Characterization of inhibition by vardenafil analogues of ATP-dependent transport of cGMP by the ABCC5 transporter.

Abstract

Background: Clinical studies have reported overexpression of PDE5 and elevation of intracellular cyclic GMP in various types of cancer cells. ABCC5 transports intracellular cGMP out of the cells with high affinity, while PDE5 inhibitors prevent high affinity cGMP efflux by inhibiting ABCC5. Increasing intracellular cGMP levels through inhibition of PDE5 and PDE5 export activity is hypothesized to promote apoptosis and growth restriction in tumor cells the tumor cells. Vardenafil is a potent inhibitor of both PDE5 and ABCC5-mediated cGMP cellular efflux (Ki=3.4μl). Nineteen novel vardenafil analogs that have been predicted as potent inhibitors by VLS were chosen for tests of their ability to inhibit ATP- dependent transport of cGMP by measuring the accumulation of cyclic GMP in inside-out vesicles.

Aim: In this study, we investigated the ability of nineteen new compounds to inhibit ABCC5-mediated cGMP transport. We also determined the Ki values of the six most potent compounds.

Methods: Preparation of inside out vesicles and transport assay (12-well manifolds and 96-format assembly)

Results: Ki values for six of nineteen compounds that showed more than 50% inhibition of cGMP transport in the screening test were determined. Two of them were more potent than the positive control, sildenafil.