Human myeloperoxidase in innate and acquired immunity

Loading of bacterial cellulose dressing with frutalin, a lectin from Artocarpus incisa L

Bacterial cellulose (BC), produced by bacterial fermentation, is a high-purity material. BC can be oxidized (BCOXI), providing aldehyde groups for covalent bonds with drugs. Frutalin (FTL) is a lectin capable of modulating cell proliferation and remodeling, which accelerates wound healing. This study aimed to develop an FTL-incorporated dressing based on BC, and to evaluate its physicochemical properties and biological activity in vitro. An experimental design was employed to maximize FTL loading yield onto the BC and BCOXI, where independent variables were FTL concentration, temperature and immobilization time. BCOXI-FTL 1 (44.96 % ± 1.34) had the highest incorporation yield (IY) at the experimental conditions: 6 h, 5 °C, 20 μg mL-1. The second highest yield was BCOXI-FTL 6 (23.28 % ± 1.43) using 24 h, 5 °C, 100 μg mL-1. Similarly, the same reaction parameters provided higher immobilization yields for native bacterial cellulose: BC-FTL 6 (16.91 % ± 1.05) and BC-FTL 1 (21.71 % ± 1.57). Purified FTL displayed no cytotoxicity to fibroblast cells (<50 μg mL-1 concentration) during 24 h. Furthermore, BCOXI-FTL and BC-FTL were non-cytotoxic during 24 h and stimulated fibroblast migration. BCOXI-FTL demonstrated neutrophil activation in vitro similar to FTL. These promising results indicate that the bacterial cellulose matrices containing FTL at low concentrations, could be used as an innovative biomaterial for developing wound dressings.

Novel quinazoline sulfonamide-based scaffolds modulate methicillin-resistant Staphylococcus aureus (MRSA) pneumonia in immunodeficient irradiated model: Regulatory role of TGF-β

A library of new quinazoline pharmacophores bearing benzenesulfonamide moiety was designed and synthesized. Compounds 3a-n were screened for their in vitro antimicrobial activity against eight multidrug-resistant clinical isolates. Compounds 3d and 3n exhibited prominent antibacterial activity, specifically against MRSA. After exhibiting relative in vitro and in vivo safety, compound 3n was selected to assess its anti-inflammatory activity displaying promising COX-2 inhibitory activity compared to Ibuprofen. In vivo experimental MRSA pneumonia model was conducted on immunodeficient (irradiated) mice to reveal the antimicrobial and anti-inflammatory responses of compound 3n compared to azithromycin (AZ). Treatment with compound 3n (10 and 20 mg/kg) as well as AZ resulted in a significant decrease in bacterial counts in lung tissues, suppression of serum C-reactive protein (CRP), lung interleukin-6 (IL-6), myeloperoxidase activity (MPO) and transforming growth factor-β (TGF-β). Compound 3n showed a non-significant deviation of lung TGF-β1 from normal values which in turn controlled the lung inflammatory status and impacted the histopathological results. Molecular docking of 3n showed promising interactions inside the active sites of TGF-β and COX-2. Our findings present a new dual-target quinazoline benzenesulfonamide derivative 3n, which possesses significant potential for treating MRSA-induced pneumonia in an immunocompromised state.

Elucidation of 7,8-dihydroxy flavone in complexing with the oxidative stress-inducing enzymes, its impact on radical quenching and DNA damage: an in silico and in vitro approach

Oxidative stress (OS) has been attributed to the progression of various disorders, including cancer, diabetes, and cardiovascular diseases. Several antioxidant compounds and free radical quenchers have been shown to mitigate oxidative stress. However, large-scale randomized controlled trials of such compounds on chronic disease aversion have yielded paradoxical and disappointing results due to the constrained cognizance of their oxidative mechanisms and therapeutic targets. The current study sought to identify the potential therapeutic targets of 7,8-Dihydroxyflavone (7,8-DHF) by analyzing its interactions with the enzymes implicated in oxidative stress and also to explore its radicle quenching potential and prophylactic impact on the H2O2-induced DNA damage. Through the in silco approach, we investigated the antioxidant potential of 7,8-DHF by evaluating its interactions with the human oxidative stress-inducing enzymes such as myeloperoxidase (MPO), NADPH oxidase (NOX), nitric oxide synthase (NOS), and xanthine oxidase (XO) and a comparative analysis of those interactions with known antioxidants (Ascorbic acid, Melatonin, Tocopherol) used as controls. The best-scoring complex was adopted for the simulation analysis in investigating protein-ligand conformational dynamics. The in vitro radicle quenching potential was evaluated by performing a spectrum of antioxidant assays, and radical quenching was observed in a dose-dependent fashion with IC50 values of < 60 µM/mL. Further, we probed its anti-hemolytic potential and prophylactic impact in avian erythrocytes subjected to H2O2-induced hemolysis and DNA damage by implementing hemolysis and comet assays. The protective effect was more pronounced at higher concentrations of the drug.Communicated by Ramaswamy H. Sarma.

Reactive Halogen Species: Role in Living Systems and Current Research Approaches

Reactive halogen species (RHS) are highly reactive compounds that are normally required for regulation of immune response, inflammatory reactions, enzyme function, etc. At the same time, hyperproduction of highly reactive compounds leads to the development of various socially significant diseases - asthma, pulmonary hypertension, oncological and neurodegenerative diseases, retinopathy, and many others. The main sources of (pseudo)hypohalous acids are enzymes from the family of heme peroxidases - myeloperoxidase, lactoperoxidase, eosinophil peroxidase, and thyroid peroxidase. Main targets of these compounds are proteins and peptides, primarily methionine and cysteine residues. Due to the short lifetime, detection of RHS can be difficult. The most common approach is detection of myeloperoxidase, which is thought to reflect the amount of RHS produced, but these methods are indirect, and the results are often contradictory. The most promising approaches seem to be those that provide direct registration of highly reactive compounds themselves or products of their interaction with components of living cells, such as fluorescent dyes. However, even such methods have a number of limitations and can often be applied mainly for in vitro studies with cell culture. Detection of reactive halogen species in living organisms in real time is a particularly acute issue. The present review is devoted to RHS, their characteristics, chemical properties, peculiarities of interaction with components of living cells, and methods of their detection in living systems. Special attention is paid to the genetically encoded tools, which have been introduced recently and allow avoiding a number of difficulties when working with living systems.

Heterogeneity in Neutrophil Extracellular Traps from Healthy Human Subjects

Neutrophil extracellular traps (NETs), a key component of early defense against microbial infection, are also associated with tissue injury. NET composition has been reported to vary with some disease states, but the composition and variability of NETs across many healthy subjects provide a critical comparison that has not been well investigated. We evaluated NETs from twelve healthy subjects of varying ages isolated from multiple blood draws over a three-and-one-half-year period to delineate the variability in extracellular DNA, protein, enzymatic activities, and susceptibility to protease inhibitors. We calculated correlations for NET constituents and loss of human bronchial epithelial barrier integrity, measured by transepithelial electrical resistance, after NET exposure. We found that although there was some variability within the same subject over time, the mean NET total DNA, dsDNA, protein, LDH, neutrophil elastase (NE), and proteinase 3 (PR3) in isolated NETs were consistent across subjects. NET serine protease activity varied considerably within the same donor from day to day. The mean NET cathepsin G and MPO were significantly different across donors. IL-8 > IL-1RA > G-CSF were the most abundant cytokines in NETs. There was no significant difference in the mean concentration or variability of IL-8, IL-1RA, G-CSF, IL-1α, IL-1β, or TNF-α in different subjects' NETs. NET DNA concentration was correlated with increased NET neutrophil elastase activity and higher NET IL-1RA concentrations. The mean reduction in protease activity by protease inhibitors was significantly different across donors. NET DNA concentration correlated best with reductions in the barrier integrity of human bronchial epithelia. Defining NET concentration by DNA content correlates with other NET components and reductions in NET-driven epithelial barrier dysfunction, suggesting DNA is a reasonable surrogate measurement for these complex structures in healthy subjects.

Inflammation-Associated Cytotoxic Agents in Tumorigenesis

Chronic inflammatory processes are related to all stages of tumorigenesis. As inflammation is closely associated with the activation and release of different cytotoxic agents, the interplay between cytotoxic agents and antagonizing principles is highlighted in this review to address the question of how tumor cells overcome the enhanced values of cytotoxic agents in tumors. In tumor cells, the enhanced formation of mitochondrial-derived reactive species and elevated values of iron ions and free heme are antagonized by an overexpression of enzymes and proteins, contributing to the antioxidative defense and maintenance of redox homeostasis. Through these mechanisms, tumor cells can even survive additional stress caused by radio- and chemotherapy. Through the secretion of active agents from tumor cells, immune cells are suppressed in the tumor microenvironment and an enhanced formation of extracellular matrix components is induced. Different oxidant- and protease-based cytotoxic agents are involved in tumor-mediated immunosuppression, tumor growth, tumor cell invasion, and metastasis. Considering the special metabolic conditions in tumors, the main focus here was directed on the disturbed balance between the cytotoxic agents and protective mechanisms in late-stage tumors. This knowledge is mandatory for the implementation of novel anti-cancerous therapeutic approaches.

The association between oral inflammatory load and semen and sperm functional analysis: A cross-sectional study

Background

Studies have suggested a correlation between periodontitis and reduced male fertility. Inflammation has been described as the link between these ailments. Oral inflammatory load (OIL) can be measured through oral polymorphonuclear neutrophil (oPMN) count, which is associated with periodontal diseases. This cross-sectional study assessed the possible correlation between OIL and the functional parameters of sperm cells.

Methods

In 229 volunteers, oral rinse and semen samples were assessed for oPMN, semen polymorphonuclears (sPMNs), sperm concentration, total sperm count, motility, morphology, and sperm DNA fragmentation index (SDFi). A multiple linear regression model was conducted to evaluate the relationships between oPMN and semen parameters.

Results

The effect of elevated oPMN counts on total motility rate, progressive rate, and percentage of sperm cells with normal morphology was significant (P<0.001), with an inverse relationship, i.e., with every unit increase in oPMN count, the mentioned parameters would decline by 0.573, 0.367, and 0.407 units, respectively. oPMN counts also correlated positively with sPMN counts and SDFi (P<0.001), i.e., with every unit increase in the oPMN measures, sPMN counts would increase by 0.126 million/mL, with an 0.733% increase in SDFi. However, there was no significant association between oPMN counts and sperm concentration.

Conclusion

OIL, as represented by oPMN counts, might affect male fertility as there is a positive correlation between the levels of these inflammatory cells and decreased sperm motility, abnormal morphological changes, increased sPMN counts, and increased SDFi.

Heterogeneity in Neutrophil Extracellular Traps from Healthy Human Subjects

Neutrophil Extracellular Traps (NETs), a key component of early defense against microbial infection, are also associated with tissue injury. NET composition has been reported to vary with some disease states, but the composition and variability of NETs across many healthy subjects provides a critical comparison that has not been well investigated. We evaluated NETs from twelve healthy subjects of varying ages isolated from multiple blood draws over a three and one half-year period to delineate the variability in extracellular DNA, protein, enzymatic activities, and susceptibility to protease inhibitors. We calculated correlations for NET constituents and loss of human bronchial epithelial barrier integrity, measured by transepithelial electrical resistance, after NET exposure. We found that although there was some variability within the same subject over time, the mean numbers of neutrophils, protein, LDH, serine protease activities, and cytokines IL-8, IL-1RA, and G-CSF in isolated NETs were consistent across subjects. Total DNA and double stranded DNA content in NETs were different across donors. NETs had little or no TNFα, IL-17A, or GM-CSF. NET DNA concentration correlated with increased NET neutrophil elastase activity and higher NET IL-1RA concentrations. NET serine protease activity varied considerably within the same donor from day-to-day. Mean response to protease inhibitors was significantly different across donors. NET DNA concentration correlated best with reductions in barrier integrity of human bronchial epithelia. Defining NET concentration by DNA content correlates with other NET components and reductions in NET-driven epithelial barrier dysfunction, suggesting DNA is a reasonable surrogate measurement for these complex structures in healthy subjects.

Multi-Oxidant Environment as a Suicidal Inhibitor of Myeloperoxidase

Tissue inflammation drives the infiltration of innate immune cells that generate reactive species to kill bacteria and recruit adaptive immune cells. Neutrophil activation fosters the release of myeloperoxidase (MPO) enzyme, a heme-containing protein generating hypochlorous acid (HOCl) from hydrogen peroxide (H2O2) and chloride ions. MPO-dependent oxidant formation initiates bioactive oxidation and chlorination products and induces oxidative post-translational modifications (oxPTMs) on proteins and lipid oxidation. Besides HOCl and H2O2, further reactive species such as singlet oxygen and nitric oxide are generated in inflammation, leading to modified proteins, potentially resulting in their altered bioactivity. So far, knowledge about multiple free radical-induced modifications of MPO and its effects on HOCl generation is lacking. To mimic this multi-oxidant microenvironment, human MPO was exposed to several reactive species produced simultaneously via argon plasma operated at body temperature. Several molecular gas admixes were used to modify the reactive species type profiles generated. MPO was investigated by studying its oxPTMs, changes in protein structure, and enzymatic activity. MPO activity was significantly reduced after treatment with all five tested plasma gas conditions. Dynamic light scattering and CD-spectroscopy revealed altered MPO protein morphology indicative of oligomerization. Using mass spectrometry, various oxPTMs, such as +1O, +2O, and +3O, were determined on methionine and cysteine (Cys), and -1H-1N+1O was detected in asparagine (Asp). The modification types identified differed between argon-oxygen and argon-nitrogen plasmas. However, all plasma gas conditions led to the deamidation of Asp and oxidation of Cys residues, suggesting an inactivation of MPO due to oxPTM-mediated conformational changes.

Elevated Fecal Calprotectin Accompanied by Intestinal Neutrophil Infiltration and Goblet Cell Hyperplasia in a Murine Model of Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system caused by myelin-specific autoreactive T cells. We previously demonstrated intestinal barrier disruption and signs of inflammation in experimental autoimmune encephalomyelitis (EAE), a model of MS. Fecal calprotectin is a disease activity biomarker in inflammatory bowel diseases, released by neutrophils in response to inflammation. We aimed to further investigate EAE manifestations in the gastrointestinal tract and to determine whether calprotectin is a useful biomarker of intestinal inflammation in EAE. Calprotectin was analyzed in feces, cecal contents, and plasma of EAE mice. Infiltrating neutrophils and goblet cells were investigated in different parts of the gastrointestinal tract before the onset of neurological symptoms and during established disease. We found increased calprotectin levels in feces, cecal content, and plasma preceding EAE onset that further escalated during disease progression. Increased neutrophil infiltration in the intestinal tissue concomitant with IL-17 expression and myeloperoxidase activity was found to correlate well with clinical activity. Increased goblet cells in the intestine, similar to irritable bowel syndrome (IBS), were also observed. The results suggest calprotectin as a good biomarker of gastrointestinal inflammation in EAE and the potential of this model as a useful animal model for IBS.

Modulation of the Proliferative Pathway, Neuroinflammation and Pain in Endometriosis

Endometriosis is a chronic disease characterized by pelvic inflammation. This study aimed at investigating the molecular mechanisms underlying the pathology and how they can be modulated by the administration of a natural compound, Actaea racemosa (AR). We employed an in vivo model of endometriosis in which rats were intraperitoneally injected with uterine fragments from donor animals. During the experiment, rats were monitored by abdominal high-frequency ultrasound analysis. AR was able to reduce the lesion's size and histological morphology. From a molecular point of view, AR reduced hyperproliferation, as shown by Ki-67 and PCNA expression and MAPK phosphorylation. The impaired apoptosis pathway was also restored, as shown by the TUNEL assay and RT-PCR for Bax, Bcl-2, and Caspase levels. AR also has important antioxidant (reduced Nox expression, restored SOD activity and GSH levels, and reduced MPO activity and MDA levels) and anti-inflammatory (reduced cytokine levels) properties. Moreover, AR demonstrated its ability to reduce the pain-like behaviors associated with the pathology, the neuro-sensitizing mediators (c-FOS and NGF) expression, and the related central astrogliosis (GFAP expression in the spinal cord, brain cortex, and hippocampus). Overall, our data showed that AR was able to manage several pathways involved in endometriosis suppression.

Mass spectrometric investigations of the action of hypochlorous acid on monomeric and oligomeric components of glycosaminoglycans

Hypochlorous acid (HOCl) is a strong non-radical oxidant, which is generated during inflammatory processes under the catalysis of the enzyme myeloperoxidase (MPO). HOCl reacts particularly with sulfhydryl and amino acid residues but affects also many other biomolecules. For instance, the glycosaminoglycans of articular cartilage and synovial fluids (such as hyaluronan) undergo degradation in the presence of HOCl at which the native polysaccharide is fragmented into oligosaccharides in a complex reaction. This is an initial mass spectrometry (MS)-based investigation dealing with the HOCl-induced degradation of glycosaminoglycans and the conversion of the related monosaccharides into chlorinated products. In particular, it will be shown that the reaction between HOCl and hyaluronan is slower than originally assumed and results in the generation of different products (particularly the hyaluronan monosaccharides) by the cleavage of the β-1,3/1,4-glycosidic linkages. The MS detection of chlorinated products is, however, only possible in the case of the monosaccharides. Potential reasons will be discussed.

Discovery of a novel, highly potent and orally bioavailable pyrrolidinone indole series of irreversible Myeloperoxidase (MPO) inhibitors

Myeloperoxidase (MPO) is a heme-containing peroxidase from phagocytic cells, which plays an important role in the innate immune response. The primary anti-microbial function of MPO is achieved by catalyzing the oxidation of halides by hydrogen peroxide (H₂O₂). Upon activation of phagocytes, MPO activity is detectable in both phagosomes and extracellularly, where it can remain or transcytose into interstitial compartments. Activated MPO leads to oxidative stress and tissue damage in many inflammatory states, including cardiovascular disease. Starting from a low molecular weight (LMW) high throughput screening (HTS) hit, here we report the discovery of a novel pyrrolidinone indole (IN-4) as a highly potent MPO inhibitor. This compound displays similar in vitro potency across peroxidation, plasma and NETosis assays. In a dilution/dialysis study, <5% of the original MPO activity was detected post-incubation of MPO with IN-4, suggesting irreversible enzyme inhibition. A fast MPO inactivation rate (k_inact/K_i) and low partition ratio (k₃/k₄) make IN-4 kinetic properties attractive for an MPO inhibitor. This compound also displays significant selectivity over the closely related thyroid peroxidase (TPO), and is selective for extracellular MPO over intracellular (neutrophil) MPO. Moreover, IN-4 shows good exposure, low clearance and high oral bioavailability in mice, rats and dogs. The high in vitro MPO activity and high oral exposure observed with IN-4 result in a dose-dependent inhibition of MPO activity in three mouse models of inflammation. In conclusion, IN-4 is a novel, potent, mechanism-based and selective MPO inhibitor, which may be used as superior therapeutic agent to treat multiple inflammatory conditions, including cardiovascular disease.

Host-Derived Cytotoxic Agents in Chronic Inflammation and Disease Progression

At inflammatory sites, cytotoxic agents are released and generated from invading immune cells and damaged tissue cells. The further fate of the inflammation highly depends on the presence of antagonizing principles that are able to inactivate these host-derived cytotoxic agents. As long as the affected tissues are well equipped with ready-to-use protective mechanisms, no damage by cytotoxic agents occurs and resolution of inflammation is initiated. However, long-lasting and severe immune responses can be associated with the decline, exhaustion, or inactivation of selected antagonizing principles. Hence, cytotoxic agents are only partially inactivated and contribute to damage of yet-unperturbed cells. Consequently, a chronic inflammatory process results. In this vicious circle of permanent cell destruction, not only novel cytotoxic elements but also novel alarmins and antigens are liberated from affected cells. In severe cases, very low protection leads to organ failure, sepsis, and septic shock. In this review, the major classes of host-derived cytotoxic agents (reactive species, oxidized heme proteins and free heme, transition metal ions, serine proteases, matrix metalloproteases, and pro-inflammatory peptides), their corresponding protective principles, and resulting implications on the pathogenesis of diseases are highlighted.

Effects and mechanism of myeloperoxidase on microglia in the early stage of intracerebral hemorrhage

Objectives

(1) To clarify the dynamic relationship between the expression of myeloperoxidase (MPO) and microglial activation of intracerebral hemorrhage (ICH), (2) to explore the effect of inhibition of MPO on microglial activation, and (3) to observe the improvement in the neurobehavior of mice with inhibition of MPO.

Methods

C57 BL/6 mice and CX3CR1 + /GFP mice were used to establish a phosphate-buffered saline (PBS) group, an ICH group, and a 4-aminobenzoic acid hydrazide (ABAH) group. Longa score, open field locomotion, hind-limb clasping test, immunohistochemistry, immunofluorescence, blood routine detection, and flow cytometry were used.

Results

The neurobehavior of the mice was significantly impaired following ICH (P < 0.01); the expression of MPO was significantly increased following ICH, and reached a peak value at 6 h post-injury (P < 0.001). Moreover, the microglial activation increased significantly following ICH, and reached a peak level at 24 h post-injury (P < 0.01). Following inhibition of MPO, the activation of microglia in the ICH group decreased significantly (P < 0.001). Moreover, the neurobehavior of the ICH group was significantly improved with MPO inhibition (P < 0.05).

Conclusion

MPO may be an upstream molecule activated by microglia and following inhibition of MPO can improve secondary injury resulting from ICH.

Chronic Methylmercury Intoxication Induces Systemic Inflammation, Behavioral, and Hippocampal Amino Acid Changes in C57BL6J Adult Mice

Methylmercury (MeHg) is highly toxic to the human brain. Although much is known about MeHg neurotoxic effects, less is known about how chronic MeHg affects hippocampal amino acids and other neurochemical markers in adult mice. In this study, we evaluated the MeHg effects on systemic lipids and inflammation, hippocampal oxidative stress, amino acid levels, neuroinflammation, and behavior in adult male mice. Challenged mice received MeHg in drinking water (2 mg/L) for 30 days. We assessed weight gain, total plasma cholesterol (TC), triglycerides (TG), endotoxin, and TNF levels. Hippocampal myeloperoxidase (MPO), malondialdehyde (MDA), acetylcholinesterase (AChE), amino acid levels, and cytokine transcripts were evaluated. Mice underwent open field, object recognition, Y, and Barnes maze tests. MeHg-intoxicated mice had higher weight gain and increased the TG and TC plasma levels. Elevated circulating TNF and LPS confirmed systemic inflammation. Higher levels of MPO and MDA and a reduction in IL-4 transcripts were found in the hippocampus. MeHg-intoxication led to increased GABA and glycine, reduced hippocampal taurine levels, delayed acquisition in the Barnes maze, and poor locomotor activity. No significant changes were found in AChE activity and object recognition. Altogether, our findings highlight chronic MeHg-induced effects that may have long-term mental health consequences in prolonged exposed human populations.

Immune-biochemical response and immune gene expression profiling of Labeo rohita fingerlings fed with ethanolic tea leaf extracts and its survivability against Aeromonas hydrophila infection

The present study was conducted to evaluate the immunostimulatory effect of tea leaf extract (Camellia sinensis) on Labeo rohita and its resistance against Aeromonas hydrophila infection. The ethanolic extract of green tea (GTEE) was found to be the most potent as compared to other solvent extract which was used for further study. It was used to evaluate immune-biochemical response of L. rohita fingerlings, fed with tea leaf extract (control- 0.0%, 0.2% (T1), 0.4% (T2), 0.8% (T3) and 1% (T4) of GTEE kg^-1 feed). Different biochemical parameters like glucose, ALP, GPT, GOT, and immunological parameters like lysozyme activity, NBT, anti-protease activity, myeloperoxidase activity, plasma protein, and immune relevant genes (IL-10, C3, Lysozyme G type and iNOS) expressions were carried out. The immunological parameters such as lysozyme activity, NBT and myeloperoxidase activity showed significantly high value once fed with GTEE incorporated diets. Significant up-regulation of immune genes indicated the enhancement of immune response at molecular level. The biochemical parameters were found to be significantly decreasing, indicating that the extract had hepato-protective effect and can help to overcome stress. The fish, fed with GTEE incorporated diets, showed resistance against A. hydrophila when compared with the control group. 0.2% GTEE showed the highest post-challenged survival (76.67%). From the present study, it is concluded that GTEE @ 0.2% can be used as potent immunostimulant as a sustainable alternative prophylactic and therapeutic agent in aquaculture.

Involvement of Anti-Inflammatory and Stress Oxidative Markers in the Antidepressant-like Activity of Aloysia citriodora and Verbascoside on Mice with Bacterial Lipopolysaccharide- (LPS-) Induced Depression

Aloysia citriodora Palau is popularly used to treat nervous disorders. Experimental evidence has indicated that verbascoside (VBS) isolated from A. citriodora has pharmacological potential. In this study, we evaluated the antidepressant-like effects of a hydroalcoholic extract of A. citriodora (HEAc) and VBS against lipopolysaccharide- (LPS-) induced depressive-like behavior in mice. In the pretreatment protocol (performed to evaluate the preventive potential), mice were pretreated with HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg) before the administration of LPS. In the posttreatment protocol (performed to evaluate the therapeutic potential), mice were initially administered LPS and were subsequently given HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg). In both treatments, the mice were submitted to an open-field test and tail suspension test (TST) at 6 and 24 h after LPS administration. The posttreatment evaluation revealed that HEAc (30 or 300 mg/kg) and VBS produced an antidepressant-like effect, as indicated by a reduction in the time spent with no movement in the TST. Moreover, HEAc (30 or 300 mg/kg) was found to reduce interleukin-6 (IL-6) levels and N-acetyl-glycosaminidase activity in the hippocampus, increase glutathione (GSH) levels in the hippocampus and cortex, and enhance IL-10 in the cortex and, at a dose of 300 mg/kg, reduced myeloperoxidase activity in the cortex. Contrastingly, no comparable effects were detected in mice subjected to the pretreatment protocol. Administration of VBS similarly reduced the levels of IL-6 in the hippocampus and increased GSH levels in the cortex. Our observations indicate that both HEAc and VBS show promising antidepressant-like potential, which could be attributed to their beneficial effects in reducing neuroinflammatory processes and antioxidant effects in the central nervous system.

Identification of New Toxicity Mechanisms in Drug-Induced Liver Injury through Systems Pharmacology

Among adverse drug reactions, drug-induced liver injury presents particular challenges because of its complexity, and the underlying mechanisms are still not completely characterized. Our knowledge of the topic is limited and based on the assumption that a drug acts on one molecular target. We have leveraged drug polypharmacology, i.e., the ability of a drug to bind multiple targets and thus perturb several biological processes, to develop a systems pharmacology platform that integrates all drug–target interactions. Our analysis sheds light on the molecular mechanisms of drugs involved in drug-induced liver injury and provides new hypotheses to study this phenomenon.

Myeloperoxidase and Advanced Oxidation Protein Products in the Cerebrospinal Fluid in Women and Men with Parkinson's Disease

Background: Myeloperoxidase (MPO) and advanced oxidation protein products, or AOPP (a type of MPO-derived chlorinated adducts), have been implicated in Parkinson´s disease (PD). Human MPO also show sex-based differences in PD. The objective was to study the relationship of MPO and AOPP in the cerebrospinal fluid (CSF) with motor features of idiopathic PD in male and female patients. Methods: MPO concentration and activity and AOPP content were measured in the CSF and serum in 34 patients and 30 controls. CSF leukocytes and the integrity of the blood-brain barrier were evaluated. Correlations of MPO and AOPP with clinical variables were examined. Results: The blood-brain barrier was intact and CSF leukocyte count was normal in all patients. CSF MPO concentration and activity were similar in the cohort of patients and controls, but CSF MPO content was significantly higher in male patients than in PD women (p = 0.0084). CSF MPO concentration correlated with disease duration in male and female patients (p < 0.01). CSF MPO concentration was significantly higher in men with disease duration ≥12 years versus the remainder of the male subjects (p < 0.01). Changes in CSF MPO in women were not significant. Serum MPO concentration and activity were significantly higher in all PD patients relative to controls (p < 0.0001). CSF MPO was not correlated with serum MPO. Serum AOPP were detected in all patients, but CSF AOPP was undetectable in 53% of patients. AOPP were not quantifiable in controls. Conclusions: CSF MPO is not a good biomarker for PD because mean CSF MPO concentration and activity are not different between the cohort of patients and controls. CSF MPO concentration positively correlated with disease duration in men and women, but CSF MPO is significantly enhanced only in male patients with disease duration longer than 12 years. It can be hypothesized that the MPO-related immune response in early-stage PD might be weak in all patients, but then the MPO-related immune response is progressively enhanced in men, not women. Since the blood-brain barrier is intact, and CSF MPO is not correlated with serum MPO, CSF myeloperoxidase would reflect MPO content in brain cells, not blood-derived cells. Finally, serum AOPP was detected in all patients, but not controls, which is consistent with the occurrence of chlorinative stress in blood serum in PD. The study of CSF AOPP as biomarker could not be assessed because the ELISA assay was hampered by its detection limit in the CSF.

Anti-Inflammatory and Antioxidant Effects of the Indole-Derived N-Salicyloyltryptamine on Peritonitis and Joint Disability Induced by Carrageenan in Rodents

Purpose

To investigate the anti-inflammatory and antioxidant activities of N-salicyloyltryptamine (NST) in experimental models of carrageenan (Cg)-induced peritonitis in mice, and evaluation of the effects of NST on Cg-induced joint disability in rats.

Methods

Female Swiss mice were submitted to Cg-induced peritonitis in mice or Cg-induced joint disability in rats after intraperitoneal injection of NST (100 or 200 mg/kg). Total leukocyte count, total protein concentration, myeloperoxidase (MPO) and catalase (CAT) activities, and nitrite (NO₂⁻) and thiobarbituric acid reactive species (TBARS) levels were determined.

Results

NST significantly decrease the migration of leukocytes to peritoneal exudate. Cg induces inflammatory responses mediated by expression of reactive oxygen species (ROS). The results further showed that NST significantly decreased MPO and CAT activities, as well as reduced NO₂⁻ and TBARS levels, compared with the vehicle group. Animals treated with NST significantly reduced paw elevation time (PET) on the first hour after induction of joint injury, and this effect was sustained throughout the analysis.

Conclusion

NST presented anti-inflammatory and antioxidant effects in experimental models of carrageenan-induced peritonitis and joint disability in mice and rats, respectively, which may be related to the modulation of neutrophils migration as well as the involvement of antioxidant mechanisms.

Halogenation Activity of Mammalian Heme Peroxidases

Mammalian heme peroxidases are fascinating due to their unique peculiarity of oxidizing (pseudo)halides under physiologically relevant conditions. These proteins are able either to incorporate oxidized halides into substrates adjacent to the active site or to generate different oxidized (pseudo)halogenated species, which can take part in multiple (pseudo)halogenation and oxidation reactions with cell and tissue constituents. The present article reviews basic biochemical and redox mechanisms of (pseudo)halogenation activity as well as the physiological role of heme peroxidases. Thyroid peroxidase and peroxidasin are key enzymes for thyroid hormone synthesis and the formation of functional cross-links in collagen IV during basement membrane formation. Special attention is directed to the properties, enzymatic mechanisms, and resulting (pseudo)halogenated products of the immunologically relevant proteins such as myeloperoxidase, eosinophil peroxidase, and lactoperoxidase. The potential role of the (pseudo)halogenated products (hypochlorous acid, hypobromous acid, hypothiocyanite, and cyanate) of these three heme peroxidases is further discussed.

Myeloperoxidase Deficiency Alters the Process of the Regulated Cell Death of Polymorphonuclear Neutrophils

Polymorphonuclear neutrophils (PMNs) play a key role in host defense. However, their massive accumulation at the site of inflammation can delay regenerative healing processes and can initiate pathological inflammatory processes. Thus, the efficient clearance of PMNs mediated by the induction of regulated cell death is a key process preventing the development of these pathological conditions. Myeloperoxidase (MPO), a highly abundant enzyme in PMN granules, primarily connected with PMN defense machinery, is suggested to play a role in PMN-regulated cell death. However, the contribution of MPO to the mechanisms of PMN cell death remains incompletely characterized. Herein, the process of the cell death of mouse PMNs induced by three different stimuli – phorbol 12-myristate 13-acetate (PMA), opsonized streptococcus (OST), and N-formyl-met-leu-phe (fMLP) – was investigated. MPO-deficient PMNs revealed a significantly decreased rate of cell death characterized by phosphatidylserine surface exposure and cell membrane permeabilization. An inhibitor of MPO activity, 4-aminobenzoic acid hydrazide, did not exhibit a significant effect on PMA-induced cell death compared to MPO deficiency. Interestingly, only the limited activation of markers related to apoptotic cell death was observed (e.g. caspase 8 activation, Bax expression) and they mostly did not correspond to phosphatidylserine surface exposure. Furthermore, a marker characterizing autophagy, cleavage of LC3 protein, as well as histone H3 citrullination and its surface expression was observed. Collectively, the data show the ability of MPO to modulate the life span of PMNs primarily through the potentiation of cell membrane permeabilization and phosphatidylserine surface exposure.

Insight into the Structure, Functions, and Dynamics of the Leptospira Outer Membrane Proteins with the Pathogenicity

Leptospirosis is a widespread zoonosis that frequently occurs in tropical and subtropical countries. Leptospira enters the host through wounds or mucous membranes and spreads to the whole body through the blood, causing systemic infection. Kidneys are the preferential site where Leptospira accumulates, especially in the renal interstitium and renal tubule epithelial cells. Clinical symptoms in humans include high fever, jaundice, renal failure, and severe multiple-organ failure (Weil’s syndrome). Surface-exposed antigens are located at the outermost layer of Leptospira and these potential virulence factors are likely involved in primary host-pathogen interactions, adhesion, and/or invasion. Using the knockout/knockdown techniques to the evaluation of pathogenicity in the virulence factor are the most direct and effective methods and many virulence factors are evaluated including lipopolysaccharides (LPS), Leptospira lipoprotein 32 (LipL32), Leptospira ompA domain protein 22 (Loa22), LipL41, LipL71, Leptospira immunoglobulin-like repeat A (LigA), LigB, and LipL21. In this review, we will discuss the structure, functions, and dynamics of these virulence factors and the roles of these virulence factors in Leptospira pathogenicity. In addition, a protein family with special Leucine-rich repeat (LRR) will also be discussed for their vital role in Leptospira pathogenicity. Finally, these surface-exposed antigens are discussed in the application of the diagnosis target for leptospirosis and compared with the serum microscope agglutination test (MAT), the gold standard for leptospirosis.

D-Mannose Slows Glioma Growth by Modulating Myeloperoxidase Activity

Simple Summary

Inflammation and oxidative stress are important host defense responses. However, while the host response can be cytotoxic and kill tumor cells, tumor cells can also alter and exploit the host immune environment to further their survival. Thus, the host response can impact both tumor suppression and progression. Modulating the tumor–host response interaction to favor tumor suppression would be highly desirable. D-mannose has been found to have anti-inflammatory properties and can block signaling related to myeloperoxidase (MPO), a highly oxidizing pro-inflammatory enzyme secreted in host defense. However, the effect of D-mannose on host immune response in the glioma microenvironment has not been explored. We found that D-mannose slowed glioma growth by increasing MPO activity and oxidative stress in the glioma microenvironment. Our findings revealed that D-mannose may be able to shift the host immune response toward tumor suppression and could be a potential new therapeutic direction for these difficult-to-treat tumors.

Abstract

Host immune response in the tumor microenvironment plays key roles in tumorigenesis. We hypothesized that D-mannose, a simple sugar with anti-inflammatory properties, could decrease oxidative stress and slow glioma progression. Using a glioma stem cell model in immunocompetent mice, we induced gliomas in the brain and tracked MPO activity in vivo with and without D-mannose treatment. As expected, we found that D-mannose treatment decreased the number of MPO⁺ cells and slowed glioma progression compared to PBS-treated control animals with gliomas. Unexpectedly, instead of decreasing MPO activity, D-mannose increased MPO activity in vivo, revealing that D-mannose boosted the MPO activity per MPO⁺ cell. On the other hand, D-glucose had no effect on MPO activity. To better understand this effect, we examined the effect of D-mannose on bone marrow-derived myeloid cells. We found that D-mannose modulated MPO activity via two mechanisms: directly via N-glycosylation of MPO, which boosted the MPO activity of each molecule, and indirectly by increasing H₂O₂ production, the main substrate for MPO. This increased host immune response acted to reduce tumor size, suggesting that increasing MPO activity such as through D-mannose administration may be a potential new therapeutic direction for glioma treatment.

Inhibition of NADPH oxidase blocks NETosis and reduces thrombosis in heparin-induced thrombocytopenia

ROS generation is essential for thrombus formation in HIT.

NOX2 inhibition prevents thrombus formation in a murine model of HIT.

Heparin-induced thrombocytopenia (HIT) is associated with severe and potentially lethal thrombotic complications. NETosis was recently shown to be an important driver of thrombosis in HIT. We investigated the role of reactive oxygen species (ROS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) and their contributions to thrombus development in HIT. We showed that neutrophil activation by HIT immune complexes induced ROS-dependent NETosis. Analysis of thrombi formed in a microfluidics system showed ROS production in both platelets and neutrophils, and abundant neutrophil extracellular traps (NETs) and ROS distributed throughout the clot. Neutrophil-targeted ROS inhibition was sufficient to block HIT-induced NETosis and thrombosis using human blood. Inhibition of NOX2 with diphenyleneiodonium chloride or GSK2795039 abrogated HIT-induced thrombi in vivo using FcγRIIa⁺/hPF4⁺-transgenic mice. Thrombocytopenia in mice remained unaffected by ROS inhibition. Increased ROS production in activated neutrophils was also confirmed using fresh blood from patients with active HIT. Our findings show that ROS and NOX2 play a crucial role in NETosis and thrombosis in HIT. This enhances our understanding of the processes driving thrombosis in HIT and identifies NOX2 as a potential new therapeutic target for antithrombotic treatment of HIT.

Heme Peroxidases at Unperturbed and Inflamed Mucous Surfaces

In our organism, mucous surfaces are important boundaries against the environmental milieu with defined fluxes of metabolites through these surfaces and specific rules for defense reactions. Major mucous surfaces are formed by epithelia of the respiratory system and the digestive tract. The heme peroxidases lactoperoxidase (LPO), myeloperoxidase (MPO), and eosinophil peroxidase (EPO) contribute to immune protection at epithelial surfaces and in secretions. Whereas LPO is secreted from epithelial cells and maintains microbes in surface linings on low level, MPO and EPO are released from recruited neutrophils and eosinophils, respectively, at inflamed mucous surfaces. Activated heme peroxidases are able to oxidize (pseudo)halides to hypohalous acids and hypothiocyanite. These products are involved in the defense against pathogens, but can also contribute to cell and tissue damage under pathological conditions. This review highlights the beneficial and harmful functions of LPO, MPO, and EPO at unperturbed and inflamed mucous surfaces. Among the disorders, special attention is directed to cystic fibrosis and allergic reactions.

Role of myeloperoxidase and oxidant formation in the extracellular environment in inflammation-induced tissue damage

The heme peroxidase family generates a battery of oxidants both for synthetic purposes, and in the innate immune defence against pathogens. Myeloperoxidase (MPO) is the most promiscuous family member, generating powerful oxidizing species including hypochlorous acid (HOCl). Whilst HOCl formation is important in pathogen removal, this species is also implicated in host tissue damage and multiple inflammatory diseases. Significant oxidant formation and damage occurs extracellularly as a result of MPO release via phagolysosomal leakage, cell lysis, extracellular trap formation, and inappropriate trafficking. MPO binds strongly to extracellular biomolecules including polyanionic glycosaminoglycans, proteoglycans, proteins, and DNA. This localizes MPO and subsequent damage, at least partly, to specific sites and species, including extracellular matrix (ECM) components and plasma proteins/lipoproteins. Biopolymer-bound MPO retains, or has enhanced, catalytic activity, though evidence is also available for non-catalytic effects. These interactions, particularly at cell surfaces and with the ECM/glycocalyx induce cellular dysfunction and altered gene expression. MPO binds with higher affinity to some damaged ECM components, rationalizing its accumulation at sites of inflammation. MPO-damaged biomolecules and fragments act as chemo-attractants and cell activators, and can modulate gene and protein expression in naïve cells, consistent with an increasing cycle of MPO adhesion, activity, damage, and altered cell function at sites of leukocyte infiltration and activation, with subsequent tissue damage and dysfunction. MPO levels are used clinically both diagnostically and prognostically, and there is increasing interest in strategies to prevent MPO-mediated damage; therapeutic aspects are not discussed as these have been reviewed elsewhere.

Evidence for antioxidant and anti-inflammatory potential of mango (Mangifera indica L.) in naproxen-induced gastric lesions in rat

This study investigated the anti-inflammatory and antioxidant effects of hydroalcoholic extracts of mango peel and pulp on oxidative damage in a naproxen-induced gastric injury rat model. The extracts were assessed for antioxidant activity (ABTS and FRAP methods), and the phenolic profile was investigated with UPLC-QToF-MS^E . Gastric damage was evaluated in vivo by assessing the membrane lipid peroxidation (malondialdehyde (MDA) content), myeloperoxidase (MPO) enzyme activity, and glutathione (GSH) content. Mango peel and pulp contained high contents of bioactive compounds, particularly phenolics (69.50-5.287.70 mg gallic acid equivalents/100 g), carotenoids (651.30-665.50 μg/100 g), and vitamin C (21.59-108.19 mg/100 g). UPLC-QToF-MSE analysis identified 17 phenol compounds, including gallotannins, glycosylated flavonoids, and xanthone. The hydroalcoholic extracts of mango peel and pulp (LPe and LPu, respectively) significantly reduced the MPO activity and MDA content. In addition to preventing naproxen-induced GSH decline, LPe (30 mg/kg) and LPu (10 mg/kg) restored its content to normal levels. LPe and LPu neutralized the oxidizing agents triggered by naproxen and reduced the severity of gastric lesions owing to their antioxidant properties.

Hidrox® and Endometriosis: Biochemical Evaluation of Oxidative Stress and Pain

Endometriosis is a gynecological and painful condition affecting women of reproductive age. It is characterized by dysfunctional endometrium-like implants outside of the uterine cavity. The purpose of this study was to evaluate the effects of Hidrox^®, an aqueous extract of olive pulp containing hydroxytyrosol, on endometriotic lesions associated with pro-oxidative alterations and pain-like behaviors. Endometriosis was induced by intraperitoneal injection of uterine fragments, and Hidrox^® was administered daily. At the end of the 14-day treatment, behavioral alterations were assessed and hippocampal tissues were collected. Laparotomy was performed, and the endometrial implants were harvested for histological and biochemical analysis. Hidrox^® treatment reduced endometriotic implant area, diameter and volumes. Vehicle-treated rats showed lesional fibrosis, epithelial–mesenchymal transition and fibroblast–myofibroblast transdifferentiation, angiogenesis and pro-oxidative alterations in the peritoneal cavity. Hidrox^® treatment reduced the aniline blue-stained area, α-smooth muscle actin (α-sma) and CD34 positive expressions. Moreover, it reduced mast cell recruitment into the lesions, myeloperoxidase activity and lipid peroxidation and increased superoxide dismutase (SOD) activity and glutathione levels in the endometrial explants. In the peritoneal fluid, Hidrox^® treatment reduced interleukin (IL)-1β, IL2, IL6, tumor necrosis factor-α (TNF-α) and vascular endothelial grow factor (VEGF) levels increased by the disease. Hidrox^® administration also reduced peripheral and visceral sensibility as shown by the behavioral tests (open field test, hot plate test, elevated plus maze test and acetic-acid-induced abdominal contractions). Animals treated with Hidrox^® also showed reduced blood–brain barrier permeability and mast cell infiltration in the hippocampus, as well as astrocyte and microglia activation and brain oxidative status restoring brain-derived neurotrophic factor (BDNF) protein expression and increasing Nuclear factor erythroid 2-related factor 2 (Nfr2) nuclear translocation. In conclusion, Hidrox^® displayed potential ameliorative effects on endometriotic implants and related pain-induced behaviors due to its potent antioxidative properties.

Characterization of the turbot Scophthalmus maximus (L.) myeloperoxidase. An insight into the evolution of vertebrate peroxidases

We have completed the characterization of the turbot (Scophthalmus maximus) myeloperoxidase (mpx) gene and protein, which we partially described in a previous study. The turbot mpx gene has 15 exons that encode a protein of 767 aa, with a signal peptide, propeptide and light and heavy chains, and also with haem cavities, a Ca⁺²-binding motif and several N- and O-glycosylation sites. The mature protein forms homodimers of about 150 kDa and is very abundant in turbot neutrophils. In addition to the mpx (epx2a) gene, another three peroxidase genes, named epx1, epx2b1 and epx2b2, were identified in the turbot genome. Epx1, Epx2b1 and Epx2b2 proteins also have signal peptides and many structural characteristics of mammalian MPO and eosinophil peroxidase (EPX). Mpx was strongly expressed in head kidney, while epx2b1 and epx2b2 were strongly expressed in the gills, and epx1 was not expressed in any of the tissues or organs analysed. In vitro stimulation of head kidney leucocytes with the parasite Philasterides dicentrarchi caused a decrease in mpx expression and an increase in epx2b1 expression over time. In turbot infected experimentally with P. dicentrarchi a significant increase in mpx expression in the head kidney was observed on day 7 postinfection, while the other genes were not regulated. However, mpx, epx2b1 and epx2b2 were downregulated in the gills of infected fish, and epx1 expression was not affected. These results suggest that the four genes responded differently to the same stimuli. Interestingly, BLAST analysis revealed that Epx1 and Mpx showed greater similarity to mammalian EPX than to MPO. Considering the phylogenetic and synteny data obtained, we concluded that the epx/mpx genes of Gnathostomes can be divided into three main clades: EPX1, which contains turbot epx1, EPX2, which contains turbot mpx (epx2a) and epx2b1 and epx2b2 genes, and a clade containing mammalian EPX and MPO (EPX/MPO). EPX/MPO and EPX2 clades share a common ancestor with the chondrichthyan elephant shark (Callorhinchus milii) and the coelacanth (Latimeria chalumnae) peroxidases. EPX2 was only found in fish and includes two sister groups. One of the groups includes turbot mpx and was only found in teleosts. Finally, the other group contains epx2b1 and epx2b2 genes, and epx2b1-2b2 loci share orthologous genes with other teleosts and also with holosteans, suggesting that these genes appeared earlier on than the mpx gene.

β2 Integrin Regulation of Neutrophil Functional Plasticity and Fate in the Resolution of Inflammation

Neutrophils act as the first line of cellular defense against invading pathogens or tissue injury. Their rapid recruitment into inflamed tissues is critical for the elimination of invading microorganisms and tissue repair, but is also capable of inflicting damage to neighboring tissues. The β₂ integrins and Mac-1 (CD11b/CD18, α_Mβ₂ or complement receptor 3) in particular, are best known for mediating neutrophil adhesion and transmigration across the endothelium and phagocytosis of microbes. However, Mac-1 has a broad ligand recognition property that contributes to the functional versatility of the neutrophil population far beyond their antimicrobial function. Accumulating evidence over the past decade has demonstrated roles for Mac-1 ligands in regulating reverse neutrophil transmigration, lifespan, phagocytosis-induced cell death, release of neutrophil extracellular traps and efferocytosis, hence extending the traditional β₂ integrin repertoire in shaping innate and adaptive immune responses. Understanding the functions of β₂ integrins may partly explain neutrophil heterogeneity and may be instrumental to develop novel therapies specifically targeting Mac-1-mediated pro-resolution actions without compromising immunity. Thus, this review details novel insights on outside-in signaling through β₂ integrins and neutrophil functional heterogeneity pertinent to the resolution of inflammation.

Interleukin-13 Propagates Prothrombin Kringle-2-Induced Neurotoxicity in Hippocampi In Vivo via Oxidative Stress

The present study investigated expression of endogenous interleukin-13 (IL-13) and its possible function in the hippocampus of prothrombin kringle-2 (pKr-2)-lesioned rats. Here we report that intrahippocampal injection of pKr-2 revealed a significant loss of NeuN-immunopositive (NeuN⁺) and Nissl⁺ cells in the hippocampus at 7 days after pKr-2. In parallel, pKr-2 increased IL-13 levels, which reached a peak at 3 days post pKr-2 and sustained up to 7 days post pKr-2. IL-13 immunoreactivity was seen exclusively in activated microglia/macrophages and neutrophils, but not in neurons or astrocytes. In experiments designed to explore the involvement of IL-13 in neurodegeneration, IL-13 neutralizing antibody (IL-13Nab) significantly increased survival of NeuN⁺ and Nissl⁺ cells. Accompanying neuroprotection, immunohistochemical analysis indicated that IL-13Nab inhibited pKr-2-induced expression of inducible nitric oxide synthase and myeloperoxidase within activated microglia/macrophages and neutrophils, possibly resulting in attenuation of reactive oxygen species (ROS) generation and oxidative damage of DNA and protein. The current findings suggest that the endogenous IL-13 expressed in pKr-2 activated microglia/macrophages and neutrophils might be harmful to hippocampal neurons via oxidative stress.

Neutrophil-Derived Myeloperoxidase Facilitates Both the Induction and Elicitation Phases of Contact Hypersensitivity

Background

Allergic contact dermatitis (ACD) is a common skin disorder affecting an estimated 15-20% of the general population. The mouse model of ACD is contact hypersensitivity (CHS), which consists of two phases: induction and elicitation. Although neutrophils are required for both CHS disease phases their mechanisms of action are poorly understood. Neutrophils release myeloperoxidase (MPO) that through oxidation of biomolecules leads to cellular damage.

Objectives

This study investigated mechanisms whereby MPO contributes to CHS pathogenesis.

Methods

CHS was induced in mice using oxazolone (OX) as the initiating hapten applied to the skin. After 7 days, CHS was elicited by application of OX to the ear and disease severity was measured by ear thickness and vascular permeability in the ear. The role of MPO in the two phases of CHS was determined utilizing MPO-deficient mice and a specific MPO inhibitor.

Results

During the CHS induction phase MPO-deficiency lead to a reduction in IL-1β production in the skin and a subsequent reduction in migratory dendritic cells (DC) and effector T cells in the draining lymph node. During the elicitation phase, inhibition of MPO significantly reduced both ear swelling and vascular permeability.

Conclusion

MPO plays dual roles in CHS pathogenesis. In the initiation phase MPO promotes IL-1β production in the skin and activation of migratory DC that promote effector T cell priming. In the elicitation phase MPO drives vascular permeability contributing to inflammation. These results indicate that MPO it could be a potential therapeutic target for the treatment of ACD in humans.

Hemokinin-1 as a Mediator of Arthritis-Related Pain via Direct Activation of Primary Sensory Neurons

The tachykinin hemokinin-1 (HK-1) is involved in immune cell development and inflammation, but little is known about its function in pain. It acts through the NK1 tachykinin receptor, but several effects are mediated by a yet unidentified target. Therefore, we investigated the role and mechanism of action of HK-1 in arthritis models of distinct mechanisms with special emphasis on pain. Arthritis was induced by i.p. K/BxN serum (passive transfer of inflammatory cytokines, autoantibodies), intra-articular mast cell tryptase or Complete Freund's Adjuvant (CFA, active immunization) in wild type, HK-1- and NK1-deficient mice. Mechanical- and heat hyperalgesia determined by dynamic plantar esthesiometry and increasing temperature hot plate, respectively, swelling measured by plethysmometry or micrometry were significantly reduced in HK-1-deleted, but not NK1-deficient mice in all models. K/BxN serum-induced histopathological changes (day 14) were also decreased, but early myeloperoxidase activity detected by luminescent in vivo imaging increased in HK-1-deleted mice similarly to the CFA model. However, vasodilation and plasma protein extravasation determined by laser Speckle and fluorescent imaging, respectively, were not altered by HK-1 deficiency in any models. HK-1 induced Ca2+-influx in primary sensory neurons, which was also seen in NK1-deficient cells and after pertussis toxin-pretreatment, but not in extracellular Ca2+-free medium. These are the first results showing that HK-1 mediates arthritic pain and cellular, but not vascular inflammatory mechanisms, independently of NK1 activation. HK-1 activates primary sensory neurons presumably via Ca2+ channel-linked receptor. Identifying its target opens new directions to understand joint pain leading to novel therapeutic opportunities.

Exercise-induced muscle damage: mechanism, assessment and nutritional factors to accelerate recovery

There have been a multitude of reviews written on exercise-induced muscle damage (EIMD) and recovery. EIMD is a complex area of study as there are a host of factors such as sex, age, nutrition, fitness level, genetics and familiarity with exercise task, which influence the magnitude of performance decrement and the time course of recovery following EIMD. In addition, many reviews on recovery from exercise have ranged from the impact of nutritional strategies and recovery modalities, to complex mechanistic examination of various immune and endocrine signaling molecules. No one review can adequately address this broad array of study. Thus, in this present review, we aim to examine EIMD emanating from both endurance exercise and resistance exercise training in recreational and competitive athletes and shed light on nutritional strategies that can enhance and accelerate recovery following EIMD. In addition, the evaluation of EIMD and recovery from exercise is often complicated and conclusions often depend of the specific mode of assessment. As such, the focus of this review is also directed at the available techniques used to assess EIMD.

Myeloperoxidase mediated alteration of endothelial function is dependent on its cationic charge

Endothelial cell (EC) glycocalyx (GLX) comprise a multicomponent layer of proteoglycans and glycoproteins. Alteration of its integrity contributes to chronic vascular inflammation and leads to the development of cardiovascular diseases. Myeloperoxidase (MPO), a highly abundant enzyme released by polymorphonuclear neutrophils, binds to the GLX and deleteriously affects vascular EC functions. The focus of this study was to elucidate the mechanisms of MPO-mediated alteration of GLX molecules, and to unravel subsequent changes in endothelial integrity and function. MPO binding to GLX of human ECs and subsequent internalization was mediated by cell surface heparan sulfate chains. Moreover, interaction of MPO, which is carrying a cationic charge, with anionic glycosaminoglycans (GAGs) resulted in reduction of their relative charge. By means of micro-viscometry and atomic force microscopy, we disclosed that MPO can crosslink GAG chains. MPO-dependent modulation of GLX structure was further supported by alteration of wheat germ agglutinin staining. Increased expression of ICAM-1 documented endothelial cell activation by both catalytically active and also inactive MPO. Furthermore, MPO increased vascular permeability connected with reorganization of intracellular junctions, however, this was dependent on MPO's catalytic activity. Novel proteins interacting with MPO during transcytosis were identified by proteomic analysis. Altogether, these findings provide evidence that MPO through interaction with GAGs modulates overall charge of the GLX, causing modification of its structure and thus affecting EC function. Importantly, our results also suggest a number of proteins interacting with MPO that possess a variety of cellular localizations and functions.

Ethanol exacerbates manganese-induced oxidative/nitrosative stress, pro-inflammatory cytokines, nuclear factor-κB activation, and apoptosis induction in rat cerebellar cortex

Manganese (Mn) exposure is causing public health concerns as well as heavy alcohol consumption. This study investigates the mechanisms of neurotoxicity associated with Mn and ethanol (EtOH) exposure in the rat cerebellar cortex. Experimental animals received 30 mg/kg of Mn alone, 5 g/kg of EtOH alone, co-exposed with 30 mg/kg of Mn and 1.25 or 5 g/kg EtOH, while control animals received water by oral gavage for 35 days. Subsequently, alterations in the neuronal morphology of the cerebellar cortex, oxidative/nitrosative stress, acetylcholinesterase (AChE) activity, neuro-inflammation and protein expression of p53, BAX, caspase-3, and BCL-2 were investigated. The results indicate that Mn alone and EtOH alone induce neuronal alterations in the cerebellar cortex, decrease glutathione level and antioxidant enzyme activities, along with an increase in AChE activity, lipid peroxidation, and hydrogen peroxide generation. Mn alone and EtOH alone also increased neuro-inflammatory markers, namely nitric oxide, myeloperoxidase activity, interleukin-1β, tumor necrosis factor-α, and nuclear factor-κB (NF-κB) levels in the cerebellar cortex. Immunohistochemistry analysis further revealed that exposure of Mn alone and EtOH alone increases the protein expression of cyclooxygenase-2, BAX, p53, and caspase-3 and decrease BCL-2 in the rat cerebellar cortex. Furthermore, the results indicated that Mn co-exposure with EtOH at 1.25 and 5 g/kg EtOH significantly (p ≤ .05) increases the toxicity in the cerebellum when compared with the toxicity of Mn or EtOH alone. Taken together, co-exposure of Mn and EtOH exacerbates neuronal alterations, oxidative/nitrosative stress, AChE activity, pro-inflammatory cytokines, NF-κB signal transcription, and apoptosis induction in the rat cerebellar cortex.

Interleukin-4-Mediated Oxidative Stress Is Harmful to Hippocampal Neurons of Prothrombin Kringle-2-Lesioned Rat In Vivo

The present study investigated the effects of reactive microglia/macrophages-derived interleukin-4 (IL-4) on hippocampal neurons in prothrombin kringle-2 (pKr-2)-lesioned rats. pKr-2 was unilaterally injected into hippocampus in the absence or presence of IL-4 neutralizing antibody (IL-4Nab). Immunohistochemical analysis showed a significant loss of Nissl⁺ and NeuN⁺ cells and activation of microglia/macrophages (increase in reactive OX-42⁺ and OX-6⁺ cells) in the hippocampus at 7 days after pKr-2 injection. The levels of IL-4 expression were upregulated in the reactive OX-42⁺ microglia/macrophages as early as 1 day, maximal at 3 days and maintained up to 7 days after pKr-2 injection. Treatment with IL-4Nab significantly increased neuronal survival in pKr-2-treated CA1 layer of hippocampus in vivo. Accompanying neuroprotection, IL-4 neutralization inhibited activation of microglia/macrophages, reactive oxygen species-derived oxidative damages, production of myeloperoxidase- and inducible nitric oxide synthase-derived reactive nitrogen species and nitrosative damages as analyzed by immunohistochemistry and hydroethidine histochemistry. These results suggest that endogenous IL-4 expressed on reactive microglia/macrophages mediates oxidative/nitrosative stress and play a critical role on neurodegeneration of hippocampal CA1 layer in vivo.

The Dual Role of Myeloperoxidase in Immune Response

The heme protein myeloperoxidase (MPO) is a major constituent of neutrophils. As a key mediator of the innate immune system, neutrophils are rapidly recruited to inflammatory sites, where they recognize, phagocytose, and inactivate foreign microorganisms. In the newly formed phagosomes, MPO is involved in the creation and maintenance of an alkaline milieu, which is optimal in combatting microbes. Myeloperoxidase is also a key component in neutrophil extracellular traps. These helpful properties are contrasted by the release of MPO and other neutrophil constituents from necrotic cells or as a result of frustrated phagocytosis. Although MPO is inactivated by the plasma protein ceruloplasmin, it can interact with negatively charged components of serum and the extracellular matrix. In cardiovascular diseases and many other disease scenarios, active MPO and MPO-modified targets are present in atherosclerotic lesions and other disease-specific locations. This implies an involvement of neutrophils, MPO, and other neutrophil products in pathogenesis mechanisms. This review critically reflects on the beneficial and harmful functions of MPO against the background of immune response.

Oxidative cross-linking of fibronectin confers protease resistance and inhibits cellular migration

The oxidation of tyrosine residues to generate o,o'-dityrosine cross-links in extracellular proteins is necessary for the proper function of the extracellular matrix (ECM) in various contexts in invertebrates. Tyrosine oxidation is also required for the biosynthesis of thyroid hormone in vertebrates, and there is evidence for oxidative cross-linking reactions occurring in extracellular proteins secreted by myofibroblasts. The ECM protein fibronectin circulates in the blood as a globular protein that dimerizes through disulfide bridges generated by cysteine oxidation. We found that cellular (fibrillar) fibronectin on the surface of transforming growth factor-β1 (TGF-β1)-activated human myofibroblasts underwent multimerization by o,o'-dityrosine cross-linking under reducing conditions that disrupt disulfide bridges, but soluble fibronectin did not. This reaction on tyrosine residues required both the TGF-β1-dependent production of hydrogen peroxide and the presence of myeloperoxidase (MPO) derived from inflammatory cells, which are active participants in wound healing and fibrogenic processes. Oxidative cross-linking of matrix fibronectin attenuated both epithelial and fibroblast migration and conferred resistance to proteolysis by multiple proteases. The abundance of circulating o,o'-dityrosine-modified fibronectin was increased in a murine model of lung fibrosis and in human subjects with interstitial lung disease compared to that in control healthy subjects. These studies indicate that tyrosine can undergo stable, covalent linkages in fibrillar fibronectin under inflammatory conditions and that this modification affects the migratory behavior of cells on such modified matrices, suggesting that this modification may play a role in both physiologic and pathophysiologic tissue repair.

Proteomic analysis of human cervical adenocarcinoma mucus to identify potential protein biomarkers

Background

Cervical cancer is the most common gynecological cancer, encompassing cervical squamous cell carcinoma, adenocarcinoma, and other epithelial tumors. There are many diagnostic methods to detect cervical cancers but no precision screening tool for cervical adenocarcinoma at present.

Material and methods

The cervical mucus from three normal cervices (Ctrl), three endocervical adenocarcinoma (EA), and three cervical adenocarcinoma in situ (AIS) was collected for proteomic analysis. The proteins were screened using liquid chromatography-mass spectrometry analysis (LC-MS). The biological function of the differently expressed proteins were predicted by Gene Ontology (GO).

Results

A total of 711 proteins were identified, including 237 differently expressed proteins identified in EA/Ctrl comparison, 256 differently expressed proteins identified in AIS/Ctrl comparison, and 242 differently expressed proteins identified in AIS/EA comparison (up-regulate ≥ 1.5 or down-regulate ≤ 0.67). Functional annotation was performed using GO analysis on 1,056 differently expressed proteins to identify those that may impact cervical cancer, such as heme protein myeloperoxidase, which is involved in the immune process, and APOA1, which is associated with lipid metabolism.

Conclusion

We used proteomic analysis to screen out differently expressed proteins from normal cervical mucus and cervical adenocarcinoma mucus samples. These differently expressed proteins may be potential biomarkers for the diagnosis and treatment of cervical adenocarcinoma but require additional study.

Radiation activates myeloperoxidase (MPO) to generate active chlorine species (ACS) via a dephosphorylation mechanism - inhibitory effect of LGM2605

BACKGROUND

Radiation exposure of tissues is associated with inflammatory cell influx. Myeloperoxidase (MPO) is an enzyme expressed in granulocytes, such as neutrophils (PMN) and macrophages, responsible for active chlorine species (ACS) generation. The present study aimed to: 1) determine whether exposure to γ-irradiation induces MPO-dependent ACS generation in murine PMN; 2) elucidate the mechanism of radiation-induced ACS generation; and 3) evaluate the effect of the synthetic lignan LGM2605, known for ACS scavenging properties.

METHODS

MPO-dependent ACS generation was determined by using hypochlorite-specific 3'-(p-aminophenyl) fluorescein (APF) and a highly potent MPO inhibitor, 4-aminobenzoic acid hydrazide (ABAH), and confirmed in PMN derived from MPO-/- mice. Radiation-induced MPO activation was determined by EPR spectroscopy and computational analysis identified tyrosine, serine, and threonine residues near MPO's active site.

RESULTS

γ-radiation increased MPO-dependent ACS generation dose-dependently in human MPO and in wild-type murine PMN, but not in PMN from MPO-/- mice. LGM2605 decreased radiation-induced, MPO-dependent ACS. Protein tyrosine phosphatase (PTP) and protein serine/threonine phosphatase (PSTP) inhibitors decreased the radiation-induced increase in ACS. Peroxidase cycle results demonstrate that tyrosine phosphorylation blocks MPO Compound I formation by preventing catalysis on H2O2 in the active site of MPO. EPR data demonstrate that γ-radiation increased tyrosyl radical species formation in a dose-dependent manner.

CONCLUSIONS

We demonstrate that γ-radiation induces MPO-dependent generation of ACS, which is dependent, at least in part, by protein tyrosine and Ser/Thr dephosphorylation and is reduced by LGM2605. This study identified for the first time a novel protein dephosphorylation-dependent mechanism of radiation-induced MPO activation.

Vascular permeability disruption explored in the proteomes of mouse lungs and human microvascular cells following acute bromine exposure

Bromine (Br₂) is an organohalide found in nature and is integral to many manufacturing processes. Br₂ is toxic to living organisms, and high concentrations can prove fatal. To meet industrial demand, large amounts of purified Br₂ are produced, transported, and stored worldwide, providing a multitude of interfaces for potential human exposure through either accidents or terrorism. To identify the key mechanisms associated with acute Br₂ exposure, we have surveyed the lung proteomes of C57BL/6 male mice and human lung-derived microvascular endothelial cells (HMECs) at 24 h following exposure to Br₂ in concentrations likely to be encountered in the vicinity of industrial accidents. Global discovery proteomics applications combined with systems biology analysis identified robust and highly significant changes in proteins associated with three biological processes: 1) exosome secretion, 2) inflammation, and 3) vascular permeability. We focused on the latter, conducting physiological studies on isolated perfused lungs harvested from mice 24 h after Br₂ exposure. These experiments revealed significant increases in the filtration coefficient (K_f) indicating increased permeability of the pulmonary vasculature. Similarly, confluent monolayers of Br₂ and Br-lipid-treated HMECs exhibited differential levels of zona occludens-1 that were found to be dissociated from cell wall localization, an increase in phosphorylation and internalization of E-cadherin, as well as increased actin stress fiber formation, all of which are consistent with increased permeability. Taken as a whole, our discovery proteomics and systems analysis workflow, combined with physiological measurements of permeability, revealed both profound and novel biological changes that contribute to our current understanding of Br₂ toxicity.

Mayaro Virus Induction of Oxidative Stress is Associated With Liver Pathology in a Non-Lethal Mouse Model

Mayaro virus (MAYV) causes Mayaro fever in humans, a self-limiting acute disease, with persistent arthralgia and arthritis. Although MAYV has a remerging potential, its pathogenic mechanisms remain unclear. Here, we characterized a model of MAYV infection in 3-4-week BALB/c mice. We investigated whether the liver acts as a site of viral replication and if the infection could cause histopathological alterations and an imbalance in redox homeostasis, culminating with oxidative stress. MAYV-infected mice revealed lower weight gain; however, the disease was self-resolving. High virus titre, neutralizing antibodies, and increased levels of aspartate and alanine aminotransferases were detected in the serum. Infectious viral particles were recovered in the liver of infected animals and the histological examination of liver tissues revealed significant increase in the inflammatory infiltrate. MAYV induced significant oxidative stress in the liver of infected animals, as well as a deregulation of enzymatic antioxidant components. Collectively, this is the first study to report that oxidative stress occurs in MAYV infection in vivo, and that it may be crucial in virus pathogenesis. Future studies are warranted to address the alternative therapeutic strategies for Mayaro fever, such as those based on antioxidant compounds.

Origin and pathophysiology of protein carbonylation, nitration and chlorination in age-related brain diseases and aging

Non-enzymatic protein modifications occur inevitably in all living systems. Products of such modifications accumulate during aging of cells and organisms and may contribute to their age-related functional deterioration. This review presents the formation of irreversible protein modifications such as carbonylation, nitration and chlorination, modifications by 4-hydroxynonenal, removal of modified proteins and accumulation of these protein modifications during aging of humans and model organisms, and their enhanced accumulation in age-related brain diseases.

Peritoneal endometriosis induces time-related depressive- and anxiety-like alterations in female rats: involvement of hippocampal pro-oxidative and BDNF alterations

Endometriosis is a gynecological condition affecting 10% of women in reproductive age. High rates of depression and anxiety are observed in these patients. The mechanisms underlying endometriosis-induced behavioral alterations are still elusive. Animal models provide a useful tool to study the temporal sequence and biological pathways involved in this disease and comorbid states. Here, we sought to characterize time-related behavioral alterations in rats submitted to endometriosis model (EM) induced by peritoneal auto-transplantation of uterine tissues weekly for three weeks. Corticosterone stress reactivity, oxidative stress markers - reduced glutathione (GSH), lipid peroxidation, activity of superoxide dismutase (SOD) and myeloperoxidase (MPO) - and brain-derived-neurotrophic factor (BDNF) levels in the hippocampus were also evaluated. We observed a progressive increase in anxiety-like behavior from 14th to 21st days post-EM. Despair-like behavior was observed from the 14th day post-EM on, while anhedonia and apathetic-like behaviors accompanied by increased corticosterone stress response were detected on 21 days post-EM. Increased pain sensitivity was observed from the 7th day post-EM and was accompanied by increased endometrioma weight. The pro-oxidative alterations, decreased GSH and increased SOD activity were observed on 21 days post-EM, except for lipid peroxidation that was altered from the 14th day. Decreased BDNF also occurred on the 21st day. Therefore, this study demonstrates that EM is related to several features of clinical depression and proposes the contribution of hippocampal oxidative state and neurotrophic support for the emergence of these changes. Our results support the use of this model as a useful tool to test new strategies for endometriosis-related neuropsychiatric symptoms.

Cellular Toxicity and Immunological Effects of Carbon-based Nanomaterials

BACKGROUND

Carbon nanomaterials are a growing family of materials featuring unique physicochemical properties, and their widespread application is accompanied by increasing human exposure.

MAIN BODY

Considerable efforts have been made to characterize the potential toxicity of carbon nanomaterials in vitro and in vivo. Many studies have reported various toxicology profiles of carbon nanomaterials. The different results of the cytotoxicity of the carbon-based materials might be related to the differences in the physicochemical properties or structures of carbon nanomaterials, types of target cells and methods of particle dispersion, etc. The reported cytotoxicity effects mainly included reactive oxygen species generation, DNA damage, lysosomal damage, mitochondrial dysfunction and eventual cell death via apoptosis or necrosis. Despite the cellular toxicity, the immunological effects of the carbon-based nanomaterials, such as the pulmonary macrophage activation and inflammation induced by carbon nanomaterials, have been thoroughly studied. The roles of carbon nanomaterials in activating different immune cells or inducing immunosuppression have also been addressed.

CONCLUSION

Here, we provide a review of the latest research findings on the toxicological profiles of carbon-based nanomaterials, highlighting both the cellular toxicities and immunological effects of carbon nanomaterials. This review provides information on the overall status, trends, and research needs for toxicological studies of carbon nanomaterials.