Deletion of vascular thromboxane A2 receptors and its impact on angiotensin II-induced hypertension and atherosclerotic lesion formation in the aorta of Ldlr-deficient mice.

ABSTRACT

The thromboxane A2 receptor (TP) has been shown to play a role in angiotensin II (Ang II)-mediated hypertension and pathological vascular remodeling. To assess the impact of vascular TP on Ang II-induced hypertension, atherogenesis, and pathological aortic alterations, i.e. aneurysms, we analysed Western-type diet-fed and Ang II-infused TPVSMC KO/Ldlr KO, TPEC KO/Ldlr KO mice and their respective wild-type littermates (TPWT/Ldlr KO). These analyses showed that neither EC- nor VSMC-specific deletion of the TP significantly affected basal or Ang II-induced blood pressure or aortic atherosclerotic lesion area. In contrast, VSMC-specific TP deletion abolished and EC-specific TP deletion surprisingly reduced the ex vivo reactivity of aortic rings to the TP agonist U-46619, whereas VSMC-specific TP knockout also diminished the ex vivo response of aortic rings to Ang II. Furthermore, despite similar systemic blood pressure, there was a trend towards less atherogenesis in the aortic arch and a trend towards fewer pathological aortic alterations in Ang II-treated female TPVSMC KO/Ldlr KO mice. Survival was impaired in male mice after Ang II infusion and tended to be higher in TPVSMC KO/Ldlr KO mice than in TPWT/Ldlr KO littermates. Thus, our data may suggest a deleterious role of the TP expressed in VSMC in the pathogenesis of Ang II-induced aortic atherosclerosis in female mice, and a surprising role of the endothelial TP in TP-mediated aortic contraction. However, future studies are needed to substantiate and further elucidate the role of the vascular TP in the pathogenesis of Ang II-induced hypertension, aortic atherosclerosis and aneurysm formation.