Angiotensin II upregulates LDL receptor-related protein (LRP1) expression in the vascular wall: a new pro-atherogenic mechanism of hypertension.

AIMS: Hypertension is a risk factor for atherothrombotic vascular events. Angiotensin II (Ang II), one of the main vasoactive hormones of the renin-angiotensin system, has been associated with the development and progression of atherosclerosis. However, it is not fully known how Ang II contributes to lipid-enriched atherosclerotic lesion formation. In human vascular smooth muscle cells (VSMC), low density lipoprotein (LDL) receptor-related protein (LRP1) internalizes cholesteryl esters (CE) from extracellular matrix-bound aggregated LDL (agLDL). The aim of this study was to investigate the effect of Ang II on LRP1 expression and function in VSMC.

METHODS AND RESULTS: Here, we report for the first time that Ang II induces the upregulation of LRP1 expression in VSMC. Ang II (1 microM) induced maximal LRP1 mRNA expression at 12 h and maximal protein overexpression (by 4.10-fold) at 24 h in cultured human VSMC. Ang II effects were functionally translated into an increased CE accumulation from agLDL uptake (by two-fold at 50 microg/mL) that was prevented by the LRP1 ligand lactoferrin and by siRNA-LRP1 treatment. Ang II-LRP1 upregulation and excess CE accumulation from agLDL were prevented by losartan (an AT1 blocker) but not by PD123319 (a specific AT2 blocker). Additionally, in a normolipidaemic rat model, Ang II infusion produced a significant increase in aortic LRP1 expression and lipid infiltration in the arterial intima.

CONCLUSION: The in vitro and in vivo data reported here indicate that Ang II upregulates LRP1 receptor expression and LRP1-mediated aggregated LDL uptake in vascular cells.