Expression patterns of leptin receptor (OB-R) isoforms and direct in vitro effects of recombinant leptin on OB-R, leptin expression and cytokine secretion by human hematopoietic malignant cells.

Several studies have implicated leptin in the pathophysiology of neoplasias. We investigated the direct effect of leptin on malignant hematopoietic tissue that included: primary acute myeloid leukemia (AML) cells, leukemic cell lines and bone marrow biopsies from multiple myeloma (MM) patients. PBMC, T-cells, B-cells and monocytes from healthy subjects served as controls. We defined the patterns of OB-R isoform expression in AML cells and leukemic cell lines in comparison to control cells by RT-PCR. rLeptin upregulated the expression of OB-R and endogenous leptin in AML blasts and certain cell lines but not in control cells. Cytometric Bead Array analysis of pro- and anti-inflammatory cytokines showed that rleptin upregulates IL-6 secretion by AML cells, various cytokines by the leukemic cell lines tested and IL-10 secretion by control PBMC, contributed by monocytes. Western immunoblotting revealed that the effect of rleptin was independent of JAK-2/phospho-JAK-2 protein levels. Finally, MM biopsies stained positive for leptin and, to a lesser extend, OB-R. Immunoreactivity was confined mostly to the nucleus of the myeloma cells. Normal myelocytes, promyelocytes and megakaryocytes stained weakly positive, and erythroid cells were constantly negative. We propose that the leptin/OB-R system is strongly and directly involved in supporting the growth of hematopoietic malignancies.

Effect of splenectomy on type-1/type-2 cytokine gene expression in a patient with adult idiopathic thrombocytopenic purpura (ITP).

BACKGROUND: In view of clinical observations and laboratory results that support a central role of the spleen in idiopathic thrombocytopenic purpura (ITP) pathophysiology, we studied the effect of splenectomy on type-1 and type-2 cytokine gene expression in an adult ITP case, refractory to conservative treatment. CASE PRESENTATION: The patient was subjected to splenectomy 9 months after the diagnosis with complete response, attaining platelet counts over 150 x 106/L within 10 days after the operation. Two consecutive blood samples were obtained from the patient, 3 and 7 months after the splenectomy for the purposes of this study. A control group consisted of 11 healthy adults. Peripheral blood mononuclear cells were prepared from each blood sample and cultured in vitro for 8 h with the addition of the mitogens phorbol myristate acetate and ionomycin. Total cellular RNA extracted from 106 cells was submitted to semiquantitave reverse transcriptase-polymerase chain reaction (RT-PCR) for the amplification of IL-2, IFN-gamma, IL-4, IL-5, and IL-10 metagraphs. The PCR products were run on ethidium-stained agarose gels, photographed and quantified by densitometry.A steep decrease of type-1 cytokine expression (IL-2, IFN-gamma) and their calculated sum expressing Th1 activity was observed at 7 months post-splenectomy compared to 3 months post-splenectomy, in parallel with a rise of platelet count from 190 x 106/L to 265 x 106/L. The change of type-2 cytokine expression (IL-4, IL-5, IL-10) was slight and the Th2 activity (IL-4+IL-5) remained largely unchanged. The Th1/Th2 ratio, that reflects the pathogenic disease-specific T-cell immune deviation, was accordingly reduced 7 months post-splenectomy (Th1/Th2 = 1.3) compared to 3 months (Th1/Th2 = 3.5). CONCLUSIONS: The reduction of the Th1/Th2 cytokine ratio that was observed over time after splenectomy was accompanied by full clinical remission. Nevertheless, the persistence of a type-1 polarization, even after several months following spleen removal, is suggestive of a more basic abnormality of the immune function in these patients.

Adult chronic idiopathic thrombocytopenic purpura (ITP) is the manifestation of a type-1 polarized immune response.

Derangement of cellular immunity is central in the pathophysiology of adult autoimmune/idiopathic thrombocytopenic purpura (ITP). Herein we investigated cytokine gene expression in peripheral blood mononuclear cells (PBMCs) of adult chronic ITP patients and attempted to correlate cytokine polarization with the degree of thrombocytopenia. We used semiquantitative reverse-transcriptase-polymerase chain reaction (RT-PCR) to measure the expression of type-1 (interleukin-2 [IL-2], interferon gamma [IFN-gamma]) and type-2 (IL-4, IL-5, IL-10, IL-3, IL-13) cytokines by PBMCs from 21 patients and 11 controls. Plasma transforming growth factor beta1 (TGF-beta1) levels were measured by enzyme-linked immunoassay (ELISA). T helper 1 (Th1)/Th2 ([IL-2 + IFN-gamma]/[IL-4 + IL-5]) cytokine mRNA ratios, thought to reflect the Th deviation of the pathogenic disease-specific T cells, and type-1/type-2 mRNA ratios, thought to reflect the overall immune response polarization, were significantly increased in ITP patients. The Th1/Th2 ratio was inversely correlated with platelet counts. TGF-beta1 levels appeared suppressed in patients with active disease, though not significantly. Our findings show a clear type-1 cytokine polarization of the autoimmune response in adult ITP that persists irrespective of disease status.