Role of the estrogen receptor beta in the aortic aneurysm of patients with bi- and tricuspid aortic valve

• Applicant: Dr. Josephina Haunschild
• Subject Area: Cardiac and Vascular Surgery
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 421990031

Numerous studies demonstrated a higher incidence of thoracic and abdominal aortic aneurysm in men. Women appear to be protected by their sex hormones and are affected later in life, mostly after menopause.However, current data suggest that once women are afflicted the disease progresses more rapidly and the risk of rupture is higher,accompanied by worse outcome. Clinical studies investigating the effect of hormone therapy have shown diverging results (less atherosclerosis vs. more CV events).Major influence in the development of aortic aneurysm are the endothelial cell function, (acute/chronic) inflammation and apoptosis. Currently the expression and function of the various hormone receptors is not well known, however one study demonstrated a NOTCH1 and estrogen receptor beta(ERb)-mediated reduction of the TNF alpha (TNFa)-induced apoptosis in human umbilical vein endothelial cells. The interdependence of these key players will be investigated in the proposed project. The focus is on patients with bicuspid (BAV) or tricuspid aortic valve (TAV) who are prone to developing proximal aortic aneurysms and–in worst case-acute aortic dissection.Preliminary work: The expression of the three subtypes of estrogen receptor (ERa, ERb and GPR30) has been realized in 36 aortic specimen of patients with BAV and TAV. The ERb displayed a significant difference–women with TAV had a significantly higher expression of the receptor (p=0.0023) compared to their male peers. Within the BAV cohort no difference was detectable (p=0.189). The hypothesis that binding of estradiol (E2) to ERb is protective against the development of a thoracic aortic aneurysm mediated by the inhibition of the TNFa-induced apoptosis via Akt and NOTCH 1 signaling will be evaluated in this project.Further inhibition is achieved via mTOR.These protective mechanisms are counteracted by increased shear stress as well as mechanical stress of the endothelial cells inducing a decrease in the expression of ERb.A total of 50 aortic specimen (25 BAV, 25 TAV) will be analyzed concerning expression of ERb, caspase 3, NOTCH 1, mTOR utilizing Western Blot analysis and immunohistochemistry. Human aortic endothelial cells will be cultivated and exposed to mechanical stretch for 24 and 48 hours. Afterwards, TNFa will be investigated in the cell supernatant and ERb, caspase 3, NOTCH 1, mTOR will be analyzed in the lysed cells. Detection of apoptosis will be carried out using TUNEL assay. In addition,a shear stress model will be established to investigate the influence of laminar and oscillatory flow (for 24/48 hours) on the endothelial cells.The proposed study will clarify the influence of mechanical stress and shear stress on the expression of ERb and the mechanism of TNFa-induced apoptosis in human aortic endothelial cells and by analyzing speimen of the human aneurysmatic aorta of male and female patients as well as BAV and TAV translate findings in the cell model to the patient.

• DFG Programme: Research Grants