Synergistic apoptosis of CML cells by buthionine sulfoximine and hydroxychavicol correlates with activation of AIF and GSH-ROS-JNK-ERK-iNOS pathway

S-nitrosoglutathione (GSNO) induces necroptotic cell death in K562 cells: Involvement of p73, TSC2 and SIRT1

BACKGROUND

Nitric oxide and Reactive Nitrogen Species are known to effect tumorigenicity. GSNO is one of the main NO carrying signalling moiety in cell. In the current study, we tried to delve into the effect of GSNO induced nitrosative stress in three different myelogenous leukemic K562, U937 and THP-1 cell lines.

METHOD

WST-8 assay was performed to investigate cell viability. RT-PCR and western-blot analysis were done to investigate mRNA and protein expression. Spectrophotometric and fluorimetric assays were done to investigate enzyme activities.

RESULT

We found that GSNO exposure led to reduced cell viability and the mode of cell death in K562 was non apoptotic in nature. GSNO promoted impaired autophagic flux and necroptosis. GSNO treatment heightened phosphorylation of AMPK and TSC2 and inhibited mTOR pathway. We observed increase in NAD+/ NADH ratio following GSNO treatment. Increase in both SIRT1 m-RNA and protein expression was observed. While total SIRT activity remained unaltered. GSNO increased tumor suppressor TAp73/ oncogenic ∆Np73 ratio in K562 cells which was correlated with cell mortality. Surprisingly, GSNO did not alter cellular redox status or redox associated protein expression. However, steep increase in total SNO and PSNO content was observed. Furthermore, inhibition of autophagy, AMPK phosphorylation or SIRT1 exacerbated the effect of GSNO. Altogether our work gives insights into GSNO mediated necroptotic event in K562 cells which can be excavated to develop NO based anticancer therapeutics.

CONCLUSION

Our data suggests that GSNO could induce necroptotic cell death in K562 through mitochondrial dysfunctionality and PTM of different cellular proteins.

Targeting bone cancer with 4-Allylbenzene-1,2-diol purified from Piper betle L.: an in silico and cytotoxicity scrutiny

Piper betle L., a well-known medicinal plant with rich source of bioactive compounds, is widely used in several therapeutics. The present study was performed to scrutinize the anti-cancer potential of compounds P. betle petiole by means of in silico studies, purification of 4-Allylbenzene-1,2-diol from petioles and assessing its cytotoxicity on bone cancer metastasis. Subsequent to SwissADME screening, 4-Allylbenzene-1,2-diol and Alpha terpineol were chosen for molecular docking together with eighteen approved drugs against fifteen important bone cancer targets accompanied with molecular dynamics simulation studies. 4-Allylbenzene-1,2-diol was found to be multi-targeting, interacted effectively with all targets, particularly exhibited good stability with MMP9 and MMP2 during molecular dynamics simulations and Molecular Mechanics- Generalized Born and Surface Area (MM-GBSA) analysis using Schrodinger. Later, the compound was isolated, purified and the cytotoxicity studies on MG63 bone cancer cell lines confirmed the cytotoxicity nature (75.98% at 100 µg/ml concentration). The results demonstrated the compound as a matrix metalloproteinase inhibitor, and therefore 4-Allylbenzene-1,2-diol may possibly be prescribed in targeted therapy for alleviating the bone cancer metastasis upon further wet lab experimental validations.Communicated by Ramaswamy H. Sarma.

Hydroxychavicol as a potential anticancer agent (Review)

Piper betle leaves are widely cultivated in Malaysia, India, Indonesia and Thailand. They have been used as a traditional medicine for centuries due to their medicinal properties, including antioxidant, antiproliferative, antibacterial, antifungal and anti-inflammatory properties, which are attributable to their high phenolic contents. Hydroxychavicol (HC), a primary constituent of P. betle leaves, is known to possess antiproliferative activity at micromolar doses on various cancer cell lines of different origins while leaving normal cells unharmed. The present review summarises the mechanisms of action of HC reported in the literature, reviews the scope of work done thus far and outlines the direction of future research on the potential of HC as an anticancer agent. PubMed, Scopus and Web of Science were searched using the keywords (hydroxychavicol OR 4-allylpyrocatechol OR 4-allylcatechol) AND (cancer OR carcinogenesis OR tumour OR carcinoma) to acquire research articles. In vitro studies reported several possible mechanisms for the chemopreventive effects of HC against cancer cell lines, including chronic myelogenous leukaemia (CML), prostate, glioma, breast and colorectal cancers, while in vivo studies encompassed investigations on Ehrlich ascites carcinoma cells in Swiss albino mice and a CML mouse model. These studies suggest that HC exerts its anticancer effect via the modulation of mitochondrial membrane potential and the c-Jun N-terminal kinase, mitogen-activated protein kinase and endoplasmic reticulum-unfolded protein responses pathways and the generation of reactive oxygen species. In summary, future research should focus on combinations of HC with other anticancer drugs and testing in animal models to evaluate its bioavailability, potency and tissue and dose selectivity.

Nitric Oxide Trickle Drives Heme into Hemoglobin and Muscle Myoglobin

Ever since the days of NO being proclaimed as the “molecule of the year”, the molecular effects of this miracle gas on the globins have remained elusive. While its vasodilatory role in the cardiopulmonary system and the vasculature is well recognized, the molecular underpinnings of the NO–globin axis are incompletely understood. We show, by transwell co-culture of nitric oxide (NO) generating, HEK eNOS/nNOS cells, and K562 erythroid or C2C12 muscle myoblasts, that low doses of NO can effectively insert heme into hemoglobin (Hb) and myoglobin (Mb), making NO not only a vasodilator, but also a globin heme trigger. We found this process to be dependent on the NO flux, occurring at low NO doses and fading at higher doses. This NO-triggered heme insertion occurred into Hb in just 30 min in K562 cells and into muscle Mb in C2C12 myoblasts between 30 min and 1 h, suggesting that the classical effect of NO on upregulation of globin (Hb or Mb) is just not transcriptional, but may involve sufficient translational events where NO can cause heme-downloading into the apo-globins (Hb/Mb). This effect of NO is unexpected and highlights its significance in maintaining globins in its heme-containing holo-form, where such heme insertions might be required in the circulating blood or in the muscle cells to perform spontaneous functions.

Anti-Inflammatory Mechanism of An Alkaloid Rutaecarpine in LTA-Stimulated RAW 264.7 Cells: Pivotal Role on NF-κB and ERK/p38 Signaling Molecules

Lipoteichoic acid (LTA) is a key cell wall component and virulence factor of Gram-positive bacteria. LTA contributes a major role in infection and it mediates inflammatory responses in the host. Rutaecarpine, an indolopyridoquinazolinone alkaloid isolated from Evodia rutaecarpa, has shown a variety of fascinating biological properties such as anti-thrombotic, anticancer, anti-obesity and thermoregulatory, vasorelaxing activity. It has also potent effects on the cardiovascular and endocrine systems. Herein, we investigated rutaecarpine’s (Rut) anti-inflammatory effects in LTA-stimulated RAW macrophage cells. The Western blot and spectrophotometric results revealed that Rut inhibited the production of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and interleukin (IL)-1β in the LTA-induced macrophage cells. Successively, our mechanistic studies publicized that Rut inhibited LTA-induced phosphorylation of mitogen-activated protein kinase (MAPK) including the extracellular signal-regulated kinase (ERK), and p38, but not c-Jun NH2-terminal kinase (JNK). In addition, the respective Western blot and confocal image analyses exhibited that Rut reserved nuclear transcription factor kappa-B (NF-κB) by hindering inhibitor of nuclear factor κB-α (IκBα) and NF-κB p65 phosphorylation and p65 nuclear translocation. These results indicate that Rut exhibits its anti-inflammatory effects mainly through attenuating NF-κB and ERK/p38 signaling pathways. Overall, this result suggests that Rut could be a potential therapeutic agent for the treatment of Gram-positive bacteria induced inflammatory diseases.

Inhibitory Mechanism of Combined Hydroxychavicol With Epigallocatechin-3-Gallate Against Glioma Cancer Cell Lines: A Transcriptomic Analysis

Emerging reports have shown therapeutic potential of hydroxychavicol (HC) and epigallocatechin-3-gallate (EGCG) against cancer cells, however high concentrations are required to achieve the anticancer activity. We reported the synergy of low combination doses of EGCG+HC in glioma cell lines 1321N1, SW1783, and LN18 by assessing the effects of EGCG+HC through functional assays. Using high throughput RNA sequencing, the molecular mechanisms of EGCG+HC against glioma cell lines were revealed. EGCG/HC alone inhibited the proliferation of glioma cell lines, with IC50 values ranging from 82 to 302 µg/ml and 75 to 119 µg/ml, respectively. Sub-effective concentrations of combined EGCG+HC enhanced the suppression of glioma cell growth, with SW1783 showing strong synergism with a combination index (CI) of 0.55 and LN18 showing a CI of 0.51. A moderate synergistic interaction of EGCG+HC was detected in 1321N1 cells, with a CI value of 0.88. Exposure of 1321N1, SW1783, and LN18 cells to EGCG+HC for 24 h induces cell death, with caspase-3 activation rates of 52%, 57%, and 9.4%, respectively. However, the dose for SW1783 is cytotoxic to normal cells, thus this dose was excluded from other tests. EGCG+HC induced cell cycle arrest at S phase and reduced 1321N1 and LN18 cell migration and invasion. Combined EGCG+HC amplified its anticancer effect by downregulating the axon guidance process and metabolic pathways, while simultaneously interfering with endoplasmic reticulum unfolded protein response pathway. Furthermore, EGCG+HC exerted its apoptotic effect through the alteration of mitochondrial genes such as MT-CO3 and MT-RNR2 in 1321N1 and LN18 cells respectively. EGCG+HC dynamically altered DYNLL1 alternative splicing expression in 1321N1 and DLD splicing expression in LN18 cell lines. Our work indicated the pleiotropic effects of EGCG+HC treatment, as well as particular target genes that might be investigated for future glioma cancer therapeutic development.

Synergistic Combination of Facile Thiol-Maleimide Derivatization and Supramolecular Solvent-Based Microextraction for UHPLC-HRMS Analysis of Glutathione in Biofluids

Glutathione (GSH) is the most abundant non-protein thiol in biofluids, enabling diverse physiological functions. Among the proposed methods for GSH detection, ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution mass spectrometry (HRMS) has the advantages of high sensitivity and efficiency. In this study, a novel analytical method was developed for the determination of GSH using supramolecular solvent (SUPRAS)-based dispersive liquid–liquid microextraction (DLLME) and UHPLC–HRMS. N-Laurylmaleimide was dissolved in tetrahydrofuran, which served three functions: 1) precipitate the proteins present in the biofluid sample, 2) provide a reaction environment for derivatization, and 3) enable the use of SUPRAS as the dispersing agent. Critical parameters were optimized based on single factor testing and response surface methodology. The established method was validated in terms of linearity, accuracy, precision, and successful quantitative analysis of GSH in saliva, urine, and plasma samples. Experimental results showed that SUPRAS as an extraction solvent was particularly suitable for the extraction of GSH from complex matrices. The current study provides a useful tool for accurate measurements of GSH concentrations, which could potentially be used for clinical diagnostics.

Imbalanced GSH/ROS and sequential cell death

Reactive oxygen species (ROS) are produced in cells during metabolic processes. Excessive intracellular ROS may react with large biomolecules, such as DNA, RNA, proteins, and small biomolecules, that is, glutathione (GSH) and unsaturated fatty acids. GSH has physiological functions, including free radical scavenging, anti-oxidation, and electrophile elimination. The disruption of ROS/GSH balance results in the deleterious oxidation and chemical modification of biomacromolecules, which eventually leads to cell-cycle arrest and proliferation inhibition, and even induces cell death. Imbalanced ROS/GSH may result from a direct increase of ROS, consumption of GSH, intracellular oxidoreductase interference, or thioredoxin activity reduction. Some chemicals including arsenic trioxide (ATO), pyrogallol (PG), and carbobenzoxy-Leu-Leu-leucinal (MG132) could also disrupt the balance of GSH and ROS. This article reviews the occurrence and consequences of the imbalance between GSH and ROS and introduces factors responsible for the disruption of cellular ROS and GSH balance, resulting in cell death. "GSH" and "ROS" were used as keywords to search the relevant literaturess.

2-Methoxy-6-Acetyl-7-Methyljuglone: A Bioactive Phytochemical with Potential Pharmacological Activities

Natural products have been the focus of biomedical and pharmaceutical research to develop new therapies in recent years. 2-methoxy-6-acetyl-7-methyljuglone (2-methoxystypandrone, MAM), a natural bioactive juglone derivative, is known to have various levels of pharmacotherapeutic efficacies as an anti-inflammatory, anticancer, antioxidant, antimicrobial, and anti-HIV activity. MAM fights cancer progression by inducing apoptosis, necroptosis, and deregulating signaling pathways through H2O2-induced JNK/iNOS/NO and MAPK, ERK1/2 pathways, JNK activation, and the RIP1/RIP3 complex. In this review, we summarize the pharmacological importance of MAM in the field of drug discovery. Furthermore, this review not only emphasizes the medicinal properties of MAM but also discusses its potential efficacy in future medicinal products.

Tanshinone I inhibited growth of human chronic myeloid leukemia cells via JNK/ERK mediated apoptotic pathways

Tanshinone I (Tan I) is one of the main bioactive ingredients derived from Salvia miltiorrhiza Bunge, which has exhibited antitumor activities toward various human cancer cells. However, its effects and underlying mechanisms on human chronic myeloid leukemia (CML) cells still require further investigation. This study determined the effects and mechanisms of anti-proliferative and apoptosis induction activity induced by Tan I against K562 cells. The cytotoxic effect of Tan I at varying concentrations on K562 cells was evaluated via MTT assay. Cell apoptosis was further investigated through DAPI staining and flow cytometry analysis. The expression levels of apoptosis-related proteins and activities of JNK/ATF2 and ERK signaling pathways were analyzed by western blot. Quantitative PCR was performed to further determine mRNA expression levels of JNK1/2 and ERK1/2 after Tan I treatment. The results indicated that Tan I significantly inhibited K562 cell growth and induced apoptosis in a concentration- and time-dependent manner. It induced significant cellular morphological changes and increased apoptosis rates in CML cells. Tan I promoted the cleavages of caspase-related proteins, as well as increased the expression levels of PUMA. Furthermore, Tan I significantly activated JNK and inhibited ATF-2 and ERK signaling pathways. The mRNA expression levels of JNK1/2 and ERK1/2 were up-regulated by Tan I, further confirming its regulatory effects on JNK/ERK signaling pathways. Overall, our results indicated that Tan I suppressed cell viability via JNK- and ERK-mediated apoptotic pathways in K562 cells, suggesting that it might be a promising candidate as a novel anti-leukemia drug.

Hydroxychavicol, a polyphenol from Piper betle leaf extract, induces cell cycle arrest and apoptosis in TP53-resistant HT-29 colon cancer cells

This study aims to elucidate the antiproliferative mechanism of hydroxychavicol (HC). Its effects on cell cycle, apoptosis, and the expression of c-Jun N-terminal kinase (JNK) and P38 mitogen-activated protein kinase (MAPK) in HT-29 colon cancer cells were investigated. HC was isolated from Piper betle leaf (PBL) and verified by high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and gas chromatography-mass spectrometry (GC-MS). The cytotoxic effects of the standard drug 5-fluorouracil (5-FU), PBL water extract, and HC on HT-29 cells were measured after 24, 48, and 72 h of treatment. Cell cycle and apoptosis modulation by 5-FU and HC treatments were investigated up to 30 h. Changes in phosphorylated JNK (pJNK) and P38 (pP38) MAPK expression were observed up to 18 h. The half maximal inhibitory concentration (IC₅₀) values of HC (30 μg/mL) and PBL water extract (380 μg/mL) were achieved at 24 h, whereas the IC₅₀ of 5-FU (50 μmol/L) was obtained at 72 h. Cell cycle arrest at the G₀/G₁ phase in HC-treated cells was observed from 12 h onwards. Higher apoptotic cell death in HC-treated cells compared to 5-FU-treated cells (P<0.05) was observed. High expression of pJNK and pP38 MAPK was observed at 12 h in HC-treated cells, but not in 5-FU-treated HT-29 cells (P<0.05). It is concluded that HC induces cell cycle arrest and apoptosis of HT-29 cells, with these actions possibly mediated by JNK and P38 MAPK.

A novel bio-active adhesive monomer induces odontoblast differentiation: a comparative study

AIM

To evaluate the in vitro effect of the novel adhesive monomer CMET, a calcium salt of 4-methacryloxyethyl trimellitate (4-MET), on the proliferation, mineralization and differentiation of odontoblast-like cells, comparing with 4-MET, calcium hydroxide (CH) and mineral trioxide aggregate (MTA).

METHODOLOGY

Rat odontoblast-like MDPC-23 cells were cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with 5% foetal bovine serum. The powder of four tested materials (CMET, 4-MET, CH and MTA) was first dissolved in distilled water (dH₂O) and then was diluted by DMEM to yield final concentrations. Solvent (dH₂O) was used as a control. Cell viability was assessed using CCK-8 assay. Real-time RT-PCR was used to quantify the mRNA expression of odontogenic markers, cytokines and integrins. Mineralization inducing capacity was evaluated by alkaline phosphatase (ALPase) activity and alizarin red S staining. Statistical analyses were performed using one-way anova and post hoc Tukey's HSD test, with the significance level at 1%.

RESULTS

Cell viability was significantly greater in the CMET- (83 to 828 mmol L^-1), CH- and MTA-treated (low concentrations) groups than that in the control group (P < 0.01). Higher concentrations of each material decreased the viable cells to different extents (P < 0.01). CMET treatment augmented the expression of several integrin subunits and exhibited the highest mRNA expression levels of odontogenic markers among all groups (P < 0.01). CH and MTA treatment caused significantly greater upregulation of pro-inflammatory cytokines expression than the other groups (P < 0.01). The calcific deposition of MDPC-23 cells was dose-dependently accelerated by the addition of CMET (P < 0.01); the enhancement of mineralization was also found in the fresh prepared CH and MTA treatments. Besides, CMET showed consistency in mineralization induction after 8 weeks storage. Exposure to SB202190, a specific p38 mitogen-activated protein kinases inhibitor, significantly decreased the ALPase activity as well as the mineral deposition which was enhanced by CMET treatment (P < 0.01).

CONCLUSIONS

The novel bio-active monomer had the lowest cytotoxicity among all groups and it induced the proliferation, mineralization and differentiation of odontoblast-like cells under appropriate concentrations. This adhesive monomer possesses excellent biocompatibility and hence exhibits great potential in dentine regeneration.

Platycodin D alleviates liver fibrosis and activation of hepatic stellate cells by regulating JNK/c-JUN signal pathway

Liver fibrosis is involved in the progression of most chronic liver diseases. Even though we have made a huge progress in order to understand the pathogenesis of liver fibrosis, however, there is still a lack of productive treatments. Being a traditional Chinese medicine, Platycodin D (PD), an oleanane kind of triterpenoid saponin has been put to extensive use for treating different kinds of illnesses that include not just anti-nociceptive, but also antiviral, anti-inflammatory, and anti-cancer for thousands of years. Nonetheless, there has been no clarification made for its effects on the progression of liver fibrosis. In this manner, we carried out in vitro studies for the purpose of investigating the anti-fibrosis impact of PD. Activation of hepatic stellate cells was evaluated by means of the detection of the proliferation of HSCs and the expression of specific proteins. We discovered the fact that PD had the potential of activating HSCs. Thereafter, we detected the apoptosis and autophagy of the HSCs; as the results suggested, PD induced apoptosis and autophagy of the HSCs. It augmented the expression level of apoptotic proteins that included Bax, Cytochrome C (cyto-c), cleaved caspase3 and cleaved caspase9, in addition to the autophagy relevant proteins, for instance, LC3II, beclin1, Atg5 and Atg9. Further research was carried out for the investigation of the underlying molecular mechanism, and discovered that PD promoted the phosphorylation of JNK and c-Jun. Treating the JNK inhibitor P600125 inhibited the effect of PD, confirming the impact of PD on the regulation of JNK/c-Jun pathway. Thus, we speculated that PD alleviates liver fibrosis and activation of hepatic stellate via promoting phosphorylation of JNK and c-Jun and further altering the autophagy along with apoptosis of HSCs.

Aminooxyacetic acid (AOAA) sensitizes colon cancer cells to oxaliplatin via exaggerating apoptosis induced by ROS

Background: As the third confirmed gaseous transmitter, the role of hydrogen sulfide (H₂S) in the pathogenesis of multiple types of cancer has been attracting increasing attention. Increased expression of cystathionine β-synthase (CBS) and H₂S in colon cancer tissue samples has been validated and tumor-derived H₂S, mainly produced by CBS, stimulates bioenergetics, cell proliferation, and angiogenesis in colon cancer. Recently, the therapeutic manipulation of H₂S has been proposed as a promising anticancer approach. However, the effect of aminooxyacetic acid (AOAA), which has been widely used as an inhibitor of CBS dependent synthesis of H₂S, on the chemotherapeutic effect of oxaliplatin (OXA) and the underlying mechanisms remain to be illustrated.

Methods: We examined the expression of CBS in human colorectal cancer specimens and matched normal mucosa by immunohistochemistry. The effect of AOAA on the sensitivity of colon cancer cells to OXA and the level of apoptosis induced by caspase cascade was investigated in both HCT116 and HT29 cell lines utilizing CCK-8 assays, flow cytometry analysis and western blot analysis. The endogenous levels of reactive oxygen species (ROS) were detected fluorescently by DCF-DA, and glutathione (GSH) levels were measured by a Total GSH Detection Kit. Tumor bearing xenograft mouse models and in vivo imaging systems were further used to investigate the effect of AOAA in vivo and immunohistochemistry (IHC) and TUNEL analysis were performed.

Results: In the current study, we confirmed CBS, the main target of AOAA, is overexpressed in human colorectal cancer by immunohistochemistry. The inhibitory effect of AOAA on the synthesis of H₂S was validated utilizing fluorescent probe and specific electrode. AOAA significantly reduced the IC50 values of OXA in both colon cancer cell lines. Co-incubation with AOAA elicited increased apoptosis induced by OXA, featured by increased activation of caspase cascade. Besides, AOAA further increased the levels of ROS induced by OXA and attenuated the synthesis of glutathione (GSH), which is a vital antioxidant. Besides, the results of in vivo imaging and following IHC and TUNEL analysis were in accordance with cellular experiments, indicating that AOAA sensitizes colon cancer cells to OXA via exaggerating intrinsic apoptosis.

Conclusion: The results suggested that CBS is overexpressed in colorectal cancer tissues and AOAA sensitizes colon cancer cells to OXA via exaggerating apoptosis both in vitro and in vivo. Decreasing the endogenous level of GSH and consequently impaired detoxification of ROS might be one of the mechanisms underlying the effect of AOAA.

The role of phosphorylation of MLF2 at serine 24 in BCR-ABL leukemogenesis

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder defined by the presence of the fusion gene BCR-ABL1 in primitive hematopoietic progenitors. The myeloid leukemia factors (MLFs) were identified in the fly and human, and are involved in acute leukemia and enhancing the myeloid factor; however, the function of MLF2 in CML is poorly understood. In this study, we demonstrated that MLF2 may play an oncogenic role in CML. The expression level of MLF2 was related to the proliferation, colony-formation ability, and sensitivity to imatinib in K562 cells. Moreover, phosphorylation at serine 24, detected through Phos-tag sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was required to maintain the activity of MLF2 in CML. The effects of MLF2 overexpression on the colony-formation ability in vitro and mouse survival in vivo could be alleviated by point mutation of MLF2 at serine 24. These findings uncover the oncogenic role of MLF2 through phosphorylation at serine 24 and provide a novel therapeutic target in CML.

Preclinical development of a novel BCR-ABL T315I inhibitor against chronic myeloid leukemia

Chronic Myeloid Leukemia (CML) is a myeloproliferative neoplasm primarily due to the presence of the BCR-ABL fusion gene that produces the constitutively active protein, BCR-ABL. Imatinib, a BCR-ABL-targeted drug, is a first-line drug for the treatment of CML. Resistance to imatinib occurs as a result of mutations in the BCR-ABL kinase domains. In this study, we evaluated S116836, a novel BCR-ABL inhibitor, for its anti-cancer efficacy in the wild-type (WT) and T315I mutant BCR-ABL. S116836 was efficacious in BaF3 cells with WT or T315I mutated BCR-ABL genotypes. S116836 inhibits the phosphorylation of BCR-ABL and its downstream signaling in BaF3/WT and BaF3/T315I cells. Mechanistically, S116836 arrests the cells in the G0/G1 phase of cell cycle, induces apoptosis, increases ROS production, and decreases GSH production in BaF3/WT and BaF3/T315I cells. Moreover, in mouse tumor xenografts, S116836 significantly inhibits the growth and volume of tumors expressing the WT or T315I mutant BCR-ABL without causing significant cardiotoxicity. Overall, our results indicate that S116836 significantly inhibits the imatinib-resistant T315I BCR-ABL mutation and could be a novel drug candidate for treating imatinib-resistant CML patients.

Arsenic Disulfide Combined with L-Buthionine-(S, R)-Sulfoximine Induces Synergistic Antitumor Effects in Two-Dimensional and Three-Dimensional Models of MCF-7 Breast Carcinoma Cells

Three-dimensionally (3D) cultured tumor cells (spheroids) exhibit more resistance to therapeutic agents than the cells cultured in traditional two-dimensional (2D) system (monolayers). We previously demonstrated that arsenic disulfide (As₂S2) exerted significant anticancer efficacies in both 2D- and 3D-cultured MCF-7 cells, whereas 3D spheroids were shown to be resistant to the As₂S₂ treatment. L-buthionine-(S, R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, has been regarded to be a potent candidate for combinatorial treatment due to its GSH modulation function. In the present study, we introduced BSO in combination with As₂S₂ at a low concentration to investigate the possible enhancing anticancer efficacy by the combinatorial treatment on 2D- and 3D-cultured MCF-7 cells. Our results presented for the first time that the combination of As₂S₂ and BSO exerted potent anticancer synergism in both MCF-7 monolayers and spheroids. The IC50 values of As₂S₂ in combinatorial treatment were significantly lower than those in treatment of As₂S₂ alone in both 2D- and 3D-cultured MCF-7 cells (P<0.01, respectively). In addition, augmented induction of apoptosis and enhanced cell cycle arrest along with the regulation of apoptosis- and cell cycle-related proteins, as well as synergistic inhibitions of PI3K/Akt signals, were also observed following co-treatment of As₂S₂ and BSO. Notably, the combinatorial treatment significantly decreased the cellular GSH levels in both 2D- and 3D-cultured MCF-7 cells in comparison with each agent alone (P<0.05 in each). Our results suggest that the combinatorial treatment with As₂S₂ and BSO could be a promising novel strategy to reverse arsenic resistance in human breast cancer.

Apoptotic effects of hsian-tsao (Mesona procumbens Hemsley) on hepatic stellate cells mediated by reactive oxygen species and ERK, JNK, and caspase-3 pathways

The activation of hepatic stellate cells (HSCs) is an important step in the progress of liver fibrosis. Fibrosis can be impeded by HSC reversion to a quiescent state or HSC clearance through apoptosis. To investigate the apoptotic effects of hsian-tsao (Mesona procumbens Hemsl) on human HSCs, the expression levels of cleaved caspase-3, p38, and c-Jun N-terminal kinase (JNK) were assessed using Western blotting, and the caspase-3 activity was measured using caspase-3/CPP32 colorimetric assay kit. Hsian-tsao extract (HTE) increased the activity of caspase-3 and the level of activated caspase-3, indicating the activation of apoptosis. The intracellular reactive oxygen species (ROS) level increased in a dose-dependent manner. This increase was prevented by an antioxidant, suggesting that HTE induces ROS accumulation. In addition, we found that HTE induced the phosphorylation of the mitogen-activated protein kinases JNK and p38. These collective data indicate that HTE induces apoptosis via ROS production through the p38, JNK, and caspase-3-dependent pathways. HTE may decrease HSC activation in liver fibrosis and may have a therapeutic potential.

More than Just an Immunosuppressant: The Emerging Role of FTY720 as a Novel Inducer of ROS and Apoptosis

Fingolimod hydrochloride (FTY720) is a first-in-class of sphingosine-1-phosphate (S1P) receptor modulator approved to treat multiple sclerosis by its phosphorylated form (FTY720-P). Recently, a novel role of FTY720 as a potential anticancer drug has emerged. One of the anticancer mechanisms of FTY720 involves the induction of reactive oxygen species (ROS) and subsequent apoptosis, which is largely independent of its property as an S1P modulator. ROS have been considered as a double-edged sword in tumor initiation/progression. Intriguingly, prooxidant therapies have attracted much attention due to its efficacy in cancer treatment. These strategies include diverse chemotherapeutic agents and molecular targeted drugs such as sulfasalazine which inhibits the CD44v-xCT (cystine transporter) axis. In this review, we introduce our recent discoveries using a chemical genomics approach to uncover a signaling network relevant to FTY720-mediated ROS signaling and apoptosis, thereby proposing new potential targets for combination therapy as a means to enhance the antitumor efficacy of FTY720 as a ROS generator. We extend our knowledge by summarizing various measures targeting the vulnerability of cancer cells' defense mechanisms against oxidative stress. Future directions that may lead to the best use of FTY720 and ROS-targeted strategies as a promising cancer treatment are also discussed.

The Bioactive Extract of Pinnigorgia sp. Induces Apoptosis of Hepatic Stellate Cells via ROS-ERK/JNK-Caspase-3 Signaling

The activation of hepatic stellate cells (HSCs) is a significant phenomenon during the pathogenesis of liver disorders, including liver cirrhosis and fibrosis. Here, we identified that the extract from a gorgonian coral Pinnigorgia sp. (Pin) induced apoptosis of HSC-T6 cells. Pin inhibited the viability of HSC-T6 cells and increased their subG1 population, DNA fragmentation, caspase-3 activation, and reactive oxygen species (ROS) production in a concentration-dependent manner. The Pin-induced ROS generation and apoptotic effects were significantly reversed by a thiol antioxidant, N-acetylcysteine (NAC). Additionally, Pin induced ERK/JNK phosphorylation and pharmacological inhibition of ERK/JNK rescued the Pin-induced cell death. Pin-activated ERK/JNK were significantly reduced after the administration of NAC; however, the inhibition of ERK/JNK failed to change the Pin-induced ROS production. Similarly, pinnigorgiol A, a pure compound isolated from Pin, elicited ROS production and apoptosis in HSC-T6 cells. The pinnigorgiol A-induced apoptosis was retrained by NAC. Together, it appears that Pin leads to apoptosis in HSC-T6 cells through ROS-mediated ERK/JNK signaling and caspase-3 activation. Pinnigorgiol A serves as a bioactive compound of Pin and may exhibit therapeutic potential by clearance of HSCs.

A large scale Plasmodium vivax- Saimiri boliviensis trophozoite-schizont transition proteome

Plasmodium vivax is a complex protozoan parasite with over 6,500 genes and stage-specific differential expression. Much of the unique biology of this pathogen remains unknown, including how it modifies and restructures the host reticulocyte. Using a recently published P. vivax reference genome, we report the proteome from two biological replicates of infected Saimiri boliviensis host reticulocytes undergoing transition from the late trophozoite to early schizont stages. Using five database search engines, we identified a total of 2000 P. vivax and 3487 S. boliviensis proteins, making this the most comprehensive P. vivax proteome to date. PlasmoDB GO-term enrichment analysis of proteins identified at least twice by a search engine highlighted core metabolic processes and molecular functions such as glycolysis, translation and protein folding, cell components such as ribosomes, proteasomes and the Golgi apparatus, and a number of vesicle and trafficking related clusters. Database for Annotation, Visualization and Integrated Discovery (DAVID) v6.8 enriched functional annotation clusters of S. boliviensis proteins highlighted vesicle and trafficking-related clusters, elements of the cytoskeleton, oxidative processes and response to oxidative stress, macromolecular complexes such as the proteasome and ribosome, metabolism, translation, and cell death. Host and parasite proteins potentially involved in cell adhesion were also identified. Over 25% of the P. vivax proteins have no functional annotation; this group includes 45 VIR members of the large PIR family. A number of host and pathogen proteins contained highly oxidized or nitrated residues, extending prior trophozoite-enriched stage observations from S. boliviensis infections, and supporting the possibility of oxidative stress in relation to the disease. This proteome significantly expands the size and complexity of the known P. vivax and Saimiri host iRBC proteomes, and provides in-depth data that will be valuable for ongoing research on this parasite’s biology and pathogenesis.

Visfatin stimulates endometrial cancer cell proliferation via activation of PI3K/Akt and MAPK/ERK1/2 signalling pathways

OBJECTIVE

Endometrial carcinoma is one of the most common malignancies of the female reproductive system, but the aetiology and pathogenesis are not well understood, although adipokines such as visfatin may be involved. Our study provides insight into the mechanism underlying the tumorigenic effects of visfatin in endometrial carcinoma.

METHODS

We investigated the effect of visfatin on endometrial carcinoma cell proliferation, cell cycle, and apoptosis using well-differentiated Ishikawa cells and poorly differentiated KLE cells. We also assessed the effect of visfatin on tumour growth in vivo.

RESULTS

Visfatin stimulated the proliferation of both Ishikawa and KLE cells, and visfatin treatment promoted G1/S phase progression and inhibited endometrial carcinoma cell apoptosis. Visfatin promoted endometrial carcinoma tumour growth in BALB/c-nu mice. Transplanted tumour tissues from an endometrial carcinoma mouse model were analysed using immunohistochemical staining, which revealed much stronger positive signals for Ki-67 with over-abundant visfatin. Western blot analysis revealed that insulin receptor (IR), insulin receptor substrate (IRS)1/2 and key components of the phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK)1/2 signalling pathways were highly expressed in endometrial carcinoma cells exposed to visfatin. Treated cells showed increased C-MYC and cyclin D1 and reduced caspase-3 expression. The effects of visfatin on proliferation and apoptosis were abrogated by treatment with the PI3K inhibitor LY294002 and MEK inhibitor U0126.

CONCLUSIONS

Visfatin promotes the malignant progression of endometrial carcinoma via activation of IR and PI3K/Akt and MAPK/ERK signalling. Visfatin may serve as a therapeutic target in the treatment of endometrial carcinoma.

Phenyl 2-pyridyl ketoxime induces cellular senescence-like alterations via nitric oxide production in human diploid fibroblasts

Phenyl-2-pyridyl ketoxime (PPKO) was found to be one of the small molecules enriched in the extracellular matrix of near-senescent human diploid fibroblasts (HDFs). Treatment of young HDFs with PPKO reduced the viability of young HDFs in a dose- and time-dependent manner and resulted in senescence-associated β-galactosidase (SA-β-gal) staining and G2/M cell cycle arrest. In addition, the levels of some senescence-associated proteins, such as phosphorylated ERK1/2, caveolin-1, p53, p16(ink4a), and p21(waf1), were elevated in PPKO-treated cells. To monitor the effect of PPKO on cell stress responses, reactive oxygen species (ROS) production was examined by flow cytometry. After PPKO treatment, ROS levels transiently increased at 30 min but then returned to baseline at 60 min. The levels of some antioxidant enzymes, such as catalase, peroxiredoxin II and glutathione peroxidase I, were transiently induced by PPKO treatment. SOD II levels increased gradually, whereas the SOD I and III levels were biphasic during the experimental periods after PPKO treatment. Cellular senescence induced by PPKO was suppressed by chemical antioxidants, such as N-acetylcysteine, 2,2,6,6-tetramethylpiperidinyloxy, and L-buthionine-(S,R)-sulfoximine. Furthermore, PPKO increased nitric oxide (NO) production via inducible NO synthase (iNOS) in HDFs. In the presence of NOS inhibitors, such as L-NG-nitroarginine methyl ester and L-NG-monomethylarginine, PPKO-induced transient NO production and SA-β-gal staining were abrogated. Taken together, these results suggest that PPKO induces cellular senescence in association with transient ROS and NO production and the subsequent induction of senescence-associated proteins.

Protective Effect of Tempol on Buthionine Sulfoximine-Induced Mitochondrial Impairment in Hippocampal Derived HT22 Cells

Using a simulated oxidative stress model of hippocampus-derived immortalized cell line (HT22), we report that prooxidant buthionine sulfoximine (BSO, 1 mM, 14 h), without adversely affecting cell viability or morphology, induced oxidative stress by inhibiting glutathione synthesis. BSO treatment also significantly reduced superoxide dismutase (SOD) activity (p < 0.05) and significantly lowered total antioxidant capacity (p < 0.001) in HT22 cells when compared to vehicle treated control cells. Antioxidant tempol, a piperidine nitroxide considered a SOD mimetic, reversed BSO-induced decline in SOD activity (p < 0.01) and also increased BSO-induced decline in total antioxidant capacity (p < 0.05). Interestingly, BSO treatment significantly reduced mitochondrial oxygen consumption (p < 0.05), decreased mitochondrial membrane potential (p < 0.05), and lowered ATP production (p < 0.05) when compared to vehicle treated control cells, collectively indicative of mitochondrial impairment. Antioxidant tempol treatment mitigated all three indicators of mitochondrial impairment. We postulate that BSO-induced oxidative stress in HT22 cells caused mitochondrial impairment, and tempol by increasing SOD activity and improving antioxidant capacity presumably protected the cells from BSO-induced mitochondrial impairment. In conclusion, present study provides an interesting simulation of oxidative stress in hippocampal cells, which will serve as an excellent model to study mitochondrial functions.

Selenium Alleviates Aflatoxin B₁-Induced Immune Toxicity through Improving Glutathione Peroxidase 1 and Selenoprotein S Expression in Primary Porcine Splenocytes

Selenium (Se) is generally known as an essential micronutrient and antioxidant for humans and animals. Aflatoxin B1 (AFB1) is a frequent contaminant of food and feed, causing immune toxicity and hepatotoxicity. Little has been done about the mechanisms of how Se protects against AFB1-induced immune toxicity. The aim of this present study is to investigate the protective effects of Se against AFB1 and the underlying mechanisms. The primary splenocytes isolated from healthy pigs were stimulated by anti-pig-CD3 monoclonal antibodies and treated by various concentrations of different Se forms and AFB1. The results showed that Se supplementation alleviated the immune toxicity of AFB1 in a dose-dependent manner, as demonstrated by increasing T-cell proliferation and interleukin-2 production. Addition of buthionine sulfoximine abrogated the protective effects of SeMet against AFB1. SeMet enhanced mRNA and protein expression of glutathione peroxidase 1 (GPx1), selenoprotein S (SelS), and thioredoxin reductase 1 without and with AFB1 treatments. Furthermore, knockdown of GPx1 and SelS by GPx1-specific siRNA and SelS-specific siRNA diminished the protective effects of SeMet against AFB1-induced immune toxicity. It is concluded that SeMet diminishes AFB1-induced immune toxicity through increasing antioxidant ability and improving GPx1 and SelS expression in splenocytes. This study suggests that organic selenium may become a promising supplementation to protect humans and animals against the decline in immunity caused by AFB1.

Isolation of a novel bio-peptide from walnut residual protein inducing apoptosis and autophagy on cancer cells

Background

Walnut is unique because they have a perfect balance of n-6 and n-3 polyunsaturated fatty acids. The increasing market demand of walnut lipids results in the large amount of the oil extraction residue. The walnut residue is rich in nutritional proteins, and the uneconomic use of the by-product discouraged the development of walnut industry. Anticancer peptides have recently received attention as alternative chemotherapeutic agents that overcome the limits of current drugs. The aim of this study was to investigate whether anticancer bioactive peptide is contained in walnut.

Methods

Walnut residual protein was hydrolyzed separately by five different proteases. The sequential purification of the hydrolysates was carried out by ultra-filtration, gel filtration chromatography and RP-HPLC to obtain a cancer cell growth inhibitory peptide. Cell cycle distribution, Annexin V-FITC/PI double staining, TUNEL assay, western blot and immunofluorescence for LC3-II assay were used to detect apoptosis and autophagy on cells. Cytokine production was measured by ELISA kits, macrophage phagocytosis was measured by neutral red uptake assay, nitric oxide production was measured by Griess reagent.

Results

The hydrolysates of walnut residual protein produced by papain under the optimal conditions (5 % substrate concentration and an enzyme-substrate ratio of 10 % at temperature 60 C for 3 h), showed significant growth inhibitory activity on MCF-7. The amino acid sequence of the purified peptide was identified as CTLEW with a molecular weight of 651.2795 Da. It is a novel bio-peptide with an amphiphilic structure. CTLEW induced both apoptosis and autophagy on MCF-7 cells, inhibited the cancer cells growth of Caco-2 and HeLa significantly, but did not show any cytotoxic activity against non-cancerous IEC-6 cells. Moreover, the bio-peptide enhanced proliferation and IL-2 secretion of spleen lymphocytes, promoted phagocytosis and NO production of macrophages.

Conclusion

These results suggested that a novel bio-peptide, CTLEW inducing apoptosis and autophagy on MCF-7 cells can be released from walnut residual protein through papain hydrolyzing under the certain condition. The bio-peptide shows selective inhibition towards cancer cells growth and immunomodulatory activity.

Protective effect of Edaravone against hypoxia-induced cytotoxicity in osteoblasts MC3T3-E1 cells

Edaravone is a newly developed clinical medicine for the treatment of acute cerebral infarction. Reduced blood supply to bones (hypoxia) has been involved in the pathological development of osteoporosis. In this study, we investigated the effect of Edaravone and its latent mechanism on hypoxia-induced cell toxicity in MC3T3-E1 cells. Cell viability was determined by the 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Intracellular reactive oxygen species (ROS) and nitric oxide (NO) were determined by the fluorescence dyes 2',7'-dichlorofluorescein diacetate (DCFH-DA) and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA), respectively. mRNA and proteins were determined by real-time polymerase chain reaction and Western blot analysis, respectively. Edaravone significantly restored the hypoxia-induced reduction of MC3T3-E1 cell viability and inhibited lactate dehydrogenase release. In addition, we found that Edaravone inhibits the generation of ROS and NO. Hoechst staining results indicated that the nuclear condensation characteristic of apoptosis was increased in MC3T3-E1 cells after hypoxia exposure, which was significantly suppressed by Edaravone treatment. Mechanistically, we found that Edaravone markedly reduced the expression of cleaved caspase-3 and blunted the release of cytochrome c. These findings strongly suggested that Edaravone suppresses hypoxia-induced cytotoxicity in MC3T3-E1 cells. The pleiotropic effects of Edaravone on hypoxia exposure in osteoblasts suggest potential antiosteoporosis mechanisms of Edaravone.

The effects of buthionine sulfoximine on the proliferation and apoptosis of biliary tract cancer cells induced by cisplatin and gemcitabine

Patients with biliary tract cancer (BTC) have a poor prognosis. Advanced BTC patients have been treated with cisplatin in combination with gemcitabine, however, the treatment has had little impact on survival rates, and more effective treatments are urgently required for this disease. Previous studies discovered that buthionine sulfoximine (BSO), a potent inhibitor of glutathione (GSH) synthesis, was able to enhance the cytotoxic effect of various drugs in cancer cells. Phase I studies demonstrated that continuous-infusion of BSO was relatively non-toxic and resulted in the depletion of tumor GSH. However, the synergistic effect of BSO and cisplatin in BTC cells remains unknown, and no reports are available regarding sensitization to gemcitabine by BSO. In the present study, the effect of BSO in combination with cisplatin or gemcitabine in the treatment of BTC cells was examined in vitro. Cytotoxic effects were measured using an MTT assay, Annexin V assay and fluorescence-activated cell sorting analysis. Antiapoptotic protein expression levels were examined using western blot analysis. The results revealed that a sub-toxic concentration of BSO was capable of significantly enhancing cisplatin-induced apoptosis in BTC cells. The mechanisms of BSO's effect on BTC cells may be attributable to the reduction of GSH levels and downregulation of the expression of antiapoptotic proteins (Bcl-2, Bcl-xL and Mcl-1). Furthermore, BSO enhanced the antiproliferative effect of gemcitabine. In conclusion, the present data are the first results to indicate that BSO may sensitize BTC cells to standard first-line chemotherapeutic agents (cisplatin and gemcitabine). Combining BSO with cisplatin and gemcitabine is a promising therapeutic strategy for the treatment of BTC.

Role of Oxidative Stress in Modulating Unfolded Protein Response Activity in Chronic Myeloid Leukemia Cell Line

Background:

Recently, it has been revealed that tyrosine kinase inhibitors (TKIs) act through inducing both oxidative and endoplasmic reticulum (ER) stress in chronic myeloid leukemia cells. However, ER stress signaling triggers both apoptotic and survival processes within cells. Nevertheless, mechanisms by which TKIs avoid the pro-survival effects are not clear. The aim of this study was to evaluate the potential role of oxidative stress in activity of unfolded protein response (UPR) survival pathway within K562 cell line.

Methods:

The expression of UPR survival target genes, Xbp1, and Grp94 (glucose requiring protein 94) was studied in single and combined exposure to oxidative and ER stress in K562 cell line by quantitative and qualitative PCR.

Results:

The expression of UPR-related survival gene Grp94 was hampered by exposing to oxidative stress in cell induced with ER stress.

Conclusion:

Interaction of oxidative and ER stress may role as a mediator influencing UPR signaling activity.

Targeting the Ataxia Telangiectasia Mutated-null phenotype in chronic lymphocytic leukemia with pro-oxidants

Inactivation of the Ataxia Telangiectasia Mutated gene in chronic lymphocytic leukemia results in resistance to p53-dependent apoptosis and inferior responses to treatment with DNA damaging agents. Hence, p53-independent strategies are required to target Ataxia Telangiectasia Mutated-deficient chronic lymphocytic leukemia. As Ataxia Telangiectasia Mutated has been implicated in redox homeostasis, we investigated the effect of the Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia genotype on cellular responses to oxidative stress with a view to therapeutic targeting. We found that in comparison to Ataxia Telangiectasia Mutated-wild type chronic lymphocytic leukemia, pro-oxidant treatment of Ataxia Telangiectasia Mutated-null cells led to reduced binding of NF-E2 p45-related factor-2 to antioxidant response elements and thus decreased expression of target genes. Furthermore, Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia cells contained lower levels of antioxidants and elevated mitochondrial reactive oxygen species. Consequently, Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia, but not tumors with 11q deletion or TP53 mutations, exhibited differentially increased sensitivity to pro-oxidants both in vitro and in vivo. We found that cell death was mediated by a p53- and caspase-independent mechanism associated with apoptosis inducing factor activity. Together, these data suggest that defective redox-homeostasis represents an attractive therapeutic target for Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia.

Reactive oxygen species mediate nitric oxide production through ERK/JNK MAPK signaling in HAPI microglia after PFOS exposure

Perfluorooctane sulfonate (PFOS), an emerging persistent contaminant that is commonly encountered during daily life, has been shown to exert toxic effects on the central nervous system (CNS). However, the molecular mechanisms underlying the neurotoxicity of PFOS remain largely unknown. It has been widely acknowledged that the inflammatory mediators released by hyper-activated microglia play vital roles in the pathogenesis of various neurological diseases. In the present study, we examined the impact of PFOS exposure on microglial activation and the release of proinflammatory mediators, including nitric oxide (NO) and reactive oxidative species (ROS). We found that PFOS exposure led to concentration-dependent NO and ROS production by rat HAPI microglia. We also discovered that there was rapid activation of the ERK/JNK MAPK signaling pathway in the HAPI microglia following PFOS treatment. Moreover, the PFOS-induced iNOS expression and NO production were attenuated after the inhibition of ERK or JNK MAPK by their corresponding inhibitors, PD98059 and SP600125. Interestingly, NAC, a ROS inhibitor, blocked iNOS expression, NO production, and activation of ERK and JNK MAPKs, which suggested that PFOS-mediated microglial NO production occurs via a ROS/ERK/JNK MAPK signaling pathway. Finally, by exposing SH-SY5Y cells to PFOS-treated microglia-conditioned medium, we demonstrated that NO was responsible for PFOS-mediated neuronal apoptosis.

Levosimendan inhibits peroxidation in hepatocytes by modulating apoptosis/autophagy interplay

Background

Levosimendan protects rat liver against peroxidative injuries through mechanisms related to nitric oxide (NO) production and mitochondrial ATP-dependent K (mitoK_ATP) channels opening. However, whether levosimendan could modulate the cross-talk between apoptosis and autophagy in the liver is still a matter of debate. Thus, the aim of this study was to examine the role of levosimendan as a modulator of the apoptosis/autophagy interplay in liver cells subjected to peroxidation and the related involvement of NO and mitoK_ATP.

Methods and Findings

In primary rat hepatocytes that have been subjected to oxidative stress, Western blot was performed to examine endothelial and inducible NO synthase isoforms (eNOS, iNOS) activation, apoptosis/autophagy and survival signalling detection in response to levosimendan. In addition, NO release, cell viability, mitochondrial membrane potential and mitochondrial permeability transition pore opening (MPTP) were examined through specific dyes. Some of those evaluations were also performed in human hepatic stellate cells (HSC). Pre-treatment of hepatocytes with levosimendan dose-dependently counteracted the injuries caused by oxidative stress and reduced NO release by modulating eNOS/iNOS activation. In hepatocytes, while the autophagic inhibition reduced the effects of levosimendan, after the pan-caspases inhibition, cell survival and autophagy in response to levosimendan were increased. Finally, all protective effects were prevented by both mitoK_ATP channels inhibition and NOS blocking. In HSC, levosimendan was able to modulate the oxidative balance and inhibit autophagy without improving cell viability and apoptosis.

Conclusions

Levosimendan protects hepatocytes against oxidative injuries by autophagic-dependent inhibition of apoptosis and the activation of survival signalling. Such effects would involve mitoK_ATP channels opening and the modulation of NO release by the different NOS isoforms. In HSC, levosimendan would also play a role in cell activation and possible evolution toward fibrosis. These findings highlight the potential of levosimendan as a therapeutic agent for the treatment or prevention of liver ischemia/reperfusion injuries.

Ras/ERK signaling pathway is involved in curcumin-induced cell cycle arrest and apoptosis in human gastric carcinoma AGS cells

Curcumin, the biologically active compound from the rhizome of Curcuma longa, could inhibit cell growth and induce apoptosis in gastric carcinoma. However, the underlying mechanism of curcumin on gastric carcinoma cells still needs further investigation. In this study, morphological observation indicated that curcumin inhibited the proliferation of AGS cells in a dose-dependent manner. According to the flow cytometric analysis, curcumin treatment resulted in G2/M arrest in AGS cells, accompanied with an increased expression of cyclin B1 and a decreased expression of cyclin D1. In addition, DNA ladders were observed by gel electrophoresis. Meanwhile, the activities of caspase-3, -8, and -9 were also enhanced in curcumin-treated AGS cells. Nevertheless, the increased activities could be inhibited by benzyloxycarbonyl-Val-Ala-Asp (OME)-fluoromethylketone (z-VAD-fmk), which suggested that the apoptosis was caspase-dependent. Furthermore, downregulation of rat sarcoma (Ras) and upregulation of extracellular-signal-regulated kinase (ERK) were also observed in AGS cells treated with curcumin by Western blot. U0126, an ERK inhibitor, blocked curcumin-induced apoptosis. The results suggested that curcumin inhibited the growth of the AGS cells and induced apoptosis through the activation of Ras/ERK signaling pathway and downstream caspase cascade, and curcumin might be a potential target for the treatment of gastric carcinoma.

Protective efficacy of vitamins C and E on p,p'-DDT-induced cytotoxicity via the ROS-mediated mitochondrial pathway and NF-κB/FasL pathway

Dichlorodiphenoxytrichloroethane (DDT) is a known persistent organic pollutant and liver damage toxicant. However, there has been little emphasis on the mechanism underlying liver damage toxicity of DDT and the relevant effective inhibitors. Hence, the present study was conducted to explore the protective effects of vitamin C (VC) and vitamin E (VE) on the cytotoxicity of DDT in HL-7702 cells and elaborate the specific molecular mechanisms. The results demonstrated that p,p'-DDT exposure at over 10 µM depleted cell viability of HL-7702 cells and led to cell apoptotic. p,p'-DDT treatment elevated the level of reactive oxygen species (ROS) generation, induced mitochondrial membrane potential, and released cytochrome c into the cytosol, with subsequent elevations of Bax and p53, along with suppression of Bcl-2. In addition, the activations of caspase-3 and -8 were triggered. Furthermore, p,p'-DDT promoted the expressions of NF-κB and FasL. When the cells were exposed to the NF-κB inhibitor (PDTC), the up-regulated expression of FasL was attenuated. Strikingly, these alterations caused by DDT treatment were prevented or reversed by the addition of VC or VE, and the protective effects of co-treatment with VC and VE were higher than the single supplement with p,p'-DDT. Taken together, these findings provide novel experimental evidences supporting that VC or/and VE could reduce p,p'-DDT-induced cytotoxicity of HL-7702 cells via the ROS-mediated mitochondrial pathway and NF-κB/FasL pathway.

Inducible nitric oxide synthase mediates MG132 lethality in leukemic cells through mitochondrial depolarization

Proteasomes are highly expressed in rapidly growing neoplastic cells and essential for controlling the cell cycle process and mitochondrial homeostasis. Pharmacological inhibition of the proteasome shows a significant anticancer effect on hematopoietic malignancies that is usually associated with the generation of reactive oxygen species. In this study, we comprehensively investigated the role of endogenous oxidants in various cellular events of K562 leukemic cells in response to treatment with MG132, a proteasome inhibitor. MG132 at 1.4 µM potently triggered G2/M arrest, mitochondrial depolarization, and apoptosis. By such treatment, the protein level of inducible nitric oxide synthase (iNOS) was doubled and cellular oxidants, including nitric oxide, superoxide, and their derivatives, were increasingly produced. In MG132-treated cells, the increase in iNOS-derived oxidants was responsible for mitochondrial depolarization and caspase-dependent apoptosis, but was insignificant in G2/M arrest. The amount of iNOS was negatively correlated with that of manganese superoxide dismutase (MnSOD). Whereas iNOS activity was inhibited by aminoguanidine, cellular MnSOD levels as well as mitochondrial membrane potentials were upregulated, and consequentially G2/M arrest and apoptosis were thoroughly reversed. It is suggested that cells rich in functional mitochondria possess improved proteasome activity, which antagonizes the cytotoxic and cytostatic effects of MG132. In contrast to iNOS, endothelial NOS-driven cGMP-dependent signaling promoted mitochondrial function and survival of MG132-stressed cells. In conclusion, the functional interplay of proteasomes and mitochondria is crucial for leukemic cell growth, wherein iNOS plays a key role.

Intracellular glutathione depletion by oridonin leads to apoptosis in hepatic stellate cells

Proliferation of hepatic stellate cells (HSCs) plays a key role in the pathogenesis of liver fibrosis. Induction of HSC apoptosis by natural products is considered an effective strategy for treating liver fibrosis. Herein, the apoptotic effects of 7,20-epoxy-ent-kaurane (oridonin), a diterpenoid isolated from Rabdosia rubescens, and its underlying mechanisms were investigated in rat HSC cell line, HSC-T6. We found that oridonin inhibited cell viability of HSC-T6 in a concentration-dependent manner. Oridonin induced a reduction in mitochondrial membrane potential and increases in caspase 3 activation, subG1 phase, and DNA fragmentation. These apoptotic effects of oridonin were completely reversed by thiol antioxidants, N-acetylcysteine (NAC) and glutathione monoethyl ester. Moreover, oridonin increased production of reactive oxygen species (ROS), which was also inhibited by NAC. Significantly, oridonin reduced intracellular glutathione (GSH) level in a concentration- and time-dependent fashion. Additionally, oridonin induced phosphorylations of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK). NAC prevented the activation of MAPKs in oridonin-induced cells. However, selective inhibitors of MAPKs failed to alter oridonin-induced cell death. In summary, these results demonstrate that induction of apoptosis in HSC-T6 by oridonin is associated with a decrease in cellular GSH level and increase in ROS production.