Mechanism of apoptosis induced by apigenin in HepG2 human hepatoma cells: involvement of reactive oxygen species generated by NADPH oxidase

Protective effects of macromolecular polyphenols, metals (zinc, selenium, and copper) - Polyphenol complexes, and different organs with an emphasis on arsenic poisoning: A review

For the potential health benefits and nutritional value, polyphenols are one of the secondary metabolites of plants that have received extensive research. It has anti-inflammatory and cytotoxicity-reducing properties in addition to a high antioxidant content. Macromolecular polyphenols and polysaccharides are biologically active natural polymers with antioxidant and anti-inflammatory potential. Arsenic is an ecologically toxic metalloid. Arsenic in drinking water is the most common way people come into contact with this metalloid. While arsenic is known to cause cancer, it is also used to treat acute promyelocytic leukemia (APL). The treatment's effectiveness is hampered by the adverse effects it can cause on the body. Oxidative stress, inflammation, and the inability to regulate cell death cause the most adverse effects. Polyphenols and other macromolecules like polysaccharides act as neuroprotectants by mitigating free radical damage, inhibiting nitric oxide (NO) production, lowering A42 fibril formation, boosting antioxidant levels, and controlling apoptosis and inflammation. To prevent the harmful effects of toxins, polyphenols and pectin lower oxidative stress, boost antioxidant levels, improve mitochondrial function, control apoptosis, and suppress inflammation. Therefore, it prevents damage to the heart, liver, kidneys, and reproductive system. This review aims to identify the effects of the polyphenols in conjugation with polysaccharides as an ameliorative strategy for arsenic-induced toxicity in various organs.

A delve into the pharmacological targets and biological mechanisms of Paederia foetida Linn.: a rather invaluable traditional medicinal plant

Drug development from herbal medicines or botanical sources is believed to have a prominent role in the exploration of novel counteractive drugs that has sparked much interest in recent times. Paederia foetida is one such medicinal plant used in both traditional and folkloric medicine. Several parts of the herb are locally utilised as a natural curative agent for several ailments since time immemorial. Paederia foetida indeed possesses anti-diabetic, anti-hyperlipidaemic, antioxidant, nephro-protective, anti-inflammatory, antinociceptive, antitussive, thrombolytic, anti-diarrhoeal, sedative-anxiolytic, anti-ulcer, hepatoprotective activity, anthelmintic and anti-diarrhoeal activity. Furthermore, growing evidence shows many of its active constituents to be effective in cancer, inflammatory diseases, wound healing and spermatogenesis as well. These investigations shed light on possible pharmacological targets and attempts to establish a mechanism of action for these pharmacological effects. These findings contrast the significance of this medicinal plant for further research and for the exploration of novel counteractive drugs to establish a mechanism of action before being employed to healthcare. Pharmacological activities of Paederia foetida and their mechanism of action.

Investigating the Metabolic Level of Endogenous and Exogenous Substances on the Intervention of Traditional Chinese Medicine Fuzheng Yiliu Decoction in a Rat Orthotopic Liver Cancer Model

Background

Fuzheng Yiliu decoction (FZYLD), a Chinese formula consisting of four herbs, can be clinically used as an adjuvant therapy after surgery or palliative treatment for advanced liver cancer.

Methods

This study identified the endogenous and exogenous metabolites of FZYLD in rat serum to characterize the underlying mechanism of its antitumor activity, as well as relieving cancer-related weakness. An orthotopic transplantation rat model of HepG2 cells was established and administered with FZYLD by gastric perfusion for 14 days. Cardiopulmonary function and tail suspension test were used to evaluate the bodily weakness of hepatocellular carcinoma (HCC) rats. Tumor weight and size were measured to calculate inhibition ratios. Serum of different concentrations of FZYLD was used to culture the 2-[N-(7-nitrobenz-2-oxa-1, 3-diaxol-4-yl) amino]-2-deoxyglucose-labeled HepG2 cells. IC₅₀ value was measured using MTT assay. Endogenous and exogenous metabolites in rat serum were detected using nuclear magnetic resonance or LC-MS/MS spectroscopy.

Results

FZYLD improved cardiopulmonary function, decreased immobility time in tail suspension test, and yielded tumor inhibition ratios of up to 27%. Serum endogenous markers, such as lipoproteins (high- and low-density lipoproteins), glucose, and valine, and lactic acid metabolic disturbance were recovered, to some extent, in HCC rats. Exogenous metabolites, diosgenin, apigenin-7-O-acetyl-β-D-glucoside, calycosin-7-glucoside, calycosin, ganoderic-acid-A, formononetin, and methylnissolin, became detectable in the blood. FZYLD-containing serum substantially inhibited the proliferation of HepG2-cells. IC₅₀ value was found to be 24.31%. Further, we confirmed that FZYLD could revert energy and lipid metabolism disorders and that its constituents could be bioactive components that induce apoptosis in cancer cells.

Conclusion

The present study explained the mechanism of the effect of FZYLD on body empty, fatigue, and low immunity in patients with cancer, offering an efficient way for research of natural compounds in traditional Chinese medicine.

The effect of apigenin and chemotherapy combination treatments on apoptosis-related genes and proteins in acute leukaemia cell lines

Apigenin is a dietary polyphenol found abundantly in fruit and vegetables, which sensitizes leukaemia cells to topoisomerase inhibitor agents (e.g., etoposide), and alkylating agents (e.g., cyclophosphamide), reducing ATP levels and inducing apoptosis; whilst being protective to control haematopoietic stem cells. This study analysed the expression profiles of intrinsic and extrinsic apoptosis-related genes and proteins to help elucidate the mechanisms of action of apigenin when used in combination with etoposide or cyclophosphamide in lymphoid and myeloid leukaemia cell lines (Jurkat and THP-1). Expression of apoptosis-related genes were measured using a TaqMan® Human Apoptosis Array and the StepOne Plus RT-qPCR System, whilst apoptosis-related proteins were determined using a protein profiler™-human apoptosis array and the LI-COR Odyssey^R Infrared Imaging System. Apigenin when combined with etoposide or cyclophosphamide-induced apoptosis via the mitochondrial pathway, increasing the expression of pro-apoptotic cytochrome c, SMAC/DIABLO, and HTRA2/OMI, which promoted caspase-9 and -3 activation. Targeting anti-apoptotic and/or pro-apoptotic members of the apoptotic pathways is a promising strategy to induce cancer cell death and improve sensitivity to chemotherapy agents. Here the apoptotic pathways induced by apigenin in combination with etoposide or cyclophosphamide were identified within human leukaemia cell lines, such applications could provide combination therapies for the treatment of leukaemia.

Oxime derivative TFOBO promotes cell death by modulating reactive oxygen species and regulating NADPH oxidase activity in myeloid leukemia

Several derivatives derived from the oxime structure have been reported as potential anticancer agents in various cancers. Here, we first tested a novel oxime-containing derivative of 2-((2,4,5-trifluorobenzyl)oxy)benzaldehyde oxime (TFOBO) to evaluate its anticancer effect in myeloid leukemic cells. Compared to (2-((2,4,5-trifluorobenzyl)oxy)phenyl)methanol (TFOPM), the oxime derivative TFOBO suppresses leukemic cell growth by significantly increasing reactive oxygen species (ROS) levels and cell death. Leukemic cells treated with TFOBO displayed apoptotic cell death, as indicated by nuclear condensation, DNA fragmentation, and annexin V staining. TFOBO increases Bax/Bcl2 levels, caspase9, and caspase3/7 activity and decreases mitochondrial membrane potential. ROS production was reduced by N-acetyl-L-cysteine, a ROS scavenger, diphenyleneiodonium chloride, a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, after exogenous TFOBO treatment. ROS inhibitors protect leukemic cells from TFOBO-induced cell death. Thus, our study findings suggest that TFOBO promotes apoptosis by modulating ROS and regulating NADPH oxidase activity. Collectively, the oxime-containing derivative TFOBO is a novel therapeutic drug for myeloid leukemia.

Nanoencapsulation as a Promising Platform for the Delivery of the Morin-Cu(II) Complex: Antibacterial and Anticancer Potential

Nanoencapsulation has emerged as a promising approach for the effective delivery of poorly aqueous soluble compounds. The current study focuses on the preparation of human serum albumin (HSA)-based nanoparticles (NPs) and poly lactic-co-glycolic acid (PLGA)-based nanoparticles for effective delivery of the morin-Cu(II) complex. The NPs were analyzed based on different parameters such as particle size, surface charge, morphology, encapsulation efficiency, and in vitro release properties. The average particle sizes were found to be 214 ± 6 nm for Mor-Cu-HSA-NPs and 185 ± 7.5 nm for Mor-Cu-PLGA-NPs. The release of the morin-Cu(II) complex from both the NPs (Mor-Cu-HSA-NPs and Mor-Cu-PLGA-NPs) followed a biphasic behavior, which comprises an early burst release followed by a sustained and controlled release. The resulting NPs also exhibit free radical scavenging activity confirmed by a standard antioxidant assay. The antibacterial activities of the NPs were investigated using a disk diffusion technique, and it was observed that both the NPs showed better antibacterial activity than morin and the morin-Cu(II) complex. The anticancer activities of the prepared NPs were examined on MDA-MB-468 breast cancer cell lines using a cytotoxicity assay, and the mode of cell death was visualized using fluorescence microscopy. Our results revealed that NPs kill the cancer cells with greater efficiency than free morin and the morin-Cu(II) complex. Thus, both HSA-based NPs and PLGA-based NPs can act as promising delivery systems for the morin-Cu(II) complex and can be utilized for further biomedical applications.

Plant based radioprotectors as an adjunct to radiotherapy: advantages and limitations

Radioprotectors are agents that have the potential to act against radiation damage to cells. These are equally invaluable in radiation protection, both in intentional and unintentional radiation exposure. It is however, complex to use a universal radioprotector that could be beneficial in diverse contexts such as in radiotherapy, nuclear accidents, and space travel, as each of these circumstances have unique requirements. In a clinical setting such as in radiotherapy, a radioprotector is used to increase the efficacy of cancer treatment. The protective agent must act against radiation damage selectively in normal healthy cells while enhancing the radiation damage imparted on cancer cells. In the context of radiotherapy, plant-based compounds offer a more reliable solution over synthetic ones as the former are less expensive, less toxic, possess synergistic phytochemical activity, and are environmentally friendly. Phytochemicals with both radioprotective and anticancer properties may enhance the treatment efficacy by two-fold. Hence, plant based radioprotective agents offer a promising field to progress forward, and to expand the boundaries of radiation protection. This review is an account on radioprotective properties of phytochemicals and complications encountered in the development of the ideal radioprotector to be used as an adjunct in radiotherapy.

Reactive oxygen species: Key players in the anticancer effects of apigenin?

Reactive oxygen species (ROS) exhibit a double-edged sword in cancer-hence their modulation has been an attractive strategy in cancer prevention and therapy. The abundance of scientific information on the pro-oxidant effects of apigenin in cancer cells suggests the crucial role of ROS in its mechanisms of action. Although apigenin is known to enhance the cellular ROS levels to cytotoxic degrees in cancer cells in vitro, it remains to be determined if these pro-oxidant effects prevail or are relevant in experimental tumor models and clinical trials. Here, we critically examine the pro-oxidant and antioxidant effects of apigenin in cancer to provide insightful perspectives on the association between its ROS-modulating action and anticancer potential. We also discussed these effects in a cell/tissue type-specific context to highlight the factors influencing the switch between antioxidant and pro-oxidant effects. Finally, we raised some questions that need addressing for the potential translation of these studies into clinical applications. Further research into this duality in oxidant actions of apigenin, especially in vivo, may enable better exploitation of its anticancer potential. PRACTICAL APPLICATION: Apigenin is a naturally occurring compound found in chamomile flowers, parsley, celery, peppermint, and citrus fruits. Many human trials of dietary interventions with apigenin-containing herbs and flavonoid mixture on oxidative stress markers, for instance, point to their antioxidant effects and health benefits in many diseases. Preclinical studies suggest that apigenin alone or its combination with chemotherapeutics has a strong anti-neoplastic effect and can induce ROS-mediated cytotoxicity at concentrations in the micromolar (μM) range, which may not be feasible with dietary interventions. Enhancing the in vivo pharmacokinetic properties of apigenin may be indispensable for its potential cancer-specific pro-oxidant therapy and may provide relevant information for clinical studies of apigenin either as a single agent or an adjuvant to chemotherapeutics.

Rationalizing the therapeutic potential of apigenin against cancer

BACKGROUND

Despite the remarkable advances made in the diagnosis and treatment of cancer during the past couple of decades, it remains the second largest cause of mortality in the world, killing approximately 9.6 million people annually. The major challenges in the treatment of the advanced stage of this disease are the development of chemoresistance, severe adverse effects of the drugs, and high treatment cost. Therefore, the development of drugs that are safe, efficacious, and cost-effective remains a 'Holy Grail' in cancer research. However, the research over the past four decades shed light on the cancer-preventive and therapeutic potential of natural products and their underlying mechanism of action. Apigenin is one such compound, which is known to be safe and has significant potential in the prevention and therapy of this disease.

AIM

To assess the literature available on the potential of apigenin and its analogs in modulating the key molecular targets leading to the prevention and treatment of different types of cancer.

METHOD

A comprehensive literature search has been carried out on PubMed for obtaining information related to the sources and analogs, chemistry and biosynthesis, physicochemical properties, biological activities, bioavailability and toxicity of apigenin.

KEY FINDINGS

The literature search resulted in many in vitro, in vivo and a few cohort studies that evidenced the effectiveness of apigenin and its analogs in modulating important molecular targets and signaling pathways such as PI3K/AKT/mTOR, JAK/STAT, NF-κB, MAPK/ERK, Wnt/β-catenin, etc., which play a crucial role in the development and progression of cancer. In addition, apigenin was also shown to inhibit chemoresistance and radioresistance and make cancer cells sensitive to these agents. Reports have further revealed the safety of the compound and the adaptation of nanotechnological approaches for improving its bioavailability.

SIGNIFICANCE

Hence, the present review recapitulates the properties of apigenin and its pharmacological activities against different types of cancer, which warrant further investigation in clinical settings.

Distinct phenolic, alkaloid and antioxidant profile in betel quids from four regions of Indonesia

Betel quid (BQ) is a chewing mixed package that mainly contains areca nut (AN), betel leaf (Leaf) or betel stem inflorescence (SI), and slaked lime, and is consumed with or without tobacco BQ chewing is common in South East Asia and has been strongly associated with malignant and potentially malignant diseases of the oral cavity. Alkaloids such as arecoline are often accounted for the carcinogenic potential of BQ, however the chemical composition of BQ has not been studied in detail. In the current study, we investigated the total phenolic content (TPC), antioxidant activity (by mean of ferric reducing antioxidant power, FRAP), radical scavenging activity (DPPH test), polyphenolic profile and arecoline content in different components of BQ, namely AN, Leaf or SI, Husk, and blended BQ (BQ mix, containing AN, Leaf or SI and slaked lime). Samples were imported from 4 major regions of Indonesia, namely: Banda Aceh (BA), North Sumatra (NS), West Kalimantan (WK) and West Papua (WP). The highest TPC, FRAP, and DPPH values were detected in AN samples compared to other BQ components, while samples from WP region were of higher values compared to the other regions. High performance liquid chromatography—Mass Spectrometry (LC–MS) analysis showed that Husk contains the widest range of polyphenols, including hydroxybenzoic acids, hydroxycinnamic acids, flavanols, flavonols and stilbenes. Catechin and epicatechin were the main polyphenols detected in BQ, and they were present at the highest concentrations in WP–AN sample. Arecoline was detected in all AN and BQ mix samples and was significantly correlated with catechin and epicatechin, and significantly negatively correlated with p-hydroxybenzoic acid. Notably, arecoline concentration changed significantly when AN was blended in BQ mixtures. The current study is the first to extensively characterise the chemical composition of BQ and provides insight for a better understanding of the interactions of BQ alkaloids and phenolics in the development of oral submucous fibrosis and oral cancer.

A natural flavonoid, apigenin isolated from Clerodendrum viscosum leaves, induces G2/M phase cell cycle arrest and apoptosis in MCF-7 cells through the regulation of p53 and caspase-cascade pathway

BACKGROUND

With 9.6 million deaths in 2018, cancer remains the second leading cause of death worldwide. Breast cancer is the most deadly type of cancer among females, with 55.2% of crude incidence rate and 16.6% of crude mortality rate.

PURPOSE

The present study was aimed to investigate the anti-breast cancer potential of natural dietary flavonoid, apigenin isolated from Clerodendrum viscosum leaves.

METHODS

Apigenin was evaluated for in-depth anticancer activity in MCF-7 cells using cell viability assay, cell cycle analysis, Annexin-V-FLUOS staining, ROS induction, morphological analysis, and western blot analysis.

RESULTS

Apigenin showed selective cytotoxicity on MCF-7 cells with an IC₅₀-56.72 ± 2.35 µM, while negligible cytotoxicity was observed on WI-38 cells. Further, the flow cytometer-based analysis showed that apigenin halted MCF-7 cells in the G2/M phase arrest followed by dose-dependent apoptosis. Moreover, the FACS and confocal microscopy results confirmed the elevation of intracellular ROS and nuclear fragmentation in apigenin-treated MCF-7 cells. Western blots showed up-regulation of cell cycle regulatory proteins, increased p53 expression, Bax/Bcl-2 ratio, activation of caspases, and cleavage of PARP. Finally, apigenin treatment in the presence of Pifithrin-µ showed decreased apoptotic population and it was further confirmed through western blotting study. The results revealed the vital role of p53 in apigenin-induced apoptosis in MCF-7 cells.

CONCLUSIONS

In the present findings, treatment of apigenin-induced intracellular ROS in MCF-7 cells followed by induction of G2/M phase cell cycle arrest and further apoptosis through the regulation of p53 and caspase-cascade signaling pathway.

Apigenin as an anticancer agent

Apigenin is an edible plant-derived flavonoid that has been reported as an anticancer agent in several experimental and biological studies. It exhibits cell growth arrest and apoptosis in different types of tumors such as breast, lung, liver, skin, blood, colon, prostate, pancreatic, cervical, oral, and stomach, by modulating several signaling pathways. Apigenin induces apoptosis by the activation of extrinsic caspase-dependent pathway by upregulating the mRNA expressions of caspase-3, caspase-8, and TNF-α. It induces intrinsic apoptosis pathway as evidenced by the induction of cytochrome c, Bax, and caspase-3, while caspase-8, TNF-α, and B-cell lymphoma 2 levels remained unchanged in human prostate cancer PC-3 cells. Apigenin treatment leads to significant downregulation of matrix metallopeptidases-2, -9, Snail, and Slug, suppressing invasion. The expressions of NF-κB p105/p50, PI3K, Akt, and the phosphorylation of p-Akt decreases after treatment with apigenin. However, apigenin-mediated treatment significantly reduces pluripotency marker Oct3/4 protein expression which might be associated with the downregulation of PI3K/Akt/NF-κB signaling.

β3-Adrenoreceptor Activity Limits Apigenin Efficacy in Ewing Sarcoma Cells: A Dual Approach to Prevent Cell Survival

Ewing Sarcoma (ES) is an aggressive paediatric tumour where oxidative stress and antioxidants play a central role in cancer therapy response. Inhibiting antioxidants expression, while at the same time elevating intracellular reactive oxygen species (ROS) levels, have been proposed as a valid strategy to overcome ES cancer progression. Flavonoid intake can affect free radical and nutritional status in children receiving cancer treatment, but it is not clear if it can arrest cancer progression. In particular, apigenin may enhance the effect of cytotoxic chemotherapy by inducing cell growth arrest, apoptosis, and by altering the redox state of the cells. Little is known about the use of apigenin in paediatric cancer. Recently, β3-adrenergic receptor (β3-AR) antagonism has been proposed as a possible strategy in cancer therapy for its ability to induce apoptosis by increasing intracellular levels of ROS. In this study we show that apigenin induces cell death in ES cells by modulating apoptosis, but not increasing ROS content. Since ES cells are susceptible to an increased oxidative stress to reduce cell viability, here we demonstrate that administration of β3-ARs antagonist, SR59230A, improves the apigenin effect on cell death, identifying β3-AR as a potential discriminating factor that could address the use of apigenin in ES.

Impact of glutamine on the effect of neopterin in methyl mercury-exposed neurons

Exposure to methyl mercury (MeHg), induces blood-brain barrier damage leading to non-selective influx of cytotoxic agents, besides the entrance of inflammatory cells into the brain. However, there is no data available regarding the effects of co-treatment of neopterin and interferon-gamma (IFN-gamma) in MeHgexposed SH-SY5Y dopaminergic neurons. MeHg-exposed SH-SY5Y human neuroblastoma cells were treated with neopterin and IFN-gamma in the presence and absence of L-Glutamine. Cell viability was determined by MTT assay. Oxidative stress intensity coefficient was calculated by taking into consideration the amount of nitric oxide production per viable neuron. 5μM MeHg was found to be more toxic than 1μM or 2μM doses of MeHg for SH-SY5Y cells in glutamine-containing medium. Furthermore, 0.1μM neopterin supplementation significantly increased the neuronal cell viability while, oxidative stress significantly decreased. Glutamine supplementation in culture medium, not only enhanced the MeHg toxicity, but also supported the antioxidant effect of neopterin. These results indicate that neopterin has a protective effect on MeHg toxicity in SH-SY5Y neurons. Neopterin was more effective in improving the total mitochondrial metabolic activity of cells exposed to 5μM MeHg in comparison to IFN-gamma. Although IFN-gamma supplementation alone partially improved 5μM MeHg toxicity on neurons, it weakened the protective effect of neopterin.

Effect of silibinin on CFLAR-JNK pathway in oleic acid-treated HepG2 cells

AIMS

Silibinin is a flavonolignan from milk thistle with many pharmacological activities including lipid-lowering and antioxidant. Caspase 8 and Fas-associated protein with death domain-like apoptosis regulator (CFLAR) is an important target gene in regulating non-alcoholic steatohepatitis (NASH). At present, the effect of silibinin on CFLAR-JNK pathway related to NASH was unknown. Here the effect of silibinin on CFLAR-JNK pathway and its downstream target genes involved in lipid metabolism, glucose uptake, oxidative stress and inflammatory response were studied in oleic acid (OA)-treated HepG2 cells.

MAIN METHODS

OA-treated HepG2 cells were employed as a in vitro model of steatosis, insulin resistance and oxidative stress. The model cells were then treated by silibinin (5, 20, 50, and 100 μM) for 24 h and detected for the related indicators as follows: (1) cellular triglycerides (TG), nitric oxide (NO) and glucose uptake; (2) the mRNA levels of the sterol regulatory element binding protein-1C (SREBP-1C), patatin-like phospholipase domain containing 3 (PNPLA3) and peroxisome proliferator activated receptor-α (PPARα); (3) the protein levels of PPARα, SREBP-1C, PNPLA3, CFLAR, phosphorylated c-Jun N-terminal kinase (pJNK), phosphatidylinositol 3-kinase (PI3K), phosphorylated serine-threonine protein kinase (pAKT), nuclear factor E2-related factor 2 (NRF2), cytochrome P450 2E1 (CYP2E1) and 4A (CYP4A).

KEY FINDINGS

Compared to the control, OA-treatment led to a result as follows: (1) increased the intracellular levels of TG and NO; (2) up-regulated the protein expression of SREBP-1C, PNPLA3, pJNK, CYP 2E1 and CYP 4A; (3) decreased the uptake of 2-NBDG; (4) down-regulated the protein expression of CFLAR, PPARα, PI3K, pAKT and NRF2. Compared to OA-treated HepG2 cells, silibinin treatment could improve the indicators as follows: (1) decreased the intracellular levels of TG and NO; (2) down-regulated the protein expression of SREBP-1C, PNPLA3, pJNK, CYP 2E1 and CYP 4A; (3) increased the uptake of 2-NBDG; (4) up-regulated the protein expression of CFLAR, PPARα, PI3K, pAKT and NRF2.

SIGNIFICANCE

Silibinin can ameliorate some metabolic alterations and induce some molecular changes by activating the CFLAR-JNK pathway and thereby regulating its downstream target genes involved in lipid metabolism (PPARα, SREBP-1C and PNPLA3), glucose uptake (PI3K-AKT), oxidative stress (NRF2, CYP2E1, CYP4A) and inflammatory response(NO) in OA-treated HepG2 cells demonstrating its possible use in ameliorating various symptoms of NASH.

Cryptotanshinone induces ROS-mediated apoptosis in human gastric cancer cells

Cryptotanshinone (CT), isolated from the plant Salvia miltiorrhiza Bunge, has been reported to have potential anticancer effects on human prostate and breast cancer cells. However, the mechanisms of action of CT on gastric cancer (GC) cells are not well understood. Here we investigated the antitumor effects of CT on GC cells and its possible molecular mechanism. We found CT suppressed viability of twelve GC cell lines in a dose-dependent manner. CT induced cell cycle arrest at the G2/M phase and mitochondrial apoptosis accompanying the accumulation of reactive oxygen species (ROS). Pretreatment with ROS inhibitor N-acetyl-L-cysteine (NAC) blocked CT-induced apoptosis. CT increased p-JNK and p-p38, and decreased p-ERK and p-STAT3 protein expression, these effects were prevented by NAC. Furthermore, a xenograft assay showed that CT significantly inhibited MKN-45 cell-induced tumor growth in vivo by increasing expression of pro-apoptotic proteins (p-JNK, p-38 and cleaved-caspase-3) and reducing expression of anti-apoptotic proteins (p-ERK and p-STAT3) without adverse effects on nude mice weight. In conclusion, CT induced apoptosis and cell cycle arrest in GC cells via ROS-mediated MAPK and AKT signaling pathways, and this CT may be a useful compound for the developing anticancer agents for GC.

Plant flavone apigenin: An emerging anticancer agent

Research in cancer chemoprevention provides convincing evidence that increased intake of vegetables and fruits may reduce the risk of several human malignancies. Phytochemicals present therein provide beneficial anti-inflammatory and antioxidant properties that serve to improve the cellular microenvironment. Compounds known as flavonoids categorized anthocyanidins, flavonols, flavanones, flavonols, flavones, and isoflavones have shown considerable promise as chemopreventive agents. Apigenin (4', 5, 7-trihydroxyflavone), a major plant flavone, possessing antioxidant, anti-inflammatory, and anticancer properties affecting several molecular and cellular targets used to treat various human diseases. Epidemiologic and case-control studies have suggested apigenin reduces the risk of certain cancers. Studies demonstrate that apigenin retain potent therapeutic properties alone and/or increases the efficacy of several chemotherapeutic drugs in combination on a variety of human cancers. Apigenin's anticancer effects could also be due to its differential effects in causing minimal toxicity to normal cells with delayed plasma clearance and slow decomposition in liver increasing the systemic bioavailability in pharmacokinetic studies. Here we discuss the anticancer role of apigenin highlighting its potential activity as a chemopreventive and therapeutic agent. We also highlight the current caveats that preclude apigenin for its use in the human trials.

Oxidative Stress: Harms and Benefits for Human Health

Oxidative stress is a phenomenon caused by an imbalance between production and accumulation of oxygen reactive species (ROS) in cells and tissues and the ability of a biological system to detoxify these reactive products. ROS can play, and in fact they do it, several physiological roles (i.e., cell signaling), and they are normally generated as by-products of oxygen metabolism; despite this, environmental stressors (i.e., UV, ionizing radiations, pollutants, and heavy metals) and xenobiotics (i.e., antiblastic drugs) contribute to greatly increase ROS production, therefore causing the imbalance that leads to cell and tissue damage (oxidative stress). Several antioxidants have been exploited in recent years for their actual or supposed beneficial effect against oxidative stress, such as vitamin E, flavonoids, and polyphenols. While we tend to describe oxidative stress just as harmful for human body, it is true as well that it is exploited as a therapeutic approach to treat clinical conditions such as cancer, with a certain degree of clinical success. In this review, we will describe the most recent findings in the oxidative stress field, highlighting both its bad and good sides for human health.

Apigenin Inhibits Human SW620 Cell Growth by Targeting Polyamine Catabolism

Apigenin is a nonmutagenic flavonoid that has antitumor properties. Polyamines are ubiquitous cellular polycations, which play an important role in the proliferation and differentiation of cancer cells. Highly regulated pathways control the biosynthesis and degradation of polyamines. Ornithine decarboxylase (ODC) is the rate-limiting enzyme in the metabolism, and spermidine/spermine-N1-Acetyl transferase (SSAT) is the rate-limiting enzyme in the catabolism of polyamines. In the current study, the effect of increasing concentrations of apigenin on polyamine levels, ODC and SSAT protein expression, mRNA expression, cell proliferation and apoptosis, and the production of reactive oxygen species (ROS) was investigated in SW620 colon cancer cells. The results showed that apigenin significantly reduced cell proliferation, decreased the levels of spermidine and spermine, and increased previously downregulated putrescine contents. Apigenin also enhanced SSAT protein and mRNA levels and the production of reactive oxygen species in SW620 cells, though it had no significant effect on the levels of ODC protein or mRNA. Apigenin appears to decrease the proliferation rate of human SW620 cells by facilitating SSAT expression to induce polyamine catabolism and increasing ROS levels to induce cell apoptosis.

Resveratrol, piperine and apigenin differ in their NADPH-oxidase inhibitory and reactive oxygen species-scavenging properties

BACKGROUND

Many plant-derived chemicals have been studied for their potential benefits in ailments including inflammation, cancer, neurodegeneration, and cardiovascular disease. The health benefits of phytochemicals are often attributed to the targeting of reactive oxygen species (ROS). However, it is not always clear whether these agents act directly as antioxidants to remove ROS, or whether they act indirectly by blocking ROS production by enzymes such as NADPH oxidase (NOX) enzymes, or by influencing the expression of cellular pro- and anti- oxidants.

HYPOTHESIS/PURPOSE

Here we evaluate the pro- and anti-oxidant and NOX-inhibiting qualities of four phytochemicals: celastrol, resveratrol, apigenin, and piperine.

STUDY DESIGN

This work was done using the H661 cell line expressing little or no NOX, modified H661 cells expressing NOX1 and its subunits, and an EBV-transformed B-lymphoblastoid cell line expressing endogenous NOX2. ROS were measured using Amplex Red and nitroblue tetrazolium assays. In addition, direct ROS scavenging of hydrogen peroxide or superoxide generated were measured using Amplex Red and methyl cypridina luciferin analog (MCLA).

RESULTS

Of the four plant-derived compounds evaluated, only celastrol displayed NOX inhibitory activities, while celastrol and resveratrol both displayed ROS scavenging activity. Very little impact on ROS was observed with apigenin, or piperine.

CONCLUSION

The results of this study reveal the differences that exist between cell-free and intracellular pro-oxidant and antioxidant activities of several plant-derived compounds.

Indole-3- carbinol enhances sorafenib cytotoxicity in hepatocellular carcinoma cells: A mechanistic study

Sorafenib is the only chemotherapeutic agent currently approved for unresectable hepatocellular carcinoma (HCC). However, poor response rates have been widely reported. Indole-3-carbinol (I3C) is a potential chemopreventive phytochemical. The present study aimed to explore the potential chemomodulatory effects of I3C on sorafenib in HCC cells as well as the possible underlying mechanisms. I3C exhibited a greater cytotoxicity in HepG2 cells compared to Huh-7 cells (p < 0.0001). Moreover, the co-treatment of HepG2 cells with I3C and sorafenib was more effective (p = 0.002). Accordingly, subsequent mechanistic studies were carried on HepG2 cells. The results show that the ability of I3C to enhance sorafenib cytotoxicity in HCC cells could be partially attributed to increasing the apoptotic activity and decreasing the angiogenic potentials. The combination had a negative effect on epithelial-mesenchymal transition (EMT). Increased NOX-1 expression was also observed which may indicate the involvement of NOX-1 in I3C chemomodulatory effects. Additionally, the combination induced cell cycle arrest at the G0/G1 phase. In conclusion, these findings provide evidence that I3C enhances sorafenib anti-cancer activity in HCC cells.

Oral Efficacy of Apigenin against Cutaneous Leishmaniasis: Involvement of Reactive Oxygen Species and Autophagy as a Mechanism of Action

Background

The treatment for leishmaniasis is currently based on pentavalent antimonials and amphotericin B; however, these drugs result in numerous adverse side effects. The lack of affordable therapy has necessitated the urgent development of new drugs that are efficacious, safe, and more accessible to patients. Natural products are a major source for the discovery of new and selective molecules for neglected diseases. In this paper, we evaluated the effect of apigenin on Leishmania amazonensis in vitro and in vivo and described the mechanism of action against intracellular amastigotes of L. amazonensis.

Methodology/Principal Finding

Apigenin reduced the infection index in a dose-dependent manner, with IC₅₀ values of 4.3 μM and a selectivity index of 18.2. Apigenin induced ROS production in the L. amazonensis-infected macrophage, and the effects were reversed by NAC and GSH. Additionally, apigenin induced an increase in the number of macrophages autophagosomes after the infection, surrounding the parasitophorous vacuole, suggestive of the involvement of host autophagy probably due to ROS generation induced by apigenin. Furthermore, apigenin treatment was also effective in vivo, demonstrating oral bioavailability and reduced parasitic loads without altering serological toxicity markers.

Conclusions/Significance

In conclusion, our study suggests that apigenin exhibits leishmanicidal effects against L. amazonensis-infected macrophages. ROS production, as part of the mechanism of action, could occur through the increase in host autophagy and thereby promoting parasite death. Furthermore, our data suggest that apigenin is effective in the treatment of L. amazonensis-infected BALB/c mice by oral administration, without altering serological toxicity markers. The selective in vitro activity of apigenin, together with excellent theoretical predictions of oral availability, clear decreases in parasite load and lesion size, and no observed compromises to the overall health of the infected mice encourage us to supports further studies of apigenin as a candidate for the chemotherapeutic treatment of leishmaniasis.

Leishmaniasis is an important neglected disease caused by protozoa of the genus Leishmania and affects more than 12 million people worldwide. Pentavalent antimonials and amphotericin B have been used for decades to treat leishmaniasis; however, these drugs result in numerous adverse side effects, have variable efficacy and are subject to parasite resistance. The lack of suitable therapy necessitates the development of novel antileishmanial compounds. In this study, we investigated the antileishmanial activity of apigenin in vitro and in vivo and described the mechanism of action against intracellular amastigotes of Leishmania amazonensis. Apigenin reduced the infection index in a dose-dependent manner and increased reactive oxygen species (ROS) generation. Additionally, apigenin induced an increase in the number of macrophages autophagosomes after the infection, surrounding the parasitophorous vacuole, suggestive of the involvement of host autophagy probably due to ROS generation induced by apigenin. Furthermore, treatment with apigenin was also effective in vivo, showing oral bioavailability and significantly reducing lesion sizes and parasite burden without altering serological toxicity markers.

Solubility enhancement of morin and epicatechin through encapsulation in an albumin based nanoparticulate system and their anticancer activity against the MDA-MB-468 breast cancer cell line

Mor-HSA-NPs and EC-HSA-NPs are effective on MDA-MB-468 breast cancer cell lines.

Validation of a RP-HPLC-DAD Method for Chamomile (Matricaria recutita) Preparations and Assessment of the Marker, Apigenin-7-glucoside, Safety and Anti-Inflammatory Effect

Chamomile is a medicinal plant, which presents several biological effects, especially the anti-inflammatory effect. One of the compounds related to this effect is apigenin, a flavonoid that is mostly found in its glycosylated form, apigenin-7-glucoside (APG), in natural sources. However, the affectivity and safety of this glycoside have not been well explored for topical application. In this context, the aim of this work was to develop and validate a reversed-phase high-performance liquid chromatography (RP-HPLC-DAD) method to quantify APG in chamomile preparations. Additionally, the safety and the anti-inflammatory potential of this flavonoid were verified. The RP-HPLC-DAD method was developed and validated with linearity at 24.0-36.0 μg/mL range (r = 0.9994). Intra- and interday precision (RSD) were 0.27-2.66% and accuracy was 98.27-101.21%. The validated method was applied in the analysis of chamomile flower heads, glycolic extract, and Kamillen cream, supporting the method application in the quality control of chamomile preparations. Furthermore, the APG safety was assessed by MTT cytotoxicity assay and mutagenic protocols and the anti-inflammatory activity was confirmed by a diminished TNF-α production showed by mice macrophages treated with APG following LPS treatment.

Pro-oxidant activity of polyphenols and its implication on cancer chemoprevention and chemotherapy

Reactive oxygen species (ROS) play a major role in carcinogenesis: pro-oxidant agents like tobacco smoke, asbestos or N-nitrosamines, are known as mutagenic and carcinogenic, and cancer cells show increased levels of ROS and redox deregulation. However, pro-oxidant molecules can also act as selective cytotoxic agents against cancer cells by achieving toxic levels of ROS. Although polyphenols are well-known as potent antioxidants, a pro-oxidant effect has been associated with their pro-apoptotic effect in various types of tumor cells. The aim of the present review is to present the main evidences of the pro-oxidant-related cytotoxic activity of naturally occurring polyphenols and their underlying mechanisms.

Cytotoxicity of dietary flavonoids on different human cancer types

Flavonoids are ubiquitous in nature. They are also in food, providing an essential link between diet and prevention of chronic diseases including cancer. Anticancer effects of these polyphenols depend on several factors: Their chemical structure and concentration, and also on the type of cancer. Malignant cells from different tissues reveal somewhat different sensitivity toward flavonoids and, therefore, the preferences of the most common dietary flavonoids to various human cancer types are analyzed in this review. While luteolin and kaempferol can be considered as promising candidate agents for treatment of gastric and ovarian cancers, respectively, apigenin, chrysin, and luteolin have good perspectives as potent antitumor agents for cervical cancer; cells from main sites of flavonoid metabolism (colon and liver) reveal rather large fluctuations in anticancer activity probably due to exposure to various metabolites with different activities. Anticancer effect of flavonoids toward blood cancer cells depend on their myeloid, lymphoid, or erythroid origin; cytotoxic effects of flavonoids on breast and prostate cancer cells are highly related to the expression of hormone receptors. Different flavonoids are often preferentially present in certain food items, and knowledge about the malignant tissue-specific anticancer effects of flavonoids could be purposely applied both in chemoprevention as well as in cancer treatment.

Effects of Medicinal herb Extracts and their Components on Steatogenic Hepatotoxicity in Sk-hep1 Cells

Herbal medicines are widely used in many countries for the treatment of many diseases. Although the use of herb extracts as alternative medicine is growing, their toxicological properties have not been thoroughly investigated. In this study, we have investigated the effects of water and ethanol extracts of 18 herbs on the hepatic lipid metabolism and steatogenic hepatotoxicity. Ethanol extracts of Cirsium japonicum, Carthamus tinctorius, Rehmanniae glutinosa (preparata), Polygala tenuifolia, Foeniculum vulgare, Polygonum multiflorum, and Acorus gramineus and water extracts of Polygonum multiflorum and Rehmanniae glutinosa induced lipid accumulation in Sk-hep1 human hepatoma cells as determined by Nile red staining. These extracts increased the luciferase activity of sterol regulatory element (SRE) and decreased that of peroxisome proliferator response element (PPRE), indicating the possibilities of enhanced fatty acid synthesis and decreased fatty acid oxidation. To identify the components responsible for the fat accumulation, we tested 50 chemicals isolated from the nine herbs. Apigenin, luteolin, pectolinarin and lupeol from Cirsium japonicum, 8-methoxypsoralen and umbelliferone from Foeniculum vulgare and pomonic acid and jiocerebroside from Rehmanniae glutinosa significantly increased the accumulation of lipid droplets. These results suggest that ethanol extracts of Cirsium japonicum, Carthamus tinctorius, Rehmanniae glutinosa (preparata), Polygala tenuifolia, Foeniculum vulgare, Polygonum multiflorum, and Acorus gramineus and water extracts of Polygonum multiflorum and Rehmanniae glutinosa can cause fatty liver disease by decreasing β-oxidation of fatty acid and increasing lipogenesis.

Time course changes of anti- and pro-apoptotic proteins in apigenin-induced genotoxicity

Background

Apigenin (4′,5,7-trihydroxyflavone, AP), an active component of many medicinal Chinese herbs, exhibits anticancer properties in vitro and in vivo. This study aims to investigate the genotoxic, cytostatic, and cytotoxic effects of AP and time course changes in the levels of anti- and pro-apoptotic proteins involved in the DNA damage response in HepG2 cells.

Methods

The genotoxic potential of AP was determined by sister chromatid exchanges (SCEs) and chromosomal aberrations (CAs) analysis. The levels of cytostaticity and cytotoxicity were evaluated by the proliferation rate and mitotic indices, respectively. MTT was used to study cytotoxicity, while the induction of apoptosis and the expression of apoptosis-related proteins were determined by ELISA.

Results

At concentrations greater than 10 μM, AP decreased cell survival in a dose- (48 h: 10 vs. 20 μΜ, P < 0.001 and 20 vs. 50 μΜ, P = 0.005; 72 h: 10 vs. 20 μΜ, P < 0.001 and 20 vs. 50 μΜ, P = 0.001) and time-dependent manner (20 μΜ: 24 vs. 48 h, P < 0.001 and 48 vs. 72 h, P = 0.003; 50 μΜ: 24 vs. 48 h, P < 0.001 and 48 vs. 72 h, P < 0.001; 100 μΜ: 24 vs. 48 h, P < 0.001 and 48 vs. 72 h, P < 0.001). SCEs rates, cell proliferation, and mitotic divisions were also affected in a dose-dependent manner (P < 0.001). There was no change in the frequency of aberrant cells (1 μΜ ΑP: P = 0.554; 10 μM AP: P = 0.337; 20 μΜ AP: P = 0.239). Bcl-2 levels were reduced 3 h after AP administration (P = 0.003) and remained reduced throughout the 48 h observation period (6 h, P = 0.044; 12 h, P = 0.001; 24 h, P = 0.042; 48 h, P = 0.012). Bax and soluble Fas exhibited a transient upregulation 24 h after AP treatment. The Bax/Bcl-2 ratio was also increased at 12 h and remained increased throughout the 48 h observation period.

Conclusion

AP exhibited dose-dependent genotoxic potential in HepG2 cells. The protein levels of sFas, Bcl-2, and Bax were affected by AP to promote cell survival and cell death, respectively.

Ocimum sanctum L (Holy Basil or Tulsi) and its phytochemicals in the prevention and treatment of cancer

Ocimum sanctum L. or Ocimum tenuiflorum L, commonly known as the Holy Basil in English or Tulsi in the various Indian languages, is a important medicinal plant in the various traditional and folk systems of medicine in Southeast Asia. Scientific studies have shown it to possess antiinflammatory, analgesic, antipyretic, antidiabetic, hepatoprotective, hypolipidemic, antistress, and immunomodulatory activities. Preclinical studies have also shown that Tulsi and some of its phytochemicals eugenol, rosmarinic acid, apigenin, myretenal, luteolin, β-sitosterol, and carnosic acid prevented chemical-induced skin, liver, oral, and lung cancers and to mediate these effects by increasing the antioxidant activity, altering the gene expressions, inducing apoptosis, and inhibiting angiogenesis and metastasis. The aqueous extract of Tulsi and its flavanoids, orintin, and vicenin are shown to protect mice against γ-radiation-induced sickness and mortality and to selectively protect the normal tissues against the tumoricidal effects of radiation. The other important phytochemicals like eugenol, rosmarinic acid, apigenin, and carnosic acid are also shown to prevent radiation-induced DNA damage. This review summarizes the results related to the chemopreventive and radioprotective properties of Tulsi and also emphasizes aspects that warrant future research to establish its activity and utility in cancer prevention and treatment.

Sub-toxic dose of apigenin sensitizes HepG2 cells to TRAIL through ERK-dependent up-regulation of TRAIL receptor DR5

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is regarded as a promising candidate for anticancer therapy due to its selective toxicity to cancer cells. Nevertheless, because of TRAIL resistance in some cancer cells, combined treatment with sensitizing agents is required to enhance the anticancer potential of TRAIL. In this study, we investigated the underlying mechanism of apigenin-induced sensitization of HepG2 cells to TRAIL-induced cell death. Synergistic induction of apoptosis by combination was confirmed by examining the typical morphology changes of apoptosis, PARP-cleavage, and activation of effector caspases. Z-VAD-fmk, a pan-caspase inhibitor, inhibited the enhanced cell death by combined treatment of apigenin and TRAIL, demonstrating that a caspase-dependent pathway is involved in apigenin/TRAIL-mediated apoptosis. In addition, we found that apigenin/ TRAIL co-treatment up-regulates DR5 cell surface expression. The synergistic induction of cell death by the apigenin/ TRAIL combination was significantly attenuated by DR5 blocking chimera antibody. Next, using pharmacological inhibitors, we found that ERK activation is involved in the induction of DR5 expression. Inhibition of ERK1/2 by U0126 significantly decreased the apigenin/TRAIL-induced DR5 expression and apoptosis. Taken together, our results indicate that apigenin can enhance the apoptotic effect of TRAIL via ERK-induced up-regulation of DR5.

Apigenin induces apoptosis via tumor necrosis factor receptor- and Bcl-2-mediated pathway and enhances susceptibility of head and neck squamous cell carcinoma to 5-fluorouracil and cisplatin

BACKGROUND

Apigenin, a natural plant flavone, may have chemopreventive and therapeutic potentials for anti-inflammatory, antioxidant, and anti-cancer. Nevertheless, the anti-tumor effect of apigenin on human head and neck squamous cell carcinoma (HNSCC) is not fully understood.

METHODS

The antioxidant capacity and protective effects of apigenin against oxidative stress in murine normal embryonic liver BNLCL2 cells are examined. Cell viability, morphologic change, clonogenic survival, cell cycle distribution, reactive oxygen species (ROS) production, glutathione formation, and death receptors- and Bcl-2-mediated caspase pathways of HNSCC SCC25 cells and A431 cells with apigenin are investigated.

RESULTS

Apigenin inhibits the growth of SCC25 and A431 cells and induces cell cycle arrest in the G2/M phase. Apigenin has an antioxidant capacity as well as the ability to inhibit lipid peroxidation. It protects BNLCL2 cells against oxidative damage, and is potentially able to prevent cancer. Apigenin increases intracellular ROS levels and reduces levels of glutathione; it also induces cell apoptosis via tumor necrosis factor receptor (TNF-R)-, TNF-related apoptosis-inducing ligand receptor (TRAIL-R)-, and Bcl-2-mediated caspase-dependent cell death pathways in SCC25 cells. The combination of apigenin with 5-fluorouracil (5-Fu) or cisplatin induces the dramatic death of SCC25 cells.

CONCLUSIONS

Apigenin induces SCC25 cell apoptosis via the up-regulation of both TNF-R and TRAIL-R signaling pathways, and has a synergistic effect on the inhibition of cell proliferation in combination with 5-Fu or cisplatin.

GENERAL SIGNIFICANCE

These analytical findings suggest that apigenin may be a good therapeutic agent against HNSCC cells.

Identification and analysis of the active phytochemicals from the anti-cancer botanical extract Bezielle

Bezielle is a botanical extract that has selective anti-tumor activity, and has shown a promising efficacy in the early phases of clinical testing. Bezielle inhibits mitochondrial respiration and induces reactive oxygen species (ROS) in mitochondria of tumor cells but not in non-transformed cells. The generation of high ROS in tumor cells leads to heavy DNA damage and hyper-activation of PARP, followed by the inhibition of glycolysis. Bezielle therefore belongs to a group of drugs that target tumor cell mitochondria, but its cytotoxicity involves inhibition of both cellular energy producing pathways. We found that the cytotoxic activity of the Bezielle extract in vitro co-purified with a defined fraction containing multiple flavonoids. We have isolated several of these Bezielle flavonoids, and examined their possible roles in the selective anti-tumor cytotoxicity of Bezielle. Our results support the hypothesis that a major Scutellaria flavonoid, scutellarein, possesses many if not all of the biologically relevant properties of the total extract. Like Bezielle, scutellarein induced increasing levels of ROS of mitochondrial origin, progressive DNA damage, protein oxidation, depletion of reduced glutathione and ATP, and suppression of both OXPHOS and glycolysis. Like Bezielle, scutellarein was selectively cytotoxic towards cancer cells. Carthamidin, a flavonone found in Bezielle, also induced DNA damage and oxidative cell death. Two well known plant flavonoids, apigenin and luteolin, had limited and not selective cytotoxicity that did not depend on their pro-oxidant activities. We also provide evidence that the cytotoxicity of scutellarein was increased when other Bezielle flavonoids, not necessarily highly cytotoxic or selective on their own, were present. This indicates that the activity of total Bezielle extract might depend on a combination of several different compounds present within it.

Involvement of catalase in the apoptotic mechanism induced by apigenin in HepG2 human hepatoma cells

Apigenin has been reported to inhibit proliferation of cancer cells; however, the mechanism underlying its action is not completely understood. Here, we evaluated the effects of apigenin on the levels of expression and activity of antioxidant enzymes, and the involvement of ROS in the mechanism of cell death induced by apigenin in HepG2 human hepatoma cells. Upon treatment with apigenin, HepG2 cells displayed a reduction in cell viability in a dose- and time-dependent manner, and some morphological changes. In addition, apigenin treatment induced ROS generation and significantly decreased the mRNA levels and activity of catalase and levels of intracellular GSH. On the other hand, apigenin treatment did not alter the expression or activity levels of other antioxidant enzymes. Addition of exogenous catalase significantly reduced the effects of apigenin on HepG2 cell death. We also demonstrated that HepG2 cells are more sensitive to apigenin-mediated cell death than are primary cultures of mouse hepatocytes, suggesting a differential toxic effect of this agent in tumor cells. Our results suggest that apigenin-induced apoptosis in HepG2 cells may be mediated by a H(2)O(2)-dependent pathway via reduction of the antioxidant defenses.

Apigenin inhibits hepatoma cell growth through alteration of gene expression patterns

Apigenin, a common plant flavonoid, has been shown to possess anti-tumor properties; however, the underlying molecular mechanisms are still not completely understood. In the present study, we investigated the effects of apigenin on human hepatoma Huh7 cell proliferation, cell cycle distribution, apoptosis, and colony formation in vitro, as well as on the tumorigenicity of Huh7 cells in vivo. To get more insight into the mechanism of apigenin action, we performed genome-wide expression profiling of apigenin-treated Huh7 cells using cDNA microarrays (Agilent Whole Human Genome Oligo Microarray) that contain 41,000 genes. Ten of the most differentially expressed genes (≧5-fold changes) were selected for further evaluation by quantitative RT-PCR (qPCR) and Western blot analyses. Notably, apigenin (5-20 μg/ml) remarkably inhibited Huh7 cell proliferation and colony formation as compared to the vehicle control, which was in a dose-dependent manner. Accompanying with the decreased growth, apigenin-treated cells showed a cell cycle arrest at G2/M phase and an increased rate of apoptosis. Moreover, the xenografts derived from Huh7 cells were significantly (p<0.05) retarded by the delivery of apigenin (50 μg/mouse/day) relative to the control counterparts. Gene expression profile analysis revealed that 1336 genes were up-regulated and 428 genes were down-regulated by apigenin. The down-regulation of interleukin-4 receptor and ubiquitin specific protease 18 and the up-regulation of SLC27A3 and chemokine (C-C motif) receptor 2 were further confirmed by the qPCR and Western blot results. In conclusion, apigenin exhibits inhibitory effects on hepatoma cell growth, which is likely mediated through alteration of gene expression profiles.

Apigenin inhibits cell growth and alters expression of multiple genes in human hepatoma cell line Huh-7

AIM: To investigate the effects of apigenin on cell growth and gene expression in human hepatoma cell line Huh-7.

METHODS: After Huh-7 cells was cultured and treated with different concentrations of apigenin, cell proliferation was measured by colorimetric methyl thiazolyl tetrazolium (MTT) assay; cell clonogenicity was detected by colony-forming assay; and cell cycle distribution and apoptosis were examined by flow cytometry. The impact of apigenin on the tumorigenicity of Huh-7 cells in nude mice was also detected. The differential gene expression between cells treated and untreated with apigenin was detected by cDNA microarray and verified by quantitative real-time reverse transcription-polymerase chain reaction and Western blot.

RESULTS: Compared with untreated cells, cells treated with apigenin exhibited a marked growth inhibition. The half maximal inhibitory concentration (IC₅₀) of apigenin on cell growth was approximately 10.5 mg/L ± 0.3 mg/L. Apigenin treatment could cause a cell cycle block at G2/M phase, decrease the percentage of cells at G₀/G₁ phase, promote apoptosis, and inhibit the tumorigenicity of Huh-7 cells in vivo. Apigenin treatment could also dramatically alter the expression of 1 764 functionally related genes in Huh-7 cells. Of these differentially expressed genes, the majority are involved in nucleic acid binding and transport, enzyme catalytic activity regulation, transcriptional regulation, cytoskeletal structure and/or adhesion, signal transduction, metabolism, apoptosis or the immune response. Of note, apigenin could significantly downregulate the expression of interleukin-4 receptor and ubiquitin-specific protease 18.

CONCLUSION: Apigenin partially inhibits Huh-7 cell growth in vitro and in vivo by blocking cell cycle at G₂/M phase and promoting apoptosis. Apigenin treatment alters the expression of multiple genes in Huh-7 cells.

Peroxiredoxin I contributes to TRAIL resistance through suppression of redox-sensitive caspase activation in human hepatoma cells

Reactive oxygen species (ROS) have been implicated in tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) resistance of many cancers. We evaluated the role of peroxiredoxin (Prx) I in TRAIL resistance governed by coupling of nicotinamide adenosine dinucleotide phosphate oxidase (Nox)-derived ROS signaling with the p38 mitogen-activated protein kinase (MAPK)/caspase-signaling cascade in liver cancer cells. Upregulated Prx I expression was found in neoplastic regions of human patient liver, and Prx I knockdown resulted in accelerated TRAIL-induced cell death in SK-Hep-1 human hepatoma cells. The TRAIL cytotoxicity by Prx I knockdown was dependent on activation of caspase-8/3 cascades, which was ablated by addition of inhibitors for p38 MAPK, ROS or Nox, suggesting the association with Nox-driven redox signaling. Furthermore, we found that Nox4 was constitutively expressed in both SK-Hep-1 cells and tumor regions of patient livers, knockdown of Nox4 expression could alleviate ROS generation and TRAIL-mediated cytotoxicity. In accordance with previous findings, increased activation of both p38 MAPK and caspase cascades by Prx I knockdown was inhibited by either Nox4 knockdown or SB203580 addition. Collectively, these data suggest that Prx I functions to block propagation of Nox-derived ROS signaling to the p38 MAPK/caspase/cell death cascade during TRAIL treatment and also provides a molecular mechanism by which Prx I contributes to TRAIL resistance in liver cancers.

Plant flavonoid apigenin inactivates Akt to trigger apoptosis in human prostate cancer: an in vitro and in vivo study

Inappropriate activation of phosphatidylinositol 3-kinase-Akt signaling contributes to the development of several human malignancies. Modulation of Akt activity is a strategy that may be valuable in chemopreventive and chemotherapeutic regimens. We have previously demonstrated that apigenin, a plant flavone, causes decreased survival in human prostate cancer cells. However, the molecular mechanism underlying this observation remains elusive. In the present study, we investigated the mechanisms of apigenin action on human prostate cancer PC-3 cells, which possess constitutively active Akt. Treatment of PC-3 cells with apigenin (5-40 microM) resulted in significant dose- and time-dependent decrease in Akt phosphorylation at Serine473. Apigenin-mediated dephosphorylation of Akt resulted in inhibition of its kinase activity, which was confirmed by reduced phosphorylation of proapoptotic proteins BAD and glycogen synthase kinase-3, essential downstream targets of Akt. Hypophosphorylation of BAD resulted in reduced interaction with 14-3-3beta protein after 20 microM apigenin exposure to PC-3 cells for 24 h. Inactivation of Akt seems to be associated with downregulation of insulin-like growth factor receptor 1 protein level and inhibition of its autophosphorylation upon apigenin treatment. Exposure to apigenin significantly induced caspase-9 activity and decreased the survival of PC-3 cells in a dose-dependent manner. Furthermore, Serine473 phosphorylation of ectopically expressed Akt in DU145 cells was significantly reduced upon 20 microM apigenin treatment. In vivo, apigenin intake through gavage resulted in inactivation of Akt and induction of apoptosis in PC-3 tumors. These results suggest that Akt inactivation and dephosphorylation of BAD is a critical event, at least in part, in apigenin-induced decreased cell survival and apoptosis.

Structurally related cytotoxic effects of flavonoids on human cancer cells in vitro

Flavonoids exist extensively in the human diet, and a variety of health effects have been ascribed to them. The cytotoxic effects of 23 flavonoids on breast cancer cells (MDA-MB-231 and MCF-7), colorectal carcinoma cells (LoVo and DLD-1) and prostatic cancer cells (PC3) were investigated. By comparing the cytotoxicity (EC(50)) of selected molecules that differ in only one structure element, we identified several structural properties associated with enhanced cytotoxicity, including the presence of the 2,3-double bond, appropriate hydroxyl numbers, 3-OH, 6-OH and ortho-hydroxylation in ring B. Flavonoids with a 5-OH exhibited lower cytotoxicity than their non-hydroxylated counterparts. Results indicated that 3,6-dihydroxylflavone showed the most potent cytotoxic effect on these cancer cells. The appearance of apoptotic cells with DAPI staining was observed in cancer cells under 3,6-dihydroxylflavone treatment, and the apoptosis analysis by flow cytometry also showed that 3,6-dihydroxylflavone induced apoptotic cell death in these cancer cells. These results revealed the structurally related toxicity of flavonoids on human cancer cells, and indicates that 3,6-dihydroxylflavone is an active compound worthy of development for cancer chemotherapy.