Targeting cardiomyocyte ADAM10 ectodomain shedding promotes survival early after myocardial infarction.

After myocardial infarction the innate immune response is pivotal in clearing of tissue debris as well as scar formation, but exaggerated cytokine and chemokine secretion with subsequent leukocyte infiltration also leads to further tissue damage. Here, we address the value of targeting a previously unknown a disintegrin and metalloprotease 10 (ADAM10)/CX3CL1 axis in the regulation of neutrophil recruitment early after MI. We show that myocardial ADAM10 is distinctly upregulated in myocardial biopsies from patients with ischemia-driven cardiomyopathy. Intriguingly, upon MI in mice, pharmacological ADAM10 inhibition as well as genetic cardiomycyte-specific ADAM10 deletion improves survival with markedly enhanced heart function and reduced scar size. Mechanistically, abolished ADAM10-mediated CX3CL1 ectodomain shedding leads to diminished IL-1ß-dependent inflammation, reduced neutrophil bone marrow egress as well as myocardial tissue infiltration. Thus, our data shows a conceptual insight into how acute MI induces chemotactic signaling via ectodomain shedding in cardiomyocytes.

Synthesis of 13C Labeled Vitamin D Metabolites for Their Use in LC-MS/MS: Valuable Tools for Cancer Research and Other Applications.

BACKGROUND/AIM: Simultaneous assessment of various vitamin D metabolites in human biofluids by liquid chromatography tandem mass spectrometry (LC-MS/MS) represents a new promising tool for the differential diagnosis of vitamin D-related diseases. Particularly, besides 25(OH)VD2/3, low-abundant medicinally relevant vitamin D metabolites, such as 24,25(OH)2VD2/3, 1,25(OH)2VD2/3, and 1,24,25(OH)3VD2/3, along with their 3-epi-derivatives have to be considered. MATERIALS AND METHODS: The assessment of these metabolites by LC-MS/MS requires the development of calibration and reference standards, that is, their labeling with multiple deuterium-, or even better, 13C- atoms. RESULTS: Overall, 10 13C-labeled vitamin D metabolites have been chemically synthesized and obtained in good yield and high purity. CONCLUSION: Access to a wide variety of 13C-labeled highly pure vitamin D metabolites enables the advancement of LC-MS/MS applications towards a better understanding of differential diagnosis of vitamin D-related diseases.

Novel approach to A-ring synthon for Pd-catalyzed synthesis of 1α-hydroxylated vitamin D metabolites.

A novel approach to an A-ring synthon for Pd-catalyzed synthesis of 1α-hydroxylated vitamin D metabolites is described. Key step is an asymmetric glyoxylate ene reaction to access a highly diastereomerically pure α-hydroxy ester. Subsequent stereospecific transformation to an anti-1,3-diol and appropriate chemical modifications at both ends of the acyclic precursor leads to a diastereomerically and enantiomerically pure silylated anti-1,3-diol enyne, serving as a versatile A-ring synthon for its use in vitamin D synthesis.

Sulfoximines as Rising Stars in Modern Drug Discovery? Current Status and Perspective on an Emerging Functional Group in Medicinal Chemistry.

Sulfoximines have been largely disregarded in medicinal chemistry for a long time. However, recently, they have risen to the apparent level of stardom on the drug discovery scene. Considering the outstanding properties of sulfoximines, this versatile functional group has advanced to implementation in several drug discovery programs. Currently, this fashionable functional group can be found in various hit-to-lead and lead optimization studies in early stages and in several compounds currently in clinical trials. Herein, we review recent developments to demonstrate the scope and limitations of this interesting and versatile functional group in medicinal chemistry and drug discovery.

Efficient synthesis of 3-TBDMS-11α,25-dihydroxyvitamin D3 and D2 ethers.

Vitamin D deficiency might cause a wide variety of human disorders. As a prerequisite for appropriate diagnosis and therapy, medicinally relevant vitamin D metabolites have to be assayed most accurately and with high specificity. It has been demonstrated, that vitamin D conjugates, linked via a hydroxyl group at C11, might be promising for the development of highly specific antibodies to be employed in competitive protein binding assays. The connective synthesis of 3-TBDMS-11α,25-dihydroxyvitamin D3 and D2 ethers in 500 mg scale, starting from vitamin D2, is described. For installation of a hydroxyl group at C11 a sequence of Pd(OAc)2 mediated oxidation of an enone, epoxidation and subsequent epoxide ring opening was applied to obtain a suitable CD-ring precursor, that was connected with an A-ring diphenylphosphine oxide by Wittig-Horner reaction. Finally, an appropriate side chain was installed, respectively.

Recent Developments Towards the Synthesis of Vitamin D Metabolites.

Due to latest advancements in the development of LC-MS/MS based assays and their applications in clinical chemistry, low abundant vitamin D metabolites can be detected at low concentration with high specificity. Consequently, there is a growing need for their synthesis as stable isotopically labeled compounds to be used as calibration and reference standards. Most commonly, ex chiral pool synthesis, starting with vitamin D2, and palladium(0) catalyzed coupling reactions are applied in vitamin D synthesis. By contrast, little is known so far regarding the application of cobalt complexes for this purpose. In fact, the Pausen-Khand reaction can be applied for the synthesis of a wide range of isotopically labeled vitamin D metabolites that are hardly accessible by other known methods. Applications, scope and limitations of the most recent vitamin D synthesis methods, with a particular focus on this new promising methodology using Co-complexes, are discussed.

Highly regio- and stereoselective hydroxylation of vitamin D2 by CYP109E1.

Vitamin D2 is a form of vitamin D derived from mushrooms and plants which is structurally modified in the body due to the action of several enzymes. The resulting metabolites represent important compounds with potential bioactive properties. However, they are poorly studied and their availability is mostly limited. In order to identify new enzymes capable of producing vitamin D2 metabolites, we investigated a bacterial P450 monooxygenase, CYP109E1, which was previously shown to be a vitamin D3 hydroxylase. It was found that CYP109E1 catalyzes a vitamin D2 two-step hydroxylation at positions C24 and C25 resulting in the generation of 24(R),25-diOH VD2. Interestingly, the enzyme showed high selectivity towards vitamin D2, whereas it showed an unselective product pattern for the structurally similar vitamin D3. Our docking results for vitamin D2 and D3 revealed favorable hydroxylation positions for both substrates and suggested an explanation for the high selectivity of CYP109E1 towards vitamin D2. In addition, we established a whole-cell biocatalyst expressing CYP109E1 in Bacillus megaterium to produce 24(R),25-diOH VD2 and a production yield of 12.3 ± 1.2 mg/L was obtained after 48 h. To the best of our knowledge, this is the first report on the generation of 24(R),25-diOH VD2 by a microbial biocatalyst allowing a low-cost and eco-friendly production of this pharmaceutically interesting and expensive metabolite from the relatively cheap substrate, VD2.

Sarcoplasmic reticulum calcium leak contributes to arrhythmia but not to heart failure progression.

Increased sarcoplasmic reticulum (SR) Ca2+ leak via the cardiac ryanodine receptor (RyR2) has been suggested to play a mechanistic role in the development of heart failure (HF) and cardiac arrhythmia. Mice treated with a selective RyR2 stabilizer, rycal S36, showed normalization of SR Ca2+ leak and improved survival in pressure overload (PO) and myocardial infarction (MI) models. The development of HF, measured by echocardiography and molecular markers, showed no difference in rycal S36- versus placebo-treated mice. Reduction of SR Ca2+ leak in the PO model by the rycal-unrelated RyR2 stabilizer dantrolene did not mitigate HF progression. Development of HF was not aggravated by increased SR Ca2+ leak due to RyR2 mutation (R2474S) in volume overload, an SR Ca2+ leak-independent HF model. Arrhythmia episodes were reduced by rycal S36 treatment in PO and MI mice in vivo and ex vivo in Langendorff-perfused hearts. Isolated cardiomyocytes from murine failing hearts and human ventricular failing and atrial nonfailing myocardium showed reductions in delayed afterdepolarizations, in spontaneous and induced Ca2+ waves, and in triggered activity in rycal S36 versus placebo cells, whereas the Ca2+ transient, SR Ca2+ load, SR Ca2+ adenosine triphosphatase function, and action potential duration were not affected. Rycal S36 treatment of human induced pluripotent stem cells isolated from a patient with catecholaminergic polymorphic ventricular tachycardia could rescue the leaky RyR2 receptor. These results suggest that SR Ca2+ leak does not primarily influence contractile HF progression, whereas rycal S36 treatment markedly reduces ventricular arrhythmias, thereby improving survival in mice.

An efficient synthesis of 1α,25-dihydroxyvitamin D3 LC-biotin.

In recent years the apparent impact of vitamin D deficiency on human health has gained increased awareness. Consequently, the development of appropriate assays to measure the status of medicinally most relevant vitamin D metabolites in human blood, serum or relevant tissue is continuously being improved. Particularly, assaying of 1α,25-dihydroxyvitamin D3, in turn considered as the most active metabolite, is mainly indicated in disorders leading to calcaemia or those resulting from an impaired 1α-hydroxylation of 25-hydroxyvitamin D3. Thus, in some competitive protein binding and ELISA assays, biotin-linked 1α,25-dihydroxyvitamin D3 (1α,25-dihydroxyvitamin D3 LC-biotin) is employed for measurement of actual calicitriol concentration. A new efficient synthesis of 1α,25-dihydroxyvitamin D3 LC-biotin is described, starting with readily available vitamin D2, and combining a classical approach to access 1α,25-dihydroxyvitamin D3, appropriate OH-protective group transformations, and a C-3-O-alkylation, suitable to connect the biotin-linker in a reliable, selective and high yielding strategy. The developed methodology is applicable to the synthesis of a wide variety of C-3-OH-linked vitamin D3 and D2 derivatives.

Optimization of Chemical Syntheses of Vitamin D C3-Epimers.

Due to the widespread impact of vitamin D on human health, the development of appropriate assays to detect deficiency of all vitamin D metabolites of pharmacological interest is being continuously improved. Although over 50 naturally-occurring metabolites of vitamin D are known to date, only very few are routinely detected in commercially available assays. This is particularly true regarding C3-epimers of vitamin D3 and D2, which not only may interfere in analytical measurements with other metabolites of interest, but also have controversial and not yet fully understood physiological functions. In this study we optimized a synthetic method to obtain various vitamin D3 and D2 C3-epimers in order to make them available in gram quantities for further evaluation and for their use in assay development or drug discovery. Particularly, the inversion of the C3-OH group at the A-ring of vitamin D2, which, in turn, serves as a suitable starting material for most of chemical syntheses of vitamin D metabolites, can be converted to the corresponding C3-epimer under so-called "Mitsunobu conditions". Thus, the C3-OH group is converted into the corresponding ester by treatment with an aromatic acid, subsequent addition of an azodicarboxlate and triphenylphoshine, leading to the corresponding ester, concomitant to the inversion of the stereogenic center at C3. Reduction or saponification of the resulting ester finally leads to the corresponding C3-epimer, that may serve as starting material for a wide variety of vitamin D3 and D2 C3-epimers.

Development of efficient chemical syntheses of vitamin D degradation products.

In recent years it has been recognized that vitamin D deficiency is associated with a wide range of diseases, including various types of cancers. Due to the enormous medical importance of vitamin D and its metabolites, their status in blood serum has to be accurately measured. Thus, the metabolites actually used as reference standards and also others of relevant biological activity have to be provided for validation and continuous improvement of appropriate diagnostic devices. Efficient chemical syntheses of vitamin D derivatives described in the literature are herein proven in a comparative study and applied to the synthesis of some of the most relevant natural metabolites as representative examples.

Development of a colorimetric and a fluorescence phosphatase-inhibitor assay suitable for drug discovery approaches.

Protein phosphatases (PP) are interesting drug targets. However, their ubiquitous presence and involvement in different, partially opposing signal pathways suggest that specificity may be achieved rather by targeting their interaction with subunits determining substrate specificity than the enzyme itself. An interesting subunit is phosphatase inhibitor-1 (I-1), which, in its protein kinase A-phosphorylated form (I-1(P)), inhibits the catalytic subunit of type 1 phosphatase (PP1c). In the current study, we established a colorimetric and a fluorescence-based assay system for the identification of compounds interfering with the inhibitory effect of I-1(P) on PP1c. The fluorescence assay exhibited 500-fold higher sensitivity toward PP1c. A nine-residue peptide containing the PP1c-binding motif (RVxF) of I-1 stimulated PP1c activity in the presence of I-1(P) (EC50 27 µM and 2.3 µM in the colorimetric and fluorescence assay, respectively). This suggests that the peptide interfered with the inhibitory effect of I-1(P) on PP1c and represents a proof-of-principle. The calculated Z' factor for PP1c (0.84) and the PP1c-I-1(P) complex (0.73) confirmed the suitability of the fluorescence assay for high-throughput screenings (HTS). By testing several thousand small molecules, we suggest the advantages of kinetic measurements over single-point measurements using the fluorescence-based assay in an HTS format.

Combined Na(+)/Ca(2+) exchanger and L-type calcium channel block as a potential strategy to suppress arrhythmias and maintain ventricular function.

BACKGROUND: L-type calcium channel (LTCC) and Na(+)/Ca(2+) exchanger (NCX) have been implicated in repolarization-dependent arrhythmias, but also modulate calcium and contractility. Although LTCC inhibition is negative inotropic, NCX inhibition has the opposite effect. Combined block may, therefore, offer an advantage for hemodynamics and antiarrhythmic efficiency, particularly in diseased hearts. In a model of proarrhythmia, the dog with chronic atrioventricular block, we investigated whether combined inhibition of NCX and LTCC with SEA-0400 is effective against dofetilide-induced torsade de pointes arrhythmias (TdP), while maintaining calcium homeostasis and hemodynamics. METHODS AND RESULTS: Left ventricular pressure (LVP) and ECG were monitored during infusion of SEA-0400 and verapamil in anesthetized dogs. Different doses were tested against dofetilide-induced TdP in chronic atrioventricular block dogs. In ventricular myocytes, effects of SEA-0400 were tested on action potentials, calcium transients, and early afterdepolarizations. In cardiomyocytes, SEA-0400 (1 µmol/L) blocked 66±3% of outward NCX, 50±2% of inward NCX, and 33±9% of LTCC current. SEA-0400 had no effect on systolic calcium, but slowed relaxation, despite action potential shortening, and increased diastolic calcium. SEA-0400 stabilized dofetilide-induced lability of repolarization and suppressed early afterdepolarizations. In vivo, SEA-0400 (0.4 and 0.8 mg/kg) had no effect on left ventricular pressure and suppressed dofetilide-induced TdPs dose dependently. Verapamil (0.3 mg/kg) also inhibited TdP, but caused a 15±8% drop of left ventricular pressure. A lower dose of verapamil without effects on left ventricular pressure (0.06 mg/kg) was not antiarrhythmic. CONCLUSIONS: In chronic atrioventricular block dogs, SEA-0400 treatment is effective against TdP. Unlike specific inhibition of LTCC, combined NCX and LTCC inhibition has no negative effects on cardiac hemodynamics.

Chemical, biochemical and microbiological properties of a brominated nitrovinylfuran with broad-spectrum antibacterial activity.

A di-bromo substituted nitrovinylfuran with reported broad-spectrum antibacterial activity was found to be a potent inhibitor of MurA, a key enzyme in peptidoglycan biosynthesis. Further characterization of the compound was carried out to assess its reactivity towards thiol nucleophiles, its stability and degradation under aqueous conditions, inhibitory potential at other enzymes, and antibacterial and cytotoxic activity. Our results indicate that the nitrovinylfuran derivative is reactive towards cysteine residues in proteins, as demonstrated by the irreversible inhibition of MurA and bacterial methionine aminopeptidase. Experiments with proteins and model thiols indicate that the compound forms covalent adducts with SH groups and induces intermolecular disulfide bonds, with the intermediate formation of a monobromide derivative. The parent molecule as well as most of its breakdown products are potent antibiotics with MIC values below 4 µg/mL and are active against multiresistant strains such as methicillin-resistant Staphylococcus aureus (MRSA). Further development of the bromonitrovinyl scaffold towards antibiotics with clinical relevance, however, requires optimization of the antibiotic-cytotoxic selectivity profile.

Optimization of assay conditions for dengue virus protease: effect of various polyols and nonionic detergents.

The aim of this work was to perform a systematic study of the effect of nonionic detergents on the activity of the dengue virus NS2B-NS3 protease. To ensure a high activity of the protease, the assay procedures for the dengue virus and other flaviviral proteases published to date are performed in the presence of up to 35% glycerol, which does not represent the cellular physicochemical environment. In addition, the high viscosity of glycerol-containing solutions leads to various experimental problems in miniaturized assays. Using an internally quenched peptide substrate, the authors show that glycerol is not essential for enzymatic activity if certain nonionic detergents are added to the assay buffer. In addition, nonionic detergents may help to avoid false-positive screening results caused by "promiscuous" inhibitors. Other polyalcohols can substitute glycerol and have less effect on the viscosity of the assay buffer. The assay was used to screen a compound library and allowed the identification of small-molecular nonpeptidic inhibitors of dengue NS3 protease. Finally, the authors discuss the mode of action of nonionic detergents and the influence that they may have on the conformational properties of the NS2B-NS3 protease.

Identification of terfenadine as an inhibitor of human CD81-receptor HCV-E2 interaction: synthesis and structure optimization.

Terfenadine (4-[4-(hydroxydiphenylmethyl)-1-piperidyl]-1-(4-tert-butylphenyl)-butan-1-ol) was identified in a biological screening to be a moderate inhibitor (27% inhibition) of the CD81-LEL-HCV-E2 interaction. To increase the observed biological activity, 63 terfenadine derivates were synthesized via microwave assisted nucleophilic substitution. The prepared compounds were tested for their inhibitory potency by means ofa fluorescence labeled antibody assay using HUH7.5 cells. Distinct structure-activity relationships could be derived. Optimization was successful, leading to 3g, identified as the most potent compound (69 % inhibition). Experiments with viral particles revealed that there might be additional HCV infection reducing mechanisms.