ESPE Abstracts (2016) 86 RFC1.3

Impaired Cardiac Function in a Mouse Model of Generalized Glucocorticoid Resistance

Agaristi Lamprokostopouloua, Aimilia Varelab, Michalis Katsimpoulasb, Constantinos Dimitrioub, Nikos Athanasiadisb, Eleana Soultoub, Alketa Stefaa, Manolis Mavroidesb, Constantinos H. Davosb, George P. Chrousosa, Tomoshige Kinoc, Spiros Georgopoulosd & Evangelia Charmandaria

aDivision of Endocrinology and Metabolism, Biomedical Research Foundation of the Academy of Athens, Athens, Greece; bClinical, Experimental Surgery and Translational Research Center,
Biomedical Research Foundation of the Academy of Athens, Athens, Greece; cDepartment of Experimental Therapeutics, Division of Experimental Biology, Sidra Medical and Research Center, Doha, Qatar; dDepartment of Cell Biology, Biomedical Research
Foundation of the Academy of Athens, Athens, Greece

Background: Glucocorticoids regulate a broad spectrum of physiologic functions essential for life and exert their actions through their ubiquitously expressed glucocorticoid receptor (GR). The GR interacts with several molecules, including the non-coding RNA growth arrest-specific 5 (Gas5), which decreases the transcriptional activity of the GR by preventing its binding to DNA, and reduces tissue sensitivity to glucocorticoids.

Objective and Hypotheses: To create a mouse model of Generalized Glucocorticoid Resistance by inducible overexpression of Gas5 and to investigate its myocardial function.

Methods: Two transgenic lines expressing the reverse transactivator (rtTA) under hnRNP promoter and the Gas5 under Tet responsive P tight promoter were generated and then crossed to create double transgenic mice (Gas5/rtTA), which were then tested for Gas5 inducibility of overexpression by qRT-PCR. The cardiac function was evaluated by echocardiography and 24-hour electrocardiography (ECG).

Results: Genetic constructs of double transgenic mice inducibly overexpressing Gas5 after doxycycline administration (DOX+) were generated. The induction of overexpression of Gas5 in: Gas5/rtTA mice (2 weeks DOX+; 0.78±0.37) compared with i) Gas5/rtTA mice without doxycycline administration (DOX−; 0.14±0.04), ii) single transgenic DOX+ mice where the TetOn system is not functional (0.3*10−4±0.5*10−5), and iii) wild-type (WT) DOX+ mice (0.7*10−5±0.8*10−5) was verified in the myocardium. The cardiac function (% fractional shortening) was significantly decreased in Gas5/rtTA/DOX+ compared with Gas5/rtTA/DOX− mice (44.6±0.8 vs 48.5±0.4; P=0.003) but not compared with WT/DOX+ mice (46.9±0.4, P=0.2). This was mainly due to decreased systolic function in Gas5/rtTA/DOX+ vs Gas5/rtTA/DOX− mice (end-systolic dimension: 1.6±0.1 vs 1.8±0.1 mm; P=0.05). ECG studies did not show differences among the three groups of mice in terms of heart rate, ECG interval measurements and arrhythmias.

Conclusion: We created a mouse model of Generalized Glucocorticoid Resistance and demonstrated impaired cardiac function. Ongoing studies aim to investigate the molecular mechanisms through which glucocorticoid resistance affects myocardial function.