Associate Professor Lerner Research Institute, Cleveland Clinic and Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Ohio
Rationale: Pharmacoresistance in epilepsy is a major challenge to successful clinical therapy. Glucocorticoid receptor (GR) dysfunction can affect the underlying disease pathologies. We recently reported that local drug biotransformation at the blood brain barrier is upregulated by GR, which controls drug metabolizing enzymes (e.g., cytochrome P450s) and efflux drug transporters (MDR) in human epileptic brain endothelial cells (EPI-ECs). Here we establish that this mechanism is influenced by GR and its association with heat shock proteins/co-chaperones (Hsps) during maturation, which differently affect human epileptic tissue and brain endothelial cells. Methods: Surgical brain resections from focal (EPI) areas were obtained from patients (n = 21, mostly focal cortical dysplasia) with medically refractory epilepsy and compared with relatively nonfocal (NON-EPI) regions of the same tissue, precharacterized by electrophysiology and histopathology. GR and Hsps were analyzed by immunoblotting and immunohistochemistry. Immunoprecipitation of GR in EPI-ECs / epileptic brain tissue was performed; GR interactions with Hsp90/Hsp70 and ATPase activity of the chaperones were evaluated. GR silencing (siRNA) on EPI-ECs was performed to assess the consequence on GR-Hsp binding and GR maturation after drug exposure. Results: Elevated neurovascular GR expression and co-localization with Hsps was evident in the EPI regions with cortical dysplasia, predominantly in the brain micro-capillaries and neurons. Overexpressed GR, Hsp90, Hsp70, Hsp40 were found in EPI vs. NON-EPI brain regions. A corresponding increase in ATPase activity (*p < 0.05) was found in the EPI regions. The GR-Hsp90/ Hsp70 binding patterns indicated faster chaperone-promoted maturation of GR, leading to its overactivation in both in the brain tissue and EPI-ECs derived from EPI/focal regions; GR silencing in EPI-ECs slowed down such GR-Hsp interactions. Significantly accelerated GR nuclear translocation was determined in EPI-ECs following treatment with GR modulators/ ligands (dexamethasone, rifampicin or phenytoin). Conclusions: Our findings reveal that overexpressed GR co-localizes with Hsps in the neurovasculature of the epileptic brain, increased GR maturation by Hsp accelerates EPI GR machinery and further that this change in EPI and NON-EPI GR-Hsp interactions alters with the age of seizure-onset in epileptic patients, together affecting the pathophysiology and drug regulation in the epileptic brain endothelial cells. Funding: Please list any funding that was received in support of this abstract.: This study is supported in part by NIH-NINDS grant R01NS095825 awarded to Dr. Chaitali Ghosh.