Volatile anaesthetics reduce neutrophil inflammatory response by interfering with CXC receptor-2 signalling.

BACKGROUND: Growing evidence suggests a protective effect of volatile anaesthetics in ischaemia-reperfusion (I/R)-injury, and the accumulation of neutrophils is a crucial event. Pro-inflammatory cytokines carrying the C-X-C-motif including interleukin-8 (IL-8) and CXC-ligand 1 (CXCL1) activate CXC receptor-1 (CXCR1; stimulated by IL-8), CXC receptor-2 (CXCR2; stimulated by IL-8 and CXCL1), or both to induce CD11b-dependent neutrophil transmigration. Inhibition of CXCR1, CXCR2, or both reduces I/R-injury by preventing neutrophil accumulation. We hypothesized that interference with CXCR1/CXCR2 signalling contributes to the well-established beneficial effect of volatile anaesthetics in I/R-injury. METHODS: Isolated human neutrophils were stimulated with IL-8 or CXCL1 and exposed to volatile anaesthetics (sevoflurane/desflurane). Neutrophil migration was assessed using an adapted Boyden chamber. Expression of CD11b, CXCR1, and CXCR2 was measured by flow cytometry. Blocking antibodies against CXCR1/CXCR2/CD11b and phorbol myristate acetate were used to investigate specific pathways. RESULTS: Volatile anaesthetics reduced CD11b-dependent neutrophil transmigration induced by IL-8 by >30% and CD11b expression by 18 and 27% with sevoflurane/desflurane, respectively. This effect was independent of CXCR1/CXCR2 expression and CXCR1/CXCR2 endocytosis. Inhibition of CXCR1 signalling did not affect downregulation of CD11b with volatile anaesthetics. Blocking of CXCR2-signalling neutralized effects by volatile anaesthetics on CD11b expression. Specific stimulation of CXCR2 with CXCL1 was sufficient to induce upregulation of CD11b, which was impaired with volatile anaesthetics. No effect of volatile anaesthetics was observed with direct stimulation of protein kinase C located downstream of CXCR1/CXCR2. CONCLUSION: Volatile anaesthetics attenuate neutrophil inflammatory responses elicited by CXC cytokines through interference with CXCR2 signalling. This might contribute to the beneficial effect of volatile anaesthetics in I/R-injury.

Acute lung injury: apoptosis in effector and target cells of the upper and lower airway compartment.

Apoptotic cell death has been considered an underlying mechanism in acute lung injury. To evaluate the evidence of this process, apoptosis rate was determined in effector cells (alveolar macrophages, neutrophils) and target cells (tracheobronchial and alveolar epithelial cells) of the respiratory compartment upon exposure to hypoxia and endotoxin stimulation in vitro. Cells were exposed to 5% oxygen or incubated with lipopolysaccharide (LPS) for 4, 8 and 24 h, and activity of caspase-3, -8 and -9 was determined. Caspase-3 of alveolar macrophages was increased at all three time-points upon LPS stimulation, while hypoxia did not affect apoptosis rate at early time-points. In neutrophils, apoptosis was decreased in an early phase of hypoxia at 4 h. However, enhanced expression of caspase-3 activity was seen at 8 and 24 h. In the presence of LPS a decreased apoptosis rate was observed at 8 h compared to controls, while it was increased at 24 h. Tracheobronchial as well as alveolar epithelial cells experienced an enhanced caspase-3 activity upon LPS stimulation with no change of apoptosis rate under hypoxia. While increased apoptosis rate is triggered through an intrinsic and extrinsic pathway in alveolar macrophages, intrinsic signalling is activated in tracheobronchial epithelial cells. The exact pathway pattern in neutrophils and alveolar epithelial cells could not be determined. These data clearly demonstrate that upon injury each cell type experiences its own apoptosis pattern. Further experiments need to be performed to determine the functional role of these apoptotic processes in acute lung injury.

[Malassezia furfur colonising the respiratory tract of mechanically ventilated neonates]. / Malassezia furfur im trachealsekret beatmeter frühgeborener.

BACKGROUND: Ventilated neonates are prone to acquire ventilator-associated pneumonia (VAP). Consequently early diagnosis of pneumonia is required. Beside bacteria, fungi are suspected as a cause of VAP. However, fungal colonisation and infection of the lung have not been studied systematically. The purpose of this study was to evaluate pulmonary fungal colonisation in ventilated neonates and premature infants. MATERIALS AND METHODS: 187 tracheal aspirates (TA) from 29 ventilated neonates (23-35 weeks gestational age) were investigated. TAs were evaluated microscopically and by culture. Data were matched with clinical signs of VAP or sepsis. RESULTS: Candida species were not detected in TA or culture. In contrast, Malassezia furfur (Mf), a lipophilic fungus, was detected from the 10th, 21st and 31st postnatal days onwards in TAs of 3 out of 17 extremely prematures (gestational age at birth < 25 weeks). The presence of Mf was associated with clinical deterioration either immediately or a few days after the first positive Mf smear. Topic steroids were more frequently applied to Mf-positive ELBW infants (p = 0.03). In vitro, natural surfactant was demonstrated to be a sufficient substrate for Mf in culture. CONCLUSION AND DISCUSSION: This is the first report on Mf lung colonisation of ELBWI during mechanical ventilation. Because Mf is generally not detected in standard cultures it appears to be an overlooked, potentially pathogenic fungus in prematures. Mf must be considered in the differential diagnosis of VAP in ELBWI exposed to topical steroids, especially when natural surfactant was administered.