High flux haemodialysis with polysulfone dialysers reduces peripheral blood lymphocyte apoptosis

Abstract

Background: Apoptosis appears to be the major mechanism by which mature lymphocytes maintain homeostasis. This study aims to analyse whether different types of haemodialysis (HD) therapies (low and high flux dialysers) could modify peripheral blood lymphocyte activation status and apoptosis death. Methods: Forty-six stable chronic HD patients were enrolled in this clinical study (median age 60.6±17.4 years-old). They were randomly split into three groups – Group 1 (n=20)dialyzed with cellulose derivated low-flux dialysers (KUF<10ml/h/mmHg); Group 2 (n=10) dialyzed with polysulfone (PS) low flux dialysers (KUF<10ml/h/mmHg); Group 3 (n=16) dialyzed with PS high-flux dialysers (KUF>20ml/h/mmHg). There was a control group of 30 healthy subjects (61.6±19.8 years-old). Peripheral blood specimens were collected before and after a dialysis session and the following variables were analysed: membrane IL2–R (CD25) and HLA-DR T-lymphocyte expression; lymphocyte dipeptyldipeptidase (CD26), Fas and FasL expression; lymphocyte expression of a cytoplasmic membrane apoptosis marker (flipping of the phosphatidylserine residues on cell surface/Annexin V-FITC assay); IL1β, TNFα, IL2 cytokines plasmic concentrations and plasmic enzymatic activity of caspase-1. Methods used for this experiment were flow cytometry and enzyme-linked immunoassay. Circulating mononuclear cells lymphocyte enriched were also cultured for 36 hours in vitro and supernatants analysed to measure IL1β, TNFα, IL2 cytokines concentrations and enzymatic activity of caspase-1. Results: Lymphocytes of HD patients presented higher HLA-DR expression and Annexin V affinity than the control group (HLA-DR: 11.6±7%, Annexin V: 32.2 ± 20.5% versus 8.2±5% and 19.4±9.5%; p<0.001, p<0.01 respectively). After a dialysis session there was a significant reduction of Annexin V and Fas labeled lymphocytes in the high flux group (Annexin V: preHD: 34.5±21.3%; postHD: 25.6±17.3%, p=0.02; Fas: preHD: 57.3±8.3%; postHD: 52.7±7.1%, p=0.001). This was associated with a significant increase of CD25 and CD26 expression in peripheral blood T lymphocytes and higher IL1β mononuclear supernatant concentrations. Conclusions: We concluded that HD patients presented increased lymphocyte apoptosis compared to a normal population with the same age. Lymphocyte apoptosis was improved by high flux haemodialysis with PS dialysers. A more significant improvement of apoptotic lymphocyte death after high-flux HD compared to low flux HD coupled with an elevation of pro-inflammatory mediators such as IL1β suggest that this treatment may counteract immune cell death by continuous generation of cell survival factors and/or removal of high molecular weight pro-apoptotic factors (“death factors”).