Search

The antiproliferative and immunosuppressive in vitro effects of immunocortin, a synthetic adrenocorticotropin-like (ACTH-like) decapeptide H-Val-Lys-Lys-Pro-Gly-Ser-Ser-Val-Lys-Val-OH, whose sequence corresponds to segment 11-20 of the variable part of the human IgG1 heavy chain, were studied. At concentrations of 10(-11)-10(-7) M, immunocortin was found to inhibit the growth of the human MT-4 T-lymphoblastoid cell line, to suppress the blast transformation of thymocytes, and to decrease the spontaneous mobility of peritoneal macrophages and their bactericidal action toward the virulent strain Salmonella typhimurium 415. By using a 125I-labeled "addressing" fragment of ACTH ¿[125I]ACTH-(13-24)¿, we showed that MT-4 cells express specific receptors for ACTH (Kd 97 pM). Immunocortin and human ACTH (but not the heavy chain of IgG1) competitively inhibited the binding of [125I]ACTH-(13-24) to these receptors with Ki1 of 0.38 and Ki2 of 0.34 nM, respectively. Specific receptors for ACTH (Kd 5.8 nM) on mouse thymocytes were detected and characterized. The unlabeled immunocortin was shown to complete with labeled ACTH-(13-24) for binding to these receptors (Ki = 1.8 nM) and this binding of immunocortin to receptors on thymocytes activates adenylate cyclase from these cells and increases the intracellular concentration of cAMP.

The effects of L-glutamic acid on the differentiation of HL-60 and K-562 cell lines and on the expression level of mRNAs encoding IL-1 beta, IL-6, and TNF alpha were studied. It was shown that TNF alpha actively induces the differentiation of these cell lines, whereas L-glutamic acid enhances its effect. Our results indicated that L-glutamic acid modulates the physiological state of the myeloid cell line in blood, in particular, by affecting both the reception and expression of cytokines functionally important for these cells.

The synthetic ACTH-like decapeptide H-Val-Lys-Lys-Pro-Gly- Ser-Ser-Val-Lys-Val-OH, corresponding to amino acid residues 11-20 of the variable part of the human IgG1 heavy chain (referred to as immunocortin) was found to have an immunosuppressive effect on cells in vitro: it inhibits blast transformation of mouse thymocytes and reduces spontaneous motility of mouse peritoneal macrophages as well as their bactericidal activity against the virulent bacterial strain Salmonella typhimurium 415. Tritium-labeled immunocortin binds with high affinity to ACTH receptors on thymocytes and macrophages (Kd 2. 1 and 2.5 nM, respectively) and activates adenylate cyclase in these cells. Thus, the interaction of immunocortin with the target cell includes the following main steps: binding to the receptor, activation of adenylate cyclase, and elevation of the intracellular content of cAMP.

L-Glutamic acid at a concentration of 0.1 microM was found to induce differentiation of the cell line of HL-60 promyelocytic leukemia into granulocytes or neutrophils. The HL-60 cells have no specific glutamate-binding sites, but L-glutamic acid influences the reception of several cytokines by these cells. At a concentration of 0.1 microM, L-glutamic acid completely inhibits the high-affinity binding of 125I-labeled human recombinant interleukin-1 beta (Kd = 0.32 nM) to the HL-60 cells, but does not affect their low-affinity binding (Kd = 13.3 nM) and does not change the total number of the IL-1 beta-binding sites. Preincubation of the HL-60 cells with 0.1 microM of L-glutamic acid increases 2.5 times the number of receptors for 125I-labeled human recombinant tumor necrosis factor beta. These results suggest that L-glutamic acid plays an important role in the differentiation of the blood myeloid cells.

A specific interaction of [3H]Glu with T lymphocytes from the blood of healthy donors (Kd = 0.236 microM) was revealed and described. It was found that unlabeled quisqualate, a structural analogue of L-glutamic acid, and unlabeled dipeptides Ala-Glu, Glu-Ala, and Glu-Glu competitively inhibit the specific binding of [3H]Glu to T lymphocytes (with Ki 0.19, 2.4, 3.4, and 1.2 microM, respectively). Binding experiments with conjugates of labeled and unlabeled glutamic acid with dextran showed that the receptors of [3H]Glu are localized on the outer surface of the plasma membrane of T lymphocytes.

The mechanisms of action of total saponins from Panax Ginseng C.A. Meyer on the elements of intracellular signalling system in Ehrlich ascites tumor cells were studied. The action of total saponins was compared with the effect of ATP, a classical activator of these cells. Saponins at concentrations of 10(-6)-10(-3)% increased [Ca2+]i, mobilized Ca2+ ions from the endoplasmic reticulum (ER) and activated the influx of Ca2+ to cells. Like ATP, saponins activated the Na+/H+ exchange and Ca(2+)-dependent K+ channels. Of all the parameters, only the activation of Ca2+ influx in cell is directly affected by saponins. The changes in other parameters are connected with nonspecific activation of purinoreceptors. The analysis of the kinetic data suggests that, as distinct from ATP-dependent activation of purinoreceptor, saponins first activate the Ca2+ influx to cells and only then induce the mobilization of Ca2+ from ER.

The influence of the dammarane triterpene glycosides Rb1, Rb2, Rg1 and Rf and their aglycones 20(S) protopanaxatriol and 20(S) protopanaxadiol on fluctuation of the K+ and H+ flows in erythrocytes induced by ionophore A23187 and Ca2+ was studied. It was shown that glycoside Rb1 (10 to 50 micrograms/ml) and 20(S) protopanaxatriol (30 micrograms/ml) had a property of inducing fluctuation of the K+ and H+ flows in erythrocytes. In case of Rb1 the system entirely reversed to the initial state whereas in case of the protopanaxatriol use after the fluctuation the system did not reverse to the initial state. Glycosides Rb2 (10 to 30 micrograms/ml), Rg1 (5 to 20 micrograms/ml) and Rf (10 to 100 micrograms/ml) and 20(S) protopanaxadiol (30 micrograms/ml) in the concentrations used did not initiate the fluctuations. The above substances increased the extracellular concentration of K+ and pH without the system reversion to the initial state.

Molecular mechanisms of action of the total fraction of saponins from Red Korean Ginseng on the elements of the intracellular signalling system of the cells of ascitic Ehrlich carcinoma (AEC) were studied. The action of the total fraction of the saponins on the AEC cells was compared with that of the classic activator of such cells i.e. ATP. It was shown that the action of the total fraction of the saponins was similar to that of ATP. In concentrations of 10(-6) to 10(-3) per cent saponin induced an increase of [Ca2+]j mobilizing Ca2+ from the endoplasmic reticulum (ER) and activating the Ca2+ inlet to the cells. The same as in case with the use of ATP the Ca2+ mobilization from ER was reversible. In comparison to ATP saponin induced higher activation of the Ca2+ inlet to ER and the cells. The same as ATP saponin activated the Na+/H+ exchange and the Ca2+ - dependent K+-channels. Out of all the mention-ed parameters only the activation of the Ca2+ inlet to the cells was probably the direct result of the saponin action. The changes in the other parameters were mediated by nonspecific activation of the purine receptor. The analysis of the kinetic data demonstrated that unlike the ATP-dependent activation of the purine receptor the saponins first of all activated the inlet of Ca2+ to the cells and only after that the mobilization of the latter from ER.