title: Toll-like receptor prestimulation increases phagocytosis of Escherichia coli DH5alpha and Escherichia coli K1 strains by murine microglial cells.
abstract: Meningitis and meningoencephalitis caused by Escherichia coli are associated with high rates of mortality. When an infection occurs, Toll-like receptors (TLRs) expressed by microglial cells can recognize pathogen-associated molecular patterns and activate multiple steps in the inflammatory response that coordinate the brain's local defense, such as phagocytosis of invading pathogens. An upregulation of the phagocytic ability of reactive microglia could improve the host defense in immunocompromised patients against pathogens such as E. coli. Here, murine microglial cultures were stimulated with the TLR agonists Pam(3)CSK(4) (TLR1/TLR2), lipopolysaccharide (TLR4), and CpG oligodeoxynucleotide (TLR9) for 24 h. Upon stimulation, levels of tumor necrosis factor alpha and the neutrophil chemoattractant CXCL1 were increased, indicating microglial activation. Phagocytic activity was studied after adding either E. coli DH5alpha or E. coli K1 strains. After 60 and 90 min of bacterial exposure, the number of ingested bacteria was significantly higher in cells prestimulated with TLR agonists than in unstimulated controls (P < 0.01). Addition of cytochalasin D, an inhibitor of actin polymerization, blocked >90% of phagocytosis. We also analyzed the ability of microglia to kill the ingested E. coli strains. Intracellularly surviving bacteria were quantified at different time points (90, 150, 240, and 360 min) after 90 min of phagocytosis. The number of bacteria killed intracellularly after 6 h was higher in cells primed with the different TLR agonists than in unstimulated microglia. Our data suggest that microglial stimulation by the TLR system can increase bacterial phagocytosis and killing. This approach could improve central nervous system resistance to infections in immunocompromised patients.
authors.affiliation: Department of Neurology, University of Göttingen, Robert Koch Str. 40, D-37075 Göttingen, Germany. sribes@med.uni-goettingen.de
authors.forename: Sandra
authors.initials: S
authors.lastname: Ribes
authors.forename: Sandra
authors.initials: S
authors.lastname: Ebert
authors.forename: Dirk
authors.initials: D
authors.lastname: Czesnik
authors.forename: Tommy
authors.initials: T
authors.lastname: Regen
authors.forename: Andre
authors.initials: A
authors.lastname: Zeug
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bukowski
authors.forename: Alexander
authors.initials: A
authors.lastname: Mildner
authors.forename: Helmut
authors.initials: H
authors.lastname: Eiffert
authors.forename: Uwe-Karsten
authors.initials: UK
authors.lastname: Hanisch
authors.forename: Sven
authors.initials: S
authors.lastname: Hammerschmidt
authors.forename: Roland
authors.initials: R
authors.lastname: Nau
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002460:Cell Line; D054360:Chemokine CXCL1 / Q000096:biosynthesis / Q000276:immunology; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000276:immunology*; D007155:Immunologic Factors; D055666:Lipopeptides / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D050296:Microbial Viability; D017628:Microglia / Q000276:immunology*; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D010587:Phagocytosis; D051193:Toll-Like Receptors / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000276:immunology
chemical_list: C408982:CPG-oligonucleotide; D054360:Chemokine CXCL1; D007155:Immunologic Factors; D055666:Lipopeptides; D008070:Lipopolysaccharides; D009838:Oligodeoxyribonucleotides; C508075:Pam(3)CSK(4) peptide; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha