Myeloperoxidase: friend and foe

Non-Canonical Functions of Myeloperoxidase in Immune Regulation, Tissue Inflammation and Cancer

Myeloperoxidase (MPO) is one of the most abundantly expressed proteins in neutrophils. It serves as a critical component of the antimicrobial defense system, facilitating microbial killing via generation of reactive oxygen species (ROS). Interestingly, emerging evidence indicates that in addition to the well-recognized canonical antimicrobial function of MPO, it can directly or indirectly impact immune cells and tissue responses in homeostatic and disease states. Here, we highlight the emerging non-canonical functions of MPO, including its impact on neutrophil longevity, activation and trafficking in inflammation, its interactions with other immune cells, and how these interactions shape disease outcomes. We further discuss MPO interactions with barrier forming endothelial and epithelial cells, specialized cells of the central nervous system (CNS) and its involvement in cancer progression. Such diverse function and the MPO association with numerous inflammatory disorders make it an attractive target for therapies aimed at resolving inflammation and limiting inflammation-associated tissue damage. However, while considering MPO inhibition as a potential therapy, one must account for the diverse impact of MPO activity on various cellular compartments both in health and disease.

Prevention of mortality in acute lung injury induced by oleic acid: Application of polyherbal decoction (bronco T)

Acute lung injury (ALI) is a lethal respiratory disorder; directed uncontrolled inflammation, sloughing of the alveolar cells and their diffusion, and altered cardiorespiratory parameters with a global mortality rate of 40%. This study was designed to assess the preventive effect of a polyherbal decoction (Bronco T, 1.5 g/kg b. w.) on cardiorespiratory variables in oleic acid-induced ALI in rats. Oleic acid increases the level of neutrophil infiltration leading to pulmonary edema and alters the cardiorespiratory dynamics. The adult male rats were surgically cannulated and treated with intravenous oleic acid (0.38 ml/kg b. w.) to establish the ALI model. Bronco T was pre-administered orally 3 hours before oleic acid. The biophysical, histological, biochemical, and molecular effects were compared with dexamethasone (5 mg/kg b. w. i. p.). The animals were randomly divided into control, lethal, standard, and treatment groups. Respiratory frequency (RF), heart rate (HR), and mean arterial pressure (MAP) were recorded on a computerized chart recorder; arterial blood sample was collected to determine PaO₂/FiO₂, TNF-α, and MPO. Lipid peroxidation, superoxide dismutase, and catalase activity were evaluated to measure oxidative stress in bronchoalveolar lavage. Additionally, the pulmonary water content, COX-2 expression and histological examination were determined in the lung. A molecular docking study of the active phytoconstituent of BT obtained from HR-LCMS analysis against reported targets (IL-6, COX-2, TNFα, MPO and ENaC) of ALI was carried out. The B.T. pretreatment prevents mortality in comparison to the oleic acid group. It protects the lungs and heart from the detrimental effect of oleic acid, on par with dexamethasone. COX-2 mRNA expression was significantly down-regulated in the treatment group. The reduced level of TNF-α, MPO, SOD and catalase supported the protective effect of B.T. The in silico study revealed strong binding interaction between the phytoconstituent (Galangin 3- [galactosyl-(1–4)-rhamnoside and Beta solamarine] of BT and the reported target. The B.T. pre-administration attenuates the oleic acid-induced mortality and cardiorespiratory toxicity.

Propofol metabolites and derivatives inhibit the oxidant activities of neutrophils and myeloperoxidase

In previous studies, propofol has shown immunomodulatory abilities on various in vitro models. As this anesthetic molecule is extensively used in intensive care units, its anti-inflammatory properties present a great interest for the treatment of inflammatory disorders like the systemic inflammatory response syndrome. In addition to its inhibition abilities on important neutrophils mechanisms (chemotaxis, reactive oxygen species (ROS) production, Neutrophil Extracellular Traps (NETs) formation, …), our group has shown that propofol is also a reversible inhibitor of the oxidant myeloperoxidase (MPO) activity. Propofol being subject to rapid metabolism, its derivatives could contribute to its anti-inflammatory action. First, propofol-β-glucuronide (PPFG), 2,6-diisopropyl-1,4-p-benzoquinone (PPFQ) and 3,5,3',5'-tetraisopropyl-(4,4')-diphenoquinone (PPFDQ) were compared on their superoxide (O₂^.-) scavenging properties and more importantly on their inhibitory action on the O₂^.- release by activated neutrophils using EPR spectroscopy and chemiluminescence assays. PPFQ and PPFDQ are potent superoxide scavengers and also inhibit the release of ROS by neutrophils. An Enzyme-Linked Immunosorbent Assay (ELISA) has also highlighted the ability of both molecules to significantly decrease the MPO degranulation process of neutrophils. Fluorescence enzymatic assays helped to investigate the action of the propofol derivatives on the peroxidase and chlorination activities of MPO. In addition, using SIEFED (Specific Immunological Extraction Followed by Enzyme Detection) assays and docking, we demonstrated the concentration-dependent inhibitory action of PPFQ and its ability to bind to the enzyme active site while PPFG presented a much weaker inhibitory action. Overall, the oxidation derivatives and metabolites PPFQ and PPFDQ can, at physiological concentrations, perpetuate the immunomodulatory action of propofol by acting on the oxidant response of PMN and MPO.

The staphylococcal inhibitory protein SPIN binds to human myeloperoxidase with picomolar affinity but only dampens halide oxidation

The heme enzyme myeloperoxidase (MPO) is one of the key players in the neutrophil-mediated killing of invading pathogens as part of the innate immune system. MPO generates antimicrobial oxidants which indiscriminately and effectively kill phagocytosed pathogens. Staphylococcus aureus however is able to escape this fate, in part by secreting a small protein called SPIN (Staphylococcal Peroxidase Inhibitor), which specifically targets and inhibits MPO in a structurally complex manner. Here we present the first crystal structures of the complex of SPIN-aureus and a truncated version (SPIN-truncated) with mature dimeric leukocyte MPO. We unravel the contributions of the two domains to the kinetics and thermodynamics of SPIN-aureus binding to MPO by using a broad array of complementary biochemical and biophysical methods. The C-terminal "recognition" domain is shown to mediate specific binding to MPO, while interaction of the N-terminal "inhibitory" domain is guided mainly by hydrophobic effects and thus is less sequence-dependent. We found that inhibition of MPO is achieved by reducing substrate migration, but SPIN-aureus cannot completely block MPO activity. Its' effectiveness is inversely related to substrate size, with no discernible dependence on other factors. Thus, SPIN-aureus is an extremely high-affinity inhibitor and highly efficient for substrates larger than halogens. As aberrant MPO activity is implicated in a number of chronic inflammatory diseases, SPIN-aureus is the first promising protein inhibitor for specific inhibition of human MPO.

Elucidation of physicochemical properties of polysaccharides extracted from Cordyceps militaris fruiting bodies with different drying treatments and their effects on ulcerative colitis in zebrafish

Dry fruiting bodies of Cordyceps militaris (CMF) have been widely used in folk tonic foods and traditional herbal medicine in East Asia. Drying treatment serves as the last step in CMF industrial processes. In this work, the physicochemical properties of polysaccharides from C. militaris fruiting bodies (CMFPs) with hot air drying (HD), far-infrared radiation drying (ID) and vacuum freeze-drying (FD) treatments were analyzed, and their effects on ulcerative colitis (UC) were further investigated in oxazolone-induced zebrafish. The results showed that physicochemical properties of CMFP-H, CMFP-I and CMFP-F were obvious different. CMFPs could repair the intestinal mucosal barrier, inhibit ROS generation and the activities of MDA and MPO, and improve the activities of SOD, CAT, ACP, AKP and LZM. Further detection indicated that CMFPs could better improve UC via activating the MyD88/NF-κB signaling pathway in vivo. However, CMFP-H, CMFP-F and CMFP-I exhibited diverse regulation effects on specific immune-related enzymes and cytokines. The data would be helpful for finding practical and rapid drying methods for macro-fungi and further exploring CMFPs as functional food ingredients or complementary medicines for the treatments of UC.

Sexually Dimorphic Increases in Bone Mass Following Tissue-specific Overexpression of Runx1 in Osteoclast Precursors

Many metabolic bone diseases arise as a result excessive osteoclastic bone resorption, which has motivated efforts to identify new molecular targets that can inhibit the formation or activity of these bone-resorbing cells. Mounting evidence indicates that the transcription factor Runx1 acts as a transcriptional repressor of osteoclast formation. Prior studies using a conditional knockout approach suggested that Runx1 in osteoclast precursors acts as an inhibitor of osteoclastogenesis; however, the effects of upregulation of Runx1 on osteoclast formation remain unknown. In this study, we investigated the skeletal effects of conditional overexpression of Runx1 in preosteoclasts by crossing novel Runx1 gain-of-function mice (Rosa26-LSL-Runx1) with LysM-Cre transgenic mice. We observed a sex-dependent effect whereby overexpression of Runx1 in female mice increased trabecular bone microarchitectural indices and improved torsion biomechanical properties. These effects were likely mediated by delayed osteoclastogenesis and decreased bone resorption. Transcriptomics analyses during osteoclastogenesis revealed a distinct transcriptomic profile in the Runx1-overexpressing cells, with enrichment of genes related to redox signaling, apoptosis, osteoclast differentiation, and bone remodeling. These data further confirm the antiosteoclastogenic activities of Runx1 and provide new insight into the molecular targets that may mediate these effects.

Alpha-Chymotrypsin Protects Against Acute Lung, Kidney, and Liver Injuries and Increases Survival in CLP-Induced Sepsis in Rats Through Inhibition of TLR4/NF-κB Pathway

Abstract

Inflammation and oxidative stress play a major role in the development of sepsis and its associated complications, leading to multiple organ failure and death. The lungs, liver, and kidneys are among the early affected organs correlated with mortality in sepsis. Alpha-chymotrypsin (α-ch) is a serine protease that exerts anti-inflammatory, anti-edematous, and anti-oxidant properties.

Purpose

This study was undertaken to elucidate if the anti-inflammatory and anti-oxidant effects of α-ch observed in previous studies can alleviate lung, liver, and kidney injuries in a cecal ligation and puncture (CLP)-induced sepsis model, and thus decrease mortality.

Materials and Methods

Septic animals were given α-ch 2 h post CLP procedure. Sepsis outcomes were assessed in the lungs, liver, and kidneys. Separate animal groups were investigated for a survival study.

Results

CLP resulted in 0% survival, while α-chymotrypsin post-treatment led to 50% survival at the end of the study. Administration of α-chymotrypsin resulted in a significant attenuation of sepsis-induced elevated malonaldehyde (MDA) and total nitrite/nitrate (NOx) levels. In addition, there was a significant increase in reduced glutathione (GSH) content and superoxide dismutase (SOD) activity in the lungs, liver, and kidneys. Administration of α-ch reduced elevated tissue expression of toll-like receptor-4 (TLR4), nuclear factor kappa-B (NF-κB), myeloperoxidase (MPO), and inducible nitric oxide synthase (iNOS). Alpha-chymotrypsin resulted in a significant reduction in serum levels of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6). Alpha-chymotrypsin attenuated the rise in serum creatinine, cystatin C, blood urea nitrogen (BUN), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels that was observed in the septic group. In addition, α-ch significantly reduced the lung wet/dry weight ratio, total protein content, and leukocytic counts in bronchoalveolar lavage fluid (BALF). Histopathological examination of the lungs, liver, and kidneys confirmed the protective effects of α-ch on those organs.

Conclusion

α-ch has protective potential against sepsis through lowering tissue expression of TLR4, NF-κB, MPO, and iNOS leading to decreased oxidative stress and inflammatory signals induced by sepsis. This effect appeared to alleviate the damage to the lungs, liver, and kidneys and increase survival in rats subjected to sepsis.

Cinnamaldehyde-Based Self-Nanoemulsion (CA-SNEDDS) Accelerates Wound Healing and Exerts Antimicrobial, Antioxidant, and Anti-Inflammatory Effects in Rats’ Skin Burn Model

Cinnamaldehyde, the main phytoconstituent of the cinnamon oil, has been reported for its potential wound healing activity, associated to its antimicrobial and anti-inflammatory effects. In this study, we are reporting on the cinnamaldehyde-based self-nanoemulsifying drug delivery system (CA-SNEDDS), which was prepared and evaluated for its antimicrobial, antioxidant, anti-inflammatory, and wound healing potential using the rat third-degree skin injury model. The parameters, i.e., skin healing, proinflammatory, and oxidative/antioxidant markers, were evaluated after 3 weeks of treatment regimens with CA-SNEDDS. Twenty rats were divided randomly into negative control (untreated), SNEDDS control, silver sulfadiazine cream positive control (SS), and CA-SNEDDS groups. An aluminum cylinder (120 °C, 10-s duration) was used to induce 3rd-degree skin burns (1-inch square diameter each) on the rat’s dorsum. At the end of the experiment, skin biopsies were collected for biochemical analysis. The significantly reduced wound size in CA-SNEDDS compared to the negative group was observed. CA-SNEDDS-treated and SS-treated groups demonstrated significantly increased antioxidant biomarkers, i.e., superoxide dismutase (SOD) and catalase (CAT), and a significant reduction in the inflammatory marker, i.e., NAP-3, compared to the negative group. Compared to SNEDDS, CA-SNEDDS exhibited a substantial antimicrobial activity against all the tested organisms at the given dosage of 20 µL/disc. Among all the tested microorganisms, MRSA and S. typhimurium were the most susceptible bacteria, with an inhibition zone diameter (IZD) of 17.0 ± 0.3 mm and 19.0 ± 0.9 mm, respectively. CA-SNEDDS also exhibited strong antifungal activity against C. albicans and A. niger, with IZD of 35.0 ± 0.5 mm and 34.0 ± 0.5 mm, respectively. MIC and MBC of CA-SNEDDS for the tested bacteria ranged from 3.125 to 6.25 µL/mL and 6.25 to 12.5 µL/mL, respectively, while the MIC and MBC for C. albicans and A. niger were 1.56 µL/mL and 3.125 µL/mL, respectively. The MBIC and MBEC of CA-SNEDDS were also very significant for the tested bacteria and ranged from 6.25 to 12.5 µL/mL and 12.5 to 25.0 µL/mL, respectively, while the MBIC and MBEC for C. albicans and A. niger were 3.125 µL/mL and 6.25 µL/mL, respectively. Thus, the results indicated that CA-SNEDDS exhibited significant wound healing properties, which appeared to be attributed to the formulation’s antimicrobial, antioxidant, and anti-inflammatory effects.

Platelets in the NETworks interweaving inflammation and thrombosis

Platelets are well characterized for their indispensable role in primary hemostasis to control hemorrhage. Research over the past years has provided a substantial body of evidence demonstrating that platelets also participate in host innate immunity. The surface expression of pattern recognition receptors, such as TLR2 and TLR4, provides platelets with the ability to sense bacterial products in their environment. Platelet α-granules contain microbicidal proteins, chemokines and growth factors, which upon release may directly engage pathogens and/or contribute to inflammatory signaling. Additionally, platelet interactions with neutrophils enhance neutrophil activation and are often crucial to induce a sufficient immune response. In particular, platelets can activate neutrophils to form neutrophil extracellular traps (NETs). This specific neutrophil effector function is characterized by neutrophils expelling chromatin fibres decorated with histones and antimicrobial proteins into the extracellular space where they serve to trap and kill pathogens. Until now, the mechanisms and signaling pathways between platelets and neutrophils inducing NET formation are still not fully characterized. NETs were also detected in thrombotic lesions in several disease backgrounds, pointing towards a role as an interface between neutrophils, platelets and thrombosis, also known as immunothrombosis. The negatively charged DNA within NETs provides a procoagulant surface, and in particular NET-derived proteins may directly activate platelets. In light of the current COVID-19 pandemic, the topic of immunothrombosis has become more relevant than ever, as a majority of COVID-19 patients display thrombi in the lung capillaries and other vascular beds. Furthermore, NETs can be found in the lung and other tissues and are associated with an increased mortality. Here, virus infiltration may lead to a cytokine storm that potently activates neutrophils and leads to massive neutrophil infiltration into the lung and NET formation. The resulting NETs presumably activate platelets and coagulation factors, further contributing to the subsequent emergence of microthrombi in pulmonary capillaries. In this review, we will discuss the interplay between platelets and NETs and the potential of this alliance to influence the course of inflammatory diseases. A better understanding of the underlying molecular mechanisms and the identification of treatment targets is of utmost importance to increase patients’ survival and improve the clinical outcome.

Potential Utility of Natural Products against Oxidative Stress in Animal Models of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune-mediated degenerative disease of the central nervous system (CNS) characterized by immune cell infiltration, demyelination and axonal injury. Oxidative stress-induced inflammatory response, especially the destructive effect of immune cell-derived free radicals on neurons and oligodendrocytes, is crucial in the onset and progression of MS. Therefore, targeting oxidative stress-related processes may be a promising preventive and therapeutic strategy for MS. Animal models, especially rodent models, can be used to explore the in vivo molecular mechanisms of MS considering their similarity to the pathological processes and clinical signs of MS in humans and the significant oxidative damage observed within their CNS. Consequently, these models have been used widely in pre-clinical studies of oxidative stress in MS. To date, many natural products have been shown to exert antioxidant effects to attenuate the CNS damage in animal models of MS. This review summarized several common rodent models of MS and their association with oxidative stress. In addition, this review provides a comprehensive and concise overview of previously reported natural antioxidant products in inhibiting the progression of MS.

Molecular feature of neutrophils in immune microenvironment of muscle atrophy

Homeostasis in skeletal muscle is sustained by the balance of functional and physical interactions between muscle and myofibre microenvironment. Various factors, such as ageing, disuse and denervation, tip the balance and induce skeletal muscle atrophy. Skeletal muscle atrophy, which involves complex physiological and biochemical changes, is accompanied by adverse outcomes and even increased mortality. Multiple studies have investigated the role of neutrophils in atrophied skeletal muscles; however, neutrophil intrusion in muscle is still a polemical knot. As technical obstacles have been overcome, people have gradually discovered new functions of neutrophils. The classical view of neutrophils is no longer applicable to their biological characteristics. To date, no clear association between the hidden injurious effect of neutrophil intrusion and muscle atrophy has been convincingly proven. Throughout this review, we have discussed the neutrophil activities that mediate muscle atrophy for distinct disease occurrences. Hopefully, this review will help both clinicians and researchers of skeletal muscle atrophy with relevant targets to further explore efficient medical interventions and treatments.

Myeloperoxidase as a Marker to Differentiate Mouse Monocyte/Macrophage Subsets

Macrophages are present in every tissue in the body and play essential roles in homeostasis and host defense against microorganisms. Some tissue macrophages derive from the yolk sac/fetal liver that populate tissues for life. Other tissue macrophages derive from monocytes that differentiate in the bone marrow and circulate through tissues via the blood and lymphatics. Circulating monocytes are very plastic and differentiate into macrophages with specialized functions upon entering tissues. Specialized monocyte/macrophage subsets have been difficult to differentiate based on cell surface markers. Here, using a combination of "pan" monocyte/macrophage markers and flow cytometry, we asked whether myeloperoxidase (MPO) could be used as a marker of pro-inflammatory monocyte/macrophage subsets. MPO is of interest because of its potent microbicidal activity. In wild-type SPF housed mice, we found that MPO⁺ monocytes/macrophages were present in peripheral blood, spleen, small and large intestines, and mesenteric lymph nodes, but not the central nervous system. Only monocytes/macrophages that expressed cell surface F4/80 and/or Ly6C co-expressed MPO with the highest expression in F4/80^HiLy6C^Hi subsets regardless of tissue. These cumulative data indicate that MPO expression can be used as an additional marker to differentiate between monocyte/macrophage subsets with pro-inflammatory and microbicidal activity in a variety of tissues.

Properties and functions of myeloperoxidase and its role in ovarian cancer

Background: Elevated levels of myeloperoxidase in body fluids are increasingly being used as an indicator for the diagnosis of cancer. Aim of the study: The aim of this study was to review the literature on the physical and chemical properties of myeloperoxidase, its role in carcinogenesis, the role of tumor-associated neutrophils in cancer, and the role of myeloperoxidase in ovarian cancer. Material and methods: The research literature published between January 1999 and December 2019 was reviewed. The properties and role of myeloperoxidase in the development of ovarian cancer were selected from publications available in selected online databases, including MEDLINE, PubMed, Scopus, and Web of Science. Searches were performed using the following word combinations: “myeloperoxidase”, “ovarian cancer”, “reactive oxygen species”, “expression”, “polymorphism”, and “tumor-associated neutrophils”. Results: Thirty-five scientific articles were included in the final review. Of the 35 articles, 11 discussed the role of myeloperoxidase in carcinogenesis, and five discussed its role in the development of ovarian cancer. Conclusions: Elevated myeloperoxidase levels are associated with many types of cancer, including ovarian cancer. In the studied group of invasive ovarian tumors, up to 65% exhibited elevated levels of myeloperoxidase. Continued research on myeloperoxidase expression in ovarian cancer cells is vital and warranted.

The Protective Effect of Rheum Ribes L., and Quercetin on Protein Carbonyl Levels Against Carbon Tetrachloride-Induced Liver and Kidney Damage in the Rats

Objective: Carbonyl formation between various oxidative modifications of amino acids in proteins can be an early sign of protein oxidation. Methods: The 2,4-dinitrophenylhydrazine (DNPH) method is the most reliable method widely used to measure carbonyl levels in proteins. In this study, the effect of Rheum ribes L. (Rr) and quercetin on proteın carbonyl, trace elements (Fe, Cu, Zn) and mineral (P) levels against carbon tetrachloride (CCl4) mediated liver and kidney damage was investigated. For this purpose, 56 Wistar albino female rats weighing 200 ± 220 g were used. Groups were designed as: controls, 0.3 ml DMSO, 1 ml/kg olive oil, 1 ml/kg CCl4, 100 mg/kg Rr, 100 mg/kg quercetin, 100 mg/kg Rr+1 ml/kg CCl4 and 100 mg/kg quercetin+1 ml/kg CCl4 groups. Results: Statistical analysis showed that in the CCl4 group was significantly higher than the control, olive oil, Rr., and quercetin groups in the PCO levels (p

Structure-biological activity relationships of myeloperoxidase to effect on platelet activation

Myeloperoxidase (MPO), an oxidant-producing enzyme of neutrophils, has been shown to prime platelet activity promoting immunothrombosis. Native MPO is a homodimer, consisting of two identical protomers (monomer) connected by a single disulfide bond. But in inflammatory foci, MPO can be found both in the form of a monomer and in the form of a dimer. Beside MPO can also be in complexes with other molecules and be modified by oxidants, which ultimately affect its physicochemical properties and functions. Here we compared the effects of various forms of MPO as well as MPO in complex with ceruloplasmin (CP), a physiological inhibitor of MPO, on the platelet activity. Monomeric MPO (hemi-MPO) was obtained by treating the dimeric MPO by reductive alkylation. MPO was modified with HOCl in a molar ratio of 1:100 (MPO-HOCl). Using surface-enhanced Raman scattering (SERS) spectroscopy we showed that peaks at about 510 and 526 cm^-1 corresponded to disulfide bond was recognizable in the SERS-spectra of dimeric MPO, absent in the spectrum of hemi-MPO and less intense in the spectra of MPO-HOCl, which indicates the partial decomposition of dimeric MPO with a disulfide bond cleavage under the HOCl modification. It was shown hemi-MPO to a lesser extent than dimeric MPO bound to platelets and enhanced their agonist-induced aggregation and platelet-neutrophil aggregate formation. MPO modified by HOCl and MPO in complex with CP did not bind to platelets and have no effect on platelet activity. Thus, the modification of MPO by HOCl, its presence in monomeric form as well as in complex with CP reduces MPO effect on platelet function and consequently decreases the risk of thrombosis in inflammatory foci.

Regulation of Neutrophil NADPH Oxidase, NOX2: A Crucial Effector in Neutrophil Phenotype and Function

Reactive oxygen species (ROS), produced by the phagocyte NADPH oxidase, NOX2, are involved in many leukocyte functions. An excessive or inappropriate ROS production can lead to oxidative stress and tissue damage. On the other hand, an absence of ROS production due to a lack of a functional NADPH oxidase is associated with recurrent infections as well as inflammation disorders. Thus, it is clear that the enzyme NADPH oxidase must be tightly regulated. The NOX2 complex bears both membrane and cytosolic subunits. The membrane subunits constitute the flavocytochrome b₅₅₈, consisting of gp91^phox (Nox2) and p22^phox subunits. The cytosolic subunits form a complex in resting cells and are made of three subunits (p47^phox, p40^phox, p67^phox). Upon leukocyte stimulation, the cytosolic subunits and the small GTPase Rac assemble with the flavocytochrome b₅₅₈ in order to make a functional complex. Depending on the stimulus, the NADPH oxidase can assemble either at the phagosomal membrane or at the plasma membrane. Many studies have explored NOX2 activation; however, how this activation is sustained and regulated is still not completely clear. Here we review the multiple roles of NOX2 in neutrophil functions, with a focus on description of its components and their assembly mechanisms. We then explain the role of energy metabolism and phosphoinositides in regulating NADPH oxidase activity. In particular, we discuss: 1) the link between metabolic pathways and NOX2 activity regulation through neutrophil activation and the level of released ROS, and 2) the role of membrane phosphoinositides in controlling the duration of NOX2 activity.

Faecal Myeloperoxidase as a Biomarker of Endoscopic Activity in Inflammatory Bowel Disease

BACKGROUND AND AIMS

Inflammatory bowel disease [IBD], consisting of Crohn's disease [CD] and ulcerative colitis [UC], is a relapsing-remitting illness. Treat-to-target IBD management strategies require monitoring of gastrointestinal inflammation. This study aimed to investigate faecal myeloperoxidase [fMPO], a neutrophil granule enzyme, as a biomarker of IBD activity.

METHODS

Prospectively recruited participants with IBD, undergoing ileocolonoscopy for disease assessment, provided biological samples and completed symptom questionnaires prior to endoscopy. fMPO, C-reactive protein [CRP], and faecal calprotectin [fCal] were compared with validated endoscopic indices [simple endoscopic score for CD and UC endoscopic index of severity]. Receiver operating characteristic [ROC] curves assessed the performance of fMPO, CRP, and fCal in predicting endoscopic disease activity. Baseline biomarkers were used to predict a composite endpoint of complicated disease at 12 months [need for escalation of biologic/immunomodulator due to relapse, steroid use, IBD-related hospitalisation, and surgery].

RESULTS

A total of 172 participants were recruited [91 female, 100 with CD]. fMPO was significantly correlated with endoscopic activity in both CD [r = 0.53, p < 0.01] and UC [r = 0.63, p < 0.01], and with fCal in all patients with IBD [r = 0.82, p < 0.01]. fMPO was effective in predicting moderate-to-severely active CD [AUROC 0.86, p < 0.01] and UC [AUROC 0.92, p < 0.01]. Individuals with a baseline fMPO > 26 µg/g were significantly more likely to reach the composite outcome at 12 months (hazard ratio [HR] 3.71, 95% confidence interval [CI] 2.07-6.64, p < 0.01).

CONCLUSIONS

Faecal myeloperoxidase is an accurate biomarker of endoscopic activity in IBD and predicted a more complicated IBD course during follow-up.

HDAC4 Inhibitors as Antivascular Senescence Therapeutics

Aging is an inevitable consequence of life, and during this process, the epigenetic landscape changes and reactive oxygen species (ROS) accumulation increases. Inevitably, these changes are common in many age-related diseases, including neurodegeneration, hypertension, and cardiovascular diseases. In the current research, histone deacetylation 4 (HDAC4) was studied as a potential therapeutic target in vascular senescence. HDAC4 is a specific class II histone deacetylation protein that participates in epigenetic modifications and deacetylation of heat shock proteins and various transcription factors. There is increasing evidence to support that HDAC4 is a potential therapeutic target, and developments in the synthesis and testing of HDAC4 inhibitors are now gaining interest from academia and the pharmaceutical industry.

Rare germline alterations of myeloperoxidase predispose to myeloid neoplasms

Myeloperoxidase (MPO) gene alterations with variable clinical penetrance have been found in hereditary MPO deficiency, but their leukemia association in patients and carriers has not been established. Germline MPO alterations were found to be significantly enriched in myeloid neoplasms: 28 pathogenic/likely pathogenic variants were identified in 100 patients. The most common alterations were c.2031-2 A > C, R569W, M519fs* and Y173C accounting for about half of the cases. While functional experiments showed that the marrow stem cell pool of Mpo^-/- mice was not increased, using competitive repopulation demonstrated that Mpo^-/- grafts gained growth advantage over MPO wild type cells. This finding also correlated with increased clonogenic potential after serial replating in the setting of H₂O₂-induced oxidative stress. Furthermore, we demonstrated that H₂O₂-induced DNA damage and activation of error-prone DNA repair may result in secondary genetic damage potentially predisposing to leukemia leukemic evolution. In conclusion, our study for the first time demonstrates that germline MPO variants may constitute risk alleles for MN evolution.

Singlet Oxygen, Photodynamic Therapy, and Mechanisms of Cancer Cell Death

Photodynamic therapy (PDT) can be developed into an important arsenal against cancer; it is a minimally invasive therapy, which is used in the treatment or/and palliation of a variety of cancers and benign diseases. The removal of cancerous tissue is achieved with the use of photosensitizer and a light source, which excites the photosensitizer. This excitation causes the photosensitizer to generate singlet oxygen and other reactive oxygen species. PDT has been used in several types of cancers including nonmelanoma skin cancer, bladder cancer, esophageal cancer, head and neck cancer, and non-small cell lung cancer (NSCLC). Although it is routinely used in nonmelanoma skin cancer, it has not been widely adopted in other solid cancers due to a lack of clinical data showing the superiority of PDT over other forms of treatment. Singlet oxygen used in PDT can alter the activity of the catalase, which induces immunomodulation through HOCl signaling. The singlet oxygen can induce apoptosis through both the extrinsic and intrinsic pathways. The extrinsic pathway of apoptosis starts with the activation of the Fas receptor by singlet oxygen that leads to activation of the caspase-7 and caspase-3. In the case of the intrinsic pathway, disruption caused by singlet oxygen in the mitochondria membrane leads to the release of cytochrome c, which binds with APAF-1 and procaspase-9, forming a complex, which activates caspase-3. Mechanisms of PDT action can vary according to organelles affected. In the plasma membrane, membrane disruption is caused by the oxidative stress leading to the intake of calcium ions, which causes swelling and rupture of cells due to excess intake of water, whereas disruption of lysosome causes the release of the cathepsins B and D, which cleave Bid into tBid, which changes the mitochondrial outer membrane permeability (MOMP). Oxidative stress causes misfolding of protein in the endoplasmic reticulum. When misfolding exceeds the threshold, it triggers unfolding protein response (UPR), which leads to activation of caspase-9 and caspase-3. Finally, the activation of p38 MAPK works as an alternative pathway for the induction of MOMP.

Detection of HOCl-driven degradation of the pericardium scaffolds by label-free multiphoton fluorescence lifetime imaging

Artificial biomaterials can significantly increase the rate of tissue regeneration. However, implantation of scaffolds leads not only to accelerated tissue healing but also to an immune response of the organism, which results in the degradation of the biomaterial. The synergy of the immune response and scaffold degradation processes largely determines the efficiency of tissue regeneration. Still, methods suitable for fast, accurate and non-invasive characterization of the degradation degree of biomaterial are highly demandable. Here we show the possibility of monitoring the degradation of decellularized bovine pericardium scaffolds under conditions mimicking the immune response and oxidation processes using multiphoton tomography combined with fluorescence lifetime imaging (MPT-FLIM). We found that the fluorescence lifetimes of genipin-induced cross-links in collagen and oxidation products of collagen are prominent markers of oxidative degradation of scaffolds. This was verified in model experiments, where the oxidation was induced with hypochlorous acid or by exposure to activated neutrophils. The fluorescence decay parameters also correlated with the changes of micromechanical properties of the scaffolds as assessed using atomic force microscopy (AFM). Our results suggest that FLIM can be used for quantitative assessments of the properties and degradation of the scaffolds essential for the wound healing processes in vivo.

Prostaglandin D2 Attenuates Lipopolysaccharide-Induced Acute Lung Injury through the Modulation of Inflammation and Macrophage Polarization

Acute lung injury (ALI) is a well-known respiratory disease and a leading cause of death worldwide. Despite advancements in the medical field, developing complete treatment strategies against this disease is still a challenge. In the current study, the therapeutic role of prostaglandin D2 (PGD2) was investigated on lipopolysaccharide (LPS)-induced lung injury in mice models and RAW264.7 macrophages through anti-inflammatory, histopathology, immunohistochemistry, and TUNEL staining. The overproduction of cytokines by RAW264.7 macrophages was observed after stimulation with LPS. However, pretreatment with PGD2 decreased the production of cytokines. The level of inflammatory markers was significantly restored in the PGD2 treatment group (TNF-α = 58.6 vs. 78.5 pg/mL; IL-1β = 29.3 vs. 36.6 pg/mL; IL-6 = 75.4 vs. 98.2 pg/mL; and CRP = 0.84 vs. 1.14 ng/mL). The wet/dry weight ratio of the lungs was quite significant in the disease control (LPS-only treatment) group. Moreover, the histological changes as determined by haematoxylin and eosin (H&E) staining clearly showed that PGD2 treatment maintains the lung tissue architecture. The iNOS expression pattern was increased in lung tissues of LPS-treated animals, whereas, in mice treated with PGD2, the expression of iNOS protein decreased. Flow cytometry data demonstrated that LPS intoxication enhanced apoptosis, which significantly decreased with PGD2 treatment. In conclusion, all these observations indicate that PGD2 provides an anti-inflammatory response in RAW264.7 macrophages and in ALI, and they suggest a therapeutic potential in lung pathogenesis.

A dual-channel chemodosimetric sensor for discrimination between hypochlorite and nerve-agent mimic DCP: application on human breast cancer cells

A styryl bridge containing a triphenylamine-thioimidazole hydrazine-based dual-analyte-responsive fluorescent sensor was designed and synthesized for the detection of the nerve gas simulant diethyl chlorophosphate (DCP) and hypochlorite (OCl^-) for the first time. Hypochlorite induces oxidative intramolecular cyclization to give a triazole structure, which exhibited blue fluorescence with excellent selectivity and a low detection limit (8.05 × 10^-7 M) in solution. Conversely, the probe forms a phosphorylated intermediate with diethyl chlorophosphate, which undergoes further hydrolyzation and presents green fluorescence in a ratiometric mode with a low detection limit (3.56 × 10^-8 M). Additionally, the as-designed sensor was utilized to construct a portable kit for real-time monitoring of DCP in a discriminatory, simple and safe manner. Lastly, the probe was also productively employed for in situ imaging of OCl^- and DCP in the living cell.

Stunting Status and Exposure to Infection and Inflammation in Early Life Shape Antibacterial Immune Cell Function Among Zimbabwean Children

Background

Children who are stunted (length-for-age Z-score<-2) are at greater risk of infectious morbidity and mortality. Previous studies suggest that stunted children have elevated inflammatory biomarkers, but no studies have characterised their capacity to respond to new infections (i.e., their immune function). We hypothesised that antibacterial immune function would differ between stunted and non-stunted children and relate to their health and environment during early life.

Methods

We enrolled a cross-sectional cohort of 113 HIV-negative children nested within a longitudinal cluster-randomised controlled trial of household-level infant and young child feeding (IYCF) and water, sanitation and hygiene (WASH) interventions in rural Zimbabwe (SHINE; Clinical trials registration: NCT01824940). Venous blood was collected at 18 months of age and cultured for 24 h without antigen or with bacterial antigens: heat-killed Salmonella typhimurium (HKST) or Escherichia coli lipopolysaccharide (LPS). TNFα, IL-6, IL-8, IL-12p70, hepcidin, soluble (s)CD163, myeloperoxidase (MPO) and IFNβ were quantified in culture supernatants by ELISA to determine antigen-specific immune function. The effect of stunting status and early-life exposures (anthropometry, inflammation at 18 months, maternal health during pregnancy, household WASH) on immune function was tested in logit and censored log-normal (tobit) regression models.

Results

Children who were stunted (n = 44) had higher proportions (86.4% vs. 65.2%; 88.6% vs. 73.4%) and concentrations of LPS-specific IL-6 (geometric mean difference (95% CI): 3.46 pg/mL (1.09, 10.80), p = 0.035) and IL-8 (3.52 pg/mL (1.20, 10.38), p = 0.022) than non-stunted children (n = 69). Bacterial antigen-specific pro-inflammatory cytokine concentrations were associated with biomarkers of child enteropathy at 18 months and biomarkers of systemic inflammation and enteropathy in their mothers during pregnancy. Children exposed to the WASH intervention (n = 33) produced higher LPS- (GMD (95% CI): 10.48 pg/mL (1.84, 60.31), p = 0.008) and HKST-specific MPO (5.10 pg/mL (1.77, 14.88), p = 0.003) than children in the no WASH group (n = 80). There was no difference in antigen-specific immune function between the IYCF (n = 55) and no IYCF groups (n = 58).

Conclusions

Antibacterial immune function among 18-month-old children in a low-income setting was shaped by their stunting status and prior exposure to maternal inflammation and household WASH. Heterogeneity in immune function due to adverse exposures in early life could plausibly contribute to infection susceptibility.

Early taurine administration as a means for halting the cytokine storm progression in COVID-19 patients

Around the world, more than 6.2 million individuals have died as a result of coronavirus disease 2019 (COVID-19). According to a recent survey conducted among immunologists, epidemiologists, and virologists, this disease is expected to become endemic. This implies that the disease could have a continuous presence and/or normal frequency in the population. Pharmacological interventions to prevent infection, as well as to treat the patients at an early phase of illness to avoid hospitalization are essential additions to the vaccines. Taurine is known to inhibit the generation of all inflammatory mediators linked to the cytokine storm. It can also protect against lung injury by suppressing increased oxidants production and promoting the resolution of the inflammatory process. Neutrophil lactoferrin degranulation stimulated by taurine may have antiviral effects against SARS-CoV-2, limiting viral replication. It is hypothesized that if taurine is administered early in the onset of COVID-19 disease, it may stop the cytokine storm from progressing, lowering morbidity and mortality.

Uric Acid Reacts with Peroxidasin, Decreases Collagen IV Crosslink, Impairs Human Endothelial Cell Migration and Adhesion

Uric acid is considered the main substrate for peroxidases in plasma. The oxidation of uric acid by human peroxidases generates urate free radical and urate hydroperoxide, which might affect endothelial function and explain, at least in part, the harmful effects of uric acid on the vascular system. Peroxidasin (PXDN), the most recent heme-peroxidase described in humans, catalyzes the formation of hypobromous acid, which mediates collagen IV crosslinks in the extracellular matrix. This enzyme has gained increasing scientific interest since it is associated with cardiovascular disease, cancer, and renal fibrosis. The main objective here was to investigate whether uric acid would react with PXDN and compromise the function of the enzyme in human endothelial cells. Urate decreased Amplex Red oxidation and brominating activity in the extracellular matrix (ECM) from HEK293/PXDN overexpressing cells and in the secretome of HUVECs. Parallelly, urate was oxidized to 5-hydroxyisourate. It also decreased collagen IV crosslink in isolated ECM from PFHR9 cells. Urate, the PXDN inhibitor phloroglucinol, and the PXDN knockdown impaired migration and adhesion of HUVECs. These results demonstrated that uric acid can affect extracellular matrix formation by competing for PXDN. The oxidation of uric acid by PXDN is likely a relevant mechanism in the endothelial dysfunction related to this metabolite.

Multiplex analysis of mass imaging data: Application to the pathology of experimental myocardial infarction

Aim

Imaging mass cytometry (IMC) affords simultaneous immune‐labelling/imaging of multiple antigens in the same tissue. Methods utilizing multiplex data beyond co‐registration are lacking. This study developed and applied an innovative spatial analysis workflow for multiplex imaging data to IMC data determined from cardiac tissues and revealed the mechanism(s) of neutrophil‐mediated post‐myocardial‐infarction damage.

Methods

IMC produced multiplex images with various redox/inflammatory markers. The cardiac peri‐infarct zone (PIZ) was determined to be up to 240 µm from the infarct border based on the presence of neutrophils. The tissue region beyond the infarct was defined as the remote area (RA). ImageJ was used to quantify the immunoreactivity. Functional assessments included infarct size, cell necro/apoptosis, total thiol assay and echocardiogram.

Results

Expression of damage markers decreased in order from the infarct area to PIZ and then RA, reflecting the neutrophil density in the regions. Concentrically spaced “shoreline contour analysis” around the cardiac infarct extending into the PIZ showed that immunoreactivity for damage markers decreased linearly with increasing distance from the infarct, concomitant with a decreasing neutrophil‐myeloperoxidase (MPO) gradient from the infarct to the PIZ. Stratifying by concentric bands around individual MPO⁺‐signal identified that the immunoreactivity of haem‐oxygenase‐1 (HO‐1) and phosphorylated‐p38 mitogen‐activated protein kinase (pP38) peaked near neutrophils. Furthermore, spatial dependence between neutrophils and markers of cardiac cellular damage was confirmed by nearest‐neighbour distance analysis. Post‐infarction tissue exhibited declined functional parameters that were associated with neutrophil migration from the infarct to PIZ.

Conclusion

This image‐based quantitative protocol revealed the spatial association and provided potential molecular pathways responsible for neutrophil‐mediated damage post‐infarction.

Neutrophil Myeloperoxidase-Mediated N-Demethylation of Quetiapine Leads to N-Desalkylquetiapine, a Pharmacologically Active Cytochrome P450 Metabolite

The atypical antipsychotic drugs, quetiapine and clozapine, are associated with idiosyncratic drug reactions (such as agranulocytosis or neutropenia) that are thought to involve reactive metabolites. Neutrophil myeloperoxidase (MPO) metabolism of quetiapine is not well-studied, but is metabolized by cytochrome P450. Based on structural similarity to clozapine, we hypothesized that quetiapine can be metabolized by MPO and that there is overlap between cytochrome P450 and MPO metabolism of quetiapine. The interaction of quetiapine and clozapine with MPO and MPO chlorination activity was studied using UV-vis spectrophotometry. The metabolites were characterized using liquid chromatography-mass spectrometry (LC-MS), and electron paramagnetic resonance (EPR) spectroscopy was used for detecting drug-catalyzed glutathione oxidation. In the presence of quetiapine, MPO compound II accumulated for about 7.5 min, whereas in the presence of clozapine, MPO compound II was not observed as it was rapidly reduced back to the resting state. Increasing quetiapine concentrations resulted in a decrease in MPO chlorination activity, while the opposite result was found in the case of clozapine. UV-vis spectral studies showed no change when quetiapine was oxidized in the absence and presence of chloride anion (Cl^-, to catalyze chlorination reactions). Significant changes, however, were observed in the same assay with clozapine, where Cl^- appeared to hinder the rate of clozapine metabolism. The MPO-catalyzed hydroxylated and dealkylated metabolites of quetiapine and hydroxylated metabolites of clozapine were observed from the LC-MS analyses, particularly when Cl^- was included in the reaction. In addition, hydroxylated, dealkylated, and a proposed sulfoxide metabolite of quetiapine were also observed in the reaction catalyzed by human microsomes/NADPH. Lastly, compared to quetiapine, clozapine metabolism by MPO/H₂O₂ and glutathione produced more glutathionyl radicals using EPR spin trapping. In conclusion, MPO/H₂O₂/Cl^- was shown to metabolize quetiapine to S-oxidation and P450-like dealkylation products, and quetiapine metabolites were generally less reactive than clozapine.

Colon targeted chitosan-melatonin nanotherapy for preclinical Inflammatory Bowel Disease

Inflammatory Bowel (IBD) is an umbrella term which includes Crohn's Disease (CD) and Ulcerative Colitis (UC). At present, therapies available for management of the UC includes, corticosteroid, immuno-suppressants and antibiotics are used for mild to moderate UC conditions which can cause nephrotoxicity, hepatotoxicity and cardiotoxicity. Hence, a novel therapeutic candidate having potent anti-inflammatory effect is urgently warranted for the management of UC. Melatonin has emerged as a potent anti-inflammatory agent. However, poor solubility limits its therapeutic potential. Therefore, colon targeted Eudragit-S-100 coated chitosan nanoparticles have been demonstrated to improve melatonin therapeutic efficacy. It was found that melatonin loaded chitosan and colon targeted chitosan nanoparticles had promising anti-inflammatory efficacy in terms of NO scavenging activity in an in-vitro LPS challenged macrophages. Also, colon targeted oral chitosan nano-formulation exhibited remarkable protection in an in vivo UC mice model by improving gross pathological parameters, histo-architectural protection, goblet cell depletion, and immune cells infiltration which can be extrapolated to clinical studies.

Neutrophil dysfunction in the pathogenesis of cystic fibrosis

Polymorphonuclear neutrophils (PMNs) figure prominently in host defense against infection and in noninfectious inflammation. Mobilized early in an inflammatory response, PMNs mediate immediate cellular defense against microbes and orchestrate events that culminate in cessation of inflammation and restoration of homeostasis. Failure to terminate the inflammatory response and its causes can fuel exuberant inflammation characteristic of many human diseases, including cystic fibrosis (CF), an autosomal recessive genetic disease caused by mutations in the CF transmembrane conductance regulator. CF affects multiple end organs, with persistent bacterial infection and chronic neutrophilic inflammation in airways predominating the clinical picture. To match the diverse microbial challenges that they may encounter, PMNs possess a variety of antimicrobial systems to slow or kill invading microorganisms confined in their phagosomes. Prominent among PMN defense systems is their ability to generate hypochlorous acid, a potent microbicide, by reacting oxidants generated by the NADPH oxidase with myeloperoxidase (MPO) released from azurophilic granules in the presence of chloride (Cl-). Products of the MPO-H2O2-Cl system oxidize susceptible biomolecules and support robust antimicrobial action against many, but not all, potential human pathogens. Underscoring that the MPO-H2O2-Cl system is integral to optimal host defense and proper regulation of inflammation, individuals with defects in any component of this system, as seen in chronic granulomatous disease or MPO deficiency, incur increased rates or severity of infection and signs of dysregulated inflammatory responses. We focus attention in this review on the molecular basis for and the clinical consequences of defects in the MPO-H2O2-Cl system because of the compromised Cl transport seen in CF. We will discuss first how the MPO-H2O2-Cl system in healthy PMNs participates in host defense and resolution of inflammation and then review how a defective MPO-H2O2-Cl system contributes to the increased susceptibility to infection and dysregulated inflammation associated with the clinical manifestations of CF.

Lycopodium Mitigates Oxidative Stress and Inflammation in the Colonic Mucosa of Acetic Acid-Induced Colitis in Rats

Inflammatory bowel diseases (IBDs) such as ulcerative colitis (UC) and Crohn’s disease (CD) are diseases of the gastrointestinal system involving genetic and environmental factors attributed to oxidative stress and inflammation. Targeting oxidative stress and inflammation by novel dietary compounds of natural origin convincingly appears to be one of the important therapeutic strategies to keep the disease in remission. As there is no permanent cure for IBD except for chronic long-term treatment or surgery, it is therefore imperative to investigate plant-based agents that are receiving attention for their therapeutic benefits to overcome the debilitating clinical conditions of IBD. Lycopodium (LYCO), a plant of tropical and subtropical origin and known by numerous names such as ground pine, club moss, or devil’s claw, has been popularly used for centuries in traditional medicine including Chinese and Indian medicines. In the present study, the effect of LYCO has been investigated in an acetic acid (AA)-induced colitis model in Wistar rats. LYCO was orally administered at the dose of 50 mg/kg/day either 3 days before or 30 min after the induction of IBD and continued for 7 days by intrarectal administration of AA. The changes in body weight and macroscopic and microscopic analysis of the colon of rats of different experimental groups were observed on days 0, 2, 4, and 7. The levels of myeloperoxidase (MPO), reduced glutathione (GSH), and malondialdehyde (MDA) were measured. AA caused a significant reduction in body weight and increased macroscopic and microscopic ulcer scores along with a significant decline in antioxidant enzymes, superoxide dismutase (SOD), and catalase and antioxidant substrate, glutathione (GSH). There was a concomitant increased formation of malondialdehyde (MDA), a marker of lipid peroxidation, and raised myeloperoxidase (MPO) activity, a marker of neutrophil activation. Treatment with LYCO significantly improved IBD-induced reduction in body weight, improved histology, inhibited MDA formation, and restored antioxidants along with reduced MPO activity. AA also caused the release of proinflammatory cytokines such as interleukin-1β (IL-1β) and interleukin-23 (IL-23). Furthermore, AA also increased the levels of calprotectin, a protein released by neutrophils under inflammatory conditions of the gastrointestinal tract. LYCO treatment significantly reduced the release of calprotectin and proinflammatory cytokines. The results demonstrate that LYCO treatment has the potential to improve disease activity by inhibiting oxidative stress, lipid peroxidation, and inflammation along with histological preservation of colonic tissues.

Ascorbic Acid Ameriolates Liver Damage by Myeloperoxidase Oxidative Products in a Hamster Model of Amoebic Liver Abscess

Entamoeba histolytica is a protozoan-pathogen-causing amoebic liver abscess (ALA). After amoeba establishment in the liver, it causes abundant infiltrate of neutrophils. Liver tissue damage by neutrophils results in part from anti-amoebic oxidative intermediates, including reactive oxygen species (ROS), reactive nitrogen species (RNS), and hypochlorous acid (HOCl), derived from the myeloperoxidase (MPO) enzyme. Ascorbic acid (ASC) is an antioxidant that acts as a scavenger for ROS and NOS-derived free radicals. No previous information regarding the effect of ASC concerning the participation of MPO in an experimental model of ALA in hamsters has been reported. Thus, the aim of the present work was to analyze the effect of ASC on acute ALA development and to measure the activity and gene expression of the MPO enzyme. Hamsters were treated with ASC (800 mg/kg) and then intrahepatically inoculated with E. histolytica trophozoites. Animals were sacrificed at 3, 6, and 12 h post-inoculation (p.i.), and liver samples were collected. The percentage of lesions, amoeba in situ count, MPO activity, and mpo gene expression were ascertained. Compared to ALA hamsters without ASC treatment as the control group (CT), the ALA group treated with ASC had a significant decrease in liver lesions (all p.i. hours) and viable amoeba count (12 h p.i.) and an increase in MPO activity (12 h p.i.) and mpo gene expression (6 h/12 h p.i.). These data suggest that ASC ameliorated liver damage caused by oxidizing products via modulation of mpo expression and activity.

PEP-sNASP Peptide Alleviates LPS-Induced Acute Lung Injury Through the TLR4/TRAF6 Axis

Acute lung injury (ALI) is a severe inflammatory lung disease associated with macrophages. Somatic nuclear autoantigenic sperm protein (sNASP) is a negative regulator of Toll-like receptor (TLR) signaling that targets tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) in macrophages, which is required to maintain homeostasis of the innate immune response. In the present study, we generated a cell permeable PEP-sNASP peptide using the sNASP protein N-terminal domain, and examined its potential therapeutic effect in a mouse model of ALI induced by the intranasal administration of lipopolysaccharide (LPS) and elucidated the underlying molecular mechanisms in RAW 264.7 cells. In vivo, PEP-sNASP peptide treatment markedly ameliorated pathological injury, reduced the wet/dry (W/D) weight ratio of the lungs and the production of proinflammatory cytokines (interleukin (IL)-1β, IL-6, and TNF-α). In vitro, we demonstrated that when the PEP-sNASP peptide was transduced into RAW 264.7 cells, it bound to TRAF6, which markedly decreased LPS-induced proinflammatory cytokines by inhibiting TRAF6 autoubiquitination, nuclear factor (NF)-κB activation, reactive oxygen species (ROS) and cellular nitric oxide (NO) levels. Furthermore, the PEP-sNASP peptide also inhibited NLR family pyrin domain containing 3 (NLRP3) inflammasome activation. Our results therefore suggest that the PEP-sNASP may provide a potential protein therapy against oxidative stress and pulmonary inflammation via selective TRAF6 signaling.

Targeting Neutrophils for Promoting the Resolution of Inflammation

Acute inflammation is a localized and self-limited innate host-defense mechanism against invading pathogens and tissue injury. Neutrophils, the most abundant immune cells in humans, play pivotal roles in host defense by eradicating invading pathogens and debris. Ideally, elimination of the offending insult prompts repair and return to homeostasis. However, the neutrophils` powerful weaponry to combat microbes can also cause tissue damage and neutrophil-driven inflammation is a unifying mechanism for many diseases. For timely resolution of inflammation, in addition to stopping neutrophil recruitment, emigrated neutrophils need to be disarmed and removed from the affected site. Accumulating evidence documents the phenotypic and functional versatility of neutrophils far beyond their antimicrobial functions. Hence, understanding the receptors that integrate opposing cues and checkpoints that determine the fate of neutrophils in inflamed tissues provides insight into the mechanisms that distinguish protective and dysregulated, excessive inflammation and govern resolution. This review aims to provide a brief overview and update with key points from recent advances on neutrophil heterogeneity, functional versatility and signaling, and discusses challenges and emerging therapeutic approaches that target neutrophils to enhance the resolution of inflammation.

Liver ischaemia-reperfusion injury: a new understanding of the role of innate immunity

Liver ischaemia-reperfusion injury (LIRI), a local sterile inflammatory response driven by innate immunity, is one of the primary causes of early organ dysfunction and failure after liver transplantation. Cellular damage resulting from LIRI is an important risk factor not only for graft dysfunction but also for acute and even chronic rejection and exacerbates the shortage of donor organs for life-saving liver transplantation. Hepatocytes, liver sinusoidal endothelial cells and Kupffer cells, along with extrahepatic monocyte-derived macrophages, neutrophils and platelets, are all involved in LIRI. However, the mechanisms underlying the responses of these cells in the acute phase of LIRI and how these responses are orchestrated to control and resolve inflammation and achieve homeostatic tissue repair are not well understood. Technological advances allow the tracking of cells to better appreciate the role of hepatic macrophages and platelets (such as their origin and immunomodulatory and tissue-remodelling functions) and hepatic neutrophils (such as their selective recruitment, anti-inflammatory and tissue-repairing functions, and formation of extracellular traps and reverse migration) in LIRI. In this Review, we summarize the role of macrophages, platelets and neutrophils in LIRI, highlight unanswered questions, and discuss prospects for innovative therapeutic regimens against LIRI in transplant recipients.

In vitro effects of cantharidin on gilthead seabream (Sparus aurata) head-kidney leucocytes

Cantharidin is a toxic vesicant terpene used in folk and traditional medicine due to its various therapeutic effects. Since there are no previous data on the effect of cantharidin in fish, this study aimed to investigate the in vitro related-inflammatory effects of cantharidin in gilthead seabream (Sparus aurata L.) head-kidney leucocytes (HKLs). In the first experiment, the HKLs were incubated with 0, 5 and 10 μg mL^-1 of cantharidin for 24 h to delimit its possible toxic effects. In a second experiment, leucocytes were incubated with ranging concentrations from 0 to 10 μg mL^-1 for 3, 6, or 12 h. Cell viability was higher in acidophilic granulocytes than in monocytes/macrophages and lymphocytes. Cantharidin caused apoptosis as was evidenced by transmission electron microscopy. In addition, cantharidin produced a time- and dose-dependent decrease of respiratory burst and phagocytic activities in HKLs, while their peroxidase activity was increased at 24 h of incubation with 5 and 10 μg mL^-1 of cantharidin. Different changes in the gene expression were observed after incubation with cantharidin. While the gene expression of tnfa, il1b and crel was up-regulated in HKLs, the nfkb1 and igmh genes were down-regulated in comparison to the expression found in control HKLs. Present results offer a first view of the possible effects and action mechanisms of cantharidin in HKLs, as well as its implication in the inflammatory process, which could be of interest not only for basic research but also in the aquaculture sector.

Selenium Alleviates Inflammation in Staphylococcus aureus-Induced Mastitis via MerTK-Dependent Activation of the PI3K/Akt/mTOR Pathway in Mice

Mastitis caused by Staphylococcus aureus infection not only causes serious economic losses, but also affects human health. Se plays an important role in body immunity. However, the mechanisms by which Se regulates mastitis induced by S. aureus are still principally unknown. The purpose of this study is to investigate whether Se can inhibit mastitis induced by S. aureus through regulation of MerTK. Sixty BALB/c female mice were fed low, normal, or high Se concentrations for 7 weeks and then randomly divided into six groups (Se-Low Control group (LSN), Se-Normal Control group (NSN), Se-High Control group (HSN), Se-Low S. aureus group (LSS), Se-Normal S. aureus group (NSS), Se-High S. aureus group (HSS)). The regulation of Se on MerTK was detected via histopathological staining, western blot analysis, enzyme-linked immunosorbent assay, and qRT-PCR. With increased selenium concentrations, the levels of IL-1β, IL-6, and TNF-α decreased, while the phosphorylation levels of MerTK, PI3K, AKT, and mTOR increased. Therefore, this study showed that Se could alleviate S. aureus mastitis by activating MerTK and PI3K/AKT/mTOR pathway.

Dual-Ratiometric Fluorescent Probe for H2O2 and HClO in Living Cells and Zebrafish and Application in Alcoholic Liver Injury Monitoring

Reactive oxygen species (ROS) are an important component for maintaining normal physiological activities in organisms, and abnormal changes in their level are often accompanied by many diseases. As the two most representative components of ROS, HClO and H₂O₂ play vital roles in many physiological and pathological processes and are interdependent and mutually transformable. Although there is a lot of work that has specifically detected HClO or H₂O₂, there are few reports on the simultaneous differential detection of HClO and H₂O₂. Here, we report a ratio-based fluorescent probe capable of simultaneously distinguishing HClO and H₂O₂ based on making the best use of the untapped potential of coumarin derivatives. This probe was triumphantly put into use in the discriminative identification of HClO and H₂O₂ in aqueous media with high sensitivity and selectivity, and the probe was appropriate in a wide pH range. Furthermore, the imaging experiment for HClO and H₂O₂ in cells and zebrafish was eventually proven to be feasible. Importantly, this probe was qualified for monitoring the variation of HClO and H₂O₂ levels in organisms with alcoholic liver injury.

Synthesis and evaluation of wound healing properties of hydro-diab hydrogel loaded with green-synthetized AGNPS: in vitro and in ex vivo studies

In diabetic patients, the presence of neuropathy, peripheral vascular diseases and ischemia, leads to the formation of foot ulcerations with a higher risk of infection because the normal response to bacterial infection is missing. In the aim to control and treat diabetic foot ulcerations (DFUs), wound dressings that are able to absorb exudate, to prevent infections, and to promote wound healing are needed. For this reason, the aim of the present research was to synthetize a biocompatible hydrogel (called HyDrO-DiAb) composed of carboxymethylcellulose loaded with silver nanoparticles (AgNPs) for the treatment of diabetic foot ulcers. In this study, AgNPs were obtained by a green synthesis and, then, were dissolved in a CMC hydrogel that, after a freeze drying process, becomes a flexible and porous structure. The in vitro and in ex vivo wound healing activity of the obtained HyDrO-DiAb hydrogel was evaluated.

Health consequences of disinfection against SARS-CoV-2: Exploring oxidative stress damage using a biomonitoring approach

Individuals who get involved in the disinfection of public settings using sodium hypochlorite might suffer adverse health effects. However, scarce information is available on the potential oxidative stress damage caused at low concentrations typically used for disinfection. We aimed to assess whether exposure to sodium hypochlorite during the COVID-19 pandemic causes oxidative stress damage in workers engaged in disinfection tasks. 75 operators engaged in the disinfection of public places were recruited as the case group, and 60 individuals who were not exposed to disinfectant were chosen as the control group. Spot urine samples were collected before (BE) and after exposure (AE) to disinfectants in the case group. Likewise, controls provided two spot urine samples in the same way as the case group. Urinary malondialdehyde (MDA) levels were quantified by forming thiobarbituric acid reactive substances in the urine. In addition, the concentration of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the urine was determined using an ELISA kit. Results showed significant differences in the urinary levels of oxidative stress markers, where median 8-OHdG (AE case: 3.84 ± 2.89 μg/g creatinine vs AE control 2.54 ± 1.21 μg/g creatinine) and MDA (AE case: 169 ± 89 μg/g creatinine vs AE control 121 ± 47 μg/g creatinine) levels in case group AE samples were 1.55 and 1.35-times higher than the control group AE samples (P < 0.05), respectively. Besides, urinary levels of oxidative stress markers in AE samples of the case group were significantly higher than in BE samples (8-OHdG BE 3.40 ± 1.95 μg/g creatinine, MDA BE 136 ± 51.3 μg/g creatinine, P < 0.05). Our results indicated that exposure to even low levels of sodium hypochlorite used in disinfection practices might cause oxidative stress related damage. With this in mind, implementing robust protective measures, such as specific respirators, is crucial to reduce the health burdens of exposure to disinfectants.

Early Immune Response in Foreign Body Reaction Is Implant/Material Specific

The design of novel biomaterials should directly influence the host-immune system and steer it towards high biocompatibility. To date, new implants/materials have been tested for biocompatibility in vitro in cell cultures and in vivo in animal models. The current methods do not reflect reality (cell cultures) or are very time-consuming and deliver results only after weeks (animal model). In this proof-of-concept study, the suitability of a Whole Blood Stimulation Assay (WBSA) in combination with a Protein Profiler Array (PPA), as a readily available and cost-effective screening tool, was investigated. Three different biomaterials based on poly(lactic-co-glycolic acid (PLGA), calcium sulphate/-carbonate (CS) and poly(methyl methacrylate) (PMMA) were exposed to native whole blood from three volunteers and subsequently screened with a PPA. Individual reproducible protein profiles could be detected for all three materials after 24 h of incubation. The most intense reaction resulted from the use of PLGA, followed by CS. If even marginal differences in implants can be reflected in protein profiles, the combination of WBSA and PPA could serve as an early biocompatibility screening tool in the development of novel biomaterials. This may also lead to a reduction in costs and the amount of animal testing required.

Understanding Myeloperoxidase-Induced Damage to HDL Structure and Function in the Vessel Wall: Implications for HDL-Based Therapies

Atherosclerosis is a disease of increased oxidative stress characterized by protein and lipid modifications in the vessel wall. One important oxidative pathway involves reactive intermediates generated by myeloperoxidase (MPO), an enzyme present mainly in neutrophils and monocytes. Tandem MS analysis identified MPO as a component of lesion derived high-density lipoprotein (HDL), showing that the two interact in the arterial wall. MPO modifies apolipoprotein A1 (apoA-I), paraoxonase 1 and certain HDL-associated phospholipids in human atheroma. HDL isolated from atherosclerotic plaques depicts extensive MPO mediated posttranslational modifications, including oxidation of tryptophan, tyrosine and methionine residues, and carbamylation of lysine residues. In addition, HDL associated plasmalogens are targeted by MPO, generating 2-chlorohexadecanal, a pro-inflammatory and endothelial barrier disrupting lipid that suppresses endothelial nitric oxide formation. Lesion derived HDL is predominantly lipid-depleted and cross-linked and exhibits a nearly 90% reduction in lecithin-cholesterol acyltransferase activity and cholesterol efflux capacity. Here we provide a current update of the pathophysiological consequences of MPO-induced changes in the structure and function of HDL and discuss possible therapeutic implications and options. Preclinical studies with a fully functional apoA-I variant with pronounced resistance to oxidative inactivation by MPO-generated oxidants are currently ongoing. Understanding the relationships between pathophysiological processes that affect the molecular composition and function of HDL and associated diseases is central to the future use of HDL in diagnostics, therapy, and ultimately disease management.

A Smart Theranostic Prodrug System Activated by Reactive Oxygen Species for Regional Chemotherapy of Metastatic Cancer

Metastatic cancer is difficult to cure because of its uncontrollable nature and side effects during treatment. We constructed a reactive oxygen species (ROS)-activated smart theranostic prodrug system based on an ROS active site linked with both a targeting group and an anticancer drug for efficient regional chemotherapy of metastatic cancers. The optimized prodrug (Bio-(8)-MB-CPT) with biotin as the targeting group displayed high sensitivity towards ROS and selectively targeting ability towards cervical cancer cells, showing highly efficient drug release (up to 92 %) in vitro. Bio-(8)-MB-CPT thus exerted strong toxicity towards cervical cancer cells, but unlike the parent drug (camptothecin), showed no toxicity towards normal cells. Moreover, the prodrug displayed significantly enhanced antitumor efficacy in vivo and eradicated the tumor with no obvious side effects (inhibition of the tumor reached up to 99.9 %).