Decreased Glucocorticoid Receptor Expression and Function in Cord Blood Immune Cells from Preterm Neonates with Morbidity

Glucocorticoids are essential for fetal organ maturation and form the basis of antenatal corticosteroid therapy that has significantly reduced preterm-related morbidity such as respiratory distress syndrome (RDS). However, neonatal morbidity remains a clinical challenge regardless of antenatal corticosteroid therapy. Currently, it is thought that adverse intrauterine environments dysregulate glucocorticoid receptor (GR) homeostasis, yet the biological mechanisms remain poorly understood. Therefore, we aimed to study ex vivo glucocorticoid sensitivity in cord blood immune cells from two independent preterm cohorts to identify associations with neonatal morbidity and uncover potential mechanisms of dysregulated glucocorticoid homeostasis. In the first cohort, thawed cord blood mononuclear cells were exposed to betamethasone in the presence of lipopolysaccharides (LPS) for 4 h. In the second cohort, freshly isolated white blood cells were treated with dexamethasone under unstimulated and LPS-stimulated conditions for 48 h. GR isoform expression and regulation of transactivated and transrepressed genes were assessed via qPCR, immunoblotting, flow cytometry, and ELISA. In both cohorts, reduced GR expression, particularly of the GRα isoform, was observed in neonates with morbidity, but only with culture time and not in freshly isolated cells. Ex vivo impaired glucocorticoid-mediated transrepression of proinflammatory genes <i>IL6</i> and <i>TNF</i> was also observed in the morbidity groups. In contrast, all samples were comparable in basal immune cell distributions and transactivation of glucocorticoid response element (GRE)-dependent genes <i>GILZ</i> and <i>FKBP5</i>, irrespective of neonatal morbidity. These findings suggest that neonates that develop morbidities experience an early postnatal GR dysfunction that is potentially programmed in utero. Moreover, under conditions of decreased GR abundance, classical transactivation functions appear to be preserved at the expense of more complex regulatory mechanisms such as transrepression.