Angiotensin 'antipeptides': (-)messenger RNA complementary to human angiotensin II (+)messenger RNA encodes an angiotensin receptor antagonist

(-)mRNA complementary to human angiotensin II (+)mRNA encodes the 'antipeptide' Glu-Gly-Val-Tyr-Val-His-Pro-Val which is structurally related to angiotensin II. Angiotensin II 'antipeptide' (antiANG II) and the desglutamyl heptapeptide (antiANG III) are Type I antagonists which inhibit the contractile action of angiotensin at smooth muscle receptors by binding to a negative modulatory site on the angiotensin receptor which is distinct from the angiotensin binding site. These findings may illustrate that the inhibitory binding site on the angiotensin receptor exists to accomodate a naturally occurring inhibitor(s), which is encoded by the DNA strand complementary to that encoding angiotensin II.     

Removal of the 9-methyl group of retinal inhibits signal transduction in the visual process. A Fourier transform infrared and biochemical investigation

The photoreaction of opsin regenerated with 9-demethylretinal has been investigated by UV-vis spectroscopy, flash photolysis experiments, and Fourier transform infrared difference spectroscopy. In addition, the capability of the illuminated pigment to activate the retinal G-protein has been tested. The photoproduct, which can be stabilized at 77 K, resembles more the lumirhodopsin species, and only minor further changes occur upon warming the sample to 170 K (stabilizing lumirhodopsin). UV-vis spectroscopy reveals no further changes at 240 K (stabilizing metarhodopsin I), but infrared difference spectroscopy shows that the protein as well as the chromophore undergoes further molecular changes which are, however, different from those observed for unmodified metarhodopsin I. UV-vis spectroscopy, flash photolysis experiments, and infrared difference spectroscopy demonstrate that an intermediate different from metarhodopsin II is produced at room temperature, of which the Schiff base is still protonated. The illuminated pigment was able to activate G-protein, as assayed by monitoring the exchange of GDP for GTP gamma S in purified G-protein, only to a very limited extent (approximately 8% as compared to rhodopsin). The results are interpreted in terms of a specific steric interaction of the 9-methyl group of the retinal in rhodopsin with the protein, which is required to initiate the molecular changes necessary for G-protein activation. The residual activation suggests a conformer of the photolyzed pigment which mimics metarhodopsin II to a very limited extent.     

The vectoring of cactophilic yeasts by Drosophila

Summary At two locations in the Sonoran Desert, yeasts were sampled from species of Drosophila, the flies' cactus hosts, and other neighboring sources of cactophilic yeasts to determine the relation between the yeasts vectored by the fly and the yeasts found in their breeding sites. D. mojavensis, D. nigrospiracula, and D. mettleri vectored yeast assemblages significantly more similar to the yeast species found on the rot from which the flies were collected than to the yeasts found on other rots from the flies host cactus or other rotting cactus at the same site. Rots with Drosophila had fewer yeast species than those without flies, suggesting that flies were associated with younger rots. Rots with flies and the Drosophila also had more yeast species with the capability to produce ethyl acetate than rots without flies. The results support the contention that cactophilic Drosophila feed on a subset of the yeasts available in an area, and may act to maintain differences among the yeast communities found on different species of cactus.     

Synthesis and biological activities of angiotensin II and Sarmesin analogues containing cyclohexylalanine

Analogues of angiotensin II with cyclohexylalanine (Cha) at position 4 or 8, and analogues of the competitive (type II) angiotensin antagonist [Sar1,Tyr(Me)4]ANG II (Sarmesin) with Cha at position 8, have been prepared by the solid phase method and purified by reversed-phase HPLC. Analogues of ANG II with Cha at position 8 in which the position 1 residue was substituted with sarcosine (Sar) or amino-isobutyric acid (Aib) or was deleted (Des), were slowly reversing (Type I) antagonists with "pA2" values in the rat isolated uterus assay of approximately 8.5. The additional substitution of Tyr(Me) for Tyr at position 4 of these peptides gave reversible competitive (Type I/II) antagonists with pA2 values of 6.7, 5.8, and less than 5, while substitution of Phe for Tyr gave pA2 values of 7.4, 6.7, and less than 5, respectively. All 19 peptides synthesized in this study had low intrinsic agonist activity in the rat isolated uterus assay except for the type I antagonists [Sar1, Cha8]ANG II (7%), [Aib1, Cha8]ANG II (12%) and [Des1, Cha8]ANG II (20%). These data illustrate that the substitution of Cha at position 8 of ANG II analogues produces potent antagonists; however, Type I antagonists retain significant agonist activity whereas Type I/II antagonists do not. In contrast, substitution of Cha at position 4 in a variety of ANG II analogues resulted in severely diminished biological activity, illustrating that the presence of an aromatic ring quadrupole at position 4 is obligatory for receptor binding and activity.     

Receptor interactions of the position 4 side chains of angiotensin II analogues: Importance of aromatic ring quadrupole

A triad of interacting group (TyrOH? His$ \underline\ominus$O₂C) in angiotensin II (ANG II) has been postulated to create the tyrosinate anion pharmacophore (tyanophore) responsible for receptor activation/triggering (Biochim. Biophys. Acta 1991, 1065, 21). In the present study we investigated the effects on bioactivity of substituting the Tyr⁴ residue in [Sar¹]ANG II with other anionic or electronegative amino acids, and with a number of aromatic amino acids lacking a hydroxyl group. [Sar¹ Nva(δ-OH)⁴]ANG II, [Sar¹ Nva(δ-OCH₃)⁴]ANG II, [Sar¹ Met⁴]ANG II, [Sar¹ Gln⁴]ANG II, [Sar¹ Glu⁴]ANG II and [Sar¹ DL -Alg⁴]ANG II had agonist activities in the rat isolated uterus assay of 4, 3, 19, 10, > 0.1 and > 0.1%, respectively, of that of ANG II. [Sar¹ Nal⁴]ANG II, [Sar¹ Pal⁴]ANG II, [Sar¹ DL -Phg(4′-F)⁴]ANG II, [Sar¹ Phe(4′-F)⁴]ANG II, [Sar¹ Phe(F₅)⁴]ANG II and [Sar¹ His⁴]ANG II had agonist activities of 4.5, 7, < 0.1, 0.2, 1 and 0.6%, respectively. All peptides investigated were devoid of measurable antagonist activity except [Sar¹] Phe(4′-F)⁴ ANG II (pA₂ = 7.7). These findings illustrate that anionic or electronegative aliphatic side chains replacing tyrosinate at position 4 can partially activate the angiotension receptor. For ANG II analogues containing an aromatic amino acid other than Tyr at position 4, ligand binding and agonist activity are not dependent on the electronegativity or dipole moment of the aromatic ring, or on the ability of the 4′ ring substituent to accept a proton. Modelling based on ab initio calculations of aromatic ring multipoles illustrate that the apparent binding affinity (PA₂) of ANG II analogues is associated with a perpendicular electrostatic interaction of the position 4 aromatic ring with a receptor-based group. In addition, intramolecular interactions providing for the conformation of the ligand as it approaches its receptor appear to have a role in determining agonist vs antagonist activity.     

Oligosaccharides derived from the xyloglucan isolated from the seeds of Hymenaea courbaril var. stilbocarpa

On aqueous extraction, Hymenaea courbaril var. stilbocarpa, known in Brazil as jatobá, furnishes a high yield of viscous xyloglucan (45%) from its seeds. The crude polysaccharide (B1) was hydrolysed and the products, analysed as alditol acetates, were glucose, xylose, galactose and arabinose in the ratio 50:35:13:2. After further fractionation on a DEAE-cellulose column (chloride form), the main fraction (70% yield, B2) was obtained. The basic structure of the xyloglucan was determined as a cellulose-type (1 → 4)-linked β-d-glucan backbone partially substituted with side chains at 06 of -d-xylopyranose, some of which were themselves substituted at 02 by the units of β-d-galactopyranose. Treatment of the xyloglucan (B2) with commercial cellulase from Trichoderma sp. yielded six oligosaccharides. These oligosaccharides were isolated by preparative paper chromatography, and their structures were determined by gas-liquid chromatography-mass spectroscopy of the derived partially O-methylated alditol acetates. These results confirm the structure proposed for jatobá seed xyloglucan.     

Polysaccharides from the seeds of Senna multijuga

The seeds of Senna multijuga were extracted with water or 1% acetic acid and treated with ethanol, resulting in two insoluble fractions. After purification, the major one (FIA, 23%) was shown to be a galactomannan (Man:Gal 2.3:1;[] = + 54.6;[η]=1340mlg⁻¹). It consists of a main chain of (1 → 4)-linked β-d-mannopyranosyl residues substituted at 06 by single-unit -d-galactopyranosyl side chains. The second fraction (FIB, 2.5%) was an O-acetyl-glucuronoarabinoxylan from the seed coats (O-acetyl 8.3 mol%; glucuronic acid 11.7%, Xyl:Ara ratio 20:1), which showed a predominance of 4-O-substituted Xylp units (84.4%), branched at 03 with non-reducing end units of Xylp, Araf and glucuronic acid. The O-acetyl positions in d-xylosyl units are at 02 (4.8%), 03 (4.4%) and 02,3 (0.9%). The ratio between 03 and 02 determined by ¹³C-nuclear magnetic resonance spectroscopy is 1.5:1.     

Treatment with apolipoprotein A-1 mimetic peptide reduces lupus-like manifestations in a murine lupus model of accelerated atherosclerosis

Introduction

The purpose of this study was to evaluate the effects of L-4F, an apolipoprotein A-1 mimetic peptide, alone or with pravastatin, in apoE^-/-Fas^-/-C57BL/6 mice that spontaneously develop immunoglobulin G (IgG) autoantibodies, glomerulonephritis, osteopenia, and atherosclerotic lesions on a normal chow diet.

Methods

Female mice, starting at eight to nine weeks of age, were treated for 27 weeks with 1) pravastatin, 2) L-4F, 3) L-4F plus pravastatin, or 4) vehicle control, followed by disease phenotype assessment.

Results

In preliminary studies, dysfunctional, proinflammatory high-density lipoproteins (piHDL) were decreased six hours after a single L-4F, but not scrambled L-4F, injection in eight- to nine-week old mice. After 35 weeks, L-4F-treated mice, in the absence/presence of pravastatin, had significantly smaller lymph nodes and glomerular tufts (P_{L, LP} < 0.05), lower serum levels of IgG antibodies to double stranded DNA (dsDNA) (P_L < 0.05) and oxidized phospholipids (oxPLs) (P_{L, LP} < 0.005), and elevated total and vertebral bone mineral density (P_{L, LP} < 0.01) compared to vehicle controls. Although all treatment groups presented larger aortic root lesions compared to vehicle controls, enlarged atheromas in combination treatment mice had significantly less infiltrated CD68⁺ macrophages (P_LP < 0.01), significantly increased mean α-actin stained area (P_LP < 0.05), and significantly lower levels of circulating markers for atherosclerosis progression, CCL19 (P_{L, LP} < 0.0005) and VCAM-1 (P_L < 0.0002).

Conclusions

L-4F treatment, alone or with pravastatin, significantly reduced IgG anti-dsDNA and IgG anti-oxPLs, proteinuria, glomerulonephritis, and osteopenia in a murine lupus model of accelerated atherosclerosis. Despite enlarged aortic lesions, increased smooth muscle content, decreased macrophage infiltration, and decreased pro-atherogenic chemokines in L-4F plus pravastatin treated mice suggest protective mechanisms not only on lupus-like disease, but also on potential plaque remodeling in a murine model of systemic lupus erythematosus (SLE) and accelerated atherosclerosis.