The development of myeloperoxidase inhibitors

Evaluating the protective effect of dapsone on experimental osteoarthritis models induced by MIA in male rats

OBJECTIVES

Osteoarthritis, a degenerative condition that results in significant morbidity, is typically managed with treatments aimed at symptom relief rather than addressing the underlying degeneration. Dapsone, recognized for its anti-inflammatory, antioxidant, antiexcitotoxic, and antiapoptotic properties, has demonstrated promising effects in various neurodegenerative diseases. This study explores the potential of dapsone to mitigate articular destruction, inflammation, and pain in rat models of osteoarthritis.

METHODS

Osteoarthritis was induced in rats by injecting MIA into the right knee joint. Dapsone was then administered intraperitoneally at 5, 10, or 20 mg/kg every 2 days for 2 weeks. Behavioural tests were done on days 0, 7, and 14. On day 14, the articular cartilage was histologically analysed using H&E staining. Serum levels of NF-kB, IL-1β, and TNF-α were evaluated by ELISA.

RESULTS

Dapsone effectively reduces pain, inflammation, and articular cartilage damage in osteoarthritis. Specifically, it improves mechanical allodynia and thermal hyperalgesia, reduces inflammatory markers (TNF-α, IL-1β, and NF-κB), and protects against cartilage destruction and chondrocyte loss, with the most significant effects at 20 mg/kg.

CONCLUSIONS

Dapsone effectively prevents pain, inflammation, and cartilage damage in osteoarthritis rats, suggesting its potential as a therapeutic option for managing osteoarthritis.

Myeloperoxidase as a Promising Therapeutic Target after Myocardial Infarction

Coronary artery disease (CAD) and myocardial infarction (MI) remain leading causes of death and disability worldwide. CAD begins with the formation of atherosclerotic plaques within the intimal layer of the coronary arteries, a process driven by persistent arterial inflammation and oxidation. Myeloperoxidase (MPO), a mammalian haem peroxidase enzyme primarily expressed within neutrophils and monocytes, has been increasingly recognised as a key pro-inflammatory and oxidative enzyme promoting the development of vulnerable coronary atherosclerotic plaques that are prone to rupture, and can precipitate a MI. Mounting evidence also implicates a pathogenic role for MPO in the inflammatory process that follows a MI, which is characterised by the rapid infiltration of activated neutrophils into the damaged myocardium and the release of MPO. Excessive and persistent cardiac inflammation impairs normal cardiac healing post-MI, resulting in adverse cardiac outcomes and poorer long-term cardiac function, and eventually heart failure. This review summarises the evidence for MPO as a significant oxidative enzyme contributing to the inappropriate inflammatory responses driving the progression of CAD and poor cardiac healing after a MI. It also details the proposed mechanisms underlying MPO's pathogenic actions and explores MPO as a novel therapeutic target for the treatment of unstable CAD and cardiac damage post-MI.

Increased levels of advanced oxidation protein products (AOPPs) were associated with nociceptive behavior and clinical scores in an experimental progressive autoimmune encephalomyelitis model (PMS-EAE)

Multiple sclerosis (MS) is a neurodegenerative disease that affects the central nervous system (CNS) generating neuropathic pain and anxiety. Primary progressive MS (PPMS) is the most disabling clinical form, and the patients present an intense neurodegenerative process. In this context, the advanced oxidation protein products (AOPPs) are oxidized compounds and their accumulation in plasma has been related to clinical disability in MS patients. However, the involvement of AOPPs in neuropathic pain- and anxiety-like symptoms was not previously evaluated. To assess this, female mice C57BL/6J were used to induce progressive experimental autoimmune encephalomyelitis (PMS-EAE). Clinical score, weight, strength of plantar pressure, rotarod test, mechanical allodynia, and cold hypersensitivity were evaluated before induction (baseline) and on days 7th, 10th, and 14th post-immunization. We assessed nest building, open field, and elevated plus-maze tests 13 days post-immunization. Animals were killed at 14 days post-immunization; then, AOPPs levels, NADPH oxidase, and myeloperoxidase (MPO) activity were measured in the prefrontal cortex, hippocampus, and spinal cord samples. The clinical score increased 14th post-immunization without changes in weight and mobility. Reduced paw strength, mechanical allodynia, and cold allodynia increased in the PMS-EAE animals. PMS-EAE mice showed spontaneous nociception and anxiety-like behavior. AOPPs concentration, NADPH oxidase, and MPO activity increase in CNS structures. Multivariate analyses indicated that the rise of AOPPs levels, NADPH oxidase, and MPO activity influenced the clinical score and cold allodynia. Thus, we indicated the association between non-stimuli painful perception, anxiety-like, and CNS oxidative damage in the PMS-EAE model.

Cirsimaritin Alleviates Dextran Sodium Sulfate-Induced Acute Colitis in Experimental Animals: A Therapeutic Approach for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic disease that affects the entire digestive tract. IBD can be classified as ulcerative colitis or Crohn's disease. The key symptoms of IBD include the emergence of abscesses or pustules, pronounced abdominal discomfort, diarrhea, fistulas, and intestinal narrowing, all of which can greatly affect a patient's daily well-being. Several factors, including bacterial infections, immune response irregularities, and changes in the intestinal milieu, can contribute to the onset of IBD. The aim of this study was investigating the role of cirsimaritin in reducing the severity of colitis in animal model. To induce colitis in laboratory Swiss albino mice, a 4% dextran sulfate sodium (DSS) concoction was provided in their hydration source for a duration of six days. Before the onset of colitis, mice were treated with cirsimaritin (10 mg/kg) once daily to evaluate its potential treatment effects against DSS-induced inflammation. The results showed that 10 mg/kg of cirsimaritin decreased colitis severity (P<0.05). Moreover, cirsimaritin successfully reversed the detrimental effects induced by DSS, including weight reduction, colon truncation, tissue-related damage, increased levels of inflammatory cells in the affected region, and secretion of proinflammatory cytokines. Our findings suggest that cirsimaritin can effectively alleviate acute colitis triggered by DSS.

Effects of myeloperoxidase on inflammatory responses with hypoxia in Citrobacter rodentium-infectious mice

PURPOSE

Myeloperoxidase (MPO) has been identified as a mediator in various inflammatory diseases. Bacterial infection of the intestine and hypoxia can both lead to inflammatory responses, but the role of MPO in these phenomena remains unclear.

METHODS

By building the MPO-/- mice, we evaluated relevant inflammatory factors and tissue damage in mice with intestinal Citrobacter rodentium infection and hypoxia. The body weight and excreted microorganisms were monitored. Intestinal tissues were collected 7 days after bacterial infection under hypoxia to undergo haematoxylin-eosin staining and assess the degree of pathological damage. ELISA assays were performed to quantify the serum levels of TNF-α, IFN-γ, IL-6, and IL-1β inflammatory cytokines. PCR, WB, and IF assays were conducted to determine the expression of chemokines MCP1, MIP2, and KC in the colon and spleen.

RESULTS

The C. rodentium infection and hypoxia caused weight loss, intestinal colitis, and splenic inflammatory cells active proliferation in wild-type mice. MPO deficiency alleviated this phenomenon. MPO-/- mice also displayed a significant decline in bacteria clearing ability. The level of TNF-α in the serum and spleen was both lower in MPO-/- hypoxia C. rodentium-infected mice than that in wild-type mice. The chemokines expression levels of MIP2, KC, and MCP1 in the spleen and colon of each bacterial infected group were significantly increased (p < .05), while in hypoxia, the factors in the spleen and colon were decreased (p < .05). MPO deficiency was found to lower the levels of these chemokines compared with wild-type mice.

CONCLUSION

MPO plays an important role of the inflammatory responses in infectious enteritis and hypoxia in mice, and the loss of MPO may greatly reduce the body's inflammatory responses to fight diseases.

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.

An eosinophil peroxidase activity assay accurately predicts eosinophilic chronic rhinosinusitis

BACKGROUND

A definitive diagnosis of eosinophilic chronic rhinosinusitis (eCRS) requires invasive surgical tissue sampling and histologic enumeration of intact eosinophils. Eosinophil peroxidase (EPX) is an accurate biomarker of sinonasal tissue eosinophilia in CRS regardless of polyp status. A less invasive and rapid method that accurately identifies tissue eosinophilia would be of great benefit to patients.

OBJECTIVE

We sought to evaluate a new clinical tool that uses a nasal swab and colorimetric EPX activity assay to predict a diagnosis of eCRS.

METHODS

A prospective, observational cohort study was conducted using nasal swabs and sinonasal tissue biopsies obtained from patients with CRS electing endoscopic sinus surgery. Patients were classified as non-eCRS (n = 19) and eCRS (n = 35) on the basis of pathologically determined eosinophil counts of less than 10 or greater than or equal to 10 eosinophils/HPF, respectively. Swab-deposited EPX activity was measured and compared with tissue eosinophil counts, EPX levels, and CRS-specific disease metrics.

RESULTS

EPX activity was significantly increased in patients with eCRS than in patients without eCRS (P < .0001). With a relative absorbance unit cutoff value of greater than or equal to 0.80, the assay demonstrated high sensitivity (85.7%) and moderate specificity (79.0%) for confirming eCRS. Spearman correlations between EPX activity and tissue eosinophil counts (rs = 0.424), EPX levels (rs = 0.503), and Lund-Kennedy endoscopy scores (rs = 0.440) in eCRS were significant (P < .05).

CONCLUSIONS

This investigation evaluates a nasal swab sampling method and EPX activity assay that accurately confirms eCRS. This method could potentially address the unmet need to identify sinonasal tissue eosinophilia at the point-of-care, as well as to longitudinally monitor eosinophil activity and treatment response.

Novel Strategies in the Early Detection and Treatment of Endothelial Cell-Specific Mitochondrial Dysfunction in Coronary Artery Disease

Although elevated cholesterol and other recognised cardiovascular risk factors are important in the development of coronary artery disease (CAD) and heart attack, the susceptibility of humans to this fatal process is distinct from other animals. Mitochondrial dysfunction of cells in the arterial wall, particularly the endothelium, has been strongly implicated in the pathogenesis of CAD. In this manuscript, we review the established evidence and mechanisms in detail and explore the potential opportunities arising from analysing mitochondrial function in patient-derived cells such as endothelial colony-forming cells easily cultured from venous blood. We discuss how emerging technology and knowledge may allow us to measure mitochondrial dysfunction as a potential biomarker for diagnosis and risk management. We also discuss the "pros and cons" of animal models of atherosclerosis, and how patient-derived cell models may provide opportunities to develop novel therapies relevant for humans. Finally, we review several targets that potentially alleviate mitochondrial dysfunction working both via direct and indirect mechanisms and evaluate the effect of several classes of compounds in the cardiovascular context.

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

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

The Role of Myeloperoxidase in Clozapine-Induced Inflammation: A Mechanistic Update for Idiosyncratic Drug-Induced Agranulocytosis

The risk of idiosyncratic drug-induced agranulocytosis (IDIAG) markedly constrains the use of clozapine, a neuroleptic with unparalleled efficacy. Most clozapine patients experience an early inflammatory response, likely a necessary step in IDIAG onset. However, most patients do not progress to IDIAG, presumably because of the requirement of specific human leukocyte antigen (HLA) haplotypes, T cell receptors, and other unknown factors. We established that clozapine activates inflammasomes and that myeloperoxidase bioactivation of clozapine generates neoantigens, but the connection between these early mechanistic events remained unknown and, thus, was the aim of this work. We found that the myeloperoxidase inhibitor PF-1355 attenuated myeloperoxidase activity in phorbol myristate acetate (PMA)-differentiated THP-1 macrophages, and it also attenuated clozapine-induced release of inflammatory mediators (e.g., IL-1β, CXCL1, and C-reactive protein). In vivo, pretreatment of Sprague Dawley rats with PF-1355 significantly attenuated clozapine-induced increases in neutrophil mobilization from the bone marrow to the blood and spleen, as determined using differential blood counts and flow cytometry. Moreover, the clozapine-triggered release of inflammatory mediators (e.g., IL-1β, calprotectin, CXCL1, and α-1-acid glycoprotein) from the liver, spleen, and bone marrow was dampened by myeloperoxidase inhibition. These data support the working hypothesis that oxidation of clozapine to a reactive metabolite by myeloperoxidase is critical for induction of the inflammatory response to clozapine. Ultimately, a better mechanistic understanding of the early events involved in the immune response to clozapine may elucidate ways to prevent IDIAG, enabling safer, more frequent therapeutic use of this and potentially other highly efficacious drugs.

A comprehensive insight into the anti-inflammatory properties of dapsone

The 4,4'-diaminodiphenyl sulfone (DDS), also known as dapsone, is traditionally used as a potent anti-bacterial agent in clinical management of leprosy. For decades, dapsone has been among the first-line medications used in multidrug treatment of leprosy recommended by the World Health Organization (WHO). Shortly after dapsone's discovery as an antibiotic in 1937, the dual function of dapsone (anti-microbial and anti-inflammatory) was elucidated. Dapsone exerts its anti-bacterial effects by inhibiting dihydrofolic acid synthesis, leading to inhibition of bacterial growth, while its anti-inflammatory properties are triggered by inhibiting reactive oxygen species (ROS) production, reducing the effect of eosinophil peroxidase on mast cells and downregulating neutrophil-mediated inflammatory responses. Among the leading mechanisms associated with its anti-microbial/anti-protozoal effects, dapsone clearly has multiple antioxidant, anti-inflammatory, and anti-apoptotic functions. In this regard, it has been described in treating a wide variety of inflammatory and infectious skin conditions. Previous reports have explored different molecular targets for dapsone and provided insight into the anti-inflammatory mechanism of dapsone. This article reviews several basic, experimental, and clinical approaches on anti-inflammatory effect of dapsone.

Myeloperoxidase: Regulation of Neutrophil Function and Target for Therapy

Neutrophils, the most abundant white blood cells in humans, are critical for host defense against invading pathogens. Equipped with an array of antimicrobial molecules, neutrophils can eradicate bacteria and clear debris. Among the microbicide proteins is the heme protein myeloperoxidase (MPO), stored in the azurophilic granules, and catalyzes the formation of the chlorinating oxidant HOCl and other oxidants (HOSCN and HOBr). MPO is generally associated with killing trapped bacteria and inflicting collateral tissue damage to the host. However, the characterization of non-enzymatic functions of MPO suggests additional roles for this protein. Indeed, evolving evidence indicates that MPO can directly modulate the function and fate of neutrophils, thereby shaping immunity. These actions include MPO orchestration of neutrophil trafficking, activation, phagocytosis, lifespan, formation of extracellular traps, and MPO-triggered autoimmunity. This review scrutinizes the multifaceted roles of MPO in immunity, focusing on neutrophil-mediated host defense, tissue damage, repair, and autoimmunity. We also discuss novel therapeutic approaches to target MPO activity, expression, or MPO signaling for the treatment of inflammatory and autoimmune diseases.

Sanguinarine Enhances the Integrity of the Blood-Milk Barrier and Inhibits Oxidative Stress in Lipopolysaccharide-Stimulated Mastitis

Mastitis is a common clinical disease which threatens the welfare and health of dairy cows and causes huge economic losses. Sanguinarine (SG) is a plant-derived alkaloid which has many biological functions, including antibacterial and antioxidant properties. The present study attempted to evaluate the effect of SG on lipopolysaccharide (LPS)-induced oxidative stress reactions and explore its potential mechanisms. The expression profile of SG was analyzed by network pharmacology, and it was found that differentially expressed genes were mainly involved in the Wnt signaling pathway and oxidative stress through GO and KEGG enrichment. In in vitro experiments, the dosage of SG was non-toxic to mouse mammary epithelial cells (mMECs) (p > 0.05). SG not only inhibited the increase in ROS induced by LPS, but also enhanced the activity of antioxidant enzymes (p < 0.05). Moreover, the results of the in vivo experiments showed that SG alleviated LPS-induced inflammatory damage of mouse mammary glands and enhanced the integrity of the blood-milk barrier (p < 0.05). Further studies suggested that SG promoted Nrf2 expression and suppressed the activation of the Wnt signaling pathway (p < 0.05). Conclusively, this study clarified the protective effect of SG on mastitis and provided evidence for new potential mechanisms. SG exerted its antioxidant function through activating Nrf2 and inhibiting the Wnt/β-catenin pathway, repairing the blood-milk barrier.

Chemical fingerprinting, comparative in vitro antioxidant properties, and biochemical effects of ginger and bitterleaf infusion

Botanicals with remarkable pharmacological properties include Zingiber officinale Roscoe [Zingiberaceae] (ginger) and Gymnanthemum amygdalinum (Delie) Sch. Bip [Asteraceae] (bitterleaf). The plants are frequently used as teas and decoctions, and have been studied in the treatment of various illnesses. Thus, this study investigated the in vitro antioxidant activities and chemical fingerprints of ginger and bitter leaf infusions separately and as a combination. In addition, we assessed the effects of the tea infusions on rat liver and kidney indices. The findings from this study showed that the bitterleaf infusion had the highest phenolic content (21.77 ± 3.140 µg gallic acid equivalent/mg) in comparison with that of ginger (15.17 ± 1.50 µg gallic acid equivalent/mg) and their combination (8.81 ± 0.48 µg gallic acid equivalent/mg). The ginger infusion had the highest flavonoid content (547.15 ± 1.17 µg quercetin equivalent/mg), which was preceded by bitterleaf (473.02 ± 10.48 µg quercetin equivalent/mg) and the ginger and bitterleaf infusion (415.08 ± 4.15 µg quercetin equivalent/mg). Furthermore, our results showed that the tea infusions had no significant effect on the liver function indices (ALT and AST) compared to the control. In contrast, the rat plasma urea significantly increased in the groups given bitterleaf and a combination of ginger and bitterleaf infusions, while creatinine significantly decreased in the group that received the combined form of the infusion. The GC-MS analysis of ginger and bitterleaf infusions revealed that n-hexadecanoic acid, oleic acid, and ergosterol were most abundant in the bitterleaf infusion. At the same time, gingerol, 2-butanone, and 4-(4-hydroxy-3-methoxyphenyl) were the most abundant in the ginger infusion. Together, the findings are not only evidence in support of the medicinal value of these plants but also reinforce their prospects as nutriceuticals.

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.

Hypochlorous Acid Chemistry in Mammalian Cells—Influence on Infection and Role in Various Pathologies

This review discusses the formation of hypochlorous acid HOCl and the role of reactive chlorinated species (RCS), which are catalysed by the enzyme myeloperoxidase MPO, mainly located in leukocytes and which in turn contribute to cellular oxidative stress. The reactions of RCS with various organic molecules such as amines, amino acids, proteins, lipids, carbohydrates, nucleic acids, and DNA are described, and an attempt is made to explain the chemical mechanisms of the formation of the various chlorinated derivatives and the data available so far on the effects of MPO, RCS and halogenative stress. Their presence in numerous pathologies such as atherosclerosis, arthritis, neurological and renal diseases, diabetes, and obesity is reviewed and were found to be a feature of debilitating diseases.

Discovery of AZD4831, a Mechanism-Based Irreversible Inhibitor of Myeloperoxidase, As a Potential Treatment for Heart Failure with Preserved Ejection Fraction

Myeloperoxidase is a promising therapeutic target for treatment of patients suffering from heart failure with preserved ejection fraction (HFpEF). We aimed to discover a covalent myeloperoxidase inhibitor with high selectivity for myeloperoxidase over thyroid peroxidase, limited penetration of the blood-brain barrier, and pharmacokinetics suitable for once-daily oral administration at low dose. Structure-activity relationship, biophysical, and structural studies led to prioritization of four compounds for in-depth safety and pharmacokinetic studies in animal models. One compound (AZD4831) progressed to clinical studies on grounds of high potency (IC₅₀, 1.5 nM in vitro) and selectivity (>450-fold vs thyroid peroxidase in vitro), the mechanism of irreversible inhibition, and the safety profile. Following phase 1 studies in healthy volunteers and a phase 2a study in patients with HFpEF, a phase 2b/3 efficacy study of AZD4831 in patients with HFpEF started in 2021.

Traditional Chinese Medicine and Natural Products: Potential Approaches for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a rare, recurrent, and intractable inflammation obstruction of the stomach tract, usually accompanied by inflammation of cell proliferation and inflammation of the colon and carries a particular cause of inflammation. The clinical use of drugs in western countries affects IBD treatment, but various adverse effects and high prices limit their application. For these reasons, Traditional Chinese Medicine (TCM) is more advantageous in treating IBD. This paper reviews the mechanism and research status of TCM and natural products in IBD treatment by analyzing the relevant literature to provide a scientific and theoretical basis for IBD treatment.

Liver proteomic analysis reveals acute liver failure induced by lipopolysaccharide/D-galactosamine in rats involved in neutrophil extracellular trap formation

Objectives

Acute liver failure (ALF) is a rare life-threatening condition that leads to rapid deterioration of liver function. Although global awareness of ALF consequences is increasing, the precise molecular mechanisms associated with its rapid progression remain unclear. In the present study, we established a rat model of ALF using Lipopolysaccharide (LPS)/D-galactosamine (D-Gal) and explored the potential molecular mechanism of ALF.

Methods

Multiplexed isobaric tandem mass tag labelling combined with liquid chromatography-mass spectrometry was used to thoroughly screen for differentially expressed proteins in liver samples from LPS/D-Gal-induced ALF rat models.

Results

We identified 175 proteins, whose expression was altered by at least 1.5-fold, between the liver samples of ALF and control groups. Of these, 14 dysregulated proteins mainly participated in the regulation of neutrophil extracellular trap (NET) formation. Furthermore, rats with severe ALF showed elevated levels of cathelicidin antimicrobial peptide, myeloperoxidase, and fibrinogen gamma chain, consistent with NET formation. These findings suggest that the NET formation pathway may have contributed to the regulation of the clinical features and progression of liver injury in ALF rats.

Conclusion

To our knowledge, this study is the first to report a global differential protein expression profile of liver samples from rats with LPS/D-Gal-induced ALF. Our TMT-based quantitative proteomic analysis revealed molecular differences involved in NET formation between the ALF and control rat groups, potential therapeutic targets for ALF treatment as well as fundamental information for further detailed experimental research.

Albiflorin ameliorates inflammation and oxidative stress by regulating the NF-κB/NLRP3 pathway in Methotrexate-induced enteritis

Methotrexate (MTX) treats various diseases but also damages intestinal barrier and leads to enteritis. Albiflorin (ALB) has a variety of pharmacological effects, including antioxidant, anti-inflammation and anti-apoptosis. In the present study, we evaluated the therapeutic effect of ALB on MTX-induced enteritis and investigated the possible mechanisms involved. Male SD rats were intraperitoneally injected with 7 mg/kg MTX for three consecutive days to establish the enteritis model. ALB (20 or 40 mg/kg/day) was intragastrically administrated since two days prior MTX treatment and lasted for six days. We found that ALB treatment increased body weight and intestinal weight of rats with MTX injection. The disease activity index (DAI) score was also decreased after ALB administration. In histological examination, ALB treatment attenuated inflammatory cells infiltration and promoted survival of goblet cells. In detection of inflammatory-associated factors, ALB treatment decreased CD68⁺ cells infiltration, inhibited myeloperoxidase activity, and suppressed intercellular cell adhesion molecule-1 and cyclooxygenase-2 expression. Additionally, ALB reduced malondialdehyde, glutathione levels, inhibited superoxide dismutase activity and suppressed reactive oxygen species production. Moreover, ALB treatment effectively inhibited NLRP3, as well as caspase 1 p20 and interleukin (IL)-1β and 18 expression. Finally, nuclear factor-κB (NF-κB) p65 phosphorylation and nuclear translocation were also demonstrated to be blocked upon ALB treatment. In conclusion, our findings indicated that ALB alleviated MTX-induced enteritis via inhibiting the NF-κB/NLRP3 pathway.

Propofol inhibits the myeloperoxidase activity by acting as substrate through a redox process

BACKGROUND

Propofol (2,6-diisopropylphenol) is frequently used as intravenous anesthetic agent, especially in its injectable form (Diprivan), to initiate and maintain sedative state during surgery or in intensive care units. Numerous studies have reported the antioxidant and anti-inflammatory effect of propofol. The oxidant enzyme myeloperoxidase (MPO), released from activated neutrophils, plays a key role in host defense. An increase of the circulating MPO concentration has been observed in patients admitted in intensive care unit and presenting a systemic inflammatory response related to septic shock or trauma.

METHODS

This study investigates the immunomodulatory action of propofol and Diprivan as inhibitor of the oxidant activity of MPO. The understanding of the redox action mechanism of propofol and Diprivan on the myeloperoxidase chlorination and peroxidase activities has been refined using the combination of fluorescence and absorption spectroscopies with docking and cyclic voltammetry.

RESULTS

Propofol acts as a reversible MPO inhibitor. The molecule interacts as a reducing substrate in the peroxidase cycle and promotes the accumulation of compound II. At acidic pH (5.5), propofol and Diprivan do not inhibit the chlorination activity, but their action increases at physiological pH (7.4). The main inhibitory action of Diprivan could be attributed to its HOCl scavenging property.

GENERAL SIGNIFICANCE

Propofol can act as a reversible MPO inhibitor at clinical concentrations. This property could, in addition to other previously proven anti-inflammatory actions, induce an immunomodulatory action, beneficial during clinical use, particularly in the treatment of systemic inflammation response syndrome.

Neutrophils and their role in the aetiopathogenesis of type 1 and type 2 diabetes

Multiple and complex aetiological processes underlie diabetes mellitus, which invariably result in the development of hyperglycaemia. Although there are two prevalent distinct forms of the disease, that is, type 1 and type 2 diabetes, accumulating evidence indicates that these syndromes share more aetiopathological mechanisms than originally thought. This compels a rethinking of the approaches to prevent and treat the different manifestations of what eventually becomes a hyperglycaemic state. This review aims to address the involvement of neutrophils, the most abundant type of granulocytes involved in the initiation of the acute phase of inflammation, in the aetiopathogenesis of diabetes mellitus, with a focus on type 1 and type 2 diabetes. We review the evidence that neutrophils are the first leucocytes to react to and accumulate inside target tissues of diabetes, such as the pancreas and insulin-sensitive tissues. We then review available data on the role of neutrophils and their functional alteration, with a focus on NETosis, in the progression towards clinical disease. Finally, we review potential approaches as secondary and adjunctive treatments to limit neutrophil-mediated damage in the prevention of the progression of subclinical disease to clinical hyperglycaemia.

Synthesis of sulfamoyl-triazolyl-carboxamides as pharmacological myeloperoxidase inhibitors

Sulfamoyl-triazolyl-carboxamides were synthesized using DBU as a catalyst, and their molecular docking and MPO activity analyses were performed.

Role of Inflammation and Redox Status on Doxorubicin-Induced Cardiotoxicity in Infant and Adult CD-1 Male Mice

Doxorubicin (DOX) is a topoisomerase II inhibitor commonly used in the treatment of several types of cancer. Despite its efficacy, DOX can potentially cause fatal adverse effects, like cardiotoxicity. This work aimed to assess the role of inflammation in DOX-treated infant and adult mice and its possible link to underlying cardiotoxicity. Two groups of CD-1 male mice of different ages (infants or adults) were subjected to biweekly DOX administrations, to reach a cumulative dose of 18.0 mg/kg, which corresponds approximately in humans to 100.6 mg/m2 for infants and 108.9 mg/m2 for adults a clinically relevant dose in humans. The classic plasmatic markers of cardiotoxicity increased, and that damage was confirmed by histopathological findings in both groups, although it was higher in adults. Moreover, in DOX-treated adults, an increase of cardiac fibrosis was observed, which was accompanied by an increase in specific inflammatory parameters, namely, macrophage M1 and nuclear factor kappa B (NF-κB) p65 subunit, with a trend toward increased levels of the tumor necrosis factor receptor 2 (TNFR2). On the other hand, the levels of myeloperoxidase (MPO) and interleukin (IL)-6 significantly decreased in DOX-treated adult animals. In infants, a significant increase in cardiac protein carbonylation and in the levels of nuclear factor erythroid-2 related factor 2 (Nrf2) was observed. In both groups, no differences were found in the levels of tumor necrosis factor (TNF-α), IL-1β, p38 mitogen-activated protein kinase (p38 MAPK) or NF-κB p52 subunit. In conclusion, using a clinically relevant dose of DOX, our study demonstrated that cardiac effects are associated not only with the intensity of the inflammatory response but also with redox response. Adult mice seemed to be more prone to DOX-induced cardiotoxicity by mechanisms related to inflammation, while infant mice seem to be protected from the damage caused by DOX, possibly by activating such antioxidant defenses as Nrf2.

Phenolic Composition, Toxicity Potential, and Antimicrobial Activity of Licania rigida Benth (Chrysobalanaceae) Leaf Extracts

This study was conducted to evaluate the phenolic composition, toxicity, and antimicrobial activity of Licania rigida Benth, an underexploited wild Licania species. L. rigida leaf fractions (ethyl alcohol and ethyl acetate) were analyzed for their phenolic compound and flavonoid total, and high-performance liquid chromatography/ultraviolet spectra chromatographic profiles. Regarding the extract biological effects, toxicity was measured by acute oral toxicity in Wistar rats, MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method, and apoptosis indicators with DAPI in VERO cells, whereas well-agar diffusion and broth microdilution assays were applied to evaluate the antimicrobial ability. The phytochemical analysis resulted in significant amounts of phenolic compounds and total flavonoids in the extract and fraction, with flavonol-3-O-glycosylates as the main constituent. Regarding the extract and fraction antimicrobial activity, the results showed a significant effect against gram-positive bacteria and fungi, among which Staphylococcus epidermidis and Candida krusei displayed more susceptibility. No toxicity effects were observed in animals. Concerning the cytotoxicity assay, only the highest dose tested exhibited a minimal toxic effect on the analyzed cell lines. These results are relevant considering the increase of multiresistant microorganisms to conventional treatments applied. Therefore, investigating the pharmacological properties of the genus Licania is promising in the search for new sources of antimicrobial compounds.

Alendronate sodium-polymeric nanoparticles display low toxicity in gastric mucosal of rats and Ofcol II cells

The use of bisphosphonates constitutes the gold-standard therapy for the control and treatment of bone diseases. However, its long-term use may lead to gastric problems, which limits the treatment. Thus, this study aimed to formulate a nanostructured system with biodegradable polymers for the controlled release of alendronate sodium. The nanoparticles were characterized, and its gastric toxicity was investigated in rats. The synthesis process proved to be effective for encapsulating alendronate sodium, exhibiting nanoparticles with an average size of 51.02 nm and 98.5% of alendronate sodium incorporation. The release tests demonstrated a controlled release of the drug in 420 min, while the morphological analyzes showed spherical shapes and no apparent roughness. The biological tests demonstrated that the alendronate sodium nanoformulation reversed the gastric lesions, maintaining the normal levels of malondialdehyde and myeloperoxidase. Also, the encapsulated alendronate sodium showed no toxicity in murine osteoblastic cells, even at high concentrations.

The Critical Role of Cannabinoid Receptor 2 in URB602-Induced Protective Effects Against Renal Ischemia-Reperfusion Injury in the Rat

Renal ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and even induces remote organ damage. Accumulating proofs demonstrates that the endocannabinoid system may provide a promising access for treatment strategy of renal IRI associated AKI. In the current study, using the established renal IRI model of rat, we tested the hypothesis that pretreatment of URB602, 30 min before renal IRI, alleviates kidney injury and relevant distant organ damage via limiting oxidative stress and inflammation. Using Western blot analysis and LC-MS/MS, renal IRI showed to increase the levels of 2-arachidonoylglycerol (2-AG) in kidneys as well as COX-2, PGE2, TXA2, and decrease N-arachidonoylethanolamine (anandamide, AEA); the expressions of renal cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2) were unchanged. The URB602 pretreatment in renal IRI, further enhanced renal 2-AG which is high affinity to both CB1 and CB2, and reduced renal COX-2 which is involved in the regulation of renal perfusion and inflammation. AM630 (CB2 antagonist) almost blocked all the antioxidant, anti-inflammatory and nephroprotective effects of URB602, whereas AM251 (CB1 antagonist) showed limited influence, and parecoxib (COX-2 inhibitor) slightly ameliorated renal function at the dose of 10 mg/kg. Taken together, our data indicate that URB602 acts as a reactive oxygen species scavenger and anti-inflammatory media in renal IRI mainly depending on the activation of CB2.

Longitudinal proteomic profiling of dialysis patients with COVID-19 reveals markers of severity and predictors of death

End-stage kidney disease (ESKD) patients are at high risk of severe COVID-19. We measured 436 circulating proteins in serial blood samples from hospitalised and non-hospitalised ESKD patients with COVID-19 (n = 256 samples from 55 patients). Comparison to 51 non-infected patients revealed 221 differentially expressed proteins, with consistent results in a separate subcohort of 46 COVID-19 patients. Two hundred and three proteins were associated with clinical severity, including IL6, markers of monocyte recruitment (e.g. CCL2, CCL7), neutrophil activation (e.g. proteinase-3), and epithelial injury (e.g. KRT19). Machine-learning identified predictors of severity including IL18BP, CTSD, GDF15, and KRT19. Survival analysis with joint models revealed 69 predictors of death. Longitudinal modelling with linear mixed models uncovered 32 proteins displaying different temporal profiles in severe versus non-severe disease, including integrins and adhesion molecules. These data implicate epithelial damage, innate immune activation, and leucocyte-endothelial interactions in the pathology of severe COVID-19 and provide a resource for identifying drug targets.

Modulation of Leukocytes of the Innate Arm of the Immune System as a Potential Approach to Prevent the Onset and Progression of Type 1 Diabetes

Type 1 diabetes (T1D) is characterized by insulin deficiency resulting from the selective destruction of pancreatic β-cells by self-reactive T cells. Recent evidence demonstrates that innate immune responses substantially contribute to the pathogenesis of T1D, as they represent a first line of response to danger/damage signals. Here we discuss evidence on how, in a relapsing-remitting pattern, pancreas remodeling, diet, microbiota, gut permeability, and viral/bacterial infections induce the accumulation of leukocytes of the innate arm of the immune system throughout the pancreas. The subsequent acquisition and presentation of endocrine and exocrine antigens to the adaptive arm of the immune system results in a chronic progression of pancreatic damage. This process provides for the generation of self-reactive T-cell responses; however, the relative weight that genetic and environmental factors have on the etiopathogenesis of T1D is endotype imprinted and patient specific. With this Perspectives in Diabetes, our goal is to encourage the scientific community to rethink mechanisms underlying T1D pathogenesis and to consider therapeutic approaches that focus on these processes in intervention trials within new-onset disease as well as in efforts seeking the disorder's prevention in individuals at high risk.

Quercetin Attenuated Myeloperoxidase-Dependent HOCl Generation and Endothelial Dysfunction in Diabetic Vasculature

Myeloperoxidase (MPO)-dependent hypochlorous acid (HOCl) generation plays crucial roles in diabetic vascular complications. As a natural polyphenol, quercetin has antioxidant properties in various diabetic models. Herein, we investigated the therapeutic mechanism for quercetin on MPO-mediated HOCl generation and endothelial dysfunction in diabetic vasculature. In vitro, the presence of MPO could amplify high glucose-induced endothelial dysfunction which was significantly inhibited by the NADPH oxidase inhibitor, HOCl or H₂O₂ scavengers, revealing the contribution of MPO/H₂O₂/HOCl to vascular endothelial injury. Furthermore, quercetin effectively inhibited MPO/high glucose-mediated HOCl generation and cytotoxicity to vascular endothelial cells. The inhibitive effect on MPO activity was related to the fact that quercetin reduced high glucose-induced H₂O₂ generation in endothelial cells and directly acted as a competitive substrate for MPO, thus limiting MPO/H₂O₂-dependent HOCl production. Moreover, quercetin could attenuate HOCl-caused endothelial dysfunction in endothelial cells and isolated aortas. In vivo, dietary quercetin significantly inhibited aortic endothelial dysfunction in diabetic mice, while this compound simultaneously suppressed vascular MPO expression and activity. Therefore, it was demonstrated herein that quercetin inhibited endothelial injury in diabetic vasculature via suppression of MPO/high glucose-dependent HOCl formation.

Safety of systemic treatments for Behçet's syndrome

INTRODUCTION

Treatment of Behçet's syndrome (BS) is aimed at controlling all symptoms of such a complex disorder, ensuring a good quality of life and preventing life-threatening complications. A better understanding of the pathogenic role of different chemokines has improved our knowledge of BS and elicited a more specific use of therapies currently available, minimizing the burden of potential side-effects related to treatment.

AREAS COVERED

This work aims to provide a detailed overview of the safety profile for current therapies available in the treatment of BS, focusing on the main side-effects, toxicity and contraindications.

EXPERT OPINION

The greatest experience in the management of BS has been achieved with the employment of monoclonal anti-tumor necrosis factor antibodies which have been advocated for BS refractory manifestations. Moreover, interleukin-1 inhibitors have proven to be effective as well as safe, despite escalation of their dosage, especially to manage the most severe and difficult-to-treat ocular manifestations. However, general treatment of BS patients remains awkward as protean clinical features may respond differently to the same treatment or even worsen. Therefore, patients' safety for therapies used in BS promotes the implementation of precision medicine, which could help targeting accurately the pathogenetic mechanisms concealed behind specific clinical phenotypes.

Loss-of-Function Myeloperoxidase Mutations Are Associated with Increased Neutrophil Counts and Pustular Skin Disease

The identification of disease alleles underlying human autoinflammatory diseases can provide important insights into the mechanisms that maintain neutrophil homeostasis. Here, we focused our attention on generalized pustular psoriasis (GPP), a potentially life-threatening disorder presenting with cutaneous and systemic neutrophilia. Following the whole-exome sequencing of 19 unrelated affected individuals, we identified a subject harboring a homozygous splice-site mutation (c.2031-2A>C) in MPO. This encodes myeloperoxidase, an essential component of neutrophil azurophil granules. MPO screening in conditions phenotypically related to GPP uncovered further disease alleles in one subject with acral pustular psoriasis (c.2031-2A>C;c.2031-2A>C) and in two individuals with acute generalized exanthematous pustulosis (c.1705C>T;c.2031-2A>C and c.1552_1565del;c.1552_1565del). A subsequent analysis of UK Biobank data demonstrated that the c.2031-2A>C and c.1705C>T (p.Arg569Trp) disease alleles were also associated with increased neutrophil abundance in the general population (p = 5.1 × 10^-6 and p = 3.6 × 10^-5, respectively). The same applied to three further deleterious variants that had been genotyped in the cohort, with two alleles (c.995C>T [p.Ala332Val] and c.752T>C [p.Met251Thr]) yielding p values < 10^-10. Finally, treatment of healthy neutrophils with an MPO inhibitor (4-Aminobenzoic acid hydrazide) increased cell viability and delayed apoptosis, highlighting a mechanism whereby MPO mutations affect granulocyte numbers. These findings identify MPO as a genetic determinant of pustular skin disease and neutrophil abundance. Given the recent interest in the development of MPO antagonists for the treatment of neurodegenerative disease, our results also suggest that the pro-inflammatory effects of these agents should be closely monitored.

The role of neutrophils in innate immunity-driven nonalcoholic steatohepatitis: lessons learned and future promise

The enrichment of innate immune cells and the enhanced inflammation represent the hallmark of non-alcoholic steatohepatitis (NASH), the advanced subtype with a significantly increased risk of progression to end-stage liver diseases within the spectrum of non-alcoholic fatty liver disease. Neutrophils are traditionally recognized as key components in the innate immune system to defend against pathogens. Recently, a growing body of evidence supports neutrophils as emerging key player in mediating the transition from steatosis to NASH, which is largely inspired by the histological findings in human liver biopsy indicating the enhanced infiltration of neutrophils as one of the key histological features of NASH. In this review, we discuss data regarding histological perspectives of hepatic infiltration of neutrophils in NASH. We also highlight the pathophysiological role of neutrophils in promoting metabolic inflammation in the liver through the release of a vast array of granule proteins, the interaction with other pro-inflammatory immune cells, and the formation of neutrophil extracellular traps. Neutrophil granule proteins possess pleiotropic effects on regulating neutrophil biology and functions. A variety of granule proteins (including lipocalin-2, myeloperoxidase, proteinase 3, neutrophil elastase, etc.) produced by neutrophils enhance liver metabolic inflammation, thereby promoting NASH progression by mediating neutrophil-macrophage interaction. Therapeutically, pharmacological inhibitors targeting neutrophil granule proteins hold promise to combat NASH. In addition, this article also summarizes potentials of neutrophils and its derived various granule proteins for the accurate, even non-invasive diagnosis of NASH.

Myeloperoxidase instigates proinflammatory responses in a cecal ligation and puncture rat model of sepsis

Myeloperoxidase (MPO)-derived hypochlorous (HOCl) reacts with membrane plasmalogens to yield α-chlorofatty aldehydes such as 2-chlorofatty aldehyde (2-ClFALD) and its metabolite 2-chlorofatty acid (2-ClFA). Recent studies showed that 2-ClFALD and 2-ClFA serve as mediators of the inflammatory responses to sepsis by as yet unknown mechanisms. Since no scavenger for chlorinated lipids is available and on the basis of the well-established role of the MPO/HOCl/chlorinated lipid axis in inflammatory responses, we hypothesized that treatment with MPO inhibitors (N-acetyl lysyltyrosylcysteine amide or 4-aminobenzoic acid hydrazide) would inhibit inflammation and proinflammatory mediator expression induced by cecal ligation and puncture (CLP). We used intravital microscopy to quantify in vivo inflammatory responses in Sham and CLP rats with or without MPO inhibition. Small intestines, mesenteries, and lungs were collected to assess changes in MPO-positive staining and lung injury, respectively, as well as free 2-ClFA and proinflammatory mediators levels. CLP caused neutrophil infiltration, 2-ClFA generation, acute lung injury, leukocyte-/platelet-endothelium interactions, mast cell activation (MCA), plasminogen activator inhibitor-1 (PAI-1) production, and the expression of several cytokines, chemokines, and vascular endothelial growth factor, changes that were reduced by MPO inhibition. Pretreatment with a PAI-1 inhibitor or MC stabilizer prevented CLP-induced leukocyte-endothelium interactions and MCA, and abrogated exogenous 2-ClFALD-induced inflammatory responses. Thus, we provide evidence that MPO instigates these inflammatory changes in CLP and that chlorinated lipids may serve as a mechanistic link between the enzymatic activity of MPO and PAI-1- and mast cell-dependent adhesive interactions, providing a rationale for new therapeutic interventions in sepsis.NEW & NOTEWORTHY Using two distinct myeloperoxidase (MPO) inhibitors, we show for the first time that MPO plays an important role in producing increases in free 2-chlorofatty aldehyde (2-ClFALD)-a powerful proinflammatory chlorinated lipid in plasma and intestine-a number of cytokines and other inflammatory mediators, leukocyte and platelet rolling and adhesion in postcapillary venules, and lung injury in a cecal ligation and puncture model of sepsis. In addition, the use of a plasminogen activator inhibitor-1 (PAI-1) inhibitor or a mast cell stabilizer prevented inflammatory responses in CLP-induced sepsis. PAI-1 inhibition also prevented the proinflammatory responses to exogenous 2-ClFALD superfusion. Thus, our study provides some of the first evidence that MPO-derived free 2-ClFA plays an important role in CLP-induced sepsis by a PAI-1- and mast cell-dependent mechanism.

Myeloperoxidase: a potential therapeutic target for coronary artery disease

INTRODUCTION

Coronary artery disease (CAD) poses significant morbidity and mortality globally. Despite significant advances in treatment interventions, residual cardiovascular risks remain unchecked. Recent clinical trials have shed light on the potential therapeutic benefits of targeting anti-inflammatory pathways. Myeloperoxidase (MPO) plays an important role in atherosclerotic plaque formation and destabilization of the fibrous cap; both increase the risk of atherosclerotic cardiovascular disease and especially CAD.

AREAS COVERED

This article examines the role of MPO in the pathogenesis of atherosclerotic CAD and the mechanistic data from several key therapeutic drug targets. There have been numerous interesting studies on prototype compounds that directly or indirectly attenuate the enzymatic activities of MPO, and subsequently exhibit atheroprotective effects; these include aminobenzoic acid hydrazide, ferulic acid derivative (INV-315), thiouracil derivatives (PF-1355 and PF-06282999), 2-thioxanthines derivative (AZM198), triazolopyrimidines, acetaminophen, N-acetyl lysyltyrosylcysteine (KYC), flavonoids, and alternative substrates such as thiocyanate and nitroxide radical.

EXPERT OPINION

Future investigations must determine if the cardiovascular benefits of direct systemic inhibition of MPO outweigh the risk of immune dysfunction, which may be less likely to arise with alternative substrates or MPO inhibitors that selectively attenuate atherogenic effects of MPO.

Protective effect of dapsone against renal ischemia-reperfusion injury in rat

Background: Ischemia/reperfusion can cause injury to tissues and compromise functionality of organs due to inflammatory processes. Significantly, development of these effects in kidney tissue has been a challenging issue that leads to acute renal injury. In this study, anti-inflammatory, anti-oxidative, and protective features of dapsone on kidney ischemia/reperfusion injury were investigated.Material and methods: Renal ischemia was induced in rats by bilateral renal arteries clamping for 45 min followed by 24 h reperfusion phase. The effects of different doses of dapsone (1, 3, 10 mg/kg) on ischemia/reperfusion injury in kidney tissue were investigated by targeting BUN, Creatinine, LDH, MDA, MPO, IL-1β, TNF-α, and NFκB. In addition histopathological examination was performed by H&E staining method.Results and discussion: Comparing the findings of this study showed significant reduction in BUN and LDH in 10 mg/kg dapsone received groups, and Cr, MDA, and MPO in 3 mg/kg dapsone received groups. The serum level of TNF-α was significantly decreased with both doses of 3 and 10 mg/kg dapsone. The same results were observed in the serum level of IL-1β and NFκB. Besides, remarkable improvement in histological damages was also observed with dapsone treatment.Conclusion: These results support the hypothesis that the positive effects of dapsone on the renal ischemia/reperfusion injury are mediated by modulating inflammatory cascades.

Morin alleviates LPS-induced mastitis by inhibiting the PI3K/AKT, MAPK, NF-κB and NLRP3 signaling pathway and protecting the integrity of blood-milk barrier

Mastitis is a common veterinary clinical disease that restricts the development of dairy farming around the world. Morin, extracted from Mulberry Tree and other herbs, has been reported to possess the function of anti-bacteria, anti-oxidant, and anti-inflammatory. However, whether morin could protect lipopolysaccharide (LPS)-induced mouse mastitis in vivo has not well known. This study firstly aims to evaluate the effects of morin on LPS-induced mouse mastitis in vivo, and then try to illustrate the mechanism involved in the process. Before injected with LPS, mice were intraperitoneally pre-injected with different concentrations of morin, and mice of the control and LPS group were injected with the same amount of saline. Pathologic changes of mammary gland were determined by histopathological examination. Myeloperoxidase (MPO) activities of mammary gland were determined by the MPO kits. The mRNA expressions of inflammatory cytokines including TNF-α, IL-1β and IL-6, and those of chemokine factors CCL2 and CXCL2, and those of tight junctions occludin claudin-3 were examined by qRT-PCR analysis. The activities of IκB, p65, ERK, P38, AKT, PI3K, NLPR3, claudin-1, claudin-3 and occludin were determined by western blotting. The results showed that morin alleviated LPS-induced edema, destructed structures and infiltrated inflammatory cells of mammary gland. Morin administration significantly decreased LPS-induced TNF-α, IL-1β, IL-6, CCL2 and CXCL2 mRNA expressions. Furthermore, western blot analysis also showed that morin significantly reduced LPS-induced phosphorylation of p65, IκB, p38 and ERK, and enhanced LPS-induced phosphorylation of AKT and PI3K. It was also found that LPS-decreased claudin-3 and occludin expressions were also inhibited by morin treatment. In summary, above results suggest that morin indeed protect LPS-induced mouse mastitis in vivo, and the mechanism was through inhibiting the PI3K/AKT, MAPK, NF-κB and NLRP3 signaling pathways and protecting the integrity of blood-milk barrier by regulating the tight junction proteins expressions.