[Deposition of von Willebrand factor in human endothelial cells HUVEC in the endoplasmic reticulum stress induced by an excess of homocysteine in vitro].

Von Willebrand factor (vWF) is an adhesive glycoprotein synthesized and secreted by endothelial cells and megakaryocytes. Violation of vWF secretion by endothelial cells is a characteristic feature of endothelial dysfunction in hyperhomocysteinemia. In our study we examined to clarify the concentration-dependent effect of homocysteine (Hcy) on the expression of vWF. Our studies have shown that homocysteine excess induces changes in the intracellular deposition of von Willebrand factor in cultured human endothelial cells in vitro. Primary cultures of human umbilical vein endothelial cells (HUVEC) were incubated with the various concentrations of D,L-homocysteine (0.025 - 5 mM). Homocysteine at a concentration of 0.025 and 0.25 mM after 18 h incubation caused an increase in the intracellular fraction of vWF in HUVEC cells. High concentrations of homocysteine induced a dose-dependent decrease in the intracellular fraction of vWF. These dose-dependent variations may indicate the modulation by homocysteine of different mechanisms of the deposition, the constitutive secretion and the degradation of vWF in human endothelial cells. We proposed that Endoplasmic reticulum stress, in HUVEC cells by the action of an excess of homocysteine associated with increased intracellular levels of vWF at a relatively low concentration of the inducer. We found decline in intracellular vWF at the same duration but higher concentrations of inducer, which may be due to the ER-associated protein degradation.

[Induction of the endoplasmic reticulum stress in conditions of acid-base imbalance in human cells of T-lymphoblastic leukemia].

Endoplasmic reticulum stress - typical molecular pathophysiological process that underlies many cardiovascular, endocrine and other diseases. Violations of the protein conformational maturation processes in the endoplasmic reticulum can cause proteotoxic stress. Compensatory mechanisms are activated in response to ER stress include increased expression of enzymes involved in the formation of disulfide bonds in proteins. The sulfhydryl groups oxidation in the electron transport chain (PDI-ERO1-O2) is associated with reactive oxygen species (ROS) generation. Increased activity of oxidoreductase ERO1 could be one of the mechanisms of oxidative stress - however, a direct relationship of ER stress with the overproduction of ROS remains a subject of debate. In this study we have shown that induced by dithiothreitol (DTT) violation of the redox balance with low ROS production leads to the endoplasmic reticulum stress in Jurkat cells. ER-stress in these cells is not associated with increased ROS production, DTT treatment leads to induction of apoptosis. Modulation of intracellular levels of ROS can influence the apoptosis-inducing effects of ER-stress. Given the possible involvement of ROS in the generation of disulfide bonds, the role of ROS in ER stress may be a modulation of disulfide proteome including client proteins.

[Multiple medication resistance of apoptosis-resistant tumoral cells].

A4 clone cells, received by CD95-mediated selection from the parental line of Jurkat T-lymphoblast human leukosis, lost their ability of apoptosis as a result of programmed cell death mechanism breakdown. The complex of their acquired phenotypic properties meets tumor progression criteria: oxidative stress resistance, active immune suppression, and low requirement for growth factors. The loss of A4 cell ability of apoptosis is accompanied by acquisition of the phenotype of multiple medication resistance to a wide spectrum of antineoplastic chemotherapeutic drugs and cytotoxins.

[Apoptosis and proliferative activity of bone marrow cells in patients with aplastic syndromes as evidenced by trephine biopsy]. / Apoptoz i proliferativnaia aktivnost' kletok kostnogo mozga u bol'nykh s aplasticheskimi sindromami po dannym trepanobiopsii.

AIM: To clarify the effect of cyclosporin A (CSA) on the apoptosis and proliferative activity of bone marrow cells in patients with aplastic syndromes by trepanobiopsy evidence. MATERIALS AND METHODS: The TUNEL immunohistochemical assay was used to study apoptosis of bone marrow cells in the histological specimens from 24 patients: 8 with refractory anemia (RA), 8 with acute small-proportion leukemias [RA with excessive blasts (RAEB) + RAEB in transformation (RAEBt)], 3 with acute non-lymphoblastic leukemia (ANLL), 5 with lymphogranulomatosis (LGM). Control apoptosis examination was made in 10 patients treated with CSA. The proliferative activity of bone marrow cell was evaluated by bone marrow histological specimens from 10 patients (8 patients with RA and 2 with RAEB + RAEBt) at the onset of disease and during CSA therapy in the immunohistochemical test with primary nuclear antigen Ki-67 antigen antibodies. Changes in the proliferative activity and degree of apoptosis of bone marrow cells were assessed in relation to the cellularity detectable by the histological specimens. RESULTS: Patients with RA showed an increase in bone marrow cell apoptosis to 25.375 +/- 6.874 (-10.8 +/- 5.122 and 8.333 +/- 5.84 in controls and ANLL patients, respectively). The cells of hemopoiesis and stromal microenvironment are in the process of cell death. Higher bone marrow cellularity is observed in CSA-treated patients at clinical and hematological remission, which is followed by rises in the index of proliferation and the degree of apoptosis. CONCLUSION: The clinical effect of CSA in patients with aplastic syndromes is induced by its direct or mediated stimulating effect on pluripotent stem cells of hemopoiesis, by increasing bone marrow cellularity at the expense of clonal and/or normal hemopoiesis.