Characterization of immunostimulatory pectic polysaccharide isolated from leaves of Diospyros kaki Thumb. (Persimmon)

Abstract

In this study, three polysaccharide fractions (PLE-I–III) were purified from crude polysaccharides from leaves of Diospyros kaki Thumb. (Persimmon) that were hydrolysed with pectinase, and their monosaccharide composition was analysed. Among the three fractions, PLE-I was found to markedly stimulate the immune activity (IL-6/IL-12 and TNF-α production) of peritoneal macrophages cells. Signal transduction studies showed that PLE-I phosphorylated MAPK and NF-κB in RAW264.7 cells in a concentration-dependent manner. The effect of PLE-I on IL-6 production was found to be completely suppressed by specific inhibitors of JNK (SP) and ERK (U0126), but not a p38 inhibitor. Moreover, PLE-I-induced phosphorylation of the transcription factor c-Jun was inhibited by SP and U0126 treatment, whereas iNOS expression was blocked by inhibitors of JNK, p38, and NF-κB. Collectively, these results suggest that PLE-I-induced macrophage activation is regulated via JNK/ERK and not p38, whereas iNOS expression is primarily regulated via MAPK and NF-κB.

Keywords

• Diospyros kaki Thumb. leaves
• Polysaccharide
• Macrophage activation
• MAPK
• NF-κB