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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2000;20:e34.)
© 2000 American Heart Association, Inc.

Vascular Biology

Inhibition of Type 4 Phosphodiesterase by Rolipram and Ginkgo biloba Extract (EGb 761) Decreases Agonist-Induced Rises in Internal Calcium in Human Endothelial Cells

Manuel Campos-Toimil; Claire Lugnier; Marie-Thérèse Droy-Lefaix; Kenneth Takeda

From Pharmacologie et Physico-chimie des Interactions Cellulaires et Moléculaires (M.C.-T., C.L., K.T.), UMR CNRS 7034, Faculté de Pharmacie, Université Louis Pasteur de Strasbourg, Illkirch, and IPSEN (M.-T.D.-L.), Paris, France. Dr Campos-Toimil is currently at the Department of Pharmacology, University of Cambridge, Cambridge, UK.

Correspondence to Dr K. Takeda, Pharmacologie et Physico-chimie des Interactions Cellulaires et Moléculaires, UMR CNRS 7034, Faculté de Pharmacie, BP 24, 67401 Illkirch, France. E-mail kt{at}aspirine.u-strasbg.fr

Abstract—The effects of Gingko biloba extract EGb 761 on 5 isolated, vascular, cyclic nucleotide phosphodiesterase (PDE) isoforms were evaluated. EGb 761 preferentially inhibited PDE4 (IC₅₀=25.1 mg/L), the isoform that is mainly present in endothelial cells, in a competitive manner (K_i=12.5 mg/L). Because changes in cyclic nucleotide levels may affect intracellular calcium ([Ca²⁺]_i) levels in endothelial cells, we examined the effects of EGb 761 on both resting [Ca²⁺]_i levels and agonist-induced rises in [Ca²⁺]_i in single human umbilical vein endothelial cells (HUVECs) in culture. The effects of EGb 761 were compared with those of rolipram, a selective PDE4 inhibitor that increases cellular cAMP levels, and the cAMP analogue dibutyryl cAMP (db-cAMP). EGb 761 (20 and 100 mg/L), rolipram (50 µmol/L), and db-cAMP (100 µmol/L) significantly inhibited histamine-, ATP-, and thrombin-induced [Ca²⁺]_i increases in HUVECs without modifying resting [Ca²⁺]_i levels. Similar results were obtained by using a Ca²⁺-free bath solution. EGb 761 (100 mg/L), but not rolipram (50 µmol/L) or db-cAMP (100 µmol/L), also inhibited Ca²⁺ influx into cells having thapsigargin-depleted internal Ca²⁺ stores and bathed in a Ca²⁺-free external solution. Our results are consistent with an inhibition of PDE activity that causes a reduction of agonist-induced increases in [Ca²⁺]_i in HUVECs, mainly by inhibition of Ca²⁺ mobilization from internal stores. It thus may be that the cardiovascular effects of EGb 761 involve inhibition of PDE4 activity and subsequent modification of Ca²⁺ signaling in endothelial cells.

Key Words: Gingko biloba • calcium • phosphodiesterases • rolipram • human umbilical vein endothelial cells