Effect of erythropoietin on primed leucocyte expression profile

Resistance to erythropoietin (EPO) affects a significant number of anaemic patients with end-stage renal disease. Previous reports suggest that inflammation is one of the major independent predictors of EPO resistance, and the effects of EPO treatment on inflammatory mediators are not well established. The aim of this study was to investigate EPO-induced modification to gene expression in primary cultured leucocytes. Microarray experiments were performed on primed ex vivo peripheral blood mononuclear cells (PBMCs) and treated with human EPO-α. Data suggested that EPO-α modulated genes involved in cell movement and interaction in primed PBMCs. Of note, EPO-α exerts anti-inflammatory effects inhibiting the expression of pro-inflammatory cytokine IL-8 and its receptor CXCR2; by contrast, EPO-α increases expression of genes relating to promotion of inflammation encoding for IL-1β and CCL8, and induces de novo synthesis of IL-1α, CXCL1 and CXCL5 in primed cells. The reduction in MAPK p38-α activity is involved in modulating both IL-1β and IL-8 expression. Unlike the induction of MAPK, Erk1/2 activity leads to upregulation of IL-1β, but does not affect IL-8 expression and release. Furthermore, EPO-α treatment of primed cells induces the activation of caspase-1 upstream higher secretion of IL-1β, and this process is not dependent on caspase-8 activation. In conclusion, our findings highlight new potential molecules involved in EPO resistance and confirm the anti-inflammatory role for EPO, but also suggest a plausible in vivo scenario in which the positive correlation found between EPO resistance and elevated levels of some pro-inflammatory mediators is due to treatment with EPO itself.

Abstract 3358: Resistance to Endogenous Erythropoietin Predicts Survival in Anemic Heart Failure Patients

Background In response to hypoxia the kidney produces erythropoietin (EPO). Elevated levels of EPO are observed in patients with chronic heart failure (CHF) and are related to an impaired outcome. However it is unknown whether these EPO-levels are adequate for the degree of anemia and how the adequacy of EPO levels relates to prognosis. Methods Therefore, we studied 240 CHF patients (96% were in NYHA functional class III). The adequacy of EPO levels was assessed by an observed-predicted ratio. A value <0.9 indicates inadequate low EPO levels (=blunted EPO-response), whereas >1.1 indicates inappropriate high EPO levels (=EPO resistance). Group comparisons were therefore made between low EPO responders n = 30 normal EPO responders n = 25 EPO-resistance n = 22. Anemia was defined according to the WHO definition (males and postmenopausal females Hemoglobin (Hb) < 3.0 g/dL and premenopausal females Hb < 12.0 g/dL). The primary endpoint was mortality. Results During a median follow up of 3.8 years, 98 patients died (41.4% mortality rate). EPO levels were an independent predictor of mortality, also adjusted for hemoglobin levels (HR 1.013, 95%CI [1.007–1.018], p=0.001). Anemia was present in 77 (32%) patients. Inadequate low EPO levels were observed in 30 anemic patients (39%) and related to renal failure (glomerular filtration rate < 30 ml/min/1.73m2 (p<0.009). EPO resistance was present in 22 anemic patients (29%) and was associated with a significant higher mortality rate compared to patients with a normal EPO response and a low EPO response, 72.7% vs 34.8% and 40.0% respectively (p=0.012 and p=0.021, respectively). EPO resistance was an independent predictor of an increased mortality risk in Cox regression analyses adjusted for variables with p<0.10 in the univariate analysis including age, sex and high sensitive CRP; HR 2.63 95%CI [1.12– 6.17], p=0.026, whereas a low EPO response was not associated with an impaired outcome; HR 1.12 95% CI [0.45–2.79], p=0.81, compared to normal EPO responders. Conclusion EPO resistance is common in CHF patients and is associated with a high mortality.