Tellimagrandin I enhances gap junctional communication and attenuates the tumor phenotype of human cervical carcinoma HeLa cells in vitro

Tellimagrandin-I and camptothin a exhibit chemopreventive effects in Salmonella enterica serovar Typhimurium strains and human lymphocytes

Tellimagrandin-I (TL) and camptothin A (CA) are ellagitannins widely found in diverse plant species. Numerous studies demonstrated their significant biological activities, which include antitumor, antioxidant, and hepatoprotective properties. Despite this protective profile, the effects of TL and CA on DNA have not been comprehensively investigated. Thus, the aim of this study was to determine the mutagenic and antimutagenic effects attributed to TL and CA exposure on Salmonella enterica serovar Typhimurium strains using the Ames test. In addition, the cytotoxic and genotoxic effects were examined on human lymphocytes, employing both trypan blue exclusion and CometChip assay. The antigenotoxic effect was determined following TL and CA exposure in the presence of co-treatment with doxorubicin (DXR). Our results from the Ames test indicated that TL or CA did not display marked mutagenic activity. However, TL or CA demonstrated an ability to protect DNA against the damaging effects of the mutagens 4-nitroquinoline-1-oxide and sodium azide, thereby exhibiting antimutagenic properties. In relation to human lymphocytes, TL or CA did not induce significant cytotoxic or genotoxic actions on these cells. Further, these ellagitannins exhibited an ability to protect DNA from damage induced by DOX during co-treatment, indicating their potential beneficial usefulness as antigenotoxic agents. In conclusion, the protective effects of TL or CA against mutagens, coupled with their absence of genotoxic and cytotoxic effects on human lymphocytes, emphasize their potential therapeutic value in chemopreventive strategies.

Pedunculagin and tellimagrandin-I stimulate inflammation and angiogenesis and upregulate vascular endothelial growth factor and tumor necrosis factor-alpha in vivo

Pedunculagin (PD) and tellimagrandin-I (TL), isolated from Myrciaria cauliflora seeds and Eucaliptus microcorys leaves, respectively, have attracted great attention owing to their relevant biological activities, such as antitumor, antioxidant, and hepatoprotective activities. This study investigated the angiogenic potential of PD and TL using a chick embryo chorioallantoic membrane (CAM) assay. Using the CAM assay, our results showed that both PD and TL promoted a significant increase in the number and caliber of blood vessels, the thickness of the CAM, and the presence of fibroblasts and inflammatory cells. Moreover, an increase of tumor necrosis factor-α and vascular endothelial growth factor was observed in the CAM treated with PD and TL, indicating the induction of angiogenic factors. Thus, the remarkable profile of PD and TL in inducing angiogenesis opens up new perspectives for their potential utilization in different therapeutic approaches involving neovascularization.

Chebulinic Acid: An Incipient Anticancer Agent

BACKGROUND

Terminalia chebula (T. chebula) comprising chebulinic acid as its principle active constituent is used to cure various diseases. T. chebula and chebulinic acid are used as antimicrobial, antioxidant, antidiabetic, anti-inflammatory, hepatoprotective, antimutagenic, radioprotective, cardioprotective, antiproliferative, antiarthritic, anticaries, and so on.

OBJECTIVE

The objective of this current study is to give an overview of the recent literature and patents of T. chebula and chebulinic acid including methods of its isolation/extraction and their application in the prevention of various cancers and other diseases.

METHODS

Present research and patents highlighting the anti-cancer potential of T. chebula and chebulinic acid have been studied and discussed keeping in view the scientific novelty and impact.

RESULTS

Both T. chebula and chebulinic acid are currently being explored for their anticancer potential in vitro and in vivo. They are either incorporated alone or in combination with other plants or drugs to show their activity and many clinical trials are also going on various potentials of the plant and chebulinic acid. Novel extraction techniques are also explored and patented. Efforts are being made to improve the bioavailability by developing Novel herbal drug delivery systems of the plant extract or chebulinic acid itself.

CONCLUSION

Anti-cancer potential of T. chebula and chebulinic acid may be well established by promising clinical trials and may open new interventions in various tumors. Clinical trials in conjunction with standard therapies are required to explore and validate the actual potential of T. chebula and chebulinic acid respectively.

Inhibition of protein phosphatase-1 and -2A by ellagitannins: structure-inhibitory potency relationships and influences on cellular systems

Several ellagitannins inhibited the activity of protein phosphatase-1 (PP1) and -2 A (PP2A) catalytic subunits (PP1c and PP2Ac) with preferential suppression of PP1c over PP2Ac. The inhibitory potency for PP1c followed the order of tellimagrandin I > mahtabin A > praecoxin B > 1.2-Di-O-galloyl-4.6-(S)-HHDP-β-D-glucopyranose > pedunculagin with IC₅₀ values ranging from 0.20 µM to 2.47 µM. The interaction of PP1c and tellimagrandin I was assessed by NMR saturation transfer difference, surface plasmon resonance, isothermal titration calorimetry, and microscale thermophoresis based binding techniques. Tellimagrandin I suppressed viability and phosphatase activity of HeLa cells, while mahtabin A was without effect. Conversely, mahtabin A increased the phosphorylation level of SNAP-25^Thr138 and suppressed exocytosis of cortical synaptosomes, whereas tellimagrandin I was without influence. Our results establish ellagitannins as partially selective inhibitors of PP1 and indicate that these polyphenols may act distinctly in cellular systems depending on their membrane permeability and/or their actions on cell membranes.

Potential anti-cholinesterase and β-site amyloid precursor protein cleaving enzyme 1 inhibitory activities of cornuside and gallotannins from Cornus officinalis fruits

Cholinesterase (ChE) and β-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitors are promising agents for the treatment of Alzheimer's disease (AD). In the present study, we examined the inhibitory activity of seven compounds isolated from the fruits of Cornus officinalis, cornuside, polymeric proanthocyanidins, 1,2,3-tri-O-galloyl-β-D-glucose, 1,2,3,6-tetra-O-galloyl-β-D-glucose, tellimagrandin I, tellimagrandin II, and isoterchebin, against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and BACE1. All of the compounds displayed concentration-dependent in vitro inhibitory activity toward the ChEs and BACE1. Among them, tellimagrandin II exhibited the best inhibitory activity toward ChEs, whereas the best BACE1 inhibitor was 1,2,3,6-tetra-O-galloyl-β-D-glucose. Isoterchebin and polymeric proanthocyanidins were also significant ChE inhibitors. The kinetic and docking studies demonstrated that all compounds interacted with both the catalytic active sites and the peripheral anionic sites of the ChEs and BACE1. Tellimagrandin II, isoterchebin, and the polymeric proanthocyanidins exhibited concentration-dependent inhibition of peroxynitrite-mediated protein tyrosine nitration. In conclusion, we identified significant ChE and BACE1 inhibitors from Corni Fructus that could have value as new multi-targeted compounds for anti-AD agents.

Ellagitannins in Cancer Chemoprevention and Therapy

It is universally accepted that diets rich in fruit and vegetables lead to reduction in the risk of common forms of cancer and are useful in cancer prevention. Indeed edible vegetables and fruits contain a wide variety of phytochemicals with proven antioxidant, anti-carcinogenic, and chemopreventive activity; moreover, some of these phytochemicals also display direct antiproliferative activity towards tumor cells, with the additional advantage of high tolerability and low toxicity. The most important dietary phytochemicals are isothiocyanates, ellagitannins (ET), polyphenols, indoles, flavonoids, retinoids, tocopherols. Among this very wide panel of compounds, ET represent an important class of phytochemicals which are being increasingly investigated for their chemopreventive and anticancer activities. This article reviews the chemistry, the dietary sources, the pharmacokinetics, the evidence on chemopreventive efficacy and the anticancer activity of ET with regard to the most sensitive tumors, as well as the mechanisms underlying their clinically-valuable properties.

Overexpression of connexin 43 reduces melanoma proliferative and metastatic capacity

Background:

Alterations in connexin 43 (Cx43) expression and/or gap junction (GJ)-mediated intercellular communication are implicated in cancer pathogenesis. Herein, we have investigated the role of Cx43 in melanoma cell proliferation and apoptosis sensitivity in vitro, as well as metastatic capability and tumour growth in vivo.

Methods:

Connexin 43 expression levels, GJ coupling and proliferation rates were analysed in four different human melanoma cell lines. Furthermore, tumour growth and lung metastasis of high compared with low Cx43-expressing FMS cells were evaluated in vivo using a melanoma xenograft model.

Results:

Specific inhibition of Cx43 channel activity accelerated melanoma cell proliferation, whereas overexpression of Cx43 increased GJ coupling and reduced cell growth. Moreover, Cx43 overexpression in FMS cells increased basal and tumour necrosis factor-α-induced apoptosis and resulted in decreased melanoma tumour growth and lower number and size of metastatic foci in vivo.

Conclusions:

Our findings reveal an important role for Cx43 in intrinsically controlling melanoma growth, death and metastasis, and emphasise the potential use of compounds that selectively enhance Cx43 expression on melanoma in the future chemotherapy and/or immunotherapy protocols.

Cytotoxic effects of ellagitannins isolated from walnuts in human cancer cells

Walnuts contain many bioactive components that may slow cancer growth. A previous report showed that a diet supplemented with walnuts decreased the tumor size formed by MDA-MB-231 human cancer cells injected into nude mice. However, the mechanism of action was never determined. We characterized the effects of a methanol extract prepared from walnuts on human MDA-MB-231, MCF7, and HeLa cells. The extract was cytotoxic to all cancer cells. We identified compounds from the methanol extract that induced this cytotoxicity. The predominant compounds were Tellimagrandin I and Tellimagrandin II, members of the ellagitannin family. We also show a walnut extract decreases the intracellular pH, depolarizes the mitochondrial membrane with release of cytochrome c and phosphatidylserine flipping. The antimitogenic effects of walnut extract were associated with a twofold reduction of mitochondria respiration. These results suggest impairment of mitochondrial function and apoptosis as relevant mechanism of anticancer effects of the walnut extract.

Antiproliferative Action of Conjugated Linoleic Acid on Human MCF-7 Breast Cancer Cells Mediated by Enhancement of Gap Junctional Intercellular Communication through Inactivation of NF- κ B

The major conjugated linoleic acid (CLA) isomers, c9,t11-CLA and t10,c12-CLA, have anticancer effects; however, the exact mechanisms underlying these effects are unknown. Evidence suggests that reversal of reduced gap junctional intercellular communication (GJIC) in cancer cells inhibits cell growth and induces cell death. Hence, we determined that CLA isomers enhance GJIC in human MCF-7 breast cancer cells and investigated the underlying molecular mechanisms. The CLA isomers significantly enhanced GJIC of MCF-7 cells at 40 μM concentration, whereas CLA inhibited cell growth and induced caspase-dependent apoptosis. CLA increased connexin43 (Cx43) expression both at the transcriptional and translational levels. CLA inhibited nuclear factor-κB (NF-κB) activity and enhanced reactive oxygen species (ROS) generation. No significant difference was observed in the efficacy of c9,t11-CLA and t10,c12-CLA. These results suggest that the anticancer effect of CLA is associated with upregulation of GJIC mediated by enhanced Cx43 expression through inactivation of NF-κB and generation of ROS in MCF-7 cells.

All-trans retinoic acid restores gap junctional intercellular communication between oral cancer cells with upregulation of Cx32 and Cx43 expressions in vitro

OBJECTIVE

All-trans retinoic acid (ATRA) has been demonstrated to inhibit tumor growth by restoration of gap junctional intercellular communication (GJIC) via upregulation of connexin (Cx) expression in some solid tumors. However, the relationship between ATRA and GJIC remains unclear in oral squamous cell carcinoma (OSCC). The aim of this study was to investigate the effect of ATRA on the GJIC function of OSCC.

STUDY DESIGN

We measured the effects of ATRA on the viability and cell cycle distribution of SCC9 and Tca8113 OSCC cells. The GJIC function was observed using the scrape-loading dye transfer technique, and the mRNA and protein levels of Cx32 and Cx43 were detected by qRT-PCR, Western blot, and immunofluorescence assays.

RESULTS

ATRA inhibited the growth of OSCC cells in a dose- and time-dependent manner (P <0.05) and caused cell cycle arrest. ATRA-treated cells showed a 2.69-fold and 2.06-fold enhancement of GJIC in SCC9 and Tca8113 cells, respectively (P <0.05). Moreover, ATRA induced upregulation of Cx32 and Cx43 at both the mRNA and protein levels in OSCC cells.

CONCLUSION

Our results indicated that restoration of GJIC via enhanced Cx32 and Cx43 expression might serve as a novel mechanism for the anti-tumor effect of ATRA in OSCC.

Anti-oxidative and anti-proliferative activity on human prostate cancer cells lines of the phenolic compounds from Corylopsis coreana Uyeki

Fifteen phenolic compounds, including three caffeoyl derivatives, four gallotannins, three ellagitannins and five flavonoids, were isolated from an 80% MeOH extract of the leaves of Corylopsis coreana Uyeki (Korean winter hazel; CL). The anti-oxidative activities [1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and xanthine oxidase superoxide scavenging activities (NBT)] and the anti-proliferative activity on human prostate cancer cell lines (DU145 and LNCaP) were also evaluated.

Synthesis and biological profiling of tellimagrandin I and analogues reveals that the medium ring can significantly modulate biological activity

A novel synthesis of the ellagitannin natural product tellimagrandin I and a series of medium ring analogues is described. These compounds were all subsequently screened for redox activity, ability to precipitate protein and cellular phenotype in HeLa cells. From this we have shown that all properties can be modulated independently by varying ring size and by moving the ester out of conjugation with the biaryl ring system. Increasing ring size increased redox activity and cytotoxicity, leading to the identification of a compound (10) which was significantly more cytotoxic. In addition compounds identified with a redox active scaffold and low cytotoxicity may be employed as a new class of redox probes.

Nedd4-interacting protein 2, a short half-life membrane protein degraded in lysosomes, negatively controls down-regulation of connexin43

Nedd4-interacting protein 2 (NDFIP2) has three transmembrane domains and interacts with multiple Nedd4 family ubiquitin ligases through polyprolinetyrosine (PY) motifs located in its N-terminal cytoplasmic domain. It has been postulated that NDFIP2 acts as an adaptor for the ubiquitylation of substrates with Nedd4 ubiquitin ligase. However, whether NDFIP2 promotes or inhibits the ubiquitylation of Nedd4 substrates is still under debate. We show here that although NDFIP2 is detected in the Golgi/trans-Golgi network (TGN) area, it is rapidly delivered to and degraded in lysosomes with its half-life ca. 1.5 h. Intriguingly, knockdown (KD) of NDFIP2 with small interfering RNA (siRNA) impaired both the formation and function of gap junctions. Indeed, KD of NDFIP2 destabilized the gap junction protein connexin43 that contains PY motif. In support of this, overexpression of NDFIP2 stabilized connexin43 and enhanced the formation of gap junctions. Furthermore, the PY motifs of NDFIP2, which are required for its interaction with Nedd4, Atrophin-1 interacting protein (AIP) 4 (AIP4)/Itch, and AIP2/WWP2, were necessary for the targeting of NDFIP2 to lysosomes and/or the stability of connexin43 and gap junctions. Collectively these findings suggest that NDFIP2 may inhibit the Nedd4-dependent ubiquitylation of membrane proteins containing PY motifs, such as connexin43, in a competitive manner.

Advanced glycation end products down-regulate gap junctions in human hepatoma SKHep 1 cells via the activation of Src-dependent ERK1/2 and JNK/SAPK/AP1 signaling pathways

Hyperglycemia and advanced glycation end products (AGEs) are associated with an elevated risk of developing several cancers in diabetic patients. However, the detailed mechanisms remain to be elucidated. The mechanism of AGE-bovine serum albumin (BSA) on gap junction intercellular communication in human hepatoma cell line, SKHep 1, was investigated. Both Cx32 and Cx43 are major gap junction forming proteins in the liver, the loss of which has been shown to facilitate tumorigenesis. Although the MTT assay results showed that AGE-BSA significantly increased cell growth by 31%, AGE-BSA down-regulated Cx32 and Cx43 expression in a dose- and time-dependent manner. The present study also demonstrated that ERK1/2 and JNK/SAPK were significantly activated by AGE-BSA and that Src, ERK1/2, and JNK/SAPK inhibitors significantly reversed the reduction of Cx32 and Cx43 proteins by AGE-BSA. Taken together, these results strongly support the hypothesis that Src-dependent ERK1/2 and JNK/SAPK/AP1 signaling pathways play a key role in AGE-BSA-mediated down-regulation of Cx32 and Cx43 protein expression in SKHep 1 cells.

Prooxidant action of chebulinic acid and tellimagrandin I: causing copper-dependent DNA strand breaks

The prooxidant activity of two hydrolysable tannins, chebulinic acid and tellimagrandin I, on plasmid DNA and genomic DNA of cultured MRC-5 human embryo lung fibroblasts was assessed. The results revealed that both hydrolysable tannins in combination with Cu(II) induced DNA strand breaks in pBR322 plasmid DNA in a concentration-dependent manner. Chebulinic acid and tellimagrandin I also induced genomic DNA strand breaks of MRC-5 human embryo lung fibroblasts in the presence of Cu(II). After treatment with chebulinic acid or tellimagrandin I alone, the pBR322 plasmid DNA and genomic DNA in MRC-5 cells kept intact. In addition, addition of Cu(I) reagent bathocuproinedisulfonic acid or catalase markedly inhibited the copper-dependent DNA strand breaks by both tannins. However, three typical hydroxyl radical scavengers, DMSO, ethanol and mannitol, did not inhibit the DNA strand breaks. Both tannins were able to reduce Cu(II) to Cu(I). These results indicated that chebulinic acid and tellimagrandin I induced the copper-dependent strand breaks of pBR322 plasmid DNA and MRC-5 genomic DNA with prooxidant action, in which Cu(II)/Cu(I) redox cycle and H(2)O(2) were involved and hydroxyl radical formation is important in the hypothetical mechanism by which DNA strand breaks are formed.

Downregulation of connexin 43 in nasopharyngeal carcinoma cells is related to promoter methylation

Down-regulation of Cx43 expression had been shown to occur in nasopharyngeal carcinoma cells. The present study was undertaken to estimate if methylation of the promoter region in Cx43 gene was responsible for the repression of Cx43 expression in the CNE-1 nasopharyngeal carcinoma cells. Calcein transfer and lucifer yellow transfer were detected to evaluate gap junction intercellular communication (GJIC) in CNE-1 cells. It was found that the control CNE-1 cells showed no fluorescent dye transfer. After treatment with DNA methyltransferase inhibitor 5-aza-CdR, fluorescent dye transfer between cells became obvious. RT-PCR and Western blot were performed to determine the expression of Cx43 gene. The control CNE-1 cells showed a low expression level of Cx43, whereas 5-aza-CdR-treated CNE-1 cells showed an enhanced level of Cx43 expression. Methylation-sensitive restriction enzyme and PCR analysis showed that the methylation of the Cx43 gene promoter region occurred in CNE-1 cells. In addition, treatment with 5-aza-CdR inhibited the growth (including anchorage-independent growth) of CNE-1 cells, and resulted in an accumulation of cells in G0/G1 phase. These results indicate the promoter methylation as an important role in inactivation of Cx43 in CNE-1 cells.

Changes in cell morphology affect the quantification of intercellular communication

The scrape loading and dye transfer (SL/DT) method is a functional assay widely used to evaluate the level of the intercellular communication via gap junction. Initially, the evaluation of the degree of communication was done by counting the rows of fluorescent cells from the scrape. Its substitution by fluorescence distance or area, determinated by morphometric softwares, was proposed as the best way of communication measurement. Considering that normal cells change their morphology during different phases of growth in monolayer cultures we proposed to evaluate the possible influence of the cell morphology changes on the quantification of intercellular communication when the SL/DT method is used. The present data indicates that GJIC capacity should be rather quantified by counting the fluorescent cell rows than by the measurement of the fluorescence distance or area, when the goal is to evaluate the cell communication along different phases of cell culture. Normal cells growing in monolayer culture decrease their diameter according to their final density of saturation, impairing the quantification of GJIC capacity by morphometric analysis.