U0126 Treatment Research Articles

Inhibition of SlMPK1, SlMPK2, and SlMPK3 Disrupts Defense Signaling Pathways and Enhances Tomato Fruit Susceptibility to Botrytis cinerea.

Mitogen-activated protein kinases (MAPKs) are major components of defense signaling pathways that transduce extracellular stimuli into intracellular responses in plants. Our previous study indicated that SlMPK1/2/3 were associated with nitric oxide-induced defense response in tomato fruit. In this study, we determine whether SlMPK1/2/3 influence the tomato fruit's innate immunity and whether plant hormones and reactive oxygen species (ROS) are involved in SlMPK1/2/3 defense signaling pathways. Treatment with 10 μM U0126 significantly inhibited the relative expression of SlMPK1, SlMPK2, and SlMPK3 (P < 0.05). U0126-treated fruit showed higher concentrations of auxin indole acetic acid (IAA), abscisic acid (ABA), and gibberellic acid (GA), but a lower concentration of methyl jasmonate (MeJA). The activities of defense enzymes, including β-1,3-glucanases (GLU), chitinase (CHI), phenylalanine ammonia lyase (PAL), and polyphenol oxidase (PPO), decreased after U0126 treatment. Meanwhile, H2O2 content increased, and catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) activities decreased after U0126 treatment. U0126 treatment enhanced the susceptibility of tomato fruit to Botrytis cinerea and resulted in more severe gray mold rot. These results demonstrate that inhibition of SlMPK1/2/3 disrupts tomato fruit defense signaling pathways and enhances the susceptibility to B. cinerea and also that plant hormones and ROS are associated with SlMPK1/2/3 defense signaling pathways.

Co-operation between the AKT and ERK signaling pathways may support growth of deep endometriosis in a fibrotic microenvironment in vitro.

How can deep endometriotic stromal cells proliferate and persist in a fibrotic environment? The serine/threonine kinase AKT and extracellular regulated kinase (ERK) signaling pathways may co-operate to support growth of deep endometriotic lesions by enhancing endometriotic stromal cell proliferation and survival in a fibrotic microenvironment in vitro. Endometriosis, particularly deep infiltrating endometriosis, is characterized histologically by dense fibrous tissue that is primarily composed of type I collagen. This tissue may cause pelvic pain and infertility, which are major clinical issues associated with endometriosis. Proliferation of normal fibroblasts is tightly regulated, and fibrillar, polymerized type I collagen inhibits normal fibroblast proliferation. However, no studies to date have investigated how deep endometriotic stromal cells can proliferate and persist in a fibrotic environment. Endometrial and/or endometriotic tissues from 104 patients (61 with and 43 without endometriosis) of reproductive age with normal menstrual cycles were analyzed. A total of 25 nude mice received a single injection of endometrial fragments from a total of five samples. We evaluated cell proliferation, caspase 3/7 activity, and the AKT and ERK signaling pathways in endometrial and endometriotic stromal cells on three-dimensional (3D) polymerized collagen matrices in vitro. In addition, to determine whether aberrant activation of the AKT and ERK pathways is involved during progression of fibrosis in endometriosis in vivo, we evaluated the expression of phosphorylated AKT and ERK1/2 in endometriotic implants in a nude mouse model of endometriosis. Finally, we evaluated the effects of MK2206 (an AKT inhibitor) and U0126 (a MEK inhibitor) on cell proliferation, caspase 3/7 activity, and phosphorylation of AKT and ERK1/2 of endometriotic stromal cells on 3D polymerized collagen matrices. Proliferation of endometriotic stromal cells was significantly less inhibited than that of endometrial stromal cells (P < 0.05) on 3D polymerized collagen. Levels of phosphorylated AKT, phosphorylated p70S6K and phosphorylated ERK1/2 were significantly higher in endometriotic stromal cells than in endometrial stromal cells at 24 h (P < 0.05) and at 72 h (P < 0.05) on 3D polymerized collagen. Phosphorylated AKT expression was significantly increased on Days 21 and 28 compared with those on Days 3 and 7 (all P < 0.05) in endometriotic implants during progression of fibrosis in a nude mouse model of endometriosis. Inhibition of AKT or ERK1/2 with MK2206 or U0126, respectively, did not significantly increase caspase 3/7 activity in endometriotic stromal cells on either two-dimensional or 3D collagen matrices. Western blot analysis showed that MK2206 alone decreased levels of phosphorylated AKT; however, it increased levels of phosphorylated ERK in endometriotic cells compared with vehicle-treated cells (both P < 0.05). In addition, U0126 treatment decreased levels of phosphorylated ERK; however, it resulted in increased levels of phosphorylated AKT in endometriotic stromal cells compared with vehicle-treated cells (both P < 0.05). Endometriosis involves a number of processes, such as invasion, metastasis, angiogenesis, and apoptosis resistance, and a variety of signaling pathways may be involved in promoting development and progression of the disease. In addition, further animal experiments are required to determine whether the AKT and ERK signaling pathways co-operate to support growth of endometriotic lesions in a fibrotic microenvironment in vivo. Co-targeting the AKT and ERK pathways may be an effective therapeutic strategy for endometriosis treatment. This study was supported in part by Karl Storz Endoscopy & GmbH (Tuttlingen, Germany). No competing interests are declared.

ERK1/2 acts as a switch between necrotic and apoptotic cell death in ether phospholipid edelfosine-treated glioblastoma cells

Glioblastoma is characterized by constitutive apoptosis resistance and survival signaling expression, but paradoxically is a necrosis-prone neoplasm. Incubation of human U118 glioblastoma cells with the antitumor alkylphospholipid analog edelfosine induced a potent necrotic cell death, whereas apoptosis was scarce. Preincubation of U118 cells with the selective MEK1/2 inhibitor U0126, which inhibits MEK1/2-mediated activation of ERK1/2, led to a switch from necrosis to caspase-dependent apoptosis following edelfosine treatment. Combined treatment of U0126 and edelfosine totally inhibited ERK1/2 phosphorylation, and led to RIPK1 and RelA/NF-κB degradation, together with a strong activation of caspase-3 and -8. This apoptotic response was accompanied by the activation of the intrinsic apoptotic pathway with mitochondrial transmembrane potential loss, Bcl-xL degradation and caspase-9 activation. Inhibition of ERK phosphorylation also led to a dramatic increase in edelfosine-induced apoptosis when the alkylphospholipid analog was used at a low micromolar range, suggesting that ERK phosphorylation acts as a potent regulator of apoptotic cell death in edelfosine-treated U118 cells. These data show that inhibition of MEK1/2-ERK1/2 signaling pathway highly potentiates edelfosine-induced apoptosis in glioblastoma U118 cells and switches the type of edelfosine-induced cell death from necrosis to apoptosis.

Mitogen-activated protein kinase signaling controls basal and oncostatin M-mediated JUNB gene expression.

The mitogen-activated protein kinase (MAPK) pathway is aberrantly activated in many human cancers, including breast cancer. Activation of MAPK signaling is associated with the increased expression of a wide range of genes that promote cell survival, proliferation, and migration. This report investigated the influence of MAPK signaling on the regulation and expression of JUNB in human breast cancer cell lines. JUNB has been associated with tumor suppressor and oncogenic functions, with most reports describing JUNB as an oncogene in breast cancer. Our results indicated that JUNB expression is elevated in MCF10A(met), SKBR3, and MDA-MB-231 human breast cancer cell lines compared to nontransformed MCF10A mammary epithelial cells. Increased RAS/MAPK signaling in MCF10A(met) cells correlates with the increased association of RNA polymerase II (Pol II) phosphorylated on serine 5 (Pol IIser5p) with the JUNB proximal promoter. Pol IIser5p is the "transcription initiating" form of Pol II. Treatment with U0126, a MAPK pathway inhibitor, reduces Pol IIser5p association with the JUNB proximal promoter and reduces JUNB expression. Oncostatin M (OSM) enhances MAPK and STAT3 signaling and significantly induces JUNB expression. U0126 treatment reduces OSM-induced Pol IIser5p binding to the JUNB proximal promoter and JUNB expression, but does not reduce pSTAT3 levels or the association of pSTAT3 with the JUNB proximal promoter. These results demonstrate that the MAPK pathway plays a primary role in the control of JUNB gene expression by promoting the association of Pol IIser5p with the JUNB proximal promoter.

Restoration of IRF1-dependent anticancer effects by MEK inhibition in human cancer cells

Interferon regulatory factor (IRF1) is a potent antiviral, antitumor and immune regulatory protein. Recently, we found that activated Ras/MEK inhibits antiviral response by downregulating IRF1 expression and renders cancer cells susceptible to oncolytic viruses. In this study, we sought to determine whether IRF1 downregulation underlies oncogenesis induced by Ras/MEK activation in human cancer cells. Treatment of the MEK inhibitor U0126 promoted IRF1 expression in 7 of 11 cancer cell lines we tested. IRF1 promotion was also observed in human cancer cell lines treated with different MEK inhibitors or with RNAi oligonucleotides against extracellular signal-regulated kinases (ERKs). Restoration of the expression of antitumor genes, p27 and p53 upregulated modulator of apoptosis (PUMA), by MEK inhibition was less in IRF1 shRNA knockdown cancer cells than in vector control cancer cells, suggesting that Ras/MEK targets IRF1 for the downregulation of the antitumor genes. Moreover, apoptosis induction by U0126 was significantly reduced in IRF1 shRNA knockdown cells than vector control cells. This study demonstrates that IRF1 expression is suppressed by activated Ras/MEK in human cancer cells and that IRF1 plays essential roles in apoptosis induced by Ras/MEK inhibition.

MEK/ERK signaling pathway is required for enterovirus 71 replication in immature dendritic cells.

BackgroundThe mitogen-activated protein kinase kinase/extracellular-signal-regulated kinase (MEK/ERK) signaling pathway is involved in viral life cycle. However, the effect of MEK/ERK pathway in enterovirus 71(EV71)-infected immature dendritic cells (iDCs) is still unclear.MethodsHuman peripheral blood mononuclear cells (PBMCs) were isolated and induced to generate iDCs. Unifected iDCs and EV71-infected iDCs with a multiplicity of infection (MOI = 5) were analyzed by flow cytometry. Differential gene expressions of MEK/ERK signaling pathway molecules in EV71-infected iDCs were performed by PCR arrays. The phosphorylation of MEK/ERK pathway molecules in EV71-infected iDCs preincubated without or with U0126 (20 μM) at indicated times was detected by Western blot. The concentrations of IL-1α, IL-2, IL-6, IL-12, TNF-α, IFN-α1, IFN-β and IFN-γ in culture supernatant were analyzed by the luminex fluorescent technique.ResultsWhen iDCs were infected with EV71 for 24 h, the percentage of CD80, CD83, CD86 and HLA-DR expressed on iDCs significantly increased. PCR arrays showed that gene expressions of molecules in MEK/ERK signaling pathway were remarkably upregulated in EV71-infected iDCs. EV71 infection activated both MEK1/2 and ERK1/2, which phosphorylated their downstream transcription factor c-Fos, c-Jun, c-myc and Elk1. Importantly, the treatment of U0126 significantly inhibited MEK/ERK signaling pathway molecules and severely impaired virus replication., Additionally, EV71 infection promoted the expression of son of sevenless (SOS1) and increased the secretion of IL-1α, IL-2, IL-6, IL-12, TNF-α,IFN-β and IFN-γ. Furthermore,the release of IL-1α, IL-2,IL-6 and TNF-α could be effectively suppressed by inhibitor U0126.ConclusionsOur data suggest that the MEK/ERK signaling pathway plays an important role in EV71-infected iDCs and these molecules may be potential targets for the development of new anti-EV71 drugs.

Lipopolysaccharide augments the uptake of oxidized LDL by up-regulating lectin-like oxidized LDL receptor-1 in macrophages

There is a growing body of evidence supporting an intimate association of immune activation with the pathogenesis of cardiovascular diseases, including atherosclerosis. Uptake of oxidized low-density lipoprotein (oxLDL) through scavenging receptors promotes the formation of mature lipid-laden macrophages, which subsequently leads to exacerbation of regional inflammation and atherosclerotic plaque formation. In this study, we first examined changes in the mRNA level of the lectin-like oxLDL receptor-1 (LOX-1) in the mouse macrophage cell line RAW264.7 and the human PMA-induced macrophage cell line THP-1 after LPS stimulation. LPS significantly up-regulated LOX-1 mRNA in RAW264.7 cells; LOX-1 cell-surface protein expression was also increased. Flow cytometry and fluorescence microscopy analyses showed that cellular uptake of fluorescence (Dil)-labeled oxLDL was significantly augmented with LPS stimulation. The augmented uptake of Dil-oxLDL was almost completely abrogated by treatment with an anti-LOX-1 antibody. Of note, knockdown of Erk1/2 resulted in a significant reduction of LPS-induced LOX-1 up-regulation. Treatment with U0126, a specific inhibitor of MEK, significantly suppressed LPS-induced expression of LOX-1 at both the mRNA and protein levels. Furthermore, LOX-1 promoter activity was significantly augmented by LPS stimulation; this augmentation was prevented by U0126 treatment. Similar results were also observed in human PMA-induced THP-1 macrophages. Taken together, our results indicate that LPS up-regulates LOX-1, at least in part through activation of the Erk1/2 signaling pathway, followed by augmented cellular oxLDL uptake, thus highlighting a critical role of TLR4-mediated aberrant LOX-1 signaling in the pathogenesis of atherosclerosis.

MEK/ERK activation plays a decisive role in yellow fever virus replication: Implication as an antiviral therapeutic target

Exploiting the inhibition of host signaling pathways aiming for discovery of potential antiflaviviral compounds is clearly a beneficial strategy for the control of life-threatening diseases caused by flaviviruses. Here we describe the antiviral activity of the MEK1/2 inhibitor U0126 against Yellow fever virus 17D vaccine strain (YFV-17D). Infection of VERO cells with YFV-17D stimulates ERK1/2 phosphorylation early during infection. Pharmacological inhibition of MEK1/2 through U0126 treatment of VERO cells blockades not only the YFV-stimulated ERK1/2 phosphorylation, but also inhibits YFV replication by ∼99%. U0126 was also effective against dengue virus (DENV-2 and -3) and Saint-Louis encephalitis virus (SLEV). Levels of NS4AB, as detected by immunofluorescence, are diminished upon treatment with the inhibitor, as well as the characteristic endoplasmic reticulum membrane invagination stimulated during the infection. Though not protective, treatment of YFV-infected, adult BALB/c mice with U0126 resulted in significant reduction of virus titers in brains. Collectively, our data suggest the potential targeting of the MEK1/2 kinase as a therapeutic tool against diseases caused by flaviviruses such as yellow fever, adverse events associated with yellow fever vaccination and dengue.

Erk1/2 activation and modulation of STAT3 signaling in oral cancer.

Constitutive activation of the signal transducer and activator of transcription 3(STAT3) signaling pathway possesses confirmed oncogenic potential in oral squamous cell carcinoma(OSCC). Crosstalk with other molecular pathways contributes to STAT3 regulation in cancer. The effects of mitogen-activated protein kinases(MAPKs) and particularly extracellular signal-regulated kinase 1/2(Erk1/2) on STAT3 signaling in OSCC have not been thoroughly investigated. The present study examined the effects of Erk1/2 modulation on STAT3 signaling and cell growth in OSCC cells. Constitutive expression levels of phosphorylated (tyrosine and serine) and total STAT3, Erk1/2 and cyclinD1 were assessed in OSCC cell lines. Erk1/2 modulation was achieved by pharmacological agents; siRNA silencing against Erk1/2 was also performed. Cell proliferation and viability were assessed. Erk1/2 inhibition with either U0126 treatment or specific siRNA silencing resulted in decreases in p-serSTAT3 and cyclinD1 levels and increases in p-tyr STAT3 in OSCC cells. Moreover, Erk1/2 inhibition resulted in a dose-dependent reduction in OSCC cell growth and viability. Erk1/2 induction had the opposite effects. Taken together, these results are supportive of an active crosstalk between the oncogenic Erk1/2 and STAT3 pathways in OSCC, the significance of which requires further investigation.

EPO gene expression induces the proliferation, migrationand invasion of bladder cancer cells through the p21WAF1‑mediated ERK1/2/NF-κB/MMP-9 pathway.

Erythropoietin(EPO) is a cytokine that modulates the production of red blood cells. Previous studies have contradicted the assumed role of EPO in tumor cell proliferation. In the present study, we investigated the effect of EPO in the proliferation, migration and invasion that is involved in the signaling pathways and cell-cycle regulation of bladder cancer 5637 cells. The results showed that an overexpression of the EPO gene has a potent stimulatory effect on DNA synthesis, migration and invasion. EPO gene expression increased the expression of matrix metalloproteinase(MMP)-9 via the binding activity of NF-κB, AP-1 and Sp-1 in 5637 cells. The transfection of 5637 cells with the EPO gene induced the phosphorylation of ERK1/2. Treatment with ERK1/2 inhibitor U0126 significantly inhibited the increased proliferation, migration and invasion of EPO gene-transfected cells. U0126 treatment suppressed the induction of MMP-9 expression through NF-κB binding activity in EPO gene transfectants. In addition, EPO gene expression was correlated with the upregulation of cyclins/CDKs and the upregulation of the CDK inhibitor p21WAF1 expression. Finally, the inhibition of p21WAF1 function by siRNA blocked the proliferation, migration, invasion and phosphorylation of ERK1/2 signaling, as well as MMP-9 expression and activation of NF-κB in EPO gene-transfected cells. These novel findings suggest that the molecular mechanisms of EPO contribute to the progression and development of bladder tumors.

15-Deoxy-Δ12,14-prostaglandin J2 induces expression of 15-hydroxyprostaglandin dehydrogenase through Elk-1 activation in human breast cancer MDA-MB-231 cells

Overproduction of prostaglandin E2 (PGE2) has been reported to be implicated in carcinogenesis. The intracellular level of PGE2 is maintained not only by its biosynthesis, but also by inactivation/degradation. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyzes the conversion of oncogenic PGE2 to a biologically inactive keto metabolite. In the present study, we demonstrate that 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), one of the terminal products of cyclooxygenase-2, updregulates the expression and the activity of 15-PGDH in human breast cancer MDA-MB-231 cells. By using deletion constructs of the 15-PGDH promoter, we have found that E-twenty six (Ets) is the most essential determinant for 15-PGDH induction. 15d-PGJ2 induced phosphorylation of Elk-1, one of Ets transcription factor family members, in the nucleus. Knockdown of Elk-1 abolished the ability of 15d-PGJ2 to upregulate 15-PGDH expression. Furthermore, 15d-PGJ2-mediated activation of Elk-1 was found to be dependent on activation of extracellular-signal related kinase (ERK) 1/2. Treatment of U0126, a pharmacological inhibitor of MEK1/2-ERK, abolished phosphorylation and DNA binding of Elk-1 as well as 15-PGDH induction in 15d-PGJ2-treated MDA-MB-231 cells. Moreover, 15d-PGJ2 generated reactive oxygen species (ROS), which contribute to the expression of 15-PGDH as well as phosphorylation of ERK1/2 and Elk-1. 15d-PGJ2 inhibited the migration of MDA-MB-231 cells, which was attenuated by transient transfection with 15-PGDH siRNA. Taken together, these findings suggest that 15d-PGJ2 induces the expression of 15-PGDH through ROS-mediated activation of ERK1/2 and subsequently Elk-1 in the MDA-MB-231 cells, which may contribute to tumor suppressive activity of this cyclopentenone prostaglandin.

Inhibition of hTERT and telomerase activity via hampering MAPK kinase signaling in renal cell carcinoma cell lines.

e13501 Background: Telomerase adds species specific telomeric repeats onto the ends of chromosomes. Inhibition of telomerase and Human telomerase reverse transcriptase (hTERT) is an exciting therapeutic target since it is required for the long term proliferation of most cancer. In this study we use hTERT inhibition as a anticancer approach in renal cell carcinoma. Methods: 82 cases of RCC were included in the present study. Relative telomerase activity was measured by Telo TAGGG Telomerase PCR ELISA PLUSsupplied by Roche applied science as per the manufacturer’s instruction. Gene expression of hTERT was estimated by real time PCR. RCC cell lines ACHN and A498 were used in the study. Activator and inhibitor of MAPK pathway EGF and U0126 was used at 80ng/ml and 20µM concentration respectively. To confirm the activation and inhibition of MAPK pathway phosphorylation of ERK was checked by RayBio cell based ERK1/2 (Thr202/Tyr204) ELISA kit as per manfacturer’s instructions. Effect of hTERT inhibition on cancer properties of RCC cell lines ACHN & A498 was tested by MTT assay, Propidium iodide staining and cytofluorimetric analysis. Results: The expression of hTERT and telomerase activity were significantly higher in the tumor tissue in comparison with normal renal parenchyma (p=0.000). Cell proliferation was inhibited significantly after treatment with U0126 in ACHN and A498 cells as compare to untreated cells (p=0.001). Cell cycle analysis by Propidium iodide staining showed that the growth of the U0126 cells was arrested in SubG0/G1 phase (p=0.001).Whereas Cytofluorimetric analysis of the AnnexinV-FITC versus PI staining revealed that U0126 treatment induced apoptosis in ACHN and A498 cells (p=0.001). Conclusions: Our result suggests the expression of hTERT was significantly higher in tumor tissue as compare to normal renal tissue. Inhibition of hTERT, drove RCC cancer cells into crisis and death. Thus inhibition of hTERT via inhibition of MAPK pathway may offer new opportunities for realizing the promise of telomerase inhibition therapy.

P26 Hydrogen sulfide elongates primary cilia in the kidney tubular epithelial cells

Primary cilium is associated with numbers of kidney diseases including polycystic kidney diseases and acute kidney injury. Recently, we reported that the length of primary cilium largely depends on oxidative stress and intracellular signaling molecules such as ERK in the kidney tubular epithelial cells. Hydrogen sulfide (H 2 S), a novel biological gas, plays a signaling molecule in kidney cells. Here, we investigated the role of H 2 S in primary ciliogenesis and its underlying mechanisms in the Madin Darby Canine Kidney (MDCK) cell. Primary cilia were gradually lengthened overtime after cells were confluent. Expressions of H 2 S-producing enzymes, cystathionine beta synthase (CBS) and cystathionine gamma lyase (CSE), increased overtime with increases of H 2 S levels in the cells and medium. Treatment of NaHS, a donor of H 2 S, lengthened primary cilia, whereas propargylglycine (PAG, an inhibitor of CSE) and hydroxylamine (HA, an inhibitor of CBS) shortened the primary cilia. NaHS increased levels of activated ERK. Treatment of U0126, an inhibitor of ERK signal, shortened primary cilia. U0126 prevented elongation of primary cilia induced by NaHS. In addition NaHS treatment increased expressions of ADP-ribosylation factor-like 13B (Arl13b) and Sec10 which regulate cilia formation and elongation. In conclusion, H 2 S elongates the length of primary cilia through ERK activation and increase of Sec10 and Arl13b expression, and these results providing H 2 S as a novel target for the regulation of primary cilia length in kidney tubule cells.

17β-Estradiol Regulates SKP2 Expression in Cultured Immature Boar Sertoli Cells Mainly via Estrogen Receptor β, cAMP-PKA and ERK1/2

Estrogen plays an important role in regulating testicular Sertoli cell number. Furthermore, S-phase kinase-associated protein 2 (SKP2) plays a central role in mammalian cell cycle progression. The objective of this study was to determine whether 17β-estradiol can regulate the expression of SKP2, and the Sertoli cell cycle, via estrogen receptor β (ERβ), the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) and extracellular signal-regulated kinase (ERK1/2) pathway. When cultured immature boar Sertoli cells were treated with 17β-estradiol, a time-dependent increase in SKP2 mRNA and protein level was observed by real-time PCR and Western blot, and 17β-estradiol activity peaked at 30 min. Treatment with ICI182780 and ERβ antagonist reduced 17β-estradiol-induced expression of SKP2 and proliferating cell nuclear antigen (PCNA), while increasing the protein concentration of p27kip1. However, the effect of ERα antagonist on these parameters was lower than that of ICI182780 and ERβ. Forskolin had a similar effect as 17β-estradiol on the expression of SKP2, PCNA and p27kip1. Rp-cAMP, H-89 and U0126 treatment reduced 17β-estradiol-induced changes, while H-89 also inhibited ERK1/2 activation. Therefore, 17β-estradiol mainly regulates SKP2 mRNA and protein expression via ERβ-cAMP-PKA and ERK1/2 activation. SKP2 and PCNA expression were positively correlated, while increased SKP2 expression likely resulted in p27kip1 degradation.

Neuroprotective Effects of 3,6′-Disinapoyl Sucrose Through Increased BDNF Levels and CREB Phosphorylation via the CaMKII and ERK1/2 Pathway

3,6'-Disinapoyl sucrose (DISS) is an oligosaccharide ester natural product originating from the root of wild Polygala tenuifolia. Our previous reports suggested that DISS can have neuroprotective effects and antidepressive activity in rats, at least in part, by increased expression of cyclic AMP response element (CRE)-binding protein (CREB) and its downstream target protein, brain-derived neurotrophic factor (BDNF). The aim of the present study was to explore the mechanism of DISS-modulated BDNF and CREB expression. In this study, we confirmed its neuroprotective effect by showing that DISS, at concentrations above 30 μM, could promote the neuron cell viability and protected the glutamate and H2O2-induced toxicity in the human neuroblastoma (SH-SY5Y) cell line. DISS treatment also increased acute (from 15 to 30 min) BDNF expression and CREB phosphorylation in a dose-dependent manner. Pharmacological inhibition of mitogen-activated protein kinase 1 (ERK1/2), CaMKII, and Trk (with U0126, KN93, or K252a, respectively) partially attenuated the stimulatory effect of DISS on phospho-CREB and BDNF expression; however, it was not inhibited by pharmacological inhibition of PKA or PI3K (with H89 and LY294002, respectively). The results are consistent with the effects of DISS on CRE-directed gene transcription, as U0126 and KN-93 treatment also blocked the DISS-induced expression of the CRE-luciferase reporter gene. The results from the present study suggest that DISS-mediated regulation of BDNF gene expression is associated with CREB-mediated transcription of BDNF and upstream activation of ERK1/2 and CaMKII. Finally, DISS may exert neuroprotective and antidepressant effects through these signaling pathways in neuronal cells.

Glioma Cell Proliferation Controlled by ERK Activity-Dependent Surface Expression of PDGFRA

Increased PDGFRA signaling is an essential pathogenic factor in many subtypes of gliomas. In this context the cell surface expression of PDGFRA is an important determinant of ligand sensing in the glioma microenvironment. However, the regulation of spatial distribution of PDGFRA in glioma cells remains poorly characterized. Here, we report that cell surface PDGFRA expression in gliomas is negatively regulated by an ERK-dependent mechanism, resulting in reduced proliferation of glioma cells. Glioma tumor tissues and their corresponding cell lines were isolated from 14 patients and analyzed by single-cell imaging and flow cytometry. In both cell lines and their corresponding tumor samples, glioma cell proliferation correlated with the extent of surface expression of PDGFRA. High levels of surface PDGFRA also correlated to high tubulin expression in glioma tumor tissue in vivo. In glioma cell lines, surface PDGFRA declined following treatment with inhibitors of tubulin, actin and dynamin. Screening of a panel of small molecule compounds identified the MEK inhibitor U0126 as a potent inhibitor of surface PDGFRA expression. Importantly, U0126 inhibited surface expression in a reversible, dose- and time-dependent manner, without affecting general PDGFRA expression. Treatment with U0126 resulted in reduced co-localization between PDGFRA and intracellular trafficking molecules e.g. clathrin, RAB11 and early endosomal antigen-1, in parallel with enhanced co-localization between PDGFRA and the Golgi cisternae maker, Giantin, suggesting a deviation of PDGFRA from the endosomal trafficking and recycling compartment, to the Golgi network. Furthermore, U0126 treatment in glioma cells induced an initial inhibition of ERK1/2 phosphorylation, followed by up-regulated ERK1/2 phosphorylation concomitant with diminished surface expression of PDGFRA. Finally, down-regulation of surface PDGFRA expression by U0126 is concordant with reduced glioma cell proliferation. These findings suggest that manipulation of spatial expression of PDGFRA can potentially be used to combat gliomas.

ERK1/2-Egr-1 Signaling Pathway-Mediated Protective Effects of Electroacupuncture in a Mouse Model of Myocardial Ischemia-Reperfusion.

Early growth response- (Egr-) 1 is an upstream master switch in controlling inflammatory responses following myocardial ischemia-reperfusion (I/R). Activation of extracellular signal-regulated protein kinase-1 and kinase-2 (ERK1/2) signaling is known to upregulate Egr-1. ERK1/2 pathway has been previously shown to mediate the therapeutic action of electroacupucture (EA). Thus, we hypothesized that EA would reduce myocardial I/R injury and inflammatory responses through inhibiting Egr-1 expression via the ERK1/2 pathway. Mice were pretreated with EA, U0126, or combination of EA and U0126 and then underwent 1 h myocardial ischemia and 3 h reperfusion. We investigated that EA significantly attenuated the I/R-induced upregulation of both Egr-1 and phosporylated-ERK1/2 (p-ERK1/2), decreased myocardial inflammatory cytokines including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and reduced the infarct size and the release of cardiac troponin I (cTnI). U0126 treatment also exhibited the same effect as EA on Egr-1 level and subsequent cardioprotective effects. There was no additive effect of cotreatment with EA and U0126 on the expression of Egr-1 and its downstream target genes (TNF-α, IL-1β) or serum cTnI level. Collectively, these observations suggested that EA attenuates myocardial I/R injury, possibly through inhibiting the ERK1/2-Egr-1 signaling pathway and reducing the release of proinflammatory cytokines.

PO-0944: FTS (Fused Toes Homolog) is required for radiation-induced nuclear translocation and phosphorylation of EGFR

Results: The specific MEK/ERK inhibitor, U0126, reduced the clonogenic potential of the three cell lines, and was affected by radiation. U0126 inhibited phospho-active ERK1/2 and reduced DNA protein kinase catalytic subunit (DNA-PKcs) suggesting that ERKs and DNA-PKcs cooperate in radioprotection of rhabdomyosarcoma cells. The TE671 cell line xenotransplanted in mice showed a reduction in tumor mass and increase in the time of tumor progression with U0126 treatment associated with reduced DNA-PKcs, an effect enhanced by radiotherapy.

Plasmalogens Rescue Neuronal Cell Death through an Activation of AKT and ERK Survival Signaling

Neuronal cells are susceptible to many stresses, which will cause the apoptosis and neurodegenerative diseases. The precise molecular mechanism behind the neuronal protection against these apoptotic stimuli is necessary for drug discovery. In the present study, we have found that plasmalogens (Pls), which are glycerophospholipids containing vinyl ether linkage at sn-1 position, can protect the neuronal cell death upon serum deprivation. Interestingly, caspse-9, but not caspase-8 and caspase-12, was cleaved upon the serum starvation in Neuro-2A cells. Pls treatments effectively reduced the activation of caspase-9. Furthermore, cellular signaling experiments showed that Pls enhanced phosphorylation of the phosphoinositide 3-kinase (PI3K)-dependent serine/threonine-specific protein kinase AKT and extracellular-signal-regulated kinases ERK1/2. PI3K/AKT inhibitor LY294002 and MAPK/ERK kinase (MEK) inhibitor U0126 treatments study clearly indicated that Pls-mediated cell survival was dependent on the activation of these kinases. In addition, Pls also inhibited primary mouse hippocampal neuronal cell death induced by nutrient deprivation, which was associated with the inhibition of caspase-9 and caspase-3 cleavages. It was reported that Pls content decreased in the brain of the Alzheimer’s patients, which indicated that the reduction of Pls content could endanger neurons. The present findings, taken together, suggest that Pls have an anti-apoptotic action in the brain. Further studies on precise mechanisms of Pls-mediated protection against cell death may lead us to establish a novel therapeutic approach to cure neurodegenerative disorders.

Phosphorylation Influences The Binding Of Bim To Anti-Apoptotic Proteins In Multiple Myeloma

Multiple myeloma cells are strongly dependent on the anti-apoptotic protein Mcl-1 for survival. However, several studies have shown that some myeloma cells are sensitive to treatment with ABT-737 and related compounds, which target Bcl-2 and Bcl-xL, but not Mcl-1. These studies suggest that sensitive cells have more of the direct-activating, pro-apoptotic protein Bim bound to Bcl-2 and Bcl-xL than to Mcl-1. We have previously shown that the expression levels of pro- and anti-apoptotic proteins have little influence on which anti-apoptotic protein binds Bim, leading us to further explore what factors influence the preferential binding of Bim. We have found that IL-6 stimulation of myeloma cells results in both the phosphorylation of Bim at serine 69, and a shift in Bim from Bcl-2 and Bcl-xL to Mcl-1. These observations suggest a role for phosphorylation in determining the anti-apoptotic protein that Bim binds to. To determine if constitutive phosphorylation of Bim regulates the steady state binding of Bim to anti-apoptotic Bcl-2 family members, we utilized phospho-affinity gel electrophoresis (Phos-Tag). We determined that Bim is constitutively phosphorylated in unstimulated myeloma cells. However, unlike what is observed following IL-6 stimulation, phosphorylation does not occur at serine 69. Through use of co-immunopreciptation studies, we found that phosphorylation status of Bim affects its binding to anti-apoptotic proteins. The phosphorylated species are preferentially bound to Bcl-2 and Bcl-xL, and not to Mcl-1. Additionally, we observed that phosphorylated Bim species bound to Bcl-2 and Bcl-xL were present at a significantly lower level in myeloma cells that were more dependent on Mcl-1, such as OPM2, than in KMS18 cells, which exhibited greater Bcl-2/Bcl-xL dependency. This pattern also held true for myeloma cells that had been selected for resistance to ABT-737. ABT-737 resistant KMS18 cells had no detectable phosphorylated species of Bim, and all of the Bim was bound to Mcl-1. We have begun to identify the phosphorylated amino acids in Bim through the use of phospho-Bim-specific antibodies. In addition to serine 69, we have determined that the constitutive phosphorylation does not occur at serine 59 or serine 87. However, preliminary data suggests that Bim phosphorylated at threonine 116 preferentially binds to Bcl-xL in KMS18 cells. We have also taken initial steps to identify signaling pathways and kinases that are phosphorylating Bim, and altering its affinity. We treated KMS18 myeloma cells for 12 hours with 10 μM of the MEK inhibitor U0126, the JNK inhibitor SP600125, or the p38 inhibitor SB203580, and ran lysates from each of these conditions on PhosTag gels. While U0126 and SB203580 treatment did not result in the loss of any phosphorylated Bim species, treatment with SP600125 resulted in a loss of phosphorylated Bim species comparable to treatment of myeloma cell lysates with lambda protein phosphatase. These results suggest that JNK mediates phosphorylation of Bim in myeloma cells. Interestingly, threonine 116 is contained within a JNK consensus sequence. Therefore, JNK could directly influence the preferential binding of Bim. Together, these results suggest that combining Bim kinase inhibitors with agents that result in decreased Mcl-1 (e.g. CDK9 inhibitors) or inducers of the Mcl-1 inhibitor Noxa (proteasome inhibitors) represents a novel approach in cancer cells that demonstrate Mcl-1 dependence. Disclosures: Boise: Onyx Pharmaceuticals: Consultancy.