The effects of wild bitter gourd fruit extracts on ICAM-1 expression in pulmonary epithelial cells of C57BL/6J mice and microRNA-221/222 knockout mice: Involvement of the miR-221/-222/PI3K/AKT/NF-κB pathway

Abstract

Background: The extracts from wild bitter gourd fruit (WBGE) were reported to possess numerous pharmacological activities. However, the anti-inflammatory effects of WBGE on human lung epithelial cells and the underlying mechanisms have not been determined.

Purpose: To evaluate the molecular basis of the effects of WBGE on intercellular adhesion molecule-1 (ICAM-1) expression in alveolar epithelial (A549) cells, C57BL/6 wild-type (WT) mice and microRNA (miR)-221/-222 knockout (KO) mice with or without tumor necrosis factor (TNF-α; 3 ng/ml) treatment.

Study design/methods: WT mice and miR-221/-222 KO mice were fed a control diet and divided into four groups (C: control mice; T: treated with TNF-α alone; WBGE/T: pretreated with WBGE and then stimulated with TNF-α; WBGE: treated with WBGE alone). The effects of WBGE on ICAM-1 expression and the related signals in A549 cells and mice with or without TNF-α treatment were examined by Western blot and immunofluorescent staining.

Results: WBGE significantly decreased the TNF-α-induced ICAM-1 expression in A549 cells through the inhibition of phosphoinositide 3-kinase (PI3K)/ protein kinase B (AKT)/ nuclear factor- kappa B (NF-κB)/ inhibitor of NF-κB (IκB) phosphorylation and decreased leukocyte adhesion. In addition, WBGE reduced endogenous ICAM-1 expression and upregulated miR-221/-222 expression. The overexpression of miR-222 decreased PI3K/AKT/NF-κB/IκB and ICAM-1 expression, which resulted in reducing monocyte adhesion. Moreover, WBGE reduced ICAM-1 expression in lung tissues of WT mice with or without TNF-α treatment and upregulated miR-221/222. WBGE did not affect the miR-221/-222 level and had little effect on ICAM-1 expression in miR-221/-222 KO mice.

Conclusions: These results suggest that WBGE reduced ICAM-1 expression both under in vitro and in vivo conditions. The protective effects were mediated partly through the miR-221/-222/PI3K/AKT/NF-κB pathway.

Keywords: ICAM-1; Inflammation; NF-κB; PI3K/AKT; WBGE; miR-221/-222.