Functional properties of the high-affinity TRPV1 (VR1) vanilloid receptor antagonist (4-hydroxy-5-iodo-3-methoxyphenyl acetate ester) iodo-resiniferatoxin
Functional properties of the high-affinity TRPV1 (VR1) vanilloid receptor antagonist (4-hydroxy-5-iodo-3-methoxyphenyl acetate ester) iodo-resiniferatoxin
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DOI：
10.1124/jpet.102.040394
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发表时间：
2002-12-01
影响因子：
3.5
通讯作者：
Jones, AB
中科院分区：
文献类型：
--
作者：
Seabrook, GR;Sutton, KG;Jones, AB
我们已经合成了带有4-羟基-5-碘-3-甲氧基苯乙酸酯（I-RTX）的碘化树脂毒素，并表征了其对大鼠和人TRPV 1（VR 1）受体的活性，以及在伤害感受的行为测定中的活性。在转染细胞的全细胞膜片钳记录中，测定了I-RTX的功能活性。辣椒素激活的电流表现出特征性的外向整流，并被辣椒平和I-RTX拮抗。在大鼠TRPV 1上，I-RTX的亲和力比辣椒平高800倍（IC 50分别为0.7和562 nM），对大鼠受体的亲和力比对人受体的亲和力高10倍（IC 50分别为0.7和5.4 nM）。当比较RTX和I-RTX对[H-3]RTX与大鼠和人TRPV 1膜结合的抑制时，观察到相同的差异。使用质子作为刺激揭示了其他药理学差异。在这些条件下，辣椒平仅部分阻断通过大鼠TRPV 1受体的电流（阻断70 - 80%），但对人受体是完全拮抗剂。与此相反，I-RTX完全阻断质子诱导的电流在这两个物种和激活的有毒热。I-RTX还在大鼠体外皮肤神经测定中阻断辣椒素诱导的C纤维放电。尽管这种活性和高亲和力的I-RTX大鼠TRPV 1，只有辣椒平被证明是一种有效的拮抗剂辣椒素诱导的大鼠缩足。因此，虽然I-RTX在体内行为研究中的效用有限，但它是一种高亲和力TRPV 1受体拮抗剂，可用于体外表征克隆和天然香草素受体亚型的功能特性。
We have synthesized iodinated resiniferatoxin bearing a 4-hydroxy-5-iodo-3-methoxyphenylacetate ester (I-RTX) and have characterized its activity on rat and human TRPV1 (VR1) receptors, as well as in behavioral assays of nociception. In whole cell patch-clamp recordings from transfected cells the functional activity of I-RTX was determined. Currents activated by capsaicin exhibited characteristic outward rectification and were antagonized by capsazepine and I-RTX. On rat TRPV1 the affinity of I-RTX was 800-fold higher than that of capsazepine (IC50 = 0.7 and 562 nM, respectively) and 10-fold higher on rat versus human receptors (IC50 = 0.7 and 5.4 nM, respectively). The same difference was observed when comparing the inhibition of [H-3]RTX binding to rat and human TRPV1 membranes for both RTX and I-RTX. Additional pharmacological differences were revealed using protons as the stimulus. Under these conditions capsazepine only partly blocked currents through rat TRPV1 receptors (by 70 to 80% block), yet was a full antagonist on human receptors. In contrast, I-RTX completely blocked proton-induced currents in both species and that activated by noxious heat. I-RTX also blocked capsaicin-induced firing of C-fibers in a rat in vitro skin-nerve assay. Despite this activity and the high affinity of I-RTX for rat TRPV1, only capsazepine proved to be an effective antagonist of capsaicin-induced paw flinching in rats. Thus, although I-RTX has limited utility for in vivo behavioral studies it is a high-affinity TRPV1 receptor antagonist that will be useful to characterize the functional properties of cloned and native vanilloid receptor subtypes in vitro.