Amyloid beta peptide 1–40 enhances the action of Toll-like receptor-2 and -4 agonists but antagonizes Toll-like receptor- 9-induced inflammation in primary mouse microglial cell cultures Miriam Lotz,* ,1 Sandra Ebert,* ,1 Hermann Esselmann, Asparouh I. Iliev,à Marco Prinz,§ Nicole Wiazewicz,* Jens Wiltfang,¶ Joachim Gerber* and Roland Nau* *Department of Neurology, Georg-August-University, Go ¨ ttingen, Germany  Department of Psychiatry, Georg-August-University, Go ¨ttingen, Germany àCell Biophysics Group, European Neuroscience Institute-Go ¨ttingen, Go ¨ttingen, Germany §Department of Neuropathology, Georg-August-University, Go ¨ ttingen, Germany ¶Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Erlangen, Germany Abstract The interaction of endogenous and exogenous stimulators of innate immunity was examined in primary cultures of mouse microglial cells and macrophages after application of defined Toll-like receptor (TLR) agonists [lipopolysaccharide (LPS) (TLR4), the synthetic lipopeptide Pam3Cys-Ser-Lys4 (Pam3- Cys) (TLR2) and single-stranded unmethylated CpG-DNA (CpG) (TLR9)] alone and in combination with amyloid beta peptide (Abeta) 1–40. Abeta 1–40 stimulated microglial cells and macrophages primed by interferon-c in a dose-dependent manner. Co-administration of Abeta1–40 with LPS or Pam3- Cys led to an additive release of nitric oxide (NO) and tumour necrosis factor alpha (TNF-a). This may be one reason for the clinical deterioration frequently observed in patients with Alz- heimer’s disease during infections. In contrast, co-application of Abeta1–40 with CpG led to a substantial decrease of NO and TNF- a release compared with stimulation with CpG alone. Abeta 1–40 and CpG did not co-localize within the same subcellular compartment, making a direct physico- chemical interaction as the cause of the observed antagonism very unlikely. This suggests that not all TLR agonists enhance the stimulatory effect of Abeta on innate immunity. Keywords: amyloid beta 1–40 peptide, cytosin-guanosin oligodesoxynucleotide, lipopolysaccharide, microglia, nitric oxide, tripalmytoyl-cysteinyl-seryl-(lysyl)3-lysine. J. Neurochem. (2005) 94, 289–298. A significant inflammatory component contributes to the pathology of Alzheimer’s dementia (Bamberger and Land- reth 2001). The clinical status of patients suffering from neurodegenerative diseases, in particular Alzheimer’s and Parkinson’s disease, frequently deteriorates during infec- tions (Perry et al. 2003). A study of the course of Alzheimer’s disease in monozygotic and dizygotic twins, in which one twin had suffered serious infection and developed Alzheimer’s dementia, showed that persons who had not suffered from serious infections developed Alzheimer’s dementia later or not at all, and also lived longer (Nee and Lippa 1999). Moreover, delirium is a frequent consequence of infection in the elderly, parti- cularly prevalent in demented patients (Elie et al. 1998). It can occur in early stages of Alzheimer’s dementia (Lerner et al. 1997). A strong association between delirium during the acute phase and functional decline up to six months after discharge from hospital has been noted, suggesting that an insult precipitating delirium accelerates long-term Received February 14, 2005; accepted February 23, 2005. Address correspondence and reprint requests to Prof. Dr med. Roland Nau, Department of Neurology, Georg-August-University, Robert-Koch- Straße 40, D-37075 Go ¨ttingen, Germany. E-mail: rnau@gwdg.de 1 Miriam Lotz and Sandra Ebert contributed equally to this work. Abbreviations used: Abeta, amyloid beta peptide; BSA, bovine serum albumin; CFU/mL, colony-forming units/mL; CpG, cytosin-guanosin oligodesoxynucleotide; DMEM, Dulbecco’s modified Eagle’s medium; FCS, fetal calf serum; IL-10, interleukin 10; LPS, lipopolysaccharide; NO, nitric oxide; Pam3Cys, tripalmytoyl-cysteinyl-seryl-(lysyl)3-lysine; PAGE, polyacrylamide gel electrophoresis; PBS, phosphate-buffered saline; PVDF, hydrophilized polyvinylidene fluoride; SDS, sodium do- decyl sulfate; TBS, Tris-buffered saline; TLR, Toll-like receptor; TNF-a, tumour necrosis factor alpha; WST-1, water-soluble tetratolium salt-1. Journal of Neurochemistry , 2005, 94, 289–298 doi:10.1111/j.1471-4159.2005.03188.x Ó 2005 International Society for Neurochemistry, J. Neurochem. (2005) 94, 289–298 289