Albumin stimulation of eosinophil migration involves PI3-kinases and is associated with diminished eosinophil CD49d and CD49f expression

Epstein-Barr Virus-induced Gene 2 Mediates Allergen-induced Leukocyte Migration into Airways

RATIONALE

Leukocyte recruitment to sites of allergic inflammation depends on the local production of priming cytokines, chemokines, and potentially other mediators. Previously, we showed that eosinophils (Eos) express numerous orphan G-protein-coupled receptors, including Epstein-Barr virus-induced gene 2 (EBI2). Despite its contribution to inflammatory diseases, the role of EBI2 in pulmonary eosinophilia is unknown.

OBJECTIVES

To determine whether oxysterol ligands for EBI2 are increased in asthma exacerbation, and if or how they promote Eos pulmonary migration.

METHODS

EBI2 ligands and pulmonary eosinophilia were measured in the bronchoalveolar lavage fluid from patients with mild asthma 48 hours after acute allergen challenge. In vitro, the ability of EBI2 ligands alone or in combination with IL-5 priming to induce the migration of human blood Eos was assessed.

MEASUREMENTS AND MAIN RESULTS

EBI2 was constitutively and stably expressed in peripheral blood Eos. Eos treated with the EBI2 ligands showed significantly increased transwell migration that was enhanced by priming with physiologic doses of IL-5. Migration was suppressed by inhibitors of the prolyl isomerase Pin1 or extracellular signal-regulated kinases (ERK) 1/2 or by pertussis toxin. EBI2 signaling activated Pin1 isomerase activity through a cascade that was sensitive to ERK inhibitors and pertussis toxin. The concentration of EBI2 ligands was significantly increased in the bronchoalveolar lavage fluid 48 hours after segmental allergen challenge and strongly correlated with the increased numbers of Eos, lymphocytes, and neutrophils in the airways.

CONCLUSIONS

Oxysterols are increased in inflamed airways after allergen challenge and, through G-protein subunit α, ERK, and Pin1 signaling, likely participate in the regulation of Eos migration into the lung in people with asthma.

Evans blue staining reveals vascular leakage associated with focal areas of host-parasite interaction in brains of pigs infected with Taenia solium

Cysticidal drug treatment of viable Taenia solium brain parenchymal cysts leads to an acute pericystic host inflammatory response and blood brain barrier breakdown (BBB), commonly resulting in seizures. Naturally infected pigs, untreated or treated one time with praziquantel were sacrificed at 48 hr and 120 hr following the injection of Evans blue (EB) to assess the effect of treatment on larval parasites and surrounding tissue. Examination of harvested non encapsulated muscle cysts unexpectedly revealed one or more small, focal round region(s) of Evans blue dye infiltration (REBI) on the surface of otherwise non dye-stained muscle cysts. Histopathological analysis of REBI revealed focal areas of eosinophil-rich inflammatory infiltrates that migrated from the capsule into the tegument and internal structures of the parasite. In addition some encapsulated brain cysts, in which the presence of REBI could not be directly assessed, showed histopathology identical to that of the REBI. Muscle cysts with REBI were more frequent in pigs that had received praziquantel (6.6% of 3736 cysts; n = 6 pigs) than in those that were untreated (0.2% of 3172 cysts; n = 2 pigs). Similar results were found in the brain, where 20.7% of 29 cysts showed histopathology identical to muscle REBI cysts in praziquantel-treated pigs compared to the 4.3% of 47 cysts in untreated pigs. Closer examination of REBI infiltrates showed that EB was taken up only by eosinophils, a major component of the cellular infiltrates, which likely explains persistence of EB in the REBI. REBI likely represent early damaging host responses to T. solium cysts and highlight the focal nature of this initial host response and the importance of eosinophils at sites of host-parasite interaction. These findings suggest new avenues for immunomodulation to reduce inflammatory side effects of anthelmintic therapy.

C3b-induced eosinophil degranulation involves PI3-kinases and is inhibited by protein kinase C activity

Selective release of individual eosinophil granule proteins has been demonstrated in eosinophilic conditions and in vitro using different stimuli. The aim of this study was to investigate if selective release of eosinophil cationic protein (ECP), eosinophil protein X/eosinophil derived-neurotoxin (EPX/EDN) and eosinophil peroxidase (EPO) could be due to the involvement of different signal transduction pathways. Peripheral blood granulocytes from healthy donors were incubated with Wortmannin, LY294002, Genistein, Staurosporine, GÖ6976 or PD98059 prior to the induction of degranulation by C3b. The released amounts of ECP, EPO and EPX/EDN were determined by immunoassays, and related to the total cell content of respective protein. Wortmannin caused a significant, dose-dependent inhibition of all three granule proteins. LY294002 (10⁻⁶ M) also inhibited the release of all proteins. Genistein (10⁻⁶ M) inhibited the release of ECP, whereas the release of EPO was increased. However, there was a tendency towards similar concentration-dependent patterns of release of all three proteins. Staurosporine (10⁻⁷ M), GÖ6976 (10⁻⁶ M) and PD98059 (10⁻⁵ M) caused an increased release of the three proteins. PI3-kinases play an important role in the C3b-induced release of ECP, EPO and EPX/EDN, whereas protein kinase C seems to have inhibitory effects on C3b-induced degranulation.

Serum albumin protects from cytokine-induced pancreatic beta cell death by a phosphoinositide 3-kinase-dependent mechanism

The present study was undertaken to investigate the biological activity of serum albumin when pancreatic beta cells were challenged by cytokines and pro-apoptotic reactive oxygen species like H(2)O(2). Culture of mouse islets or INS-1E beta cells for 24 h in the presence of H(2)O(2) (25 micromol/l) increased cell death. This demise was prevented by serum albumin, dependent on its free sulfhydryl group, emphasizing that albumin may scavenge H(2)O(2) due to its antioxidant properties. Culture for 48 h with a cytokine mixture of IL-1beta (160 pg/ml), IFN-gamma (200 ng/ml), and TNF-alpha (2 ng/ml) revealed that albumin, also protected against cytokine-induced death of both mouse islets and INS-1E beta cells. This protective effect against cytokine-induced beta cell death was, however, not dependent on albumins free sulfhydryl group, but was inhibited by the phosphoinositide 3-kinase (PI3K) inhibitors LY294002 (25 micromol/l) and wortmannin (1 micromol/l), suggesting that albumin may rescue beta cells from cytokine-induced cell death by activation of PI3K. In accordance, albumin stimulated phosphorylation of Akt, a down-stream target for PI3K. In conclusion, it is suggested that albumin may be a survival factor for pancreatic beta cells through scavenging of reactive oxygen species and by PI3K-dependent activation of Akt.