The molecular mechanism of polygalasaponin F-mediated decreases in TNFα: emphasizing the role of the TLR4-PI3K/AKT-NF-κB pathway

Abstract

Polygalasaponin F (PS-F), an oleanane-type triterpenoid saponin extracted from Polygala japonica, decreases the release of the inflammatory cytokine tumor necrosis factor α (TNFα), but the precise molecular mechanisms by which this event occurs are not fully understood. To study the anti-neuroinflammatory mechanisms of PS-F, enzyme-linked immunosorbent assay was used to detect the secretion of TNFα from BV-2 microglial cells. Nuclear proteins extracted from BV-2 microglial cells stimulated by lipopolysaccharide (LPS) and pretreated with/without inhibitors were measured by Western blotting, and cell viability was evaluated by MTT analysis. The results indicated that inhibition of toll-like receptor (TLR) 4 (CLI-095 1 μg/ml), phosphatidylinositol 3-kinase (PI3K) (Ly294002 10 μM) or IκBα phosphorylation (Bay11-7082 10 μM) completely prevents the release of TNFα induced by LPS without affecting cell viability and attenuated the nuclear translocation of p65 stimulated by LPS. In addition, PS-F exhibited a similar trend regarding TNFα release, AKT phosphorylation and NF-κB translocation. These results suggest that PS-F reduces neuroinflammatory cytokine secretion through the regulation of the TLR4-PI3K/AKT-NF-κB signaling pathway.

Keywords::

• polygalasaponin F
• TNFα
• TLR4
• PI3K/AKT

Disclosure statement

These data have not been previously published or submitted for publication elsewhere. The authors involved in this study have no conflict of interests to declare.

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China [grant number 81274122], [grant number 81373997]; Studies on Structure and Function of Bioactive Substances from Natural Medicines [grant number IRT1007]; the Beijing Natural Science Foundation [grant number 7131013]; the Research Fund for the Doctoral Program of Higher Education of China [grant number 20121106130001].