Foenumoside B isolated from Lysimachia foenum-graecum extract suppresses LPS-induced inflammatory response via NF-κB/AP-1 inactivation in murine macrophages and in endotoxin-induced shock model

Abstract

Foenumoside B (FSB), a bioactive component isolated from the Lysimachia foenum-graecum extract (LFE), has been shown to possess anti-inflammatory effects, but the underlying molecular mechanisms involved have not been elucidated. Accordingly, the authors investigated the mechanisms responsible for the anti-inflammatory effects of FSB in murine macrophages activated by LPS. FSB suppressed the LPS-induced expressions of iNOS and COX-2 at protein and mRNA levels and consequently decreased NO and PGE2 production in RAW264.7 and primary macrophages. FSB also reduced the LPS-induced inductions of TNF-α, IL-6 and IL-1β at protein and mRNA levels. Studies of the molecular mechanisms involved in the anti-inflammatory effects of FSB showed that it inhibited the transcriptional activities of NF-κB and AP-1, and the nuclear translocation of NF-κB via inhibition of the phosphorylations of AKT, p38 and STAT3. In a sepsis model, pretreatment with FSB inhibited the LPS-stimulated mRNA and protein levels of proinflammatory mediators, such as, iNOS, COX-2, TNF-α, IL-6 and IL-1β in plasma and liver. Importantly, FSB increased the survival rate of mice in the LPS-induced sepsis model. Taken together, these results show that the anti-inflammatory effects of FSB against LPS-induced inflammatory conditions are associated with inhibitions of the phosphorylations of AKT, p38 and STAT3 followed by the transcriptional suppressions of NF-κB and AP-1, and thus, reduced expressions of pro-inflammatory genes.