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International Journal of Medicinal Mushrooms

ISSN for PRINT: 1521-9437

Institutional price:	$538.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2006, Volume8

107 pages

DOI: 10.1615/IntJMedMushr.v8.i3

Issue price - $138.00

An Immunomodulating Polysaccharide in Agaricus brasiliensis S. Wasser et al. (Agaricomycetideae) Activates Macrophages through Toll-like Receptor 4

Masashi Mizuno
Faculty of Agriculture, Kobe University; and Graduate School of Science and Technology, Kobe University, Nada-ku, Kobe 657-8501, Japan

Sachiko Kawakami
Graduate School of Science and Technology, Kobe University, Kobe, Japan

ABSTRACT

Peritoneal macrophages from toll-like receptor (TLR) 4 and TLR2 knockout mice (TLR4−/− and TLR2−/−) were stimulated with a water-insoluble hetero-glycan (ABHG), purified from a fruit body of Agaricus brasiliensis. TLR4−/− mice did not produce tumor necrosis factor (TNF)−α and nitric oxide (NO), but TLR2−/− did. However, ABHG did not inhibit TNF-α and NO production by macrophages in the presence of polymyxin B, which could bind to lipid A in lipopolysaccharide (LPS); suggesting that ABHG did not contain LPS as contaminants. These results indicated that ABHG was recognized through TLR4−/− to produce inflammatory cytokines such as TNF-α and NO. RT-PCR was used to investigate the effect of ABHG on mRNA expression of TNF-α and inducible nitric oxide synthase (iNOS) in RAW 264.7. TNF-α mRNA expression was induced 0.5 hr after stimulation, peaked in 3 hr, and thereafter decreased to reach a stable level after 24 hr. On the other hand, iNOS mRNA induction was delayed for 3 hr and thereafter remained at the same level until 24 hr after stimulation. Furthermore, the DNA binding activity of NF-κB was observed as early as 0.5 hr after treatment and rapidly increased to its peak value 2 hr later, and thereafter decreased. When RAW 264.7 was stimulated with ABHG in the presence of an anti-TNF-α antibody, TNF-α mRNA expression was not affected and iNOS was downregulated. These results indicate that TNF-α production by RAW 264.7, stimulated with an immunomodulating polysaccharide such as ABHG, was enhanced by upregulating of NF-κB through TLR4, and the newly produced TNF-α enhanced NO production trough an autocrine pathway.