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Biomedical subjects

C Devaux

Publications and source records attributed to C Devaux.

At least 19 recordsLinked to original sources
PubMed2001

Disulfide bridge reorganization induced by proline mutations in maurotoxin.

Maurotoxin (MTX) is a 34-residue toxin that has been isolated from the venom of the chactidae scorpion Scorpio maurus palmatus, and characterized. Together with Pi1 and HsTx1, MTX belongs to a family of short-chain four-disulfide-bridged scorpion toxins acting on potassium channels. However, contrary to other members of this family, MTX exhibits an uncommon disulfide bridge organization of the type C1-C5, C2-C6, C3-C4 and C7-C8, versus C1-C5, C2-C6, C3-C7 and C4-C8 for both Pi1 and HsTx1. Here, we report that the substitution of MTX proline residues located at positions 12 and/or 20, adjacent to C3 (Cys(13)) and C4 (Cys(19)), results in conventional Pi1- and HsTx1-like arrangement of the half-cystine pairings. In this case, this novel disulfide bridge arrangement is without obvious incidence on the overall three-dimensional structure of the toxin. Pharmacological assays of this structural analog, [A(12),A(20)]MTX, reveal that the blocking activities on Shaker B and rat Kv1.2 channels remain potent whereas the peptide becomes inactive on rat Kv1.3. These data indicate, for the first time, that discrete point mutations in MTX can result in a marked reorganization of the half-cystine pairings, accompanied with a novel pharmacological profile for the analog.

Amino Acid Sequence↗
PubMed2001

In vivo neurotoxicity of Androctonus australis hector scorpion venom: evidence that the supra-thoracic nervous system is not implicated in the clinical manifestations.

The severity of scorpion stings is related to the highly active neurotoxins in the venom. In this study, rats whose supra-spinal central nervous system was deprived of its peripheral connections were experimentally poisoned by the venom of Androctonus australis hector scorpion. Clinical signs of severity were not modified when the rats had previously undergone high medullar section. These results suggest that the supra-thoracic nervous system is not implicated in the neurotoxicity manifestations of scorpion envenomation.

Animals↗
PubMed2001

Construction and functional evaluation of a single-chain antibody fragment that neutralizes toxin AahI from the venom of the scorpion Androctonus australis hector.

9C2 is a murine monoclonal IgG that participates in the neutralization of Androctonus australis hector scorpion venom. It recognizes AahI and AahIII, two of the three main neurotoxins responsible for almost all the toxicity of the venom when injected into mammals. Using PCR we cloned the antibody variable region coding genes from 9C2 hybridoma cells and constructed a gene encoding a single-chain antibody variable fragment molecule (scFv). This scFv was produced in the periplasm of Escherichia coli in a soluble and functional form and purified in a single step using protein L-agarose beads yielding 1-2 mg.L(-1) of bacterial culture. scFv9C2 was predominantly monomeric but also tended to form dimeric and oligomeric structures, all capable of binding toxin AahI. The affinity of scFv and the parental mAb for toxin AahI and homologous toxin AahIII was of the same magnitude, in the nanomolar range. Similarly, purified forms of scFv9C2 completely inhibited the binding of toxin AahI to rat brain synaptosomes. Finally, scFv9C2 was efficient in protecting mice against the toxic effects of AahI after injection of the toxin and scFv to mice by the intracerebroventricular route in a molar ratio as low as 0.36 : 1. Thus, we produced a recombinant scFv that reproduces the recognition properties of the parent antibody and neutralizes the scorpion neurotoxin AahI, thereby opening new prospects for the treatment of envenomation.

Amino Acid Sequence↗
PubMed2000

Maurotoxin versus Pi1/HsTx1 scorpion toxins. Toward new insights in the understanding of their distinct disulfide bridge patterns.

Maurotoxin (MTX) is a scorpion toxin acting on several K(+) channel subtypes. It is a 34-residue peptide cross-linked by four disulfide bridges that are in an "uncommon" arrangement of the type C1-C5, C2-C6, C3-C4, and C7-C8 (versus C1-C5, C2-C6, C3-C7, and C4-C8 for Pi1 or HsTx1, two MTX-related scorpion toxins). We report here that a single mutation in MTX, in either position 15 or 33, resulted in a shift from the MTX toward the Pi1/HsTx1 disulfide bridge pattern. This shift is accompanied by structural and pharmacological changes of the peptide without altering the general alpha/beta scaffold of scorpion toxins.

Amino Acid Sequence↗
PubMed2000

Modulation of adenosine concentration by opioid receptor agonists in rat striatum.

There is evidence that adenosine and morphine interact in the striatum. However, little is known about the precise role of the opioid receptor subtypes implicated in the modulation of adenosine tissue concentration and in adenosine receptor expression and function. We sought to evaluate, in the absence of withdrawal symptoms, the effects of the short-term administration of selective mu-, delta- or kappa-opioid receptor agonists on adenosine concentration and on adenosine A(2A) receptor function in rat striatum. Adenosine A(2A) receptor was chosen because the neuronal sub-population expressing this receptor coexpresses enkephalin, suggesting that adenosine A(2A) receptor may be regulated by opioid receptor agonists. Oxymorphone hydrochloride mu-opioid receptor agonist, 6 mg/kg/day), +[-(5 alpha,7 alpha, 8 beta)-(-)-N-methyl-N(7-(1-pyrrolidinyl)1-oxaspiro (4.5)dec-8-yl) benzenacetamide] (U69593) (kappa-opioid receptor agonist, 0.75 mg/kg/day), and (+)-4[(alpha R)-alpha-((2S,5R)-4-allyl-2, 5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide) (SNC80) (delta-opioid receptor agonist, 9 mm/kg/day), or vehicle, were administered i.p 3 x daily during 5 days to groups of rats (n=6). We also investigated the effects of opioid receptor agonists on adenosine uptake by striatal cell extracts. We found that administration of mu- or delta-opioid receptor agonists significantly decreased adenosine uptake in striatal cell extracts and increased adenosine concentration (mean+24% and +45% for mu- and delta-opioid receptor agonist, respectively, relative to controls). None of the receptor agonists tested induced obvious modifications of adenosine A(2A) receptor function. However, the delta-opioid receptor agonist induced an increase in adenosine A(2A) mRNA expression (mean 44%). We conclude that mu and delta receptor agonists inhibit adenosine uptake by striatal cell extracts and increase adenosine concentrations in rat striatum.

Adenosine↗
PubMed2000

Hemodynamic stresses induce endothelial dysfunction and remodeling of pulmonary artery in experimental compensated heart failure.

BACKGROUND: We hypothesized that, in compensated heart failure (HF), hemodynamic perturbations and their consequences exist in pulmonary artery (PA) despite the absence of any perturbation in thoracic aorta (TA). METHODS AND RESULTS: The left coronary artery was ligated in 20 male Wistar rats with compensated HF. Four months after ligation, these rats were compared with 20 sham-operated control rats. Blood pressure, velocity, viscosity, luminal diameter, and wall tensile and shear stresses were determined in PA and TA. Arterial rings were mounted in a myograph for ex vivo study. Endothelial nitric oxide synthase (eNOS) mRNA expression was determined in lung and aorta. Sections of PA and TA were used for histomorphometric study. In PA from rats with compensated HF, (1) blood pressure and wall tensile stress increased, whereas blood velocity and wall shear stress decreased; (2) contractions to KCl were not altered, but maximal contraction to phenylephrine and EC(50) decreased; (3) endothelium-dependent relaxation to acetylcholine and basal NO activity were blunted, whereas endothelium-independent relaxation was preserved; (4) eNOS mRNA levels and eNOS transcription in lung nuclei decreased; and (5) medial cross-sectional area, thickness, smooth muscle cell number, elastin, and collagen contents increased. Conversely, no such changes were found in TA from rats with compensated HF. CONCLUSIONS: In compensated HF induced by small myocardial infarction, hemodynamics, vascular wall function, and structure are altered in PA but preserved in TA. These results indicate that the pulmonary vascular bed is an early target of regional circulatory alterations in HF.

Animals↗
PubMed2000

Plasma beta-endorphin and adenosine concentration in pulmonary hypertension.

To determine whether beta-endorphin plays a role in the regulation of pulmonary vascular tone in patients with pulmonary hypertension, we investigated the relations between hemodynamics and beta-endorphin and adenosine concentrations in 3 clinical situations: (1) normal hemodynamics (7 subjects, mean pulmonary artery [PA] pressure 18.5 +/- 1 mm Hg); (2) moderate pulmonary hypertension secondary to chronic obstructive pulmonary disease (COPD) (8 patients, mean PA pressure 31 +/- 3 mm Hg); and (3) severe primary pulmonary hypertension (PPH) (8 patients, mean PA pressure 70 +/-5 mm Hg). Plasma beta-endorphin and adenosine were measured in a distal PA and in the femoral artery in room air and during oxygen inhalation. Beta-endorphin levels were similar in the pulmonary and systemic circulations. No difference was observed between patients with COPD and PPH, but relative to controls, both had significantly higher beta-endorphin levels. Pulmonary adenosine was significantly lower in patients with pulmonary hypertension than in controls (-60% in COPD [p <0.005] and -70% in PPH [p <0.001]). Pure oxygen administration significantly decreased adenosine and beta-endorphin levels, much more so in patients with COPD and PPH. We found a negative correlation between beta-endorphin and adenosine concentrations (r = -0.751, p <0.001): the higher the adenosine, the lower the beta-endorphin level. These observations suggest that because adenosine release by pulmonary vascular endothelium is reduced in pulmonary hypertension, the resulting worsened hypoperfusion and tissue oxygenation may cause increased beta-endorphin release.

Adenosine↗
PubMed2000

Caspase-dependent apoptosis of cells expressing the chemokine receptor CXCR4 is induced by cell membrane-associated human immunodeficiency virus type 1 envelope glycoprotein (gp120).

Human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins interact with CD4 and chemokine receptors on T cells to deliver signals that trigger either activation, anergy, or apoptosis. However, the molecular mechanisms driving these responses remain poorly understood. In this study we demonstrate that apoptosis is induced upon HIV-1 envelope binding to the chemokine receptor CXCR4. Cells expressing a mutant form of CXCR4 with a C-terminal deletion were also sensitive to HIV-1 envelope-mediated apoptosis, indicating that the cytoplasmic tail of CXCR4 is not required to induce the apoptotic pathway. The specificity of this process was analyzed using several inhibitors of gp120-CD4-CXCR4 interaction. Monoclonal antibodies directed against the gp120-binding site on CD4 (ST4) and against CXCR4 (MAB173) prevented the apoptotic signal in a dose-dependent manner. The cell death program was also inhibited by SDF-1alpha, the natural ligand of CXCR4, and by suramin, a G protein inhibitor that binds with a high affinity to the V3 loop of HIV-1 gp120 envelope protein. These results highlight the role played by gp120-binding on CXCR4 to trigger programmed cell death. Next, we investigated the intracellular signal involved in gp120-induced apoptosis. This cell death program was insensitive to pertussis toxin and did not involve activation of the stress- and apoptosis-related MAP kinases p38(MAPK) and SAPK/JNK but was inhibited by a broad spectrum caspase inhibitor (z-VAD.fmk) and a relatively selective inhibitor of caspase 3 (z-DEVD.fmk). Altogether, our results demonstrate that HIV induces a caspase-dependent apoptotic signaling pathway through CXCR4.

Apoptosis↗
PubMed2000

Molecular cloning of a novel human I-mfa domain-containing protein that differently regulates human T-cell leukemia virus type I and HIV-1 expression.

Regulation of viral genome expression is the result of complex cooperation between viral proteins and host cell factors. We report here the characterization of a novel cellular factor sharing homology with the specific cysteine-rich C-terminal domain of the basic helix-loop-helix repressor protein I-mfa. The synthesis of this new factor, called HIC for Human I-mfa domain-Containing protein, is controlled at the translational level by two different codons, an ATG and an upstream non-ATG translational initiator, allowing the production of two protein isoforms, p32 and p40, respectively. We show that the HIC protein isoforms present different subcellular localizations, p32 being mainly distributed throughout the cytoplasm, whereas p40 is targeted to the nucleolus. Moreover, in trying to understand the function of HIC, we have found that both isoforms stimulate in T-cells the expression of a luciferase reporter gene driven by the human T-cell leukemia virus type I-long terminal repeat in the presence of the viral transactivator Tax. We demonstrate by mutagenesis that the I-mfa-like domain of HIC is involved in this regulation. Finally, we also show that HIC is able to down-regulate the luciferase expression from the human immunodeficiency virus type 1-long terminal repeat induced by the viral transactivator Tat. From these results, we propose that HIC and I-mfa represent two members of a new family of proteins regulating gene expression and characterized by a particular cysteine-rich C-terminal domain.

Amino Acid Sequence↗
PubMed2000

Toxicity during early development of the mouse nervous system of a scorpion neurotoxin active on sodium channels.

The lethal effects of scorpion envenomation is due to neurotoxins active on voltage-sensitive sodium channels. Dysfunctions of the peripheral and central nervous systems with neurological manifestations are commonly observed after scorpion stings, specially in young children. Since the neurotoxicity of venom fraction is greatly higher by intracerebroventricular than by subcutaneous injections, a direct effect of venom on CNS cannot be excluded specially in infants where the blood-brain barrier is not fully functional. We investigated the activity of a neurotoxin from the scorpion Androctonus australis hector (AahII) in newborn mice at 3, 7 and 14 days after birth and in adults. Young mice (P3, P7) were more sensitive to AahII injected subcutaneously than were adults, but were less sensitive to intracerebroventricular injection. The affinity of AahII for its receptor site on brain synaptosomes from P3 and P7 mice was slightly higher and the density of the binding sites was half that of adult mice. After subcutaneous injection of [125I]-AahII it was also observed that a small amount of radioactivity was found in brains of neonate mice but not in that of adults. This amount is however extremely lower than the value of the LD50 determined by intracerebroventricular injection. Results are consistent with a peripheral action of AahII and show that its toxic activity changes during the mouse nervous system development.

Age Factors↗
PubMed2000

Sequence requirement for the nucleolar localization of human I-mfa domain-containing protein (HIC p40).

The human I-mfa domain-containing protein (HIC) mRNA produces two protein isoforms, HIC p32 and p40, synthesized from alternative translational initiations. p32 translation is initiated from a standard AUG codon and p40 is an N-terminal extension of p32 generated from an upstream GUG codon. The two isoforms show different subcellular localization: p32 is distributed throughout the cytoplasm whereas p40 can be found both in the cytoplasm and the nucleolus. To investigate the possibility that p40 contains a nucleolus targeting sequence in its N-terminal region, COS cells were transfected with an eukaryotic expression vector coding for green fluorescent protein (GFP) fused to the p40 N terminus. The localization of this fusion protein in the nucleolus indicated that the N-terminal amino acids of p40 probably contain a nucleolar localization signal (NoLS). To find the structural motifs required for nucleolar localization of p40, deletion mutants were expressed in COS cells as fusion polypeptides with GFP. We defined a domain of 19 amino acids near the N terminus that contains an arginine-rich subdomain that conforms to other known NoLS. To demonstrate that this sequence is an authentic NoLS, the sequence was fused to GFP. This fusion protein was observed to migrate into the nucleolus. Taken together, our studies demonstrate that p40 contains a NoLS.

Amino Acid Motifs↗
PubMed2000

Molecular interactions involved in the transactivation of the human T-cell leukemia virus type 1 promoter mediated by Tax and CREB-2 (ATF-4).

The human T-cell leukemia virus type 1 (HTLV-1) Tax protein activates viral transcription through three 21-bp repeats located in the U3 region of the HTLV-1 long terminal repeat and called Tax-responsive elements (TxREs). Each TxRE contains nucleotide sequences corresponding to imperfect cyclic AMP response elements (CRE). In this study, we demonstrate that the bZIP transcriptional factor CREB-2 is able to bind in vitro to the TxREs and that CREB-2 binding to each of the 21-bp motifs is enhanced by Tax. We also demonstrate that Tax can weakly interact with CREB-2 bound to a cellular palindromic CRE motif such as that found in the somatostatin promoter. Mutagenesis of Tax and CREB-2 demonstrates that both N- and C-terminal domains of Tax and the C-terminal region of CREB-2 are required for direct interaction between the two proteins. In addition, the Tax mutant M47, defective for HTLV-1 activation, is unable to form in vitro a ternary complex with CREB-2 and TxRE. In agreement with recent results suggesting that Tax can recruit the coactivator CREB-binding protein (CBP) on the HTLV-1 promoter, we provide evidence that Tax, CREB-2, and CBP are capable of cooperating to stimulate viral transcription. Taken together, our data highlight the major role played by CREB-2 in Tax-mediated transactivation.

Activating Transcription Factor 2↗
PubMed2000

Overexpression of the reg gene in non-obese diabetic mouse pancreas during active diabetogenesis is restricted to exocrine tissue.

We demonstrated pancreatic reg gene overexpression in non-obese diabetic (NOD) mice during active diabetogenesis. The aim of this study was to determine in which part of the pancreas (endocrine and/or exocrine) the gene(s) and the protein(s) were expressed and if their localization changed with progression of the disease. In situ hybridization analysis and immunocytochemical studies were carried out on pancreas of female and male NOD mice. Both develop insulitis but diabetes develops only in females and in males only when treated by cyclophosphamide. Our results show that whatever the age, sex, and presence of insulitis and/or diabetes, the expression of reg mRNAs and of the corresponding protein(s) was restricted to exocrine tissue. Moreover, reg remains localized in acinar cells in the two opposite situations of (a) cyclophosphamide-treated males in a prediabetic stage presenting a high level of both insulin and reg mRNAs, and (b) the overtly diabetic females with no insulin but a high level of reg mRNA. These findings suggest that overexpression of the reg gene(s) might represent a defense of the acinar cell against pancreatic aggression.

Animals↗
PubMed2000

Evaluation of the potential promoting effect of 60 Hz magnetic fields on N-ethyl-N-nitrosourea induced neurogenic tumors in female F344 rats.

The present study investigated the possible effect of 60 Hz magnetic fields (MFs) as promoters of neurogenic tumors initiated transplacentally by a chemical carcinogen, N-ethyl-N-nitrosourea (ENU). In a preliminary study, 5 mg of ENU was shown to induce 30 to 40% neurogenic tumors in F344 rats offspring after 420 days of observation. In the present study, 400 female rats were divided into eight different groups (50 animals/group) and exposed in utero (on day 18 of gestation) to a single intravenous dose of either Saline (Group I), or ENU, 5 mg/kg (Group II to VIII). Dams in group II were given no further treatment while dams in Groups III to VII were exposed to 5 different intensities of MFs forty eight hours later. Animals in group III were sham exposed (<0.02 microT) while groups IV to VII were exposed to 2, 20, 200, and 2000 microT, respectively. Dams in Group VIII were injected intraperitoneally with 12-O-tetradecanoylphrobol-13-acetate (TPA; 10 micrograms/kg) from day 19 until delivery, and then their female offspring continued to be injected every 15 days, starting at day 14 after birth until sacrifice (positive controls). Accordingly, this study included three different types of controls: Internal controls (Groups II and III) and positive control (Group VIII). Body weight, mortality and clinical observations were evaluated in all groups of animals during in-life exposure. Necropsy was performed on all exposed and control animals that died, were found moribund or sacrificed at termination of the study. Histopathological evaluation was done for all brains, spinal cords, cranial nerves, major organs (lungs, liver, spleen, kidneys, pituitary, thyroid and adrenals) and all gross lesions observed during necropsy. All clinical observations and pathological evaluations were conducted under "blinded" conditions. The findings from this ENU/MFs promotion study clearly demonstrate that, under our defined experimental conditions, exposure to 60 Hz linear (single axis) sinusoidal, continuous wave MFs had no effect on the survival of female F344 rats or on the number of animals bearing neurogenic tumors. These results suggest that MFs have no promoting effect on neurogenic tumors in the female F344 rats exposed transplacentally to ENU.

Animals↗
PubMed1999

Monoclonal antibodies against the Androctonus australis hector scorpion neurotoxin I: characterisation and use for venom neutralisation.

A series of monoclonal antibodies (mAbs) specific for the alpha-neurotoxin I (Aah I) from the venom of the dangerous Androctonus australis hector scorpion were obtained using carrier protein-coupled toxin. Competitive RIA, receptor assays and mouse toxicity tests were performed to characterise mAbs in terms of affinity and neutralisation. Cross-reactivity studies and two-site ELISA results allowed some classification of mAbs into three groups. One mAb, 9C2, was particularly interesting since it recognised the parent toxin I with a K(D) of 0.15 nM and was also reactive with toxins of the same immunological group. Its ability to neutralise the toxic effect of the parent toxin and the venom fraction has been investigated. This anti-Aah I mAb 9C2, associated with anti-Aah II mAb 4C1, provides a valuable tool to neutralise the toxicity of the venom.

Amino Acid Sequence↗
PubMed1999

A new potent HIV-1 reverse transcriptase inhibitor. A synthetic peptide derived from the interface subunit domains.

The biologically relevant and active forms of human immunodeficiency viruses type 1 and 2 reverse transcriptase found in infectious virions are heterodimers produced in a two-step dimerization process. Dimerization involves first the rapid association of the two subunits, followed by a slow conformational change yielding a fully active form. We have shown that the dimeric nature of reverse transcriptase represents a important target for the design of a new class of antiviral agents. In this work, we propose a new strategy for its inhibition by targeting protein/protein interactions during viral formation in infected cells. From the screening of peptides derived from the tryptophan cluster at the interface of the connection subdomain, we have designed a short peptide (10 residues) corresponding to residues 395-404, which can block dimerization of reverse transcriptase in vitro and in infected cells. This peptide is highly efficient in abolishing the production of viral particles, without any adverse toxic side effects, when transduced into human immunodeficiency virus type 1-infected cells together with a new peptide carrier.

Amino Acid Sequence↗