Impedimetric Detection of Transient Receptor Potential (TRP) Channel Activity

Abstract

Transient receptor potential (TRP) channels are non-selective ion channels permeable to cations including Na⁺, Ca^2 +, and Mg^2 +. They play a unique role as cell sensors and are involved in many Ca^2 +-mediated cell functions. The variety of functions to which TRP channels contribute predict that failure in channel gating will contribute to complex pathophysiological mechanisms. Dysfunctions of TRP channels cause diseases but are also involved in the progress of diseases. We present a novel method to screen chemical compounds as potential activators or inhibitors of TRP channels to provide pharmaceutical tools to regulate channel activity in disease control. Compared to common methods such as patch clamp or Ca2+ imaging, the presented impedance assay is automatable, experimental less demanding, and not restricted to the ion flow of Ca^2 +. We have chosen TRPA1 from the TRPA (‘ankyrin’) family as a model ion channel which was stimulated by allyl isothiocyanate (AITC). HEK293 cells stably transfected with human TRPA1 cDNA were grown on microelectrode arrays (MEA). Confluent cell layers of high density were analyzed. Impedance spectra of cell-covered and noncovered Pt electrodes showed a cell-specific signal at 90 kHz, which was chosen to monitor TRPA1 activity thereupon. An impedance decrease to 70-90 % of its original value was observed after application of 10 μM AITC indicating an increased conductance of the cell layer mediated by TRPA1. Control cells lacking TRPA1 showed no changes upon AITC stimuli.