Effects Of Phosphodiesterase Inhibitors Research Articles

Effects of phosphodiesterase inhibitors on oesophageal neuromuscular functions.

The cyclic nucleotides adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) mediate the inhibitory effects of vasoactive intestinal polypeptide and nitric oxide on oesophageal smooth muscle. Phosphodiesterases (PDE) terminate their actions. We hypothesized that PDE inhibitors alter nerve-induced responses of oesophageal and lower oesophageal sphincter (LES) smooth muscle. An electrical field known to activate intrinsic oesophageal nerves was used to stimulate transverse muscle strips from the opossum oesophagus. This produced a contractile off-response from circular oesophageal muscle and a biphasic relaxation of the LES - an initial rapid relaxation (R1) and a slower sustained relaxation (R2). The effects on LES and oesophageal muscle of zaprinast (type V), zardaverine (type III/IV) and theophylline (non-specific) PDE inhibitors were explored. All three PDE inhibitors decreased LES tone and attenuated the off-response. Zaprinast and theophylline increased the latency of the off-response. Zaprinast prolonged R1, and slowed its recovery. It also increased the percentage relaxation of the second R2. Zardaverine increased the percentage relaxation of R2. Theophylline slowed the recovery of R2. PDEs play a role in maintaining LES tone and its recovery after LES relaxation. They may also modulate oesophageal motor activity.

Phosphodiesterase inhibitors suppress IL-12 production with microglia and T helper 1 development.

The effects of phosphodiesterase inhibitors (PDEIs) on interleukin (IL)-12 production by microglia, antigen-presenting cells in the central nervous system (CNS), were examined to learn how they affect T cell differentiation in the CNS. PDEIs significantly suppressed the microglial IL-12 production, as determined by reverse transcriptase-polymerase chain reaction for IL-12 p35 and p40 mRNA expression and by an ELISA specific for IL-12 functional heterodimer, p70. In addition, the PDEI ibudilast also suppressed interferon-gamma, but not IL-4 or IL-10, production by myelin oligodendrocyte glycoprotein (MOG)-specific T cells reactivated with MOG in the presence of microglia. Thus, PDEIs may also suppress differentiation of T helper 1 (Th1) in the CNS. PDEIs can be of use for future therapeutic strategy to treat Th1-mediated diseases, such as multiple sclerosis.

Effects of phosphodiesterase inhibitors on spontaneous nuclear maturation and cAMP concentrations in bovine oocytes

It was previously demonstrated that inhibition of cAMP degradation with phosphodiesterase type 3 (PDE3) inhibitors resulted in the maintenance of bovine cumulus–oocyte complexes (COC) and denuded oocytes (DO) in meiotic arrest, while a PDE4 inhibitor was without effect. In this study, different inhibitors of PDE3 and PDE4 were tested for their effects on bovine oocyte nuclear maturation. Bovine COC and DO were cultured in TCM-199+10% fetal bovine serum (FBS) with or without different concentrations of the PDE inhibitors. The PDE3 inhibitor trequinsin significantly increased the percentage of COC remaining at the germinal vesicle (GV) stage after 7 h of culture (19.3, 60.3, and 67.8% GV for control and trequinsin 10 and 50 nM, respectively) while Ro 20-1724 (a PDE4 inhibitor) was without effect. In DO, only trequinsin at 10 nM had a significant effect after 7 h of culture (51.3 and 86.1% GV for control and trequinsin 10 nM, respectively). Trequinsin reduced the percentage of COC reaching the mature phase after 22 h, but was without effect on DO. The protein kinase A (PKA) inhibitor H-89 reversed the inhibitory effect of trequinsin in COC and DO, indicating that inhibition of nuclear maturation by trequinsin involves activation of PKA. Trequinsin increased cAMP concentrations in COC but not in DO, suggesting that cumulus cells may also contain a PDE3 isoenzyme.

130 Effect of phosphodiesterase inhibitors on splenic lymphocytes proliferation

130 Effect of phosphodiesterase inhibitors on splenic lymphocytes proliferation

Effects of phosphodiesterase inhibitors on l-arginine pathways in rat alveolar macrophages

Effects of phosphodiesterase inhibitors on l-arginine-dependent pathways in rat alveolar macrophages, inducible nitric oxide (NO) synthase (iNOS) and arginase, were studied. Culture of rat alveolar macrophages in the presence of lipopolysaccharides (20 h) caused an increase of arginase activity (by 135%) and nitrite concentration (fourfold). The nonselective phosphodiesterase inhibitor IBMX (2-isobutyl-1-methylxanthine) enhanced arginase activity by 35% and nitrite accumulation by 130%. IBMX caused a clear increase in iNOS protein levels and a relatively smaller increase in iNOS mRNA. The effect of IBMX on nitrite accumulation was largely attenuated by the protein kinase A inhibitor K 5720. The phosphodiesterase 4 inhibitor rolipram enhanced nitrite accumulation more effectively than the phosphodiesterase 3 inhibitor siguadozan (about 50% and 20% of IBMX effect, respectively), whereas the phosphodiesterase 3/4 inhibitor benzafendrine was as effective as IBMX. In conclusion, in rat alveolar macrophages, phosphodiesterase 4 and, to a smaller extent, phosphodiesterase 3 play a role in the control of iNOS-mediated NO synthesis.

Rolipram, a specific type IV phosphodiesterase inhibitor, ameliorates indomethacin-induced gastric mucosal injury in rats

Inhibition of type IV phosphodiesterase activity is beneficial in various inflammation mediated by its function to suppress the production of inflammatory cytokines in inflammatory cells. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin are well known to develop gastric mucosal lesion. As pathogenesis of indomethacin induced gastric mucosal lesion, activation of neutrophils and inflammatory cytokine production play critical roles. However, the effect of phosphodiesterase inhibitors on development of gastric mucosal lesion has not been reported. In the present study, we examined the effect of specific type IV phosphodiesterase inhibitor (rolipram) on NSAIDs-induced gastric mucosal lesion. Also, we examined the effect of rolipram on tissue prostaglandin E2 (PGE2) production. Indomethacin-induced gastric mucosal injury was produced by the intragastric administration of indomethacin (30 mg/kg). Rolipram was injected to the rats intraperitoneally 30 min before the indomethacin administration. Ulcer index and tissue myeloperoxidase (MPO) activity of the gastric mucosa was evaluated. The gastric concentration of PGE2 was determined by RIA. Gastric mucosal lesion induced by indomethacin was significantly inhibited with treatment of rolipram. Mucosal MPO activity was also suppressed by administration of rolipram. Gastric mucosal PGE2 concentration was not affected by intraperitoneal injection of rolipram. Based on these data, the beneficial effects of rolipram on indomethacin-induced gastric mucosal injury may be attributed to its anti-inflammatory properties.

Happily at Work

Happily at Work

The Effect of Phosphodiesterase Inhibition on Gallbladder Motility in Vitro

Background. Coffee consumption decreases the risk of gallstone disease. The proposed motility effects of caffeine, a phosphodiesterase (PDE) inhibitor, are unknown. The aim of our study was to determine the effect of caffeine and specific PDE inhibitors on gallbladder motility in vitro.Methods. Gallbladder muscle strips from opossums were attached to force transducers. Baseline tone, electrical field stimulation (EFS)-induced nitric oxide-mediated off responses, and changes in the cholecystokinin (CCK)-8 dose–response relationship were measured. Caffeine; vinpocetine (VIN), type I PDE inhibitor; erythro-9-[2-hydroxy-3-nonyl]adenine HCl (EHNA), type II PDE inhibitor; zarderverine (ZARD), type III/IV PDE inhibitor; Ro 20-1724, type IV PDE inhibitor; and zaprinast (ZAP), type V PDE inhibitor were added to the tissue baths.Results. Caffeine and all specific PDE inhibitors decreased baseline tone. Caffeine, VIN, EHNA, ZARD, Ro 20-1724, and ZAP decreased the EFS-induced off response. Caffeine (10−5 M) and EHNA increased the CCK-8 dose–response contractions. This effect was not inhibited by atropine. Caffeine increased the tissue levels of cyclic 3′,5′-guanosine monophosphate but not cyclic 3′,5′-adenosine monophosphate. Caffeine decreases baseline tone and the off response via type I–V PDE pathways. Caffeine also increases CCK-induced gallbladder contractions via type II PDE pathways.Conclusion. These effects may be a mechanism that contributes to the decreased gallstone formation with caffeine consumption.

Airway relaxant and anti-inflammatory properties of a PDE4 inhibitor with low affinity for the high-affinity rolipram binding site.

Inhibitors of phosphodiesterase 4 (PDE4) possess bronchospasmolytic and anti-inflammatory properties, which make them very attractive drugs for the treatment of asthma and COPD. Unfortunately, many PDE4 inhibitors also produce central nervous and gastrointestinal side effects, which have limited their clinical application. PDE4 has two binding sites for the archetypal PDE4 inhibitor rolipram, and it has been suggested that binding to the high-affinity rolipram binding site (HARBS) is responsible for the side effects of PDE4 inhibitors. Recently, we have synthesised the PDE4 inhibitor CC3 which shows low affinity to the HARBS. In the present study we investigated the bronchospasmolytic and anti-inflammatory properties of this novel compound in comparison to rolipram and the PDE3 inhibitor motapizone. The airway-relaxant properties of the PDE inhibitors were analysed in rat precision-cut lung slices (PCLS) in which airways were contracted by methacholine or in passively sensitised PCLS exposed to ovalbumin. The anti-inflammatory properties were investigated by measuring the release of TNF from endotoxin-treated human monocytes.Up to concentrations of 10 microM none of the PDE inhibitors significantly affected bronchoconstriction elicited by 10 microM methacholine. However, if rolipram or CC3 were given in combination with motapizone, methacholine-induced bronchoconstriction was concentration-dependently attenuated. Allergen-induced bronchoconstriction in passively sensitised PCLS was attenuated by CC3 (IC(50) 2.7 microM), rolipram (0.23 microM) and motapizone (8 microM). Combination of equimolar concentrations of motapizone and CC3 (0.34 microM) or rolipram (0.005 microM) showed an additive effect. Endotoxin-induced TNF release from human monocytes was attenuated by all three PDE inhibitors, i.e. CC3 (IC(50) 4.6 microM), rolipram (0.18 microM) and motapizone (5.8 microM). Our findings suggest that PDE4 inhibitors with only low affinity for the HABRS have bronchospasmolytic and anti-inflammatory properties.

Phyllodulcin, a constituent of "Amacha", inhibits phosphodiesterase in bovine adrenocortical cells.

Phyllodulcin, a constituent of "Amacha", inhibits phosphodiesterase in bovine adrenocortical cells.

Cyclic AMP-dependent Cl secretion is regulated by multiple phosphodiesterase subtypes in human colonic epithelial cells.

The role of phosphodiesterase (PDE) isoforms in regulation of transepithelial Cl secretion was investigated using cultured monolayers of T84 cells grown on membrane filters. Identification of the major PDE isoforms present in these cells was determined using ion exchange chromatography in combination with biochemical assays for cGMP and cAMP hydrolysis. The most abundant PDE isoform in these cells was PDE4 accounting for 70-80% of the total cAMP hydrolysis within the cytosolic and membrane fractions from these cells. The PDE3 isoform was also identified in both cytosolic and membrane fractions accounting for 20% of the total cAMP hydrolysis in the cytosolic fraction and 15-30% of the total cAMP hydrolysis observed in the membrane fraction. A large portion of the total cGMP hydrolysis detected in cytosolic and membrane fractions of T84 cells was mediated by PDE5 (50-75%). Treatment of confluent monolayers of T84 cells with various PDE inhibitors produced significant increases in short-circuit current (Isc). The PDE3-selective inhibitors terqinsin, milrinone and cilostamide produced increases in Isc with EC50 values of 0.6 nM, 8.0 nM and 0.5 microM respectively. These values were in close agreement with the IC50 values for cAMP hydrolysis. The effects of the PDE1-(8-MM-IBMX) and PDE4-(RP-73401) selective inhibitors on Isc were significantly less potent than PDE3 inhibitors with EC50 values of >7 microM and >50 microM respectively. However, the effects of 8-MM-IBMX and terqinsin on Cl secretion were additive, suggesting that inhibition of PDE1 also increases Cl secretion. The effect of PDE inhibitors on Isc were significantly blocked by apical treatment with glibenclamide (an inhibitor of the CFTR Cl channel) and by basolateral bumetanide, an inhibitor of Na-K-2Cl cotransport activity. These results indicate that inhibition of PDE activity in T84 cells stimulates transepithelial Cl secretion and that PDE1 and PDE3 are involved in regulating the rate of secretion.

Effect of Phosphodiesterase Inhibitors on Nitric Oxide Production by Glial Cells.

Nitric oxide (NO) is considered to play a crucial role in the development of various pathological processes in the CNS, such as neuronal degeneration, inflammation and demyelination. In order to search for the agents which suppress NO production in the CNS, we examined the effects of one of the agents which elevate cyclic AMP production, phosphodiesterase inhibitors (PDEIs), on NO production by glial cells in vitro. All the types of PDEIs, from type I- to V-specific and non-specific, suppressed the production of NO by mouse microglia and astrocytes stimulated with lipopolysaccharide, in a dose-dependent manner. Suppression of inducible NO synthase by PDEIs was confirmed by the expression of mRNA by RT-PCR. Although it required 10 microM or higher concentration to effectively suppress NO production in vitro, certain combinations of three different PDEIs synergistically suppressed NO production by astrocytes at 1 microM which could be obtained in vivo at usual therapeutic doses. Similary, combinations of three PDEIs at 1 microM synergistically increased intracellular cAMP in astrocytes. The suppressive effects of PDEIs on NO production were abolished by addition of tumor necrosis factor alpha (TNFalpha). Thus, the main suppression mechanism of NO might be indirect through suppression of TNFalpha. Since some PDEIs are reported to pass through the blood-brain-barrier, the combination of three PDEIs may be worth trying in neurological diseases, such as multiple sclerosis, human immunodeficiency virus-related neurological diseases and other neurodegenerative disorders in which NO may play a crucial role.

Effect of inhibitors of cyclic nucleotide phosphodiesterases on electrical and contractile activity of smooth muscle cells.

Double sucrose gap experiments were carried out to study the effect of phosphodiesterase inhibitors and penetrating analogs of cyclic nucleotides on action potential and contraction of guinea pig ureteral smooth muscle cells. 3-Isobutyl-1-methylxanthine (10 microM) and dibutyryl-cAMP (20 microM) shortened the plateau of action potential and inhibited contraction of smooth muscle cells by increasing potassium permeability of their membrane. Vinpocetine (1 microM) and dibutyryl-cAMP (100 microM) strengthened contraction of smooth muscle cells and shortened action potentials by decreasing sodium permeability of their membrane.

Vasodilation and Mechanoenergetic Inefficiency Dominates the Effect of the "Ca 2+ -sensitizer" MCI-154 in Intact Pigs

Objective : Ca 2+ -sensitizing agents hold potential as ideal cardiac inotropes, but effects in intact animals are scarcely described. We evaluated a pyridazinone derivative, MCI-154, for hemodynamic, inotropic, mechanoenergetic and oxidative metabolic effects. Design : Intracavitary left ventricular (LV) pressure and conductance (volume) was assessed in open chest anesthetized pigs ( n = 6). Contractile performance, pressure-volume area (PVA) and myocardial oxygen consumption (MVO 2 ) were assessed. Myocardial substrate uptake and production of 14 CO 2 (from glucose) and 3 H 2 O (from fatty acids) were monitored. MCI-154 administration: "low range": 0.1, 0.2, 0.3, 0.5 µ g/kg/min and "high range": 0.75, 1.0, 2.0, 3.0 µ g/kg/min. Parameters were compared with baseline and a time reference group ( n = 7). Results : MCI-154 induced a progressive dose-dependent decrease in systemic vascular resistance, with a concomitant increase in heart rate and cardiac output. Contractility increased only in the high-dose range, and mechanoenergetic efficiency was significantly reduced by drug infusion in all doses. Conclusion : The pyridazinone derivative MCI-154 has minimal inotropic action, induces a significant "oxygen waste", and decreases vascular resistance in intact pigs. A potent phosphodiesterase inhibitory effect may explain this, which suggests further drug refinement.

Hypoxic Vasoconstriction of Rat Main Pulmonary Artery: Role of Endogenous Nitric Oxide, Potassium Channels, and Phosphodiesterase Inhibition

This study investigated the influence of NO, potassium (K+) channel blockade, and the phosphodiesterase inhibitors (PDEIs) theophylline (non-selective PDEI), siguazodan (PDE3I), rolipram (PDE4I), and zaprinast (PDE5I) on rat isolated main pulmonary artery hypoxic (95% N2 and 5% CO2) vasoconstriction. Hypoxic vasoconstriction increased by 27% (p < 0.01) in the presence of the NO synthase inhibitor L-NAME (10(-4) M), and by 15% (p < 0.05) in the presence of the K(ATP) channel blocker glibenclamide (10(-6) M), without potentiation by the combination of these two drugs. Hypoxic vasoconstriction decreased by 28% (p < 0.01) in presence of the Kv,-voltage-dependent channel blocker 4-aminopyridine (10(-3) M), whereas the other K+ channel blockers, charybdotoxin (BKCa, large-conductance Ca2+-sensitive K+ channels) and apamin (SKCa, small-conductance Ca2+-sensitive K+ channels) had no effect. The nonselective PDEI theophylline induced a concentration-dependent relaxation (pD2 = 4.05, Emax = 90% [expressed as a percentage of maximal relaxation induced by papaverine 10(-4) M]). Among the selective PDEIs, siguazodan was significantly (p < 0.01) more efficient than rolipram and zaprinast (Emax values were 84%, 67%, and 58%, respectively) and significantly (p < 0.05) more potent than zaprinast (pD2 values were 6.48, 6.34, and 6.16 for siguazodan, rolipram, and zaprinast). Glibenclamide and L-NAME significantly (p < 0.05) shifted the concentration-response curve (CRC) for zaprinast to the right, and L-NAME shifted the CRC significantly to the right for siguazodan. In the presence of L-NAME, glibenclamide had no effect on the CRC of zaprinast. We conclude that (a) NO exerts a permanent inhibitory effect against hypoxic vasoconstriction that might be mediated in part by an activation of K(ATP) channels; (b) a 4-aminopyridine-sensitive K+ channel is involved in vasoconstriction under hypoxic conditions; (c) PDEs 3 and 5 are the predominant PDE isoforms in rat pulmonary artery relaxation; and (d) NO and K(ATP), but neither BK(Ca), SK(Ca), nor Kv channels, are involved in the relaxant effect of PDEIs.

Effects of phosphodiesterase inhibitors on hypoxic pulmonary vasoconstriction. Influence of K + channels and nitric oxide

We studied the relaxant effects of the cyclic nucleotide phosphodiesterase inhibitors theophylline (non-selective), rolipram (type IV, 3′,5′-cyclic monophosphate (cAMP)-specific) and zaprinast (type V, 3′,5′-cyclic monophosphate (cGMP)-specific) on the hypoxic vasoconstriction in the isolated perfused rat lung and the involvement of K + channels and nitric oxide (NO) in these effects. K + channels were inhibited by glibenclamide, charybdotoxin, apamin and 4-aminopyridine and nitric oxide synthase by L-N G-nitroarginine methyl ester ( l-NAME). Hypoxic ventilation produced a significant pressure response. l-NAME and 4-aminopyridine increased this response. Rolipram, zaprinast and theophylline shared the ability to oppose the hypoxic pulmonary vasoconstriction. The order of potency was zaprinast>rolipram>theophylline. Glibenclamide partially inhibited the relaxant effects of rolipram and theophylline. Charybdotoxin inhibited the dilator response to rolipram. Apamin inhibited partially the vasodilation induced by rolipram and zaprinast. 4-Aminopyridine inhibited partially the relaxant effects of theophylline. l-NAME failed to block the effects of the three compounds. These data illustrate different pharmacological profiles according to the phosphodiesterase inhibitors and support the potential interest of selective inhibitors as relaxant agents in pulmonary vessels.

Effects of PDE4 inhibitors on lipopolysaccharide-induced priming of superoxide anion production from human mononuclear cells.

Phosphodiesterase 4 (PDE4) inhibitors have been described as potent anti-inflammatory compounds, involving an increase in intracellular levels of cyclic 3',5'-adenosine monophosphate (AMP). The aim of this study was to compare the effects of selective PDE4 inhibitors, rolipram and RP 73-401 with the cell permeable analogue of cyclic AMP, dibutyryl-cyclic AMP (db-cAMP) and the anti-inflammatory cytokine interleukin-10 (IL-10) on superoxide anion production from peripheral blood mononuclear cells preincubated with lipopolysaccharide (LPS). We report that, after incubation of the cells with LPS, a large increase in superoxide anion production was observed. Rolipram or RP 73-401 (10(-8) to 10(-5) M) induced significant reductions of fMLP-induced superoxide anion production in cells incubated with or without LPS. The db-cAMP (10(-5) to 10(-3) M) also elicited dose-dependent inhibitions of the fMLP-induced superoxide anion production. In contrast, IL-10 (1 or 10 ng/ml) did not elicit a reduction in fMLP-induced superoxide anion production in both conditions. These results suggest that the inhibitory activity of PDE4 inhibitors on fMLP-induced production of superoxide anion production is mediated by db-cAMP rather than IL-10.

The effects of phosphodiesterase inhibition on cyclic GMP and cyclic AMP accumulation in the hippocampus of the rat

The effects of selective and non-selective 3′,5′-cyclic nucleotide phosphodiesterase (PDE) inhibitors on cGMP and cAMP accumulation were studied in rat hippocampal slices incubated in vitro. The following PDE inhibitors were used: vinpocetine and calmidazolium (PDE1 selective), erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA, PDE2 selective), SK&F 95654 (PDE3 selective), rolipram (PDE4 selective), SK&F 96231 (PDE5 selective), the mixed type inhibitors zaprinast and dipyridamole, and the non-selective inhibitors 3-isobutyl-1-metylxanthine (IBMX) and caffeine. cGMP levels were increased in the presence of different concentrations of IBMX, EHNA, dipyridamole, vinpocetine and rolipram. cGMP immunocytochemistry showed that incubation with different inhibitors in the presence and/or absence of sodium nitroprusside resulted in pronounced differences in the extent and regional localization of the cGMP response and indicate that PDE activity in the hippocampus is high and diverse in nature. The results suggest an interaction between cGMP and cAMP signalling pathways in astrocytes of the rat hippocampus.

The effect of phosphodiesterase inhibition on sphincter of Oddi motility: Another mechanism to decrease gallstone formation

ELECTROACUPUNCTURE MAY RELAX THE CONTRACTION OF HUMAN SPHINCTER OF ODDI VIA THE CHOLECYSTOKININ RELEASE. Sung-Koo Lee, Myung-Hwan Kim, Hong-Ja Kim, Hyun-Ju Park, KyoSang Yoo, Dong-Wan Seo, Young-II Min, Ji-Hoon Kim, Byung-I1 Min, Asan Med Ctr, Univ of Ulsan Coil of Medicine, Seoul, South Korea; Asan Med Ctr, Seoul, South Korea; Myung-Ji Hosp Kwandong Univ Coil of Medicne, Seoul, South Korea; Univ of Kyung Hee Coil of Oriental Medicine, Seoul, South Korea.

Effects of phosphodiesterase inhibitors on epithelial function in an animal model of reactivated colitis

Effects of phosphodiesterase inhibitors on epithelial function in an animal model of reactivated colitis