Anti-inflammation effects of highly purified low-Mw RG-I pectins on LPS-activated macrophages

Abstract

Pectic oligosaccharides are viewed as excellent immunomodulator, but the specific molecular weight (Mw) range required for anti-inflammatory effects remains unclear. In this study, citrus pectins was depolymerized by the ultrasound/H2O2/Vc system and the pectic mixtures was separated through the superdex 30 chromatography column. Three highly purified pectin fractions (USP1, USP2, USP3) were obtained, with the Mw of 2713 g/mol, 3683 g/mol, and 7469 g/mol. All of them were RG-I pectins and USP3 contained more arabinan sidechains than USP1 and USP2. In vitro anti-inflammation assays based on LPS-induced RAW264.7 macrophages indicated that these pectins could suppress the NO release, ROS production and down-regulated the level of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α in a Mw-dependent manner. The inhibitory effects increased in the order of USP1<USP2<USP3. Meanwhile, the regulation of pro-inflammatory cytokines were closely related to the content of arabinan sidechains in pectin. Thus, low-Mw pectins with Mw>3KD should be effective as a prophylactic agent against inflammatory diseases in functional food.