Portimine A maintains bioactivity following exposure to liver microsomes and cell lysates: no evidence for significant metabolic inactivation.

Purpose: Portimine is a marine cyclic imine toxin produced by the dinoflagellate Vulcanodinium rugosum. This compound has potent apoptotic activity against cancer cells in culture. However, despite the high cytotoxicity of portimine in vitro, it has low toxicity in vivo in comparison to related cyclic imine compounds.

Biomarkers of Oxidative and Mitochondrial Stress Are Associated With Accelerated Pace of Aging at Midlife in a Birth Cohort.

Oxidative stress and mitochondrial dysfunction are proposed to play prominent roles in the biology of aging. Human studies are limited and confounded by metabolic disturbances associated with age-related diseases. In this study, we have measured biomarkers of oxidative and mitochondrial stress in blood samples from up to 864 participants in the longitudinal Dunedin Multidisciplinary Health and Development Study at age 45.

Redox proteomic analysis of HO -treated Jurkat cells and effects of bicarbonate and knockout of peroxiredoxins 1 and 2.

Oxidation of thiol proteins and redox signaling occur in cells exposed to HO but mechanisms are unclear. We used redox proteomics to seek evidence of oxidation of specific proteins either by a mechanism involving reaction of HO with CO/bicarbonate to give the more reactive peroxymonocarbonate, or via a relay involving peroxiredoxins (Prdxs). Changes in oxidation state of specific Cys-SH residues on treating Jurkat T lymphoma cells with HO were measured by isotopically labeling reduced thiols and analysis by mass spectrometry.

Effect of peroxiredoxin 1 or peroxiredoxin 2 knockout on the thiol proteome of Jurkat cells.

Peroxiredoxins are important regulators of cellular peroxide metabolism. As antioxidants, they restrict oxidation of other cell proteins, but as signaling molecules they can act as sensors and promote thiol protein oxidation via a redox relay mechanism. The presence of peroxiredoxins could therefore influence other thiol proteins, even in cells experiencing endogenous redox activity.

Widespread genomic DNA methylation occurs following CD8 T cell activation and proliferation.

This research investigates the intricate dynamics of DNA methylation in the hours following CD8+ T cell activation, during a critical yet understudied temporal window. DNA methylation is an epigenetic modification central to regulation of gene expression and directing immune responses. Our investigation spanned 96-h post-activation and unveils a nuanced tapestry of global and site-specific methylation changes.

Comparing automated cell imaging with conventional methods of measuring cell proliferation and viability.

The ability to assess cell proliferation and viability is essential for assessing new drug treatments, particularly in cancer drug discovery. This study describes a new method that uses a plate reader digital microscopy cell imaging and analysis system to assess cell proliferation and viability. This imaging system utilizes high throughput fluorescence microscopy with two fluorescent probes: cell membrane-impermeable SYTOX green and nuclear binding Hoechst-33342.

Identification of genes associated with hypothiocyanous acid tolerance through genome-wide screening.

is a commensal bacterium and invasive pathogen that causes millions of deaths worldwide. The pneumococcal vaccine offers limited protection, and the rise of antimicrobial resistance will make treatment increasingly challenging, emphasizing the need for new antipneumococcal strategies. One possibility is to target antioxidant defenses to render more susceptible to oxidants produced by the immune system.

Oxidation of caspase-8 by hypothiocyanous acid enables TNF-mediated necroptosis.

Necroptosis is a form of regulated cell death triggered by various host and pathogen-derived molecules during infection and inflammation. The essential step leading to necroptosis is phosphorylation of the mixed lineage kinase domain-like protein by receptor-interacting protein kinase 3. Caspase-8 cleaves receptor-interacting protein kinases to block necroptosis, so synthetic caspase inhibitors are required to study this process in experimental models.

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.

Insights into HO-induced signaling in Jurkat cells from analysis of gene expression.

Hydrogen peroxide (HO) is a ubiquitous oxidant produced in a regulated manner by various enzymes in mammalian cells. HO reversibly oxidizes thiol groups of cysteine residues to mediate intracellular signaling. While examples of HOdependent signaling have been reported, the exact molecular mechanism(s) of signaling and the pathways affected are not well understood.

Inside the phagosome: A bacterial perspective.

The neutrophil phagosome is one of the most hostile environments that bacteria must face and overcome if they are to succeed as pathogens. Targeting bacterial defense mechanisms should lead to new therapies that assist neutrophils to kill pathogens, but this has not yet come to fruition. One of the limiting factors in this effort has been our incomplete knowledge of the complex biochemistry that occurs within the rapidly changing environment of the phagosome.

Site-specific decreases in DNA methylation in replicating cells following exposure to oxidative stress.

Oxidative stress is a common feature of inflammation-driven cancers, and it promotes genomic instability and aggressive tumour phenotypes. It is known that oxidative stress transiently modulates gene expression through the oxidation of transcription factors and associated regulatory proteins. Neutrophils are our most abundant white blood cells and accumulate at sites of infection and inflammation.

A newly identified flavoprotein disulfide reductase Har protects Streptococcus pneumoniae against hypothiocyanous acid.

Hypothiocyanous acid (HOSCN) is an antimicrobial oxidant produced from hydrogen peroxide and thiocyanate anions by heme peroxidases in secretory fluids such as in the human respiratory tract. Some respiratory tract pathogens display tolerance to this oxidant, which suggests that there might be therapeutic value in targeting HOSCN defense mechanisms. However, surprisingly little is known about how bacteria protect themselves from HOSCN.

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

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

Oxidation of bacillithiol during killing of Staphylococcus aureus USA300 inside neutrophil phagosomes.

Targeting immune evasion tactics of pathogenic bacteria may hold the key to treating recalcitrant bacterial infections. Staphylococcus aureus produces bacillithiol (BSH), its major low-molecular-weight thiol, which is thought to protect this opportunistic human pathogen against the bombardment of oxidants inside neutrophil phagosomes. Here, we show that BSH was oxidized when human neutrophils phagocytosed S.

Hypothiocyanous Acid Disrupts the Barrier Function of Brain Endothelial Cells.

Inflammation is a common feature of neurological diseases. During neuroinflammation, neutrophils are recruited to the brain vasculature, where myeloperoxidase can produce hypochlorous acid and the less well-studied oxidant hypothiocyanous acid (HOSCN). In this study, we exposed primary brain endothelial cells (BECs) to HOSCN and observed a rapid loss of transendothelial electrical resistance (TEER) at sublethal concentrations.

Neutrophil-vascular interactions drive myeloperoxidase accumulation in the brain in Alzheimer's disease.

Introduction: Neutrophil accumulation is a well-established feature of Alzheimer's disease (AD) and has been linked to cognitive impairment by modulating disease-relevant neuroinflammatory and vascular pathways. Neutrophils express high levels of the oxidant-generating enzyme myeloperoxidase (MPO), however there has been controversy regarding the cellular source and localisation of MPO in the AD brain.

Materials And Methods: We used immunostaining and immunoassays to quantify the accumulation of neutrophils in human AD tissue microarrays and in the brains of APP/PS1 mice.

Resistance of Streptococcus pneumoniae to Hypothiocyanous Acid Generated by Host Peroxidases.

Streptococcus pneumoniae is a serious human respiratory pathogen. It generates hydrogen peroxide (HO) as part of its normal metabolism, yet it lacks enzymes that remove this oxidant. Here we show that lactoperoxidase and myeloperoxidase, two host enzymes present in the respiratory tract, convert bacterial HO into HOSCN that S.

Antimicrobial Activity of Neutrophils Against Mycobacteria.

The mycobacterium genus contains a broad range of species, including the human pathogens and . These bacteria are best known for their residence inside host cells. Neutrophils are frequently observed at sites of mycobacterial infection, but their role in clearance is not well understood.

Glutathione utilization protects Streptococcus pneumoniae against lactoperoxidase-derived hypothiocyanous acid.

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia, resulting in more than one million deaths each year worldwide. This pathogen generates large amounts of hydrogen peroxide (HO), which will be converted to hypothiocyanous acid (HOSCN) by lactoperoxidase (LPO) in the human respiratory tract. S.

Neutrophil NET Formation with Microbial Stimuli Requires Late Stage NADPH Oxidase Activity.

Neutrophils respond to a range of stimuli by releasing extracellular traps (NETs), a mesh consisting of chromatin plus granule and cytoplasmic proteins. We have investigated NET release in response to phorbol myristate acetate (PMA), (PAO1), and , and the involvement of NADPH oxidase (NOX2) and myeloperoxidase (MPO) activities. An oxidative mechanism was involved with each stimulus, and the NOX2 inhibitor diphenylene iodonium (DPI) gave almost total inhibition.

Ascorbate Inhibits Proliferation and Promotes Myeloid Differentiation in -Mutant Leukemia.

Loss-of-function mutations in the DNA demethylase TET2 are associated with the dysregulation of hematopoietic stem cell differentiation and arise in approximately 10% of acute myeloid leukemia (AML). mutations coexist with other mutations in AML, including mutations, which can indicate a particularly poor prognosis. Ascorbate can function as an epigenetic therapeutic in pathological contexts involving heterozygous mutations by restoring activity.

Peroxiredoxin 2 oxidation reveals hydrogen peroxide generation within erythrocytes during high-dose vitamin C administration.

Intravenous infusion of high dose (>10 g) vitamin C (IVC) is a common alternative cancer therapy. IVC results in millimolar levels of circulating ascorbate, which is proposed to generate cytotoxic quantities of HO in the presence of transition metal ions. In this study we report on the in vitro and in vivo effects of millimolar ascorbate on erythrocytes.

Macrophage migration inhibitory factor (MIF) enhances hypochlorous acid production in phagocytic neutrophils.

Background: Macrophage migration inhibitory factor (MIF) is an important immuno-regulatory cytokine and is elevated in inflammatory conditions. Neutrophils are the first immune cells to migrate to sites of infection and inflammation, where they generate, among other mediators, the potent oxidant hypochlorous acid (HOCl). Here, we investigated the impact of MIF on HOCl production in neutrophils in response to phagocytic stimuli.