Structural characteristics of a lipid peroxidation product, trans-2-nonenal, that favour inhibition of membrane-associated phosphotyrosine phosphatase activity

Modulation in the expression of SHP-1, SHP-2 and PTP1B due to the inhibition of MAPKs, cAMP and neutrophils early on in the development of cerulein-induced acute pancreatitis in rats

The protein tyrosine phosphatases (PTPs) SHP-1, SHP-2 and PTP1B are overexpressed early on during the development of cerulein -induced acute pancreatitis (AP) in rats, and their levels can be modulated by some species of mitogen-activated protein kinases (MAPKs), the intracellular levels of cAMP and by general leukocyte infiltration, the latter at least for SHP-2 and PTP1B. In this study we show that cerulein treatment activates extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) but not p38 MAPK during the early phase of cerulein-induced AP (2h after the first injection of cerulein). Therefore, by using the MAPK inhibitors SP600125 (a specific JNK inhibitor) and PD98059 (a specific ERK inhibitor), we have unmasked the particular MAPK that underlies the modulation of the expression levels of these PTPs. JNK would act by preventing SHP-1 protein expression from increasing beyond a certain level. ERK 1/2 was the main MAPK involved in the increase in SHP-2 protein expression due to cerulein. JNK negatively modulated the SH2-domain containing PTPs. Both MAPKs played a role in the increase in PTP1B protein expression due to cerulein. Finally, by using the white blood cell inhibitors vinblastine sulfate, gadolinium chloride and FK506 (tacrolimus), we show that the macrophage activity or T-lymphocytes does not modulate the expression of any of the PTPs, although neutrophil infiltration was found to be a regulator of SHP-2 and PTP1B protein expression due to cerulein.

Redox regulation of protein tyrosine phosphatases: methods for kinetic analysis of covalent enzyme inactivation

Phosphorylation of tyrosine residues is an important posttranslational modification that modulates the function of proteins involved in many important cell signaling pathways. Protein tyrosine kinases and protein tyrosine phosphatases (PTPs) work in tandem to control the phosphorylation status of target proteins. Not surprisingly, the activity of some PTPs is regulated as part of the endogenous cellular mechanisms for controlling the intensity and duration of responses to various stimuli. One important mechanism for the regulation of PTPs involves endogenous production of hydrogen peroxide (H2O2) that inactivates enzymes via covalent modification of an active site cysteine thiolate group. Other endogenous metabolites and xenobiotics that inactivate PTPs via covalent mechanisms also have the potential to modulate signal transduction pathways and may possess either therapeutic or toxic properties. This chapter discusses methods for quantitative kinetic analysis of covalent inactivation of PTPs by small molecules.

Hydroxyalkenals and oxidized phospholipids modulation of endothelial cytoskeleton, focal adhesion and adherens junction proteins in regulating endothelial barrier function

Lipid peroxidation of polyunsaturated fatty acids generates bioactive aldehydes, which exhibit pro- and anti-inflammatory effects in cells and tissues. Accumulating evidence indicates that 4-hydroxynonenal (4-HNE), a major aldehyde derived from lipid peroxidation of n-6 polyunsaturated fatty acids trigger signals that modulates focal adhesion and adherens junction proteins thereby inducing endothelial barrier dysfunction. Similarly, oxidized phospholipids (Ox-PLs) generated by lipid peroxidation of phospholipids with polyunsaturated fatty acids have been implicated in atherogenesis, inflammation and gene expression. Interestingly, physiological concentration of Ox-PLs is anti-inflammatory and protect against endotoxin- and ventilator-associated acute lung injury. Thus, excess generation of bioactive hydroxyalkenals and Ox-PLs during oxidative stress contributes to pathophysiology of various diseases by modulating signaling pathways that regulate pro- and anti-inflammatory responses and barrier regulation. This review summarizes the role of 4-HNE and Ox-PLs affecting cell signaling pathways and endothelial barrier dysfunction through modulation of the activities of proteins/enzymes by Michael adducts formation, enhancing the level of protein tyrosine phosphorylation of the target proteins, and by reorganization of cytoskeletal, focal adhesion, and adherens junction proteins. A better understanding of molecular mechanisms of hydroxyalkenals- and Ox-PLs-mediated pro-and anti-inflammatory responses and barrier function may lead to development of novel therapies to ameliorate oxidative stress related cardio-pulmonary disorders.

Photo-oxidation of proteins

Photo-induced damage to proteins occurs via multiple pathways. Direct damage induced by UVB (λ 280-320 nm) and UVA radiation (λ 320-400 nm) is limited to a small number of amino acid residues, principally tryptophan (Trp), tyrosine (Tyr), histidine (His) and disulfide (cystine) residues, with this occurring via both excited state species and radicals. Indirect protein damage can occur via singlet oxygen ((1)O(2)(1)Δ(g)), with this resulting in damage to Trp, Tyr, His, cystine, cysteine (Cys) and methionine (Met) residues. Although initial damage is limited to these residues multiple secondary processes, that occur both during and after radiation exposure, can result in damage to other intra- and inter-molecular sites. Secondary damage can arise via radicals (e.g. Trp, Tyr and Cys radicals), from reactive intermediates generated by (1)O(2) (e.g. Trp, Tyr and His peroxides) and via molecular reactions of photo-products (e.g. reactive carbonyls). These processes can result in protein fragmentation, aggregation, altered physical and chemical properties (e.g. hydrophobicity and charge) and modulated biological turnover. Accumulating evidence implicates these events in cellular and tissue dysfunction (e.g. apoptosis, necrosis and altered cell signaling), and multiple human pathologies.

The effects of acrolein on the thioredoxin system: implications for redox-sensitive signaling

The reactive aldehyde acrolein is a ubiquitous environmental pollutant and is also generated endogenously. It is a strong electrophile and reacts rapidly with nucleophiles including thiolates. This review focuses on the effects of acrolein on thioredoxin reductase (TrxR) and thioredoxin (Trx), which are major regulators of intracellular protein thiol redox balance. Acrolein causes irreversible effects on TrxR and Trx, which are consistent with the formation of covalent adducts to selenocysteine and cysteine residues that are key to their activity. TrxR and Trx are more sensitive than some other redox-sensitive proteins, and their prolonged inhibition could disrupt a number of redox-sensitive functions in cells. Among these effects are the oxidation of peroxiredoxins and the activation of apoptosis signal regulating kinase (ASK1). ASK1 promotes MAP kinase activation, and p38 activation contributes to apoptosis and a number of other acrolein-induced stress responses. Overall, the disruption of the TrxR/Trx system by acrolein could be significant early and prolonged events that affect many aspects of redox-sensitive signaling and oxidant stress.

Reactive oxygen species: are they important for haematopoiesis?

The production of reactive oxygen species (ROS) has traditionally been related to deleterious effects for cells. However, it is now widely accepted that ROS can play an important role in regulating cellular signalling and gene expression. NADPH oxidase ROS production seems to be especially important in this regard. Some lines of evidence suggest that ROS may be important modulators of cell differentiation, including haematopoietic differentiation, in both physiologic and pathologic conditions. Here we shall review how ROS can regulate cell signalling and gene expression. We shall also focus on the importance of ROS for haematopoietic stem cell (HSC) biology and for haematopoietic differentiation. We shall review the involvement of ROS and NADPH oxidases in cancer, and in particular what is known about the relationship between ROS and haematological malignancies. Finally, we shall discuss the use of ROS as cancer therapeutic targets.

Rolipram and SP600125 suppress the early increase in PTP1B expression during cerulein-induced pancreatitis in rats

OBJECTIVES

To analyze the expression modulation of pancreatic protein tyrosine phosphatase (PTP)1B during the development of cerulein (Cer)-induced acute pancreatitis (AP) and the effect of inhibition of type 4 phosphodiesterase and c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2 on its expression levels.

METHODS

Acute pancreatitis was induced in rats by subcutaneous injections of 20 microg Cer per kilogram body weight at hourly intervals, and the animals were killed at 2, 4, or 9 hours after the first injection. Neutropenia was induced with vinblastine sulfate. Phosphodiesterase and the mitogen-activated protein kinases were inhibited with rolipram and SP600125, respectively, before the induction of AP.

RESULTS

Protein tyrosine phosphatase 1B increases its expression at the levels of both protein and messenger RNA during the early phase of Cer-induced AP. The increase in protein expression persisted along the development of the disease, and neutrophil infiltration seemed to play a central role. Rolipram and SP600125 pretreatments mostly suppressed the increase in the expression of PTP1B during the early phase of AP.

CONCLUSIONS

Cerulein-induced AP is associated with an increase in the expression of PTP1B in its early phase. An increase in cyclic adenosine monophosphate levels in inflammatory cells and the inhibition of c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2 are able to suppress the increase in PTP1B protein level.

Platelet linoleic acid is a potential biomarker of advanced non-small cell lung cancer

New parameters that could be used as tumor markers for lung cancer would be valuable. Our aim was to analyze the fatty acid profiles of total lipids from erythrocytes and platelets from patients with advanced non-small cell lung cancer (NSCLC), chronic obstructive pulmonary disease (COPD) and asthma to reveal the fatty acids that could be used as NSCLC biomarkers. In our study, 50, 15 and 15 patients with advanced NSCLC, COPD and asthma and 50 healthy subjects were enrolled. Fatty acid profiles were investigated using gas chromatography/mass spectrometry followed by ROC (receiver operating characteristics) curves analysis to gain information about biomarkers. Sialic acid (SA) and cytokeratins were measured by the thiobarbituric acid and immunoradiometric methods respectively. Useful fatty acid markers were as follows: erythrocytes, 22:0 and linoleic acid (LA, 18:2n6); platelets, 16:0, 18:0, and LA. At the cutoff value to obtain maximum accuracy, the best biomarker was platelet LA, with higher diagnostic yields than the commonly used markers SA or cytokeratins (100%, 76%, 75% and 86% sensitivity, specificity, positive predictive value and accuracy, respectively). These findings suggest that platelet LA might be used as a biomarker of NSCLC in relation to different aspects of the disease process that now needs to be explored.

Erythrocyte and platelet phospholipid fatty acids as markers of advanced non-small cell lung cancer: comparison with serum levels of sialic acid, TPS and Cyfra 21-1

The phospholipid fatty acid profiles of erythrocytes and platelets from fifty patients with advanced non-small cell lung cancer were investigated using gas chromatography/mass spectrometry, followed by "ROC" curves analysis to gain novel biomarker information. Sialic acid and cytokeratins were also examined. Potentially useful fatty acid markers: Erythrocytes: phosphatidylcholine, 18:2n6 and 20:4n6; phosphatidylethanolamine, 22:4n6 and 22:6n3 + 24:1n9. Platelets: phosphatidylcholine, 22.0; phosphatidylethanolamine, 22:5n3 + 24:0. At the cut-off value to obtain maximum accuracy, the best biomarkers were found in platelets: phosphatidylserine + phosphatidylinositol (PS + PI), 21:0; sphyngomyelin: 20:1n9 and 22:1n9. All these fatty acids showed similar/higher diagnostic yields than the commonly used markers sialic acid or cytokeratins.

SHP-1 inhibition by 4-hydroxynonenal activates Jun N-terminal kinase and glutamate cysteine ligase

4-Hydroxy-2-nonenal (HNE), a major lipid peroxidation product, is toxic at high concentrations, but at near-physiological concentrations it induces detoxifying enzymes. Previous data established that in human bronchial epithelial (HBE1) cells, both genes for glutamate cysteine ligase (GCL) are induced by HNE through the c-Jun N-terminal kinase (JNK) pathway. The protein-tyrosine phosphatase SH2 domain containing phosphatase-1 (SHP-1) is thought to play a role as a negative regulator of cell signaling, and has been implicated as such in the JNK pathway. In the present study, SHP-1 was demonstrated to contribute to HNE-induced-gclc expression via regulation of the JNK pathway in HBE1 cells. Treatment of HBE1 cells with HNE induced phosphorylation of mitogen-activated protein kinase kinase 4 (MKK4), JNK, and c-Jun. HNE was able to inhibit protein tyrosine phosphatase activity of SHP-1 through increased degradation of the protein. Furthermore, transfection with small interference RNA SHP-1 showed an enhancement of JNK and c-Jun phosphorylation, but not of MKK4, leading to increased gclc expression. These results demonstrate that SHP-1 plays a role as a negative regulator of the JNK pathway and that HNE activated the JNK pathway by inhibiting SHP-1. Thus, SHP-1 acts as a sensor for HNE and is responsible for an important adaptive response to oxidative stress.

Changes in the expression and dynamics of SHP-1 and SHP-2 during cerulein-induced acute pancreatitis in rats

Protein tyrosine phosphatases (PTPs) are important regulators of cell functions but data on different PTP expression and dynamics in acute pancreatitis (AP) are very scarce. Additionally, both c-Jun N-terminal kinases (JNK) and extracellular signal-regulated kinases (ERK1/2), together with intracellular cAMP levels in inflammatory cells, play an essential role in AP. In this study we have detected an increase in PTP SHP-1 and SHP-2 in the pancreas at the level of both protein and mRNA as an early event during the development of Cerulein (Cer)-induced AP in rats. Nevertheless, while SHP-2 protein returned to baseline levels in the intermediate or later phases of AP, SHP-1 protein expression remained increased throughout the development of the disease. The increase in SHP-2 protein expression was associated with changes in its subcellular distribution, with higher percentages located in the fractions enriched in lysosomes+mitochondria or microsomes. Furthermore, while the increase in SHP-2 protein was also observed in sodium-taurocholate duct infusion or bile-pancreatic duct obstruction AP, that of SHP-1 was specific to the Cer-induced model. Neutrophil infiltration did not affect the increase in SHP-1 protein, but favoured the return of SHP-2 protein to control levels, as indicated when rats were rendered neutropenic by the administration of vinblastine sulfate. Inhibition of JNK and ERK1/2 with SP600125 pre-treatment further increased the expression of both SHP-1 and SHP-2 proteins in the early phase of Cer-induced AP, while the inhibition of type IV phosphodiesterase with rolipram only suppressed the increase in SHP-2 protein expression during the same phase. Our results show that AP is associated with increases in the expression of SHP-1 and SHP-2 and changes in the dynamics of SHP-2 subcellular distribution in the early phase of Cer-induced AP. Finally, both JNK and ERK1/2 and intracellular cAMP levels are able to modulate the expression of these PTPs.

Kinetics and mechanism of protein tyrosine phosphatase 1B inactivation by acrolein

Human cells are exposed to the electrophilic alpha,beta-unsaturated aldehyde acrolein from a variety of sources. The reaction of acrolein with functionally critical protein thiol residues can yield important biological consequences. Protein tyrosine phosphatases (PTPs) are an important class of cysteine-dependent enzymes whose reactivity with acrolein previously has not been well-characterized. These enzymes catalyze the dephosphorylation of phosphotyrosine residues on proteins via a phosphocysteine intermediate. PTPs work in tandem with protein tyrosine kinases to regulate a number of critically important mammalian signal transduction pathways. We find that acrolein is a potent time-dependent inactivator of the enzyme PTP1B ( k inact = 0.02 +/- 0.005 s (-1) and K I = 2.3 +/- 0.6 x 10 (-4) M). The enzyme activity does not return upon gel filtration of the inactivated enzyme, and addition of the competitive phosphatase inhibitor vanadate slows inactivation of PTP1B by acrolein. Together, these observations suggest that acrolein covalently modifies the active site of PTP1B. Mass spectrometric analysis reveals that acrolein modifies the catalytic cysteine residue at the active site of the enzyme. Aliphatic aldehydes such as glyoxal, acetaldehyde, and propanal are relatively weak inactivators of PTP1B under the conditions employed here. Similarly, unsaturated aldehydes such as crotonaldehyde and 3-methyl-2-butenal bearing substitution at the alkene terminus are poor inactivators of the enzyme. Overall, the data suggest that enzyme inactivation occurs via conjugate addition of the catalytic cysteine residue to the carbon-carbon double bond of acrolein. The results indicate that inactivation of PTPs should be considered as a possible contributor to the diverse biological activities of acrolein and structurally related alpha,beta-unsaturated aldehydes.

Comparison of changes in erythrocyte and platelet phospholipid and fatty acid composition and protein oxidation in chronic obstructive pulmonary disease and asthma

OBJECTIVE

To analyse and compare the phospholipid and fatty acid composition of total lipids and the occurrence of lipid peroxidation and protein oxidation directly in erythrocytes or platelets from chronic obstructive pulmonary disease (COPD) and asthma patients.

PATIENTS

Fifteen consecutive outpatients with COPD (all smokers) and asthma (non-smokers) recruited during a moderate-to-severe (COPD) or moderate (asthma) exacerbation. Fifteen subjects with smoking habits similar to those of COPD patients were studied as a control group.

METHODS

Phospholipid and total fatty acid compositions were analysed by two-dimensional thin layer chromatography or gas chromatography-mass spectrometry, respectively. The lipid fluorescence of lipid extracts was measured by spectrofluorimetry. Protein carbonyl contents and profiles were measured by immunoblot detection.

RESULTS

No differences were found either in erythrocyte or platelet cholesterol or phospholipid levels. Only a decrease in the content of phosphatidylserine + phosphatidylinositol (P<0.003) was detected in platelets from the asthma patients. In erythrocytes, the fatty acid profile changed in both lung pathologies, especially as regards polyunsaturated fatty acids (decreases in arachidonic and 22:4 fatty acid contents). Other observed changes were: COPD, an increase in palmitic fatty acid; asthma, an increase in oleic and decreases in eicosapentaenoic and 22:6 + 24:1 fatty acids. In platelets, the fatty acid profiles revealed many differences between both lung pathologies: COPD, a decrease in 18:1 and increases in 20:5 and 22:5 + 24:0; asthma, a decrease in 20:4 and increase in 22:6 + 24:1. In COPD vs. asthma patients, fatty acid changes were mainly detected in platelets, especially in 18-carbon species, with decreases in stearic and 18:1 fatty acids in the COPD patients. Protein oxidation levels were increased in both lung pathologies in both erythrocytes and platelets.

CONCLUSIONS

COPD and asthma are associated with common or specific changes in the lipid composition of erythrocytes and/or platelets. The data point to lipid peroxidation and protein oxidation phenomena in both types of blood cell, although platelets would be more susceptible to stress.

Alterations in erythrocyte membrane protein composition in advanced non-small cell lung cancer

Cancer can be associated with hematological complications related to red blood cell (RBC) function, whose physiological roles have now been expanded since it is now known that RBC are also signalling cells. The aim of this study was to explore the alterations occurring in the protein composition of RBC in advanced non-small cell lung cancer (NSCLC). Blood samples from 21 patients with advanced (stages III-IV) NSCLC (16 squamous cell carcinomas and 5 adenocarcinomas), and from 21 healthy volunteers were used. Samples from 6 randomly selected patients and 6 controls were used for the screening of erythrocyte ghost alterations by Differential Scanning Calorimetry (DSC). Samples from 15 patients and 15 controls, different from those used in the DSC measurements, were randomly selected for analysis of the expression of glycophorin (GP) species, band 3, and glycoproteins by SDS-PAGE and Western blotting or lectin enzyme immunoassays. Additionally, 5 patients with chronic obstructive pulmonary disease (COPD) were used as a control group representative of a benign inflammatory disease. Blood samples from the COPD patients were used to analyze the expression of GPs, band 3 and syaloglycoproteins. We observed the following in NSCLC: (a) changes in GP expression levels, mainly decreases in the GPA and GPC monomers, and in the GPAB dimers; (b) a decrease in the band 3 protein level, and (c) alterations in the expression of different sialoglycoproteins. RBC from the COPD patients also showed protein abnormalities, some of them, especially at the level of band 3 and the syaloglycoproteins, being similar to those in NSCLC.