title: Regulation of peroxisome proliferator-activated receptor β/δ expression and activity levels by toll-like receptor agonists and MAP kinase inhibitors in rat astrocytes.
abstract: Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) is a potential regulator of neuroinflammation. Toll-like receptors (TLR) are innate immunity-related receptors of inflammatory stimuli. In the present report, we evaluate the molecular mechanisms of regulation of mRNA, protein, and transcriptional activity levels of PPARβ/δ by agonists of TLR4, TLR1/2, and TLR5, using lipopolysaccharide (LPS), peptidoglycan, and flagellin, respectively. We found that these stimuli increase the PPARβ/δ levels in astrocytes. Expression and activity of PPARβ/δ are separately regulated by inhibitors of p38, MEK1/2, extracellular signal-regulated kinases 1/2, and c-Jun N-terminal Kinase mitogen-activated protein kinases. The LPS-induced kinetics of PPARβ/δ expression is similar to that of the proinflammatory gene cyclooxygenase 2. Moreover, for both genes the expression depends on nuclear factor kappa-light-chain-enhancer of activated B cells and p38, and is induced after inhibition of protein synthesis. The up-regulation of the expression after inhibition of protein synthesis signifies the participation of a labile protein in regulation of PPARβ/δ expression. In contrast to cyclooxygenase 2, the cycloheximide-sensitive PPARβ/δ expression was not responsive to nuclear factor kappa-light-chain-enhancer of activated B cells inhibition. Measurements of PPARβ/δ mRNA stability showed that the PPARβ/δ mRNA levels are regulated post-transcriptionally. We found that in LPS-stimulated astrocytes, the half-life of PPARβ/δ mRNA was 50 min. Thus, we demonstrate that PPARβ/δ expression and activity are regulated in TLR agonist-stimulated astrocytes by mechanisms that are widely used for regulation of proinflammatory genes. Protein expression level of nuclear receptor PPARβ/δ is important for functions of this transcription factor. We investigate the regulatory mechanisms of PPARβ/δ in rat primary astrocytes stimulated by agonists of toll-like receptors (TLR): TLR4, TLR1/2, and TLR5. Expression, activity, mRNA stability, and superinduction of PPARβ/δ were up-regulated after TLR stimulation. These processes are sensitive to MAPKs and NF-kB inhibitors. Superinduction is up-regulation of mRNA expression after inhibition of protein synthesis.
authors.affiliation: Otto-von-Guericke-Universität Magdeburg, Medizinische Fakultät, Institut für Neurobiochemie, Magdeburg, Germany; Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Chistyakov
authors.forename: Stepan
authors.initials: S
authors.lastname: Aleshin
authors.forename: Marina G
authors.initials: MG
authors.lastname: Sergeeva
authors.forename: Georg
authors.initials: G
authors.lastname: Reiser
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D008070:Lipopolysaccharides / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D047494:PPAR delta / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D061251:Primary Cell Culture; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012313:RNA / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D051193:Toll-Like Receptors / Q000819:agonists*; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D047494:PPAR delta; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D012313:RNA; D051546:Cyclooxygenase 2; D020928:Mitogen-Activated Protein Kinases; D015232:Dinoprostone
keywords: inflammation; peroxisome proliferator-activated receptors; superinduction; toll-like receptors