Possible role of a hydrogen peroxide-mediated mechanism in glucocorticoid receptor functional alterations associated with moderate asthma

Abstract

It is well known that pathogenesis and maintenance of chronic asthma is associated with alterations of glucocorticoid receptor (GR) function, and also with persistent pulmonary inflammation, the important mediators of which are reactive oxygen and nitrogen species. In this paper, we tested a hypothesis that GR functional alterations in asthma result from the action of oxidants. To that end, we conducted a series of ex vivo treatments of peripheral blood mononuclear cells (PBMCs) of healthy donors with oxidizing agents (3 morpholinosydnonimine, SIN1; S-nitroso-N-acetyl-penicillamine, SNAP; and hydrogen peroxide, H2O2) and compared the resulting GR modifications with those previously noticed in asthmatic patients. The results show that treatment of PBMCs by H2O2 provoked an increase in the level of GR protein, accompanied by a rise in the number of hormone-binding sites and a decline in the receptor's affinity for the hormone. The H2O2 induced changes, including a characteristic GR isoprotein expression pattern, were found to be very similar to the GR changes previously observed in PBMCs of moderate asthmatic patients, but not in mild asthmatics and healthy subjects. Treatment with the other oxidants applied herein produced different effects or exerted no influence on GR. Thus, this study provides preliminary data suggesting that functional alterations of the GR associated with moderate asthma may be mediated by redox mechanisms that are based on oxidative and regulatory actions of H2O2.Poznato je da su patogeneza i napredovanje hronične astme povezani sa funkcionalnim promenama glukokortikoidnog receptora (GR) i dugotrajnom inflamacijom disajnih puteva, čiji su medijatori reaktivne vrste kiseonika i azota. U ovom radu testirali smo hipotezu da funkcionalne promene GRu astmi nastaju kao posledica delovanja oksidanata. U tom cilju sproveli smo seriju ex vivo tretmana mononuklearnih ćelija periferne krvi zdravih donora oksidujućim agensima (3-morfolinosidnoniminom, SIN-1; S-nitrozo-N-acetil-penicilaminom, SNAP; i vodonik peroksidom, H2O2) i uporedili nastale modifikacije GR sa onima koje su ranije zapažene kod astmatičnih pacijenata. Rezultati su pokazali da je tretman perifernih limfocita vodonik peroksidom izazvao povećanje koncentracije GR proteina, koje je bilo praćeno povećanjem broja mesta vezivanja hormona i smanjenjem afiniteta receptora prema hormonu. Promene indukovane vodonik peroksidom, uključujući i karakterističnu ekspresiju izoformi GR proteina, bile su vrlo slične promenama koje su ranije zapažene u perifernim limfocitima pacijenata obolelih od srednje teškog oblika astme, ali ne i kod blagih astmatičara i zdravih donora. Tretman drugim primenjenim oksidantima proizveo je drugačije efekte, ili nije imao uticaja na GR. Prema tome, ova studija je dala preliminarne podatke koji ukazuju da su funkcionalne promene GR povezane sa srednje teškom astmom verovatno posredovane redoks mehanizmima koji se zasnivaju na oksidativnoj i regulatornoj ulozi vodonikperoksida.Projekat ministarstva br. 14300