leukotriene-b4 and Myeloproliferative-Disorders

The expression of neurotrophin and neurotrophin receptor mRNAs in human granulocytes and bone marrow cells was examined using ribonuclease protection assay and reverse transcription-polymerase chain reaction. The granulocytes expressed mRNA coding for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-4 (NT-4), but not neurotrophin-3 (NT-3). Moreover, the inflammatory mediator leukotriene B4 (LTB4) up-regulated the expression of NT-4 mRNA in granulocytes, but did not affect the expression of other neurotrophin mRNAs. Granulocytes generally lacked expression of mRNA coding for neurotrophin receptors. In contrast, human bone marrow cells consistently expressed mRNA for trkB (the BDNF and NT-4 receptor) and displayed variable expression of mRNA coding for trkA (the tyrosine kinase NGF receptor) and LNGFR (the low-affinity NGF receptor), whereas mRNA for trkC (the NT-3 receptor) was not expressed. Contrary to granulocytes, normal bone marrow cells generally expressed only low levels of mRNA encoding BDNF and NT-4. Expression of mRNA encoding NGF and NT-3 was not detected. However, significantly increased expression of BDNF mRNA was observed when bone marrow cells from patients with chronic myeloproliferative disorders (MPD) were analyzed. The results suggest that neurotrophins may act as granulocyte-derived effector molecules and that human bone marrow cells may be targets for these compounds, in particular BDNF and NT-4.

Topics: Bone Marrow Cells; Brain-Derived Neurotrophic Factor; Chronic Disease; Gene Expression; Granulocytes; Humans; Leukotriene B4; Myeloproliferative Disorders; Nerve Growth Factors; Neuroprotective Agents; Neurotrophin 3; Receptor Protein-Tyrosine Kinases; Receptor, Ciliary Neurotrophic Factor; Receptors, Nerve Growth Factor; RNA, Messenger; Up-Regulation

The effect of human platelets with deficient lipoxygenase activities on leukotriene B4 (LTB4) synthesis by neutrophils was studied. When arachidonic acid (AA) metabolites obtained from the incubation of washed normal neutrophils and platelets with N-formylmethionylleucylphenylalanine (FMLP), cytochalasin B, and AA were analyzed by reversed-phase high-performance liquid chromatography, the synthesis of 5-lipoxygenase products, including LTB4, was remarkably stimulated by platelets, with their maximal effect at a ratio of platelets to neutrophils of 15:1. However, the use of lipoxygenase-deficient platelets obtained from four patients with myeloproliferative disorders instead of normal platelets showed the deficient production of 5-lipoxygenase-derived products, whereas platelets with normal lipoxygenase activities obtained from MPD patients stimulated the 5-lipoxygenase pathway similarly to the way in which normal platelets did. The addition of 12-hydroperoxyeicosatetraenoic acid (12-HPETE), a labile AA metabolite via the platelet lipoxygenase pathway, could activate the 5-lipoxygenase pathway in neutrophils incubated with FMLP, cytochalasin B and AA, but its stable end product, 12-hydroxyeicosatetraenoic acid, could not. Thus, it is suggested that lipoxygenase-deficient platelets did not sufficiently stimulate LTB4 synthesis during platelet-neutrophil interactions because of defective formation of 12-HPETE. This altered interaction between platelets and neutrophils through the lipoxygenase pathway might result in deficient responses at sites of thrombosis or inflammation in patients with deficient platelet lipoxygenase activities.

Topics: Adult; Arachidonic Acid; Arachidonic Acids; Blood Platelets; Cytochalasin B; Female; Humans; Hydroxyeicosatetraenoic Acids; Leukotriene B4; Lipoxygenase; Male; Middle Aged; Myeloproliferative Disorders; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils

The arachidonate metabolism by leukocytes and platelets was studied in 14 patients with myeloproliferative disorders including 7 patients with chronic myeloid leukemia (CML), 5 with polycythemia vera (PV) and 2 with essential thrombocythemia (ET). When the leukocytes were incubated with arachidonate and A23187, leukotriene B4 and hydroxyeicosatetraenoic acids (HETEs) were constantly detected using reversed-phase high-performance liquid chromatography in normal subjects, while selective deficiency of 5-lipoxygenase products (leukotriene B4 and 5-HETE) was found in 4 patients with CML. this novel abnormality of the leukocytes seemed to be derived from the possible deficiency of 5-lipoxygenase in these patients' polymorphonuclear neutrophils (PMNNs). The formation of 15-HETE appeared to be almost normal in all the patients. Platelet 12-lipoxygenase deficiency was detected in 2 patients with PV and 2 with CML in whom one was associated with the deficiency of 5-lipoxygenase products. These bicellular abnormalities of the arachidonate metabolism might contribute to understand dysfunctions of PMNNs and platelets in some patients with myeloproliferative disorders.

Topics: Arachidonate Lipoxygenases; Arachidonic Acid; Arachidonic Acids; Blood Platelets; Calcimycin; Humans; In Vitro Techniques; Leukemia, Myeloid; Leukocytes; Leukotriene B4; Lipoxygenase; Myeloproliferative Disorders; Polycythemia Vera; Prostaglandin-Endoperoxide Synthases; Thrombocytosis