Effect of eosinphil granule proteins on beta-adrenergic receptor

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Effect of eosinophil peroxidase (EPO) + H_2O_2 on beta-adrenergic receptor number was studied. Human EPO was obtained from eosinophils of hypereosinophilic syndrome patients by sequential chromatograph on Sephadex G-50 and CM-Sepharose column. Guinea pig lung membrane fraction was first preincubated with EPO, then incubated with H_2O_2 for 2 hours. The number of beta-adrenergic receptor was measured by binding assay. The number of beta adrenergic receptor was significantly decreased by 3-10 U/ml EPO and 10^<-4>M H_2O_2. Beta-receptor number was also decreased by 10 U/ml EPO and 10^<-6>M H_2O_2.Next effect of EPC on beta-adrenergic receptor-adenylate cyclase system was studied. S 49 cells were preincubated with EPO for 15 minutes, and then incubated with 10^<-4>M H_2O_2 for 45 minutes. The cells were centrifuged, resuspended in culture medium including xanthine, then stimulated by 10^<-4>M isoproterenol to generate intracellular cyclic AMP (CAMP). Intracellular cyclic AMP production wap … More significantly inhibited by the pretreatment with 0.1-1 U/ml EPO and 10^<-3>M H_2O_2, and the degree of inhibition was EPO concentration dependent. CAMP production was inhibited by 91 % by pretreatment with 1 U/ml FPO and 10^<-3>M H_2O_2. CAMP production was also inhibited when 10^<-4>M or 10^<-5>M H_2O_2 was applied with EPO. EPO or H_2O_2 alone did not inhidited CAMP production. The number of beta-adrener gic receptor on S49 cells did not change by EPO + H_2O_2 system, however, the affinity of beta-adrenergic receptor to isoproterenol was decreased. CAMP production stimulated by 10^<-5>M forskolin was also inhibited by EPO + H_2O_2, however, the degree of inhibition was greater in isoproterenol stimulation than in forskolin stimulation.Major basic protein and eosinophil cationic protein did not have significant suppressive effects either on beta-adrenergic receptor number or on CAMP production.These results suggest that EPO is one of the factors that induce betaadrenergic hyporesponsiveness in patients with bronchial asthma. Less