[Vasonatrin peptide attenuates hypoxia-induced increase in [Ca(2+)] (i) of culured rat cardiac fibroblasts].

The purpose of this work was to test the hypothesis that vasonatrin peptide (VNP) can attenuate the growth-promoting effect by hypoxia in cardiac fibroblasts of cultured neonatal rats. Cultured fibroblasts were divided into four groups: control group, hypoxia group, VNP group and VNP+hypoxia group. The growth of cardiac fibroblasts was observed using MTT method and the incorporation of (3)H-TdR, and the effect of VNP on the intracellular level of Ca(2+) was measured by means of interactive laser cytometry. It was found that hypoxia (2% - 3%) increased significantly the MTT optical density (OD) of cardiac fibroblasts (P<0.05 vs control group), but the increase was greatly attenuated in the VNP (10(- 6)mol/L) group and also the incorporation of (3)H-TdR in cardiac fibroblasts (P<0.05 vs hypoxia group). VNP (10(- 6)mol/L) also decreased the intracellular level of Ca(2+) which was increased by hypoxia (P<0.05) as compared with control and hypoxia group. These findings demonstrate that VNP can attenuate the hypoxia-induced growth-promoting effect in cardiac fibroblasts, which may be associated with the elevation of intracellular Ca(2+).

[Comparison of vasorelaxing actions of vasonatrin peptide, C-type natriuretic peptide and atrial natriuretic peptide].

The vasorelaxing effects of vasonatrin peptide (VNP), C-type natriuretic peptide (CNP) and atrial natriuretic peptide (ANP) on isolated rat pulmonary artery, abdominal aorta and celiac vein were measured by in vitro perfusion. The results showed that VNP, CNP and ANP caused concentration-dependent relaxation in isolated rat pulmonary artery, abdominal aorta and celiac vein with endothelium or without endothelium. The maximal responses (Rmax) of VNP were (76 +/- 17)%, (51 +/- 14)% and (62 +/- 14)% in pulmonary artery, abdominal aorta and celiac vein with endothelium respectively, whereas those of CNP were (31 +/- 8)%, (22 +/- 7)% and (41 +/- 8)%, and ANP (38 +/- 10)%, (41 +/- 10)% and (11 +/- 4)%. The median effective concentration (EC50) of VNP were 16 +/- 11, 35 +/- 18 and 12 +/- 8 nmol/L in pulmonary artery, abdominal aorta and celiac vein with endothelium respectively, while those of CNP were 148 +/- 112, 299 +/- 84 and 14 +/- 12 nmol/L, and ANP 66 +/- 47, 16 +/- 15 and 909 +/- 445 nmol/L. VNP were more effective than CNP and ANP, and the differences were statistically significant (P < 0.05-0.01). The potency of these peptides for relaxing the blood vessels can be summarized as: VNP > ANP > or = CNP for pulmonary artery; VNP > ANP > CNP for abdominal aorta; VNP > CNP > ANP for celiac vein. There was no significant difference between vessels with intact endothelium and those denuded of endothelium (P > 0.05).

[The solid-phase synthesis of methotrexate-alpha-peptides].

Methotrexate(MTX) and the methotrexate-alpha-peptides(MTX-alpha-phenylalanine and MTX-alpha-arginine i.e. MTX-alpha-Phe and MTX-alpha-Arg) were prepared with the technique of solid-phase peptide synthesis. Its purity was verified as a single peak by HPLC and its molecular weight was measured by mass spectrometry. MTX-alpha-Phe could be hydrolyzed to MTX by carboxypeptidase A. The cytotoxic effect of released MTX was found to be 100 times stronger than that of the peptide in vitro. It is suggested that MTX-alpha-Phe is a satisfactory prodrug in the treatment of cancer.

Antinociceptive effect of intracerebroventricular injection of a tetrapeptide Asn-Ala-Gly-Ala in rats.

The antinociceptive effect of intracerebroventricular injection (icv) of Asn-Ala-Gly-Ala (NAGA), a partial sequence of beta-lipotropin, was studied in rats. The potassium iontophoresis-induced tail flick was used to measure the pain threshold. The antinociceptive effect of NAGA, which was dose-dependent (icv, 0.03-0.24 mumol/rat) and long-lasting (90 min), was reversed by naloxone (icv, 0.26 mg.kg-1) and inhibited by anti-MEK serum (titre: 1:5000, 5 microliters) or anti-LEK serum (titre: 1:5000, 5 microliters). NAGA-induced antinociception was scarcely affected by anti-beta-EP serum (titre: 1:30,000, 5 microliters) or anti-Dyn A1-13 serum (titre: 1:30,000, 5 microliters). It was suggested that the antinociceptive effect of NAGA may be associated with the release of met-enkephalin and leu-enkephalin in rat brain.

Synthesis and biological activity of atriopeptin III and its small molecular analog.

Atriopeptin III (AP III) and its small molecular analog were synthesized manually by stepwise solid-phase method. The peptides were oxidized with iodine in 30% acetic acid at very high dilution to form intramolecular disulfide bridge and purified to homogeneity by conventional means, including Sephadex G15, dialysis and reversed-phase HPLC. Bioassay study demonstrated that the synthetic AP III possesses potent bioactivities identical to those of the same product of Peninsula Lab both in vitro and in vivo; whereas the linear peptide, having the same primary structure as AP III, showed very limited bioactivity. The small analog, with Ser-Ser-residue deleted from the N-terminal of AP III, was equipotent as AP III while exhibiting a longer half-life in vivo resulting from the peptide modification.

Curative effects of highly active atrial natriuretic peptide on severe pregnancy-induced hypertension.

A new highly active atrial natriuretic peptide (haANP), synthesized by a solid phase technique, was given by intravenous infusion to 20 patients with severe pregnancy-induced hypertension (PIH) and the curative result of haANP was observed. Compared with basal values, supine systolic and diastolic BP was lowered significantly (P < 0.01), which may be related to the specific receptor of hANP and inhibition of renin-angiotensin-aldosterone system (RAAS). The haANP was found to possess significant effects of antispasm, detumescence and reducing proteinuria, probably by repairing mildly injured glomerulae, strong effects of diuresis and improving heart function with no side effects. Auto-antibody of hANP was found in patients with severe PIH, which affected the function of target cells of highly concentrated endogenous hANP. This auto-antibody might be one of the causes for PIH.

Binding of anti-human-interleukin-6 monoclonal antibodies to synthetic peptides of human interleukin-6 studied using surface plasmon resonance.

Biosensor technology employing surface plasmon resonance (SPR) detection provides a highly-sensitive (sub ng), non-extrinsic labelling approach for monitoring protein interactions in real-time. We have used this approach to map the binding sites on human interleukin-6 (hIL-6) for a series of anti-hIL-6 monoclonal antibodies (mAbs). Epitopes were localised by monitoring the ability of ten synthetic peptides, spanning the sequence of hIL-6, to inhibit the binding of anti-hIL-6 mAbs to immobilised hIL-6. Peptide P8 (Pro139-Gln153) inhibited binding of anti-IL-6-mAbs 1, 2 and 7. To increase the sensitivity of detection of antibody-synthetic peptide interactions, a procedure was developed for immobilising the synthetic peptides directly to the sensor surface of the SPR instrument. From this study, association equilibrium constants of 2.1 x 10(6)M-1 and 3.6 x 10(4)M-1 were calculated for the mAb7-immobilised P8 and mAb7-free P8 interactions, respectively.

Changes in repeat number, sequence, and reading frame in S-antigen genes of Plasmodium falciparum.

The S antigens from different isolates of Plasmodium falciparum exhibit extensive size, charge, and serological diversity. We show here that the S-antigen genes behave as multiple alleles of a single locus. The size heterogeneity results from different numbers, lengths, and/or sequences of tandem repeat units encoded within the S-antigen genes. Two genes studied here encode antigenically different S antigens but nevertheless have closely related tandem repeat sequences. We show that antigenic differences can arise because repeats are translated in different reading frames.

Antigenic repeat structures in proteins of Plasmodium falciparum.

The majority of malaria antigens that have been cloned contain short sequence repeats which encode antigenic epitopes that are naturally immunogenic. Synthetic peptides have been used to show that natural antibody responses to a strain-specific Plasmodium falciparum S antigen are largely directed against epitopes encoded in an 11-amino acid sequence that is repeated approximately 100 times in the molecule. A 16-amino acid peptide conjugated to bovine serum albumin induced antibodies specific for the S antigen of the homologous isolate. Synthetic peptides have also been used to confirm the natural immunogenicity of epitopes encoded within two blocks of related repeats in the Ring-infected Erythrocyte Surface Antigen (RESA). A 16-amino acid peptide, comprising four repeats of the tetrameric sequence EENV, induced antibodies reactive with the native molecule. Detailed analyses of these anti-peptide antisera indicate that short sequence repeats express more than one epitope, some of which may cross-react with other repeat structures.

Two large immunogenic and antigenic myoglobin peptides and the effects of cyclisation.

Peptides corresponding to sequences (72-88) and (26-54) of beef myoglobin have been synthesised in their open-chain and cyclised forms (using a disulphide bridge) and tested for their antigenicity and immunogenicity. Antibodies raised to beef myoglobin bound to both peptides but more strongly to the 29-residue than to the 17-residue peptide. Cyclisation increased the antigenicity of the larger peptide. In this form the peptide competed much more strongly than in the uncyclised form for specific antibodies to beef myoglobin. The peptides are immunogenic in mice without being coupled to a protein carrier and produce antibodies which bind to beef myoglobin. Peptide (26-54) is the more immunogenic in producing a larger antibody titre to the parent myoglobin and cyclisation again enhances this property. The findings lend weight to the view that longer peptide sequences might be expected to favour the folded state, therefore binding more strongly to antibodies raised to the native protein and eliciting a population of antibodies which contain a larger proportion specific for that conformation. Cyclisation enhances antigenicity and immunogenicity presumably by decreasing the number of degrees of conformational freedom of a peptide without excluding native-like conformations.

The antigenicity of myoglobin-related peptides synthesised on polyacrylamide and polystyrene resin supports.

Polyacrylamide resins [Atherton et al., Bioorg. Chem. 8, 351-370 (1979)] have been found suitable for solid-phase radioimmunoassay of peptides synthesised on the same supports; they are sufficiently stable during side-chain deprotection and swell sufficiently in aq. media to admit antibody molecules to the sites of peptide attachment. A re-examination of five synthetic peptide sequences corresponding to (15-21), (56-62), (94-99), (113-119) and (145-151) of beef myoglobin analogous to those delineated by Atassi [Immunochemistry 12, 423-438 (1975)] for sperm whale myoglobin shows that they all bind anti-beef myoglobin antibodies raised in rabbits, with binding capacities in the order V = III greater than IV greater than I = II. The resin-bound peptide (72-88) binds such antibodies even more extensively, as do certain sequential variants of peptide V. Other peptides, bound to polyacrylamide or polystyrene resins but unrelated to any of the five sequences and varying in size and amino acid composition and sequence were also tested with various antisera. It was concluded that the antibody binding properties of the 30 or so small peptides (two-seven residues) are dominated by their cationic and/or hydrophobic properties. In small peptides, therefore, antibody binding can be safely interpreted only in terms of general structural properties but not in terms of biological specificity. The latter property becomes assessable only with peptides representing larger areas of antigenic protein surfaces.

Conformation of Asn-Ala-Gly-Ala-Asn and its derivatives in solution--a CD spectra analysis.

The CD method has been used to study the conformation of the pentapeptide Asn-Ala-Gly-Ala-Asn (NAGAN) and the tetrapeptides Asn-Ala-Gly-Ala (NAGA) and Asn-D-Ala-Gly-Ala-NH2 (NDAGA) in solution. At low pH the far UV CD spectra of aqueous solutions of NAGAN show a positive extremum at 215 nm and a negative extremum at 232.5 nm. Under this condition, the molecule of NAGAN may assume a beta-turn structure. In the solution of 90% ethanol or tri-fluoroethanol at pH 5.8, NAGAN reveals CD spectra with a negative 218 nm extremum. The[theta]218 values are independent of the concentration of NAGAN. Au intramolecular beta-pleated sheet-like structure is suggested to explain the negative peak. The CD spectra of NAGA show a single positive band at around 215 nm. The possibility of forming a beta-turn by NAGA has been discussed. Only the 196 nm negative extremum can be seen in the spectra of NDAGA. It seems as if NDAGA is in the form of a random coil. According to the report made by Pan et al. all these peptides possess analgesic activity. Therefore, it seems that the analgesic activity is not related to the special conformation of the peptides.