Parthenolide induces autophagy via the depletion of 4E-BP1

Anti-Leukemic Attributes of Natural Compounds Targeting Autophagy: A Closer Look into the Molecular Mechanisms

Leukemia is a heterogeneous clonal cancer that affects millions of individuals around the world. Despite substantial breakthroughs in cancer treatment, traditional chemotherapy and radiotherapy remain ineffective, and therapeutic resistance still stands as a big obstacle. As a result, there is an increasing attention being paid currently toward the potency of natural compounds as a complementary or alternative therapy for leukemia. Autophagy, a conserved cellular process where damaged or defective cytosolic components and macromolecules are destroyed and recycled, plays a dual role in promoting or suppressing the continuance of cancer at different junctures of its development. Current studies have reported that autophagy has a cardinal function in the genesis and progression of leukemia, making it a promising target for novel treatments. In this review, we have explored the effectiveness of certain natural compounds, such as curcumin, resveratrol, tanshinone IIA, quercetin, tetrandrine, parthenolide, berberine, pristimerin, and alantolactone, that modulate autophagy and regulate its associated signaling cascades at a molecular level in different types of leukemia. They have been shown to have synergistic effects with conventional chemotherapy, emphasizing their potential as supplementary medicines. However, additional research is required to fully comprehend their mechanisms of action and to maximize their role in clinical perspectives.

Restoration of PM2.5-induced spermatogonia GC-1 cellular damage by parthenolide via suppression of autophagy and inflammation: An in vitro study

Particulate matter (PM) generated by environmental and air pollution is known to have detrimental effects on human health. Among these, PM2.5 particles (diameter < 2.5 µm) can breach the alveolar-capillary barrier and disseminate to other organs, posing significant health risks. Numerous studies have shown that PMs can harm various organs, including the reproductive system. Therefore, this study aimed to investigate the harmful effects of PM2.5 on mouse GC-1 spermatogonia cells (GC-1 spg cells) and to verify the ameliorative effects of parthenolide (PTL) treatment on damaged GC-1 spg cells. We observed a significant dose-dependent reduction in cell proliferation after PM2.5 concentration of 2.5 μg/cm2. Additionally, treatment with 20 μg/cm2 PM2.5 concentration significantly increased the expression of autophagy-related proteins ATG7, the ratio of LC3-II/LC3-I, and decreased phosphorylation of PI3K and AKT. Furthermore, PM2.5 exposure augmented inflammation mediator gene expressions, the phosphorylation of the inflammation-related transcription factor NF-κB p65 at Ser536, and ubiquitination. Treatment of PM2.5-exposed GC-1 spg cells with PTL significantly reduced NF-κB p65 phosphorylation and the expression of autophagy-related proteins ATG7 and LC3-II, leading to a statistically significant recovery in cell proliferation. Together, our findings elucidated the detrimental effects of PM2.5 exposure on male germ cells, and the restorative properties of PTL against air pollutants.

The Impact of Oxidative Stress and AKT Pathway on Cancer Cell Functions and Its Application to Natural Products

Oxidative stress and AKT serine-threonine kinase (AKT) are responsible for regulating several cell functions of cancer cells. Several natural products modulate both oxidative stress and AKT for anticancer effects. However, the impact of natural product-modulating oxidative stress and AKT on cell functions lacks systemic understanding. Notably, the contribution of regulating cell functions by AKT downstream effectors is not yet well integrated. This review explores the role of oxidative stress and AKT pathway (AKT/AKT effectors) on ten cell functions, including apoptosis, autophagy, endoplasmic reticulum stress, mitochondrial morphogenesis, ferroptosis, necroptosis, DNA damage response, senescence, migration, and cell-cycle progression. The impact of oxidative stress and AKT are connected to these cell functions through cell function mediators. Moreover, the AKT effectors related to cell functions are integrated. Based on this rationale, natural products with the modulating abilities for oxidative stress and AKT pathway exhibit the potential to regulate these cell functions, but some were rarely reported, particularly for AKT effectors. This review sheds light on understanding the roles of oxidative stress and AKT pathway in regulating cell functions, providing future directions for natural products in cancer treatment.

Parthenolide and Its Soluble Analogues: Multitasking Compounds with Antitumor Properties

Due to its chemical properties and multiple molecular effects on different tumor cell types, the sesquiterpene lactone parthenolide (PN) can be considered an effective drug with significant potential in cancer therapy. PN has been shown to induce either classic apoptosis or alternative caspase-independent forms of cell death in many tumor models. The therapeutical potential of PN has been increased by chemical design and synthesis of more soluble analogues including dimethylaminoparthenolide (DMAPT). This review focuses on the molecular mechanisms of both PN and analogues action in tumor models, highlighting their effects on gene expression, signal transduction and execution of different types of cell death. Recent findings indicate that these compounds not only inhibit prosurvival transcriptional factors such as NF-κB and STATs but can also determine the activation of specific death pathways, increasing intracellular reactive oxygen species (ROS) production and modifications of Bcl-2 family members. An intriguing property of these compounds is its specific targeting of cancer stem cells. The unusual actions of PN and its analogues make these agents good candidates for molecular targeted cancer therapy.

Terpenoids' anti-cancer effects: focus on autophagy

Terpenoids are the largest class of natural products, most of which are derived from plants. Amongst their numerous biological properties, their anti-tumor effects are of interest for they are extremely diverse which include anti-proliferative, apoptotic, anti-angiogenic, and anti-metastatic activities. Recently, several in vitro and in vivo studies have been dedicated to understanding the 'terpenoid induced autophagy' phenomenon in cancer cells. Light has already been shed on the intricacy of apoptosis and autophagy relationship. This latter crosstalk is driven by the delicate balance between activating or silencing of certain proteins whereby the outcome is expressed via interrelated signaling pathways. In this review, we focus on nine of the most studied terpenoids and on their cell death and autophagic activity. These terpenoids are grouped in three classes: sesquiterpenoid (artemisinin, parthenolide), diterpenoids (oridonin, triptolide), and triterpenoids (alisol, betulinic acid, oleanolic acid, platycodin D, and ursolic acid). We have selected these nine terpenoids among others as they belong to the different major classes of terpenoids and our extensive search of the literature indicated that they were the most studied in terms of autophagy in cancer. These terpenoids alone demonstrate the complexity by which these secondary metabolites induce autophagy via complex signaling pathways such as MAPK/ERK/JNK, PI3K/AKT/mTOR, AMPK, NF-kB, and reactive oxygen species. Moreover, induction of autophagy can be either destructive or protective in tumor cells. Nevertheless, should this phenomenon be well understood, we ought to be able to exploit it to create novel therapies and design more effective regimens in the management and treatment of cancer.

Recent Advances in Characterizing Natural Products that Regulate Autophagy

Autophagy, an intricate response to nutrient deprivation, pathogen infection, Endoplasmic Reticulum (ER)-stress and drugs, is crucial for the homeostatic maintenance in living cells. This highly regulated, multistep process has been involved in several diseases including cardiovascular and neurodegenerative diseases, especially in cancer. It can function as either a promoter or a suppressor in cancer, which underlines the potential utility as a therapeutic target. In recent years, increasing evidence has suggested that many natural products could modulate autophagy through diverse signaling pathways, either inducing or inhibiting. In this review, we briefly introduce autophagy and systematically describe several classes of natural products that implicated autophagy modulation. These compounds are of great interest for their potential activity against many types of cancer, such as ovarian, breast, cervical, pancreatic, and so on, hoping to provide valuable information for the development of cancer treatments based on autophagy.

Anticancer and apoptotic activities of parthenolide in combination with epirubicin in mda-mb-468 breast cancer cells

Breast cancer is the most common malignancy in women worldwide. Unfortunately, current therapeutic methods are not completely efficient. Hence, combination therapy with medicinal plants has attracted several kinds of research. In the current study, we aimed to investigate the apoptotic and anti-cancer effect of Parthenolide in combination with Epirubicin in the MDA-MB-468 breast cancer cell line. In this study,  the anti-proliferative and pro-apoptotic effect of Parthenolide in combination with Epirubicin and without it, in the MDA-MB-468 cell line have been assessed by MTT test, Hoescht staining and flow cytometry methods. Our outcomes showed that Parthenolide treatment in the present of Epirubicin led to a decrease in the minimum toxic concentration of Parthenolide and Epirubicin in comparison with individual treatments. Then, to achieve a likely molecular mechanism of mentioned drugs Bax and Bcl2 expression level evaluated by Real-time PCR and subsequently, Western blotting has been estimated the protein level of Caspase 3. Our data indicated that the treatment of cells with Parthenolide led to up-regulation of Bax and downregulation of Bcl2 at mRNA level. Moreover, Parthenolide treatment led to the obvious alternation of Caspase3 protein level. These results indicated that Parthenolide in combination with Epirubicin have significant cytotoxicity due to targeting the main regulators of apoptosis. Hence, according to lack of cytotoxicity of Parthenolide on normal cells that lead to reduction of drug side effects, it could be suggested as an adjuvant therapy with Epirubicin after complementary research on animal model and clinical trial.

Design, synthesis, and cytotoxic activities of novel hybrids of parthenolide and thiazolidinedione via click chemistry

A series of novel parthenolide-thiazolidinedione hybrids have been synthesized via a click chemistry-mediated coupling between parthenolide and thiazolidinedione, and evaluated for their cytotoxic activities. The results indicated that all the hybrids showed moderate cytotoxic effects on human cancer cell lines, including human erythroleukemia cell line (HEL), prostate (PC3), and breast (MDA-MB-231) by MTT assay. In particular, compound VI-6 exhibited the best cytotoxic activities against the MDA-MB-231 cells with IC₅₀ value of 2.07 µM, which was about eight times more active than that of the original compound (PTL). These interesting results might be used to develop novel lead scaffolds for potential anticancer agents.

Autophagy Regulation by the Translation Machinery and Its Implications in Cancer

Various metabolic pathways and molecular processes in the cell act intertwined, and dysregulating the interplay between some of them may lead to cancer. It is only recently that defects in the translation process, i.e., the synthesis of proteins by the ribosome using a messenger (m)RNA as a template and translation factors, have begun to gain strong attention as a cause of autophagy dysregulation with effects in different maladies, including cancer. Autophagy is an evolutionarily conserved catabolic process that degrades cytoplasmic elements in lysosomes. It maintains cellular homeostasis and preserves cell viability under various stress conditions, which is crucial for all eukaryotic cells. In this review, we discuss recent advances shedding light on the crosstalk between the translation and the autophagy machineries and its impact on tumorigenesis. We also summarize how this interaction is being the target for novel therapies to treat cancer.

Advances in chemistry and bioactivity of parthenolide

(−)-Parthenolide is a germacrane sesquiterpene lactone, available in ample amounts from the traditional medical plant feverfew (Tanacetum parthenium).

Natural Compounds As Modulators of Non-apoptotic Cell Death in Cancer Cells

Cell death is an innate capability of cells to be removed from microenvironment, if and when they are damaged by multiple stresses. Cell death is often regulated by multiple molecular pathways and mechanism, including apoptosis, autophagy, and necroptosis. The molecular network underlying these processes is often intertwined and one pathway can dynamically shift to another one acquiring certain protein components, in particular upon treatment with various drugs. The strategy to treat human cancer ultimately relies on the ability of anticancer therapeutics to induce tumor-specific cell death, while leaving normal adjacent cells undamaged. However, tumor cells often develop the resistance to the drug-induced cell death, thus representing a great challenge for the anticancer approaches. Numerous compounds originated from the natural sources and biopharmaceutical industries are applied today in clinics showing advantageous results. However, some exhibit serious toxic side effects. Thus, novel effective therapeutic approaches in treating cancers are continued to be developed. Natural compounds with anticancer activity have gained a great interest among researchers and clinicians alike since they have shown more favorable safety and efficacy then the synthetic marketed drugs. Numerous studies in vitro and in vivo have found that several natural compounds display promising anticancer potentials. This review underlines certain information regarding the role of natural compounds from plants, microorganisms and sea life forms, which are able to induce non-apoptotic cell death in tumor cells, namely autophagy and necroptosis.

Parthenolide suppresses pancreatic cell growth by autophagy-mediated apoptosis

Pancreatic cancer is an aggressive malignancy and is unresponsive to conventional chemotherapies. Parthenolide, a sesquiterpene lactone isolated from feverfew, has exhibited potent anticancer effects against various cancers. The purpose of this report was to investigate the effect and underlying mechanism of parthenolide in human pancreatic cancer Panc-1 and BxPC3 cells. The results demonstrated that parthenolide suppressed the growth and induced apoptosis of Panc-1 and BxPC3 pancreatic cancer cells with the half maximal inhibitory concentration (IC₅₀) ranging between 7 and 9 μM after 24 h of treatment. Significant autophagy was induced by parthenolide treatment in pancreatic cancer cells. Parthenolide treatment concentration-dependently increased the percentage of autophagic cells and significantly increased the expression levels of p62/SQSTM1, Beclin 1, and LC3II in Panc-1 cells. Punctate LC3II staining confirmed autophagy. Furthermore, inhibiting autophagy by chloroquine, 3-methyladenine, or LC3II siRNA significantly blocked parthenolide-induced apoptosis, suggesting that parthenolide induced apoptosis through autophagy in this study. In conclusion, these studies established that parthenolide inhibits pancreatic cell growth by autophagy-mediated apoptosis. Data of the present study suggest that parthenolide can serve as a potential chemotherapeutic agent for pancreatic cancer.

Targeting Thioredoxin Reductase by Parthenolide Contributes to Inducing Apoptosis of HeLa Cells

Parthenolide (PTL), a major active sesquiterpene lactone from the herbal plant Tanacetum parthenium, has been applied in traditional Chinese medicine for centuries. Although PTL demonstrates potent anticancer efficacy in numerous types of malignant cells, the cellular targets of PTL have not been well defined. We reported here that PTL interacts with both cytosolic thioredoxin reductase (TrxR1) and mitochondrial thioredoxin reductase (TrxR2), two ubiquitous selenocysteine-containing antioxidant enzymes, to elicit reactive oxygen species-mediated apoptosis in HeLa cells. PTL selectively targets the selenocysteine residue in TrxR1 to inhibit the enzyme function, and further shifts the enzyme to an NADPH oxidase to generate superoxide anions, leading to reactive oxygen species accumulation and oxidized thioredoxin. Under the conditions of inhibition of TrxRs in cells, PTL does not cause significant alteration of cellular thiol homeostasis, supporting selective target of TrxRs by PTL. Importantly, overexpression of functional TrxR1 or Trx1 confers protection, whereas knockdown of the enzymes sensitizes cells to PTL treatment. Targeting TrxRs by PTL thus discloses an unprecedented mechanism underlying the biological activity of PTL, and provides deep insights to understand the action of PTL in treatment of cancer.

A novel eremophilane lactone inhibits FcεRI-dependent release of pro-inflammatory mediators: structure-dependent bioactivity

BACKGROUND

Allergic inflammation is primarily mediated by immune effector cells such as mast cells and basophils that release proinflammatory cytokines. Both mast cells and basophils are activated via their high affinity IgE receptor (FcεRI) which initiates the release of proinflammatory mediators such as histamine and tumor necrosis factor (TNF). Considerable effort has been focused on finding an effective basophil stabilizer that inhibits the activation of FcεRI-activated mediator release. Recently, eremophilane lactones, a novel family of sesquiterpene compound originally isolated from Petasites japonicas (Sieb. et Zucc.), have been described, and it has been postulated that they may have anti-inflammatory activity, particularly in allergic disease.

OBJECTIVE

Our objective was to determine the effect of two eremophilane lactones derived from 6β-angeloyloxy-3β,8-dihydroxyeremophil-7(11)-en-12,8β-olide (F-1) on immunoglobulin E (IgE)-dependent release of pro-inflammatory mediators by a basophil cell line, RBL-2H3, a model system for FcεRI-mediated activation of pro-inflammatory mediator release.

METHODS

The parent compound (F-1) was chemically modified to produce F-1a [6β-angeloyloxy-3β-benzoyloxy-8-hydroxyeremophil-7(11)-en-12,8β-olide] and F-1b [6β-angeloyloxy-3β,8-diacetoxyeremophil-7(11)-en-12,8β-olide]. RBL-2H3 cells were sensitized with DNP-specific IgE and then activated with DNP-BSA. The effect of these compounds on IgE-dependent basophil degranulation was assessed by measuring the release of β-hexosaminidase (b-hex). In addition, TNF release was measured via ELISA.

RESULTS

The phenylacetyl reaction modified C-8 and produced F-1a whereas acetylation of F-1 produced F-1b. F-1a was not cytotoxic to RBL-2H3 cells even at 50 μM, but F-1b was slightly cytotoxic at 50 μM, reducing viability of the cells by approximately 15 %. Neither F-1a nor F-1b inhibited FcεRI-dependent activation of RBL-2H3 cells when the cells were pretreated for only 30 min with the compounds. However, 24 h pretreatment with F-1a inhibited antigen-dependent degranulation by as much as 60 % and TNF production by as much as 90 %. F-1b had no effect on RBL-2H3 activation via FcεRI.

CONCLUSIONS

These results indicate that F-1a inhibits degranulation of RBL-2H3 cells activated via the high affinity IgE receptor, FcεRI, and that this effect is dependent upon hydroxylation of the third carbon.