Targeted overexpression of the human urotensin receptor transgene in smooth muscle cells: effect of UT antagonism in ApoE knockout mice fed with Western diet.

Urotensin II (UII) and its receptor UT are upregulated in the pathological setting of various cardiovascular diseases including atherosclerosis. However, their exact role in atherosclerosis remains to be determined. In the present study we used four strains of mice; wild-type (WT), UT+ (a transgenic strain expressing human UT driven by the α-smooth muscle-specific, SM22, promoter), ApoE knockout (ko), and UT+/ApoE ko. All animals were fed high fat diet for 12 weeks. Western blot analysis revealed a significant increase in aortic UT expression in UT+ relative to WT mice (P<0.05). Aortas of ApoE ko mice expressed comparable UT protein level to that of UT+. Immunohistochemistry revealed the presence of strong expression of UT and UII proteins in the atheroma of UT+, ApoE ko and UT+/ApoE ko mice, particularly in foam cells. Serum cholesterol and triglyceride levels were significantly increased in ApoE ko and in UT+/ApoE ko but not in UT+ mice when compared to WT mice (P<0.0001). Analysis of aortas showed a significant increase in atherosclerotic lesion in the UT+, ApoE ko and UT+/ApoE ko compared to WT mice (P<0.05). Oral administration of the UT receptor antagonist SB-657510A (30μg/Kg/day gavage) for 10 weeks in a group of ApoE ko mice fed on high fat diet resulted in a significant reduction of lesion (P<0.001). SB-657510A also significantly reduced ACAT-1 protein expression in the atherosclerotic lesion of ApoE ko mice (P<0.05). The present findings demonstrate an important role for UT in the pathogenesis of atherosclerosis. The use of UT receptor antagonists may provide a beneficial tool in the management of this debilitating disease process.