Activation of inducible nitric oxide synthase by Taraxacum officinale in mouse peritoneal macrophages.
The objective of the current study was to determine the effect of Taraxacum officinale (TO) on the production of nitric oxide (NO). Stimulation of mouse peritoneal macrophages with TO after the treatment of recombinant interferon-gamma (rIFN-gamma) resulted in increased NO synthesis. TO had no effect on NO synthesis by itself. When TO was used in combination with rIFN-gamma, there was a marked cooperative induction of NO synthesis in a dose-dependent manner. The optimal effect of TO on NO synthesis was shown 6 h after treatment with rIFN-gamma. This increase in NO synthesis was manifested as an increased amount of inducible NO synthase (iNOS) protein. NO production was inhibited by N(G)-monomethyl-L-arginine. The increased production of NO from rIFN-gamma plus TO-stimulated cells was decreased by treatment with a protein kinase C inhibitor such as staurosporin. In addition, synergy between rIFN-gamma and TO was mainly dependent on TO-induced tumor necrosis factor-alpha (TNF-alpha) secretion. All the preparations of TO were endotoxin free. These results suggest that the capacity of TO to increase NO production from rIFN-gamma-primed mouse peritoneal macrophages is the result of TO-induced TNF-alpha secretion.
Department of Oriental Pharmacy, College of Pharmacy, Wonkwang University, Iksan, Chonbuk, South Korea. hmkim@med.wonkwang.ac.kr
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D000818:Animals; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry; D007371:Interferon-gamma / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology*; D010946:Plants, Medicinal; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D019311:Staurosporine / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects / Q000378:metabolism; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D009573:Nitrites; D010936:Plant Extracts; D014409:Tumor Necrosis Factor-alpha; D019323:omega-N-Methylarginine; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D011493:Protein Kinase C; D019311:Staurosporine