Prevention of aortic elastic lamina defects by losartan in apolipoprotein(E)-deficient mouse.

1. In a previous study, we identified prevalent internal elastic lamina (IEL) defects in the aorta of hyperlipidaemic apolipoprotein E (ApoE)-deficient mice that are thought to provide a structural basis for the development of atherosclerosis and intimal thickening. In the present study, we examined the effects of losartan, an angiotensin AT1 receptor antagonist, on the development of IEL defects. 2. Male 18-week-old ApoE-deficient mice (maintained on a normal diet) were treated with losartan (3 or 30 mg/kg per day) for 10 weeks via the drinking water. The IEL defects were quantified histologically by measuring the continuity of the IEL within the inner curvature of the aortic arch. 3. In untreated animals, there was an age-dependent increase in IEL defects from 7.2 ± 2.1% at 18 weeks to 13.8 ± 4.0% at 28 weeks. Treatment with the high dose of losartan significantly prevented the development of IEL defects (4.7 ± 1.3% at 28 weeks; P < 0.05 vs untreated). This effect was independent of changes in blood pressure or plasma lipid levels. Using quantitative real-time polymerase chain reaction, we found that the effects of losartan were not associated with changes in levels of matrix metalloproteinase (MMP)-2 and MMP-9, tissue inhibitor of matrix metalloproteinase-1 or inflammatory markers in the aorta. 4. The results suggest that the renin-angiotensin system may contribute to the development of aortic IEL defects in a blood pressure-independent manner.