Tay-Sachs disease. Our data revealed accumulated autophagosomes and autophagolysosomes indicating impairment in autophagic flux in the brain. We suggest that autophagy might be a new therapeutic target for the treatment of devastating Tay-Sachs disease.

Measurement of Autophagy Activity Reveals Time-Dependent, Bacteria-Specific Turnover during Mycobacterium tuberculosis Infection

The intracellular pathogen, Mycobacterium tuberculosis (M. tb) uses various mechanisms to evade its killing. One of such is phagosomal damage and cytosolic translocation which is then targeted by the host's bactericidal autophagy pathway. It is suggested that cytosolic translocation of M. tb is time-dependent, occurring at later time points of 48 to 72 h post-infection. It is, however, not known whether increased autophagic targeting correlates with these time points of infection. We investigated the time-dependent profile of autophagy activity through the course of M. tb infection in mammalian macrophages. Autophagy activity was inferred by the turnover measurement of autophagy markers and M. tb bacilli in THP-1 and RAW 264.7 macrophages. Over a period of 4 to 72 h, we observed highest autophagy turnover at 48 h of infection in M. tb-containing cells. This was evident by the highest turnover levels of p62 and intracellular M. tb. This supports observations of phagosomal damage mostly occurring at this time point and reveal the correlation of increased autophagy activity. The findings support the preservation of autophagy activity despite M. tb infection while also highlighting time-dependent differences in M. tb-infected macrophages. Future studies may explore time-dependent exogenous autophagy targeting towards host-directed anti-tuberculosis therapy.

Bortezomib abrogates temozolomide-induced autophagic flux through an ATG5 dependent pathway

Introduction: Glioblastoma (GBM) is invariably resistant to temozolomide (TMZ) chemotherapy. Inhibiting the proteasomal pathway is an emerging strategy to accumulate damaged proteins and inhibit their lysosomal degradation. We hypothesized that pre-treatment of glioblastoma with bortezomib (BTZ) might sensitize glioblastoma to temozolomide by abolishing autophagy survival signals to augment DNA damage and apoptosis. Methods: P3 patient-derived glioblastoma cells, as well as the tumour cell lines U87, HF66, A172, and T98G were investigated for clonogenic survival after single or combined treatment with temozolomide and bortezomib in vitro. We investigated the requirement of functional autophagy machinery by utilizing pharmacological inhibitors or CRISPR-Cas9 knockout (KO) of autophagy-related genes -5 and -7 (ATG5 and ATG7) in glioblastoma cells and monitored changes in autophagic flux after temozolomide and/or bortezomib treatments. P3 wild-type and P3 ATG5-/- (ATG5 KO) cells were implanted orthotopically into NOD-SCID mice to assess the efficacy of bortezomib and temozolomide combination therapy with and without functional autophagy machinery. Results: The chemo-resistant glioblastoma cells increased autophagic flux during temozolomide treatment as indicated by increased degradation of long-lived proteins, diminished expression of autophagy markers LC3A/B-II and p62 (SQSTM1), increased co-localisation of LC3A/B-II with STX17, augmented and no induction of apoptosis. In contrast, bortezomib treatment abrogated autophagic flux indicated by the accumulation of LC3A/B-II and p62 (SQSTM1) positive autophagosomes that did not fuse with lysosomes and thus reduced the degradation of long-lived proteins. Bortezomib synergistically enhanced temozolomide efficacy by attenuating cell proliferation, increased DNA double-strand breaks, and apoptosis in an autophagy-dependent manner. Abolishing autophagy in ATG5 KOs reversed the bortezomib-induced toxicity, rescued glioblastoma cell death and reduced animal survival. Discussion: We conclude that bortezomib abrogates temozolomide induced autophagy flux through an ATG5 dependent pathway.

Roles of NAD+ in Acute and Chronic Kidney Diseases

Nicotinamide adenine dinucleotide (oxidized form, NAD⁺) is a critical coenzyme, with functions ranging from redox reactions and energy metabolism in mitochondrial respiration and oxidative phosphorylation to being a central player in multiple cellular signaling pathways, organ resilience, health, and longevity. Many of its cellular functions are executed via serving as a co-substrate for sirtuins (SIRTs), poly (ADP-ribose) polymerases (PARPs), and CD38. Kidney damage and diseases are common in the general population, especially in elderly persons and diabetic patients. While NAD⁺ is reduced in acute kidney injury (AKI) and chronic kidney disease (CKD), mounting evidence indicates that NAD⁺ augmentation is beneficial to AKI, although conflicting results exist for cases of CKD. Here, we review recent progress in the field of NAD⁺, mainly focusing on compromised NAD⁺ levels in AKI and its effect on essential cellular pathways, such as mitochondrial dysfunction, compromised autophagy, and low expression of the aging biomarker αKlotho (Klotho) in the kidney. We also review the compromised NAD⁺ levels in renal fibrosis and senescence cells in the case of CKD. As there is an urgent need for more effective treatments for patients with injured kidneys, further studies on NAD⁺ in relation to AKI/CKD may shed light on novel therapeutics.

Upregulation of the EGFR/MEK1/MAPK1/2 signaling axis as a mechanism of resistance to antiestrogen‑induced BimEL dependent apoptosis in ER+ breast cancer cells

The epidermal growth factor receptor (EGFR) is commonly upregulated in multiple cancer types, including breast cancer. In the present study, evidence is provided in support of the premise that upregulation of the EGFR/MEK1/MAPK1/2 signaling axis during antiestrogen treatment facilitates the escape of breast cancer cells from BimEL‑dependent apoptosis, conferring resistance to therapy. This conclusion is based on the findings that ectopic BimEL cDNA overexpression and confocal imaging studies confirm the pro‑apoptotic role of BimEL in ERα expressing breast cancer cells and that upregulated EGFR/MEK1/MAPK1/2 signaling blocks BimEL pro‑apoptotic action in an antiestrogen‑resistant breast cancer cell model. In addition, the present study identified a pro‑survival role for autophagy in antiestrogen resistance while EGFR inhibitor studies demonstrated that a significant percentage of antiestrogen‑resistant breast cancer cells survive EGFR targeting by pro‑survival autophagy. These pre‑clinical studies establish the possibility that targeting both the MEK1/MAPK1/2 signaling axis and pro‑survival autophagy may be required to eradicate breast cancer cell survival and prevent the development of antiestrogen resistance following hormone treatments. The present study uniquely identified EGFR upregulation as one of the mechanisms breast cancer cells utilize to evade the cytotoxic effects of antiestrogens mediated through BimEL‑dependent apoptosis.

ALDH1-Mediated Autophagy Sensitizes Glioblastoma Cells to Ferroptosis

The fatal clinical course of human glioblastoma (GBM) despite aggressive adjuvant therapies is due to high rates of recurrent tumor growth driven by tumor cells with stem-cell characteristics (glioma stem cells, GSCs). The aldehyde dehydrogenase 1 (ALDH1) family of enzymes has been shown to be a biomarker for GSCs, and ALDH1 seems to be involved in the biological processes causing therapy resistance. Ferroptosis is a recently discovered cell death mechanism, that depends on iron overload and lipid peroxidation, and it could, therefore, be a potential therapeutic target in various cancer types. Since both ALDH1 and ferroptosis interact with lipid peroxidation (LPO), we aimed to investigate a possible connection between ALDH1 and ferroptosis. Here, we show that RSL3-induced LPO and ferroptotic cell death revealed RSL3-sensitive and -resistant malignant glioma cell lines. Most interestingly, RSL3 sensitivity correlates with ALDH1a3 expression; only high ALDH1a3-expressing cells seem to be sensitive to ferroptosis induction. In accordance, inhibition of ALDH1a3 enzymatic activity by chemical inhibition or genetic knockout protects tumor cells from RSL3-induced ferroptotic cell death. Both RSL-3-dependent binding of ALDH1a3 to LC3B and autophagic downregulation of ferritin could be completely blocked by ALDH inhibition. Therefore, ALDH1a3 seems to be involved in ferroptosis through the essential release of iron by ferritinophagy. Our results also indicate that ferroptosis induction might be a particularly interesting clinical approach for targeting the highly aggressive cell population of GSC.

The battle for autophagy between host and influenza A virus

Influenza A virus (IAV) is an infectious pathogen, threatening the population and public safety with its epidemics. Therefore, it is essential to better understand influenza virus biology to develop efficient strategies against its pathogenicity. Autophagy is an important cellular process to maintain cellular homeostasis by cleaning up the hazardous substrates in lysosome. Accumulating research has also suggested that autophagy is a critical mechanism in host defense responses against IAV infection by degrading viral particles and activating innate or acquired immunity to induce viral clearance. However, IAV has conversely hijacked autophagy to strengthen virus infection by blocking autophagy maturation and further interfering host antiviral signalling to promote viral replication. Therefore, how the battle for autophagy between host and IAV is carried out need to be known. In this review, we describe the role of autophagy in host defence and IAV survival, and summarize the role of influenza proteins in subverting the autophagic process as well as then concentrate on how host utilize antiviral function of autophagy to prevent IAV infection.

N6-methyladenosine (m6A) RNA modification in the pathophysiology of heart failure: a narrative review

Background and Objective

Heart failure is the end-stage of various cardiovascular diseases. Recent progress in molecular biology has facilitated the understanding of the mechanisms of heart failure development at the molecular level. N6-adenosine methylation (m6A) is a post-transcriptional modification of RNA. Recent research work reported that m6A regulates gene expression and subsequently affects the activation of cell signaling pathways related to heart failure. Moreover, m6A regulators like methyltransferase-like 3 (METTL3) were reported to participate in myocardium hypertrophy. However, the current research work related to the role of m6A participating in the occurrence of heart failure is rare in some aspects like immune cell infiltration and diabetic heart diseases. Thus, it is reasonable to review the current achievements and provide further study orientation.

Methods

We searched related literature using the keywords: m6A AND heart failure in PubMed, Web of Science and Medline. The language was confined to English. The published year of searched literature ranged from 2012 to 2022. The searched results were put into Endnote software for management. Two authors investigated the searching terms and reviewed the full text of selected terms.

Key Content and Findings

m6A and its regulators are involved in the metabolism of various types of RNAs. m6A modification can regulate various types of cell signaling pathways related to the heart failure via interaction with m6A regulators. m6A and its regulators broadly participate in the myocardium fibrosis, myocardium hypertrophy, myocardial cell apoptosis, and ischemic reperfusion injury. Specifically, m6A participates in the cell apoptosis via regulation of autophagy flux. However, the current research work does not have enough evidence to prove that m6A regulator played its specific effect on the target transcript via regulating the m6A level.

Conclusions

m6A and its regulators participates in the progression of heart failure via modifying the RNA level. Future investigation of m6A should focus on the interaction between the m6A regulators and targeted transcript. Besides, the regulation role of m6A in immune cell infiltration and diabetic heart diseases should also be focused.

Attenuated iron stress and oxidative stress may participate in anti-seizure and neuroprotective roles of xenon in pentylenetetrazole-induced epileptogenesis

The previous studies have demonstrated the excellent neuroprotective effects of xenon. In this study, we verified the anti-seizure and neuroprotective roles of xenon in epileptogenesis and evaluated the involvement of oxidative stress and iron accumulation in the protective roles of xenon. Epileptogenesis was induced by pentylenetetrazole (PTZ) treatment in Sprague-Dawley rats. During epileptogenesis, we found increased levels of iron and oxidative stress accompanied by elevated levels of divalent metal transporter protein 1 and iron regulatory protein 1, which are closely associated with iron accumulation. Meanwhile, the levels of autophagy and mitophagy increased, alongside significant neuronal damage and cognitive deficits. Xenon treatment reversed these effects: oxidative stress and iron stress were reduced, neuronal injury and seizure severity were attenuated, and learning and memory deficits were improved. Thus, our results confirmed the neuroprotective and anti-seizure effects of xenon treatment in PTZ-induced epileptogenesis. The reduction in oxidative and iron stress may be the main mechanisms underlying xenon treatment. Thus, this study provides a potential intervention strategy for epileptogenesis.

Microglia autophagy in ischemic stroke: A double-edged sword

Ischemic stroke (IS) is one of the major types of cerebrovascular diseases causing neurological morbidity and mortality worldwide. In the pathophysiological process of IS, microglia play a beneficial role in tissue repair. However, it could also cause cellular damage, consequently leading to cell death. Inflammation is characterized by the activation of microglia, and increasing evidence showed that autophagy interacts with inflammation through regulating correlative mediators and signaling pathways. In this paper, we summarized the beneficial and harmful effects of microglia in IS. In addition, we discussed the interplay between microglia autophagy and ischemic inflammation, as along with its application in the treatment of IS. We believe this could help to provide the theoretical references for further study into IS and treatments in the future.

Mechanism of autophagy induced by low concentrations of chlorantraniliprole in silk gland, Bombyx mori

Chlorantraniliprole (CAP) is widely used in the control of agricultural pests, and its residues can affect the formation of silkworm (Bombyx. mori) cocoon easily. To accurately evaluate the toxicity of CAP to silkworms and clarify the mechanism of its effect on silk gland function, we proposed a novel toxicity evaluation method based on the body weight changes after CAP exposure. We also analyzed the Ca²⁺-related ATPase activity, characterized energy metabolism and transcriptional changes about the autophagy key genes on the downstream signaling pathways. The results showed that after a low concentration of CAP exposed for 96 h, there were CAP residues in the silk glands of B. mori, the activities of Ca²⁺-ATPase and Ca²⁺-Mg²⁺-ATPase decreased significantly (P ≤ 0.01), and the activation of AMPK-related genes AMPK-α and AMPK-β were up-regulated by 6.39 ± 0.02-fold and 12.33 ± 1.06-fold, respectively, reaching a significant level (P ≤ 0.01)). In addition, the autophagy-related genes Atg1, Atg6, Atg5, Atg7, and Atg8 downstream AMPK were significantly up-regulated at 96 h (P ≤ 0.05). The results of immunohistochemistry and protein expression assay for autophagy marker Atg8 further confirmed the occurrence of autophagy. Overall, our results indicate that CAP exposure leads to autophagy in the silk gland of B. mori and affects their physiological functions, which provides guidance for the evaluation of toxicity of low concentration environmental CAP residues to insects.

A combination of plasma membrane sterol biosynthesis and autophagy is required for shade-induced hypocotyl elongation

Plant growth ultimately depends on fixed carbon, thus the available light for photosynthesis. Due to canopy light absorption properties, vegetative shade combines low blue (LB) light and a low red to far-red ratio (LRFR). In shade-avoiding plants, these two conditions independently trigger growth adaptations to enhance light access. However, how these conditions, differing in light quality and quantity, similarly promote hypocotyl growth remains unknown. Using RNA sequencing we show that these two features of shade trigger different transcriptional reprogramming. LB induces starvation responses, suggesting a switch to a catabolic state. Accordingly, LB promotes autophagy. In contrast, LRFR induced anabolism including expression of sterol biosynthesis genes in hypocotyls in a manner dependent on PHYTOCHROME-INTERACTING FACTORs (PIFs). Genetic analyses show that the combination of sterol biosynthesis and autophagy is essential for hypocotyl growth promotion in vegetative shade. We propose that vegetative shade enhances hypocotyl growth by combining autophagy-mediated recycling and promotion of specific lipid biosynthetic processes.

Plants subject to vegetative shade receive a low quantity of blue light (LB) and a low ratio of red to far-red light (LFLR). Here the authors show that while LB induces autophagy, LFLR leads to changes in lipid metabolism, and propose that these processes may contribute to shade avoidance responses.

Redox status regulates autophagy in thymic stromal cells and promotes T cell tolerance

Thymic stromal cells (TSCs) are critical regulators of T cell tolerance, but their basic biology has remained under-characterized because they are relatively rare and difficult to isolate. Recent work has revealed that constitutive autophagy in TSCs is required for self-antigen presentation and central T cell tolerance induction; however, the mechanisms regulating constitutive autophagy in TSCs are not well understood. Hydrogen peroxide has been shown to increase autophagy flux in other tissues, and we previously identified conspicuously low expression of the hydrogen peroxide-quenching enzyme catalase in TSCs. We investigated whether the redox status of TSCs established by low catalase expression regulates their basal autophagy levels and their capacity to impose central T cell tolerance. Transgenic overexpression of catalase diminished autophagy in TSCs and impaired thymocyte clonal deletion, concomitant with increased frequencies of spontaneous lymphocytic infiltrates in lung and liver and of serum antinuclear antigen reactivity. Effects on clonal deletion and autoimmune indicators were diminished in catalase transgenic mice when autophagy was rescued by expression of the Becn1F121A/F121A knock-in allele. These results suggest a metabolic mechanism by which the redox status of TSCs may regulate central T cell tolerance.

Trim25 restricts rabies virus replication by destabilizing phosphoprotein

Tripartite motif-containing protein 25 (Trim25) is an E3 ubiquitin ligase that activates retinoid acid-inducible gene I (RIG-I) and promotes the antiviral interferon response. Recent studies have shown that Trim25 can bind and degrade viral proteins, suggesting a different mechanism of Trim25 on its antiviral effects. In this study, Trim25 expression was upregulated in cells and mouse brains after rabies virus (RABV) infection. Moreover, expression of Trim25 limited RABV replication in cultured cells. Overexpression of Trim25 caused attenuated viral pathogenicity in a mouse model that was intramuscularly injected with RABV. Further experiments confirmed that Trim25 inhibited RABV replication via two different mechanisms: an E3 ubiquitin ligase-dependent mechanism and an E3 ubiquitin ligase-independent mechanism. Specifically, the CCD domain of Trim25 interacted with RABV phosphoprotein (RABV-P) at amino acid (AA) position at 72 and impaired the stability of RABV-P via complete autophagy. This study reveals a novel mechanism by which Trim25 restricts RABV replication by destabilizing RABV-P, which is independent of its E3 ubiquitin ligase activity.

Akt Inhibition Promotes Autophagy and Clearance of Group B Streptococcus from the Alveolar Epithelium

Group B Streptococcus (GBS) is a gram-positive bacterium that is harmless for healthy individuals but may provoke invasive disease in young infants and immunocompromised hosts. GBS invades the epithelial barriers to enter the bloodstream, and thus strategies that enhance epithelial cell responses may hamper GBS invasion. In the present study, we sought to investigate whether the inhibition of Akt, a kinase that regulates host inflammatory responses and autophagy via suppression of mTOR, can enhance the response of non-phagocytic alveolar epithelial cells against GBS. Treatment of the alveolar epithelial cell line A549 with the Akt inhibitor MK-2206 resulted in the enhanced production of reactive oxygen species and inflammatory mediators in response to GBS. Additionally, Akt inhibition via MK-2206 resulted in elevated LC3II/I ratios and increased autophagic flux in alveolar epithelial cells. Importantly, the inhibition of Akt promoted GBS clearance both in alveolar epithelial cells in vitro and in lung tissue in vivo in a murine model of GBS pneumonia. The induction of autophagy was essential for GBS clearance in MK-2206 treated cells, as knockdown of ATG5, a critical component of autophagy, abrogated the effect of Akt inhibition on GBS clearance. Our findings highlight the role of Akt kinase inhibition in promoting autophagy and GBS clearance in the alveolar epithelium. The inhibition of Akt may serve as a promising measure to strengthen epithelial barriers and prevent GBS invasion in susceptible hosts.

Co-ingestion of glutamine and leucine synergistically promotes mTORC1 activation

Leucine (Leu) regulates protein synthesis and degradation via activation of mammalian target of rapamycin complex 1 (mTORC1). Glutamine (Gln) synergistically promotes mTORC1 activation with Leu via glutaminolysis and Leu absorption via an antiporter. However, Gln has also been shown to inhibit mTORC1 activity. To resolve this paradox, we aimed to elucidate the effects of Gln on Leu-mediated mTORC1 activation. We administered Leu, Gln, tryptophan, Leu + Gln, or Leu + tryptophan to mice after 24-h fasting. The mice were then administered puromycin to evaluate protein synthesis and the gastrocnemius muscle was harvested 30 min later. Phosphorylated eukaryotic initiation factor 4E-binding protein 1, 70-kDa ribosomal protein S6 kinase 1, and Unc-51 like kinase 1 levels were the highest in the Leu + Gln group and significantly increased compared with those in the control group; however, Gln alone did not increase the levels of phosphorylated proteins. No difference in glutamate dehydrogenase activity was observed between the groups. Leu concentrations in the gastrocnemius muscle were similar in the Leu-intake groups. Our study highlights a novel mechanism underlying the promotive effect of Gln on Leu-mediated mTORC1 activation, providing insights into the pathway through which amino acids regulate muscle protein metabolism.

A bibliometric analysis of autophagy in atherosclerosis from 2012 to 2021

Background: Regulation of autophagy affects the progression of atherosclerosis. In recent years, research on autophagy in atherosclerosis has been widely concerned. However, there is no bibliometric analysis in this field.

Objective: The purpose of this study was to explore the general situation, hot spots, and trends of the research in this field through bibliometric analysis.

Methods: Articles related to autophagy in atherosclerosis from 2012 to 2021 were retrieved from the Web of Science Core Collection. VOSviewer and CiteSpace were used for data analysis and visualization of countries, institutions, authors, keywords, journals, and citations.

Results: A total of 988 articles were obtained in the last 10 years. The number of publications and citations increased rapidly from 2012 to 2021, especially after 2019. The most productive countries, institutions, journals, and authors were the People’s Republic of China, Shandong University, Arteriosclerosis Thrombosis and Vascular Biology, and Wim Martinet, respectively. The primary keywords were “oxidative stress,” “apoptosis,” “activated protein kinase,” and “inflammation.” The burst detection analysis of keywords found that “SIRT1” and “long non-coding RNA” might be regarded as the focus of future research.

Conclusion: This is the first bibliometric analysis of autophagy in atherosclerosis, which reports the hot spots and emerging trends. The interaction between oxidative stress and autophagy, programmed cell death, and activated protein kinases are considered to be the current research priorities. Molecular mechanisms and therapeutic target for the intervention of atherosclerosis by regulating autophagy will become an emerging research direction.

Transcription factor p8 regulates autophagy in response to disulfiram via PI3K/mTOR/p70S6K signaling pathway in pancreatic cancer cells

Disulfiram (DSF), which is an inhibitor of aldehyde dehydrogenase (ALDH) and approved by the FDA for the treatment of alcoholism previously, has been repurposed for use as a cancer treatment because of its potent effect in preclinical studies. In this study, we found that disulfiram forms potent complexes with copper (DSF/Cu) inhibited cell proliferation, induced apoptosis in human pancreatic cancer cells, which was detected by flow cytometry and western blotting. Meanwhile, autophagy and autophagic flux also clearly observed by transmission electron microscopy, confocal microscopy and flow cytometry. Our results also showed that DSF/Cu induced transcription factor p8 upregulation and PI3K/mTOR signaling pathway activation detected by real-time PCR and western blotting. Additionally, suppression of p8 inactivated the mTOR signaling pathway and autophagic flux maintained. Furthermore, mechanism study indicated that autophagy induced by DSF/Cu was regulated by p8 and was related to PI3K/mTOR/p70S6K signaling pathway in pancreatic cancer cells. Our findings provide insights into the role of p8 in regulating autophagy induced by DSF/Cu effects in pancreatic cancer cells.

Negative pressure wound therapy improves bone regeneration by promoting osteogenic differentiation via the AMPK-ULK1-autophagy axis

Deficient bone regeneration causes bone defects or nonunion in a substantial proportion of trauma patients that urges for novel therapies. To develop a reliable therapy, we investigated the effect of negative pressure wound therapy (NPWT) on bone regeneration in vivo in a rat calvarial defect model. Negative pressure (NP) treatment in vitro was mimicked to test its effect on osteoblast differentiation in rat mesenchymal stem cells (MSCs) and MC3T3-E1 cells. Transcriptomic analyses, pharmaceutical interventions, and shRNA knockdowns were conducted to explore the underlying mechanism and their clinical relevance was investigated in samples from patients with nonunion. The potential application of a combined therapy of MSCs in hydrogels with negative pressure was tested in the rat critical-size calvarial defect model. We found that NPWT promoted bone regeneration in vivo and NP treatment induced osteoblast differentiation in vitro. NP induced osteogenesis via activating macroautophagy/autophagy by AMPK-ULK1 signaling that was impaired in clinical samples from patients with nonunion. More importantly, the combined therapy involving MSCs in hydrogels with negative pressure significantly improved bone regeneration in rat critical-size calvarial defect model. Thus, our study identifies a novel AMPK-ULK1-autophagy axis by which negative pressure promotes osteoblast differentiation of MSCs and bone regeneration. NPWT treatment can potentially be adopted for therapy of bone defects.Abbreviations: ADP, adenosine diphosphate; AICAR/Aic, acadesine; ALP, alkaline phosphatase; ALPL, alkaline phosphatase, biomineralization associated; AMP, adenosine monophosphate; AMPK, AMP-activated protein kinase; ARS, alizarin red S staining; ATG7, autophagy related 7; ATP, adenosine triphosphate; BA1, bafilomycin A₁; BGLAP/OCN, bone gamma-carboxyglutamate protein; BL, BL-918; BS, bone surface; BS/TV, bone surface per tissue volume; BV/TV, bone volume per tissue volume; C.C, compound C; CCN1, cellular communication network factor 1; COL1A1, collagen type I alpha 1 chain; COL4A3, collagen type IV alpha 3 chain; COL4A4, collagen type IV alpha 4 chain; COL18A1, collagen type XVIII alpha 1 chain; CQ, chloroquine; GelMA, gelatin methacryloyl hydrogel; GO, Gene Ontology; GSEA, gene set enrichment analysis; HIF1A, hypoxia inducible factor 1 subunit alpha; HPLC, high-performance liquid chromatography; ITGAM/CD11B, integrin subunit alpha M; ITGAX/CD11C, integrin subunit alpha X; ITGB1/CdD9, integrin subunit beta 1; KEGG, Kyoto Encyclopedia of Genes and Genomes; MAP1LC3B/LC3B, microtubule associated protein 1 light chain 3 beta; micro-CT, microcomputed tomography; MSCs, mesenchymal stem cells; MTOR, mechanistic target of rapamycin kinase; NP, negative pressure; NPWT, negative pressure wound therapy; PRKAA1/AMPKα1, protein kinase AMP-activated catalytic subunit alpha 1; PRKAA2, protein kinase AMP-activated catalytic subunit alpha 2; PTPRC/CD45, protein tyrosine phosphatase receptor type C; ROS, reactive oxygen species; RUNX2, RUNX family transcription factor 2; SBI, SBI-0206965; SPP1/OPN, secreted phosphoprotein 1; THY1/CD90, Thy-1 cell surface antigen; SQSTM1, sequestosome 1; TGFB3, transforming growth factor beta 3; ULK1/Atg1, unc-51 like autophagy activating kinase 1.

TBK1 and GABARAP family members suppress Coxsackievirus B infection by limiting viral production and promoting autophagic degradation of viral extracellular vesicles

Host-pathogen dynamics are constantly at play during enteroviral infection. Coxsackievirus B (CVB) is a common juvenile enterovirus that infects multiple organs and drives inflammatory diseases including acute pancreatitis and myocarditis. Much like other enteroviruses, CVB is capable of manipulating host machinery to hijack and subvert autophagy for its benefit. We have previously reported that CVB triggers the release of infectious extracellular vesicles (EVs) which originate from autophagosomes. These EVs facilitate efficient dissemination of infectious virus. Here, we report that TBK1 (Tank-binding kinase 1) suppresses release of CVB-induced EVs. TBK1 is a multimeric kinase that directly activates autophagy adaptors for efficient cargo recruitment and induces type-1 interferons during viral-mediated STING recruitment. Positioning itself at the nexus of pathogen elimination, we hypothesized that loss of TBK1 could exacerbate CVB infection due to its specific role in autophagosome trafficking. Here we report that infection with CVB during genetic TBK1 knockdown significantly increases viral load and potentiates the bulk release of viral EVs. Similarly, suppressing TBK1 with small interfering RNA (siRNA) caused a marked increase in intracellular virus and EV release, while treatment in vivo with the TBK1-inhibitor Amlexanox exacerbated viral pancreatitis and EV spread. We further demonstrated that viral EV release is mediated by the autophagy modifier proteins GABARAPL1 and GABARAPL2 which facilitate autophagic flux. We observe that CVB infection stimulates autophagy and increases the release of GABARAPL1/2-positive EVs. We conclude that TBK1 plays additional antiviral roles by inducing autophagic flux during CVB infection independent of interferon signaling, and the loss of TBK1 better allows CVB-laden autophagosomes to circumvent lysosomal degradation, increasing the release of virus-laden EVs. This discovery sheds new light on the mechanisms involved in viral spread and EV propagation during acute enteroviral infection and highlights novel intracellular trafficking protein targets for antiviral therapy.

Coxsackievirus B (CVB) is a significant human enterovirus that can cause myocarditis, meningitis, and pancreatitis. The subversion of host immunity and mechanisms of viral dissemination are critical factors which promote pathogenesis. We had previously reported that following infection, CVB becomes engulfed by autophagosomes which evade lysosomal degradation and instead get released as infectious extracellular vesicles (EVs). In this current study, we report that in addition to its traditional role in interferon-mediated antiviral signaling, TANK-binding kinase (TBK1) is crucial in limiting viral production and EV-based viral egress through the autophagy pathway. Indeed, in the absence of TBK1, we observe (i) a disruption in autophagic flux, (ii) significant increases in intracellular viral burden and viral EV release, and (iii) elevated viral load in both in vitro and in vivo models of infection. EVs isolated from TBK1-deficient cells or mice treated with the TBK1-inhibitor Amlexanox were more infectious compared to controls. In all, the dual role TBK1 plays in suppressing viral escape in addition to mediating antiviral immunity makes it a promising therapeutic target for the treatment of CVB infection.

The microRNA-10b-Bim axis promotes cancer progression through activating autophagy in oral squamous cell carcinoma

Autophagy is related to many cellular mechanisms and dysregulation of autophagy involves the pathological process in cancer. miR-10b activates autophagy, which promotes invasion and migration of OSCC. Its functional role in the mechanism of OSCC to autophagy remains to be unclear. Overexpression of miR-10b was followed by enhanced OSCC invasion and migration and activated autophagic protein, such as LC3II/ATG5. MiR-10b attracted Bim directly according to the Bio-informatics analyses and double luciferases reporter assays. Functional experiments further revealed that miR-10b could promote invasion and migration in vitro. In addition, miR-10b induced autophagy via inhibiting Bim in invasion and migration of OSCC. Notably, animal experiments confirmed that miR-10b-Bim promoted proliferation and autophagy in OSCC. In addition, this study provides a theoretical support for regulating the mechanism of OSCC by inducing autophagy with miR-10b-Bim as a target.

PTK2 regulates tau-induced neurotoxicity via phosphorylation of p62 at Ser403

Tau is a microtubule-associated protein that forms insoluble filaments that accumulate as neurofibrillary tangles in neurodegenerative diseases such as Alzheimer's disease and other related tauopathies. A relationship between abnormal Tau accumulation and ubiquitin-proteasome system impairment has been reported. However, the molecular mechanism linking Tau accumulation and ubiquitin proteasome system (UPS) dysfunction remains unclear. Here, we show that overexpression of wild-type or mutant (P301L) Tau increases the abundance of polyubiquitinated proteins and activates the autophagy-lysosome pathway in mammalian neuronal cells. Previous studies found that PTK2 inhibition mitigates toxicity induced by UPS impairment. Thus, we investigated whether PTK2 inhibition can attenuate Tau-induced UPS impairment and cell toxicity. We found that PTK2 inhibition significantly reduces Tau-induced death in mammalian neuronal cells. Moreover, overexpression of WT or mutant Tau increased the phosphorylation levels of PTK2 and p62. We also confirmed that PTK2 inhibition suppresses Tau-induced phosphorylation of PTK2 and p62. Furthermore, PTK2 inhibition significantly attenuated the climbing defect and shortened the lifespan in the Drosophila model of tauopathy. In addition, we observed that phosphorylation of p62 is markedly increased in Alzheimer's disease patients with tauopathies. Taken together, our results indicate that the UPS dysfunction induced by Tau accumulation might contribute directly to neurodegeneration in tauopathies and that PTK2 could be a promising therapeutic target for tauopathies.

A novel mutation located in the intermembrane space domain of AFG3L2 causes dominant optic atrophy through decreasing the stability of the encoded protein

Dominant optic atrophy (DOA) is the most common hereditary optic neuropathy. Although DOA is caused by mutations in several genes, there are still many cases that have not been diagnosed or misdiagnosed. Herein, we present a large family of 11 patients with DOA. To identify potential pathogenic mutations, whole exome sequencing (WES) was performed on the proband, a 35-year-old woman. WES revealed a novel pathogenic mutation (c.524T>C, p.F175S) in the AFG3L2 intermembrane space domain, rather than in the ATPase domain, which is the hot mutation region associated with most of the previously reported DOA cases. Functional studies on skin fibroblasts generated from patients and HEK293T cells showed that the mutation may impair mitochondrial function and decrease the ability of AFG3L2 protein to enter the mitochondrial inner membrane. In addition, this novel mutation led to protein degradation and reduced the stability of the AFG3L2 protein, which appeared to be associated with the proteasome-ubiquitin pathway.

Anionic nanoplastic exposure induces endothelial leakiness

The global-scale production of plastics has been instrumental in advancing modern society, while the rising accumulation of plastics in landfills, oceans, and anything in between has become a major stressor on environmental sustainability, climate, and, potentially, human health. While mechanical and chemical forces of man and nature can eventually break down or recycle plastics, our understanding of the biological fingerprints of plastics, especially of nanoplastics, remains poor. Here we report on a phenomenon associated with the nanoplastic forms of anionic polystyrene and poly(methyl methacrylate), where their introduction disrupted the vascular endothelial cadherin junctions in a dose-dependent manner, as revealed by confocal fluorescence microscopy, signaling pathways, molecular dynamics simulations, as well as ex vivo and in vivo assays with animal model systems. Collectively, our results implicated nanoplastics-induced vasculature permeability as primarily biophysical-biochemical in nature, uncorrelated with cytotoxic events such as reactive oxygen species production, autophagy, and apoptosis. This uncovered route of paracellular transport has opened up vast avenues for investigating the behaviour and biological effects of nanoplastics, which may offer crucial insights for guiding innovations towards a sustainable plastics industry and environmental remediation.

Branched-chain amino acid transaminase 1 inhibition attenuates childhood asthma in mice by effecting airway remodeling and autophagy

Childhood asthma is a common chronic childhood disease. Branched-chain amino acid transaminase 1 (BCAT1) was reported to be upregulated in chronic airway diseases, while its role in childhood asthma is unclear. Asthma mouse models were established in neonatal mice by 10 µg ovalbumin (OVA) intraperitoneal injection and 3% OVA inhalational challenge. In OVA-challenged mice, BCAT1 levels were upregulated. BCAT1 inhibitor alleviated airway structure and inflammation by suppressing IgE, OVA-specific IgE and inflammatory cytokine release and inflammatory cell infiltration. BCAT1 inhibitor alleviated airway remodeling by inhibiting goblet cell hyperplasia, mucus secretion and the expression of α-SMA and collagen I/III. The BCAT1 inhibitor prevented OVA-enhanced autophagy by decreasing Beclin-1, Atg5 and LC3I/II and increasing p65 levels. In IL-13-stimulated BEAS-2B cells, rapamycin promoted inflammatory cytokine release and autophagy after BCAT1 inhibitor administration. Our research revealed that BCAT1 was upregulated in neonatal asthmatic mice and that a BCAT1 inhibitor might restrain airway inflammation and remodeling by decreasing autophagy, which offered a novel mechanistic understanding of childhood asthma.

Melatonin modulates metabolic adaptation of pancreatic stellate cells subjected to hypoxia

Pancreatic stellate cells (PSCs), the main cell type responsible for the development of fibrosis in pancreatic cancer, proliferate actively under hypoxia. Melatonin has received attention as a potential antifibrotic agent due to its anti-proliferative actions on PSCs. In this work, we investigated the activation of the PI3K/Akt/mTOR pathway and the metabolic adaptations that PSCs undergo under hypoxic conditions, as well as the probable modulation by melatonin. Incubation of cells under hypoxia induced an increase in cell proliferation, and in the expression of alpha-smooth muscle actin and of collagen type 1. In addition, an increase in the phosphorylation of Akt was observed, whereas a decrease in the phosphorylation of PTEN and GSK-3b was noted. The phosphorylation of mTOR and its substrate p70 S6K was decreased under hypoxia. Treatment of PSCs with melatonin under hypoxia diminished cell proliferation, the levels of alpha-smooth muscle actin and of collagen type 1, the phosphorylation of Akt and increased phosphorylation of mTOR. Mitochondrial activity decreased in PSCs under hypoxia. A glycolytic shift was observed. Melatonin further decreased mitochondrial activity. Under hypoxia, no increase in autophagic flux was noted. However, melatonin treatment induced autophagy activation. Nevertheless, inhibition of this process did not induce detectable changes in the viability of cells treated with melatonin. We conclude that PSCs undergo metabolic adaptation under hypoxia that might help them survive and that pharmacological concentrations of melatonin modulate cell responses to hypoxia. Our results contribute to the knowledge of the mechanisms by which melatonin could modulate fibrosis within the pancreas.

Autophagy: Guardian of Skin Barrier

Autophagy is a major degradation pathway that removes harmful intracellular substances to maintain homeostasis. Various stressors, such as starvation and oxidative stress, upregulate autophagy, and the dysregulation of autophagy is associated with various human diseases, including cancer and skin diseases. The skin is the first defense barrier against external environmental hazards such as invading pathogens, ultraviolet rays, chemical toxins, and heat. Although the skin is exposed to various stressors that can activate autophagy, the roles of autophagy in the skin have not yet been fully elucidated. Accumulating evidence suggests that autophagy is closely associated with pathogenesis and the treatment of immune-related skin diseases. In this study, we review how autophagy interacts with skin cells, including keratinocytes and immune cells, enabling them to successfully perform their protective functions by eliminating pathogens and maintaining skin homeostasis. Furthermore, we discuss the implications of autophagy in immune-related skin diseases, such as alopecia areata, psoriasis, and atopic dermatitis, and suggest that a combination of autophagy modulators with conventional therapies may be a better strategy for the treatment of these diseases.

The Cytoprotective, Cytotoxic and Nonprotective Functional Forms of Autophagy Induced by Microtubule Poisons in Tumor Cells—Implications for Autophagy Modulation as a Therapeutic Strategy

Microtubule poisons, as is the case with other antitumor drugs, routinely promote autophagy in tumor cells. However, the nature and function of the autophagy, in terms of whether it is cytoprotective, cytotoxic or nonprotective, cannot be predicted; this likely depends on both the type of drug studied as well as the tumor cell under investigation. In this article, we explore the literature relating to the spectrum of microtubule poisons and the nature of the autophagy induced. We further speculate as to whether autophagy inhibition could be a practical strategy for improving the response to cancer therapy involving these drugs that have microtubule function as a primary target.

Alkalization of cellular pH leads to cancer cell death by disrupting autophagy and mitochondrial function

We previously found that lactic acidosis in the tumor environment was permissive to cancer cell surviving under glucose deprivation and demonstrated that neutralizing lactic acidosis restored cancer cell susceptibility to glucose deprivation. We then reported that alternate infusion of bicarbonate and anticancer agent into tumors via tumor feeding artery markedly enhanced the efficacy of transarterial chemoembolization (TACE) in the local control of hepatocellular carcinoma (HCC). Here we sought to further investigate the mechanism by which bicarbonate enhances the anticancer activity of TACE. We propose that interfering cellular pH by bicarbonate could induce a cascade of molecular events leading to cancer cell death. Alkalizing cellular pH by bicarbonate decreased pH gradient (ΔpH), membrane potential (ΔΨ_m), and proton motive force (Δp) across the inner membrane of mitochondria; disruption of oxidative phosphorylation (OXPHOS) due to collapsed Δp led to a significant increase in adenosine monophosphate (AMP), which activated the classical AMPK-mediated autophagy. Meanwhile, the autophagic flux was ultimately blocked by increased cellular pH, reduced OXPHOS, and inhibition of lysosomal proton pump in alkalized lysosome. Bicarbonate also induced persistent mitochondrial permeability (MPT) and damaged mitochondria. Collectively, this study reveals that interfering cellular pH may provide a valuable approach to treat cancer.

Resistance Training Attenuates Activation of STAT3 and Muscle Atrophy in Tumor-Bearing Mice

Purpose

Although the role of signal transducers and activators of transcription (STAT3) in cachexia due to the association of circulating IL-6 and muscle wasting has been extensively demonstrated, the effect of resistance training on STAT3 in mediating muscle atrophy in tumor-bearing mice is unknown. The aim of this study is to investigate the effects of resistance exercise training on inflammatory cytokines and oxidative-mediated STAT3 activation and muscle loss prevention in tumor-bearing mice.

Methods

Male Swiss mice were inoculated with Ehrlich tumor cells and exposed or not exposed to resistance exercise protocol of ladder climbing. Skeletal muscle STAT3 protein content was measured, compared between groups, and tested for possible association with plasma interleukins and local oxidative stress markers. Components of the ubiquitin-proteasome and autophagy pathways were assessed by real-time PCR or immunoblotting.

Results

Resistance training prevented STAT3 excessive activation in skeletal muscle mediated by the overabundance of plasma IL-6 and muscle oxidative stress. These mechanisms contributed to preventing the increased key genes and proteins of ubiquitin-proteasome and autophagy pathways in tumor-bearing mice, such as Atrogin-1, LC3B-II, and Beclin-1. Beyond preventing muscle atrophy, RT also prevented strength loss and impaired locomotor capacity, hallmarks of sarcopenia.

Conclusion

Our results suggest that STAT3 inhibition is central in resistance exercise protective effects against cancer-induced muscle atrophy and strength loss.

Human platelets display dysregulated sepsis-associated autophagy, induced by altered LC3 protein-protein interaction of the Vici-protein EPG5

Platelets mediate central aspects of host responses during sepsis, an acute profoundly systemic inflammatory response due to infection. Macroautophagy/autophagy, which mediates critical aspects of cellular responses during inflammatory conditions, is known to be a functional cellular process in anucleate platelets, and is essential for normal platelet functions. Nevertheless, how sepsis may alter autophagy in platelets has never been established. Using platelets isolated from septic patients and matched healthy controls, we show that during clinical sepsis, the number of autophagosomes is increased in platelets, most likely due to an accumulation of autophagosomes, some containing mitochondria and indicative of mitophagy. Therefore, autophagy induction or early-stage autophagosome formation (as compared to decreased later-stage autophagosome maturation or autophagosome-late endosome/lysosome fusion) is normal or increased. This was consistent with decreased fusion of autophagosomes with lysosomes in platelets. EPG5 (ectopic P-granules autophagy protein 5 homolog), a protein essential for normal autophagy, expression did increase, while protein-protein interactions between EPG5 and MAP1LC3/LC3 (which orchestrate the fusion of autophagosomes and lysosomes) were significantly reduced in platelets during sepsis. Furthermore, data from a megakaryocyte model demonstrate the importance of TLR4 (toll like receptor 4), LPS-dependent signaling for regulating this mechanism. Similar phenotypes were also observed in platelets isolated from a patient with Vici syndrome: an inherited condition caused by a naturally occurring, loss-of-function mutation in EPG5. Together, we provide evidence that autophagic functions are aberrant in platelets during sepsis, due in part to reduced EPG5-LC3 interactions, regulated by TLR4 engagement, and the resultant accumulation of autophagosomes.Abbreviations: ACTB: beta actin; CLP: cecal ligation and puncture; Co-IP: co-immunoprecipitation; DAP: death associated protein; DMSO: dimethyl sulfoxide; EPG5: ectopic P-granules autophagy protein 5 homolog; ECL: enhanced chemiluminescence; HBSS: Hanks' balanced salt solution; HRP: horseradish peroxidase; ICU: intensive care unit; LPS: lipopolysaccharide; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; MKs: megakaryocytes; PFA: paraformaldehyde; PBS: phosphate-buffered saline; PLA: proximity ligation assay; pRT-PCR: quantitative real-time polymerase chain reaction; RT: room temperature; SQSTM1/p62: sequestosome 1; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TLR4: toll like receptor 4; TEM: transmission electron microscopy; WGA: wheat germ agglutinin.

Metformin inactivates the cGAS-STING pathway through autophagy and suppresses senescence in nucleus pulposus cells

Intervertebral disc degeneration (IVDD) is a complex process involving many factors, among which excessive senescence of nucleus pulposus cells (NPCs) is considered to be the main factor. Our previous study found that metformin may inhibit senescence in nucleus pulposus cells; however, its working mechanism is still largely unknown. In the current study, we found that metformin may inactivate cGAS-STING pathway during oxidative stress. Knock-down of STING may further suppress senescence, indicating metformin may exert its effect through cGAS-STING pathway. Damaged DNA is a major inducer of the activation of cGAS-STING pathway. Mechanistically, our study showed that DNA damage was reduced during metformin treatment; however, suppression of autophagy by 3-methyladenine (3MA) may compromise the effect of metformin on DNA damage. The in vivo study also showed that 3MA may recede the therapeutic effect of metformin on IVDD. Taken together, our results reveal that metformin may suppress senescence via inactivating the cGAS-STING pathway through autophagy, implying the new application of metformin in cGAS-STING pathway related diseases.

Hormetic Heat Shock Enhances Autophagy through HSF1 in Retinal Pigment Epithelium Cells

To maintain homeostasis, cells have evolved stress-response pathways to cope with exogenous and endogenous stress factors. Diverse stresses at high doses may be detrimental, albeit low doses of stress, known as hormesis, can be beneficial. Upon exposure to stress, such as temperature rise, the conventional heat shock response (HSR) regulated by the heat shock transcription factor 1 (HSF1) facilitates refolding of misfolded proteins with the help of heat shock proteins (HSPs). However, the role and molecular mechanisms underlying the beneficial effects of HSR with other clearance processes, such as autophagy, remain poorly understood. In this study, human ARPE-19 cells, an in vitro model of retinal pigment epithelium, were treated with hormetic heat shock (HHS) and the autophagy expression profile was examined using quantitative PCR (qPCR), immunoblotting, immunoprecipitation, and immunofluorescence. We demonstrate that HHS enhances the expression of fundamental autophagy-associated genes in ARPE-19 cells through the activation of HSF1. HHS transiently increases the level of SQSTM1 and LC3B-II and activates autophagy. These findings reveal a role for autophagic HSF1-regulated functions and demonstrate the contribution of autophagy to hormesis in the HSR by improving proteostasis.

Chloroquine modulates the sulforaphane anti-obesity mechanisms in a high-fat diet model: Role of JAK-2/ STAT-3/ SOCS-3 pathway

The phytochemical sulforaphane (SFN) has been studied for its potential anti-obesity effect, but neither its molecular targets nor its interaction with the antimalarial drug chloroquine (CQ) has been fully delineated. Therefore, high-fat diet (HFD) obese rats were randomly allocated into one of five groups and were left untreated or gavaged orally with SFN (0.5 or 1 mg/kg), CQ (5 mg/kg), or their combination (0.5/5 mg/kg) for six successive weeks to assess their potential interaction and the enrolled mechanisms. SFN effectively reduced the HFD-induced weight gain, blood glucose, and serum leptin levels, and improved lipid profile. On the molecular level, SFN inhibited the lipogenesis-related enzymes, namely sterol regulatory element-binding protein (SREBP)-1c, fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) in both liver and visceral white adipose tissue (vWAT) of HFD obese rats. SFN also turned off the inflammatory pathway conserved Janus kinase/signaling transducers and activators of transcription/suppressor of cytokine signaling (JAK-2/STAT-3/SOCS-3) in these tissues, as well as the inflammatory markers nuclear factor-kappa (NF-κ) B and interleukin (IL)-22 in serum. In contrast, SFN downregulated the gene expression of microRNA (miR-200a), while significantly increasing the autophagic parameters; viz., beclin-1, autophagy-related protein (ATG)-7, and microtubule-associated protein 2 light chain 3 (LC3-II) in both liver and vWAT. On most of the parameters mentioned above, treatment with CQ solely produced a satisfactory effect and intensified the low dose of SFN in the combination regimen. These findings demonstrated the beneficial effects of using CQ as an add-on anti-obesity medicine to SFN.

Purinergic P2X7 Receptor: A Therapeutic Target in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by upper and lower motor neuron loss. The pathomechanisms of ALS are still poorly understood with current hypotheses involving genetic mutations, excitotoxicity, and reactive oxygen species formation. In the absence of a disease-altering clinically approved therapeutic, there is an ever-increasing need to identify new targets to develop drugs that delay disease onset and/or progression. The purinergic P2X₇ receptor (P2X₇R) has been implicated widely across the ALS realm, providing a potential therapeutic strategy. This review summarizes the current understanding of ALS, the P2X₇R and its role in ALS, the current landscape of P2X₇R antagonists, and the in vivo potential of these antagonists in preclinical ALS models.

A novel ATG5 interaction with Ku70 potentiates DNA repair upon genotoxic stress

The maintenance of cellular homeostasis in living organisms requires a balance between anabolic and catabolic reactions. Macroautophagy (autophagy herein) is determined as one of the major catabolic reactions. Autophagy is an evolutionarily conserved stress response pathway that is activated by various insults including DNA damage. All sorts of damage to DNA potentially cause loss of genetic information and trigger genomic instability. Most of these lesions are repaired by the activation of DNA damage response following DNA repair mechanisms. Here we describe, a novel protein complex containing the autophagy protein ATG5 and the non-homologous end-joining repair system proteins. We discovered for the first time that ATG5 interacted with both Ku80 (XRCC5) and Ku70 (XRCC6). This novel interaction is facilitated mainly via Ku70. Our results suggest that this interaction is dynamic and enhanced upon genotoxic stresses. Strikingly, we identified that ATG5-Ku70 interaction is necessary for DNA repair and effective recovery from genotoxic stress. Therefore, our results are demonstrating a novel, direct, dynamic, and functional interaction between ATG5 and Ku70 proteins that plays a crucial role in DNA repair under genotoxic stress conditions.

Myocilin Gene Mutation Induced Autophagy Activation Causes Dysfunction of Trabecular Meshwork Cells

Trabecular meshwork dysfunction is the main cause of primary open angle glaucoma (POAG) associated with elevated intraocular pressure (IOP). Mutant myocilin causes glaucoma mainly via elevating IOP. Previously we have found that accumulated Asn 450 Tyr (N450Y) mutant myocilin impairs human trabecular meshwork (TM) cells by inducing chronic endoplasmic reticulum (ER) stress response in vitro. However, it is unclear how ER stress leads to TM damage and whether N450Y myocilin mutation is associated with POAG in vivo. Here we found that N450Y mutant myocilin induces autophagy, which worsens cell viability, whereas inhibition of autophagy increases viability and decreases cell death in human TM cells. Furthermore, we construct a transgenic mouse model of N450Y myocilin mutation (Tg-MYOC^N450Y) and Tg-MYOC^N450Y mice exhibiting glaucoma phenotypes: IOP elevation, retinal ganglion cell loss and visual impairment. Consistent with our published in vitro studies, mutant myocilin fails to secrete into aqueous humor, causes ER stress and actives autophagy in Tg-MYOC^N450Y mice, and aqueous humor dynamics are altered in Tg-MYOC^N450Y mice. In summary, our studies demonstrate that activation of autophagy is correlated with pathogenesis of POAG.

Increase of autophagy marker p62 in the placenta from pregnant women with preeclampsia

Preeclampsia (PE) is a multisystemic disorder characterized by abnormal placentation. Autophagy is a lysosomal degradation pathway that removes protein aggregates and damaged organelles, and it seems to be essential for cell survival during stress, hypoxia, and for implantation and development of the placenta. p62/SQSTM1 is an autophagy marker that not only binds proteins destined for elimination but is also constitutively degraded by this mechanism. Considering that the placenta plays an important role in the pathogenesis of PE, the present study aimed to evaluate the gene and protein expression of p62/SQSTM1 in placentas from pregnant women with PE. Placental tissues from 20 women with PE classified into three groups according to gestational age, 27-31 weeks (n = 8); 32-36 weeks (n = 6); 37-39 weeks (n = 6), and 20 normotensives (NT) pregnant women were collected and employed for p62/SQSTM1 expression by quantitative polymerase chain reaction (qPCR), immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) techniques. p62/SQSTM1 mRNA levels were significantly lower, while protein expression was significantly higher in the placenta of pregnant women with PE than in NT pregnant women, and these results remained similar after separating the groups by gestational age. In conclusion, the results suggest that there is a reduction of autophagic activity in pregnant women with PE. Studies involving cross-talk between autophagy, inflammasomes, nuclear transcription factor (NF-κB) activation pathways, and aggregation of protein in the placenta from women with PE might help to better understand the pathogenesis of this important obstetric pathology.

Improvement of autophagic flux mediates the protection of hydrogen sulfide against arecoline-elicited neurotoxicity in PC12 cells

Arecoline, the most abundant alkaloid of the areca nut, induces toxicity to neurons. Hydrogen sulfide (H₂S) is an endogenous gas with neuroprotective effects. We recently found that arecoline reduced endogenous H₂S content in PC12 cells. In addition, exogenously administration of H₂S alleviated the neurotoxicity of arecoline on PC12 cells. Increasing evidence has demonstrated the neuroprotective role of improvement of autophagic flux. Therefore, the aim of the present work is to explore whether improvement of autophagic flux mediates the protection of H₂S against arecoline-caused neurotoxicity. Transmission electron microscope (TEM) for observation of ultrastructural morphology. Western blotting was used to detect protein expression of the related markers. Functional analysis contained LDH release assay, Hoechst 33,258 nuclear staining and flow cytometry were used to detect cytotoxicity and apoptosis. In the present work, we found that arecoline disrupted autophagy flux in PC12 cells as evidenced by accumulation of autophagic vacuoles, increase in LC3II/LC3I, and upregulation of p62 expression in PC12 cells. Notably, we found that sodium hydrosulfide (NaHS), the donor of H₂S improved arecoline-blocked autophagy flux in PC12 cells. Furthermore, we found that blocking autophagic flux by chloroquine (CQ), the inhibitor of autophagy flux, antagonized the inhibitory role of NaHS in arecoline-induced cytotoxicity apoptosis and endoplasmic reticulum (ER) stress. In conclusion, H₂S improves arecoline-caused disruption of autophagic flux to exert its protection against the neurotoxicity of arecoline.

Everolimus (RAD001) combined with programmed death-1 (PD-1) blockade enhances radiosensitivity of cervical cancer and programmed death-ligand 1 (PD-L1) expression by blocking the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR)/S6 kinase 1 (S6K1) pathway

Cervical cancer (CC) is the 4^th most prevalent malignancy in females. This study explored the mechanism of everolimus (RAD001) combined with programmed death-1 (PD-1) blockade on radiosensitivity by phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway and autophagy in CC cells. Low-radiosensitive CaSki cells were selected as study objects. After RAD001 treatment, PI3K/AKT/mTOR pathway activation, autophagy, migration and invasion abilities, autophagy-related proteins (LC3-I, LC3-II, and p62), and PD-L1 expression in CC cells were detected. After triple treatment of radiotherapy (RT), RAD001, and PD-1 blockade to the CC mouse models, tumor weight and volume were recorded. Ki67 expression, the number of CD8 + T cells, and the ability to produce IFN-γ and TNF-α in tumor tissues were determined. RAD001 promoted autophagy by repressing PI3K/AKT/mTOR pathway, augmented RT-induced apoptosis, and weakened migration and invasion, thereby increasing CC cell radiosensitivity. RAD001 elevated RT-induced PD-L1 level. RT combined with RAD001 and PD-1 blockade intensified the inhibitory effect of RT on tumor growth, reduced the amount of Ki67-positive cells, enhanced radiosensitivity of CC mice, and increased the quantity and killing ability of CD8 + T cells. Briefly, RAD001 combined with PD-1 blockade increases radiosensitivity of CC by impeding the PI3K/AKT/mTOR pathway and potentiating cell autophagy.