Proteinase-activated receptor 2-mediated potentiation of transient receptor potential vanilloid subfamily 1 activity reveals a mechanism for proteinase-induced inflammatory pain - PubMed (original) (raw)

The PAR2 agonist SL-NH2 potentiates or sensitizes capsaicin- and proton-activated currents in a PKC-dependent manner in HEK293 cells. A, A representative trace of increase of capsaicin (Cap, 20 n

m

)-activated current in transfected HEK293 cells expressing rat TRPV1 and rat PAR2. Cells were perfused for 2 min with solution containing SL-NH2 (100 μ

m

) before capsaicin applications. Capsaicin was reapplied 0.5, 3, and 7 min after SL-NH2 treatment. Holding potential (_V_h)= –60 mV. B, Time course of the potentiating effect after SL-NH2 treatment. Numbers in parentheses indicate cells tested. *p < 0.05 versus before SL-NH2 treatment (Bef); unpaired t test. C, A PKC-dependent pathway is involved in the SL-NH2-induced potentiation of capsaicin-activated currents. Capsaicin was reapplied 2 min after exposure to bath solution with or without SL-NH2(SL–) or LR-NH2(LR–). Currents were normalized to values first induced by capsaicin application in the absence of SL-NH2 or LR-NH2. In some experiments, calphostin C (Calp.C) at 1 μ

m

or PKCϵ translocation inhibitor (PKCϵ-I) at 200 μ

m

was included in the pipette solution. Cont, Control group (preperfused with bath solution without SL-NH2 before reapplication of capsaicin); S502A/S800, cells expressing a TRPV1 mutant lacking sites for PKC-dependent phosphorylation. Numbers in parentheses indicate cells tested. *p < 0.05 versus Cont;ζ p < 0.05 versus LR-NH2; #p < 0.05 versus SL-NH2; unpaired t test. D, Capsaicin dose–response curves for TRPV1 activation in the absence (•) and presence (○) of 100 μ

m

SL-NH2. Currents were normalized to the currents maximally activated by 1 μ

m

capsaicin in the absence of SL-NH2. The figure shows averaged data fitted with the Hill equation. EC50 = 153 n

m

and Hill coefficient = 1.96 in the absence of SL-NH2. EC50 = 100 n

m

and Hill coefficient = 1.76 in the presence of SL-NH2. Values were obtained from 32 different cells. E, A representative trace of increase of proton (pH 6.2)-activated current in transfected HEK293 cells expressing TRPV1 and PAR2. F, SL-NH2 but not LR-NH2 potentiates proton-evoked TRPV1 responses. _V_h= –60 mV. Currents were normalized to values induced by first proton application in the absence of SL-NH2 or LR-NH2. Numbers in parentheses indicate cells tested. *p < 0.05 versus Cont; ζ p < 0.05 versus LR-NH2; unpaired t test.