SARS-CoV-2 Receptors and Their Involvement in Cell Infection.

The new coronavirus infection (COVID-19) pandemic caused by SARS-CoV-2 has many times surpassed the epidemics caused by SARS-CoV and MERS-CoV. The reason for this was the presence of sites in the protein sequence of SARS-CoV-2 that provide interaction with a broader range of receptor proteins on the host cell surface. In this review, we consider both already known receptors common to SARS-CoV and SARS-CoV-2 and new receptors specific to SARS-CoV-2.

Erratum to: Experimental Search for New Means of Pathogenetic Therapy COVID-19: Inhibitor of H2-Receptors Famotidine Increases the Effect of Oseltamivir on Survival and Immune Status of Mice Infected by A/PR/8/34 (H1N1).

[This corrects the article DOI: 10.1134/S0022093022010203.].

Experimental Search for New Means of Pathogenetic Therapy COVID-19: Inhibitor of H2-Receptors Famotidine Increases the Effect of Oseltamivir on Survival and Immune Status of Mice Infected by A/PR/8/34 (H1N1).

The development of drugs for the therapy of COVID-19 is one of the main problems of modern physiology, biochemistry and pharmacology. Taking into account the available information on the participation of mast cells and the role of histamine in the pathogenesis of COVID-19, as well as information on the positive role of famotidine in the prevention and treatment of coronavirus infection, an experiment was carried out using famotidine in a mouse model. We used a type A/PR/8/34 (H1N1) virus adapted to mice. The antiviral drug oseltamivir (Tamiflu), which belongs to the group of neuraminidase inhibitors, was used as a reference drug. The use of famotidine in combination with oseltamivir can increase survival, improve the dynamics of animal weight, reduce the level of NKT cells and increase the level of naive T-helpers. Further studies of famotidine in vivo should be aimed at optimizing the regimen of drug use at a higher viral load, as well as with a longer use of famotidine.

Markers of Endothelial Cells in Normal and Pathological Conditions.

Endothelial cells (ECs) line the blood vessels and lymphatic vessels, as well as heart chambers, forming the border between the tissues, on the one hand, and blood or lymph, on the other. Such a strategic position of the endothelium determines its most important functional role in the regulation of vascular tone, hemostasis, and inflammatory processes. The damaged endothelium can be both a cause and a consequence of many diseases. The state of the endothelium is indicated by the phenotype of these cells, represented mainly by (trans)membrane markers (surface antigens). This review defines endothelial markers, provides a list of them, and considers the mechanisms of their expression and the role of the endothelium in certain pathological conditions.

[Clinical observation of a patient with thrombotic thrombocytopenic purpura with renal and intestinal lesions].

The article presents a brief description of a rare disease - thrombotic thrombocytopenic purpura (Moshkovits - disease), which is based on the deficiency of ADAMTS-13 metalloproteinase, leading to the development of thrombotic microangiopathy with the defeat of vital organs. The article also describes the clinical observation of a patient with the Moshkovits - disease. The features of the above observation are involvement in the pathological process of the kidneys and intestines, while in the classical descriptions of the disease there is a predominant lesion of the Central nervous system, as well as the genetic form of the disease.

Involvement of two-pore channels in hydrogen peroxide-induced increase in the level of calcium ions in the cytoplasm of human umbilical vein endothelial cells.

Hydrogen peroxide at concentrations below cytotoxic ones causes an increase in the cytoplasmic calcium concentration in human umbilical vein endothelial cells as a result of calcium release from intracellular stores. Two-pore calcium channel blocker trans-NED19 partially suppresses the increase in the level of calcium ions in the cells in response to the addition of hydrogen peroxide. The staining of endothelial cells with the fluorescent stereoisomer cis-NED19 and LysoTracker confirmed the localization of two-pore calcium channels in lysosomes and endolysosomal vesicles.

Suppression of Histamine-Induced Relaxation of Rat Aorta and Calcium Signaling in Endothelial Cells by Two-Pore Channel Blocker trans-NED19 and Hydrogen Peroxide.

The blocker of two-pore channels trans-NED 19 and hydrogen peroxide were found to inhibit histamine-induced relaxation of rat-aorta. The degree of inhibition depended on histamine concentration. The relaxation in response to I µM histamine of rat aorta preconstricted with 30 mM KCI, serotonin, or endothelin- 1, was completely abolished by 30 µM trans-NED 19. On the other hand, trans-NED 19 decreased the relaxation of the aorta in the presence of 10 µM histamine only by 2.1-fold to 2.4-fold, and there was almost no inhibition by trans-NED 19 of the relaxationinduced by 100 ptM histamine.) Relaxation of precontracted with serotonin aorta in response to 10 and 100 µM histamine was reduced by hydrogen peroxide (200 M) by 10- and 2.5-fold, respectively. Suppression of aorta relaxation by trans-NED 19 and H202 correlated with their inhibitory effect on the histamine-induced increase in the cytoplasmic free calcium concentration in human umbilical vein endothelial cells. With the use of a fluorescent probe LysoTracker, the cis-NED19 binding sites were demonstrated to be localized in endolysosomes of the endothelial cells. These data indicate that two-pore calcium channels participate in the histamine-induced endothelium-dependent relaxation of rat aorta. Furthermore, their functional role is exhibited much more clearly at low histamine concentrations. We suggest that hydrogen peroxide evokes depletion of intracellular calcium depots thereby suppressing the response to histamine.

[DUAL PROAPOPTOTIC AND PRONECROTIC EFFECT OF HYDROGEN PEROXIDE ON HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS].

The ratio of early apoptosis and late apoptosis (necrosis) in the cultured human umbilical vein endothelial cells was estimated after exposure to hydrogen peroxide (H2O2) in vitro trying to keep them close to the physiological conditions (high cell density, high serum content, H2O2 concentration not over 500 µM). Cell viability was assessed using flow cytometry and simultaneous staining with fluorescent dyes PO-PRO-1 to detect early apoptotic cells, and DRAQ7 to detect late apoptotic and necrotic cells. The data obtained suggest that the primary mechanism of cytotoxic response is apoptosis. The critical concentration of H2O2 causing the death of the cell population in a dense monolayer is 250 µM. Lower concentrations of H2O2 (up to 200 µM) cause death of individual cells; however, viability of endothelial cell population is retained, and response to calcium activating agonists does not change compared with control cells.

[Serotonin and its receptors in the cardiovascular system].

Serotonin in cardiovascular system plays an important role in blood coagulation, allergy, and inflammation, as well as in blood vessel tone regulation. In this review, the mechanisms of serotonin effects upon the cells of blood vessels are considered and the list of main agonists and antagonists is presented. The signaling pathways activated by serotonin and their interaction in normal and pathological states are described.

Arachidonic acid activates release of calcium ions from reticulum via ryanodine receptor channels in C2C12 skeletal myotubes.

Arachidonic acid causes an increase in free cytoplasmic calcium concentration ([Ca2+]i) in differentiated skeletal multinucleated myotubes C2C12 and does not induce calcium response in C2C12 myoblasts. The same reaction of myotubes to arachidonic acid is observed in Ca2+-free medium. This indicates that arachidonic acid induces release of calcium ions from intracellular stores. The blocker of ryanodine receptor channels of sarcoplasmic reticulum dantrolene (20 µM) inhibits this effect by 68.7 ± 6.3% (p < 0.001). The inhibitor of two-pore calcium channels of endolysosomal vesicles trans-NED19 (10 µM) decreases the response to arachidonic acid by 35.8 ± 5.4% (p < 0.05). The phospholipase C inhibitor U73122 (10 µM) has no effect. These data indicate the involvement of ryanodine receptor calcium channels of sarcoplasmic reticulum in [Ca2+]i elevation in skeletal myotubes caused by arachidonic acid and possible participation of two-pore calcium channels from endolysosomal vesicles in this process.

[Calmodulin inhibitors suppress a calcium signal from serotonin receptors in smooth muscle cells and remove the vasoconstrictive response upon intravenous introduction of serotonin].

Comparative study of the effect of calmodulin inhibitors (trifluoperazine, W-12, and W-13) and the TRPVI channel blocker (capsazepine) on receptor-dependent calcium exchange in smooth muscle cells of the rat aorta and on the contractility of the isolated aorta was conducted. It was determined that trifluoperazine almost completely removes an increase in the concentration of calcium ions in the cytoplasm of smooth muscle cells (isolated from the rat aorta) and smooth muscle cells of the A7r5 line in response to serotonin and does not influence the cell response to vasopressin and angiotensin II. W-12 and W-13 also do not reduce calcium ion concentration increase (induced by vasopressin and angiotensin II) but reduces by two times its rise in response to serotonin. It was found that the efficiency of calcium exchange suppression by calmodulin inhibitors correlates with the intensity at which they inhibit the contractile response of the aorta on the effect of serotonin. It was detected that the inhibiting effect of calmodulin blockers on calcium exchange in smooth muscle cells and the contractility of the rat isolated aorta during the activation of serotonin vasoconstrictive receptors are realized by a TRPV1-independent mechanism. It was demonstrated in experiments in vivo that trifluoperazine does not influence hypotensive reaction in rats (normally observed in response to intravenous serotonin introduction), but removes the hypertensive effect of this neurotransmitter in rats after chronic introduction of dexamethasone. The results obtained confirm the hypothesis (that we previously stated) about the direct involvement of calmodulin in signal transmission from vasoconstrictive serotonin receptors.

[Involvement of calmodulin in realization of vasoconstrictive effects of serotonin and norepinephrin].

Possible involvement ofcalmodulin in adrenergic and serotoninergic regulation of vascular contractility has been studied. Calmodulin inhibitors trifluoperazine and W-13 suppress vasoconstriction of the rat aorta in response to norepinephrine, serotonin, and serotonin 5HT1A- and 5HT2A-receptor agonists (8-OH-DPAT and DOI, respectively) and do not affect the vasodilatory effect of 5HT1B-, 5HT2B-, and 5HT4-receptors. The force of aorta contraction in response to 8-OH-DPAT increases after the activation of calcium entry through voltage-gated Ca2+-channels. This effect is not related to non-specific activation of alpha1-adrenoceptors, since it is realized in the presence of prazosin. The inhibitor of calmodulin-dependent myosin light chain kinase KN93 decreases the vasoconstrictive response in response to norepinephrine and serotonin by only 20%. Calmodulin inhibitors slightly decrease aortic constriction in response to endothelin-1, vasopressin, angiotensin II, and KCl. Trifluoperazine does not suppress vasoconstriction induced by the G-protein activator AlF4(-). It is assumed that the target of trifluoperazine and W-13 is calmodulin interacting directly with alpha1-adrenoceptors and serotonin 5HT1A- and 5HT2A-receptors.

[Activation of "silent" vasoconstrictive 5-HT1A receptors as a possible mechanism of synergism in angiotensin II and serotonin effect on vascular tone].

It has been shown that the agonist of 5HT1A-receptors 8-OH-DPAT induces contraction of aortic rings in the presence of angiotensin II. This effect is not associated with activation of alpha1-adrenoceptors by 8-OH-DPAT as it is reproduced in the presence of prazosin which completely suppresses the nonspecific vasoconstrictive effect of 8-OH-DPAT via alpha1-adrenoceptors on the aorta incubated without angiotensin II. Synergism in the action of angiotensin II and 8-OH-DPAT is completely preserved after partial desensitization of the receptors of angiotensin II. It has been found that 8-OH-DPAT increases the free cytoplasmic calcium concentration in cultured smooth muscle cells from the rat aorta. The data obtained support the hypothesis about the existence of "silent" vasoconstrictive 5HT1A-receptors. It has been suggested that activation of these receptors underlies synergism in vasoconstrictive action of serotonin and angiotensin II.

[A case of hemolytic-uremic syndrome with development of catastrophic antiphospholipid syndrome: diagnosis and clinical tactics].

The paper describes a case of practically simultaneous development of the hemolytic-uremic syndrome (HUS) and the catastrophic antiphospholipid syndrome (CAPS) complicated by mesenteric vessel thrombosis and small bowel necrosis. Multimodality treatment comprising volume plasmapheresis, fresh frozen plasma transfusion, hemodialysis, anticoagulant and disaggregant therapy could relieve thrombogenic events, such as pulmonary artery thromboembolism and intestinal necrosis.

[Agonist 5HT1A-receptors of serotonin 8-OH-DPAT increase the power of collapse of the aorta and mesenteric artery in rats in the presence of endothelin-1 or vasopressin and cause vessel relaxation precollapsing with noradrenaline].

Agonist 5HT1A serotonin receptors 8-OH-DPAT at 70-80% in rats relax the isolated aorta and mesenteric artery, precollapsed with noradrenaline. An inhibitor of NO-synthase L-NAME two or more times suppresses vazodilatatomyh reaction in response to the effect of 8-OH-DPAT. The addition of 8-OH-DPAT to the aorta in a state of rest or precollapsed with endothelin-1 or vasopressin causes an increase in power reduction. A blocker of alpha1-adrenoceptors prazosin almost completely suppress the aorta collapse reaction to the effect of 8-OH-DPAT in the absence of vasoconstrictives, but does not affect the contraction force in response to 8-OH-DPAT of the aorta in the presence of endothelin-1 or vasopressin and does not shift the curve of the dependence of force collapse on the concentration of 8-OH-DPAT. Our data show the existence in the rat aorta of vasodilator and vasoconstrictive 5HT1A receptors. The vasodilator receptors act according to a NO-dependent mechanism. Vasoconstrictive 5HT1A-receptors are in a latent state (silent receptors) and begin to function after preactivation of endothelin-1 or vasopressin receptors. The ability ofvasoconstrictive 5HT1A-receptors to cause aorta reduction remains after washing endothelin-1 off of the aorta and its relaxation.

[Plasma membrane depolarization and activation of receptors for endogenous vasoconstrictors as possible mechanisms of potentiation of vasoconstrictive response to serotonin in traumatic shock in rats].

The goal of this work was to study possible mechanisms underlying the potentiation of vasopressor response to serotonin observed in traumatic shock. Experiments with isolated aorta and mesenteric artery of the rat showed that vasoconstriction is caused by the activation of 5HT2A receptors. Agonists of 5HT1B, 5HT1D, 5HT2B, and 5HT4 receptors induced vasodilation. Agonists of 5HT1A receptors had a dual effect determined by interaction with alpha1-adrenergic receptors and 5HT1A receptors. Plasma membrane depolarization with 15 mM KCl increased the vasoconstrictive force in response to serotonin. This effect was determined by the ability of KCl to activate voltage-gated calcium channels, as a result of which the intracellular calcium stores are replenished. Inhibition of serotonin response by ketanserin, a 5HT2A receptor blocker, did not depend on the presence of 15 mM KCl. Constriction in response to serotonin was potentiated after its addition to vessels preconstricted with noradrenaline or endothelin-1. The constriction response partially retained in the presence of 2 x 10(-7) M ketanserin, which completely suppressed the serotonin-induced constriction of dilated vessels both at normal membrane potential and after plasma membrane depolarization. It can be assumed that noradrenalin and endothelin-1 alter the characteristics of 5HT2A receptors and possibly 5HT1A receptors as a result of their heterodimerization with the receptors for these vasoconstrictive hormones or interreceptor interaction at the level of signaling systems. Along with the potentiating effect of KCl, this mechanism may underlie the enhancement of vasopressor response to serotonin in shock.

Inversion of the response to serotonin in rats with traumatic shock.

Normally serotonin reduced blood pressure. It was shown that in rats with traumatic shock its hypotensive effect was transformed into hypertensive one. In vitro serotonin exhibited a slight vasoconstrictor effect on isolated rat aorta, while 24 h after injury, the strength of aortic contractions in response to serotonin increased 2.2 times. Desensitization of glucocorticoid receptors caused by injection of high doses of dexamethasone (3 mg/kg) to rats for 5 days led to similar changes in serotonin effect. We hypothesized that inversion of the response to serotonin in shock was caused by increased activity and/or expression of vasoconstrictor serotonin receptors in blood vessels.

[The role of desensitization of glucocorticoid receptors in the development of vascular resistance to endogenous vasoconstrictors in traumatic shock].

The fact that the activity of cytosol glucocorticoid receptors decreases in shock have been shown before [Golikov P. P. et al., 2001]. The connection between the development of vascular hyporeactivity to endogenous vasoconstrictors and desensitization of glucocorticoid receptors was studied in this investigation. On Kenton traumatic model in a rat experiment, it was shown that the strength of the isometric constriction of the isolated aorta in response to angiotensin II, endothelin-1, phenylephrine, noradrenaline, and vasopressin falls on the second day after a severe mechanical injury (3.3, 2.1, 1.7, 1.6, and 1.5 times, respectively; p < 0.01). On the contrary, the strength of the constriction in response to serotonin increases more then twice. Artificial desensitization of glucocorticoid receptors by long-term administration of dexamethasone (3 mg per kg during five days) results in similar changes of vascular reactivity i.e. a 2.5, 2, 7, and 1.4-fold decrease in the strength of aortal constriction in response to angiotensin II, vasopressin, and endothelin-1, respectively. The strength of the constriction in response to serotonin tended to increase as well. Carbahol-induced relaxation of the aorta pre-constricted with noradrenaline did not change compared with control, being 70 to 80%, both in shock and after desensitization of glucocorticoid receptors with dexamethasone. Presumably, the pathogenetic mechanism of pressor reaction suppression, connected with a decrease in cytosol glucocorticoid receptor activity and thus with inhibition of glucocorticoid-induced expression of the membrane receptors of endogenous vasoconstrictors, is realized in traumatic shock together with other mechanisms.

[Activation of cardiac contractivity of the edible snail H. pomatia under effect of thrombin. Study of role of cAMP].

Thrombin acts on mammalian cells through specific, the so-called protease-activated receptors (PARs). The thrombin action is mediated via three out of four known types of these receptors PAR(1, 3, 4). Mammalian thrombin receptors, apart from performance of other functions, control cardiac and vascular contractility. It is not known whether receptors of such kind exist in invertebrate animals. In the present work we have showed for the first time that thrombin in the concentration range of 0.01-1 units/ml increases amplitude of contractions of the isolated heart ventricle of the edible snail Helix pomatia. Its effect is reproduced by peptide ligands of receptors PAR1 and PAR4 that have sequences Ser-Phe-Leu-Leu-Arg-Asn (SFLLRN) and Glu-Tyr-Pro-Gly-Lys-Phe (QYPGKF), respectively. A potent activati of cardiac contractivity of H. pomatia is serotonin. A comparative study of mechanisms of action of serotonin and thrombin on the edible snail heart was carried out. cAMP participates in transduction of signal from serotonin receptors. On the membrane preparation from the H. pomatia heart, it was shown that thrombin and peptide ligands PAR(1, 4), unlike serotonin, did not increase adenylyl cyclase activity. Thus, mechanism of activation of cardiac contractivity of H. pomatia by thrombin differs from the action mechanism of serotonin. It is suggested that molluscs have receptors homologous to protease activated mammalian receptors.