Motta Emerson Marcelo, Calixto João Batista, Rae Giles Alexander
Department of Pharmacology, Universidade Federal de Santa Catarina, Campus, Trindade, Florianópolis, Santa Catarina 88040-900, Brazil.
Exp Biol Med (Maywood). 2006 Jun;231(6):1141-5.
In addition to causing overt nociception, intraplantar (ipl) endothelin (ET)-1 injection into the rat hind paw induces hyperalgesia to mechanical stimuli, mediated via local ET(B) receptors coupled to protein kinase (PK) C, but not PKA. The present study further examines the intracellular signaling mechanisms underlying this effect of ET-1. ET-1 (30 pmol) or phospate-buffered saline (PBS) was injected ipl in rats and the threshold of responsiveness to mechanical stimulation was assessed repeatedly each hour up to 8 hrs and 24 hrs, using the dynamic plantar aesthesiometer test, which detects the minimal pressure required to evoke paw withdrawal. Different groups were treated, 15 mins before ET-1 administration, with ipsilateral injection of selective inhibitors of either phospholipase (PL) A2 (1 nmol PACOCF3), PLC (30 pmol U73122), PKC (1 nmol GF109203X), p38 mitogen-activated protein kinase (MAPK; 30 nmol SB203580), extracellular signal-regulated kinase (ERK1/2; 30 nmol PD98059), c-Jun N-terminal kinase (JNK; 30 nmol SP600125), or vehicle, to assess their influence on the hyperalgesic response. The mechanical hyperalgesia caused by ET-1 started 2 hrs after injection, peaked at 5 hrs (PBS, 29 +/- 0.5 g; ET-1, 17 +/- 1.3 g) and lasted up to 8 hrs. The inhibitors of PLC, PKC, p38 MAPK, ERK1/2, and JNK caused long-lasting reductions of the mechanical hyperalgesia (inhibitions at 4 hrs of 100%, 90%, 97%, 90%, and 100%, respectively), but the PLA2 inhibitor reduced hyperalgesia only at 4 hrs (by 58%). Thus, mechanical hyperalgesia triggered by ET-1 in the rat hind paw depends importantly on signaling pathways involving PLC, PKC, p38 MAPK, ERK1/2, and JNK, whereas the contribution of PLA2 is relatively minor.
除了引起明显的伤害感受外，向大鼠后爪足底内注射内皮素（ET）-1会诱发对机械刺激的痛觉过敏，这是通过与蛋白激酶（PK）C偶联的局部ET（B）受体介导的，而非PKA。本研究进一步探讨了ET-1这种作用背后的细胞内信号传导机制。将ET-1（30 pmol）或磷酸盐缓冲盐水（PBS）注射到大鼠足底内，使用动态足底触觉测量仪测试，每小时重复评估对机械刺激的反应阈值，持续8小时和24小时，该测试可检测引起爪退缩所需的最小压力。在给予ET-1前15分钟，对不同组大鼠同侧注射磷脂酶（PL）A2（1 nmol PACOCF3）、磷脂酶C（PLC；30 pmol U73122）、蛋白激酶C（PKC；1 nmol GF109203X）、p38丝裂原活化蛋白激酶（MAPK；30 nmol SB203580）、细胞外信号调节激酶（ERK1/2；30 nmol PD98059）、c-Jun氨基末端激酶（JNK；30 nmol SP600125）的选择性抑制剂或溶剂，以评估它们对痛觉过敏反应的影响。ET-1引起的机械性痛觉过敏在注射后2小时开始，5小时达到峰值（PBS组为29±0.5 g；ET-1组为17±1.3 g），并持续长达8小时。PLC、PKC、p38 MAPK、ERK1/2和JNK的抑制剂导致机械性痛觉过敏长期减轻（4小时时的抑制率分别为100%、90%、97%、90%和100%），但PLA2抑制剂仅在4小时时减轻痛觉过敏（减轻58%）。因此，ET-1在大鼠后爪引发的机械性痛觉过敏主要依赖于涉及PLC、PKC、p38 MAPK、ERK1/2和JNK的信号通路，而PLA2的作用相对较小。
