Induction of intercellular adhesion molecule-1 by water-soluble components of Hericium erinaceum in human monocytes

Hericium erinaceum is a medicinal mushroom that has been traditionally used in Asian countries for the treatment of cancers and infectious diseases. Although the immunomodulating activity of H. erinaceum is considered to be responsible for its medicinal activity, its action mechanisms are poorly understood. In the present study, we investigated the capability of water-extracted H. erinaceum (WEHE) to induce the expression of intercellular adhesion molecule-1 (ICAM-1), which regulates the migration of immune cells.

THP-1, a human monocytic cell-line, or human peripheral blood mononuclear cells (PBMC) were stimulated with WEHE (0-30 μg/mL) and subsequently analyzed using flow cytometry to examine the surface expression of ICAM-1 protein. Steady-state levels of ICAM-1 mRNA were estimated using real-time reverse transcription-polymerase chain reaction analysis. Electrophoretic mobility shift assay was conducted to examine transcription factors involved in ICAM-1 transcription.

WEHE induced ICAM-1 expression at both protein and mRNA levels in THP-1 cells in a dose- and time-dependent fashion. A similar pattern of ICAM-1 induction was also observed in CD14(+) monocytes in human PBMC that were stimulated with WEHE. The ICAM-1 expression on THP-1 cells stimulated with WEHE was suppressed by specific inhibitors for extracellular signal-regulated kinases (ERK) and reactive oxygen species (ROS). Additionally, exposure of THP-1 cells to WEHE increased the DNA binding activities of NF-κB, AP-1, SP-1 and STAT-1 transcription factors, all of which are known to be required for ICAM-1 gene expression.

These results suggest that WEHE induces ICAM-1 expression in human monocytes through ERK- and ROS-dependent signaling pathways, resulting in the subsequent activations of NF-κB, AP-1, SP-1, and STAT-1 transcription factors.