cyclic-gmp and epigallocatechin-gallate

Green tea is rich in polyphenol flavonoids including catechins. Epigallocatechin 3-gallate (EGCG) is the most abundant and potent green tea catechin. EGCG has been extensively studied for its beneficial health effects as a nutriceutical agent. Based upon its chemical structure, EGCG is often classified as an antioxidant. However, treatment of cells with EGCG results in production of hydrogen peroxide and hydroxyl radicals in the presence of Fe (III). Thus, EGCG functions as a pro-oxidant in some cellular contexts. Recent investigations have revealed many other direct actions of EGCG that are independent from anti-oxidative mechanisms. In this review, we discuss these novel molecular mechanisms of action for EGCG. In particular, EGCG directly interacts with proteins and phospholipids in the plasma membrane and regulates signal transduction pathways, transcription factors, DNA methylation, mitochondrial function, and autophagy to exert many of its beneficial biological actions.

Topics: Animals; Antioxidants; Autophagy; Calcium Signaling; Catechin; Cell Membrane; Cyclic AMP; Cyclic GMP; DNA Methylation; Gene Expression Regulation; Humans; Hydrogen Peroxide; Mitochondria; Oxidants; Oxidation-Reduction; Polyphenols; Signal Transduction; Tea; Transcription Factors; Transcription, Genetic

Epigallocatechin gallate (EGCG) has been shown to have antihypertensive activity. However, the role of epigallocatechin gallate (EGCG) in improving vascular function via modulation of endothelial nitric oxide synthase (eNOS) in hypertensive subjects is not well researched. Angiotensin II-infused hypertensive mice (8-10 weeks old) received EGCG (50 mg/kg/day) for 14 days via oral gavage. The arterial systolic blood pressure (SBP) was measured using the tail-cuff method every three days. At the end of the treatment, the vascular reactivity of the isolated aortae was studied using wire myographs. The level of nitric oxide (NO), cyclic guanosine monophosphate (cGMP) and tetrahydrobiopterine (BH

Topics: Angiotensin II; Animals; Antihypertensive Agents; Cyclic GMP; Endothelium, Vascular; Guanosine Monophosphate; Hypertension; Mice; Nitric Oxide; Nitric Oxide Synthase Type III; Oxidative Stress; Reactive Oxygen Species

Epigallocatechin-3-O-gallate (EGCG)-induced cyclic guanosine monophosphate (cGMP) plays a crucial role in EGCG-induced cell death in various types of cancer cells. However, little is known regarding the early molecular events after cGMP induction. In this study, we showed that cGMP induction is sufficient to induce the phosphorylation of protein kinase C delta (PKCδ) at Ser664, the crucial kinase for EGCG-induced activation of acid sphingomyelinase (ASM). Using a chemical inhibitor library, we revealed that the inhibitors of the negative regulators of diacylglycerol strongly increase the effect of EGCG. We also showed that EGCG treatment increased phospholipase C (PLC) activity, and the same results were obtained with cGMP inducer treatment. EGCG-induced ASM activation was completely suppressed by pharmacological inhibition of PLC. Collectively, EGCG-induced cGMP activated the cGMP/PLC/PKCδ/ASM signaling axis in multiple myeloma cells.

Topics: Apoptosis; Catechin; Cell Line, Tumor; Cyclic GMP; Enzyme Activation; Gene Expression Regulation, Neoplastic; Humans; Multiple Myeloma; Phosphorylation; Signal Transduction; Sphingomyelin Phosphodiesterase; Type C Phospholipases

Recurrence following chemotherapy is observed in the majority of patients with pancreatic ductal adenocarcinoma (PDAC). Recent studies suggest that cancer stem cells (CSCs) may be involved in PDAC recurrence and metastasis. However, an efficient approach to targeting pancreatic CSCs remains to be established. Here we show that in cancer cells overexpressing the 67-kDa laminin receptor (67LR)-dependent cyclic GMP (cGMP) inducer, epigallocatechin-3-O-gallate (EGCG) and a phosphodiesterase 3 (PDE3) inhibitor in combination significantly suppressed the Forkhead box O3 and CD44 axis, which is indispensable for the CSC properties of PDAC. We confirmed that the EGCG and PDE3 inhibitor in combination strongly suppressed tumour formation and liver metastasis in vivo. We also found that a synthesized EGCG analog capable of inducing strong cGMP production drastically suppressed the CSC properties of PDAC and extended the survival period in vivo. In conclusion, the combination treatment of EGCG and a PDE3 inhibitor as a strong cGMP inducer could be a potential treatment candidate for the eradication of CSCs of PDAC.

Topics: Animals; Biomarkers, Tumor; Carcinoma, Pancreatic Ductal; Catechin; Cell Line, Tumor; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 3; Disease Models, Animal; Drug Synergism; Fluorescent Antibody Technique; Gene Expression; Humans; Mice; Neoplastic Stem Cells; Phosphodiesterase 3 Inhibitors; Xenograft Model Antitumor Assays

Topics: Animals; Catechin; Cyclic GMP; DNA-Binding Proteins; Intracellular Signaling Peptides and Proteins; Male; Mice; Mice, Inbred BALB C; Nuclear Proteins; Protein Phosphatase 2; Second Messenger Systems; Tea; Toll-Like Receptor 4; Transcription Factors; Up-Regulation

(-)-Epigallocatechin-3-O-gallate (EGCG), a polyphenol in green tea, induces apoptosis in acute myeloid leukemia (AML) cells without affecting normal cells. In this study, we observed that cGMP acts as a cell death mediator of the EGCG-induced anti-AML effect through acid sphingomyelinase activation. EGCG activated the Akt/eNOS axis, a well-known mechanism in vascular cGMP upregulation. We also observed that a major cGMP negative regulator, phosphodiesterase 5, was overexpressed in AML cells, and PDE5 inhibitor, an anti-erectile dysfunction drug, synergistically enhanced the anti-AML effect of EGCG. This combination regimen killed AML cells via overexpressed 67-kDa laminin receptors.

Topics: Apoptosis; Catechin; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Drug Synergism; Enzyme Activation; Gene Expression Regulation, Leukemic; HL-60 Cells; Humans; Leukemia, Myeloid, Acute; Nitric Oxide Synthase Type III; Oncogene Protein v-akt; Phosphodiesterase 5 Inhibitors; Primary Cell Culture; Receptors, Laminin; Signal Transduction; Sphingomyelin Phosphodiesterase

The 67-kDa laminin receptor (67LR) is a laminin-binding protein overexpressed in various types of cancer, including bile duct carcinoma, colorectal carcinoma, cervical cancer, and breast carcinoma. 67LR plays a vital role in growth and metastasis of tumor cells and resistance to chemotherapy. Here, we show that 67LR functions as a cancer-specific death receptor. In this cell death receptor pathway, cGMP initiated cancer-specific cell death by activating the PKCδ/acid sphingomyelinase (PKCδ/ASM) pathway. Furthermore, upregulation of cGMP was a rate-determining process of 67LR-dependent cell death induced by the green tea polyphenol (-)-epigallocatechin-3-O-gallate (EGCG), a natural ligand of 67LR. We found that phosphodiesterase 5 (PDE5), a negative regulator of cGMP, was abnormally expressed in multiple cancers and attenuated 67LR-mediated cell death. Vardenafil, a PDE5 inhibitor that is used to treat erectile dysfunction, significantly potentiated the EGCG-activated 67LR-dependent apoptosis without affecting normal cells and prolonged the survival time in a mouse xenograft model. These results suggest that PDE5 inhibitors could be used to elevate cGMP levels to induce 67LR-mediated, cancer-specific cell death.

Topics: Animals; Apoptosis; Caspases; Catechin; Cell Line, Tumor; Cell Proliferation; Cyclic GMP; Cyclic Nucleotide Phosphodiesterases, Type 5; Female; Humans; Imidazoles; Male; Membrane Potential, Mitochondrial; Mice; Mice, Inbred BALB C; Molecular Weight; Multiple Myeloma; Neoplasms; Phosphodiesterase 5 Inhibitors; Piperazines; Receptors, Laminin; Signal Transduction; Sulfones; Triazines; Vardenafil Dihydrochloride; Xenograft Model Antitumor Assays

In this study, we investigated the effect of (-)-epigallocatechin-3-gallate (EGCG) on cyclic nucleotide production and vasodilator-stimulated phosphoprotein (VASP) phosphorylation in collagen (10 µg/mL)-stimulated platelet aggregation.. Washed platelets (10(8)/mL) from Sprague-Dawley rats (6-7 weeks old, male) were preincubated for 3 min at 37°C in the presence of 2 mM exogenous CaCl(2) with or without EGCG or other materials, stimulated with collagen (10 µg/mL) for 5 min, and then used for the determination of intracellular cytosolic Ca(2+) ([Ca(2+)](i)), thromboxane A(2) (TXA(2)), adenosine 3',5'-cyclic monophosphate (cAMP), guanosine 3',5'-cyclic monophosphate (cGMP), and VASP phosphorylation.. EGCG dose-dependently inhibited collagen-induced platelet aggregation by inhibiting both [Ca(2+)](i) mobilization and TXA(2) production. Of two aggregation-inhibiting molecules, cAMP and cGMP, EGCG significantly increased intracellular levels of cAMP, but not cGMP. EGCG-elevated cAMP level was decreased by SQ22536, an adenylate cyclase inhibitor, but not by etazolate, a cAMPspecific phosphodiesterase inhibitor. In addition, EGCG elevated the phosphorylation of VASP-Ser(157), a cAMP-dependent protein kinase (A-kinase) substrate, but not the phosphorylation of VASP-Ser(239), a cGMP-dependent protein kinase substrate, in intact platelets and collagen-induced platelets, and VASP-Ser(157) phosphorylation by EGCG was inhibited by both an adenylate cyclase inhibitor SQ22536 and an A-kinase inhibitor Rp-8-Br-cAMPS. We have demonstrated that EGCG increases cAMP via adenylate cyclase activation and subsequently phosphorylates VASP-Ser(157) through A-kinase activation to inhibit [Ca(2+)](i) mobilization and TXA(2) production on collagen-induced platelet aggregation.. These results strongly indicate that EGCG is a beneficial compound elevating cAMP level in collagen-platelet interaction, which may result in the prevention of platelet aggregation-mediated thrombotic diseases.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Animals; Catechin; Collagen; Cyclic AMP; Cyclic GMP; Male; Phosphorylation; Platelet Aggregation Inhibitors; Rats; Rats, Sprague-Dawley

The present study investigates the direct action and the underlying mechanism(s) of epigallocatechin-3-gallate (EGCG) vasomotor effects on the bovine isolated ophthalmic artery. Adjacent rings were cut from each artery and mounted in a wire miograph system for isometric recording. Concentration-response curves for EGCG were constructed by adding cumulative concentrations of the drug to arterial rings pre-contracted with 5-HT (1 microM). Effects of mechanical endothelial cell removal and of selective blockers of the nitric oxide (NO)/cGMP pathways were investigated on the EGCG relaxant responses. EGCG relaxed ophthalmic arteries and maximum relaxation was 78.4+/-2.64%. Mechanical removal of endothelium, blockade of soluble guanylyl cyclase by 1H-1,2,4-oxadiazolo [4,3-a]quinoxalin-1-one (ODQ, 1 and 5 microM) or inhibition of nitric oxide (NO) synthase by N(G)-nitro-L-arginine (L-NAME, 50 and 100 microM) reduced significantly the relaxant response to catechin; moreover, the NO donor S-nitroso-N-acetylpenicillamine (SNAP, 100 microM) significantly increased the vasorelaxant responses to EGCG. Relaxation to EGCG was inhibited by iberiotoxin (200 nM), a blocker of big-conductance Ca(2+)-activated K(+) (BK(Ca)) channel, whereas the blockade of K(ATP) channel by glibenclamide (5 microM) and of small-conductance Ca(2+)-activated K(+) (SK(Ca)) channel by apamin (100 nM) elicited no effect. Interestingly, also inhibition of phosphoinositide-3-kinase (PI3K) by wortmannin (100 nM) and of Akt by SH6 (1 microM) markedly decreased the EGCG-evoked vasorelaxation. These data suggest that EGCG induced vasorelaxation in ophthalmic arteries with endothelium-intact via the activation of the NO/cGMP signalling pathway and defined an intriguing role for PI3K and Akt as upstream mediators for activation of NO-mediated relaxant responses.

Topics: Androstadienes; Animals; Catechin; Cattle; Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanylate Cyclase; Models, Biological; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Ophthalmic Artery; Oxadiazoles; Penicillamine; Peptides; Phosphatidylinositols; Proto-Oncogene Proteins c-akt; Quinoxalines; Serotonin; Signal Transduction; Vasodilation; Wortmannin

Tumor cell migration is considered as a major event in the metastatic cascade. Here we examined the effect of (-)-epigallocatechin-3-gallate (EGCG) on migration capacity and molecular mechanism using 4T1 murine mammary cancer cells as a model. Using an in vitro migration assay, we found that treatment of 4T1 cells with EGCG resulted in concentration-dependent inhibition of migration of these cells. The migration capacity of cells was reduced in presence of N(G)-nitro-l-arginine methyl ester (l-NAME), an inhibitor of nitric oxide synthase. EGCG suppressed the elevated levels of endogenous NO/NOS in 4T1 cells and blocked the migration promoting capacity of l-arginine. Treatment with guanylate cyclase inhibitor 1-H-[1,2,4]oxadiaxolo[4,3-a]quinolalin-1-one (ODQ) reduced the migration of 4T1 cells. EGCG reduced the elevated levels of cGMP in cancer cells and blocked the migration restoring activity of 8-Br cGMP (cGMP analogue). These results indicate for the first time that EGCG inhibits mammary cancer cell migration through the inhibition of NO/NOS and guanylate cyclase.

Topics: Animals; Anticarcinogenic Agents; Carcinoma; Catechin; Cell Line, Tumor; Cell Movement; Cyclic GMP; Enzyme Inhibitors; Guanylate Cyclase; Mammary Neoplasms, Animal; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitrogen Oxides; Oxadiazoles; Quinoxalines

This study investigated several mechanisms involved in the vasorelaxant effects of (-)-epigallocatechin-3-gallate (EGCG). EGCG (1 microM-1 mM) concentration dependently relaxed, after a transient increase in tension, contractions induced by noradrenaline (NA, 1 microM), high extracellular KCl (60 mM), or phorbol 12-myristate 13-acetate (PMA, 1 microM) in intact rat aortic rings. In a Ca2+ -free solution, EGCG (1 microM-1 mM) relaxed 1 microM PMA-induced contractions, without previous transient contraction. However, EGCG (1 microM-1 mM) did not affect the 1 microM okadaic acid-induced contractions. Removal of endothelium and/or pretreatment with glibenclamide (10 microM), tetraethylammonium (2 mM) or charybdotoxin (100 nM) plus apamin (500 nM) did not modify the vasorelaxant effects of EGCG. In addition, EGCG noncompetitively antagonized the contractions induced by NA (in 1.5 mM Ca2+ -containing solution) and Ca2+ (in depolarizing Ca2+ -free high KCl 60 mM solution). In rat aortic smooth muscle cells (RASMC), EGCG (100 microM) reduced increases in cytosolic free Ca2+ concentration ([Ca2+]i) induced by angiotensin II (ANG II, 100 nM) and KCl (60 mM) in 1.5 mM CaCl2 -containing solution and by ANG II (100 nM) in the absence of extracellular Ca2+. In RASMC, EGCG (100 microM) did not modify basal generation of cAMP or cGMP, but significantly reversed the inhibitory effects of NA (1 microM) and high KCl (60 mM) on cAMP and cGMP production. EGCG inhibited the enzymatic activity of all the cyclic nucleotide PDE isoenzymes present in vascular tissue, being more effective on PDE2 (IC50 approximately 17) and on PDE1 (IC50 approximately 25). Our results suggest that the vasorelaxant effects of EGCG in rat aorta are mediated, at least in part, by an inhibition of PDE activity, and the subsequent increase in cyclic nucleotide levels in RASMC, which, in turn, can reduce agonist- or high KCl concentration-induced increases in [Ca2+]i.

Topics: Angiotensin II; Animals; Aorta; Calcium; Catechin; Cells, Cultured; Cyclic AMP; Cyclic GMP; Dose-Response Relationship, Drug; Male; Norepinephrine; Phosphodiesterase Inhibitors; Rats; Rats, Inbred WKY; Vasodilation