Ethyl gallate isolated from Pistacia integerrima Linn. inhibits cell adhesion molecules by blocking AP-1 transcription factor

Abstract

Ethnopharmacological relevance: Galls from Pistacia integerrima Linn. (kakadshringhi) have been used as therapeutic agent for various inflammatory diseases in Indian system of traditional medicine. However, the active constituents underlying the medicinal properties of the Pistacia integerrima Linn. have not been thoroughly investigated yet. Aim of the study: Deregulated expression of cell adhesion molecules (CAMs) on vascular endothelium aggravates the inflammatory condition in various chronic diseases. In this work, we aimed to identify the active constituent from leaf gall of Pistacia integerrima Linn. using CAMs expression assay in activity guided purification, followed by determining the molecular mechanism of action. Material and methods: Cell based ELISA for LPS induced CAMs expression in human vein endothelial cells (HUVECs) was used for the activity guided isolation form Pistacia galls followed by structural determination of active constituent using IR, MS and NMR spectroscopy. Mechanism of action of the active constituent was investigated by western blot, RT-PCR and EMSA experiments. Results: In our study, ethyl gallate (EG) was identified as the active constituent of Pistacia integerrima Linn. for mediating its anti-inflammatory activity. It significantly attenuated LPS induced ICAM-1 and VCAM-1 at the protein and mRNA levels. At a functional level, it inhibited the adhesion of neutrophils to LPS activated endothelium. To identify its mechanism of action, we demonstrated that EG inhibited LPS induced cell adhesion molecules expression by blocking AP-1 transcription factor without affecting nuclear transcription factor-κB (NF-κB). Conclusion: Our results suggest that EG could be useful as a lead molecule for developing therapeutic agent for various inflammatory diseases.