Role of cytokines in the response to erythropoietin in hemodialysis patients

Background. Cytokines are regulatory factors of erythropoiesis, especially in pathologic conditions. Even though a relevant role for a deranged cytokine production in the pathogenesis of dialysis anemia has been suggested, no data are available that analyze the role of cytokines in the key therapeutic issue of the needs of erythropoietin. The aim of the present study in hemodialysis patients was, therefore, to examine the relationship between the dose of recombinant human erythropoietin (EPO) and the production of cytokines by peripheral blood mononuclear cells (PBMC). Methods. After the exclusion of subjects with major active causes of EPO resistance, data from 34 hemodialysis patients were available for analysis. Cytokine levels were measured in the supernatants of stimulated [with bacterial lipopolysaccharide and interferon gamma (IFN-gamma)] and unstimulated PBMC. Mean yearly values of hematocrit, hemoglobin, transferrin saturation, ferritin, parathormone (PTH) and aluminum levels and EPO doses (U/kg/wek) were calculated. For analysis, the 34 patients were divided according to their cutoff requirements for EPO: patients with requirements of EPO greater than or equal to 60 U/kg/week (group A(1), 26 subjects) versus EPO < 60 U/kg/week (group B-1, 8 subjects) and patients with requirements of EPO greater than or equal to 100 U/kg/week (group A(2) 18 subjects) versus <100 U/kg/week (group B-2, 16 subjects). Results. A significant direct correlation between interleukin-6 (IL-G) and tumor necrosis factor alpha (TNF-alpha) production values and EPO doses was found (P = 0.039 and P = 0.02 respectively). On the other hand, there was a significantly negative correlation between interleukin-l? (IL-12) production values and EPO doses (P = 0.029). Patients of groups A(1) and A(2) had spontaneously higher tumor necrosis factor-alpha (TNF-alpha) and lower IL-12 and IFN gamma production compared to patients from groups B-1 and B-2. Conclusions. Our data disclose a previously undescribed pattern of cytokine alteration that is relevant to determine increased needs of EPO in hemodialysis patients. The present results have potential applicability in designing strategies to improve EPO resistance.