3-Methyladenine prevents energy stress-induced necrotic death of melanoma cells through autophagy-independent mechanisms

Autophagy as a potential therapeutic target in regulating improper cellular proliferation

Autophagy is a degradative process that makes rapid turnover of old and impaired proteins and organelles possible. It is highly instigated by stress signals, like starvation, and contributes to the cell's homeostasis. Autophagy performs a crucial function in keeping cell genomic integrity stable. Impaired autophagic flux is implicated in neurodegenerative diseases, abnormal ageing, and cancerous diseases. In diseases like cancer, autophagy performs a dualistic function; it can have both a tumor-suppressive and supportive role. Autophagy in the initial phases of tumorigenesis maintains the integrity of the genome and, if it fails, leads to cell death, thus having a tumor-suppressive role. Meanwhile, autophagy also imparts the function of the pro-survival mechanism in the latter stages of tumorigenesis and supports the cancerous cells in surviving conditions like hypoxia and increased oxidative stress. Autophagy also helps cancerous cells develop drug resistance in some cases. Thus, modulation of the autophagic mechanism is a possible therapeutic strategy in cancer therapy as its inhibition can sensitise cancer cells to anti-cancerous drugs. The promotion of autophagy, in some cases, can also safeguard cells from toxic protein aggregation and enhanced oxidative stress. Excessive autophagy can result in autophagic cell death. Autophagy also regulates several cellular processes and cell death pathways, like apoptosis. Therefore, an in-depth knowledge of the autophagy process and its regulating molecules is critically important. Pharmaceutical small molecules or cellular target modulation can help modulate the cellular autophagy process in the context of specific disease conditions.

N-acetylserotonin derivative ameliorates hypoxic-ischemic brain damage by promoting PINK1/Parkin-dependent mitophagy to inhibit NLRP3 inflammasome-induced pyroptosis

Neonatal hypoxic-ischemic brain damage is the main cause of hypoxic-ischemic encephalopathy and cerebral palsy, whose clinical treatment is still limited to therapeutic hypothermia with limited efficacy. N-[2-(5-hydroxy-1H-indol-3-yl) ethyl]-2-oxopiperidine-3-carboxamide (HIOC), a derivative of N-acetylserotonin, has shown neuroprotective properties. This study was conducted to evaluate the neuroprotective and molecular mechanisms of HIOC. We established an in vitro model using Oxygen-glucose deprivation/reoxygenation (OGD/R) in HT22 cells, alongside an in vivo model via the modified Rice-Vannucci method. The results showed that HIOC reduced OGD/R-induced HT22 cell pyroptosis and inhibited NOD-like receptor pyrin domain- containing protein 3 (NLRP3) inflammasome activation. With the addition of the mitophagy inhibitor 3-MA, we demonstrated that HIOC promoted PTEN-induced putative kinase 1 (PINK1)/Parkin-mediated mitophagy to reduce HT22 cell pyroptosis. Mechanistically, HIOC stimulated mitophagy to remove damaged mitochondria. The clearance of injured mitochondria reduced reactive oxygen species generation, which consequently inhibited NLRP3 inflammasome expression. In vivo, HIOC remarkably lessened cerebral blood flow, infarct volume, neuronal injury by activating mitophagy. HIOC activated mitophagy to produce antipyroptosis effects. Together, our finding demonstrated that HIOC improves brain injury by promoting PINK1/Parkin-dependent mitophagy to inhibit NLRP3 inflammasome activation and pyroptosis, suggesting its potential for hypoxic-ischemic brain damage treatment.

Doramectin Induces Apoptosis in B16 Melanoma Cells

INTRODUCTION/OBJECTIVE

Metastatic melanoma resists current pharmacological regimens that act through apoptosis. This indicates that therapies acting via non-apoptotic cell-death pathways could be pursued. Doramectin has shown promising results in another cancer of neural crest origin, neuroblastoma, through the inhibition of growth via autophagy. Our research hypothesis is that doramectin induces autophagy in B16F10 melanoma cells.

METHODS

Cells were treated with doramectin (15 uM) or a combination of both doramectin and a cell-death inhibitor, compared to untreated control cells (media), and then analyzed with MTT analysis. Likewise, MDC analysis was completed to detect autophagy involvement with doramectin treatment. Flow cytometry and TUNEL Assay were conducted to observe cell death-related effects.

RESULTS

MTT analysis of doramectin-treated cells displayed a decrease in cell growth compared to control. Apoptotic morphology was prominent in melanoma cells treated with doramectin. Increased autophagy was not detected by fluorometric microscopic analysis. Flow cytometry analysis of doramectin-treated cells showed apoptosis as a major mode of cell death with some necrosis.

CONCLUSION

Doramectin induces a novel cell-death mechanism in melanoma compared to other forms of cancer and should be studied as an effective anti-cancer agent for melanoma treatment.

No energy, no autophagy-Mechanisms and therapeutic implications of autophagic response energy requirements

Autophagy is a lysosome-mediated self-degradation process of central importance for cellular quality control. It also provides macromolecule building blocks and substrates for energy metabolism during nutrient or energy deficiency, which are the main stimuli for autophagy induction. However, like most biological processes, autophagy itself requires ATP, and there is an energy threshold for its initiation and execution. We here present the first comprehensive review of this often-overlooked aspect of autophagy research. The studies in which ATP deficiency suppressed autophagy in vitro and in vivo were classified according to the energy pathway involved (oxidative phosphorylation or glycolysis). A mechanistic insight was provided by pinpointing the critical ATP-consuming autophagic events, including transcription/translation/interaction of autophagy-related molecules, autophagosome formation/elongation, autophagosome fusion with the lysosome, and lysosome acidification. The significance of energy-dependent fine-tuning of autophagic response for preserving the cell homeostasis, and potential implications for the therapy of cancer, autoimmunity, metabolic disorders, and neurodegeneration are discussed.

Targeting the PINK1/Parkin pathway: A new perspective in the prevention and therapy of diabetic retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes characterized by neurovascular impairment of the retina. The dysregulation of the mitophagy process occurs before apoptotic cell death and the appearance of vascular damage. In particular, mitochondrial alterations happen during DR development, supporting the hypothesis that mitophagy is negatively correlated to disease progression. This process is mainly regulated by the PTEN-induced putative kinase protein 1 (PINK1)/Parkin pathway whose activation promotes mitophagy. In this review, we will summarize the evidence reported in the literature demonstrating the involvement of the PINK1/Parkin pathway in diabetic retinopathy-induced retinal degeneration.

Quercetin activates autophagy to protect rats ovarian granulosa cells from H2O2-induced aging and injury

Autophagy is closely related to the aging of various organ systems, including ovaries. Quercetin has a variety of biological activities, including potential regulation of autophagy. However, whether quercetin-regulated autophagy activity affects the process of ovarian aging and injury has not been clarified yet. This study explores whether quercetin can resist H2O2-induced aging and injury of granulosa cells by regulating autophagy and its related molecular mechanisms in vitro experiments. The cell viability, endocrine function, cell aging, and apoptosis were detected to evaluate the effects of quercetin and autophagy regulators like 3-methyladenine and rapamycin. The levels of autophagy markers Atg5, Atg12, Atg16L, Lc3B II/I, and Beclin1 were determined by Western blot to assess the effects of quercetin, 3-methyladenine and rapamycin on autophagy. Our results showed quercetin resisted H2O2-induced granulosa cell aging and injury by activating protective autophagy. The treatment of 3-methyladenine and rapamycin confirmed the protective function of autophagy in H2O2-induced granulosa cells. 3-methyladenine treatment inhibited the expression of autophagy markers Atg5, Atg12, Atg16L, Lc3B II/I, and Beclin1 and abolished the positive effects on cell viability, estradiol secretion, and cell apoptosis activated by quercetin. In conclusion, quercetin activates autophagy by upregulating the expression of autophagy-related proteins to resist H2O2-induced aging and injury, which is crucial for stabilizing the function of granulosa cells under oxidative injury conditions and delaying aging. This study may explain the protective effects of quercetin on ovarian aging and injury from the perspective of regulating autophagy.

Reinventing the Penumbra - the Emerging Clockwork of a Multi-modal Mechanistic Paradigm

The concept of the ischemic penumbra was originally defined as the area around a necrotic stroke core and seen as the tissue at imminent risk of further damage. Today, the penumbra is generally considered as time-sensitive hypoperfused brain tissue with decreased oxygen and glucose availability, salvageable tissue as treated by intervention, and the potential target for neuroprotection in focal stroke. The original concept entailed electrical failure and potassium release but one short of neuronal cell death and was based on experimental stroke models, later confirmed in clinical imaging studies. However, even though the basic mechanisms have translated well, conferring brain protection, and improving neurological outcome after stroke based on the pathophysiological mechanisms in the penumbra has yet to be achieved. Recent findings shape the modern understanding of the penumbra revealing a plethora of molecular and cellular pathophysiological mechanisms. We now propose a new model of the penumbra, one which we hope will lay the foundation for future translational success. We focus on the availability of glucose, the brain's central source of energy, and bioenergetic failure as core pathophysiological concepts. We discuss the relation of mitochondrial function in different cell types to bioenergetics and apoptotic cell death mechanisms, autophagy, and neuroinflammation, to glucose metabolism in what is a dynamic ischemic penumbra.

Arabidopsis cell suspension culture and RNA sequencing reveal regulatory networks underlying plant-programmed cell death

Programmed cell death (PCD) facilitates selective, genetically controlled elimination of redundant, damaged, or infected cells. In plants, PCD is often an essential component of normal development and can mediate responses to abiotic and biotic stress stimuli. However, studying the transcriptional regulation of PCD is hindered by difficulties in sampling small groups of dying cells that are often buried within the bulk of living plant tissue. We addressed this challenge by using RNA sequencing and Arabidopsis thaliana suspension cells, a model system that allows precise monitoring of PCD rates. The use of three PCD-inducing treatments (salicylic acid, heat, and critical dilution), in combination with three cell death modulators (3-methyladenine, lanthanum chloride, and conditioned medium), enabled isolation of candidate core- and stimuli-specific PCD genes, inference of underlying regulatory networks and identification of putative transcriptional regulators of PCD in plants. This analysis underscored a disturbance of the cell cycle and mitochondrial retrograde signaling, and repression of pro-survival stress responses, as key elements of the PCD-associated transcriptional signature. Further, phenotyping of Arabidopsis T-DNA insertion mutants in selected candidate genes validated the potential of generated resources to identify novel genes involved in plant PCD pathways and/or stress tolerance.

Lower dose of metformin combined with artesunate induced autophagy-dependent apoptosis of glioblastoma by activating ROS-AMPK-mTOR axis

Glioblastoma multiform (GBM), one of the most common, aggressive primary brain tumours, demonstrates resistance to radiotherapy and chemotherapy after surgical resection and treatment failure. Metformin (MET) has been shown to suppress the proliferative capacity and invasion ability of GBM cells by activating AMPK and inhibiting mTOR, but the effective dose exceeded the maximum tolerated dose. Artesunate (ART) can exert certain anti-tumour effects by activating the AMPK-mTOR axis and inducing autophagy in tumour cells. Therefore, this study investigated the effects of MET combined with ART combination therapy on autophagy and apoptosis in GBM cells. MET combined with ART treatment effectively suppressed the viability, mono-cloning ability, migration and invasion capacities, as well as metastatic ability of GBM cells. The underlying mechanism involved modulation of the ROS-AMPK-mTOR axis, which was confirmed using 3-methyladenine and rapamycin to inhibit or promote the effects of MET combined with ART, respectively. The study findings suggest that MET used in combination with ART can induce autophagy-dependent apoptosis in GBM cells by activating the ROS-AMPK-mTOR pathway, providing a potential new treatment for GBM.

Autophagy in cancer resistance to paclitaxel: Development of combination strategies

Paclitaxel, a compound naturally occurring in yew, is a commonly used drug for the treatment of different types of cancer. Unfortunately, frequent cancer cell resistance significantly decreases its anticancer effectivity. The main reason for the resistance development is the paclitaxel-induced phenomenon of cytoprotective autophagy occurring by different mechanisms of action in dependence on a cell type and possibly even leading to metastases. Paclitaxel also induces autophagy in cancer stem cells, which greatly contributes to tumor resistance development. Paclitaxel anticancer effectivity can be predicted by the presence of several autophagy-related molecular markers, such as tumor necrosis factor superfamily member 13 in triple-negative breast cancer or cystine/glutamate transporter encoded by the SLC7A11 gene in ovarian cancer. Nevertheless, the undesired effects of paclitaxel-induced autophagy can be eliminated by paclitaxel co-administration with autophagy inhibitors, such as chloroquine. Interestingly, in certain cases, it is worthy of potentiating autophagy by paclitaxel combination with autophagy inducers, for instance, apatinib. A modern strategy in anticancer research is also to encapsulate chemotherapeutics into nanoparticle carriers or develop their novel derivatives with improved anticancer properties. Hence, in this review article, we summarize not only the current knowledge of paclitaxel-induced autophagy and its role in cancer resistance but mainly the possible drug combinations based on paclitaxel and their administration in nanoparticle-based formulations as well as paclitaxel analogs with autophagy-modulating properties.

miR-141-Modified Bone Marrow Mesenchymal Stem Cells (BMSCs) Inhibits the Progression of Severe Acute Pancreatitis

The therapeutic effects of bone marrow mesenchymal stem cells (BMSCs) on severe acute pancreatitis (SAP) and miRNAs are currently the research hotspots. This study intends to explore the potential impact of miR-141-modified BMSCs on SAP. After establishment of rat model of SAP, the animals were grouped into control group, model group, BMSCs group, miR-141 group, positive control group, and PI3K/mTOR signaling agonist group (agonist group) followed by analysis of miR-141 expression by RT-qPCR and the expression of serum amylase, IL-6, TNF-α, TAP, PI3K, mTOR, and LC3-II by Western blot and ELISA. miR-141 was significantly up-regulated in the miR-141-modified BMSCs group (p > 0.05). The contents of serum amylase, IL-6, TNF-α, and TAP was increased in SAP rats and decreased after BMSC treatment (p > 0.05). The increased autophagy flux in the rats with SAT was reduced upon treatment with BMSCs and autophagy flux was decreased in miR-141 group but increased in positive control group. The model and positive control group presented highest expression of LC3-II, p-PI3K and p-mTOR, followed by BMSCs group and miR-141 group (p < 0.05). In conclusion, miR-141-modified BMSCs decrease the phosphorylation of PI3K and mTOR to inhibit PI3K/mTOR signaling activity and downregulate LC3-II protein to inhibit autophagy, thereby ameliorating the development of SAP, indicating that miR-141 might be a therapeutic target for SAP.

Screening of anti-cancerous potential of classical Raudra rasa and modified Raudra rasa modified with hiraka bhasma (nanodiamond) through FTIR & LC-MS analysis

OBJECTIVES

Raudra rasa is an ayurvedic medicine explicitly prescribed for the treatment of arbuda (cancer), whereas hiraka bhasma has the potential to promote cancer healing properties. Together, these two medicines provide multifunction benefits. This paper analyses the functional groups of Raudra rasa modified with hiraka bhasma and compares it with the classically prepared raudra rasa. To identify the functional group, organic ligands, and active compounds present in samples of raudra rasa (CRR) and modified raudra rasa with hiraka bhasma (MRR) contributing to cancer alleviation by using Fourier transform infrared spectroscopy (FTIR) & LC-MS analysis.

METHODS

Classical raudra rasa (CRR), its ingredients, shadguna kajjali (SK); decoction of Piper betel Linn. (PBD); Amaranthus spinosus Linn. (ASD); Boerhaavia diffusa Linn. (BDD); Piper longum Linn. (PLD); cow urine (GM), & similarly modified raudra rasa (MRR), its ingredients, hiraka bhasma (HB); shadguna rasasindura (SHR); water-soluble extract of Piper betel Linn. (PBE); Amaranthus spinosus Linn. (ASE); Boerhaavia diffusa Linn. (BDE); cow urine ark (GA); Piper Longum Linn. (PLE) were subjected to FTIR and LC-MS analysis.

RESULTS

Among all 15 samples studied, maximum numbers of peaks (21) were seen in MRR indicating a greater number of functional groups. Further, in MRR, a maximum peak in the double bond region is suggestive of its higher stability compared to CRR. Both the compound is preliminarily a mixture of the number of functional groups like; fluoro, methyl, amino, hydroxy, nitro, methylamino, carbonyl, and iodo groups, having known anti-proliferative activities. By the FT-IR analysis, the biologically active compounds in aqueous and methanol extract of CRR & MRR were identified that have anti-cancerous compounds. In the present study, a total of 40 major compounds like alkaloids, amino acid, carboxylic acid, Flavonoids, Nucleoside, Nucleotide, phenylpropanoid, Sphingosine, stilbenoid, sugar, phosphate, terpenoids, vitamin from aqueous & methanol extract of CRR & MRR were identified by LC-MS.

CONCLUSIONS

This research paper highlights the presence of different functional groups and bioactive compounds known to have anti-cancer activities. Thus, this review suggests future recommendations for the design and development of improved anticancer drugs with higher efficacy.

Modulation of Cancer Cell Autophagic Responses by Graphene-Based Nanomaterials: Molecular Mechanisms and Therapeutic Implications

Simple Summary

Graphene-based nanomaterials (GNM) are one-to-several carbon atom-thick flakes of graphite with at least one lateral dimension <100 nm. The unique electronic structure, high surface-to-volume ratio, and relatively low toxicity make GNM potentially useful in cancer treatment. GNM such as graphene, graphene oxide, graphene quantum dots, and graphene nanofibers are able to induce autophagy in cancer cells. During autophagy the cell digests its own components in organelles called lysosomes, which can either kill cancer cells or promote their survival, as well as influence the immune response against the tumor. However, a deeper understanding of GNM-autophagy interaction at the mechanistic and functional level is needed before these findings could be exploited to increase GNM effectiveness as cancer therapeutics and drug delivery systems. In this review, we analyze molecular mechanisms of GNM-mediated autophagy modulation and its possible implications for the use of GNM in cancer therapy.

Abstract

Graphene-based nanomaterials (GNM) are plausible candidates for cancer therapeutics and drug delivery systems. Pure graphene and graphene oxide nanoparticles, as well as graphene quantum dots and graphene nanofibers, were all able to trigger autophagy in cancer cells through both transcriptional and post-transcriptional mechanisms involving oxidative/endoplasmic reticulum stress, AMP-activated protein kinase, mechanistic target of rapamycin, mitogen-activated protein kinase, and Toll-like receptor signaling. This was often coupled with lysosomal dysfunction and subsequent blockade of autophagic flux, which additionally increased the accumulation of autophagy mediators that participated in apoptotic, necrotic, or necroptotic death of cancer cells and influenced the immune response against the tumor. In this review, we analyze molecular mechanisms and structure–activity relationships of GNM-mediated autophagy modulation, its consequences for cancer cell survival/death and anti-tumor immune response, and the possible implications for the use of GNM in cancer therapy.