The flavonoid quercetin induces apoptosis and inhibits migration through a MAPK-dependent mechanism in osteoblasts

Isoginkgetin exerts apoptotic effects on A375 melanoma cells

Many plants produce secondary metabolites, known as flavonoids, which are thought to exhibit anti-cancer properties. Ginkgo biloba , a plant traditionally used in Chinese herbal medicine, is known to produce over 40 different secondary metabolites. Isoginkgetin, a biflavanoid from this species, has been demonstrated to be cytotoxic to different cancer cell lines. In this study, the anti-cancer effects of isoginkgetin were tested on A375 melanoma cells. XTT cell viability analysis revealed that isoginkgetin treatment resulted in a concentration dependent decrease in cell viability. To investigate whether apoptosis was induced in A375 cell treated with isoginkgetin, a western blot analysis was performed to detect PARP cleavage which is indicative of apoptosis. PARP cleavage was detected at all concentrations tested, with more pronounced cleavage observed with increasing isoginkgetin concentrations. To obtain insight into the potential mechanism of isoginkgetin induced apoptosis, we examined the involvement of the MAPK signaling pathway. We detected phosphorylated ERK in A375 cells treated with isoginkgetin which suggests that isoginkgetin might induce apoptosis of A375 cells through activation of the MAPK signaling pathway.

Kaempferol induces apoptosis through the MAPK pathway and regulates JNK-mediated autophagy in MC-3 cells

This study sought to determine the anticancer effect of kaempferol, a glycone-type flavonoid glycoside with various pharmacological benefits, on human oral cancer MC-3 cells. In vitro studies comprised a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, annexin V and propidium iodide staining, western blotting analysis, and acridine orange staining, while the in vivo studies entailed a xenograft model, hematoxylin and eosin staining, and TdT-mediated dUTP-biotin nick end labelling. In vitro, kaempferol reduced the rate of survival of MC-3 cells, mediated intrinsic apoptosis, increased the number of acidic vesicular organelles, and altered the expression of autophagy-related proteins. Further, treatment with the autophagy inhibitors revealed that the induced autophagy had a cytoprotective effect on apoptosis in kaempferol-treated MC-3 cells. Kaempferol also decreased the expression of phosphorylated extracellular signal-regulated kinase and increased that of phosphorylated c-Jun N-terminal kinase (p-JNK) and phosphorylated p38 kinase in MC-3 cells, suggesting the occurrence of mitogen-activated protein kinase-mediated apoptosis and JNK-mediated autophagy. In vivo, kaempferol reduced tumor growth inducing apoptosis and autophagy. These results showed that kaempferol has the potential use as an adjunctive agent in treating oral cancer.

Re-appraising the role of flavonols, flavones and flavonones on osteoblasts and osteoclasts- A review on its molecular mode of action

Bone disorders have become a global concern illustrated with decreased bone mineral density and disruption in microarchitecture of natural bone tissue organization. Natural compounds that promote bone health by augmenting osteoblast functions and suppressing osteoclast functions has gained much attention and offer greater therapeutic value compared to conventional therapies. Amongst several plant-based molecules, flavonoids act as a major combatant in promoting bone health through their multi-faceted biological activities such as antioxidant, anti-inflammatory, and osteogenic properties. They protect bone loss by regulating the signalling cascades involved in osteoblast and osteoclast functions. Flavonoids augment osteoblastogenesis and inhibits osteoclastogenesis through their modulation of various signalling pathways. This review discusses the role of various flavonoids and their molecular mechanisms involved in maintaining bone health by regulating osteoblast and osteoclast functions.

In vitro and in vivo effects of inhibitors on actin and myosin

The interaction of actin and myosin is essential for cell migration. We have identified kaempferol and pentahalogenated pseudilins as efficient inhibitors of migration of MDA-MB-231 breast adenocarcinoma cells. The compounds were studied with respect to possible effects on myosin-2-ATPase activity. The pentahalogenated pseudilins inhibited the enzyme activity in vitro. Flavonoids showed no effect on enzyme activity. The polymerization dynamics of actin was measured to test whether the integrity of F-actin is essential for the migration of MDA-MB-231 cells. Quercetin and kaempferol depolymerized F-actin with similar efficiencies as found for the pentahalogenated pseudilins, whereas epigallocatechin showed the weakest effect. As the inhibitory effect on cell migration may be caused by a toxic effect, we have performed a cytotoxicity test and, furthermore, investigated the influence of the test compounds on cardiac function in eleutheroembryos of medaka (Oryzias latipes). Compared with the pentahalogenated pseudilins, the cytotoxic and cardiotoxic effects of flavonoids on medaka embryos were found to be moderate.

Apigenin 7-O-glucoside promotes cell apoptosis through the PTEN/PI3K/AKT pathway and inhibits cell migration in cervical cancer HeLa cells

Epidemiologic evidence promote the inclusion of flavones in diet due to their inhibitory effects on certain types of cancers, particularly in women. Among the naturally occurring plant flavonoids, Apigenin 7-O-glucoside (AGL) is endowed with anti-inflammatory, anti-oxidant, and anti-cancer activities. However, its mechanism of action on cervical cancer, the fourth largest cancer in women, has not yet been clarified. In the current study, we have determined the effect of AGL on human cervical cancer cells and studied its molecular mechanism against cervical cancer. The results showed that AGL inhibited the proliferation of HeLa cells (IC₅₀ was 47.26 μM at 48 h) by inducing apoptosis. Furthermore, AGL treatment caused G0/G1 phase arrest, reduced mitochondrial membrane potential (MMP), and upgraded intracellular ROS production. AGL could promote the release of cytochrome c by regulating Bcl-2 family proteins, and then activated caspase 9/3 to promote cell apoptosis. Moreover, AGL treatment promoted the expression of p16 INK4A, while inhibited the expression of Cyclin A/D/E and CDK2/6. At the same time in HeLa cells treated with AGL, the PTEN/PI3K/AKT pathway was inhibited in a concentration-dependent manner, and cell migration was also impeded correspondingly through the matrix metalloproteinase 2 and 9. Our study may provide a new research direction for harnessing the novel natural compounds in cervical cancer treatment.

Antiangiogenic Activity of Flavonoids: A Systematic Review and Meta-Analysis

Abstract: An imbalance of angiogenesis contributes to many pathologies such as cancer, arthritis and retinopathy, hence molecules that can modulate angiogenesis are of considerable therapeutic importance. Despite many reports on the promising antiangiogenic properties of naturally occurring flavonoids, no flavonoids have progressed to the clinic for this application. This systematic review and meta-analysis therefore evaluates the antiangiogenic activities of a wide range of flavonoids and is presented in two sections. The first part of the study (Systematic overview) included 402 articles identified by searching articles published before May 2020 using ScienceDirect, PubMed and Web of Science databases. From this initial search, different classes of flavonoids with antiangiogenic activities, related pathologies and use of in vitro and/or in/ex vivo angiogenesis assays were identified. In the second part (Meta-analysis), 25 studies concerning the antiangiogenic evaluation of flavonoids using the in vivo chick chorioallantoic membrane (CAM) assay were included, following a targeted search on articles published prior to June 2020. Meta-analysis of 15 out of the 25 eligible studies showed concentration dependent antiangiogenic activity of six compared subclasses of flavonoids with isoflavones, flavonols and flavones being the most active (64 to 80% reduction of blood vessels at 100 µM). Furthermore, the key structural features required for the antiangiogenic activity of flavonoids were derived from the pooled data in a structure activity relationship (SAR) study. All in all, flavonoids are promising candidates for the development of antiangiogenic agents, however further investigations are needed to determine the key structural features responsible for their activity.

p38MAPK controls fibroblast growth factor 23 (FGF23) synthesis in UMR106-osteoblast-like cells and in IDG-SW3 osteocytes

BACKGROUND

p38 mitogen-activated protein kinase (p38MAPK) is a serine/threonine kinase activated by cellular stress stimuli including radiation, osmotic shock, and inflammation and influencing apoptosis, cell proliferation, and autophagy. Moreover, p38MAPK induces transcriptional activity of the transcription factor complex NFκB mediating multiple pro-inflammatory cellular responses. Fibroblast growth factor 23 (FGF23) is produced by bone cells, and regulates renal phosphate and vitamin D metabolism as a hormone. FGF23 expression is enhanced by NFκB. Here, we analyzed the relevance of p38MAPK activity for the production of FGF23.

METHODS

Fgf23 expression was analyzed by qRT-PCR and FGF23 protein by ELISA in UMR106 osteoblast-like cells and in IDG-SW3 osteocytes.

RESULTS

Inhibition of p38MAPK with SB203580 or SB202190 significantly down-regulated Fgf23 expression and FGF23 protein expression. Conversely, p38MAPK activator anisomycin increased the abundance of Fgf23 mRNA. NFκB inhibitors wogonin and withaferin A abrogated the stimulatory effect of anisomycin on Fgf23 gene expression.

CONCLUSION

p38MAPK induces FGF23 formation, an effect at least in part dependent on NFκB activity.

Molecular signaling mechanisms behind polyphenol-induced bone anabolism

For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.

Dietary flavonoids, luteolin and quercetin, inhibit invasion of cervical cancer by reduction of UBE2S through epithelial-mesenchymal transition signaling

We previously reported that the dietary flavonoids, luteolin and quercetin, might inhibit the invasiveness of cervical cancer by reversing epithelial-mesenchymal transition (EMT) signaling. However, the regulatory mechanism exerted by luteolin and quercetin is still unclear. This study analyzed the invasiveness activation by ubiquitin E2S ligase (UBE2S) through EMT signaling and inhibition by luteolin and quercetin. We found that UBE2S expression was significantly higher in highly invasive A431 subgroup III (A431-III) than A431-parental (A431-P) cells. UBE2S small interfering (si)RNA knockdown and overexpression experiments showed that UBE2S increased the migratory and invasive abilities of cancer cells through EMT signaling. Luteolin and quercetin significantly inhibited UBE2S expression. UBE2S showed a negative correlation with von Hippel-Lindau (VHL) and a positive correlation with hypoxia-induced factor (Hif)-1α. Our findings suggest that high UBE2S in malignant cancers contributes to cell motility through EMT signaling and is reversed by luteolin and quercetin. UBE2S might contribute to Hif-1α signaling in cervical cancer. These results show the metastatic inhibition of cervical cancer by luteolin and quercetin through reducing UBE2S expression, and provide a functional role for UBE2S in the motility of cervical cancer. UBE2S could be a potential therapeutic target in cervical cancer.

Quercetin-induced changes in femoral bone microstructure of adult male rabbits

Flavonoids are a group of plant metabolites with antioxidant effects. One of the most abundant flavonoids in the human diet is quercetin. It is found widely in fruits, vegetables and has a lot of beneficial effects on human health. Quercetin has a positive pharmacological effect on bone metabolism and it prevents the organism against bone loss. However, its impact on the size of basic structural units of the compact bone is still unknown. Therefore, the aim of present study was to investigate the impact of the quercetin on femoral bone microstructure in 5-month-old male rabbits. Five rabbits of Californian broiler line were randomly divided into two groups. In the experimental group (E group; n=3), animals were intramuscularly injected with quercetin at dose 1000 μg.kg-1 body weight (bw) for 90 days, 3 times per week. Two rabbits without quercetin administration served as a control group (C group). According to our results, intramuscular application of quercetin had an insignificant effect on cortical bone thickness in male rabbits. In these rabbits, changes in qualitative histological characteristics were present in the middle part of the compacta, where primary vascular longitudinal bone tissue was present and expanded there from the periosteum. Also, a lower number of secondary osteons was found in these animals. From the histomorphometrical point of view, significantly decreased sizes of primary osteons' vascular canals and secondary osteons (p <0.05) were found in rabbits administered by quercetin. Our findings indicate that subchronic administration of quercetin at the dose used in our study had considerable impact on both qualitative and quantitative histological characteristics of the compact bone in adult male rabbits.

p38 MAPK Signaling in Osteoblast Differentiation

The skeleton is a highly dynamic tissue whose structure relies on the balance between bone deposition and resorption. This equilibrium, which depends on osteoblast and osteoclast functions, is controlled by multiple factors that can be modulated post-translationally. Some of the modulators are Mitogen-activated kinases (MAPKs), whose role has been studied in vivo and in vitro. p38-MAPK modifies the transactivation ability of some key transcription factors in chondrocytes, osteoblasts and osteoclasts, which affects their differentiation and function. Several commercially available inhibitors have helped to determine p38 action on these processes. Although it is frequently mentioned in the literature, this chemical approach is not always as accurate as it should be. Conditional knockouts are a useful genetic tool that could unravel the role of p38 in shaping the skeleton. In this review, we will summarize the state of the art on p38 activity during osteoblast differentiation and function, and emphasize the triggers of this MAPK.

Biphasic Response to Luteolin in MG-63 Osteoblast-Like Cells under High Glucose-Induced Oxidative Stress

BACKGROUND

Clinical evidence indicates the diabetes-induced impairment of osteogenesis caused by a decrease in osteoblast activity. Flavonoids can increase the differentiation and mineralization of osteoblasts in a high-glucose state. However, some flavonoids such as luteolin may have the potential to induce cytotoxicity in osteoblast-like cells. This study was performed to investigate whether a cytoprotective concentration range of luteolin could be separated from a cytotoxic concentration range in human MG-63 osteoblast-like cells in high-glucose condition.

METHODS

Cells were cultured in a normal- or high-glucose medium. Cell viability was determined with the MTT assay. The formation of intracellular reactive oxygen species (ROS) was measured using probe 2',7' -dichlorofluorescein diacetate, and osteogenic differentiation was evaluated with an alkaline phosphatase bioassay.

RESULTS

ROS generation, reduction in alkaline phosphatase activity, and cell death induced by high glucose were inhibited by lower concentrations of luteolin (EC50, 1.29±0.23 µM). Oxidative stress mediated by high glucose was also overcome by N-acetyl-L-cysteine. At high concentrations, luteolin caused osteoblast cell death in normal- and high-glucose states (IC50, 34±2.33 and 27±2.42 µM, respectively), as represented by increased ROS and decreased alkaline phosphatase activity.

CONCLUSION

Our results indicated that the cytoprotective action of luteolin in glucotoxic condition was manifested in much lower concentrations, by a factor of approximately 26 and 20, than was its cytotoxic activity, which occurred under normal or glucotoxic condition, respectively.

Relationships among alcoholic liver disease, antioxidants, and antioxidant enzymes

Excessive consumption of alcoholic beverages is a serious cause of liver disease worldwide. The metabolism of ethanol generates reactive oxygen species, which play a significant role in the deterioration of alcoholic liver disease (ALD). Antioxidant phytochemicals, such as polyphenols, regulate the expression of ALD-associated proteins and peptides, namely, catalase, superoxide dismutase, glutathione, glutathione peroxidase, and glutathione reductase. These plant antioxidants have electrophilic activity and may induce antioxidant enzymes via the Kelch-like ECH-associated protein 1-NF-E2-related factor-2 pathway and antioxidant responsive elements. Furthermore, these antioxidants are reported to alleviate cell injury caused by oxidants or inflammatory cytokines. These phenomena are likely induced via the regulation of mitogen-activating protein kinase (MAPK) pathways by plant antioxidants, similar to preconditioning in ischemia-reperfusion models. Although the relationship between plant antioxidants and ALD has not been adequately investigated, plant antioxidants may be preventive for ALD because of their electrophilic and regulatory activities in the MAPK pathway.

Quercetin and the mitochondria: A mechanistic view

Quercetin is an important flavonoid that is ubiquitously present in the diet in a variety of fruits and vegetables. It has been traditionally viewed as a potent antioxidant and anti-inflammatory molecule. However, recent studies have suggested that quercetin may exert its beneficial effects independent of its free radical-scavenging properties. Attention has been placed on the effect of quercetin on an array of mitochondrial processes. Quercetin is now recognized as a phytochemical that can modulate pathways associated with mitochondrial biogenesis, mitochondrial membrane potential, oxidative respiration and ATP anabolism, intra-mitochondrial redox status, and subsequently, mitochondria-induced apoptosis. The present review evaluates recent evidence on the ability of quercetin to interact with the abovementioned pathways, and critically analyses how, such interactions can exert protection against mitochondrial damage in response to toxicity induced by several exogenously and endogenously-produced cellular stressors, and oxidative stress in particular.

Signaling proteins and pathways affected by flavonoids in leukemia cells

Flavonoids are a class of plant secondary metabolites that are found ubiquitously in plants and in the human diet. Our objective is to investigate the antiproliferative effects of flavonoids (baicalein, luteolin, genistein, apigenin, scutellarin, galangin, chrysin, and naringenin) toward leukemia cells (HL-60, NB4, U937, K562, Jurkat) as well as the relationship between their antileukemic potencies and molecular structures. At the proteomic level, we evaluate the effects of different flavonoids on the expression levels of various proteins using Protein Pathway Array (PPA) technology. Our results showed a dose-dependent cytotoxicity of flavonoids toward various types of leukemia cells. The results of PPA illustrated that flavonoids, such as baicalein, genistein, and scutellarin affected different proteins in different leukemia cell lines. Cell cycle regulatory proteins, such as CDK4, CDK6, Cyclin D1, Cyclin B1, p-CDC2, and p-RB were affected in different leukemia cells. Furthermore, we found that baicalein suppresses CDK4 and activates p-ERK in most leukemia cells; genistein mainly affects CDK4, p-ERK, p-CDC2, while scutellarin dysregulated the proteins, cell division control protein 42, Notch4, and XIAP. Collectively, a wide variety of dysregulation of key signaling proteins related to apoptosis and cell-cycle regulation contributes to the antileukemic properties of these flavonoids.

Flavonoids promoting HaCaT migration: II. Molecular mechanism of 4',6,7-trimethoxyisoflavone via NOX2 activation

Flavonoids are major active ingredients in plants and are considered components of food that provide medical or health benefits. They have diversified structures and have effects on human health, including wound healing induction. More than a hundred flavonoids were screened for HaCaT keratinocytes cellular migration measurements and the relationships between their structural properties and the effects promoting cellular migration were examined. Here, among flavonoids used in the previous structure-activity relationship calculations, 4',6,7-trimethoxyisoflavone (TMF) was one of the compounds showing the best activity, so that its molecular mechanism of the wound healing effect on HaCaT keratinocytes was investigated in more detail. Our data revealed that TMF increased the wound healing rate, but not the proliferation rate, in a dose-dependent manner. Treatment of keratinocytes with TMF influenced signaling pathways, affecting the phosphorylation of AKT and ERK in a time-dependent manner. TMF also induced the cell-cell adhesion protein E-cadherin, which is essential for promoting collective cell migration. Furthermore, the TMF treatment group also showed higher ROS and NOX2 transcriptional and protein levels. Correlating with matrix metalloproteinase induction by TMF, levels of extracellular matrix proteins such as collagens I and III were significantly lower in the treatment group. To confirm that the effects of TMF occur through the NOX2 pathway, we co-treated cells with TMF plus an NADPH inhibitor (DPI) or a ROS scavenger (NAC). Western blotting revealed that DPI and NAC attenuated the effect of TMF, suggesting that TMF induces ROS through the NOX2 pathway and regulates keratinocyte migration. In summary, TMF promotes wound healing through NOX2 induction, which leads to collective migration and MMP activation.

Quercetin reduces pluripotency, migration and adhesion of human teratocarcinoma cell line NT2/D1 by inhibiting Wnt/β-catenin signaling

In human teratocarcinoma cell line NT2/D1 quercetin exerts its anticancer effect through the inhibition of Wnt signaling.

Quercetin protects primary human osteoblasts exposed to cigarette smoke through activation of the antioxidative enzymes HO-1 and SOD-1

Smokers frequently suffer from impaired fracture healing often due to poor bone quality and stability. Cigarette smoking harms bone cells and their homeostasis by increased formation of reactive oxygen species (ROS). The aim of this study was to investigate whether Quercetin, a naturally occurring antioxidant, can protect osteoblasts from the toxic effects of smoking. Human osteoblasts exposed to cigarette smoke medium (CSM) rapidly produced ROS and their viability decreased concentration- and time-dependently. Co-, pre- and postincubation with Quercetin dose-dependently improved their viability. Quercetin increased the expression of the anti-oxidative enzymes heme-oxygenase- (HO-) 1 and superoxide-dismutase- (SOD-) 1. Inhibiting HO-1 activity abolished the protective effect of Quercetin. Our results demonstrate that CSM damages human osteoblasts by accumulation of ROS. Quercetin can diminish this damage by scavenging the radicals and by upregulating the expression of HO-1 and SOD-1. Thus, a dietary supplementation with Quercetin could improve bone matter, stability and even fracture healing in smokers.

4-Methylcatechol-induced oxidative stress induces intrinsic apoptotic pathway in metastatic melanoma cells

There has been a steady rise in fatalities associated with thick melanomas (>4mm). Although understanding of the biology of the disease has improved, effective treatment strategies for patients with advanced metastatic melanoma remain elusive. Therefore, more intensive testing of agents with therapeutic potential are needed to improve survival of patients with metastatic malignant melanoma. We have tested the ability of 4-methylcatechol, a metabolite of quercetin; a naturally occurring compound that is commonly found in a variety of fruits for its potential as an anti-melanoma agent. Our results show that 4-methylcatechol inhibits proliferation of melanoma cells in culture while not affecting the growth of normal human epidermal melanocytes. Further, the ability of metastatic melanoma cells to form colonies on soft agar was also inhibited. 4-Methylcatechol caused the accumulation of cells in G2/M phase of the cell cycle and induced apoptosis. There was an increase in reactive oxygen species following treatment with 4-methylcatechol that led to apoptosis through the intrinsic mitochondrial pathway. Treatment also inhibited cell survival mediated by Akt, a key player in melanoma cell survival. Taken together our results suggest that 4-methylcatechol exhibits cytotoxicity towards metastatic malignant melanoma cells while sparing normal melanocytes and should be tested further as a potential drug candidate for malignant melanoma.

Quercetin reduces neutrophil recruitment induced by CXCL8, LTB4, and fMLP: inhibition of actin polymerization

Recent in vitro data have suggested that the flavonoid quercetin (1) does not affect the functioning of neutrophils. Therefore, we evaluated in vivo and in vitro whether or not 1 affects neutrophil function, focusing on recruitment. The in vivo treatment with 1 inhibited in a dose-dependent manner the recruitment of neutrophils to the peritoneal cavity of mice induced by known chemotatic factors such as CXCL1, CXCL5, LTB(4), and fMLP. Furthermore, 1 also inhibited in a concentration-dependent manner the chemoattraction of human neutrophils induced by CXCL8, LTB(4), and fMLP in a Boyden chamber. In vitro treatment with 1 did not affect human neutrophil surface expression of CXCR1, CXCR2, BLT1, or FLPR1, but rather reduced actin polymerization. These results suggest that 1 inhibits actin polymerization, hence, explaining the inhibition of neutrophil recruitment in vivo and in vitro and highlighting its possible usefulness to diminish excessive neutrophil migration during inflammation.

Polyphenol-rich extracts from Solanum nigrum attenuated PKC alpha-mediated migration and invasion of hepatocellular carcinoma cells

Solanum nigrum L. (SN) has exhibited multiple biological effects such as anti-inflammation and antiproliferation. Protein kinase C (PKC) regulates cellular functions including proliferation, migration, and invasion. In the present investigation, we demonstrated that 12-o-tetradecanoylphobor-13-acetate (TPA) and constitutively activated PKC alpha significantly increased migration and invasion of HepG2 cells, while treatment with water or polyphenol extracts of SN (SNWE or SNPE) attenuated TPA-induced migration and invasion. SNWE and SNPE reduced TPA-elicited PKC alpha expression in a dose-dependent manner and obviously inhibited TPA-induced phosphorylation of p38 and ERK, respectively. Constitutively activated PKC alpha (caPKC alpha) significantly reversed the inhibitory effects of SNWE and SNPE on ERK and p38 activation. However, the antimigration effect of SNWE and SNPE could not be abrogated by caPKC alpha. Our results revealed the antimigration and anti-invasion effects of both extracts derived from SN, which may act as a promising therapeutic agent for the treatment of hepatocellular carcinoma.

The combination of baicalin and baicalein enhances apoptosis via the ERK/p38 MAPK pathway in human breast cancer cells

AIM

To examine whether the cell growth inhibitory effect of the combination of baicalin and baicalein is related to apoptosis. Moreover, to determine whether the expression of some apoptosis-related proteins is regulated by the ERK/p38 MAPK pathway.

METHODS

Cell viability was measured using a 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was detected by acridine orange (AO) staining, DNA ladder assay and flow cytometric analysis. Apoptosis-related proteins were observed using Western blot analysis.

RESULTS

Compared with baicalin or baicalein alone, the combination treatment of baicalin (50 micromol/L) and baicalein (25 micromol/L) had an anti-proliferative effect in a time-dependent manner. Isobologram analysis demonstrated that the combination treatment had a synergistic effect. Moreover, apoptosis in MCF-7 cells was increased by 12% and 20% with the combination treatment at 24 h and 48 h, respectively. With the combination treatment in MCF-7 cells, cleaved caspase-3 and caspase-9 were observed, and the level of bcl-2 expression was decreased approximately 20% and 40% at 24 h and 48 h, respectively. The expression of bax and p53 were increased about 25% and 15% at 48 h, respectively. Moreover, the activation of caspase-3, -9 and the regulation of bcl-2, bax and p53 were related to ERK /p38 MAPK activation.

CONCLUSION

In this study, apoptosis was enhanced by the combination treatment of baicalin and baicalein, which activated caspases-3 and caspase-9, downregulated the level of bcl-2 and upregulated the level of bax or p53 via the ERK/p38 MAPK pathway.

Resveratrol and quercetin cooperate to induce senescence-like growth arrest in C6 rat glioma cells

Glioma is the most frequent and malignant primary human brain tumor with dismal prognosis despite multimodal therapy. Resveratrol and quercetin, two structurally related and naturally occurring polyphenols, are proposed to have anticancer effects. We report here that resveratrol and quercetin decreased the cell number in four glioma cell lines but not in rat astrocytes. Low doses of resveratrol (10 microM) or quercetin (25 microM) separately had no effect on apoptosis induction, but had a strong effect on caspase 3/7 activation when administered together. Western blot analyses showed that resveratrol (10 microM) and quercetin (25 microM) caused a reduction in phosphorylation of Akt, but this reduction was not sufficient by itself to mediate the effects of these polyphenols. Most important, resveratrol and quercetin chronically administered presented a strong synergism in inducing senescence-like growth arrest. These results suggest that the combination of polyphenols can potentialize their antitumoral activity, thereby reducing the therapeutic concentration needed for glioma treatment.