RhoA- and RhoD-dependent regulatory switch of Galpha subunit signaling by PAR-1 receptors in cellular invasion

Thrombin and proteinase-activated receptors (PAR) specifically regulate several functions that markedly enhance the transformation phenotype such as inflammation, cell proliferation, tumor growth, and metastasis. We recently reported that thrombin inhibits cellular invasion induced by src, hepatocyte growth factor (HGF), and leptin in kidney and colonic epithelial cells via predominant activation of the pertussis toxin (PTx) -sensitive G-proteins Galphao/Galphai. We provide pharmacological and biochemical evidence that in the presence of PTx, PAR-1 induced cellular invasion through Galpha12/Galpha13- and RhoA/Rho kinase (ROCK) -dependent signaling. However, inhibition of the endogenous small GTPase RhoA by the C3 exoenzyme, dominant-negative N19-RhoA, activated G26V-RhoD, and activators of the nitric oxide/cGMP pathways conferred invasive activity to PAR-1 via a signaling cascade using Galphaq, phospholipase C (PLC), Ca(2+)/calmodulin myosin light chain kinase (CaM-MLCK), and phosphorylation of MLC. We found that cellular invasion induced by the src oncogene is abrogated by inhibitors of the RhoA/ROCK pathway and is independent of PLC/CaM-MLCK signaling. Our data demonstrate that the RhoA and RhoD small GTPases are acting as a molecular switch of cellular invasion and reveal a novel critical mechanism by which PAR-1 bypass Galphao/i and RhoA inhibition via differential coupling to heterotrimeric G-proteins linked to divergent or convergent biological responses. Our data also indicate that Rho GTPases and ROCK mediate a src-dependent invasion signal in kidney and colonic cancer cells. We conclude that dynamic regulation of Rho GTPases activation and inactivation by oncogenes, growth factors, cGMP-inducing agents, and adhesion molecules can initiate convergent invasion signals controlled by the thrombin PAR-1 in cancer cells.-Nguyen, Q.-D., Faivre, S., Bruyneel, E., Rivat, C., Seto, M., Endo, T., Mareel, M., Emami, S., Gespach, C. RhoA- and RhoD-dependent regulatory switch of Galpha subunit signaling by PAR-1 receptors in cellular invasion.

Long-lasting hyperalgesia induced by fentanyl in rats: preventive effect of ketamine

BACKGROUND

It has been reported that mu-opioid receptor activation leads to a sustained increase in glutamate synaptic effectiveness at the N-methyl-D-aspartate (NMDA) receptor level, a system associated with central hypersensitivity to pain. One hypothesis is that postoperative pain may result partly from the activation of NMDA pain facilitatory processes induced by opiate treatment per se. The authors tested here the effectiveness of the opiate analgesic fentanyl for eliciting a delayed enhancement in pain sensitivity.

METHODS

The consequences of four bolus injections (every 15 min) of fentanyl (20-100 microg/kg per injection, subcutaneously) on immediate (for several hours) and long-term (for several days) sensitivity to nociceptive stimuli in the rat (paw-pressure vocalization test) were evaluated. The effects of the combination of the NMDA-receptor antagonist ketamine (10 mg/kg, subcutaneously) with fentanyl also were assessed.

RESULTS

Fentanyl administration exhibited a biphasic time-dependent effect: first, an early response (for 2-5 h) associated with a marked increase in nociceptive threshold (analgesia), and second, a later response associated with sustained lowering of the nociceptive threshold (5 days for the longest effect) below the basal value (30% of decrease for the maximal effect) indicative of hyperalgesia. The higher the fentanyl dose used, the more pronounced was the fentanyl-induced hyperalgesia. Ketamine pretreatment, which had no analgesic effect on its own, enhanced the earlier response (analgesia) and prevented the development of long-lasting hyperalgesia.

CONCLUSIONS

Fentanyl activates NMDA pain facilitatory processes, which oppose analgesia and lead to long-lasting enhancement in pain sensitivity.

Microporous microparticles designed as stable immunoadsorbents

We have developed a solid-phase immunoadsorbent based on encapsulated goat anti-apolipoprotein B polyclonal antibodies previously crosslinked with a 0.25% glutaraldehyde solution, and designed to remove by immunoaffinity the excess of apolipoproteins B from the plasma of patients affected by familial hypercholesterolemia. Compared to a classical immunoadsorbent prepared by activation of Sepharose CL-4B with cyanogen bromide, the resulting immunoadsorbent exhibits both optimal adsorption capacity and stability over the entire range of chemical and biochemical conditions during its practical handling. This approach will serve as a model system to demonstrate the applicability of microparticles as immunoadsorbents, which can be achieved for other encapsulated crosslinked proteins.

Selective in vitro removal of anti-A antibodies by adsorption on encapsulated erythrocyte-ghosts

Large volume plasma exchanges are used for the removal of anti-A or anti-B antibodies from the plasma of patients undergoing transplantation from donors with major ABO incompatibility. Previous works suggest that solid-phase immunoadsorption can be substituted for plasma exchange in situations where antigens can be purified and immobilized on columns through which plasma is percolated. However, the preparation of purified antigens of the ABO system is large quantities is laborious and requires the use of considerable blood volumes. Studies were therefore undertaken to determine the feasibility of an original immunoadsorbent based on porous microparticles prepared by a water/oil/water emulsification-solvent evaporation method, within which erythrocytes-ghosts carrying blood group antigens were entrapped. The decrease of the antibody hemagglutinating titre after adsorption onto encapsulated ghosts suggests that antibodies can cross the polymeric membrane and bind to the antigens. This original approach of using encapsulated antigens for the batchwise removal of antibodies could be extended to affinity chromatography, and immunoadsorption therapy with a chromatographic column linked to an extracorporeal circulation could be considered.

Regenerated cellulose-based hemodialyzers with immobilized proteins as potential devices for extracorporeal immunoadsorption procedures: an assessment of protein coupling capacity and in vitro dialysis performances

The development of immunoadsorbents usable with whole blood should offer the potential for making significant improvements in extracorporeal immunoadsorption procedures. In contrast to traditional chromatographic media, these hemocompatible matrices could be used without requiring the previous step of the separation of blood cells and plasma. Conventional hemodialyzers seem to be particularly appropriate for such a purpose. This paper describes a feasibility study of the preparation of immunoaffinity supports, from regenerated cellulose (Cuprophan)-based dialyzers by cyanogen bromide activation and coupling of bovine serum albumin or human immunoglobin G, used as models for immunochemical ligands. Several parameters of the activation and coupling steps were studied in order to define the optimum preparation conditions. In addition, the preservation of the transport properties (clearance and ultrafiltration) of the modified hemodialyzers was evaluated in vitro to ensure that the device potentially could be used in future human therapeutic applications with no risk of massive removal of solutes and fluid from the blood. Results indicate that 150-300 mg of immunoglobulins can be immobilized per square meter of Cuprophan. Modified hemodialyzers show a slight decrease of their clearance values and a slight increase of their ultrafiltration coefficients, and thus they can be proposed as reliable carrier material for extracorporeal cleansing systems.

Antibodies released from immunoadsorbents: effect of support, activation and elution conditions

Immunoadsorption is an application of affinity chromatography, as a therapeutic method to specifically deplete biological fluids such as blood plasma from proteins in excess, or to extract a biomolecule from a complex mixture. However, the leakage of small amounts of antibodies covalently immobilized on the support hampers the practical use of this method. In fact, these released antibodies contaminate the purified proteins or depleted media and, when they are of animal nature, they may lead to immunization of patients, or cause an anaphylactic shock when a clinical use is concerned. It is therefore of prime importance that the immunoadsorbents exhibit a satisfactory stability over the whole range of chemical and biochemical conditions involved during their clinical handling. To determine optimal conditions for the preparation of stable immunoadsorbents designed to remove selectively Low Density Lipoproteins (LDLs) from the plasma of patients affected by familial hypercholesterolemia, various immunoadsorbents were prepared by covalent immobilization of goat anti-apolipoprotein B polyclonal antibodies on different supports (Sepharose CL-4B, Sepharose 6 Fast Flow, Sphérodex and Fractogel) previously activated by various chemical reagents (cyanogen bromide, divinyl sulphone, tresyl chloride and trichloro-s-triazine). Their adsorption capacity, specificity, stability and the amount of immobilized antibodies were compared in terms of the activation method and the support used. It turns out that the immunoadsorbents prepared with Sepharose 6 Fast Flow lead to optimal yield of coupling, adsorption capacity, and an excellent stability at neutral pH. TC-activated-Fractogel turns out as well to afford an excellent coupling yield, a good adsorption capacity and an optimal stability in the whole pH range tested.

Immunoadsorption procedure as a potential method for the specific beta 2-microglobulin removal from plasma of patients with chronic renal failure

beta 2-Microglobulin (beta 2-M), which accumulates in the plasma of patients undergoing long-term dialysis, has been identified as the principal precursor protein of amyloid fibrils in dialysis-related amyloidosis. As no specific treatment for this affection has been yet established, an extracorporeal immunoadsorption procedure appears to be an attractive therapeutic approach to remove beta 2-M. Several murine monoclonal antibodies to human beta 2-M were developed and compared as affinity ligands. One of them was selected on the basis of its specificity and adsorption capacity. In order to achieve maximum efficiency in protein removal, different parameters of the procedure were studied and optimized: effect of antibody coupling density, determination of maximum adsorption capacity of the immunoadsorbents and influence of antigen concentration and of flow-rate on antigen capture efficiency. The conditions of regeneration of immunoaffinity sorbents were also investigated to allow their multiple use without loss of adsorption capacity. The results show the validity of the proposed technique in removing beta-M from plasma of patients with chronic renal failure.

Importance of the matrix and its chemical activation on the stability of immuno-adsorbents

Various matrices were reacted with four different activation reagents, in order to prepare immuno-adsorbents for the selective removal of low-density lipoproteins from blood plasma of patients affected by hypercholesterolaemia. The resulting immuno-adsorbents were compared to that obtained earlier with cyanogen bromide activation, in terms of coupling yield, adsorption capacity and moreover stability towards the various chemical and biochemical conditions to which they are submitted during their handling. Tresyl chloride-activated Sepharose 6 Fast Flow turns out to afford optimal stability in the whole pH range tested.

Compared stability of Sepharose-based immunoadsorbents prepared by various activation methods

During the use of chromatographic supports for the purification of proteins or the selective removal of substances by immunoaffinity, leakage of the antibodies immobilized on the matrix is systematically observed. When the cleansing of blood plasma by extracorporeal circulation is concerned, it is of prime importance that the immunoadsorbents exhibit an extensive chemical stability over the whole range of experimental conditions. To study and minimize this leakage, a matrix, Sepharose CL-4B, was activated by various chemical reagents and coupled to goat anti-apolipoprotein B polyclonal antibodies. Immunoadsorbents thus prepared were compared with those obtained earlier by cyanogen bromide activation. It turns out that divinyl sulphone- and tresyl chloride-activated supports lead to similar results in terms of coupling yield and adsorption capacity, but to a significant reduction in released antibodies.

Purification of biologically active human plasma transthyretin by dye-affinity chromatography: studies on dye leakage and possibility of heat treatment for virus inactivation

The application of a purification procedure for the industrial preparation from human plasma of a therapeutic protein may be hindered by several safety concerns. The dye leaching from Remazol Yellow GGL-Sepharose used for the affinity chromatography of human plasma transthyretin was quantitatively studied by a sensitive competitive enzyme immunoassay. The possibility of including a heat treatment step for virus inactivation in the purification process while preserving the biochemical and functional characteristics of the protein is also reported.

A sensitive enzyme immunoassay for the detection of a synthetic affinity ligand, the reactive yellow 13 dye

Dye-affinity chromatography is widely and increasingly used for the isolation of various proteins. In particular, the purification of transthyretin can be efficiently achieved by affinity chromatography on immobilized Reactive Yellow 13. Measurement of trace-amounts of dye leaching from affinity columns is important because of possible toxicity or side effects linked with the presence of dye in therapeutic transthyretin preparations. A competitive enzyme immunoassay was developed to monitor yellow-dye column leaching. Biotinylated rabbit anti-Reactive Yellow 13 antibodies (immunoglobulin G fraction) were used as principal reagent. The assay is specific sensitive to 1 ng/ml of Reactive Yellow 13, has a good reproducibility and allows the accurate detection of the dye in the presence of transthyretin.

Dye-affinity purification of transthyretin from an unexploited by-product of human plasma chromatographic fractionation

Dye-affinity chromatography of human plasma transthyretin on Remazol Yellow GGL-Sepharose from an unexploited by-product of chromatographic fractionation of plasma was optimized for large-scale preparation of a therapeutic product. With this system, transthyretin is only weakly bound to the gel. The residence time on gel and the transthyretin level in the by-product were observed to have no influence on the binding capacity of gel, and the optimum amount of transthyretin to be applied to the gel was found to be 1 g/l of gel. The adsorbent can be used more than ten times. The procedure resulted in the isolation, with a 30% yield with respect to plasma, of an 80% pure protein, which retained its thyroxine-binding capacity. Although the purity is acceptable for substitutive therapy, it can be improved further with a second chromatography on Cibacron Blue-Sepharose.

Single-step method for purification of human transferrin from a by-product of chromatographic fractionation of plasma

A rapid, simple and convenient method is described for the isolation, on a pilot scale, of pure and functional human transferrin from an unexploited by-product of chromatographic fractionation of plasma. In a single chromatographic step on DEAE-Spherodex, 97% pure transferrin was obtained in 75% yield. A virus inactivation treatment was included in the preparative process in order to guarantee the safety of the final product, which could be used in culture media.

Specific removal of transthyretin from plasma of patients with familial amyloidotic polyneuropathy: optimization of an immunoadsorption procedure

Familial amyloidotic polyneuropathy is characterized by the presence in patients plasma of a genetic variant of transthyretin. No specific treatment has been found and extracorporeal immunoadsorption on immobilized anti-transthyretin antibodies appears as a potentially attractive procedure. Parameters involved in specific immunoadsorption of transthyretin were studied and optimized. Several monoclonal anti-TTR antibodies were compared as affinity ligands and one of them was found to be suitable for such purposes. Optimum quantities of antibodies to be immobilized on the gel were determined. Three desorption agents were tested for regenerating immunoadsorbents and best results were obtained with basic variation of pH, allowing total desorption of TTR and possibility of multiple use without loss of adsorption capacity. Simulation of an immunoadsorption procedure in well-defined conditions showed efficiency and specificity of adsorption to remove TTR and the system thus should be subjected to clinical trials.

Monoclonal antibodies against human plasma protein C and their uses for immunoaffinity chromatography

Human protein C, isolated by conventional multistep methods, was used for immunization of mice. Monoclonal antibodies were prepared and screening of antibodies to human protein C was achieved using an immunoblotting technique. Five monoclonal anti-protein C antibodies were compared as affinity ligands. Different parameters were studied (adsorption capacity, specificity of adsorption, possibility of desorption under mild conditions) and two antibodies were selected. One antibody allows preparation of highly purified protein C in a single-step procedure from a fraction of plasma containing high levels of coagulation factors whereas the other can be used for preparation of protein C deficient plasma.

[Human plasma fibronectin. Comparison of methods for preparation of a concentrate for therapeutic use from different sources]

Three methods, successive precipitations, affinity chromatography on immobilized gelatin and immunoaffinity chromatography with monoclonal anti-fibronectin antibodies were optimized and compared in order to be used for large scale preparation of human plasma fibronectin (Fn). The functional properties of the various Fn preparations were investigated by means of two assays: quantitation of the gelatin-binding activity by ELISA and quantitation of the Fn-mediated attachment of fibroblasts on plastic. Functional alterations of the purified Fn were observed when it was isolated by successive precipitations. Both chromatographic methods provide a rapid and convenient way for isolation of pure and functional Fn. Mass production of monoclonal antibodies is too expensive and legislative requirements for the therapeutic use of monoclonal antibodies are limiting factors for the choice of immunopurification as large scale isolation procedure. Plasma Fn can be isolated from different sources: fresh frozen plasma, cryoprecipitate supernatant or by-products from factor VIII preparation. When gelatin-Sepharose chromatography is performed under optimized conditions, fibronectins isolated from these sources show similar properties. Large scale purifications of Fn from a by-product of factor VIII preparation were performed either by gelatin affinity chromatography or by successive precipitations. These two purification methods can be easily scaled-up since the data obtained closely correlate with analytical results. The chromatographic method supplies a higher purified (98 vs 75%) and functional (95 vs 50%) material when compared with successive precipitations. Yield is also higher (50 vs 26%). The starting material undergoes viral inactivation and the affinity purified Fn, sterile, atoxic, apyrogen, which can be freeze-dried without additives fulfils all requirements for an injectable product.

Study of parameters involved in specific immunoadsorption of apolipoprotein B

A therapeutic immunoadsorption system on immobilized and anti-apolipoprotein B as a plasma cholesterol lowering procedure was optimized. Several antibodies were compared and highest adsorption capacity was obtained with goat polyclonal antibodies. Optimum quantities of antibodies to be immobilized on the gel and quantities of apo-B to be applied to columns were determined. The amount of antibodies released from immunoadsorbents can be minimized by treatment with a 0.005% glutaraldehyde solution with an acceptable reduction rate of adsorption capacity. Each phase, adsorption and desorption respectively, were well-defined and synchronized so two columns could be used in parallel in an automated procedure. In these conditions, the immunoadsorption system can efficiently, specifically and safely remove cholesterol and has to be subjected to clinical trials.

Affinity purification of human plasma fibronectin on immobilized gelatin

Several problems are associated with the biospecific affinity purification of plasma fibronectin on gelatin-Sepharose. Large-scale development of this purification procedure requires optimization of adsorption and elution conditions. The adsorption capacity depends on the amount of gelatin coupled to the Sepharose, the residence time, the temperature and the amount of fibronectin loaded on the adsorbent. Elution of adsorbed fibronectin with 3 M urea leads to incomplete recovery. The elution yield was found to vary with both the gelatin concentration and the amount of adsorbed fibronectin. Despite the incomplete elution, the adsorption capacity did not decrease after twelve consecutive isolation procedures. Under optimized conditions, the method described here provides a rapid, single-step and convenient way for the isolation of pure and functional fibronectin, either for analytical or large-scale preparative purposes.

[Highly purified, functionally active human fibronectin preparation]

Fibronectin has been purified by gelatin-Sepharose affinity chromatography from fresh frozen human plasma. The bound fibronectin was eluted with 3 M urea. The purity of the fibronectin obtained has been checked on (immunoelectrophoresis, polyacrylamide gel electrophoresis, FPLC). Biological activity of the purified molecule has been monitored by means of three assays: quantitation of the gelatin-binding activity by ELISA, quantitation of the fibronectin-mediated attachment of fibroblasts on plastic and evaluation of the opsonic activity (uptake of gelatin latex particles by a murine macrophage line). When deep-frozen, fibronectin retains all of its properties. This highly purified and functional fibronectin fulfills the basic requirements for a standard reagent. It will allow to investigate physicochemical and functional alterations of various fibronectins.

A potential new procedure for removing anti-factor VIII antibodies from hemophilic plasma

A new approach for removing the anti-factor VIII antibodies in hemophilic patients by immunoadsorption is proposed. The method is based on the fact that the anti-factor VIII antibodies were predominantly of the IgG4 subclass; anti-human IgG4 antibodies were covalently linked to agarose and large amounts of anti-factor VIII antibodies can be eliminated. A study of 21 blood samples from hemophilic patients with anti-factor VIII antibodies allows us to confirm the large predominance of IgG4 in the anti-factor VIII population. In some samples, the presence of IgG3 related anti-VIII:C was checked by adsorption on an anti-IgG3 column. In a majority of cases, after IgG4 (or IgG4 + IgG3) immunoadsorption, the substitution therapy becomes possible or easier.

An extracorporeal hollow-fiber reactor for phenylketonuria using immobilized phenylalanine ammonia lyase

A hollow-fiber hemodialyzer with immobilized phenylalanine ammonia lyase was tested in vitro for depletion of blood phenylalanine in a recirculating system. A sustained reduction of phenylalanine was obtained in less than 1 h. The product of phenylalanine deamination, trans-cinnamic acid, is a nontoxic compound metabolized to benzoic acid by the liver and eliminated in the urine as hippuric acid. As a model, this reactor may be relevant not only for the short-term management of hyperphenylalaninemia (particularly in pregnant phenylketonuric mothers), but for other metabolic diseases as well, provided that a biocatalyst effective on the accumulating substance is available.

Alpha-1-antitrypsin phenotypes in a population of Jordan

Frequencies of the three common subtypes of PI M were studied in a Jordanian population. In comparison with other populations, PI*M3 was found to be low (0.038) and PI*M2 rather high (0.155).

Genetic variants of factor B in a population of Jordan

BF phenotyping was performed in a population of Jordan. The observed allele frequencies were as follows: BF*S = 0.5457, BF*F = 0.3744, BF*SO7 = 0.0763, BF*F1 = 0.0075. These values are in agreement with the geographic position and the ethnic composition of Jordan.