Myeloperoxidase mediates neutrophil activation by association with CD11b/CD18 integrins

Involvement of peroxinectin in the defence of red swamp crayfish Procambarus clarkii against pathogenic Aeromonas hydrophila

Cell adhesion factors are important immune components for invertebrate to immobilize, phagocytose or encapsulate invasive microorganisms and foreign particles. In this study, a new cell adhesion factor, peroxinectin (refered as Pcpxin) was isolated from hemocytes of red swamp crayfish (Procambarus clarkii). The full-length cDNA of Pcpxin was 3014 bp encoding a protein of 819 amino acid residues with a predicted molecular weight of 89.0 kDa and a calculational isoelectric point of 6.93. The putative amino acid sequence contained a peroxidase domain and a signal peptide of 21 amino acid residues, and exhibited high identity to peroxinectin from Pacifastacus leniusculus (85%), Fenneropenaeus chinensis (62%) and Scylla serrata (58%), as well as peroxidase from Camponotus floridanus (40%), Pediculus humanus corporis (39%), and Culex quinquefasciatus (38%). Quantitative real time PCR revealed that mRNA expression of Pcpxin in hemocytes could be inhibited by challenge with heat-killed Aeromonas hydrophila, suggesting that Pcpxin was involved in immune responses to A. hydrophila. RNA interference (RNAi) experiment demonstrated that silencing Pcpxin significantly reduced the survival rate of red swamp crayfishes after challenge with A. hydrophila, which indicated that Pcpxin was important for P. clarkii to survive A. hydrophila infection. Moreover, silencing Pcpxin inhibited the up-regulation of crustin1 and lysozyme expression in response to challenge with heat-killed A. hydrophila. This result suggested that Pcpxin might participate in antibacterial peptide gene expression and thereby might be involved in signal transduction pathway regulating the expression of antibacterial peptide gene.

Anti-inflammatory activity of Terminalia paniculata bark extract against acute and chronic inflammation in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia paniculata Roxb. (Family-Combretaceae) is a wild tree commonly used in traditional ayurvedic medicine for the treatment of inflammation of parotid glands and in menstrual disorders.

AIM OF THE STUDY

To explore the folk use of Terminalia paniculata on pharmacological grounds to evaluate the scientific basis of anti-inflammatory activity.

MATERIALS AND METHODS

The anti-inflammatory activity of Terminalia paniculata was studied against carrageenan-induced hind paw edema, air pouch inflammation and complete Freund's adjuvant (CFA)-induced arthritis in rats. The aqueous extract of Terminalia paniculata bark (TPW) was administered at the concentrations of 100, 200 and 400mg/kg body weight.

RESULTS

TPW showed significant (p<0.05) anti-inflammatory activity by reducing the edema volume in carrageenan-induced paw edema in rats. Further, TPW (400mg/kg) also reduced the carrageenan-induced leukocyte migration (50.92 ± 5.71%) and myeloperoxidase activity (49.31 ± 5.24%) in air pouch exudates. TPW (200mg/kg) exhibits anti-rheumatic and analgesic activities by improving the altered haematological milieu (ESR, CRP, RF, WBC, RBC and Hb) and also by inhibiting the flexion scores and radiographic changes in CFA-induced arthritis. This extract also had significant (p<0.05) effects on the occurrence of secondary lesions compared to CFA control.

CONCLUSIONS

Terminalia paniculata bark may be a potential preventive or therapeutic candidate for the treatment of chronic inflammation and arthritis.

Solid-phase extraction and GC-MS analysis of potentially genotoxic cleavage products of β-carotene in primary cell cultures

A validated method for the simultaneous determination of prominent volatile cleavage products (CPs) of β-carotene in cell culture media has been developed. Target CPs comprised β-ionone (β-IO), cyclocitral (CC), dihydroactinidiolide (DHA), and 1,1,6-trimethyltetraline (TMT). CPs were extracted by solid-phase extraction applying a phenyl adsorbent, eluted with 10% (v/v) tetrahydrofuran in n-hexane, and identified and quantified by gas chromatography-mass spectrometry with electron impact ionization. Method validation addressed linearity confirmation over two application ranges and homoscedasticity testing. Recoveries from culture media were between 71.7% and 95.7% at 1.0 μg/ml. Precision of recoveries determined in intra-day (N = 5) and inter-day (N = 15) assays were <2.0% and <4.8%, respectively. Limit of detection and limit of quantification of the analysis method were <18.0 and <53.0 ng/ml for β-IO, CC, and TMT, whereas 156 and 474 ng/ml were determined for DHA, respectively. Although extractions of blank matrix proved the absence of interfering peaks, statistical comparison between slopes determined for instrumental and total method linearity revealed significant differences. The method was successfully applied in selecting an appropriate solvent for the fortification of culture media with volatile CPs, including the determination of their availability over the incubation period. For the first time, quantification of volatile CPs in treatment solutions and culture media for primary cells becomes accessible by this validated method.

Figure

Increased myeloperoxidase plasma levels in rheumatoid arthritis

High myeloperoxidase (MPO) serum levels have been shown in several inflammatory diseases, including rheumatoid arthritis (RA). However, the correlation between MPO levels and disease activity in RA patients is still controversial. The aim of the study was to determine MPO plasma levels in RA patients and to investigate potential correlations between MPO levels and disease activity and treatment. MPO plasma levels were measured by ELISA according the manufacturer's instructions. Disease activity was measured by DAS28 ESR and DAS28 CRP scores, and patients were classified into 4 groups: group 1 DAS28 < 2.6; group 2: 2.6 ≤ DAS28 ≤ 3.2; group 3: 3.2 < DAS28 ≤ 5.1 and group 4: DAS28 > 5.1. Rheumatoid factor (RF) was measured by latex agglutination test, and anti-cyclic citrullinated peptide (anti-CCP) antibodies were detected by ELISA with a commercial kit. Fifty-seven female RA patients (mean age: 46.02 ± 13.47 years, mean disease duration: 115.77 ± 99.44 months) and sixty gender- and age-paired healthy controls were included. Mean MPO plasma levels were significantly higher in patients than in controls (72.27 pM vs. 40.78 pM, P = 0.007). RF was found in 59.6% and anti-CCP in 80.7% of the RA patients. No significant difference in MPO levels was seen among the four RA disease activity groups. We did not find significant correlation between MPO levels and disease activity as measured by DAS28 score. In conclusion, we observed significantly higher MPO plasma levels in RA patients when compared to healthy controls. However, we did not find correlation between MPO plasma level and disease activity.

Microparticles initiate decompression-induced neutrophil activation and subsequent vascular injuries

Progressive elevations in circulating annexin V-coated microparticles (MPs) derived from leukocytes, erythrocytes, platelets, and endothelial cells are found in mice subjected to increasing decompression stresses. Individual MPs exhibit surface markers from multiple cells. MPs expressing platelet surface markers, in particular, interact with circulating neutrophils, causing them to degranulate and leading to further MP production. MPs can be lysed by incubation with polyethylene glycol (PEG) telomere B surfactant, and the number of circulating MPs is reduced by infusion of mice with PEG or antibody to annexin V. Myeloperoxidase deposition and neutrophil sequestration in tissues occur in response to decompression, and the pattern differs among brain, omentum, psoas, and leg skeletal muscle. Both MP abatement strategies reduce decompression-induced intravascular neutrophil activation, neutrophil sequestration, and tissue injury documented as elevations of vascular permeability and activated caspase-3. We conclude that MPs generated by decompression stresses precipitate neutrophil activation and vascular damage.

Myeloperoxidase attracts neutrophils by physical forces

Recruitment of polymorphonuclear neutrophils (PMNs) remains a paramount prerequisite in innate immune defense and a critical cofounder in inflammatory vascular disease. Neutrophil recruitment comprises a cascade of concerted events allowing for capture, adhesion and extravasation of the leukocyte. Whereas PMN rolling, binding, and diapedesis are well characterized, receptor-mediated processes, mechanisms attenuating the electrostatic repulsion between the negatively charged glycocalyx of leukocyte and endothelium remain poorly understood. We provide evidence for myeloperoxidase (MPO), an abundant PMN-derived heme protein, facilitating PMN recruitment by its positive surface charge. In vitro, MPO evoked highly directed PMN motility, which was solely dependent on electrostatic interactions with the leukocyte's surface. In vivo, PMN recruitment was shown to be MPO-dependent in a model of hepatic ischemia and reperfusion, upon intraportal delivery of MPO and in the cremaster muscle exposed to local inflammation or to intraarterial MPO application. Given MPO's affinity to both the endothelial and the leukocyte's surface, MPO evolves as a mediator of PMN recruitment because of its positive surface charge. This electrostatic MPO effect not only displays a so far unrecognized, catalysis-independent function of the enzyme, but also highlights a principal mechanism of PMN attraction driven by physical forces.

Hyperlipidemia-Triggered Neutrophilia Promotes Early Atherosclerosis

Background—

Inflammation and activation of immune cells are key mechanisms in the development of atherosclerosis. Previous data indicate important roles for monocytes and T lymphocytes in lesion formation, whereas the contribution of neutrophils remains to be firmly established. Here, we investigate the effect of hypercholesterolemia on peripheral neutrophil counts, neutrophil recruitment to atherosclerotic lesions, and the importance of neutrophils in atherosclerotic lesion formation in Apoe −/− mice.

Methods and Results—

Hypercholesterolemia induces neutrophilia, which was attributable to enhanced granulopoiesis and enhanced mobilization from the bone marrow. The degree of hypercholesterolemia-induced neutrophilia was positively correlated with the extent of early atherosclerotic lesion formation. In turn, neutropenic mice display reduced plaque sizes at early but not late stages of atherosclerotic lesion formation. Flow cytometry of enzymatically digested aortas further shows altered cellular plaque composition in neutropenic mice with reduced numbers of inflammatory monocytes and macrophages. Aortic neutrophil infiltration peaks 4 weeks after the start of a high-fat diet and decreases afterward. The recruitment of neutrophils to large arteries was found to depend on CCR1, CCR2, CCR5, and CXCR2, which contrasts to peripheral venous recruitment, which requires CCR2 and CXCR2 only. The involvement of CCR1 and CCR5 corresponded to the endothelial deposition of the platelet-derived chemokine CCL5 in arteries but not in veins.

Conclusions—

Our data provide evidence that hypercholesterolemia-induced neutrophilia is multifactorial and that neutrophils infiltrate arteries primarily during early stages of atherosclerosis. Collectively, these data suggest an important role of neutrophils in the initiation of atherosclerosis.

Recent developments in the inhibitors of neuroinflammation and neurodegeneration: inflammatory oxidative enzymes as a drug target

IMPORTANCE OF THE FIELD

Increasing evidence indicates that glial cells play a pivotal role in a wide range of brain diseases. As glial cells orchestrate inflammatory responses in the CNS, recent studies have focused on glial cells and neuroinflammation as drug targets for the treatment of neuroinflammatory and neurodegenerative diseases.

AREAS COVERED IN THIS REVIEW

In this review, we aim to give an overview of the current literature and patents for inhibitors of inflammatory oxidative enzymes in glia such as NADPH oxidase, myeloperoxidase, COX-2 and 5-lipooxygenase.

WHAT THE READER WILL GAIN

Recent literature and patents on natural products or small molecule-based inhibitors of glial oxidative enzymes are reviewed.

TAKE HOME MESSAGE

Extensive studies and patents recently reported in this field suggest that glial inhibitors may soon proceed to clinical trials. However, before glial inhibitors can serve as novel drugs for the treatment of neuroinflammatory disorders, the neurotoxic and neuroprotective effects of glial neuroinflammatory responses need to be better dissected.

Cot/tpl2 (MAP3K8) mediates myeloperoxidase activity and hypernociception following peripheral inflammation

Cot/tpl2 (also known as MAP3K8) has emerged as a new and potentially interesting therapeutic anti-inflammatory target. Here, we report the first study of Cot/tpl2 involvement in acute peripheral inflammation in vivo. Six hours after an intraplantar injection of zymosan, Cot/tpl2(-/-) mice showed a 47% reduction in myeloperoxidase activity, concomitant with a 46% lower neutrophil recruitment and a 40% decreased luminol-mediated bioluminescence imaging in vivo. Accordingly, Cot/tpl2 deficiency provoked a 25-30% reduction in luminol-mediated bioluminescence and neutrophil recruitment together with a 65% lower macrophage recruitment 4 h following zymosan-induced peritonitis. Significantly impaired levels of G-CSF and GM-CSF and of other cytokines such as TNFα, IL-1β, and IL-6, as well as some chemokines such as MCP-1, MIP-1β, and keratinocyte-derived chemokine, were detected during the acute zymosan-induced intraplantar inflammatory response in Cot/tpl2(-/-) mice. Moreover, Cot/tpl2 deficiency dramatically decreased the production of the hypernociceptive ligand NGF at the inflammatory site during the course of inflammation. Most importantly, Cot/tpl2 deficiency significantly reduced zymosan-induced inflammatory hypernociception in mice, with a most pronounced effect of a 50% decrease compared with wild type (WT) at 24 h following intraplantar injection of zymosan. At this time, Cot/tpl2(-/-) mice showed significantly reduced NGF, TNFα, and prostaglandin E(2) levels compared with WT littermates. In conclusion, our study demonstrates an important role of Cot/tpl2 in the NGF, G-CSF, and GM-CSF production and myeloperoxidase activity in the acute inflammatory response process and its implication in inflammatory hypernociception.

Paroxetine prevents loss of nigrostriatal dopaminergic neurons by inhibiting brain inflammation and oxidative stress in an experimental model of Parkinson's disease

The present study examined whether the antidepressant paroxetine promotes the survival of nigrostriatal dopaminergic (DA) neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease. MPTP induced degeneration of nigrostriatal DA neurons and glial activation as visualized by tyrosine hydroxylase, macrophage Ag complex-1, and/or glial fibrillary acidic protein immunoreactivity. Real-time PCR, Western blotting, and immunohistochemistry showed upregulation of proinflammatory cytokines, activation of microglial NADPH oxidase and astroglial myeloperoxidase, and subsequent reactive oxygen species production and oxidative DNA damage in the MPTP-treated substantia nigra. Treatment with paroxetine prevented degeneration of nigrostriatal DA neurons, increased striatal dopamine levels, and improved motor function. This neuroprotection afforded by paroxetine was associated with the suppression of astroglial myeloperoxidase expression and/or NADPH oxidase-derived reactive oxygen species production and reduced expression of proinflammatory cytokines, including IL-1beta, TNF-alpha, and inducible NO synthase, by activated microglia. The present findings show that paroxetine may possess anti-inflammatory properties and inhibit glial activation-mediated oxidative stress, suggesting that paroxetine and its analogues may have therapeutic value in the treatment of aspects of Parkinson's disease related to neuroinflammation.

Endothelial microparticles induce inflammation in acute lung injury

BACKGROUND

Previously, we have shown that endothelial microparticles (EMPs) injected into mice induce acute lung injury (ALI) [1]. In this study, we hypothesize that EMPs induce ALI by initiating cytokine release in the lung, leading to recruitment and activation of neutrophils.

MATERIALS AND METHODS

C57BL/6J male mice (8-10 wk old) were intravenously injected with EMPs (200,000/mL), LPS (2 mg/kg), or both. Bronchoalveolar lavage (BAL) and serum levels of IL-1β and TNF-α were analyzed by enzyme-linked immunoassay (ELISA). Morphometric analysis was performed on H and E stained lung sections. Myeloperoxidase (MPO) levels were determined via an enzymatic assay and immunofluorescence of stained sections.

RESULTS

EMPs led to significantly increased pulmonary and systemic IL-1β and TNF-α levels, which correlated with increased neutrophil recruitment to the lung. MPO levels in the lungs were increased significantly following injection of EMPs or LPS, compared to PBS. In mice treated with EMPs and LPS either simultaneously or successively, the cytokine and MPO levels were significantly increased over that of either treatment alone.

CONCLUSION

EMPs contribute to lung injury through the initiation of a cytokine cascade that increases recruitment of neutrophils and subsequent release of MPO. Furthermore, treatment of mice with both EMPs and LPS induced greater lung injury than either treatment alone, suggesting that EMPs prime the lung for increased injury by other pathogens. Therapies aimed at reducing or blocking EMPs may be a useful strategy for attenuating lung injury.

Extracellular DNA: a major proinflammatory component of Pseudomonas aeruginosa biofilms

We previously demonstrated that extracellular bacterial DNA activates neutrophils through a CpG- and TLR9-independent mechanism. Biofilms are microbial communities enclosed in a polymeric matrix that play a critical role in the pathogenesis of many infectious diseases. Because extracellular DNA is a key component of biofilms of different bacterial species, the aim of this study was to determine whether it plays a role in the ability of biofilms to induce human neutrophil activation. We found that degradation of matrix extracellular DNA with DNase I markedly reduced the capacity of Pseudomonas aeruginosa biofilms to induce the release of the neutrophil proinflammatory cytokines IL-8 and IL-1beta (>75%); reduced the upregulation of neutrophil activation markers CD18, CD11b, and CD66b (p < 0.001); reduced the number of bacteria phagocytosed per neutrophil contacting the biofilm; and reduced the production of neutrophil extracellular traps. Consistent with these findings, we found that biofilms formed by the lasI rhlI P. aeruginosa mutant strain, exhibiting a very low content of matrix extracellular DNA, displayed a lower capacity to stimulate the release of proinflammatory cytokines by neutrophils, which was not decreased further by DNase I treatment. Together, our findings support that matrix extracellular DNA is a major proinflammatory component of P. aeruginosa biofilms.

Glycosylation pattern of mature dimeric leukocyte and recombinant monomeric myeloperoxidase: glycosylation is required for optimal enzymatic activity

The involvement of myeloperoxidase (MPO) in various inflammatory conditions has been the scope of many recent studies. Besides its well studied catalytic activity, the role of its overall structure and glycosylation pattern in biological function is barely known. Here, the N-glycan composition of native dimeric human MPO purified from neutrophils and of monomeric MPO recombinantly expressed in Chinese hamster ovary cells has been investigated. Analyses showed the presence of five N-glycans at positions 323, 355, 391, 483, 729 in both proteins. Site by site analysis demonstrated a well conserved micro- and macro-heterogeneity and more complex-type N-glycans for the recombinant form. Comparison of biological functionality of glycosylated and deglycosylated recombinant MPO suggests that glycosylation is required for optimal enzymatic activity. Data are discussed with regard to biosynthesis and the three-dimensional structure of MPO.

Cyclooxygenases-1 and -2 differentially modulate leukocyte recruitment into the inflamed brain

Peripheral leukocyte recruitment in neuroinflammatory conditions can exacerbate brain tissue damage by releasing cytotoxic mediators and by increasing vascular permeability. Cyclooxygenase (COX)-derived prostaglandins promote the migration of several immune cells in vitro, however, the specific roles of COX-1 and -2 on leukocyte recruitment in vivo have not been investigated. To examine the specific effects of COX-1 or COX-2 deficiency on neuroinflammation-induced leukocyte infiltration, we used a model of intracerebroventricular lipopolysaccharide (LPS)-induced neuroinflammation in COX-1(-/-), COX-2(-/-), and their respective wild-type (WT) ((+/+)) mice. After LPS, leukocyte infiltration and inflammatory response were attenuated in COX-1(-/-) and increased in COX-2(-/-) mice, compared with their respective WT controls. This influx of leukocytes was accompanied by a marked disruption of blood-brain barrier and differential expression of chemokines. These results indicate that COX-1 and COX-2 deletion differentially modulate leukocyte recruitment during neuroinflammation, and suggest that inhibition of COX-1 activity is beneficial, whereas COX-2 inhibition is detrimental, during a primary neuroinflammatory response.

Myeloperoxidase: molecular mechanisms of action and their relevance to human health and disease

Myeloperoxidase (MPO) is a heme-containing peroxidase abundantly expressed in neutrophils and to a lesser extent in monocytes. Enzymatically active MPO, together with hydrogen peroxide and chloride, produces the powerful oxidant hypochlorous acid and is a key contributor to the oxygen-dependent microbicidal activity of phagocytes. In addition, excessive generation of MPO-derived oxidants has been linked to tissue damage in many diseases, especially those characterized by acute or chronic inflammation. It has become increasingly clear that MPO exerts effects that are beyond its oxidative properties. These properties of MPO are, in many cases, independent of its catalytic activity and affect various processes involved in cell signaling and cell-cell interactions and are, as such, capable of modulating inflammatory responses. Given these diverse effects, an increased interest has emerged in the role of MPO and its downstream products in a wide range of inflammatory diseases. In this article, our knowledge pertaining to the biologic role of MPO and its downstream effects and mechanisms of action in health and disease is reviewed and discussed.

Oxidative stress and myeloperoxidase activity during bacterial meningitis: effects of febrile episodes and the BBB permeability

OBJECTIVE

To investigate participation of extracellular myeloperoxidase (MPO) in oxidative stress during different courses of the bacterial meningitis (BM).

MATERIALS AND METHODS

We sequentially assessed WBC count, blood-brain barrier (BBB) permeability, serum and cerebrospinal fluid (CSF) lipid peroxidation (LPO), MPO and antioxidative activity (AOA) in proven pediatric BM.

RESULTS

BM patients exhibited increased systemic and local LPO and MPO, and reduced AOA, which was exaggerated in the febrile episodes. Serum MPO and LPO products were related to the BBB permeability at the baseline. CSF hydroperoxide level was influenced by the BBB permeability, CSF albumin concentration, and serum hydroperoxide (r=0.502; p<0.001, and r=0.611; p<0.001, and r=0.358; p<0.001, respectively). CSF hydroperoxide and MPO correlated in complicated cases during the study.

CONCLUSIONS

These results suggest that CSF LPO and MPO were closely related in BM, had different courses if febrile episodes had occurred, but were partly influenced by the BBB permeability.

Caffeine and CSC, adenosine A2A antagonists, offer neuroprotection against 6-OHDA-induced neurotoxicity in rat mesencephalic cells

In this study, the cytoprotective effects of caffeine (CAF) and 8-(3-chlorostyryl)-caffeine (CSC), A(2A) receptor antagonists, were tested against 6-OHDA-induced cytotoxicity, in rat mesencephalic cells. Both drugs significantly increased the number of viable cells, after their exposure to 6-OHDA, as measured by the MTT assay. While nitrite levels in the cells were drastically increased by 6-OHDA, their concentrations were brought toward normality after CAF or CSC, indicating that both drugs block 6-OHDA-induced oxidative stress which leads to free radicals generation. A complete blockade of 6-OHDA-induced lipid peroxidation, considered as a major source of DNA damage, was observed after cells treatment with CAF or CSC. 6-OHDA decreased the number of normal cells while increasing the number of apoptotic cells. In the CAF plus 6-OHDA group, a significant recover in the number of viable cells and a decrease in the number of apoptotic cells were seen, as compared to the group treated with 6-OHDA alone. A similar effect was observed after cells exposure to CSC in the presence of 6-OHDA. Unexpectedly, while a significant lower number of activated microglia was observed after cells exposure to CAF plus 6-OHDA, this was not the case after cells exposure to CSC under the same conditions. While CAF lowered the percentage of reactive astrocytes increased by 6-OHDA, CSC presented no effect. The effects of these drugs were also examined on the releases of myeloperoxidase (MPO), an inflammatory marker, and lactate dehydrogenase (LDH), a marker for cytotoxicity, in human neutrophils, in vitro. CSC and CAF (0.1, 1 and 10 microg/ml) produced inhibitions of the MPO release from PMA-stimulated cells, ranging from 45 to 83%. In addition, CSC and CAF (5, 50 and 100 microg/ml) did not show any cytotoxicity in the range of concentrations used, as determined by the LDH assay. All together, our results showed a strong neuroptrotection afforded by caffeine or CSC, on rat mesencephalic cells exposed to 6-OHDA. Furthermore, CSC and caffeine actions, inhibiting MPO as well as LDH releases, would contribute to their possible benefit in the treatment of neurodegenerative diseases, including DP. These effects are partially due to the ability of these A(2A) antagonists to decrease the cells free radicals production and oxidative stress, that are major components of 6-OHDA-induced cytotoxicity.

Increased plasma myeloperoxidase levels in systemic lupus erythematosus

The objective of the study was to quantify plasma myeloperoxidase (MPO) levels in systemic lupus erythematosus (SLE) patients and to evaluate a correlation between MPO levels and disease activity. 71 female SLE patients and 70 controls were studied. Patients were divided into two groups: Group I (n = 48) with SLEDAI-2K score 0-5 and Group II (n = 23) with SLEDAI-2K score > or = 6. Mann-Whitney test and Spearman rank correlation were used. Two-sided P values < 0.05 were considered significant and P values > or = 0.05 and < 0.08 were considered as a tendency. The median age of patients and controls were comparable and the mean disease duration was 99.2 +/- 61.7 months. MPO levels were higher in patients than controls [5.99 (4.38-8.64) vs. 5.00 (3.33-7.08) ng/ml, P = 0.02]. We did not find correlation between MPO levels and SLEDAI-2k (r = 0.07, P = 0.58). MPO levels were not affected by treatment with prednisone, cyclophosphamide or azathioprine, however, a tendency of lower levels was observed among patients under antimalarial drugs. There was no significant difference in MPO plasma levels between Group I and Group II (5.83 vs. 6.02 ng/ml, P = 0.99). MPO levels were higher in patients with arthritis than in those without arthritis (8.15 vs. 5.56 ng/ml, P = 0.010). No difference was observed among patients with and without other organs/systems involvement. SLE patients presented increased MPO plasma levels than healthy controls. Despite the lack of correlation between MPO plasma levels and disease activity, the higher MPO levels in patients with articular involvement suggests MPO may play a different role in the inflammatory process of some SLE manifestations.

Reactive oxygen intermediate-induced pathomechanisms contribute to immunosenescence, chronic inflammation and autoimmunity

Deregulation of reactive oxygen intermediates (ROI) resulting in either too high or too low concentrations are commonly recognized to be at least in part responsible for many changes associated with aging. This article reviews ROI-dependent mechanisms critically contributing to the decline of immune function during physiologic - or premature - aging. While ROI serve important effector functions in cellular metabolism, signalling and host defence, their fine-tuned generation declines over time, and ROI-mediated damage to several cellular components and/or signalling deviations become increasingly prevalent. Although distinct ROI-associated pathomechanisms contribute to immunosenescence of the innate and adaptive immune system, mutual amplification of dysfunctions may often result in hyporesponsiveness and immunodeficiency, or in chronic inflammation with hyperresponsiveness/deregulation, or both. In this context, we point out how imbalanced ROI contribute ambiguously to driving immunosenescence, chronic inflammation and autoimmunity. Although ROI may offer a distinct potential for therapeutic targeting along with the charming opportunity to rescue from deleterious processes of aging and chronic inflammatory diseases, such modifications, owing to the complexity of metabolic interactions, may carry a marked risk of unforeseen side effects.

Crucial role of TNF receptors 1 and 2 in the control of polymicrobial sepsis

Sepsis is still a major cause of mortality in the intensive critical care unit and results from an overwhelming immune response to the infection. TNF signaling pathway plays a central role in the activation of innate immunity in response to pathogens. Using a model of polymicrobial sepsis by i.p. injection of cecal microflora, we demonstrate a critical role of TNFR1 and R2 activation in the deregulated immune responses and death associated with sepsis. A large and persistent production of TNF was found in wild-type (B6) mice. TNFR1/R2-deficient mice, compared with B6 mice, survive lethal polymicrobial infection with enhanced neutrophil recruitment and bacterial clearance in the peritoneal cavity. Absence of TNFR signaling leads to a decreased local and systemic inflammatory response with diminished organ injury. Furthermore, using TNFR1/R2-deficient mice, TNF was found to be responsible for a decrease in CXCR2 expression, explaining reduced neutrophil extravasation and migration to the infectious site, and in neutrophil apoptosis. In line with the clinical experience, administration of Enbrel, a TNF-neutralizing protein, induced however only a partial protection in B6 mice, with no improvement of clinical settings, suggesting that future TNF immunomodulatory strategies should target TNFR1 and R2. In conclusion, the present data suggest that the endogenous TNFR1/R2 signaling pathway in polymicrobial sepsis reduces neutrophil recruitment contributing to mortality and as opposed to pan-TNF blockade is an important therapeutic target for the treatment of polymicrobial sepsis.

15-epi-lipoxin A4 inhibits myeloperoxidase signaling and enhances resolution of acute lung injury

RATIONALE

Apoptosis is essential for removal of neutrophils from inflamed tissues and efficient resolution of inflammation. Myeloperoxidase (MPO), abundantly expressed in neutrophils, not only generates cytotoxic oxidants but also signals through the beta(2) integrin Mac-1 to rescue neutrophils from constitutive apoptosis, thereby prolonging inflammation.

OBJECTIVES

Because aspirin-triggered 15-epi-lipoxin A(4) (15-epi-LXA(4)) modulates Mac-1 expression, we investigated the impact of 15-epi-LXA(4) on MPO suppression of neutrophil apoptosis and MPO-mediated neutrophil-dependent acute lung injury.

METHODS

Human neutrophils were cultured with MPO with or without 15-epi-LXA(4) to investigate development of apoptosis. Acute lung injury was produced by intratracheal injection of carrageenan plus MPO or intraperitoneal injection of live Escherichia coli in mice, and the animals were treated with 15-epi-LXA(4) at the peak of inflammation.

MEASUREMENTS AND MAIN RESULTS

15-Epi-LXA(4) through down-regulation of Mac-1 expression promoted apoptosis of human neutrophils by attenuating MPO-induced activation of extracellular signal-regulated kinase and Akt-mediated phosphorylation of Bad and by reducing expression of the antiapoptotic protein Mcl-1, thereby aggravating mitochondrial dysfunction. The proapoptotic effect of 15-epi-LXA(4) was dominant over MPO-mediated effects even when it was added at 4 hours post MPO. In mice, treatment with 15-epi-LXA(4) accelerated the resolution of established carrageenan plus MPO-evoked as well as E. coli-induced neutrophil-dependent pulmonary inflammation through redirecting neutrophils to caspase-mediated cell death and facilitating their removal by macrophages.

CONCLUSIONS

These results demonstrate that aspirin-triggered 15-epi-LXA(4) enhances resolution of inflammation by overriding the powerful antiapoptosis signal from MPO, thereby demonstrating a hitherto unrecognized mechanism by which aspirin promotes resolution of inflammation.

Antimyeloperoxidase antibodies rapidly induce alpha-4-integrin-dependent glomerular neutrophil adhesion

Patients with antineutrophil cytoplasmic antibodies (ANCAs) frequently develop severe vasculitis and glomerulonephritis. Although ANCAs, particularly antimyeloperoxidase (anti-MPO), have been shown to promote leukocyte adhesion in postcapillary venules, their ability to promote adhesion in the glomerular vasculature is less clear. We used intravital microscopy to examine glomerular leukocyte adhesion induced by anti-MPO. In mice pretreated with LPS, 50 microg anti-MPO induced LFA-1-dependent adhesion in glomeruli. In concert with this finding, in mice pretreated with LPS, more than 80% of circulating neutrophils bound anti-MPO within 5 minutes of intravenous administration. However, even in the absence of LPS, more than 40% of circulating neutrophils bound anti-MPO in vivo, a response not seen in MPO(-/-) mice. In addition, a higher dose of anti-MPO (200 microg) induced robust glomerular leukocyte adhesion in the absence of LPS. The latter response was beta2-integrin independent, instead requiring the alpha4-integrin, which was up-regulated on neutrophils in response to anti-MPO. These data indicate that anti-MPO antibodies bind to circulating neutrophils, and can induce glomerular leukocyte adhesion via multiple pathways. Lower doses induce adhesion only after an infection-related stimulus, whereas higher doses are capable of inducing responses in the absence of an additional inflammatory stimulus, via alternative adhesion mechanisms.

Bone marrow aspirate and biopsy: a pathologist's perspective. II. interpretation of the bone marrow aspirate and biopsy

Bone marrow examination has become increasingly important for the diagnosis and treatment of hematologic and other illnesses. Morphologic evaluation of the bone marrow aspirate and biopsy has recently been supplemented by increasingly sophisticated ancillary assays, including immunocytochemistry, cytogenetic analysis, flow cytometry, and molecular assays. With our rapidly expanding knowledge of the clinical and biologic diversity of leukemia and other hematologic neoplasms, and an increasing variety of therapeutic options, the bone marrow examination has became more critical for therapeutic monitoring and planning optimal therapy. Sensitive molecular techniques, in vitro drug sensitivity testing, and a number of other special assays are available to provide valuable data to assist these endeavors. Fortunately, improvements in bone marrow aspirate and needle technology has made the procurement of adequate specimens more reliable and efficient, while the use of conscious sedation has improved patient comfort. The procurement of bone marrow specimens was reviewed in the first part of this series. This paper specifically addresses the diagnostic interpretation of bone marrow specimens and the use of ancillary techniques.

Effects of amburoside A and isokaempferide, polyphenols from Amburana cearensis, on rodent inflammatory processes and myeloperoxidase activity in human neutrophils

The present study evaluated the anti-inflammatory activity of amburoside A (a phenol glucoside) and isokaempferide (a flavonol) isolated from the trunk bark of Amburana cearensis, a medicinal plant used in northeast Brazil for the treatment of asthma. Animals (male Wistar rats or Swiss mice) pre-treated with amburoside A (25 and 50 mg/kg) or isokaempferide (12.5, 25 and 50 mg/kg), orally or intraperitoneally, showed a significant inhibition of the paw oedema induced by carrageenan (1%), prostaglandin E(2) (30 nmol/paw), histamine (200 microg/paw) or serotonin (200 microg/paw). Histological and morphometric evaluations of the rat paw oedema induced by carrageenan showed that amburoside A and isokaempferide also inhibited the accumulation of inflammatory cells. Amburoside A reduced significantly the paw oedema and the increase in vascular permeability induced by dextran, as related to the control group. Similar results were observed with the isokaempferide pre-treatment. Furthermore, amburoside A or isokaempferide inhibited both leucocyte and neutrophil migrations, in mouse peritoneal cavity, after the carrageenan injection. The polyphenols were not cytotoxic and blocked N-formyl-methyl-leucyl-phenylalanine-induced myeloperoxidase release and activity in human neutrophils. In addition, amburoside A and isokaempferide at 50 and 100 microg/ml concentrations reduced significantly the lipopolysaccharide-mediated increase in tumour necrosis factor-alpha (TNF-alpha) levels. These results provide, for the first time, evidence to support the anti-inflammatory activity of amburoside A and isokaempferide that seems to be related to an inhibition of inflammatory mediators, such as TNF-alpha, as well as histamine, serotonin and prostaglandin E(2), besides leucocyte infiltration in a dose- or concentration-dependent manner. These anti-inflammatory effects can be explained, at least in part, by the ability of these compounds to reduce neutrophil degranulation, myeloperoxidase activity, mediators as well as TNF-alpha secretion.

Myeloperoxidase-positive cell infiltration in colorectal carcinogenesis as indicator of colorectal cancer risk

Colorectal mucosa is targeted by toxic agents, which can initiate or promote colon cancer. The mechanism of damage might be a focal irritation with loss of normal epithelial cell barrier function. Genetic alterations in tumors may also affect host inflammatory response. The aim of this study was to define the extent of inflammation in colorectal mucosa, along colorectal carcinogenesis, and in microsatellite stable and unstable colorectal carcinomas. We collected 103 samples of normal colorectal mucosa from 65 patients (35 with colorectal cancer or adenoma, 8 with inflammatory bowel diseases, and 22 controls with normal colonoscopy). We also examined 24 aberrant crypt foci, 14 hyperplastic polyps, 16 adenomas, and 67 samples of colorectal carcinoma. Immunohistochemistry was used to count myeloperoxidase (MPO)-positive cells (neutrophils and monocytes) in x100 optical fields under a light microscope. Patients with colorectal tumors had a higher mean number of MPO-positive cells in normal mucosa than controls (mean +/- SD, 2.7 +/- 2.0 versus 1.4 +/- 1.4; P = 0.017). MPO-positive cell number was tightly linked to dysplasia in aberrant crypt foci and adenomas, and it was higher in carcinomas microsatellite unstable than those microsatellite stable (21.6 +/- 15.5 versus 11.9 +/- 8.0; P < 0.01). MPO immunohistochemistry is a simple and reliable technique for the quantification of inflammation in colorectal mucosa., and it may be a potential marker of colorectal cancer risk. Microsatellite instability seems to influence host immune responses to colorectal carcinoma. These observations strongly support a key role of inflammation in colorectal carcinogenesis.

Redox control of endothelial function and dysfunction: molecular mechanisms and therapeutic opportunities

The endothelium is essential for the maintenance of vascular homeostasis. Central to this role is the production of endothelium-derived nitric oxide (EDNO), synthesized by the endothelial isoform of nitric oxide synthase (eNOS). Endothelial dysfunction, manifested as impaired EDNO bioactivity, is an important early event in the development of various vascular diseases, including hypertension, diabetes, and atherosclerosis. The degree of impairment of EDNO bioactivity is a determinant of future vascular complications. Accordingly, growing interest exists in defining the pathologic mechanisms involved. Considerable evidence supports a causal role for the enhanced production of reactive oxygen species (ROS) by vascular cells. ROS directly inactivate EDNO, act as cell-signaling molecules, and promote protein dysfunction, events that contribute to the initiation and progression of endothelial dysfunction. Increasing data indicate that strategies designed to limit vascular ROS production can restore endothelial function in humans with vascular complications. The purpose of this review is to outline the various ways in which ROS can influence endothelial function and dysfunction, describe the redox mechanisms involved, and discuss approaches for preventing endothelial dysfunction that may highlight future therapeutic opportunities in the treatment of cardiovascular disease.

Nitro-oleic acid protects the mouse kidney from ischemia and reperfusion injury

Nitroalkene derivatives of linoleic acid (nitrolinoleic acid; LNO2) and nitro-oleic acid (OA-NO2) are endogenous lipid products with potent anti-inflammatory properties. The present study was undertaken to evaluate the therapeutic potential of OA-NO2 in a mouse model of renal ischemia-reperfusion (I/R) injury. B6129SF2/J mice were subjected to bilateral renal ischemia for 30 min, followed by 24 h of reperfusion. Fifty minutes after ischemia, mice received intraperitoneal (ip) injections of OA-NO2 (500 microg/kg; I/R OA-NO2), vehicle for OA-NO2 (i.e., 0.8 ml/kg ethanol; I/R veh), or oleic acid (500 microg/kg; I/R OA) every 6 h during the 24-h recovery period. A sham-operated group was not subjected to ischemia and received 0.8 ml/kg ethanol ip every 6 h during the 24-h recovery period (sham veh). While plasma urea and creatinine were elevated (P<0.05) in I/R veh vs. sham veh mice, the severity was less (P<0.05) in I/R OA-NO2 animals. Indices of histological damage, polymorphonucleocyte infiltration, together with expression of intracellular adhesion molecule-1, interleukin-1beta, and tumor necrosis factor-alpha, p47(phox), and gp91(phox) were greater in I/R veh vs. sham veh mice, but were attenuated (P<0.05) in I/R OA-NO2 animals. Because indices of renal dysfunction were similar between I/R veh and I/R OA mice (P>0.05), but less (P<0.05) in I/R OA-NO2 animals compared with both groups, protection from bilateral renal ischemia is afforded by the nitrated but not free form of oleic acid. Together, delayed administration of nitrated fatty acid OA-NO2 attenuates renal I/R injury in the mouse likely via inhibition of the inflammatory response.

Myeloperoxidase Delays Neutrophil Apoptosis Through CD11b/CD18 Integrins and Prolongs Inflammation

Polymorphonuclear neutrophil granulocytes have a central role in innate immunity and their programmed cell death and removal are critical for efficient resolution of acute inflammation. Myeloperoxidase (MPO), a heme protein abundantly expressed in neutrophils, is generally associated with killing of bacteria and oxidative tissue injury. Because MPO also binds to neutrophils, we investigated whether MPO could affect the lifespan of neutrophils. Here, we report that MPO independent of its catalytic activity through signaling via the adhesion molecule CD11b/CD18 rescued human neutrophils from constitutive apoptosis and prolonged their life span. MPO evoked a transient concurrent activation of extracellular signal-regulated kinase and Akt, leading to phosphorylation of Bad at both Ser112 and Ser136, prevention of mitochondrial dysfunction, and subsequent activation of caspase-3. Consistently, pharmacological inhibition of extracellular signal-regulated kinase, Akt, or caspase-3 reversed the antiapoptosis action of MPO. Acute increases in plasma MPO delayed murine neutrophil apoptosis assayed ex vivo. In a mouse model of self-resolving inflammation, MPO also prolonged the duration of carrageenan-induced acute lung injury, as evidenced by enhanced alveolar permeability and accumulation of neutrophils parallel with suppression of neutrophil apoptosis. Our results indicate that MPO functions as a survival signal for neutrophils and thereby contribute to prolongation of inflammation.

Cyclooxygenase-2 deficiency enhances Th2 immune responses and impairs neutrophil recruitment in hepatic ischemia/reperfusion injury

Cyclooxygenase-2 (COX-2) is a prostanoid-synthesizing enzyme that is critically implicated in a variety of pathophysiological processes. Using a COX-2-deficient mouse model, we present data that suggest that COX-2 has an active role in liver ischemia/reperfusion (I/R) injury. We demonstrate that COX-2-deficient mice had a significant reduction in liver damage after I/R insult. The inability of COX-2(-/-) to elaborate COX-2 products favored a Th2-type response in these mice. COX-2(-/-) livers after I/R injury showed significantly decreased levels of IL-2, as well as IL-12, a cytokine known to have a central role in Th1 effector cell differentiation. Moreover, such livers expressed enhanced levels of the anti-inflammatory cytokine IL-10, shifting the balance in favor of a Th2 response in COX-2-deficient mice. The lack of COX-2 expression resulted in decreased levels of CXCL2, a neutrophil-activating chemokine, reduced infiltration of MMP-9-positive neutrophils, and impaired late macrophage activation in livers after I/R injury. Additionally, Bcl-2 and Bcl-x(L) were normally expressed in COX-2(-/-) livers after injury, whereas respective wild-type controls were almost depleted of these two inhibitors of cell death. In contrast, caspase-3 activation and TUNEL-positive cells were depressed in COX-2(-/-) livers. Therefore, our data support the concept that COX-2 is involved in the pathogenic events occurring in liver I/R injury. The data also suggest that potential valuable therapeutic approaches in liver I/R injury may result from further studies aimed at identifying specific COX-2-derived prostanoid pathways.

Hypochlorite-modified high-density lipoprotein acts as a sink for myeloperoxidase in vitro

AIMS

Myeloperoxidase (MPO), a cardiovascular risk factor in humans, is an in vivo catalyst for lipoprotein modification via intermediate formation of reactive chlorinating species. Among the different lipoprotein classes, anti-atherogenic high-density lipoprotein (HDL) represents a major target for modification by hypochlorous acid (HOCl), generated from H2O2 by MPO in the presence of physiological chloride concentrations. As MPO was identified as an HDL-associated protein that could facilitate selective oxidative modification of its physiological carrier, the aim of the present study was to investigate whether and to what extent modification of HDL by HOCl affects the binding affinity of MPO in vitro.

METHODS AND RESULTS

We show that binding affinity of 125I-labelled MPO to HDL markedly increases as a function of increasing extent of HOCl modification of HDL. In contrast to native HDL, HOCl-HDL potently inhibits MPO binding/uptake by endothelial cells and effectively attenuates metabolism of MPO by macrophages. Reduction of HDL-associated chloramines with methionine strongly impaired binding affinity of MPO towards HOCl-HDL. This indicates that N-chloramines generated by HOCl are regulators of the high-affinity interaction between HOCl-HDL and positively charged MPO. Most importantly, the presence of HOCl-HDL is almost without effect on the halogenating activity of MPO.

CONCLUSION

We propose that MPO-dependent modification of HDL and concomitant increase in the binding affinity for MPO could generate a vicious cycle of MPO transport to and MPO-dependent modification at sites of chronic inflammation.

Analyzing M-CSF dependent monocyte/macrophage differentiation: expression modes and meta-modes derived from an independent component analysis

Background

The analysis of high-throughput gene expression data sets derived from microarray experiments still is a field of extensive investigation. Although new approaches and algorithms are published continuously, mostly conventional methods like hierarchical clustering algorithms or variance analysis tools are used. Here we take a closer look at independent component analysis (ICA) which is already discussed widely as a new analysis approach. However, deep exploration of its applicability and relevance to concrete biological problems is still missing. In this study, we investigate the relevance of ICA in gaining new insights into well characterized regulatory mechanisms of M-CSF dependent macrophage differentiation.

Results

Statistically independent gene expression modes (GEM) were extracted from observed gene expression signatures (GES) through ICA of different microarray experiments. From each GEM we deduced a group of genes, henceforth called sub-mode. These sub-modes were further analyzed with different database query and literature mining tools and then combined to form so called meta-modes. With them we performed a knowledge-based pathway analysis and reconstructed a well known signal cascade.

Conclusion

We show that ICA is an appropriate tool to uncover underlying biological mechanisms from microarray data. Most of the well known pathways of M-CSF dependent monocyte to macrophage differentiation can be identified by this unsupervised microarray data analysis. Moreover, recent research results like the involvement of proliferation associated cellular mechanisms during macrophage differentiation can be corroborated.

Metalloproteinase-9 deficiency protects against hepatic ischemia/reperfusion injury

Leukocyte transmigration across endothelial and extracellular matrix protein barriers is dependent on adhesion and focal matrix degradation events. In the present study we investigated the role of metalloproteinase-9 (MMP-9/gelatinase B) in liver ischemia/reperfusion (I/R) injury using MMP-9-deficient (MMP-9(-/-)) animals and mice treated with a specific anti-MMP-9 neutralizing antibody or with a broad gelatinase inhibitor for both MMP-9 and metalloproteinase-2 (MMP-2/gelatinase A). Compared to wild-type mice, MMP-9(-/-) mice and mice treated with an anti-MMP-9 antibody showed significantly reduced liver damage. In contrast, mice treated with a broad gelatinase inhibitor showed rather inferior protection against I/R injury and were characterized by persistent ongoing liver inflammation, suggesting that MMP-2 and MMP-9 may have distinct roles in this type of injury. MMP-9 was mostly detected in Ly-6G and macrophage antigen-1 leukocytes adherent to the vessel walls and infiltrating the damaged livers of wild-type mice after liver I/R injury. Leukocyte traffic and cytokine expression were markedly impaired in livers of MMP-9(-/-) animals and in livers of mice treated with anti-MMP-9 antibody after I/R injury; however, initiation of the endothelial adhesion cascades was similar in both MMP-9(-/-) and control livers. We also showed that MMP-9-specific inhibition disrupted neutrophil migration across fibronectin in transwell filters and depressed myeloperoxidase (MPO) activation in vitro.

CONCLUSION

These results support critical functions for MMP-9 in leukocyte recruitment and activation leading to liver damage. Moreover, they provide the rationale for identifying inhibitors to specifically target MMP-9 in vivo as a potential therapeutic approach in liver I/R injury.

Isolation and molecular cloning of a fish myeloperoxidase

Myeloperoxidase (MPO) is a conspicuous enzyme in neutrophils of many fish species. Although the MPO gene has been identified in some fish species, the structure and functions of the protein remain to be determined in these vertebrates. In the present study, we isolated turbot neutrophil MPO from kidney cells by affinity chromatography, with Ulva rigida acidic sulphated polysaccharides (ASP), some of which resemble glycosaminoglycans, and Sepharose. The product obtained, of approximately 150kDa molecular weight and with peroxidase activity, was examined by SDS-page electrophoresis under reduced conditions and immunoblotting, and a single band of about 75kDa was observed. The results obtained suggest that turbot MPO is a dimer and that the band of 75kDa probably corresponds to a monomer generated by treatment of the samples with the reducing agent. The band was analysed by electromatrix-assisted laser desorption ionization-time-of flight-mass spectrometry (MALDI-TOF-MS) and liquid chromatography-electrospray ionization-ion trap mass spectrometry, dynamic exclusion mode (LC-ESI-IT DE), to determine the amino acid composition of some peptides. The peptides obtained were very similar to myeloperoxidases of other organisms, including other fish and mammals, and were used to design the primers for cDNA amplification. A 567bp product was amplified and the deduced amino acid sequence, which contains several putative N-glycosylation and O-glycosylation sites, was compared with other myeloperoxidases. As expected, turbot MPO was more similar to MPO from other fish species (67-86% identity), where the phylogenetic tree obtained agrees with the taxonomic hierarchy, than to MPO from mammals (55-57% identity) and other groups. The results obtained in the present study will also allow functional studies to be carried out with turbot neutrophil MPO enzyme, as well as analysis of MPO gene expression under different stimuli.

Myeloperoxidase is critically involved in the induction of organ damage after renal ischemia reperfusion

In this study the role of myeloperoxidase (MPO) in a murine (C57BL/6) model of ischemia and reperfusion (I/R)-induced renal failure was investigated. The renal function after I/R was analyzed in MPO-deficient (Mpo(-/-)) mice and compared with wild-type (WT) controls. A significant reduction in renal function loss (blood urea nitrogen) was observed after 24 hours of reperfusion of ischemically damaged kidneys in Mpo(-/-) mice compared with I/R WT controls (I/R Mpo(-/-) = 31.3 +/- 1.7 mmol/L versus I/R WT = 42.8 +/- 2.1 mmol/L, sham = 7.0 +/- 0.5 mmol/L; P = 0.003). The early reperfusion phase (2 hours of reperfusion) was characterized by a substantial increase in apoptosis and early complement activation, surprisingly similar in Mpo(-/-) and WT mice. Improved renal function in Mpo(-/-) mice after extended reperfusion was accompanied by a reduced neutrophil influx (P = 0.017) compared with WT controls. Activation and deposition of complement was not significantly reduced in Mpo(-/-) mice compared with WT controls after 24 hours of reperfusion, indicating no specific in vivo role for MPO in activating complement after renal I/R. Taken together, these results demonstrated an important contribution of MPO in the induction of organ damage after renal I/R by influencing critical factors such as neutrophil extravasation but not complement activation.

Effects of Unfractionated Heparin and Glycoprotein IIb/IIIa Antagonists Versus Bivalirdin on Myeloperoxidase Release From Neutrophils

OBJECTIVES The objective of this study was to determine whether adjunctive therapy during percutaneous coronary intervention (PCI) affects markers of systemic inflammation or platelet activation. Despite different mechanisms of action, direct-thrombin inhibition with bivalirudin during PCI provided similar protection from periprocedural and chronic ischemic complications as compared with unfractionated heparin (UFH) plus planned use of GPIIb/IIIa antagonists in the REPLACE-2 and ACUITY trials.

METHODS AND RESULTS

Patients undergoing nonurgent PCI of a native coronary artery were randomized to receive adjunctive therapy with bivalirudin or UFH+eptifibatide. Interleukin (IL)-6 and C-reactive protein (CRP) transiently increased in both groups after PCI. In the UFH+eptifibatide, but not the bivalirudin group, myeloperoxidase (MPO) levels were elevated 2.3-fold above baseline (P=0.004) immediately after PCI. In an in vitro assay, heparin and to a lesser extent enoxaparin, but not bivalirudin or eptifibatide, stimulated MPO release from and binding to neutrophils and neutrophil activation. A mouse model of endoluminal femoral artery denudation was used to investigate further the importance of MPO in the context of arterial injury.

CONCLUSIONS

Adjuvant therapy during PCI may have undesired effects on neutrophil activation, MPO release, and systemic inflammation.

Myeloperoxidase interacts with endothelial cell-surface cytokeratin 1 and modulates bradykinin production by the plasma Kallikrein-Kinin system

During an inflammatory state, functional myeloperoxidase (MPO) is released into the vessel as a result of intravascular neutrophil degradation. One mechanism of resulting cellular injury involves endothelial internalization of MPO, which causes oxidative damage and impairs endothelial signaling. We report the discovery of a protein that facilitates MPO internalization, cytokeratin 1 (CK1), identified using affinity chromatography and mass spectrometry. CK1 interacts with MPO in vitro, even in the presence of 100% human plasma, thus substantiating biological relevance. Immunofluorescent microscopy confirmed that MPO added to endothelial cells can co-localize with endogenously expressed CK1. CK1 acts as a scaffolding protein for the assembly of the vasoregulatory plasma kallikrein-kinin system; thus we explored whether MPO and high molecular weight kininogen (HK) reside on CK1 together or whether they compete for binding. The data support cooperative binding of MPO and HK on cells such that MPO masked the plasma kallikrein cleavage site on HK, and MPO-generated oxidants caused inactivation of both HK and kallikrein. Collectively, interactions between MPO and the components of the plasma kallikrein-kinin system resulted in decreased bradykinin production. This study identifies CK1 as a facilitator of MPO-mediated vascular responses and thus provides a new paradigm by which MPO affects vasoregulatory systems.

Topical p38 MAPK inhibition reduces bacterial growth in an in vivo burn wound model

BACKGROUND

Although the inflammatory response is a prerequisite for wound healing, excessive activation of the innate immune system can induce epithelial cell damage and apoptosis, which may further compromise dermal integrity. In a noninfectious burn wound model, we previously demonstrated that topical inhibition of p38 MAPK, an important inflammatory signaling pathway, attenuated epithelial cell damage and apoptosis. We now question whether attenuating local inflammation would weaken bacterial wound resistance and compromise host defense.

METHODS

Rats received 30% total body surface area burn, and the wound was treated with topical application of a p38 MAPK inhibitor or vehicle. At 24 hours after injury, burn wounds were inoculated with Pseudomonas aeruginosa. At 48 hours postinjury, animals were sacrificed, and the burn wound was analyzed.

RESULTS

Inoculating burn wounds induced significant bacterial growth. Dermal inflammatory changes were markedly accentuated in the inoculated animals. Topical p38 MAPK inhibition reduced the proinflammatory cytokine expression in the burn wounds and neutrophil sequestration with or without bacterial inoculation. Interestingly, the bacterial wound growth was significantly attenuated in animals treated with topical p38 MAPK inhibitor.

CONCLUSIONS

Topical p38 MAPK inhibition attenuated wound inflammation without interfering with bacterial host defense. Attenuation of excessive burn wound inflammatory signaling may prevent secondary damage of the dermal barrier and reduce the growth of opportunistic pathogens.

Inactivation of anthracyclines by serum heme proteins

We have previously shown that the anticancer agent doxorubicin undergoes oxidation and inactivation when exposed to myeloperoxidase-containing human leukemia HL-60 cells, or to isolated myeloperoxidase, in the presence of hydrogen peroxide and nitrite. In the current study we report that commercial fetal bovine serum (FBS) alone oxidizes doxorubicin in the presence of hydrogen peroxide and that nitrite accelerates this oxidation. The efficacy of inactivation was dependent on the concentration of serum present; no reaction was observed when hydrogen peroxide or serum was omitted. Peroxidase activity assays, based on oxidation of 3,3',5,5'-tetramethylbenzidine, confirmed the presence of a peroxidase in the sera from several suppliers. The peroxidative activity was contained in the >10000 MW fraction. We also found that hemoglobin, a heme protein likely to be present in commercial FBS, is capable of oxidizing doxorubicin in the presence of hydrogen peroxide and that nitrite further stimulates the reaction. In contrast to intact doxorubicin, the serum + hydrogen peroxide + nitrite treated drug appeared to be nontoxic for PC3 human prostate cancer cells. Together, this study shows that (pseudo)peroxidases present in sera catalyze oxidation of doxorubicin by hydrogen peroxide and that this diminishes the tumoricidal activity of the anthracycline, at least in in vitro settings. Finally, this study also points out that addition of H2O2 to media containing FBS will stimulate peroxidase-type of reactions, which may affect cytotoxic properties of studied compounds.

Inhibition of the MEK/ERK pathway reduces microglial activation and interleukin-1-beta expression in spinal cord ischemia/reperfusion injury in rats

OBJECTIVES

Ischemic spinal cord injury is a serious complication of aortic surgery. Although the extracellular signal-regulated kinases 1 and 2 are generally regarded as related to cell proliferation and survival, increasing evidence suggests that the role of the extracellular signal-regulated kinase pathway in ischemia/reperfusion injury is much more sophisticated.

METHODS

Spinal cord ischemia in rats was induced by occluding the thoracic descending aorta with a balloon catheter introduced through a femoral artery, accompanied by concomitant exsanguination. Rats in the control group were given dimethyl sulfoxide (vehicle) before undergoing spinal cord ischemia/reperfusion injury. In the U0126-treated group, rats were pretreated with a specific inhibitor of the mitogen-activated protein kinase/extracellular signal-regulated kinases 1 and 2, U0126, to inhibit extracellular signal-regulated kinases 1 and 2 phosphorylation. The sham-operated rats underwent aortic catheterization without occlusion. Parameters, including neurologic performance, neuronal survival, inflammatory cell infiltration, and interleukin-1beta production in the spinal cords, were compared between groups.

RESULTS

Early extracellular signal-regulated kinases 1 and 2 phosphorylation was observed after injury in the control group, followed by abundant microglial accumulation in the infarct area and increased interleukin-1beta expression. In the U0126 group, U0126 treatment completely blocked extracellular signal-regulated kinases 1 and 2 phosphorylation. Microglial activation and spinal cord interleukin-1beta levels were significantly reduced. Neuronal survival and functional performance were improved.

CONCLUSIONS

The mitogen-activated protein kinase/extracellular signal-regulated kinase pathway may play a noxious role in spinal cord ischemia/reperfusion injury by participating in inflammatory reactions and cytokine production. Targeting this pathway may be of potential value in terms of therapeutic intervention.

Spatial coordination of cell-adhesion molecules and redox cycling of iron in the microvascular inflammatory response to pulmonary injury

Transmigration of phagocytic leukocytes (PLCs) from the peripheral blood into injured lung requires a conversion of the microvascular endothelial cells (ECs) to the proinflammatory phenotypes and spatiotemporal interplay of different types of cell adhesion molecules (CAMs) on PLC and endothelium. The present report is focused on involvement of iron-dependent redox signaling in spatial coordination of lung CAM due to either a pulmonary trauma or endotracheal iron administration in rats. Redox alterations, deposition of 3-nitrotyrosine, expression of VE-cadherin, ICAM-1, and the PLC integrins, and the status of thioredoxin, Ref-1, NF-kappaB and Nrf2 redox-sensitive elements in the alveolar microvasculature were assessed with EPR spectroscopy, immunobloting, and confocal microscopy. We demonstrated for the first time in vivo that the presence of catalytically active iron, deposition of myeloperoxidase, and induction of the oxidative stress in the lung-injury models were accompanied by (a) downregulation of VE-cadherin, (b) upregulation and polarization of ICAM-1 and the PLC integrins, and (c) nuclear translocation and interaction of thioredoxin, Ref-1, and NF-kappaB and complex structural changes in EC and PLC at the sites of their contacts. The studies suggested that a part of the proinflammatory action of iron in the lung resulted from its stimulation of the redox-sensitive factors.

Antineutrophil Cytoplasm Antibody–Stimulated Neutrophil Adhesion Depends on Diacylglycerol Kinase–Catalyzed Phosphatidic Acid Formation

Patients with certain forms of systematic vasculitis, such as Wegener's granulomatosis, have circulating antineutrophil cytoplasmic antibodies (ANCA). These inappropriately stimulate circulating neutrophils adhere to and thereby obstruct small vessels. This, together with ANCA-induced degranulation and an oxidative burst, leads to local tissue damage. The signaling pathways that are activated by ANCA IgG are distinct from those that are involved in normal neutrophil activation. This study shows that diacylglycerol kinase is selectively activated by ANCA and that the generated phosphatidic acid is responsible for promoting neutrophil adhesion, in part through integrin activation. The data presented point to diacylglycerol kinase alpha as a novel but selective target for the development of drugs to treat this potentially fatal disorder.

Molecular basis of pregnancy-induced breast cancer protection

We have postulated that the lifetime protective effect of an early pregnancy against breast cancer is due to the complete differentiation of the mammary gland characterized by a specific genomic signature imprinted by the physiological process of pregnancy. In the present work, we show evidence that the breast tissue of postmenopausal parous women has had a shifting of stem cell 1 to stem cell 2 with a genomic signature different from similar structures derived from postmenopausal nulliparous women that have stem cell 1. Those genes that are significantly different are grouped in major categories on the basis of their putative functional significance. Among them are those gene transcripts related to immune surveillance, DNA repair, transcription, chromatin structure/activators/co-activators, growth factor and signal transduction pathway, transport and cell trafficking, cell proliferation, differentiation, cell adhesion, protein synthesis and cell metabolism. From these data, it was concluded that during pregnancy there are significant genomic changes that reflect profound alterations in the basic physiology of the mammary gland that explain the protective effect against carcinogenesis. The implication of this knowledge is that when the genomic signature of protection or refractoriness to carcinogenesis is acquired by the shifting of stem cell 1 to stem cell 2, the hormonal milieu induced by pregnancy or pregnancy-like conditions is no longer required. This is a novel concept that challenges the current knowledge that a chemopreventive agent needs to be given for a long period to suppress a metabolic pathway or abrogate the function of an organ.

Hypochlorite-modified albumin colocalizes with RAGE in the artery wall and promotes MCP-1 expression via the RAGE-Erk1/2 MAP-kinase pathway

Signal transduction via the endothelial receptor for advanced glycation end products (RAGE) plays a key role in vascular inflammation. Recent observations have shown that the myeloperoxidase-H2O2-chloride system of activated phagocytes is highly up-regulated under inflammatory conditions where hypochlorous acid (HOCl) is formed as the major oxidant. Albumin, an in vivo carrier for myeloperoxidase is highly vulnerable to oxidation and a major representative of circulating advanced oxidized proteins during inflammatory diseases. Immunohistochemical studies performed in the present study revealed marked colocalization of HOCl-modified epitopes with RAGE and albumin in sections of human atheroma, mainly at the endothelial lining. We show that albumin modified with physiologically relevant concentrations of HOCl, added as reagent or generated by the myeloperoxidase-H2O2-chloride system, is a high affinity ligand for RAGE. Albumin, modified by HOCl in the absence of free amino acids/carbohydrates/lipids to exclude formation of AGE-like structures, induced a rapid, RAGE-dependent activation of extracellular signal-regulated kinase 1/2 and up-regulation of the proinflammatory mediator monocyte chemoattractant protein-1. Cellular activation could be blocked either by a specific polyclonal anti-RAGE IgG and/or a specific mitogen-activated protein-kinase kinase inhibitor. The present study demonstrates that HOCl-modified albumin acts as a ligand for RAGE and promotes RAGE-mediated inflammatory complications.