Huang Shih-Che
Department of Internal Medicine, E-Da Hospital, Kaohsiung, Taiwan; School of Medicine, I-Shou University, Kaohsiung, Taiwan.
Regul Pept. 2014 Feb 10;189:46-50. doi: 10.1016/j.regpep.2014.03.001. Epub 2014 Mar 11.
Activation of proteinase-activated receptor-1 (PAR1) and PAR2 stimulates contraction of the rat but relaxation of the guinea pig colon. The aim of the present study was to investigate PAR effects on internal anal sphincter (IAS) motility. We measured relaxation of isolated muscle strips from the guinea pig IAS caused by PAR agonists using isometric transducers. Reverse transcription polymerase chain reaction (RT-PCR) was performed to determine the existence of PAR. In the IAS, thrombin and PAR1 peptide agonists TFLLR-NH2 and SFLLRN-NH2 evoked moderate to marked relaxation in a concentration-dependent manner. In addition, trypsin and PAR2 peptide agonists 2-furoyl-LIGRLO-NH2, SLIGRL-NH2 and SLIGKV-NH2 produced relaxation. In contrast, both PAR1 and PAR2 inactive control peptides did not elicit relaxation. Furthermore, the selective PAR1 antagonist vorapaxar and PAR2 antagonist GB 83 specifically inhibited thrombin and trypsin-induced relaxations, respectively. RT-PCR revealed the presence of PAR1 and PAR2 in the IAS. This indicates that PAR1 and PAR2 mediate the IAS relaxation. The relaxant responses of TFLLR-NH2 and trypsin were attenuated by N(omega)-Nitro-L-arginine (L-NNA), indicating involvement of NO. These responses were not affected by tetrodotoxin, implying that the PAR effects are not neurally mediated. On the other hand, PAR4 agonists GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2 did not cause relaxation or contraction, suggesting that PAR4 is not involved in the sphincter motility. Taken together, these results demonstrate that both PAR1 and PAR2 mediate relaxation of the guinea pig IAS through the NO pathway. PAR1 and PAR2 may regulate IAS tone and might be potential therapeutic targets for anal motility disorders.
蛋白酶激活受体-1（PAR1）和PAR2的激活可刺激大鼠结肠收缩，但可使豚鼠结肠松弛。本研究的目的是探讨PAR对肛门内括约肌（IAS）运动的影响。我们使用等长换能器测量了PAR激动剂引起的豚鼠IAS离体肌条的松弛情况。进行逆转录聚合酶链反应（RT-PCR）以确定PAR的存在。在IAS中，凝血酶以及PAR1肽激动剂TFLLR-NH2和SFLLRN-NH2以浓度依赖性方式引起中度至显著的松弛。此外，胰蛋白酶以及PAR2肽激动剂2-呋喃甲酰-LIGRLO-NH2、SLIGRL-NH2和SLIGKV-NH2也产生松弛作用。相比之下，PAR1和PAR2的无活性对照肽均未引起松弛。此外，选择性PAR1拮抗剂沃拉帕沙和PAR2拮抗剂GB 83分别特异性抑制凝血酶和胰蛋白酶诱导的松弛。RT-PCR显示IAS中存在PAR1和PAR2。这表明PAR1和PAR2介导IAS松弛。TFLLR-NH2和胰蛋白酶的松弛反应被N（ω）-硝基-L-精氨酸（L-NNA）减弱，表明一氧化氮（NO）参与其中。这些反应不受河豚毒素影响，这意味着PAR的作用不是神经介导的。另一方面，PAR4激动剂GYPGKF-NH2、GYPGQV-NH2和AYPGKF-NH2未引起松弛或收缩，表明PAR4不参与括约肌运动。综上所述，这些结果表明PAR1和PAR2均通过NO途径介导豚鼠IAS的松弛。PAR1和PAR2可能调节IAS张力，并且可能是肛门运动障碍的潜在治疗靶点。
