The Effects And Mechanisms Of Erythropoietin On Hepcidin And Proinflammatory Factors Of Human Monocytes

[BACKGROUND]The current view is that the pathogenesis of anemia of chronic disease (ACD) is mediated by the immune response initiated by primary disease. Abnormal elevated inflammatory cytokines, mostly IL-6, lead to the iron metabolism disorder and anemia through elevating hepcidin level in liver, and directly inhibit the proliferation and differentiation of erythroid precursor cells, shorten life span of red blood cell, blunt response to EPO, interfere with iron metabolism related proteins in transcription. Monocytes are major source of inflammatory cytokines generated in chronic anemia; they are also iron storage cells, regulated by hepcidin, which play a key role in the pathogenesis of ACD. Recent studies have shown that monocyte is similar to liver in increasing the expression of hepcidin significantly by inflammation stimulation. Hepcidin from monocyte also regulate iron metabolism. The monocyte hepcidin is increased in patients with ACD and related significantly with anemia and elevated IL-6, indicated that it may play a role in the pathogenesis of ACD. Erythropoietin (EPO) is the primary means of treating ACD through combining with the receptors and stimulating hematopoiesis, inhibiting hepatic hepcidin and decreasing inflammatory factors. EPO can reduce hepcidin expression but the specific mechanism is unclear now. It may be associated with decreased C/EBPa, and depressed phosphorylation of STAT3; but whether there are other signaling pathways, whether there is similar role on monocyte is not clear, in addition, the mechanism of EPO decreasing inflammatory cytokines is not clear, either. Multiple myeloma and non-Hodgkin's lymphoma can lead to tumor-associated ACD. Patients of multiple myeloma have elevated levels of serum and urinary hepcidin, but there is not such research on patients of non-Hodgkin's lymphoma. In both diseases, whether monocyte hepcidin is increased, and whether it plays a role in ACD is not clear.[OBJECTIVE]1 The effect of EPO on monocytes hepcidin and its molecular mechanism.2 The molecular mechanism of IL-6 reduced by EPO. 3 The role of monocytes hepcidin in MM and NHL patients.[METHODS]1 THP-1 monocytes are stimulated by IL-6, hepcidin is detected by Real time PCR.Observing the impact of EPO on monocytes hepcidin.Hepcidin and signaling molecule including C/EBPa, Smadl/5/8, P-Smadl/5/8 and P-STAT3 are detected by Western blot. To observe the antagonistic effect on EPO by adding EPOR antibody.2 THP-1 monocytes and primary human monocytes stimulated by LPS, the expression of IL-6 and TNF-a mRNA detected by Real time PCR. PARP-1 detected by Western blot. Adding EPOR antibody and/or PARP-1 inhibitor to observe the antagonistic effect on EPO and the impact on the signaling proteins.3 Collecting the clinical information and serum of multiple myeloma and non-Hodgkin's lymphoma.Serum concentration of IL-6 and TNF-a is detected by ELISA.4 Peripheral blood monocytes is isolated by Magnetic beads.Hepcidin, IL-6, TNF-a and C/EBPa mRNA of monocytes is detected by Real time PCR quantitative assay.[RESULTS]1 EPO can suppress the monocyte hepcidin mRNA expression and protein induced by IL-6 in THP-1 cells. C/EBPa, P-Smadl/5/8 and P-STAT3 reduced at the same time. EPOR antibody can antagonize the effect of EPO on hepcidin and signaling proteins.2 EPO can decrease the levels of IL-6 and TNF-a stimulated by LPS both in THP-1 cells and in primary human monocytes. PARP-1 protein is decreased at the same time. The decline of IL-6 by EPO can be antagonized by both EPOR antibody and 3AB.3 In MM patients, the expression of monocyte hepcidin mRNA is higher than normal and negatively correlated with Hb,positively correlated with SF, IL-6 levels, CRP and 132 microglobulin in newly diagnosed patients,but unrelated with LDH and the TNF-a levels. C/EBPa expression in monocytes is positively correlated with monocyte hepcidin and IL-6 levels,but unrelated with the TNF-a levels.4 In NHL patients, the expression of monocyte hepcidin mRNA is higher than normal.Monocyte hepcidin in patients with newly diagnosed negatively correlated with Hb, IL-6 levels, CRP and LDH, but not associated with TSAT%, SF and TNF-a levels. C/EBPa expression in monocyte is unrelated with monocyte hepcidin levels. [CONCLUSIONS]1 Monocyte hepcidin mRNA and protein levels can be reduced by EPO when stimulated by IL-6 in monoytes. EPO inhibits the monocyte hepcidin, at least in part,via combination with EPOR and suppression of C/EBPa, P-Smadl/5/8 and P-STAT3 signaling in vitrol.2 EPO can block the expression of IL-6 and TNF-a in monocytes stimulated by LPS, EPO may inhibit IL-6 expression via combination of EPOR and suppression of PARP-1.3 The expression of monocyte hepcidin is increased in patients of multiple myeloma and non-Hodgkin's lymphoma, and has an association with ACD, the increased hepcidin levels play an etiologic role in ACD.CRP or LDH may be able to monitor the level of hepcidin.