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Ketamine inhibits nitric oxide synthase in lipopolysaccharide-treated rat alveolar macrophages
1Department of Anesthesiology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China. cyli@ndmcl.ndmctsgh.edu.tw
Purpose:
To evaluate the effects of ketamine on the activity and protein expression of inducible nitric oxide synthase (iNOS) induced by lipopolysaccharide (LPS) in rat alveolar macrophages.
Methods:
Pulmonary alveolar macrophages isolated from Wistar-Kyoto rats were used. After incubation of macrophages with ketamine (1, 10, or 100 microM) and LPS (1 microgram.ml-1) for 24 hr, the cell-free medium was removed for measuring the nitrite and tumour necrosis factor-alpha (TNF-alpha) levels by Griess reaction and ELISA kit, respectively. The harvested macrophages were also used to determine the activity of iNOS by using the conversion of [3H]-L-arginine to [3H]-L-citrulline method. In addition, the protein expression of iNOS was detected by Western blot analysis.
Results:
In rat alveolar macrophages, (i) ketamine (1 to 100 microM) caused a dose-dependent suppression of the production of nitrite and TNF-alpha induced by LPS and (ii) ketamine (100 microM) inhibited the activity (46.5 +/- 4.8%, P < 0.05) and protein expression (35 +/- 11%, P < 0.05) of iNOS in response to LPS.
Conclusion:
These results show that ketamine inhibits the activity and expression of iNOS in LPS-activated alveolar macrophages, which may be associated with the reduction of the release of TNF-alpha following LPS treatment.
Insights
Ketamine suppresses inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) in lipopolysaccharide (LPS)-activated rat macrophages. This suggests ketamine may reduce inflammatory responses in the lungs.
Area of Science:
- Immunology
- Pharmacology
- Cell Biology
Background:
- Lipopolysaccharide (LPS) triggers inflammation in macrophages via inducible nitric oxide synthase (iNOS).
- Nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) are key inflammatory mediators.
- Alveolar macrophages play a crucial role in lung immune responses.
Purpose of the Study:
- To investigate the impact of ketamine on iNOS activity and protein expression.
- To assess ketamine's effect on nitrite and TNF-alpha production in LPS-stimulated rat alveolar macrophages.
Main Methods:
- Rat alveolar macrophages were incubated with varying concentrations of ketamine and LPS.
- Nitrite and TNF-alpha levels were quantified using Griess reaction and ELISA.
- iNOS activity and protein expression were measured via enzymatic assay and Western blot analysis.
Main Results:
- Ketamine demonstrated a dose-dependent inhibition of LPS-induced nitrite and TNF-alpha production.
- High-dose ketamine (100 microM) significantly reduced iNOS activity by 46.5% and protein expression by 35%.
- These effects were statistically significant (P < 0.05).
Conclusions:
- Ketamine inhibits both the activity and expression of iNOS in LPS-activated alveolar macrophages.
- This inhibitory effect of ketamine may contribute to the observed reduction in TNF-alpha release.
- Ketamine shows potential as a modulator of inflammatory processes involving iNOS in the lungs.