Angiotensin receptor blocker (ARB) treatment causes paradoxical microvascular endothelial cell proliferation

Abstract

Aim: Previously our laboratory has shown that cerebral angiogenesis in rats is stimulated by chronic treatment with the angiotensin II (ANG II) type 1 receptor (AT1R) antagonist, Losartan (LOS). Because the pro‐angiogenic actions of ANG II via AT1R have been well documented in the peripheral microvasculature, the finding that an AT1R antagonist stimulates cerebral angiogenesis is paradoxical. The aim of this study is to determine whether the in vivo findings are due to receptor blockade per se or whether LOS might exert nonspecific actions in the cerebral vasculature that could explain the in vivo paradox.Methods: Primary human cerebral and dermal microvascular endothelial cells (ECs), passage 3–8, were seeded into 96‐well plates (5000 cells/well) and allowed to adhere for 24 hrs. Cells were exposed to serum‐free media (SFM) alone and in the presence of LOS (10 μM), ANG II (1 μM) or both for 48 hours. Cell density was measured by a fluorescent cell proliferation assay (CyQUANT, Molecular Probes) on a plate reader at 480/520 nm.Results: Cell density increased with ANG II treatment of both cerebral (27.5%) and dermal ECs (8.9%) compared to SFM. LOS treatment elicited a similar response (cerebral: 27.1%, dermal: 19.0%). Treatment with both LOS and ANG II, which would simulate AT1R blockade, also stimulated EC proliferation (cerebral 33.7%, dermal: 15.2%).Conclusion: Since LOS alone, either in the presence or absence of agonist, stimulated cell proliferation in cells derived from both brain and skin, it would suggest that 1) LOS stimulates EC proliferation directly, not by receptor blockade, and 2) tissue differences are not detectable in cultured ECs derived from neural tissue compared to peripheral tissue. Future studies are needed to determine the mechanism for this effect and the cause of observed tissue differences in vivo.Supported by NIH HL29587 and HV28182