Short-term erythropoietin treatment does not substantially modulate monocyte transcriptomes of patients with combined heart and renal failure

Abstract

Background: Combined heart and renal failure is associated with high cardiovascular morbidity and mortality. Anti-oxidant and anti-inflammatory, non-hematopoietic effects of erythropoietin (EPO) treatment have been proposed. Monocytes may act as biosensors of the systemic environment. We hypothesized that monocyte transcriptomes of patients with cardiorenal syndrome (CRS) reflect the pathophysiology of the CRS and respond to short-term EPO treatment at a recommended dose for treatment of renal anemia.

Methods: Patients with CRS and anemia (n = 18) included in the EPOCARES trial were matched to healthy controls (n = 12). Patients were randomized to receive 50 IU/kg/week EPO or not. RNA from CD14(+)-monocytes was subjected to genome wide expression analysis (Illumina) at baseline and 18 days (3 EPO injections) after enrolment. Transcriptomes from patients were compared to healthy controls and effect of EPO treatment was evaluated within patients.

Results: In CRS patients, expression of 471 genes, including inflammation and oxidative stress related genes was different from healthy controls. Cluster analysis did not separate patients from healthy controls. The 6 patients with the highest hsCRP levels had more differentially expressed genes than the 6 patients with the lowest hsCRP levels. Analysis of the variation in log(2) ratios of all individual 18 patients indicated that 4 of the 18 patients were different from the controls, whereas the other 14 were quite similar. After short-term EPO treatment, every patient clustered to his or her own baseline transcriptome. Two week EPO administration only marginally affected expression profiles on average, however, individual gene responses were variable.

Conclusions: In stable, treated CRS patients with mild anemia, monocyte transcriptomes were modestly altered, and indicated imprints of inflammation and oxidative stress. EPO treatment with a fixed dose has hematopoietic effects, had no appreciable beneficial actions on monocyte transcription profiles, however, could also not be associated with undesirable transcriptional responses.

Figure 1. Validation of differentially expressed genes on microarray by quantitative polymerase chain reaction.

*P-value<0.05 for gene expression in patients at baseline vs. healthy controls as determined with qPCR technique; ^oP-value<0.05 for gene expression in patients at baseline vs. healthy controls as determined with microarray technique. ADRB2 adrenergic receptor, β2; CX3CR1 chemokine (C-X3-C motif) receptor 1; EGR1 early growth response 1; FOS FBJ murine osteosarcoma viral oncogene homolog; GPX3 glutathione peroxidase 3; IL8 interleukin 8; qPCR quantitative polymerase chain reaction.

Figure 2. Euclidean cluster analysis for patients before and after erythropoietin treatment.

Patient number and time point of sample collection (patient 1, timepoint 1 = 11; patient 1, timepoint 2 = 12, etc) are listed in order of monocyte transcriptomes similarity. The closer samples are depicted to each other, the more comparable transcriptomes are. Only the first 50 genes are depicted, the full figure is online.