Chlamydophila pneumoniae induces p44/p42 mitogen-activated protein kinase activation in human fibroblasts through Toll-like receptor 4

Chlamydophila pneumoniae, an obligately intracellular Gram-negative bacterium and a common causative agent of respiratory tract infections, has been implicated in the induction and progression of atherosclerosis and coronary artery disease. In this study, the signalling mechanism of C. pneumoniae in human fibroblasts, a prominent cell population in chronic inflammation and persistent infection, contributing to plaque formation, was investigated. C. pneumoniae elementary bodies were demonstrated to up-regulate the phosphorylation of p44/p42 mitogen-activated protein kinase (MAPK) in human fibroblasts. The effect was independent of the chlamydial lipopolysaccharide and was likely to be mediated by a heat-labile chlamydial protein. Furthermore, an anti-Toll-like receptor 4 (TLR4) antibody was shown to abolish C. pneumoniae-induced cell activation, whereas an anti-TLR2 antibody had no effect, indicating the role of TLR4 in p44/p42 MAPK activation. Ca2+/calmodulin-dependent protein kinase inhibitor KN-62 and phosphodiesterase 4 (PDE 4) inhibitor Rolipram enhanced C. pneumoniae-induced MAPK phosphorylation and attenuated C. pneumoniae infectivity in vitro. Together the results indicate that C. pneumoniae triggers rapid TLR4-mediated p44/p42 MAPK activation in human fibroblasts and chemical enhancement of MAPK phosphorylation modulates in vitro infection at the molecular level.

The novel phosphodiesterase 4 inhibitor, CI-1044, inhibits LPS-induced TNF-alpha production in whole blood from COPD patients

Chronic obstructive pulmonary disease (COPD) is a common, progressive respiratory disease that causes great morbidity and mortality despite treatment. Tumor necrosis factor alpha (TNF-alpha) plays a central role as a pro-inflammatory cytokine in COPD. TNF-alpha release is markedly inhibited by phosphodiesterase type 4 (PDE4) inhibitors that have proven efficacious in COPD clinical trials. The aim of this study was to compare the in vitro activities of the novel selective PDE4 inhibitors CI-1044 compared to well-known PDE4 inhibitors, rolipram and cilomilast, and to the glucocorticoid dexamethasone at reducing lipopolysaccharide (LPS)-induced TNF-alpha release in whole blood from COPD patients and healthy subjects. In the whole blood from COPD patients pre-incubation with PDE4 inhibitors or dexamethasone resulted in a dose-dependent inhibition of LPS-induced TNF-alpha release with IC(50) values of 1.3+/-0.7, 2.8+/-0.9 microM, higher to 10 microM and lesser than 0.03 microM for CI-1044, rolipram, cilomilast and dexamethasone, respectively. We observed a similar inhibition in the whole blood from healthy volunteers with, however, higher IC(50) values. These results indicate that CI-1044 inhibits in vitro LPS-induced TNF-alpha release in whole blood from COPD patients better than rolipram and cilomilast and suggested that it could be a useful anti-inflammatory therapy in COPD.

Protection against doxorubicin cardiomyopathy in rats: role of phosphodiesterase inhibitors type 4

Selective cardiotoxicity of doxorubicin (DOX) remains a significant and dose-limiting clinical problem. The mechanisms implicated are not yet fully defined but may involve the production of reactive oxygen species or expression of cytokines. Although patients with advanced congestive heart failure express elevated circulating levels of tumour necrosis factor-alpha (TNFalpha), little is known about the prognostic importance and regulation of TNF in the heart in cardiac disease states. Here we tested whether the expression of TNFalpha, along with oxidative stress, is associated with the development of DOX-induced cardiomyopathy (DOX-CM) and whether concurrent treatment with taurine (Taur), an antioxidant, or rolipram (Rolp), a TNFalpha inhibitor, offer a certain protection against DOX cardiotoxic properties. DOX (cumulative dose, 12 mg kg(-1)) was administered to rats in six equal (intraperitoneal) injections over a period of 6 weeks. Cardiomyopathy was evident by myocardial cell damage, which was characterized by a dense indented nucleus with peripheral heterochromatin condensation and distorted mitochondria, as well as significant increase in serum levels of creatine kinase and lactate dehydrogenase. DOX also induced an increment (P<0.001) in serum TNF and plasma nitric oxide levels. The extent of left ventricular (LV) superoxide anion, lipid peroxide measured as malondialdehyde, catalase and calcium content were markedly elevated, whereas superoxide dismutase, total and non-protein-bound thiol were dramatically decreased in DOX-treated rats. Exaggeration of DOX-CM was achieved by intraperitoneal injection of lipopolysaccharide (LPS) (1 mg kg(-1)) 18 h before sampling and evaluated by highly significant increase in heart enzymes (P<0.001), oxidative stress biomarkers and TNFalpha production. Pre- and co-treatment of DOX or DOX-LPS rats with Taur (1% daily supplemented in drinking water, 10 days before and concurrent with DOX) or Rolp (3 mg kg(-1), intraperitoneally, one dose before DOX administration then every 2 weeks throughout the experimental period) ameliorated the deleterious effect of both DOX and LPS on the aforementioned parameters. Meanwhile, it is noteworthy that Rolp exhibited a more preferable effect on serum TNFalpha level. Taur and rolipram also restored the myocardial apoptosis induced by DOX. In conclusion, a cumulative dose of DOX affected free radical and TNFalpha production in the heart of an experimental cardiomyopathy animal model. The current results suggest that down-regulation of these radicals and cytokines could be maintained by using the free radical scavenger Taur or, more favourably, the TNFalpha inhibitor Rolp.

Repetitive exposures to nicotine induce a hyper-responsiveness via the cAMP/PKA/CREB signal pathway in Drosophila

Nicotine, in addition to acute effects, has long-lasting effects on mammalian behaviors, such as those leading to addiction. Here we present genetic and pharmacological evidence in Drosophila suggesting that repetitive exposures to nicotine induce a hyper-responsiveness through synthesis of new protein(s) via CREB-mediated gene transcription. Single exposure to volatilized nicotine dose-dependently inhibited the startle-induced climbing response. Compared with this effect of nicotine in wild-type flies, it was stronger in dunce, which has defective phosphodiesterase, and in wild-type flies treated with a phosphodiesterase inhibitor, whereas it was weaker in DC0, which has defective protein kinase A (PKA), and in wild-type flies treated with a PKA blocker. Thus, the effect of nicotine is enhanced by a mechanism involving the cAMP/PKA cascade. However, in wild-type flies, an increase in head cAMP was not detected within 2 min after single exposure to nicotine, during which the nicotine effect on the behavior was maximal. In wild-type flies, after repetitive exposures to nicotine, the nicotine effect was significantly enhanced and the head cAMP was elevated. The responsiveness to nicotine at second exposure increased with a 4 h interval but not with a 2 h interval, suggesting that the observed hyper-responsiveness was not due to accumulation of residual nicotine. Both enhancement of the nicotine effect and elevation of cAMP during repetitive exposures to nicotine were blocked by a protein synthesis inhibitor. Induction of a dominant negative CREB transgene also blocked the enhancement, suggesting that CREB-mediated gene transcription is required for the hyper-responsiveness.

Effect of Specific Phosphodiesterase Isoenzyme Inhibitors During In Vitro Maturation of Bovine Oocytes on Meiotic and Developmental Capacity1

Compared with oocytes matured in vivo, in vitro-matured oocytes are compromised in their capacity to support early embryo development. Delaying spontaneous in vitro meiotic maturation using specific phosphodiesterase (PDE) isoenzyme inhibitors may permit more complete oocyte cytoplasmic maturation, possibly by prolonging cumulus cell (CC)-oocyte gap junctional communication during meiotic resumption. This study aimed to investigate the effect of the isoenzyme 3- (oocyte) and isoenzyme 4- (granulosa cell) specific PDE inhibitors on the kinetics of in vitro maturation and on subsequent oocyte developmental competence. Cumulus-oocyte complexes from antral bovine follicles were isolated and cultured in the presence of the specific PDE inhibitors milrinone (type 3) or rolipram (type 4) (100 microM). In the presence of FSH, both PDE inhibitors only slightly extended CC-oocyte gap junctional communication over the first 9 h, but they completely blocked meiotic resumption during this period (P < 0.001). The indefinite inhibitory effect of milrinone on meiotic resumption (30% at germinal vesicle stage after 48 h) was overridden by 24 h when treated with FSH, but not with hCG, suggesting a form of induced meiotic resumption. Oocytes treated with FSH with or without either PDE inhibitor were inseminated at either 24, 26, or 28 h. Treated with either the type 3 or type 4 PDE inhibitor significantly (P < 0.05) increased embryo development to the blastocyst stage by 33%-39% (to an average of 52% blastocysts) compared with control oocytes (38%) after insemination at 28 h, and significantly (P < 0.05) increased blastocyst cell numbers when inseminated at 24 h. These results suggest that delayed spontaneous meiotic maturation, coupled with extended gap junctional communication between the CCs and the oocyte has a positive effect on oocyte cytoplasmic maturation, thereby improving oocyte developmental potential.

Differential control of TH1 versus TH2 cell responses by the combination of low-dose steroids with beta2-adrenergic agonists

BACKGROUND

Combination treatment with steroids and long-acting beta2-agonists provides greater asthma control than simply increasing the dose of steroids.

OBJECTIVE

Although the effects of combination treatment with steroids and long-acting beta2-agonists have been attributed to their anti-inflammatory and bronchodilator effects, the ability of this combination to act synergistically on T cells has not been explored.

METHODS

PBMCs from control subjects and allergic asthmatic patients were stimulated with PHA in the presence of low doses of fluticasone propionate (FP) with or without salmeterol for 72 hours. The inhibition of T-cell proliferation, cytokine production, and glucocorticoid receptor translocation was measured.

RESULTS

Both groups showed a similar degree of inhibition of PHA-induced T-cell proliferation with FP (inhibitory concentration of 50% approximately 10(-9) mol/L) alone. Use of lower concentrations of FP (10(-12) to 10(-11) mol/L) in combination with salmeterol (10(-10) to 10(-7) mol/L) in control subjects provided similar inhibition of proliferation. This combination treatment was associated with significantly greater glucocorticoid receptor translocation into the cell nucleus compared with that seen with FP alone (10(-12) mol/L; P <.01). In contrast, FP-salmeterol failed to act synergistically in asthmatic patients. The 2-drug combination significantly inhibited production of TNF-alpha and IFN-gamma in both groups (P <.05) but failed to inhibit TH2 cytokine (IL-5 and IL-13) production by PBMCs from asthmatic patients. Because allergic inflammation is associated with increased levels of cellular phosphodiesterases that might degrade salmeterol-induced cyclic adenosine monophosphate, rolipram (10(-6) mol/L), a phosphodiesterase 4 inhibitor, was added to the FP-salmeterol combination. This triple combination of drugs enhanced inhibitory activity of low-dose steroids on T-cell proliferation in asthmatic patients and inhibited IL-13 production.

CONCLUSION

These data suggest that beta2-agonists in combination with low doses of steroids can suppress T-cell proliferation and TH1 cytokine production from healthy individuals, but suppression of T cells with a combination of FP and salmeterol in asthmatic patients requires inhibition of phosphodiesterases.

Rolipram reduces the inotropic tachyphylaxis of glucagon in rat ventricular myocardium

Glucagon increases cardiac contractility through G(s) protein-coupled glucagon receptors, but the inotropic responses fade. The fade could be due to receptor desensitisation or to the action of phosphodiesterases (PDE), or to both mechanisms. We investigated the effects of the PDE4 inhibitor rolipram (1 microM) on the inotropic and cAMP-responses to glucagon in paced right ventricular strips of the rat heart. Responses to the partial agonist dobutamine, mediated through beta(1)-adrenoceptors, were studied for comparison. Glucagon increased contractility (-logEC(50)M=7.3 for maximum responses with E(max)=32% of the response to 9 mM Ca(2+)), but the responses tended to fade (-logEC(50)M=7.1 for faded responses with E(max)=11.5%). Dobutamine (-logEC(50)M=5.8, E(max)=56%) produced positive inotropic effects that did not fade. Rolipram did not affect basal contractility and cAMP levels. Rolipram enhanced the contractile responses to glucagon and reduced fade (-logEC(50)M=7.5 and 7.3 with E(max)=74% and 45% for maximum and faded responses respectively). The response to glucagon (0.1 microM) completely faded in the absence of rolipram, but only partially faded and then remained stable in the presence of rolipram (1 microM). Rolipram enhanced contractile responses to dobutamine (-logEC(50)M=6.0, E(max)=75%). Dobutamine (3 microM), but not glucagon (0.1 microM), increased tissue levels of cAMP. Consistent with the inotropic data, rolipram caused glucagon to augment cAMP and enhanced the effects of dobutamine. Thus, PDE4 activity limits the responses mediated through both glucagon receptors and beta(1)-adrenoceptors. PDE4-catalysed hydrolysis of cAMP contributes to the inotropic tachyphylaxis of glucagon.

Discovery of BRL 50481 [3-(N,N-dimethylsulfonamido)-4-methyl-nitrobenzene], a Selective Inhibitor of Phosphodiesterase 7: In Vitro Studies in Human Monocytes, Lung Macrophages, and CD8+T-Lymphocytes

The biochemical and pharmacological characteristics in human proinflammatory cells of BRL 50481 [3-(N,N-dimethylsulfonamido)-4-methyl-nitrobenzene], a novel and selective inhibitor of phosphodiesterase (PDE) 7, are described. BRL 50481 inhibited the activity of hrPDE7A1 expressed in baculovirus-infected Spodoptera frugiperda 9 cells in a competitive manner (Ki value of 180 nM) and was 416 and 1884 times less potent against PDE3 and 38 and 238 times less potent against PDE4 at a substrate concentration of 1 microM and 50 nM cAMP, respectively. Western blotting identified HSPDE7A1 but not HSPDE7A2 in three human cell types that are implicated in the pathogenesis of chronic obstructive lung disease, namely, CD8+ T-lymphocytes, monocytes, and lung macrophages. BRL 50481 had no effect on the proliferation of CD8+ T-lymphocytes and only marginally (approximately 2-11%) reduced the generation of tumor necrosis factor (TNF)alpha from blood monocytes and lung macrophages. However, in the presence of BRL 50481 the inhibitory effect of rolipram was enhanced on all three cell types. The expression of HSPDE7A1 was increased in a time-dependent manner in monocytes that were "aged" in culture medium. Under this condition, BRL 50481 now inhibited TNFalpha generation in a concentration-dependent manner. In aged monocytes, rolipram, Org 9935 (a PDE3 inhibitor), and prostaglandin E2 inhibited TNFalpha generation in a concentration-dependent manner and interacted additively with BRL 50481. BRL 50481 is the first fully documented PDE7 inhibitor that has acceptable selectivity for in vitro studies. Furthermore, although BRL 50481 had only a modest inhibitory effect per se on the proinflammatory cells studied, it acted at least additively with other cAMP-elevating drugs, especially when HSPDE7A1 was up-regulated.

Cyclic nucleotide-dependent phosphodiesterases (PDEI) inhibition by muscarinic antagonists in bovine tracheal smooth muscle

In bovine tracheal smooth muscle (TSM) strips, muscarinic antagonists (atropine, 4-DAMP, AFDX-116 and methoctramine) were able to increase simultaneously and a similar fashion the intracellular levels of cyclic nucleotides, with a cAMP/cGMP ratio higher than 2.0. These original pharmacological responses were time-and dose-dependent, exhibiting maximal values at 15 min, with a pEC(50) of 7.4 +/- 0.2 for atropine and 4-DAMP. These effects on cAMP and cGMP levels were similar to the ones obtained with isobutyl-methylxantine (IBMX, 10 microM), a non-selective cyclic nucleotide phosphodiesterase (PDE) inhibitor, suggesting the involvement of PDEs in these muscarinic antagonist responses. Neither, rolipram (10 microM), a specific PDEIV inhibitor, nor zaprinast (10 microM), a PDEV inhibitor, exhibited this "atropine-like" responses. Instead, atropine enhanced the increments of cAMP levels induced by rolipram and cGMP levels by zaprinast. However, vinpocetine (20 microM), a non-calmodulin dependent PDEIC inhibitor was able to mimic these muscarinic antagonist responses in intact smooth muscle strips. In addition, in cell free systems, muscarinic antagonists inhibited the membrane-bound PDEIC activity whereas soluble (cytosol) PDEIC activity was not affected by these muscarinic drugs. These results indicate that muscarinic antagonists acting possibly as inverse agonists on M(2)/M(3)mAChRs anchored to sarcolemma membranes can initiate a new signal transducing cascade leading to the PDEIC inhibition, which produced a simultaneous rise in both cAMP and cGMP intracellular levels in tracheal smooth muscle.

Selective inhibition of purified human phosphodiesterase 4A expressed in yeast cell GL62 by ciclamilast, piclamilast, and rolipram

AIM

To improve the specific activity of human phosphodiesterase 4A (PDE4A) expressed in yeast cell GL62 and investigate the effects of selective phosphodiesterase 4 (PDE4) inhibitors (ciclamilast, piclamilast, and rolipram), selective phosphodiesterase 5 (PDE5) inhibitor zaprinast, and cyclooxygenase (COX) inhibitors (aspirin, indomethacin) on human PDE4A activity expressed in yeast cell GL62.

METHODS

Human PDE4A was expressed in yeast cell GL62 after CuSO4 induction and the specific activity of human PDE4A was improved by ammonium sulfate fractionation, DEAE Sephadex A-50 chromatography, and Sephadex G-100 chromatography. The activity of PDE4A was measured by high performance liquid chromatography (HPLC).

RESULTS

Induced PDE4A activity expressed in crude yeast cell GL62 supernatant and pellet was (340+/-21) nmol/g/min and (250+/-25) nmol/g/min respectively. The specific activity of recombinant PDE4A in supernatant was improved 6.4 fold. Ciclamilast, piclamilast, and rolipram could inhibit PDE4A activity. The IC50 values (95 % confidence limits) of ciclamilast, piclamilast, and rolipram were 1.27 (0.84-1.91), 66.4 (33.3-132.2), and 3.73 (2.51-5.53) micromol/L respectively. Zaprinast, aspirin, and indomethacin had no obvious inhibitory effect on PDE4A activity.

CONCLUSION

The specific activity of PDE4A expressed in yeast cell GL62 can be improved by ammonium sulfate fractionation, DEAE Sephadex A-50 chromatography, and Sephadex G-100 chromatography. Ciclamilast, piclamilast, and rolipram can inhibit PDE4A activity while zaprinast, aspirin, and indomethacin have no obvious inhibitory effect on PDE4A activity. Human PDE4A expressed in GL62 might be useful in the research and screening of new selective PDE4 inhibitors.

The effect of the indomethacin on phosphodiesterase inhibitors mediated responses in isolated trachea preparations

The aim of this study was to investigate the effects of indomethacin alone and with phosphodiesterase (PDE) inhibitory agents (rolipram, theophylline) on the isolated trachea preparations from control and ovalbumin sensitized guinea-pigs. Adult male guinea-pigs, weighing 300-350 g, were randomly allocated to 2 experimental groups each consisting of 12 animals. Guinea-pigs were sensitized by i.m. injections of 0.35 ml of a 5% (w/v) ovalbumin/saline solution into each thigh (0.7 ml total) on days 1 and 4. Tissues were first contracted with a submaximal concentration of histamine (10(-6) M). We tested the effects of indomethacin (10(-7)-10(-4) M) on the resting tension and precontracted with histamine on the isolated trachea preparations from control and ovalbumin sensitized guinea-pigs. We also tested the effects of the rolipram, theophylline and isoproterenol isolated trachea preparations precontracted with histamine in indomethacin incubated or non-incubated groups. We found that the relaxant effects of rolipram and theophylline increased, but not of isoproterenol, in the presence of indomethacin in isolated trachea preparations precontracted from control and ovalbumin-sensitized guinea-pigs. In the presence of indomethacin there was no difference in relaxant responses between both groups. Therefore, we concluded that the increased relaxant responses may be due to inhibitor effect of this agent on PDE isoenzymes.

Effects of rolipram, a phosphodiesterase 4 inhibitor, in combination with imipramine on depressive behavior, CRE-binding activity and BDNF level in learned helplessness rats

The brain cAMP regulating system and its downstream elements play a pivotal role in the therapeutic effects of antidepressants. We previously reported the increase in activities of phosphodiesterase 4, a major phosphodiesterase isozyme hydrolyzing cAMP, in the frontal cortex and hippocampus of learned helplessness rats, an animal model for depression. The present study was undertaken to examine the combination of effects of rolipram, a phosphodiesterase 4 inhibitor, with imipramine, a typical tricyclic antidepressant, on depressive behavior in learned helplessness rats. Concurrently, cAMP-response element (CRE)-binding activity and brain-derived neurotrophic factor (BDNF) levels related to the therapeutic effects of antidepressants were determined. Repeated administration of imipramine (1.25-10 mg/kg, i.p.) or rolipram (1.25 mg/kg, i.p.) reduced the number of escape failures in learned helplessness rats. Imipramine could not completely ameliorate the escape behavior to a level similar to that of non-stressed rats even at 10 mg/kg. However, repeated coadministration of rolipram with imipramine (1.25 and 2.5 mg/kg, respectively) almost completely eliminated the escape failures in learned helplessness rats. The reduction of CRE-binding activities and BDNF levels in the frontal cortex or hippocampus in learned helplessness rats were ameliorated by treatment with imipramine or rolipram alone. CRE-binding activities and/or BDNF levels of the frontal cortex and hippocampus were significantly increased by treatment with a combination of rolipram and imipramine compared to those in imipramine-treated rats. These results indicated that coadministration of phosphodiesterase type 4 inhibitors with antidepressants may be more effective for depression therapy and suggest that elevation of the cAMP signal transduction pathway is involved in the antidepressive effects.

Activation and induction of cyclic AMP phosphodiesterase (PDE4) in rat pulmonary microvascular endothelial cells

Regulation of the rolipram-sensitive cAMP-specific phosphodiesterase 4 (PDE4) gene family was studied in rat pulmonary microvascular endothelial cells (RPMVECs). Total PDE4 hydrolysis was increased within 10 min after addition of forskolin (10 microM), reached a maximum at 20-40 min, and then gradually declined in the cells. A similar activation of PDE4 activity was observed using a protein kinase A (PKA) activator, N(6)-monobutyryl cAMP. Both the forskolin and the N(6)-monobutyryl cAMP activated PDE4 activities were blocked by the PKA-specific inhibitor, H89. This forskolin-stimulated and PKA-mediated short-term activation of PDE4 activity was further confirmed by in vitro phosphorylation of 87kDa PDE4A6 and 83kDa PDE4B3 polypeptides using exogenous PKA Calpha. Increased immunoreactivity of phosphorylated PDE4A6 in situ was detected in Western blots by a PDE4A-phospho antibody specific to the putative PKA phosphorylation sites. Following long-term treatment of RPMVECs with rolipram and forskolin medium (RFM) for more than 60 days, PDE4 activity reached ten-fold higher values than control RPMVECS with twenty-fold increases detected in intracellular cAMP content. The RFM cells showed increased immunoreactivities of the constitutive 4A6 and 4B3 isoforms plus two novel splice variants at 101kDa (4B1) and 71kDa (4B2). Treatment with H89 did not inhibit the PDE4 elevation in RFM cells. In addition to the increased levels of PDE4 in RFM cells, immunofluorescence showed a translocation of PDE4A and 4B to a nuclear region, which was normally not observed in RPMVECs. The PDE4 activity in RFM cells decayed rapidly with an even faster decline of intracellular cAMP content when forskolin/rolipram were removed from the medium. These results suggest that both the activation (short-term) and induction (long-term) of PDE4A/4B isoforms in RPMVECs are closely modulated by the intracellular cAMP content via both post-translational and synthetic mechanisms.

Role of PDE4 in superoxide anion generation through p44/42MAPK regulation: a cAMP and a PKA-independent mechanism

We investigated the generation of reactive oxygen species (ROS) from bronchoalveolar lavage (BAL) cells of either control or LPS-exposed rats and the effects of PDE4 inhibitors on ROS production. The PDE4 inhibitors, rolipram and Ariflo (cilomilast, SB 207499) dose-dependently (0.1-10 microm) inhibited fMLP-induced superoxide anion (O(2)(*-)) production (IC(50)s: 0.03 and 0.55 microm, respectively) in BAL cells of Wistar rats collected 3 h after an LPS-aerosol (200 micrograms ml(-1), 1 h). These BAL contained 85-95% neutrophils (BAL cells enriched in neutrophils). In contrast, BAL cells collected at the end of the challenge contained only macrophages and in these conditions, rolipram and Ariflo (0.1-10 microm) could only inhibit 25 and 45% of fMLP-induced O(2)(*-) release, respectively. We also observed that the inhibition of p44/42(MAPK) by PD98059 (1-10 microm) increased O(2)(*-) release by BAL cells enriched in neutrophils, but not by macrophages, and prevented the inhibition of O(2)(*-) production induced by PDE4 inhibitors. Western blot analysis showed that PDE4 inhibitors strongly activated p44/42(MAPK) in BAL cells enriched in neutrophils but not in macrophages. And in these cells, PDE4 and p44/42(MAPK) were co-immunoprecipitated by a polyclonal anti-PDE4 antibody. The following cell permeable-cAMP analogues, dbcAMP (10 microm-1 mm), 8-CPT-cAMP (1 mm) and 8-pMeOPT-2'-O-Me-cAMP (0.5 mm), could not reduce fMLP-induced O(2)(*-) production and both PKA inhibitors, PKA inhibitor 14-22 amide myristoylated (50 nm-1 microm) and H-89 (100 nm-1 microm), did not affect the decrease of O(2)(*-) release induced by PDE4 inhibitors in BAL cells enriched in neutrophils. These data suggest that PDE4 inhibitors decreased fMLP-induced O(2)(*-) release in BAL cells enriched in neutrophils but not in macrophages, through p44/42(MAPK) activation by a cAMP- and a PKA-independent mechanism.

Impaired host defense to Klebsiella pneumoniae infection in mice treated with the PDE4 inhibitor rolipram

The increase in levels of cAMP in leukocytes by selective inhibitors of PDE4 may result in reduction of inflammation, and may be useful in the treatment of pulmonary inflammatory disorders in humans. Here, we have assessed whether oral treatment with the prototype PDE4 inhibitor, rolipram, interfered with the antibacterial host response following pulmonary infection of mice with Klebsiella pneumoniae. K. pneumoniae infection induced a marked increase in the recruitment of neutrophils to the lungs and the production of proinflammatory cytokines and chemokines, including tumor necrosis factor-alpha (TNF-alpha) and keratinocyte-derived chemokine (KC), in bronchoalveolar (BAL) fluid and lung tissue. There were also detectable amounts of interleukin-10 (IL-10) and significant lethality. Treatment with rolipram (3-30 mg kg-1) was associated with earlier lethality and significant inhibition of the TNF-alpha production. This was associated with enhanced production of IL-10 in lung tissue of rolipram-treated animals. Rolipram treatment did not affect KC expression and the recruitment of neutrophils in the lung tissue. Over 70% of neutrophils that migrated into the BAL fluid following K. pneumoniae infection ingested bacteria. Treatment with rolipram inhibited the percentage of neutrophils undergoing phagocytosis of K. pneumoniae in a dose-dependent manner. Maximal inhibition (62%) occurred at doses equal to or greater than 10 mg kg-1. Thus, treatment of mice with the PDE4 inhibitor rolipram is accompanied by earlier lethality, enhanced bacterial load and decreased capacity of the responding host to produce TNF-alpha and of neutrophils to phagocytose bacteria. It will be important to investigate whether the shown ability of PDE4 inhibitors to inhibit neutrophil phagocytosis and control experimental bacterial infection will translate into an inhibition of the ability of neutrophils to deal with infectious microorganisms in the clinical setting.

Chromatin acetylation, memory, and LTP are impaired in CBP+/- mice: a model for the cognitive deficit in Rubinstein-Taybi syndrome and its amelioration

We studied a mouse model of the haploinsufficiency form of Rubinstein-Taybi syndrome (RTS), an inheritable disorder caused by mutations in the gene encoding the CREB binding protein (CBP) and characterized by mental retardation and skeletal abnormalities. In these mice, chromatin acetylation, some forms of long-term memory, and the late phase of hippocampal long-term potentiation (L-LTP) were impaired. We ameliorated the L-LTP deficit in two ways: (1) by enhancing the expression of CREB-dependent genes, and (2) by inhibiting histone deacetyltransferase activity (HDAC), the molecular counterpart of the histone acetylation function of CBP. Inhibition of HDAC also reversed the memory defect observed in fear conditioning. These findings suggest that some of the cognitive and physiological deficits observed on RTS are not simply due to the reduction of CBP during development but may also result from the continued requirement throughout life for both the CREB co-activation and the histone acetylation function of CBP.

The synergistic effect of adenosine A2A receptors agonist, type IV phosphodiestease inhibitor and ATP-sensitive K channels activation on free radicals production and aggregation of human polymorphoneuclear leukocytes

The adenosine A2A receptor agonist CGS21680 (50, 100 and 200 microg/ml), the phosphodiserease type IV (PDE IV) inhibitor Rolipram (50, 100 and 200 microg/ml) and, ATP-sensitive K+ channels activator Cromakalim (30 and 40 microg/ml), when added separately, inhibit oxygen free radicals production from isolated human polymorphoneuclear leukocytes (PMNLs), stimulated with phorbol myristate acetate (PMA), in a dose dependent manner. When both CGS21680 and Rolipram were combined, in vitro, the inhibitory effect on PMNLs free radicals production was synergistic. On the other hand, when both the ATP-sensitive K+ channels opener (KATP) Cromakalim and the type IV PDE inhibitor Rolipram were combined, produced negative synergism (the inhibitory effect of both drugs disappeared). Furthermore, CGS21680, Rolipram, Cromakalim and Forskolin produced no significant inhibitory effect on PMNLs aggregation when added separately. But when various combinations of the above drugs were used, produced significant inhibition of aggregation. Only CGS21680 exhibited a scavenging effect on free radicals production. From the above results, combination of adenosine A2A agonists and type IV PDE inhibitors could serve as potentially novel anti-inflammatory drugs. Furthermore, ATP-sensitive K+ channels activators should be considered for further investigation as anti-inflammatory drug.

Effects of Rolipram, a Selective Inhibitor of Type 4 Phosphodiesterase, on Lipopolysaccharide-Induced Uveitis in Rats

PURPOSE

To investigate effects of rolipram, an inhibitor of type 4 phosphodiesterase, on lipopolysaccharide (LPS)-induced uveitis in Wistar rats.

METHODS

A total of 100 microg LPS was injected into the rat footpad. Rolipram (Wako Pure Chemical, Osaka, Japan) was injected intraperitoneally 30 minutes before administration of LPS. Levels of intracameral protein, cells, E-selectin, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and nitrite were determined. E-selectin, TNF-alpha, IL-6, and inducible nitric oxide synthase (iNOS) mRNAs and immunohistochemical reactivity of nuclear factor (NF)-kappa B and TNF-alpha were also examined in the iris-ciliary body.

RESULTS

After LPS injection, intracameral protein and cells increased from 18 to 30 hours later. Rolipram, however, inhibited elevation of protein and cells. After LPS injection, mRNA levels of E-selectin, TNF-alpha, and IL-6 in the iris-ciliary body increased 3 hours later, and iNOS mRNA increased 6 hours later. Elevation of mRNA levels for E-selectin, TNF-alpha, and IL-6 was inhibited by rolipram. After LPS injection, intracameral TNF-alpha and IL-6 levels increased 4 to 6 hours later, and nitrite levels increased 14 to 20 hours later. Elevation of TNF-alpha and IL-6 levels was decreased by rolipram. Rolipram did not affect iNOS mRNA and nitrite levels. Immunoreactivity of NF-kappa B was strong 1 hour after LPS injection, and was decreased by rolipram. Immunoreactivity of TNF-alpha was strong 4 hours after LPS injection and was decreased by rolipram.

CONCLUSIONS

NF-kappa B translocation and expression of E-selectin, TNF-alpha, and IL-6 are involved in the pathogenesis of LPS-induced uveitis and are inhibited by rolipram. The inhibitory effect of rolipram in uveitis may be independent of iNOS synthesis.

Inhibition of the phosphodiesterase 4 (PDE4) enzyme reverses memory deficits produced by infusion of the MEK inhibitor U0126 into the CA1 subregion of the rat hippocampus

Cyclic AMP-specific phosphodiesterase 4 (PDE4), which is an integral component of NMDA receptor-mediated cAMP signaling, is involved in the mediation of memory processes. Given that NMDA receptors also mediate MEK/mitogen-activated protein kinase (MAPK, ERK) signaling, which is involved in synaptic plasticity, and that some PDE4 subtypes are phosphorylated and regulated by ERK, it was of interest to determine if PDE4 is involved in MEK/ERK signaling-mediated memory. It was found that rolipram, a PDE4-selective inhibitor, reversed the amnesic effect in the radial-arm maze test of the MEK inhibitor U0126 administered into the CA1 subregion of the rat hippocampus. Consistent with this, rolipram, either by peripheral administration or direct intra-CA1 infusion, enhanced the retrieval of long-term memory impaired by intra-CA1 infusion of U0126 using the step-through inhibitory avoidance test. The same dose of rolipram did not affect U0126-induced reduction of phospho-ERK1/2 levels in the CA1 subregion. However, in primary cultures of rat cerebral cortical neurons, pretreatment with U0126 increased PDE4 activity; this was correlated with the U0126-induced reduction of phospho-ERK1/2 levels. These results suggest that MEK/ERK signaling plays an inhibitory role in regulating PDE4 activity in the brain; this may be a novel mechanism by which MEK/ERK signaling mediates memory. PDE4 is likely to be an important link between the cAMP/PKA and MEK/ERK signaling pathways in the mediation of memory.

Phosphoinositide 3-kinase is involved in Xenopus and Labrus melanophore aggregation

Melanophores are pigmented cells capable of quick colour changes through coordinated transport of their intracellular pigment granules. We demonstrate the involvement of phosphoinositide 3-kinase (PI3-K) in Xenopus and Labrus aggregation by the use of the PI3-K inhibitor, LY-294002. In Xenopus, wortmannin-insensitive PI3-K was found to be essential for the aggregation, mitogen-activated protein kinase (MAPK) activation and tyrosine phosphorylation of a 280-kDa protein, and for the maintenance of low cyclic adenosine 3':5'-monophosphate (cAMP) during the aggregated state. Pre-aggregated cells disperse completely to LY-294002 at 50-100 muM, involving a transient elevation in cAMP due to adenylate cyclase (AC) stimulation or to inhibition of cyclic nucleotide phosphodiesterase (PDE). The inactive analogue LY-303511 did not induce dispersion at the same concentrations. PDE4 and/or PDE2 was found to be involved in melanosome aggregation. The similar kinetics of LY-294002 and various PDE inhibitors indicates that the elevation of cAMP might be due to inhibition of PDE. In Labrus melanophores, LY-294002 had a less dramatic effect, probably due to less dependence on PDE in regulation of cAMP levels. In Xenopus aggregation, we suggest that melatonin stimulation of the Mel1c receptor via G(beta gamma) activates PI3-K that, directly or indirectly via MAPK, activates PDE.

Inhibitory effects of group II mGluR-related drugs on memory performance in mice

The cAMP/protein kinase A signaling pathway is negatively modulated by group II metabotropic glutamate receptors (mGluRs), and the cross-talk that occurs between these receptors may modulate learning and memory. To examine the relationship among cAMP/PKA-signaling pathway activity, group II mGluRs, and learning and memory, mice were trained to perform a step-through-type passive avoidance task, and 10 min before each avoidance trial the following drugs were injected intracisternally (i.cist.): vehicle (0.05% dimethylsulfoxide); a specific group II mGluR agonist, DCG-IV (1-50 ng/mouse); a specific group II mGluR antagonist, LY341495 (10-300 ng); a selective inhibitor of cAMP-specific phosphodiesterase, rolipram (100-1000 ng); an activator of adenylyl cyclase, forskolin (25-250 ng); a specific inhibitor of PKA, H-89 (150 or 300 ng) or; an activator of protein kinase C, phorbol 12-myristate 13-acetate (PMA 200 ng). DCG-IV (25 and 50 ng) or LY341495 (150 and 300 ng) reduced the latency in the avoidance task. The reduction of latency by DCG-IV was not observed in mice coinjected with DCG-IV (50 ng) together with rolipram (500 ng) or forskolin (25 ng). Conversely, coinjection of LY341495 with 100 or 1000 ng rolipram, or with 25 or 250 ng forskolin tended to potentiate the LY341495-induced shortening of latency. In addition, the reduction of latency by DCG-IV (50 ng) was not observed in mice coinjected with DCG-IV and PMA together. However, the reduction of latency by LY341495 (300 ng) was potentiated when the drug was coadministered with PMA. These results suggest that changes in the cAMP/PKA-signaling pathway, mediated by group II mGluRs, influence memory in the passive avoidance task, and that both the excessive activation and deactivation of this pathway may induce the impairment of learning and memory.

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.

The Type IV phosphodiesterase inhibitor rolipram interferes with drug-induced conditioned place preference but not immediate early gene induction in mice

Behavioural effects of psychostimulant and opiate drugs are mediated in part by cAMP pathways operating in the nucleus accumbens. Degradation of cAMP occurs through the action of phosphodiesterases, such as the Type IV phosphodiesterases (PDE4s) that are found throughout the brain. To examine the potential role of PDE4 in reward-mediated behaviour, we measured the effects of rolipram, a PDE4 selective inhibitor, on cocaine (18 mg/kg i.p.) and morphine (5 mg/kg s.c.) conditioned place preference in Swiss Webster mice. Rolipram (0, 0.2 or 1.0 mg/kg i.p.) given 30 min prior to drug administration dose-dependently reduced conditioning due to both cocaine and morphine. However, rolipram did not affect place preference induced by food, nor did it prevent the expression of a previously established place preference conditioned by cocaine or morphine. In a second experiment, rolipram administered 30 min prior to a single cocaine injection (50 mg/kg i.p.), did not alter cocaine-induced c-Fos expression in the caudate putamen or nucleus accumbens core. However, rolipram, but not cocaine, induced c-Fos in the nucleus accumbens shell. These results indicate that elevation of cAMP in neurons that express PDE4s may attenuate the rewarding properties of cocaine and morphine, but does not alter the cocaine signalling cascade that induces c-Fos expression. Thus, PDE4-mediated regulation of cAMP levels could underlie the establishment of reward valence to abused drugs.

Pharmacological inhibition of Mannheimia haemolytica lipopolysaccharide and leukotoxin-induced cytokine expression in bovine alveolar macrophages

The inflammatory cytokines tumor necrosis factor-alpha (TNFalpha), interleukin-1 beta (IL-1beta), and interleukin-8 (IL-8) are believed to contribute to the pathogenesis of lung injury in bovine pneumonic mannheimiosis (BPM) caused by Mannheimia (Pasteurella) haemolytica. Inflammatory cytokines may, therefore, represent therapeutic targets to be modulated for the purpose of treating or preventing this important disease of cattle. The purpose of this study was to evaluate the ability of six pharmacological agents to suppress the expression of TNFalpha, IL-1beta, and IL-8 genes and proteins in bovine alveolar macrophages (AM) exposed to M. haemolytica lipopolysaccharide (LPS) and leukotoxin (LktA) in vitro. The compounds tested included dexamethasone (DEX), tetrahydropapaveroline (THP), pentoxifylline (PTX), rolipram (ROL), SB203580 (SB), and thalidomide (THL). Cytokine expression was induced by the addition of purified M. haemolytica LPS and LktA to AM cell cultures following pretreatment with inhibitor compounds. Secretion of TNFalpha, IL-1beta, and IL-8 proteins into the cell culture supernatant was measured using enzyme-linked immunosorbent assays, and steady-state accumulation of cytokine-specific mRNA was measured by northern blot analysis. Dose-dependent inhibition of cytokine secretion occurred in response to pretreatment of AM with DEX (TNFalpha, IL-1beta, IL-8), THP (TNFalpha, IL-1beta, IL-8), PTX (TNFalpha, IL-1beta, IL-8), ROL (TNFalpha, IL-1beta), and SB (TNFalpha, IL-8). Significant dose-dependent inhibition of cytokine mRNA expression occurred in response to pretreatment with DEX (TNFalpha, IL-1beta, IL-8), THP (TNFalpha, IL-1beta, IL-8), and PTX (TNFalpha). DEX was the most effective inhibitor by far; pretreatment with this compound yielded greater than 95% inhibition of cytokine gene and protein expression over a broad range of concentrations. These findings demonstrate that DEX, THP, PTX, ROL, and SB are capable of suppressing inflammatory cytokine secretion by bovine AM in vitro. If pulmonary cytokine secretion may be similarly inhibited in vivo, anti-cytokine therapy may represent a novel strategy for the management of BPM.

Paradoxical cAMP-induced lung endothelial hyperpermeability revealed by Pseudomonas aeruginosa ExoY

Mammalian transmembrane adenylyl cyclases synthesize a restricted plasmalemmal cAMP pool that is intensely endothelial barrier protective. Bacteria have devised mechanisms of transferring eukaryotic factor-dependent adenylyl cyclases into mammalian cells. Pseudomonas aeruginosa ExoY is one such enzyme that catalyzes cytosolic cAMP synthesis, with unknown function. Pseudomonas aeruginosa genetically modified to introduce only the ExoY toxin elevated cAMP 800-fold in pulmonary microvascular endothelial cells over 4 hours, whereas a catalytically deficient (ExoY(K81M)) strain did not increase cAMP. ExoY-derived cAMP was localized to a cytosolic microdomain not regulated by phosphodiesterase activity. In contrast to the barrier-enhancing actions of plasmalemmal cAMP, the ExoY cytosolic cAMP pool induced endothelial gap formation and increased the filtration coefficient in the isolated perfused lung. These findings collectively illustrate a previously unrecognized mechanism of hyperpermeability induced by rises in cytosolic cAMP.