Induction of ICAM-1 by Armillariella mellea is mediated through generation of reactive oxygen species and JNK activation

Abstract

Ethnopharmacological relevance Armillariella mellea is an edible mushroom that has been traditionally used as an alternative medicine in many countries because of its anti-microbial and anti-cancer effects. Aim of the study In this study, we examined the ability of Armillariella mellea to induce the expression of intercellular adhesion molecule (ICAM)-1, an important cellular adhesion molecule for the recruitment of immune cells to regional inflammatory sites. Materials and methods A human monocytic cell line, THP-1 or human peripheral blood mononuclear cells (PBMC) were stimulated with Armillariella mellea extract (AME) and subjected to flow cytometry to examine the expression of ICAM-1 protein on the cell surface. Steady-state mRNA level of ICAM-1 was determined by real-time reverse transcription-polymerase chain reaction. The phosphorylation of JNK protein was examined by Western blot analysis using antibodies specific for non-phosphorylated and phosphorylated forms of JNK. For the analysis of transcription factors regulating ICAM-1 transcription, the nuclear fraction was extracted from AME-treated THP-1 cells and subjected to electrophoretic mobility shift assay. Results AME induced expression of ICAM-1 and its mRNA in THP-1 cells in dose- and time-dependent manners. AME-induced ICAM-1 expression was also observed on CD14-positive monocytes in human PBMC. Interestingly, AME-induced ICAM-1 production was inhibited by the specific inhibitors of reactive oxygen species (ROS) and JNK, whereas no inhibitory effect was observed when inhibitors of ERK, p38 kinase, phosphatidylinositol 3-kinase, or protein kinase C were used. Concomitantly, AME increased phosphorylation of JNK in a time-dependent fashion. DNA binding activities of NF-κB, AP-1, SP-1, and STAT-1 were increased by AME treatment. Conclusion These results suggest that AME induces ICAM-1 expression in human monocytic cells through ROS/JNK-dependent signaling pathways leading to the activation of NF-κB, AP-1, SP-1, and STAT-1 transcription factors.