Erythropoietin Effect on Complement Activation in Chronic Kidney Disease

Abstract

The complement system is an important part of innate immunity. Despite its known protective role, the complement system may contribute to increased inflammation and tissue injury in cases where its balanced activation is disrupted. The kidneys have been shown to be largely affected by complement dysregulation. The aim of the present study was to investigate the effect of erythropoietin administration, on the complement system, in chronic kidney disease patients. The study involved 20 patients with CKD who received erythropoietin and measurements of levels of complement factors C3a and C5a and complement regulatory proteins (CregPs) CD55, CD46, and CD59. An increase in serum C3a and C5a levels was observed in response to EPO therapy. The increase in C3a was statistically significant (p < 0.05) and concurrent with a statistically significant decrease in CD55 in CD4⁺ T cells (p < 0.05) and B cells (p < 0.05) and CD59 levels in CD4⁺ and CD8⁺ T cells (p < 0.05) at completion of EPO therapy compared with healthy controls. The above observations demonstrate that EPO induces complement activation in patients undergoing EPO therapy with a simultaneous restriction of CRegPs expression, thus possibly allowing the uncontrolled complement activation, which may contribute to tissue injury and disease progression.

Keywords: chronic kidney disease; complement; erythropoietin; lymphocytes.

Figure 1

Increased levels of C3a and C5a in CKD patients in response to erythropoietin. (a) C3a and (b) C5a levels were measured prior to and following the completion of EPO therapy and compared to the healthy controls. Statistical analysis was performed by one-way ANOVA. Post-hoc analysis was carried out with an uncorrected Fisher’s test. * p < 0.05; ** p < 0.01.

Figure 2

Effect of EPO on C3a and C5a levels in female and male CKD patients. (a) C3a and (b) C5a levels in female and male CKD patients following EPO administration. Statistical analysis was performed by one-way ANOVA. Post-hoc analysis with uncorrected Fisher’s test. * p < 0.05; ** p < 0.01.

Figure 3

Effect of erythropoietin on complement regulatory protein expression on CD4⁺, CD8⁺ T cells, and B cells in CKD patients. (a) CD55, (b) CD46, and (c) CD59 levels were determined on CD4⁺, CD8⁺ T cells, and B cells by flow cytometric analysis. Results are represented as mean fluorescence intensity (MFI). Statistical analysis was performed with one-way ANOVA. Post-hoc analysis with an uncorrected Fisher’s test. * p < 0.05; ** p < 0.01.

Figure 4

Complement factors and regulatory protein correlations with patient clinical parameters following EPO therapy. Spearman’s correlation of (a) C3a and hematocrit levels (b) C3a and hemoglobin levels (c) C3a levels and CD46 expression on CD4⁺ T cells, (d) C3a and Vitamin D levels, (e) Albumin and CD55 expression on CD4⁺ T cells, (f) Albumin and CD55 expression on B cells, (g) Ca levels and CD46 expression on CD8⁺ T cells, (h) Vitamin D levels and CD46 expression on CD4⁺ T cells and (i) Vitamin D levels and CD8⁺ T cells. All correlations were performed with Spearman’s correlation.