Quantification and clinical validation of the selective MET kinase inhibitor DO-2 and its metabolites DO-5 and M3 in human plasma

DO-2 is a highly selective MNNG HOS transforming (MET) inhibitor. This deuterated drug is thought to diminish the formation of the Aldehyde Oxidase 1 inactive metabolite M3. For various reasons, quantification of DO-2 and its metabolites M3 and DO-5 is highly relevant. In this study, we present an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method to quantify DO-2, M3 and DO-5. Rolipram served as the internal standard. Aliquots of 25 µL were mixed with 100 µL internal standard consisting of 10 ng/mL rolipram in acetonitrile. Separation of the analytes was achieved on an Acquity UPLC ® HSS T3 column, utilizing gradient elution with water/formic acid and acetonitrile/formic acid at a flow-rate of 0.400 mL/min. Calibration curves were linear in the range of 1.00 - 1000 ng/mL for DO-2 and DO-5, and 2.00 - 2000 ng/mL for M3 in human plasma. The within-run and between-run precisions of DO-2, DO-5 and M3, also at the level of the LLQ, were within 12.1%, while the accuracy ranged from 89.5 to 108.7%. All values for accuracy, within-run and between-run precisions met the criteria set by the Food and Drug Administration. The method was effectively employed in the analysis of samples obtained from a clinical trial.

Urinary liver-type fatty acid binding protein is a biomarker reflecting renal damage and the ameliorative effect of drugs at an early stage of histone-induced acute kidney injury

AIM

Circulated histones play a crucial role in the pathogenesis of infectious diseases and severe trauma, and it is one of the potential molecular targets for therapeutics. Recently, we reported that histone is one of the causative agents for urinary L-FABP increase. However, the mechanism is still unclear, especially in severe cases. We further investigated the mechanism of urinary L-FABP increase using a more severe mouse model with histone-induced kidney injury. This study also aims to evaluate the therapeutic responsiveness of urinary L-FABP as a preliminary study.

METHODS

Human L-FABP chromosomal transgenic mice were administrated 30 mg/kg histone from a tail vein with a single dose. We also performed a comparative study in LPS administration model. For the evaluation of the therapeutic responsiveness of urinary L-FABP, we used heparin and rolipram.

RESULTS

The histological change with cast formation as a characteristic of the models was observed in proximal tubules. Urinary L-FABP levels were significantly elevated and these levels tended to be higher in those with more cast formation. Heparin and rolipram had the ameliorative effect of the cast formation induced by histone and urinary L-FABP levels significantly decreased.

CONCLUSION

Histone is one of the causative agents for the increase of urinary L-FABP at an early stage of AKI. In addition, it suggested that urinary L-FABP may be useful as a subclinical AKI marker reflecting kidney damage induced by histone. Furthermore, urinary L-FABP reflected the degree of the damage after the administration of therapeutic agents such as heparin and PDE4 inhibitor.

Caffeine-induced protein kinase A activation restores cognitive deficits induced by sleep deprivation by regulating O-GlcNAc cycling in adult zebrafish

Sleep deprivation (SD) is widely acknowledged as a significant risk factor for cognitive impairment. In this study, intraperitoneal caffeine administration significantly ameliorated the learning and memory (L/M) deficits induced by SD and reduced aggressive behaviors in adult zebrafish. SD led to a reduction in protein kinase A (PKA) phosphorylation, phosphorylated-cAMP response element-binding protein (p-CREB), and c-Fos expression in zebrafish brain. Notably, these alterations were effectively reversed by caffeine. In addition, caffeine mitigated neuroinflammation induced by SD, as evident from suppression of the SD-mediated increase in glial fibrillary acidic protein (GFAP) and nuclear factor-κB (NF-κB) activation. Caffeine restored normal O-GlcNAcylation and O-GlcNAc transferase (OGT) levels while reversing the increased expression of O-GlcNAcase (OGA) in zebrafish brain after SD. Intriguingly, rolipram, a selective phosphodiesterase 4 (PDE4) inhibitor, effectively mitigated cognitive deficits, restored p-CREB and c-Fos levels, and attenuated the increase in GFAP in brain induced by SD. In addition, rolipram reversed the decrease in O-GlcNAcylation and OGT expression as well as elevation of OGA expression following SD. Treatment with H89, a PKA inhibitor, significantly impaired the L/M functions of zebrafish compared with the control group, inducing a decrease in O-GlcNAcylation and OGT expression and, conversely, an increase in OGA expression. The H89-induced changes in O-GlcNAc cycling and L/M dysfunction were effectively reversed by glucosamine treatment. H89 suppressed, whereas caffeine and rolipram promoted O-GlcNAc cycling in Neuro2a cells. Our collective findings underscore the interplay between PKA signaling and O-GlcNAc cycling in the regulation of cognitive function in the brain, offering potential therapeutic targets for cognitive deficits associated with SD.NEW & NOTEWORTHY Our observation highlights the intricate interplay between cAMP/PKA signaling and O-GlcNAc cycling, unveiling a novel mechanism that potentially governs the regulation of learning and memory functions. The dynamic interplay between these two pathways provides a novel and nuanced perspective on the molecular foundation of learning and memory regulation. These insights open avenues for the development of targeted interventions to treat conditions that impact cognitive function, including SD.

Ameliorative role of rolipram, PDE-4 inhibitor, against sodium arsenite-induced vascular dementia in rats

Arsenic exposure to the population leads to serious health problems like neurotoxicity, nephrotoxicity, and cardiovascular abnormality. In the present study, the work has been commenced to discover the prospect of rolipram a phosphodiestrase-4 (PDE-4) inhibitor against sodium arsenite (SA)-induced vascular endothelial dysfunction (EnDF) leading to dementia in rats. Wistar rats were treated with SA (5 mg/kg body weight/day orally) for 44 days for induction of vascular EnDF and dementia. Learning and memory were evaluated using Morris water maze (MWM) test. Vascular EnDF was evaluated using aortic ring preparation. Various biochemical parameters were also evaluated like brain oxidative stress (viz. reduced glutathione and thiobarbituric acid reactive substances level), serum nitrite/nitrate activity, acetylcholinesterase activity, and inflammatory markers (viz. neutrophil infiltration in brain and myeloperoxidase). SA-treated rats showed poor performance in water maze trials indicating attenuated memory and ability to learn with significant rise (p < 0.05) in brain acetylcholinesterase activity, brain oxidative stress, neutrophil count, and significant decrease (p < 0.05) in serum nitrite/nitrate levels and vascular endothelial functions. Rolipram (PDE-4 inhibitor) treatment (0.03 mg/kg and 0.06 mg/kg body weight, intraperitoneally daily for 14 days) significantly improved memory and learning abilities, and restored various biochemical parameters and EnDF. It is concluded that PDE-4 modulator may be considered the prospective target for the treatment of SA-induced vascular EnDF and related dementia.

STIMULATION OF THE CYCLIC AMP/GMP SIGNALLING ENHANCES THE RELAXATION OF ISOLATED HUMAN DETRUSOR SMOOTH MUSCLE ACHIEVED BY PHOSPHODIESTERASE INHIBITORS

Phosphodiesterase (PDE) enzymes are considered being key proteins in controlling the function of smooth musculature in the human urinary tract. The use of PDE inhibitors (PDE-Is) to treat erectile dysfunction and lower urinary tract symptomatology (LUTS) secondary to benign prostatic hyperplasia (BPH) is well established. It has been shown that PDE-Is can reverse the tension induced by means of muscarinergic agents of detrusor smooth muscle and enhance the production of cyclic nucleotides. In clinical settings, the PDE1 inhibitor vinpocetine had beneficial effects in patients presenting with voiding dysfunctions. This prompted us to evaluate further the mechanism of action of PDE-Is on bladder smooth musculature. Using the tissue bath technique, relaxant responses of human detrusor smooth muscle, challenged by acetylcholine (1 µM), to vinpocetine (PDE1-I), rolipram (PDE4-I), MY 5445 and sildenafil (PDE5-Is) (0.1 µM, 1 µM, and 10 µM) were investigated with and without pre-exposure of the tissue to threshold concentrations of the NO donor drug sodium nitroprusside (SNP) or adenylyl cyclase activator forskolin (0.02 µM). The non-specific PDE-I papaverine was used as a reference compound. The cumulative addition of forskolin or SNP exerted a pronounced reversion of the tension induced by means of ACh, starting at a concentration of 1 µM (forskolin, -25,6%) and 0.1 µM (SNP, -20%), respectively. There were marginal responses of the detrusor smooth musculature to the PDE-Is, the relaxation measured ranged from -12% (vinpocetine/sildenafil) to -19% (rolipram, MY 5445). Exposure of the tissue to a threshold concentration of SNP increased the reversion of tension induced by vinpocetine (-40%), rolipram (-50%) and MY 5445 (-45%). An enhancement in the potency of the drugs was also registered. A threshold concentration of SNP did not significantly affect the maximum reversion of tension brought about by sildenafil but added positively to the in vitro potency of the PDE5-I. PDE inhibitors may tend to be more effective in systems characterized by an enhanced production of cyclic AMP/GMP (such as urogenital tissues in vivo). Our findings may explain how PDE inhibitors can affect symptoms of the overactive bladder.

NADPH oxidase 4 deficiency reduces aquaporin-2 mRNA expression in cultured renal collecting duct principal cells via increased PDE3 and PDE4 activity

The final control of renal water reabsorption occurs in the collecting duct (CD) and relies on regulated expression of aquaporin-2 (AQP2) in principal CD cells. AQP2 transcription is primarily induced by type 2 vasopressin receptor (V₂R)-cAMP-protein kinase A (PKA) signaling but also by other factors, including TonEBP and NF-κB. NAPDH oxidase 4 (NOX4) represents a major source of reactive oxygen species (ROS) in the kidney. Because NOX-derived ROS may alter PKA, TonEBP and NF-κB activity, we examined the effects of NOX4 depletion on AQP2 expression. Depleted NOX4 expression by siRNA (siNOX4) in mpkCCD_cl4 cells attenuated increased AQP2 mRNA expression by arginine vasopressin (AVP) but not by hypertonicity, which induces both TonEBP and NF-κB activity. AVP-induced AQP2 expression was similarly decreased by the flavoprotein inhibitor diphenyleneiodonium. siNOX4 altered neither TonEBP nor NF-κB activity but attenuated AVP-inducible cellular cAMP concentration, PKA activity and CREB phosphorylation as well as AQP2 mRNA expression induced by forskolin, a potent activator of adenylate cyclase. The repressive effect of siNOX4 on AVP-induced AQP2 mRNA expression was abolished by the non-selective phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX) and was significantly decreased by selective PDE antagonists cilostamide and rolipram, but not vinpocetine, which respectively target PDE3, PDE4 and PDE1. Thus, by inhibiting PDE3 and PDE4 activity NOX4-derived ROS may contribute to V₂R-cAMP-PKA signaling and enhance AQP2 transcription.

Partially purified extract and viscolin from Viscum coloratum attenuate airway inflammation and eosinophil infiltration in ovalbumin-sensitized mice

AIM OF THE STUDY

Viscum coloratum Nakai is used in traditional Chinese medicine to treat various diseases, including hemorrhage, hypertension, and inflammatory diseases. A previous study demonstrated a partially purified extract (PPE-SVC) and viscolin from Viscum coloratum Nakai inhibited phosphodiesterase activity. In this study, we evaluated the anti-asthmatic effects of PPE-SVC and viscolin, from Viscum coloratum Nakai, in OVA-sensitized mice.

MATERIALS AND METHODS

Female BALB/c mice were sensitized and challenged with ovalbumin (OVA). The mice were randomized into groups and treated with PPE-SVC, viscolin, or rolipram by intraperitoneal injection on 1h before each inhalation of OVA and airway hyperresponsiveness (AHR).

RESULTS

PPE-SVC and viscolin suppressed AHR and reduced eosinophil infiltration of the lungs in OVA-sensitized mice. Moreover, PPE-SVC and viscolin inhibited chemokines, including CCL11 and CCL24, and Th2-associated cytokines in bronchoalveolar lavage fluid. However, PPE-SVC and viscolin could not decrease IL-4, IL-5, and IL-13 levels in cultures of OVA-activated spleen cells.

CONCLUSION

PPE-SVC and viscolin attenuate airway inflammation and eosinophil infiltration in OVA-sensitized mice.

Preliminary evidence for an involvement of the cholinergic system in the sedative effects of rolipram in rats

Rolipram is a specific cAMP phosphodiesterase type 4 (PDE4) inhibitor in the brain, which induces an increase in the intracellular levels of cAMP. Rolipram produces characteristic alterations in animal behavior, which have been suggested to be mediated mainly through an intracellular mechanism involving an increase in cAMP. However, specific mechanisms mediating the sedative effects of this compound have not yet been investigated. Because several lines of evidence indicate that the acetylcholine neural system may be involved in some effects of PDE4 inhibitors, the aim of this study was to elucidate whether the neurotransmitter acetylcholine is involved in the sedative effects induced by rolipram. The present study assessed the motor effects of rolipram in an exploratory behavioral test, the open field, in Wistar rats. The results show that rolipram (0.1-3.0 mg/kg SC) induced potent and dose-dependent hypoactivity, decreasing both locomotion and rearing. Physostigmine (0.03-0.3 mg/kg SC) potentiated a subeffective dose of rolipram (0.03 mg/kg SC), resulting in strong sedation, similar to that following higher doses of either rolipram or physostigmine alone, whereas the reduction in locomotor activity induced by rolipram (0.3 mg/kg SC) was completely reversed by scopolamine (0.03-0.3 mg/kg SC). These data provide preliminary evidence suggesting the involvement of the acetylcholinergic system in the sedative effects of rolipram.

Regulation of IL-15-stimulated TNF-alpha production by rolipram

Agents that increase intracellular cAMP have been shown to reduce joint inflammation in experimental arthritis, presumably by lowering the release of proinflammatory cytokines, such as TNF-alpha. Recent studies suggest that, in joints of patients with rheumatoid arthritis, TNF-alpha release from macrophages is triggered by their interaction with IL-15-stimulated T lymphocytes. In this report, we analyze the effect of rolipram, a cAMP-specific phosphodiesterase inhibitor, on TNF-alpha production in this experimental system. Cocultures of U937 cells with IL-15-stimulated T cells, but not control T cells, resulted in increased release of TNF-alpha. Pretreatment of T cells with rolipram or cAMP analogues inhibited the IL-15-stimulated increases in proliferation, expression of cell surface molecules CD69, ICAM-1, and LFA-1, and release of TNF-alpha from macrophages. Addition of PMA to T cells dramatically increased the expression of cell surface molecules, but had little or no effect on TNF-alpha release from either T cells or from cocultures, suggesting that other surface molecules must also be involved in T cell/macrophage contact-mediated production of TNF-alpha. Addition of PMA synergistically increased the proliferation of IL-15-stimulated T cells and the secretion of TNF-alpha from IL-15-stimulated T cell/macrophage cocultures. Rolipram and 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) blocked these increases. Measurement of protein kinase A (PKA) activity and the use of inhibitory cAMP analogues (RpCPT-cAMP) confirmed that rolipram worked by stimulating PKA. These data suggest that PKA-activating agents, such as rolipram, can block secretion of TNF-alpha from macrophages by inhibiting T cell activation and expression of surface molecules.

Differential effects of phosphodiesterase type 4-specific inhibition on human autoreactive myelin-specific T cell clones

Proinflammatory cytokines, secreted by autoreactive CD4+ T lymphocytes may contribute to the pathogenesis of several human autoimmune diseases, including multiple sclerosis (MS). Since the antigen specificities of these T cells are not known at present, therapeutic strategies aiming at common effector pathways, in particular cytokine secretion, may be more feasible in the near future. We have studied the influence of the isoenzyme-specific phosphodiesterase inhibitor rolipram on the proliferation and cytokine secretion of human myelin basic protein-specific T cell clones. The inhibition of proliferation correlated with interference with the IL-2/IL-2 receptor system, while the effects of rolipram on several T helper 1-(TNF-alpha, TNF-beta, IFN-gamma) and T helper 2-like cytokines (IL-4, IL-13) as well as IL-10 revealed an interesting drug profile, with preferential inhibition of TNF-beta, TNF-alpha and IL-10. This profile suggest that rolipram differs from other currently used immunomodulatory drugs.

Alterations of second messenger systems in the rat brain after 6-hydroxydopamine lesions of the medial forebrain bundle

We studied the sequential changes in second messenger systems in the striatum and substantia nigra (SN) after 6-hydroxydopamine lesions of the medial forebrain bundle in rats. The animals were unilaterally lesioned in the medial forebrain bundle and the brains were analyzed at 1, 2, 4 and 8 weeks postlesion. [3H]Phorbol-12, 13-dibutyrate (PDBu), [3H]forskolin and [3H]rolipram were used to label protein kinase C (PKC), adenylyl cyclase and calcium/calmodulin-independent cyclic-AMP phosphodiesterase, respectively. The degeneration of nigrostriatal pathway produced a significant increase in [3H]PDBu binding in the ventromedial part of the ipsilateral striatum from 2 to 8 weeks postlesion. In the contralateral side, [3H]PDBu binding showed a transient increase in the SN only 4 weeks after lesioning. [3H]Forskolin binding showed a significant increase in the ipsilateral and contralateral striatum from 2 to 4 weeks postlesion. In the ipsilateral SN, a significant increase in [3H]forskolin binding was observed at 4 weeks after lesioning. However, no significant change in [3H]forskolin binding was observed in the contralateral SN during postlesion. On the other hand, [(3)H]rolipram binding showed no conspicuous alteration in the brain during postlesion. These results demonstrate that rats made hemiparkinsonism by unilateral 6-hydroxydopamine injection have a significant increase in [3H]PDBu and [3H]forskolin binding in the striatum and/or SN, whereas no significant change in [3H]rolipram binding is observed in these areas during postlesion. Our findings also suggest that the increase in [3H]forskolin binding is more pronounced than that in [3H]PDBu binding in the brain after unilateral 6-hydroxydopamine injection. Thus, our studies may provide valuable information concerning degeneration of the nigrostriatal pathway such as Parkinson's disease.

Lymphocyte suppression by rolipram with other immunosuppressive drugs

Pentoxifylline, a nonselective phosphodiesterase inhibitor, has immunomodulatory activity in vitro and in vivo and potentiates the suppressive effects of glucocorticoids and cyclosporine on lymphocyte proliferation in vitro. Since phosphodiesterase isotypes 3 and 4 predominate in lymphocytes, the authors measured the suppressive effect of rolipram alone and in combination with low concentrations of methylprednisolone and calcineurin enzyme inhibitors, compared to that of pentoxifylline on mitogen-stimulated lymphocyte proliferation. The percent inhibition of 3H-thymidine incorporation by both 10(-5) and 10(-8) mol/L concentrations of rolipram were significantly greater than that by both 10(-4) mol/L pentoxifylline and 10(-8) mol/L methylprednisolone. The percent inhibition by the combination of 10(-5), but not 10(-6), mol/L rolipram and methylprednisolone was significantly greater than that by 10(-4) mol/L pentoxifylline and methylprednisolone. Potentiation of the suppressive effects of cyclosporine and tacrolimus by rolipram was less consistent. Measurement of cell culture supernatant concentrations of interferon gamma and interleukin-10 indicate that one of the mechanisms underlying the immunosuppressive activity of rolipram is a significantly disproportionate inhibition of the proinflammatory cytokine, interferon gamma.

The role of tumour necrosis factor-alpha (TNF-alpha) in fever and the acute phase reaction in rabbits

We investigated the role of tumour necrosis factor-alpha (TNF-alpha) in fever and the acute phase reaction using a specific type-IV phosphodiesterase inhibitor, rolipram, that inhibits the production of TNF-alpha. The body temperatures and serum iron concentrations of rabbits were measured following injections of lipopolysaccharide (LPS) or Staphylococcus aureus (S. aureus) with either rolipram, diclofenac sodium or the appropriate control solutions. Rolipram significantly (P<0.05) inhibited the first phase of both LPS and Staphylococcal fever, but had no effect on the second phase. The fall in serum iron concentration was not significantly affected by the injection of rolipram together with LPS or S. aureus. These results suggest that TNF-alpha is a pyrogen that plays a role during the first phase of fever, at least. However, TNF-alpha appears not to mediate the fall in serum iron concentration during the acute phase reaction.

Protection by a cyclic AMP-specific phosphodiesterase inhibitor, rolipram, and dibutyryl cyclic AMP against Propionibacterium acnes and lipopolysaccharide-induced mouse hepatitis

OBJECTIVE AND DESIGN

To study the effect of cellular cAMP-increasing agents on Propionibacterium acnes (P. acnes) and lipopolysaccharide (LPS)-induced mouse hepatitis.

MATERIAL

Male BALB/c mice were used. Macrophages/Kupffer cells isolated from P. acnes-primed murine liver were used for the in vitro study.

TREATMENT

Type IV phosphodiesterase (PDE)-specific inhibitor, rolipram, was administered (10, 30 mg/kg, p. o.). Dibutyryl cyclic AMP (dbcAMP) was injected (10, 100 mg/kg, i.p.) into the mice.

METHOD

Plasma TNFalpha estimated by the use of an L-929 cell cytotoxic assay and plasma transaminase activities were measured for the in vivo study. The LPS-induced production of TNFalpha in vitro from the cultured macrophage/Kupffer cells was determined by ELISA.

RESULTS

Rolipram suppressed the elevation of plasma transaminases induced by injection of LPS, and dbcAMP had a tendency to suppress them. Both agents attenuated the LPS-induced release of TNFalpha in vivo, and suppressed the TNFalpha production from the cultured macrophage/Kupffer cells.

CONCLUSIONS

These results suggest that rolipram and dbcAMP have potential to inhibit TNFalpha production from activated macrophage/Kupffer cells, and it may be partially involved in the protecting effect in the P. acnes/LPS hepatitis model.

Rolipram inhibits staphylococcal enterotoxin B-mediated induction of the human skin-homing receptor on T lymphocytes

The cutaneous lymphocyte-associated antigen defines T lymphocytes with cutaneous tropism under inflammatory conditions. Bacterial infections participate in cutaneous inflammations, such as atopic dermatitis or psoriasis. Bacterial superantigens, such as staphylococcal enterotoxin B, can activate peripheral blood mononuclear cells to induce effector T cells bearing the T cell skin homing receptor cutaneous lymphocyte-associated antigen via enhancement of interleukin-12 production. We have identified and characterized the anti-inflammatory effects of different phosphodiesterase inhibitors on this system. Our data indicate that the selective type 4 phosphodiesterase inhibitor rolipram inhibits the Staphylococcal enterotoxin B-mediated generation of cutaneous lymphocyte-associated antigen positive CD3+ cells from peripheral blood mononuclear cells by reducing interleukin-12 production in a concentration-dependent manner. Conversely, type 3 phosphodiesterase or type 5 phosphodiesterase selective inhibitors were not effective. The rolipram inhibitory effect was on interleukin-12 production, as exogenously added interleukin-12 could revert rolipram suppression. These results suggest that selective type 4 phosphodiesterase inhibition may have beneficial effects on T cell mediated skin inflammatory processes characterized by the presence of bacterial infections, that are thought to exacerbate ongoing skin inflammation.

Treatment with BBB022A or rolipram stabilizes the blood-brain barrier in experimental autoimmune encephalomyelitis: an additional mechanism for the therapeutic effect of type IV phosphodiesterase inhibitors

We examined the treatment effects of two structurally distinct phosphodiesterase type IV (PDE IV) inhibitors, BBB022 and rolipram, in murine and rat models of experimental autoimmune encephalomyelitis (EAE). Based on our data, we propose a mechanism of action which may supplement immunomodulatory effects of PDE IV inhibitors. In particular, PDE inhibitors promote elevation of intracellular cAMP levels, increasing the electrical resistance of endothelial monolayers by stabilizing intercellular junctional complexes. Such an effect on central nervous system (CNS) vascular endothelium has the potential to reduce disease severity in EAE, because both inflammatory cells and humoral factors readily cross a disrupted blood-brain barrier (BBB). In this report, we demonstrate the capacity of BBB022 and rolipram to decrease clinical severity of EAE. further, PDE IV inhibitors significantly reduced BBB permeability in the spinal cords of mice with EAE. These results provide evidence that PDE IV-inhibitors may exert therapeutic effects in EAE by modifying cerebrovascular endothelial permeability, reducing tissue edema as well as entry of inflammatory cells and factors.

Pharmacological modulation of secondary mediator systems--cyclic AMP and cyclic GMP--on inflammatory hyperalgesia

1. The objective of the present paper was to evaluate the relevance of neuronal balance of cyclic AMP and cyclic GMP concentration for functional regulation of nociceptor sensitivity during inflammation. 2. Injection of PGE2 (10-100 ng paw-1) evoked a dose-dependent hyperalgesic effect which was mediated via a cyclic AMP-activated protein kinase (PKA) inasmuch as hyperalgesia was blocked by the PKA inhibitor H89. 3. The PDE4 inhibitor rolipram and RP73401, but not PDE3 and PDE5 inhibitors potentiated the hyperalgesic effects of PGE2. The hyperalgesic effect of dopamine was also enhanced by rolipram. Moreover, rolipram significantly potentiated hyperalgesia induced by carrageenan, bradykinin, TNF alpha, IL-1 beta, IL-6 and IL-8. This suggests that neuronal cyclic AMP mediates the prostanoid and sympathetic components of mechanical hyperalgesia. Moreover, in the neuron cyclic AMP is mainly metabolized by PDE4. 4. To examine the role of the NO/cyclic GMP pathway in modulating mechanical hyperalgesia, we tested the effects of the soluble guanylate cyclase inhibitor, ODQ. This substance counteracts the inhibitory effects of the NO donor, SNAP, on the hyperalgesia induced by PGE2. 5. The ODQ potentiated hyperalgesia induced by carrageenan, bradykinin, TNF alpha, IL-1 beta, IL-6 and IL-8. In contrast, ODQ had no significant effect on the hyperalgesia induced by PGE2 and dopamine. This indicates that the hyperalgesic cytokines may activate soluble guanylate cyclase, which down-regulate the ability of these substances to cause hyperalgesia. This event appears not to be mediated by prostaglandin or dopamine. 6. In conclusion, the results presented in this paper confirm an association between (i) hyperalgesia and elevated levels of cyclic AMP as well as (ii) antinociception and elevated levels of cyclic GMP. The intracellular levels of cyclic AMP that enhance hyperalgesia are controlled by the PDE4 isoform and appear to result in activation of protein kinase A whereas the intracellular levels of cyclic GMP results from activation of a soluble guanylate cyclase.

Effects of rolipram and cilostamide on renal functions and cyclic AMP release in anesthetized dogs

The present study was undertaken to examine whether phosphodiesterases III and IV regulate renal cAMP level and whether inhibition of these enzymes influences renal functions in anesthetized dogs. The intrarenal arterial infusion of rolipram (0.1, 0.3, and 1 microgram/kg/min), a selective phosphodiesterase IV inhibitor, increased renal blood flow, glomerular filtration rate, urine flow rate, and urinary Na+ excretion with elevating arterial and renal venous plasma cAMP concentrations and urinary cAMP excretion. However, cilostamide (0.1, 0.3, and 1 microgram/kg/min), a selective phosphodiesterase III inhibitor, did not affect the values of these parameters. Indomethacin (3 mg/kg i.v. bolus and 1 mg/kg/min i.v. infusion), a cyclooxygenase inhibitor, reduced the basal arterial and renal venous plasma cAMP concentrations and blunted the rolipram-induced elevation of cAMP concentrations and urinary cAMP excretion. The effects of rolipram on renal hemodynamics and urine formation were attenuated in the presence of indomethacin. These results suggest that in the dog kidney in vivo, 1) phosphodiesterase IV, but not phosphodiesterase III, participates in degradation of cAMP and 2) the inhibition of phosphodiesterase IV enhances glomerular filtration and urinary Na+ excretion, the responses of which depend in part on indomethacin-susceptible (prostaglandin-mediated, probably) control of basal cAMP level.

Effects of mitogen-activated protein kinase inhibitors or phosphodiesterase inhibitors on interleukin-1-induced cytokines production in synovium-derived cells

The effects of mitogen-activated protein (MAP) kinase inhibitors or phosphodiesterase (PDE) inhibitors on interleukin (IL)-1-induced cytokines production in synovium-derived cells were investigated. Human synoviocyte (HS) or synovial sarcoma (SW982) stimulated by IL-1beta (100 ng/ml) produced various cytokines including IL-6, IL-8, GROalpha, VEGF, basic FGF and tumor necrosis factor alpha (TNFalpha) in vitro. SB202190 or SB203580, an inhibitor of p38 MAP kinase, inhibited all cytokines production in both cells. PD98059, an inhibitor of MAP kinase kinase (MEK), inhibited IL-6, IL-8 and basic FGF production in HS and all cytokines production except basic FGF in SW982. However, many of its effects were weaker than those of SB202190 or SB203580. Quazinone, an inhibitor of cyclic GMP-inhibited PDE, scarcely affected cytokines production in both cells. Rolipram or R0201724, an inhibitor of cyclic AMP-specific PDE, inhibited IL-8 and basic FGF production in HS and TNFalpha production in SW982, however, it enhanced the other cytokines production in SW982. These results suggest that the activation of MAP kinase cascade may be important for IL-1-induced cytokines production in synovium-derived cells. On the other hand, the role of cyclic AMP may be dependent on cell and cytokine types.

The effect of vesnarinone on TNF alpha production in human peripheral blood mononuclear cells and microglia: a preclinical study for the treatment of multiple sclerosis

Vesnarinone (OPC-8212) is a synthetic quinolinone derivative with inotropic and immunomodulatory effects. Vesnarinone has been shown to inhibit tumor necrosis factor-alpha (TNF alpha) produced by mitogen stimulated macrophages, and to inhibit phosphodiesterase (PDE) type III in cardiac muscle. TNF alpha and interferon-gamma (IFNgamma) have been implicated in the pathogenesis of autoimmune diseases, and both cytokines are targets for therapeutic intervention. IFNgamma can enhance autoimmune disease through direct effects, and indirectly by priming macrophages to produce TNF alpha. In this study, we demonstrate that while vesnarinone enhances basal TNF alpha levels, it inhibits TNF alpha production in peripheral blood mononuclear cells from multiple sclerosis (MS) patients and healthy donors stimulated with lipopolysaccharide (LPS) or primed with IFNgamma and stimulated with suboptimal doses of LPS. In addition, vesnarinone inhibited TNF alpha production in primary adult human microglial cultures. However, in contrast to rolipram, another TNF alpha inhibiting agent, vesnarinone failed to inhibit TNF alpha production by myelin basic protein specific T-cell lines. As oral TNF inhibitors are currently being considered in the USA for clinical application in MS, the implications of our findings on the development of vesnarinone for treatment of MS are discussed.

The role of brain cytokines in mediating the behavioral and neuroendocrine effects of intracerebral mycoplasma fermentans

Intracerebral administration of Mycoplasma fermentans (MF), a small microorganism that has been found in the brain of some AIDS patients, induces behavioral and neuroendocrine alterations in rats. To examine the role of tumor necrosis factor-alpha (TNFalpha) and interleukin-1 (IL-1) in mediating these effects we measured MF-induced expression of TNFalpha and IL-1beta mRNA in various brain regions, and the effects of TNFalpha synthesis blockers and IL-1 receptor antagonist (IL-1ra) on MF-induced sickness behavior and adrenocortical activation. Intracerebroventricular (i.c.v.) administration of heat-inactivated MF induced the expression of both TNFalpha and IL-1beta mRNA in the cortex, dorsal hippocampus, amygdala, and hypothalamus. Pre-treatment of rats with either TNFalpha synthesis blockers, pentoxifylline or rolipram, or with IL-1ra did not attenuate MF-induced anorexia, body weight loss, and suppression of social behavior. However, simultaneous administration of both pentoxifylline and IL-1ra markedly attenuated MF-induced anorexia and body weight loss, but had no effect on the suppression of social behavior. Pre-treatment with pentoxifylline, but not with IL-1ra, significantly attenuated MF-induced corticosterone (CS) secretion. Together, these findings indicate that both TNFalpha and IL-1 participate, in a complementary manner, in mediating some of the behavioral effects of MF, whereas only TNFalpha, but not IL-1, is involved in mediating MF-induced adrenocortical activation. We suggest that cytokines within the brain are involved in mediating at least some of the neurobehavioral and neuroendocrine abnormalities that may be produced by MF in AIDS patients.

Effects of NKH477 on renal functions and cyclic AMP production in anesthetized dogs

The present study was undertaken to evaluate the effects of an adenylate cyclase activator N,N-dimethyl-beta-alanine[3R-(3alpha, 4alphabeta, 5beta, 6beta, 6aalpha, 10alpha, 10abeta, 10balpha)]-5(acetyloxy)-3-ethenyldodecahydro-10, 10b-dihydroxy-3, 4a, 7, 7, 10a-pentamethyl-1-oxo-1H-naphtho [2,1-b] pyran-6-yl ester hydrochloride (NKH477) on renal functions and cyclic AMP production in the dog kidney. The intrarenal arterial infusion of NKH477 (30, 100 and 300 ng kg(-1) min(-1)) increased renal blood flow, glomerular filtration rate, urine flow rate, urinary Na+ and cyclic AMP excretion, fractional Na+ excretion and arterial and renal venous plasma cyclic AMP concentrations in a dose-dependent manner. The intrarenal arterial infusion of rolipram (0.3 microg kg(-1) min(-1)), a cyclic AMP-specific phosphodiesterase inhibitor, also caused the same renal responses as NKH477. The increasing effects of NKH477 on renal blood flow, fractional Na+ excretion and renal venous plasma cyclic AMP concentration were facilitated in the presence of rolipram. NKH477 reduced glomerular filtration rate and filtration fraction in the presence of rolipram. The increasing effects of NKH477 on urine flow rate and urinary Na+ excretion were not affected by rolipram. The present results suggest that NKH477 increases glomerular filtration and suppresses tubular sodium reabsorption through activation of cyclic AMP production, and thereby induces natriuresis. The results also demonstrate that renal cyclic AMP level during the activation of adenylate cyclase is regulated by phosphodiesterase IV in both the vascular and tubular sites.

Cyclic AMP phosphodiesterases are localized in regions of the mouse brain associated with reinforcement, movement, and affect

Four cyclic AMP-specific, rolipram-inhibited phosphodiesterases (PDE4s) have been identified in mammals; all four are homologs of dunce, a gene required for learning and memory in Drosophila. To determine the distribution of PDE4s in the mammalian brain, specific antibodies were generated against the proteins encoded by each of three dunce homologs PDE4A, PDE4B, and PDE4D in the mouse. On Western blots, these antibodies recognized multiple protein species in all brain regions studied. Immunohistochemical studies showed that both cell bodies and neuropil were well labeled in selected regions throughout the brain. Immunoreactivity for PDE4A was found predominantly in the anterior olfactory nucleus, subiculum, layer V pyramidal neurons from the cerebral cortex, and corticospinal tracts. By contrast, anti-PDE4B-labeled neurons were observed in the inferior olive, the paraventricular and supraoptic nuclei of the hypothalamus, and in the ventral striatum. Regions of neuropil containing high levels of PDE4B immunoreactivity included the cerebellar molecular layer, globus pallidus, nucleus accumbens, and substantia nigra. Anti-PDE4D antibody distinctly labeled cerebellar Purkinje cells as well as neurons in the medial habenula and thalamic nuclei. Fibers in the fasciculus retroflexus, interpeduncular nuclei, and periaqueductal gray were also stained with this antibody. These findings indicate that the distribution of PDE4s in the brain is remarkably segregated, and suggest that each of these enzymes has a unique functional role. Furthermore, the data support the notion that rolipram, the PDE4-specific inhibitor that acts as an antidepressant in humans, may mediate its behavioral effects through PDE4B, which is highly localized to neural pathways known to underlie reward and affect in mammals.

Behavioral effects of family-selective inhibitors of cyclic nucleotide phosphodiesterases

The effects of family selective inhibitors of phosphodiesterase (PDEI, PDE2, PDE3, PDE4, and PDE5) on the behavior of rats under either a differential-reinforcement-of-low-rate (DRL) 72-s schedule or a variable-interval (VI) 30-s schedule were determined; previous work has shown that antidepressant drugs increase reinforcement rate under long DRL schedules. The PDE4-selective inhibitor rolipram (0.03-0.1 mg/kg) reduced response rate and increased reinforcement rate under the DRL schedule in a dose-dependent manner; similar effects were observed with the tricyclic antidepressant drug desipramine (3-10 mg/kg). Both of these drugs produced biphasic effects on behavior maintained under the VI schedule, increasing response rate at the lower doses tested (rolipram: 0.003 mg/kg; desipramine: 0.03 mg/kg) and decreasing response rate at higher doses (rolipram: 0.1 mg/kg; desipramine: 0.3-18 mg/kg). Of the other PDE inhibitors tested, only the PDE5-selective inhibitor zaprinast (10 mg/kg) produced an antidepressant-like effect on DRL behavior. However, in contrast to the biphasic effects of rolipram and desipramine on VI behavior, zaprinast produced monotonic decreases in response rate (10-30 mg/kg). The PDE2-selective inhibitor trequinsin produced biphasic effects on response rate under the VI schedule, increasing rates at low doses (3-5.6 mg/kg) and decreasing rates at higher doses (18-30 mg/kg). Trequinsin also reduced response rate under the DRL schedule (30 mg/kg); however, the reduction in response rate was not accompanied by increased reinforcement rate. The PDE3-selective inhibitor milrinone (1-10 mg/kg) tended to increase response rates under both schedules while the PDE1-selective inhibitor vinpocetine did not affect behavior at the dose range tested (1-30 mg/kg). These findings suggest that inhibition of PDE4 results in a rather unique pattern of behavioral effects, most notably an antidepressant-like effect on DRL behavior. It remains to be determined if a similar effect produced by zaprinast also implicates PDE5 in the mediation of antidepressant activity or represents an effect of this drug on PDE4 activity at high doses.

Consequences for rolipram inhibition

The cAMP-specific phosphodiesterase (PDE) HSPDE 4A4B(pde46) selectively bound SH3 domains of SRC family tyrosyl kinases. Such an interaction profoundly changed the inhibition of PDE4 activity caused by the PDE4-selective inhibitor rolipram and mimicked the enhanced rolipram inhibition seen for particulate, compared with cytosolic pde46 expressed in COS7 cells. Particulate pde46 co-localized with LYN kinase in COS7 cells. The unique N-terminal and LR2 regions of pde46 contained the sites for SH3 binding. Altered rolipram inhibition was triggered by SH3 domain interaction with the LR2 region. Purified LYN SH3 and human PDE4A LR2 could be co-immunoprecipitated, indicating a direct interaction. Protein kinase A-phosphorylated pde46 remained able to bind LYN SH3. pde46 was found to be associated with SRC kinase in the cytosol of COS1 cells, leading to aberrant kinetics of rolipram inhibition. It is suggested that pde46 may be associated with SRC family tyrosyl kinases in intact cells and that the ensuing SH3 domain interaction with the LR2 region of pde46 alters the conformation of the PDE catalytic unit, as detected by altered rolipram inhibition. Interaction between pde46 and SRC family tyrosyl kinases highlights a potentially novel regulatory system and point of signaling system cross-talk.

Protective effect of the type IV phosphodiesterase inhibitor rolipram in EAU: protection is independent of IL-10-inducing activity

PURPOSE

Experimental autoimmune uveoretinitis (EAU) is a cell-mediated model of retinal autoimmunity that is negatively regulated by interleukin (IL)-10. The antidepressant drug rolipram, a type IV phosphodiesterase inhibitor, enhances IL-10 production by monocyte/macrophages. The effect of rolipram on induction of EAU and its associated immunologic responses was investigated.

METHODS

Mice were challenged for EAU induction by immunization with the retinal antigen interphotoreceptor retinoid-binding protein (IRBP) or by adoptive transfer of uveitogenic T cells and were treated with rolipram. EAU severity and immunologic responses to IRBP were analyzed. In addition, the effect of rolipram added to the culture on antigen-driven responses of primed lymph node cells was tested.

RESULTS

Rolipram treatment from days -1 to 7 after immunization (afferent phase) was not protective, but severity of EAU was reduced to 50% by treatment from days 8 to 16 after immunization or when EAU was induced by adoptive transfer (efferent phase). Antigen-specific proliferation and interferon (IFN)-gamma production ex vivo by lymph node cells of protected mice were not reduced. However, the addition of rolipram directly to the culture suppressed IRBP-driven proliferation and IFN-gamma production by primed lymph node cells. Freshly explanted lymph node cells of treated mice showed inhibition of IFN-gamma mRNA but no parallel enhancement of IL-10 mRNA by quantitative polymerase chain reaction. Rolipram inhibited EAU in IL-10 knockout mice equally well compared with controls and suppressed their primed lymph node cells in culture.

CONCLUSIONS

Rolipram appears to inhibit the expansion and effector function of uveitogenic T cells, raising the possibility that it may be useful for treatment of established disease. Contrary to expectations based on in vitro studies, the protective effects in vivo appear to be independent of IL-10. The observation that suppression of antigen-specific responses is demonstrable only in the physical presence of the drug suggests that, in a clinical setting, continuous administration of rolipram might be needed to sustain its therapeutic effect.

A comparison of the inhibitory activity of PDE4 inhibitors on leukocyte PDE4 activity in vitro and eosinophil trafficking in vivo

1. Phosphodiesterase (PDE) 4 inhibitors have been shown to inhibit eosinophil PDE4 activity in vitro and accumulation of eosinophils in experimental airways inflammation. However, direct effects on eosinophil trafficking have not been studied in detail and it is not known if activity in vitro translates into efficacy in vivo. In the present study, we compared the activity of five PDE4 inhibitors in vitro and against trafficking of (111)In-eosinophils in cutaneous inflammation in the guinea-pig. 2. The rank order of potency for inhibition of PDE4 activity in guinea-pig eosinophil, neutrophil and macrophage, and human neutrophil lysates was RP73401 > SB207499 >CDP840 > rolipram > LAS31025. On TNFalpha production by human PBMC, all inhibitors with the exception of rolipram showed potency similar to their effect on neutrophil lysates. 3. In a brain cerebellum binding assay, the rank order of potency at displacing [3H]-rolipram was RP73401 > rolipram > SB207499 > CDP840 > LAS30125. 4. Trafficking of (111)In-eosinophils to skin sites injected with PAF, ZAP or antigen in sensitized sites was inhibited by oral administration of all PDE4 inhibitors. The rank order of potency was RP73401 = rolipram > LAS31025 > SB207499 > CDP840. 5. With the exception was RP73401, which was the most potent compound in all assays, there was no clear relationship between activity of PDE4 inhibitors in vitro and capacity to inhibit eosinophil trafficking in vivo. Thus, we conclude that in vitro activity of PDE4 inhibitors does not predict in vivo efficacy in an experimental model of eosinophil trafficking.

Effects of XT-44, a phosphodiesterase 4 inhibitor, in osteoblastgenesis and osteoclastgenesis in culture and its therapeutic effects in rat osteopenia models

We have reported that denbufylline, a phosphodiesterase 4 (PDE4) inhibitor, inhibits bone loss in Walker256/S tumor-bearing rats, suggesting therapeutic potentiality of a PDE4 inhibitor in osteopenia. In the present study, effects of a new PDE4 inhibitor, 1-n-butyl-3-n-propylxanthine (XT-44), in bone were evaluated in cell cultures and animal experiments. In rat bone marrow culture, XT-44 stimulated mineralized-nodule formation, whereas it inhibited osteoclast-like cell formation in mouse bone marrow culture. In Walker256/S-bearing rats (6-week-old female Wistar Imamichi rats), rapid decrease in bone mineral density (BMD) was prominent, and oral administration of XT-44 (0.3 mg/kg, every 2 days) inhibited the decrease in BMD. In the second animal experiment, female Wistar rats (6-week-old) were sciatic neurectomized, and XT-44 was orally administered to these rats every 2 days for 4 weeks. XT-44 administration (0.3 mg/kg) recovered BMD in these neurectomized animals. Furthermore, 19-week-old, female Wistar rats were ovariectomized (OVX), and 15 weeks after surgery, these rats were orally administered XT-44 every 2 days for 8 weeks. XT-44 treatment (1 mg/kg) increased the BMD of OVX rats. These results indicate that XT-44 could be a candidate as a therapeutic drug for treating osteopenia including osteoporosis.

Effects of phosphodiesterase inhibitors on cytokine production by microglia

Type III and IV phosphodiesterase inhibitors (PDEIs) have recently been shown to suppress the production of TNF-alpha in several types of cells. In the present study, we have shown that all the types of PDEIs, from type I- to V-specific and non-specific, suppress the production of TNF-alpha by mouse microglia stimulated with lipopolysaccharide (LPS) in a dose-dependent manner. Certain combinations of three different types of PDEIs synergistically suppressed TNF-alpha production by microglia at a very low concentration (1 microM). Since some PDEIs reportedly pass through the blood-brain barrier (BBB), the combination of three PDEIs may be worth trying in neurological diseases, such as multiple sclerosis and HIV-related neurological diseases in which TNF-alpha may play a critical role. Some PDEIs also suppressed interleukin-I (IL-I) and IL-6 production by mouse microglia stimulated with LPS. In contrast, the production of IL-10, which is known to be an inhibitory cytokine, was upregulated by certain PDEIs. The suppression of TNF-alpha and induction of IL-10 were confirmed at the mRNA level by RT-PCR. PDEIs may be useful anti-inflammatory agents by downregulating inflammatory cytokines and upregulating inhibitory cytokines in the central nervous system. (CNS).

Type IV phosphodiesterase inhibition in experimental allergic encephalomyelitis of Lewis rats: sequential gene expression analysis of cytokines, adhesion molecules and the inducible nitric oxide synthase

Type IV phosphodiesterase inhibitors are able to suppress EAE. To investigate the effects of this therapy in the central nervous system, we serially analyzed from days 7 to 17 postinoculation the gene expression pattern of tumor necrosis factor (TNF), lymphotoxin, interferon-gamma, interleukin-1beta, the inducible nitric oxide synthase (iNOs), interleukin-10, the vascular cell adhesion molecule-1 (VCAM-1) and the intercellular adhesion molecule-1 (ICAM-1) in the spinal cord of Lewis rats with actively induced EAE, treated with Rolipram. Treated rats had a delayed and milder disease, and reduced numbers of infiltrates in the nervous tissue. The gene expression profile was similar to that of untreated rats, although delayed, with no evidence of IL-10 upregulation during the observation period. The delayed inflammation was not associated with changes in the expression of VCAM-1 and ICAM-1. In peripheral blood mononuclear cells, TNF mRNA levels were decreased and interleukin-10 was unchanged. This therapy did not alter the proliferative ability of T lymphocytes against myelin basic protein. The encephalitogenic potential of splenocytes from treated animals was also unaffected. The high levels of both iNOs mRNA and nitric oxide (NO) found before the appearance of clinical signs, suggests that NO generation might be a contributing factor to the therapeutic benefit achieved by Rolipram in the rat.

Effects of interleukin-10 and modulators of cyclic AMP formation on endotoxin-induced inflammation in rat lung

The aim of this study was to investigate the effects of IL-10, a cell permeable analogue of cyclic AMP, dibutyryl-cAMP (db-cAMP), modulators of intracellular cyclic AMP such as phosphodiesterase (PDE) inhibitors and a beta 2-adrenoceptor agonist, salmeterol, on pulmonary inflammation following acute lung injury induced by endotoxin exposure in rats. Pulmonary inflammation was induced in adult Wistar rats by a 60-min exposure to endotoxin (lipopolysaccharide, LPS, 100 micrograms/mL). 4 h later bronchoalveolar lavage (BAL) was performed. The PDE inhibitors, rolipram (3 and 5 mg/kg) and theophylline (30 and 100 mg/kg) inhibited neutrophil recruitment, TNF-alpha release and cellular activation in BAL. Salmeterol (0.5 mg/mL) and IL-10 (0.1 microgram) only inhibit TNF-alpha increase in the BAL fluid and db-AMPc (2.5 micrograms/rat) was ineffective. The present data show that the selective PDE4 inhibitor, rolipram, and the non-selective PDE inhibitor, theophylline, markedly reduced the pulmonary inflammation associated with acute lung injury in the rat. These effects may be mediated in part by IL-10 rather than by cyclic AMP, as demonstrated by the potent inhibitory activity of exogenous IL-10 on the increase in TNF-alpha release in BAL fluid of rats exposed to LPS.

Prevention by rolipram of concanavalin A-induced T-cell-dependent hepatitis in mice

Rolipram is a type IV phosphodiesterase inhibitor endowed with powerful immunomodulatory properties. In this study, we evaluated the effects of this drug on the development of the T-cell-mediated hepatitis inducible in mice by concanavalin A. The results indicated that prophylactic treatment with either 5 or 10 mg/kg rolipram injected intraperitoneally 24 h and 1 h prior to intravenous (i.v.) challenge with 20 mg/kg concanavalin A successfully ameliorated serological and histological signs of liver damage, so that the treated mice showed lower transaminase levels in the plasma and milder mononuclear cell infiltration of the liver as compared to vehicle-treated controls. Moreover, this effect was associated with profound modifications of circulating levels of cytokines released after concanavalin A injection, with the blood levels of interferon-gamma and tumor necrosis factor-alpha being significantly lower and those of interleukin-10 higher than those of the control mice. In particular, the increased blood levels of interleukin-10 might play an important role in the anti-hepatitic effects of rolipram as coadministering this compound with anti-interleukin-10 monoclonal antibody significantly reduced its anti-inflammatory action. These results suggest that rolipram may be useful in the clinical setting for the treatment of cell-mediated immunoinflammatory diseases such as immunoinflammatory hepatitis.

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) in the ferret

Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) has been investigated in the ferret. The PDE IV inhibitors studied were: RS14203, R-rolipram and CT-2450 (i.e. (R)-N-[4-[1-(3-cyclopentyloxy-4-methoxyphenyl)-2-(4-pyridyl)ethyl]phenyl ]N'-ethylurea), in addition to the less active enantiomers S-rolipram and CT-3405. Following oral administrations, different emetic profiles were observed with time. Emesis induced by RS14203 exhibited a dose-response relationship but no such relationship was seen for R-rolipram or CT-2450. The incidence of emesis was positively influenced by the dose of PDE IV inhibitors administered, allowing a rank order of potency: RS14203 > R-rolipram > S-rolipram > CT-2450 > CT-3405. PDE IV inhibitor-induced emesis was abolished by the tachykinin NK1 receptor antagonist, CP-99,994. No peripheral release of substance P by PDE IV inhibitors seems to be involved in triggering the emetic reflex since L-743,310, which only has peripheral NK1 receptor antagonist activity, was without effect. The implication of 5-HT3 receptors in PDE IV inhibitor-induced emesis was variable. Our results suggest that the PDE IV inhibitors studied are mixed peripheral-central emetogens. PDE IV inhibition itself could be plausible mechanism of action of these agents. However, whether emesis is mediated via a specific isoform of PDE IV remains to be established.

Ontogeny of rolipram-sensitive, low-K(m), cyclic AMP-specific phosphodiesterase in rat brain

The postnatal development of rolipram-sensitive, low-K(m), cyclic AMP-specific phosphodiesterase (PDE4) was investigated in discrete regions of rat brain using a PDE4 activity assay and immunoblot analyses with K116, a PDE4 antibody. The Vmax for cyclic AMP hydrolysis by PDE4 was lower at birth when compared to adult levels in cerebral cortex, cerebellum, and neostriatum. K(m) values for cyclic AMP hydrolysis by PDE4, in contrast, did not change throughout the observed period in any brain region tested. The developmental patterns for PDE4 were significantly different among the examined brain regions. PDE4 activity in olfactory bulb and hippocampus also was found to be lower at birth in comparison to adult levels. Immunoblot analyses showed that developmental patterns of PDE4 were significantly different for the various subtypes, and also varied substantially across brain regions. The results suggest that PDE4 might be differentially regulated by different ontogenetic events.

Reduced ischemia-reperfusion injury with rolipram in rat cadaver lung donors: effect of cyclic adenosine monophosphate

BACKGROUND

The perfusion of rat lungs retrieved from cadavers with a solution containing isoproterenol has been shown to ameliorate the ischemia-reperfusion injury seen in lungs retrieved after death, and this protective effect parallels increases in tissue cyclic adenosine monophosphate levels. In this study, we investigated the effect of rolipram, a phosphodiesterase inhibitor, on capillary permeability and lung cyclic adenosine monophosphate levels in lungs retrieved from circulation-arrested rats.

METHODS

Using an isolated perfused lung circuit, we retrieved lungs from circulation-arrested donor rats either ventilated with 100% oxygen or not ventilated for varying postmortem times. The lungs were reperfused with or without rolipram (2 micromol/L). The capillary filtration coefficient and wet to dry weight ratio, indicators of pulmonary vascular integrity, were determined, and tissue levels of adenine nucleotides and cyclic adenosine monophosphate were measured by high-performance liquid chromatography.

RESULTS

The capillary filtration coefficient was significantly reduced in nonventilated cadaver lungs reperfused with rolipram 120 minutes after death (p<0.05). Oxygen ventilation or reperfusion with rolipram had a similar effect on the capillary filtration coefficient. Cyclic adenosine monophosphate levels were significantly higher in rolipram-reperfused lungs retrieved 120 minutes after death in both oxygen-ventilated (p<0.01) and nonventilated (p<0.01) lungs.

CONCLUSIONS

In lungs from nonventilated, circulation-arrested donors, reperfusion with rolipram reduces the ischemia-reperfusion injury that may be due to intracellular cyclic adenosine monophosphate. Alteration of perfusate may have an impact on capillary leak caused by antecedent ischemia. Thus, rolipram may be a useful adjunct in the preservation of donor lungs retrieved after death.

The type IV phosphodiesterase inhibitors, Ro 20-1724 and rolipram, block the initiation of cocaine self-administration

The hypothesis that the selective activation of cyclic AMP (cAMP) signal transduction pathways will suppress the initiation of cocaine self-administration was examined in this investigation. To test this hypothesis, the effects of the administration of the cAMP-specific (type IV) phosphodiesterase inhibitors, rolipram and Ro 20-1724, on cocaine self-administration were determined. The effects of Ro 20-1724 treatment on operant responding for food also were examined. Both cocaine and food were delivered following a fixed-ratio 5 schedule. A significant increase in the latency for the delivery of the first cocaine infusion and a reduction in the number of infusions obtained per session were produced by treatment with either rolipram or Ro 20-1724. Similar effects on responding for food were seen with Ro 20-1724 administration. Responding after drug-induced delays tended to be at control levels. These results suggest that cAMP-specific phosphodiesterase inhibitors may inhibit the initiation of operant responding for either cocaine or food. However, the extent to which these actions involve specific effects on central motivational systems as opposed to other mechanisms remains to be determined.

Does tumor necrosis factor-alpha (TNF-alpha) contribute to myocardial reperfusion injury in anesthetized rats?

1. This study examined the potential role of tumor necrosis factor-alpha (TNF-alpha) in myocardial ischemia-reperfusion injury using an anesthetized rat model of myocardial infarction. 2. The key endpoints were infarct size and serum TNF-alpha levels (measured by a specific ELISA technique). 3. Three groups of rats were studied: vehicle controls (n=6); positive controls for infarct size reduction (ischemic preconditioning; n=6); and a group treated with the selective inhibitor of PDE-IV and TNF-alpha production, rolipram (1 mg/kg i.v. 10-min prereperfusion + 1 microg/kg per minute through 1-hr reperfusion, n=6). 4. Baseline preischemia levels of serum TNF-alpha were low (approximately 0.1 nM) and showed a trend for further reduction in all treatment groups at 1 min and 3 hr into the postischemia reperfusion period. 5. Infarct size (68+/-2% of the ischemic area in controls) was significantly reduced (41% decrease) by preconditioning, but was unchanged in rolipram-treated animals. 6. Collectively, these data argue against an important role for TNF-alpha in lethal reperfusion injury in this rat model of myocardial infarction.

Imaging of cAMP-specific phosphodiesterase-IV: comparison of [11C]rolipram and [11C]Ro 20-1724 in rats

The phosphodiesterase type IV (PDEIV) family of enzymes contributes to the metabolism of cAMP formed by the stimulation of beta-adrenergic, A2-adenosine, and H2-histamine receptors in the brain. Disturbances in cAMP-mediated signaling have been implicated in several neuropsychiatric disorders, and there is evidence that increasing cAMP levels through PDEIV inhibition improves the symptoms of these disorders. In the present study, the selective PDEIV inhibitors rolipram and Ro 20-1724, labeled with C-11, were evaluated in vivo in rats, as potential radioligands for imaging PDEIV enzymes with positron emission tomography (PET). Biodistribution experiments revealed a greater than threefold increased regional brain retention of [11C]rolipram as compared to [11C]Ro 20-1724. [nC]Rolipram uptake was higher in rat brain areas (e.g., cortical regions and olfactory system) showing higher expression of PDEIV enzymes, as determined previously using [3H]rolipram autoradiography or molecular genetic techniques. Binding of [n1C]rolipram and [11C]Ro 20-1724 was specific, since coadministration of high doses of unlabeled rolipram (10 mg/Kg, i.v.) or Ro 20-1724 (30 mg/Kg with [11C]rolipram and 10 mg/Kg with [11C]Ro 20-1724, i.v.) reduced radioactivity uptake in brain regions. Pretreatment with high doses of the PDEI selective inhibitor vinpocetine (10 mg/Kg, i.p., 15 min prior), or the noradrenaline reuptake inhibitor desipramine (10 mg/Kg, i.p., 30 min prior), or coinjection with the adenylyl cyclase activator forskolin (6.5 or 15 mg/Kg, i.v.), did not inhibit [11C]rolipram uptake in brain areas, suggesting binding selectivity for PDEIV enzymes. We conclude that [11C]rolipram, but not [11C]Ro 20-1724, is a promising radioligand for imaging the PDEIV enzymes with PET.

Release of cAMP gating by the alpha6beta4 integrin stimulates lamellae formation and the chemotactic migration of invasive carcinoma cells

The alpha6beta4 integrin promotes carcinoma in-vasion by its activation of a phosphoinositide 3-OH (PI3-K) signaling pathway (Shaw, L.M., I. Rabinovitz, H.H.-F. Wang, A. Toker, and A.M. Mercurio. Cell. 91: 949-960). We demonstrate here using MDA-MB-435 breast carcinoma cells that alpha6beta4 stimulates chemotactic migration, a key component of invasion, but that it has no influence on haptotaxis. Stimulation of chemotaxis by alpha6beta4 expression was observed in response to either lysophosphatidic acid (LPA) or fibroblast conditioned medium. Moreover, the LPA-dependent formation of lamellae in these cells is dependent upon alpha6beta4 expression. Both lamellae formation and chemotactic migration are inhibited or "gated" by cAMP and our results reveal that a critical function of alpha6beta4 is to suppress the intracellular cAMP concentration by increasing the activity of a rolipram-sensitive, cAMP-specific phosphodiesterase (PDE). This PDE activity is essential for lamellae formation, chemotactic migration and invasion based on data obtained with PDE inhibitors. Although PI3-K and cAMP-specific PDE activities are both required to promote lamellae formation and chemotactic migration, our data indicate that they are components of distinct signaling pathways. The essence of our findings is that alpha6beta4 stimulates the chemotactic migration of carcinoma cells through its ability to influence key signaling events that underlie this critical component of carcinoma invasion.

Rolipram, a type IV-specific phosphodiesterase inhibitor, facilitates the establishment of long-lasting long-term potentiation and improves memory

In an attempt to improve behavioral memory, we devised a strategy to amplify the signal-to-noise ratio of the cAMP pathway, which plays a central role in hippocampal synaptic plasticity and behavioral memory. Multiple high-frequency trains of electrical stimulation induce long-lasting long-term potentiation, a form of synaptic strengthening in hippocampus that is greater in both magnitude and persistence than the short-lasting long-term potentiation generated by a single tetanic train. Studies using pharmacological inhibitors and genetic manipulations have shown that this difference in response depends on the activity of cAMP-dependent protein kinase A. Genetic studies have also indicated that protein kinase A and one of its target transcription factors, cAMP response element binding protein, are important in memory in vivo. These findings suggested that amplification of signals through the cAMP pathway might lower the threshold for generating long-lasting long-term potentiation and increase behavioral memory. We therefore examined the biochemical, physiological, and behavioral effects in mice of partial inhibition of a hippocampal cAMP phosphodiesterase. Concentrations of a type IV-specific phosphodiesterase inhibitor, rolipram, which had no significant effect on basal cAMP concentration, increased the cAMP response of hippocampal slices to stimulation with forskolin and induced persistent long-term potentiation in CA1 after a single tetanic train. In both young and aged mice, rolipram treatment before training increased long- but not short-term retention in freezing to context, a hippocampus-dependent memory task.

Relaxing effects of cyclic GMP and cyclic AMP-enhancing agents on the long-lasting contraction to endothelin-1 in the porcine coronary artery

In the coronary circulation, endothelin-1 (ET-1) evokes spasms which are difficult to treat when the endothelial integrity is compromised. This study compares several classes of relaxing agents on already established contractions to ET-1 in an in vitro model using ring segments of the porcine left descending coronary artery (pLAD). All segments were precontracted with 10 nmol/L ET-1. The calcium channel blocker isradipine was 300 times more potent than verapamil, but was only a partial relaxant; the maximal relaxation obtained was 52 +/- 2% (n = 6). Atrial natriuretic peptide (ANP) was an equally potent relaxant of the ET-1 contraction; however, it too was an incomplete relaxant, maximal relaxation being < 60%. A 50% relaxation of the ET-1 contraction was obtained with 0.28 +/- 0.24 mumol/L ANP, n = 4 (IC50). Comparison of cyclic nucleotide analogues revealed a 30 times higher potency for 8-bromo-cyclic guanosine monophosphate (8-Br-cGMP)(IC50 44 +/- 11 mumol/L, n = 6) than for 8-bromo-cyclic adenosine monophosphate (8-Bi-cAMP) (IC50 1600 mumol/L, n = 6). The cyclic nucleotide phosphodiesterase (PDE) inhibitor milrinone, a PDE 3-inhibitor with an IC50 2.4 +/- 1.8 mumol/L, (n = 6) was 10 times more potent than rolipram (PDE 4-inhibitor), zaprinast (PDE 5-inhibitor) and vinpocentine (PDE 1-inhibitor). Withdrawal of these analogues and inhibitors from segments continuously exposed to 10 nmol/l ET-1 revealed that vinpocentine and 8-Br-cGMP were irreversible relaxants, in contrast to milrinone and 8-Br-cAMP. In conclusion, this study has demonstrated that cGMP-enhancing agents, such as the naturally occurring ANP, the calcium channel blocker isradipine, and the synthetic inhibitor of PDE 3, were the most effective relaxants of ET-1 evoked contractions in pLAD in vitro.

Selective phosphodiesterase inhibitors modulate the activity of alveolar macrophages from sensitized guinea-pigs

The aim of this study was to investigate the effects of selective phosphodiesterase (PDE)3 and PDE4 inhibitors on arachidonate release by alveolar macrophages from sensitized and challenged guinea-pigs. Guinea-pigs were sensitized and challenged with ovalbumin administered by aerosol. Bronchoalveolar lavage was performed 48 h later and the PDE and cyclic adenosine monophosphate (cAMP) contents of or the arachidonate release from alveolar macrophages, stimulated in vitro with N-formyl-Met-Leu-Phe (fMLP), were evaluated. PDE3 and PDE4 activities were detected in preparations of macrophage lysate from sensitized challenged and sensitized control animals. Oral pretreatment, prior to antigen challenge in sensitized guinea-pigs, with rolipram or Ro 20-1724 (PDE4 inhibitors) but not milrinone (PDE3 inhibitor) significantly reduced the arachidonate release from alveolar macrophages. In vitro incubation of alveolar macrophages from challenged guinea-pigs with Ro 20-1724 or the cAMP analogue dibutyryl cAMP (db-cAMP) but not milrinone or the cyclic guanosine monophosphate (cGMP) analogue 8-bromo-cGMP (8-br-cGMP) significantly reduced arachidonate release. Incubation of the cells with a combination of milrinone plus rolipram or Ro 20-1724 elicited a marked and significant reduction in arachidonate release by alveolar macrophages stimulated with fMLP. In conclusion, these data show that phosphodiesterase-4 isoenzyme may regulate the release of inflammatory mediators such as arachidonate from macrophages through an increase in intracellular cyclic adenosine monophosphate. This suggests that phosphodiesterase-4 inhibitors have potential in the treatment of inflammatory disorders of the lung.

N-arylrolipram derivatives as potent and selective PDE4 inhibitors

Derivatization of rolipram led to the identification of 3-[4-(3-cyclopentyloxy-4-methoxyphenyl)-2-oxo-pyrrolidin-1-yl]-5-( 3- methoxybenzyloxy)-benzoic acid N',N'-dimethylhydrazide (4), a potent and selective inhibitor of PDE4, which inhibits the activation of human leukocytes with pIC50 values in the range of 7.3-7.8, and blocks antigen induced eosinophilia in Brown Norway rats at a dose of 1 mg/kg (i.t.).

Phosphodiesterase activity in intrapulmonary arteries and veins of perinatal lambs

The transition from fetal to newborn life is marked by a reduction in pulmonary vascular tone mediated by the intracellular second messengers, cGMP and cAMP. We have compared the rates of phosphodiesterase (PDE)-catalyzed hydrolysis of cGMP and cAMP in intrapulmonary vessels of fetal (146 +/- 2 days gestation) and newborn (3-7-day-old) lambs, each n = 6. Lung vessels of second to sixth generations were dissected and cytosol was prepared by differential centrifugation. PDE activity in cytosol was determined by radiometric assay of the hydrolysis of exogenous nucleotides at 30 degrees C for 10 min. Rates of hydrolysis (pmol/min/mg protein) of cGMP were 225 +/- 38 in fetal arteries and different from 151 +/- 7 in veins. In newborn vessels, the rates were 155 +/- 49 and 63 +/- 13 in arteries and veins, respectively. Rates of cAMP hydrolysis by the fetus were 80 +/- 11 in arteries and 45 +/- 16 veins. In newborn lambs the rates were 69 +/- 10 in arteries and different from 18 +/- 4 in veins. Inhibition of PDE activity by zaprinast, a cGMP-specific PDE inhibitor, and rolipram, a cAMP-specific PDE inhibitor, was more in veins of fetal and newborn lambs. Our data show that rates of hydrolysis of the cyclic nucleotides were faster in fetal vessels than in the newborn. We speculate that this would result in a greater accumulation of the cyclic nucleotides in newborn vessels, particularly the veins, and therefore endow the veins with less vascular tone.

SB 207499 (Ariflo), a second generation phosphodiesterase 4 inhibitor, reduces tumor necrosis factor alpha and interleukin-4 production in vivo

The ability of the second generation phosphodiesterase 4 inhibitor SB 207499 (Ariflo), [c-4-cyano-4-(3-cyclopentyloxy-4-methoxyphenyl)-r-l-cyclohexane carboxylic acid], to inhibit inflammatory cytokine production in vivo was evaluated and compared to that of rolipram, a first generation phosphodiesterase 4 inhibitor. To examine human tumor necrosis factor alpha (TNFalpha) production, human monocytes were adoptively transferred into Balb/c mice and challenged with lipopolysaccharide (LPS). In this model, SB 207499 inhibited human TNFalpha production with oral ED50 of 4.9 mg/kg. Similarly, R-rolipram inhibited human TNFalpha production with an ED50 of 5.1 mg/kg, p.o. In contrast to their equipotent activity against TNFalpha production, SB 207499 (ED50 = 2.3 mg/kg, p.o.) was 10-fold less potent than R-rolipram (ED50 = 0.23 mg/kg, p.o.) in reversing reserpine-induced hypothermia, a model of antidepressant activity. In time course studies, SB 207499 (30 mg/kg, p.o.) inhibited TNFalpha production for at least 10 hr; substantial plasma concentrations of SB 207499 were detected over the same interval. The ability of SB 207499 to modulate interleukin-4 production in vivo was assessed in a chronic oxazolone-induced contact sensitivity model in Balb/c mice. In this model, topical administration of SB 207499 (1000 microgram) inhibited intralesional concentrations of interleukin-4 (55%; P <.01). The results demonstrate that SB 207499 is a potent inhibitor of inflammatory cytokine production in a variety of settings in vivo. Moreover, although it is as potent as R-rolipram in inhibiting TNFalpha production, it has substantially less central nervous system activity. Thus SB 207499 represents an excellent candidate with which to evaluate the antiinflammatory potential of PDE4 inhibitors.

Effect of CI-930 [3-(2H)-pyridazinone-4,5-dihydro-6-[4-(1H-imidazolyl) phenyl]-5-methyl-monohydrochloride] and rolipram on human coronary artery smooth muscle cell proliferation

Experiments were conducted to determine how selective inhibitors of certain cyclic nucleotide phosphodiesterase (PDE) families, namely CI-930 (PDE3 inhibitor; 3-(2H)-pyridazinone-4,5-dihydro-6-[4-(1H-imidazolyl) phenyl]-5-methyl monohydro chloride) and rolipram (PDE4 inhibitor), may affect human coronary artery smooth muscle cell (HCASMC) proliferation. CI-930- and rolipram-inhibitable PDEs accounted for most of the cyclic AMP hydrolyzing activity in HCASMC. Twenty micromolar CI-930 and 20 microM rolipram used individually attenuated proliferation of HCASMC from some, but not all donors, as measured by flow cytometry. The simultaneous addition of 10 microM CI-930 plus 10 microM rolipram caused greater attenuation. This attenuation represented a reduction of the number of cells entering the S phase of the cell cycle and not merely a delay in cell cycle traverse. No statistically significant elevation of cyclic AMP was detected following the addition of either PDE inhibitor individually, but the combination produced significant elevations. It is concluded that CI-930- and rolipram-inhibitable PDE isozymes are expressed in HCASMC and that selective inhibitors of these isozymes can attenuate HCASMC proliferation. The data suggest that selective PDE inhibitors may prevent restenosis in patients following percutaneous transluminal coronary angioplasty because of their effect on HCASMC proliferation, and they may also be useful in retarding the progression of atherosclerosis in individuals at risk. PDE3 and PDE4 inhibitors in combination are more effective than the inhibitors used individually.

Design, synthesis, and biological activities of new thieno[3,2-d] pyrimidines as selective type 4 phosphodiesterase inhibitors

A common pharmacophore for compounds structurally related to nitraquazone has been derived. Using this pharmacophore, new structures have been designed, synthesized, and evaluated for their inhibitory potencies against cyclic adenosine 5'-monophosphate (cAMP) specific phosphodiesterase (PDE 4). From these compounds, 4-benzylamino-2-butylthieno[3,2-d]pyrimidine (4) was selected for optimization. The effects of changes to the lipophilic groups and the amino linkage on the PDE 4 activity have been investigated. As a result, some potent PDE 4 inhibitors, selective with respect to PDE 3, have been identified. A selected group of compounds have been further evaluated for their ability to displace [3H]rolipram from its binding site and also to potentiate isoprenaline-induced cAMP accumulation in isolated guinea pig eosinophils. Of these, 2-butyl-4-cyclohexylaminothieno[3,2-d]pyrimidine (33) has an interesting profile, with an important improvement in PDE 4/[3H]rolipram ratio with respect to reference drugs, and good activity in cAMP potentiation, consistent with efficient cell penetration.

Aryl sulfonamides as selective PDE4 inhibitors

A series of novel selective phosphodiesterase 4 (PDE4) inhibitors has been developed which displays activity both in vitro and in vivo. These compounds possess good selectivity for the catalytic site of PDE4 over the high affinity Rolipram binding site. In vivo studies demonstrate a reduced propensity to display the emetic side effects which are commonly observed with PDE4 inhibitors.

Phosphodiesterase expression in human epithelial cells

Epithelial cells play a critical role in airway inflammation and have the capacity to produce many inflammatory mediators, including bioactive lipids and proinflammatory cytokines. Intracellular levels of cAMP and cGMP are important in the control of inflammatory cell function. These cyclic nucleotides are inactivated via a family of phosphodiesterase (PDE) enzymes, providing a possible site for drug intervention in chronic inflammatory conditions. We studied the expression of PDE activity in an epithelial cell line (A549) and in primary human airway epithelial cells (HAECs). We measured PDE function using specific inhibitors to identify the PDE families present and used RT-PCR to elucidate the expression of PDE isogenes. Both A549 cells and HAECs predominantly expressed PDE4 activity, with lesser PDE1, PDE3, and PDE5 activity. RT-PCR identified HSPDE4A5 and HSPDE4D3 together with HSPDE7. Inhibition of PDE4 and PDE3 reduced secretion by these cells. Epithelial PDE may be an important target for PDE4 inhibitors in the development of the control of asthmatic inflammation, particularly when delivered via the inhaled route.