Mouse TLR4 peptide

Euterpe oleraceaMart., commonly known as acai, has been demonstrated to exhibit significantly antioxidant and inflammatory activities in experimental models. These effects of the hydroalcoholic extract from the acai seed (ASE) were investigated in TNBS-induced (2,4,6-trinitrobenzenesulfonic acid) acute colitis model in rats. Wistar rats (180-220 g) were orally pretreated with saline (0.3 mL), ASE (10, 30 and 100 mg/kg) and dexamethasone (control group, 1 mg/kg) once daily for 3 days starting before TNBS instillation. On day 3 after TNBS, the animals were euthanized, the portion of distal colon was collected and washed with 0.9% saline for macroscopy and histological evaluation, glutathione (GSH) and malonyldialdehyde (MDA) levels, myeloperoxidase (MPO) and catalase (CAT) activity, nitrate and nitrite (NO3/NO2) concentration, pro-inflammatory cytokines levels and intestinal barrier integrity. We also evaluated Toll-like Receptor 4/cyclooxygenase-2/nuclear factor kappa B expression as a possible mechanism related to the ASE effects. Treatment with ASE 100 mg/kg decreased significantly macroscopic and microscopic damage induced by TNBS. In addition, MPO activity, TNF-alpha (tumor necrosis factor-alpha) and IL-1 beta (interleukin 1) levels were reduced in rats with colitis. ASE 100 mg/kg restored GSH and MDA levels, CAT activity, NO3/NO(2)concentration and improved the intestinal barrier integrity in the TNBS group. ASE 100 mg/kg significantly reduced TNBS-induced expression of the TLR4, COX-2 and NF-kappa B p65. ASE 100 mg/kg improved macroscopy and histological parameters, inflammation, intestinal barrier integrity and nitric and oxidative stress through the TLR-4/COX-2/NF-kappa B pathway.

Author summary IFI16 is a nuclear protein involved in a variety of physiological processes, including cell cycle regulation, tumor suppression, and virus sensing. Emerging evidence indicates that IFI16 is released in the extracellular milieu under injury or stress conditions. Here we show that extracellular IFI16 acts as a damage-associated molecular pattern (DAMP), triggering inflammation through Toll-like receptor 4 (TLR4) activation. Furthermore, we demonstrate that IFI16 activity is potentiated upon binding to subtoxic concentrations of strong TLR4-activating lipopolysaccharide (LPS) variants, which are known to be present in various pathological settings other than gram-negative infections. Our study provides new insights into the role of extracellular IFI16 during low-grade endotoxemia. Damage-associated molecular patterns (DAMPs) are endogenous molecules activating the immune system upon release from injured cells. Here we show that the IFI16 protein, once freely released in the extracellular milieu of chronically inflamed tissues, can function as a DAMP either alone or upon binding to lipopolysaccharide (LPS). Specifically, using pull-down and saturation binding experiments, we show that IFI16 binds with high affinity to the lipid A moiety of LPS. Remarkably, IFI16 DAMP activity is potentiated upon binding to subtoxic concentrations of strong TLR4-activating LPS variants, as judged by TLR4-MD2/TIRAP/MyD88-dependent IL-6, IL-8 and TNF-alpha transcriptional activation and release in stimulated monocytes and renal cells. Consistently, using co-immunoprecipitation (co-IP) and surface plasmon resonance (SPR) approaches, we show that IFI16 is a specific TLR4-ligand and that IFI16/LPS complexes display a faster stimulation turnover on TLR4 than LPS alone. Altogether, our findings point to a novel pathomechanism of inflammation involving the formation of multiple complexes between extracellular IFI16 and subtoxic doses of LPS variants, which then signal through TLR4.