Retinoic acid induces PGI synthase expression in human endothelial cells

Mercedes Camacho,Cristina Rodríguez,Juliana Salazar,José Martínez-González,Josep Ribalta,José-Román Escudero,Lluís Masana,Luis Vila

doi:10.1194/jlr.m700559-jlr200

Abstract

Retinoic acid (RA) exhibits anti-inflammatory, anti-tumor, and immuno-modulatory actions, and affects angiogenesis and thrombosis. Arachidonic acid (AA) metabolites are involved in all these processes. We explored the effect of RA on AA metabolism in human umbilical vein endothelial cells (HUVECs). 13-cis-RA increased the release of prostaglandin I(2) (PGI(2)), both spontaneous and thrombin-induced, in terms of 6-oxo-PGF(1alpha) analyzed by enzyme-immunoassay. Coincubation with 13-cis-RA and interleukin-1beta resulted in a synergic increase in the release of PGI(2). Consistently, 13-cis-RA increased the ability of HUVECs to inhibit AA-induced platelet aggregation. 13-cis-RA did not induce cyclooxygenase-isoenzyme expression, determined by immunoblotting, or activity, evaluated by analyzing eicosanoids formed from exogenous labeled AA by HPLC. In contrast, RA induced PGI synthase (PGIS) activity and expression in terms of mRNA and protein determined by real-time PCR and Western blotting, respectively. Results from experiments with several species of RA and with retinoic acid receptor (RAR) and retinoid X receptor (RXR) antagonists showed that the effect of RA on PGIS expression was mediated by RAR. Actinomycin D and cycloheximide both inhibited RA-induced PGIS expression. Furthermore, RA increased PGIS transcriptional activity in transient transfection assays, an effect that was prevented by an RAR antagonist. These results reinforce the concept that RA could be beneficial for patients with cardiovascular risk.

Highlights

Retinoic acid (RA) exhibits anti-inflammatory, anti-tumor, and immuno-modulatory actions, and affects angiogenesis and thrombosis
Prostanoids accumulated in the medium were analyzed by enzyme immunoassay (EIA); prostaglandin I2 (PGI2) was measured as 6-oxo-PGF1a stable metabolite of PGI2 (n 5 5, mean 6 SEM). * P, 0.05, ** P, 0.01 when compared with control cells
Medium when compared with controls without 13-cis-RA. 13-cis-RA increased PGI2 accumulation when cells were coincubated with IL-1b (Fig. 1B)

Summary

Introduction

Retinoic acid (RA) exhibits anti-inflammatory, anti-tumor, and immuno-modulatory actions, and affects angiogenesis and thrombosis. RA increased PGIS transcriptional activity in transient transfection assays, an effect that was prevented by an RAR antagonist. These results reinforce the concept that RA could be beneficial for patients with cardiovascular risk.—Camacho, M., C. Retinoic acid induces PGI synthase expression in human endothelial cells. COX-2 is present after vascular damage and is highly expressed in atherosclerotic lesions and aortic aneurysms in animal models and human tissue [2]. It probably plays a protective role in moderate vascular inflammation, promoting PGI2 biosynthesis. The scenario could be different if COX-2 were highly expressed in a severely inflamed area, potentially producing large amounts of other prostanoids, such as PGE2 or PGH2 [8, 13]

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Conclusion