Lipoteichoic acid-induced TNF-α and IL-6 gene expressions and oxidative stress production in macrophages are suppressed by ketamine through downregulating Toll-like receptor 2-mediated activation oF ERK1/2 and NFκB.
Lipoteichoic acid (LTA), a gram-positive bacterial outer membrane component, can cause septic shock. Our previous studies showed that ketamine has anti-inflammatory and antioxidant effects on gram-negative LPS-induced macrophage activation. In this study, we further evaluated the effects of ketamine on the regulation of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production in macrophages and its possible mechanisms. Exposure of macrophages to a therapeutic concentration of ketamine (100 microM) inhibited LTA-induced TNF-alpha and IL-6 expressions at protein or mRNA levels. In parallel, ketamine at 100 microM reduced LTA-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Sequentially, ketamine reduced the LTA-triggered translocation of nuclear factor-kappaB (NFkappaB) from the cytoplasm to nuclei and its transactivation activity. Pretreatment with PD98059, an inhibitor of ERK, decreased LTA-enhanced NFkappaB activation and TNF-alpha and IL-6 mRNA syntheses. Cotreatment with ketamine and PD98059 synergistically suppressed the LTA-induced translocation and transactivation of NFkappaB and biosyntheses of TNF-alpha and IL-6 mRNA. Application of Toll-like receptor 2 (TLR2) small interfering RNA (si)RNA into macrophages decreased the levels of this receptor, and simultaneously ameliorated LTA-augmented NFkappaB transactivation and consequent production of TNF-alpha and IL-6 mRNA. Cotreatment with ketamine and TLR2 siRNA synergistically lowered TNF-alpha and IL-6 mRNA syntheses in LTA-activated macrophages. Ketamine and TLR2 siRNA could reduce the LTA-induced increases in production of nitrite and intracellular reactive oxygen species in macrophages, and their combination had better effects than a single exposure. Thus, this study shows that one possible mechanism involved in ketamine-induced inhibition of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production is through downregulating TLR2-mediated phosphorylation of ERK1/2 and the subsequent translocation and transactivation of NFkappaB.
Chang
Huai-Chia
HC
Graduate Institute of Medical Sciences, Taipei Medical University, 250 Wu-Xing Street, Taipei, Taiwan.
Lin
Ke-Hsun
KH
Tai
Yu-Ting
YT
Chen
Juei-Tai
JT
Chen
Ruei-Ming
RM
D000818:Animals; D002460:Cell Line; D015536:Down-Regulation; D015870:Gene Expression / Q000187:drug effects; D015850:Interleukin-6 / Q000096:biosynthesis*; D007649:Ketamine / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D048370:MAP Kinase Kinase 2 / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects* / Q000502:physiology*; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects; D013682:Teichoic Acids / Q000494:pharmacology*; D051195:Toll-Like Receptor 2 / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D015850:Interleukin-6; D008070:Lipopolysaccharides; D016328:NF-kappa B; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; D014409:Tumor Necrosis Factor-alpha; C009900:lipoteichoic acid; D007649:Ketamine; D048052:Mitogen-Activated Protein Kinase 3; D048370:MAP Kinase Kinase 2