Biomedical subjects

Do Sik Min

Publications and source records attributed to Do Sik Min.

At least 37 records · Page 2Linked to original sources

PubMed2005

Phospholipase D1 is up-regulated in the retina of Lewis rats with experimental autoimmune uveoretinitis.

To investigate whether phospholipase D1 (PLD1) is involved in autoimmune damage to the eyes, we used Western blotting and immunohistochemistry to examine the expression and distribution of PLD1 in the retinas of Lewis rats with experimental autoimmune uveoretinitis (EAU). Western blot analysis showed that the level of expression of PLD1 was significantly increased in EAU-affected retinas compared to that of control. Immunohistochemical analysis showed that ganglion cells and Muller cells, which express PLD1 weakly in the normal retina, showed increased expression of PLD1 in EAU-affected retinas; some ED1-immunopositive cells were also immunopositive for PLD1 in lesions at post-immunization days 14 and 21. These results suggest that the increased expression of PLD1 in inflammatory cells exacerbates an autoimmune response in EAU, while its expression in ganglion cells limits cell loss by activation of survival factors in eyes with autoimmune injury.

Animals↗

PubMed2004

Pleckstrin homology domains of phospholipase C-gamma1 directly interact with beta-tubulin for activation of phospholipase C-gamma1 and reciprocal modulation of beta-tubulin function in microtubule assembly.

Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) has two pleckstrin homology (PH) domains, an N-terminal domain and a split PH domain. Here we show that pull down of NIH3T3 cell extracts with PLC-gamma1 PH domain-glutathione S-transferase fusion proteins, followed by matrix-assisted laser desorption ionization-time of flight-mass spectrometry, identified beta-tubulin as a binding protein of both PLC-gamma1 PH domains. Tubulin is a main component of microtubules and mitotic spindle fibers, which are composed of alpha- and beta-tubulin heterodimers in all eukaryotic cells. PLC-gamma1 and beta-tubulin colocalized in the perinuclear region in COS-7 cells and cotranslocated to the plasma membrane upon agonist stimulation. Membrane-targeted translocation of depolymerized tubulin by agonist stimulation was also supported by immunoprecipitation analyses. The phosphatidylinositol 4,5-bisphosphate (PIP(2)) hydrolyzing activity of PLC-gamma1 was substantially increased in the presence of purified tubulin in vitro, whereas the activity was not promoted by bovine serum albumin, suggesting that beta-tubulin activates PLC-gamma1. Furthermore, indirect immunofluorescent microscopy showed that PLC-gamma1 was highly concentrated in mitotic spindle fibers, suggesting that PLC-gamma1 is involved in spindle fiber formation. The effect of PLC-gamma1 in microtubule formation was assessed by overexpression and silencing PLC-gamma1 in COS-7 cells, which resulted in altered microtubule dynamics in vivo. Cells overexpressing PLC-gamma1 showed higher microtubule densities than controls, whereas PLC-gamma1 silencing with small interfering RNAs led to decreased microtubule network densities as compared with control cells. Taken together, our results suggest that PLC-gamma1 and beta-tubulin transmodulate each other, i.e. that PLC-gamma1 modulates microtubule assembly by beta-tubulin, and beta-tubulin promotes PLC-gamma1 activity.

Animals↗

PubMed2004

Point mutations in the split PLC-gamma1 PH domain modulate phosphoinositide binding.

A number of signaling molecules contain small pleckstrin homology (PH) domains capable of binding phosphoinositides or proteins. Phospholipase C (PLC)-gamma1 has two putative PH domains, an NH(2)-terminal (PH(1)) and a split PH domain (nPH(2) and cPH(2)). We previously reported that the split PH domain of PLC-gamma1 binds to phosphatidylinositol 4-phosphate (PI(4)P) and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) (Chang et al., 2002). To identify the amino acid residues responsible for binding with PI(4)P and PI(4,5)P(2), we used site-directed mutagenesis to replace each amino acid in the variable loop-1 (VL-1) region of the PLC-gamma1 nPH(2) domain with alanine (a neutral amino acid). The phosphoinositide-binding affinity of these mutant molecules was analyzed by Dot-blot assay followed by ECL detection. We found that two PLC-gamma1 nPH2 domain mutants, P500A and H503A, showed reduced affinities for phosphoinositide binding. Furthermore, these mutant PLC-gamma1 molecules showed reduced PI(4,5)P(2) hydrolysis. Using green fluorescent protein (GFP) fusion protein system, we showed that both PH(1) and nPH(2) domains are responsible for membrane-targeted translocation of PLC-gamma1 upon serum stimulation. Together, our data reveal that the amino acid residues Pro(500) and His(503) are critical for binding of PLC-gamma1 to one of its substrates, PI(4,5)P(2) in the membrane.

Amino Acid Sequence↗

PubMed2004

Inhibitory effects of epicatechin on interleukin-1beta-induced inducible nitric oxide synthase expression in RINm5F cells and rat pancreatic islets by down-regulation of NF-kappaB activation.

Cytokines that are released by infiltrating inflammatory cells around the pancreatic islets are involved in the pathogenesis of type 1 diabetes mellitus. Specifically, interleukin-1beta (IL-1beta) stimulates inducible nitric oxide synthase (iNOS) expression and nitric oxide overproduction, leading to the beta-cell damage. In activating this pathway, nuclear factor-kappaB (NF-kappaB) plays a crucial role, and many of the IL-1beta-sensitive genes contain NF-kappaB binding sites in their promoter regions. We have recently shown that epicatechin, which is a flavonoid, had a protective effect on pancreatic beta-cells in both streptozotocin-treated rats and islets. In the present study, the effects of epicatechin on IL-1beta-induced beta-cell damage were examined. RINm5F cells and islets were pretreated with epicatechin and next incubated with IL-1beta. The released nitrite, iNOS protein and mRNA expression levels were then measured. IkappaBalpha protein, nuclear translocation of NF-kappaB, and NF-kappaB DNA binding activity were also determined. Following the transient transfection of an iNOS promoter into the cells, the iNOS promoter activity was measured. ATP- or D-glucose-induced insulin release was measured in RINm5F cells and islets, respectively. Epicatechin significantly reduced IL-1beta-induced nitrite production, iNOS protein and mRNA expressions, and it also inhibited IL-1beta-induced IkappaBalpha protein degradation, NF-kappaB activation, and iNOS promoter activity. Epicatechin partly restored the IL-1beta-induced inhibition of insulin release. These results suggest that epicatechin inhibits the IL-1beta-induced iNOS expression by down-regulating NF-kappaB activation, and protecting beta-cells from IL-1beta.

Animals↗

PubMed2004

Phospholipase D activity is elevated in hepatitis C virus core protein-transformed NIH3T3 mouse fibroblast cells.

Hepatitis C Virus (HCV) is associated with a severe liver disease and increased frequency in the development of hepatocellular carcinoma. Overexpression of HCV core protein is known to transform fibroblast cells. Phospholipase D (PLD) activity is commonly elevated in response to mitogenic signals, and has also been overexpressed and hyperactivated in some human cancer cells. The aim of this study was to understand how PLD was regulated in the HCV core protein-transformed NIH3T3 mouse fibroblast cells. We observed that PLD activity was elevated in the NIH3T3 cells overexpressing HCV core protein over the vector alone-transfected control cells, however, expression levels of PLD protein and protein kinase C (PKC) in the HCV core protein-transformed cells was similar to the control cells. Phorbol 12-myristate 13-acetate (PMA), which is known to activate PKC, stimulated PLD activity significantly more in the core protein-transformed cells, in comparison with that of the control cells. PLD activity assay using PKC isozyme-specific inhibitor and PKC translocation experiment showed that PKC-delta was mainly involved in the PMA- induced PLD activation in the core-transformed cells. Moreover, in cells overexpressing HCV core protein, PMA also stimulated p38 kinase more potently than that of the control cells, and an inhibitor of p38 kinase abolished PMA-induced PLD activation in cells overexpressing HCV core protein. Taken together, these results suggest that PLD might be implicated in core protein-induced transformation.

Animals↗

PubMed2004

Involvement of c-Src kinase in the regulation of TGF-beta1-induced apoptosis.

Transforming growth factor-beta1 (TGF-beta1) is a potent inducer of apoptosis in normal hepatocytes, and acquiring resistance to TGF-beta1 may be a critical step in the development of hepatocellular carcinoma (HCC). In this study, we investigated the possible involvement of c-Src in the regulation of TGF-beta1-induced apoptosis. TGF-beta1 induced transient activation of c-Src and its subsequent caspase-mediated degradation concomitant with cell death in FaO hepatoma cells, which are sensitive to TGF-beta1. In response to TGF-beta1, activated c-Src was translocated into the cytoplasmic membrane, then relocated to the nuclei of apoptotic cells during its cleavage. In TGF-beta1-induced apoptotic cells, c-Src maintained its tight association with p85 FAK fragment cleaved by caspases, possibly contributing to focal adhesion disassembly. TGF-beta1-induced apoptosis was enhanced by either inhibition of c-Src activity using PP1 or PP2, or by overexpression of dominant-negative c-Src. In contrast, overexpression of constitutively active c-Src inhibited apoptosis suppressing TGF-beta1-induced activation of p38, JNK and caspases. In many HCC cell lines resistant to TGF-beta1, enhanced c-Src activity was detected. We hypothesize that activated c-Src in HCC may contribute to resistance against the apoptotic and/ or antiproliferative properties of TGF-beta1.

Animals↗

PubMed2004

Transcriptional and post-transcriptional regulation of the PKC delta gene by etoposide in L1210 murine leukemia cells: implication of PKC delta autoregulation.

Protein kinase C delta (PKC delta) plays an important role in the regulation of apoptosis in response to diverse anticancer agents. PKC delta is cleaved irreversibly to a catalytically active fragment in response to apoptotic stimuli; however, little information is available about the regulation of PKC delta gene expression. In this study, we found that the amount of steady-state PKC delta mRNA and protein was increased by etoposide in mouse L1210 leukemia cells. The transcriptional rate of the PKC delta gene and the stability of PKC delta mRNA were increased by treatment with etoposide, resulting in the accumulation of PKC delta protein. Rottlerin inhibited etoposide-induced PKC delta gene expression significantly, while Go6976, LY294002 and PD98059 had no effect. Further, both stable and adenovirus-mediated expression of a dominant negative PKC delta(KR) abrogated etoposide-induced PKC delta expression. Etoposide-stimulated PKC delta transcription but not PKC delta mRNA stability was blocked completely by pretreatment with rottlerin. Our data reveal a novel mechanism whereby PKC delta gene is regulated at the transcriptional and post-transcriptional level in the L1210 leukemia cell line.

Acetophenones↗

PubMed2004

Phospholipase D isozymes mediate epigallocatechin gallate-induced cyclooxygenase-2 expression in astrocyte cells.

Little is known about the effect of epigallocatechin-3 gallate (EGCG), a major constituent of green tea, on the expression of cyclooxygenase (COX)-2. Here, we studied the role of phospholipase D (PLD) isozymes in EGCG-induced COX-2 expression. Stimulation of human astrocytoma cells (U87) with EGCG induced formation of phosphatidylbutanol, a specific product of PLD activity, and synthesis of COX-2 protein and its product, prostaglandin E(2) (PGE(2)). Pretreatment of cells with 1-butanol, but not 3-butanol, suppressed EGCG-induced COX-2 expression and PGE synthesis. Furthermore, evidence that PLD was involved in EGCG-induced COX-2 expression was provided by the observations that COX-2 expression was stimulated by overexpression of PLD1 or PLD2 isozymes and treatment with phosphatidic acid (PA), and that prevention of PA dephosphorylation by 1-propranolol significantly potentiated COX-2 expression induced by EGCG. EGCG induced activation of p38 mitogen-activated protein kinase (p38 MAPK), and specific inhibition of p38 MAPK dramatically abolished EGCG-induced PLD activation, COX-2 expression, and PGE(2) formation. Moreover, protein kinase C (PKC) inhibition suppressed EGCG-induced p38 MAPK activation, COX-2 expression, and PGE(2) accumulation. The same pathways as those obtained (2)in the astrocytoma cells were active in primary rat astrocytes, suggesting the relevance of the findings. Collectively, our results demonstrate for the first time that PLD isozymes mediate EGCG-induced COX-2 expression through PKC and p38 in immortalized astroglial line and normal astrocyte cells.

1-Butanol↗

PubMed2004

Phospholipase D is involved in oxidative stress-induced migration of vascular smooth muscle cells via tyrosine phosphorylation and protein kinase C.

Oxidative stress has been implicated in mediation of vascular disorders. In the presence of vanadate, H(2)O(2) induced tyrosine phosphorylation of PLD1, protein kinase C-alpha (PKC-alpha), and other unidentified proteins in rat vascular smooth muscle cells (VSMCs). Interestingly, PLD1 was found to be constitutively associated with PKC-alpha in VSMCs. Stimulation of the cells by H(2)O(2) and vanadate showed a concentration-dependent tyrosine phosphorylation of the proteins in PLD1 immunoprecipitates and activation of PLD. Pretreatment of the cells with the protein tyrosine kinase inhibitor, genistein resulted in a dose-dependent inhibition of H(2)O(2)-induced PLD activation. PKC inhibitor and down-regulation of PKC abolished H(2)O(2)-stimulated PLD activation. The cells stimulated by oxidative stress (H(2)O(2)) caused increased cell migration. This effect was prevented by the pretreatment of cells with tyrosine kinase inhibitors, PKC inhibitors, and 1-butanol, but not 3-butanol. Taken together, these results suggest that PLD might be involved in oxidative stress-induced migration of VSMCs, possibly via tyrosine phosphorylation and PKC activation.

Animals↗

PubMed2004

Phosphorylation of phospholipase D1 and the modulation of its interaction with RhoA by cAMP-dependent protein kinase.

Agents that elevate cellular cAMP are known to inhibit the activation of phospholipase D (PLD). We investigated whether PLD can be phosphorylated by cAMP-dependent protein kinase (PKA) and PKA-mediated phosphorylation affects the interaction between PLD and RhoA, a membrane regulator of PLD. PLD1, but not PLD2 was found to be phosphorylated in vivo by the treatment of dibutyryl cAMP (dbcAMP) and in vitro by PKA. PKA inhibitor (KT5720) abolished the dbcAMP-induced phosphorylation of PLD1, but dibutyryl cGMP (dbcGMP) failed to phosphorylate PLD1. The association between PLD1 and Val14RhoA in an immunoprecipitation assay was abolished by both dbcAMP and dbcGMP. Moreover, RhoA but not PLD1 was dissociated from the membrane to the cytosolic fraction in dbcAMP-treated cells. These results suggest that both PLD1 and RhoA are phosphorylated by PKA and the interaction between PLD1 and RhoA is inhibited by the phosphorylation of RhoA rather than by the phosphorylation of PLD1.

Bucladesine↗

PubMed2004

Resveratrol inhibits phorbol myristate acetate-induced matrix metalloproteinase-9 expression by inhibiting JNK and PKC delta signal transduction.

Proteolytic degradation of the extracellular matrix and tumor metastasis correlate with the expression of endopeptidases known as matrix metalloproteinases (MMPs). The expression of MMPs is regulated by cytokines and signal transduction pathways, including those activated by phorbol myristate acetate (PMA). We found that resveratrol, a phytoalexin present in grapes, significantly inhibits the PMA-induced increase in MMP-9 expression and activity. These effects of resveratrol are dose dependent and correlate with the suppression of MMP-9 mRNA expression levels. PMA caused about a 23-fold increase in MMP-9 promoter activity, which was suppressed by resveratrol. Transient transfection utilizing MMP-9 constructs, in which specific transcriptional factors were mutagenized, indicated that the effects of PMA and resveratrol were mediated via an activator protein-1 and nuclear factor-kappaB response element. Resveratrol inhibited PMA-mediated activation of c-Jun N-terminal kinase (JNK) and protein kinase C (PKC)-delta activation. Therefore, we conclude that the MMP-9 inhibition activity of resveratrol and its inhibition of JNK and PKC-delta may have a therapeutic potential, given that a novel means of controlling growth and invasiveness of tumors.

Antineoplastic Agents, Phytogenic↗

PubMed2004

Immunohistochemical localization of phospholipase D2 in embryonic rat brain.

The present study has characterized the cellular and temporal localization of the phospholipase D2 (PLD2) protein in the embryonic rat brain, using immunohistochemistry. PLD2 immunoreactivity was first observed in the choroid plexus and in the most ventricular zone of the lateral and third ventricles at embryonic day 15 (E15), followed by gradual restriction to the limited zone of ventricles at E20. In addition, PLD2 expression was high in the developing cerebral cortex and hippocampus. In the cortex, PLD2 expression was observed in the marginal zone from the earliest stage (E15) and then declined and had completely disappeared by E20. Double-labelling studies demonstrated co-expression of the anti-class III beta-tubulin antibody in most of the PLD2 immunoreactive cells. Therefore, our findings suggest that PLD2 may be involved in early developmental processes of some neuronal progenitors.

Animals↗

PubMed2004

Anti-apoptotic mechanism and reduced expression of phospholipase D in spontaneous and Fas-stimulated apoptosis of human neutrophils.

Neutrophil apoptosis is a constitutive process that can be enhanced or delayed by signals triggered by various stimuli. In this work, we investigated the action mechanism of phospholipase D (PLD) and its expression in the inhibition of spontaneous and Fas-mediated apoptosis. Anti-Fas antibody-stimulated apoptosis of neutrophils was significantly blocked by the exogenous addition of bacterial PLD from Streptomyces chromofuscus (scPLD), and neutrophils cultured for 24 h in the presence of anti-Fas antibody showed lower agonist-stimulated PLD activity compared to untreated cells. The amount of PLD1a protein reduced time-dependently in cultured neutrophils, but was recovered by treating with LPS or GM-CSF. The reduction in PLD1a protein level was blocked by caspase inhibitors. The exogenous addition of scPLD blocked the up-regulation of Fas-associated death domain expression, mitochondrial permeability, and the cleavages of procaspase-8, procaspase-3, and protein kinase C-delta. We also found that the protein level of apoptosis-inducing factor was increased in cultured neutrophils but its expression was reduced by scPLD. However, sulfasalazine-induced apoptosis and change of protein expression were not blocked by scPLD. Taken together, the activity and protein levels of PLD play a role as an anti-apoptotic factor by acting at multiple levels of the apoptotic cascade in neutrophils.

Apoptosis↗

PubMed2004

Up-regulation of phospholipase Cgamma1 and phospholipase D during the differentiation of human monocytes to dendritic cells.

Phospholipase C (PLC)gamma and phospholipase D (PLD) play pivotal roles in the signal transduction required for various cellular responses, including cell proliferation and differentiation. Dendritic cells (DCs), which are professional antigen-presenting cells, can be generated from human monocytes by stimulating the cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin 4 (IL-4). We investigated whether PLCgamma and PLD expression levels can be changed during the differentiation of the human monocytes into DCs. The enzymatic activity and protein level of PLC gamma1 were significantly increased in the human monocyte-derived DCs by GM-CSF/IL-4, but the protein levels of PLC gamma2 were unaltered. Moreover, the enzymatic activity and protein level of PLD1b and PLD2 were up-regulated during the differentiation of human monocytes to DCs, but those of PLD1a were not changed. A higher phagocytic activity of DCs was found to be correlated with the up-regulations of PLCgamma1 and PLD, and the phagocytic activity of DCs was inhibited by a PLC-specific inhibitor (U73122) and by a phosphatidic acid acceptor (n-butanol), but to be increased by phosphatidic acid. Thus, suggesting that PLC and PLD participate in the process. This study suggests that the up-regulations of PLCgamma1 and PLD are accompanied by the differentiation of monocytes into DCs, which results in increased phagocytic activity.

Cell Differentiation↗

PubMed2004

Increased expression of phospholipase D in the heart with experimental autoimmune myocarditis in Lewis rats.

The expression of phospholipase D (PLD) in the hearts of rats with experimental autoimmune myocarditis (EAM) was studied to elucidate the functional role of PLD in the pathogenesis of EAM. Western blot analysis showed that the level of the PLD1 isoform was significantly increased in the hearts of rats with EAM on days 14, 17 and 21 postimmunization (pi) (P < 0.01; control vs EAM at 14 pi, 17 pi and 21 pi). The phenotypes of cells exhibiting increased PLD1 expression were primarily inflammatory cells, including ED1 positive macrophages, in the inflammatory EAM lesions. Some cardiomyocytes also showed increased PLD1 immunoreaction in and around EAM lesions. Some PLD1-positive cells were also positive for proliferating cell nuclear antigen in some cardiomyocytes or terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling in some macrophages, suggesting that PLD1 positive cells have a capacity for proliferation or apoptosis depending on cell types in the target organ. Thus, it is postulated that increased expression of PLD1 in EAM may support an early inflammatory response in proliferating inflammatory cells, and its expression in cardiomyocytes may help them to survive by activation of survival factors in hearts with EAM.

Animals↗

PubMed2004

Differential expression of phospholipase D isozymes in the hippocampus following kainic acid-induced seizures.

To investigate the pathophysiological role of phospholipase D (PLD)-mediated signaling, changes in the expression of the PLD isozymes PLD1 and PLD2 were investigated in the rat kainic acid (KA) model of human temporal lobe epilepsy. Western blot analysis showed a significant increase in the expression of PLD1 and PLD2 in the postictal hippocampus. PLD1 immunoreactivity increased preferentially in the CA3 and CA1 regions, where pyramidal neurons are susceptible to temporal lobe epilepsy. Experiments employing double immunofluorescence revealed that the cells expressing PLD1 were GFAP-expressing reactive astrocytes. By contrast, PLD2 immunoreactivity increased strikingly in infrapyramidal, but not in suprapyramidal granule cells of the postictal dentate gyrus, fitting well with results of the PLD activity assay. Considering that PLD belongs to a key signaling pathway, this result suggests that changes in granule cell activity in the dentate gyrus after seizures occurs specifically between the supra- and infrapyramidal blades. In addition, enhanced immunoreactivity of PLD2 was observed in the reactive astrocytes of the CA1, CA3, and hilar subregions, but its temporal pattern is different from that of PLD1. Taken together, our results suggest that PLD1 and PLD2 exercise their unique pathophysiological functions in the rat hippocampus after KA-induced seizures.

Amino Acid Sequence↗

PubMed2004

Changes in IP3 receptor are associated with altered calcium response to cholecystokinin in diabetic rat pancreatic acini.

OBJECTIVES: Pancreatic acini of diabetic rats release amylase less than normal acini on cholecystokinin (CCK) stimulation. Pancreatic enzyme secretion by CCK is closely related to the second messenger inositol 1,4,5-trisphosphate (IP3), which mobilizes intracellular calcium stores via the endoplasmic reticulum-located receptor IP3 (IP3R). Recently, we observed altered intracellular calcium response on CCK-8 stimulation in streptozotocin (STZ)- treated diabetic rat acini. METHODS: To determine whether IP3R is involved in altered calcium response, we measured inositol phosphate (IP) formation and the expression and phosphorylation of type III IP3R protein in diabetic acini. Also, CCK receptor mRNA expression was examined to determine whether the changes in IP formation and IP3R protein phosphorylation in diabetic acini might result from the defect at the postreceptor level. RESULTS: CCK-8-induced IP formation at all concentrations used was significantly reduced in diabetic acini, though IP formation was increased in a concentration-dependent manner. The expression of type III IP3R protein was significantly reduced in diabetic acini. Additionally, CCK-8-stimulated phosphorylation of type III IP3R protein was not observed in diabetic acini. However, the reduction of CCK receptor mRNA expression was not detected in diabetic acini. CONCLUSION: Our results indicate that altered calcium response to CCK-8 in diabetic acini might be associated with a post-CCK receptor defect including the changes in IP formation, type III IP3R protein expression, and phosphorylation of type III IP3R protein.

Animals↗

PubMed2004

Phospholipase C, protein kinase C, Ca2+/calmodulin-dependent protein kinase II, and redox state are involved in epigallocatechin gallate-induced phospholipase D activation in human astroglioma cells.

We show that epigallocatechin-3 gallate (EGCG), a major component of green tea, stimulates phospholipase D (PLD) activity in U87 human astroglioma cells. EGCG-induced PLD activation was abolished by the phospholipase C (PLC) inhibitor and a lipase inactive PLC-gamma1 mutant, which is dependent on intracellular or extracellular Ca(2+), with the possible involvement of Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II). EGCG induced translocation of PLC-gamma1 from the cytosol to the membrane and PLC-gamma1 interaction with PLD1. EGCG regulates the activity of PLD by modulating the redox state of the cells, and antioxidants reverse this effect. Moreover, EGCG-induced PLD activation was reduced by PKC inhibitors or down-regulation of PKC. Taken together, these results show that, in human astroglioma cells, EGCG regulates PLD activity via a signaling pathway involving changes in the redox state that stimulates a PLC-gamma1 [Ins(1,4,5)P(3)-Ca(2+)]-CaM kinase II-PLD pathway and a PLC-gamma1 (diacylglycerol)-PKC-PLD pathway.

Antineoplastic Agents↗