Phosphodiesterase 4D Research Articles

In silico pharmacology suggests ginger extracts may reduce stroke risks.

Aberrations in cyclic adenosine monophosphate (cAMP) signaling cascade has been linked to the allergic responses that associate with the risks of stroke or cardiovascular diseases. Phosphodiesterase 4D (PDE4D) has been shown to be highly involved in cAMP regulation and is hence implied to be a potential drug target in stroke prevention. To identify potential PDE4D inhibitors from traditional Chinese medicine (TCM), we employed machine learning modeling techniques to screen a comprehensive TCM database. The multiple linear regression (MLR) and support vector machine (SVM) models constructed have correlation coefficients of 0.8234 and 0.7854 respectively. Three candidates from the ginger family were identified based on the prediction models. Molecular dynamics simulation further validated the binding stabilities of each candidate in comparison to the control inhibitor L-454560. The intermolecular distances suggested that the candidates could hinder PDE4D from binding to cAMP. Furthermore, the HypoGen validation suggested that top2, top3, and the control L-454560 mapped with the predicted pharmacophores. The results suggested that the 3 compounds identified from the ginger family were capable in inhibiting cAMP binding and hydrolysis by PDE4D. We further identified and characterized the ligand binding properties that are associated with the inhibition of PDE4D.

Traditional Chinese medicine, a solution for reducing dual stroke risk factors at once?

Based on genome wide association studies (GWAS), the activities of phosphodiesterase 4D (PDE4D) and 5-Lipoxygenase activating protein (ALOX5AP) were suggested as two of the major factors involved in ischemic stroke risks. Uncontrolled PDE4D activities often lead to cAMP-induced stroke and cardiovascular diseases. Overexpression of ALOX5AP, on the other hand, had been shown to play a major role in inflammation pathway that could induce the development of atherosclerosis and stroke. To eliminate the risk factors that lead to stroke, we reported the identification and analysis of dual-targeting compounds that could reduce PDE4D and ALOX5AP activities from traditional Chinese medicine (TCM). We employed world's largest TCM database, TCM Database@Taiwan, for in silico drug identification. We also introduced machine learning predictive models, as well as pharmacophore model, for characterizing the drug-like candidates. Both myristic acid and pentadecanoic acid were identified. The follow-up analysis on molecular dynamics simulation further determined the major roles of the carboxyl group for forming stable molecular interactions. Intriguingly, the carboxyl group demonstrated different bonding patterns with PDE4D and ALOX5AP, through electrostatic interaction and hydrogen bonds, respectively. In addition, the large volume occupied by the ligand hydrophobic regions could achieve inhibition through occupying the vacant spaces in the binding site. These pharmacophores held true for both candidates against each protein targets. Hence, we proposed the presence of the carboxyl group and hydrophobic regions as potent dual targeting features that inhibit both PDE4D and ALOX5AP activities.

Cyclic AMP Controls mTOR through Regulation of the Dynamic Interaction between Rheb and Phosphodiesterase 4D

The mammalian target of rapamycin complex 1 (mTORC1) is a molecular hub that regulates protein synthesis in response to a number of extracellular stimuli. Cyclic AMP (cAMP) is considered to be an important second messenger that controls mTOR; however, the signaling components of this pathway have not yet been elucidated. Here, we identify cAMP phosphodiesterase 4D (PDE4D) as a binding partner of Rheb that acts as a cAMP-specific negative regulator of mTORC1. Under basal conditions, PDE4D binds Rheb in a noncatalytic manner that does not require its cAMP-hydrolyzing activity and thereby inhibits the ability of Rheb to activate mTORC1. However, elevated cAMP levels disrupt the interaction of PDE4D with Rheb and increase the interaction between Rheb and mTOR. This enhanced Rheb-mTOR interaction induces the activation of mTORC1 and cap-dependent translation, a cellular function of mTORC1. Taken together, our results suggest a novel regulatory mechanism for mTORC1 in which the cAMP-determined dynamic interaction between Rheb and PDE4D provides a key, unique regulatory event. We also propose a new role for PDE4 as a molecular transducer for cAMP signaling.

Tilapia Hepcidin 2-3 Peptide Modulates Lipopolysaccharide-induced Cytokines and Inhibits Tumor Necrosis Factor-α through Cyclooxygenase-2 and Phosphodiesterase 4D

The antimicrobial peptide, tilapia hepcidin (TH) 2-3, belongs to the hepcidin family, and its antibacterial function has been reported. Here, we examined the TH2-3-mediated regulation of proinflammatory cytokines in bacterial endotoxin lipopolysaccharide (LPS)-stimulated mouse macrophages. The presence of TH2-3 in LPS-stimulated cells reduced the amount of tumor necrosis factor (TNF)-α secretion. From a microarray, real-time polymerase chain reaction (PCR), and cytokine array studies, we showed down-regulation of the proinflammatory cytokines TNF-α, interleukin (IL)-1α, IL-1β, IL-6, and the prostaglandin synthesis gene, cyclooxygenase (COX)-2, by TH2-3. Studies with the COX-2-specific inhibitor, melaxicam, and with COX-2-overexpressing cells demonstrated the positive regulation of TNF-α and negative regulation of cAMP degradation-specific phosphodiesterase (PDE) 4D by COX-2. In LPS-stimulated cells, TH2-3 acts like melaxicam and down-regulates COX-2 and up-regulates PDE4D. The reduction in intracellular cAMP by TH2-3 or melaxicam in LPS-stimulated cells supports the negative regulation of PDE4D by COX-2 and TH2-3. This demonstrates that the inhibition of COX-2 is among the mechanisms through which TH2-3 controls TNF-α release. At 1 h after treatment, the presence of TH2-3 in LPS-stimulated cells had suppressed the induction of pERK1/2 and prevented the LPS-stimulated nuclear accumulation of NF-κB family proteins of p65, NF-κB2, and c-Rel. In conclusion, TH2-3 inhibits TNF-α and other proinflammatory cytokines through COX-2-, PDE4D-, and pERK1/2-dependent mechanisms.

Cyclic AMP Phosphodiesterase 4D (PDE4D) Tethers EPAC1 in a Vascular Endothelial Cadherin (VE-Cad)-based Signaling Complex and Controls cAMP-mediated Vascular Permeability

Vascular endothelial cell (VEC) permeability is largely dependent on the integrity of vascular endothelial cadherin (VE-cadherin or VE-Cad)-based intercellular adhesions. Activators of protein kinase A (PKA) or of exchange protein activated by cAMP (EPAC) reduce VEC permeability largely by stabilizing VE-Cad-based intercellular adhesions. Currently, little is known concerning the nature and composition of the signaling complexes that allow PKA or EPAC to regulate VE-Cad-based structures and through these actions control permeability. Using pharmacological, biochemical, and cell biological approaches we identified and determined the composition and functionality of a signaling complex that coordinates cAMP-mediated control of VE-Cad-based adhesions and VEC permeability. Thus, we report that PKA, EPAC1, and cyclic nucleotide phosphodiesterase 4D (PDE4D) enzymes integrate into VE-Cad-based signaling complexes in human arterial endothelial cells. Importantly, we show that protein-protein interactions between EPAC1 and PDE4D serve to foster their integration into VE-Cad-based complexes and allow robust local regulation of EPAC1-based stabilization of VE-Cad-based adhesions. Of potential translational importance, we mapped the EPAC1 peptide motif involved in binding PDE4D and show that a cell-permeable variant of this peptide antagonizes EPAC1-PDE4D binding and directly alters VEC permeability. Collectively, our data indicate that PDE4D regulates both the activity and subcellular localization of EPAC1 and identify a novel mechanism for regulated EPAC1 signaling in these cells.

Analyses of shared genetic factors between asthma and obesity in children

Epidemiologic studies consistently show associations between asthma and obesity. Shared genetics might account for this association. We sought to identify genetic variants associated with both asthma and obesity. On the basis of a literature search, we identified genes from (1) genome-wide association studies (GWASs) of body mass index (BMI; n = 17 genes), (2) GWASs of asthma (n = 14), and (3) candidate gene studies of BMI and asthma (n = 7). We used GWAS data from the Childhood Asthma Management Program to analyze associations between single nucleotide polymorphisms (SNPs) in these genes and asthma (n = 359 subjects) and BMI (n = 537). One top BMI GWAS SNP from the literature, rs10938397 near glucosamine-6-phosphate deaminase 2 (GNPDA2), was associated with both BMI (P = 4 x 10(-4)) and asthma (P = .03). Of the top asthma GWAS SNPs and the candidate gene SNPs, none was found to be associated with both BMI and asthma. Gene-based analyses that included all available SNPs in each gene found associations (P < .05) with both phenotypes for several genes: neuronal growth regulator 1 (NEGR1); roundabout, axon guidance receptor, homolog 1 (ROBO1); diacylglycerol kinase, gamma (DGKG); Fas apoptotic inhibitory molecule 2 (FAIM2); fat mass and obesity associated (FTO); and carbohydrate (N-acetylgalactosamine 4-0) sulfotransferase 8 (CHST8) among the BMI GWAS genes; interleukin 1 receptor-like 1 / interleukin 18 receptor 1 (IL1RL1/IL18R1), dipeptidyl-peptidase 10 (DPP10), phosphodiesterase 4D (PDE4D), V-myb myeloblastosis viral oncogene homolog (MYB), PDE10A, IL33, and especially protein tyrosine phosphatase, receptor type D (PTPRD) among the asthma GWAS genes; and protein kinase C, alpha (PRKCA) among the BMI and asthma candidate genes. SNPs within several genes showed associations to BMI and asthma at a genetic level, but none of these associations were significant after correction for multiple testing. Our analysis of known candidate genes reveals some evidence for shared genetics between asthma and obesity, but other shared genetic determinants are likely to be identified in novel loci.

Evolutionarily Conserved Role of Calcineurin in Phosphodegron-Dependent Degradation of Phosphodiesterase 4D

Calcineurin is a widely expressed and highly conserved Ser/Thr phosphatase. Calcineurin is inhibited by the immunosuppressant drug cyclosporine A (CsA) or tacrolimus (FK506). The critical role of CsA/FK506 as an immunosuppressant following transplantation surgery provides a strong incentive to understand the phosphatase calcineurin. Here we uncover a novel regulatory pathway for cyclic AMP (cAMP) signaling by the phosphatase calcineurin which is also evolutionarily conserved in Caenorhabditis elegans. We found that calcineurin binds directly to and inhibits the proteosomal degradation of cAMP-hydrolyzing phosphodiesterase 4D (PDE4D). We show that ubiquitin conjugation and proteosomal degradation of PDE4D are controlled by a cullin 1-containing E(3) ubiquitin ligase complex upon dual phosphorylation by casein kinase 1 (CK1) and glycogen synthase kinase 3beta (GSK3beta) in a phosphodegron motif. Our findings identify a novel signaling process governing G-protein-coupled cAMP signal transduction-opposing actions of the phosphatase calcineurin and the CK1/GSK3beta protein kinases on the phosphodegron-dependent degradation of PDE4D. This novel signaling system also provides unique functional insights into the complications elicited by CsA in transplant patients.

The discovery and synthesis of highly potent subtype selective phosphodiesterase 4D inhibitors

The SAR study of a series of 6-aryloxymethyl-8-aryl substituted quinolines is described. Optimization of the series led to the discovery of compound 26b, a highly potent (IC 50 = 0.6 nM) and selective PDE4D inhibitor with a 75-fold selectivity over the A, B, and C subtypes and over 18,000-fold selectivity against other PDE family members. Rat pharmacokinetics and tissue distribution are also summarized.

Sex-differential genetic effect of phosphodiesterase 4D (PDE4D) on carotid atherosclerosis

BackgroundThe phosphodiesterase 4D (PDE4D) gene was reported as a susceptibility gene to stroke. The genetic effect might be attributed to its role in modulating the atherogenic process in the carotid arteries. Using carotid intima-media thickness (IMT) and plaque index as phenotypes, the present study sought to determine the influence of this gene on subclinical atherosclerosis.MethodsCarotid ultrasonography was performed on 1013 stroke-free subjects who participated in the health screening programs (age 52.6 ± 12.2; 47.6% men). Genotype distribution was compared among the high-risk (plaque index ≥ 4), low-risk (index = 1-3), and reference (index = 0) groups. We analyzed continuous IMT data and further dichotomized IMT data using mean plus one standard deviation as the cutoff level. Because the plaque prevalence and IMT values displayed a notable difference between men and women, we carried out sex-specific analyses in addition to analyzing the overall data. Rs702553 at the PDE4D gene was selected because it conferred a risk for young stroke in our previous report. Previous young stroke data (190 cases and 211 controls) with an additional 532 control subjects without ultrasonic data were shown as a cross-validation for the genetic effect.ResultsIn the overall analyses, the rare homozygote of rs702553 led to an OR of 3.1 (p = 0.034) for a plaque index ≥ 4. When subjects were stratified by sex, the genetic effect was only evident in men but not in women. Comparing male subjects with plaque index ≥ 4 and those with plaque index = 0, the TT genotype was over-represented (27.6% vs. 13.4%, p = 0.008). For dichotomized IMT data in men, the TT genotype had an OR of 2.1 (p = 0.032) for a thicker IMT at the common carotid artery compared with the (AA + AT) genotypes. In women, neither IMT nor plaque index was associated with rs702553. Similarly, SNP rs702553 was only significant in young stroke men (OR = 1.8, p = 0.025) but not in women (p = 0.27).ConclusionsThe present study demonstrates a sex-differential effect of PDE4D on IMT, plaque index and stroke, which highlights its influence on various aspects of atherogenesis.

Phosphodiesterase 4D (PDE4D) gene polymorphism in patients with acute stroke from Moscow

Two PDE4D gene polymorphisms [SNP41 (rs152312 and SNP87 (rs 2910829)] were studied in patients with acute stroke (n = 577) and in control sample (n = 270). Significant differences in the genotype and allele frequency distribution were found between these samples for polymorphism SNP41. We showed that the AA and AG genotypes of SNP41 polymorphism were associated with higher risk of acute stroke development in the Moscow population (OR = 1.6). No association of SNP87 polymorphism with the disease was observed.

Association of a Genetic Variant in the ALOX5AP with Higher Risk of Ischemic Stroke: A Case-Control, Meta-Analysis and Functional Study

Background: Variants in the 5-lipoxygenase-activating protein (ALOX5AP) and phosphodiesterase 4D (PDE4D) genes have first been associated with ischemic stroke (IS) through whole-genome linkage screens. However, association studies obtained conflicting results. We aimed to investigate the contribution of selected single nucleotide polymorphisms (SNPs) in these genes for the first time in a large Iberian population. Methods: A case-control design was used to analyze one SNP in ALOX5AP and five SNPs in PDE4D in a total of 1,092 IS patients and 781 healthy controls of two different subsets from Spain and Portugal. The analysis was adjusted for confounding variables and the results were integrated in a meta-analysis of all case-control studies. In addition, ALOX5AP gene expression levels were determined in controls and IS cases. Results: A first meta-analysis of both subsets showed that the T allele of the SG13S114 SNP in ALOX5AP was a risk factor for IS after Bonferroni correction [OR = 1.22 (1.06–1.40); p = 0.006]. A second meta-analysis of white populations confirmed these results [OR = 1.18 (1.07–1.31); p = 0.001]. ALOX5AP gene expression analysis in a subset of controls and cases revealed that the SG13S114 genotypes modulate mRNA levels of ALOX5AP (p = 0.001) and mRNA levels were higher in IS cases (2.8 ± 2.4%) than in controls (1.4 ± 1.3%; p = 0.003). No association of the variants in PDE4D with IS was observed in our study. Conclusions: The ALOX5AP SG13S114 variant is an independent risk factor for IS in the Iberian population and is associated with ALOX5AP expression levels. The role of this gene in stroke merits further investigation.

Genome-wide copy number variation analysis in attention-deficit/hyperactivity disorder: association with neuropeptide Y gene dosage in an extended pedigree

Attention-deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurodevelopmental syndrome characterized by hyperactivity, inattention and increased impulsivity. To detect micro-deletions and micro-duplications that may have a role in the pathogenesis of ADHD, we carried out a genome-wide screen for copy number variations (CNVs) in a cohort of 99 children and adolescents with severe ADHD. Using high-resolution array comparative genomic hybridization (aCGH), a total of 17 potentially syndrome-associated CNVs were identified. The aberrations comprise 4 deletions and 13 duplications with approximate sizes ranging from 110 kb to 3 Mb. Two CNVs occurred de novo and nine were inherited from a parent with ADHD, whereas five are transmitted by an unaffected parent. Candidates include genes expressing acetylcholine-metabolizing butyrylcholinesterase (BCHE), contained in a de novo chromosome 3q26.1 deletion, and a brain-specific pleckstrin homology domain-containing protein (PLEKHB1), with an established function in primary sensory neurons, in two siblings carrying a 11q13.4 duplication inherited from their affected mother. Other genes potentially influencing ADHD-related psychopathology and involved in aberrations inherited from affected parents are the genes for the mitochondrial NADH dehydrogenase 1 α subcomplex assembly factor 2 (NDUFAF2), the brain-specific phosphodiesterase 4D isoform 6 (PDE4D6) and the neuronal glucose transporter 3 (SLC2A3). The gene encoding neuropeptide Y (NPY) was included in a ∼3 Mb duplication on chromosome 7p15.2-15.3, and investigation of additional family members showed a nominally significant association of this 7p15 duplication with increased NPY plasma concentrations (empirical family-based association test, P=0.023). Lower activation of the left ventral striatum and left posterior insula during anticipation of large rewards or losses elicited by functional magnetic resonance imaging links gene dose-dependent increases in NPY to reward and emotion processing in duplication carriers. These findings implicate CNVs of behaviour-related genes in the pathogenesis of ADHD and are consistent with the notion that both frequent and rare variants influence the development of this common multifactorial syndrome.

Aging-related hyperinflammation in endotoxemia is mediated by the α 2A-adrenoceptor and CD14/TLR4 pathways

Aims Sepsis is a major cause of morbidity and mortality in the elderly population. In prior studies, we have shown that in vivo, the inflammatory response in aged animals is exaggerated as compared to young animals and that this response likely accounts for the increased morbidity and mortality. Part of this uncontrolled inflammatory response in sepsis is due to the innate immune response. However, recent studies have shown that the pathogenesis of sepsis is much more complex. The adrenergic autonomic nervous system is now thought to play a key role in modulating the inflammatory response in sepsis. In this study, we hypothesize that not only is the innate immune response enhanced in response to lipopolysaccharide (LPS) in aged animals, but that the adrenergic nervous system also plays a role in the release of excess inflammatory cytokines. Main methods Male Fischer-344 rats (young: 3 months; aged: 24 months) were used. Endotoxemia was induced by intravenous injection of lipopolysaccharide (LPS, 15 mg/kg BW). Splenic tissues were harvested and mRNA and protein were extracted. The protein expression of CD14 and TLR4, key mediators of LPS in the innate response, as well as alpha-2A adrenergic receptor (α 2A-AR) and phosphodiesterase 4D (PDE4D), as the means by which the autonomic nervous system exerts its effects were analyzed. Key findings Splenic tissue concentrations of α 2A-AR, PDE4D, CD14, and TLR4 were significantly increased in septic aged rats as compared to aged sham rats and septic young rats. The increased expression of α 2A-AR in septic aged rats was further confirmed by immunohistochemical staining of splenic tissues. Significance These data support the hypothesis that not only is the innate immune response increased in aged animals during sepsis, but that there is also an upregulated response of the adrenergic autonomic nervous system that contributes to excess proinflammatory cytokine release.

Meta-analysis of association between variation in the PDE4D gene and ischemic cerebral infarction risk in Asian populations

Phosphodiesterase 4D (PDE4D) was found to be associated with increased risk of ischemic stroke by Iceland researchers in 2003. Replication studies have produced conflicting results. A recent meta-analysis reported that no genetic variant of PDE4D demonstrated a reproducible association with ischemic stroke, especially when analyzed with respect to white subjects exclusively. In this study, we aimed to determine the association between PDE4D and ischemic infarction risk in Asian populations. After collecting all case-control studies in English or Chinese related to the association between PDE4D and ischemic infarction in Asian people, strict selection criteria and exclusion criteria were determined, and a fixed or random effects model was used on the basis of heterogeneity. To measure the strength of the genetic association, a pooled odds ratio (OR) and 95% confidence interval (CI) were calculated for each gene variant. Publication bias was evaluated. None of the Asian subjects were heterozygous for SNP 45 or SNP 41. Only seven studies involving SNP 83 and SNP 87 had sufficient data to allow inclusion into meta-analyses. Statistically significant associations with ischemic infarction in the Asian populations were determined for SNP 83 C allele (OR, 1.22; 95% CI, 1.03-1.43) and SNP 83 CC genotype (OR, 1.42; 95% CI, 1.14-1.77), but not for SNP 83 CC + CT genotypes or SNP 87. PDE4D was associated with ischemic infarction risk in Asian people, and SNP 83 was an important biomarker.

Design of phosphodiesterase 4D (PDE4D) allosteric modulators for enhancing cognition with improved safety

Phosphodiesterase 4 (PDE4), the primary cAMP-hydrolyzing enzyme in cells, is a promising drug target for a wide range of conditions. Here we present seven co-crystal structures of PDE4 and bound inhibitors that show the regulatory domain closed across the active site, thereby revealing the structural basis of PDE4 regulation. This structural insight, together with supporting mutagenesis and kinetic studies, allowed us to design small-molecule allosteric modulators of PDE4D that do not completely inhibit enzymatic activity (I(max) approximately 80-90%). These allosteric modulators have reduced potential to cause emesis, a dose-limiting side effect of existing active site-directed PDE4 inhibitors, while maintaining biological activity in cellular and in vivo models. Our results may facilitate the design of CNS therapeutics modulating cAMP signaling for the treatment of Alzheimer's disease, Huntington's disease, schizophrenia and depression, where brain distribution is desired for therapeutic benefit.

Differential Association of Phosphodiesterase 4D Isoforms with β2-Adrenoceptor in Cardiac Myocytes

cAMP and protein kinase A (PKA) activation represents a key signaling mechanism upon beta-adrenergic stimulation under stress. Both beta(1)- and beta(2)-adrenoreceptor (ARs) subtypes induce cAMP accumulation, yet play distinct roles in cardiac contraction and myocyte apoptosis. Differences in controlling cAMP/PKA activities through the assembly of complexes between the receptors and cAMP-specific phosphodiesterases contribute to the distinct biological outcomes. Here, we demonstrate that beta(2)ARs form signaling complexes with a set of PDE4D isoforms expressed in cardiac myocytes. PDE4D9 and PDE4D8 bind to the beta(2)AR at resting conditions; however, agonist stimulation induces dissociation of PDE4D9 from the receptor but recruitment of PDE4D8 to the receptor. Agonist stimulation also induces recruitment of PDE4D5 to the beta(2)AR. Moreover, the receptor-associated PDE4D isoforms play distinct roles in controlling cAMP activities and regulating the PKA phosphorylation of the receptor and myocyte contraction rate responses. Knockdown of PDE4D9 with short hairpin RNA enhances the beta(2)AR-induced cAMP signaling, whereas knockdown of PDE4D8 only slightly prolongs the receptor-induced cAMP signaling in myocytes. Inhibition of PDE4D9 and PDE4D5 enhances the base-line levels of contraction rates, whereas inhibition of PDE4D9 and PDE4D8 enhances the maximal contraction rate increases upon activation of beta(2)AR. Our data underscore the complex regulation of intracellular cAMP by beta(2)AR-associated phosphodiesterase enzymes to enforce the specificity of the receptor signaling for physiological responses.

Agonist Dose-dependent Phosphorylation by Protein Kinase A and G Protein-coupled Receptor Kinase Regulates β2 Adrenoceptor Coupling to Gi Proteins in Cardiomyocytes

Adrenoceptors receptors (ARs) play a pivotal role in regulating cardiovascular response to catecholamines during stress. beta(2)ARs, prototypical G protein-coupled receptors (GPCRs), expressed in animal hearts, display dual coupling to both G(s) and G(i) proteins to control the adenylyl cyclase-cAMP dependent protein kinase A (PKA) pathway to regulate contraction responses. Here, we showed that the beta(2)AR coupling to G(i) proteins was agonist dose-dependent and occurred only at high concentrations in mouse cardiac myocytes. Both the beta(2)AR-induced PKA activity, measured by fluorescence resonance energy transfer (FRET) imaging, and the increase in myocyte contraction rate displayed sensitivity to the G(i) inhibitor pertussis toxin (PTX). Further studies revealed that activated beta(2)ARs underwent PKA phosphorylation at a broad range of agonist concentrations. Disruption of the PKA phosphorylation sites on the beta(2)AR blocked receptor/G(i) coupling. However, a sufficient beta(2)AR/G(i) coupling was also dependent on the G protein-coupled receptor kinase (GRK)-mediated phosphorylation of the receptors, which only occurred at high concentrations of agonist (> or = 100 nm). Disruption of the GRK phosphorylation sites on the beta(2)AR blocked receptor internalization and coupling to G(i) proteins, probably by preventing the receptor's transportation to access G(i) proteins. Furthermore, neither PKA nor GRK site mutated receptors displayed sensitivity to the G(i)-specific inhibitor, G(i)CT. Together, our studies revealed distinct roles of PKA and GRK phosphorylation of the beta(2)AR for agonist dose-dependent coupling to G(i) proteins in cardiac myocytes, which may protect cells from overstimulation under high concentrations of catecholamines.

New Selective Phosphodiesterase 4D Inhibitors Differently Acting on Long, Short, and Supershort Isoforms

The lack of selective inhibitors toward the long, short, or supershort phosphodiesterases (PDE4s) prevented researchers from carefully defining the connection between different enzyme isoforms, their brain localization, and their role in neurodegenerative diseases such as Alzheimer's disease (AD). In the search for new therapeutic agents for treating memory and learning disorders, we synthesized new rolipram related PDE4 inhibitors, which had some selectivity toward the long form PDE4D3. The first series was synthesized as racemate and then resolved by semipreparative HPLC on chiral supports. Herein we report the synthetic pathways to obtain compounds 1a-c, 2a-c, 3a-c, 4a-f, 5a,b, 6a,b, 7a,b, the chiral analytical study to resolve compounds 1a-c, 2a-c, 3a-c, the molecular docking study for compound 1c, and the biological results and some SAR considerations that provide some insights and hints for the structural requirements for PDE4D subtype selectivity and enzyme inhibition.

Association of PDE4D and IL-1 gene polymorphism with ischemic stroke in a Han Chinese population

Background The single-nucleotide polymorphisms (SNPs) of the phosphodiesterase 4D (PDE4D) and interleukin-1 (IL-1) genes are associated with increased risk for the development of ischemic stroke (IS) in whites. However, little is known about whether this association could also occur in Han Chinese. Method A total of 371 patients with IS and unrelated healthy controls were recruited and the SNPs of the PDE4D (83T/C), (87T/C), IL-1 (−889C/T) and IL-1 (−511C/T) were characterized, respectively, by polymerase chain reactions-restriction fragment length polymorphism (PCR-RFLP). The genotype and allele frequencies of these SNPs in this population were statistically analyzed. Results The genotype and allele frequencies of the PDE4D (87T/C) and IL-1 (−511C/T) were similar between IS patients and controls. In contrast, the frequencies of CC genotype and C allele of the PDE4D (83T/C) and the T allele frequency of IL-1 (−889C/T) in IS patients were significantly higher than that in healthy controls ( p = 0.001, p = 0.003 and p = 0.02, respectively), independent of the conventional risk factors. The values of odds ratio (OR) reached at OR = 1.603; 95%CI = 1.032–2.489; p = 0.036 for the CC genotype of the PDE4D (83T/C) and OR = 1.913; 95%CI = 1.621–2.375; p = 0.034 for the TT genotype of the IL-1 (−889C/T), respectively. Conclusions the SNPs of the PDE4D (83T/C) and IL-1 (−889C/T) were associated with increased risk for the development of IS in Northern Han Chinese.

Phosphodiesterase 4B2 gene is an effector of Toll-like receptor signaling in astrocytes

Cyclic AMP is part of an endogenous mechanism that downregulates inflammatory response, and its intracellular concentration is regulated chiefly by cyclic nucleotide phosphodiesterases type 4. The goal of the present study was to determine whether phosphodiesterases 4 are involved in the inflammatory response of astrocytes mediated by Toll-like receptors. Astrocyte cultures established from newborn rat brain were challenged with lipoteichoic acid, a ligand of Toll-like receptor 2, polyinosinic-polycytidylic acid, a ligand of Toll-like receptor 3, or lipopolysaccharide, a ligand of Toll-like receptor 4. After 24 h the expression of genes encoding phosphodiesterase 4A, phosphodiesterase 4B and phosphodiesterase 4D was determined by real time reverse transcription polymerase chain reaction. The challenge of astrocytes with the ligands profoundly up-regulated expression of the phosphodiesterase 4B mRNA, while the phosphodiesterase 4A and 4D mRNA was either unaffected or downregulated. Moreover, Toll-like receptor ligation specifically up-regulated expression of the phosphodiesterase 4B2 transcriptional variant. Thus, polyinosinic-polycytidylic acid, lipopolysaccharide and lipoteichoic acid induced approximately 7-, 5- and 4-fold up-regulation of the message, respectively. Toll-like receptor ligation also led to an over 2-fold increase in the protein level of phosphodiesterase 4B2 as revealed by immunoblot analysis. The inactivation of Rho proteins by pretreatment with toxin B form C. difficile enhanced ligation-induced up-regulation of the phosphodiesterase 4B2 message by 4-9-fold. However, in spite of this increase in the message abundance, there was no increase in the protein level compared to cells challenged with the ligands alone. These results demonstrate that the phosphodiesterase 4B2 gene is an effector of Toll-like receptor signaling in astrocytes, and that its up-regulation at the protein level is controlled by complex mechanisms.