Human Neutrophil Function Research Articles

Role of l-amino acid oxidase isolated from Calloselasma rhodostoma venom on neutrophil NADPH oxidase complex activation

The action of Cr-LAAO, an l-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, on NADPH oxidase activation in isolated human neutrophil function was investigated. This enzyme has an intrinsic activity of hydrogen peroxide production. Cr-LAAO, in its native form, induces the ROS production in neutrophil and migration of cytosolic NADPH oxidase components p40phox, p47phox and p67phox to the membrane, and Rac, a GTPase protein member, with the involvement of intracellular signaling mediated by phospho PKC-α. In its inactive form, iCr-LAAO does not induce NADPH oxidase activation in neutrophil showing that the intrinsic enzymatic activity does not have a role in this process, suggesting that its primary structure is essential for the cell's stimulation. Accordingly, the data showed for the first time that the Cr-LAAO has a role in NADPH oxidase complex activation triggering relevant proinflammatory events in human neutrophils.

The effects of DOCK8 deficiency on human neutrophil functions

The effects of DOCK8 deficiency on human neutrophil functions

Impairment of Several Immune Functions and Redox State in Blood Cells of Alzheimer's Disease Patients. Relevant Role of Neutrophils in Oxidative Stress.

Since aging is considered the most risk factor for sporadic Alzheimer’s Disease (AD), the age-related impairment of the immune system (immunosenescence), based on a chronic oxidative-inflammatory stress situation, could play a key role in the development and progression of AD. Although AD is accompanied by systemic disturbance, reflecting the damage in the brain, the changes in immune response and redox-state in different types of blood cells in AD patients have been scarcely studied. The aim was to analyze the variations in several immune functions and oxidative-inflammatory stress and damage parameters in both isolated peripheral neutrophils and mononuclear blood cells, as well as in whole blood cells, from patients diagnosed with mild (mAD) and severe AD, and of age-matched controls (elderly healthy subjects) as well as of adult controls. The cognitive decline of all subjects was determined by Mini-Mental State Examination (MMSE) test (mAD stage was established at 20 ≤ MMSE ≤ 23 score; AD stage at <18 MMSE; elderly subjects >27 MMSE). The results showed an impairment of the immune functions of human peripheral blood neutrophils and mononuclear cells of mAD and AD patients in relation to healthy elderly subjects, who showed the typical immunosenescence in comparison with the adult individuals. However, several alterations were only observed in severe AD patients (lower chemotaxis, lipopolysaccharide lymphoproliferation, and interleukin (IL)-10 release; higher basal proliferation, tumor necrosis factor (TNF)-α release, and IL-10/TNF-α ratio), others only in mAD subjects (higher adherence), meanwhile others appeared in both mAD and AD patients (lower phytohemaglutinin lymphoproliferation and higher IL-6 release). This impairment of immune functions could be mediated by: (1) the higher oxidative stress and damage also observed in blood cells from mAD and AD patients and in isolated neutrophils [lower glutathione (GSH) levels, high oxidized glutathione (GSSG)/GSH ratio, and GSSG and malondialdehyde contents], and (2) the higher release of basal pro-inflammatory cytokines (IL-6 and TNF-α) found in AD patients. Because the immune system parameters studied are markers of health and rate of aging, our results supported an accelerated immunosenescence in AD patients. We suggest the assessment of oxidative stress and function parameters in peripheral blood cells as well as in isolated neutrophils and mononuclear cells, respectively, as possible markers of AD progression.

Differential Ability of Pandemic and Seasonal H1N1 Influenza A Viruses To Alter the Function of Human Neutrophils.

Neutrophils are essential cells of host innate immunity. Although the role of neutrophils in defense against bacterial and fungal infections is well characterized, there is a relative paucity of information about their role against viral infections. Influenza A virus (IAV) infection can be associated with secondary bacterial coinfection, and it has long been posited that the ability of IAV to alter normal neutrophil function predisposes individuals to secondary bacterial infections. To better understand this phenomenon, we evaluated the interaction of pandemic or seasonal H1N1 IAV with human neutrophils isolated from healthy persons. These viruses were ingested by human neutrophils and elicited changes in neutrophil gene expression that are consistent with an interferon-mediated immune response. The viability of neutrophils following coculture with either pandemic or seasonal H1N1 IAV was similar for up to 18h of culture. Notably, neutrophil exposure to seasonal (but not pandemic) IAV primed these leukocytes for enhanced functions, including production of reactive oxygen species and bactericidal activity. Taken together, our results are at variance with the universal idea that IAV impairs neutrophil function directly to predispose individuals to secondary bacterial infections. Rather, we suggest that some strains of IAV prime neutrophils for enhanced bacterial clearance. IMPORTANCE A long-standing notion is that IAV inhibits normal neutrophil function and thereby predisposes individuals to secondary bacterial infections. Here we report that seasonal H1N1 IAV primes human neutrophils for enhanced killing of Staphylococcus aureus. Moreover, we provide a comprehensive view of the changes in neutrophil gene expression during interaction with seasonal or pandemic IAV and report how these changes relate to functions such as bactericidal activity. This study expands our knowledge of IAV interactions with human neutrophils.

The 3-phenylcoumarin derivative 6,7-dihydroxy-3-[3',4'-methylenedioxyphenyl]-coumarin downmodulates the FcγR- and CR-mediated oxidative metabolism and elastase release in human neutrophils: Possible mechanisms underlying inhibition of the formation and release of neutrophil extracellular traps.

In this study, we report the ability of a set of eight 3-phenylcoumarin derivatives bearing 6,7- or 5,7-dihydroxyl groups, free or acetylated, bound to the benzopyrone moiety, to modulate the effector functions of human neutrophils. In general, (i) 6,7-disubstituted compounds (5, 6, 19, 20) downmodulated the Fcγ receptor-mediated neutrophil oxidative metabolism more strongly than 5,7-disubstituted compounds (21, 22, 23, 24), and (ii) hydroxylated compounds (5, 19, 21, 23) downmodulated this neutrophil function more effectively than their acetylated counterparts (6, 20, 22, 24, respectively). Compounds 5 (6,7-dihydroxy-3-[3',4'-methylenedioxyphenyl]-coumarin) and 19 (6,7-dihydroxy-3-[3',4'-dihydroxyphenyl]-coumarin) effectively downmodulated the neutrophil oxidative metabolism elicited via Fcγ and/or complement receptors. Compound 5 also downmodulated the immune complex-stimulated phagocytosis, degranulation of elastase, and production and release of neutrophil extracellular traps, as well as the human neutrophil chemotaxis towards n-formyl-methionyl-leucyl-phenylalanine, without altering the expression level of formyl peptide receptor type 1. Both compounds 5 and 19 did not impair the neutrophil capacity to recognize and kill Candida albicans. Docking calculations revealed that compounds 5 and 19 directly interacted with three catalytic residues - Gln-91, His-95, and Arg-239 - inside the myeloperoxidase active site. Together, these findings indicate that (i) inhibition of reactive oxygen species generation and degranulation of elastase are closely associated with downmodulation of release of neutrophil extracellular traps; and (ii) compound 5 can be a prototype for the development of novel immunomodulating drugs to treat immune complex-mediated inflammatory diseases.

Baccharis dracunculifolia DC (Asteraceae) selectively modulates the effector functions of human neutrophils

To examine whether the hydroalcoholic extract from Baccharis dracunculifolia leaves (BdE) modulates the human neutrophil oxidative metabolism, degranulation, phagocytosis and microbial killing capacity. In-vitro assays based on chemiluminescence, spectrophotometry, flow cytometry and polarimetry were used, as well as docking calculations. At concentrations that effectively suppressed the neutrophil oxidative metabolism elicited by soluble and particulate stimuli (<10 μg/ml), without clear signs of cytotoxicity, BdE (1) inhibited NADPH oxidase and myeloperoxidase activity; (2) scavenged H2 O2 and HOCl; (3) weakly inhibited phagocytosis; and (4) did not affect neutrophil degranulation and microbial killing capacity, the expression levels of TLR2, TLR4, FcγRIIa, FcγRIIIb and CR3 and the activity of elastase and lysozyme. Caffeic acid, one of the major B. dracunculifolia secondary metabolites, did not inhibit phagocytosis but interfered in the myeloperoxidase-H2 O2 -HOCl system by scavenging H2 O2 and HOCl, and interacting with the catalytic residues His-95, Arg-239 and Gln-91. BdE selectively modulates the effector functions of human neutrophils, inhibits the activity of key enzymes and scavenges physiological oxidant species. Caffeic acid contributes to lower the levels of oxidant species. Our findings help to unravel the mechanisms by which these natural products exert immunomodulatory action towards neutrophils.

Diminished neutrophil extracellular trap (NET) formation is a novel innate immune deficiency induced by acute ethanol exposure in polymicrobial sepsis, which can be rescued by CXCL1.

Polymicrobial sepsis is the result of an exaggerated host immune response to bacterial pathogens. Animal models and human studies demonstrate that alcohol intoxication is a key risk factor for sepsis-induced mortality. Multiple chemokines, such as CXCL1, CXCL2 and CXCL5 are critical for neutrophil recruitment and proper function of neutrophils. However, it is not quite clear the mechanisms by which acute alcohol suppresses immune responses and whether alcohol-induced immunosuppression can be rescued by chemokines. Thus, we assessed whether acute ethanol challenge via gavage diminishes antibacterial host defense in a sepsis model using cecal ligation and puncture (CLP) and whether this immunosuppression can be rescued by exogenous CXCL1. We found acute alcohol intoxication augments mortality and enhances bacterial growth in mice following CLP. Ethanol exposure impairs critical antibacterial functions of mouse and human neutrophils including reactive oxygen species production, neutrophil extracellular trap (NET) formation, and NET-mediated killing in response to both Gram-negative (E. coli) and Gram-positive (Staphylococcus aureus) pathogens. As compared with WT (C57Bl/6) mice, CXCL1 knockout mice display early mortality following acute alcohol exposure followed by CLP. Recombinant CXCL1 (rCXCL1) in acute alcohol challenged CLP mice increases survival, enhances bacterial clearance, improves neutrophil recruitment, and enhances NET formation (NETosis). Recombinant CXCL1 (rCXCL1) administration also augments bacterial killing by alcohol-treated and E. coli- and S. aureus-infected neutrophils. Taken together, our data unveils novel mechanisms underlying acute alcohol-induced dysregulation of the immune responses in polymicrobial sepsis, and CXCL1 is a critical mediator to rescue alcohol-induced immune dysregulation in polymicrobial sepsis.

Leukotriene (LT) B4 metabolites inhibit the LTB4-mediated responses of human neutrophils.

Abstract CONTEXT LTB4 is recognized as an excellent promoter of host defense. Indeed, it stimulates leukocyte functions mainly through the engagement of the BLT1 receptor. Of note, LTB4 induces phagocyte recruitment, the release of antimicrobial peptides, and potentiates the ingestion and the killing of pathogens. In humans, LTB4 has a short half-life and is rapidly metabolized into 12-oxo-LTB4 by monocytes/macrophages, or into 20-OH- and 20-COOH-LTB4 by neutrophils. Although LTB4 metabolites bind to the BLT1 receptor with high affinity, they poorly activate neutrophils. HYPOTHESIS We postulated that LTB4 metabolites might act as inhibitors of BLT1-mediated responses, therefore limiting the impact of LTB4 on human neutrophil functions and that inhibiting LTB4 degradation would enhance its effects on neutrophils. RESULTS 20-OH-, 20-COOH-, and 12-oxo-LTB4 inhibited all LTB4-mediated responses of neutrophils we tested (migration, degranulation, leukotriene biosynthesis). 20-OH-LTB4 was as efficient as the BLT1 antagonist CP 105,696 and all LTB4 metabolites were more potent than the anti-inflammatory and pro-resolving lipids resolvin E1 and 5(S),6(R)-lipoxin A4. In contrast, the fMLP- and IL-8-mediated responses were not affected by the LTB4 metabolites. Inhibiting LTB4 degradation into 20-OH-LTB4 in neutrophils notably amplified the LTB4-induced kinase phosphorylation and diminished the chemokinetic effect of LTB4. CONCLUSIONS Our data indicate that LTB4 metabolites act as natural inhibitors of LTB4-mediated responses and that preventing LTB4 metabolism can modulate some functions of neutrophils. These results support the idea that preventing LTB4 degradation might enhance host defense by boosting innate immunity.

The Endocannabinoid Metabolite Prostaglandin E2 (PGE2)-Glycerol Inhibits Human Neutrophil Functions: Involvement of Its Hydrolysis into PGE2 and EP Receptors.

The endocannabinoids 2-arachidonoyl-glycerol and N-arachidonoyl-ethanolamine mediate an array of pro- and anti-inflammatory effects. These effects are related, in part, to their metabolism by eicosanoid biosynthetic enzymes. For example, N-arachidonoyl-ethanolamine and 2-arachidonoyl-glycerol can be metabolized by cyclooxygenase-2 into PG-ethanolamide (PG-EA) and PG-glycerol (PG-G), respectively. Although PGE2 is a recognized suppressor of neutrophil functions, the impact of cyclooxygenase-derived endocannabinoids such as PGE2-EA or PGE2-G on neutrophils is unknown. This study's aim was to define the effects of these mediators on neutrophil functions and the underlying cellular mechanisms involved. We show that PGE2-G, but not PGE2-EA, inhibits leukotriene B4 biosynthesis, superoxide production, migration, and antimicrobial peptide release. The effects of PGE2-G were prevented by EP1/EP2 receptor antagonist AH-6809 but not the EP4 antagonist ONO-AE2-227. The effects of PGE2-G required its hydrolysis into PGE2, were not observed with the non-hydrolyzable PGE2-serinol amide, and were completely prevented by methyl-arachidonoyl-fluorophosphate and palmostatin B, and partially prevented by JZL184 and WWL113. Although we could detect six of the documented PG-G hydrolases in neutrophils by quantitative PCR, only ABHD12 and ABHD16A were detected by immunoblot. Our pharmacological data, combined with our protein expression data, did not allow us to pinpoint one PGE2-G lipase, and rather support the involvement of an uncharacterized lipase and/or of multiple hydrolases. In conclusion, we show that PGE2-G inhibits human neutrophil functions through its hydrolysis into PGE2, and by activating the EP2 receptor. This also indicates that neutrophils could regulate inflammation by altering the balance between PG-G and PG levels in vivo.

Bioassay-Guided Isolation of Iridoids and Phenylpropanoids from Aerial Parts of Lamium album and Their Anti-inflammatory Activity in Human Neutrophils.

In traditional medicine, flowers and aerial parts of Lamium album are assigned by their anti-inflammatory, antiseptic, and mucolytic activities, and are used in chronic bronchitis and pharyngitis as well as skin, vaginal, and cervical inflammation.The aim of the present study was to compare effects of ethanolic extracts prepared from flowers and aerial parts of L.album on selected functions of human neutrophils, which are involved in an inflammatory response. In order to identify the compounds engaged in the anti-inflammatory activity of extracts, the bioassay-guided isolation of compounds was performed based on the inhibition of cytokine secretion by stimulated neutrophils.The extracts were phytochemically characterized with the HPLC-DAD-MSn method. The inhibition of reactive oxygen species production by formyl-met-leu-phenylalanine- or phorbol 12-myristate 13-acetate-stimulated neutrophils was determined using luminol- or lucigenin-dependent chemiluminescence. The effect on myeloperoxidase secretion by neutrophils was established spectrophotometrically. The levels of cytokine (interleukin 8, TNF-α) production after extract treatment was measured by ELISA.The most abundant constituents of extracts were phenylpropanoids, iridoids, flavonoids, and phenolic acids. Both extracts at concentrations of 25 and 100 µg/mL significantly inhibited reactive oxygen species production, and myeloperoxidase and interleukin 8 secretion. The phenylethanoid glycosides, such as lamiusides A, B, and C as well as 6″-O-β-D-glucopyranosylmartynoside, were isolated and identified. The cells treated with 6″-O-β-D-glucopyranosylmartynoside and lamiuside B produced 29.47 ± 7.11 % and 64.67 ± 5.25 % of interleukin 8, respectively, compared to non-treated control cells.Our results support the traditional use of L.album and indicate it as a potential source of natural anti-inflammatory constituents, such as phenylpropanoids.

Multifaceted effects of Francisella tularensis on human neutrophil function and lifespan.

Francisella tularensis in an intracellular bacterial pathogen that causes a potentially lethal disease called tularemia. Studies performed nearly 100years ago revealed that neutrophil accumulation in infected tissues correlates directly with the extent of necrotic damage during F.tularensis infection. However, the dynamics and details of bacteria-neutrophil interactions have only recently been studied in detail. Herein, we review current understanding regarding the mechanisms that recruit neutrophils to F.tularensis-infected lungs, opsonization and phagocytosis, evasion and inhibition of neutrophil defense mechanisms, as well as the ability of F.tularensis to prolong neutrophil lifespan. In addition, we discuss distinctive features of the bacterium, including its ability to act at a distance to alter overall neutrophil responsiveness to exogenous stimuli, and the evidence which suggests that macrophages and neutrophils play distinct roles in tularemia pathogenesis, such that macrophages are major vehicles for intracellular growth and dissemination, whereas neutrophils drive tissue destruction by dysregulation of the inflammatory response.

Natural Product Anacardic Acid from Cashew Nut Shells Stimulates Neutrophil Extracellular Trap Production and Bactericidal Activity

Emerging antibiotic resistance among pathogenic bacteria is an issue of great clinical importance, and new approaches to therapy are urgently needed. Anacardic acid, the primary active component of cashew nut shell extract, is a natural product used in the treatment of a variety of medical conditions, including infectious abscesses. Here, we investigate the effects of this natural product on the function of human neutrophils. We find that anacardic acid stimulates the production of reactive oxygen species and neutrophil extracellular traps, two mechanisms utilized by neutrophils to kill invading bacteria. Molecular modeling and pharmacological inhibitor studies suggest anacardic acid stimulation of neutrophils occurs in a PI3K-dependent manner through activation of surface-expressed G protein-coupled sphingosine-1-phosphate receptors. Neutrophil extracellular traps produced in response to anacardic acid are bactericidal and complement select direct antimicrobial activities of the compound.

Guarea kunthiana Bark Extract Enhances the Antimicrobial Activities of Human and Bovine Neutrophils

Guarea kunthiana is used in folk remedies for the treatment of several diseases including microbial infections. The mechanism behind this phenomenon still needs to be elucidated. Here, we investigated the effect of G. kunthiana bark extract on antimicrobial functions of human and bovine neutrophils as the first line of defense against infections. For this aim, neutrophils were isolated from either human or bovine blood and treated with G. kunthiana bark extract. The antimicrobial activity of the neutrophils against Staphylococcus (S.) aureus and Escherichia (E.) coli was tested in a bacterial survival assay and a fluorescence-based phagocytosis assay. Furthermore, the formation of neutrophil extracellular traps (NETs) was visualized by immunofluorescence microscopy. We show that neutrophils treated with G. kunthiana extract distinctly increased phagocytosis of S. aureus or E. coli. Interestingly, we demonstrate that G. kunthiana bark extract induces the formation of NETs in both cell types. This effect was abolished when treating the cells with diphenyleniodonium chloride (DPI) pointing to a direct implication of the NADPH oxidase-dependent formation of reactive oxygen species in this process. In summary, our data strongly suggest that G. kunthiana bark extract boosts the antimicrobial activities of neutrophils as the first line of defense against invading pathogens.

P38 MAPK is involved in human neutrophil chemotaxis induced by L-amino acid oxidase from Calloselasma rhodosthoma

The action of LAAO, an L-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, on isolated human neutrophil function was investigated. Cr-LAAO showed no toxicity on neutrophils. Cr-LAAO in its native form induced the neutrophil chemotaxis, suggesting that its primary structure is essential for stimulation the cell. p38 MAPK and PI3K have a role as signaling pathways of CR-LAAO induced chemotaxis. This toxin also induced the production of hydrogen peroxide and stimulated phagocytosis in neutrophils. Furthermore, Cr-LAAO was able to stimulate neutrophils to release IL-6, IL-8, MPO, LTB4 and PGE2. Together, the data showed that the Cr-LAAO triggers relevant proinflammatory events.

Circadian regulation of human peripheral neutrophils

Neutrophils are the most abundant leukocytes in human blood. Beside being essential responders in bacterial and fungal infections, they also contribute to tissue reactions in many autoimmune and inflammatory diseases. Although several immune responses linked to neutrophil functions have been described to be rhythmic, the mechanism of the circadian regulation of these cells is still not understood. Characterization of the time-of-day-specific control of neutrophil responsiveness could help to better understand the pathomechanism of these inflammatory responses and design effective chronotherapy. Here we report that the time-dependent expression of core clock components in human neutrophils characteristically differs from that in mononuclear cells. Both the low expression and the reduced nuclear accumulation of the essential clock protein BMAL1 suggest that the molecular oscillator is down-regulated in neutrophils. By following the expression of the maturation marker Cxcr4 and morphological attributes (side-scattering properties and nuclear segmentation), we found that the distribution of young and aged cells within the peripheral neutrophil pool displays a daily rhythm. In addition, we detected synchronous fluctuations in the plasma level of the CXCR4 ligand CXCL12, an important regulator of cell trafficking within the bone marrow. We found that expression of another maturation marker, the core component of the superoxide generating NADPH oxidase, and parallelly, the superoxide producing capacity of neutrophils were also dependent on the time of the day. In line with this, number of opsonized bacteria engulfed by neutrophils also showed time-dependent differences, supporting that clearance of pathogens shows a daily rhythm. We suggest that maturation-dependent changes in neutrophil responsiveness rather than the cellular autonomous clock are involved in the daily regulation of human neutrophil functions.

Effects of APPA on human neutrophil function

Effects of APPA on human neutrophil function

Ultraviolet light A irradiation induces immunosuppression associated with the generation of reactive oxygen species in human neutrophils

Ultraviolet blood irradiation has been used as a physical therapy to treat many nonspecific diseases in clinics; however, the underlying mechanisms remain largely unclear. Neutrophils, the first line of host defense, play a crucial role in a variety of inflammatory responses. In the present work, we investigated the effects of ultraviolet light A (UVA) on the immune functions of human neutrophils at the single-cell level by using an inverted fluorescence microscope. N-Formyl-methionyl-leucyl-phenylalanine (FMLP), a classic physiological chemotactic peptide, was used to induce a series of immune responses in neutrophils in vitro. FMLP-induced calcium mobilization, migration, and phagocytosis in human neutrophils was significantly blocked after treatment with 365[Formula: see text]nm UVA irradiation, demonstrating the immunosuppressive effects of UVA irradiation on neutrophils. Similar responses were also observed when the cells were pretreated with H2O2, a type of reactive oxygen species (ROS). Furthermore, UVA irradiation resulted in an increase in NAD(P)H, a member of host oxidative stress in cells. Taken together, our data indicate that UVA irradiation results in immunosuppression associated with the production of ROS in human neutrophils.

Immunomodulatory effects of Santolina chamaecyparissus leaf extracts on human neutrophil functions

Context: Santolina chamaecyparissus L. (Asteraceae) is an aromatic plant wide spread in the Mediterranean region. It is used in folk medicine for its anti-inflammatory properties.Objective: The effects of S. chamaecyparissus aqueous extract (SCAE) and polyphenolic extract (SCPE) on human polymorphonuclear neutrophil (PMN) degranulation, chemotaxis, phagocytosis, and microbicidal capacity were examined in vitro.Materials and methods: Aqueous and polyphenolic extracts were prepared from S. chamaecyparissus leaves. The elastase release was used as a marker for measuring PMN degranulation, while chemotaxis was performed using a 48-microwell chemotaxis chamber. The phagocytosis and the microbicidal capacity were evaluated using fresh cultures of Candida albicans.Results: The treatment of neutrophils with different concentrations (10–200 µg/ml) of SCAE and SCPE caused a significant (p < 0.001) and dose-dependent inhibitory effect on elastase release in fMLP/Cytochalasin B (CB)-stimulated neutrophils. Indeed, 100 µg/ml of SCAE exerted an inhibitory effect of 51.97 ± 6.2%, whereas SCPE at the same concentration abolished completely PMN degranulation. Moreover, both extracts inhibited markedly (p < 0.01) fMLP-induced chemotactic migration. At 200 µg/ml, SCAE and SCPE exerted an inhibitory effect of 54.61 ± 7.3% and 57.71 ± 7.44%, respectively. In addition, a decline in both phagocytosis and microbicidal capacity against Candida albicans was observed when PMNs were exposed to 100 and 200 µg/ml of SCAE or SCPE.Conclusion: The exerted effects on neutrophil functions support the anti-inflammatory activity and show new mechanisms of action and effectiveness of S. chamaecyparissus leaf extracts. This plant may be considered as an interesting source of anti-inflammatory and immunomodulatory agents.

The effect of a selective CXCR2 antagonist (AZD5069) on human blood neutrophil count and innate immune functions.

The aim of the present study was to investigate whether selective antagonism of the cysteine-X-cysteine chemokine receptor-2 (CXCR2) receptor has any adverse effects on the key innate effector functions of human neutrophils for defence against microbial pathogens. In a double-blind, crossover study, 30 healthy volunteers were randomized to treatment with the CXCR2 antagonist AZD5069 (100 mg) or placebo, twice daily orally for 6 days. The peripheral blood neutrophil count was assessed at baseline, daily during treatment and in response to exercise challenge and subcutaneous injection of granulocyte-colony stimulating factor (G-CSF). Neutrophil function was evaluated by phagocytosis of Escherichia coli and by the oxidative burst response to E. coli. AZD5069 treatment reversibly reduced circulating neutrophil count from baseline by a mean [standard deviation (SD)] of -1.67 (0.67) ×10(9) l(-1) vs. 0.19 (0.78) ×10(9) l(-1) for placebo on day 2, returning to baseline by day 7 after the last dose. Despite low counts on day 4, a 10-min exercise challenge increased absolute blood neutrophil count, but the effect with AZD5069 was smaller and not sustained, compared with placebo treatment. Subcutaneous G-CSF on day 5 caused a substantial increase in blood neutrophil count in both placebo- and AZD5069-treated subjects. Superoxide anion production in E. coli-stimulated neutrophils and phagocytosis of E. coli were unaffected by AZD5069 (P = 0.375, P = 0.721, respectively vs. baseline, Day 4). AZD5069 was well tolerated. CXCR2 antagonism did not appear adversely to affect the mobilization of neutrophils from bone marrow into the peripheral circulation, phagocytosis or the oxidative burst response to bacterial pathogens. This supports the potential of CXCR2 antagonists as a treatment option for diseases in which neutrophils play a pathological role.

The uncovering of ESE-1 in human neutrophils: implication of its role in neutrophil function and survival.

Epithelium-specific Ets transcription factor 1 (ESE-1) is a member of the E26 transformation-specific family of transcription factors that has an epithelial-restricted constitutive expression but is induced by inflammatory stimuli in non-epithelial cells. Here we report that ESE-1 is constitutively expressed in human, but not in murine, neutrophils and that ESE-1 is modestly upregulated in septic patient neutrophils. In normal human neutrophils, ESE-1 was detected at both RNA and protein levels but was found to be an unstable nuclear protein ex vivo. ESE-1 transcription was also induced during all-trans retinoic acid-mediated HL-60 differentiation, a human promyelocytic cell line often used as an in vitro model of human neutrophils. Elf3-/- mice had normal neutrophils but a reduced number of circulating B-lymphocytes. These findings indicate a potential role of ESE-1 in regulating human neutrophil differentiation and function, and that it has different roles in the immune system of different species.