[Molecular basis of chronic myelogenous leukemia and significance of diagnostic methods based on BCR-ABL gene amplification]

Chronic myelogenous leukemia is characterized by an abnormal 22nd chromosome known as a Philadelphia chromosome, which can be detected in 95% of patients with CML. Molecular equivalent of this aberration is a BCR-ABL translocation resulting in chimeric gene formation. A BCR-ABL chimeric gene plays a key role in the hematopoietic cells proliferation regulation. RT-PCR can be used in diagnosis of CML, to detect chimeric BCR-ABL gene, and to reveal the type of translocation what could have prognostic importance, and in monitoring of minimal residual disease, confirming the eradication of pathological cells clone after treatment and identifying the group of patients with best prognosis and best overall survival. RT-PCR in monitoring of minimal residual disease after allo- or autologous hemopoietic cells transplantation can early reveal relapse of the disease. Detection of molecular relapse is an important prognostic factor and may implicate induction of treatment which should prevent haematological relapse of the disease.

Oxidized low density lipoprotein inhibits inducible nitric oxide synthase, GTP cyclohydrolase I and transforming growth factor beta gene expression in rat macrophages

Several studies have already demonstrated that oxidized- LDL decreases nitric oxide (NO) generation by cytokine-stimulated macrophages. However, the mechanisms of such an inhibition have not been yet elucidated. NO generation by inducible nitric oxide synthase (iNOS) is dependent on the presence of cofactors for NO generation, tetrathydrobiopterin (BH4) among them. The NO generation by these cells is also regulated by some endogenous inhibitors, like TGF-beta. Therefore, the aim of our recent study was to investigate the influence of ox-LDL on the expression of iNOS and GTP cyclohydrolase I (GTP-CH I), the key enzyme involved in the BH4 synthesis as well as the ox-LDL effect on TGF-beta expression in rat macrophages stimulated with IFNgamma (250 U/ml) and LPS (500 ng/ml). Macrophages, activated in this way, express iNOS, GTP-CH I, and TGF-beta mRNA. This expression was inhibited when the macrophages were preincubated for 24 hours with ox-LDL (100 microg/ml). Quantitative PCR revealed about 10-fold inhibition of iNOS gene expression by ox-LDL. As a consequence of down-regulation of iNOS and GTP-CH I genes, almost 3-fold diminished generation of NO2- by rat macrophages was observed. An inhibition of the TGFbeta mRNA expression was also found. Our studies indicate that decreased NO generation by ox-LDL treated macrophages may be the result of the diminished expression of both iNOS and GTP-CH I genes. This effect may be mediated by the activity of certain endogenous inhibitors of gene expression, however, our studies exclude the TGF-beta as a candidate for this activity.

Gene transfer of vascular endothelial growth factor and endothelial nitric oxide synthase--implications for gene therapy in cardiovascular diseases

Gene therapy is based on the delivery of exogenous genetic material in order to influence the endogenous genetic components involved in disease development. This new therapeutic approach has been suggested to have great potential in the treatment of insufficient angiogenesis or in prevention of restenosis after balloon angioplasty of atherosclerotic arteries. As both vascular endothelial growth factor (VEGF) and nitric oxide (NO) exert beneficial effects on vascular physiology, we studied the generation of both compounds after in vitro transfection of relevant genes. The plasmid vectors, containing VEGF cDNA were constructed and lipotransfected into vascular smooth muscle cells (VSMC). Transfected cells generated up to a few nanograms of VEGF, which induced proliferation of endothelial cells. VSMC transfected with another plasmid, containing endothelial constitutive NO synthase (ecNOS) cDNA generated micromolar quantities of nitrite. Moreover, such NO-producing cells synthesized significantly more VEGF than VSMC transfected with control plasmids. Thus, the study demonstrated that transfer of VEGF and/or NOS genes to VSMC led to the production of measurable amounts of both VEGF protein and NO. Additionally, we evidenced that NO can enhance the endogenous generation of VEGF. A new protective mechanism of NO has been thus revealed.

Regulation of inducible nitric oxide synthase (iNOS) and GTP cyclohydrolase I (GTP-CH I) gene expression by ox-LDL in rat vascular smooth muscle cells

The generation of nitric oxide is regulated by several factors, including the substrates and cofactors supplementation. Decreased expression and activity of nitric oxide synthase as well as diminished amount of L-arginine or enzyme cofactors results in the inhibition of nitric oxide generation in vascular wall cells. GTP cyclohydrolase 1 is a key enzyme involved in the synthesis of tetrahydrobiopterin, one of the most important cofactors of NO synthases. We have demonstrated that oxidized LDL inhibit not only inducible nitric oxide synthase gene expression but also GTP cyclohydrolase I gene expression in interleukin-1 beta activated rat vascular smooth muscle cells in vitro. It is postulated that diminished availability of tetrahydrobiopterin may additionally impair the generation of nitric oxide in atherosclerosis.

Influence of oxy-LDL and interleukin-8 on the platelet/PMNs adhesion and on chemotaxis-mediated induction of iNOS in neutrophils

Selectin-P expression on platelets stimulated with thrombin was measured in terms of formation of "rosettes" according to Jungi et al. [9]. Selectin-P-mediated platelet/PMNs adhesion was inhibited by iloprost (IC50 = 5.0 nM), sodium nitroprusside (NaNP, IC50 = 0.93 microM) and interleukin-8 (IL-8, IC50 = 88 ng/ml), but activated dose-dependently by oxy-LDL (3-15 micrograms/ml). Glycogen-induced peritonitis in rats up-regulated the iNOS activity measured by the 2,3-[3H]-citrulline formation by the abdominal cavity PMNs up to 6 h after insult. Pretreatment with IL-8 (3 micrograms/300 g iv) decreased the amount of PMNs in ascites as well as its iNOS activity. Chemotaxis mediated iNOS gene expression of PMNs were measured by Northern blot hybridization. IL-8 (100 ng/ml) did not influence the PMNs iNOS gene expression induced by chemotaxis. We conclude that the decrease in iNOS activity by IL-8 involves postranslational modification of the enzyme activity.

Immune-complex-trapping cells in the spleen of the oriental fire-bellied toad, Bombina orientalis

The spleen of the oriental fire-bellied toad, Bombina orientalis, consists of well-developed white pulp, separated from the lymphocytic marginal zone by the connective tissue boundary layer. Injection of peroxidase-conjugated rabbit anti-peroxidase revealed that these immune complexes were localized on the surface of acid-phosphatase-positive and non-specific-esterase-positive cells in the white pulp. The majority of immune-complex-trapping cells were present around the blood vessels. Cell processes of some of these cells penetrated into the wall of blood vessels. The significance of the present findings is discussed with respect to the evolution of immune-complex-trapping cells in the spleen.