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Chen L, Liu L, Huang S. Cadmium activates the mitogen-activated protein kinase (MAPK) pathway via induction of reactive oxygen species and inhibition of protein phosphatases 2A and 5. Free Radic Biol Med 2008; 45:1035-44. [PMID: 18703135 DOI: 10.1016/j.freeradbiomed.2008.07.011] [Citation(s) in RCA: 200] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 07/12/2008] [Accepted: 07/16/2008] [Indexed: 01/14/2023]
Abstract
Cadmium (Cd), a highly toxic environmental pollutant, induces neurodegenerative diseases. Recently we have demonstrated that Cd may induce neuronal apoptosis in part through activation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (Erk1/2) pathways. However, the underlying mechanism remains enigmatic. Here we show that Cd induced generation of reactive oxygen species (ROS), leading to apoptosis of PC12 and SH-SY5Y cells. Pretreatment with N-acetyl-L-cysteine (NAC) scavenged Cd-induced ROS, and prevented cell death, suggesting that Cd-induced apoptosis is attributed to its induction of ROS. Furthermore, we found that Cd-induced ROS inhibited serine/threonine protein phosphatases 2A (PP2A) and 5 (PP5), leading to activation of Erk1/2 and JNK, which was abrogated by NAC. Overexpression of PP2A or PP5 partially prevented Cd-induced activation of Erk1/2 and JNK, as well as cell death. Cd-induced ROS was also linked to the activation of caspase-3. Pretreatment with inhibitors of JNK (SP600125) and Erk1/2 (U0126) partially blocked Cd-induced cleavage of caspase-3 and prevented cell death. However, zVAD-fmk, a pan caspase inhibitor, only partially prevented Cd-induced apoptosis. The results indicate that Cd induction of ROS inhibits PP2A and PP5, leading to activation of JNK and Erk1/2 pathways, and consequently resulting in caspase-dependent and -independent apoptosis of neuronal cells. The findings strongly suggest that the inhibitors of JNK, Erk1/2, or antioxidants may be exploited for prevention of Cd-induced neurodegenerative diseases.
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Affiliation(s)
- Long Chen
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA
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52
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Wu F, Wilson JX. Peroxynitrite-dependent activation of protein phosphatase type 2A mediates microvascular endothelial barrier dysfunction. Cardiovasc Res 2008; 81:38-45. [PMID: 18791203 PMCID: PMC2605194 DOI: 10.1093/cvr/cvn246] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Aims We investigated the mechanism by which proinflammatory stimulation induces microvascular endothelial barrier dysfunction. Since protein phosphatase type 2A (PP2A) can mediate paracellular leak and can be inactivated by tyrosine phosphorylation in its catalytic subunit (PP2Ac), we hypothesized that microvascular endothelial cells exposed to proinflammatory stimulation produce peroxynitrite that nitrates PP2Ac, and this nitration inhibits tyrosine phosphorylation of PP2Ac and thereby increases PP2A activity to mediate endothelial barrier dysfunction. Methods and results Exposure of mouse skeletal muscle microvascular endothelial cell monolayers to a proinflammatory stimulus [lipopolysaccharide (LPS) + interferon (IFN)γ] increased permeability to albumin, and this barrier dysfunction was attenuated by PP2A inhibitor okadaic acid or by siRNA (small interfering ribonucleic acid) against PP2Ac. LPS + IFNγ increased synthesis of peroxynitrite precursors nitric oxide (NO) and superoxide by inducible NO synthase (iNOS) and NADPH oxidase, respectively. PP2Ac immunoprecipitates isolated from LPS + IFNγ- or peroxynitrite-treated cells showed increased tyrosine nitration, decreased tyrosine phosphorylation and increased phosphatase activity. 3-Nitrotyrosine immunoprecipitates from LPS + IFNγ-stimulated cells also exhibited increased PP2A activity. Further, iNOS inhibitor 1400W, iNOS deficiency, NADPH oxidase inhibitor apocynin, or p47phox deficiency prevented the increase in PP2A activity and preserved barrier function. Conclusion LPS + IFNγ stimulates endothelial cells to produce iNOS-derived NO and NADPH oxidase-derived superoxide, which form peroxynitrite that nitrates tyrosine residues in PP2Ac and inhibits their phosphorylation. This nitration in PP2Ac is correlated with PP2A activation that mediates endothelial barrier dysfunction.
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Affiliation(s)
- Feng Wu
- Department of Exercise and Nutrition Sciences, University at Buffalo, 3435 Main Street, G10 Farber Hall, Buffalo, NY 14214-8028, USA.
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53
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El-faramawy YA, El-banouby MH, Sergeev P, Mortagy AK, Amer MS, Abdel-tawab AM. Changes in glutamate decarboxylase enzyme activity and tau-protein phosphorylation in the hippocampus of old rats exposed to chronic mild stress: reversal with the neuronal nitric oxide synthase inhibitor 7-nitroindazole. Pharmacol Biochem Behav 2008; 91:339-44. [PMID: 18755209 DOI: 10.1016/j.pbb.2008.08.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 07/23/2008] [Accepted: 08/01/2008] [Indexed: 02/03/2023]
Abstract
Effects of chronic stress are not completely understood. They may underlie depression and dementia. This study assessed the association between chronic stress, glutamate levels, tau-protein phosphorylation, and nitric-oxide in old rats exposed to chronic mild stress (CMS). Old (>15 months) male Wistar rats were exposed to CMS. Comparison groups included old and young control rats, young CMS-exposed, and old CMS-exposed rats treated with the neuronal nitric-oxide synthase (nNOS) enzyme inhibitor, 7-nitroindazole (20 mg/kg/day i.p.). Hippocampal glutamate levels and glutamate decarboxylase (GAD) activity were determined and tau protein phosphorylation was assessed. Age was a significant (p=0.025) source of variation in glutamate level [811.71+/-218.1, 665.9+/-124.9 micromol/g tissue protein (M+/-SD) in young and old control rats, respectively]. Old rats exposed to CMS were characterized by an increased risk to develop anhedonia. There was significant (p=0.035) decrease in GAD enzyme activity (-60.06%) and increased tau protein hyperphosphorylation in old rats exposed to CMS compared to control. Administration of 7-nitroindazole to CMS-exposed old rats significantly (p=0.002) increased GAD activity, decreased glutamate levels (7.19+/-3.19 vs. 763.9+/-91 micromol/g tissue protein; p=0.0005), and decreased phosphorylation of tau proteins compared to CMS exposed rats.
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Affiliation(s)
- Yasser A El-faramawy
- Department of Geriatrics, Faculty of Medicine, Ain Shams University, Cairo, Egypt
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54
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Fonseca-de-Souza AL, Dick CF, Dos Santos ALA, Meyer-Fernandes JR. A Mg(2+)-dependent ecto-phosphatase activity on the external surface of Trypanosoma rangeli modulated by exogenous inorganic phosphate. Acta Trop 2008; 107:153-8. [PMID: 18599005 DOI: 10.1016/j.actatropica.2008.05.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 05/16/2008] [Accepted: 05/22/2008] [Indexed: 11/30/2022]
Abstract
In this work, we characterized a Mg(2+)-dependent ecto-phosphatase activity present in live Trypanosoma rangeli epimastigotes. This enzyme showed capacity to hydrolyze the artificial substrate for phosphatases, p-nitrophenylphosphate (p-NPP). At saturating concentration of p-NPP, half-maximal p-NPP hydrolysis was obtained with 0.23mM Mg(2+). Ca(2+) had no effect on the basal phosphatase activity, could not substitute Mg(2+) as an activator and in contrast inhibited the p-NPP hydrolysis stimulated by Mg(2+). The dependence on p-NPP concentration showed a normal Michaelis-Menten kinetics for this phosphatase activity with values of V(max) of 8.94+/-0.36 nmol p-NP x h(-1) x 10(-7) cells and apparent K(m) of 1.04+/-0.16 mM p-NPP. Mg(2+)-dependent ecto-phosphatase activity was stimulated by the alkaline pH range. Experiments using inhibitors, such as, sodium fluoride, sodium orthovanadate and ammonium molybdate, inhibited the Mg(2+)-dependent ecto-phosphatase activity. Inorganic phosphate (Pi), a product of phosphatases, inhibited reversibly in 50% this activity. Okadaic acid and microcystin-LR, specific phosphoserine/threonine phosphatase inhibitors, inhibited significantly the Mg(2+)-dependent ecto-phosphatase activity. In addition, this phosphatase activity was able to recognize as substrates only o-phosphoserine and o-phosphothreonine, while o-phosphotyrosine was not a good substrate for this phosphatase. Epimastigote forms of T. rangeli exhibit a typical growth curve, achieving the stationary phase around fifth or sixth day and the Mg(2+)-dependent ecto-phosphatase activity decreased around 10-fold with the cell growth progression. Cells maintained at Pi-deprived medium (2 mM Pi) present Mg(2+)-dependent ecto-phosphatase activity approximately threefold higher than that maintained at Pi-supplemented medium (50 mM Pi).
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Affiliation(s)
- André L Fonseca-de-Souza
- Laboratório de Bioquímica Celular, Instituto de Bioquímica Medica, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, UFRJ, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ, Brazil
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55
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Kohr MJ, Wang H, Wheeler DG, Velayutham M, Zweier JL, Ziolo MT. Biphasic effect of SIN-1 is reliant upon cardiomyocyte contractile state. Free Radic Biol Med 2008; 45:73-80. [PMID: 18433725 PMCID: PMC2493607 DOI: 10.1016/j.freeradbiomed.2008.03.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Accepted: 03/19/2008] [Indexed: 11/28/2022]
Abstract
Many studies have demonstrated a biphasic effect of peroxynitrite in the myocardium, but few studies have investigated this biphasic effect on beta-adrenergic responsiveness and its dependence on contractile state. We have previously shown that high 3-morpholinosydnonimine (SIN-1) (source of peroxynitrite, 200 micromol/L) produced significant anti-adrenergic effects during maximal beta-adrenergic stimulation in cardiomyocytes. In the current study, we hypothesize that the negative effects of high SIN-1 will be greatest during high contractile states, whereas the positive effects of low SIN-1 (10 micromol/L) will predominate during low contractility. Isolated murine cardiomyocytes were field stimulated at 1 Hz, and [Ca(2+)](i) transients and shortening were recorded. After submaximal isoproterenol (ISO) (beta-adrenergic agonist, 0.01 micromol/L) stimulation, 200 micromol/L SIN-1 induced two distinct phenomena. Cardiomyocytes undergoing a large response to ISO showed a significant reduction in contractility, whereas cardiomyocytes exhibiting a modest response to ISO showed a further increase in contractility. Additionally, 10 micromol/L SIN-1 always increased contractility during low ISO stimulation, but had no effect during maximal ISO (1 micromol/L) stimulation. SIN-1 at 10 micromol/L also increased basal contractility. Interestingly, SIN-1 produced a contractile effect under only one condition in phospholamban-knockout cardiomyocytes, providing a potential mechanism for the biphasic effect of peroxynitrite. These results provide clear evidence for a biphasic effect of peroxynitrite, with high peroxynitrite modulating high levels of beta-adrenergic responsiveness and low peroxynitrite regulating basal function and low levels of beta-adrenergic stimulation.
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Affiliation(s)
- Mark J Kohr
- Department of Physiology & Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - Honglan Wang
- Department of Physiology & Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - Debra G Wheeler
- Department of Physiology & Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - Murugesan Velayutham
- Department of Internal Medicine: Division of Cardiovascular Medicine, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - Jay L Zweier
- Department of Internal Medicine: Division of Cardiovascular Medicine, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - Mark T Ziolo
- Department of Physiology & Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
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56
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Wang H, Kohr MJ, Traynham CJ, Wheeler DG, Janssen PML, Ziolo MT. Neuronal nitric oxide synthase signaling within cardiac myocytes targets phospholamban. Am J Physiol Cell Physiol 2008; 294:C1566-75. [PMID: 18400986 DOI: 10.1152/ajpcell.00367.2007] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies have shown that neuronal nitric oxide synthase (nNOS, NOS1) knockout mice (NOS1-/-) have increased or decreased contractility, but consistently have found a slowed rate of intracellular Ca2+ ([Ca2+]i) decline and relengthening. Contraction and [Ca2+]i decline are determined by many factors, one of which is phospholamban (PLB). The purpose of this study is to determine the involvement of PLB in the NOS1-mediated effects. Force-frequency experiments were performed in trabeculae isolated from NOS1-/- and wild-type (WT) mice. We also simultaneously measured Ca2+ transients (Fluo-4) and cell shortening (edge detection) in myocytes isolated from WT, NOS1-/-, and PLB-/- mice. NOS1-/- trabeculae had a blunted force-frequency response and prolonged relaxation. We observed similar effects in myocytes with NOS1 knockout or specific NOS1 inhibition with S-methyl-l-thiocitrulline (SMLT) in WT myocytes (i.e., decreased Ca2+ transient and cell shortening amplitudes and prolonged decline of [Ca2+]i). Alternatively, NOS1 inhibition with SMLT in PLB-/- myocytes had no effect. Acute inhibition of NOS1 with SMLT in WT myocytes also decreased basal PLB serine16 phosphorylation. Furthermore, there was a decreased SR Ca2+ load with NOS1 knockout or inhibition, which is consistent with the negative contractile effects. Perfusion with FeTPPS (peroxynitrite decomposition catalyst) mimicked the effects of NOS1 knockout or inhibition. beta-Adrenergic stimulation restored the slowed [Ca2+]i decline in NOS1-/- myocytes, but a blunted contraction remained, suggesting additional protein target(s). In summary, NOS1 inhibition or knockout leads to decreased contraction and slowed [Ca2+]i decline, and this effect is absent in PLB-/- myocytes. Thus NOS1 signaling modulates PLB serine16 phosphorylation, in part, via peroxynitrite.
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Affiliation(s)
- Honglan Wang
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
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57
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Steullet P, Lavoie S, Kraftsik R, Guidi R, Gysin R, Cuénod M, Do KQ. A glutathione deficit alters dopamine modulation of L-type calcium channels via D2 and ryanodine receptors in neurons. Free Radic Biol Med 2008; 44:1042-54. [PMID: 18206662 DOI: 10.1016/j.freeradbiomed.2007.12.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Revised: 12/03/2007] [Accepted: 12/03/2007] [Indexed: 11/15/2022]
Abstract
Synthesis of glutathione, a major redox regulator, is compromised in schizophrenia. We postulated that the resulting glutathione deficit via its effect on redox-sensitive proteins could contribute to dysfunction of some neurotransmitter systems in schizophrenia. We investigated whether a glutathione deficit, induced by a blocker of glutathione synthesis, L-buthionine-(S,R)-sulfoximine, affects intracellular pathways implicated in dopamine signaling in neurons, namely dopamine modulation of calcium responses to NMDA. Such a glutathione deficit changed the modulation of responses by dopamine, from enhanced responses in control neurons (likely via D1-type receptors) to decreased responses in low-glutathione neurons (via D2-type receptors). This difference in dopamine modulation was due to a different modulation of L-type calcium channels activated during NMDA stimulation: dopamine enhanced function of these channels in control neurons but decreased it in low-glutathione neurons. The effect of a glutathione deficit on dopamine signaling was dependent on the redox-sensitive ryanodine receptors (RyRs), whose function was enhanced in low-glutathione neurons. This suggests that enhanced RyRs in low-glutathione neurons strengthens intracellular calcium-dependent pathways following activation of D2-type receptors and causes a decrease in function of L-type channels. This represents a mechanism by which dopaminergic systems could be dysfunctional under conditions of impaired glutathione synthesis as in schizophrenia.
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Affiliation(s)
- Pascal Steullet
- Center for Psychiatric Neurosciences, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Prilly-Lausanne, Switzerland.
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58
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Bergeron M, Blanchette J, Rouleau P, Olivier M. Abnormal IFN-gamma-dependent immunoproteasome modulation by Trypanosoma cruzi-infected macrophages. Parasite Immunol 2008; 30:280-92. [PMID: 18312504 DOI: 10.1111/j.1365-3024.2008.01022.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proteasomes are the main producers of Ag loaded onto MHC class I molecules. Following IFN-gamma stimulation however, the constitutive subunits of the proteasome are replaced by the immunosubunits low molecular weight protein 2 (LMP2), multicatalytic endopeptidase complex-like 1 and low molecular weight protein 7 (LMP7), which generally heighten the immunogenecity of proteasome generated epitopes. Given that Trypanosoma cruzi, the aetiological agent of Chagas' disease, elicits a T(helper)1 response from its host if the infection is to be contained, the aim of this study was to verify whether this parasite modulates J774 and B10R mouse macrophage (MuPhi) immunoproteasome subunit and MHC class I expressions and, if so, identify the mechanism(s) responsible for that modulation. Results show that T. cruzi infection of mouse MuPhi reduces IFN-gamma-mediated immunoproteasome synthesis, along with MHC class I mRNA synthesis and cell surface expression. The infection by T. cruzi induces the release of reactive oxygen species (ROS) from MuPhi, and those ROS significantly inhibit protein tyrosine phosphatase activity, thereby leading to the activation of the SAPK/JNK signalling pathway, which is responsible for the observed IFN-gamma-mediated immunoproteasome synthesis and MHC class I down-regulation. To our knowledge, this is the first report that specifically identifies a mechanism by which a pathogen achieves immunoproteasome down-modulation.
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Affiliation(s)
- M Bergeron
- Centre de recherche en infectiologie, Centre hospitalier universitaire de Québec, Pavillon CHUL, Québec, Canada
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59
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Carruthers NJ, Stemmer PM. Methionine oxidation in the calmodulin-binding domain of calcineurin disrupts calmodulin binding and calcineurin activation. Biochemistry 2008; 47:3085-95. [PMID: 18275158 DOI: 10.1021/bi702044x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Calcineurin is a Ca (2+)/calmodulin-activated Ser/Thr phosphatase important in cellular actions resulting in memory formation, cardiac hypertrophy, and T-cell activation. This enzyme is subject to oxidative inactivation by superoxide at low micromolar concentrations and by H 2O 2 at low millimolar concentrations. On the basis of the hypothesis that oxidation of Met residues in calmodulin-binding domains inhibits binding to calmodulin, purified calcineurin was used to study the susceptibility of Met residues to oxidation by H 2O 2. The rate for oxidation of Met 406 in the calmodulin-binding domain was determined to be 4.4 x 10 (-3) M (-1) s (-1), indicating a high susceptibility to oxidation. Functional repercussions of Met 406 oxidation were evaluated using native enzyme and a calcineurin mutant in which Met 406 was exchanged for Leu. Measurement of fluorescent calmodulin binding demonstrated that oxidation of Met 406 results in a 3.3-fold decrease in the affinity of calmodulin for calcineurin. Calcineurin activation exhibited a loss in cooperativity with respect to calmodulin following Met 406 oxidation as shown by a reduction in the Hill slope from 1.88 to 0.86. Maximum phosphatase activity was unaffected by Met oxidation. Changes in the calcineurin-calmodulin interaction were accompanied by a 40% loss in the ability of calmodulin to stimulate binding of immunophilin/immunosuppressant to calcineurin. All effects on calmodulin binding to the native enzyme by the treatment with H 2O 2 could be reversed by treating the enzyme with methionine sulfoxide reductase. These results indicate that the calmodulin-binding domain of calcineurin is susceptible to oxidation at Met 406 and that oxidation disrupts calmodulin binding and enzyme activation. Oxidation-dependent decreases in the affinity of calmodulin for calcineurin can potentially modulate calmodulin-dependent signaling and calmodulin distribution.
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Affiliation(s)
- Nicholas J Carruthers
- Institute of Environmental Health Sciences, Wayne State University, Detroit, Michigan 48201, USA
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60
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Liebler DC. Protein damage by reactive electrophiles: targets and consequences. Chem Res Toxicol 2007; 21:117-28. [PMID: 18052106 DOI: 10.1021/tx700235t] [Citation(s) in RCA: 197] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
It has been 60 years since the Millers first described the covalent binding of carcinogens to tissue proteins. Protein covalent binding was gradually overshadowed by the emergence of DNA adduct formation as the dominant paradigm in chemical carcinogenesis but re-emerged in the early 1970s as a critical mechanism of drug and chemical toxicity. Technology limitations hampered the characterization of protein adducts until the emergence of mass spectrometry-based proteomics in the late 1990s. The time since then has seen rapid progress in the characterization of the protein targets of electrophiles and the consequences of protein damage. Recent integration of novel affinity chemistries for electrophile probes, shotgun proteomics methods, and systems modeling tools has led to the identification of hundreds of protein targets of electrophiles in mammalian systems. The technology now exists to map the targets of damage to critical components of signaling pathways and metabolic networks and to understand mechanisms of damage at a systems level. The implementation of sensitive, specific analyses for protein adducts from both xenobiotic-derived and endogenous electrophiles offers a means to link protein damage to clinically relevant health effects of both chemical exposures and disease processes.
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Affiliation(s)
- Daniel C Liebler
- Department of Biochemistry, Vanderbilt University School of Medicine,, Nashville, Tennessee 37232, USA.
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61
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Zhang YH, Zhang MH, Sears CE, Emanuel K, Redwood C, El-Armouche A, Kranias EG, Casadei B. Reduced phospholamban phosphorylation is associated with impaired relaxation in left ventricular myocytes from neuronal NO synthase-deficient mice. Circ Res 2007; 102:242-9. [PMID: 18007024 DOI: 10.1161/circresaha.107.164798] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Stimulation of nitric oxide (NO) release from the coronary endothelium facilitates myocardial relaxation via a cGMP-dependent reduction in myofilament Ca2+ sensitivity. Recent evidence suggests that NO released by a neuronal NO synthase (nNOS) in the myocardium can also hasten left ventricular relaxation; however, the mechanism underlying these findings is uncertain. Here we show that both relaxation (TR50) and the rate of [Ca2+]i transient decay (tau) are significantly prolonged in field-stimulated or voltage-clamped left ventricular myocytes from nNOS-/- mice and in wild-type myocytes (nNOS+/+) after acute nNOS inhibition. Disabling the sarcoplasmic reticulum abolished the differences in TR50 and tau, suggesting that impaired sarcoplasmic reticulum Ca2+ reuptake may account for the slower relaxation in nNOS-/- mice. In line with these findings, disruption of nNOS (but not of endothelial NOS) decreased phospholamban phosphorylation (P-Ser16 PLN), whereas nNOS inhibition had no effect on TR50 or tau in PLN-/- myocytes. Inhibition of cGMP signaling had no effect on relaxation in either group whereas protein kinase A inhibition abolished the difference in relaxation and PLN phosphorylation by decreasing P-Ser16 PLN and prolonging TR50 in nNOS+/+ myocytes. Conversely, inhibition of type 1 or 2A protein phosphatases shortened TR50 and increased P-Ser16 PLN in nNOS-/- but not in nNOS+/+ myocytes, in agreement with data showing increased protein phosphatase activity in nNOS-/- hearts. Taken together, our findings identify a novel mechanism by which myocardial nNOS promotes left ventricular relaxation by regulating the protein kinase A-mediated phosphorylation of PLN and the rate of sarcoplasmic reticulum Ca2+ reuptake via a cGMP-independent effect on protein phosphatase activity.
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Affiliation(s)
- Yin Hua Zhang
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, United Kingdom
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62
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Ranganna K, Mathew OP, Yatsu FM, Yousefipour Z, Hayes BE, Milton SG. Involvement of glutathione/glutathione S-transferase antioxidant system in butyrate-inhibited vascular smooth muscle cell proliferation. FEBS J 2007; 274:5962-78. [PMID: 17961182 DOI: 10.1111/j.1742-4658.2007.06119.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Vascular smooth muscle cell (VSMC) proliferation is an important etiological factor in vascular proliferative diseases such as primary atherosclerosis, hypertension, arterial and in-stent restenosis, and transplant vasculopathy. Our studies established that butyrate, a bacterial fermentation product of dietary fiber and a chromatin modulator, is a potent inhibitor of VSMC proliferation. The cardiovascular health benefits of a high-fiber diet, the principle source of butyrate in the body, have been known for a long time, however, very little is known about the antiatherogenic potential of butyrate. Because oxidative stress plays an important role in the pathogenesis of atherosclerosis, we examined involvement of the glutathione/glutathione S-transferase (GST) antioxidant system in butyrate's inhibition of VSMC proliferation. Treatment of proliferating VSMCs with butyrate leads to the induction of several GSTs. Interestingly, our study also demonstrated the nuclear localization of GST-P1 (GST-7-7), which is considered to be a cytosolic protein; this was demonstrated using immunostaining and was corroborated by western blotting. Also, the butyrate-induced antiproliferative action, and the induction of GST-P1 and its nuclear localization are downregulated when butyrate is withdrawn. Furthermore, assessment of intracellular glutathione levels reveals their augmentation by butyrate. Conversely, butyrate treatment reduces the levels of reactive oxygen species in VSMCs. Collectively, the butyrate-treatment-related increase in glutathione content, the reduction in reactive oxygen species, the upregulation of GST and the nuclear localization of GST-P1 in growth-arrested VSMCs imply that butyrate's antiproliferative action involves modulation of the cellular redox state. Thus, induction of the glutathione/GST antioxidant system appears to have other regulatory role(s) besides detoxification and regulation of the cellular redox state, for example, cell-cycle control and cell proliferation, which are both critical to atherogenesis.
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Affiliation(s)
- Kasturi Ranganna
- Department of Pharmaceutical Sciences, Texas Southern University, Houston, TX 77004, USA.
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63
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Humphries KM, Pennypacker JK, Taylor SS. Redox regulation of cAMP-dependent protein kinase signaling: kinase versus phosphatase inactivation. J Biol Chem 2007; 282:22072-9. [PMID: 17548350 DOI: 10.1074/jbc.m702582200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many components of cellular signaling pathways are sensitive to regulation by oxidation and reduction. Previously, we described the inactivation of cAMP-dependent protein kinase (PKA) by direct oxidation of a reactive cysteine in the activation loop of the kinase. In the present study, we demonstrate that in HeLa cells PKA activity follows a biphasic response to thiol oxidation. Under mild oxidizing conditions, or short exposure to oxidants, forskolin-stimulated PKA activity is enhanced. This enhancement was blocked by sulfhydryl reducing agents, demonstrating a reversible mode of activation. In contrast, forskolin-stimulated PKA activity is inhibited by more severe oxidizing conditions. Mild oxidation enhanced PKA activity stimulated by forskolin, isoproterenol, or the cell-permeable analog, 8-bromo-cAMP. When cells were lysed in the presence of serine/threonine phosphatase inhibitor, NaF, the PKA-enhancing effect of oxidation was blunted. These results suggest oxidation of a PKA-counteracting phosphatase may be inhibited, thus enhancing the apparent kinase activity. Using an in vivo PKA activity reporter, we demonstrated that mild oxidation does indeed prolong the PKA signal induced by isoproterenol by inhibiting counteracting phosphatase activity. The results of this study demonstrate in live cells a unique synergistic mechanism whereby the PKA signaling pathway is enhanced in an apparent biphasic manner.
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Affiliation(s)
- Kenneth M Humphries
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0654, USA
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64
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Deem TL, Abdala-Valencia H, Cook-Mills JM. VCAM-1 activation of endothelial cell protein tyrosine phosphatase 1B. THE JOURNAL OF IMMUNOLOGY 2007; 178:3865-73. [PMID: 17339486 PMCID: PMC2710028 DOI: 10.4049/jimmunol.178.6.3865] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lymphocytes migrate from the blood into tissue by binding to and migrating across endothelial cells. One of the endothelial cell adhesion molecules that mediate lymphocyte binding is VCAM-1. We have reported that binding to VCAM-1 activates endothelial cell NADPH oxidase for the generation of reactive oxygen species (ROS). The ROS oxidize and stimulate an increase in protein kinase C (PKC)alpha activity. Furthermore, these signals are required for VCAM-1-dependent lymphocyte migration. In this report, we identify a role for protein tyrosine phosphatase 1B (PTP1B) in the VCAM-1 signaling pathway. In primary cultures of endothelial cells and endothelial cell lines, Ab cross-linking of VCAM-1 stimulated an increase in serine phosphorylation of PTP1B, the active form of PTP1B. Ab cross-linking of VCAM-1 also increased activity of PTP1B. This activation of PTP1B was downstream of NADPH oxidase and PKCalpha in the VCAM-1 signaling pathway as determined with pharmacological inhibitors and antisense approaches. In addition, during VCAM-1 signaling, ROS did not oxidize endothelial cell PTP1B. Instead PTP1B was activated by serine phosphorylation. Importantly, inhibition of PTP1B activity blocked VCAM-1-dependent lymphocyte migration across endothelial cells. In summary, VCAM-1 activates endothelial cell NADPH oxidase to generate ROS, resulting in oxidative activation of PKCalpha and then serine phosphorylation of PTP1B. This PTP1B activity is necessary for VCAM-1-dependent transendothelial lymphocyte migration. These data show, for the first time, a function for PTP1B in VCAM-1-dependent lymphocyte migration.
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Affiliation(s)
- Tracy L. Deem
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267
- Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908
| | - Hiam Abdala-Valencia
- Allergy-Immunology Division, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267
| | - Joan M. Cook-Mills
- Allergy-Immunology Division, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267
- Address correspondence and reprint requests to Dr. Joan M. Cook-Mills, Allergy-Immunology Division, Northwestern University, Feinberg School of Medicine, McGaw-304, 240 East Huron, Chicago, IL 60611. E-mail address:
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Le Prell CG, Yamashita D, Minami SB, Yamasoba T, Miller JM. Mechanisms of noise-induced hearing loss indicate multiple methods of prevention. Hear Res 2007; 226:22-43. [PMID: 17141991 PMCID: PMC1995566 DOI: 10.1016/j.heares.2006.10.006] [Citation(s) in RCA: 230] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2006] [Revised: 10/05/2006] [Accepted: 10/24/2006] [Indexed: 12/20/2022]
Abstract
Recent research has shown the essential role of reduced blood flow and free radical formation in the cochlea in noise-induced hearing loss (NIHL). The amount, distribution, and time course of free radical formation have been defined, including a clinically significant late formation 7-10 days following noise exposure, and one mechanism underlying noise-induced reduction in cochlear blood flow has finally been identified. These new insights have led to the formulation of new hypotheses regarding the molecular mechanisms of NIHL; and, from these, we have identified interventions that prevent NIHL, even with treatment onset delayed up to 3 days post-noise. It is essential to now assess the additive effects of agents intervening at different points in the cell death pathway to optimize treatment efficacy. Finding safe and effective interventions that attenuate NIHL will provide a compelling scientific rationale to justify human trials to eliminate this single major cause of acquired hearing loss.
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Affiliation(s)
- Colleen G Le Prell
- Kresge Hearing Research Institute, University of Michigan, 1301 East Ann Street, Ann Arbor, MI 48109-0506, USA.
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66
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Costelli P, Almendro V, Figueras MT, Reffo P, Penna F, Aragno M, Mastrocola R, Boccuzzi G, Busquets S, Bonelli G, Lopez Soriano FJ, Argilés JM, Baccino FM. Modulations of the calcineurin/NF-AT pathway in skeletal muscle atrophy. Biochim Biophys Acta Gen Subj 2007; 1770:1028-36. [PMID: 17442496 DOI: 10.1016/j.bbagen.2007.03.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 02/14/2007] [Accepted: 03/06/2007] [Indexed: 10/23/2022]
Abstract
Calcineurin has been proposed to regulate skeletal muscle hypertrophy, while its relevance to the pathogenesis of muscle atrophy is unknown. The present study was aimed to investigate if perturbations of the calcineurin pathway may be involved in causing skeletal muscle atrophy in two different experimental conditions: cancer cachexia (rats bearing the AH-130 hepatoma), and hyperglycemia (rats treated with streptozotocin). Calcineurin expression in the gastrocnemius was comparable between tumor hosts and controls. By contrast, besides unchanged calcineurin mRNA levels, those of protein were lower in diabetic animals than in controls. The DNA-binding activity of the transcription factors NF-AT and MEF-2 was analysed as an indirect measure of calcineurin activity in vivo. The nuclear translocation of both factors was similar in tumor hosts and controls. Consistently with the reduced calcineurin protein levels, NF-AT DNA-binding activity significantly decreased in the gastrocnemius of diabetic rats compared to controls. Finally, muscle wasting correction afforded in the AH-130 hosts by pentoxifylline or interleukin-15 was not paralleled by changes of calcineurin mRNA levels, while treatment of diabetic animals with dehydroepiandrosterone partially prevented calcineurin down-regulation. These results suggest that modulations of calcineurin activity may be involved in the pathogenesis of muscle wasting in diabetes though not in cancer cachexia.
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Affiliation(s)
- Paola Costelli
- Dipartimento di Medicina e Oncologia Sperimentale, Università di Torino, Italy.
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67
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Zingg JM. Modulation of signal transduction by vitamin E. Mol Aspects Med 2007; 28:481-506. [PMID: 17320164 DOI: 10.1016/j.mam.2006.12.009] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Accepted: 12/16/2006] [Indexed: 01/22/2023]
Abstract
The ability of vitamin E to modulate signal transduction and gene expression has been observed in numerous studies; however, the detailed molecular mechanisms involved are often not clear. The eight natural vitamin E analogues and synthetic derivatives affect signal transduction with different potency, possibly reflecting their different ability to interact with specific proteins. Vitamin E modulates the activity of several enzymes involved in signal transduction, such as protein kinase C, protein kinase B, protein tyrosine kinases, 5-, 12-, and 15-lipoxygenases, cyclooxygenase-2, phospholipase A2, protein phosphatase 2A, protein tyrosine phosphatase, and diacylglycerol kinase. Activation of some these enzymes after stimulation of cell surface receptors with growth factors or cytokines can be normalized by vitamin E. At the molecular level, the translocation of several of these enzymes to the plasma membrane is affected by vitamin E, suggesting that the modulation of protein-membrane interactions may be a common theme for vitamin E action. In this review the main effects of vitamin E on enzymes involved in signal transduction are summarized and the possible mechanisms leading to enzyme modulation evaluated. The elucidation of the molecular and cellular events affected by vitamin E could reveal novel strategies and molecular targets for developing similarly acting compounds.
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Affiliation(s)
- Jean-Marc Zingg
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland.
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Carruthers NJ, Dowd MK, Stemmer PM. Gossypol inhibits calcineurin phosphatase activity at multiple sites. Eur J Pharmacol 2007; 555:106-14. [PMID: 17141216 DOI: 10.1016/j.ejphar.2006.10.046] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Revised: 10/12/2006] [Accepted: 10/19/2006] [Indexed: 12/01/2022]
Abstract
Calcineurin, the Ca2+/calmodulin-dependant serine/threonine phosphatase is the target for the immunosuppressant drugs FK506 and cyclosporine-A. These established calcineurin inhibitors each require an immunophilin protein cofactor. Gossypol, a polyphenol produced by the cotton plant, inhibits calcineurin (IC50=15 microM), in a noncompetitive, reversible manner, and is independent of any cofactor. We found that gossypol acts by at least two mechanisms to inhibit calcineurin phosphatase activity. A calmodulin-independent form of calcineurin was less sensitive to inhibition by gossypol than native calcineurin (IC50=41 and 18 microM, respectively) indicating that gossypol may interfere with calmodulin binding. A fluorescence polarization based assay demonstrated that 100 microM gossypol reduced the affinity of calmodulin for calcineurin (from K(d)=2.4 to 250 nM). Inhibition of calcineurin phosphatase activity by gossypol could not be overcome by adding excess calmodulin or by testing the inhibition toward a calmodulin-independent calcineurin indicating that gossypol acts at a site different from the calmodulin-binding site. Gossypol decreased the affinity of calcineurin for immunosuppressant/immunophilin complexes only in the presence of calmodulin, indicating that gossypol blocks the effects of calmodulin binding to calcineurin. In addition, gossypol had a stimulatory effect on native calcineurin in the absence of calmodulin, possibly indicating a calmodulin mimetic effect. Gossypol exists in two enantiomeric forms which are reported to have different potency for cell toxicity. (+) and (-) gossypol had equivalent potency for inhibition of native and calmodulin-independent calcineurin phosphatase activity, and for inhibition of calmodulin binding. The inhibition of calcineurin by gossypol via multiple binding sites without stereo-specificity indicates that gossypol is not a specific calcineurin inhibitor.
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Affiliation(s)
- Nicholas J Carruthers
- Wayne State University, Institute of Environmental Health Sciences, Detroit, MI 48201, United States
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69
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Abdala-Valencia H, Cook-Mills JM. VCAM-1 signals activate endothelial cell protein kinase Calpha via oxidation. THE JOURNAL OF IMMUNOLOGY 2006; 177:6379-87. [PMID: 17056569 PMCID: PMC2711556 DOI: 10.4049/jimmunol.177.9.6379] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lymphocyte binding to VCAM-1 activates endothelial cell NADPH oxidase, resulting in the generation of 1 muM H(2)O(2). This is required for VCAM-1-dependent lymphocyte migration. In this study, we identified a role for protein kinase Calpha (PKCalpha) in VCAM-1 signal transduction in human and mouse endothelial cells. VCAM-1-dependent spleen cell migration under 2 dynes/cm(2) laminar flow was blocked by pretreatment of endothelial cells with dominant-negative PKCalpha or the PKCalpha inhibitors, Rö-32-0432 or Gö-6976. Phosphorylation of PKCalpha(Thr638), an autophosphorylation site indicating enzyme activity, was increased by Ab cross-linking of VCAM-1 on endothelial cells or by the exogenous addition of 1 muM H(2)O(2). The anti-VCAM-1-stimulated phosphorylation of PKCalpha(Thr638) was blocked by scavenging of H(2)O(2) and by inhibition of NADPH oxidase. Furthermore, anti-VCAM-1 signaling induced the oxidation of endothelial cell PKCalpha. Oxidized PKCalpha is a transiently active form of PKCalpha that is diacylglycerol independent. This oxidation was blocked by inhibition of NADPH oxidase. In summary, VCAM-1 activation of endothelial cell NADPH oxidase induces transient PKCalpha activation that is necessary for VCAM-1-dependent transendothelial cell migration.
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Affiliation(s)
| | - Joan M. Cook-Mills
- Address correspondence and reprint requests to Dr. Joan M. Cook-Mills, Allergy-Immunology Division, Feinberg School of Medicine, Northwestern University, McGaw-304, 240 East Huron, Chicago, IL 60611. E-mail address:
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70
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Sugden PH, Clerk A. Oxidative stress and growth-regulating intracellular signaling pathways in cardiac myocytes. Antioxid Redox Signal 2006; 8:2111-24. [PMID: 17034354 DOI: 10.1089/ars.2006.8.2111] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The toxic effects of oxidative stress on cells (including cardiac myocytes, the contractile cells of the heart) are well known. However, an increasing body of evidence has suggested that increased production of reactive oxygen species (ROS) promotes cardiac myocyte growth. Thus, ROS may be 'second messenger' molecules in their own right, and growth-promoting neurohumoral agonists might exert their effects by stimulating production of ROS. The authors review the principal growth-promoting intracellular signaling pathways that are activated by ROS in cardiac myocytes, namely the mitogen-activated protein kinase cascades (extracellular signal-regulated kinases 1/2, c-Jun N-terminal kinases, and p38-mitogen-activated protein kinases) and the phosphoinositide 3-kinase/protein kinase B (Akt) pathway. Possible mechanisms are discussed by which these pathways are activated by ROS, including the oxidation of active site cysteinyl residues of protein and lipid phosphatases with their consequent inactivation, the potential involvement of protein kinase C or the apoptosis signal-regulating kinase 1, and the current models for the activation of the guanine nucleotide binding protein Ras.
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Affiliation(s)
- Peter H Sugden
- National Heart and Lung Institute Division, Faculty of Medicine, Imperial College London, London, United Kingdom.
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71
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Kuhla B, Lüth HJ, Haferburg D, Weick M, Reichenbach A, Arendt T, Münch G. Pathological effects of glyoxalase I inhibition in SH-SY5Y neuroblastoma cells. J Neurosci Res 2006; 83:1591-600. [PMID: 16555297 DOI: 10.1002/jnr.20838] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In Alzheimer's disease (AD), in aging, and under conditions of oxidative stress, the levels of reactive carbonyl compounds continuously increase. Accumulating carbonyl levels might be caused by an impaired enzymatic detoxification system. The major dicarbonyl detoxifying system is the glyoxalase system, which removes methylglyoxal in order to minimize cellular impairment. Although a reduced activity of glyoxalase I was evident in aging brains, it is not known how raising the intracellular methylglyoxal level influences neuronal function and the phosphorylation pattern of tau protein, which is known to be abnormally hyperphosphorylated in AD. To simulate a reduced glyoxalase I activity, we applied an inhibitor of glyoxalase I, p-bromobenzylglutathione cyclopentyl diester (pBrBzGSCp(2)), to SH-SY5Y neuroblastoma cells to induce chronically elevated methylglyoxal concentrations. We have shown that 10 microM pBrBzGSCp(2) leads to a fourfold elevation of the methylglyoxal level after 24 hr. In addition, glyoxalase I inhibition leads to reduced cell viability, strongly retracted neuritis, increase in [Ca(2+)](i), and activation of caspase-3. However, pBrBzGSCp(2) did not lead to tau "hyper"-phosphorylation despite activation of p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase but rather activated protein phosphatases 2 and induced tau dephosphorylation at the Ser(202)/Thr(205) and Ser(396)/Ser(404) epitopes. Preincubation with the carbonyl scavenger aminoguanidine prevented tau dephosphorylation, indicating the specific effect of methylglyoxal. Also, pretreatment with the inhibitor okadaic acid prevented tau dephosphorylation, indicating that methylglyoxal activates PP-2A. In summary, our data suggest that a reduced glyoxalase I activity mimics some changes associated with neurodegeneration, such as neurite retraction and apoptotic cell death.
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Affiliation(s)
- Björn Kuhla
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
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72
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Steullet P, Neijt HC, Cuénod M, Do KQ. Synaptic plasticity impairment and hypofunction of NMDA receptors induced by glutathione deficit: Relevance to schizophrenia. Neuroscience 2006; 137:807-19. [PMID: 16330153 DOI: 10.1016/j.neuroscience.2005.10.014] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Revised: 09/27/2005] [Accepted: 10/07/2005] [Indexed: 11/23/2022]
Abstract
Increasing evidence suggests that the metabolism of glutathione, an endogenous redox regulator, is abnormal in schizophrenia. Patients show a deficit in glutathione levels in the cerebrospinal fluid and prefrontal cortex and a reduction in gene expression of the glutathione synthesizing enzymes. We investigated whether such glutathione deficit altered synaptic transmission and plasticity in slices of rat hippocampus, with particular emphasis on NMDA receptor function. An approximately 40% decrease in brain glutathione levels was induced by s.c. administration of L-buthionine-(S,R)-sulfoximine, an inhibitor of glutathione synthesis. Such glutathione deficit did not affect the basal synaptic transmission, but produced several NMDA receptor-dependent and -independent effects. Glutathione deficit caused an increase in excitability of CA1 pyramidal cells. The paired-pulse facilitation was diminished in glutathione-depleted slices, in a manner that was independent of NMDA receptor activity. This suggests that lowering glutathione levels altered presynaptic mechanisms involved in neurotransmitter release. NMDA receptor-dependent long-term potentiation induced by high-frequency stimulation was impaired in glutathione-depleted slices. Pharmacologically isolated NMDA receptor-mediated field excitatory postsynaptic potentials were significantly smaller in L-buthionine-(S,R)-sulfoximine-treated than in control slices. Hypofunction of NMDA receptors under glutathione deficit was explained at least in part by an excessive oxidation of the extracellular redox-sensitive sites of the NMDA receptors. These results indicate that a glutathione deficit, like that observed in schizophrenics, alters short- and long-term synaptic plasticity and affects NMDA receptor function. Thus, glutathione deficit could be one causal factor for the hypofunction of NMDA receptors in schizophrenia.
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Affiliation(s)
- P Steullet
- Center for Psychiatric Neurosciences, Department of Adult Psychiatry, University Medical Center, University of Lausanne, 1008 Prilly, Switzerland.
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73
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Kang S, Li H, Rao A, Hogan PG. Inhibition of the Calcineurin-NFAT Interaction by Small Organic Molecules Reflects Binding at an Allosteric Site. J Biol Chem 2005; 280:37698-706. [PMID: 16148011 DOI: 10.1074/jbc.m502247200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcriptional signaling from the Ca(2+)-calmodulin-activated phosphatase calcineurin to its substrate NFAT (nuclear factor of activated T cells, also termed NFATc) is critically dependent on a protein-protein docking interaction between calcineurin and the PXIXIT motif in NFAT. Several inhibitors of NFAT-calcineurin association (INCA compounds) prevent binding of NFAT or the peptide ligand PVIVIT to calcineurin. Here we show that the binding site on calcineurin for INCA1, INCA2, and INCA6 is centered on cysteine 266 of calcineurin Aalpha and does not coincide with the core PXIXIT-binding site. Although ample evidence indicates that INCA1 and INCA2 react covalently with cysteine 266, covalent derivatization alone is not sufficient for maximal inhibition of the calcineurin-PVIVIT interaction, because the maleimide INCA12 reacts with the same site and produces only very modest inhibition. Thus, inhibition arises through an allosteric change affecting the PXIXIT docking site, which may be assisted by covalent binding but depends on other specific features of the ligand. The spatial arrangement of the binding sites for PVIVIT and INCA makes it probable that the change in conformation involves the beta11-beta12 loop of calcineurin. The finding that an allosteric site controls NFAT binding opens new alternatives for inhibition of calcineurin-NFAT signaling.
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Affiliation(s)
- Sunghyun Kang
- CBR Institute for Biomedical Research, Boston, MA 02115, USA
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74
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Barthel A, Klotz LO. Phosphoinositide 3-kinase signaling in the cellular response to oxidative stress. Biol Chem 2005; 386:207-16. [PMID: 15843166 DOI: 10.1515/bc.2005.026] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Oxidative stress is linked to the pathogenesis and pathobiochemistry of various diseases, including cancer, diabetes and cardiovascular disorders. The non-specific damaging effect of reactive oxygen species (ROS) generated during oxidative stress is involved in the development of diseases, as well as the activation of specific signaling cascades in cells exposed to the higher oxidant load. A cellular signaling cascade that is activated by several types of reactive oxygen species is the phosphoinositide 3'-kinase (PI 3-kinase)/protein kinase B (PKB) pathway, which regulates cellular survival and fuel metabolism, thus establishing a link between oxidative stress and signaling in neoplastic, metabolic or degenerative diseases. Several links of PI 3-kinase/PKB signaling to ROS are discussed in this review, with particular focus on the molecular mechanisms involved in the regulation of PI 3-kinase signaling by oxidative stress and important players such as (i) the glutathione and glutaredoxin system, (ii) the thioredoxin system and (iii) Ser/Thr- and Tyr phosphatases.
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Affiliation(s)
- Andreas Barthel
- Abteilung für Endokrinologie, Diabetologie und Rheumatologie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
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75
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Narayan AV, Stadel R, Hahn AB, Bhoiwala DL, Cornielle G, Sarazin E, Koleilat I, Crawford DR. Redox response of the endogenous calcineurin inhibitor Adapt 78. Free Radic Biol Med 2005; 39:719-27. [PMID: 16109302 DOI: 10.1016/j.freeradbiomed.2005.03.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2004] [Revised: 02/20/2005] [Accepted: 03/24/2005] [Indexed: 11/22/2022]
Abstract
Adapt 78 (DSCR 1/calcipressin/MCIP 1) is a potent natural inhibitor of calcineurin, an important intracellular phosphatase that mediates many cellular responses to calcium. We previously reported two major cytosolic isoforms (1 and 4) of Adapt 78, and that isoform 4 is an oxidative and calcium stress-response protein. Using a higher cell culture density and new antibody, we again observed that both major isoforms localized to the cytosol, but a significant level of isoform 4 (but not isoform 1) was also detected in the nucleus where it was present in the non-soluble region and not associated with RNA. Exposure of cells to hydrogen peroxide led to the significant loss of isoform 4 from the nucleus with a moderate increase in cytosolic localization. The change in isoform 4 phosphorylation state in response to oxidative stress, characterized by a loss of the lesser (hypo) phosphorylated Adapt 78, was not due to accelerated degradation, although general Adapt 78 degradation was proteosome mediated. Finally, stimulation of Jurkat and primary T-lymphocyte signaling led to isoform 4 induction. This induction was BAPTA, diphenylene iodonium, and N-acetylcysteine inhibitable, and accompanied by induction of the classic immune response mediator and calcineurin-pathway-stimulated interleukin-2. These studies reveal new redox-related activities for Adapt 78 isoform 4, which may contribute to its known calcineurin-regulating and cytoprotective activities, and further suggest that Adapt 78 plays a role in basic T-cell response.
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Affiliation(s)
- Ananth V Narayan
- Center for Immunology and Microbial Disease, The Albany Medical College, Albany, NY 12208, USA
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76
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Lehen'kyi VV, Zelensky SN, Stefanov AV. Ca2+-sensitivity and cGMP-independent effects of NO in vascular smooth muscle. Nitric Oxide 2005; 12:105-13. [PMID: 15740984 DOI: 10.1016/j.niox.2005.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2004] [Revised: 10/25/2004] [Accepted: 01/13/2005] [Indexed: 10/25/2022]
Abstract
The effects of NO on Ca2+-sensitivity of vascular smooth muscle (VSM) myofilaments have been the focus of this study. Simultaneous measurements of [Ca2+]i and force were carried out in rat tail artery segments. NO, 10(-7) M, evoked a transient decrease in [Ca2+]i accompanied by sustained relaxation (45.3+/-6.3 vs. 69.45+/-7.2%, P<0.05, respectively) of VSM precontracted with K+ (70 mM), suggesting a decrease in Ca2+-sensitivity of VSM. This decrease in Ca2+-sensitivity was completely abolished by preincubation of VSM with ODQ (10(-6) M) (63.9+/-7.8% for [Ca2+]i vs. 20.5+/-8.4% for relaxation, P<0.05). Ca2+-presensitization of VSM myofilaments with PE (10(-6) M) decreased the efficacy of NO to relax VSM (44.25+/-6.9% vs. 69.45+/-7.2%, P<0.05), but increased its ability to lower [Ca2+]i (70.5+/-6.8% vs. 45.3+/-6.3%, P<0.05). Application of DTT (10(-3) M) together with ODQ (10(-6) M) to subtract possible cGMP-independent effects revealed the total suppression of both the relaxant responses and [Ca2+]i of VSM under high-K+ preactivation of VSM. The data indicate that NO not only relaxes VSM and lowers [Ca2+]i in K+-preactivated VSM, but also decreases Ca2+-sensitivity of VSM myofilaments and these effects are strongly cGMP-dependent. In PE-induced contractions of VSM, NO relaxed VSM of rat tail artery and lowered [Ca2+]i, but failed to reverse Ca2+-presensitized myofilaments. We suggest that alternative cGMP-independent effects of NO are primarily manifested via activation of K+-channels and inhibition of Ca2+ current rather than to affect relaxation. An importance of reduced SH-groups within VSM myoplasm for both relaxation and [Ca2+]i disposal evoked by NO is evident whatever Ca2+-mobilization pathways are involved.
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Affiliation(s)
- V V Lehen'kyi
- Department of Experimental Therapy, Institute of Pharmacology and Toxicology, 14 Ezhena Pot'e, 03057 Kyiv, Ukraine.
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77
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Nyunoya T, Monick MM, Powers LS, Yarovinsky TO, Hunninghake GW. Macrophages Survive Hyperoxia via Prolonged ERK Activation Due to Phosphatase Down-regulation. J Biol Chem 2005; 280:26295-302. [PMID: 15901735 DOI: 10.1074/jbc.m500185200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Macrophages exposed to hyperoxia in the lung continue to survive for prolonged periods. We previously reported (Nyunoya, T., Powers, L. S., Yarovinsky, T. O., Butler, N. S., Monick, M. M., and Hunninghake, G. W. (2003) J. Biol. Chem. 278, 36099-36106) that hyperoxia induces cell cycle arrest and sustained extracellular signal-related kinase (ERK) activity in macrophages. In this study, we determined the mechanisms of hyperoxia-induced ERK activation and how ERK activity plays a pro-survival role in hyperoxia-exposed cells. Inhibition of ERK activity decreased survival of hyperoxia-exposed macrophages. This was due, at least in part, to down-regulation of the pro-apoptotic Bcl-2 family member, BimEL. In determining the mechanism of ERK activation by hyperoxia, we found that ERK activation was not associated with hyperoxia-induced activation of the upstream ERK kinase mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2. When we examined the ability of whole cell lysates from hyperoxia-exposed cells to dephosphorylate purified phosphorylated ERK, we found decreased ERK-directed phosphatase activity. Two particular ERK-directed phosphatases (protein phosphatase 2A and MAPK phosphatase-3) demonstrated decreased activity in hyperoxia-exposed cells. Moreover, whole cell lysates from normoxia-exposed cells depleted of PP2A or MAPK phosphatase-3 were also less able to dephosphorylate ERK. These data demonstrate that, in hyperoxia-exposed macrophages, sustained activation of ERK due to phosphatase down-regulation permits macrophage survival via effects on the balance between pro- and anti-apoptotic Bcl-2 family proteins.
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Affiliation(s)
- Toru Nyunoya
- Division of Pulmonary, Critical Care, and Occupational Medicine, University of Iowa Roy J. and Lucille A. Carver College of Medicine, Iowa City, Iowa 52242, USA.
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Mallozzi C, De Franceschi L, Brugnara C, Di Stasi AMM. Protein phosphatase 1alpha is tyrosine-phosphorylated and inactivated by peroxynitrite in erythrocytes through the src family kinase fgr. Free Radic Biol Med 2005; 38:1625-36. [PMID: 15917191 DOI: 10.1016/j.freeradbiomed.2005.02.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Revised: 01/17/2005] [Accepted: 02/22/2005] [Indexed: 11/30/2022]
Abstract
Protein serine/threonine phosphorylation is a significant component of the intracellular signal that together with tyrosine phosphorylation regulates several processes, including cell-cycle progression, muscle contraction, transcription, and neuronal signaling. Cross-talk between phosphoserine/threonine- and phosphotyrosine-mediated pathways is not yet well understood. In this study we found that peroxynitrite, a physiological oxidant formed by the fast radical-radical reaction between the nitric oxide and the superoxide anion, induced tyrosine phosphorylation of the serine/threonine protein phosphatase 1alpha (PP1alpha) in human erythrocytes through activation of src family kinases. We have previously shown in mouse red cells that upregulation of the src kinase fgr phosphorylates PP1alpha, acting as an upstream negative regulator of PP1alpha, and downregulates K-Cl cotransport. Here we found that PP1alpha is a selective substrate of peroxynitrite-activated fgr and that tyrosine phosphorylation of PP1alpha corresponds to an inhibition of its enzymatic activity. Despite fgr activation and PP1alpha downregulation, peroxynitrite stimulated in a dose-dependent fashion the function of the K-Cl cotransporter. In an attempt to understand the mechanism of K-Cl cotransport activation, we found that the effect of peroxynitrite is completely reversed by dithriothreitol, suggesting that peroxynitrite acts as an oxidizing agent by an SH-dependent and PP1alpha-independent mechanism. These findings highlight a novel function of peroxynitrite in regulating the intracellular signal transduction pathways involving serine/threonine phosphorylation and the functional role of proteins that are targets of these phosphatases.
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Affiliation(s)
- Cinzia Mallozzi
- Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena, 299-00161 Rome, Italy.
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79
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Lefebvre DL, Rosen CF. Regulation of SNARK activity in response to cellular stresses. Biochim Biophys Acta Gen Subj 2005; 1724:71-85. [PMID: 15893879 DOI: 10.1016/j.bbagen.2005.03.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Revised: 03/09/2005] [Accepted: 03/22/2005] [Indexed: 11/15/2022]
Abstract
SNARK is a member of the AMPK subfamily of serine/threonine protein kinases. In this study, we examined the regulation of SNARK activity in kidney (BHK, HEK293), pancreatic beta-cell insulinoma (INS-1), hepatocarcinoma (H4IIE) and keratinocyte (NRKC)-derived cell lines in response to diverse cellular stresses. We show that SNARK activity is regulated by glucose- or glutamine-deprivation, induction of endoplasmic reticulum stress by homocysteine or DTT, elevation of cellular AMP and/or depletion of ATP, hyperosmotic stress, salt stress, ultraviolet B radiation and oxidative stress caused by hydrogen peroxide. Moreover, the regulation of SNARK activity in response to cellular stresses depends greatly upon cell type. Furthermore, SNARK activity is downregulated by metformin in a dose- and time-dependent manner in H4IIE cells. These observations support a role for SNARK as a molecular component of the cellular stress response.
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Affiliation(s)
- Diana L Lefebvre
- Department of Medicine, Division of Dermatology, University of Toronto, Toronto General Hospital, Banting Institute, Room 317, 100 College Street, Toronto, Ontario, Canada
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80
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Soloviev A, Lehen'kyi V, Zelensky S, Hellstrand P. Nitric oxide relaxes rat tail artery smooth muscle by cyclic GMP-independent decrease in calcium sensitivity of myofilaments. Cell Calcium 2005; 36:165-73. [PMID: 15193864 DOI: 10.1016/j.ceca.2004.02.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2003] [Revised: 01/26/2004] [Accepted: 02/10/2004] [Indexed: 11/18/2022]
Abstract
The effects of authentic nitric oxide (NO, 10(-6) M) and NO-donors such as sodium nitroprusside (SNP, 10(-5) M) and glyceryl trinitrate (GTN, 10(-4) M) on contractile force and free intracellular calcium level ([Ca2+]i) were studied on precontracted with high potassium chloride (KCl, 70 mM) isolated rings of rat tail artery. The sensitivity of contractile myofilaments to Ca2+ was measured using chemically permeabilized (alpha-toxin, beta-escin, Triton X-100) vascular rings. [Ca2+]i and contractile activity were measured simultaneously. The relationship of [Ca2+]i and tension developed was studied in endothelium-denuded rings and controlled calcium response was evaluated in both endothelium-denuded and permeabilized vascular rings. Both authentic NO and NO-donors decreased [Ca2+]i and high potassium-induced tension with a different time course. Inhibitor of soluble guanylyl cyclase (sGC) LY83583 (10(-5) M) did not affect SNP-induced relaxation whereas the other sGC inhibitor ODQ (10(-6) M) attenuated SNP-induced relaxation. Both inhibitors had no effect on NO- and SNP-induced reduction in [Ca2+]i. On the contrary, GTN induced neither relaxation nor decrease in [Ca2+]i on application of both LY83583 and ODQ. Tail artery rings permeabilized with alpha-toxin, beta-escin, but not with Triton X-100 were relaxed by authentic NO and NO-donors, but to a less extent than non-permeabilized rings. Dithioerythritol (DTE, 5 x 10(-3) M) that maintains sulfhydryl (SH) groups in reduced state preventing their nitrosylation attenuated NO-induced relaxation in both non-permeabilized and permeabilized tail artery rings. The cyclic heptapeptide mycrocystin-LR (MC-LR) (10(-5) M), an inhibitor of type 1 and 2A phosphatases, induced sustained increase in tension of beta-escin permeabilized rings in low Ca2+ (10(-8) M) solution. The tension was not affected by authentic NO and SNP. We conclude that authentic NO and SNP relax rat tail artery smooth muscle (SM) in the presence of inhibitors of sGC via cyclic guanosine monophosphate (cGMP)-independent pathway, whereas relaxation induced by GTN is inhibited. The data demonstrate that cGMP-dependent pathway in vascular smooth muscle is ubiquitous, but not the only way of relaxation induced by NO. NO can modulate vascular tone directly by reducing sensitivity of contractile myofilaments to [Ca2+]i and may involve activation of protein phosphatase(s).
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Affiliation(s)
- A Soloviev
- Department of Experimental Therapeutics, Institute of Pharmacology and Toxicology, Academy of Medical Sciences, 14 Ezhena Pot'e, 03057 Kiev, Ukraine.
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81
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Scholz-Starke J, Gambale F, Carpaneto A. Modulation of plant ion channels by oxidizing and reducing agents. Arch Biochem Biophys 2005; 434:43-50. [PMID: 15629107 DOI: 10.1016/j.abb.2004.06.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Revised: 06/11/2004] [Indexed: 12/19/2022]
Abstract
Ion channels are proteins forming hydrophilic pathways through the membranes of all living organisms. They play important roles in the electrogenic transport of ions and metabolites. Because of biophysical properties such as high selectivity for the permeant ion, high turnover rate, and modulation by physico-chemical parameters (e.g., membrane potential, calcium concentration), they are involved in several physiological processes in plant cells (e.g., maintenance of the turgor pressure, stomatal movements, and nutrient absorption by the roots). As plants cannot move, plant metabolism must be flexible and dynamic, to cope with environmental changes, to compete with other living species and to prevent pathogen invasion. An example of this flexibility and dynamic behavior is represented by their handling of the so-called reactive oxygen species, inevitable by-products of aerobic metabolism. Plants cope with these species on one side avoiding their toxic effects, on the other utilizing them as signalling molecules and as a means of defence against pathogens. In this review, we present the state-of-the-art of the modulation of plant ion channels by oxidizing and reducing agents.
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Affiliation(s)
- J Scholz-Starke
- Istituto di Biofisica, Genova, C.N.R., Via De Marini 6, 16149 Genova, Italy
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82
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Barrett DM, Black SM, Todor H, Schmidt-Ullrich RK, Dawson KS, Mikkelsen RB. Inhibition of protein-tyrosine phosphatases by mild oxidative stresses is dependent on S-nitrosylation. J Biol Chem 2005; 280:14453-61. [PMID: 15684422 DOI: 10.1074/jbc.m411523200] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have shown that a Ca(2+)-dependent nitric-oxide synthase (NOS) is activated as part of a cellular response to low doses of ionizing radiation. Genetic and pharmacological inhibitor studies linked this NO signaling to the radiation-induced activation of ERK1/2. Herein, a mechanism for the radiation-induced activation of Tyr phosphorylation-dependent pathways (e.g. ERK1/2) involving the inhibition of protein-Tyr phosphatases (PTPs) by S-nitrosylation is tested. The basis for this mechanism resides in the redox-sensitive active site Cys in PTPs. These studies also examined oxidative stress induced by low concentrations of H(2)O(2). S-Nitrosylation of total cellular PTP and immunopurified SHP-1 and SHP-2 was detected as protection of PTP enzymatic activity from alkylation by N-ethylmaleimide and reversal by ascorbate. Both radiation and H(2)O(2) protected PTP activity from alkylation by a mechanism reversible by ascorbate and inhibited by NOS inhibitors or expression of a dominant negative mutant of NOS-1. Radiation and H(2)O(2) stimulated a transient increase in cytoplasmic free [Ca(2+)]. Radiation, H(2)O(2), and the Ca(2+) ionophore, ionomycin, also stimulated NOS activity, and this was associated with an enhanced S-nitrosylation of the active site Cys(453) determined by isolation of S-nitrosylated wild type but not active site Cys(453) --> Ser SHP-1 mutant by the "biotin-switch" method. Thus, one consequence of oxidative stimulation of NO generation is S-nitrosylation and inhibition of PTPs critical in cellular signal transduction pathways. These results support the conclusion that a mild oxidative signal is converted to a nitrosative one due to the better redox signaling properties of NO.
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Affiliation(s)
- Daniel M Barrett
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia 23298-0058, USA
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83
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Hofseth LJ, Robles AI, Espey MG, Harris CC. Nitric Oxide Is a Signaling Molecule that Regulates Gene Expression. Methods Enzymol 2005; 396:326-40. [PMID: 16291242 DOI: 10.1016/s0076-6879(05)96027-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Nitric oxide (NO) is a dynamic and bioreactive molecule that can both participate in and inhibit the genesis of disease. Its ability to have an impact on a wide range of physiological events stems from its capacity to reversibly alter the expression of specific genes and the activities of a wide range of proteins and signaling pathways. Yet, NO* remains an enigmatic molecule. Recently developed technologies, including gene-chips, two-dimensional electrophoresis, RNA interference, matrix-assisted laser desorption ionization (MALDI)-TOF (time-of-flight) mass spectrometry, and protein arrays will allow us to better understand how NO* and associated reactive nitrogen species (RNS) regulate both physiology and disease states, toward the development of treatments using NO* synthase inhibitors or NO* donors.
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Affiliation(s)
- Lorne J Hofseth
- College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA
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84
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Howe CJ, Lahair MM, McCubrey JA, Franklin RA. Redox regulation of the calcium/calmodulin-dependent protein kinases. J Biol Chem 2004; 279:44573-81. [PMID: 15294913 DOI: 10.1074/jbc.m404175200] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Reactive oxygen intermediates (ROI) have been viewed traditionally as damaging to the cell. However, a predominance of evidence has shown that ROI can also function as important activators of key cellular processes, and ROI have been shown to play a vital role in cell signaling networks. The calcium/calmodulin-dependent protein kinases (CaM kinases) are a family of related kinases that are activated in response to increased intracellular calcium concentrations. In this report we demonstrate that hydrogen peroxide treatment results in the activation of both CaM kinase II and IV in Jurkat T lymphocytes. Surprisingly, this activation occurs in the absence of any detectable calcium flux, suggesting a novel means for the activation of these kinases. Treatment of Jurkat cells with phorbol 12-myristate 13-acetate (PMA), which does not cause a calcium flux, also activated the CaM kinases. The addition of catalase to the cultures inhibited PMA-induced activation of the CaM kinases, suggesting that similar to hydrogen peroxide, PMA also activates the CaM kinases via the production of ROI. One mechanism by which this likely occurs is through oxidation and consequential inactivation of cellular phosphatases. In support of this concept, okadaic acid and microcystin-LR, which are inhibitors of protein phosphatase 2A (PP2A), induced CaM kinase II and IV activity in these cells. Overall, these results demonstrate a novel mechanism by which ROI can induce CaM kinase activation in T lymphocytes.
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Affiliation(s)
- Christopher J Howe
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27834, USA
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85
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Chen F. Reactive Oxygen Species in the Activation and Regulation of Intracellular Signaling Events. OXYGEN/NITROGEN RADICALS 2004. [DOI: 10.1201/b14147-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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86
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Foley TD, Armstrong JJ, Kupchak BR. Identification and H2O2 sensitivity of the major constitutive MAPK phosphatase from rat brain. Biochem Biophys Res Commun 2004; 315:568-74. [PMID: 14975738 DOI: 10.1016/j.bbrc.2004.01.096] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Indexed: 11/20/2022]
Abstract
The present study examined in subcellular fractions from rat brain the nature and sensitivity to hydrogen peroxide of constitutively expressed mitogen-activated protein kinase (MAPK) phosphatase activity. MAPK phosphatase activity was defined as the activity directed towards a dual-phosphorylated (pT/pY) peptide corresponding to the activation domain of the extracellular-regulated kinase (ERK) subtype of the MAPKs. The use of phosphatase inhibitors and biochemical analyses demonstrate that the MAPK phosphatase activity, which was highest in the microsomal membrane and soluble fractions, was attributable mainly, if not entirely, to protein phosphatase 2A (PP2A). Moreover, hydrogen peroxide (in the absence and presence of reduced glutathione) and glutathione disulfide inhibited the MAPK phosphatase activity by a dithiothreitol-reversible mechanism. These results provide direct support for mounting evidence that PP2A is a major regulator of MAPK phosphorylation in brain and suggest that inhibition of PP2A activity via reversible oxidation of a cysteine thiol(s) may underlie at least in part the activation of MAPKs occurring in response to hydrogen peroxide and oxidative stress.
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Affiliation(s)
- Timothy D Foley
- Department of Chemistry, University of Scranton, Scranton, PA 18510, USA.
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87
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Lee M, Petrovics G, Anderson WB. The synergistic activation of Raf-1 kinase by phorbol myristate acetate and hydrogen peroxide in NIH3T3 cells. Biochem Biophys Res Commun 2003; 311:1026-33. [PMID: 14623285 DOI: 10.1016/j.bbrc.2003.10.107] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have previously demonstrated that a 33kDa C-terminal fragment of c-Raf-1 underwent a mobility shift in response to hydrogen peroxide (H(2)O(2)) and phorbol myristate acetate (PMA), respectively. In this study, we have demonstrated that H(2)O(2) induced the activation of N-terminal deletion mutant as well as full length Raf-1 kinase. The pharmacological PKC activator PMA also induced a weak increase in Raf-1 kinase activity through PKC-epsilon activation as determined by the transient expression of dominant negative mutants of PKC-epsilon-K436R. Interestingly, H(2)O(2) produced synergistic increase of PMA-stimulated Raf-1 kinase activation after simultaneous treatment of PMA and H(2)O(2). This synergistic activation of Raf-1 kinase was further enhanced by cypermethrin (an inhibitor of protein phosphatase 2B) and dephostatin (tyrosine kinase inhibitor) implying an inhibitory role for these phosphatases in the Raf-1 signaling pathway. Taken together, our data suggest that the synergistic activation of Raf-1 kinase in response to PMA and H(2)O(2) occurs via mechanisms that involve an interaction of Raf-1 kinase and PKC-epsilon, along with a transient phosphorylation of both Raf-1 kinase and PKC.
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Affiliation(s)
- Michael Lee
- Korea Institute of Toxicology, Korea Research Institute of Chemical Technology, P.O. Box 123, Yusong, 305-600, Daejeon, Republic of Korea.
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88
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Oishi K, Miyazaki K, Kadota K, Kikuno R, Nagase T, Atsumi GI, Ohkura N, Azama T, Mesaki M, Yukimasa S, Kobayashi H, Iitaka C, Umehara T, Horikoshi M, Kudo T, Shimizu Y, Yano M, Monden M, Machida K, Matsuda J, Horie S, Todo T, Ishida N. Genome-wide expression analysis of mouse liver reveals CLOCK-regulated circadian output genes. J Biol Chem 2003; 278:41519-27. [PMID: 12865428 DOI: 10.1074/jbc.m304564200] [Citation(s) in RCA: 272] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CLOCK is a positive component of a transcription/translation-based negative feedback loop of the central circadian oscillator in the suprachiasmatic nucleus in mammals. To examine CLOCK-regulated circadian transcription in peripheral tissues, we performed microarray analyses using liver RNA isolated from Clock mutant mice. We also compared expression profiles with those of Cryptochromes (Cry1 and Cry2) double knockout mice. We identified more than 100 genes that fluctuated from day to night and of which expression levels were decreased in Clock mutant mice. In Cry-deficient mice, the expression levels of most CLOCK-regulated genes were elevated to the upper range of normal oscillation. Most of the screened genes had a CLOCK/BMAL1 binding site (E box) in the 5'-flanking region. We found that CLOCK was absolutely concerned with the circadian transcription of one type of liver genes (such as DBP, TEF, and Usp2) and partially with another (such as mPer1, mPer2, mDec1, Nocturnin, P450 oxidoreductase, and FKBP51) because the latter were damped but remained rhythmic in the mutant mice. Our results showed that CLOCK and CRY proteins are involved in the transcriptional regulation of many circadian output genes in the mouse liver. In addition to being a core component of the negative feedback loop that drives the circadian oscillator, CLOCK also appears to be involved in various physiological functions such as cell cycle, lipid metabolism, immune functions, and proteolysis in peripheral tissues.
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Affiliation(s)
- Katsutaka Oishi
- Clock Cell Biology Research Group, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
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89
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Kim HS, Song MC, Kwak IH, Park TJ, Lim IK. Constitutive induction of p-Erk1/2 accompanied by reduced activities of protein phosphatases 1 and 2A and MKP3 due to reactive oxygen species during cellular senescence. J Biol Chem 2003; 278:37497-510. [PMID: 12840032 DOI: 10.1074/jbc.m211739200] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The mechanism of senescence-associated cytoplasmic induction of p-Erk1/2 (SA-p-Erk1/2) proteins in human diploid fibroblasts was investigated. p-Erk1/2 proteins were efficiently dephosphorylated in vitro by protein phosphatases 1 and 2A (PP1/2A) and MAPK phosphatase 3 (MKP3). Specific activity of PP1/2A and MKP3 activity significantly decreased during cellular senescence, whereas their protein expression levels did not. To investigate possible mechanism of phosphatase inactivation, we measured reactive oxygen species (ROS) generation by fluorescence-activated cell sorting analysis and found it was much higher in mid-old cells than the young cells. Treating the young cells once with 1 mm H2O2 remarkably induced p-Erk1/2 expression; however, it was transient unless repeatedly treated until 72 h. Multiple treatment of the cells with 0.2 mm H2O2 significantly duplicated inactivation of PP1/2A; however, thiol-specific reagents could reverse the PP1/2A activities, suggesting the oxidation of cysteine molecule in PP1/2A by the increased ROS. When the cells were pretreated with 10 mm N-acetyl-l-cysteine for 1 h, Erk1/2 activation was completely blocked. To elucidate which cysteine residue and/or metal ion in PP1/2A was modified by H2O2, electrospray ionization-tandem mass spectrometry analyses were performed with purified PP1C-alpha and found Cys62-SO3H and Cys105-SO3H, implicating the tertiary structure perturbation. H2O2 inhibited purified PP1C-alpha activity by both oxidation of Cys residues and metal ion(s), evidenced by dithiothreitol and ascorbate-restoration assay. In summary, SA-p-Erk1/2 was most likely due to the oxidation of PP1/2A, which resulted from the continuous exposure of the cells to vast amounts of ROS generated during cellular senescence by oxidation of Cys62 and Cys105 in PP1C-alpha and metal ion(s).
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Affiliation(s)
- Hong Seok Kim
- Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 442-721, Korea
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90
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O'Loghlen A, Pérez-Morgado MI, Salinas M, Martín ME. Reversible inhibition of the protein phosphatase 1 by hydrogen peroxide. Potential regulation of eIF2 alpha phosphorylation in differentiated PC12 cells. Arch Biochem Biophys 2003; 417:194-202. [PMID: 12941301 DOI: 10.1016/s0003-9861(03)00368-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Oxidative inactivation of protein tyrosine phosphatases and calcineurin is a well established mechanism; however, little information with regard to the effect of oxidants on PP1 and PP2A activity is available. Herein, we show that PP1 activity is inhibited by H(2)O(2) treatment in differentiated PC12 cells both in vitro and in vivo experiments. Thiol-antioxidant N-acetyl-cysteine (NAC) and reduced glutathione (GSH), when added in vitro to lysates from H(2)O(2)-treated cells, reversed PP1 inhibition. H(2)O(2) treatment increased eIF2 alpha phosphorylated levels (eIF2 alpha P) in a time- and dose-dependent fashion and promoted protein synthesis inhibition. Interestingly, NAC pretreatment protected cells from H(2)O(2)-induced PP1 inactivation and, consequently, it abolished increased H(2)O(2)-induced eIF2 alpha phosphorylation and protein synthesis inhibition. In addition, PP1 inhibitor tautomycin prevented both NAC-induced PP1 reactivation and eIF2 alpha P dephosphorylation in H(2)O(2)-treated cells. Taken together, our findings support a role for PP1 in eIF2 alpha phosphorylation and oxidative stress-triggered translation down regulation.
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Affiliation(s)
- A O'Loghlen
- Departamento de Investigación, Hospital Ramón y Cajal, 28034 Madrid, Spain
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91
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Atmane N, Dairou J, Paul A, Dupret JM, Rodrigues-Lima F. Redox regulation of the human xenobiotic metabolizing enzyme arylamine N-acetyltransferase 1 (NAT1). Reversible inactivation by hydrogen peroxide. J Biol Chem 2003; 278:35086-92. [PMID: 12832400 DOI: 10.1074/jbc.m303813200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Oxidative stress is increasingly recognized as a key mechanism in the biotransformation and/or toxicity of many xenobiotics. Human arylamine N-acetyltransferase 1 (NAT1) is a polymorphic ubiquitous phase II xenobiotic metabolizing enzyme that catalyzes the biotransformation of primary aromatic amine or hydrazine drugs and carcinogens. Functional and structural studies have shown that NAT1 catalytic activity is based on a cysteine protease-like catalytic triad, containing a reactive cysteine residue. Reactive protein cysteine residues are highly susceptible to oxidation by hydrogen peroxide (H2O2) generated within the cell. We, therefore, investigated whether human NAT1 activity was regulated by this cellular oxidant. Using purified recombinant NAT1, we show here that NAT1 is rapidly (kinact = 420 m-1.min-1) inactivated by physiological concentrations of H2O2. Reducing agents, such as reduced glutathione (GSH), reverse the H2O2-dependent inactivation of NAT1. Kinetic analysis and protection experiments with acetyl-CoA, the physiological acetyl-donor substrate of the enzyme, suggested that the H2O2-dependent inactivation reaction targets the active-site cysteine residue. Finally, we show that the reversible inactivation of NAT1 by H2O2 is due to the formation of a stable sulfenic acid group at the active-site cysteine. Our results suggest that, in addition to known genetically controlled interindividual variations in NAT1 activity, oxidative stress and cellular redox status may also regulate NAT1 activity. This may have important consequences with regard to drug biotransformation and cancer risk.
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Affiliation(s)
- Noureddine Atmane
- CNRS-UMR 7000, Faculté de Médecine Pitié-Salpêtrière, 75013 Paris, France
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