General trends in the effects of VX-661 and VX-445 on the plasma membrane expression of clinical CFTR variants

Cystic fibrosis (CF) is caused by mutations that compromise the expression and/or function of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. Most people with CF harbor a common misfolded variant (ΔF508) that can be partially rescued by therapeutic "correctors" that restore its expression. Nevertheless, many other CF variants are insensitive to correctors. Using deep mutational scanning, we quantitatively compare the effects of two correctors on the plasma membrane expression of 129 CF variants. Though structural calculations suggest corrector binding provides similar stabilization to most variants, it's those with intermediate expression and mutations near corrector binding pockets that exhibit the greatest response. Deviations in sensitivity appear to depend on the degree of variant destabilization and the timing of misassembly. Combining correctors appears to rescue more variants by doubling the binding energy and stabilizing distinct cotranslational folding transitions. These results provide an overview of rare CF variant expression and establish new tools for precision pharmacology.

ABCB1 and ABCG2 limit brain penetration and, together with CYP3A4, total plasma exposure of abemaciclib and its active metabolites

Abemaciclib is the third cyclin-dependent kinase (CDK) 4/6 inhibitor approved for the treatment of breast cancer and currently under investigation for other malignancies, including brain cancer. Primarily CYP3A4 metabolizes abemaciclib, forming three active metabolites (M2, M20 and M18) that are likely relevant for abemaciclib efficacy and toxicity. We investigated the impact of ABCB1 (P-gp), ABCG2 (BCRP) and CYP3A on the pharmacokinetics and tissue distribution of abemaciclib and its metabolites using genetically modified mice. In vitro, abemaciclib was efficiently transported by hABCB1 and mAbcg2, and slightly by hABCG2, but the active metabolites were transported even better. Upon oral administration of 10mg/kg abemaciclib, absence of Abcg2 and especially Abcb1a/1b significantly increased the plasma AUC_0-24h and C_max of M2 and M18. Furthermore, the relative brain penetration of abemaciclib, M2 and M20 was dramatically increased by 25-, 4- and 60-fold, respectively, in Abcb1a/1b;Abcg2^-/- mice, and to a lesser extent in single Abcb1a/1b- or Abcg2-deficient mice. The recovery of all active compounds in the small intestine content was profoundly reduced in Abcb1a/1b;Abcg2^-/- mice, with smaller effects in single Abcb1a/1b^-/- and Abcg2^-/- mice. Our results indicate that Abcb1a/1b and Abcg2 cooperatively and profoundly limit the brain penetration of abemaciclib and its active metabolites, and likely also participate in their hepatobiliary or direct intestinal elimination. Moreover, transgenic human CYP3A4 drastically reduced the abemaciclib plasma AUC_0-24h and C_max by 7.5- and 5.6-fold, respectively, relative to Cyp3a^-/- mice. These insights may help to optimize the clinical development of abemaciclib, especially for the treatment of brain malignancies.

KRIBB11 Induces Apoptosis in A172 Glioblastoma Cells via MULE-Dependent Degradation of MCL-1

KRIBB11, an HSF1 inhibitor, was shown to sensitize various types of cancer cells to treatment with several anticancer drugs. However, the exclusive effects of KRIBB11 in preventing the growth of glioblastoma cells and the related mechanisms have not been elucidated yet. Herein, we aimed to examine the potential of KRIBB11 as an anticancer agent for glioblastoma. Using MTT and colony formation assays and Western blotting for c-PARP, we demonstrated that KRIBB11 substantially inhibits the growth of A172 glioma cells by inducing apoptosis. At the molecular level, KRIBB11 decreased anti-apoptotic protein MCL-1 levels, which was attributable to the increase in MULE ubiquitin ligase levels. However, the constitutive activity of HSF1 in A172 cells was not influenced by the exclusive treatment with KRIBB11. Additionally, based on cycloheximide chase assay, we found that KRIBB11 markedly retarded the degradation of MULE. In conclusion, stabilization of MULE upon KRIBB11 treatment is apparently an essential step for degradation of MCL-1 and the subsequent induction of apoptosis in A172 cells. Our results have expanded the knowledge on molecular pathways controlled by KRIBB11 and could be potentially effective for developing an inhibitory therapeutic strategy for glioblastoma.

Head-to-Head Comparison of the Two MAO-B Radioligands, 18F-THK5351 and 11C-L-Deprenyl, to Visualize Astrogliosis in Patients With Neurological Disorders

Three patients with neurological disorders (cerebral infarction, progressive multifocal leukoencephalopathy, and multiple sclerosis) underwent F-THK5351 and C-L-deprenyl PET on the same day to visualize lesions undergoing astrogliosis by measuring MAO-B activity. BPND map and SUV image with F-THK5351 as well as Ki map, Ki/K1 map and SUV image with C-L-deprenyl were created. F-THK5351 BPND maps and SUV images clearly identified the lesions undergoing astrogliosis. C-L-deprenyl Ki/K1 maps were close to F-THK5351 images, but very noisy. Ki maps and SUV images were likely affected by the effect of blood flow. Hence, F-THK5351 is superior to C-L-deprenyl for visualizing lesions undergoing astrogliosis.

The Specific IKKε/TBK1 Inhibitor Amlexanox Suppresses Human Melanoma by the Inhibition of Autophagy, NF-κB and MAP Kinase Pathways

Inhibitor-kappaB kinase epsilon (IKKε) and TANK-binding kinase 1 (TBK1) are non-canonical IκB kinases, both described as contributors to tumor growth and metastasis in different cancer types. Several hints indicate that they are also involved in the pathogenesis of melanoma; however, the impact of their inhibition as a potential therapeutic measure in this "difficult-to-treat" cancer type has not been investigated so far. We assessed IKKε and TBK1 expression in human malignant melanoma cells, primary tumors and the metastasis of melanoma patients. Both kinases were expressed in the primary tumor and in metastasis and showed a significant overexpression in tumor cells in comparison to melanocytes. The pharmacological inhibition of IKKε/TBK1 by the approved drug amlexanox reduced cell proliferation, migration and invasion. Amlexanox did not affect the cell cycle progression nor apoptosis induction but significantly suppressed autophagy in melanoma cells. The analysis of potential functional downstream targets revealed that NF-кB and ERK pathways might be involved in kinase-mediated effects. In an in vivo xenograft model in nude mice, amlexanox treatment significantly reduced tumor growth. In conclusion, amlexanox was able to suppress tumor progression potentially by the inhibition of autophagy as well as NF-кB and MAP kinase pathways and might therefore constitute a promising candidate for melanoma therapy.

The role of P2X4 receptor in neuropathic pain and its pharmacological properties

Neuropathic pain (NPP) is a common symptom of most diseases in clinic, which seriously affects the mental health of patients and brings certain pain to patients. Due to its pathological mechanism is very complicated, and thus, its treatment has been one of the challenges in the field of medicine. Therefore, exploring the pathogenesis and treatment approach of NPP has aroused the interest of many researchers. ATP is an important energy information substance, which participates in the signal transmission in the body. The P2 × 4 receptor (P2 × 4R) is dependent on ATP ligand-gated cationic channel receptor, which can be activated by ATP and plays an important role in the transmission of information in the nervous system and the formation of pain. In this paper, we provide a comprehensive review of the structure and function of the P2 × 4R gene. We also discuss the pathogenesis of NPP and the intrinsic relationship between P2 × 4R and NPP. Moreover, we explore the pharmacological properties of P2 × 4R antagonists or inhibitors used as targeted therapies for NPP.

Persistence of fluazinam in soil under boreal conditions

Fluazinam, a widely used pesticide in conventional potato cultivation, is effective against epidemics of the fungal disease late blight. To assess fluazinam persistence in soil, laboratory experiments were conducted with fluazinam added to soil as a pure chemical or contained in the commercial product Shirlan^®. In a follow-up experiment, the persistence was monitored under constant temperature and water content conditions during a maximum period of 1 year. In an annual climatic rotation experiment, fluazinam added to soil was exposed to the year-round temperature and water content conditions occurring in the boreal zone. A third experiment was undertaken to clarify the effect of soil organic matter (SOM) on the recovery of fluazinam. In the follow-up and annual climatic rotation experiments, more than half of the added fluazinam was recovered after 1 year of incubation. The estimated half-life of fluazinam ranged between 355 and 833 days. The degradation of fluazinam was enhanced by an abundance of SOM, a warm temperature, and wetness. Additionally, in over half of soil samples collected from fields where potato had been intensively cultivated for many years, varying concentrations of fluazinam were detected. Fluazinam can carry over to the next growing season in professional potato production.

Structural basis for neutralization of hepatitis A virus informs a rational design of highly potent inhibitors

Hepatitis A virus (HAV), an enigmatic and ancient pathogen, is a major causative agent of acute viral hepatitis worldwide. Although there are effective vaccines, antivirals against HAV infection are still required, especially during fulminant hepatitis outbreaks. A more in-depth understanding of the antigenic characteristics of HAV and the mechanisms of neutralization could aid in the development of rationally designed antiviral drugs targeting HAV. In this paper, 4 new antibodies—F4, F6, F7, and F9—are reported that potently neutralize HAV at 50% neutralizing concentration values (neut₅₀) ranging from 0.1 nM to 0.85 nM. High-resolution cryo-electron microscopy (cryo-EM) structures of HAV bound to F4, F6, F7, and F9, together with results of our previous studies on R10 fragment of antigen binding (Fab)-HAV complex, shed light on the locations and nature of the epitopes recognized by the 5 neutralizing monoclonal antibodies (NAbs). All the epitopes locate within the same patch and are highly conserved. The key structure-activity correlates based on the antigenic sites have been established. Based on the structural data of the single conserved antigenic site and key structure-activity correlates, one promising drug candidate named golvatinib was identified by in silico docking studies. Cell-based antiviral assays confirmed that golvatinib is capable of blocking HAV infection effectively with a 50% inhibitory concentration (IC₅₀) of approximately 1 μM. These results suggest that the single conserved antigenic site from complete HAV capsid is a good antiviral target and that golvatinib could function as a lead compound for anti-HAV drug development.

Structures of hepatitis A virus in complex with five neutralizing antibodies reveal a single conserved antigenic site and pinpoint key structure-activity correlates, allowing in silico screening to identify a potent candidate inhibitor drug, golvatinib.

Hepatitis A virus (HAV) is a unique, hepatotropic human picornavirus that infects approximately 1.5 million people annually and continues to cause mortality despite a successful vaccine. There are no licensed therapeutic drugs to date. Better knowledge of HAV antigenic features and neutralizing mechanisms will facilitate the development of HAV-targeting antiviral drugs. In this study, we report 4 potent HAV-specific neutralizing monoclonal antibodies (NAbs), together with our previous reported R10, that efficiently inhibit HAV infection by blocking attachment to the host cell. All 5 epitopes are located within the same patch and are highly conserved across 6 genotypes of human HAV, which suggests a single antigenic site for HAV, highlighting a prime target for structure-based drug design. Analysis of complexes with the 5 NAbs with varying neutralizing activities pinpointed key structure-activity correlates. By using a robust in silico docking method, one promising inhibitor named golvatinib was successfully identified from the DrugBank Database. In vitro assays confirmed its ability to block viral infection and revealed its neutralizing mechanism. Our approach could be useful in the design of effective drugs for picornavirus infections.

Efficiency and Safety Assurance of Six Fungicides Applied on Postharvest Cabbages Stored in a Natural Environment

Postharvest disease is a major factor in the limited shelf life of many fruits and vegetables, and it is often managed using fungicidal spraying or soaking. In this study, we first tested the efficiency of six common fungicides on postharvest head cabbage ( Brassica oleracea var. capitata) against Botrytis cinerea. Afterward, the elimination abilities of these six fungicides on different layers of cabbage heads were examined, and the effects of the household processes on residue removal were evaluated. Results showed that very low contents of residues reached the inner layers and that peeling the three outmost leaves of cabbage could eliminate most of the investigated fungicides. All six fungicides disappeared during washing, stir-frying, or boiling, among which cyprodinil was the easiest to be eliminated. Furthermore, the combined processes reduced the residues below the limits of quantification for all six investigated fungicides, even after 2 days of spraying.

Differences in gray and white matter 18F-THK5351 uptake between behavioral-variant frontotemporal dementia and other dementias

PURPOSE

We investigated the regional distribution of ¹⁸F-THK5351 uptake in gray (GM) and white matter (WM) in patients with behavioral-variant frontotemporal dementia (bvFTD) and compared it with that in patients with Alzheimer's disease (AD) or semantic dementia (SD).

METHODS

¹⁸F-THK-5351 positron emission tomography (PET), ¹⁸F-florbetaben PET, magnetic resonance imaging, and neuropsychological testing were performed in 103 subjects including 30, 24, 9, and 8 patients with mild cognitive impairment, AD, bvFTD, and SD, respectively, and 32 normal subjects. Standardized uptake value ratios (SUVRs) of ¹⁸F-THK-5351 PET images were measured from six GM and WM regions using cerebellar GM as reference. GM and WM SUVRs and WM/GM ratios, the relationship between GM SUVR and WM/GM ratio, and correlation between SUVR and cognitive function were compared.

RESULTS

In AD, both parietal GM (p < 0.001) and WM (p < 0.001) SUVRs were higher than in bvFTD. In AD and SD, the WM/GM ratio decreased as the GM SUVR increased, regardless of lobar region. In AD, memory function correlated with parietal GM (ρ = -0.74, p < 0.001) and WM (ρ = -0.53, p < 0.001) SUVR. In SD, language function correlated with temporal GM SUVR (ρ = -0.69, p = 0.006). The frontal WM SUVR was higher in bvFTD than in AD (p = 0.003) or SD (p = 0.017). The frontal WM/GM ratio was higher in bvFTD than in AD (p < 0.001). In bvFTD, the WM/GM ratio increased more prominently than the GM SUVR only in the frontal lobe (R² = 0.026). In bvFTD, executive function correlated with frontal WM SUVR (ρ = -0.64, p = 0.014).

CONCLUSIONS

Frontal WM ¹⁸F-THK5351 uptake was higher in bvFTD than in other dementias. The increase in frontal WM uptake was greater than the increase in GM uptake and correlated with executive function. This suggests that frontal lobe WM ¹⁸F-THK5351 uptake reflects neuropathological differences between bvFTD and other dementias.

Single-word comprehension deficits in the nonfluent variant of primary progressive aphasia

BACKGROUND

A subset of patients with the nonfluent variant of primary progressive aphasia (PPA) exhibit concomitant single-word comprehension problems, constituting a 'mixed variant' phenotype. This phenotype is rare and currently not fully characterized. The aim of this study was twofold: to assess the prevalence and nature of single-word comprehension problems in the nonfluent variant and to study multimodal imaging characteristics of atrophy, tau, and amyloid burden associated with this mixed phenotype.

METHODS

A consecutive memory-clinic recruited series of 20 PPA patients (12 nonfluent, five semantic, and three logopenic variants) were studied on neurolinguistic and neuropsychological domains relative to 64 cognitively intact healthy older control subjects. The neuroimaging battery included high-resolution volumetric magnetic resonance imaging processed with voxel-based morphometry, and positron emission tomography with the tau-tracer [18F]-THK5351 and amyloid-tracer [11C]-Pittsburgh Compound B.

RESULTS

Seven out of 12 subjects who had been classified a priori with nonfluent variant PPA showed deficits on conventional single-word comprehension tasks along with speech apraxia and agrammatism, corresponding to a mixed variant phenotype. These mixed variant cases included three females and four males, with a mean age at onset of 65 years (range 44-77 years). Object knowledge and object recognition were additionally affected, although less severely compared with the semantic variant. The mixed variant was characterized by a distributed atrophy pattern in frontal and temporoparietal regions. A more focal pattern of elevated [18F]-THK5351 binding was present in the supplementary motor area, the left premotor cortex, midbrain, and basal ganglia. This pattern was closely similar to that seen in pure nonfluent variant PPA. At the individual patient level, elevated [18F]-THK5351 binding in the supplementary motor area and premotor cortex was present in six out of seven mixed variant cases and in five and four of these cases, respectively, in the thalamus and midbrain. Amyloid biomarker positivity was present in two out of seven mixed variant cases, compared with none of the five pure nonfluent cases.

CONCLUSIONS

A substantial proportion of PPA patients with speech apraxia and agrammatism also have single-word comprehension deficits. At the neurobiological level, the mixed variant shows a high degree of similarity with the pure nonfluent variant of PPA.

TRIAL REGISTRATION

EudraCT, 2014-002976-10 . Registered on 13-01-2015.

Head to head comparison of [18F] AV-1451 and [18F] THK5351 for tau imaging in Alzheimer's disease and frontotemporal dementia

PURPOSE

Tau accumulation is a core pathologic change in various neurodegenerative diseases including Alzheimer's disease and frontotemporal lobar degeneration-tau. Recently, tau positron emission tomography tracers such as [¹⁸F] AV-1451 and [¹⁸F] THK5351 have been developed to detect tau deposition in vivo. In the present study, we performed a head to head comparison of these two tracers in Alzheimer's disease and frontotemporal dementia cases and aimed to investigate which tracers are better suited to image tau in these disorders.

METHODS

A cross-sectional study was conducted using a hospital-based sample at a tertiary referral center. We recruited eight participants (two Alzheimer's disease, four frontotemporal dementia and two normal controls) who underwent magnetic resonance image, amyloid positron emission tomography with [¹⁸F]-Florbetaben and tau positron emission tomography with both THK5351 and AV-1451. To measure regional AV1451 and THK5351 uptakes, we used the standardized uptake value ratios by dividing mean activity in target volume of interest by mean activity in the cerebellar hemispheric gray matter.

RESULTS

Although THK5351 and AV-1451 uptakes were highly correlated, cortical uptake of AV-1451 was more striking in Alzheimer's disease, while cortical uptake of THK5351 was more prominent in frontotemporal dementia. THK5351 showed higher off-target binding than AV-1451 in the white matter, midbrain, thalamus, and basal ganglia.

CONCLUSIONS

AV-1451 is more sensitive and specific to Alzheimer's disease type tau and shows lower off-target binding, while THK5351 may mirror non-specific neurodegeneration.

Differential Regulation of G1 CDK Complexes by the Hsp90-Cdc37 Chaperone System

Selective recruitment of protein kinases to the Hsp90 system is mediated by the adaptor co-chaperone Cdc37. We show that assembly of CDK4 and CDK6 into protein complexes is differentially regulated by the Cdc37-Hsp90 system. Like other Hsp90 kinase clients, binding of CDK4/6 to Cdc37 is blocked by ATP-competitive inhibitors. Cdc37-Hsp90 relinquishes CDK6 to D3- and virus-type cyclins and to INK family CDK inhibitors, whereas CDK4 is relinquished to INKs but less readily to cyclins. p21CIP1 and p27KIP1 CDK inhibitors are less potent than the INKs at displacing CDK4 and CDK6 from Cdc37. However, they cooperate with the D-type cyclins to generate CDK4/6-containing ternary complexes that are resistant to cyclin D displacement by Cdc37, suggesting a molecular mechanism to explain the assembly factor activity ascribed to CIP/KIP family members. Overall, our data reveal multiple mechanisms whereby the Hsp90 system may control formation of CDK4- and CDK6-cyclin complexes under different cellular conditions.

Novel Pieces for the Emerging Picture of Sulfoximines in Drug Discovery: Synthesis and Evaluation of Sulfoximine Analogues of Marketed Drugs and Advanced Clinical Candidates

Sulfoximines have gained considerable recognition as an important structural motif in drug discovery of late. In particular, the clinical kinase inhibitors for the treatment of cancer, roniciclib (pan-CDK inhibitor), BAY 1143572 (P-TEFb inhibitor), and AZD 6738 (ATR inhibitor), have recently drawn considerable attention. Whilst the interest in this underrepresented functional group in drug discovery is clearly on the rise, there remains an incomplete understanding of the medicinal-chemistry-relevant properties of sulfoximines. Herein we report the synthesis and in vitro characterization of a variety of sulfoximine analogues of marketed drugs and advanced clinical candidates to gain a better understanding of this neglected functional group and its potential in drug discovery.

Identification, characterization and in silico ADMET prediction of Roflumilast degradation products

The present study reports the degradation behavior of roflumilast (RFL), a new drug developed for the treatment of chronic obstructive pulmonary disease. The degradation of RFL was tested under various stress conditions as per the guidelines of the International Conference on Harmonization. The degradation products (DPs) of RFL were identified, characterized and in silico predictions were made of their pharmacokinetic properties, absorption, distribution, metabolism, excretion and toxicity (ADMET). RFL was subjected to various stress conditions including photodegradation, alkaline and acidic hydrolysis, oxidative and metallic degradation. After analysis by HPLC-DAD, the DPs were isolated by preparative TLC and characterized by high resolution mass spectrometry (HRMS), ¹H NMR, ¹³C NMR and infrared (IR) spectroscopy. RFL tablets were prepared by the addition of solid stressing substances such as excipients and storage in an accelerated stability chamber (40°C; 75% r.h.) for sixteen months. Resulting DPs from the tablets were analyzed by UFLC-QTOF. The most drastic degradation conditions for RFL were 5M NaOH_(aq), 6M HCl_(aq), 7.5% v/v peracetic acid, which resulted in the isolation of four DPs. However, milder degradation conditions (1M NaOH_(aq) and photolysis) generated six DPs (DP-1, 2, 3, 5, 7 and 8), and are more similar to the actual conditions the drug will be exposed. For tablets containing RFL exposed to an alkaline reagent, two DPs were formed: DP-1 and DP-11. Whereas RFL-containing tablets exposed to acid and oxidizing agents, formed one product DP-11. Forced degradation of RFL led to the formation of eleven DPs, seven of which have never been previously reported. RFL is stable under metallic stress and it is relatively stable during photodegradation testing. The UFLC-QTOF methodology detected a greater number of DPs that formed during the stress conditions tested when compared to the HPLC-DAD methodology. In silico prediction of the ADMET properties of the RFL degradation products and metabolites produced in this study are potentially hepatotoxic.

Sequence-selective recognition of double-stranded RNA and enhanced cellular uptake of cationic nucleobase and backbone-modified peptide nucleic acids

Sequence-selective recognition of complex RNAs in live cells could find broad applications in biology, biomedical research, and biotechnology. However, specific recognition of structured RNA is challenging, and generally applicable and effective methods are lacking. Recently, we found that peptide nucleic acids (PNAs) were unusually well-suited ligands for recognition of double-stranded RNAs. Herein, we report that 2-aminopyridine (M) modified PNAs and their conjugates with lysine and arginine tripeptides form strong (Ka = 9.4 to 17 × 107 M-1) and sequence-selective triple helices with RNA hairpins at physiological pH and salt concentration. The affinity of PNA-peptide conjugates for the matched RNA hairpins was unusually high compared to the much lower affinity for DNA hairpins of the same sequence (Ka = 0.05 to 1.1 × 107 M-1). The binding of double-stranded RNA by M-modified PNA-peptide conjugates was a relatively fast process (kon = 2.9 × 104 M-1 sec-1) compared to the notoriously slow triple helix formation by oligodeoxynucleotides (kon ∼ 103 M-1 sec-1). M-modified PNA-peptide conjugates were not cytotoxic and were efficiently delivered in the cytosol of HEK293 cells at 10 µM. Surprisingly, M-modified PNAs without peptide conjugation were also taken up by HEK293 cells, which, to the best of our knowledge, is the first example of heterocyclic base modification that enhances the cellular uptake of PNA. Our results suggest that M-modified PNA-peptide conjugates are promising probes for sequence-selective recognition of double-stranded RNA in live cells and other biological systems.

Synthesis, characterization and biological studies of a charge transfer complex: 2-aminopyridinium-4-methylbenzenesulfonate

A single crystal charge transfer (CT) complex, 2-aminopyridinium-4-methylbenzenesulfonate (APTS) was synthesized and recrystallized by slow solvent evaporation solution growth method at room temperature. The complex has been characterized with the elemental analysis, UV-visible, infrared (IR), (1)H and (13)C nuclear magnetic resonance (NMR) spectra. Thermogravimetric (TG) and differential thermal analysis (DTA) were reported the thermal behaviour of the complex. Single crystal XRD studies showed that the orthorhombic nature of the crystal with space group Pbca. The biological activities of CT complex, such as DNA binding and antioxidant activity has been carried out. The results indicated that the compound could interact with DNA through intercalation and show significant capacity of scavenging with 2,2-diphenyl-2-picryl-hydrazyl (DPPH).

A novel system for xylem cell differentiation in Arabidopsis thaliana

During vascular development, procambial and cambial cells give rise to xylem and phloem cells. Because the vascular tissue is deeply embedded, it has been difficult to analyze the processes of vascular development in detail. Here, we establish a novel in vitro experimental system in which vascular development is induced in Arabidopsis thaliana leaf-disk cultures using bikinin, an inhibitor of glycogen synthase kinase 3 proteins. Transcriptome analysis reveals that mesophyll cells in leaf disks synchronously turn into procambial cells and then differentiate into tracheary elements. Leaf-disk cultures from plants expressing the procambial cell markers TDR(pro):GUS and TDR(pro):YFP can be used for spatiotemporal visualization of procambial cell formation. Further analysis with the tdr mutant and TDIF (tracheary element differentiation inhibitory factor) indicates that the key signaling TDIF-TDR-GSK3s regulates xylem differentiation in leaf-disk cultures. This new culture system can be combined with analysis using the rich material resources for Arabidopsis including cell-marker lines and mutants, thus offering a powerful tool for analyzing xylem cell differentiation.

The roles of phosphorylation and SHAGGY-like protein kinases in geminivirus C4 protein induced hyperplasia

Even though plant cells are highly plastic, plants only develop hyperplasia under very specific abiotic and biotic stresses, such as when exposed to pathogens like Beet curly top virus (BCTV). The C4 protein of BCTV is sufficient to induce hyperplasia and alter Arabidopsis development. It was previously shown that C4 interacts with two Arabidopsis Shaggy-like protein kinases, AtSK21 and 23, which are negative regulators of brassinosteroid (BR) hormone signaling. Here we show that the C4 protein interacts with five additional AtSK family members. Bikinin, a competitive inhibitor of the seven AtSK family members that interact with C4, induced hyperplasia similar to that induced by the C4 protein. The Ser49 residue of C4 was found to be critical for C4 function, since: 1) mutagenesis of Ser49 to Ala abolished the C4-induced phenotype, abolished C4/AtSK interactions, and resulted in a mutant protein that failed to induce changes in the BR signaling pathway; 2) Ser49 is phosphorylated in planta; and 3) plant-encoded AtSKs must be catalytically active to interact with C4. A C4 N-myristoylation site mutant that does not localize to the plasma membrane and does not induce a phenotype, retained the ability to bind AtSKs. Taken together, these results suggest that plasma membrane associated C4 interacts with and co-opts multiple AtSKs to promote its own phosphorylation and activation to subsequently compromise cell cycle control.

Quantitative LC-MS/MS determination of flupirtine, its N-acetylated and two mercapturic acid derivatives in man

The non-opiate analgesic drug flupirtine was shown in vitro to undergo hydrolysis followed by N-acetylation to form D13223, glucuronidation and conjugation with glutathione to form the stable mercapturic acid derivatives M-424 and M-466. To quantify flupirtine and its metabolites in samples obtained in a clinical study in healthy subjects selected on their genotype of NAT2, UGT1A1 and GSTP1, two LC-MS/MS methods were developed. The validation range for flupirtine and D-13223 in serum was 0.5-500 ng/ml. For urine and feces, the validation ranges for flupirtine and D-13223 were 20-5000 ng/ml and 5.0-5000 ng/ml, respectively. M-424 and M-466 could be quantified in urine between 5.0 and 5000 ng/ml. Free flupirtine and D-13223 were separated from serum, urine and feces with liquid-liquid extraction. For flupirtine and D-13223, the chromatography was performed on a XTerra C18 column isocratically with a mobile phase consisting of ammonium formate buffer (pH 3.5mM) and acetonitrile (50:50; v/v), for M-466 and M-424 a Synergi(®) Fusion-RP column was used and a linear gradient method with water/HCOOH (pH 3) and acetonitrile. The mass spectrometer operated both with electro spray ionization in positive multiple reaction monitoring mode. The developed methods fulfilled the current FDA criteria on bioanalytical method validation for accuracy (error: -16.9 to 11.2%), precision (1.2-13.4%), recovery, stability and matrix effects over the observed analytical range. Thus, the methods were suitable to quantify flupirtine absorption and metabolic disposition in man after single intravenous and oral dosing (100mg) and repeated oral administration (400mg once daily).

Bikinin-like inhibitors targeting GSK3/Shaggy-like kinases: characterisation of novel compounds and elucidation of their catabolism in planta

BACKGROUND

Plant GSK-3/Shaggy-like kinases are key players in brassinosteroid (BR) signalling which impact on plant development and participate in response to wounding, pathogens and salt stress. Bikinin was previously identified in a chemical genetics screen as an inhibitor targeting these kinases. To dissect the structural elements crucial for inhibition of GSK-3/Shaggy-like kinases by bikinin and to isolate more potent compounds we synthesised a number of related substances and tested their inhibitory activity in vitro and in vivo using Arabidopsis thaliana.

RESULTS

A pyridine ring with an amido succinic acid residue in position 2 and a halogen in position 5 were crucial for inhibitory activity. The compound with an iodine substituent in position 5, denoted iodobikinin, was most active in inhibiting BIN2 activity in vitro and efficiently induced brassinosteroid-like responses in vivo. Its methyl ester, methyliodobikinin, showed improved cell permeability, making it highly potent in vivo although it had lower activity in vitro. HPLC analysis revealed that the methyl residue was rapidly cleaved off in planta liberating active iodobikinin. In addition, we provide evidence that iodobikinin and bikinin are inactivated in planta by conjugation with glutamic acid or malic acid and that the latter process is catalysed by the malate transferase SNG1.

CONCLUSION

Brassinosteroids participate in regulation of many aspects of plant development and in responses to environmental cues. Thus compounds modulating their action are valuable tools to study such processes and may be an interesting opportunity to modify plant growth and performance in horticulture and agronomy. Here we report the development of bikinin derivatives with increased potency that can activate BR signalling and mimic BR action. Methyliodobikinin was 3.4 times more active in vivo than bikinin. The main reason for the superior activity of methyliodobikinin, the most potent compound, is its enhanced plant tissue permeability. Inactivation of bikinin and its derivatives in planta involves SNG1, which constitutes a novel pathway for modification of xenobiotic compounds.

Transgenic rice seeds accumulating recombinant hypoallergenic birch pollen allergen Bet v 1 generate giant protein bodies

A versatile hypoallergenic allergen derivative against multiple allergens is an ideal tolerogen for allergen-specific immunotherapy. Such a tolerogen should exhibit high efficacy, without side effects, when administered at high doses and should be applicable to several allergens. Tree pollen chimera 7 (TPC7), a hypoallergenic Bet v 1 tolerogen against birch pollen allergy, was previously selected by DNA shuffling of 14 types of Fagales tree pollen allergens. In this study, transgenic rice seed accumulating TPC7 was generated as an oral vaccine against birch pollen allergy by expressing this protein as a secretory protein using the N-terminal signal peptide and the C-terminal KDEL tag under the control of an endosperm-specific glutelin promoter. The highest level of TPC7 accumulation was approximately 207 µg grain(-1). Recombinant TPC7 is a glycoprotein with high mannose-type N-glycan, but without β1,2-xylose or α1,3-fucose, suggesting that TPC7 is retained in the endoplasmic reticulum (ER). TPC7 is deposited as a novel, giant spherical ER-derived protein body, >20 µm in diameter, which is referred to as the TPC7 body. Removal of the KDEL retention signal or mutation of a cysteine residue resulted in an alteration of TPC7 body morphology, and deletion of the signal peptide prevented the accumulation of TPC7 in rice seeds. Therefore, the novel TPC7 bodies may have formed aggregates within the ER lumen, primarily due to the intrinsic physicochemical properties of the protein.

Monitoring phosphodiesterase-4 inhibitors using liquid chromatography/(tandem) mass spectrometry in sports drug testing

RATIONALE

The recent discovery of resveratrol's capability to inhibit cAMP-specific phosphodiesterases (PDEs) and, as a consequence, to enhance particularly the activity of Sirt1 in animal models has reinforced the interest of preventive doping research organizations, especially in PDE4 inhibitors. Among these, the archetypical PDE4-inhibitor rolipram significantly increased the number of mitochondria in laboratory rodents, which further demonstrated a performance increase in a treadmill-test (time-to-exhaustion) of approximately 40%. Besides rolipram, a variety of new PDE4-inhibiting substances including cilomilast, roflumilast, and numerous additional new drug entities were described, with roflumilast being the first-in-class having received clinical approval for the treatment of chronic obstructive pulmonary disease (COPD). Due to the availability of these substances, and the fact that a misuse of such compounds in sport cannot be excluded, it deems relevant to probe for the prevalence of these compounds in sports drug testing programs.

METHODS

Known urinary phase-I metabolites of rolipram, roflumilast, and cilomilast were generated by in vitro incubations employing human liver microsomal preparations. The metabolites obtained were studied by liquid chromatography with high-resolution/high-accuracy tandem mass spectrometry (LC/MS/MS) and the reference product ion mass spectra of established and most relevant metabolites were utilized to provide the information necessary for comprehensive doping controls. The analytical procedure was based on conventional routine doping control assays employing enzymatic hydrolysis followed by liquid-liquid extraction and subsequent LC/MS/MS measurement.

RESULTS

Structures of diagnostic product ions and dissociation pathways of target analytes were elucidated, providing the information required for implementation into an existing test method for routine sports drug testing. The established method allowed for detection limits for the intact drugs of 1-5 ng/mL, and further assay characteristics (intraday precision 1.5-13.7%, interday precision 7.3-18.6%, recovery 20-100%, ion suppression/enhancement, and specificity) were determined. In addition, proof-of-concept analyses concerning roflumilast were conducted with a urine sample obtained from a COPD patient under roflumilast treatment.

A drug resistance screen using a selective MET inhibitor reveals a spectrum of mutations that partially overlap with activating mutations found in cancer patients

The emergence of drug resistance is a primary concern in any cancer treatment, including with targeted kinase inhibitors as exemplified by the appearance of Bcr-Abl point mutations in chronic myeloid leukemia (CML) patients treated with imatinib. In vitro approaches to identify resistance mutations in Bcr-Abl have yielded mutation spectra that faithfully recapitulated clinical observations. To predict resistance mutations in the receptor tyrosine kinase MET that could emerge during inhibitor treatment in patients, we conducted a resistance screen in BaF3 TPR-MET cells using the novel selective MET inhibitor NVP-BVU972. The observed spectrum of mutations in resistant cells was dominated by substitutions of tyrosine 1230 but also included other missense mutations and partially overlapped with activating MET mutations that were previously described in cancer patients. Cocrystallization of the MET kinase domain in complex with NVP-BVU972 revealed a key role for Y1230 in binding of NVP-BVU972, as previously reported for multiple other selective MET inhibitors. A second resistance screen in the same format with the MET inhibitor AMG 458 yielded a distinct spectrum of mutations rich in F1200 alterations, which is consistent with a different predicted binding mode. Our findings suggest that amino acid substitutions in the MET kinase domain of cancer patients need to be carefully monitored before and during treatment with MET inhibitors, as resistance may preexist or emerge. Compounds binding in the same manner as NVP-BVU972 might be particularly susceptible to the development of resistance through mutations in Y1230, a condition that may be addressed by MET inhibitors with alternative binding modes.

F15599, a preferential post-synaptic 5-HT1A receptor agonist: activity in models of cognition in comparison with reference 5-HT1A receptor agonists

We assessed the activity of F15599, a selective and high efficacy 5-HT(1A) agonist that preferentially activates post- versus pre-synaptic receptors, in rat cognition/memory models. F15599 (0.16 mg/kg i.p.) partially alleviated detrimental effects of phencyclidine on working and reference memory deficit in a hole-board model. It also attenuated phencyclidine-induced deficit of cognitive flexibility in a reversal learning task, without effects of its own. F13714 (0.04 mg/kg) a chemical congener of F15599, and 8-OH-DPAT (0.01 or 0.16), were inactive against these phencyclidine-induced deficits, and/or even worsened basal performances. F15599 (0.04-2.5) was less disruptive than F13714 (0.005-0.16) or 8-OH-DPAT (0.01-0.63), on basal performance in models of attention (5-choice serial reaction time task) and working memory (delayed non-matching to position). Finally, unlike either comparator, F15599 reduced PPI with modest potency and only partially. To conclude, F15599, in models of memory/cognition, has a more favourable profile than F13714 and 8-OH-DPAT. This suggests that preferential activation of post-synaptic 5-HT(1A) receptors could prove useful in pathologies characterized by cognitive/memory deficiencies, such as schizophrenia and depression.

3D-QSAR and docking studies of aminopyridine carboxamide inhibitors of c-Jun N-terminal kinase-1

In order to better understand the structural and chemical features of c-Jun N-terminal kinase-1 (JNK-1), which is a member of the mitogen activated protein kinase (MAP kinase) family of enzymes responsible for the serine/threonine phosphorylation of intracellular targets, 3D-QSAR studies of some aminopyridine carboxamides as c-Jun N-terminal kinase inhibitors were performed by comparative molecular field analysis (CoMFA) to rationalize the structural requirements responsible for the inhibitory activity of these compounds. The genetic algorithm of GOLD3.1 has been employed to position 54 aminopyridine carboxamides in the active sites of JNK-1 to determine the probable binding conformation. The docking results provided a reliable conformational alignment scheme for 3D-QSAR model. Based on the docking conformations, highly predictive comparative molecular field analysis (CoMFA) was performed with a cross-validated q(2) of 0.585. The non-cross-validated analysis with six optimum components revealed a conventional r(2) value of 0.988, F=510.200, and an estimated standard error of 0.071. Furthermore, the CoMFA model was mapped back to the binding sites of JNK-1, to get a better understanding of vital interactions between the aminopyridine carboxamides and the kinase. Based on the docking and CoMFA analyses, we have identified some key features in the aminopyridine carboxamides that are responsible for JNK-1 inhibitory activity. The analyses may be used to design more potent aminopyridine carboxamides and predict their activity prior to synthesis.

Discovery and design of novel HSP90 inhibitors using multiple fragment-based design strategies

The molecular chaperone HSP90 has been shown to facilitate cancer cell survival by stabilizing key proteins responsible for a malignant phenotype. We report here the results of parallel fragment-based drug design approaches in the design of novel HSP90 inhibitors. Initial aminopyrimidine leads were elaborated using high-throughput organic synthesis to yield nanomolar inhibitors of the enzyme. Second site leads were also identified which bound to HSP90 in two distinct conformations, an 'open' and 'closed' form. Intriguingly, linked fragment approaches targeting both of these conformations were successful in producing novel, micromolar inhibitors. Overall, this study shows that, with only a few fragment hits, multiple lead series can be generated for HSP90 due to the inherent flexibility of the active site. Thus, ample opportunities exist to use these lead series in the development of clinically useful HSP90 inhibitors for the treatment of cancers.

Effect of fluvoxamine on the pharmacokinetics of roflumilast and roflumilast N-oxide

OBJECTIVE

To investigate the effects of steady-state dosing of fluvoxamine, an inhibitor of cytochrome P450 (CYP) 1A2 and CYP2C19, on the pharmacokinetics of roflumilast, an oral, once-daily phosphodiesterase 4 (PDE4) inhibitor and its pharmacodynamically active metabolite roflumilast N-oxide.

METHODS

In an open-label, non-randomised, one-sequence, two-period, two-treatment crossover study, 14 healthy subjects received a single oral dose of roflumilast 500 microg on study day 1. After a 6-day washout period, repeated doses of fluvoxamine 50 mg once daily were given from days 8 to 21. On day 15, roflumilast 500 microg and fluvoxamine 50 mg were taken concomitantly. Percentage ratios of test/reference (reference: roflumilast alone; test: roflumilast plus steady-state fluvoxamine) of geometric means and their 90% confidence intervals for area under the plasma concentration-time curve, maximum plasma concentration (roflumilast and roflumilast N-oxide) and plasma clearance of roflumilast were calculated.

RESULTS

Upon co-administration with steady-state fluvoxamine, the exposure to roflumilast as well as roflumilast N-oxide increased by a factor of 2.6 and 1.5, respectively. Roflumilast plasma clearance decreased by a factor of 2.6, from 9.06 L/h (reference) to 3.53 L/h (test). The combined effect of fluvoxamine co-administration on roflumilast and roflumilast N-oxide exposures resulted in a moderate (i.e. 59%) increase in total PDE4 inhibitory activity.

CONCLUSION

Co-administration of roflumilast and fluvoxamine affects the disposition of roflumilast and its active metabolite roflumilast N-oxide most likely via a potent dual pathway inhibition of CYP1A2 and CYP2C19 by fluvoxamine. The exposure increases observed for roflumilast N-oxide are suggested to be attributable to CYP2C19 co-inhibition by fluvoxamine and thus, are not to be expected to occur when roflumilast is co-administered with more selective CYP1A2 inhibitors.

Steady-state pharmacokinetics of roflumilast and roflumilast N-oxide in patients with mild and moderate liver cirrhosis

BACKGROUND

Roflumilast and its primary N-oxide metabolite are targeted phosphodiesterase 4 (PDE4) inhibitors with similar in vivo potency. Roflumilast is being developed for the treatment of inflammatory airway diseases such as chronic obstructive pulmonary disease and asthma.

OBJECTIVE

To investigate the effects of mild and moderate liver cirrhosis on the steady-state pharmacokinetics of roflumilast and roflumilast N-oxide.

METHODS

Patients with mild (n = 8, Child-Pugh A) and moderate (n = 8, Child-Pugh B) liver cirrhosis and healthy subjects (n = 8) matched with patients with cirrhosis with regard to sex, age and bodyweight received oral roflumilast 250 microg once daily for 14 days. Blood samples were collected for 24 hours after the last dose on day 14. Steady-state plasma concentrations of roflumilast and roflumilast N-oxide were determined using a validated high-performance liquid chromatography with tandem mass spectrometry assay. The pharmacokinetics were compared between groups using ANOVA.

RESULTS

In patients with liver cirrhosis, the average total exposure (area under the plasma concentration-time curve from 0 to 24 hours [AUC(24)]) of roflumilast was approximately 51% (Child-Pugh A) and 92% (Child-Pugh B) higher than in healthy subjects. In contrast, roflumilast maximum plasma concentration (C(max)) was unaltered in Child-Pugh A patients and was increased by 27% in Child-Pugh B patients. Changes in the AUC(24) of roflumilast N-oxide were less distinct, with 24% and 41% increases and corresponding C(max) increases of 26% and 40% in Child-Pugh A and B patients, respectively, compared with healthy subjects. Overall, changes in average potency-corrected exposure to the sum of the free fractions of both compounds were estimated to result in approximately 26% and 46% increases in total PDE4 inhibitory capacity (tPDE4i) in Child-Pugh A and B patients, respectively, relative to healthy subjects. Roflumilast was well tolerated.

CONCLUSIONS

Mild and moderate liver cirrhosis resulted in distinct alterations of exposure to roflumilast but only in modest alterations of exposure to roflumilast N-oxide. The integrated exposure-weighted assessment of the observed pharmacokinetic changes of roflumilast and roflumilast N-oxide (tPDE4i) indicates modest average exposure increases to the sum of both compounds. These findings and the favourable tolerability profile suggest that roflumilast can be safely used in patients with mild and moderate liver cirrhosis without special precautions or dose adjustment.

Flupirtine attenuates sodium nitroprusside-induced damage to retinal photoreceptors, in situ

Flupirtine has been shown to function as a neuroprotectant and is presently used in man to treat a number of conditions. The aim of this study was to investigate the specific antioxidant properties of flupirtine in relation to oxidant-induced damage to retinal photoreceptors. Initial in vitro studies on brain membranes showed that flupirtine was approximately 20 times more potent than trolox (vitamin E analogue) and 8 times more potent than metipranolol at attenuating lipid peroxidation caused by the nitric oxide donor, sodium nitroprusside (SNP). Subsequent immunohistochemical studies revealed that following an intraocular injection of SNP, retinal photoreceptors are the only retinal cell types that appear to be clearly affected. This was supported by electroretinogram (ERG) recordings which showed both the a- and b-wave amplitudes to be significantly reduced. Western blotting techniques showed that SNP caused a significant decrease in photoreceptor-specific markers (RET-P1, rhodopsin kinase), an increase in cleaved caspase-3, Bcl-2, and cleaved PARP proteins that are associated with apoptosis and no change in the ganglion cell specific marker, neurofilament (NF-L). This was supported by RT-PCR data where rhodopsin (photoreceptor specific) mRNA was reduced while Thy-1 and NF-L (ganglion cell specific) mRNAs were unaffected. In addition SNP caused an elevation of glial cell response mRNAs primarily associated with Müller cells (GFAP, CNTF, bFGF) as well as caspase-3 and Bcl-2. Importantly, when flupirtine was co-injected, the effects to the retina caused by SNP on retinal proteins and mRNAs were in most cases significantly blunted. The conclusion reached from this study is that flupirtine is a powerful antioxidant and when injected into the eye with SNP attenuates the detrimental influence of SNP to retinal photoreceptors. Since oxidative stress has been implicated in retinal diseases like age-related macular degeneration (AMD) this study provides "proof of principle" for the idea that flupirtine may help individuals suffering from such retinal diseases.

Investigation of a potential food effect on the pharmacokinetics of roflumilast, an oral, once-daily phosphodiesterase 4 inhibitor, in healthy subjects

This open, randomized, single-dose crossover study investigated effects of a high-fat meal on the pharmacokinetics of roflumilast and its major active N-oxide metabolite. Twelve healthy subjects received oral roflumilast 500 microg (2 x 250 microg) after overnight fasting and after breakfast. Blood was sampled up to 54 hours for pharmacokinetic profiling of roflumilast and N-oxide. Geometric mean ratios (fed/fasted) for point estimates (PE) and 90% confidence intervals (CI) were calculated for AUC(0-last), AUC(0-infinity), and C(max) of both compounds. After the meal, roflumilast C(max) (PE, 0.59; 90% CI, 0.49-0.70) was modestly reduced; N-oxide C(max) (PE, 0.95; 90% CI, 0.90-1.01) was unchanged. Roflumilast t(max) was delayed in fed state (2.0 +/- 0.4 hours) versus fasted state (1.0 +/- 0.2 hours); N-oxide t(max) was unaltered. No significant food effect on roflumilast AUC(0-last) (PE, 1.04; 90% CI, 0.90-1.21), AUC(0-infinity) (PE, 1.12; 90% CI, 1.00-1.25), and respective N-oxide AUCs (PE, 0.91; 90% CI, 0.79-1.04; PE, 0.99; 90% CI, 0.92-1.06) occurred. Because roflumilast N-oxide is the major contributor to roflumilast's overall pharmacologic effects, these findings suggest that roflumilast can be taken with or without food.

Molecular docking study of the binding of aminopyridines within the K+ channel

We present a molecular docking study aimed to identify the binding site of protonated aminopyridines for the blocking of voltage dependent K(+) channels. Several active aminopyridines are considered: 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 3,4-diaminopyridine, and 4-aminoquinoleine. We apply the AutoDock force field with a lamarckian genetic algorithm, using atomic charges for the ligands derived from the electrostatic potential obtained at the B3LYP/cc-pVDZ level. We find a zone in the alpha-subunit of the K(+) channel bearing common binding sites. This zone corresponds to five amino acids comprised between residuals Thr107 and Ala111, in the KcsA K(+) channel (1J95 pdb structure). The 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, and 3,4-diaminopyridine bind to the carboxylic oxygens of Thr107 and Ala111. In all cases aminopyridines are perpendicular to the axis of the pore. 4-aminoquinoleine binds to the carboxylic oxygen of Ala111. Due to its large size, the molecular plane is parallel to the axis of the pore. The charge distributions and the structures of the binding complexes suggest that the interaction is driven by formation of several hydrogen bonds. We find 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, and 3,4-diaminopyridine with similar binding energy. Considering the standard error of the estimate of the AutoDock force field, this energy should lie, as a rough estimation, in the interval 3-7 kcal mol(-1). On the other hand, 4-aminoquinoleine seems to have a smaller binding energy.

Voltage-Dependent N-Type Ca2+ Channel Activity Regulates the Interaction Between FGF-1 and S100A13 for Stress-Induced Non-Vesicular Release

1. The Ca(2+)-mediated regulation of interaction between FGF-1 and S100A13 in NG108-15 cells was studied. When the stress by depriving B27 supplement from the culture was given, cellular levels of both proteins were decreased, while their releases were significantly increased within 3 h. These stress-induced changes were all abolished by amlexanox, an anti-allergic drug. 2. These releases were significantly inhibited by the addition of EGTA or BAPTA-AM, cellular or extracellular Ca(2+)-chelating agent, respectively. The addition of omega-conotoxin GVIA, a N-type Ca(2+)-channel blocker caused a complete inhibition of the release, while increased the cytosolic levels of both proteins. However, omega-conotoxin MVIIC, the non-N-type Ca(2+)-channel blocker was ineffective. 3. In NG108-15 cells, which had been transfected with Venus-FGF-1 and CFP-S100A13, the supplement-deprivation stress caused several spike-type fluorescence resonance energy transfer (FRET) signals, suggesting that both proteins showing interaction would be immediately released. These spikes were completely abolished by the addition of omega-conotoxin GVIA. However, the addition of amlexanox caused bell-shaped FRET signals without spikes. 4. Thus, it is suggested that the interaction between FGF-1 and S100A13 responsible for stress-induced non-vesicular release is dependent of Ca(2+)-influx through N-type Ca(2+)-channels.

Prolonged treatment with ligands affects ligand binding to the human serotonin(1A) receptor in Chinese hamster ovary cells

1. The serotonin(1A) receptors are members of a superfamily of seven transmembrane domain receptors that couple to G-proteins, and appear to be involved in several behavioral and cognitive functions. 2. We monitored the effect of prolonged treatment of the human serotonin(1A) receptor expressed in Chinese hamster ovary (CHO) cells with pharmacologically well-characterized ligands on its binding to the agonist 8-hydroxy-2(di-N-propylamino)tetralin (8-OH-DPAT) and antagonist 4-(2'-methoxy)-phenyl-1-[2'-(N-2''-pyridinyl)-p-fluorodobenzamido]ethyl-piperazine (p-MPPF). 3. Our results indicate that prolonged treatment with the specific agonist (8-OH-DPAT) differentially affects subsequent binding of the agonist and antagonist to the receptor in a manner independent of receptor-G-protein coupling. Importantly, our results show that prolonged treatment with the commonly used antagonist p-MPPF, and its iodinated analogue 4-(2'-methoxy)-phenyl-1-[2'-(N-2''-pyridinyl)-p-iodobenzamido]ethyl-piperazine (p-MPPI), which have earlier been reported to display similar binding properties to serotonin(1A) receptors, induces significantly different effects on the ligand binding function of serotonin(1A) receptors.

Bioactivation of 2,3-diaminopyridine-containing bradykinin B1 receptor antagonists: irreversible binding to liver microsomal proteins and formation of glutathione conjugates

The 2,3-diaminopyridine (DAP) moiety was found to represent a core structure essential for the potency of a new series of human bradykinin B(1) receptor antagonists. However, incubation of (14)C-labeled 2,3-DAP derivatives with rat and human liver microsomes resulted in substantial irreversible binding of radioactive material to macromolecules by a process that was NADPH-dependent. Trapping the reactive species with GSH led to significant reduction of the irreversible binding of radioactivity, with concomitant formation of abundant GSH adducts. One type of thiol adducts (detected in both human and rat liver microsomes), resulting from addition of 305 Da to the parent compound, was observed with all 2,3-DAP compounds. These adducts also were detected in rat hepatocyte incubates, as well as in rat bile, following intravenous administration of 2,3-DAPs. Formation of the conjugates appeared to involve modification of the DAP ring, based upon mass spectral analysis of a number of representative GSH adducts; this was corroborated by detailed LC NMR analysis of one compound. Formation of this type of GSH conjugate was markedly reduced when the 2-amino methyl group linking the 2,3-DAP and the biphenyl moiety was replaced with an ether oxygen atom. It is postulated, therefore, that oxidation of the 2-amino group serves as a key step leading to the formation of reactive species associated with the DAP core. In addition, this step appears to be mediated primarily by P450 3A, as evidenced by the marked decrease in both the irreversible binding of radioactivity and the formation of the GSH adducts in human liver microsomes following treatment with ketoconazole and monoclonal antibodies against P450 3A. A mechanism for the bioactivation of 2,3-DAP is proposed wherein oxidation (dehydrogenation or N-hydroxylation followed by dehydration) of the 2-amino group, catalyzed by P450 3A, results in the formation of a highly electrophilic species, pyridine-2,3-diimine.

Cholesterol modulates the antagonist-binding function of hippocampal serotonin1A receptors

The serotonin1A receptor is the most extensively studied member of the family of seven transmembrane domain G-protein coupled serotonin receptors. Serotonergic signaling appears to play a key role in the generation and modulation of various cognitive and behavioral functions such as sleep, mood, pain, addiction, locomotion, sexual activity, depression, anxiety, alcohol abuse, aggression and learning. Since a significant portion of the protein lies embedded in the membrane and the ligand-binding pocket is defined by the transmembrane stretches in such receptors, membrane composition and organization represent a crucial parameter in the structure-function analysis of G-protein coupled receptors. In this paper, we have monitored the role of membrane cholesterol in the ligand-binding function of the hippocampal serotonin1A receptor. Our results demonstrate that the reduction of membrane cholesterol significantly attenuates the antagonist-binding function of the serotonin1A receptor. Based on prior pharmacological knowledge regarding the requirements for the antagonist to bind the receptor, our results indicate that membrane cholesterol modulates receptor function independently of its ability to interact with G-proteins. These effects on ligand-binding function of the receptor are predominantly reversed upon cholesterol-replenishment of cholesterol-depleted membranes. When viewed in the light of our earlier results on the effect of cholesterol depletion on the serotonin1A receptor/G-protein interaction, these results comprehensively demonstrate the importance of cholesterol in the serotonin1A receptor function and form the basis for understanding lipid-protein interactions involving this important neuronal receptor.

Mechanisms of action of differentiation inducers: detection of inducer binding protein(s) in murine erythroleukemia cells

We have shown previously that murine erythroleukemia (MEL) and human neuroectodermal RD/TE-671 cells are induced to differentiate by ureido derivatives of pyridine (UDPs) and may contain inducer binding protein(s). In the present study, we prepared radiolabeled [3H]UDP [2-(3-ethylureido)-6-[3H]-acetylaminopyridine] as ligand and investigated whether it interacts selectively with novel binding proteins. MEL and RD/TE-671 cells, incubated with the inducer [3H]UDP and subsequently fractionated, yielded a radiolabeled postmitochondrial soluble fraction containing the [3H]UDP-protein complex. We purified the UDP binding protein by using UDP-sepharose affinity chromatography, gel filtration, and SDS-PAGE electrophoresis and analyzed its structure. The data presented here indicate for the first time that the inducer UDP interacts with a 38,333 +/- 30 Da binding protein(s) (p38), of unknown function, in both cell lines. Microsequencing and sequence alignment search revealed that the p38 protein(s) contains at least two homologous domains, one being part of ABC-type transporters and another found in the Wingless-type (Wnt) proteins. Kinetic analysis revealed that the p38 forms a relatively stable protein complex with [3H]UDP that accumulates within the cytosol and nucleus of MEL cells during the precommitment period. This complex, however, decays later on after commitment to erythroid maturation has been initiated. De novo protein and mRNA synthesis is needed for the UDP-p38 complex to form, as shown by the use of metabolic inhibitors. Purified p38 was used to develop an anti-p38 polyclonal serum, and Western blot analysis revealed that the level of p38 was quite similar in both UDP-inducible and -resistant MEL subclones that we developed. Although only a portion of the primary structure of the p38 is known from microsequencing, the mechanism by which the UDP-p38 complex contributes to induction of differentiation in both UDP-responsive mouse MEL and human RD/TE-671 cells is discussed.

PnuC and the utilization of the nicotinamide riboside analog 3-aminopyridine in Haemophilus influenzae

The utilization pathway for the uptake of NAD and nicotinamide riboside was previously characterized for Haemophilus influenzae. We now report on the cellular location, topology, and substrate specificity of PnuC. pnuC of H. influenzae is only distantly related to pnuC of Escherichia coli and Salmonella enterica serovar Typhimurium. When E. coli PnuC was expressed in an H. influenzae pnuC mutant, it was able to take up only nicotinamide riboside and not nicotinamide mononucleotide. Therefore, we postulated that PnuC transporters in general possess specificity for nicotinamide riboside. Earlier studies showed that 3-aminopyridine derivatives (e.g., 3-aminopyridine adenine dinucleotide) are inhibitory for H. influenzae growth. By testing characterized strains with mutations in the NAD utilization pathway, we show that 3-aminopyridine riboside is inhibitory to H. influenzae and is taken up by the NAD-processing and nicotinamide riboside route. 3-Aminopyridine riboside is utilized effectively in a pnuC+ background. In addition, we demonstrate that 3-aminopyridine adenine dinucleotide resynthesis is produced by NadR. 3-Aminopyridine riboside-resistant H. influenzae isolates were characterized, and mutations in nadR could be detected. We also tested other species of the family Pasteurellaceae, Pasteurella multocida and Actinobacillus actinomycetemcomitans, and found that 3-aminopyridine riboside does not act as a growth inhibitor; hence, 3-aminopyridine riboside represents an anti-infective agent with a very narrow host range.

Synthesis and evaluation of substituted 4-alkoxy-2-aminopyridines as novel neuropeptide Y1 receptor antagonists

A series of substituted 4-alkoxy-2-aminopyridines 2, which were formally derived from neuropeptide Y1 antagonist 1 by replacing the morpholino portion with alkoxy groups, were synthesized and evaluated as neuropeptide Y Y1 receptor antagonists. Primary structure-activity relationships and identification of potent 4-alkoxy derivatives are described.

Displacement of the PET ligand 18F-MPPF by the electrically evoked serotonin release in the rat hippocampus

The effects of the electrically evoked serotonin release were evaluated on the binding of (18)F-MPPF in the hippocampus of anesthetized rats. The specific binding of (18)F-MPPF was measured by an implanted beta-microprobe and the serotonin (5-HT) extracellular concentration was measured by microdialysis under the same conditions. Our results showed that the 10-, 20-, or 30-min electrical stimulation of the raphe nucleus elicited a significant increase in extracellular 5-HT, only detectable in the presence of a 5-HT reuptake inhibitor in the perfusate (5 microM clomipramine). Interestingly, the raphe stimulations were associated with a 27-76% reversible decrease of the (18)F-MPPF specific binding in the hippocampus, but an unchanged extracellular (18)F-MPPF collected in dialysates. Considered together, these observations suggest that (18)F-MPPF binding is sensitive to 5-HT released at a neuronal level. This compartment, explored by the beta-microprobe, is probably distinct from the extracellular compartment, explored by microdialysis.

Rational modelling of the voltage-dependent K+ channel inactivation by aminopyridines

A functional model for the in vitro inactivation of voltage-dependent K(+) channels is developed. The model expresses the activity as a function of the aminopyridine pK(a), the interaction energy with the receptor, and a quotient of partition functions. Molecular quantum similarity theory is introduced in the model to express the activity as a function of the principal components of the similarity matrix for a series of agonists. To validate the model, a set of five active (protonated) aminopyridines is considered: 2-aminopyridine, 3-aminopyridine, 4-aminoquinoleine, 4-aminopyridine, and 3,4-diaminopyridine. A regression analysis of the model gives good results for the variation of the observed activity with the overlap similarity index when pyridinic rings are superposed. The results support the validity of the model, and the hypothesis of a ligand-receptor entropy variation depending mainly on the nature of the ligand. In addition, the results suggest that the pyridinic ring must play an active role in the interaction with the receptor site. This interaction with the protonated pyridinic nitrogen can involve a cation-pi interaction or a donor hydrogen bond. The amine groups, at different relative positions of the pyridinic nitrogen, can form one or more hydrogen bonds due to the C(4) symmetry of the inner part of the pore in the K(+) channel.

Enhancement of in vitro and in vivo microdialysis recovery of SB-265123 using Intralipid and Encapsin as perfusates

This study was conducted to compare the ability of two potential microdialysis perfusates to enhance the recovery of SB-265123, a lipophilic, highly protein-bound compound, both in vitro and in vivo. Initial in vitro experiments established that the recovery of SB-265123 by microdialysis using normal saline as a perfusate was poor (1.7%). Different concentrations of Intralipid and Encapsin also were evaluated in an identical in vitro setting, to determine enhancement of recovery. In vitro recovery was enhanced to approximately 24 and 65% with 5 and 20% Intralipid, and to approximately 59 and 62% with 5 and 20% Encapsin, respectively. A rat in vivo study was conducted with 20% Encapsin to confirm the in vitro observations. In the in vivo study, 75-80% recovery of free SB-265123 was achieved using 20% Encapsin as a perfusate. The results from this study indicate that for SB-265123, a lipophilic, highly protein-bound molecule, Encapsin is an efficient recovery enhancer in vitro. The results from this investigation further demonstrate that a recovery enhancer may be useful for in vivo applications, even with a compound that is highly bound to plasma protein.

An enzymatic method of analysis for GDP-L-fucose in biological samples, involving high-performance liquid chromatography

To investigate the biological significance of GDP-L-fucose, we established a unique method for the determination of GDP-L-fucose levels in microsomal fractions, using an HPLC assay of alpha 1-6-fucosyltransferase (alpha1-6-FucT), an enzyme that catalyzes the synthesis of core fucosylation in N-glycans. A microsomal protein and a large excess of fluorescence-labeled synthetic oligosaccharide (a substrate) were incubated with a large excess of alpha1-6-FucT. The fluorescent intensity of the fucosylated reaction product, which was analyzed by isocratic reverse phase HPLC, was proportional to the level of GDP-L-fucose in the microsomal fractions over the range 0.20-10 pmol. This assay is applicable to the determination of the GDP-L-fucose content in various cancer cell lines as well as rat liver and would be useful in developing a better understanding of the fucosylation potential of such cells and tissues.

5-HT(1A) receptor imaging in the human brain: effect of tryptophan depletion and infusion on [(18)F]MPPF binding

The 5-HT(1A) receptor has been implicated in a variety of physiological processes, psychiatric disorders, and neurodegenerative disorders. [(18)F]MPPF is a useful radioligand for quantitative imaging of 5-HT(1A) receptors in human subjects. Previous studies have shown that the binding of some radioligands is sensitive to changes in neurotransmitter concentration, whereas in other cases, binding is not affected. In the present study we investigated if [(18)F]MPPF binding to the 5-HT(1A) receptor is sensitive to changes in 5-HT. Changes in 5-HT levels were achieved by influencing its synthesis through tryptophan depletion, including a tryptophan-free amino acid drink 4.5 h prior to the PET scan and tryptophan infusion (10 mg/ml, 50 mg/kg, 30 min, starting 60 min prior to the PET scan). Binding of [(18)F]MPPF in the brain of six healthy, male volunteers was compared in these two conditions. Mean binding potentials in the medial temporal cortex, cortical regions, and raphe nucleus did not significantly differ between the two conditions. The results of the study show that, under the experimental conditions used, [(18)F]MPPF binding was not affected. It is hypothesized that the increases in 5-HT levels needed to produce a measurable effect on [(18)F]MPPF binding would be significantly greater than that possible with tryptophan manipulation. Therefore, in pathological conditions, where such large increases in 5-HT levels are not expected, [(18)F]MPPF seems a useful ligand to measure 5-HT(1A) receptor distribution without the interference of endogenous 5-HT.

Interaction of S100 proteins with the antiallergic drugs, olopatadine, amlexanox, and cromolyn: identification of putative drug binding sites on S100A1 protein

S100 proteins are a multigenic family of low-molecular-weight Ca(2+)-binding proteins comprising 19 members. These proteins undergo a conformational change by Ca(2+)-binding and consequently interact with their target proteins. Recently, we reported that two antiallergic drugs, Amlexanox and Cromolyn, bind to S100A12 and S100A13 of the S100 protein family. In the present study, we used a newly developed antiallergic drug, Olopatadine, as a ligand for affinity chromatography and examined binding specificity of the drug to S100 protein family. Olopatadine binds specifically to S100 proteins, such as S100A1, S100B, S100L, S100A12, and S100A13, in a Ca(2+)-dependent manner but not to calmodulin. Mutagenesis study showed that amino acid residues 76-85 in S100A1 are necessary for its binding to Olopatadine. In contrast, residues 89-94 were identified as an Amlexanox-binding site in S100A1. Moreover, Olopatadine did not competitively inhibit S100A1-binding site of Amlexanox. Furthermore, we showed that Olopatadine inhibited the binding of S100A1 target protein's binding site peptides to S100A1. These results indicate that C-terminal region of S100A1 is important for antiallergic drug binding, although the drug binding sites are different according to each antiallergic drug. Differences in the binding sites of S100A1 to antiallergic drugs suggest that the regulatory functions of S100 proteins may exist in several regions. Therefore, these drugs may serve as useful tools for evaluating the physiological significance of S100 protein family.

Development status of second generation PDE4 inhibitors for asthma and COPD: the story so far

The beginning of the 1990s saw the synthesis and evaluation of orally-active, second generation phosphodiesterase (PDE) inhibitors that have high specificity for the PDE4 subtype. In vitro and in vivo studies established that this class of compounds suppresses the activity of many pro-inflammatory and immune cells indicating that they may be effective in the treatment of airway inflammatory diseases. In this article we review the development status of the most advanced and extensively studied PDE4 inhibitors for asthma and chronic obstructive pulmonary disease.

Lack of DNA binding in the rat nasal mucosa and other tissues of the nasal toxicants roflumilast, a phosphodiesterase 4 inhibitor, and a metabolite, 4-amino-3,5-dichloropyridine, in contrast to the nasal carcinogen 2,6-dimethylaniline

The phosphodiesterase 4 inhibitor Roflumilast (B9302-107) (RF) and its metabolite 4-amino-3,5-dichloropyridine (ADCP) produced nasal toxicity in preclinical safety studies with rats. The purpose of this study was to assess the possible formation of DNA adducts, by RF and ADCP, in the nasal mucosa, liver and testes of male rats using the 32P-postlabeling assay. For comparison, rats were exposed to the DNA-reactive carcinogens 2,6-dimethylaniline (DMA), also known as 2,6-xylidine, a nasal carcinogen, and the aromatic amine carcinogens 4,4'-methylene-bis(2-chloroaniline) (MOCA), which yields monocyclic DNA adducts, and 2-acetylaminofluorene (2-AAF). In the case of RF, possible sources of DNA adducts include the parent molecule and its ADCP moiety by enzymatic N-hydroxylation and sulfation, reactions typical of carcinogenic aromatic amines. 4-Acetoxylamino-3,5-dichloropyridine (N-acetoxy-ADCP), a chemically activated derivative of ADCP, was prepared and used to modify DNA which was then used to establish the chromatographic conditions with which to reliably detect whether or not such adducts were formed metabolically from RF and ADCP. Similarly, a standard N-hydroxy-DMA was prepared, but the corresponding N-acetoxy derivative was unstable and decomposed during synthesis. Both N-hydroxy-DMA and N-acetoxy-ADCP were mutagenic in the Salmonella typhimurium Ames assay using strain TA100 without an exogenous bioactivation system, with the former being more potent. N-hydroxy-ADCP was essentially inactive in this assay. For the 32P-postlabeling assay, male Wistar rats were exposed to the test substances and carrier control compounds by intragastric instillation at the selected dose levels for 7 days. Subsequently, the nasal mucosa, liver, and testes of the rats exposed to the test or control compounds were extirpated, the DNA extracted and the samples postlabeled. The patterns of adducts formed with the test compounds were compared to those formed in N-acetoxy-ADCP- and N-hydroxy-DMA-adducted DNA, which were assayed by both nuclease P1 and butanol enhancement methods. Based upon the similarity of results from the two enhancement methods, only the former was used for the in vivo studies. No evidence was obtained for the formation of DNA adducts from RF or its metabolites, specifically ADCP, under the conditions of these assays despite the ability to detect adducts from DNA modified chemically with N-acetoxy-ADCP and DNA adducts from the other compounds in their target organs. In the absence of a pattern of compound-related spots, we conclude that RF does not form DNA adducts having the potential to initiate neoplasia in these three tissues.

Comparative study of hippocampal neuronal loss and in vivo binding of 5-HT1a receptors in the KA model of limbic epilepsy in the rat

A high density of 5-HT1a receptors is present in pyramidal hippocampal cells. Mapping of these receptors may be performed in vivo using the tracer no-carrier-added 4-(18)F-fluoro-N-2-(1-(2-methoxyphenyl)-1-piperazinyl)ethyl-N-2-pyridinyl-benzamide (MPPF). We tested the hypothesis of a relationship between MPPF binding and post-epileptic neuronal loss in the hippocampus. The model of limbic epilepsy induced by kainic acid (KA) in the rat was used. Rats were sacrificed at various times (1 h-240 days) after systemic injection of 10 mg/kg KA. Determination of MPPF binding in the brain was combined with a quantification of neuronal loss using DNA labeling with propidium iodide and confocal microscopy. Hippocampal MPPF binding varied according to time elapsed from KA injection. An initial decrease from day 1 to day 6 post injection was followed by a relative increase between day 6 and day 30. This effect was observed in rats which showed hippocampal neuronal loss but also in one rat which did not. In KA treated rats, statistically significant relationship between MPPF binding and neuronal count was found during the acute period (rats sacrificed 1 h-day 6 after KA injection) and the chronic phase (rats sacrificed beyond day 60 after KA injection). The late relative increase of MPPF binding suggests an epilepsy-induced increase of 5-HT1a receptors in the hippocampus. This effect needs to be further characterized before considering PET determination of hippocampal MPPF binding as a method of post-epileptic neuronal loss assessment.

5-HT1A receptor activation and antidepressant-like effects: F 13714 has high efficacy and marked antidepressant potential

To examine further the hypothesis that the magnitude of the intrinsic activity of agonists at 5-HT1A receptors determines the magnitude of their psychotropic activity, we studied the relationship between the maximal receptor activation produced by various 5-HT1A receptor ligands and their antidepressant-like effects (i.e., decreased immobility in the forced swimming test in rats). Using three different in vitro assays suitable to measure differences among high, intermediate, and low efficacy 5-HT1A receptor agonists, ligands were identified with intrinsic activities ranging from low-negative (i.e., the inverse agonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane-carboxamide (WAY 100635)) to high-positive (i.e., 3-chloro-4-fluorophenyl-(4-fluoro-4-[[(5-methyl-6-methylamino-pyridin-2-ylmethyl)-amino]-methyl]-piperidin-1-yl-methanone (F 13714)). In addition, novel compounds with intermediate intrinsic activity, like buspirone, but with high selectivity for 5-HT1A receptors, unlike buspirone, were identified. The maximal effects of the 5-HT1A receptor ligands in the forced swimming test correlated positively (rS=0.91, P<0.005) with the rank order of their intrinsic activity at 5-HT1A receptors. This relationship constitutes evidence that the magnitude of the psychotropic activity of 5-HT1A receptor ligands is a positive function of their intrinsic activity at the receptor, and suggests that F 13714, which had maximal effects in the forced swimming test significantly larger than any of the other compounds examined here, did so because of its higher intrinsic activity at 5-HT1A receptors.

Simultaneous determination of flupirtine and its major active metabolite in human plasma by liquid chromatography-tandem mass spectrometry

A rapid, selective and sensitive HPLC-tandem mass spectrometry method was developed and validated for simultaneous determination of flupirtine and its active metabolite D-13223 in human plasma. The analytes and internal standard diphenhydramine were extracted from plasma samples by liquid-liquid extraction, and chromatographed on a C18 column. The mobile phase consisted of acetonitrile-water-formic acid (60:40:1, v/v/v), at a flow rate of 0.5 ml/min. Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via atmospheric pressure chemical ionization (APCI). The method has a limit of quantitation of 10 ng/ml for flupirtine and 2 ng/ml for D-13223, using 0.5-ml plasma sample. The linear calibration curves were obtained in the concentration range of 10.0-1500.0 ng/ml for flupirtine and 2.0-300.0 ng/ml for D-13223. The intra- and inter-run precision (RSD), calculated from quality control (QC) samples was less than 7.2% for flupirtine and D-13223. The accuracy as determined from QC samples was less than 5% for the analytes. The overall extraction recoveries of flupirtine and D-13223 were determined to be about 66% and 78% on average, respectively. The method was applied for the evaluation of the pharmacokinetics of flupirtine and active metabolite D-13223 in volunteers following peroral administration.