A novel class of cardiotonic agents: synthesis and biological evaluation of pyridazino[4,5-b]indoles with cyclic AMP phosphodiesterases inhibiting properties

Multistep Microwave Assisted Solvent Free Green Chemical Synthesis of 2,7-Dihydro-3H-Pyridazino[3′,4′:4,5]Indolo[3,2-c]Quinoline-3,13(12H)-Dione

A novel class of biologically active compound 2,7-dihydro-3 H-pyridazino[3′,4′:4,5]indolo[3,2- c]quinoline-3,13(12 H)-dione (10a–b)has been achieved efficiently and quickly under solvent free conditions in an open vessel microwave system. The multi step one pot synthesis involved the reaction of 8,9,10,11-tetrahydro-6 H-indolo[3,2- c]quinoline-6,7(5 H)-dione (6a–d) and glyoxylic acid monohydrate followed by cyclocondensation with hydrazine hydrate under microwave irradiation. The synthesis of 8,9,10,11-tetrahydro-6 H-indolo[3,2- c]quinoline-6,7(5 H)-dione(6a–d) has also been described from the reaction of (2-oxo-1,2-dihydroquinolin-4-yl)hydrazine with 1,3-cyclohexanedione in the absence of any solvent/catalyst/strong acid or solid support using microwaves.

Contribution of phosphodiesterase isoenzymes and cyclic nucleotide efflux to the regulation of cyclic GMP levels in aortic smooth muscle cells

Involvement of phosphodiesterase isoenzymes (PDEs) in guanosine-3',5'-cyclic monophosphate (cGMP) hydrolysis was analyzed in aortic smooth muscle cells. Four families of PDEs were separated from pig aorta: PDE1 (calcium-calmodulin-activated), PDE3 (cGMP-inhibited), PDE4 (adenosine 3',5'-cyclic monophosphate [cAMP]-specific), and PDE5 (cGMP-specific). Within this PDE complement, PDE1 and PDE5 mostly contributed to the hydrolysis of cGMP both in the presence and absence of calcium-calmodulin. The role of these isoenzymes in cGMP degradation was analyzed in primary cultures of porcine aortic smooth muscle cells after stimulation with sodium nitroprusside (SNP) or atrial natriuretic factor (ANF). Pretreatment with 10 microM zaprinast, a concentration that selectively inhibits PDE5, did not potentiate the SNP- or ANF-induced rise of cGMP, questioning the widespread opinion that only PDE5 accounts for cGMP hydrolysis in this tissue. Further evidence came from experiments assessing the effect of zaprinast or 3-isobutyl-1-methylxanthine at concentrations inhibiting both type 1 and type 5 isoenzymes, in which this potentiation was clearly seen. Contribution of cGMP egression to the control of intracellular cGMP levels after SNP or ANF stimulation was also investigated. Shortly after guanylate cyclase activation, extracellular cGMP levels surpassed intracellular levels. However, comparison of the amounts of cGMP extruded to the extracellular medium with those degraded by PDEs leads to the conclusion that efflux is of relatively minor importance in regulating intracellular cGMP levels. In cells made tolerant to SNP, selective PDE5 inhibition synergistically increased intra- and extracellular cGMP amounts after SNP stimulation. These results indicate a previously undescribed greater relevance of PDE5 after tolerance development in aortic smooth muscle cells.

New indole and pyridazinoindole analogs--synthesis and study as inhibitors of phosphodiesterases and as inhibitors of blood platelet aggregation

This paper presents the synthesis of new indole, pyridazino[4,5-b]-indole, and pyridazino[4,5-a]indole analogs as well as a study of their "in vitro" activity as inhibitors of different phosphodiesterases isolated from dog cardiac tissue, dog aorta, and bovine platelets; the study of their activity as inhibitors of platelet aggregation in guinea pig whole blood, with ADP and arachidonic acid (AA) as pro-aggregants, is also included. The selected compounds 8-benzyloxy-3,4-dihydro-1-(3,4,5-trimethoxy)benzylideneaminopyridazin o[4,5- b]indole 14g, and 8-benzyloxy-4-[(3,4-dimethyl)pyrazolyl]pyridazino[4,5-b]indo le 20 present an interesting profile as potential inodilators, with a complementary, beneficial activity as inhibitors of the aggregation, activities which could possibly be related to the inhibition of the PDE's. Among the other compounds studied, 8-benzyloxy-3,4-dihydro-1-[4-(methyl)piperazino]acetamidopyrida zino[4,5- b]indol-4-one 16c and 8-benzyloxy-3,4-dihydro-1-[4-(2- methoxyphenyl)piperazino]acetamidopyridazino[4,5-b]indol-4-o ne 16f stood out as inhibitors of platelet aggregation, with a mechanism that could possibly be related to the AA cascade.