Severe chronic non-bacterial osteomyelitis in combination with total MPO deficiency and responsiveness to TNFα inhibition.

We describe a female patient suffering from severe chronic non-bacterial osteomyelitis (CNO) with systemic inflammation and advanced malnutrition and complete deficiency of myeloperoxidase (MPO). CNO is a rare autoinflammatory bone disorder associated with dysregulation of the innate immune system. MPO deficiency is a genetic disorder with partial or complete absence of the phagocyte peroxidase MPO. MPO deficiency has no established clinical phenotype but reports indicate increased susceptibility to infection and chronic inflammation. The patient's symptoms began at 10 years of age with pain in the thighs, systemic inflammation and malnutrition. She was diagnosed with CNO at 14 years of age. Treatment with nonsteroidal anti-inflammatory drugs, corticosteroids, bisphosphonates or IL1-receptor antagonists (anakinra) did not relieve the symptoms. However, the patient responded instantly and recovered from her clinical symptoms when treated with TNFα blockade (adalimumab). Three years after treatment initiation adalimumab was withdrawn, resulting in rapid symptom recurrence. When reintroducing adalimumab, the patient promptly responded and went into remission. In addition to clinical and laboratory profiles, neutrophil functions (reactive oxygen species, ROS; neutrophil extracellular traps, NETs; degranulation; apoptosis; elastase activity) were investigated both in a highly inflammatory state (without treatment) and in remission (on treatment). At diagnosis, neither IL1ß, IL6, nor TNFα was significantly elevated in serum, but since TNFα blockade terminated the inflammatory symptoms, the disease was likely TNFα-driven. All neutrophil parameters were normal both during treatment and treatment withdrawal, except for MPO-dependent intracellular ROS- and NET formation. The role of total MPO deficiency for disease etiology and severity is discussed.

Candida albicans induces neutrophil extracellular traps and leucotoxic hypercitrullination via candidalysin.

The peptide toxin candidalysin, secreted by Candida albicans hyphae, promotes stimulation of neutrophil extracellular traps (NETs). However, candidalysin alone triggers a distinct mechanism for NET-like structures (NLS), which are more compact and less fibrous than canonical NETs. Candidalysin activates NADPH oxidase and calcium influx, with both processes contributing to morphological changes in neutrophils resulting in NLS formation. NLS are induced by leucotoxic hypercitrullination, which is governed by calcium-induced protein arginine deaminase 4 activation and initiation of intracellular signalling events in a dose- and time-dependent manner. However, activation of signalling by candidalysin does not suffice to trigger downstream events essential for NET formation, as demonstrated by lack of lamin A/C phosphorylation, an event required for activation of cyclin-dependent kinases that are crucial for NET release. Candidalysin-triggered NLS demonstrate anti-Candida activity, which is resistant to nuclease treatment and dependent on the deprivation of Zn2+ . This study reveals that C. albicans hyphae releasing candidalysin concurrently trigger canonical NETs and NLS, which together form a fibrous sticky network that entangles C. albicans hyphae and efficiently inhibits their growth.

Protein N-glycosylation in the bronchoalveolar space differs between never-smokers and long-term smokers with and without COPD.

Chronic obstructive pulmonary disease (COPD) kills millions of people annually and patients suffering from exacerbations of this disorder display high morbidity and mortality. The clinical course of COPD is associated with dysbiosis and infections, but the underlying mechanisms are poorly understood. Glycosylation of proteins play roles in regulating interactions between microbes and immune cells, and knowledge on airway glycans therefore contribute to the understanding of infections. Furthermore, glycans have biomarker potential for identifying smokers with enhanced risk for developing COPD as well as COPD subgroups. Here, we characterized the N-glycosylation in the lower airways of healthy never-smokers (HNS, n = 5) and long-term smokers (LTS) with (LTS+, n = 4) and without COPD (LTS-, n = 8). Using mass spectrometry, we identified 57 highly confident N-glycan structures whereof 38 oligomannose, complex, and paucimannose type glycans were common to BAL samples from HNS, LTS- and LTS+ groups. Hybrid type N-glycans were identified only in the LTS+ group. Qualitatively and quantitatively, HNS had lower inter-individual variation between samples compared to LTS- or LTS+. Cluster analysis of BAL N-glycosylation distinguished LTS from HNS. Correlation analysis with clinical parameters revealed that complex N-glycans were associated with health and absence of smoking whereas oligomannose N-glycans were associated with smoking and disease. The N-glycan profile from monocyte-derived macrophages differed from the BAL N-glycan profiles. In conclusion, long-term smokers display substantial alterations of N-glycosylation in the bronchoalveolar space, and the hybrid N-glycans identified only in long-term smokers with COPD deserve to be further studied as potential biomarkers.

A rare CTSC mutation in Papillon-Lefèvre Syndrome results in abolished serine protease activity and reduced NET formation but otherwise normal neutrophil function.

Papillon-Lefèvre Syndrome (PLS) is an autosomal recessive monogenic disease caused by loss-of-function mutations in the CTSC gene, thus preventing the synthesis of the protease Cathepsin C (CTSC) in a proteolytically active form. CTSC is responsible for the activation of the pro-forms of the neutrophil serine proteases (NSPs; Elastase, Proteinase 3 and Cathepsin G), suggesting its involvement in a variety of neutrophil functions. In PLS neutrophils, the lack of CTSC protease activity leads to inactivity of the NSPs. Clinically, PLS is characterized by an early, typically pre-pubertal, onset of severe periodontal pathology and palmoplantar hyperkeratosis. However, PLS is not considered an immune deficiency as patients do not typically suffer from recurrent and severe (bacterial and fungal) infections. In this study we investigated an unusual CTSC mutation in two siblings with PLS, a 503A>G substitution in exon 4 of the CTSC gene, expected to result in an amino acid replacement from tyrosine to cysteine at position 168 of the CTSC protein. Both patients bearing this mutation presented with pronounced periodontal pathology. The characteristics and functions of neutrophils from patients homozygous for the 503A>G CTSC mutation were compared to another previously described PLS mutation (755A>T), and a small cohort of healthy volunteers. Neutrophil lysates from patients with the 503A>G substitution lacked CTSC protein and did not display any CTSC or NSP activity, yet neutrophil counts, morphology, priming, chemotaxis, radical production, and regulation of apoptosis were without any overt signs of alteration. However, NET formation upon PMA-stimulation was found to be severely depressed, but not abolished, in PLS neutrophils.

Systemic Galectin-3 in Smokers with Chronic Obstructive Pulmonary Disease and Chronic Bronchitis: The Impact of Exacerbations.

PURPOSE: The carbohydrate-binding protein Galectin-3 is increased in several inflammatory diseases and has recently been forwarded as a systemic biomarker in chronic obstructive pulmonary disease (COPD). In this longitudinal study, we characterized the level of systemic Galectin-3 using blood from smokers with a history of COPD and chronic bronchitis (COPD-CB), during stable clinical conditions and exacerbations. PATIENTS AND METHODS: The study population comprised 56 long-term smokers with COPD-CB, 10 long-term smokers without lung disease (LTS) and 10 clinically healthy never-smokers (HNS). Blood samples were analyzed for levels of Galectin-3, leukocyte populations and C-reactive protein (CRP). In addition, sputum samples from the COPD-CB group were analyzed for bacterial growth. RESULTS: When comparing stable clinical conditions and exacerbations in the COPD-CB group, we found that the level of Galectin-3, just like that of CRP, leukocytes and neutrophils, respectively, was increased during exacerbations. However, this exacerbation-associated increase of Galectin-3 was modest. During stable clinical conditions of COPD-CB, the level of Galectin-3 was not elevated in comparison with HNS or LTS. Nor did this level of Galectin-3 distinguish patients that remained in a clinically stable condition throughout the study to those that developed an exacerbation. In addition, neither during stable clinical conditions nor during exacerbations, did the presence of bacterial growth in sputum alter Galectin-3 levels. In contrast to Galectin-3, the level of CRP, leukocytes and neutrophils, respectively, were increased during clinical stable conditions in the COPD-CB group compared with the other groups and were further enhanced during exacerbations. CONCLUSION: Systemic Galectin-3 is increased in a reproducible but modest manner during exacerbations in smokers with COPD-CB. During stable clinical conditions, the level of systemic Galectin-3 does not distinguish patients that remain clinically stable from those that develop exacerbations. This makes it less likely that systemic Galectin-3 may become a clinically useful biomarker in the current setting.

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

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

Increased CD11b and Decreased CD62L in Blood and Airway Neutrophils from Long-Term Smokers with and without COPD.

There is incomplete mechanistic understanding of the mobilization of neutrophils in the systemic and local compartment in smokers with chronic obstructive pulmonary disease (COPD). In this pilot study, we characterized how the adhesion molecules CD11b and CD62L, surface markers indicative of priming, are altered as neutrophils extravasate, and whether surface density of CD11b and CD62L differs between long-term tobacco smokers (LTS) with and without COPD compared with healthy never-smokers (HNS). Unstimulated blood neutrophils from LTS with (n = 5) and without (n = 9) COPD displayed lower surface density of CD62L compared with HNS (n = 8). In addition, surface density of CD11b was higher in bronchoalveolar lavage (BAL) neutrophils from LTS without COPD compared with those with COPD and HNS. Moreover, in BAL neutrophils from all study groups, CD62L was lower compared with matched blood neutrophils. In addition, BAL neutrophils responded with a further decrease in CD62L to ex vivo TNF stimulation. Thus, neutrophils in the airway lumen display a higher state of priming than systemic neutrophils and bear the potential to be further primed by local cytokines even with no smoking or the presence of COPD, findings that may represent a universal host defense mechanism against local bacteria. Moreover, systemic neutrophils are primed in LTS regardless of COPD. Further studies in larger materials are warranted to determine whether the priming of neutrophils is protective against COPD or merely preceding it.

In Vivo Transmigrated Human Neutrophils Are Highly Primed for Intracellular Radical Production Induced by Monosodium Urate Crystals.

Gout is an inflammatory disease caused by monosodium urate (MSU) crystals. The role of neutrophils in gout is less clear, although several studies have shown neutrophil extracellular trap (NET) formation in acutely inflamed joints of gout patients. MSU crystals are known to induce the production of reactive oxygen species (ROS) and NET formation in neutrophils isolated from blood, but there is inconclusive knowledge on the localization of ROS production as well as whether the ROS are required for NET formation. In this report we demonstrate that MSU crystals activate human neutrophils to produce ROS exclusively in intracellular compartments. Additionally, in vivo transmigrated neutrophils derived from experimental skin chambers displayed markedly increased ROS production as compared to resting blood neutrophils. We also confirmed that MSU stimulation potently induced NET formation, but this response was not primed in in vivo transmigrated neutrophils. In line with this we found that MSU-triggered NET formation was independent of ROS production and proceeded normally in neutrophils from patients with dysfunctional respiratory burst (chronic granulomatous disease (CGD) and complete myeloperoxidase (MPO) deficiency). Our data indicate that in vivo transmigrated neutrophils are markedly primed for oxidative responses to MSU crystals and that MSU triggered NET formation is independent of ROS production.

Functional characteristics of circulating granulocytes in severe congenital neutropenia caused by ELANE mutations.

BACKGROUND: Neutrophils and eosinophils are multifunctional granulocytes derived from common myelocytic-committed progenitor cells. Severe congenital neutropenia 1 (SCN1) caused by ELANE mutations is a rare disease characterized by very low numbers of circulating neutrophils. Little is known about the functional characteristics of the SCN1 granulocytes, except that eosinophilia has been noticed in both bone marrow and peripheral blood. In this study, we profiled the number and function of granulocytes in patients suffering from SCN1. METHODS: Nine patients diagnosed with SCN1 were enrolled in this study and absolute counts of eosinophils and neutrophils from bone marrow aspirates and peripheral blood samples were analysed. In addition, Ficoll-Paque enriched granulocytes from patients and healthy controls were analysed for specific eosinophil and neutrophil markers using flow cytometry and for NADPH-oxidase activity-profile by chemiluminescence. RESULTS: Our data demonstrate a skewed granulocyte population in SCN1 patients dominated by eosinophils in both bone marrow and peripheral blood. The latter was detected only by blood smear examination, but not by automated blood analysers. Furthermore, we show that the SCN1 eosinophils exerted normal production of reactive oxygen species generated by the NADPH-oxidase, however the response was profoundly different from that of healthy control neutrophils. CONCLUSIONS: SCN1 patients with ELANE mutations suffer from neutropenia yet display eosinophilia in the bone marrow and blood, as revealed by smear examination but not by automatic blood analysers. The SCN1 eosinophils are functionally normal regarding production of reactive oxygen species (ROS). However, the ROS profile produced by eosinophils differs drastically from that of neutrophils isolated from the same blood donor, implying that the eosinophilia in SCN1 cannot compensate for the loss of neutrophils regarding ROS-mediated functions.

Intracellular Neutrophil Oxidants: From Laboratory Curiosity to Clinical Reality.

The phagocyte NADPH oxidase is responsible for the neutrophil's great capacity to produce reactive oxygen species (ROS). The NADPH oxidase can be assembled in the plasma membrane, as well as in membranes of intracellular vesicles, giving neutrophils the ability to direct ROS production to distinct subcellular sites. Neutrophil ROS contribute to microbial killing, trigger formation of neutrophil extracellular traps and appear to partake in inflammation control. Consequently, function-disrupting mutations in the NADPH oxidase lead to chronic granulomatous disease, characterized by severe infections and inflammatory disorders. Recent experimental data and description of a novel chronic granulomatous disease subtype (p40phox-deficiency) imply that ROS generated in intracellular compartments are key for NETosis and for controlling inflammatory signaling. We foresee boosted interest in intracellular ROS production. To fully understand where and how such ROS function, however, limitations of assay systems to measure ROS need to be appreciated, and the development of novel techniques/reagents would be highly useful.

Galectin-3 enhances monocyte-derived macrophage efferocytosis of apoptotic granulocytes in asthma.

BACKGROUND: Galectin-3 is a 32 kDa protein secreted by macrophages involved in processes such as cell activation, chemotaxis and phagocytosis. Galectin-3 has previously been shown to improve the ability of airway macrophages to ingest apoptotic cells (efferocytosis) in chronic obstructive pulmonary disease (COPD) and may be of interest in non-eosinophilic asthma (NEA) which is also characterised by impaired efferocytosis. It was hypothesised that the addition of exogenous galectin-3 to monocyte-derived macrophages (MDMs) derived from donors with NEA would enhance their ability to engulf apoptotic granulocytes. METHODS: Eligible non-smoking adults with asthma (n = 19), including 7 with NEA and healthy controls (n = 10) underwent a clinical assessment, venepuncture and sputum induction. MDMs were co-cultured with apoptotic granulocytes isolated from healthy donors with or without exogenous recombinant galectin-3 (50 µg/mL) and efferocytosis was assessed by flow cytometry. Galectin-3 expression and localisation in MDMs was visualised by immunofluorescence staining and fluorescence microscopy. Galectin-3, interleukin (IL)-6 and CXCL8 secretion were measured in cell culture supernatants by ELISA and cytometric bead array. RESULTS: Baseline efferocytosis (mean (±standard deviation)) was lower in participants with asthma (33.2 (±17.7)%) compared with healthy controls (45.3 (±15.9)%; p = 0.081). Efferocytosis did not differ between the participants with eosinophilic asthma (EA) (31.4 (±19.2)%) and NEA (28.7 (±21.5)%; p = 0.748). Addition of galectin-3 significantly improved efferocytosis in asthma, particularly in NEA (37.8 (±18.1)%) compared with baseline (30.4 (±19.7)%; p = 0.012). Efferocytosis was not associated with any of the clinical outcomes but was negatively correlated with sputum macrophage numbers (Spearman r = - 0.671; p = 0.017). Galectin-3 was diffusely distributed in most MDMs but formed punctate structures in 5% of MDMs. MDM galectin-3 secretion was lower in asthma (9.99 (2.67, 15.48) ng/mL) compared with the healthy controls (20.72 (11.28, 27.89) ng/mL; p = 0.044) while IL-6 and CXCL8 levels were similar. CONCLUSIONS: Galectin-3 modulates macrophage function in asthma, indicating a potential role for galectin-3 to reverse impaired efferocytosis in NEA.

Elevated Mitochondrial Reactive Oxygen Species and Cellular Redox Imbalance in Human NADPH-Oxidase-Deficient Phagocytes.

Chronic granulomatous disease (CGD) is caused by mutations in genes that encode the NADPH-oxidase and result in a failure of phagocytic cells to produce reactive oxygen species (ROS) via this enzyme system. Patients with CGD are highly susceptible to infections and often suffer from inflammatory disorders; the latter occurs in the absence of infection and correlates with the spontaneous production of inflammatory cytokines. This clinical feature suggests that NADPH-oxidase-derived ROS are not required for, or may even suppress, inflammatory processes. Experimental evidence, however, implies that ROS are in fact required for inflammatory cytokine production. By using a myeloid cell line devoid of a functional NADPH-oxidase and primary CGD cells, we analyzed intracellular oxidants, signs of oxidative stress, and inflammatory cytokine production. Herein, we demonstrate that phagocytes lacking a functional NADPH-oxidase, namely primary CGD phagocytes and a gp91phox-deficient cell line, display elevated levels of ROS derived from mitochondria. Accordingly, these cells, despite lacking the major source of cellular ROS, display clear signs of oxidative stress, including an induced expression of antioxidants and altered oxidation of cell surface thiols. These observed changes in redox state were not due to abnormalities in mitochondrial mass or membrane integrity. Finally, we demonstrate that increased mitochondrial ROS enhanced phosphorylation of ERK1/2, and induced production of IL8, findings that correlate with previous observations of increased MAPK activation and inflammatory cytokine production in CGD cells. Our data show that elevated baseline levels of mitochondria-derived oxidants lead to the counter-intuitive observation that CGD phagocytes are under oxidative stress and have enhanced MAPK signaling, which may contribute to the elevated basal production of inflammatory cytokines and the sterile inflammatory manifestations in CGD.

The Neutrophil Response Induced by an Agonist for Free Fatty Acid Receptor 2 (GPR43) Is Primed by Tumor Necrosis Factor Alpha and by Receptor Uncoupling from the Cytoskeleton but Attenuated by Tissue Recruitment.

Ligands with improved potency and selectivity for free fatty acid receptor 2 (FFA2R) have become available, and we here characterize the neutrophil responses induced by one such agonist (Cmp1) and one antagonist (CATPB). Cmp1 triggered an increase in the cytosolic concentration of Ca(2+), and the neutrophils were then desensitized to Cmp1 and to acetate, a naturally occurring FFA2R agonist. The antagonist CATPB selectively inhibited responses induced by Cmp1 or acetate. The activated FFA2R induced superoxide anion secretion at a low level in naive blood neutrophils. This response was largely increased by tumor necrosis factor alpha (TNF-α) in a process associated with a recruitment of easily mobilizable granules, but neutrophils recruited to an aseptic inflammation in vivo were nonresponding. Superoxide production induced by Cmp1 was increased in latrunculin A-treated neutrophils, but no reactivation of desensitized FFA2R was induced by this drug, suggesting that the cytoskeleton is not directly involved in terminating the response. The functional and regulatory differences between the receptors that recognize short-chain fatty acids and formylated peptides, respectively, imply different roles of these receptors in the orchestration of inflammation and confirm the usefulness of a selective FFA2R agonist and antagonist as tools for the exploration of the precise role of the FFA2R.

A pepducin designed to modulate P2Y2R function interacts with FPR2 in human neutrophils and transfers ATP to an NADPH-oxidase-activating ligand through a receptor cross-talk mechanism.

Several G-protein-coupled receptors (GPCRs) can be activated or inhibited in a specific manner by membrane-permeable pepducins, which are short palmitoylated peptides with amino acid sequences identical to an intracellular domain of the receptor to be targeted. Unlike the endogenous P2Y2R agonist ATP, the P2Y2PalIC2 pepducin, which has an amino acid sequence corresponding to the second intracellular loop of the human ATP receptor (P2Y2R), activated the superoxide anion-generating NADPH-oxidase in neutrophils. In addition to having a direct effect on neutrophils, the P2Y2R pepducin converted naïve neutrophils to a primed state, which secondarily responded to ATP by producing superoxide. A pepducin with a peptide identical to the third intracellular loop of P2Y2R (P2Y2PalIC3) exhibited the same basic functions as P2Y2PalIC2, whereas one with a peptide that was identical to the first intracellular loop (P2Y2PalIC1) lacked these functions. The responses induced in neutrophils by the P2Y2R pepducins were not inhibited by the P2Y2R antagonist AR-C118925, and the receptor desensitization profile suggested the involvement of FPR2 rather than P2Y2R. Accordingly, antagonists/inhibitors of FPR2 attenuated the activities of the P2Y2R pepducins, which also selectively activated FPR2-overexpressing cells. In summary, we show that pepducins supposed to target P2Y2R activate human neutrophils through FPR2. We also show that the P2Y2PalIC2 pepducin can convert ATP from a non-activating agent to a potent neutrophil NADPH-oxidase activator. The molecular basis of this phenomenon involves cross-talk between the receptor/ligand pairs of P2Y2R/ATP and FPR2/P2Y2-pepducin.

Optimizing DMPK Properties: Experiences from a Big Pharma DMPK Department.

BACKGROUND: The disposition of a drug is dependent on interactions between the body and the drug, its molecular properties and the physical and biological barriers presented in the body. In order for a drug to have a desired pharmacological effect it has to have the right properties to be able to reach the target site in sufficient concentration. This review details how drug metabolism and pharmacokinetics (DMPK) and physicochemical deliveries played an important role in data interpretation and compound optimization at AstraZeneca R&D in Södertälje, Sweden. METHODS: A selection of assays central in the evaluation of the DMPK properties of new chemical entities is presented, with guidance and consideration on assay outcome interpretation. Early in projects, solubility, LogD, permeability and metabolic stability were measured to support effective optimization of DMPK properties. Changes made to facilitate high throughput, efficient bioanalysis and the handling of large amounts of samples are described. Already early in drug discovery, we used an integrated approach for the prediction of the fate of drugs in human (early dose to man) based on data obtained from in vitro experiments. The early dose to man was refined with project progression, which triggered more intricate assays and experiments. At later stages, preclinical in vivo pharmacokinetic (PK) data was integrated with pharmacodynamics (PD) to allow predictions of required dose, dose intervals and exposure profile to achieve the desired effect in man. RESULTS AND CONCLUSIONS: A well-defined work flow of DMPK activities from early lead identification up to the selection of a candidate drug was developed. This resulted in a cost effective and efficient optimization of chemical series, and facilitated informed decision making throughout project progress.

Phagocyte interactions with Mycobacterium tuberculosis--Simultaneous analysis of phagocytosis, phagosome maturation and intracellular replication by imaging flow cytometry.

Utilization of compounds that enhance the innate immune response against Mycobacterium tuberculosis is an attractive strategy for combating tuberculosis in the post-antibiotic era. Thus, it is crucial to develop methods that can be used to screen for such compounds and to investigate their mechanisms of action. Here, we used imaging flow cytometry (ImageStreamX Mk II),which enables rapid quantification of microscopic images in flow, to study the interaction between phagocytes and M. tuberculosis. Macrophage-differentiated THP-1 cells were infected with GFP-expressing M. tuberculosis H37Ra, and methods for rapidly assessing phagocytosis, phagosome maturation, and bacterial replication inside the cells were developed and evaluated. These aspects of innate immunity are essential in determining the outcome of mycobacterial infection of phagocytes. The technique was found effective for monitoring phagocytosis of mycobacteria, phagosomal acidification and phagolysosomal fusion, as well as for measuring mycobacterial replication inside the cells. Several of these aspects could be analyzed simultaneously in the same sample, providing a great deal of information about the phagocyte­mycobacterial interaction at once. Thus, this method has great potential to be useful both for basic research questions and for evaluating compounds that enhance the innate immune response against M. tuberculosis.

P2Y2 receptor signaling in neutrophils is regulated from inside by a novel cytoskeleton-dependent mechanism.

Functional selectivity, a process by which G-protein coupled receptors (GPCRs) can activate one signaling route while avoiding another, is regulated by ligand-mediated stabilization of specific receptor states that modulate different downstream signaling events. We propose a novel mechanism for functional selectivity, induced by the endogenous P2Y2R agonist ATP and regulated at the signaling interface by the cytoskeleton. Upon ATP stimulation of human neutrophils, a transient rise in the cytosolic concentration of free Ca(2+) was not followed by activation of the superoxide anion-generating NADPH-oxidase. This was in contrast to signals generated through the formyl peptide receptor 1 (FPR1), as its activation was accompanied by both a mobilization of Ca(2+) and activation of the NADPH-oxidase. The phospholipase C/Ca(2+) signaling route is not modulated by the cytoskeleton-disrupting drug latrunculin A, but this drug was able to launch a new signaling route downstream of P2Y2R that led to NADPH-oxidase activation. The signaling downstream of P2Y2R was rapidly terminated and the receptors were desensitized; however, in contrast to desensitized FPR1, no P2Y2 receptor reactivation could be induced by latrunculin A. Thus, P2Y2R desensitization does not appear to involve the cytoskeleton, contrary to FPR1 desensitization. In summary, we hereby describe how ATP regulates functional selectivity via the cytoskeleton, leading to intracellular Ca(2+) increase, alone or with simultaneous NADPH-oxidase activation in neutrophils.

CTLA4 Immunoglobulin but Not Anti-Tumor Necrosis Factor Therapy Promotes Staphylococcal Septic Arthritis in Mice.

BACKGROUND: The development of biologics has greatly increased the quality of life and the life expectancy of many patients with rheumatoid arthritis. However, a large number of these patients have an increased risk of developing serious infections. The aim of this study was to examine differential effects of anti-tumor necrosis factor (TNF) treatment and CTLA4 immunoglobulin (Ig) treatment on both immunological response and host defense in a murine model of septic arthritis. METHODS: Abatacept (CTLA4-Ig), etanercept (anti-TNF), or phosphate-buffered saline were given to NMRI mice intravenously inoculated with Staphylococcus aureus. The clinical course of septic arthritis and histopathological and radiological changes of joints were compared among the groups. RESULTS: Mice receiving CTLA4-Ig treatment had more-severe septic arthritis, compared with controls and mice receiving anti-TNF treatment. Anti-TNF treatment led to more-severe weight loss and kidney abscesses, as well as a higher bacterial burden in the kidneys. Mice receiving CTLA4-Ig therapy had lower serum levels of interleukin 4, whereas mice receiving anti-TNF therapy had higher levels of TNF-α. Both iNOS and arginase-1 expression were reduced in peritoneal macrophages from mice receiving CTLA4-Ig, compared with expression in the anti-TNF group. CONCLUSIONS: CTLA4-Ig therapy significantly increased the susceptibility to S. aureus septic arthritis in mice, whereas anti-TNF therapy deteriorated host bacterial clearance, resulting in more-severe weight loss and kidney abscesses.

Signal regulatory protein alpha is present in several neutrophil granule populations and is rapidly mobilized to the cell surface to negatively fine-tune neutrophil accumulation in inflammation.

Signal regulatory protein alpha (SIRPα) is a cell surface glycoprotein with inhibitory functions, which may regulate neutrophil transmigration. SIRPα is mobilized to the neutrophil surface from specific granules, gelatinase granules, and secretory vesicles following inflammatory activation in vitro and in vivo. The lack of SIRPα signaling and the ability to upregulate SIRPα to the cell surface promote neutrophil accumulation during inflammation in vivo.