title: Microglia are required for astroglial Toll-like receptor 4 response and for optimal TLR2 and TLR3 response.
abstract: Within the central nervous system, astrocytes and microglia are the primary responders to endogenous ligands released upon injury and stress, as well as to infectious pathogens. Toll-like receptors (TLRs) are implicated in recognition of both types of stimulus. Whether astrocytes respond as strongly as microglia to TLR agonists remains contentious. In this study, we have rigorously purified astrocytes to determine their capacity for autonomous TLR response, in absence of microglia. We used flow cytometry and differential adhesion as well as a myeloid lineage-specific suicide gene to purify astrocytes from mixed glial cultures and measured their response to TLR agonists. Our results show that the response of astrocytes to TLR2 and TLR3 agonists is greatly enhanced by, and response to TLR4 agonists is completely dependent on, the presence of functional microglia. In the case of the TLR4 response to lipopolysaccharide, microglia exert their effect on astrocytes at least partially through release of soluble mediators that directly activate or facilitate astrocyte responses. Our findings underline the contribution of glial crosstalk in CNS responses to injury or inflammation.
authors.affiliation: Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Odense C, Denmark.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Holm
authors.forename: Dina
authors.initials: D
authors.lastname: Draeby
authors.forename: Trevor
authors.initials: T
authors.lastname: Owens
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015703:Antigens, CD / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000166:cytology; D039481:CD11b Antigen / Q000235:genetics; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D018920:Coculture Techniques; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005973:Glutamine / Q000031:analogs & derivatives / Q000494:pharmacology; D007369:Interferon Inducers / Q000494:pharmacology; D053583:Interleukin-1beta / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D017628:Microglia / Q000187:drug effects / Q000502:physiology*; D009942:Organometallic Compounds / Q000494:pharmacology; D011070:Poly I-C / Q000494:pharmacology; D011134:Polysaccharides / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D051196:Toll-Like Receptor 3 / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D039481:CD11b Antigen; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D005904:Glial Fibrillary Acidic Protein; D007369:Interferon Inducers; D053583:Interleukin-1beta; C533573:L-glutamine-o-vanillin-copper; D009942:Organometallic Compounds; D011134:Polysaccharides; C519703:TLR3 protein, mouse; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D005973:Glutamine; D011070:Poly I-C