Biomedical subjects

E Dicou

Publications and source records attributed to E Dicou.

At least 19 recordsLinked to original sources

PubMed2001

Neuroprotective effects of leptin in vivo and in vitro.

The present study explored the efficacy of leptin in protecting against in vivo induction of excitotoxic lesions by the glutamatergic analogue ibotenate injected into the developing mouse brain and against in vitro NMDA-induced cell death in primary neuronal cultures. Ibotenate injected intracerebrally (i.c.) to mice on postnatal day 5 produced transcortical necrosis and white matter cysts. Co-treatment with leptin administered i.c. or i.p. reduced ibotenate-induced cortical lesions and white matter cysts by 50%. in vitro, leptin afforded significant neuroprotection of mouse cortical neurons against NMDA cytotoxicity. The neuroprotective effect of leptin was antagonized both in vivo and in vitro by the Jak2 inhibitor AG490, indicating that it was mediated via the leptin receptor and Jak2 activation. These findings are the first evidence for a role of leptin in neuroprotection.

Animals↗

PubMed2000

Characterization and visualization of [125I] stromal cell-derived factor-1alpha binding to CXCR4 receptors in rat brain and human neuroblastoma cells.

Stromal cell-Derived Factor-1 (SDF-1alpha), binds to the seven-transmembrane G protein-coupled CXCR4 receptor and modulates cell migration, differentiation, and proliferation. CXCR4 has been reported to be expressed in various tissues including brain. Moreover, CXCR4 has recently been shown to be one of the coreceptors for HIV-1 infection which could be implicated in HIV encephalitis. In the present study, the binding properties and autoradiographic distribution of [125I]SDF-1alpha binding to CXCR4 were characterized in the adult rat brain. SDF-1alpha binding and CXCR4 coupling system were also studied in human neuroblastoma cell line SK-N-SH. The binding of [125I]SDF-1alpha on rat brain sections was specific, time-dependent and reversible. The highest densities of CXCR4 were detected in the choroid plexus of the lateral and the dorsal third ventricle. Lower densities of [125I]SDF-1alpha binding sites were observed in various brain regions including cerebral cortex, anterior olfactory nuclei, hippocampal formation, thalamic nuclei, blood vessels and pituitary gland. In the choroid plexus, the IC(50) and K(d) of [125I]SDF-1alpha binding were respectively 0.6 nM and 0. 36 nM. Similar IC(50) values were obtained in other brain structures. A CXCR4 antagonist, bicyclam, competed with SDF-1alpha binding (30% inhibition at 10(-6) M). In SK-N-SH cells, [125I]SDF-1alpha bound to CXCR4 with a K(d) of 5.0 nM and a maximal binding capacity of 460 fmol/mg of protein. SDF-1alpha induced a rapid and transient intracellular calcium increase in SK-N-SH cells. These findings suggest that CXCR4 is highly expressed in some brain structures and have a regulatory role in the nervous system. The significance of this expression in the brain parenchyma and more specifically in the choroid plexus remains to be clarified in the normal as well as in the infected brain.

Animals↗

PubMed1997

Two peptides derived from the nerve growth factor precursor enhance cholinergic enzyme activities in vivo.

LIP1, a 29-amino acid (aa) peptide, and LIP2, a 38aa peptide, corresponding to sequences within the nerve growth factor (NGF) precursor that are flanked by basic amino acid processing sites, were shown to be present in the rat intestine and to induce in PC12 cells several early cellular events, such as F-actin rearrangement and tyrosine phosphorylation of the Trk protein. In this report, we provide evidence that the two propeptides can affect cholinergic enzyme activities in vivo. Intracerebroventricular injections of LIP1 or LIP2 in neonatal hypothyroid rats significantly increased choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in forebrain regions with an apparent regional specificity. Moreover, antibodies against LIP1 or LIP2 injected intracerebroventricularly in neonatal rats significantly decreased ChAT and AChE in the same regions of the brain. These data suggest a physiological role for the two propeptides derived from the proNGF in the development of forebrain cholinergic neurons.

Acetylcholinesterase↗

PubMed1997

Characterization of nerve growth factor precursor protein expression in rat round spermatids and the trophic effects of nerve growth factor in the maintenance of Sertoli cell viability.

Nerve growth factor (NGF) is expressed by rat round spermatids and is thought to participate in the paracrine regulation of spermatogenesis. In order to elucidate the role of NGF in the rat testis, we further characterized the NGF immunoreactive protein secreted by round spermatids and examined the effect of NGF beta and related neurotrophin family members on the maintenance of Sertoli cell viability. Round spermatids were isolated from rat testes by centrifugal elutriation and the conditioned medium dialyzed/concentrated for the preparation of round spermatid protein (RSP). Immunoblot analysis of RSP with anti-NGF beta antibody identified two immunoreactive bands of 31 and 22 kD, whereas the 13 kD mature form of NGF beta was not observed. Similarly, immunoblot analysis of RSP with an antibody raised against a synthetic peptide (L38) corresponding to the -3 to -40 sequence of proNGF also recognized two immunoreactive bands of 31 and 22 kD. These results are consistent with the identification of two NGF precursors. Interestingly, immunoblot analysis of RSP with an antibody raised against a synthetic peptide (N4) corresponding to the -71 to -46 sequence of proNGF only recognized one immunoreactive band of 31 kD, consistent with the larger NGF precursor observed with the L38 antibody. In a bioactivity test of PC-12 neurite outgrowth, the 31 kD NGF precursor induced flattening and neurite outgrowth of PC-12 cells, consistent with NGF bioactivity. The 22 kD NGF precursor induced modest and inconsistent neurite outgrowth. These results suggest that round spermatids express the 31 and 22 kD precursor forms of the NGF gene product, and that processing of this gene product is incomplete such that the 13 kD mature form of NGF beta is not observed. In view of the role of round spermatids in the paracrine regulation of spermatogenesis, we examined the effect of RSP on the rescue of the viability of Sertoli cells cultured under serum deprived conditions. In the absence of serum, RSP was able to extend the viability of Sertoli cells, and the elimination of this activity by anti-NGF antibody immunoprecipitation of RSP suggests that the NGF precursors in RSP support the maintenance of Sertoli cell viability. In addition, treatment with exogenous NGF beta was able to rescue Sertoli cell viability, whereas L38 peptide, N4 peptide, or the neurotrophins, brain derived neurotrophic factor, neurotrophin-3 and neurotrophin-4/5 were unable to rescue Sertoli cell viability above control levels. Hence, it appears that round spermatids express the precursor forms of the NGF gene product, but not the mature form of NGF beta, and that the NGF beta moiety of the NGF precursor proteins exhibits trophic activity in the rescue of Sertoli cell viability, consistent with the paracrine regulation of spermatogenesis.

Animals↗

PubMed1997

Two peptides derived from the nerve growth factor precursor are biologically active.

This report provides evidence that the proregion of the NGF precursor protein contains two novel bioactive peptides. The presence of pairs of basic amino acid (aa) residues in the NGF proregion suggests that two or three peptides other than NGF may be generated by proteolytic cleavage. Synthetic peptides of 29 aa (LIP1) and 38aa (LIP2) corresponding to the sequences -71 to -43 and -40 to -3 of the proNGF, respectively, were used in this study. ELISA specific for these two peptides revealed their presence in the rat intestine. LIP1 was localized by immunohistochemistry in endocrine cells of the intestinal epithelium, and LIP2 was immunoprecipitated from an intestinal extract. We also provide evidence for the presence of specific receptors for LIP2 in several cell lines. Scatchard analysis indicated the presence of a low affinity binding site with a Kd of approximately 10(-7) M and a high affinity binding site of 10(-9) M. Cross-linking studies revealed receptor forms of about 140 kD and 93 kD in a prostatic adenocarcinoma cell line. LIP1 and LIP2 induced rapid F-actin redistribution in PC12 cells within 2 min of incubation, which suggests a role of LIP1 and LIP2 in the process of neurite outgrowth. Furthermore, both propeptides induced rapid tyrosine phosphorylation of the Trk protein in both prostatic adenocarcinoma cells and PC12 cells, thus implicating trk in their mechanism of action. These results support our hypothesis that two peptides within the NGF precursor protein are biologically active.

Actins↗

PubMed1997

Evidence that natural autoantibodies against the nerve growth factor (NGF) may be potential carriers of NGF.

Nerve growth factor (NGF) was detected by enzyme-linked immunosorbent assay using the monoclonal anti-NGF antibody 27/21 in natural NGF autoantibodies (NGF NA) purified from sera of control human subjects as well as from sera of patients with rheumatoid arthritis, autoimmune thyroiditis and to a lesser degree in patients with systemic lupus erythematosus as well as in NGF NA from the synovial fluid of patients with spondylarthropathies. Our results suggest that NGF NA may be potential carriers of NGF in the circulation.

Adult↗

PubMed1997

Anti-NGF autoantibodies and NGF in sera of Alzheimer patients and in normal subjects in relation to age.

It has been suggested that inflammation may be a possible cause of Alzheimer's disease (AD). Increased anti-NGF autoantibody levels and increased NGF frequency in serum have previously been associated with inflammatory responses. In this study no changes in anti-NGF autoantibody titers or in NGF frequency were detected in sera of AD patients, suggesting that they are not involved in the neuroimmunological mechanisms underlying AD. There were neither age-associated changes in NGF frequency in sera of four groups of normal subjects between 18-91 years of age. In contrast, anti-NGF autoantibodies were significantly increased in sera of the 31-45 yr age group.

Adolescent↗

PubMed1996

Regulation of NGF, BDNF and LNGFR gene expression in ROS 17/2.8 cells.

The secosteroid hormone 1.25-dihydroxyvitamin D3 (1,25(OH)2D3) has been recently shown to enhance the synthesis of NGF to mouse L929 fibroblasts. In view of the critical role of 1,25(OH)2D3 on bone metabolism, it has been investigated if ROS 17/2.8 osteoblastic cells were able to express the nerve growth factor (NGF) gene and if this process was responsive to 1,25(OH)2D3. Results indicate that these cells respond in a dose-dependent manner to the presence of 1,25(OH)2D3 by an increase in NGF mRNA levels. However, the phorbol ester PMA, previously reported to augment the synthesis of NGF via the recruitment of AP-1 complexes, depressed the expression of the NGF gene in ROS cells. In contrast, the mRNA levels of an NGF-related trophic factor, brain-derived neurotrophic factor (BDNF), was increased by PMA but not following 1,25(OH)2D3 treatment. Binding of 125I-NGF to ROS cells displayed the properties of a low affinity NGF receptor (dissociation constant Kd approximately 10(-9) M). In agreement with this result, the mRNA encoding the low affinity NGF receptor (LNGFR) was detected in ROS 17/2.8 cells, unlike trkA transcripts which encode the high affinity receptor. These data suggest that neurotrophins and their low affinity receptor could play an unsuspected role in bone tissue.

Animals↗

PubMed1996

Nerve growth factor (NGF) autoantibodies and NGF in the synovial fluid: implications in spondylarthropathies.

We investigated the presence of nerve growth factor (NGF) autoantibodies and NGF in the synovial fluid (SF) of patients with different forms of chronic arthritis such as spondylarthropathy (SpA), rheumatoid arthritis (RA), calcium pyrophosphate dihydrate crystal deposition disease (CPPD) and osteoarthritis (OA) and compared them to their levels in serum. NGF autoantibodies were detected by ELISA and by their capacity to immunoprecipitate NGF and to inhibit its biological activity. NGF was measured with a two-site enzyme-linked immunosorbent assay. Significantly high NGF autoantibody levels (p < 10(-4)) and high frequency of detectable NGF (p < 0.01) were observed in the SF of SpA patients and to a lesser degree in RA patients as compared to CPPD and OA patients. In the serum high frequency of detectable NGF was observed only in RA patients. These results suggest a role of NGF autoantibodies and NGF in joint inflammation especially in spondylarthropathies.

Adolescent↗

PubMed1995

Presence of nerve growth factor and its receptors in an in vitro model of islet cell development: implication in normal islet morphogenesis.

In vivo, the differentiation of pancreatic islet stem cells depends on unknown soluble factors produced by the mesenchyme surrounding these cells. We have previously demonstrated that, like some neuronal cells, different beta-cell lines express functional nerve growth factor (NGF) receptors and can respond to NGF by extending neurite-like processes. NGF receptors are also expressed in vivo in mature rat islets and early during development in pancreatic ductular cells, which represent putative beta-stem cells. In this study, we have further characterized an in vitro model of islet development and studied the expression of NGF receptors and its ligand in this model. We have demonstrated the expression of Trk-A messenger RNA coding for the high affinity NGF receptor in islet cells and the localization of Trk protein in both alpha- and beta-islet cells. Moreover, the cells, from which islet cells "bud," also express Trk-A. Furthermore, NGF is produced and secreted by the nonendocrine cells surrounding the islets, suggesting a possible paracrine mode of action of NGF on the adjacent islet cells. Finally, islet morphogenesis is significantly retarded in the presence of K252a, an inhibitor of the tyrosine kinase activity of the family of Trk receptors, suggesting an implication of the neurotrophin-neurotrophin receptor axis in islet development.

Animals↗

PubMed1994

NGF involvement in ocular inflammation: secretion by rat resident retinal cells.

Nerve growth factor (NGF) has been reported to be involved in immune and inflammatory reactions. We provide evidence that NGF may play a role in ocular immune responses. Experimental autoimmune uveoretinitis (EAU) causes ocular inflammation in susceptible (Lewis, Lew x Brown-Norway (BN) F1 hybrid) but not in resistant or poorly susceptible BN and Long Evans rat strains. We examined NGF production by two resident ocular cell types, retinal Müller glia (RMG) and retinal pigmented epithelium (RPE). Interferon-gamma (IFN-gamma) or lipopolysaccharide (LPS) alone had no effect on NGF production while combined treatment with IFN-gamma and LPS strongly stimulated NGF secretion by both RMG and RPE cells. Furthermore, NGF secretion correlated with the degree of susceptibility to EAU of the different rat strains. RMG and RPE cells isolated from susceptible rats secrete high NGF levels while cells from resistant rats secrete low NGF levels.

Animals↗

PubMed1993

Increased frequency of NGF in sera of rheumatoid arthritis and systemic lupus erythematosus patients.

Nerve growth factor (NGF) levels were measured by a two-site enzyme-linked immunosorbent assay (ELISA) in sera of patients with three autoimmune diseases, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and thyroiditis. Serum NGF levels were variable (15 pg ml(-1)-1.6 ng ml-1) but not significantly different among these groups compared with control subjects. However the frequency of detectable circulating NGF was significantly higher in RA and SLE patients but not in thyroiditis patients compared with controls. The present data provides evidence for NGF involvement in two autoimmune rheumatic diseases and suggests a possible differential role of NGF as immunomodulatory agent in systemic versus certain organ-specific autoimmune diseases.

Adolescent↗

PubMed1993

Natural autoantibodies against the nerve growth factor in autoimmune diseases.

High titers of natural autoantibodies against the nerve growth factor (NGF) were detected in the sera of patients with systemic lupus erythematosus, autoimmune thyroiditis and rheumatoid arthritis. Autoantibodies to NGF from these pathological cases displayed higher avidity for NGF and a higher polyreactivity with certain cytoskeletal proteins and with DNA as compared to those from control human subjects. The biological activity, immunoglobulin composition and physiological relevance of these autoantibodies are discussed.

Antibody Specificity↗

PubMed1993

Patterns of nerve growth factor (NGF), proNGF, and p75 NGF receptor expression in the rat incisor: comparison with expression in the molar.

Nerve growth factor (NGF), a target-derived neurotrophic substance, may have broader biological functions in various types of non-neuronal differentiating cells. The effects of NGF are dependent on initial binding of NGF to specific cell-surface receptors (p75NGFR and p140prototrk) on responsive cells. The continuously growing rat incisor offers an excellent model demonstrating defined territories of differentiation of specific cell populations. We used immunohistochemistry to determine sites of NGF, proNGF and p75NGFR accumulation in the rat incisor, whereas NGF mRNA expression was visualized by in situ hybridization in the developing rat molar and incisor. Strictly similar patterns of NGF mRNA, proNGF and NGF expression were observed in differentiating cells responsible for the production of the main structural matrices of the tooth. Thus, proNGF-like and NGF-like immunoreactivity, as well as the NGF mRNA signal were observed in preameloblasts and young ameloblasts of the dental epithelium and in polarizing odontoblasts of the dental mesenchyme. In contrast, the distribution of p75NGFR was correlated with differentiation event only in dental mesenchyme: polarizing odontoblasts expressed p75NGFR whereas the molecule was absent in functional odontoblasts. In dental epithelium, the restricted expression of p75NGFR in ameloblast precursor cells was correlated with proliferative phenomena. The patterns of proNGF, NGF and p75NGFR expression in epithelium and mesenchyme implicate both an autocrine and paracrine mode of action of the NGF molecule in dental tissues. The findings reported here are important for understanding NGF action in specific dental cell populations and suggest that this molecule is involved in the cascade of events that directs tooth development.

Animals↗

PubMed1992

Nerve growth factor precursors in the rat thyroid and hippocampus.

A nerve growth factor (NGF) precursor form of about 24 kDa was identified in homogenates of rat thyroid and hippocampus by immunoprecipitation using three sera raised against a synthetic peptide that reproduces the sequence -71 to -46 of the proNGF molecule. Besides this species, a 31 kDa protein, as well as a cleavage product of 12 kDa were also immunoprecipitated in both tissues by one of these sera.

Animals↗

PubMed1992

Expression of recombinant human nerve growth factor in Escherichia coli.

Nerve growth factor (NGF) is a neurotrophic factor for basal forebrain cholinergic neurons and may be of benefit in neurodegenerative diseases of humans. A method is described to obtain significant amounts of biologically active recombinant human NGF (rhNGF) in one step. RhNGF was expressed in E. coli and the majority of the protein accumulated in inclusion bodies. It was immunoprecipitated by a serum against mouse NGF. Solubilization of the inclusion bodies was done in 3M guanidine HCl and renaturation was effected by dilution and air oxidation in the presence of 6 microM CuSO4. Recoveries were 10-12 micrograms of rhNGF per ml of bacterial suspension. Its biological activity was tested in a bioassay system employing sympathetic chick embryo ganglia and was inhibited by the monoclonal antibody 27/21 against mouse NGF.

Animals↗

PubMed1992

Immunohistochemical localization of nerve growth factor (NGF) and NGF receptor (NGF-R) in the developing first molar tooth of the rat.

Nerve growth factor (NGF) is a well established target-derived trophic factor supporting sympathetic and sensory innervation in the peripheral tissues as well as cholinergic innervation in the brain. Despite its name, NGF may have broader biological functions early in development in a wide range of non-neuronal differentiating cells. The many effects of NGF are directly dependent on initial binding of NGF to specific plasma membrane receptors on target cells. Here we use immunohistochemical methods to show that NGF and its receptor (NGF-R) are localized in a variety of embryonic epithelial and mesenchymal cells in the rat developing molar tooth. Dental cells known to play important roles in morphogenesis and inductive tissue interactions show NGF-like reactivity. Thus, labelling is seen in epithelial preameloblasts and mesenchymal odontoblasts. We also show a transient expression of NGF-R in restricted parts of the dental epithelium (inner dental epithelium) and dental mesenchyme differentiating cells (post-mitotic, polarizing odontoblasts). The expression patterns of NGF are different to those of NGF-R during embryogenesis and this is illustrated in detail in the developing tooth. The histochemical findings reported here support the notion that NGF may have multiple roles during morphogenetic and cytodifferentiation events in the tooth.

Animals↗

PubMed1992

Expression of nerve growth factor and nerve growth factor receptor genes in human tissues and in prostatic adenocarcinoma cell lines.

Nerve growth factor (NGF) mRNAs were detected and quantified in a variety of normal and neoplastic human tissues by northern blot hybridization. Human heart contained the highest NGF mRNA levels, whereas lower but comparable levels were found in the placenta, prostate, and kidney. All tissues examined coexpressed the low-affinity NGF receptor (LNGFR), whereas none of these tissues expressed the high-affinity NGF receptor encoded by the trk protooncogene. The widespread distribution of the LNGFR suggests that it plays a role in the regulation of normal cell growth. No overexpression of NGF or LNGFR mRNA was detected in neoplastic tissues, whereas LNGFR-like immunoreactivity was localized outside of tumor cells. Transforming growth factor-alpha and protooncogene c-fos expression in these tissues did not show a systematic correlation with NGF/LNGFR expression. Furthermore, regulation of the human NGF gene was studied in DU145 cells, a prostatic adenocarcinoma cell line that synthesizes significant NGF mRNA levels. Serum induced, whereas dexamethasone inhibited, NGF mRNA synthesis in these cells. Serum induction was preceded by a rapid and transient activation of the c-fos protooncogene.

Adenocarcinoma↗