Apoptosis induced by a new flavonoid in human hepatoma HepG2 cells involves reactive oxygen species-mediated mitochondrial dysfunction and MAPK activation

The protective role of resveratrol against high glucose-induced oxidative stress and apoptosis in HepG2 cells

High glucose concentrations result in oxidative stress, leading to damage of cellular constituents like DNA, proteins, and lipids, ultimately resulting in apoptosis. Resveratrol, a polyphenol phytoalexin, has been studied for its potential therapeutic effects on diabetes. This study investigated the influence of high glucose (HG) on HepG2 cells and assessed resveratrol's effect on high-glucose-induced oxidative stress and apoptosis. HepG2 cells were cultured for 48 and 72 h with high glucose (40 mM), low resveratrol (25 μM), high resveratrol (50 μM), high glucose + low resveratrol, and high glucose + high resveratrol. After exposure, oxidative and apoptosis-related gene expression was evaluated using quantitative polymerase chain reaction (qPCR), and lactate dehydrogenase (LDH) release was measured using the supernatant. In HepG2 cells cultured with high glucose, all antioxidant enzymes (SOD, superoxide dismutase; GPx1, glutathione peroxidase 1; CAT, catalase; Nrf2, nuclear factor erythroid 2-related factor 2; and NQO1, NAD(P)H quinone oxidoreductase 1) were significantly reduced; however, when HepG2 cells were cultured with resveratrol (25 and 50 μM) and high glucose, the expression levels of all antioxidant enzymes were increased. The anti-apoptotic gene (B-cell lymphoma 2; Bcl2) and the DNA repair gene (Oxoguanine glycosylase-1, OGG1) were significantly decreased following high glucose exposure to HepG2 cells. Surprisingly, the expression levels of Bcl2 and OGG1 were notably elevated after resveratrol treatment. Furthermore, high glucose levels increased the LHD release in HepG2 cells, whereas resveratrol treatment reduced the LDH release. Our results demonstrate that resveratrol provides protection against oxidative stress and apoptosis induced by high glucose in HepG2 cells. Hence, resveratrol shows potential as an effective approach to address the impaired antioxidant response resulting from elevated glucose levels commonly observed in diabetes and metabolic disorders.

Lactobacillus paracasei subsp. paracasei X12 Strain Induces Apoptosis in HT-29 Cells through Activation of the Mitochondrial Pathway

L. paracasei subsp. paracasei X12 was obtained from traditional cheese produced in northwestern China. In this study, we showed that whole peptidoglycan (WPG), extracted from L. paracasei subsp. paracasei X12, inhibited proliferation and induced apoptosis in HT-29 cells in a dose-dependent manner. In addition, WPG-induced apoptosis was associated with the loss of mitochondrial membrane potential (Ψm), the release of cytochrome c (Cyto-C) from mitochondrialto cytosolic spaces, activation of Caspase 3, and accumulation of intracellular reactive oxygen species (ROS). Finally, semi-quantitative RT-PCR showed that these events were accompanied by upregulation of proapoptotic genes (Bax or Bad) and downregulation of antiapoptotic genes (Bcl-xl). Taken together, our results demonstrated that WPG induced apoptosis in HT-29 cells through activation of the mitochondrial pathway. WPG exerted only minor toxicity upon noncancerous cells and therefore might be used as a natural agent in the treatment of cancer in future.

Effects of Lactobacillus acidophilus KLDS1.0901 on Proliferation and Apoptosis of Colon Cancer Cells

Colon cancer is the most common type of malignant tumor. The cytotoxicity effect of lactic acid bacteria may be active by inhibiting cancer cell proliferation, producing anticancer compounds, and inducing apoptosis in cancer cells, but the mechanism is unclear. Our previous study revealed that Lactobacillus acidophilus KLDS1.0901 has good probiotic properties. In this study, We screened out the highest inhibition rate of L. acidophilus KLDS1.0901 and assessed the effects on the proliferation of HT-29, Caco-2, and IEC-6 cells. Then, the apoptosis mechanism of HT-29 cells was studied when treated with L. acidophilus KLDS1.0901. Results showed that L. acidophilus KLDS1.0901 inhibited the proliferation of HT-29 and Caco-2 cells in a dose-dependent manner and reached the maximum under the condition of multiplicity of infection (MOI) = 100 (rate of Lactobacillus to cells) at 48 h. With the increase in time and MOI, reactive oxygen species in HT-29 cells, the apoptosis rates of HT-29 cells were increased, and the amount of blue fluorescence of the cells was also increased after Hoechst 33258 staining. Furthermore, L. acidophilus KLDS1.0901 reduced the mitochondrial membrane potential of HT-29 cells. Notably, 1,133 differentially expressed genes were screened by transcriptomics research, including 531 up-regulated genes and 602 down-regulated genes. These genes were involved in the nuclear factor κB and PI3K-AKT signaling pathways related to the apoptosis of HT-29 cells. These findings suggested that L. acidophilus KLDS1.0901 has the potential to be used in the development of a new type of functional foods for adjuvant treatment of colon cancer.

Kushenol C Prevents Tert-Butyl Hydroperoxide and Acetaminophen-Induced Liver Injury

Sophora flavescens, also known as Kushen, has traditionally been used as a herbal medicine. In the present study we evaluated the ameliorative effects of kushenol C (KC) from S. flavescens against tBHP (tert-Butyl hydroperoxide)-induced oxidative stress in hepatocellular carcinoma (HEPG2) cells and acetaminophen (APAP)-induced hepatotoxicity in mice. KC pretreatment protected the HEPG2 cells against oxidative stress by reducing cell death, apoptosis and reactive oxygen species (ROS) generation. KC pretreatment also upregulated pro-caspase 3 and GSH (glutathione) as well as expression of 8-Oxoguanine DNA Glycosylase (OGG1) in the HEPG2 cells. The mechanism of action was partly related by KC's activation of Akt (Protein kinase B (PKB)) and Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) in the HepG2 cells. In in vivo investigations, coadministration of mice with KC and APAP significantly attenuated APAP-induced hepatotoxicity and liver damage, as the serum enzymatic activity of aspartate aminotransferase and alanine aminotransferase, as well as liver lipid peroxidation and cleaved caspase 3 expression, were reduced in APAP-treated mice. Coadministration with KC also up-regulated antioxidant enzyme expression and prevented the production of proinflammatory mediators in APAP-treated mice. Taken together, these results showed that KC treatment has potential as a therapeutic agent against liver injury through the suppression of oxidative stress.

Recent Research on Flavonoids and their Biomedical Applications

Flavonoids, commonly found in various plants, are a class of polyphenolic compounds having a basic structural unit of 2-phenylchromone. Flavonoid compounds have attracted much attention due to their wide biological applications. In order to facilitate further research on the biomedical application of flavonoids, we surveyed the literature published on the use of flavonoids in medicine during the past decade, documented the commonly found structures in natural flavonoids, and summarized their pharmacological activities as well as associated mechanisms of action against a variety of health disorders including chronic inflammation, cancer, cardiovascular complications and hypoglycemia. In this mini-review, we provide suggestions for further research on the biomedical applications of flavonoids.

Chemical modifications of polysaccharides and their anti-tumor activities

With the rising trend of incidence of cancers, effective therapies are urgently needed to control human malignancies. However, the chemotherapy drugs currently on the market cause serious side effects. Polysaccharides belong to a class of biomacromolecules, which have drawn considerable research interest over the years as it possess anti-cancer activities or can increase the efficacy of conventional chemotherapy drugs with fewer side effects. The antitumor activity of many polysaccharides was significantly increased after modification. Based on these encouraging observations, a great deal of effort has been focused on discovering anti-cancer polysaccharides and modified derivatives for the development of effective therapeutics for various human cancers. This review highlights recent advances on the major chemical modification methods of polysaccharides, and discusses the effect of molecular modification on the physicochemical properties and anti-tumor activities of polysaccharides. Meanwhile, the underlying anti-tumor mechanisms of polysaccharide and its modified derivatives were also discussed.

Pinocembrin-Enriched Fractions of Elytranthe parasitica (L.) Danser Modulates Apoptotic and MAPK Cellular Signaling in HepG2 Cells

Background:

Hepatocellular carcinoma (HCC) is the fifth leading cause of cáncer mortality. Elytranthe parasitica (L.) Danser (EP), a hemiparasitic plant (Loranthaceae) has potent anti-cancer properties.

Objective:

In the study, we investigated the effect of EP fractions on the expression of apoptosis and mitogenactivated protein kinase (MAPK) markers deregulated in HCC. Bioactivity fractionation was performed to isolate the phytochemical(s) exerting anti-tumor activity in HepG2 cells.

Method:

Anti-proliferative, clonogenic and anti-metastatic effects of EP fractions were examined in hepatocellular carcinoma cell line, HepG2 by Sulphorhodamine B, colony formation and scratch wound assays respectively in hepatocellular cell line, HepG2. The effects of EP fractions on key markers of apoptosis and MAPK signaling pathways were explored. </P><P> Key findings: EP bioactive fractions showed significant anti-tumor potential, reduced clonogenicity and considerably inhibited cell migration in HepG2 cells in vitro. The fractions augmented annexin V binding and induced apoptosis by causing cell cycle arrest at G2/M and S phase checkpoints. The fractions increased expression levels of p53, bad, cleaved PARP (Poly ADP ribose polymerase) and cleaved Caspase-3. Expression levels of phosphorylated ERK1/2 (Extracellular signal-regulated kinase) were downregulated. Pinocembrin-7-O-ß-D-glucoside and chrysin were isolated and characterized for the first time from Elytranthe parasitica (L.) Danser.

Conclusion:

Our findings reveal that EP fractions induced cell cycle arrest and triggered apoptosis in HepG2 cells by upregulating apoptosis and deactivating MAPK pathway. It signifies that pinocembrin glycoside and chrysin are bioactive phytochemicals contributing to the potent anti-hepatocarcinoma effects on HepG2 cells. Hence, bioactive EP fractions could be used as a therapeutic agent for effective HCC therapy.

HPLC analysis, optimization of extraction and purification conditions, biological evaluation of total protoflavones from Macrothelypteris viridifrons

The present study aims to evaluate phytochemical and pharmacological potential of total protoflavones from Macrothelypteris viridifrons. In the phytochemical study, an HPLC analysis method was established, and the optimal extraction and purification conditions were analyzed. The extractive condition was optimized as follows: the backflow extraction with 20 folds of 70% ethanol at 80◦C for 1 h twice. Moreover, by combining the alkali-extraction and acid-precipitation method with the macroporous resin purification technology, the final purity rate of total protoflavones was no less than 54.85%. In the pharmacological study, the total protoflavones from M. viridifrons showed a significant tumor-inhibitory effect in the H22 hepatoma cells transplantation model with a higher inhibitory rate of 55.76% in high dosage (100mg/kg) treatment group compared with the positive control group (20 mg/kg cyclophosphamide). Taken of all, these results support that protoflavones are the material basis of M. viridifrons as an anticancer folk medicine.

Exopolysaccharides produced by Lactobacillus strains suppress HT-29 cell growth via induction of G0/G1 cell cycle arrest and apoptosis

In the present study, the effects of exopolysaccharides (EPS) from nine Lactobacillus strains with a high degree of bio-activity on human colon cancer cell line HT-29 were studied. The extracellular polymeric substances from 4 strains, namely K11, M5, SB27 and ×12, displayed desirable anti-proliferative activity against HT-29 cells. Crude and acidic EPS were purified from the 4 strains and the inhibitory effects were further investigated. The crude and acidic EPS from these 4 strains exerted anti-proliferation effects on HT-29 cells in a dose-dependent manner but were nontoxic to Vero cells. Treatment with EPS significantly induced G0/G1 cell cycle arrest and apoptosis of HT-29 cells. Hoechst 33258 staining of acidic EPS-treated HT-29 cells revealed different degrees of morphological changes within the nucleus and the formation of apoptotic bodies. Caspase-3 activity was markedly upregulated in HT-29 cells following treatment with acidic EPS. In addition, acidic EPS from the SB27 strain demonstrated the most robust inhibitory effect on HT-29 cells. The results of the present study suggest that as an inducer of apoptosis EPS has the potential to be applied in the treatment of colorectal cancer.

Cudraflavone C Induces Apoptosis of A375.S2 Melanoma Cells through Mitochondrial ROS Production and MAPK Activation

Melanoma is the most malignant form of skin cancer and is associated with a very poor prognosis. The aim of this study was to evaluate the apoptotic effects of cudraflavone C on A375.S2 melanoma cells and to determine the underlying mechanisms involved in apoptosis. Cell viability was determined using the MTT and real-time cytotoxicity assays. Flow cytometric evaluation of apoptosis was performed after staining the cells with Annexin V-FITC and propidium iodide. The mitochondrial membrane potential was evaluated using the JC-1 assay. Cellular ROS production was measured using the CellROX assay, while mitochondrial ROS production was evaluated using the MitoSOX assay. It was observed that cudraflavone C inhibited growth in A375.S2 melanoma cells, and promoted apoptosis via the mitochondrial pathway mediated by increased mitochondrial ROS production. In addition, cudraflavone C induced phosphorylation of MAPKs (p38, ERK, and JNK) and up-regulated the expression of apoptotic proteins (Puma, Bax, Bad, Bid, Apaf-1, cytochrome C, caspase-9, and caspase-3/7) in A375.S2 cells. Pretreatment of A375.S2 cells with MitoTEMPOL (a mitochondria-targeted antioxidant) attenuated the phosphorylation of MAPKs, expression of apoptotic proteins, and the overall progression of apoptosis. In summary, cudraflavone C induced apoptosis in A375.S2 melanoma cells by increasing mitochondrial ROS production; thus, activating p38, ERK, and JNK; and increasing the expression of apoptotic proteins. Therefore, cudraflavone C may be regarded as a potential form of treatment for malignant melanoma.

Crosstalk of mitochondria with NADPH oxidase via reactive oxygen and nitrogen species signalling and its role for vascular function

Cardiovascular diseases are associated with and/or caused by oxidative stress. This concept has been proven by using the approach of genetic deletion of reactive species producing (pro-oxidant) enzymes as well as by the overexpression of reactive species detoxifying (antioxidant) enzymes leading to a marked reduction of reactive oxygen and nitrogen species (RONS) and in parallel to an amelioration of the severity of diseases. Likewise, the development and progression of cardiovascular diseases is aggravated by overexpression of RONS producing enzymes as well as deletion of antioxidant RONS detoxifying enzymes. Thus, the consequences of the interaction (redox crosstalk) of superoxide/hydrogen peroxide produced by mitochondria with other ROS producing enzymes such as NADPH oxidases (Nox) are of outstanding importance and will be discussed including the consequences for endothelial nitric oxide synthase (eNOS) uncoupling as well as the redox regulation of the vascular function/tone in general (soluble guanylyl cyclase, endothelin-1, prostanoid synthesis). Pathways and potential mechanisms leading to this crosstalk will be analysed in detail and highlighted by selected examples from the current literature including hypoxia, angiotensin II-induced hypertension, nitrate tolerance, aging and others. The general concept of redox-based activation of RONS sources via "kindling radicals" and enzyme-specific "redox switches" will be discussed providing evidence that mitochondria represent key players and amplifiers of the burden of oxidative stress.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Stevioside induced cytotoxicity in colon cancer cells via reactive oxygen species and mitogen-activated protein kinase signaling pathways-mediated apoptosis

The role of mitogen-activated protein kinase (MAPK) signaling pathways in cell growth and differentiation has been well established. The present study aimed to investigate the anti-proliferative effect of stevioside on human colon cancer HT-29 cells. Additionally, the effect of stevioside on cell cycle arrest and MAPK signaling pathways in HT-29 cells was explored. Stevioside was observed to significantly inhibit cancer cell growth at a dose of 5 µM at 48 and 72 h. A dose-dependent increase in the apoptosis rate was observed with cell cycle arrest at G2/M phase. In addition, caspase-9 and caspase-3 activity also increased. An increase in reactive oxygen species (ROS) production and a decrease in the mitochondrial membrane potential indicated that the mitochondrial-mediated intrinsic pathway is responsible for apoptotic activity. These results were additionally verified by the elevated expression level of phosphorylated p38 and extracellular signal-regulated kinase mitogen-activated protein kinases (MAPKs). Additionally, by inhibiting ROS production and MAPK activation, the antiproliferative effect of stevioside was suppressed, confirming the hypothesis that ROS and MAPK proteins induce apoptosis in human colon cancer HT-29 cells.

Phytochemicals from fern species: potential for medicine applications

Ferns are an important phytogenetic bridge between lower and higher plants. Historically they have been used in many ways by humans, including as ornamental plants, domestic utensils, foods, and in handicrafts. In addition, they have found uses as medicinal herbs. Ferns produce a wide array of secondary metabolites endowed with different bioactivities that could potentially be useful in the treatment of many diseases. However, there is currently relatively little information in the literature on the phytochemicals present in ferns and their pharmacological applications, and the most recent review of the literature on the occurrence, chemotaxonomy and physiological activity of fern secondary metabolites was published over 20 years ago, by Soeder (Bot Rev 51:442-536, 1985). Here, we provide an updated review of this field, covering recent findings concerning the bioactive phytochemicals and pharmacology of fern species.

Mitogen-activated protein kinases are involved in hepatocanalicular dysfunction and cholestasis induced by oxidative stress

In previous studies, we showed that the pro-oxidant model agent tert-butyl hydroperoxide (tBuOOH) induces alterations in hepatocanalicular secretory function by activating Ca²⁺-dependent protein kinase C isoforms (cPKC), via F-actin disorganization followed by endocytic internalization of canalicular transporters relevant to bile formation (Mrp2, Bsep). Since mitogen-activated protein kinases (MAPKs) may be downstream effectors of cPKC, we investigated here the involvement of the MAPKs of the ERK1/2, JNK1/2, and p38^MAPK types in these deleterious effects. tBuOOH (100 µM, 15 min) increased the proportion of the active, phosphorylated forms of ERK1/2, JNK1/2, and p38^MAPK, and panspecific PKC inhibition with bisindolylmaleimide-1 (100 nM) or selective cPKC inhibition with Gö6976 (1 μM) prevented the latter two events. In isolated rat hepatocyte couplets, tBuOOH (100 µM, 15 min) decreased the canalicular vacuolar accumulation of the fluorescent Bsep and Mrp2 substrates, cholylglycylamido fluorescein, and glutathione-methylfluorescein, respectively, and selective inhibitors of ERK1/2 (PD098059), JNK1/2 (SP600125), and p38^MAPK (SB203580) partially prevented these alterations. In in situ perfused rat livers, these three MAPK inhibitors prevented tBuOOH (75 µM)-induced impairment of bile flow and the decrease in the biliary output of the Bsep and Mrp2 substrates, taurocholate, and dinitrophenyl-S-glutathione, respectively. The changes in Bsep/Mrp2 and F-actin localization induced by tBuOOH, as assessed by (immuno)fluorescence staining followed by analysis of confocal images, were prevented total or partially by the MAPK inhibitors. We concluded that MAPKs of the ERK1/2, JNK1/2, and p38^MAPK types are all involved in cholestasis induced by oxidative stress, by promoting F-actin rearrangement and further endocytic internalization of canalicular transporters critical for bile formation.

Functional Toxicogenomic Assessment of Triclosan in Human HepG2 Cells Using Genome-Wide CRISPR-Cas9 Screening

There are thousands of chemicals used by humans and detected in the environment for which limited or no toxicological data are available. Rapid and cost-effective approaches for assessing the toxicological properties of chemicals are needed. We used CRISPR-Cas9 functional genomic screening to identify the potential molecular mechanism of a widely used antimicrobial triclosan (TCS) in HepG2 cells. Resistant genes at IC50 (the concentration causing a 50% reduction in cell viability) were significantly enriched in the adherens junction pathway, MAPK signaling pathway, and PPAR signaling pathway, suggesting a potential role in the molecular mechanism of TCS-induced cytotoxicity. Evaluation of the top-ranked resistant genes, FTO (encoding an mRNA demethylase) and MAP2K3 (a MAP kinase kinase family gene), revealed that their loss conferred resistance to TCS. In contrast, sensitive genes at IC10 and IC20 were specifically enriched in pathways involved with immune responses, which was concordant with transcriptomic profiling of TCS at concentrations of <IC10. It is suggested that the CRISPR-Cas9 fingerprint may reveal the patterns of TCS toxicity at low concentration levels. Moreover, we retrieved the potential connection between CRISPR-Cas9 fingerprint and disease terms, obesity, and breast cancer from an existing chemical-gene-disease database. Overall, CRISPR-Cas9 functional genomic screening offers an alternative approach for chemical toxicity testing.

Oxalicumone A, a new dihydrothiophene-condensed sulfur chromone induces apoptosis in leukemia cells through endoplasmic reticulum stress pathway

Oxalicumone A (POA1), a novel dihydrothiophene-condensed sulfur chromone isolated from the marine fungus Penicillium oxalicum SCSGAF 0023, showed cytotoxicity against several cancer cells previously. In this study, its anti-cancer activity and underlying mechanism of this action were investigated in leukemia cells like KG-1a, HL60, U937, and K562. The results showed that POA1 inhibited dose-/time-dependently cell growth and induced apoptosis in leukemia cells. Also, POA1 caused cleavages of caspase-3, 8, 9 and PARP1, loss of mitochondrial membrane potential, up-regulations of phosphorylated p38 and JNK, and activation of endoplasmic reticulum stress (ER stress). Furthermore, 4-PBA (an ER stress inhibitor) but not SP600125 and SB203580 (JNK and p38 inhibitor, respectively) could largely inhibit POA1-induced growth suppression. Additionally, 4-PBA obstructed mitochondrial depolarization and cleavage of PARP1. These data suggested that ER stress pathway might be an important mediator in POA1-induced apoptosis. In conclusion, POA1 may have antitumor effects in leukemia cells through the induction of ER stress pathway.

FV-429 Induced Apoptosis Through ROS-Mediated ERK2 Nuclear Translocation and p53 Activation in Gastric Cancer Cells

Following our previous finding which revealed that FV-429 induces apoptosis in human hepatocellular carcinoma HepG2 cells, in this study, we found that FV-429 could also induce apoptosis in human gastric cancer cells. Firstly, FV-429 inhibited the viability of BGC-823 and MGC-803 cells with IC50 values in the range of 38.10 ± 6.28 and 31.53 ± 6.84 µM for 24 h treatment by MTT-assay. Secondly, FV-429 induced apoptosis in BGC-823 and MGC-803 cells through the mitochondrial-mediated pathway, showing an increase in Bax/Bcl-2 ratios, and caspase-9 activation, without change in caspase-8. Further research revealed that the mitogen-activated protein kinases, including c-Jun N-terminal kinase, extracellular regulated kinase, and p38 mitogen-activated protein kinase, could be activated by FV-429-induced high level ROS. Moreover, FV-429 also promoted the ERK2 nuclear translocation, resulting in the co-translocation of p53 to the nucleus and increased transcription of p53-regulated proapoptotic genes. FV-429 significantly inhibited the nude mice xenograft tumors growth of BGC-823 or MGC-803 cells in vivo.

The p53-inducible gene 3 involved in flavonoid-induced cytotoxicity through the reactive oxygen species-mediated mitochondrial apoptotic pathway in human hepatoma cells

Flavonoids have been reported to exhibit prooxidant cytotoxicity against cancer cells, but the underlying mechanism is still poorly understood. Here we investigated the potential mechanism that p53-inducible gene 3 (PIG3), a NADPH:quinone oxidoreductase, mediated the prooxidant cytotoxicity of flavonoids on human hepatoma HepG2 cells. The results showed that flavonoids (apigenin, luteolin, kaempferol, and quercetin) inhibited the growth of HepG2 cells in a dosage- and time-dependent manner, and induced the morphological changes characteristic of apoptosis in HepG2 cells. We also found that expression of PIG3 was increased markedly in HepG2 cells treated with flavonoids at both mRNA and protein levels, which was accompanied by increased intracellular ROS production and a decreased mitochondrial membrane potential (ΔΨm). All these effects were largely reversed through knockdown of the PIG3 gene in HepG2 cells. Western blotting indicated that flavonoids increased cytochrome c release, upregulated the ratio of Bax/Bcl-2, and activated the caspases-9 and -3. Moreover, knockdown of PIG3 could reverse the changes of these apoptotic-related proteins. These results suggest that PIG3 plays an important role in regulating the prooxidant activity and apoptosis-inducing action of flavonoids on HepG2 cells though the ROS-triggered mitochondrial apoptotic pathway.

Apoptotic events induced by high glucose in human hepatoma HepG2 cells involve endoplasmic reticulum stress and MAPK's activation

To investigate whether endoplasmic reticulum (ER) stress participates in the induction of apoptosis in HepG2 cells exposed to high glucose and explore its probable mechanism. A series of experiments were performed following HepG2 cells treated with different concentrations of glucose for 48 h. The apoptosis was detected by means of Hoechst staining and flow cytometry. Caspase-3 activity assay was performed by measuring the pNA (p-nitroaniline) to indirectly reveal the catalytic activity of caspase-3. The expression levels of apoptosis-, ER stress-associated proteins and MAPKs were analyzed by western blot. To further characterize the molecular mechanisms, the effects of antioxidant alpha-lipoic acid (ALA) and specific inhibitors for JNK and p38 (SP600125 and SB203580, respectively) were examined by Hoechst staining, immunofluorescence, and western blot. After HepG2 cells were incubated with high glucose for 48 h, both Hoechst staining and flow cytometry analyses unveiled the apoptosis of HepG2 cells. Caspase-3 activity assay revealed that the activity of caspase-3 was enhanced. Western blot showed an enhancement of pro-caspase-9 degradation, a reduction of Bcl-2/Bax ratio, a decrease in GRP78 expression, and increases in CHOP and p47/phox levels. In addition, western blot analysis presented that phosphorylation of p38 and JNK was triggered and that the expression of ASK1 was elevated. In the case of the contributions of oxidative stress and the MAPK signaling pathways, all ALA, SP600125 and SB203580 were able to largely rescue high glucose-induced apoptosis. High glucose induced the apoptosis in HepG2 cells through the activation of ASK1-p38/JNK pathway mediated by ER stress and oxidative stress.

Alkali-soluble polysaccharide, isolated from Lentinus edodes, induces apoptosis and G2/M cell cycle arrest in H22 cells through microtubule depolymerization

The aim of the study was to evaluate the pro-apoptotic effects of polysaccharides derived from Lentinus edodes and further elucidated the mechanisms of this action. Our results demonstrated that marked morphological changes of apoptosis were observed after treatment of L. edodes polysaccharides [Lentinan (LTN)]. Moreover, LTN-induced cell apoptosis was characterized by a rapid stimulation of reactive oxygen species production, the loss of mitochondrial membrane potential and an increase in intracellular concentration of Ca(2+) . In addition, the results of the haematoxylin and eosin and TUNEL assay further confirmed that LTN-induced apoptosis in vivo. Furthermore, flow cytometry analysis showed that LTN could arrest the cell cycle at G2/M phase, and immunofluorescence showed LTN caused disruption of microtubule. These results suggest that disruption of cellular microtubule network, arrest of the cell cycle at G2/M phase and induction of apoptosis may be one of the possible mechanisms of anti-tumour effect of LTN.

N-acetyl-serotonin protects HepG2 cells from oxidative stress injury induced by hydrogen peroxide

Oxidative stress plays an important role in the pathogenesis of liver diseases. N-Acetyl-serotonin (NAS) has been reported to protect against oxidative damage, though the mechanisms by which NAS protects hepatocytes from oxidative stress remain unknown. To determine whether pretreatment with NAS could reduce hydrogen peroxide- (H₂O₂-) induced oxidative stress in HepG2 cells by inhibiting the mitochondrial apoptosis pathway, we investigated the H₂O₂-induced oxidative damage to HepG2 cells with or without NAS using MTT, Hoechst 33342, rhodamine 123, Terminal dUTP Nick End Labeling Assay (TUNEL), dihydrodichlorofluorescein (H2DCF), Annexin V and propidium iodide (PI) double staining, immunocytochemistry, and western blot. H₂O₂ produced dramatic injuries in HepG2 cells, represented by classical morphological changes of apoptosis, increased levels of malondialdehyde (MDA) and intracellular reactive oxygen species (ROS), decreased activity of superoxide dismutase (SOD), and increased activities of caspase-9 and caspase-3, release of cytochrome c (Cyt-C) and apoptosis-inducing factor (AIF) from mitochondria, and loss of membrane potential (ΔΨ_m). NAS significantly inhibited H₂O₂-induced changes, indicating that it protected against H₂O₂-induced oxidative damage by reducing MDA levels and increasing SOD activity and that it protected the HepG2 cells from apoptosis through regulating the mitochondrial apoptosis pathway, involving inhibition of mitochondrial hyperpolarization, release of mitochondrial apoptogenic factors, and caspase activity.

Apoptosis Induction by the Total Flavonoids from Arachniodes exilis in HepG2 Cells through Reactive Oxygen Species-Mediated Mitochondrial Dysfunction Involving MAPK Activation

Arachniodes exilis is used as a folk medicine in China and proved to have antibacterial, anti-inflammatory, and sedative activities. In the present study, the antitumor effect of the total flavonoids of A. exilis (TFAE) against HepG2 cells was evaluated. The results showed that TFAE inhibited the growth of HepG2 cells in a dosage- and time-dependent manner. Flow cytometry and Hoechst 33342 fluorescence staining results showed that TFAE could significantly increase the apoptosis ratio of HepG2 cells, which is accompanied with increased intracellular reactive oxygen species (ROS) production and decreased mitochondrial membrane potential (ΔΨm). Western blotting indicated that TFAE downregulated the ratio of Bcl-2/Bax, increased cytochrome c release, and activated the caspases-3 and -9. Further analysis showed that TFAE stimulated the mitogen-activated protein kinase (MAPK). However, treatment with NAC (reactive oxygen species scavenger) and MAPK-specific inhibitors (SP600125 and SB203580) could reverse the changes of these apoptotic-related proteins. These results suggested that TFAE possessed potential anticancer activity in HepG2 cells through ROS-mediated mitochondrial dysfunction involving MAPK pathway.

A novel compound RY10-4 induces apoptosis and inhibits invasion via inhibiting STAT3 through ERK-, p38-dependent pathways in human lung adenocarcinoma A549 cells

Previous reports suggested that protoapigenone showed remarkable antitumor activities against a broad spectrum of human cancer cell lines, but had no effect on human lung adenocarcinoma A549 cell. The lack of effective remedies had necessitated the application of new therapeutic scheme. A novel compound RY10-4 which has the similar structure close to protoapigenone showed better antitumor activity. Treatment with RY10-4 inhibited the expression of pro-caspase-3, pro-caspase-9, Bcl-2 as well as phosphorylation of signal transducer and activator of transcription-3 (p-STAT3). It also reduced the expressions of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and increases the expressions of reversion-inducing cysteine-rich protein with kazal motifs (RECK), as well as tissue inhibitor of metalloproteinase (TIMP) via inhibiting STAT3 by activating the mitogen-activated protein (MAP) kinases (the c-Jun N-terminal kinase (JNK), the p38 and extracellular signal-regulated kinase (ERK)) in A549 cells treated with RY10-4. Moreover, the cytotoxic effect of RY10-4 was induction of apoptosis in A549 cells by enhancing production of reactive oxygen species (ROS). Taken together, the observations suggested that RY10-4 had affected Bcl-2 family members, caspases, MMPs, TIMPs expressions and ROS production via inhibiting STAT3 activities through ERK and p38 pathways in A549 cells.

Structure and inducing tumor cell apoptosis activity of polysaccharides isolated from Lentinus edodes

In this study, five novel polysaccharides SLNT1, SLNT2, JLNT1, JLNT2, and JLNT3 were isolated from the fruit body of Lentinus edodes. Chemical and physical analyses showed that the five polysaccharides consist of glucose with the structure of β-(1→3)-d-glucose main chains and β-(1→6)-d-glucose side chains. Moreover, all of them had triple-helical conformation and different molecular weight distributions. Animal studies further demonstrated that the antitumor effects were remarkably improved by SLNT1 and JLNT1 treatments with the inhibitory rates of 65.41% and 61.07% in H22-bearing mice, respectively. Additionally, both of them significantly increased the levels of serum IL-2 and TNF-α production and induced the tumor cell apoptosis. Taken together, our findings revealed that the involved antitumor mechanisms possibly in part were mediated not only by enhancing the immunity but also by directly killing the tumor and the induction of tumor cell apoptosis in H22-bearing mice.

Olaquindox-induced apoptosis is suppressed through p38 MAPK and ROS-mediated JNK pathways in HepG2 cells

We investigated mitogen-activated protein kinase (MAPK) pathways as well as reactive oxygen species (ROS) in olaquindox-induced apoptosis. Exposure of HepG2 cells to olaquindox resulted in the phosphorylation of p38 MAPK and c-Jun N-terminal kinases (JNK). To confirm the role of p38 MAPK and JNK, HepG2 cells were pretreated with MAPKs-specific inhibitors prior to olaquindox treatment. Olaquindox-induced apoptosis was significantly potentiated by the JNK inhibitor (SP600125) or the p38 MAPK inhibitor (SB203580). Furthermore, we observed that olaquindox treatment led to ROS generation and that olaquindox-induced apoptosis and ROS generation were both significantly reduced by the antioxidants, superoxide dismutase and catalase. In addition, the levels of phosphorylation of JNK, but not p38 MAPK, were significantly suppressed after pretreatment of the antioxidants, while inhibition of the activations of JNK or p38 MAPK had no effect on ROS generation. This result suggested that ROS may be the upstream mediator for the activation of JNK. Conclusively, our results suggested that apoptosis in response to olaquindox treatment in HepG2 cells might be suppressed through p38 MAPK and ROS-JNK pathways.

The synthetic flavonoid WYC02-9 inhibits colorectal cancer cell growth through ROS-mediated activation of MAPK14 pathway

AIM

Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. In this study, we explored the anti-cancer activity of WYC02-9, a synthetic protoapigenone, on human HCT116 CRC cells.

MAIN METHODS

The anti-cancer activity of WYC02-9 and its underlying mechanisms were analyzed using XTT cell proliferation assays, colony formation assays, FACS analysis, annexin V staining, immunoblotting analysis, reactive oxygen species (ROS) generation assays, soft agar assays, a nude mice xenograft study and immunohistochemistry assays.

KEY FINDINGS

Data showed that WYC02-9 suppressed CRC cell growth by arresting cells at G2/M and inducing cell death via apoptotic pathways. Further analysis demonstrated that WYC02-9-induced apoptosis was mediated by the activation of a ROS-mediated MAPK14 pathway. An in vivo xenograft study revealed that WYC02-9 enhanced MAP2K3/6 and MAPK14 phosphorylation, induced apoptosis, and suppressed CRC tumor growth.

SIGNIFICANCE

WYC02-9 exerts its anti-tumor effect via ROS/MAPK14-induced apoptosis and has the potential to be developed as a chemotherapeutic agent for CRC.

DICO, a novel nonaromatic B-ring flavonoid, induces G2/M cell cycle arrest and apoptosis in human hepatoma cells

DICO was a novel nonaromatic B-ring flavonoid obtained from Macrothelypteris torresiana. In the present work, we investigated the antitumor activity and the antineoplastic mechanism of DICO. Our study showed that DICO inhibited the growth of HepG2 cells in dose and time-dependent manners. As well as DICO induced G2/M cell cycle arrest and apoptosis via a ROS-mediated mitochondrial pathway. Western blot assay demonstrated that DICO decreased Bcl-2 level and induced Bax translocation to cause cytochrome c release. Subsequently, caspase-9 and caspase-3 were activated. Meanwhile, the alterations of cyclin A and B1, p-CDK1 and p-cdc25c levels were also observed in response to DICO treatment. Taken together, DICO displayed a significant antitumor effect through G2/M cell cycle arrest and apoptosis induction, which suggested DICO might have therapeutic potential against tumors.

Deltonin induces apoptosis in MDA‑MB‑231 human breast cancer cells via reactive oxygen species‑mediated mitochondrial dysfunction and ERK/AKT signaling pathways

Deltonin, a steroidal saponin isolated from Dioscorea zingiberensis Wright, exhibits high cytotoxic activity in cancer cells. In the present study, the effects of deltonin on cell proliferation and apoptosis were evaluated in the MDA‑MB‑231 human breast carcinoma cell line. Following treatment with deltonin, the viability of MDA‑MB‑231 cells was analyzed using MTT assay and apoptosis, mitochondrial membrane potential (∆Ψm) alternation and intracellular reactive oxygen species (ROS) generation was determined by flow cytometry. In addition, western blot analysis was performed to examine the expression of apoptosis‑associated proteins. The results demonstrated that deltonin induced apoptosis in MDA‑MB‑231 cells in a time‑ and concentration‑dependent manner. Apoptosis was associated with depolarization of ∆Ψm and time‑dependent ROS generation. Deltonin treatment also resulted in Bax upregulation, Bcl-2 downregulation, activation of caspase‑3 and ‑8 and poly (ADP ribose) polymerase cleavage. Decreased levels of phosphorylated extracellular signal‑regulated kinase (ERK) and phosphorylated AKT were also observed. Results indicate that the proliferation inhibitory effect of deltonin is associated with its apoptosis‑inducing effect, which may correlate with ROS‑mediated mitochondrial dysfunction as well as activation of the ERK/AKT signaling pathways. Therefore, deltonin may be a potential chemotherapeutic agent for the treatment of breast cancer.

A new protoapigenone analog RY10-4 induces apoptosis and suppresses invasion through the PI3K/Akt pathway in human breast cancer

RY10-4, a novel protoapigenone analog, shows potent cytotoxicity against a broad spectrum of human cancer cells. Here we investigate its anti-tumor activity on breast cancer. The results indicated that RY10-4 suppressed proliferation, arrested cell cycle, induced apoptosis and inhibited invasion in MDA-MB-231, MCF-7 and SKBR3 breast cancer cells. Western blot analysis showed that RY10-4 down-regulated the PI3K/Akt signaling pathway and inhibited doxorubicin-induced p-Akt. Moreover, it effectively suppressed tumor growth in mice without major side effects. Therefore, RY10-4 had potential anti-tumor activity, and could be used as a lead to design more potent derivatives.

Hispolon induces apoptosis and cell cycle arrest of human hepatocellular carcinoma Hep3B cells by modulating ERK phosphorylation

Hispolon is an active phenolic compound of Phellinus igniarius , a mushroom that has recently been shown to have antioxidant, anti-inflammatory, and anticancer activities. This study investigated the antiproliferative effect of hispolon on human hepatocellular carcinoma Hep3B cells by using the MTT assay, DNA fragmentation, DAPI (4,6-diamidino-2-phenylindole dihydrochloride) staining, and flow cytometric analyses. Hispolon inhibited cellular growth of Hep3B cells in a time-dependent and dose-dependent manner, through the induction of cell cycle arrest at S phase measured using flow cytometric analysis and apoptotic cell death, as demonstrated by DNA laddering. Hispolon-induced S-phase arrest was associated with a marked decrease in the protein expression of cyclins A and E and cyclin-dependent kinase (CDK) 2, with concomitant induction of p21waf1/Cip1 and p27Kip1. Exposure of Hep3B cells to hispolon resulted in apoptosis as evidenced by caspase activation, PARP cleavage, and DNA fragmentation. Hispolon treatment also activated JNK, p38 MAPK, and ERK expression. Inhibitors of ERK (PB98095), but not those of JNK (SP600125) and p38 MAPK (SB203580), suppressed hispolon-induced S-phase arrest and apoptosis in Hep3B cells. These findings establish a mechanistic link between the MAPK pathway and hispolon-induced cell cycle arrest and apoptosis in Hep3B cells.

A novel non-aromatic B-ring flavonoid: isolation, structure elucidation and its induction of apoptosis in human colon HT-29 tumor cell via the reactive oxygen species-mitochondrial dysfunction and MAPK activation

The aim of the present study was to elucidate the chemical structure of a novel non-aromatic B-ring flavonoid (DHEC) isolated from Macrothelypteris viridifrons and to evaluate its putative molecular mechanism of action on induction of apoptosis in human colon HT-29 cancer cell. On the basis of MS, UV, IR, 1D and 2D NMR data, DHEC was identified as 2-(cis-1, 2-dihydroxy-4-oxo-cyclohex-5-enyl)-5-hydroxy-7-ethoxy-chromone. In addition, the cytotoxicity of DHEC and its effect on induction of apoptosis were confirmed by several assays. After treatment of HT-29 cell with DHEC, we observed the accumulation of intracellular reactive oxygen species, the loss of mitochondrial membrane potential, the alteration of expression of the Bcl-2 family members, the releasing of cytochrome c, the cleavage of poly (ADP-ribose) polymerase (PARP), and the activation of caspase-3, -8, and -9. Further analysis showed that the mitogen-activated protein kinase (MAPK) related proteins were stimulated by treatment with DHEC. These results suggest that DHEC exhibits potential anti-cancer activity in HT-29 cell through induction of apoptosis, which may highly be associated with reactive oxygen species-mitochondrial dysfunction as well as activation of MAPK signaling pathway.