Kinetics of inflammatory response of astrocytes induced by TLR 3 and TLR4 ligation.
Toll-like receptors (TLRs) are sentinels of the innate immune system that recognize an array of exogenous and endogenous pathogenic molecules. The ligation of the receptors triggers inflammatory response necessary for pathogen elimination and for the healing process. In the present study we examined inflammatory response of astrocytes elicited by the ligation of TLR3 and TLR4. Astrocytic cultures established from newborn rat brains were exposed to double stranded RNA (dsRNA) and lipopolysaccharide (LPS), the ligands for TLR3 and TLR4, respectively. The expression of cytokine genes was determined by RNase protection assay, and the generation of nitric oxide (NO) was measured by Griess technique. Both ligands upregulated the expression of several cytokines (i.e., IL-1alpha, IL-1beta, IL-6, TNFalpha, GM-CSF, LTbeta, and TGFbeta3) and downregulated the expression of MIF, but have no effect on the expression of IL-2, IL-3, IL-4, IL-5, IL-10, TGFbeta1, TGFbeta2, TNFbeta, and IFNgamma. Although dsRNA upregulated the expression of IFNbeta, LPS did not indicating that the TRIF-dependent branch of TLR4 signaling is inactive in astrocytes. Proinflammatory response as seen from upregulated cytokine expression and NO generation reached a peak within the first day of exposure, and was subsequently abrogated. The cells also became refractory to subsequent stimulation by the ligands indicating the existence of negative feedback mechanisms that control proinflammatory response in astrocytes.
Krasowska-Zoladek
Alicja
A
Department of Neurobiology and Anatomy, West Virginia University School of Medicine, Morgantown, West Virginia 26506, USA.
Banaszewska
Monika
M
Kraszpulski
Michal
M
Konat
Gregory W
GW
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000166:cytology; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D007249:Inflammation / Q000139:chemically induced / Q000473:pathology*; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013997:Time Factors; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
D016207:Cytokines; D008024:Ligands; D008070:Lipopolysaccharides; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; C495347:Tlr4 protein, rat; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D009569:Nitric Oxide