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Transient Activation (transient + activation)
Selected AbstractsDifferential Changes in MAP Kinases, Histone Modifications, and Liver Injury in Rats Acutely Treated With EthanolALCOHOLISM, Issue 9 2010Annayya R. Aroor Background:, Acute ethanol is known to affect cells and organs but the underlying molecular mechanisms are poorly explored. Recent developments highlight the potential importance of mitogen-activated protein kinases, MAPKs (i.e., ERK1/2, p38, and JNK1/2) signaling, and histone modifications (i.e., acetylation, methylation, and phosphorylation) in the actions of ethanol in hepatocytes. We have therefore investigated significance of these molecular steps in vivo using a model in which rats were acutely administered ethanol intraperitoneally (IP). Methods:, Ethanol was administered IP (3.5 gm/kg body weight) to 12-week-old male Sprague,Dawley rats. Liver was subsequently removed at 1 and 4 hours. Serum was used for alcohol and ALT assays. At the time of the removal of liver, small portions of each liver were formalin-fixed and stained with hematoxylin and eosin (H&E) and used for light microscopy. Western blot analysis was carried out with specific primary antibodies for various parameters. Results:, There were clear differences at 1 and 4 hours in blood ethanol, ALT, steatosis, and cleaved caspase 3. Apoptosis at 1 hour was followed by necrosis at 4 hours. Acute alcohol elicited a marked increase in the phosphorylation of ERK1/2 and moderate increases in the phosphorylation of p38 MAPK and JNK. Temporally different phosphorylation of histone H3 at ser-10 and ser-28 occurred and acetylation of histone H3 at lys 9 increased progressively. Conclusions:, There were distinct differences in the behavior of the activation of the 3 MAP kinases and histone modifications after acute short exposure of liver to ethanol in vivo. Although all 3 MAPKs were rapidly activated at 1 hour, the necrosis, occurring at 4 hours, correlated to sustained activation of ERK1/2. Transient activation of p38 is associated with rapid phosphorylation of histone H3, whereas prolonged activation of ERK1/2 is correlated to persistent histone H3 acetylation. [source] Activation of M2 muscarinic receptors leads to sustained suppression of hippocampal transmission in the medial prefrontal cortexTHE JOURNAL OF PHYSIOLOGY, Issue 21 2009Lang Wang Cholinergic innervation of the prefrontal cortex is critically involved in arousal, learning and memory. Dysfunction of muscarinic acetylcholine receptors and their downstream signalling pathways has been identified in mental retardation. To assess the role played by the muscarinic receptors at the hippocampal,frontal cortex synapses, an important relay in information storage, we used a newly developed frontal slice preparation in which hippocampal afferent fibres are preserved. Transient activation of muscarinic receptors by carbachol results in a long-lasting depression of synaptic efficacy at the hippocampal but not cortical pathways or local circuitry. On the basis of a combination of electrophysiological, pharmacological and anatomical results, this input-specific muscarinic modulation can be partially attributed to the M2 subtype of muscarinic receptors, possibly through a combination of pre- and postsynaptic mechanisms. [source] Analysis of the role of GADD153 in the control of apoptosis in NS0 myeloma cellsBIOTECHNOLOGY & BIOENGINEERING, Issue 7 2002Idsada Lengwehasatit Abstract Apoptosis can limit the maximum production of recombinant protein expression from cultured mammalian cells. This article focuses on the links between nutrient deprivation, ER perturbation, the regulation of (growth arrest and DNA damage inducible gene 153) GADD153 expression and apoptosis. During batch culture, decreases in glucose and glutamine correlated with an increase in apoptotic cells. This event was paralleled by a simultaneous increase in GADD153 expression. The expression of GADD153 in batch culture was suppressed by the addition of nutrients and with fed-batch culture the onset of apoptosis was delayed but not completely prevented. In defined stress conditions, glucose deprivation had the greatest effect on cell death when compared to glutamine deprivation or the addition of tunicamycin (an inhibitor of glycosylation), added to generate endoplasmic reticulum stress. However, the contribution of apoptosis to overall cell death (as judged by morphology) was smaller in conditions of glucose deprivation than in glutamine deprivation or tunicamycin treatment. Transient activation of GADD153 expression was found to occur in response to all stresses and occurred prior to detection of the onset of cell death. These results imply that GADD153 expression is either a trigger for apoptosis or offers a valid indicator of the likelihood of cell death arising from stresses of relevance to the bioreactor environment. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 719,730, 2002. [source] Overproduction of BCR-ABL induces apoptosis in imatinib mesylate-resistant cell linesCANCER, Issue 1 2005Vanessa Desplat Ph.D. Abstract BACKGROUND Imatinib mesylate, a BCR-ABL tyrosine kinase inhibitor, induces apoptosis in chronic myeloid leukemia cells. Resistance to imatinib is currently the most important concern of this treatment. One of the main mechanisms of this resistance is overexpression of BCR-ABL. METHODS In the current study, the authors investigated the correlation between BCR-ABL overexpression and apoptosis in BaF/BCR - ABL and LAMA84 cell lines resistant to imatinib suddenly deprived of the inhibitor, and compared with their sensitive counterpart. RESULTS Removal of imatinib from culture medium led to a decrease in Bcr-Abl protein expression by Day 5, which was sustained for , 3 weeks of imatinib deprivation. Apoptosis was observed after 3 days of imatinib deprivation in resistant lines accompanied by caspase activation, loss of membrane asymmetry (annexin V staining), and alteration of mitochondrial potential (dihexyloxacarbocyanine iodide [DiOC6]). Transient activation of the STAT5/Bcl-xL pathway and Akt kinase activity preceded these responses. CONCLUSIONS Thus, imatinib removal led to apoptosis of BCR-ABL,overexpressing leukemic cells, a phenomenon that could be exploited to sensitize imatinib-resistant cells to the cytotoxic effect of other drugs. Cancer 2005. © 2004 American Cancer Society. [source] Sustained activation of M-Ras induced by nerve growth factor is essential for neuronal differentiation of PC12 cellsGENES TO CELLS, Issue 9 2006Peng Sun Neuronal differentiation in PC12 cells induced by nerve growth factor (NGF) requires sustained activation of ERK/MAP kinase pathway (Raf,MEK,ERK cascade). Although classical Ras (H-Ras, K-Ras, and N-Ras) activated by NGF signaling induces activation of ERK pathway, the activation is transient and not sufficient for PC12 cell differentiation. Instead, it has been widely accepted that NGF signaling-mediated Rap1 activation causes sustained activation of ERK pathway. There has been no direct evidence, however, that Rap1 participates in neuronal differentiation. Here we show that NGF signaling induces sustained activation of M-Ras and subsequent sustained activation of ERK pathway and the transcription factor CREB leading to PC12 cell differentiation. Exogenously expressed constitutively active mutant of M-Ras caused neurite outgrowth in PC12 cells and activating phosphorylation of ERK, whereas activated Rap1 did not. Knockdown of endogenous M-Ras by small interfering RNAs as well as the expression of a dominant,negative mutant of M-Ras interfered with NGF-induced neuritogenesis. Since MEK inhibitors prevented M-Ras-induced neurite outgrowth, ERK pathway participates in this differentiation pathway. Furthermore, M-Ras brought about ERK pathway-mediated activating phosphorylation of CREB and the CREB-mediated transcription. In addition, a dominant,negative mutant of CREB inhibited M-Ras-induced neuritogenesis. Taken together, NGF-induced PC12 cell differentiation requires M-Ras,ERK pathway-mediated activation of CREB. M-Ras was predominantly expressed in the hippocampus and cerebellum of mouse brain and in the gray matter of the spinal cord. All these properties of M-Ras were apparently indistinguishable from those of H-Ras. However, NGF stimulation caused transient activation of classical Ras proteins but sustained activation of M-Ras as well as sustained activating phosphorylation of ERK and CREB. Therefore, M-Ras is essential for neuronal differentiation in PC12 cells by inducing sustained activation of ERK pathway. [source] Lysophosphatidic acid induces ovarian cancer cell dispersal by activating Fyn kinase associated with p120-cateninINTERNATIONAL JOURNAL OF CANCER, Issue 4 2008Ruby Yun-Ju Huang Abstract Lysophosphatidic acid (LPA), known as the "ovarian cancer activating factor," is a natural phospholipid involved in important biological functions, such as cell proliferation, wound healing and neurite retraction. LPA causes colony dispersal in various carcinoma cell lines by inducing morphological changes, including membrane ruffling, lamellipodia formation, cell,cell dissociation and single cell migration. However, its effects on cell,cell dissociation and cell,cell adhesion of ovarian cancer cells have not been studied. In our study, we showed that LPA induced sequential events of intercellular junction dispersal and "half-junction" formation in ovarian cancer SKOV3 cells and that Src-family kinases were involved in both processes, since the effects were abolished by the selective tyrosine kinase inhibitor PP2. LPA induced rapid and transient activation of Src family kinases, which were recruited to cell,cell junctions by increasing the association with the adherens junction protein p120-catenin. We identified the Src family kinase, Fyn, as the key component associated with p120-catenin after LPA stimulation in SKOV3 cells. Our study provides evidence that LPA induces junction dispersal in ovarian cancer SKOV3 cells by activating the Src family kinase Fyn and increasing its association with p120-catenin at the cell,cell junction. © 2008 Wiley-Liss, Inc. [source] Minocycline attenuates microglial activation but fails to mitigate striatal dopaminergic neurotoxicity: role of tumor necrosis factor-,JOURNAL OF NEUROCHEMISTRY, Issue 3 2006Krishnan Sriram Abstract Activated microglia are implicated in the pathogenesis of disease-, trauma- and toxicant-induced damage to the CNS, and strategies to modulate microglial activation are gaining impetus. A novel action of the tetracycline derivative minocycline is the ability to inhibit inflammation and free radical formation, factors that influence microglial activation. Minocycline is therefore being tested as a neuroprotective agent to alleviate CNS damage, although findings so far have yielded mixed results. Here, we showed that administration of a single low dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (METH), a paradigm that causes selective degeneration of striatal dopaminergic nerve terminals without affecting the cell body in substantia nigra, increased the expression of mRNAs encoding microglia-associated factors F4/80, interleukin (IL)-1,, IL-6, monocyte chemoattractant protein-1 (MCP-1, CCL2) and tumor necrosis factor (TNF)-,. Minocycline treatment attenuated MPTP- or METH-mediated microglial activation, but failed to afford neuroprotection. Lack of neuroprotection was shown to be due to the inability of minocycline to abolish the induction of TNF-, and its receptors, thereby failing to modulate TNF signaling. Thus, TNF-, appeared to be an obligatory component of dopaminergic neurotoxicity. To address this possibility, we examined the effects of MPTP or METH in mice lacking genes encoding IL-6, CCL2 or TNF receptor (TNFR)1/2. Deficiency of either IL-6 or CCL2 did not alter MPTP neurotoxicity. However, deficiency of both TNFRs protected against the dopaminergic neurotoxicity of MPTP. Taken together, our findings suggest that attenuation of microglial activation is insufficient to modulate neurotoxicity as transient activation of microglia may suffice to initiate neurodegeneration. These findings support the hypothesis that TNF-, may play a role in the selective vulnerability of the nigrostriatal pathway associated with dopaminergic neurotoxicity and perhaps Parkinson's disease. [source] pH is an intracellular effector controlling differentiation of oligodendrocyte precursors in culture via activation of the ERK1/2 pathwayJOURNAL OF NEUROSCIENCE RESEARCH, Issue 7 2006Frédéric Bernard Abstract We reported previously that onset of oligodendrocyte precursor cell (OPC) differentiation is accompanied by an increase in intracellular pH (pHi). We show that OPC differentiation is dependent primarily on a permissive pHi value. The highest differentiation levels were observed for pHi values around 7.15 and inhibition of differentiation was observed at slightly more acidic or alkaline values. Clamping the pHi of OPCs at 7.15 caused a transient activation of ERK1/2 that was not observed at more acidic or alkaline values. Furthermore, inhibition of ERK activation with the UO126 compound totally prevented OPC differentiation in response to pHi shift. These results indicate that pHi, acting through the ERK1/2 pathway, is a key determinant for oligodendrocyte differentiation. We also show that this pHi pathway is involved in the process of retinoic acid-induced OPC differentiation. © 2006 Wiley-Liss, Inc. [source] Activation of adenosine triphosphate-sensitive potassium channels confers protection against rotenone-induced cell death: Therapeutic implications for Parkinson's diseaseJOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2002Kwok-Keung Tai Abstract It is anticipated that further understanding of the protective mechanism induced by ischemic preconditioning will improve prognosis for patients of ischemic injury. It is not known whether preconditioning exerts beneficial actions in neurodegenerative diseases, in which ischemic injury plays a causative role. Here we show that transient activation of ATP-sensitive potassium channels, a trigger in ischemic preconditioning signaling, confers protection in PC12 cells and SH-SY5Y cells against neurotoxic effect of rotenone and MPTP, mitochondrial complex I inhibitors that have been implicated in the pathogenesis of Parkinson's disease. The degree of protection is in proportion to the bouts of exposure to an ATP-sensitive potassium channel opener, a feature reminiscent of ischemic tolerance in vivo. Protection is sensitive to a protein synthesis inhibitor, indicating the involvement of de novo protein synthesis in the protective processes. Pretreatment of PC12 cells with preconditioning stimuli FeSO4 or xanthine/xanthine oxidase also confers protection against rotenone-induced cell death. Our results demonstrate for the first time the protective role of ATP-sensitive potassium channels in a dopaminergic neuronal cell line against rotenone-induced neurotoxicity and conceptually support the view that ischemic preconditioning-derived therapeutic strategies may have potential and feasibility in therapy for Parkinson's disease. © 2002 Wiley-Liss, Inc. [source] Early signalling events in the Avr9/Cf-9-dependent plant defence responseMOLECULAR PLANT PATHOLOGY, Issue 1 2000Tina Romeis Resistance of tomato to the leaf mould fungus Cladosporium fulvum is controlled by the interaction between a plant-encoded resistance gene (Cf-9) and pathogen-encoded avirulence (Avr9) gene. Our objective is to understand the underlying molecular mechanisms that transmit the Cf-9/Avr9-dependent pathogen perception event and activate the plant defence response. Our approach toward the understanding of Cf -function is based on the analysis of early Cf-9/Avr9-mediated responses and signalling events. Because Cf-9 transgenically expressed in tobacco retains its specificity and activity to the Avr9 elicitor, signalling experiments were conducted in the heterologous system using these transgenic lines or derived Cf9 tobacco cell cultures. Among the earliest responses to the Avr9/Cf-9 elicitation event were rapid changes in ion-fluxes, the synthesis of active oxygen species (AOS), probably catalysed by a plant NADPH-oxidase, and the transient activation of two MAP kinases. These kinases were identified as WIPK (wounding-induced protein kinase) and SIPK (salicylic-acid induced kinase) from tobacco. Studies with pharmacological inhibitors suggested that the MAP kinases are located in an independent signalling pathway from the Avr9/Cf-9-dependent synthesis of AOS. SIPK and WIPK were involved in pathogen-related elicitation processes as well as in abiotic stress responses. This indicates that the plant defence is triggered via a signalling network that shares components with pathways originating from abiotic environmental stress stimuli. [source] | |||||||||||||