Celastrol induces apoptosis and autophagy via the ROS/JNK signaling pathway in human osteosarcoma cells: an in vitro and in vivo study

The cardiotoxicity of the common carp (Cyprinus carpio) exposed to environmentally relevant concentrations of arsenic and subsequently relieved by zinc supplementation

Waterborne exposure to arsenic trioxide (As₂O₃) is inevitable due to its widespread industrial and agricultural applications. Oxidative stress and cascaded programmed cell death is now hypothesized to be the dominant mechanisms of arseniasis evidenced in vivo and in vitro. This study aimed to explore the interaction of divalent zinc ion (Zn²⁺), an efficient reactive oxygen species (ROS) scavenger with arsenite in the heart of common carp, and extensively investigated the exact signaling molecules involved. Significant induction of cardiotoxicity including oxidative stress, apoptosis and autophagy was evident in heart tissues following arsenite exposure (P < 0.05). The dissipation of antioxidant enzymes (SOD and CAT) was induced by ROS burst, leading to oxidative damage and lipid peroxidation (MDA). Arsenite induced classic apoptotic hallmarks, characterized by chromatin degradation and subsequent formation of clumps adjacent, and elevated expression of Bax/Bcl-2 and Caspase family, and also increased autophagic flux evidenced by accelerated formation (LC3) and degradation (p62) of autophagosomes. PI3K/Akt/mTOR pathway was phosphorylated inhibited, while MAPK signaling (p38, ERK and JNK) displayed elevated phosphorylation levels in arsenite-exposed heart tissues. In contrast, above phenomena were effectively inhibited by Zn²⁺, which supplement attenuated arsenite-induced myocardial toxicity through inhibition of apoptosis and autophagy via PI3K/Akt/mTOR pathway, as well as suppressing intracellular ROS cluster via activating antioxidative system via MAPK pathway. Our results provided experimental explanation and evidences for cardiotoxicity of arsenite. Furthermore, our findings hint that the application of zinc preparations may provide a candidate for the prevention and treatment for arsenic poisoning.

Celastrol enhances TRAIL-induced apoptosis in human glioblastoma via the death receptor pathway

PURPOSE

Glioblastoma is the most common, malignant and devastating type of primary brain tumor. Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) is characterized by its lethality to precancerous and cancerous cells. However, many kinds of tumor cells, including most glioma cells, tend to evade TRAIL-induced apoptosis. Celastrol is a pleiotropic compound from a traditional Chinese medicine that has proven to be useful as a sensitizer for TRAIL treatment. However, the underlying mechanism and role of celastrol in the sensitization of glioma cells remain to be elucidated.

METHODS

The viability of glioma cell lines was examined by the CCK-8 assay. The expression of DR5 was detected by reverse transcriptase quantitative real-time PCR. The protein expression of DR5, cleaved caspase-8, cleaved caspase-3 and PARP were measured by western blot. The apoptosis rates and the sub-G1 population were detected by flow cytometry. The cellular morphological changes were assessed by TUNEL apoptosis and Hoechst 33258 staining assays. The knockdown of DR5 expression was conducted by siRNA.

RESULTS

In this study, we observed that celastrol treatment inhibited cell viability in a dose-dependent manner, while glioma and normal human astroglial cell lines were resistant to TRAIL treatment. We also observed that the antiproliferative effects of TRAIL in combination with a noncytotoxic concentration of celastrol were significantly greater than those of celastrol or TRAIL alone. In addition, cell death induced by the combination treatment was apoptotic and occurred through the death receptor pathway via activation of caspase-8, caspase-3, and PARP. Furthermore, celastrol upregulated death receptor 5 (DR5) at the mRNA and protein levels, and siRNA-mediated DR5 knockdown reduced the killing effect of the combination drug treatment on glioma cells and reduced the activation of caspase-3, caspase-8 and PARP.

CONCLUSIONS

Taken together, the results of our study demonstrate that celastrol sensitizes glioma cells to TRAIL via the death receptor pathway and that DR5 plays an important role in the effects of this cotreatment. The results indicate that this cotreatment is a promising tumor-killing therapeutic strategy with high efficacy and low toxicity.

Targeting Reactive Oxygen Species in Cancer via Chinese Herbal Medicine

Recently, reactive oxygen species (ROS), a class of highly bioactive molecules, have been extensively studied in cancers. Cancer cells typically exhibit higher levels of basal ROS than normal cells, primarily due to their increased metabolism, oncogene activation, and mitochondrial dysfunction. This moderate increase in ROS levels facilitates cancer initiation, development, and progression; however, excessive ROS concentrations can lead to various types of cell death. Therefore, therapeutic strategies that either increase intracellular ROS to toxic levels or, conversely, decrease the levels of ROS may be effective in treating cancers via ROS regulation. Chinese herbal medicine (CHM) is a major type of natural medicine and has greatly contributed to human health. CHMs have been increasingly used for adjuvant clinical treatment of tumors. Although their mechanism of action is unclear, CHMs can execute a variety of anticancer effects by regulating intracellular ROS. In this review, we summarize the dual roles of ROS in cancers, present a comprehensive analysis of and update the role of CHM—especially its active compounds and ingredients—in the prevention and treatment of cancers via ROS regulation and emphasize precautions and strategies for the use of CHM in future research and clinical trials.

Polyphyllin VI induces apoptosis and autophagy in human osteosarcoma cells by modulation of ROS/JNK activation

Purpose

Polyphyllin VI, a main active saponin isolated from traditional medicinal plant Paris polyphylla, has exhibited antitumor activities in several cancer cell lines. In the present study, we investigated the antitumor effect of Polyphyllin VI against human osteosarcoma cells (U2OS) and the underlying molecular mechanisms.

Methods

The U2OS cell lines were used to determine the antiproliferative effect of Polyphyllin VI by CCK8 assay. Cell cycle was analyzed by flow cytometry. The Polyphyllin VI-induced apoptosis was determined by Annexin V-APC/7-AAD apoptosis detection kit and JC-1 staining. Meanwhile, the autophagy was determined by acridine orange staining. The apoptosis and autophagy-related proteins were monitored by Western blot assay. Subsequently, intracellular hydrogen peroxide (H₂O₂) and the activation of ROS/JNK pathway were detected.

Results

Polyphyllin VI could potently inhibit cell proliferation by causing G2/M phase arrest. Polyphyllin VI induced mitochondria-mediated apoptosis with the upregulation of proapoptotic proteins Bax and poly ADP-ribose polymerase, and downregulation of antiapoptotic protein Bcl-2 in U2OS cells. Concomitantly, Polyphyllin VI provoked autophagy with the upregulation of critical Atg proteins and accumulation of LC3B-II. Intracellular H₂O₂ production was triggered upon exposure to Polyphyllin VI, which could be blocked by ROS scavenger. Polyphyllin VI dramatically promoted JNK phosphorylation, whereas it decreased the levels of phospho-p38 and ERK.

Conclusion

Our results reveal that Polyphyllin VI may effectively induce apoptosis and autophagy to suppress cell growth via ROS/JNK activation in U2OS cells, suggesting that Polyphyllin VI is a potential drug candidate for the treatment of osteosarcomas.

Prooxidative Activity of Celastrol Induces Apoptosis, DNA Damage, and Cell Cycle Arrest in Drug-Resistant Human Colon Cancer Cells

Cancer resistance to chemotherapy is closely related to tumor heterogeneity, i.e., the existence of distinct subpopulations of cancer cells in a tumor mass. An important role is assigned to cancer stem cells (CSCs), a small subset of cancer cells with high tumorigenic potential and capacity of self-renewal and differentiation. These properties of CSCs are sustained by the ability of those cells to maintain a low intracellular reactive oxygen species (ROS) levels, via upregulation of ROS scavenging systems. However, the accumulation of ROS over a critical threshold disturbs CSCs—redox homeostasis causing severe cytotoxic consequences. In the present study, we investigated the capacity of celastrol, a natural pentacyclic triterpenoid, to induce the formation of ROS and, consequently, cell death of the colon cancer cells with acquired resistant to cytotoxic drugs (LOVO/DX cell line). LOVO/DX cells express several important stem-like cell features, including a higher frequency of side population (SP) cells, higher expression of multidrug resistant proteins, overexpression of CSC-specific cell surface marker (CD44), increased expression of DNA repair gene (PARP1), and low intracellular ROS level. We found that celastrol, at higher concentrations (above 1 μM), significantly increased ROS amount in LOVO/DX cells at both cytoplasmic and mitochondrial levels. This prooxidant activity was associated with the induction of DNA double-strand breaks (DSBs) and apoptotic/necrotic cell death, as well as with inhibition of cell proliferation by S phase cell cycle arrest. Coincubation with NAC, a ROS scavenger, completely reversed the above effects. In summary, our results provide evidence that celastrol exhibits effective cytotoxic effects via ROS-dependent mechanisms on drug-resistant colon cancer cells. These findings strongly suggest the potential of celastrol to effectively kill cancer stem-like cells, and thus, it is a promising agent to treat severe, resistant to conventional therapy, colon cancers.

In silico evaluation of apoptogenic potential and toxicological profile of triterpenoids

AIM:

Caspases-3 and 8 are key mediators of intrinsic and extrinsic pathway of apoptosis, respectively. Triterpenoids of natural and synthetic origin reported as anticancer agents with apoptotic potential and hence may prove to be good candidates for in silico testing against caspases-3 and 8.

MATERIALS AND METHODS:

Various naturally-occurring and synthetic triterpenoids were subjected to activity prediction using PASS Online software, and among them, 67 compounds were selected for further processing. Protein structure of caspase-3 (3DEI) and caspase-8 (3KJQ) was obtained from the protein data bank and docked with selected triterpenoids using AutoDock Tools and AutoDock Vina. Toxicological profile was predicted based on clinical manifestations using PASS online software.

RESULTS:

The high docking score of -10.0, -9.9, -9.8, and -9.5 were shown by friedelin, tingenone, albiziasaponin A, and albiziasaponin C, respectively, for caspase-3, and -11.0, -9.6, -9.6, and -9.4 by β-boswellic acid, bryonolic acid, canophyllic acid, and CDDO, respectively, for caspase-8. Possible adverse events were predicted with varying degree of probability and major relevant effects were reported. Hydrostatic interactions along with formation of hydrogen bonds with specific amino acids in the binding pocket were identified with each triterpenoid.

CONCLUSION:

Lead molecules identified through this in silico study such as friedelin, tingenone, albiziasaponin, bryonolic acid, and canophyllic acid may be utilized for further in vitro/in vivo studies as apoptotic agents targeting caspases-3 and 8.

Pristimerin induces apoptosis and autophagy via activation of ROS/ASK1/JNK pathway in human breast cancer in vitro and in vivo

Breast cancer is the most common malignant tumor in women, and progress toward long-term survival has stagnated. Pristimerin, a natural quinonemethide triterpenoid, exhibits potential anti-tumor effects on various cancers. However, the underlying mechanism remains poorly understood. In this study, we found that pristimerin reduced the viability of breast cancer cells in vitro and the growth of xenografts in vivo, and these reductions were accompanied by thioredoxin-1 (Trx-1) inhibition and ASK1 and JNK activation. The results showed that pristimerin inhibited cell cycle progression and triggered cell apoptosis and autophagy. Furthermore, we found that the generation of reactive oxygen species (ROS) was a critical mediator in pristimerin-induced cell death. Enhanced ROS generation by pristimerin activated the ASK1/JNK signaling pathway. Inhibition of ROS with N-acetyl cysteine (NAC) significantly decreased pristimerin-induced cell death by inhibiting the phosphorylation of ASK1 and JNK. Taken together, these results suggest a critical role for the ROS/ASK1/JNK pathway in the anticancer activity of pristimerin.

Pristimerin Induces Autophagy-Mediated Cell Death in K562 Cells through the ROS/JNK Signaling Pathway

Chronic myeloid leukemia (CML) is a lethal malignancy, and the progress toward long-term survival has stagnated in recent decades. Pristimerin, a quinone methide triterpenoid isolated from the Celastraceae and Hippocrateaceae families, is well-known to exert potential anticancer activities. In this study, we investigated the effects and the mechanisms of action on CML. We found that pristimerin inhibited cell proliferation of K562 CML cells by causing G1 phase arrest. Furthermore, we demonstrated that pristimerin triggered autophagy and apoptosis. Intriguingly, pristimerin-induced cell death was restored by an autophagy inhibitor, suggesting that autophagy is cross-linked with pristimerin-induced apoptosis. Further studies revealed that pristimerin could produce excessive reactive oxygen species (ROS), which then induce JNK activation. These findings provide clear evidence that pristimerin might be clinical benefit to patients with CML.

Lumiflavin increases the sensitivity of ovarian cancer stem-like cells to cisplatin by interfering with riboflavin

Here, we used lumiflavin, an inhibitor of riboflavin, as a new potential therapeutic chemosensitizer to ovarian cancer stem‐like cells (CSCs). This study demonstrates that the enrichment of riboflavin in CSCs is an important cause of its resistance to chemotherapy. Lumiflavin can effectively reduce the riboflavin enrichment in CSCs and sensitize the effect of cisplatin Diamminedichloroplatinum (DDP) on CSCs. In this study, CSCs of human ovarian cancer cell lines HO8910 were separated using a magnetic bead (CD133+). We also show the overexpression of the mRNA and protein of riboflavin transporter 2 and the high content of riboflavin in CSCs compared to non‐CSCs (NON‐CSCs). Moreover, CSCs were less sensitive to DDP than NON‐CSCs, whereas, the synergistic effect of lumiflavin and DDP on CSCs was more sensitive than NON‐CSCs. Further research showed that lumiflavin had synergistic effects with DDP on CSCs in increasing mitochondrial function damage and apoptosis rates and decreasing clonic function. In addition, we found that the combination of DDP and lumiflavin therapy in vivo has a synergistic cytotoxic effect on an ovarian cancer nude mice model by enhancing the DNA‐damage response and increasing the apoptotic protein expression. Notably, the effect of lumiflavin is associated with reduced riboflavin concentration, and riboflavin could reverse the effect of DDP in vitro and in vivo. Accordingly, we conclude that lumiflavin interfered with the riboflavin metabolic pathways, resulting in a significant increase in tumour sensitivity to DDP therapy. Our study suggests that lumiflavin may be a novel treatment alternative for ovarian cancer and its recurrence.

Celastrol mediates autophagy and apoptosis via the ROS/JNK and Akt/mTOR signaling pathways in glioma cells

Background

Celastrol, a triterpene compound derived from the traditional Chinese medicine Tripterygium wilfordii, has been reported to possess potential antitumor activity towards various malignancies. However, the effect of celastrol on glioma cells and the underlying molecular mechanisms remain elusive.

Methods

Glioma cells, including the U251, U87-MG and C6 cell lines and an animal model were used. The effects of celastrol on cells were evaluated by flow cytometry, confocal microscopy, reactive oxygen species production assay and immunoblotting after treatment of celastrol. Fisher’s exact test, a one-way ANOVA and the Mann-Whitney U-test were used to compare differences between groups. All data were analyzed using SPSS version 21.0 software.

Results

Here, we found that exposure to celastrol induced G2/M phase arrest and apoptosis. Celastrol increased the formation of autophagosomes, accumulation of LC3B and the expression of p62 protein. Celastrol-treated glioma cells exhibited decreased cell viability after the use of autophagy inhibitors. Additionally, autophagy and apoptosis caused by celastrol in glioma cells inhibited each other. Furthermore, celastrol induced JNK activation and ROS production and inhibited the activities of Akt and mTOR kinases. JNK and ROS inhibitors significantly attenuated celastrol-trigged apoptosis and autophagy, while Akt and mTOR inhibitors had opposite effects.

Conclusions

In conclusion, our study revealed that celastrol caused G2/M phase arrest and trigged apoptosis and autophagy by activating ROS/JNK signaling and blocking the Akt/mTOR signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1173-4) contains supplementary material, which is available to authorized users.

Celastrol, a plant-derived triterpene, induces cisplatin-resistance nasopharyngeal carcinoma cancer cell apoptosis though ERK1/2 and p38 MAPK signaling pathway

BACKGROUND

Developing resistance to chemotherapeutic drugs has become a major problem in the management of nasopharyngeal carcinoma (NPC). To overcome this issue, use of natural plant products as chemosensitizers is gaining importance at a fast pace.

HYPOTHESIS/PURPOSE

The present study was designed to evaluate the cytotoxic effect and mode of action of a natural pentacyclic triterpenoid, celastrol, on cisplatin-resistant NPC cells.

RESULTS

Study results revealed that celastrol treatment significantly reduced the viability of NPC cells in dose and time dependent manners, as compared to untreated control cells. The cytotoxic effect of celastrol was mediated by cell cycle arrest at G2/M phase and induction of intrinsic and extrinsic apoptotic pathways. With further analysis, we observed that celastrol-induced activation of caspases was accompanied by increased phosphorylation of MAPK pathway proteins, p38, ERK1/2.

CONCLUSION

Taken together, our observation provides a novel insight on use of a natural plant product, celastrol, in the management of chemoresistant NPC.

Antitumor activity of Raddeanin A is mediated by Jun amino-terminal kinase activation and signal transducer and activator of transcription 3 inhibition in human osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor. Raddeanin A (RA) is an active oleanane‐type triterpenoid saponin extracted from the traditional Chinese herb Anemone raddeana Regel that exerts antitumor activity against several cancer types. However, the effect of RA on osteosarcoma remains unclear. In the present study, we showed that RA inhibited proliferation and induced apoptosis of osteosarcoma cells in a dose‐ and time‐dependent way in vitro and in vivo. RA treatment resulted in excessive reactive oxygen species (ROS) generation and JNK and ERK1/2 activation. Apoptosis induction was evaluated by the activation of caspase‐3, caspase‐8, and caspase‐9 and poly‐ADP ribose polymerase (PARP) cleavage. RA‐induced cell death was significantly restored by the ROS scavenger glutathione (GSH), the pharmacological inhibitor of JNK SP600125, or specific JNK knockdown by shRNA. Additionally, signal transducer and activator of transcription 3 (STAT3) activation was suppressed by RA in human osteosarcoma, and this suppression was restored by GSH, SP600125, and JNK‐shRNA. Further investigation showed that STAT3 phosphorylation was increased after JNK knockdown. In a tibial xenograft tumor model, RA induced osteosarcoma apoptosis and notably inhibited tumor growth. Taken together, our results show that RA suppresses proliferation and induces apoptosis by modulating the JNK/c‐Jun and STAT3 signaling pathways in human osteosarcoma. Therefore, RA may be a promising candidate antitumor drug for osteosarcoma intervention.

Role of autophagy in osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumour in children and adolescents. It is a highly aggressive tumor with a tendency to spread to the lungs, which are the most common site of metastasis. Advanced osteosarcoma patients with metastasis share a poor prognosis. Despite the use of chemotherapy to treat OS, the 5-year overall survival rate for patients has remained unchanged at 65–70% for the past 20 years. In addition, the 5-year survival of patients with a metastatic disease is around 20%, highlighting the need for novel therapeutic targets.

Autophagy is an intracellular degradation process which eliminates and recycles damaged proteins and organelles to improve cell lifespan. In the context of cancer, numerous studies have demonstrated that autophagy is used by tumor cells to repress initial steps of carcinogenesis and/or support the survival and growth of established tumors. In osteosarcoma, autophagy appears to be deregulated and could also act both as a pro or anti-tumoral process. In this manuscript, we aim to review these major findings regarding the role of autophagy in osteosarcoma.

Daucosterol induces autophagic-dependent apoptosis in prostate cancer via JNK activation

Plant sterols (phytosterols) have been widely accepted as a natural anti-cancer agent in multiple malignant tumors. This study was designed to investigate the functions of daucosterol in prostate cancer progression and its possible molecular mechanisms. Our results showed that daucosterol inhibited cell proliferation and induced cell cycle arrest. Moreover, daucosterol treatment obviously promoted apoptosis and autophagy. An autophagy inhibitor, 3-methyladenine (3-MA) was proved to counteract daucosterol-triggered autophagy, growth inhibition, and apoptosis, indicating that daucosterol-induced apoptotic response was dependent on autophagy. Additionally, treatment with daucosterol resulted in increased phosphorylation of c-Jun N-terminal kinase (JNK). Furthermore, pre-treatment with a JNK-specific inhibitor SP600125 abated daucosterol-elicited autophagy and apoptotic cell death. Taken together, our findings demonstrated that daucosterol blocked prostate cancer growth at least partly through inducing autophagic-dependent apoptosis via activating JNK signaling, providing a promising candidate for the development of antitumor drugs in prostate cancer treatment.

Tomentosin Displays Anti-Carcinogenic Effect in Human Osteosarcoma MG-63 Cells via the Induction of Intracellular Reactive Oxygen Species

Tomentosin is a natural sesquiterpene lactone extracted from various plants and is widely used as a medicine because it exhibits essential therapeutic properties. In this study, we investigated the anti-carcinogenic effects of tomentosin in human osteosarcoma MG-63 cells by performing cell migration/viability/proliferation, apoptosis, and reactive oxygen species (ROS) analysis assays. MG-63 cells were treated with various doses of tomentosin. After treatment with tomentosin, MG-63 cells were analyzed using the MTT assay, colony formation assay, cell counting assay, wound healing assay, Boyden chamber assay, zymography assay, cell cycle analysis, FITC Annexin V apoptosis assay, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, western blot analysis, and ROS detection analysis. Our results indicated that tomentosin decreased cell viability and migration ability in MG-63 cells. Moreover, tomentosin induced apoptosis, cell cycle arrest, DNA damage, and ROS production in MG-63 cells. Furthermore, tomentosin-induced intracellular ROS decreased cell viability and induced apoptosis, cell cycle arrest, and DNA damage in MG-63 cells. Taken together, our results suggested that tomentosin exerted anti-carcinogenic effects in MG-63 cells by induction of intracellular ROS.

Cleavage of GSDME by caspase-3 determines lobaplatin-induced pyroptosis in colon cancer cells

Pyroptosis, a form of programmed cell death (PCD), has garnered increasing attention as it relates to innate immunity and diseases. However, the involvement of pyroptosis in the mechanism by which lobaplatin acts against colorectal cancer (CRC) is unclear. Our study revealed that treatment with lobaplatin reduced the viability of HT-29 and HCT116 cells in a dose-dependent manner. Morphologically, HT-29 and HCT116 cells treated with lobaplatin exhibited microscopic features of cell swelling and large bubbles emerging from the plasma membrane, and transmission electron microscopy (TEM) revealed multiple pores in the membrane. GSDME, rather than GSDMD, was cleaved in lobaplatin-induced pyroptosis in HT-29 and HCT116 cells due to caspase-3 activation. Knocking out GSDME switched lobaplatin-induced cell death from pyroptosis to apoptosis but did not affect lobaplatin-mediated inhibition of growth and tumour formation of HT-29 and HCT116 cells in vivo and in vitro. Further investigation indicates that lobaplatin induced reactive oxygen species (ROS) elevation and JNK phosphorylation. NAC, a ROS scavenger, completely reversed the pyroptosis of lobaplatin-treated HT-29 and HCT116 and JNK phosphorylation. Activated JNK recruited Bax to mitochondria, and thereby stimulated cytochrome c release to cytosol, followed by caspase-3/-9 cleavage and pyroptosis induction. Therefore, in colon cancer cells, GSDME mediates lobaplatin-induced pyroptosis downstream of the ROS/JNK/Bax-mitochondrial apoptotic pathway and caspase-3/-9 activation. Our study indicated that GSDME-dependent pyroptosis is an unrecognized mechanism by which lobaplatin eradicates neoplastic cells, which may have important implications for the clinical application of anticancer therapeutics.

Celastrol ameliorates Aspergillus fumigatus keratitis via inhibiting LOX-1

PURPOSE

To investigate the effect of Celastrol (CLT) on Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

Primary peritoneal macrophages of C57BL/6 mice were pretreated with CLT before A. fumigatus hyphae stimulation. C57BL/6 mice were infected with A. fumigatus. Mice corneas were treated with CLT from 1 day post infection. Clinical score, PCR, ELISA and Western blot were used to test expression of anti-inflammatory mediators, proinflammatory mediators and Lectin-like oxidized low-density lipoprotein receptor 1(LOX-1). The protein levels of p38MAPK after pretreated with CLT in macrophages of C57BL/6 mice challenged with A. fumigatus were tested by Western blot.

RESULTS

C57BL/6 mice treated with CLT from 1 day post infection showed decreased disease, IL-1β, TNF-α, IL-10, TGF-β, MIP-2 and LOX-1 levels. CLT treatment markedly inhibiting mRNA and proteins levels of anti-inflammatory mediators, proinflammatory mediators and LOX-1 in macrophages of C57BL/6 mice compared with control group. CLT pretreatment before A. fumigatus stimulation obviously inhibiting protein levels of p38MAPK versus DMSO pretreated group in macrophages of C57BL/6 mice challenged with A. fumigatus.

CONCLUSION

These data provide evidences that CLT ameliorates A. fumigatus keratitis of C57BL/6 mice via inhibiting LOX-1. CLT pretreatment before A. fumigatus stimulation decreased levels of inflammation in macrophages of C57BL/6 mice, which may be regulated by p-p38MAPK.

An investigation on the cytotoxicity and caspase-mediated apoptotic effect of biologically synthesized gold nanoparticles using Cardiospermum halicacabum on AGS gastric carcinoma cells

Background

Gastric cancer is the fourth most common cancer and second leading cause of cancer death worldwide. Cardiospermum halicacabum is used to treat nerve disorders, stiffness, rheumatism, ear ache, snake bite, and so on.

Methods

In this study, the reaction parameters were optimized to control the size of the nanoparticle, which was confirmed by transmission electron microscopy. Various characterization techniques such as selected area diffraction pattern, UV-visible spectroscopy, energy-dispersive X-ray analysis, dynamic light scattering, Fourier-transform infrared spectroscopy, and atomic force microscopy were employed to analyze the synthesized AuNPs obtained from C. halicacabum (CH-AuNP) against gastric carcinoma cell line.

Results

The cytotoxic effect of CH-AuNP against AGS, SNU-5, and SNU-16 cell lines was detected by MTT assay. The induction of apoptosis by CH-AuNP in AGS was analyzed by double staining technique using TUNEL and DAPI staining assays. Further to confirm the molecular mechanism exhibited by CH-AuNP to induce apoptosis, the intracellular ROS level was assessed and immunoblotting was performed to assess the apoptotic signaling molecules that often deregulated in cancerous condition.

Conclusion

The results clearly prove that CH-AuNP increases ROS and induces apoptosis in AGS, suggesting that CH-AuNP may be an effective anticancer drug with no side effects to treat gastric cancer.

Autophagy in Human Health and Disease: Novel Therapeutic Opportunities

SIGNIFICANCE

In eukaryotes, autophagy represents a highly evolutionary conserved process, through which macromolecules and cytoplasmic material are degraded into lysosomes and recycled for biosynthetic or energetic purposes. Dysfunction of the autophagic process has been associated with the onset and development of many human chronic pathologies, such as cardiovascular, metabolic, and neurodegenerative diseases as well as cancer. Recent Advances: Currently, comprehensive research is being carried out to discover new therapeutic agents that are able to modulate the autophagic process in vivo. Recent evidence has shown that a large number of natural bioactive compounds are involved in the regulation of autophagy by modulating several transcriptional factors and signaling pathways.

CRITICAL ISSUES

Critical issues that deserve particular attention are the inadequate understanding of the complex role of autophagy in disease pathogenesis, the limited availability of therapeutic drugs, and the lack of clinical trials. In this context, the effects that natural bioactive compounds exert on autophagic modulation should be clearly highlighted, since they depend on the type and stage of the pathological conditions of diseases.

FUTURE DIRECTIONS

Research efforts should now focus on understanding the survival-supporting and death-promoting roles of autophagy, how natural compounds interact exactly with the autophagic targets so as to induce or inhibit autophagy and on the evaluation of their pharmacological effects in a more in-depth and mechanistic way. In addition, clinical studies on autophagy-inducing natural products are strongly encouraged, also to highlight some fundamental aspects, such as the dose, the duration, and the possible synergistic action of these compounds with conventional therapy.

Celastrol Inhibits the Growth of Ovarian Cancer Cells in vitro and in vivo

Celastrol is a natural triterpene isolated from the Chinese plant Thunder God Vine with potent antitumor activity. However, the effect of celastrol on the growth of ovarian cancer cells in vitro and in vivo is still unclear. In this study, we found that celastrol induced cell growth inhibition, cell cycle arrest in G2/M phase and apoptosis with the increased intracellular reactive oxygen species (ROS) accumulation in ovarian cancer cells. Pretreatment with ROS scavenger N-acetyl-cysteine totally blocked the apoptosis induced by celastrol. Additionally, celastrol inhibited the growth of ovarian cancer xenografts in nude mice. Altogether, these findings suggest celastrol is a potential therapeutic agent for treating ovarian cancer.

Inhibition of G9a promoted 5-fluorouracil (5-FU) induced gastric cancer cell apoptosisviaROS/JNK signaling pathwayin vitroandin vivo

A histone methyltransferase G9a, encoded by euchromatic histone-lysine N-methyltransferase 2 (EHMT2), is up-regulated in various cancers, and is involved in their poor prognosis. In the study reported here, the abnormal expression of G9a in gastric cancer it was investigated in vitro and in vivo. Furthermore, the expression of G9a was revealed to have a negative correlation with chemotherapy response in gastric cancer patients. Next, the effect of G9a knockdown on fluorouracil (5-FU) induced cell apoptosis in gastric cancer cells was focused on. The results demonstrated that G9a knockdown significantly activated the expression level of phospho c-Jun N-terminal kinase (p-JNK) and increased the intracellular reactive oxygen species (ROS) levels in the gastric cancer cells. Inhibition of the ROS/JNK signaling partial reversed the effect of G9a knockdown on 5-FU treated gastric cancer cells. Down-regulation of G9a enhanced the sensitivity of 5-FU to the gastric cancer cells in vitro and in vivo, which was involved in the activation of the ROS/JNK signaling pathway. These results demonstrated that G9a could play a critical role in the sensitivity of chemotherapy for gastric cancer and might be a novel method for treating gastric cancer in the clinic.

A histone methyltransferase G9a, encoded by euchromatic histone-lysine N-methyltransferase 2 (EHMT2), is up-regulated in various cancers, and is involved in their poor prognosis.

Chrysanthemulide A induces apoptosis through DR5 upregulation via JNK-mediated autophagosome accumulation in human osteosarcoma cells

Osteosarcoma is the most frequent malignant primary bone tumor, and it generally develops a multidrug resistance. Chrysanthemulide A (CA) is a sesquiterpenoid from the herb Chrysanthemum indicum that has demonstrated a great anti-osteosarcoma potential. In this study, CA-induced apoptotic cell death resulted in the activation of the caspase-8-mediated caspase cascade, as evidenced by the cleavage of the substrate protein Bid and the caspase-8 inhibitor Z-VAD-FMK. The CA treatment upregulated the expression of death receptor 5 (DR5) in both whole cells and the cell membrane. Blocking DR5 expression by the small interfering RNA (siRNA) treatment decreased the caspase-8-mediated caspase cascade and efficiently attenuated CA-induced apoptosis, suggesting the critical role of DR5 in CA-induced apoptotic cell death. CA-induced upregulation of the DR5 protein was accompanied by the accumulation of LC3B-II, indicating the formation of autophagosomes. Importantly, DR5 upregulation was mediated by transcriptionally controlled autophagosome accumulation, as blockade of autophagosomes by LC3B or ATG-5 siRNA substantially decreased DR5 upregulation. Furthermore, CA activated the c-Jun N-terminal kinase (JNK) signaling pathway, and treatment with JNK siRNAs or inhibitor SP600125 significantly attenuated CA-mediated autophagosome accumulation and DR5-mediated cell apoptosis. Finally, CA sensitized the osteosarcoma cells to the DR5 ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptotic cell death. Above all, these results suggest that CA induces apoptosis through upregulating DR5 via JNK-mediated autophagosome accumulation and that combined treatment with CA and TRAIL might be a promising therapy for osteosarcoma.

Chinese Herbal Medicine for Osteosarcoma in the Mouse: A Systematic Review and Meta-Analysis

OBJECTIVE

To summarize and critically assess the inhibitory effects of Chinese herbal medicine (CHM) on tumor volume and tumor weight for the treatment of osteosarcoma (OS) in mouse models.

METHODS

PubMed, Embase, Web of Science, China Knowledge Resource Integrated Database (CNKI), Wanfang Database, VIP Database, and Chinese BioMedical (CBM) were searched since their inception dates to March 10, 2016. Two reviewers independently selected the controlled studies estimating effects of CHM on mouse OS by administration in vivo. A pair-wise meta-analysis was performed. Twenty-five studies with adequate randomization were included in the systematic review.

RESULTS

CHM may significantly inhibit OS growth in mice, as assessed using the tumor weight [20 studies, n=443; 290 for CHM and 153 for the control: pooled mean difference (MD)=-2.90; 95% confidence interval (Cl): -3.50 to -2.31: P<0.01], tumor volume (16 studies, n=382; 257 for CHM and 125 for the control; pooled MD =-2.57; 95% Cl: -3.33 to -1.80; P<0.01) and tumor growth inhibition rate.

CONCLUSION

CHM could significantly inhibit the growth of OS in mouse models, which might be supportive for the design of preclinical and clinical trials in future.

Celastrol inhibits microglial pyroptosis and attenuates inflammatory reaction in acute spinal cord injury rats

Pyroptosis pathway is closely related to inflammation. However, Celastrol effect on pyroptosis pathway after spinal cord injury (SCI) are poorly understood. We studied the anti-inflammatory and neuroprotective effects of Celastrol on acute spinal cord injury in rats, and its anti-inflammatory effects on lipopolysaccharide (LPS)/ATP-induced microgliosis. Our results show that Celastrol can improve the recovery of hindlimb motor function after SCI in Sprague-Dawley (SD) rats, and reduce the cavity area of spinal cord injury along with the neuronal loss. Celastrol simultaneously reduced the activation of microglia (especially M1 microglia) in the spinal cord, inhibited the pyroptosis-related proteins (NLRP3 ASC Caspase-1 GSDMD), reduced the release of TNF-α IL-1β and IL-18 inflammatory factors, and increased the release of IL10 cytokines. In vitro studies showed that Celastrol reduced the toxicity resulting from the administration of LPS with ATP to BV-2 cells, inhibited the pyroptosis-related proteins (NLRP3 Caspase-1 GSDMD), and inhibited the release of corresponding inflammatory factors. Finally, Celastrol can inhibit the expression of NFκB/p-p65 in vitro and in vivo. Our results show that Celastrol can attenuate the inflammatory response of the spinal cord after SCI, which is associated with inhibition of microglial activation and pyroptosis pathway. Further study to explore the use of Celastrol to treat SCI is warranted.

High Glucose-Induced ROS Production Stimulates Proliferation of Pancreatic Cancer via Inactivating the JNK Pathway

Aberrant glucose metabolism of diabetes mellitus or hyperglycemia stimulates pancreatic tumorigenesis and progression. Hyperglycemic environment can increase the ROS level of tumors, but the role of upregulation of ROS levels in pancreatic cancer (PC) still remains controversial. Here, the same as other reports, we demonstrate that high glucose promoted pancreatic cancer cell growth and resulted in an increase in the level of ROS. However, it is interesting that the phosphorylation of JNK was reduced. When treating PC cells with N-acetyl-L-cysteine (NAC), the intracellular ROS generation is repressed, but the expression of phosphorylation of JNK and c-Jun increased. Moreover, the JNK inhibitor SP600125 significantly promoted cell proliferation and suppressed cell apoptosis of pancreatic cancer cells under high glucose conditions. Collectively, high levels of ROS induced by high glucose conditions stimulated the proliferation of pancreatic cancer cells, and it may be achieved by inactivating the JNK pathway.

Celastrol Alleviates Chronic Obstructive Pulmonary Disease by Inhibiting Cellular Inflammation Induced by Cigarette Smoke via the Ednrb/Kng1 Signaling Pathway

Chronic obstructive pulmonary disease (COPD) is a debilitating disease caused by chronic exposure to cigarette smoke (CS). Celastrol is a pentacyclic triterpenoid compound exhibits potent antioxidant and anti-inflammatory activities. Also it is presently known to protect against liver damage induced by type II diabetes. However, its role in COPD is unclear. In this study, we investigated the effects of Celastrol on cellular inflammation in mice exposed to CS and Beas-2B cells treated with CS extract (CSE). C57BL/6 mice and Beas-2B cells were randomly divided into three groups: control group, COPD or CSE group, and Celastrol treatment group. The COPD mice models were subjected to smoke exposure and cell models were treated with CSE. Bioinformatics analysis was performed to identify differentially expressed genes following treatment with Celastrol in COPD, the molecular networks was mapped by Cytoscape. The levels of inflammatory cytokinesinterleukin-8, tumor necrosis factor α, monocyte chemoattractant protein-1, and oxidative stress factors superoxide dismutase and catalase were measured by enzyme-linked immunosorbent assay. Hematoxylin and eosin staining to detect the injury of mouse lung tissue. mRNA and protein levels of Ednrb and Kng1 in the tissues and cells were measured by quantitative polymerase chain reaction (PCR) and western blotting, respectively. Apoptosis was measured by flow cytometry and TUNEL staining. Compared to mice in the COPD group, mice treated with Celastrol had significantly reduced levels of inflammatory cytokines interleukin-8, tumor necrosis factor α and monocyte chemoattractant protein-1 in the serum and bronchoalveolar lavage fluid, and significantly increased levels of oxidative stress factors superoxide dismutase and catalase. The same results were obtained at the cellular level using Beas-2B cells. Compared to the model groups, Celastrol reduced lung injury in mice and significantly reduced cellular apoptosis. Bioinformatics analysis showed that Ednrb is a target gene of Celastrol and differentially expressed in COPD. Quantitative PCR analysis showed that Ednrb expression in patients with COPD was significantly increased compared to that in healthy controls. Additionally, Celastrol effectively reduced Ednrb/Kng1 expression in both cell and animal models. Celastrol has a therapeutic effect on COPD and may alleviate COPD by inhibiting inflammation development by suppressing the Ednrb/Kng1 signaling pathway.

Autophagy and its potent modulators from phytochemicals in cancer treatment

Autophagy is a ubiquitous catabolic process by which damaged or harmful intracellular components are delivered to the lysosomes for self-digestion and recycling. It is critical in cancer treatment. Therapy-induced autophagy predominantly acts as a pro-survival mechanism, but progressive autophagy can lead to non-apoptotic cell death, also known as autophagic cell death. Plants or herbs contain various natural compounds that are widely used in the treatment of many types of malignancies. Emerging evidence indicates that phytochemicals targeting the autophagic pathway are promising agents for cancer treatment. However, these compounds play different roles in autophagy. In this review, we discussed the role of autophagy in cancer development and therapy, and focussed on elucidating the anti-cancer activities of autophagic modulators, especially phytochemicals. Notably, we described a novel premise that the dynamic role of phytochemicals should be evaluated in regulation of autophagy in cancer.

Autophagy therapeutics: preclinical basis and initial clinical studies

Autophagy captures and degrades intracellular components such as proteins and organelles to sustain metabolism and homeostasis. Rapidly accumulating attention is being paid to the role of autophagy in the development of cancer, which makes autophagy attractive tools and targets for novel therapeutic approaches. Functional studies have confirmed that autophagy dysregulation is causal in many cases of cancer, with autophagy acting as tumor suppressors or tumor promoters, and autophagy inhibitor or promoter has shown promise in preclinical studies. The autophagy-targeted therapeutics using chloroquine/hydroxychloroquine have reached clinical development for treating cancer, but these drugs are actually not efficient probably because of a reduced penetration within the tumor. In this review, we first discuss the discoveries related to dual function of autophagy in cancer. Then, we provide an overview of preclinical studies and clinical trials involved in the development of autophagy therapeutics and finally discuss the future of such therapies.

Chinese Propolis Exerts Anti-Proliferation Effects in Human Melanoma Cells by Targeting NLRP1 Inflammatory Pathway, Inducing Apoptosis, Cell Cycle Arrest, and Autophagy

Melanoma is a malignant tumor that begins in the melanocyte and has the highest mortality rate among all cutaneous tumors. Chinese propolis (CP) has been shown to have a potent antitumor effect against various cancers. In this study, we uncovered the combined effects of antiproliferation and anti-inflammation of CP on suppressing the progression of human melanoma cell line A375. We evaluated the alterations of protein expression after CP treatment by Western blot. After CP treatment, A375 cells underwent intrinsic apoptosis and cell cycle arrest. Furthermore, we found that CP suppressed inflammation in A375 cells. NLRP1 (NLR family pyrin domain containing 1), confirmed as a proinflammatory protein in melanoma progression, was downregulated significantly by CP, as were the NLRP1-related caspase activation and recruitment domains (CARD) proteins, including caspase-1 and caspase-4. Additionally, decreasing mRNA levels of IL-1α, IL-1β, and IL-18 further proved the negative regulation of CP on the melanoma inflammatory environment. We also discovered that CP induced autophagy in A375 cells. Interestingly, inhibiting autophagy in CP-treated cells diminished its antitumor effect, suggesting that the autophagy was attributed to CP-induced apoptosis. Collectively, CP is a promising candidate for drug development for melanoma therapy.

Accumulation of polystyrene microplastics in juvenile Eriocheir sinensis and oxidative stress effects in the liver

As a widespread and ubiquitous pollutant of marine ecosystems, microplastic has the potential to become an emerging global threat for aquatic organisms. The present study aims to elucidate the effects of microplastics on the growth, accumulation and oxidative stress response in the liver of Eriocheir sinensis. Fluorescent microplastic particles (diameter = 0.5 μm) accumulated in the gill, liver and gut tissues of E. sinensis were investigated when crabs were exposed to a concentration of 40000 μg/L for 7 days. A 21 day toxicity test suggested that the rate of weight gain, specific growth rate, and hepatosomatic index of E. sinensis decreased with increasing microplastic concentration (0 μg/L, 40 μg/L, 400 μg/L, 4000 μg/L and 40000 μg/L). The activities of AChE and GPT in crabs exposed to microplastics were lower than those in control group. GOT activity increased significantly after exposure to a low concentration of microplastics and then decreased continuously with increasing microplastic concentrations. The activities of superoxide dismutase (SOD), aspartate transaminase (GOT), glutathione (GSH), and glutathione peroxidase (GPx) increased in specimens exposed to low concentrations of microplastics (40 and 400 μg/L) compared to the control and decreased in organisms exposed to high concentrations (4000 and 40000 μg/L). In contrast, the activities of acetylcholinesterase, catalase (CAT), and alanine aminotransferase were significantly lower in the organisms exposed to microplastics compared to control animals. Upon exposure to increasing microplastic concentrations, the expression of genes encoding the antioxidants SOD, CAT, GPx and glutathione S-transferase in the liver decreased after first increasing. Exposure to microplastics increased the expression of the gene encoding p38 in the MAPK signaling pathway and significantly decreased the expressions of genes encoding ERK, AKT, and MEK. The results of this study demonstrate that microplastics can accumulate in the tissues of E. sinensis and negatively affect growth. In addition, exposure to microplastics causes damage and induces oxidative stress in the hepatopancreas of E. sinensis. The findings provide basic biological data for environmental and human risk assessments of microplastics of high concern.

Celastrol attenuates symptoms of preeclampsia in rats by inhibiting matrix metalloproteinase-9

Preeclampsia is reported in pregnant women around the world and often causes maternal/fetal mortality and morbidity. In the current study, we assessed the efficacy of celastrol on a rat preeclampsia model induced by N^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME). Pregnant rats were administered L-NAME to establish preeclampsia. A total of 48 animals were randomly assigned into 4 groups (n = 12 each): control, control plus celastrol treatment (control+celastrol), preeclampsia, and preeclampsia plus celastrol. Physiological parameters including total urine protein, urine volume and blood pressure were evaluated. Urinary messenger RNA (mRNA) levels of podocin and nephrin were determined using RT-PCR. Further, levels of serum placenta growth factor (PlGF), matrix metalloproteinase (MMP)-9 and renal renal soluble fms-like tyrosine kinase-1 (sFlt-1) were also measured. In rats with preeclampsia, there were robust increases in total urine protein, urine volume and blood pressure, which were significantly attenuated in rats treated with celastrol. Urinary mRNA levels of podocin and nephrin, as well as PlGF, MMP-9 and sFlt-1, were all reversed in preeclampsia plus celastrol group compared to rats in the preeclampsia group without celastrol treatments. MMP-9 overexpression in rats completely abolished the alleviating effect of celastrol. We hereby presented the first evidence that celastrol attenuated preeclampsia symptoms in an L-NAME-induced rat model of preeclampsia through inhibition of MMP-9 expression, supporting the potential therapeutic value of celastrol in the treatment of preeclampsia.

Chemopreventive activity of celastrol in drug-resistant human colon carcinoma cell cultures

Celastrol (tripterine) a pentacyclic triterpenoid extracted from the roots of Tripterygium wilfordii Hook f., exhibits potent antioxidant and anti-inflammatory activity and also exerts important anti-cancer effects, as induction of apoptosis and lowering the level of drug resistance of several cancers. Increased level of cellular resistance to cytostatic drugs is typical for colorectal cancers, and largely determines the failure of chemotherapy for this tumor. The purpose of our research was to evaluate the chemopreventive effect of celastrol on cultures of colon cancer cells resistant to doxorubicin (LOVO/DX). With the use of flow cytometry we have shown that celastrol reduces the cell size of the SP (side population; subpopulation of cancer cells enriched with cancer stem cells), increases frequency of apoptosis and binds to Pgp protein in cell membranes inhibiting its transport function. The inhibition of the Pgp transport function has been shown to increase the accumulation of rhodamine-123 and standard cytostatic- doxorubicin in LOVO/DX cells. Our results prove that celastrol exhibits significant chemopreventive and chemosensitizing activities on drug resistant colon cancer cells. Celastrol appears to be a good candidate for adjuvant medicine that can improve the effectiveness of standard cytostatic therapy in humans.

Myricetin treatment induces apoptosis in canine osteosarcoma cells by inducing DNA fragmentation, disrupting redox homeostasis, and mediating loss of mitochondrial membrane potential

Canine osteosarcoma is an aggressive primary bone tumor that shows metastasis to distal regions and is associated with a high mortality rate. However, the pathophysiological mechanisms of canine osteosarcoma are not well characterized. In addition, development of prognostic factors and novel therapeutic agents is necessary to efficiently treat osteosarcoma. Therefore, we studied the effects of myricetin, an antioxidant found in berries, nuts, teas, wine, and vegetables, on apoptosis and signal transduction in the canine osteosarcoma cell lines, D-17 and DSN. Results of the present study demonstrated that treatment with myricetin decreased cell proliferation and DNA replication, while it increased apoptotic DNA fragmentation in D-17 and DSN cells. In addition, it increased generation of ROS, lipid peroxidation, and depolarization of MMP in both D-17 and DSN cells. Myricetin treatment activated phosphorylation of AKT, p70S6K, ERK1/2, JNK, and p90RSK in canine osteosarcoma cells. Moreover, inhibition of PI3K and MAPK using LY294002, U0126, or SP600125, in addition to myricetin treatment, effectively suppressed cell proliferation compared to treatment with myricetin or each inhibitor alone. Therefore, we concluded that myricetin may be a potentially effective and less toxic therapeutic agent to prevent and control progression of canine osteosarcoma.

Juglone induces apoptosis and autophagy via modulation of mitogen-activated protein kinase pathways in human hepatocellular carcinoma cells

Juglone (JG), a naturally-occurring naphthoquinone of Manchurian walnut (Juglans mandshurica) was shown to inhibit proliferation in various tumor types. However, the molecular mechanisms of JG on the induction of apoptosis and autophagy in HepG2 cells have not been examined. Herein, we investigated that JG could inhibit cell proliferation by induction of G2/M phase arrest. Also, occurrence of apoptosis was closely related with loss of mitochondrial membrane potential, the changes of apoptosis-related proteins after treatment with JG. In addition, we found that JG caused autophagy, as evidenced by increased expressions of LC3-II and Beclin-1. Interestingly, inhibition of JG-induced autophagy by 3-methyladenine (3-MA) and wortmannin (WT) significantly decreased apoptosis, whereas the apoptosis inhibitor z-VAD-fmk slightly enhanced autophagy. Furthermore, the induction of autophagy and apoptosis was associated with activation of MAPK family members (p38 and JNK) and production of reactive oxygen species (ROS). Both JNK inhibitor (SP600125) and ROS scavenger (N-acetylcysteine, NAC) could attenuate JG-induced autophagy and apoptosis. However, the p38-specific inhibitor SB203580 enhanced autophagic and apoptotic death. Moreover, the ROS scavenger NAC prevented phosphorylation of both p38 and JNK. Collectively, our data revealed that JG induced G2/M phase arrest, apoptosis, and autophagy through the ROS-dependent signaling pathway.

Ameliorative effects of selenium on arsenic-induced cytotoxicity in PC12 cells via modulating autophagy/apoptosis

Arsenic is well known toxicant responsible for human diseases including cancers. On the other hand, selenium is an essential trace element with significant chemopreventive effects, anticancer potentials and antioxidant properties. Although previous studies have reported antagonism/synergism between arsenic and selenium in biological systems, the biomolecular mechanism/s is still inconclusive. Therefore, to elucidate the molecular phenomena in cellular level, we hypothesized that co-exposure of selenium with arsenic may have suppressive effects on arsenic-induced cytotoxicity. We found that selenium in co-exposure with arsenic increases cell viability, and suppresses oxidative stress induced by arsenic in PC12 cells. Consequently, DNA fragmentation due to arsenic exposure was also reduced by arsenic and selenium co-exposure. Furthermore, western blot analyses revealed that simultaneous exposure of both metals significantly inhibited autophagy which further suppressed apoptosis through positively regulation of key proteins; p-mTOR, p-Akt, p-Foxo1A, p62, and expression of ubiquitin, Bax, Bcl2, NFкB, and caspases 3 and 9, although those are negatively regulated by arsenic. In addition, reverse transcriptase PCR analysis confirmed the involvement of caspase cascade in cell death process induced by arsenic and subsequent inhibition by co-exposure of selenium with arsenic. The cellular accumulation study of arsenic in presence/absence of selenium via inductively coupled plasma mass spectrometry confirmed that selenium effectively retarded the uptake of arsenic in PC12 cells. Finally, these findings imply that selenium is capable to modulate arsenic-induced intrinsic apoptosis pathway via enhancement of mTOR/Akt autophagy signaling pathway through employing antioxidant potentials and through inhibiting the cellular accumulation of arsenic in PC12 cells.

Activation of autophagy by stress-activated signals as a cellular self-defense mechanism against the cytotoxic effects of MBIC in human breast cancer cells in vitro

We recently reported that methyl 2-(-5-fluoro-2-hydroxyphenyl)-1H-benzo[d]imidazole-5-carboxylate (MBIC) is a microtubule targeting agent (MTA) with multiple mechanisms of action including apoptosis in two human breast cancer cell-lines MCF-7 and MDA-MB-231. In the present study, investigation of early molecular events following MBIC treatment demonstrated the induction of autophagy. This early (<24 h) response to MBIC was characterized by accumulation of autophagy markers; LC3-II, Beclin1, autophagic proteins (ATGs) and collection of autophagosomes but with different variations in the two cell-lines. MBIC-induced autophagy was associated with generation of reactive oxygen species (ROS). In parallel, an increased activation of SAPK/JNK pathway was detected, as an intersection of ROS production and induction of autophagy. The cytotoxic effect of MBIC was enhanced by inhibition of autophagy through blockage of SAPK/JNK signaling, suggesting that MBIC-induced autophagy, is a possible cellular self-defense mechanism against toxicity of this agent in both breast cancer cell-lines. The present findings suggest that inhibition of autophagy eliminates the cytoprotective activity of MDA-MB-231 and MCF-7 cells, and sensitizes both the aggressive and non-aggressive human breast cancer cell-lines to the cytotoxic effects of MBIC.

Celastrol increases osteosarcoma cell lysis by γδ T cells through up-regulation of death receptors

γδ T cells has been shown to exhibit profound antitumor effects in a broad range of tumor entities, including OS. However, resistance to γδ T cells is a serious problem in the management of OS. This study investigates the impact of celastrol on the expression of death receptors 4/5 (DR4/5) on OS cell lines (HOS, U2OS) and cancer cell lysis by γδ T cells. The results showed that celastrol increased transcription of DR4/5 in HOS and U2OS, leading to increased cell surface, and total DR4/5 protein expression. Celastrol sensitizes OS cell lines or autologous OS cells to healthy donors-derived or OS patient-derived γδ T cell cytotoxicity in vitro. The induction of DR4/5 molecules increased lysis of HOS and U2OS by γδ T cells which was abolished by addition of a blocking TRAIL antibody. Importantly, the cytotoxic activity of γδ T cells was unaltered by small-dose celastrol. Taken together, our data show that celastrol up-regulated DR4/5 on OS cells to be responsible for intercellular TRAIL/APO-2L crosslink that confers increased cancer cell lysis by γδ T cells. These results suggest the clinical evaluation of celastrol in OS, especially in combination with immunotherapy approaches employing adoptive γδ T cell transfer.

Valproic Acid Combined with Zoledronate Enhance γδ T Cell-Mediated Cytotoxicity against Osteosarcoma Cells via the Accumulation of Mevalonate Pathway Intermediates

The long-term survival of osteosarcoma has remained unchanged in the last several decades. Immunotherapy is proved to be a promising therapeutic strategy against osteosarcoma, especially for those with metastasis. Our previous study explored the sensibilization of zoledronate (ZOL) in γδ T cell-mediated cytotoxicity against osteosarcoma, but we have not yet elucidated the specific mechanism. Besides, high concentration is required to achieve these effects, whereas plasma ZOL concentration declines rapidly in the circulation. Valproic acid (VPA), a histone deacetylase inhibitor commonly used as the antiepileptic drug, has attracted much attention due to its synergistic antitumor efficacy with chemotherapy or immunotherapy. Here, we demonstrated that VPA combined with ZOL revealed the synergistic effect in enhancing antitumor efficacy of γδ T cells against osteosarcoma cells. This enhancement was mainly TCR-mediated and largely dependent on granule exocytose pathway. Of note, our findings indicated that ZOL sensitized osteosarcoma cells to γδ T cells by increasing the accumulation of the mevalonate pathway intermediates, which could be facilitated by VPA. We also found that this combination had similar effects on primary osteosarcoma cells. All the results suggested that VPA combined with ZOL could reduce the dose required to achieve a significant antitumor effect of γδ T cells, promoting it to be a novel therapy against osteosarcoma.

MiR-29b reverses oxaliplatin-resistance in colorectal cancer by targeting SIRT1

Oxaliplatin is a commonly used chemotherapeutic drug for the treatment of advanced colorectal cancer. However, acquired drug resistance against oxaliplatin remains a major obstacle for efficient use of it, and mechanisms underlying oxaliplatin resistance are still required to be explored. In the present study, we exposed colorectal cancer cell line SW480 to oxaliplatin for a long time to obtain oxaliplatin-resistant colorectal cancer cell model (OR-SW480). We found that intracellular expression of miR-29b was decreased when the SW480 cells became oxaliplatin-resistant. More importantly, overexpression of miR-29b resensitized OR-SW480 cells to oxaliplatin treatment. Mechanically, gene of SIRT1 was identified to be the target of miR-29b. Overexpression of miR-29b in oxaliplatin-treated OR-SW480 decreased the expression of SIRT1 to enhance the ROS production and JNK phosphorylation, and thus promoting apoptosis via activation of caspase 9, 7 and 3. On the other hand, expression plasmid of SIRT1, N-acetyl cysteine or SP600125 (JNK specific inhibitor) abolished the effect of miR-29b on oxaliplatin-treated OR-SW480. We therefore demonstrated that miR-29b reverses oxaliplatin-resistance in colorectal cancer by targeting SIRT1/ROS/JNK pathway.

Phytochemicals as potent modulators of autophagy for cancer therapy

The dysregulation of autophagy is involved in the pathogenesis of a broad range of diseases, and accordingly universal research efforts have focused on exploring novel compounds with autophagy-modulating properties. While a number of synthetic autophagy modulators have been identified as promising cancer therapy candidates, autophagy-modulating phytochemicals have also attracted attention as potential treatments with minimal side effects. In this review, we firstly highlight the importance of autophagy and its relevance in the pathogenesis and treatment of cancer. Subsequently, we present the data on common phytochemicals and their mechanism of action as autophagy modulators. Finally, we discuss the challenges associated with harnessing the autophagic potential of phytochemicals for cancer therapy.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.