Features of Neutrophils From Atopic and Non-Atopic Elite Endurance Runners.

We collected peripheral blood from thirty-nine elite male endurance runners at rest (24 hours after the last exercise session) and used the Allergy Questionnaire for Athletes score and plasma specific IgE level to separate them into atopic and non-atopic athletes. Neutrophils obtained from atopic and non-atopic athletes were subsequently stimulated in vitro with fMLP (N-formyl-methionyl-leucyl-phenylalanine), LPS (lipopolysaccharide), or PMA (phorbol 12-myristate 13-acetate). Neutrophils from non-atopic runners responded appropriately to LPS, as evidenced by the production of pro (IL-8, TNF-α, and IL-6) and anti-inflammatory (IL-10) cytokines. Neutrophils from atopic elite runners exhibited lower responses to LPS stimulus as indicated by no increase in IL-1ß, TNF-α, and IL-6 production. Neutrophils from non-atopic and atopic runners responded similarly to fMLP stimulation, indicating that migration function remained unaltered. Both groups were unresponsive to PMA induced reactive oxygen species (ROS) production. Training hours and training volume were not associated with neutrophil IgE receptor gene expression or any evaluated neutrophil function. Since non-atopic runners normally responded to LPS stimulation, the reduced neutrophil response to the stimuli was most likely due to the atopic state and not exercise training. The findings reported are of clinical relevance because atopic runners exhibit a constant decline in competition performance and are more susceptible to invading microorganisms.

Influence of prosthetic radioiodination on the chemical and biological behavior of chemotactic peptides labeled at high specific activity.

The influence of radioiodination made through prosthetic group N-succinimidyl-3-[131I]iodo-benzoate ([131I]SIB) on the behavior of small peptides was investigated using as model the chemotactic hexapeptide Nalpha-for-Nle-Leu-Phe-Nle-Tyr-Lys. No carrier added labeled peptide was isolated by reverse-phase HPLC (RP-HPLC) with coupling efficiencies up to 59-75%. Biodistribution in normal and infected C57 mice showed mainly a hepatobiliary clearance, a very low thyroid uptake and the highest uptake at the infection site was within 1h of injection. Superoxide production and competitive binding assays studies in human polymorphonuclear leukocytes showed a preserved biological activity and high-affinity specific binding. However, the results indicated that the changes observed in the receptor-binding properties with an IC50 almost twice than the unlabeled peptide and the increasing in the hepatobiliary excretion could be the consequence of the increased lipophicity observed due to the presence of the prosthetic group together with a strong influence of the radioisotope per se.

A study of granulocyte respiratory burst in patients with allergic bronchial asthma.

The respiratory burst of phagocytes plays an important role in the tissue damage that accompanies the inflammatory response. One of these conditions is allergic bronchial asthma, therefore, to evaluate the activation state of peripheral granulocytes the generation of reactive oxygen metabolites was evaluated using Luminol-enhanced chemiluminescence (LCL) and reduction of cytochrome C by superoxide. The resting granulocytes of the asthmatic patients under crisis showed a higher LCL compared to the noncrisis patients and control subjects. The granulocytes stimulated with PMA presented a significant increase in the respiratory burst in both groups of asthmatics. The granulocytes of noncrisis asthmatics challenged with Ops-Zym and with fMLP + Ops-Zym showed a higher metabolic activity, whereas the asthmatics under crisis presented no difference between reactive oxygen generation and that of the control group. The quantitative analysis of superoxide generation by granulocytes of the same patients did not show differences among the groups. Our findings suggest that the granulocytes of crisis and noncrisis asthmatics seem to be in a hyperreactive state and with a higher metabolic response when compared to the control group. However, the patients present a different behavior depending on stimulus used to activate cells. This could indicate that in peripheral blood exist different granulocyte populations depending on the inflammatory response taking place in the respiratory tract.

Losartan, a selective inhibitor of subtype AT1 receptors for angiotensin II, inhibits the binding of N-formylmethionyl-leucyl-phenylalanine to neutrophil receptors.

Losartan, a selective antagonist of AT1 receptors for angiotensin II, is widely used clinically to manage hypertension. We report here that losartan markedly inhibits neutrophil shape change, adherence and chemiluminescence responses triggered by N-formylmethionyl-leucyl-phenylalanine (fMLP), without affecting responses induced by immune complexes, zymosan or concanavalin A. Neither saralasin, another antagonist of angiotensin II receptors, nor captopril, an angiotensin-converting enzyme inhibitor, reproduced the effects of losartan. It was also observed that neutrophil responses triggered by fMLP were not affected by exogenously added angiotensin II. The effect of losartan on the binding of fMLP was measured using [3H]fMLP. It was found that losartan inhibits the binding of [3H]fMLP to neutrophil receptors. As observed for neutrophils, studies performed with monocytes showed that losartan inhibits chemiluminescence emission triggered by fMLP, without affecting chemiluminescence responses triggered by immune complexes, zymosan or concanavalin A.

Impairment of neutrophil chemotactic and bactericidal function in children infected with human immunodeficiency virus type 1 and partial reversal after in vitro exposure to granulocyte-macrophage colony-stimulating factor.

Because polymorphonuclear neutrophils are the most important component of host defense against bacteria, we assessed their function in 13 children with asymptomatic and 12 with symptomatic infection with human immunodeficiency virus type 1 (HIV-1), and compared their values with healthy adult control values. The functions assessed were (1) chemotaxis, (2) bacterial phagocytosis, (3) superoxide generation, and (4) bactericidal activity. Chemotaxis of polymorphonuclear neutrophils toward the chemoattractant N-formylmethionyl leucyl phenylalanine (FMLP) was significantly decreased in symptom-free infected children compared with control subjects (p less than 0.0001), but was increased in children with symptomatic infection (p less than 0.025). Bactericidal activity of the neutrophils against Staphylococcus aureus was defective in 8 of 12 children with asymptomatic infection (p = 0.016), and in 8 of 9 children with symptomatic infection (p less than 0.00001). Superoxide generation by polymorphonuclear neutrophils on stimulation with FMLP and phagocytosis of S. aureus were normal. Serum from patients with symptomatic HIV-1 infection was not as efficient in low concentrations as normal serum in the ability to opsonize S. aureus. The in vitro bactericidal defect was partially corrected by granulocyte-macrophage colony-stimulating factor (GM-CSF). The results suggest that both cellular (neutrophils) and humoral defects contribute to the increased incidence of bacterial infections in HIV-1-infected children, and that GM-CSF may improve the defective bactericidal activity of polymorphonuclear neutrophils in these patients.

Characterization of a class of nonformylated Enterococcus faecalis-derived neutrophil chemotactic peptides: the sex pheromones.

Bacteria produce a heterogeneous mixture of neutrophil chemotactic agents in culture filtrates. Formylmethionyl peptides have been shown to comprise a significant portion of the chemotactic activity in bacterial culture filtrates; however, not all of the chemotactic agents in bacterial culture filtrates are formylated peptides. To examine whether nonformylated peptides derived from bacteria could act as chemotactic agents, we studied several nonformylated hepta- and octapeptide Enterococcus faecalis-derived sex pheromones, their modified derivatives, and their competitive inhibitors for activation of rat peritoneal neutrophils. Several of these peptides, in particular cAM373 and cPD1, proved to be potent chemotactic agents in submicromolar concentrations as well as inducers of lysosomal granule enzyme secretion. Moreover, the more biologically active peptides were able to compete with fMet-Leu-[3H]Phe for binding to the formyl peptide receptor. These studies demonstrate that the formylmethionyl moiety may be an absolute requirement only for the binding of di- and tripeptides to the formyl peptide receptor. Larger peptides that may have or that may allow for additional contact points between the peptide and receptor may require N-formylation only relatively. Indeed, by removing this structural restraint, the formyl peptide receptor may interact with an unlimited number of peptide fragments of both infectious and host origins to then modulate neutrophil responses to infection and inflammation.

[Neutrophil-dependent inflammatory reactions in systemic lupus erythematosus]. / Reacciones inflamatorias neutrofilo-dependientes en Lupus Eritematoso Sistémico.

We studied the possible role of polymorphonuclear neutrophil (PMN) aggregation in Systemic Lupus Erythematosus (SLE) by the capacity of sera from 32 lupus patients to induce in vitro normal PMN aggregation. Neutrophil aggregating activity (NAA) in this group was significantly greater than that found in 8 inactive SLE patients and in 8 controls. In patients with SLE, there was a positive correlation between disease severity and the quantitative measure of NAA. High levels of NAA were particularly characteristic of central nervous system SLE. These data suggest that the formation of intravascular leukoaggregates may contribute to morbidity in SLE. Normal PMN increase their spontaneous superoxide anion production (0.21 nmol/min 10(7) PMN) when stimulated with sera from SLE patients. Lupus PMN also show an enhancement of 100% in superoxide production in vitro when stimulated with lupus sera. When N formyl methionine leucyl phenylalanine (FMLP) was used, lupus PMN showed an O2-production of 2.1 nmol/min 10(7) which is 5-fold the response of normal PMN stimulated by FMLP. Our results show the existence of seric factors in SLE patients that can stimulate O2-production by PMN. Lupus neutrophils show an increased response to membrane stimuli such as FMLP, capable of triggering the respiratory burst. Lupus neutrophils appear more responsive membrane stimuli such as FMLP, capable of triggering the respiratory burst. Lupus neutrophils appear more responsive to membrane stimuli. The seric and the cellular factors seem to indicate an increased rate of superoxide production by PMN in SLE patients, which can be relevant to vasculitis and tissue damage.