Papers by Laurent Pradier
Journal of Neurochemistry
During its physiopathological maturation, the beta-amyloid precursor protein undergoes several di... more During its physiopathological maturation, the beta-amyloid precursor protein undergoes several distinct proteolytic events by activities called secretases. In Alzheimer's disease, the main histological hallmark called senile plaque is clearly linked to the overproduction of the amyloid peptides Abeta40 and Abeta42, two highly aggregable betaAPP-derived fragments generated by combined cleavages by beta- and gamma-secretases. Recently, an alternative hydrolytic pathway was described, involving another category of proteolytic activities called caspases, responsible for the production of a 31 amino acids betaAPP C-terminal fragment called C31. C31 was reported to lower the viability of N2a cells but the exact mechanisms mediating C31-toxicity remained to be established. Here we show that the transient transfection of pSV2 vector encoding C31 lowers by about 80% TSM1 neuronal cells viability. Arguing against a C31-stimulated apoptotic response, we demonstrate by combined enzymatic and immunological approaches that C31 expression did not modulate basal or staurosporine-induced caspase 3-like activity and pro-caspase-3 activation. Furthermore, C31 did not modify Bax and p53 expressions, poly-(ADP-ribose)-polymerase cleavage and cytochrome c translocation into the cytosol. However, we established that C31 overexpression triggers selective increase of Abeta42 but not Abeta40 production by HEK293 cells expressing wild-type betaAPP751. Altogether, our data demonstrate that C31 induces a caspase-independent toxicity in TSM1 neurons and potentiates the pathogenic betaAPP maturation pathway by increasing selectively Abeta42 species in wild type-betaAPP-expressing human cells.
Journal of Pharmacology and Experimental Therapeutics
The human NK-1 receptor transfected in Chinese hamster ovary (CHO) cells was studied with use of ... more The human NK-1 receptor transfected in Chinese hamster ovary (CHO) cells was studied with use of different tachykinin analogs: Substance P, [Pro9]SP, [Sar9, Met(O2)11]SP, [Gly9 psi (CH2CH2) Leu10]SP, Ac-Arg-septide, septide, [Gly9 psi (CH2CH2) Gly10]SP, NKA, [pGlu6]SP(6-11) and [Lys5]NKA(4-10). Binding experiments with [3H][Pro9]SP discriminated two classes of peptides with either high affinity (K iota in the nanomolar range) for the human NK-1 receptor or with low affinity (K iota in the micromolar range); this second group of peptides included NKA and [pGlu6]SP(6-11). In spite of these differences, both peptide families evoked potent stimulation of phosphatidylinositol hydrolysis (EC50 in the nanomolar range). In contrast, only NK-1 agonists, with high affinity, stimulated with great potency cyclic AMP formation (EC50 from 8 to 50 nM), whereas the second family of peptides were only weak agonists (EC50 in the micromolar range). RP 67580, CP 96345 and GR 94800, a NK-2 antagonist, were either competitive or uncompetitive inhibitors of inositol phosphates or cyclic AMP formations induced by [Pro9]SP, septide or NKA, independently of the agonist or the response studied. Thus, NKA, the presumed NK-2 endogenous peptide that may be co-released with SP, and the enzymatically produced C-terminal fragment of SP, [pGlu6]SP(6-11), may trigger specific pharmacological responses via the NK-1 receptor, at nanomolar concentrations, and thus regulate the action of SP at the NK-1 receptor.
Alzheimer's & Dementia, 2014
Molecular Pharmacology
Most nonpeptide neurokinin (NK)1 antagonists display a marked difference in affinity for rat vers... more Most nonpeptide neurokinin (NK)1 antagonists display a marked difference in affinity for rat versus human NK1 receptors. The molecular basis for the species selectivity of RP67580 and CP96,345 has been previously addressed [J. Biol. Chem. 267:25668-25671 (1992); J. Biol. Chem. 268:2319-2323 (1993)]. We are extending these previous results to additional NK1 antagonists, which are members of different chemical families. Included is a new perhydroisoindolol, RPR100893, which unlike its parent compound (RP67580) is human receptor selective. Chimeric rat/human NK1 receptors, as well as rat and human mutant NK1 receptors, were constructed and expressed in COS-1 cells, and affinities for substance P and the various antagonists were determined in binding studies. With human receptor-selective antagonists, the rat R290(S-->I) mutation was the most effective in increasing antagonist affinity (from 7- to 23-fold). Combination with the R116(L-->V) mutation led to an additional increase in...
The neuropathological hallmarks of Alzheimer's disease (AD) include senile plaques made of Ab... more The neuropathological hallmarks of Alzheimer's disease (AD) include senile plaques made of Abeta peptide, neurofibrillary tangles containing hyperphosphorylated tau protein and neuronal loss. The pro-apoptotic kinase PKR can be activated by Abeta and can phosphorylate tau protein via GSK3beta kinase activation. The activated form of PKR (pPKR) accumulates in affected neurons and could participate in neuronal degeneration in AD. The mechanism of abnormal PKR activation in AD is not elucidated but could be linked to the PKR activator PACT. PACT stainings, and levels were assessed in the brains of AD patients and in APP/PS1 knock-in transgenic mice and in cell cultures exposed to stresses. We showed that PACT and pPKR colocalizations are enhanced in AD brains. Their levels are increased and correlated in AD and APP/PS1 knock-in mice brains. In human neuroblastoma cells exposed to Abeta, tunicamycin or H2O2, PACT and pPKR concentrations are increased. PACT then PKR inhibitions indic...
Neurobiology of disease, 2005
Oxidative stress plays an important role in the pathogenesis of Alzheimer's disease. To deter... more Oxidative stress plays an important role in the pathogenesis of Alzheimer's disease. To determine which mechanisms cause the origin of oxidative damage, we analyzed enzymatic antioxidant defense (Cu/Zn-superoxide dismutase Cu/Zn-SOD, glutathione peroxidase GPx and glutathione reductase GR) and lipid peroxidation products malondialdehyde MDA and 4-hydroxynonenal HNE in two different APP transgenic mouse models at 3-4 and 12-15 months of age. No changes in any parameter were observed in brains from PDGF-APP695(SDL) mice, which have low levels of Abeta and no plaque load. In contrast, Thy1-APP751(SL) mice show high Abeta accumulation with aging and plaques from an age of 6 months. In brains of these mice, HNE levels were increased at 3 months (female transgenic mice) and at 12 months (both gender), that is, before and after plaque deposition, and the activity of Cu/Zn-SOD was reduced. Interestingly, beta-amyloidogenic cleavage of APP was increased in female Thy1-APP751(SL) mice, wh...
Molecular pharmacology, 1994
The hexapeptide [pGlu6,Pro9]substance P (SP)6-11, septide, has been shown to be an agonist as pot... more The hexapeptide [pGlu6,Pro9]substance P (SP)6-11, septide, has been shown to be an agonist as potent as SP in eliciting smooth muscle contraction in several in vitro preparations, while being a poor competitor of labeled SP binding. These results, as well as other pharmacological data, have suggested the existence of either a specific septide receptor or a septide site on the neurokinin (NK)1 receptor distinct from that for SP. We have used rat recombinant NK1 receptor expressed in COS-1 cells to address this issue. Both functional (agonist-induced inositol phosphate accumulation) and radioligand binding studies were conducted on transiently transfected cells. SP and septide elicited similar maximal increases (4-6-fold) in inositol phosphate levels in transfected cells, with EC50 values of 0.05 +/- 0.02 nM for SP and 5 +/- 2 nM for septide. No additivity of the maximal responses to the two agonists was observed, and neither agonist evoked any response in sham-transfected cells. RP 6...
Neuroscience, 2000
We investigated whether the nucleus basalis lesion induced by quisqualic acid was associated with... more We investigated whether the nucleus basalis lesion induced by quisqualic acid was associated with a more severe impairment of spatial navigation in a water maze, a greater reduction in frontal choline acetyltransferase activity and decrease in the number of choline acetyltransferase-positive neurons in the nucleus basalis in apolipoprotein E-deficient mice than in control mice. We also studied the effect of ageing on water maze spatial navigation and cortical choline acetyltransferase activity in 16-month-old control and apolipoprotein E-deficient mice. We found that the lesion decreased choline acetyltransferase-positive neurons in the nucleus basalis and frontal choline acetyltransferase activity equally in control and apolipoprotein E-deficient mice. The nucleus basalis lesion had no effect on the initial acquisition in the water maze in control and apolipoprotein E-deficient mice after 25 or 106 days of recovery. However, the nucleus basalis lesion impaired the reversal learning in the water maze similarly in both strains after 25 days of recovery, but had no effect after 106 days of recovery. Finally, water maze spatial navigation and cortical choline acetyltransferase activity were similar in old control and apolipoprotein E-deficient mice. These results suggest that young and old apolipoprotein E-deficient mice do not have impairments in cholinergic activity or spatial navigation. Furthermore, apolipoprotein E deficiency does not increase the sensitivity to cholinergic and spatial navigation deficits induced by lesioning of the nucleus basalis with an excitatory amino acid and does not slow down the behavioral recovery.
Neurobiology of Aging, 2000
Abnormalities and impairments in axonal transport are suggested to strongly contribute to the pat... more Abnormalities and impairments in axonal transport are suggested to strongly contribute to the pathological alterations underlying AD. The exact mechanisms leading to axonopathy are currently unclear, but it was recently suggested that APP expression itself triggers axonal degeneration. We used APP transgenic mice and crossed them on a hemi- or homozygous PS1 knock-in background (APP/PS1KI). Depending on the mutant PS1 dosage, we demonstrate a clear aggravation in both plaque-associated and plaque-distant axonal degeneration, despite of an unchanged APP expression level. Amyloid-β (Aβ) peptides were found to accumulate in axonal swellings as well as in axons and apical dendrites proximate to neurons accumulating intraneuronal Aβ in their cell bodies. This suggests that Aβ can be transported within neurites thereby contributing to axonal deficits. In addition, diffuse extracellular Aβ deposits were observed in the close vicinity of axonal spheroids accumulating intracellular Aβ, which might be indicative of a local Aβ release from sites of axonal damage.
Autosomal recessive juvenile parkinsonism (AR-JP, PARK2; OMIM 602544), one of the monogenic forms... more Autosomal recessive juvenile parkinsonism (AR-JP, PARK2; OMIM 602544), one of the monogenic forms of Parkinson's disease (PD), was initially described in Japan. It is characterized by early onset (before age 40), marked response to levodopa treatment and levodopa-induced dyskinesias. The gene responsible for AR-JP was recently identified and designated parkin. We have analysed the 12 coding exons of the parkin gene in 35 mostly European families with early onset autosomal recessive parkinsonism. In one family, a homozygous deletion of exon 4 could be demonstrated. By direct sequencing of the exons in the index patients of the remaining 34 families, eight previously undescribed point mutations (homozygous or heterozygous) were detected in eight families that included 20 patients. The mutations segregated with the disease in the families and were not detected on 110-166 control chromosomes. Four mutations caused truncation of the parkin protein. Three were frameshifts (202-203delAG, 255delA and 321-322insGT) and one a nonsense mutation (Trp453Stop). The other four were missense mutations (Lys161Asn, Arg256Cys, Arg275Trp and Thr415Asn) that probably affect amino acids that are important for the function of the parkin protein, since they result in the same phenotype as truncating mutations or homozygous exon deletions. Mean age at onset was 38 ± 12 years, but onset up to age
The FASEB Journal, 2003
Nonhuman primates (NHPs) have provided robust experimental animal models for many human-related d... more Nonhuman primates (NHPs) have provided robust experimental animal models for many human-related diseases due to their similar physiologies. Nonetheless, profound differences remain in the acquisition, progression, and outcome of important diseases such as AIDS and Alzheimer's, for which the underlying basis remains obscure. We explored the utility of human high-density oligonucleotide arrays to survey the transcription profile of NHP genomes. Total RNA from prefrontal cortices of human (Homo sapiens), common chimpanzee (Pan troglodytes), cynomolgous macaque (Macaca fascicularis), and common marmoset (Callithrix jacchus) was labeled and hybridized to Affymetrix U95A GeneChip probe arrays. Corresponding data obtained previously from common chimpanzee and orangutan (Pongo pygmaeus) were added for comparison. Qualitative (present or not detected) and quantitative (expression level) analysis indicated that many genes known to be involved in human neurological disorders were present and regulated in NHPs. A gene involved in dopamine metabolism (catechol-O-methyltransferase) was absent in macaque and marmoset. Glutamate receptor 2 was up-regulated, and transcription-associated genes were down-regulated in NHPs compared with humans. We demonstrate that transcript profiling of NHPs could provide comparative genomic data to validate and better focus experimental animal models of human neurological disorders.
Revue Neurologique, 2004
SOCIÉTÉ FRANÇAISE DE NEUROPATHOLOGIE toxine cholérique qui se fixe avec une haute affinité au GM1... more SOCIÉTÉ FRANÇAISE DE NEUROPATHOLOGIE toxine cholérique qui se fixe avec une haute affinité au GM1. Ce marqueur a mis en évidence du GM1 à la périphérie du dépôt amyloïde de la plaque sénile, alors que les dépôts diffus en étaient dépourvus. Nous testons actuellement l'hypothèse selon laquelle GM1 serait abondant dans les prolongements microgliaux qui entourent le coeur amyloïde.
Revue Neurologique, 2005
Compte rendu de congrès • Résumés de la réunion de la Société Française de Neuropathologie 1233 R... more Compte rendu de congrès • Résumés de la réunion de la Société Française de Neuropathologie 1233 RÉSUMÉS DE LA RÉUNION DE LA SOCIÉTÉ FRANÇAISE DE NEUROPATHOLOGIE tance du lactate. L'apoptose neuronale était plus élevée chez les souris CE, suggérant une action synergique de l'éthanol combinée au blocage de transport de monocarboxylates privant les neurones de toute ressource énergétique.
Psychopharmacology, 1999
Rationale: Recent studies suggest that apoEdeficient mice may have impaired central cholinergic f... more Rationale: Recent studies suggest that apoEdeficient mice may have impaired central cholinergic function and neuronal recovery capacity. Objective: We investigated whether apoE-deficient mice are more susceptible to the biochemical and EEG defects induced by ageing or nucleus basalis (NB) lesion. Methods: ApoEdeficient and control mice were used. The baseline EEG activity and EEG response to a muscarinic acetylcholine receptor antagonist, scopolamine (0.05 and 0.2 mg/kg) and a benzodiazepine receptor agonist, diazepam (0.5 and 2.0 mg/kg), were studied during ageing. In addition, the cortical and hippocampal ChAT activities were measured in aged mice. The baseline EEG activity and EEG response to scopolamine (0.05 and 0.2 mg/kg), and cortical ChAT activity, were studied after quisqualic acid-induced unilateral NB lesion. Results: The baseline EEG fast wave activity (relative alpha and beta) was higher in apoE-deficient mice. Ageing decreased relative alpha activity similarly in both strains. The scopolamine induced EEG slowing was less prominent in apoE-deficient than in control mice, and the difference between the strains became slightly clearer during ageing. The NB lesion failed to produce more severe changes in cortical EEG and ChAT activity in apoE-deficient mice. Cortical and hippocampal ChAT activity was equal in young and aged apoE-deficient and control mice. The EEG response to diazepam in young and aged mice was similar in both strains. Conclusions: The regulation of cortical EEG activity of apoE-deficient mice was somewhat altered during ageing and the response to scopolamine treatment was blunted. However, the cholinergic cells of the NB of apoE-deficient mice were not more sensitive to lesion or to ageing, suggesting that apoE does not have to be present to preserve the viability of cholinergic neurons.
Progress in Neurobiology, 2000
Alzheimer's disease (AD) is the most common cause of dementia in the elderly population. ... more Alzheimer's disease (AD) is the most common cause of dementia in the elderly population. Dementia is associated with massive accumulation of fibrillary aggregates in various cortical and subcortical regions of the brain. These aggregates appear intracellularly as neurofibrillary tangles, extracellularly as amyloid plaques and perivascular amyloid in cerebral blood vessels. The causative factors in AD etiology implicate both, genetic and environmental factors. The large majority of early-onset familial Alzheimer's disease (FAD) cases are linked to mutations in the genes coding for presenilin 1 (PS1) and presenilin 2 (PS2). The corresponding proteins are 467 (PS1) and 448 (PS2) amino-acids long, respectively. Both are membrane proteins with multiple transmembrane regions. Presenilins show a high degree of conservation between species and a presenilin homologue with definite conservation of the hydrophobic structure has been identified even in the plant Arabidopsis thaliana. More than 50 missense mutations in PS1 and two missense mutations in PS2 were identified which are causative for FAD. PS mutations lead to the same functional consequence as mutations on amyloid precursor protein (APP), altering the processing of APP towards the release of the more amyloidogenic form 1-42 of Abeta (Abeta42). In this regard, the physical interaction between APP and presenilins in the endoplasmic reticulum has been demonstrated and might play a key role in Abeta42 production. It was hypothesized that PS1 might directly cleave APP. However, extracellular amyloidogenesis and Abeta production might not be the sole factor involved in AD pathology and several lines of evidence support a role of apoptosis in the massive neuronal loss observed. Presenilins were shown to modify the apoptotic response in several cellular systems including primary neuronal cultures. Some evidence is accumulating which points towards the beta-catenin signaling pathways to be causally involved in presenilin mediated cell death. Increased degradation of beta-catenin has been shown in brain of AD patients with PS1 mutations and reduced beta-catenin signaling increased neuronal vulnerability to apoptosis in cell culture models. The study of presenilin physiological functions and the pathological mechanisms underlying their role in pathogenesis clearly advanced our understanding of cellular mechanisms underlying the neuronal cell death and will contribute to the identification of novel drug targets for the treatment of AD.
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Papers by Laurent Pradier