Relaxant effect and possible mechanism of 17-nor-subincanadine E in rabbit corpora cavernosa

Compounds with dual action on cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) may be a treatment option for erectile dysfunction, as they not only promote penile erection but also prevent the upregulation of phosphodiesterase-5. In this study, we examined the possible relaxant effect and mechanism of 17-nor-subincanadine E (SEC, 0.2–200 µmol l⁻¹), a plant-derived alkaloid, in rabbit corpus cavernosum (RbCC) strips that had been precontracted by exposure to phenylephrine (10 µmol l⁻¹) or a high concentration of K⁺ (60 mmol l⁻¹) in vitro. In addition to SEC''s effect on cAMP and cGMP levels, electrical field stimulation (EFS) in phenylephrine-precontracted RbCC and calcium chloride (1–100 mmol l⁻¹) evoked responses in depolarized RbCC were analysed. SEC relaxed the phenylephrine-precontracted RbCCs in a concentration-dependent manner. Atropine, guanethidine and N-ω-nitro-ℓ-arginine methyl ester (L-NAME) did not have any effect on the relaxation of RBCCs. When 1H-^{1, 2, 4}oxadiazole[4,3-a] quinoxalin-1-one (ODQ) was added, it effectively blocked the relaxant response of SEC. Although SEC enhanced the maximal relaxation produced by sodium nitroprusside (SNP) and forskolin in phenylephrine-precontracted cavernosal smooth muscle, it caused a decrease in the maximal contractile response induced by calcium chloride in depolarized RbCCs. The relaxant effect of SEC was paralleled by an increase in the tissue levels of the cyclic nucleotides cAMP and cGMP. We conclude that SEC promotes the relaxation of RbCC, possibly favouring cAMP and cGMP accumulation and calcium blockade. This novel mechanism could be useful for patients who do not benefit from phosphodiesterase inhibitors and for those with endothelial and nitrergic dysfunction, such as patients with diabetes, hypertension and dyslipidaemias.     

Nicotine metabolic rate predicts successful smoking cessation with transdermal nicotine: A validation study

Transdermal nicotine is widely used for smoking cessation, but only ~ 20% of smokers quit successfully with this medication. Interindividual variability in nicotine metabolism rate may influence treatment response. This study sought to validate, and extend in a larger sample, our previous finding that the ratio of plasma nicotine metabolites 3′-hydroxycotinine (3-HC)/cotinine, a measure of nicotine metabolism rate, predicts response to nicotine patch. A sample of 568 smokers was enrolled in a study that provided counseling and 8-weeks of 21 mg nicotine patch. Pretreatment 3-HC/cotinine ratio was examined as a predictor of 7-day point prevalence abstinence, verified with breath carbon monoxide (CO), 8 weeks after the quit date. Controlling for sex, race, age, and nicotine dependence, smokers in the upper 3 quartiles of 3-HC/cotinine ratio (faster metabolizers) were ~ 50% less likely to be abstinent vs. smokers in the first quartile (slow metabolizers; 28% vs. 42%; OR = .54 [95% CI:.36-.82], p = .003). Among abstainers, plasma nicotine levels (assessed 1 week after treatment began) decreased linearly across the 3-HC/cotinine ratio (β = − 3.38, t[355] = − 3.09, p < .05). These data support the value of the 3-HC/cotinine ratio as a biomarker to predict success with transdermal nicotine for smoking cessation.     

中国成人硒需要量研究

目的 探讨使人体血浆硒蛋白P(SEPPI)达到饱和的硒摄入量,以评估硒需要量,为膳食硒参考摄入量DRIB的修订提供参考.方法 时98名低硒健康受试者(体重平均58kg)进行为期40w的双盲补硒实验.随机分为七组,补硒(以硒蛋氨酸形式)剂量分别为0、21、35、55、79、102和125 μg/d.定期检测血浆中谷胱甘肽...     

Rat brain CYP2B-enzymatic activation of chlorpyrifos to the oxon mediates cholinergic neurotoxicity

Chlorpyrifos is a commonly used insecticide that can be metabolically activated by CYP2B to the acetylcholinesterase inhibitor chlorpyrifos-oxon causing cholinergic overstimulation and neurotoxicity. Rat brain extracts can also activate chlorpyrifos in vitro, and the lack of circulating oxon in serum suggests that metabolic activation within the brain may be responsible for chlorpyrifos neurotoxicity. Rats received intracerebroventricular (ICV) injections of CYP2B mechanism-based inhibitors (MBI), once or repeatedly, followed by chlorpyrifos (62.5-250 mg/kg sc). Rats were assessed for neurochemical (acetylcholinesterase activity), physiological (temperature), and behavioral measures (e.g., gait, righting reflex, arousal, incline angles) at 4 hours 3 days after chlorpyrifos treatment. ICV CYP2B MBIs increased brain chlorpyrifos levels, decreased brain chlorpyrifos-oxon levels, and attenuated the reduction in brain acetylcholinesterase; there was no effect on serum chlorpyrifos levels or acetylcholinesterase activity reduction. Inhibition of brain chlorpyrifos metabolism by CYP2B MBIs blocked centrally mediated hypothermia but not peripherally mediated hyperthermia. A single ICV MBI treatment significantly attenuated chlorpyrifos neurotoxicity mediated behavioral outcomes at 1 day after chlorpyrifos treatment with a gradual worsening of behavioral scores through day 3, suggesting a recovery of brain CYP2B activity and an increase in local chlorpyrifos activation. Daily ICV MBI injections attenuated neurotoxicity across all test days consistent with prolonged inhibition of brain chlorpyrifos activation. Thus, rat brain CYP2B contributes significantly to chlorpyrifos's neurotoxic effects. Variable human brain CYP2B levels, influenced by genetics and environmental exposures, may contribute to interindividual differences in neurotoxicity. Therapeutic inhibition of brain CYP2B could also be explored as a treatment for exposure to CYP2B-activated neurotoxins.     

Characterization and comparison of nicotine and cotinine metabolism in vitro and in vivo in DBA/2 and C57BL/6 mice

DBA/2 and C57BL/6 are two commonly used mouse strains that differ in response to nicotine. Previous studies have shown that the nicotine-metabolizing enzyme CYP2A5 differs in coumarin metabolism between these two strains, suggesting differences in nicotine metabolism. Nicotine was metabolized to cotinine in vitro by two enzymatic sites. The high-affinity sites exhibited similar parameters (Km, 10.7 +/- 4.8 versus 11.4 +/- 3.6 microM; Vmax, 0.58 +/- 0.18 versus 0.50 +/- 0.07 nmol/min/mg for DBA/2 and C57BL/6, respectively). In vivo, the elimination half-lives of nicotine (1 mg/kg, s.c.) were also similar between DBA/2 and C57BL/6 mice (8.6 +/- 0.4 versus 9.2 +/- 1.6 min, respectively); however, cotinine levels were much higher in DBA/2 mice. The production and identity of the putative cotinine metabolite 3'-hydroxycotinine in mice was confirmed by liquid chromatography/mass spectrometry/mass spectrometry. The in vivo half-life of cotinine (1 mg/kg, s.c.) was significantly longer in the DBA/2 mice compared with the C57BL/6 mice (50.2 +/- 4.7 versus 37.5 +/- 9.6 min, respectively, p < 0.05). The in vitro metabolism of cotinine to 3'-hydroxycotinine was also less efficient in DBA/2 than C57BL/6 mice (Km, 51.0 +/- 15.6 versus 9.5 +/- 2.1 microM, p < 0.05; Vmax, 0.10 +/- 0.01 versus 0.04 +/- 0.01 nmol/min/mg, p < 0.05, respectively). Inhibitory antibody studies demonstrated that the metabolism of both nicotine and cotinine was mediated by CYP2A5. Genetic differences in Cyp2a5 potentially contributed to similar nicotine but different cotinine metabolism, which may confound the interpretation of nicotine pharmacological studies and studies using cotinine as a biomarker.     

纳米羟基磷灰石/硫酸庆大霉素缓释系统的制备及体内释放实验

目的:制备纳米羟基磷灰石/硫酸庆大霉素缓释系统(drug delivery system,DDS),观察其体内释药特性,为慢性骨髓炎的治疗寻找更好的方法。方法:实验于2004-05/2005-03在南方医科大学珠江医院中心实验室和华南理工大学生物工程与材料学院实验室完成。实验材料:纳米羟基磷灰石(nano-hydroxypatite,nano-HA)、聚羟基丁酸酯-羟基戊酸酯共聚物[poly(3-hydroxybutyrate-hydroxyvalerate),PHBV]、聚乙二醇(polyethylene glycol,PEG)、硫酸庆大霉素(gentamicin,GM)。新西兰大白兔24只。实验方法:①nano-HA/PHBV-PEG-GM-DDS的制备:以nano-HA为载药核心,外包裹生物相容性好且降解可调控的PHBV、PEG,承载GM制成。②采用SPSS10.0统计软件包绘制庆大霉素浓度与抑菌环直径的半对数标准曲线。③体内释放实验:在新西兰大白兔左股骨外上髁钻孔,刮除部分骨质和骨髓,将nano-HA-PHBV/PEG-GM微球自骨窗内植入,分别于术后1,3,5,7,10,14,21,28d8个时间点各选3只大白兔,麻醉后取干骺端松质骨及骨干皮质骨标本。用标准曲线计算出各标本药物浓度,用SPSS10.0统计软件包绘制nano-HA/PHBV-PEG-GM-DDS的释药浓度与时间关系曲线。实验评估:①扫描电镜下观察nano-HA/PHBV-PEG-GM-DDS的微球形态。②nano-HA/PHBV-PEG-GM-DDS的释药浓度与时间的关系。结果:纳入兔24只,均进入结果分析。①nano-HA/PHBV-PEG-GM-DDS微球形态:大小均匀规整,微球平均粒径为345μm,小微球粒径为78μm,微球表面形态一致,为多孔皱缩结构。②nano-HA/PHBV-PEG-GM-DDS释药浓度与时间的关系:术后第1天nano-HA/PHBV-PEG-GM-DDS周围皮质骨和松质骨中庆大霉素质量浓度分别为(110.10±11.70),(97.30±9.60)mg/L,其后逐渐下降,至术后第28天时皮质骨和松质骨中庆大霉素质量浓度仍可分别达(7.30±1.40),(6.80±1.10)mg/L,局部骨组织中庆大霉素质量浓度仍在金黄色葡萄球菌最小抑菌浓度(2mg/L)以上。结论:nano-HA/PHBV-PEG-GM-DDS具有较好的体内缓释作用。