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Nitric oxide synthesis by rat pleural mesothelial cells: induction by growth factors and lipopolysaccharide
M W Owens1, S A Milligan, M B Grisham
1Department of Medicine, Overton Brooks Veterans Affairs, Shreveport, Louisiana, USA.
Abstract:
The purpose of this study was to determine if certain growth factors and bacterial products induce pleural mesothelial cells (PMC) to produce nitric oxide (NO). Confluent monolayers of rat PMC were exposed to epidermal growth factor (EGF), platelet-derived growth factor (PDGF), or lipopolysaccharide (LPS) individually and in various combinations for 24-72 h. Concentrations of nitrite and nitrate were quantified and used as an indirect measure of NO production. LPS stimulation resulted in a significant increase in nitrite/nitrate concentration, but neither EGF nor PDGF alone or combined had any significant effect relative to control. However, LPS combined with either EGF or PDGF caused a significant increase in nitrite/nitrate concentration relative to LPS alone and growth factor alone. The highest level level of nitrite/nitrate concentration was observed with the triple combination of LPS, EGF, and PDGF. Nitrite/nitrate accumulation was significantly increased at 24 h by all combinations, and continued to increase, with the highest concentration observed after 72 h of exposure. Nitrite/nitrate production was significantly inhibited by NG-nitro-L-arginine methyl ester and this inhibition was reversed by the addition of L-arginine, 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 relatively large amounts of NO in response to growth factors combined with LPS.
Insights
Bacterial products like LPS, combined with growth factors, significantly increase nitric oxide (NO) production in pleural mesothelial cells (PMC). This synergistic effect, particularly with LPS, EGF, and PDGF, highlights a key pathway for NO generation in these cells.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Pleural mesothelial cells (PMC) play a role in inflammation.
- Nitric oxide (NO) is a signaling molecule involved in various physiological processes.
Purpose of the Study:
- To investigate if growth factors and bacterial products stimulate nitric oxide (NO) production in rat PMC.
- To determine the role of epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and lipopolysaccharide (LPS) in NO synthesis by PMC.
Main Methods:
- Cultured rat PMC were treated with EGF, PDGF, and LPS individually and in combination.
- Nitrite and nitrate concentrations, indirect measures of NO, were quantified over 24-72 hours.
- Inhibition studies using NG-nitro-L-arginine methyl ester and L-arginine confirmed NO pathway involvement.
Main Results:
- LPS significantly increased nitrite/nitrate levels, while EGF and PDGF alone did not.
- Combinations of LPS with EGF or PDGF markedly enhanced nitrite/nitrate production compared to LPS alone.
- The highest NO production was observed with the triple combination of LPS, EGF, and PDGF, with levels increasing up to 72 hours.
Conclusions:
- PMC can be induced to produce significant amounts of NO.
- Growth factors potentiate LPS-induced NO production in PMC.
- The L-arginine-dependent pathway is responsible for NO formation in response to these stimuli.