Results of the apoptosis percentage are referred to this basal value. In our study, neither FPR2/ALX agonists nor CysLT1 antagonists exerted any effect on the inhibition of neutrophil survival induced by IL-8 (100 nM) at the concentrations tested (0·1 nM–1 μM) (Fig. 4). Caspase inhibitor I was used as a control of apoptosis inhibition, resulting in a complete blockade of caspase 3/7 activity. Similar results were observed using annexin V staining as a marker Doxorubicin of apoptotic cells and propidium iodide as a control of the number

of necrotic cells (Figs 5 and 5). 15-epi-LXA4 (100 nM) could not reverse the percentage of neutrophil apoptosis arrest induced by IL-8 stimulation (21% and 23% of apoptotic cells in IL-8 alone and IL-8 plus 15-epi-LXA4, respectively). As expected, the CXCR2 antagonist SCH527123 reversed IL-8-induced apoptosis

arrest and returned the apoptotic cell index to the basal conditions (Fig. 6). Of interest, compound 43 (100 nM) by itself increased neutrophil survival in the absence of IL-8, confirming the recent published data regarding the inflammatory actions associated with this small molecule FPR2/ALX agonist [28, 32]. All the other reference compounds tested showed no effect on neutrophil survival by themselves (Fig. 6). Overall, these results indicate that 15-epi-LXA4 is inactive in reversing the survival signal induced by proinflammatory find more chemokines such as IL-8 in human neutrophils, and compound 43 by itself induces proinflammatory signals in neutrophils. LXs and 15-epi-LXs are arachidonic acid-derived metabolites suggested to play an important

role as novel anti-inflammatory and pro-resolution agents. LX stable analogues display potent bioactivity in vivo in several murine model systems of acute inflammation [25] and block airway hyper-responsiveness and allergic inflammation in ovalbumin and cockroach allergen-induced airway inflammation models [26]. In addition, transgenic over-expressing mice of human FPR2/ALX receptor show shorter resolution times and doses required in response to lipoxin stable Bacterial neuraminidase analogues [16], and are protected from acid-induced acute lung injury [33] and allergen-induced pulmonary inflammation [34]. FPR2 knock-down cell lines no longer signal in response to LXA4 and deficiency of FPR2 in mice decreases the ability of lipoxin A4 and annexin peptide to reduce inflammation in vivo [14, 15]. Nevertheless, all the in-vivo data supporting the role of FPR2/ALX mediating the anti-inflammatory actions of LXs has been generated in mice and differences in FPR2/ALX signalling between species cannot be discarded. Moreover, no FPR2/ALX knock-out or transgenic mice studies have been addressed to study in particular the relevance of the LX–FPR2/ALX axis in neutrophil migration in vivo. In humans, differences in FPR2/ALX expression have been observed in acute and chronic inflammatory responses.