Marian Gorecki

RECOMBINANT HUMAN SUPEROXIDE DISMUTASES: PRODUCTION AND POTENTIAL THERAPEUTICAL USES

In many pathological situations, tissue damage is caused by cellular generation of superoxide free radicals (O2-). These active species are generated during post-ischemic reperfusion of organs, in hyperoxic tissue, during acute and chronic inflammation and during exposure to ionizing radiation. Exogenous superoxide dismutase (SOD) was shown to significantly prevent such damage. The genes for human cytosolic Cu/ZnSOD and mitochondrial MnSOD were cloned and introduced into an E. coli expression system. The proteins were expressed in high yields and purified to homogeneity, yielding pharmaceutical-grade materials. These enzymes were used in a variety of in vivo animal models for the demonstration of their protective effects against oxidative damage. Comparative pharmacokinetic studies in rats have revealed that the half-life of Cu/ZnSOD was 6-10 min., while that of MnSOD was 5-6 hours, thus indicating that MnSOD may be superior to Cu/ZnSOD for the treatment of chronic diseases. Indeed, MnSOD was found to be effective as an anti-inflammatory agent in the rat carrageenan induced paw edema acute inflammation model. Both enzymes were also effective in ameliorating post-irradiation damage in mice exposed to whole-body or localized chest X-ray radiation.

Expression and Reconstitution of Biologically Active Human Acetylcholinesterase from Escherichia coli

Summary1.Authentic human acetylcholinesterase (AChE) was expressed inEscherichia coli under regulation of the constitutivedeo promoter or the thermoinducibleλPL promoter.2.To facilitate expression in the prokaryotic system, recombinant human AChE (rhAChE) cDNA was modified at the N terminus by oligonucleotide substitutions in order to replace some of the GC-rich regions by AT. These modifications did not alter the amino acid sequence but resulted in ample production of the protein.3.rhAChE accumulated in the cells and reached a level of 10% of total bacterial proteins. A partially purified inactive recombinant protein was recovered from inclusion bodies.4.Active rhAChE was obtained after solubilization, folding, and oxidation, although the recovery of the active enzyme was low. A 20- to 40-fold increase in enzymatically active rhAChE was achieved by replacing Cys580 by serine.5.The recombinant enzyme analogue was indistinguishable from native AChE isolated from erythrocytes in terms of substrate specificity and inhibitor selectivity.

Cloning of bovine growth hormone gene and its expression in bacteria.

A hybrid plasmid was constructed containing beta-lactamase gene of plasmid pBR322 and cloned coding sequences of bovine growth hormone (BGH). The constructed plasmid contains all DNA sequences required to encode BGH, and when used as a hybridization probe it detects one growth hormone gene in the bovine genome. The cloned DNA sequences are inserted into the beta-lactamase gene in the correct reading frame for BGH synthesis. The hybrid gene is expressed in bacteria and the product, a fused beta-lactamase-bovine growth hormone protein, is specifically immunoprecipitated with anti-serum to BGH. Unlike beta-lactamase, very little growth hormone containing sequences can be detected in the periplasmic space.

Superoxide dismutase inhibits radiation-induced lung injury in hamsters.

An animal model of pulmonary radiation-induced lung injury was established in the hamster and the effects of pretreatment with recombinant human CuZn superoxide dismutase (SOD) on the development of the lesion were evaluated. Hamsters exposed to a single irradiation dose of 2000 cGy delivered to the thorax were treated with 150 mg/kg body weight of SOD or an equivalent volume of saline intraperitoneally 75 min and subcutaneously 5 min before receiving irradiation. At 4, 8, and 16 weeks following irradiation, pulmonary injury was evaluated by the grading of morphologic changes semiquantitatively, measurement of lung hydroxyproline content, and analysis of bronchoalveolar lavage fluid for total and differential cell counts and total protein concentration. Radiation-induced lung injury in saline-pretreated animals was documented at 16 weeks by histologic morphology and increased protein in bronchoalveolar lavage fluid. SOD protected against radiation-induced pulmonary injury as indicated by the absence of severe histopathologic changes and prevention of elevation in bronchoalveolar lavage protein levels. The beneficial effects of SOD in preventing radiation-induced pulmonary toxicity suggests that this recombinant enzyme may play a role in protection against radiation-induced pulmonary injury in humans.

Polymer-bound dihydrolipoic acid: a new insoluble reducing agent for disulfides.

Abstract A quantitative method for reduction of disulfides by means of polymeric reagents has been developed. Lipoic acid was coupled covalently to different aminoethyl solid matrices. The disulfide-containing polymers were reduced with NaBH4 to the corresponding thiols. These thiolated polymers were used for the quantitative reduction of oxidized glutathione and cystine as well as for activation of papain and mercuripapain. A further advantage of this method is the ease of removal of the insoluble polymeric reagents.

Adhesion of Blood Platelets Is Inhibited by VCL, a Recombinant Fragment (Leucine504 to Lysine728) of von Willebrand Factor

VCL, fragment Leu504 to Lys728 of von Willebrand factor (vWF) expressed in Escherichia coli, contains the glycoprotein (GP) Ib-binding domain of vWF. This fragment inhibited ristocetin-induced platelet aggregation with an IC50 of 0.2 mumol/L and botrocetin-induced platelet aggregation with an IC50 of 0.08 mumol/L. We studied the antiadhesive profile of VCL by adding it to blood that was circulated over various adhesive surfaces. VCL inhibited adhesion to endothelial cell matrix, which served as a model of the vessel wall. Maximal inhibition at a high shear rate of 1600 s-1 was stronger (60%) than at a low shear rate of 300 s-1 (40%). Half maximal inhibition was found to be 1.5 mumol/L at both shear rates. The role of various adhesive molecules was investigated in more detail by coating glass coverslips with collagen type I, laminin, fibronectin, or vWF. Fibrinogen was studied as well. Platelet adhesion to laminin and vWF was not inhibited by VCL. Adhesion to collagen, fibronectin, and fibrinogen was particularly inhibited at a high shear rate. VCL coated to a coverslip caused a concentration-dependent adhesion that was blocked by antibodies against GPIb, which block interaction with vWF. Binding studies showed a nonsaturable ristocetin binding of VCL to platelets that was blocked by vWF or inhibitory antibodies against GPIb. Binding to collagen was weak, and VCL did not inhibit binding of vWF at a 5000-fold excess. From these data, we conclude that VCL inhibits adhesion in all cases in which adhesion is vWF dependent by competing for vWF binding to activated GPIb. The lack of inhibition of adhesion to vWF as a single molecule may be explained by assuming that this adhesion is determined by interaction of nonactivated GPIb with vWF that has been changed in conformation by adsorption. Studies investigating thrombus formation on the connective tissue of an atherosclerotic plaque in a human coronary artery showed that VCL was able to partially prevent this thrombus formation. VCL may be of value in preventing adhesion and thrombus formation under conditions in which these processes are dependent on vWF.

A NEW APPROACH FOR THE ISOLATION OF BIOLOGICALLY ACTIVE COMPOUNDS BY AFFINITY CHROMATOGRAPHY: ISOLATION OF TRYPSIN

Affinity chromatography has recently been introduced as a method for purification of biologically active compounds [ 11. The method depends on the affinity of a protein towards its specific hapten or inhibitor covalently coupled to an insoluble matrix. In contrast to other chromatographic methods which separate proteins according to their size and charge, affinity chromatography separates proteins on the basis of their functional specificity and has been applied to the isolation of enzymes [ 1, 21, antibodies [3], antigens [4, 51 and receptors [6]. Several laboratories have reported the purification of trypsin by using a protein inhibitor covalently attached to Sepharose [7,8] . We report here a new approach for the isolation of trypsin as its soluble complex with dinitrophenylated soybean trypsin inhibitor (DNP-STI) on an antidinitrophenyl antibody column [4,5] . The procedure involves the following steps: i) Dinitrophenylation of ST1 with dinitrobenzene sulfonate. ii) Formation of the complex between the DNP-ST1 and trypsin. iii) The complex is adsorbed to the anti-DNP-column and eluted from the column under conditions which dissociate antigenantibody complexes. iv) Separation of the complex to its components to give pure trypsin. Although this paper describes the isolation of trypsin, the principles and techniques are clearly applicable to virtually all interacting systems comprised of two or more components, such as hormone-receptor interactions.

Method for recovering a purified animal growth hormone or polypeptide analog thereof from a bacterial cell

A method is provided for recovering a purified animal growth hormone or a polypeptide analog thereof having substantially the same amino acid sequence as, and the biological activity of, the corresponding naturally-occurring animal growth hormone from a bacterial cell in which the animal growth hormone or polypeptide analog has been produced by means of expression of a plasmid encoding the hormone or polypeptide analog which comprises: (a) disrupting the cell wall of the bacterial cell in a buffered neutral pH solution so as to produce a lysate containing precipitated hormone or polypeptide analog; (b) recovering the resulting precipitated hormone or polypeptide analog; (c) suspending the precipitated hormone or polypeptide analog so recovered in distilled water; (d) treating the resulting precipitate-containing suspension with a sodium hydroxide solution having an alkaline pH of about 11.8 so as to solubilize the precipitate and thus the hormone or polypeptide analog contained therein; (e) separating the solubilized hormone or polypeptide analog from other soluble components by gel filtration chromatography; and (f) subjecting the hormone or polypeptide analog thus separated to ion exchange chromatography to purify the hormone or analog and thereby recover purified hormone or polypeptide analog.

The conversion of 3-monoazotyrosine to 3-aminotyrosine in peptides and proteins

Abstract A method is described for the conversion of 3-monoazotyrosine to 3-aminotyrosine in model peptides and ribonuclease A modified at tyrosine 73 with 5′-(4-aminophenyl-phosphoryl)-uridine 2′(3′)-phosphate. This method can be used for the quantitative estimation of azotyrosine residues in proteins as well as for the introduction of 3-aminotyrosine residues in proteins after modification with diazonium salts.

Mode of transport and possible mechanism of action of l-phenylalanine benzyl ester as an anti-sickling agent

L-Phenylalanine benzyl ester (Phe-Bz) and a number of ester analogues prevent sickling of erythrocytes from sickle cell disease patients. The compounds tested exhibit anti-sickling activity in the concentration range 0.5-3.0 mM. A general feature of these compounds is the presence of two aromatic rings in their molecular structure. The anti-sickling agents rapidly enter the erythrocyte and are hydrolysed to their component molecules. Incubation of human erythrocytes with 3.0 mM L-phenylalanine for 30 min at 37 degrees C results in accumulation of 2.0 mmol L-phenylanine/l cells, while incubation of erythrocytes with 3.0 mM Phe-Bz under similar conditions results in the production of 4.0 mmol L-phenylalanine/l cells and an equivalent amount of benzyl alcohol. Both L-phenylalanine and benzyl alcohol are inhibitors of the gelation of deoxyhaemoglobin S (deoxy-HbS) in vitro. Moreover, Phe-Bz and related anti-sickling agents fluidize the lipid bilayer of the erythrocyte membrane, inhibiting several transport systems, including those for L-phenylalanine, uridine and sulphate ions, as well as the Na+ pump and the Na+/K+ cotransporter, but increasing the passive influx and efflux of both cations and anions. The accumulation of Phe-Bz hydrolysis products within the erythrocyte together with the effects of Phe-Bz on cation permeability result in the influx of water causing the cell to swell. Thus, treatment of erythrocytes with 3.0 mM Phe-Bz at 37 degrees C for 30 min causes an increase in mean cell volume of 14.8%, decreasing the mean intracellular haemoglobin concentration from 34 to 29.6 g%. The increase in cell volume caused by Phe-Bz and its analogues together with the direct effects of their hydrolysis products on HbS probably act in concert to bring about the anti-sickling effect.