Inhibition of NF-κB-Dependent Cytokine and Inducible Nitric Oxide Synthesis by the Macrocyclic Ellagitannin Oenothein B in TLR-Stimulated RAW 264.7 Macrophages

Abstract

Immunomodulatory effects of oenothein B (1), a macrocyclic ellagitannin from various Onagraceae species, have been described previously. However, the mechanisms underlying the anti-inflammatory activity of 1 have not been fully clarified. The effects of 1 were investigated on inducible nitric oxide synthase, TLR-dependent and TLR-independent signal transduction cascades, and cytokine expression using murine macrophages (RAW 264.7). Compound 1 (10-60 μg/mL) reduced NO production, iNOS mRNA, and iNOS protein levels in a dose-dependent manner, without inhibition of iNOS enzymatic activity. It reduced the binding of the NF-κB p50 subunit to the biotinylated-consensus sequence and decreased nuclear p65 translocation. Gallic acid as a subunit of the macrocyclic ellagitannin 1 showed a far lower inhibitory activity. Nitric oxide production was reduced by 1 after stimulation using TLR2 (Pam2CSK4) and TLR4 (Kdo2) agonists, but this compound did not inhibit inducible nitric oxide synthesis after stimulation using interferon-gamma. IL-1beta, IL-6, and TNF-alpha mRNA synthesis was clearly reduced by the addition of 1. Oenothein B (1) inhibits iNOS after stimulation with LPS, TLR2, and TLR4 agonists via inhibition of TLR/NF-κB-dependent inducible nitric oxide and cytokine synthesis independent from IFN-gamma/JAK/STAT pathways. The full molecular structure of this macrocyclic ellagitannin seems to be required for its immunomodulatory actions.

Investigation on the Interaction Behavior Between Oenothein B and Pepsin by Isothermal Titration Calorimetry and Spectral Studies

“…Previous research on the biological activities of OeB has mainly been in vitro (Ducrey, Marston, Göhring, Hartmann, & Hostettmann, 1997;Schmid et al, 2012;Silva et al, 2014;Yoshimura et al, 2012). However, it has been reported that orally administered OeB can inhibit Ehrlich ascites tumors, as well as reduce neuroinflammation in the brain during systemic inflammation (Okud et al, 1986;Okuyama et al, 2013), demonstrating the potential efficacy of orally administered OeB.…”

Oenothein B Suppresses Lipopolysaccharide (LPS)-Induced Inflammation in the Mouse Brain

“…The active components responsible for the therapeutic effects of their extracts had not been well defined for a long time, but recent in vitro and in vivo studies revealed that oenothein B is one of the main biologically active components present in these extracts [5–8]. Detailed in vitro examination showed that oenothein B has anti-inflammatory activity against Toll-like receptor (TLR)-stimulated RAW 264.7 macrophages [9]; immunomodulatory activity toward human monocytic THP-1 Blue cells and human leukemia HL-60 cells [6]; and inhibitory activity against prostatic 5α-reductase and aromatase in prostate cancer cell lines PC-3 cells [10]. As part of studies on the activities of oenothein B, we earlier reported that it has anti-tumor activity against MM2 ascites tumors [11] and human oral squamous cell carcinoma [12,13], anti-oxidant activity [1], and an immunomodulatory effect on human dendritic cells [14].…”

Oenothein B, a Cyclic Dimeric Ellagitannin Isolated from Epilobium angustifolium, Enhances IFNγ Production by Lymphocytes

“…It has been studied for antitumor, antiviral, antibacterial, antioxidant, pro-inflammatory, and anti-inflammatory properties [7], [26]–[31]. Oenothein B has been reported to inhibit inflammatory responses by phagocytes induced by TLR agonists and other stimulants [30], [31]. However, in the absence of additional stimulation, oenothein B promotes inflammatory responses by phagocytes.…”