Honokiol blocks store operated calcium entry in CHO cells expressing the M3 muscarinic receptor: honokiol and muscarinic signaling

Adam L Martin,Yue-wern Huang,Ming-Huan Chan,Hsiu-Jen Wang,Po-Kuan Chao,Alexis G Martin,Rhett A Reichard,Robert S Aronstam

doi:10.1186/1423-0127-20-11

Abstract

BackgroundHonokiol, a cell-permeable phenolic compound derived from the bark of magnolia trees and present in Asian herbal teas, has a unique array of pharmacological actions, including the inhibition of multiple autonomic responses. We determined the effects of honokiol on calcium signaling underlying transmission mediated by human M3 muscarinic receptors expressed in Chinese hamster ovary (CHO) cells. Receptor binding was determined in radiolabelled ligand binding assays; changes in intracellular calcium concentrations were determined using a fura-2 ratiometric imaging protocol; cytotoxicity was determined using a dye reduction assay.ResultsHonokiol had a potent (EC50 ≈ 5 μmol/l) inhibitory effect on store operated calcium entry (SOCE) that was induced by activation of the M3 receptors. This effect was specific, rapid and partially reversible, and was seen at concentrations not associated with cytotoxicity, inhibition of IP3 receptor-mediated calcium release, depletion of ER calcium stores, or disruption of M3 receptor binding.ConclusionsIt is likely that an inhibition of SOCE contributes to honokiol disruption of parasympathetic motor functions, as well as many of its beneficial pharmacological properties.

Highlights

Honokiol, a cell-permeable phenolic compound derived from the bark of magnolia trees and present in Asian herbal teas, has a unique array of pharmacological actions, including the inhibition of multiple autonomic responses
We report that honokiol is a potent inhibitor of store operated calcium entry (SOCE), with lesser effects on resting calcium concentrations and calcium release from the endoplasmic reticulum
Chinese hamster ovary (CHO) cells express components of both the phospholipase Cβ [15] and adenylate cyclase [16] signaling pathways, and CHO cells transfected with transgenes for the different muscarinic receptor subtypes respond to muscarinic agonists in pharmacologically and physiologically appropriate fashions: Activation of human M1, M3 or M5 receptors expressed in CHO cells leads to the production of Inositol trisphosphate (IP3), release of calcium from the endoplasmic reticulum (ER), activation of SOCE, and modulation of the expression of genes under control of

Summary

Introduction

A cell-permeable phenolic compound derived from the bark of magnolia trees and present in Asian herbal teas, has a unique array of pharmacological actions, including the inhibition of multiple autonomic responses. We determined the effects of honokiol on calcium signaling underlying transmission mediated by human M3 muscarinic receptors expressed in Chinese hamster ovary (CHO) cells. Cell-permeable phenolic compound derived from the bark of magnolia trees that is present in Asian herbal teas. Honokiol has a unique array of antiangiogenic, antitumor and anti-inflammatory actions [1]. Honokiol is an effective scavenger of reactive oxygen species [2], which may be an important factor in its anti-inflammatory and neuroprotective actions [3,4,5].

Methods

Results

Discussion

Conclusion