Mulè F, Pizzuti R, Capparelli A, Vergnolle N
Dipartimento di Biologia cellulare e dello Sviluppo, Laboratorio di Fisiologia Generale, Università di Palermo, Viale delle Scienze, 90128 Palermo, Italy.
Gut. 2004 Feb;53(2):229-34. doi: 10.1136/gut.2003.021899.
Protease activated receptors (PARs) have been postulated to play a role during intestinal inflammation. The presence and role played by PAR(4) in gastrointestinal functions have not been fully clarified. The aims of this study were: (i) to examine expression of PAR(4) in rat proximal colon; (ii) to determine the mechanical effects induced by PAR(4) activation in longitudinal muscle; and (iii) to characterise the underlying mechanisms.
PAR(4) expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Mechanical activity was recorded as changes in isometric tension.
A PCR product corresponding to the predicted size of the PAR(4) signal was amplified from RNA prepared from the colon of rats, showing the presence of PAR(4) in those tissues. Immunohistochemistry revealed that PAR(4) protein was expressed on epithelial surfaces and submucosa. PAR(4) activating peptides, GYPGKF-NH(2) and AYPGKG-NH(2), produced concentration dependent contractile effects on longitudinal muscle. Tetrodotoxin (TTX) or atropine significantly reduced the contractile responses to AYPGKG-NH(2), and atropine after TTX did not cause any further reduction. NK(1) receptor antagonist, SR140333, or NK(2) receptor antagonist, SR48968, alone or in combination, produced a reduction in PAR(4) induced contractile effect, and when coadministered with TTX abolished it. Capsaicin markedly reduced the contractions evoked by AYPGKG-NH(2).
The present results suggest that PAR(4) is functionally expressed in rat colon and its activation induces contraction of the longitudinal muscle both through TTX sensitive release of acetylcholine and release of tachykinins, probably from sensory nerves. These actions may contribute to motility disturbances during intestinal trauma and inflammation.
蛋白酶激活受体（PARs）被推测在肠道炎症过程中发挥作用。PAR(4)在胃肠功能中的存在情况及作用尚未完全阐明。本研究的目的是：（i）检测PAR(4)在大鼠近端结肠中的表达；（ii）确定PAR(4)激活对纵行肌产生的力学效应；（iii）阐明其潜在机制。
通过逆转录-聚合酶链反应（RT-PCR）和免疫组织化学法检测PAR(4)的表达。力学活性记录为等长张力的变化。
从大鼠结肠制备的RNA中扩增出与预测的PAR(4)信号大小相符的PCR产物，表明这些组织中存在PAR(4)。免疫组织化学显示PAR(4)蛋白在上皮表面和黏膜下层表达。PAR(4)激活肽GYPGKF-NH₂和AYPGKG-NH₂对纵行肌产生浓度依赖性收缩效应。河豚毒素（TTX）或阿托品显著降低对AYPGKG-NH₂的收缩反应，TTX处理后再用阿托品不会导致进一步降低。NK(1)受体拮抗剂SR140333或NK(2)受体拮抗剂SR48968单独或联合使用可降低PAR(4)诱导的收缩效应，与TTX共同给药时可消除该效应。辣椒素显著降低AYPGKG-NH₂诱发的收缩。
目前的结果表明，PAR(4)在大鼠结肠中功能性表达，其激活通过乙酰胆碱的TTX敏感释放和速激肽的释放（可能来自感觉神经）诱导纵行肌收缩。这些作用可能导致肠道创伤和炎症期间的运动障碍。
