Biomedical subjects

Jean-Pierre Vincent

Publications and source records attributed to Jean-Pierre Vincent.

At least 19 recordsLinked to original sources

PubMed2006

Internalization and recycling properties of neurotensin receptors.

The targeting, internalization and recycling of membrane receptors in response to extracellular ligands involve a series of molecular mechanisms which are beginning to be better understood. The receptor-dependent internalization of neurotensin has been widely investigated using endogenous or heterologous receptor expression systems. This review focuses on the general properties of neurotensin sequestration and on the characterization of the receptors involved in this process.

Adaptor Proteins, Vesicular Transport↗

PubMed2006

Functional roles of the NTS2 and NTS3 receptors.

Neurotensin exerts its actions in the central nervous system and the periphery through three identified receptors. Two of them, the NTS2 and NTS3, display unusual properties either because of their complex signal transduction mechanisms (NTS2) or because of their structural composition as a non-G-protein-coupled receptor (NTS3). Here, we review the transduction mechanisms, cellular trafficking, and potential physiological roles of these two unconventional receptors.

Adaptor Proteins, Vesicular Transport↗

PubMed2006

Morphine and pain-related stimuli enhance cell surface availability of somatic delta-opioid receptors in rat dorsal root ganglia.

The present study demonstrates that perikaryaldelta-opioid receptors (deltaORs) in rat dorsal root ganglion (DRG) neurons bind and internalize opioid ligands circulating in the CSF. Using confocal and electron microscopy, we found that prolonged morphine treatment increased the cell surface density of these perikaryal deltaORs and, by way of consequence, receptor-mediated internalization of the fluorescent deltorphin (DLT) analog omega-Bodipy 576/589 deltorphin-I 5-aminopentylamide (Fluo-DLT) in all three types of DRG neurons (small, medium, and large). In contrast, chronic inflammatory pain induced by the injection of complete Freund's adjuvant (CFA) into one hindpaw selectively increased Fluo-DLT internalization in small and medium-sized DRG neurons ipsilateral to the inflammation. Based on our previous studies in the spinal cord of mu-opioid receptor (muOR) knock-out mice, it may be assumed that the enhanced membrane recruitment of deltaORs observed after sustained morphine is attributable to stimulation of muORs. However, the selectivity of the effect induced by inflammatory pain suggests that it involves a different mechanism, namely a modality-specific and pain-related activation of C and Adelta fibers. Indeed, stimulation by capsaicin of transient receptor potential vanilloid 1 receptors, which are selectively expressed by small diameter (< 600 microm2) DRG neurons, increased Fluo-DLT internalization exclusively in this cell population. The present results, therefore, demonstrate that DRG neurons express perikaryal deltaORs accessible to CSF-circulating ligands and that the density and, hence, presumably also the responsiveness, of these receptors may be modulated by both pain-related stimuli and sustained exposure to muOR agonists.

Animals↗

PubMed2005

Neurotensin and the neurotensin receptor-3 in microglial cells.

Microglia motility plays a crucial role in response to lesion or exocytotoxic damage of the cerebral tissue. The neuropeptide neurotensin elicited the migration of the human microglial cell line C13NJ by a mechanism dependent on both phosphatidylinositol-3 kinase (PI3 kinase) and mitogen-activated protein (MAP) kinases pathways. The effect of neurotensin on cell migration was blocked by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. The type I neurotensin receptor-3 was the only known neurotensin receptor expressed in these microglial cells, and its activation led to the phosphorylation of both extracellular signaling-regulated kinases Erk1/2 and Akt. Furthermore, the effect of neurotensin on cell migration was preceded by a profound modification of the F-actin cytoskeleton, particularly by the rapid formation of numerous cell filopodia. Both the motility and the filopodia appearance induced by neurotensin were totally blocked by selective inhibitors of MAP kinases or PI3 kinase pathways. In the murine microglial cell line N11, the neurotensin receptor-3 is also the only neurotensin receptor expressed, and its activation by neurotensin leads to the phosphorylation of both Erk1/2 and Akt. In these cells, neurotensin induces the gene expression of several cytokines/chemokines, including MIP-2, MCP-1, interleukin-1beta and tumor necrosis factor-alpha. This induction is dependent on both protein kinases pathways. We observed that the effect of neurotensin on the cytokine/chemokine expression is also inhibited by the neurotensin receptor-3 propeptide. This is the demonstration that the neurotensin receptor-3 is functional and mediates both the migratory action of neurotensin and its induction of chemokines/cytokines expression.

Adaptor Proteins, Vesicular Transport↗

PubMed2005

Geriatric Nutritional Risk Index: a new index for evaluating at-risk elderly medical patients.

BACKGROUND: Patients at risk of malnutrition and related morbidity and mortality can be identified with the Nutritional Risk Index (NRI). However, this index remains limited for elderly patients because of difficulties in establishing their normal weight. OBJECTIVE: Therefore, we replaced the usual weight in this formula by ideal weight according to the Lorentz formula (WLo), creating a new index called the Geriatric Nutritional Risk Index (GNRI). DESIGN: First, a prospective study enrolled 181 hospitalized elderly patients. Nutritional status [albumin, prealbumin, and body mass index (BMI)] and GNRI were assessed. GNRI correlated with a severity score taking into account complications (bedsores or infections) and 6-mo mortality. Second, the GNRI was measured prospectively in 2474 patients admitted to a geriatric rehabilitation care unit over a 3-y period. RESULTS: The severity score correlated with albumin and GNRI but not with BMI or weight:WLo. Risk of mortality (odds ratio) and risk of complications were, respectively, 29 (95% CI: 5.2, 161.4) and 4.4 (95% CI: 1.3, 14.9) for major nutrition-related risk (GNRI: <82), 6.6 (95% CI: 1.3, 33.0), 4.9 (95% CI: 1.9, 12.5) for moderate nutrition-related risk (GNRI: 82 to <92), and 5.6 (95% CI: 1.2, 26.6) and 3.3 (95% CI: 1.4, 8.0) for a low nutrition-related risk (GNRI: 92 to < or =98). Accordingly, 12.2%, 31.4%, 29.4%, and 27.0% of the 2474 patients had major, moderate, low, and no nutrition-related risk, respectively. CONCLUSION: GNRI is a simple and accurate tool for predicting the risk of morbidity and mortality in hospitalized elderly patients and should be recorded systematically on admission.

Aged↗

PubMed2004

[Impact of nasal colonization by methicillin-resistant Staphylococcus aureus among geriatric intermediate care facility patients].

OBJECTIVE: To evaluate the impact of nasal carriage of Methicillin Resistant Staphylococcus aureus (MRSA) on antibiotic cost, infection morbidity, mortality and length of stay in a geriatric population. METHODS: 341 consecutive elderly patients (mean age 83.4 +/- 8.7 years) admitted to an intermediate care facility were prospectively include between November 1998 and October 1999. Nasal swab cultures were taken on admission. RESULTS: In sixty patients (17.6%) no nasal swab was taken. Among the 281 patients screened, 52 were identified as MRSA carriers. The principle predictive factors were: diabetes (p=0,046), sores (p=0,03), malnutrition (p=0,02), polypathology (p=0,02) and prolongation of previous hospitalisation (p=0,09). CONCLUSION: Nasal carriage of MRSA on admission to the facility was not a deleterious prognostic factor regarding duration of stay, infectious morbidity and antibiotic cost, but was associated with higher mortality risk.

Aged↗

PubMed2004

Neurotensin receptor-3/sortilin mediates neurotensin-induced cytokine/chemokine expression in a murine microglial cell line.

We show that the type I neurotensin receptor-3 (also called sortilin) is the only known neurotensin receptor expressed in a murine microglial cell line and that its activation leads to phosphorylation of both extracellular signaling-regulated (Erk1/2) and Akt kinases. Using semiquantitative reverse-transcriptase (RT) PCR, we demonstrate that neurotensin induces gene expression of several cytokines/chemokines including macrophage inflammatory protein (MIP)-2, monocyte chemotactic protein (MCP)-1, interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. This induction is dependent on both phosphatidylinositol 3-kinase and mitogen-activated protein kinases pathways. We observe that the effect of neurotensin on cytokine/chemokine expression is inhibited by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. These results demonstrate that the neurotensin receptor-3 is functional in microglial cells where it mediates the induction of chemokines/cytokines expression by neurotensin.

Adaptor Proteins, Vesicular Transport↗

PubMed2004

[Morning stiffness].

STIFFNESS AND UNSTRETCHING: Morning stiffness in the elderly is a painful entity often ignored, but frequent in institutions. Unstretching in the morning is part of the criteria in the diagnosis of inflammatory pathologies, but morning stiffness in old patients appears different from that described in rheumatological diseases and arthrosis. FROM AN AETIOLOGICAL POINT OF VIEW: Various affections can be accompanied by morning stiffness in an elderly patient: arthrosis, but also various consequential affections, static disorders, deformity. We felt it was important to define the precise criteria that individualise this pathology so as to improve its management. MANAGEMENT: Non-medicinal measures often reduce the intensity and duration of this symptom and implicate all those attending to the patient. Medicinal treatment has a more limited place in the fragile elderly patient, but its role remains to be assessed.

Aged↗

PubMed2004

[Headaches in the elderly].

ACCORDING TO AGE: It is generally thought that the prevalence of headaches decreases with ageing. However recent studies, with stricter epidemiology and methodology, clearly indicate that this decreases is less obvious than that perceived. PRIMARY AND SECONDARY HEADACHES: In elderly patients, primary headaches and notably migraine (often with altered presentation) are less frequent, even though new authentic cases may appear. However the other types of headache are clearly present. In particular, the incidence and prevalence of secondary headaches slightly increases and they represent up to 30% of all the headaches observed, compared with less than 10% in young or adult patients. The causes of such symptomatic headaches are multiple and it is important to be able to identify them since an aetiological treatment is often possible. REGARDING TREATMENT: The symptomatic treatment of headaches in the elderly follows the same principles as that of younger patients. However, the side effects and drug interactions related to pharmacological treatments can be disastrous in fragilised patients. It is therefore important to emphasize the interest of physical methods of analgesia, particularly adapted to the elderly. Some of these methods have demonstrated their efficacy and are recommended by international consensuses.

Aged↗

PubMed2004

Morphine-induced changes in delta opioid receptor trafficking are linked to somatosensory processing in the rat spinal cord.

An in vivo fluorescent deltorphin (Fluo-DLT) internalization assay was used to assess the distribution and regulation of pharmacologically available delta opioid receptors (deltaORs) in the rat lumbar (L4-5) spinal cord. Under basal conditions, intrathecal injection of Fluo-DLT resulted in the labeling of numerous deltaOR-internalizing neurons throughout dorsal and ventral horns. The distribution and number of Fluo-DLT-labeled perikaryal profiles were consistent with that of deltaOR-expressing neurons, as revealed by in situ hybridization and immunohistochemistry, suggesting that a large proportion of these cells was responsive to intrathecally administered deltaOR agonists. Pretreatment of rats with morphine for 48 hr resulted in a selective increase in Fluo-DLT-labeled perikaryal profiles within the dorsal horn. These changes were not accompanied by corresponding augmentations in either deltaOR mRNA or (125)I-deltorphin-II binding levels, suggesting that they were attributable to higher densities of cell surface deltaOR available for internalization rather than to enhanced production of the receptor. Unilateral dorsal rhizotomy also resulted in increased Fluo-DLT internalization in the ipsilateral dorsal horn when compared with the side contralateral to the deafferentation or to non-deafferented controls, suggesting that deltaOR trafficking in dorsal horn neurons may be regulated by afferent inputs. Furthermore, morphine treatment no longer increased Fluo-DLT internalization on either side of the spinal cord after unilateral dorsal rhizotomy, indicating that microOR-induced changes in the cell surface availability of deltaOR depend on the integrity of primary afferent inputs. Together, these results suggest that regulation of deltaOR responsiveness through microOR activation in this region is linked to somatosensory information processing.

Animals↗

PubMed2004

Crucial role of neuron-enriched endosomal protein of 21 kDa in sorting between degradation and recycling of internalized G-protein-coupled receptors.

Recycling of endocytosed G-protein-coupled receptors involves a series of molecular events through early and recycling endosomes. The purpose of this work was to study the role of neuron-enriched endosomal protein of 21 kDa (NEEP21) in the recycling process of neurotensin receptors-1 and -2. Here we showed that suppression of NEEP21 expression does not modify the internalization rate of both receptors but strongly inhibited the recycling of the neurotensin receptor-2. In contrast, overexpression of NEEP21 changes the behavior of the neurotensin receptor-1 from a non-recycling to a recycling state. Recycling of the neurotensin receptor-2 involves both the phosphatidylinositol 3-kinase and the recycling endosome pathways, whereas recycling of the neurotensin receptor-1 induced by overexpression of NEEP21 only occurs by the phosphatidylinositol 3-kinase-dependent pathway. Taken together, these results confirm the essential role of NEEP21 in the recycling mechanism and show that this protein acts at the level of early endosomes to promote sorting of receptors toward a recycling pathway.

Animals↗

PubMed2004

Internalization and trafficking of neurotensin via NTS3 receptors in HT29 cells.

The neurotensin receptor-3, originally identified as sortilin, is unique among neuropeptide receptors in that it is a single trans-membrane domain, type I receptor. To gain insight into the functionality of neurotensin receptor-3, we examined the neurotensin-induced intracellular trafficking of this receptor in the human carcinoma cell line HT29, which expresses both neurotensin receptor-1 and -3 sub-types. At steady state, neurotensin receptor-3 was found by sub-cellular fractionation and electron microscopic techniques to be predominantly associated with intracellular elements. A small proportion (approximately 10%) was associated with the plasma membrane, but a significant amount (approximately 25%) was observed inside the nucleus. Following stimulation with neurotensin (NT), neurotensin/neurotensin receptor-3 complexes were internalized via the endosomal pathway. This internalization entailed no detectable loss of cell surface receptors, suggesting compensation through either recycling or intracellular receptor recruitment mechanisms. Internalized ligand and receptors were both sorted to the pericentriolar recycling endosome/Trans-Golgi Network (TGN), indicating that internalized neurotensin is sorted to this compartment via neurotensin receptor-3. Furthermore, within the Trans-Golgi Network, neurotensin was bound to a lower molecular form of the receptor than at the cell surface or in early endosomes, suggesting that signaling and transport functions of neurotensin receptor-3 may be mediated through different molecular forms of the protein. In conclusion, the present work suggests that the neurotensin receptor-3 exists in two distinct forms in HT29 cells: a high molecular weight, membrane-associated form responsible for neurotensin endocytosis from the cell surface and a lower molecular weight, intracellular form responsible for the sorting of internalized neurotensin to the Trans-Golgi Network.

Adaptor Proteins, Vesicular Transport↗

PubMed2004

Risk factors for deep vein thrombosis in inpatients aged 65 and older: a case-control multicenter study.

OBJECTIVES: To identify independent risk factors of symptomatic deep vein thrombosis (DVT) in geriatric inpatients and to define high-risk patients likely to benefit from preventive treatment. DESIGN: Hospital-based case-control multicenter study with prospective data collection. SETTINGS: Geriatric university hospitals with long-, intermediate-, and short-term care facilities. PARTICIPANTS: All patients aged 65 and older in 19 geriatric departments were submitted to clinical surveillance over a 16-month period. MEASUREMENTS: Twenty-three potential risk factors of phlebitis were screened for. Comparison using logistic regression of 310 consecutive patients with symptomatic DVT versus 310 randomly selected controls was performed. The risk for symptomatic DVT in geriatrics was then scored from the clinical risk factors identified using multivariate analysis. This score is defined by the sum of the odds ratio (OR) of each risk factor present. RESULTS: Six factors were identified as independently related to the development of DVT: restriction of mobility (from OR=1.73, limited mobility without immobilization, to OR=5.64, bedridden during <15 days), aged 75 and older (OR=1.5/10 years), history of DVT or pulmonary embolism (OR=3.38), acute heart failure (OR=2.52), chronic edema of the lower limbs (OR=2.51), and paresis or paralysis of a lower limb (OR=2.06). The defined score of 8 or higher corresponded to an 88.7% probability of having symptomatic DVT. CONCLUSION: Treatments to prevent symptomatic DVT in hospitalized elderly should be evaluated on patients with these factors.

Age Factors↗

PubMed2003

Involvement of the neurotensin receptor-3 in the neurotensin-induced migration of human microglia.

Microglia motility plays a crucial role in response to lesion or exocytotoxic damage of the cerebral tissue. We used two in vitro assays, a wound-healing model and a chemotaxis assay, to show that the neuropeptide neurotensin elicited the migration of the human microglial cell line C13NJ by a mechanism dependent on both phosphatidylinositol 3-kinase (PI 3-kinase) and mitogen-activated protein (MAP) kinase pathways. The effect of neurotensin on cell migration was blocked by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. We demonstrate, by using RT-PCR, photoaffinity labeling, and Western blot analysis, that the type I neurotensin receptor-3 was the only known neurotensin receptor expressed in these microglial cells and that its activation led to the phosphorylation of both extracellular signal-regulating kinases 1/2 and Akt. Furthermore, the effect of neurotensin on cell migration was preceded by a profound modification of the F-actin cytoskeleton, particularly by the rapid formation of numerous cell filopodia. Both the motility and the filopodia appearance induced by neurotensin were totally blocked by selective inhibitors of MAP kinases or PI 3-kinase pathways. This demonstrates that the neurotensin receptor-3 is functional and mediates the migratory actions of neurotensin.

Actin Cytoskeleton↗

PubMed2003

In vivo and in vitro neurotoxicity of the human prion protein (PrP) fragment P118-135 independently of PrP expression.

We recently demonstrated that the 118-135 putative transmembrane domain of prion protein (PrP) exhibited membrane fusogenic properties and induced apoptotic neuronal cell death of rat cortical neurons, independently of its aggregation state. The aim of the present study was to analyze the in vivo neurotoxicity of the prion fragment P118-135 and to evaluate the potential role of the physiological isoform of PrP in the P118-135-induced cell death. Here, we demonstrate that the nonfibrillar P118-135 is cytotoxic to retinal neurons in vivo as monitored by intravitreal inoculation and recording of the electrical activity of retina and tissue examination. Moreover, knock-out PrP gene mice exhibit similar sensitivity to the nonfibrillar P118-135-induced cell death and electrical perturbations, strongly suggesting that cell death occurs independently of PrP expression. Interestingly, a variant nonfusogenic P118-135 peptide (termed P118-135theta) had no effects on in vivo neuronal viability, suggesting that the P118-135-induced cell death is mediated by its membrane destabilizing properties. These data have further been confirmed in vitro. We show that the fusogenic peptide P118-135 induces death of cultured neurons from both wild-type and knock-out PrP gene mice via an apoptotic-mediated pathway, involving early caspase activation and DNA fragmentation. Altogether these results emphasize the neurotoxicity of the fusogenic nonfibrillar PrP transmembrane domain and indicate that fibril formation and PrP expression are not obligatory requirements for neuronal cell death. The use of synthetic prion peptides could provide insights into the understanding of neuronal loss mechanisms that take place during the development of the various types of spongiform encephalopathies.

Animals↗

PubMed2002

Shedding of the luminal domain of the neurotensin receptor-3/sortilin in the HT29 cell line.

The neurotensin (NT) receptor-3/sortilin (NTR3) belongs to the new receptor family of VPS10P domain containing receptors. The NTR3 is expressed in all cancer cells on which NT activates cell growth and its cellular location is mainly intracellular within the endoplasmic reticulum and the trans-Golgi network. However, the NTR3 is also present at the cell surface of the HT29 cell line from which it is released by a mechanism activated by phorbol 12-myristate 13-acetate (PMA). The shedding of the NTR3 is sensitive to protein kinase C (PKC) and mitogen-activated protein (MAP) kinase inhibitors and to 1,10-phenanthroline and BB3103, suggesting the activation of zinc-metalloproteases and the ADAM10 (a desintegrin and metalloprotease). The shedding of the membrane NTR3 leads to a soluble protein able to bind exogenous NT, suggesting a role of this process in the biological activity of the peptide.

Adaptor Proteins, Vesicular Transport↗

PubMed2002

Beta-arrestin is involved in the desensitization but not in the internalization of the somatostatin receptor 2A expressed in CHO cells.

The interaction of beta-arrestin-1 with the somatostatin receptor type 2A (sst2A) was monitored using both biochemical and confocal imaging approaches. We show that, using transient transfection of either beta-arrestin-1 or its dominant negative Delta-arrestin-1 in CHO cells stably transfected with the sst2A, beta-arrestin-1 is colocalized with the receptor in endosomal vesicles after somatostatin-induced sequestration. However, this interaction leads to a role of beta-arrestin-1 in the desensitization of the sst2A rather than in the internalization process of the receptor-ligand complex.

Animals↗

PubMed2002

Recycling ability of the mouse and the human neurotensin type 2 receptors depends on a single tyrosine residue.

Receptor recycling plays a key role in the modulation of cellular responses to extracellular signals. The purpose of this work was to identify residues in G-protein coupled neurotensin receptors that are directly involved in recycling. Both the high affinity receptor-1 (NTR1) and the levocabastine-sensitive NTR2 are internalized after neurotensin binding. Here, we show that only the mouse NTR2 recycled to the plasma membrane, whereas the rat NTR1 and the human NTR2 did not. Using site-directed mutagenesis, we demonstrate that tyrosine 237 in the third intracellular loop is crucial for recycling of the mouse NTR2. We show that the mouse NTR2 is phosphorylated on tyrosine residues by NT. This phosphorylation is essential for receptor recycling since the tyrosine kinase inhibitor genistein blocks this process. The absence of recycling observed with the human NTR2 could be completely explained by the presence of a cysteine instead of a tyrosine in position 237. Indeed, substitution of this cysteine by a tyrosine gave a mutant receptor that has acquired the ability to recycle to the cell surface after neurotensin-induced internalization. This work demonstrates that a single tyrosine residue in the third intracellular loop of a G-protein-coupled receptor is responsible for receptor phosphorylation and represents an essential structural element for receptor recycling.

Amino Acid Sequence↗