Ro 20-1724 is a cell-permeable, cAMP-specific phosphodiesterase type IV (PDE4) inhibitor (IC50 = 2 μM).[1],[2] It weakly inhibits PDE3 with a Ki value greater than 25 μM.1 Ro 20-1724 inhibits the release of cytokines and other inflammatory signals as well as prevents the development of reactive oxygen species.[3] It is often used to study cAMP-related functions in vascular cells.[4]

Reference:
[1]. Reeves, M.L., Leigh, B.K., and England, P.J. The identification of a new cyclic nucleotide phosphodiesterase activity in human and guinea-pig cardiac ventricle. Implications for the mechanism of action of selective phosphodiesterase inhibitors. Biochemistry Journal 241, 535-541 (1987).
[2]. Soderling, S.H., Bayuga, S.J., and Beavo, J.A. Cloning and characterization of a cAMP-specific cyclic nucleotide phosphodiesterase. Proceedings of the National Academy of Sciences of the United States of America 95, 8991-8996 (1998).
[3]. Totani, L., Piccoli, A., Dell'Elba, G., et al. Phosphodiesterases type-4 blockade prevents platelet-mediated neutrophil recruitment at the site of vascular injury. Arteriosclerosis, Thrombosis, and Vascular Biology 34(8), 1689-1696 (2014).
[4]. Zhai, K., Hubert, F., Nicolas, V., et al. β-Adrenergic cAMP signals are predominantly regulated by phosphodiesterase type 4 in cultured adult rat aortic smooth muscle cells. PLoS One 7(10), 1-13 (2012).