Neutrophils employ the myeloperoxidase system to generate antimicrobial brominating and chlorinating oxidants during sepsis

The dynamic changes of peripheral blood cell counts predict the clinical outcomes of aneurysmal subarachnoid hemorrhage

Background

Aneurysmal subarachnoid hemorrhage (aSAH) is a serious type of hemorrhagic stroke. It is very important to predict the prognosis at early phase. In this work, we intend to characterize early changes in peripheral blood cells after aSAH and explore the association between peripheral blood cells and clinical outcomes after aSAH.

Methods

aSAH patients admitted between December 2019 and September 2022 were enrolled. A retrospective observational study was performed. Total leukocytes, monocytes, neutrophils, erythrocytes, lymphocytes and platelets counts were recorded on the day of admission (day 1), day 3, day 5 and day 7. Statistical tests included Chi-square test, analysis of variance and multivariate logistic regression (MLR) models. 197 patients were analyzed.

Results

Leukocytes and neutrophils were higher in poor outcome groups from day 1 to day 7 and in delayed cerebral ischemia (DCI) groups from day 3 to day 7. Lymphocytes were higher at day 5 and day 7 in good outcome groups and no DCI groups. Neutrophil-to-lymphocyte ratio (NLR) was lower from day 3 to day 7 in good outcome groups and no DCI groups. Erythrocytes were higher from day 3 to day 7 in good outcome groups and no DCI groups. Lymphocytes were negatively related to poor outcomes on day 1 (OR = 0.457), indicating higher lymphocytes predicted good outcomes, Neutrophils were positively related to poor outcomes on day 3 (OR = 3.003) indicating higher neutrophils predicted poor outcomes. Lymphocytes were negatively related to DCI on day 5 (OR = 0.388) indicating higher lymphocytes predicted no DCI, Erythrocytes were negatively related to DCI on day 5 (OR = 0.335) and day 7 (OR = 0.204) indicating higher erythrocytes predicted no DCI. The improved ability of neutrophils, lymphocytes and erythrocytes to predict DCI or poor functional outcomes were revealed by ROC curve analysis.

Conclusions

The dynamic changes of peripheral blood cell counts were related to poor functional outcomes and DCI after aSAH. Elevated neutrophils, leukocytes, NLR, and decreased lymphocytes, erythrocytes were accompanied by DCI and poor outcome. Neutrophils, lymphocytes and erythrocytes counts could be beneficial to predict DCI and outcomes after aSAH.

Delocalization Engineering of Heme-Mimetic Artificial Enzymes for Augmented Reactive Oxygen Catalysis

Developing artificial enzymes based on organic molecules or polymers for reactive oxygen species (ROS)-related catalysis has broad applicability. Herein, inspired by porphyrin-based heme mimics, we report the synthesis of polyphthalocyanine-based conjugated polymers (Fe-PPc-AE) as a new porphyrin-evolving structure to serve as efficient and versatile artificial enzymes for augmented reactive oxygen catalysis. Owing to the structural advantages, such as enhanced π-conjugation networks and π-electron delocalization, promoted electron transfer, and unique Fe-N coordination centers, Fe-PPc-AE showed more efficient ROS-production activity in terms of Vmax and turnover numbers as compared with porphyrin-based conjugated polymers (Fe-PPor-AE), which also surpassed reported state-of-the-art artificial enzymes in their activity. More interestingly, by changing the reaction medium and substrates, Fe-PPc-AE also revealed significantly improved activity and environmental adaptivity in many other ROS-related biocatalytic processes, validating the potential of Fe-PPc-AE to replace conventional (poly)porphyrin-based heme mimics for ROS-related catalysis, biosensors, or biotherapeutics. It is suggested that this study will offer essential guidance for designing artificial enzymes based on organic molecules or polymers.

Upregulation of PD-1/PD-L1 and downregulation of immune signaling pathways lead to more severe visceral leishmaniasis in undernutrition mice

BACKGROUND

Leishmaniasis is mainly prevalent in tropical and subtropical developing countries, where chronic undernutrition often co-exists. Undernutrition is reported to promote the progression of leishmaniasis, but its immune mechanisms have not been fully elucidated.

METHODS

To simulate chronic undernutrition of patients in epidemic areas and explore the immune mechanism of undernutrition promoting leishmaniasis, BALB/c mouse models with different nutritional imbalances were established, including undernutrition 75%, undernutrition 65% and obesity mouse models. After infection with Leishmania donovani in these model mice, we focused on evaluating the progress of leishmaniasis in the spleen and liver, the expression of important immunosuppressive and immunoactivation molecules, and changes of spleen transcriptome. The immune signaling pathways enriched by differentially expressed genes and hub genes were analyzed.

RESULTS

The results showed that among the mouse infection models, undernutrition 75% + infection group had the highest parasite load in the spleen and liver at the 8th week post-infection, possibly due to the continuous increase of PD-1, PD-L1 and TCR. Spleen RNA-seq results suggested that some immune signaling pathways were downregulated in undernutrition 75% + infection group, including neutrophil extracellular trap formation, IL-17 signaling pathway, natural killer cell-mediated cytotoxicity, etc. Among them, neutrophil extracellular trap formation pathway had the largest number of downregulated genes. This also explained why undernutrition 75% + infection group had the highest parasite load. Through PPI network analysis, hub genes such as Lcn2, Ltf, Mpo, Dnaja1, Hspa1a, Hspa1b and Hsph1 were screened out and might play important roles in the process of undernutrition promoting leishmaniasis.

CONCLUSIONS

Undernutrition upregulated PD-1 and PD-L1 expression and downregulated immune signaling pathways in mice with visceral leishmaniasis. The signaling pathways and hub genes may serve as drug targets or intervention targets for the treatment of leishmaniasis patients with undernutrition.

An Overview of Stimuli-Responsive Intelligent Antibacterial Nanomaterials

Drug-resistant bacteria and infectious diseases associated with biofilms pose a significant global health threat. The integration and advancement of nanotechnology in antibacterial research offer a promising avenue to combat bacterial resistance. Nanomaterials possess numerous advantages, such as customizable designs, adjustable shapes and sizes, and the ability to synergistically utilize multiple active components, allowing for precise targeting based on specific microenvironmental variations. They serve as a promising alternative to antibiotics with diverse medical applications. Here, we discuss the formation of bacterial resistance and antibacterial strategies, and focuses on utilizing the distinctive physicochemical properties of nanomaterials to achieve inherent antibacterial effects by investigating the mechanisms of bacterial resistance. Additionally, we discuss the advancements in developing intelligent nanoscale antibacterial agents that exhibit responsiveness to both endogenous and exogenous responsive stimuli. These nanomaterials hold potential for enhanced antibacterial efficacy by utilizing stimuli such as pH, temperature, light, or ultrasound. Finally, we provide a comprehensive outlook on the existing challenges and future clinical prospects, offering valuable insights for the development of safer and more effective antibacterial nanomaterials.

Methionine oxidation in bacteria: A reversible post-translational modification

Methionine is a sulfur-containing residue found in most proteins which are particularly susceptible to oxidation. Although methionine oxidation causes protein damage, it can in some cases activate protein function. Enzymatic systems reducing oxidized methionine have evolved in most bacterial species and methionine oxidation proves to be a reversible post-translational modification regulating protein activity. In this review, we inspect recent examples of methionine oxidation provoking protein loss and gain of function. We further speculate on the role of methionine oxidation as a multilayer endogenous antioxidant system and consider its potential consequences for bacterial virulence.

The application of optical technology in the diagnosis and therapy of oxidative stress-mediated hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is defined as liver tissue damage and cell death caused by reperfusion during liver transplantation or hepatectomy. Oxidative stress is one of the important mechanisms of HIRI. Studies have shown that the incidence of HIRI is very high, however, the number of patients who can get timely and efficient treatment is small. The reason is not hard to explain that invasive ways of detection and lack of timely of diagnostic methods. Hence, a new detection method is urgently needed in clinic application. Reactive oxygen species (ROS), which are markers of oxidative stress in the liver, could be detected by optical imaging and offer timely and effective non-invasive diagnosis and monitoring. Optical imaging could become the most potential tool of diagnosis of HIRI in the future. In addition, optical technology can also be used in disease treatment. It found that optical therapy has the function of anti-oxidative stress. Consequently, it has possibility to treat HIRI caused by oxidative stress. In this review, we mainly summarized the application and prospect of optical techniques in oxidative stress-induced by HIRI.

Microbe capture by splenic macrophages triggers sepsis via T cell-death-dependent neutrophil lifespan shortening

The mechanisms linking systemic infection to hyperinflammation and immune dysfunction in sepsis are poorly understood. Extracellular histones promote sepsis pathology, but their source and mechanism of action remain unclear. Here, we show that by controlling fungi and bacteria captured by splenic macrophages, neutrophil-derived myeloperoxidase attenuates sepsis by suppressing histone release. In systemic candidiasis, microbial capture via the phagocytic receptor SIGNR1 neutralizes myeloperoxidase by facilitating marginal zone infiltration and T cell death-dependent histone release. Histones and hyphae induce cytokines in adjacent CD169 macrophages including G-CSF that selectively depletes mature Ly6G^high neutrophils by shortening their lifespan in favour of immature Ly6G^low neutrophils with a defective oxidative burst. In sepsis patient plasma, these mediators shorten mature neutrophil lifespan and correlate with neutrophil mortality markers. Consequently, high G-CSF levels and neutrophil lifespan shortening activity are associated with sepsis patient mortality. Hence, by exploiting phagocytic receptors, pathogens degrade innate and adaptive immunity through the detrimental impact of downstream effectors on neutrophil lifespan.

Hyperinflammation and immune dysfunction are key drivers of immunopathology in sepsis. Here the authors show microbial exploitation of phagocytic receptors is linked to triggering of sepsis and the immune cell mediated reduction in neutrophil life span.

Singlet O2 Reactions with Radical Cations of 8-Bromoguanine and 8-Bromoguanosine: Guided-Ion Beam Mass Spectrometric Measurements and Theoretical Treatments

8-Bromoguanosine is generated in vivo as a biomarker for early inflammation. Its formation and secondary reactions lead to a variety of biological sequelae at inflammation sites, most of which are mutagenic and linked to cancer. Herein, we report the formation of radical cations of 8-bromoguanine (8BrG^•+) and 8-bromoguanosine (8BrGuo^•+) and their reactions toward the lowest excited singlet molecular oxygen (¹O₂)─a common reactive oxygen species generated in biological systems. This work aims to investigate synergistic, oxidatively generated damage of 8-brominated guanine and guanosine that may occur upon ionizing radiation, one-electron oxidation, and ¹O₂ oxidation. Capitalizing on measurements of reaction product ions and cross sections of 8BrG^•+ and 8BrGuo^•+ with ¹O₂ using guided-ion beam tandem mass spectrometry and augmented by computational modeling of the prototype reaction system, 8BrG^•+ + ¹O₂, using the approximately spin-projected ωB97XD/6-31+G(d,p) density functional theory, the coupled cluster DLPNO-CCSD(T)/aug-cc-pVTZ and the multireference CASPT2(21,15)/6-31G**, probable reaction products, and potential energy surfaces (PESs) were mapped out. 8BrG^•+ and 8BrGuo^•+ present similar exothermic oxidation products, and their reaction efficiencies with ¹O₂ increase with decreasing collision energy. Both single- and multireference theories predicted that the two most energetically favorable reaction pathways correspond to ¹O₂-addition to the C8 and C5-positions of 8BrG^•+, respectively. The CASPT2-calculated PES represents the best quantitative agreement with the experimental benchmark, in that the oxidation exothermicity is close to the water hydration energy of product ions and, thus, is able to eliminate a water ligand in the product ions.

BODIPY derivatives as fluorescent reporters of molecular activities in living cells

Fluorescent compounds have become indispensable tools for imaging molecular activities in the living cell. 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) is currently one of the most popular fluorescent reporters due to its unique photophysical properties. This review provides a general survey and presents a summary of recent advances in the development of new BODIPY-based cellular biomarkers and biosensors. The review starts with the consideration of the properties of BODIPY derivatives required for their application as cellular reporters. Then review provides examples of the design of sensors for different biologically important molecules, ions, membrane potential, temperature and viscosity defining the live cell status. Special attention is payed to BODPY-based phototransformable reporters.

The bibliography includes 339 references.

Increase in the Antioxidant and Anti-Inflammatory Activity of Euterpe oleracea Martius Oil Complexed in β-Cyclodextrin and Hydroxypropyl-β-Cyclodextrin

Reactive oxygen species (ROS) are aerobic products generated during cellular respiration, but in the case of oxidative stress, they become key factors in the development of inflammatory processes and chronic diseases such as diabetes and rheumatoid arthritis. In this work, Euterpe oleracea oil (EOO), as well as the complexes produced by slurry (S) and kneading (K), were analyzed for antioxidant capacity in vitro, while only the β-cyclodextrin complex obtained by kneading (EOO-βCD-K), which showed better complexation, was selected for anti-inflammatory assays in vivo. In the scavenging activity of OH·, the hydroxypropyl-β-cyclodextrin complex obtained by kneading (EOO-HPβCD-K) exhibited an activity 437% higher than the pure oil. In the paw edema assay, EOO-βCD-K reduced edema by 200% and myeloperoxidase (MPO) activity by 112%. In an air pouch model, this treatment showed a reduction in leukocyte, MPO, and Interleukin-1β (IL-1β) levels; meanwhile those of glutathione and IL-10 were increased, demonstrating its ability to potentiate the anti-inflammatory effect of EOO.

Hedgehog artificial macrophage with atomic-catalytic centers to combat Drug-resistant bacteria

Pathogenic drug-resistant bacteria represent a threat to human health, for instance, the methicillin-resistant Staphylococcus aureus (MRSA). There is an ever-growing need to develop non-antibiotic strategies to fight bacteria without triggering drug resistance. Here, we design a hedgehog artificial macrophage with atomic-catalytic centers to combat MRSA by mimicking the “capture and killing” process of macrophages. The experimental studies and theoretical calculations reveal that the synthesized materials can efficiently capture and kill MRSA by the hedgehog topography and substantial generation of •O₂⁻ and HClO with its Fe₂N₆O catalytic centers. The synthesized artificial macrophage exhibits a low minimal inhibition concentration (8 μg/mL Fe-Art M with H₂O₂ (100 μM)) to combat MRSA and rapidly promote the healing of bacteria-infected wounds on rabbit skin. We suggest that the application of this hedgehog artificial macrophage with “capture and killing” capability and high ROS-catalytic activity will open up a promising pathway to develop antibacterial materials for bionic and non-antibiotic disinfection strategies.

The increase in drug-resistant bacteria is a world-wide health issue that demands the development of alternatives to standard antibiotic treatments. In this study, the authors synthesise a hedgehog artificial macrophage with heme-mimetic catalytic centres, and peroxidase- and haloperoxidase-mimicking activities, for the treatment of methicillin-resistant Staphylococcus aureus.

Site-Specific Scissors Based on Myeloperoxidase for Phosphorothioate DNA

The tool box of site-specific cleavage for nucleic acid has been an increasingly attractive subject. Especially, the recent emergence of the orthogonally activatable DNA device is closely related to the site-specific scission. However, most of these cleavage strategies are based on exogenous assistance, such as laser irradiation. Endogenous strategies are highly desirable for the orthogonally regulatable DNA machine to explore the crucial intracellular biological process and cell signal network. Here, we found that the accurate site-specific cleavage reaction of phosphorothioate (PT) modified DNA by using myeloperoxidase (MPO). A scissors-like mechanism by which MPO breaks PT modification through chloride oxidation has been revealed. Furthermore, we have successfully applied the scissors to activate PT-modified hairpin-DNA machines to produce horseradish peroxidase (HRP)-mimicking DNAzyme or initiate hybridization chain reaction (HCR) amplification. Since MPO plays an important role in the pathway related to oxidative stress in cells, through the HCR amplification activated by this tool box, the oxidative stress in living cells has been robustly imaged. This work proposes an accurate and endogenous site-specific cleavage tool for the research of biostimuli and the construction of DNA molecular devices.

Time Course of Peripheral Leukocytosis and Clinical Outcomes After Aneurysmal Subarachnoid Hemorrhage

Objective: Systemic inflammation after subarachnoid hemorrhage (SAH) is implicated in delayed cerebral ischemia (DCI) and adverse clinical outcomes. We hypothesize that early changes in peripheral leukocytes will be associated with outcomes after SAH.

Methods: SAH patients admitted between January 2009 and December 2016 were enrolled into a prospective observational study and were assessed for Hunt Hess Scale (HHS) at admission, DCI, and modified Ranked Scale (mRS) at discharge. Total white blood cell (WBC) counts and each component of the differential cell count were determined on the day of admission (day 0) to 8 days after bleed (day 8). Global cerebral edema (GCE) was assessed on admission CT, and presence of any infection was determined. Statistical tests included student's t-test, Chi-square test, and multivariate logistic regression (MLR) models.

Results: A total of 451 subjects were analyzed. Total WBCs and neutrophils decreased initially reaching a minimum at day 4–5 after SAH. Monocyte count increased gradually after SAH and peaked between day 6–8, while basophils and lymphocytes decreased initially from day 0 to 1 and steadily increased thereafter. Neutrophil to lymphocyte ratio (NLR) reached a peak on day 1 and decreased thereafter. WBCs, neutrophils, monocytes, and NLR were higher in patients with DCI and poor functional outcomes. WBCs, neutrophils, and NLR were higher in subjects who developed infections. In MLR models, neutrophils and monocytes were associated with DCI and worse functional outcomes, while NLR was only associated with worse functional outcomes. Occurrence of infection was associated with poor outcome. Neutrophils and NLR were associated with infection, while monocytes were not. Monocytes were higher in males, and ROC curve analysis revealed improved ability of monocytes to predict DCI and poor functional outcomes in male subjects.

Conclusions: Monocytosis was associated with DCI and poor functional outcomes after SAH. The association between neutrophils and NLR and infection may impact outcomes. Early elevation in monocytes had an improved ability to predict DCI and poor functional outcomes in males, which was independent of the occurrence of infection.

Behavioral and Neuronal Effects of Inhaled Bromine Gas: Oxidative Brain Stem Damage

The risk of accidental bromine (Br2) exposure to the public has increased due to its enhanced industrial use. Inhaled Br2 damages the lungs and the heart; however, adverse effects on the brain are unknown. In this study, we examined the neurological effects of inhaled Br2 in Sprague Dawley rats. Rats were exposed to Br2 (600 ppm for 45 min) and transferred to room air and cage behavior, and levels of glial fibrillary acidic protein (GFAP) in plasma were examined at various time intervals. Bromine exposure resulted in abnormal cage behavior such as head hitting, biting and aggression, hypervigilance, and hyperactivity. An increase in plasma GFAP and brain 4-hydroxynonenal (4-HNE) content also was observed in the exposed animals. Acute and delayed sympathetic nervous system activation was also evaluated by assessing the expression of catecholamine biosynthesizing enzymes, tryptophan hydroxylase (TrpH1 and TrpH2), and tyrosine hydroxylase (TyrH), along with an assessment of catecholamines and their metabolites. TyrH was found to be increased in a time-dependent manner. TrpH1 and TrpH2 were significantly decreased upon Br2 exposure in the brainstem. The neurotransmitter content evaluation indicated an increase in 5-HT and dopamine at early timepoints after exposure; however, other metabolites were not significantly altered. Taken together, our results predict brain damage and autonomic dysfunction upon Br2 exposure.

Assessment of anti-inflammatory-like, antioxidant activities and molecular docking of three alkynyl-substituted 3-ylidene-dihydrobenzo[d]isothiazole 1,1-dioxide derivatives

The presence of enyne and benzoisothiazole functions in the molecular architecture of compounds 1, 2 and 3 were expected to provide biochemical activities. In the present work, we first examined the molecular surface contact of three alkynyl-substituted 3-ylidenedihydrobenzo[d] isothiazole 1,1-dioxides. The analysis of the Hirshfeld surfaces reveals that only compound 3 exhibited a well-defined red spots, indicating intermolecular interactions identified as S-O⋯H, C-H⋯O and C-O⋯H contacts. Comparative fingerprint histograms of the three compounds show that close pair interactions are dominated by C-H⋯H-C contact. By UV-visible analysis, compound 1 showed the most intense absorbances at 407 and 441 nm, respectively. The radical scavenging activity explored in the DPPH test, shows that only 1 exhibited low anti-radical activity. Furthermore, cellular antioxidant capacity of benzoisothiazoles 1-3 was investigated with PMA-activated HL-60 cells using chemiluminescence and fluorescence techniques in the presence of L-012 and Amplex Red probe, respectively. Results highlight that compound 1 exhibited moderate anti-ROS capacity while compounds 2 and 3 enhanced ROS production. The cytotoxicity test performed on HL-60 cells, using the MTS assay, confirmed the lack of toxicity of the tested benzoisothiazole 1 compared to 2 and 3 which show low cytotoxicity (≤30%). Anti-catalytic activity was evaluated by following the inhibitory potential of the benzoisothiazoles on MPO activity and depicted benzoisothiazoles-MPO interactions by docking. Both SIEFED and docking studies demonstrated an anti-catalytic activity of the tested benzoisothiazoles towards MPO with the best activity for compound 2.

Elevation of the serotonin-derived quinone, tryptamine-4,5-dione, in the intestine of ICR mice with dextran sulfate-induced colitis

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are chronic inflammatory disorders associated with oxidative stress. The intestines produce 5-hydroxytryptamine that may negatively affect disease state under inflammatory conditions when overproduced. 5-Hydroxytryptamine is a substrate for myeloperoxidase and is converted into reactive tryptamine-4,5-dione. Here, an experimental colitis model was established through oral administration of 5% dextran sulfate sodium to ICR mice for 7 days. Furthermore, the formation of tryptamine-4,5-dione in the colorectal mucosa/submucosa and colorectal tissue was analyzed by chemical and immunochemical methodologies. First, free tryptamine-4,5-dione in the homogenate was chemically trapped by o-phenylenediamine and analyzed as the stable phenazine derivative. Tryptamine-4,5-dione localization as adducted proteins in the colorectal tissue was immunohistochemically confirmed, and as demonstrated by both methods, this resulted in the significant increase of tryptamine-4,5-dione in dextran sulfate sodium-challenged mice compared with control mice. Immunohistochemical staining confirmed tryptamine-4,5-dione-positive staining at the myeloperoxidase accumulation site in dextran sulfate sodium-challenged mice colorectal tissue. The tryptamine-4,5-dione locus in the mice was partly matched with that of a specific marker for myeloperoxidase, halogenated tyrosine. Overall, the results possibly indicate that tryptamine-4,5-dione is generated by neutrophil myeloperoxidase in inflammatory tissue and may contribute to the development of inflammatory bowel disease.

Is carbonyl/AGE/RAGE stress a hallmark of the brain aging?

Recent studies have linked carbonyl stress to many physiological processes. Increase in the levels of carbonyl compounds, derived from both endogenous and exogenous sources, is believed to accompany normal age-related decline as well as different pathologies. Reactive carbonyl species (RCS) are capable of damaging biomolecules via their involvement in a net of nonspecific reactions. In the advanced stages of RCS metabolism, variety of poorly degraded adducts and crosslinks, collectively named advanced glycoxidation end products (AGEs), arises. They are accumulated in an age-dependent manner in different tissues and organs and can contribute to inflammatory processes. In particular, detrimental effects of the end products are realized via activation of the specific receptor for AGEs (RAGE) and RAGE-dependent inflammatory signaling cascade. Although it is unclear, whether carbonyl stress is causal for age-associated impairments or it results from age- and disease-related cell damages, increased levels of RCS and AGEs are tightly related to inflammaging, and therefore, attenuation of the RAGE signaling is suggested as an effective approach for the treatment of inflammation and age-related disorders. The question raised in this review is whether specific metabolism in the aging brain related to carbonyl/RCS/AGE/RAGE 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.

Correlative light electron ion microscopy reveals in vivo localisation of bedaquiline in Mycobacterium tuberculosis-infected lungs

Correlative light, electron, and ion microscopy (CLEIM) offers huge potential to track the intracellular fate of antibiotics, with organelle-level resolution. However, a correlative approach that enables subcellular antibiotic visualisation in pathogen-infected tissue is lacking. Here, we developed correlative light, electron, and ion microscopy in tissue (CLEIMiT) and used it to identify the cell type–specific accumulation of an antibiotic in lung lesions of mice infected with Mycobacterium tuberculosis. Using CLEIMiT, we found that the anti-tuberculosis (TB) drug bedaquiline (BDQ) is localised not only in foamy macrophages in the lungs during infection but also accumulate in polymorphonuclear (PMN) cells.

This study uses correlative light, electron and ion microscopy (CLEIM) in vivo to reveal the intracellular fate of an antibiotic in lung lesions of mice infected with Mycobacterium tuberculosis, with organelle-level resolution.

Reactions of kynurenic acid with hypobromous acid and hypochlorous acid

Kynurenic acid, a tryptophan metabolite, acts as antagonist or agonist of several receptors. Hypobromous acid (HOBr) and hypochlorous acid (HOCl) are generated by eosinophils and neutrophils. At inflammation sites, kynurenic acid may encounter HOBr and HOCl to generate products. When kynurenic acid was incubated with HOBr under neutral conditions, kynurenic acid generated a single product almost exclusively. This was identified as 3-bromokynurenic acid. Kynurenic acid reacted with HOCl, generating two products. The major product was identified as 3-chlorokynurenic acid with its oxidative decarboxylation product, 3-chloro-4-hydroxy-2(1H)-quinolinone as a by-product. Free amino acids suppressed the reactions of kynurenic acid with HOBr and HOCl. Taurine suppressed the HOCl reaction but not the HOBr reaction. An eosinophil peroxidase system containing H₂O₂, NaCl, and NaBr reacted with kynurenic acid, generating 3-bromokynurenic acid under mildly acidic conditions. Although a myeloperoxidase system containing H₂O₂ and NaCl reacted with kynurenic acid to generate 3-chlorokynurenic acid under mildly acidic conditions, the product was altered to 3-bromokynurenic acid by addition of NaBr to the system. These results suggest that 3-bromokynurenic acid and 3-chlorokynurenic acid may be generated from kynurenic acid at inflammation sites in humans, although their formation will be suppressed by coexistent amino acids.

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.

Acute kidney injury pathology and pathophysiology: a retrospective review

Acute kidney injury (AKI) is the clinical term used for decline or loss of renal function. It is associated with chronic kidney disease (CKD) and high morbidity and mortality. However, not all causes of AKI lead to severe consequences and some are reversible. The underlying pathology can be a guide for treatment and assessment of prognosis. The Kidney Disease: Improving Global Outcomes guidelines recommend that the cause of AKI should be identified if possible. Renal biopsy can distinguish specific AKI entities and assist in patient management. This review aims to show the pathology of AKI, including glomerular and tubular diseases.

NADPH Oxidase Inhibition in Fibrotic Pathologies

Significance: Fibrosis is a stereotypic, multicellular tissue response to diverse types of injuries that fundamentally result from a failure of cell/tissue regeneration. This complex tissue remodeling response disrupts cellular/matrix composition and homeostatic cell-cell interactions, leading to loss of normal tissue architecture and progressive loss of organ structure/function. Fibrosis is a common feature of chronic diseases that may affect the lung, kidney, liver, and heart. Recent Advances: There is emerging evidence to support a combination of genetic, environmental, and age-related risk factors contributing to susceptibility and/or progression of fibrosis in different organ systems. A core pathway in fibrogenesis involving these organs is the induction and activation of nicotinamide adenine dinucleotide phosphate oxidase (NOX) family enzymes. Critical Issues: We explore current pharmaceutical approaches to targeting NOX enzymes, including repurposing of currently U.S. Food and Drug Administration (FDA)-approved drugs. Specific inhibitors of various NOX homologs will aid establishing roles of NOXs in the various organ fibroses and potential efficacy to impede/halt disease progression. Future Directions: The discovery of novel and highly specific NOX inhibitors will provide opportunities to develop NOX inhibitors for treatment of fibrotic pathologies.

Neuregulin-1β Protects the Rat Diaphragm during Sepsis against Oxidative Stress and Inflammation by Activating the PI3K/Akt Pathway

Sepsis-induced diaphragm dysfunction (SIDD) which is mainly characterized by decrease in diaphragmatic contractility has been identified to cause great harms to patients. Therefore, there is an important and pressing need to find effective treatments for improving SIDD. In addition, acetylcholinesterase (AChE) activity is a vital property of the diaphragm, so we evaluated both diaphragmatic contractility and AChE activity. Though neuregulin-1β (NRG-1β) is known to exert organ-protective effects in some inflammatory diseases, little is known about the potential of NRG-1β therapy in the diaphragm during sepsis. Our study was aimed at exploring the effects of NRG-1β application on diaphragmatic contractility and AChE activity during sepsis. Proinflammatory cytokines, muscle injury biomarkers in serum, contractile force, AChE activity, proinflammatory cytokines, oxidative parameters, histological condition, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, and expression of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB/Akt) signaling proteins in the diaphragm were measured and compared between nonseptic and septic groups with or without NRG-1β treatment. In vitro, the effects of NRG-1β on reactive oxygen species (ROS) production in the lipopolysaccharide- (LPS-) stimulated L6 rat muscle skeletal cells with or without the Akt inhibitor MK-2206 were detected. NRG-1β inhibited proinflammatory cytokine release and muscle injury biomarkers soaring in serum and improved the sepsis-induced diaphragm dysfunction and AChE activity decrease significantly during sepsis. Meanwhile, the inflammatory response, oxidative stress, pathological impairment, and cell apoptosis in the diaphragm were mitigated by NRG-1β. And NRG-1β activated the PI3K/Akt signaling in the diaphragm of septic rats. Elevated ROS production in the LPS-stimulated L6 rat skeletal muscle cells was reduced after treatment with NRG-1β, while MK-2206 blocked these effects of NRG-1β. In conclusion, our findings underlined that NRG-1β could reduce circulating levels of proinflammatory cytokines in rats with sepsis, adjust diaphragmatic proinflammatory cytokine level, mitigate diaphragmatic oxidative injury, and lessen diaphragm cell apoptosis, thereby improving diaphragmatic function, and play a role in diaphragmatic protection by activating PI3K/Akt signaling.

Phagocyte activity reflects mammalian homeo- and hetero-thermic physiological states

BACKGROUND

Emergence of both viral zoonoses from bats and diseases that threaten bat populations has highlighted the necessity for greater insights into the functioning of the bat immune system. Particularly when considering hibernating temperate bat species, it is important to understand the seasonal dynamics associated with immune response. Body temperature is one of the factors that modulates immune functions and defence mechanisms against pathogenic agents in vertebrates. To better understand innate immunity mediated by phagocytes in bats, we measured respiratory burst and haematology and blood chemistry parameters in heterothermic greater mouse-eared bats (Myotis myotis) and noctules (Nyctalus noctula) and homeothermic laboratory mice (Mus musculus).

RESULTS

Bats displayed similar electrolyte levels and time-related parameters of phagocyte activity, but differed in blood profile parameters related to metabolism and red blood cell count. Greater mouse-eared bats differed from mice in all phagocyte activity parameters and had the lowest phagocytic activity overall, while noctules had the same quantitative phagocytic values as mice. Homeothermic mice were clustered separately in a high phagocyte activity group, while both heterothermic bat species were mixed in two lower phagocyte activity clusters. Stepwise regression identified glucose, white blood cell count, haemoglobin, total dissolved carbon dioxide and chloride variables as the best predictors of phagocyte activity. White blood cell counts, representing phagocyte numbers available for respiratory burst, were the best predictors of both time-related and quantitative parameters of phagocyte activity. Haemoglobin, as a proxy variable for oxygen available for uptake by phagocytes, was important for the onset of phagocytosis.

CONCLUSIONS

Our comparative data indicate that phagocyte activity reflects the physiological state and blood metabolic and cellular characteristics of homeothermic and heterothermic mammals. However, further studies elucidating trade-offs between immune defence, seasonal lifestyle physiology, hibernation behaviour, roosting ecology and geographic patterns of immunity of heterothermic bat species will be necessary. An improved understanding of bat immune responses will have positive ramifications for wildlife and conservation medicine.

The two faces of Coprinus comatus-Functional properties and potential hazards

Mushrooms have been used for centuries not only as food but also in traditional medicine as a source of components with pro‐health activity. One of them is Coprinus comatus (O.F.Müll.) Pers. also called shaggy mane, chicken drumstick mushroom, or lawyer's wig. In Asian countries, C. comatus (CC) is approved as edible mushroom and often cultivated for consumption, whereas in many other countries, although it is widespread, it is unrecognized and not used. In this review, for the first time, we discussed about the composition related to functional properties as well as the potential risks associated with consumption of CC by reviewing scientific literature. The information has been collected in order to get to know this species thoroughly. Various studies show many of the physiological activities, such as antioxidant, anticancer, antiandrogenic, hepatoprotective, acetylcholinesterase inhibitory, antiinflammatory, antidiabetic, antiobesity, antibacterial, antifungal, antinematode, and antiviral. Besides positive physiological properties, CC has also negative features, for example, skin reactions in patients with dermatitis and atopic predisposition, risk of confusion with poisonous mushrooms, quick autolysis after collection, and contamination of toxic elements.

Circulating myeloperoxidase is elevated in septic shock and is associated with systemic organ failure and mortality in critically ill patients

BACKGROUND

Neutrophils are elevated in critically ill patients during the systemic inflammatory response to trauma and sepsis. The neutrophil-derived enzyme myeloperoxidase generates reactive oxygen species which can react with host tissue resulting in cell damage and dysfunction. Thus, elevated myeloperoxidase in the circulation may be associated with adverse patient outcomes.

METHODS

Circulating myeloperoxidase concentrations were measured in a cohort of 44 critically ill patients, 55% of whom were diagnosed with septic shock, and 44 healthy controls. Intensive care mortality prediction scores (SOFA, SAPS, APACHE) and ICU and hospital mortality were obtained from the patients' clinical notes. Hematological and biochemical assessments included blood cell counts, lactate, alanine transaminase, creatinine, bilirubin, C-reactive protein, and PaO₂. Myeloperoxidase was measured using a commercial ELISA kit and cell free DNA was detected using SytoxGreen™ fluorescence staining.

RESULTS

Myeloperoxidase concentrations were significantly higher in critically ill patients than control samples (234 ± 30 ng/ml versus 15 ± 4 ng/ml, p < 0.001), and were elevated in septic shock relative to non-septic patients (302 ± 42 ng/ml versus 156 ± 38 ng/ml, p = 0.02), despite neutrophil counts being comparable between the two subgroups (p = 0.6). Myeloperoxidase correlated with SOFA scores in the critically ill patients (r = 0.395, p = 0.02), and with markers of tissue dysfunction and injury such as lactate (r = 0.572, p < 0.001), log₁₀ alanine transferase (r = 0.392, p = 0.016) and log₁₀ cell free DNA (r = 0.371, p = 0.03). The subgroup of patients with higher than mean APACHE III scores (i.e. >78, n = 16) exhibited significantly elevated myeloperoxidase concentrations in the non-survivors compared with survivors (416 ± 59 ng/ml versus 140 ± 33 ng/mL, p = 0.001). Hospital mortality for the whole cohort was 27%; mortality in the high APACHE III subgroup was 38%, and when combined with higher than mean myeloperoxidase (i.e. >234 ng/mL), mortality increased to 71%.

CONCLUSIONS

Myeloperoxidase is associated with markers of tissue injury and systemic organ failure, particularly in septic patients. The enzyme is also associated with mortality in patients with higher APACHE III scores, and thus has potential as an additional diagnostic marker to improve mortality prediction.

The Role of Halogenative Stress in Atherogenic Modification of Low-Density Lipoproteins

This review discusses formation of reactive halogen species (RHS) catalyzed by myeloperoxidase (MPO), an enzyme mostly present in leukocytes. An imbalance between the RHS production and body's ability to remove or neutralize them leads to the development of halogenative stress. RHS reactions with proteins, lipids, carbohydrates, and antioxidants in the content of low-density lipoproteins (LDLs) of the human blood are described. MPO binds site-specifically to the LDL surface and modifies LDL properties and structural organization, which leads to the LDL conversion into proatherogenic forms captured by monocytes/macrophages, which causes accumulation of cholesterol and its esters in these cells and their transformation into foam cells, the basis of atherosclerotic plaques. The review describes the biomarkers of MPO enzymatic activity and halogenative stress, as well as the involvement of the latter in the development of atherosclerosis.

High Dose Pomegranate Extract Suppresses Neutrophil Myeloperoxidase and Induces Oxidative Stress in a Rat Model of Sepsis

Abstract. Introduction: The effect of using high dose pomegranate extract on sepsis and its safety is not clarified. Considering the fact that proper immune and inflammatory responses are needed to cope with infection, the aim of current study was to assess the effect of high dose pomegranate extract consumption on oxidative and inflammatory responses after disease induction in rat model of sepsis. Methods: Sepsis was induced by Cecal Ligation and Perforation (CLP) surgery. Adult male Wistar rats were divided into three groups of eight animals: Sham; CLP and POMx [consumed POMx (250 mg of pomegranate fruit extract/kg/day) for four weeks before CLP]. Results: Peritoneal neutrophil myeloperoxidase activity was significantly lower in POMx compared with Sham and CLP groups ( p < 0.01 and p < 0.05, respectively). Although antioxidant enzymes were higher in POMx group after sepsis induction, lower serum total antioxidant status (TAS) (p < 0.01 compared with both CLP and Sham groups) and higher liver thiobarbituric acid reactive species (TBARS) levels were observed in this group ( p < 0.01 and p < 0.05, compared with Sham and CLP groups, respectively). Conclusion: High dose POMx consumption prior to sepsis induction, suppressed the vital function of neutrophils in early hours after sepsis initiation, resulting in higher oxidative stress. These findings indicate that caution should be made in using high dose pomegranate products. The main message of current study is that such useful compounds as antioxidants including pomegranate juice which have beneficial effects on general health status may have detrimental effects if misused or used in high doses.

A versatile imaging platform with fluorescence and CT imaging capabilities that detects myeloperoxidase activity and inflammation at different scales

Aberrant innate immune response drives the pathophysiology of many diseases. Myeloperoxidase (MPO) is a highly oxidative enzyme secreted by activated myeloid pro-inflammatory immune cells such as neutrophils and macrophages, and is a key mediator of the damaging innate immune response. Current technologies for detecting MPO activity in living organisms are sparse and suffer from any combination of low specificity, low tissue penetration, or low spatial resolution. We describe a versatile imaging platform to detect MPO activity using an activatable construct conjugated to a biotin moiety (MPO-activatable biotinylated sensor, MABS) that allows monitoring the innate immune response and its modulation at different scales and settings.

Methods:We designed and synthesized MABS that contains MPO-specific and biotin moieties, and validated its specificity and sensitivity combining with streptavidin-labeled fluorescent agent and gold nanoparticles imaging in vitro and in vivo in multiple mouse models of inflammation and infection, including Matrigel implant, dermatitis, cellulitis, cerebritis and complete Fraud's adjuvant (CFA)-induced inflammation.

Results: MABS MPO imaging non-invasively detected varying MPO concentrations, MPO inhibition, and MPO deficiency in vivo with high sensitivity and specificity. MABS can be used to obtain not only a fluorescence imaging agent, but also a CT imaging agent, conferring molecular activity information to a structural imaging modality. Importantly, using this method on tissue-sections, we found that MPO enzymatic activity does not always co-localize with MPO protein detected with conventional techniques (e.g., immunohistochemistry), underscoring the importance of monitoring enzymatic activity.

Conclusion:By choosing from different available secondary probes, MABS can be used to create systems suitable to investigate and image MPO activity at different scales and settings.

Myeloperoxidase and Eosinophil Peroxidase Inhibit Endotoxin Activity and Increase Mouse Survival in a Lipopolysaccharide Lethal Dose 90% Model

Myeloperoxidase (MPO) and eosinophil peroxidase (EPO) are cationic haloperoxidases with potent microbicidal and detoxifying activities. MPO selectively binds to and kills some Gram-positive bacteria (GPB) and all Gram-negative bacteria (GNB) tested. GNB contain endotoxin, i.e., lipopolysaccharide (LPS) comprising a toxic lipid A component. The possibility that MPO and EPO bind and inhibit the endotoxin of GNB was tested by mixing MPO or EPO with LPS or lipid A and measuring for inhibition of endotoxin activity using the chromogenic Limulus amebocyte lysate (LAL) assay. The endotoxin-inhibiting activities of MPO and EPO were also tested in vivo using an LPS 90% lethal dose (LD90) mouse model studied over a five-day period. Mixing MPO or EPO with a fixed quantity of LPS from Escherichia coli O55:B5 or with diphosphoryl lipid A from E. coli F583 inhibited LAL endotoxin activity in proportion to the natural log of the MPO or EPO concentration. MPO and EPO enzymatic activities were not required for inhibition, and MPO haloperoxidase action did not increase endotoxin inhibition. Both MPO and EPO increased mouse survival in the LPS LD90 model. In conclusion, MPO and EPO nonenzymatically inhibited in vitro endotoxin activity using the LAL assay, and MPO and high-dose EPO significantly increased mouse survival in a LPS LD90 model, and such survival was increased in a dose-dependent manner.

The role of endogenous bromotyrosine in health and disease

Bromotyrosine is a stable by-product of eosinophil peroxidase activity, a result of eosinophil activation during an inflammatory immune response. The elevated presence of bromotyrosine in tissue, blood, and urine in medical conditions involving eosinophil activation has highlighted the potential role of bromotyrosine as a medical biomarker. This is highly beneficial in a paediatric setting as a urinary noninvasive biomarker. However, bromotyrosine and its derivatives may exert biological effects, such as protective effects in the brain and pathogenic effects in the thyroid. Understanding these pathways may yield therapeutic advancements in medicine. In this review, we summarize the existing evidence present in literature relating to bromotyrosine formation and metabolism, identify the biological actions of bromotyrosine and evaluate the feasibility of bromotyrosine as a medical biomarker.

FACS isolation and analysis of human circulating and tumor neutrophils

The role of neutrophils in tumor growth and metastasis is still controversial. Studies in clinically relevant models of cancer have shown that neutrophils can promote tumor growth and development and metastasis, or inhibit it. Thus, further analysis is required to fully elucidate the role of neutrophils in cancer. A number of different methods are available for neutrophil isolation and characterization. However, Fluorescence-activated cell sorting (FACS) is particularly effective for isolating neutrophils and assessing their phenotype as it allows for the simultaneous use of multiple cell surface markers, can be used for isolation of both blood and tumor neutrophils and features a high purity and high yields.

Effects of Myeloperoxidase on Methicillin-Resistant Staphylococcus aureus-Colonized Burn Wounds in Rats

Objective: To achieve better therapeutic results in burn wound infections and to examine alternatives to antibiotics, we designed this study to elaborate the role of myeloperoxidase (MPO) on infected burn wounds in rats. Approach: We compared chemical properties as well as bacteriostatic ability of MPO in different concentrations with NeutroPhase. Subsequently, we applied MPO (MPO group), NeutroPhase (NeutroPhase group), NaCl+H₂O₂ (NaCl+H₂O₂ group), or NaCl (control group) on rat dorsal burn wounds inoculated with methicillin-resistant Staphylococcus aureus (MRSA). Their effects on MRSA-colonized wounds were evaluated by microscopy, histologic section, and Western blot. Results: MPO produced more H⁺ and HClO^-, leading to a more acidic environment. Moreover, MPO inhibited the growth of MRSA more intensely after 6 h of inoculation ex vivo. In vivo the open wound rate in the MPO group was significantly lower, while the contraction rate and epithelialization rate of MPO group were higher than that of the control group, NaCl+H₂O₂ group, and NeutroPhase group on day 20. The hematoxylin and eosin staining of MPO group showed better wound healing than other groups. More vascular endothelial growth factor (VEGF) was expressed in wound tissue of MPO group by Western blot. Innovation: This is the first study to use MPO for MRSA-colonized burn wound therapy. Conclusion: MPO displayed more effective bacteriostatic ability, possibly beneficial for MRSA-colonized wound healing.

Small-Molecule-Based Fluorescent Sensors for Selective Detection of Reactive Oxygen Species in Biological Systems

Reactive oxygen species (ROS) encompass a collection of intricately linked chemical entities characterized by individually distinct physicochemical properties and biological reactivities. Although excessive ROS generation is well known to underpin disease development, it has become increasingly evident that ROS also play central roles in redox regulation and normal physiology. A major challenge in uncovering the relevant biological mechanisms and deconvoluting the apparently paradoxical roles of distinct ROS in human health and disease lies in the selective and sensitive detection of these transient species in the complex biological milieu. Small-molecule-based fluorescent sensors enable molecular imaging of ROS with great spatial and temporal resolution and have thus been appreciated as excellent tools for aiding discoveries in modern redox biology. We review a selection of state-of-the-art sensors with demonstrated utility in biological systems. By providing a systematic overview based on underlying chemical sensing mechanisms, we wish to highlight the strengths and weaknesses in prior sensor works and propose some guiding principles for the development of future probes.

Neutrophils mediate early cerebral cortical hypoperfusion in a murine model of subarachnoid haemorrhage

Cerebral hypoperfusion in the first hours after subarachnoid haemorrhage (SAH) is a major determinant of poor neurological outcome. However, the underlying pathophysiology is only partly understood. Here we induced neutropenia in C57BL/6N mice by anti-Ly6G antibody injection, induced SAH by endovascular filament perforation, and analysed cerebral cortical perfusion with laser SPECKLE contrast imaging to investigate the role of neutrophils in mediating cerebral hypoperfusion during the first 24 h post-SAH. SAH induction significantly increased the intracranial pressure (ICP), and significantly reduced the cerebral perfusion pressure (CPP). At 3 h after SAH, ICP had returned to baseline and CPP was similar between SAH and sham mice. However, in SAH mice with normal neutrophil counts cortical hypoperfusion persisted. Conversely, despite similar CPP, cortical perfusion was significantly higher at 3 h after SAH in mice with neutropenia. The levels of 8-iso-prostaglandin-F2α in the subarachnoid haematoma increased significantly at 3 h after SAH in animals with normal neutrophil counts indicating oxidative stress, which was not the case in neutropenic SAH animals. These results suggest that neutrophils are important mediators of cortical hypoperfusion and oxidative stress early after SAH. Targeting neutrophil function and neutrophil-induced oxidative stress could be a promising new approach to mitigate cerebral hypoperfusion early after SAH.

Mouse neutrophils release extracellular traps in response to Naegleria fowleri

Naegleria fowleri is a free-living amoeba, which is able to infect humans through the nasal mucosa causing a disease in the central nervous system known as primary amoebic meningoencephalitis (PAM). Polymorphonuclear cells (PMNs) play a critical role in the early phase of N fowleri infection. Recently, a new biological defence mechanism called neutrophil extracellular traps (NETs) has been attracting attention. These structures represent an important strategy to immobilize and kill invading microorganisms. In this work, we evaluate the capacity of N fowleri to induce the NETs release by PMNs cells in mice in vitro and in vivo. In vitro: Neutrophils from bone marrow were cocultured with N fowleri trophozoites. In vivo: we employed a mouse model of PAM. We evaluated DNA, histone and myeloperoxidase (MPO) and the formation of NETs by confocal microscopy. Our results showed N fowleri induce both NETs and MPO release by PMNs cells in mice after trophozoite exposure, which increased through time, in vitro and in vivo. These results demonstrate that NETs are somehow associated with the amoebas. We suggest PMNs release their traps trying to avoid N fowleri attachment at the apical side of the nasal epithelium.

Peroxidasin is a novel target of the redox-sensitive transcription factor Nrf2

Peroxidasin (PXDN) facilitates peroxidative reactions via utilisation of hydrogen peroxide (H2O2) and has been shown to crosslink collagen IV through sulfilimine bond formation in the presence of hypohalous acids. Aberrant PXDN expression has been associated with kidney fibrosis, cancer, congenital eye defects and various cardiovascular disorders. Since PXDN expression is modified by H2O2, we hypothesized that a major antioxidant response transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), may regulate PXDN expression. PXDN expression in response to H2O2 and the Nrf2-specific inducers, tert-butylhydroquinone (tBHQ) and sulforaphane (SFN), was determined by western blotting and immunofluorescence microscopy, in HeLa and HEK293 cells. Chromatin immunoprecipitation and luciferase reporter assays were used to investigate the regulation of PXDN by Nrf2. We observed elevated Nrf2 nuclear translocation and increased PXDN protein expression in response to H2O2, tBHQ and SFN, in both cell lines. We found that Nrf2 binds to and increases luciferase reporter gene expression from the PXDN promoter via a putative Nrf2-binding site. In summary, we show that PXDN is a novel target of the redox sensitive transcription factor Nrf2. This finding further highlights the role of PXDN in redox-related processes and compliments the currently understood pathophysiological functions of PXDN.

Comparative Analysis of Microbicidal and Anti-inflammatory Properties of Novel Taurine Bromamine Derivatives and Bromamine T

Taurine, the most abundant free amino acid in leukocyte cytosol traps hypohalous acids (HOCl and HOBr) to produce N-chlorotaurine (taurine chloramine, NCT and N-bromotaurine (taurine bromamine, Tau-NHBr,) respectively. Both haloamines show anti-inflammatory and antimicrobial properties. However, the therapeutic applicability of Tau-NHBr is limited due to its relatively poor stability. To overcome this disadvantage, we have synthesized the stable N-bromotaurine compounds N-monobromo-2,2-dimethyltaurine (Br-612) and N-dibromo-2,2-dimethyltaurine (Br-422). The aim of this study was to compare anti-inflammatory and microbicidal properties of Br-612 and Br-422 with that of Tau-NHBr and bromamine T (BAT). We have shown that all the tested compounds show similar anti-inflammatory properties. Importantly, the stable N-bromotaurine compounds exerted even stronger microbicidal activity than Tau-NHBr. Finally, for the purpose of topical application of these compounds we have developed a carbomer-based bioadhesive solid dosage form of BAT and Br-612, featuring sustained release of the active substance.

Healthy brain aging: Interplay between reactive species, inflammation and energy supply

Brains' high energy expenditure with preferable utilization of glucose and ketone bodies, defines the specific features of its energy homeostasis. The extensive oxidative metabolism is accompanied by a concomitant generation of high amounts of reactive oxygen, nitrogen, and carbonyl species, which will be here collectively referred to as RONCS. Such metabolism in combination with high content of polyunsaturated fatty acids creates specific problems in maintaining brains' redox homeostasis. While the levels of products of interaction between RONCS and cellular components increase slowly during the first two trimesters of individuals' life, their increase is substantially accelerated towards the end of life. Here we review the main mechanisms controlling the redox homeostasis of the mammalian brain, their age-dependencies as well as their adaptive potential, which might turn out to be much higher than initially assumed. According to recent data, the organism seems to respond to the enhancement of aging-related toxicity by forming a new homeostatic set point. Therefore, further research will focus on understanding the properties of the new set point(s), the general nature of this phenomenon and will explore the limits of brains' adaptivity.

Uric acid disrupts hypochlorous acid production and the bactericidal activity of HL-60 cells

Uric acid is the end product of purine metabolism in humans and is an alternative physiological substrate for myeloperoxidase. Oxidation of uric acid by this enzyme generates uric acid free radical and urate hydroperoxide, a strong oxidant and potentially bactericide agent. In this study, we investigated whether the oxidation of uric acid and production of urate hydroperoxide would affect the killing activity of HL-60 cells differentiated into neutrophil-like cells (dHL-60) against a highly virulent strain (PA14) of the opportunistic pathogen Pseudomonas aeruginosa. While bacterial cell counts decrease due to dHL-60 killing, incubation with uric acid inhibits this activity, also decreasing the release of the inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF- α). In a myeloperoxidase/Cl^-/H₂O₂ cell-free system, uric acid inhibited the production of HOCl and bacterial killing. Fluorescence microscopy showed that uric acid also decreased the levels of HOCl produced by dHL-60 cells, while significantly increased superoxide production. Uric acid did not alter the overall oxidative status of dHL-60 cells as measured by the ratio of reduced (GSH) and oxidized (GSSG) glutathione. Our data show that uric acid impairs the killing activity of dHL-60 cells likely by competing with chloride by myeloperoxidase catalysis, decreasing HOCl production. Despite diminishing HOCl, uric acid probably stimulates the formation of other oxidants, maintaining the overall oxidative status of the cells. Altogether, our results demonstrated that HOCl is, indeed, the main relevant oxidant against bacteria and deviation of myeloperoxidase activity to produce other oxidants hampers dHL-60 killing activity.

•

Uric acid decreased microbicide activity and release of cytokines by dHL-60 cells.

•

Uric acid decreased HOCl in cells and in the myeloperoxidase/Cl^-/H₂O₂ system.

•

Uric acid induces a pro-oxidant redox imbalance.

•

HOCl is crucial for Pseudomonas aeruginosa killing by dHL-60.

Neutrophils in tissue injury and repair

As one of the first defenders of innate immune response, neutrophils make a rapid and robust response against infection or harmful agents. While traditionally regarded as suicidal killers that cause collateral tissue damage, recent findings on neutrophil extracellular trap formation, heterogeneity and plasticity and novel reparative functions have expanded our understanding of their diverse roles in health and disease. This review summarizes our current understanding of neutrophil-associated tissue injury, highlighting the emerging roles of neutrophil extracellular traps. This review will also focus on scrutinizing the roles of neutrophils in tissue repair and regeneration and will examine data on unexpected aspects of involvement of neutrophils in regulating normal tissue homeostasis.

Hypochlorous Acid Promoted Platinum Drug Chemotherapy by Myeloperoxidase-Encapsulated Therapeutic Metal Phenolic Nanoparticles

This study applies in situ production of hypochlorous acid (HOCl) to improve the therapeutic efficacy of platinum drugs. The phagocytic enzyme myeloperoxidase (MPO) is coated with two functional polyphenol derivatives (platinum prodrug polyphenols and PEG polyphenols) and ferric ion by metal phenolic coordination, which can shield MPO from degradation by other compounds in the blood. Moreover, the platinum prodrug can be reduced to cisplatin in cells and produce hydrogen peroxide (H₂O₂). The MPO catalyzes the conversion of H₂O₂ to HOCl in the intercellular environment. The as-prepared MPO Pt PEG nanoparticles (MPP NPs) can be employed as a reactive oxygen species cascade bioreaction to enhance platinum drug therapy. The MPP NPs show prolonged blood circulation and high tumor accumulation as evidenced by ⁸⁹Zr-based positron emission tomography imaging. The MPP NPs effectively inhibit tumor growth in vivo. As a first-in-class platform to harness the highly toxic HOCl in nanomedicine for cancer therapy, this strategy may open doors for further development of progressive therapeutic systems.

Myeloperoxidase: Its role for host defense, inflammation, and neutrophil function

Myeloperoxidase (MPO) is a heme-containing peroxidase expressed mainly in neutrophils and to a lesser degree in monocytes. In the presence of hydrogen peroxide and halides, MPO catalyzes the formation of reactive oxygen intermediates, including hypochlorous acid (HOCl). The MPO/HOCl system plays an important role in microbial killing by neutrophils. In addition, MPO has been demonstrated to be a local mediator of tissue damage and the resulting inflammation in various inflammatory diseases. These findings have implicated MPO as an important therapeutic target in the treatment of inflammatory conditions. In contrast to its injurious effects at sites of inflammation, recent studies using animal models of various inflammatory diseases have demonstrated that MPO deficiency results in the exaggeration of inflammatory response, and that it affects neutrophil functions including cytokine production. Given these diverse effects, a growing interest has emerged in the role of this well-studied enzyme in health and disease.