Effects of the combined arginase and canavanine treatment on leukemic cells in vitro and in vivo.

It was previously demonstrated in in vitro experiments that canavanine (Cav), a natural toxic arginine analogue of plant origin, is a promising candidate for augmenting the antineoplastic effects of arginine starvation. We demonstrated herein that recombinant human arginase, an arginine degrading enzyme, abrogated growth and significantly increased Cav cytotoxicity toward cultured L1210 murine leukemic cells. Cav co-treatment further reduced cells viability in a time-dependent manner and significantly promoted apoptosis induction. In the pilot study we also evaluated for the first time the potential toxicity of the combined arginine deprivation and Cav treatment in healthy mice. Administration of Cav alone or in combination with pegylated cobalt-containing human arginase (Co-hARG) did not evoke any apparent toxic effects in these animals, with no significant behavioural and survival changes after several weeks of the treatment. The therapeutic effects of the combination of Co-hARG and Cav were provisionally evaluated on the highly aggressive murine L1210 leukemia, which is semi-sensitive to arginine deprivation as a monotreatment. Combination of two drugs did not result in significant prolongation of the survival of leukemia-bearing mice. Thus, we have shown that the proposed combinational treatment is rather non-toxic for the animals. It has to be further evaluated in animal studies with alternative tumor models and/or drug doses and treatment modalities.

[Participation of phosphatidylinositol-3'-kinase in signal transduction through galactosyl-containing glycoprotein receptors of segmentonuclear leukocytes under type 1 diabetes mellitus].

It is shown that reduction of beta,D-galactosyl-containing carbohydrate determinants ofglycoconjugates on theplasmatic membrane of segmentonuclear neutrophills of peripheral blood under type 1 diabetes mellitus (DM) is correlated with changes in aggregation of these cells and may cause their functional disorder. Changes in the parameters of ricin-induced neutrophil activation after inhibition of the phosphatidylinositol-3'-kinase (PI-3'-kinase) enzyme with wortmannin indicated that the functional state ofpolymorphonuclear leukocytes is mediated by signaling pathways in which PI-3'-kinase is involved. Thus, PI-3'-kinase-dependent signal networks are involved in the processes of signal transduction through galactosyl-containing glycoprotein receptors into neutrophilic leukocytes. Inertness of the intensity formation in time ofneutrophil granulocyte cell response on RCA-induced translocation of the p85alpha regulatory subunit of PI-3'-kinase from the cytosolic to the membrane fraction under type 1 DM is a consequence of changes in the number or structure of plasmatic galactosyl-containing glycoprotein receptors. The revealed changes may be etiologic premise of diabetic complications and chronic diseases that impair the functional condition of patients with type 1 DM.

[Activation of the phosphatidylinositol-3'-kinase pathway with lectin-induced signal through sialo-containing glycoproteins of leukocyte membranes under type 1 diabetes mellitus].

The influence of wortmannin and sialospecific lectins on the translocation of p85alpha regulatory subunit of phosphatidylinositol-3'-kinase (PI-3'-kinase) between membrane and cytosolic fractions of the mononuclear and polymorphonuclear leukocytes in healthy donors and patients with type 1 diabetes mellitus (DM) was investigated. It was found out that under type 1 DM PI-3'-kinase takes active part in the transduction of lectin-induced signal through membrane glycoprotein receptors that contain terminal sialic acids linked to subterminal carbohydrate residues with (alpha2-->6) glycosidic bond.

[Role of phosphatidylinositol 3-kinase in platelet aggregation in type 1 diabetes mellitus]. / Rol' fosfatydylinozytol-3-kinazy v rehuliatsiï ahrehatsiinoï zdatnosti trombotsytiv za tsukrovoho diabetu 1-ho typu.

It was found that incubation of platelet rich plasma with wortmannin, an irreversible selective inhibitor of phosphoinositide 3-kinase (PI3K), leads to sharp drop in platelet aggregation ability in healthy donors, whereas in type 1 diabetes mellitus patients this effect was less manifested or not quite determined. Translocation dynamics of PI3K regulatory subunit into cytoskeleton fraction under induction of platelet aggregation by various ADP concentrations and after wortmannin treatment was studied. Reciprocal interaction of endothelial constitutive NO synthase with PI3K in mechanisms of platelet functional state regulation under studied pathological and normal conditions have been analyzed.

[Changes in functional state of the low-molecular G-proteins of platelets in type 1 diabetes mellitus]. / Zminy funktsional'noho stanu nyz'komolekuliarnykh G-bilkiv trombotdytiv za tsukrovoho diabetu 1-ho typu.

Platelets from healthy donors and insuline dependent patients with type 1 diabetes mellitus were examined for proteins specifically interacting in vitro with GST-fused constitutively active (Val12) forms of small GTPases of Rac, Rho and Cdc42. Differential changes in pattern of proteins which bind to these G-proteins in diabetic platelets have been revealed. Obtained results suggest that signalling pathways mediated by Rho GTPases are altered under type I diabetes mellitus. Such changes of actin cytoskeleton regulation may contribute to the higher level of platelet aggregation, which prove to be the etiological background of the late diabetes complications.