Phosphodiesterase 2 inhibitors promote axonal outgrowth in organotypic slice co-cultures

The development of appropriate models assessing the potential of substances for regeneration of neuronal circuits is of great importance. Here, we present procedures to analyze effects of substances on fiber outgrowth based on organotypic slice co-cultures of the nigrostriatal dopaminergic system in combination with biocytin tracing and tyrosine hydroxylase labeling and subsequent automated image quantification. Selected phosphodiesterase inhibitors (PDE-Is) were studied to identify their potential growth-promoting capacities. Immunohistochemical methods were used to visualize developing fibers in the border region between ventral tegmental area/substantia nigra co-cultivated with the striatum as well as the cellular expression of PDE2A and PDE10. The quantification shows a significant increase of fiber density in the border region induced by PDE2-Is (BAY60-7550; ND7001), comparable with the potential of the nerve growth factor and in contrast to PDE10-I (MP-10). Analysis of tyrosine hydroxylase-positive fibers indicated a significant increase after treatment with BAY60-7550 and nerve growth factor in relation to dimethyl sulfoxide. Additionally, a dose-dependent increase of intracellular cGMP levels in response to the applied PDE2-Is in PDE2-transfected HEK293 cells was found. In summary, our findings show that PDE2-Is are able to significantly promote axonal outgrowth in organotypic slice co-cultures, which are a suitable model to assess growth-related effects in neuro(re)generation.

5-(4-Hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-7-phenyl-2,3,6,7-tetrahydro-1,4-thiazepines as compounds with high affinity at the benzodiazepine binding site on GABA(A) receptors

A series of thiazepines has been studied as new ligands for the benzodiazepine binding site of the GABAA receptor. Compounds with high affinity and weak selectivity regarding alpha beta3gamma2, alpha2beta3gamma2, alpha3beta3gamma2, and alpha5beta3gamma2 subtypes were found. The pharmacophore is discussed based on experimental and theoretical results. The thiazepine sulfur atom was found to be able to act as hydrogen bond acceptor.

[Synthesis of substituted 6-phenylpyrazolo[3,4-d]pyrimidines with potential adenosin-A2A antagonistic activity]

Substituted pyrazolo[3,4-d]pyrimidines were prepared by reaction of methyl- or phenylhydrazine with pyrimidine derivatives containing a methylthio or chlorine substituent as nucleofuge. Using a methylthio-6-imino-1,3-thiazine as starting material instead of a methylthiopyrimidine the conversion with phenylhydrazine could already be achieved under mild conditions thus leading first to the formation of a hydrazinopyrimidine. The affinity of the products against the human adenosine A2A receptor was determined.

Refolding, purification, and characterization of human recombinant PDE4A constructs expressed in Escherichia coli

A 5'-truncated PDE4A-cDNA corresponding to the amino acid positions 200-886 of the "full-length" sequence (Accession No. L20965) was generated from human leukocyte mRNA by RT-PCR. Several PDE4A constructs containing the catalytic region and differing in their degree of N- and/or C-terminal truncation (amino acid positions 200-886, 200-704, 342-886, and 342-704) were expressed in Escherichia coli to investigate the effect of truncations on purification characteristics, long-term stability, and aggregation. All peptides accumulated as inclusion bodies, necessitating refolding prior to purification by dye and metal chelate affinity chromatography. The constructs differed in long-term stability due to variable levels of protease contamination. The position of the His-tag also influenced the purification results. The best results were obtained with the N- and C-truncated form C-terminally His-tagged, appropriate quantities of which were obtained in pure form and was found to be stable against proteolysis at 4 degrees C for at least 6 weeks. The comparison of the molecular mass of the investigated PDE4A constructs obtained by SDS electrophoresis, size-exclusion chromatography, and analytical ultracentrifugation indicated that C-terminal truncated PDE4A forms dimers whereas PDE4A constructs with a complete C-terminus tend to form larger aggregates.

1,5-Disubstituted indazol-3-ols with anti-inflammatory activity

A series of new indazol-3-ol derivatives was synthesized. Some of these compounds exhibit interesting anti-inflammatory activities in various models of inflammation. 5-Methoxy-1-[quinoline-2-yl-methoxy)-benzyl]-1H-indazol-3-ol (27) strongly inhibits the oxidation of arachidonic acid to 5-hydroperoxyeicosatetraenoic acid catalyzed by 5-lipoxygenase (IC50 = 44 nM). 27 also inhibits the contraction of sensitized guinea pig tracheal segments (IC50 = 2.9 microM). In guinea pigs treated with 27 (1 mg/kg i.p.) 2 h before antigen provocation, there was a marked inhibition (47%) of the antigen-induced airway eosinophilia. After topical application of 1 microgram/ear 27 inhibits the arachidonic acid induced mouse ear edema (41%).

New 5-aminoacyl-5,10-dihydro-11H-dibenzo[b,e][1,4]diazepin-11-ones with antiarrhythmic activity

A series of new 5-substituted tricyclic 5,10-dihydro-11H-dibenzo[b,e][1,4]-diazepin-11-ones was identified as potential antiarrhythmic agents against bradyarrhythmias [1, 2]. The in vitro and in vivo interactions of the compounds with muscarinic receptors and the antiarrhythmic activity were examined. In receptor binding studies some derivatives showed a high affinity to the cardiac M2 receptor (Ki 10 nmol/l), an equal or smaller affinity to cortical M1 receptor and a lower affinity to the glandular M3 binding site. Functional experiments showed the derivatives as competitive antagonists with high affinity to the cardiac and smaller affinity to the intestinal muscarinic receptor. In vivo experiments correspond with the M2 selectivity. First the vagal or agonist-induced bradycardia was inhibited in rats and guinea pigs while the McNA-343 induced increase of blood pressure, methacholine-induced bronchi and bladder constriction as well as the salivation were inhibited only at higher doses. In conscious cats the tachycardia was examined in comparison with pupillomotoricity. The effect duration and the therapeutical range were determined in comparison to the M2 selective blocking agent AF-DX116. The antiarrhythmic activity was examined compared to quinidine sulfate in CaCl2-arrhythmia of rats, in atrial fibrillation and atrial flutter in dogs according to Scherf [2] and in electric induced atrial fibrillation under vagal stimulation in cats. In the atrial arrhythmias the derivatives are clearly longer effective than quinidine sulfate. The antiischemic activity was examined in the two-stages coronary ligature in dogs according to Harris. The long-running regularization of ectopies (about 2 h after i.v. injection) occurred without decrease of the heart rate, an effect particularly convenient to therapy of bradycardic dysrhythmias.