Correlation analysis of cytokine gene expression changes and antiulcer effects of Pro-Gly-Pro and N-Acetyl-Pro-Gly-Pro in experimental models of ulceration.

Direct correlation of the cytokine gene expression level in peripheral blood mononuclear cells (BMNCs) and gastric mucosa (GM) cells with the development of gastric ulcers of various etiologies was shown for the first time. Ethanol-induced ulceration causes an increased transcription of IFNa, IL-8, and IL-12 mRNA in BMNCs. GM damages caused by water immersion stress were accompanied by an increased transcription of TNFa. The sizes of acetate-induced damages were positively correlated with the expression of IL-10 and IL-8 genes in BMNCs and with the expression of IFNa, IL-2, IL-12, and TNF genes in GM cells. Intranasal administration of Pro-Gly-Pro (PGP) reduced ethanol-induced ulceration, activating the transcription of IFNγ, IL-2, and IL-4 mRNA in BMNCs and prevents the formation of stress- and acetateinduced ulcers by inhibiting the expression of IL-8 and IL-10 genes, respectively.

Tripeptide Pro-Gly-Pro prevents disturbances in osmotic resistance of rat erythrocytes under conditions of inflammation.

The development of inflammation (experimental model of peritonitis induced by administration of sodium thioglycolate) was accompanied by a decrease in osmotic resistance of erythrocytes. Changes in osmotic resistance of erythrocytes associated with preliminary (15 min before induction of inflammation) administration of peptide Pro-Gly-Pro were significantly weaker, and the percentage of hemolyzed cells was reduced. The peptide injected against the background of developed inflammation (1 h 45 min after induction) had no corrective effect on osmotic resistance. During in vitro experiments, Pro-Gly-Pro did not affect hemolysis of intact erythrocytes. These results support the assumption that prophylactic administration of the peptide protects erythrocyte membranes and increases their osmotic resistance.

Effects of Prolyl-Glycyl-Proline (PGP) peptide on disorders in rat mesenteric lymphatic vessel function induced by injection of substance 48/80.

Injection of substance 48/80 to rats led to dysfunction of mesenteric lymphatic microvessels, in particular inhibition of their contractility and modification of their reaction to norepinephrine. Injection of PGP peptide before and after substance 48/80 alleviated these disorders. The results indicated the possibility of peptide correction of lymphatic vessel dysfunction.

[Study of gly-proline-containing peptides (PGP and GPGPGP) degradation by aggressive factors in vitro].

PGP, as well as GPGPGP remain stable after 24-hour incubation in a proteolytic environment (in vitro), like equine and rat gastric juice, hydrochloric acid and pepsin in the solution of hydrochloric acid. Perhaps the appearance of PGP's metabolites--PG and GP, that found in the stomachic tissues, is associated with the action of tissue and blood peptidases. Thus, the effects of PGP and GPGPGP cause by the influences both of the peptides and their metabolites, that agree with previously results.

Effects of Pro-Gly-Pro tripeptide on the dopamine system.

Tripeptide Pro-Gly-Pro interacted with dopamine receptors in vitro and reduced behavioral manifestations of apomorphine-induced hyperfunction of the dopamine system in verticalization, stereotypy, and yawning tests. Presumably, the behavioral effects of Pro-Gly-Pro tripeptide were mediated through post- and presynaptic D(2)and D(3)receptors.

Effect of glyprolines PGP, GP, and PG on homeostasis of gastric mucosa in rats with experimental ethanol-induced gastric ulcers.

The decrease in the severity of erosions and ulcer lesions after preventive treatment with PGP or PG correlated with a decrease in the content of lipid peroxidation products to a control level. Activities of SOD and catalase also returned to control values. GP produced the weakest effect on pro- and antioxidant state of the gastric mucosa. We concluded that the pronounced preventive effect of PGP and PG on the development of ethanol-induced erosions and ulcer lesions is largely determined by their antioxidant properties. Glyprolines can be considered as a promising means for prevention and treatment of stomach and duodenal ulcers.

Effect of glyprolines on homeostasis of gastric mucosa in rats with stress ulcers.

Pro-Gly-Pro and its metabolite Gly-Pro effectively prevented the development of erosive and ulcerative lesions of the gastric mucosa in rats under conditions of water-immersion restraint stress by restoring the oxidatant-antioxidant balance in the total fraction of gastric mucosa cells. Pro-Gly was least effective in this respect. We conclude that glyprolines hold much promise as pharmaceutical products, which can be used in gastroenterological practice for the prevention and therapy of ulcer disease of the stomach and duodenum.

Effect of acute and moderate repeated stress on disturbances in reactivity of mesenteric lymphatic vessels during inflammation in rats.

We studied the effect of acute (single immobilization for 1 h) and repeated (daily immobilization for 1 min, 5 days) moderate stress on disturbances in contractility of mesenteric lymphatic vessels in rats with experimental peritonitis. Acute stress was shown to potentiate, while moderate repeated stress attenuate the effect of inflammatory stimulus. It can be hypothesized that moderate repeated stress improves adaptive capacities of the organism, which manifests in reduction or prevention of dysfunction in contractile activity of lymphatic vessels.

[A comparative analysis of distribution of glyprolines administered by various routes].

The distribution of the glyprolines Pro-Gly-Pro and Thr-Lys-Pro-Arg-Pro-Gly-Pro (Selanc) was analyzed and compared in tissues of rat organs after different ways of their administration using the peptides uniformly labeled with tritium. Comparative data on changes in concentrations of the peptides in the rat organs after their intraperitoneal, intranasal, intragastric, and intravenous administration are given. The intranasal administration of both peptides was shown to be optimal for the delivery of glyproline molecules in the CNS. A high affinity of the studied glyprolines for gastric tissues was found for all the ways of their administration. We suggest that a high efficiency of action of glyprolines on homeostasis of the gastric mucous tunic was partially provided by accumulation of these peptides (to high concentrations) in gastric tissues.

Therapeutic effects of glyprolines (PGP, GP, and PG) in rats with stress-induced behavioral disorders.

Experiments on male outbred albino rats showed that stress (10-min swimming) increased anxiety and inhibited orientation and exploratory activities. Poststress (15 min after the end of swimming) intranasal administration of peptides Pro-Gly-Pro and Gly-Pro in a dose of 3.7 micromol/kg prevented stress-induced behavioral disorders. This effect persisted for 3 h.

Selank and its metabolites maintain homeostasis in the gastric mucosa.

Antiulcer properties of a synthetic anxiolytic Selank and in vivo formed metabolites of this compound were studied on 3 experimental models of ulceration. The test peptides decreased the area of experimental gastric ulcers.

Histomorphological characteristics of accelerated healing of acetate ulcers under the effect of glyprolines.

Glyprolines (PGP, GPG, GPGP, PGPGP, and GPGPGP) modulated histomorphological characteristics of acetate ulcers. They accelerated healing of acetate ulcers, promote complete differentiation of the surface epithelium and glands in the gastric mucosa, contributed to the appearance of a considerable number of fibroblasts at the site of the regenerating mucosa, and significantly decreased the count of macrophages.

Peptide correction of disorders in rat mesenteric microcirculatory system during inflammation.

PGP peptide had a protective effect in contractile dysfunction of the rat mesenteric lymph vessels under conditions of inflammation, irrespective of the time of its injection (before or after inflammatory agent). The preventive effect of this peptide is largely determined by its capacity to prevent mast cells activation. PGP injected 2 h after induction of inflammation did not inhibit secretory activity of mast cells, which suggests other mechanisms of its therapeutic action.

[Reculatory fragments of collagen in gastric mucosa homeostasis].

The new glyproline family was distinguished from the regulatory peptides recently. It includes the simplest proline- and glycine-containing peptides: PG, GP, PGP, and respective peptides with hydroxylated proline residues. Glyproline's bioactivity covers many important systems of the body including suppression of some reaction in the blood coagulation and platelet aggregation and gastric mucosal maintenance. It was shown that PGP, PG and GP have a wide spectrum of antiulcer activity with respect to gastric mucosal damages of various aetiology. GHyp and HypGP show also antiulcer action. In vivo glyprolines being fragments of collagen may be generated during synthesis and catabolism of collagen. It is well known that approximately 10-60% of newly synthesized collagen degrade intracellularly with succeeding secretion of small peptides composed of less than 5 aminoacid residues out of cells. Different simplest proline and hydroxyproline fragments of glyprolines are revealed in various type of collagen: GP, GHyp, PG, PPG, PGP, PHypG., GPHyp, GPP, GPG, GHypP, HypGP. It is possible that these fragments may be also secreted out of cells during the stage of degradation of newly synthesized collagen. We showed that the intragastric (per oral) introduction of hydrolyzed gelatin, having 20 small peptide fragments, including PGP and HypGP, also increase gastric stability showing protective and therapeutic antiulcer effect. The corresponding receptors for glyprolines are not completely identified yet but it may be supposed that PGP, GP and other glyprolines interact with the same receptors with which the III type collagen is binding with platelet's receptors. It is supposed that octapeptide sequence KPGGluPGPK of collagen is rather important for binding with receptor. When this sequence in the structure of collagen's molecule binds with the receptor, platelet aggregation is induced. Free octapeptide blocks the receptor and inhibits platelet aggregations. Qualitatve characteristics of parameters of inhibition with intact octapeptide and glyproline, as well as the receptor's structure--that's our concern for the nearest future.

Effects of glyprolines on stress-induced behavioral disorders in rats.

We report here studies on the antistress protective actions of three peptides of the glyproline family: Pro-Gly-Pro, Pro-Gly, and Gly-Pro. Stress (10 min forced swimming) evoked typical changes in the behavioral activity of rats in the elevated cross maze and hole board tests, providing evidence of a significant increase in anxiety and a decrease in the level of orientational-investigative activity. Prior (15 min before stress) i.p. administration of Pro-Gly-Pro and Gly-Pro at a dose of 3.7 microM/kg significantly decreased the stress-induced behavioral abnormalities. This demonstrates the possibility that peptides Pro-Gly-Pro and Gly-Pro may affect CNS structures involved in forming the body's responses to stress-inducing factors. Peptide Pro-Gly, at an equimolar dose, had no marked protective effect and only slightly decreased the stress-induced abnormalities in the behavior of rats.

[Comparison of anticoagulant effects of regulatory proline-containing oligopeptides. Specificity of glyprolines, semax, and selank and potential of their practical application].

Experimental and theoretical demonstration of different effect of certain regulatory peptides (RPs) on blood coagulation is available. The problem of the role of RPs in hemostatic processes becomes particularly significant since, first, the peptides are widespread in nature both in animal and plant tissues, second, there is a relationship between the peptide structure and function and, third, both natural and synthetic peptides are used in practical medicine to correct functions of some factors of the hemostatic system. Many peptide inhibitors of the primary and plasma hemostasis potentiating anticoagulant effects in the body have been described.

[Evenly tritium-labeled peptides and their in vivo and in vitro biodegradation].

Biologically active peptides evenly labeled with tritium were used for studying the in vitro and in vivo biodegradation of the peptides. Tritium-labeled peptides with a specific radioactivity of 50-150 Ci/mmol were obtained by high temperature solid phase catalytic isotope exchange (HSCIE) with spillover tritium. The distribution of the isotope label among all amino acid residues of these peptides allows the simultaneous determination of practically all possible products of their enzymatic hydrolysis. The developed analytical method includes extraction of tritium-labeled peptides from organism tissues and chromatographic isolation of individual labeled peptides from the mixture of degradation products. The concentrations of a peptide under study and the products of its biodegradation were calculated from the results of liquid scintillation counting. This approach was used for studying the pathways of biodegradation of the heptapeptide TKPRPGP (Selank) and the tripeptide PGP in blood plasma. The pharmacokinetics of Selank, an anxiolytic peptide, was also studied in brain tissues using the intranasal in vivo administration of this peptide. The concentrations of labeled peptides were determined, and the pentapeptide TKPRP, tripeptide TKP, and dipeptides RP and GP were shown to be the major products of Selank biodegradation. The study of the biodegradation of the heptapeptide MEHFPGP (Semax) in the presence of nerve cells showed that the major products of its biodegradation are the pentapeptide HFPGP and tripeptide PGP. The enkephalinase activity of blood plasma was studied with the use of evenly tritium-labeled [Leu]enkephalin. A high inhibitory effect of Semax on blood plasma enkephalinases was shown to arise from its action on aminopeptidases. The method, based on the use of evenly tritium-labeled peptides, allows the determination of peptide concentrations and the activity of enzymes involved in their degradation on a tg scale of biological samples both in vitro and in vivo.

[Short peptide fragments with antiulcer activity from a collagen hydrolysate].

A peptide acidic hydrolysate of collagen (PHC) was obtained under conditions (4 N HCl) ensuring the predominant formation of short peptides, glyprolines. They were separated and their antiulcer activity was studied. Thirty individual peptides with molecular masses of 174-420 amu were isolated from the PHC by HPLC. The PHC was shown to predominantly contain 2- to 4-aa peptides, including PG, GP, and PGP. Experiments on rats demonstrated that, on intragastric administration at a dose of 1 mg/kg, PHC enhances the stability of the gastric mucosa to the action of ulcerogenic factors, such as ethanol and stress, and exhibits a protecting antiulcer effect. Even a lesser dose (0.1 mg/kg), which reduced ulcer area twofold, was effective in the stress model of ulcer formation. The intraperitoneal and intragastric administration of PHC at a dose of 1 mg/kg was found to exhibit a therapeutic effect in the acetate model of ulcer formation.

The role of protective effects of proline-containing peptides (PGP, PG, and GP) in contractile dysfunction of mesenteric lymphatic vessels in rats with experimental acute peritonitis.

The development of acute peritonitis in rats induced by intraperitoneal injection of thioglycollate was accompanied by a decrease in contractile function of mesenteric lymphatic vessels and impaired response to norepinephrine. Administration of proline-containing peptides after induction of inflammation significantly decreased the severity of these disorders. Our results attest to the possibility of using peptides for the correction of mesenteric microcirculatory disturbances during inflammation.