THE SELECTIVE DELETION OF TYROSYNE HYDROXYLASE GENE IN THE ENDOTHELIUM AFFECTS CARDIOVASCULAR FUNCTION

Abstract

Objective: We showed that the endothelium can synthesize and release catecholamines in response to hypoxia. However, the pathophysiological implications of such findings are still unknown since no mouse model is available to achieve this goal. The aim of the study is the generation and characterization of a transgenic mouse model in which the tyrosine hydroxylase (TH) gene is selectively deleted in the endothelium. Design and method: The animal model was generated using the CRE-LOX system with specific tissue expression of the CRE recombinase. TH-FLOX mice and Tie2-CRE mice were crossed to obtain mice with endothelial knock-out of the TH gene (TH - / -). The level of circulating CA was assessed by ELISA assay. We measured blood pressure with a non-invasive method (CODA Tail-Cuff). In vitro, TH gene was deleted in mouse endothelial cells by a specific siRNA to evaluate its effects on endothelial function. Results: The level of circulating catecholamines is significantly reduced in TH -/- mice compared to TH +/+ mice, suggesting a key role of the endothelium in the production of circulating CAs. We evaluated blood pressure levels and found a significant increase in TH -/- young mice compared to TH +/+ mice. In vitro, we evaluated the effects of TH deletion on endothelial function. The deletion induced a significant reduction of nitric oxide, angiogenesis on Matrigel, and an increase in apoptosis and inflammatory cytokines suggesting an autocrine effect of catecholamines produced by the endothelium. Conclusions: These data indicate that the reduced production of endothelial CA alters vascular function, suggesting that endothelial catecholamines are essential for the proper functioning of the cardiovascular system.