Samsoeum, a traditional herbal medicine, elicits apoptotic and autophagic cell death by inhibiting Akt/mTOR and activating the JNK pathway in cancer cells

Qing Yan Li Ge Tang, a Chinese Herbal Formula, Induces Autophagic Cell Death through the PI3K/Akt/mTOR Pathway in Nasopharyngeal Carcinoma Cells In Vitro

Since a portion of patients with nasopharyngeal carcinoma (NPC) do not benefit much from current standard treatments, it is still needed to discover new therapeutic drugs to improve the prognosis of the patients. Considering that Chinese traditional medicine plays a role in inhibiting tumor progression, in this study, we aimed to investigate whether a Chinese herbal formula, Qing Yan Li Ge Tang (QYLGT), has the anticancer activity in NPC cells and explore the underlying mechanism as well. MTT assay, colony formation assay, immunoblotting assay, and DNA laddering assay were performed to assess cell viability, cell colony formation, protein expression, and DNA fragmentation, respectively. Results show that QYLGT was able to inhibit the cell viability and decrease colony formation ability in NPC cells. QYLGT could also increase the formation of intracellular vacuoles and induce the autophagy-related protein expressions, including Atg3, Atg6, and Atg12-Atg5 conjugate in NPC cells. Treatment with an autophagy inhibitor, 3-methyladenine, could significantly recover QYLGT-inhibited cell viability of NPC cells. In addition, QYLGT did not significantly induce apoptosis in NPC cells. We also found that QYLGT had the ability to activate phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of the rapamycin (mTOR) pathway. Treatment with PI3K inhibitors, LY294002 and wortmannin, or mTOR inhibitors, rapamycin and Torin 1, could not only recover QYLGT-inhibited cell viability of NPC cells but also inhibit Atg3 expression. Taken together, our results demonstrated that QYLGT could induce autophagic cell death in NPC cells through the PI3K/Akt/mTOR pathway.

Autophagy Modulators From Chinese Herbal Medicines: Mechanisms and Therapeutic Potentials for Asthma

Asthma has become a global health issue, suffering more than 300 million people in the world, which is a heterogeneous disease, usually characterized by chronic airway inflammation and airway hyperreactivity. Combination of inhaled corticosteroids (ICS) and long acting β-agonists (LABA) can relieve asthma symptoms and reduce the frequency of exacerbations, especially for patients with refractory asthma, but there are limited treatment options for people who do not gain control on combination ICS/LABA. The increase in ICS dose generally provides little additional benefit, and there is an increased risk of side effects. Therefore, therapeutic interventions integrating the use of different agents that focus on different targets are needed to overcome this set of diseases. Some findings suggest autophagy is closely correlated with the severity of asthma through eosinophilic inflammation, and its modulation may provide novel therapeutic approaches for severe allergic asthma. The chinese herbal medicine (CHM) have been demonstrated clinically as potent therapeutic interventions for asthma. Moreover some reports have found that the bioactive components isolated from CHM could modulate autophagy, and exhibit potent Anti-inflammatory activity. These findings have implied the potential for CHMs in asthma or allergic inflammation therapy via the modulation of autophagy. In this review, we discuss the basic pathomechanisms underpinning asthma, and the potential role of CHMs in treating asthma with modulating autophagy.

Natural Polyphyllins (I, II, D, VI, VII) Reverses Cancer Through Apoptosis, Autophagy, Mitophagy, Inflammation, and Necroptosis

Cancer is the second leading cause of mortality worldwide. Conventional therapies, including surgery, radiation, and chemotherapy, have limited success because of secondary resistance. Therefore, safe, non-resistant, less toxic, and convenient drugs are urgently required. Natural products (NPs), primarily sourced from medicinal plants, are ideal for cancer treatment because of their low toxicity and high success. NPs cure cancer by regulating different pathways, such as PI3K/AKT/mTOR, ER stress, JNK, Wnt, STAT3, MAPKs, NF-kB, MEK-ERK, inflammation, oxidative stress, apoptosis, autophagy, mitophagy, and necroptosis. Among the NPs, steroid saponins, including polyphyllins (I, II, D, VI, and VII), have potent pharmacological, analgesic, and anticancer activities for the induction of cytotoxicity. Recent research has demonstrated that polyphyllins (PPs) possess potent effects against different cancers through apoptosis, autophagy, inflammation, and necroptosis. This review summarizes the available studies on PPs against cancer to provide a basis for future research.

A 13-week repeated oral dose toxicity evaluation and a 4-week recovery evaluation of the Sam So Eum (SSE) in male and female rats

ETHNOPHAMACOLOGICAL RELEVANCE

Sam So Eum (SSE), used in traditional Korean medicine, has been prescribed for the treatment of various ailments including emesis, and fever for centuries. SSE is known by several different names (Shen Su Yin in traditional Chinese medicine; Jin So In traditional Japanese Kampo medicine). It is a mixture of medicinal plants including Panax ginseng C. A. Mey., Perilla frutescens (L.) Britton, and Peucedanum praeruptorum Dunn. Studies have revealed that SSE has many pharmacological effects including anti-inflammatory, anti-cancer, and anti-allergic properties, but its toxic effects have not been evaluated in vivo. Recently, the use of traditional medicinal herbs to treat various diseases has increased, owing to increased number of studies supporting their efficacy. However, safety evaluations for toxicity and other adverse effects have not been extensive. It is commonly considered that natural products extracted from traditional medicinal herbs are safer than synthetic drugs, but this lacks a scientific basis. Thus, in this study, we evaluated the toxicity of SSE in male and female rats.

AIM OF THE STUDY

To evaluated the safety of SSE in male and female rats.

MATERIALS AND METHODS

SSE was administered orally for 13 weeks at 1000, 2000, and 4000 mg kg^-1·day^-1, and then the rats were maintained for 4 weeks without SSE administration (recovery evaluation).

RESULTS

We observed the animals for changes in clinical signs, including hematological parameters, and food consumption; serum chemistry profiling and urinalysis were also carried out. Creatinine levels in the serum were significantly increased following oral administration of SSE at 2000 and 4000 mg kg^-1·day^-1 in male and female rats, but returned to the normal levels during the recovery period. In addition, SSE administration does not cause kidney and liver toxicity. Thus, we determined that the no-observed-adverse-effect level of SSE is 4000 mg kg^-1·day^-1. The no-observed-effect level of SSE was determined to be 1000 mg kg^-1·day^-1, because serum creatinine was increased by oral administration of SSE at 2000 and 4000 mg kg^-1·day^-1 in male and female rats.

CONCLUSIONS

SSE administration does not cause toxicity at 4000 mg kg^-1·day^-1 in male and female rats.

Protective effects of circulating microvesicles derived from ischemic preconditioning on myocardial ischemia/reperfusion injury in rats by inhibiting endoplasmic reticulum stress

Microvesicles (MVs) have been shown to be involved in pathophysiology of ischemic heart diseases. However, the underlying mechanisms are still unclear. Here we investigated the effects of MVs derived from ischemic preconditioning (IPC-MVs) on myocardial ischemic/reperfusion (I/R) injury in rats. Myocardial IPC model was elicited by three cycles of ischemia and reperfusion of the left anterior descending (LAD) coronary artery. IPC-MVs from the peripheral blood of the above animal model were isolated by ultracentrifugation and characterized by flow cytometry and transmission electron microscopy. IPC-MVs were administered intravenously (7 mg/kg) at 5 min before reperfusion procedure in I/R injury model which was induced by 30-min ischemia and 120-min reperfusion of LAD in rats. We found that total IPC-MVs and different phenotypes, including platelet-derived MVs (PMVs), endothelial cell-derived MVs (EMVs), leucocyte-derived MVs and erythrocyte-derived MVs (RMVs) were all isolated which were identified membrane vesicles (< 1 µm) with corresponding antibody positive. The numbers of PMVs, EMVs and RMVs were significantly increased in circulation of IPC treated rats respectively. Additionally, treatment with IPC-MVs significantly alleviated damage of myocardium, and restored cardiac function of I/R injury rats, as evidenced by increased heart rate, and decreased the elevation of ST-segment. The size of myocardial infarction, lactate dehydrogenase activity, and the number of apoptotic cardiomyocytes were also reduced significantly with IPC-MVs treatment, coincident with the above function amelioration. Moreover, IPC-MVs decreased the activity of caspase 3, and the expression of endoplasmic reticulum stress (ERS) markers, GRP78, CHOP and caspase 12 indicating the involvement of ERS-specific apoptosis in I/R injury, and cardioprotective effects of IPC-MVs. In summary, our study demonstrated a novel mechanism of IPC in which circulating IPC-MVs could protect hearts from I/R injury in rats through attenuation of ERS-induced apoptosis. These findings provide new insight into therapeutic potential of IPC-induced MVs in cardioprotection against I/R injury.

NF-κB/mTOR-mediated autophagy can regulate diquat-induced apoptosis

Autophagy and apoptosis are the major types of cell death in pesticide-induced neurotoxicity, and autophagy is known to play a role in cell protection by inhibiting apoptosis. In this study, we characterized the relationship between autophagy and apoptosis in diquat (DQ)-induced cell death and explored a novel pharmacotherapeutic approach involving autophagy regulation to prevent DQ neurotoxicity. DQ was cytotoxic to PC12 cells in a concentration-dependent manner, as shown by decreased cell viability and decreased dopamine (DA) levels. DQ-induced apoptosis was found in PC12 cells, as demonstrated by activation of caspase-3 and -9 and by nuclear condensation. By monitoring expression of microtubule-associated protein 1A/1B light chain 3B (LC3-II) and p62, DQ was found to induce autophagy. Exposure of PC12 cells to DQ led to the production of reactive oxygen species (ROS), and N-acetyl-cysteine (NAC) antioxidant effectively blocked both apoptosis and autophagy. Interestingly, DQ in PC12 cells showed increased p53 and NF-κB in a time-dependent manner; furthermore, pifithrin-α (PFT-α), a p53 inhibitor, downregulates the cytotoxicity of DQ, as shown by decreased LC3-II and cleaved caspase-3. SN50, an NF-κB inhibitor, results in diminished LC3-II, cleaved caspase-3, and p53. DQ induces mitogen-activated protein kinase (MAPK) signaling including ERK, JNK, and p38, which inhibit regulated apoptosis and autophagic cell death by controlling mTOR signaling. In addition, modulation of DQ-induced apoptosis in response to autophagy regulation was investigated. Pretreatment with rapamycin, an autophagy inducer, significantly enhanced the viability of DQ-exposed cells by alleviating DQ-induced apoptosis. Conversely, cell pretreatment with 3-methyladenine (3MA), an autophagy inhibitor increased DQ toxicity. Our results suggest that DQ-induced cytotoxicity is modified by autophagy regulation. Pharmacologic induction of autophagy may be a useful treatment strategy in neurodegenerative disorders.

[Pt(O,O'-acac)(γ-acac)(DMS)] Induces Autophagy in Caki-1 Renal Cancer Cells

We have demonstrated the cytotoxic effects of [Pt(O,O′-acac)(γ-acac)(dimethyl sulfide (DMS))] on various immortalized cell lines, in primary cultures, and in murine xenograft models in vivo. Recently, we also showed that [Pt(O,O′-acac)(γ-acac)(DMS)] is able to kill Caki-1 renal cells both in vivo and in vitro. In the present paper, apoptotic and autophagic effects of [Pt(O,O′-acac)(γ-acac)(DMS)] and cisplatin were studied and compared using Caki-1 cancerous renal cells. The effects of cisplatin include activation of caspases, proteolysis of enzyme poly ADP ribose polymerase (PARP), control of apoptosis modulators B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), and BH3-interacting domain death agonist (Bid), and cell cycle arrest in G2/M phase. Conversely, [Pt(O,O′-acac)(γ-acac)(DMS)] did not induce caspase activation, nor chromatin condensation or DNA fragmentation. The effects of [Pt(O,O′-acac)(γ-acac)(DMS)] include microtubule-associated proteins 1A/1B light chain 3B (LC3)-I to LC3-II conversion, Beclin-1 and Atg-3, -4, and -5 increase, Bcl-2 decrease, and monodansylcadaverine accumulation in autophagic vacuoles. [Pt(O,O′-acac)(γ-acac)(DMS)] also modulated various kinases involved in intracellular transduction regulating cell fate. [Pt(O,O′-acac)(γ-acac)(DMS)] inhibited the phosphorylation of mammalian target of rapmycin (mTOR), p70S6K, and AKT, and increased the phosphorylation of c-Jun N-terminal kinase (JNK1/2), a kinase activity pattern consistent with autophagy induction. In conclusion, while in past reports the high cytotoxicity of [Pt(O,O′-acac)(γ-acac)(DMS)] was always attributed to its ability to trigger an apoptotic process, in this paper we show that Caki-1 cells die as a result of the induction of a strong autophagic process.

Resveratrol sensitizes lung cancer cell to TRAIL by p53 independent and suppression of Akt/NF-κB signaling

AIMS

TRAIL is a promising anticancer agent that has the potential to sensitize a wide variety of cancer or transformed cells by inducing apoptosis. However, resistance to TRAIL is a growing concern. Current manuscript aimed to employ combination treatment to investigate resveratrol induced TRAIL sensitization in NSCLC.

METHOD

A549 and HCC-15 cells were used in an experimental design. Cell viability was determined by morphological image, crystal violet staining and MTT assay. Apoptosis was evaluated by LDH assay, Annexin V and DAPI staining. Autophagy and apoptosis indicator protein were examined by western blotting. TEM and puncta assay was carried out to evaluate the autophagy. MTP and ROS activity was evaluated by JC-1 and H₂DCFDA staining.

FINDINGS

Resveratrol is a polyphenolic compound capable of activation of tumor suppressor p53 and its pro-apoptotic modulator PUMA. Herein, we showed the p53-independent apoptosis by decrease the expression of phosphorylated Akt-mediated suppression of NF-κB that is also substantiated with the downregulation of anti-apoptotic factors Bcl-2 and Bcl-xl in NSCLC, resulting in an attenuation of TRAIL resistance in combined treatment. Furthermore, apoptosis was induced in TRAIL-resistant lung cancer cells with a co-treatment of resveratrol and TRAIL assessed by the loss of MMP, ROS generations which resulting the translocation of cytochrome c from the mitochondria into the cytosol due to mitochondrial dysfunction. Moreover, autophagy flux was not affected by resveratrol-induced TRAIL-mediated apoptosis in NSCLC.

SIGNIFICANCE

Overall, targeting the NF-κB (p65) pathway via resveratrol attenuates TRAIL resistance and induces TRAIL-mediated apoptosis which could be the effective TRAIL-based cancer therapy regimen.

Triptolide induces protective autophagy and apoptosis in human cervical cancer cells by downregulating Akt/mTOR activation

Triptolide exhibits immunosuppressive, anti-inflammatory, antifertility and antineoplastic functions. However, the anticancer effect of triptolide on cervical cancer and the underlying mechanism remains to be fully understood. The present study assessed the mechanisms underlying the effect of triptolide on the viability and apoptosis of human cervical cancer cells. SiHa cells were treated with 12.5-100.0 nM triptolide for 12, 24 or 48 h. The present study demonstrated that triptolide inhibited viability and induced apoptosis in SiHa cells time- and dose-dependently. Furthermore, treatment with triptolide promoted autophagy and activated microtubule associated protein 1 light chain 3 α expression in SiHa cells. Triptolide treatment suppressed the expression of phosphorylated (p)-protein kinase B (Akt), p-mechanistic target of rapamycin (mTOR), and p-p70S6K, activated the expression of p-p38, mitogen-activated protein kinase (MAPK) and p53 and inhibited the expression of p-forkhead box O3 (Foxo3a) in SiHa cells. These results suggested that triptolide induces protective autophagy, suppresses cell viability and promotes apoptosis in human cervical cancer cells by inducing the autophagy-targeting phosphoinositide 3-kinase/Akt/mTOR, p38, MAPK, p53 and Foxo3a pathways.

6-Gingerol Activates PI3K/Akt and Inhibits Apoptosis to Attenuate Myocardial Ischemia/Reperfusion Injury

6-Gingerol (6-G) is known to alleviate myocardial ischemia/reperfusion injury. However, the underlying molecular mechanisms of 6-G myocardial protection are not known. In this study, the protective effect of 6-G on ischemia/reperfusion (I/R) damage and whether such a mechanism was related to apoptosis inhibition and activation of phosphoinositide 3-kinases (PI3K)/serine/threonine kinase (Akt) signaling pathway were investigated. Rats were subjected to I/R in the presence or absence of 6-G and the changes of cardiac function, infarct size and histopathological changes, and the levels of cardiac troponin T, creatine kinase-MB, and myocardial apoptosis were examined. The expression of caspase-3, PI3K, p-Akt, and Akt was also determined. We found that 6-G (6 mg/kg) pretreatment significantly improved heart function and ameliorated infarct size and histopathological changes and cardiac troponin T and creatine kinase-MB levels induced by I/R. Moreover, pretreatment with 6-G significantly inhibited myocardial apoptosis and caspase-3 activation induced by I/R. 6-G also upregulated expression of PI3K, p-Akt, and Akt in myocardial tissues. Taken together, these findings suggest that 6-G inhibits apoptosis and activates PI3K/Akt signaling in response to myocardial I/R injury as a possible mechanism to attenuate I/R-induced injury in heart. These results might be important for developing novel strategies for preventing myocardial I/R injury.

PPARγ activation by troglitazone enhances human lung cancer cells to TRAIL-induced apoptosis via autophagy flux

Members of the tumor necrosis factor (TNF) transmembrane cytokine superfamily, such as TNFα and Fas ligand (FasL), play crucial roles in inflammation and immunity. TRAIL is a member of this superfamily with the ability to selectively trigger cancer cell death but does not motive cytotoxicity to most normal cells. Troglitazone are used in the cure of type II diabetes to reduce blood glucose levels and improve the sensitivity of an amount of tissues to insulin. In this study, we revealed that troglitazone could trigger TRAIL-mediated apoptotic cell death in human lung adenocarcinoma cells. Pretreatment of troglitazone induced activation of PPARγ in a dose-dependent manner. In addition conversion of LC3-I to LC3-II and PPARγ was suppressed in the presence of GW9662, a well-characterized PPARγ antagonist. Treatment with troglitazone resulted in a slight increase in conversion rate of LC3-I to LC3-II and significantly decreased p62 expression levels in a dose-dependent manner. This indicates that troglitazone induced autophagy flux activation in human lung cancer cells. Inhibition of autophagy flux applying a specific inhibitor and genetically modified ATG5 siRNA enclosed troglitazone-mediated enhancing effect of TRAIL. These data demonstrated that activation of PPARγ mediated by troglitazone enhances human lung cancer cells to TRAIL-induced apoptosis via autophagy flux and also suggest that troglitazone may be a combination therapeutic target with TRAIL protein in TRAIL-resistant cancer cells.

Polyphyllin G induce apoptosis and autophagy in human nasopharyngeal cancer cells by modulation of AKT and mitogen-activated protein kinase pathways in vitro and in vivo

Polyphyllin G (also call polyphyllin VII), extract from rhizomes of Paris yunnanensis Franch, has been demonstrated to have strong anticancer activities in a wide variety of human cancer cell lines. Previous studies found that Polyphyllin G induced apoptotic cell death in human hepatoblastoma cancer and lung cancer cells. However, the underlying mechanisms of autophagy in human nasopharyngeal carcinoma (NPC) remain unclear. In this study, Polyphyllin G can potently induced apoptosis dependent on the activations of caspase-8, -3, and -9 and the changes of Bcl-2, Bcl-xL and Bax protein expression in different human NPC cell lines (HONE-1 and NPC-039). The amount of both LC3-II and Beclin-1 was intriguingly increased suggest that autophagy was induced in Polyphyllin G-treated NPC cells. To further clarify whether Polyphyllin G-induced apoptosis and autophagy depended on AKT/ERK/JNK/p38 MAPK signaling pathways, cells were combined treated with AKT inhibitor (LY294002), ERK1/2 inhibitor (U0126), p38 MAPK inhibitor (SB203580), or JNK inhibitor (SP600125). These results demonstrated that Polyphyllin G induced apoptosis in NPC cells through activation of ERK, while AKT, p38 MAPK and JNK were responsible for Polyphyllin G-induced autophagy. Finally, an administration of Polyphyllin G effectively suppressed the tumor growth in the NPC carcinoma xenograft model in vivo. In conclusion, our results reveal that Polyphyllin G inhibits cell viability and induces apoptosis and autophagy in NPC cancer cells, suggesting that Polyphyllin G is an attractive candidate for tumor therapies. Polyphyllin G may promise candidate for development of antitumor drugs targeting nasopharyngeal carcinoma.

PPARgamma agonists sensitize PTEN-deficient resistant lung cancer cells to EGFR tyrosine kinase inhibitors by inducing autophagy

We aimed to develop novel drug combination strategy to overcome drug resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) in the treatment of non-small cell lung cancer (NSCLC). Peroxisome proliferator-activated receptor gamma (PPARγ) is a nuclear receptor, which upon activation upregulates phosphatase and tensin homolog (PTEN) to inhibit cell signaling downstream of PI3K to mediate apoptosis. To this end, PTEN loss is a known mechanism contributing to resistance to EGFR TKIs. Therefore, PPARγ agonists are hypothesized to overcome EGFR TKI resistance. Using human NSCLC cell models with PTEN deficiency, the potentiation of EGFR TKI anticancer activity by PPARγ agonists was evaluated. PPARγ agonists were found to upregulate PTEN, subsequently inhibiting the PI3K-Akt signaling pathway, and thus enhancing the anticancer activity of gefitinib (a first generation EGFR TKI). Chemical and genetic inhibition of PPARγ were shown to prevent this potentiation of anticancer activity by PPARγ agonists, thus confirming the crucial role played by PPARγ activation. Interestingly, the tested PPARγ agonists were also found to induce autophagy, as evidenced by the increased expression of an autophagy marker LC3-II and the autophagic degradation of p62/SQSTM1. PPARγ agonists-induced autophagic cell death was believed to contribute to the circumvention of resistance in PTEN-deficient cells because the genetic silencing of ATG5 (an autophagy mediator) was found to eliminate the drug potentiation effect by the PPARγ agonists. Our findings thus provide the basis for the rational and personalized use of PPARγ agonists in combination with EGFR TKIs in lung cancer patients.

Norcantharidin Inhibits SK-N-SH Neuroblastoma Cell Growth by Induction of Autophagy and Apoptosis

Norcantharidin, a low-toxic analog of the active anticancer compound cantharidin in Mylabris, can inhibit proliferation and induce apoptosis of multiple types of cancer cells. However, the anticancer activities of norcantharidin with respect to neuroblastoma, and its underlying mechanisms, have not been investigated. Therefore, our study was designed to determine the efficacy of norcantharidin on SK-N-SH neuroblastoma cell death and to elucidate detailed mechanisms of activity. In the present study, norcantharidin suppressed the proliferation and cloning ability of SK-N-SH cells in a dose-dependent manner, apparently by reducing the mitochondrial membrane potential and arresting SK-N-SH cells at the G2/M stage, accompanied by elevated expressions of p21 and decreased expressions of cyclin B1 and cell division control 2. Treatment by norcantharidin induced significant mitophagy and autophagy, as demonstrated by a decrease in Translocase Of Outer Mitochondrial Membrane 20 (TOM20), increased beclin1 and LC3-II protein expression, reduced protein SQSTM1/p62 expression, and accumulation of punctate LC3 in the cytoplasm of SK-N-SH cells. In addition, norcantharidin induced apoptosis through regulating the expression of B-cell lymphoma 2-associated X protein/B-cell lymphoma 2 and B-cell lymphoma 2-associated X protein/myeloid cell leukemia 1 and activating caspase-3 and caspase-9-dependent endogenous mitochondrial pathways. We also observed an increase in phosphor-AMP-activated protein kinase accompanied with a decrease in phosphor-protein kinase B and mammalian target of rapamycin expression after treatment with norcantharidin. Subsequent studies indicated that norcantharidin participates in cellular autophagy and apoptosis via activation of the c-Jun NH2-terminal kinases/c-Jun pathway. In conclusion, our results demonstrate that norcantharidin can reduce the mitochondrial membrane potential, induce mitophagy, and subsequently arouse cellular autophagy and apoptosis; the AMP-activated protein kinase, protein kinase B/mammalian target of rapamycin, and c-Jun NH2-terminal kinases/c-Jun signaling pathways are widely involved in these processes. Thus, the traditional Chinese medicine norcantharidin could be a novel therapeutic strategy for treating neuroblastoma.

A platycoside-rich fraction from the root of Platycodon grandiflorum enhances cell death in A549 human lung carcinoma cells via mainly AMPK/mTOR/AKT signal-mediated autophagy induction

ETHNOPHARMACOLOGICAL RELEVANCE

The root of Platycodon grandiflorum (PG), commonly known as Kilkyong in Korea, Jiegeng in China, and Kikyo in Japan, has been extensively used as a traditional anti-inflammatory medicine in Asia for the treatment of respiratory conditions, such as bronchitis, asthma, and tonsillitis. Platycosides isolated from PG are especially well-known for their anti-cancer effects.

AIM OF THE STUDY

We investigated the involvement of autophagic cell death and other potential molecular mechanisms induced by the platycoside-containing butanol fraction of PG (PGB) in human lung carcinoma cells.

MATERIALS AND METHODS

PGB-induced growth inhibition and cell death were measured using a 5-diphenyl-tetrazolium bromide (MTT) assay. The effects of PGB on autophagy were determined by observing microtubule-associated protein 1 light chain 3 (LC3) redistribution with confocal microscopy. The PGB-mediated regulation of autophagy-associated proteins was investigated using Western blotting analysis. Furthermore, the anti-cancer mechanism of PGB was confirmed using chemical inhibitors. A high-performance liquid chromatography (HPLC)-DAD system was used to analyze the platycosides in PGB.

RESULTS

In A549 cells, PGB induced significant autophagic cell death. Specifically, PGB upregulated LC3-II in a time- and dose-dependent manner, and it redistributed LC3 via autophagosome formation in the cytoplasm. PGB treatment increased the phosphorylation of AMP-activated protein kinase (AMPK) and subsequently suppressed the AKT/mammalian target of the rapamycin (mTOR) pathway. Furthermore, PGB inhibited cell proliferation by regulating the mitogen-activated protein kinase (MAPK) pathways. In this study, six types of platycosides were identified in the PGB using HPLC.

CONCLUSIONS

PGB efficiently induced cancer cell death via autophagy and the modulation of the AMPK/mTOR/AKT and MAPK signaling pathways in A549 cells. Therefore, PGB may be an efficacious herbal anti-cancer therapy.

Polyphyllin G induces apoptosis and autophagy cell death in human oral cancer cells

BACKGROUND

Polyphyllin G (also called polyphyllin VII), extract from rhizomes of Paris yunnanensis Franch, has been shown to have strong anticancer activities in a wide variety of human cancer cell lines. However, the underlying influences of autophagy in human oral squamous cell carcinoma (OSCC) remain unclear.

METHODS

In this study, the roles of apoptosis and autophagy in polyphyllin G-induced death in human oral cancer cells were investigated. Moreover, the molecular mechanism of the anticancer effects of polyphyllin G in human oral cancer cells was investigated.

RESULTS

The results revealed that polyphyllin G significantly inhibited cell proliferation in human oral cancer cells; it dose-dependently induced apoptosis in SAS and OECM-1 cells through caspase-3, -8, and -9 activation and poly (ADP-ribose) polymerase cleavage. In addition, changes were observed in Bcl-2 and proapoptosis-related protein expression in different human oral cancer cell lines. The expression of both LC3-II and beclin-1 was markedly increased, suggesting the induction of autophagy in polyphyllin G-treated oral cells. To further clarify whether polyphyllin G-induced apoptosis and autophagy depended on Akt/extracellular signal-regulated kinases (ERK)/c-Jun N-terminal kinases (JNK)/p38 mitogen-activated protein kinases (MAPK) signaling pathways, the cells were cotreated with inhibitors. The results demonstrated polyphyllin G-induced apoptosis in oral cells through the activation of ERK, Akt, p38 MAPK, and JNK, whereas ERK and JNK accounted for polyphyllin G-induced autophagy.

CONCLUSION

This study is the first to demonstrate apoptosis and autophagy during polyphyllin G-induced cell death in human oral cancer cell lines. These results suggest that polyphyllin G is a promising candidate for developing antitumor drugs targeting human oral squamous cell carcinoma.

Polyphyllin VII Induces an Autophagic Cell Death by Activation of the JNK Pathway and Inhibition of PI3K/AKT/mTOR Pathway in HepG2 Cells

Polyphyllin VII (PP7), a pennogenyl saponin isolated from Rhizoma Paridis, exhibited strong anticancer activities in various cancer types. Previous studies found that PP7 induced apoptotic cell death in human hepatoblastoma cancer (HepG2) cells. In the present study, we investigated whether PP7 could induce autophagy and its role in PP7-induced cell death, and elucidated its mechanisms. PP7 induced a robust autophagy in HepG2 cells as demonstrated by the conversion of LC3B-I to LC3B-II, degradation of P62, formation of punctate LC3-positive structures, and autophagic vacuoles tested by western blot analysis or InCell 2000 confocal microscope. Inhibition of autophagy by treating cells with autophagy inhibitor (chloroquine) abolished the cell death caused by PP7, indicating that PP7 induced an autophagic cell death in HepG2 cells. C-Jun N-terminal kinase (JNK) was activated after treatment with PP7 and pretreatment with SP600125, a JNK inhibitor, reversed PP7-induced autophagy and cell death, suggesting that JNK plays a critical role in autophagy caused by PP7. Furthermore, our study demonstrated that PP7 increased the phosphorylation of AMPK and Bcl-2, and inhibited the phosphorylation of PI3K, AKT and mTOR, suggesting their roles in the PP7-induced autophagy. This is the first report that PP7 induces an autophagic cell death in HepG2 cells via inhibition of PI3K/AKT/mTOR, and activation of JNK pathway, which induces phosphorylation of Bcl-2 and dissociation of Beclin-1 from Beclin-1/Bcl-2 complex, leading to induction of autophagy.

Bauhinia championii flavone inhibits apoptosis and autophagy via the PI3K/Akt pathway in myocardial ischemia/reperfusion injury in rats

This study aimed to determine the effects of Bauhinia championii flavone (BCF) on myocardial ischemia/reperfusion injury (MI/RI) in rats and to explore potential mechanisms. The MI/RI model in rats was established by ligating the left anterior descending coronary artery for 30 minutes, then reperfusing for 3 hours. BCF at 20 mg/kg was given 20 minutes prior to ischemia via sublingual intravenous injection, with 24 μg/kg phosphoinositide 3-kinase inhibitor (PI3K; wortmannin) as a control. The creatine kinase-MB and nitric oxide content were assessed by colorimetry. The levels of mitochondrial permeability transition pores and tumor necrosis factor alpha were determined by an enzyme-linked immunosorbent assay. Cardiomyocyte apoptosis was detected by the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Additionally, the expression of PI3K, endothelial nitric oxide synthase, caspase-3, and Beclin1 was analyzed by fluorescence quantitative polymerase chain reaction and Western blotting, respectively. Akt and microtubule-associated protein 1 light chain 3-II protein levels were also evaluated. Pretreatment with BCF significantly decreased the levels of creatine kinase-MB, tumor necrosis factor alpha, and mitochondrial permeability transition pores, but increased the nitric oxide content. Furthermore, BCF inhibited apoptosis, downregulated caspase-3, Beclin1, and microtubule-associated protein 1 light chain 3-II, upregulated PI3K, and increased the protein levels of phosphorylated Akt and endothelial nitric oxide synthase. However, all of the previously mentioned effects of BCF were blocked when BCF was coadministered with wortmannin. In conclusion, these observations indicated that BCF has cardioprotective effects against MI/RI by reducing cell apoptosis and excessive autophagy, which might be related to the activation of the PI3K/Akt signaling pathway.

Anticancer activities of self-assembled molecular bowls containing a phenanthrene-based donor and Ru(II) acceptors

Nano-sized multinuclear ruthenium complexes have rapidly emerged as promising therapeutic candidates with unique anticancer activities. Here, we describe the coordination-driven self-assembly and anticancer activities of a set of three organometallic tetranuclear Ru(II) molecular bowls. [2+2] Coordination-driven self-assembly of 3, 6-bis(pyridin-3- ylethynyl) phenanthrene (bpep) (1) and one of the three dinuclear arene ruthenium clips, [(η6-p-iPrC6H4Me)2Ru2-(OO\OO)][OTf]2 (OO\OO =2, 5-dioxido-1, 4-benzoquinonato, OTf = triflate) (2), 5, 8-dioxido-1, 4-naphthoquinonato (3), or 6, 11-dioxido-5, 12-naphthacenediona (4), resulted in three molecular bowls 5-7 of general formula [{(η6-p-iPrC6H4Me)2Ru2-(OO\OO)}2(bpep)2][OTf]4. All molecular bowls were obtained as triflate salts in very good yields (>90%) and were fully characterized using multinuclear nuclear magnetic resonance (NMR), electrospray ionization-mass spectrometry (ESI-MS), and elemental analysis. The structure of the representative molecular bowl 5 was confirmed by single-crystal X-ray diffraction analysis. The anticancer activities of molecular bowls 5-7 were determined by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide, autophagy, and Western blot analysis. Bowl 6 showed the strongest cytotoxicity in AGS human gastric carcinoma cells and was more cytotoxic than doxorubicin. In addition, autophagic activity and the ratio of apoptotic cell death increased in AGS cells by treatment with bowl 6. Bowl 6 also induced autophagosome formation via upregulation of p62 and promotion of the conversion of LC3-I to LC3-II. Moreover, bowl 6 promoted apoptotic cell death through downregulation of Akt/mTOR activation, followed by increased caspase-3 activity. These results suggest that bowl 6 induces gastric cancer cell death via modulation of autophagy and apoptosis. Bowl 6 is a potent anticancer agent and a potential treatment for human gastric cancer that merits further study.

Autophagic Cell Death by Poncirus trifoliata Rafin., a Traditional Oriental Medicine, in Human Oral Cancer HSC-4 Cells

Poncirus trifoliata Rafin. has long been used as anti-inflammatory and antiallergic agent to treat gastrointestinal disorders and pulmonary diseases such as indigestion, constipation, chest fullness, chest pain, bronchitis, and sputum in Korea. P. trifoliata extract has recently been reported to possess anticancer properties; however, its mechanisms of action remain unclear. In this study, its antiproliferative effects and possible mechanisms were investigated in HSC-4 cells. The methanol extract of P. trifoliata (MEPT) significantly decreased the proliferation of HSC-4 cells (inhibitory concentration (IC)₅₀ = 142.7 μg/mL) in a dose-dependent manner. While there were no significant changes observed upon cell cycle analysis and ANNEXIN V and 7-AAD double staining in the MEPT-treated groups, the intensity of acidic vesicular organelle (AVO) staining and microtubule-associated protein 1 light chain (LC) 3-II protein expression increased in response to MEPT treatment. Furthermore, 3-methyladenine (3-MA, autophagy inhibitor) effectively blocked the MEPT-induced cytotoxicity of HSC-4 cells and triggered the activation of p38 and extracellular signal-regulated kinases (ERK) proteins. Taken together, our results indicate that MEPT is a potent autophagy agonist in oral cancer cells with antitumor therapeutic potential that acts through the mitogen-activated protein kinase (MAPK) pathway.

Naringin induces autophagy-mediated growth inhibition by downregulating the PI3K/Akt/mTOR cascade via activation of MAPK pathways in AGS cancer cells

Naringin, one of the major bioflavonoid of Citrus, has been demonstrated as potential anticancer agent. However, the underlying anticancer mechanism still needs to be explored further. This study investigated the inhibitory effect of Naringin on human AGS cancer cells. AGS cell proliferation was inhibited by Naringin in a dose- and time-dependent manner. Naringin did not induce apoptotic cell death, determined by no DNA fragmentation and the reduced Bax/Bcl-xL ratio. Growth inhibitory role of Naringin was observed by western blot analysis demonstrating downregulation of PI3K/Akt/mTOR cascade with an upregulated p21CIPI/WAFI. Formation of cytoplasmic vacuoles and autophagosomes were observed in Naringin-treated AGS cells, further confirmed by the activation of autophagic proteins Beclin 1 and LC3B with a significant phosphorylation of mitogen activated protein kinases (MAPKs). Collectively, our observed results determined that anti-proliferative activity of Naringin in AGS cancer cells is due to suppression of PI3K/Akt/mTOR cascade via induction of autophagy with activated MAPKs. Thus, the present finding suggests that Naringin induced autophagy- mediated growth inhibition shows potential as an alternative therapeutic agent for human gastric carcinoma.

Jaeumganghwa-Tang Induces Apoptosis via the Mitochondrial Pathway and Lactobacillus Fermentation Enhances Its Anti-Cancer Activity in HT1080 Human Fibrosarcoma Cells

Jaeumganghwa-tang (JGT, Zi-yin-jiang-huo-tang in Chinese and Jiin-koka-to in Japanese) is an oriental herbal formula that has long been used as a traditional medicine to treat respiratory and kidney diseases. Recent studies revealed that JGT exhibited potent inhibitory effects on allergies, inflammation, pain, convulsions, and prostate hyperplasia. Several constituent herbs in JGT induce apoptotic cancer cell death. However, the anti-cancer activity of JGT has not been examined. In this study, we investigated the anti-cancer effects of JGT using highly tumorigenic HT1080 human fibrosarcoma cells and elucidated the underlying mechanisms. In addition, we examined whether the Lactobacillus fermentation of JGT enhanced its anti-cancer activity using an in vivo xenograft model because fermentation of herbal extracts is thought to strengthen their therapeutic effects. Data revealed that JGT suppressed the growth of cancer cells efficiently by stimulating G1 cell cycle arrest and then inducing apoptotic cell death by causing mitochondrial damage and activating caspases. The phosphorylation of p38 and ERK also played a role in JGT-induced cell death. In vitro experiments demonstrated that JGT fermented with Lactobacillus acidophilus, designated fJGT162, elicited similar patterns of cell death as did non-fermented JGT. Meanwhile, the daily oral administration of 120 mg/kg fJGT162 to HT1080-bearing BALB/c nude mice suppressed tumor growth dramatically (up to 90%) compared with saline treatment, whereas the administration of non-fermented JGT suppressed tumor growth by ~70%. Collectively, these results suggest that JGT and fJGT162 are safe and useful complementary and alternative anti-cancer herbal therapies, and that Lactobacillus fermentation improves the in vivo anti-cancer efficacy of JGT significantly.

Elaborating the role of natural products-induced autophagy in cancer treatment: achievements and artifacts in the state of the art

Autophagy is a homeostatic process that is highly conserved across different types of mammalian cells. Autophagy is able to relieve tumor cell from nutrient and oxidative stress during the rapid expansion of cancer. Excessive and sustained autophagy may lead to cell death and tumor shrinkage. It was shown in literature that many anticancer natural compounds and extracts could initiate autophagy in tumor cells. As summarized in this review, the tumor suppressive action of natural products-induced autophagy may lead to cell senescence, provoke apoptosis-independent cell death, and complement apoptotic cell death by robust or target-specific mechanisms. In some cases, natural products-induced autophagy could protect tumor cells from apoptotic death. Technical variations in detecting autophagy affect data quality, and study focus should be made on elaborating the role of autophagy in deciding cell fate. In vivo study monitoring of autophagy in cancer treatment is expected to be the future direction. The clinical-relevant action of autophagy-inducing natural products should be highlighted in future study. As natural products are an important resource in discovery of lead compound of anticancer drug, study on the role of autophagy in tumor suppressive effect of natural products continues to be necessary and emerging.

Induction of α-Phellandrene on Autophagy in Human Liver Tumor Cells

α-Phellandrene (α-PA) is a cyclic monoterpene. To investigate the induction of autophagy by α-PA and its mechanism, human liver tumor cells (J5) were incubated with α-PA and analyzed for cell viability and the molecular regulation of pre-autophagosome origination and autophagosome formation. According to the results, PI3K-I, mTOR, and Akt protein levels were decreased after α-PA treatment compared to those of the control group (p < 0.05). The phosphorylation of Bcl-2, and PI3K-III, LC3-II and Beclin-1 protein levels in J5 cells were increased after α-PA treatment (p < 0.05). In addition, α-PA up-regulated nuclear p53 and down-regulated cytoplasmic p53 expression in J5 cells. The NF-κB pathway was activated, as indicated by increase in cytosolic phosphorylated IκB, nuclear NF-κB levels, and the DNA-binding activity of NF-κB after α-PA treatment in J5 cells (p < 0.05). These results suggest that α-PA can induce J5 cell autophagy by regulating mTOR and LC-3II expression, p53 signaling, and NF-κB activation in J5 cells.

Ethanol extract of Remotiflori radix induces endoplasmic reticulum stress-mediated cell death through AMPK/mTOR signaling in human prostate cancer cells

Remotiflori radix is the root of Mosidae, which has long been used as a traditional medicine to treat chills, fever, and phlegm discharge. The ethanol extract of Mosidae leaves (MLE) possesses strong antioxidant and chemopreventive activities. However, the anti-cancer effects of the Remotiflori radix have not been examined. We used the ethanol extract of Remotiflori radix (ERR) and the PC-3 and DU145 prostate cancer cell lines in this study. We found that > 100 μg/mL ERR caused dose- and time-dependent cell death. Autophagic and apoptotic cell numbers increased in a dose-dependent manner as incubation time was prolonged, and LC3 punctuation, YO-PRO-1 uptake, DNA fragmentation, activation of caspases, and PARP cleavage were induced. Phosphorylation of AMPK, ULK, and p38 was increased after ERR treatment, and the level of the ER stress marker CHOP was also elevated. AMPK knockdown dramatically blocked ERR-mediated CHOP expression and cell death, suggesting that AMPK activation and ER stress play a critical role in ERR-induced cell death. Furthermore, oral administration of ERR at 50 mg/kg efficiently suppressed tumorigenic growth of PC-3 cells with no adverse effects. These results suggest that the ERR can be used as a safe and potent alternative therapy for patients with prostate cancer.

The role of autophagy in usnic acid-induced toxicity in hepatic cells

The use of usnic acid and usnic acid-containing products is associated with acute liver failure; however, mechanistic studies of hepatotoxicity caused by usnic acid are limited. In this study, we investigated and characterized the possible mechanisms, especially the role of autophagy in usnic acid's toxicity in human HepG2 cells. Usnic acid caused apoptosis as demonstrated by an increased caspase-3/7 activity and an increased subdiploid nucleus formation. Usnic acid-induced autophagy as demonstrated by the conversion of LC3B-I to LC3B-II, degradation of P62, and an increased number of puncta. Inhibition of autophagy by treating cells with autophagy inhibitors (3-methyladenine or chloroquine) or by small interfering RNA against Atg7 aggravated usnic acid-induced apoptosis and decreased cell viability, indicating that autophagy plays a protective role against usnic acid-induced toxicity. Moreover, usnic acid activated the MAPK signaling pathway. Usnic acid-elicited apoptosis was enhanced and autophagy was decreased when JNK was suppressed by a specific inhibitor. Additionally, inhibition of autophagy decreased the activity of JNK. Taken together, our results suggest that usnic acid perturbs various interrelated signaling pathways and that autophagy induction is a defensive mechanism against usnic acid-induced cytotoxicity.

Clinical significance of aberrant mammalian target of rapamycin expression in stage IIIB colon cancer

The aim of the present study was to investigate the significance of aberrant expression of mammalian target of rapamycin (mTOR) and the activated form of mTOR kinase, phosphorylated mTOR (pmTOR), in human stage IIIB colon cancer. The expression of mTOR and pmTOR was detected by immunohistochemistry in the tumor tissue of stage IIIB colon cancer patients. The association between the expression of mTOR, pmTOR and clinicopathological parameters of patients was analyzed. The positive expression of mTOR and pmTOR was observed to be higher in 75.5% (80/106) and 76.4% (81/106) of the 106 colon cancer specimens, compared with the adjacent normal tissues. The high level of pmTOR expression was found to be significantly higher in the invasive tumor front cells and resulted in a higher risk of mortality. The results suggested that mTOR and pmTOR may be promising clinical markers and present novel molecular targets for designing novel therapeutic strategies to treat this malignancy.