The other myeloperoxidase: Emerging functions

Indole-3-Aldehyde alleviates lung inflammation in COPD through activating Aryl Hydrocarbon Receptor to inhibit HDACs/NF-κB/NLRP3 signaling pathways

Indole-3-aldehyde (I3A) is an intestinal microbial metabolite that regulates inflammation in various inflammatory diseases; however, its role in chronic obstructive pulmonary disease (COPD) remains unclear. This study aimed to investigate the anti-inflammatory effects and molecular mechanisms of I3A in COPD. We constructed in vivo models using cigarette smoke (CS)-stimulated mice and in vitro models using cigarette smoke extract (CSE)-stimulated MH-S cells. The results demonstrated that I3A significantly alleviated bronchial obstruction in mice with COPD and reduced the expression of inflammatory factors such as TNF-α, IL-1β, and IL-6. Additionally, I3A decreased the levels of matrix metalloproteinases MMP2, MMP12, and inhibited the NF-κB p65/NLRP3 pathways. Further investigation revealed that I3A inhibited NF-κB activity by suppressing p65 phosphorylation and nuclear translocation in CSE-stimulated MH-S cells. The activation of the NF-κB and NLRP3 signaling pathways is mediated by histone deacetylase 5 (HDAC5) and HDAC6, both of which are inhibited by I3A. Subsequent experiments indicated that aryl hydrocarbon receptor (AHR) knockdown attenuated the inhibitory effect of I3A on pro-inflammatory cytokines and the HDACs/NF-κB/NLRP3 signaling pathways, highlighting the dependence of I3A's anti-inflammatory effects on the AHR receptor. KEY MESSAGES: I3A effectively reduced lung inflammation in COPD mice by inhibiting the NF-κB pathway. In CSE-stimulated MH-S cells, I3A suppressed p65 phosphorylation and nuclear translocation, thereby inhibiting NF-κB activity. The activation of the NF-κB/NLRP3 pathways by HDAC5 and HDAC6 was diminished by I3A. Through the activation of the AHR receptor, I3A suppressed the activities of HDAC5/6, leading to a decrease in inflammatory factor levels.

Association of the ACE2-Angiotensin1-7-Mas axis with lung damage caused by cigarette smoke exposure: a systematic review

Through the Mas receptor, angiotensin-(1-7) [Ang-(1-7)] has been shown to have a key role in the development of lung inflammation. This systematic review (SR) sought to identify the relationship between lung damage brought on by exposure to cigarette smoke (CS) and the ACE2-Ang-(1-7)-Mas pathway. In this investigation, relevant keywords were used to search PubMed (MEDLINE), Scopus (Elsevier), and Institute for Scientific Information (ISI) Web of Science up to December 2022. Nine studies were chosen because they satisfied the inclusion/exclusion criteria. The majority of research concluded that exposure to CS increased the risk of lung damage. Smoking cigarettes is the main cause of COPD because it causes massive amounts of reactive oxygen and nitrogen species to enter the lungs, which stimulate the production of inflammatory cytokines like IL-1 β, IL-6, and TNF-α, as well as the invasion of inflammatory cells like neutrophils and macrophages. These findings support the renin-angiotensin system's (RAS) involvement in the pathophysiology of smoking-induced damage. Additionally, via stimulating pro-inflammatory mediators, aberrant RAS activity has been linked to lung damage. Lung inflammation's etiology has been shown to be significantly influenced by the protective known RAS arm ACE2-Ang-(1-7)-Mas. In conclusion, these are important for informing policymakers to pass legislation limiting the use of smoking and other tobacco to prevent their harmful effects.

Multi-modal analysis reveals tumor and immune features distinguishing EBV-positive and EBV-negative post-transplant lymphoproliferative disorders

The oncogenic Epstein-Barr virus (EBV) can drive tumorigenesis with disrupted host immunity, causing malignancies including post-transplant lymphoproliferative disorders (PTLDs). PTLD can also arise in the absence of EBV, but the biological differences underlying EBV(+) and EBV(-) B cell PTLD and the associated host-EBV-tumor interactions remain poorly understood. Here, we reveal the core differences between EBV(+) and EBV(-) PTLD, characterized by increased expression of genes related to immune processes or DNA interactions, respectively, and the augmented ability of EBV(+) PTLD B cells to modulate the tumor microenvironment through elaboration of monocyte-attracting cytokines/chemokines. We create a reference resource of proteins distinguishing EBV(+) B lymphoma cells from EBV(-) B lymphoma including the immunomodulatory molecules CD300a and CD24, respectively. Moreover, we show that CD300a is essential for maximal survival of EBV(+) PTLD B lymphoma cells. Our comprehensive multi-modal analyses uncover the biological underpinnings of PTLD and offer opportunities for precision therapies.

Environment-sensitive turn-on fluorescent probe enables live cell imaging of myeloperoxidase activity during NETosis

Myeloperoxidase (MPO) plays an important role in the immune response of human neutrophils and has been implicated in autoimmune conditions, cardiovascular disorders, and neurodegeneration. Current methods to detect MPO activity rely on the detection of HOCl using activatable probes or require challenging experimental procedures. Therefore, these tools provide limited information about the dynamics and localization of MPO in complex molecular processes such as NETosis in real time. In this study, we report a ''turn-on" activity-based probe that fluoresces exclusively upon binding to MPO, exhibits minimal background fluorescence in buffered aqueous media, and is blocked by MPO inhibitors. Our probe facilitates real-time imaging of direct MPO activity in human neutrophils and HL-60-derived granulocytes during NETosis under wash-free conditions. Furthermore, it allows for the discrimination between different triggers of NETosis in human neutrophils. These findings hold promise for advancing our understanding of the role of MPO in immune responses and inflammatory conditions.

Exploring mammalian heme peroxidases: A comprehensive review on the structure and function of myeloperoxidase, lactoperoxidase, eosinophil peroxidase, thyroid peroxidase and peroxidasin

The peroxidase family of enzymes is a ubiquitous cluster of enzymes primarily responsible for the oxidation of organic and inorganic substrates. The mammalian heme peroxidase subfamily is characterized by a covalently linked heme prosthetic group which plays a key role in the oxidation of halides and psuedohalides into their respective hypohalous acid and hypothiocyanous acid under the influence of H2O2 as substrate. The members of the heme peroxidase family include Lactoperoxidase (LPO), Eosinophil peroxidase (EPO), Myeloperoxidase (MPO), Thyroid peroxidase (TPO) and Peroxidasin (PXDN). The biological activity of LPO, MPO and EPO pertains to antibacterial, antifungal and antiviral while TPO is involved in the biosynthesis of the thyroid hormone and PXDN helps maintain the ECM. While these enzymes play several immunomodulatory roles, aberrations in their activity have been implicated in diseases such as myocardial infarction, asthma and Alzheimer's amongst others. The sequence and structural similarities amongst the members of the family are strikingly high while the substrate specificities and subcellular locations vary. Hence, it becomes important to provide a consortium of information regarding the members to study their biochemical, pathological and clinical function.

NDRG2 Deficiency Exacerbates UVB-Induced Skin Inflammation and Oxidative Stress Damage

UVB radiation induces inflammatory and oxidative stress responses, contributing to skin damage, yet the underlying mechanisms are not fully understood. N-Myc downstream-regulated gene 2 (NDRG2), an emerging stress-associated gene, remains unexplored in UVB-induced skin injury. In this study, we detected skin NDRG2 expression after UVB irradiation for the first time and further used Ndrg2 knockout mice to clarify the role of NDRG2 in UVB-induced skin injury. Three-month-old male Ndrg2+/+ and Ndrg2-/- mice (16-18g) were exposed to UVB to induce acute skin damage, and then dorsal skin samples were collected for subsequent analyses. UVB-induced skin damage was scored. Western Blot Analysis, immunofluorescence (IF) double labeling, and immunohistochemistry (IHC) were employed to assess NDRG2 expression and/or distribution. The concentrations of TNF-α, IL-6, IL-1β, MPO, MMP8, superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) were quantitatively assessed using enzyme-linked immunosorbent assay (ELISA). Hematoxylin and eosin (HE) staining were employed to determine pathological changes. RNA sequencing and analysis were performed to estimate transcript expression levels and analyze mRNA expression. DESeq2 software was employed to identify differentially expressed genes (DEGs). DEGs were visualized using volcanic and heat maps. Gene Ontology (GO) functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were analyzed to identify primary biological functions, metabolic pathways, or signal transduction pathways associated with DEGs. UVB-challenged Ndrg2-/- mice exhibited significantly exacerbated skin damage (erythema, edema, and erosion), neutrophil infiltration, and apoptosis compared to Ndrg2+/+ mice. Furthermore, UVB-challenged Ndrg2-/- mice displayed significantly elevated pro-inflammatory cytokines, myeloperoxidase (MPO), matrix metalloproteinase-8 (MMP8), and reduced antioxidant expression. RNA sequencing identified 1091 significantly differentially expressed genes enriched in inflammation, immune response, and oxidative stress pathways. In conclusion, the deficiency of Ndrg2 markedly exacerbated UVB-induced skin damage by promoting inflammatory responses and inhibiting antioxidant responses. This suggests that stabilizing NDRG2 expression holds promise as a therapeutic strategy for protecting against UVB-induced skin damage.

A Potential Link between Myeloperoxidase Modified LDL, Atherosclerosis and Depression

Atherosclerosis is a chronic inflammatory disease that involves modified low-density lipoproteins (LDL) which play a pivotal role in the initiation and progression of the disease. Myeloperoxidase oxidized LDL (Mox-LDL) is considered to be the most patho-physiologically relevant type of modified LDL and has been reported to be ubiquitously present in atheroma plaques of patients with atherosclerosis. Besides its involvement in the latter disease state, Mox-LDL has also been shown to be implicated in the pathogenesis of various illnesses including sleep disorders, which are in turn associated with heart disease and depression in many intricate ways. Meanwhile, we have recently shown that lox-1-mediated Mox-LDL signaling modulates neuroserpin activity in endothelial cells, which could have major implications that go beyond the pathophysiology of stroke and cerebrovascular disease (CD). Of note is that tissue plasminogen activator (tPA), which is the main target of neuroserpin in the brain, has a crucial function in the processing of brain-derived neurotrophic factor (BDNF) into its mature form. This factor is known to be involved in major depressive disorder (MDD) development and pathogenesis. Since tPA is more conventionally recognized as being involved in fibrinolytic mechanisms, and its effect on the BDNF system in the context of MDD is still not extensively studied, we speculate that any Mox-LDL-driven change in the activity of tPA in patients with atherosclerosis may lead to a decrease in the production of mature BDNF, resulting in impaired neural plasticity and depression. Deciphering the mechanisms of interaction between those factors could help in better understanding the potentially overlapping pathological mechanisms that regulate disease processes in CD and MDD, supporting the possibility of novel and common therapeutic opportunities for millions of patients worldwide.

Exploring the role of myeloperoxidase in the atherosclerotic process in hypoxic mice based on the MAPK signaling pathway

Atherosclerosis (AS) is the common pathophysiological basis of various cardiovascular diseases and the leading cause of death from cardiovascular disease worldwide. When the body is in a hypoxic environment, enhanced oxidative stress and significant accumulation of reactive oxygen species (ROS) in tissue cells exacerbate the inflammatory response, resulting in increased release of myeloperoxidase (MPO), catalyzing the formation of large quantities of hypochlorous acid (HOCl), further oxidative modification of low-density lipoprotein (LDL), and exacerbating the formation and progression of atherosclerotic plaques. The MAPK signaling pathway is important in oxidative stress-mediated promotion of atherogenesis. MPO -/- mice were used in this study to establish a hypoxia model simulating 5000 m altitude and a Western high-fat diet-induced atherosclerosis model for 12 weeks. Exploring the role of MPO in the atherosclerotic process in hypoxic mice by observing the MAPK signaling pathway to provide a therapeutic target for the prevention and treatment of hypoxic atherosclerotic disease in the plateau. We found that hypoxia promotes the formation of atherosclerosis in mice, and the mechanism may be that increased MPO in vivo promotes an inflammatory response, which plays a crucial role in the formation of atherosclerosis. In addition, hypoxia further exacerbates plaque instability by activating the MAPK signaling pathway to upregulate vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP9), which in turn promotes angiogenesis within the plaque. Therefore, a potential target for preventing and treating hypoxic atherosclerotic disease is the inhibition of MPO.

Effect of co-administration of gallic acid and quercetin or gallic acid and rutin on impaired spermatogenesis and oxidative damage in a busulfan-treated rat model

Gallic acid (GAL), rutin (RUT), and quercetin (QUE) are common antioxidant agents in fruits and vegetables with intriguing pharmacological effects. In the present study, we compared the therapeutic outcomes of GAL + QUE in comparison with GAL + RUT co-treatment in a busulfan (BUS) model of testicular injury in Wistar rats. BUS (4 mg kg-1 body weight (b.w) was injected intraperitoneally daily for 4 days. GAL + RUT or GAL + QUE (20 mg kg-1 b. w) was delivered by oral gavage for 52 days. Examination of the testes of BUS-treated rats both biochemically and under light microscopy revealed an increased level of lipid peroxidation, DNA fragmentation, glutathione-S-transferase, lactate dehydrogenase, gamma-glutamyl transpeptidase, alkaline phosphatase and acid phosphatase with a concomitant decrease in the level of antioxidants: glutathione, ascorbic acid, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities, suggesting testicular injury. Tissue sections confirmed the testicular injury-induced by BUS, including diminished spermatogenesis score index, tubular diameter, gonado-somatic index, testis weight, epithelia thickness and higher percentage of aberrant tubules. GAL + QUE co-administration had better recovery effects than GAL + RUT on the biochemical markers and protected against BUS-induced testicular damage. GAL + QUE treatment regimen has better capacity to maintain the antioxidant capacity of the testes and is more potent at reducing BUS-induced oxidative damage compared to GAL + RUT.

The in vitro effect of myeloperoxidase oxidized LDL on THP-1 derived macrophages

Cardiovascular diseases (CVDs) linked to atherosclerosis remains the leading cause of death worldwide. Atherosclerosis is primarily caused by the accumulation of oxidized forms of low density lipoprotein (LDL) in macrophages (MΦs) in the subendothelial layer of arteries leading to foam cell and fatty streak formation. Many studies suggest that LDL that is modified by myeloperoxidase (MPO) is a key player in the development of atherosclerosis. MΦs can adopt a variety of functional phenotypes that include mainly the proinflammatory M1 and the anti-inflammatory M2 MΦ phenotypes which are both implicated in the process of atherogenesis. In fact, MΦs that reside in atherosclerostic lesions were shown to express a variety of phenotypes ranging between the M1- and M2 MΦ types. Recently, we pointed out the involvement of MPO oxidized-LDL (Mox-LDL) in increasing inflammation in MΦs by reducing their secretion of IL-10. Since little is known about Mox-LDL-mediated pro-atherosclerostic responses in MΦs, our study aimed at analyzing the in vitro effects of Mox-LDL at this level through making use of the well-established model of human THP-1-derived Mφs. Our results demonstrate that Mox-LDL has no effect on apoptosis, reactive oxygen species (ROS) generation and cell death in our cell model; yet, interestingly, our results show that Mox-LDL is significantly engulfed at a higher rate in the different MΦ subtypes supporting its key role in foam cell formation during the progression of the disease as well as previous data that were generated using another primary MΦ cell model of atherosclerosis.

The role of predictive and prognostic values of inflammatory markers in acute pancreatitis: a narrative review

Pancreatitis is an inflammatory condition affecting the pancreas and is classified into 2 types, acute and chronic, which can manifest in various forms. This review article summarizes the role of predictive and prognostic values of inflammatory markers in the pathogenesis of acute pancreatitis, mainly focused on preclinical and clinical studies. It includes serum amyloid A (SAA), monocyte chemotactic protein-1 (MCP-1), erythrocyte sedimentation rate (ESR), interleukin-6 (IL-6), C-reactive protein (CRP), IL-10, myeloperoxidase, pentraxin 3, and plasminogen activator inhibitor 1. SAA3 plays a crucial role in developing acute pancreatitis by triggering a receptor-interacting protein 3–dependent necroptosis pathway in acinar cells. Targeting SAA3 could be a potential strategy for treating acute pancreatitis. The recruitment of monocytes/macrophages and the activation of the systemic MCP-1 signaling pathway play a role in the progression of pancreatitis, and blocking MCP-1 may have a suppressive effect on the development of pancreatic fibrosis. The ESR can predict severe acute pancreatitis with slightly lower accuracy than CRP. When ESR and CRP levels are combined at 24 hours, they predict severe acute pancreatitis accurately. IL-6 plays a crucial role in activating the Janus kinase/signal transducers and activators of the transcription pathway, exacerbating pancreatitis and contributing to the initiation and progression of pancreatic cancer. Endogenous IL-10 plays a crucial role in controlling the regenerative phase and limiting the severity of fibrosis and glandular atrophy induced by repeated episodes of acute pancreatitis in mice. The predictive and diagnostic roles of these inflammatory factors in pancreatitis were introduced in detail in this review.

Myeloid-specific deletion of group VIA calcium-independent phospholipase A2 induces pro-inflammatory LPS response predominantly in male mice via MIP-1α activation

Polymorphisms of group VIA calcium-independent phospholipase A2 (PLA2G6) are associated with blood C-reactive protein suggesting its role in inflammation. We showed that myeloid-specific Pla2g6-deficiency in Pla2g6M-/- mice led to exaggerated inflammation and fibrosis in a lean fatty liver model. We here investigated whether these mutants display alteration in immune response after treatment with E. coli lipopolysaccharides (LPS) under acute (a single dose) and persistent (four doses) conditions. Without LPS treatment, male Pla2g6M-/- (but not Flox) mice at 12 months of age exhibited splenomegaly and hepatic necrosis, and ~ 30 % of them exhibited autoimmune hepatitis showing lymphoplasma cells with CD3(+) and CD45R(+) staining. Under acute LPS, male mutants showed an elevation of plasma MIP-1α and immunoglobulinA as well as upregulation of hepatic apoptosis and fibrosis PARP-1, Bax, MCP-1, α-SMA, and collagen I proteins. Their bone-marrow-derived macrophages also showed an elevation of MIP-1α release upon LPS stimulation in vitro. Female mutants under acute LPS showed a moderate increase in plasma KC/CXCL1, MCP-1, and IL10, and they showed no remarkable increase in hepatic fibrosis under acute or persistent LPS. Male mutants under persistent LPS displayed an elevation of aspartate aminotransferase, blood eosinophils, and hepatic apoptosis. Moreover, ~30 % of these mutants exhibited eosinophilic sclerosing portal hepatitis associated with an upregulated protein expression of hepatic CD8α, CD68, eosinophilic cationic protein, and Ly6G. Thus, myeloid-PLA2G6 deficiency led to an autoimmune and LPS-induced inflammatory liver disease via MIP-1α in a male-predominant manner. Our results may be applicable to patients with PLA2G6 mutations who undergo bacterial infection and sepsis.

Polysaccharide-rich extract of Genipa americana leaves exerts anti-inflammatory effects modulated by platelet mediators

ETHNOPHARMACOLOGICAL RELEVANCE

Genipa americana L. (Rubiaceae) leaves are traditionally used to treat fever, pharyngitis, healing, luxation and bruises.

AIM OF THE STUDY

This study aimed to investigate the anti-inflammatory effect of the polysaccharide-rich extract of G. americana leaves (PE-Ga) in acute inflammation models and underlying mechanisms associated with platelet activity.

MATERIALS AND METHODS

Rats received PE-Ga (0.3-3.0 mg/kg; IV) 30 min before injection (IP or SC) of zymosan, serotonin, PGE2, PLA2, PAF or L-arginine, and evaluated in the models of paw edema and acute peritonits. The blockage of plasma serotonin reuptake into platelets was performed with fluoxetine (40 mg/kg; IP).

RESULTS

In vitro, PE-Ga inhibited ADP-induced platelet aggregation up to 49%. In the edema model, PE-Ga reduced (41%) the time-course of the edema induced by zymosan, mainly the last phase (62%), as well as that induced by PLA2 (32%), PAF (35%), L-arginine (36%), PGE2 (49%) or serotonin (54% AUC); and reversed paw hypernociception induced by PGE2 or serotonin. In the peritonitis model, PE-Ga reversed abdominal hypernociception and reduced leukocyte migration induced by zymosan to blood (38%) and peritoneal cavity (55%), mainly neutrophils (70%). PE-GA also decreased leukocyte rolling (32%) and adhesion (47%), and increased the rolling velocity 2.2-fold. In the peritoneal fluid, PE-Ga reversed P-selectin and reduced total proteins (17%), MDA (40%), NO2-/NO3- (27%), and MPO activity (43%) but increased catalase activity 3.3-fold compared to zymosan. In addition, fluoxetine reversed PE-Ga anti-inflammatory effect on leukocyte migration and adhesion.

CONCLUSIONS

PE-Ga exerts antiplatelet and anti-inflammatory effects in acute inflammation induced by zymosan, being modulated by P-selectin and platelet serotonin, among other inflammatory mediators.

The Roles of Neutrophil-Derived Myeloperoxidase (MPO) in Diseases: The New Progress

Myeloperoxidase (MPO) is a heme-containing peroxidase, mainly expressed in neutrophils and, to a lesser extent, in monocytes. MPO is known to have a broad bactericidal ability via catalyzing the reaction of Cl- with H2O2 to produce a strong oxidant, hypochlorous acid (HOCl). However, the overproduction of MPO-derived oxidants has drawn attention to its detrimental role, especially in diseases characterized by acute or chronic inflammation. Broadly speaking, MPO and its derived oxidants are involved in the pathological processes of diseases mainly through the oxidation of biomolecules, which promotes inflammation and oxidative stress. Meanwhile, some researchers found that MPO deficiency or using MPO inhibitors could attenuate inflammation and tissue injuries. Taken together, MPO might be a promising target for both prognostic and therapeutic interventions. Therefore, understanding the role of MPO in the progress of various diseases is of great value. This review provides a comprehensive analysis of the diverse roles of MPO in the progression of several diseases, including cardiovascular diseases (CVDs), neurodegenerative diseases, cancers, renal diseases, and lung diseases (including COVID-19). This information serves as a valuable reference for subsequent mechanistic research and drug development.

The role of the SIRT1-BMAL1 pathway in regulating oxidative stress in the early development of ischaemic stroke

Oxidative stress is the primary cause of ischaemic stroke and is closely related to circadian rhythm. However, the mechanism by which circadian rhythm regulates oxidative stress in ischaemic stroke remains elusive. The Silent Information Regulator 1 (SIRT1) controls circadian rhythm by activating the transcription of the circadian clock core protein Basic Helix-Loop-Helix ARNT Like 1 (BMAL1) through deacetylation. Studies have shown that the SIRT1-BMAL1 pathway can regulate oxidative stress. To investigate its correlation with oxidative stress, we examined the expression levels and influencing factors of SIRT1-BMAL1 at different times in ischaemic stroke patients and analyzed their clinical indexes, oxidative stress, and inflammatory factor indicators. The expression levels of oxidative stress and inflammatory factor indicators, including malondialdehyde (MDA), superoxide dismutase (SOD), interleukin-6 (IL-6), and tumor necrosis factor-a (TNF-α), SIRT1, and BMAL1, were detected in ischaemic stroke patients within 4.5 h of onset and in non-stroke patients. Patients were divided into four subgroups based on onset time: subgroup 1 (0:00-05:59); subgroup 2 (06:00-11:59); subgroup 3 (12:00-17: 59); and subgroup 4 (18:00-23:59). Our results showed higher MDA, IL-6, and TNF-α levels, and lower SOD, SIRT1, and BMAL1 levels in ischaemic stroke patients compared to control patients (P < 0.05). Among the four subgroups, the content of MDA, IL-6, and TNF-α was highest in patients with ischaemic stroke onset from subgroup 2 (06:00-11:59), while the expression levels of SOD, BMAL1, and SIRT1 were lowest in patients with ischaemic stroke in subgroup 2. Additionally, myeloperoxidase (MPO) reached the highest value showing the same trends consistent with MDA, IL-6, and TNF-ɑ and opposite trends consistent with SOD, BMAL1, and SIRT1. However, triglycerides (TGs), total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), immediate blood glucose, immediate diastolic blood pressure, immediate systolic blood pressure, and homocysteine (HCY) did not show any statistically significant circadian rhythm changes (P > 0.05). Our findings suggest that the SIRT1-BMAL1 pathway may be involved in early oxidative stress in ischaemic stroke, which may be related to MPO.

Sleeve Gastrectomy Provides Cardioprotection from Oxidative Stress In Vitro Due to Reduction of Circulating Myeloperoxidase

Bariatric surgery, including sleeve gastrectomy (SG), improves systolic and diastolic function, which is independent of weight loss in rodent models. The cause of weight loss-independent improvements in cardiac function are unknown but may originate from the gastrointestinal tract. In this study, we investigated whether a circulating blood factor is a mechanism for acute cardioprotection after SG by testing the utility of rodent SG plasma to reduce metabolic stress in vitro. For the initial experiment, obese male Zucker rats underwent SG, ad lib sham, or pair-fed sham surgeries (n = six SG, n = eight SH, n = eight PF). For all other studies, a second group of Zucker rats underwent SG or ad lib sham surgeries (n = eight SH, n = six SG). Six weeks following surgery, plasma was collected from each group, both in the fasting and post-prandial (pp) state. This plasma was then pooled per surgical group and nutrient state and tested in multiple in vitro cell culture and extra-cellular assays to determine the effect of SG on myotubular metabolic stress compared to the sham surgeries. Post-prandial SG plasma (ppSG), but not fasting SG, pp, or fasting sham plasma, reduced the metabolic stress of the H9c2 cells as measured by lactate dehydrogenase (LDH) release (p < 0.01). Unlike SG, weight reduction through pair-feeding did not prevent H9c2 metabolic stress. The PpSG plasma had the slowest rate of extracellular hydrogen peroxide consumption and peroxidatic activity compared to the pp sham, fasting SG, and fasting sham groups. Redox testing of plasma with aminiobenzoic acid hydrazide and edaravone suggested a pattern supporting myeloperoxidase (MPO), or other peroxidases, as the primary component responsible for reduced metabolic stress with ppSG plasma. The PpSG plasma contained 35% less circulating MPO protein as compared to the pp sham and fasting SG plasma. The plasma from an MPO global knockout rat also prevented metabolic stress of the H9c2 cells, compared to the significant increase in LDH release from the plasma of the WT controls (p < 0.01). The MPO global knockout plasma also had a rate of extracellular hydrogen peroxide consumption and peroxidatic activity comparable to the ppSG plasma. These studies suggest that one of the weight loss-independent mechanisms by which SG improves myocellular function could be a reduced pro-oxidative environment due to lower circulating levels of MPO. It appears that the gastrointestinal tract is of critical importance to these findings, as the MPO levels were only lowered after enteral, nutrient stimulation in the SG rats. If this surgical effect is confirmed in humans, SG may be a unique surgical treatment for multiple diseases with a pathogenesis of inflammation and oxidative damage, including obesity-associated heart failure with preserved ejection fraction.

Boronate-Based Oxidant-Responsive Derivatives of Acetaminophen as Proinhibitors of Myeloperoxidase

Myeloperoxidase (MPO) is an important component of the human innate immune system and the main source of a strong oxidizing and chlorinating species, hypochlorous acid (HOCl). Inadvertent, misplaced, or excessive generation of HOCl by MPO is associated with multiple human inflammatory diseases. Therefore, there is a considerable interest in the development of MPO inhibitors. Here, we report the synthesis and characterization of a boronobenzyl derivative of acetaminophen (AMBB), which can function as a proinhibitor of MPO and release acetaminophen, the inhibitor of chlorination cycle of MPO, in the presence of inflammatory oxidants, i.e., hydrogen peroxide, hypochlorous acid, or peroxynitrite. We demonstrate that the AMBB proinhibitor undergoes conversion to acetaminophen by all three oxidants, with the involvement of the primary phenolic product intermediate, with relatively long half-life at pH 7.4. The determined rate constants of the reaction of the AMBB proinhibitor with hydrogen peroxide, hypochlorous acid, or peroxynitrite are equal to 1.67, 1.6 × 104, and 1.0 × 106 M-1 s-1, respectively. AMBB showed lower MPO inhibitory activity (IC50 > 0.3 mM) than acetaminophen (IC50 = 0.14 mM) toward MPO-dependent HOCl generation. Finally, based on the determined reaction kinetics and the observed inhibitory effects of two plasma components, uric acid and albumin, on the extent of AMBB oxidation by ONOO- and HOCl, we conclude that ONOO- is the most likely potential activator of AMBB in human plasma.

Myeloperoxidase Alters Lung Cancer Cell Function to Benefit Their Survival

Myeloperoxidase (MPO) is a neutrophil-derived enzyme that has been recently associated with tumour development. However, the mechanisms by which this enzyme exerts its functions remain unclear. In this study, we investigated whether myeloperoxidase can alter the function of A549 human lung cancer cells. We observed that MPO promoted the proliferation of cancer cells and inhibited their apoptosis. Additionally, it increased the phosphorylation of AKT and ERK. MPO was rapidly bound to and internalized by A549 cells, retaining its enzymatic activity. Furthermore, MPO partially translocated into the nucleus and was detected in the chromatin-enriched fraction. Effects of MPO on cancer cell function could be reduced when MPO uptake was blocked with heparin or upon inhibition of the enzymatic activity with the MPO inhibitor 4-aminobenzoic acid hydrazide (4-ABAH). Lastly, we have shown that tumour-bearing mice treated with 4-ABAH had reduced tumour burden when compared to control mice. Our results highlight the role of MPO as a neutrophil-derived enzyme that can alter the function of lung cancer cells.

The Nasal Innate Immune Proteome After Saline Irrigation: A Pilot Study in Healthy Individuals

BACKGROUND

Previous research has shown diminished nasal immune function following nasal saline irrigation (NSI), returning to baseline at 6 hours. The aim of this study was to examine the immune nasal proteome before and after 14 days of nasal irrigation.

METHODS

Seventeen healthy volunteers received either isotonic (IsoSal) or low salt (LowNa) NSI. Nasal secretions were collected before and 30 min after NSI at baseline and again after 14 days. Specimens were analyzed using mass spectrometry to detect proteins of relevance to nasal immune function.

RESULTS

One thousand eight hundred and sixty-five proteins were identified with significant changes in 71 proteins, of which 23 were identified as part of the innate immune system. Baseline analysis demonstrated an increase of 9 innate proteins after NSI, most after IsoSal. After 14 days, a greater increase in innate peptides was present, with most now in the LowNa group. When NSI solutions were compared, a significant increase in 4 innate proteins, including a 211% in lysozyme, was detected in the LowNa group.

CONCLUSION

LowNa NSI demonstrates evidence of improving the innate immune secretions, especially lysozyme, in healthy volunteers.

Therapeutic effects of fenticonazole on bacterial vaginosis in mice

Bacterial vaginitis (BV) is a syndrome of increased vaginal discharge, fishy smelling leucorrhea, and itching and burning vulva caused by the microecological imbalance in the vagina induced by mixture of Gardnerella vaginalis (GV) and some anaerobic bacteria. Fenticonazole, an imidazole derivative and antimicrobial compound, has been demonstrated to exert effective therapeutic effects in mixed vaginitis. Accordingly, our study was designed to explore the potential role of fenticonazole in GV-infected BV mouse models. Female C57/BL6 mice were injected intraperitoneally with β-estradiol 3 days before and on the day of GV infection to maintain a pseudoestrus state. On the day of infection, mice were intravaginally inoculated with 20 µl of a suspension of GV (6 × 106 CFU/ml). Fenticonazole was administered as 2% vaginal cream (0.2 mg each mouse) by intravaginal application once a day for 3 days beginning the day of infection. At day 3 postinfection, the mice were sacrificed and vaginal washes were harvested. GV proliferation and Lactobacillus content were calculated in the vaginal lavage. Neutrophil counts in the vaginal lavage were observed through Pap staining. Myeloperoxidase (MPO) activity and proinflammatory cytokine (TNF-α, IL-1β, IL-6, iNOS, COX2, and NF-κB) levels in vaginal tissues were measured by ELISA and western blotting. Vaginal tissues were stained by hematoxylin and eosin (H&E) to examine the exfoliation of vaginal epithelial cells. GV infection increased GV proliferation and neutrophil counts but reduced Lactobacillus content in the vaginal lavage, as well as enhanced MPO activity, proinflammatory cytokine levels, and the exfoliation of vaginal epithelial cells in vaginal tissues of BV mouse models. However, administration of fenticonazole significantly ameliorated the above phenomena. Fenticonazole greatly improves the symptoms of GV-induced BV in mouse models.

Integrating network pharmacology and transcriptomic validation to investigate the efficacy and mechanism of Mufangji decoction preventing lung cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Mufangji decoction (MFJD), a famous traditional Chinese medicine formula in Synopsis of Golden Chamber (Jingui yaolue), has been utilized to treat cough and asthma and release chest pain over 2000 years in China. Chinese old herbalist doctor use MFJD to treat lung cancer and cancerous pleural fluid, but the preventive effect of MFJD on lung cancer and the underlying mechanism are indefinite.

AIM OF THE STUDY

The goal of this study is to explore the efficacy and mechanism of Mufangji decoction preventing lung cancer referring to the traditional use.

MATERIALS AND METHODS

Tumor allograft experiment and host versus tumor experiment were used to observe the direct anti-tumor effect and indirect anti-tumor immune effect, the mouse lung carcinogenic model was used to evaluate the dose-response and the preventive effect of MFJD on lung cancer. The active ingredients of MFJD were obtained by UPLC-MS/MS. The potential targets of MFJD were screened by network pharmacology and transcriptomics. The therapeutic targets and pathways of MFJD on lung cancer were obtained by protein-protein interaction, molecular docking and David database. The predicted results were verified in vitro and in vivo.

RESULTS

MFJD could significantly prevent tumor growth in host versus tumor experiment but could not in tumor allograft experiment, indicating an anti-tumor immune effect against lung cancer. MFJD could reduce lung nodules with a dose-response in mouse lung carcinogenic model. Myeloperoxidase (MPO) was selected as the core target due to the highest degree value in Protein-Protein interaction network and had potently binding activity to sinomenine and dehydrocostus lactone in molecular docking. In vivo, MPO-expressed neutrophils are negatively correlated with lung cancer progression and MFJD could promote the neutrophil-related immune surveillance. In vitro, sinomenine and dehydrocostus lactone could promote neutrophil phagocytosis, MPO and ROS production in a dose dependent manner. The major compounds from MFJD were identified to regulate 36 targets for lung cancer prevention by UPLC-MS/MS, network pharmacology and transcriptomics. David database exhibited that MFJD plays an important role in immunoregulation by modulating 4 immune-related biological processes and 3 immune-related pathways.

CONCLUSIONS

MFJD prevents lung cancer by mainly promoting MPO expression to maintain neutrophil immune surveillance, its key compounds are sinomenine and dehydrocostus lactone.

Elevation of Myeloperoxidase Correlates with Disease Severity in Patients with Hantaan Virus Infection

Hantaan orthohantavirus (HTNV) can cause hemorrhagic fever with renal syndrome (HFRS) characterized by acute kidney injury and hemorrhage. Neutrophils are the most abundant innate immune cell and the body's first line of defense against pathogens. Currently, an increasing number of studies have shown that neutrophils may be a mixed blessing in terms of viral infections. However, the role of neutrophils in HFRS patients with HTNV infection has not been fully declared. In this study, we analyzed plasma levels of both myeloperoxidase (MPO) and MPO-DNA in HFRS patients, together with the clinical parameters. Neutrophil-platelet aggregates (NPAs) during the acute and convalescent phases of HFRS were also assessed. The results showed that plasma MPO-DNA levels had no change in different disease phases or severities of HFRS patients. Whereas plasma MPO significantly increased in the acute phase and critical/severe groups of HFRS patients. Furthermore, plasma MPO was positively correlated with inflammatory clinical parameters, such as white blood cell counts, neutrophil counts, and renal injury-related parameters, such as blood urea nitrogen, blood uric acid, and serum creatinine, as well as negatively correlated with and platelet counts. In addition, NPAs increased both in acute and convalescent phase in HFRS patients compared with normal controls. These results suggested that elevated plasma MPO in HFRS patients correlated with disease severity, together with the increases of NPAs in HFRS patients, which may provide new insights into potential role of neutrophils in the pathogenesis of HFRS.

Role of myeloperoxidase in inflammation and atherosclerosis (Review)

Myeloperoxidase (MPO) belongs to the heme peroxidase family, which includes a set of enzymes with potent oxidoreductase activity. MPO is considered an important part of the innate immune system's microbicidal arm and is secreted by neutrophils and macrophages. Interestingly, this enzyme has been implicated in the pathogenesis of several diseases including atherosclerosis. MPO is ubiquitous in atherosclerotic lesions and contributes to the initiation and progression of the disease primarily by oxidizing low-density lipoprotein (LDL) particles. MPO is the only human enzyme with the ability to produce hypochlorous acid (HOCl) at physiological chloride concentrations and HOCl-LDL epitopes were shown to be present inside atheromatous lesions making it a physiologically relevant model for the oxidation of LDL. It has been shown that MPO modified LDL is not able to bind to the native LDL receptor and is recognized instead by scavenger receptors on both endothelial cells and macrophages, which can lead to endothelial dysfunction and foam cell formation, respectively; both of which are instrumental in the progression of the disease. Meanwhile, several studies have proposed MPO as a biomarker for cardiovascular diseases where high levels of this enzyme were linked to an increased risk of developing coronary artery disease. Overall, there is sufficient evidence supporting the value of MPO as a crucial player in health and disease. Thus, future research should be directed towards investigating the still unknown processes associated with this enzyme. This may assist in better understanding the pathophysiological role of MPO, as well in the development of therapeutic strategies for protecting against the deleterious effects of MPO in numerous pathologies such as atherosclerosis.

Optimization of methods for the accurate characterization of whole blood neutrophils

Neutrophils are the most abundant circulating leukocyte population with critical roles in immune defense, regulation of innate and adaptive immune systems, and disease pathogenesis. Our progress in understanding precise mechanisms of neutrophil activation, recruitment, and function has been hampered by the lack of optimized and standardized methods for the characterization and phenotyping of this readily activated population. By comparing eight methods of neutrophil characterization, we demonstrate that the level of neutrophil activation and degranulation is associated with specific experimental conditions and the number and type of manipulation steps employed. Staining whole blood at 4 °C and removal of remaining unbound antibodies prior to one-step fixation and red blood cell lysis minimizes neutrophil activation, decreases phenotypic alterations during processing, and prevents nonspecific antibody binding. The effects of anticoagulants used for collection, processing delays, and time and temperature during sample analysis on neutrophil phenotype are addressed. The presented data provide a foundation for higher quality standards of neutrophil characterization improving consistency and reproducibility among studies.

Myeloperoxidase: Growing importance in cancer pathogenesis and potential drug target

Myeloperoxidase is a heme-peroxidase which makes up approximately 5% of the total dry cell weight of neutrophils where it is predominantly found in the primary (azurophilic) granules. Other cell types, such as monocytes and certain macrophage subpopulations also contain myeloperoxidase, but to a much lesser extent. Initially, the function of myeloperoxidase had been mainly associated with its ability as a catalyzer of reactive oxidants that help to clear pathogens. However, over the past years non-canonical functions of myeloperoxidase have been described both in health and disease. Attention has been specially focused on inflammatory diseases, in which an exacerbate infiltration of leukocytes can favor a poorly-controlled production and release of myeloperoxidase and its oxidants. There is compelling evidence that myeloperoxidase derived oxidants contribute to tissue damage and the development and propagation of acute and chronic vascular inflammation. Recently, neutrophils have attracted much attention within the large diversity of innate immune cells that are part of the tumor microenvironment. In particular, neutrophil-derived myeloperoxidase may play an important role in cancer development and progression. This review article aims to provide a comprehensive overview of the roles of myeloperoxidase in the development and progression of cancer. We propose future research approaches and explore prospects of inhibiting myeloperoxidase as a strategy to fight against cancer.

Promoting Oral Mucosal Wound Healing with a Hydrogel Adhesive Based on a Phototriggered S-Nitrosylation Coupling Reaction

The wet and highly dynamic environment of the mouth makes local treatment of oral mucosal diseases challenging. To overcome this, a photo-crosslinking hydrogel adhesive is developed inspired by the success of light-curing techniques in dentistry. The adhesive operates on a fast (within 5 s) phototriggered S-nitrosylation coupling reaction and employs imine anchoring to connect to host tissues. Unlike other often-used clinical agents that adhere weakly and for short durations, this thin, elastic, adhesive, and degradable cyclic o-nitrobenzyl-modified hyaluronic acid gel protects mucosal wounds from disturbance by liquid rinsing, oral movement, and friction for more than 24 h. The results from both rat and pig oral mucosa repair models demonstrate that this new gel adhesive creates a favorable microenvironment for tissue repair and can shorten tissue healing time. This study thus illustrates a therapeutic strategy with the potential to advance the treatment of oral mucosal defects in the clinic.

Molecular and Histological Profiling Reveals an Innate-Shaped Immune Microenvironment in Solitary Juvenile Polyps

INTRODUCTION

Solitary juvenile polyps (JP) are characterized by a benign disease course with low recurrence rate but present with signs of intestinal inflammation. To better understand the underlying pathogenesis, we performed histological and molecular evaluation targeting distinct immune mechanisms.

METHODS

Pediatric patients with JP (n = 12), with treatment-naïve inflammatory bowel disease (IBD; [n = 41]) as inflammatory control, and non-IBD controls (n = 14) were investigated. For a comparative analysis of infiltrating immune cells, a next-generation tissue microarray of biopsies was assembled, immunostained, and scored. Targeted transcriptional profiling was performed using a customized immunology panel.

RESULTS

In JP, a predominant accumulation of neutrophils and eosinophils was observed. RNA expression profiles revealed increased levels of CXCL8, CXCL5, and CCL11 transcripts in JP, indicating an enhanced recruitment of neutrophils and eosinophils. Moreover, messenger RNA levels of the proinflammatory cytokine IL1b and the inflammation-amplifying receptor TREM1 were higher in JP, whereas we could not find signs of a functionally polarized Tcell response in JP when compared with IBD.

DISCUSSION

Patients with JP and patients with treatment-naïve IBD have distinct cell infiltrates during active disease. The ample presence of eosinophils in JP supports neutrophil accumulation, which is responsible for the elevated release of calprotectin. Intriguingly, however, we were not able to identify a functionally polarized T-cell response in JP, which indicates that during the acute onset of inflammation in JP, a potent adaptive immune memory is not established. This may explain the low reoccurrence rate of JP.

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

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

Polysaccaride-rich extract of Caesalpina ferrea stem barks attenuates mice acute inflammation induced by zymosan: Oxidative stress modulation

ETHNOPHARMACOLOGICAL RELEVANCE

Stem barks of Caesalpinia ferrea Mart. Ex Tul. (Caesalpiniaceae), also known as pau-ferro jucá or jucaína, are popularly used to treat contusions, diabetes, rheumatism and other inflammatory conditions in the form of tea, lick or decoction.

OBJECTIVE

To evaluate the effect of the polysaccharide-rich extract obtained from C. ferrea stem barks (PE-Cf) in mice models of acute inflammation induced by zymosan and the involvement of oxidative stress biomarkers.

MATERIALS AND METHODS

Mice were treated with PE-Cf (0.001, 0.01, 0.1, 1 mg/kg) by endovenous route (i.v.) or per oral (p.o.) 30 or 60 min before injection of the inflammatory stimuli zymosan (0.5 mg; intraperitoneal or subcutaneous intraplantar). The inflammatory parameters (edema, nociception, leukocyte migration) and oxidative stress markers (myeloperoxidase-MPO, malondialdehyde-MDA, nitrite, reduced glutathione-GSH, glutathione peroxidase-GPx) were evaluated in the models of paw edema (hidropletysmometry/expressed as ml or area under curve-AUC) and peritonitis (optical microscopy/expressed as n° of cells/mm³ of peritoneal fluid). Statistical analysis was performed by ANOVA, followed by Bonferroni test.

RESULTS

PE-Cf (0.1, 0.01 and 1 mg/kg) dose-dependently inhibited paw edema, showing maximal effect (74%) at 1 mg/kg in the 5th (52 ± 9.6 μl vs. zymosan: 204 ± 3.6 μl). PE-Cf (1 mg/kg) also inhibited by 43% MPO activity in the paw tissues (17 ± 1 vs. zymosan: 30 ± 2.6 U/mg). Besides, 4 h after peritonitis induction, PE-Cf (1 mg/kg) reduced neutrophil migration by 84% (432 ± 45 vs. zymosan: 2651 ± 643 cells/mm³); visceral nociception by 76% (3 ± 0.6 vs. zymosan: 16 ± 4 writhes); nitric oxide by 73% (0.131 ± 0.033 vs. zymosan: 0.578 ± 0.185 NO_2^-/NO_3^-ml); MDA (98 ± 10 vs. zymosan:156 ± 21 U/ml), and increased GSH by 65% (736 ± 65 vs. zymosan: 259 ± 58 μmol/ml) and GPx by 72% (0.037 ± 0.007 vs. zymosan: 0.010 ± 0.005 U/mg protein).

CONCLUSION

The polysaccharide-rich extract of Caesalpinia ferrea stem barks present anti-inflammatory and antioxidant effects in mice models of acute inflammation induced by zymosan.

Myeloperoxidase Controls Bone Turnover by Suppressing Osteoclast Differentiation Through Modulating Reactive Oxygen Species Level

Myeloperoxidase (MPO) is a heme peroxidase that plays an important role in innate immunity for host defense against invading microorganisms by catalyzing hydrogen peroxide (H₂ O₂ )-mediated reactions. Although many reports indicate MPO exerts beneficial or detrimental effects on a variety of inflammatory diseases, little is known with regard to its functional role in bone homeostasis in vivo. Here, our work demonstrates that MPO was transcriptionally downregulated in response to osteoclastogenic stimuli and that exogenous alteration of MPO expression negatively regulated osteoclast (OC) differentiation in vitro. Genetic ablation of Mpo resulted in osteoporotic phenotypes and potentiated bone-resorptive capacity in mice. Mechanistically, accumulation of intracellular H₂ O₂ and reactive oxygen species (ROS) were observed in MPO deficiency, and MPO overexpression suppressed ROS production in mouse OC precursors. Moreover, a ROS scavenger Tempol inhibited the effect of MPO deficiency on OC formation and function as well as on receptor activator of nuclear factor-κB ligand (RANKL)-initiated transduction signal activation including NF-κB, mitogen-activated protein kinases (MAPKs), and Akt, indicating the increased ROS caused by MPO deficiency contributes to osteoclastogenesis. Taken together, our data demonstrate that MPO has a protective role in bone turnover by limiting osteoclastogenesis and bone resorption physiologically through modulating intracellular H₂ O₂ level. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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

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

Hyper-truncated Asn355- and Asn391-glycans modulate the activity of neutrophil granule myeloperoxidase

Myeloperoxidase (MPO) plays essential roles in neutrophil-mediated immunity via the generation of reactive oxidation products. Complex carbohydrates decorate MPO at discrete sites, but their functional relevance remains elusive. To this end, we have characterised the structure-biosynthesis-activity relationship of neutrophil MPO (nMPO). Mass spectrometry demonstrated that nMPO carries both characteristic under-processed and hyper-truncated glycans. Occlusion of the Asn355/Asn391-glycosylation sites and the Asn323-/Asn483-glycans, located in the MPO dimerisation zone, was found to affect the local glycan processing, thereby providing a molecular basis of the site-specific nMPO glycosylation. Native mass spectrometry, mass photometry and glycopeptide profiling revealed significant molecular complexity of diprotomeric nMPO arising from heterogeneous glycosylation, oxidation, chlorination and polypeptide truncation variants and a previously unreported low-abundance monoprotomer. Longitudinal profiling of maturing, mature, granule-separated and pathogen-stimulated neutrophils demonstrated that nMPO is dynamically expressed during granulopoiesis, unevenly distributed across granules and degranulated upon activation. We also show that proMPO-to-MPO maturation occurs during early/mid-stage granulopoiesis. While similar global MPO glycosylation was observed across conditions, the conserved Asn355-/Asn391-sites displayed elevated glycan hyper-truncation, which correlated with higher enzyme activities of MPO in distinct granule populations. Enzymatic trimming of the Asn355-/Asn391-glycans recapitulated the activity gain and showed that nMPO carrying hyper-truncated glycans at these positions exhibits increased thermal stability, polypeptide accessibility and ceruloplasmin-mediated inhibition potential relative to native nMPO. Finally, molecular modelling revealed that hyper-truncated Asn355-glycans positioned in the MPO-ceruloplasmin interface are critical for uninterrupted inhibition. Here, through an innovative and comprehensive approach, we report novel functional roles of MPO glycans, providing new insight into neutrophil-mediated immunity.

Looking Back at the Early Stages of Redox Biology

The beginnings of redox biology are recalled with special emphasis on formation, metabolism and function of reactive oxygen and nitrogen species in mammalian systems. The review covers the early history of heme peroxidases and the metabolism of hydrogen peroxide, the discovery of selenium as integral part of glutathione peroxidases, which expanded the scope of the field to other hydroperoxides including lipid hydroperoxides, the discovery of superoxide dismutases and superoxide radicals in biological systems and their role in host defense, tissue damage, metabolic regulation and signaling, the identification of the endothelial-derived relaxing factor as the nitrogen monoxide radical (more commonly named nitric oxide) and its physiological and pathological implications. The article highlights the perception of hydrogen peroxide and other hydroperoxides as signaling molecules, which marks the beginning of the flourishing fields of redox regulation and redox signaling. Final comments describe the development of the redox language. In the 18th and 19th century, it was highly individualized and hard to translate into modern terminology. In the 20th century, the redox language co-developed with the chemical terminology and became clearer. More recently, the introduction and inflationary use of poorly defined terms has unfortunately impaired the understanding of redox events in biological systems.

Activation of angiotensin II type-2 receptor protects against cigarette smoke-induced COPD

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally. Cumulative evidence has implicated renin-angiotensin system (RAS) in the pathogenesis of COPD. This study aimed to investigate potential protective effects of angiotensin II type-2 receptor (AT2R) activation in cigarette smoke (CS)-induced COPD models. Compound 21 (C21), a selective and potent non-peptide small molecule AT2R agonist, was evaluated for anti-inflammatory, anti-oxidative and anti-remodeling activities in a two-week (acute) and an eight-week (chronic) CS-induced COPD models. C21 inhibited CS-induced increases in macrophage and neutrophil counts, pro-inflammatory cytokines and oxidative damage markers in bronchoalveolar lavage (BAL) fluid, and TGF-β1 in lung tissues, from COPD models. C21 restored phosphatase activities and reduced phospho-p38 MAPK, phospho-ERK and p65 subunit of NF-κB levels in CS-exposed lung tissues. C21 also suppressed CS-induced increases in α-Sma, Mmp9, Mmp12 and hydroxyproline levels in lung tissues, and neutrophil elastase activity in BAL fluid. C21 modulated RAS in CS-exposed lungs by downregulating Ang II but upregulating Ang-(1–7) and Mas receptor levels. C21 prevented CS-induced emphysema and improved lung functions in chronic COPD model. We report here for the first time the protective effects of AT2R agonist C21 against CS-induced COPD, and provide strong evidence for further development of AT2R agonist for the treatment of COPD.

Nectandra cuspidata fraction and the isolated polyphenols protect fibroblasts and hairless mice skin from UVB-induced inflammation and oxidative stress

Excessive exposure to UVB radiation can lead to oxidative and inflammatory damage that compromises the cutaneous integrity. The application on the skin of photochemoprotective products is considered a relevant approach for the prevention of oxidative damage. In this study the in vitro and in vivo photochemoprotective effects of antioxidant plant materials obtained from the leaves of Nectandra cuspidata Nees following UVB irradiation were evaluated. The cytoprotective effect, reactive oxygen species (ROS) production and lipid peroxidation (LPO) were assessed in L-929 fibroblasts treated with the ethyl acetate fraction (EAF) or isolated compounds (epicatechin, isovitexin and vitexin) before or after irradiation with UVB (500 mJ/cm²). EAF substantially reduced the dead of cells and inhibited the UVB-induced ROS production and LPO in both treatments, compared with the irradiated untreated fibroblasts, presenting effects similar or better than pure compounds. The in vivo photochemoprotective effects of a topical emulsion containing 1% EAF (F2) were evaluated in hairless mice exposed to UVB. F2 improved all evaluated parameters in the skin of animals, inhibited ROS production, increased antioxidant defenses by decreasing reduced glutathione (GSH) and catalase depletion, reduced the activities of metalloproteinases (MMP-2 and MMP-9) and myeloperoxidase, decreased epidermal thickness and skin edema, and inhibited the appearance of sunburn cells as well as the recruitment of neutrophils and mast cell inflammatory infiltrates. These findings show that EAF presents high photochemoprotective effects, and that a topical formulation containing it may have potential for skin care.

High density of CD66b in primary high-grade ovarian cancer independently predicts response to chemotherapy

PURPOSE

Ovarian carcinoma (OC) is the most lethal female genital cancer. After a primary curative surgical approach followed by chemotherapy, a fraction of the patients recur with chemoresistant disease. Data indicate a favorable therapeutic effect of tumor-infiltrating neutrophils (TIN) in OC. Our aim was to investigate the prognostic role of CD66b expression, corresponding to neutrophilic infiltration for recurrence-free survival (RFS) and overall survival (OS) in patients with OC.

METHODS

A collective of 47 primary serous ovarian carcinoma and their matching recurrences were processed and stained with CD66b using immunohistochemistry. Tumors from patients with RFS of more than 6 months were defined as chemosensitive. Statistical analysis of CD66b expression was performed to assess the clinical endpoints.

RESULTS

High density of CD66b expressing neutrophils in primary carcinoma was associated with chemosensitivity (p = 0.014) and longer RFS (p = 0.001). Univariate analysis identified high density of CD66b expressing neutrophils as a predictor for favorable RFS (HR 0.41, 95% CI 0.22-0.76, p < 0.005). Residual disease > 2 cm (HR 3.67, 95% CI 1.62-8.31, p < 0.002) and higher number of chemotherapy cycles (HR 1.28, 95% CI 1.05-1.55, p < 0.013) were associated with worse RFS. Multivariate analysis showed that high density of CD66b expressing neutrophils (HR 0.22, 95% CI 0.10-0.48, p < 0.001) and residual disease > 2 cm (HR 3.69, 95% CI 1.43-9.53, p < 0.007) were independent predictors of RFS but had no impact on OS.

CONCLUSION

High CD66b neutrophil density in primary high-grade OC predicts good response to initial chemotherapy and longer recurrence-free survival independent of known risk factors.

Reduced inflammatory and phagocytotic responses following normobaric hypoxia exercise despite evidence supporting greater immune challenge

This study examined changes in immune markers following sustained treadmill exercise in normobaric hypoxia. Ten subjects performed 1 h of treadmill exercise (65% maximal oxygen uptake) under normoxic (NORM: fraction of inspired oxygen (F_IO₂) = 20.9%) and normobaric hypoxic (HYP: F_IO₂ = 13.5%) conditions. Blood samples, collected before, after (Post), 1 h after (1-Post), and 4 h after (4-Post) exercise, were assayed for plasma cytokines (interleukin (IL)-1RA/IL-1β/IL-8/tumor necrosis factor alpha (TNF-α)) and markers of leukocyte activation (macrophage inflammatory protein-1β (MIP-1β)/myeloperoxidase (MPO)/soluble intercellular adhesion molecule-1 (sICAM-1)) using ELISA. Pro- to anti-inflammatory cytokine ratios (TNF-α/IL-1RA; IL-1β/IL-1RA) were calculated. Peripheral blood mononuclear cells (PBMC) were analyzed for changes in inflammatory status (phosphorylated nuclear factor kappa B/nuclear factor kappa B) using Western Blot. Data were analyzed with 2-way (condition × time) repeated-measure ANOVAs with Newman-Keuls post hoc tests. MIP-1β was elevated at 1-Post HYP exercise (+11%; p < 0.01) but did not increase following exercise in NORM. TNF-α/IL-1RA and IL-1β/IL-1RA ratios were both reduced (p < 0.05) following HYP exercise (-16% and -52%, respectively, at 1-Post and -7% and -32%, respectively, at 4-Post). IL-8 increased (p < 0.05) at Post and 1-Post NORM (+33% and +57%, respectively) and HYP (+60% and +83%, respectively) exercise, but was not different between conditions (p > 0.05). Interestingly, plasma sICAM-1 did not increase (p > 0.05) following NORM exercise but was increased (p < 0.05) at Post (+17%), 1-Post (+16%), and 4-Post (+14%) HYP exercise. There was also a delayed peak in plasma MPO concentrations following HYP exercise and PBMC exhibited a reduced (p < 0.05) inflammatory capacity at Post (-38%) and 1-Post (-49%). Novelty Following HYP exercise, participants exhibited (i) circulatory bias towards anti-inflammation; (ii) elevated sICAM; (iii) delayed peak in plasma MPO; and (iv) diminished inflammatory response in PBMC. Collectively, these data suggest immunosuppression. This is undesirable, given that elevated MIP-1β (reported here) and elevated intestinal fatty acid binding protein (reported previously) both suggest higher lipopolysaccharide concentrations following HYP exercise.

Bioguided Fractionation, and Antioxidant, Antiproliferative, and Anti-Inflammatory Activity of Annona cacans Warm

This study evaluated to determine the phenolic and flavonoids contents, and antioxidant, anti-inflammatory, and antiproliferative activity of the hydromethanolic extracts of the leaves, pulp, and seeds of Annona cacans. The isolation and structural identification of the constituent acetogenin, phenolic acid, and flavonoids were also reported. Antioxidant capacity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), ethylbenzothiazoline-6-sulfonic acid (ABTS), and β-carotene/linoleic acid methods. Cell proliferation was determined by spectrophotometric quantification of the cellular protein content using a sulforhodamine B assay. Anti-inflammatory activity was evaluated in paw edema model, to myeloperoxidase (MPO) activity induced by carrageenan in mice. Fractionation resulted in the isolation of one acetogenin (annoreticuin-9-one), two flavonoids (quercetin-3-O-β-glucoside-6-O-α-rhamnoside and kaempferol-3-O-β-glucoside), and one phenolic acid (p-coumaric acid). The pulp extract presented potent antioxidant activities by the DPPH (IC₅₀ = 44.08 μg/mL) and ABTS (IC₅₀ = 39.32 μg/mL) methods, as well as high contents of phenols (618.95 mg GA/g) and flavonoids (477.35 mg QE/g). The bioguided fractionation demonstrated that the ethyl acetate fraction of the pulp extract and annoreticuin-9-one showed potent antiproliferative activity against ovarian cancer (GI₅₀ = 6.4 μg/mL). The anti-inflammatory activity demonstrated significant inhibition of edema compared to the control group in 2 and 4 h; in addition, the extracts inhibited the increase in MPO activity after 6 h, when compared to the DEX and control groups. For the first time, this study demonstrated antioxidant, anti-inflammatory, and antiproliferative activity, as well as compounds isolated, suggesting that A. cacans could also be potential sources for prevention of cancer and other diseases associated with oxidative stress.

Human myeloperoxidase (hMPO) is expressed in neurons in the substantia nigra in Parkinson's disease and in the hMPO-α-synuclein-A53T mouse model, correlating with increased nitration and aggregation of α-synuclein and exacerbation of motor impairment

α-Synuclein (αSyn) is central to the neuropathology of Parkinson's disease (PD) due to its propensity for misfolding and aggregation into neurotoxic oligomers. Nitration/oxidation of αSyn leads to dityrosine crosslinking and aggregation. Myeloperoxidase (MPO) is an oxidant-generating enzyme implicated in neurodegenerative diseases. In the present work we have examined the impact of MPO in PD through analysis of postmortem PD brain and in a novel animal model in which we crossed a transgenic mouse expressing the human MPO (hMPO) gene to a mouse expressing human αSyn-A53T mutant (A53T) (hMPO-A53T). Surprisingly, our results show that in PD substantia nigra, the hMPO gene is expressed in neurons containing aggregates of nitrated αSyn as well as MPO-generated HOCl-modified epitopes. In our hMPO-A53T mouse model, we also saw hMPO expression in neurons but not mouse MPO. In the mouse model, hMPO was expressed in neurons colocalizing with nitrated αSyn, carbamylated lysine, nitrotyrosine, as well as HOCl-modified epitopes/proteins. RNAscope in situ hybridization confirmed hMPO mRNA expression in neurons. Interestingly, the hMPO protein expressed in hMPO-A53T brain is primarily the precursor proMPO, which enters the secretory pathway potentially resulting in interneuronal transmission of MPO and oxidative species. Importantly, the hMPO-A53T mouse model, when compared to the A53T model, exhibited significant exacerbation of motor impairment on rotating rods, balance beams, and wire hang tests. Further, hMPO expression in the A53T model resulted in earlier onset of end stage paralysis. Interestingly, there was a high concentration of αSyn aggregates in the stratum lacunosum moleculare of hippocampal CA2 region, which has been associated in humans with accumulation of αSyn pathology and neural atrophy in dementia with Lewy bodies. This accumulation of αSyn aggregates in CA2 was associated with markers of endoplasmic reticulum (ER) stress and the unfolded protein response with expression of activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), MPO, and cleaved caspase-3. Together these findings suggest that MPO plays an important role in nitrative and oxidative damage that contributes to αSyn pathology in synucleinopathies.

Infiltration by myeloperoxidase-positive neutrophils is an independent prognostic factor in breast cancer

PURPOSE

Myeloperoxidase (MPO) is an enzyme secreted by neutrophil granulocytes as a result of phagocytosis during inflammation. In colorectal cancer, tumour infiltration by MPO expressing cells has been shown to be independently associated with a favourable prognosis. In this study, we explored the role of MPO-positive cell infiltration and its prognostic significance in invasive breast cancer.

METHODS

We performed immunohistochemical staining for MPO on multiple tissue microarrays comprising a total of 928 human breast cancer samples with detailed clinical-pathological annotation and outcome data.

RESULTS

MPO-positive cell infiltration (≥ 5 cells/tissue punch) was found in 150 (16%) of the 928 evaluable breast cancer cases. In univariate survival analyses, infiltration by MPO-positive cells was associated with a significantly better overall survival (p < 0.001). In subset univariate analyses, the infiltration by MPO-positive cells was associated with significantly better overall survival in the Luminal B/HER2-negative subtype (p = 0.005), the HER2 enriched subtype (p = 0.011), and the Triple Negative subtype (p < 0.001). In multivariate analysis, MPO expression proved to be an independent prognostic factor for improved overall survival (p < 0.001).

CONCLUSIONS

This is the first study to show that infiltration of MPO-positive cells is an independent prognostic biomarker for improved overall survival in human breast cancer.

Myeloperoxidase - A bridge linking inflammation and oxidative stress with cardiovascular disease

Myeloperoxidase (MPO) is a member of the superfamily of heme peroxidases that is mainly expressed in neutrophils and monocytes. MPO-derived reactive species play a key role in neutrophil antimicrobial activity and human defense against various pathogens primarily by participating in phagocytosis. Elevated MPO levels in circulation are associated with inflammation and increased oxidative stress. Multiple lines of evidence suggest an association between MPO and cardiovascular disease (CVD) including coronary artery disease, congestive heart failure, arterial hypertension, pulmonary arterial hypertension, peripheral arterial disease, myocardial ischemia/reperfusion-related injury, stroke, cardiac arrhythmia and venous thrombosis. Elevated MPO levels are associated with a poor prognosis including increased risk for overall and CVD-related mortality. Elevated MPO may signify an increased risk for CVD for at least 2 reasons. First, low-grade inflammation and increased oxidative stress coexist with many metabolic abnormalities and comorbidities and consequently an elevated MPO level may represent an increased cardiometabolic risk in general. Second, MPO produces a large number of highly reactive species which can attack, destroy or modify the function of every known cellular component. The most common MPO actions relevant to CVD are generation of dysfunctional lipoproteins with an increased atherogenicity potential, reduced NO availability, endothelial dysfunction, impaired vasoreactivity and atherosclerotic plaque instability. These actions strongly suggest that MPO is directly involved in the pathophysiology of CVD. In this regard MPO may be seen as a mediator or an instrument through which inflammation promotes CVD at molecular and cellular level. Clinical value of MPO therapeutic inhibition remains to be tested.

Neutralization of macrophage migration inhibitory factor improves host survival after Clostridium difficile infection

Clostridium difficile is an important cause of nosocomial diarrhea in the western world. Toxins (A, B, and binary toxins) generated by C. difficile bacteria damage intestinal epithelial cells. Hallmarks of host response to C. difficile infection (CDI) include upregulation of inflammatory mediators and tissue infiltration by immune cells. Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine that is known to enhance the host immune response to infectious pathogens. Additionally, MIF can adversely impact host survival to numerous infections. The role of MIF in the pathogenesis of CDI remains poorly understood. Here, we show that patients with CDI had significantly higher circulating MIF compared to patients who had diarrhea but tested negative for C. difficile (non-CDI controls). Similarly, in a mouse model, C. difficile challenge significantly increased levels of plasma and tissue MIF. Antibody-mediated depletion of MIF decreased C. difficile-induced inflammatory responses, clinical disease, and mortality. Together, these results uncover a potential role for MIF in exacerbating CDI and suggest that use of anti-MIF antibodies may represent a therapeutic strategy to curb host inflammatory responses and improve disease outcomes in CDI.