, 2009 and Mattsson et al., 2010). Furthermore, systemic bacterial infections are considered to be a risk factor for sporadic AD, connecting infection, inflammation and alterations in amyloid metabolism and leading to cognitive disturbances (Dunn et al., 2005, Honjo et al., 2009 and Eikelenboom et al., 2012). A potential function of the Aβ-peptides in this context may be to opsonize pathogens to support their clearance and/or act as soluble factors with cytokine or chemokine activities.

We have previously reported that monocyte activation by the phagocytosis of polystyrene beads induces APP glycosylation and Aβ-peptide secretion (Spitzer et al., 2010). We observed a relative increase in the release of N-terminally truncated Anti-infection Compound Library Aβ peptide species from

activated monocytes (Maler et al., 2008 and Spitzer et al., 2010). In the current study, we used mononuclear phagocytes as a model to investigate the impact of various Aβ-peptides on the phagocytosis of polystyrene particles or Escherichiacoli bacteria and on concurrent macrophage polarization. Human peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll (Biochrom, Germany) density gradient centrifugation from buffy coats purchased at Transfusionsmedizin Suhl, Germany. Thrombocytes were removed by under-laying an Crenolanib mw FCS-gradient and centrifugation at 75g for 15 min. Monocytes were isolated from PBMCs by the antibody-mediated removal of non-monocytes using a MACS Monocyte Isolation Kit II (Miltenyi Biotec, Germany) and MACS LS Columns (Miltenyi Biotec, Germany). For the analysis of undifferentiated

monocytes, the cells were resuspended in serum-free AIM-V medium and seeded at a density of 1 × 106 cells/ml in 96-well ultra-low attachment plates (Corning, USA). Differentiated macrophages were obtained by cultivating monocytes for seven days at 8 × 105 cells/ml in RPMI 1640 with 10% FCS in 96-well plates (Biochrom, Germany). For the polarization of macrophages, 40 ng/ml rhGM-CSF (Immunotools, Germany) FER or 80 ng/ml rhM-CSF (Immunotools, Germany) was added to the culture medium, respectively. After three days, 50% of the medium was exchanged. THP-1 cells were obtained from ATCC and maintained below 1 × 106 cells/ml in RPMI 1640 supplemented with 10% FCS. For differentiation to macrophages, THP-1 cells were cultured at 2 × 106 cells/ml for three days in RPMI 1640 medium supplemented with 10% FCS and 50 ng/ml phorbol 12-myristate 13-acetate (PMA, Sigma–Aldrich, Germany). Primary cultures of porcine microglia were isolated following a protocol adapted from Franke (Franke et al., 2000). Briefly, the secretory areas, cerebellum and meninges were removed from brain hemispheres obtained from a local abattoir. After mincing the tissue, it was incubated for 2 h with 6.5% (v/v) dispase (BD, Germany) at 37 °C. Lipids were removed by mixing 100 mL of the cell suspension with 150 mL of dextran solution (ρ = 1.