Solid-phase synthesis and evaluation of libraries of substituted 4,5-dihydropyridazinones as vasodilator agents.

The solid-phase parallel preparation of a library of 4,5-dihydropyridazin-3(2H)-one derivatives substituted at position 6 with piperazinylmethyl or tetrahydroquinolinylmethyl groups and analogues (3) is reported. Polymer-supported gamma-keto-delta-aminoesters prepared from Wang resin reacted with hydrazine or methylhydrazine to afford pyridazinones in good yields after a cyclization cleavage approach. We have evaluated these novel analogues and several compounds of other series (1, 2) for their vasorelaxant effect. Among the products tested, 3l and 3d proved to be efficacious and potent relaxant agents of the isolated rat aorta. Inhibitors of phosphodiesterase (PDE3), responsible for the breakdown of cyclic AMP in the vascular smooth muscle, are currently developed for cardiac heart failure because of their inotropic effect and coronary vasodilatation. We had expected that the vasodilatation induced by 3l, as efficient as reference PDE3 inhibitors, milrinone or CI-930, to be due to PDE3 inhibition. However 3l and 3d exhibited a low inhibitory effect against PDE3 isoenzyme activity. These compounds induced a significant vasorelaxation, which could be of therapeutic interest even if their mechanism of action remains to be determined.

Modulation of matrix metalloproteinase production from human lung fibroblasts by type 4 phosphodiesterase inhibitors.

Over-expression of matrix metalloproteinases by lung fibroblasts has been blamed for much of the tissue destruction associated with airway inflammation. Because cyclic AMP is known to regulate fibroblast proliferation, as well as cytokine and extracellular matrix protein production, the current study was designed to evaluate the ability of three selective phosphodiesterase (PDE) type 4 inhibitors, rolipram, cilomilast and CI-1044, to inhibit extracellular matrix degradation. Using zymography and ELISA, we found that pro-MMP-2 release was enhanced following 24 h treatment of human lung fibroblast (MRC-5) with TGF-beta1 (10 ng/ml) or TNF-alpha (10 ng/ml), whereas PMA (0.02 microM) had no effect. One hour of pre-incubation with PDE4 inhibitors (10 microM) induced an inhibition of TNF-alpha-stimulated pro-MMP-2 release. Zymography and immunoblotting revealed that fibroblasts cultured with PMA or TNF-alpha released increased amounts of pro-MMP-1, whereas TGF-beta1 had no effect. Incubation with CI-1044 or cilomilast significantly prevented the TNF-alpha increase in pro-MMP-1. These results suggest that PDE4 inhibitors are effective in inhibiting the pro-MMP-2 and pro-MMP-1 secretion induced by TNF-alpha and might underline a potential therapeutic benefit of selective PDE4 inhibitors in lung diseases associated with abnormal tissue remodelling.

Synthesis and potential anti-inflammatory activity of some tetrahydrophthalazinones.

A solid-phase route for the preparation of 4a,5,8,8a-tetrahydrophthalazinon-1-ones employing the Diels-Alder reaction has been developed. Some of the new compounds have been tested for inhibition of LPS-stimulated TNF-alpha production in human whole blood from patients with chronic obstructive pulmonary disease (COPD). This evaluation revealed two compounds 17 and 18 of interest, incorporating an arylpiperazine moiety, which were found to inhibit LPS-induced TNF-alpha release like the well known anti-inflammatory PDE4 inhibitors, rolipram and roflumilast.