Cytotoxicity of sanguinarine in primary rat hepatocytes is attenuated by dioxin and phenobarbital.

Putative interactions between quaternary benzo[c]phenanthridine alkaloid sanguinarine (SA) and aryl hydrocarbon receptor/cytochrome P450 CYP1A (AhR/CYP1A) regulatory pathway are the subject of perpetual disputations. The role of CYP1A enzymes and AhR receptor in SA cytotoxicity was anticipated. In this paper, we tested, whether selected inducers of CYP enzymes modulate cytotoxicity of SA in primary cultures of rat hepatocytes.

Involvement of cytoskeleton in AhR-dependent CYP1A1 expression.

Cytochrome P450 (CYP) 1A1 attracts attention mainly because of its role in production of carcinogenic reactive metabolites from polycyclic aromatic hydrocarbons such as benzo[a]pyrene, but recent developments indicate its apparent role in cell cycle progression. Expression of the enzyme is subject to regulation by aryl hydrocarbon receptor (AhR). It has been shown that induction of CYP 1A1 in HepG2 cells and primary rat hepatocytes by tetrachloro-p-dibenzodioxin (TCDD) is diminished by colchicine and nocodazole.

Microtubule disruptors and their interaction with biotransformation enzymes.

Microtubule disruptors, widely known as antimitotics, have broad applications in human medicine, especially as anti-neoplastic agents. They are subject to biotransformation within human body frequently involving cytochromes P450. Therefore antimitotics are potential culprits of drug-drug interactions on the level of activity as well as expression of cytochromes P450.

Silybin and dehydrosilybin inhibit cytochrome P450 1A1 catalytic activity: a study in human keratinocytes and human hepatoma cells.

The flavonolignan silybin and its derivative dehydrosilybin have been proposed as candidate UV-protective agents in skin care products. This study addressed the effect of silybin and dehydrosilybin on the activity of cytochrome P450 isoform CYP1A1 in human keratinocytes (HaCaT) and human hepatoma cells (HepG2). CYP1A1 catalytic activity was assessed as O-deethylation of 7-ethoxyresorufin using fluorescence detection.

Role of microtubules network in CYP genes expression.

Superfamily of cytochrome P450 enzymes (CYPs), a distinctive enzyme system by which human body defends itself against toxic compounds, is the subject of a complex regulation process involving various mechanisms, on the levels of expression and activity. Apart from physiological factors, several patho-physiological ones such as inflammation, infection, and stress affect CYP expression. The aim of this review is to summarize the current knowledge on the role of microtubules network in the regulation of drug metabolizing CYPs.

Differential effects of selected natural compounds with anti-inflammatory activity on the glucocorticoid receptor and NF-kappaB in HeLa cells.

Natural compounds have been used in the treatment of various diseases for centuries. Herein, we investigated the effects of structurally diverse alkaloids with anti-inflammatory activity (berberine, sanguinarine, chelerythrine, and colchicine) on two important anti-inflammatory and pro-inflammatory players, i.e.

Investigation of sanguinarine and chelerythrine effects on CYP1A1 expression and activity in human hepatoma cells.

Quaternary benzo[c]phenanthridine alkaloids (QBA) sanguinarine and chelerythrine exhibit a wide spectrum of biological activities whence they are used in dental care products. Recent studies indicated that cytochrome P450 CYP1A attenuates sanguinarine toxicity both in vivo [Williams, M.K.

Activation of the aryl hydrocarbon receptor by berberine in HepG2 and H4IIE cells: Biphasic effect on CYP1A1.

Berberine has long been considered a candidate for an antimalarial drug. It exerts a plethora of biological activities and has been used in the treatment of diarrhea and gastro-enteritis for centuries. Here we provide evidence that berberine activates the aryl hydrocarbon receptor (AhR) in human hepatoma (HepG2) and rat hepatoma cells stably transfected with a dioxin responsive element fused to the luciferase gene (H4IIE.

Effect of silybin and its glycosides on the expression of cytochromes P450 1A2 and 3A4 in primary cultures of human hepatocytes.

Four beta-glycosides of flavonoligan silybin, i.e. silybin beta-galactoside, silybin beta-glucoside, silybin beta-maltoside, silybin beta-lactoside were synthesized in order to improve silybin water solubility and bioavailability (Kren et al.

Speculations on the role of the microtubule network in glucocorticoid receptor signaling.

The glucocorticoid receptor (GR) is an important player in the life of a cell. This is underlined by a cohort of protein and nucleic acid structures interacting with the GR. Among many issues surrounding GR activity that are under active investigation, the role of microtubules (MTs) is still unclear.

Microtubule disarray in primary cultures of human hepatocytes inhibits transcriptional activity of the glucocorticoid receptor via activation of c-jun N-terminal kinase.

The human glucocorticoid receptor (hGR) plays a pivotal role in cellular processes such as development, differentiation, homeostasis, immune response and in regulation of xenobiotic metabolism. It has been demonstrated recently that colchicine inhibits hGR transcriptional activity in primary cultures of human hepatocytes by a mechanism involving impairment of hGR nucleo-cytoplasmic shuttling. In the present work, we investigated the role of the nuclear factor kappa B (NFkappaB) and c-jun-N-terminal kinase (JNK), the functional hGR antagonists, in this process.

Aromatic hydrocarbon receptor status in the metabolism of xenobiotics under normal and pathophysiological conditions.

The aryl hydrocarbon receptor (AhR), a cytosolic protein belonging to the family of nuclear receptors, controls transcription of a wide range of structurally unrelated genes. To date, the most potent AhR ligand is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Exposure to TCDD leads to a number of toxic effects, in particular to tumor promotion and immunosuppression.

Disruption of microtubules leads to glucocorticoid receptor degradation in HeLa cell line.

The role of microtubules (MTs) in steroid hormone-dependent human glucocorticoid receptor (hGR) activation/translocation is controversial. It was demonstrated recently that colchicine (COL) down-regulates hGR-driven genes in primary human hepatocytes by a mechanism involving inhibition of hGR translocation to the nucleus. To investigate whether inhibition of hGR translocation is the sole reason for its inactivation, we used human cervical carcinoma cells (HeLa) as a model.

[Mini-invasive treatment of hemorrhoids using the Hemoron apparatus. Personal experience].

The miniinvasion therapy of hemorrhoids using the Hemoron instrument is counted among the modern methods of the out-patient treatment for the internal hemorrhoids. The aim of this work was to assess the miniinvasion therapy of the internal hemorrhoids, applying D.C.

Approaches to messenger RNA detection - comparison of methods.

Detection of messenger RNA is an important part of current biomedical research, although utilized for decades. This communication endeavors to compare three most commonly used techniques of mRNA detection, i.e.

Pathophysiological factors affecting CAR gene expression.

The body defends itself against potentially harmful compounds, such as drugs and toxic endogenous compounds and their metabolites, by inducing the expression of enzymes and transporters involved in their metabolism and elimination. The orphan nuclear receptor CAR (NR1I3 controls phase I (CYP2B, CYP2C, CYP3A), phase II (UGT1A1), and transporter (SLC21A6, MRP2) genes involved in drug metabolism and bilirubin clearance. Constitutive androstane receptor (CAR) is activated by xenobiotics, such as phenobarbital, but also by toxic endogenous compounds such as bilirubin metabolite(s).

Colchicine down-regulates cytochrome P450 2B6, 2C8, 2C9, and 3A4 in human hepatocytes by affecting their glucocorticoid receptor-mediated regulation.

The xenobiotic-mediated induction of three major human liver cytochrome P450 genes, CYP2B6, CYP2C9, and CYP3A4, is known to be regulated by the constitutive androstane receptor (CAR) and the pregnane X receptor (PXR). CAR and PXR are regulated, at least in part, by the glucocorticoid receptor (GR) and the hypothesis of a signal transduction cascade GR-[CAR/PXR]-P450 has been proposed. This study was aimed at testing this hypothesis in primary human hepatocytes by using the tubulin network disrupting agent colchicine.

Primary cultures of human hepatocytes as a tool in cytotoxicity studies: cell protection against model toxins by flavonolignans obtained from Silybum marianum.

The aim of this study was to evaluate the cytoprotective effects upon primary human hepatocytes of silymarin extract and its main flavonolignans following exposure to the cytotoxic actions of model toxins. The conditions for the hepatocyte intoxication were optimised for allyl alcohol, carbon tetrachloride, D-galactosamine and paracetamol. Silymarin extract, silychristin and silydianin did not exert cytotoxicity (10-100 microM), whereas silybin and isosilybin at higher concentrations and after longer incubation periods were cytotoxic.

Effect of silybin and its congeners on human liver microsomal cytochrome P450 activities.

Silybin and related flavonolignans form a major part of the Silybum marianum extract, silymarin, which has been used to treat liver diseases for hundreds of years. Although regarded as safe, many of the extract constituents remain thus far untested for their possible effects on liver biotransformation enzymes. Cytochromes P450 (CYP) are very important in this regard.

Comparative effect of colchicine and colchiceine on cytotoxicity and CYP gene expression in primary human hepatocytes.

The aims of the present study were (1) to determine the cytotoxicity of colchiceine (EIN) in comparison with that of colchicine (COL); (2) to evaluate the effect of EIN on cytochrome P450 (CYP) expression and activity. Primary human hepatocytes were the model of choice for cytotoxicity and CYP expression experiments. LDH leakage and albumin secretion served as cytotoxicity parameters.

Cytotoxicity of natural compounds in hepatocyte cell culture models. The case of quaternary benzo[c]phenanthridine alkaloids.

The quaternary benzo[c]phenanthridine alkaloids (QBA) produce a plethora of species- and tissue-specific effects but the molecular basis of their biological activities remain mysterious. The objective of the present study was to investigate the cytotoxicity of QBA alkaloids, sanguinarine (SA), chelerythrine (CHE), fagaronine (FA), and the extract from Macleaya cordata in primary cultures of human and porcine hepatocytes. The cellular damage was assessed by the MTT assay, lactate dehydrogenase (LDH) leakage and the determination of intracellular glutathione (GSH) levels.

Effect of colchicine and its derivatives on the expression of selected isoforms of cytochrome P450 in primary cultures of human hepatocytes.

The study addressed the effect of colchicine and its derivatives on the protein levels of cytochrome P450 (CYP) 1A2, 2A6, 3A4, 2C9/19, and 2E1 isoforms. Primary human hepatocyte culture was the model of choice. Levels of individual CYP isoforms were detected using immunoblotting.

[The human hepatocyte. II. Cryopreservation].

Human hepatocytes (HH) are an optimal in vitro model for the study of xenobiotics metabolism and toxicity. However, there is still a problem of HH availability. A promising possibility for the storage of HH for later utilization is cryopreservation.

[The human hepatocyte: I. A model for studying metabolism and toxicity of xenobiotics].

Isolated human hepatocytes have become one of the most attractive experimental approaches to the study of the specific metabolic functions of the human liver, interactions between liver cells and infectious agents, and metabolism and pharmacotoxicity of drugs. Particularly the primary cell culture model provides an in vitro system for investigating specific mechanisms in a precisely controlled conditions. In the present paper the legislative and ethical problems concerning availability of human liver samples, techniques developed for isolation, preservation and cultivation of hepatocytes are discussed.