Oxidation-triggered c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein (MAP) kinase pathways for apoptosis in human leukaemic cells stimulated by epigallocatechin-3-gallate (EGCG): a distinct pathway from those of chemically induced and receptor-mediated apoptosis

Versatile lipoprotein-inspired nanocomposites rescue Alzheimer's cognitive dysfunction by promoting Aβ degradation and lessening oxidative stress

The accumulation of amyloid-β (Aβ) into senile plaques and the resulting continuous oxidative stress are major pathogenic mechanisms in Alzheimer's disease (AD). In this study, we designed a lipoprotein-inspired nanoparticle to facilitate Aβ clearance and alleviate oxidative stress for the treatment of AD. Lipoprotein-like nanocomposites (RLA-rHDL@ANG) were fabricated by assembling reconstituted high density lipoprotein (rHDL) with an apoE-derived peptide (RLA) with Aβ binding and clearance capabilities, and were subsequently camouflaged using reactive oxygen species (ROS)-sensitive DSPE-TK-mPEG2000 and DSPE-TK-PEG3400-ANG with brain penetration as well as ROS scavenging ability. Immunoelectron microscopy, fluorescence colocalization, and enzyme linked immunosorbent assay, together with a thioflavin-T (ThT) fluorescence quantitative test, showed that RLA-rHDL@ANG possessed the ability of high binding affinity to both Aβ monomers and oligomers, and disintegration of pre-formed Aβ aggregates. ROS level monitoring and transmission electron microscopy (TEM) showed that RLA-rHDL@ANG possessed ROS sensitivity and consumption properties. Transcellular assay and in vivo imaging showed that RLA-rHDL@ANG effectively facilitated blood-brain barrier (BBB) penetration and intracerebral accumulation. It promoted the efficient degradation of Aβ by microglia and neurons through lysosomal transport and elimination approaches. Four-week administration of RLA-rHDL@ANG effectively reduced Aβ deposition, decreased the ROS level and improved cognitive functions in AD mice. These findings indicate that multifunctional RLA-rHDL@ANG may serve as a promising and feasible candidate for managing the progression of AD.

The Effects of Green Tea Catechins in Hematological Malignancies

Green tea catechins are bioactive polyphenol compounds which have attracted significant attention for their diverse biological activities and potential health benefits. Notably, epigallocatechin-3-gallate (EGCG) has emerged as a potent apoptosis inducer through mechanisms involving caspase activation, modulation of Bcl-2 family proteins, disruption of survival signaling pathways and by regulating the redox balance, inducing oxidative stress. Furthermore, emerging evidence suggests that green tea catechins can modulate epigenetic alterations, including DNA methylation and histone modifications. In addition to their apoptotic actions, ROS signaling effects and reversal of epigenetic alterations, green tea catechins have shown promising results in promoting the differentiation of leukemia cells. This review highlights the comprehensive actions of green tea catechins and provides valuable insights from clinical trials investigating the therapeutic potential of green tea catechins in leukemia treatment. Understanding these multifaceted mechanisms and the outcomes of clinical trials may pave the way for the development of innovative strategies and the integration of green tea catechins into clinical practice for improving leukemia patient outcomes.

Graphene Oxide Enhances Biogenesis and Release of Exosomes in Human Ovarian Cancer Cells

BACKGROUND

Exosomes, which are nanovesicles secreted by almost all the cells, mediate intercellular communication and are involved in various physiological and pathological processes. We aimed to investigate the effects of graphene oxide (GO) on the biogenesis and release of exosomes in human ovarian cancer (SKOV3) cells.

METHODS

Exosomes were isolated using ultracentrifugation and ExoQuick and characterized by various analytical techniques. The expression levels of exosome markers were analyzed via quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Graphene oxide (10-50 μg/mL), cisplatin (2-10 μg/mL), and C6-ceramide (5-25 μM) inhibited the cell viability, proliferation, and cytotoxicity in a dose-dependent manner. We observed that graphene oxide (GO), cisplatin (CIS), and C6-Ceramide (C6-Cer) stimulated acetylcholine esterase and neutral sphingomyelinase activity, total exosome protein concentration, and exosome counts associated with increased level of apoptosis, oxidative stress and endoplasmic reticulum stress. In contrast, GW4869 treatment inhibits biogenesis and release of exosomes. We observed that the human ovarian cancer cells secreted exosomes with typical cup-shaped morphology and surface protein biomarkers. The expression levels of TSG101, CD9, CD63, and CD81 were significantly higher in GO-treated cells than in control cells. Further, cytokine and chemokine levels were significantly higher in exosomes isolated from GO-treated SKOV3 cells than in those isolated from control cells. SKOV3 cells pre-treated with N-acetylcysteine or GW4869 displayed a significant reduction in GO-induced exosome biogenesis and release. Furthermore, endocytic inhibitors decrease exosome biogenesis and release by impairing endocytic pathways.

CONCLUSION

This study identifies GO as a potential tool for targeting the exosome pathway and stimulating exosome biogenesis and release. We believe that the knowledge acquired in this study can be potentially extended to other exosome-dominated pathologies and model systems. Furthermore, these nanoparticles can provide a promising means to enhance exosome production in SKOV3 cells.

Downregulation of inflammatory mediators by ethanolic extract of Bergenia ligulata (Wall.) in oxalate injured renal epithelial cells

ETHNOPHARMACOLOGICAL RELEVANCE

In the Indian traditional system of medicine, Bergenia ligulata (Wall.) Engl. has been used for treatment of urolithiasis. Its efficacious nature has led to its incorporation in various commercial herbal formulations such as Cystone and Neeri which are prescribed for kidney related ailments.

AIM OF THE STUDY

To assess whether ethanolic extract of B. ligulata can mitigate the cascade of inflammatory responses that cause oxidative stress and ultimately cell death in renal epithelial cells exposed to hyperoxaluric conditions.

MATERIAL AND METHODS

Bioactivity guided fractionation using solvents of varying polarities was employed to evaluate the potential of the extracts of B. ligulata to inhibit the crystallization process. Modulation of crystal morphology was visualized through Scanning electron microscopy (SEM) analysis. Cell death was assessed using flow cytometry based assays. Alteration in the inflammatory mediators was evaluated using real time PCR and immunocytochemistry. Phytochemical characterization of the ethanolic extract was carried out using FTIR, LC-MS and GC-MS.

RESULTS

Bioactivity guided fractionation for the assessment of antilithiatic activity revealed dose dependent inhibition of nucleation and aggregation process of calcium oxalate crystals in the presence of various extracts, however ethanolic extract showed maximum inhibition and was chosen for further experiments. Studies on renal epithelial NRK-52E cells showed, cytoprotective efficacy of B. ligulata extract against oxalate injury. SEM anaysis further revealed the potential of the extract to modulate the crystal structure and adhesion to renal cell surface. Exposure of the renal cells to the extract led to conversion of the calcium oxalate monohydrate (COM) crystals to the less injurious calcium oxalate dihydrate (COD) form. Expression analysis for oxidative stress and inflammatory biomarkers in NRK-52E cells revealed up-regulation of Mitogen activated protein kinase (MAPK), Osteopontin (OPN) and Nuclear factor- ĸB (NF-ĸB), in response to calcium oxalate insult; which was drastically reduced in the presence of B. ligulata extract. Flow cytometric evaluation pointed to caspase 3 mediated apoptotic cell death in oxalate injured cells, which was attenuated by B. ligulata extract.

CONCLUSION

Considering the complex multifactorial etiology of urolithiasis, ethanolic extract from B. ligulata can be a promising option for the management of kidney stones, as it has the potential to limit inflammation and the subsequent cell death.

Photothermal Killing of A549 Cells and Autophagy Induction by Bismuth Selenide Particles

With a highly efficient optical absorption capability, bismuth selenide (Bi2Se3) can be used as an outstanding photothermal agent for anti-tumor treatment and shows promise in the field of nanotechnology-based biomedicine. However, little research has been completed on the relevant mechanism underlying the photothermal killing effect of Bi2Se3. Herein, the photothermal effects of Bi2Se3 particles on A549 cells were explored with emphasis put on autophagy. First, we characterized the structure and physicochemical property of the synthesized Bi2Se3 and confirmed their excellent photothermal conversion efficiency (35.72%), photostability, biocompatibility and ability of photothermal killing on A549 cells. Enhanced autophagy was detected in Bi2Se3-exposed cells under an 808 nm laser. Consistently, an elevated expression ratio of microtubule-associated protein 1 light chain 3-II (LC3-II) to LC3-I, a marker of autophagy occurrence, was induced in Bi2Se3-exposed cells upon near infrared (NIR) irradiation. Meanwhile, the expression of cleaved-PARP was increased in the irradiated cells dependently on the exposure concentrations of Bi2Se3 particles. Pharmacological inhibition of autophagy by 3-methyladenine (3-MA) further strengthened the photothermal killing effect of Bi2Se3. Meanwhile, stress-related signaling pathways, including p38 and stress activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), were activated, coupled with the attenuated PI3K/Akt signaling. Our study finds that autophagy and the activation of stress-related signaling pathways are involved in the photothermal killing of cancerous cells by Bi2Se3, which provides a more understanding of photothermal materials.

Discovery and development of ASK1 inhibitors

Aberrant activation of mitogen-activated protein kinases (MAPKs) like c-Jun N-terminal kinase (JNK) and p38 is an event involved in the pathophysiology of numerous human diseases. The apoptosis signal-regulating kinase 1 (ASK1) is an upstream target that gets activated only under pathological conditions and as such is a promising target for therapeutic intervention. In the first part of this review the molecular mechanisms leading to ASK1 activation and regulation will be described as well as the evidences supporting a pathogenic role for ASK1 in human disease. In the second part, an update on drug discovery efforts towards the discovery and development of ASK1-targeting therapies will be provided.

Small-molecule compounds target paraptosis to improve cancer therapy

According to its different occurrence mechanism, programmed cell death (PCD) is divided into apoptosis, autophagy, necrosis, paraptosis and so on. Paraptosis is morphologically different from apoptosis and autophagy, which exhibit cytoplasmic vacuolation derived from the ER, independent of caspase, absence of apoptotic morphology. Recent researches have implied that a variety of small molecule compounds, such as celastrol, curcumin, can induce paraptosis-associated cell death as the reagent to enhance anti-cancer activity. A better understanding of paraptosis will lay the foundation to develop new therapeutic strategies to treat human cancers that make full use of small-molecule compounds.

Enhanced susceptibility to apoptosis and growth arrest of human breast carcinoma cells treated with silica nanoparticles loaded with monohydroxy flavone compounds

The treatment of drug-resistant cancer is a clinical challenge, hence screening for novel anticancer drugs is critically important. In this study, we investigated the anti-tumor potential of three plant-derived flavone compounds: 3-hydroxy flavone (3-HF), 6-hydroxy flavone (6-HF), and 7-hydroxy flavone (7-HF), either alone or combined with silica nanoparticles (3-HF + NP, 6-HF + NP, and 7-HF + NP), on the human breast carcinoma cell lines MDA-MB-231 and MCF-7, as well as on non-tumorigenic normal breast epithelial cells (MCF-10). The IC₅₀ values of these flavone compounds loaded with NP (flavones + NP) in these cell lines were determined to be 1.5 μg/mL without affecting the viability of normal MCF-10 cells. Additionally, using annexin V - propidium iodide double-staining followed by flow cytometry analysis, we found that the combination of flavones with NP significantly induced apoptosis in MCF-7 and MDA-MB-231 cancer cells. Furthermore, flavones + NP increased the expression of cytochrome c and caspase-9, mediating the growth arrest of these cancer cells. Most importantly, the combination of flavones with NP significantly abolished the expression of ATF-3, which is responsible for the proliferation and invasion of bone-metastatic breast cancer cells. Our data revealed the potential therapeutic effects of these flavones in fighting breast cancer cells, and provide the first insights concerning the underlying molecular mechanisms.

A novel Rhein derivative: Activation of Rac1/NADPH pathway enhances sensitivity of nasopharyngeal carcinoma cells to radiotherapy

Radiation resistance and recurrent have become the major factors resulting in poor prognosis in the clinical treatment of patients with nasopharyngeal carcinoma (NPC). New strategies to enhance the efficacy of radiotherapy have been focused on the development of radiosensitizers and searching for directly targets that modulated tumor radiosensitivity. A novel potential radiosensitizer 1,8-Dihydroxy -3-(2'-(4″-methylpiperazin-1″-yl) ethyl-9,10-anthraquinone -3-carboxylate (RP-4) was designed and synthesized based on molecular docking technology, which was expected to regulate the radiosensitivity of tumor cells through targeting Rac1. In order to assess the radiosensitization activity of RP-4 on NPC cells, the highly differentiated CNE1 and poorly differentiated CNE2 cells NPC lines were employed. According to the results, RP-4 showed higher binding affinity toward the interaction with Rac1 than lead compounds. We found that RP-4 could inhibit cell viability and proliferation in CNE1 and CNE2 cells and significantly induced apoptosis after non-toxic concentration of RP-4 combined with 2Gy irradiation. RP-4 could effectively modulated the radiosensitivity both CNE1 cells and CNE2 cells through activating Rac1/NADPH signaling pathway and its downstream JNK/AP-1 pathway. What's more, Rac1/NADPH signaling pathway were significantly activated in Rac1-overexpressed CNE1 and CNE2 cells after treated with RP-4. Taken together, Rac1 and its downstream pathway may probably be the direct targets of RP-4 in regulating radiosensitivity of NPC cells, our finding provided a novel strategy for the development of therapeutic agents in response to tumorous radiation resistance.

Epigallocatechin-3-Gallate Suppresses Human Herpesvirus 8 Replication and Induces ROS Leading to Apoptosis and Autophagy in Primary Effusion Lymphoma Cells

Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, has been shown to induce cell death in cancer cells. Primary effusion lymphoma (PEL) is an aggressive neoplasm caused by human herpesvirus 8 (HHV8). In this study, we examined the role of EGCG on PEL cells in cell death and HHV8 replication. We performed trypan blue exclusion assay to assess the cell viability of PEL cells, flow cytometry analysis to examine the cell cycle distribution and reactive oxygen species (ROS) generation, caspase-3 activity to assay apoptosis, acridine orange staining to determine autophagy, and immunoblotting to detect the protein levels involved in apoptosis and autophagy as well as mitogen activated protein kinases (MAPKs) activation upon EGCG treatment. The expression of the HHV8 lytic gene was determined by luciferase reporter assay and reverse transcription-PCR, and viral progeny production was determined by PCR. Results revealed that EGCG induced cell death and ROS generation in PEL cells in a dose-dependent manner. N-acetylcysteine (NAC) inhibited the EGCG-induced ROS and rescued the cell from EGCG-induced cell death. Even though EGCG induced ROS generation in PEL cells, it reduced the production of progeny virus from PEL cells without causing HHV8 reactivation. These results suggest that EGCG may represent a novel strategy for the treatment of HHV8 infection and HHV8-associated lymphomas.

Gallic Acid and Gallates in Human Health and Disease: Do Mitochondria Hold the Key to Success?

Gallic acid and gallate esters are widely used as dietary supplements or additives with clinical significances. Over the last few decades, a large number of publications have been reported stating the antioxidative, antiapoptotic, cardioprotective, neuroprotective, and anticancer properties of gallic acid and gallates, and mostly demonstrated their antioxidative or prooxidative properties influencing the reactive oxygen species (ROS) signaling networks. However, very little focus has been paid to clinical trials, and this restricted their use as a prescribed preventative supplement. Since mitochondria are the principal organelles responsible for ROS generation, we reviewed the existing literature of mitochondria-specific effects of gallates including ROS production, respiration, mitochondrial biogenesis, apoptosis, and the physico-chemical parameters affecting the outcome of gallate supplementation to various health scenarios such as cardiovascular diseases, neurodegeneration, hepatic ailments, or cancers. The major signaling pathways and the molecules targeted by gallic acid and its derivatives have also been discussed with emphasis on mitochondria as the target site. This review provides a better understanding of the effect of gallic acid and gallate esters on mitochondrial functions and in designing effective preventative measures against the onset of various diseases.

A novel porcine ex vivo retina culture model for oxidative stress induced by H₂O₂

Oxidative stress is a key player in many ophthalmic diseases. However, the role of oxidative stress in most degenerative processes is not yet known. Therefore, accurate and practical models are required to efficiently screen for therapeutics. Porcine eyes are closely related to the human eye, and can be obtained from the abattoir as a by-product of the food industry. Therefore, they offer excellent opportunities for the development of culture models with which to pre-screen potential therapies, while reducing the use of laboratory animals. To induce oxidative stress, organotypic cultures of porcine retina were treated with different doses of hydrogen peroxide (H₂O₂; 100, 300 and 500μM) for three hours. On days 3 and 8, the retinas were conserved for histological and Western blotting analyses and for evaluation of gene expression, which determined the number of retinal ganglion cells (RGCs), the activation state of glial cells, and the expression levels of several oxidative stress markers. H₂O₂ treatment led to a reduction in the number of RGCs and to an increase in apoptotic RGCs. In addition, a dose-dependent increase of microglia and an elevation of CD11b expression was observed. On day 3, a reduction of IL-1β, and an increase of iNOS, as well as of HSP70 mRNA were found. On day 8, an increase in TNF-α and IL-1β mRNA expression was detected. In conclusion, this ex vivo model offers an opportunity to study the molecular mechanisms underlying certain eye disorders and to test new therapeutic approaches to diminish the effects of oxidative stress.

Anti-Cancer Effects of Green Tea by Either Anti- or Pro- Oxidative Mechanisms

Tea derived from the leaves and buds of Camellia sinensis (Theaceae) is consumed worldwide. Green tea contains various components with specific health-promoting effects, and is believed to exert protective effects against diseases including cancer, diabetes and hepatitis, as well as obesity. Of the various tea components, the polyphenol catechins have been the subject of extensive investigation and among the catechins, (-)-epigallocatechin gallate has the strongest bioactivity in most cases. Our research group has postulated that hepatocyte nuclear factor-4α, sterol regulatory element-binding proteins, and tumor necrosis factor-α are targets of green tea constituents including (-)-epigallocatechin gallate for their anti-diabetes, anti-obesity, and anti-hepatitis effects, respectively. Published papers were reviewed to determine whether the observed changes in these factors can be correlated with anti-cancer effects of green tea. Two major action mechanisms of (-)-epigallocatechin gallate have been proposed; one associated with its anti-oxidative properties and the other with its pro-oxidative activity. When reactive oxygen species are assumed to be involved, our findings that (-)-epigallocatechin gallate down- regulated hepatocyte nuclear factor-4α, sterol regulatory element-binding proteins, and tumor necrosis factor-α may explain the anti-cancer effect of green tea as well. However, further studies are required to elucidate which determinant directs (-)-epigallocatechin gallate action as an anti-oxidant or a pro-oxidant for favorable activity.

The protective role of (-)-epigallocatechin-3-gallate in thrombin-induced neuronal cell apoptosis and JNK-MAPK activation

(−)-Epigallocatechin-3-gallate (EGCG), the major polyphenolic component of green tea, has anti-inflammatory and antioxidant properties and provides neuroprotection against central nervous system diseases. Yet, it is not known whether EGCG may be neuroprotective against intracerebral hemorrhage. In this study, we used a simplified in-vitro model of thrombin neurotoxicity to test whether EGCG provides neuroprotection against thrombin-associated toxicity. Exposure of primary cortical neurons to thrombin (100 U/ml) caused dose-dependent and time-dependent cytotoxicity. Cell Counting Kit 8 and lactate dehydrogenase were used to monitor cell viability after exposure of neurons to thrombin or EGCG and after EGCG pretreatment. Flow cytometric analysis and western blotting demonstrated that thrombin-induced neuron degeneration occurs through apoptosis. A concentration of 25 μM EGCG significantly abolished thrombin-induced toxicity and prevented apoptosis by suppressing c-Jun-N-terminal kinase (JNK) phosphorylation, and the JNK inhibitor SP600125 reduced thrombin-induced caspase 3 activation and apoptosis. These data suggest that EGCG may have protective effects against thrombin-induced neuroapoptosis by inhibiting the activation of JNK, leading to caspase 3 cleavage. EGCG is a novel candidate neuroprotective agent against intracerebral hemorrhage-induced neurotoxicity.

Hyperbaric oxygen preconditioning inhibits skin flap apoptosis in a rat ischemia-reperfusion model

BACKGROUND

Hyperbaric oxygen (HBO) improves skin flap function and inhibits partial necrosis induced by ischemia-reperfusion (I/R) injury. Our study aimed to evaluate the mechanism underlying HBO regulation of the antiapoptosis factors associated with I/R injury of skin flaps.

METHODS

The rats were divided into sham surgery, I/R, and HBO groups. Rats from the HBO group received HBO preconditioning followed by I/R surgery. Blood perfusion of the skin flaps was measured with laser Doppler flowmeters. Tissue morphology and apoptosis were subsequently assessed based on hematoxylin-eosinhe and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining. Protein expression of phosphorylated apoptosis signal-regulating kinase 1 (pASK-1), phosphorylated c-Jun N-terminal kinase (pJNK), B-cell lymphoma-2 (Bcl-2), and Bcl2-associated X protein (Bax) was examined by immunodetection, and Bcl-2 messenger RNA expression was detected by quantitative polymerase chain reaction. In addition, caspase-3 activity was also measured.

RESULTS

The result of microcirculation analysis showed that the survival and blood perfusion rates significantly increased in the skin flap after HBO exposure. Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining revealed that cell apoptosis was significantly attenuated in the HBO group. Furthermore, HBO preconditioning increased the expression of Bcl-2 and inhibited pASK-1, pJNK, and Bax expression as determined by both immunohistochemistry and Western blot. Caspase-3 activity and the Bax/Bcl-2 ratio declined in the HBO group.

CONCLUSIONS

HBO preconditioning effectively ameliorates I/R injury by regulating the apoptosis signal-regulating kinase 1 and/or c-Jun N-terminal kinase pathway and anti- and proapoptosis factors.

Mechanism of action of (-)-epigallocatechin-3-gallate: auto-oxidation-dependent activation of extracellular signal-regulated kinase 1/2 in Jurkat cells

AIM

(-)-Epigallocatechin-3-gallate (EGCG), a major compound of tea polyphenols, exhibited antitumor activity in previous studies. In these studies, EGCG usually inhibits EGFR, and impairs the ERK1/2 phosphorylation in tumor cells. The aim was to clarify the mechanism of ERK1/2 activation induced by EGCG.

METHOD

Jurkat and 293T cells were treated with EGCG in different culture conditions. Western Blotting (WB) was employed to analyze ERK1/2 and MEK phosphorylation. Cetuximab and FR180204 were used to inhibit cell signaling. The stability of EGCG was assessed by HPLC. The concentration of hydrogen peroxide generated by the auto-oxidation of EGCG was determined by photocolorimetric analysis.

RESULTS

Activation of ERK1/2 was observed to be both time-and dose-dependent. Stimulation of cell signaling was dependent on MEK activity, but independent of EGFR activity. Unexpectedly, EGCG was depleted within one hour of incubation under traditional culture conditions. Auto-oxidation of EGCG generated a high level of hydrogen peroxide in the medium. Addition of catalase and SOD to the acidic medium inhibited the oxidation of EGCG. However, this particular condition also prevented the phosphorylation of ERK1/2. The generation of ROS by hydrogen peroxide may also induce ERK1/2 activation in Jurkat cells.

CONCLUSION

ERK1/2 phosphorylation was caused by auto-oxidation of EGCG. Traditional culture conditions were determined to be inappropriate for EGCG research.

EGCG prevents tryptophan oxidation of cataractous ocular lens human γ-crystallin in presence of H2O2

Disruption of the short range order of proteins present in the ocular lens leads to cataract resulting in a loss of transparency. Human γ-crystallin (HGC), a water soluble protein present in the lens is known to aggregate with aging. A modified form of HGC (HGC(c)) was isolated from cataractous human ocular lens extract and the number of Trp residues that undergo oxidation was determined. The extent of oxidized Trp (N-formyl kynurenine) in HGC due to cataract formation was determined, primarily using fluorescence spectroscopy. The ability of (-)-epigallocatechin gallate (EGCG) to retain its antioxidant effect even in the presence of H2O2 was investigated. This was monitored by its ability to prevent the modification of intact Trp residues in HGC(c) isolated from cataractous human eye lens. Significant Trp fluorescence quenching occurs on interaction of the green tea component, EGCG with HGC(c) accompanied by a red shift. Docking studies were employed to substantiate the experimental results. As eye lens proteins are prone to oxidative stress it is essential that a clear understanding of the effects of the components generated in vivo vis-à-vis the antioxidant effects of natural polyphenols be obtained.

Hydrogen-rich saline attenuates skin ischemia/reperfusion induced apoptosis via regulating Bax/Bcl-2 ratio and ASK-1/JNK pathway

INTRODUCTION

Many pathways have been reported involving the effect of hydrogen-rich saline on protecting skin flap partial necrosis induced by the inflammation of ischemia/reperfusion injury. This study focused on the influence of hydrogen-rich saline treatment on apoptosis pathway of ASK-1/JNK and Bcl-2/Bax radio in I/R injury of skin flaps.

METHODS

Adult male Sprague-Dawley rats were divided into three groups. Group 1 was sham surgery group, Group 2 and 3 were ischemia/reperfusion surgery treated with physiological saline and hydrogen-rich saline respectively. Blood perfusion of flap was measured by Laser doppler flowmeters. Hematoxylin and eosin staining was used to observe morphological changes. Early apoptosis in skin flap was observed through TUNEL staining and presented as the percentage of TUNEL-positive cells of total cells. pASK-1, pJNK, Bcl-2 and Bax were examined by immunodetection. In addition Bcl-2, Bax and caspase-3 were detected by qPCR. Caspase-3 activity was also measured.

RESULTS

Compared to the Group 2, tissues from the group 3 were observed with a high expression of Bcl-2 and a low expression of pASK-1, pJNK, and Bax, a larger survival area and a high level of blood perfusion. Hydrogen-rich saline ameliorated inflammatory infiltration and decreased cell apoptosis.

CONCLUSION

The results indicate that hydrogen-rich saline could ameliorate ischemia/reperfusion injury and improve flap survival rate by inhibiting the apoptosis factor and, at the same time, promoting the expression of anti-apoptosis factor.

The neurotoxicity of 5-S-cysteinyldopamine is mediated by the early activation of ERK1/2 followed by the subsequent activation of ASK1/JNK1/2 pro-apoptotic signalling

5-S-cysteinyldopamine is an endogenous neurotoxin with relevance to Parkinson's disease. The present study shows for the first time that the endogenous formation of 5-S-cysteinyldopamine in the Parkinsonian brain may be causally related to nigrostriatal tract degeneration.

Khz-cp (crude polysaccharide extract obtained from the fusion of Ganoderma lucidum and Polyporus umbellatus mycelia) induces apoptosis by increasing intracellular calcium levels and activating P38 and NADPH oxidase-dependent generation of reactive oxygen species in SNU-1 cells

Background

Khz-cp is a crude polysaccharide extract that is obtained after nuclear fusion in Ganoderma lucidum and Polyporus umbellatus mycelia (Khz). It inhibits the growth of cancer cells.

Methods

Khz-cp was extracted by solvent extraction. The anti-proliferative activity of Khz-cp was confirmed by using Annexin-V/PI-flow cytometry analysis. Intracellular calcium increase and measurement of intracellular reactive oxygen species (ROS) were performed by using flow cytometry and inverted microscope. SNU-1 cells were treated with p38, Bcl-2 and Nox family siRNA. siRNA transfected cells was employed to investigate the expression of apoptotic, growth and survival genes in SNU-1 cells. Western blot analysis was performed to confirm the expression of the genes.

Results

In the present study, Khz-cp induced apoptosis preferentially in transformed cells and had only minimal effects on non-transformed cells. Furthermore, Khz-cp was found to induce apoptosis by increasing the intracellular Ca²⁺ concentration ([Ca²⁺]_i) and activating P38 to generate reactive oxygen species (ROS) via NADPH oxidase and the mitochondria. Khz-cp-induced apoptosis was caspase dependent and occurred via a mitochondrial pathway. ROS generation by NADPH oxidase was critical for Khz-cp-induced apoptosis, and although mitochondrial ROS production was also required, it appeared to occur secondary to ROS generation by NADPH oxidase. Activation of NADPH oxidase was shown by the translocation of the regulatory subunits p47^phox and p67^phox to the cell membrane and was necessary for ROS generation by Khz-cp. Khz-cp triggered a rapid and sustained increase in [Ca²⁺]_i that activated P38. P38 was considered to play a key role in the activation of NADPH oxidase because inhibition of its expression or activity abrogated membrane translocation of the p47^phox and p67^phox subunits and ROS generation.

Conclusions

In summary, these data indicate that Khz-cp preferentially induces apoptosis in cancer cells and that the signaling mechanisms involve an increase in [Ca²⁺]_i, P38 activation, and ROS generation via NADPH oxidase and mitochondria.

Sulindac compounds facilitate the cytotoxicity of β-lapachone by up-regulation of NAD(P)H quinone oxidoreductase in human lung cancer cells

β-lapachone, a major component in an ethanol extract of Tabebuia avellanedae bark, is a promising potential therapeutic drug for various tumors, including lung cancer, the leading cause of cancer-related deaths worldwide. In the first part of this study, we found that apoptotic cell death induced in lung cancer cells by high concentrations of β-lapachone was mediated by increased activation of the pro-apoptotic factor JNK and decreased activation of the cell survival/proliferation factors PI3K, AKT, and ERK. In addition, β-lapachone toxicity was positively correlated with the expression and activity of NAD(P)H quinone oxidoreductase 1 (NQO1) in the tumor cells. In the second part, we found that the FDA-approved non-steroidal anti-inflammatory drug sulindac and its metabolites, sulindac sulfide and sulindac sulfone, increased NQO1 expression and activity in the lung adenocarcinoma cell lines CL1-1 and CL1-5, which have lower NQO1 levels and lower sensitivity to β-lapachone treatment than the A549 cell lines, and that inhibition of NQO1 by either dicoumarol treatment or NQO1 siRNA knockdown inhibited this sulindac-induced increase in β-lapachone cytotoxicity. In conclusion, sulindac and its metabolites synergistically increase the anticancer effects of β-lapachone primarily by increasing NQO1 activity and expression, and these two drugs may provide a novel combination therapy for lung cancers.

Procyanidin induces apoptosis of esophageal adenocarcinoma cells via JNK activation of c-Jun

Procyanidins are polymeric flavanols found in fruits and vegetables and have shown anticarcinogenic/chemopreventive properties. We previously showed that oligomeric procyanidin extracted from apples induced cell cycle arrest and apoptosis in esophageal adenocarcinoma (OA) cells. To understand the mechanism of action, we determined transcriptomic changes induced by procyanidin in OA cells. Pathway analysis implicated mitogen-activated protein kinase signaling pathways in eliciting these responses. Procyanidin induced the activation of JNK and p38 and the phosphorylation and expression of c-Jun. Inhibition of JNK but not p38 kinase activity prevented the procyanidin-induced phosphorylation and expression of c-Jun. Knockdown of the expression of JNK1, JNK2, or JUN diminished procyanidin-induced effects on cell proliferation and apoptosis. c-Jun is a component of the transcription factor AP-1 and AP-1 binding sites are overrepresented in the promoters of procyanidin-induced genes. This indicates that JNK activation of c-Jun by procyanidin leads to the induction of apoptosis of OA cells and suggests a role for a c-Jun-mediated transcriptional program. These data provide a mechanistic understanding of how procyanidin specifically targets a distinct pathway involved in the induction of apoptosis in OA cells and will inform future studies investigating its use as a chemopreventive/therapeutic agent.

Epigallocatechin gallate inhibits growth and epithelial-to-mesenchymal transition in human thyroid carcinoma cell lines

Well-differentiated papillary and follicular thyroid carcinoma are the most frequent types of thyroid cancer and the prognosis is generally favorable however, a number of patients develops recurrences. Epigallocatechin-3-gallate (EGCG), a major catechin in green tea, was shown to possess remarkable therapeutic potential against various types of human cancers, although data on thyroid cancer cells are still lacking. The aim of this study was to investigate the effect of EGCG on the proliferation and motility of human thyroid papillary (FB-2) and follicular (WRO) carcinoma cell lines. Our results demonstrate that EGCG (10, 40, 60 μM) treatment inhibited the growth of FB-2 and WRO cells in a dose-dependent manner. These changes were associated with reduced cyclin D1, increased p21 and p53 expression. Furthermore, EGCG suppressed phosphorylation of AKT and ERK1/2. In addition EGCG treatment results in reduction of cell motility and migration. Changes in motility and migration in FB-2 were associated with modulation in the expression of several proteins involved in cell adhesion and reorganization of actin cytoskeleton. After 24 h EGCG caused an increase of the E-cadherin expression and a concomitant decrease of SNAIL, ZEB and the basic helix-loop-helix transcription factor TWIST. Besides expression of Vimentin, N-cadherin and α5-integrin was down-regulated. These data well correlate with a reduction of MMP9 activity as evidenced by gelatin zymography. Our findings support the inhibitory role of EGCG on thyroid cancer cell proliferation and motility with concomitant loss of epithelial-to-mesenchymal cell transition markers.

Epigallocatechin-3-gallate inhibits hepatoblastoma growth by reactivating the Wnt inhibitor SFRP1

Activation of Wnt signaling plays a central role in the formation of hepatoblastoma (HB), the most common pediatric liver cancer. Blocking this pathway with specific inhibitors is currently the target of various research endeavours. This study provides evidence that the naturally occurring flavonoid epigallocatechin-3-gallate (EGCG) is highly effective against HB growth through inhibition of Wnt signaling. We demonstrate that EGCG has a strong cytotoxic effect on HB cells in a time- and dose-dependent manner by impinging on cell viability, while leaving normal fibroblasts unaffected. Apoptotic features, including morphological changes, caspase 3 activity, and proteolytic cleavage of poly(ADP-ribose) polymerase, were frequently found in EGCG-treated HB cells, thereby suggesting involvement of the mitochondrial intrinsic apoptotic pathway. We furthermore show that EGCG effectively inhibits Wnt signaling, as evidenced by down-regulation of Wnt-responsive reporter gene activity and expression of the Wnt target genes MYC and CCND1. Interestingly, EGCG induced reexpression of the tumor suppressor gene SFRP1, which is transcriptionally silenced in HB cells and known to down-regulate Wnt signaling. Considering the lack of toxic effects on normal cells, EGCG should be preclinically validated as an adjuvant therapy in vivo with the ultimate goal of determining its efficacy in human trials.

Oxidative stress: the mitochondria-dependent and mitochondria-independent pathways of apoptosis

Oxidative stress basically defines a condition in which prooxidant-antioxidant balance in the cell is disturbed; cellular biomolecules undergo severe oxidative damage, ultimately compromising cells viability. In recent years, a number of studies have shown that oxidative stress could cause cellular apoptosis via both the mitochondria-dependent and mitochondria-independent pathways. Since these pathways are directly related to the survival or death of various cell types in normal as well as pathophysiological situations, a clear picture of these pathways for various active molecules in their biological functions would help designing novel therapeutic strategy. This review highlights the basic mechanisms of ROS production and their sites of formation; detail mechanism of both mitochondria-dependent and mitochondria-independent pathways of apoptosis as well as their regulation by ROS. Emphasis has been given on the redox-sensitive ASK1 signalosome and its downstream JNK pathway. This review also describes the involvement of oxidative stress under various environmental toxin- and drug-induced organ pathophysiology and diabetes-mediated apoptosis. We believe that this review would provide useful information about the most recent progress in understanding the mechanism of oxidative stress-mediated regulation of apoptotic pathways. It will also help to figure out the complex cross-talks between these pathways and their modulations by oxidative stress. The literature will also shed a light on the blind alleys of this field to be explored. Finally, readers would know about the ROS-regulated and apoptosis-mediated organ pathophysiology which might help to find their probable remedies in future.

Oxidative stress and potential applications of free radical scavengers in glaucoma

Glaucoma is the leading cause of irreversible blindness in industrialized countries and comprises a group of diseases characterized by progressive optic nerve degeneration. Glaucoma is commonly associated with elevated intraocular pressure due to impaired outflow of aqueous humor resulting from abnormalities within the drainage system of the anterior chamber angle (open-angle glaucoma) or impaired access of aqueous humor to the drainage system (angle-closure glaucoma). Oxidative injury and altered antioxidant defense mechanisms in glaucoma appear to play a role in the pathophysiology of glaucomatous neurodegeneration that is characterized by death of retinal ganglion cells. Oxidative protein modifications occurring in glaucoma serve as immunostimulatory signals and alter neurosupportive and immunoregulatory functions of glial cells. Initiation of the apoptotic cascade observed in glaucomatous retinopathy can involve oxidant mechanisms and different agents have been shown to be neuroprotective. This review focuses on the molecular mechanisms of oxidant injury and summarizes studies that have investigated novel free radical scavengers in the treatment of glaucomatous neurodegeneration.

Aluminum induces osteoblast apoptosis through the oxidative stress-mediated JNK signaling pathway

Aluminum (Al) is considered to be a potentially toxic metal. Al exposure inhibits bone formation. Few studies have investigated the mechanism of inhibitory effects of Al on bone formation. Thus, in this study, osteoblasts were cultured and exposed to different concentrations of Al to investigate the mechanism behind the inhibitory effects of Al on bone formation. Al-treated osteoblasts showed signs of oxidative stress and a high apoptosis rate. The levels of osteoblasts activity markers (bone gamma-carboxyglutamic acid protein and bone alkaline phosphatase) were significantly lower in the Al-treated groups than in the control group. The c-Jun N-terminal kinase (JNK), a major signaling pathway in regulating cell apoptosis, was activated. The phosphorylation state of JNK was significantly increased. The mRNA and protein expression of c-Jun were both significantly upregulated. The pro-apoptotic genes (caspase 3, caspase 9, bax, and factor-related apoptosis ligand) were significantly increased. However, Bcl-2, an anti-apoptotic gene, was significantly decreased. In conclusion, the results of this study indicate that Al induces osteoblast apoptosis by activating the oxidative stress-mediated JNK pathway, which causes cell injuries and reduces the number and function of osteoblasts, thereby inhibiting bone formation.

Khz (fusion of Ganoderma lucidum and Polyporus umbellatus mycelia) induces apoptosis by increasing intracellular calcium levels and activating JNK and NADPH oxidase-dependent generation of reactive oxygen species

Khz is a compound derived from the fusion of Ganoderma lucidum and Polyporus umbellatus mycelia that inhibits the growth of cancer cells. The results of the present study show that Khz induced apoptosis preferentially in transformed cells and had only minimal effects on non-transformed cells. Furthermore, Khz induced apoptosis by increasing the intracellular Ca²⁺ concentration ([Ca²⁺]_i) and activating JNK to generate reactive oxygen species (ROS) via NADPH oxidase and the mitochondria. Khz-induced apoptosis was caspase-dependent and occurred via a mitochondrial pathway. ROS generation by NADPH oxidase was critical for Khz-induced apoptosis, and although mitochondrial ROS production was also required, it appeared to occur secondary to ROS generation by NADPH oxidase. Activation of NADPH oxidase was demonstrated by the translocation of regulatory subunits p47^phox and p67^phox to the cell membrane and was necessary for ROS generation by Khz. Khz triggered a rapid and sustained increase in [Ca²⁺]_i, which activated JNK. JNK plays a key role in the activation of NADPH oxidase because inhibition of its expression or activity abrogated membrane translocation of the p47^phox and p67^phox subunits and ROS generation. In summary, these data indicate that Khz preferentially induces apoptosis in cancer cells, and the signaling mechanisms involve an increase in [Ca²⁺]_i, JNK activation, and ROS generation via NADPH oxidase and mitochondria.

Green Tea Polyphenol Epigallocatechin Gallate Inhibits Adipogenesis and Induces Apoptosis in 3T3-L1 Adipocytes

OBJECTIVE

Green tea catechins have been shown to promote loss of body fat and to inhibit growth of many cancer cell types by inducing apoptosis. The objective of this study was to determine whether epigallocatechin gallate (EGCG), the primary green tea catechin, could act directly on adipocytes to inhibit adipogenesis and induce apoptosis.

RESEARCH METHODS AND PROCEDURES

Mouse 3T3-L1 preadipocytes and mature adipocytes were used. To test the effect of EGCG on viability, cells were incubated for 3, 6, 12, or 24 hours with 0, 50, 100, or 200 microM EGCG. Viability was quantitated by MTS assay. To determine the effect of EGCG on apoptosis, adipocytes were incubated for 24 hours with 0 to 200 microM EGCG, then stained with annexin V and propidium iodide and analyzed by laser scanning cytometry. Both preadipocytes and adipocytes were also analyzed for apoptosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. To determine the effect of EGCG on adipogenesis, maturing preadipocytes were incubated during the 6-day induction period with 0 to 200 microM EGCG, then stained with Oil-Red-O and analyzed for lipid content.

RESULTS

EGCG had no effect on either viability or apoptosis of preconfluent preadipocytes. EGCG also did not affect viability of mature adipocytes; however, EGCG increased apoptosis in mature adipocytes, as demonstrated by both laser scanning cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling assays. Furthermore, EGCG dose-dependently inhibited lipid accumulation in maturing preadipocytes.

DISCUSSION

These results demonstrate that EGCG can act directly to inhibit differentiation of preadipocytes and to induce apoptosis of mature adipocytes and, thus, could be an important adjunct in the treatment of obesity.

(-)-Epigallocatechin-3-gallate induces apoptosis in human endometrial adenocarcinoma cells via ROS generation and p38 MAP kinase activation

(-)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, has been shown to inhibit carcinogenesis of various tumor types. The aim of this study was to elucidate the antiproliferative potential of EGCG and its mechanism in human endometrial cancer cells (Ishikawa cells) and primary endometrial adenocarcinoma cells. The antiproliferative effect of EGCG was evaluated by cell viability assay. Apoptosis was measured by annexin/propidium iodide staining. Reactive oxygen species (ROS) generation was measured by using 2',7'-dichlorofluorescin diacetate dye. Expression of mitogen-activated protein kinases, proliferation and apoptotic markers were measured by immunoblot analysis. EGCG was found to inhibit proliferation in Ishikawa as well as in primary endometrial adenocarcinoma cells and effectively down-regulated the expression of proliferation markers, i.e., estrogen receptor α, progesterone receptor, proliferating cell nuclear antigen and cyclin D1. EGCG also decreased the activation of ERK and downstream transcription factors fos and jun. EGCG caused apoptotic cell death accompanied by up-regulation of proapoptotic Bax and down-regulation of antiapoptotic protein Bcl2. EGCG induced the cleavage of caspase-3 and poly(ADP-ribose) polymerase, the hallmark of apoptosis. EGCG significantly induced the ROS generation as well as p38 activation in Ishikawa cells, which appeared to be a critical mediator in EGCG-induced apoptosis. The apoptotic effect of EGCG and the p38 activation were blocked by pretreatment of cells with the ROS scavenger N-acetylcysteine. EGCG reduced the glutathione levels, which might be responsible for enhanced ROS generation causing oxidative stress in endometrial cancer cells. Taken together, these results suggest that EGCG inhibits cellular proliferation via inhibiting ERK activation and inducing apoptosis via ROS generation and p38 activation in endometrial carcinoma cells.

Diosgenin Induces Apoptosis in HepG2 Cells through Generation of Reactive Oxygen Species and Mitochondrial Pathway

Diosgenin, a naturally occurring steroid saponin found abundantly in legumes and yams, is a precursor of various synthetic steroidal drugs. Diosgenin is studied for the mechanism of its action in apoptotic pathway in human hepatocellular carcinoma cells. Based on DAPI staining, diosgenin-treated cells manifested nuclear shrinkage, condensation, and fragmentation. Treatment of HepG2 cells with 40 μM diosgenin resulted in activation of the caspase-3, -8, -9 and cleavage of poly-ADP-ribose polymerase (PARP) and the release of cytochrome c. In the upstream, diosgenin increased the expression of Bax, decreased the expression of Bid and Bcl-2, and augmented the Bax/Bcl-2 ratio. Diosgenin-induced, dose-dependent induction of apoptosis was accompanied by sustained phosphorylation of JNK, p38 MAPK and apoptosis signal-regulating kinase (ASK)-1, as well as generation of the ROS. NAC administration, a scavenger of ROS, reversed diosgene-induced cell death. These results suggest that diosgenin-induced apoptosis in HepG2 cells through Bcl-2 protein family-mediated mitochndria/caspase-3-dependent pathway. Also, diosgenin strongly generated ROS and this oxidative stress might induce apoptosis through activation of ASK1, which are critical upstream signals for JNK/p38 MAPK activation in HepG2 cancer cells.

Epigallocatechin-3-gallate and penta-O-galloyl-β-D-glucose inhibit protein phosphatase-1

Protein phosphatase-1 (PP1) and protein phosphatase-2A (PP2A) are responsible for the dephosphorylation of the majority of phosphoserine/threonine residues in cells. In this study, we show that (-)-epigallocatechin-3-gallate (EGCG) and 1,2,3,4,6-penta-O-galloyl-β-D-glucose (PGG), polyphenolic constituents of green tea and tannins, inhibit the activity of the PP1 recombinant δ-isoform of the PP1 catalytic subunit and the native PP1 catalytic subunit (PP1c) with IC(50) values of 0.47-1.35 μm and 0.26-0.4 μm, respectively. EGCG and PGG inhibit PP2Ac less potently, with IC(50) values of 15 and 6.6 μm, respectively. The structure-inhibitory potency relationships of catechin derivatives suggests that the galloyl group may play a major role in phosphatase inhibition. The interaction of EGCG and PGG with PP1c was characterized by NMR and surface plasmon resonance-based binding techniques. Competitive binding assays and molecular modeling suggest that EGCG docks at the hydrophobic groove close to the catalytic center of PP1c, partially overlapping with the binding surface of microcystin-LR or okadaic acid. This hydrophobic interaction is further stabilized by hydrogen bonding via hydroxyl/oxo groups of EGCG to PP1c residues. Comparative docking shows that EGCG binds to PP2Ac in a similar manner, but in a distinct pose. Long-term treatment (24 h) with these compounds and other catechins suppresses the viability of HeLa cells with a relative effectiveness reminiscent of their in vitro PP1c-inhibitory potencies. The above data imply that the phosphatase-inhibitory features of these polyphenols may be implicated in the wide spectrum of their physiological influence.

Activation of spleen tyrosine kinase is required for TNF-α-induced endothelin-1 upregulation in human aortic endothelial cells

Endothelin-1 (ET-1) promotes atherosclerosis. We tested whether spleen tyrosine kinase (Syk) mediates tumor necrosis factor-α (TNF-α)-induced ET-1 upregulation in human aortic endothelial cells (HAECs) and sought to identify the signal pathways involved. TNF-α-induced reactive oxygen species (ROS) activated Syk and phosphatidylinositol 3-kinase (PI3K), which was required for the activation of AP-1 and subsequent ET-1 gene transcription. ROS mediated c-Jun NH(2)-terminal kinase (JNK) is also required for AP-1 activation, but Syk and PI3K regulated AP-1 activation independently of JNK. Through regulation of ET-1 production, Syk could be implicated in atherosclerosis.

Health-promoting effects of green tea

Green tea is manufactured from the leaves of the plant Camellia sinensis Theaceae and has been regarded to possess anti-cancer, anti-obesity, anti-atherosclerotic, anti-diabetic, anti-bacterial, and anti-viral effects. Many of the beneficial effects of green tea are related to the activities of (-)-epigallocatechin gallate (EGCG), a major component of green tea catechins. For about 20 years, we have engaged in studies to reveal the biological activities and action mechanisms of green tea and EGCG. This review summarizes several lines of evidence to indicate the health-promoting properties of green tea mainly based on our own experimental findings.

Panaxydol induces apoptosis through an increased intracellular calcium level, activation of JNK and p38 MAPK and NADPH oxidase-dependent generation of reactive oxygen species

Panaxydol, a polyacetylenic compound derived from Panax ginseng roots, has been shown to inhibit the growth of cancer cells. In this study, we demonstrated that panaxydol induced apoptosis preferentially in transformed cells with a minimal effect on non-transformed cells. Furthermore, panaxydol was shown to induce apoptosis through an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), activation of JNK and p38 MAPK, and generation of reactive oxygen species (ROS) initially by NADPH oxidase and then by mitochondria. Panaxydol-induced apoptosis was caspase-dependent and occurred through a mitochondrial pathway. ROS generation by NADPH oxidase was critical for panaxydol-induced apoptosis. Mitochondrial ROS production was also required, however, it appeared to be secondary to the ROS generation by NADPH oxidase. Activation of NADPH oxidase was demonstrated by the membrane translocation of regulatory p47(phox) and p67(phox) subunits and shown to be necessary for ROS generation by panaxydol treatment. Panaxydol triggered a rapid and sustained increase of [Ca(2+)](i), which resulted in activation of JNK and p38 MAPK. JNK and p38 MAPK play a key role in activation of NADPH oxidase, since inhibition of their expression or activity abrogated membrane translocation of p47(phox) and p67(phox) subunits and ROS generation. In summary, these data indicate that panaxydol induces apoptosis preferentially in cancer cells, and the signaling mechanisms involve a [Ca(2+)](i) increase, JNK and p38 MAPK activation, and ROS generation through NADPH oxidase and mitochondria.

SU5416 and EGCG work synergistically and inhibit angiogenic and survival factors and induce cell cycle arrest to promote apoptosis in human malignant neuroblastoma SH-SY5Y and SK-N-BE2 cells

Malignant neuroblastomas are solid tumors in children. Available therapeutic agents are not highly effective for treatment of malignant neuroblastomas. Therefore, new treatment strategies are urgently needed. We tested the efficacy of combination of SU5416 (SU), an inhibitor of the vascular endothelial growth factor receptor-2 (VEGFR-2), and (-)-epigallocatechin-3-gallate (EGCG), a polyphenolic compound from green tea, for controlling growth of human malignant neuroblastoma SH-SY5Y and SK-N-BE2 cells. Combination of 20 μM SU and 50 μM EGCG synergistically inhibited cell survival, suppressed expression of VEGFR-2, inhibited cell migration, caused cell cycle arrest, and induced apoptosis. Combination of SU and EGCG effectively blocked angiogenic and survival pathways and modulated expression of cell cycle regulators. Apoptosis was induced by down regulation of Bcl-2, activation of caspase-3, and cleavage of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP). Taken together, this combination of drugs can be a promising therapeutic strategy for controlling the growth of human malignant neuroblastoma cells.

HIV infection enhances TRAIL-induced cell death in macrophage by down-regulating decoy receptor expression and generation of reactive oxygen species

BACKGROUND

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) could induce apoptosis of HIV-1-infected monocyte-derived macrophage (MDM), but the molecular mechanisms are not well understood.

METHODOLOGY/PRINCIPAL FINDINGS

By using an HIV-1 Env-pseudotyped virus (HIV-1 PV)-infected MDM cell model we demonstrate that HIV-1 PV infection down-regulates the expression of TRAIL decoy receptor 1 (DcR1) and 2 (DcR2), and cellular FLICE-inhibitory protein (c-FLIP), but dose not affect the expression of death receptor 4 and 5 (DR4, DR5), and Bcl-2 family members in MDM cells. Furthermore, recombinant soluble TRAIL and an agonistic anti-DR5 antibody, AD5-10, treatment stimulates reactive oxygen species (ROS) generation and JNK phosphorylation.

CONCLUSIONS/SIGNIFICANCE

HIV infection facilitates TRIAL-induced cell death in MDM by down-regulating the expression of TRAIL decoy receptors and intracellular c-FLIP. Meanwhile, the agonistic anti-DR5 antibody, AD5-10, induces apoptosis synergistically with TRAIL in HIV-1-infected cells. ROS generation and JNK phosphorylation are involved in this process. These findings potentiate clinical usage of the combination of TRAIL and AD5-10 in eradication of HIV-infected macrophage and AIDS.

Molecular bases of thioredoxin and thioredoxin reductase-mediated prooxidant actions of (-)-epigallocatechin-3-gallate

Thioredoxin (Trx) and thioredoxin reductase (TrxR) function as antioxidant and anti-apoptotic proteins, which are often up-regulated in drug-resistant cancer cells. (-)-epigallocatechin-3-gallate (EGCG) is a naturally occurring antioxidant in green tea, but also exhibits prooxidant and apoptosis-inducing properties. We have previously showed a linkage between EGCG-induced inactivation of TrxR and decreased cell survival, revealing TrxR as a new target of EGCG. However, the molecular events underlying the importance of Trx/TrxR in EGCG-induced cytotoxicity remain unclear. Here, we show that the crosstalk between EGCG and Trx/TrxR occurred in a redox-dependent manner, and EGCG induced inactivation of Trx/TrxR in parallel with increased ROS levels in HeLa cells. Moreover, EGCG displayed great reactivity with Cys/Sec residues that have low pK(a) values. The structure of EGCG suggests that its quinone form would readily react with thiolate and selenolate nucleophiles. Using mass spectrometry, we have demonstrated the formation of EGCG-Trx1 (Cys(32)) and EGCG-TrxR (Cys/Sec) conjugates, confirming that EGCG quinone specifically conjugates with active-site Cys(32) in Trx or C-terminal Cys/Selenocysteine (Sec) couple in TrxR under conditions where Trx/TrxR are reduced. Non-reduced form of Trx/TrxR could escape from EGCG inhibition. These data reveal a potential mechanism for enhancing EGCG-induced cancer cell death by the NADPH-dependent reduction of Trx/TrxR.

Microbial and host cells acquire enhanced oxidant-scavenging abilities by binding polyphenols

The dilemma whether supplementations of dietary antioxidants might prevent the adverse consequences of oxidative stress, the inadequacy of the analytical methods employed to quantify oxidant scavenging ability (OSA) levels in whole blood and the distribution and fate of polyphenols and their metabolites in various body compartments following oral consumption are discussed. While none-metabolized polyphenols might exert their antioxidant effects mainly in the oral cavity, metabolized polyphenols might be beneficial in the gastrointestinal tract to counteract the toxicity of oxidants and also of the sequelae of inflammatory processes. Although only micromolar amounts of polyphenols and their metabolites eventually reach the blood circulation, these may nevertheless still be highly effective as scavengers of reactive oxygen and nitrogen species because of their ability to synergize with plasma low molecular-weight antioxidants and with albumin. Polyphenols can avidly bind to surfaces of microorganisms and of blood cells to markedly enhance their OSA, therefore the routine quantifications of antioxidant levels conducted in clinical settings should always use catalase-rich whole blood but not as customary, plasma alone. In addition to their antioxidant and metal chelating properties, polyphenols may also act as signaling agents capable of affecting metabolic, inflammatory, autoimmune, carcinogenic and aging processes.