Down-regulation of CXCR2 on Neutrophils in Severe Sepsis Is Mediated by Inducible Nitric Oxide Synthase–derived Nitric Oxide

Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, Monte Alegre, 14049-900 Ribeirão Preto, SP, Brazil.
American Journal of Respiratory and Critical Care Medicine (Impact Factor: 13). 04/2007; 175(5):490-7. DOI: 10.1164/rccm.200601-103OC
Source: PubMed


The failure of neutrophils to migrate to an infection focus during severe sepsis is an important determinant of the inability of a host to deal with an infectious insult. Our laboratory has shown that inducible nitric oxide synthase (iNOS) induction and NO production contribute to the failure of neutrophils to migrate in the context of sepsis. Objectives and
We investigated whether CXCR2 expression contributed to the failure of neutrophils to migrate during severe sepsis and the role of NO in modulating CXCR2 expression on neutrophils in mice subjected to nonsevere (NS) or severe (S) cecal ligation and puncture (CLP).
Neutrophil migration to the infection focus was deficient in S-CLP mice, a phenomenon prevented by pharmacologic (aminoguanidine, l-canavanine) or genetic (iNOS gene deletion) inhibition of iNOS. The expression of CXCR2 on neutrophils from S-CLP mice was significantly reduced when compared with neutrophils from NS-CLP or sham-operated mice. CXCR2 expression was reestablished by pharmacologic and genetic inhibition of iNOS. Immunofluorescence and confocal analysis revealed that iNOS blockade reduced neutrophil CXCR2 internalization. Adhesion and emigration of neutrophils in macrophage inflammatory protein-2-stimulated mesentery microcirculation were reduced in S-CLP mice, compared with NS-CLP mice, and reestablished by pretreatment with aminoguanidine or l-canavanine. The NO donor S-nitroso-N-acetyl-d,l-penicillamine inhibited CXCL8-induced human neutrophil chemotaxis and CXCR2 expression on human and murine neutrophils.
These results highlight evidences that the failure of neutrophils to migrate to an infection focus during severe sepsis is associated with excessive NO production and NO-dependent regulation of the expression of CXCR2 on the neutrophil surface.

Download full-text


Available from: Fabrício Rios-Santos,
  • Source
    • "In contrast, it inhibits neutrophil migration in CLP-induced murine sepsis [120] and in NO pre-treated human neutrophils from healthy donors [121]. This defect appears to be, at least in part, dependent on the reduced expression of β 2 integrins [120], and further compounded by the NO-mediated reduction of CXCR2 surface expression on circulating neutrophils [122]. Nitric oxide reaction with reactive oxygen species (ROS) during inflammation produces peroxynitrite, which further decreases neutrophil adhesion and migration by inhibiting actin polymerization via actin S-nitrosylation [7] [123]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Neutrophil migration is critical for pathogen clearance and host survival during severe sepsis. Interaction of neutrophil adhesion receptors with ligands on endothelial cells results in firm adhesion of the circulating neutrophils, followed by neutrophil activation and directed migration to sites of infection through the basement membrane and interstitial extracellular matrix. Proteolytic enzymes and reactive oxygen species are produced and released by neutrophils in response to a variety of inflammatory stimuli. Although these mediators are important for host defense, they also promote tissue damage. Excessive neutrophil migration during the early stages of sepsis may lead to an exaggerated inflammatory response with associated tissue damage and subsequent organ dysfunction. On the other hand, dysregulation of migration and insufficient migratory response that occurs during the latter stages of severe sepsis contributes to neutrophils' inability to contain and control infection and impaired wound healing. This review discusses the major steps and associated molecules involved in the balance of neutrophil trafficking, the precise regulation of which during sepsis spells life or death for the host.
    Cardiovascular & Haematological Disorders - Drug Targets(Formerly Current Drug Targets - Cardiovascular & Hematological Disorders) 01/2015; 15(1). DOI:10.2174/1871529X15666150108113236
  • Source
    • "In addition, reduced surface levels of CXCR2 are observed during different pathologies such as sepsis due to receptor internalization, and results in impaired neutrophil trafficking to infection foci and reduced bactericidal effects (e.g. reduced ROS production) (Rios-Santos et al., 2007; Rose et al., 2004). Taken together, by investigating the effect of TSD on neutrophil subtypes and function , this study offers possible explanations through which sleep deprivation may increase our vulnerability to infections. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Lack of sleep greatly affects our immune system. The present study investigates the acute effects of total sleep deprivation on blood neutrophils, the most abundant immune cell in our circulation and the first cell type recruited to sites of infection. Thus, the population diversity and function of circulating neutrophils were compared in healthy young men following one night of total sleep deprivation (TSD) or after 8 h regular sleep. We found that neutrophil counts were elevated after nocturnal wakefulness (2.0±0.2×109/l vs. 2.6±0.2×109/l, sleep vs. TSD, respectively) and the population contained more immature CD16dim/CD62Lbright cells (0.11±0.040×109/l [5.5±1.1%] vs. 0.26±0.020×109/l [9.9±1.4%]). As the rise in numbers of circulating mature CD16bright/CD62Lbright neutrophils was less pronounced, the fraction of this subpopulation showed a significant decrease (1.8±0.15×109/l [88±1.8%] vs. 2.1±0.12×109/l [82±2.8%]). The surface expression of receptors regulating mobilization of neutrophils from bone marrow was decreased (CXCR4 and CD49d on immature neutrophils; CXCR2 on mature neutrophils). The receptor CXCR2 is also involved in the production of reactive oxygen species (ROS), and in line with this, total neutrophils produced less ROS. In addition, following sleep loss, circulating neutrophils exhibited enhanced surface levels of CD11b, which indicates enhanced granular fusion and concomitant protein translocation to the membrane. Our findings demonstrate that sleep loss exerts significant effects on population diversity and function of circulating neutrophils in healthy men. To which extent these changes could explain as to why people with poor sleep patterns are more susceptible to infections warrants further investigation.
    Brain Behavior and Immunity 06/2014; 41(1). DOI:10.1016/j.bbi.2014.05.010 · 5.89 Impact Factor
  • Source
    • "This reduced expression may be an attempt by the host to limit excessive inflammation induced by granulocytes at the site of infection but may also be detrimental. A study from Rios-Santos et al. (40) demonstrated that mice subjected to CLP show deficient neutrophil migration to the site of infection during severe sepsis, which is associated with decreased expression of CXCR2 on the cell surface. In the present study, the expression of CXCR2 differed between survivors and nonsurvivors at follow-up. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Recognition of pathogens is performed by specific receptors in cells of the innate immune system, which may undergo modulation during the continuum of clinical manifestations of sepsis. Monocytes and neutrophils play a key role in host defense by sensing and destroying microorganisms. This study aimed to evaluate the expression of CD14 receptors on monocytes; CD66b and CXCR2 receptors on neutrophils; and TLR2, TLR4, TLR5, TLR9, and CD11b receptors on both cell types of septic patients. Seventy-seven septic patients (SP) and 40 healthy volunteers (HV) were included in the study, and blood samples were collected on day zero (D0) and after 7 days of therapy (D7). Evaluation of the cellular receptors was carried out by flow cytometry. Expression of CD14 on monocytes and of CD11b and CXCR2 on neutrophils from SP was lower than that from HV. Conversely, expression of TLR5 on monocytes and neutrophils was higher in SP compared with HV. Expression of TLR2 on the surface of neutrophils and that of TLR5 on monocytes and neutrophils of SP was lower at D7 than at D0. In addition, SP who survived showed reduced expression of TLR2 and TLR4 on the surface of neutrophils at D7 compared to D0. Expression of CXCR2 for surviving patients was higher at follow-up compared to baseline. We conclude that expression of recognition and cell signaling receptors is differentially regulated between SP and HV depending on the receptor being evaluated.
    Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas / Sociedade Brasileira de Biofisica ... [et al.] 04/2014; DOI:10.1590/1414-431X20143190 · 1.01 Impact Factor
Show more