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Title: Ketamine inhibits tumor necrosis factor-{alpha} and interleukin-6 gene expressions in lipopolysaccharide-stimulated macrophages through suppression of toll-like receptor 4-mediated c-Jun N-terminal kinase phosphorylation and activator protein-1 activation

Our previous study showed that ketamine, an intravenous anesthetic agent, has anti-inflammatory effects. In this study, we further evaluated the effects of ketamine on the regulation of tumor necrosis factor-{alpha} (TNF-{alpha}) and interlukin-6 (IL-6) gene expressions and its possible signal-transducing mechanisms in lipopolysaccharide (LPS)-activated macrophages. Exposure of macrophages to 1, 10, and 100 {mu}M ketamine, 100 ng/ml LPS, or a combination of ketamine and LPS for 1, 6, and 24 h was not cytotoxic to macrophages. A concentration of 1000 {mu}M of ketamine alone or in combined treatment with LPS caused significant cell death. Administration of LPS increased cellular TNF-{alpha} and IL-6 protein levels in concentration- and time-dependent manners. Meanwhile, treatment with ketamine concentration- and time-dependently alleviated the enhanced effects. LPS induced TNF-{alpha} and IL-6 mRNA syntheses. Administration of ketamine at a therapeutic concentration (100 {mu}M) significantly inhibited LPS-induced TNF-{alpha} and IL-6 mRNA expressions. Application of toll-like receptor 4 (TLR4) small interfering (si)RNA into macrophages decreased cellular TLR4 levels. Co-treatment of macrophages with ketamine and TLR4 siRNA decreased the LPS-induced TNF-{alpha} and IL-6 productions more than alone administration of TLR4 siRNA. LPS stimulated phosphorylation of c-Jun N-terminal kinase and translocation of c-Jun and c-Fos from the cytoplasm to nuclei. However,more » administration of ketamine significantly decreased LPS-induced activation of c-Jun N-terminal kinase and translocation of c-Jun and c-Fos. LPS increased the binding of nuclear extracts to activator protein-1 consensus DNA oligonucleotides. Administration of ketamine significantly ameliorated LPS-induced DNA binding activity of activator protein-1. Therefore, a clinically relevant concentration of ketamine can inhibit TNF-{alpha} and IL-6 gene expressions in LPS-activated macrophages. The suppressive mechanisms occur through suppression of TLR4-mediated sequential activations of c-Jun N-terminal kinase and activator protein-1.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [2] ;  [4] ;  [5]
  1. Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan (China)
  2. (China)
  3. Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan (China)
  4. National Research Institute of Chinese Medicine, Taipei, Taiwan (China)
  5. Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan (China), E-mail: rmchen@tmu.edu.tw
Publication Date:
OSTI Identifier:
21140806
Resource Type:
Journal Article
Resource Relation:
Journal Name: Toxicology and Applied Pharmacology; Journal Volume: 228; Journal Issue: 1; Other Information: DOI: 10.1016/j.taap.2007.11.027; PII: S0041-008X(07)00549-2; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ANESTHETICS; APOPTOSIS; CYTOPLASM; GENES; INFLAMMATION; INHIBITION; MACROPHAGES; OLIGONUCLEOTIDES; PHOSPHORYLATION; RECEPTORS; RNA; TIME DEPENDENCE; TRANSLOCATION