Differential modulation of cisplatin accumulation in leukocytes and tumor cell lines by the paclitaxel vehicle Cremophor EL

Background: Several clinical studies have shown that poly-chemotherapy with the taxanes paclitaxel or docetaxel preceded or followed by cisplatin is associated with important schedule-dependent differences in toxicities, such as leukocytopenia. In general, the pharmacokinetics of both drugs during the combined treatment are unaltered, suggesting that a pharmacodynamic interaction might have occurred.Materials and methods: In order to gain insight into this pharmacologic interaction, we performed in vitro drug accumulation studies using peripheral blood leukocytes and a panel of tumor and non-malignant cell lines with paclitaxel and docetaxel, as wel as with their respective formulation vehicles Cremophor EL and Tween 80.Results: Our results show a significant reduction in the intracellular cisplatin concentration in leukocytes of up to 42% in the presence of Cremophor EL and Tween 80 as compared to the control. This pharmacodynamic interaction of these surfactants with cisplatin seems to be specific for haematopoietic cells, and does not occur in solid tumor cells.Conclusion: The present data suggest that the pharmaceutical vehicles Cremophor EL and Tween 80 might contribute to the reduced cisplatin-associated myelotoxicity observed in the clinical combination chemotherapy studies with paclitaxel and docetaxel.     

Informed consent, parental awareness, and reasons for participating in a randomised controlled study

BACKGROUND: The informed consent procedure plays a central role in randomised controlled trials but has only been explored in a few studies on children. AIM: To assess the quality of the informed consent process in a paediatric setting. METHODS: A questionnaire was sent to parents who volunteered their child (230 children) for a randomised, double blind, placebo controlled trial of ibuprofen syrup to prevent recurrent febrile seizures. RESULTS: 181 (79%) parents responded. On average, 73% of parents were aware of the major study characteristics. A few had difficulty understanding the information provided. Major factors in parents granting approval were the contribution to clinical science (51%) and benefit to the child (32%). Sociodemographic status did not influence initial participation but west European origin of the father was associated with willingness to participate in future trials. 89% of participants felt positive about the informed consent procedure; however, 25% stated that they felt obliged to participate. Although their reasons for granting approval and their evaluation of the informed consent procedure did not differ, relatively more were hesitant about participating in future. Parents appreciated the investigator being on call 24 hours a day (38%) and the extra medical care and information provided (37%) as advantages of participation. Disadvantages were mainly the time consuming aspects and the work involved (23%). CONCLUSIONS: Parents' understanding of trial characteristics might be improved by designing less difficult informed consent forms and by the investigator giving extra attention and information to non-west European parents. Adequate measures should be taken to avoid parents feeling obliged to participate, rather than giving true informed consent.     

Pachymeningitis luetica: a case report

Pachymeningitis luetica is extremely rare in developed countries. We describe a 41-year-old male patient with pachymeningitis luetica, multiple ischaemic infarctions, and severe hydrocephalus. The delay in making the diagnosis contributed to patient's death. Rapid diagnosis is essential on the slightest suspicion of an infection by Treponema pallidum, because timely treatment with antibiotics is effective.     

Structure-based thresholds of toxicological concern (TTC): guidance for application to substances present at low levels in the diet.

The threshold of toxicological concern (TTC) is a pragmatic risk assessment tool that is based on the principle of establishing a human exposure threshold value for all chemicals, below which there is a very low probability of an appreciable risk to human health. The concept that there are levels of exposure that do not cause adverse effects is inherent in setting acceptable daily intakes (ADIs) for chemicals with known toxicological profiles. The TTC principle extends this concept by proposing that a de minimis value can be identified for many chemicals, in the absence of a full toxicity database, based on their chemical structures and the known toxicity of chemicals which share similar structural characteristics. The establishment and application of widely accepted TTC values would benefit consumers, industry and regulators. By avoiding unnecessary toxicity testing and safety evaluations when human intakes are below such a threshold, application of the TTC approach would focus limited resources of time, cost, animal use and expertise on the testing and evaluation of substances with the greatest potential to pose risks to human health and thereby contribute to a reduction in the use of animals. An Expert Group of the European branch of the International Life Sciences Institute-ILSI Europe-has examined the TTC principle for its wider applicability in food safety evaluation. The Expert Group examined metabolism and accumulation, structural alerts, endocrine disrupting chemicals and specific endpoints, such as neurotoxicity, teratogenicity, developmental toxicity, allergenicity and immunotoxicity, and determined whether such properties or endpoints had to be taken into consideration specifically in a step-wise approach. The Expert Group concluded that the TTC principle can be applied for low concentrations in food of chemicals that lack toxicity data, provided that there is a sound intake estimate. The use of a decision tree to apply the TTC principle is proposed, and this paper describes the step-wise process in detail. Proteins, heavy metals and polyhalogenated-dibenzodioxins and related compounds were excluded from this approach. When assessing a chemical, a review of prior knowledge and context of use should always precede the use of the TTC decision tree. The initial step is the identification and evaluation of possible genotoxic and/or high potency carcinogens. Following this step, non-genotoxic substances are evaluated in a sequence of steps related to the concerns that would be associated with increasing intakes. For organophosphates a TTC of 18microg per person per day (0.3 microg/kg bw/day) is proposed, and when the compound is not an OP, the TTC values for the Cramer structural classes III, II and I, with their respective TTC levels (e.g. 1800, 540 and 90 microg per person per day; or 30, 9 and 1.5 microg/kg bw /day), would be applied sequentially. All other endpoints or properties were shown to have a distribution of no observed effect levels (NOELs) similar to the distribution of NOELs for general toxicity endpoints in Cramer classes I, II and III. The document was discussed with a wider audience during a workshop held in March 2003 (see list of workshop participants).     

Joint analysis of multiple longitudinal outcomes: application of a latent class model

We address the problem of joint analysis of more than one series of longitudinal measurements. The typical way of approaching this problem is as a joint mixed effects model for the two outcomes. Apart from the large number of parameters needed to specify such a model, perhaps the biggest drawback of this approach is the difficulty in interpreting the results of the model, particularly when the main interest is in the relation between the two longitudinal outcomes. Here we propose an alternative approach to this problem. We use a latent class joint model for the longitudinal outcomes in order to reduce the dimensionality of the problem. We then use a two-stage estimation procedure to estimate the parameters in this model. In the first stage, the latent classes, their probabilities and the mean and covariance structure are estimated based on the longitudinal data of the first outcome. In the second stage, we study the relation between the latent classes and patient characteristics and the other outcome(s). We apply the method to data from 195 consecutive lung cancer patients in two outpatient clinics of lung diseases in The Hague, and we study the relation between denial and longitudinal health measures. Our approach clearly revealed an interesting phenomenon: although no difference between classes could be detected for objective measures of health, patients in classes representing higher levels of denial consistently scored significantly higher in subjective measures of health. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Exhaled Nitric Oxide: A Novel Biomarker of Adverse Respiratory Health Effects in Epidemiological Studies

The sampling of exhaled breath is a noninvasive procedure that can be performed easily in adults, children, and patients with respiratory disease. Several studies have demonstrated increased exhaled nitric oxide in patients with pulmonary disease, including asthma. In addition, exhaled nitric oxide may be an elegant tool for monitoring of environmental health effects of air pollution and the prevalence of atopy in epidemiological surveys. Recent literature about exhaled nitric oxide is presented in this article. Technical, physiological, and behavioral confounding factors of exhaled nitric oxide measurement are outlined.     

Identification of the human P450 enzymes involved in the in vitro metabolism of the synthetic steroidal hormones Org 4060 and Org 30659

1. The type of human P450 enzymes involved in the in vitro metabolism of Org 4060 and Org 30659, two synthetic steroidal hormones currently under clinical development by NV Organon for use in oral contraceptive and hormone replacement therapy, was investigated. 2. Both steroids were mainly hydroxylated at the 6 β -position in incubations with human liver microsomes. 3. The results from experiments with supersomes, correlation studies as well as inhibition studies with ketoconazole, a selective inhibitor of CYP3A, strongly suggest that the CYP3A family plays a significant role in the 6 β -hydroxylation of both steroids. 4. Measurements of kinetic parameters of P450 enzymes that could metabolize both steroids, combined with the fact that CYP3A4 is known to be the most abundant P450 enzyme in the human liver, indicate that CYP3A4 will be of major importance for the in vivo human metabolism of Org 4060 and Org 30659.     

Comparative analysis of genes regulated by PML/RAR alpha and PLZF/RAR alpha in response to retinoic acid using oligonucleotide arrays

Acute promyelocytic leukemia (APL) is associated with chromosomal translocations involving retinoic acid receptor alpha (RAR alpha) and its fusion partners including promyelocytic leukemia (PML) and promyelocytic leukemia zinc finger (PLZF). Using oligonucleotide arrays, we examined changes in global gene expression mediated by the ectopic expression of either PML/RAR alpha (retinoid-sensitive) or PLZF/RAR alpha (retinoid-resistant) in U937 cells. Of more than 5000 genes analyzed, 16 genes were commonly up-regulated, and 57 genes were down-regulated by both fusion proteins suggesting their role in the APL phenotype. In our APL model, for example, TNFAIP2, TNFR2, ELF4, RAR gamma, and HoxA1 were down-regulated by both fusion proteins in the absence of retinoic acid (RA). RA strongly up-regulated these genes in PML/RAR alpha, but not in PLZF/RAR alpha expressing U937 cells. Expression studies in NB4, retinoid-resistant NB4-R2, normal human CD34+ cells, and APL patient samples strongly suggest their role in the regulation of granulocytic differentiation. Furthermore, combined treatment with tumor necrosis factor alpha (TNF alpha) and RA synergistically enhanced granulocytic differentiation in NB4 cells but not in NB4-R2 cells. Our data indicate that APL pathogenesis and retinoid-induced granulocytic differentiation of APL cells involve genes in the cell death pathway, and that cooperation between the RA and TNFalpha signaling pathways exists. Targeting both the retinoid-dependent differentiation and the cell death pathways may improve leukemic therapy, especially in retinoid-resistant acute myeloid leukemia.