Esculetin induces mitochondria-mediated apoptosis in 3T3-L1 adipocytes

Therapeutic Effects of Coumarins with Different Substitution Patterns

The use of derivatives of natural and synthetic origin has gained attention because of their therapeutic effects against human diseases. Coumarins are one of the most common organic molecules and are used in medicine for their pharmacological and biological effects, such as anti-inflammatory, anticoagulant, antihypertensive, anticonvulsant, antioxidant, antimicrobial, and neuroprotective, among others. In addition, coumarin derivates can modulate signaling pathways that impact several cell processes. The objective of this review is to provide a narrative overview of the use of coumarin-derived compounds as potential therapeutic agents, as it has been shown that substituents on the basic core of coumarin have therapeutic effects against several human diseases and types of cancer, including breast, lung, colorectal, liver, and kidney cancer. In published studies, molecular docking has represented a powerful tool to evaluate and explain how these compounds selectively bind to proteins involved in various cellular processes, leading to specific interactions with a beneficial impact on human health. We also included studies that evaluated molecular interactions to identify potential biological targets with beneficial effects against human diseases.

Chlorogenic acid suppresses miR-460a in the regulation of Bcl-2, causing interleukin-1β reduction in thiram exposed chondrocytes via caspase-3/caspase-7 pathway

BACKGROUND

Apoptosis is thought to be involved in all processes, including normal cell cycle, immune system, atrophy, embryonic development, and chemical-induced cellular damage. However, if the normal apoptotic process fails, the results might be disastrous, e.g., chondrocytes damage in tibial dyschondroplasia (TD). TD is a worldwide issue in the poultry sector due to thiram toxicity. Thiram (Tetramethyl thiuram disulfide) is a dithiocarbamate pesticide and fungicide commonly used in horticulture to treat grains meant for seed protection and preservation.

PURPOSE

According to prior studies, chlorogenic acid (CGA) is becoming essential for regulating apoptosis. But still, the specific role of CGA in chondrocyte cells remains unclear. The present study explored the molecular mechanism of CGA on chondrocytes' apoptosis with B-cell lymphoma 2 signaling under the effect of miR-460a.

METHODS

An in vivo and in vitro study was performed according to our previously developed methodology. Flow cytometry, western blotting, reverse transcription-quantitative polymerase chain reaction, and immunofluorescence assay were used to investigate the involvement of apoptosis and inflammasome related pathways.

RESULTS

The CGA decreased the apoptosis rate with the deactivation of miR-460a, accompanied by the activation of Bcl-2. The high expression of miR-460a reduced the cell viability of chondrocytes in vitro and in vivo, that led to the interleukin-1β production. While the apoptotic executioners (caspase-3 and caspase-7) acted upstream in miR-460a overexpressing cells, and its depletion downgraded these executioners. The CGA administrated cells negatively regulated miR-460a expression and thus indicating the deactivation of the apoptotic and inflammasome related pathways.

CONCLUSION

Chlorogenic acid had a negative effect on miR-460a, setting off specific feedback to regulate apoptotic and inflammasome pathways, which might be a key feature for chondrocytes' survival.

Chlorogenic acid suppresses mitochondrial apoptotic effectors Bax/Bak to counteract Nod-like receptor pyrin domain 3 (NLRP3) inflammasome in thiram exposed chondrocytes

BACKGROUND

Tibial dyschondroplasia (TD) is a common disease characterized by proliferation and the deterioration of growth plate's chondrocytes due to widespread utilization of thiram in the agriculture and industrial sector.

PURPOSE

In recent years, Nod-like receptor pyrin domain 3 (NLRP3) inflammasome has become a dilemma in the occurrence of many diseases. According to many research investigations, NLRP3 inflammasome has been linked to various diseases caused by pesticides and environmental toxins. Its involvement in such conditions opens up new treatment approaches. However, the role of the NLRP3 inflammasome in the development of TD is not fully understood under the impact of chlorogenic acid (CGA).

METHODS

Chondrocytes were cultured with our previously developed methodology from growth plates. After morphological and molecular identification, chondrocytes were split into different groups to investigate the efficacy of chlorogenic acid. Cell apoptosis was determined through flow cytometry and Tunnel assay. Furthermore, RT-qPCR, immunofluorescence, and western blotting techniques were used to check marker genes and proteins expression.

RESULTS

In thiram-induced TD, Bax/Bak activation persuade a parallel pathway, mediated by the NLRP3 base inflammasome. It is worth mentioning that the apoptotic executioners (caspase-3 and caspase-7) act upstream for inflammasome. Furthermore, chondrocytes' ability to undergo mitochondrial apoptosis was governed by anti-apoptotic members, e.g., Bcl-2 and Bcl-xl. Equilibrium of these anti-apoptotic proteins ensured appropriate regulation of apoptosis during the development and survival of chondrocytes.

CONCLUSION

Chondrocytes have ability to undergo Bax/Bak-mediated apoptosis and generate pro-inflammatory signals, e.g., NLRP3 in thiram-induced TD. So, the Nod-like receptor pyrin domain 3 is the potential target to eliminate TD at all stages of pathology, while drugs, e.g., CGA, can significantly improve chondrocytes' survival by targeting these pro-inflammatory signals.

Hepatoprotective effect of the tyrosine kinase inhibitor nilotinib against cyclosporine-A induced liver injury in rats through blocking the Bax/Cytochrome C/caspase-3 apoptotic signaling pathway

Cyclosporine-A (CsA) is a powerful immunosuppressive agent and hepatotoxicity results from CsA treatment. This study aimed to elucidate the effectiveness of tyrosine kinase inhibitor nilotinib against CsA-induced hepatotoxicity and the underlying molecular mechanisms. Male Sprague-Dawley rats were allocated into four groups and received drugs for 28 days as follows: Control group: received vehicle, Nilotinib group: received nilotinib (20 mg/kg orally), CsA group: received CsA by subcutaneous injection (20 mg/kg daily), CsA-nilotinib: received nilotinib and CsA. Serum lactate dehydrogenase (LDH), liver function biomarkers, hepatic levels of oxidative stress biomarkers, nuclear factor erythroid-2 like-2 (Nrf2), total antioxidant capacity (TAC), interleukin-2 (IL-2), IL-1β, IL-6, and cytochrome-C were assessed. Additionally, the protein levels and mRNA expression of Bcl2 associated X protein (Bax), caspase-3, nuclear factor-κB (NF-κB), hemoxygenase-1 (HO-1) were measured. Moreover, liver tissues were assessed histopathologically using hematoxylin-eosin and Masson trichrome stain. Nilotinib treatment decreased serum LDH, alanine aminotransferase, aspartate aminotransferase, and γ-glutamyltransferase (γ-GT), hepatic malondialdehyde, and cytochrome-C. It also increased superoxide dismutase, reduced glutathione, glutathione reductase, glutathione peroxidase, glutathione-S-transferase (GST), TAC, and Nrf2 compared to CsA-injected rats. In addition, nilotinib decreased NF-κB, IL-1β, IL-6, Bax, and caspase-3, while elevated IL-2 and immunoexpression of HO-1. Additionally, mRNA expression of Bax and caspase-3 was elevated and that of HO-1 and inhibitory protein κB-α was reduced in the nilotinib-treated group. Moreover, nilotinib significantly attenuated CsA-induced histopathological alterations. Nilotinib may have a promising role as a hepato-protective through its antiapoptotic, antioxidant, and anti-inflammatory effects.

Artemisia scoparia and Metabolic Health: Untapped Potential of an Ancient Remedy for Modern Use

Botanicals have a long history of medicinal use for a multitude of ailments, and many modern pharmaceuticals were originally isolated from plants or derived from phytochemicals. Among these, artemisinin, first isolated from Artemisia annua, is the foundation for standard anti-malarial therapies. Plants of the genus Artemisia are among the most common herbal remedies across Asia and Central Europe. The species Artemisia scoparia (SCOPA) is widely used in traditional folk medicine for various liver diseases and inflammatory conditions, as well as for infections, fever, pain, cancer, and diabetes. Modern in vivo and in vitro studies have now investigated SCOPA's effects on these pathologies and its ability to mitigate hepatotoxicity, oxidative stress, obesity, diabetes, and other disease states. This review focuses on the effects of SCOPA that are particularly relevant to metabolic health. Indeed, in recent years, an ethanolic extract of SCOPA has been shown to enhance differentiation of cultured adipocytes and to share some properties of thiazolidinediones (TZDs), a class of insulin-sensitizing agonists of the adipogenic transcription factor PPARγ. In a mouse model of diet-induced obesity, SCOPA diet supplementation lowered fasting insulin and glucose levels, while inducing metabolically favorable changes in adipose tissue and liver. These observations are consistent with many lines of evidence from various tissues and cell types known to contribute to metabolic homeostasis, including immune cells, hepatocytes, and pancreatic beta-cells. Compounds belonging to several classes of phytochemicals have been implicated in these effects, and we provide an overview of these bioactives. The ongoing global epidemics of obesity and metabolic disease clearly require novel therapeutic approaches. While the mechanisms involved in SCOPA's effects on metabolic, anti-inflammatory, and oxidative stress pathways are not fully characterized, current data support further investigation of this plant and its bioactives as potential therapeutic agents in obesity-related metabolic dysfunction and many other conditions.

Tambuwala M. Dietary Crocin is Protective in Pancreatic Cancer while Reducing Radiation-Induced Hepatic Oxidative Damage

Pancreatic cancer is one of the fatal causes of global cancer-related deaths. Although surgery and chemotherapy are standard treatment options, post-treatment outcomes often end in a poor prognosis. In the present study, we investigated anti-pancreatic cancer and amelioration of radiation-induced oxidative damage by crocin. Crocin is a carotenoid isolated from the dietary herb saffron, a prospect for novel leads as an anti-cancer agent. Crocin significantly reduced cell viability of BXPC3 and Capan-2 by triggering caspase signaling via the downregulation of Bcl-2. It modulated the expression of cell cycle signaling proteins P53, P21, P27, CDK2, c-MYC, Cyt-c and P38. Concomitantly, crocin treatment-induced apoptosis by inducing the release of cytochrome c from mitochondria to cytosol. Microarray analysis of the expression signature of genes induced by crocin showed a substantial number of genes involved in cell signaling pathways and checkpoints (723) are significantly affected by crocin. In mice bearing pancreatic tumors, crocin significantly reduced tumor burden without a change in body weight. Additionally, it showed significant protection against radiation-induced hepatic oxidative damage, reduced the levels of hepatic toxicity and preserved liver morphology. These findings indicate that crocin has a potential role in the treatment, prevention and management of pancreatic cancer.

Effects of isoimperatorin on proliferation and apoptosis of human gastric carcinoma cells

Resistance to apoptosis is an characteristic of cancer cells that serves a critical function in tumor development and represents a target for antitumor therapy. Isoimperatorin (ISOIM), a coumarin compound, exhibits antitumor functions in multiple types of tumor cells. However, its antitumor effects and molecular mechanisms with respect to gastric cancer have not been elucidated. The present study assessed the anti-proliferative and apoptotic effects of ISOIM on human BGC-823 gastric cancer cells and elucidated its underlying molecular mechanisms. Cell proliferation was evaluated using MTT assays. Analysis of cell morphology was performed by hematoxylin and eosin, Hoechst 33258 and acridine orange/ethidium bromide staining. In addition, cell cycle and apoptosis was evaluated using flow cytometry analysis; expression of apoptosis-associated proteins was studied by western blotting. The results of the present study revealed that ISOIM significantly inhibited cell proliferation by arresting the cell cycle at the G₂/M phase and induced apoptosis by increasing Bcl-2-associated X (Bax) expression with a concomitant decrease in Bcl-2 expression, resulting in a decreased Bcl-2/Bax ratio compared with the control. In addition, ISOIM treatment also resulted in cytochrome c translocating from the mitochondria to the cytosol. Furthermore, caspase-3 was significantly activated in response to treatment with ISOIM, suggesting that apoptosis in BGC-823 cells is induced in the mitochondrial pathway. Taken together, the results of the present study indicate that ISOIM may significantly induce apoptosis in BGC-823 cells and that the pro-apoptotic mechanisms of ISOIM could be associated with the mitochondrial pathway.

The anti-osteosarcoma cell activity by a mTORC1/2 dual inhibitor RES-529

mTOR over-activation is important for human osteosarcoma (OS) tumorigenesis and progression. RES-529 is a mTORC1/2 dual inhibitor. Here, our results show that RES-529 inhibited viability, cell cycle progression and proliferation of the established (U2OS line) and primary human OS cells. RES-529 induced apoptosis activation in OS cells. It was yet non-cytotoxic to OB-6 osteoblastic cells and the primary human osteoblasts. RES-529 disrupted assembling of mTORC1 (mTOR-Raptor association) and mTORC2 (mTOR-Rictor-mLST8 association) in human OS cells, blocking mTORC1/2 activation. Significantly, RES-529 induced reactive oxygen species (ROS) production and mitochondrial depolarization in U2OS cells as well. RES-529-induced anti-OS cell activity was more potent than other known Akt-mTOR inhibitors. In vivo, RES-529 intraperitoneal injection significantly inhibited U2OS xenograft tumor growth in severe combined immunodeficiency (SCID) mice. mTORC1/2 activation in RES-529-treated tumor tissues was largely inhibited. Collectively, the mTOR inhibitor RES-529 efficiently inhibits human OS cell growth in vitro and in vivo.

Pharmacological Activities and Synthesis of Esculetin and Its Derivatives: A Mini-Review

Esculetin, synonymous with 6,7-dihydroxycoumarin, is the main active ingredient of the traditional Chinese medicine Cortex Fraxini. The twig skin or trunk bark of Cortex Fraxini are used by herb doctors as a mild, bitter liver and gallbladder meridians' nontoxic drug as well as dietary supplement. Recently, with a variety of novel esculetin derivatives being reported, the molecular mechanism research as well as clinical application of Cortex Fraxini and esculetin are becoming more attractive. This mini-review will consolidate what is known about the biological activities, the mechanism of esculetin and its synthetic derivatives over the past decade in addition to providing a brief synopsis of the properties of esculetin.

Structural analysis and anti-obesity effect of a pectic polysaccharide isolated from Korean mulberry fruit Oddi (Morus alba L.)

A water-soluble polysaccharide JS-MP-1 was isolated from Korean mulberry fruits Oddi (Morus alba L.). Sugar linkage analysis and NMR data confirmed that it is a rhamnogalacturonan type I (RG I) polymer carrying arabinan and arabinogalactan (AG II) side chains. JS-MP-1 reduced dose-dependently the viability of 3T3-L1 pre-adipocyte cells, significantly stimulated the cleavage of caspases 9 and 3 and poly (ADP-ribose) polymerase (PARP) and decreased the ratio of Bcl-2 to Bax expression level that led to mitochondrial dysfunction and apoptosis in pre-adipocyte cells. The apoptotic death was mediated by stimulation of MAPKs (ERK and p38) signalling pathway. These results suggest that JS-MP-1 is able to reduce the number of fat cells and the mass of adipose tissue via inhibition of pre-adipocyte proliferation and thus JS-MP-1 itself or a crude aqueous Oddi extract containing this polysaccharide can be used as functional ingredient of health-beneficial food supplements for the treatment or prevention of obesity disorders.

Single-cell microinjection assay indicates that 7-hydroxycoumarin induces rapid activation of caspase-3 in A549 cancer cells

Coumarins have attracted intense interest in recent years due to their apoptogenic effects. The aim of the present study was to determine whether 7-hydroxycoumarin (7-HC) induces changes in caspase-3 (C-3) activity in A549 human lung carcinoma cells. A range of analytical techniques, including colorimetric and fluorometric assays, western blotting, single-cell microinjection, fluorescence microscopy and image analysis were conducted to elucidate the effects of 7-HC. A 24-h exposure to 1.85 mM 7-HC induced a 65% increase in C-3 activity, and a notable conversion of procaspase-3 to C-3, in addition to poly(ADP-ribose)polymerase cleavage. Furthermore, morphological changes associated with apoptosis were observed. Exposure of the cells to 7-HC for 3 or 6 h increased calcium conductance by 27%. By performing the single-cell microinjection of a specific fluorescent substrate of C-3 into previously 7-HC-exposed cells, a typical enzymatic kinetic profile of C-3 activation was identified a number of hours prior to the morphological and biochemical changes associated with apoptosis being observed. These results suggest that the rapid in vivo activation of C-3 is induced by 7-HC, the most relevant biotransformation product of coumarin in humans.

Sulforaphane induces apoptosis in adipocytes via Akt/p70s6k1/Bad inhibition and ERK activation

Sulforaphane (SFN), an isothiocyanate isolated from cruciferous vegetables, possesses anti-oxidant and anti-cancer bioactivities. Moreover, SFN exerts its pro-apoptotic effects in some cancer lines. However, the effects and mechanisms of SFN on the regulation of apoptosis of adipocytes are still unknown. In this study, we found that SFN induced significant apoptosis in 3T3-L1 adipocytes and markedly decreased the cellular lipid content. Western blot demonstrated that SFN-induced apoptosis was mediated via the mitochondrial apoptosis pathway based on increased cleavage of poly-ADP-ribose-polymerase (PARP), release of cytochrome c into the cytoplasm, and activation of caspase-3, as well as decreased Bcl-2/Bax ratio. In addition, SFN markedly decreased phosphorylation of Akt and downstream proteins, p70s6k1 and Bad, and increased phosphorylation of ERK. Therefore, our findings clarified that SFN could induce 3T3-L1 adipocyte apoptosis via down-regulation of the Akt/p70s6k1/Bad pathway and up-regulation of the ERK pathway, suggesting SFN may be a promising agent for the treatment or prevention of obesity.

Curcumin triggers apoptosis via upregulation of Bax/Bcl-2 ratio and caspase activation in SW872 human adipocytes

Induction of adipocyte apoptosis has been postulated as a novel strategy with which to treat obesity. The effects of curcumin, a polyphenol compound, on the apoptotic signaling pathway in SW872 adipocytes were investigated in the present study. The results showed that cell viability decreased following curcumin treatment in a time- and dose-dependent manner. The results from a single-stranded DNA ELISA assay indicated that curcumin causes the number of apoptotic cells to increase in a concentration-dependent manner. In addition, curcumin treatment resulted in an increased expression of Bax, and a decrease in that of of Bcl-2, with a concomitant upregulation of the Bax/Bcl-2 ratio. Curcumin treatment also led to the release of cytochrome c from mitochondria into the cytosol. Similarly, caspase-dependent poly (ADP) ribose polymerase (PARP) cleavage by curcumin was observed in the current study. In conclusion the results indicate that curcumin is an effective therapeutic agent with which to induce apoptosis in adipocytes. This effect is, in part, mediated through the mitochondrial pathway, which involves upregulation of the Bax/Bcl-2 ratio, cytochrome c release, activation of caspase-3 and the cleavage of PARP.

Human acute promyelocytic leukemia NB4 cells are sensitive to esculetin through induction of an apoptotic mechanism

Acute promyelocytic leukemia (APL) is a type of cancer, in which immature cells called promyelocytes proliferate abnormally. Human NB4 cell line appears to be a suitable in vitro model to express the characteristics of APL. In this work, we have investigated the effects of esculetin, a coumarin derivative with antioxidant properties, on the viability, the induction of apoptosis and the expression of apoptotic factors in NB4 cells. Cells treated with esculetin at several concentrations (20-500 μM) and for different times (5-24 h) showed a concentration- and time-dependent viability decrease with increased subdiploid DNA production. Esculetin inhibited cell cycle progression and induced DNA fragmentation. Moreover, annexin-V-FITC cytometry assays suggested that increased toxicity is due to both early and late apoptosis. This apoptosis process is be mediated by activation of caspase-3 and caspase-9. Treatments with progressively increasing concentrations (from 100 μM to 500 μM) of esculetin produced a reduction of Bcl2/Bax ratio in NB4 cells at 19 h, without affecting p53 levels. Proapoptotic action of esculetin involves the ERK MAP kinase cascade since increased levels of phosphorylated ERK were observed after those treatments. Increments in the levels of phosphorylated-Akt were also observed. Additionally, esculetin induced the loss of mitochondrial membrane potential with a release of cytochrome c into the cytosol which starts at 6 h of treatment with esculetin and increases up to 24 h. Esculetin induced an increase in superoxide anion at long times of treatment and a reduction of peroxides at short times (1 h) with an observed increase at 2-4 h of treatment. No significant changes in NO production was observed. Esculetin reduced the GSH levels in a time-dependent manner. In summary, the present work shows the cytotoxic action of esculetin as an efficient tool to study apoptosis mechanism induction on NB4 cell line used as a relevant model of APL disease.

Furocoumarin derivatives from radix Angelicae dahuricae and their effects on RXRα transcriptional regulation

A novel furocoumarin derivative named oxyalloimperatorin (1), together with seventeen furocoumarins 2–18 were isolated from the radix of Angelica dahurica. The chemical structure of new metabolite was characterized by analysis of IR, NMR, and HR-ESI-MS spectroscopic data. Among the isolated compounds, 13, 16, and 18 (each at 20 μM) could significantly promote the gene transcriptional function of nuclear receptor RXRα. While 7–9, 13, 14, and the new structure 1 (each at 20 μM) showed significant reduction in RXRα gene transcriptional activities induced by 9-cis-retinoid acid. The findings indicated that these furocoumarin skeleton derivatives might hold beneficial effects on many intractable diseases, such as cancer and metabolic diseases, due to their potential activities on regulating the transcriptional activation function of RXRα.

Aesculetin-induced apoptosis through a ROS-mediated mitochondrial dysfunction pathway in human cervical cancer cells

Aesculetin (1) is an important coumarin found in various plant materials. It has been shown to have antiproliferative effects on several types of human cancer cells, but its effect on cervical cancer cells in vitro is unknown. In this study, we investigated that the cytotoxic effect of 1 on a non-cancer cell line (293) was smaller than on a tumor cell line (HeLa). This is the first report showing the possible mechanism of antiproliferative effect of 1 for the prevention of cervical cancer in cell culture models. It was found that 1 inhibited cell viability by inducing apoptosis, as evidenced by the formation of apoptotic bodies, generation of reactive oxygen species (ROS), and the accumulation of cells in the sub-G1 phase. Treatment with compound 1 decreased the cell growth in a dose-dependent manner with an IC(50) value of 37.8 microM. Aesculetin-induced apoptosis was correlated with mitochondrial dysfunction (DeltaPsi(m)), leading to the release of cytochrome c from the mitochondria to the cytosol, as well as the proteolytic activation of caspases in HeLa cells. These results indicate that 1 induces apoptosis in HeLa cells through a ROS-mediated mitochondrial dysfunction pathway.

Biotransformation of aesculin by human gut bacteria and identification of its metabolites in rat urine

AIM: To observe the biotransformation process of a Chinese compound, aesculin, by human gut bacteria, and to identify its metabolites in rat urine.

METHODS: Representative human gut bacteria were collected from 20 healthy volunteers, and then utilized in vitro to biotransform aesculin under anaerobic conditions. At 0, 2, 4, 8, 12, 16, 24, 48 and 72 h post-incubation, 10 mL of culture medium was collected. Metabolites of aesculin were extracted 3 × from rat urine with methanol and analyzed by HPLC. For in vivo metabolite analysis, aesculetin (100 mg/kg) was administered to rats via stomach gavage, rat urine was collected from 6 to 48 h post-administration, and metabolite analysis was performed by LC/ESI-MS and MS/MS in the positive and negative modes.

RESULTS: Human gut bacteria could completely convert aesculin into aesculetin in vitro. The biotransformation process occurred from 8 to 24 h post-incubation, with its highest activity was seen from 8 to 12 h. The in vitro process was much slower than the in vivo process. In contrast to the in vitro model, six aesculetin metabolites were identified in rat urine, including 6-hydroxy-7-gluco-coumarin (M1), 6-hydroxy-7-sulf-coumarin (M2), 6, 7-di-gluco-coumarin (M3), 6-glc-7-gluco-coumarin (M4), 6-O-methyl-7-gluco-coumarin (M5) and 6-O-methyl-7-sulf-coumarin (M6). Of which, M2 and M6 were novel metabolites.

CONCLUSION: Aesculin can be transferred into aesculetin by human gut bacteria and is further modified by the host in vivo. The diverse metabolites of aesculin may explain its pleiotropic pharmaceutical effects.

Apoptogenic effect of 7,8-diacetoxy-4-methylcoumarin and 7,8-diacetoxy-4-methylthiocoumarin in human lung adenocarcinoma cell line: role of NF-kappaB, Akt, ROS and MAP kinase pathway

Coumarin (1,2-benzopyrone) is a naturally occurring fragrant compound found in a variety of plants and spices. Coumarins have attracted intense interest in recent years because of their diverse pharmacological activities. This study examines the antioxidant coumarin 7,8-diacetoxy-4-methylcoumarin (DAMC) and its thiocoumarin derivative 7,8-diacetoxy-4-methylthiocoumarin (DAMTC) for their effect on human non-small cell lung cancer A549 cells. Here we show that both DAMC and DAMTC not only inhibited cell proliferation, but also induced apoptosis with an IC(50) of 160 microg/ml as confirmed by morphological examination, annexin-V assay and flow cytometric analysis. Interestingly, it was observed that these two coumarin compounds exhibited little cytotoxicity towards peripheral blood mononuclear cells but induced apoptosis in malignant cells. DAMC/DAMTC treatment also resulted in pronounced release of apoptogenic cytochrome c from mitochondria to cytosol, alteration of mitochondrial membrane potential (DeltaPsi(m)), and activation of caspase-9 and caspase-3. Although an increase in the levels of reactive oxygen species (ROS) was observed, pre-treatment with antioxidant showed no protective effect against DAMC/DAMTC-induced apoptosis. Results of present study suggest that downregulation of Bcl-xl, Cox-2 and mitogen activated protein kinase pathway and upregulation of p53, Akt and NF-kappaB pathway are involved in the underlying molecular mechanism of apoptosis induction by DAMC and DAMTC in A549 cells.

Enhanced inhibition of adipogenesis and induction of apoptosis in 3T3-L1 adipocytes with combinations of resveratrol and quercetin

Certain flavonoids have been shown to have specific effects on biochemical and metabolic functions of adipocytes. In this study, we investigated the effects of combinations of resveratrol and quercetin on adipogenesis and apoptosis in 3T3-L1 cells. In maturing preadipocytes resveratrol and quercetin at 25 microM individually suppressed intracellular lipid accumulation by 9.4+/-3.9% (p<0.01) and 15.9+/-2.5%, respectively, (p<0.001). The combination of resveratrol and quercetin at the same dose, however, decreased lipid accumulation by 68.6+/-0.7% (p<0.001). In addition, combinations of resveratrol and quercetin at 25 microM significantly decreased the expression of peroxisome proliferators-activated receptor gamma (PPAR gamma) and CCAAT/enhancer-binding protein (C/EBP)alpha, both of which act as key transcription factors. In mature adipocytes resveratrol and quercetin at 100 microM individually decreased viability by 18.1+/-0.6% (p<0.001) and 15.8+/-1% (p<0.001) and increased apoptosis (100 microM) by 120.5+/-8.3% (p<0.001) and 85.3+/-10% (p<0.001) at 48 h, respectively. Combinations of resveratrol and quercetin further decreased viability (73.5+/-0.9%, p<0.001) and increased apoptosis (310.3+/-9.6%, p<0.001) more than single compounds alone. The combination of resveratrol and quercetin at 100 muM increased release of cytochrome c from mitochondria to cytosol and decreased ERK 1/2 phosphorylation. Taken together, our data indicate that combinations of resveratrol and quercetin can exert potential anti-obesity effects by inhibiting differentiation of preadipocytes and inducing apoptosis of mature adipocytes.

Plant phenolics regulate neoplastic cell growth and survival: a quantitative structure-activity and biochemical analysis

The anti-tumour activities of many plant phenolics at high concentrations (>100 micromol/L) suggest their potential use as dietary supplements in cancer chemoprevention and cancer chemotherapy. However, it is not clear what impact phenolic compounds have at the physiological concentrations obtained through consumption of high phenolic diets on neoplastic cells. In the present study, 54 naturally occurring phenolics were evaluated at physiologically relevant concentrations for their capacity to alter PC12 cell viability in response to serum deprivation, the chemotherepeutic agent etoposide, and the apoptogen C2-ceramide. Surprisingly, novel mitogenic, cytoprotective, and antiapoptotic activities were detected. Quantitative structure-activity relationship modelling indicated that many of these activities could be predicted by compound lipophilicity, steric bulk, and (or) antioxidant capacity, with the exception of inhibition of ceramide-induced apoptosis. Where quantitative structure-activity relationship analysis was insufficient, biochemical assessment demonstrated that the benzoate orsellinic acid blocked downstream caspase-12 activation following ceramide challenge. These findings demonstrate substantive mitogenic, cytoprotective, and antiapoptotic biological activities of plant phenolics on neoplastic cells at physiologically relevant dietary concentrations that should be considered in chemopreventive and chemotherapeutic strategies.

Withaferin A induces apoptosis and inhibits adipogenesis in 3T3-L1 adipocytes

Withaferin A (WA), a highly oxygenated steroidal lactone that is found in the medicinal plant Withania somnifera (also called ashwagandha) has been reported to have anti-tumor, anti-angiogenesis, and pro-apoptotic activity. We investigated the effects of WA on viability, apoptosis and adipogenesis in 3T3-L1 adipocytes. Pre- and post-confluent preadipocytes and mature adipocytes were treated with WA (1-25 microM) up to 24 hrs. Viability and apoptosis were measured by CellTiter-Blue Cell Viability Assay and single strand DNA ELISA Assay, respectively. WA decreased viability and induced apoptosis in all stages of cells. Induction of apoptosis by WA in mature adipocytes was mediated by increased ERK1/2 phosphorylation and altered Bax and Bcl2 protein expression. The effect of WA on adipogenesis was examined by AdipoRed Assay after treating with WA (0.1-1 microM) during the differentiation period. WA decreased lipid accumulation in a dose-dependent manner and decreased the expression of peroxisome proliferator-activated receptor gamma, CCAAT/enhancer binding protein alpha and adipocyte fatty acid binding protein. The effects on apoptosis and lipid accumulation were also confirmed with Hoechst staining and Oil Red O staining, respectively. These results show that WA acts on adipocytes to reduce cell viability and adipogenesis and also induce apoptosis.

Enhancement of ajoene-induced apoptosis by conjugated linoleic acid in 3T3-L1 adipocytes

Ajoene has been shown to induce apoptosis in 3T3-L1 adipocytes. In this report the effects on apoptosis of combinations of ajoene and trans-10, cis-12 conjugated linoleic acid (t10,c12CLA) in 3T3-L1 adipocytes were investigated. Although t10,c12CLA alone had no effect, ajoene plus t10,c12CLA reduced cell viability more than ajoene alone at 24 h (59.1 vs. 85.9% of control, respectively; p<0.05). Compared to treatment with t10,c12CLA, ajoene increased apoptosis 218% after 24 h (p<0.01), whereas ajoene plus t10,c12CLA increased apoptosis 122% over that caused by ajoene alone (p<0.01). Immunoblotting analysis also indicated that ajoene plus t10,c12CLA caused a greater increase in phosphorylation of c-Jun N-terminal kinase (JNK) and Bax expression and a greater release of mitochondrial proteins (cytochrome c, AIF) than additive responses to each compound alone. Ajoene plus t10,c12CLA also increased ROS production more than that resulting from ajoene treatment alone (264 vs 204% after 40 min, respectively; p<0.01). Furthermore, the antioxidant NAC prevented ROS generation and apoptosis by ajoene plus t10,c12CLA. Interestingly, the combination of ajoene and t10,c12CLA increased NF-kappaB activation and decreased the level of phosphorylated Akt more than each compound alone. Altogether, our observations indicate that t10,c12CLA potentiates the effect of ajoene on apoptosis in 3T3-L1 adipocytes.

Esculetin induces apoptosis and inhibits adipogenesis in 3T3-L1 cells

OBJECTIVE

To determine the effects of esculetin, a plant phenolic compound with apoptotic activity in cancer cells, on 3T3-L1 adipocyte apoptosis and adipogenesis.

RESEARCH METHODS AND PROCEDURES

3T3-L1 pre-confluent preadipocytes and lipid-filled adipocytes were incubated with esculetin (0 to 800 microM) for up to 48 hours. Viability was determined using the Cell Titer 96 Aqueous One Solution cell proliferation assay; apoptosis was quantified by measurement of single-stranded DNA. Post-confluent preadipocytes were incubated with esculetin for up to 6 days during maturation. Adipogenesis was quantified by measuring lipid content using Nile Red dye; cells were also stained with Oil Red O for visual confirmation of effects on lipid accumulation.

RESULTS

In mature adipocytes, esculetin caused a time- and dose-related increase in adipocyte apoptosis and a decrease in viability. Apoptosis was increased after only 6 hours by 400 and 800 microM esculetin (p < 0.05), and after 48 hours, as little as 50 microM esculetin increased apoptosis (p < 0.05). In preadipocytes, apoptosis was detectable only after 48 hours (p < 0.05) with 200 microM esculetin and higher concentrations. However, results of the cell viability assay indicated a reduction in preadipocyte number in a time- and dose-related manner, beginning as early as 6 hours with 400 and 800 microM esculetin (p < 0.05). Esculetin also inhibited adipogenesis of 3T3-L1 preadipocytes. Esculetin-mediated inhibition of adipocyte differentiation occurred during the early, intermediate, and late stages of the differentiation process. In addition, esculetin induced apoptosis during the late stage of differentiation.

DISCUSSION

These findings suggest that esculetin can alter fat cell number by direct effects on cell viability, adipogenesis, and apoptosis in 3T3-L1 cells.