A novel class of adenosine A3 receptor ligands. 2. Structure affinity profile of a series of isoquinoline and quinazoline compounds

1-Substituted 3-(2-pyridinyl)isoquinolines have been shown to form a novel class of adenosine A3 receptor ligands. In the present study further investigations of this new lead and the structure affinity relationships of this class of compounds are described. First, the influence of an amide group at position 1 of the isoquinoline ring on the adenosine A3 receptor affinity was determined. A carboxamide proved to be a useful spacer between the isoquinoline and a phenyl ring. N-[2-(2-pyridinyl)isoquinolin-4-yl]benzamide (VUF8507, compound 6) had an affinity of 200 nM at the adenosine A3 receptor. Second, we investigated the effects of substitution of the benzamide ring of 6 with a series of mono- and disubstituted N-[3-(2-pyridinyl)isoquinoline]benzamides. The ratio of the tautomers of the benzamides was determined in the solid state and in solution by spectroscopic techniques (IR and NMR). Affinities were determined in radioligand binding assays at rat brain A1 and A2A receptors and at cloned human A3 receptor. The benzamides showed higher adenosine A3 receptor affinity than aliphatic amides. We propose that the adenosine A3 receptor affinity of the different benzamides is related to their presence in either the iminol or amide form. Ligands present in the iminol form showed relatively high adenosine A3 receptor affinity. Finally, we explored the influence of replacement of C4 of the isoquinoline ring by a nitrogen atom. Comparison of isoquinolines with the corresponding quinazolines revealed that both compounds showed similar adenosine A3 receptor affinity. These investigations led to potent and selective human adenosine A3 receptor ligands with affinities in the nanomolar range. The subtype-selective compound 4-methoxy-N-[2-(2-pyridinyl)quinazolin-4-yl]benzamide (VUF8504, 13) with an affinity of 17.0 nM at the human adenosine A3 receptor might become a useful tool in the pharmacological characterization or the investigation of the physiological function of this receptor.

A novel class of adenosine A3 receptor ligands. 1. 3-(2-Pyridinyl)isoquinoline derivatives

A series of 3-(2-pyridinyl)isoquinoline derivatives was synthesized as potential antagonists for the human adenosine A3 receptor by substitution of the 1-position. The compounds were obtained by various synthetic routes from 1-amino-3-(2-pyridinyl)isoquinoline. The affinity was determined in radioligand binding assays for rat brain A1 and A2A receptors and for the cloned human A3 receptor. A structure-activity relationship analysis indicated that a phenyl group when coupled by a spacer allowing conjugation on position 1 of the isoquinoline ring increased the adenosine A3 receptor affinity. In contrast, such a phenyl group directly bound to position 1 of the isoquinoline ring decreased affinity. Since the combination of a phenyl group together with a spacer raised adenosine A3 receptor affinity, various spacers were investigated. VUF8501 (N-[3-(2-pyridinyl)isoquinolin-1-yl]benzamidine (15) showed an affinity at the human adenosine A3 receptor of 740 nM. Substituent effects on the phenyl group were investigated by in vitro evaluation of a series of substituted benzamidines. Electron-donating groups at the para position of the benzamidine ring increased adenosine A3 receptor affinity. These investigations led to VUF8505 (4-methoxy-N-[3-(2-pyridinyl)isoquinolin-1-yl]benzamidine(22)), which is a moderately potent and selective ligand for the human adenosine A3 receptor with an affinity of 310 nM in our test system having negligible affinity for rat A1 and A2A receptors.

A functional screening of adenosine analogues at the adenosine A2B receptor: a search for potent agonists

Various adenosine analogues were tested at the adenosine A2B receptor. Agonist potencies were determined by measuring the cyclic AMP production in Chinese Hamster Ovary cells expressing human A2B receptors. 5'-N-Substituted carboxamidoadenosines were most potent. 5'-N-Ethylcarboxamidoadenosine (NECA) was most active with an EC50 value of 3.1 microM. Other ribose modified derivatives displayed low to negligible activity. Potency was reduced by substitution on the exocyclic amino function (N6) of the purine ring system. The most active N6-substituted derivative N6-methyl-NECA was 5 fold less potent than NECA. C8- and most C2-substituted analogues were virtually inactive. 1-Deaza-analogues had a reduced potency, 3- and 7-deazaanalogues were not active.

Study of the interaction between aryloxypropanolamines and Asn386 in helix VII of the human 5-hydroxytryptamine1A receptor

We studied the stereoselective interaction between aryloxypropanolamines and the human 5-hydroxytryptamine1A (5-HT1A) receptor. R- and S-enantiomers of propranolol, penbutolol, and alprenolol were investigated for their ability to bind to human 5-HT1A wild-type and Asn386Val mutant receptors. Asn386 seemed to act as a chiral discriminator. Although both aryloxypropanol enantiomers displayed lower affinity for the mutant receptors, the affinities for the S-enantiomers were more affected. Receptor affinities of other structurally unrelated 5-HT1A ligands were not decreased by the mutation of Asn386 to valine. In addition, a series of analogues of propranolol with structural variation in the oxypropanolamine moiety was synthesized, and affinities for wild-type and Asn386Val mutant 5-HT1A receptors were determined. Both the hydroxyl and the ether oxygen atoms of the oxypropanol moiety seem to be required for binding at wild-type 5-HT1A receptors. The hydroxyl group of propranolol probably directly interacts with Asn386. The ether oxygen atom may be important for steric reasons but can also be involved in a direct interaction with Asn386. These findings are in agreement with the interactions of aryloxypropanolamines with Asn386 in rat 5-HT1A receptors that we previously proposed. The loss of affinity for propranolol by the Asn386Val mutation could be regained by replacement of the hydroxyl group of the ligand by a methoxy group. This modification of the propranolol structure has no effect on the affinity of both enantiomers for the wild-type 5-HT1A receptor, which provides an alternative hypothesis for the interaction of Asn386 with the oxypropanol oxygen atoms. According to this novel hypothesis, the oxypropanol oxygen atoms may both act as hydrogen bond acceptors from the NH2 group of Asn386.

Subtype-specific differences in the intracellular sorting of G protein-coupled receptors

We have examined the subcellular distribution of three subtypes of adrenergic receptor by immunocytochemical localization of wild-type and epitope-tagged proteins expressed in Cos-7 and K293 cells. Two subtypes (beta 2 and M alpha 2-10H) are localized in the plasma membrane at steady state in untreated cells, while another subtype (M alpha 2-4H) is found both in the plasma membrane and in a population of intracellular vesicles. Within 15 min following the addition of adrenergic agonists, beta 2 and M alpha 2-10H receptors are differentially sorted; beta 2 receptors are selectively internalized to intracellular vesicles, which are distinct from those containing M alpha 2-4H receptors, while M alpha 2-10H receptors remain in the plasma membrane. Subtype-specific sorting suggests a new class of functional properties that may differentiate the signaling and regulation of homologous G protein-coupled receptors.

Analysis of mono-, di- and triglycerides in pharmaceutical excipients by capillary supercritical fluid chromatography

Mono-, di- and triglycerides are important components of oils, fats and other natural products. Since in general fatty acids are mixtures and glycerol can be differently substituted, finger-prints of the composition are suitable for better characterization. Since capillary supercritical fluid chromatography (SFC) employing carbon dioxide as mobile phase is compatible with flame ionization detection, it is possible to analyse many solutes at trace levels. Supercritical carbon dioxide offers higher solute diffusivity compared with the inert carrier gas conventionally used in gas chromatography and has a lower viscosity than the liquid solvents used in HPLC. Thus, glycerides of fatty acids can be separated and eluted at a lower temperature and with shorter analysis time in SFC. In this study the analysis of mono-, di- and triglyceride mixtures in several pharmaceutical excipients is reported using capillary SFC. Quantitative analysis is possible on the basis of a response factor established for each analyte. The accuracy of the method and its advantages are demonstrated.

Cloning of two mouse genes encoding alpha 2-adrenergic receptor subtypes and identification of a single amino acid in the mouse alpha 2-C10 homolog responsible for an interspecies variation in antagonist binding

Molecular cloning and ligand binding studies have shown the alpha 2 class of adrenergic receptor (alpha 2-AR) to be a family of at least three related subtypes in humans. These studies have not, however, identified distinct subtype-specific functions for these receptors in vivo. It should be possible to extend the analysis of alpha 2-AR subtype function to the animal level through the use of experimental mammalian embryology in mice. To begin this process, we have isolated two mouse genomic clones encoding alpha 2-AR subtypes and expressed these genes in COS-7 cells for binding studies. Sequence homology and ligand binding data allow the assignment of one clone (M alpha 2-4H) as the mouse homolog of the human alpha 2-C4 subtype. The other clone (M alpha 2-10H) closely resembles the human alpha 2-C10 subtype in sequence but binds with significantly lower affinity to yohimbine and rauwolscine, members of a distinct class of bulky alpha 2-selective antagonists commonly used to evaluate alpha 2-AR function in vivo. To define the domain(s) responsible for this unusual binding property, we constructed a series of M alpha 2-10H/human alpha 2-C10 chimeric receptors. Analysis of these receptors identified a conservative Cys201 to Ser201 change in the fifth transmembrane domain of M alpha 2-10H as being responsible for the low affinity of the mouse receptor for yohimbine.

Histopathological studies on the local reactions induced by complete Freund's adjuvant (CFA), bacterial lipopolysaccharide (LPS), and synthetic lipopeptide (P3C) conjugates

The inflammatory reactions following subcutaneous application of adjuvants revealed characteristic pathological patterns. The injection of complete Freund's adjuvant (CFA) resulted in the formation of large lipid deposits encircled by an inflammatory reaction and concentrically arranged collagen bundles. Bacterial lipopolysaccharide (LPS) caused granulomatous aggregations of mononuclear cells with thrombotic vessel occlusions. Inoculation of the lipopeptide adjuvants induced accumulation of mononuclear cells with only minimal fibrotic changes which were resolved after day 28. Lipopeptide conjugates based on the head group tripalmitoyl-S-glyceryl-cysteinyl-serin (P3CS) can thus be used as effective immunogens and adjuvants without long-term tissue damage.

Spinal empyema in Crohn's disease

A 19-year-old man with a 1-year history of Crohn's disease of the ileum and rectosigmoid developed back and leg pain with neurological deficits. He proved to have an epidural and subdural spinal empyema originating from a rectal fistula. Drainage of the empyema, a diverting sigmoid colostomy, and appropriate antibiotics allowed full recovery of neurologic function and resolution of infection. We review the applicable literature.

Dispase, a neutral protease from Bacillus polymyxa, is a powerful fibronectinase and type IV collagenase

Dispase, a neutral protease isolated from culture filtrates of Bacillus polymyxa, has proven to be a rapid, effective, but gentle agent for separating intact epidermis from the dermis and intact epithelial sheets in culture from the substratum. In both cases it effects separation by cleaving the basement membrane zone region while preserving the viability of the epithelial cells. Because it is not known what or where in the basement membrane zone Dispase cleaves, we set up studies to define its substrate specificity. Using purified basement membrane components and sodium dodecyl sulfate-polyacrylamide gel electrophoresis we show that Dispase cleaves fibronectin and type IV collagen, but not laminin, type V collagen, serum albumin, or transferrin. The action of Dispase on collagen appears to be selective for type IV collagen in that several stable degradation products are formed, whereas the enzyme degrades type I collagen only minimally. In newborn human skin, as seen by electron microscopy, Dispase removes the lamina densa, rich in type IV collagen, but preserves the anchoring fibrils (structures known to contain type VII collagen) and the epidermal cells. Because its action is so selective, it suggests that Dispase can serve as a powerful tool for dissecting epithelial-mesenchymal interactions.

Mortality study of persons exposed to dioxin in a trichlorophenol-process accident that occurred in the BASF AG on November 17, 1953

Twenty-seven years after an accident which occurred in the BASF, Ludwigshafen plan in 1953, a mortality study of persons exposed to dioxin in an uncontrolled reaction during a trichlorophenol process was undertaken. The follow-up was 100% successful and involved 74 persons. Overall mortality (21 deaths) did not differ in this group from the rate expected in three external reference populations or from that observed in two internal comparison groups, where 18-20 deaths were observed. Of the 21 deceased persons, 7 had cancer, compared with 4.1 expected. In addition, two other cases of cancer (one bronchial carcinoma, and one carcinoma of the prostate) are still alive. Three deaths due to stomach cancer, at ages 64, 66, and 69 years, were found, compared with 0.6 expected from regional mortality data. One stomach cancer occurred among 148 individuals in the two comparison cohorts.

Histone phosphorylation in phorbol ester stimulated and beta-adrenergically stimulated mouse epidermis in vivo and characterization of an epidermal protein phosphorylation system

Under certain physiological conditions a change in the phosphorylation of histones in mouse epidermis in vivo was observed. Thus a single local application of the tumor-promoting mitogen 12-O-tetradecanoylphorbol-13-acetate caused a long-lasting increase of histone H1 phosphorylation which paralleled stimulated cell proliferation. Injection of the antimitotic beta-adrenergic agonist isoproterenol led to a temporary decrease in the rate of phosphorylation of H1, H2A and H2B immediately after cyclic AMP accumulation. A complete protein phosphorylation system could be demonstrated in mouse epidermis homogenates. The following enzyme activities were partially purified and characterized: a cyclic AMP-dependent histone kinase; a 'casein kinase' and an 'unspecific' protein kinase; a histone-specific protein phosphatase; and two 'unspecific' phosphoprotein phosphatases. In addition, a stimulatory effect of cyclic GMP on histone phosphorylation was observed. The enzymes were found to be predominantly localized in the 105000 X g supernatant, but a small proportion of protein kinase and phosphatase activity could be regularly demonstrated in cell nuclei.