(+/-)-Domesticine, a novel and selective alpha1D-adrenoceptor antagonist in animal tissues and human alpha 1-adrenoceptors

Label-Free Dynamic Mass Redistribution Reveals Low-Density, Prosurvival α1B-Adrenergic Receptors in Human SW480 Colon Carcinoma Cells

Small molecules that target the adrenergic family of G protein-coupled receptors (GPCRs) show promising therapeutic efficacy for the treatment of various cancers. In this study, we report that human colon cancer cell line SW480 expresses low-density functional α_1B-adrenergic receptors (ARs) as revealed by label-free dynamic mass redistribution (DMR) signaling technology and confirmed by quantitative reverse-transcriptase polymerase chain reaction analysis. Remarkably, although endogenous α_1B-ARs are not detectable via either [³H]-prazosin-binding analysis or phosphoinositol hydrolysis assays, their activation leads to robust DMR and enhanced cell viability. We provide pharmacological evidence that stimulation of α_1B-ARs enhances SW480 cell viability without affecting proliferation, whereas stimulating β-ARs diminishes both viability and proliferation of SW480 cells. Our study illustrates the power of label-free DMR technology for identifying and characterizing low-density GPCRs in cells and suggests that drugs targeting both α_1B- and β-ARs may represent valuable small-molecule therapeutics for the treatment of colon cancer.

Rapid determination of isocorydine in rat plasma and tissues using liquid chromatography--tandem mass spectrometry and its applications to pharmacokinetics and tissue distribution

A rapid and sensitive method for the determination of isocorydine in rat plasma and tissues was developed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biological samples were processed by extracting with diethyl ether-dichloromethane (3:2, v/v) and tetrahydropulmatine was used as the internal standard (IS). Detection of the analytes was achieved using positive ion mode electrospray ionization in the multiple reaction monitoring mode. The MS/MS ion transitions monitored were m/z 342.0→279.0 and 356.0→191.9 for isocorydine and IS, respectively. The maximum plasma concentration (C(max) 2496.8 ± 374.4 µg/L) was achieved at 0.278 ± 0.113 h (T(max)) and the half-life (t(1/2)) of isocorydine was 0.906 ± 0.222 h after a 20 mg/kg oral administration. As for a 2 mg/kg intravenous (i.v.) administration, the C(max) and clearance (CL) were 1843.3 ± 338.3 µg/L and 2.381 ± 0.356 L/h/kg, respectively. Based on the AUC(0-∞) obtained from oral and i.v. administration, the absolute bioavailability (F) was estimated as 33.4%. Tissue distribution results indicated that isocorydine underwent a rapid and wide distribution into tissues and it could effectively cross the blood-brain barrier.

New aporphinoid 5-HT2A and α1A antagonists via structural manipulations of nantenine

A series of C1, C2, C3 and N6 analogs of nantenine (2) was synthesized and evaluated in 5-HT(2A) and α(1A) receptor functional assays. Alkyl substitution of the C1 and N6 methyl groups of nantenine provided selective 5-HT(2A) and α(1A) antagonists, respectively. The C2 alkyloxy analogs studied were generally selective for α(1A) versus 5-HT(2A). The C3 bromo analog 15 is one of the most potent aporphinoid 5-HT(2A) antagonists known presently.

Biphasic tracheal relaxation induced by higenamine and nantenine from Nandina domestica Thunberg

We compared the effects of the extract from fruits of Nandina domestica Thunberg (NDE) and its constituents, higenamine and nantenine, on contractile responses in isolated guinea-pig trachea. NDE (1 mg/ml) caused biphasic relaxation of the trachea precontracted with high-K(+) stimulation: the fast component was blocked by propranolol and mimicked by higenamine; and the slow was resistant to propranolol and mimicked by nantenine. Ca(2+)-induced contraction under high-K(+) stimulation was antagonized by nantenine or NDE + propranolol. These results suggest that NDE relaxes the trachea quickly through β-adrenoceptor stimulation by higenamine and slowly through Ca(2+) antagonism by nantenine.

Monoaminergic, Ion Channel and Enzyme Inhibitory Activities of Natural Aporphines, their Analogues and Derivatives

The aporphine alkaloids constitute the second-largest group of isoquinoline alkaloids. Nevertheless, only a relatively small number of natural aporphines and their derivatives have been studied from a pharmacological viewpoint. Here we review the pharmacological data available for these compounds as related to their dopaminergic, noradrenergic and serotonergic activities, and also some results pertaining to their effects on ion channels and enzymes.

(+)-Cyclazosin, a selective α1B-adrenoceptor antagonist: Functional evaluation in rat and rabbit tissues

To shed light on the discrepancy between reported binding and functional affinity and selectivity at alpha(1b/B)-adrenoceptors, the antagonist (+)-cyclazosin was reinvestigated in rat and rabbit tissues. It displayed a competitive antagonism at alpha(1A) and alpha(1D)-adrenoceptors of rat prostatic vas deferens and aorta with pA(2) values 7.75 and 7.27, respectively. In rabbit thoracic aorta (+)-cyclazosin competitively antagonized noradrenaline-induced contractions at alpha(1B)-adrenoceptors with a pA(2) value of 8.85, whereas its affinity at alpha(1L)-adrenoceptors was markedly lower (pA(2) = 6.75-7.09). In conclusion, these data confirmed that (+)-cyclazosin is a selective alpha(1B)-adrenoceptor antagonist also in functional assays, showing 13- and 38-fold selectivity for the alpha(1B)-adrenoceptor over alpha(1A)- and alpha(1D)-subtypes, respectively. Furthermore, (+)-cyclazosin displayed a significant selectivity for alpha(1B)-adrenoceptors relative to the alpha(1L)-subtype.

Pharmacophore identification of α1A-adrenoceptor antagonists

A chemical feature based pharmacophore model was developed for alpha(1A)-adrenoceptor antagonists by HypoGen module implemented in catalyst software package. The best scoring pharmacophore hypothesis, Hypo1, consisted of four important chemical features (one positive ion, one hydrogen-bond donor, one aromatic ring, and one hydrophobic group). The results of our study provide a valuable tool in designing new leads with desired biological activity by virtual screening.