ADAM9 disintegrin domain activates human neutrophils through an autocrine circuit involving integrins and CXCR2.

ADAM9 is a member of the ADAM family whose expression positively correlates with tumor progression. Besides the metalloprotease activity, ADAM9D interacts with different integrins, modulating cell-adhesion events. Previous studies pointed to an important role for neutrophils in tumor development, as the inhibition of neutrophil migration or depletion of this immune cell impairs tumor growth. However, our understanding of the molecular mechanisms involved in this process, as well as the main key players acting on neutrophils, is very limited. Here, we investigated the possible modulatory effects of ADAM9D on human neutrophil functions. Our results show that ADAM9D promotes neutrophil activation and chemotaxis in a process that depends on the engagement of αvß3 and α9ß1 integrins and on the activation of PI3K/Akt and MAPK signaling pathway. ADAM9D impairs migration of neutrophils toward fMLP, LTB4, and IL-8 as classic chemoattractants. This effect is blocked by PTX, a G(i)PCR inhibitor. Furthermore, CXCR2 antagonists RPTX and SB225002 also impaired neutrophil chemotaxis in response to ADAM9D, suggesting a hierarchical cross-talk of integrins with CXCR2. Our results indicate that ADAM9D activates neutrophil functions and may be implicated in the inflammatory events associated with cancer and other disorders.

Maxadilan, the Lutzomyia longipalpis vasodilator, drives plasma leakage via PAC1-CXCR1/2-pathway.

Experiments were designed to determine if the vasodilatory peptides maxadilan and pituitary adenylate cyclase-activating peptide (PACAP-38) may cause plasma leakage through activation of leukocytes and to what extent these effects could be due to PAC1 and CXCR1/2 receptor stimulation. Intravital microscopy of hamster cheek pouches utilizing FITC-dextran and rhodamine, respectively, as plasma and leukocyte markers was used to measure arteriolar diameter, plasma leakage and leukocyte accumulation in a selected area (5mm(2)) representative of the hamster cheek pouch microcirculation. Our studies showed that the sand fly vasodilator maxadilan and PACAP-38 induced arteriolar dilation, leukocyte accumulation and plasma leakage in postcapillary venules. The recombinant mutant of maxadilan M65 and an antagonist of CXCR1/2 receptors, reparixin, and an inhibitor of CD11b/CD18 up-regulation, ropivacaine, inhibited all these effects as induced by maxadilan. Dextran sulfate, a complement inhibitor with heparin-like anti-inflammatory effects, inhibited plasma leakage and leukocyte accumulation but not arteriolar dilation as induced by maxadilan and PACAP-38. In vitro studies with isolated human neutrophils showed that maxadilan is a potent stimulator of neutrophil migration comparable with fMLP and leukotriene B(4) and that M65 and reparixin inhibited such migration. The data suggest that leukocyte accumulation and plasma leakage induced by maxadilan involves a mechanism related to PAC1- and CXCR1/2-receptors on leukocytes and endothelial cells.

Inhibition of guanylyl cyclase restores neutrophil migration and maintains bactericidal activity increasing survival in sepsis.

Sepsis results from an overwhelming response to infection and is a major contributor to death in intensive care units worldwide. In recent years, we and others have shown that neutrophil functionality is impaired in sepsis. This correlates with sepsis severity and contributes to aggravation of sepsis by precluding bacterial clearance. Nitric oxide (NO) is a major contributor to the impairment of neutrophil function in sepsis. However, attempts to inhibit NO synthesis in sepsis resulted in increased death despite restoring neutrophil migration. This could be in part attributed to a reduction of the NO-dependent microbicidal activity of neutrophils. In sepsis, the beneficial effects resulting from the inhibition of soluble guanylyl cyclase (sGC), a downstream target of NO, have long been appreciated but poorly understood. However, the effects of sGC inhibition on neutrophil function in sepsis have never been addressed. In the present study, we show that TLR activation in human neutrophils leads to decreased chemotaxis, which correlated with chemotactic receptor internalization and increased G protein-coupled receptor kinase 2 expression, in a process involving the NO-sGC-protein kinase G axis. We also demonstrate that inhibition of sGC activity increased survival in a murine model of sepsis, which was paralleled by restored neutrophil migratory function and increased bacterial clearance. Finally, the beneficial effect of sGC inhibition could also be demonstrated in mice treated after the onset of sepsis. Our results suggest that the beneficial effects of sGC inhibition in sepsis could be at least in part attributed to a recovery of neutrophil functionality.

[Therapeutics of infection by Helicobacter pylori in 2008]. / Terapéutica de la infección por Helicobacter pylori en el 2008.

Eradication therapy for Helicobacter pylori is recommended in a number of clinical conditions as developed in Maastricht Consensus (I, II, III). In this state of art we discuss the results of current eradication therapies, the new approaches to the management of infection (new antibiotics and eradication schemes) and antimicrobial resistance.

Effects of a single low dose of ranitidine and effervescent antacids on intragastric acidity in healthy volunteers.

INTRODUCTION/AIMS: We hypothesized that a combination of an effervescent antacid and ranitidine could allow immediate and long-lasting increase intragastric acidity. Our aim was to determine the effect of the combined intake of both, of a low dose ranitidine (OTC) and 5 g of antacid on gastric pH. MATERIAL AND METHODS: Twenty healthy Helicobacter pylori negative volunteers were enrolled. The study consisted in a fasting 6-hour gastric ph-metric procedure performed in two different periods: baseline (1-hour before drug) and post-drug (5-hours) after oral administration of a single dose of ranitidine (75 mg) plus 5 g of a commercial composed alkaline (sodium bicarbonate, citric acid, sodium carbonate). RESULTS: While two subjects did not complete the pH-metry analysis due to technical reasons, 18 volunteers were finally assessed. Baseline intragastric pH (1.3 +/- 0.1) (mean +/- SD) rose significantly after administration of the drug (mean pH value for the whole period: 5.1 +/- 0.3; p<0.00001). The pH increased after administration of the study combination and values higher than pH 3 and pH 4 were reached immediately (median time: 27 sec, range: 0-189 and 54 sec, range 27-3,600 sec, respectively). Gastric pH was initially maintained above 4 for 23.0 +/- 5 minutes. The mean time lapsed with pH < 4 during the post-drug period was 96 +/- 17 min (32% ofthe total time). CONCLUSION: Our study confirms the fast and persistent effect produced by the administration of a combination of antacid salts plus low dose of ranitidine. We suggest that the given combination could be effective, fast and safe for sporadic pyrosis or mild grastroesophageal reflux symptoms.

Effects of a single low dose of ranitidine and effervescent antacids on intragastric acidity in healthy volunteers / Efectos de bajas dosis de ranitidina y antiácidos efervescentes sobre la acidez intragástrica en voluntarios sanos

Introduction/aims: We hypothesized that a combination of an effervescent antacid and ranitidine could allow immediate and long-lasting increase intragastric acidity. Our aim was to determine the effect of the combined intake of both, of a low dose ranitidine (OTC) and 5g of antacid on gastric pH. Material and methods: Twenty healthy Helicobacter pylori negative volunteers were enrolled. The study consisted in a fasting 6-hour gastric ph-metric procedure performed in two different periods: baseline (1-hour before drug) and post-drug (5-hours) after oral administration of a single dose of ranitidine (75 mg) plus 5 g of a commercial composed alkaline (sodium bicarbonate, citric acid, sodium carbonate). Results: While two subjects did not complete the pH-metry analysis due to technical reasons, 18 volunteers were finally assessed. Baseline intragastric pH (1.3±0.1) (mean±SD) rose significantly after administration of the drug (mean pH value for the whole period: 5.1±0.3; p<0.00001). The pH increased after administration of the study combination and values higher than pH 3 and pH 4 were reached immediately (median time: 27 sec, range: 0- 189 and 54 sec, range 27-3,600 sec, respectively). Gastric pH was initially maintained above 4 for 23.0±5 minutes. The mean time lapsed with pH<4 during the post-drug period was 96±17 min (32% of the total time). Conclusion: Our study confirms the fast and persistent effect produced by the administration of a combination of antacid salts plus low dose of ranitidine. We suggest that the given combination could be effeceffective, fast and safe for sporadic pyrosis or mild grastroesophageal reflux symptoms.

Introducción/objetivos: la combinación de un antiácido efervescente y ranitidina podría brindar un descenso inmediato y prolongado de la acidez intragástrica. Nuestro objetivo fue determinar el efecto de la ingesta conjunta de ambos (75 mg de ranitidina y 5 g de antiácidos) sobre el pH gástrico. Material y métodos: se incluyeron 20 voluntarios sanos, con anticuerpos anti- Helicobacter pylori negativos. Se realizó, en condiciones de ayuno, una pH-metría gástrica de 6 horas en dos períodos: basal (1 hora antes del medicamento) y post-droga (5 horas) luego de la administración oral de una dosis única de ranitidina (75 mg) + 5 g de antiácidos efervescentes (bicarbonato sódico, ácido cítrico, carbonato sódico). Resultados: dado que dos pacientes no completaron el estudio de pH por razones técnicas, se analizaron los resultados de 18 voluntarios. El pH intragástrico basal fue de 1.33±0.12 (promedio ± DS) y se elevó a 5.1±0.3 como promedio de todo el período post-droga (p<0.00001). El incremento de pH fue inmediato; así los valores de pH=3 y pH=4 fueron alcanzados en 27 seg, rango: 0-189 y 54 seg, rango 27- 3.600, respectivamente (mediana, rango). El pH se mantuvo inicialmente por encima de 4 durante 23.0±5 minutos. El tiempo con pH < 4 durante las 5 horas post-droga fue de 96± 17 minutos (32% del tiempo total). Conclusión: nuestro estudio confirma el efecto rápido y persistente determinado por la combinación de sales antiácidas y bajas dosis de ranitidina. De este modo esta asociación podría ser efectiva, rápida y segura frente a pirosis esporádica o síntomas de reflujo gastro-esofágico leve.