Generation of reactive oxygen species and activity of platelet-activating factor acetylhydrolase in human monocyte-derived macrophages

p47phox and reactive oxygen species production modulate expression of microRNA-451 in macrophages

The production of microRNAs (miRNA) is influenced by various stimuli, including environmental stresses. We hypothesized that reactive oxygen species (ROS)-associated stress could regulate macrophage miRNA synthesis. miRNAs undergo unique steps of maturation processing through either one of two pathways of cytoplasmic processing. Unlike the canonical pathway, the regulation of alternative cytoplasmic processing of miRNA has not been fully elucidated yet. We cultured bone marrow derived macrophages (BMDM) from wild type (WT) and p47(phox-/-) mice and profiled miRNA expression using microarrays. We analyzed 375 miRNAs including four endogenous controls to normalize the data. At resting state, p47(phox-/-) BMDM has the markedly reduced expression of miR-451 compared to WT BMDM, without other significant differences. Unlike majority of miRNAs, miR-451 goes through the unique alternative processing pathway, in which Ago2 plays a key role. In spite of significant reduction of mature miR-451, however, its precursor form, pre-mir-451, was similar in both BMDMs, suggesting that the processing of pre-mir-451 is impaired in p47(phox-/-) BMDM. Moreover, p47(phox-/-) BMDM expressed significantly reduced level of Ago2. In contrast, Ago2 mRNA levels were similar in WT and p47(phox-/-) BMDM, suggesting a post-transcriptional defect of Ago2 production in p47(phox-/-) macrophages, which resulted in impaired processing of pre-miR-451. In order to examine the functional significance of miR-451 in macrophages, we cultured BMDMs from miR-451 knock-out mice. Of interest, miR-451-deficient BMDM exhibited reduced ROS generation upon zymosan stimulation, compared to WT BMDM. Our studies suggest functional crosstalk between ROS and miR-451 in the regulation of macrophage oxidant stress.

Oral administration of alkaloid fraction from Ruta graveolens inhibits oxidative stress and inflammation in hypercholesterolemic rabbits

CONTEXT

The anti-atherogenic effect of alkaloid fraction from Ruta graveolens Linn (Rutaceae) extract is suspected to be related to its activities of antioxidation and anti-inflammation.

OBJECTIVE

This study investigated the efficacy of alkaloid fraction isolated from Ruta graveolens (AFR) in reducing oxidative damage and inflammation in hypercholesteremic rabbits.

MATERIALS AND METHODS

The New Zealand white rabbits were randomly divided into three groups: Group I rabbits were fed with normal chow diet for 90 d. Group II rabbits were fed with 1% cholesterol-enriched diet. Group III rabbits were fed with 1% cholesterol-enriched diet together with AFR (10 mg/kg/daily for 90 d).

RESULTS AND DISCUSSION

The results showed that on treatment with AFR significantly lowered the level of total cholesterol and LDL-C and showed an increment in the level of HDL-C. LD50 of the AFR in rats is greater than 525 mg/kg. Activities of antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase and GSH level were decreased in cholesterol-fed rabbit and supplementation of AFR significantly enhanced the activities of these antioxidant enzymes and GSH level. Increased activities of enzymes such as cyclooxygenase-2, 15-lipoxygenase and myeloperoxidase were significantly suppressed by AFR administration. The acute phase proteins, total WBC count and TBARS concentrations were significantly increased by hypercholesteromic diet, which were significantly decreased by AFR treatment. Histopathological studies of aorta in cholesterol-fed rabbit showed plaque formation and significant changes in aortic wall. Administration of AFR showed no changes in aortic wall.

CONCLUSION

AFR reduces oxidative stress and inflammation and reduces the aortic pathology in hypercholesteromic rabbits.

Pivotal role of reactive oxygen species in differential regulation of lipopolysaccharide-induced prostaglandins production in macrophages

Gram-negative bacterial endotoxin lipopolysaccharide (LPS) triggers the production of inflammatory cytokines, reactive oxygen species (ROS), and prostaglandins (PGs) by pulmonary macrophages. Here, we investigated if ROS influenced PGs production in response to LPS treatment in mouse bone marrow-derived macrophages (BMDM). We observed that pretreatment of BMDM with two structurally unrelated ROS scavengers, MnTMPyP and EUK-134, not only prevented LPS-induced ROS accumulation, but also attenuated the LPS-induced PGD(2), but not PGE(2), production. Conversely LPS-induced PGD(2), but not PGE(2), production, was potentiated with the cotreatment of BMDM with H(2)O(2). These data suggest that ROS differentially regulate PGD(2) and PGE(2) production in BMDM. In addition, selective inhibition of the ROS generator NADPH oxidase (NOX) using either pharmacologic inhibitors or its p47(phox) subunit deficient mouse BMDM also attenuated LPS-induced PGD(2), but not PGE(2) production, suggesting the critical role of NOX-generated ROS in LPS-induced PGD(2) production in BMDM. We further found that both hematopoietic PGD synthase (H-PGDS) siRNA and its inhibitor HQL-79, but not lipocalin PGDS (L-PGDS) siRNA and its inhibitor AT-56, significantly attenuated LPS-induced PGD(2) production, suggesting that H-PGDS, but not L-PGDS, mediates LPS-induced PGD(2) production in BMDM. Furthermore, data from our in vitro cell-free enzymatic studies showed that coincubation of the recombinant H-PGDS with either MnTMPyP, EUK-134, or catalase significantly decreased PGD(2) production, whereas coincubation with H(2)O(2) significantly increased PGD(2) production. Taken together, our results show that LPS-induced NOX-generated ROS production differentially and specifically regulates the H-PGDS-mediated production of PGD(2), but not PGE(2), in mouse BMDM.

Correlation Between Inflammation and Oxidative Stress in Normocholesterolemic Coronary Artery Disease Patients ‘on’ and ‘off’ Atorvastatin for Short Time Intervals

AIM OF THE STUDY

To assess whether variations in antioxidant and anti-inflammatory parameters occur with short term administration and discontinuation of atorvastatin in normocholesterolemic coronary artery disease (CAD) patients.

METHODS

Forty CAD patients with near normal serum cholesterol levels (total cholesterol <240 mg/dl, LDL cholesterol <130 mg/dl) were continuously enrolled and randomized to groups A and B (20 patients taking atorvastatin) and groups C and D (20 patients not taking atorvastatin). Atorvastatin (10 mg/day) was continued in group A, withdrawn in group B and started in groups C and D for 6 weeks. Thereafter atorvastatin was withdrawn in group A and C, restarted in group B, and continued in group D for further 6 weeks. CRP, FRAP and TBARS were assessed at baseline, 6 weeks and 12 weeks in all the groups.

RESULTS

Baseline CRP, TBARS and FRAP levels were significantly different (p < 0.05) between groups A and B and C and D at the time of enrollment, indicating lower levels of oxidative stress (FRAP-172.40 +/- 23.41 nmol Fe(2+)/l vs 142.62 +/- 15.73 nmol Fe(2+)/l and TBARS-3.66 +/- 1.14 nmol/ml vs 6.11 +/- 1.85 nmol/ml) and low grade inflammation (CRP-1.38 +/- 0.69 mg/l vs 3.19 +/- 1.77 mg/l) in statin treated groups. In group B, discontinuation resulted in increase in CRP (2.87 +/- 0.98 mg/l) and TBARS (5.75 +/- 1.35 nmol/ml) and decrease in FRAP (133.132 +/- 13.32 nmol Fe(2+)/l) and whereas group A patients did not show significant variation in values compared to baseline (CRP-1.36 +/- 0.33 mg/l, FRAP-155.45 +/- 19.51 and TBARS-4.22 +/- 0.81). Administration of atorvastatin caused a marked reduction in oxidative stress and inflammation in groups C and D (CRP-1.13 +/- 0.99 mg/l and 1.73 +/- 1.60 mg/l, FRAP-166.54 +/- 34.11 and 177.44 +/- 13.31 nmol Fe(2+)/l, TBARS-4.66 +/- 2.33 and 3.55 +/- 1.25 nmol/ml respectively). The values returned to pretreatment levels on discontinuation of the drug in group C (CRP-2.61 +/- 1.28 mg/l, FRAP-138.49 +/- 19.62 nmol Fe(2+)/l, TBARS-6.13 +/- 0.74 nmol/ml) whereas the decline was maintained in group D (CRP-1.62 +/- 1.48 mg/l, FRAP-173.07 +/- 9.03 nmol Fe(2+)/l, TBARS-3.75 +/- 1.03 nmol/ml).

CONCLUSION

Administration and withdrawal of atorvastatin caused changes in markers of oxidative stress which closely correlated with changes in marker of inflammation. Further, the salutary effects were of quick onset, but were rapidly reversed on withdrawal of atorvastatin.

Plasma platelet-activating factor acetylhydrolase activity in critically ill patients

OBJECTIVE

Platelet-activating factor (PAF) is a potent proinflammatory mediator in systemic inflammation and sepsis and is inactivated by the enzyme PAF-acetylhydrolase (PAF-AH). Recently, a large phase III clinical trial using recombinant PAF-AH to treat patients with severe sepsis was performed but failed to reduce 28-day mortality rate. To get more information on the activity of PAF-AH in sepsis, we repeatedly measured its activity in plasma in critically ill patients compared with healthy controls.

DESIGN

Retrospective cohort study.

SETTING

Intensive care unit.

PATIENTS

Two hundred thirty-one patients who were admitted to an operative intensive care unit within 1 yr were enrolled and evaluated daily for American College of Chest Physicians/Society of Critical Care Medicine criteria. PAF-AH activity was measured as the release of [H]-acetate from [H]-acetyl-PAF.

INTERVENTIONS

Analysis of plasma samples.

MEASUREMENTS AND MAIN RESULTS

At the day of admission, PAF-AH activity of patients was below controls but markedly increased over time. Higher activities were seen in patients with severe sepsis or septic shock compared with those without organ failure. With respect to the clinical outcome, lower values were found in nonsurvivors only as long as they had not developed organ failure. In severe sepsis/septic shock, values of nonsurvivors exceeded those of survivors. PAF-AH activity was positively correlated with plasma levels of inflammatory mediators such as neopterine and tumor necrosis factor-alpha but not with acute phase reactants such as C-reactive protein, interleukin-6, or PCT. In addition, parenteral nutrition with lipid emulsions was seemingly associated with low PAF-AH activity compared with enteral nutrition.

CONCLUSION

The data indicate severity- and time-dependent changes in PAF-AH activity and may help to explain the failure of recombinant PAF-AH treatment strategies that were not based on activity measurements.

Interaction of oxidative stress and inflammatory response in coronary plaque instability: important role of C-reactive protein

OBJECTIVE

C-reactive protein (CRP), a predictor of cardiovascular events, localizes in atherosclerotic arteries and exerts proinflammatory effects on vascular cells. Reactive oxygen species (ROS) have been implicated in atherogenesis and plaque instability.

METHODS AND RESULTS

Expressional pattern of CRP in directional coronary atherectomy specimens from 39 patients was examined. Characteristics of histological plaque instability and higher levels of serum CRP and fibrinogen were associated with the CRP immunoreactivity. In situ hybridization revealed the presence of CRP mRNA in coronary vasculature. Furthermore, the expression of CRP mRNA and protein was detected in cultured human coronary artery smooth muscle cells (CASMCs) by reverse transcriptase-polymerase chain reaction and Western blotting. In addition, CRP was frequently colocalized with p22phox, an essential component of NADH/NADPH oxidase, which is an important source of ROS in vasculature. Moreover, the incubation of cultured CASMCs with CRP resulted in the enhanced p22phox protein expression and in the generation of intracellular ROS.

CONCLUSIONS

The expression of CRP in coronary arteries was associated with histological and clinical features of vulnerable plaque, and it had a prooxidative effect on cultured CASMCs, suggesting that it might play a crucial role in plaque instability and in the pathogenesis of acute coronary syndrome via its prooxidative effect.

Proteomic characterization of early-stage differentiation of mouse embryonic stem cells into neural cells induced by all-trans retinoic acid in vitro

Embryonic stem (ES) cells are totipotent stem cells, which can differentiate into various kinds of cell types, including neurons. They are widely used as a model system for investigating mechanisms of differentiation events during early mouse development. In this study, proteomic techniques were used to approach the protein profile associated with the early-stage differentiation of ES cells into neuronal cells induced by all-trans retinoic acid (ATRA) in vitro. In comparison of the protein profile of parent ES cells with that of ES-derived neural-committed cells, which was induced by ATRA for four days, 24 differentially displayed protein spots were selected from two-dimensional electrophoresis (2-DE) gels for further protein identification by pepide mass fingerprinting (PMF). Nine proteins were known to being involved in the process of neural differentiation and/or neural survival. Of those, alpha-3/alpha-7 tubulin and vimentin were down-regulated, while cytokeratin 8, cytokeratin 18, G1/S-special cyclin D2, follistatin-related protein, NEL protein, platelet-activating factor acetylhydrolase IB alpha-subunit, and thioredoxin peroxidase 2 were upregulated during differentiation of ES cells to neural cells. Additionally, other 12 protein (five upregulated and seven downregulated) spots associated with ES cell differentiation into neuronal cells were not matched to known proteins so far, implicating that they might be novel proteins. The results above indicated that the molecular mechanisms of differentiation of ES cells to neural cells in vitro might be similar to those of other neural systems in vitro and identified that proteomic analysis is an effective strategy to comprehensively unravel the regulatory network of differentiation.

Platelet-activating factor acetylhydrolases in health and disease

The platelet-activating factor (PAF) acetylhydrolases catalyze hydrolysis of the sn-2 ester bond of PAF and related pro-inflammatory phospholipids and thus attenuate their bioactivity. One secreted (plasma) and four intracellular isozymes have been described. The intracellular isozymes are distinguished by differences in primary sequence, tissue localization, subunit composition, and substrate preferences. The most thoroughly characterized intracellular isoform, Ib, is a G-protein-like complex with two catalytic subunits (alpha1 and alpha2) and a regulatory beta subunit. The beta subunit is a product of the LIS1 gene, mutations of which cause Miller-Dieker lissencephaly. Isoform II is a single polypeptide that is homologous to the plasma PAF acetylhydrolase and has antioxidant activity in several systems. Plasma PAF acetylhydrolase is also a single polypeptide with a catalytic triad of amino acids that is characteristic of the alpha/beta hydrolases. Deficiency of this enzyme has been associated with a number of pathologies. The most common inactivating mutation, V279F, is found in >30% of randomly surveyed Japanese subjects (4% homozygous, 27% heterozygous). The prevalence of the mutant allele is significantly greater in patients with asthma, stroke, myocardial infarction, brain hemorrhage, and nonfamilial cardiomyopathy. Preclinical studies have demonstrated that recombinant plasma PAF acetylhydrolase can prevent or attenuate pathologic inflammation in a number of animal models. In addition, preliminary clinical results suggest that the recombinant enzyme may have pharmacologic potential in human inflammatory disease as well. These observations underscore the physiological importance of the PAF acetylhydrolases and point toward new approaches for controlling pathologic inflammation.

Platelets inhibit the activity of platelet-activating factor acetylhydrolase in monocyte-derived macrophages

Blood platelets are capable of interacting with monocytes and macrophages and of enhancing various functions of these cells, which are believed to play a role in thrombosis and inflammation. An increase in the uptake of oxidised low density lipoprotein (LDL), in the synthesis of procoagulant tissue factor, thrombospondin and leukotrienes, as well as stimulation of oxygen radical production by platelets has been described (1-5). In circulating blood, a substantial proportion of monocytes was found to be associated with platelets, but the pathophysiological significance of such platelet-monocyte conjugates is not yet clear (6,7). Immigration of monocytes into the arterial intima and their differentiation into macrophages are initial steps in the development of an atherosclerotic lesion (8). During differentiation, there is a tremendous increase in the activity and secretion of the enzyme PAF acetylhydrolase (PAF = platelet-activating factor = 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) (9,10), and there is some evidence that this enzyme may contribute to the development of atherosclerosis. It cleaves PAF, and the remaining lyso-PAF is chemotactic for monocytes (11). Furthermore it also acts on oxidised low density lipoproteins and enhances their uptake into macrophages (12,13). We were therefore interested in investigating whether platelets may modulate the differentiation of monocytes into macrophages and the activity of PAF acetylhydrolase.