Proliferation Signal Inhibitor–induced Decrease of Vascular Endothelial Cadherin Expression and Increase of Endothelial Permeability In Vitro Are Prevented by an Anti-oxidant
Received 24 April 2008; received in revised form 19 August 2008; accepted 26 August 2008.
Background
Rapamycins, sirolimus (SRL) and everolimus (ERL), are proliferation signal inhibitors (PSIs). PSI therapy often leads to edema. We hypothesized that increased oxidative stress in response to PSIs may modulate the expression of vascular endothelial (VE)-cadherin on endothelial cells (ECs) and, subsequently, vascular permeability, which in turn may be involved in the development of edema.
Methods
Experiments were performed on human umbilical vein ECs (HUVECs). Oxidative stress was measured by dichlorofluorescein-diacetate. Expression of VE-cadherin was evaluated by immunofluorescent staining and western blot analysis. Endothelial “permeability” was assessed using a transwell model.
Results
SRL and ERL, at concentrations of 1, 10 and 100 nmol/liter, enhanced oxidative stress (SRL: 24 ± 12%, 29 ± 9%, 41 ± 13% [p < 0.05, in all three cases]; ERL: 13 ± 10%, 27 ± 2%, 40 ± 12% [p < 0.05, in the latter two cases], respectively) on HUVECs, which was inhibited by the anti-oxidant, N-acetyl-cysteine (NAC) and, to a lesser extent, by the specific inhibitor of nitric oxide synthase, N-Ω-nitro-l-arginine methylester. By the use of NAC, VE-cadherin expression remained comparable with control, according to both immunocytochemistry and western blot analysis. Permeability was significantly increased by SRL and ERL at 100 nmol/liter (29.5 ± 6.4% and 33.8 ± 4.2%, respectively); however, co-treatment with NAC abrogated the increased permeability.
Conclusions
EC homeostasis, as indicated by VE-cadherin expression, may be damaged by SRL and ERL, but resolved by the anti-oxidant NAC.
Department of Cardiology, Heart Transplant Research Laboratory, Swiss Cardiovascular Center Bern, University Hospital Bern (Inselspital), Bern, Switzerland
Reprint requests: Paul Mohacsi, MD, Cardiology, University Hospital (Inselspital), CH-3010 Bern, Switzerland. Telephone: +41-31-632-44-64. Fax: +41-31-632-45-60
Supported by the Katharina Huber-Steiner Foundation, Bern, Switzerland.
ABSTRACT