A multifaceted examination of the action of PDE4 inhibitor rolipram on MMP2/9 reveals therapeutic implications

A PDE4 (phosphodiesterase 4) inhibitor, Rolipram, was previously found to down-regulate (in a manner dependent on cAMP (cyclic adenosine monophosphate)-PKA (protein kinase A)) MMP2 (matrix metalloproteinase 2) and MMP9 protein expression levels, important markers of epithelial-to-mesenchymal transition in human breast cancer cell lines. However, zymographic studies revealed that rolipram could also alter the enzymatic activities of these MMPs, even in the presence of the PKA inhibitor H89. This calls for more detailed investigations of the inhibitory mechanism of rolipram on MMP2 and MMP9. The prediction of ligand-based targets through online reverse screening indicated that proteases are likely targets of rolipram. Computational molecular docking also demonstrated significant binding affinities of rolipram for both MMP2 and MMP9 proteins. Concurrently, a well-known inhibitor of MMPs, SB3CT, was utilized as a positive control for this study. The best models of the docked complexes were used as initial conditions for molecular dynamics (MD) simulations to explore their dynamic behavior and stability. In particular, both the MMP2-rolipram and MMP9-rolipram complexes were found to be stable and compact for the duration of the simulation ([Formula: see text]). Several stable hydrogen bonds were also detected between the proteins and rolipram. In vitro experiments using primary cells from patients with breast cancer also showed that rolipram could alter the enzymatic activities of MMP2 and MMP9, independent of the cAMP-PKA signaling pathway, though it was thought to be cAMP-PKA dependent previously. These observations indicate the ability of rolipram to control breast cancer by regressing the functions of MMP2 and MMP9, thus having 'off-targets' other than PDE4 to have direct control over proteins that are involved in the advancement of metastasis.