Synthesis of (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐ 3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate‐1‐14C

γ‐Cyhalothrin ( 1a ), (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate, is a single‐isomer, synthetic pyrethroid insecticide marketed by Pytech Chemicals GmbH, a joint venture between Dow AgroSciences and Cheminova A/S. As a part of the registration process there was a need to incorporate a carbon‐14 label into the cyclopropyl ring of this molecule. A high yielding radiochemical synthesis of γ‐cyhalothrin was developed from readily available carbon‐14 labeled N‐t‐Boc protected glycine. This seven step synthesis, followed by a preparative normal phase HPLC separation of diastereomers, provided 21.8 mCi of γ‐cyhalothrin‐1‐¹⁴C ( 1b ) with >98% radiochemical purity. Copyright © 2007 John Wiley & Sons, Ltd.     

Conformational properties of hybrid peptides containing α‐ and ω‐amino acids*

Abstract: This review briefly surveys the conformational properties of guest ω‐amino acid residues when incorporated into host α‐peptide sequences. The results presented focus primarily on the use of β‐ and γ‐residues in αω sequences. The insertion of additional methylene groups into peptide backbones enhances the range of accessible conformations, introducing additional torsional variables. A nomenclature system, which permits ready comparisons between α‐peptides and hybrid sequences, is defined. Crystal structure determination of hybrid peptides, which adopt helical and β‐hairpin conformations permits the characterization of backbone conformational parameters for β‐ and γ‐residues inserted into regular α‐polypeptide structures. Substituted β‐ and γ‐residues are more limited in the range of accessible conformation than their unsubstituted counterparts. The achiral β,β‐disubstituted γ‐amino acid, gabapentin, is an example of a stereochemically constrained residue in which the torsion angles about the C^β–C^γ (θ₁) and C^α–C^β (θ₂) bonds are restricted to the gauche conformation. Hybrid sequences permit the design of novel hydrogen bonded rings in peptide structures.     

Synthesis of [guanido‐13C]‐γ‐hydroxyarginine

This report describes an efficient method of synthesizing [guanido‐¹³C]‐γ‐hydroxyarginine HCl salt. Iodolactonization of N‐Boc‐protected allylglycine mainly provided the cis iodo compound 2. This was converted to an amine through azide 4. The amine 5 was reacted with N‐Boc‐protected [¹³C]thiourea to afford N‐Boc‐protected [¹³C]guanidine 6, which underwent base catalyzed ring opening. Removal of the N‐Boc group afforded [guanido‐¹³C]‐γ‐hydroxyarginine HCl salt 7 giving a 30% overall yield of the final product from N‐Boc protected allylglycine 1 in five steps. Copyright © 2008 John Wiley & Sons, Ltd.     

Functional activation of Gαq/11 protein via α1‐adrenoceptor in rat cerebral cortical membranes

Although it is recognized that α₁‐adrenoceptors are coupled to diverse intracellular signalling pathways, its primary transduction mechanisms are evoked by activating phospholipase C in the cell membrane through Gα_q/11, resulting in production of inositol 1,4,5‐trisphosphate and diacylglycerol. However, there have been few studies that indicate directly the involvement of Gα_q/11 proteins in this signalling pathway in the central nervous system. In the current study, we tried to pharmacologically characterize (?)‐adrenaline‐stimulated [³⁵S]GTPγS binding to Gα_q/11 in rat brain membranes. Functional activation of Gα_q/11 coupled to α₁‐adrenoceptor was investigated by using [³⁵S]GTPγS binding/immunoprecipitation assay in the membranes prepared from rat cerebral cortex, hippocampus, and striatum. The specific [³⁵S]GTPγS binding to Gα_q/11 was stimulated by (?)‐adrenaline in a concentration‐dependent and saturable manner in rat cerebral cortical membranes. In hippocampal or striatal membranes, the stimulatory effects of (?)‐adrenaline were scarce. The effect of (?)‐adrenaline was potently inhibited by prazosin, a potent and selective α₁‐adrenoceptor antagonist, but not by yohimbine, a selective α₂‐adrenoceptor antagonist. The response was mimicked by cirazoline, but not by R(?)‐phenylephrine. Although oxymetazoline also stimulated the specific [³⁵S]GTPγS binding to Gα_q/11 as an apparent “super‐agonist”, detailed pharmacological characterization revealed that its agonistic properties in this experimental system were derived from off‐target effects on 5‐HT_2A receptors, but not via α₁‐adrenoceptors. In conclusion, functional coupling of α₁‐adrenoceptors to Gα_q/11 proteins are detectable in rat brain membranes by means of [³⁵S]GTPγS binding/immunoprecipitation assay. It is necessary to interpret the experimental data with caution when oxymetazoline is included as an agonist at α₁‐adrenoceptors.     

Agonist function of the recombinant α4β3δ GABAA receptor is dependent on the human and rat variants of the α4‐subunit

1. It is known that the α₄‐subunit is likely to occur in the brain predominantly in α₄β₃δ receptors at extrasynaptic sites. Recent studies have revealed that the α₁‐, α₄‐, γ₂‐ and δ‐subunits may colocalize extrasynaptically in dentate granule cells of the hippocampus. In the present study, we characterized a series of recombinant GABA_A receptors containing human (H) and rat (R) α₁/α₄‐, β₂/β₃‐ and γ_2S/δ‐subunits in Xenopus oocytes using the two‐electrode voltage‐clamp technique. 2. Both Hα₁β₃δ and Hα₄β₃γ_2S receptors were sensitive to activation by GABA and pentobarbital. Contrary to earlier findings that the α₄β₃δ combination was more sensitive to agonist action than the α₄β₃γ_2S receptor, we observed extremely small GABA‐ and pentobarbital‐activated currents at the wild‐type Hα₄β₃δ receptor. However, GABA and pentobarbital activated the wild‐type Rα₄β₃δ receptor with high potency (EC₅₀ = 0.5 ± 0.7 and 294 ± 5 μmol/L, respectively). 3. Substituting the Hα₄ subunit with Rα₄ conferred a significant increase in activation on the GABA and pentobarbital site in terms of reduced EC₅₀ and increased I_max. When the Hα₄ subunit was combined with the Rβ₃ and Rδ subunit in a heteropentameric form, the amplitude of GABA‐ and pentobarbital‐activated currents increased significantly compared with the wild‐type Hα₄β₃δ receptor. 4. Thus, the results indicate that the Rα₄β₃δ, Hα₁β₃δ and Hα₄β₃γ_2S combinations may contribute to functions of extrasynaptic GABA_A receptors. The presence of the Rα₄ subunit at recombinant GABA_A receptors containing the δ‐subunit is a strong determinant of agonist action. The recombinant Hα₄β₃δ receptor is a less sensitive subunit composition in terms of agonist activation.     

Synthesis of uniformly deuterated n‐dodecyl‐β‐d‐maltoside (d39‐DDM) for solubilization of membrane proteins in TROSY NMR experiments

This work reports the first synthesis of uniformly deuterated n‐dodecyl‐β‐d ‐maltoside (d₃₉‐DDM). DDM is a mild non‐ionic detergent often used in the extraction and purification of membrane proteins and for solubilizing them in experimental studies of their structure, dynamics and binding of ligands. We required d₃₉‐DDM for solubilizing large α‐helical membrane proteins in samples for [¹⁵N–¹H]TROSY (transverse relaxation‐optimized spectroscopy) NMR experiments to achieve the highest sensitivity and best resolved spectra possible. Our synthesis of d₃₉‐DDM used d₇‐d ‐glucose and d₂₅‐n‐dodecanol to introduce deuterium labelling into both the maltoside and dodecyl moieties, respectively. Two glucose molecules, one converted to a glycosyl acceptor with a free C4 hydroxyl group and one converted to a glycosyl donor substituted at C1 with a bromine in the α‐configuration, were coupled together with an α(1 → 4) glycosidic bond to give maltose, which was then coupled with n‐dodecanol by its substitution of a C1 bromine in the α‐configuration to give DDM. ¹H NMR spectra were used to confirm a high level of deuteration in the synthesized d₃₉‐DDM and to demonstrate its use in eliminating interfering signals from TROSY NMR spectra of a 52‐kDa sugar transport protein solubilized in DDM.     

Structure–activity relationship of neuropeptide γ derived from mammalian and fish

Abstract: This study of relationship between structure and biologic activity was performed using five neuropeptide γs [NPγ; mammalian‐NPγ (M‐NPγ), trout‐NPγ (T‐NPγ), goldfish‐NPγ (G‐NPγ), bowfin‐NPγ (B‐NPγ), and shark‐NPγ (S‐NPγ)]. Circular dichroism (CD) spectra showed that all peptides took random structure in buffer solution. In neutral and acidic liposomes, M‐NPγ, T‐NPγ, B‐NPγ, and S‐NPγ still adopted random structure, while G‐NPγ had an α‐helical structure. The biologic activity of NPγs has been estimated by their effects on the intestinal motility and arterial relaxation. The intestinal motility was investigated with rat duodenum (RD), carp intestine (CI), and guinea‐pig ileum (GPI). The arterial relaxing effect was tested with guinea‐pig aorta (GPA) and rat mesenteric artery (RMA). In RD, the order of potency compared with the EC₅₀ value was M‐NPγ > S‐NPγ > B‐NPγ > G‐NPγ > T‐NPγ. G‐NPγ was the most contractile agent in CI. S‐NPγ was the most contractile agent in GPI. Using an arterial relaxing test, the order of potency was G‐NPγ > T‐NPγ > B‐NPγ > S‐NPγ > M‐NPγ in GPA, and all NPγs remarkably reduced relaxing activity in RMA. Despite their structural similarities to NPγs, G‐NPγ has high affinity to tachykinin receptor‐binding sites in GPA and CI, indicating an α‐helical structure may have a critical role for receptor binding. However, an α‐helical structure does not play a critical role in recognizing receptor‐binding sites in RD and GPI.     

Novel Thiophenes,Thienopyrimidines, and Triazolothienopyrimidines for the Evaluation of Anticancer and Augmentation Effects of γ‐Radiation

New derivatives of thiophenes 2 , 12 , iminoaminothieno[2,3‐d]pyrimidines 3 , 5 , and 6 , triazolothieno[2,3‐d]pyrimidines 8–11 , pyrazolo‐ and triazinothieno[2,3‐d]pyrimidines 4 , 7 , respectively, have been prepared by different synthetic procedures. Structure elucidation of the newly synthesized compounds was carried out via elemental analyses and spectral data. The antitumor activity of compounds 2 , 3 , and 9–12 was evaluated against in‐vitro cell lines (HEPG‐2 and MCF‐7). Compounds 2 , 3 , 10 , 11 , and 12 showed significant in‐vitro cytotoxic activity against hepatocellular carcinoma (HEPG‐2) compared to the reference drug Doxorubicin. Compound 2 showed significant in‐vitro cytotoxic activity against breast cancer (MCF‐7) cells compared to the reference drug Doxorubicin. The augmenting effect of γ‐radiation was assessed; here, compounds 2 , 3 , 10 , and 11 showed the most potent in‐vitro anticancer activity.     

Comparative effects of 1α‐hydroxyvitamin D3 and 1,25‐dihydroxyvitamin D3 on transporters and enzymes in fxr(+/+) and fxr(‐/‐) mice

Previous studies have shown that 1α,25‐dihydroxyvitamin D₃ [1,25(OH)₂D₃] treatment in mice resulted in induction of intestinal and renal Cyp24a1 and Trpv6 expression, increased hepatic Cyp7a1 expression and activity, as well as higher renal Mdr1/P‐gp expression. The present study compared the equimolar efficacies of 1α‐hydroxyvitamin D₃ [1α(OH)D₃] (6 nmol/kg i.p. q2d × 4), a lipophilic precursor with a longer plasma half‐life that is converted to 1,25(OH)₂D₃, and 1,25(OH)₂D₃ on vitamin D receptor (VDR) target genes. To clarify whether changes in VDR genes was due to VDR and not secondary, farnesoid X receptor (FXR)‐directed effects, namely, lower Cyp7a1 expression in rat liver due to increased bile acid absorption, wildtype [fxr(+/+)] and FXR knockout [fxr(‐/‐)] mice were used to distinguish between VDR and FXR effects. With the exception that hepatic Sult2a1 mRNA was increased equally well by 1α(OH)D₃ and 1,25(OH)₂D₃, 1α(OH)D₃ treatment led to higher increases in hepatic Cyp7a1, renal Cyp24a1, VDR, Mdr1 and Mrp4, and intestinal Cyp24a1 and Trpv6 mRNA expression in both fxr(+/+) and fxr(‐/‐) mice compared to 1,25(OH)₂D₃ treatment. A similar induction in protein expression and microsomal activity of hepatic Cyp7a1 and renal P‐gp and Mrp4 protein expression was noted for both compounds. A higher intestinal induction of Trpv6 was observed, resulting in greater hypercalcemic effect following 1α(OH)D₃ treatment. The higher activity of 1α(OH)D₃ was explained by its rapid conversion to 1,25(OH)₂D₃ in tissue sites, furnishing higher plasma and tissue 1,25(OH)₂D₃ levels compared to following 1,25(OH)₂D₃‐treatment. In conclusion, 1α(OH)D₃ exerts a greater effect on VDR gene induction than equimolar doses of 1,25(OH)₂D₃ in mice. Copyright © 2013 John Wiley & Sons, Ltd.     

Conformational analysis of endomorphin‐1 by molecular dynamics methods

Abstract: Endomorphin‐1 (EM1, H‐Tyr‐Pro‐Trp‐Phe‐NH₂) is a highly potent and selective agonist for the μ‐opioid receptor. A conformational analysis of this tetrapeptide was carried out by simulated annealing and molecular dynamics methods. EM1 was modeled in the neutral (NH₂‐) and cationic (NH‐) forms of the N‐terminal amino group. The results of NMR measurements were utilized to perform simulations with restrained cis and trans Tyr¹‐Pro² peptide bonds. Preferred conformational regions in the Φ₂–Ψ₂, Φ₃–Ψ₃ and Φ₄–Ψ₄ Ramachandran plots were identified. The g(+), g(?) and trans rotamer populations of the side‐chains of the Tyr¹, Trp³ and Phe⁴ residues were determined in χ₁ space. The distances between the N‐terminal N atom and the other backbone N and O atoms, and the distances between the centers of the aromatic side‐chain rings and the Pro² ring were measured. The preferred secondary structures were determined as different types of β‐turns and γ‐turns. In the conformers of trans‐EM1, an inverse γ‐turn can be formed in the N‐terminal region, but in the conformers of cis‐EM1 the N‐terminal inverse γ‐turn is absent. Regular and inverse γ‐turns were observed in the C‐terminal region in both isomers. These β‐ and γ‐turns were stabilized by intramolecular H‐bonds and bifurcated H‐bonds.     

Synthesis of carbon‐14 and stable isotope labeled Avagacestat: a novel gamma secretase inhibitor for the treatment of Alzheimer's disease

Bristol‐Myers Squibb and others are developing drugs that target novel mechanisms to combat Alzheimer's disease. γ‐Secretase inhibitors are one class of potential therapies that have received considerable attention. (R)‐2‐(4‐Chloro‐N‐(2‐fluoro‐4‐(1,2,4‐oxadiazol‐3‐yl)benzyl)phenylsulfonamido)‐5,5,5‐trifluoropentanamide (Avagacestat) is a γ‐secretase‐inhibiting drug that has been investigated by Bristol‐Myers Squibb in preclinical and clinical studies. An important step in the development process was the synthesis of a carbon‐14‐labeled analog for use in a human absorption, distribution, metabolism, and excretion study and a stable isotope labeled analog for use as a standard in bioanalytical assays to accurately quantify the concentration of the drug in biological samples. Carbon‐14 labeled Avagacestat was synthesized in seven steps in a 33% overall yield from carbon‐14 labeled potassium cyanide. A total of 5.95 mCi was prepared with a specific activity of 0.81 μCi/mg and a radiochemical purity of 99.9%. ¹³C₆‐Labeled Avagacestat was synthesized in three steps in a 15% overall yield from 4‐chloro[¹³C₆]aniline. A total of 585 mg was prepared with a ultraviolet purity of 99.9%.     

Potent and selective inhibitors of 11β‐hydroxysteroid dehydrogenase type 1 labeled with carbon‐13 and carbon‐14

(S )‐6‐(2‐Hydroxy‐2‐methylpropyl)‐3‐((S )‐1‐(4‐(1‐methyl‐2‐oxo‐1,2‐dihydropyridin‐4‐yl)phenyl)ethyl)‐6‐phenyl‐1,3‐oxazinan‐2‐one (1) and (4aR ,9aS )‐1‐(1H‐benzo[d]midazole‐5‐carbonyl)‐2,3,4,4a,9,9a‐hexahydro‐1‐H‐indeno[2,1‐b]pyridine‐6‐carbonitrile hydrochloride (2) are potent and selective inhibitor of 11β‐hydroxysteroid dehydrogenase type 1 enzyme. These 2 drug candidates developed for the treatment of type‐2 diabetes were prepared labeled with carbon‐13 and carbon‐14 to enable drug metabolism, pharmacokinetics, bioanalytical, and other studies. In the carbon‐13 synthesis, benzoic‐¹³C ₆ acid was converted in 7 steps and in 16% overall yield to [¹³C₆]‐(1). Aniline‐¹³C ₆ was converted in 7 steps to 1H‐benzimidazole‐1‐2,3,4,5,6‐¹³C₆‐5‐carboxylic acid and then coupled to a tricyclic chiral indenopiperidine to afford [¹³C₆]‐(2) in 19% overall yield. The carbon‐14 labeled (1) was prepared efficiently in 2 radioactive steps in 41% overall yield from an advanced intermediate using carbon‐14 labeled methyl magnesium iodide and Suzuki‐Miyaura cross coupling via in situ boronate formation. As for the synthesis of [¹⁴C]‐(2), 1H‐benzimidazole‐5‐carboxylic‐¹⁴C acid was first prepared in 4 steps using potassium cyanide‐¹⁴C , then coupled to the chiral indenopiperidine using amide bond formation conditions in 26% overall yield.     

Anticancer Properties of Novel 4‐methylene‐1,2‐diphenylpyrazolidin‐3‐ones

The limited success of the currently used antitumor therapies is the driving force for organic chemists to seek new lead structures with anticancer potential. Two α‐methylene‐γ‐lactams with an additional nitrogen atom in the lactam ring, 5‐vinyl‐1,2‐diphenyl‐4‐methylenepyrazolidin‐3‐one ( 2a ) and 5‐phenyl‐1,2‐diphenyl‐4‐methylenepyrazolidin‐3‐one ( 2b ) have been synthesized. Their anticancer activity was assessed in MCF‐7 cells. Both compounds inhibited cell proliferation and induced DNA damage and apoptosis, with 2a being the more potent analog. Synergistic effects of 2a used in combination with known anticancer drugs, 5‐fluorouracil, taxol, and oxaliplatin were evaluated. Compound 2a significantly enhanced the antitumor action of oxaliplatin and 5‐fluorouracil, but not taxol.     

Bioactive N‐terminal undecapeptides derived from parathyroid hormone: the role of α‐helicity*

Abstract: The N‐terminal 1–34 segment of parathyroid hormone (PTH) is fully active in vitro and in vivo and it can reproduce all biological responses in bone characteristic of the native intact PTH. Recent studies have demonstrated that N‐terminal fragments presenting the principal activating domain such as PTH(1–11) and PTH(1–14) with helicity‐enhancing substitutions yield potent analogues with PTH(1–34)‐like activity. To further investigate the role of α‐helicity on biological potency, we designed and synthesized by solid‐phase methodology the following hPTH(1–11) analogues substituted at positions 1 and/or 3 by the sterically hindered and helix‐promoting C^α‐tetrasubstituted α‐amino acids α‐amino isobutyric acid (Aib), 1‐aminocyclopentane‐1‐carboxylic acid (Ac₅c) and 1‐aminocyclohexane‐1‐carboxylic acid (Ac₆c): Ac₅c‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( I ); Aib‐V‐Ac₅c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( II ); Ac₆c‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( III ); Aib‐V‐Ac₆c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( IV ); Aib‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( V ); S‐V‐Aib‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( VI ), S‐V‐Ac₅c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( VII ); Ac₅c‐V‐S‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( VIII ); Ac₆c‐V‐S‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( IX ); Ac₅c‐V‐Ac₅c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( X ); Ac₆c‐V‐Ac₆c‐E‐I‐Q‐L‐M‐H‐Q‐R‐NH₂ ( XI ). All analogues were biologically evaluated and conformationally characterized in 2,2,2‐trifluoroethanol (TFE) solution by circular dichroism (CD). Analogues I – V , which cover the full range of biological activity observed in the present study, were further conformationally characterized in detail by nuclear magnetic resonance (NMR) and computer simulations studies. The results of ligand‐stimulated cAMP accumulation experiments indicated that analogues I and II are active, analogues III , VI and VII are very weakly active and analogues IV , V , VIII–XI are inactive. The most potent analogue, I exhibits biological activity 3500‐fold higher than that of the native PTH(1–11) and only 15‐fold weaker than that of the native sequence hPTH(1–34). Remarkably, the two most potent analogues, I and II , and the very weakly active analogues, VI and VII , exhibit similar helix contents. These results indicate that the presence of a stable N‐terminal helical sequence is an important but not sufficient condition for biological activity.     

Potencies of vitamin D analogs, 1α‐hydroxyvitamin D3, 1α‐hydroxyvitamin D2 and 25‐hydroxyvitamin D3, in lowering cholesterol in hypercholesterolemic mice in vivo

Vitamin D₃ and the synthetic vitamin D analogs, 1α‐hydroxyvitamin D₃ [1α(OH)D₃], 1α‐hydroxyvitamin D₂ [1α(OH)D₂] and 25‐hydroxyvitamin D₃ [25(OH)D₃] were appraised for their vitamin D receptor (VDR) associated‐potencies as cholesterol lowering agents in mice in vivo. These precursors are activated in vivo: 1α(OH)D₃ and 1α(OH)D₂ are transformed by liver CYP2R1 and CYP27A1 to active VDR ligands, 1α,25‐dihydroxyvitamin D₃ [1,25(OH)₂D₃] and 1α,25‐dihydroxyvitamin D₂ [1,25(OH)₂D₂]_, respectively. 1α(OH)D₂ may also be activated by CYP24A1 to 1α,24‐dihydroxyvitamin D₂ [1,24(OH)₂D₂], another active VDR ligand. 25(OH)D₃, the metabolite formed via CYP2R1 and or CYP27A1 in liver from vitamin D₃, is activated by CYP27B1 in the kidney to 1,25(OH)₂D₃. In C57BL/6 mice fed the high fat/high cholesterol Western diet for 3 weeks, vitamin D analogs were administered every other day intraperitoneally during the last week of the diet. The rank order for cholesterol lowering, achieved via mouse liver small heterodimer partner (Shp) inhibition and increased cholesterol 7α‐hydroxylase (Cyp7a1) expression, was: 1.75 nmol/kg 1α(OH)D₃ > 1248 nmol/kg 25(OH)D₃ (dose ratio of 0.0014) > > 1625 nmol/kg vitamin D₃. Except for 1.21 nmol/kg 1α(OH)D₂ that failed to lower liver and plasma cholesterol contents, a significant negative correlation was observed between the liver concentration of 1,25(OH)₂D₃ formed from the precursors and liver cholesterol levels. The composite results show that vitamin D analogs 1α(OH)D₃ and 25(OH)D₃ exhibit cholesterol lowering properties upon activation to 1,25(OH)₂D₃: 1α(OH)D₃ is rapidly activated by liver enzymes and 25(OH)D₃ is slowly activated by renal Cyp27b1 in mouse.     

Linear basic peptides for targeting interferon‐γ–glycosaminoglycan interactions: synthesis and inhibitory properties

Abstract: Glycosaminoglycans (GAGs) play an important role in inflammatory responses due to their ability to interact with cytokines and chemokines, resulting in the localization of these mediators to specific anatomical sites, where they function to direct leukocyte recruitment and activation. Targeting GAG–cytokine/chemokine interactions might may thus have therapeutic applications as anti‐inflammatory or immunomodulatory therapy in vivo. Peptides that mimic the heparin‐binding domains of cytokines may have a potential use as inhibitors of GAG–cytokine interactions. A linear octapeptide (MC‐2) derived from the conserved heparin‐binding region of interferon‐γ (IFN‐γ) was synthesized along with four analogs featuring a substitution of Phe for Leu in position 1 and varying number of positive charges on the octapeptide molecule. The relative abilities of the synthesized peptides to inhibit the interactions between IFN‐γ and GAGs were compared. From the results, it follows that the inhibitory potency of the octapeptide analogs was related to the number of positive charges in the molecule, while increased hydrophobicity had no significant effect.     

Synthesis and activity of the glutathione analogue γ-(L-γ-azaglutamyl)-L-cysteinyl-glycine

The backbone-modified glutathione analogue γ-(L-γ-azaglutamyl)-L-cysteinyl-glycine 7, characterized by the presence of a NHCONH urea linkage deriving from the replacement of the native Glu γ-CH₂ with the aza (NH) group, was synthesized and fully characterized by FAB-MS, ¹H- and ¹³C-NMR. Potential of 7 and its oxidized form 6 as γ-glutamyltransferase inhibitors was investigated. Both compounds 7 and 6 were found to be competitive inhibitors of hog kidney y-glutamyltransferase (EC 2.3.2.2.) by binding at the donor site: the reduced analogue is a more efficient inhibitor than glutathione of the γ-glutamyl transfer reaction. Inhibition at the acceptor site, which is also present, appears to be more complex. In particular, un-competitive inhibition is observed for compound 7. The results indicate that γ-azapeptides of type 7 may represent interesting targets in the search for stable inhibitors of γ-glutamyltransferases. © Munksgaard 1995.     

Lack of specificity of [35S]‐ATPγS and [35S]‐ADPβS as radioligands for ionotropic and metabotropic P2 receptor binding

Adenosine‐5′‐O‐3‐thio[³⁵S]triphosphate ([³⁵S]‐ATPγS) has been reported to specifically bind several P2X receptor subtypes, including P2X₁, P2X₂, P2X₃, and P2X₄. Similarly, adenosine‐5′‐O‐2‐thio[³⁵S]diphosphate ([³⁵S]‐ADPβS) has been reported to label putative P2Y receptors. To address whether these radioligands selectively label P2 receptors, the functional activity of various P2 ligands was compared with their ability to compete for [³⁵S]‐ATPγS and [³⁵S]‐ADPβS binding to cell membrane preparations from rat brain, HEK293 cells, and to native and P2X₄ transfected 1321N1 astrocytoma cells. [³⁵S]‐ATPγS (0.2 nM) and [³⁵S]‐ADPβS (0.1 nM) displayed a high percentage of specific binding to membranes prepared from 1321N1 human astrocytoma cells, which were found to be devoid of detectable P2X and P2Y functional activity. [³⁵S]‐ATPγS and [³⁵S]‐ADPβS also exhibited equivalent high percentages of specific binding to HEK293 cell membranes, which endogenously express the P2Y₁ and P2Y₂ receptor subtypes, to 1321N1 cells stably transfected with the human P2X₄ receptor, and to rat brain membranes, which have previously been shown to contain both P2X and P2Y receptor subtypes. The potency order of P2 agonists to compete for radioligand binding to these cell membrane preparations was significantly different from the functional rank order potencies determined in HEK293 cells and 1321N1 cells expressing the P2X₄ receptor, as measured by cytosolic calcium flux. These data indicate that [³⁵S]‐ATPγS and [³⁵S]‐ADPβS appear to bind sites that do not correspond to known functional P2 receptor subtypes. The apparent lack of specificity of these radioligands for labeling P2 receptors is similar to that reported for other radiolabeled nucleotides and illustrates the need for caution in interpreting the apparent pharmacology of native P2 receptors on the basis of binding data alone. Drug Dev. Res. 48:84–93, 1999. © 1999 Wiley‐Liss, Inc.     

Third‐generation dihydropyridine‐type calcium channel blocker labedipinedilol‐B displays α/β‐adrenoceptor blocking activities

The pharmacological properties of labedipinedilol‐B {N‐[4‐[2‐hydroxy‐3‐(2‐methoxy‐1‐oxyethylaminobenzene) propoxy]‐benzyl]‐2,6‐dimethyl‐3,5‐dicarbomethoxy‐1,4‐dihydropyridine} were investigated in vivo and in vitro in comparison with labedipinedilol‐A. Intravenous labedipinedilol‐B (0.5, 1.0, and 3.0 mg kg^–1), produced dose‐dependent hypotensive and bradycardia responses in pentobarbital‐anesthetized Wistar rats. Pretreatment with labedipinedilol‐B (1.0 mg kg^–1, iv) also inhibited phenylephrine (10 μg kg^–1)‐induced hypertensive and (–)isoproterenol (0.5 μg kg^–1)‐induced tachycardia effects. In the isolated Wistar rat right and left atria and guinea pigs tracheal strips experiments, labedipinedilol‐B (10^–7, 10^–6, and 10^–5 M) competitively antagonized the (–)isoproterenol‐induced positive chronotropic and inotropic effects and tracheal relaxation responses in a concentration‐dependent manner. The parallel shift to the right of the concentration–response curve of (–)isoproterenol suggested that labedipinedilol‐B was a β₁/β₂‐adrenoceptor competitive antagonist. Labedipinedilol‐B (10^–7, 10^–6, and 10^–5 M) also prevented the rate‐increasing effects of increased extracellular Ca²⁺ (3.0–9.0 mM) in a concentration‐dependent manner. In the isolated rat aorta, labedipinedilol‐B (10^–7, 10^–6, and 10^–5 M) competitively antagonized the CaCl₂ and norepinephrine‐induced contractions with pKCa^–1 and pA₂ values of 8.02 ± 0.04 and 7.55 ± 0.05 in a concentration‐dependent manner. The parallel shift to the right of the concentration–response curves of norepinephrine suggested that labedipinedilol‐B was an α‐adrenoceptor competitive antagonist. Furthermore, labedipinedilol‐B, in an equal antagonist activity, inhibited norepinephrine‐induced phasic and tonic contraction. In the isolated rat aorta, labedipinedilol‐B also competitively antagonized CaCl₂‐induced contractions and made the parallel shift to the right of the concentration–response curve of CaCl₂. In cultured blood vessel smooth muscle cells (A7r5 cell lines), Bay K 8644‐induced intracellular calcium changes were decreased after application of labedipinedilol‐B, suggesting that the compound was a calcium channel blocker. The binding characteristics of labedipinedilol‐B were evaluated in [³H]CGP‐12177 binding to ventricle and lung and [³H]prazosin binding to brain membranes in rats. Labedipinedilol‐B also was evaluated in [³H]nitrendipine binding to brain membranes in rats. These results indicated that labedipinedilol‐B, similar to labedipinedilol‐A, has α‐adrenoceptor blocking, β‐adrenoceptor blocking, and calcium entry blocking activities in a single compound. We suggest that these two compounds represent a new generation of 1,4‐dihydropyridine‐type calcium channel blockers. Drug Dev. Res. 52:462–474, 2001. © 2001 Wiley‐Liss, Inc.