Functional rescue of CFTR in rectal organoids from patients carrying R334W variant by CFTR modulators and PDE4 inhibitor Roflumilast.

BACKGROUND: Many disease-causing variants in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene remain uncharacterized and untreated. Restoring the function of the impaired CFTR protein is the goal of personalized medicine, particularly in patients carrying rare CFTR variants. In this study, functional defects related to the rare R334W variant were evaluated after treatment with CFTR modulators or Roflumilast, a phosphodiesterase-4 inhibitor (PDE4i). METHODS: Rectal organoids from subjects with R334W/2184insA and R334W/2183AA > G genotypes were used to perform the Forskolin-induced swelling (FIS) assay. Organoids were left drug-untreated or treated with modulators VX-770 (I), VX-445 (E), and VX-661 (T) mixed, and their combination (ETI). Roflumilast (R) was used alone or as a combination of I + R. RESULTS: Our data show a significant increase in FIS rate following treatment with I alone. The combined use of modulators, such as ETI, did not increase further swelling than I alone, nor in protein maturation. Treatment with R shows an increase in FIS response similar to those of I, and the combination R + I significantly increases the rescue of CFTR activity. CONCLUSIONS: Equivalent I and ETI treatment efficacy was observed for both genotypes. Furthermore, significant organoid swelling was observed with combined I + R used that supports the recently published data describing a potentiating effect of only I in patients carrying the variant R334W and, at the same time, corroborating the role of strategies that include PDE4 inhibitors further to potentiate the effect of I for this variant.

The PDE4 Inhibitors Roflumilast and Rolipram Rescue ADO2 Osteoclast Resorption Dysfunction.

Autosomal Dominant Osteopetrosis type II (ADO2) is a rare bone disease of impaired osteoclastic bone resorption caused by heterozygous missense mutations in the chloride channel 7 (CLCN7). Adenylate cyclase, which catalyzes the formation of cAMP, is critical for lysosomal acidification in osteoclasts. We found reduced cAMP levels in ADO2 osteoclasts compared to wild-type (WT) osteoclasts, leading us to examine whether regulating cAMP would improve ADO2 osteoclast activity. Although forskolin, a known activator of adenylate cyclase and cAMP levels, negatively affected osteoclast number, it led to an overall increase in ADO2 and WT osteoclast resorption activity in vitro. Next, we examined cAMP hydrolysis by the phosphodiesterase 4 (PDE4) proteins in ADO2 versus WT osteoclasts. QPCR analysis revealed higher expression of the three major PDE4 subtypes (4a, 4b, 4d) in ADO2 osteoclasts compared in WT, consistent with reduced cAMP levels in ADO2 osteoclasts. In addition, we found that the PDE4 antagonists, rolipram and roflumilast, stimulated ADO2 and WT osteoclast formation in a dose-dependent manner. Importantly, roflumilast and rolipram displayed a concentration-dependent increase in osteoclast resorption activity which was greater in ADO2 than WT osteoclasts. Moreover, treatment with roflumilast rescued cAMP levels in ADO2 OCLs. The key findings from our studies demonstrate that osteoclasts from ADO2 mice exhibit reduced cAMP levels and PDE4 inhibition rescues cAMP levels and ADO2 osteoclast activity dysfunction in vitro. The mechanism of action of PDE4 inhibitors and their ability to reduce the high bone mass of ADO2 mice in vivo are currently under investigation. Importantly, these studies advance the understanding of the mechanisms underlying the ADO2 osteoclast dysfunction which is critical for the development of therapeutic approaches to treat clinically affected ADO2 patients.

A study of roflumilast treatment on functional and structural changes in hippocampus in depressed Adult male Wistar rats.

Depression is a common stress disability disorder that affects higher mental functions including emotion, cognition, and behavior. It may be mediated by inflammatory cytokines that interfere with neuroendocrine function, and synaptic plasticity. Therefore, reductions in inflammation might contribute to treatment response. The current study aims to evaluate the role of Protein Kinase (PKA)- cAMP response element-binding protein (CREB)- brain derived neurotropic factor (BDNF) signaling pathway in depression and the effects of roflumilast (PDE4 inhibitor) as potential antidepressant on the activity of the PKA-CREB-BDNF signaling pathway, histology, and pro-inflammatory cytokine production. Forty Adult male Wistar rats were divided into 4 groups: Control group, Positive Control group: similar to the controls but received Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment, Depressed group which were exposed to chronic stress for 6 weeks, and Roflumilast-treated group which were exposed to chronic stress for 6 weeks and treated by Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment. The depressed group showed significant increase in immobility time with significant decrease in swimming and struggling times, significant decrease in hippocampal PKA, CERB, BDNF, Dopamine, Cortisone, and Superoxide dismutase while hippocampal Phosphodiesterase-E4, Interleukin-6, and Malondialdhyde levels were significantly elevated. These findings were significantly reversed upon Roflumilast treatment. Therefore, it could be concluded that depression is a neurodegenerative inflammatory disease and oxidative stress plays a key role in depression. Roflumilast treatment attenuated the depression behavior in rats denoting its neuroprotective, and anti-inflammatory effects.

Effect of Roflumilast, a Selective PDE4 Inhibitor, on Bone Phenotypes in ADO2 Mice.

Autosomal Dominant Osteopetrosis type II (ADO2) is a rare bone disease of impaired osteoclastic bone resorption that usually results from heterozygous missense mutations in the chloride channel 7 (CLCN7) gene. We previously created mouse models of ADO2 (p.G213R) with one of the most common mutations (G215R) as found in humans and demonstrated that this mutation in mice phenocopies the human disease of ADO2. Previous studies have shown that roflumilast (RF), a selective phosphodiesterase 4 (PDE4) inhibitor that regulates the cAMP pathway, can increase osteoclast activity. We also observed that RF increased bone resorption in both wild-type and ADO2 heterozygous osteoclasts in vitro, suggesting it might rescue bone phenotypes in ADO2 mice. To test this hypothesis, we administered RF-treated diets (0, 20 and 100 mg/kg) to 8-week-old ADO2 mice for 6 months. We evaluated bone mineral density and bone micro-architecture using longitudinal in-vivo DXA and micro-CT at baseline, and 6-, 12-, 18-, and 24-week post-baseline time points. Additionally, we analyzed serum bone biomarkers (CTX, TRAP, and P1NP) at baseline, 12-, and 24-week post-baseline. Our findings revealed that RF treatment did not improve aBMD (whole body, femur, and spine) and trabecular BV/TV (distal femur) in ADO2 mice compared to the control group treated with a normal diet. Furthermore, we did not observe any significant changes in serum levels of bone biomarkers due to RF treatment in these mice. Overall, our results indicate that RF does not rescue the osteopetrotic bone phenotypes in ADO2 heterozygous mice.

Design and synthesis of pyrazole derivatives against neutrophilic inflammation.

Neutrophils are the most abundant immune cells. However, neutrophil dysregulation leads to acute and chronic inflammation and is involved in various diseases. The aim of this study was to develop anti-inflammatory agents in human neutrophils. A drug screening was conducted on in-house compounds with the potential to inhibit the respiratory burst, which involves the generation of superoxide anions in human neutrophils. Bioisosteric replacement was then applied to design more active derivatives. The most potent inhibitors of superoxide anion generation activity were compounds 58 and 59, which had IC50 values of 13.30 and 9.06 nM, respectively. The inhibitory effects of 58 and 59 were reversed by H89, a PKA inhibitor. PDE selective screening indicated that the best inhibitory effects were PDE4B1 and PDE4D2, and the inhibitory activities were 83% and 85%, respectively, at a 10 µM concentration of 59. The final molecular simulation experiment highlighted the slightly different binding poses of 58 and 59 in the PDE4 active site. An in vivo pharmacokinetic study revealed that the half-life of 59 was approximately 79 min when using intravenous bolus administration. This work introduced a new class structure of PDE4 inhibitors resulting in potent neutrophil inactivation activity, with the aim of contributing to new anti-inflammatory drug discovery.

Phosphodiesterase (PDE) 4 inhibition boosts Schwann cell myelination in a 3D regeneration model.

Phosphodiesterase 4 (PDE4) inhibitors have been extensively researched for their anti-inflammatory and neuroregenerative properties. Despite the known neuroplastic and myelin regenerative properties of nonselective PDE4 inhibitors on the central nervous system, the direct impact on peripheral remyelination and subsequent neuroregeneration has not yet been investigated. Therefore, to examine the possible therapeutic effect of PDE4 inhibition on peripheral glia, we assessed the differentiation of primary rat Schwann cells exposed in vitro to the PDE4 inhibitor roflumilast. To further investigate the differentiation promoting effects of roflumilast, we developed a 3D model of rat Schwann cell myelination that closely resembles the in vivo situation. Using these in vitro models, we demonstrated that pan-PDE4 inhibition using roflumilast significantly promoted differentiation of Schwann cells towards a myelinating phenotype, as indicated by the upregulation of myelin proteins, including MBP and MAG. Additionally, we created a unique regenerative model comprised of a 3D co-culture of rat Schwann cells and human iPSC-derived neurons. Schwann cells treated with roflumilast enhanced axonal outgrowth of iPSC-derived nociceptive neurons, which was accompanied by an accelerated myelination speed, thereby showing not only phenotypic but also functional changes of roflumilast-treated Schwann cells. Taken together, the PDE4 inhibitor roflumilast possesses a therapeutic benefit to stimulate Schwann cell differentiation and, subsequently myelination, as demonstrated in the biologically relevant in vitro platform used in this study. These results can aid in the development of novel PDE4 inhibition-based therapies in the advancement of peripheral regenerative medicine.

PDE4 inhibitor eliminates breast cancer stem cells via noncanonical activation of mTOR.

Ineffective cancer treatment is implicated in metastasis, recurrence, resistance to chemotherapy and radiotherapy, and evasion of immune surveillance. All these failures occur due to the persistence of cancer stem cells (CSCs) even after rigorous therapy, thereby rendering them as essential targets for cancer management. Contrary to the quiescent nature of CSCs, a gene profiler array disclosed that phosphatidylinositol-3-kinase (PI3K), which is known to be crucial for cell proliferation, differentiation, and survival, was significantly upregulated in CSCs. Since PI3K is modulated by cyclic adenosine 3',5' monophosphate (cAMP), analyses of cAMP regulation revealed that breast CSCs expressed increased levels of phosphodiesterase 4 (PDE4) in contrast to normal stem cells. In accordance, the effects of rolipram, a PDE4 inhibitor, were evaluated on PI3K regulators and signaling. The efficacy of rolipram was compared with paclitaxel, an anticancer drug that is ineffective in obliterating breast CSCs. Analyses of downstream signaling components revealed a switch between cell survival and death, in response to rolipram, specifically of the CSCs. Rolipram-mediated downregulation of PDE4A levels in breast CSCs led to an increase in cAMP levels and protein kinase A (PKA) expression. Subsequently, PKA-mediated upregulation of phosphatase and tensin homolog antagonized the PI3K/AKT/mTOR pathway and led to cell cycle arrest. Interestingly, direct yet noncanonical activation of mTOR by PKA, circumventing the influence of PI3K and AKT, temporally shifted the fate of CSCs toward apoptosis. Rolipram in combination with paclitaxel indicated synergistic consequences, which effectively obliterated CSCs within a tumor, thereby suggesting combinatorial therapy as a sustainable and effective strategy to abrogate breast CSCs for better patient prognosis.

α-mangostin derivative 4e as a PDE4 inhibitor promote proteasomal degradation of alpha-synuclein in Parkinson's disease models through PKA activation.

BACKGROUND: Parkinson's disease (PD) is a multi-factorial neurodegenerative disease affecting motor function of patients. The hall markers of PD are dopaminergic neuron loss in the midbrain and the presence of intra-neuronal inclusion bodies mainly composed of aggregation-prone protein alpha-synuclein (α-syn). Ubiquitin-proteasome system (UPS) is a multi-step reaction process responsible for more than 80% intracellular protein degradation. Impairment of UPS function has been observed in the brain tissue of PD patients. PDE4 inhibitors have been shown to activate cAMP-PKA pathway and promote UPS activity in Alzheimer's disease model. α-mangostin is a natural xanthonoid with broad biological activities, such as antioxidant, antimicrobial and antitumour activities. Structure-based optimizations based on α-mangostin produced a potent PDE4 inhibitor, 4e. Herein, we studied whether 4e could promote proteasomal degradation of α-syn in Parkinson's disease models through PKA activation. METHODS: cAMP Assay was conducted to quantify cAMP levels in samples. Model UPS substrates (Ub-G76V-GFP and Ub-R-GFP) were used to monitor UPS-dependent activity. Proteasome activity was investigated by short peptide substrate, Suc-LLVY-AMC, cleavage of which by the proteasome increases fluorescence sensitivity. Tet-on WT, A30P, and A53T α-syn-inducible PC12 cells and primary mouse cortical neurons from A53T transgenic mice were used to evaluate the effect of 4e against α-syn in vitro. Heterozygous A53T transgenic mice were employed to assess the effect of 4e on the clearance of α-syn in vivo, and further validations were applied by western blotting and immunohistochemistry. RESULTS: Taken together, α-mangostin derivative 4e, a PDE4 inhibitor, efficiently activated the cAMP/PKA pathway in neuronal cells, and promoted UPS activity as evidenced by enhanced degradation of UPS substrate Ub-G76V-GFP and Ub-R-GFP, as well as elevated proteasomal enzyme activity. Interestingly, 4e dramatically accelerated degradation of inducibly-expressed WT and mutant α-syn in PC12 cells, in a UPS dependent manner. Besides, 4e consistently activated PKA in primary neuron and A53T mice brain, restored UPS inhibition and alleviated α-syn accumulation in the A53T mice brain. CONCLUSIONS: 4e is a natural compound derived highly potent PDE4 inhibitor. We revealed its potential effect in promoting UPS activity to degrade pathogenic proteins associated with PD.

Mangostanin Derivatives as Novel and Orally Active Phosphodiesterase 4 Inhibitors for the Treatment of Idiopathic Pulmonary Fibrosis with Improved Safety.

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease, and its incidence rate is rapidly rising. However, effective therapies for the treatment of IPF are still lacking. Phosphodiesterase 4 (PDE4) inhibitors were reported to be potential anti-fibrotic agents, but their clinical use was hampered by side effects like emesis and nausea. Herein, structure-based hit-to-lead optimizations of natural mangostanin resulted in the novel and orally active PDE4 inhibitor 18a with potent inhibitory affinity (IC50 = 4.2 nM), favorable physico-chemical properties, and a different binding pattern from roflumilast. Emetic activity tests on dogs demonstrated that 18a cannot cause emesis even at an oral dose of 10 mg/kg, whereas rolipram had severe emetic effects at an oral dose of 1 mg/kg. Finally, the oral administration of 18a (10 mg/kg) exhibited comparable anti-pulmonary fibrosis effects with pirfenidone (150 mg/kg) in a bleomycin-induced IPF rat model, indicating its potential as a novel anti-IPF agent with improved safety.

Design, synthesis, biological evaluation and structural characterization of novel GEBR library PDE4D inhibitors.

Memory and cognitive functions depend on the cerebral levels of cyclic adenosine monophosphate (cAMP), which are regulated by the phosphodiesterase 4 (PDE4) family of enzymes. Selected rolipram-related PDE4 inhibitors, members of the GEBR library, have been shown to increase hippocampal cAMP levels, providing pro-cognitive benefits with a safe pharmacological profile. In a recent SAR investigation involving a subset of GEBR library compounds, we have demonstrated that, depending on length and flexibility, ligands can either adopt a twisted, an extended or a protruding conformation, the latter allowing the ligand to form stabilizing contacts with the regulatory domain of the enzyme. Here, based on those findings, we describe further chemical modifications of the protruding subset of GEBR library inhibitors and their effects on ligand conformation and potency. In particular, we demonstrate that the insertion of a methyl group in the flexible linker region connecting the catechol portion and the basic end of the molecules enhances the ability of the ligand to interact with both the catalytic and the regulatory domains of the enzyme.

PdCl2-catalyzed synthesis of a new class of isocoumarin derivatives containing aminosulfonyl / aminocarboxamide moiety: First identification of a isocoumarin based PDE4 inhibitor.

While anti-inflammatory properties of isocoumarins are known their PDE4 inhibitory potential was not explored previously. In our effort the non-PDE4 inhibitor isocoumarins were transformed into the promising inhibitors via introducing an aminosulfonyl/aminocarboxamide moiety to the C-3 benzene ring attached to the isocoumarin framework. This new class of isocoumarins were synthesized via a PdCl2-catalyzed construction of the 4-allyl substituted 3-aryl isocoumarin ring starting from the appropriate 2-alkynyl benzamide derivative. Several compounds showed good inhibition of PDE4B in vitro and the SAR indicated superiority of aminosulfonamide moiety over aminocarboxamide in terms of PDE4B inhibition. Two compounds 3q and 3u with PDE4B IC50 = 0.43 ± 0.11 and 0.54 ± 0.19 µM and ≥ 2-fold selectivity over PDE4D emerged as initial hits. The participation of aminosulfonamide moiety in PDE4B inhibition and the reason for selectivity though moderate shown by 3q and 3u was revealed by the in silico docking studies. In view of potential usefulness of moderately selective PDE4B inhibitors the compound 3u (that showed PDE4 selectivity over other PDEs) was further evaluated in adjuvant induced arthritic rats. At an intraperitoneal dose of 30 mg/kg the compound showed a significant reduction in paw swelling (in a dose dependent manner), inflammation and pannus formation (in the knee joints) as well as pro-inflammatory gene expression/mRNA levels and increase in body weight. Moreover, besides its TNF-α inhibition and no significant toxicity in an MTT assay the compound did not show any adverse effects in a thorough toxicity studies e.g. teratogenicity, hepatotoxicity, cardiotoxicity and apoptosis in zebrafish. Thus, the isocoumarin 3u emerged as a new, safe and moderately selective PDE4B inhibitor could be useful for inflammatory diseases possibly including COVID-19.

Drotaverine Inhibitor of PDE4: Reverses the Streptozotocin Induced Alzheimer's Disease in Mice.

Alzheimer's disease (AD) is a progressive neurodegenerative disease associated with decline in memory and cognitive impairments. Phosphodiesterase IV (PDE4) protein, an intracellular cAMP levels regulator, when inhibited act as potent neuroprotective agents by virtue of ceasing the activity of Pro-inflammatory mediators. The complexity of AD etiology has ever since compelled the researchers to discover multifunctional compounds to combat the AD and neurodegeneration. The aim of this study was to probe into role of drotaverine a PDE4 inhibitor in the management of AD. Albino mice were divided into seven groups (n = 10). Group 1 control group received carboxy methyl cellulose (CMC 1 mL/kg), group II diseased group treated with streptozotocin (STZ 3 mg/kg) by intracerebroventricular (ICV) route, group III administered standard drug Piracetam 200 mg/kg and groups IV-VII were given drotaverine (10, 20, 40, and 80 mg/kg i/p respectively). Groups II-VII were given STZ (3 mg/kg, ICV) on 1st and 3rd day of treatment to induce AD. All the groups were given their respective treatments for 23 days. Improvement in learning and memory was evaluated by using behavioral tests like open field test, elevated plus maze test, Morris water maze test and passive avoidance test. Furthermore, brain levels of biochemical markers of oxidative stress, neurotransmitters, ß-amyloid and tau protein were also measured. Drotaverine showed statistically significant dose dependent improvement in behavioral and biochemical markers of AD: the maximum response was achieved at a dose level of 80 mg/kg. The Study concluded that drotaverine ameliorates cognitive impairment and as well as exhibited modulated the brain levels of neurotransmitters.

Synthesis and bioactivity of phenyl substituted furan and oxazole carboxylic acid derivatives as potential PDE4 inhibitors.

In this present study, a series of 5-phenyl-2-furan and 4-phenyl-2-oxazole derivatives were designed and synthesized as phosphodiesterase type 4 (PDE4) inhibitors. In vitro results showed that the synthesized compounds exhibited considerable inhibitory activity against PDE4B and blockade of LPS-induced TNF-α release. Among the designed compounds, Compound 5j exhibited lower IC50 value (1.4 µM) against PDE4 than parent rolipram (2.0 µM) in in vitro enzyme assay, which also displayed good in vivo activity in animal models of asthma/COPD and sepsis induced by LPS. Docking results suggested that introduction of methoxy group at para-position of phenyl ring, demonstrated good interaction with metal binding pocket domain of PDE4B, which was helpful to enhance inhibitory activity.

Novel anilide and benzylamide derivatives of arylpiperazinylalkanoic acids as 5-HT1A/5-HT7 receptor antagonists and phosphodiesterase 4/7 inhibitors with procognitive and antidepressant activity.

A library of novel anilide and benzylamide derivatives of ω-(4-(2-methoxyphenyl)piperazin-1-yl)alkanoic acids as combined 5-HT1A/5-HT7 receptor ligands and phosphodiesterase PDE4B/PDE7A inhibitors was designed using a structure-based drug design approach. The in vitro studies of 33 newly synthesized compounds (7-39) allowed us to identify 22 as the most promising multifunctional 5-HT1A/5-HT7 receptor antagonist (5-HT1AKi = 8 nM, Kb = 0.04 nM; 5-HT7Ki = 451 nM, Kb = 460 nM) with PDE4B/PDE7A inhibitory activity (PDE4B IC50 = 80.4 µM; PDE7A IC50 = 151.3 µM). Compound 22 exerted a very good ability to passively penetrate through biological membranes and a high metabolic stability in vitro. Moreover, the pharmacological evaluation of 22 showed its procognitive and antidepressant properties in rat behavioral tests. Compound 22 at a dose of 3 mg/kg (i.p.) significantly reversed MK-801-induced episodic memory deficits in the novel object recognition test, while at a dose of 10 mg/kg (i.p.) reduced the immobility time of animals (by about 34%) in the forced swimming test. The antidepressant-like effect produced by compound 22 was stronger than that of escitalopram used as a reference drug. This study opens a new perspective in the search for efficacious drugs for the treatment of cognitive and depressive disorders.

Roflumilast, a Phosphodiesterases-4 (PDE4) Inhibitor, Alleviates Sepsis­induced Acute Kidney Injury.

BACKGROUND Sepsis causes acute kidney injury (AKI) in critically ill patients. Roflumilast, a phosphodiesterases-4 (PDE4) inhibitor, has been shown to be therapeutically effective in sepsis-induced organ injury. However, the function of roflumilast in sepsis-induced AKI is not clearly understood. The present study aimed to explore the protective effect of roflumilast on sepsis-induced AKI in mice. MATERIAL AND METHODS A sepsis model was established by cecal ligation and puncture surgery. Roflumilast (1 mg/kg and 3 mg/kg) was used once daily for 7 consecutive days for treatment. Kidney tissues were pathologically examined by hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining. The levels of kidney injury markers including blood urea nitrogen (BUN), creatinine (Cre), kidney injury molecule-1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL), and inflammatory cytokines including interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, and IL-1ß were detected by their corresponding test kits. The protein expression was measured using western blot and cell apoptosis of kidney tissue was determined by TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay. RESULTS Roflumilast was demonstrated to alleviate sepsis-induced AKI by reducing histopathological changes and decreasing the levels of kidney injury markers in a concentration-dependent way. The production of TNF-alpha, IL-6, and IL-1ß was significantly suppressed by roflumilast. Besides, roflumilast inhibited the activation of NLRP3 (nucleotide-binding domain (NOD)-like receptor protein 3) and NF-kappaB (nuclear factor kappa-light-chain-enhancer of activated B cells). Additionally, roflumilast inhibited cell apoptosis and changes in expression of apoptosis related proteins induced by sepsis. Finally, high concentration of roflumilast (3 mg/kg) did not have an adverse effect on liver, heart, lung, or spleen. CONCLUSIONS Our study indicated that roflumilast could ameliorate AKI induced by sepsis through restraining inflammatory response and apoptosis of the kidney, providing a molecular basis for a novel medical treatment of septic AKI.

Ultrasound assisted rapid synthesis of mefenamic acid based indole derivatives under ligand free Cu-catalysis: Their pharmacological evaluation.

An improved and rapid synthesis of mefenamic acid based indole derivatives has been achieved via the ligand free Cu-catalyzed coupling-cyclization method under ultrasound irradiation. This simple, straightforward and inexpensive one-pot method involved the reaction of a terminal alkyne derived from mefenamic acid with 2-iodosulfanilides in the presence of CuI and K2CO3 in PEG-400. The reaction proceeded via an initial CC bond formation (the coupling step) followed by CN bond formation (the intramolecular cyclization) to afford the mefenamic acid based indole derivatives in good to acceptable yields. Several of these compounds showed inhibition of PDE4 in vitro and the SAR (Structure Activity Relationship) within the series is discussed. The compound 3d has been identified as a promising and selective inhibitor of PDE4B (IC50 = 1.34 ± 0.46 µM) that showed TNF-α inhibition in vitro (IC50 = 5.81 ± 0.24 µM) and acceptable stability in the rat liver microsomes.

Discovery and Optimization of α-Mangostin Derivatives as Novel PDE4 Inhibitors for the Treatment of Vascular Dementia.

To validate PDE4 inhibitors as novel therapeutic agents against vascular dementia (VaD), 25 derivatives were discovered from the natural inhibitor α-mangostin (IC50 = 1.31 µM). Hit-to-lead optimization identified a novel and selective PDE4 inhibitor 4e (IC50 = 17 nM), which adopted a different binding pattern from PDE4 inhibitors roflumilast and rolipram. Oral administration of 4e at a dose of 10 mg/kg exhibited remarkable therapeutic effects in a VaD model and did not cause emesis to beagle dogs, indicating its potential as a novel anti-VaD agent.

Soft drugs for dermatological applications: recent trends.

A soft drug (SD) displays a metabolically labile spot and, after having exerted its activity in the site of action, undergoes a fast metabolism, leading to inactive metabolites. The SD approach has recently found widespread application in the dermatological field because it provides a means of localising the therapeutic effect in skin, while minimising systemic exposure. The literature is rapidly growing of successful examples of compounds targeting sphingosine-1-phosphate receptor 1 (S1PR1), transient receptor potential vanilloid 1 (TRPV1), Janus kinase (JAK), caspase 1, and histone deacetylase (HDAC), for the treatment of skin inflammatory, autoimmune, and oncological diseases. As a demonstration of the potential of this strategy, the SD approach recently led to the approval of crisaborole, a soft phosphodiesterase 4 (PDE4) inhibitor, for atopic dermatitis, while other agents are in clinical development.

Pharmacological and molecular dynamics analyses of differences in inhibitor binding to human and nematode PDE4: Implications for management of parasitic nematodes.

Novel chemical controls are needed that selectively target human, animal, and plant parasitic nematodes with reduced adverse effects on the host or the environment. We hypothesize that the phosphodiesterase (PDE) enzyme family represents a potential target for development of novel nematicides and anthelmintics. To test this, we identified six PDE families present in the nematode phylum that are orthologous to six of the eleven human PDE families. We characterized the binding interactions of family-selective PDE inhibitors with human and C. elegans PDE4 in conjunction with molecular dynamics (MD) simulations to evaluate differences in binding interactions of these inhibitors within the PDE4 catalytic domain. We observed that roflumilast (human PDE4-selective inhibitor) and zardaverine (selective for human PDE3 and PDE4) were 159- and 77-fold less potent, respectively, in inhibiting C. elegans PDE4. The pan-specific PDE inhibitor isobutyl methyl xanthine (IBMX) had similar affinity for nematode and human PDE4. Of 32 residues within 5 Å of the ligand binding site, five revealed significant differences in non-bonded interaction energies (van der Waals and electrostatic interaction energies) that could account for the differential binding affinities of roflumilast and zardaverine. One site (Phe506 in the human PDE4D3 amino acid sequence corresponding to Tyr253 in C. elegans PDE4) is predicted to alter the binding conformation of roflumilast and zardaverine (but not IBMX) into a less energetically favorable state for the nematode enzyme. The pharmacological differences in sensitivity to PDE4 inhibitors in conjunction with differences in the amino acids comprising the inhibitor binding sites of human and C. elegans PDE4 catalytic domains together support the feasibility of designing the next generation of anthelmintics/nematicides that could selectively bind to nematode PDEs.

Discovery of 2-(3,4-dialkoxyphenyl)-2-(substituted pyridazin-3-yl)acetonitriles as phosphodiesterase 4 inhibitors with anti-neuroinflammation potential based on three-dimensional quantitative structure-activity relationship study.

Phosphodiesterase 4 (PDE4) inhibitors with potential activities for CNS disorders provide a new therapeutic strategy for depression. To discover PDE4 inhibitors with anti-neuroinflammation activities, reliable three-dimensional quantitative structure-activity relationship (3D-QSAR) models on our previous reported catecholic PDE4 inhibitors was built with a statistically significant cross-validated coefficient (q2 ), conventional coefficient (r2 ), and good predictive capabilities based on the molecular docking results, using comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) methods. Based on the analysis of CoMFA and CoMSIA contour maps, a series of 2-(3,4-dialkoxyphenyl)-2-(substituted pyridazin-3-yl) acetonitriles 16a-i was designed and synthesized. Among these compounds, compound 16a exhibited good inhibitory activities toward PDE4B1 and PDE4D7 with mid-nanomolar IC50 values and potential anti-neuroinflammation activity in BV-2 cells. Docking simulation of compound 16a in the PDE4 catalytic domain activity pocket revealed that compound 16a maybe assumed a "V-shaped" conformation, extending the side chain to S-pocket.