TRPA1 is a major oxidant sensor in murine airway sensory neurons
Bret F. Bessac, … , Lauren Cohn, Sven-Eric Jordt
Bret F. Bessac, … , Lauren Cohn, Sven-Eric Jordt
Published April 8, 2008
Citation Information: J Clin Invest. 2008;118(5):1899-1910. https://doi.org/10.1172/JCI34192.
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TRPA1 is a major oxidant sensor in murine airway sensory neurons

Abstract

Sensory neurons in the airways are finely tuned to respond to reactive chemicals threatening airway function and integrity. Nasal trigeminal nerve endings are particularly sensitive to oxidants formed in polluted air and during oxidative stress as well as to chlorine, which is frequently released in industrial and domestic accidents. Oxidant activation of airway neurons induces respiratory depression, nasal obstruction, sneezing, cough, and pain. While normally protective, chemosensory airway reflexes can provoke severe complications in patients affected by inflammatory airway conditions like rhinitis and asthma. Here, we showed that both hypochlorite, the oxidizing mediator of chlorine, and hydrogen peroxide, a reactive oxygen species, activated Ca2+ influx and membrane currents in an oxidant-sensitive subpopulation of chemosensory neurons. These responses were absent in neurons from mice lacking TRPA1, an ion channel of the transient receptor potential (TRP) gene family. TRPA1 channels were strongly activated by hypochlorite and hydrogen peroxide in primary sensory neurons and heterologous cells. In tests of respiratory function, Trpa1–/– mice displayed profound deficiencies in hypochlorite- and hydrogen peroxide–induced respiratory depression as well as decreased oxidant-induced pain behavior. Our results indicate that TRPA1 is an oxidant sensor in sensory neurons, initiating neuronal excitation and subsequent physiological responses in vitro and in vivo.

Authors

Bret F. Bessac, Michael Sivula, Christian A. von Hehn, Jasmine Escalera, Lauren Cohn, Sven-Eric Jordt

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Figure 5

Activation of heterologously expressed TRPA1 channels by H2O2.

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H2O2 induces TRPA1-dependent influx of Ca2+ and ionic currents in mustar...
(A) Representative whole-cell current-voltage relationship of hTRPA1 currents in CHO cells before activation (black), during maximal activation by H2O2 (green), and at the end of the inactivation phase (red). Currents were measured using a ±80 mV voltage ramp protocol over 100 ms at 0.5-Hz intervals (0 mV holding potential throughout). Intracellular Cs-based solution contained 10 mM EGTA. (B) Single TRPA1 channel currents induced by H2O2 in the cell-attached configuration. Cell-attached patches were formed on CHO cells expressing hTRPA1. The cell was superfused with a bath solution containing 1 mM H2O2, and single-channel openings were recorded using a ±60 mV step protocol. Membrane potential was estimated to be –10 mV, where zero currents were observed. Indicated potentials are corrected values. Representative current traces from a patch containing 3 channels are shown. hTRPA1 unitary conductance was 42 ± 0.5 pS (–50 mV) and 73 ± 1.0 pS (+50 mV). Pipette and bath solutions contained 2 mM Ca2+. (C) Current-voltage relationship of open channel conductance of single hTRPA1 channels recorded in CHO cells in cell-attached configuration. Values are mean ± SEM of 10 channel openings each. Potentials were corrected as in B. (D) Requirement of covalent agonist acceptor sites for TRPA1 activation by NaOCl and H2O2. [Ca2+]i changes were compared between HEK293t cells expressing hTRPA1 WT channels and cells expressing TRPA1 channels with mutated interaction sites (C619, C639, C663, and K708; denoted 3CK). A 1-mM dose of nonreactive agonist carvacrol was given after the indicated oxidant stimulus. Values denote percent maximal response to carvacrol (n = 60 cells/trace).