Altered glucocorticoid receptor signaling cascade in lymphocytes of bipolar disorder patients

SummaryBipolar disorder (BD) is characterized by hypothalamic pituitary adrenal (HPA) axis hyperactivity, glucocorticoid insensitivity and alterations in serotonin and inflammatory mediators. The glucocorticoid receptor (GR), activator protein-1 (AP-1), nuclear factor—kappa B (NF-κB) and c-jun N-terminal kinase (JNK) regulate the above mentioned processes; we therefore assessed their role in BD. Fifteen bipolar depressed patients under multiple anti-depressant therapy, 15 bipolar euthymics under lithium monotherapy and 25 matched controls were studied. Whole cell and nuclear extracts from lymphocytes were immunoblotted for GR, c-fos, JNK and NF-κB and nuclear aliquots were submitted to electrophoretic mobility shift assay for GR, AP-1 and NF-κB. Associations with the anti-depressant therapy and the state of the disease were also sought. Results, expressed as percentage of pooled protein standard sample intergraded optical density (IOD) (mean±SD), revealed: (a) depressed patients had significantly higher GR levels than controls in whole cell (82.63±6.18 versus 76.27±4.21%, P<0.01) and nuclear extracts (86.66±3.81 versus 81.72±2.71%, P<0.001) but lower GR–DNA binding (68.75±7.91 versus 81.84±4.25%, P<0.05). Euthymics had normalized whole cell GR content (73.64±5.95%) and GR–DNA binding activity (76.82±7.29%) but higher nuclear GR content (86.89±3.96%, P<0.01) than controls; (b) nuclear c-fos content and AP-1–DNA-binding were significantly lower in depressed patients than controls (80.49±2.03 versus 84.82±3.48%, P<0.05 and 78.46±4.17 versus 84.80±5.79%, P<0.05, respectively). Euthymics however, showed similar nuclear c-fos and AP-1–DNA-binding to controls (85.48±2.71 and 87.78±3.54%, respectively) but lower whole cell c-fos than in controls (81.18±3.87 versus 87.01±4.22%, P<0.001); (c) depressed patients had significantly lower whole cell and nuclear JNK than controls (67.01±4.29 versus 72.00±3.68%, P<0.05 and 80.10±2.53 versus 86.96±2.49%, P<0.001) whereas euthymics showed lower nuclear JNK (83.27±1.93%, P<0.01); (d) whole cell NF-kB was higher in the depressed patients than in controls (67.30±5.00 versus 63.63±3.3%, P<0.05). Concluding, intracellular signaling of GR, AP-1 and JNK are altered in BD and may underly disease aetiopathogenesis and/or reflect the effect of the anti-depressants.