Effects Of Phosphodiesterase Inhibitors Research Articles

Pancreatic β‐cell dysfunction, expression of iNOS and the effect of phosphodiesterase inhibitors in human pancreatic islets of type 2 diabetes

Induction of inducible nitric oxide synthase (iNOS) in pancreatic islets leads to exaggerated nitric oxide (NO) production associated with dysfunctional β-cells. We examined insulin secretion, iNOS expression and its relationship to the cAMP system in islets from human type 2 diabetes. Insulin, glucagon and cAMP were analysed by RIA; iNOS or phosphodiesterase (PDE) expression by quantitative PCR (qPCR), Western blot and confocal microscopy; cell viability by MTS. Diabetic islets displayed impaired insulin and glucagon responses to glucose, disturbed cAMP generation and high inducible nitric oxide synthase (iNOS) mRNA and protein expression. Confocal microscopy showed iNOS protein expression in diabetic islets being confined to insulin, glucagon and somatostatin cells. Culture of diabetic islets at 5.5 mmol/l glucose with dibutyryl-cAMP (Bt(2) -cAMP) for 24 h was accompanied by marked suppression of iNOS mRNA, reduced nitrite production and increased insulin secretion. Diabetic islets displayed marked increase in PDE3A and PDE3B mRNA expression. Short-time incubation of diabetic islets showed, among the PDE inhibitors tested, cilostazol being most favourable to increase insulin secretion. Diabetic islets were most susceptible to long-term (72 h) culture at high glucose (20 mmol/l) reacting with increased apoptosis. Bt(2) -cAMP and the PDE inhibitors cilostazol, milrinone and IBMX efficiently increased cell viability at high glucose during culture. Defective glucose-stimulated insulin release upon induction of iNOS was restored by iNOS inhibitor aminoguanidine. Our results suggest that in islets from type 2 diabetes, stimulatory effects in certain cAMP-compartments induced by PDE inhibitors might play a central role in the suppression of iNOS, resulting in increased β-cell viability and improved secretory response to glucose.

The effect of phosphodiesterase inhibitors on the extinction of cocaine-induced conditioned place preference in mice

Several phosphodiesterase inhibitors (PDEis) improve cognition, suggesting that an increase in brain cAMP and cGMP facilitates learning and memory. Since extinction of drug-seeking behavior requires associative learning, consolidation and formation of new memory, the present study investigated the efficacy of three different PDEis in the extinction of cocaine-induced conditioned place preference (CPP) in B6129S mice. Mice were conditioned by escalating doses of cocaine which was resistant to extinction by free exploration. Immediately following each extinction session mice received (a) saline/vehicle, (b) rolipram (PDE4 inhibitor), (c) BAY-73-6691 (PDE9 inhibitor) or (d) papaverine (PDE10A inhibitor). Mice that received saline/vehicle during extinction training showed no reduction in CPP for >10 days. BAY-73-6691 (a) dose-dependently increased cGMP in hippocampus and amygdala, (b) significantly facilitated extinction and (c) diminished the reinstatement of cocaine CPP. Rolipram, which selectively increased brain cAMP levels, and papaverine which caused increases in both cAMP and cGMP levels, had no significant effect on the extinction of cocaine CPP. The results suggest that increase in hippocampal and amygdalar cGMP levels via blockade of PDE9 has a prominent role in the consolidation of extinction learning.

1002 EFFECTS OF COMBINED USE OF PHOSPHODIESTERASE 5 INHIBITOR AND MEDICATIONS FOR HYPERTENSION, LOWER URINARY TRACT SYMPTOMS AND DYSLIPIDEMIA ON TONE OF CORPORAL TISSUE

INTRODUCTION AND OBJECTIVES: To establish theoretical basis of choosing an appropriate medication for ED and concomitant disease, we examined the effects of combination Phosphodiesterase 5 inhibitor (PDE5I) with drug for ED comorbidities (hypertension, lower urinary tract symptoms, and dyslipidemia) on relaxation of rabbit corpus cavernosum (CC). METHODS: Contractility of CC strips was studied in organ baths. Concentration-response curves to mirodenafil were generated on phenylephrine (PE) (10 M)-precontracted strips before and after preincubation of losartan (10, 10 M), amlodipine (10, 10 M), nifedipine (10, 10 M), enalapril (10, 10 M), doxazosin (10, 10 M), tamsulosin (10, 10 M), or simvastatin(10, 10 M). Another organ bath studies were done to determine the losartan/nitric oxide interaction on CC smooth muscle function. We also determined role of potassium channel opening in synergistic effect of mirodenafil and alpha adrenergic blockers. RESULTS: The effect of mirodenafil to relax PE-induced CC tone was significantly enhanced by preincubation of losartan, nifedipine, amlodipine, tamsulosin, and doxazosin. The maximal effect was 35.8 2.0% of inhibition of PE-induced tone for mirodenafil alone vs. 47.2 3.8% for preincubation of 10 M losartan, 57.6 2.6% for 10 M nifedipine, 64.0 3.7% for 10 M amlodipine, 76.1 5.7% for 10 M doxazosin, and 71.7 5.4% for 10 M tamsulosin. But enalapril and simvastatin had no additional effect. Relaxation of CC smooth muscle induced by the nitric oxide donor sodium nitroprusside (SNP) was potentiated by losartan (p 0.05). The maximal responses to SNP alone (39.0 4.0%) were significantly enhanced in the presence of the 10 M losartan (66.0 6.0%). Nonselective K inhibitor tetraethylammonium (1mM) significantly inhibited enhancement effect of tamsulosin or doxazosin on mirodenafil-induced relaxation. CONCLUSIONS: Amlodipine, nifedipine, losartan, doxazosin, and tamsulosin enhancd relaxation effect of mirodenafil in CC. Losartan seems to exert enhancing effect by interaction with nitric oxide. And potassium channel opening effect of PDE5I and alpha adrenergic blocker could be one of action mechanism for enhancing effect. Combination of PDE5I with losartan, nifedipine, amlodipine, doxazosin, or tamsulosin could be a possible pharmacologic strategy to simultaneously treat erectile dysfunction and its comorbidities and to increase response rate to PDE5I.

Treatment of loin pain suspected to be renal colic with papaverine hydrochloride: a prospective double‐blind randomised study

• To assess the efficacy of papaverine hydrochloride combined with a diclofenac sodium suppository to relieve renal colic compared with diclofenac suppository monotherapy, as the effect of phosphodiesterase inhibitors on ureteric muscles might reduce the pain of renal colic. • A prospective, double-blind clinical study was performed. • In all, 550 patients aged 17-55 years with acute renal colic were randomised to two groups. Patients in one group (group A) received a diclofenac suppository (100 mg) plus saline 0.9% (placebo) and the other group (group B) received a diclofenac suppository (100 mg) plus intravenous (i.v.) papaverine hydrochloride (1.5 mg/kg up to 120 mg). • Pain intensity was assessed using a visual analogue scale (VAS) at 0, 20 and 40 min after treatment. Further analgesia was provided at the patients' request (25 mg pethidine intramuscularly). • Baseline characteristics (sex, age, past history of similar pains) were similar in the two groups. • There were significant differences in VAS pain scores between 0 and 20 min and 0 and 40 min in both groups (P < 0.001). • At the end of study, 71.1% of patients in group A and 90.9% of patients in group B reported pain relief and did not require pethidine, respectively. • Significantly more patients in group A required further analgesia. • According to our results, i.v. papaverine hydrochloride plus a diclofenac suppository were more effective than the diclofenac suppository alone for treating acute renal colic. • Therefore, i.v. papaverine hydrochloride is a beneficial supplemental therapy to relieve renal colic pain, particularly combined with non-steroidal anti-inflammatory drugs.

Effect of Phosphodiesterase Inhibitor on Diabetic Nephropathy

Effect of Phosphodiesterase Inhibitor on Diabetic Nephropathy

Pharmacological explanation for the medicinal use of Juniperus excelsa in hyperactive gastrointestinal and respiratory disorders

Crude extract of Juniperus excelsa (JeExt), which tested positive for the presence of anthraquinone, flavonoids, saponins, sterols, terpenes and tannin, exhibited a protective effect against castor oil-induced diarrhoea in mice at 100-1000 mg/kg. In rabbit jejunum preparations, JeExt (0.01-1.0 mg/mL) caused relaxation of spontaneous and K(+) (80 mM)-induced contractions at similar concentrations to papaverine, whereas verapamil was relatively more potent against K(+). JeExt (0.03-0.3 mg/mL) shifted Ca(2+) concentration-response curves to the right, like papaverine or verapamil. JeExt (0.003-0.01 mg/mL) caused a leftward shift of isoprenaline-induced inhibitory concentration-response curves, similar to papaverine. JeExt (1.0-30 mg/kg) caused suppression of carbachol (CCh, 100 μg/kg)-induced increase in inspiratory pressure of anaesthetized rats. In guinea-pig trachea, JeExt (0.001-3.0 mg/mL) relaxed CCh (1 μM)- and high K(+)-induced contractions and shifted isoprenaline-induced inhibitory curves to the left. This study suggests that Juniperus excelsa possibly exhibits a combination of Ca(2+) antagonist and phosphodiesterase inhibitory effects, which provides a pharmacological basis for its traditional use in disorders of gut and airways hyperactivity, such as diarrhoea, colic and asthma.

Ibudilast, a mixed PDE3/4 inhibitor, causes a selective and nitric oxide/cGMP-independent relaxation of the intracranial vertebrobasilar artery

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.

Effect of vardenafil on endothelial progenitor cells in hypogonadotrophic hypogonadal patients: role of testosterone treatment

Endothelial progenitor cells (EPCs) are bone marrow-derived cells required for endothelial repair. Circulating EPC concentration is low in conditions characterized by endothelial dysfunction but their number can be increased by treatment with phosphodiesterase-5 (PDE5) inhibitors. EPCs are also reduced in hypogonadal men and testosterone (T) treatment restores their concentration. To evaluate the relationship between the effect of PDE5 inhibitors and T on EPCs, we analysed the acute effect of vardenafil on the number of EPCs in hypogonadotrophic hypogonadal (HH) patients, before and after T treatment. A case-control study at a university andrology centre. Fifteen HH subjects and 25 aged-matched controls. The number of circulating EPCs and progenitor cells (PCs) in HH patients was evaluated after acute vardenafil administration at baseline and after 6 months of T supplementation. At baseline, HH men had significantly lower numbers of PCs and EPCs with respect to controls and vardenafil administration had no effect on the number of these cells. After 6 months of T treatment, all HH patients were eugonadal. With respect to baseline, PCs and EPCs were significantly higher and reached the levels observed in controls. Vardenafil administration in HH men at the end of T treatment induced a significant increase in PCs and EPCs in a manner similar to that in controls. This study showed that normal T levels are necessary to restore the responsiveness of EPCs to PDE5 inhibitors, suggesting that T positively modulates PDE5 in bone marrow.

Effects of Phosphodiesterase Inhibitors on Contraction Induced by Endothelin-1 of Isolated Human Prostatic Tissue

To study the effects of selective phosphodiesterase (PDE) inhibitors on the contraction induced by endothelin-1 (ET-1) of isolated human prostatic tissue. Using the organ bath technique, the effects of the cumulative addition of the PDE1 inhibitor vinpocetine, PDE2 inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA), PDE4 inhibitor rolipram, and PDE5 inhibitors sildenafil, vardenafil, and tadalafil (1 nM to 10 microM) were investigated on the contraction brought about by the peptide ET-1 (1 microM) on normal human prostatic tissue isolated from the transition zone. In the present study, the nitric oxide donor drug sodium nitroprusside and adenylyl cyclase activator forskolin were used as reference compounds. ET-1 induced stable and long-lasting contraction of the isolated prostatic tissue. The tension induced by ET-1 was dose-dependently reversed by the drugs with the following rank order of efficacy: rolipram, forskolin, tadalafil, sodium nitroprusside, sildenafil, vinpocetine, vardenafil, EHNA. The maximal reversion of tension ranged from 67% (rolipram) to 20% (EHNA). Our results have provide additional evidence that the function of prostatic smooth muscle is under the control of peptidergic and cyclic nucleotide (cyclic guanosine monophosphate, cyclic adenosine monophosphate)-mediated pathways. This might give a rationale for the use of drugs interacting with cyclic guanosine monophosphate or cyclic adenosine monophosphate signaling, such as PDE inhibitors or nitric oxide donors, in the pharmacotherapy of the benign prostatic syndrome.

Phosphodiesterase Inhibitors Enhance Object Memory Independent of Cerebral Blood Flow and Glucose Utilization in Rats

Phosphodiesterase (PDE) inhibitors prevent the breakdown of the second messengers, cyclic AMP (cAMP) and cyclic GMP (cGMP), and are currently studied as possible targets for cognitive enhancement. Earlier studies indicated beneficial effects of PDE inhibitors in object recognition. In this study we tested the effects of three PDE inhibitors on spatial memory as assessed in a place and object recognition task. Furthermore, as both cAMP and cGMP are known vasodilators, the effects of PDE inhibition on cognitive functions could be explained by enhancement of cerebrovascular function. We examined this possibility by measuring the effects of PDE5 and PDE4 inhibitor treatment on local cerebral blood flow and glucose utilization in rats using [14C]-iodoantipyrine and [14C]-2-deoxyglucose quantitative autoradiography, respectively. In the spatial location task, PDE5 inhibition (cGMP) with vardenafil enhanced only early phase consolidation, PDE4 inhibition (cAMP) with rolipram enhanced only late phase consolidation, and PDE2 inhibition (cAMP and cGMP) with Bay 60-7550 enhanced both consolidation processes. Furthermore, PDE5 inhibition had no cerebrovascular effects in hippocampal or rhinal areas. PDE4 inhibition increased rhinal, but not hippocampal blood flow, whereas it decreased glucose utilization in both areas. In general, PDE5 inhibition decreased the ratio between blood flow and glucose utilization, indicative of general oligaemia; whereas PDE4 inhibition increased this ratio, indicative of general hyperemia. Both oligaemic and hyperemic conditions are detrimental for brain function and do not explain memory enhancement. These results underscore the specific effects of cAMP and cGMP on memory consolidation (object and spatial memory) and provide evidence that the underlying mechanisms of PDE inhibition on cognition are independent of cerebrovascular effects.

Effects of Phosphodiesterase Inhibitors on the Contractile Responses of Isolated Human Seminal Vesicle Tissue to Adrenergic Stimulation

It has been suggested that the capability of the phosphodiesterase 5 (PDE5) inhibitor sildenafil citrate (VIAGRA) to retard the ejaculatory response may include modulation of the contraction of seminal vesicle (SV) smooth muscle. In fact, it has been shown that PDE inhibitors can reverse the tension of isolated human SV tissue and enhance the production of cyclic AMP and cyclic GMP. The aim of this study was to examine the effects of selective phosphodiesterase (PDE) inhibitors on both the spontaneous and electrically induced phasic contractions of isolated human SV smooth muscle. To measure the inhibition exerted by PDE inhibitors vinpocetine (PDE1-inhibitor), rolipram (PDE4-inhibitor), sildenafil, and vardenafil (PDE5-inhibitors) on the phasic contractile response of isolated SV tissue. Using the organ bath technique, the effects of increasing concentrations of the PDE inhibitors (1 nM-10 microM) were investigated on phasic contractions of SV tissue strips either mediated by means of electrical field stimulation (EFS) or the alpha(1)-adrenoceptor agonist norepinephrine. The contractile activity in response to EFS was dose-dependently reversed by the PDE inhibitors. The rank order of efficacy was: rolipram > sildenafil >or= vardenafil > vinpocetine. Mean maximum inhibition of contraction was determined as -89.6% (rolipram), -61.3% (sildenafil), -62% (vardenafil), and -46% (vinpocetine). No differences were registered with regard to the effects of sildenafil and vardenafil on the inhibition of the contraction amplitudes. The frequency of the spontaneous contractions (amplitudes/5 minutes) was reduced by 50% in the presence of 2 microM rolipram, 5 microM sildenafil or vardenafil, and 8 microM vinpocetine. Our results demonstrate that PDE inhibitors can inhibit EFS-induced and spontaneous contractile activity of isolated human SV tissue. These findings might be of importance with regard to the pharmacological treatment of premature ejaculation.

Effects of Phosphodiesterase Inhibitors on the Inflammatory Response of Endothelial Cells Stimulated by Myeloperoxidase-Modified Low-Density Lipoprotein or Tumor Necrosis Factor Alpha

BackgroundSildenafil, vardenafil, and tadalafil are phosphodiesterase type 5 inhibitors (PDE5-Is) usually used in the treatment of erectile dysfunction (ED). Previously, we have shown the presence of myeloperoxidase-modified low-density lipoprotein (Mox-LDL) in the penises of patients with ED, and we have shown the impact of Mox-LDL on cyclic monophosphate (cGMP) level. In vitro, Mox-LDL triggered the inflammatory response by increasing the release of both interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-α) by endothelial cells (ECs) and monocytes respectively. ObjectiveTo determine whether or not the three therapeutically PDE5-Is protect against the proinflammatory effects of Mox-LDL or TNF-α on ECs. Design, setting, and participantsECs (EA.hy926) were incubated in the presence of either TNF-α (100pg/ml) or Mox-LDL (200μg/ml) with each of the three PDE5-Is (1μM, 5μM, and 10μM) respectively. IL-8 production was measured in the supernatant after 48h of incubation. MeasurementsAll experiments were repeated at least three times. Statistical analysis was performed with an ANOVA. Results and limitationsTwo-way ANOVA analysis showed that TNF-α alone (p<0.001) or Mox-LDL alone (p<0.001) increased IL-8 production. Sildenafil, vardenafil, or tadalafil alone did not generate an increase of IL-8 production. Tadalafil in combination with Mox-LDL and TNF-α showed a decrease of IL-8 (p<0.05) compared with sildenafil and vardenafil. ConclusionsAmong the three available PDE5-Is, tadalafil showed an additional potentially anti-inflammatory effect on relaxation. Those data could be considered for the chronic use of PDE5-Is, but extrapolations of experimental evidence to the clinical setting should be made cautiously.

Editorial Comment on: Effects of Phosphodiesterase Inhibitors on the Inflammatory Response of Endothelial Cells Stimulated by Myeloperoxidase-Modified Low-Density Lipoprotein or Tumor Necrosis Factor Alpha

Editorial Comment on: Effects of Phosphodiesterase Inhibitors on the Inflammatory Response of Endothelial Cells Stimulated by Myeloperoxidase-Modified Low-Density Lipoprotein or Tumor Necrosis Factor Alpha

Effect of phosphodiesterase-5 inhibitor on hearing

Following a report of sudden hearing loss in a patient taking phosphodiesterase type 5 inhibitor, and a Food and Drug Administration announcement concerning this class of drugs, a study was planned to investigate if ototoxicity occurs in patients using phosphodiesterase 5 inhibitor for erectile dysfunction. Eighteen patients with erectile dysfunction who had been using phosphodiesterase 5 inhibitor were included in the study. Audiometric tests were performed on all patients, between the frequencies 250 and 16,000 Hz, before and 1, 5 and 72 hours after drug ingestion. Four patients showed a unilateral threshold decrease compatible with ototoxicity criteria; this change was reversible. A statistically significant difference in pre- versus post-drug hearing thresholds was observed in the right ear at 10,000 Hz (p = 0.008). There were no statistically significant hearing threshold differences at any other frequencies (p > 0.05). Although temporary ototoxicity was noted in four patients, we could not find any permanent, deleterious effect of phosphodiesterase type 5 inhibitor on hearing thresholds.

Effects of phosphodiesterase-4 inhibitor on the mucin secretion in airway stimulated with acrolein: experiment with rats

To examine the effects of YM976, a phosphodiesterase (PDE)4 inhibitor, on mucin hypersecretion of airway stimulated with acrolein. Forty-eight SD rat were randomly divided into 6 equal groups. Twenty-four rats underwent gastric perfusion of YM976 0.5, 1.5, or 4.5 mgxkg(-1)xd(-1) (n=8 for each group) and then underwent aerosol inhalation of 3.0 ppm acrolein 6 hours per day for 12 days so as to establish rat models of airway mucus hypersecretion. Eight rats underwent aerosol inhalation of 3.0 ppm acrolein only for 12 days to establish rat models of airway mucus hypersecretion without any drug intervention (acrolein model group). Eight rats underwent gastric perfusion of 5% methylcellulose and then acrolein inhalation for 12 days (methylcellulose group), and another 8 rats underwent gastric perfusion of YM976 4.5 mg/kg once a day and then inhalation of normal saline for 12 days (YM976 control group). On the 13th day the rats were killed. Bronchoalveolar lavage fluid (BALF) was acquired for cell count, and ELISA was used to detect the levels of tumor necrosis factor (TNF)-alpha and cytokine-induced neutrophil chemoattractant (CINC)-1 in the BALF. The mucin level in the airway mucous membrane was detected by alcian blue(AB)/periodic acid-Schiff(PAS) method. Muc5ac protein was measured by immunohistochemical staining and Western-blotting, and Muc5ac mRNA was detected by RT-PCR. The percentages of positive AB/PAS staining of the acrolein model group and the 3 YM976 groups (0.5, 1.5, and 4.5 mgxkg(-1)xd(-1)) were 23.65+/-2.86, 22.63+/-2.12, 16.34+/-1.72, and 5.03+/-0.72 respectively. The integral optical density (IOD) levels of Muc5ac immunohistochemical staining of the methylcellulose group and the 3 YM976 groups were 0.54+/-0.05, 0.49+/-0.06, 0.32+/-0.04, and 0.22+/-0.04 respectively. The IOD of Muc5ac protein expression by Western-blotting of the methylcellulose group and the 3 YM976 groups were 1.177+/-0.190, 0.806+/-0.180, 0.303+/-0.061, and 0.134+/-0.035 respectively. The IOD of Muc5ac mRNA expression by RT-PCR of the methylcellulose group and the 3 YM976 groups were 0.246+/-0.021, 0.223+/-0.020, 0.161+/-0.012, and 0.097+/-0.011 respectively. The TNF-alpha and CINC-1 levels in the BALF of the methylcellulose group and the 3 YM976 groups were (96.77+/-2.31), (87.65+/-2.75), (73.56+/-2.62), and (52.23+/-2.79) microg/L respectively, and (145.75+/-4.43), (139.73+/-5.51), (95.34+/-5.13), and (65.74+/-5.62) microg/L respectively, all significantly higher than those of the normal control group [4.38+/-0.32, 0.12+/-0.02, 0.058+/-0.024, 0.061+/-0.006, (18.23+/-2.32) microg/L and (33.56+/-3.43) microg/L respectively, all P<0.05], but those of the YM976 1.5 mgxkg(-1)xd(-1) and 4.5 mgxkg(-1)xd(-1) groups being significantly lower than those of the methylcellulose group (both P<0.05). YM976 inhibits airway inflammatory response and airway mucin hypersecretion induced by acrolein.

Effects of phosphodiesterase inhibitors on vascular development: Implications for retinopathy of prematurity

UENPS.192 Propofol clearance in neonates is reduced due to limited glucuronidation capacity Allegaert Karel⁎, Veerle Cossey, Rene Verbesselt, Christine Vanhole University Hospitals, Leuven, Belgium

Increased phosphodiesterase 3A/4B expression after angioplasty and the effect on VASP phosphorylation

The beneficial effects of coronary angioplasty are limited by the proliferation and migration of vascular smooth muscle cells leading to restenosis. We hypothesized that increased activity of phosphodiesterase (PDE) after angioplasty in response to growth factors such as platelet-derived growth factor (PDGF)-BB and fibroblast growth factor (FGF), leads to reduced cAMP levels, which, in turn, may contribute to vascular smooth muscle cell proliferation. In rats subjected to angioplasty, aortic expression and activity of PDE3/PDE4 were increased within 24 h and associated with reduced phosphorylation of vasodilator-stimulated phosphoprotein (VASP), a substrate for cAMP-dependent protein kinase A (PKA). Inhibition of PDE3 increased VASP phosphorylation in aortic rings from rats subjected to angioplasty, whereas inhibition of PDE4 or stimulation of adenylate cyclase with isoproterenol was without effect; however, combined inhibition of PDE3 and PDE4 produced a synergistic effect on VASP phosphorylation. In cultured vascular smooth muscle cells, exposure to PDGF-BB resulted in increased expression of PDE3, which was prevented by an inhibitor of PI3 kinase but not by inhibitors of the MAP kinase signaling pathway. In contrast, FGF increased the expression of PDE4 in vascular smooth muscle cells but did not influence expression of PDE3. This study shows that angioplasty results in increased expression/activity of PDE, possibly arising from stimulation by PDGF-BB and FGF, and decreased cAMP levels, which may promote restenosis. These results provide a rational explanation for the beneficial effects of PDE inhibitors.

Effects of Phosphodiesterase Inhibitors on Tension Induced by Norepinephrine and Accumulation of Cyclic Nucleotides in Isolated Human Prostatic Tissue

To further evaluate the mechanism of action of phosphodiesterase (PDE) inhibitors on the human prostate, the effects of PDE4 and PDE5 inhibitors on the tension induced by norepinephrine (NE) and on the intracellular levels of cyclic nucleotides in isolated human prostatic tissue were investigated. Using the organ bath technique, the effects of increasing concentrations (1 nM to 10 microM) of the PDE5 inhibitors sildenafil, tadalafil, and vardenafil and the PDE4 inhibitors rolipram and RP 73401 on the tension induced by NE (40 microM) of prostate strip preparations were investigated. The accumulation of cyclic guanosine monophosphate and cyclic adenosine monophosphate in response to drug exposure was determined by radioimmunoassays. The tension induced by NE was dose dependently reversed by the drugs with the following rank order of efficacy: tadalafil greater than RP 73401 greater than rolipram greater than or equal to vardenafil greater than sildenafil. The maximal reversion of tension values ranged from 52.3% (tadalafil) to 17% (sildenafil). Of the PDE inhibitors, only tadalafil induced a 50% reversion of the initial tension. The most prominent enhancement in tissue cyclic adenosine monophosphate was registered in response to RP 73401 (11-fold), and cyclic guanosine monophosphate levels were significantly elevated by tadalafil, vardenafil, and sildenafil (28-fold, 12-fold, and 3-fold, respectively). Our results have demonstrated that drugs interfering with the cyclic nucleotide-mediated pathways can reverse the tension induced by NE in isolated prostatic tissue and elevate cyclic adenosine monophosphate and cyclic guanosine monophosphate. Our findings serve to explain how PDE inhibitors can affect symptoms of lower urinary tract symptoms and benign prostatic hyperplasia.

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QS382. The Effect of Phosphodiesterase Inhibition on NF-κB Activation in LPS Stimulated THP1 Cells

Background: The activation of the transcriptional factor NF-κB has been shown to play a critical role in the host response to sepsis by increasing cellular adhesion molecules and proinflammatory cytokine synthesis. NF-κB resides in its mature form in the cytoplasm, complexed to the Inhibitor kappaB (IκB) proteins. Cell activation by various stimuli, including LPS, causes phosphorylation and degradation of IκB, which is catalyzed by the phosphorylation of IKKβ. Following degradation of IκB, NF-κB translocates to the nucleus and activates the transcription of its target genes.