Valsartan and Telmisartan Abrogate Angiotensin II–induced Downregulation of ABCA1 Expression Via AT1 Receptor, Rather than AT2 Receptor or PPARγ Activation

The possible pharmacological mechanism by which partial PPARγ-activating angiotensin II (Ang II) type 1 receptor blocker (ARB) telmisartan and non-PPARγ-activating ARB valsartan reverse Ang II-suppressed ABCA1 expression is still unclear. In this study, human monocyte-derived THP-1 cells were differentiated into macrophages. Cells were treated with various concentrations of Ang II alone or with Ang II and various drugs including highly selective ARB valsartan, partial PPARγ-activating ARB telmisartan, angiotensin II type 2 (AT2) receptor blocker PD123319, full PPARγ agonist pioglitazone, and PPARγ antagonist GW9662, respectively. After treatment, messenger RNA and protein expressions of ABCA1 and ABCG1 were analyzed by real-time polymerase chain reaction and Western blotting, respectively. ABCA1 expression was remarkably suppressed by Ang II at both messenger RNA and protein levels in a dose-dependent manner in THP-1-derived macrophages, whereas ABCG1 expression was not affected. Valsartan and telmisartan could both reverse the downregulation of Ang II on ABCA1 expression. Such effects were not affected by either AT2 receptor blocker PD123319 or PPARγ antagonist GW9662. Our findings suggest that the effect of Ang II on ABCA1 expression should be mediated by the AT1 receptor. Both valsartan and telmisartan abrogate Ang II-induced downregulation of ABCA1 expression mainly through AT1 receptor rather than through AT2 receptor or PPARγ-dependent pathway.