The PDE4 inhibitors roflumilast and rolipram augment PGE2 inhibition of TGF-β1 stimulated fibroblasts

Fibrotic diseases are characterized by the accumulation of extracellular matrix together with distortion and disruption of tissue architecture. Phosphodiesterase 4 (PDE4) inhibitors, by preventing the breakdown of cyclic AMP, can inhibit fibroblast functions and may be able to mitigate tissue remodeling. TGF-β1, a mediator of fibrosis, can potentially modulate cAMP by altering PGE2 metabolism. The current study assessed whether PDE4 inhibitors functionally antagonize the profibrotic activity of fibroblasts stimulated by TGF-β1. The PDE4 inhibitors roflumilast and rolipram both inhibited fibroblast-mediated contraction of three-dimensional collagen gels and fibroblast chemotaxis toward fibronectin in the widely studied human fetal lung fibroblast strain HFL-1 and several strains of fibroblasts from adult human lung. Roflumilast was approximately 10-fold more potent than rolipram. There was a trend for PDE4 inhibitors to inhibit more in the presence of TGF-β1 (0.05 < p <0.08). The effect of the PDE4 inhibitors was mediated through cyclic AMP stimulated protein kinase A (PKA), although a PKA-independent effect on gel contraction was also