Flow cytometric analysis of STAT5 phosphorylation and CD95 expression in CD4+ T lymphocytes treated with recombinant human erythropoietin

Immunological Effects of a Single Hemodialysis Treatment

Immune disorders, involving both innate and adaptive response, are common in patients with end-stage renal disease under chronic hemodialysis. Endogenous and exogenous factors, such as uremic toxins and the extracorporeal treatment itself, alter the immune balance, leading to chronic inflammation and higher risk of cardiovascular events. Several studies have previously described the immune effects of chronic hemodialysis and the possibility to modulate inflammation through more biocompatible dialyzers and innovative techniques. On the other hand, very limited data are available on the possible immunological effects of a single hemodialysis treatment. In spite of the lacking information about the immunological reactivity related to a single session, there is evidence to indicate that mediators of innate and adaptive response, above all complement cascade and T cells, are implicated in immune system modulation during hemodialysis treatment. Expanding our understanding of these modulations represents a necessary basis to develop pro-tolerogenic strategies in specific conditions, like hemodialysis in septic patients or the last session prior to kidney transplant in candidates for receiving a graft.

Erythropoietin, a multifaceted protein with innate and adaptive immune modulatory activity

Erythropoietin (EPO) is a glycoprotein produced mainly by the adult kidney in response to hypoxia and is the crucial regulator of red blood cell production. EPO receptors (EPORs), however, are not confined to erythroid cells, but are expressed by many organs including the heart, brain, retina, pancreas, and kidney, where they mediate EPO-induced, erythropoiesis-independent, tissue-protective effects. Some of these tissues also produce and locally release small amounts of EPO in response to organ injury as a mechanism of self-repair. Growing evidence shows that EPO possesses also important immune-modulating effects. Monocytes can produce EPO, and autocrine EPO/EPOR signaling in these cells is crucial in maintaining immunologic self-tolerance. New data in mice and humans also indicate that EPO has a direct inhibitory effect on effector/memory T cells, while it promotes formation of regulatory T cells. This review examines the nonerythropoietic effects of EPO, with a special emphasis on its modulating activity on innate immune cells and T cells and on how it affects transplant outcomes.

Effect of Erythropoietin on Lymphocytes Apoptosis in Experimental Chronic Renal Failure

Recombinant human erythropoietin was injected intraperitoneally in a total dose of 900 U/kg to rats with experimental chronic renal failure. Suspension of lymphocytes from animals with chronic renal failure was used in vitro, erythropoietin was used in concentrations of 30, 15, 7.5, 3.75, and 1.88 U/liter. Intact cells (Annexin-5-FITC(-)/7-AAD(-)), cells with early signs of apoptosis (Annexin-5-FITC(+)/7-AAD(-)), cells with late signs of apoptosis and partially necrotic cells (Annexin-5-FITC(+)/7-AAD(+)), as well as cells with early signs of necrosis (Annexin-5-FITC(-)/7-AAD(+)) were differentiated by fl ow cytometry. It was found that the number of peripheral blood lymphocytes with early and late signs of apoptosis and necrosis increased in chronic renal failure. Erythropoietin at a total dose of 900 U/kg reduced the number of blood lymphocytes with signs of apoptosis and necrosis and thus elevated the number of intact lymphocytes. Erythropoietin in concentrations ranging from 1.88 to 30.0 U/liter dose dependently lowered the number of lymphocytes with early signs of apoptosis and the number of lymphocytes with the signs of late apoptosis and necrosis in vitro.

Changes in the Expression of Transcription Factors Involved in Modulating the Expression of EPO-R in Activated Human CD4-Positive Lymphocytes

We have recently described the presence of the erythropoietin receptor (EPO-R) on CD4⁺ lymphocytes and demonstrated that its expression increases during their activation, reaching a level reported to be typical for erythroid progenitors. This observation suggests that EPO-R expression is modulated during lymphocyte activation, which may be important for the cells’ function. Here we investigated whether the expression of GATA1, GATA3 and Sp1 transcription factors is correlated with the expression of EPO-R in human CD4⁺ lymphocytes stimulated with monoclonal anti-CD3 antibody. The expression of GATA1, GATA3 and Sp1 transcription factors in CD4⁺ cells was estimated before and after stimulation with anti-CD3 antibody by Western Blot and flow cytometry. The expression of EPO-R was measured using real-time PCR and flow cytometry. There was no change in the expression of GATA1 and GATA3 in CD4⁺ lymphocytes after stimulation with anti-CD3 antibody. However, stimulation resulted in the significantly increased expression of the Sp1 factor. CD4⁺ lymphocytes stimulated with anti-CD3 antibody exhibited an increase in both the expression level of EPOR gene and the number of EPO-R molecules on the cells’ surface, the latter being significantly correlated with the increased expression of Sp1. Sp1 is noted to be the single transcription factor among the ones studied whose level changes as a result of CD4⁺ lymphocyte stimulation. It seems that Sp1 may significantly affect the number of EPO-R molecules present on the surface of activated CD4⁺ lymphocytes.

The influence of recombinant human erythropoietin on apoptosis and cytokine production of CD4+ lymphocytes from hemodialyzed patients

Recombinant human erythropoietin (rhEPO) treatment of hemodialyzed (HD) patients normalizes the altered phenotype of CD4⁺ lymphocytes and restores the balance of Th1/Th2 cytokines. We decided to test how the presence of rhEPO in cell culture modulates cytokine production of CD4⁺ lymphocytes in HD patients with stable hemoglobin level and expression of activation antigens of stimulated CD4⁺ lymphocytes similar to those observed in healthy individuals. We also tested whether the presence of rhEPO in cell culture protects stimulated CD4⁺ lymphocytes of HD patients from apoptosis. Peripheral blood mononuclear cells (PBMC) of HD patients were stimulated with an immobilized anti-CD3 antibody with or without addition of rhEPO. The percentage of apoptotic CD4⁺ lymphocytes and the level of Th1/Th2 cytokines in culture supernatants were measured with flow cytometry. HD patients showed a decrease in the percentage of apoptotic CD4⁺ cells after stimulation with the anti-CD3 antibody combined with rhEPO. The level of IFN-γ and IL-10 was increased while the level of TNF-α was decreased in the presence of rhEPO in cell culture from HD patients. These results confirm the role of rhEPO signaling in T lymphocytes of HD patients.