Phosphodiesterase 4D Inhibitors Research Articles

CAMP/PKA/CREB/GLT1 signaling involved in the antidepressant-like effects of phosphodiesterase 4D inhibitor (GEBR-7b) in rats.

ObjectivesGEBR-7b, a potential phosphodiesterase 4D inhibitor, has been shown to have memory-enhancing effects in rodents. However, it is still unknown whether GEBR-7b also has the antidepressant-like effects in rats. Herein, we examined the potential of GEBR-7b to attenuate depression-like behaviors in the rat model of depression induced by chronic unpredictable stress (CUS). Next, we also investigated the alterations of cyclic adenosine monophosphate (cAMP), protein kinase A (PKA) catalytic subunit (PKAca), cAMP response element-binding (CREB), and glutamate transporter 1 (GLT1) levels produced by GEBR-7b in the rats model of depression.MethodsEffects of GEBR-7b on CUS (35 days)-induced depression-like behaviors were examined by measuring immobility time in the forced swimming test (FST). Hippocampal cAMP levels were examined by enzyme-linked immunosorbent assay, whereas PKAca, phosphorylation of CREB (pCREB), CREB, and GLT1 in the hippocampus of rats were subjected to Western blot analysis.ResultsCUS exposure caused a depression-like behavior evidenced by the increased immobility time in FST. Depression-like behavior induced by CUS was accompanied by a significant increased GLT, decreased cAMP, PKAca, pCREB activities in hippocampus. However, repeated GEBR-7b administration significantly reversed CUS-induced depression-like behavior and changes of cAMP/PKA/CREB/GLT1 signaling. No alteration was observed in locomotor activity in open field test.ConclusionThese findings indicate that GEBR-7b reversed the depression-like behaviors induced by CUS in rats, which is at least in part mediated by modulating cAMP, PKAca, pCREB, and GLT1 levels in the hippocampus of rats, supporting its neuroprotective potential against behavioral and biochemical dysfunctions induced by CUS.

Catecholic amides as potential selective phosphodiesterase 4D inhibitors: Design, synthesis, pharmacological evaluation and structure–activity relationships

In this study, a series of catechol-based amides (8a–n) with different amide linkers linking the catecholic moiety to the terminal phenyl ring was designed and synthesized as potent phosphodiesterase (PDE) 4D inhibitors. The inhibitory activities of these compounds were evaluated against the core catalytic domains of human PDE4 (PDE4CAT), full-length PDE4B1 and PDE4D7 enzymes, and other PDE family members. The results indicated the majority of compounds 8a–n displayed moderate to good inhibitory activities against PDE4CAT. Among these compounds, compound 8j with a short amide linker (CONHCH2) displayed comparable PDE4CAT inhibitory activity (IC50=410nM) with rolipram. More interestingly, compound 8g, a potent and selective PDE4D inhibitor (IC50=94nM), exhibited a 10-fold selectivity over the PDE4B subtypes and an over 1000-fold selectivity against other PDE family members. Docking simulations suggested that 8g forms three extra H-bonds with the NH of residue Asn487 and two water molecules.

Phosphodiesterase 4D acts downstream of Neuropilin to control Hedgehog signal transduction and the growth of medulloblastoma

Alterations in Hedgehog (Hh) signaling lead to birth defects and cancers including medulloblastoma, the most common pediatric brain tumor. Although inhibitors targeting the membrane protein Smoothened suppress Hh signaling, acquired drug resistance and tumor relapse call for additional therapeutic targets. Here we show that phosphodiesterase 4D (PDE4D) acts downstream of Neuropilins to control Hh transduction and medulloblastoma growth. PDE4D interacts directly with Neuropilins, positive regulators of Hh pathway. The Neuropilin ligand Semaphorin3 enhances this interaction, promoting PDE4D translocation to the plasma membrane and cAMP degradation. The consequent inhibition of protein kinase A (PKA) enhances Hh transduction. In the developing cerebellum, genetic removal of Neuropilins reduces Hh signaling activity and suppresses proliferation of granule neuron precursors. In mouse medulloblastoma allografts, PDE4D inhibitors suppress Hh transduction and inhibit tumor growth. Our findings reveal a new regulatory mechanism of Hh transduction, and highlight PDE4D as a promising target to treat Hh-related tumors.

Phosphodiesterase 4D inhibitors limit prostate cancer growth potential.

Phosphodiesterase 4D (PDE4D) has recently been implicated as a proliferation-promoting factor in prostate cancer and is overexpressed in human prostate carcinoma. However, the effects of PDE4D inhibition using pharmacologic inhibitors have not been examined in prostate cancer. These studies examined the effects of selective PDE4D inhibitors, NVP-ABE171 and cilomilast, as anti-prostate cancer therapies in both in vitro and in vivo models. The effects of PDE4D inhibitors on pathways that are critical in prostate cancer and/or downstream of cyclic AMP (cAMP) were examined. Both NVP-ABE171 and cilomilast decreased cell growth. In vitro, PDE4D inhibitors lead to decreased signaling of the sonic hedgehog (SHH), androgen receptor (AR), and MAPK pathways, but growth inhibition was best correlated to the SHH pathway. PDE4D inhibition also reduced proliferation of epithelial cells induced by paracrine signaling from cocultured stromal cells that had activated hedgehog signaling. In addition, PDE4D inhibitors decreased the weight of the prostate in wild-type mice. Prostate cancer xenografts grown in nude mice that were treated with cilomilast or NVP-ABE171 had decreased wet weight and increased apoptosis compared with vehicle-treated controls. These studies suggest the pharmacologic inhibition of PDE4D using small-molecule inhibitors is an effective option for prostate cancer therapy. PDE4D inhibitors decrease the growth of prostate cancer cells in vivo and in vitro, and PDE4D inhibition has therapeutic potential in prostate cancer.

Natural phosphodiesterase-4 inhibitors from the leaf skin of Aloe barbadensis Miller

The ethanolic extract of Aloe barbadensis Miller leaf skin showed inhibitory activity against phosphodiesterase-4D (PDE4D), which is a therapeutic target of inflammatory disease. Subsequent bioassay-guided fractionation led to the isolation of two new anthrones, 6′-O-acetyl-aloin B (9) and 6′-O-acetyl-aloin A (11), one new chromone, aloeresin K (8), together with thirteen known compounds. Their chemical structures were elucidated by spectroscopic methods including UV, IR, 1D and 2D NMR, and HRMS. All of the isolates were screened for their inhibitory activity against PDE4D using tritium-labeled adenosine 3′,5′-cyclic monophosphate (3H-cAMP) as substrate. Compounds 13 and 14 were identified as PDE4D inhibitors, with their IC50 values of 9.25 and 4.42μM, respectively. These achievements can provide evidences for the use of A. barbadensis leaf skin as functional feed additives for anti-inflammatory purpose.

Identification of Novel Phosphodiesterase-4D Inhibitors Prescreened by Molecular Dynamics-Augmented Modeling and Validated by Bioassay

Phosphodiesterase-4D (PDE4D) has been proved to be a potential therapeutic target against strokes. In the present study, a procedure of integrating pharmacophore, molecular docking, molecular dynamics (MD) simulations, binding free energy calculations, and finally validation with bioassay was developed and described to search for novel PDE4D inhibitors from the SPECS database. Among the 29 compounds selected by our MD-augmented strategy, 15 hits were found with IC50 between 1.9 and 50 μM (a hit rate of 52%) and 6 potent hits showed IC50 less than 10 μM, which suggested that MD simulations can explore the intermolecular interactions of PDE4D-inhibitor complexes more precisely and thus significantly enhanced the hit rate of this screening. The effective and efficient integrated procedures described in this study could be readily applied to screening studies toward other drug targets.

Abstract 1835: Phosphodiesterase 4D (PDE4D) selective inhibitors as candidate drugs for prostate cancer

Abstract Our laboratory used an insertional somatic mutagenesis screen in mice to identify novel genes that may drive prostate cancer initiation and progression. Using this screen, we have identified candidate prostate cancer genes including the candidate oncogene phosphodiesterase 4D (PDE4D). Investigation of PDE4D showed that it was over-expressed in human prostate cancer cell lines and in human prostate cancers. Stable knockdown of PDE4D by shRNA reduced the growth and migration of prostate cancer cells in vitro and in vivo. Several small molecule PDE4D-selective inhibitors have been developed, including cilomilast and NVP-ABE171, and we have used them as potential anti-prostate cancer drugs in vitro and in vivo. The inhibitors were able to reduce the growth of prostate cancer cells in the context of epithelial mono-cultures or co-cultures that modeled stromal-epithelial interactions. Daily oral administration of PDE4D inhibitors for 6 weeks also reduced the growth of several prostate cancer xenograft lines in vivo through a dramatic induction of apoptosis. Interestingly, NVP-ABE171 and cilomilast also reduced the size of the prostates of treated mice without impacting overall animal health or the sizes of other organs. Under in vitro conditions in which prostate cancer cell growth was inhibited by either NVP-ABE171 or cilomilast, we also observed changes in the activation of potential downstream molecular targets of PDE4D inhibition including the sonic hedgehog and mitogen-activated protein kinase pathways. We are continuing studies with these inhibitors to further support the use of NVP-ABE171 and cilomilast as anti-prostate cancer drugs and to understand their mechanism(s) of action in the prostate. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1835. doi:1538-7445.AM2012-1835

Treat Alzheimer's disease by traditional Chinese medicine?

Upregulated phosphodiesterase 4D (PDE4D) disrupts the regulation of calcium ion channel in the central nerve system, and hence it is considered as one of the causes of Alzheimer's disease. We employed structure-based drug design techniques and the world's largest traditional Chinese medicine (TCM) database for identifying potential TCM-based PDE4D inhibitors. We then applied multiple linear regression (MLR) and support vector machine (SVM) for quantitative structure–activity relationship model, as well as for molecular dynamics simulation analysis. Screening results suggested that metal cations, Zn2+ and Mg2+, played key roles in mediating stable protein–ligand interactions with the ligand-binding residues, Asp367 and Asp484. In addition, each ligand was shown to interfere with the active residue His326 that suggested inhibitory effects. The MLR and SVM prediction models further implied the PDE4D inhibitory effect of each TCM compound. The molecular simulation further suggested the binding stability of each compound in the PDE4D binding site. We identified three TCM compounds, such as mumefural, 2-O-feruloyl tartaric acid and kainic acid, as potential PDE4D inhibitors. In addition, we further identified the key interaction features associated with the protein–ligand-binding stabilities.

Abstract 3046: Phosphodiesterase 4D (PDE4D) as a new drug target for prostate cancer

Abstract Our laboratory used an insertional somatic mutagenesis screen in mice to identify novel genes that may drive prostate cancer initiation and progression. Using this screen, we have identified candidate prostate cancer genes including the candidate oncogene phosphodiesterase 4D (PDE4D). Investigation of PDE4D showed that it was over-expressed in human prostate cancer cell lines and in human prostate cancers. Stable knockdown of PDE4D by shRNA reduced the growth and migration of prostate cancer cells in vitro and in vivo. PDE4D has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Several small molecule PDE4D selective inhibitors have been developed and tested in clinical trials for COPD. Although these studies showed that the inhibitors had modest efficacy as a therapy for COPD, they confirmed that the inhibitors were safe for use in humans at doses that inhibited PDE4D in vivo. Based on our previous studies with PDE4D, we postulated that PDE4D small molecule inhibitors would be candidate anti-prostate cancer drugs. Daily oral administration of PDE4D inhibitors, NVP-ABE171 or cilomilast, for 6 weeks significantly reduced the growth of LNCaP-C4 prostate cancer xenografts in immune-compromised mice. Under in vitro conditions in which prostate cancer cell growth was inhibited by either NVP-ABE171 or cilomilast, we also observed changes in the activation of potential downstream molecular targets of PDE4D inhibition. Affected pathways included the sonic hedgehog and mitogen-activated protein kinase pathways. We also tested the potential role of the PDE4D pathway in prostate cancer stromal-epithelial interactions by modeling these interactions using novel microchannel co-culture devices. In this context, PDE4D inhibitors reduced the activation of Shh pathway target genes in mesenchymal cells and reduced the proliferation of epithelial cancer cell lines, supporting the potential importance of the PDE4D pathway for prostate cancer stromal-epithelial interactions. We are continuing in vitro and in vivo studies with these candidate drugs to further support the use of NVP-ABE171 and cilomilast as anti-prostate cancer drugs and to understand their mechanism of action. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3046. doi:10.1158/1538-7445.AM2011-3046

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.

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.

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.