In vitro modulatory effects of flavonoids on human cytochrome P450 2C8 (CYP2C8)

The inhibitory effects of five flavonoids with distinct chemical classes (flavones [luteolin], flavonols [quercetin and quercitrin], and flavanones [hesperetin and hespiridin]) on cDNA-expressed CYP2C8 were investigated. CYP2C8 was co-expressed with NADPH-cytochrome P450 reductase in Escherichia coli and used to characterise potency and mechanism of these flavonoids on the isoform. Tolbutamide 4-methylhydroxylase, a high-performance liquid chromatography-based assay, was selected as marker activity for CYP2C8. Our results indicated that the flavonoids inhibited CYP2C8 with different potency. The order of inhibitory activities was quercetin > luteolin > hesperetin > hesperidin > quercitrin. All of these compounds however exhibited mechanism-based inhibition. A number of structural factors were found to be important for inhibition; these include the molecular shape (volume to surface ratio), the number of hydroxyl groups as well as glycosylation of the hydroxyl group. Quercetin was the most potent inhibitor among the flavonoids examined in this study, and our data suggest that it should be examined for potential pharmacokinetic drug interactions pertaining to CYP2C8 substrates in vivo.     

The effects of a new human leukocyte elastase inhibitor (recombinant guamerin) on cerulein-induced pancreatitis in rats

BACKGROUND: Pancreatic and neutrophil elastase can aggravate or induce acute pancreatitis. Although increased elastase levels in the plasma of pancreatitis patients and animal models have been reported, the mechanism by which elastase is involved in the pathogenesis of acute pancreatitis has not yet been elucidated. We aimed to investigate the effects and the possible mechanism of a new human leukocyte elastase inhibitor (recombinant guamerin) in the treatment of cerulein-induced acute pancreatitis in rats. METHODS: Fifty Sprague-Dawley rats were divided into three groups: a saline-infused control group (I), a cerulein-induced acute pancreatitis group (II), and a cerulein plus guamerin infusion group (III). Guamerin (1-2 micromol/kg/h) was infused continuously in group III. The severity of pancreatitis was determined biochemically, histologically, and by cytokine changes between groups I, II and III. RESULTS: Significant differences in serum amylase, lipase, and pancreatic wet weight were observed in each group, respectively (group I; 2346.2 IU/L, 9.9 IU/L, 1.4+/-0.3 g, group II; 13,596.8 IU/L, 7439.4 IU/L, 2.2+/-0.5 g, group III; 9443.2 IU/L, 4516.3 IU/L, 1.7+/-0.6 g). Serum IL-6 and TNF-alpha [AU1]level peaked 1-4 h and 1-2 h. After the induction of pancreatitis, IL-6 and TNF-alpha levels were decreased in group III than group II, (group I; 13.1/4.0 pg/mL, group II; 198.5/63.2 pg/mL, group III; 102.1/13.1 pg/mL), but no significant difference in IL-1beta was observed. Histologic gradings and severity, such as vacuolization, inflammation, lobular disarray, and edema of the pancreas, were significantly lower in the cerulein plus guamerin infusion group III. CONCLUSIONS: Recombinant guamerin, a new human leukocyte elastase inhibitor, may decrease the severity of pancreatitis and diminish pancreatic acinar cell injury by inhibition of neutrophilic infiltration and cytokine activation in the initial stage of cerulein-induced acute pancreatitis in rats.     

In vitro effects of nonsteroidal anti-inflammatory drugs on oxidative phosphorylation in rats liver mitochondria.

Representative potent anti-inflammatory drugs have been studied for their ability to affect energy metabolism in vitro in rat liver mitochondria. Like 2,4-dinitrophenol, flufenamic acid activated ATPase, inhibited the incorporation of ³²Pi into the ATP fraction, stimulated glutamate oxidation and coupled substrate-level phosphorylation, and promoted state-4 respiration. Aspirin and ibuprofen caused similar but lesser effects on these parameters. These three drugs are considered to be uncouplers of oxidative phosphorylation. Indomethacin and phenylbutazone inhibited both oxidative and substrate-level phosphorylations. Based on their abilities to inhibit glutamate oxidation rather directly and to block the electron transport chain, it was concluded that indomethacin and phenylbutazone could inhibit the generation of energy-rich phosphate compounds by suppressing respiration at multiple sites. Thus, these anti-inflammatory drugs could prevent mitochondrial energy metabolism in different manners.     

The effects of heparin and related molecules upon the adhesion of human polymorphonuclear leucocytes to vascular endothelium in vitro

1. The effects of an unfractionated heparin preparation (Multiparin), a low molecular weight heparin preparation (Fragmin) and a selectively O-desulphated derivative of heparin lacking anticoagulant activity, have been investigated for their effects on the adhesion of human polymorphonuclear leucocytes (PMNs) to cultured human umbilical vein endothelial cells (HUVECs) in vitro. The effect of poly-L-glutamic acid, a large, polyanionic molecule was also studied. 2. Unfractionated heparin (50-1000 U ml-1), the O-desulphated derivative (0.3-6 mg ml-1) and the low molecular weight heparin (50 U-1000 U ml-1) all inhibited significantly the adhesion of 51Cr labelled PMNs to HUVECs stimulated with interleukin-1 beta (IL-1 beta; 10 U ml-1), bacterial lipopolysaccharide (LPS; 2.5 micrograms ml-1) or tumour necrosis factor-alpha (TNF-alpha; 125 U ml-1) for 6 h, whereas poly-L-glutamic acid had no effect. In addition, the three heparin preparations in the same concentration range inhibited significantly the adhesion of f-met-leu-phe-stimulated PMNs to resting HUVECs. 3. The effects of unfractionated heparin upon the expression of adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and E-selection were also investigated, as were the effects of unfractionated heparin upon adhesion of human PMNs to previously stimulated HUVECs. Heparin had little effect upon levels of expression of these adhesion molecules on stimulated HUVECs. However, a profound effect upon PMN adhesion to previously stimulated HUVECs was demonstrated using the same preparation, suggesting that inhibition of adhesion molecule expression is not a major component of the described inhibitory effects of heparin. 4. Pre-incubation of PMNs with heparin followed by washing inhibited their adhesion to HUVECs, under different conditions of cellular activation, implying that heparin can bind to these cells and exert its anti-adhesive effects even when not directly present in the system. 5. These observations would suggest that both heparin and a low molecular weight heparin are capable of inhibiting adhesion of human PMNs to endothelial cells, an effect not dependent solely upon the polyanionic nature of these molecules, nor dependent upon their ability to act as anticoagulants.     

The in vitro vascular effects of two chirodropid (Chironex fleckeri and Chiropsella bronzie) venoms

Clinical observations suggest a primary cardiotoxic role in fatal Chironex fleckeri stings. The limited research available indicates that Chiropsella bronzie venom acts in a similar manner although appears to be less potent. The aim of the present study was to elucidate the vascular effects of C. fleckeri and C. bronzie venoms using rat isolated aorta. Both venoms produced a sustained contraction of endothelium-denuded aorta which was not significantly affected by prazosin or box jellyfish antivenom. Felodipine significantly reduced the contractile response to C. fleckeri venom but not C. bronzie venom. Both venoms produced an initial relaxation (Phase 1), followed by a sustained contraction (Phase 2), in pre-contracted endothelium-intact aorta. Removal of the endothelium significantly inhibited both phases of the response. NOLA significantly inhibited Phase 1, but not Phase 2, of the response to both venoms. Atropine, HOE 140 or BQ 123 did not have any significant inhibitory effect on either phase. In conclusion, neither C. fleckeri nor C. bronzie venoms appear to contain components with activity at alpha(1)-adrenoceptors. Antivenom was ineffective in reversing the effects of the venom suggesting it is incapable of completely neutralising nematocyst-derived venom. Determining the mechanism of action of these venoms will allow for the development of better treatment strategies.     

(-)-1-(Benzofuran-2-yl)-2-propylaminopentane enhances locomotor activity in rats due to its ability to induce dopamine release

"Catecholaminergic and serotoninergic activity enhancer" effects are newly found mechanisms of action of a class of compound that enhance impulse propagation-mediated release of catecholamines and serotonin in the brain. In the present study, (-)-1-(benzofuran-2-yl)-2-propylaminopentane hydrochloride [(-)-BPAP HCl], a compound with selective and potent "catecholaminergic and serotoninergic activity enhancer" effects, was tested for its efficacy to potentiate locomotor activity in normal rats and to attenuate hypolocomotion in reserpine-treated rats. (-)-BPAP HCl potentiated locomotor activity in non-habituated rats during a 2-h observation period dose-dependently (0.3-10 mg/kg). (-)-BPAP HCl (1-3 mg/kg) was also effective to reverse reserpine-induced hypolocomotion. The effects of (-)-BPAP HCl in normal and reserpine-treated rats were attenuated by the dopamine D1 receptor antagonist, R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH 23390), suggesting that the effects of (-)-BPAP HCl were mediated by activation of the dopaminergic system. In addition, the administration of (-)-BPAP HCl increased ipsilateral turning in unilaterally 6-hydroxydopamine-lesioned rats, implying presynaptic activation of nigrostriatal dopaminergic terminals by (-)-BPAP HCl. Furthermore, although antiparkinsonian agents, such as apomorphine and amantadine, failed to improve reserpine-induced ptosis, (-)-BPAP HCl significantly improved ptosis. These findings suggested that a "catecholaminergic and serotoninergic activity enhancer" compound, (-)-BPAP, stimulates motor function in rats and improves motor deficits in animal models of Parkinson's disease due to its ability to induce dopamine release.     

(2R,3S)-Pinobanksin-3-cinnamate improves cognition and reduces oxidative stress in rats with vascular dementia

Journal of Natural Medicines - This study investigated the neuroprotective effects of (2R,3S)-pinobanksin-3-cinnamate (PNC) in rats with occlusion-damaged bilateral common carotid arteries....     

茶多酚对人肝癌BEL- 7404细胞端粒酶的抑制作用及诱导细胞凋亡的能力(英文)

目的　探讨茶多酚诱导肝癌BEL 740 4细胞凋亡作用和在体外对端粒酶活性的影响。方法　MTT法和活细胞计数法测定茶多酚对人肝癌细胞的生长抑制作用 ,PCR ELISA试剂盒测定细胞的端粒酶活性。细胞形态学变化和DNA凝胶电泳观察细胞凋亡现象。结果　茶多酚体外对肝癌BEL 740 4细胞有明显的抑制作用 ,且这种抑制作用呈浓度和时间依赖性。采用浓度为 0 2和 0 1g·L- 1 的茶多酚作用 48h后的细胞出现DNA梯度条带和典型的凋亡形态学变化如核固缩、胞膜皱缩、胞核碎裂 ,凋亡小体形成等。茶多酚作用后 ,肝癌BEL 740 4细胞中端粒酶活性明显下降。结论　茶多酚在一定浓度下能诱导肝癌BEL 740 4细胞凋亡 ,其抗癌机制与抑制端粒酶活性有关。     

Effects of the cleavage peptides,C3a and C3ai,from the third component of hog complement on leukocyte accumulation and vascular permeability in vivo

Summary In vivo anti-platelet de-aggregatory activity of exogenous prostacyclin is enhanced after its passage through the pulmonary circulation of anaesthetized cats, probably because of a concomitant generation of endogenous prostacyclin by the lungs. Evidence is also presented that perfused lungs of guinea pigs and rats spontaneously release considerable amounts of prostacyclin. It is therefore postulated that a continuous biosynthesis of prostacyclin by pulmonary endothelium is a general physiological phenomenon, while the generation of thromboxane A₂ by lungs occurs in response to pathological stimuli. Coronary and cerebral arteries are supposed to benefit from this hormonal function of the lungs.     

The effect of ketoconazole on the jejunal permeability and CYP3A metabolism of (R/S)-verapamil in humans

AIMS: The purpose of this human intestinal perfusion study was to investigate the effect of ketoconazole on the jejunal permeability and first-pass metabolism of (R)- and (S)-verapamil in humans. METHODS: A regional single-pass perfusion of the jejunum was performed using a Loc-I-Gut(R) perfusion tube in six healthy volunteers. Each perfusion lasted for 200 min and was divided into two periods of 100 min each. The inlet concentration of (R/S)-verapamil was 120 mg l-1 in both periods, and ketoconazole was added at 40 mg l-1 in period 2. (R/S)-verapamil was also administered as a short intravenous infusion of 5 mg, over a period of 10 min. The appearance ratios of the CYP3A formed metabolites (R)- and (S)-norverapamil were also estimated in the outlet jejunal perfusate. RESULTS: The effective jejunal permeability (Peff) of both (R)- and (S)-verapamil was unaffected by the addition of ketoconazole in period 2 suggesting that ketoconazole had no effect on the P-glycoprotein mediated efflux. However, the appearance ratio of both (R)- and (S)-norverapamil in the outlet jejunal perfusate decreased in the presence of ketoconazole. The rate of absorption into plasma of (R)- and (S)-verapamil increased despite the low dose of ketoconazole added, indicating an inhibition of the gut wall metabolism of (R/S)-verapamil by ketoconazole. CONCLUSIONS: Ketoconazole did not affect the jejunal Peff of (R/S)-verapamil, but it did increase the overall transport into the systemic circulation (bioavailability), probably by inhibition of the gut wall metabolism of verapamil. This might be due to ketoconazole being less potent as an inhibitor of P-glycoprotein than of CYP3A4 in vivo in humans.     

Release of human monocytes protein C and the cofactor protein S in vitro

Monocytes may contribute to a coagulation process by expression of the tissue factor and by synthesizing factors V, VII, X and XIII. Cultured blood monocytes also express both the tissue plasminogen activator and the plasminogen activator inhibitor I. The present study assesses the ability of human monocytes to secrete protein C and its cofactor protein S, which are potent inhibitors of the clotting cascade. Monocytes derived from the blood of healthy volunteers and prepared according to Boyum were cultured for up to 36 hours with or without lipopolisaccharide from Escherichia coli. After different times of incubation, the concentrations of proteins C and S in the supernatants were measured in order to determine synthesis of proteins, monocytes were cultured in the presence or absence of cycloheximide, the protein synthesis inhibitor. The concentration of protein C was estimated by means of the ELISA Protein C test (Boehringer Mannheim). Protein S concentrations were measured by rocket immunoelectrophoresis according to Laurell, using monospecific antisera (American Diagnostica Inc., N.Y.). The study showed that human monocytes, when stimulated by lipopolisaccharide, release proteins C and S in vitro. The concentration of these proteins in the culture supernatants markedly increased with time during the 36-hour observation. The supernatants obtained from the culture of unstimulated monocytes did not contain detectable quantities of the investigated proteins. The exposure of the cells to cycloheximide did not suppress the release of proteins C and S. In conclusion, our results suggest that monocytes are not able to synthesize proteins C and S. They can only release these factors. Furthermore, monocytes may be responsible for coagulation due to the inactivation of factors Va and VIIIa by protein C.     

The disposition of a histidine decarboxylase inhibitor (S)-alpha-fluoromethylhistidine in rats

An amino acid analyser method using ninhydrin was developed for (S)-alpha-fluoromethylhistidine (FMH) with a minimum quantitation limit of 0.2 microgram mL-1. The assay was used to study the kinetics of FMH in rat. After bolus intravenous administration of FMH hydrochloride hemihydrate (50 mg kg-1), plasma concentration decreased biexponentially with half-lives of 4.4 and 32.7 min. The distribution volumes of the central and peripheral compartments were 127.4 and 166.3 mL kg-1, respectively. The tissue concentration of FMH was highest in the kidney and also decreased biphasically. The FMH concentrations in other tissues were lower, but their tissue/plasma ratios of FMH increased continuously after FMH injection, indicating that FMH partitioned into these tissues and was lost from them very slowly.     

The effects of eicosapentaenoic acid ethyl ester (EPA-E) on arterial thrombosis in rabbits and vascular lesions in rats

The effects of highly purified ethyl ester of eicosapentaenoic acid (EPA-E) on ellagic acid-induced thrombus formation in the stenosed femoral artery in rabbits and on the progression of laurate-induced vascular lesions in rats were examined. (1) EPA-E in single administration significantly prevented the thrombus formation induced by ellagic acid in the stenosed femoral artery of rabbits. (2) EPA-E restored the hypercoagulation activity at 5 min and 3 hr after the ellagic acid injection. Platelet aggregability induced by arachidonic acid decreased at 5 min and 3 hr after the ellagic acid injection; EPA-E had little effect on this change. EPA-E showed almost no effect on fibrinolytic activity, blood viscosity and filterability of washed red blood cells after the ellagic acid injection. (3) Moreover, EPA-E in daily administrations showed a significant preventative effect against the laurate-induced vascular lesions in rats. The efficacy of EPA-E on arterial thrombosis and vascular lesions observed in this study suggests that EPA-E is a candidate for the treatment of peripheral circulatory disturbance.