Auricularia auricula-judae Hot Water Extracts Activate Macrophages Toward M1 Phenotype

Proper modulation of immune response is a novel strategy for disease prevention and clinical treatment. Edible mushrooms are potent dietary sources of natural immune modulators which components are highly diversified in biological function, chemical structure and molecular weight. In the present study, we determined the immune-modulating activity of the crude hot water extract of Auricularia auricula-judae (AACE). AACE was fractionized into four subfractions based on molecular weight, assigned as F1 (＜10 kDa), F2 (10-50 kDa), F3 (50-100 kDa), and F4 (＞100 kDa). The immune-modulating activity of AACE and the sub-fractions was evaluated in murine macrophages. The results indicated that crude hot water extract and the subfractions, except low molecular weight-fraction (F1), exhibited immune-stimulating, rather than anti-inflammatory activity, by triggering macrophage activation toward M1-like functional phenotype determined by the secretion of inflammatory immune mediators, including NO, TNF-α, IL-1, and IL-6, and the induction of M1 cell specific cell surface marker, CD11c. F2 and F4 exhibited the highest capacity of macrophage activation among AACE and the sub-fractions. At the concentration of 25 μg/mL, F2 and F4 fractions exhibited similar potency of macrophage-stimulating activity as 0.5 μg/mL lipopolysaccharide, while F1 (＜10 kDa) showed limited activating effect even at the dosage of 100 μg/mL AACEs stimulated macrophages likely through toll-like receptor-4 (TLR-4) signaling. Supplementation of AACE, F2 or F3, at 50 μg/mL, exerted anti-proliferative effect on cancer cells co-cultured with macrophages. These results suggested that A. auricula-judae was a dietary source of potent immunostimulants comprising various types of macrophage-activating components. The most potent immunostimulants were the components with molecular weight at 10-50 kDa or higher than 100 kDa, and elimination of low molecular weight (＜ 10 kDa) components might enhance AACE immune-stimulating activity. Our study provides scientific data supporting nutraceuticals application of A. auricula-judae and might prompt further studies to identify specific immunostimulant compounds in AACE for nutraceutical application.