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Published on: February 5, 2019
Polygonum tinctorium extract suppresses nitric oxide production by activated macrophages through inhibiting inducible
1Fujisaki Institute, Hayashibara Biochemical Laboratories Inc., 675-1 Fujishaki, Okayama 702-8006, Japan.
Abstract:
Despite its beneficial role in host defense mechanisms, excessive nitric oxide (NO) production by activated macrophages has been implicated in several inflammatory diseases. To clarify the mechanisms of anti-inflammatory activities of Polygonum tinctorium, we evaluated whether extracts of P. tinctorium could modulate the production of NO by activated macrophages. An AcOEt extract of P. tinctorium markedly inhibited NO synthesis by interferon-gamma (IFN-gamma)/lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages and the macrophage-like cell line RAW 264.7 in a dose-dependent manner. Inhibition of NO synthesis was achieved by reducing inducible NO synthase (iNOS) expression at protein and mRNA levels. However, the AcOEt extract of P. tinctorium failed to inhibit NO synthesis when iNOS was already expressed following stimulation with IFN-gamma and LPS. The AcOEt extract also exhibited inhibitory activity on iNOS expression in human lung epithelial A549 cells stimulated with a combination of IFN-gamma, TNF-alpha and IL-1 beta without affecting the expression of constitutive isoforms of NOS. Furthermore, in vivo injection of the AcOEt extract of P. tinctorium into LPS-treated mice significantly reduced NO synthesis by peritoneal exudate cells under ex vivo conditions. These results suggest that P. tinctorium extract may be a potential therapeutic modulator of NO synthesis in various pathological conditions.
Insights
Polygonum tinctorium extract significantly inhibits nitric oxide (NO) production by reducing inducible NO synthase (iNOS) expression. This plant extract shows potential for managing inflammatory conditions by modulating NO synthesis.
Area of Science:
- Immunology
- Pharmacology
- Natural Products
Background:
- Excessive nitric oxide (NO) production by activated macrophages is linked to inflammatory diseases.
- Understanding modulators of NO production is crucial for developing anti-inflammatory therapies.
Purpose of the Study:
- To investigate the anti-inflammatory effects of Polygonum tinctorium extracts.
- To determine if P. tinctorium modulates nitric oxide (NO) production in activated macrophages.
Main Methods:
- Tested an AcOEt extract of P. tinctorium on murine peritoneal macrophages and RAW 264.7 cells stimulated with interferon-gamma (IFN-gamma)/lipopolysaccharide (LPS).
- Assessed inducible NO synthase (iNOS) expression at protein and mRNA levels.
- Evaluated extract's effect on iNOS expression in human lung epithelial A549 cells and in vivo in LPS-treated mice.
Main Results:
- The AcOEt extract of P. tinctorium dose-dependently inhibited NO synthesis in stimulated macrophages.
- Inhibition of NO synthesis correlated with reduced iNOS expression at both protein and mRNA levels.
- The extract also inhibited iNOS expression in human lung cells and reduced NO synthesis in vivo in LPS-treated mice.
Conclusions:
- Polygonum tinctorium extract effectively inhibits NO synthesis by downregulating iNOS expression.
- P. tinctorium extract demonstrates potential as a therapeutic agent for pathological conditions involving excessive NO production.
