Regulation of drug absorption by enteric nervous system: Studies on drug secretion via specialized mechanisms.

肠神经系统(ENS)独立于中枢神经系统(CNS)，调节小肠的运动以及小肠内水和/或电解质的运输。然而，关于ENS对药物从小肠吸收的影响的信息很少。我们一直在继续系统地研究ENS在药物从小肠吸收中的作用。在本项目中，我们重点研究了ENS对P-糖蛋白(P-gp)功能的影响，P-gp是众所周知的输出许多重要药物的物质。以P-gp的典型底物罗丹明123为模型化合物，采用血管腔灌流实验、离体肠片转运实验和Caco-2细胞转运实验三种不同的方法研究了肾上腺素对P-gp功能的影响。结果表明，肾上腺素刺激肾上腺素能神经元可使上述三种方法的P-gp活性减弱。Western印迹分析表明，…刷状缘膜上P-gp的表达水平降低，与P-gp活性降低呈显著正相关，提示P-gp在刷状缘膜上的表达水平降低可能是P-gp活性降低的部分原因。另一方面，肾上腺素的加入不改变P-gp在上皮细胞中的整体表达水平，提示肾上腺素的加入降低了P-gp从细胞内池向BBM的转运。由于α_2激动剂可乐定的作用类似于肾上腺素，因此受体可能参与P-gp活性的调节。肾上腺素降低细胞内cAMP水平，PICA抑制剂降低P-gp活性，二丁酰cAMP显著增强P-gp活性。综上所述，肾上腺素通过降低BBM上P-gp的表达水平来降低P-gp的活性，这可能是通过降低cAMP水平进而降低PKA活性来实现的。较少

The enteric nervous system (ENS), independent of the central nervous system (CNS), regulates the movement of small intestine and the transport of water and/or electrolytes in the small intestine. However, there is little information about the effect of ENS on drug absorption from the small intestine. We have been continuing systematically to investigate the role of ENS in drug absorption from the small intestine. In this project, we focused on the effect of ENS on function of P-glycoprotein (P-gp), which is well known to pump out many important drugs. Employing rhodamine123, a typical substrate for P-gp, as a model compound, the effect of addition of adrenaline on P-gp function was investigated with three different methods such as the vascular-luminal perfusion study, the transport study with the isolated intestinal sheet and Caco-2 cells. As a result, the stimulation of adrenergic neuron by adrenaline attenuated P-gp activity in all the three methods. Western blot analysis showed that … More the expression level of P-gp in brush border membrane (BBM) decreased, which was significantly correlated with the decrease in P-gp activity, indicating that the decrease in the expression level in BBM could be partly responsible for the decrease in P-gp activity On the other hand, the whole expression level of P-gp in the epithelial cells was found not to be changed by the addition of adrenaline, suggesting that the trafficking rate of P-gp from intracellular pool to BBM was decreased by the addition of adrenaline. Since clonidine, a selective α_2 agonist, provided the results similar with adrenaline, as receptor could be involved in the regulation of P-gp activity. It was also found that adrenaline decreased the intracellular level of cAMP and that PICA inhibitor decreased P-gp activity Furthermore, dibutyryl cAMP significantly enhanced P-gp activity. Taken all together, adrenaline decreases P-gp activity by attenuating the expression level of P-gp on BBM, which could be mediated by the decrease in cyclic AMP level and subsequent decrease in PKA activity. Less