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Christiane Lauriere - One of the best experts on this subject based on the ideXlab platform.
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involvement of mpk4 in osmotic Stress response pathways in cell suspensions and plantlets of arabidopsis thaliana activation by hypoosmolarity and negative role in hyperosmolarity tolerance
FEBS Letters, 2004Co-Authors: Mariejo Droillard, Marie Boudsocq, Helene Barbierbrygoo, Christiane LauriereAbstract:Three of the protein kinases activated by Hypoosmotic Stress in Arabidopsis thaliana cell suspensions were previously characterized [FEBS, 2002, 527, 43–50] as mitogen-activated protein (MAP) kinases and two of them corresponded to Arabidopsis mitogen-activated protein kinase 6 (MPK6) (44 kDa) and MPK3 (39 kDa). The third MAP kinase was identified here to MPK4, using a corresponding specific antibody. Like MPK6 and MPK3, MPK4 activity is clearly inhibited by apigenin and MPK4 activation by hypoosmolarity needs upstream phosphorylation events. Activation of the 3 MAP kinases, MPK3, 4 and 6, was confirmed in plantlets submitted to Hypoosmotic Stress. The action of a biotic signal, flagellin, was also demonstrated to induce the activations of the 3 MAP kinases. Using the mutant displaying MPK4 gene inactivation, the independence of the MPK3 and MPK6 activations towards the presence of MPK4 was demonstrated, both in Hypoosmotic and flagellin signalling pathways. Although MPK4 was not activated by hyperosmolarity in cell suspensions nor in seedlings, a possible negative regulation of hyperosmolarity resistance by MPK4 is suggested, based both on phenotype and downstream gene expression studies.
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map kinase activation by Hypoosmotic Stress of tobacco cell suspensions towards the oxidative burst response
Plant Journal, 1999Co-Authors: Anneclaire Cazale, Mariejo Droillard, Helene Barbierbrygoo, Cathal Wilson, Erwin Heberlebors, Christiane LauriereAbstract:Summary Hypoosmotic Stress activates a phosphorylation-dependent oxidative burst. In-gel kinase assays were performed to characterize the protein kinases that could be implicated in osmoregulation and in the activation of the oxidative burst. Hypoosmotic Stress activated several kinases among which 50 and 46 kDa proteins displayed mitogen-activated protein kinase (MAP kinase) properties. They phosphorylated myelin basic protein in the absence of calcium, were recognized by antibodies directed against human MAP kinases, and were phosphorylated on tyrosine. Immunoprecipitation with an antibody directed against the tobacco MAP kinase Ntf4 showed that at least one of the activated kinases would be Ntf4-like. Apigenin, a MAP kinase and cyclin-dependent kinase inhibitor which prevents the Hypoosmotically induced oxidative burst ( Cazaleet al. 1998 ; Plant Physiol. 116, 659–669), inhibited these kinases in vitro suggesting that they may play a role in the activation of the oxidative burst. Like the oxidative response, activation of the kinases depended on extracellular calcium influx and protein kinases sensitive to staurosporine and 6-DMAP. However, kinase activation did not depend on effluxes through anion channels or on the oxidative burst. Two-dimensional in-gel kinase assays revealed the presence of three protein kinases with an apparent molecular mass of 50 kDa and one of 46 kDa, all four being activated by Hypoosmotic Stress. The same kinases were also activated by oligogalacturonides and salicylic acid, underlying the importance of these MAP kinases as common components of different signaling pathways triggered by different extracellular stimuli.
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oxidative burst and Hypoosmotic Stress in tobacco cell suspensions
Plant Physiology, 1998Co-Authors: Anneclaire Cazale, Helene Barbierbrygoo, Marieaude Rouetmayer, Yves Mathieu, Christiane LauriereAbstract:Oxidative burst constitutes an early response in plant defense reactions toward pathogens, but active oxygen production may also be induced by other stimuli. The oxidative response of suspension-cultured tobacco (Nicotiana tabacum cv Xanthi) cells to Hypoosmotic and mechanical Stresses was characterized. The oxidase involved in the Hypoosmotic Stress response showed similarities by its NADPH dependence and its inhibition by iodonium diphenyl with the neutrophil NADPH oxidase. Activation of the oxidative response by Hypoosmotic Stress needed protein phosphorylation and anion effluxes, as well as opening of Ca2+ channels. Inhibition of the oxidative response impaired Cl− efflux, K+ efflux, and extracellular alkalinization, suggesting that the oxidative burst may play a role in ionic flux regulation. Active oxygen species also induced the cross-linking of a cell wall protein, homologous to a soybean (Glycine max L.) extensin, that may act as part of cell volume and turgor regulation through modification of the physical properties of the cell wall.
Ravi S Chari - One of the best experts on this subject based on the ideXlab platform.
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activator protein 1 activation following Hypoosmotic Stress in hepg2 cells is actin cytoskeleton dependent
Journal of Surgical Research, 2001Co-Authors: Robin D Kim, Chad E Darling, Timothy P Roth, Rocco Ricciardi, Ravi S ChariAbstract:Background. Following Hypoosmotic Stress-induced cell volume change, the actin cytoskeleton reorganizes itself. The role of this reorganization in the activation of the phosphatidylinositol 3-OH-kinase/protein kinase B/activator protein 1 (PI-3-K/PKB/AP-1) proliferative signaling cascade is unknown. Focal adhesion kinase (FAK) participates in the cytoskeleton-based activation of PI-3-K. We hypothesized that Hypoosmotic Stress-induced activation of PKB and AP-1 in HepG2 cells is dependent on an intact actin cytoskeleton and subsequent FAK phosphorylation. Methods. HepG2 cells were incubated for 1 h with or without 20 μM cytochalasin D, an actin disrupter, and were then exposed for up to 30 min to Hypoosmotic medium (200 mOsm/L) to induce swelling. Tumor necrosis factor α (1.4 nM) and medium alone served as positive and negative controls, respectively. Western blots measured cytoplasmic phosphorylated or total FAK and PKB. EMSAs measured nuclear AP-1. All experiments were performed in triplicate. Results. Exposure to Hypoosmotic Stress resulted in activation of the following signaling messengers in a sequential fashion: (1) phosphorylation of FAK occurred by 2 min, (2) phosphorylation of PKB occurred by 10 min, (3) nuclear translocation of AP-1 occurred by 30 min. All three signaling events were abolished when these cells were pretreated with cytochalasin D. Conclusion. Actin reorganization following Hypoosmotic Stress is essential for the FAK-mediated activation of the PI-3-K/PKB/AP-1 proliferative cascade. These data delineate a possible mechanism by which the cell swelling-induced cytoskeletal changes can initiate proliferative signal transduction in human liver cancer.
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Hypoosmotic Stress stimulates growth in hepg2 cells via protein kinase b dependent activation of activator protein 1
Journal of Gastrointestinal Surgery, 2001Co-Authors: Robin D Kim, Chad E Darling, Timothy P Roth, Rocco Ricciardi, Bradley K Schaffer, Ravi S ChariAbstract:Although Hypoosmotic Stress-induced cell swelling activates phosphatidylinositol-3-kinase, its impact on the downstream signal protein kinase B and cell growth is unknown. Activator protein-1 is in part phosphatidylinositol-3-kinase dependent, and is important in proliferation. We hypothesized that cell swelling modulates proliferation in HepG2 cells via the protein kinase B-dependent activation of activator protein-1. HepG2 cells pretreated with or without LY294002 were exposed for up to 30 minutes to Hypoosmotic medium (160 mOsm/L). Tumor necrosis factor-alpha (1.4 nmol/L) or normoosmolar medium (270 mOsm/L) served as positive and negative controls, respectively. Western immunoblots measured cytoplasmic phosphorylated and total protein kinase B. Electromobility shift assays measured nuclear activator protein-1. Methylene blue assays measured cell proliferation at 24, 48, and 72 hours after stimulation. Hypoosmotic Stress phosphorylated protein kinase B by 10 minutes. Subsequently, Hypoosmotic exposure stimulated activator protein-1 by 30 minutes. Pulse exposure to Hypoosmotic Stress potentiated HepG2 proliferation by 72 hours as compared to both negative controls and LY-inhibited cells (n = 4 per group, P = 0.009 and P = 0.004, respectively; P <0.001 analysis of variance. All three activation events were abolished with LY294002 pretreatment. In HepG2 cells, Hypoosmotic Stress-induced swelling stimulates proliferation via protein kinase B-mediated activation of activator protein-1. These data delineate a possible mechanism linking changes in cell volume to growth in human liver cancer.
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Hypoosmotic Stress activates p38 erk 1 and 2 and sapk jnk in rat hepatocytes
Journal of Surgical Research, 2000Co-Authors: Robin D Kim, Chad E Darling, Herwig Cerwenka, Ravi S ChariAbstract:Abstract Background. Following hepatocyte injury, changes in the perihepatocyte milieu modulate cell volume and influence growth. Hypoosmotic Stress activates nuclear factor-kappa B (NF-κB), a transcription factor believed to prime cell cycle progression in hepatocytes. In this study, we investigate the role of mitogen-activated protein kinases (MAPKs) in the activation of NF-κB. Materials and methods. Quiescent primary hepatocytes were exposed to Hypoosmotic serum-free William's E (WE) medium (200 mOsm/liter), with or without a 1-h pretreatment with either PD 98059 (15 μM) or SB 202190 (3 μM). Parallel experiments were conducted using hepatocyte growth factor (HGF) at 0.1 mg/ml and normoosmotic WE medium as positive and negative controls, respectively ( n = 3). Relative densitometries of Western blots measured phosphorylated cytoplasmic p38, ERK 1 and 2, and SAPK/JNK. Electromobility shift assays examined nuclear NF-κB activation. Results. (i) Hypoosmolar WE medium phosphorylated p38, ERK 1 and 2, and SAPK/JNK by 5 min. (ii) Hypoosmolar WE medium activated NF-κB at 60 min. (iii) HGF phosphorylated all three MAPKs and activated NF-κB with profiles similar to those of Hypoosmotic Stress. (iv) Both PD 98059 and SB 202190 abrogated the activation of NF-κB in HGF-stimulated cells but not in Hypoosmotically Stressed cells. Conclusion. (i) Both Hypoosmotic cell swelling and HGF phosphorylate p38, ERK 1 and 2, and SAPK/JNK, and (ii) HGF, but not Hypoosmotic Stress, activates NF-κB via p38 and ERK 1 and 2 phosphorylation. These data suggest that cell swelling activates NF-κB through a pathway separate from that of growth factors.
Sidney K Pierce - One of the best experts on this subject based on the ideXlab platform.
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the taurine efflux portal used to regulate cell volume in response to Hypoosmotic Stress seems to be similar in many cell types lessons to be learned from molluscan red blood cells
Integrative and Comparative Biology, 2001Co-Authors: Sidney K Pierce, James W WarrenAbstract:SYNOPSIS. The control of cell volume in all cell types is accomplished by the regulation of two general categories of osmolytes: inorganic ions, most commonly K 1 and Cl 2 , and small molecular weight organic compounds, usually certain amino acids and certain quaternary ammonium compounds. The difference in who regulates what does not depend phylogeny, but instead upon the type of osmotic environment that a cell expects (in an evolutionary sense) to encounter. Cells that exist in extracellular osmotic concentrations up to 300‐400 mosmol/kg (mosm) rely primarily on inorganic osmolytes for volume control, while cells that exist at greater osmotic concentrations rely more on organic osmolytes for volume control. Usually, strange or unique volume regulatory mechanisms are found in cells that exist in particularly demanding osmotic conditions. In order to provide further support the foregoing generalizations, the following paper will focus on comparisons between the Hypoosmotically induced mechanism of taurine efflux regulation by red blood cells of the bivalve, Noetia ponderosa, probably the best understood ‘‘invertebrate’’ cell type in this regard, and taurine efflux from a variety of ‘‘vertebrate’’ cells.
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specific protein phosphorylation occurs in molluscan red blood cell ghosts in response to Hypoosmotic Stress
The Journal of Membrane Biology, 1991Co-Authors: Alexander D Politis, Sidney K PierceAbstract:The regulation of cellular volume upon exposure to Hypoosmotic Stress is accomplished by specific plasma membrane permeability changes that allow the efflux of certain intracellular solutes (osmolytes). The mechanism of this membrane permeability regulation is not understood; however, previous data implicate Ca2+ as an important component in the response. The regulation of protein phosphorylation is a pervasive aspect of celllular physiology that is often Ca2+ dependent. Therefore, we tested for osmotically induced protein phosphorylation as a possible mechanism by which Ca2+ may mediate osmotically dependent osmolyte efflux. We have found a rapid increase in32Pi incorporation into two proteins in clam blood cell ghosts after exposure of the intact cells to a Hypoosmotic medium. The osmotic component of the Stress, not the ionic dilution, was the stimulus for the phosphorylations. The osmotically induced phosphorylation of both proteins was significantly inhibited when Ca2+ was omitted from the medium, or by the calmodulin antagonist. chlorpromazine. These results correlate temporally with cell volume recovery and osmolyte (specifically free amino acid) efflux. The two proteins that become phosphorylated in response to Hypoosmotic Stress may be involved in the regulation of plasma membrane permeability to organic solutes, and thus. contribute to Hypoosmotic cell volume regulation.
Lisa Campbell - One of the best experts on this subject based on the ideXlab platform.
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chemical analysis of karenia papilionacea
Toxicon, 2015Co-Authors: Nicholas Fowler, Lisa Campbell, Daniel G. Baden, Carmelo Tomas, Andrea J. BourdelaisAbstract:One of the most widely studied organisms responsible for Harmful Algal Blooms (HABs) is the marine dinoflagellate Karenia brevis. This organism produces neurotoxic compounds known as brevetoxins. A related dinoflagellate, Karenia papilionacea, has been reported to occasionally co-bloom with K. brevis but has received little attention as a possible toxin producing species. Therefore, our aim was to investigate the toxin profile for K. papilionacea. A toxic fraction was identified using a cell based cytotoxicity assay and the toxin was isolated and identified as the ladder frame polyether brevetoxin-2 (PbTx-2) using mass spectrometry (MS) and nuclear magnetic resonance (NMR). Toxin production in K. papilionacea increased in response to Hypoosmotic Stress, as previously observed in K. brevis.
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Osmotic Stress does trigger brevetoxin production in the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Although a number of factors may influence its production, the physiological role of brevetoxin in the dinoflagellate Karenia brevis is still open to debate. Not to be left out of the discussion, Sunda et al. (1) challenge our suggestion that salinity Stress may be a possible trigger for brevetoxin production. Their “repeat” of our experiment is not an actual replication (extraction protocols, analytical method, K. brevis isolates, and culturing conditions differed among their three laboratories). Moreover, a number of experimental details, including use of internal standards and preparation of toxin standards, are omitted. Internal standards are important because extraction efficiency varies among samples and could affect results. Nevertheless, both reports show that there is no long-term increase in brevetoxin production after salinity Stress (1, 2) and that low-toxin cultures [SP1 (2) and “nontoxic” Wilson (1)] do not increase brevetoxin production in response to Hypoosmotic Stress.
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osmotic Stress triggers toxin production by the dinoflagellate karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Abstract With the increase in frequency of harmful algal blooms (HABs) worldwide, a better understanding of the mechanisms that influence toxin production is needed. Karenia brevis, the major HAB dinoflagellate in the Gulf of Mexico, produces potent neurotoxins, known as brevetoxins. Human health is directly impacted by blooms of K. brevis through consumption of shellfish contaminated by accumulated brevetoxins (neurotoxic shellfish poisoning) or from aerosolized brevetoxins in sea spray (reduced respiratory function); however, the reason for brevetoxin production has remained a mystery. Here we show that brevetoxin production increased dramatically in response to osmotic Stress in three of the four K. brevis clones examined. By rapidly changing salinity to simulate a shift from oceanic conditions to a decreased salinity typical of coastal conditions, brevetoxin production was triggered. As a result, brevetoxin cell quota increased by >14-fold, while growth rate remained unchanged. Live images of K. brevis cells were also examined to assess changes in cell volume. In the K. brevis Wilson clone, cells responded quickly to Hypoosmotic Stress by increasing their brevetoxin cell quota from ∼10 to 160 pg of brevetoxin per cell, while cell volume remained stable. In contrast, the K. brevis SP1 clone, which has a consistently low brevetoxin cell quota (<1 pg per cell), was unable to balance the Hypoosmotic Stress, and although brevetoxin production remained low, average cell volume increased. Our findings close a critical gap in knowledge regarding mechanisms for toxin production in K. brevis by providing an explanation for toxin production in this harmful dinoflagellate.
Heinz C Schroder - One of the best experts on this subject based on the ideXlab platform.
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effect of Hypoosmotic Stress by low salinity acclimation of mediterranean mussels mytilus galloprovincialis on biological parameters used for pollution assessment
Aquatic Toxicology, 2008Co-Authors: Bojan Hamer, željko Jaksic, Dijana Pavicichamer, Lorena Peric, Davorin Medakovic, Dusica Ivankovic, Jasenka Pavicic, Carla Zilberberg, Heinz C SchroderAbstract:Abstract In the present study, we investigated the progressive acclimation of the mussel Mytilus galloprovincialis to different reduced seawater (SW) salinities and its effect on several biochemical markers and biotests. Mussels were purchased from a local mariculture facility during summer (SW temperature 27 °C, salinity 37.5 psu) and winter (13 °C, 37 psu) seasons, and transferred to the laboratory for acclimation to reduced SW salinities (37, 28, 18.5 and 11 psu). At the beginning and at the end of acclimation processes tests of mussel survival in air were provided. After 14 days of acclimation the DNA integrity, p38-MAPK activation, metallothionein induction, oxygen consumption rate, and condition index were measured. Survival in air (SOS test), as a physiological index of mussel's health and vitality, had significantly lower LT50 values (11 psu) in the summer than in the winter, and it seems to be negatively affected by acclimation in comparison to controls (37 psu and mariculture). Condition indexes (CIs) were not significantly different, but mussel's acclimation resulted in decline (i.e., a negative trend), especially of CI-2 and CI-3 calculated on the basis of mussel tissue weight and shell sizes. Oxygen consumption rate ( V O 2 ) of M. galloprovincialis acclimated to reduced salinities was a concentration-dependent process and increased considerably to about 51 and 65% in lower SW concentrations (28 and 18 psu) compared to control mussels (37 psu). DNA integrity, determined by Fast Micromethod®, was negatively impacted by salinity acclimation and corresponding physiological Stress as well. Some differences in 1D protein expression patterns between control groups and mussels acclimated to 28, 18.5 and 11 psu (SW) were established. Reduced SW salinities (18.5 and 11 psu) resulted in significantly higher p38-MAPK phosphorylation, whereas the SW salinity of 28 psu decreased p-p38 significantly compared to control (37 psu). The concentration of metallothioneins in mussels’ gills was reduced at 28 and 18.5 psu, while it was significantly higher at 11 psu. Results indicated that SW salinity variation (i.e., Hypoosmotic Stress) in the marine environment can affect all investigated parameters. This investigation expands our understanding of multifactorial effects of the physical marine environment on the specificity of investigated biomarkers and biotests, providing insight into the acclimation, adaptive and Stress response processes of mussels. Effects of environmental factors have to be considered in sampling strategies for monitoring programmes to prevent false interpretation of results.
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effect of Hypoosmotic Stress by low salinity acclimation of mediterranean mussels mytilus galloprovincialis on biological parameters used for pollution assessment
Aquatic Toxicology, 2008Co-Authors: Bojan Hamer, željko Jaksic, Dijana Pavicichamer, Lorena Peric, Davorin Medakovic, Dusica Ivankovic, Jasenka Pavicic, Carla Zilberberg, Heinz C SchroderAbstract:In the present study, we investigated the progressive acclimation of the mussel Mytilus galloprovincialis to different reduced seawater (SW) salinities and its effect on several biochemical markers and biotests. Mussels were purchased from a local mariculture facility during summer (SW temperature 27 degrees C, salinity 37.5 psu) and winter (13 degrees C, 37 psu) seasons, and transferred to the laboratory for acclimation to reduced SW salinities (37, 28, 18.5 and 11 psu). At the beginning and at the end of acclimation processes tests of mussel survival in air were provided. After 14 days of acclimation the DNA integrity, p38-MAPK activation, metallothionein induction, oxygen consumption rate, and condition index were measured. Survival in air (SOS test), as a physiological index of mussel's health and vitality, had significantly lower LT50 values (11 psu) in the summer than in the winter, and it seems to be negatively affected by acclimation in comparison to controls (37 psu and mariculture). Condition indexes (CIs) were not significantly different, but mussel's acclimation resulted in decline (i.e., a negative trend), especially of CI-2 and CI-3 calculated on the basis of mussel tissue weight and shell sizes. Oxygen consumption rate (VO2) of M. galloprovincialis acclimated to reduced salinities was a concentration-dependent process and increased considerably to about 51 and 65% in lower SW concentrations (28 and 18 psu) compared to control mussels (37 psu). DNA integrity, determined by Fast Micromethod, was negatively impacted by salinity acclimation and corresponding physiological Stress as well. Some differences in 1D protein expression patterns between control groups and mussels acclimated to 28, 18.5 and 11 psu (SW) were established. Reduced SW salinities (18.5 and 11 psu) resulted in significantly higher p38-MAPK phosphorylation, whereas the SW salinity of 28 psu decreased p-p38 significantly compared to control (37 psu). The concentration of metallothioneins in mussels' gills was reduced at 28 and 18.5 psu, while it was significantly higher at 11 psu. Results indicated that SW salinity variation (i.e., Hypoosmotic Stress) in the marine environment can affect all investigated parameters. This investigation expands our understanding of multifactorial effects of the physical marine environment on the specificity of investigated biomarkers and biotests, providing insight into the acclimation, adaptive and Stress response processes of mussels. Effects of environmental factors have to be considered in sampling strategies for monitoring programmes to prevent false interpretation of results.