Differential effects of oilseed protein hydrolysates in attenuating inflammation in murine macrophages

Proteins from underutilized defatted oilseed meals have been proposed as promising sources of bioactive peptides. This study was conducted to determine the anti-inflammatory activities of five oilseed proteins (flaxseed, rapeseed, sunflower, sesame and soybean) hydrolysed via alcalase, pepsin (at pH 1.3 and pH 2.1), respectively, and to compare these against two dairy proteins (whey, casein). The potential of protein hydrolysates of three different molecular weight fractions (Mw > 10 kDa, 3–10 kDa, < 3 kDa) to modulate nuclear factor kappa B (NF-κB) signalling was screened via RAW-Blue™ reporter cells. Fractions with Mw < 3 kDa of pepsin (pH 1.3)-treated protein hydrolysates were subsequently selected to validate anti-inflammatory properties in RAW 264.7 macrophages. Rapeseed fractions showed greatest potency to attenuate inflammation, via efficiently down-regulating the expression of IL-6 (−49.1%), IL-1β (−58.6%), iNOS (−41.9%) and COX-2 (−58.7%) and up-regulating the IL-10 (+47.2%) mRNA level at 2000 μg peptides/mL. Rapeseed, sesame and casein demonstrated marked repression of NF-κB pathway, through down-regulating NF-κB1, p65 and/or IκBα mRNA levels. In addition, rapeseed, sesame and soybean reduced the expression of TLR4 and/or CD14 associated with attenuated LPS recognition. In addition, it was confirmed that rapeseed and soybean hydrolysates showed capabilities to bind 43.9 and 52.4% of LPS in solution, thereby weakening inflammatory response; an effect that could at least partially be related to the presence of hydrophobic amino acids. To summarize, current data demonstrate differing capacity of plant protein hydrolysates to interact with inflammatory signalling, indicating the need for further research into the molecular mechanisms of peptide action.