Sara Prutchi-Sagiv

Erythropoietin enhances immune responses in mice

Erythropoietin (Epo) is the main erythropoietic hormone. Recombinant human Epo (rHuEpo) is thus used in clinical practice for the treatment of anemia. Accumulating data reveals that Epo exerts pleiotropic activities. We have previously shown an anti‐neoplastic activity of Epo in murine multiple myeloma (MM) models, and in MM patients. Our findings that this anti‐neoplastic effect operates via CD8+ T lymphocytes led us to hypothesize that Epo possesses a wider range of immunomodulatory functions. Here we demonstrate the effect of Epo on B lymphocyte responses, focusing on three experimental models: (i) tumor‐bearing mice, (5T2 MM mouse); (ii) antigen‐injected healthy mice; and (iii) antigen‐injected transgenic mice (tg6), overexpressing human Epo. In the MM model, despite bone marrow dysfunction, Epo‐treated mice retained higher levels of endogenous polyclonal immunoglobulins, compared to their untreated controls. In both Epo‐treated wild type and tg6 mice, Epo effect was manifested in the higher levels of splenocyte proliferative response induced in vitro by lipopolysaccharide. Furthermore, these mice had increased in vivo production of anti‐dinitrophenyl (DNP) antibodies following immunization with DNP‐keyhole limpet hemocyanin. Epo‐treated mice showed an enhanced immune response also to the clinically relevant hepatitis B surface antigen. These findings suggest a potential novel use of rHuEpo as an immunomodulator.

Erythropoietin treatment in advanced multiple myeloma is associated with improved immunological functions : could it be beneficial in early disease?

Erythropoietin (Epo) is the main growth regulator of red blood cells, and recombinant human erythropoietin (rHuEpo) is thus used in clinical practice for the treatment of anaemia, primarily in kidney disease and cancer. rHuEpo treatment was found to be associated with prolonged survival of multiple myeloma (MM) patients. This clinical observation was then supported by studies on murine myeloma models. It thus appeared that rHuEpo had an anti‐myeloma effect, causally related to an immunomodulatory function of rHuEpo. The present study investigated whether rHuEpo‐treated MM patients acquire improved immunological functions. Treatment with rHuEpo, prescribed for anaemia that occurs in advanced disease, was associated with effects on a variety of immunological parameters and functions. This was expressed in an actual normalisation of the CD4:CD8 cell ratio, enhanced T cell phytohaemagglutinin‐mediated activation and proliferation potential, T cell expression of the costimulatory CD28 and inhibitory CTLA‐4 molecules, as well as reduced interleukin‐6 serum values to normal levels. Furthermore, it was demonstrated that immunological abnormalities manifest in patients even in the early stages of MM. Our findings thus suggest that rHuEpo treatment might be effective in the early stages of MM, before anaemia develops. It is expected that this would boost the immune system, consequently achieving an anti‐myeloma function; affecting disease progression and improving the prognosis.

Non-erythroid activities of erythropoietin: Functional effects on murine dendritic cells

Erythropoietin (EPO) is the main hormone that promotes proliferation and differentiation of erythroid progenitor cells via binding to its surface receptor (EPO-R). Recent studies suggest that this hormone may affect also other cell types, besides the red blood cell lineage. We have previously demonstrated that the immune system is a target of EPO; however, the direct target cells of EPO, as well as the molecular mechanisms underlying its role as an immunomodulator, are unknown. Here we present evidence for functional effects of EPO on dendritic cells (DCs), which are known to initiate the immune response. In-vivo experiments in EPO-injected mice and in transgenic mice over-expressing human EPO showed an increased splenic DC population with a higher cell surface expression of CD80 and CD86. Further analysis based on mouse models, showed that DCs derived in-vitro from bone marrow (BM-DCs) express EPO-R mRNA. In-vitro stimulation of these DCs with recombinant human EPO enhanced viability, upregulated CD80, CD86 and MHC class II and augmented the secretion of IL-12. Biochemical analysis of EPO mediated signaling in the BM-DCs showed activation of the AKT, MAPK and NF-kappaB pathways. EPO stimulation of the BM-DCs led to Tyr-phosphorylation of STAT3. The inability to detect EPO mediated activation of STAT5 in the BM-DCs, suggests that in DCs, STAT3 may play a more important role than STAT5 in EPO-R signaling. Taken together, our data support the premise that DCs are direct targets of EPO, thereby providing an insight to the immunomodulatory functions of EPO.

Non-erythroid effects of erythropoietin: Are neutrophils a target?

We have previously shown that erythropoietin (EPO) potentiates the immune response. Analysis of various possible cellular mediators was performed on EPO-injected mice and transgenic mice overexpressing human EPO (tg6). Here we present our studies on neutrophils, peritoneal (casein induced), and from the peripheral blood, spleen and bone marrow. Neutrophil counts were elevated in peripheral blood and spleens of the tg6 mice, yet, no other EPO-associated effects were detected in the count and function of the different neutrophil populations. Hence, neutrophils are probably not mediators of the EPO immunological effects, although their counts may be affected by extreme EPO levels.

Erythropoietin—A Hematopoietic Hormone with Emerging Diverse Activities

ABSTRACT Erythropoietin (Epo), the major hormone that regulates erythropoiesis, is produced mainly in the adult kidney in response to hypoxia. Recombinant human Epo (rHuEpo) is thus considered a major treatment for various types of anemias. The past decade has revealed extra-hematopoietic sites of Epo production along with an abundance of Epo receptors in various tissues and cell lines, suggesting that this hormone may have pleiotropic activities. The unexpected discovery that Epo and its receptor are expressed also in cells of the central nervous system has opened new avenues for research regarding the biological effects of Epo in the brain. This chapter reviews the classic well-known features of Epo, as well as the more novel findings on its various effects and the possible underlying mechanisms.

Erythropoietin receptor is detectable on peripheral blood lymphocytes and its expression increases in activated T lymphocytes (reply)

We have read with interest the letter of Lisowska et al. , submitted to Haematologica in response to our manuscript “Macrophages as novel target cells for erythropoietin” by Lifshitz et al. , published in Haematologica in June 2010. In their commentary, Lisowska et al. claim that: (1) we have