Figure 2.

Characterization of UV-induced activation of hTRPA1 and hTRPV1. A, UV light (390 nm, 85 s illumination within 90 s) evokes calcium transients in hTRPA1-expressing HEK293t cells (n = 108) and, to a lesser extent, in cells expressing hTRPV1 (n = 170), but does not activate untransfected cells (n = 91). Carvacrol (Carv., 100 μm) and capsaicin (Caps., 300 nm) were used to confirm functional expression of hTRPA1 and hTRPV1. B, The action spectrum of hTRPA1 activation was tested using monochromatic light stimulation for 120 s at the given wavelength ±5 nm. C, Compared with control conditions (n = 92), light-induced activation was absent without extracellular calcium, but large calcium transients were observed when calcium was resupplied (n = 97). In the absence of UV stimulation, the rebound calcium transient was substantially smaller (n = 83). D, hTRPA1-expressing cells were stimulated with 390 nm in the absence (n = 289) and in the presence (n = 103) of the TRPA1 antagonist HC-030031 (10 μm HC). E, F, The UV-induced activation of TRPA1 depends on critical N-terminal cysteines. Compared with WT hTRPA1 (n = 289 and n = 71), the hTRPA1–3C mutant (hTRPA1–C621S/C641S/C665S; n = 222) and the hTRPA1–2C mutant (hTRPA1–C633S/C651S, n = 54) showed a reduced response UV. G, H, The UV-induced activation of TRPA1 is mediated by ROS production. HEK293-hTRPA1 were illuminated with UV light in control conditions (n = 178 and n = 77), or upon pretreatment with NAC (10 mm, 4 h; G, n = 129) or DTT (5 mm, 4 h; H, n = 110). Both NAC and DTT reduced the UV response amplitude, whereas the carvacrol response is unaffected. Data are mean ± SEM.