, 2010), here we studied the participation of 5-lipoxygenase in rHPU-activated neutrophil signaling. Western blot analyses of rHPU-activated neutrophils showed significantly increased levels of 5-LO (Fig. 6) while no alterations of cyclooxygenase-2 levels were observed (not shown), suggesting the possible involvement of leukotrienes or 5-HETE in neutrophil’s response to rHPU. Contrasting to these results, stimulation of neutrophils by LPS (1 μg/mL) under the same experimental conditions did not alter their 5-LO content
(not LDK378 concentration shown). Table 1 summarizes these data. Ureases (EC 22.214.171.124) are highly homologous nickel-dependent enzymes that hydrolyze urea into ammonia and carbon dioxide (Dixon et al., 1975; Mobley et al., 1995). We have previously reported that canatoxin (Carlini and Guimaraes, 1981), an isoform of jackbean (C. ensiformis) urease ( Follmer et al., 2001), presents biological properties that are independent of its enzyme activity, including activation of blood platelets ( Barja-Fidalgo et al., 1991; Carlini et al., 1985; Ghazaleh et al., 1997) and pro-inflammatory effect ( Barja-Fidalgo et al., 1992; Benjamin et al., 1992). Submicromolar PCI-32765 nmr concentrations of canatoxin induced exocytosis in a number of cell systems in vitro such as platelets, synaptosomes, pancreatic islets, macrophages, neutrophils and mast cells (reviewed in Olivera-Severo et al.,
2006b). Lipoxygenase metabolites were shown to modulate most of canatoxin’s pharmacological effects, either in vivo or in vitro ( Barja-Fidalgo et al., 1991; Benjamin else et al., 1992; Carlini et al., 1985). Jackbean, soybean and Bacillus
pasteurii ureases induce aggregation of platelets in nanomolar concentrations independently of enzyme activity ( Follmer et al., 2004; Olivera-Severo et al., 2006a). More recently, we demonstrated that purified recombinant H. pylori urease also promotes activation of rabbit platelets recruiting the lipoxygenase pathway ( Wassermann et al., 2010). The fact that bacterial and plant ureases evolutionarily conserved the property of activating some cell types may shed new lights into the so far poorly understood biological functions of these proteins, which clearly are not restricted only to their ureolytic activities. The data gathered here show that the cell-free, purified rHPU displays potent pro-inflammatory properties. Fig. 7 summarizes these and other previous results pointing to a relevant participation of HPU in the gastric inflammatory disease caused by H. pylori. The time-course of HPU-induced mouse paw edema is very similar to that described for the rat paw edema induced by canatoxin (Benjamin et al., 1992). rHPU is at least 100-fold more potent than canatoxin in its ability to induce paw edema, although differences in inflammatory reactions of animal models have also to be considered.