ABSTRACT
Ketamine (KTM), a N-methyl-D-aspartate (NMDA) receptor antagonist, was found to has an anti-inflammatory effect, but some patients suffered from exacerbated pro-inflammatory reactions after anesthesia with KTM. The present study was aimed to examine the underlying mechanism of pro-inflammatory effects of KTM. In this study, RAW264.7 cells were exposed to KTM and NMDA alone or combined for 30 min before lipopolysaccharide (LPS) stimulation. The expression levels of IL-6 and TNF-α were detected by RT-PCR and ELISA, and those of NMDA receptors by RT-PCR in RAW264.7 cells. Additionally, the TLR4 expression was determined by RT-PCR and flow cytometry, respectively. The results showed that in RAW264.7 cells, KTM alone promoted the TLR4 expression, but did not increase the expression of IL-6 or TNF-α. In the presence of LPS, KTM caused a significantly higher expression of IL-6 and TNF-α than LPS alone. NMDA could neither alter the IL-6 and TNF-α mRNA expression, nor reverse the enhanced expression of IL-6 and TNF-α mRNA by KTM in LPS-challenged cells. After TLR4-siRNA transfection, RAW264.7 cells pretreated with KTM no longer promoted the IL-6 and TNF-α expression in the presence of LPS. In conclusion, KTM accelerated LPS-induced inflammation in RAW264.7 cells by promoting TLR4 expression, independent of NMDA receptor.
Subject(s)
Animals , Male , Mice , Anesthetics, Dissociative , Pharmacology , Cell Survival , Gene Expression Regulation , Inflammation Mediators , Pharmacology , Interleukin-6 , Genetics , Ketamine , Pharmacology , Lipopolysaccharides , Pharmacology , Macrophages , Metabolism , N-Methylaspartate , Pharmacology , Signal Transduction , Toll-Like Receptor 4 , Genetics , Metabolism , Tumor Necrosis Factor-alpha , GeneticsABSTRACT
Ketamine (KTM), a N-methyl-D-aspartate (NMDA) receptor antagonist, was found to has an anti-inflammatory effect, but some patients suffered from exacerbated pro-inflammatory reactions after anesthesia with KTM. The present study was aimed to examine the underlying mechanism of pro-inflammatory effects of KTM. In this study, RAW264.7 cells were exposed to KTM and NMDA alone or combined for 30 min before lipopolysaccharide (LPS) stimulation. The expression levels of IL-6 and TNF-α were detected by RT-PCR and ELISA, and those of NMDA receptors by RT-PCR in RAW264.7 cells. Additionally, the TLR4 expression was determined by RT-PCR and flow cytometry, respectively. The results showed that in RAW264.7 cells, KTM alone promoted the TLR4 expression, but did not increase the expression of IL-6 or TNF-α. In the presence of LPS, KTM caused a significantly higher expression of IL-6 and TNF-α than LPS alone. NMDA could neither alter the IL-6 and TNF-α mRNA expression, nor reverse the enhanced expression of IL-6 and TNF-α mRNA by KTM in LPS-challenged cells. After TLR4-siRNA transfection, RAW264.7 cells pretreated with KTM no longer promoted the IL-6 and TNF-α expression in the presence of LPS. In conclusion, KTM accelerated LPS-induced inflammation in RAW264.7 cells by promoting TLR4 expression, independent of NMDA receptor.
ABSTRACT
<p><b>BACKGROUND</b>Volatile anesthetics (VAs) may affect varied and complex physiology processes by manipulating Ca(2+)-calmodulin (CaM). However, the detailed mechanism about the action of VAs on CaM has not been elucidated. This study was undertaken to examine the effects of VAs on the conformational change, hydrophobic site, and downstream signaling pathway of CaM, to explore the possible mechanism of anesthetic action of VAs.</p><p><b>METHODS</b>Real-time second-harmonic generation (SHG) was performed to monitor the conformational change of CaM in the presence of VAs, each plus 100 µmol/L Ca(2+). A hydrophobic fluorescence indicator, 8-anilinonaphthalene-1-sulfonate (ANS), was utilized to define whether the VAs would interact with CaM at the hydrophobic site or not. High-performance liquid chromatography (HPLC) was carried out to analyze the activity of CaM-dependent phosphodiesterase (PDE1) in the presence of VAs. The VAs studied were ether, enflurane, isoflurane, and sevoflurane, with their aqueous concentrations 7.6, 9.5, 11.4 mmol/L; 0.42, 0.52, 0.62 mmol/L; 0.25, 0.31, 0.37 mmol/L and 0.47, 0.59, 0.71 mmol/L respectively, each were equivalent to their 0.8, 1.0 and 1.2 concentration for 50% of maximal effect (EC50) for general anesthesia.</p><p><b>RESULTS</b>The second-harmonic radiation of CaM in the presence of Ca(2+) was largely inhibited by the VAs. The fluorescence intensity of ANS, generated by binding of Ca(2+) to CaM, was reversed by the VAs. HPLC results also showed that AMP, the product of the hydrolysis of cAMP by CaM-dependent PDE1, was reduced by the VAs.</p><p><b>CONCLUSIONS</b>Our findings demonstrate that the above VAs interact with the hydrophobic core of Ca(2+)-CaM and the interaction results in the inhibition of the conformational change and activity of CaM. This in vitro study may provide us insight into the possible mechanism of anesthetic action of VAs in vivo.</p>