Effect of oral carbohydrate intake on labor progress: randomized controlled trial

BACKGROUND

Lack of information regarding biochemical changes in women during labor and its outcomes on maternal and neonatal health still is an unanswered question. This study aims to explore the effectiveness of oral carbohydrate intake during labor on the duration of the active phase and other maternal and neonatal outcomes.

METHODS

A parallel prospective randomized controlled trial, conducted at the University Affiliated Teaching Hospital in Gonabad. Totally, 190 women were randomly assigned to an intervention (N=87) or control (N=90) group. Inclusion criteria were low-risk women with singleton cephalic presentation; and cervical dilatation 3-4 cm. Randomization was used by random number generator on every day. Odd numbers was used for intervention and even numbers for control group. Intervention was based on the preferences between: 3 medium dates plus 110 ml water; 3 dates plus 110 ml light tea without sugar; or 110 ml orange juice. The protocol is only run once but women ate and drank gradually before second stage of labor. Control group were fasted as routine practice. Neither participants nor care givers or staff could be blinded to group allocation. Differences between duration of the active phase of labor were assessed as primary outcome measure.

RESULTS

There was significant difference in the length of second stage of labor (P <.05). The effect size for this variable was 0.48. There were no significant differences in other maternal and neonatal outcomes.

CONCLUSIONS

Oral intake of carbohydrate was an effective method for shortening the duration of second stage of labor in low-risk women.

Parametric modelling of cardiac system multiple measurement signals: an open-source computer framework for performance evaluation of ECG, PCG and ABP event detectors

The major focus of this study is to present a performance accuracy assessment framework based on mathematical modelling of cardiac system multiple measurement signals. Three mathematical algebraic subroutines with simple structural functions for synthetic generation of the synchronously triggered electrocardiogram (ECG), phonocardiogram (PCG) and arterial blood pressure (ABP) signals are described. In the case of ECG signals, normal and abnormal PQRST cycles in complicated conditions such as fascicular ventricular tachycardia, rate dependent conduction block and acute Q-wave infarctions of inferior and anterolateral walls can be simulated. Also, continuous ABP waveform with corresponding individual events such as systolic, diastolic and dicrotic pressures with normal or abnormal morphologies can be generated by another part of the model. In addition, the mathematical synthetic PCG framework is able to generate the S4-S1-S2-S3 cycles in normal and in cardiac disorder conditions such as stenosis, insufficiency, regurgitation and gallop. In the PCG model, the amplitude and frequency content (5-700 Hz) of each sound and variation patterns can be specified. The three proposed models were implemented to generate artificial signals with varies abnormality types and signal-to-noise ratios (SNR), for quantitative detection-delineation performance assessment of several ECG, PCG and ABP individual event detectors designed based on the Hilbert transform, discrete wavelet transform, geometric features such as area curve length (ACLM), the multiple higher order moments (MHOM) metric, and the principal components analysed geometric index (PCAGI). For each method the detection-delineation operating characteristics were obtained automatically in terms of sensitivity, positive predictivity and delineation (segmentation) error rms and checked by the cardiologist. The Matlab m-file script of the synthetic ECG, ABP and PCG signal generators are available in the Appendix.

Clotrimazole protects the liver against normothermic ischemia-reperfusion injury in rats

OBJECTIVE

To investigate the possible antiapoptotic prosurvival role of the pregnane X receptor (PXR) in hepatic ischemia-reperfusion injury in rats using clotrimazole (CTZ), a strong PXR transactivator.

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into 3 groups of 6 each: sham-treated, control, and CTZ-treated animals. Control and CTZ-treated animals were subjected to 30 minutes of normothermic ischemia of the whole liver followed by 6 hours of reperfusion. The animals were then killed, and the liver was excised and blood samples collected.

RESULTS

Clotrimazole induced a significant increase in expression of the CYP3A gene, indicating PXR transactivation, whereas expression of the antiapoptotic Bcl-xL gene was not increased. Serum concentrations of aspartate aminotransaminase and alanine aminotransaminase were lower in CTZ-treated animals than in control animals (difference not significant). Levels of poly(adenosine diphosphate-ribose) polymerase, a caspase-3 substrate, remained significantly higher in the CTZ-treated group compared with controls (P < .05). Clotrimazole increased the expression of phospho-p 44/42 extracellular signal-regulated kinase 1,2 (P < .05). The gene expression of the heat shock proteins 27, 70 and 90 was significantly lower in CTZ-treated animals than in controls (P < .05).

CONCLUSION

Clotrimazole-mediated PXR transactivation protects the liver against ischemia-reperfusion apoptosis in rats. Phospho-p 44/42 extracellular signal-regulated kinase 1,2 is activated, whereas gene expression of heat shock proteins 27, 70, and 90 is downregulated by induction of PXR.

Stand structure and spatial patterns of trees in mixed Hyrcanian Beech forest, Iran

The mixed beach forests (Fagus orientalis) commonly dominate by shade tolerance species with irregular uneven age stand structure. The aim of this study was to analyze the stand structure and spatial pattern in order to identify specific structural patterns. Data was collected from a 16 ha permanent plot. We mapped all stems > 7.5 cm in diameter at breast height on permanent plot. The six main species were divided into two groups based on density and stand structure. Group A had higher density than group B, as well as L-shaped DBH distribution of live stems. Species in group B had bell-shaped DBH distributions. Species in group A have clump spatial distribution pattern in all layers but clump intensity is more than in understory layer and size of patch clump is small in this group. This phenomenon for group A may explaining by having numerous coppice, sucker and patch regeneration in the understory layer. Middlestory and understory stems of the six major tree species were patchily distributed throughout the plot but for Alder and Maple species common pattern in canopy layer was complete spatial randomness. The distribution of Beech and Hornbeam trees were negatively associated with other species. These results suggest species differences in favorable canopy condition.

Cadmium-induced apoptosis through the mitochondrial pathway in rainbow trout hepatocytes: involvement of oxidative stress

Cadmium (Cd) induces oxidative stress and apoptosis in trout hepatocytes. We therefore investigated the involvement of the mitochondrial pathway in the initiation of apoptosis and the possible role of oxidative stress in that process. This study demonstrates that hepatocyte exposure to Cd (2, 5 and 10 microM) triggers significant caspase-3, but also caspase-8 and -9 activation in a dose-dependent manner. Western-blot analysis of hepatocyte mitochondrial and cytosolic fractions revealed that cytochrome c (Cyt c) was released in the cytosol in a dose-dependent manner, whereas the pro-apoptotic protein Bax was redistributed to mitochondria after 24 and 48 h exposure. We also found that the expression of anti-apoptotic protein Bcl-xL, known to be regulated under mild oxidative stress to protect cells from apoptosis, did not change after 3 and 6 h exposure to Cd, then increased after 24 and 48 h exposure to 10 microM Cd. In the second part of this work, two antioxidant agents, 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) (100 microM) and N-acetylcysteine (NAC, 100 microM) were used to determine the involvement of reactive oxygen species (ROS) in Cd-induced apoptosis. Simultaneously exposing trout hepatocytes to Cd and TEMPO or NAC significantly reduced caspase-3 activation after 48 h and had a suppressive effect on caspase-8 and -9 also, mostly after 24 h. Lastly, the presence of either one of these antioxidants in the treatment medium also attenuated Cd-induced Cyt c release in cytosol and the level of Bax in the mitochondria after 24 and 48 h, while high Bcl-xL expression was observed. Taken together, these data clearly evidenced the key role of mitochondria in the cascade of events leading to trout hepatocyte apoptosis in response to Cd and the relationship that exists between oxidative stress and cell death.

The role of protein tyrosine kinases in CYP1A1 induction by omeprazole and thiabendazole in rat hepatocytes

Benzimidazoles compounds like omeprazole (OME) and thiabendazole (TBZ) mediate CYP1A1 induction differently from classical aryl hydrocarbon receptor (AhR) ligands, 3-methylcholanthrene (3-MC) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). To clarify the involvement of an intracellular signal pathway in CYP1A1 induction by OME and TBZ, the TBZ, OME and 3-MC signal-transducing pathways were compared by using specific protein tyrosine kinase inhibitors in primary culture of rat hepatocytes. The effect of OME and TBZ (75-250 microM) on cytochrome P450 1A1 (CYP1A1) expression was therefore studied in primary cultures of rat hepatocytes after 24 h, 48 h and 72 h of exposure. Both compounds provoked a dose- and time-dependent increase in CYP1A1 (EROD activity, protein and mRNA levels), but OME was less effective at all the concentrations and times tested. The mechanism of benzimidazole-mediated induction of CYP1A1 was investigated by comparison with 3-MC, a prototypical AhR ligand. As expected, OME and TBZ were unable to displace [(3)H]-TCDD from its binding sites to the AhR in competitive binding studies. Moreover, classic tyrosine kinase inhibitor herbimycin A (HA) inhibited the two benzimidazoles-mediated CYP1A1 inductions, but only partially inhibited the 3-MC-mediated one. Another two tyrosine kinase inhibitors, Lavendustin A (LA) and genistein (GEN), had no effect on CYP1A1 induction by benzimidazoles and 3-MC. These results are consistent with the implication of a tyrosine kinase, most probably the Src tyrosine kinase, in the mechanism of CYP1A1 induction in rat hepatocytes.

Spontaneous apoptosis in primary cultures of human and rat hepatocytes: molecular mechanisms and regulation by dexamethasone

To elucidate the biochemical pathways leading to spontaneous apoptosis in primary cultures of human and rat hepatocytes, we examined the activation of the caspase cascade, the expression of Bcl-2-related-proteins and heat shock proteins. Comparisons were made before and after dexamethasone (DEX) treatment. We show that DEX inhibited spontaneous apoptosis in a dose-dependent manner. DEX increases the expression of anti-apoptotic Bcl-2 and Bcl-x(L) proteins, decreases the expression of pro-apoptotic Bax and inhibits Bad translocation thereby preventing the release of cytochrome c, the activation of caspases, and cell death. Although, the expression of Hsp27 and Hsp70 proteins remained unchanged, the oncogenic protein c-Myc is upregulated upon DEX-treatment. These results indicate that DEX mediates its survival effect against spontaneous apoptosis by acting upstream of the mitochondrial changes. Thus, the mitochondrial apoptotic pathway plays a major role in regulating spontaneous apoptosis in these cells. Blocking this pathway therefore may assist with organ preservation for transplant, drug screening, and other purposes.

QSAR modeling of the adult and developmental toxicity of glycols, glycol ethers and xylenes to Hydra attenuata

Autocorrelation descriptors encoding lipophilicity, molar refractivity, the H-bonding acceptor ability and H-bonding donor ability of the molecules were used to describe glycols, glycol ethers, and xylenes characterized by their adult and developmental toxicities to Hydra attenuata. A PLS regression analysis was employed to derive a QSAR model allowing to simulate both endpoints. Comparisons were made with classical regression analyses using the 1-octanol/water partition coefficient as molecular descriptor.

Spot 14 protein interacts and co-operates with chicken ovalbumin upstream promoter-transcription factor 1 in the transcription of the L-type pyruvate kinase gene through a specificity protein 1 (Sp1) binding site

In hepatocytes, the amount of the Spot 14 (S14) protein is closely related to the full expression of enzymes involved in the glycolytic and lipogenic pathways. In the present study we address the role played by this protein in the control of transcription of the L-type pyruvate kinase (L-PK) gene in primary hepatocytes. We show that human S14, which by itself does not bind to the L-PK promoter, physically interacts with the human chicken ovalbumin upstream promoter-transcription factor 1 (COUP-TF1) and induces the switch of this factor from a repressor to an activator. However, the enhancing activity of S14 and COUP-TF1 depends on the presence of a proximal GC-rich box (the L0 element) that specifically binds nuclear proteins from the livers of rats fed a glucose-rich diet. Moreover, the L0 element, which strongly binds dephosphorylated specificity protein 1 (Sp1), loses all affinity when this factor is phosphorylated by cAMP-dependent protein kinase. Mutations that affect binding of Sp1 and nuclear proteins to the L0 box also decrease basal transcription and impair glucose responsiveness of the promoter. These results therefore shed light on the mechanism by which the S14 protein, whose concentration rapidly rises after glucose intake, contributes to the full activity of the L-PK promoter.

Toxic effects of wastewaters collected at upstream and downstream sites of a purification station in cultures of rainbow trout hepatocytes

The toxic effects of wastewater samples, collected in December 1998, from upstream (U) and downstream (D) sites of the purification station of the town of Nice (South-East France on the coast of the Mediterranean Sea) were assessed undiluted and at various dilutions (75%, 50%, and 25% of collected water sample), on trout hepatocyte cultures treated for 48 or 72 h. Chemical contamination (PCBs, PAHs, Cd, Cu, Pb, and Zn) was also evaluated by chemical analysis. The water samples from the upstream site were more cytotoxic than those from the downstream site. The induction of CYP1A enzyme and metallothioneins (MTs) were selected as specific indicators of exposure to organic contaminants and metals, respectively. CYP1A-related EROD activity as well as protein expression were found to be greatly induced after 72 h exposure of the hepatocytes to the undiluted water samples (U(100%) and D(100%)), but CYP1A1 mRNA was significantly overexpressed only by samples from the upstream site. Maximal MT levels were reached after 48 h of treatment with the least concentrated water samples (U(25%) and D(25%)). Glutathione S-transferase (GST) activities were similarly increased under the same conditions. On the other hand, there was no significant glutathione peroxidase (GPx) activity response. Induction of apoptosis was analyzed by using as markers both the fragmentation of the nuclear DNA into oligonucleosomal-length fragments recognized as a "DNA ladder" and the activation of DEVD (Asp-Glu-Val-Asp)-dependent protease considered as the central mediator of programmed cell death. Significant DNA cleavage was only detectable after 72-h exposure to the most concentrated water samples from upstream sites (U(75%) and U(100%)). DEVD-dependent protease activities were significantly increased, mainly in cells exposed to U(75%) and D(25%) for 72 h. In addition, pollution-related DNA damage assessed by using the Comet assay was approximatively 1.5 times greater than that of the control level with the undiluted water samples U(100%) and D(100%), after 72-h and 48-h exposure, respectively. The present study shows that such a multibiomarker-based approach could provide complementary information, for aquatic pollution monitoring, about the early biochemical effects in cells exposed to complex chemical pollution and could be considered as early warning systems to aquatic pollution.

Cadmium induces apoptosis and genotoxicity in rainbow trout hepatocytes through generation of reactive oxygene species

Cadmium poses a serious environmental threat in aquatic ecosystems but the mechanisms of its toxicity remain unclear. The purpose of this work was first to determine whether cadmium induced apoptosis in trout hepatocytes, second to determine whether or not reactive oxygen species (ROS) were involved in cadmium-induced apoptosis and genotoxicity. Hepatocytes exposed to increasing cadmium concentrations (in the range of 1-10 microM) showed a molecular hallmark of apoptosis which is the fragmentation of the nuclear DNA into oligonucleosomal-length fragments, resulting from an activation of endogenous endonucleases and recognized as a 'DNA ladder' on conventional agarose gel electrophoresis. Exposure of hepatocytes to cadmium led clearly to the DEVD-dependent protease activation, acting upstream from the endonucleases and considered as central mediators of apoptosis. DNA strand breaks in cadmium-treated trout hepatocytes was assessed using the comet assay, a rapid and sensitive single-cell gel electrophoresis technique used to detect DNA primary damage in individual cells. Simultaneous treatment of trout hepatocytes with cadmium and the nitroxide radical TEMPO used as a ROS scavenger, reduced significantly DNA fragmentation, DEVD-related protease activity and DNA strand breaks formation. These results lead to a working hypothesis that cadmium-induced apoptosis and DNA strand breaks in trout hepatocytes are partially triggered by the generation of ROS. Additional studies are required for proposing a mechanistic model of cadmium-induced apoptosis and genotoxicity in trout liver cells, in underlying the balance between DNA damage and cellular defence systems in fish.

Dexamethasone inhibits spontaneous apoptosis in primary cultures of human and rat hepatocytes via Bcl-2 and Bcl-xL induction

We examined the effects of dexamethasone (DEX) on the apoptotic process in primary cultures of human and rat hepatocytes. DEX prolonged cell viability, inhibited the development of an apoptotic morphology, and stabilised the expression of procaspase-3 in both human and rat hepatocytes. In addition, the inhibition of apoptosis by DEX was strongly correlated with a decrease of caspase-3-like protease activity. Moreover, DEX treatment increased the expression of anti-apoptotic Bcl-2 and Bcl-xL proteins in human and rat hepatocytes, respectively, whereas the expression of pro-apoptotic proteins Bcl-xS or Bad was not detected or remained unchanged. The bcl-xL transcript is regulated at the transcriptional level and its expression paralleled that of Bcl-xL protein in DEX-treated rat hepatocytes. Taken together, these results indicate that this glucocorticoid exerts a protective role on cell survival and it delays apoptosis of human and rat hepatocytes by modulating caspase-3-like protease activity and bcl-2 and bcl-x gene expression.

Induction of cytochrome P450 1A1 gene expression, oxidative stress, and genotoxicity by carbaryl and thiabendazole in transfected human HepG2 and lymphoblastoid cells

Carbaryl and thiabendazole, two widely used pesticides, have been shown to induce cytochrome P450 1A1 (CYP1A1) expression, but neither compound is capable of displacing [3H] 2,3,7,8-tetrachlorodibenzo-P-dioxin from its aryl hydrocarbon receptor binding site. In the present study, we investigated the transcriptional regulation of CYP1A1 as well as other genes in various human hepatoma HepG2 cell lines stably transfected with the chloramphenicol acetyl transferase (CAT) reporter gene and cloned under the control of each of 14 promoters or response elements from relevant stress genes. Carbaryl and thiabendazole were found to activate CYP1A1 at the level of transcription, as demonstrated by the dose-dependent increase in reporter CAT and CYP1A1 mRNAs. Moreover, this effect appeared to be mediated via the xenobiotic responsive element (XRE), because both pesticides specifically activated various fusion constructs containing XRE sequences (CYP1A, glutathione S-transferase, and XRE). Carbaryl and to a lesser extent thiabendazole also activated other stress genes such as c-fos and NF-kappaBRE, HSP70 and GRP78, and GADD153 at a transcriptional level. These data suggest that these molecules induce early alert genes, including those known to be sensitive to oxidative stress. This led us to examine the genotoxic effect of carbaryl and thiabendazole by an in vitro DNA repair solid-phase assay. Both compounds provoked a strong DNA-damaging activity in the human lymphoblastoid cell line that constitutively expresses human CYP1A1 cDNA, but not in the parental line, indicating that CYP1A1 is chiefly implicated in carbaryl and thiabendazole genotoxicity. This effect was confirmed on HepG2 cells. These observations support the notion that intracellular signals leading to CYP1A1 induction, oxidative stress, and genotoxicity are intimately related.

Effects of macrolide antibiotics on CYP3A expression in human and rat hepatocytes: interspecies differences in response to troleandomycin

The effects of various macrolide antibiotics [triacetyloleandomycin (TAO), clarithromycin, azithromycin, roxithromycin, erythromycin base] and the new ketolide HMR3004 on CYP3A expression were evaluated in human and rat hepatocytes. Cells were treated for 3 days with nontoxic concentrations of the drugs, and CYP3A induction was assessed through midazolam hydroxylase activity and Western and Northern blot analyses. In rat hepatocytes, no induction of CYP3A1 expression was observed following exposure to macrolides, even to erythromycin base and TAO (well known in vivo CYP3A1 inducers), whereas dexamethasone and phenobarbital were confirmed to induce this enzyme. In contrast, treatment of fresh and thawed human hepatocytes with TAO, produced an increase of midazolam hydroxylation (4-fold over control). This result was in agreement with the high amount of CYP3A4 protein and mRNA revealed by Western and Northern blot analyses. Other tested macrolides had no induction effect on CYP3A expression. These results confirmed the interspecies variability of CYP3A regulation in hepatocytes and raised the question of its mechanism of induction by macrolides in human liver.

Is CYP1A1 induction always related to AHR signaling pathway?

Humans are daily subjected to ever increasing amounts of exogenous compounds. Some of them are capable of inducing cytochrome P450s, a process that allows the cell to adapt to changes in its chemical environment. One of the most widely CYP studied is CYP1A1 because it metabolises a large number of xenobiotics to cytotoxic and/or mutagenic derivatives. To date, results from the literature indicate that induction of CYP1A1 does not only involve the classical activation cascade of the Ah receptor, e.g. binding of the ligand to the AhR, heterodimerisation with Arnt protein, constitution of a complex with XRE responsive element and subsequent gene activation. Indeed, some xenobiotics do activate CYP1A1 gene expression in spite of their inability to compete with TCDD for binding to the AhR. Other signaling pathways must therefore also be considered. Firstly, the CYP1A1 inducer compounds could be very weak AhR ligands or may be metabolized into a form which is in turn capable of binding to the Ah receptor. A second hypothesis would be that these molecules could act through other signaling cascades. At this time, two of them seem to be implicated. One concerns the RARs signal transduction pathway, as already described for retinoic acid. The second may involve tyrosine kinase activation, but the precise relationship between this activation and CYPA1 induction remains yet to be established. For the moment there is still a black box which needs to be investigated.

Diflubenzuron, a benzoyl-urea insecticide, is a potent inhibitor of TCDD-induced CYP1A1 expression in HepG2 cells

Diflubenzuron (DFB) belongs to a group of compounds called benzoyphenyl ureas acting as chitin synthesis inhibitors, which also inhibit growth of B16 murine melanomas. The present study was designed to investigate the effect of this insecticide, on CYP1A1 expression and induction in human hepatoma cells HepG2. Treatment of HepG2 cells over 72 h with noncytotoxic concentrations of DFB resulted in a strong dose-dependent decrease in constitutive ethoxyresorufin-O-deethylase activity. Moreover, DFB significantly decreased CYP1A1 induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) after 24 h exposure, as demonstrated by ethoxyresorufin-O-deethylase (EROD) activity and Northern blot analysis. Additional studies were performed both on parental HepG2 cells and HepG2-241c.1, which were stably transfected with the chloramphenicol acetyltransferase (CAT) reporter gene, cloned under the control of the human CYP1A1 promoter (-1140 to +59). Ribonuclease protection assays (RPA) analysis clearly demonstrated an inhibition of CYP1A1 transcription in both cell lines. Surprisingly, in corresponding experiments using 3-methylcholanthrene (3-MC) as a CYP1A1 inducer, DFB was less effective. Finally, in competitive binding studies using a 9S-enriched fraction of HepG2 cytosol, DFB was capable of displacing [(3)H]-2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) from its Ah receptor binding site. Taken together, these results support the involvement of a transcriptional mechanism in the inhibition of CYP1A1 expression in HepG2 cells by DFB, possibly via an Ah receptor antagonism.

Role of cytochrome P450 3A in the metabolism of mefloquine in human and animal hepatocytes

We studied mefloquine metabolism in cells and microsomes isolated from human and animal (monkey, dog, rat) livers. In both hepatocytes and microsomes, mefloquine underwent conversion to two major metabolites, carboxymefloquine and hydroxymefloquine. In human cells and microsomes these metabolites only were formed, as already demonstrated in vivo, while in other species several unidentified metabolites were also detected. After a 48 hr incubation with human and rat hepatocytes, metabolites accounted for 55-65% of the initial drug concentration, whereas in monkey and dog hepatocytes, mefloquine was entirely metabolized after 15 and 39 hrs, respectively. The consumption of mefloquine was less extensive in microsomes, and unchanged drug represented 60% (monkey) to 85-100% (human, dog, rat) of the total radioactivity after 5 hr incubations. The involvement of the cytochrome P450 3A subfamily in mefloquine biotransformation was suggested by several lines of evidence. Firstly, mefloquine metabolism was strongly increased in hepatic microsomes from dexamethasone-pretreated rats, and also in human and rat hepatocytes after prior treatment with a cytochrome P450 3A inducer. Secondly, mefloquine biotransformation in rifampycin-induced human hepatocytes was inhibited in a concentration-dependent manner by the cytochrome P450 3A inhibitor ketoconazole and thirdly, a strong correlation was found between erythromycin-N-demethylase activity (mediated by cytochrome P450 3A) and mefloquine metabolism in human microsomes (r=0.81, P < 0.05, N=13). Collectively, these findings concerning the role of cytochrome P450 3A in mefloquine metabolism may have important in vivo consequences especially with regard to the choice of agents used in multidrug antimalarial regimens.

The nitroxide stable radical tempo prevents metal-induced inhibition of CYP1A1 expression and induction

Heavy metals are known to provoke oxidative stress in fish liver cells. Because H2O2, OH*- and intracellular superoxide are involved in this oxidation, we investigated the effect of nitroxide radical, 2,2,6,6-tetramethylpiperidinyl-N-oxyl (abbreviated as TEMPO), a cell-permeable agent possessing antioxidant properties, on CYP1A expression in trout (Oncorhynchus mykiss) hepatocytes. 3-methylcholanthrene (3-MC) induced the CYP1A-related EROD activity. This induction was inhibited by concomitant exposure to Cd (II), Cu (II), Pb (II) or Zn (II). CYP1A mRNA levels were also reduced. Simultaneous treatment with 3-MC, a heavy metal and TEMPO suppressed both the inhibition of EROD activity and the decrease of CYP1A mRNA expression. These results suggest a working hypothesis that heavy metals produce multiple oxidative effects, including generation of hydroxyl radicals, which could down-regulate CYP1A1 expression. This metal-induced inhibition was prevented by TEMPO, which might protect trout hepatocytes by scavenging free radicals and thus preventing their inhibitory effects on CYP1A induction and expression.

Comparative effects of rifabutin and rifampicin on cytochromes P450 and UDP-glucuronosyl-transferases expression in fresh and cryopreserved human hepatocytes

The aim of this study was to evaluate rifabutin (RBT) and rifampicin (RIF) capabilities in inducing various xenobiotic metabolizing enzymes such as cytochromes P450 (CYPs) and UDP-glucuronosyl-transferases (UGTs) in cultured fresh and cryopreserved human hepatocytes. Enzyme induction was assessed through the use of several diagnostic markers, i.e. testosterone, midazolam (MDZ), diazepam (DZP) and 7-ethoxyresorufin for CYP-dependent enzyme reactions; and AZT for UGT-dependent enzyme reactions. RBT concentrations (0.118, 0.708 microM) were selected according to previously published pharmacokinetic data in patients. The known CYP3A4 inducer in humans, RIF, was used as a positive control. At the concentrations used, no sign of cytotoxicity was evidenced. Both compounds were able to dose-dependently induce the overall metabolism of testosterone (approximately 2-fold for RBT, 4-fold for RIF) and the formation of the 6beta-hydroxylated-derivative (up to approximately 4-fold over control for RBT and approximately 10-fold for RIF), which is CYP3A4 dependent. The other hydroxylated metabolites (16alpha-OH and 2alpha-OH) were also enhanced. The metabolism of MDZ, which is specifically metabolized by CYP3A4 in humans, was also investigated following drug's exposure to hepatocytes. DZP one, which is governed by various CYPs, including CYP3A, was also investigated. RBT was shown to increase the biotransformation of both benzodiazepines (approximately 1.9-fold over control). Moreover, the effects of both drugs on ethoxyresorufin O-deethylase activity (EROD), which is representative of CYPIA1/2 isoforms, were tested. Results showed only a moderate induction of this marker (approximately 2-fold over control) when compared to the high effect observed after hepatocyte exposure to 3-methylcholantene (approximately 14-fold over control). Finally, the action of RBT and RIF on UGTs expression was investigated by using AZT as diagnostic substrate: glucuronides formation was not significantly affected by the two rifamycin derivatives. On the whole, exposure of fresh or cryopreserved human hepatocytes to RBT dose-dependently affected the levels of drug metabolizing enzymes in a dose-dependent manner. However, as already demonstrated by in vivo pharmacokinetic studies, its inducing properties towards CYPs, CYP3A in particular, are less pronounced than RIF.

Present status of the application of cryopreserved hepatocytes in the evaluation of xenobiotics: consensus of an international expert panel

Successful cryopreservation of freshly isolated hepatocytes would significantly decrease the need for freshly-procured livers for the preparation of hepatocytes for experimentation. Hepatocytes can be prepared, cryopreserved, and used for experimentation as needed at different times after isolation. Cryopreservation is especially important for research with human hepatocytes because of the limited availability of fresh human livers. Based on the cumulative experience of this international expert panel, a consensus was reached on the various aspects of hepatocyte cryopreservation, including cryopreservation and thawingprocedures and applications of the cryopreserved hepatocytes. Key to successful cryopreservation includes slow addition of cryopreservants, controlled-rate freezing with adjustment for the heat of crystallization, storage at -150 degrees C, and rapid thawing. There is a general consensus that cryopreserved hepatocytes are useful for short-term xenobiotic metabolism and cytotoxicity evaluation.

A multi-laboratory evaluation of cryopreserved monkey hepatocyte functions for use in pharmaco-toxicology

Ethical, economic and technical reasons hinder regular supply of freshly isolated hepatocytes from higher mammals such as monkey for preclinical evaluation of drugs. Hence, we aimed at developing optimal and reproducible protocols to cryopreserve and thaw parenchymal liver cells from this major toxicological species. Before the routine use of these protocols, we validated them through a multi-laboratory study. Dissociation of the whole animal liver resulted in obtaining 1-5 billion parenchymal cells with a viability of about 86%. An appropriate fraction (around 20%) of the freshly isolated cells was immediately set in primary culture and various hepato-specific tests were performed to examine their metabolic, biochemical and toxicological functions as well as their ultrastructural characteristics. The major part of the hepatocytes was frozen and their functionality checked using the same parameters after thawing. The characterization of fresh and thawed monkey hepatocytes demonstrated the maintenance of various hepato-specific functions. Indeed, cryopreserved hepatocytes were able to survive and to function in culture as well as their fresh counterparts. The ability for synthesis (proteins, ATP, GSH) and conjugation and secretion of biliary acids was preserved after deep freeze storage. A better stability of drug metabolizing activities than in rodent hepatocytes was observed in monkey. After thawing, Phase I and Phase II activities (cytochrome P450, ethoxycoumarin-O-deethylase, aldrin epoxidase, epoxide hydrolase, glutathione transferase, glutathione reductase and glutathione peroxidase) were well preserved. The metabolic patterns of several drugs were qualitatively and quantitatively similar before and after cryopreservation. Lastly, cytotoxicity tests suggested that the freezing/thawing steps did not change cell sensitivity to toxic compounds.