Katell Peoc’h

Alpha- and beta- cleavages of the amino-terminus of the cellular prion protein

Abstract It is commonly assumed that the physiological isoform of prion protein, PrPC, is cleaved during its normal processing between residues 111/112, whereas the pathogenic isoform, PrPSc, is cleaved at an alternate site in the octapeptide repeat region around position 90. Here we demonstrated both in cultured cells and in vivo, that PrPC is subject to a complex set of post‐translational processing with the molecule being cleaved upstream of position 111/112, in the octapeptide repeat region or at position 96. PrP has therefore two main cleavage sites that we decided to name α and β. Cleavage of PrPC at these sites leads us to re‐evaluate the function of both N‐ and C‐terminus fragments thus generated.

Cerebrospinal fluid biomarker supported diagnosis of Creutzfeldt-Jakob disease and rapid dementias: a longitudinal multicentre study over 10 years.

To date, cerebrospinal fluid analysis, particularly protein 14-3-3 testing, presents an important approach in the identification of Creutzfeldt–Jakob disease cases. However, one special point of criticism of 14-3-3 testing is the specificity in the differential diagnosis of rapid dementia. The constant observation of increased cerebrospinal fluid referrals in the national surveillance centres over the last years raises the concern of declining specificity due to higher number of cerebrospinal fluid tests performed in various neurological conditions. Within the framework of a European Community supported longitudinal multicentre study (‘cerebrospinal fluid markers’) we analysed the spectrum of rapid progressive dementia diagnoses, their potential influence on 14-3-3 specificity as well as results of other dementia markers (tau, phosphorylated tau and amyloid-β1–42) and evaluated the specificity of 14-3-3 in Creutzfeldt–Jakob disease diagnosis for the years 1998–2008. A total of 29 022 cerebrospinal fluid samples were analysed for 14-3-3 protein and other cerebrospinal fluid dementia markers in patients with rapid dementia and suspected Creutzfeldt–Jakob disease in the participating centres. In 10 731 patients a definite diagnosis could be obtained. Protein 14-3-3 specificity was analysed for Creutzfeldt–Jakob disease with respect to increasing cerebrospinal fluid tests per year and spectrum of differential diagnosis. Ring trials were performed to ensure the comparability between centres during the reported time period. Protein 14-3-3 test specificity remained high and stable in the diagnosis of Creutzfeldt–Jakob disease during the observed time period across centres (total specificity 92%; when compared with patients with definite diagnoses only: specificity 90%). However, test specificity varied with respect to differential diagnosis. A high 14-3-3 specificity was obtained in differentiation to other neurodegenerative diseases (95–97%) and non-neurological conditions (91–97%). We observed lower specificity in the differential diagnoses of acute neurological diseases (82–87%). A marked and constant increase in cerebrospinal fluid test referrals per year in all centres did not influence 14-3-3 test specificity and no change in spectrum of differential diagnosis was observed. Cerebrospinal fluid protein 14-3-3 detection remains an important test in the diagnosis of Creutzfeldt–Jakob disease. Due to a loss in specificity in acute neurological events, the interpretation of positive 14-3-3 results needs to be performed in the clinical context. The spectrum of differential diagnosis of rapid progressive dementia varied from neurodegenerative dementias to dementia due to acute neurological conditions such as inflammatory diseases and non-neurological origin.

Pharmacogenetics of opiates in clinical practice: the visible tip of the iceberg

Opioids are the cornerstone of analgesic therapy and are used as a substitution therapy for opiate addiction. Interindividual variability in response to opioids is a significant challenge in the management of pain and substitution. Therefore, treatment with opioids requires a careful individualization of dosage to achieve an appropriate balance of efficacy and adverse effects and, consequently, avoid toxicity, particularly respiratory depression, sedation and for some, cardiac ventricular fibrillations. Many studies have investigated the association between genetic factors and the variability of response to opioids. Variants in genes encoding proteins implied in opioid pharmacokinetics (absorption, distribution, metabolism, excretion and toxicity), together with those implied in opioids direct and indirect pharmacodynamics (genes of opioid receptors and monoaminergic systems), are the most studied. Many association studies have not been replicated. The purpose of this article is to summarize pharmacogenetic data associated with some opioids frequently encountered in managed care settings.

A new VKORC1 mutation leading to an isolated resistance to fluindione

ical patients. Circulation, 110, 874–879. Malone, P.C. & Agutter, P.S. (2006) The aetiology of deep vein thrombosis. The Quarterly Journal of Medicine, 99, 581–593. Malone, P.C. & Agutter, P.S. (2009) Is ‘Virchow’s triad’ useful? British Journal of Haematology, doi:10.1111/j.1365-2141.2009.07685.x Matsuno, H., Okada, K., Ueshima, S., Matsuo, O. & Kozawa, O. (2003) Alpha2-antiplasmin plays a significant role in acute pulmonary embolism. Journal of Thrombosis & Haemostasis, 1, 1734–1739. Myers, Jr, D.D., Wrobleski, S.K., Londy, F.J., Fex, B., Hawley, A., Schaub, R.G., Greenfield, L. & Wakefield, T.W. (2002) New and effective treatment of experimentally induced venous thrombosis with anti-inflammatory rPSGL-Ig. Thrombosis & Haemostasis, 87, 374–382. Virchow, R.K.L. (1856a) Gessamelte Abhandlungen zur wissenschaftlichen Medizin von Rudolf Virchow. Meidinger, Frankfurt am Main, pp. 514–515 [In: Malone, P.C. & Agutter, P.S. (2006) The aetiology of deep vein thrombosis. Quarterly Journal of Medicine, 99, 581– 593]. Virchow, R.L.K. (1856b) Gesammelte Abhandlungen zur Wissenschaftlichen Medicine. Meidinger Sohn & Co., Frankfurt, [Reprint edition: Virchow R.L.K. Thrombosis und Emboli (1846–1856) In: Klassiker der medizin herausgegeben von Karl Sudhoff. Von Johann Ambrosius Barth V. 1910, Leipzig (Matzdorff, A.C., Bell, W.R. transl). Canton, Science History Publications, 1998] pp. 110.

Study of Blood and Brain Lithium Pharmacokinetics in the Rat According to Three Different Modalities of Poisoning

Lithium-induced neurotoxicity may be life threatening. Three patterns have been described, including acute, acute-on-chronic, and chronic poisoning, with unexplained discrepancies in the relationship between clinical features and plasma lithium concentrations. Our objective was to investigate differences in plasma, erythrocyte, cerebrospinal fluid, and brain lithium pharmacokinetics using a multicompartmental approach in rat models mimicking the three human intoxication patterns. We developed acute (intraperitoneal administration of 185 mg/kg Li₂CO₃ in naive rats), acute-on-chronic (intraperitoneal administration of 185 mg/kg Li₂CO₃ in rats receiving 800 mg/l Li₂CO₃ in water during 28 days), and chronic poisoning models (intraperitoneal administration of 74 mg/kg Li₂CO₃ during 5 days in rats with 15 mg/kg K₂Cr₂O₇-induced renal failure). Delayed absorption (4.03 vs 0.31 h), increased plasma elimination (0.65 vs 0.37 l/kg/h) and shorter half-life (1.75 vs 2.68 h) were observed in acute-on-chronically compared with acutely poisoned rats. Erythrocyte and cerebrospinal fluid kinetics paralleled plasma kinetics in both models. Brain lithium distribution was rapid (as early as 15 min), inhomogeneous and with delayed elimination (over 78 h). However, brain lithium accumulation was more marked in acute-on-chronically than acutely poisoned rats [area-under-the-curve of brain concentrations (379 ± 41 vs 295 ± 26, P < .05) and brain-to-plasma ratio (45 ± 10 vs 8 ± 2, P < .0001) at 54 h]. Moreover, brain lithium distribution was increased in chronically compared with acute-on-chronically poisoned rats (brain-to-plasma ratio: 9 ± 1 vs 3 ± 0, P < .01). In conclusion, prolonged rat exposure results in brain lithium accumulation, which is more marked in the presence of renal failure. Our data suggest that differences in plasma and brain kinetics may at least partially explain the observed variability between human intoxication patterns.

New highly sensitive rodent and human tests for soluble amyloid precursor protein alpha quantification: preclinical and clinical applications in Alzheimer’s disease

BackgroundAmyloid precursor protein (APP), a key molecule in Alzheimer’s disease (AD), is metabolized in two alternative cleavages, generating either the amyloidogenic peptides involved in AD pathology or the soluble form of APP (sAPPα). The level of amyloidogenic peptides in human cerebrospinal fluid (CSF) is considered to be a biomarker of AD, whereas the level of sAPPα in CSF as a biomarker has not been clearly established. sAPPα has neurotrophic and neuroprotective properties. Stimulating its formation and secretion is a promising therapeutic target in AD research. To this end, very sensitive tests for preclinical and clinical research are required.MethodsThe tests are based on homogenous time-resolved fluorescence and require no washing steps.ResultsWe describe two new rapid and sensitive tests for quantifying mouse and human sAPPα. These 20 μl-volume tests quantify the levels of: i) endogenous mouse sAPPα in the conditioned medium of mouse neuron primary cultures, as well as in the CSF of wild-type mice, ii) human sAPPα in the CSF of AD mouse models, and iii) human sAPPα in the CSF of AD and non-AD patients. These tests require only 5 μl of conditioned medium from 5 × 104 mouse primary neurons, 1 μl of CSF from wild-type and transgenic mice, and 0.5 μl of human CSF.ConclusionsThe high sensitivity of the mouse sAPPα test will allow high-throughput investigations of molecules capable of increasing the secretion of endogenous sAPPα in primary neurons, as well as the in vivo validation of molecules of interest through the quantification of sAPPα in the CSF of treated wild-type mice. Active molecules could then be tested in the AD mouse models by quantifying human sAPPα in the CSF through the progression of the disease. Finally, the human sAPPα test could strengthen the biological diagnosis of AD in large clinical investigations. Taken together, these new tests have a wide field of applications in preclinical and clinical studies.

Can Mu-opioid Receptor A118G Gene Polymorphism be Predictive of Acute Poisoning Severity in the Emergency Department?

To the Editor,We have read with a great interest the manuscript by Maninietal.[1]reportingtheassociationofmu-opioidreceptorgene(OPRM1) A118G polymorphism with clinical severity ofacute poisonings admitted to the emergency department. Inpatients carrying at least one G allele of the c.A118G poly-morphism (rs1799971), these authors reported increasedpoisoning severity defined as the occurrence of respiratoryarrest, cardiac arrest, or in-hospital mortality with an adjust-ed 5.3 odds ratio whatever the responsible drug was.This finding is quite promising since suggesting that onesimple test could be helpful in identifying acutely poisonedpatients with major risk for severe outcome. However, sev-eral significant biases may temperate possible enthusiasm.The association between the 118G allele and poisoningseverity may have resulted from a confounding factor, i.e.,the surprising severity of poisonings with opioids and benzo-diazepines reported in Manini’s patient population as assessedin the univariate analysis (Table 2) and confirmed in themultivariate analysis identifying a significant link betweenthe clinical outcome and recreational intent of drug abuse(Table4).Toouropinion,theauthorsshouldhavelimitedtheiranalysisto the group oftoxicants witheither obvious(opioids)or possible molecular interactions with MOR like previouslyreported(benzodiazepines)[2],whileothertoxicantslikesym-pathomimetics, antipsychotics, and antidepressants do notclearly interact with MOR.Previous studies have associated the 118G allele with lessmorphine-related pupil-constricting and gastrointestinaleffects [3] and no increased respiratory depression [4]. Amore recent study has evidenced that infants with neonatalabstinence syndrome due to in utero exposure to opioidsneeded less treatments and presented shortened length ofstay, if carrying almost one 118G allele [5]. Taken together,all these data support increased resistance rather than in-creased susceptibility or vulnerability to opioids in the pres-ence of the 118G allele, in contrast to Manini’s findings [1].Additionally, as partly acknowledged by the authors, wecannot exclude that ethnical differences according to severityexplain the observed association between the 118G allele andsevere poisoning outcome, sin cethe118Galleleismorecom-moninAsiandescent( http://www.ncbi.nlm.nih.gov/projects/SNP/snp_ref.cgi?rs=1799971).Thus,webelievethatdeterminationofpatients’ ethnical origin is mandatory to allow any definitiveconclusion, even though the Hardy –Weinberg Equilibrium isrespected. Moreover, we cannot e xclude that ethnical origin isassociated with socioeconomical factors or morbidities thatmayhavecontributedtoworsenthefinaloutcomeofpoisoning.Inconclusion,Manini’sdataarequitepromisingtoperson-alizemonitoringofpoisonedpatients,especiallythatthe118Gallele is frequent in the general population. However, consid-ering possible major limitations of their study, a reproductionin a well-characterized independent cohort appears necessary.References

Characterization and origin of heme precursors in amniotic fluid: lessons from normal and pathological pregnancies

BackgroundHeme is the prosthetic group of numerous proteins involved in vital processes such as oxygen transport, oxidative stress, and energetic mitochondrial metabolism. Free heme also plays a significant role at early stages of development and in cell differentiation processes. The metabolism of heme by the fetal placenta unit is not well-established in humans.MethodsIn a retrospective study, we measured heme precursors in the amniotic fluid (AF) of 51 healthy women, and 10 AF samples from pregnancies with either upper or lower intestinal atresia or ileus were also analyzed.ResultsWe showed that the porphyrin precursors aminolevulinic acid, porphobilinogen, and protoporphyrin IX are present at the limit of detection in the AF. Total porphyrin levels decreased progressively from week 13 to week 33 (p < 0.01). Interestingly, uroporphyrin, initially detected as traces, increased with maturation, in contrast to coproporphyrin. Uro- and coproporphyrins were type I immature isomers (>90%), suggesting a lack of maturity in the fetal compartment of the heme pathway. Finally, the differential analysis of AF from normal and pathological pregnancies demonstrated the predominant hepatic origin of fetal porphyrins excreted in the AF.ConclusionThis study gives the first insight into heme metabolism in the AF during normal and pathological pregnancies.

A Case Report of Transient but Clinically Relevant Interaction between Methadone and Duloxetine: A Reply to McCance-Katz et al.

Florence Vorspan, MD, MSc,1,2 Kamilia Ksouda, MD, MSc,1,2 Vanessa Bloch, PharmD, PhD,1,2 Jean-Louis Laplanche, PharmD, PhD,1,3 Katell Peoc’h, PharmD, PhD,1,3 Aline Hajj, PharmD,1,3 Jean-Michel Scherrmann, PharmD, PhD,1 Stéphane Mouly, MD, PhD,1,4 Jean-Pierre Lépine, MD1,2 1Neuropsychopharmacologie des Addictions, Université Paris Descartes et Paris Diderot, hôpital Fernand Widal, Paris, France 2Service de psychiatrie, hôpital Fernand Widal, Paris, France 3Laboratoire de Biochimie A, hôpital Lariboisière AP-HP, Paris, France 4Service de Médecine Interne A, hôpital Lariboisière, Paris, France