Vizantin Inhibits Endotoxin-Mediated Immune Responses via the TLR 4/MD-2 Complex

Abstract

Vizantin has immunostimulating properties and anticancer activity. In this study, we investigated the molecular mechanism of immune activation by vizantin. THP-1 cells treated with small interfering RNA for TLR-4 abolished vizantin-induced macrophage activation processes such as chemokine release. In addition, compared with wild-type mice, the release of MIP-1β induced by vizantin in vivo was significantly decreased in TLR-4 knockout mice, but not in TLR-2 knockout mice. Vizantin induced the release of IL-8 when HEK293T cells were transiently cotransfected with TLR-4 and MD-2, but not when they were transfected with TLR-4 or MD-2 alone or with TLR-2 or TLR-2/MD-2. A dipyrromethene boron difluoride–conjugated vizantin colocalized with TLR-4/MD-2, but not with TLR-4 or MD-2 alone. A pull-down assay with vizantin-coated magnetic beads showed that vizantin bound to TLR-4/MD-2 in extracts from HEK293T cells expressing both TLR-4 and MD-2. Furthermore, vizantin blocked the LPS-induced release of TNF-α and IL-1β and inhibited death in mice. We also performed in silico docking simulation analysis of vizantin and MD-2 based on the structure of MD-2 complexed with the LPS antagonist E5564; the results suggested that vizantin could bind to the active pocket of MD-2. Our observations show that vizantin specifically binds to the TLR-4/MD-2 complex and that the vizantin receptor is identical to the LPS receptor. We conclude that vizantin could be an effective adjuvant and a therapeutic agent in the treatment of infectious diseases and the endotoxin shock caused by LPS.

Chemical Hybridization of Vizantin and Lipid A to Generate a Novel LPS Antagonist

“…Our group recently demonstrated that vizantin represses TNF-α production triggered by LPS in the same assay system. 19) Among the synthesized compounds, 5 effectively inhibited LPS-induced release of TNF-α in a dosedependent manner (Fig. 4A) with an IC 50 value of 3.8 nM.…”

“…During the course of these investigations we recently developed vizantin (3) [15][16][17] based on a structure-activity relationship (SAR) study of trehalose 6,6′-dicorynomycolate (TDCM), which was first characterized in 1963 as a cell surface glycolipid of Corynebacterium spp. by Ioneda et al 18) Vizantin also triggers the innate immune response through the specific binding to the same TLR4/MD2 protein complex as lipid A, 19) and effectively activates some types of immune system. However, the finding that vizantin induces almost no TNF-α production is clearly different from that of lipid A (or LPS).…”

Fisiopatología de la sepsis por bacterias gram negativas: bases moleculares

“…proinfl amatorios efectores de la respuesta inmune inducida por los gram negativos en la sepsis. Un mecanismo idéntico como antagonista del lipopolisacárido se ha descrito y probado en modelos animales para el quercetín, principal fl avonoide de las plantas y uno de los principales constituyentes de la dieta humana presente en frutas, verduras y bebidas (16)(17)(18)(19).…”

Sulfated vizantin induces formation of macrophage extracellular traps

“…Our previous findings suggest that vizantin contributes minimally to immunotoxicity. Furthermore, vizantin competes with LPS for TLR4 binding, suggesting that it may be a safe therapeutic agent for endotoxemic phenomena, including sepsis‐like symptoms and septic shock . However, the pharmacokinetics of vizantin is limited because it is hydrophobic.…”

“…binding, suggesting that it may be a safe therapeutic agent for endotoxemic phenomena, including sepsis-like symptoms and septic shock (1). However, the pharmacokinetics of vizantin is limited because it is hydrophobic.…”