Trowaglerix Venom Polypeptides As a Novel Antithrombotic Agent by Targeting Immunoglobulin-Like Domains of Glycoprotein VI in Platelet.

OBJECTIVE: Currently prescribed antiplatelet drugs have 1 common side effect-an increased risk of hemorrhage and thrombocytopenia. On the contrary, bleeding defects associated with glycoprotein VI (GPVI) expression deficiency are usually slightly prolonged bleeding times. However, GPVI antagonists are lacking in clinic. APPROACH AND RESULTS: Using reverse-phase high-performance liquid chromatography and sequencing, we revealed the partial sequence of trowaglerix α subunit, a potent specific GPVI-targeting snaclec (snake venom C-type lectin protein). Hexapeptide (Troα6 [trowaglerix a chain hexapeptide, CKWMNV]) and decapeptide (Troα10) derived from trowaglerix specifically inhibited collagen-induced platelet aggregation through blocking platelet GPVI receptor. Computational peptide design helped to design a series of Troα6/Troα10 peptides. Protein docking studies on these decapeptides and GPVI suggest that Troα10 was bound at the lower surface of D1 domain and outer surface of D2 domain, which was at the different place of the collagen-binding site and the scFv (single-chain variable fragment) D2-binding site. The newly discovered site was confirmed by inhibitory effects of polyclonal antibodies on collagen-induced platelet aggregation. This indicates that D2 domain of GPVI is a novel and important binding epitope on GPVI-mediated platelet aggregation. Troα6/Troα10 displayed prominent inhibitory effect of thrombus formation in fluorescein sodium-induced platelet thrombus formation of mesenteric venules and ferric chloride-induced carotid artery injury thrombosis model without prolonging the in vivo bleeding time. CONCLUSIONS: We develop a novel antithrombotic peptides derived from trowaglerix that acts through GPVI antagonism with greater safety-no severe bleeding. The binding epitope of polypeptides on GPVI is novel and important. These hexa/decapeptides have therapeutic potential for developing ideal small-mass GPVI antagonists for arterial thrombogenic diseases.

4-Acetylantroquinonol B inhibits lipopolysaccharide-induced cytokine release and alleviates sepsis through of MAPK and NFκB suppression.

BACKGROUND: Antrodia cinnamomea is an indigenous medicinal mushroom in Taiwan, commonly used for the treatment of cancers and inflammatory disorders. 4-acetylantroquinonol B (4AAQB) is one of the active component isolated from the mycelium of A. cinnamomea. However, whether 4AAQB exhibits anti-inflammatory effect is not clear. METHODS: The anti-inflammatory activity of 4AAQB was examined by ELISA to measure the pro-inflammatory cytokines production in lipopolysaccharide (LPS)-simulated RAW264.7 cells, peritoneal macrophages and in mice. The effect of 4AAQB for MAPK kinase molecules phosphorylation in LPS-stimulated RAW264.7 macrophage including ERK, JNK and p38 were evaluated. The in vivo efficacy of 4AAQB was also demonstrated. RESULTS: In the present study, we found that 4AAQB exhibits anti-inflammatory effects inhibit tumor necrosis factor-α (TNF-α)/interleukin-6 (IL-6) releasing and LPS-stimulated phagocytes migration without affect cell growth. In addition, the MAPK kinase molecules phosphorylation in LPS-stimulated RAW264.7 macrophage including ERK, JNK and p38 was inhibited by 4AAQB. The phosphorylation of NFκB subunit p65 and IkBα were also decreased after 4AAQB treatment. Furthermore, 4AAQB attenuates the cytokine production in LPS-induced and CLP-induced septic mice. CONCLUSION: These results showed that 4AAQB exhibited anti-inflammatory property both in vitro and in vivo, suggesting that 4AAQB may be a therapeutic candidate which used in inflammatory disorders treatment.

Butein inhibits metastatic behavior in mouse melanoma cells through VEGF expression and translation-dependent signaling pathway regulation.

BACKGROUND: Melanoma is an aggressive skin cancer and a predominant cause of skin cancer-related deaths. A previous study has demonstrated the ability of butein to inhibit tumor proliferation and invasion. However, the anti-metastatic mechanisms and in vivo effects of butein have not been fully elucidated. METHODS: MTT cell viability assays were used to evaluate the antitumor effects of butein in vitro. Cytotoxic effects of butein were measured by lactate dehydrogenase assay. Anti-migratory effects of butein were evaluated by two-dimensional scratch and transwell migration assays. Signaling transduction and VEGF-releasing assays were measured by Western blotting and ELISA. We also conducted an experimental analysis of the metastatic potential of tumor cells injected into the tail vein of C57BL/6 mice. RESULTS: We first demonstrated the effect of butein on cell viability at non-cytotoxic concentrations (1, 3, and 10 µM). In vitro, butein was found to inhibit the migration of B16F10 cells in a concentration-dependent manner using transwell and scratch assays. Butein had a dose-dependent effect on focal adhesion kinase, Akt, and ERK phosphorylation in B16F10 cells. Butein efficiently inhibited the mTOR/p70S6K translational inhibition machinery and decreased the production of VEGF in B16F10 cells. Furthermore, the in vivo antitumor effects of butein were demonstrated using a pulmonary metastasis model. CONCLUSION: The results of the present study indicate the potential utility of butein in the treatment of melanoma.

FcgammaRII mediates platelet aggregation caused by disintegrins and GPIIb/IIIa monoclonal antibody, AP2.

OBJECTIVE: Disintegrins, snake venom-derived Arg-Gly-Asp (RGD)-containing polypeptides, and GPIIb/IIIa antagonist (AP2) block fibrinogen binding to GPIIb/IIIa of activated platelets, however, the combination of these two agents caused platelet aggregation. We hypothesize that disintegrin initially binds to specific epitope of GPIIb/IIIa, causing conformational change, and the recruitment of FcgammaRII, which can be bound by AP2, and finally triggering platelet aggregation. MATERIALS AND METHODS: We prepared human platelet suspensions and measured platelet aggregation, Ca2+ mobilization, thromboxane B2 formation, and signal transduction. RESULTS: Disintegrin (e.g., accutin) and AP2 (a monoclonal antibody [mAb]-raised against GPIIb/IIIa) individually inhibited human platelet aggregation caused by collagen. However, as both accutin and AP2 were sequentially added into platelet suspension, platelet aggregation occurred. Accutin/AP2 caused shape change, cytosolic Ca2+ mobilization, P-selectin expression, and thromboxane A2 formation. Tirofiban, FcgammaRII mAb, or indomethacin completely inhibited platelet aggregation caused by accutin/AP2. Accutin/AP2 also caused tyrosine phosphorylation of signal molecules. Disintegrins enhanced AP2 binding to platelets, and AP2 also promoted disintegrin binding to platelets. FcgammaRII mAb inhibited the enhanced fluorescein isothiocyanate-disintegrin binding to platelet caused by AP2. Immunoprecipitation of the lysates of disintegrin/AP2-treated platelets using FcgammaRII Ab showed complex formation of GPIIb/IIIa and FcgammaRII. CONCLUSION: FcgammaRII mediates platelet aggregation caused by disintegrin and AP2, triggering a phospholipase C, phospholipase A2, Src-, Syk kinases, and Ca2+-dependent activation process. AP2 triggers platelet aggregation via binding to accessible FcgammaRII and the conformation-altered GPIIb/IIIa caused by disintegrin.

Novel Antrodia cinnamomea Extract Reduced Cancer Stem-Like Phenotype Changes and Resensitized KRAS-Mutant Colorectal Cancer via a MicroRNA-27a Pathway.

Colorectal cancer (CRC) is one of the most common causes of death in Taiwan. Previous studies showed that Antrodia cinnamomea (AC) can treat poisoning, diarrhea, and various types of cancer. Therefore, we purified a novel ubiquinone derivative, AC009, and investigated its antitumor effects. Cell viability assays revealed that AC009 reduced the viability of several human CRC cell lines. AC009 treatment resulted in cell-cycle arrest/apoptosis, and these effects may occur via caspase and Bcl-2 signaling pathways. We demonstrated that AC009 could significantly inhibit in vivo tumor growth in xenograft mouse models. Using messenger RNA (mRNA) and microRNA (miRNA) microarrays, we found that KRAS gene expression was also regulated by AC009, possibly through specific miRNAs. AC009 also reduced cancer stem-cell marker CD44+/CD24+ expression and restored the tumor inhibition effect of cetuximab in KRAS-mutant CRC. Moreover, we found that miRNA-27a could restore the tumor inhibition effect of cetuximab in KRAS-mutant CRC cells. Taken together, our results suggest that AC009 has therapeutic potential against human wild-type and KRAS-mutant CRC.

Aggretin Venom Polypeptide as a Novel Anti-angiogenesis Agent by Targeting Integrin alpha2beta1.

VEGF and VEGFR antibodies have been used as a therapeutic strategy to inhibit angiogenesis in many diseases; however, frequent and repeated administration of these antibodies to patients induces immunogenicity. In previous studies, we demonstrated that aggretin, a heterodimeric snake venom C-type lectin, exhibits pro-angiogenic activities via integrin α2ß1 ligation. We hypothesised that small-mass aggretin fragments may bind integrin α2ß1 and act as antagonists of angiogenesis. In this study, the anti-angiogenic efficacy of a synthesised aggretin α-chain C-terminus (AACT, residue 106-136) was evaluated in both in vitro and in vivo angiogenesis models. The AACT demonstrated inhibitory effects on collagen-induced platelet aggregation and HUVEC adhesion to immobilised collagen. These results indicated that AACT may block integrin α2ß1-collagen interaction. AACT also inhibited HUVEC migration and tube formation. Aortic ring sprouting and Matrigel implant models demonstrated that AACT markedly inhibited VEGF-induced neovascularisation. In addition, induction of FAK/PI3K/ERK1/2 tyrosine phosphorylation and talin 1/2 associated with integrin ß1 which are induced by VEGF were blocked by AACT. Similarly, tyrosine phosphorylation of VEFGR2 and ERK1/2 induced by VEGF was diminished in integrin α2-silenced endothelial cells. Our results demonstrate that AACT is a potential therapeutic candidate for angiogenesis related-diseases via integrin α2ß1 blockade.

Improved antithrombotic activity and diminished bleeding side effect of a PEGylated αIIbß3 antagonist, disintegrin.

INTRODUCTION: The applicability of protein drugs is confined by protein degradation and rapid elimination. PEGylation of polypeptides improves protein stability by sterically obstructing the degradation by serum proteases and reduces renal clearance by the increased mass. EXPERIMENTAL APPROACH: We compared the antithrombotic activities of intact rhodostomin (Rn) and PEGylated rhodostomin (PRn) both in vitro and in vivo systems. In addition, the functional half-life in inhibiting platelet aggregation and the tendency in causing bleeding side effect were investigated. RESULTS: Rn and PRn both potently inhibited human and mouse platelet aggregation induced by collagen, thrombin or ADP in vitro with a similar IC50 around 60-100nM. Rotational thromboelastometry assay indicated that PRn was more effective than Rn in preventing clot formation in human whole blood. In platelet-rich plasma from mice injected with Rn or PRn, the inhibitory effects on collagen-induced platelet aggregation were also comparable, but Rn caused higher bleeding tendency. In ferric chloride-induced arterial thrombosis, Rn and PRn significantly prolonged occlusion time at high dosage (0.2µg/g). However, PRn obviously prolonged the occlusion time even given at a lower dosage (0.06µg/g). The functional half-life assay revealed that PEGylation prolonged the in vivo half-life of Rn. CONCLUSIONS: PRn exhibits higher antithrombotic potency and longer half-life in vivo as compared with native Rn on a molar basis. In addition, PRn exhibits a better safety profile at an efficacious antithrombotic dose in vivo. Therefore, PEGylation may be one of the ideal options in modifying disintegrin derivatives as the safe therapeutic agents for integrin-related diseases.

Snake Venom Disintegrin Inhibits the Activation of Toll-Like Receptors and Alleviates Sepsis through Integrin alphaVbeta3 Blockade.

Bacterial infection-induced sepsis is the leading cause of septic inflammatory disease. Rhodostomin (Rn), a snake venom disintegrin, was previously reported to interact with the αVß3 integrin and the TLR4 on phagocyte in attenuating LPS-induced endotoxemia. In this report, we further evaluated the effects of Rn on TLR2-activated monocytes and its in vivo efficacy. Rn effectively suppressed the adhesion, migration, and cytokine release of Pam3CSK4-activated THP-1 cells. Rn specifically bound to integrin αVß3 of TLR2-activated THP-1. Integrin αV and Akt siRNA transfection both restrained Pam3CSK4-elicited cytokine release. Rn decreased the Pam3CSK4-induced phosporylation of MAPKs, degradation of IκB and activation of FAK, Akt, c-Src and Syk. The Pam3CSK4-induced translocation of MyD88, a central adaptor of TLR2, to the cell membrane was also inhibited by Rn treatment. In the polymicrobial inflammatory caecal ligation and puncture model, Rn significantly reduced pro-inflammatory cytokine and chemokine release, alleviated tissue injury and elevated survival rate in vivo. Taken together, in addition to inhibiting the activation of TLR4, Rn exhibits anti-inflammatory activity through antagonizing the activation of phagocytes and interrupting the crosstalk between αVß3 and TLR2-dependent signaling pathways.

4-Acetylantroquinonol B suppresses tumor growth and metastasis of hepatoma cells via blockade of translation-dependent signaling pathway and VEGF production.

Hepatocellular carcinoma (HCC) has become one of most common malignancies and a leading cause of cancer mortality worldwide. Previous study has shown that 4-acetylantroquinonol B (4AAQB) isolated from Antrodia cinnamomea (or niu-chang-chih) was observed to inhibit HepG2 cell proliferation via affecting cell cycle. However, the in vivo effects and antimetastatic activity of 4AAQB have not yet been addressed. This study found that 4AAQB inhibited HepG2 and HuH-7 hepatoma cell growth in both in vitro and in vivo models and exhibited pronounced inhibitory effects on HuH-7 tumor growth in xenograft and orthotopic models. 4AAQB efficiently inhibited the phosphorylation of mTOR and its upstream kinases and the downstream effectors and decreased the production of VEGF and activity of Rho GTPases in HuH-7 cells. Furthermore, 4AAQB inhibited in vitro HuH-7 cell migration and in vivo pulmonary metastasis. The results suggested that 4AAQB is a potential candidate for HCC therapy.

Yuwen02f1 suppresses LPS-induced endotoxemia and adjuvant-induced arthritis primarily through blockade of ROS formation, NFkB and MAPK activation.

Phagocytes release inflammatory mediators to defense harmful stimuli upon bacterial invasion, however, excessive inflammatory reaction leads to tissue damage and manifestation of pathological states. Therefore, targeting on uncontrolled inflammation seems feasible to control numerous inflammation-associated diseases. Under the drug screening process of synthetic diphenylpyrazole derivatives, we discovered compound yuwen02f1 possesses anti-inflammatory effects in decreasing the release of pro-inflammatory cytokines including TNFα and IL-6, nitric oxide, reactive oxygen species (ROS) as well as inhibiting migration of LPS-stimulated phagocytes. In addition, we observed that the molecular mechanism of yuwen02f1-mediated anti-inflammation is associated with decreasing phosphorylation of MAPK molecules including ERK1/2, JNK and p38, and attenuating translocation of p47(phox) and p67(phox) to the cell membrane. Yuwen02f1 also reverses IκBα degradation and attenuates the expression of NFκB-related downstream inducible enzymes like iNOS and COX-2. Furthermore, we found that yuwen02f1 attenuates some pathological syndromes of LPS-induced sepsis and adjuvant-induced arthritis in mice, as evidenced by decreasing the cytokine production, reversing thrombocytopenic syndrome, protecting the mice from tissue injury in septic mice, and attenuating paw edema in arthritic mice as well. These results suggest that yuwen02f1 is a potential anti-inflammatory agent for alleviating syndromes of acute and chronic inflammatory diseases as evidenced by attenuating the generation of cytokines and down-regulating the expression of iNOS and COX-2 through the blockade of ROS generation and NADPH oxidase, NFκB and MAPK activation pathways in LPS-stimulated phagocytes.

Butein Inhibits Angiogenesis of Human Endothelial Progenitor Cells via the Translation Dependent Signaling Pathway.

Compelling evidence indicates that bone marrow-derived endothelial progenitor cells (EPCs) can contribute to postnatal neovascularization and tumor angiogenesis. EPCs have been shown to play a "catalytic" role in metastatic progression by mediating the angiogenic switch. Understanding the pharmacological functions and molecular targets of natural products is critical for drug development. Butein, a natural chalcone derivative, has been reported to exert potent anticancer activity. However, the antiangiogenic activity of butein has not been addressed. In this study, we found that butein inhibited serum- and vascular endothelial growth factor- (VEGF-) induced cell proliferation, migration, and tube formation of human EPCs in a concentration dependent manner without cytotoxic effect. Furthermore, butein markedly abrogated VEGF-induced vessels sprouting from aortic rings and suppressed microvessel formation in the Matrigel implant assay in vivo. In addition, butein concentration-dependently repressed the phosphorylation of Akt, mTOR, and the major downstream effectors, p70S6K, 4E-BP1, and eIF4E in EPCs. Taken together, our results demonstrate for the first time that butein exhibits the antiangiogenic effect both in vitro and in vivo by targeting the translational machinery. Butein is a promising angiogenesis inhibitor with the potential for treatment of cancer and other angiogenesis-related diseases.

Antirestenosis effect of butein in the neointima formation progression.

The development of restenosis involves migration and hyperproliferation of vascular smooth muscle cells (VSMCs). Platelet-derived growth factor (PDGF) is one of the major factors. Butein modulates inflammatory pathways and affects the proliferation and invasion of the tumor. We investigated the hypothesis that butein might prevent the restenosis process via a similar pathway. Our results demonstrated that butein inhibited PDGF-induced VSMC proliferation and migration as determined by BrdU proliferation and two-dimensional migration scratch assay. Butein also concentration-dependently repressed PDGF-induced phosphorylation of PDGF-receptor ß, mitogen-activated protein kinases, phosphoinositide 3-kinase/Akt, and phopholipase Cγ/c-Src in VSMCs. In addition, in vivo results showed that butein attenuated neointima formation in balloon-injured rat carotid arteries. These results indicate that butein may inhibit PDGF-induced VSMC proliferation and migration, resulting in attenuation of neointima formation after percutaneous transluminal coronary angioplasty. Our study demonstrates for the first time that systemic administration of butein is able to reduce neointima formation after vascular injury.

NP-313, 2-acetylamino-3-chloro-1,4-naphthoquinone, a novel antithrombotic agent with dual inhibition of thromboxane A(2) synthesis and calcium entry.

BACKGROUND AND PURPOSE: 1,4-Naphthoquinones exhibit antiplatelet activity both in vivo and in vitro. In the present study, we investigated the antiplatelet effect of a novel naphthoquinone derivative NP-313, 2-acetylamino-3-chloro-1,4-naphthoquinone and its mechanism of action. EXPERIMENTAL APPROACH: We measured platelet aggregation, Ca(2+) mobilization, thromboxane B2 formation and P-selectin expression and examined several enzymatic activities. Furthermore, we used the irradiated mesenteric venules in fluorescein sodium-treated mice to monitor the antithrombotic effect of NP-313 in vivo. KEY RESULTS: NP-313 concentration-dependently inhibited human platelet aggregation induced by collagen, arachidonic acid, thapsigargin, thrombin and A23187. NP-313 also inhibited P-selectin expression, thromboxane B(2) formation and [Ca(2+) ](i) elevation in platelets stimulated by thrombin and collagen. NP-313 at 10 µM inhibited cyclooxygenase, thromboxane A(2) synthase, and protein kinase Cα, whereas it did not affect phospholipase A(2) or phospholipase C activity. In the presence of indomethacin and an adenosine 5-diphosphate scavenger, NP-313 concentration-dependently inhibited thrombin- and A23187-induced [Ca(2+)](i) increase through its inhibitory effects on Ca(2+) influx, rather than blocking Ca(2+) release from intracellular stores. NP-313 also inhibited thapsigargin-mediated Ca(2+) influx through store-operated calcium channel but had no effect on Ca(2+) influx through store-independent calcium channel evoked by the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol. Nevertheless, it had little effect on cyclic AMP and cyclic GMP levels. Also, intravenously administered NP-313 dose-dependently inhibited the thrombus occlusion of the irradiated mesenteric vessels of fluorescein-pretreated mice. CONCLUSIONS AND IMPLICATIONS: Taken together, these results indicate that NP-313 exerts its antithrombotic activity through dual inhibition of thromboxane A(2) synthesis and Ca(2+) influx through SOCC.

NP-184[2-(5-methyl-2-furyl) benzimidazole], a novel orally active antithrombotic agent with dual antiplatelet and anticoagulant activities.

The established antiplatelet and anticoagulant agents show beneficial effects in the treatment of thromboembolic diseases; however, these drugs still have considerable limitations. The effects of NP-184, a synthetic compound, on platelet functions, plasma coagulant activity, and mesenteric venule thrombosis in mice were investigated. NP-184 concentration-dependently inhibited the human platelet aggregation induced by collagen, arachidonic acid (AA), and U46619, a thromboxane (TX)A(2) mimic, with IC(50) values of 4.5 +/- 0.2, 3.9 +/- 0.1, and 9.3 +/- 0.5 microM, respectively. Moreover, NP-184 concentration-dependently suppressed TXA(2) formations caused by collagen and AA. In exploring effects of NP-184 on enzymes involved in TXA(2) synthesis, we found that NP-184 selectively inhibited TXA(2) synthase activity with an IC(50) value of 4.3 +/- 0.2 microM. Furthermore, NP-184 produced a right shift of the concentration-response curve of U46619, indicating a competitive antagonism on TXA(2)/prostaglandin H(2) receptor. Intriguingly, NP-184 also caused a concentration-dependent prolongation of the activated partial thromboplastin time (aPTT) with no changes in the prothrombin and thrombin time, indicating that it selectively impairs the intrinsic coagulation pathway. Oral administration of NP-184 significantly inhibited thrombus formation of the irradiated mesenteric venules in fluorescein sodium-treated mice without affecting the bleeding time induced by tail transection. However, after oral administration, NP-184 inhibited the ex vivo mouse platelet aggregation triggered by collagen and U46619 and also prolonged aPTT. Taken together, the dual antiplatelet and anticoagulant activities of NP-184 may have therapeutic potential as an oral antithrombotic agent in the treatment of thromboembolic disorders.

The integrin alpha2beta1 agonist, aggretin, promotes proliferation and migration of VSMC through NF-kB translocation and PDGF production.

BACKGROUND AND PURPOSE: During the development of atherosclerotic plaques, vascular smooth muscle cells (VSMCs) migrate from the media to the intima through the basement membrane and interstitial collagenous matrix, and proliferate to form neointima. Here, we investigate the mechanism of VSMC migration and proliferation caused by aggretin, a snake venom integrin alpha2beta1 agonist. EXPERIMENTAL APPROACH: Cultures of rat and human VSMCs were treated with aggretin and the signal transduction pathways induced by this agonist were examined by Western blotting, immunoprecipitation and electrophoretic mobility shift assay techniques. KEY RESULTS: Aggretin-induced VSMC proliferation was blocked by a monoclonal antibody (mAb) against integrin alpha2 (AII2E10) or against the platelet-derived growth factor receptor (PDGFR)-beta. Proliferation was also blocked by inhibition of the tyrosine kinase Src with PP2, phospholipase C (PLC) with U73122, extracellular signal-regulated kinase (ERK) with PD98059 or nuclear factor-kappa B (NF-kB) activation with pyrrolidine dithiocarbamate (PDTC). VSMC migration towards immobilized aggretin was increased in a modified Boyden chamber and this effect was blocked by alpha2beta1-Src-PLC-MAPK axis inhibitors, but not by PDTC, PDGFR-beta mAb, or a phosphoinositide-3 kinase inhibitor, LY294002. Aggretin stimulated the phosphorylation of PDGFR-beta, Src and ERK in a time-dependent manner. NF-kB translocation and platelet-derived growth factor (PDGF)-BB production were also observed. The ERK activation, NF-kB translocation and PDGF-BB production were blocked by PP2, U73122 and PD98059. CONCLUSIONS AND IMPLICATIONS: Aggretin induces VSMC proliferation and migration mainly through binding to integrin alpha2beta1, and subsequently activates Src, PLC and ERK pathways, inducing NF-kB activation and PDGF production.