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Published on: December 15, 2014
Nitric oxide synthesis by rat pleural mesothelial cells: induction by cytokines and lipopolysaccharide
1Department of Medicine, Overton Brooks Veterans Affairs Medical Center, Shreveport, Louisiana 71101-4295.
Abstract:
The close proximity of pleural mesothelial cells (PMC) and mononuclear cells during pleural inflammation suggests that leukocyte-derived products (e.g., cytokines) may play an important role in modulating PMC function. The purpose of this study was to determine whether certain cytokines and bacterial products induce PMC to produce nitric oxide (NO). Confluent monolayers of rat PMC were exposed to tumor necrosis factor (TNF), interleukin-1 beta (IL-1), gamma-interferon (IFN), or lipopolysaccharide (LPS) individually and in various double and triple combinations for 6-72 h. Concentrations of nitrite and nitrate were quantified and used as indirect indices of NO production. Nitrite/nitrate accumulation was maximal at 72 h, with most of the increase occurring from 48 to 72 h. Maximal nitrite/nitrate production was observed with triple combinations with the combination of LPS, IL-1, and TNF giving the highest concentration (137.4 +/- 2.8 microM). Nitrite/nitrate production was significantly inhibited by NG-nitro-L-arginine methyl ester, suggesting that nitrite and nitrate were derived from the L-arginine-dependent formation of NO. These data indicate that PMC can be induced to produce large amounts of NO in response to specific combinations of proinflammatory cytokines and LPS.
Insights
Pleural mesothelial cells (PMC) produce nitric oxide (NO) when exposed to combinations of inflammatory cytokines and bacterial products. This NO production, measured via nitrite/nitrate, is significant and L-arginine dependent.
Area of Science:
- Immunology
- Cell Biology
- Respiratory Medicine
Background:
- Pleural inflammation involves close contact between mesothelial cells and leukocytes.
- Leukocyte-derived products, such as cytokines, may influence mesothelial cell function.
Purpose of the Study:
- To investigate if cytokines and bacterial products induce nitric oxide (NO) production in pleural mesothelial cells (PMC).
Main Methods:
- Rat PMC monolayers were treated with tumor necrosis factor (TNF), interleukin-1 beta (IL-1), gamma-interferon (IFN), and lipopolysaccharide (LPS) individually and in combinations.
- Nitrite and nitrate concentrations were measured as indirect indicators of NO production over 6-72 hours.
- Inhibition studies using NG-nitro-L-arginine methyl ester confirmed L-arginine-dependent NO synthesis.
Main Results:
- PMC produced nitric oxide (NO) in response to specific cytokine and LPS combinations.
- Maximal NO production occurred at 72 hours, particularly with triple combinations (LPS, IL-1, TNF).
- NG-nitro-L-arginine methyl ester significantly inhibited NO production, confirming its L-arginine-dependent pathway.
Conclusions:
- Pleural mesothelial cells possess the capacity to generate substantial amounts of nitric oxide (NO).
- Pro-inflammatory cytokines and bacterial products, especially in combination, are potent inducers of NO production by PMC.
- This finding highlights a potential mechanism in pleural inflammation involving mesothelial cell-derived NO.
