Effect of bile and lipids on the stereoselective metabolism of halofantrine by rat everted‐intestinal sacs

The everted rat intestinal‐sac model was utilized to assess the effect of post‐prandial conditions on the stereoselective intestinal metabolism of halofantrine to its active metabolite desbutylhalofantrine. Everted intestinal sacs were incubated with (±)‐halofantrine HCl in the presence of simulated bile solution (containing lecithin, lipase and cholesterol) and lipids to mimic post‐prandial conditions in the small intestine. The halofantrine enantiomer concentrations in intestinal sacs were relatively constant in the presence of bile, but decreased significantly on addition of lipids to the incubation media. Formation of desbutylhalofantrine enantiomers was inversely proportional to bile concentration whereas addition of lipids in the presence of bile caused a significant decrease in desbutylhalofantrine:halofantrine ratio of (?) enantiomers. Pre‐treatment of rats with peanut oil had no significant effect on desbutylhalofantrine formation in the incubated sacs or microsomal preparations, nor did it affect the expression of intestinal cytochrome P450. Addition of extra cholesterol to the bile incubations caused a significant increase in tissue halofantrine and desbutylhalofantrine concentrations, which as for lower cholesterol, were diminished on addition of other lipids. The results were consistent with previous in vivo evaluations showing that the desbutylhalofantrine to halofantrine ratio was decreased by the ingestion of a high fat meal. Chirality, 2010. © 2009 Wiley‐Liss, Inc.     

The role of aryl hydrocarbon receptor and the reactive oxygen species in the modulation of glutathione transferase by heavy metals in murine hepatoma cell lines

Glutathione transferase (GST) is a phase II detoxifying enzyme that plays a protective mechanism against oxidizing substances and toxic contaminants. Among these contaminants, heavy metals and polycyclic and halogenated aromatic hydrocarbons (PHAHs) have been shown to exert their toxic effects through the modulation of detoxifying enzymes, including the GSTs. Recently, we showed that heavy metals particularly Hg2+, Pb2+, and Cu2+ modulate the expression of phase II detoxifying enzymes such as NAD(P)H:quinone oxidoreductase 1 and Gsta1 in a concentration- and time-dependent manner. However, the effect of heavy metals and their potential interactions with aryl hydrocarbon receptor (AhR) ligands, PHAHs, on total Gst activity is still unknown. In the current study, we have investigated the effects of Hg2+, Pb2+, and Cu2+ in the absence and presence of four AhR ligands on the total Gst activity and reactive oxygen species (ROS) production in wild-type and AhR-deficient Hepa 1c1c7 cells. Our results showed that Hg2+ and Cu2+, but not Pb2+, significantly induced Gst activity in wild-type cells, whereas all metals induced the Gst activity in AhR-deficient cells. The induction of Gst activity by heavy metals was strongly correlated with an increase in the ROS production in wild-type, but not in AhR-deficient cells. Co-administration of heavy metals with AhR ligands differentially modulated Gst activity, in that co-exposure to Hg2+ plus AhR ligands could be beneficial in protecting against cytotoxicity as demonstrated by the increase in Gst activity with a proportional decrease in ROS production. Whereas co-exposure to Cu2+ plus AhR ligands was more toxic in that a decrease in Gst activity and an increase in oxidative stress of the cell were observed. We concluded that heavy metals differentially modulate the Gst activity through oxidative stress- and AhR-mediated mechanisms.     

Up- and down-modulation of liver cytochrome P450 activities and associated events in two murine malaria models

Background

The mechanisms by which malaria up and down-regulates CYP activities are not understood yet. It is also unclear whether CYP activities are modulated during non-lethal malaria infections. This study was undertaken to evaluate the time course of CYP alterations in lethal (Plasmodium berghei ANKA) and non-lethal (Plasmodium chabaudi chabaudi) murine malaria. Additionally, hypotheses on the association of CYP depression with enhanced nitric oxide (NO) production, and of CYP2a5 induction with endoplasmic reticulum dysfunction, enhanced haem metabolism and oxidative stress were examined as well.

Methods

Female DBA-2 and C57BL/6 mice were infected with P.berghei ANKA or P. chabaudi and killed at different post-infection days. Infection was monitored by parasitaemia rates and clinical signs. NO levels were measured in the serum. Activities of CYP1a (ethoxyresorufin-O-deethylase), 2b (benzyloxyresorufin-O-debenzylase), 2a5 (coumarin-7-hydroxylase) and uridine-diphosphoglucuronyl-transferase (UGT) were determined in liver microsomes. Glutathione-S-transferase (GST) activity and concentrations of gluthatione (GSH) and thiobarbituric acid-reactive substances (TBARS) were determined in the liver. Levels of glucose-regulated protein 78 (GRP78) were evaluated by immunoblotting, while mRNAs of haemoxygenase-1 (HO-1) and inducible nitric oxide synthase (iNOS) were determined by quantitative RT-PCR.

Results

Plasmodium berghei depressed CYP1a and 2b and induced 2a5 in DBA-2 mice. In P.berghei-infected C57BL/6 mice CYP activities remained unaltered. In both strains, GST and UGT were not affected by P.berghei. Plasmodium c. chabaudi depressed CYP1a and 2b and induced 2a5 activities on the day of peak parasitaemia or near this day. CYP2a5 induction was associated with over-expression of HO-1 and enhanced oxidative stress, but it was not associated with GRP78 induction, a marker of endoplasmic reticulum stress. Plasmodium chabaudi increased serum NO on days near the parasitaemia peak in both strains. Although not elevating serum NO, P.berghei enhanced iNOS mRNA expression in the liver.

Conclusion

Down-regulation of CYP1a and 2b and induction of 2a5 occurred in lethal and non-lethal infections when parasitaemia rates were high. A contribution of NO for depression of CYP2b cannot be ruled out. Results were consistent with the view that CYP2a5 and HO-1 are concurrently up-regulated and suggested that CYP2a5 induction may occur in the absence of enhanced endoplasmic reticulum stress.     

Benzo[a]pyrene, 3-methylcholanthrene and beta-naphthoflavone induce oxidative stress in hepatoma hepa 1c1c7 Cells by an AHR-dependent pathway

Polycyclic aromatic hydrocarbons have been shown to cause oxidative stress in vitro and in vivo in various animal models but the mechanisms by which these compounds produce oxidative stress are unknown. In the current study we have investigated the role of the aryl hydrocarbon receptor (AHR) in the production of reactive oxygen species (ROS) by its cognate ligands and the consequent effect on cyp1a1 activity, mRNA and protein expressions. For this purpose, Hepa 1c1c7 cells wild-type (WT) and C12 mutant cells, which are AHR-deficient, were incubated with increasing concentrations of the AHR-ligands, benzo[a]pyrene (B[a]P, 0.25-25 μM), 3-methylcholanthrene (3MC, 0.1-10 μM) and β-naphthoflavone (βNF, 1-50 μM). The studied AHR-ligands dose-dependently increased lipid peroxidation in WT but not in C12 cells. However, only B[a]P and βNF, at the highest concentrations tested, significantly increased H₂O₂ production in WT but not C12 cells. The increase in lipid peroxidation and H₂O₂ production by AHR-ligands were accompanied by a decrease in the cyp1a1 catalytic activity but not mRNA or protein expressions, which were significantly induced in a dose-dependent manner by all AHR-ligands, suggesting a post-translational mechanism is involved in the decrease of cyp1a1 activity. The AHR-ligand-mediated decrease in cyp1a1 activity was reversed by the antioxidant N-acetylcysteine. Our results show that the AHR-ligands induce oxidative stress by an AHR-dependent pathway.     

Antibodies to citrullinated proteins and differences in clinical progression of rheumatoid arthritis

Antibodies to citrullinated proteins (anti-cyclic-citrullinated peptide [anti-CCP] antibodies) are highly specific for rheumatoid arthritis (RA) and precede the onset of disease symptoms, indicating a pathogenetic role for these antibodies in RA. We recently showed that distinct genetic risk factors are associated with either anti-CCP-positive disease or anti-CCP-negative disease. These data are important as they indicate that distinct pathogenic mechanisms are underlying anti-CCP-positive disease or anti-CCP-negative disease. Likewise, these observations raise the question of whether anti-CCP-positive RA and anti-CCP-negative RA are clinically different disease entities. We therefore investigated whether RA patients with anti-CCP antibodies have a different clinical presentation and disease course compared with patients without these autoantibodies. In a cohort of 454 incident patients with RA, 228 patients were anti-CCP-positive and 226 patients were anti-CCP-negative. The early symptoms, tender and swollen joint count, and C-reactive protein level at inclusion, as well as the swollen joint count and radiological destruction during 4 years of follow-up, were compared for the two groups. There were no differences in morning stiffness, type, location and distribution of early symptoms, patients' rated disease activity and C-reactive protein at inclusion between RA patients with and without anti-CCP antibodies. The mean tender and swollen joint count for the different joints at inclusion was similar. At follow-up, patients with anti-CCP antibodies had more swollen joints and more severe radiological destruction. Nevertheless, the distribution of affected joints, for swelling, bone erosions and joint space narrowing, was similar. In conclusion, the phenotype of RA patients with or without anti-CCP antibodies is similar with respect to clinical presentation but differs with respect to disease course.     

Cost-effectiveness of abatacept,rituximab, and TNFi treatment after previous failure with TNFi treatment in rheumatoid arthritis: a pragmatic multi-centre randomised trial

IntroductionFor patients with rheumatoid arthritis (RA) whose treatment with a tumour necrosis factor inhibitor (TNFi) is failing, several biological treatment options are available. Often, another TNFi or a biological with another mode of action is prescribed. The objective of this study was to compare the effectiveness and cost-effectiveness of three biologic treatments with different modes of action in patients with RA whose TNFi therapy is failing.MethodsWe conducted a pragmatic, 1-year randomised trial in a multicentre setting. Patients with active RA despite previous TNFi treatment were randomised to receive abatacept, rituximab or a different TNFi. The primary outcome (Disease Activity Score in 28 joints) and the secondary outcomes (Health Assessment Questionnaire Disability Index and 36-item Short Form Health Survey scores) were analysed using linear mixed models. Cost-effectiveness was analysed on the basis of incremental net monetary benefit, which was based on quality-adjusted life-years (calculated using EQ-5D scores), and all medication expenditures consumed in 1 year. All analyses were also corrected for possible confounders.ResultsOf 144 randomised patients, 5 were excluded and 139 started taking abatacept (43 patients), rituximab (46 patients) or a different TNFi (50 patients). There were no significant differences between the three groups with respect to multiple measures of RA outcomes. However, our analysis revealed that rituximab therapy is significantly more cost-effective than both abatacept and TNFi over a willingness-to-pay range of 0 to 80,000 euros.ConclusionsAll three treatment options were similarly effective; however, when costs were factored into the treatment decision, rituximab was the best option available to patients whose first TNFi treatment failed. However, generalization of these costs to other countries should be undertaken carefully.

Trial registration

Netherlands Trial Register number NTR1605. Registered 24 December 2008.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0630-5) contains supplementary material, which is available to authorized users.     

Biased estimates of clonal evolution and subclonal heterogeneity can arise from PCR duplicates in deep sequencing experiments

Accurate allele frequencies are important for measuring subclonal heterogeneity and clonal evolution. Deep-targeted sequencing data can contain PCR duplicates, inflating perceived read depth. Here we adapted the Illumina TruSeq Custom Amplicon kit to include single molecule tagging (SMT) and show that SMT-identified duplicates arise from PCR. We demonstrate that retention of PCR duplicate reads can imply clonal evolution when none exists, while their removal effectively controls the false positive rate. Additionally, PCR duplicates alter estimates of subclonal heterogeneity in tumor samples. Our method simplifies PCR duplicate identification and emphasizes their removal in studies of tumor heterogeneity and clonal evolution.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0420-4) contains supplementary material, which is available to authorized users.