Search

Background: The aim of this work was to study the mechanisms of action of IL-5 on the subsequent stimulation of the oxidative metabolism of blood eosinophils by serum-treated zymosan (STZ), in terms of signal transduction characteristics, and by comparing the response of cells from healthy and allergic subjects during environmental exposure to birch pollen. Methods: Eosinophils from healthy controls and allergic patients were purified to over 95% by Percoll gradients and the MACS system. Oxidative metabolism was measured by a lucigenin-enhanced chemiluminescence (CL) assay. Eosinophils were primed with IL-5 and subsequently stimulated with STZ. The signal transduction mechanisms of IL-5 priming were studied with the MEK inhibitor PD 98059,the PkC inhibitors staurosporine and Ro 318220, and the PI3 kinase inhibitor wortmannin. Results: IL-5 increased the maximum radical production (P =0.0079) and reduced the t½ rise (0.000018) of the CL reactions. The t½ rise was PkC dependent and MEK independent, while the maximum radical production was PkC, MEK, and PI3 kinase dependent. During the pollen season, IL-5 reduced the total STZ-induced CL response in the patients' cells (P =0.016), but not in the control cells, whereas it primed the response to STZ of both cell populations in terms of the t½ rise (P =0.012 and 0.00066, respectively). Conclusions: STZ-induced oxidative metabolism consists of different stages. The initial stage (t½ rises of the curves) is PkC dependent and MEK independent, while the end stage (maximum radical production) is PkC, MEK, and PI3 kinase dependent. IL-5 shortened the initial stage, and increased the end stage. During allergen exposure, however, the end stage was reduced by IL-5. This could be due to increased amounts of hypodense eosinophils and/or some abnormality in cell responses. [ABSTRACT FROM AUTHOR]

AimTo study the effect of IL-5 priming on the PMA-induced oxidative metabolism of blood eosinophils from allergic patients and healthy controls, during pollen exposure. MethodsTwenty birch pollen allergic patients with seasonal symptoms of rhinitis or rhinitis plus asthma were studied during the birch pollen season of Sweden. Eosinophils were purified to > 95% by Percoll gradients followed by the MACS system. Oxidative metabolism was measured by a lucigenin enhanced chemiluminescence (CL) assay. Eosinophils were primed with IL-5 and subsequently stimulated with PMA. The signal transduction mechanisms of IL-5 priming were studied using the MEK inhibitor PD 98059, the PkC inhibitors Staurosporine, Ro 318220, Gö 6983 and the PI3kinase inhibitor Wortmannin. ResultsDuring the season, the eosinophils from the allergic patients showed a reduced t½rise compared to the non-allergic controls (P = 0.019) after stimulation. IL-5 reduced the total PMA CL response both in control and patients’ cells (P = 0.012 and 0.0054 resp.), whereas it primed it in terms of the t½rise of the curves, in both groups (P = 0.012 and 0.0015 resp.). The PMA-induced CL reactions were inhibited by PD 98059, all PkC-inhibitors and Wortmannin. IL-5 priming counteracted only the MEK inhibition significantly. ConclusionsBlood eosinophils from allergic patients are primed in vivo, as compared to eosinophils from non-allergic controls, during a pollen season. Interleukin-5 primes equally the PMA-induced oxidative metabolism of human eosinophils from healthy or allergic subjects. The mechanism of IL-5 priming after PMA stimulation of oxygen radical production is MEK independent. [ABSTRACT FROM AUTHOR]

Background The eosinophil granulocyte is an inflammatory cell that plays an active part in diseases such as asthma and rhinitis. This study aimed to investigate oxidative metabolism by blood eosinophils taken from allergic rhinitis patients, asthmatics, and nonallergic controls before and during the birch-pollen season. Methods Twenty patients with allergy to birch pollen and seasonal symptoms of rhinitis, some of whom were also asthmatic, were followed before and during the birch-pollen season in Sweden. The cells were purified using a Percoll gradient and the MACS system. Eosinophil purity in all samples was >95%. Oxidative metabolism was measured by a chemiluminescence (CL) assay, with luminol and lucigenin acting as enhancers, and PMA, serumtreated zymosan (STZ), interleukin (IL)-5. or RANTES as stimuli. Results The allergic subjects showed reduced luminol CL when activated before the season with PMA (P = 0.040) or STZ (P = 0.0055). This was not seen during pollen exposure. STZ-activated lucigenin CL was also reduced before the season (P = 0.0027). The reduction was most evident in the group with asymptomatic rhinitis. In terms of eosinophil stimulation. IL-5 and RANTES were equally effective in allergic and nonallergic subjects, both before and during the pollen season. Conclusions Blood eosinophils from asymptomatic allergies may have a lower capacity to produce oxygen-free radicals than eosinophils from nonallergics. [ABSTRACT FROM AUTHOR]