JCI - Intracellular alkalization causes pain sensation through activation of TRPA1 in mice

Intracellular alkalization causes pain sensation through activation of TRPA1 in mice

Fumitaka Fujita, Kunitoshi Uchida, Tomoko Moriyama, Asako Shima, Koji Shibasaki, Hitoshi Inada, Takaaki Sokabe, Makoto Tominaga

Published in Volume 118, Issue 12

J Clin Invest. 2008; 118(12):4049–4057 doi:10.1172/JCI35957

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Figure 1

TRPA1 mediates increases in [Ca²⁺]_i following intracellular alkalization in HEK293 cells.

(A) Tris buffer solution (pH 8.5) caused an increase in [Ca²⁺]_i in HEK293 cells expressing mouse TRPA1 in the presence of extracellular Ca²⁺ (filled circles, n = 37), but not in cells expressing vector alone (filled squares, n = 22). Moreover, 5 mM NH₄Cl also caused a [Ca²⁺]_i increase (open circles, n = 32), but not in cells expressing vector alone (open squares, n = 23). Horizontal bars indicate the duration of applied stimulus. Ratio 340/380, ratio of fluorescence intensities of fura-2 emissions at 340 nm and 380 nm; sol., solution. (B) Tris buffer solution increased intracellular pH in HEK293 cells loaded with BCECF in a dose-dependent manner (n = 14–31). Tris buffer solution (pH 8.5) caused intracellular alkalization of pH 7.43. (C) NH₄Cl increased intracellular pH in HEK293 cells loaded with BCECF in a dose-dependent manner (n = 12–38). NH₄Cl (5 mM) caused intracellular alkalization of pH 7.76. The data were fitted with the least-squares linear regression in B and C. (D) Tris buffer solution (pH 8.5) increased [Ca²⁺]_i in HEK293 cells expressing TRPA1 (n = 35) but not in cells expressing TRPV1 (n = 123), TRPV2 (n = 165), TRPM8 (n = 184), or vector alone (control, n = 61). (E) NH₄Cl (5 mM) increased [Ca²⁺]_i in HEK293 cells expressing TRPA1 (n = 48), but not in cells expressing TRPV1 (n = 172), TRPV2 (n = 154), TRPM8 (n = 196), or vector alone (n = 67). *P < 0.05, **P < 0.01.