cyclic-gmp and ibudilast

Ibudilast, a mixed phosphodiesterase (PDE) 3/4 inhibitor, is a cerebral vasodilator widely used in Japan for treating post-stroke dizziness. However, little studies have been conducted on the vasorelaxant effects of PDE inhibitors in the vertebrobasilar artery associated with dizziness onset. The in vitro vasorelaxant properties of ibudilast were, therefore, investigated by comparing with known selective PDE inhibitors, using vertebrobasilar arteries. Vasorelaxant activities of PDE3, PDE4, PDE5 inhibitors, and ibudilast were assessed in 5-hydroxytryptamine precontracted ring preparations from rabbit intracranial and extracranial vertebrobasilar arteries. Ibudilast more selectively relaxed the intracranial than extracranial artery. Similarly, selective PDE3 and PDE4 inhibitors showed higher selectivity for intracranial arteries. Furthermore, like selective PDE4 inhibitor, the vasorelaxation by ibudilast accompanied by increase in cAMP levels was inhibited by the adenylyl cyclase inhibitor SQ22536 in intracranial arteries. Next, it was examined whether nitric oxide (NO)/cGMP signaling is involved in this vasorelaxation in intracranial arteries. The suppression of NO/cGMP signaling by an NO synthase inhibitor or a guanylyl cyclase inhibitor potentiated the vasorelaxion by a PDE3 inhibitor and reduced that by a PDE4 inhibitor, while either suppression of the signaling had little influence on that by ibudilast. These results suggest that ibudilast has the high vasoselectivity for intracranial artery based on a mixed PDE3 and PDE4-inhibition, and effectively relaxes intracranial arteries independently of NO/cGMP signaling because of its vasorelaxation compensated by either PDE3- or PDE4-inhibition depending on the state of NO/cGMP signaling change.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Animals; Basilar Artery; Cyclic GMP; Guanylate Cyclase; In Vitro Techniques; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Phosphodiesterase 3 Inhibitors; Phosphodiesterase 4 Inhibitors; Pyridines; Rabbits; Signal Transduction; Vasodilator Agents; Vertebral Artery

The mechanism by which ibudilast induces vasodilation was examined in isolated endothelium-denuded rat aorta. Ibudilast inhibited the contractions induced by phenylephrine (PE) and high K(+) with decrease of [Ca(2+)](i) level in a concentration-dependent manner, to the same degree. 3-Isobutyl-1-methylxanthine (IBMX) inhibited PE-induced contraction and [Ca(2+)](i) level in a concentration-dependent manner, but it inhibited high K(+)-induced contraction without decrease of [Ca(2+)](i) level. In comparison with IBMX, the increases of cAMP and cGMP contents in ibudilast were much smaller than that of muscle tension. Ibudilast did not inhibit 12-deoxyphorbol 13-isobutyrate (DPB)-induced contraction in the presence of verapamil. Treatment with 30 microM ibudilast inhibited the extracellularly added Ca(2+)-induced muscle tension and increases in [Ca(2+)](i) level during high K(+) depolarization. These results suggested that ibudilast inhibited PE- and high K(+)-induced muscle contractions mainly by the inhibition of [Ca(2+)](i) level in endothelium-denuded rat aorta.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Aorta, Thoracic; Calcium; Cyclic AMP; Cyclic GMP; Cytosol; Dose-Response Relationship, Drug; Male; Muscle Contraction; Muscle Tonus; Muscle, Smooth, Vascular; Phenylephrine; Phosphodiesterase Inhibitors; Potassium; Pyridines; Rats; Rats, Wistar; Vasodilator Agents; Verapamil

Ibudilast is widely used in Japan to treat ischemic stroke and bronchial asthma. Its mode of action is through the inhibition of cyclic nucleotide phosphodiesterases (PDEs). Growing evidence suggests this compound has utility in a range of neurological conditions linked to its ability to elevate cellular cyclic nucleotide concentrations, however limited data exists on Ibudilast's action on individual PDE families. We therefore used an extensive panel of human PDE enzymes to define the PDE inhibitory profile of this compound. Ibudilast preferentially inhibits PDE3A, PDE4, PDE10 and PDE11 with lesser inhibition of a number of other families. The significance of these findings is discussed in relation to Ibudilast's observed effects on certain disease states.

Topics: Animals; Cell Line; Cyclic AMP; Cyclic GMP; Humans; Hydrolysis; Isoenzymes; Kinetics; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Pyridines; Spodoptera; Substrate Specificity

The effects of ibudilast, an inhibitor of phosphodiesterases (PDEs), on tension, levels of guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP) were investigated in bovine tracheal smooth muscle. We especially examined the combined effect of ibudilast with the cGMP-elevating agents on these parameters. Ibudilast was equipotent to attenuate the precontractions induced by both 0.3 microM methacholine and 40 mM K(+). By contrast, the relaxant effects of sodium nitroprusside and salbutamol on 40 mM K(+)-contracted preparations were smaller than those on 0.3 microM methacholine-contracted ones. Neither N(omega)-nitro-L-arginine (100 microM), an inhibitor of nitric oxide synthase, nor ODQ (1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one; 5 microM), an inhibitor of soluble guanylyl cyclase, affected the ibudilast-induced relaxation. The relaxations induced by ibudilast and diltiazem on 40 mM K(+)-contracted preparations were significantly attenuated when extracellular CaCl(2) was increased from 2.54 mM to 10 mM. Ibudilast (10 microM), which caused only minor effect by itself, significantly ( P<0.05) shifted the concentration-response curves for the relaxant responses to sodium nitroprusside (SNP), atrial natriuretic peptide (ANP) and salbutamol to the left. On the other hand, ibudilast did not change the relaxant responses to diltiazem. Unlike ibudilast, diltiazem (3 microM) failed to affect the SNP- and salbutamol-induced relaxations. Ibudilast significantly ( P<0.05) increased basal levels of cGMP and cAMP. Furthermore, ibudilast enhanced SNP (0.3 microM)- and ANP (0.3 microM)-induced cGMP accumulation and salbutamol (10 nM)-induced cAMP accumulation. Zaprinast (10 microM), a type 5 PDE inhibitor, enhanced both relaxation and cGMP accumulation induced by SNP and ANP without changing salbutamol-induced responses. These findings suggest that blockade of voltage-gated Ca(2+) channels is involved in the relaxing action of ibudilast in bovine tracheal smooth muscle. However, ibudilast potentiates relaxation responses to ANP and SNP by inhibition of PDE 5, not by blockade of Ca(2+) channels. The enhancement of cGMP-mediated response may contribute to the therapeutic effects of ibudilast.

Topics: Albuterol; Analysis of Variance; Animals; Atrial Natriuretic Factor; Bronchodilator Agents; Cattle; Cyclic GMP; Dose-Response Relationship, Drug; In Vitro Techniques; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Nitric Oxide Donors; Nitroprusside; Phosphodiesterase Inhibitors; Purinones; Pyridines; Trachea

We examined the effect of 3-isobutyryl-2-isopropylpyrazolo[1,5-a]pyridine (ibudilast), which has been clinically used for bronchial asthma and cerebrovascular disorders, on cell viability induced in a model of reperfusion injury. Ibudilast at 10 - 100 microM significantly attenuated the H(2)O(2)-induced decrease in cell viability. Ibudilast inhibited the H(2)O(2)-induced cytochrome c release, caspase-3 activation, DNA ladder formation and nuclear condensation, suggesting its anti-apoptotic effect. Phosphodiesterase inhibitors such as theophylline, pentoxyfylline, vinpocetine, dipyridamole and zaprinast, which increased the guanosine-3',5'-cyclic monophosphate (cyclic GMP) level, and dibutyryl cyclic GMP attenuated the H(2)O(2)-induced injury in astrocytes. Ibudilast increased the cyclic GMP level in astrocytes. The cyclic GMP-dependent protein kinase inhibitor KT5823 blocked the protective effects of ibudilast and dipyridamole on the H(2)O(2)-induced decrease in cell viability, while the cyclic AMP-dependent protein kinase inhibitor KT5720, the cyclic AMP antagonist Rp-cyclic AMPS, the mitogen-activated protein/extracellular signal-regulated kinase inhibitor PD98059 and the leukotriene D(4) antagonist LY 171883 did not. KT5823 also blocked the effect of ibudilast on the H(2)O(2)-induced cytochrome c release and caspase-3-like protease activation. These findings suggest that ibudilast prevents the H(2)O(2)-induced delayed apoptosis of astrocytes via a cyclic GMP, but not cyclic AMP, signalling pathway.

Topics: Alkaloids; Animals; Animals, Newborn; Apoptosis; Astrocytes; Carbazoles; Cell Survival; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cytochrome c Group; Dipyridamole; DNA; Dose-Response Relationship, Drug; Enzyme Inhibitors; Hydrogen Peroxide; Indoles; Mitochondria; Pentoxifylline; Peptide Hydrolases; Phosphodiesterase Inhibitors; Purinones; Pyridines; Rats; Rats, Wistar; Reperfusion Injury; Signal Transduction; Theophylline; Vinca Alkaloids

3-Isobutyryl-2-isopropylpyrazolo[1,5-a]pyridine (ibudilast) has been widely used in Japanese clinics for its antiasthmatic and antithrombotic effects. We investigated the mechanisms involved in the antiplatelet effects of the agent, specifically focusing on platelet-endothelium interaction. Ibudilast inhibits both phosphodiesterase (PDE) 3 and 5, the two major PDE isoforms of human platelets, with an IC50 of 31 and 2.2 microM, respectively. Cyclic guanosine monophosphate (GMP) accumulation in washed human platelets exposed to ibudilast alone increased significantly only at high concentrations of the agent (100 microM), whereas > or = 1 microM ibudilast enhanced cyclic GMP levels in the platelets cocultured with bovine aorta endothelial cells (ECs). In contrast, ibudilast enhanced cyclic AMP accumulation only at 100 microM, either with or without ECs. The synergistic effect of ibudilast and EC on cyclic nucleotide accumulation also was demonstrated by the inhibitory capability of the drug and the cells on platelet aggregation. The synergism between ibudilast and aspirin-pretreated ECs was more pronounced than that between ibudilast and N(omega)-nitro-L-arginine (L-NNA)-pretreated ECs. Ibudilast affected neither ATP diphosphohydrolase activity nor NO release from EC up to a concentration of 10 microM. We conclude that ibudilast exhibits antiplatelet properties mainly by inhibiting PDE5 to potentiate antiplatelet function of endothelium-derived NO.

Topics: Animals; Blood Platelets; Cattle; Cells, Cultured; Cyclic AMP; Cyclic GMP; Endothelium, Vascular; Humans; Phosphoric Diester Hydrolases; Platelet Aggregation; Platelet Aggregation Inhibitors; Pyridines

Previously we have demonstrated that ibudilast, which is used clinically for treating patients with asthma and cerebrovascular diseases, prevents excitotoxicity of oligodendroglial lineage mediated by Ca2+ influx via non-N-methyl-D-aspartate (NMDA) glutamate receptor (GluR) channels. We here present a finding that ibudilast prevents oxygen-glucose deprivation (OGD)-induced oligodendroglial injury. The oligodendrocyte-like cells (OLC), differentiated from the CG-4 cell line established from rat oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, were exposed to hypoxia in the absence of glucose for 12 h and subsequent reoxygenation for 2 h. Cell damage was evaluated by measuring activity of lactate dehydrogenase (LDH) released into the culture medium. OGD for 12 h induced 30 to 50% LDH release into the medium. OLC damage induced by deprivation of oxygen and glucose was prevented by ibudilast at concentrations of > or = 50 microM. The protection given by ibudilast against OGD-induced injury was enhanced by prostacyclin (PGI2). OGD-induced OLC injury was prevented by 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX), an inhibitor of non-NMDA GluR or deprivation of Ca2+ from culture medium. While ibudilast increased intracellular cAMP at concentrations of > or = 10 microM, at least 100 microM concentrations were needed to increase intracellular cGMP. Therefore, we concluded that ibudilast prevented OGD-induced oligodendroglial injury possibly by increasing intracellular cAMP which modulates Ca2+ influx via non-NMDA GluR channels.

Topics: Animals; Bronchodilator Agents; Cell Hypoxia; Cells, Cultured; Cyclic AMP; Cyclic GMP; Epoprostenol; Glucose; Oligodendroglia; Pyridines; Rats; Vasodilator Agents