Nuclear bioavailability of the glucocorticoid receptor in a pediatric asthma cohort with variable corticosteroid responsiveness.
BACKGROUND
Despite the overall effectiveness of glucocorticoids (GCs) in the treatment of asthma, a large proportion of patients do not fully respond to this medication. The objective of the present study was to investigate the potential molecular mechanisms responsible for corticosteroid insensitivity in pediatric asthma.


METHODS
Asthmatic children were classified as good (GSR) or poor corticosteroid responders (PSR) based on the changes in pulmonary function following GC treatment. Immortalized B-cells derived from patients at two ends of the spectrum of GC responsiveness (five each) were grown in culture and treated with hydrocortisone (10(-6)M). Baseline and temporal changes in GC receptor (GR) protein and mRNA were evaluated by western blot and quantitative reverse transcription PCR respectively. The effect of GC treatment on GR nuclear levels was assessed by western blots.


RESULTS
Cells derived from PSR asthmatics displayed lower GR protein levels when compared to GSR. Moreover, in PSR cells GC-induced nuclear translocation of GR was short-lived and homologous downregulation of GR mRNA and protein was faster than in GSR.


CONCLUSIONS
Our data demonstrate the existence of a novel mechanism of GC insensitivity resulting from limited GR nuclear bioavailability as a consequence of decreased baseline GR protein expression and more rapid hormone-induced downregulation.
McGill University - Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.|Department of Human Genetics, McGill University, Montreal, Quebec, Canada.
Salomon
S
Cornejo
Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.|Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
Kelan
K
Tantisira
Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.|Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
Benjamin A
BA
Raby
Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
Scott T
ST
Weiss
McGill University - Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.|Department of Human Genetics, McGill University, Montreal, Quebec, Canada.|Department of Paediatrics, McGill University, Montreal, Quebec, Canada.
Feige
F
Kaplan
D021581:Active Transport, Cell Nucleus; D000293:Adolescent; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D001402:B-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D015536:Down-Regulation; D004351:Drug Resistance; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology*; D008168:Lung / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D016896:Treatment Outcome
D000893:Anti-Inflammatory Agents; C497713:NR3C1 protein, human; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D006854:Hydrocortisone