Many clinical studies have shown that daily intake of soybean [ Glycine max (L.) Merr., Fabacease] or its foods may reduce the risk of
osteoporosis,
heart attack,
hyperlipidemia,
coronary heart disease, cardiovascular and
chronic renal diseases, and
cancers, including prostate, colon, and breast
cancers. Of the soy constituents, soyasaponins exhibit anti-aging,
antioxidant, apoptotic, and anti-inflammatory effects. However, the anti-inflammatory effect of
soyasaponin Ab has not been thoroughly studied. Therefore, we investigated its anti-inflammatory effects in
2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitic mice and
lipopolysaccharide (LPS)-stimulated peritoneal macrophages.
Soyasaponin Ab inhibited colon shortening,
myeloperoxidase activity, the expression of
cyclooxygenase-2 (COX-2) and
inducible nitric oxide synthase (iNOS), and activation of the
transcription factor nuclear factor-κB (NF-κB).
Soyasaponin Ab (1, 2, 5, and 10 μM) inhibited the production of NO (IC(50) = 1.6 ± 0.1 μM) and
prostaglandin E(2) (IC(50) = 2.0 ± 0.1 ng/mL), the expression of
tumor necrosis factor (TNF)-α (IC(50) = 1.3 ± 0.1 ng/mL),
interleukin (IL)-1β (IC(50) = 1.5 ± 0.1 pg/mL), and
toll-like receptor (TLR)4, and the phosphorylation of
interleukin-1 receptor-associated kinase (IRAK)-1 in LPS-stimulated peritoneal macrophages.
Soyasaponin Ab weakly inhibited the phosphorylation of ERK, JNK, and p38.
Soyasaponin Ab significantly reduced the binding of Alexa-Fluor-594-conjugated LPS to peritoneal macrophages.
Soyasaponin Ab did not affect TLR4 expression or LPS-induced NF-κB activation in TLR4
siRNA-treated peritoneal macrophages (knockdown efficiency of TLR4 > 94%). On the basis of these findings,
soyasaponin Ab may ameliorate
colitis by inhibiting the binding of LPS to TLR4 on macrophages.