Simulations of biomolecule unbinding from protein using DL_POLY

This paper briefly reviews the ideas leading to ligand–receptor interaction being a central topic of research in the biological sciences, especially in pharmacology. The simulation methods for studying ligand–receptor interaction dynamically through ligand unbinding are reviewed, together with the analysis methods devised to examine the unbinding trajectory. Examples of applying DL_POLY in these simulations are given; they include retinol unbinding from the retinol-binding protein, and of serotonin and granisetron unbinding from the 5-HT₃ receptor.     

Direct plasma liquid chromatographic-tandem mass spectrometric analysis of granisetron and its 7-hydroxy metabolite utilizing internal surface reversed-phase guard columns and automated column switching devices

An alternative on-line automated sample enrichment technique useful for the direct determination of various drugs and their metabolites in plasma is described for rapid development of highly sensitive and selective liquid chromatographic methods using mass spectrometric detection. The method involves direct injection of plasma onto an internal surface reversed-phase (ISRP) guard column, washing the proteins from the column to waste with aqueous acetonitrile, and backflushing the analytes onto a reversed-phase octyl silica column using switching valves. The analytes were detected using a tandem mass spectrometer operated in selected reaction monitoring (SRM) mode using atmospheric pressure chemical ionization (APCI). Use of two ISRP guard columns in parallel configuration allowed alternate injections of plasma samples on these columns for sample enrichment and shortened the column equilibration and LCMSMS analysis times, thereby increasing the sample throughput. The total run time, including both sample enrichment and chromatography, was about 6 min. Using this technique, an analytical method was developed for the quantitation of granisetron and its active 7-hydroxy metabolite in dog plasma. Granisetron is a selective 5-HT3 receptor antagonist used in the prevention and treatment of cytostatic induced nausea and vomiting. Recovery of the analytes was quantitative and the method displayed excellent linearity over the concentration ranges tested. Results from a three day validation study for both compounds demonstrated excellent precision (1.3–8.7%) and accuracy (93–105%) across the calibration range of 0.1 to 50 ng/ml using an 80 μl plasma sample. The automated method described here was simple, reliable and economical. This on-line approach using ISRP columns and column switching with LCMSMS is applicable for the quantification of other pharmaceuticals in pharmacokinetics studies in animals and humans which require high sensitivity.     

格拉司琼联合隔药灸治疗肝癌介入术后恶心呕吐临床观察

目的:观察格拉司琼联合隔药灸治疗肝癌介入术后恶心呕吐临床疗效。方法:将符合纳入标准的肝癌介入术后恶心呕吐患者72例,分为治疗组与对照组,每组36例,对照组给予注射用盐酸格拉司琼静脉滴注治疗,治疗组在对照组的基础上给予隔药灸治疗。观察两组患者恶心、呕吐症状、胃液引流量及胃管留置时间,统计临床疗效。结果:治疗后治疗组在恶心、呕吐症状评分、胃液引流量、胃管留置时间方面明显均低于对照组(均P0.05)。治疗组、对照组临床疗效总有效率分别为91.67%、72.22%,比较有统计学意义(P0.05)。结论:格拉司琼联合隔药灸可以明显改善肝癌介入术后恶心呕吐症状,缩短胃管留置时间,临床疗效显著。     

Granisetron protects polymicrobial sepsis-induced acute lung injury in mice

Sepsis is a serious condition with a high mortality rate worldwide. Granisetron is an anti-nausea drug for patients undergoing chemotherapy. Here we aimed to identify the novel effect of granisetron on sepsis-induced acute lung injury (ALI). Our results showed that mice treated with granisetron displayed less severe lung damage than controls. Granisetron administration reduced pulmonary neutrophil recruitment after CLP. Moreover, the expressions of Cxcl1 and Cxcl2 were diminished in the presence of granisetron in THP-1 macrophages after lipopolysaccharide exposure. Additionally, granisetron could inhibit the activation of p38 MAPK and NLRP3 inflammasome both in vivo and in vitro. Collectively, granisetron protects against sepsis-induced ALI by suppressing macrophage Cxcl1/Cxcl2 expression and neutrophil recruitment in the lung.     

Allosteric Interactions Among Agonists and Antagonists at 5-Hydroxytryptamine3 Receptors

Abstract: Cooperation in the action of agonists suggests that there are multiple binding sites on 5-hydroxytryptamine₃ (5-HT₃) receptors. The purpose of this study was to characterize these binding sites and their interactions on both native and cloned 5-HT₃ receptors. The affinities of competitive 5-HT₃ receptor antagonists were similar regardless of whether the receptors were labeled with [³H]RS-42358, [³H]granisetron, or 1-( m -[³H]chlorophenyl)biguanide ([³H]mCPG). By contrast, the affinities of the agonists 5-HT, mCPG, and phenylbiguanide were approximately 10-fold higher when the receptors were labeled with [³H]mCPG. The dissociation of [³H]mCPG, [³H]RS-42358, and [³H]RS-25259, but not [³H]granisetron, from both cloned and native 5-HT₃ receptors was markedly slower in the presence of 5-HT or 2-methyl-5-HT than in the presence of antagonists such as RS-42358. This suggests that the binding of these agonists to unoccupied sites on the receptor can increase the receptor's affinity for prebound ligands and thereby slow their dissociation. These data support previous indications of positive cooperation among multiple binding sites on both native and cloned 5-HT₃ receptors, and they extend this idea by demonstrating that agonists can modify the interaction of some, but not all, antagonists with the receptor.     

Simultaneous measurement of blood and brain microdialysates of granisetron in rat by high-performance liquid chromatography with fluorescence detection

Simultaneous microdialysis probes in the blood and brain and sensitive high-performance liquid chromatography with fluorescence detection were used to examine the granisetron concentration in the jugular vein and frontal cortex of rats after drug administration. Two microdialysis probes were inserted into the right jugular vein and frontal cortex of male Sprague–Dawley rats to which granisetron (6 mg/kg, i.v.) had been administered. Dialysates were automatically collected using a microfraction collector. Samples were eluted with a mobile phase containing 25 mM acetate buffer (pH 4.8)–acetonitrile (72:28, v/v). Excitation and emission wavelengths were set at 305 and 360 nm, respectively, on a scanning fluorescence detector. The limit of quantification for granisetron was 0.5 ng/ml. The in vitro recovery of granisetron was 29.7±1.2% (n=6) for the jugular vein microdialysis probe and 6.1±0.5% (n=6) for the frontal cortex microdialysis probe. The increasing brain/blood concentration ratio of granisetron suggests that granisetron penetrates the blood–brain barrier.     

Distinct Thermodynamic Parameters of Serotonin 5-HT3 Agonists and Antagonists to Displace [3H]Granisetron Binding

Abstract: Specific binding of [³H]granisetron was examined to serotonin 5-HT₃ receptors in synaptosomal membranes of rat cerebral cortex between 1 and 37°C. Displacing potencies were determined for 5-HT₃ antagonists (granisetron, ondansetron, tropisetron, and d -tubocurarine) and agonists (5-hydroxytryptamine, 2-methyl-5-hydroxytryptamine, phenylbiguanide, m -chlorophenylbiguanide, and SR 57227A). Displacing potencies of the agonists decreased with decreasing temperature. In contrast, displacing potencies of all antagonists increased with decreasing temperature, whereas those of tropisetron and d -tubocurarine passed a maximum. Scatchard analysis of [³H]granisetron binding resulted in K _D values lower than the IC₅₀ values of granisetron and a decreasing number of binding sites at higher temperatures. It can be reconciled with temperature-dependent agonist and antagonist states of 5-HT₃ receptors. A semiquantitative thermodynamic analysis was based on displacing potencies. The distinct patterns for the signs of entropy, enthalpy, and heat capacity changes on binding can be reconciled with ionic interactions for agonists and hydrophobic interactions for antagonists. The distinctive differences in these thermodynamic parameters exceed those for GABA_A and glycine receptor-ionophore complexes.