Protein adsorption during LDL-apheresis: proteomic analysis

Abstract

Background. The aim of our study was to investigate the clearance of functional proteins by different low-density lipoprotein-apheresis (LDL-A) methods with the help of proteomic analyses. Methods. Proteins were eluated from the different LDL-A columns and investigated with 2D electrophoresis combined with mass spectrometry methods. In parallel, we quantified the plasma protein loss from patients treated with double-filtration plasmapheresis (DFPP; n = 9), direct adsorption of lipoproteins (DALI; n = 5) or heparin-induced extracorporeal LDL precipitation (HELP; n = 7) with routine laboratory methods and western blots. Results. Proteomic analyses of the column-bound proteins revealed a column-type-dependent loss with the highest number of protein spots in DALI-treated patients (1001 +/- 36), followed by HELP (881 +/- 25) and DFPP (535 +/- 20). More than 70 functional proteins were identified. These proteins are involved in the coagulation pathway (e.g. kininogen 1) and have adhesive (e.g. fibronectin), rheological (e.g. fibrinogen) and immunological/inflammatory properties (e.g. complement components). Quantification with western blot analyses demonstrated a significant depletion (P < 0.01) of these proteins comparing serum samples before and after the column with a systemic lowering in patients' serum. Conclusions. These data reveal strong interaction between column and serum proteins during LDL-A. The clearance of proteins with adhesive, rheological, and inflammatory characteristics may have beneficial effects on microcirculation and reduce chronic inflammation but may also concomitantly induce side effects such as an increased bleeding risk.