Inside the Neutrophil Phagosome: Oxidants, Myeloperoxidase, and Bacterial Killing

Management of ROS and Regulatory Cell Death in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion injury (MIRI) is fatal to patients, leading to cardiomyocyte death and myocardial remodeling. Reactive oxygen species (ROS) and oxidative stress play important roles in MIRI. There is a complex crosstalk between ROS and regulatory cell deaths (RCD) in cardiomyocytes, such as apoptosis, pyroptosis, autophagy, and ferroptosis. ROS is a double-edged sword. A reasonable level of ROS maintains the normal physiological activity of myocardial cells. However, during myocardial ischemia-reperfusion, excessive ROS generation accelerates myocardial damage through a variety of biological pathways. ROS regulates cardiomyocyte RCD through various molecular mechanisms. Targeting the removal of excess ROS has been considered an effective way to reverse myocardial damage. Many studies have applied antioxidant drugs or new advanced materials to reduce ROS levels to alleviate MIRI. Although the road from laboratory to clinic has been difficult, many scholars still persevere. This article reviews the molecular mechanisms of ROS inhibition to regulate cardiomyocyte RCD, with a view to providing new insights into prevention and treatment strategies for MIRI.

Precise modulation and use of reactive oxygen species for immunotherapy

Reactive oxygen species (ROS) play an important role in regulating the immune system by affecting pathogens, cancer cells, and immune cells. Recent advances in biomaterials have leveraged this mechanism to precisely modulate ROS levels in target tissues for improving the effectiveness of immunotherapies in infectious diseases, cancer, and autoimmune diseases. Moreover, ROS-responsive biomaterials can trigger the release of immunotherapeutics and provide tunable release kinetics, which can further boost their efficacy. This review will discuss the latest biomaterial-based approaches for both precise modulation of ROS levels and using ROS as a stimulus to control the release kinetics of immunotherapeutics. Finally, we will discuss the existing challenges and potential solutions for clinical translation of ROS-modulating and ROS-responsive approaches for immunotherapy, and provide an outlook for future research.

Dihydrophenazine: a multifunctional new weapon that kills multidrug-resistant Acinetobacter baumannii and restores carbapenem and oxidative stress susceptibilities

AIMS

The current work aims to fully characterize a new antimicrobial agent against Acinetobacter baumannii, which continues to represent a growing threat to healthcare settings worldwide. With minimal treatment options due to the extensive spread of resistance to almost all the available antimicrobials, the hunt for new antimicrobial agents is a high priority.

METHODS AND RESULTS

An Egyptian soil-derived bacterium strain NHM-077B proved to be a promising source for a new antimicrobial agent. Bio-guided fractionation of the culture supernatants of NHM-077B followed by chemical structure elucidation identified the active antimicrobial agent as 1-hydroxy phenazine. Chemical synthesis yielded more derivatives, including dihydrophenazine (DHP), which proved to be the most potent against A. baumannii, yet it exhibited a marginally safe cytotoxicity profile against human skin fibroblasts. Proteomics analysis of the cells treated with DHP revealed multiple proteins with altered expression that could be correlated to the observed phenotypes and potential mechanism of the antimicrobial action of DHP. DHP is a multipronged agent that affects membrane integrity, increases susceptibility to oxidative stress, interferes with amino acids/protein synthesis, and modulates virulence-related proteins. Interestingly, DHP in subinhibitory concentrations re-sensitizes the highly virulent carbapenem-resistant A. baumannii strain AB5075 to carbapenems providing great hope in regaining some of the benefits of this important class of antibiotics.

CONCLUSIONS

This work underscores the potential of DHP as a promising new agent with multifunctional roles as both a classical and nonconventional antimicrobial agent that is urgently needed.

Targeting brain-peripheral immune responses for secondary brain injury after ischemic and hemorrhagic stroke

The notion that the central nervous system is an immunologically immune-exempt organ has changed over the past two decades, with increasing evidence of strong links and interactions between the central nervous system and the peripheral immune system, both in the healthy state and after ischemic and hemorrhagic stroke. Although primary injury after stroke is certainly important, the limited therapeutic efficacy, poor neurological prognosis and high mortality have led researchers to realize that secondary injury and damage may also play important roles in influencing long-term neurological prognosis and mortality and that the neuroinflammatory process in secondary injury is one of the most important influences on disease progression. Here, we summarize the interactions of the central nervous system with the peripheral immune system after ischemic and hemorrhagic stroke, in particular, how the central nervous system activates and recruits peripheral immune components, and we review recent advances in corresponding therapeutic approaches and clinical studies, emphasizing the importance of the role of the peripheral immune system in ischemic and hemorrhagic stroke.

Urinary metabolic characterization of advanced tuberculous meningitis cases in a South African paediatric population

Tuberculous meningitis (TBM) is a severe form of tuberculosis with high neuro-morbidity and mortality, especially among the paediatric population (aged ≤12 years). Little is known of the associated metabolic changes. This study aimed to identify characteristic metabolic markers that differentiate severe cases of paediatric TBM from controls, through non-invasive urine collection. Urine samples selected for this study were from two paediatric groups. Group 1: controls (n = 44): children without meningitis, no neurological symptoms and from the same geographical region as group 2. Group 2: TBM cases (n = 13): collected from paediatric patients that were admitted to Tygerberg Hospital in South Africa on the suspicion of TBM, mostly severely ill; with a later confirmation of TBM. Untargeted 1H NMR-based metabolomics data of urine were generated, followed by statistical analyses via MetaboAnalyst (v5.0), and the identification of important metabolites. Twenty nine urinary metabolites were identified as characteristic of advanced TBM and categorized in terms of six dysregulated metabolic pathways: 1) upregulated tryptophan catabolism linked to an altered vitamin B metabolism; 2) perturbation of amino acid metabolism; 3) increased energy production-metabolic burst; 4) disrupted gut microbiota metabolism; 5) ketoacidosis; 6) increased nitrogen excretion. We also provide original biological insights into this biosignature of urinary metabolites that can be used to characterize paediatric TBM patients in a South African cohort.

Analyzing Blood Cells of High-Risk Myelodysplastic Syndrome Patients Using Interferometric Phase Microscopy and Fluorescent Flow Cytometry

Myelodysplastic syndromes (MDSs) are a group of potentially deadly diseases that affect the morphology and function of neutrophils. Rapid diagnosis of MDS is crucial for the initiation of treatment that can vastly improve disease outcome. In this work, we present a new approach for detecting morphological differences between neutrophils isolated from blood samples of high-risk MDS patients and blood bank donors (BBDs). Using fluorescent flow cytometry, neutrophils were stained with 2',7'-dichlorofluorescin diacetate (DCF), which reacts with reactive oxygen species (ROS), and Hoechst, which binds to DNA. We observed that BBDs possessed two cell clusters (designated H and L), whereas MDS patients possessed a single cluster (L). Later, we used FACS to sort the H and the L cells and used interferometric phase microscopy (IPM) to image the cells without utilizing cell staining. IPM images showed that H cells are characterized by low optical path delay (OPD) in the nucleus relative to the cytoplasm, especially in cell vesicles containing ROS, whereas L cells are characterized by low OPD in the cytoplasm relative to the nucleus and no ROS-containing vesicles. Moreover, L cells present a higher average OPD and dry mass compared to H cells. When examining neutrophils from MDS patients and BBDs by IPM during flow, we identified ~20% of cells as H cells in BBDs in contrast to ~4% in MDS patients. These results indicate that IPM can be utilized for the diagnosis of complex hematological pathologies such as MDS.

NADPH Oxidase 3: Beyond the Inner Ear

Reactive oxygen species (ROS) were formerly known as mere byproducts of metabolism with damaging effects on cellular structures. The discovery and description of NADPH oxidases (Nox) as a whole enzyme family that only produce this harmful group of molecules was surprising. After intensive research, seven Nox isoforms were discovered, described and extensively studied. Among them, the NADPH oxidase 3 is the perhaps most underrated Nox isoform, since it was firstly discovered in the inner ear. This stigma of Nox3 as "being only expressed in the inner ear" was also used by me several times. Therefore, the question arose whether this sentence is still valid or even usable. To this end, this review solely focuses on Nox3 and summarizes its discovery, the structural components, the activating and regulating factors, the expression in cells, tissues and organs, as well as the beneficial and detrimental effects of Nox3-mediated ROS production on body functions. Furthermore, the involvement of Nox3-derived ROS in diseases progression and, accordingly, as a potential target for disease treatment, will be discussed.

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.

Multifunctional Hydrogels for the Healing of Diabetic Wounds

The healing of diabetic wounds is hindered by various factors, including bacterial infection, macrophage dysfunction, excess proinflammatory cytokines, high levels of reactive oxygen species, and sustained hypoxia. These factors collectively impede cellular behaviors and the healing process. Consequently, this review presents intelligent hydrogels equipped with multifunctional capacities, which enable them to dynamically respond to the microenvironment and accelerate wound healing in various ways, including stimuli -responsiveness, injectable self-healing, shape -memory, and conductive and real-time monitoring properties. The relationship between the multiple functions and wound healing is also discussed. Based on the microenvironment of diabetic wounds, antibacterial, anti-inflammatory, immunomodulatory, antioxidant, and pro-angiogenic strategies are combined with multifunctional hydrogels. The application of multifunctional hydrogels in the repair of diabetic wounds is systematically discussed, aiming to provide guidelines for fabricating hydrogels for diabetic wound healing and exploring the role of intelligent hydrogels in the therapeutic processes.

Nanotechnology and Cancer Bioelectricity: Bridging the Gap Between Biology and Translational Medicine

Bioelectricity is the electrical activity that occurs within living cells and tissues. This activity is critical for regulating homeostatic cellular function and communication, and disruptions of the same can lead to a variety of conditions, including cancer. Cancer cells are known to exhibit abnormal electrical properties compared to their healthy counterparts, and this has driven researchers to investigate the potential of harnessing bioelectricity as a tool in cancer diagnosis, prognosis, and treatment. In parallel, bioelectricity represents one of the means to gain fundamental insights on how electrical signals and charges play a role in cancer insurgence, growth, and progression. This review provides a comprehensive analysis of the literature in this field, addressing the fundamentals of bioelectricity in single cancer cells, cancer cell cohorts, and cancerous tissues. The emerging role of bioelectricity in cancer proliferation and metastasis is introduced. Based on the acknowledgement that this biological information is still hard to access due to the existing gap between biological findings and translational medicine, the latest advancements in the field of nanotechnologies for cellular electrophysiology are examined, as well as the most recent developments in micro- and nano-devices for cancer diagnostics and therapy targeting bioelectricity.

Hydrogen sulfide releasing poly(γ-glutamic acid) biocomposite hydrogel with monitoring, antioxidant, and antibacterial properties for diabetic wound healing

Adverse factors such as high levels of glucose, oxidative stress, inflammation, and bacterial infection impede diabetic wound healing and even worsen wounds. Owing to its outstanding anti-inflammatory and antioxidant properties as well as the potential to promote cell migration and proliferation, hydrogen sulfide(H2S) gas therapy is promising for chronic diabetic wound recovery. In this work, a multifunctional poly(γ-glutamic acid)(PGA) hydrogel encapsulated with keratin-based H2S donor(KTC), ciprofloxacin(Cip), and anthocyanins(Ant) was developed. The resultant hydrogel was capable of releasing H2S, thereby promoting cell proliferation and enhancing anti-inflammation and antioxidant activity. The release of antibiotic Cip was accelerated under a diabetic wound microenvironment, thereby enhancing the antibacterial activity of the hydrogel. The encapsulated Ant could serve as a pH monitor, sensitively indicating wound pH conditions in situ and indirectly reflecting wound infection. In vivo results in diabetic wound healing suggested that PGA/Ant/KTC/Cip hydrogel reduced inflammation and promoted angiogenesis and collagen deposition, thereby accelerating wound healing.

TRPV1+ neurons alter Staphylococcus aureus skin infection outcomes by affecting macrophage polarization and neutrophil recruitment

BACKGROUND

The interaction between the nervous system and the immune system can affect the outcome of a bacterial infection. Staphylococcus aureus skin infection is a common infectious disease, and elucidating the relationship between the nervous system and immune system may help to improve treatment strategies.

RESULTS

In this study, we found that the local release of calcitonin gene-related peptide (CGRP) increased during S. aureus skin infection, and S. aureus could promote the release of CGRP from transient receptor potential cation channel subfamily V member 1 (TRPV1+) neurons in vitro. The existence of TRPV1+ neurons inhibited the recruitment of neutrophils to the infected region and regulated the polarization of macrophages toward M2 while inhibiting polarization toward M1. This reduces the level of inflammation in the infected area, which aggravates the local infection. Furthermore, this study demonstrates that TRPV1 may be a target for the treatment of S. aureus skin infections and that botulinum neurotoxin A (BoNT/A) and BIBN4096 may reverse the inhibited inflammatory effect of CGRP, making them potential therapeutics for the treatment of skin infection in S. aureus.

CONCLUSIONS

In S. aureus skin infection, TRPV1+ neurons inhibit neutrophil recruitment and regulate macrophage polarization by releasing CGRP. BoNT/A and BIBN4096 may be potential therapeutic agents for S. aureus skin infection.

Dipeptidyl peptidase 1 inhibition as a potential therapeutic approach in neutrophil-mediated inflammatory disease

Neutrophils have a critical role in the innate immune response to infection and the control of inflammation. A key component of this process is the release of neutrophil serine proteases (NSPs), primarily neutrophil elastase, proteinase 3, cathepsin G, and NSP4, which have essential functions in immune modulation and tissue repair following injury. Normally, NSP activity is controlled and modulated by endogenous antiproteases. However, disruption of this homeostatic relationship can cause diseases in which neutrophilic inflammation is central to the pathology, such as chronic obstructive pulmonary disease (COPD), alpha-1 antitrypsin deficiency, bronchiectasis, and cystic fibrosis, as well as many non-pulmonary pathologies. Although the pathobiology of these diseases varies, evidence indicates that excessive NSP activity is common and a principal mediator of tissue damage and clinical decline. NSPs are synthesized as inactive zymogens and activated primarily by the ubiquitous enzyme dipeptidyl peptidase 1, also known as cathepsin C. Preclinical data confirm that inactivation of this protease reduces activation of NSPs. Thus, pharmacological inhibition of dipeptidyl peptidase 1 potentially reduces the contribution of aberrant NSP activity to the severity and/or progression of multiple inflammatory diseases. Initial clinical data support this view. Ongoing research continues to explore the role of NSP activation by dipeptidyl peptidase 1 in different disease states and the potential clinical benefits of dipeptidyl peptidase 1 inhibition.

Gaining knowledge about biomarkers of the immune system and inflammation in the saliva of pigs: The case of myeloperoxidase, S100A12, and ITIH4

An assay for the measurement of myeloperoxidase (Mpx) in porcine saliva was developed and validated, and factors influencing Mpx and another two biomarkers of inflammation and immune system, the protein S100A12 and the inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4), were studied. The spectrophotometric method for Mpx measurement validated in this assay showed an adequate analytical performance including precision and accuracy. When a group of twenty healthy pigs was sampled every 4 h from 8 a.m. until 8 p.m., Mpx and S100A12 showed significant increases at 4 p.m., whereas ITIH4 concentration showed a significant decrease at 12 a.m. Increases were also seen in salivary Mpx, S100A12, and ITIH4 levels 24 h after the intramuscular administration of Escherichia coli lipopolysaccharide in five pigs; whereas in a non-septic inflammation after the subcutaneous administration of turpentine oil to five pigs changes were seen in S100A12 at 3 h and in ITIH4 at 48 h. When a stressful situation consisting of the transportation and stay of 4 h to a slaughterhouse of 24 pigs was performed, all analytes were increased after 4 h of lairage in the slaughterhouse compared with the values that were obtained the day before at the same time of the day. Mpx can be measured in the saliva of pigs with the automated assay described in this report. Mpx, S100A12, and ITIH4 salivary levels can change depending on the hour of the day in which the sample is taken, and increases can be produced due to sepsis, non-septic inflammation and stress.

Taurine reduction of injury from neutrophil infiltration ameliorates Streptococcus uberis-induced mastitis

Mastitis is a common disease of dairy cows characterized by infiltration of leukocytes, especially neutrophils, resulting in increased permeability of the blood-milk barrier (BMB). Taurine, a functional nutrient, has been shown to have anti-inflammatory and antioxidant effects. Here, we investigated the regulatory effects and mechanisms of taurine on the complex immune network of the mammary gland in Streptococcus uberis (S. uberis) infection. We found that taurine had no direct effect on CXCL2-mediated neutrophil chemotaxis. However, it inhibited MAPK and NF-κB signalings by modulating the activity of TAK1 downstream of TLR2, thereby reducing CXCL2 expression in macrophages to reduce neutrophil recruitment in S. uberis infection. Further, the AMPK/Nrf2 signaling pathway was activated by taurine to help mitigate oxidative damage, apoptosis and disruption of tight junctions in mammary epithelial cells caused by hypochlorous acid, a strong oxidant produced by neutrophils, thus protecting the integrity of the mammary epithelial barrier. Taurine protects the BMB from damage caused by neutrophils via blocking the macrophage-CXCL2-neutrophil signaling axis and increasing the antioxidant capacity of mammary epithelial cells.

Multi-Oxidant Environment as a Suicidal Inhibitor of Myeloperoxidase

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

Exploring the Relationship between Neutrophil Activation and Different States of Canine L. infantum Infection: Nitroblue Tetrazolium Test and IFN-γ

This study aimed to investigate the role of neutrophils in canine leishmaniosis by assessing neutrophil activation and its relationship with different states of L. infantum infection and antibody and IFN-γ production. Dogs were categorized into five groups: healthy-seronegative (n = 25), healthy-seropositive (n = 21), LeishVet-stage I (n = 25), Leishvet-stage II (n = 41), and LeishVet-stage III-IV (n = 16). Results of the nitroblue tetrazolium reduction test (NBT) showed significantly higher neutrophil activation in stage I (median:17.17, range: [7.33-31.50]%) compared to in healthy-seronegative (4.10 [1.20-18.00]%), healthy-seropositive (7.65 [3.98-21.74]%), stage II (6.50 [1.50-28.70]%), and stage III-IV (7.50 [3.00-16.75]%) groups (p < 0.0001). Healthy-seropositive dogs also displayed higher values than all groups except stage I. Stages II and III-IV did not show significant differences compared to healthy-seronegative. Regarding IFN-γ, stage I dogs had higher concentrations (median:127.90, range: [0-3998.00] pg/mL) than healthy-seronegative (0 [0-109.50] pg/mL) (p = 0.0002), stage II (9.00 [0-5086.00] pg/mL) (p = 0.045), and stage III-IV (3.50 [80.00-548.80] pg/mL) (p = 0.02) dogs. Stage II dogs showed increased IFN-γ compared to healthy-seronegative dogs (p = 0.015), while stage III-IV dogs had no significant differences compared to healthy-seronegative dogs (p = 0.12). Healthy-seropositive dogs had elevated IFN-γ concentrations compared to healthy-seronegative dogs (p = 0.001) and dogs in stage III-IV (p = 0.03). In conclusion, neutrophil activation was higher in dogs with mild disease and healthy-seropositive dogs, and a relationship between neutrophil activation and the production of IFN-γ was found.

Oxidant-modified amylin fibrils and aggregates alter the inflammatory profile of multiple myeloid cell types, but are non-toxic to islet β cells

Diabetes mellitus currently affects ∼10% of the population worldwide, with Type 2 predominating, and this incidence is increasing steadily. Both Type 1 and 2 are complex diseases, involving β-cell death and chronic inflammation, but the pathways involved are unresolved. Chronic inflammation is characterized by increased oxidant formation, with this inducing protein modification, altered function and immunogenicity. Amylin, a peptide hormone co-secreted with insulin by β-cells, has attracted considerable interest for its amyloidogenic properties, however, the effects that oxidants have on amylin aggregation and function are poorly understood. Amylin was exposed in vitro to hypochlorous acid, hydrogen peroxide and peroxynitrous acid/peroxynitrite to investigate the formation of post-translational oxidative modifications (oxPTMs, via mass spectrometry) and fibril formation (via transmission electron microscopy). Amylin free acid (AFA) was also examined to investigate the role of the C-terminal amide in amylin. Oxidant exposure led to changes in aggregate morphology and abundance of oxPTMs in a concentration-dependent manner. The toxicity and immunogenic potential of oxidant-modified amylin or AFA on pancreatic islet cells (INS-1E), human monocyte cell line (THP-1) and monocyte-derived dendritic cells (moDCs) were examined using metabolic activity and cytokine assays, and flow cytometry. No significant changes in vitality or viability were detected, but exposure to oxidant-modified amylin or AFA resulted in altered immunogenicity when compared to the native proteins. THP-1 and moDCs show altered expression of activation markers and changes in cytokine secretion. Furthermore, oxidant-treated amylin and AFA promoted maturation of THP-1 and pre-mature moDCs, as determined by changes in size, and maturation markers.

Neutrophils and the Systemic Inflammatory Response Syndrome (SIRS)

We are not entirely able to understand, assess, and modulate the functioning of the immune system in clinical situations that lead to a systemic inflammatory response. In the search for diagnostic and treatment strategies (which are still far from perfect), it became very important to study the pathogenesis and participation of endogenous inflammation mediators. This study attempts to more precisely establish the role of neutrophils in individual phenomena occurring during an inflammatory and anti-inflammatory reaction, taking into account their cidal, immunoregulatory, and reparative abilities. Pro- and anticoagulatory properties of endothelium in systemic inflammatory response syndrome (SIRS) are emphasised, along with the resulting clinical implications (the application of immunotherapy using mesenchymal stem/stromal cells (MSCs) or IL-6 antagonists in sepsis and COVID-19 treatment, among others). Special attention is paid to reactive oxygen species (ROS), produced by neutrophils activated during "respiratory burst" in the course of SIRS; the protective and pathogenic role of these endogenous mediators is highlighted. Moreover, clinically useful biomarkers of SIRS (neutrophil extracellular traps, cell-free DNA, DAMP, TREMs, NGAL, miRNA, selected cytokines, ROS, and recognised markers of endothelial damage from the group of adhesins by means of immunohistochemical techniques) related to the neutrophils are presented, and their role in the diagnosing and forecasting of sepsis, burn disease, and COVID-19 is emphasised. Finally, examples of immunomodulation of sepsis and antioxidative thermal injury therapy are presented.

Mechanistic and structural insights into the bifunctional enzyme PaaY from Acinetobacter baumannii

PaaY is a thioesterase that enables toxic metabolites to be degraded through the bacterial phenylacetic acid (PA) pathway. The Acinetobacter baumannii gene FQU82_01591 encodes PaaY, which we demonstrate to possess γ-carbonic anhydrase activity in addition to thioesterase activity. The crystal structure of AbPaaY in complex with bicarbonate reveals a homotrimer with a canonical γ-carbonic anhydrase active site. Thioesterase activity assays demonstrate a preference for lauroyl-CoA as a substrate. The AbPaaY trimer structure shows a unique domain-swapped C-termini, which increases the stability of the enzyme in vitro and decreases its susceptibility to proteolysis in vivo. The domain-swapped C-termini impact thioesterase substrate specificity and enzyme efficacy without affecting carbonic anhydrase activity. AbPaaY knockout reduced the growth of Acinetobacter in media containing PA, decreased biofilm formation, and impaired hydrogen peroxide resistance. Collectively, AbPaaY is a bifunctional enzyme that plays a key role in the metabolism, growth, and stress response mechanisms of A. baumannii.

Diagnostic value of myeloperoxidase and eosinophil cationic protein in nasal secretions for endotypes of chronic rhinosinusitis

OBJECTIVES

To explore associations between inflammatory endotypes and clinical presentations in CRS. To investigate the value of secretions myeloperoxidase (MPO) and eosinophilic cationic protein (ECP) detections in the diagnosis of endotypes of chronic rhinosinusitis (CRS), so as to provide guidance for the clinical application of MPO and ECP detection in secretions.

METHODS

We collected clinical symptom scores from patients with CRS and examined the differences between endotypes in clinical features. Patients' nasal secretions and polyps (or middle turbinate for control) were collected and their NEU number, EOS%, MPO and ECP levels were measured. Correlation analysis was performed for these biomarkers in secretions and tissues, respectively. Receiver operating characteristic curves were used to assess the predictive potential of the biomarkers mentioned above in nasal secretions.

RESULTS

Patients with Eos+Neu+ and Eos+Neu-CRS scored highest in most clinical symptom scores, while Eos-Neu+ and Eos-Neu-CRS scored lowest. Correlation analysis showed that tissues NEU number was correlated with NEU number and MPO level in nasal secretions (R = 0.4088; 0.6613); tissues EOS % was correlated with EOS% and ECP level in nasal secretions (R = 0.2344; 0.5774). To diagnose Neu+CRS, the highest area under the curve (AUC) (0.8961) was determined for MPO in secretions; the highest AUC (0.7400) was determined for NEU number in secretions. To diagnose Eos+Neu-CRS from Eos-Neu-CRS in Neu-CRS, the highest AUC (0.8801) was determined for ECP in secretions.

CONCLUSIONS

Clinical presentations are directly associated with CRS endotypes. Measurement of MPO and ECP in nasal secretions is useful for the endotypes diagnosis of CRS.

Ultrasound-responsive low-dose doxorubicin liposomes trigger mitochondrial DNA release and activate cGAS-STING-mediated antitumour immunity

DNA derived from chemotherapeutics-killed tumor cells is one of the most important damage-associated molecular patterns that can activate the cGAS-STING (cyclic GMP-AMP synthase-stimulator of interferon genes) pathway in antigen-presenting cells (APCs) and promote antitumor immunity. However, conventional chemotherapy displays limited tumor cell killing and ineffective transfer of stable tumor DNA to APCs. Here we show that liposomes loaded with an optimized ratio of indocyanine green and doxorubicin, denoted as LID, efficiently generate reactive oxygen species upon exposure to ultrasound. LID plus ultrasound enhance the nuclear delivery of doxorubicin, induce tumor mitochondrial DNA oxidation, and promote oxidized tumor mitochondrial DNA transfer to APCs for effective activation of cGAS-STING signaling. Depleting tumor mitochondrial DNA or knocking out STING in APCs compromises the activation of APCs. Furthermore, systemic injection of LID plus ultrasound over the tumor lead to targeted cytotoxicity and STING activation, eliciting potent antitumor T cell immunity, which upon the combination with immune checkpoint blockade leads to regression of bilateral MC38, CT26, and orthotopic 4T1 tumors in female mice. Our study sheds light on the importance of oxidized tumor mitochondrial DNA in STING-mediated antitumor immunity and may inspire the development of more effective strategies for cancer immunotherapy.

In Vivo Activity of Hydrogen-Peroxide Generating Electrochemical Bandage Against Murine Wound Infections

Biofilms formed by antibiotic-resistant bacteria in wound beds present unique challenges in terms of treating wound infections. In this work, the in vivo activity of a novel electrochemical bandage (e-bandage) composed of carbon fabric and controlled by a wearable potentiostat, designed to continuously deliver low amounts of hydrogen peroxide (H2O2) was evaluated against methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant Pseudomonas aeruginosa (MDR-PA) and mixed-species (MRSA and MDR-PA) wound infections. Wounds created on Swiss Webster mice were infected with the above-named bacteria and biofilms allowed to establish on wound beds for 3 days. e-Bandages, which electrochemically reduce dissolved oxygen to H2O2 when polarized at -0.6 VAg/AgCl, were placed atop the infected wound bed and polarized continuously for 48 hours. Polarized e-bandage treatment resulted in significant reductions (p <0.001) of both mono-species and mixed-species wound infections. After e-bandage treatment, electron microscopy showed degradation of bacterial cells, and histopathology showed no obvious alteration to the inflammatory host response. Blood biochemistries showed no abnormalities. Taken all together, results of this work suggest that the described H2O2-producing e-bandage can effectively reduce in vivo MRSA, MDR-PA and mixed-species wound biofilms, and should be further developed as a potential antibiotic-free strategy for treatment of wound infections.

Subcellular localization of DNA nanodevices and their applications

The application of nanodevices based on DNA self-assembly in the field of cell biology has made significant progress in the past decade. In this study, the development of DNA nanotechnology is briefly reviewed. The subcellular localization of DNA nanodevices, and their new progress and applications in the fields of biological detection, subcellular and organ pathology, biological imaging, and other fields are reviewed. The future of subcellular localization and biological applications of DNA nanodevices is also discussed.

The formation and function of the neutrophil phagosome

Neutrophils are the most abundant circulating leukocyte and are crucial to the initial innate immune response to infection. One of their key pathogen-eliminating mechanisms is phagocytosis, the process of particle engulfment into a vacuole-like structure called the phagosome. The antimicrobial activity of the phagocytic process results from a collaboration of multiple systems and mechanisms within this organelle, where a complex interplay of ion fluxes, pH, reactive oxygen species, and antimicrobial proteins creates a dynamic antimicrobial environment. This complexity, combined with the difficulties of studying neutrophils ex vivo, has led to gaps in our knowledge of how the neutrophil phagosome optimizes pathogen killing. In particular, controversy has arisen regarding the relative contribution and integration of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived antimicrobial agents and granule-delivered antimicrobial proteins. Clinical syndromes arising from dysfunction in these systems in humans allow useful insight into these mechanisms, but their redundancy and synergy add to the complexity. In this article, we review the current knowledge regarding the formation and function of the neutrophil phagosome, examine new insights into the phagosomal environment that have been permitted by technological advances in recent years, and discuss aspects of the phagocytic process that are still under debate.

Translational Fidelity during Bacterial Stresses and Host Interactions

Translational fidelity refers to accuracy during protein synthesis and is maintained in all three domains of life. Translational errors occur at base levels during normal conditions and may rise due to mutations or stress conditions. In this article, we review our current understanding of how translational fidelity is perturbed by various environmental stresses that bacterial pathogens encounter during host interactions. We discuss how oxidative stress, metabolic stresses, and antibiotics affect various types of translational errors and the resulting effects on stress adaption and fitness. We also discuss the roles of translational fidelity during pathogen-host interactions and the underlying mechanisms. Many of the studies covered in this review will be based on work with Salmonella enterica and Escherichia coli, but other bacterial pathogens will also be discussed.

MerA functions as a hypothiocyanous acid reductase and defense mechanism in Staphylococcus aureus

The major pathogen Staphylococcus aureus has to cope with host-derived oxidative stress to cause infections in humans. Here, we report that S. aureus tolerates high concentrations of hypothiocyanous acid (HOSCN), a key antimicrobial oxidant produced in the respiratory tract. We discovered that the flavoprotein disulfide reductase (FDR) MerA protects S. aureus from this oxidant by functioning as a HOSCN reductase, with its deletion sensitizing bacteria to HOSCN. Crystal structures of homodimeric MerA (2.4 Å) with a Cys₄₃ -Cys₄₈ intramolecular disulfide, and reduced MerACys₄₃ S (1.6 Å) showed the FAD cofactor close to the active site, supporting that MerA functions as a group I FDR. MerA is controlled by the redox-sensitive repressor HypR, which we show to be oxidized to intermolecular disulfides under HOSCN stress, resulting in its inactivation and derepression of merA transcription to promote HOSCN tolerance. Our study highlights the HOSCN tolerance of S. aureus and characterizes the structure and function of MerA as a major HOSCN defense mechanism. Crippling the capacity to respond to HOSCN may be a novel strategy for treating S. aureus infections.

Significance of Singlet Oxygen Molecule in Pathologies

Reactive oxygen species, including singlet oxygen, play an important role in the onset and progression of disease, as well as in aging. Singlet oxygen can be formed non-enzymatically by chemical, photochemical, and electron transfer reactions, or as a byproduct of endogenous enzymatic reactions in phagocytosis during inflammation. The imbalance of antioxidant enzymes and antioxidant networks with the generation of singlet oxygen increases oxidative stress, resulting in the undesirable oxidation and modification of biomolecules, such as proteins, DNA, and lipids. This review describes the molecular mechanisms of singlet oxygen production in vivo and methods for the evaluation of damage induced by singlet oxygen. The involvement of singlet oxygen in the pathogenesis of skin and eye diseases is also discussed from the biomolecular perspective. We also present our findings on lipid oxidation products derived from singlet oxygen-mediated oxidation in glaucoma, early diabetes patients, and a mouse model of bronchial asthma. Even in these diseases, oxidation products due to singlet oxygen have not been measured clinically. This review discusses their potential as biomarkers for diagnosis. Recent developments in singlet oxygen scavengers such as carotenoids, which can be utilized to prevent the onset and progression of disease, are also described.

Profiling protein targets of cellular toxicant exposure

Environmental agents of exposure can damage proteins, affecting protein function and cellular protein homeostasis. Specific residues are inherently chemically susceptible to damage from individual types of exposure. Amino acid content is not completely predictive of protein susceptibility, as secondary, tertiary, and quaternary structures of proteins strongly influence the reactivity of the proteome to individual exposures. Because we cannot readily predict which proteins will be affected by which chemical exposures, mass spectrometry-based proteomic strategies are necessary to determine the protein targets of environmental toxins and toxicants. This review describes the mechanisms by which environmental exposure to toxins and toxicants can damage proteins and affect their function, and emerging omic methodologies that can be used to identify the protein targets of a given agent. These methods include target identification strategies that have recently revolutionized the drug discovery field, such as activity-based protein profiling, protein footprinting, and protein stability profiling technologies. In particular, we highlight the necessity of multiple, complementary approaches to fully interrogate how protein integrity is challenged by individual exposures.

Superoxide: The enigmatic chemical chameleon in neutrophil biology

The burst of superoxide produced when neutrophils phagocytose bacteria is the defining biochemical feature of these abundant immune cells. But 50 years since this discovery, the vital role superoxide plays in host defense has yet to be defined. Superoxide is neither bactericidal nor is it just a source of hydrogen peroxide. This simple free radical does, however, have remarkable chemical dexterity. Depending on its environment and reaction partners, superoxide can act as an oxidant, a reductant, a nucleophile, or an enzyme substrate. We outline the evidence that inside phagosomes where neutrophils trap, kill, and digest bacteria, superoxide will react preferentially with the enzyme myeloperoxidase, not the bacterium. By acting as a cofactor, superoxide will sustain hypochlorous acid production by myeloperoxidase. As a substrate, superoxide may give rise to other forms of reactive oxygen. We contend that these interactions hold the key to understanding the precise role superoxide plays in neutrophil biology. State-of-the-art techniques in mass spectrometry, oxidant-specific fluorescent probes, and microscopy focused on individual phagosomes are needed to identify bactericidal mechanisms driven by superoxide. This work will undoubtably lead to fascinating discoveries in host defense and give a richer understanding of superoxide's varied biology.

New Insights of Early Brain Injury after Subarachnoid Hemorrhage: A Focus on the Caspase Family

Spontaneous subarachnoid hemorrhage (SAH), primarily caused by ruptured intracranial aneurysms, remains a prominent clinical challenge with a high rate of mortality and morbidity worldwide. Accumulating clinical trials aiming at the prevention of cerebral vasospasm (CVS) have failed to improve the clinical outcome of patients with SAH. Therefore, a growing number of studies have shifted focus to the pathophysiological changes that occur during the periods of early brain injury (EBI). New pharmacological agents aiming to alleviate EBI have become a promising direction to improve outcomes after SAH. Caspases belong to a family of cysteine proteases with diverse functions involved in maintaining metabolism, autophagy, tissue differentiation, regeneration, and neural development. Increasing evidence shows that caspases play a critical role in brain pathology after SAH. Therefore, caspase regulation could be a potential target for SAH treatment. Herein, we provide an overview pertaining to the current knowledge on the role of caspases in EBI after SAH, and we discuss the promising therapeutic value of caspase-related agents after SAH.

Rational Design of a Dual-Channel Fluorescent Probe for the Simultaneous Imaging of Hypochlorous Acid and Peroxynitrite in Living Organisms

Hypochlorous acid (HOCl) and peroxynitrite (ONOO^-) are two important highly reactive oxygen/nitrogen species, which commonly coexist in biosystems and play pivotal roles in many physiological and pathological processes. To investigate their function and correlations, it is urgently needed to construct chemical tools that can track the production of HOCl and ONOO^- in biological systems with distinct fluorescence signals. Here, we found that the coumarin fluorescence of coumarin-benzopyrylium (CB) hydrazides (spirocyclic form) is dim, and their fluorescence properties are controlled by their benzopyran moiety via an intramolecular photo-induced electron transfer (PET) process. Based on this mechanism, we report the development of a fluorescent probe CB2-H for the simultaneous detection of HOCl and ONOO^-. ONOO^- can selectively oxidize the hydrazide group of CB2-H to afford the parent dye CB2 (Abs_max/Em_max = 631/669 nm). In the case of HOCl, it undergoes an electrophilic attack on the benzopyran moiety of CB2-H to give a chlorinated product CB2-H-Cl, which inhibits the PET process within the probe and thus affords a turn-on fluorescence response at the coumarin channel (Abs_max/Em_max = 407/468 nm). Due to the marked differences in absorption/emission wavelengths between the HOCl and ONOO^- products, CB2-H enables the concurrent detection of HOCl and ONOO^- at two independent channels without spectral cross-interference. CB2-H has been applied for dual-channel fluorescence imaging of endogenously produced HOCl and ONOO^- in living cells and zebrafish under different stimulants. The present probe provides a useful tool for further exploring the distribution and correlation of HOCl and ONOO^- in more biosystems.

What improves access to primary healthcare services in rural communities? A systematic review

BACKGROUND

To compile key strategies from the international experiences to improve access to primary healthcare (PHC) services in rural communities. Different innovative approaches have been practiced in different parts of the world to improve access to essential healthcare services in rural communities. Systematically collecting and combining best experiences all over the world is important to suggest effective strategies to improve access to healthcare in developing countries. Accordingly, this systematic review of literature was undertaken to identify key approaches from international experiences to enhance access to PHC services in rural communities.

METHODS

All published and unpublished qualitative and/or mixed method studies conducted to improvement access to PHC services were searched from MEDLINE, Scopus, Web of Science, WHO Global Health Library, and Google Scholar. Articles published other than English language, citations with no abstracts and/or full texts, and duplicate studies were excluded. We included all articles available in different electronic databases regardless of their publication years. We assessed the methodological quality of the included studies using mixed methods appraisal tool (MMAT) version 2018 to minimize the risk of bias. Data were extracted using JBI mixed methods data extraction form. Data were qualitatively analyzed using emergent thematic analysis approach to identify key concepts and coded them into related non-mutually exclusive themes.

RESULTS

Our analysis of 110 full-text articles resulted in ten key strategies to improve access to PHC services. Community health programs or community-directed interventions, school-based healthcare services, student-led healthcare services, outreach services or mobile clinics, family health program, empanelment, community health funding schemes, telemedicine, working with traditional healers, working with non-profit private sectors and non-governmental organizations including faith-based organizations are the key strategies identified from international experiences.

CONCLUSION

This review identified key strategies from international experiences to improve access to PHC services in rural communities. These strategies can play roles in achieving universal health coverage and reducing disparities in health outcomes among rural communities and enabling them to get healthcare when and where they want.

Efficacy and toxicity of hydrogen peroxide producing electrochemical bandages in a porcine explant biofilm model

AIMS

Effects of H₂ O₂ producing electrochemical-bandages (e-bandages) on methicillin-resistant Staphylococcus aureus colonization and biofilm removal were assessed using a porcine explant biofilm model. Transport of H₂ O₂ produced from the e-bandage into explant tissue and associated potential toxicity were evaluated.

METHODS AND RESULTS

Viable prokaryotic cells from infected explants were quantified after 48 h treatment with e-bandages in three ex vivo S. aureus infection models: (1) reducing colonization, (2) removing young biofilms and (3) removing mature biofilms. H₂ O₂ concentration-depth profiles in explants/biofilms were measured using microelectrodes. Reductions in eukaryotic cell viability of polarized and nonpolarized noninfected explants were compared. e-Bandages effectively reduced S. aureus colonization (p = 0.029) and reduced the viable prokaryotic cell concentrations of young biofilms (p = 0.029) with limited effects on mature biofilms (p > 0.1). H₂ O₂ penetrated biofilms and explants and reduced eukaryotic cell viability by 32-44% compared to nonpolarized explants.

CONCLUSIONS

H₂ O₂ producing e-bandages were most active when used to reduce colonization and remove young biofilms rather than to remove mature biofilms.

SIGNIFICANCE AND IMPACT OF STUDY

The described e-bandages reduced S. aureus colonization and young S. aureus biofilms in a porcine explant wound model, supporting their further development as an antibiotic-free alternative for managing biofilm infections.

The Role of Oxidative Stress in Acute Ischemic Stroke-Related Thrombosis

Acute ischemic stroke is a serious life-threatening disease that affects almost 600 million people each year throughout the world with a mortality of more than 10%, while two-thirds of survivors remain disabled. However, the available treatments for ischemic stroke are still limited to thrombolysis and/or mechanical thrombectomy, and there is an urgent need for developing new therapeutic target. Recently, intravascular oxidative stress, derived from endothelial cells, platelets, and leukocytes, has been found to be tightly associated with stroke-related thrombosis. It not only promotes primary thrombus formation by damaging endothelial cells and platelets but also affects thrombus maturation and stability by modifying fibrin components. Thus, oxidative stress is expected to be a novel target for the prevention and treatment of ischemic stroke. In this review, we first discuss the mechanisms by which oxidative stress promotes stroke-related thrombosis, then summarize the oxidative stress biomarkers of stroke-related thrombosis, and finally put forward an antithrombotic therapy targeting oxidative stress in ischemic stroke.

Tracking HOCl by an incredibly simple fluorescent probe with AIE plus ESIPT in vitro and in vivo

Hypochlorous acid is an important active substance involved in a variety of physiological processes in living organisms, while abnormal concentrations of HOCl are strongly associated with a variety of diseases such as cancer, inflammation, atherosclerosis, and Alzheimer's disease. As a result, it's crucial to establish a reliable method for tracking HOCl in vivo in order to investigate its physiological consequences. In this work, we developed a fluorescent probe DFSN with both AIE and ESIPT for imaging HOCl in vivo. DFSN not only has a basic structure and is easy to synthesize, but also has superior performance. The probe responds to HOCl in less than 10 s and has good selectivity and sensitivity to HOCl (DL = 6.3 nM), with a 110-fold increase in fluorescence intensity following response. In addition, DFSN can realize the rapid detection of hypochlorous acid with naked eyes. Moreover, DFSN can be used for the detection of exogenous and endogenous HOCl in RAW264.7 cells, and additionally enables the tracking of HOCl in cancer cells (Hela cells and HepG2 cells). More notably, it has been utilized to image hypochlorous acid in zebrafish with great success. The probe DFSN will be useful in determining the physiological significance of HOCl.

An activatable Mn(II) MRI probe for detecting peroxidase activity in vitro and in vivo

Myeloperoxidase (MPO), a hallmark of the function and activation of innate immune cells, can act as a 'double-edged sword', contributing to clear infection as well as causing tissue oxidizing damage in various inflammatory diseases. In this study, an activatable Mn(II) chelate-based magnetic resonance imaging (MRI) contrast agent (CA), Mn-TyEDTA (TyEDTA = tyrosine derived ethylenediaminetetraacetic acid) structurally featuring a phenol group as the electron-donor, was developed to sense the activity of peroxidase in vitro and in vivo. Mn-TyEDTA demonstrated a peroxidase activity-dependent relaxivity in the presence of horseradish peroxidase (HRP)/H₂O₂ with more than a 2.6-fold increase in water proton relaxivity produced (HRP, 500 U; H₂O₂, 4.5 eq). A mechanism of peroxidase-mediated Mn(II) monomer radical polymerization was confirmed with those oligomers of Mn-TyEDTA such as dimer, trimer and tetramer were found in the LC-MS study. Dynamic MR imaging of normal mice revealed rapid blood clearance and mixed renal and hepatobiliary elimination of Mn-TyEDTA. Furthermore, compared to liver-specific and non-specific extracellular contrast agents (Mn-BnO-TyEDTA (BnO-TyEDTA = benzyl tyrosine-derived ethylenediaminetetraacetic acid) and Gd-DTPA (DTPA = diethylene triamine penta-acetic acid)), MRI on a monosodium urate (MSU) crystal-induced acute mice model of arthritis showed that inflamed tissues could be selectively enhanced by Mn-TyEDTA, suggesting that this peroxidase-activatable Mn(II) MRI probe could potentially be used for noninvasive detection of MPO activity in vivo.

Gas Plasma Protein Oxidation Increases Immunogenicity and Human Antigen-Presenting Cell Maturation and Activation

Protein vaccines rely on eliciting immune responses. Inflammation is a prerequisite for immune responses to control infection and cancer but is also associated with disease onset. Reactive oxygen species (ROSs) are central during inflammation and are capable of inducing non-enzymatic oxidative protein modifications (oxMods) associated with chronic disease, which alter the functionality or immunogenicity of proteins that are relevant in cancer immunotherapy. Specifically, antigen-presenting cells (APCs) take up and degrade extracellular native and oxidized proteins to induce adaptive immune responses. However, it is less clear how oxMods alter the protein's immunogenicity, especially in inflammation-related short-lived reactive species. Gas plasma technology simultaneously generates a multitude of ROSs to modify protein antigens in a targeted and controlled manner to study the immunogenicity of oxMods. As model proteins relevant to chronic inflammation and cancer, we used gas plasma-treated insulin and CXCL8. We added those native or oxidized proteins to human THP-1 monocytes or primary monocyte-derived cells (moDCs). Both oxidized proteins caused concentration-independent maturation phenotype alterations in moDCs and THP-1 cells concerning surface marker expression and chemokine and cytokine secretion profiles. Interestingly, concentration-matched H2O2-treated proteins did not recapitulate the effects of gas plasma, suggesting sufficiently short diffusion distances for the short-lived reactive species to modify proteins. Our data provide evidence of dendric cell maturation and activation upon exposure to gas plasma- but not H2O2-modified model proteins. The biological consequences of these findings need to be elucidated in future inflammation and cancer disease models.

The design of fluorescein-ferrocene derivatives as HOCl-triggered turn-on fluorescent probes and anticancer prodrugs

Overexpressed HOCl in tumors can behave as an activator for imaging-guided precision therapy. Herein, a new kind of HOCl-activated molecular platform has been developed aiming at the integration of detection, imaging, and anticancer functions. The design strategy uses a five-membered heterocyclic ring to bridge the fluorescent fluorescein part (FL) and the anticancer ferrocene part (Fc). Three derivatives, namely FL-Fc, FL-NP-Fc and FL-TEG-Fc, were designed with different grafted chains on the fluorescein mother to modulate the hydrophilic and biocompatible capacity. In these molecular platforms, the ferrocene unit serves as the fluorescence emission quencher and masked prodrug. These three could respond to HOCl with good selectivity and sensitivity, showing a turn-on fluorescence signal and anticancer efficacy. FL-TEG-Fc with the highest sensitivity (6.5 × 10^-6 M) was successfully used for imaging endogenous HOCl in AGS cells, in which it presented strong toxicity IC₅₀ = 9.5 ± 0.3 μM. The mechanistic study revealed that the five-membered heterocyclic ring of FL-TEG-Fc was broken specifically and effectively by HOCl to release strongly fluorescent fluorescein and a bioactive ferrocene derivative; the obtained ferrocene derivative further generated cytotoxic ˙OH through a Fenton-like reaction. This study provides a potential theranostic strategy against HOCl-overexpressing cancers.

Redox-Mediated Inactivation of the Transcriptional Repressor RcrR is Responsible for Uropathogenic Escherichia coli's Increased Resistance to Reactive Chlorine Species

The ability to overcome stressful environments is critical for pathogen survival in the host. One challenge for bacteria is the exposure to reactive chlorine species (RCS), which are generated by innate immune cells as a critical part of the oxidative burst. Hypochlorous acid (HOCl) is the most potent antimicrobial RCS and is associated with extensive macromolecular damage in the phagocytized pathogen. However, bacteria have evolved defense strategies to alleviate the effects of HOCl-mediated damage. Among these are RCS-sensing transcriptional regulators that control the expression of HOCl-protective genes under non-stress and HOCl stress. Uropathogenic Escherichia coli (UPEC), the major causative agent of urinary tract infections (UTIs), is particularly exposed to infiltrating neutrophils during pathogenesis; however, their responses to and defenses from HOCl are still completely unexplored. Here, we present evidence that UPEC strains tolerate higher levels of HOCl and are better protected from neutrophil-mediated killing compared with other E. coli. Transcriptomic analysis of HOCl-stressed UPEC revealed the upregulation of an operon consisting of three genes, one of which encodes the transcriptional regulator RcrR. We identified RcrR as a HOCl-responsive transcriptional repressor, which, under non-stress conditions, is bound to the operator and represses the expression of its target genes. During HOCl exposure, however, the repressor forms reversible intermolecular disulfide bonds and dissociates from the DNA resulting in the derepression of the operon. Deletion of one of the target genes renders UPEC significantly more susceptible to HOCl and phagocytosis indicating that the HOCl-mediated induction of the regulon plays a major role for UPEC’s HOCl resistance.

Role of nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 6 in activation of inflammation in human umbilical vein endothelial cells stimulated by Porphyromonas gingivalis-an in vitro study

Background/purpose

Porphyromonas gingivalis (P. gingivalis) could induce the activation of vascular endothelial cells and promote the formation of atherosclerosis. Nucleotide-binding oligomerization domain-like receptor family pyrin domain containing (NLRP) 6 could recognize P. gingivalis, but its role in atherosclerosis was unknown. The purpose of this study is to investigate the role of NLRP6 in the activation of inflammation in human umbilical vein endothelial cells (HUVECs) stimulated by P. gingivalis.

Materials and methods

The expression level of NLRP6 in HUVECs with or without P. gingivalis-challenge was observed. Down-regulating the expression of NLRP6 in HUVECs, the expression levels of interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein (MCP)-1 were detected. Then, the HUVECs with NLRP6-overexpressed were stimulated by P. gingivalis, the levels of inflammatory cytokines above were examined and compared with those in HUVECs triggered by P. gingivalis only. To evaluate the effect of NLRP6 on bacterial immune escape, the NLRP6 was overexpressed, and the colonies of P. gingivalis that survived in HUVECs were calculated.

Results

NLRP6 was expressed in HUVECs and decreased after P. gingivalis stimulation. Downregulation of NLRP6 decreased the expression levels of IL-1β, IL-6, IL-8, TNF-α and MCP-1 in HUVECs. Those cytokines above in NLRP6-overexpressed HUVECs with P. gingivalis-stimulation significantly increased than in the cells with P. gingivalis-stimulation only. Furthermore, over-expression of NLRP6 decreased the colonies of P. gingivalis survival in HUVECs.

Conclusion

NLRP6 regulated the activation of inflammation in HUVECs triggered by P. gingivalis and played an important role in P. gingivalis survival in endothelial cells.

Influence of plasma halide, pseudohalide and nitrite ions on myeloperoxidase-mediated protein and extracellular matrix damage

Myeloperoxidase (MPO) mediates pathogen destruction by generating the bactericidal oxidant hypochlorous acid (HOCl). Formation of this oxidant is however associated with host tissue damage and disease. MPO also utilizes H₂O₂ to oxidize other substrates, and we hypothesized that mixtures of other plasma anions, including bromide (Br^-), iodide (I^-), thiocyanate (SCN^-) and nitrite (NO₂^-), at normal or supplemented concentrations, might modulate MPO-mediated HOCl damage. For the (pseudo)halide anions, only SCN^- significantly modulated HOCl formation (IC₅₀ ∼33 μM), which is within the normal physiological range, as judged by damage to human plasma fibronectin or extracellular matrix preparations detected by ELISA and LC-MS. NO₂^- modulated HOCl-mediated damage, in a dose-dependent manner, at physiologically-attainable anion concentrations. However, this was accompanied by increased tyrosine and tryptophan nitration (detected by ELISA and LC-MS), and the overall extent of damage remained approximately constant. Increasing NO₂^- concentrations (0.5-20 μM) diminished HOCl-mediated modification of tyrosine and methionine, whereas tryptophan loss was enhanced. At higher NO₂^- concentrations, enhanced tyrosine and methionine loss was detected. These analytical data were confirmed in studies of cell adhesion and metabolic activity. Together, these data indicate that endogenous plasma levels of SCN^- (but not Br^- or I^-) can modulate protein modification induced by MPO, including the extent of chlorination. In contrast, NO₂^- alters the type of modification, but does not markedly decrease its extent, with chlorination replaced by nitration. These data also indicate that MPO could be a major source of nitration in vivo, and particularly at inflammatory sites where NO₂^- levels are often elevated.

Hypochlorous acid triggered fluorescent probes for in situ imaging of a psoriasis model

Psoriasis is a common skin disease with complex pathogenesis that lacks diagnostic methods. Typically, psoriasis is an inflammation-related disease accompanied by high expression of reactive oxygen species (ROS) in the infected part. However, due to the lack of suitable tools, it is difficult to identify the ROS, especially certain types of ROS (e.g., HOCl) in the psoriasis model. Here, two HOCl-specific fluorescent probes, G1 and G2, were designed and synthesized based on oxazine 1. Both probes could react with HOCl with high selectivity among other ROS under physiological conditions. The selected probe G2 could detect HOCl in HL-60 cells without special stimulation and detect endogenously produced HOCl in the mouse model of arthritis. Thus, G2 was used to identify and image HOCl in situ in the imiquimod induced psoriasis model. The result showed that HOCl was a potential pathological marker of psoriasis.

Nociceptor Neurons are Involved in the Host Response to Escherichia coli Urinary Tract Infections

Purpose

Urinary tract infections (UTIs) can evoke a rapid host immune response leading to bladder inflammation and epithelial damage. Neuroimmune interactions are critical for regulating immune function in mucosal tissues. Yet the role of nociceptor neurons in bladder host defense has not been well defined. This study aimed to explore the interaction between nociceptor neurons and bladder immune system during UTIs.

Methods

In this study, whether uropathogenic Escherichia coli (UPEC) and lipopolysaccharide (LPS) can directly stimulate nociceptor neurons was detected. Female C57BL/6J mice were treated with high dose of capsaicin, a high-affinity TRPV1 agonist, to ablate nociceptor neurons. Bladder inflammation, barrier epithelial function and bladder immune cell infiltration were assessed after UPEC infection. The level of neuropeptide calcitonin gene-related peptide (CGRP) in infected bladder was detected. Furthermore, the effects of CGRP on neutrophils and macrophages were evaluated both in vitro and in vivo.

Results

We found that UPEC and its pathogenic factor LPS could directly excite nociceptor neurons, releasing CGRP into infected bladder, which suppressed the recruitment of neutrophils, the polarization of macrophages and the killing function of UPEC. Both Botulinum neurotoxin A (BoNT/A) and BIBN4096 (CGRP antagonism) blocked neuronal inhibition and prevented against UPEC infection.

Conclusion

The present study showed a novel mechanism by which UPEC stimulated the secretion of CGRP from nociceptor neurons to suppress innate immunity.

Transcriptomic profiles of Florida pompano (Trachinotus carolinus) gill following infection by the ectoparasite Amyloodiniumocellatum

The dinoflagellate Amyloodinium ocellatum is an important pathogenic parasite infecting cultured marine and brackish water fishes worldwide. This includes cultured Florida pompano (Trachinotus carolinus), which is one of the most desirable marine food fish with high economic value in the USA. A. ocellatum infects fish gills and causes tissue damage, increased respiratory rate, reduced appetite, and mortality, especially in closed aquaculture systems. This study mimicked the natural infection of A. ocellatum in cultured pompano and conducted a transcriptomic comparison of gene expression in the gills of control and A. ocellatum infected fish to explore the molecular mechanisms of infection. RNA-seq data revealed 604 differentially expressed genes in the infected fish gills. The immunoglobulin genes (including IgM/T) augmentation and IL1 inflammation suppression were detected after infection. Genes involved in reactive oxygen species mediating parasite killing were also highly induced. However, excessive oxidants have been linked to oxidative tissue damage and apoptosis. Correspondingly, widespread down-regulation of collagen genes and growth factor deprivation indicated impaired tissue repair, and meanwhile the key executor of apoptosis, caspase-3 was highly expressed (25.02-fold) in infected fish. The infection also influenced the respiratory gas sensing and transport genes and established hypoxic conditions in the gill tissue. Additionally, food intake and lipid metabolism were also affected. Our work provides the transcriptome sequencing of Florida pompano and provides key insights into the acute pathogenesis of A. ocellatum. This information can be utilized for designing optimal disease surveillance strategies, future selection for host resistance, and development of novel therapeutic measures.

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

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