Jitka Ulrichová

Valproic Acid Induces CYP3A4 and MDR1 Gene Expression by Activation of Constitutive Androstane Receptor and Pregnane X Receptor Pathways

In our study, we tested the hypothesis whether valproic acid (VPA) in therapeutic concentrations has potential to affect expression of CYP3A4 and MDR1 via constitutive androstane receptor (CAR) and pregnane X receptor (PXR) pathways. Interaction of VPA with CAR and PXR nuclear receptors was studied using luciferase reporter assays, real-time reverse transcriptase polymerase chain reaction (RT-PCR), electrophoretic mobility shift assay (EMSA), and analysis of CYP3A4 catalytic activity. Using transient transfection reporter assays in HepG2 cells, VPA was recognized to activate CYP3A4 promoter via CAR and PXR pathways. By contrast, a significant effect of VPA on MDR1 promoter activation was observed only in CAR-cotransfected HepG2 cells. These data well correlated with up-regulation of CYP3A4 and MDR1 mRNAs analyzed by real-time RT-PCR in cells transfected with expression vectors encoding CAR or PXR and treated with VPA. In addition, VPA significantly up-regulated CYP3A4 mRNA in primary hepatocytes and augmented the effect of rifampicin. EMSA experiments showed VPA-mediated augmentation of CAR/retinoid X receptor α heterodimer binding to direct repeat 3 (DR3) and DR4 responsive elements of CYP3A4 and MDR1 genes, respectively. Finally, analysis of specific CYP3A4 catalytic activity revealed its significant increase in VPA-treated LS174T cells transfected with PXR. In conclusion, we provide novel insight into the mechanism by which VPA affects gene expression of CYP3A4 and MDR1 genes. Our results demonstrate that VPA has potential to up-regulate CYP3A4 and MDR1 through direct activation of CAR and/or PXR pathways. Furthermore, we suggest that VPA synergistically augments the effect of rifampicin in transactivation of CYP3A4 in primary human hepatocytes.

Investigation of phenolic acids in yacon (Smallanthus sonchifolius) leaves and tubers.

Thin-layer chromatographic (TLC) screening of crude extracts of dried leaves and tubers of yacon (Smallanthus sonchifolius, Asteraceae) and products of acid hydrolysis of tubers on the silica gel HPTLC plates using the developing solvents ethyl acetate-formic acid-water (85:10:15, v/v/v) and n-hexane-ethyl acetate-formic acid (20:19:1, v/v/v) proved the presence of chlorogenic, caffeic and ferulic acid. These phenolic acids were isolated from the crude extract of yacon leaves by preparative TLC, and identified after elution by HPLC/MS, as well as by direct injection of the crude extract into the HPLC/MS system. Acid hydrolysis of tubers released the increased amount of phenolic acids (e.g. caffeic acid and ferulic acid), flavonoid quercetin and an unidentified flavonoid, which was detected by TLC analysis. Ferulic acid, isomers of dicaffeoylquinic acid and still an unidentified derivative of chlorogenic acid (Mr = 562) as constituents of yacon leaves and ferulic acid as constituent of yacon tubers are reported here for the first time. These acids gave significant contribution to the radical scavenging activity detected directly on the TLC plate sprayed with 1,1-diphenyl-2-picrylhydrazyl (DPPH).

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. All main flavonolignans of silymarin tested displayed concentration-dependent cytoprotection against the toxic effects of both allyl alcohol and carbon tetrachloride but neither paracetamol nor galactosamine. The best protection was achieved by silydianin and silychristin and to a lesser degree by silymarin, while silybin and isosilybin were less effective. It is concluded that these differing outcomes result from the varying abilities of the Silybum marianum substances tested to stabilize the cell membrane, exert antioxidant properties and exhibit intrinsic toxicity.

The effect of chelerythrine on cell growth, apoptosis, and cell cycle in human normal and cancer cells in comparison with sanguinarine.

We compared the effects of chelerythrine (CHE) and sanguinarine (SA) on human prostate cancer cell lines (LNCaP and DU-145) and primary culture of human gingival fibroblasts. CHE and SA treatment of cell lines for 24 h resulted in (1) inhibition of cell viability in a dose-dependent manner in all tested cells (as evaluated by MTT test and bromodeoxyuridine incorporation assay); (2) dose-dependent increase in DNA damage in all tested cells (as evaluated by DNA comet assay); (3) changes in apoptosis (assessed by western blot analysis and TUNEL assay); and (4) significant induction of cyclin kinase inhibitors p21Waf1/Cip1 and p27Kip1 in prostate cancer cells (identified by western blot analysis). Our study demonstrates that CHE had significant cytotoxic effect, independent of p53 and androgen status, on human prostate cancer cell lines. Normal gingival fibroblasts and DU-145 cells were more sensitive to the treatment with both alkaloids than were LNCaP cells. CHE and SA may be prospective natural molecules for use in the treatment of prostate cancer owing to their involvement in apoptosis and cell cycle regulation.

DNA adduct formation from quaternary benzo[c]phenanthridine alkaloids sanguinarine and chelerythrine as revealed by the 32P-postlabeling technique

Using the 32P-postlabeling assay, we investigated the ability of quaternary benzo[c]phenanthridine alkaloids, sanguinarine, chelerythrine and fagaronine, to form DNA adducts in vitro. Two enhanced versions of the assay (enrichment by nuclease P1 and 1-butanol extraction) were utilized in the study. Hepatic microsomes of rats pre-treated with beta-naphthoflavone or those of uninduced rats, used as metabolic activators, were incubated in the presence of calf thymus DNA and the alkaloids, with NADPH used as a cofactor. Under these conditions sanguinarine and chelerythrine, but not fagaronine, formed DNA adducts detectable by 32P-postlabeling. DNA adduct formation by both alkaloids was found to be concentration dependent. When analyzing different atomic and bond indices of the C11-C12 bond (ring B) in alkaloid molecules we found that fagaronine behaved differently from sanguinarine and chelerythrine. While sanguinarine and chelerythrine showed a preference for electrophilic attack indicating higher potential to be activated by cytochrome P450, fagaronine exhibited a tendency for nucleophilic attack. Our results demonstrate that sanguinarine and chelerythrine are metabolized by hepatic microsomes to species, which generate DNA adducts.

Prunella vulgaris extract and rosmarinic acid suppress lipopolysaccharide-induced alteration in human gingival fibroblasts.

Periodontitis is a chronic disease associated with inflammation of the tooth-supporting tissues. The inflammation is initiated by a group of gram-negative anaerobic bacteria. These express a number of irritating factors including a lipopolysaccharide (LPS), which plays a key role in periodontal disease development. Plant extracts with anti-inflammatory and anti-microbial properties have been shown to inhibit bacterial plaque formation and thus prevent chronic gingivitis. In this study we tested effects of Prunella vulgaris L. extract (PVE; 5, 10, 25microg/ml) and its component rosmarinic acid (RA; 1microg/ml) on LPS-induced oxidative damage and inflammation in human gingival fibroblasts. PVE and RA reduced reactive oxygen species (ROS) production, intracellular glutathione (GSH) depletion as well as lipid peroxidation in LPS-treated cells. Treatment with PVE and RA also inhibited LPS-induced up-regulation of interleukin 1beta (IL-1beta), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and suppressed expression of inducible nitric oxide synthase (iNOS). The results indicate that PVE and RA are able to suppress LPS-induced biological changes in gingival fibroblasts. The effects of PVE and RA are presumably linked to their anti-inflammatory activities and thus use of PVE and RA may be relevant in modulating the inflammation process, including periodontal disease.

Phytochemical and antimicrobial characterization of Macleaya cordata herb

Macleaya cordata (plume poppy) is a source of bioactive compounds, mainly isoquinoline alkaloids which are used in phytopreparations with anti-inflammatory and antimicrobial activities. In this study, the alkaloids sanguinarine, chelerythrine, their dihydro derivatives, protopine and allocryptopine and phenolics, gallic, protocatechuic, p-hydroxybenzoic, m-hydroxybenzoic, gentisic, p-coumaric, caffeic, ferulic and sinapic acids were determined in extracts prepared from M. cordata aerial part, seeds, and seed capsules using HPLC with UV detection and/or LC/MS with electrospray ionization. The highest content of sanguinarine and chelerythrine was found in capsules. Protopine and allocryptopine were major alkaloids in leaves including footstalks. The seed oil contained dihydrosanguinarine, dihydrochelerythrine and twelve fatty acids of which linoleic, oleic, palmitic and stearic acids predominated. In addition, sanguinarine reductase, a key enzyme in sanguinarine/dihydrosanguinarine equilibrium in plants, was found for the first time, in the soluble proteins of leaves. Finally, extracts were tested for antimicrobial activity using the microdilution method on standard reference bacterial strains.

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. The results are summarised as follows: (i) The alkaloids tested in doses 0.1 and 10 microM did not display statistically significant cytotoxicity for 0-3 h incubation; (ii) SA and CHE showed the dose- and time-dependent toxicity within the range 25-100 microM whereas FA was not toxic; (iii) the LDH leakage into the medium was higher for SA than for CHE, thus revealing a potent potential of SA to disturb cell-membrane integrity; (iv) after 3 h incubation with 100 microM SA/CHE, mitochondrial dehydrogenase activity (MTT assay) and the cellular GSH levels decreased to residual values of about 40% suggesting that mitochondria are unlikely to be a primary target for SA/CHE in the cell; (v) no differences were found in the response to QBA application in human vs porcine hepatocyte.

Inhibition of liver alanine aminotransferase activity by some benzophenanthridine alkaloids

The quaternary benzophenanthridine alkaloids sanguinarine (1) and chelerythrine (2) inhibit rat liver L-alanine-:2-oxoglutarate aminotransferase (EC 2.6.1.2) activity. Nitidine (3) has no inhibitory effect. The inhibitory activity of alkaloids depends on the reactivity of the iminium bond with the nucleophilic reagent, e.g., the thiol group. The stability constants of adduct formation for thioethanol, cysteine, and glutathione with sanguinarine (1) and chelerythrine (2) are given. The mechanism of the inhibition of alanine aminotransferase activity by the alkaloids 1 and 2 is discussed.

SB203580, a pharmacological inhibitor of p38 MAP kinase transduction pathway activates ERK and JNK MAP kinases in primary cultures of human hepatocytes.

Mitogen-activated protein kinases (MAPKs) were extensively studied in cancer-derived cell lines; however, studies in non-transformed human cells are scarce. In the current paper, we studied the effect of SB203580, a pharmacological inhibitor of p38 MAPK, on activation and inhibition of p38 MAPK transduction partway in primary human hepatocytes (in vitro model of differentiated cells) in comparison with several tumor cell lines (proliferating non-differentiated in vitro model). In addition, we analyzed the effect of SB203580 on extracellular-regulated protein kinase (ERK) and c-jun-N-terminal kinase (JNK) pathways both in primary human hepatocytes and tumor cell lines employing primary antibodies detecting phosphorylated kinases. We show that SB203580 activates ERK and JNK in primary cultures of human hepatocytes. The levels of ERK-P(Thr202/Tyr204), JNK-P(Thr183/Tyr185) and c-Jun-P(Ser63/73), a target down-stream protein of JNK, were increased by SB203580. In contrast, SB203580 activated ERK but not JNK in HepG2, HL-60, Saos-2 and HaCaT human cancer cell lines. We tested, whether the effects of SB203580 are due to metabolism. Using liquid chromatography/mass spectrometry, we found one minor metabolite in human liver microsomes but not in HepG2 cells. These data imply that biotransformation could be responsible for the effects of SB203580 in human hepatocytes. This study is the first report on the effects of MAPK activators (sorbitol, anisomycin, EGF) and MAPK inhibitors in primary human hepatocytes. We observed differential effects of these compounds in primary human hepatocytes and in cancer cells, implying the cell-type specificity and the essential differences between the role and function of MAPKs in normal and cancer cells.