摘要:

The skin and liver may be targets for cytotoxicity induced by oxidative drug metabolites. We used human epidermoid A431 cells and human hepatoblastoma Hep G2 cells as the experimental model. The aim of the study was to investigate and evaluate the effect of silymarin on acetaminophen (APAP)-induced toxicity under controlled conditions. Silymarin is known to be a potent antioxidant that diminishes toxicity induced by a variety of other hepatotoxins (e.g. Amanita phaloides, algae’s toxins, carbon tetrachloride). Glutathione (GSH) depletion was enhanced by adding to the medium buthionine sulfoximine [L-buthionine- (SR)-sulfoximine, BSO]. Cells were incubated with high-concentration 5-20 mM APAP or α-(minimum essential medium for 2-24 h to evaluate the drug’s ability to reduce cytoviability. Viability was then quantitated by metabolism of the tetrazolium dyes (MTT) and neutral red (NR). Cytoviability was 100% for controls. For Hep G2 treated for 24 h with 20 mM, APAP viability was 56.0% by MTT and 62.5% by NR. BSO-treated cells showed an enhanced cytotoxicity, determined by both assays. Administration of 0.5 mM silymarin reduced cytotoxicity significantly. In A431 cells, treatment with 20 mM APAP reduced viability by 57% (MTT) and 69% (NR) versus control (100%). BSO further decreased viability. Since incubation with silymarin showed significant protection against APAP toxicity, it can be considered a cytoprotective agent in this in vitro model of drug toxicity. GSH concentrations in both cell lines decrease significantly after exposure to 20 mM APAP, or 0.5 mM versus control (p < 0.05), and increased (p < 0.001) if incubated with APAP and silymarin. The protective effect could be through mitochondrial membrane stabilization and/or an increase in available GSH.

ISSN:1660-5527    

DOI:10.1159/000211359

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The three retinoic acid receptors (RARα, RARβ and RARγ) are known to modulate the transcription of target genes through interaction of the individual receptors with their naturally occurring ligand, retinoic acid (RA). Since RA has multiple effects in vivo, considerable effort has recently been devoted to finding selective compounds to elucidate the functions of individual receptors and to relate these functions to specific in vivo effects. The racemic synthetic retinoid 6-[(5,5,8,8-tetramethyl- 5,6,7,8-tetrahydro-2 – naphthyl)hydroxy-methyl]-2-naphthalene carboxylic acid has recently been identified as an RARγ-selective agonist. A synthetic method involving lipase-mediated transformation has been developed to prepare the individual enantiomers. Discrimination between the two enantiomers is seen in both transcriptional activity and binding to recombinant receptors with the (S)-enantiomer being the more active. Differences between the two compounds are also seen in the Rhino mouse utriculi reduction assay and the rabbit irritation model. In both animal models, the (S)-enantiomer consistently gave a greater response. Taken together, these results suggest that the activity and irritation seen with RA and related compounds is receptor mediated. Further, the strong selectivity of the compounds reported here for RARγ suggests that this receptor plays an important role in these in vivo biological activities. The discrimination between these enantiomers may be useful in the design of novel retinoids with uniquely defined biological properties.

ISSN:1660-5527    

DOI:10.1159/000211360

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Several novel inhibitors of human synovial fluid phospholipase A2 (HSF-PLA2) were evaluated in cellular models of inflammatory mediator release (murine macrophage and human neutrophil) and topical in vivo inflammatory skin models in mice to ascertain the scope of effects which might be observed for PLA2 inhibitors. Potent inhibition of HSF-PLA2 in vitro can be observed with compounds such as scalaradial and ellagic acid, which both have IC50 values of 0.02 μM (using autoclaved [3H]-arachi-donic-acid (AA)-labelled Escherichia coli membranes as substrate). Luffariellolide, a manoalide analog, and aristolochic acid are less potent (IC50 = 5 and 46 μM, respectively) in this assay. An interesting observation is that ellagic acid in cellular assays does not inhibit macrophage eicosanoid production and only 30% inhibition of PAF biosynthesis can be obtained at 50 μM in the human neutrophil. Possibly due to its irreversible mechanism of action, scalaradial retained its potent activity in both the macrophage (IC50 for PGE2 production = 0.05 μM) and neutrophil assays (IC50 for PAF biosynthesis = 1 μM). Aristolochic acid is active in these cellular assays (macrophage IC50 = 2.5 μM and neutrophil IC50 = 100 μM), but is consistently less active than either scalaradial or luffariellolide. The relative potencies of these compounds were determined in several murine in vivo inflammatory models such as oxazolone contact hypersensitivity, AA-induced ear edema and phorbol ester (PMA)-induced ear edema. In the mouse model of oxazolone contact hypersensitivity, these PLA2 inhibitors have little effect ( ≤ 30% inhibition at 400 μg/ear) with scalaradial and luffariellolide being less effective than either aristolochic or ellagic acid. PMA-induced ear edema was effectively inhibited by scalaradial, luffariellolide and aristolochic acid (ED50 = 70, 50 and 50 μg/ear, respectively) whereas ellagic acid was less effective (ED50 = 230 μg/ear). In AA-induced ear edema, these PLA2 inhibitors had minimal effects, as would be expected for compounds which inhibit PLA2. These results, especially those of ellagic acid, suggest that caution should be taken in the extrapolation of potency against a purified human extracellular type PLA2 to the scope of activities these compounds might have in the cellular and in vivo models. The consistency of scalaradial and luffariellolide may be inherent to their irreversible mechanism of action, which is a factor to be accounted for in the extrapolation of enzyme data to cellular and in vivo models.

ISSN:1660-5527    

DOI:10.1159/000211361

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

We have used fura-2/AM to investigate the effect of diazoxide on the cytosolic calcium concentration (Cai) in primary mouse keratinocyte cultures. Treatment of keratinocytes with 100 μM diazoxide induced a transient peak in Cai, followed by a sustained elevation. Depletion of medium calcium by addition of EGTA abolished the diazoxide-induced Cai response, indicating that the agent promoted calcium influx withou release of calcium from intracellular stores. The diazoxide-induced rise in Cai was inhibited both by addition of 60 mM KC1 to the assay buffer and by preincubation with glibenclamide, a specific K+ channel blocker. In addition, studies with the membrane potential-sensitive fluorescent probe bis-oxonol demonstrated that diazoxide hyperpolarized keratinocyte membranes. These findings suggest that keratinocytes possess K+ channels, and that the previously reported proliferation effects of K+ channel openers such as diazoxide on keratinocytes may result from hyperpolarization-induced elevation of Cai.

ISSN:1660-5527    

DOI:10.1159/000211362

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Erythromycin (ERY) is used in the topical treatment of acne vulgaris. In order to decrease the amount of microorganisms markedly, the antibiotic must penetrate into the sebaceous follicles. Firstly, the aim of this study was to improve the lipo-philicity of ERY by ion pairing. Secondly, a formulation with optimized penetration of the ion pair was developed. Thirdly, the optimized formulation was compared with formulations containing ethanol and with the commercial product Zine-ryt®. The determination of lipophilicity was based on partition coefficients (PC) and on the penetration of ERY into a modified multilayer membrane system (MMS). It was shwon that the penetration of ERY into a lipophilic acceptor system was three times higher when ion pairing between ERY and octadecansulfonate was used in comparison with the penetration of the ERY base alone. The dosage of the antibiotic used can be markedly reduced by optimizing a vehicle for the ion pair.

ISSN:1660-5527    

DOI:10.1159/000211363

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The aim of this investigation was to ascertain possible inhibitory effects of the antimycotic agent croconazole on eicosanoid biosynthesis. Human polymorphonuclear leukocytes (PMN) and whole blood of healthy donors were pretreated with croconazole in different concentrations (0.8-100 μM) for 5 min followed by the addition of Ca ionophore A23187 (10 μM) and subsequent incubation for 10 min (PMN) and 30 min (whole blood), respectively. Thereupon the eicosanoids were determined by reversed-phase high-performance liquid chromatography. Croconazole exhibited dose-dependent inhibitory activity on the 5-lipoxygenase (5-LOX) of neutrophils. The mean half maximum inhibition concentration (IC50) of croconazole for synthesis of leukotriene B4 (LTB4) and 5-hy-droxyeicosatetraenoic acid (5-HETE) was determined as 7.8 ± 1.7 and 7.6 ± 0.3 μM, respectively. The mean IC50 value for LTB4 estimated in whole blood was distinctly higher (27.0 ± 3.1 μM) compared with that determined in PMN. Additionally, an inhibitory effect (IC50 9.8 ± 2.0 μM) on the production of the cyclooxygenase (COX) product 12-hydroxyhepta-decatrienoic acid (HHT) was demonstrated, whereas the production and/ or releasing of 12-hydroxyeicosatetraenoic acid (12-HETE) was not attenuated by the azole. Our results in the cell-free 5-LOX system favor a direct inhibitory action of croconazole on 5-LOX, with a relatively high portion (45-77%) of reversibility. In spite of distinctly lower inhibitory potency compared with reference inhibitors such as nordihydroguaiaretic acid and indomethacin, croconazole is an effective inhibitor of arachidonic acid metabolism. Our results suggest that croconazole may be of some benefit in anti-inflammatory therapy.

ISSN:1660-5527    

DOI:10.1159/000211364

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1660-5527    

DOI:10.1159/000211365

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1660-5527    

DOI:10.1159/000211366

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1660-5527    

DOI:10.1159/000211367

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1660-5527    

DOI:10.1159/000211358

出版商:S. Karger AG    

年代:1995

数据来源: Karger