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Activation of NADPH oxidase‐related proton and electron currents in human eosinophils by arachidonic acid
Author(s) -
Cherny V. V.,
Henderson L. M.,
Xu W.,
Thomas L. L.,
DeCoursey T. E.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00783.x
Subject(s) - arachidonic acid , chemistry , nadph oxidase , biophysics , superoxide , oxidase test , stimulation , conductance , patch clamp , electrophysiology , biochemistry , enzyme , medicine , endocrinology , biology , receptor , mathematics , combinatorics
1 Effects of arachidonic acid (AA) on proton and electron currents in human eosinophils were studied using the permeabilized‐patch voltage‐clamp technique, using an applied NH 4 + gradient to control pH i . 2 Superoxide anion (O 2 − ) release was assessed by cytochrome c reduction in human eosinophils. Significant O 2 − release was stimulated by 5‐10 μ m AA. 3 AA activated diphenylene iodinium (DPI)‐inhibitable inward current reflecting electron efflux through NADPH oxidase. These electron currents ( I e ) were elicited in human eosinophils at AA concentrations (3‐10 μ m ) similar to those that induced O 2 − release. 4 The voltage‐gated proton conductance ( g H ) in eosinophils stimulated with AA was profoundly enhanced: H + current amplitude ( I H ) increased 4.6 times, activation was 4 times faster, and the H + conductance‐voltage ( g H ‐ V) relationship was shifted to substantially more negative voltages. The electrophysiological effects of AA resembled those reported for PMA, except that AA did not consistently slow τ tail (deactivation of H + currents). 5 The stimulation of both proton and electron currents by AA was reversible upon washout. Repeated exposure elicited repeated responses. The activation of H + currents by AA was dissociable from its activation of NADPH oxidase; H + currents were enhanced at low concentrations of AA that did not elicit detectable I e or when NADPH oxidase was inhibited by DPI. 6 Most of the effects of AA on H + currents qualitatively resemble those reported in whole‐cell studies, reflecting a more direct action than PMA. The results are compatible with AA being an immediate activator of both NADPH oxidase and proton channels in human eosinophils.