Electronic monitoring of variation in drug intakes can reduce bias and improve precision in pharmacokinetic/pharmacodynamic population studies

Population pharmacokinetic (PK) and pharmacodynamic (PD) studies evaluate drug concentration profiles and pharmacological effects over time when standard drug dosage regimens are assigned. They constitute a scientific basis for the determination of the optimal dosage of a new drug. Population PK/PD analyses can be performed on relatively few measures per patient enabling the study of a sizable sample of patients who take the drug over a possibly long period of time. We expose the problem of bias in PK/PD estimators in the presence of partial compliance with assigned treatment as it occurs in practice. We propose to solve this by recording accurate data on a number of previous dose timings and using timing-explicit hierarchical non-linear models for analysis. In practice, we rely on electronic measures of an ambulatory patient's drug dosing histories. Especially for non-linear PD estimation, we found that not only bias can be reduced, but higher precision can also be retrieved from the same number of data points when irregular drug intake times occur in well-controlled studies. We apply methods proposed by Mentré et al. to investigate the information matrix for hierarchical non-linear models. This confirms that a substantial gain in precision can be expected due to irregular drug intakes. Intuitively, this is explained by the fact that regular takers experience a relatively small range of concentrations, which makes it hard to estimate any deviation from linearity in the effect model. We conclude that estimators of PK/PD parameters can benefit greatly from information that enters through greater variation in the drug exposure process.     

Synergy of Nf2 and p53 mutations in development of malignant tumours of neural crest origin

Previously, we have mimicked human neurofibromatosis type 2 (NF2) in conditional Nf2 mutant (P0Cre;Nf2flox2/flox2) mice. Schwannomas, characteristic for NF2, were found at low frequency in older mice. Here, we report that these mice, upon additional hemizygosity for p53, rapidly develop multiple tumours showing features consistent with malignant peripheral nerve sheath tumours. Thus, p53 hemizygosity promotes tumorigenesis of mutant Nf2 peripheral nerve cells. In contrast, young P0Cre;Nf2flox2/+;p53+/- cis mice mainly succumb to Nf2/p53-related osteogenic tumours. Therefore, Cre-mediated early biallelic loss of Nf2 function in neural crest-derived cells hemizygous for p53 results in resistance to osteogenic tumours and increased susceptibility to peripheral nerve sheath tumours.     

Myocytes die by multiple mechanisms in failing human hearts

We tested the hypothesis that myocyte loss in failing human hearts occurs by different mechanisms: apoptosis, oncosis, and autophagic cell death. Explanted hearts from 19 patients with idiopathic dilated cardiomyopathy (EF< or =20%) and 7 control hearts were analyzed. Myocyte apoptosis revealed by caspase-3 activation and TUNEL staining occurred at a rate of 0.002+/-0.0005% (P<0.05 versus control) and oncosis assessed by complement 9 labeling at 0.06+/-0.001% (P<0.05). Cellular degeneration including appearance of ubiquitin containing autophagic vacuoles and nuclear disintegration was present at the ultrastructural level. Nuclear and cytosolic ubiquitin/protein accumulations occurred at 0.08+/-0.004% (P<0.05). The ubiquitin-activating enzyme E1 and the ligase E3 were not different from control. In contrast, ubiquitin mRNA levels were 1.8-fold (P<0.02) elevated, and the conjugating enzyme E2 was 2.3-fold upregulated (P<0.005). The most important finding, however, is the 2.3-fold downregulation of the deubiquitination enzyme isopeptidase-T and the 1.5-fold reduction of the ubiquitin-fusion degradation system-1, which in conjunction with unchanged proteasomal subunit levels and proteasomal activity results in massive storage of ubiquitin/protein complexes and in autophagic cell death. A 2-fold decrease of cathepsin D might be an additional factor responsible for the accumulation of ubiquitin/protein conjugates. It is concluded that in human failing hearts apoptosis, oncosis, and autophagy act in parallel to varying degrees. A disturbed balance between a high rate of ubiquitination and inadequate degradation of ubiquitin/protein conjugates may contribute to autophagic cell death. Together, these different types of cell death play a significant role for myocyte disappearance and the development of contractile dysfunction in failing hearts.     

Rnf2 (Ring1b) deficiency causes gastrulation arrest and cell cycle inhibition

The highly homologous Rnf2 (Ring1b) and Ring1 (Ring1a) proteins were identified as in vivo interactors of the Polycomb Group (PcG) protein Bmi1. Functional ablation of Rnf2 results in gastrulation arrest, in contrast to relatively mild phenotypes in most other PcG gene null mutants belonging to the same functional group, among which is Ring1. Developmental defects occur in both embryonic and extraembryonic tissues during gastrulation. The early lethal phenotype is reminiscent of that of the PcG-gene knockouts Eed and Ezh2, which belong to a separate functional PcG group and PcG protein complex. This finding indicates that these biochemically distinct PcG complexes are both required during early mouse development. In contrast to the strong skeletal transformation in Ring1 hemizygous mice, hemizygocity for Rnf2 does not affect vertebral identity. However, it does aggravate the cerebellar phenotype in a Bmi1 null-mutant background. Together, these results suggest that Rnf2 or Ring1-containing PcG complexes have minimal functional redundancy in specific tissues, despite overlap in expression patterns. We show that the early developmental arrest in Rnf2-null embryos is partially bypassed by genetic inactivation of the Cdkn2a (Ink4aARF) locus. Importantly, this finding implicates Polycomb-mediated repression of the Cdkn2a locus in early murine development.     

Epigenetic silencing of the tetraspanin CD9 during disease progression in multiple myeloma cells and correlation with survival.

PURPOSE: The purpose of this study was to investigate expression and epigenetic regulation of CD9 in multiple myeloma (MM) cells during disease progression. EXPERIMENTAL DESIGN: CD9 expression was retrospectively analyzed on bone marrow myeloma samples from 81 patients by immunophenotyping. CD9 expression by murine 5TMM cells was detected by flow cytometric staining and quantitative PCR. The methylation status of the CD9 promoter was determined by bisulfite PCR sequencing. RESULTS: Primary plasma cells in the majority of MM patients with nonactive disease (n = 28) showed CD9 expression, whereas most cases with active disease (n = 53) were CD9 negative. CD9 expression in diagnostic bone marrow samples (n = 74) correlated with survival. Moreover, CD9 expression on murine 5T33 and 5T2MM cells was significantly down-regulated during disease development. Treatment of CD9-nonexpressing 5T33MMvt cells with the clinically relevant histone deacetylase inhibitor LBH589 resulted in a significant increase in CD9 expression. In contrast, cells treated with the demethylation agent 5-aza-2'deoxycytidine barely showed any increase. A combination study with both compounds resulted in a strong synergistic reactivation of CD9. CD9-expressing 5T33MMvv cells and 5T33MMvt cells stably transduced with a mCD9 lentiviral transferplasmid were shown to be more susceptible to natural killer cell-mediated cytolysis than CD9-negative 5T33MMvt cells. CONCLUSIONS: CD9 expression correlates with disease status and survival of MM patients. In the murine 5T33MM model, we show that histone modifications, and to a lesser extent CpG methylation, are key epigenetic events in CD9 down-regulation. Furthermore, as CD9 expression becomes down-regulated, 5T33MM cells become less susceptible to natural killer cell-mediated cytolysis.     

The phenotype of the first otosclerosis family linked to OTSC5.

OBJECTIVE: To report the audiometric and radiologic findings in the first otosclerosis family linked to OTSC5. STUDY DESIGN: A clinical investigation of a family linked to OTSC5, including analyses of audiometric data and of high-resolution computed tomography (CT) images of the temporal bones from genetically affected family members. SETTING: Tertiary referral center. PATIENTS: Family members from a four-generation pedigree with otosclerosis segregating as an autosomal dominant trait. MAIN OUTCOME MEASURE(S): Pre-surgery pure tone audiometric data. Classification of otosclerotic foci on high-resolution spiral CT images of the temporal bones of genetically affected individuals. RESULTS: Audiometric data showed a considerable degree of phenotypic variability. Cross-sectional regression analysis did not disclose any clear age dependence of threshold-related data. Systematic differences between mean parameter values relating to the thresholds in the best or the worst ear were found. High-resolution CT images revealed a fenestral otosclerotic focus in seven of nine (78%) clinically affected individuals and cochlear foci in one of these seven patients. CONCLUSION: The phenotype of OTSC5 seems to be variable. Additional long-term audiometric data are needed to construct age-related typical audiograms, which may also facilitate the comparison between phenotypes of the different otosclerosis loci. The detection rate of otospongiotic foci in our study group is similar or lower compared with previous reports on CT data in consecutive otosclerosis patients who had stapes replacing surgery.     

Complexity in caring for an ageing heart failure population: concomitant chronic conditions and age related impairments.

The complexity of caring for the ageing heart failure (HF) population is further complicated by concomitant chronic conditions (i.e., polypharmacy, depression), age related impairments (i.e., hearing, visual and cognitive impairments, impairments in activities of daily living (ADL/IADL), and other issues (e.g., health illiteracy, lack of social support). This paper provides an overview of these risk factors, outlines how they individually and in interplay endanger favourable outcome by putting patients at risk for poor self-management. Moreover, suggestions are made on how these issues could be addressed and integrated in heart failure management by applying gerontological care principles in caring for the ageing heart failure population.     

Selective decontamination of the digestive tract to prevent postoperative infection: a randomized placebo-controlled trial in liver transplant patients

OBJECTIVE: To determine the efficacy of selective decontamination of the digestive tract (SDD) in patients undergoing elective transplantation of the liver. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Two academic teaching hospitals. PATIENTS: Adult patients undergoing elective liver transplantation: 26 patients receiving SDD and 29 patients receiving a placebo. INTERVENTIONS: Patients undergoing SDD were administered 400 mg of norfloxacin once daily as soon as they were accepted for transplantation. Postoperative treatment for this group consisted of 2 mg of colistin, 1.8 mg of tobramycin, and 10 mg of amphotericin B, four times daily, combined with an oral paste containing a 2% solution of the same drugs until postoperative day 30. Prophylactic intravenous administration of antibiotics was not part of the SDD regimen in this study. Control patients were given a similar regimen with placebo drugs. MEASUREMENTS: The mean number of postoperative bacterial and fungal infections in the first 30 days after transplantation was the primary efficacy end point. Days on a ventilator, days spent in the intensive care unit, and medical costs were registered as secondary outcome variables. MAIN RESULTS: Of the 26 patients undergoing SDD, 22 (84.5%) developed an infection in the postoperative study period; in the placebo group (n = 29), these numbers were not significantly different (25 patients, 86%). The mean number of postoperative infectious episodes per patient was also not significantly different: 1.77 (SDD) vs. 1.93 (placebo). Infections involving Gram-negative aerobic bacteria and Candida species were significantly less frequent in patients receiving SDD (p <.001 and p <.05). Total costs were higher in the group receiving SDD. CONCLUSIONS: Selective decontamination of the digestive tract does not prevent infection in patients undergoing elective liver transplantation and increases the cost of their care. It does, however, affect the type of infection. Infections with Gram-negative bacilli and with Candida species are replaced by infections with Gram-positive cocci.