Autophagy-related Signaling Pathways Research Articles

TRAIL DR5-CTSB crosstalk participates in breast cancer autophagy initiated by SAHA

To investigate the ability of SAHA-induced TRAIL DR5-CTSB crosstalk to initiate the breast cancer autophagy, RTCA assay was performed to assess the effect of SAHA on breast cancer cells, and western blot and ELISA were used to verify the inductive effects on expression of CTSB. Breast cancer cells were transfected with TRAIL DR5 siRNA to block the function of TRAIL DR5. Cell viability and apoptosis of breast cancer cells were analyzed using a muse cell analyzer. The distribution of LC3-II in TRAIL DR5-silenced breast cancer cells treated with SAHA was observed by immunofluorescence microscopy, the mRNA levels of autophagy-related genes were detected by RNA microarray, and the activity of autophagy-related signaling pathways was screened by MAPK antibody array. Results indicated that SAHA did indeed repress the growth of breast cancer cell lines with inducing CTSB expression. Western blot and ELISA results indicated that TRAIL DR5 was involved in the expression of CTSB in SAHA-induced breast cancer cells. Cell viability and apoptosis assays showed that the inactivation of TRAIL DR5 can significantly inhibit the effects of SAHA. An immunofluorescence assay indicated that, with SAHA treatment, MDA-MB-231 and MCF-7 cells underwent apparent morphological changes. While SAHA was added in the TRAIL-DR5 blocked cells, the distribution of LC3-II signal was dispersed, the intensity of fluorescence signal was weaker than that of SAHA alone. RNA array indicated that SAHA significantly increased mRNA expression of autophagy marker LC3A/B whereas the change was significantly reversed in TRAIL DR5-silenced cells. The results of MAPK antibody array showed that SAHA and TRAIL DR5 could affect the activity of AKT1, AKT2, and TOR protein in breast cancer cells. These results provide more evidence that SAHA may stimulate TRAIL DR5-CTSB crosstalk, influence the activity of downstream TOR signalling pathway mainly through the AKTs pathway, and initiate the autophagy of breast cancer cells.

Modified Panax ginseng extract regulates autophagy by AMPK signaling in A549 human lung cancer cells.

Panaxginseng has been used worldwide as a traditional medicine for the treatment of cancer and other diseases. The antiproliferative activity of ginseng has been increased after enzymatic processing of ginseng saponin, which may result in the accumulation of minor saponins, such as Rh2, Rg3, compoundK and protopanaxatriol type (PPT) in modified regular ginseng extract (MRGX). In the present study, the anticancer activity and the associated mechanisms of MRGX were investigated using A549 human lung cancer cells. To elucidate the mechanisms underlying the effects of MRGX, we performed a microarray analysis of gene expression in the A549 cells. Molecular mechanisms that were associated with the anticancer activity of MRGX were studied, with a special focus on the autophagy-related multiple signaling pathways in lung cancer cells. Microarray analyses elucidated autophagy-related genes affected by MRGX. Administration of MRGX at 100µg/ml induced punctate cytoplasmic expression of LC3, Beclin-1 and ATG5 and increased expression of endogenous LC3-II whereas 50µg/ml did not inhibit the proliferation of A549 cells. Compared to the control cells, in cells treated with MRGX at 100µg/ml, the level of p-Akt was increased, while that of mTOR-4EBP1 was decreased. Downregulation of mTOR and 4EBP1 in the MRGX-treated cells was found not to be a p-Ulk (S757)-dependent pathway, but a p-Ulk (S317)-dependent autophagic pathway, using AMPK. These data suggest that MRGX regulates AMPK and induces autophagy in lung cancer cells.

RETRACTED: The effects of the long non-coding RNA MALAT-1 regulated autophagy-related signaling pathway on chemotherapy resistance in diffuse large B-cell lymphoma.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. An Expression of Concern for this article was previously published while an investigation was conducted (see related editorial: https://doi.org/10.1016/j.biopha.2022.113812). This retraction notice supersedes the Expression of Concern published earlier. Concern was raised about the reliability of the images in Figure 5B, and the Western blots shown in Figure 9A+B, which appear to contain similar repeated features, and a phenotype found in other publications, as detailed here: https://pubpeer.com/publications/81D7B72D646EC532D0DFF63338A55F; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Independent analysis confirmed these findings and identified additional suspected image duplications in Figures 5A+B and 9A+B. The journal requested the corresponding author comment on these concerns and provide the associated raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Syringin prevents cardiac hypertrophy induced by pressure overload through the attenuation of autophagy.

Syringin, extracted from Eleutherococcus senticosus, is a major biologically active component of Chinese herbs. Studies have certified the multiple pharmacological properties of syringin. However, the role of syringin in cardiac hypertrophy and the mechanisms involved remain unclear. In this study, aortic banding was performed on mice in order to induce cardiac hypertrophy, and the animals were then treated with syringin for 7weeks. Echocardiography and catheter-based measurements of hemodynamic parameters were performed to evaluate cardiac function at 8weeks following aortic banding. Morphological and pathological changes were also evaluated. Alterations in the expression levels of hypertrophy- and autophagy-related markers[atrial natriuretic peptide(ANP), β-myosin heavy chainMHC), α-MHC, B-type natriuretic peptide(BNP), autophagy-related gene(ATG)5, ATG7, beclin1, light chain3(LC3)A/B] were measured by reverse transcription-quantitative PCR and western blot analysis. The effects of syringin on cardiomyocyte hypertrophy induced by angiotensinII in H9c2 cells were also investigated. The results revealed that syringin attenuated cardiac hypertrophy induced by aortic banding via the activation of AMP-activated protein kinaseα(AMPKα) and autophagy-related signaling pathways. Thus, we our data suggest that syringin possesses therapeutic potential to attenuate the progression of cardiac hypertrophy.

The peiminine stimulating autophagy in human colorectal carcinoma cells via AMPK pathway by SQSTM1

AbstractAutophagy is a conserved catabolic process, which functions in maintenance of cellular homeostasis in eukaryotic cells. The self-eating process engulfs cellular long-lived proteins and organelles with double-membrane vesicles, and forms a so-called autophagosome. Degradation of contents via fusion with lysosome provides recycled building blocks for synthesis of new molecules during stress, e.g. starvation. Peiminine is a steroidal alkaloid extracted from Fritillaria thunbergii which is widely used in Traditional Chinese Medicine. Previously, peiminine has been identified to induce autophagy in human colorectal carcinoma cells. In this study, we further investigated whether peiminine could induce autophagic cell death via activating autophagy-related signaling pathway AMPK-mTOR-ULK by promoting SQSTM1(P62). Xenograft tumor growth in vivo suggested that both peiminine and starvation inhibit the growth of tumor size and weight, which was prominently enhanced when peiminine and starvation combined. The therapeutical effect of peiminine in cancer treatment is to be expected.

The Neuroprotective Effect of Erythropoietin on Rotenone-Induced Neurotoxicity in SH-SY5Y Cells Through the Induction of Autophagy.

Currently, the autophagy pathway is thought to be important for the pathogenesis of Parkinson's disease (PD), and the modulation of autophagy may be a novel strategy for the treatment of this disease. Erythropoietin (EPO) has been reported to have neuroprotective effects through anti-oxidative, anti-apoptotic, and anti-inflammatory mechanisms, and it has also been shown to modulate autophagy signaling in an oxygen toxicity model. Therefore, we investigated the effects of EPO on autophagy markers and evaluated its neuroprotective effect on rotenone-induced neurotoxicity. We adapted the rotenone-induced neurotoxicity model to SH-SY5Y cells as an in vitro model of PD. We measured cell viability using MTT and annexin V/propidium iodide assays and measured intracellular levels of reactive oxygen species. Immunofluorescence analysis was performed to measure the expression of LC3 and α-synuclein. Intracellular signaling proteins associated with autophagy were examined by immunoblot analysis. EPO mono-treatment increased the levels of mammalian target of rapamycin (mTOR)-independent/upstream autophagy markers, including Beclin-1, AMPK, and ULK-1. Rotenone treatment of SH-SY5Y cells reduced their viability, increased reactive oxygen species levels, and induced apoptosis and α-synuclein expression, and simultaneous exposure to EPO significantly reduced these effects. Rotenone enhanced mTOR expression and suppressed Beclin-1 expression, indicating suppression of the autophagy system. However, combined treatment with EPO restored Beclin-1 expression and decreased mTOR expression. EPO protects against rotenone-induced neurotoxicity in SH-SY5Y cells by enhancing autophagy-related signaling pathways. The experimental evidence for the EPO-induced neuroprotection against rotenone-induced dopaminergic neurotoxicity may significantly impact the development of future PD treatment strategies.

Inhibition of autophagy recovers cardiac dysfunction and atrophy in response to tail-suspension

AimsPhysical inactivity during space flight or prolonged bed rest may cause cardiac dysfunction and atrophy, but the exact mechanism that governs the regulation of myocardial dysfunction and cardiac atrophy remains poorly understood. Autophagy, a protein degradation pathway, has recently been shown to be involved in the regulation of cardiac dysfunction and atrophy. In this study, we investigated the relationships between dysfunction and inactivity-induced atrophy and autophagy in rat cardiac tissue. Main methodsPhysical inactivity was simulated by a tail suspension model, and cardiac function was examined by echocardiography. Cardiac atrophy was measured by wheat germ agglutinin staining and autophagic activity was detected by Western blot analysis and immunofluorescence staining. Key findingsWe demonstrated that cardiac function, especially contractility, declined and the area of cardiac atrophy increased in the tail-suspended cardiac tissue. Additionally, the cross-sectional area of myocardial cells decreased; however, apoptosis did not increase with tail suspension. Similarly, the expression of autophagy-related proteins and the number of autophagosomes were elevated in the tail-suspended cardiac tissue. Moreover, the administration of chloroquine, an autophagy inhibitor, reversed cardiac dysfunction and atrophy via the suppression of autophagic activity during suspension. Our results indicate that autophagy facilitates the development and progression of cardiac dysfunction and atrophy induced by tail suspension. SignificanceOur studies hint that the components of the autophagy-related signaling pathway are potential therapeutic targets for the treatment of cardiac diseases induced by physical inactivity.

The regulation of autophagy by influenza A virus.

Influenza A virus is a dreadful pathogen of animals and humans, causing widespread infection and severe morbidity and mortality. It is essential to characterize the influenza A virus-host interaction and develop efficient counter measures against the viral infection. Autophagy is known as a catabolic process for the recycling of the cytoplasmic macromolecules. Recently, it has been shown that autophagy is a critical mechanism underlying the interaction between influenza A virus and its host. Autophagy can be induced by the infection with influenza A virus, which is considered as a necessary process for the viral proliferation, including the accumulation of viral elements during the replication of influenza A virus. On the other hand, influenza A virus can inhibit the autophagic formation via interaction with the autophagy-related genes (Atg) and signaling pathways. In addition, autophagy is involved in the influenza virus-regulated cell deaths, leading to significant changes in host apoptosis. Interestingly, the high pathogenic strains of influenza A virus, such as H5N1, stimulate autophagic cell death and appear to interplay with the autophagy in distinct ways as compared with low pathogenic strains. This review discusses the regulation of autophagy, an influenza A virus driven process.

Cathepsin E Deficiency Impairs Autophagic Proteolysis in Macrophages

Cathepsin E is an endosomal aspartic proteinase that is predominantly expressed in immune-related cells. Recently, we showed that macrophages derived from cathepsin E-deficient (CatE −/−) mice display accumulation of lysosomal membrane proteins and abnormal membrane trafficking. In this study, we demonstrated that CatE −/− macrophages exhibit abnormalities in autophagy, a bulk degradation system for aggregated proteins and damaged organelles. CatE −/− macrophages showed increased accumulation of autophagy marker proteins such as LC3 and p62, and polyubiquitinated proteins. Cathepsin E deficiency also altered autophagy-related signaling pathways such as those mediated by the mammalian target of rapamycin (mTOR), Akt, and extracellular signal-related kinase (ERK). Furthermore, immunofluorescence microscopy analyses showed that LC3-positive vesicles were merged with acidic compartments in wild-type macrophages, but not in CatE −/− macrophages, indicating inhibition of fusion of autophagosome with lysosomes in CatE −/− cells. Delayed degradation of LC3 protein was also observed under starvation-induced conditions. Since the autophagy system is involved in the degradation of damaged mitochondria, we examined the accumulation of damaged mitochondria in CatE −/− macrophages. Several mitochondrial abnormalities such as decreased intracellular ATP levels, depolarized mitochondrial membrane potential, and decreased mitochondrial oxygen consumption were observed. Such mitochondrial dysfunction likely led to the accompanying oxidative stress. In fact, CatE −/− macrophages showed increased reactive oxygen species (ROS) production and up-regulation of oxidized peroxiredoxin-6, but decreased antioxidant glutathione. These results indicate that cathepsin E deficiency causes autophagy impairment concomitantly with increased aberrant mitochondria as well as increased oxidative stress.