Protective effects of the thiophosphate amifostine (WR 2721) and a lazaroid (U83836E) on lipid peroxidation in endothelial cells during hypoxia/reoxygenation

Little is known about pharmacological interventions with thiophosphates or lazaroids in endothelial cells injured by hypoxia/reoxygenation with respect to membrane lipid peroxidation (LPO) caused by reactive oxygen species. Therefore, a cell line of bovine aortic endothelial cells was studied after 120-min hypoxia followed by 30-min reoxygenation, resulting in moderate and predominantly reversible injury (energy depression/cytosolic Ca2+-accumulation during hypoxia, which almost normalized during reoxygenation; membrane blebs, an increasing amount of lysosomes, vacuolization, lipofuscin formation, alterations in mitochondria size, some lyzed cells). 18.9 +/- 4.3% of the cells died. Radical-induced LPO measured as malondialdehyde continuously increased to 2.18 +/- 0.17 nmol/mg of protein after reoxygenation vs control (0.41 +/- 0.13, P < 0.05). Simultaneously, the content of 4-hydroxynonenal, a novel indicator of LPO, increased from 0.02 +/- 0.01 to 0.11 +/- 0.02 nmol/mg of protein (P < 0.01). The results support the assumption that reoxygenation injury is accompanied by an increase in membrane LPO, causing structural and functional disturbances in the monolayer. The thiophosphate WR 2721 [S-2-(3-aminopropylamino) ethylphosphorothioic acid] and the lazaroid U83836E [(-)-2-[[4-(2,6-di-1-pyrrolidinyl-4-pyrimidinyl)-1-piperazinyl] methyl]-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-6-ol (dihydrochloride)] were effective scavengers of .OH, being more efficient than trolox C (6-hydroxy-2,5,7,8-tetramethylchroman-2-carbon acid) used as standard (EC50: 12, 5 and 15 microM, respectively, measured by electron spin resonance spectroscopy). One mM WR 2721, 10 microM U83836E, and 5 microM trolox C reduced formation of malondialdehyde during hypoxia/reoxygenation to 53 +/- 7, 51 +/- 10 and 48 +/- 6%, respectively (P < 0.05 each, versus control). In general, WR 2721 and U83836E prevent radical-induced membrane LPO in a model of endothelial cells injured by hypoxia/reoxygenation. The use of these two agents is a new approach to protect the endothelium against oxidative stress.

The rat female protein, a pentraxin with lectinic properties

The C-reactive protein is the major acute phase protein (APP) in humans which binds lectin-like to different membraneous structures and exerts an important function in non-specific defense. Because of a pentameric molecular symmetry CRP as well as serum amyloid P component (SAP) and hamster female protein (FP) was merged into a special protein family named pentraxins. In rats a protein was found referred to as rat FP which was close related to hamster FP with respect to hormonal regulation and APP nature as well. Based on this conformity the molecular structure of rat FP was analyzed and as the results a pentameric structure could be demonstrated for rat FP, too. Furthermore, the response of rat CRP and FP on injection of adrenal hormones, agents being involved in acute phase reaction, was investigated. Epinephrine administration led to an increase in CRP and a decrease in FP serum concentration. Dexamethasone has the same effect in case of FP and changed the CRP concentration in a biphasic way with a maximum at about 0.01 mg/kg, a minimum at 0.6 mg/kg and a return to control values at 1.8 mg/kg. Thus, the results indicate a neuroendocrine control of CRP and FP but probably in a different way. Using FITC-labelled lectin the exposition of galactose-containing membraneous structures could be demonstrated in carbon tetrachloride-injured liver tissue in contrast to controls. These binding sites are in accordance with increased FP-binding shown by immunofluorescence histochemistry. Thus, lectin-like properties may be ascribed to rat FP comparable to CRP and SAP activity. The results are discussed with respect to findings from literature that also the acetylcholine receptor seems to have a pentameric structure.

Interaction between anti-influenza viral polymerase antibodies and RNP particles using the in vitro transcription process and an immunogold labelling technique

Immunogold labelling and in vitro transcription of influenza virus vRNA have been used to analyse the interaction of anti-influenza polymerase antibodies with influenza-ribonucleoprotein (RNP) complexes. The polymerase proteins (P proteins) were localized exclusively at one end of the RNP segments. In the course of transcription the amount of P protein decreased significantly. The in vitro transcriptase activity y of influenza A virus RNP complexes in the presence of anti-polymerase antibodies to the strain A/PR/8/34 was inhibited by 60%. In contrast, RNP transcriptase activity of influenza B virus was not inhibited by these antibodies.

Preparation, characterization, therapeutic efficacy and toxicity of liposomes, containing the antitumour drug cis-dichlorodiamineplatinum(II)

Cis-dichlorodiamineplatinum(II) (cis-DDP) was encapsulated in reverse phase evaporation vesicles (REV, 0.6 mg cis-DDP/ml lipid solution) and multilayered liposomes (MLV, 0.3 mg cis-DDP/ml lipid solution) with different cholesterol content. The identity of cis-DDP in free and encapsulated form was checked by various techniques. Particle size, homogeneity of liposomes and distribution of cis-DDP in REVs were shown by electron microscopy. The examination of entrapped cis-DDP in REVs relating to buffer and serum stability, in vitro and in vivo antitumour activity and nephrotoxicity proved that all points are strongly influenced by the cholesterol (CH) content. Enclosed cis-DDP in phosphatidyl (PC)-REV has the same, and in PC: CH-REV, a lower effect in vitro and in vivo compared to treatment with the free drug. Irrespective of the application of tumour cells and substance (i.v., i.p.) in optimal therapeutic doses, an equal increase in life-span (ILS) was registered with the free drug and with PC-cis-DDP-REV, while cis-DDP in PC: CH-REV had a significantly reduced effectiveness. Liposomal encapsulation of cis-DDP also influenced body weight change and leucocyte counts. The blood urea nitrogen (BUN) level, as an indicator of renal toxicity, was only moderately increased after very high doses of cis-DDP (24 mg/kg) in PC: CH-REV.

Structural alterations of the human erythrocyte membrane upon influenza virus attachment

Molecular events on the human erythrocyte membrane subsequent to influence virus binding were investigated by electron spin resonance (ESR) measurements after spin labeling of the cell membrane at different positions. Virus binding affected the glycocalyx structure as well as the physical state of the cytoskeleton at the inner leaflet, but not the lipid phase. A lateral reorganization of spin-labeled glycophorin was not indicated after virus attachment.

Spectroscopic characterization of vesicle formation on heated human erythrocytes and the influence of the antiviral agent amantadine

EPR investigations on the vesiculation process of heated human erythrocytes were performed, using different fatty acid spin labels. Spectrin denaturation and vesiculation do not influence the fluidity of the lipid phase of the remaining membrane of human erythrocytes: Vesicles released differ in chemical composition as well as in the lipid fluidity of their membrane from the intact human erythrocyte membrane. A reduced cholesterol-to-phospholipid ratio and a depletion of spectrin was found. By changing the ionic concentration of the suspension medium an effect on membrane spectra and on vesicle release was established. The adamantane derivative amantadine causes fluidization of the human erythrocyte membrane and inhibits vesicle release. Based on these results, a model for the mechanism by which adamantane-like molecules could interact with membranes is proposed.

Lateral lipid distribution and phase transition in phosphatidylethanolamine/phosphatidylserine vesicles. A cross-linking study

To determine the nonideal mixing of two lipid components within the membrane, lipid cross-linking experiments were carried out on dipalmitoylphosphatidylethanolamine (DPPE) vesicles and on dipalmitoylphosphatidylethanolamine/dipalmitoylphosphatidylserine (DPPE/DPPS) vesicles. By comparison of the cross-linking reactions on both types of vesicle the mean neighbourhood relations within the binary lipid mixture can be obtained. To elucidate the relationship between cluster formation and phase transition, the temperature dependences of the lipid arrangement within the vesicle membrane and of the lipid order parameter describing the fluidity of the membrane were measured. Cluster size and phase transition correlate: during the phase transition of the lipid species with the lower phase-transition temperature (DPPS) the nonideality of the mixture increases by phase separation. Above the phase transition temperature of the second lipid species (DPPE) the clusters disappear and a slight alternating lipid arrangement is characteristic of the fluid phase.

Auto-oxidation-induced fusion of lipid vesicles

Spontaneous size changes of small unilamellar vesicles with initial mean diameters of 25 nm measured by quasi-elastic light scattering (QELS) and electron microscopy are reported. After the size conversion the vesicles have mean diameters of about 70 nm and are of the unilamellar and multilamellar type. The fact that auto-oxidation initiates this process is established by the comparison of the results for vesicles which differ only in the degree of auto-oxidation. The role of phosphatidylcholine hydroperoxides as fusogens is discussed.

Electron microscopic evidence of circular molecules in 9-S globin mRNA from rabbit reticulocytes

9S globin mRNA prepared by the proteinase K method from polysomes of rabbit reticulocytes consists of 40% circular molecules as revealed by electron microscopy, if spreading of the molecules is performed from a solution of 50% formamide, 0.5 M NaCl, 25 mM Tris, 10 mM EDTA, pH 8, after 16 h incubation at 42 degrees C. We assume a noncovalent nature of the circularization because of the fact that a total transformation into the well known linear form occurs if strong denaturing conditions for spreading were used. The biological significance of the circular globin mRNA molecules is unknown.

Precursor mRNA from erythroid-enriched bone-marrow cells of the rabbit. Electron microscope investigation of precursor mRNA molecules, molecular weight about 1.7 X 10(7), containing mRNA-like structures at one end

Precursor mRNA (pre-mRNA) molecules, sedimenting at greater than 45 S, from erythroid-enriched bone marrow cells of the rabbit and hemoglobin mRNA molecules from rabbit reticulocytes were investigated by electron microscopy. Four of 98 measured pre-mRNA molecules had a length between 15 and 17.1 mum. In some of the pre-mRNA molecules a characteristic condensed structure was observed at one end, strikingly resembling the structure of the mRNA molecules.