The review addresses new data on the involvement of mast cells (MCs) in the regulation of cardiac function during the development of some cardiovascular pathologies. Under normal conditions, the number of MCs in the heart is very small compared to their abundance in barrier tissues. They provide cardiac tissue homeostasis and the life-long interaction of the heart with the nervous and endocrine systems. Cardiac pathology is accompanied by the development of the inflammatory response, with MCs playing a significant role at all stages of this process. The number of MCs significantly increases as myocardial infarction, cardiac fibrosis and coronary atherosclerosis develop. Meanwhile, their pathogenic contribution to cardiovascular pathologies is ambiguous because, on the one hand, it is aimed at cardiac tissue adaptation to injury, while on the other hand, the avalanche-like synthesis and release of mediators from activated MCs exacerbates the clinical course of the process. As a result, MCs change their secretory profile, interfere in the realization of cardiac functions against the background of inflammation, but at the same time modulate the afferent information flow from the heart and efferent influences of the nervous system. The coordinated activity of the system loses its stability, leading as a rule to severe consequences for the whole organism. The current status quo analysis of the problem indicates that cardiac activity depends on the functional state of MCs and their complex interaction with the nervous system both under normal conditions and, especially, against the background of developing pathological processes.

The HRV analysis in rats was used to evaluate the relationship between the initial level of total HRV and regulatory changes in the heart function before and on days 1, 3, and 28 after modeling irreversible ischemia (II). According to the level of total HRV, rats were divided into two groups: with initially “low” and “high” levels of HRV, the LV (SDRR = 5.0 ± 0.8 ms) and HV (SDRR = 8.2 ± 0.8 ms) groups, respectively. LV and HV rats reacted differently to the cold test before and after II. Three days after II, LV rats had a better maintenance of the autonomic regulation of the heart, and 28 days later, a smaller size of myocardial area and mortality. In HV rats, the quantity of mast cells in the ischemic area was higher, and the ratio of degranulated cells in the zone unaffected by ischemia was higher in LV rats.

It has previously been shown that many of the peptides that contain proline and glycine amino acids have a pronounced physiological activity, however, the amino acid sequence, which to the greatest extent determines their properties, remains unknown. In this paper, we studied the effect of modified forms of the Prolyl-Glycyl-Proline (PGP) peptide on the secretion of histamine from isolated mast cells and the permeability of vessels in the skin of rats after intradermal administering of Synacthen, lipopolysaccharide LPS and compound 48/80. We have shown that peptides Semax, Selank, PGPL FPG, GPG, PG and GP reduced the secretion of histamine from mast cells and increased the vascular permeability after the administration of Synacthen and LPS, but not compound 48/80. At the same time peptides PLP, PGA and RGP had no effect on these parameters. Thus, the structural modification of PGP affects its properties only if a glycine or proline is replaced by another amino acid.

This study was aimed at investigating the effect of prolyl-glycyl-proline (PGP) tripeptide on vascular permeability in rats with an inflammation. It was found that the peptide reduces the rat paw edema induced by a subcutaneous administration of histamine to the same extent as the conventional anti-inflammatory agent diclofenac. However, an assessment of the relative expression level of the cox-2 gene at the inflammation focus using real-time PCR showed that, in contrast to diclofenac, PGP does not affect the cox-2 gene expression. This is indicative of the fact that they have different mechanisms of action. We used the model of acute peritonitis induced by an intraperitoneal injection of thioglycolate to demonstrate that the inflammatory response of an organism is accompanied by increased vascular permeability in the tissues of the stomach and small intestine. Pre-administration (30 minutes before the induction of the inflammation) of PGP prevented this increase, whereby the level of vascular permeability, exudate volume in the peritoneal cavity, and the amount of the Evans Blue dye in this exudate remained at the control level. Therefore, these results suggest that the anti-inflammatory action of PGP is based on its ability to prevent an increase in vascular permeability.

Изучено влияние трипептида пролил-глицил-пролина (PGP) на проницаемость кровеносных сосудов крыс в условиях воспаления. Установлено, что пептид уменьшает отек лапы крыс, вызванный подкожным введением гистамина, в той же степени, что и классический противовоспалительный препарат диклофенак. Однако определение относительного уровня экспрессии гена cox-2 в очаге воспаления с помощью ПЦР в реальном времени показало, что, в отличие от диклофенака, PGP не влиял на экспрессию гена cox-2. Это свидетельствует о различии механизмов их действия. На экспериментальной модели острого перитонита, вызванного внутрибрюшинной инъекцией тиогликолата, показано, что воспалительная реакция сопровождается повышением проницаемости сосудов в тканях желудка и тонкого кишечника. Предварительное (за 30 мин до индукции воспаления) введение PGP предотвращало это повышение, вследствие чего проницаемость сосудов, объем экссудата в перитонеальной полости и количество красителя Evans Blue в нем оставались на уровне контрольных значений. Таким образом, полученные нами результаты свидетельствуют, что в основе противовоспалительного действия PGP лежит его способность предотвращать повышение проницаемости кровеносных сосудов.

This study is dedicated to the research of the regulatory peptide PGP and its acetylated form (N-AcPGP) effect on the paw edema formation and vascular permeability in rat skin. Edema was induced by subcutaneous administration of histamine. Vascular permeability was determined by intradermal injection of mast cells activators corticotropin-releasing hormone (CRH), lipopoly-saccharide (LPS), Synacthen (corticotropin analogue), histamine and compound 48/80. We established that PGP reduced the size of the paw edema, but N-AcPGP had an opposite effect increasing paw edema. Skin vascular permeability didn't increase in rats under the administration of PGP or N-AcPGP with additional injections of CRH, LPS and Synacthen, but with additional injections of histamine and substance 48/80. We demonstrated in vitro that pretreatment with both PGP and N-AcPGP reduced histamine secretion by rat's peritoneal mast cells under activation by Synacthen. These results provide evidence that the effect of the peptides on vascular permeability is mainly mediated by the influence on the secretory activity of mast cells.

Tripeptide glycyl-prolyl-proline (PGP), a regulatory peptide of the glyproline family, possesses a pronounced anti-inflammatory effect primarily due to its ability to prevent secretion of the proinflammatory mediator histamine by rat peritoneal mast cells. Activation of mast cell with synacthen (ACTH1-24) and substance 48/80 leads to an increase in intracellular calcium concentration. Pretreatment of mast cells with PGP prevented calcium entry into the cytoplasm from both intercellular space and intracellular stores. Acetylated peptide (N-AcPGP) produced a similar effect on histamine release and intracellular calcium content in mast cells activated with synacthen. These findings indicate that both forms of the peptide can stabilize mast cells and prevent intracellular calcium increase.

The influences of PGP on compound 48/80-induced anaphylactoid reaction development in mice and on histamine secretion from rat peritoneal mast cells (RPMC) were investigated. Anaphylactoid reaction was induced by intraperitoneal injection of compound 48/80 into mice. The amount of histamine secreted by RPMC was evaluated. Injection of PGP 15 min before injection of compound 48/80 led to decrease of mortality, and some of anaphylactoid reaction symptoms reduced. PGP had no effect on compound 48/80-induced histamine secretion from (RPMC) in vitro.

The effect of prolyl-glycyl-proline (Pro-Gly-Pro) peptide on morphometric parameters of mast cells under activation by compound 48/80 and synacthen was investigated. Cell image obtained by the laser interference microscopy method (LIM) is a distribution of the optical path difference of light (OPD). It allows evaluation of changes of individual components of cytoplasm (maximal OPD, mOPD) and the total distribution of OPD ("amount of substance"). The changes of the "amount of substance" in the cytoplasm correlate with changes of the amount of secreted histamine (-0.86). Preliminary incubation of mast cells with PRO-GLY-PRO (6 x 10(-5) M) does not change the area, the state of individual components of the cytoplasm (nucleus) and the "amount of substance" (histamine vesicles) in cells. The "amount of substance" (histamine vesicles) and mOPD under activation of mast cells by compound 48/80 (0.02 mg/mL) decrease whereas the release of histamine increases. Preincubation of cells with PRO-GLY-PRO has no effect. Activation of cells by synacthen (2 and 20 mu mol/L) leads to the increase of the cell area, reduction of mOPD and the "amount of substance" (histamine vesicles). Preincubation of cells with PRO-GLY-PRO prevents these changes. So, the protective effect of PRO-GLY-PRO was observed in the case of mast cells' activation by synacthen, but not in case of compound 48/80.

The effect of peptide prolyl-glycyl-proline (Pro-Gly-Pro) on morphometric parameters of mast cells upon their activation by compound 48/80 or synacten was investigated. Cell image, obtained by the method of laser interference microscopy (LIM), is a distribution of the optical path difference of light (OPD). It evaluates the changes of the individual components of cytoplasm (maxOPD) and the total distribution of OPD (“dry mass”). The changes of “dry mass” in cytoplasm correlate with the changes of the secreted histamine amount (−0.86). Preliminary incubation of mast cells with Pro-Gly-Pro (6 × 10−5 M) did not change the area, the state of the individual components of the cytoplasm (nucleus) and “dry mass” (histamine vesicles) in cells. The “dry mass” (histamine vesicles) and maxOPD decreased while the release of histamine increased upon the activation of mast cells by compound 48/80 (0.02 mg/mL). Preincubation of cells with Pro-Gly-Pro had no effect. Activation of cells by synacten (2 and 20 μM) led to the increase of the cell area and the reduction of maxOPD and “dry mass” (histamine vesicles). Preincubation of the cells with Pro-Gly-Pro prevented these changes. So, the protective effect of Pro-Gly-Pro was observed in the case of the activation of mast cells by synacten but not by compound 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.

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.

The investigation of the effect of peptide prolyl-glycyl-proline (PGP) on β-hexosaminidase and histamine secretion by mast cells in primary culture has shown that incubation of mast cells with PGP (6 × 10 −5 M) before their activation by synacten significantly decreased the amount of secreted histamine and β-hexosaminidase in comparison with the action of synacten only. The peptide in investigated concentration had no influence on the level of spontaneous secretion. Incubation of cells with PGP did not prevent their activation by compound 48/80. Therefore, PGP can have a direct effect on isolated rat mast cells in vitro and diminish their secretory activity under activation by synacten.

The influence of PGP on compound 48/80-induced anaphylactoid reaction development in mice and on histamine secretion from rat peritoneal mast cells (RPMS) under their activation by compound 48/80 were investigated. Anaphylactoid reaction was caused by intraperitoneal injection of compound 48/80 into mice. The number of animals with manifestations of anaphylactoid reaction symptoms, the severity of these symptoms, the amount of died animals and the time of death were registering during an hour. Mast cells for in vitro investigations were obtained from rats’ peritoneal cavity. Secreted histamine was evaluated from formation of fluorescent product of it’s condensation with ortho-phthalaldehyde. The preventive injection of PGP in mice (15 min before compound 48/80) decreased the mortality rate of animals and intensity of anaphylactoid reaction symptoms. But PGP had no effect on histamine secretion from mast cells under their activation by compound 48/80 in vitro. Results show that there is a component in the mechanism of PGP protective effect under anaphylactoid reaction which is not connected with mast cells stabilization.

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.

The Pro-Gly-Pro glyproline increases a resistance of the gastric mucosa (GM) to ulcerogenic factors in various models of ulceration and exhibits therapeutic properties in acceleration of the healing of an acetate ulcer. The study of the effects of a wide range of glyprolines on gastric homeostasis did not reveal any dependence of the antiulcer efficacy of the peptides on their chemical structure. Statistically reliable antiulcer effects in all the ulceration models were found for only two peptides: PGP and GPGPGP. The antiulcer activity of PGP exceeded 50% in all the experiments. The PGP tripeptide displays a wide spectrum of physiological activities and affects a number of mechanisms that cause the development of GM ulceration. PGP is shown to pass through the blood-brain barrier and, therefore, can act not only at the periphery, but can also directly affect the CNS structures responsible for the regulatory effects involved in maintaining GM homeostasis.

Stress and the induction of inflammation result in disorders in the microcirculation bed of rat mesentery as well as inhibition of the reaction of lymphatic vessels in response to application of noradrenaline (NA). These disorders are associated with increased secretion by mast cells and point to the important role of these cells in the development of pathological changes in functions of lymphatic vessels. Peptides of the glyproline fan-Lily can prevent disorders of the functional state of the microcirculation bed of the mesentery during both inflammation and stress reactions. This property is associated, to some extent, with their stabilizing effect on mast cells. Inhibition of mast cell activity by glyprolines may be one of the mechanisms of their action in a wide spectrum of pathological processes.