Ginsenoside Rh2 Downregulates LPS-Induced NF-κB Activation through Inhibition of TAK1 Phosphorylation in RAW 264.7 Murine Macrophage

Abstract

The present study was carried out to evaluate the inhibitory effects of ginsenoside Rh2 on nuclear-factor- (NF-) κB in lipopolysaccharide- (LPS-) activated RAW 264.7 murine macrophages. RAW 264.7 cells were pretreated with indicated concentrations of ginsenoside Rh2 for 1 h prior to the incubation of LPS (1 μg/mL) for indicated time period. Ginsenoside Rh2 reduced CD14 and Toll-like receptor 4 (TLR4) expressions 24 h after LPS stimulation. Furthermore, ginsenoside Rh2 significantly inhibited TGF-beta-activated kinase 1 (TAK1) phosphorylation 30 min after LPS stimulation. Ginsenoside Rh2 was further shown to inhibit NF-κB p65 translocation into the nucleus by suppressing IκB-α degradation. Also, LPS increased mRNA expression of TNF-α and IL-1α time-dependently, while TQ reduced TNF-α within 3 h and IL-1α within 1 h. And we firstly found that pretreatment of ginsenoside Rh2 successively inhibited hypoxia-inducible factor- (HIF-) 1α expression increased by LPS. In conclusion, ginsenoside Rh2 may inhibit LPS-induced NF-κB activation and reduce HIF-1α accumulation, suggesting that ginsenoside Rh2 may be considered as a potential therapeutic candidate for chronic inflammatory diseases.

Cellular stress response mechanisms as therapeutic targets of ginsenosides

“…Nuclear translocation, NF‐κB phosphorylation, and DNA binding are three important events in the final stage of NF‐κB pathway activation and have been shown to be inhibited by ginsenosides under various conditions. Nuclear translocation of NF‐κB p65 can be blocked by Rg1, 20( S )‐protopanaxatriol, Rh1, Rh2, Rb1, CK, Rg3, PF11, Rf, Rd, and Rb3 . The phosphorylation of NF‐κB p65 was found to be inhibited by Rg1, Rg3, and Ro .…”

“…Activated NF‐κB eventually binds to κB elements in the promoter region of target genes and initiates the transcriptional process of numerous genes . Recent investigations have demonstrated that the NF‐κB pathway is suppressed by a large number of ginsenosides, including Rg1, Rh2, Rb1, Compound K (CK), Rg3, Rb3, Rd, Pseudoginsenoside‐F11 (PF11), Re, Rh1, Rf, 20( S )‐protopanaxatriol, and Ro (Fig. ).…”

“…Upon TLR4 activation by LPS, the myeloid differentiation primary response gene 88 (MyD88) results in the initiation of a signaling cascade including TNF receptor‐associated factor 6 (TRAF6), IL‐1 receptor‐associated kinase (IRAK) 1, and TGF‐beta‐activated kinase 1 (TAK1), which phosphorylates MAPK and eventually the IKK complex . Recently, Rh2 was demonstrated to downregulate LPS‐induced NF‐κB activation through reducing CD14 and TLR4 expression and inhibiting TAK1 phosphorylation in RAW 264.7 cells . Similarly, PF11 also exerted an inhibitory effect on NF‐κB in LPS‐activated N9 microglia by blocking TLR4‐mediated TAK1/IKK, MAPKs, and Akt signaling pathways .…”

The expression of epidermal growth factor-like domain 7 regulated by oxygen tension via hypoxia inducible factor (HIF)-1α activity

“…Egfl7 and HIF-1a expression were determined using the SYBR Green Quantitect PCR Kit (Qiagen, Limburg, the Netherlands). The Egfl7 forward primer is 5'-TGCGACG-GACACAGA GCCTGCA-3' and the reverse primer is 5'-CAAGTATCTCCCTGCCATCCCA-3' [14,15]. The HIF-1a forward primer is CTCGGCGAA GCAAAGAGT and the reverse primer is GCCATCTA GGGCTTTCAG.…”

Protective Effect of Ginsenosides Rg1 and Re on Lipopolysaccharide-Induced Sepsis by Competitive Binding to Toll-Like Receptor 4

“…By prompting the release of these inflammatory mediators, LPS not only activates both innate and adaptive immune responses at distal sites from the infection but also, in many cases, causes shock and death (11). Consequently, strategies that include prevention of ligand binding to TLR4 (12), blocking the interactions of TLR4 and adaptors in signaling pathways (13), and suppressing NF-B signaling pathways (14) have been reported to be effective in intervening in the development of experimental sepsis.…”