Nune Raviprakash

Advanced Glycation End Products (AGEs) Induce Apoptosis via a Novel Pathway INVOLVEMENT OF CA2+ MEDIATED BY INTERLEUKIN-8 PROTEIN

Advanced glycation end products (AGEs) accumulate in diabetic patients due to high blood glucose levels and cause multiple deleterious effects. In this study, we provide evidence that the AGE increased cell death, one such deleterious effect. Methyl glyoxal-coupled human serum albumin (AGE-HSA) induced transcription factors such as NF-κB, NF-AT, and AP-1. AGE acts through its cell surface receptor, RAGE, and degranulates vesicular contents including interleukin-8 (IL-8). The number of RAGEs, as well as the amount of NF-κB activation, is low, but the cell death is higher in neuronal cells upon AGE treatment. Degranulated IL-8 acts through its receptors, IL-8Rs, and induces sequential events in cells: increase in intracellular Ca2+, activation of calcineurin, dephosphorylation of cytoplasmic NF-AT, nuclear translocation of NF-AT, and expression of FasL. Expressed FasL increases activity of caspases and induces cell death. Although AGE increases the amount of reactive oxygen intermediate, accompanying cell death is not dependent upon reactive oxygen intermediate. AGE induces autophagy, which partially protects cells from cell death. A novel mechanism of AGE-mediated cell death in different cell types, especially in neuronal cells where it is an early event, is provided here. Thus, this study may be important in several age-related neuronal diseases where AGE-induced apoptosis is observed because of high amounts of AGE.

Novel Derivative of Benzofuran Induces Cell Death Mostly by G2/M Cell Cycle Arrest through p53-dependent Pathway but Partially by Inhibition of NF-κB

The Dracaena resin is widely used in traditional medicine as an anticancer agent, and benzofuran lignan is the active component. In this report, we provide evidence that the synthetic derivative of benzofuran lignan (Benfur) showed antitumor activities. It induced apoptosis in p53-positive cells. Though it inhibited endotoxin-induced nuclear factor κB (NF-κB) activation in both p53-positive and -negative cells, the activation of caspase 3 was observed in p53-positive cells. It showed partial cell death effect in both p53-positive and -negative cells through inhibition of NF-κB. Cell cycle analysis using flow cytometry showed that treatment with this novel benozofuran lignan derivative to Jurkat T-cells, but not U-937 cells, resulted in a G2/M arrest in a dose- and time-dependent manner. It increased amounts of p21, p27, and cyclin B, but not phospho-Rb through p53 nuclear translocation in Jurkat T-cells, but not in U-937 cells. It inhibited amounts of MDM2 (murine double minute 2) by repressing the transcription factor Sp1, which was also proved in silico. It induced cell death in tumor cells, but not in primary T-cells. Overall, our data suggest that Benfur-mediated cell death is partially dependent upon NF-κB, but predominantly dependent on p53. Thus, this novel benzofuran lignan derivative can be effective chemopreventive or chemotherapeutic agent against malignant T-cells.

Inhibiting TRAF2-mediated Activation of NF-κB Facilitates Induction of AP-1

The compound 5-(4-methoxyarylimino)-2-N-(3,4-dichlorophenyl)-3-oxo-1,2,4-thiadiazolidine (P3-25) is known to possess anti-bacterial, anti-fungal, and anti-tubercular activities. In this report, we provide evidence that P3-25 inhibits NF-κB, known to induce inflammatory and tumorigenic responses. It activates AP-1, another transcription factor. It inhibits TRAF2-mediated NF-κB activation but not TRAF6-mediated NF-κB DNA binding by preventing its association with TANK (TRAF for NF-κB). It facilitates binding of MEKK1 with TRAF2 and thereby activates JNK and AP-1. We provide evidence, for the first time, that suggests that the interaction of P3-25 with TRAF2 leads to inhibition of the NF-κB pathway and activation of AP-1 pathway. These results suggest novel approaches to design of P3-25 as an anti-cancer/inflammatory drug for therapy through regulation of the TRAF2 pathway.

Synthesis, photophysical properties and structures of organotin-Schiff bases utilizing aromatic amino acid from the chiral pool and evaluation of the biological perspective of a triphenyltin compound

Five new organotin(IV) complexes of compositions [Me2SnL1] (1), [Me2SnL2]n (2), [Me2SnL3] (3), [Ph3SnL1H]n (4) and [Ph3SnL3H] (5) (where L1=(2S)-2-((E)-((Z)-4-hydroxypent-3-en-2-ylidene)amino)-3-(1H-indol-3-yl)propanoate, L2=(2S)-(E)-2-((2-hydroxybenzylidene)amino)-3-(1H-indol-3-yl)propanoate and L3=(2S)-(E)-2-((1-(2-hydroxyphenyl)ethylidene)amino)-3-(1H-indol-3-yl)propanoate were synthesized and spectroscopically characterized. The crystal structures of 1-4 were determined. For the dimethyltin derivative 2, a polymeric chain structure was observed as a result of a long Sn∙∙∙O contact involving the exocyclic carbonyl oxygen-atom from the tridentate ligand of a neighboring Sn-complex unit. The tin atom in this complex has a distorted octahedral coordination geometry, in which the long Sn-O bond is almost trans to the tridentate ligand nitrogen-atom. In contrast, the dimethyltin(IV) complexes 1 and 3 displayed discrete monomeric structures where the tin atom has distorted trigonal-bipyramidal geometry with the two coordinating L oxygen atoms defining the axial positions. On the other hand, 4 is a chain polymer in the solid state. The ligand-bridged Sn atoms adopt a trans-Ph3SnO2 trigonal-bipyramidal configuration with equatorial phenyl groups. A carboxylato oxygen atom from one and the hydroxyl oxygen of the successive ligand in the chain occupy the axial positions. The solution structures were predicted by the use of 119Sn NMR chemical shifts. The photophysical properties of the complexes were investigated in the solid and in solution. The triphenyltin(IV) compound 4 was tested in detail ex vivo against A375 (human melanoma) cell line, exhibiting an IC50 value of 261nM to induce cell death as assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay without significant alteration of cytolysis as determined by lactate dehydrogenase (LDH) assay. Compound 4-mediated potent cell death was also determined by Live and Dead assay and caspase-mediated cleavage of poly-ADP ribose polymerase (PARP). Potent cell death activity was not observed in primary cells, like blood-derived peripheral mononuclear cells (PBMC). Compound 4 inhibited the diphenyl hexatriene (DPH) binding to cells and decreased the micro viscosity in a dose-dependent manner. Additionally, the ability of 4 and cyclodextrin (CD) to interact was determined by molecular modelling.

A natural xanthone increases catalase activity but decreases NF-kappa B and lipid peroxidation in U-937 and HepG2 cell lines.

Mangiferin, a C-glycosyl xanthone, has shown anti-inflammatory, antioxidant, and anti-tumorigenic activities. In the present study, we investigated the molecular mechanism for the antioxidant property of mangiferin. Considering the role of nuclear transcription factor kappa B (NF-κB) in inflammation and tumorigenesis, we hypothesized that modulating its activity will be a viable therapeutic target in regulating the redox-sensitive ailments. Our results show that mangiferin blocks several inducers, such as tumor necrosis factor (TNF), lypopolysaccharide (LPS), phorbol-12-myristate-13-acetate (PMA) or hydrogen peroxide (H2O2) mediated NF-κB activation via inhibition of reactive oxygen species generation. In silico docking studies predicted strong binding energy of mangiferin to the active site of catalase (-9.13 kcal/mol), but not with other oxidases such as myeloperoxidase, glutathione peroxidase, or inducible nitric oxide synthase. Mangiferin increased activity of catalase by 44%, but had no effect on myeloperoxidase activity in vitro. Fluorescence spectroscopy further revealed the binding of mangiferin to catalase at the single site with binding constant and binding affinity of 3.1×10(-7) M(-1) and 1.046 respectively. Mangiferin also inhibits TNF-induced lipid peroxidation and thereby protects apoptosis. Hence, mangiferin with its ability to inhibit NF-κB and increase the catalase activity may prove to be a potent therapeutic.

Ras Puts the Brake on Doxorubicin-mediated Cell Death in p53-expressing Cells

Doxorubicin is one of the most effective molecules used in the treatment of various tumors. Contradictory reports often open windows to understand the role of p53 tumor suppressor in doxorubicin-mediated cell death. In this report, we provide evidences that doxorubicin induced more cell death in p53-negative tumor cells. Several cells, having p53 basal expression, showed increase in p53 DNA binding upon doxorubicin treatment. Doxorubicin induced cell death in p53-positive cells through expression of p53-dependent genes and activation of caspases and caspase-mediated cleavage of cellular proteins. Surprisingly, in p53-negative cells, doxorubicin-mediated cell death was more aggressive (faster and intense). Doxorubicin increased the amount of Fas ligand (FasL) by enhancing activator protein (AP) 1 DNA binding in both p53-positive and p53-negative cells, but the basal expression of Fas was higher in p53-negative cells. Anti-FasL antibody considerably protected doxorubicin-mediated cell death in both types of cells. Activation of caspases was faster in p53-negative cells upon doxorubicin treatment. In contrast, the basal expression of Ras oncoprotein was higher in p53-positive cells, which might increase the basal expression of Fas in these cells. Overexpression of Ras decreased the amount of Fas in p53-negative cells, thereby decreasing doxorubicin-mediated aggressive cell death. Overall, this study will help to understand the much studied chemotherapeutic drug, doxorubicin-mediated cell signaling cascade, that leads to cell death in p53-positive and -negative cells. High basal expression of Fas might be an important determinant in doxorubicin-mediated cell death in p53-negative cells.

Short‐term exposure to oleandrin enhances responses to IL‐8 by increasing cell surface IL‐8 receptors

One of the first steps in host defence is the migration of leukocytes. IL‐8 and its receptors are a chemokine system essential to such migration. Up‐regulation of these receptors would be a viable strategy to treat dysfunctional host defence. Here, we studied the effects of the plant glycoside oleandrin on responses to IL‐8 in a human monocytic cell line.

Profilin potentiates chemotherapeutic agents mediated cell death via suppression of NF-κB and upregulation of p53

The molecular mechanism by which Profilin acts as a tumor suppressor is still unclear. Several chemotherapeutic agents, used till date either have unfavorable side effects or acquired resistance in tumor cells. Our findings show that Profilin enhances cell death mediated by several chemotherapeutic-agents. The activation of NF-κB and its dependent genes, mediated by paclitaxel and vinblastine, was completely inhibited in Profilin overexpressing cells. This inhibition was due to the Profilin mediated attenuation of IκBα degradation, thereby preventing p65 nuclear translocation and low NF-κB DNA binding activity.Moreover, Profilin increases level of p53 in the presence of known inducers, such as doxorubicin, vinblastine, and benzofuran. This increased p53 level leads to enhanced cell death as indicated by activation of caspases 3, 8, 9, which results in cleavage of PARP.Furthermore, knocking down of p53 in Profilin overexpressing cells leads to decreased cell death. Ectopic expression of Profilin in HCT116 p53 knock out cells showed lesser cell death as compared to the HCT116 p53 wild type cells. For the first time, we provide evidences, which suggest that Profilin synergizes with chemotherapeutic drugs to induce tumor cell death by regulating NF-κB and p53. Thus, modulation of Profilin may be a useful strategy for effective combination therapy.

Abstract 5508: Fucoidan from Turbinaria conoides attenuates pancreatic cancer progession by regulating p53 - NFκB crosstalk

Poor prognosis of pancreatic cancer (PC) has been attributed to its resistance to apoptosis and propensity for early systemic dissemination. Existing therapeutic strategies are often circumvented by the molecular crosstalk between cell signaling pathways. The fact that p53 is mutated in more than 50% of PC tissues and NFκB is constitutively activated in therapy resistant residual PC accounts for the evaded cell death and dissemination. In this study, we examined the benefit of fucoidan from a marine brown alga, Turbinaria conoides against PC progression. Five fractions of fucoidan isolated and fractionated using ion exchange chromatography were tested for their potential in this setting using two (MiaPaCa-2, Panc-1) genetically diverse human PC cell-lines. All fractions investigated exerted significant dose dependent and time dependent regulation of cell survival. Coherently, fucoidans induced apoptosis and activated caspase -3, -8 and -9 and cleaved PARP. Pathway-specific transcriptional analysis (QPCR profiling) recognized inhibition of 57 and 38 NFκB pathway molecules with fucoidan-F5 in MiaPaCa-2 and Panc-1 cells, respectively. In addition, fucoidan-F5 was also found to inhibit both the constitutive and TNFα mediated NFκB DNA-binding activity (EMSA) in PC cells. Upregulation of cytoplasmic IκB levels and significant reduction of NFκB dependent luciferase activity further substantiate inhibitory potential of seaweed fucoidans on NF-κB. Moreover, fucoidan(s) treatment increases cellular p53 in PC cells. Together, the results suggests that fucoidan regulates PC progression and further imply that fucoidans may selectively target p53-NFκB crosstalk and dictate apoptosis in PC cells. Citation Format: Caroline R. Delma, Guru Prasad Srinivasan, Nune Raviprakash, Sunil K. Manna, Somasundaram T. Somasundaram, Natarajan Aravindan. Fucoidan from Turbinaria conoides attenuates pancreatic cancer progession by regulating p53 - NFκB crosstalk. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5508. doi:10.1158/1538-7445.AM2015-5508

Ras puts the brake on doxorubicin-mediated cell death in p53-expressing cells.: FIGURE 1.

Line 7 from the bottom should read as follows. Nuclear fragmentation data as detected by propidium iodide-stained cell nuclei supported the similar cell death in these cells (Fig. 1B). Doxorubicin-induced cell death 68% (p 0.01), 76% (p 0.005), 56% (p 0.005), 80% (p 0.01), and 72% (p 0.005) in U-937, THP1, MCF-7, HeLa, and SKBr3 cells, respectively, at 72 h of treatment as detected by LIVE/DEAD assay (Fig. 1C).